Abstract
Objectives:
Lateral epicondylitis is the most common condition affecting the elbow however conservative treatment for the condition remains controversial. Various approaches have been described including braces, physical therapy, corticosteroid injections, and platelet-rich-plasma (PRP) injections. PRP is taken from a centrifuged blood sample and consists mainly of platelets and growth factors. Although research surrounding injections in lateral epicondylitis continues to evolve, randomized controlled trials have shown that PRP injections are associated with decreased pain at two-year follow-up. Visual analog scale (VAS) pain scores and other patient reported outcome measures (PROMs) such as Disabilities of the Arm, Shoulder, and Hand (DASH) have been used previously; however, no studies to date have used the Single Assessment Numeric Evaluation (SANE). It was hypothesized that patients would report improvements in pain and function at four weeks and four months after PRP injection. The primary outcomes were SANE and VAS pain scores. The secondary aim was to determine a minimum clinically important difference (MCID) value for SANE for this procedure.
Methods:
This was a retrospective review of a prospectively collected PROM database from 2021-2023. All patients who received a PRP injection for lateral epicondylitis were included in this study. Patients were excluded if they were missing baseline SANE or VAS pain scores, received an injection anywhere besides the common extensor tendon origin, or had overlapping conditions such as cervical radiculopathy, cubital tunnel or carpal tunnel syndrome. Baseline patient characteristics including sex, age, smoking history, history of depression or anxiety, disease chronicity, and hand dominance were collected. Previous history of physical therapy, corticosteroid injection, PRP injection, and procedure characteristics including milliliters (ml) of PRP injected and number of fenestrations were also collected. All PRP injections were ultrasound guided and conducted using the health-system standardized protocol with leukocyte-rich plasma. Primary outcomes included SANE and VAS pain scores at baseline, four weeks, and four months post-injection. MCID was calculated using the distribution-based method, calculated as half of the standard deviation of the change in SANE score. Additional outcomes included if the patient experienced any adverse events following injection, underwent subsequent injection within the study period.
Results:
A total of 36 patients met criteria for analysis. More than half the patients were male (n=20, 55.6%), and the average age was 50.15±9.31 years. Only 5.6% of patients were current smokers (n=2). Fifteen patients (41.7%) had histories of depression, and 10 patients (27.8%) had histories of anxiety. Most patients received an injection after experiencing symptoms for 10.62±9.56 months on average. The majority of patients previously tried or were concurrently going to physical therapy (n=28, 77.8%). Fourteen patients (38.9%) had received a previous corticosteroid injection, and five patients (13.9%) had received a previous PRP injection.
The injection procedure typically consisted of 2.36±0.66 ml of PRP with 5.74±3.03 fenestrations. Most injections were done in the dominant arm (n=28, 77.8%). A total of six patients went on to have a repeat injection (16.7%). There were five patients who experienced increased post-procedure pain (13.9%) and one who experienced nerve irritation (2.8%). All adverse events eventually resolved.
SANE scores at baseline, four-week, and four-month follow-up were 53.06±23.28, 57.22±27.32, 65.19±27.07. The difference between baseline and follow-up at four weeks was not statistically significant (p=0.245), but the follow-up scores at four months were found to be statistically higher than baseline scores (p=0.044). The average changes from baseline to four weeks and baseline to four months were 7.04±30.77 and 15.50±28.13, respectively. VAS pain scores at baseline, four-week, and four-month follow-up were 5.14±2.10, 4.25±2.66, 3.17±2.81. Follow-up scores at four weeks and four months were found to be statistically lower than baseline scores (p=0.006, p=0.003). The average changes from baseline to four weeks and baseline to four months were -1.29±2.29 and -2.44±2.99, respectively. A history of prior corticosteroid injection was not significantly associated with changes in SANE scores at four weeks or four months after PRP injection (p=0.149, p=0.602, respectively). The SANE MCID values at four weeks and four months were 15.39 and 14.07, respectively. Of those patients who reported, 44.4% met the four-week value and 37.5% met the four-month value.
Conclusions:
Patients after PRP injection for lateral epicondylitis demonstrated increased SANE scores at four months and decreased VAS pain scores at four weeks and four months. The change in SANE scores at four weeks was not statistically significant. These results may indicate that there are greater pain reducing effects as well as milder extremity functionality improvement effects associated with PRP injection. This may be in part due to the inherent nature of the disease with the more prevalent symptom being pain over loss of function. PRP injections are a safe and effective conservative treatment method for reducing pain symptoms and increasing functionality in patients with lateral epicondylitis. Physicians should discuss patient expectations for improvement during the early post-injection period.
