Does PRP Have Promise For Advanced Posterior Tibial Tendinopathy In Athletes?

The posterior tibial tendon, due to its anatomical structure, is prone to interstitial tearing as it degenerates, causing progressive debilitating disease, which clinicians commonly refer to as tendinosis or tendinopathy.  

Like the Achilles tendon, the posterior tibial tendon has an area of hypovascularity, which makes it more susceptible to injury. Unlike the Achilles tendon, posterior tibial tendinopathy is eventually accompanied by the collapse of the foot into valgus deformity. This acquired flatfoot deformity may eventually develop arthritis of the hindfoot joints.¹

The retromalleolar area is the most frequently ruptured area of the posterior tibial tendon.² It receives the majority of its blood supply from branches of the posterior tibial artery.¹ The muscular branches supply the proximal portion of the posterior tibial tendon.¹ The paratenon has web-like blood vessels, which enter the posterior tibial tendon, and is well-vascularized.² It anastomoses with the longitudinal arterial network in the tendon, which is inhomogeneous.² The periosteal branches feed the distal portion of the posterior tibial tendon.1 When the tendon passes behind the medial malleolus, the intratendinous arterial network is interrupted, which causes the anterior portion of this area to be avascular.² Due to the posterior tibial tendon’s area of hypovascularity, researchers believe the tissue degenerates through hypoxia or repetitive microtrauma.^1,2 A study by Petersen and colleagues found there was a significantly reduced intravascular volume in the retromalleolar region in comparison to the distal and proximal portions of the tendon.²  

Prado and coworkers believe the retromalleolar area is vulnerable to rupture due to mechanical stress from friction behind the bone.³ From their immunohistochemical findings, Petersen and coworkers found there is also no laminin in the anterior tendon in the avascular area.² In place of the laminin, which makes up the basement membrane, fibrocartilage prevents friction and deterioration of the tendon.^2,3 Since the posterior tibial tendon changes direction while coursing behind the medial malleolus, the avascular area corresponds to areas that need fibrocartilage for a gliding zone.² The fibrocartilage makes the tendon susceptible to degeneration.          

Key Insights On The Healing Potential Of PRP       

There are conservative and surgical treatment options for posterior tibial tendon dysfunction. Generally, one would reserve conservative options for milder disease and poor surgical candidates. Conservative treatment includes a medial wedge, ankle-foot orthotics (AFO), orthotics and temporary immobilization.⁴ Surgical treatment includes tenosynovectomy, flexor digitorum longus tendon transfer, calcaneal osteotomy, lateral column lengthening, heel cord lengthening and triple arthrodesis.⁴

Platelet-rich plasma (PRP) is an autologous blood product, which releases growth factors and bioactive molecules when the platelets are activated.^5,6 Platelets are part of the process of hemostasis.⁷ Platelet-rich plasma has three to five times the normal platelet concentration found in plasma, which consists of growth factors, cytokines and biofactors. Growth factors are needed in all phases of tissue healing and assist in protein formation, which initiates many regenerative pathways. Once injected, PRP can enhance the recruitment, proliferation and differentiation for tissue regeneration.⁶ In a review by Baksh and colleagues, eight in-vivo studies showed decreased tendon repair time and increased fiber organization, and eight in-vitro studies found increased cell proliferation with PRP treatment.⁸          

Over the last few years, there has been extensive discussion about PRP in the orthopedic literature.⁶ Surgeons have used PRP injections for rotator cuff tears, lateral epicondylitis and arthritic knee joints. Of interest, increasing studies have focused on Achilles tendinopathy and plantar fasciitis.⁶ The efficacy of PRP administration for musculoskeletal conditions remains controversial. There is no standardized way of administering PRP and the preparation, methods and postoperative care have differed in the randomized controlled studies in orthopedic literature.⁸ However, because PRP is an autologous agent, it avoids potential reactions to other products and researchers have demonstrated that PRP is safe.⁸ Thus far, there have not been any studies particularly focusing on the effects of PRP injections on the posterior tibial tendon.

Case Study: When An Active 50-Year-Old Patient Has Had Left Medial Ankle Pain For Two Years

A 50-year-old physically active male presented to the clinic two years after the onset of left medial ankle pain. He denied any particular trauma but stated that he ran frequently and played soccer at least twice a week. He failed conservative care attempts. Other physicians suggested calcaneal osteotomy and posterior tibial tendon transfer.

The patient presented to the senior author for a second opinion. His left foot was pronated but symmetrically the same, and he had pain along the posterior tibial tendon, particularly distal to the medial malleolus. Magnetic resonance imaging (MRI) showed severe posterior tibial tendinitis with a longitudinal tear at the level of the malleolus. The patient did not display evidence of hindfoot arthrosis. The senior author advised him to consider calcaneal osteotomy and posterior tibial tendon transfer. However, the senior author cautioned the patient that if he had this traditional surgery, his goal of returning back to soccer could not be guaranteed.

After eight months of contemplating surgery, the patient solicited other opinions and had another MRI, which showed further degeneration with advanced tendinopathy in comparison to his previous MRI. The patient continued to decline a calcaneal osteotomy and tendon transfer. For an alternative option, we discussed an isolated primary repair and PRP injection. He received instruction that there were no long-term studies on PRP and, if he proceeded with the PRP option, he may need additional surgery in the future. Accepting these limitations, the patient elected to move forward with a repair of his posterior tibial tendon and PRP injection.

The patient was otherwise healthy. The procedure occurred with the patient under general anesthesia. After harvesting of 30 mL of the patient’s blood in a sterile manner for the PRP injection, we utilized the GPS III Platelet Concentration System (Zimmer Biomet).

In regard to the procedure, one would prep the left lower extremity and drape it in a sterile fashion. Make a 10 cm curvilinear incision along the course of the posterior tibial tendon, starting proximally at the medial malleolus and continuing it down distally to the insertion site. We raised a U-shaped periosteal flap off the medial malleolus as a reference point for closure. Then we identified the longitudinal tear on the posterior tibial tendon and along the medial malleolus, and proceeded to debride any frankly degenerative tendon.

We extracted the platelet concentrate from the GPS III tube and combined half of it with thrombin. Then we placed this activated PRP, in clot form, into the tendon defect created by the debridement of the abnormal intratendinous tissue. We proceeded to repair the tendon with a continuous running 4-0 Mersilene (Ethicon) suture. In this case, we injected the remaining half of the platelet concentrate proximally and distally to the tear, where early tendinitis was visible on the MRI but where there were no frank tears in this region. Then we repaired the flap by inserting a 3.0 Arthrex suture anchor into the medial malleolus and subsequently performed a complete layered closure. After deflation of the ankle tourniquet, the patient received a local injection of Marcaine 0.5% plain in the ankle.

The patient’s recovery was uneventful. He started passive sagittal plane limited motion at four weeks while he was in the posterior splint. The patient wore a controlled ankle motion (CAM) walking boot at six weeks and started partial weightbearing. The patient transitioned to full weightbearing in the CAM boot at eight weeks. At 12 weeks, we instructed him to wear an ankle brace and he started physical therapy. The patient started using the elliptical machine at 18 weeks, began running on a treadmill gradually at 24 weeks and had no symptoms. He returned to playing soccer at 31 weeks without any complications and had orthotics made for daily use and sports.

At nine months postoperatively, the patient had an MRI, which showed an improved postoperative appearance to the tibialis posterior tendon in comparison to a prior MRI. We instructed him to be cautious while progressing to his regular sporting activities as tolerated. Five years after his surgery, he had another MRI, which showed a normal posterior tibial tendon.  

What The Research Reveals About PRP In Athletes

For an athletic patient whose goal is to return to sports, traditional treatment options for posterior tibial tendon dysfunction are not practical.

Tellisi and coworkers did a study that looked at surgical reconstruction for stage 2 posterior tibial tendon insufficiency in active patients under the age of 50.⁹ The authors do note that previous studies have shown good intermediate and long-term results for older, less active patients. Out of all 30 patients, all had a flexor digitorum longus tendon transfer and calcaneal osteotomy with others having additional procedures. Overall, they noted postoperative improvement with more of their patients being able to walk for daily activities or exercise. The study authors also cited significant improvement in the Short Form-36 (SF-36) physical subcomponent and the American Orthopaedic Foot and Ankle Society (AOFAS) score, demonstrating that these procedures are sensible options for posterior tibial tendon dysfunction. However, only five of the study patients were able to return to running or moderate athletics.   

There is a demand to search for alternatives for athletes, who not only desire relief of symptoms but would also like to participate in higher-level activities. So-called tendon wraps to augment diseased tendons are available although functional outcome studies for posterior tibial tendon dysfunction are lacking.

Regenerative medicine has emerged as an alternative approach to traditional surgery to address such issues. However, the efficacy of using such biologics remains controversial. One such example is the use of PRP. Numerous studies have looked at the benefits of PRP in the lower extremity for Achilles tendinosis and chronic plantar fasciitis. The senior author was involved in a retrospective study comparing patients who had Achilles tendon surgery and PRP injections or PRP injection alone.⁶ The study compared MRI and clinical changes in pre- and post-treatment. The study authors found that both interventions had statistically significant improvement post-treatment but there was no significant difference between the two treatment types.

Platelet-rich plasma appears to be promising for the treatment of tendinopathy but there needs to be further study for the posterior tibial tendon.⁶ Results with one tendon do not imply success with other tendons.

Very few studies have examined the effects of PRP on the posterior tibial tendon. All of the studies involving the posterior tibial tendon had small sample sizes and include evaluation of other foot tendinopathies. Angthong and colleagues injected four posterior tibial tendons in three patients.⁵ There was significant difference between the pre- and post-treatment Visual Analogue Scale Foot and Ankle (VAS-FA) scores, but not for the SF-36 score.⁵ Finoff and coworkers included one patient with a posterior tibial tendon PRP injection.¹⁰ The study authors looked generally at foot tendinopathy and reported improved function scores, pain scores and echotexture on ultrasound.

The use of PRP for treatment was inconclusive in regard to benefits in these studies.⁵ One study mentions the use of PRP for “early stage PT tears” but offers little more in regard to the actual severity of disease, MRI staging of the patients and the activity level of the treated patients.¹¹

It is essential to recognize that posterior tibial tendon dysfunction is unique in comparison to other tendinopathies because it is often accompanied by progressive deformity.¹ As the diseased tendon degenerates, it elongates, leading to collapse of the foot.¹ Many patients with posterior tibial tendon dysfunction have preexisting pronated feet and equinus.¹ All of these issues typically necessitate calcaneal osteotomy and considerations for posterior release. In our patient, there was pronation but not worse than what he had on the contralateral side. We felt that orthotic control would prove adequate in preventing excessive loading of the repaired tendon. We suspect that calcaneal osteotomy would be necessary in cases in which pronation control is not expected postoperatively.

The aforementioned patient initially had advanced tendinopathy and was forced to give up athletic activities. Currently, as of a recent five-year follow up visit, the patient has no return of symptoms, has a normal appearing tendon on follow-up MRI and actively engages in competitive soccer. However, this is only a case report so it is hard to draw any concrete conclusions with this case.

In Conclusion

There is still a need for prospective randomized studies with larger sample sizes to evaluate the longevity of the results and possible long-term complications. However, for active patients with advanced posterior tibial tendinopathy, who do not display resultant collapse or associated hindfoot arthrosis, primary debridement and repair of the tendon and PRP injection may offer potential hope as an alternative combination treatment option. We hope this article will generate further studies for this complex condition, particularly in regard to active patients with posterior tibial tendon dysfunction.

Dr. Oloff is in private practice at Sports Orthopedic and Rehabilitation Medicine Associates in Redwood City, Calif. He is the team podiatrist for the San Francisco Giants.

Dr. Lam is affiliated with St. Mary’s Medical Center in San Francisco.

References

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