Our study demonstrated that PRP is not inferior to CS in any of the measured parameters. Both of the groups experienced similar benefits from the injection therapies with no statistical differences detected in WORC, ROM or VAS scores at 6, 12 and 18 months. No adverse effects were detected in either of the two groups. This is the first study of RCRSP patients treated with either PRP or CS injections showing that PRP is not inferior to CS even in the long-term follow-up.
Our results are consistent with current literature, showing that PRP can be beneficial treatment in RCRSP. [5, 20, 22, 25] Previous studies are controversial in interpreting the efficacy of PRP injections due to the different research and treatment protocols, in many cases involving arthroscopy or different products of PRP, for example PRP fibrin matrix. [5, 23, 24] There are only three similarly conducted previous studies comparing subacromial injections of PRP to CS. [19, 21, 25] Among them, only Say et al. reported CS to be superior to PRP in the treatment of subacromial impingement syndrome, in their study including 60 patients. [19] However, the study was not randomized and the follow-up was short (six months). [19] Then, Shams et al. demonstrated that PRP group had better results in early stages of follow-up (three months), but no statistical differences were detected in the long-term (six months) results. [22] Their study was randomized, including MRI for confirmed partial RC ruptures with persistent (over three months) shoulder pain, but only 40 patients were enrolled without documentation of detailed demographic data. [22] Finally, von Wehren et al. reported that there was earlier benefit favoring PRP in their study of 50 patients with partial RC tear, however no difference was detected at six months of follow-up. [25] Their limitations were the absence of randomization and relatively few patients. [25] Both Shams et al. and von Wehren et al. concluded that PRP might be a good alternative instead of subacromial CS injections. [22, 25]
The strength of our study included a larger number of patients and a long follow-up in a comparative matter compared to the previous published studies. The mean follow-up clearly was longer than in previous studies, exceeding over a year. Preintervention inclusion and exclusion criteria were strict and thorough with up to three imaging modalities involved as well as an experienced orthopedist in order to include only patients with RC tendinosis/tendinitis sometimes accompanied with subacromial bursitis or rarely a small/marginal tear in the RC tendon. Demographic and clinical data were meticulously collected.
Retrospective design and lack of randomization are the major limitations of this study. However, due to the heterogenic and multifaceted nature of shoulder and RC problems, there are often multiple imaging findings involved such as RC tendon degeneration, bursitis or minimal tears. This may limit the interpretation and generalization of the results because of multiple pathological structures involved. The rotational ROM data was incomplete which is why it was not always included in the analysis, which leaves an uncharted area in the clinical response to the treatments. PRP group included more females than the CS group, this might explain the lower mean pretreatment WORC emotions subscore in the CS group, because females usually report more symptoms than men. [26]. Furthermore, CS group had significantly more comorbidities than the PRP group, which may affect the joint pathology and symptom scores. We have no accurate information about the type and amount of NSAIDs used by the patients, which may also have affected the preintervention results. Physical therapy that all the patients received was not only a limitation to this study, but also a necessary one. Physical therapy is essential part of the treatment and rehabilitation in shoulder area diseases. However, it must be noted that often injection therapies and analgesics may enable the struggling patient to even begin the physical therapy, which may otherwise prove to be too difficult due to symptoms. The physical therapy may explain some of the symptoms’ changes during the follow-up, but its impact is dramatically reduced since the same protocol was applied to both groups.
We lost 20 patients (33%) of the CS group and three patients (7.9%) of the PRP group due to the strict inclusion and exclusion criteria or patients’ not completing any of the follow-up controls. The most common reason for losing a patient during the follow-up before 18 months was surgery of the shoulder area, which accounted up to seven patients (20%) in the PRP group and up to 11 patients (27.5%) in the corticosteroid group. The other factor for losing eight (22.9%) patients in the PRP group, was simply because patients did not complete the follow-up. The loss of patients leaves always an open interpretation that perhaps their symptoms were improved and they did not want to receive further treatment. Although larger than previous studies, our sample size was relatively small, with a post hoc statistical power of 47.5%.
Management of symptoms and improving function are the main goals of the treatment. [2, 3] Current literature strongly advices against surgery in conditions that RCRSP covers, and favors conservative treatment options. [4] In this perspective, PRP may offer a valid alternative to CS, considering that there are no documented significant adverse effects in PRP treatments unlike in CS treatments. [6, 8, 12, 22] The advantages of PRP over CS are the absence of severe complications locally and systematically. It is safe and simple treatment. Disadvantages of PRP would be more injections required to achieve similar outcomes as a single CS injection. PRP treatment may be repeated whether symptoms return, but multiple CS injections should be avoided. Concurrent physical therapy is still advised because of its proven benefits.
Further larger randomized controlled trials (RCT) are warranted to validate this promising treatment modality. Moreover, the role of PRP as a potential disease modifying agent is unclear and combining imaging to the follow-up protocol would be beneficial.
Given the outcomes of our study, we recommend considering PRP as an alternative treatment to CS in order to reduce local and systemic effects involved with CS injections.