U.S. Military Recruits Waived for Pathological Curvature of the Spine: Increased Risk of Discharge From Service

MILITARY MEDICINE, 176, 5:519, 2011 U.S. Military Recruits Waived for Pathological Curvature of the Spine: Increased Risk of Discharge From Service MAJ Sheryl A. Bedno, MC USA * ; MAJ Bradley Gardiner, MC USA ; Yuanzhang Li, PhD * ; COL Andrew R. Wiesen, MC USA ; Jordan A. Firestone, MD, PhD, MPH ; COL David W. Niebuhr, MC USA * ABSTRACT Selective accession waivers for medically disqualifying conditions like spinal curvature are one way the military meets its manpower needs. We evaluated retention patterns during the first 2 years of service of a cohort of military recruits with waivers for pathological curvature of the spine (spinal curvature). Recruits waived for spinal curvature ( n = 417), who accessed from 1998 to 2005 were identified and matched with 3 qualified recruits. Kaplan Meier survival analysis and Cox proportional hazards model were used to compare survival patterns and adjusted attrition hazard estimates. Waived recruits experienced significantly increased risk of all cause discharge (relative risk = 1.3; 95% confidence interval: 1.1, 1.5) and existing prior to service discharge (relative risk = 2.4; confidence interval: 1.6, 3.5). Despite the increased risk of discharge, current waiver criteria allowed a majority with spinal curvature to complete at least 2 years of service. Policy makers must consider risks and benefits before modifying the current accession standard for spinal curvature. * Department of Epidemiology, Walter Reed Army Institute of Research, 503 Robert Grant Road, Silver Spring, MD 20910. Occupational and Environmental Medicine Residency Program, Department of Preventive Medicine and Biometrics, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814. Public Health Residency, Madigan Army Medical Center, ATTN: MCHJ-PV, Tacoma, WA 98431. Department of Environmental and Occupational Health Sciences, School of Public Health, Box 357234, University of Washington, Seattle, WA 98195-7234. The views expressed in this article are those of the authors and should not be construed to represent the positions of the Department of the Army or Department of Defense. INTRODUCTION Scoliosis is the most common curvature of the spine among adolescents and young adults, with a prevalence estimated at 3% in the United States. 1 Scoliosis is a lateral curvature of the spine measuring at least 10 on an x-ray as determined commonly by the Cobb method. 2 The Armed Services use a fixed set of criteria for those applying to serve in the military. Applicants undergo a medical evaluation to assess their suitability, which includes screening for common medical and behavioral conditions at the Military Entrance Processing Station (MEPS). The screening test specific for scoliosis during this evaluation is the Adams forward bend test. 2 An abnormal test result leads to an x-ray examination of the spine and potentially an orthopedic consultation. Lumbar or thoracic scoliosis greater than 30 or kyphosis and lordosis greater than 50 as measured by the Cobb method preclude the applicant from serving. The individual is also disqualified if the condition is symptomatic, if the condition prevents physically active civilian life, or if the condition interferes with proper wear of the military uniform. 3 In 2008, there were 310 individuals disqualified for deviation and curvature of the spine among enlisted applicants for all military services.4 Candidates with a disqualifying condition who still wish to serve in the military may seek a medical waiver. Waivers are granted by authorized, service-specific officials after a detailed individual case review to include medical records, examinations, and consultations. Each branch of the Armed Services may adjust their waiver criteria to meet manpower needs and consider the service-specific rigors of basic combat training. From 2002 to 2007, there were approximately 230 individuals per year across all services who applied for a waiver for spinal curvature-related conditions with an overall approval rate of approximately 45%. 5 Department of Defense accession standards are periodically reviewed to ensure relevance and utility. A previous report from the Accession Medical Standards Analysis and Research Activity, using recruit data collected between 1995 and 2001, demonstrated that recruits with medical waivers for spinal curvature had a statistically significant but relatively small absolute increased risk of premature discharge for any reason ( all cause discharge) and risk of discharge within 180 days of military service for medical conditions that existed prior to service (EPTS). 6 EPTS discharges for spinal curvature within the first 180 days of service are relatively rare, with only 102 reported in 2008. 5 The purpose of this study was to evaluate the ability of recruits with waivers for pathological curvature of the spine (spinal curvature) to complete their initial minimum enlistment period and estimate their risk of premature discharge from the service. We hypothesized that receiving a waiver for spinal curvature would increase the risk of premature discharge from military service, for all cause and for spinerelated conditions. MILITARY MEDICINE, Vol. 176, May 2011 519

METHODS Study Population and Study Design This is a matched cohort study utilizing pre-existing data on U.S. military recruits. All subjects in the study entered the Armed Services from January 1998 to December 2005. In this study, the endpoint of interest is any discharge for specific reasons other than successful completion of a minimum enlistment obligation. Reasons for discharge were classified as EPTS discharge and all cause discharge. EPTS discharge is defined as a disqualifying medical condition that existed prior to service, presenting within 180 days of enlistment. All cause discharge represents discharges related to medical (including both EPTS and service related), behavioral, performance, or other reasons. All subjects were censored at 2 years after accession because of discharge data availability through December 2007 at the time the analysis was performed. The International Classification of Diseases 9th Revision Clinical Modification (ICD-9) code 737 applies to diagnoses associated with deviation or curvature of the spine. 7 It is used for individuals with a history of spinal curvature, regardless of severity or treatment, and for those newly diagnosed during the accession medical examination. The specific inclusion criteria for primary spinal curvature waived recruits in this study was the presence of 1 of the following ICD-9 diagnoses codes: 737 (curvature of the spine), 737.1 (kyphosis, acquired), 737.2 (lordosis, acquired), and 737.3 (kyphoscoliosis and scoliosis). Waivers for ICD-9 diagnoses coded as 737.4 (curvature of the spine associated with other conditions), 737.8 (other acquired deformities), and 737.9 (unspecified curvature of spine) were excluded from analysis. We identified 506 recruits who were granted waivers for spinal curvature at initial enlistment. After excluding recruits with waiver applications unapproved at the beginning of the study ( n = 61), with an exclusionary diagnosis ( n = 7), with a follow-up time equal to 0 ( n = 6), or with incomplete records ( n = 15), a total of 417 spinal curvature waived recruits remained in the study. Of the total waived recruits in the study, 47% had waivers for curvature of the spine, 32% for scoliosis, 18% for kyphosis, and 2% for lordosis. Each spinal curvature-waived recruit was matched with 3 qualified recruits, yielding a total study size of 1,668 subjects. Each member of the comparison group was chosen at random from qualified recruits during that time period, after matching on the date of entry into service (continuous scale within 2 months), age (continuous scale within 1 year), race (white, black, and other), gender, body mass index (continuous scale within 2 units), Armed Forces Qualification Test (continuous scale from 0 to 100, matched within 25 points), and military service branch (Army, Navy, Marines, and Air Force), to minimize potential confounding from these known risk factors for early attrition. 8 EPTS discharge data were provided by U.S. Military Entrance Processing Command, and all cause discharge data were provided by the Defense Manpower Data Center. Interservice separation codes (ISC) were used to categorize reasons for discharge. Statistical Analysis The 2 main outcomes of interest, EPTS discharge and all cause discharge, were analyzed separately using categorical analyses. All statistical analyses were performed using SAS version 9.2 (SAS Institute, Cary, NC) and Epi Info version 3.5.1 (Centers for Disease Control and Prevention, Atlanta, GA). Significance was defined as p < 0.05. Kaplan Meier survival analysis was used to estimate the survival functions or retention patterns for service on active duty for the spinal curvature-waived group compared to the qualified group for all cause discharge. The Cox proportional hazards (PH) model for all cause discharge was adjusted for sex, age, race, and Armed Forces Qualification Test scores because previous studies have shown an association between military discharge and these demographics. 8 This analysis entails the specification of a linear-like model for the log hazard and the estimation of the hazard ratio (HR) for all factors in the model, including the status for the spinal curvaturewaived group compared to the qualified group. PH assumption for Cox modeling was examined by hazard function and by comparing the stability of the HRs at 6-month intervals from 6 to 24 months of military service. RESULTS The entire study cohort (spinal curvature waived and qualified) was compared to a published, fiscal year, active duty, enlisted recruit population 9 (Table I ). Both groups were predominantly male, white, and aged 17 19 years. Females, blacks, age less than 20 years, and Navy recruits were over-represented in the study compared to the total enlisted population. Reasons for EPTS discharge differed between groups ( Table II ). Curvature of the spine accounted for 66% of all EPTS discharges in the spinal curvature-waived group compared to 2% among qualified recruits. Frequencies of other spine or back conditions, including ankylosing spondylitis, spondylosis, intervertebral disc disorders, and other unspecified cervical and back disorders, were similar in both study groups. Nonmusculoskeletal reasons for discharge were more common among the qualified (77%) than in the spinal curvature-waived recruits (20%). Reasons for all cause discharge also differed between groups (Table III ). Unqualified for active duty other was twice as common in spinal curvature-waived than in qualified recruits. This category of unqualified for active duty-other discharge is used when a recruit develops a new medical condition that does not meet medical retentions standards, and the recruit waives the right to either an occupational reclassification or a medical evaluation board review, with potential for a service-related disability discharge. The proportion of fraudulent entry and erroneous enlistment was less common in spinal curvature-waived than qualified recruits. The proportion of 520 MILITARY MEDICINE, Vol. 176, May 2011

TABLE I. Frequency of Demographics by Study Groups and Comparison Recruit Population TABLE III. Reasons for All Cause 2-Year Discharge: Spinal Curvature-Waived vs. Recruits N = 417 N = 1,251 Active Duty Enlisted Population a (%) Gender Male 302 (72.4) 906 (72.4) 83.3 Female 115 (27.6) 345 (27.6) 16.7 Race White 281 (67.4) 843 (67.4) 75.4 Black 106 (25.4) 318 (25.4) 13.0 Other 30 (7.2) 90 (7.2) 11.6 b Age (Years) 17 19 281 (67.4) 860 (68.8) 54.8 20 23 111 (26.6) 322 (25.7) 33.5 24 34 25 (6.0) 69 (5.5) 11.7 Body Mass Index <25 364 (87.3) 1,086 (86.8) NA 25 53 (12.7) 165 (13.2) NA Service Army 208 (49.9) 624 (49.9) 41.7 Navy 136 (32.6) 408 (32.6) 21.4 Marines 67 (16.1) 201 (16.1) 18.7 Air Force 6 (1.4) 18 (1.4) 18.2 NA, not applicable or data not available. a Active duty enlisted (accessions) population data (FY06). b Includes unknown and 2 or more races. TABLE II. Categoriesa Reasons for EPTS Discharge: Spinal Curvature- Waived vs. Recruits Curvature of the Spine * 27 (65.9) 1 (1.9) Musculoskeletal 4 (9.8) 9 (17.3) Dorsopathies 2 (4.9) 2 (3.9) Other, Nonmusculoskeletal * 8 (19.5) 40 (76.9) Total 41 (100) 52 (100) * p < 0.01. a Diagnostic categories are mutually exclusive. entry level performance and conduct and character or behavior disorder discharges was similar in both study groups. The spinal curvature-waived subjects had a significantly lower ( p < 0.01) cumulative survival for all cause discharge within the 2-year study period ( Fig. 1 ). The waived group had an approximately 10% net decreased survival compared to qualified recruits from approximately 3 to 24 months of military service. The spinal curvature-waived group had a higher rate of both EPTS and all cause discharge outcomes ( Table IV ). These waived recruits were 2.4 times more likely to be discharged due to an EPTS condition compared to qualified recruits. They were 1.3 times more likely to be discharged for any reason compared to qualified recruits. The stability of the HR (1.4 1.6) with overlapping 95% confidence intervals [CIs] from 6 to 24 months for the all cause model confirmed that the PHs model assumption was appropriate (results not shown). Across the entire 2-year study Discharge Categories Unqualified for Active 55 (40.4) 50 (16.0) Duty Other a, * Entry Level Performance 19 (14.0) 48 (15.3) and Conduct b Fraudulent Entry c, ** 7 (5.2) 41 (13.1) Erroneous Enlistment d 5 (3.7) 20 (6.4) Character or Behavior 6 (4.4) 15 (4.8) e Disorder f, Other ** 44 (32.4) 139 (44.4) Total 136 (100) 313 (100) * p < 0.01; **p < 0.05. a Discharge for medical conditions that develop on active duty and do not meet retention standards where the recruit waives their right to a medical evaluation or reclassification board. b Includes failure to meet physical fitness standards or weapons qualifications. c Includes falsification of information on application for military service. d Includes incorrect qualification for military service through no fault of the applicant. e Includes personality disorders and enuresis. f Includes EPTS, disability evaluations, and numerous other categories. TABLE IV. Relative Risk for EPTS Discharge and All Cause 2-Year Discharge, Relative Risk (95% CI) EPTS discharge 41 (9.8) 52 (4.2) 2.4 (1.6, 3.5) All cause 2-year discharge 136 (32.6) 313 (25.0) 1.3 (1.1, 1.5) period, the HR was 1.4 (95% CI: 1.1, 1.7) for all cause discharge for spinal curvature-waived compared to qualified recruits. DISCUSSION This study demonstrated a significantly greater risk of both all cause and EPTS discharge for recruits who were granted waivers for spinal curvature compared to qualified recruits. The top reasons for EPTS discharge (curvature of the spine) and for all cause discharge (unqualified for active duty other) may represent a post-enlistment aggravation of a medical condition. Although recruits may have misrepresented a history of back pain or physical activity limitations at the time of spinal curvature screening at the MEPS, the low rate of EPTS discharge (2%) among qualified recruits suggests that diagnoses missed at MEPS would only account for a small portion of the observed difference. It seems more likely that the physical demands of military duties, especially during basic training, would aggravate an underlying condition and thereby increase EPTS discharge rates. Back pain is the most commonly reported symptom of curvature of the spine and may interfere with military performance. Back pain has been reported to be more frequent and of greater intensity among people with scoliosis, the most MILITARY MEDICINE, Vol. 176, May 2011 521

FIGURE 1. Retention probability for all cause discharge within 2 years of military service: spinal curvature-waived vs. qualified recruits. *Includes the following tests: Log Rank, Wilcoxon, and Log Likelihood ratio. common curvature of the spine. 10 12 These studies have shown that return to sports is inversely associated with back pain and functional impairment, 13 and the association is variable between individuals. 14 Although scoliosis curve severity has not been found to predict back pain, 15 certain radiographic features (eg, lateral listhesis) tend to have a higher frequency of back pain. 10 A 50-year follow-up of untreated adults with late-onset scoliosis found minimal physical impairment among these individuals, except for back pain and cosmetic concerns. 16 Based on these observations, it is important that criteria used for service qualification address more than the severity of spinal curvature. Criteria should address the individual s overall history, including symptom description and duration, objective examination findings including radiographic testing, and most importantly the individual s functional capacities. One limitation of this study is that ICD-9 diagnosis codes for spinal curvature-waived recruits do not detail clinical information such as duration, severity, treatment, or impairment related to the diagnosis. Furthermore, diagnoses associated with attrition were available only for soldiers who had an EPTS discharge. Soldiers who were discharged for non-epts medical reasons have only a Defense Manpower Data Center ISC. This is an administrative code that denotes a medical discharge related to military service but does not specify a diagnosis. In these cases, the primary reason for discharge could be any medical condition, and pathological curvature of the spine cannot be ruled out as an underlying contributor. Nonetheless, it is reasonable to expect that a soldier with a waiver for deviation or curvature of the spine who is discharged for a spine-related condition would be categorized with an EPTS designation, and would, therefore, be included in the EPTS discharge outcome. Unfortunately, these 2 are not directly comparable because the ISC for all cause discharge is provided by administrative personnel, whereas the diagnosis for EPTS medical is obtained from medical records. Another limitation is that the medical accession standards are updated approximately every 4 years. The conditions included in this study were evaluated according to the Department of Defense Instruction 6130.4 (Medical Standards for Appointment, Enlistment, or Induction in the Military Services).17 The changes to the spinal curvature standard from the 2005 to 2010 versions are slightly more restrictive (addition of thoracic scoliosis and decrease from 55 to 50 for kyphosis and lordosis) and additionally specify measurement by the Cobb method. Since the study was matched on several variables associated with attrition to include service, gender, age, and race, we could not analyze whether these variables contribute to differences in outcomes between the 2 groups. This evaluation was not thought to be critical because medical accession standards are not based on demographic characteristics. Future research into those variables could be done with multivariate survival analysis using an unmatched, qualified comparison group representing the general population of recruits, rather than a group matched to the spinal curvature-waived recruits. Of course, this would require adequate numbers of subjects across the various strata within the selected covariates of interest. In the future, it may also be useful to perform a case control study that estimates the risk of having had a spinal curvature waiver for cases discharged from service compared to controls who were not discharged. This study gives a clearer picture of how spinal curvature affects success as indicated by retention in the military. The survival curve for all cause discharge indicates that after 2 years, approximately 65% of the waived recruits remain in military service compared to 75% of qualified recruits. These individuals may not have had the opportunity to serve in the military if waiver criteria were more restrictive or if waivers were not granted at all. Recruits are granted waivers for spinal curvature so that soldiers with minimal disease and potential to remain asymptomatic under physically demanding military conditions can serve. Although this difference (65% vs. 75%) was statistically significant, it is not clear whether it is operationally significant to the U.S. military. The small difference suggests that recruits who are motivated enough to go through the entire waiver process, including medical history review, diagnostic testing, and specialty consultation, are as motivated to serve as qualified recruits. The findings of this study generally validate the services disqualifications and waiver policies for pathological curvature of the spine and should be included in future review of the accession standard. Policy makers will need to consider the potential costs of a more lenient spinal curvature accession standard, including potential occupational and deployment limitations, associated morbidity, and disability attrition, against the potential benefits of increased accessions in their 522 MILITARY MEDICINE, Vol. 176, May 2011

goal to ensure that standards are based on the best available medical and scientific evidence. ACKNOWLEDGMENT This study was funded by the Defense Health Program (no. 847714). REFERENCES 1. Aebi M : The adult scoliosis. Eur Spine J 2005 ; 14: 925 48. 2. Bunnell WP : Selective screening for scoliosis. Clin Orthop Relat Res 2005 ; 434 : 40 5. 3. Department of Defense Instruction 6130.03 : Medical Standards for Appointment, Enlistment, or Induction in the Armed Forces. Available at www.dtic.mil/whs/directives/corres/pdf/613003p.pdf, January 18, 2005; accessed August 20, 2010. 4. Accession Medical Standards Analysis and Research Activity (AMSARA) : 2009 Annual Report. Available at http://www.amsara.amedd.army.mil/ 5. Accession Medical Standards Analysis and Research Activity (AMSARA) : 2008 Annual Report. Available at http://www.amsara.amedd.army.mil/ 6. Accession Medical Standards Analysis and Research Activity (AMSARA) : 2003 Annual Report. Available at http://www.amsara.amedd.army.mil/ 7. Hart A, Stegman M, Ford B (editors): International Classification of Diseases, 9th Revision, Clinical Modification (2010). Eden Prairie, MN, Ingenix. 8. Niebuhr DW, Powers TE, Li Y, Millikan AM : The enlisted accession medical process. In: Morbidity and Attrition Related to Medical Conditions in Recruits, pp 59 79. Edited by Department of the Army, Office of the Surgeon General. Washington, DC, Borden Institute, 2006. 9. Population Representation in the Military Services (2006) : Office of the Under Secretary of Defense, Personnel and Readiness. Available at http:// prhome.defense.gov/mpp/accession%20policy/poprep_fy06/ ; accessed August 20, 2010. 10. Ascani E, Bartolozzi P, Logroscino CA, et al : Natural history of untreated idiopathic scoliosis after skeletal maturity. Spine 1986 ; 11: 784 9. 11. Cordover AM, Betz RR, Clements DH, Bosacco SJ : Natural history of adolescent thoracolumbar and lumbar idiopathic scoliosis into adulthood. J Spinal Disord 1997 ; 10: 193 6. 12. Goldberg MS, Mayo NE, Poitras B, Scott S, Hanley J : The Ste-Justine Adolescent Idiopathic Scoliosis Cohort Study. Part I: Description of the study. Spine 1994 ; 19: 1551 61. 13. Parsch D, Gartner V, Brocai DR, Carstens C, Schmitt H : Sports activity of patients with idiopathic scoliosis at long-term follow-up. Clin J Sport Med 2002 ; 12: 95 8. 14. Schiller JR, Eberson CP. Spinal Deformity and Athletics : Sports Med Arthrosc 2008 ; 16: 26 31. 15. Hill D, Parent E, Lou E, Mahood J : Can future back pain in AIS subjects be predicted during adolescence from the severity of the deformity? Stud Health Technol Inform 2008 ; 140: 249 53. 16. Weinstein SL, Dolan LA, Spratt KF, et al : Health and function of patients with untreated idiopathic scoliosis: a 50-year natural history study. JAMA 2003 ; 289: 559 67. 17. Department of Defense Instruction 6130.4 : Medical Standards for Appointment, Enlistment, or Induction in the Armed Forces. Available at http://biotech.law.lsu.edu/blaw/dodd/corres/html/61304.htm, April 2, 2004; accessed August 20, 2010. MILITARY MEDICINE, Vol. 176, May 2011 523