Equivalent wear performance of dual mobility bearing compared with standard bearing in total hip arthroplasty: in vitro study.

PURPOSE: Osteolysis in total hip arthroplasty (THA) depends on polyethylene wear and dictates the survival of the prosthesis. Dual mobility in THAs, which is claimed to reduce dislocation risk, has very good long-term clinical results. However, little is known about how the liner wears in this design, compared to the standard single mobility model. METHODS: A comparative study looking at wear of a conventional ultra-high-molecular-weight polyethylene liner, using gravimetric measurement, between dual mobility implants and standard implants, was performed on a simulator in accordance with a normed protocol based on the same dimensions, environmental conditions and stresses. A linear regression test was employed. RESULTS: Under the same conditions (loading, cycles, sterilization, material and surface roughness), the gravimetric wear (for conventional polyethylene) is comparable between a standard and a dual mobility cup. This correlates to ten year follow-up results of dual mobility cup. DISCUSSION - CONCLUSION: This in vitro equivalent wear serves to confirm the very good long-term clinical results observed with dual mobility bearing, whose use should not be restricted by concerns about increased polyethylene wear.

Incidence and outcomes of revision surgery after first metatarsophalangeal joint arthrodesis: Multicenter study of 158 cases.

INTRODUCTION: First metatarsophalangeal (MTP1) joint arthrodesis, described as a safe and effective procedure, has complications that may require surgical revision. These complications are rarely studied. The aim of this study was to determine the incidence and outcomes of revision surgery after MT1 arthrodesis. HYPOTHESIS: The incidence of surgical revision after MTP1 arthrodesis is not insignificant; however, the outcomes are satisfactory. MATERIALS AND METHODS: In this multicenter retrospective study between January 2014 and December 2015, 190 forefoot revisions in patients who had previously undergone MTP1 arthrodesis were included by 8 surgeons. There were no exclusion criteria and all patients had at least 1 year of follow-up. Over the same period, 958 primary MTP1 arthrodesis procedures were performed. RESULTS: The mean time to revision was 4.6±10.9 years. At a mean follow-up of 20.5±7.4 months, 158 cases were available for analysis in 135 women and 20 men who had a mean age of 67.1±10.5 years. These revision procedures were carried out because of discomfort related to the hardware at the arthrodesis site (n=86, 54%), nonunion (n=22, 14%), malunion (n=13, 8%) metatarsalgia or claw toe (n=18, 11%) and first interphalangeal (IP1) joint disorders (n=13, 8%). The mean postoperative scores were 75±13.9 for the AOFAS and 65±19.6 for the SF36 total. In the nonunion cases, removal of the hardware led to better outcomes than repeating the arthrodesis procedure. Osteotomy in the malunion cases healed successfully. In the cases of IP1 osteoarthritis, secondary arthrodesis or arthroplasty led to good outcomes. DISCUSSION: Relative to published results of primary MTP1 arthrodesis, the outcomes in our series of revision MTP1 arthrodesis surgery cases are practically equivalent, thus considered acceptable. LEVEL OF EVIDENCE: IV, Retrospective study.