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Purpose. To investigate the source of osteoprogenitor cells responsible for heterotopic ossification (HO) following total hip arthroplasty in an animal model.Methods. New Zealand White (NZW) rabbits ( n = 20) received a radiation treatment 24 h preoperatively to the hip joint of one hindquarter and to the femoral shaft of the contralateral side. Subjects underwent bilateral hip surgery 24 h after treatment. Subjects were euthanized and radiographed 4 months postoperatively. Heterotopic ossification was graded according to a modified Brooker scale. Mean grade, intra-observer reliability, and statistical significance 0, < 0.05) were evaluated to compare the severity of heterotopic ossification between hindquarters treated with hip irradiation versus those treated with femoral shaft irradiation.Results. The Fleiss Weighted Kappa Statistic indicated "almost perfect" (0.872) intra-rater reliability of radiographic heterotopic ossification grading. The average heterotopic ossification grade for the group receiving radiation to the hip was significantly greuter than that for the group receiving radiation to the femoral shaft (2.575 versus 2.0, p < 0.02).C~inclusion. Although both have some beneficial effect, our results demonstrate that irradiation of the femoral canal is significantly more effective than irradiation of the hip joint and abductor musculature for heterotopic ossification prophylaxis. This suggests that osteoprogenitor cells responsible for heterotopic ossification originate from both the hip abductors and the femoral canal, but the data provide indirect evidence that the femoral canal may be a more dominant source of these cells in the rabbit model.

The vastus-splitting approach offers a viable alternative to the median parapatellar approach for primary total knee arthroplasty that reduces the need for lateral retinacular release without impairment of quadriceps function. Electromyographic abnormalities in the quadriceps muscle have no functional consequence and most likely represent reversible neurapraxic injury that may be avoided by blunt dissection in the vastus medialis muscle.

Preoperative irradiation to prevent heterotopic ossification optimally should be administered twenty-four hours before the operation. This latency period probably allows expression of radiation-induced sublethal mutations in the genetic code of pluripotential stem cells and precludes differentiation to osteoblastic cell lines.

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The vastus-splitting approach offers a viable alternative to the median parapatellar approach for primary total knee arthroplasty that reduces the need for lateral retinacular release without impairment of quadriceps function. Electromyographic abnormalities in the quadriceps muscle have no functional consequence and most likely represent reversible neurapraxic injury that may be avoided by blunt dissection in the vastus medialis muscle.

Transjugular intrahepatic portosystemic shunt has become an accepted intervention to treat sequelae of end-stage liver disease such as refractory ascites and esophageal varices for patients awaiting liver transplantation. Technical difficulties in such patients at the time of transplantation are usually limited to malpositioning of the stent requiring modification of the usual vascular anastomoses. Migration of the stent intraoperatively has not been a reported complication in the literature. We report a case in which a patient with a previously placed transjugular intrahepatic portosystemic shunt underwent successful liver transplantation complicated by intraoperative migration of the stent into the left pulmonary artery. The stent was removed from the pulmonary artery postoperatively using interventional radiology techniques.

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