Article
Midcarpal instability after hemitrapeziectomy, total trapeziectomy and distal resection of the scaphoid pole
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Authors
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Luzian Haug
- Inselspital, Bern, Switzerland
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Leo Paeffgen
- Inselspital Bern, University Hospital, Bern, Switzerland
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Tom Adler
- Orthoklinik Dornach, Dornach, Switzerland
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Esther Vögelin
- Inselspital, Universität Bern, Bern, Switzerland
| Published: | February 6, 2020 |
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Outline
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Objectives/Interrogation: Non-dissociative carpal instability (CIND) is a challenging pathology that can lead to severe functional impairment of the wrist. Removal of the distal scaphoid pole or trapeziectomy in patients with advanced osteoarthritis of the thumb were identified as possible causes of midcarpal instability and even symptomatic carpal collapse. Destabilization of the scapho-trapezial-trapezoidal (STT) ligament complex seems to lead to a CIND in certain circumstances. In a biomechanical study, the behaviour of the carpus after trapeziectomy and resection of distal scaphoid pole will be investigated for a better understanding of the importance of the involved ligaments.
Methods: 16 cadaver arms were randomly divided into two groups. In the first group distal scaphoid pole was resected with the adjacent ligaments, in the other group hemitrapeziectomy was performed followed by total trapeziectomy. Before and after the resection, a CT scan was performed in wrist extension, flexion, fist, radial and ulnar deviation with standardized load from 5 to 10kg. The three series were then reconstructed using a 3D model and the positional changes of scaphoid, lunate and capitate were measured in comparison to the non-operated wrists.
Results and Conclusions: After trapeziectomy the scaphoid, lunate and capitate rotate dorsally in wrist extension (capitate: -2.9° ±0.7), at fist closure (-17.9° ±9.9) and during radial deviation (-3.0° ±1.4). In wrist flexion, the proximal carpal row remains unchanged, while the distal row tilts palmarly (2.7° ±1.0). In ulnar deviation, both the proximal and distal row experience a palmar torque. Dissociation of the rows is most obvious at fist closure (capitolunar angle: 12.9° ±4.9).
After resection of the scaphoid pole, a similar behavior is observed, with more pronounced tilting in radial and ulnar deviation (scaphoid: -22.7° vs. -4.0°).
The scapholunar angle remains unchanged except in the group of scaphoid pole resection during flexion and radial deviation (6.1° and 11.3°).
Destabilization of the STT ligament complex by total trapeziectomy or scaphoid pole resection leads in this cadaver model to dissociation of the proximal and distal carpal row during fist closure and wrist flexion, but without instability within the proximal or distal row corresponding to a CIND.
The clearest destabilization of the carpus is seen at fist closure, with the highest axial load. Scaphoid pole resection may have some influence on SL instability.
