Radiographic Analysis of the Lumbosacral Juncture: Is There a Critical Sacral Angle for Total Disc Replacement?

STUDY DESIGN: Retrospective review of a patient cohort through a prospective study. PURPOSE: To determine whether there are correlations between radiographic measurements, including sacral slope (SS) and pelvic incidence (PI), and self-reported clinical outcomes among single-level L5/S1 ProDisc-L patients. OVERVIEW OF LITERATURE: The lumbosacral juncture presents unique biomechanical challenges with respect to artificial disc replacement (ADR) because of its orientation and consequential shear loading. Reports of inferior outcomes at L5/S1 compared to those of the outcomes at the levels above, including increased facet joint pain, suggest a relationship with the sacral inclination at L5/S1. METHODS: Plain standing lateral radiographs of 71 patients (age, 26–65 years) who underwent ADR at L5/S1 for degenerative disc disease were reviewed. SS and PI were measured based on pretreatment and initial follow-up standing films. Patient's average adjusted self assessments included the Oswestry disability index and visual analog scale for pain 2 years after ADR. Correlation coefficients were computed to evaluate relationships between radiographic parameters and clinical outcomes. Analysis of covariance was used to evaluate multivariate relationships among factors, including radiographic parameters, body mass index (BMI), and clinical outcomes. RESULTS: SS and PI values were obtained from 71 patients. The average SS was 33.3° and average PI was 39.9°. At the 24-month follow-up, no significant correlations (p≥0.05) were observed between radiographic parameters and clinical outcomes. BMI, age, and sex did not explain any variability in the relationships between clinical outcomes and SS and PI. CONCLUSIONS: We reviewed a large range of SS angles and found no associations between SS, PI, or BMI and clinical outcomes after ADR at L5/S1. These preliminary results demonstrate that ADR provided maintainence of pain relief and functional improvement for a wide range of SS angles, suggesting that steeper angles are not a contraindication for ADR.

The 15-Year Evolution of the Thoracoscopic Anterior Release: Does It Still Have a Role?

STUDY DESIGN: Retrospective. PURPOSE: To determine how the indications for anterior thoracoscopic release and fusion have evolved over time. OVERVIEW OF LITERATURE: Anterior release was commonly performed to correct severe spinal deformities before the advent of pedicle screw fixation. The thoracoscopic approach significantly reduced the morbidity, as compared to open thoracotomy procedures. METHODS: We reviewed charts and radiographs of pediatric spinal deformity patients who underwent thoracoscopic release/fusion for their deformity from 1994 to 2008. Indications for the thoracoscopic procedure were assigned to one of the following categories: hyperkyphosis, large/stiff scoliosis, crankshaft prevention, and 'other'. We analysed indications grouped in 3-year intervals to determine how the indications for this procedure evolved over the past 15 years. RESULTS: One hundred and thirty-eight patients (mean age, 15 years; range, 2-28 years) underwent the procedure, with 160 identified indications. The frequency of thoracoscopic anterior release/fusion decreased after peaking in the years 2000-2002. Initially, hyperkyphosis was the most frequent indication (15/33, 45%; 1994-1996), but declined to an intermittent indication since 2006. The use of thoracoscopy to prevent crankshaft has also declined, but remains an indication for the most immature cases (2/17, 12%; 2006-2008). Severe or rigid scoliosis is currently the most common indication for thoracoscopic release/fusion at our center (11/17, 65%; 2006-2008). CONCLUSIONS: The indications for a thoracoscopic anterior release/fusion has evolved with our increased understanding of this procedure and improved posterior fixation with pedicle screw instrumentation. Thoracoscopy in select spinal deformity patients still has an important role despite its less frequent use, as compared to the past decade.