Muscle atrophy and fatty infiltration in rotator cuff tears: Can surgery stop muscular degenerative changes?

Editorial Commentary: Monitoring Tendon and Muscle Recovery After Rotator Cuff Repair Using Diagnostic Ultrasound Demonstrates that Early Repair is Beneficial for Many Patients With Reparable Tears

Rotator cuff repair is performed to effect healing of the enthesis; to restore shoulder comfort, strength, and function; to prevent tear propagation; and to prevent progression of atrophic muscle changes (fatty degeneration, fatty infiltration, and fatty atrophy) that eventually occur. Non-retracted and moderately retracted rotator cuff tears usually heal after repair, and muscle atrophy may recover over time. It follows that early rotator cuff repair is beneficial for many patients with chronic but reparable rotator cuff tears. Diagnostic ultrasound can provide quantitative information about the recovery of both muscle and tendon and represents a viable alternative to magnetic resonance imaging for evaluating healing after rotator cuff repair.

Surgical and Non-Surgical Interventions in Complete Rotator Cuff Tears

BACKGROUND

This systematic review compares the efficacy and safety of surgical and non-surgical interventions for full- thickness rotator cuff tears.

METHODS

A systematic literature search was conducted in five databases. Randomized (RCTs) and non-randomized controlled trials of interventions (non-RCTs) for the surgical or non-surgical treatment of patients with traumatic or atraumatic full-thickness rotator cuff tears were included. The review protocol was published in the PROSPERO registry (CRD42018100343).

RESULTS

Ten studies (three RCTs with 332 participants; seven non-RCTs with 650 participants) met the inclusion criteria. One year after treatment, shoulder function, measured with the 100-point Constant score, had improved by 6.7 points (95% confidence interval [2.3; 11.0]) and pain, measured with the 10-cm visual analog scale, by 1.1 cm (0.5; 1.7] in the full-thickness rotator cuff tears treated surgically compared with non-surgical treatment. In one study the difference in favor of surgery persisted after 10 years' follow-up. For other outcomes, such as range of motion, muscle strength, quality of life, and adverse events, the data were sparse and the group differences were similar. The findings of the non-RCTs were comparable with those of the RCTs.

CONCLUSION

With regard to functional improvement and pain reduction, surgical treatment of full-thickness rotator cuff tears was superior to non-surgical treatment in the short and the long term. Whether the differences between the groups are relevant for individual cases is uncertain, as the measured results were distributed below and above the threshold of clinical relevance. The conclusions may not be applicable to rotator cuff tears over 3 cm in size or to young persons.

Down-Regulation of Mitochondrial Metabolism after Tendon Release Primes Lipid Accumulation in Rotator Cuff Muscle

Atrophy and fat accumulation are debilitating aspects of muscle diseases and are rarely prevented. Using a vertical approach combining anatomic techniques with omics methodology in a tenotomy-induced sheep model of rotator cuff disease, we tested whether mitochondrial dysfunction is implicated in muscle wasting and perturbed lipid metabolism, speculating that both can be prevented by the stimulation of β-oxidation with l-carnitine. The infraspinatus muscle lost 22% of its volume over the first 6 weeks after tenotomy before the area-percentage of lipid increased from 8% to 18% at week 16. Atrophy was associated with the down-regulation of mitochondrial transcripts and protein and a slow-to-fast shift in muscle composition. Correspondingly, amino acid levels were increased 2 weeks after tendon release, when the levels of high-energy phosphates and glycerophospholipids were lowered. l-Carnitine administration (0.9 g/kg per day) prevented atrophy over the first 2 weeks, and mitigated alterations of glutamate, glycerophospholipids, and carnitine levels in released muscle, but did not prevent the level decrease in high-energy phosphates or protein constituents of mitochondrial respiration, promoting the accumulation of longer lipids with an increasing saturation. We conclude that the early phase of infraspinatus muscle degeneration after tendon release involves the elimination of oxidative characteristics associated with an aberrant accumulation of lipid species but is largely unrelated to the prevention of atrophy with oral l-carnitine administration.

The effect of subscapularis tenotomy in athletes operated on for recurrent anterior shoulder dislocation

PURPOSE

Some authors consider preservation of the subscapularis tendon as one of the most important elements for a successful long-term outcome in patients operated on with open capsulorrhaphy for recurrent anterior shoulder dislocation. The purpose of this study was to evaluate whether vertical tenotomy of the subscapularis tendon might affect internal rotation strength recovery in patients operated on with open capsulorrhaphy for recurrent anterior shoulder dislocation.

METHODS

Ninety-six patients were retrospectively followed up at a mean of 72.5 months. They underwent clinical evaluation, Rowe and Walch-Duplay scoring scales, the Visual Analog Scale (VAS), and dynamometric measurements (side-to-side) of internal and external rotation, forward elevation, and abduction. All patients were athletes: 25% were practising risk-free sports, 44% contact sports, 14.5% sports with cocking of the arm, and 14.5% high-risk sports activities.

RESULTS

Five (5.2%) recurrences were registered, and all patients returned to pre-operative sports activity. The Rowe score was 98.12, the Walch-Duplay score 92.25, and the VAS score 0.1. Dynamometric assessment showed no significant differences (side-to-side) in internal rotation (p = 0.34), external rotation (p = 0.9), flexion (p = 0.7), and abduction (p = 0.7). Dominant arms showed better results than non-dominant arms (p < 0.01).

CONCLUSION

Complete tenotomy of the subscapularis tendon does not seem to negatively affect internal rotation strength recovery or external rotation movement in athletes.

Proton Density Fat-Fraction of Rotator Cuff Muscles Is Associated With Isometric Strength 10 Years After Rotator Cuff Repair: A Quantitative Magnetic Resonance Imaging Study of the Shoulder

BACKGROUND

Quantitative muscle fat-fraction magnetic resonance (MR) imaging techniques correlate with semiquantitative Goutallier scores with failure after rotator cuff (RC) repair.

PURPOSE

To investigate the relationship of proton density fat fraction (PDFF) of the RC muscles with semiquantitative MR scores, cartilage T2 relaxation times, and clinical isometric strength measurements in patients 10 years after unilateral RC repair.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Bilateral shoulder MR imaging was performed in 13 patients (11 male, 2 female; age, 72 ± 8 years) 10.9 ± 0.4 years after unilateral autologous periosteal flap augmented RC repair (total shoulders assessed, N = 26). Goutallier classification, muscle atrophy, RC tendon integrity, and cartilage defects were determined based on morphological MR sequences. A paracoronal 2D multi-slice multi-echo sequence was used for quantitative cartilage T2 mapping. A chemical shift-encoding-based water-fat separation technique (based on a 6-echo 3D spoiled gradient echo sequence) was used for quantification of the PDFF of RC muscles. Isometric shoulder abduction strength was measured clinically. Mean and SD, Pearson correlation, and partial Spearman correlation were calculated.

RESULTS

There were 6 RC full-thickness retears in ipsilateral shoulders and 6 RC full-thickness tears in contralateral shoulders. Isometric shoulder abduction strength was not significantly different between ipsilateral and contralateral shoulders (50 ± 24 N vs 54 ± 24 N; P = .159). The mean PDFF of RC muscles was 11.7% ± 10.4% (ipsilateral, 14.2% ± 8.5%; contralateral, 9.2% ± 7.8%; P = .002). High supraspinatus PDFF correlated significantly with higher Goutallier scores ( R = 0.75, P < .001) and with lower isometric muscle strength ( R = -0.49, P = .011). This correlation remained significant after adjustment for muscle area measurements and tendon rupture ( R = -0.41, P = .048). More severe cartilage defects at the humerus were significantly associated with higher supraspinatus PDFF ( R = 0.44; P = .023). Cartilage T2 values did not correlate with muscle PDFF ( P > .05).

CONCLUSION

MR imaging-derived RC muscle PDFF is associated with isometric strength independent of muscle atrophy and tendon rupture in shoulders with early and advanced degenerative changes. It therefore provides complementary, clinically relevant information in tracking RC muscle composition on a quantitative level.