Intravertebral pressure gradient during vertebroplasty.

OBJECTIVE: Intravertebral pressure (IP) is considered a possible factor influencing cement leakage in vertebroplasty (VP). Reports of measuring IP during the injection of the cement reveal rather low values in the periphery of the vertebral body but fail to determine the situation in the center. Hypothesizing there is a significant IP gradient between both areas intravertebral pressure measurements were conducted in a comparative biomechanical study. METHODS: VP was performed in ten lumbar cadaveric spines. A pressure sensor was either placed in the center or in the periphery of the vertebral body, while bone cement was delivered in 1.5-cc increments. Volume flow, cement mixing time, and room temperature were standardized and kept constant during cement injection. RESULTS: During the administration of the first 1.5 cc of bone cement, the central IP (C-IP) increased to 23.6 kPa and the peripheral IP (P-IP) to 0.9 kPa on average. With the second injection, the mean C-IP was 42.8 kPa while the mean P-IP was 3.8 kPa. During the 3rd filling, C-IP averaged 69.9 kPa and P-IP 12.8 kPa, respectively. At the last increment, C-IP was at 70.7 kPa and P-IP at 24.5 kPa on average. CONCLUSIONS: A centroperipheral IP gradient (∆IP) was monitored during cement delivery in VP. ∆IP decreases with increasing bone cement charge of the vertebra, but C-IP stays significantly higher than P-IP at all times. C-IP was consistently higher than IP values reported for VP so far.

How to store autologous bone graft perioperatively: an in vitro study.

INTRODUCTION: Autologous bone graft is the golden standard for bone grafting, but little is known about the influence of various preservation techniques used during surgery immediately following harvest on the osseous structures and graft vitality. Several studies focussed on the optimal treatment of the bone during harvest and implantation, but only few examined the intraoperative storage conditions on the back table. The aim of our study was to examine the influence of various intraoperative preservation techniques on human cancellous bone at different points to optimize the storage during surgery. MATERIALS AND METHODS: Cancellous bone was harvested during hip arthroplasty and stored for 2 and 4 h under dry conditions, inside a swab moistened with saline solution or in saline solution, 5% glucose solution or culture medium. After the storage period, the bone was cultured and examined 7 days after the first cells grew out in one of these groups. Following the identification of the cells as osteoblast-like cells, the cultures were analysed by fluorescence staining, cell count and the XTT-test. RESULTS: Fluorescence staining revealed no avital cells in all groups. Dry storage of the bone led to significantly lower cell metabolism after 2 h compared to saline solution and 5% glucose solution. The same was true after 4 h dry storage compared to the moistened swab, and glucose and culture medium. Cell count was significantly lower after 2 h of dry storage compared to saline solution and culture medium. CONCLUSIONS: Perioperative storage of cancellous bone under dry conditions should be avoided. The bone graft should be stored in saline or 5% glucose solution or a moistened swab.

Early polyethylene wear and excessive acetabular granuloma in an uncemented HA-coated total hip arthroplasty--midterm results of a prospective study.

This is a prospective review of 135 HA-coated ABG I total hip arthroplasty (THA) systems with a mean clinical and radiographic follow-up of 8.5 years. The 5-year survival rate was 85%, but 22% of the patients were dissatisfied. Revision THA was already indicated in 28% of the patients, with 26% indicated for cup loosening. PE wear was detected by x-ray in 42%. Disproportionate substantial wear with an average linear loss of 2.6 mm at the inner rim of the insert was observed in 23% of the cases. The mean annual wear rate was calculated 0.1-0.25 mm/year. Laboratory examination of the retrieved PE revealed polishing, cracks, and subsurface delamination. Radiographic evidence of acetabular cysts were found to be excessive granuloma during surgery. Polarization microscopy revealed debris particles phagocytized by reticuloendothelial cells. Results confirm the general opinion that aseptic osteolysis is a cell-mediated process driven by the presence of particles generated from wear debris. The findings also suggest that the main reasons for the failure of the first-generation ABG hip system were an insufficient locking mechanism and poor PE congruency, and not solely poor PE quality.