A. Arnould

Tantalum cones and bone defects in revision total knee arthroplasty.

Management of bone loss is a major challenge in revision total knee arthroplasty (TKA). The development of preformed porous tantalum cones offers new possibilities, because they seem to have biological and mechanical qualities that facilitate osseointegration. Compared to the original procedure, when metaphyseal bone defects are too severe, a single tantalum cone may not be enough and we have developed a technique that could extend the indications for this cone in these cases. We used 2 cones to fill femoral bone defects in 7 patients. There were no complications due to wear of the tantalum cones. Radiological follow-up did show any migration or loosening. The short-term results confirm the interest of porous tantalum cones and suggest that they can be an alternative to allografts or megaprostheses in case of massive bone defects.

Excellent short-term results of hip resurfacing in a selected population of young patients.

BACKGROUND Hip resurfacing (HR) is an alternative option to total hip arthroplasty (THA) in a population of selected patients (young and/or active). HYPOTHESIS The short-term survivorship rate is as least as good as that for THA with no abnormal increase in serum metal ion levels. MATERIALS AND METHODS A continuous prospective series of 502 hip resurfacings in 481 patients mean age 48.7 years old (±10.3; 18-68) (Conserve Plus, Wright Medical Technology) was analyzed clinically, radiologically and biologically (total blood chrome, cobalt and titanium metal ion levels). Mean follow up was 4.1 years (1.9-4.9). RESULTS There were no dislocations. There were 5 cases of revision surgery with component replacement (including 2 infections). Implant survivorship using implant removal as the criteria (excluding infection) was 99.4% at 4 years (CI 95%: 98.1-99.8). The evaluation of metal ion levels showed a significant increase in cobalt from a preoperative level of 0.24 μg/L (0.01-3.6) to 0.86 μg/L (0.01-5.7) at the final follow-up (P<0.001). Chrome and titanium levels went from 0.68 μg/L (0.01-4.4) and 2.36 μg/L (0.39-7) to 1.28 μg/L (0.1-5.5) and 4.49 μg/L (1.29-8.21) respectively (P<0.001). All clinical scores had significantly improved at the final follow-up. Mean frontal plane cup inclination was 42.7° (35-62). DISCUSSION In a selected population of young and/or active patients, the short-term results of hip resurfacing are excellent. At the postoperative 4-year follow-up the rate of complications (in particular the absence of dislocations) was less than that for THA in young and/or active patients. Certain conditions must be respected to obtain these results; frontal plane cup inclination of between 40 and 45°, a femoral head diameter of at least 48 mm and good quality femoral bone. LEVEL OF EVIDENCE IV.

Computed tomography evaluation of hip geometry restoration after total hip resurfacing

BACKGROUND Anatomic reconstruction of the hip is among the main requirements for hip arthroplasty to be successful. Resurfacing arthroplasty may improve replication of the native joint geometry but has been evaluated only using standard radiographs. We therefore performed a computed tomography (CT) study to assess restoration of hip geometry after total hip resurfacing (HR), comparatively with the non-operated side. HYPOTHESIS HR does not change native extra-medullary hip geometry by more than 5mm and/or 5°. PATIENTS AND METHODS CT was used to evaluate unilateral HR in 75 patients with a mean age of 52.2years (range, 22-67years). The normal non-operated side served as the control in each patient. Mean follow-up was 2.5years (range, 1.9-3.1years). The primary evaluation criteria were femoral offset (FO) and femoral neck anteversion (FNA) and the secondary criteria were cup inclination angle, cup anteversion angle, and lower-limb length. RESULTS FO showed a non-significant decrease (mean, -2.2mm; range, -4.5 to +3.7mm). FNA was preserved, with a difference of less than 2° at last follow-up versus the preoperative value. Cup measurements showed a mean anteversion angle of 24.8° (0.9-48.6) and mean inclination angle of 44.1° (32.1-56.3); corresponding values for the native acetabulum were 38.9° (20.5-54.8) and 24.8° (4.8-33.6). The residual lower-limb length discrepancy was less than 1mm (mean, -0.04mm [-1.2 to +1.6mm]). The mean angle between the femoral implant and the femoral neck axis was 5.4° of valgus. DISCUSSION Our results show that HR accurately restored the native extra-medullary hip geometry. LEVEL OF EVIDENCE III, prospective diagnostic case-control study.