The scaphoid : from fracture to fusion

Abstract

In paper I, the incidence, treatment approaches, and rates of nonunion in scaphoid fractures were examined using data from 34,377 patients recorded in the Swedish National Patient Register (NPR) between 2006-2015. The accuracy of NPR data was confirmed through validation involving 300 patients, revealing that approximately 41% of diagnosed scaphoid fractures were false positives. The overall incidence rate was found to be around 22 per 105 person-years. Median age was 26 years and 69% of the patients were men. 5% of the patients were operated and 2% developed scaphoid nonunion.

Paper II evaluated the outcomes of scaphoid nonunion surgery in 63 patients in a retrospective study with a mean follow-up of 7 years. Patients were divided into two groups: those with residual deformity and those without. The calculation of scaphoid deformity was based on computed tomography (CT) scans, comparing the heightlength (H/L) ratio of the operated scaphoid to that of the uninjured one. There were no significant differences between the two groups in Disabilities of the Arm, Shoulder and Hand score (DASH), Patient-Rated Wrist Evaluation score (PRWE), wrist range of motion (ROM), and grip strength. Wrist extension was slightly worse in the deformity group.

In paper III, we analyzed the direct motion between the scaphoid and lunate during the dart-throwing motion (DTM) in vivo with a volume registration technique (computed tomography based micromotion analysis, CTMA). We found motion between the scaphoid and lunate, including translation and rotation and that scapholunate ligament injury leads to increased motion.

Paper IV was a pragmatic randomized controlled trial (RCT) which compared lunocapitate fusion (LCF) and four-corner fusion (4CF) as surgical treatments for scapholunate advanced collapse (SLAC) and scaphoid nonunion advanced collapse (SNAC). There was only a small improvement in grip strength with no clinically significant difference between the two treatment groups. No differences between groups were found in DASH, PRWE, European quality of life-5 dimensions-3 level (EuroQol-5D-3L), wrist ROM, key pinch strength, and complications at 12 months postoperatively.

In paper V we examined seven patients who had undergone LCF at least one year before. CT scans were performed in maximal radial extension and maximal ulnar flexion. Using CTMA, motion of the triquetrum was analyzed compared to the contralateral side. Triquetral movement was observed in all patients but significantly less than in the nonsurgical wrist. There also was minor motion between the hamate and fused lunocapitate bones.

In conclusion, Scaphoid fractures primarily occur in young males, and the risk of developing a nonunion after such a fracture is relatively low. Residual scaphoid deformity has no relevant negative impact on mid-term wrist function. There is scapholunate motion during DTM and caution should be taken when implementing dart-throwing exercises during early rehabilitation after scapholunate repair surgery. LCF is not inferior to 4CF in terms of strength, range of motion or patient-reported outcome measures. Triquetral motion is limited after lunocapitate arthrodesis.