Purpose of the study

to verify, after a period of 5 years, that no particular complication overshadows the benefits of a large diameter metal-on-metal articulation in combination with a conventional femoral stem with regard to stability and functional result.

Purpose of the study: The tribologic characteristics of the metal-on-metal bearing enabled the introduction of large-diameter femoral heads on a conventional stem with the aim of improving implant stability. Our work was designed to determine whether the short-term outcomes corroborate this hypothesis and identify any specific complications.

Material and methods: This was a comparative study of two series of non-cemented total hip arthroplasties (THA) with a high-carbon content metal-on-metal bearing: 250 25 mm arthroplasties implanted from August 2001 to April 2004; 250 large-diameter arthroplasties implanted from August 2003 to December 2006. The two series were comparable regarding age, gender, BMI, aetiology, Devane and Harris scores preoperatively (r2=0.98; p< 0.001). Patients were reviewed at mean 5 years 5 months (28mm) and 3 years 1 months (large diameter).

Results: The analysis was possible for 224 implants in the 28 mm series and 242 in the large diameter series. Clinically, the Merle-d’Aubigné et Harris scores were highly comparable between the series; the activity item on the UCLA score revealed better results in the anatomic head series (6.09 versus 6.81; p< 0.0039). Regarding complications: There was one cases of implant migration in the large diameter series with preservation of the good outcome and no revision. For dislocations: anatomic head (n=1, 0.4% with revision); 28 mm head (n=7, 2.8% with four revisions). One particular case of one patient with a large diameter head presented two episodes of localised recurrent cellulitis under regular surveillance. Metal ion assays (medians): Cr.− 1.55μg/l for 28mm; 2.21μg/l for large diameter; Co. − 1.10μg/l for 28mm; 1.92μg/l for large diameter.

Discussion: Our results provide objective evidence of the improvement in the stability of the prosthesis joint and in the functional outcome, confirming the few results published to date. Conversely, while we did have less technical failures than published series, we did find significantly higher metal ion levels in the large diameter series, in contrast with prior data. The neck length being modulated with the intermediary piece, the potential corrosion might be the only cause of this difference.

Purpose of the study: Use of the metal-on-metal bearing has been validated in total hip arthroplasty (THA) for conventional diameters and for resurfacing but not with large-diameter implants. The purpose of our study was to establish the short-term clinical validity of large diameter implants.

Material and methods: This was a retrospective study of a consecutive series of 106 press-fit cups (Durom^®) in 102 patients with minimum two years follow-up. Mean age at surgery was 66 years. Aetiologies were primary degenerative diseases (n=83), aseptic osteonecrosis (n=11), secondary degeneration (n=7), degeneration on acetabular dysplasia (n=2), rapid destructive osteoarthritis (n=1), fracture of the femoral neck (n=1) rheumatoid disease (n=1). Patients were reviewed with mean 30 months follow-up with the PMA and Harris scores. Radiographic measurements were made on semi-automatically (Imagicka^®) and included the ratio of prosthesis head to native head diameter, acetabular offset, and any implant migration, gap or lucency.

Results: There were two traumatic dislocations due to falls with regressive tendonitis of the gluteus medius with no later consequence. The mean Harris score was 91.6 and the mean PMA score 17. Outcome was excellent (n=70), good (n=31), fair (n=3) and poor (n=2). The ratio showed that head diameter had been restored for 65 hips (0.95 to 1.05). There were no cases of cup migration. Acetabular offset showed a mean lateralization of 1.1 mm. For 67 immediate posterior gaps, including ten measuring > 2mm, only two had not filled at review. None of the radiographic measurements had an effect on the clinical outcome.

Discussion: These results are comparable with those published for metal-on-metal bearings with 28mm heads and press fit cups. We did not find any mechanical or medical cause explaining the persistent pain observed in our patients with fair or poor outcome. The low level of dislocation (1.8%) confirms the improved prosthetic stability compared with 28 mm heads.

Conclusion: In our opinion, these early results demonstrate a clear improvement in stability, but at the cost of possible unexplained pain. Long term clinical and radiographic surveillance is needed to validate this option in terms of implant wear and survival.

Introduction: The purpose of this prospective randomized study was to compare the minimum 4-year follow-up penetration of polyethylene inserts of identical desing in two configurations in a consecutive series of hybrid total hip arthroplasty.

Method: Between August 2000 and december 2001, 102 patients (102 hips) with a mean age of 69.2 years were randomized to receive either highly cross-linked (Durasul, 49 hips) or contemporary (Sulene, 53 hips) polyethylene inserts. Other parameters, including the 28 mm cobalt-chrome femoral head, the cementless cup (Fitmore, Zimmer) and cemented stem (Emeraude, Zimmer), were identical in both groups. The primary criterion for evaluation was head penetration measurement, using the Martell System.

Results: At a minimum 4-year follow-up evaluation, 34 hips in the durasul group and 30 hips in the Sulene group had complete radiologic data available for analysis (median follow-up of 4.8 and 4.9 years in the Durasul and Sulene group, respectively). The median femoral head penetration rate was 0.029 mm/year in the Durasul group versus 0.123 mm/year in the Sulene group (Mann and Whitney test, p=0.0027). The median volumetric penetration rate was 7.99 mm3/year in the Durasul group versus 41.93 mm3/year in the Sulene group. The yearly volumetric penetration rate was 80% lower in the Durasul group (Mann and Whitney test, p=0.0034).

Discussion and Conclusion: This study demonstrate a signifiant reduction of the yearly linear and volumetric femoral head penetration in highly cross-linked poly-ethylene. Longer-term results ae needed to warrant that these early data generate less occurence of osteolysis.

Purpose of the study: The limitations of conventional polyethylene are well known (osteolysis). New bearing surfaces have been proposed for hip arthroplasty including new-generation polyethylene products.

Material and methods: We compared four bearings including one metal-on-metal and one ceramic-on-ceramic bearing with results not available for analysis at this 4 years 8 month follow-up. The comparative randomized study included 102 first intention total hip arthroplasties comparing a single variable: the bearing. Common elements were: metal-back press-fit cup (Fitmore) and cemented anatomic stem (Emeraude). Variable elements were: alpha Sulène insert + 28 metal head (n=53) versus alpha Dursul insert + 28 metal head (n=49). Clinical outcome was assessed with the Postel-Merle-d’Aubigné score and the Harris score. Radiological outcome was assessed with: wear (EBRA, semiautomatic linear radiographic penetration), cup migration according to EBRA, and radiographic changes in zone 7.

Results: After checking the validity of the files studied, clinical outcome was strictly the same for the two series: wear Sulène polyethylene 0.21 mm; Durasul polyethylene 0.1 mm. Cup migration was: Sulène polyethylene 0.13 mm; Durasul polyethylene 0.08 mm. Modifications of zone 7 were: Sulène polyethylene 17.8%; Durasul polyethylene 6.6%.

Conclusion: With 4 years 8 months follow-up, several elements are in favor of the new-generation polyethylene inserts, confirming theoretical results with mathematical models. This length of follow-up is insufficient to draw formal conclusions concerning in vivo aging.

We carried out a prospective randomised study designed to compare the penetration rate of acetabular polyethylene inserts of identical design but different levels of cross-linking at a minimum of four years follow-up. A total of 102 patients (102 hips) were randomised to receive either highly cross-linked Durasul, or contemporary Sulene polyethylene inserts at total hip replacement. A single blinded observer used the Martell system to assess penetration of the femoral head. At a mean follow-up of 4.9 years (4.2 to 6.1) the mean femoral head penetration rate was 0.025 mm/year (sd 0.128) in the Durasul group compared with 0.106 mm/year (sd 0.109) in the Sulene group (Mann-Whitney test, p = 0.0027). The mean volumetric penetration rate was 29.24 mm³/year (sd 44.08) in the Durasul group compared with 53.32 mm³/year (sd 48.68) in the Sulene group. The yearly volumetric penetration rate was 55% lower in the Durasul group (Mann-Whitney test, p = 0.0058). Longer term results are needed to investigate whether less osteolysis will occur.