by Tyler Tice, PT, DPT, MS, ATC
Background:
Rotator cuff disorders have been reported to occur in 30-50% of people over the age of 50 and the number of rotator cuff repair surgeries performed each year continues to rise. The rotator cuff is comprised of four muscles: supraspinatus, infraspinatus, teres minor, and subscapularis, and plays a vital role in stabilizing the shoulder during arm movements. Previous research has demonstrated that rotator cuff healing correlates with outcome. In patients that had an intact supraspinatus had improved functional outcome scores and satisfaction, along with a reduction in osteoarthritis progression compared to those who experience a re-tear. In surgeries that were deemed to be biomechanically superior, research has demonstrated only modest improvements in healing rates. This suggests a need for further improvement in the biological environment rather than the mechanical environment to substantially improve rotator cuff healing.
Pathology of rotator cuff tendon:
Rotator cuff disease is a spectrum ranging from tendinopathy to eventual degenerative tear. One research study has suggested the gradual degeneration of the tendons occurs as a consequence of simple anatomical variation, inciting repetitive microtrauma to the rotator cuff. Because of the repetitive trauma and inefficient loading of the tendon that would assist in the natural repair process, eventual tendon failure will occur, resulting in a tear. After undergoing a surgical repair, remodeling at the site where the tendon meets the bone gradually occurs over time. Animal studies have demonstrated that following repair the tensile strength that is achieved is approximately half the amount of normal tissue, putting the individual at risk for a re-tear.
Patient factors and clinical decision making:
Prior to any surgical procedure, there is the potential to influence the biological environment and outcome of repair through clinical decision making. Patient factors to consider are history of smoking and presence of comorbidities such as Diabetes Mellitus (DM). Presence of factors like this have been shown to have negative impacts on tendon healing, which would put the patient at further risk for re-tear following repair. A patient’s BMI may also play a role in tendon healing, however there is current insufficient evidence available. History of receiving corticosteroid injections have also been shown to impact tendon healing, despite them frequently being used in the treatment of rotator cuff disease. The size and location of the rotator cuff tear as well as fatty infiltration has also been shown to impact post-repair outcomes. In animal studies, vitamin D levels have been implicated in cuff healing however there is insufficient evidence in human studies.
Growth factor/cytokine-based augmentation:
Growth factors have the potential to improve the environment in which the repair occurs.
Matrix metalloproteinase (MMP) inhibitors: One study demonstrated tendon degeneration in the presence of overactivity of MMPs or underactivity of tissue inhibitors. One animal study demonstrated the effectiveness in MMP inhibitors following repair however further research in human participants needs to be conducted.
Rotator cuff repair and platelet rich plasma (PRP): One meta-analysis demonstrated a significantly higher healing rate in small-medium and medium-large rotator cuff tears when PRP was administered at the time of surgery. Another meta-analysis demonstrated conflicting results regarding the use of PRP as both groups, control and experimental, had significant reduction in re-tears. One study proposed delayed application of PRP intra-operatively may be more beneficial and improve retention at the repair site, however no significant improvement in healing or functional outcomes was observed.
Partial thickness rotator cuff tear/tendinopathy and PRP: One meta-analysis demonstrated short-term benefit from receiving a PRP injection in the non-operative management of either partial rotator cuff tear or tendinopathy. Another study demonstrated PRP injections were only beneficial in reducing pain in rotator cuff tendinopathy after 24 weeks, however no functional improvement was observed at any point throughout the study.
Stem cell-based augmentation:
There are a number of techniques that have been developed to be utilized in treating rotator cuff tears and tendinopathies. However, research on these techniques either has shown minimal benefit in the utilization of these procedures or were tested on small sample sizes, making the application of the results difficult to the general population.
Biomaterials/scaffold-based augmentation:
In rotator cuff repairs, scaffolds are principally used to mechanically and/or biologically augment the repair site. They improve the biomechanics of the repair site and induces a more acute inflammatory response for improved healing. Extracellular matrix (ECM) scaffolds are biocompatible as they can be derived from human or animal sources, however there is an argument that re-purposed and structurally do not resemble tendon. In two studies that utilized this type of scaffold, reduced re-tear rates were observed up to two years after the surgical procedure. Synthetic scaffolds have also been utilized and research has demonstrated reduced re-tear rates in those who receive this type of scaffold vs. control participants. Degradable synthetic scaffolds are recently emerging, however current research demonstrates high re-tear rates after 1.5 years post-surgery. Bio-inductive scaffolds that are designed to induce biological repair while having little to no mechanical support to repair construct. There is currently little research regarding this technique, however smaller studies utilizing it have produced promising results.
Take Home Message:
There are a number of biologic techniques that are available to improve tendon healing either rotator cuff tendinopathy or following rotator cuff repair. Those who are experiencing rotator cuff tendinopathy or have sustained a rotator cuff tear should look into their available options for treatment before considering surgical intervention. Keeping open communication with your doctor about different ways to manage pain and function will ultimately give you the tools to manage your diagnosis in a way that is most suitable to you.
Reference:
Rohman, M. L., & Snow, M. (2021). Use of biologics in rotator cuff disorders: Current concept review. Journal of clinical orthopaedics and trauma, 19, 81–88. https://doi.org/10.1016/j.jcot.2021.05.005