Comparison between scaphotrapeziotrapezoid arthrodesis and Pyrocardan® implant for isolated scaphotrapeziotrapezoid osteoarthritis.

INTRODUCTION: Scaphotrapeziotrapezoid (STT) arthrodesis and Pyrocardan® implant for painful isolated STT osteoarthritis have shown good results, but no paper has compared their medium-term outcomes.

HYPOTHESES: Our main hypothesis would be that the Pyrocardan® implant, by preserving the carpal biomechanics, could lead to better wrist mobility. Our secondary hypotheses would be that no other clinical and radiological differences will be found between these two procedures at a mean 5 years follow-up.

PATIENTS: In this non-randomised retrospective study, performed at two healthcare facilities, we report and compare the outcomes of STT arthrodesis with staple fixation versus the Pyrocardan® implant in 38 patients (40 thumbs) from 2 previously published cohorts. Twenty-one patients with a mean age of 68 years (range, 46 - 79) underwent STT arthrodesis in facility 1. Seventeen patients with a mean age of 61 years (range, 41 - 80) received a Pyrocardan® implant in facility 2. Patients were reviewed at both facilities by the same examiner who performed a clinical and radiographical assessment.

RESULTS: At a mean follow-up of 8 years (range, 2-20 years) for the STT group and 5 years (range 3-8 years) for the Pyrocardan® group, we found no significant differences in the clinical and radiological outcomes between the two procedures except in wrist active extension and ulnar deviation, where Pyrocardan® appears to produce better mobility (extension 58°± 9 vs 38°± 14 and ulnar deviation 35°(25, 40) versus 45°(40, 50)) (p<.001 and p<.008 respectively). The two surgical techniques led to significantly improvement in terms of pain relief, function, and strength. For the STT arthrodesis group, two complete nonunions were found (9%), while narrowing of the styloscaphoid joint space was found in eight thumbs (36%). For the Pyrocardan® group, four postoperative DISI (22%), four calcifications around the trapezium and/ or distal scaphoid (22%) and one asymptomatic dislocation (6%) of the implant were observed.

DISCUSSION: Pyrocardan® implant seems to result in better mobility in extension and ulnar deviation. STT arthrodesis and Pyrocardan® implant to treat isolated STT osteoarthritis led to less pain, better strength and functional scores, and restored wrist stability. A future study with a larger population will be needed to confirm these results.

LEVEL OF EVIDENCE: IV.