Survival of cementless dual mobility socket with a mean 17 years follow-up.

PURPOSE OF THE STUDY: As part of the 2006 symposium of the French Hip and Knee Society devoted to the dual mobility socket, we report a retrospective multicentric series of 438 first-intention total hip prostheses with a dual mobility socket at a mean 17 years follow-up. The purpose of our report was to ascertain the 15-year survival of this socket and analyze failures. MATERIAL AND METHODS: The series included 438 primary replacements. This was a homogeneous multicentric series. The cementless sockets were 80 Novae-1 titanium Serf cups and 358 Novae-1 stainless steel Serf cups. All stems were inserted without cement: 185 Pf((R)) stainless steel screwed Serf stems, 228 PRO titanium screwed Serf stems, and 25 Corail stems. The mobile polyethylene insert was retaining. All of the heads were 22.2-mm chromium-cobalt heads. Degenerative hip disease was the main etiology and mean follow-up was 17 years (range, 12-20). Mean age at implantation was 54.8 years (range, 23-87). The actuarial method with a 95% confidence interval was used to determine the 15-year cup survival rate. RESULTS: At the last follow-up, none of the patients had presented an episode of early or late instability. Analysis of the socket at last follow-up showed 13 aseptic loosenings, 23 intraprosthetic dislocations, and seven replacements of the polyethylene insert for wear. The overall 15-year prosthesis survival rate was 89.2+/-8.7%. The overall 15-year socket survival rate was 96.3+/-3.7%. DISCUSSION: The fact that, at last follow-up, none of the implants had shown instability confirms the long-term stability of the dual mobility socket. The results in terms of 15-year survival confirm earlier reports. The main cause of failure was cup fixation, which is the weak point of this technique with the initial Novae cup design, which did not have hydroxyapatite coating. The second leading cause was intraprosthetic dislocation, which can be divided into three main categories. The first is intraprosthetic dislocation in a context of pure wear with normal function of the dual mobility socket; the retaining feature of the insert loses its efficacy due to wear. The second category is intraprosthetic dislocation in a context of cup loosening with a third-body effect and increased retention wear, in which case we consider that cup loosening is the primary event leading to rapid secondary wear and subsequent intraprosthetic dislocation. The third category is intraprosthetic dislocation caused by a blockage in a context of fibrosis or impingement involving severe heterotopic ossifications. We had only two femoral failures related to aseptic loosening, most certainly related to use of noncemented implants, which limits the extension of granulomas to the polyethylene. Studying the three series from Saint-Etienne more specifically, where three different configurations were used, it would appear that the titanium cup has a better survival rate and that the titanium used for the thinner necks may be an unfavorable factor for intraprosthetic dislocation.

[Survival of dual mobility socket with a mean 17 years follow-up]. / Etude d'une série de 438 cupules non cimentées à double mobilité

PURPOSE OF THE STUDY: Within the framework of the 2007 symposium of the French Hip and Knee Society devoted to the dual mobility socket, we report a retrospective multicentric series of 438 first-intention total hip prostheses with a dual mobile socket at 17 years mean follow-up. The purpose of our report was to ascertain the 15-year survival and analyze failures. MATERIAL AND METHODS: The series included 438 first-intention prostheses. This was a homogeneous multicentric series. Sockets were: 80 Novae-1 titanium Serf cups and 358 Novae-1 stainless steel Serf cups. All stems were inserted without cement: 185 Pf) stainless steel screwed Serf stems, 228 PRO titanium screwed Serf stems, 25 Corail stems. The mobile polyethylene insert was retaining. All of the heads were 22.2mm chromium-cobalt heads. Degenerative hip disease was the main etiology and mean follow-up was 17.18 years (range: 12-20). Mean age at implantation was 54.8 years (range: 23-87). The actuarial method with 95% interval of confidence was used to determine the 15-year cup survival. RESULTS: At last follow-up, none of the patients had presented an episode of early or late instability. Analysis of the socket at last follow-up showed: 13 aseptic loosenings, 23 intraprosthetic dislocations, and seven replacements of the polyethylene insert for wear. The overall 15-year prosthesis survival was 89.2+/-8.7%. The overall 15-year socket survival was 96.3+/-3.7%. DISCUSSION: The fact that at last follow-up none of the implants had exhibited instability confirms the long-term stability of the dual mobility socket. The results in terms of 15-year survival confirm earlier reports. The main cause of failure was cup fixation, which is the weak point of this technique with the initial Novae cup, which did not have hydroxyapatite coating. The second leading cause was intraprosthetic dislocation, which can be divided into three main categories. The first is intraprosthetic dislocation in a context of pure wear with normal function of the dual mobility; the retaining feature of the insert looses its efficacy due to wear. The second category is intraprosthetic dislocation in a context of cup loosening with a third-body effect and increased retention wear, in which case we consider that the cup loosening is the primary event leading to secondary rapid wear and subsequent intraprosthetic dislocation. The third category is intraprosthetic dislocation cause by a cam effect in a context of fibrosis or impingement involving a large calcification. We have had only two femoral failures by aseptic loosening, most certainly related to use of noncemented implants, which limits the extension of granulomas to the polyethylene. Studying more specifically the three series from Saint-Etienne where three different configurations were used, it would appear that the titanium cup has a better survival and that the titanium used for the thinner necks would be an unfavorable factor for intraprosthetic dislocation.