Daisuke Suzuki1, Shohei Omokawa2, Akio Iida3, Yasuaki Nakanishi4, Hisao Moritomo5, Pasuk Mahakkanukrauh6, Yasuhito Tanaka4. 1. Department of Orthopaedic Surgery, Nishi-Nara Central Hospital, Nara, Japan; Department of Orthopaedic Surgery, Nara Medical University, Nara, Japan. 2. Department of Hand Surgery, Nara Medical University, Nara, Japan. Electronic address: omokawa@gaia.eonet.ne.jp. 3. Department of Orthopaedic Surgery, Hanna Central Hospital, Nara, Japan. 4. Department of Orthopaedic Surgery, Nara Medical University, Nara, Japan. 5. Yukioka Hospital Hand Center, Osaka Yukioka College of Health Science, Osaka, Japan. 6. Excellence in Osteology Research and Training Center (ORTC), Chiang Mai University, Chiang Mai, Thailand; Department of Anatomy, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
Abstract
PURPOSE: Distal scaphoid and triquetrum excisions can improve the range of wrist motion after radioscapholunate (RSL) fusion, but little is known about the kinematics of dart-throwing and global circumduction motions. We hypothesized that these excisions could increase the range of motion without causing midcarpal instability. METHODS: Seven fresh-frozen cadaver upper extremities were mounted on a testing apparatus after isolation and preloading of the tendons of the flexor carpi radialis, flexor carpi ulnaris, extensor carpi radialis, and extensor carpi ulnaris. Sequential loadings of the flexor carpi ulnaris and extensor carpi radialis simulated active dart-throwing motion. Passive circumferential loading produced the wrist circumduction motion. We measured the range of wrist motions with an electromagnetic tracking system in 4 experiments: intact, simulated RSL fusion, RSL fusion with distal scaphoid excision, and RSL fusion with distal scaphoid and total triquetrum excisions. To evaluate midcarpal stability, we conducted passive mobility testing of the distal carpal row in the radial, volar, ulnar, and dorsal directions. RESULTS: Radioscapholunate fusion decreased the dart-throwing motion to a mean of 46% of the baseline value; distal scaphoid and triquetrum excisions increased the mean arc to 50% and 62%, respectively. Radioscapholunate fusion diminished the wrist circumduction to a mean of 43% of the baseline value, which increased to a mean of 58% and 74% after distal scaphoid and triquetrum excision, respectively. A significant increase in radial deviation was noted after distal scaphoid excision, and subsequent triquetrum excision significantly increased motion in the ulnar-palmar direction. Regarding midcarpal stability, dorsal translation significantly increased after distal scaphoid and triquetrum excisions. CONCLUSIONS: Distal scaphoid and triquetrum excision after RSL fusion improved both dart-throwing and circumduction motions, but dorsal midcarpal instability occurred. CLINICAL RELEVANCE: Subsequent carpal excisions may improve short-term outcome by increasing motions in a RSL-fused wrist; however, a potential risk of midcarpal instability should be considered.
PURPOSE: Distal scaphoid and triquetrum excisions can improve the range of wrist motion after radioscapholunate (RSL) fusion, but little is known about the kinematics of dart-throwing and global circumduction motions. We hypothesized that these excisions could increase the range of motion without causing midcarpal instability. METHODS: Seven fresh-frozen cadaver upper extremities were mounted on a testing apparatus after isolation and preloading of the tendons of the flexor carpi radialis, flexor carpi ulnaris, extensor carpi radialis, and extensor carpi ulnaris. Sequential loadings of the flexor carpi ulnaris and extensor carpi radialis simulated active dart-throwing motion. Passive circumferential loading produced the wrist circumduction motion. We measured the range of wrist motions with an electromagnetic tracking system in 4 experiments: intact, simulated RSL fusion, RSL fusion with distal scaphoid excision, and RSL fusion with distal scaphoid and total triquetrum excisions. To evaluate midcarpal stability, we conducted passive mobility testing of the distal carpal row in the radial, volar, ulnar, and dorsal directions. RESULTS: Radioscapholunate fusion decreased the dart-throwing motion to a mean of 46% of the baseline value; distal scaphoid and triquetrum excisions increased the mean arc to 50% and 62%, respectively. Radioscapholunate fusion diminished the wrist circumduction to a mean of 43% of the baseline value, which increased to a mean of 58% and 74% after distal scaphoid and triquetrum excision, respectively. A significant increase in radial deviation was noted after distal scaphoid excision, and subsequent triquetrum excision significantly increased motion in the ulnar-palmar direction. Regarding midcarpal stability, dorsal translation significantly increased after distal scaphoid and triquetrum excisions. CONCLUSIONS: Distal scaphoid and triquetrum excision after RSL fusion improved both dart-throwing and circumduction motions, but dorsal midcarpal instability occurred. CLINICAL RELEVANCE: Subsequent carpal excisions may improve short-term outcome by increasing motions in a RSL-fused wrist; however, a potential risk of midcarpal instability should be considered.