Objective To determine the change in humeral head anterosuperior migration after releasing the coracoacromial l igament in shoulders from cadavers with simulated intact or irreparable teared rotator cuff, to provide biomechanical basis for preserving the coracoacromial l igament or not during hemiarthroplasty. Methods Twelve freshfrozen cadaveric glenohumeral joints of adult preserving the scapula, upper 2/3 of the humerus, articular capsule and the coracoacromial l igament, were divided into 2 groups. The suprascapularis was preserved in group A (6 shoulders) and excised in group B (6 shoulders). Positioning the joint in a combination of 30° extension, 0° abduction and 30° external rotation, and imposing a 50 N axial compressive load to the humeral shaft, the anterosuperior displacement of the humeral head weremeasured before and after excising the coracoacromial l igament. Results In group A, the displacement of the humeral head was (5.96 ± 0.77）mm with intact coracoacromial l igament and (6.83 ± 0.84）mm after transecting the l igament. In group B, the displacement of the humeral head was (8.07 ± 2.46）mm with intact coracoacromial l igament and (9.92 ± 3.29）mm after transecting the coracoacromial l igament. So the mean increase of anterosuperior migration of the humeral head was (0.88 ± 0.34) mm (P lt; 0.01) in group A, and (1.85 ± 0.99) mm (P lt; 0.01) in group B, which was greater than the former (P lt; 0.05). Conclusion The coracoacromial l igament restrained anterosuperior translation of the humeral head, especially for patients with rotator cuff deficiency, so it should be preserved as far as possible during hemiarthroplasty.
Objective To simulate anterosuperior instabil ity of the shoulder by a combination of massive irreparable rotator cuff tears and coracoacromial arch disruption in cadaveric specimens, use proximally based conjoined tendon transfer forcoracoacromial l igament (CAL) reconstruction to restrain against superior humeral subluxation, and investigate its feasibility and biomechanics property. Methods Nine donated male-adult and fresh-frozen cadaveric glenohumeral joints were applied to mimic a massive irreparable rotator cuff tear in each shoulder. The integrity of the rotator cuff tendons and morphology of the CAL were visually inspected in the course of specimen preparation. Cal ipers were used to measure the length of the CAL’s length of the medial and the lateral bands, the width of coracoid process and the acromion attachment, and the thickness in the middle, as well as the length, width and thickness of the conjoined tendon and the lateral half of the removed conjoined tendon. The glenohumeral joints were positioned in a combination of 30° extension, 0° abduction and 30° external rotation. The value of anterosuperior humeral head translation was measured after the appl ication of a 50 N axial compressive load to the humeral shaft under 4 sequential scenarios: intact CAL, subperiosteal CAL release, CAL anatomic reattachment, entire CAL excision after lateral half of the proximally based conjoined tendon transfer for CAL reconstruction. Results All specimens had an intact rotator cuff on gross inspection. CAL morphology revealed 1 Y-shaped, 4 quadrangular, and 4 broad l igaments. The length of the medial and lateral bands of the CAL was (28.91 ± 5.56) mm and (31.90 ± 4.21) mm, respectively; the width of coracoid process and acromion attachment of the CAL was (26.80 ± 10.24) mm and (15.86 ± 2.28) mm, respectively; and the thickness of middle part of the CAL was (1.61 ± 0.36) mm. The length, width, and thickness of the proximal part of the proximally based conjoined tendon was (84.91 ± 9.42), (19.74 ± 1.77), and (2.09 ± 0.45) mm, respectively. The length and width of the removed lateral half of the proximally conjoined tendon was (42.67 ± 3.10) mm and (9.89 ± 0.93) mm, respectively. The anterosuperior humeral head translation was intact CAL (8.13 ± 1.99) mm, subperiosteal CAL release (9.68 ± 1.97) mm, CAL anatomic reattachment (8.57 ± 1.97) mm, and the lateral half of the proximally conjoined tendon transfer for CAL reconstruction (8.59 ± 2.06) mm. A significant increase in anterosuperior migration was found after subperiosteal CAL release was compared with intact CAL (P lt; 0.05). The translation after CAL anatomic reattachment and lateral half of the proximally conjoined tendon transfer for CAL reconstruction increased over intact CAL, though no significance was found (P gt; 0.05); when they were compared with subperiosteal CAL release, the migration decreased significantly (P lt; 0.05). The translation of lateral half of the proximally conjoined tendon transfer for CAL reconstruction increased over CAL anatomic reattachment, but no significance was evident (P gt; 0.05). Conclusion The CAL should be preserved or reconstructed as far as possible during subacromial decompression, rotator cuff tears repair, and hemiarthroplasty for patients with massive rotator cuff deficiency. If preservation or the insertion reattachment after subperiosteal release from acromion of the CAL of the CAL is impossible, or CAL is entirely resected becauseof previous operation, the use of the lateral half of the proximally based conjoined tendon transfer for CAL reconstruction isfeasible.
Objective To investigate the clinicalvalue of modified Weaver-Dunn technique in repair of acute acromioclavicular dislocation. Methods From January 1993 to December 1998, 18 cases of acromioclavicular dislocation were treated bymodified Weaver-Dunn technique, and other 17 cases of the same suffering were treated by tension band fixation of the acromioclavicular joints. All of the patients were followed up for 12-36 months before clinical evaluation of the functionof shoulder joints, according to University of Pennsylvanian Shoulder Score System. Results In short term, the shoulder joints recovered much more rapidly in the cases repaired by modified Weaver-Dunn technique; 12, 24 and 36 months after operation, the scores of the cases repaired by modified Weaver-Dunn technique were (1897±67), (193.7±3.6) and (194.7±3.4) respectively according to the Shoulder Score System, while those of the cases treated by tension band fixation were (167.3±7.8), (170.2±6.3) and (165.6±5.9) respectively. The above data indicated that there was significant difference between two groups (P＜0.05). Conclusion The modified Weaver-Dunn technique was a better surgical approach than tension band fixation for repair of acute acromioclavicular dislocation.