Study examines treatment effects in insertional and noninsertional cases

Pain of the Achilles tendon is among the most frequent causes of pain among patients seen at foot and ankle practices. The common cause, chronic Achilles tendinosis, is the result of poor vascularization and of microtears in the collagen fibers due to repetitive overuse.

At the 2010 annual meeting of the American Orthopaedic Foot & Ankle Society (AOFAS), Martin J. O’Malley, MD, reviewed his experience with platelet-rich plasma (PRP) in managing Achilles tendinosis. His retrospective study demonstrated good outcomes in patients treated with PRP.

Dr. O’Malley noted that the hallmark of tendinopathy is the presence of degenerative changes, including disorganized collagen fibers and neovascularity. The poor vascularization hampers repair, he noted. Treatment, therefore, should focus on “jump starting tissue repair and regeneration rather than reducing an inflammatory process,” he said.

Common conservative treatments include physical therapy, eccentric stretching exercises, corticosteroid injections, and glyceryl nitrate patches. But Dr. O’Malley pointed out that conservative treatment is unsuccessful in 25 percent to 45 percent of patients.

Growth factors at work
In such cases, PRP has a strong theoretical potential. Healing of hard and soft tissue is mediated by the expression and proliferation of an array of growth factors, which are released with the activation of platelets. By definition, Dr. O’Malley noted, PRP is the plasma portion of whole blood (prepared in a centrifuge or by filtration) that contains a higher level of platelet and growth factors than baseline. In in vitro studies, the growth factors released during coagulation have been shown to increase the survival, proliferation, and angiogenesis process of human tendon cells.

His study reviewed 34 consecutive patients who were treated with PRP for noninsertional (20) and insertional (14) Achilles tendinosis and had symptoms lasting more than 6 months. Conservative treatment had failed and patients had no history of Achilles tendon surgery. The average length of symptoms was 15 months (range 6 to 60 months). All the patients were considered candidates for surgery.

The patients were instructed to stop taking nonsteroidal anti-inflammatory drugs 2 weeks before the procedure. The PRP injection was done by one surgeon under ultrasound guidance, with local anesthesia.

After the procedure, the patients were prescribed 2 weeks in a CAM boot, with weight bearing as tolerated and instructions to exercise and stretch. All patients had a follow-up examination at 4 weeks.

After the initial injection, 10 patients (4 with insertional and 6 with noninsertional tendinosis) reported complete relief of symptoms. Eight patients who were not satisfied with the results from a single injection received a second one. At final follow-up, a total of 19 patients (8 with insertional and 11 with noninsertional tendinosis) had improved and no longer required medical treatment (Fig. 1). Five patients (3 with insertional and 2 with noninsertional tendinosis) underwent surgery at an average of 59 days after the last injection.

There were no complications—specifically, no cellulitis, superficial or deep tissue infections, or tendon rupture. The most common complaint was postinjection pain.

Patients were asked to complete the Foot and Ankle Outcome Score (FAOS), visual analog scale (VAS), and SF-12 prior to the initial injection and at a minimum of 6 months after the last injection. Overall, significant improvement was seen in VAS scores and in the pain, symptoms, and quality of life subscales of the FAOS scores. VAS scores for patients with insertional tendinosis improved from 6.3 to 4 (p <0.005); scores for patients with noninsertional tendinosis improved from 5.5 to 3.3 (>p <0.001).>

Discoveries await
Dr. O’Malley noted that in addition to the use of PRP, variables in the study that could have contributed to or accounted for the favorable result were the CAM walker boot, the prescribed eccentric stretching, and the stimulation by the needle. His own study has the limitation of no placebo, and its retrospective nature “may have introduced variability in the postinjection recovery.” Furthermore, he said, it did not vary the PRP concentration, “which has been shown to correlate with the age and the gender of the donor, as well as the platelet count.”

“Each of these products has a different concentration,” he said. “Some scientists at our institution say you can overstimulate receptors if the growth factors are too high.” He noted that small office systems yield PRP that vary in platelet collection from 35 percent to 85 percent of available platelets, with concentration varying from two- to eightfold.

Because most clinical studies have shown “encouraging outcomes,” Dr. O’Malley said, further randomized controlled trials are warranted.

User-friendly
Dr. O’Malley started exploring the use of PRP several years ago, with the advent of tabletop machines for processing the blood. Once he became convinced that it was safe for patients and easy for staff to administer, he began to study its use in earnest.

He noted the purchase and use of ultrasound equipment—which he uses for localization and not for diagnosis—may require a learning period. Although he initially used an 18-gauge needle, he went to a smaller gauge to prevent the PRP from backing out.

“My office staff likes to do it,” he said, and “the patients like having an alternative to surgery.”

Disclosure information: Dr. O’Malley reports no conflicts.

Terry Stanton is senior science writer for AAOS Now. He can be reached at tstanton@aaos.org

Bottom line

• Chronic Achilles tendinosis is partly related to poor vascularization but not to an “inflammatory” process.
• Growth factors released by platelet activation upon interaction with collagen may promote healing.
• Patients receiving PRP injections showed significant improvement in this small, retrospective study of one doctor’s patients.
• Further randomized, controlled trials are warranted.