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Partial-width injuries of the rat rotator cuff heal with fibrosis.

ABSTRACT: PURPOSE:Identify the healing outcomes following a partial-width, full-thickness injury to the rotator cuff tendon-bone attachment and establish if the adult attachment can regenerate the morphology of the healthy attachment. HYPOTHESIS:We hypothesized that a partial-width injury to the attachment would heal via fibrosis and bone remodeling, resulting in increased cellularity and extra-cellular matrix deposition, reduced bone volume (BV), osteoclast presence, and decreased collagen organization compared to shams. MATERIALS AND METHODS:A partial-width injury was made using a biopsy punch at the center one-third of the rat infraspinatus attachment. Contralateral limbs underwent a sham operation. Rats were sacrificed at 3 and 8 weeks after injury for analyses. Analyses performed at each time point included cellularity (Hematoxylin & Eosin), ECM deposition (Masson's Trichrome), BV (micro-computed tomography; microCT), osteoclast activity (Tartrate Resistant Acid Phosphatase; TRAP), and collagen fibril organization (Picrosirius Red). Injured and sham shoulders were compared at both 3 and 8 weeks using paired, two-way ANOVAs with repeated measures (Sidak's correction for multiple comparisons). RESULTS:Cellularity and ECM deposition increased at both 3 and 8 weeks compared to sham contralateral attachments. BV decreased and osteoclast presence increased at both 3 and 8 weeks compared to sham contralateral limbs. Collagen fibril organization was reduced at 3 weeks after injury compared to 3-week sham attachments. CONCLUSIONS:These findings suggest that a partial-width injury to the rotator cuff attachment does not fully regenerate the native structure of the healthy attachment. The injury model healed via scar-like fibrosis and did not propagate into a full-width tear after 8 weeks of healing.

SUBMITTER: Lemmon EA

PROVIDER: S-EPMC6324170 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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Partial-width injuries of the rat rotator cuff heal with fibrosis.

Lemmon Elisabeth A EA Locke Ryan C RC Szostek Adrianna K AK Ganji Elahe E Killian Megan L ML

Connective tissue research 20180702 5

<h4>Purpose</h4>Identify the healing outcomes following a partial-width, full-thickness injury to the rotator cuff tendon-bone attachment and establish if the adult attachment can regenerate the morphology of the healthy attachment.<h4>Hypothesis</h4>We hypothesized that a partial-width injury to the attachment would heal via fibrosis and bone remodeling, resulting in increased cellularity and extra-cellular matrix deposition, reduced bone volume (BV), osteoclast presence, and decreased collagen ...[more]

PMID: 29874950

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Project description:Myosteatosis is the pathological accumulation of lipid that occurs in conjunction with atrophy and fibrosis following skeletal muscle injury or disease. Little is known about the mechanisms by which lipid accumulates in myosteatosis, but many studies have demonstrated the degree of lipid infiltration negatively correlates with muscle function and regeneration. Our goal was to identify biochemical pathways that lead to muscle dysfunction and lipid accumulation in injured rotator cuff muscles, a model that demonstrates severe myosteatosis. Adult rats were subjected to a massive tear to the rotator cuff musculature. After a period of either 0 (healthy control), 10, 30, or 60 days, muscles were prepared for RNA sequencing, shotgun lipidomics, metabolomics, biochemical measures, electron microscopy, and muscle fiber contractility. Following rotator cuff injury, there was a decrease in muscle fiber specific force production that was lowest at 30d. There was a dramatic time dependent increase in triacylglyceride content. Interestingly, genes related to not only triacylglyceride synthesis, but also lipid oxidation were largely downregulated over time. Using bioinformatics techniques, we identified that biochemical pathways related to mitochondrial dysfunction and reactive oxygen species were considerably increased in muscles with myosteatosis. Long chain acyl-carnitines and L-carnitine, precursors to beta-oxidation, were depleted following rotator cuff tear. Electron micrographs showed injured muscles displayed large lipid droplets within mitochondria at early time points, and an accumulation of peripheral segment mitochondria at all time points. Several markers of oxidative stress were elevated following rotator cuff tear. The results from this study suggest that the accumulation of lipid in myosteatosis is not a result of canonical lipid synthesis, but occurs due to decreased lipid oxidation in mitochondria. A failure in lipid utilization by mitochondria would ultimately cause an accumulation of lipid even in the absence of increased synthesis. Further study will identify whether this process is required for the onset of myosteatosis.

Project description:PurposeTo determine the significance of initial and residual rotator cuff tear defect size on the need for revision surgery or additional nonsurgical therapy, in a consecutive group of patients undergoing partial repair of massive rotator cuff tears.MethodsA retrospective chart review was carried out for all arthroscopic rotator cuff repairs performed by a single surgeon between January of 2013 and December of 2016. All patients with massive rotator cuff tears (>30 cm2) who underwent partial repair were included in the study. Outcomes for the surgical procedure were measured based on the necessity for revision surgery or adjunct therapy, including steroid injections or additional physical therapy after initial release from care.ResultsIn total, 1954 patients who underwent arthroscopic rotator cuff repair were identified. Thirty-eight of these met the inclusion criteria. Those patients undergoing revision surgery represented 5.2% (2/38) of the series and had an average initial/residual tear defect area of 45.0/7.0 cm2. Patients requiring adjunct therapy represented 7.9% (3/38) of the series and possessed an average initial/residual tear defect size of 40.0/16.0 cm2. The remaining 33 (86.9%) patients did not require revision surgery or adjunct therapy at a minimum follow-up of 2 years. There was no significance between initial and/or residual rotator cuff tear defect size and the need for revision surgery. However, there was a significant difference in the mean residual defect size in the patients requiring additional nonoperative treatment after initial release from care (P = .012).ConclusionsThere was no relationship between residual defect size after partial repair and the need for revision surgery. Patients who returned for additional nonoperative treatment after being released from care were noted to have a statistically larger residual defect size at the time of index surgical intervention. Only 5% of patients underwent subsequent surgery at an average of more than 4 years' follow-up, suggesting that partial repair of massive rotator cuff tears can provide a durable, joint-preserving intervention.Level of evidenceLevel IV, Therapeutic Case Series.

Project description:Background Rotator cuff tears are a common source of shoulder pain and dysfunction. An irreparable rotator cuff tear poses a particular treatment challenge. There have been few studies reporting the outcomes of lower trapezius tendon (LTT) transfer for irreparable rotator cuff injuries. Therefore, the purpose of this review is to summarize the postoperative functional outcomes and complications of patients undergoing a LTT transfer for massive irreparable rotator cuff injuries. Methods A scoping review was performed using the Medline, Embase, Cochrane Central Register of Controlled Trials, and Google Scholar databases with the search terms “trapezius” AND “transfer.” Of 362 studies included for initial screening, 37 full-text citations were reviewed, with 5 studies meeting all the inclusion criteria to be included in the review. Two reviewers extracted data on study design, patient demographics, surgical technique, functional outcomes, range of motion (ROM), and complications for each study according to the predefined criteria. Results Improvements in the preoperative to postoperative functional status, identified using the Disabilities of the Arm, Shoulder, and Hand (50.34 to 18), The American Shoulder and Elbow Surgeons Score (48.56 to 80.24), Visual Analog Scale (5.8 to 1.89), Single Assessment Numeric Evaluation (34.22 to 69.86), and Subjective Shoulder Value (52.24 to 77.66), were evident across all 5 studies. Preoperative to postoperative increases in ROM were seen for flexion (85 to 135), external rotation (18 to 52), and abduction (50 to 98). The overall complication rate was 18%, with seroma formation (8%) as the most common postoperative complication. Discussion/Conclusion Our analysis showed that LTT transfer improved postoperative function, ROM, and pain for patients with irreparable rotator cuff tears with an overall complication rate of 18%. Future controlled studies are required to directly compare LTT transfer to other tendon transfers and other surgical techniques for irreparable rotator cuff tears.

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Partial-width injuries of the rat rotator cuff heal with fibrosis.

Publications

Partial-width injuries of the rat rotator cuff heal with fibrosis.

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