Return-to-Duty Rates Following Minimally Invasive Spine Surgery Performed on Active Duty Military Patients in an Ambulatory Surgery Center

Return-to-Duty Rates Following Minimally Invasive Spine Surgery Performed on Active Duty Military... Abstract Background Low back pain is a primary health care utilization driver in the US population. Health care evaluation visits for low back pain are as common as medical evaluation for the common cold. Low back pain is the most common reason for reductions in activities of daily living and work activity in the general population. Although these statistics are compelling, in the military population, there is arguably a significantly greater economic impact on the military population, as the cost to train, retain, and deploy a service member is a tremendous cost. Methods The current study retrospectively examines surgical outcomes, return to duty, and patient-centric outcomes among 82 active duty or reserve military patients who underwent an outpatient minimally invasive spine surgery Laminotomy Foraminotomy Decompression for the treatment of lumbar spinal stenosis in an ambulatory surgery center. Findings Overall, our results indicate that within the 82 active duty military service members, 100% of the service members return to duty within 3 mo. Additionally, there was a significant reduction in self-reported pain and disability 12 mo postoperative, whereas the average length of surgery was 62 min with an average estimated blood loss of 30.64 mL. Discussion The current study indicates that minimally invasive procedures for the treatment of lumbar spinal stenosis in an ambulatory surgery center setting are an effective option for active duty servicemen to reduce return-to-duty rates and symptomatic back-related pain and disability. BACKGROUND Low back pain (LBP) is one of the most common reasons for visiting a physician in the United States.1 To put this into perspective, medical visits for LBP are second only to the common cold. In the US population, LBP is the most common reason for reductions in activities of daily living and work activity limitations in individuals younger than 45 years. Additionally, LBP is the third most common indication for all spine-related surgical procedures.2 Annual direct health care costs in the United States for spine disorders have been estimated at more than $85 billion, with indirect costs from lost work productivity resulting from LBP in the United States estimated to exceed $7 billion annually.3,4 Given the epidemiological data and health care costs, LBP is a significant issue for today’s health care system and society as a whole. Similarities exist between the US population and the US military cohort across a multitude of health criteria. Similar to the general US population, LBP is also one of the most common forms of chronic pain in the US military population. Moreover, LBP has been associated with high rates of medical expenses and increased time to return to duty (RTD). Military duty presents a unique spectrum of intrinsic and extrinsic factors, not typical to the general population, that increase the risk factors associated with musculoskeletal disorders specific to spine-related pathologies. Recent research reported that within the military population, there is approximately 20% 6-mo prevalence of axial lower back pain necessitating medical evaluation.5 Active duty military service has been shown to result in a 2.4-fold increase in the prevalence of axial lower back pain resulting in a medical exam, whereas 70% and 46% of deployed active duty military members (with non-traumatic lumbar spine pain complaints) reported new radicular and axial pain symptoms, respectively.6 Although costs to train a single military serviceman/woman vary, ranges are estimated from $200,000 to $9,000,000. Due to the high cost of training and the extensive knowledge gained through the training, having military servicemen/women on active duty is critical. As such, the length in which it takes to have a military servicemen/women return to full duty post-surgery is a vital metric in surgical efficacy.5 RTD rates and length of time for spine pathology treatment protocols vary significantly in published research.5–7 Houghton et al (2016) presented a comprehensive review of RTD rates compared in the context of the treatments and reported RTD between 3 and 17 mo depending on treatment. Lunsford et al (2016) reported on the percentage of military service members RTD following elective lumbar spine surgery. The RTD rate following elective lumbar spine surgery is 64% within 1 year. When stratified by procedure type, isolated decompression procedures (63% RTD rate) and fusion procedures (66% RTD rate) displayed similar 1-year results. Over the past decade, advancements in instrumentation, surgical access technology, and navigation have expanded the breadth of treatment applications for spine surgery. Specifically, the adoption of minimally invasive techniques has supplemented the practice of contemporary spine surgery. Minimally invasive spine surgery (MISS) has demonstrated comparable efficacy to traditional open procedures and has garnered popularity among surgeons. The limitations associated with open spine surgery, including extensive tissue dissection, muscle injury, blood loss, and greater hospital resource utilization have impacted patient outcomes.8,9 In addition to improvements in instrumentation and technology, outpatient surgery has seen a significant rise in utilization compared with the traditional hospital setting.10 Although outpatient surgery centers are freestanding or hospital-based with care extending 23 h, ambulatory surgery centers (ASC) are health care facilities focused on providing same-day surgical care of up to 23 h. Outpatient procedures represented over 60% of all surgeries in the United States in 2011, up from 19% in 1981.10 Outpatient surgery volume across both hospital-based and freestanding facilities grew by 64% between 1996 and 2011, according to the National Survey of Ambulatory Surgery.11 There is a breadth of research indicating the benefits of outpatient versus inpatient lumbar spine surgery and minimally invasive lumbar spine surgery techniques on patient-centric outcomes.12–14 Benefits range from self-reported pain and disability improvement, blood loss, length of surgery, postoperative length of stay, and return to activities of daily living.15 More importantly in the context of this research, there is a paucity of literature examining these factors on the military population. Furthermore, to our knowledge, there is a gap in the literature investigating elective lumbar spine surgery and patient-centric outcomes in an ASC in the active duty military population. The objective of this research is to retrospectively examine surgical outcomes, RTD, and self-reported patient-centric outcomes at preoperative and 12 mo postoperative among active duty or reserve military patients who underwent an outpatient MISS Laminotomy Foraminotomy Decompression (LFD) for the treatment of lumbar spinal stenosis (LSS) in an ASC. METHODS The current study conducted a retrospective analysis of 82 active duty service members diagnosed with symptomatic, painful LSS indicated for a single-level LFD between December 2013 and January 2015. Specifically, the LFD procedure was planned as an outpatient procedure within an ASC setting. An extensive preoperative clinical examination was performed to evaluate motor, sensory, and reflex deficits. Radiological examinations consisting of lumbar spine magnetic resonance imaging, computed tomography, and plain X-rays with flexion and extension views were performed to confirm clinical diagnoses. LSS was the primary diagnosis and was defined as spinal stenosis (central/lateral recess or foraminal stenosis) graded as moderate, moderate to severe, or severe with unremitting pain, confirmed by imaging studies (e.g., computed tomography or magnetic resonance imaging) at the level corresponding to neurological findings. The presence of neurological abnormalities (e.g., reflex change, positive straight leg raising, sensory loss, and weakness) was evaluated and would have persisted on examination and correspond to the specific affected nerve root. The conservative management treatment comprised the prescription of effective pain management according to prevailing guidelines and the advice to resume daily duty activities if feasible. A mobilization/ activity program, based on time rather than pain, was recommended without directly checking the compliance. If patients had considerable fear of movement, guidance from a physiotherapist was recommended. Specifically, the course of conservative care followed physical therapy, spinal injections, and medications when each were appropriate. Preoperative and follow-up self-reported pain (visual analog scale [VAS]), disability (Oswestry Disability Index [ODI]), and RTD status were collected at 12 mo postoperative. All service members passed a clinical assessment to RTD in accordance with their respective service requirements. Clinical parameters such as estimated blood loss, length of surgery, and complications of the surgical procedure were retrospectively collected. There were 0 reported intraoperative complications. Each service has medical fitness requirements that detail medical conditions and the procedure required when a service member does not meet medical retention standards (i.e., SECNAVINST 1850.E, Army Regulation 40-501).16–18 Furthermore, within these regulations, points in time are defined in which a service member is referred to a physical evaluation board or medical evaluation board. This occurs once the service member reaches a medical retention determination or after 12 mo of being diagnosed with/treated for a medical condition that does not appear to meet medical retention standards. Although these regulations vary across services, the determinations are fairly uniformed. As such, similar to previous research, we define RTD as a period from 1 mo to 12 mo in duration.5 Details of Surgical Technique Although the decompression via laminotomy and foraminotomy vary slightly across surgeons, in general, a scalpel was used to make a stab wound through which a guide-wire was inserted down to the facet region of the vertebral body. Over this guide-wire, the tissues were dilated with the use of a series of increasing diameter dilating tubes to approximately 18 mm. A drill bit was used to create a window into the lamina. This was confirmed through the use of fluoroscopy to determine the depth of penetration of the drill unit. Electrocautery and holmium lasers were used for hemocoagulation and soft tissue removal. Once this was accomplished, a standard mechanical burr system was utilized to grind away the lamina of the vertebral body and widen the opening that was created with the bit. Kerrison and pituitaries rongeurs were utilized during the entire process to assist in bone removal and for general debulking of soft tissues and loose bone fragments. Once the region of the lamina and foraminal canal was properly opened and decompressed, the tube was removed and the procedure was completed. Empirical Analysis Patients were stratified by age, gender, rank, and RTD duration from 1 mo to 12 mo. Univariate comparisons were statistically evaluated using Student’s t-test across gender and rank for ODI, VAS, and RTD metrics. Empirical analysis was conducted in STATA 13.0 (STATA Corp, College Station, TX). FINDINGS A retrospective analysis of 82 active duty service members diagnosed with LSS and a single-level lumbar LFD performed in a single ASC between December 2013 and January 2015 was examined. Table I presents the clinical data for ODI, VAS, RTD, estimated blood loss, and length of surgery. Significant reductions in VAS (6.03–3.71) and ODI (24.84–14.35) were observed from preoperative to postoperative across all demographics. ODI was recorded on a 0–50 scale. Additionally, 81% (66 of 82 service members) returned to duty in less than 1 mo. Furthermore, 17% (13 of 82 service members) returned to duty in 1–2 mo and 2% (two of 82 service members) returned to duty between 2 and 3 mo. Overall, 100% of the service members returned to duty within 3 mo. The average length of surgery was 62 minutes with an average estimated blood loss of 30.64 mL. Table I. Summary Statistics for Service Member Reported Pain, Disability, and RTD. Additionally, Retrospectively Collected Data for Estimated Blood Loss and Length of Surgery are Reported.   Mean  Standard Deviation  Min  Max  Pre-Op VAS  6.03  2.31  0  10  Post-Op VAS  3.71  2.75  0  10  Pre-Op ODI  24.84  9.17  7  44  Post-Op ODI  14.35  9.87  0  39  RTD < 1 mo  0.81  0.38  0  1  RTD 1–2 mo  0.17  0.37  0  1  RTD 2–3 mo  0.02  0.13  0  1  RTD > 3 mo  0  0  0  1  Estimated blood loss (mL)  30.64  23.32  4.81  64.87  Length of surgery (min)  60.11  27.84  43.12  98.41    Mean  Standard Deviation  Min  Max  Pre-Op VAS  6.03  2.31  0  10  Post-Op VAS  3.71  2.75  0  10  Pre-Op ODI  24.84  9.17  7  44  Post-Op ODI  14.35  9.87  0  39  RTD < 1 mo  0.81  0.38  0  1  RTD 1–2 mo  0.17  0.37  0  1  RTD 2–3 mo  0.02  0.13  0  1  RTD > 3 mo  0  0  0  1  Estimated blood loss (mL)  30.64  23.32  4.81  64.87  Length of surgery (min)  60.11  27.84  43.12  98.41  Table I. Summary Statistics for Service Member Reported Pain, Disability, and RTD. Additionally, Retrospectively Collected Data for Estimated Blood Loss and Length of Surgery are Reported.   Mean  Standard Deviation  Min  Max  Pre-Op VAS  6.03  2.31  0  10  Post-Op VAS  3.71  2.75  0  10  Pre-Op ODI  24.84  9.17  7  44  Post-Op ODI  14.35  9.87  0  39  RTD < 1 mo  0.81  0.38  0  1  RTD 1–2 mo  0.17  0.37  0  1  RTD 2–3 mo  0.02  0.13  0  1  RTD > 3 mo  0  0  0  1  Estimated blood loss (mL)  30.64  23.32  4.81  64.87  Length of surgery (min)  60.11  27.84  43.12  98.41    Mean  Standard Deviation  Min  Max  Pre-Op VAS  6.03  2.31  0  10  Post-Op VAS  3.71  2.75  0  10  Pre-Op ODI  24.84  9.17  7  44  Post-Op ODI  14.35  9.87  0  39  RTD < 1 mo  0.81  0.38  0  1  RTD 1–2 mo  0.17  0.37  0  1  RTD 2–3 mo  0.02  0.13  0  1  RTD > 3 mo  0  0  0  1  Estimated blood loss (mL)  30.64  23.32  4.81  64.87  Length of surgery (min)  60.11  27.84  43.12  98.41  Specific to this patient cohort, there were no referrals to a Medical Evaluation Board that would have been made when a health care practitioner determines that the patient did not meet medical retention standards and indicates that the individual has a medical condition or physical limitation that would result in the patient being non-deployable. This cohort of patients was cleared for normal physical activity, returned to pre-surgery duty status, and was deployable within the 1- to 3-mo time frame. At 12 mo post-surgery, all patients were still in the pre-surgery activity duty status. Table II presents a breakdown of the RTD measures across demographics. Male service members accounted for 83% (68 of 82 service embers) of the sample, whereas female service members accounted for the remaining 17% (14 of 82 service members). Army, Navy, Marine Corps, and Air Force service members were present in the sample. Specifically, enlisted service members made up 84% (69 of 82 service members) of the sample, whereas the remaining 16% were officers in one of the four aforementioned branches. In regard of the enlisted sample, 51 out of the 69 were mid-level enlisted service members between the ranks of E5 and E9. There were no statistically significant differences across services or ranks in any of the results. Table II. Percentage of Service Members RTD Stratified by Duration. Data are Present for All Service Members, by Gender and Rank.   RTD <1 mo  RTD 1–2 mo  RTD 2–3 mo  RTD > 3 mo  All patients (N = 82)  66  13  2  0   Male  51  15  2  0   Female  11  3  0  0  Rank   E1–E4  10  8  0  0   E5–E9  34  16  1  0   WO1–O8  7  5  1  0    RTD <1 mo  RTD 1–2 mo  RTD 2–3 mo  RTD > 3 mo  All patients (N = 82)  66  13  2  0   Male  51  15  2  0   Female  11  3  0  0  Rank   E1–E4  10  8  0  0   E5–E9  34  16  1  0   WO1–O8  7  5  1  0  Table II. Percentage of Service Members RTD Stratified by Duration. Data are Present for All Service Members, by Gender and Rank.   RTD <1 mo  RTD 1–2 mo  RTD 2–3 mo  RTD > 3 mo  All patients (N = 82)  66  13  2  0   Male  51  15  2  0   Female  11  3  0  0  Rank   E1–E4  10  8  0  0   E5–E9  34  16  1  0   WO1–O8  7  5  1  0    RTD <1 mo  RTD 1–2 mo  RTD 2–3 mo  RTD > 3 mo  All patients (N = 82)  66  13  2  0   Male  51  15  2  0   Female  11  3  0  0  Rank   E1–E4  10  8  0  0   E5–E9  34  16  1  0   WO1–O8  7  5  1  0  In Table II, the summary statistics show that 75% of male and 78% of female service members returned to duty within 1 mo postoperative. Additionally, 22% of male and 22% of female service members returned to duty within 2 mo postoperative. Furthermore, the remaining 3% of male service members returned to duty within 3 mo. It should be noted that 100% of female service members returned to duty within 2 mo and 100% of male service members within 3 mo. Table II also reports on the RTD duration across rank. Specifically, 64% of enlisted service members and 54% of officers returned to duty within 1 mo of surgery (55% of E1–E4; 67% of E5–E9). Furthermore, 35% of enlisted service members (45% of E1–E4; 31% of E5–E9) and 39% of officers returned to duty within 2 mo. Two service members (1: E5–E9 and 1: Officer) returned to duty within 3 mo. The univariate analysis of the VAS and ODI scores is presented in Table III. Specifically, the differences between preoperative and postoperative VAS and preoperative and postoperative ODI are presented in column I and column II, respectively. Column I reports a significant difference between preoperative and postoperative VAS of 2.32. Additionally, these results are consistent across male and female service members indicating a 2.65 and 2.00 difference in preoperative and postoperative VAS, respectively. Although there are no statistical differences between ranks, there are reported statistically significant differences in preoperative and postoperative VAS scores for each rank with deltas of 2.08, 2.25, and 2.45 for E1–E4, E5–E9, and Officers, respectively. Table III. Univariate Results Between Preoperative and Postoperative Pain and Disability. Data are Present for All Service Members and by Gender and Rank. Column I Reports the Student’s t-Test Results on the Difference Between Preoperative and Postoperative VAS, whereas Column II Reports the Student’s t-Test Results on the Difference Between Preoperative and Postoperative ODI.   I  II  Pre-Op VAS  Post-Op VAS  Difference  Pre-Op ODI  Post-Op ODI  Difference  All patients (N = 82)  6.03  3.71  2.32***  24.84  14.35  10.49***  (2.31)  (2.75)    (9.17)  (9.87)     Male  5.96  3.31  2.65***  23.12  12.38  10.74***  (2.21)  (2.19)    (8.72)  (7.21)     Female  6.11  4.11  2.00**  26.58  16.34  10.24***  (2.12)  (2.81)    (9.87)  (8.44)    Rank   E1–E4  5.41  3.33  2.08**  23.64  13.45  10.19***  (2.41)  (2.06)    (8.67)  (8.87)     E5–E9  6.12  3.87  2.25**  25.61  13.64  11.97***  (2.47)  (2.03)    (9.16)  (9.56)     WO1–O8  6.57  4.12  2.45**  25.16  15.87  9.29**  (2.64)  (2.24)    (9.44)  (10.23)      I  II  Pre-Op VAS  Post-Op VAS  Difference  Pre-Op ODI  Post-Op ODI  Difference  All patients (N = 82)  6.03  3.71  2.32***  24.84  14.35  10.49***  (2.31)  (2.75)    (9.17)  (9.87)     Male  5.96  3.31  2.65***  23.12  12.38  10.74***  (2.21)  (2.19)    (8.72)  (7.21)     Female  6.11  4.11  2.00**  26.58  16.34  10.24***  (2.12)  (2.81)    (9.87)  (8.44)    Rank   E1–E4  5.41  3.33  2.08**  23.64  13.45  10.19***  (2.41)  (2.06)    (8.67)  (8.87)     E5–E9  6.12  3.87  2.25**  25.61  13.64  11.97***  (2.47)  (2.03)    (9.16)  (9.56)     WO1–O8  6.57  4.12  2.45**  25.16  15.87  9.29**  (2.64)  (2.24)    (9.44)  (10.23)    ***1% level of significance; **5% level of significance; *10% level of significance. Table III. Univariate Results Between Preoperative and Postoperative Pain and Disability. Data are Present for All Service Members and by Gender and Rank. Column I Reports the Student’s t-Test Results on the Difference Between Preoperative and Postoperative VAS, whereas Column II Reports the Student’s t-Test Results on the Difference Between Preoperative and Postoperative ODI.   I  II  Pre-Op VAS  Post-Op VAS  Difference  Pre-Op ODI  Post-Op ODI  Difference  All patients (N = 82)  6.03  3.71  2.32***  24.84  14.35  10.49***  (2.31)  (2.75)    (9.17)  (9.87)     Male  5.96  3.31  2.65***  23.12  12.38  10.74***  (2.21)  (2.19)    (8.72)  (7.21)     Female  6.11  4.11  2.00**  26.58  16.34  10.24***  (2.12)  (2.81)    (9.87)  (8.44)    Rank   E1–E4  5.41  3.33  2.08**  23.64  13.45  10.19***  (2.41)  (2.06)    (8.67)  (8.87)     E5–E9  6.12  3.87  2.25**  25.61  13.64  11.97***  (2.47)  (2.03)    (9.16)  (9.56)     WO1–O8  6.57  4.12  2.45**  25.16  15.87  9.29**  (2.64)  (2.24)    (9.44)  (10.23)      I  II  Pre-Op VAS  Post-Op VAS  Difference  Pre-Op ODI  Post-Op ODI  Difference  All patients (N = 82)  6.03  3.71  2.32***  24.84  14.35  10.49***  (2.31)  (2.75)    (9.17)  (9.87)     Male  5.96  3.31  2.65***  23.12  12.38  10.74***  (2.21)  (2.19)    (8.72)  (7.21)     Female  6.11  4.11  2.00**  26.58  16.34  10.24***  (2.12)  (2.81)    (9.87)  (8.44)    Rank   E1–E4  5.41  3.33  2.08**  23.64  13.45  10.19***  (2.41)  (2.06)    (8.67)  (8.87)     E5–E9  6.12  3.87  2.25**  25.61  13.64  11.97***  (2.47)  (2.03)    (9.16)  (9.56)     WO1–O8  6.57  4.12  2.45**  25.16  15.87  9.29**  (2.64)  (2.24)    (9.44)  (10.23)    ***1% level of significance; **5% level of significance; *10% level of significance. Column II (Table III) reports the results for the ODI measures. Similar to VAS, ODI scores report a statistically significant difference of 10.49 from preoperative to postoperative. Results across gender are also similar as male and female service members show a 10.74 and 10.24 difference in preoperative and postoperative ODI scores, respectively. Lastly, there are reported statistically significant differences in preoperative and postoperative ODI scores for each rank with deltas of 210.19, 11.97, and 9.29 for E1–E4, E5–E9, and Officers, respectively. DISCUSSION The primary objective of the current study is to examine the RTD rates in an active duty military population following a single-level LFD procedure for the treatment of LSS. Specifically, the procedure was an elective MISS performed in a 24-h ASC setting. Research and anecdotal evidence suggest that given the economic factors associated with training and deployment, as well as military force readiness implications, the length of time to return to full duty post-injury/surgery is a vital metric in the military health care sector.5 The current results are the first to report on RTD metrics following an elective minimally invasive LFD surgery for the treatment of LSS in an ASC setting. Overall, our results indicate that within our sample of 82 active duty military service members, 100% of the service members RTD within 3 mo. The results, which were consistent across gender and rank, are noticeably faster than previous research. There are limited studies reporting on RTD in the active duty military population following spine surgery.5–7 The most recent, and likely relevant, study compared decompression procedures (microdiscectomy, laminectomy, and foraminal decompression) without fusion and decompression procedures with fusion (ALIF, XLIF, PLIF, TLIF, Interbody fusion + PL fusion). The overall results report a 64% RTD within 12 mo. The current study reported 100% RTD within 3 mo; however, it should be noted that the Lunsford et al’s (2016) study reported on a wide range of procedures, which may or may not have been performed with a minimally invasive technique. Of relevance to the current study, Lunsford et al (2016) reported that patients who underwent isolated decompression procedures made up 59% of the total study population with the RTD rate being 63% within 12 mo. Although it is unknown within the Lunsford et al (2016) what subsection of the patient population was treated with an MISS approach or in an outpatient and/or outpatient ASC setting, the surgical type and patient population was similar. Our results compliment the Lunsford et al’s (2016) study by showing the significant improvement in RTD rates when incorporating an MISS LFD outpatient procedure into the treatment algorithm for the treatment of LSS in the active duty military population. It should be noted that the sample population is different and continuity does not exist between surgical approaches (i.e., Open, MISS) and surgical settings (i.e., hospital, outpatient, ASC). A secondary objective of the current study is to determine the efficacy of an LFD procedure for the treatment of LSS in an active duty military population. The results indicate that across gender and rank, there are statically significant reductions in both pain (VAS) and disability (ODI) following an LFD procedure for the treatment of LSS in an active duty military population. Additionally, there is minimal estimated blood loss and surgical/OR time. These results are important as the current study focused on LFD procedures that were performed in an outpatient ASC setting. Although the benefits of MISS techniques are well documented,12–15 no research to date has examined the benefits of MISS techniques in an ASC, more importantly in a defined population of military service members. There is a lack of literature examining spine surgery efficacy in a military population; however, there are a number of studies detailing the safety and efficacy of decompression surgeries without stabilization in the general population. Crawford et al (2016) demonstrated that patients with lumbar stenosis undergoing a decompression only procedure received clinically significant pain relief from their back pain. Similar to studies of the general population19 who realized pain relief with decompression surgery, the current study of active duty service members reported comparable patient report outcomes of pain relief. Service members in the current study experienced a significant reduction in pain (VAS) and disability (ODI) following surgery, while experiencing a short length of surgery and estimated blood loss. Specially, within the current patient population, 100% of the patients remained in their respective pre-surgery duty status at 12 mo postoperative. Additionally, all of the current cases were performed in an ASC where service members were released within 23 h of surgery, whereas previous research on elective spine surgery in the military population reports the mean length of stay as 1.81 d.19 CONCLUSION The current study is believed to be the first to examine RTD and efficacy of spine surgery in the active duty military population in an ASC setting. The results indicate that regardless of gender and rank, 100% of service members RTD within 3 mo of an LFD procedure. Furthermore, service members reported a significant reduction in postoperative pain and disability. This study demonstrates that the minimally invasive LFD procedures resulted in no complications, minimal blood loss, and a reduced length of surgery. 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Google Scholar PubMed  14 Rosen D, O’Toole J, Eichholz K: Minimally invasive lumbar spinal decompression in the elderly: outcome of 50 patients aged 75 years and older. Neurosurgery  2007; 60( 3): 503– 9. Google Scholar CrossRef Search ADS PubMed  15 Hudak E, Perry M: Outpatient minimally invasive spine surgery using endoscopy for the treatment of lumbar spinal stenosis among obese patients. J Orthop  2015; 12( 3): 156– 9. Google Scholar CrossRef Search ADS PubMed  16 Army Regulation 40-501: Standards of medical fitness. Washington, DC, Headquarters, Department of the Army, 2011. Available at http://annypubs.army.mil/epubs/40_Series_Collection_l.html; accessed March 30, 2015. 17 Army Regulation 635-40: Physical evaluation for retention, retirement, or separation. Washington, DC. Headquarters, Department of the Army, 2012. Available at http://armypubs.army.mil/epubs/635_Series_Collection_l.html; accessed March 30. 2015. 18 SECNAVINST 1850.4E. Enclosure 8: Medical Conditions and Physical defects Which Normally Are Cause for Referral to the Physical Evaluation Board (PEB). Available at http://www.secnav.navy.mil/mra/CORB/Documents/SECNAV%20INST%201850_4e.pdf; accessed 30 April 2002. 19 Crawford C, Glassman S, Mummaneni P, Knightly J, Asher A: Back pain improvement after decompression without fusion or stabilization in patients with lumbar spinal stenosis and clinically significant preoperative back pain. J Neurosurg Spine  2016; 25: 596– 601. Google Scholar CrossRef Search ADS PubMed  © Association of Military Surgeons of the United States 2018. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Military Medicine Oxford University Press

Return-to-Duty Rates Following Minimally Invasive Spine Surgery Performed on Active Duty Military Patients in an Ambulatory Surgery Center

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Association of Military Surgeons of the United States
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© Association of Military Surgeons of the United States 2018. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
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0026-4075
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1930-613X
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10.1093/milmed/usx104
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Abstract

Abstract Background Low back pain is a primary health care utilization driver in the US population. Health care evaluation visits for low back pain are as common as medical evaluation for the common cold. Low back pain is the most common reason for reductions in activities of daily living and work activity in the general population. Although these statistics are compelling, in the military population, there is arguably a significantly greater economic impact on the military population, as the cost to train, retain, and deploy a service member is a tremendous cost. Methods The current study retrospectively examines surgical outcomes, return to duty, and patient-centric outcomes among 82 active duty or reserve military patients who underwent an outpatient minimally invasive spine surgery Laminotomy Foraminotomy Decompression for the treatment of lumbar spinal stenosis in an ambulatory surgery center. Findings Overall, our results indicate that within the 82 active duty military service members, 100% of the service members return to duty within 3 mo. Additionally, there was a significant reduction in self-reported pain and disability 12 mo postoperative, whereas the average length of surgery was 62 min with an average estimated blood loss of 30.64 mL. Discussion The current study indicates that minimally invasive procedures for the treatment of lumbar spinal stenosis in an ambulatory surgery center setting are an effective option for active duty servicemen to reduce return-to-duty rates and symptomatic back-related pain and disability. BACKGROUND Low back pain (LBP) is one of the most common reasons for visiting a physician in the United States.1 To put this into perspective, medical visits for LBP are second only to the common cold. In the US population, LBP is the most common reason for reductions in activities of daily living and work activity limitations in individuals younger than 45 years. Additionally, LBP is the third most common indication for all spine-related surgical procedures.2 Annual direct health care costs in the United States for spine disorders have been estimated at more than $85 billion, with indirect costs from lost work productivity resulting from LBP in the United States estimated to exceed $7 billion annually.3,4 Given the epidemiological data and health care costs, LBP is a significant issue for today’s health care system and society as a whole. Similarities exist between the US population and the US military cohort across a multitude of health criteria. Similar to the general US population, LBP is also one of the most common forms of chronic pain in the US military population. Moreover, LBP has been associated with high rates of medical expenses and increased time to return to duty (RTD). Military duty presents a unique spectrum of intrinsic and extrinsic factors, not typical to the general population, that increase the risk factors associated with musculoskeletal disorders specific to spine-related pathologies. Recent research reported that within the military population, there is approximately 20% 6-mo prevalence of axial lower back pain necessitating medical evaluation.5 Active duty military service has been shown to result in a 2.4-fold increase in the prevalence of axial lower back pain resulting in a medical exam, whereas 70% and 46% of deployed active duty military members (with non-traumatic lumbar spine pain complaints) reported new radicular and axial pain symptoms, respectively.6 Although costs to train a single military serviceman/woman vary, ranges are estimated from $200,000 to $9,000,000. Due to the high cost of training and the extensive knowledge gained through the training, having military servicemen/women on active duty is critical. As such, the length in which it takes to have a military servicemen/women return to full duty post-surgery is a vital metric in surgical efficacy.5 RTD rates and length of time for spine pathology treatment protocols vary significantly in published research.5–7 Houghton et al (2016) presented a comprehensive review of RTD rates compared in the context of the treatments and reported RTD between 3 and 17 mo depending on treatment. Lunsford et al (2016) reported on the percentage of military service members RTD following elective lumbar spine surgery. The RTD rate following elective lumbar spine surgery is 64% within 1 year. When stratified by procedure type, isolated decompression procedures (63% RTD rate) and fusion procedures (66% RTD rate) displayed similar 1-year results. Over the past decade, advancements in instrumentation, surgical access technology, and navigation have expanded the breadth of treatment applications for spine surgery. Specifically, the adoption of minimally invasive techniques has supplemented the practice of contemporary spine surgery. Minimally invasive spine surgery (MISS) has demonstrated comparable efficacy to traditional open procedures and has garnered popularity among surgeons. The limitations associated with open spine surgery, including extensive tissue dissection, muscle injury, blood loss, and greater hospital resource utilization have impacted patient outcomes.8,9 In addition to improvements in instrumentation and technology, outpatient surgery has seen a significant rise in utilization compared with the traditional hospital setting.10 Although outpatient surgery centers are freestanding or hospital-based with care extending 23 h, ambulatory surgery centers (ASC) are health care facilities focused on providing same-day surgical care of up to 23 h. Outpatient procedures represented over 60% of all surgeries in the United States in 2011, up from 19% in 1981.10 Outpatient surgery volume across both hospital-based and freestanding facilities grew by 64% between 1996 and 2011, according to the National Survey of Ambulatory Surgery.11 There is a breadth of research indicating the benefits of outpatient versus inpatient lumbar spine surgery and minimally invasive lumbar spine surgery techniques on patient-centric outcomes.12–14 Benefits range from self-reported pain and disability improvement, blood loss, length of surgery, postoperative length of stay, and return to activities of daily living.15 More importantly in the context of this research, there is a paucity of literature examining these factors on the military population. Furthermore, to our knowledge, there is a gap in the literature investigating elective lumbar spine surgery and patient-centric outcomes in an ASC in the active duty military population. The objective of this research is to retrospectively examine surgical outcomes, RTD, and self-reported patient-centric outcomes at preoperative and 12 mo postoperative among active duty or reserve military patients who underwent an outpatient MISS Laminotomy Foraminotomy Decompression (LFD) for the treatment of lumbar spinal stenosis (LSS) in an ASC. METHODS The current study conducted a retrospective analysis of 82 active duty service members diagnosed with symptomatic, painful LSS indicated for a single-level LFD between December 2013 and January 2015. Specifically, the LFD procedure was planned as an outpatient procedure within an ASC setting. An extensive preoperative clinical examination was performed to evaluate motor, sensory, and reflex deficits. Radiological examinations consisting of lumbar spine magnetic resonance imaging, computed tomography, and plain X-rays with flexion and extension views were performed to confirm clinical diagnoses. LSS was the primary diagnosis and was defined as spinal stenosis (central/lateral recess or foraminal stenosis) graded as moderate, moderate to severe, or severe with unremitting pain, confirmed by imaging studies (e.g., computed tomography or magnetic resonance imaging) at the level corresponding to neurological findings. The presence of neurological abnormalities (e.g., reflex change, positive straight leg raising, sensory loss, and weakness) was evaluated and would have persisted on examination and correspond to the specific affected nerve root. The conservative management treatment comprised the prescription of effective pain management according to prevailing guidelines and the advice to resume daily duty activities if feasible. A mobilization/ activity program, based on time rather than pain, was recommended without directly checking the compliance. If patients had considerable fear of movement, guidance from a physiotherapist was recommended. Specifically, the course of conservative care followed physical therapy, spinal injections, and medications when each were appropriate. Preoperative and follow-up self-reported pain (visual analog scale [VAS]), disability (Oswestry Disability Index [ODI]), and RTD status were collected at 12 mo postoperative. All service members passed a clinical assessment to RTD in accordance with their respective service requirements. Clinical parameters such as estimated blood loss, length of surgery, and complications of the surgical procedure were retrospectively collected. There were 0 reported intraoperative complications. Each service has medical fitness requirements that detail medical conditions and the procedure required when a service member does not meet medical retention standards (i.e., SECNAVINST 1850.E, Army Regulation 40-501).16–18 Furthermore, within these regulations, points in time are defined in which a service member is referred to a physical evaluation board or medical evaluation board. This occurs once the service member reaches a medical retention determination or after 12 mo of being diagnosed with/treated for a medical condition that does not appear to meet medical retention standards. Although these regulations vary across services, the determinations are fairly uniformed. As such, similar to previous research, we define RTD as a period from 1 mo to 12 mo in duration.5 Details of Surgical Technique Although the decompression via laminotomy and foraminotomy vary slightly across surgeons, in general, a scalpel was used to make a stab wound through which a guide-wire was inserted down to the facet region of the vertebral body. Over this guide-wire, the tissues were dilated with the use of a series of increasing diameter dilating tubes to approximately 18 mm. A drill bit was used to create a window into the lamina. This was confirmed through the use of fluoroscopy to determine the depth of penetration of the drill unit. Electrocautery and holmium lasers were used for hemocoagulation and soft tissue removal. Once this was accomplished, a standard mechanical burr system was utilized to grind away the lamina of the vertebral body and widen the opening that was created with the bit. Kerrison and pituitaries rongeurs were utilized during the entire process to assist in bone removal and for general debulking of soft tissues and loose bone fragments. Once the region of the lamina and foraminal canal was properly opened and decompressed, the tube was removed and the procedure was completed. Empirical Analysis Patients were stratified by age, gender, rank, and RTD duration from 1 mo to 12 mo. Univariate comparisons were statistically evaluated using Student’s t-test across gender and rank for ODI, VAS, and RTD metrics. Empirical analysis was conducted in STATA 13.0 (STATA Corp, College Station, TX). FINDINGS A retrospective analysis of 82 active duty service members diagnosed with LSS and a single-level lumbar LFD performed in a single ASC between December 2013 and January 2015 was examined. Table I presents the clinical data for ODI, VAS, RTD, estimated blood loss, and length of surgery. Significant reductions in VAS (6.03–3.71) and ODI (24.84–14.35) were observed from preoperative to postoperative across all demographics. ODI was recorded on a 0–50 scale. Additionally, 81% (66 of 82 service members) returned to duty in less than 1 mo. Furthermore, 17% (13 of 82 service members) returned to duty in 1–2 mo and 2% (two of 82 service members) returned to duty between 2 and 3 mo. Overall, 100% of the service members returned to duty within 3 mo. The average length of surgery was 62 minutes with an average estimated blood loss of 30.64 mL. Table I. Summary Statistics for Service Member Reported Pain, Disability, and RTD. Additionally, Retrospectively Collected Data for Estimated Blood Loss and Length of Surgery are Reported.   Mean  Standard Deviation  Min  Max  Pre-Op VAS  6.03  2.31  0  10  Post-Op VAS  3.71  2.75  0  10  Pre-Op ODI  24.84  9.17  7  44  Post-Op ODI  14.35  9.87  0  39  RTD < 1 mo  0.81  0.38  0  1  RTD 1–2 mo  0.17  0.37  0  1  RTD 2–3 mo  0.02  0.13  0  1  RTD > 3 mo  0  0  0  1  Estimated blood loss (mL)  30.64  23.32  4.81  64.87  Length of surgery (min)  60.11  27.84  43.12  98.41    Mean  Standard Deviation  Min  Max  Pre-Op VAS  6.03  2.31  0  10  Post-Op VAS  3.71  2.75  0  10  Pre-Op ODI  24.84  9.17  7  44  Post-Op ODI  14.35  9.87  0  39  RTD < 1 mo  0.81  0.38  0  1  RTD 1–2 mo  0.17  0.37  0  1  RTD 2–3 mo  0.02  0.13  0  1  RTD > 3 mo  0  0  0  1  Estimated blood loss (mL)  30.64  23.32  4.81  64.87  Length of surgery (min)  60.11  27.84  43.12  98.41  Table I. Summary Statistics for Service Member Reported Pain, Disability, and RTD. Additionally, Retrospectively Collected Data for Estimated Blood Loss and Length of Surgery are Reported.   Mean  Standard Deviation  Min  Max  Pre-Op VAS  6.03  2.31  0  10  Post-Op VAS  3.71  2.75  0  10  Pre-Op ODI  24.84  9.17  7  44  Post-Op ODI  14.35  9.87  0  39  RTD < 1 mo  0.81  0.38  0  1  RTD 1–2 mo  0.17  0.37  0  1  RTD 2–3 mo  0.02  0.13  0  1  RTD > 3 mo  0  0  0  1  Estimated blood loss (mL)  30.64  23.32  4.81  64.87  Length of surgery (min)  60.11  27.84  43.12  98.41    Mean  Standard Deviation  Min  Max  Pre-Op VAS  6.03  2.31  0  10  Post-Op VAS  3.71  2.75  0  10  Pre-Op ODI  24.84  9.17  7  44  Post-Op ODI  14.35  9.87  0  39  RTD < 1 mo  0.81  0.38  0  1  RTD 1–2 mo  0.17  0.37  0  1  RTD 2–3 mo  0.02  0.13  0  1  RTD > 3 mo  0  0  0  1  Estimated blood loss (mL)  30.64  23.32  4.81  64.87  Length of surgery (min)  60.11  27.84  43.12  98.41  Specific to this patient cohort, there were no referrals to a Medical Evaluation Board that would have been made when a health care practitioner determines that the patient did not meet medical retention standards and indicates that the individual has a medical condition or physical limitation that would result in the patient being non-deployable. This cohort of patients was cleared for normal physical activity, returned to pre-surgery duty status, and was deployable within the 1- to 3-mo time frame. At 12 mo post-surgery, all patients were still in the pre-surgery activity duty status. Table II presents a breakdown of the RTD measures across demographics. Male service members accounted for 83% (68 of 82 service embers) of the sample, whereas female service members accounted for the remaining 17% (14 of 82 service members). Army, Navy, Marine Corps, and Air Force service members were present in the sample. Specifically, enlisted service members made up 84% (69 of 82 service members) of the sample, whereas the remaining 16% were officers in one of the four aforementioned branches. In regard of the enlisted sample, 51 out of the 69 were mid-level enlisted service members between the ranks of E5 and E9. There were no statistically significant differences across services or ranks in any of the results. Table II. Percentage of Service Members RTD Stratified by Duration. Data are Present for All Service Members, by Gender and Rank.   RTD <1 mo  RTD 1–2 mo  RTD 2–3 mo  RTD > 3 mo  All patients (N = 82)  66  13  2  0   Male  51  15  2  0   Female  11  3  0  0  Rank   E1–E4  10  8  0  0   E5–E9  34  16  1  0   WO1–O8  7  5  1  0    RTD <1 mo  RTD 1–2 mo  RTD 2–3 mo  RTD > 3 mo  All patients (N = 82)  66  13  2  0   Male  51  15  2  0   Female  11  3  0  0  Rank   E1–E4  10  8  0  0   E5–E9  34  16  1  0   WO1–O8  7  5  1  0  Table II. Percentage of Service Members RTD Stratified by Duration. Data are Present for All Service Members, by Gender and Rank.   RTD <1 mo  RTD 1–2 mo  RTD 2–3 mo  RTD > 3 mo  All patients (N = 82)  66  13  2  0   Male  51  15  2  0   Female  11  3  0  0  Rank   E1–E4  10  8  0  0   E5–E9  34  16  1  0   WO1–O8  7  5  1  0    RTD <1 mo  RTD 1–2 mo  RTD 2–3 mo  RTD > 3 mo  All patients (N = 82)  66  13  2  0   Male  51  15  2  0   Female  11  3  0  0  Rank   E1–E4  10  8  0  0   E5–E9  34  16  1  0   WO1–O8  7  5  1  0  In Table II, the summary statistics show that 75% of male and 78% of female service members returned to duty within 1 mo postoperative. Additionally, 22% of male and 22% of female service members returned to duty within 2 mo postoperative. Furthermore, the remaining 3% of male service members returned to duty within 3 mo. It should be noted that 100% of female service members returned to duty within 2 mo and 100% of male service members within 3 mo. Table II also reports on the RTD duration across rank. Specifically, 64% of enlisted service members and 54% of officers returned to duty within 1 mo of surgery (55% of E1–E4; 67% of E5–E9). Furthermore, 35% of enlisted service members (45% of E1–E4; 31% of E5–E9) and 39% of officers returned to duty within 2 mo. Two service members (1: E5–E9 and 1: Officer) returned to duty within 3 mo. The univariate analysis of the VAS and ODI scores is presented in Table III. Specifically, the differences between preoperative and postoperative VAS and preoperative and postoperative ODI are presented in column I and column II, respectively. Column I reports a significant difference between preoperative and postoperative VAS of 2.32. Additionally, these results are consistent across male and female service members indicating a 2.65 and 2.00 difference in preoperative and postoperative VAS, respectively. Although there are no statistical differences between ranks, there are reported statistically significant differences in preoperative and postoperative VAS scores for each rank with deltas of 2.08, 2.25, and 2.45 for E1–E4, E5–E9, and Officers, respectively. Table III. Univariate Results Between Preoperative and Postoperative Pain and Disability. Data are Present for All Service Members and by Gender and Rank. Column I Reports the Student’s t-Test Results on the Difference Between Preoperative and Postoperative VAS, whereas Column II Reports the Student’s t-Test Results on the Difference Between Preoperative and Postoperative ODI.   I  II  Pre-Op VAS  Post-Op VAS  Difference  Pre-Op ODI  Post-Op ODI  Difference  All patients (N = 82)  6.03  3.71  2.32***  24.84  14.35  10.49***  (2.31)  (2.75)    (9.17)  (9.87)     Male  5.96  3.31  2.65***  23.12  12.38  10.74***  (2.21)  (2.19)    (8.72)  (7.21)     Female  6.11  4.11  2.00**  26.58  16.34  10.24***  (2.12)  (2.81)    (9.87)  (8.44)    Rank   E1–E4  5.41  3.33  2.08**  23.64  13.45  10.19***  (2.41)  (2.06)    (8.67)  (8.87)     E5–E9  6.12  3.87  2.25**  25.61  13.64  11.97***  (2.47)  (2.03)    (9.16)  (9.56)     WO1–O8  6.57  4.12  2.45**  25.16  15.87  9.29**  (2.64)  (2.24)    (9.44)  (10.23)      I  II  Pre-Op VAS  Post-Op VAS  Difference  Pre-Op ODI  Post-Op ODI  Difference  All patients (N = 82)  6.03  3.71  2.32***  24.84  14.35  10.49***  (2.31)  (2.75)    (9.17)  (9.87)     Male  5.96  3.31  2.65***  23.12  12.38  10.74***  (2.21)  (2.19)    (8.72)  (7.21)     Female  6.11  4.11  2.00**  26.58  16.34  10.24***  (2.12)  (2.81)    (9.87)  (8.44)    Rank   E1–E4  5.41  3.33  2.08**  23.64  13.45  10.19***  (2.41)  (2.06)    (8.67)  (8.87)     E5–E9  6.12  3.87  2.25**  25.61  13.64  11.97***  (2.47)  (2.03)    (9.16)  (9.56)     WO1–O8  6.57  4.12  2.45**  25.16  15.87  9.29**  (2.64)  (2.24)    (9.44)  (10.23)    ***1% level of significance; **5% level of significance; *10% level of significance. Table III. Univariate Results Between Preoperative and Postoperative Pain and Disability. Data are Present for All Service Members and by Gender and Rank. Column I Reports the Student’s t-Test Results on the Difference Between Preoperative and Postoperative VAS, whereas Column II Reports the Student’s t-Test Results on the Difference Between Preoperative and Postoperative ODI.   I  II  Pre-Op VAS  Post-Op VAS  Difference  Pre-Op ODI  Post-Op ODI  Difference  All patients (N = 82)  6.03  3.71  2.32***  24.84  14.35  10.49***  (2.31)  (2.75)    (9.17)  (9.87)     Male  5.96  3.31  2.65***  23.12  12.38  10.74***  (2.21)  (2.19)    (8.72)  (7.21)     Female  6.11  4.11  2.00**  26.58  16.34  10.24***  (2.12)  (2.81)    (9.87)  (8.44)    Rank   E1–E4  5.41  3.33  2.08**  23.64  13.45  10.19***  (2.41)  (2.06)    (8.67)  (8.87)     E5–E9  6.12  3.87  2.25**  25.61  13.64  11.97***  (2.47)  (2.03)    (9.16)  (9.56)     WO1–O8  6.57  4.12  2.45**  25.16  15.87  9.29**  (2.64)  (2.24)    (9.44)  (10.23)      I  II  Pre-Op VAS  Post-Op VAS  Difference  Pre-Op ODI  Post-Op ODI  Difference  All patients (N = 82)  6.03  3.71  2.32***  24.84  14.35  10.49***  (2.31)  (2.75)    (9.17)  (9.87)     Male  5.96  3.31  2.65***  23.12  12.38  10.74***  (2.21)  (2.19)    (8.72)  (7.21)     Female  6.11  4.11  2.00**  26.58  16.34  10.24***  (2.12)  (2.81)    (9.87)  (8.44)    Rank   E1–E4  5.41  3.33  2.08**  23.64  13.45  10.19***  (2.41)  (2.06)    (8.67)  (8.87)     E5–E9  6.12  3.87  2.25**  25.61  13.64  11.97***  (2.47)  (2.03)    (9.16)  (9.56)     WO1–O8  6.57  4.12  2.45**  25.16  15.87  9.29**  (2.64)  (2.24)    (9.44)  (10.23)    ***1% level of significance; **5% level of significance; *10% level of significance. Column II (Table III) reports the results for the ODI measures. Similar to VAS, ODI scores report a statistically significant difference of 10.49 from preoperative to postoperative. Results across gender are also similar as male and female service members show a 10.74 and 10.24 difference in preoperative and postoperative ODI scores, respectively. Lastly, there are reported statistically significant differences in preoperative and postoperative ODI scores for each rank with deltas of 210.19, 11.97, and 9.29 for E1–E4, E5–E9, and Officers, respectively. DISCUSSION The primary objective of the current study is to examine the RTD rates in an active duty military population following a single-level LFD procedure for the treatment of LSS. Specifically, the procedure was an elective MISS performed in a 24-h ASC setting. Research and anecdotal evidence suggest that given the economic factors associated with training and deployment, as well as military force readiness implications, the length of time to return to full duty post-injury/surgery is a vital metric in the military health care sector.5 The current results are the first to report on RTD metrics following an elective minimally invasive LFD surgery for the treatment of LSS in an ASC setting. Overall, our results indicate that within our sample of 82 active duty military service members, 100% of the service members RTD within 3 mo. The results, which were consistent across gender and rank, are noticeably faster than previous research. There are limited studies reporting on RTD in the active duty military population following spine surgery.5–7 The most recent, and likely relevant, study compared decompression procedures (microdiscectomy, laminectomy, and foraminal decompression) without fusion and decompression procedures with fusion (ALIF, XLIF, PLIF, TLIF, Interbody fusion + PL fusion). The overall results report a 64% RTD within 12 mo. The current study reported 100% RTD within 3 mo; however, it should be noted that the Lunsford et al’s (2016) study reported on a wide range of procedures, which may or may not have been performed with a minimally invasive technique. Of relevance to the current study, Lunsford et al (2016) reported that patients who underwent isolated decompression procedures made up 59% of the total study population with the RTD rate being 63% within 12 mo. Although it is unknown within the Lunsford et al (2016) what subsection of the patient population was treated with an MISS approach or in an outpatient and/or outpatient ASC setting, the surgical type and patient population was similar. Our results compliment the Lunsford et al’s (2016) study by showing the significant improvement in RTD rates when incorporating an MISS LFD outpatient procedure into the treatment algorithm for the treatment of LSS in the active duty military population. It should be noted that the sample population is different and continuity does not exist between surgical approaches (i.e., Open, MISS) and surgical settings (i.e., hospital, outpatient, ASC). A secondary objective of the current study is to determine the efficacy of an LFD procedure for the treatment of LSS in an active duty military population. The results indicate that across gender and rank, there are statically significant reductions in both pain (VAS) and disability (ODI) following an LFD procedure for the treatment of LSS in an active duty military population. Additionally, there is minimal estimated blood loss and surgical/OR time. These results are important as the current study focused on LFD procedures that were performed in an outpatient ASC setting. Although the benefits of MISS techniques are well documented,12–15 no research to date has examined the benefits of MISS techniques in an ASC, more importantly in a defined population of military service members. There is a lack of literature examining spine surgery efficacy in a military population; however, there are a number of studies detailing the safety and efficacy of decompression surgeries without stabilization in the general population. Crawford et al (2016) demonstrated that patients with lumbar stenosis undergoing a decompression only procedure received clinically significant pain relief from their back pain. Similar to studies of the general population19 who realized pain relief with decompression surgery, the current study of active duty service members reported comparable patient report outcomes of pain relief. Service members in the current study experienced a significant reduction in pain (VAS) and disability (ODI) following surgery, while experiencing a short length of surgery and estimated blood loss. Specially, within the current patient population, 100% of the patients remained in their respective pre-surgery duty status at 12 mo postoperative. Additionally, all of the current cases were performed in an ASC where service members were released within 23 h of surgery, whereas previous research on elective spine surgery in the military population reports the mean length of stay as 1.81 d.19 CONCLUSION The current study is believed to be the first to examine RTD and efficacy of spine surgery in the active duty military population in an ASC setting. The results indicate that regardless of gender and rank, 100% of service members RTD within 3 mo of an LFD procedure. Furthermore, service members reported a significant reduction in postoperative pain and disability. This study demonstrates that the minimally invasive LFD procedures resulted in no complications, minimal blood loss, and a reduced length of surgery. Given the extensive training, economic cost of training and deployment, and cost of operational readiness, MISS procedures for the treatment of LSS in an ASC setting are an effective option for active duty servicemen/women to reduce RTD rates and symptomatic back-related pain and disability. REFERENCES 1 Hoy D, Brooks P, Blyth F, Buchbinder R: The epidemiology of low back pain. Best Pract Res Clin Rheumatol  2010; 24( 6): 769– 81. Google Scholar CrossRef Search ADS PubMed  2 van Dongen J, van Hooff M, Spruit M, de Kleuver M, Ostelo R: Which patient-reported factors predict referral to spinal surgery? A cohort study among 4987 chronic low back pain patients. Eur Spine J  2017; 30: 1– 7. 3 Katz J: Lumbar disc disorders and low-back pain: socioeconomic factors and consequences. J Bone Joint Surg  2014; 88: 21– 4. 4 Joish V, Brixner D: Back pain and productivity: measuring worker productivity from an employer’s perspective. J Pain Palliat Care Pharmacother  2004; 18( 2): 78– 85. 5 Lunsford J, Lawson B, Johnson A, Topp R: Return to duty rates in active duty service members after elective surgery of the lumbar spine. Mil Med  2016; 181( 6): 572– 6. Google Scholar CrossRef Search ADS PubMed  6 Cohen S, Gallagher R, Davis S, Griffith S, Carragee E: Spine area pain in military personnel: a review of epidemiology, etiology, diagnosis, and treatment. Spine  2012; 12( 9): 833– 42. Google Scholar CrossRef Search ADS   7 Houghton N, Maynard J, Aikena A: Functional rehabilitation criteria required for a safe return to active duty in military personnel following a musculoskeletal injury: a scoping review. J Mil Veteran Fam Health  2016; 2( 1): 1– 12. Google Scholar CrossRef Search ADS   8 O’Toole J, Eichholz K, Fessler R: Surgical site infection rates after minimally invasive spinal surgery: clinical article. J Neurosurg  2009; 11( 4): 471– 6. 9 Lawton C, Smith Z, Barnawi A, Fessler R: The surgical technique of minimally invasive transforaminal lumbar interbody fusion. J Neurosurg Sci  2011; 55( 3): 259– 64. Google Scholar PubMed  10 American Hospital Association: Chartbook: trends affecting hospitals and health systems [Internet]. Chicago (IL): AHA; [cited 2014 Mar 25]. Available at http://www.aha.org/research/reports/tw/chartbook/index.shtml 11 Munnich E, Parente S: Procedures take less time at ambulatory surgery centers, keeping costs down and ability to meet demand up. Health Aff  2014; 33( 5): 764– 9. Google Scholar CrossRef Search ADS   12 Foley K, Holly L, Schwender J: Minimally invasive lumbar fusion. Spine  2003; 28( 15): S26– 35. Google Scholar PubMed  13 Khoo L, Fessler R: Microendoscopic decompressive laminotomy for the treatment of lumbar stenosis. Neurosurgery  2002; 51( 5): S146– 54. Google Scholar PubMed  14 Rosen D, O’Toole J, Eichholz K: Minimally invasive lumbar spinal decompression in the elderly: outcome of 50 patients aged 75 years and older. Neurosurgery  2007; 60( 3): 503– 9. Google Scholar CrossRef Search ADS PubMed  15 Hudak E, Perry M: Outpatient minimally invasive spine surgery using endoscopy for the treatment of lumbar spinal stenosis among obese patients. J Orthop  2015; 12( 3): 156– 9. Google Scholar CrossRef Search ADS PubMed  16 Army Regulation 40-501: Standards of medical fitness. Washington, DC, Headquarters, Department of the Army, 2011. Available at http://annypubs.army.mil/epubs/40_Series_Collection_l.html; accessed March 30, 2015. 17 Army Regulation 635-40: Physical evaluation for retention, retirement, or separation. Washington, DC. Headquarters, Department of the Army, 2012. Available at http://armypubs.army.mil/epubs/635_Series_Collection_l.html; accessed March 30. 2015. 18 SECNAVINST 1850.4E. Enclosure 8: Medical Conditions and Physical defects Which Normally Are Cause for Referral to the Physical Evaluation Board (PEB). Available at http://www.secnav.navy.mil/mra/CORB/Documents/SECNAV%20INST%201850_4e.pdf; accessed 30 April 2002. 19 Crawford C, Glassman S, Mummaneni P, Knightly J, Asher A: Back pain improvement after decompression without fusion or stabilization in patients with lumbar spinal stenosis and clinically significant preoperative back pain. J Neurosurg Spine  2016; 25: 596– 601. Google Scholar CrossRef Search ADS PubMed  © Association of Military Surgeons of the United States 2018. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

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Military MedicineOxford University Press

Published: May 21, 2018

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