INTRODUCTION
Isolated infraspinatus lesions are exceedingly rare among shoulder injuries involving the rotator cuff [1,2]. Various causes of such lesions have been documented in the literature, including Parsonage-Turner syndrome, suprascapular nerve entrapment, tumors, vascular malformations, and steroid use [1-4]. Isolated infraspinatus tears are particularly challenging because the outcomes of arthroscopic repair are often unpredictable and unsatisfactory [1,2]. Unlike classic rotator cuff tears, isolated infraspinatus tears can result in rapid atrophy and high fatty infiltration within the infraspinatus muscle, rendering the lesion irreparable and posing significant challenges to effective treatment [2].
Arthroscopically-assisted lower trapezius tendon (aLTT) transfer has shown favorable outcomes in patients with posterior superior irreparable rotator cuff tears [5,6], where such lesions involve both the supraspinatus and infraspinatus. This success may be attributed to the biomechanical and anatomical similarities between the lower trapezius tendon and the infraspinatus, including a similar line of pull and excursion [7]. To the best of our knowledge, there have been limited studies primarily addressing the treatment of isolated infraspinatus tears with aLTT transfer. This study evaluates the clinical and radiological outcomes of aLTT transfer in patients with isolated irreparable infraspinatus tears.
METHODS
The current study is a retrospective single-center case series, which was approved by the Institutional Review Board of Yeosu Baek Hospital (No. P01-202305-01-006). The requirement for informed consent was waived owing to the retrospective design of the study and the lack of additional harm to the patients.
Patients
We retrospectively reviewed 9 patients who underwent aLTT transfer for isolated irreparable infraspinatus tears from December 2017 to June 2022. Indications for aLTT transfer in isolated irreparable infraspinatus tears were as follows: (1) persistent shoulder pain even after conservative treatment; (2) no advanced glenohumeral arthritis, with grade ≤2 Hamada [8] classification; (3) irreparable infraspinatus tear with medial retraction and high-grade fatty infiltration, categorized as Goutallier [9] grade 3 or 4; (4) intact remaining rotator cuff including subscapularis, supraspinatus, and teres minor; and (5) no neurologic/infectious disorders of the shoulder. Patients were excluded if they were unavailable for follow-up visits or were lost to follow-up (n=2).
Clinical and Radiological Evaluation
The degree of pain and function were evaluated both preoperatively and postoperatively. Data collected preoperatively included sex, age, follow-up period, dominant arm involvement, body mass index, prior cuff repair status, and prior steroid injection. Pain was evaluated using a 10-point visual analog scale (VAS). Various standardized measurements, including Constant score, American Shoulder and Elbow Society (ASES) score, and Single Assessment Numeric Evaluation (SANE), were also taken. The active range of motion (ROM) of the shoulder was measured for forward elevation (FE), abduction (Abd), and external rotation at side (ERS) using a standardized goniometer. Internal rotation (IR) at back was measured at the thumb position in the back. All patients presented with main complaints of pain and weakness, external rotation deficit in the affected arm, and had experienced shoulder symptoms for 6 months to 1 year before visiting our clinic. Different radiographic views including true anteroposterior, lateral scapular, and axillary lateral were obtained preoperatively and postoperatively. The Hamada [8] grading system was used to evaluate the progression of glenohumeral joint arthritis. At the final follow-up visit, postoperative magnetic resonance imaging (MRI) scans were assessed to evaluate retears, where discontinuity in the transferred tendon was considered a retear. The degree of fatty infiltration in all of the rotator cuff muscles was assessed in sagittal oblique images (the Y-view) using Goutallier [9] grading system. Electromyography studies showed no signs of nerve-related lesions, such as suprascapular or axillary nerve damage, in any patient. The integrity of the transferred tendon was confirmed by both MRI and physical palpation, which demonstrated synchronized movement of the lower trapezius during external rotation.
Surgical Technique
The surgical procedure followed the general steps previously described in the literature [10,11]. The patient was positioned in the lateral decubitus position and administered general anesthesia. An initial arthroscopic procedure was performed to open the rotator interval and release the capsule to prevent postoperative stiffness. The infraspinatus footprint was prepared for graft attachment, with any identified calcific deposits debrided and removed. Two medial-row anchors (5.5 mm Healix Advance BR 3 Suture Anchor with Permacord, DePuy Mitek) were inserted into the infraspinatus footprint.
For the interpositional graft, patients chose between an Achilles tendon allograft and a fascia lata autograft after being informed of their respective advantages and disadvantages. For the fascia lata autograft (patients #1, #3, and #5), a segment measuring 15 cm by 4 cm in dimension was harvested from the ipsilateral thigh, folded, and secured with traction sutures at its distal end. For the Achilles tendon allograft (patients #2, #4, and #6), traction sutures were placed at each end. The lower trapezius was then harvested by locating its lateral border above a triangular fat area and separating it from the scapular spine. The harvested lower trapezius was prepared with traction sutures (Fig. 1A).
To create a path for the graft, an incision was made in the infraspinatus fascia, through which the graft was delivered and positioned on the infraspinatus footprint. Side-to-side sutures were applied anteriorly (supraspinatus) and posteriorly (remnant infraspinatus or teres minor) using two sutures from medial-row anchors for each, while the remaining sutures were threaded through the graft. The posterior side-to-side sutures were specifically placed to support the stability of the graft by securing it to the remnant posterior cuff structures, ensuring proper integration and stability. Multiple lateral row anchors (4.75-mm SwiveLock anchor, Arthrex Inc.) were used to secure the graft onto the infraspinatus footprint, creating a suture bridge configuration. Finally, the other end of the graft was attached to the lower trapezius using a continuous running configuration (Fig. 1B), with the patient’s arm positioned in maximal external rotation at a 60° Abd angle to achieve physiological tensioning.
Postoperative Management
Postoperatively, patients were placed in a brace with their shoulder held at 0° external rotation for 4 weeks, complemented by the use of a continuous passive motion machine. After 4 weeks, patients began active-assisted ROM exercises and gradually progressed to full ROM and gentle strengthening exercises. For the first 6 months postoperatively, patients were advised to refrain from engaging in high-level activities.
RESULTS
After excluding two patients who were unavailable for final follow-up, a total of 7 patients were included in the study, with a mean age of 60.7±4.1 years and a mean follow-up duration of 36.7±9.8 months (range, 24–75 months). Table 1 shows the demographics of the six patients. None of the patients had a history of trauma. Five patients (patients #1, #3, #4, #5, #6) had received multiple steroid injections (average 3; range, 2–10 times) prior to their visit. Preoperative MRI scans revealed an isolated tear within the infraspinatus at the tendinous level for three patients (patients #2 [Fig. 2], #4, and #6) and at the musculotendinous junction for the other patients (patients #1, #3 [Fig. 3], and #5), along with advanced atrophy and high-grade fatty infiltration in all patients. Two patients (patients #3 and #5) exhibited calcific tendinopathy, with patient #5 having previously undergone surgery on the affected arm 2 years prior, with arthroscopic debridement and removal of calcific deposits. None of the patients exhibited glenohumeral arthritis, and no significant lesions were observed in the remaining rotator cuff muscles, including the subscapularis, supraspinatus, and teres minor.
At the final follow-up, pain VAS significantly decreased from 6.0±1.4 to 1.7±0.8 (P<0.05). Patients reported significant improvements in all measures, including SANE score (from 48.0±6.7 to 79.1±8.0), Constant score (from 51.5±5.6 to 72.0±6.4), and ASES score (from 60.5±4.5 to 82.0±6.3), all with P<0.05 (Table 2). Furthermore, shoulder ROM significantly improved, with FE increasing from 115°±12° to 170°±9° (P<0.05), ABD from 95°±15° to 143°±16° (P<0.05), and ERS from 22°±11° to 51°±11° (P<0.05). IR at back showed no significant difference with P=0.102 (Table 3). At final follow-up, radiological evaluation showed no signs of glenohumeral arthritis progression, and there were no indications of tendon retear, as confirmed by MRI scan, physical palpation, and synchronized movement of the lower trapezius during ERS. No other complications were documented.
DISCUSSION
This study evaluated the outcomes of aLTT for patients with isolated irreparable infraspinatus tears characterized by advanced atrophy and high-grade fatty infiltration. A total of six patients, with a mean follow-up period of 36.7±9.8 months, showed significant postoperative improvements in pain (VAS decrease from 6.0±1.4 to 1.7±0.8), functional scores (Constant, ASES, and SANE), and shoulder range of motion (FE, ABD, and ERS; all P<0.001). Radiological evaluation at the final follow-up confirmed no tendon retears or glenohumeral arthritis progression. MRI and physical palpation demonstrated synchronized movement of the transferred tendon with external rotation, and no complications were documented.
Isolated infraspinatus tears are uncommon in the literature, as most rotator cuff injuries typically involve the supraspinatus. These tears typically manifest with severe pain and weakness during ER, often attributed to causes such as suprascapular nerve damage or brachial neuropathy [1,2,4,12]. Other contributing factors include direct trauma, steroid injections, and calcific tendinopathy, all of which have been confirmed to be unrelated to nerve damage based on normal electromyography findings [1,2]. Lunn et al. [1] delineated the progression of infraspinatus tears through distinct phases, beginning with severe inflammation and muscle retraction, leading to chronic changes characterized by significant fatty infiltration and rapid atrophy of the infraspinatus. Highlighting the rapid structural changes in the infraspinatus upon lesion occurrence, Walch et al. [2] noted that isolated infraspinatus musculotendinous junction lesions exhibit anatomical, epidemiological, and imaging characteristics distinct from typical rotator cuff tears. Direct repair for isolated infraspinatus tears often leads to unpredictable and poor clinical results [1,2,4,13]. For example, Lunn et al. [1] reported that none of the five patients who underwent surgical repair of the infraspinatus tear in their case series showed functional improvement. Instead, severe fatty infiltration was evident, and all 19 patients progressed to stage 4 fatty infiltration of the infraspinatus muscle. Similarly, Walch et al. [2] found no significant improvement in Constant scores between 24 surgically treated patients and 35 conservatively managed patients in their study. Despite treatment, all patients initially presenting with acute painful edema progressed to stage 4 complete fatty infiltration, with no regression observed in surgically treated patients.
Given the success of conventional lower trapezius tendon transfer in managing paralytic shoulder conditions following brachial plexus injury [14,15], this technique has been expanded to treat posterior superior irreparable rotator cuff tears [16]. With advancements in arthroscopic techniques and various modifications explored by several authors [10,11,17], numerous studies have demonstrated satisfactory clinical outcomes after aLTT transfer [5,6,17,18]. Anatomically aligned with the infraspinatus in terms of line of pull and excursion, the lower trapezius transfer offers biomechanical advantages over conventional latissimus dorsi transfer, particularly in enhancing external rotation [7,17]. These features might contribute to the promising clinical outcomes achieved with aLTT transfer for isolated, irreparable infraspinatus lesions, as opposed to the poor outcomes from direct repair [1,2], potentially establishing it as a favorable treatment option.
This study has several limitations. First, its retrospective nature inherently limits its statistical power, increasing the risk of type II error due to the small sample size. Isolated infraspinatus lesions are rare, and encountering patients with irreparable infraspinatus tears is even more uncommon in outpatient settings, which constrained our patient pool. Second, this study has a relatively short follow-up period, so longer follow-up studies are warranted to better assess the durability of clinical outcomes over time. Lastly, external rotation strength was not measured quantitatively. However, qualitative improvements in external rotation function were noted through physical palpation and patient-reported outcomes.
PDF Links
PubReader
ePub Link
XML Download
Full text via DOI
Download Citation
Print
