Platelet Concentration Does Not Influence Clinical Efficacy and Retear Rates of Rotator Cuff Repair With Platelet-Rich Plasma: A Systematic Review and Meta-analysis With Meta-Regression

Abstract

Background:

Platelet-rich plasma (PRP) is emerging as a popular augmentation technique in the context of rotator cuff repair (RCR) to strengthen the repair construct and promote healing. Previous studies examining the efficacy of PRP augmentation during RCR have described heterogeneous results.

Purpose:

To determine whether platelet concentration of a PRP injection as an adjunct of RCR impacts clinical outcomes and retear rates.

Study Design:

Systematic review and meta-analysis; Level of evidence, 2.

Methods:

A systematic review was performed by searching the PubMed, Cochrane Library, and Embase databases to identify level 1 and 2 studies that evaluated the clinical efficacy of RCR augmented with PRP. The search phrase used was “rotator cuff repair AND (PRP OR platelet rich plasma OR platelet-rich plasma).” Included randomized controlled trials were classified as utilizing high-dose or low-dose PRP based on their platelet concentration factor as a >4-fold increase over whole blood. The outcomes evaluated were the standardized mean differences of visual analog scale scores, Constant-Murley scores, American Shoulder and Elbow Surgeons scores, and University of California–Los Angeles scores, and pooled odds ratios of retear rates. Mixed-effects and random-effects meta-analyses were performed along with meta-regression to evaluate relationships in patient outcomes associated with PRP platelet dose.

Results:

Ten studies (level 1 or 2) met inclusion criteria, including 696 patients (346 PRP, 350 control). The mean patient age at the time of repair was 54.3 years, and the mean follow-up time was 25.7 months. Of the 10 studies, 6 utilized low-dose PRP and 4 utilized high-dose PRP. In both the meta-analysis and meta-regression analyses, there were no significant differences in mean postoperative scores for all patient-reported outcomes or in mean retear rates between platelet dosage groups (all P > .05).

Conclusion:

Platelet concentration may not influence the clinical outcomes and retear rates of patients undergoing RCR with PRP augmentation. Further studies that adequately report PRP procedures and composition regarding PRP as an RCR augmentation are necessary to achieve confidence in their clinical application and efficacy.

Keywords

rotator cuff repair dose platelet-rich plasma platelet concentration shoulder

Rotator cuff tears are a common shoulder injury with a 20% population prevalence rate presenting as limited range of motion and pain with overhead motion in patients, significantly decreasing one's quality of life.^7,26,41 In the United States, rotator cuff repair (RCR) is considered the standard of treatment for rotator cuff tears, with around 250,000 procedures being performed annually.^23,25 RCR has been shown to significantly reduce pain and enhance both function and strength in patients.¹⁷ However, even after surgical intervention, retears are common, with retear rates ranging from 13% to 41% with patient-related factors including older age, larger tear size, lower education level, and fatty infiltration leading to increased retear rates.^18,30,42 In recent years, to combat the recurrence of retears after RCR, the use of augmentation techniques during RCR, such as platelet-rich plasma (PRP), has been growing in popularity to promote the healing process and reduce retear rates.

PRP is an autologous whole blood–derived product concentrated with platelets and growth factors offering immunomodulatory effects that increase its potential to accelerate muscle and tendon healing on a cellular level, leading to its growing popularity as an augmentation for RCR to support postoperative healing.^1,36 Recent studies have supported the growing popularity of PRP as an RCR augmentation technique, finding significantly greater improvement in pain and clinical outcomes and lower retear rates as compared to RCR alone.^19,20,37,38 However, several studies have also found no significant difference in the postoperative outcomes between patients undergoing RCR with PRP and those undergoing RCR alone.^9,22,32,40 The heterogeneity of findings in the context of utilizing PRP as an adjunct to RCR may be related to the varying preparation and platelet concentration of the injected PRP among studies, which includes the platelet concentration increase factor, which has ranged from as low as 2 to as high as 8 times over the whole blood platelet concentration.^11,15,22

Previous systematic reviews have found higher platelet concentrations of PRP to be associated with higher clinical efficacy in the setting of lateral epicondylitis (LE) and knee osteoarthritis (OA).^3,28 However, to the best of our knowledge, the impact of platelet concentration of the injected PRP as an augmentation for RCR on clinical efficacy and retear rates has yet to be studied. Therefore, the purpose of this study was to determine whether the platelet concentration of a PRP injection as an adjunct of RCR impacts clinical outcomes and retear rates. The authors hypothesized that a higher platelet dose concentration of the augmented PRP during RCR would be associated with improved clinical outcomes and lower retear rates.

Methods

This systematic review was conducted according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines using a PRISMA checklist. Two independent reviewers (J.J.L. and J.W.B.) searched the PubMed, Embase, and Cochrane Library databases up to July 26, 2025. The electronic search strategy used was “rotator cuff repair AND (PRP OR platelet rich plasma OR platelet-rich plasma).” A total of 489 studies were reviewed by title and/or abstract to determine study eligibility based on inclusion criteria. In cases of disagreement, a third reviewer (R.M.F.) made the final decision. Inclusion and exclusion criteria followed the PICOS (participants, interventions, comparators, outcomes, study design) strategy. Studies selected for inclusion met the following criteria: (1) participants: patients undergoing arthroscopic RCR (2) intervention: PRP augmentation; (3) comparator: no augmentation; (4) outcomes: clinical efficacy and adverse events, and (5) study design: level 1 and 2 randomized controlled trials (RCTs) that were published in the English language. Exclusion criteria included level 3 to 5 studies that did not meet the aforementioned inclusion criteria, studies that did not have a minimum follow-up of 1 year, and studies that did not report adequate detail on PRP composition. Ten studies were determined to meet inclusion criteria (Figure 1). Data extraction from each study was performed independently and then reviewed by a second author (J.J.L.). During the cases in which the final platelet concentration of the administered PRP or platelet concentration increase factor was not reported,^9,34 the platelet concentration increase factor was calculated as the initial volume of blood collected for PRP preparation divided by the volume of PRP obtained.²⁸ There was no need for funding or a third party to obtain any of the collected data. Risk of bias was assessed according to the Cochrane Collaboration's risk of bias tool¹² which incorporates an assessment of randomization, blinding, completeness of outcome data, selection of outcomes reported, and other sources of bias.

Reporting Outcomes

Outcomes assessed included patient-reported outcomes (PROs). PROs included the visual analog scale (VAS) pain score, the Constant-Murley (CM) score,⁶ the American Shoulder and Elbow Surgeons (ASES) score,³³ and the University of California–Los Angeles (UCLA) shoulder score.² Additional outcomes assessed included rotator cuff retear rates. Six studies^{15,16,22,29,32,34} used the VAS score, in which all scores were standardized to a 100-point scale. Eight studies^{9,11,15,16,22,29,31,32} used the CM score. Six studies^{9,15,16,29,32,34} used the ASES score. Seven studies^{15,16,22,29,31,32,35} reported results of the UCLA shoulder score. All 10 included studies reported on rotator cuff retear rates.

Study Methodology Assessment

The Modified Coleman Methodology Score (MCMS)⁵ was used to evaluate study methodology quality. The MCMS has a scaled potential score ranging from 0 to 100. Scores ranging from 85 to 100 are excellent, 70 to 84 are good, 55 to 69 are fair, and <55 are poor. The primary outcomes assessed by the MCMS are study size and type, follow-up time, attrition rates, number of interventions per group, and proper description of study methodology.

High-Dose PRP and Low-Dose PRP Terminology

In the current study, high-dose PRP and low-dose PRP follow the same definitions and cutoff points from a previous meta-analysis done by Oeding et al²⁸ evaluating the effect of platelet concentration on the clinical efficacy of PRP for patients with LE. A platelet concentration increase factor >4 over whole blood was deemed as high-dose PRP, whereas PRP with a <4-fold increase was deemed as low-dose PRP. Whole blood platelet concentration is found to be around 150 × 10³ to 450 × 10³ per microliter. The current literature defines PRP as having a platelet concentration 3 to 5 times that of whole blood platelet concentration.^10,24 Therefore, supported by the previous literature, we decided it was reasonable to follow the definitions established by Oeding et al²⁸ as well as their determination of high-dose PRP as true PRP.

Statistical Analysis

For the continuous outcomes of VAS, CM, ASES, and UCLA scores, mixed-effects meta-analysis models were constructed using Hedges g (bias-corrected standardized mean difference [SMD], calculated with exact formulae), where the difference is based on the postoperative values between the 2 dosage groups. Pooled estimates were derived with the inverse variance method, and between-study variance (τ²) was estimated using restricted maximum likelihood. Confidence intervals for τ² and τ were obtained via the Q-profile method, and heterogeneity was quantified using I² statistics derived from the Cochran Q. In the case in which standard deviations were not provided,³⁵ one-quarter of the mean was used as the standard deviation, as previously described.³⁹ For dichotomous outcomes (retear rate), mixed-effects meta-analysis models were constructed to estimate pooled odds ratios. The Mantel-Haenszel method was used for common-effect models, while the inverse variance method with restricted maximum-likelihood estimation was applied for random-effects models. Confidence intervals for τ² and τ were obtained using the Q-profile method, I² was calculated from Q, and a continuity correction of 0.5 was applied in studies with zero cell frequencies.

Subgroup analyses were performed by stratifying studies according to PRP platelet dose. To further investigate heterogeneity, meta-regression models were constructed with PRP dose as the moderator. Forest plots were generated to display pooled effect estimates and study-level contributions. Regression coefficients from meta-regression models were reported with standard errors, test statistics, P values, and 95% confidence intervals.

Results

Ten studies met inclusion and exclusion criteria (Figure 1), including 696 patients (346 PRP, 350 control). The mean patient age at the time of repair was 54.3 years, and the mean follow-up time was 25.7 months. Of the 10 studies, 6 utilized low-dose PRP and 4 utilized high-dose PRP (Table 1).

Table 1

Studies Included ^a

Study	LOE	No.	Patient Age, y	PRP Type	Platelet Concentration Increase Factor	Platelet Concentration, ×10³/µL	Follow-up, mo
Flury et al, 2016⁹	1	103	57.8 ± 8.0	LP-PRP	2.5	NR	24
Gumina et al, 2012¹¹	1	76	60.0 ± 4.4	LR-PRP	1.7	400	12
Jo et al, 2013¹⁵	1	48	64.2 ± 6.1	LP-PRP	4.6	1096.5	12
Jo et al, 2015¹⁶	1	74	60.1 ± 4.9	LP-PRP	7.1	1218.4	12
Malavolta et al, 2018²²	2	51	55.4 ± 8.4	LP-PRP	7.7	1185.2	60
Pandey et al, 2016²⁹	1	102	54.8 ± 8.4	LP-PRP	2.2	474.0	24
Randelli et al, 2011³¹	1	45	61.6 ± 8.3	LR-PRP	3.0	NR	24
Randelli et al, 2022³²	2	38	61.5 ± 15.4	LR-PRP	3.0	NR	120
Rossi et al, 2024³⁴	1	96	56.1 ± 3.0	LP-PRP	6.0	NR	12
Ruiz-Moneo et al, 2013³⁵	1	63	56.0 ± 14.0	LP-PRP	2.3	600.0	12

Patient age is reported as a mean ± SD, and follow-up duration is reported as a minimum follow-up. LOE, level of evidence; LP-PRP, leukocyte-poor platelet-rich plasma; LR-PRP, leukocyte-rich platelet-rich plasma; NR, not reported; PRP, platelet-rich plasma; RCR, rotator cuff repair.

PRP Preparation and Administration Method

All 10 included studies described details of PRP preparation. Specific machines or processing kits used for PRP preparation were highly variable but were reported as a centrifugation system or a plateletpheresis system^15,16 in all studies. All the studies that reported using a centrifugation system reported drawing blood from the peripheral antecubital vein while also adequately describing the spin details of the centrifugation to isolate the red blood cells from the upper plasma layer. In 3 studies^31,32,34 (30.0%), the supernatant layer was transferred to a new centrifuge tube for a second centrifugation to separate the platelet-poor plasma layer from the PRP layer, and all 3 studies reported these second spin details. In 8 studies^{11,15,16,22,29,31,32,35} (80.0%), the PRP was then activated by adding calcium chloride^{22,29,31,32,35} or calcium gluconate^11,15,16 before injection, while 1 study⁹ reported no activation. Among the included studies, platelet concentration was reported to be between 1.7 and 7.7 times baseline values. Four of the studies^9,31,32,34 (40.0%) did not report on the final injected platelet concentration. All included studies administered PRP intraoperatively and did not have additional injections postoperation.

Tear Type

Two studies^22,34 included patients with small or medium rotator cuff tears. Two studies^32,35 included patients with small to large tears. Two studies^9,31 included patients with small to massive tears. One study²⁹ included patients with medium tears only. Two studies^11,16 included patients with medium or large tears. One study¹⁵ included patients with large or massive tears (Table 2).

Table 2

Tear Size Included ^a

Study	Small	Medium	Large	Massive
Flury et al, 2016⁹	x	x	x	x
Gumina et al, 2012¹¹		x	x
Jo et al, 2013¹⁵			x	x
Jo et al, 2015¹⁶		x	x
Malavolta et al, 2018²²	x	x
Pandey et al, 2016²⁹		x
Randelli et al, 2011³¹	x	x	x	x
Randelli et al, 2022³²	x	x	x
Rossi et al, 2024³⁴	x	x
Ruiz-Moneo et al, 2013³⁵	x	x	x

x denotes an individual study including that tear type.

Modified Coleman Methodology Score

Table 3 shows the MCMS values from the 10 included studies. Nine studies^‡ received excellent scores and 1 study¹⁵ received a good score.

Table 3

Modified Coleman Methodology Score

Study	Modified Coleman Methodology Score
Flury et al, 2016⁹	93
Gumina et al, 2012¹¹	88
Jo et al, 2013¹⁵	84
Jo et al, 2015¹⁶	88
Malavolta et al, 2018²²	87
Pandey et al, 2016²⁹	91
Randelli et al, 2011³¹	86
Randelli et al, 2022³²	92
Rossi et al, 2024³⁴	91
Ruiz-Moneo et al, 2013³⁵	86
Mean	88.6 ± 2.8

Methodological Quality Assessment

The results of the methodological quality assessment of included studies using the Cochrane Collaboration's risk of bias tool are presented in Figure 2. Sequence generation was adequately reported by all studies (low risk of bias). In all studies, concealment of allocation from the investigators was not possible due to the nature of the intervention (high risk of bias). All studies were deemed to be at low risk for detection bias because of the blinding of the outcome assessor. Patients in all studies were blinded to their intervention group (low risk of bias). Two studies^16,32 reported a minor loss of follow-up of between 10% and 20% without proper explanation (unclear risk of bias), while no other studies reported significant loss of follow-up (low risk of bias).

Visual Analog Scale

In the overall meta-analysis for VAS pain scores, there were 6 studies^{15,16,22,29,32,34} with 409 observations (204 experimental, 205 control). The pooled SMD was −0.2093 (95% CI, −0.4040 to −0.0145) under both common-effect and random-effects models, indicating that PRP was associated with significantly lower pain scores compared to the control (Table 4). Between-study heterogeneity was negligible (τ² = 0.0000; 95% CI, 0.0000 to 0.0750; I² = 0.0%; 95% CI, 0.0% to 74.6%), and the test of heterogeneity was nonsignificant (Q = 1.97; df = 5; P = .8534), suggesting highly consistent findings across studies.

Table 4

Summary of Overall Meta-analyses for Functional Outcomes and Retear Rates ^a

	Studies	Observations	Effect Size (95% CI)	P Value	τ²	I ², %
VAS score
Common	6	409	–0.21 (–0.40 to −0.015)	.035	0	0
Random	6	409	–0.21 (–0.40 to −0.020)	.035	0	0
CM score
Common	8	535	0.40 (0.23 to 0.57)	<.0001	0.034	30.2
Random	8	535	0.39 (0.18 to 0.61)	.0004	0.034	30.2
ASES score
Common	6	462	0.12 (–0.06 to 0.31)	.19	0.0043	0
Random	6	462	0.13 (–0.07 to 0.32)	.20	0.0043	0
UCLA score
Common	7	421	0.34 (0.15 to 0.54)	.0005	0.11	63.1
Random	7	421	0.31 (–0.0071 to 0.62)	.055	0.11	63.1
Retear rate
Common	10	661	0.41 (0.27 to 0.62)	<.0001	0.094	5.0
Random	10	661	0.42 (0.26 to 0.67)	.0003	0.094	5.0

Overall results of all included studies are shown for both common-effect and random-effects models. Effect sizes are presented as standardized mean difference for continuous outcomes and odds ratio for dichotomous outcomes, with 95% confidence intervals), between-study variance (τ²), and heterogeneity (I²). P values between the platelet-rich plasma and control groups are also reported. ASES, American Shoulder and Elbow Surgeons; CM, Constant-Murley; UCLA, University of California–Los Angeles; VAS, visual analog scale.

In subgroup analyses, in the high-dose subgroup (k = 4) the pooled effect size was −0.1438 (95% CI, −0.3833 to 0.0958), while in the low-dose subgroup (k = 2) the pooled effect size was −0.3368 (95% CI, −0.6713 to −0.0024) (Table 5). Heterogeneity was negligible within both subgroups (I² = 0.0%). Tests for subgroup differences were not statistically significant under either the common-effect (Q = 0.85; df = 1; P = .3576) or random-effects (Q = 0.85; df = 1; P = .3576) model (Figure 3). In meta-regression analyses, platelet dose was not significantly associated with VAS scores (Table 6).

Table 5

Summary of Subgroup Meta-analyses for Functional Outcomes and Retear Rates ^a

	Subgroup	Subgroup k	Subgroup Effect (95% CI)	Subgroup I², %	Test for Subgroup Difference, P Value
VAS score
Common	High-dose	4	–0.14 (–0.38 to 0.096)	0	.3576
Random	Low-dose	2	–0.34 (–0.67 to −0.0024)	0
CM score
Common	High-dose	3	0.26 (–0.040 to 0.56)	0	.2707
Random	Low-dose	5	0.47 (0.17 to 0.77)	47.6
ASES score
Common	High-dose	3	0.078 (–0.19 to 0.34)	23.2	.6456
Random	Low-dose	3	0.17 (–0.10 to 0.43)	0
UCLA score
Common	High-dose	3	0.13 (–0.17 to 0.43)	0	.0673
Random	Low-dose	4	0.44 (–0.055 to 0.94)	74.8
Retear rate
Common	High-dose	4	0.28 (0.15 to 0.54)	0	.1407
Random	Low-dose	6	0.54 (0.28 to 1.055)	15.1

Results are shown for both common-effect and random-effects models of platelet-rich plasma dose-stratified subgroups. Effect sizes are presented as standardized mean difference for continuous outcomes and odds ratio for dichotomous outcomes, with 95% confidence intervals, between-study variance (τ²), and heterogeneity (I²). P values for tests of subgroup differences are also reported. ASES, American Shoulder and Elbow Surgeons; CM, Constant-Murley; UCLA, University of California–Los Angeles; VAS, visual analog scale.

Table 6

Meta-regression Results Evaluating the Effect of Platelet-Rich Plasma Dose (Low vs High) on Patient-Reported Outcomes ^a

Outcome	Statistic	Coefficient	SE	Statistic	P Value	95% CI
VAS score	SMD	–0.193	0.21	–0.92	.358	–0.6 to 0.22
CM score	SMD	0.215	0.24	0.913	.361	–0.25 to 0.68
ASES score	SMD	0.084	0.21	0.394	.693	–0.33 to 0.5
UCLA score	SMD	0.328	0.32	1.027	.305	–0.3 to 0.96
Retear rate	OR	0.688	0.44	1.554	.12	–0.18 to 1.56

Coefficients represent the difference between low-dose and high-dose groups for continuous outcomes (SMD) and dichotomous outcomes (OR). ASES, American Shoulder and Elbow Surgeons; CM, Constant-Murley; SE, standard error; SMD, standardized mean difference; UCLA, University of California–Los Angeles; VAS, visual analog scale.

Constant-Murley Score

In the overall meta-analysis for the CM score, there were 8 studies^{9,11,15,16,22,29,31,32} with a total of 535 observations (266 experimental, 269 control). The overall SMD for the CM score was estimated at 0.3980 (95% CI, 0.2258-0.5701) under a common-effect model and 0.3927 (95% CI, 0.1756-0.6098) under a random-effects model (Table 4). Between-study heterogeneity was modest (τ² = 0.0338; 95% CI, 0.0000-0.2437; I² = 30.2%; 95% CI, 0.0%-68.8%). The test of heterogeneity was not statistically significant (Q = 10.02; df = 7; P = .1873).

In subgroup analyses, in the high-dose subgroup (k = 3) the pooled effect size was 0.2600 (95% CI, −0.0400 to 0.5599), while in the low-dose subgroup (k = 5) the pooled effect size was 0.4658 (95% CI, 0.17 to 0.77) (Table 5). Heterogeneity was negligible in the high-dose group (I² = 0.0%) but moderate in the low-dose group (I² = 47.6%). Tests for subgroup differences were not statistically significant under either the common-effect (Q = 1.21; df = 1; P = .2707) or random-effects (Q = 0.92; df = 1; P = .3364) model (Figure 4). In meta-regression analyses, platelet dose was not significantly associated with CM scores (Table 6).

American Shoulder and Elbow Surgeons

In the overall meta-analysis for ASES, there were 6 studies^{9,15,16,29,32,34} with a total of 462 observations (228 experimental, 234 control). The overall SMD for the ASES score was estimated at 0.1234 (95% CI, −0.0598 to 0.3066) under a common-effect model and 0.1258 (95% CI, −0.0655 to 0.3172) under a random-effects model (Table 4). Between-study heterogeneity was negligible (τ² = 0.0043; 95% CI, 0.0000 to 0.2278; I² = 0.0%; 95% CI, 0.0% to 74.6%). The test of heterogeneity was not statistically significant (Q = 4.74; df = 5; P = .4480).

In subgroup analyses, the high-dose group (k = 3) showed an effect size of 0.0780 (95% CI, −0.1884 to 0.3444), while the low-dose group (k = 3) showed an effect size of 0.17 (95% CI, −0.10 to 0.43) (Table 5). Tests for subgroup differences were nonsignificant in both the common-effect (Q = 0.21; df = 1; P = .6456) and random-effects (Q = 0.13; df = 1; P = .7199) models (Figure 5). In meta-regression analyses, platelet dose was not significantly associated with ASES scores (Table 6).

University of California–Los Angeles

In the overall meta-analysis for UCLA, there were 7 studies^{15,16,22,29,31,32,35} with a total of 421 observations (210 experimental, 211 control). The overall SMD for UCLA was estimated at 0.3444 (95% CI, 0.1497 to 0.5390) under a common-effect model and 0.3075 (95% CI, −0.0071 to 0.6222) under a random-effects model (Table 4). Between-study heterogeneity was substantial (τ² = 0.1077; 95% CI, 0.0066 to 0.6681; I² = 63.1%; 95% CI, 16.2% to 83.7%). The test of heterogeneity was statistically significant (Q = 16.24; df = 6; P = .0125), suggesting true differences in effect sizes across studies. The coefficient for low-dose versus high-dose PRP was 0.328 (SE, 0.320; 95% CI, −0.30 to 0.96; P = .305), indicating no significant difference in effect size between dosage groups.

In subgroup analyses, high-dose studies (k = 3) produced an SMD of 0.1326 (95% CI, −0.1662 to 0.4315), whereas low-dose studies (k = 4) showed a larger effect (SMD, 0.44; 95% CI, –0.055 to 0.94) under the common-effect model (Table 5). Subgroup differences approached significance in the common-effect model (Q = 3.35; df = 1; P = .0673) but were not significant under the random-effects model (Q = 1.09; df = 1; P = .2958) (Figure 6). In meta-regression analyses, platelet dose was not significantly associated with UCLA scores (Table 6).

Rotator Cuff Retear Rates

All included studies reported on rotator cuff retear rates. In the overall meta-analysis for retear rates, there were 10 studies with a total of 661 observations (332 experimental, 329 control) and 140 total events. The pooled odds ratio for retears was estimated at 0.4124 (95% CI, 0.2728-0.6234) under a common-effect model and 0.4165 (95% CI, 0.2578-0.6728) under a random-effects model, demonstrating a significant association of PRP with lower retear rates compared to control (Table 4). Between-study heterogeneity was low (τ² = 0.0940; 95% CI, 0.0000-1.2055; I² = 5.0%; 95% CI, 0.0%-64.3%), and the test of heterogeneity was nonsignificant (Q = 9.47; df = 9; P = .3947), suggesting consistency across studies.

Subgroup analyses between platelet dose groups showed that high-dose studies (k = 4) reported stronger effects (OR, 0.2840; 95% CI, 0.1485-0.5434) than low-dose studies (k = 6; OR, 0.5355; 95% CI, 0.28 to 1.055) under the common-effect model (Table 5). However, subgroup differences were not statistically significant under either the common-effect model (Q = 2.17; df = 1; P = .1407) or the random-effects model (Q = 1.67; df = 1; P = .1956) (Figure 7). In meta-regression analyses, platelet dose was not significantly associated with retear rates (Table 6).

Discussion

The current systematic review and meta-analysis is, to our knowledge, the first to evaluate the effect of platelet dose concentration in the context of PRP augmentation during RCR on PROs and retear rates in patients undergoing RCR with PRP in only level 1 and 2 RCTs. The most important finding of this study was that a higher platelet dose concentration of the PRP augmentation during RCR was not significantly associated with improved clinical outcomes or lower retear rates. Despite basic science studies observing higher platelet concentration as promoting growth factors and greater healing at the repair site,⁸ this finding does not support the idea that a PRP platelet concentration 4 times greater than that of whole blood correlates with improved patient outcomes as an adjunct of RCR. However, the wide confidence intervals and small effect sizes demonstrating nonsignificance by the current study may not mean no effect. These statistical findings may suggest the need for more and larger studies to sufficiently evaluate the impact of platelet concentration of PRP as an RCR augment. In a related effort to assess the utilization of PRP during RCR, Hurley et al¹³ evaluated the effect of leukocyte concentration, finding no significant difference between leukocyte-poor PRP (LP-PRP) and leukocyte-rich PRP (LR-PRP), thereby presenting no significant influence of leukocyte concentration in postoperative outcomes. Overall, the current study's finding of no effect of platelet dose concentration on the clinical outcomes and retear rates of patients undergoing RCR with PRP shares a similar sentiment in that the influence of the platelet concentration of PRP on patient postoperative outcomes in the context of RCR is yet unclear.

Lower PRP doses may achieve outcomes comparable to those of higher doses in RCR because of differences in the target tissue, healing environment, and delivery method compared to conditions such as knee OA and LE, where prior studies have associated higher PRP doses with improved clinical outcomes.^3,28 During RCR, PRP is applied directly to the tendon-bone interface during surgery, where the mechanical fixation and biological scaffold already create a favorable healing environment. This localized application means that even a small amount of PRP can effectively stimulate cell proliferation, collagen synthesis, and angiogenesis exactly where it is needed, without significant dilution or loss. In contrast, when PRP is injected into the knee joint for OA, it becomes diluted in the synovial fluid and must act on a large, diffuse, and largely avascular surface of cartilage and synovium. Because these tissues have low metabolic activity and poor intrinsic healing potential, higher doses or repeated PRP injections are required to deliver sufficient growth factors and achieve a meaningful therapeutic effect. Similarly, in LE, the degenerated tendon tissue is poorly vascularized and not surgically repaired, so PRP must diffuse through dense tissue to reach tenocytes, often requiring higher platelet concentrations or multiple treatments to sustain growth factor exposure and stimulate repair. Mechanistically, PRP enhances healing by releasing growth factors while modulating inflammation, but the effectiveness depends on how long these bioactive molecules remain in contact with the target cells. In surgical repairs, inflammation and mechanical signaling already promote healing, so PRP may serve as a biological boost, whereas in chronic degenerative conditions, the tissue environment is catabolic and requires stronger stimulation. Additionally, PRP applied during RCR often forms a fibrin gel that remains localized, while intra-articular injections in the knee or percutaneous injections at the elbow are rapidly cleared from the site.

In addition, regarding the clinical use of PRP in RCR, the status of PRP injection procedures is investigational and thereby has not received approval by the Food and Drug Administration. As a result, PRP is not covered by most insurance carriers; thus, it requires expensive personal payments by the patients that can reach up to thousands of dollars. Most patients will have to pay this significant cost out-of-pocket when utilizing PRP as an augmentation to RCR, an important consideration for both the physician and patient given the significant variability in PRP preparation and composition that could result in differing outcomes. However, with evidence from the current study demonstrating no influence of the platelet concentration of the PRP on clinical outcomes in the context of its augmentation during RCR, there remains questions that require further study to better understand the optimal application of PRP within RCR. Such questions relate to several other factors in the preparation and composition of PRP that could influence postoperative outcomes and retear rates, such as growth factor concentration, preparation systems, activation of PRP, and the direct comparison of LP-PRP and LR-PRP in reference to the findings of Hurley et al.¹³ Future RCTs evaluating such factors are of interest.

It should also be noted that, although it was not the primary focus of this study, pooled analyses of the overall meta-analysis demonstrated RCR with PRP to be significantly associated with lower pain scores, improved patient outcomes, and lower retear rates as compared to RCR alone. Despite the primary observation of platelet concentration not impacting retear rates or patient outcomes, the current study supports the use of PRP as an adjunct to RCR, adding to the complexity of findings from previous meta-analyses.^37,40 It is also important to note that there are no RCTs that have directly compared the preparation of PRP with a higher platelet concentration to that with a lower platelet concentration as an RCR adjunct. This adds another area of interest for future studies to determine if there is any superiority related to the platelet concentration of PRP.

The strengths of this study include a comprehensive systematic review and meta-analysis of level 1 and level 2 RCTs performed by 2 independent reviewers. The limitations of this study should also be noted. The included studies differed regarding surgical techniques, follow-up periods, rehabilitation protocols, and grade of tears for included patients. Because of the high variability in tear type included among studies, a subanalysis categorizing results by tear type could not be performed. In addition, there was high variability in the composition and preparation of PRP, which similarly prevented a subanalysis on this topic from being performed. Related to the variability of PRP composition and preparation, there is a possibility that the calculated value of the 2 studies^9,34 in which the platelet increase factor was not reported, and thereby we calculated it by volume of whole blood and PRP, may not correspond with the platelet concentration of the injected PRP. This limitation also speaks to the several cases in which studies have reported the platelet increase factor but not the final platelet concentration of the injected PRP. Therefore, the current study emphasizes the importance of reporting of the platelet concentration and related details of PRP composition to obtain a clear idea of what kind of PRP was utilized given the extensive heterogeneity within the literature. The issue of the lack of reporting has been explored by previous systematic reviews,^4,21 and the current study suggests that future studies be required to follow reporting guidelines such as those of MIBO (Minimum Information for Studies Evaluating Biologics in Orthopaedics) by Murray et al²⁷ and the most recent consensus by members of the Biologics Association.¹⁴ Overall, the heterogeneous nature of the study design of the included RCTs, the included patient population, the PRP preparation, and the lack of adequate reporting of the injected PRP composition serve as confounding factors in the current systematic review and meta-analysis. Furthermore, these limitations suggest the need for more and larger studies evaluating the platelet concentration of PRP as an adjunct to RCR to adequately support its use in shoulder practice, as the current study suggests equal outcomes regardless of platelet concentration.

Conclusion

Platelet dose concentration may not influence the clinical outcomes and retear rates of patients undergoing RCR with PRP augmentation. Further studies that adequately report PRP procedures and composition regarding PRP as an RCR augmentation are necessary to achieve confidence in their clinical application and efficacy.

Footnotes

Submitted October 11, 2025; accepted February 14, 2026.

One or more of the authors has declared the following potential conflict of interest or source of funding: J.F.O. reports professional activities for Kaliber.ai and serving on the editorial or governing board of Arthroscopy Journal. J.L.D. reports professional activities for APEX Biologix, OSSUR, SBM, Averitas, Organogenesis, Zimmer Biomet Holdings, CONMED Corporation, Arthrex, CAREstream, RTI Surgical, Bioventus LLC, and MOXIMED; and serving on the board of directors or as committee member for the AAOS. E.C.M. reports professional activities for and intellectual property in Zimmer Biomet Holdings, serving as president elect and on the board of directors or as committee member for AOSSM, and serving on the editorial or governing board of AJSM and Orthopedics Today. R.M.F. reports professional activities for Elsevier, Joint Restoration Foundation, Bodycad USA Corp, and Arthrex; and serving on the editorial or governing board of Elsevier (editor in chief of JCJP and associate editor of JSES).

ORCID iDs

Joseph J. Lim

Jacob F. Oeding

An online CME course associated with this article is available for 1 AMA PRA Category 1 Credit™ at https://education.sportsmed.org/Public/Catalog/Home.aspx?CourseSearch=1&Criteria=9&Option=25. In accordance with the standards of the Accreditation Council for Continuing Medical Education (ACCME), it is the policy of The American Orthopaedic Society for Sports Medicine that authors, editors, and planners disclose to the learners all financial relationships during the past 12 months with any commercial interest (A ‘commercial interest’ is any entity producing, marketing, re-selling, or distributing health care goods or services consumed by, or used on, patients). Any and all disclosures are provided in the online journal CME area which is provided to all participants before they actually take the CME activity. In accordance with AOSSM policy, authors, editors, and planners’ participation in this educational activity will be predicated upon timely submission and review of AOSSM disclosure. Noncompliance will result in an author/editor or planner to be stricken from participating in this CME activity.

Notes

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