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BACKGROUND: Because of its regenerative potential, platelet-rich plasma, an autologous blood sample containing high-concentrations of growth factors, has been studied extensively both in the laboratory and in animal models. To date, platelet-rich plasma animal studies have been carried out in mammalian species. Chickens contain nucleated thrombocytes, rich in cytoplasmic granules that reportedly contain many of the growth factors contained within mammalian platelets. We aimed to separate the thrombocyte-rich fraction (TRP) from avian whole blood, deliver this growth factor-rich concentrate to a traumatic flexor tendon laceration and evaluate its effect on flexor tendon healing, specifically the formation of peritendinous adhesions.
METHODS: 9 chicken surgeries were performed on 18 digits (3rd, 4th digit). Prior to surgery, the digits were randomized to undergo laceration and repair - in an area homologous to zone two in the human hand -followed by the addition of thrombocyte-rich plasma (treatment) or closure without TRP (control). 5 cc of whole blood, separated via the Biomet GPS III system generated 1 cc of thrombocyte-rich concentrate. Post-operatively, all chicken feet were immobilized using a plaster cast. Three weeks later, subjects were euthanized and the tendons were examined histologically for the presence peritendinous adhesions by five independent, study-blinded pathologists. The specimens were graded on a previously validated scale of 1 to 5 and a mean value for each specimen was calculated. The difference in severity of tendon adhesions between the treatment and control groups was calculated using a paired t-test.
RESULTS: Mean adhesion score for the treatment group was 3.40 and mean adhesion score for the control group was 3.36 (p= 0.90). Mean Olympic adhesion scores (highest and lowest score not included) for the treatment and control tendons were 3.40 and 3.44, (p=0.91) respectively. A score of 3 suggests moderate adhesions, peritendinous space preserved in more than 50 % of the circumference and a score of 4 denotes severe adhesions, peritendinous space obliterated in more than 50 % of the tendon circumference. Adhesion formation varied between hosts, but there were no differences between treatment and control groups or between digits 3 and 4.
CONCLUSIONS: The efficacy and reproducibility of platelet-rich plasma delivery is controversial. The literature is varied with respect to its efficacy as a primary treatment or an adjunct following surgery. Laboratory evidence suggests that the addition of platelet-rich plasma may aid in tendon healing, but thus far there is no literature detailing its effect on adhesion formation.
Though we have shown no difference in adhesion formation between control and study tendons, there are two significant limitations to this study: our ability to reliably quantify the growth factors within the thrombocyte-rich fraction and to consistently deliver the same volume to the repair site. These limitations will be addressed in future studies.