Health Care Resource Utilization in Commercially Insured Patients Undergoing Anterior Cervical Discectomy and Fusion for Degenerative Cervical Pathology

Anterior Cervical Discectomy and Fusion With Structural Allograft is Associated With Lower Postoperative Health Care Utilization and Reoperations Compared With Cage Implants

BACKGROUND AND OBJECTIVES

Implants represent a large component of surgical cost, with several available options for anterior cervical discectomy and fusion (ACDF). Rising ACDF volume highlights the need for accurate cost characterization among implant configurations to inform efficient utilization.

METHODS

A cohort study of patients who underwent 1-level or 2-level ACDF in 2017 was conducted using the MarketScan national insurance databases, which contain deidentified clinical and financial data. Implant configurations included plate with cage, standalone cage, and plate with structural allograft. Patients who switched insurance providers within 2 years after surgery or underwent concurrent posterior cervical surgery, cervical disk arthroplasty, or cervical corpectomy were excluded. A combined plate/cage and standalone cage group was compared with the allograft group followed by the comparison of the plate/cage and standalone cage groups. In total, 30-day, 90-day, and 2-year aggregate costs; component costs of physical therapy, injections, medications, psychological treatment, and subsequent spine surgery; and reoperation rates were evaluated.

RESULTS

Of 1723 patients identified, 360 (20.9%) underwent surgery with plate/cage, 184 (10.7%) with standalone cage, and 1179 (68.4%) with allograft. Aggregate costs were lower in the allograft group compared with the combined cage group at 90 days ($36 428 vs $39 875, P = .04) and 2 years ($64 951 vs $74 965, P = .005) postoperatively. There were no significant differences in aggregate costs between the plate/cage and standalone cage groups. The 2-year reoperation rate was higher in the combined cage compared with the allograft group (23.9% vs 10.9%, P < .001) and was also higher in the standalone cage compared with the plate/cage group (32.0% vs 19.7%, P = .002).

CONCLUSION

Compared with alternative ACDF constructs, allograft is associated with lower postoperative costs and reoperation rates. Although costs are similar, reoperation rates are lower with plate/cage constructs compared with those of standalone cages. Surgeons should consider these financial and clinical differences when selecting implant configurations.

Investigating the mechanical effect of the sagittal angle of the cervical facet joint on the cervical intervertebral disc

BACKGROUND

Facet tropism is defined as the asymmetry between the left and right facet joints relative to the sagittal plane. Published clinical studies have found that facet tropism is associated with cervical disc herniation. However, the relationship between the facet orientation and the side of cervical disc herniation remains controversial. Therefore, this study used the finite-element technique to investigate the biomechanical effects of the sagittal angle of the cervical facet joints on the cervical intervertebral disc.

OBJECTIVE

The biomechanical effects of the sagittal angle of the cervical facet joint on the cervical disc and facet joint were investigated using the finite-element technique.

METHODS

The finite-element model was constructed using computed tomography scans of a 26-year-old female volunteer. First, a cervical model was constructed from C3 to C7. The model was verified using data from previously published studies. Second, the facet orientation at the C5-C6 level was altered to simulate different sagittal angles of cervical facet joints. Five models, F70, F80, F90, F100, and F110, were simulated with different facet joint orientations (70°, 80°, 90°, 100°, and 110° facet joint angles at the left side, respectively, and 90° facet joint angles at the right side) at the C5-C6 facet joints. In each model, annular fibres stress and facet cartilage pressure were studied under six pure moments and two combined moments.

RESULTS

Comparing the stress of the annulus fibres in flexion combined with right axial rotation and in flexion combined with left axial rotation in the same model, no difference in the maximum stress of the annulus fibres was noted between these two different moments in the F90 model, whereas differences of 12.80%, 8.84%, 14.95% and 33.32% were noted in the F70, F80, F100 and F110 models, respectively. The same trend was observed when comparing the maximum stress of the annulus fibres in each model during left and right axial rotation. No differences in annular fibres stress and facet cartilage pressure were noted among the five models in flexion, extension, lateral bending, left axial rotation, and flexion combined with left axial rotation in this study. However, compared with the F70 model in flexion combined with right axial rotation, the annulus fibres stress of the F80, F90, F100, and F110 models increased by 5.53%, 13.03%, 35.04%, and 72.94%, respectively, and the pressure of the left facet joint of these models decreased by 5.65%, 12.10%, 18.41%, and 25.74%, respectively. The same trend was observed in the right axial moment.

CONCLUSION

Facet tropism leads to unbalanced stress distribution on the annulus fibres at the cervical intervertebral disc. The greater the sagittal angle of the facet joint, the greater the annular fibres stress on this side. We hypothesised that the side with the larger sagittal angle of the facet joint exhibits a greater risk of disc herniation.