Clinical presentation of intra-articular osteoid osteoma of the hip and preliminary outcomes after arthroscopic resection: a case series

Clinical presentation of intra-articular osteoid osteoma of the hip and preliminary outcomes... Journal of Hip Preservation Surgery Vol. 5, No. 1, pp. 88–99 doi: 10.1093/jhps/hnx042 Advance Access Publication 28 December 2017 Research article Clinical presentation of intra-articular osteoid osteoma of the hip and preliminary outcomes after arthroscopic resection: a case series 1 2 2 3 Andrea M. Spiker *, Ben-Zion Rotter , Brenda Chang , Douglas N. Mintz and Bryan T. Kelly Department of Orthopedic Surgery, Sports Medicine and Hip Preservation, University of Wisconsin-Madison, Madison, WI, USA, Department of Orthopaedic Surgery, Hospital for Special Surgery, 535 E. 70th St, New York, NY 10021, USA and Department of Radiology, Hospital for Special Surgery, 535 E. 70th St, New York, NY 10021, USA *Correspondence to: A. M. Spiker. E-mail: spiker@ortho.wisc.edu Submitted 1 June 2017; revised version accepted 26 September 2017 ABSTRACT Intra-articular osteoid osteoma (IAOO) of the hip is a relatively rare diagnosis, but one that can closely mimic symptomatic presentation of femoroacetabular impingement (FAI). Although there are multiple case reports of osteoid osteoma (OO) in the hip, we present the largest case series of hip IAOO treated with hip arthroscopy and discuss limited patient-reported outcomes after treatment with hip arthroscopy. We retrospectively identified patients diagnosed with IAOO of the hip with confirmatory computed tomography, magnetic resonance imaging or biopsy diagnoses of OO. We analyzed lesion location, main presenting symptoms, symptom duration and treatment undertaken. For the patients who underwent hip arthroscopy for treatment of their IAOO, we reviewed patient-reported outcome scores when available. Forty patients with confirmed IAOO were identified. Thirteen underwent excision with hip arthroscopy. The most common presenting symptom was groin pain. In limited patients who had pre- and post-operative outcome scores, we found significant improvements in modified Harris Hip Score (mHHS), Hip Outcome Score-Activity of Daily Living (HOS-ADL) and international Hip Outcomes Tool (iHot33) scores. Compared with patients under- going hip arthroscopy for FAI alone, baseline mHHS, HOS-ADL, Hip Outcome Score–Sport-Specific Subscale and iHot33 scores were almost identical. We found that the presenting symptoms of hip IAOO closely mimic sympto- matic FAI, including groin pain and anterior hip pain, so it is important to keep IAOO of the hip in the differential diagnosis of hip pain. Based on our experience, arthroscopy can be an effective treatment option for excision of intra-articular OO and is especially effective in patients with concomitant FAI in treating both pathologies. INTRODUCTION diagnosis, its presentation can mimic many other hip path- Osteoid osteomas (OOs) represent approximately 10% of ologies, so is an important entity to keep in the differential benign bone tumors and were first identified as a separate diagnosis. The typical presentation of an extra-articular OO is severe entity by Jaffe [1]. OOs are most commonly found in the femur, the tibia and the spine, but can be found throughout pain, often including night pain in 80% of patients [2], the body [2]. Approximately 1–3% of OOs are localized to which is relieved with administration of aspirin or non- the pelvic region [3, 4] and approximately 20% of all OOs steroidal anti-inflammatory drugs (NSAIDs) [7]. The proximal femur, along with the proximal humerus, the are located in the proximal femur [5]. Five to 12% of OOs have an intra-articular location [1], and approximately 13% proximal radius and the distal fibula, is unique in that the of intra-articular osteoid osteoma (IAOO) lesions occur at metaphysis is partially intracapsular. It has been reported the hip joint [6]. While IAOO at the hip is a relatively rare that IAOOs can present with atypical symptoms, but there V C The Author 2017. Published by Oxford University Press. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by- nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com Downloaded from https://academic.oup.com/jhps/article-abstract/5/1/88/4838313 by Ed 'DeepDyve' Gillespie user on 16 March 2018 Clinical presentation of IAOO of the hip and preliminary outcomes  89 has not been a clear consensus on the hip IAOOs presenta- While multiple case reports have described IAOOs in the acetabulum [9, 10, 17, 19–21, 30–44] and femoral tion. Hip IAOOs have been reported as presenting with synovitis, joint effusion, decreased ROM, muscle atrophy neck [11, 12, 19, 23, 30, 33–35, 37, 45–49], as well as the in the affected leg or abductor muscles [8], limb length dis- femoral head [35–37, 50, 51](Table I), we report the larg- est case series of OOs of the intra-articular region of the crepancy [3] or even hip contractures [9]. In the acetabu- hip treated with hip arthroscopy. We share limited pre- lar OO lesions specifically, patients have presented with chronic pain [10], chronic synovitis [9, 11], normal hip and post-surgical outcome scores after treatment with hip arthroscopy. We also discuss the presentation (symptom mobility [10] and partial pain relief with NSAIDs [10]. location and duration) and imaging findings in patients Hip IAOOs have also been associated with growth distur- with IAOO of the hip. bances of the hip [12], rapid development of osteoarthritis (OA) [13], severe radicular pain, progressive and diffuse MATERIALS AND METHODS muscular atrophy and weakness in the affected limb, and diminished deep tendon reflexes [14, 15]. These some- Study population times subtle and non-specific presentations can be a diag- We retrospectively identified all patients in our institution’s nostic challenge. The lag in diagnosis of patients with hip preservation group who had been given a diagnosis of general IAOO has been reported to be up to three times OO of the hip (acetabulum or intra-articular proximal longer (26.6 months) than those with more classic extra- femur). We reviewed available radiographic, computed articular lesions (8.5 months) [6]. tomography (CT) and magnetic resonance imaging (MRI) Treatment of OO can be non-surgical. Prolonged of the lesions to describe lesion location. We excluded any administration of oral salicylates and NSAIDs has been patient who did not have a confirmed diagnosis of OO reported to take 2–15 years for the OO pain to resolve (either biopsy confirmed or definitive diagnosis made from [16]. Surgical treatment of OO lesions in the acetabulum either CT or MRI imaging by a fellowship trained muscu- has included open surgical hip dislocation [9], percutane- loskeletal radiologist. If MRI was not pathognomonic and ous radiofrequency ablation (RFA), hip arthroscopy [17], CT was not available, we excluded the patient). the use of an intra-articular laser with en block excision Of these patients, we further selected those who were [18], burring the lesion [17, 19] or using a curette to enrolled in our institutional review board–approved hip excise the lesion [20], arthroscopically assisted RFA [21], registry of prospectively collected data on over 1800 proce- or intraoperative percutaneous RFA [22]. Surgical treat- dures in 1600 patients since 2010. Patients are enrolled ment of femoral neck OOs has included excision with the after providing informed consent, and data collected arthroscopic burr and electrosurgical instruments [11, 19], include pre-, intra-, and post-operative findings, patient- a modified core decompression technique [8], excisional reported outcomes pre- and post-operatively, and radio- biopsy or intralesional curettage through an anterior hip graphic reports. From these patients, we were able to approach [23], with internal fixation or cast immobilization analyse patient-reported outcome scores. [23], and a lateral approach and en bloc excision through the greater trochanter [24]. The standard treatment most Outcome measures often reported for acetabular OOs has been an open surgi- Patient-reported outcome scores were tabulated when avail- cal procedure to access the cartilage surface [25, 26]. RFA able. The hip registry includes scores for the modified is also commonly used to treat OOs in all locations, and Harris Hip Score (mHHS), the international Hip has a reported overall success rate of up to 90% in perma- Outcomes Tool (iHot33), the Hip Outcome Score-Activity nently treating OOs [10, 27]. However, complications of of Daily Living (HOS-ADL) and the Hip Outcome Score– RFA include infections, skin burns, bleeding, nerve injury, Sport-Specific Subscale (HOS-SSS). These scores are rou- tendonitis or thrombosis. There has also been a report of tinely obtained pre-operatively, at 6 months, 1 year and long-term (10 years) femur fracture after RFA of a proxi- yearly thereafter through final follow-up. mal femur lesion [28], and mid-term (1 year after proce- dure) symptomatic articular damage has been reported Statistical analysis after treatment with RFA [10]. RFA is contraindicated Descriptive statistics were reported in terms of means and when in close proximity to the spinal cord or peripheral standard deviations for continuous demographic variables, nerves adjacent to disrupted cortical bone [10]. If and in terms of total number and percentage of patients the entire lesion is not ablated with RFA, recurrence can for discrete variables. Descriptive statistics were similarly occur [29]. reported for clinical characteristics in terms of total Downloaded from https://academic.oup.com/jhps/article-abstract/5/1/88/4838313 by Ed 'DeepDyve' Gillespie user on 16 March 2018 90  A. M. Spiker et al. Table I. Review of the literature—previous reports of IAOO of the hip Citation Year Number Age/ Location of lesion Treatment Follow-up Outcome of average (months) scores? patients age with hip IAOO Agrawal et al. [14] 2009 1 11 Proximal femoral NR NR No shaft Ahlfeld et al. [23] 1990 5 15 Femoral neck Open excision 48 No Alvarez et al. [18] 2001 1 16 Acetabulum Arthroscopy 1 No Asik et al. [20] 2014 1 7 Acetabulum Arthroscopy þRFA 8 No Banga et al. [52] 2014 1 52 Femoral neck Non-op 7 No Barnhard et al. [31] 2011 1 20 Acetabulum Arthroscopy NR No Bettelli et al. [3] 1989 2 NR Acetabulum Open excision 37 No Bosschaert et al. [10] 2010 1 17 Acetabulum RFA 12 No Callaghan et al. [25] 1998 6 Five acetabulum, 1 Open excision NR No femoral neck Carter et al. [8] 1990 1 17 Femoral neck Open excision 24 No Cassar-Pullicino et al. [56] 1992 2 23 Femoral neck, Open excision 36 No acetabulum Chang et al. [32] 2010 1 29 Acetabulum Arthroscopy 12 No de los Santos et al. [26] 2013 1 12 Acetabulum Open excision 36 No Dunlap et al. [50] 1985 1 14 Aemoral head Non-op NR No Foeldvari et al. [13] 1998 1 14 Femoral neck Open excision 5 No Gille et al. [9] 1990 2 14 Acetabulum Open excision 3 No Giustra et al. [12] 1970 2 14 One femoral neck, 1 Open excision NR No proximal femoral shaft Goldberg et al. [33] 1975 31 NR Femoral neck, Twenty-nine open NR No (range acetabulum excision, 2 non-op 2-16) Herget et al. [11] 2012 1 21 Femoral neck Arthroscopy NR No Kang et al. [61] 2014 1 24 Femoral neck CT-guided excision 43 No Karray et al. [44] 2010 1 16 Acetabulum Open excision NR No Kattapuram et al. [54] 1983 11 NR Seven femoral neck, NR NR No 2 acetabulum, 2 NR (continued) Downloaded from https://academic.oup.com/jhps/article-abstract/5/1/88/4838313 by Ed 'DeepDyve' Gillespie user on 16 March 2018 Clinical presentation of IAOO of the hip and preliminary outcomes  91 Table I. Continued Citation Year Number Age/ Location of lesion Treatment Follow-up Outcome of average (months) scores? patients age with hip IAOO Khapchik et al. [19] 2001 2 26 One acetabulum, 1 Arthroscopy 21 No femoral neck Lee et al. [34] 2009 2 11 One acetabulum, 1 Arthroscopy 19 No femoral neck Marwan et al. [17] 2015 1 31 Acetabulum Arthroscopy 44 No Muscolo et al. [35] 1994 4 19 Three femoral neck, CT-guided excision 27 No 1 femoral head Nehme et al. [30] 2012 2 27 One femoral neck, 1 Arthroscopy 24 No acetabulum Ninomiya et al. [36] 1989 2 12 One acetabulum, 1 Open excision 14 and NR No femoral head Papagelopoulos et al. [37] 2006 16 NR Eight femoral head, RFA 30 No 6 femoral neck, 2 acetabulum Parlier-Cuau et al. [38] 1999 3 20 Acetabulum CT-guided excision 36 No Pianta et al. [46] 2012 1 16 Femoral neck RFA 12 No Raux et al. [47] 2014 26 NR Femoral neck CT-guided excision NR No Raux et al. [39] 2013 5 17 Acetabulum CT-guided excision 18 No Ricci et al. [21] 2013 1 47 Acetabulum Arthroscopy þ RFA 22 No Richardson et al. [48] 2009 1 18 Femoral neck CT-guided excision NR No Scalici et al. [51] 2011 1 24 Femoral head Open excision 60 No Sestan et al. [49] 2005 1 11 Femoral neck Non-op 60 No Shoji et al. [40] 2014 1 12 Acetabulum Arthroscopy 16 No Szendroi et al. [6] 2004 9 20 Three acetabulum, 6 Two open excision, 29 No femoral neck 7 curettage Tamam et al. [41] 2014 1 23 Acetabulum Arthroscopy NR No Tokis et al. [29] 2013 1 19 Acetabulum Arthroscopy 12 No Tsuruomto et al. [42] 2005 1 15 Acetabulum Open excision 96 No Xiao et al. [62] 2011 1 9 Femoral neck Open excision 12 No number of procedures. Paired t-tests were used to compare arthroscopic treatment of femoroacetabular impingement the latest post-operative scores at 6 months or greater to (FAI) were calculated. pre-operative scores. Frequency and percentage of patients A comparison group of all patients undergoing hip achieving a minimal clinically important difference for arthroscopy for isolated cam- or rim-impingement was Downloaded from https://academic.oup.com/jhps/article-abstract/5/1/88/4838313 by Ed 'DeepDyve' Gillespie user on 16 March 2018 92  A. M. Spiker et al. included for demographic and baseline outcome score decompression, 2 had iliopsoas release and 4 had labral comparison in a non-matched case–control design. These debridement. All 13 patients who underwent arthroscopic included unilateral or bilateral scopes between 10 July excision of the OO had the lesion confirmed by pathology. 2007 and 14 April 2016 with completed survey scores at The main presenting symptom for each patient was baseline. documented (Table III). The duration of symptoms at the All analyses were conducted using SAS version 9.3 time of initial evaluation at our institution was also noted (SAS Inc., Cary, NC, USA). (Table IV), as was the prevalence of night pain and pain relief with NSAIDs (Table V). RESULTS We reviewed the CT imaging available on our IAOO Forty patients from the hip preservation group database patients (13 of 40). The average alpha angle in these were identified as having a hip IAOO between 2000 and patients was 64.6 (613.1 ), coronal center edge angle 2015. Ten lesions were located in the acetabulum, 29 in 30.2 (63.8 ), femoral neck shaft angle 133.2 (64.9 ), the femoral neck and 1 in the femoral head. Twenty-four acetabular version at 1 o’clock 3 (66.9 ), 2 o’clock 8.8 patients were male and 16 female, with the average age of (68.3 ) and 3 o’clock 16 (65.4 ). On MRI review, 65% 24.5 years (range 11–57). (26 of 40) of the patients had edema surrounding the OO Thirty of the 40 patients underwent intervention for lesions. their OO at our institution. Ten patients were either lost Of the 13 patients treated with hip arthroscopy, 5 had to follow-up or were treated non-operatively (Table II). Of both pre- and post-operative mHHS and HOS-ADL. Four those who sought treatment, 16 underwent RFA, 13 under- had both pre- and post-op iHot33 scores, and three had went hip arthroscopy and 1 underwent open excision. Of both pre- and post-op HOS-SSS scores. The mean pre-op the patients who were treated with RFA, 13 of the lesions mHHS in these patients was 58.1, HOS-ADL 65.3, HOS- were located in the femoral neck and 3 in the acetabulum. SSS 41.7, iHot33 37.5. At final follow-up, the mean scores Of the patients treated with hip arthroscopy, nine lesions were in the femoral neck, three were in the acetabulum Table III. Main presenting symptoms of patients with and one was in the inferior femoral head. The one patient confirmed IAOO of the hip who underwent open excision had a lesion in the acetabu- Main presenting symptom Number %of lum. Of the 13 patients who had arthroscopic excision of of patients patients the OO, the concomitant arthroscopic procedures per- formed were as follows: 8 had labral repair, 7 had rim Groin pain 9 23 decompression, 9 had cam decompression, 1 had subspine Anterior hip pain 6 15 Table II. Treatment course of patients who did not Groin pain w/anterior hip pain 4 10 undergo treatment at our institution (10 of 40 Lateral hip pain 4 10 patients) Generalized hip pain 4 10 Patients treated non-operatively or lost Number Groin pain w/radiation to leg 1 3 to follow-up of patients Groin pain w/lateral hip pain 1 3 Initiated PT—lost to follow-up 3 Groin pain w/anterior and 13 Lost to follow-up 2 posterior hip pain Pain level manageable—patient opted 1 Groin pain w/anterior and 13 for conservative management lateral hip pain Recommended RFA—patient refused 1 Buttock pain w/radiation to 13 Recommended arthroscopy—patient 1 groin and leg refused Anterior hip pain w/posterior pain 1 3 Recommended RFA—lost to follow-up 1 Pelvic pain 1 3 Intra-articular injection þ initiated PT 1 Not recorded 6 15 —lost to follow-up Downloaded from https://academic.oup.com/jhps/article-abstract/5/1/88/4838313 by Ed 'DeepDyve' Gillespie user on 16 March 2018 Clinical presentation of IAOO of the hip and preliminary outcomes  93 were mHHS 93.9 (D35.9, P ¼ 0.002), HOS-ADL 98.2 time of last follow-up (average 27 months, range 3–105 (D33.0, P ¼ 0.006), HOS-SSS 90.7 (D49.1, P ¼ 0.06) and months). iHot33 80.0 (D42.5, P ¼ 0.006). We had no reported sur- A comparison group of all patients undergoing hip gical complications and no recurrences of the lesion at the arthroscopy for isolated cam- or rim-impingement was included. There were no statistically significant differences in gender or age between these groups (Table VI), nor Table IV. Duration of symptoms upon initial evalua- were there any statistically significant differences between tion at our institution baseline pre-operative scores (mHHS, HOS-ADL, HOS- SSS and iHot33) (Table VII). Given the small number of Duration of symptoms Number %of hip IAOO patients with post-operative outcome scores, we of patients patients were not able to directly compare post-operative scores 0–6 months 10 25 between our study group and the group of FAI patients undergoing hip arthroscopy. 6 months to 1 year 9 23 1–2 years 6 15 DISCUSSION IAOO of the hip may be a confounding diagnosis in >2 years 8 20 patients presenting with hip pain and symptoms consistent Not recorded 7 18 with FAI. Diagnosis of this rare but treatable benign bone tumor is often delayed due to its atypical presentation [6], and based on our findings, its similarity with symptomatic Table V. Presence of night pain and pain relief with presentation of FAI. Case reports in the literature have pre- NSAIDs viously reported of the coexistence of OO and FAI [52] and described multiple treatment options, including hip Presence of night pain Number %of arthroscopy [11, 17, 19]. We report the largest case series of patients patients of hip IAOO treated with hip arthroscopy (13 patients), Night pain 15 38 and discuss the clinical presentation of a total of 40 patients with confirmed diagnosis of IAOO of the hip. No night pain 3 8 Males are more commonly affected by OO than females, Not recorded 22 55 at a rate of 2:1 [2]to 3:1 [27]. In our series of hip IAOO, Pain relief with NSAIDs Number % of 24 patients were male and 16 were female, a male to female of patients patients ratio of 1.5:1. The location of the IAOO lesions was on both sides of the hip joint; however, there was almost a 3:1 Pain relief with NSAIDs 23 58 ratio of lesions in the femoral neck compared with the ace- No pain relief with NSAIDs 10 25 tabulum (29 IAOO in the femoral neck, 10 IAOO in the acetabulum and 1 in the inferior femoral head). OO with Not recorded 13 33 intra-articular location has been reported to present with Table VI. Demographic comparison of patients undergoing hip arthroscopy for FAI only and patients under- going hip arthroscopy with IAOO in a non-matched case–control design Patients with IAOO Patients with FAI only N % N % Odds ratios (95% CI) P-value Total number of patients 14 153 Female 6 42.9 106 69.3 0.3 (0.1 to 1.0) 0.39 Bilateral 3 21.4 16 10.5 2.3 (0.6 to 9.3) 0.14 Revision 1 7.1 9 5.9 1.2 (0.1 to 10.5) 0.39 Mean SD Mean SD Difference in means (95% CI) P-value Age (years) 23.7 8.4 29.2 10.6 5 (–6 to 10) 0.064 Downloaded from https://academic.oup.com/jhps/article-abstract/5/1/88/4838313 by Ed 'DeepDyve' Gillespie user on 16 March 2018 94  A. M. Spiker et al. Table VII. Comparison of preoperative scores for patients undergoing hip arthroscopy for FAI only and patients undergoing hip arthroscopy for IAOO Preoperative survey score Patients with IAOO Patients with FAI Unadjusted P-value Adjusted P-value (N¼ # IAOO, N ¼ # FAI) (N ¼ 14) only (N ¼ 153) difference difference (95% CI) (95% CI) mHHS (mean6 SD) 62 15 60 13 2(9 to 7) 0.63 1 (6 to 9) 0.70 (N¼ 13, N ¼ 153) HOS ADL (mean6 SD) 74 21 72 17 1(13 to 10) 0.80 1 (9 to 11) 0.77 (N¼ 13, N ¼ 153) HOS Sport (mean6 SD) 61 24 49 24 12 (26 to 1) 0.099 6(21 to 8) 0.40 (N¼ 11, N ¼ 153) iHot33 (mean6 SD) 41 24 38 19 3(17 to 11) 0.64 5 (7 to 18) 0.41 (N¼ 9, N¼ 153) Differences in means are adjusted for age, sex, bilaterality and revision status atypical and varied symptoms, different from the classic Additional intra-articular imaging findings include joint night pain relieved by NSAIDs found with extra-articular effusion (Fig. 3), periarticular osteoporosis and periosteal OO [3, 8–15]. Our patients had a wide range of presenta- reaction [54]. Varying amounts of tumor mineralization tions consistent with previous reports of IAOO, but the may be present, with more calcification often correlated most common presenting symptom was groin pain (Table with more mature lesions [56]. While lesions located in III). Groin pain is also the most common presenting symp- the bone cortex may present with large periosteal reaction, tom of FAI [53]. This overlap in symptoms of IAOO and the lack of adjacent periosteum in intra-articular lesions more common causes of hip pathology, such as FAI, can be often results in only a mild osteoblastic response [56]. MRI appearance of OO is often more aggressive than the part of the reason IAOO of the hip is misdiagnosed or missed. Previous reports have emphasized the delay in diag- lesion actually is, with extensive bone marrow edema and nosis of OO of the proximal femur, which have been even adjacent soft tissue signal changes can be seen [56, 57] reported to range between 12 months and 2 years after pain (Figs 2, 3 and 4B). MRI can demonstrate variable signal onset [23]. In our series, patients presented with a more intensity and juxta-lesional edema of the OO depending on evenly distributed duration of symptoms between acute, the amount of calcification present, the vascularity and age of the lesion [58]. Chondral hypertrophy has also been sub-acute and chronic (Table IV). Radiographic features of hip IAOO may differ from described with intra-articular hip OO lesions [56], which extra-articular lesions. The IAOO may not be evident on could be identified on MRI. Sixty-five percent of the MRI plain radiograph (Figs 1A and 4A), as the nidus of OO is reports in our series (26 of 40) describe significant edema. not visible on plain radiographs until the lesion is greater This is consistent with previous findings, where 63% of OOs than 4 mm in size [54]. Additionally, in a majority of sub- on MRI (12 of 19) showed perinidal bone marrow edema chondral or subperiosteal intra-articular lesions, there is no and inflammation [59]. While MRI is often the imaging surrounding sclerosis on plain radiograph [6]. CT is the modality used to assess hip and groin pain, the diagnostic gold standard for diagnosing OO [23] as it is the most use- accuracy of MRI in detecting OO is not as reliable as with ful imaging modality to identify the OO nidus [6], which CT [58, 59]. MRI fails to identify 21% of intra-articular OOs classically appears as a central calcification and surrounding and only poorly identifies them in an additional 29% [58]. Multiple treatment options exist for treatment of symp- sclerosis (Figs 1F and 4C). When the OO is near a joint, CT may demonstrate changes on both sides of the joint, tomatic OO, including open excision, RFA or arthroscopic including osteophyte formation, a localized soft-tissue excision. The gold standard treatment for OO in all loca- mass, reduced bone density or increased bone density in tions is RFA [10, 27]. Patients in our series were referred the subchondral bone of the abutting joint surface [55]. RFA if the lesion was a safe distance from the articular Downloaded from https://academic.oup.com/jhps/article-abstract/5/1/88/4838313 by Ed 'DeepDyve' Gillespie user on 16 March 2018 Clinical presentation of IAOO of the hip and preliminary outcomes  95 Fig. 1. The radiographic imaging of one patient in our series with IAOO of the hip who presented with left groin pain. (A) AP pelvis. (B) Lateral radiograph demonstrates loss of femoral head neck offset with a small cortical irregularity at the head-neck junction. (C) 3D CT scan demonstrates large cam lesion. (D) MRI demonstrates superior labral tear. (E) MRI shows OO lesion. (F)CT shows characteristic appearance of OO. cartilage, and they had no evidence of other intra-articular Norman et al. [60] looked at a series of 182 OOs over pathology that could be addressed with hip arthroscopy. 24 years and found 30 of which were intra-articular at the The decision to proceed with arthroscopic excision of hip joint. Of these 30 lesions, 50% were associated with the hip IAOO in our patient population was based on the development of OA [60]. Rapid development of OA (i) lesion accessibility with hip arthroscopy instrumenta- has also been described as beginning as early as 5 months tion, (ii) the presence of additional pathology which could after OO lesion excision [13]. None of our patients with be addressed with hip arthroscopy and (iii) in depth dis- IAOO had concomitant diagnoses of OA; however, we cussion with the patient about available options and the would require longer and more complete follow-up to patient’s treatment preference. determine the incidence of degenerative changes related to Marwan et al. [17] recently published a systematic review the IAOO. This strong correlation of OA with IAOO does, of all acetabular IAOO treated with hip arthroscopy. From however, give us incentive to identify these lesions early, this review of 11 cases, they reported a success rate of and treat symptomatic IAOO more aggressively to prevent greater than 90% in treating acetabular OOs with hip arthro- the theoretical sequela of early hip OA. scopy and noted no recurrences of the lesion at last follow- There have been multiple case reports and a number of up ranging between 6 months and 2 years, and one study case series of hip IAOO (Table I). Ourcaseseriesisthe not reporting follow-up duration [17]. Similarly, in our case largest of hip IAOO of the hip treated by hip arthroscopy series, none of our patients treated with hip arthroscopy had (Fig. 5). While we had a very small number of patients who recurrence of the lesion after our treatment at an average had both pre- and post-operative outcome scores after treat- 27-months follow-up (range 3–105 months). There were, ment with hip arthroscopy, this is the first report of patient- however, three patients who presented to our institution reported outcomes in this subset of patients. We noted a sig- after previous intervention for their IAOO, and at the time nificant improvement in mHHS, HOS-ADL and iHot33 of our initial evaluation, had either persistent or recurrent scores. Our comparison group of patients (Tables VI and IAOO. All three patients had previously undergone RFA: VII), included patients undergoing hip arthroscopy for FAI one patient proceeded with no further treatment, another only, as this was the closest group of patients to a control patient underwent subsequent hip arthroscopy and the third group who had taken the pre-operative patient-reported out- patient had a repeat CT-guided RFA. come surveys. The FAI only and IAOO patients were Downloaded from https://academic.oup.com/jhps/article-abstract/5/1/88/4838313 by Ed 'DeepDyve' Gillespie user on 16 March 2018 96  A. M. Spiker et al. matched in age, gender and unilaterality/bilaterality of sur- small number of patients who had long-term follow-up. We excluded patients who had OA, although it is possible that gery as well as revision status. When comparing baseline, pre-operative patient-reported outcome scores, the FAI-only older patients who had advanced OA once had an OO, espe- cially given the high incidence of OA associated with hip hip arthroscopy patient scores were not statistically different IAOO [60]. If IAOO wasinthe differential basedonhip from the scores of those patients with hip IAOO undergoing MRI, but the patient did not have a confirmatory CT scan, hip arthroscopy. This emphasizes that patients with hip IAOO can present almost identically to patients with FAI. The physician should be extra vigilant to keep the diagnosis of hip IAOO in the differential. Limitations Given that the diagnosis of IAOO is relatively rare, we have limited numbers of patients who had this diagnosis and were treated with hip arthroscopy. This case series includes only a Fig. 2. (A) Coronal STIR MRI demonstrating edema of the right acetabulum surrounding the OO lesion. (B) Coronal CT Fig. 3. (A) STIR coronal MRI demonstrating bone marrow demonstrating OO lesion (arrow). (C) Axial T2 FSE fat satu- edema of the left femoral neck surrounding the OO lesion and rated MRI again demonstrating bone marrow edema. (D) Axial left hip joint effusion. (B) T2 Axial MRI fat-saturated sequence CT of OO (arrow). demonstrating OO (arrow) at left anteromedial femoral neck. Fig. 4. (A) Pre-operative AP Pelvis of a left inferior femoral neck IAOO. (B) Pre-operative MRI demonstrating significant edema in the femoral neck surrounding the OO lesion. (C) Pre-operative CT scan of characteristic CT findings of OO, demonstrating a nidus with surrounding sclerotic bone. Downloaded from https://academic.oup.com/jhps/article-abstract/5/1/88/4838313 by Ed 'DeepDyve' Gillespie user on 16 March 2018 Clinical presentation of IAOO of the hip and preliminary outcomes  97 Fig. 5. In this left hip with femoral neck OO, intraoperative radiographic image demonstrating the contour of the femoral head-neck junction prior to (A) and after (B) CAM decompression and OO excision. Intraoperative arthroscopic image showing OO of the femoral neck prior to (C, D), during (E) and after (F) excision with a curette an arthroscopic burr. CONCLUSIONS they were also excluded. Given the limitations of MRI to Our series presents 13 patients with IAOO of the hip definitively identify OO [58], it is possiblewemissedOO treated with hip arthroscopy and the clinical presentation lesions that would have been present on CT scan if the of 40 patients with confirmed diagnosis of hip IAOO. patient had undergone CT. While all excised IAOO were While OO in the intra-articular hip location is a relatively confirmed by histology, we did not obtain post-operative CT rare diagnosis, our findings highlight the importance of to evaluate the lesion (as this practice is not standard of keeping IAOO in the differential diagnosis of patients with care). Additionally, many of our patients had multiple proce- hip pain. If an IAOO is diagnosed in the hip joint, we pro- dures in addition to the arthroscopic excision and ablation of pose the following treatment algorithm: If there is no coex- the IAOO. This does confound the post-surgical PROs, as there is no way to delineate what benefit the patients istence of FAI or other intra-articular pathology, RFA remains a viable option with a proven success rate if the received from IAOO excision versus treatment of other lesion is far enough away from the articular cartilage to intra-articular pathology. Another significant limitation to this study was that we did not have patient-reported out- minimize concern for cartilaginous injury. If FAI or intra- articular pathology is also present, RFA of the IAOO with come scores or long-term follow-up on those patients who underwent RFA, as our registry only collects data on post- a staged treatment of the FAI is also an option, especially if operative patients and those that follow for non-operative it is unclear which pathology is the predominant etiology of the patient’s symptoms. If the OO is in the setting of, or treatment of hip pain. Those patients who underwent RFA had post-procedure follow-up outside of our practice. A com- exacerbating, symptomatic FAI, we believe that hip arthro- parison between patients who underwent IAOO with RFA scopy is the preferred treatment method to address all of versus hip arthroscopy would be clinically useful, but in our the patient’s hip pathology during one intervention, and series patients were indicated for hip arthroscopy over the has the added benefit of obtaining tissue for a definitive gold standard RFAiftheymet anumberofcriteria. We diagnosis of the OO lesion. favored hip arthroscopy in patients who had a lesion close to the articular cartilage where there was concern for the poten- ACKNOWLEDGEMENTS tial detrimental effects of RFA to the cartilage; or if they had concomitant intra-pathology that could be addressed with We would like to thank Eilish O’Sullivan, PT, DPT, OCS, hip arthroscopy. 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Clinical presentation of intra-articular osteoid osteoma of the hip and preliminary outcomes after arthroscopic resection: a case series

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Journal of Hip Preservation Surgery Vol. 5, No. 1, pp. 88–99 doi: 10.1093/jhps/hnx042 Advance Access Publication 28 December 2017 Research article Clinical presentation of intra-articular osteoid osteoma of the hip and preliminary outcomes after arthroscopic resection: a case series 1 2 2 3 Andrea M. Spiker *, Ben-Zion Rotter , Brenda Chang , Douglas N. Mintz and Bryan T. Kelly Department of Orthopedic Surgery, Sports Medicine and Hip Preservation, University of Wisconsin-Madison, Madison, WI, USA, Department of Orthopaedic Surgery, Hospital for Special Surgery, 535 E. 70th St, New York, NY 10021, USA and Department of Radiology, Hospital for Special Surgery, 535 E. 70th St, New York, NY 10021, USA *Correspondence to: A. M. Spiker. E-mail: spiker@ortho.wisc.edu Submitted 1 June 2017; revised version accepted 26 September 2017 ABSTRACT Intra-articular osteoid osteoma (IAOO) of the hip is a relatively rare diagnosis, but one that can closely mimic symptomatic presentation of femoroacetabular impingement (FAI). Although there are multiple case reports of osteoid osteoma (OO) in the hip, we present the largest case series of hip IAOO treated with hip arthroscopy and discuss limited patient-reported outcomes after treatment with hip arthroscopy. We retrospectively identified patients diagnosed with IAOO of the hip with confirmatory computed tomography, magnetic resonance imaging or biopsy diagnoses of OO. We analyzed lesion location, main presenting symptoms, symptom duration and treatment undertaken. For the patients who underwent hip arthroscopy for treatment of their IAOO, we reviewed patient-reported outcome scores when available. Forty patients with confirmed IAOO were identified. Thirteen underwent excision with hip arthroscopy. The most common presenting symptom was groin pain. In limited patients who had pre- and post-operative outcome scores, we found significant improvements in modified Harris Hip Score (mHHS), Hip Outcome Score-Activity of Daily Living (HOS-ADL) and international Hip Outcomes Tool (iHot33) scores. Compared with patients under- going hip arthroscopy for FAI alone, baseline mHHS, HOS-ADL, Hip Outcome Score–Sport-Specific Subscale and iHot33 scores were almost identical. We found that the presenting symptoms of hip IAOO closely mimic sympto- matic FAI, including groin pain and anterior hip pain, so it is important to keep IAOO of the hip in the differential diagnosis of hip pain. Based on our experience, arthroscopy can be an effective treatment option for excision of intra-articular OO and is especially effective in patients with concomitant FAI in treating both pathologies. INTRODUCTION diagnosis, its presentation can mimic many other hip path- Osteoid osteomas (OOs) represent approximately 10% of ologies, so is an important entity to keep in the differential benign bone tumors and were first identified as a separate diagnosis. The typical presentation of an extra-articular OO is severe entity by Jaffe [1]. OOs are most commonly found in the femur, the tibia and the spine, but can be found throughout pain, often including night pain in 80% of patients [2], the body [2]. Approximately 1–3% of OOs are localized to which is relieved with administration of aspirin or non- the pelvic region [3, 4] and approximately 20% of all OOs steroidal anti-inflammatory drugs (NSAIDs) [7]. The proximal femur, along with the proximal humerus, the are located in the proximal femur [5]. Five to 12% of OOs have an intra-articular location [1], and approximately 13% proximal radius and the distal fibula, is unique in that the of intra-articular osteoid osteoma (IAOO) lesions occur at metaphysis is partially intracapsular. It has been reported the hip joint [6]. While IAOO at the hip is a relatively rare that IAOOs can present with atypical symptoms, but there V C The Author 2017. Published by Oxford University Press. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by- nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com Downloaded from https://academic.oup.com/jhps/article-abstract/5/1/88/4838313 by Ed 'DeepDyve' Gillespie user on 16 March 2018 Clinical presentation of IAOO of the hip and preliminary outcomes  89 has not been a clear consensus on the hip IAOOs presenta- While multiple case reports have described IAOOs in the acetabulum [9, 10, 17, 19–21, 30–44] and femoral tion. Hip IAOOs have been reported as presenting with synovitis, joint effusion, decreased ROM, muscle atrophy neck [11, 12, 19, 23, 30, 33–35, 37, 45–49], as well as the in the affected leg or abductor muscles [8], limb length dis- femoral head [35–37, 50, 51](Table I), we report the larg- est case series of OOs of the intra-articular region of the crepancy [3] or even hip contractures [9]. In the acetabu- hip treated with hip arthroscopy. We share limited pre- lar OO lesions specifically, patients have presented with chronic pain [10], chronic synovitis [9, 11], normal hip and post-surgical outcome scores after treatment with hip arthroscopy. We also discuss the presentation (symptom mobility [10] and partial pain relief with NSAIDs [10]. location and duration) and imaging findings in patients Hip IAOOs have also been associated with growth distur- with IAOO of the hip. bances of the hip [12], rapid development of osteoarthritis (OA) [13], severe radicular pain, progressive and diffuse MATERIALS AND METHODS muscular atrophy and weakness in the affected limb, and diminished deep tendon reflexes [14, 15]. These some- Study population times subtle and non-specific presentations can be a diag- We retrospectively identified all patients in our institution’s nostic challenge. The lag in diagnosis of patients with hip preservation group who had been given a diagnosis of general IAOO has been reported to be up to three times OO of the hip (acetabulum or intra-articular proximal longer (26.6 months) than those with more classic extra- femur). We reviewed available radiographic, computed articular lesions (8.5 months) [6]. tomography (CT) and magnetic resonance imaging (MRI) Treatment of OO can be non-surgical. Prolonged of the lesions to describe lesion location. We excluded any administration of oral salicylates and NSAIDs has been patient who did not have a confirmed diagnosis of OO reported to take 2–15 years for the OO pain to resolve (either biopsy confirmed or definitive diagnosis made from [16]. Surgical treatment of OO lesions in the acetabulum either CT or MRI imaging by a fellowship trained muscu- has included open surgical hip dislocation [9], percutane- loskeletal radiologist. If MRI was not pathognomonic and ous radiofrequency ablation (RFA), hip arthroscopy [17], CT was not available, we excluded the patient). the use of an intra-articular laser with en block excision Of these patients, we further selected those who were [18], burring the lesion [17, 19] or using a curette to enrolled in our institutional review board–approved hip excise the lesion [20], arthroscopically assisted RFA [21], registry of prospectively collected data on over 1800 proce- or intraoperative percutaneous RFA [22]. Surgical treat- dures in 1600 patients since 2010. Patients are enrolled ment of femoral neck OOs has included excision with the after providing informed consent, and data collected arthroscopic burr and electrosurgical instruments [11, 19], include pre-, intra-, and post-operative findings, patient- a modified core decompression technique [8], excisional reported outcomes pre- and post-operatively, and radio- biopsy or intralesional curettage through an anterior hip graphic reports. From these patients, we were able to approach [23], with internal fixation or cast immobilization analyse patient-reported outcome scores. [23], and a lateral approach and en bloc excision through the greater trochanter [24]. The standard treatment most Outcome measures often reported for acetabular OOs has been an open surgi- Patient-reported outcome scores were tabulated when avail- cal procedure to access the cartilage surface [25, 26]. RFA able. The hip registry includes scores for the modified is also commonly used to treat OOs in all locations, and Harris Hip Score (mHHS), the international Hip has a reported overall success rate of up to 90% in perma- Outcomes Tool (iHot33), the Hip Outcome Score-Activity nently treating OOs [10, 27]. However, complications of of Daily Living (HOS-ADL) and the Hip Outcome Score– RFA include infections, skin burns, bleeding, nerve injury, Sport-Specific Subscale (HOS-SSS). These scores are rou- tendonitis or thrombosis. There has also been a report of tinely obtained pre-operatively, at 6 months, 1 year and long-term (10 years) femur fracture after RFA of a proxi- yearly thereafter through final follow-up. mal femur lesion [28], and mid-term (1 year after proce- dure) symptomatic articular damage has been reported Statistical analysis after treatment with RFA [10]. RFA is contraindicated Descriptive statistics were reported in terms of means and when in close proximity to the spinal cord or peripheral standard deviations for continuous demographic variables, nerves adjacent to disrupted cortical bone [10]. If and in terms of total number and percentage of patients the entire lesion is not ablated with RFA, recurrence can for discrete variables. Descriptive statistics were similarly occur [29]. reported for clinical characteristics in terms of total Downloaded from https://academic.oup.com/jhps/article-abstract/5/1/88/4838313 by Ed 'DeepDyve' Gillespie user on 16 March 2018 90  A. M. Spiker et al. Table I. Review of the literature—previous reports of IAOO of the hip Citation Year Number Age/ Location of lesion Treatment Follow-up Outcome of average (months) scores? patients age with hip IAOO Agrawal et al. [14] 2009 1 11 Proximal femoral NR NR No shaft Ahlfeld et al. [23] 1990 5 15 Femoral neck Open excision 48 No Alvarez et al. [18] 2001 1 16 Acetabulum Arthroscopy 1 No Asik et al. [20] 2014 1 7 Acetabulum Arthroscopy þRFA 8 No Banga et al. [52] 2014 1 52 Femoral neck Non-op 7 No Barnhard et al. [31] 2011 1 20 Acetabulum Arthroscopy NR No Bettelli et al. [3] 1989 2 NR Acetabulum Open excision 37 No Bosschaert et al. [10] 2010 1 17 Acetabulum RFA 12 No Callaghan et al. [25] 1998 6 Five acetabulum, 1 Open excision NR No femoral neck Carter et al. [8] 1990 1 17 Femoral neck Open excision 24 No Cassar-Pullicino et al. [56] 1992 2 23 Femoral neck, Open excision 36 No acetabulum Chang et al. [32] 2010 1 29 Acetabulum Arthroscopy 12 No de los Santos et al. [26] 2013 1 12 Acetabulum Open excision 36 No Dunlap et al. [50] 1985 1 14 Aemoral head Non-op NR No Foeldvari et al. [13] 1998 1 14 Femoral neck Open excision 5 No Gille et al. [9] 1990 2 14 Acetabulum Open excision 3 No Giustra et al. [12] 1970 2 14 One femoral neck, 1 Open excision NR No proximal femoral shaft Goldberg et al. [33] 1975 31 NR Femoral neck, Twenty-nine open NR No (range acetabulum excision, 2 non-op 2-16) Herget et al. [11] 2012 1 21 Femoral neck Arthroscopy NR No Kang et al. [61] 2014 1 24 Femoral neck CT-guided excision 43 No Karray et al. [44] 2010 1 16 Acetabulum Open excision NR No Kattapuram et al. [54] 1983 11 NR Seven femoral neck, NR NR No 2 acetabulum, 2 NR (continued) Downloaded from https://academic.oup.com/jhps/article-abstract/5/1/88/4838313 by Ed 'DeepDyve' Gillespie user on 16 March 2018 Clinical presentation of IAOO of the hip and preliminary outcomes  91 Table I. Continued Citation Year Number Age/ Location of lesion Treatment Follow-up Outcome of average (months) scores? patients age with hip IAOO Khapchik et al. [19] 2001 2 26 One acetabulum, 1 Arthroscopy 21 No femoral neck Lee et al. [34] 2009 2 11 One acetabulum, 1 Arthroscopy 19 No femoral neck Marwan et al. [17] 2015 1 31 Acetabulum Arthroscopy 44 No Muscolo et al. [35] 1994 4 19 Three femoral neck, CT-guided excision 27 No 1 femoral head Nehme et al. [30] 2012 2 27 One femoral neck, 1 Arthroscopy 24 No acetabulum Ninomiya et al. [36] 1989 2 12 One acetabulum, 1 Open excision 14 and NR No femoral head Papagelopoulos et al. [37] 2006 16 NR Eight femoral head, RFA 30 No 6 femoral neck, 2 acetabulum Parlier-Cuau et al. [38] 1999 3 20 Acetabulum CT-guided excision 36 No Pianta et al. [46] 2012 1 16 Femoral neck RFA 12 No Raux et al. [47] 2014 26 NR Femoral neck CT-guided excision NR No Raux et al. [39] 2013 5 17 Acetabulum CT-guided excision 18 No Ricci et al. [21] 2013 1 47 Acetabulum Arthroscopy þ RFA 22 No Richardson et al. [48] 2009 1 18 Femoral neck CT-guided excision NR No Scalici et al. [51] 2011 1 24 Femoral head Open excision 60 No Sestan et al. [49] 2005 1 11 Femoral neck Non-op 60 No Shoji et al. [40] 2014 1 12 Acetabulum Arthroscopy 16 No Szendroi et al. [6] 2004 9 20 Three acetabulum, 6 Two open excision, 29 No femoral neck 7 curettage Tamam et al. [41] 2014 1 23 Acetabulum Arthroscopy NR No Tokis et al. [29] 2013 1 19 Acetabulum Arthroscopy 12 No Tsuruomto et al. [42] 2005 1 15 Acetabulum Open excision 96 No Xiao et al. [62] 2011 1 9 Femoral neck Open excision 12 No number of procedures. Paired t-tests were used to compare arthroscopic treatment of femoroacetabular impingement the latest post-operative scores at 6 months or greater to (FAI) were calculated. pre-operative scores. Frequency and percentage of patients A comparison group of all patients undergoing hip achieving a minimal clinically important difference for arthroscopy for isolated cam- or rim-impingement was Downloaded from https://academic.oup.com/jhps/article-abstract/5/1/88/4838313 by Ed 'DeepDyve' Gillespie user on 16 March 2018 92  A. M. Spiker et al. included for demographic and baseline outcome score decompression, 2 had iliopsoas release and 4 had labral comparison in a non-matched case–control design. These debridement. All 13 patients who underwent arthroscopic included unilateral or bilateral scopes between 10 July excision of the OO had the lesion confirmed by pathology. 2007 and 14 April 2016 with completed survey scores at The main presenting symptom for each patient was baseline. documented (Table III). The duration of symptoms at the All analyses were conducted using SAS version 9.3 time of initial evaluation at our institution was also noted (SAS Inc., Cary, NC, USA). (Table IV), as was the prevalence of night pain and pain relief with NSAIDs (Table V). RESULTS We reviewed the CT imaging available on our IAOO Forty patients from the hip preservation group database patients (13 of 40). The average alpha angle in these were identified as having a hip IAOO between 2000 and patients was 64.6 (613.1 ), coronal center edge angle 2015. Ten lesions were located in the acetabulum, 29 in 30.2 (63.8 ), femoral neck shaft angle 133.2 (64.9 ), the femoral neck and 1 in the femoral head. Twenty-four acetabular version at 1 o’clock 3 (66.9 ), 2 o’clock 8.8 patients were male and 16 female, with the average age of (68.3 ) and 3 o’clock 16 (65.4 ). On MRI review, 65% 24.5 years (range 11–57). (26 of 40) of the patients had edema surrounding the OO Thirty of the 40 patients underwent intervention for lesions. their OO at our institution. Ten patients were either lost Of the 13 patients treated with hip arthroscopy, 5 had to follow-up or were treated non-operatively (Table II). Of both pre- and post-operative mHHS and HOS-ADL. Four those who sought treatment, 16 underwent RFA, 13 under- had both pre- and post-op iHot33 scores, and three had went hip arthroscopy and 1 underwent open excision. Of both pre- and post-op HOS-SSS scores. The mean pre-op the patients who were treated with RFA, 13 of the lesions mHHS in these patients was 58.1, HOS-ADL 65.3, HOS- were located in the femoral neck and 3 in the acetabulum. SSS 41.7, iHot33 37.5. At final follow-up, the mean scores Of the patients treated with hip arthroscopy, nine lesions were in the femoral neck, three were in the acetabulum Table III. Main presenting symptoms of patients with and one was in the inferior femoral head. The one patient confirmed IAOO of the hip who underwent open excision had a lesion in the acetabu- Main presenting symptom Number %of lum. Of the 13 patients who had arthroscopic excision of of patients patients the OO, the concomitant arthroscopic procedures per- formed were as follows: 8 had labral repair, 7 had rim Groin pain 9 23 decompression, 9 had cam decompression, 1 had subspine Anterior hip pain 6 15 Table II. Treatment course of patients who did not Groin pain w/anterior hip pain 4 10 undergo treatment at our institution (10 of 40 Lateral hip pain 4 10 patients) Generalized hip pain 4 10 Patients treated non-operatively or lost Number Groin pain w/radiation to leg 1 3 to follow-up of patients Groin pain w/lateral hip pain 1 3 Initiated PT—lost to follow-up 3 Groin pain w/anterior and 13 Lost to follow-up 2 posterior hip pain Pain level manageable—patient opted 1 Groin pain w/anterior and 13 for conservative management lateral hip pain Recommended RFA—patient refused 1 Buttock pain w/radiation to 13 Recommended arthroscopy—patient 1 groin and leg refused Anterior hip pain w/posterior pain 1 3 Recommended RFA—lost to follow-up 1 Pelvic pain 1 3 Intra-articular injection þ initiated PT 1 Not recorded 6 15 —lost to follow-up Downloaded from https://academic.oup.com/jhps/article-abstract/5/1/88/4838313 by Ed 'DeepDyve' Gillespie user on 16 March 2018 Clinical presentation of IAOO of the hip and preliminary outcomes  93 were mHHS 93.9 (D35.9, P ¼ 0.002), HOS-ADL 98.2 time of last follow-up (average 27 months, range 3–105 (D33.0, P ¼ 0.006), HOS-SSS 90.7 (D49.1, P ¼ 0.06) and months). iHot33 80.0 (D42.5, P ¼ 0.006). We had no reported sur- A comparison group of all patients undergoing hip gical complications and no recurrences of the lesion at the arthroscopy for isolated cam- or rim-impingement was included. There were no statistically significant differences in gender or age between these groups (Table VI), nor Table IV. Duration of symptoms upon initial evalua- were there any statistically significant differences between tion at our institution baseline pre-operative scores (mHHS, HOS-ADL, HOS- SSS and iHot33) (Table VII). Given the small number of Duration of symptoms Number %of hip IAOO patients with post-operative outcome scores, we of patients patients were not able to directly compare post-operative scores 0–6 months 10 25 between our study group and the group of FAI patients undergoing hip arthroscopy. 6 months to 1 year 9 23 1–2 years 6 15 DISCUSSION IAOO of the hip may be a confounding diagnosis in >2 years 8 20 patients presenting with hip pain and symptoms consistent Not recorded 7 18 with FAI. Diagnosis of this rare but treatable benign bone tumor is often delayed due to its atypical presentation [6], and based on our findings, its similarity with symptomatic Table V. Presence of night pain and pain relief with presentation of FAI. Case reports in the literature have pre- NSAIDs viously reported of the coexistence of OO and FAI [52] and described multiple treatment options, including hip Presence of night pain Number %of arthroscopy [11, 17, 19]. We report the largest case series of patients patients of hip IAOO treated with hip arthroscopy (13 patients), Night pain 15 38 and discuss the clinical presentation of a total of 40 patients with confirmed diagnosis of IAOO of the hip. No night pain 3 8 Males are more commonly affected by OO than females, Not recorded 22 55 at a rate of 2:1 [2]to 3:1 [27]. In our series of hip IAOO, Pain relief with NSAIDs Number % of 24 patients were male and 16 were female, a male to female of patients patients ratio of 1.5:1. The location of the IAOO lesions was on both sides of the hip joint; however, there was almost a 3:1 Pain relief with NSAIDs 23 58 ratio of lesions in the femoral neck compared with the ace- No pain relief with NSAIDs 10 25 tabulum (29 IAOO in the femoral neck, 10 IAOO in the acetabulum and 1 in the inferior femoral head). OO with Not recorded 13 33 intra-articular location has been reported to present with Table VI. Demographic comparison of patients undergoing hip arthroscopy for FAI only and patients under- going hip arthroscopy with IAOO in a non-matched case–control design Patients with IAOO Patients with FAI only N % N % Odds ratios (95% CI) P-value Total number of patients 14 153 Female 6 42.9 106 69.3 0.3 (0.1 to 1.0) 0.39 Bilateral 3 21.4 16 10.5 2.3 (0.6 to 9.3) 0.14 Revision 1 7.1 9 5.9 1.2 (0.1 to 10.5) 0.39 Mean SD Mean SD Difference in means (95% CI) P-value Age (years) 23.7 8.4 29.2 10.6 5 (–6 to 10) 0.064 Downloaded from https://academic.oup.com/jhps/article-abstract/5/1/88/4838313 by Ed 'DeepDyve' Gillespie user on 16 March 2018 94  A. M. Spiker et al. Table VII. Comparison of preoperative scores for patients undergoing hip arthroscopy for FAI only and patients undergoing hip arthroscopy for IAOO Preoperative survey score Patients with IAOO Patients with FAI Unadjusted P-value Adjusted P-value (N¼ # IAOO, N ¼ # FAI) (N ¼ 14) only (N ¼ 153) difference difference (95% CI) (95% CI) mHHS (mean6 SD) 62 15 60 13 2(9 to 7) 0.63 1 (6 to 9) 0.70 (N¼ 13, N ¼ 153) HOS ADL (mean6 SD) 74 21 72 17 1(13 to 10) 0.80 1 (9 to 11) 0.77 (N¼ 13, N ¼ 153) HOS Sport (mean6 SD) 61 24 49 24 12 (26 to 1) 0.099 6(21 to 8) 0.40 (N¼ 11, N ¼ 153) iHot33 (mean6 SD) 41 24 38 19 3(17 to 11) 0.64 5 (7 to 18) 0.41 (N¼ 9, N¼ 153) Differences in means are adjusted for age, sex, bilaterality and revision status atypical and varied symptoms, different from the classic Additional intra-articular imaging findings include joint night pain relieved by NSAIDs found with extra-articular effusion (Fig. 3), periarticular osteoporosis and periosteal OO [3, 8–15]. Our patients had a wide range of presenta- reaction [54]. Varying amounts of tumor mineralization tions consistent with previous reports of IAOO, but the may be present, with more calcification often correlated most common presenting symptom was groin pain (Table with more mature lesions [56]. While lesions located in III). Groin pain is also the most common presenting symp- the bone cortex may present with large periosteal reaction, tom of FAI [53]. This overlap in symptoms of IAOO and the lack of adjacent periosteum in intra-articular lesions more common causes of hip pathology, such as FAI, can be often results in only a mild osteoblastic response [56]. MRI appearance of OO is often more aggressive than the part of the reason IAOO of the hip is misdiagnosed or missed. Previous reports have emphasized the delay in diag- lesion actually is, with extensive bone marrow edema and nosis of OO of the proximal femur, which have been even adjacent soft tissue signal changes can be seen [56, 57] reported to range between 12 months and 2 years after pain (Figs 2, 3 and 4B). MRI can demonstrate variable signal onset [23]. In our series, patients presented with a more intensity and juxta-lesional edema of the OO depending on evenly distributed duration of symptoms between acute, the amount of calcification present, the vascularity and age of the lesion [58]. Chondral hypertrophy has also been sub-acute and chronic (Table IV). Radiographic features of hip IAOO may differ from described with intra-articular hip OO lesions [56], which extra-articular lesions. The IAOO may not be evident on could be identified on MRI. Sixty-five percent of the MRI plain radiograph (Figs 1A and 4A), as the nidus of OO is reports in our series (26 of 40) describe significant edema. not visible on plain radiographs until the lesion is greater This is consistent with previous findings, where 63% of OOs than 4 mm in size [54]. Additionally, in a majority of sub- on MRI (12 of 19) showed perinidal bone marrow edema chondral or subperiosteal intra-articular lesions, there is no and inflammation [59]. While MRI is often the imaging surrounding sclerosis on plain radiograph [6]. CT is the modality used to assess hip and groin pain, the diagnostic gold standard for diagnosing OO [23] as it is the most use- accuracy of MRI in detecting OO is not as reliable as with ful imaging modality to identify the OO nidus [6], which CT [58, 59]. MRI fails to identify 21% of intra-articular OOs classically appears as a central calcification and surrounding and only poorly identifies them in an additional 29% [58]. Multiple treatment options exist for treatment of symp- sclerosis (Figs 1F and 4C). When the OO is near a joint, CT may demonstrate changes on both sides of the joint, tomatic OO, including open excision, RFA or arthroscopic including osteophyte formation, a localized soft-tissue excision. The gold standard treatment for OO in all loca- mass, reduced bone density or increased bone density in tions is RFA [10, 27]. Patients in our series were referred the subchondral bone of the abutting joint surface [55]. RFA if the lesion was a safe distance from the articular Downloaded from https://academic.oup.com/jhps/article-abstract/5/1/88/4838313 by Ed 'DeepDyve' Gillespie user on 16 March 2018 Clinical presentation of IAOO of the hip and preliminary outcomes  95 Fig. 1. The radiographic imaging of one patient in our series with IAOO of the hip who presented with left groin pain. (A) AP pelvis. (B) Lateral radiograph demonstrates loss of femoral head neck offset with a small cortical irregularity at the head-neck junction. (C) 3D CT scan demonstrates large cam lesion. (D) MRI demonstrates superior labral tear. (E) MRI shows OO lesion. (F)CT shows characteristic appearance of OO. cartilage, and they had no evidence of other intra-articular Norman et al. [60] looked at a series of 182 OOs over pathology that could be addressed with hip arthroscopy. 24 years and found 30 of which were intra-articular at the The decision to proceed with arthroscopic excision of hip joint. Of these 30 lesions, 50% were associated with the hip IAOO in our patient population was based on the development of OA [60]. Rapid development of OA (i) lesion accessibility with hip arthroscopy instrumenta- has also been described as beginning as early as 5 months tion, (ii) the presence of additional pathology which could after OO lesion excision [13]. None of our patients with be addressed with hip arthroscopy and (iii) in depth dis- IAOO had concomitant diagnoses of OA; however, we cussion with the patient about available options and the would require longer and more complete follow-up to patient’s treatment preference. determine the incidence of degenerative changes related to Marwan et al. [17] recently published a systematic review the IAOO. This strong correlation of OA with IAOO does, of all acetabular IAOO treated with hip arthroscopy. From however, give us incentive to identify these lesions early, this review of 11 cases, they reported a success rate of and treat symptomatic IAOO more aggressively to prevent greater than 90% in treating acetabular OOs with hip arthro- the theoretical sequela of early hip OA. scopy and noted no recurrences of the lesion at last follow- There have been multiple case reports and a number of up ranging between 6 months and 2 years, and one study case series of hip IAOO (Table I). Ourcaseseriesisthe not reporting follow-up duration [17]. Similarly, in our case largest of hip IAOO of the hip treated by hip arthroscopy series, none of our patients treated with hip arthroscopy had (Fig. 5). While we had a very small number of patients who recurrence of the lesion after our treatment at an average had both pre- and post-operative outcome scores after treat- 27-months follow-up (range 3–105 months). There were, ment with hip arthroscopy, this is the first report of patient- however, three patients who presented to our institution reported outcomes in this subset of patients. We noted a sig- after previous intervention for their IAOO, and at the time nificant improvement in mHHS, HOS-ADL and iHot33 of our initial evaluation, had either persistent or recurrent scores. Our comparison group of patients (Tables VI and IAOO. All three patients had previously undergone RFA: VII), included patients undergoing hip arthroscopy for FAI one patient proceeded with no further treatment, another only, as this was the closest group of patients to a control patient underwent subsequent hip arthroscopy and the third group who had taken the pre-operative patient-reported out- patient had a repeat CT-guided RFA. come surveys. The FAI only and IAOO patients were Downloaded from https://academic.oup.com/jhps/article-abstract/5/1/88/4838313 by Ed 'DeepDyve' Gillespie user on 16 March 2018 96  A. M. Spiker et al. matched in age, gender and unilaterality/bilaterality of sur- small number of patients who had long-term follow-up. We excluded patients who had OA, although it is possible that gery as well as revision status. When comparing baseline, pre-operative patient-reported outcome scores, the FAI-only older patients who had advanced OA once had an OO, espe- cially given the high incidence of OA associated with hip hip arthroscopy patient scores were not statistically different IAOO [60]. If IAOO wasinthe differential basedonhip from the scores of those patients with hip IAOO undergoing MRI, but the patient did not have a confirmatory CT scan, hip arthroscopy. This emphasizes that patients with hip IAOO can present almost identically to patients with FAI. The physician should be extra vigilant to keep the diagnosis of hip IAOO in the differential. Limitations Given that the diagnosis of IAOO is relatively rare, we have limited numbers of patients who had this diagnosis and were treated with hip arthroscopy. This case series includes only a Fig. 2. (A) Coronal STIR MRI demonstrating edema of the right acetabulum surrounding the OO lesion. (B) Coronal CT Fig. 3. (A) STIR coronal MRI demonstrating bone marrow demonstrating OO lesion (arrow). (C) Axial T2 FSE fat satu- edema of the left femoral neck surrounding the OO lesion and rated MRI again demonstrating bone marrow edema. (D) Axial left hip joint effusion. (B) T2 Axial MRI fat-saturated sequence CT of OO (arrow). demonstrating OO (arrow) at left anteromedial femoral neck. Fig. 4. (A) Pre-operative AP Pelvis of a left inferior femoral neck IAOO. (B) Pre-operative MRI demonstrating significant edema in the femoral neck surrounding the OO lesion. (C) Pre-operative CT scan of characteristic CT findings of OO, demonstrating a nidus with surrounding sclerotic bone. Downloaded from https://academic.oup.com/jhps/article-abstract/5/1/88/4838313 by Ed 'DeepDyve' Gillespie user on 16 March 2018 Clinical presentation of IAOO of the hip and preliminary outcomes  97 Fig. 5. In this left hip with femoral neck OO, intraoperative radiographic image demonstrating the contour of the femoral head-neck junction prior to (A) and after (B) CAM decompression and OO excision. Intraoperative arthroscopic image showing OO of the femoral neck prior to (C, D), during (E) and after (F) excision with a curette an arthroscopic burr. CONCLUSIONS they were also excluded. Given the limitations of MRI to Our series presents 13 patients with IAOO of the hip definitively identify OO [58], it is possiblewemissedOO treated with hip arthroscopy and the clinical presentation lesions that would have been present on CT scan if the of 40 patients with confirmed diagnosis of hip IAOO. patient had undergone CT. While all excised IAOO were While OO in the intra-articular hip location is a relatively confirmed by histology, we did not obtain post-operative CT rare diagnosis, our findings highlight the importance of to evaluate the lesion (as this practice is not standard of keeping IAOO in the differential diagnosis of patients with care). Additionally, many of our patients had multiple proce- hip pain. If an IAOO is diagnosed in the hip joint, we pro- dures in addition to the arthroscopic excision and ablation of pose the following treatment algorithm: If there is no coex- the IAOO. This does confound the post-surgical PROs, as there is no way to delineate what benefit the patients istence of FAI or other intra-articular pathology, RFA remains a viable option with a proven success rate if the received from IAOO excision versus treatment of other lesion is far enough away from the articular cartilage to intra-articular pathology. Another significant limitation to this study was that we did not have patient-reported out- minimize concern for cartilaginous injury. If FAI or intra- articular pathology is also present, RFA of the IAOO with come scores or long-term follow-up on those patients who underwent RFA, as our registry only collects data on post- a staged treatment of the FAI is also an option, especially if operative patients and those that follow for non-operative it is unclear which pathology is the predominant etiology of the patient’s symptoms. If the OO is in the setting of, or treatment of hip pain. Those patients who underwent RFA had post-procedure follow-up outside of our practice. A com- exacerbating, symptomatic FAI, we believe that hip arthro- parison between patients who underwent IAOO with RFA scopy is the preferred treatment method to address all of versus hip arthroscopy would be clinically useful, but in our the patient’s hip pathology during one intervention, and series patients were indicated for hip arthroscopy over the has the added benefit of obtaining tissue for a definitive gold standard RFAiftheymet anumberofcriteria. We diagnosis of the OO lesion. favored hip arthroscopy in patients who had a lesion close to the articular cartilage where there was concern for the poten- ACKNOWLEDGEMENTS tial detrimental effects of RFA to the cartilage; or if they had concomitant intra-pathology that could be addressed with We would like to thank Eilish O’Sullivan, PT, DPT, OCS, hip arthroscopy. SCS for her assistance in the completion of this project, Downloaded from https://academic.oup.com/jhps/article-abstract/5/1/88/4838313 by Ed 'DeepDyve' Gillespie user on 16 March 2018 98  A. M. Spiker et al. 18. Alvarez MS, Moneo PR, Palacios JA. Arthroscopic extirpation of Kara Fields and Emily Lai for their assistance with statisti- an osteoid osteoma of the acetabulum. Arthroscopy 2001; 17: cal analysis. 768–71. 19. Khapchik V, O’Donnell RJ, Glick JM. Arthroscopically assisted CONFLICT OF INTEREST STATEMENT excision of osteoid osteoma involving the hip. Arthroscopy 2001; None declared. 17:56–61. 20. As¸ık M, Ers¸en A, Polat G. Arthroscopic excision of acetabular REFERENCES osteoid osteoma in a 7-year-old patient. Knee Surg Sports Traumatol Arthrosc 2015; 23:3432–5. 1. Jaffe H. Osteoid Osteoma: a benign osteoblastic tumor com- 21. Ricci D, Grappiolo G, Franco M et al. Case report: osteoid posted of osteoid and atypical bone. 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Journal of Hip Preservation SurgeryOxford University Press

Published: Jan 1, 2018

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