2013 by Taylor & Francis Group, LLC. Overall, musculoskeletal ailments comprise more than 14% of health care expenditures in the United States. Ligament and tendon damage account for a signicant portion of these ailments with over 32 million traumatic and repetitive motion injuries reported in the United States each year. Although numerous tendon injuries can be surgically repaired, large gaps and missing tendons require a gra or replacement device. Among the most common tendon injuries are traumatic and attritional tears of the rotator cu, resulting in 4.4 million physician visits and over 50,000 repair surgeries performed each year (Praemer et al. 1999; Butler et al. 2008). However, tendons repaired in this manner are oen weak and susceptible to reinjury. Excessive muscle contraction and neurovascular damage following surgical repair of rotator cu injuries result in failure rates as high as 40%. Tendon injuries can dramatically aect a patients quality of life; however, improving functional outcomes aer tendon injury remains a signicant clinical challenge.
