The 45-year evolution of the Mathys RM monoblock cups: have the paradigm shifts been worthwhile?

INTRODUCTION: The Robert Mathys (RM) monoblock uncemented cup is a design less commonly used in primary total hip replacement. It's purported advantages over modular cemented cups are: (1) its modulus of elasticity approximating bone, thus mimicking load transmission and the biomechanical behaviour of the cup to better match stresses on the acetabulum, leading to bone-preservation; and (2) as a 1-piece cup there is absence of a mobile interface between a liner and shell, preventing backside wear. Since its inception in 1983 there have been 3 major design changes: the RM Classic, the RM Pressfit, and the RM Vitamys with the most modern polyethylene (vitamin E). METHODS: In a retrospective cohort study of the New Zealand Joint Registry, all designs of RM acetabular cup were reviewed. Data were included from1998 to 2018. All-cause revision rates, reasons for revision and the Oxford Hip Score (OHS) were assessed. RESULTS: In total 13,272 acetabular cups were included. The all-cause revision rates did not differ between the designs. Revision rates for aseptic loosening in the RM Vitamys were lower, but the follow-up was shorter and more larger heads were used. There was no difference in the OHS. CONCLUSION: All implant designs were safe. The use of larger heads led to a decrease in revisions due to dislocation. It has to be waited out whether the RM Vitamys performs superior in the long-term due to the highly cross-linked polyethylene.

A Meta-Analysis of the Incidence and Temporal Trends of Postoperative Dislocation in Revision Total Hip Arthroplasty Utilizing Constrained Acetabular Components or Dual Mobility Implants.

BACKGROUND: The incidence of dislocation after revision total hip arthroplasty (rTHA) is reported to be up to 25% and remains a common source of failure. Constrained acetabular components and dual mobility implants are two implant classes being utilized to alleviate this burden in patients who have recurrent instability or major intraoperative instability. This meta-analysis evaluated the incidence and temporal trends of dislocation after implantation with constrained acetabular components and dual mobility implants in rTHA. METHODS: Longitudinal studies reporting dislocation after the use of constrained acetabular components or dual mobility implants in rTHA were sought from Medline and Embase to October 2022. Secondary outcomes included re-revision surgery for dislocation and all causes. A total of 75 relevant citations were identified comprising 36 datasets of 3,784 constrained acetabular components and 47 datasets of 10,216 dual mobility implants. RESULTS: For constrained acetabular components, the pooled incidence of dislocation was 9% (95% confidence interval: 7.2, 11.7) (range 0.0%-35.3%) over a weighted mean follow-up of 6 years, in contrast to 3% (95% confidence interval: 2.2, 4.4) (range 0.0%-21.4%) over 5 years for dual mobility implants. Re-revision rates for dislocation after using constrained acetabular components were around 9%, in contrast to 2% for dual mobility implants. Re-revision rates for all causes after using constrained acetabular components were around 19%, in contrast to 8% for dual mobility implants. CONCLUSION: Dual mobility implants in the context of rTHA demonstrate lower incidences of dislocation (3% versus 9%), re-revision for dislocation (2% versus 9%), and rer-evision for any cause (8% versus 19%) in contrast to constrained acetabular components. This must be considered by surgeons when implanting such devices, often selected to treat instability.

Surgical Versus Non-surgical Treatment of Unstable Lateral Compression Type I (LC1) Injuries of the Pelvis With Complete Sacral Fractures in Non-fragility Fracture Patients: A Systematic Review.

Lateral compression type 1 (LC1) injuries comprise two-thirds of pelvic fractures. Approximately one-third of LC1 fractures are unstable and may benefit from surgical fixation to improve stability but it is not clear if this leads to better clinical or cost-effectiveness outcomes. This study explores differences in patient-reported outcomes, complications, time-to-mobilisation, cost-effectiveness, and length of hospital stay between surgically and non-surgically treated unstable LC1 non-fragility fractures. We performed a systematic review to determine whether surgical or non-surgical treatment yielded better clinical and cost-effectiveness outcomes for the treatment of unstable LC1 pelvic injuries with complete sacral fractures, excluding fragility fractures. We searched Medline, Embase and Cochrane databases from inception to June 2022, as well as clinical trial registries. A formal meta-analysis was not possible due to available study designs and heterogeneity. Therefore, a narrative review of the findings has been provided. Five observational studies met the inclusion criteria. A total of 183 patients were treated surgically, and 314 patients were treated non-surgically. Patients treated surgically had lower pain levels (Visual Analogue Scale) and fewer days to mobilisation. Quality of life (EuroQol-5 domains and 36-Item Short Form questionnaires) was better in the surgical group, but not statistically significant. No statistical differences in the length of hospital stay or complication rates were found. This review highlights the low quantity and quality of existing data on patients with unstable LC1 pelvic fractures and the need for a definitive randomised controlled trial to determine whether surgical or non-surgical care should be the preferred treatment concerning clinical and cost-effective care.

The Incidence and Temporal Trends of Dislocation After the Use of Constrained Acetabular Components and Dual Mobility Implants in Primary Total Hip Replacements: A Systematic Review and Meta-Analysis of Longitudinal Observational Studies.

BACKGROUND: Dislocation after a primary total hip replacement (pTHR) remains a common cause of treatment failure. Constrained acetabular components (CACs) and dual mobility implants (DMIs) may mitigate this in patients at high risk of dislocation or with significant intraoperative instability. This meta-analysis evaluated the incidence and temporal trends of dislocation after implantation with CACs and DMIs in pTHR. METHODS: Longitudinal studies reporting dislocation after the use of CACs or DMIs in pTHR were sought from Medline and Embase to September 2020. Secondary outcomes included revision surgery for dislocation and for all causes. RESULTS: A total of 46 studies (3 CAC and 43 DMI) comprising 582 CACs and 18,748 DMIs were included. The pooled incidence of dislocation was 1.08% (95% confidence interval [CI]: 0.00-3.72; range 0.27%-2.60%) over a weighted mean follow-up of 4.1 years for CACs, compared with 0.25% (95% CI: 0.08-0.46; range 0.00%-4.72%) over 6.2 years for DMIs. For DMIs, there was a temporal decline in dislocations from the 1980s onward, and dislocation rates remained low (<1%) until 15 years postoperatively. There were insufficient data for similar analysis of CACs. All studies were at high risk of bias. The incidence of revision for dislocation after CACs was 0.3% vs 0.1% for DMIs, and the incidence of revision for all causes after CACs was 4.8% vs 2.7% for DMIs. CONCLUSION: DMIs demonstrated a lower incidence of dislocation compared with CACs; however, there was a relative absence of CACs used in the context of pTHR in the literature. Temporal trends in dislocation have improved over time for DMIs.

The use of silver coating in hip megaprostheses: a systematic review.

Retrospective studies of silver-coated hip implants have demonstrated promising results and safety profile, however, the potential benefits are so far unproven in prospective studies. Silver-coated implants may have a role in patients undergoing revision or primary surgery with a high risk of infection but as yet there are no human studies investigating silver in primary hip arthroplasty. Adequately powered robust prospective studies are needed in this area to determine if silver-coated implants would be efficacious and cost-effective. The purpose of this systematic review article is to review the current literature regarding the use of silver in hip arthroplasty. Our review showed that there is some encouraging evidence that silver coatings can reduce infection.