Previously, radiostereometric analysis following hip revision performed using impacted morsellised allograft bone and a cemented Exeter stem has shown continuous subsidence of the stem for up to five years. It is not known whether the subsidence continues thereafter. In our study, 17 of 25 consecutive osteo-arthritic patients with aseptically loose stems who underwent first-time revision using impacted morsellised allograft bone and a cemented Exeter stem were followed by yearly radiostereometric examinations for nine years. The mean subsidence at six weeks was 1.1 mm (0.1 to 2.3), from six weeks to one year 1.3 mm (0 to 2.6), from one to five years 0.7 mm (0 to 2.0), and from five to nine years 0.7 mm (0.1 to 3.1). That from six weeks to nine years was 2.7 mm (0 to 6.4) (95% confidence interval 2.0 to 3.5). The Charnley pain score significantly improved after revision, and was maintained at nine years, but walking ability deteriorated slightly as follow-up extended. Of the eight patients who were not followed for nine years, two had early subsidence exceeding 11 mm.

Our findings show that in osteo-arthritic patients who undergo revision for aseptic loosening of the stem using impacted morsellised allograft bone and a cemented Exeter stem, migration of the stem continues over nine years at a slower rate after the first year, but without clinical deterioration or radiological loosening.

Introduction The aim of this study was to describe the migration pattern of the Exeter stem after revision with morsellised allograft bone and cement, to evaluate if restricted weight bearing had any influence on migration, and to measure, before and after revision, the quality of life comparing it to primary cemented hip arthroplasties.

Methods Forty-one consecutive stem revisions were followed by radiostereometry (RSA, 1. Selvik 1989). The accuracy of the RSA set-up was between 0.3 mm and 0.7 mm. The surgical procedure described by the Exeter group (2. Gie 1993) was used. All were first time revisions for aseptic loosening and all patients had had their primary arthroplasty for osteoarthritis. Bone stock deficiency was classified according to Gustilo and Pasternak. Sixteen were type I, 20 type II, five type III but none was classified as type IV. The Nottingham Health Profile was used to measure quality of life before and after revision.

Results All stems migrated distally and most of them also migrated medially or laterally and posteriorly. Migration was still observed in one third of stems between 1.5 and two year follow-ups. At two years stem subsidence averaged 2.5 mm, medial or lateral migration averaged 1.2 mm and posterior migration averaged 2.9 mm. No correlation to the pre-operative bone stock deficiency was observed. Between two and five years only marginal migration occurred in 12 of the 15 stems followed for five years. No differences in the migration pattern were detected when free weight bearing was allowed immediately after revision in hips without intra-operative skeletal complications compared to when restricted weight bearing was practiced. Most migration occurs within the first two weeks after surgery. NHP scales for pain, physical mobility, sleep and energy scales improved significantly. NHP scores were in all six scales comparable to those of primary arthroplasties. No rerevision was performed and no stem had radiographic sings of loosening.

Conclusions Most migration occurred early after revision and decreased gradually. Marginal migration after two years does not deteriorate the results during the first five years after surgery. Quality of life (patient outcome) after revision with impacted morsellised allograft bone and cement was comparable to that of primary arthroplasties.

In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source.

Our aim was to determine whether tantalum markers improved the accuracy and/or precision of methods for the measurement of migration in total hip replacement based on conventional measurements without mathematical correction of the data, and with Ein Bild Roentgen Analyse – Femoral Component Analysis (EBRA-FCA) which allows a computerised correction. Three observers independently analysed 13 series of roentgen-stereophotogrammetric-analysis (RSA)-compatible radiographs (88). Data were obtained from conventional measurements, EBRA-FCA and the RSA method and all the results were compared with the RSA data. Radiological evaluation was also used to quantify in how many radiographs the intraosseous position of the bone markers had been simulated. The results showed that tantalum markers improve reliability whereas they do not affect accuracy for conventional measurements and for EBRA-FCA. Because of the danger of third-body wear their implantation should be avoided unless they are an integral part of the method.

Several methods of measuring the migration of the femoral component after total hip replacement have been described, but they use different reference lines, and have differing accuracies, some unproven. Statistical comparison of different studies is rarely possible.

We report a study of the EBRA-FCA method (femoral component analysis using Einzel-Bild-Röntgen-Analyse) to determine its accuracy using three independent assessments, including a direct comparison with the results of roentgen stereophotogrammetric analysis (RSA).

The accuracy of EBRA-FCA was better than ±1.5 mm (95% percentile) with a Cronbach’s coefficient alpha for interobserver reliability of 0.84; a very good result.

The method had a specificity of 100% and a sensitivity of 78% compared with RSA for the detection of migration of over 1 mm. This is accurate enough to assess the stability of a prosthesis within a relatively limited period. The best reference line for downward migration is between the greater trochanter and the shoulder of the stem, as confirmed by two experimental analyses and a computer-assisted design.