Basal osteotomy of the first metacarpal using patient-specific guides and instrumentation: biomechanical and 3D CT-based analysis

IntroductionThe aim of this study was to investigate the radiological outcomes of proximal closing metacarpal extension osteotomies using patient-specific guides and instruments (PSI) in early-stage trapeziometacarpal osteoarthritis to gain further insight into the joint loading surface and the benefits of the procedure.MethodsIn a prospective observational study, nine patients were included between 11/2020 and 12/2021, undergoing a total of ten proximal metacarpal extension osteotomies for basal thumb osteoarthritis. Computer-assisted surgical planning was performed using computed tomography (CT) and three-dimensional (3D) segmentation, allowing the fabrication of 3D-printed PSIs for surgical treatment. Inclusion criteria were a 1-year follow-up by CT to assess postoperative correction of the positional shift of the first metacarpal (MC1) and the location of peak loads compared with the preoperative situation.ResultsRadiographic analysis of the peak loading zone revealed a mean displacement on the articular surface of the trapezius of 0.4 mm +/- 1.4 mm to radial and 0.1 mm +/- 1.2 mm to palmar, and on the articular surface of the MC1 of 0.4 mm +/- 1.4 mm to radial and 0.1 mm +/- 1.2 mm to dorsal.ConclusionThere were trends indicating that a flatter pressure distribution and a dorsal shift of the peak loading zone may contribute to an improvement in subjective pain and patient satisfaction associated with this surgical procedure. The non-significant radiological results and the minor dorsal-radial shifts in our small study group limit a firm conclusion.Level of evidenceIII.