Abstract
Objectives:
The potential applications of platelet rich plasma (PRP) in orthopedics are vast, yet there remain many unanswered questions regarding the use of PRP for the treatment of soft tissue pathologies. For tendon injuries, there is strong evidence recommending leukocyte-rich PRP (LR-PRP) for lateral epicondylitis and promising evidence for patellar tendinopathy and rotator cuff injuries (1-4).
Apart from these conditions, evidence supporting routine use of PRP for tendinopathies is mixed or lacking standardization.
Proximal hamstring tendinopathy (PHT) is a common condition that can cause significant pain and dysfunction in active patients, recreational athletes, and professional athletes alike (5,6). Hamstring injuries account for 12-29% of all injuries in athletes, and approximately 12% of these are proximal hamstring tendon injuries (7-13). Currently, the body of research detailing the use of PRP for the treatment of PHT is sparse. A prospective cohort study and one retrospective chart review evaluated leukocyte poor PRP; the prospective study found no difference in patient reported outcomes (PROs) while the chart review found 80% subjective improvement (6,15). Three more Level IV studies found significant improvement in patient-reported pain and function scores following PRP but did not consistently report the type of PRP used (16-18). None of these included information on PRP volume injected or amount of time from blood draw to injection.
PRP has generated much interest in the orthopedic sports community given the prospects of enhanced healing, improved function, and reduced pain. However, current literature assessing the efficacy of PRP for PHT is mixed. The sound scientific principles behind PRP, success of PRP in other tendinopathies, and high prevalence of PHT urge us to better understand the role of PRP in PHT treatment. This study examines the effect of standardized LR-PRP injections for PHT on patient-reported pain and physical function outcomes at 2-week, 3 months, and 6-month timepoints. The study also evaluates any impact that volume of PRP injected or time from blood drawn to PRP administration may have on PROs.
Methods:
Following IRB approval, subjects who were enrolled in a PRP Data Registry and who had a PRP injection for documented PHT were included in this study. Exclusion criterion was age less than 18 years. All injections were prepared in the same fashion and administeredby the same physician using Zimmer Biomet LR-PRP with GPS III Platelet Concentration System. Each patient had 25-25.5 cc of blood drawn per hamstring, with 4.5-5cc of anticoagulant added. All were centrifuged for 15 minutes resulting in 2- 6ml of LR-PRP. Following collection and centrifuge, LP-PRP was injected under ultrasound guidance.
De-identified data was collected from September 2020 to August 2022. When bilateral injections occurred, each injection was treated separately. The following items were collected: time from blood draw to injection, volume of LR-PRP injected, standardized PRO measures, and a unique patient survey (Table 1).
A one-sided paired t-test was completed for each patient’s PRO score between baseline and each time intervals (alpha 0.05) and summary statistics were collected. Pearson correlations were performed for PRP volume and PRO results as well as between time from blood draw to injection and PRO results.
Results:
16 patients (17 hips) met inclusion criteria. 6 patient forms were completed at various timepoints (Table 2). 3 of these forms were standardized PRO surveys and 3 collected the information demonstrated in Table 1. The median volume of PRP injected was 3.2mL (2.5mL – 4mL) and the median time from blood draw to PRP injection was 34.0 minutes (18 – 50 minutes). An increasing proportion of patients reported satisfaction with their injection across all timepoints. PROMIS Pain scores significantly improved from baseline vs 2WPI (p = 0.03551, n = 17), baseline vs 3MPI (p = 0.003371, n = 15), baseline vs 6MPI (p = 0.006832, n = 11) and baseline vs 1YPI (p = 0.01858, n = 6). PROMIS Physical Function test showed significant improvement at baseline vs 3MPI (p = 0.03042, n = 14), baseline vs 6MPI (p = 0.01469, n = 11) and baseline vs 1YPI (p = 0.04541, n = 6). The iHOT test showed significant improvement from baseline to 1 year post injection (p = 0.03936, n = 5). There was a high correlation between PRP volume and iHOT scores at 1YPI (r = -9023969). There was moderate correlation between PRP volume injected and both PROMIS Pain scores at 1YPI (r = 0.6775792) as well as PROMIS Physical Function scores at 1YPI (r = -0.6559364).
Conclusions:
This study aimed to examine the effect of LR-PRP injections for PHT on patient-reported pain and physical function outcomes and to assess for any difference in outcomes related to volume of PRP injected or amount of time from blood draw to injection. The results demonstrate that PROMIS Pain and PROMIS Physical Functions scores at 3 months, 6 months and 1 year were significantly improved compared to baseline. A strong correlation was demonstrated between increased PRP volume injected and improved iHOT scores. Correlations were also found between increased PRP volume and improved pain and function PRO measures. While this study is currently limited by a small sample size, the data reported here is part of a growing database for PRP injections. The results of this study add to the limited body of literature on LR-PRP for PHT and may support the use of LR-PRP for improving patient hip pain and function associated with PHT.
