Nonsurgical treatment of partial ACL tears: intraarticular injection of Platelet-rich plasma did not change the progression rate to knee instability

OBJECTIVE: Diagnosis and treatment of partial tears of the ACL remains controversial. Patients that present a hard end positive Lachman and negative pivot shift in the context of a partial tear in the magnetic resonance imaging (MRI) have a healing potential that could avoid surgery. Platelet-Rich-Plasma (PRP) provides certain growth factors that could improve healing and therefore, clinical outcomes after partial ACL tears. The aim of this study was to report the results of autologous intraarticular PRP injection in patients with partial ACL tears. METHODS: Prospective cohort of patients between 2015 and 2017 with acute ACL partial tear, treated either with autologous PRP therapy combined with a rehabilitation protocol (group 1) or rehabilitation alone (group 2). The primary outcome was to evaluate return to sports and recurrent knee instability requiring surgery. We performed pre and postoperative subjective evaluation using Tegner, IKDC and Lysholm scores and an objective evaluation using KT1000 arthrometer. and return-to-sports were performed. An MRI was performed at 6 months. Platelets and leukocyte concentration in PRP preparation was analyzed RESULTS: A total of 40 patients were included in this study, 21 in group 1 and 19 in group 2. Median age was 26 yeas (IQR 22-35), 85% (n=34) were men with a median follow up of 12 months (IQR 8–15). Eighteen patients (85%) in group 1 and 15 (79%) patients in group 2 were Tegner 7 or above. All patients returned to sports at a mean of 3.8 months in group 1 and 4.2 months in group 2. Five (23,8%) patients in group 1 (1 proximal and 4 mid-third lesions) and four (21%) in group 2 (3 proximal and 1 mid-third lesion) failed and had an ACL reconstruction because of knee instability (p 0.99). All after a new sport trauma. Lysholm score improved from 62 (SD 20) to 70 (SD 24) in group one and from 67 (SD 14) to 74 (SD 16) in group 2. IKDC score improved from 51 (SD 11) to 68 (SD 19) in group 1 and from 55 (SD 17) to 69 (SD 9) in group 2. Side-to-side difference in arthrometric KT1000 evaluation was less than 3 mm in 80% of patients that did not fail. In MRI studies, twenty-two (55%) had a proximal ACL lesion and eighteen (45%) a mid-substance ACL lesion. Fifteen (71%) patients in group 1 and twelve (63%) in group 2 presented an improvement in signal intensity at 6 months. The platelet concentration was 478% and the leukocyte concentration was 9% in relation to the patient´s baseline serum concentration. CONCLUSION: Return to sports after a partial ACL tear was similar in both groups. Almost 25% of patients progressed to knee instability, without significant differences between those treated or not with an intra-articular PRP injection. Longer follow-up is required before any conclusions.