Poor results of the Freeman uncemented metal-backed acetabular component

Abstract

The Freeman metal-backed acetabular component is specifically designed for use with a Freeman-neck-retaining stem.1 Among its several unique features are an arc of 140°; subtended in relation to the prosthetic femoral head and a titanium metal back with a superolateral flange through which a screw can be inserted to supplement uncemented press-fit fixation. Into this metal back is inserted a high-density polyethylene (HDP) liner which has a central peg and two superolateral lugs that lock into the metal back (Fig. 1). Over a period of five years 120 cups were inserted by the senior author (DAFM) using three configurations of the femoral stem, all of which had fixed heads of 32 mm in diameter. We report the results using this acetabular component and describe a typical pattern of failure. Patients and MethodsBetween January 1987 and February 1991, 120 primary hip arthroplasties were carried out on 109 patients using a Freeman metal-backed acetabular cup (Corin Medical, Cirencester, UK) and a Freeman neck-retaining femoral prosthesis (Corin Medical). The femoral stem was used in one of three configurations; a cemented smooth stem in 71, an uncemented smooth stem in nine and an uncemented ridged stem in 40. There were 51 men and 58 women with a mean age at operation of 58.9 years for the men (30 to 85) and 64.8 years for the women (22 to 87). Of the 109 patients, operation was carried out for osteoarthritis in 86%, inflammatory arthritis in 10%, trauma in 2%, and for other causes in 2%. A Hardinge approach was used for all the patients. 2Those femoral prostheses which were cemented were implanted using a second-generation technique with lowviscosity polymethylmethacrylate containing gentamicin. The minimum follow-up was for 62 months. A total of 26 patients had died. Of the four perioperative deaths, three were due to cardiovascular causes and one to a perforated viscus. Four patients were lost to follow-up. The 73 patients (82 hips) who did not have an infection were subjected to a clinical assessment and radiological review. The radiographs were assessed for the presence of radiolucent lines according to the zones described by DeLee and Charnley.3 Because of significant interobserver and intraobserver error in the interpretation and reporting of radiolucent lines only those of 2 mm or more and occupying at least one-third of a zone were reported. 4 A titanium screw was used in all cups to aid primary stability and the presence of a fractured screw was recorded at the latest follow-up. Failure was defined as an acetabular cup which required revision for aseptic loosening or had migrated obviously on the plain radiographs.Survival rates were calculated using life tables and the Kaplan-Meier method.

Failure of an uncemented non-porous metal-backed prosthesis with augmentation using impacted allograft for acetabular revision

“…A similar problem was noted by Harris 21 In primary replacement, a similar acetabular implant has given disappointing results with survival ranging from 69% at five years 23 to 83% at ten years. 24 The press-fit nature of the polyethylene insert into the metal backing allows some micromovement between the respective parts. This provides a source of wear particles which produce an inflammatory reaction causing loosening.…”

The relationship between cup design and the radiological signs of aseptic loosening in total hip arthroplasty

“…[13][14][15][16] Other factors contributing to loosening of the cup include previous surgery, infection, impingement, and failure of the implant. [17][18][19][20] In addition to surgical technique, the physical properties of the material and its surface structure play an important role in loosening of the cup. Our study focused on the different incidences of the radiological signs of loosening between various cup systems over a long period of time.…”