A Closer Look At Platelet-Rich Plasma For Achilles Tendon Pathology
A recent double-blind, randomized study by de Vos and colleagues looked at PRP injection in patients with chronic Achilles tendinopathy.10 The study involved 54 patients who ranged between 18 to 70 years of age and were evenly divided into the PRP group and control group. The clinical diagnosis was based on findings of a painful and thickened tendon in relation to activity and on palpation with symptoms lasting greater than two months.
Researchers used 54 mL of whole blood to derive the PRP that was mixed with sodium bicarbonate to match the pH of tendon tissue.11 Study authors injected a non-disclosed amount of PRP into five sites along the injured tendon under ultrasound guidance. Patients were only allowed to walk short distances indoors in the first 48 hours. In days three to seven, patients were allowed walks up to 30 minutes. After one week, patients started an exercise routine with one week of stretching and a 12-week daily eccentric exercise program with heel drops off a step. The study authors allowed no weightbearing sports activities for four weeks followed by a gradual return to those activities. Patients were only to use acetaminophen during the follow-up period.
The results were based on patient questionnaires that quantified pain and activity level. The results showed an improvement in 24 weeks by 21.7 points in the PRP group and 20.5 points in the placebo group. The authors concluded there was no significant difference between the groups.11 This study is limited by a number of factors. They did not identify any characteristics of the anatomy of the tendon pre- and post-injection, neither clinically nor with imaging techniques. Their sample size was small. They could not quantify the concentrations of PRP that were used in each patient.
One can use PRP in the form of a fibrin gel (when combined with thrombin) as a tendon scaffold. Surgeons can use it as a bridge and augmentation within the rupture defect, or they can wrap it around the tendon repair. In most cases, surgeons combine the fibrin gel with bone marrow aspirate for further enhancement of the PRP matrix.
Researchers have also evaluated PRP for Achilles rupture repair in the rat model.15,18,19 In one study, surgically transected tendons treated with PRP showed a 42 percent increase in their force to failure, a 61 percent increase in ultimate stress and a 90 percent increase in energy after two weeks in comparison to the control.17 In another study, those tendons treated with PRP had a 30 percent increase in strength and stiffness after one week.20
Sánchez and colleagues investigated the augmentation of Achilles tendon rupture repair with PRP in athletes (six each in the PRP group and control group).21 They used two PRP preparations on the primary repair of the Achilles in comparison with controls. Researchers mixed 4 mL of PRP with CaCl2. This mixture formed a fibrin scaffold after 30 minutes and the researchers subsequently incorporated this into the repair site between the tendon ends. They again mixed the remaining PRP with CaCl2 but immediately sprayed it onto the wound site before closure.
Sánchez and co-authors followed the patients for one year via ultrasound imaging and physical examination.21 They found that in comparison to the control, the PRP group was able to return to mild running with earlier range of motion and without wound complication.