PURPOSE: To evaluate the clinical outcomes of arthroscopically assisted lower trapezius tendon (aLTT) transfer using Achilles tendon allograft in patients with irreparable infraspinatus musculotendinous tears (IISMTTs). METHODS: We conducted a retrospective analysis of patients who underwent aLTT transfer for IISMTTs. The inclusion criteria were minimal glenohumeral arthritis (Hamada grade ≤ 1), isolated infraspinatus musculotendinous tear with poor muscle quality (Goutallier grade ≥ 3), and intact remaining rotator cuff muscles. The exclusion criteria included less than 5-year follow-up, loss to follow-up, or insufficient data. Clinical outcomes were assessed using the visual analog scale (VAS) pain score, Constant score, American Shoulder and Elbow Surgeons (ASES) score, Subjective Shoulder Value (SSV), range of motion, tendon integrity, and arthritis progression. RESULTS: A total of 20 patients were included, with a mean follow-up period of 7.4 years. Significant improvements were observed in all clinical scores: VAS pain score, 7.9 ± 1.2 to 1.1 ± 0.7
Constant score, 33.7 ± 5.9 to 67.6 ± 16.3
ASES score, 38.0 ± 6.0 to 68.8 ± 16.2
and SSV, 20.2 ± 7.8 to 67.5 ± 18.1 (all with P <
.001). Significant range-of-motion improvements were observed forward elevation (100° ± 13° to 139° ± 30°), abduction (77° ± 20° to 119° ± 13°), and external rotation (24° ± 9° to 56° ± 12°). Regarding the minimal clinically important difference (MCID), determined using the 0.5 standard deviation distribution-based method, all 20 patients (100%) achieved the MCID for the VAS pain score
17 patients (85%), for the Constant score
17 patients (85%), for the ASES score
and all 20 patients (100%), for the SSV. In all patients, glenohumeral joint integrity was maintained without the development of arthritis. No retears were observed. CONCLUSIONS: The aLTT transfer effectively alleviated pain and improved shoulder function in patients with IISMTTs at mid-term follow-up. Significant improvements in pain and external rotation were observed without any progression of glenohumeral arthritis, and no retears were reported. LEVEL OF EVIDENCE: Level IV, retrospective case series.