Can a simple fall cause a rotator cuff tear? Literature review and biomechanical considerations

Establishing a rabbit model with massive supraspinatus tendon defect for investigating scaffold-assisted tendon repair

BACKGROUND

Shoulder pain and disability from rotator cuff tears remain challenging clinical problem despite advancements in surgical techniques and materials. To advance our understanding of injury progression and develop effective therapeutics using tissue engineering and regenerative medicine approaches, it is crucial to develop and utilize animal models that closely resemble the anatomy and display the pathophysiology of the human rotator cuff. Among various animal models, the rabbit shoulder defect model is particularly favored due to its similarity to human rotator cuff pathology. However, a standardized protocol for creating a massive rotator cuff defect in the rabbits is not well defined. Therefore, the objective of our study was to establish a robust and reproducible model of a rotator cuff defect to evaluate the regenerative efficacy of scaffolds.

RESULTS

In our study, we successfully developed a rabbit model with a massive supraspinatus tendon defect that closely resembles the common rotator cuff injuries observed in humans. This defect involved a complete transection of the tendon, spanning 10 mm in length and encompassing its full thickness and width. To ensure stable scaffolding, we employed an innovative bridging suture technique that utilized a modified Mason-Allen suture as a structural support. Moreover, to assess the therapeutic effectiveness of the model, we utilized different scaffolds, including a bovine tendon extracellular matrix (ECM) scaffold and a commercial acellular dermal matrix (ADM) scaffold. Throughout the observation period, no scaffold damage was observed. Notably, comprehensive histological analysis demonstrated that the regenerative tissue in the tendon ECM scaffold group exhibited an organized and aligned fiber structure, indicating tendon-like tissue regeneration while the tissue in the ADM group showed comparatively less organization.

CONCLUSIONS

This study presents a comprehensive description of the implemented procedures for the development of a highly reproducible animal model that induces massive segmental defects in rotator cuff tendons. This protocol can be universally implemented with alternative scaffolds to investigate extensive tendon defects and evaluate the efficacy of regenerative treatments. The application of our animal model offers a standardized and reproducible platform, enabling researchers to systematically evaluate, compare, and optimize scaffold designs. This approach holds significant importance in advancing the development of tissue engineering strategies for effectively repairing extensive tendon defects.

[Can a fall onto the shoulder (direct impact) cause a rotator cuff tear?]

The question of whether a fall directly onto the shoulder can cause a rotator cuff tear has occupied doctors (and courts) for many years. Experts who rely on the medical insurance literature usually reject the causality of the incident. There are no scientific studies on this. The report below describes a typical case in which a fall directly onto the shoulder caused a massive rotator cuff tear.

Combination of autologous osteochondral and periosteum transplantation effectively promotes fibrocartilage regeneration at the tendon-bone junction of the rotator cuff in rabbits

PURPOSE

Rotator cuff tendon-bone healing often leads to scarring and low biomechanical strength, resulting in a tendency to re-tear. This study examined whether combining autologous osteochondral transplantation and periosteum transplantation increases fibrocartilage transition zone regeneration and improves biomechanical fixation.

METHODS

A total of 48 New Zealand white rabbits were divided into the periosteum, autologous osteochondral, combination of autologous osteochondral and periosteum, and control groups. The supraspinatus tendon was cut from the greater tuberosity and repaired by different transplants. A total of 12 rabbits were used for histological examination (haematoxylin and eosin staining, Masson's staining and Safranin-O staining) at 4, 8 and 12 weeks after the repair, and 36 rabbits were used for biomechanical tests (maximal failure load and stiffness).

RESULTS

At 4 weeks following the operation, each group had a large tendon-bone gap with a small number of disordered collagen fibres. At 8 weeks, the tendon-bone gap was smaller than that before the operation, and the tendon-bone gap in each experimental group was smaller with neater and denser collagen fibres and chondrocytes than in the control group, with the osteochondral combined periosteum group having the best results. At 12 weeks, the typical tendon-bone transitional structure was observed in the osteochondral combined periosteum group, and more collagen fibres and chondrocytes were generated in each group. The osteochondral combined periosteum group had the largest staining area and the largest amount of cartilage. The maximum tensile strength and stiffness of each group increased over time. There was no significant difference in each group's maximum tensile strength and stiffness at 4 weeks after the operation. However, the maximum tensile strength and stiffness of the osteochondral combined periosteum group at 8 and 12 weeks after operation were significantly higher than those of other groups (P < 0.05).

CONCLUSION

Histological and biomechanical results show that autologous osteochondral transplantation combined with periosteum transplantation can effectively promote the regeneration of fibrous cartilage in the tendon-bone junction of the rotator cuff. It is concluded that this technique is a new treatment method to promote tendon-bone healing in the rotator cuff.

[Evaluation methods of postoperative healing of supraspinatus tendon tear]

Objective

To summarize the evaluation methods of postoperative healing of supraspinatus tendon tear in recent years, in order to provide reference for clinic.

Methods

CNKI, Wanfang, PubMed, and Foreign Medical Literature Retrieval Service (FMRS) databases were used to search the literatures between 2005 and 2022. The literature related to the diagnosis and postoperative healing of supraspinatus tendon tear was included. Finally, 50 articles were reviewed.

Results

Supraspinatus tendon tear is a common shoulder disease. Physical examination, clinical score, and imaging examination are used to predict and evaluate the postoperative healing. Among them, physical examination and clinical score are non-invasive and the most economical methods, but their accuracy and sensitivity are lower than imaging examination, so they can only be used as auxiliary methods. The acromio-humeral distance (AHD) and upward migration index (UMI) measured by X-ray films can directly reflect the change of supraspinatus tendon thickness, but they are impossible to distinguish whether there is tear or not. Ultrasound and MRI are the main methods for the clinical diagnosis of supraspinatus tendon tear, but the commonly used MRI sequence can not accurately judge the internal healing of the tendon. Shear wave elastrography (SWE) and ultrashort-echo-time (UTE) techniques are the latest research directions in recent years, but different studies have shown opposite conclusions on the application of SWE technique. This conclusion shows that the principle of SWE technique and its relationship with tendons need to be further studied. UTE technique has good clinical effect, and the T2* value obtained by UTE technique is more accurate than that of traditional Sugaya typing, but there are still few research samples.

Conclusion

AHD and UMI measured by X-ray film and T2* value measured by UTE technique can be used as effective methods for evaluating the healing of supraspinatus tendon tear after repairing, and can be used as a follow-up evaluation method combined with physical examination and clinical score for patients with supraspinatus tendon tear.