We performed 83 consecutive cemented revision total hip arthroplasties in 77 patients between 1977 and 1983 using improved cementing techniques. One patient (two hips) was lost to follow-up. The remaining 76 patients (81 hips) had an average age at revision of 63.7 years (23 to 89). At the final follow-up 18 hips (22%) had had a reoperation, two (2.5%) for sepsis, three (4%) for dislocation and 13 (16%) for aseptic loosening. The incidence of rerevision for aseptic femoral loosening was 5.4% and for aseptic acetabular loosening 16%. These results confirm that cemented femoral revision is a durable option in revision hip surgery when improved cementing techniques are used, but that cemented acetabular revision is unsatisfactory

Summary Statement. We analysed impaction bone grafting used together with cemented or uncemented fixation in acetabular revision surgery. The overall risk for re-revision did not differ between the cemented and uncemented group. However, aseptic loosening was more common in the cemented group. Background. Several surgical techniques address bone defects in cup revision surgery. Bone impaction grafting, introduced more than thirty years ago, is a biologically and mechanically appealing method. The primary aim of this study was to evaluate the effect of bone impaction grafting when used with uncemented and cemented fixation in cup revision surgery. Uncemented cups resting on more than 50% host bone were used as controls. Patient and Methods. Cup fixation was studied in ninety hips (eighty-two patients), revised due to loosening between 1993 and 1997. There were fifty-three isolated cup and thirty-seven total revisions. Patients were followed for thirteen years using conventional radiography, radiostereometry (RSA), Harris Hip score and a pain questionnaire. Peroperatively the surgeon assessed the acetabular bone bed vitality. In hips where the cup was judged to rest on > 50% vital bone (group I, n=43), an uncemented cup was used. If the cup was resting on ≤ 50% living bone, uncemented (group IIa, n=21,) or cemented (group IIb, n=26) technique was chosen, according to the surgeon's preference. The mean age of patients at index revision was 61±12 years, 56% were females. The most common index diagnosis was primary osteoarthritis (n=45) followed by rheumatoid arthritis (n=10). Results. At thirteen years, acetabular component failure had necessitated a second revision in 6/7/8 hips in Groups I/IIa/IIb respectively. These re-revisions were performed 1–10 (mean 7.1) years after index revision. Moreover four cup / liner revisions were performed in hips with femoral loosening, not allowing further RSA measurements. These twenty-five hips were followed until re-revision. Deceased patients (n=21) and patients with deteriorating medical condition, not able to attend the follow-up (n=7), were censored in the survival statistics. Aseptic loosening was the most common reason of re-revision. However, in the uncemented groups (I/IIa), four cups were re-revised due to liner wear, osteolysis or instability. In the total study population, and up to two years, the median proximal migration was lowest in Group I followed by Group IIa and Group IIb (p≤0,006). At thirteen years the mean proximal migration was highest in Group IIb 1.29 mm (SD 1.23) followed by Group I 0.30 mm (SD 0.40) and Group IIa 0.22 mm (SD 0.22), p = 0.05. In cases subsequently re-revised because of loosening or with radiographically loose cups at the last follow-up, a higher proximal migration was observed compared to the non-revised and radiographically well-fixed group (up to seven years: p < 0.001; thirteen years: p=0.04). Discussion/Conclusion. We found an increased risk for rerevision in cases with less than 50% host bone-implant contact. These cups showed high early proximal migration, measured by RSA, indicating poor initial fixation. Rate of re-revision due to any reason did not differ between cemented and uncemented cups. The cemented group (IIb) had a higher risk of being re-revised due to aseptic loosening. Poor bone stock, use of small bone chips, inferior impaction technique, and no or restricted contact with living bone are probable reasons for failures when extensive bone grafting is needed

Background and aim. Recent proposals have been introduced to modify stem design and/or femoral fixation in total hip replacement (THR). New designs need to consider previous design features and their results. The aim of this study has been to evaluate the clinical and radiological results of six different designs of tapered uncemented stems implanted in our Institution. Methods. 1918 uncemented hips were prospectively assessed from 1999 to 2011 (minimum follow-up of five years for the unrevised hips). All hips had a 28 or 32 mm femoral head and metal-on-polyethylene or alumina-on-alumina bearing surface. Six uncemented femoral designs that shared a femoral tapered stem incorporating a coating surface were included in the study. The different design features included the type of coating, metaphyseal filling, and sectional shape. Results. Intra-operative proximal femoral crack was 6.7% in one of the designs (p=0.01), univariate analysis showing a lower risk of crack in the other designs. The position of the stem was neutral in 80% of the cases for all designs. Femoral canal filing was related to the stem design (p<0.001 at the three levels) and to the femoral level assessed (subset alpha=0.005). Twelve stems were revised for aseptic loosening (6 from two different designs). The survival rate for femoral aseptic loosening at 15 years was 96.6% (95% CI 93.8 to 99.4) for one of these two designs ad 97.4% (95% CI95.5 to 99.6) for the other. Regression analysis showed that stem design was the only factor related to aseptic loosening when adjusted for femoral canal filling (at the three levels) stem position (neutral or not) and femoral type (cylindrical or not). Conclusion. Tapered uncemented stems consistently provide excellent bone fixation. New designs need to avoid changing successful features and concentrate on the less successful aspects

Aims

Second-generation metal-on-metal (MoM) articulations in total hip arthroplasty (THA) were introduced in order to reduce wear-related complications. The current study reports on the serum cobalt levels and the clinical outcome at a minimum of 20 years following THA with a MoM (Metasul) or a ceramic-on-polyethylene (CoP) bearing.

Introduction. Total hip prostheses which use a ceramic head within a metal liner are a relatively recent introduction. As such, survivorship rates from independent centres alongside explant analysis are rare. The early experience with this novel ceramic-on-metal (CoM) bearing couple is reported. Methods and Materials. All CoM hips implanted between 2008 and 2009 at a single hospital by a single surgeon were reviewed. Radiographs were analysed using EBRA software to determine acetabular cup inclination and anteversion angles. Blood metal ion concentrations were measured using inductively coupled plasma mass spectroscopy (ICPMS). Explants were measured for bearing surface and taper wear using a high precision co-ordinate measuring machine. The roughness of the articulating surfaces was measured with a non-contact profilometer. Results. In 54 patients 56 CoM hips were implanted. Mean (range) age was 64 years (34-87). There were 41 females and 15 males. Patients were followed-up for a mean of 1.5 years. Three hips were revised at mean of 1.2 years (2 female, 1 male) with a further 3 listed for revision under 1.5 years giving an overall failure rate of 10.7%. All these patients reported with pain. X-rays of failed devices showed a characteristic pattern of femoral stem loosening. Serum cobalt and chromium were less than 2 micrograms/L. Explant analysis of the three revised hips showed wear at the liner rim in each case. In two of these cases the wear extended completely around the circumference. The wear volumes were 4.1, 2.0 and 2.3mm3 respectively. The ceramic heads were unworn but some transfer of metal could be seen visually. There was no significant wear or deformation at the taper junctions. Typical ceramic head roughness values were 3nm Ra and so most of the surface area of the heads remained in a pristine condition. Discussion. The very high early failure rate using COM is concerning. Explant analysis suggests equatorial contacts with propagation of high frictional forces distally. These forces may have caused early loosening of the femoral stems. Orthopaedic surgeons need to be aware of this new mechanism of failure which is associated with low metal ions

Studies on the migration of an implant may be the only way of monitoring the early performance of metal-on-metal prostheses. The Ein Bild Roentgen Analyse - femoral component analysis (EBRA-FCA) method was adapted to measure migration of the femoral component in a metal-on-metal surface arthroplasty of the hip using standard antero-posterior radiographs. In order to determine the accuracy and precision of this method a prosthesis was implanted into cadaver bones. Eleven series of radiographs were used to perform a zero-migration study. After adjustment of the femoral component to simulate migration of 3 mm the radiographs were repeated. All were measured independently by three different observers.

The accuracy of the method was found to be ± 1.6 mm for the x-direction and ± 2 mm for the y-direction (95% percentile). The method was validated using 28 hips with a minimum follow-up of 3.5 years after arthroplasty. Seventeen were sound, but 11 had failed because of loosening of the femoral component. The normal (control) group had a different pattern of migration compared with that of the loose group. At 29.2 months, the control group showed a mean migration of 1.62 mm and 1.05 mm compared with 4.39 mm and 4.05 mm in the failed group, for the centre of the head and the tip of the stem, respectively (p = 0.001). In the failed group, the mean time to migration greater than 2 mm was earlier than the onset of clinical symptoms or radiological evidence of failure, 19.1 versus 32.2 months (p = 0.001) and 24.8 months (p = 0.012), respectively.

EBRA-FCA is a reliable and valid tool for measuring migration of the femoral component after surface arthroplasty and can be used to predict early failure of the implant. It may be of value in determining the long-term performance of surface arthroplasty.

The effects of the method of fixation and interface conditions on the biomechanics of the femoral component of the Birmingham hip resurfacing arthroplasty were examined using a highly detailed three-dimensional computer model of the hip. Stresses and strains in the proximal femur were compared for the natural femur and for the femur resurfaced with the Birmingham hip resurfacing. A comparison of cemented versus uncemented fixation showed no advantage of either with regard to bone loading. When the Birmingham hip resurfacing femoral component was fixed to bone, proximal femoral stresses and strains were non-physiological. Bone resorption was predicted in the inferomedial and superolateral bone within the Birmingham hip resurfacing shell. Resorption was limited to the superolateral region when the stem was not fixed. The increased bone strain observed adjacent to the distal stem should stimulate an increase in bone density at that location. The remodelling of bone seen during revision of failed Birmingham hip resurfacing implants appears to be consistent with the predictions of our finite element analysis.