We concluded that the stem failure was initiated by a fretting fatigue mechanism and was propagated by a pure bending fatigue mechanism. Risk factors for fractures of the modular junction include excessive body weight and inadequate proximal osseous support because of trochanteric osteotomy, reduced preoperative bone stock, osteolysis, loosening, and/or implant undersizing. Surgeons should consider the use of implants with strengthened junctions when using modular stems in such patients.
Pelvic discontinuity with associated bone loss is a complex challenge in acetabular revision surgery. Reconstruction using ilio-ischial cages combined with trabecular metal acetabular components and morsellised bone (the component-cage technique) is a relatively new method of treatment. We reviewed a consecutive series of 26 cases of acetabular revision reconstructions in 24 patients with pelvic discontinuity who had been treated by the component-cage technique. The mean follow-up was 44.6 months (24 to 68). Failure was defined as migration of a component of > 5 mm. In 23 hips (88.5%) there was no clinical or radiological evidence of loosening at the last follow-up. The mean Harris hip score improved significantly from 46.6 points (29.5 to 68.5) to 76.6 points (55.5 to 92.0) at two years (p < 0.001). In three hips (11.5%) the construct had migrated at one year after operation. The complications included two dislocations, one infection and one partial palsy of the peroneal nerve. Our findings indicate that treatment of pelvic discontinuity using the component-cage construct is a reliable option.
Distal femoral varus osteotomy (DFVO) may be indicated for symptomatic lateral compartment gonarthrosis associated with valgus deformity in younger, active patients. Thirty-three consecutive DFVOs (31 patients) with a minimum follow-up of ten years (mean 15.1, range 10-25) were reviewed. Fifteen DFVOs were converted to total knee arthroplasty (TKA) and one DFVO was awaiting TKA, reaching an overall failure rate of 48.5% at a mean of 15.6 years (range 6-21.5). Of the remaining 17 DFVOs, ten (58.8%) had good or excellent results, two (11.8%) had fair results and five (29.4%) had poor results. Mean modified Knee Society scores improved significantly (p< 0.01) from 36.8 preoperatively to 77.5 at one year post DFVO. DFVO is a viable treatment alternative for lateral compartment gonarthrosis. Conversion to TKA is expected to be required in approximately half of the patients at a mean of 15.6 years.
Acetabular component revision in the context of large contained bone defects with less than 50% host bone contact traditionally have been treated with roof reinforcement or antiprotrusio cages. Trabecular Metal TM cups (Zimmer, Inc, Warsaw, IN) may offer a reasonable treatment alternative. We evaluated the clinical and radiographic outcome of this mode of treatment. We prospectively followed 53 hip revision acetabular arthroplasty procedures performed with Trabecular Metal TM cups for contained defects with 50% or less contact with native bone. All patients were clinically and radiographically evaluated for evidence of loosening or failure. Minimum followup was 24 months (average, 45 months; range, 24-71 months). Contact with host bone ranged from 0% to 50% (average, 19%). The mean postoperative Merle d'Aubigne-Postel score was 10.6 (range, 1-12), with a mean improvement of 5.2 (range, À4-10) compared to the preoperative score. Two failed cups (4%) were revised. Two additional cups (4%) had radiographic evidence of probable loosening. Complications included four dislocations and one sciatic nerve palsy. The data suggest treatment of cavitary defects with less than 50% host bone contact using Trabecular Metal TM cups, without structural support by augments or structural bone grafts, is a reasonable option.
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