Allograft reconstruction after resection of primary bone sarcomas has a non-union rate of approximately 20%. Achieving a wide surface area of contact between host and allograft bone is one of the most important factors to help reduce the non-union rate. We developed a novel technique of haptic robot-assisted surgery to reconstruct bone defects left after primary bone sarcoma resection with structural allograft. Using a sawbone distal femur joint-sparing hemimetaphyseal resection/reconstruction model, an identical bone defect was created in six sawbone distal femur specimens. A tumor-fellowship trained orthopedic surgeon reconstructed the defect using a simulated sawbone allograft femur. First, a standard, ‘all-manual’ technique was used to cut and prepare the allograft to best fit the defect. Then, using an identical sawbone copy of the allograft, the novel haptic-robot technique was used to prepare the allograft to best fit the defect. All specimens were scanned via CT. Using a separately validated technique, the surface area of contact between host and allograft was measured for both (1) the all-manual reconstruction and (2) the robot-assisted reconstruction. All contact surface areas were normalized by dividing absolute contact area by the available surface area on the exposed cut surface of host bone.INTRODUCTION
METHODS
We present the results of 15 patients revised with a Compress® prosthesis secondary to failure of other distal femur reconstruction. One prosthesis had to be removed because of deep infection. Three patients needed a second surgery due to a vertical crack proximal to the anchor plug at the level of a cortical bone defect. At last follow-up, radiologic evaluation of the entire series showed a mean bone growth ratio higher than did preoperative radiographs. All patients had mainly good or excellent MSTS functional results. Distal femoral prosthetic replacement with a Compress® implant in severe cases of bone loosening and instability provides a reliable reconstruction alternative that promotes bone formation. Patients with cortical defects proximal to the anchor plug should be protected with extracortical supports.
Doxorubicin-containing pellets were incubated with sarcoma cultures at 37°C for 24 hours. A significantly higher cell death rate(as measured by flow cytometry) was seen in the plates exposed to Doxorubicin compared to those exposed only to plain PMMA, indicating that the Doxorubicin released from the cement pellets retained its cytotoxic capability. PMMA-Doxorubicin cement pellets were implanted in rat tibiae and the animals killed at intervals over three weeks. HPLC analysis showed that this technique produced high concentrations of Doxorubicin adjacent to the implant but negligible systemic levels(heart, kidney, lung, liver). Four groups of rats had sarcomas established in their tibiae and then treated either by excision of tumour and Doxorubicin/PMMA implantation, excision and plain PMMA implantation, excision only or no treatment. The animals were then observed for tumour regrowth. A survival advantage was demonstrated for those animals treated by tumour excision and Doxorubicin/PMMA implantation. Conclusion: These experiments demonstrate that PMMA is an effective medium for the delivery of cytotoxic chemotherapy. This method has scope for early translation to the human situation.
Thirteen patients suffering from rheumatoid arthritis had 19 stress fractures of the tibia or fibula. These patients characteristically presented with sudden, severe, unexplained pain with localised tenderness just below the knee or above the ankle. In seven patients examination of the adjacent joint indicated a flare-up of disease activity or a pyogenic arthritis. In six patients the diagnosis was delayed by the late appearance of callus in minute fractures. All patients had rheumatoid deformities of the ipsilateral lower limb: valgus deformities of the knee and subtalar joints occurred most frequently. All patients had osteoporosis; all except two had received steroid treatment and five had abnormalities of calcium metabolism. We suggest that deformities of the knee and ankle predispose patients with rheumatoid arthritis and osteoporosis to stress fractures of the tibia and fibula.
