Reduced wear of cross-linked UHMWPE using magnesia-stabilized zirconia femoral heads in a hip simulator.

Background: To reduce wear, the ideal bearing surface in joint arthroplasty should be smooth and hydrophilic. Ceramics generally offer better wettability than metals and can be polished to a smoother finish. However, clinical studies have found no reduction in liner wear when using yttria-stabilized zirconia (Y-TZP) instead of cobalt chromium alloy (CoCr) femoral heads.

Minimal backside surface changes observed in retrieved acetabular liners.

Modular polyethylene liners offer versatility in total hip arthroplasty, but the locking mechanism may allow micromotion and backside wear. We evaluated the backside surface of 56 retrieved acetabular liners (mean 5.54 years in vivo, range 0.

Diamond-like carbon coatings enhance scratch resistance of bearing surfaces for use in joint arthroplasty: hard substrates outperform soft.

The purpose of this study was to test the hypotheses that diamond-like carbon (DLC) coatings will enhance the scratch resistance of a bearing surface in joint arthroplasty, and that a hard ceramic substrate will further enhance scratch resistance by reducing plastic deformation. We tested these hypotheses by applying a hard DLC coating to medical-grade cobalt chromium alloy (CoCr) and magnesia-stabilized zirconia (Mg-PSZ) femoral heads and performing scratch tests to determine the loads required to cause cohesive and adhesive fracture of the coating. Scratch tracks of DLC-coated and noncoated heads were then scanned by optical profilometry to determine scratch depth, width, and pile-up (raised edges), as measures of susceptibility to scratching.

Not all zirconia femoral heads degrade in vivo.

Degradation of yttria-stabilized zirconia femoral heads in vivo has been linked to increased roughening and even fracture of the femoral head. To determine whether magnesia-stabilized zirconia is better suited to resist degradation, we characterized the monoclinic phase concentration, surface topography, and microhardness of retrieved zirconia femoral heads. From previous work, we expected yttria-stabilized zirconia heads to undergo considerable tetragonal-to-monoclinic phase transformation in vivo, leading to considerably increased roughness and decreased microhardness, whereas magnesia-stabilized zirconia heads would not experience phase transformation and thus would not roughen or exhibit decreased microhardness.

Gluteus maximus flap transfer for greater trochanter reconstruction in revision THA.

We evaluated the results of an operative technique used in five patients (five hips) to reconstruct the greater trochanter with a gluteus maximus flap transfer during revision total hip arthroplasty. We exposed the hip through a posterior approach that split the gluteus maximus in its midsubstance. We then raised a flap from the posterior portion of the gluteus muscle that was elevated proximally to create a triangular muscle flap.