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Introduction There are relatively few, non-industry sponsored studies examining the outcomes and complications of cervical disc arthroplasty (CDA). In addition, there is very little literature examining optimal radiographic parameters for placement of CDA. Therefore, we set out to perform a single-center evaluation of the radiographic outcomes and association with complications following CDA. Methods We performed a retrospective review from August 2008 to August 2012 of all patients from a single military tertiary medical center undergoing cervical disc arthroplasty. Preoperative, immediate postoperative, and final follow-up films were evaluated. The clinical outcomes and complications associated with the procedure were also examined. Results A total of 312 patients were included in the review, with an average radiographic follow-up of 14 months and a 15.1% rate of persistent axial neck pain. For patients with persistent neck pain, the rates of heterotopic ossification (HO) formation and osteolysis were 27.7% and 14.9%, respectively, while the rates were significantly lower for patients without neck pain (12.8% and 6.2%, respectively, p = 0.01). There were no differences in preoperative facet arthrosis, pre- or postoperative disc height, segmental range of motion, or placement of the device relative to the posterior edge of the vertebral body. However, patients with implants more centered between the uncovertebral joints were more likely to experience posterior neck pain ( p =0.03). Conclusions We found that posterior, axial neck pain is relatively frequent after cervical disc arthroplasty, and patients with persistent neck pain were significantly more likely to develop heterotopic ossification or implant-related osteolysis. We also found that patients with implants that were placed off-centered were less likely to also complain of neck pain, though the reasons for this finding are unclear.

Introduction Few studies have evaluated the outcomes following C1–C2 fusion for atlanto–axial osteoarthritis (AAOA). Previous studies in rheumatoid arthritis (RA) patients with atlanto–axial instability have demonstrated unexpected development of subaxial kyphosis following C1–C2 fusion; however, this complication in patients with AAOA remains unknown. Therefore, we set out to evaluate the subaxial cervical sagittal alignment following C1–C2 fusion for AAOA. Methods We performed a retrospective review of all patients following C1–C2 fusion from a single center, single-surgeon from 2002 to 2012. All charts, records, and imaging studies were reviewed for each case, and preoperative, immediate postoperative, and final follow-up plain films were evaluated. Patients were divided into three diagnosis categories for further comparison: AAOA, rheumatoid, and trauma. Results A total of 29 patients were included in the review, with an average radiographic follow-up of 38 months. There were 14 patients with AAOA, 4 patients with RA/gout (1 gout patient with C1–C2 pannus causing spinal cord compression), and 11 patients treated for a traumatic etiology. Overall, we found that patients with AAOA did not have a significant change in subaxial sagittal alignment from preoperative to final follow-up (−11.7 to −13.8 degrees, p = 0.23, [− degrees] = lordosis, [+ degrees] = kyphosis), which was similar in the trauma group (−9.7 to −8.4 degrees, p = 0.47). This was comparable to the RA/gout group that demonstrated a significant change in sagittal alignment from −20.5 to −0.2 degrees ( p = 0.04). Conclusion Our study demonstrates that patients with nonrheumatologic conditions (AAOA and trauma) undergoing C1–C2 fusion do not develop postoperative subaxial cervical kyphosis. We postulate that the loss of subaxial lordosis in the rheumatologic patients may be a function of their underlying systemic disease.

Introduction Anterior plate constructs for cervical discectomy and fusion have been linked to postoperative dysphagia, increased operative times, and wider surgical exposures. Several “low profile” integrated stand-alone spacers (SAS) have been developed. While these spacers have demonstrated successful clinical outcomes and similar biomechanical stability to anterior plate constructs in single-level fusions, their biomechanical stability in multi-level constructs has not yet been established. Methods Twelve human cadaveric cervical spines (C2-T2) were nondestructively tested with a six-degree-of-freedom simulator under axial rotation (AR), flexion-extension (FE), and lateral bending (LB) loading. After intact analysis, each specimen underwent sequential instrumentation and testing: (A) C5-6 spacer/plate with C6-7 SAS; (B) C5-7 SAS; (C) C5-7 spacer/plate. Range of motion (ROM) data was obtained and analyzed with paired t-tests and Bonferroni correction. Results The 2-level plate construct significantly reduced flexion-extension ROM compared to the 2-level SAS (5.6 ± 3.4 degrees versus 11.6 ± 4.6 degrees, respectively; p 0.05) between the three different 2-level constructs. Conclusions Our study found that hybrid and 2-level SAS constructs are comparable to conventional anterior plate constructs in lateral bending and axial rotation, but there was an increase in flexion-extension motion allowed with constructs that incorporated a SAS. Stand-alone cervical spacers with integrated screws for hybrid and 2-level SAS constructs are reasonable alternatives to two-level plate fixation; however, clinical trials are necessary to determine if the increased ROM in flexion-extension noted in the SAS constructs translates to clinical outcome.

Introduction Long instrumented posterior fusion constructs to the lumbosacral spine have a significant rate of pseudoarthrosis and S1 screw failure. With the increasing popularity of Sacral Alar-Iliac (S2AI) fixation with its purported advantages of (1) decreased implant profile and (2) obviating the need for a lateral offset connector, the biomechanical properties with respect to S1 screw strain remain unknown. We set out to compare the biomechanical effect of S2AI versus traditional iliac screw fixation on S1 screw strain. Methods Five fresh-frozen human cadaveric specimens were instrumented from L2–pelvis, maintaining all osteoligamentous structures, with bilateral titanium 6.0 × 40-mm pedicle screws and 5.5-mm cobalt–chromium rods. Bilateral S1 pedicles were instrumented with 8.0 × 50-mm screws that were centrally cored out and two uniaxial strain gauges inserted at 0 and 90 degrees. S2AI fixation and/or iliac fixation with 8.0 × 80-mm titanium pedicle screws was performed to evaluate the following four different constructs: (1) bilateral S1 screws (control); (2) bilateral S2AI; (3) bilateral iliac; (4) hybrid (S2AI with contralateral iliac). Bilateral S1 screw strain was measured (microstrain), and pure moment loads (12.0 Nm) were applied in axial rotation (AR), flexion extension (FE), and lateral bending (LB). One way repeated measure ANOVA was used to analyze the S1 screw strain data. Results Compared with S1 screws alone, both S2AI fixation and iliac fixation significantly reduced sacral screw strain in FE by 58 and 67%, respectively ( p 0.05). Hybrid constructs demonstrated a significant reduction in only FE, with reduction in screw strain by 56% for S2AI fixation and 59% for iliac fixation, with no difference in AR and LB moments. When S2AI fixation and iliac fixation were compared, there was no significant difference in screw strain for all bending moments ( p > 0.05). Similarly, hybrid constructs demonstrated no side-to-side significant difference between S2AI fixation and iliac fixation for all bending moments ( p > 0.05). Conclusion Both S2AI fixation and iliac fixation provide significant reduction in S1 sacral screw strain compared with sacral fixation alone. Bilateral S2AI fixation is a viable and biomechanically comparable to alternative traditional iliac fixation, and presents another option to achieve protection of the S1 sacral screws for long segment constructs to the pelvis.

Introduction As war injury patterns have changed throughout Operations Iraqi and Enduring Freedom (OIF/OEF), a relative increase in the incidence of complex lumbosacral dissociation (LSD) injuries has been noted. LSD injuries are an anatomic separation of the spinal column from the pelvis, and represent a manifestation of severe, high energy trauma. We assessed the clinical outcomes of combat-related LSD injuries after operative treatment. Methods We performed a retrospective review of all patients surgically managed for complex LSD injuries since the beginning of current combat operations in the Middle East. Results A total of 20 patients met inclusion criteria and were treated as follows: posterior spinal fusion (12), sacroiliac screw fixation (7), and combined anterior–posterior fusion (1). The mean age was 28.2 years. The most common mechanism of injury was mounted improvised explosive device (IED, 50%). On average, 2.2 spinal regions were injured per patient. Neurologic dysfunction was present in four patients. Three patients underwent operative stabilization of their injuries before evacuation to the United States. Median time to surgery from injury was 12 days (range, 0–111 days). There was a 20% wound infection rate. Median follow-up was 45.5 months (range, 23.2–105.3 months), and one-third of all patients were medically retired because of their injuries. At most recent follow-up, 45% complained of chronic low back pain and 35% had persistent neurologic deficits; however, 30% were actively engaged in strenuous physical activities, including swimming, distance running, and training for special forces. Conclusion This is the largest series of operatively managed lumbosacral dissociation patients currently reported. Our series suggests that combat-related lumbosacral dissociation injuries frequently result in persistent, long-term neurologic dysfunction, disability, and chronic pain. Operative management carries a high postoperative risk of infection. However, two-thirds of patients were able to remain on active duty after their injuries, and two patients were able to complete marathon training.

Introduction The biomechanical effect of augmentation of a longitudinal constructs with one or two transverse connectors (TC) after a thoracic pedicle subtraction osteotomy (PSO) has not been evaluated previously. Previous investigations have suggested the role of transverse connectors for long segment thoracic constructs in enhancing torsional rigidity. We set out to evaluate the biomechanical contribution of TC to the stability of a long-segment pedicle screw–rod construct after a thoracic PSO. Methods Seven human cadaveric thoracic spines were prepared and instrumented from T4 to T10 with bilateral pedicle screws/rods and a PSO was performed at T7. Intact range of motion (ROM) testing was performed with nondestructive loading and analyzed by loading modality (axial rotation, flexion/extension, and lateral bending). ROM analysis was performed in the unaugmented construct, the construct augmented with one TC, and the construct augmented with two TC. No outside funding sources were utilized for this study. The authors have no potential conflicts of interest to report. Results Following PSO and an unaugmented longitudinal pedicle screw–rod construct, T4–T10 (overall construct) and T6–T8 (PSO site). ROM was significantly reduced in all planes of motion compared with intact condition ( p 0.05). In contrast, during axial rotation, global ROM was significantly reduced by 43% and by 48% at T6–T8 following addition of two TC ( p Conclusions Two transverse connectors significantly improved torsional rigidity of the entire construct and at the PSO site, with no differences in stability for flexion-extension and lateral bending, or with the addition of only one transverse connector. In the setting of a PSO and long segment pedicle screw–rod construct, augmentation with at least two transverse connectors should be considered to improve torsional rigidity.