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We report the three-year results of a new flexible, horseshoe-shaped acetabular cup, with a carbon fibre reinforced polyetheretherketone (CFR-PEEK) bearing surface. The 3 mm thick composite cup is designed to conserve acetabular bone stock and reproduce a near-physiological stress distribution to the adjacent bone. The cup is intended to articulate against a large diameter ceramic femoral head to produce a low-wear bearing couple that generates minimal wear debris. A prospective, two-centre clinical study of the MITCH PCR cup was started in January 2007, to verify its safety and performance. Twenty-five MITCH PCR cups were implanted by three surgeons. There were 12 men and 13 women, with a mean age of 67.9 years (range 57.4 to 74.9). The mean Oxford hip score improved from 19.6 (SD 7.5) preoperatively to 43.5 (SD 7) at 3 years. The mean Harris hip score improved from 52.9 (SD 7) to 91.4 (SD 13.8) and the Euroqol-5D score increased from 62.6 (SD 18.4) to 82.8 (SD 19). One revision of the acetabular cup was undertaken at 21 months for squeaking. This has been investigated and modification of the articular geometry has resolved the problem, on in-vitro testing. Radiological analysis showed good early osseointegration of the MITCH PCR cup. However at three years, five cases of acetabular component migration and calcar resorption were observed. Three patients have subsequently undergone revision of the acetabular cup, at 41, 42 and 50 months respectively. The cause of the osteolysis is the subject of on-going investigation.

Arthroscopy is used increasingly in the diagnosis and treatment of hip disorders of both natural and prosthetic hip joints. Complications tend to be transient and self-resolving. This is the first report of a hip arthroscopy destabilizing a prosthetic hip resulting in dislocation of the joint.

A new uncemented acetabular component, the Cambridge cup, has been designed to mimic the anatomy and physiology of subchondral bone in order to minimise stress shielding and enhance long-term component stability. Cambridge cups were implanted in a cohort of 50 women who presented with displaced sub-capital fracture of the femoral neck. The cups were manufactured with an hydroxyapatite (HA) coating. Twenty six cups were implanted after removal of the HA. Twelve Cambridge cups were retrieved post-mortem between two and 84 months after implantation. Histological and histomorphometric testing was undertaken to analyse the residual HA coating thickness, bone apposition to the implant surface and particulate wear debris in the surrounding tissues.The HA-coated implants showed significantly greater bone apposition to the implant surface with significantly less fibrous tissue formation than the uncoated implants. Where HA resorption occurred, bone and bone marrow was seen adjacent to the implant. Excessive wear of the ultra high molecular weight polyethylene liner was not seen.The HA-coated components demonstrated good initial bone implant bonding and the flexible carbon polymer appeared to maintain stability following HA resorption. The uncoated implants showed little or no bony apposition but had a fibrous membrane apposed to the implant surface. This may be explained by a combination of micro-motion at the bone implant interface and having a component surface finish that was poorly suited to osseous attachment.Hydroxyapatite coated acetabular components can provide reliable osseous attachment. Subsequent HA resorption need not compromise medium-term osseous fixation to an appropriate implant surface.