Cost Advantages of Two-Level Anterior Cervical Fusion with Rigid Internal Fixation for Radiculopathy and Degenerative Disease

Graft migration after anterior cervical discectomy and fusion (ACDF) s a known complication, the frequency of which increases proportionately to the number of levels fused (14,20,22,27). Surgeons, in an attempt to decrease this incidence, routinely prescribe postoperative neck immobilization for several weeks after ACDF. Furthermore, most surgeons are reluctant to liberalize a patient's return to activities, driving, and work during the first few postoperative weeks fearing that this early mobilization may increase graft related complications. This physician–mandated restriction in activities and external neck bracing prevents patients from returning to their normal activity level until the surgeon is confident that the grafts are stable.

Several reports have recently advocated the use of rigid internal fixation (RIF) with anterior metallic plating in cervical degenerative disease to augment fusion. However, there are no reports that address the advantages of metallic plating to obviate the use of postoperative neck immobilization and thus promote early mobilization (1,3,5,11,16,23,26,30,31,33,34). We reviewed a consecutive series of patients treated with two–level ACDF before and after the institution of RIF to analyze whether the augmented construct allowed patients to return to work earlier without an increased complication rate. The potential cost advantages of early mobilization were calculated comparing ACDF to ACDF with RIF.

The limitations of this study include: (1) changing practice patterns during the study period, (2) the automatic immobilization of patients using external orthosis, and (3) physician–defined activity restrictions. Despite these limitations, RIF increases a surgeon's confidence to allow patients early mobilization without external orthosis. This early mobilization allowed patients to return to the work force sooner without increased complications, thus reducing the economic effect of lost work hours.

MATERIALS and METHODS

A retrospective review was conducted on a consecutive series of patients who underwent two–level allograft ACDF with and without RIF between 1989 and 1994 performed by a single surgeon (FJP). The review focused on operating room time, hospital stay, overall cost, outcome, and time to return to normal activities including work. The senior author at the beginning of this study date was well experienced with ACDF and had performed this procedure over 200 times previously. All patients had clinical evidence of cervical radiculopathy unresponsive to conservative therapy with MRI confirmation of nerve root impingement with a degenerative disc at an adjacent level above or below the symptomatic level. Two patients in the RIF group and one patient in the ACDF group also had signs of mild myelopathy.

Between the years of 1989 and 1991 a total of 25 patients underwent two adjacent level ACDF (Cloward technique) with allograft. During the following 3 years a total of 39 patients underwent similar discectomy and fusion (Cloward technique) of adjacent levels with allograft using Synthes anterior cervical locking plates (Synthes CSLP, Synthes Spine, Paoli, Pennsylvania) (Figures 1 and 2). We reviewed all hospital records and office charts and recorded time of procedure, estimated blood loss, intraoperative and postoperative complications, length of hospital stay, number of days before patients returned to light activities, driving, and full unrestricted work duty. In an effort to maintain surgical homogeneity, we excluded patients with single and three– or four–level disease in this study. Because of the increased incidence of graft complications and the limited benefit of autograft (22), the surgeon used allograft in all patients.

Figure 1. AP view of patient status post C5–C7 ACDF with RIF.	Figure 2. Lateral view of same patient showing good bony fusion and incorporation of allograft into the interspaces.

Patients' jobs were recorded and stratified into minimal (sedentary desk jobs), moderate (jobs that require some element of physical activity without heavy lifting), and heavy labor (jobs with primary or major component of heavy lifting). All patients who did not undergo RIF were discharged with a sternal occipital mandibular immobilizer (SOMI) brace for a period of 8 weeks postoperatively. Because of the external orthosis, these patients were unable to return to normal activities including driving until the brace was removed. At the time of discontinuation of the brace, patients were instructed to begin range of motion exercises and to return to normal activities, driving, and full work duty as tolerated, except for patients with heavy labor duties who were allowed to return to work at 12 weeks.

Patients who underwent RIF were discharged without external orthosis and began range of motion exercises on postoperative Day 5. Depending on the level of job activity, patients were instructed to resume normal activities, driving, and full work duties at 2 weeks if their job required minimal labor, at 6 weeks if their job required moderate labor, and at 12 weeks if their job required heavy labor. Postoperative evaluations for both groups included examinations and lateral cervical spine radiographs at 4, 8, and 12 weeks. Patients were also called beyond the 1–year follow–up for updates regarding outcome classified by Odom outcome criteria. We chose Odom criteria because they are easily understandable and evaluate patient's satisfaction regarding outcome. No patients were lost to follow–up.

Cost analysis was conducted using 1995 current procedural terminology (CPT) codes as well as standard hospital charges to patients and included length of hospitalization, SOMI brace, operating room and anesthesia time, instrumentation, and complications requiring intervention. Total charges for ACDF with and without RIF were calculated and compared with the number of days gained from decreased convalescence time related to the surgeon's added confidence to liberalize patient's activities earlier. It should be understood that all costs represent charges and not actual reimbursement, or adjustment to any true cost basis.

RESULTS

Follow–up was 6 months to 4 years (mean, 31 months). The age and sex distributions were similar in both groups. The mean duration of symptoms was 3.5 years in the RIF group compared with 2 years in the ACDF group. The labor distribution showed a higher number of heavy and moderate laborers in the RIF group compared with the ACDF group. In the group that underwent RIF, there were 3 heavy, 23 moderate, and 10 light laborers, with 3 patients' occupations not listed. In the group that underwent ACDF there were 1 heavy, 5 moderate, and 19 light laborers. In the nonplated group 23 of 25 patients and 36 of 39 patients in the plated group achieved excellent or good outcomes using Odom criteria (23). Patients who underwent plating returned to light activities sooner than nonplated patients (mean, 17 versus 28 days) although this was not statistically significant (p = 0.08). Patients who underwent plating returned to driving (28 versus 57 days), and unrestricted work (66 versus 136 days) sooner than nonplated patients (p < 0.05, two–tailed, paired t test). No patient with plates was given external immobilization. There was some discrepancy between the actual time returned to unrestricted work and the prescribed protocol that can only be explained by patient noncompliance with activities protocols.

There were six complications (two major and four minor) in each group (Table 1). Follow–up postoperative radiographic studies at 4, 8, and 12 weeks showed evidence of plate migration in only one patient in the plated group. Another patient in the plated group had a postoperative epidural hematoma requiring reexploration. There was one patient who was found to have screw migration, and two patients who had screw misplacement into the disc space; neither of which was clinically significant. In the nonplated group there was one patient who had graft migration requiring reexploration, and one patient who had postoperative hemiparesis that resolved without intervention. There were two superficial wound infections in the ACDF group and one in the RIF group, all of which were treated successfully with oral antibiotics. Mean operating room time was 9 minutes longer in the plated group and estimated blood loss was not significantly different between the two groups.

TABLE 1: Complications

Mean length–of–stay charges to patients were $581 in the RIF group versus $1,084 in the group undergoing ACDF. Mean operating room charges were $1,456 in the RIF group versus $1,301 in the group undergoing ACDF. Mean anesthesia charges were $505 in the group undergoing RIF versus $488 in the ACDF group. Mean complication charges were $447 in the RIF group versus $335 in the ACDF group. The overall mean charge included all of the above charges as well as plate and screw charges and brace charges for the nonplated group and was $13,098 in the RIF group versus $10,624 in the ACDF group. Length–of–stay charges were significantly lower in the RIF group (p = 0.003) and probably reflected changes in practice patterns in more recent years. Operating room and total charges were significantly higher in the RIF group (p = 0.05, p < 0.05, respectively). The incremental cost effectiveness was calculated at $86/day for driving, $213/day for returning to normal activities, and $31/day to return to work sooner. To minimize bias and account for recent changes in practice patterns we equalized the length–of–stay costs between the two groups. The equalized length–of–stay adjusted overall charges of the ACDF group down to a mean of $9,701 per procedure. With equalized length–of–stay, the incremental cost effectiveness of RIF was $293, $118, $42 for return to activities, driving, and unrestricted work, respectively.

DISCUSSION

Although documentation of spinal instability is a well–established concept, factors constituting graft stability are not well defined (7,24). A surgeon's confidence in a fusion construct significantly influences when patients return to normal activities, especially work. There is much variability in postoperative restrictions imposed by surgeons regarding what type of immobilization patients should have after ACDF. These range from the use of a soft cervical collar to halo immobilization (3,4,8,9,11,13,26,28,35). This variability affects the timing of return to normal daily activities and work. The restriction instituted in our ACDF patient population of SOMI brace immobilization for 8 weeks seemed reasonable and within the guidelines suggested by others (13). This restriction, however, prevents patients from driving and full work duty. The addition of RIF in the second patient population greatly improved the surgeon's confidence to liberalize patients' activities sooner without the use of a hard cervical collar. The benefits realized in this patient population were decreased convalescence without increased complications.

Anterior metallic plating for RIF in the treatment of acute unstable cervical spine injuries is well established; however, indications for instrumentation in patients with degenerative cervical disease are less clear (1,2,3,4,8 –12,16,17,21,25,28,30 – 34). The excellent outcome of RIF in traumatic cervical instability, the immediate stabilization characteristics, and the theoretical advantages of decreasing graft migration have made RIF an attractive option for patients with degenerative disease (1,4, 6,8,10,12,15,17 – 19,26,29,31,33,36).

Despite the widespread and increasing use of RIF for degenerative diseases of the cervical spine, little has been written regarding outcome and early patient mobilization with the use of anterior metallic plating compared with conventional fusion techniques. Several recent reports have suggested that RIF may be superior to conventional ACDF in patients with degenerative cervical spine disease (3,5,16,18,31). Shapiro found that there were fewer graft–related complications and shorter time to return to work in patients with RIF compared with a similar population of patients undergoing conventional ACDF (31). Some concern has arisen, however, that RIF for this patient population may be unnecessary. Caspar and Piltzen (5) reported that graft migration was decreased in multilevel fusions and eliminated in single level fusions in patients with RIF. They also showed that fusion rates were increased with anterior plating (5).

Zdeblick et al. in a goat model of multilevel fusion found that anterior plate fixation did not significantly increase fusion rate, but did increase biomechanical rigidity. From this, they concluded that increased rigidity from RIF supported its use in traumatic conditions, but because fusion rates were unchanged they did not support RIF in degenerative disease (36).

Their conclusions are well founded; however, there are other advantages of RIF. In particular, RIF increases a surgeon's security of fixation of the construct and may obviate the use of external orthosis, thereby promoting early mobilization. Although morbidity from immobilization was not seen in our patient population, early mobilization theoretically could lead to improved pulmonary care, decreased incidence of deep venous thrombosis, and other morbidity associated with prolonged neck immobilization. Another benefit of early mobilization is decreased convalescence, thus allowing patients to return to normal activities, as well as to the work force, sooner. The complications were similar in both groups and not statistically different. Early mobilization without external orthosis in patients with RIF did not seem to lead to increased complications despite the higher number of moderate and heavy laborers in the RIF group.

In our series patients undergoing RIF incurred a mean higher total charge but returned to activities sooner without an increased rate of complications. Because of this we performed an incremental cost analysis to estimate the cost of returning to activity, driving, and work sooner with the more expensive RIF procedure. When viewed in this fashion the advantages of earlier mobilization and activity liberalization with RIF can be evaluated on a $/day sooner basis. The results suggest that a more formal cost analysis is warranted for this procedure.

Two–level ACDF with anterior plating for radiculopathy is safe, effective, and provides shorter convalescence compared with conventional ACDF. Patients returned to unrestricted work sooner, thus reducing short–term disability. The authors believe that rigid internal fixation provides cost advantages to patients and insurance disability providers.

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