Higher re-tear rates after arthroscopic single row rotator cuff repairs have been linked with the inability to restore the native footprint. The objective in our study was to evaluate the biomechanical properties and anatomic footprint restoration after both single and double row repairs.

Human cadaveric shoulders (n=22) were tested using a materials testing machine. Cyclic loading was performed on intact, injured (3cm tear), and arthroscopically repaired rotator cuff. Repairs tested: 1) single row A (Lateral Simple, n=6); 2) single row B (Lateral Mattress, n=5); 3) double row A (Medial Mattress/Lateral Simple, n=6); and 4) double row B (Transosseus Simple, n=5). Percentage of footprint restoration was calculated for each repair followed by a load-to-failure protocol. Biomechanical properties were determined from the load-displacement curves.

Single and double row repairs restored an average of 40% and 90% of the native footprint (p< 0.05) with small amounts of cyclic creep and permanent elongation. No differences were detected between any of the repairs for the ultimate load (724±344N, 879±247N, 741±339N and 896±229N) and stiffness (100±43N/mm, 106±31N/mm, 89±34N/mm and 100±14N/mm), respectively.

Double row repairs have comparable initial strength and increased footprint restoration compared to single row repairs. These similarities can be attributed to the inclusion of surrounding soft tissue structures during testing; however, the increased restoration of the anatomic footprint may lead to increased tendon-to-bone healing with the possibility of improved biomechanical properties and should be examined in the future.

The characteristic U-shaped tear confirms clinically observed scenarios which may be caused by overuse after a RC injury has been sustained. The small amount of cyclic creep and permanent deformation in all arthroscopic repairs suggest that initial rehabilitation could be prescribed after surgery without compromising the initial stability of the repair; however, surgeons should carefully select a RC repair based on the state of the surrounding tissue.