Effect of Vitamin D Supplementation on the Rehabilitation of Patients After Rotator Cuff Tear Repair

Rotator cuff tears is one of the diseases that severely affect the movement of the shoulder joint in patients. The clinical manifestations of rotator cuff tears typically include shoulder pain, restricted range of motion, joint instability, muscle weakness, and functional disability. Epidemiological data reveal a progressive increase in the prevalence of rotator cuff injuries among middle-aged and older adults. The prevalence is estimated to be approximately 15-20% in individuals aged 60 years, 26-30% in those aged 70 years, and up to 50% in individuals aged 80 years.

Risk factors for rotator cuff tears are multifactorial, including age, smoking, hypercholesterolemia, history of trauma or repetitive overhead activity, dominant arm injury, and family history of shoulder problems. The wide variation in the causes of rotator cuff tears, coupled with the prevalence of asymptomatic tears, has contributed to a lack of standardization in treatment approaches. While physical therapy and regenerative medicine treatments, such as platelet-rich plasma (PRP) and stem cell therapy, have been explored as potential alternatives, evidence suggests that the intrinsic healing capacity of the rotator cuff is limited. Arthroscopic rotator cuff repair is considered the treatment of choice for acute tears across all age groups, as well as for patients under the age of 65 with chronic, large (>1 cm), reparable tears and no irreversible muscle changes. Despite advancements in surgical techniques, the rehabilitation process remains challenging due to the biomechanical complexity of the shoulder and the multifactorial nature of recovery. Many patients experience suboptimal outcomes, including muscle weakness, persistent pain, functional limitations, and re-tearing of the rotator cuff.

Vitamin D insufficiency or deficiency is widely recognized as being closely associated with the development of various conditions, including osteoporosis, fractures, and muscle weakness. It is estimated that up to 32% of the U.S. population and as many as one billion people worldwide are affected by Vitamin D deficiency or insufficiency (defined as a 25(OH)D3 level >20 ng/mL but <30 ng/mL). The prevalence of Vitamin D deficiency is notably high among orthopedic patient populations. A retrospective study revealed that 43% of patients undergoing preoperative evaluation exhibited Vitamin D insufficiency, with 40% classified as deficient. Vitamin D deficiency prevalence ranges from 8.3% to 71% in patients with rotator cuff tears. Vitamin D's impact on muscle strength and function has made it a subject of increasing interest in the management of musculoskeletal disorders, including rotator cuff injuries.

Current research on rotator cuff injuries has indicated a potential role for vitamin D in enhancing tendon healing. By inhibiting matrix metalloproteinases (MMPs), which hinder rotator cuff repair, vitamin D facilitates the accumulation of fibrocartilage and collagen, thereby improving tendon healing. Animal experiments have shown that vitamin D supplementation can enhance muscle fiber size, improve muscle function, reduce the expression of pro-fibrotic genes, and increase the expression of anti-fibrotic genes. This, in turn, helps mitigate muscle fatty infiltration and improve skeletal muscle quality regulation signaling pathways. One study reported through regression analysis that serum vitamin D levels were significantly negatively correlated with rotator cuff fatty degeneration. Furthermore, another study conducted muscle biopsies on patients undergoing rotator cuff repair and compared those deficient in vitamin D with patients who had sufficient levels. They found significantly increased expression of pro-inflammatory genes IL1β and IL6 in the deltoid and supraspinatus muscles of vitamin D-deficient individuals. This heightened postoperative inflammatory response may delay muscle repair and functional recovery, leading to suboptimal rehabilitation outcomes. Low vitamin D concentrations may serve as an independent variable contributing to fatty infiltration and degeneration of the supraspinatus and infraspinatus muscles. Another study demonstrated a significant association between low preoperative vitamin D levels and increased complications following rotator cuff repair. In patients undergoing arthroscopic rotator cuff repair, lower vitamin D levels were correlated with more severe muscle weakness at one year postoperatively. Additionally, preoperative vitamin D deficiency has been linked to higher re-tear rates and increased early postoperative pain.

Despite the promising evidence, the specific role of vitamin D in postoperative rehabilitation remains unclear. Given the ease of diagnosis and treatment of vitamin D deficiency, it is considered a highly modifiable risk factor in orthopedic care. Vitamin D supplementation holds promise as a cost-effective and efficient intervention that may improve postoperative outcomes, including enhanced muscle strength and joint function, in patients undergoing rotator cuff repair. Therefore, this study aims to investigate the effects of vitamin D supplementation on postoperative outcomes in patients undergoing arthroscopic rotator cuff repair. Using a randomized controlled trial (RCT) design, this study will evaluate the impact of vitamin D supplementation on muscle strength, postoperative pain, and joint function in patients with rotator cuff tears.