Sinus Tarsi syndrome is a condition that presents as lateral midfoot heel pain that is located in the “funnel-shaped” space between the calcaneus, talus, and talocalcaneonavicular and subtalar joints [1]. Patients with sinus tarsi syndrome generally complain of instability with functional activities and persistent anterolateral ankle discomfort [2]. The instability occurs when the associated ligaments are damaged or ruptured; clinically, compression of the sinus tarsi area elicits acute pain. Also, patients will frequently describe aching pain while lying on their back with their foot plantar flexed and inverted. Recent literature describes the instability primarily stemming from ligamentous injuries, inflammation from damage to the synovium, and fibrotic tissue infiltration of the subtalar joint space [2]. For decades, Parker Foot and Ankle have studied the innovations of the sinus tarsi and found that not only the superficial fibular but also the deep fibular nerve innervates the sinus tarsi area in the subtalar area with multiple branches. Injury in this area creates nerve pain, frequently experienced by patients, of burning, numbness, and tingling. The incidence rate of sinus tarsi syndrome is unknown, but it is proposed that a large percentage of reported ankle sprain injuries include an injury to the subtalar joint ligaments [3]. Treatment recommendations include balance and proprioceptive training, muscle strengthening exercises, bracing, taping, and foot orthosis. These treatments aim to allow the ligament to heal naturally. NSAIDs are often used to help with pain management. They function to decrease swelling and relieve pain, but they do not address the root problem. Steroid injections function similarly to reduce pain and swelling. With a short lifespan, several injections are often required, ultimately decreasing the cost-efficiency of the treatment. For patients who fail standard-care treatments and rehabilitation, the option of arthroscopy exists for a more precise examination of the joint and to allow for surgical treatment [4]. While surgery can be effective, it is invasive, and the mean return to total activity is four months.

Given that there is no single, optimal treatment option for sinus tarsi, there is a need for alternative interventions. This retrospective study assesses the efficacy of Wharton’s Jelly (WJ) application to the damaged ligaments to minimize the pain associated with sinus tarsi. WJ is a loose connective tissue found in the umbilical cord that cushions and protects the vessels within the cord from external forces and stretching. It contains collagen types I and III, hyaluronic acid, proteoglycans, growth factors, and cytokines that supplement the damaged tissue. This retrospective case series presents the application of WJ to ligament defects in the sinus tarsi of five females who have all failed previous standard-care treatments.

This study has shown significant pain improvement within a small cohort of females presenting with tissue defects to the sinus tarsi, causing pain and aching in the foot. Limitations of the study include a small cohort size along with following a non-blinded design. A small cohort size impacts the diversity of the patients, may present more variability in results, and cannot show statistical significance. The effect of a non-blinded study design may lead to the placebo effect. By not including a placebo, some patients may report an imagined improvement. The patients rated their pain on the NPRS scale to combat this effect. The results of this study warrant continued research on more extensive and more diverse cohorts to evaluate further the safety and efficacy of WJ in combination with EPAT, laser therapy, and a pneumatic boot to treat tissue defects associated with sinus tarsi. Each modality used in this study has an independent function and has been tested independently to show improvement in a patient’s path to recovery.

EPAT has been reported to show successful outcomes in treating Achilles tendinopathy in a study completed by Saxena, which included 60 patients who received EPAT treatment for three weeks [5]. This study discovered that 78.38% of tendons showed clinically significant improvement by at least one-year post-treatment. Another study by Furia, with 35 patients, produced similar results, stating that 83% of the cohort had shown successful results [6]. This study also identified that local field anesthesia may decrease the effectiveness of the EPAT procedure. Current literature agrees that EPAT is an effective technique in relieving pain and has the potential to promote exponential pain improvement associated with sinus tarsi defects when used in conjunction with WJ.

After EPAT and WJ Application, each patient received class IV laser therapy. Class IV laser therapy has been shown to reduce pain and inflammation and improve tissue quality. It also can decrease erythrocyte deformability and platelet coagulation, resulting in membrane revitalization, viscosity reduction, and erythrocyte stress adaptation [7]. Brandl found that blood flow increased significantly by 86.38 arbitrary units [7]. Decreasing erythrocyte deformability and platelet coagulation allows for more effective blood flow, which allows the body’s natural healing factors to be administered at a quicker rate, ultimately improving patient recovery.

The final aspect of the multi-modality patient care protocol is the pneumatic boot application and orthotics. The boot and orthotics function to stabilize and limit the range of motion to allow for safe and effective recovery while preventing further injury. While all care methods used have evidence of success when used independently, the protocol presented in this study was designed to maximize patient recovery by combining the benefits of each therapy for a higher success rate of patients who perceived pain improvements.

This study exemplifies significant pain improvement of the sinus tarsi ligaments after applying WJ in combination with EPAT, laser therapy, orthotics, and a pneumatic boot. The results align with other literature’s positive outcomes regarding each element used in the care procedure as stand-alone applications. Further research regarding the use of WJ for sinus tarsi ligament defects could be completed to compare the efficacy of WJ to standard-care treatments and surgery. Limitations to the study include a small cohort and a non-blinded design. A more extensive, more diverse, and randomized study would be beneficial in future studies to define dosage protocols further and confirm safety and efficacy.