Experience with a modular PEEK system for cervical vertebral body replacement.

STUDY DESIGN: A retrospective case series. SUMMARY OF BACKGROUND DATA: The authors present their experience with the ATHLET vertebral body replacement (VBR) system in combination with the TOSCA plating system for the treatment of cervical spondylotic myelopathy. METHODS: Data obtained from 20 cases were reviewed. Corpectomy and VBR with the ATHLET system was performed in all cases. Patients underwent preoperative and postoperative assessment involving the Japanese Orthopedic Association score, Odom criteria, and radiographic studies to determine the position of the implant as well as cervical lordosis. The mean follow-up period was 20 months (16-28 mo). RESULTS: Implantation of the ATHLET VBR itself was uncomplicated in all cases. The adjustment of the implants' height could be done in 2 mm steps. With increasing height of the implant, the angle of lordosis increases comparable with physiological conditions. The authors performed 13 one-level and 7 two-level corpectomies; from the latter group there were 2 revision cases (10%) with implant dislocation. Four cases (20%) of secondary subsidence of the implant were observed radiographs 12 months postoperatively; in all cases treatment remained conservative. Ten patients (50%) had excellent, 4 (30%) good, 2 (10%) satisfactory, and 2 (10%) poor outcome according to Odom criteria. The average improvement of the Japanese Orthopedic Association score was 1.6. All cases achieved osseous fusion without complications, 55% of them had an improvement, and 15% of them had no change of the sagittal contour. CONCLUSIONS: The ATHLET VBR is easy to implant and avoids bone graft site morbidity. Due to a relatively high rate of secondary subsidence of the implant (20%) and secondary dislocation (10%) in combination to a poor to satisfactory outcome according to Odom criteria in 20%, the authors do not recommend the use of this PEEK implant for cervical VBR.

Anatomical data on the craniocervical junction and their correlation with degenerative changes in 30 cadaveric specimens.

OBJECT: The goal of this project was to measure vertebral dimensions at the craniocervical junction and to investigate degenerative changes in this region and their correlations with the anatomical data. These studies will assist in an understanding of biomechanical conditions in this region, which are clinically relevant in cases of cervicogenic headaches and vertigo. METHODS: The authors examined 30 cadaveric specimens obtained from patients ranging in age from 24 to 88 years at death. Measurements of angles of the vertebrae were conducted using an imprint method. Microsections of osseous endplates and articular cartilage were graded according to their degrees of degeneration by using the Petersson classification (0, no sign of degeneration; I, superficial degeneration with several fragmentations; II, deeper degeneration with cartilaginous disintegration and penetrating ulceration; or III, complete cartilaginous degeneration with the appearance of subchondral bone in > 50% of the articular surface). The authors found Grade I changes in 100% of the occiput specimens. In the superior articular cartilage of C-1 no changes (Grade 0) were found in two specimens, whereas 6% of the specimens exhibited Grade II changes and 89% exhibited Grade I changes. In the inferior articular cartilage of C-1, 57% of the specimens displayed Grade I changes, 14% Grade II, and 20% Grade III changes. In the superior articular cartilage of C-2, 62.5% of the specimens displayed Grade I changes and 25% Grade II changes. At the occiput-C1 level the authors found a higher frequency of degeneration at the upper left articular surface of the atlas (Quadrants 1 and 3), and at the C1-2 level they found a higher frequency of degeneration at the upper left and upper right articular surfaces of the axis (Quadrants 2 and 3, respectively). Using the McNemar test, the authors investigated the frequency of affection of single quadrants in a left-right side comparison (lateral reversal). Significant differences were identified for Quadrant 2 of the upper left articular surface of C-2 and Quadrant 3 of the upper right articular surface of C-2. These results correlate with the analysis of single articular surfaces of the axis, but contradict the results for the atlas, in which no significant difference in the left-right side comparison was found. CONCLUSIONS: Severe degeneration in the atlantooccipital joints appears to be a rare condition, with no Grade II or III degeneration found in the occipital condyles and 6% Grade I, 89% Grade II, but no Grade III changes in the superior articular cartilage of the atlas. Degeneration of the inferior articular cartilage of C-1 and the superior articular cartilage of C-2 indicates that the atlantoaxial joint faces more intense mechanical exposure, which is increased at the upper joint surfaces.