Koji Shibano1, Hayato Koishi2, Kazuma Futai3, Hideki Yoshikawa3, Kazuomi Sugamoto4. 1. Department of Orthopaedic Biomaterial Science, Osaka University Graduate School of Medicine, Osaka, Japan. 2. Koishi Orthopaedic Clinic, Kyoto, Japan. 3. Department of Orthopaedic Surgery, Osaka University Graduate School of Medicine, Osaka, Japan. 4. Department of Orthopaedic Biomaterial Science, Osaka University Graduate School of Medicine, Osaka, Japan. Electronic address: sugamoto@ort.med.osaka-u.ac.jp.
Abstract
BACKGROUND: Bankart repair postoperative complications include loss of shoulder motion and shoulder instability. The primary reason that postoperative complications develop may be excessive imbrication of the anterior band of the inferior glenohumeral ligament (AIGHL) or inadequate repair position. The purpose of this study was to quantitatively evaluate the influence of inadequate repair by computer simulation for a normal shoulder joint. METHODS: Magnetic resonance images of 10 normal shoulder joints were acquired for 7 positions every 30° from the maximum internal rotation to the maximum external rotation with the arm abducted at 90°. The shortest 3-dimensional path of the AIGHL in each rotational orientation was calculated. We used computer simulations to anticipate the loss of motion and instability by changing the AIGHL length and insertion sites on the glenoid. RESULTS: The AIGHL length measured 50 ± 5 mm at the maximum external shoulder rotation. AIGHL shortening by 3, 6, and 9 mm made the angle of maximum external rotation 80°, 68°, and 54°, respectively. A superior deviation of 3, 6, and 9 mm on the glenoid insertion resulted in a maximum external rotation angle of 85°, 79°, and 77°. An inferior deviation of 3, 6, and 9 mm produced humeral head translation of 1.7, 2.9, and 3.6 mm. CONCLUSION: Simulation of both excessive imbrication and deviation of the insertion position led to quantitative prediction of the resulting loss of motion and instability. These findings will be useful for anticipating complications after Bankart repair. LEVEL OF EVIDENCE: Basic science study, computer modeling, imaging.
BACKGROUND: Bankart repair postoperative complications include loss of shoulder motion and shoulder instability. The primary reason that postoperative complications develop may be excessive imbrication of the anterior band of the inferior glenohumeral ligament (AIGHL) or inadequate repair position. The purpose of this study was to quantitatively evaluate the influence of inadequate repair by computer simulation for a normal shoulder joint. METHODS: Magnetic resonance images of 10 normal shoulder joints were acquired for 7 positions every 30° from the maximum internal rotation to the maximum external rotation with the arm abducted at 90°. The shortest 3-dimensional path of the AIGHL in each rotational orientation was calculated. We used computer simulations to anticipate the loss of motion and instability by changing the AIGHL length and insertion sites on the glenoid. RESULTS: The AIGHL length measured 50 ± 5 mm at the maximum external shoulder rotation. AIGHL shortening by 3, 6, and 9 mm made the angle of maximum external rotation 80°, 68°, and 54°, respectively. A superior deviation of 3, 6, and 9 mm on the glenoid insertion resulted in a maximum external rotation angle of 85°, 79°, and 77°. An inferior deviation of 3, 6, and 9 mm produced humeral head translation of 1.7, 2.9, and 3.6 mm. CONCLUSION: Simulation of both excessive imbrication and deviation of the insertion position led to quantitative prediction of the resulting loss of motion and instability. These findings will be useful for anticipating complications after Bankart repair. LEVEL OF EVIDENCE: Basic science study, computer modeling, imaging.