The biomechanical response and injury tolerance of the shoulder in lateral impacts is not well understood. These data are needed to better understand human injury tolerance, validate finite element models and develop biofidelic shoulders in side impact dummies. Seventeen side impact sled tests were performed with unembalmed human cadavers by Cavanaugh et al (1993). Data reanalyzed for this study included shoulder and thoracic load plate forces, T1-Y, upper sternum x and y, and struck side acromion x, y and z accelerations. One dimensional deflection at the shoulder level was determined from high-speed film. Force-time response corridors were obtained. Maximum shoulder plate forces in unpadded 9 m/s tests (5.5 kN) were larger than In 6.7 m/s tests (3.3 kN). T1-Y acceieratlons were larger In unpadded 9 m/s flat wall tests and unpadded pelvic offset 10.5 m/s tests (peak values of 130 and 145 g’s) than In other test conditions. Deflections between T1 and the struck wall ranged from 88 to 154 mm In unpadded tests and 95 to 128 mm In padded tests. Eighteen AIS 2 level shoulder Injuries occurred In 11 test subjects. Padding of 4 to 6 Inches (101.6 mm to 152.4 mm) reduced shoulder Injury approximately one AIS level. Shoulder deflection of 106 mm predicted 50% probability of MAIS 2.

The tensile properties of the shoulder ligaments under dynamic loading had not been Investigated prior to this study. Thirty-three fresh human shoulders were harvested and bone-ligament-bone specimens of acromioclavicular joint (N=32), coracoclavicular joint (N=31) and sternoclavicular joint (N=20) were obtained. A test fixture and clamps specifically designed for this ligament study and a high-speed Instron machine were used. One quasl-static rate (0.1 %/sec) and two high rates (40,000 %/sec and 15,000 %/sec) were used for this study. There was no significant relationship between the cross sectional area and age, height and weight. In acromioclavicular joint tests, ligament failure was the most common failure mode. In coracoclavicular joint tests, the majority of specimens failed at the ligament. In sternoclavicular joint tests, the specimen failed at the bone in most cases. In acromioclavicular joint and coracoclavicular joint tests, 15,000 %/sec tests and quasi-static tests had more bone fracture cases than 40,000/sec tests. Mechanical and structural properties of three shoulder joints were found. The following table summarized the findings:​

[TABLE]

The Young’s modulus and ultimate load of the three joints were found to be significantly lower in the 0.1 %/sec tests compared to the 15,000 %/sec tests but not significantly different between 40,000 %/sec and 15,000 %/sec tests.