Vincent M. Wang,Anthony A. Romeo

Given the high prevalence of rotator cuff injury, considerable attention has been focused on identifying risk factors for tear initiation as well as extension of these tears. To improve the treatment of rotator cuff tears, it is necessary to better understand how anatomic variables such as the size and location of the tear influence its biomechanical function. These parameters may provide additional insight into the long-term prognosis following rotator cuff injury, improving physician ability to explain to patients the expected outcomes from nonoperative treatment.

Using a human cadaveric model, Araki et al. surgically created either an anterior or a central region full-thickness supraspinatus tendon laceration (each 1 cm in width) and examined biomechanical loading characteristics of the “torn” tendons. The mechanical testing protocol consisted of consecutive sets of 100 cycles, beginning with a 50 to 100-N set, followed by a 100-N increase in the maximum load for each subsequent cycle set. Loading continued until a critical tear retraction of 2 cm (medial to lateral) was reached or when tissue failure was evident. Changes in both tendon tear length and area were measured from digital images taken at the conclusion of each loading set.

No significant differences were noted between the two groups with respect to the maximum load at which the critical tear retraction was reached or the tear area at the conclusion of the cycle set preceding failure. However, the mean load (and standard deviation) at which the critical tear size was reached was significantly lower (p = 0.03) for the anterior tears (389 ± 237 N) relative to the central region tears (714 ± 168 N). Furthermore, the authors noted a strong negative correlation between cadaver age and the maximum cyclic load sustained prior to failure in both groups. For the anterior tendon tear group, age also demonstrated a negative correlation with the load required to cause a 100% increase in the tear area.