Surface replacement trapeziometacarpal joint arthroplasty--early results

MAÏA Trapeziometacarpal Joint Arthroplasty: Clinical and Radiological Outcomes of 76 Patients With More Than 10 Years of Follow-Up

PURPOSE

Trapeziometacarpal (TMC) joint replacement has become a valid option in the therapeutic arsenal of TMC joint osteoarthritis in Europe. Good mid-term results of the MAÏA TMC joint prosthesis suggested that it is a reliable procedure. This study aimed to assess the long-term results of this modular uncemented ball-and-socket hydroxyapatite-coated implant.

METHODS

This single-center retrospective study evaluated 92 MAÏA TMC joint prostheses in 76 patients with a minimum of 10 years of follow-up. Indications for the procedure were painful TMC joint osteoarthritis both at rest and during activity, despite nonsurgical treatment for more than six months. Pre- and postoperative clinical and radiographic outcomes were compared.

RESULTS

Mean follow-up was 134 months (range: 120-158 months). Mean age at the time of surgery was 67 years (range: 53-84 years). The cohort comprised 86.8% of women (n = 66). The mean Quick Disabilities of the Arm, Shoulder, and Hand score improved from 61.3 ± 17.1 to 19.6 ± 16. Range of motion was restored, and postoperative mobility was comparable with that of the contralateral side. Final Kapandji opposition score was almost normal (9.2 ± 0.7). Final key pinch and grip strength improved by 26% and 39%, respectively. Eight implants were surgically revised, six for trapezium cup loosening and two for instability because of polyethylene wear. Three cases of traumatic fracture of the trapezium in older patients were successfully treated with a cast for eight weeks. Five of 26 (20.8%) cases of preoperative-reducible z-deformity were not totally corrected after surgery. The Kaplan-Meier survival over 10 years was 88% (95% confidence interval: 84-93) versus 93% (95% confidence interval: 87-98) over 5 years.

CONCLUSIONS

MAÏA TMC joint prosthesis is a reliable long-term surgical procedure for TMC joint osteoarthritis, improving overall function beyond 10 years.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Arthroplasty in thumb trapeziometacarpal (CMC joint) osteoarthritis: An alternative to excision arthroplasty

Trapeziectomy for base of thumb arthritis is well established, but base of thumb arthroplasty offers potential advantages. The review covers the development of arthroplasty for the thumb from interposition arthroplasty to total joint replacement. It discusses contemporary prosthesis designs and results, including trapezial component geometry, bearing surfaces, and dual mobility.

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

A radiostereometric and clinical long-term follow-up study of the surface replacement trapeziometacarpal joint prosthesis

Background

The aim of this study was to determine long-term survival and clinical outcomes of the surface replacement trapeziometacarpal joint prosthesis (SR™TMC) and to evaluate implant migration using radiostereometric analysis (RSA).

Methods

In this clinical long-term follow-up study outcomes of ten patients who received the SR™TMC joint prosthesis were evaluated using DASH and Nelson scores, Visual Analogue Scale (VAS) of pain, and key pinch strength. RSA-radiographs were obtained direct postoperatively and 6 months, 1, 5 and 10 years postoperatively and were analyzed using model-based RSA software.

Results

During follow-up, two early revisions took place. Mean pre-operative DASH and Nelson scores were 54 (SD 15) and 54 (SD 17), improved significantly after 6 months (DASH 25 (SD 20), Nelson 75 (SD 18)) and remained excellent during long-term follow-up in all patients with a stable implant. At final follow-up, clinical scores deteriorated clearly in two patients with a loose implant in situ.

Conclusions

Long-term survival of the SR™TMC joint prosthesis is relatively poor. However, clinical outcomes improved significantly in the short-term and remained excellent in the long-term in those patients with a stable implant, but deteriorated clearly in case of loosening. The role of RSA in TMC joint arthroplasty is potentially valuable but needs to be further investigated. Several challenges of RSA in the TMC joint have been addressed by the authors and suggestions to optimize RSA-data are given.

Trial registration

This study was registered in the Netherlands Trial Register (NL7126).

Joint replacement for trapeziometacarpal osteoarthritis: implants and outcomes

For thumb carpometacarpal osteoarthritis, trapeziectomy provides generally good results with reduction of pain and restoration of thumb mobility, but shortening of the thumb may at least in theory lead to reduction in grip and pinch strength. Furthermore, instability of the base of the first metacarpal and contact with the scaphoid may occur regardless of the several described techniques with ligament reconstruction and tendon interposition. Thus, for years alternatives to trapeziectomy have been explored and reported with disputable success. Often the road from idea to implantation in patients seems to have been short, and high complication rates and failure of new implant designs have been fairly common. This has led to the general impression that the implants do not provide sufficient benefits compared with simple trapeziectomy. More recent uncemented total joint replacement designs have shown rapid rehabilitation, reduction of pain, restoration of grip strength and movement, and much improved long-term implant survival. These factors may make total joint replacement a realistic alternative to trapeziectomy. Still, patient selection has to be improved, as the benefits may be small in the low activity elderly patient.

Reporting Outcomes and Outcome Measures in Thumb Carpometacarpal Joint Osteoarthritis: A Systematic Review

PURPOSE

In the thumb carpometacarpal (CMC) joint osteoarthritis (OA) literature, there is substantial heterogeneity in outcome and outcome measure reporting. This could be rectified by a standardized core outcome set (COS). This study aimed to identify a comprehensive list of outcomes and outcome measures for thumb CMC joint OA, which represents the first step in developing a COS.

METHODS

A computerized search of MEDLINE, EMBASE, Cochrane, and CINAHL was performed to identify randomized controlled trials, as well as observational studies involving at least 50 participants aged greater than 18 years undergoing surgery for thumb CMC joint OA. Reported outcomes and outcome measures were extracted from these trials and summarized.

RESULTS

This search yielded 3,498 unique articles, 97 of which were used for analysis. A total of 33 unique outcomes and 25 unique outcome measures were identified. The most frequently used outcomes were complications (78), postoperative pain (73), radiologic outcomes (64), and grip strength (63). Within each reported outcome, there was substantial variation in how the outcome was measured. Of the 25 unique outcome measures, 10 were validated. Of the remaining 15, 12 were created ad hoc by the author. The Disabilities of the Arm, Shoulder, and Hand questionnaire was the most commonly reported outcome measure (34%).

CONCLUSIONS

There is a lack of consensus on critical outcomes after surgery for thumb CMC joint OA. A standardized COS created by stakeholder consensus would improve the consistency and therefore the quality of future research.

CLINICAL RELEVANCE

This systematic review of outcomes represents the first step in developing a core outcome set for thumb CMC joint OA.

Trends in Trapeziometacarpal Implant Design: A Systematic Survey Based on Patents and Administrative Databases

Hand function is inseparably linked to the condition of the thumb. The trapeziometacarpal (TMC) joint that provides the different movements of opposition is one of the joints most affected by osteoarthritis, which causes an irreversible deformation of the bone. The ideal thumb carpometacarpal implant must restore range of movement, prevent complications, be biocompatible, and have good mechanical properties (ie, low wear, high corrosion resistance, and osteointegration properties where it is anchored in a bone). The integrity of the implant and the surrounding biological structures must be long-lasting and withstand constant stresses induced by the prosthesis. Three main types of implant systems for the thumb are currently clinically available; others are under investigation in human subjects. This systematic review is based on administrative databases, patents, the literature, and information from orthopedic companies. It provides a summary of strategies and design changes and an overview of the biomechanical characteristics of currently available carpometacarpal implants for treating osteoarthritis of the thumb.

Functional outcomes after surgery for thumb carpometacarpal joint arthritis

There are a number of possible assessments of functional outcomes for thumb carpometacarpal joint arthritis. The most important and easiest to measure is pain, but it is not the only material outcome. Functional scores for measuring the outcome of the treatment of thumb carpometacarpal joint arthritis have been recommended for some time, but are still not widely used even in published studies. It is also unclear which functional scores are the most valuable. Easily used scores, such as the Disabilities of the Arm Shoulder and Hand questionnaire, are freely available, but may not be sensitive enough to assess outcomes especially of thumb carpometacarpal joint arthroplasty. The optimal functional outcome measurement would be weighted for the individual patient. A minimum dataset needs to be defined in order to compare studies and derive meaningful data.

Failure Rates of Base of Thumb Arthritis Surgery: A Systematic Review

PURPOSE

The purpose of the current review was to estimate failure rates of trapeziometacarpal (TMC) implants and compare against failure rates of nonimplant techniques for surgical treatment of TMC joint (basal thumb joint) arthritis.

METHODS

A systematic review was conducted to identify articles reporting on thumb implant arthroplasty and on nonimplant arthroplasty techniques for treatment of base of thumb arthritis in the English literature. The collected data were combined to calculate failure rates per 100 procedure-years. Failure was defined by the requirement for a secondary salvage procedure. The failure rates between different implant and nonimplant arthroplasty groups were compared directly and implants with higher than anticipated failure rates were identified.

RESULTS

One hundred twenty-five articles on implant arthroplasty and 33 articles on the outcome of nonimplant surgical arthroplasty of the TMC joint were included. The implant arthroplasty failure rates per 100 procedure-years were total joint replacement (2.4), hemiarthroplasty (2.5), interposition with partial trapezial resection (4.5), interposition with complete trapezial resection (1.7), and interposition with no trapezial resection (4.5). The nonimplant arthroplasty failure rates per 100 procedure-years were: trapeziectomy (0.49), joint fusion (0.52), and trapeziectomy with ligament reconstruction ± tendon interposition (0.23).

CONCLUSIONS

Several implant designs (arthroplasties) had high rates of failure due to aseptic loosening, dislocation, and persisting pain. Furthermore, some implants had higher than anticipated failure rates than other implants within each class. Overall, the failure rates of nonimplant techniques were lower than those of implant arthroplasty.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Arthroscopic treatment of basal joint arthritis by partial trapeziectomy with ligament reconstruction: Short-term results from a prospective study of 20 patients

Partial trapeziectomy for basal joint arthritis is an alternative to total trapeziectomy that preserves the height of the thumb column. Using arthroscopy reduces the incidence of periarticular lesions and the risks of complications. The purpose of this prospective single-center study was to evaluate the results of arthroscopic partial trapeziectomy combined with suspension and interposition ligament reconstruction using half of the abductor pollicis longus tendon. Twenty patients (18 women, 2 men) with a mean age of 55 years (43-65 years) were operated using this technique between November 2013 to February 2015. Patients were evaluated clinically and radiologically at 1 month, 3 months, 6 months and 12 months after surgery. The 20 patients were reviewed after 12 months. The subjective QuickDASH score improved from the 3rd post-operative month (P = 0.0029) from 50.6 preoperatively to 30.3 after 3 months, 17.6 after 6 months and 9.6 after 12 months. Pain was reduced in the 1st month post-operative (P < 0.0001). The Kapandji Score and pinch strength improved from the 3rd month (P = 0.034). Return to work was possible for 19% of employed patients after 1 month, 44% after 3 months and 87.5% after 6 and 12 months. Eighty-eight percent of the patients were satisfied or very satisfied after 3 months and 95% after 6 and 12 months. Pain levels, range of motion and QuickDASH Score are similar to those of open partial trapeziectomy described in the literature. However, recovery seems to be faster with this arthroscopic technique. Arthroscopic treatment of basal joint arthritis, which limits capsule and ligament lesions, leads to good short- and medium-term results in terms of pain relief and thumb motion while preserving strength. LEVEL OF EVIDENCE: 4 (Prospective, non-randomized).

Implant Arthroplasty for Proximal Interphalangeal, Metacarpophalangeal, and Trapeziometacarpal Joint Degeneration

Arthritis of the hand can result from inflammatory arthritis, osteoarthritis (OA), or be posttraumatic and can cause pain and debilitation. Arthroplasty serves as 1 surgical option in the surgical management of arthritis and aims to create a pain-free joint with preservation of motion. Although implant arthroplasty of the proximal interphalangeal (PIP), metacarpophalangeal (MCP), and trapeziometacarpal (TMC) joints predictably produce pain relief and high satisfaction, it has historically suffered from high rates of complications. The hinged silicone prosthesis was 1 of the early implants and, in many cases, remains the gold standard. However, problems with deformity correction, implant fracture, and synovitis remain. Implants made of alternative materials such as metal-plastic and pyrocarbon have evolved; however, survivorship and reoperation rates remain a concern. This review details the evolution and current options available for small joint implant arthroplasty involving the MCP, PIP, and TMC joints.

Results of 115 Rubis II reverse thumb carpometacarpal joint prostheses with a mean follow-up of 10 years

The aim of this study was to assess the clinical and radiological results of the Rubis II thumb carpometacarpal joint reverse prosthesis, at a mean follow-up of 10 years. Between 1997 and 2008, 253 prostheses were implanted in 199 patients; 115 were reviewed. The survival after a mean of 10 years was 89%. At the last follow-up, 70% of prostheses were painless; the others reported moderate or intermittent pain. The satisfaction rate was 98%. The mean opposition was 9 on the Kapandji scale; the mean QuickDASH score was 30. Wrist, key and tip pinch strengths were comparable with the non-operated side. Of the 115 implants, one was radiologically loose (1%) and 15 had suffered dislocations (13%), 12 of which were caused by an injury. Eleven thumbs had revision surgery. This study confirms that the good clinical results of the Rubis II prosthesis are maintained in the medium and long term, and represents a useful alternative to trapeziectomy for selected patients.

LEVEL OF EVIDENCE

IV.

Model-based roentgen stereophotogrammetric analysis of the surface replacement trapeziometacarpal total joint arthroplasty

The primary aim of this clinical and radiostereometric study was to study the migration pattern of the surface replacement trapeziometacarpal joint prosthesis (SR^TMTMC, Avanta^®, San Diego, CA). The secondary aims were to assess patient-related outcomes and prosthesis survival 5 years after surgery. Ten patients received the prosthesis. Radiostereometric radiographs were obtained 6 weeks, 6 months, 1 year and 5 years post-operatively and were analysed using model-based software. All patients completed DASH and Nelson Hospital scores at these follow-ups. Mean translations varied between 0.0 and 0.5 mm after 5 years. Rotation values could be calculated in six patients and mean rotations varied between -0.3 and 2.3°, although the precision of rotation values seems to be poor. The 5-year survival rate was 80%. Mean pre-operative DASH and Nelson Hospital scores were 53 (SD 14) and 51 (SD 13), respectively. Six months post-operatively, the DASH and Nelson Hospital scores had both significantly improved to 25 (SD 20) and 74 (SD 18) and remained high after 5 years. Implant stability was good 5 years post-operatively, and early migration did not predict implant failure in this study.

LEVEL OF EVIDENCE

IV.

Intra-articular corticosteroid injections to manage trapeziometacarpal osteoarthritis-a systematic review

BACKGROUND

Osteoarthritis of the trapeziometacarpal joint (TMJ) is a common condition causing significant disability. The aim of this study is to ascertain whether an intra-articular corticosteroid injection leads to pain relief and increased function and what is the duration and magnitude of this effect.

METHODS

A systematic review with a critical appraisal of identified studies that met the inclusion criteria was performed. Two authors performed the literature review by independently searching the Cochrane, PubMed and Google Scholar databases.

RESULTS

A total of 118 relevant articles were found, but only nine studies met the inclusion criteria which included 4 double-blinded randomised control trials (RCTs) and 5 prospective case series. There is some evidence in the literature to support the efficacy of steroid injections into the TMJ. Most studies do suggest a good short-term benefit. However, one identifies no benefit over placebo but two studies found a benefit lasting at least 6 months.

CONCLUSIONS

This study demonstrates that there are potentially significant although short-term benefits to be gained from steroid injections into the TMJ. They can lead to pain relief and improved function, certainly in the first 1 to 3 months post-injection. Steroid injections are a low-risk procedure and are helpful in delaying or avoiding the need for surgery.

Feasibility of model-based Roentgen Stereophotogrammetric Analysis to evaluate early migration of the trapeziometacarpal joint prosthesis

Background

The purpose of this study was to determine the feasibility of Roentgen Stereophotogrammetric Analysis (RSA) in total joint arthroplasty of the trapeziometacarpal (TMC) joint of the thumb.

Methods

In five cadaveric hands the TMC-joint was replaced by the Surface Replacement Trapeziometacarpal prosthesis (SR™ TMC prosthesis; Avanta, San Diego, CA) and tantalum beads of 0.8 mm were implanted for RSA. RSA radiographs in two directions were made in ten positions to calculate the measurement error. Migration values from zero are indicative for the measurement error. The number of detected markers was recorded.

Results

The accuracy analysis showed that for the translations the mean measurement error varied between 0.003 mm (SD 0.057) and 0.055 mm (SD 0.133). For the rotations values ranged from 0.034° (SD 1.759) to 0.502° (SD 1.617).

Conclusions

RSA analysis of the SR™ TMC prosthesis is feasible. The measurement error is good for the translations but high for the rotations. The latter is due to the close position of the markers relative to each other. Level of evidence III.

Thumb carpometacarpal joint total arthroplasty: a systematic review

Thumb carpometacarpal joint total arthroplasty has been undertaken for many years. The proponents believe the short-term outcomes are better than trapeziectomy and its variants, but the longer term complications are often higher. This systematic review of all peer reviewed articles on thumb carpometacarpal joint total arthroplasty for osteoarthritis shows that there are reports of many implants. Some are no longer available. The reported outcomes are very variable: for some there are good long-term outcomes to beyond 10 years ; for others there are unacceptably high early rates of failure. Overall the published evidence does not show that total arthroplasty is better than trapeziectomy and its variants yet there is a higher complication rate and significant extra cost of using an implant. Future research needs to compare total arthroplasty with trapeziectomy to assess short term results where the arthroplasties may be better, long-term outcomes and the healthcare and personal costs so that surgeons and patients can make fully informed choices about the treatment of symptomatic thumb carpometacarpal joint osteoarthritis.

Ten-year long-term results of total joint arthroplasties with ARPE® implant in the treatment of trapeziometacarpal osteoarthritis

Between May 1999 and April 2002 a total of 69 consecutive thumb carpometacarpal joint arthoplasties were performed in a total of 64 patients for carpometacarpal joint osteoarthritis using the cementless hydroxyapatite (HA)-coated unconstrained ARPE implant. Clinical, functional and radiological results at 10-year follow-up are presented. Survival analysis was performed using the Kaplan-Meier method. Of the 64 patients, four were lost to follow-up, 60 implants (92.3%) were functional and five (7.7%) were not (two dislocated, two were removed and one with aseptic loosening). Survival estimate for functional implants over 10 years was 93.9% (95% confidence interval 82.3-97.9). The radiographs were satisfactory in 82.4%. There was subsidence of the cup in 15.8%. Thumb carpometacarpal joint arthroplasty with the ARPE implant offers a reliable treatment alternative in patients with Eaton grade III or IV thumb carpometacarpal joint arthritis in the presence of good bone stock.

Outcome comparison of primary trapeziectomy versus secondary trapeziectomy following failed total trapeziometacarpal joint replacement

PURPOSE

To compare the clinical outcome between secondary trapezial excision after failed total trapeziometacarpal joint replacement and primary trapeziectomy.

METHODS

Between October 2003 and July 2008, we performed 16 revision procedures in our institution because of failed trapeziometacarpal joint replacements. Of these patients, 15 were followed up. We compared clinical outcomes between this group and 15 patients treated with primary trapeziectomy in a matched-pair analysis. The matching criteria were sex, age, and time from surgery. The mean follow-up period was 48 months. We evaluated mobility (radial and palmar abduction, opposition, and Kapandji score), grip strength, and patient self-assessment (pain; satisfaction; Disabilities of the Arm, Shoulder, and Hand score; and activity restriction).

RESULTS

According to most of the clinical evaluation methods (range of motion and Kapandji score) and subjective assessments (pain; Disabilities of the Arm, Shoulder, and Hand), outcome did not differ considerably between the 2 study groups. In particular, the results of strength testing were not significantly different between groups.

CONCLUSIONS

The present study showed that the outcomes of secondary trapeziectomy after failed trapeziometacarpal joint replacement arthroplasty generally do not differ from the primary trapeziectomy results. Although it shows high revision rates in the literature, trapeziometacarpal total joint arthroplasty might be a treatment option. In the case of failure, the outcome of secondary trapeziectomy is comparable to that of primary trapeziectomy.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic III.

De la Caffinière thumb trapeziometacarpal joint arthroplasty: 16-26 year follow-up

Seventy-one patients (93 implants) had a de la Caffinière prosthesis implanted between 1980 and 1989 and were reviewed and reported in 1997. We reviewed this series 10 years later. Similar outcome measures were used as in the original study, pinch and grip strength measured and validated outcome scores obtained (DASH and EQ-5D). Radiographic outcome was assessed. Twenty-six patients with 39 implants were available for review at a mean of 19 years (range, 16-26 years). Survivorship at 26 years was 73.9% (95% CI, 61.2 to 86.6) for re-operation and 26.0% (95% CI, 0 to 52.7) for all failure. Patients had satisfactory power and thumb mobility and continued to be satisfied without pain. Registries should log such prostheses and add to implant survival data.

High frequency failure of the Moje thumb carpometacarpal joint arthroplasty

Arthroplasty is one of several options for treating symptomatic osteoarthritis of the thumb carpometacarpal joint. There are various hemi- and total arthroplasties available on the market. We report our experience of treating 12 patients with the Moje Acamo CMC1 prosthesis. We reviewed all the patients at a mean of 50 months postoperatively. All patients presented with loosening, migration or tilting of one or both implant components. Nine patients were symptomatic enough to warrant revision surgery with removal of the implant leaving a pseudarthrosis. At the last follow-up, five patients (42%) had already received revision surgery. All patients still possessing an implant showed progressive signs of implant loosening, although some of them had no symptoms. In order to assess their overall disadvantage compared with patients treated by primary trapeziectomy, the outcomes of these two groups were compared (matched pairs). The outcomes after revision surgery were comparable with those of primary trapeziectomy. We no longer use the Moje Acamo CMC1 implant and recommend that patients who have received this implant should be monitored carefully both clinically and radiologically.

Fixation of trapezial implants in a trapeziometacarpal total joint prosthesis tested in a model of porcine bone

High aseptic loosening rates have been reported in total joint prostheses of the carpometacarpal joint of the thumb, particularly in the trapezial component. The primary fixation of new implants may be tested in cadaver bones, but the anatomy of the pig is in many ways similar to that of the human, so we compared the central carpal bone from the forefoot of 6-month-old pigs, which has a saddle joint surface similar to the trapezium, to the trapezium in patients with carpometacarpal osteoarthritis. The mean (SD) bone mineral density of the 13 pig forefoot bones was 0.88 (0.12) g/cm(2) compared with 0.63 (0.16) g/cm(2) in the 31 human trapeziums. The measured size of the porcine bones was slightly larger than that of the human trapeziums. The similarity in form, size, and bone mineral density means that the central bone of the forefoot of 6-month-old pigs may be used for fixation tests in trapezial implants.