Chronic Achilles pain affects a disproportionate amount of former runners compared to the general population. Over half (52%) of former runners suffer with Achilles tendinopathy; stiffness, and pain at the Achilles tendon. Recent advances in imaging have revealed that Achilles pain lasting longer that 3 months is associated with a thickening of tendon tissue. This article discusses common treatment options and recent studies showing how platelet rich plasma injections can benefit patients with refractory Achilles tendinopathy.¹

The Achilles Tendon and Tendinopathy Pathogenesis

The Achilles tendon connects the calf muscle to the heel bone, which means that this tendon is involved in every activity that moves the foot. It is composed primarily of type I collagen organized into fibrous tissues and tightly bound by matrix molecules (such as proteoglycans). The Achilles is the strongest and longest tendon in the human body, it’s elastic and can bear up to 3500 N or 790 lbs. of force before rupture.² While running, the elastic properties of the Achilles allow for energy recovery and power amplification. Evolutionary biologists emphasize how the storage of elastic energy in the Achilles lead to human bipedal running, a key turning point in the evolution of our species.³

Before the advent of magnetic resonance imaging, Achilles tendinopathy was often diagnosed as tendinitis. The key difference between tendinopathy and tendinitis is the role of inflammation in damaged tissue. With the use of imaging technologies, doctors are able to see that inflammation is not the key factor in Achilles tendinopathy. Instead, we find that Achilles tendinopathy develops from poor healing of accumulated micro-traumas. Micro-traumas accumulated from the stress of athletic activity and daily living. These tiny injuries may go unnoticed, but the tendon thickens over time and chronic pain develops.

How is Achilles Tendinopathy Treated?

There is no consensus in the medical community regarding treatment of Achilles tendinopathy. Common treatment options include; eccentric exercise, glyceryl trinitrate patches, micro-current and microwave electrotherapy, non‐steroidal anti‐inflammatory drugs (NSAIDs), corticosteroids, or orthotic treatments such as heel lifts, and specialized shoes to correct misalignment.

Studies have found NSAIDs to have little effect on chronic Achilles tendinopathy, which makes sense because inflammation is not a key factor in pathogenesis. Corticosteroid injections have been shown to relieve pain on a short term basis, but the effects don’t last. Compared to physiotherapy, pain and functionality outcomes with corticosteroid injections are worse at intermediate and long term follow ups. Adverse effects are reported in over 80% of studies involving corticosteroids and tendinopathy. Corticosteroid injections are also associated with Achilles tendon atrophy, according to a 2011 study.

Study Finds Positive Outcomes with PRP Injections for Achilles Tendinopathy

A 2014 study from researchers in Italy found long lasting positive outcomes for refractory achilles tendinopathy treated with platelet rich plasma injections.¹ The study included 27 patients, 7 of which had bilateral achilles tendinopathy for a total of 34 tendons treated. All patients had achilles tendinopathy lasting longer than 3 months which failed to respond to previous treatment. Researchers assessed each patient according to 4 separate metrics; the Blanzina scale grades tendinopathy severity from I to IV, the Victorian Institute of Sports Assessment – Achilles (VISA-A) is a subjective functional analysis, the EuroQol Visual Analogue Scale was utilized to assess general health, and the Tegner score was used to assess the patient’s level of athletic activity. Patients were assessed at baseline, two months, six months and up to an average of 4.5 years after PRP injections.

PRP was prepared from a 150 ml blood draw and spun at 1480 rpm for 6 minutes to separate erythrocytes and again at 3400 rpm for 15 minutes to concentrate platelets. The PRP preparation process produced four 5 ml tubes of leukocyte rich PRP. The researchers sent one tube to the lab for testing and found, on average, PRP serums had 5 times the platelets of whole blood. One tube was activated with 10% calcium chloride and immediately injected into achilles lesions under ultrasound guidance. Two remaining tubes were stored at -30 °C for later injections. Each tendon received a total of three PRP injections at two week intervals.

All recorded metrics improved over time. Improvement in EQ-VAS and VISA-A scores reached statistical significance at 2 months, VISA-A scores improved again at the 6 month follow up and both scores stabilized thereafter. Blanzina scores improved significantly at every evaluation and Tegner scores showed statistically significant improvement over time.¹

Efficacy of PRP Injections for Achilles Tendinopathy

Results of the aforementioned study show how sequential PRP injections can lead to positive outcomes for patients with refractory achilles tendinopathy without adverse side effects, though previous studies have found contrary results. One 2011 study from researchers in Rotterdam was designed to assess the effect of PRP on tendon structure. The researchers used colour doppler ultrasonography to assess tendon structure and compared a single 4 ml PRP injection with eccentric exercise to a single saline injection with the same exercise program. The PRP was prepared according to manufacturer’s protocols (‘Recover Platelet Separation Kit – Gravitational Platelet Separation’ III), but the procedure was not discussed. Ultimately researchers found no significant difference between the groups.

The significant differences between study designs and PRP preparation processes often leads to disparate results. For example, researchers in the Rotterdam study did not activate the PRP preparation, they instead relied upon local collagen for activation. This means slower platelet clot formation and increased potential for tendon contraction to squeeze the PRP away from the injection site. Also, the needling action from injecting the saline placebo could have it’s own therapeutic effects. Dry needling at the lesion site can contribute to an inflammatory response and increase local healing.¹

Biological Effects of PRP Injections for Tendinopathy

The efficacy of PRP injections for refractory Achilles tendinopathy depends on a number of variables including PRP preparation protocols, the total number of injections, activation of PRP serum prior to injection, and the age of participants. Once PRR is injected at the site of damaged tissue, the platelets degranulate and release growth factors, bioactive proteins such as platelet-derived growth factor and transforming growth factor which initiate a healing cascade that stimulates the gene expression of matrix molecules, regulates the proliferation and migration of mesenchymal stem cells, collagen synthesis and tendon cell proliferation.¹

References

    1. Filardo G, Kon E, Di Matteo B, et al. Platelet-rich plasma injections for the treatment of refractory Achilles tendinopathy: results at 4 years. Blood Transfusion. 2014;12(4):533-540. doi:10.2450/2014.0289-13.[ncbi]
    2. Freedman BR, Gordon JA, Soslowsky LJ. The Achilles tendon: fundamental properties and mechanisms governing healing. Muscles, Ligaments and Tendons Journal. 2014;4(2):245-255.[ncbi]
    3. Sellers WI, Pataky TC, Caravaggi P, Crompton RH. Evolutionary Robotic Approaches in Primate Gait Analysis. International Journal of Primatology. 2010;31(2):321-338.[ncbi]
    4. Alfredson H, Cook J. A treatment algorithm for managing Achilles tendinopathy: new treatment options. Br J Sports Med. 2007;41(4):211-6.[ncbi]
    5. Hart L. Corticosteroid and other injections in the management of tendinopathies: a review. Clin J Sport Med. 2011;21(6):540-1.[ncbi]
    6. De vos RJ, Weir A, Tol JL, Verhaar JA, Weinans H, Van schie HT. No effects of PRP on ultrasonographic tendon structure and neovascularization in chronic midportion Achilles tendinopathy. Br J Sports Med. 2011;45(5):387-92.[ncbi]

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