Assessment of trapezial prosthetic cup migration: A biomechanical study

Proposed Radiographic Parameters to Optimize Clinical Outcomes in Trapezio-Metacarpal Prosthesis Placement Using CT Imaging, with 1-Year Follow-Up

PURPOSE

Addressing trapezio-metacarpal (TMC) osteoarthritis often involves considering TMC joint replacement. Utilizing TMC prostheses offers advantages such as preserving the thumb length and more accurately replicating the thumb's range of motion (ROM). TMC prostheses have an intrinsic risk of dislocation and aseptic loosening. Analyzing pre- and postoperative imaging can mitigate complications and improve prosthetic placement, providing insights into both successes and potential challenges, refining overall clinical outcomes.

MATERIALS AND METHODS

We conducted a prospective analysis of 30 patients with severe TMC arthritis treated with a Touch© (Kerimedical, Geneva, Switzerland) prosthesis in 2021-2023: X-ray and CT protocols were developed to analyze A) the correct prosthesis placement and B) its correlation with clinical outcomes (VAS, Kapandji and QuickDASH scores) by performing Spearman correlation analysis.

RESULTS

The average differences in trapezium height and M1-M2 ratio pre- and post-surgery were, respectively, 1.8 mm (SD ± 1.7; p < 0.001) and 0.04 mm (SD ± 0.04; p = 0.017). Pre-to-postoperative M1 axis length increased by an average of 2.98 mm (SD ± 3.84; p = 0.017). Trapezial cup sinking, indicated by the trapezium index, measured 4.6 mm (SD ± 1.2). The metacarpal index averaged at 11.3 mm (SD ± 3.3). The distance between the centers of the trapezium distal surface and the prosthesis cup was 2.23 mm (SD ± 1.4). The Spearman correlation analysis gave the following results: negative correlations were highlighted between postoperative VAS scores and the M1/M2 ratio and residual trapezium height (correlation coefficient: -0.7, p = 0.03 and -0.064, p = 0.03, respectively) at 6 months; a negative correlation was found at the 3-month mark between QuickDASH and the trapezium residual height (correlation coefficient: -0.07, p = 0.01); and a positive correlation was found for the trapezium index at 1 month (correlation coefficient: 0.07, p = 0.03) and 3 months (p = 0.04) using the Kapandji score. Similarly, we found a positive correlation between the distance between the prosthesis and trapezium centers and QuickDASH score at 1 and 3 months (correlation coefficient: 0.066, p = 0.03; correlation coefficient: 0.07, p = 0.05, respectively) and a positive correlation between prosthesis axis and the residual first metacarpal angle with QuickDASH score at 3 months (correlation coefficient: 0.07, p = 0.02).

CONCLUSIONS

Pre- and postoperative systematic imaging analysis should become a method for predicting complications and guiding recovery in TMC prosthesis: CT imaging could provide us with radiographical landmarks that are intrinsically linked to clinical outcomes. Further research is necessary to fuel a protocol for the correct intraoperative TMC prosthesis implantation.

Thumb basal joint arthritis in 2023

Thumb carpometacarpal or basal joint arthritis is the second most common location for osteoarthritis in the hand. It mainly affects women over 50years of age. Basal joint arthritis causes pain, loss of strength during pinch grips, and eventually stiffness and progressive deformity of the thumb column. Conservative treatment must be implemented first. It aims to spare the joint by using standardized methods. It must be initiated as soon as pain starts, not once the deformity has settled in. There is broad agreement that surgery is indicated when pain relief is not achieved after at least 6months of conservative treatment. The available surgical techniques can be classified as joint-sparing (extra-articular) and joint-sacrificing (intra-articular). The former consists of trapeziometacarpal stabilizing ligament reconstruction, subtraction osteotomy of the first metacarpal and thumb carpometacarpal denervation. The latter consists of trapeziometacarpal fusion, trapeziectomy (and its variants) and implant arthroplasty. Except in very specific cases, trapeziectomy and trapeziometacarpal implant arthroplasty with a total joint prosthesis or an interposition implant are the two main surgical techniques for treating basal joint arthritis. After reviewing the pathophysiology and the diagnosis of thumb basal joint arthritis, we will provide an overview of the available treatment options, with emphasis on the accepted surgical strategies in 2023. LEVEL OF EVIDENCE: III.

Does trapezium remodeling correlate with cup shape?

We investigated whether trapezium bone reaction was different following implantation of a trapeziometacarpal total joint replacement with a hemispheric or a conical cup. Fifty-three Keri Medical Touch implants with hemispheric cup and 53 with conical cup were prospectively followed up radiographically. We compared radiographs taken immediately and one year after surgery for cup subsidence, tilt, heterotopic ossification and loosening. Cup subsidence of at least 1 mm was detected in 4% of cases for both cup types. Additive bone reaction around the cup of more than 1 mm was present in 62% of conical cups and 47% of hemispheric cups. These were minor and there were no large ossifications with risk of impingement. Minor radiolucency was seen superficially at the implant-bone interface of 13% of the hemispheric cups and 9% of the conical cups. None of these bone reactions differed significantly according to cup design.