The effect of a mismatched center of rotation on the clinical outcomes and flexion-extension range of motion: lumbar total disk replacement using mobidisc at a 5.5-year follow-up.

STUDY DESIGN: Retrospective clinical and radiographic assessment of 21 levels of 18 consecutive patients treated using total lumbar disk replacement (TDR) for degenerative disk disease. OBJECTIVES: To report clinical and radiographic outcomes after TDR using the Mobidisc prosthesis. In addition, to determine whether there is a correlation between clinical and radiologic outcomes and prosthesis positioning. SUMMARY OF BACKGROUND DATA: TDR for lumbar degenerative disk disease is reported to provide good clinical and radiographic outcomes. However, TDR can alter the kinematics of the facet joint during flexion and extension. If prosthesis positioning is poor, the facet joint loading is increased upto 2.5-fold. No study has examined whether differences between the prosthesis center of rotation (COR) and the individual's COR have an effect on the clinical or radiographic outcomes after TDR. METHODS: A retrospective study of 21 levels from 18 consecutive degenerative disk disease patients who underwent lumbar TDR. The Mobidisc prosthesis was used in all cases. Clinical parameters measured were lower back and leg pain [both assessed using the Oswestry Disability Index (ODI)]. These parameters were measured preoperatively and at the last follow-up. Radiographic assessment involved examining standard lateral flexion/extension views taken at the preoperative, postoperative 6-month, and the last follow-up assessments to determine disk space height (DSH) and range of motion (ROM). Patient satisfaction (subjective outcome) was determined by telephone questioning. For analysis, TDR cases were categorized into 3 groups on the basis of the size of the "COR index," which represented the difference between an individual's inherent COR and the inherent prosthesis COR. Group 1, COR index <5 mm, consisted of 13 levels; group 2, COR index >5 mm, and <10 mm, consisted of 5 levels; and group 3, COR index >10 mm, consisted of 3 levels. RESULTS: Overall, 77.8% of patients stated that they were highly satisfied with their surgical outcome. Low back pain visual analogue scale scores decreased from 7.61±2.17 (mean±SD) preoperatively to 2.33±2.679 at the last follow-up (P<0.001). The function increased postoperatively (ODI: 25.89±7.77 preoperative vs. 5.89±7.21 at last follow-up; P<0.001). The difference between preoperative and the last follow-up ODI was greater in group 1 than in groups 2 and 3 (P=0.034). Radiographic findings showed that TDR resulted in improved disk space height and segmental ROM (P<0.05). Analysis of the 3 groups showed that ROM preservation decreased as the COR index increased. CONCLUSIONS: The present study found that lumbar TDR using the Mobidisc prosthesis resulted in good clinical and radiologic outcomes and good patient satisfaction. Furthermore, we found that patient satisfaction, function, and ROM preservation correlated with correct COR positioning of the prosthesis.

Predictive factors for residual equinovarus deformity following Ponseti treatment and percutaneous Achilles tenotomy for idiopathic clubfoot: a retrospective review of 50 cases followed for median 2 years.

BACKGROUND AND PURPOSE: There is no consensus on how to predict residual equinovarus deformities after application of the Ponseti method. We assessed the prognostic value of clinical scoring systems, and also radiographic parameters that can be measured just before percutaneous Achilles tenotomy (PAT). METHOD: We reviewed 50 cases of clubfoot in 35 patients who were treated using the Ponseti method, including PAT, to analyze the factors that are predictive of residual equinovarus deformities. Mean age at the time of PAT was 2.4 (1.4-3.5) months, and the mean follow-up period was 23 (9-61) months. We divided these cases into 2 groups according to the need for further surgery to treat the residual deformities. RESULTS: 40 feet with satisfactory results were included in group 1, whereas the remaining 10 feet that required further surgery for unsatisfactory residual deformities were included in group 2. We compared the initial Dimeglio and Pirani scores obtained before the first Ponseti casting, follow-up Pirani scores, and radiographic parameters determined just before PAT between these 2 groups. There was no statistically significant difference between the groups in terms of the initial Dimeglio and Pirani scores, although the follow-up Pirani scores and lateral tibiocalcaneal angle were higher and the lateral talocalcaneal angle was lower in group 2 at the time of PAT. INTERPRETATION: We conclude that the Pirani score, lateral tibiocalcaneal angle, and talocalcaneal angle, when assessed immediately before PAT, might be predictive factors for residual equinovarus deformity following Ponseti treatment for severe idiopathic clubfoot.

Analysis of sagittal spinal alignment in 181 asymptomatic children.

STUDY DESIGN: A cross-sectional study. OBJECTIVES: To determine the "normal" radiographic parameters of the sagittal profile of the spine in asymptomatic children. SUMMARY OF BACKGROUND DATA: There was consensus that cervical kyphosis is pathologic, but we suspected that the cervical kyphosis or loss of cervical lordosis is abnormal in asymptomatic children and adolescents. And we measured the pediatric sagittal profiles including the cervical lordosis for asymptomatic subjects. MATERIALS AND METHODS: Analysis of 181 children without spinal pathology was performed. Radiographic measurements consisted of the following: cervical lordosis; thoracic kyphosis; thoracolumbar sagittal angle; thoracic apex; lumbar apex; lumbar lordosis; sacral inclination; sacral slope; pelvic tilt; and sagittal vertebral axis. RESULTS: The mean cervical lordosis was -4.8 ± 12.0 degrees (negative = lordotic), sagittal vertebral axis -2.1 ± 2.4 cm, thoracic kyphosis +33.2 ± 9.0 degrees, thoracolumbar sagittal angle 5.6 ± 8.4 degrees, lumbar lordosis -48.8 ± 9.0 degrees, sacral inclination 43.9 ± 7.6 degrees, sacral slope 34.9 ± 6.6 degrees, and pelvic tilt 9.4 ± 6.1 degrees. One hundred nine (60.2%) patients had hypolordotic cervical spine (≥ -5 degrees). Cervical kyphosis was present in 80 (44.2%) patients. CONCLUSIONS: There is significant variability in sagittal profile of the cervical spine in asymptomatic children. Cervical kyphosis was found in approximately 40% of our study cohort.

A CT-Based Simulation Study to Compare the Risk of Facet Joint Violation by the Cervical Pedicle Screw Between Degenerative and Nondegenerative Cervical Spines.

STUDY DESIGN: A retrospective case-control study. OBJECTIVE: This study aimed (A) to compare entry points and trajectories of the cervical pedicle screw (CPS) between degenerative and nondegenerative spines, and (B) to evaluate the risk of facet joint violation by the CPS according to the degree of facet degeneration. SUMMARY OF BACKGROUND DATA: Entry point, trajectories, and risk of misplacement of the CPS have been widely researched; however, its application to degenerative cervical spine has to be elucidated. METHODS: Sixty patients who underwent cervical surgeries at our institution were classified into two groups according to cervical facet joint degeneration. A simulation program with 0.7-mm thickness axial computed tomographic images was used to evaluate facet joint violation by the CPS from C3 to C6. Horizontal and vertical offsets of entry points were measured from two different anatomical landmarks on lateral mass, namely the lateral notch and the center of the superior ridge. The transverse and sagittal angles of the screws were also measured. Facet joint violation was evaluated and classified into either "minor" (<50% of screw diameter) or "major" (≥50% of screw diameter). RESULTS: The mean transverse and sagittal angles showed no difference between the two groups. However, a more superior vertical offset from the superior ridge in terms of entry point was observed in the degenerative cervical spine group at all levels (P = 0.001-0.026). In addition, facet joint violation was more frequently found in severely degenerated facet joints than in mild to moderately degenerated facet joints (P = 0.011). CONCLUSION: The entry point of CPS was moved more superiorly in the degenerative cervical spine in this study, which increased the risk of facet joint violation in our patients. Thus, surgeons need to modify the insertion technique of the CPS or to insert lateral mass screw instead of the CPS when it is considered to insert screws at the uppermost vertebra in the degenerative cervical spine. LEVEL OF EVIDENCE: 4.