Outcomes of and factors influencing the arthroscopic treatment of rotator cuff injury with the patient in the lateral-lying and beach chair positions.

To compare the postoperative effects of arthroscopy for rotator cuff injury with patients in the lateral-lying position (LLP) and beach chair position (BCP), and to identify factors influencing these effects.Data from patients with rotator cuff injuries who underwent shoulder arthroscopy in the LLP (n = 115, 53.24%) or BCP (n = 101, 46.76%) between January 2013 and 2016 and were followed for >3 years were analyzed. The American Shoulder and Elbow Surgeons shoulder score, University of California at Los Angeles shoulder score (UCLASS), and visual analog scale (VAS) score were used to evaluate patients' shoulder function and pain preoperatively and at the last follow-up examination. The abduction and lateral rotation angles were measured. The influences of patient characteristics were compared between the LLP and BCP subgroups defined by UCLASSs (excellent, good, acceptable, poor).Postoperative injury characteristics, UCLASSs, and VAS scores were better in the LLP group than in the BCP group (all P < .05). Among patients with good UCLASSs, preoperative pain duration was longer in the LLP group than in the BCP group (P < .05); among those with acceptable UCLASSs, this duration was longer in the BCP group than in the LLP group (P < .05). The preoperative flexion angle differed between groups (P < .05). Among patients with excellent and good UCLASSs, the postoperative external rotation angle was greater in the LLP group than in the BCP group (P < .05). The LLP group contained more excellent UCLASSs than did the BCP group (P < .05). It also contained more small, medium, and large tear cases than did the BCP group (all P < .05).The effect of arthroscopy for rotator cuff injury was better when the operation was performed with the patient in the LLP. Either position is suitable for the arthroscopic treatment of partial rotator cuff tears. The LLP is more suitable in cases of small and medium-sized tears and those with large preoperative lateral rotation angles. The BCP should be used for patients with large preoperative flexion angles.