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PRP for Arthroscopic Repair of Medium to Large Rotator Cuff Tears: Letter to the Editor

Dear Editor: We read with interest the paper by Jo et al, ‘‘PlateletRich Plasma for Arthroscopic Repair of Medium to Large Rotator Cuff Tears: A Randomized Controlled Trial.’’ We would first like to congratulate the authors on performing a randomized controlled trial in an important and interesting area of practice. There are, however, several areas of interest in the paper that we would like to point out to the readership of the journal. Firstly, the paper concludes that platelet-rich plasma (PRP) application in the repair of medium to large rotator cuff tears significantly improved the quality of tendon healing, as evidenced by a decreased retear rate and increased cross-sectional area of the supraspinatus assessed on magnetic resonance imaging (MRI). We feel that the study results do not support this finding. The study was not powered to find a difference in retear rates or change in supraspinatus cross-sectional area; these were secondary outcome measures. The primary outcome measure was stated to be the Constant score at 3 months postoperatively. Accordingly, the study power calculation was performed with this in mind, not quality of tendon healing. There was also a loss to MRI follow-up of 15% of the study participants, which weakens this conclusion further. Although the study was randomized, we would like to highlight the data presented in Table 1. The data report a substantial difference in the number of participants with Goutallier grade 3 and 4 changes in the supraspinatus. In the PRP group, 5 and 0 participants had Goutallier grade 3 and 4 changes, respectively, compared with 9 and 4, respectively, in the non-PRP group. Although the authors report this to be statistically not significant in the context of their statistical analysis, we find this to be a clinically significant difference between the 2 groups and a difference that could have contributed to the higher percentage of tendon retears in the non-PRP group. Furthermore, Table 1 also reports that the mean anteroposterior size of the rotator cuff tear in the non-PRP group was over 4 mm larger than that of the PRP group. Again, this was found to be not statistically significant, but again we feel clinically very relevant in view of the conclusions drawn by the authors. There is strong evidence in the published literature that a higher Goutallier grade and larger tear size are poor prognostic indicators in terms of tendon retear and correlate with a poor functional outcome. 9 It is unfortunate that the authors chose to use a functional outcome measure such as the Constant score as the primary outcome measure for the study. It is known that the retear rate and healing are not directly proportional to functional outcome. Indeed, the functional outcome could have been affected by other factors that were not adequately controlled for, such as the extent of subacromial decompression and acromioclavicular joint osteophyte debridement. This is not clear in the paper. We would also like to point out that, when calculating the power analysis for the study, it would have been methodologically better to have used data from studies that had actually used PRP in their rotator cuff repairs, as well as those that had not used PRP in their rotator cuff repairs. Three studies were referenced for the power analysis in the paper, but none of these used PRP. It is not clear from which of these studies the standard deviation of 13.3 was derived. One of these studies focused on repair integrity after rotator cuff repair accompanied by a ‘‘multiple channeling’’ technique, similar to microfracture, of the greater tuberosity. This study did not report Constant scores. The second referenced study does involve rotator cuff repair and does report the Constant score, but it does not quote the standard deviation that was used in the power analysis. This second study also reports on partialand full-thickness rotator cuff tears of differing sizes, some of which were treated by subacromial decompression alone. The final study referenced is a study comparing acupuncture and placebo needling in patients with rotator cuff tendinitis. These studies are all unsuitable to use for the power analysis in a study that investigates functional outcome after rotator cuff repair with and without PRP application. We understand that the minimal clinically important difference (MCID) of the Constant score (the authors quoted 10 points) may have been taken from the above studies, but it is not clear where the assumed standard deviation of 13.3 was derived from.