Frontal plane biomechanics of the operated and non-operated knees before and after unilateral total knee arthroplasty.

BACKGROUND: After unilateral total knee arthroplasty, frontal plane loading patterns on the operated knee remain pathological in the long term, but it is unclear how they change in the early postoperative period. Additionally, researchers have suggested that the non-operated knee bears greater frontal plane loads postoperatively, but this effect is unclear. The objective of the present study was to compare the preoperative and early postoperative frontal plane loading patterns of both knees after unilateral total knee arthroplasty. METHODS: Fifty patients with end-stage knee osteoarthritis were examined prior to and six weeks after surgery. Patients underwent a three-dimensional gait analysis that determined the frontal plane loading patterns of knee varus angle and knee adduction moment during gait, and completed self-evaluative questionnaires and functional tests. FINDINGS: There were no significant loading differences between limbs preoperatively. The operated knee showed large reductions in varus angle and adduction moment after surgery (all p<0.001). The non-operated knee showed no increases in varus angle or adduction moment, but did show a small reduction in the adduction moment (p<0.001). Both knees showed reduction in pain after surgery (p<0.001) and the operated Knee Society Score improved after surgery (p=0.01). INTERPRETATION: Total knee arthroplasty reduces frontal plane loading in the operated knee and does not worsen frontal plane loading in the non-operated knee. Therapy after surgery should focus on retaining the reduction in knee adduction moment in the operated knee and preventing further worsening loading patterns in the non-operated knee.

[Rapidly vanishing hip--a mystery].

Rapidly destructive hip disease is a rare condition, the cause of which is yet to be clarified, and is described in the literature by scant case reports. The disease was first described by Forestier in 1957, and since then many names have been proposed to describe the rapid vanishing of the femoral head, and occasionally the acetabulum. This condition initially represents as acute hip pain, and rapidly progresses to complete vanishing of the proximal femur, within a few months. We briefly discuss the literature regarding this phenomenon, and describe a case of a female patient who suffered from complete disappearance of the femoral head within 9 weeks.

Early results of total hip replacement with the Metasul metal-on-metal cementless prosthesis.

BACKGROUND: The need for better durability and longevity in total hip arthroplasty in high demand patients is a constant challenge. For this purpose, a metal-on-metal prosthesis with improved tribology was developed. Our early results using this implant are presented. MATERIALS AND METHODS: A prospective analysis was performed for 56 Metasul hip arthroplasties between 1997 and 2001. There were 39 patients (43 hips) available for both clinical and radiographic evaluation at an average follow-up period of 42 months. Outcomes were measured using the Harris hip score. DISCUSSION: The average Harris hip score increased from 40.7 to 81.1. Subjectively, 87% of the primary cases were satisfied. The majority of patients had pain-free range of motion and had returned to improved daily functions. One technical intraoperative complication (false route) was resolved with immediate revision. Two patients required cerclage wiring, due to a femoral crack. There were two cases of persistent distal peroneal nerve palsy. Three cases of anterior dislocations were reduced and did not recur. A case of positive intraoperative culture was successfully treated with intravenous antibiotics. Two patients required revision to a cemented acetabular prosthesis, one due to cup loosening and the other due to a painful hip with a suspected infection. Radiolucent lines were seen in the acetabulum in one case, which underwent revision. No femoral or pelvic radiolucent lines were found. CONCLUSIONS: We have had relatively satisfactory results in the early follow-up period. It remains premature to draw conclusions as to the superiority of this system over a conventional metal-on-polyethylene bearing prosthesis. Long-term follow-up studies are needed.