In 33 dogs we implanted femoral stems made either of carbon composite, some coated with hydroxyapatite, or of titanium alloy with a porous coating. Osseointegration was greater in the hydroxyapatite-coated than in the un-coated stems (p less than 0.001). Push-out tests, at an average of 7.2 months after implantation, showed a six-fold increase in interface shear strength and a twelve-fold increase in shear stiffness in the hydroxyapatite-coated group compared with noncoated implants. The highest shear-strength values were found in the porous-coated titanium alloy stems, around which there was also the most resorptive bone remodelling.

The purpose of this study was to determine the biological effects of the elastic modulus of the femoral stem in canine hip arthroplasty. Cementless total hip arthroplasty was performed in 12 dogs, six had a low elastic modulus polyacetal resin stem and six had a high modulus stainless steel stem. The components were otherwise similar. At six and 12 months after operation, radiographic and histomorphometric analysis showed that those with steel implants had more cortical porosity than did the other group (p less than 0.01). We suggest that the elastic modulus of the implant is an important factor in controlling cortical bone resorption. A low modulus femoral prosthesis can significantly decrease bone resorption which might otherwise eventually lead to implant failure.

We reviewed 83 patients after below-knee amputation. In 56 with 69 amputations early management was by plaster-pylon. A plaster cast is applied in the operating room, and a pylon added one week later, after which full weight-bearing is allowed. We compared these patients with 27 who had soft bandaging. The 'healing' time was reduced from 98 days to 40 days, and there were no major complications in the plaster-pylon group. The technique is simple and cheap and can be used by paramedical staff without specialised training or equipment.

Failure of fixation is a major complication of the treatment of unstable intertrochanteric fractures. A retrospective review was performed of 54 such fractures treated with a sliding screw-plate device. Linear and angular displacements were calculated from radiographs taken at operation and serially until healing was complete. Linear displacement was related to fracture instability, but the neck-shaft angle was relatively constant during healing. Complications were often due to failure of the sliding mechanism of the implant. We conclude that a sliding screw-plate allows controlled collapse of the major fragments but maintains the neck-shaft angle even in unstable fractures.

The Roger Anderson external fixator was used in the treatment of unstable fractures of the distal radius in 52 patients, and the results evaluated after a follow-up averaging 58 months. The indications for its use were failure to maintain adequate closed reduction using plaster, and instability of the fracture as determined by the initial radiographs. Our radiological criteria for instability included dorsal angulation of more than 20 degrees, fractures involving the joint, radial shortening of more than 10 mm, and severe dorsal comminution. Using the Lucas modification of the Sarmiento demerit point-rating system, we found that 46 patients (89%) had good or excellent results and six (11%) were classified as fair. There were no poor results. Seven patients (14%) developed complications. None of these affected the long-term results except in one elderly woman where the pins loosened and had to be removed.