In Vivo Measurement of Rotator Cuff Tear Tension: Medial Versus Lateral Footprint Position
We conducted a study to evaluate in vivo tension applied to the rotator cuff tendon positioned at the medial versus lateral footprint during arthroscopic rotator cuff repair.
We evaluated 20 consecutive patients who underwent arthroscopic rotator cuff repair. During repair, a grasper was inserted through a lateral portal, and a digital weigh scale was attached. The tendon was grasped and translated to the medial footprint, and tension recorded. After a relaxation period, the tendon edge was translated to the lateral footprint, and tension recorded. Mean (SD) tension was 0.41 (0.33) pound when tendons were positioned at the medial footprint and 2.21 (1.20) pounds when they were positioned at the lateral footprint, representing a 5.4-fold difference (P < .0001). For smaller tears (≤20 mm anterior-posterior), 7.6 times less tension was applied to the tendons when pulled to the medial versus lateral footprint. For larger tears, 4.1 times less tension was applied to the tendons when pulled to the medial versus lateral footprint. This study demonstrated a significant, 5.4-fold increase in tension when the tendon edge was reduced to the lateral as opposed to the medial footprint in vivo.
This study had several weaknesses. Its data represent a static measurement of time-zero rotator cuff tension, which greatly simplifies the biomechanics of the torn rotator cuff and repair construct as well as changes that occur with healing. During cuff repair, forces typically are distributed through several fixation points in stepwise process and are not focused on a single point of tissue with a grasper. Therefore, the findings of this study may not directly correlate with medially versus laterally based repairs in vivo. Furthermore, as this is a time-zero measurement, we could not determine whether the tension differential between the 2 repair positions remained static over time. Current literature suggests that muscle atrophy, fatty infiltration, and loss of elasticity of the musculotendinous unit are relatively irreversible.35,37,49 In addition, determining the precise apex of a cuff tear can be difficult, so error may have been introduced during this process. Last, although placement of the cuff tissue at the medial or lateral footprint position was based on visual estimation by an experienced and skilled arthroscopist, error may have been introduced based on this imprecise technique.
Conclusion
This study demonstrated a significant, 5.4-fold increase in in vivo time-zero rotator cuff tension with the tendon edge reduced to the lateral footprint rather than the medial footprint.
