MID-TERM CLINICAL AND RADIOLOGICAL RESULTS WITH 36 MM FEMORAL HEADS, XLINKED DURASUL® LINERS ASSOCIATED WITH ALLOFIT® CUPS

Abstract

Cross-linked PE theoretically allows the use of thinner inserts and larger diameter heads than UHMWPE. This participates in reducing the risk of dislocation. Durasul^® liners have demonstrated improved wear performance over UHMWPE in laboratory testing. This may also result in lower migration and loosening rates of the implants.

Our first aim was the assessment of linear wear of Durasul^® inserts associated with Protasul^® 36 mm CoCr prosthetic heads. We compared the results with our data on 28 mm CoCr and Biolox heads.

The first hypothesis was that Durasul^® inserts combined with a 36 mm CoCr head would not produce more wear than would Durasul^® inserts in association with a 28 mm CoCr prosthetic head.

The second hypothesis was that Durasul^® inserts combined with a 36 mm head could even produce less wear than a UHMWPE liner in association with a Biolox^® 28 mm prosthetic head.

The second aim was to correlate cup migration with polyethylene wear rate.

111 patients (37 men, 74 women) with a median age of 74 years (range: 54–90) received Durasul^® liners in an Allofit Ti cup and Protasul^® 36 mm heads. They were followed for minimum 5 years.

16 patients with a Durasul^® liner received a 28 mm Protasul^® head (control A) and 40 received a UHMWPE liner combined with a Biolox^® 28 mm head (control B).

Patient outcome was assessed with the HHS. PE wear assessment was performed using a specific analysis model created in the Imagika^® software. Cup migration was evaluated using the EBRA-CUP^® software.

The preoperative and last follow-up HHS were 50.4+/−10.5 and 97.5+/−5.5 respectively.

The bedding-in penetration of the prosthetic head were 0.054+/−0.009 mm (Durasul^®, 36 mm CoCr head), 0.056+/−0.008 mm (Durasul^®, 28 mm CoCr head) and 0.057+/−0.010 mm (UHMWPE, Biolox^® 28 mm head). There were no significant differences between the different groups.

The annual linear wear rates were 0.029+/−0.003 mm (Durasul^®, 36 mm CoCr head), 0.032+/−0.014 mm (Durasul^®, 28 mm CoCr head) and 0.087+/−0.056 mm (UHMWPE, Biolox^® 28 mm head). There were no significant differences between Durasul^® groups, but a P value of 0.00027 was observed between the study group and the control B group.

We didn’t observed cup migration in our patients (0.09 mm medially and 0.13 mm cranially).

Patient satisfaction was high with improvement of quality of life.

Combined with the Durasul^® inserts used in this series, 36 mm CoCr prosthetic heads had no unfavourable influence on the wear assessment compared with the use of 28 mm prosthetic heads. The annual linear wear rate of Durasul^® liners was 37.84% of that seen with the UHMWPE liner. The absence of cup migration at last follow-up may indicate very low PE wear rates.