Stability of internal versus external fixation in osteoporotic pelvic fractures - a biomechanical analysis.

INTRODUCTION: Osteoporosis-related fragility fractures of the pelvic ring (FFP) differ fundamentally from pelvic fractures in younger patients. However, very little is known about biomechanical stability of different osteosynthesis procedures addressing the anterior pelvic ring in these fractures. The aim of this study was to compare standard external fixation with internal fixation using a novel screw-and-rod system in osteoporotic fractures of the pelvic ring in terms of stiffness, plastic deformation and maximum load under cyclic loading in a human cadaveric model. MATERIALS AND METHODS: A total of 18 embalmed osteoporotic cadaver pelvis specimens were randomized based on the T-score into a group for external fixation and a group for internal fixation. FFP type-IIB fractures were created. In addition to the external or internal fixator, a cement-augmented sacroiliac screw was implanted. Afterwards, axial cyclic loading was performed in a testing setup simulating one-leg stand. RESULTS: Mean plastic deformation and stiffness both were significantly better in the internal fixation group than in the external fixation group (plastic deformation: 0.37 mm (SD: 0.23) versus 0.71 mm (SD: 0.26), p = 0.011; stiffness: 43.69 N/mm (SD: 18.39) versus 26.52 N/mm (SD: 9.76), p = 0.029). Maximum load did not differ significantly between internal fixator (506.3 N; SD: 129.4) and external fixator (461.1 N; SD: 147.4) (p = 0.515). CONCLUSIONS: Submuscular internal fixation might be an interesting alternative to external fixation in clinical practice because of better biomechanical properties as well as several advantages in clinical use.

CD44: survival and metastasis in chondrosarcoma.

OBJECTIVE: Recent studies have shown abnormal expression of CD44s and some of its isoforms in many human malignancies, but little is known about the presence of CD44 in chondrosarcoma. In this study the expression of CD44s and two variant isoforms was evaluated. It was assumed that abnormalities in these receptor proteins may be associated with clinical outcome of the patients. METHOD: Thirty paraffin-embedded chondrosarcoma samples were immunostained with monoclonal antibodies for CD44s, CD44v5 and CD44v6. Two independent examiners who were unaware of the clinical status of the patients evaluated the immunohistochemical results. The percentage of CD44-positive cells was scored semiquantitatively. A rate of higher than 10% was considered as overexpression. RESULTS: Among the 30 patients (median age 50 years) there were 22 conventional chondrosarcomas, two dedifferentiated chondrosarcomas, two extraskeletal chondrosarcomas, and one periostal, mesenchymal, clear cell and myxoid chondrosarcoma each. In the immunochemistry staining overexpression (>10% of cells) of CD44s was shown in 56.7% (17 of 30), of CD44v5 in 43.3% (13 of 30) and of CD44v6 in 6.7% (two of 30) of the tumors. Four grade III chondrosarcomas (80%) and 10 (71.4%) grade II chondrosarcomas showed overexpression for CD44s, whereas CD44s was overexpressed in only three (27.3%) grade I chondrosarcomas. Cox regression suggests overexpression of CD44s to be an additional prognostic marker for chondroid bone tumors independent of grading and other covariates. CONCLUSIONS: Overexpression of CD44s correlated significantly with metastatic potential and with poorer survival in patients with chondrosarcoma. CD44s might be an independent additional marker, but small sample size remains to be considered.