There are distinct implications to the management decisions of a unilateral cervical radiculopathy in active-duty military patients. Whereas anterior or posterior cervical approaches for symptomatic radiculopathy without myelopathy may have equivalent clinical efficacy,5,6,16 these interventions have their own respective limitations with regard to an individual's capacity to return to unrestricted military service. Governing instructions from the Naval Bureau of Medicine and Surgery, Naval Aerospace Medical Institute, and Naval Undersea Medical Institute collectively establish criteria for the capacity of service members to return to unrestricted full duty after recovering from surgical intervention. Under certain circumstances, the consequences of a surgical approach may delay a return to active duty.
The purpose of this study was to identify the difference in time to return to active duty between a PCF and ACDF. In addition, we sought to examine the cost effectiveness and the clinical outcomes in those patients with unilateral cervical radiculopathy who underwent either ACDF or PCF with or without discectomy in the military. The direct costs of performing the procedure, as well as indirect costs of time away from duty, are examined and compared to determine whether there is a benefit of PCF relative to ACDF in the management of unilateral cervical radiculopathy in the military.
Methods
Patient Population
We retrospectively reviewed data obtained in 19 active-duty military patients who were identified to have a unilateral cervical radiculopathy without myelopathy presenting between July 2007 and August 2009. The diagnosis of cervical radiculopathy was made by clinical history, neurological examination, and MR imaging. Review of the imaging studies demonstrated lateral disc herniations or disc osteophyte complexes without central canal impingement. Patients without advanced disc collapse, cervical spondylosis, or segmental kyphosis were preferentially selected for a PCF (19 patients). Four of these patients had soft-disc herniations, and the remaining 15 had disc osteophyte complexes resulting in foraminal stenosis.
The 19 patients in the PCF cohort were matched by age, treatment level, and surgeon with 19 patients identified from our institution's neurosurgical database; these patients had undergone ACDF for unilateral cervical radiculopathy. In the event a patient was unable to be matched for a surgeon, a patient was selected from the senior author's (W.M.G.'s) database. Institutional review board permission was sought and approved to review all outpatient, inpatient, procedural, anesthesia, and radiographic data in the 38 patients included in this study. Hospital records were reviewed for operating room times, estimated blood loss, and length of hospital stay. Clinical records were reviewed for postoperative narcotic medication refills and the time required for return to unrestricted full duty.
All patients underwent a period of nonoperative management including limited duty, physical therapy, antiinflammatory medications, or opioid analgesics. Additionally, all patients underwent MR imaging and had proven disc herniations or disc osteophyte complexes corresponding to the side and level of their clinical symptoms. Exclusion criteria included previous cervical surgery, myelopathy, spinal infection or tumor, and psychiatric illness.
The cost effectiveness of PCF and ACDF was compared by analyzing direct and indirect costs of both procedures, the former associated with the cost of time away from active duty. Direct costs included surgical instrumentation and subsequent hospitalization. Hospital and instrumentation expenses were determined for the PCF cohort and the ACDF cohort using TRICARE military health plan reimbursement figures.
Indirect cost was evaluated by multiplying the service member's monthly salary by the difference in time away from active duty. Monthly salary was based on 2009 fiscal year figures. This monthly salary is composed of base salary, Basic Allowance for Housing, and Basic Allowance for Subsistence. Given the numerous ranks and corresponding salaries within the navy, the authors chose to use the salaries of a junior enlisted service member (E4), a senior enlisted member (E7), a junior officer (O1), and a senior officer (O4) to give a range that would best represent indirect costs.
Diagnostic Imaging
Preoperative imaging studies consisted of anteroposterior and lateral radiographs, flexion-extension radiographs of cervical spine, and an MR images of the cervical spine. A 1.5-T MR imaging system (Signa, General Electric Medical Systems) was used for all studies, and all MR images were obtained at our facility. The MR imaging sequences included axial and sagittal T1-weighted fat-saturation and T2-weighted studies from which the measurements were obtained.
Surgical Technique
Patients underwent either PCF or ACDF performed by 2 neurosurgeons. Intraoperative fluoroscopic imaging was used to confirm the surgical level.
The PCF was performed using either a Frykholm midline open technique or a lateral minimally invasive technique as described by Fessler and Khoo3 and others.1,10,12 The anterior cervical fusions were performed using the Smith-Robinson technique with cortical-cancellous allograft and a dynamic plate.
Postoperative management included short periods of light or limited duty when indicated to protect service members from excessively strenuous training exercises. All aviators who underwent ACDF were grounded until they met criteria for a waiver to return to flying status (see below). All special operations personnel who had undergone ACDF were restricted from parachute jumps until there was radiographic evidence of a solid arthrodesis. In all patients who underwent ACDF, anteroposterior and lateral cervical radiographs were obtained between 4 and 6 weeks postoperatively and CT scans were acquired between 3 and 6 months postoperatively. Flexion-extension cervical radiography was performed as part of the criteria to establish a radiographic fusion. Flexion-extension cervical radiographs were obtained in all patients who underwent PCF to rule out abnormal spinal motion.18
Outcomes Measures
Successful outcome was determined by return to full, unrestricted active-duty military service within the service member's presurgical military occupational specialty. This includes the capacity to pass a physical readiness test, a combat fitness test (applicable only to the Marines), be cleared for shipboard duty, and be worldwide assignable without restrictions or limitations.
Statistical Analysis
Analysis was based on pairings of patients for demographic variables. Descriptive statistics were frequencies and percentage of occurrence (rate) for categorical variables and mean and range for continuous variables. Differences between PCF and ACDF pair members were tested against a 0 difference using the Wilcoxon signedrank test.
Results
A total of 21 levels were operated upon in each group (Table 1). The PCF group comprised 17 men and 2 women, whereas all 19 patients in the ACDF group were male. The PCF group contained 4 smokers (21%), while the ACDF group had 1 smoker (5%). The mean age at the time of surgery was 41.4 years (range 27–56 years) and 39.3 years (range 24–52 years) for PCF and ACDF groups, respectively. The mean follow-up for the ACDF group was 18.1 months (range 6–34 months) and 11.2 months (range 5–24 months) for the PCF group.
Summary of data obtained in patients who underwent PCF or ACDF
| Case No. | Sex | Age at Op (yrs) | No. of Levels | Op Time (mins) | EBL (ml) | Narcotic Refills | Tobacco | Return to Full Duty (wks) |
|---|---|---|---|---|---|---|---|---|
| PCF | ||||||||
| 1 | M | 51 | 1 | 180 | 50 | yes | no | 6 |
| 2 | M | 43 | 2 | 149 | 50 | yes | no | 8 |
| 3 | M | 44 | 2 | 231 | 50 | no | no | 2 |
| 4 | M | 43 | 1 | 126 | 15 | no | no | 1 |
| 5 | M | 37 | 1 | 175 | 25 | no | yes | 4 |
| 6 | M | 37 | 1 | 197 | 50 | yes | no | 4 |
| 7 | M | 37 | 1 | 131 | 20 | no | yes | 4 |
| 8 | M | 47 | 1 | 157 | 75 | no | no | 4 |
| 9 | M | 36 | 1 | 120 | 10 | no | no | 7 |
| 10 | M | 45 | 1 | 132 | 75 | no | no | 4 |
| 11 | M | 56 | 1 | 209 | 75 | no | no | * |
| 12 | M | 34 | 1 | 109 | 50 | yes | yes | 8 |
| 13 | F | 27 | 1 | 116 | 10 | no | no | 4 |
| 14 | M | 54 | 1 | 164 | 75 | no | no | 2 |
| 15 | F | 51 | 1 | 182 | 100 | no | no | 6 |
| 16 | M | 49 | 1 | 140 | 15 | no | no | 5 |
| 17 | M | 33 | 1 | 128 | 10 | no | no | 4 |
| 18 | M | 31 | 1 | 141 | 15 | no | yes | 7 |
| 19 | M | 33 | 1 | 137 | 15 | no | no | 7 |
| mean | 41.4 | 153.9 | 39.7 | 4.8 | ||||
| ACDF | ||||||||
| 20 | M | 48 | 1 | 139 | 10 | no | no | 12 |
| 21 | M | 38 | 2 | 187 | 50 | no | no | 12 |
| 22 | M | 46 | 2 | 291 | 50 | no | no | 19 |
| 23 | M | 38 | 1 | 148 | 25 | no | no | 12 |
| 24 | M | 33 | 1 | 133 | 10 | yes | no | 28 |
| 25 | M | 47 | 1 | 134 | 30 | no | no | 32 |
| 26 | M | 34 | 1 | 130 | 30 | yes | no | 18 |
| 27 | M | 47 | 1 | 172 | 100 | no | no | 24 |
| 28 | M | 30 | 1 | 146 | 30 | yes | no | 14 |
| 29 | M | 45 | 1 | 150 | 49 | yes | no | 16 |
| 30 | M | 44 | 1 | 144 | 50 | no | no | 16 |
| 31 | M | 33 | 1 | 133 | 10 | yes | no | 28 |
| 32 | M | 24 | 1 | 135 | 20 | yes | yes | 32 |
| 33 | M | 52 | 1 | 130 | 50 | no | no | 26 |
| 34 | M | 48 | 1 | 158 | 20 | no | no | 27 |
| 35 | M | 45 | 1 | 128 | 20 | no | no | 12 |
| 36 | M | 35 | 1 | 143 | 30 | no | no | 20 |
| 37 | M | 30 | 1 | 149 | 25 | no | no | 13 |
| 38 | M | 30 | 1 | 131 | 10 | no | no | 12 |
| mean | 39.3 | 151.6 | 32.6 | 19.6 | ||||
Levels of surgery in the PCF group were as follows: C-7 in 11 (58%), C-6 in 3 (16%), C-8 in 2 (11%), C-5 in 1 (5%), and C-6 and C-7 in 2 (11%) patients. Surgical sites in the ACDF group were as follows: C6–7 in 11 (58%), C5–6 in 5 (26%), C4–5 in 1 (5%) patient, and C5–6 and C6–7 in 2 (11%) patients. (In the event that a patient was unable to be matched for age and level, an adjacent level was used.)
The average time to return to unrestricted full duty was 4.8 weeks (range 1–8 weeks) in the PCF group and 19.6 weeks (range 12–32 weeks) in the ACDF group. The difference in time was 14.8 weeks, which was statistically significant (p < 0.001). One patient from the PCF group was excluded from data analysis because he did not return to unrestricted full duty (Table 1).
Direct cost consisted of institutional and instrumentation costs. The institutional costs were $3096 in the PCF group and $5999 in the ACDF group, a difference of $2903. Average instrumentation costs were $474 in the PCF group and $4079 in the ACDF group, a difference of $3605. (The 12 minimally invasive PCF cases also had a rental fee of $750 per case.) The total difference in direct cost between the 2 procedures was $6508 (Table 2).
Summary of direct costs, in dollars, of each procedure
| Procedure | Instrumentation Cost | Institutional Cost | Total Direct Cost |
|---|---|---|---|
| PCF | 474 | 3,096 | 3,570 |
| ACDF | 4079 | 5,999 | 10,078 |
Indirect cost was calculated by multiplying the mean difference in time to return to active duty (14.8 weeks) by the salary of 4 different service ranks. The indirect cost difference for an E1, E7, O1, and O7 service member were $13,586, $17,797, $17,475, and $24,045, respectively (Table 3).
Summary of indirect costs associated with each procedure
| Rank | Cost Effectiveness ($) | ||
|---|---|---|---|
| Direct | Indirect | Total | |
| junior enlisted (E4) | 6,508 | 13,586 | 20,094 |
| senior enlisted (E7) | 6,508 | 17,797 | 24,305 |
| junior officer (O1) | 6,508 | 17,475 | 23,983 |
| senior officer (O4) | 6,508 | 24,045 | 30,553 |
The total (indirect and direct) cost differences between procedures for an E1, E7, O1, and O7 service member were $20,094, $24,305, $23,983, and $30,553, respectively (Table 3).
Postoperative complications included 2 cases of transient recurrent laryngeal nerve palsy in the ACDF group. See Table 1 for a summary of individual data.
Clinical and Radiographic Outcomes
Eighteen of the 19 patients in the PCF group returned to full unrestricted full duty and had complete resolution of preoperative symptoms. One service member (Case 11) was unable to return to full duty because he could not tolerate the pain associated with wearing a Kevlar helmet. Another service member (Case 5), after returning to unrestricted full duty, would return 8 weeks after surgery with contralateral radicular symptoms. This patient underwent anterior decompression and then returned to unrestricted full duty 3 months afterward. Additionally, one service member (Case 16) in the PCF group had a subtotal foraminotomy, which required revision surgery. This patient returned to unrestricted full duty 5 weeks after the initial surgery. In the end, 16 individuals in this group returned to unrestricted full duty without further intervention.
In all 19 patients in the ACDF group, radiographic fusion was established by both flexion-extension cervical radiographs and CT scans between 3 and 6 months after surgery. Eighteen patients had complete resolution of their symptoms and returned to unrestricted full duty in the capacity in which they previously served. One patient (Case 22), despite a radiographic fusion, had persistent neck pain and returned to a purely administrative role.
Discussion
The essence of military medicine is the identification, diagnosis, and timely treatment of the injured service member. Allowing the individual a period of convalescence to recover from an injury or surgery is a necessary step to optimize the operational readiness of the fleet and minimize the risk of further injury to the service member. During this time, the injured service member's billet may be “backfilled” by another service member to prevent overburdening the remaining members of a unit or squadron. Other times, the billet may be left open depending on available personnel. Nevertheless, the goal for the military surgeon remains to return that individual to his unit or squadron to serve in the capacity for which he or she had been trained, without restrictions or limitations and in a timely fashion. This is especially true for those individuals in the aviation, special warfare, and diving communities, which are modest in size, but have significant physical and operational demands. Therefore, minimizing the time from surgery to return to unrestricted full duty is crucial. Given this as a context, we reviewed our experience in the management of unilateral cervical radiculopathy in the military.
In our review of data obtained in these 38 active-duty patients with unilateral cervical radiculopathy, 17 (89.5%) of 19 cases in the PCF group and 18 (94.7%) of 19 cases in the ACDF group were deemed successful long-term interventions. Our sample was too small to draw meaningful conclusions between the efficacies of these procedures (p = 1.000) or to establish superiority of one procedure over the other. Still, at first glance the anterior approach appears to have achieved greater long-term success. Consequently, there is value in further examining those cases in which the individuals did not return to full duty.
First, we acknowledge the inherent limitation of the PCF to address unilateral disease. This is critical with regard to patient selection. In a review of Case 5, the patient presented clinically with unilateral symptoms, but from a radiographic standpoint he had bilateral neural foraminal stenosis. While bilateral foraminotomies may be readily performed via an anterior approach, the very nature of the minimally invasive posterior approach precludes this without a second incision. In hindsight, the anterior approach may have been a superior approach in this case. Accordingly, the lack of success in this patient was more a consequence of patient selection than to surgical technique. This underscores the principal of patient selection: not all patients may benefit from the PCF.17
Second, despite resolution in his preoperative radiculopathy, the patient in Case 11 was unable to return to full duty because of pain associated with wearing his Kevlar helmet. In the end, the patients in Cases 5 and 11 had resolution of preoperative radiculopathy but were unable to reach the outcome measure of returning to unrestricted full duty. The inability to return to full duty was limited to one individual (Case 22) in the ACDF group.
In well-selected patients, the literature has shown that decompression of the cervical neural foramen and the lateral recess for unilateral cervical radiculopathy may be accomplished by either a PCF with or without discectomy or ACDF with equal efficacy.5,6 Nevertheless, the trend in the US over the last decade has drifted in favor of anterior approaches, whereas posterior approaches have declined dramatically.11,15 More recently, the traditional advantages of the anterior approach appear to have been equaled by the introduction of the minimally invasive PCF. Some authors have suggested that the risks of instrumentation and increased cost of anterior surgery may be avoided by a posterior approach, without the significant postoperative pain or muscle spasms in those patients with lateral disc herniations or unilateral disc osteophyte complexes.7 The recent publication of large series of cases involving posterior cervical foraminotomies further corroborates this and suggests a tapering to the anterior trend.2,4,7–9,13,14 We have observed a similar trend in our own institution. Over the last 5 years, review of the neurosurgery database at our institution reveals 156 ACDFs were performed compared with 22 PCFs. One-third of the PCF procedures have been performed in the last year.
Cost Analysis
Under ideal circumstances, indirect costs should represent lost productivity due to the patient's absence from work. In the absence of detailed job analysis for each patient, indirect costs were calculated by the salaries paid to active-duty military members who were not able to perform full, unrestricted physical activity because of their surgery. While imperfect, salaries are the only available surrogate marker for lost productivity. Furthermore, the authors recognize the difficulty in calculating the cost of a service member unable to perform his duty while recovering from surgery, given the numerous ranks and corresponding salaries in the military. Therefore, the authors chose to create a 4-tier system: junior enlisted, senior enlisted, junior officer, and senior officer. This creates a range that would best illustrate the indirect costs. These estimates were intentionally underestimated to provide a low end value to the indirect cost. Service members are given financial compensation in the form of bonuses and incentives for various qualifications or specialized training. The military has a multitude of bonuses with varying amounts. Examples include flight pay, dive duty pay submarine duty pay, and hazardous duty pay. These were not included in our estimation.
The total cost difference, including both direct and indirect, between a PCF and ACDF ranged from $20,094 to $30,553 depending on the service member's rank (Table 3). As would be expected, direct costs were significantly higher in the ACDF group than in the PCF group. The average cost, institutional and instrumentation, equaled $10,078 for the ACDF group, while the PCF group totaled $3,570 per surgery, a difference of $6,508. (The second surgery performed on the 2 patients in the PCF group only increased the average cost for the entire PCF group by $718.) But the most significant contribution to the total cost was indirect costs, which ranged from $13,586 to $24,045 depending on the service member's rank. The large difference in indirect cost was reflective of those in the PCF group returning to unrestricted full duty 14.8 weeks earlier than those in the ACDF group, a statistically significant difference. On average, patients in the PCF group returned to unrestricted full duty 4.8 weeks after surgery, compared with 19.6 weeks in the ACDF group.
The difference in indirect costs between a PCF and ACDF is further accentuated when analyzing certain occupations within the military. For instance, the US Navy Manual of the Medical Department issued by the US Navy Bureau of Medicine and Surgery lists the criteria to obtain a medical waiver and return to active duty after surgical procedures. The manual states those service members in the aviation community who undergo a single-level ACDF may not return to duty any earlier than 6 months from surgery. Additional waiver criteria are as follows: single-level surgery, 6 months from the date of surgery, free of pain, complete resolution of radicular symptoms, and radiographs that demonstrate fusion with no instability in flexion and extension views. Once a waiver is granted, the service member may return to unrestricted full duty. The diving and special warfare communities have similar criteria for a waiver before returning to duty. A medical waiver for a PCF simply necessitates the service member be free of pain and have complete resolution of radicular symptoms.
Given the aforementioned criteria, the PCF has a distinct advantage. Once the foraminotomy is completed and the radicular symptoms resolved, the only thing that remains for the service member to return to active duty is to have a completely healed incision and be off all narcotic pain medications. As the authors noted above, this takes on average 4.8 weeks. For members with specialized occupations (aviation, undersea, or special warfare), the very nature of the ACDF requires a minimum of 24 weeks before the service member may be considered for return to full duty.
Conclusions
In the management of unilateral cervical radiculopathy for military active-duty personnel, PCF offers a benefit relative to ACDF in immediate short-term direct costs and long-term indirect costs. The indirect cost of time away from duty was the more significant contributor to difference in cost effectiveness.
The military spine surgeon must consider the operational demands of the service member prior to selecting the surgical approach for a unilateral cervical radiculopathy without myelopathy, as the anterior and posterior approaches result in different periods of time away from unrestricted active duty.
Disclosure
No financial support was received for the generation of this study. No grant assistance was received for the generation of this study. The authors have no financial interest in the materials mentioned in this paper. The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Navy, Department of Defense, or the US government.
Author contributions to the study and manuscript preparation include the following. Conception and design: LM Tumialán. Acquisition of data: LM Tumialán, RP Ponton. Analysis and interpretation of data: LM Tumialán, RP Ponton. Drafting the article: all authors. Critically revising the article: LM Tumialán, W Gluf. Reviewed final version of the manuscript and approved it for submission: LM Tumialán, W Gluf. Statistical analysis: LM Tumialán, RP Ponton. Administrative/technical/material support: LM Tumialán, RP Ponton.
Acknowledgments
The authors are grateful for the assistance given by Lieutenant Ryan Gnandt and Patrick M. Kearney in data collection, and for the editorial assistance rendered by Ms. Andrea J. Porter.
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