Aims

Young adults undergoing total hip arthroplasty (THA) largely have different indications for surgery, preoperative function, and postoperative goals compared to a standard patient group. The aim of our study was to describe young adult THA preoperative function and quality of life, and to assess postoperative satisfaction and compare this with functional outcome measures.

A statement of the purposes of the study and background:

Merely publishing clinical guidelines is insufficient to ensure their implementation in clinical practice. We aimed to clarify the decision-making processes that result in the delivery of particular treatments to patients with low back pain (LBP) in primary care and to examine clinicians' perspectives on the National Institute for Health and Care Excellence (NICE) clinical guidelines for managing LBP in primary care.

This study evaluated the biologic fixation of two different titanium porous coatings: a clinically successful sintered spherical bead coating [1] and a new sintered asymmetric particle coating (STIKTITE™, Smith & Nephew). The spherical bead coating has a porosity of about 50% and an average pore size of about 220 μm, whereas the STIKTITE coating has greater porosity (about 62%) and slightly smaller average pore size (about 200 μm). Biologic fixation was assessed using a load-bearing ovine model in which coated semi-circular disc implants were inserted into a defect created in the cancellous bone parallel to and approximately 3 mm below the medial tibial plateau [2] similar to the method reported by Ignatius [3]. The implants were slightly thicker than the defect created, producing a 0.2-mm overall pressfit. Initial implant stability was assessed using mechanical push-out (n = 3) immediately after implantation into cadaveric ovine bone. Quantitative mechanical push-out testing and qualitative histology (n = 9 and n = 2, respectively, per group per time point) was performed after six and 26 weeks in vivo.

The time-zero average peak push-out load (±S.D.) of the STIKTITE group (95±3 N) was found to be significantly greater (p < 0.02) than that of the spherical bead group (36±5 N). By six weeks in vivo, the average peak push-out load for the STIKTITE group was up to 1001±362 N, and that for the spherical bead group was up to 985±425 N, both representing a significant increase compared to their time-zero results (p < 0.0005). From six to twenty-six weeks in vivo, there was again a significant increase in the peak push-out load irrespective of group (p < 0.0005), with the average peak push-out loads up to 1620±406 N and 1444±446 N for the STIK-TITE and spherical bead groups, respectively. Histology revealed bone ingrowth in both groups that confirmed the findings of the mechanical push-out testing. While the STIKTITE group showed a trend toward greater biologic fixation, overall there was insufficient evidence to support differences between the two groups (p = 0.47) irrespective of the amount of time in vivo.

The results of this study confirm the ability of the STIK-TITE coating to achieve superior initial stability. This improved initial stability reduces the reliance on adjunct fixation (such as screws) or large amounts of press-fit to prevent micromotion and create an environment suitable for long-term bone ingrowth. The results also suggest that the STIKTITE coating had a tendency to initiate and maintain bone ingrowth under load-bearing conditions to a level greater than that of a clinically successful sintered bead coating. Because loading of the implant can cause micromotion at the bone/implant interface, models like the one used in this study likely provide a more challenging and realistic representation of anticipated clinical conditions than models with minimal implant loading.