Biomechanical and histological analysis of an HA coated, arc deposited CPTi canine hip prosthesis.

The interfacial shear strength and bone tissue response was investigated for an arc deposited (AD) commercially pure titanium implant surface, with (AD/HA) and without (AD) plasma-sprayed hydroxyapatite (HA) coating. Ten purpose bred coonhounds received bilateral femoral stem implantation (AD and AD/HA) in the proximal femurs (hemiarthroplasty). The femoral prosthesis consisted of a modular CoCr alloy head, modular Ti-6Al-4V neck, and a 10-mm diameter cylindrical Ti-6Al-4V femoral stem. The AD surface had 30-35% greater surface roughness than the AD/HA surface. The HA coating had a purity greater than 90% and a crystallinity greater than 65%. After 6, 12, and 24 weeks, the implants were retrieved and analyzed with mechanical testing, qualitative and quantitative histology, and electron microscopy. The AD/HA implants had equivalent interfacial shear strengths to the AD implants at all time periods. The AD/HA implants had significantly greater linear bone contact than the AD implants. The 6-week implants had significantly thicker cortical bone than the 12- and 24-week implants. The HA coating was very stable in vivo, evidenced by no thickness reduction at any time period. Qualitatively, the AD/HA implants primarily had bone contacting the implant surface with little fibrous tissue present, and the AD implants had bone and fibrous tissue contacting the implant surface. The electron microscopy analysis showed that the mechanically tested implants exhibited a mixed failure mode at the bone, HA coating, and titanium interfaces.

Bicondylar tibial plateau fractures treated with a hybrid ring external fixator: a preliminary study.

Twenty-three knees in 22 patients with Schatzker type VI tibial plateau fractures were treated with a hybrid ring external fixator using tensioned wires proximally and half-pins distally. All but two injuries were secondary to high-energy trauma. Six were open injuries, and eight patients had other major musculoskeletal trauma. Eight patients were treated with limited open reduction and internal fixation before application of the frame. The remainder received percutaneous cannulated screw fixation to stabilize the articular surface without opening the fracture site. Twenty-three fractures were followed to complete healing. Average time to healing was 4.4 months. Arc of motion averaged 107 degrees, and there were four flexion contractures of 5-15 degrees. Complications consisted of three deep wound infections, one deep venous thrombosis (DVT), one malunion, and one pin tract infection. The average knee score and patient function score were 84.7 and 80.5, respectively (Knee Society Clinical Rating System). There were 13 excellent, three good, one fair, and six poor results. The poor results were in patients who either developed deep wound infections or in those who sustained multiple musculoskeletal trauma compromising the patients' function score and ultimately the average score. This method provides good stabilization and allows early range of motion for complex tibial plateau fractures where extensive dissection and internal fixation are contraindicated due to traumatized soft tissue, osteopenia, and fracture comminution.