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Thumb CMCJ prosthetic total joint replacement: a systematic review

Thumb carpometacarpal joint (CMCJ) arthritis is a common and painful condition. Thumb CMCJ prosthetic replacement aims to restore thumb biomechanics and improve pain and function. Early reviews demonstrated a lack of high-quality studies, but more recently a significant number of higher-quality studies have been published. This review provides a concise and systematic overview of the evidence to date. A systematic review of several databases was conducted according to PRISMA guidelines. Studies evaluating the outcomes of thumb CMCJ prosthetic total joint replacement were included. Data extracted included patient-reported outcome measures (PROMs), pain scores, range of motion, strength, survival rates and complications. A total of 56 studies met all inclusion criteria and were analysed. There was one randomized controlled trial, three prospective comparative cohort studies, five retrospective comparative cohort studies, and 47 descriptive cohort studies. The reported studies included 2731 patients with 3048 thumb total CMCJ prosthetic joint replacements. Follow up ranged from 12 months to 13.1 years. In general, good results were demonstrated, with improvements in PROMs, pain scores and strength. Failure rates ranged from 2.6% to 19.9% depending upon implant studied. Comparative studies demonstrated promising results for replacement when compared to resection arthroplasty, with modest improvements in PROMs but at a cost of increased rates of complications. Studies reporting outcomes in thumb CMCJ prosthetic total joint replacement are increasing in both number and quality. Failure, in terms of loosening and dislocation, remains a concern, although in the medium-term follow up for modern implants this issue appears to be lower when compared to their predecessors. Functional outcomes also look promising compared to resection arthroplasty, but further high-quality studies utilizing a standardized resection arthroplasty technique and modern implants, together with standardized core outcome sets, will be of value. Cite this article: EFORT Open Rev 2021;6:316-330. DOI: 10.1302/2058-5241.6.200152

Thumb carpometacarpal joint (CMCJ) arthritis is a common and painful condition. Thumb CMCJ prosthetic replacement aims to restore thumb biomechanics and improve pain and function. Early reviews demonstrated a lack of high-quality studies, but more recently a significant number of higherquality studies have been published. This review provides a concise and systematic overview of the evidence to date. A systematic review of several databases was conducted according to PRISMA guidelines. Studies evaluating the outcomes of thumb CMCJ prosthetic total joint replacement were included. Data extracted included patientreported outcome measures (PROMs), pain scores, range of motion, strength, survival rates and complications. A total of 56 studies met all inclusion criteria and were analysed. There was one randomized controlled trial, three prospective comparative cohort studies, five retrospective comparative cohort studies, and 47 descriptive cohort studies. The reported studies included 2731 patients with 3048 thumb total CMCJ prosthetic joint replacements. Follow up ranged from 12 months to 13.1 years. In general, good results were demonstrated, with improvements in PROMs, pain scores and strength. Failure rates ranged from 2.6% to 19.9% depending upon implant studied. Comparative studies demonstrated promising results for replacement when compared to resection arthroplasty, with modest improvements in PROMs but at a cost of increased rates of complications. Studies reporting outcomes in thumb CMCJ prosthetic total joint replacement are increasing in both number and quality. Failure, in terms of loosening and dislocation, remains a concern, although in the medium-term follow up for modern implants this issue appears to be lower when compared to their predecessors. Functional outcomes also look promising compared to resection arthroplasty, but further high-quality studies

Introduction
Thumb carpometacarpal joint (CMCJ) arthritis is a painful and debilitating condition with a preponderance for women and clinically affecting around 1.4% of the population. 1 Surgical treatment options include trapeziectomy, interposition arthroplasty, arthrodesis, or total joint replacement. Despite the use of total joint arthroplasty being widespread in Europe, early systematic reviews have highlighted a lack of high-quality evidence to support its use. 2 More recently, however, a large number of articles have been published on this topic, and therefore a contemporary review of the literature is necessary. This review aims to provide a systematic and concise update of the available evidence for the use of thumb CMCJ prosthetic total joint replacement.

Search strategy
We conducted an online systematic literature search in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. It was prospectively registered on the International Prospective Register of Systematic Reviews (PROSPERO).
Thumb CMCJ prosthetic total joint replacement: a systematic review

Results
The initial literature search resulted in a total of 1047 articles. Fig. 1 shows the PRISMA flowchart for study selection. A total of 56 studies met all inclusion criteria and were analysed. There was one randomized controlled trial, three prospective comparative cohort studies, five retrospective comparative cohort studies, and 47 descriptive cohort studies. The methodological bias assessment for all 56 studies is included in Table 1.

Study characteristics
The 56 studies (Table 1) included a total of 2731 patients with 3048 thumb total CMCJ prosthetic joint replacements; 84% of patients were female (2210/2632 reported), with a mean age of 62.5 years (range, 50 to 71). Methodological analysis was poor to moderate across most of the studies, with higher Coleman scores for those with a more rigorous study design i.e. comparative cohorts or randomized controlled trials. Surgical experience level, surgical approaches, and post-operative rehabilitation were sporadically reported.

Follow up
All studies reported their follow up period, with mean follow up ranging from 12 months to 13.1 years.

Underlying aetiology
In all but one study the underlying aetiology was exclusively osteoarthritis (OA), and in the remaining study the underlying aetiology was inflammatory joint disease. 4 Of the 16 studies excluded due to mixed aetiologies, few of these included a significant proportion of inflammatory arthritis cases.

Assessment of clinical outcomes
Quantifiable patient-reported outcome measures were reported in 34 studies.  Comparable pre and postoperative values were reported in 12 studies. 7,9,10,13,16,17,19,23,27,29,32,33 The most commonly used patient-reported outcome measures (PROMs) were the Disabilities of the Arm Shoulder and Hand measure (DASH) or quick DASH which are general upper extremity scoring systems. Other measures included the Michigan Hand Questionnaire (MHQ) which is more specific to hand complaints, the Nelson score, which is specific to thumb outcomes, the Patient Related Wrist Evaluation (PRWE) score which is a wrist-specific measure, and the Sollerman score which is a measure of hand function. Most studies reporting pre and post-operative PROMs demonstrated a significant improvement from pre-operative values. The measures of spread of data (i.e. standard deviation or equivalent) were inconsistently reported.
The most significant complications were those of failure, loosening or dislocation of implants. A number of other complications including fracture, infection, chronic regional pain syndrome, superficial radial nerve symptoms, tendon irritation, and heterotopic ossification were noted, but only reported in this review for the comparative studies.

Outcomes of different prostheses
The ARPE prosthesis was reported in 11 studies comprising three comparative cohorts 8-10 and eight descriptive cohorts, [5][6][7]11,12,40,42,43 with a total of 735 replacements (Tables 2 and 3, Figures 2 and 3). Two studies reported >    10 year survival rates with cumulative survivorship analysis. One study reported significantly better survivorship after correcting for the learning curve procedures (15 year survival 80% to 85% after correction), demonstrating the importance of technical performance in obtaining good long-term results and minimizing complications. 5 The other study reported 93% survival at 10 years as defined by being offered revision surgery, although 50% of these declined. 7 One study demonstrated much poorer survival rates of 79% at 11 years with most of the failures being due to loosening. 12 A small trapezium was found to be a risk factor for trapezial loosening/failure, 7 emphasizing the importance of appropriate patient selection. At a mean of 78 months follow up, failure rates were 10.3%, loosening rates 4.8%, and dislocation rates 6.8%. The de la Caffinière (DlC) prosthesis was reported in five studies, 4,14,45-47 all of which were descriptive cohorts, with a total of 171 replacements (144 for osteoarthritis). Two studies reported survival rates with cumulative survival analysis. One of these reported 72% survival at 16 years. 45 The other study reported 87% survival at 10 years. 4 At a mean of 68 months follow up, cases undertaken for osteoarthritis demonstrated failure rates of 14.5%, loosening rates of 38.2%, and dislocation rates of 13.8%. The single series evaluating cases undertaken for inflammatory arthritis evaluating outcomes at a mean of 13 years demonstrated, out of 27 cases, failure rates of 26%, loosening rates of 29.6%, and dislocation rates of 11.1%. 4 The Elektra prosthesis was reported in nine studies, comprising one randomized controlled trial, 48 two comparative cohorts, 15,41 and six descriptive cohorts, [16][17][18]54,57,58 with a total of 281 replacements. Two studies reported survival rates with cumulative survival analysis, demonstrating 72% survival at two years 48 and 90% survival at five years 57 respectively. At a mean of 48 months follow up, failure rates were 19.9%, loosening rates 19.6%, and dislocation rates 5%.
The IVORY prosthesis was reported in five studies, comprising two comparative cohorts, 21,22 and three descriptive cohorts, 20,23,24 with a total of 274 replacements. Two studies reported survival rates with cumulative survival analysis, demonstrating 95.5% survival at 10 years 20 and 96.4% survival at five years 21 respectively. At a mean of 82 months follow up, failure rates were 6.2%, loosening rates 1.5%, and dislocation rates 4.4%.  The Maia prosthesis was reported in five studies, 25-29 all of which were descriptive cohorts, with a total of 451 replacements. One study reported survival rates with cumulative survival analysis, demonstrating 93% survival at five years. 27 At a mean of 59 months follow up, failure rates were 9.8%, loosening rates 2.4%, and dislocation rates 4.4%.
The Moovis prosthesis was reported in three studies, 32-34 all of which were descriptive cohorts, with a total of 265 replacements. At a mean of 48 months follow up, failure rates were 2.6%, loosening rates 0.4%, and dislocation rates 0.4%.
The Roseland prosthesis was reported in five studies, 36,39,51,52,59 all of which were descriptive cohorts, with a total of 255 replacements. At a mean of 60 months follow up, failure rates were 9.2%, loosening rates 6.3%, and dislocation rates 2%.
Radiolucencies were common in some series, 19,25,27, 48,50,55,56 but most cases were minor with no significant progression or clinical symptoms. 37 Heterotopic ossification was identified post-operatively in some series, but only rarely causing significant enough symptoms to warrant intervention. 6,7,12,25,27,37,38 Trapezial fracture, either intra-operatively, or after surgery due to trauma was identified in several studies, but in most cases the fracture was not severe enough to cause cup loosening or displacement and responded well to a period of immobilization. 5,33,36,46,52 Outcomes of comparative studies The resection arthroplasty groups underwent trapeziectomy with ligament reconstruction and tendon interposition (lRTI) using flexor carpi radialis (FCR) in five studies, 9,10,13,21,48 abductor pollicis longus (APl) in two studies, 22,41 extensor carpi radialis longus (ECRl) in one study, 15 and a synthetic interposition in one study 8 (Table  4). Due to both the heterogeneity of surgical techniques and outcome measures, it was not possible to perform a meta-analysis of these data.
Thorkildsen et al 48 undertook a randomized controlled trial (RCT) comparing the Elektra prosthesis to trapeziectomy with lRTI using FCR with 20 patients in each group, with a follow up of two years. qDASH scores were better in the replacement group at three and six months but not at one to two years (based upon a minimally clinical important difference (MCID) of 15). The Nelson score demonstrated better results in the replacement group at three months but not beyond this. Range of movement and grip strength were not significantly different between the two groups. The prosthetic group demonstrated five failures (two for cup loosening, three for dislocation) and one infection. The trapeziectomy group demonstrated three complications, with one haematoma, one FCRrelated pain, and one base of thumb pain.
The other studies were comparative cohorts comparing ARPE, [8][9][10]21,22 Elektra, 15,41 and beznoska 13 prostheses against resection arthroplasty. Follow up ranged from 12 months to 13.6 years. PROMs were shown to be statistically significantly better in the replacement group in 4/7 studies, 8,13,21,22 pain relief better in 3/7 studies, 9,21,41 range of motion better in 4/6 studies, 9,10,21,41 and strength better in 4/5 studies. 9,10,21,41 In the remainder of studies any difference seen was statistically insignificant. There were no studies demonstrating a statistically significant superiority of resection arthroplasty over replacement. Pain relief was achieved faster in the replacement group in three studies, 21,22,41 and return to work was faster in one study. 22 Complications were more common in the replacement groups in terms of failures, with the majority of issues in the replacement group being loosening and dislocation. Out of a total of 389 replacements, there were 62 reported complications (16%). This comprised 26 cases of loosening, 17 dislocations, five superficial radial nerve symptoms, three implant failures, three infections, two tendon issues, two fractures, one suture irritation, one heterotopic ossification, one chronic regional pain syndrome (CRPS), and one allergic reaction. Out of a total of 343 resection arthroplasties, there were 31 reported complications (9%). This comprised nine superficial radial nerve symptoms, six tendon issues, three proximal migrations, two infections, two CRPS, two STTJ OA progression, two metacarpo-phalangeal joint hyperextension deformities, one case of scar tenderness, one base of thumb pain, one FCR pain, one haematoma, and one instability.

Discussion
Thumb CMCJ prosthetic total joint replacement outcomes have now been published with fair to good longterm functional outcomes, and demonstrate encouraging clinical outcomes in comparative studies with resection arthroplasty at short-medium-term follow up. This comes with a cost of increased rates of complications, largely in terms of loosening and dislocation of the implants.
Thumb CMCJ replacement is a technically demanding procedure, and appropriate patient selection and surgical experience are thought to be fundamental to obtaining

*qDASH better in
Repl at 3/6 months but not 1-2 yrs (MCID set at 15) *Nelson score better at 3 months optimal outcomes and reducing complications. There is a significant learning curve to replacement operations, with higher failure rates and complications demonstrated in one series in the first 30 cases as compared to subsequent 50 cases. 5 Accurate and comparative reporting of experience level is important to aid the interpretation of published results, with systems in existence to enable this. 60 Computer-assisted surgery has been piloted in a cadaveric study to attempt to obtain reliable and accurate position of the cup component, but has not yet been translated into clinical practice. 61 OA is the most common indication for replacement procedures. Several manufacturers advise specifically not to undertake CMCJ replacement in patients with inflammatory arthritis due to the theoretically higher risks of failure due to poor bone and soft tissue quality. Only one study evaluated CMCJ replacement in purely inflammatory arthritis cases, 4 with a failure rate of 26%, loosening rate of 30% and dislocation rate of 11%, somewhat supporting this theory.
Surgical approach is thought by some surgeons to determine either optimal exposure or preservation of important ligamentous/capsular complexes. Surgical approaches were not reported in a significant number of studies; however, dorsal approaches were described in 29 studies, and volar approaches in eight studies. Advocates of the volar (Wagner) approach suggest that because the two important structures in stability of the thumb CMCJ are the anterior oblique ligament (which is already attenuated in CMCJ OA) and the dorsal capsule, a volar approach preserves the remaining dorsal capsule to maximize post-operative stability and reduce dislocation rates. 62 Advocates of the dorsal approach suggest that the trapezial exposure is significantly better with this approach, and therefore a more accurate implantation of the trapezial component can be established. 5,7 The only study to assess this found that implant positioning was significantly better in their cohort with the dorsal approach compared to the volar approach. 7 This has yet to be validated by other studies and with other prostheses and no conclusions regarding optimal approach can be made on the basis of this.
Patient-reported outcomes are critical to evaluating the subtle differences in improvement between CMCJ replacement and resection arthroplasty. The most commonly used outcome measures, i.e. DASH/qDASH, may not be sensitive enough to assess this. Thorkildsen et al 48 reported an MCID of 15 in their randomized controlled trial using qDASH as the comparative outcome measure, but this was based upon a study evaluating a heterogenous group of hand conditions and therefore was not specific to thumb outcomes. 63 The Nelson score is a thumb-specific measure with positive ratings according to the Consensus-based Standards for the Selection of Health Status Measurement Instruments (COSMIN), 64 but is not commonly used. Pain is the major presenting feature with which patients pursue surgical intervention, and therefore the accurate and comparable recording of painrelated outcomes is essential. The use of the VAS score for pain, documented pre and post-operatively is probably the most easily comparable score available. Standardization of whether this represents pain at rest or on activity will help define outcomes even further. Survival rates are a key index reporting measure in large joint arthroplasty, and will play a useful role in the comparative outcomes of thumb CMCJ replacement. It is important, however, to standardize the definition of survival e.g. as removal or exchange of prostheses, and to perform cumulative survival analysis to enable accurate comparison of implants at different time points. A core outcome set for thumb CMCJ outcomes has not yet been defined, but will be important in future comparative studies. 65,66 Early implants, e.g. de la Caffinière, used cemented fixation techniques of the trapezial and metacarpal components with a semi-constrained prosthesis, which may explain the relatively high loosening rates for these protheses, as the thumb CMCJ will undergo significant shear as well as compressive forces. 67 Subsequent protheses (Table 5) developed either hydroxyapatite coated or porous coated titanium implants (e.g. ARPE, Elektra, IVORY, Maia, Roseland) to encourage more robust bone integration. Other implants, e.g. Moovis, have evolved to incorporate dual mobility bearing characteristics with the theoretical advantages of reducing both loosening and dislocation rates. This is borne out in the early-mediumterm data presented in this review, as Moovis has the lowest rates of both loosening and dislocation, although with a mean follow up of two years (maximum five years). longer-term results are awaited to determine the longevity of these implants. Of the commonly reported implants, DlC, Elektra, Roseland and IVORY are no longer on the market. This has occurred either due to high levels of failure (e.g. Elektra) or for commercial reasons (e.g. Roseland, IVORY). ARPE, Moovis, and Maia are CE marked for use in Europe. Another promising modern implant with CE marking is the Touch prosthesis (Keri Medical, dual mobility). It has not yet been reported upon but is commonly used in Europe and as a result Keri Medical are in the process of seeking Food and Drug Administration (FDA) approval for its use in the uSA.
Resection arthroplasty, i.e. trapeziectomy with or without lRTI, is held as the standard of surgical care for CMCJ OA for which to compare other interventions. The comparative studies in this review use a wide range of lRTI interventions, which alongside different reporting outcomes negates the usefulness of meta-analysis of the data. In addition to clinical measures, failure is often reported as a measure of comparison between the interventions. 68 One option for a failed replacement is to perform a secondary trapeziectomy, which has been shown to have equivalent outcomes when compared to patients who undergo a primary trapeziectomy from the beginning (i.e. no replacement at all). 50,56, [69][70][71] The main comparative study utilized trapeziectomy without lRTI. 70 There are concerns regarding the increased cost of using implants in replacement compared to trapeziectomy, and cost-effectiveness studies are lacking in the literature. Only one study has evaluated relative costs of trapeziectomy vs. trapeziectomy with lRTI vs. CMCJ replacement/fusion (as a combined group due to low overall numbers). 72 They looked at 3501 patients from 2001-2010, and calculated the Medicare and secondary insurance payouts for each procedure. They calculated the hospital outpatient total spending at a mean of 3199 uSD for trapeziectomy, 3412 uSD for CMCJ replacement/fusion, and 4186 uSD for trapeziectomy with lRTI. It is difficult to extrapolate this fully to our day-to-day practice due to the combined replacement/fusion group, and now relatively old data. Further studies should incorporate cost-effectiveness evaluations into the study design.
A precise definition of how loosening was identified was lacking in most studies. Only two studies specifically defined how they assessed loosening -one with radiolucent lines in three or more zones of 0.5 mm or more, 38 and one with radiolucent lines greater than 1 mm. 14 The other studies simply described radiographic loosening or migration of the implant. A universal definition of loosening would help make reliable comparisons across studies and implants.
This systematic review has some weaknesses. The quality of evidence has improved since the last systematic review on this topic, 2 with a further seven comparative trials (including one RCT), however the majority of studies are still of a moderate methodological quality, even amongst the comparative studies. The quality of reporting did not allow for a meta-analysis due to the heterogeneous datasets. Therefore it is not possible to draw a definitive conclusion regarding the superiority of replacement versus resection arthroplasty. The definitions of loosening were variable and therefore difficult to accurately report between studies. The inclusion of core outcome sets, standardizing reporting of outcomes, will help in future meta-analyses of datasets to enable more definite conclusions to be reached.

Conclusion
The number of studies reporting outcomes in thumb CMCJ prosthetic total joint replacement are increasing both in number and quality. Failure, in terms of loosening and dislocation, remains a concern, although in the medium-term follow up for modern implants this issue appears to be of less concern when compared to their predecessors. Functional outcomes also look promising compared to resection arthroplasty, but further highquality studies utilizing a standardized resection arthroplasty technique and modern implants, together with standardized core outcome sets, will be of value.

ICMJE ConflICt of IntErEst statEMEnt
The authors declare no conflict of interest relevant to this work. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.