Purpose of the study: Tibial osteotomy to correct for varus deformity is a well defined procedure. Survival has reached 80% at ten years. Nevertheless, a number of early failures are related to inadequate initial correction. Computer assisted surgery has demonstrated its efficacy for knee arthroplasty. We hypothesised that it could also improve the reliability of correction for tibial osteotomy.

Material and method: From 2007, in a prospective case-control study, 34 tibial wedge osteotomies were performed, 17 were computer assisted (Navitrack, Orthosoft) with plate fixation (Tomofix, Synthès) without wedge insertion; the objective was valgus measuring 2 to 5°.

Results: The two series were comparable for age (54.2±6 and 55.7±4.5), body mass index (28.9±6.2 and 28.7±5.7), and varus deformity (7.2±3 and 6.2±6) respectively in the standard and navigated groups. Osteoarthritis was more severe in the navigated group, with five patients stage 2 and 12 stage 2 versus one stage 1, 12 stage 2 and 4 stage 3 in the standard group (p=0.0152). The duration of the operation was not longer in the navigation group (p)0.2779). Comparisons were made for alignment at three months, between the groups and in relation to the preoperative data. There was no significant difference between the intraoperative navigation alignment and the alignment measured at 3 months: 3.6±6 and 2.5±3 at 3 months (p=0.2187). At 3 months, there was no significant difference in alignment between the two groups with 3.22 and 2.5±1.6 valgus in the standard and navigation groups respectively (p=0.2136). The objective was achieved in 25 patients: 12 in the standard group and 13 in the navigated group. In the navigation group, there were four failures, no cases of over correction, two cases of insufficient valgus at 1.5, one neutral alignment, and one recurrent varus. In the standard group, there were five failures with two over corrections at 7 and 8, two under corrections at 0 and 1, and 1 recurrent varus at 4.

Discussion: We were unable to prove that navigation improves the reliability of the correction but it did appear to avoid important errors, particularly over correction. Few series have compared standard varus navigated osteotomies, and all published series have been small. Our study has the advantage of being monocentric with two comparable series of patients. The sample size nevertheless remains small and the follow-up short.

Purpose of the study: When the acetabular component is revised alone, if the femoral stem has not been loosened, the question becomes what should be done about the osteolysis of the femur: Change the femoral piece systematically and graft the osteolysis? Curettage and grafting of the osteolysis? Curettage alone? This study reports the outcome of superior femoral osteolysis with a calcar granuloma and no other procedure (no curettage) after replacing the cup.

Material and methods: This was a retrospective analysis of 54 acetabular revisions performed from 1988 to 1998. The cemented femoral piece was stable, with no lucent line and in position since the initial implantation. The reoperation consisted in cementing a new polyethylene cup (< 32 mm) with or without a graft. The femoral head was initially ceramic (alumina 29 and zircon 25) and was preserved in ten cases (alumina) and changed systematically for the zircon heads. New heads were implanted: 20 alumina (32mm) and 24 metal. Calcar osteolysis was measured in mm² on the x-rays before and after changing the acetabular piece and then regularly every year to last follow-up (10 to 20 years).

Results: Preoperatively, superior femoral osteolysis was 156 mm² (48–576m²) situated in Guren zone 1 and 7. At last follow-up, it was 135 mm² (38–616 mm²) with no femoral loosening, decreased in 34 cases, unchanged in 11 and increased in 9. Spontaneous decline in preoperative osteolysis was observed when the bearing was alumina-polyethylne and the preoperative osteolysis was less than 100 mm². Increased osteolysis (minor but undeniable) was observed with the couple was metal-polyethylene and when the preoperative osteolysis was > 300 mm².

Discussion: If the superior femoral osteolysis does not compromise the stability of the femoral implant when undertaking isolated revision of the acetabular component alone, it can be neglected. Changing the bearing stabilizes the progression of the osteolysis and does not appear to compromise the mid-term outcome (15 years) for the femoral piece. Spontaneous decline of the osteolysis can be observed if the initial osteolysis is less than 1 cm² and if the new bearing is alumina-polyethylene.

Purpose of the study: The alumina-polyethylene bearing has been used for many years but no study has evaluated polyethylene wear and osteolysis with a 32 mm head with a follow-up exceeding 20 years.

Material and methods: Thirty-six arthroplasties implanted between 1983 and 1985 (26 patients, mean age 54 years, range 35–65 years) were studied. The same cemented implants were used in all cases, with no loosening. Penetration of the head into the polyethylene was measured annually on digital radiographs and with computer assistance. Osteolysis was quantified in mm² on the merckel.

Results: At 20 years follow-up (minimum) or more, penetration of the femoral head into the cup was on average 0.07mm/y. The characteristic feature of the wear curve was the perfect stability after the third year and the absence of any increase over time. Extrapolation of the straight part of the curve to the origin determined the creep. True wear was limited: 0.05mm/y. It was not modified by the polyethylene thickness (eight 52mm cups, twenty-three 50mm and five 48mm). Corresponding volumetric wear was estimated at 640 mm3 at maximum follow-up. At last follow-up, osteolysis measured in mm² on the meckel was 65 mm² on average. In general, this osteolysis appeared around the second year with an imprint on the merckel; it then increased linearly and regularly to the 20th year. Acetabular osteolysis was nevertheless greater than that observed with the Al/Al bearing of controlateral hips implanted at the same period when evaluated on the scan for both hips (20 cases).

Discussion: The alumina-polyethylene bearing enables long implant survival for at least 20 years, even for relatively thin polyethylene thicknesses. The characteristic feature of the bearing is the linear polyethylene wear which does not increase with time but remains constant, undoubtedly in relation to the absence of any change in the roughness of the head despite the very long follow-up. Osteolysis remains minimal, but superior to that observed with Al/Al bearings implanted during the same period in controlateral hips.