TY - JOUR
AU - Seto, Tetsuya
AB - Abstract This is a very rare case of gouty tophus in the patella of a 31-year-old male, without any medical co-morbidities. The patient initially presented after an injury to left knee but came back months later due to persistence of pain. Surgical decision was made based on imaging findings in computed tomography and magnetic resonance imaging of an intraosseous lesion that has increased in size. The initial diagnosis is that of an aggressive bone tumour. The diagnosis of an intraosseous gout was made intra-operatively upon seeing the characteristics of the lesion, and upon confirmation of the biopsy results. Gout can usually be managed medically with urate lowering drugs and lifestyle change. However, when presented with a tophus that is increasing in size and causing mass effect on the involved bone, surgical management is indicated. Gouty tophi, bipartite patella, bone tumour, curettage Introduction Gout is a very common medical condition wherein persistent increased levels of serum uric acid above a certain threshold leads to the deposition of monosodium urate crystals. It is a known fact that not all with hyperuricaemia develop gout. Other risk factors such as genetic predisposition, male gender, purine rich diet, lack of exercise, obesity and metabolic syndrome also contribute to this condition [1]. Gout commonly affects the lower extremity joints, the most common of which is the first metatarsophalangeal joint. Other commonly affected joints are the tarsal and metatarsal joints, ankles and knees. When gout becomes chronic and untreated, the deposition of urate crystals into the joints, leads to the formation of tophi, and eventual joint destruction. There are atypical areas where gouty tophi can also form, and one area that has been reported a few times in literature is the patella [2–8]. We here reported a rare case with gouty tophus, suspected to be a primary bone tumour in the patella. Case report A 31 year-old male nurse came to the orthopaedic clinic, initially because of a direct fall on his left knee. Past medical history showed that he already had an injury on his left knee 10 years prior and was diagnosed with a bipartite patella classified as Saupe type III. His initial radiographs revealed cystic lesion connected to the separation site of the patella (Figure 1). Gradual resolution of pain was noted, however, after a month the pain recurred and he came back to the clinic. His primary physician then requested for a computed tomography (CT) scan which showed intraosseous lesion of the patella and the osteosclerotic changes surrounding the intrapatellar lesion. Periosteal reaction, suggesting malignant bone tumour was not observed (Figure 2). Although his pain improved again after a month, there was recurrence of the anterior knee pain. A repeat CT scan revealed enlargement of the bone lesion, suspected aggressive bone tumour. Magnetic resonance imaging (MRI) showed heterogeneous low and high signal intensity masses on T1- and T2-weighted images and enhancement of the lesion by gadolinium contrast (Figures 3, 4). The border between the patella and intrapatellar lesion was clear. He was referred to Nagato general hospital for surgical management. Figure 1. Open in new tabDownload slide The initial radiographs of oblique (left) and lateral view revealed a bipartite patella, classified as Saupe type III and cystic lesion connected to the separation site of the patella. Figure 1. Open in new tabDownload slide The initial radiographs of oblique (left) and lateral view revealed a bipartite patella, classified as Saupe type III and cystic lesion connected to the separation site of the patella. Figure 2. Open in new tabDownload slide Computed tomography scan showed intraosseous cystic lesion of the patella, suspected aggressive bone tumour. Figure 2. Open in new tabDownload slide Computed tomography scan showed intraosseous cystic lesion of the patella, suspected aggressive bone tumour. Figure 3. Open in new tabDownload slide Magnetic resonance imaging (MRI) of coronal view of the patella showed heterogeneous low signal intensity masses on T1 weighted images and enhancement of the lesion by gadolinium contrast. Figure 3. Open in new tabDownload slide Magnetic resonance imaging (MRI) of coronal view of the patella showed heterogeneous low signal intensity masses on T1 weighted images and enhancement of the lesion by gadolinium contrast. Figure 4. Open in new tabDownload slide Gadolinium enhanced MRI of axial and sagittal view showed the intra-osseous lesion of the patella, inflammatory change of the distal quadriceps tendon and joint effusion. Figure 4. Open in new tabDownload slide Gadolinium enhanced MRI of axial and sagittal view showed the intra-osseous lesion of the patella, inflammatory change of the distal quadriceps tendon and joint effusion. His height was 170 cm and body weight was 96 kg. On physical examination, he was ambulatory, with tenderness on the lateral border of the patella but no erythema nor warmth of the area noted. Pre-operative laboratory tests showed an elevated serum uric acid at 9.1 mg/dL (normal values at 3.5–7 mg/dL). Complete blood count showed normal white blood cell count at 9400 (neutrophils, 42.3%) and C-reactive protein was 1.0 mg/dL. Initial possible diagnosis was aggressive benign bone tumour of the patella, such as giant cell tumour, chondroblastoma, aneurysmal bone cyst, etc. We didn’t perform preoperative biopsy because of negative findings of malignant bone tumour or severe infection. The patient then underwent curettage and debulking of the intraosseous lesion, followed by application of beta-tricalcium phosphate on the patellar defect. Intra-operatively, a chalky white material was noted from the mass which was located at the superolateral area of the patella with intraarticular communication into the knee joint (Figure 5). A diagnosis of intraosseous tophaceous gout was then made intraoperatively. The diagnosis was then confirmed with the histopathology report which showed piece-by-piece specimen, with fragments of bone, cartilage and irregular microcalcifications and fibrin, “feather-like” deposits, macrophage and giant-cell reaction in deposit enclosure, with fibrosis (Figure 6). Figure 5. Open in new tabDownload slide Intra-operatively, a chalky white material was noted from the mass which was located at the superolateral area of the patella with intraarticular communication into the knee joint. Figure 5. Open in new tabDownload slide Intra-operatively, a chalky white material was noted from the mass which was located at the superolateral area of the patella with intraarticular communication into the knee joint. Figure 6. Open in new tabDownload slide The histopathology report showed fragments of bone, cartilage and irregular microcalcifications and fibrin, “feather-like” deposits, macrophage and giant-cell reaction in deposit enclosure, with fibrosis. Figure 6. Open in new tabDownload slide The histopathology report showed fragments of bone, cartilage and irregular microcalcifications and fibrin, “feather-like” deposits, macrophage and giant-cell reaction in deposit enclosure, with fibrosis. The patient was then sent home 7 days postoperatively. He was given allopurinol for control of gout and serum uric acid was controlled at 5.2 mg/dL at one month after surgery. On follow-up six months after surgery, he was ambulatory and without pain on movement of the left knee. Plain radiographs showed incomplete absorption and remodelling of the implanted beta-tricalcium phosphate. Discussion Tophaceous gout of a bipartite patella The patella is one of those reported in literature as an atypical site for tophaceous gout. Several case reports were already written since 1955 (Table 1) [2–8]. Monosodium urate crystals become less soluble with lower temperatures, which could explain why gouty tophi often form in the distal end of an extremity such as the metatarsophalangeal joint of the first toes. The typical presentation of patellar gouty tophi usually involves the superolateral aspect of the patella, with noted involvement of the surrounding tendinous structures. The superficial nature and therefore lower temperature at the area of the patella could explain the formation of gouty tophi. The blood supply of the patella comes from a plexus of blood vessels [9]. The primary intraosseous blood supply of the patella has been described to flow in a retrograde fashion from distal to proximal, which is responsible for osteonecrosis of the superior fragment of the patella in cases of severely comminuted fractures [9]. In a bipartite patella, there is an avascular tissue interposed between the accessory bone and the main patellar bone fragment. This avascular tissue is composed mostly of fibrocartilage and less of fibrous and hyaline cartilage [10]. This alteration in the normal anatomy and blood flow in the patella could be one possible explanation as to why intra-osseous tophi of bipartite patellae often develops at the superolateral aspect of the patella. Table 1. Recent case reports of tophaceous gout of the patella. nd; not described, TCP; tricalcium phosphate. Author Year Age/ Gender Trauma Location Bipartite patella MRI T1W-T2W Consult to oncologist Biopsy Treatment Kobayashi et al. 2005 34/M no superolateral Yes Low no no curettage bone fixation Hopper et al. 2012 70/M yes superolateral None Low-high nd yes drugs 34/M no superolateral None Low-high nd yes drugs Clark et al. 2016 52/M yes superior None Low-high no no drugs Kester et al. 2018 59/M no superior None Low-high yes yes curettage bone graft 57/M nd superior None Low-high yes yes curettage bone graft 69/M nd superior None nd yes no drugs Chiu et al. 2020 48/M yes inferior None Low-high yes yes drugs Our case 31/M yes superolateral Yes Low-high yes none curettage beta-TCP Author Year Age/ Gender Trauma Location Bipartite patella MRI T1W-T2W Consult to oncologist Biopsy Treatment Kobayashi et al. 2005 34/M no superolateral Yes Low no no curettage bone fixation Hopper et al. 2012 70/M yes superolateral None Low-high nd yes drugs 34/M no superolateral None Low-high nd yes drugs Clark et al. 2016 52/M yes superior None Low-high no no drugs Kester et al. 2018 59/M no superior None Low-high yes yes curettage bone graft 57/M nd superior None Low-high yes yes curettage bone graft 69/M nd superior None nd yes no drugs Chiu et al. 2020 48/M yes inferior None Low-high yes yes drugs Our case 31/M yes superolateral Yes Low-high yes none curettage beta-TCP Open in new tab Table 1. Recent case reports of tophaceous gout of the patella. nd; not described, TCP; tricalcium phosphate. Author Year Age/ Gender Trauma Location Bipartite patella MRI T1W-T2W Consult to oncologist Biopsy Treatment Kobayashi et al. 2005 34/M no superolateral Yes Low no no curettage bone fixation Hopper et al. 2012 70/M yes superolateral None Low-high nd yes drugs 34/M no superolateral None Low-high nd yes drugs Clark et al. 2016 52/M yes superior None Low-high no no drugs Kester et al. 2018 59/M no superior None Low-high yes yes curettage bone graft 57/M nd superior None Low-high yes yes curettage bone graft 69/M nd superior None nd yes no drugs Chiu et al. 2020 48/M yes inferior None Low-high yes yes drugs Our case 31/M yes superolateral Yes Low-high yes none curettage beta-TCP Author Year Age/ Gender Trauma Location Bipartite patella MRI T1W-T2W Consult to oncologist Biopsy Treatment Kobayashi et al. 2005 34/M no superolateral Yes Low no no curettage bone fixation Hopper et al. 2012 70/M yes superolateral None Low-high nd yes drugs 34/M no superolateral None Low-high nd yes drugs Clark et al. 2016 52/M yes superior None Low-high no no drugs Kester et al. 2018 59/M no superior None Low-high yes yes curettage bone graft 57/M nd superior None Low-high yes yes curettage bone graft 69/M nd superior None nd yes no drugs Chiu et al. 2020 48/M yes inferior None Low-high yes yes drugs Our case 31/M yes superolateral Yes Low-high yes none curettage beta-TCP Open in new tab Another risk factor is the trauma. Kobayashi et al. [5] suggested in the case report that the destruction of barrier between tophaceous deposits and the joints led to acute arthritis [5]. In our case, it is possible that the trauma caused a destruction in the barrier between the intra-articular synovial fluid and the bipartite patella, which could have led to the gradual deposition of crystals in this area. Differential diagnosis from patella tumours The diagnosis of intra-osseous gout is not straightforward for this patient. The presence of a rapidly growing solitary lesion would also lead us to think along the lines of a tumour diagnosis instead of an inflammatory deposition disease. Several types of patella tumours should be considered as differential diagnosis [11,12]. A giant cell tumour (GCT) is one of the most common cause of solitary tumours in the patella. Characteristic image findings often show a lytic lesion that involves almost the whole patella with an ill-defined narrow zone of transition to normal bone. Cortical appearance is usually expanded and thinned, rarely finding a sclerotic rim and there is no periosteal reaction [12]. Chondroblastoma is also considered because of the solitary nature of the tumour, the age and gender of the patient, and lastly because the ossification of the patella is similar to that of an epiphysis or apophysis of a long bone. MRI findings characteristic of a chondroblastoma of the patella are of cartilaginous appearance, and edoema around the bony lesion and soft tissues [12]. Osteoid osteoma was also one of differential diagnosis, but based on the patient’s history, he did not exhibit localised pain during the night. The characteristic radiographic appearance is that of a lytic lesion with sharp margins with a nidus of small central ossification. But CT scan and MRI didn’t demonstrate a nidus and inflammatory bony lesion around nidus in this case. Aneurysmal bone cyst is also one of our considerations, but it is unlikely because the patient did not demonstrate a bulging growth of the patella. MRI showed no septations and fluid levels [12]. Other conditions such as infection, and possible metastasis from a primary malignant lesion were also considered. However, the patient did not demonstrate other constitutional symptoms and there were no obvious signs of inflammation or infection such as warmth, erythema or swelling. Diagnosis and treatment of patellar gouty tophi Imaging findings for gouty tophi tend to be non-specific [13]. On radiographs, tophi may be seen as intra-articular or peri-articular lesions, which may or may not accompany signs of arthritis. On MRI, tophi characteristically appear as homogenous to heterogeneous low to intermediate signal intensity masses on T1- and T2-weighted images. On images with gadolinium contrast, tophi may be seen as homogenous, heterogeneous or peripheral enhancing lesions [11,13]. The imaging findings of CT and MRI for our patient appear to be inconclusive. A rapidly enlarging lesion in a span of less than 6 months is also less characteristic of gout and more of a neoplastic process. Ideally, a biopsy should have been performed pre-operatively in order to rule out malignancy or infection, and to establish a tissue diagnosis for proper surgical planning. However, based on the patient’s clinical picture and imaging, there is high clinical suspicion for a benign lesion. It has been decided to go directly with complete removal of the lesion via curettage and collect this specimen for histopathology in one sitting [14,15]. Kester et al. [7] and other authors [4,8] stated that although gouty tophi may be treated nonoperatively, tophi that appear to be having a local mass effect, causing restricted range of motion, impingement symptoms, altered length and tension on tendons and ligaments, risk of tendon rupture or pathologic fracture and skin breakdown should be indications for surgery. Post-operatively, our patient has been pain free since the mass effect on the bone and the soft tissues has been removed. According to recommendations by Ragab et al. [1] and the European League against Rheumatic Diseases [16], urate lowering drugs are indicated for patients with high uriciemia at more than 8 mg/dL or young age (<40 years old). It is still prudent to give him medications for the control of his gout to avoid possible recurrence of the tophi or growth of tophi elsewhere in the body. And also, it is important to educate the patient regarding his condition, as well as to promote a low-purine diet and lifestyle change. Patient consent The authors confirm that I have obtained written consent for publication from the patient. Ethical approval Not applicable. Conflict of interest None. References Ragab G , Elshahaly M, Bardin T. Gout: an old disease in new perspective – a review . J Adv Res . 2017 ; 8 ( 5 ): 495 – 511 . Google Scholar Crossref Search ADS PubMed WorldCat Peloquin J , Graham JH. Gout of the patella; report of a case . N Engl J Med . 1955 ; 253 ( 22 ): 979 – 980 . Google Scholar Crossref Search ADS PubMed WorldCat Greenberg D Pathological fracture of the patella secondary to gout. A case report . J Bone Joint Surg Am . 1986 ; 68 : 1286 – 1288 . Google Scholar Crossref Search ADS PubMed WorldCat Chiu MK , Lewis NA Intraosseous gout mimicking giant cell tumor of the patella . Skeletal Radiol . 2020 ; 49 ( 8 ): 1325 – 1328 . Google Scholar Crossref Search ADS PubMed WorldCat Kobayashi K , Deie M, Okuhara A, et al. Tophaceous gout in the bipartite patella with intra-osseous and intra-articular lesions: a case report . J Orthop Surg . 2005 ; 13 ( 2 ): 199 – 202 . Google Scholar Crossref Search ADS WorldCat Clark S , Evans JM, Armstrong N, et al. Tophaceous gout with rare involvement of the patella . Radiol Case Rep . 2016 ; 11 ( 4 ): 380 – 385 . Google Scholar Crossref Search ADS PubMed WorldCat Kester C , Wallace MT, Jelinek J, et al. Gouty involvement of the patella and extensor mechanism of the knee mimicking aggressive neoplasm. A case series . Skeletal Radiol . 2018 ; 47 ( 6 ): 865 – 869 . Google Scholar Crossref Search ADS PubMed WorldCat Hopper G , Gupta S, Bethapudi S, et al. Tophaceous Gout of the patella: a report of two cases . Case Rep Rheumatol . 2012 ; 2012 : 1 – 6 . Google Scholar OpenURL Placeholder Text WorldCat Scapinelli R Blood supply of the human patella. Its relation to ischemic necrosis after fracture . J Bone Joint Surg Br . 1967 ; 49-B ( 3 ): 563 – 570 . Google Scholar Crossref Search ADS WorldCat Oohashi Y , Koshino T, Oohashi Y Clinical features and classification of bipartite or tripartite patella . Knee Surg Sports Traumatol Arthrosc . 2010 ; 18 ( 11 ): 1465 – 1469 . Google Scholar Crossref Search ADS PubMed WorldCat Dhanda S , Quek ST, Bathla G, et al. Intra-articular and peri-articular tumours and tumour mimics – what a clinician and onco-imaging radiologist should know . Malaysian J Med Sci . 2014 ; 21 : 4 – 19 . Google Scholar OpenURL Placeholder Text WorldCat Casadei R , Kreshak J, Rinaldi R, et al. Imaging tumors of the patella . Eur J Radiol . 2013 ; 82 ( 12 ): 2140 – 2148 . Google Scholar Crossref Search ADS PubMed WorldCat Yu J , Chung C, Recht M, et al. MR imaging of tophaceous gout . AJR Am J Roentgenol . 1997 ; 168 ( 2 ): 523 – 527 . Google Scholar Crossref Search ADS PubMed WorldCat Li Z , Jin M, Wakely P Aspiration cytopathology of tophaceous gout: a report of 22 patients . J Am Soc Cytopathol . 2018 ; 7 ( 3 ): 149 – 153 . Google Scholar Crossref Search ADS PubMed WorldCat Melloni P , Valls R, Yuguero M, et al. Unusual imaging manifestations of intraosseous tophaceous gout of the patella . J Rheumatol . 2005 ; 32 : 959 – 961 . Google Scholar PubMed OpenURL Placeholder Text WorldCat Richette P , Doherty M, Pascual E, et al. 2016 updated EULAR evidence-based recommendtaions for the management of gout . Ann Rheum Dis . 2017 ; 76 ( 1 ): 29 – 42 . Google Scholar Crossref Search ADS PubMed WorldCat © 2021 Japan College of Rheumatology This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)
TI - Intra-osseous tophaceous gout of a bipartite patella mimicking aggressive bone tumour
JO - Modern Rheumatology Case Reports
DO - 10.1080/24725625.2020.1861743
DA - 2021-04-03
UR - https://www.deepdyve.com/lp/oxford-university-press/intra-osseous-tophaceous-gout-of-a-bipartite-patella-mimicking-3yS0D8KyGD
SP - 399
EP - 403
VL - 5
IS - 2
DP - DeepDyve
ER -