Midterm Outcomes of Four-Corner Fusion Surgery Using Nitinol Staples.

Purpose: Wrist arthritis because of scaphoid nonunion advanced collapseand scapholunate advanced collapse can be treated through scaphoid excision and four-corner arthrodesis. There are many fixation techniques; however, there are few studies reporting outcomes in which only Nitinol staples were used. This study aimed to evaluate whether patients undergoing a four-corner arthrodesis using this fixation technique as well as intraoperative modifications to minimize complications will have successful outcomes.

Methods: Retrospective study of patients who underwent scaphoid excision and four-corner arthrodesis using DynaNite Nitinol Staple (Arthrex Inc) to treat scaphoid nonunion advanced collapse or scapholunate advanced collapse wrist arthritis at a single academic institution by a single surgeon. The technique and our modifications are described below. Outcome measures included radiographic union, range of motion, strength, and patient-reported outcomes such as Quick Disabilities of the Arm, Shoulder, and Hand, Michigan Hand Outcomes questionnaire, Likert patient satisfaction scale, and the visual analog scale.

Results: Eight patients were included with mean follow-up of 27 months (9-42 months). When compared to the contralateral side, patients maintained 76% wrist flexion-extension, 83% radial-ulnar deviation, and 99% pronation-supination. Key pinch, three-point pinch, and grip strength testing were 95%, 89%, and 86%, respectively. The mean Quick Disabilities of the Arm, Shoulder, and Hand score was 17, and the mean Michigan Hand Outcomes score was 85% compared to the contralateral side. The visual analog pain scale had a mean of 2.5 (range 0-6). Radiographic imaging showed that all patients had undergone union of their four-corner arthrodesis with intact hardware.

Conclusions: The results of this study show that midterm outcomes of four-corner fusions performed with Nitinol staples have promising results in overall functional and patient-reported outcomes. In addition, they offer reliable fixation for achieving union of the four-corner arthrodesis.

Type of study/level of evidence: Therapeutic IV.