Single-level fusion without decompression for high-grade spondylolithesis in adolescents: a novel surgical strategy.

PURPOSE: There is no consensus on the optimal surgical treatment for high-grade spondylolisthesis (HGS) in adolescents. The purpose of this study was to assess the radiographic and clinical outcomes of a novel surgical approach to HGS consisting of a single-level anterior reduction, placement of a lordotic cage, and circumferential fixation without decompression. METHODS: This was a retrospective consecutive case series of 11 adolescents who underwent anterior reduction through placement of a lordotic cage followed by posterior fusion using pedicle screws and rods confined to L5-S1. Radiographic data included slip percentage, slip angle, lumbar lordosis, and pelvic sagittal parameters assessed at clinical visits preoperatively and at 2 years postoperatively. A telephone survey was conducted to obtain current information about function, activity level, work status, and retrograde ejaculation. RESULTS: Patients were followed for an average of 7.8 years (range 2-16). Mean age was 15.5 years (range 12-19). The mean percent slip corrected from 55 to 18%. The average slip angle was + 17.1° preoperatively and - 14.1° at final assessment (average correction of 20.7°). Thirty-six percent (4/11) of patients improved by three Meyerding grades and an additional 55% (6/11) improved by two grades. Complications included one instance each of superficial infection, wound dehiscence, and transient neuralgia. There were no cases of instrumentation failure, cage subsidence, pseudoarthrosis, or retrograde ejaculation. Radiographic evidence of fusion was observed in all cases. CONCLUSION: Single-level anterior reduction and circumferential fusion without decompression appears to be a safe and effective alternative for the surgical treatment of pediatric HGS. LEVEL OF EVIDENCE: IV.

Comparison of infrapatellar and subcutaneous adipose tissue stromal vascular fraction and stromal/stem cells in osteoarthritic subjects.

Since inflammatory mechanisms have been postulated to link obesity to osteoarthritis, the current study evaluated the ratio of immune cells to multipotent stromal cells within the infrapatellar fat pad (IPFP) and subcutaneous adipose tissue (SQ) of the knee; each depot has potential as a source of regenerative cells. The immunophenotypes of stromal vascular fraction (SVF) and adipose-derived stem cells (ASCs) of the IPFP and SQ were determined in tissues from osteoarthritic subjects (n = 7) undergoing total knee replacement. Based on a subset of surface antigens, the immunophenotype of ASCs from SQ of OA subjects was not significantly different from that of relatively healthy and leaner subjects undergoing elective liposuction surgery. Flow-cytometry comparison of SVF cell populations in the IPFP of OA subjects resembled those within the subject's own matched SQ, with the exception of the endothelial marker CD31(+) , which was significantly greater in cells from SQ. In the OA subjects, lower numbers of capillary-like structures and higher numbers of stromal and alkaline phosphatase colony-forming units in the IPFP vs SQ were consistent with this finding; however, ASCs from both depots in OA subjects exhibited comparable adipogenic and osteogenic differentiation potential. Thus, the IPFP contains an ASC and immune cell population similar to that of donor-matched SQ, making it an alternative ASC source for tissue regeneration. Further studies will be needed to determine whether IPFP immune cell infiltrates play an aetiological role in osteoarthritis equivalent to that shown in diabetes associated with obesity.

The memory properties of cold-worked titanium rods in scoliosis constructs.

STUDY DESIGN: Time series monitoring changes in titanium and stainless steel rod curvature kept at a constant temperature of 37 C as a function of time. OBJECTIVES: To assess the possibility of loss of curvature in titanium rods after scoliosis surgery. SUMMARY OF BACKGROUND DATA: Titanium rods have gained use in scoliosis surgery due to their excellent biocompatibility, while allowing medical personnel to obtain undistorted magnetic resonance imaging scans following surgery. However, the impression of several clinicians has been that when screw pullout and/or loss of sagittal balance occurs, it may be due to the rods losing some of their curvature. METHODS: Five 6-mm rods of differing compositions and lengths (titanium 300 and 100 mm, stainless steel 300 and 100 mm, prebent titanium 85 mm) were bent at room temperature with a 3-point rod bender, then placed in an incubator at 37 C. Digital photographs were taken every 2 weeks and analyzed to extract the radius of curvature of each rod. RESULTS: The Ti rods had a significantly decreasing curvature with time. The prebent Ti and stainless steel rods did not exhibit significant change in curvature. CONCLUSIONS: Titanium rods bent at room temperature and then exposed to body temperature over time tend to exhibit "metal memory"; they gradually revert to their original shape. This may result in loss of sagittal balance and/or proximal screw pullout.