Appendix 1.Intervention and control descriptions, definitions of terms, sources of data, data collection procedures, and statistical analysis procedures
This appendix provides technical information for the reader, including descriptions of the Spine Team and current standard of care for work-disabling spine conditions, definitions of the terms disability and attrition, procedures used for data collection, and formulas for the calculation of rates used for the statistical analysis.
The Spine Team at Naval MedicalCenterPortsmouth
The Spine Team provides coordinated care and includes two fellowship-trained orthopaedic spine surgeons, one to two board-certified orthopaedic physical therapists with at least one having specialized training in the spine, a clinical psychologist with specialized training in pain management, a physician assistant, physiatrist, and a chiropractor. Once active-duty service members are referred to the Spine Team, the consult is screened by a spine surgeon who will assess the need for a surgical or nonsurgical consultation. From there the surgical patients are seen by a surgeon and the nonsurgical cases are distributed among all the other providers.If deemed necessary by the team, patients are also seen by a clinical psychologist.
Current Standard of Care at Naval MedicalCenterSan Diego
The current standard of care for active-duty service members with work-disabling spine conditions in both San Diego and the Hampton Roads catchment area is as follows: They are initially seen by their health care provider at one of several branch medical clinics or various types of operational clinics such as onboard ship, aviation squadron, etc.After initial triage/care, the members are either treated and released or referred to one of several physical therapy or chiropractic clinics. If the active-duty service member requires further evaluation, he or she is referred to a specialty clinic[15].
Definitions of Disability and Attrition
In the context of this study, disability is represented by the assignment of limited duty (LIMDU).LIMDU status relieves active-duty service members from their normal duties and allows time for recovery.Because active-duty service members are relieved of their duties, LIMDU can be perceived as having negative career consequences. Active-duty service members assigned to LIMDU are recorded in the Navy Medical Board Online Tri-service Tracking System.
Attrition is represented by a Physical Evaluation Board (PEB) dictation.Not all PEBs result in separation from military service; however, PEBs represent the formal action of US Navy Bureau of Medicine and Surgery to evaluate an active-duty service member’s fitness for duty.The outcome of a PEB in most cases is separation from military service. US Navy guidelines permit up to two LIMDU periods not exceeding a total of 12 months.If a member is unable to resume full duty after a 12-month period of LIMDU, in most cases, a PEB is dictated.The investigators chose to interpret the PEB dictation as a surrogate indicator for attrition.PEB dictations are also recorded in the Navy Medical Board Online Tri-service Tracking System.
Descriptions of Data Sources Used in the Study
US Military’s Electronic Health Care Records System
The Composite Health Care System is the administratively releasable electronic medical record extract of the Department of Defense’s Armed Forces Health Longitudinal Technology Application.Inpatient and outpatient medical records are available through the Composite Health Care System.Not all medical encounters for an active-duty service member are available through the Composite Health Care System.Information available through the Composite Health Care System includes subject demographics, clinic Medical Expense & Performance Reporting System codes, Current Procedure Terminology codes, International Classification of Diseases, 9th Revision (ICD-9) codes, and Defense Medical Information System codes.
Medical Board Online Tri-Service Tracking (MedBOLTT)
Eligible subjects for this study were identified from MEDBOLLT.MEDBOLLT is an Internet-based disability tracking system maintained by BUMED.MEDBOLLT contains information on all LIMDU assignments and PEBs for active-duty service members. This tracking system captures and shares data globally for any active-duty service member assigned to LIMDU or referred to a PEB currently or historically. MEDBOLTT data are secured with access to authorized personnel only.Multiple users with an involvement in a disability case, eg, the individual's Primary Care Manager, administrative personnel, and PEB personnel among others, contribute and update data stored in MEDBOLTT as the disability case proceeds[4]. MEDBOLLT is managed locally at Navy installations; there is a MEDBOLLT office at Portsmouth and another at San Diego.
Data Collection Procedures
The investigators requested tabulations of all MEDBOLLT data regarding LIMDU and PEB assignments made at Portsmouth and San Diego for the period of January 1, 2007, to December 31, 2009.The initial request allowed investigators to report on the number of active-duty service members with work-disabling spine conditions.
The investigators next requested MEDBOLLT records of active-duty service members assigned LIMDU or PEB referral for a work-disabling spine condition during the years 2007, 2008, and 2009.Candidate records were identified from MEDBOLLT by using selected spine-related ICD-9 codes.
Because the majority of LIMDU and PEB assignments for a work-disabling spine condition occurred at the ambulatory orthopaedic and neurosurgery clinics, the investigators selected only the assignments made at these two clinics.The investigators used clinical locator codes to identify these clinics from the MEDBOLLT data set.The tabulations were generated to categorize active-duty service members by gender, unit identification code, age at first visit, year, clinical location, and facility.The query did not distinguish whether the visit was for a new onset or followup.These counts represent the number of active-duty service members under treatment at the orthopaedic and neurosurgery clinics at Portsmouth and San Diego, respectively, and serve as the denominator for calculating proportions and risks, described subsequently.
Case Identification
The population under study included US Navy and US Marine Corps active-duty service members, aged 18 to 64 years, who had been placed on first-career LIMDU because of a work-disabling spine condition with a diagnosisindicating a specific pathology who were treated at Portsmouth,VA, USA, and San Diego,CA, USA, catchment areas.
The following ICD-9 codes were used by the investigators for inclusion in the study: root lesions (353.x); dorsopathies of the neck, back, and thoracic regions (721.x-724.x); osteopathies (737.x–739.x); and sprains and strains (847.x).These codes represent spine conditions that do not involve the central nervous system or fracture.We excluded spine-related conditions that had central nervous system involvement and vertebral fractures from the study because these conditions require specific management other than the type of care delivered by the Spine Team.
Composite Health Care System Extracts
The investigators linked the Composite Health Care System extract with the code labels for Current Procedural Terminology codes, ICD-9 codes, Medical Expense & Performance Reporting System codes, and disposition (work status) codes.Only those subjects whose LIMDU determination was completed at the ambulatory orthopaedic or neurosurgery clinic at Portsmouth or San Diego were included.Once these subjects were identified, the Composite Health Care System administratively releasable medical encounter data were pulled and linked to the MEDBOLLT records. Composite Health Care System data were requested for clinical encounters from the beginning of 2005 to the end of 2011.This gave the investigators a 2-year period before first-career LIMDU and an 18-month followup period after the assignment of the first-career LIMDU.We collected additional data 2 years before and after our study periods of 2007 to 2009 to allow us to evaluate treatment patterns for patients who received care before and after they receive LIMDU status or PEB referral. Our study included only those first-career LIMDU designations that took place in the period 2007 to 2009.
The data were analyzed with respect to two different outcomes: first-career LIMDU status for work-disabling spine conditions and the progression of a first-career LIMDU designation to a PEB, referred to as PEB conversion.
For the purpose of this study we focused on entries in MEDBOLLT for active-duty service members where the disposition field was coded as “first-career period of LIMDU.” A PEB was identified as any entry where the disposition field was coded as “refer to PEB.”
The investigators constructed three cohorts for analysis.The first cohort consisted of Navy and Marine Corps active-duty service members with a work-disabling spine condition receiving LIMDU assignment in 2007.The second cohort consisted of Navy and Marine Corps active-duty service members with work-disabling spine conditions receiving a first-career LIMDU assignment in 2008, and the third cohort consisted of Navy and Marine Corps active-duty service members with work-disabling spine conditions receiving a first-career LIMDU assignment in 2009.
Conversions were identified by matching PEB entries with first-career LIMDU dictations.We counted only those PEBs that had a final disposition listed in MEDBOLLT.
Cases in which the first-career LIMDU assignment period was for a work-disabling spine condition but the PEB was for something other than a work-disabling spine condition were excluded from our count of converters.
The investigators chose an 18-month followup from the first-career LIMDU as a cutoff to observe for a subsequent PEB.Eighteen months allowed the investigators the equivalent of three consecutive periods of LIMDU to observe for a PEB dictation.This 18-month period also allowed the subjects assigned a first-career LIMDU designation in 2009 an equivalent amount of followup time as those getting a first-career LIMDU designation in 2007.By doing so, the investigators eliminate bias in calculating rates of conversion as a result of differential followup based on year of first-career LIMDU assignment.
Formulas for Computing Rates Used in the Statistical Analysis
To evaluate differences between Portsmouth and San Diego, the investigators chose to compare rates of outcome between the two sites.The first outcome considered is the number of active-duty service members who received their first-career LIMDU assignment relative to the total number of active-duty service members who presented to orthopaedics or neurosurgery with a work-disabling spine condition complaint over a single year.We use the term “annual rate of first-career LIMDU” to represent this proportion.
The second outcome is the number of active-duty service members who were converted to PEB after receipt of their first-career LIMDU for a work-disabling spine condition.This second outcome represents the risk of PEB after LIMDU for a work-disabling spine condition.
The following formulas express these two different outcomes:
Annual rate of first-career LIMDU = incident cases of first-career LIMDU/total number of active-duty service members presenting to orthopaedic or neurosurgery for work-disabling spine conditions during a specific year at Portsmouth and San Diego, respectively.
PEB conversion risk = number of conversions from first-career LIMDU to PEB/total number of LIMDU assignments each year for work-disabling spine conditions at Portsmouth and San Diego, respectively.