Total wrist arthroplasty: commentary and opinions

Abstract

Total wrist arthroplasty (TWA) is gaining interest as a management option for wrist arthritis. This review article summarizes the current evidence base for TWA, focusing on the performance and survivorship of fourth-generation implants. These appear to offer satisfactory patient-reported outcomes and survivorship over the medium term, but heterogeneity between implants and patient populations complicates data interpretation. We discuss issues facing TWA practice, including surgical competency, volume, implant development and stewardship. We acknowledge the need for further research on this topic and highlight a number of questions that need answering.

Introduction

The surgical treatment of the painful arthritic wrist has historically revolved around partial or total arthrodesis. Total wrist arthroplasty (TWA) is an alternative option although having been used in fewer patients, the evidence base is less established. TWA design has evolved from the first-generation silastic spacer pioneered in the 1960s. Second-generation implants consisted of multiple components with hard bearing surfaces, with subsequent design alterations to arrive at the current fourth-generation implants. With the exception of the Motec (Swemac Innovation AB, Linköping, Sweden), this current generation have uncemented, porous-coated fixation and a cobalt-chrome to ultra-high molecular weight polyethylene (UHMWPE) articulation in common. They are the Freedom (Integra LifeSciences, Princeton NJ, USA and Smith & Nephew, London, UK), the Maestro (Biomet, Warsaw, IN, USA) and the ReMotion (Small Bone Innovation, Morristown, PA, USA). TWA is a ‘hot topic’, featuring heavily in recent meetings of the British Society of Surgery for the Hand (BSSH) and the Federation of European Societies for Surgery of the Hand (FESSH). In this issue of the Journal, there are a few articles on TWA that add considerably to our understanding of the topic, with particular reference to the Motec and the Freedom implants.

In the article by Redfern et al. (2023), five international centres have collaborated to present the short- and medium-term results of the Motec TWA. The authors specifically concentrate on complications, which they categorized into those that could have been preventable, potentially preventable and unpreventable. The article offers practical advice on how to avoid preventable complications. It is the largest such study to date, comprising data from 171 Motec TWAs. The results demonstrate a revision rate of 8.2% at 5 years, while the existing literature reports a revision rate of 14%–18% at 10 years (Reigstad and Røkkum, 2018). Both papers make similar recommendations for reducing complications, reoperations and revision surgery. The authors suggest a full proximal row carpectomy and radial styloidectomy to limit bony impingement, and avoidance of a short neck implant due to risk of implant impingement. Implant impingement between the titanium stem and cobalt chrome cup may lead to the production of metal debris, osteolysis and implant failure. The issue of impingement is covered in greater detail by Julian et al. (2023), with a compelling hypothesis that metal debris results from extra-articular impingement rather than articular surface wear.

In this issue, results from another fourth-generation TWA implant are presented. The group from Wrightington hospital, Wigan, UK presented the largest published series of the Freedom TWA to date (Brown et al., 2023). This report also contains the longest follow-up and doubles the number of cases reported in the existing literature (Rossello et al., 2022). The implant appears to provide effective pain relief in low-demand patients who want to preserve wrist movement. This series reports a single revision in 12 cases, but also describes a 33% lucency rate around the carpal implant. The exact significance of these lucencies is as yet unclear but is a cause for concern, which requires ongoing observation. It should be borne in mind that the Universal 2 implant (Integra Life Sciences, Plainsboro, NJ, USA), the Freedom’s predecessor, also had a high rate of lucency. The Universal 2 implant has 10-year survival rates in the region of 70%–80% at 10 years, with a deteriorating survival curve over time (Newton et al., 2023). In theory, the Freedom has an improved bearing surface comprising UHMWPE, which has been highly cross-linked on the carpal component, with improved geometry on the radial component. The impact of these changes is yet to be proven.

Discussion

The total number of procedures needed to become competent in TWA using a particular implant is unknown. The designers of the Motec implant suggest that 10 implants are carried out annually for the first 2 years, followed by a minimum sustained volume of five per year. This recommendation was based on literature regarding the reverse shoulder arthroplasty and ankle arthroplasty, which are also considered a low volume implants (Basques et al., 2016; Riedel et al., 2010). These papers explore the learning curve of such surgery, finding improved outcomes for those performing 21 cases or more annually. Reigstad et al. (2017) found the highest rate of revision was within 2 years of the index procedure, with early revisions more commonly related to surgical factors. In a report about the learning curve, also published in this edition of the Journal, Brown et al. (2023) explore this area in greater detail. They note a threefold higher risk of complications and revision in the first 15 cases performed. Logic agrees that beginners would exhibit a lower level of competency than experts but since it would be impossible to bypass this stage completely, we need practical solutions to improve safety during this critical period. The authors advocate dual consultant operating to mitigate the risk of complications during the learning process. It is advisable to only embark on an arthroplasty career if planning to maintain an adequate volume, so as to avoid the ‘forgetting curve’ demonstrated by Murre and Dross (2015).

Future comparative studies are necessary but challenging. One prospective randomized controlled trial compared the outcomes of two fourth-generation implants, the Motec and the ReMotion in non-rheumatoid wrists (Holm-Glad et al., 2022) reports equivalent early functional results at 2 years. Two ReMotion carpal components were revised due to loosening, and three Motec articulations were revised to metal on polyether ether ketone (PEEK) from metal-on-metal articulation. The medium-term results of this study will be interesting and informative when they come to term. Fourth-generation TWA are often discussed together, and their results compared in the literature. However, the Motec TWA has several unique design features, including a ball and socket geometry, metal-on-metal bearing and calcium phosphate coated stems to promote osseointegration. With this in mind, we should question how reasonable it is to compare the Motec implant with other implants, even if they are of the same generation.

As well as the variety between implants, TWA is also used in a heterogenous patient population that includes osteo- and inflammatory arthropathy as the primary pathology. It is important to question whether the evidence can be extrapolated across these different groups of patients. There are data to support the use of certain TWA implants in inflammatory arthropathy, including the Freedom TWA, which is the successor to the third-generation Universal 2 (Brown et al., 2023; Newton et al., 2023). Meanwhile, the Universal 2 performs less well in patients with osteoarthritis, with 10-year survival rates as low as 35% (Gendera et al., 2020). The Motec may perform better in the longer term and at present, there is significantly more evidence to support the use of this TWA in non-inflammatory than inflammatory arthropathy (Giwa et al., 2018; Reigstad et al., 2017). When used in these patients, the Motec TWA has a 10-year survival rate of 82%. Interestingly, after the first 2 years, the survival curve flattens, suggesting the long-term survival may remain relatively static at approximately 80% (Reigstad et al., 2012). With the limited data available, it may be reasonable to offer a non-inflammatory arthritic patient a Motec implant, while a rheumatoid patient may do well with another fourth-generation TWA.

The evolution of arthroplasty requires changes to be made as lessons are learned from ongoing research. TWA implants belonging to previous generations have been largely discontinued due to inadequacies in their performance, being replaced by the current fourth-generation models. There are data to support the use of fourth-generation implants. An extra obstacle for TWA development and marketing in Europe lies in the latest Medical Devices Regulation (Medicines and Healthcare Products Regulatory Agency [MHRA], 2017). This enforces more rigorous pre-market evaluation, certification and post-market surveillance for all implants since 2020, with the aim of improving safety and performance. This undoubtedly has the right intention, but stringent new rules risk hindering innovation due to lengthy processes and increased legal costs. This is of particular concern for low-volume devices, such as TWA, which may be deemed financially unviable to implant companies. To overcome this hurdle and facilitate implant development, collaboration between companies is key.

The argument for low-volume procedures being performed by a smaller number of units to maintain higher surgical volumes and therefore better outcomes seems convincing, as discussed in the short report on learning curves (Brown et al., 2023). The implementation of such a system is not without practical problems, with travelling distance for patients as well as surgeons, and the development of referral pathways, to name a few. Our colleagues carrying out large joint revision arthroplasty surgery, e.g. total hip arthroplasty (THA), are leading the way in the UK, with the establishment of revision arthroplasty hubs covering large geographical areas in order to get it right first time (Briggs, 2015). Indeed, it seems impossible to discuss any form of joint arthroplasty without mention of THA, which is considered one of the most successful orthopaedic operations (Learmouth et al., 2007). The question remains whether it is reasonable to compare low volume surgeries with a relatively short history like the TWA with an entirely different operation like the THA. Achieving excellence in TWA is a challenge that warrants further work, to include the establishment of realistic outcome goals.

In conclusion, the articles in this issue of the Journal, along with those referenced in this commentary, are mandatory reading for any surgeon starting a TWA programme. The learning curve should be respected, even for experienced wrist surgeons. Support during the learning process can be achieved with dual consultant operating and a consistent scrub team. Maintenance of skills requires a consistent, acceptable volume of cases, which may be best achieved by centralizing TWA practice. Including TWA in national, or even international, joint registries will also help us to further understand how these implants behave. It seems likely that registries will soon become mandatory for all joint arthroplasties; this should be embraced and encouraged if we are to aspire towards results approaching those for THA. The pooling of knowledge represents the future of TWA research, which should reduce complications and improve outcomes for patients, while adding to the collective experience of TWA. Further research is required in practically all areas surrounding TWA, especially the following: anatomic and biomechanic studies to dictate the ideal design of implants; experience of the Motec TWA in inflammatory arthropathy; and long-term survivorship of TWA.