Unconstrained tripolar hip implants provide an additional bearing using a mobile polyethylene component between the prosthetic head and the outer metal shell. Such a design increases the effective head diameter and therefore is an attractive option in challenging situations of unstable total hip arthroplasties. We report our experience with 54 patients treated using this dual mobility implant in such situations. We ascertained its ability to restore and maintain stability, and examined component loosening and component failure. At a minimum followup of 2.2 years (mean, 4 years; range, 2.2-6

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Paget's disease of bone (PDB) is a localised chronic osteopathy leading to bone deformities, bone hypervascularity, structural weakness and altered joint biomechanics. The pelvis and upper femur are frequently involved, resulting in disabling hip disease, and total hip arthroplasty (THA) may be required. We performed a retrospective study on the management and the outcome of 39 uncemented hydroxyapatite fully-coated THA in patients with PDB of the hip. The follow-up averaged 79.4 months (range 24-194). Functional scores improved significantly and, using the Harris hip score, 84% of patients had an excellent clinical outcome at the latest follow-up. Despite one case of an uncemented acetabular component with probable loosening, no implant revision had been required at our latest follow-up. Signs of implant loosening were found to be significantly more frequent in patients with active disease. For this reason, we advocate the use of pre-operative medication with bisphosphonates to reduce disease activity. Another benefit of this treatment is the significant decrease of intra-operative blood loss. Provided the control of disease activity in the pre-operative period with bisphosphonates is achieved, good outcome of cementless THAs can be expected. Bisphosphonates reduced the risk of implant loosening and excessive intra-operative blood loss

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Background Intraprosthetic dislocation is a specific complication of dual mobility cups, although it occurs less frequently with the latest generations of implants. Intraprosthetic dislocation is related to long-term polyethylene wear of the mobile component chamfer and retentive area, leading to a snap-out of the femoral head. With the increased use of dual mobility cups, even in younger and active patients, the management of intraprosthetic dislocation should be defined according to its type. However, no previous studies, except for case reports, have described the strategy to manage long-term wear-related intraprosthetic dislocation, particularly when a dual mobility cup is not loose. Questions/purposes This study aimed to (1) determine the prevalence of intraprosthetic dislocation in this patient population and the macroscopic findings at the time of surgical revision and (2) evaluate whether isolated mobile component exchange could be an option to manage intraprosthetic dislocation occurring with a well-fixed dual mobility cup metal shell. Methods From January 1991 to December 2009, a continuous series of 5274 THAs with dual mobility cups (4546 patients; 2773 women; mean [range] age 58 years [22-87]; bilateral THA = 728) were prospectively enrolled in our institutional total joint registry. A cementless, hemispherical dual mobility cup was systematically implanted, regardless of the patient’s age or indication for THA. At the latest follow-up examination, the registry was queried to isolate each occurrence of intraprosthetic dislocation, which was retrospectively analyzed regarding the patient’s demographics, indication for THA, radiographs, intraoperative findings (polyethylene wear and lesion patterns on the mobile component, periarticular metallosis, and implant damage because of intraprosthetic impingement of the femoral neck), management of intraprosthetic dislocation (isolated exchange of the mobile component or revision of the dual mobility cup), and outcome. Results At a mean (range) follow-up duration of 14 years (3-26), 3% of intraprosthetic dislocations (169 of 5274) were reported, with a mean (range) time from THA of 18 years (13-22). Intraprosthetic dislocation occurred predominantly in younger men (mean [range] age at THA, 42 years [22-64] versus 61 years [46-87]; p < 0.001, and sex ratio (male to female, 1:32 [96 male and 73 female] versus 0.62 [1677 male and 2700 female]; p < 0.001) in patients with intraprosthetic dislocation and those without, respectively, but was not influenced by the indication for THA (105 patients with intraprosthetic dislocation who underwent THA for primary hip osteoarthritis and 64 with other diagnoses versus 3146 patients without who underwent THA for primary hip osteoarthritis and 1959 for other diagnoses (p = 0.9)). In all patients with intraprosthetic dislocation, a macroscopic analysis of the explanted mobile component revealed circumferential polyethylene wear and damage to the chamfer and retentive area, with subsequent loss of retaining power for the femoral head. Nine percent of intraprosthetic dislocations (16 of 169 patients with intraprosthetic dislocations) were associated with aseptic loosening of the dual mobility cup and were managed with acetabular revision without recurrence at a mean (range) follow-up duration of 7.5 years (5-11). Ninety-one percent of intraprosthetic dislocations (153 of 169) were pure, related to wear of the mobile component chamfer and retentive area without aseptic loosening of the dual mobility cup, and managed with isolated mobile component exchange. Intraprosthetic dislocation recurred in 6% (nine of 153) at a mean (range) follow-up interval of 3 years (2-4.5). Additionally, severe premature polyethylene wear of the mobile component with loosening of the dual mobility cup occurred in 12% of patients (19 of 153) at a mean (range) follow-up duration of 1.5 years (0.5-3). Conclusions A failure rate of 18% (28 of 153 patients undergoing isolated mobile component exchange) was reported within 5 years after isolated mobile component exchange to manage intraprosthetic dislocation occurring with a well-fixed dual mobility cup metal shell. The two modes of failure were early recurrence of intraprosthetic dislocation or severe premature metallosis-related polyethylene wear of the mobile component with loosening of the dual mobility cup. Acetabular revision with synovectomy should remain the standard procedure to manage intraprosthetic dislocation, particularly if periarticular metallosis is present. The exception is intraprosthetic dislocation occurring in elderly or frail patients, for whom a conventional acetabular revision procedure would be associated with an unjustified surgical or anesthetic risk. Level of Evidence Level II, prognostic study.

The aim of this study was to evaluate the first 100 cementless ceramic-on-ceramic total hip arthroplasty (THA) performed at our institution with more than nine years of follow-up. Clinical evaluation was performed using Harris hip score. Radiological evaluation was performed by two surgeons. Four patients were lost to follow-up. Harris hip score significantly improved at latest follow-up. Radiological analysis showed calcar osteolysis for 75 patients and one cup loosening. One patient required a revision five years postoperatively for cup loosening. Based on these results and the routine use of a navigation system to optimise positioning of the implants, we advocate the use of uncemented hydroxyapatite coated ceramic-onceramic THA in young and active patients in our current practice.