Biomechanical properties of labral repair: simple versus vertical suture pattern.

The goal of this study was to evaluate contact area and surface pressure as a result of different suture patterns in the treatment of anterior shoulder instability caused by a Bankart lesion. Loads were applied through the humeral head to the glenoid surface in the intact shoulder and after simple suture labral repair (n=10) and vertical mattress labral repair (n=9). Peak contact pressure, mean contact pressure, and contact area were recorded for 0°, 45°, and 90° shoulder abduction, and then the repair was loaded to failure. A significant increase (P<.05) in mean contact pressure and peak contact pressure occurred in both repair groups at 90° abduction. No difference was seen between the 2 repair groups. Total contact area significantly decreased after both repairs at 90° abduction at 220 N force (P<.05). No significant difference occurred in load to failure between the groups. Joint loading properties can be affected by alterations in contact pressure within the glenohumeral joint. In the current study, the authors found no significant difference in contact pressure between the 2 repair groups. However, they found a significant increase in mean contact pressure and peak pressure between the intact specimen and the 2 repair groups. Both simple repair and vertical mattress repair provided similar load to failure for labral repair. Current techniques used to perform Bankart repair may need to be altered to provide the stability of current techniques with more normal glenohumeral joint contact pressure.

Biomechanical evaluation of anatomical double-bundle coracoclavicular ligament reconstruction secured with knot fixation versus screw fixation.

Methods to reconstruct the coracoclavicular ligaments anatomically have been described. No clear advantage of 1 technique has been elucidated. The authors' hypothesis was that the biomechanical properties of a modified knot fixation technique would be similar to the anatomical double-bundle technique. Sixteen matched cadaveric shoulders were used for this study, and 1 additional shoulder was used in the knot fixation group only. Shoulders were randomly assigned to the anatomical double-bundle coracoclavicular ligament reconstruction technique (n=8) or a knot fixation technique (n=9). The intact coracoclavicular ligaments were tested to failure with superior displacement at a rate of 2 mm/s. Reconstruction was performed using a semitendinosus tendon allograft, and load to failure was repeated for each construct. Ultimate failure load, stiffness, and failure mode were compared using a paired t test (P<.05). No significant difference existed in load to failure between native and reconstructed ligaments or between reconstruction techniques. Stiffness decreased significantly after reconstruction in the double-bundle group (from 32.5 to 22.5 N/mm; P=.035) and in the modified knot fixation group (from 35.5 to 21.9 N/mm; P=.043). No significant difference existed in stiffness between the 2 reconstruction groups. A significant difference (P=.003) existed between failure modes between the 2 reconstruction techniques. Although less stiff than the native ligament, either technique used to reconstruct the coracoclavicular ligament can be performed to yield a load to failure similar to the intact ligament. The majority of failures in the double-bundle group were by means of the graft slipping at the screw-tendon interface at 1 of the clavicular drill holes. The modified knot fixation technique failed the majority of the time by graft elongation.

The biomechanical stability of distal clavicle excision versus symmetric acromioclavicular joint resection.

BACKGROUND: Treatment for acromioclavicular (AC) joint pain may include distal clavicle excision (DCE). It is possible that DCE can disrupt the surrounding ligaments, leading to increased AC joint laxity. PURPOSE: To determine the load to failure and stiffness of the AC joint after DCE and symmetric acromioclavicular joint resection (ACJR). STUDY DESIGN: Controlled laboratory study. METHODS: Specimens were randomly assigned to 1 of 2 groups: 1-cm DCE (n = 10) or symmetric (5-mm excision of acromion and distal clavicle) ACJR (n = 10). The specimens were loaded intact in the anterior-posterior plane to determine anteroposterior translation. This was repeated after surgery and compared. The specimens were loaded at 2 mm/s until clinical failure. Force and displacement were recorded, and stiffness was calculated. RESULTS: The peak load to failure for the DCE group was 387.8 N (standard error of the mean [SEM], 31.4 N) and for the ACJR group was 468.5 N (SEM, 30.9 N) (P = .035). The average stiffness for the DCE group was 35.2 N/mm (SEM, 2.5 N/mm) and for the ACJR group was 37.4 N/mm (SEM, 2.3 N/mm) (P = .11). There was no significant difference in the anteroposterior translation before and after resection for either group (P > .05). CONCLUSION: This cadaveric study demonstrates that the anterior-posterior load to clinical failure of the AC joint after 5 mm of resection from the distal clavicle and medial acromion is significantly greater than 1 cm of the resected distal clavicle alone. CLINICAL RELEVANCE: Performing ACJR may improve joint stability, leading to fewer complications when compared with DCE.