Review Question - QID 217323

This patient has massive proximal tibial bone loss secondary to resection for oncologic reasons. Use of an allograft prosthetic composite (APC) should be considered in high-demanding patients with no further risk factors to provide the best possible functional result for the extensor mechanism.

Proximal tibial bone loss is very problematic. A decision is routinely made for limb salvage versus amputation in these patients. One of the major goals of limb salvage is the restoration of the extensor mechanism. The techniques to achieve this rely on the establishment of a stable scar tube around the prosthesis. Cement is commonly used in these settings for fixation and implant longevity. Both megaprosthesis (MP) and APCs have been utilized in this setting.

Pala et al. reviewed limb salvage surgery in cases of bone sarcomas. They reported that the use of modular MP are the most common method of reconstruction after segmental resection of the long bones in the extremities for their availability, immediate fixation, early weight bearing, good function. They found that mega-prostheses implanted around the knee in tumor and revision surgery had complications including issues with stem fixation, extensor mechanism reconstructions in proximal tibia resections and the preservation of growth of the lower extremity in children.

Müller et al. reviewed the use of modular MP and APC for reconstructions for large bone defects of the proximal tibia in 42 consecutive patients. There were nine reconstruction failures after an average follow-up of 62 months: five in the MP group and four in the APC group (p=0.957). They reported that a 10-year implant survival rate of 79% for the MP and 94% for the APC, with no relevant differences between the two groups in functional results. They concluded that both MP and APC are valid and satisfactory reconstructive options for massive bone defects in the proximal tibia, but in high-demanding patients with no further risk factors, an APC should be considered to provide the best possible functional result for the extensor mechanism.

Figure A is a radiograph depicting a proximal tibial modular MP. Figure B is a radiograph of a proximal tibial APC. Illustration A is an intraoperative image of the reconstruction technique shows the prosthesis cemented in the graft and implanted press-fit in the residual tibial diaphysis using a long revision stem

Incorrect Answers:
Answer 1: The reported 10-year implant survival rate is 79% for the MP and 94% for the APC
Answer 2: There are no relevant differences between the two groups in functional results
Answer 4: The differences in failure rate between MP and APC is not statistically significant
Answer 5: Either options offers the ability to restore adequate limb length