Purpose of the study: Long-term outcome of Charn-ley total hip arthroplasty (THA) (more than 30 years follow-up) has demonstrated that the longevity of these prostheses is inversely proportional to polyethylene wear and head penetration into the cup. In order to limit wear phenomena, we have used since 1997 a Charnley THA with a 22.225 mm zirconia (Zr) head (Prozyr®, Saint-Gobain Desmarquet). The goal was to reduce wear and improve implant longevity.

Material and methods: We reviewed at minimum five years follow-up 62 patients with 69 THA with a standard Zr/PE bearing. These patients had undergone surgery in 1997–1999, the cup or the high-density PE insert were furnished by Centerpulse Zimmer. The measurement method correlated the Livermore technique with determination of the center of the head using the Chevrot and Kerboull method and interobserver radiological measurements made on digitalized images after magnification.

Results: At mean six years follow-up, the Postel-Merle-d’Aubigné score was 17.6 and overall anteroposterior wear at mast follow-up was 0.76 mm (0.73 mm with the Acoplot PE cup and 0.78 mm with the hybrid THA with an isofit cup). Mean wear for this series of implants was thus 0.12 mm/year. There were no fractures of the Zr heads. The rate of osteolysis was 10% with very minimal osteolysis defects, general in the Merckel spine. Wear on the same implant in a previous series operated on in 1997 was 0.40 mm at three years, i.e. also 0.12 mm/year.

Discussion: Wear was not greater with the Zr/PE bearing than usually observed with a 22.225 metal-backed PE bearing. This is in contradiction with observations by J. Allain and D. Goutallier in 1999 and with the publication by P. Piriou (SOFCOT 2003). Furthermore, we did not observe, like Hamadouche (SOFCOT 2001) major osteolytic lesions. On the other hand, we did not observe, as was shown by Wroblewsk, any decrease in the rate of penetration of the head into the PE insert. Using the same 22.225 Prozyr bearing with conventional PE and a cemented head, Wbroblewski showed in 2004 that at mean 4.3 years follow-up (range 0–8 years) mean penetration was 0.03 mm/yr.

Conclusion: Today, at five years follow-up, we have found that with a Charnley THA wear is the same with the Zr/PE as with the metal/PE bearing.

Purpose: From 1985 to 2001, nearly 400,000 Zircone heads were implanted for total hip arthroplasty. In France, following an abnormally high rate of ruptures in two lots of heat-treated heads, production of Zircone heads was interrupted in 2001. Following work by Allain et al., another controversy developed concerning abnormal secondary wear of Zircone heads. According to certain authors, head roughness was increased by pitting phase transformation. This hypothesis was corroborated by Haraguchi (2001) who reported three explanted heads. We wanted to check the hypothesis.

Material and methods: In 2002, we explanted three Prozyr 22.2 Zircone heads for recurrent dislocation. We compared the explanted heads with a new Zircone head, a 28-mm alumina head explanted after prosthesis loosening and a new alumina head, using the same protocol as Haraguchi.

Results: On the explanted heads, the percentage of monoclinic Zircone was always less than 10% (3–10%). Roughness was also very minimal (Ra=0.01μm) for Zircone and ceramic heads, whether new or explanted, with no pitting and no notable structural change. The mean size of femoral head grains remained within the ISO 13 356 standard (1997).

Discussion: In 2003, Clark who studied three Zircone heads removed 2.8 to 10 years after implantation selected among 23 explanted heads, was unable to demonstrate any phase transformation or surface alterations. On one head explanted at eight years, Clark found significant monoclinic phase transformation. In our study, the three explanted heads did not exhibit significant monoclinic phase transformation since it remained less than 10% without pitting nor increased roughness. The behaviour of 22.2 Zircone heads may be different from 28 Zircone heads in terms of fracture (since no fractures have been observed after high-temperature furnace treatment of 22.2 heads) and in terms of monoclinic phase transformation.

Conclusion: This point is crucial for patients with a Zircone head total hip arthroplasty. Surveillance must be continued. At the present time and for mid term, we can conclude that the rate of monoclinic phase transformation of explanted Zircone heads is minimal and that production quality is good, particularly for 22.225 mm heads.

Purpose: Between 1979 and 2000, we performed 115 total hip arthroplasties with a bone block, mainly for degenerative hips secondary to congenital dislocation. Up to 1992, we used the classical bone block fixed with a screw and a cemented all-polyethylene Charnley cup inserted in the paleoacetabulum. The drawback of this technique was the two-month delay required for bone healing before weight bearing could be attempted. Since 1992, we have modified this technique, using an embedded bone block impacted into the dihedral angle between the capsule – neoacetabulum and the non-cemented press-fit cup with a screw in the paleoacetabulum. This method allowed immediate postoperative weight bearing, just like after first-intention total hip arthroplasty.

Material: Between 1992 and 2002, we operated 56 patients (63 hips) using this technique, 50 (56 hips) were reviewed at a mean five years (range 1 – 9.5). Three patients had died (three hips) and three (four hips) were lost to follow-up. The purpose of this work was to check integration of the bone block and absence of acetabular complications related to early weight bearing. Mean age at surgery was 58.5 years (range 17 – 88). There had been one earlier intervention for 17 hips, two for 13 and three for four.

Methods: Physical examination and standard x-rays (AP, lateral, Lequesne oblique views) were available at last follow-up. In addition to the radiographic assessment of the bone block, the Postel Merle d’Aubigné (PMA) objective clinical score and subjective patient satisfaction were recorded.

Results: The mean PMA score was 11.7 preoperatively and 17.6 at last follow-up. Ninety-four percent of the patients were very satisfied or satisfied, 6% were dis-satisfied (three postoperative dislocations). Radiographically, we noted block lysis (n=1), non-integrated block (n=8), perfect osteointegration (n=47). The cup showed no radiographic sign of ascension. There were two lucent lines in zone 1 (14.8%) and three in zone 3 (16.8%). There was no relation between bone block integration and presence of acetabular lucent lines. Four complications were recorded: one loosening at eight months, one sudden loosening treated by changing the cup, and three dislocations including one treated four years after implantation by anti-dislocation crescent. There was no relationship between complications and block behaviour.

Discussion: The advantage of the embedded block technique with a hybrid prosthesis using a metal-backed polyethylene cup (22.225) is that the postoperative rehabilitation is the same as after a standard prosthesis in good position. Immediate weight bearing on the press-fit cup without cement did not lead to deleterious complications whether clinically or for bone block behaviour.

Conclusion: This technique is a reliable method allowing early weight bearing and a shorter recovery time with satisfactory cup stability.

Purpose: Since 1962, when Sir John Charnley implanted the first total arthroplasty, long-term studies have demonstrated the excellent survival of these implants with greater than 85% survival at 25 years (John Older, Mike Wroblewski, ACORA group in 1995). Polyethylene wear is the main obstacle to long-term survival of the Charnley total hip arthroplasty. New friction surfaces have been proposed to reduce wear, notable the ceramic/ceramic junction proposed by Pierre Boutin since 1970 with the ceramic/polyethylene derivative. The alumine ceramic head cannot be greater than 22.225 cm due to the risk of fracture, leading to the zircone head. D. Goutallier and his school recently demonstrated (1999) that the use of zircone can increase wear with early development of osteolysis and acetabular loosening. For this reason, we compared wear between two series of prostheses using the 22.2 zircone/polyethylene combination versus the metal/polyethylene combination.

Material and methods: Two series of 37 patients were compared for wear. The first series included 41 hips with a zircone/polyethelene combination using a 22.2 cm head. The second series of 38 hips used a metal/polyethylene combination and 22.2 cm heads. The femoral components were the same in the two series with an 8/10 Morse cone. Mean follow-up in the two series was 38 months. All patients underwent surgery in 1997 for the zircone/polyethylene implants and in 1995 for the metal/polyethylene implants. Mean age in the zircone/polyethylene series was 58 years and in the metal/polyethylene series 66. The Postel Merle d’Aubigné (PMA) score at review was 16.6 for the zircone/polyethylene series and 17.7 for the metal/polyethylene series. Manual measurements of wear were made using the Livermore method with determination of the centre of the head according to Cherrot and Kerboull, doubled with computer-assisted interobserver radiological measurements.

Results: At three years, 31.5% of the metal/polyethylene implants were devoid of any signs of wear compared with 29.2% in the zircone/polyethylene implants. Mean wear was 0.19 per year for the metal/polyethylene implants versus 0.12 per year for the zircone/polyethylene implants. Overall wear on the AP view at last follow-up was 0.62 mm for the metal/polyethylene implants and 0.40 mm for the zircone/polyethylene implants at three years. This difference was significant p < à.005).

Discussion: We did not find any greater wear with the zircone/polyethylene combination compared with metal/polyethylene as was also demonstrated by D. Goutallier. M. Wroblewski (2000) demonstrated in a study with 10 years follow-up that wear was twice as great the first two years with a 22.225 diameter head using the alumine ceramic/polyethylene combination (0.1 mm per year), then stabilised. This was probably due to a stabilisation period. We are probably currently in this stabilisation period with the zircone/polyethylene implants.