We compared peri-prosthetic bone mineral density between identical cemented and cementless LCS rotating platform total knee arthroplasties. Two matched cohorts had dual energy x-ray absorptiometry scans two years post-operatively using a modified validated densitometric analysis protocol, to assess peri-prosthetic bone mineral density. The knee that was not operated on was also scanned to enable the calculation of a relative bone mineral density difference. Oxford Knee and American Knee Society scores were comparable in the two cohorts. Statistical analysis revealed no significant difference in absolute, or relative peri-prosthetic bone mineral density with respect to the method of fixation. However, the femoral peri-prosthetic bone mineral density and relative bone mineral density difference were significantly decreased, irrespective of the method of fixation, particularly in the anterior distal portion of the femur, with a mean reduction in relative bone mineral density difference of 27%. There was no difference in clinical outcome between the cemented and cementless LCS total knee arthroplasty. However, both produce stress-shielding around the femoral implants. This leads us to question the use of more expensive cementless total knee components.
Hip dislocation is common in children with total body cerebral palsy. It is associated with pain, difficulty in seating and problems with perineal hygiene. We present a retrospective study of 15 patients who had undergone 21 proximal femoral resection-interposition arthroplasties between 1990 and 2005. The mean age at the time of surgery was 16.2 years (range 11-26 years). Mean follow-up was 3.4 years (range 1-7 years). Ninety percent of patients had pain relief. Perineal hygiene and sitting was improved in all cases. A lateral femoral head defect was noted in 90% of hips and was associated with pain, and significant degenerative changes. Twelve hips had heterotopic ossification (11 type-1, one type-2 and 0 type-3). No major complications were seen. We would submit that proximal femoral resection is a good salvage procedure for the painful, dislocated hip, with an excellent chance of resolving symptoms. The finding of a lateral femoral head defect on the radiograph is associated with significant degenerative changes.
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