[Cup Placement in Thumb Carpometacarpal Joint Prostheses: The Role of the Guidewire].

Background: The increasing use of thumb carpometacarpal joint prostheses for advanced CMC 1 (carpometacarpal) joint arthritis reflects the success of the latest prosthesis generations, which has been achieved through their improved functional outcomes and lower complication rates. Precise alignment of the prosthesis cup parallel to the proximal joint surface of the trapezium is essential for stability and the prevention of dislocation. This is a challenging surgical step, particularly for surgeons new to this technique. Despite adequate positioning of the guidewire, misplacements of the cup may occur, necessitating intraoperative revision.

Material and methods: This study examined the deviations in cup and guidewire positioning in thumb carpometacarpal joint prosthesis implantations by inexperienced and experienced surgeons through radiological analysis of 65 prostheses.

Results: Both inexperienced and experienced surgeons achieved precise guidewire positioning with mean deviations of<2.2°. Inexperienced surgeons showed significantly larger cup deviations in the dorsopalmar and lateral view (7.6±6.1° and 7.3±5.9°) compared with experienced surgeons (3.6±2.7° and 3.6±2.5°; p=0.012, p=0.017). The deviation of the cup position exhibited by inexperienced surgeons tends to be in the direction opposite to the initial guidewire position (p<0.0038).

Conclusion: The results highlight the current challenges in cup positioning depending on a surgeon's level of experience, questioning the reliability of the current guidewire placement.