Return-to-active-duty rates after anterior cervical spine surgery in military pilots

Return to flight duty (RTFD) after posterior lumbar spine surgery for symptomatic lumbar disc herniation (LDH) and lumbar isthmic spondylolisthesis (LIS) in Chinese military pilots

BACKGROUND

Symptomatic lumbar disc herniation (LDH) and lumbar isthmic spondylolisthesis (LIS) present significant challenges for military pilots, which may result in grounding if not effectively managed. Surgical treatment for LDH and LIS may offer a pathway to return to flight duty (RTFD), but recent data on this crucial topic is lacking. This study seeks to address this gap by investigating the RTFD outcomes among Chinese military pilots who have undergone lumbar spine surgery for symptomatic LDH and LIS.

METHODS

A retrospective review was conducted on active-duty military pilots who underwent isolated decompressive or fusion procedures at an authorized military medical center from March 1, 2007, to March 1, 2023. The analysis utilized descriptive statistics to examine demographic, occupational, surgical, and outcome data, with a particular focus on preoperative flight status, recommended clearance by spine surgeons, and actual RTFD outcomes and time.

RESULTS

Among the identified cases of active-duty military pilots with LDH or LIS treated by lumbar surgery (n = 24), 70.8% (17 of 24) consistently maintained RTFD status without encountering surgical complications or medical issues during the follow-up period. Of the seven pilots who did not RTFD, one retired within a year of surgery, two had anterior cruciate ligament injuries, three had residual radicular symptoms, and one had chronic low back pain. Excluding pilots who retired and did not RTFD for reasons unrelated to their lumbar conditions, the RTFD rate stood at 81.0% (17 of 21). The median time for recommended clearance by spine surgeons was 143.0 days (inter-quartile range, 116.5-196.0), while the median duration for actual RTFD attainment was 221.0 days (inter-quartile range, 182.0-300.0). The median follow-up post-lumbar surgery was 1.7 years (inter-quartile range, 0.4-2.9).

CONCLUSION

Most military pilots diagnosed with symptomatic LDH and LIS can continue their careers and regain active-duty flight status following lumbar spine surgery, as reflected by the high RTFD rate. Lumbar spine surgery can successfully alleviate the physical constraints associated with spinal conditions, facilitating the return of military pilots to their demanding profession.

Subaxial Cervical Spine Motion With Different Sizes of Head-supported Mass Under Accelerative Forces

INTRODUCTION

The evolution of military helmet devices has increased the amount of head-supported mass (HSM) worn by warfighters. HSM has important implications for spine biomechanics, and yet, there is a paucity of studies that investigated the effects of differing HSM and accelerative profiles on spine biomechanics. The aim of this study is to investigate the segmental motions in the subaxial cervical spine with different sizes of HSM under Gx accelerative loading.

METHODS

A three-dimensional finite element model of the male head-neck spinal column was used. Three different size military helmets were modeled and incorporated into head-neck model. The models were exercised under Gx accelerative loading by inputting low and high pulses to the cervical vertebra used in the experimental studies. Segmental motions were obtained and normalized with respect to the non-HSM case to quantify the effect of HSM.

RESULTS

Segmental motions increased with an increase in velocity at all segments of the spine. Increasing helmet size resulted in larger motion increases. Angulations ranged from 0.9° to 9.3° at 1.8 m/s and from 1.3° to 10.3° at 2.6 m/s without a helmet. Helmet increased motion between 5% to 74% at 1.8 m/s. At 2.6 m/s, the helmet increased segmental motion anywhere from 10% to 105% in the subaxial cervical spine. The greatest motion was seen at the C5-C6 level, followed by the C6-C7 level.

CONCLUSIONS

The subaxial cervical spine experiences motion increases at all levels at both velocity profiles with increasing HSM. Larger helmet and greater impact velocity increased motion at all levels, with C5-C6 demonstrating the largest range of motion. HSM should be minimized to reduce the risk of cervical spine injury to the warfighter.

Effect of Fusion and Arthroplasty for Cervical Degenerative Disc Disease in Active Duty Service Members Performed at an Overseas Military Treatment Facility: A 2-Year Retrospective Analysis

INTRODUCTION

Among U.S. military active duty service members, cervicalgia, cervical radiculopathy, and myelopathy are common causes of disability, effecting job performance and readiness, often leading to medical separation from the military. Among surgical therapies, anterior cervical discectomy and fusion (ACDF) and cervical disc arthroplasty (CDA) are options in select cases; however, elective surgeries performed while serving overseas (OCONUS) have not been studied.

MATERIALS AND METHODS

A retrospective analysis of a prospectively collected surgical database from an OCONUS military treatment facility over a 2-year period (2019-2021) was queried. Patient and procedural data were collected to include ACDF or CDA surgery, military rank, age, tobacco use, pre- and post-operative visual analogue scales for pain, and presence of radiographic fusion after surgery for ACDF patients or heterotopic ossification for CDA patients. Chi-square and Student t-test analyses were performed to identify variables associated with return to full duty.

RESULTS

A total of 47 patients (25 ACDF and 22 CDA) underwent surgery with an average follow-up of 192.1 days (range 7-819 days). Forty-one (87.2%) patients were able to return to duty without restrictions; 10.6% of patients remained on partial or limited duty at latest follow-up and one patient was medically separated from the surgical cohort. There was one complication and one patient required tour curtailment from overseas duty for ongoing symptoms.

CONCLUSIONS

Both ACDF and CDA are effective and safe surgical procedures for active duty patients with cervicalgia, cervical radiculopathy, and cervical myelopathy. They can be performed OCONUS with minimal interruption to the patient, their family, and the military unit, while helping to maintain surgical readiness for the surgeon and the military treatment facility.

Prevalence and risk factors of occupational neck pain in Chinese male fighter pilots: a cross-sectional study based on questionnaire and cervical sagittal alignment

Background

Neck pain (NP) is a common musculoskeletal disorder among fighter pilots and has become a rising concern due to its detrimental impact on military combat effectiveness. The occurrence of NP is influenced by a variety of factors, but less attention has been paid to the association of NP with demographic, occupational, and cervical sagittal characteristics in this group. This study aimed to investigate the prevalence and risk factors of NP in Chinese male fighter pilots using a questionnaire and cervical sagittal measurements.

Methods

Demographic and flight-related data, as well as musculoskeletal pain information, were gathered from Chinese male fighter pilots via a self-report questionnaire. Cervical sagittal parameters were measured and subtypes were classified using standardized lateral cervical radiographs. Differences in various factors between the case and control groups were analyzed using t-tests or chi-square tests. Binary logistic regressions were conducted to explore potential risk factors contributing to NP. Predictors were presented as crude odds ratios (CORs) and adjusted odds ratios (AORs), along with their respective 95% confidence intervals (CIs).

Results

A total of 185 male fighter pilots were included in this cross-sectional study. Among them, 96 (51.9%) reported experiencing NP within the previous 12 months. The multivariate regression analysis revealed that continuous flight training (AOR: 4.695, 95% CI: 2.226-9.901, p < 0.001), shoulder pain (AOR: 11.891, 95% CI: 4.671-30.268, p < 0.001), and low back pain (AOR: 3.452, 95% CI: 1.600-7.446, p = 0.002) were significantly associated with NP.

Conclusion

The high 12-month prevalence of NP among Chinese male fighter pilots confirms the existence of this growing problem. Continuous flight training, shoulder pain, and low back pain have significant negative effects on pilots' neck health. Effective strategies are necessary to establish appropriate training schedules to reduce NP, and a more holistic perspective on musculoskeletal protection is needed. Given that spinal integrated balance and compensatory mechanisms may maintain individuals in a subclinical state, predicting the incidence of NP in fighter pilots based solely on sagittal characteristics in the cervical region may be inadequate.

Return to sport and active military duty after cervical disc arthroplasty: A systematic review

Introduction

Cervical disc arthroplasty (CDA) has been established as an effective treatment for cervical disc degeneration or herniation in the general population. Return to sport (RTS) outcomes in athletes remain unclear.

Objective

The purpose of this review was to evaluate RTS following single-level, multi-level, or hybrid CDA, with additional return to activity context provided by return to duty (RTD) outcomes in active-duty military.

Methods

Medline, Embase, and Cochrane were searched through August 2022 for studies that reported RTS/RTD after CDA in athletic or active-duty populations. Data was extracted on the following topics: surgical failures/reoperations, surgical complications, RTS/RTD, and postoperative time to RTS/RTD.

Results

Thirteen papers covering 56 athletes and 323 active-duty members were included. Athletes were 59% male with a mean age of 39.8 years and active-duty members were 84% male with a mean age of 40.9 years. Only 1 of 151 cases required reoperation and only 6 instances of surgical complications were reported. Classified as return to general sporting activity, RTS was observed in 100% of patients (n = 51/51) after an average of 10.1 weeks to training and 30.5 weeks to competition. RTD was observed in 88% of patients (n = 268/304) after an average of 11.1 weeks. Average follow-up was 53.1 months for athletes and 13.4 months for the active-duty population.

Conclusion

CDA displays excellent RTS and RTD rates in physically demanding populations at rates superior or equivalent to alternative treatments. Surgeons should consider these findings when determining the optimal cervical disc treatment approach in active patients.

Perspectives on Cervical Arthroplasty in Navy and Marine Corps Tactical Jet Aircrew

Symptomatic cervical spondylosis is a progressive degenerative condition of the cervical spine commonly resulting in functionally-limiting pain, weakness, and/or limited dexterity. Symptomatic cervical spondylosis is believed to occur at higher rates in military aviators than civilian counterparts and is a disqualifying condition for all Navy and Marine Corps aircrew. This condition is non-waiverable for tactical jet (ejection-seat-based) aviators. Medical attrition of experienced tactical jet aircrew from the military aviation community results in substantial cost to the U.S. Government, reduces fleet combat capability, and adversely impacts career progression and retention. The clinical maturation of cervical total disc replacement (TDR) technology over the last 2 decades has revolutionized the treatment of symptomatic cervical spondylosis and enabled a return to duty for hundreds of military service members in non-aviation fields. TDR studies demonstrate equal or superior functional outcomes, rates of symptom resolution, reduced complication and reoperation rates, and lower long-term cost compared to traditional Anterior Cervical Discectomy and Fusion (ACDF). Although initial computational modeling studies have evaluated cervical arthroplasty performance during rotary-wing crash impacts, safety within the dynamic tactical jet environment has not yet been established. The purpose of this article is to review factors relevant to TDR safety and outcomes and to propose a framework to evaluate the safety of TDR in Navy and Marine Corps tactical jet aircrew, to ultimately inform aeromedical algorithms regarding return to flight after TDR.

Is Self-reported Return to Duty an Adequate Indicator of Return to Sport and/or Return to Function in Military Patients?

BACKGROUND

In the military, return-to-duty status has commonly been used as a functional outcome measure after orthopaedic surgery. This is sometimes regarded similarly to return to sports or as an indicator of return to full function. However, there is variability in how return-to-duty data are reported in clinical research studies, and it is unclear whether return-to-duty status alone can be used as a surrogate for return to sport or whether it is a useful marker for return to full function.

QUESTIONS/PURPOSES

(1) What proportion of military patients who reported return to duty also returned to athletic participation as defined by self-reported level of physical activity? (2) What proportion of military patients who reported return to duty reported other indicators of decreased function (such as nondeployability, change in work type or level, or medical evaluation board)?

METHODS

Preoperative and postoperative self-reported physical profile status (mandated physical limitation), physical activity status, work status, deployment status, military occupation specialty changes, and medical evaluation board status were retrospectively reviewed for all active-duty soldiers who underwent orthopaedic surgery at Madigan Army Medical Center, Joint Base Lewis-McChord from February 2017 to October 2018. Survey data were collected on patients preoperatively and 6, 12, and 24 months postoperatively in all subspecialty and general orthopaedic clinics. Patients were considered potentially eligible if they were on active-duty status at the time of their surgery and consented to the survey (1319 patients). A total of 89% (1175) were excluded since they did not have survey data at the 1 year mark. Of the remaining 144 patients, 9% (13) were excluded due to the same patient having undergone multiple procedures, and 2% (3) were excluded for incomplete data. This left 10% (128) of the original group available for analysis. Ninety-eight patients reported not having a physical profile at their latest postoperative visit; however, 14 of these patients also stated they were retired from the military, leaving 84 patients in the return-to-duty group. Self-reported "full-time duty with no restrictions" was originally used as the indicator for return to duty; however, the authors felt this to be too vague and instead used soldiers' self-reported profile status as a more specific indicator of return to duty. Mean length of follow-up was 13 ± 3 months. Eighty-three percent (70 of 84) of patients were men. Mean age at the preoperative visit was 35 ± 8 years. The most common surgery types were sports shoulder (n = 22) and sports knee (n = 14). The subgroups were too small to analyze by orthopaedic procedure. Based on active-duty status and requirements of the military profession, all patients were considered physically active before their injury or surgery. Return to sport was determined by asking patients how their level of physical activity compared with their level before their injury (higher, same, or lower). We identified the number of other indicators that may suggest decreased function by investigating change in work type/level, self-reported nondeployability, or medical evaluation board. This was performed with a simple survey.

RESULTS

Of the 84 patients reporting return to duty at the final follow-up, 67% (56) reported an overall lower level of physical activity. Twenty-seven percent (23) reported not returning to the same work level, 32% (27) reported being nondeployable, 23% (19) reported undergoing a medical evaluation board (evaluation for medical separation from the military), and 11% (9) reported a change in military occupation specialty (change of job description).

CONCLUSION

Return to duty is commonly reported in military orthopaedics to describe postoperative functional outcome. Although self-reported return to duty may have value for military study populations, based on the findings of this investigation, surgeons should not consider return to duty a marker of return to sport or return to full function. However, further investigation is required to see to what degree this general conclusion applies to the various orthopaedic subspecialties and to ascertain how self-reported return to duty compares with specific outcome measures used for particular procedures and subspecialties.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

Hybrid surgery: a comparison of early postoperative outcomes between anterior cervical discectomy and fusion and cervical disc arthroplasty

OBJECTIVE

Hybrid surgery (HS) is the combination of anterior cervical discectomy and fusion (ACDF) and cervical disc arthroplasty (CDA) at different levels in the same operation. The aim of this study was to investigate perioperative variables, 30-day postoperative outcomes, and complications of HS in comparison with those of CDA and ACDF.

METHODS

The authors queried the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) registry for patients who underwent multilevel primary HS, CDA, and ACDF for degenerative disc disease from 2015 to 2019. The authors compared these three operations in terms of 30-day postoperative outcomes, specifically readmission and reoperation rates, discharge destination, and complications.

RESULTS

This analysis included 439 patients who underwent HS, 976 patients who underwent CDA, and 27,460 patients who underwent ACDF. Patients in the HS and CDA groups were younger, had fewer comorbidities, and myelopathy was less often the indication for surgery compared with patients who underwent ACDF. For the HS group, the unplanned readmission rate was 0.7%, index surgery-related reoperation rate was 0.3%, and nonroutine discharge rate was 2.1%. Major and minor complications were also rare, with rates of 0.2% for each. The mean length of stay in the HS group was 1.5 days. The association of HS with better outcomes in univariate analysis was not evident after adjustment for confounding factors.

CONCLUSIONS

The authors found that HS was noninferior to ACDF and CDA in terms of early postoperative outcomes among patients treated for degenerative disc disease.

Comparative Finite Element Modeling Study of Anterior Cervical Arthrodesis Versus Cervical Arthroplasty With Bryan Disc or Prodisc C

INTRODUCTION

Cervical disc arthroplasty (CDA), a motion-preserving alternative to anterior cervical discectomy and fusion (ACDF), is used in military patients for the treatment of disorders such as spondylosis. Since 2007, the FDA has approved eight artificial discs. The objective of this study is to compare the biomechanics after ACDF and CDA with two FDA-approved devices of differing designs under head and head supported mass loadings.

MATERIALS AND METHODS

A previously validated osteoligamentous C2-T1 finite element model was used to simulate ACDF and two types of CDA (Bryan and Prodisc C) at the C5-C6 level. The hybrid loading protocol associated with in vivo head and head supported mass was used to apply flexion and extension loading. First, intact spine was subjected to 2 Nm of flexion extension and the range of motion (ROM) was measured. Next, for each surgical option, flexion-extension moments duplicating the same ROM as the intact spine were determined. Under these surgery-specific moments, ROM and facet force were obtained at the index level, and ROM, facet force, and intradiscal pressure at the rostral and caudal adjacent levels.

RESULTS

ACDF led to increased motion, force and pressures at the adjacent levels. Prodisc C led to increased motion and facet force at the index level, and decreased motion, facet force, and intradiscal pressure at both adjacent levels. Bryan produced less dramatic biomechanical alterations compared with ACDF and Prodisc C. Numerical results are given in the article.

CONCLUSIONS

Recognizing that ROM is a clinical measure of spine stability/performance, CDA demonstrates a more physiological biomechanical response than ACDF, although the exact pattern depends on the implant design. Anterior and posterior column load-sharing patterns were different between the two implants and may affect implant selection based on the anatomical and pathological state at the index and adjacent levels.