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Early Outcomes Following a Modified Reduction and Association of the Scaphoid and Lunate With a Bioabsorbable Compression Screw
Brandon J. Ball, BSc, MD; Kevin Mowbrey, BSc; Michael Morhart, MSc, MD, FRCSC;
University of Alberta
Introduction: Scapholunate dissociation represents the most common carpal instability. Surgical approaches to scapholunate instability include capsulodesis, tenodesis, and limited arthrodesis. These procedures fail to restore normal biomechanics of wrist movement. The reduction and association of the scaphoid and lunate (RASL) is an approach whereby a fibrous union is achieved between the scaphoid and lunate by temporary fixation with a Herbert screw. To avoid subsequent hardware removal, we describe a modified RASL with a bioabsorbable compression screw in addition to a DIC capsulodesis.
Materials and Methods:A retrospective review was performed of patients who have undergone a RASL by a single surgeon. Arthrex Bio-Compression screws® (Arthrex, Naples, FL) were used to obtain an association between the scaphoid and lunate. Radiographs were reviewed pre-operatively and at various intervals post-operatively. Outcome measures included scapholunate gap, scapholunate angle, radiolunate angle, and modified carpal height ratio. Statistical comparisons were performed using a one way ANOVA.
Results: Scapholunate reconstruction was performed in 14 patients using the modified RASL procedure. 79% of the patients were males, and 57% of the injuries occurred in the non-dominant hand. The mean age was 46 years, with a mean of 40 weeks between the injury and the procedure. Preoperative radiographic measurements were compared to those from various intervals post-op. At the 6 week interval, the scapholunate gap was reduced from 3.8mm to 2.1mm (p<0.05), and the scapholunate angle was reduced from 60° to 45° (p<0.05). The radiolunate angle was reduced from 12° to 8.5°. The modified carpal height ratio was maintained, indicating that no carpal collapse had occurred (1.53 vs 1.55). When comparing pre-operative values to 3 months post-op, the scapholunate gap was reduced from 3.8mm to 3.2mm, the scapholunate angle was reduced from 60° to 48°, and the radiolunate angle was reduced from 12° to 10°, however these values were non-significant. The modified carpal height ratio was maintained at 3 months (1.53 vs 1.51).
Conclusions: A modified RASL procedure was performed using a bioabsorbable compression screw. Early radiographic outcomes demonstrate that the scapholunate gap, and scapholunate angle are reduced, indicating association between the scaphoid and lunate. The radiolunate angle was also reduced, and the modified carpal height ratio is maintained in the early follow-up period. The data demonstrate that the bioabsorbable RASL along with DIC capsulodesis is a useful technique to treat subacute and chronic scapholunate dissociation. This technique is advantageous in eliminating a second procedure for hardware removal.
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