Arthroscopic PRP gel augmentation at the tendon-bone interface accelerates functional recovery and structural healing in rotator cuff repair: a retrospective cohort study

Abstract

Objective

This study aimed to evaluate whether intraoperative application of platelet-rich plasma (PRP) gel at the tendon-bone interface during arthroscopic rotator cuff repair enhances functional recovery, reduces pain, and improves tendon healing within the critical 6-month postoperative window—a pivotal period for retear risk, socioeconomic reintegration, and ERAS (Enhanced Recovery After Surgery) outcomes.

Methods

In this retrospective cohort study, 152 patients with full-thickness supraspinatus tears underwent arthroscopic repair. The PRP group (n = 91) received thrombin-activated PRP gel injected at the tendon-bone interface under direct arthroscopic visualization, while controls (n = 61) received standard repair alone. Functional outcomes (Constant-Murley Score [CMS], American Shoulder and Elbow Surgeons [ASES] score, Subjective Shoulder Value [SSV]) and pain (Visual Analog Scale [VAS]) were assessed preoperatively and at 6 months postoperatively. Tendon healing was evaluated via MRI using Sugaya classification and tendon thickness measurement.

Results

At 6 months postoperatively, the PRP group demonstrated significantly greater improvements in all outcomes versus controls: Functional recovery: ΔCMS = 23.33 vs. 13.08 (p < 0.01); ΔASES = 45.56 vs. 38.78 (p < 0.01); SSV = 82.97% vs. 78.85% (p = 0.006); Pain reduction: ΔVAS = 3.97 vs. 3.51 (p < 0.01); Tendon healing: Sugaya grade distribution significantly favored the PRP group (p < 0.001), with 89.0% vs. 54.1% achieving favorable healing (I/II) and lower retear rates (IV/V: 2.2% vs. 13.1%); tendon thickness 0.63 ± 0.08 cm vs. 0.50 ± 0.06 cm (p < 0.001).

Conclusion

PRP gel application was associated significantly greater improvement in functional recovery, greater reduction in pain, and better structural healing at 6 months postoperatively. This approach may support the objectives of enhanced recovery pathways by potentially facilitating a timely return to productivity and reducing socioeconomic burdens, supporting its role as a cost-effective adjunct to rotator cuff repair.

Introduction

Rotator cuff injuries are prevalent musculoskeletal disorders that often require surgical intervention to restore shoulder function and alleviate pain [1]. While arthroscopic techniques have improved surgical precision, challenges such as persistent pain, delayed tendon healing, and prolonged rehabilitation remain significant clinical concerns [2–4]. These limitations impede patients’ return to daily activities and impose substantial socioeconomic burdens due to work absenteeism and healthcare costs [5–7]. Functional recovery within the first six months post-surgery is a critical determinant for successful reintegration into occupational activities, particularly for physically active individuals [8–10]. This underscores the need for surgical adjuncts that align with Enhanced Recovery After Surgery (ERAS) principles by accelerating rehabilitation [11, 12].

Platelet-rich plasma (PRP), an autologous concentrate of growth factors and cytokines, has been investigated for its potential to promote tissue healing in rotator cuff repair [13–17]. In the treatment of rotator cuff disorders, the application of PRP primarily focuses on the repair of tendinopathy and rotator cuff tears [18–20]. Clinically, however, the efficacy of PRP in rotator cuff repair remains controversial. Some meta-analyses suggest that PRP can reduce long-term re-tear rates and improve shoulder function [18], while others report no significant difference in functional or structural outcomes compared to controls in long-term follow-up [21]. For example, a randomized controlled trial found no significant difference between the PRP group and the control group in functional and structural outcomes over a 12-month follow-up [22].

A key limitation of traditional liquid PRP is its rapid dispersion from the injection site, leading to suboptimal localization of growth factors at the critical tendon-bone interface [14–16, 21, 23]. To address this, PRP gel formulations activated with thrombin and calcium gluconate have been developed. This gel form creates a fibrin scaffold that acts as a sustained-release reservoir for growth factors, improving localization and potentially enhancing the regenerative microenvironment [24, 25]. In vitro studies confirm that such activation methods optimize the release of key mediators like platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-β) [26]. Clinically, PRP gels have shown promise in improving healing in other orthopedic applications, supporting their biological rationale [27].

Despite these developments, the role of PRP gel in arthroscopic rotator cuff repair—particularly its impact on short-term functional recovery and tendon healing—remains underexplored. The 6-month postoperative period represents a pivotal window with the highest risk for re-tear and is crucial for socioeconomic reintegration. Therefore, this study aims to investigate whether intraoperative application of PRP gel at the tendon-bone interface enhances functional recovery, reduces pain, and improves structural healing within this critical 6-month period.

Methods and materials

Study population

This retrospective cohort study included 152 consecutive patients who underwent arthroscopic rotator cuff repair at Zhejiang Taizhou Hospital between August 2023 and April 2024. The assignment to the PRP or control group was based on the date of surgery. A total of 91 Patients from August 2023 to December 2023 underwent arthroscopic PRP Gel Augmentation repair (PRP group), whereas 61 patients from January 2024 to April 2024 underwent arthroscopic repair only (control group). A flowchart detailing patient screening and exclusion is provided in Fig. 1.

Fig. 1.

Patient enrollment flowchart

The inclusion criteria were as follows: (1) Isolated, full-thickness supraspinatus tear (MRI-confirmed), (2) Age 18–75 years, (3) Patte stages 1–2 tears [28], with Goutallier–Fuchs stage 0–1 fatty infiltration [29, 30].

Exclusion criteria included (1) Prior shoulder surgery, (2) Concomitant shoulder pathology (shoulder instability, significant osteoarthritis), (3) Systemic disorders known to significantly impair tendon healing, such as uncontrolled diabetes (HbA1c > 7.0%), immunosuppression, or advanced rheumatoid arthritis. Patients with well-controlled hypertension or diet-controlled/mild type 2 diabetes with normal glycemic status were not excluded. (4) Calcific tendonitis or adhesive capsulitis, (5) Glenoid labrum injury, (6) Inability to complete the 6-month follow-up.

The groups were matched based on baseline characteristics, including gender, age, body mass index (BMI), surgical side (right or left), and Cofield classification, with no significant differences noted (Table 1).

Table 1.

Baseline characteristics of the PRP and control groups

General Data	Control group (n = 61)	PRP group (n = 91)	P value
Gender, n/%			0.163
Male	12 (19.7%)	27 (29.7%)
Female	49 (80.3%)	64 (70.3%)
Age (Years)	56.65 ± 9.29	59.31 ± 8.15	0.227
BMI	24.81 ± 3.97	24.23 ± 2.77	0.296
Affected side			0.219
Left side (n/%)	17	34
Right side (n/%)	44	57
Cofield classification			0.127
Small (n/%)	3	11
Moderate(n/%)	46	55
Large (n/%)	12	25
Preoperative clinical assessments
CMS	60.84 ± 15.65	56.55 ± 18.60	0.14
ASES	41.61 ± 12.67	40.55 ± 15.04	0.652
VAS	5.23 ± 1.52	5.04 ± 1.57	0.471
SSV	51.31 ± 14.89	49.01 ± 17.45	0.4

Preoperative clinical assessments, including the Constant-Murley Score (CMS) [31], American Shoulder and Elbow Surgeons (ASES) score [32], Subjective Shoulder Value (SSV) [33], and Visual Analog Scale (VAS) [34] for pain, were conducted. No statistically significant differences were found between the groups (Table 1).

Ethical considerations

The study was approved by Ethics Committee of Zhejiang Taizhou Hospital (No. K20221219). Patient data were anonymized and securely stored to maintain confidentiality.

PRP preparation

PRP was prepared preoperatively using a dedicated PRP separation kit (Longtime Biological Co., Ltd., Hubei, China). According to the manufacturer’s protocol, venous blood was drawn from the patient using a specialized PRP blood collection needle into a PRP-specific tube containing separation gel and sodium citrate. A total of 9 mL of blood was collected, and the tubes were gently inverted 8–10 times immediately after collection to ensure adequate mixing with the anticoagulant.

The tubes were then centrifuged using a dedicated PRP centrifuge at 3,220 r/min (equivalent to 1,500 g) for 10 min. Following centrifugation, the tubes were carefully removed and placed upright. Within a biological safety cabinet, the upper platelet-poor plasma layer was aspirated and discarded using a dedicated long-needle syringe (20 mL), leaving approximately 1.5-2 mL of plasma above the separation gel. The platelet pellet, located on the surface of the separation gel, was then thoroughly resuspended by inverting the tube vigorously more than 20 times until the buffy coat was completely homogenous, ensuring the platelets were uniformly suspended in the remaining plasma. The tube was then inverted, and the PRP was aspirated into the syringe, yielding a final volume of approximately 2 mL of PRP per patient.

Quality control for PRP included verifying that the patient’s pre-donation blood met the following criteria: hemoglobin > 120 g/L and platelet count > 120 × 10⁹/L, with no recent use of oral anticoagulants. The platelet concentration in the PRP was quantified using an automated hematology analyzer and was confirmed to be ≥ 4 times the patient’s baseline peripheral blood platelet concentration. The PRP was activated intraoperatively with 1 mL of calcium gluconate (100 g/L) and 1,000 IU of thrombin to form a gel immediately before application (Fig. 2).

Fig. 2.

PRP preparation process

Intraoperative procedures and rehabilitation protocol

All surgeries were performed by a single experienced surgeon under general anesthesia, using standard arthroscopic technique. All procedures were performed in the lateral decubitus position. The arm was placed in 4 kg of traction and positioned in 30° of arm flexion and abduction. Initial diagnostic glenohumeral arthroscopy was performed and the presence of a full-thickness supraspinatus tear confirmed. After debridement of the bursal tissue, tendon margins and acromioplasty, rotator cuff reconstruction was performed. The bone bed of the supraspinatus footprint is meticulously prepared until it reaches a bleeding base. A single-row suture repair with anchors was performed. The same reconstructive technique was utilized in each case. In the PRP group, at the end of the arthroscopic procedure, the irrigation fluid in the subacromial space was aspirated, and the PRP, calcium gluconate, and thrombin were slowly injected at the tendon-bone interface through the lateral portal, covering the entire rotator cuff footprint. The PRP was activated and formed a PRP gel at the interface (Fig. 3). In the control group, the standard rotator cuff repair procedure was followed without the PRP gel injection.

Fig. 3.

Intraoperative gel application: a needle placement; b activated PRP gel at tendon-bone interface

All patients followed the same structured rehabilitation protocol under the supervision of a physical therapist: the shoulder was immobilized in a brace for the first 6 weeks, allowing immediate elbow/wrist/hand motion and intermittent passive shoulder exercises from week 3; active shoulder motion was initiated from 6 to 12 weeks; light daily activities and non-impact sports were permitted at 3 months; and return to overhead sports and heavy physical exercise was allowed after the 6-month clinical and MRI evaluation, contingent on individual progress and physician clearance.

Follow-up was conducted at six months. Clinical functional assessments were primarily conducted in person. For the few patients who could not return for an in-person visit at the exact 6-month timepoint but had undergone a recent clinical examination, telephone contact was supplemented solely to collect patient-reported outcomes, specifically the VAS and SSV scores, as well as the subjective components of the CMS and ASES scores. The objective components of the CMS and ASES scores, including range of motion and strength measurements, were not assessed via telephone, and were exclusively obtained from the most recent in-person clinical assessment, which for all included patients fell within the 6-month postoperative period. However, the critical 6-month postoperative MRI assessment was scheduled and performed in person for all patients to ensure complete and standardized structural data collection.

Outcome measures

Primary outcomes included functional recovery and pain reduction, evaluated using the Constant-Murley Score (CMS), American Shoulder and Elbow Surgeons (ASES) score, Subjective Shoulder Value (SSV), and Visual Analog Scale (VAS) for pain.

Secondary outcome measures included tendon healing assessed via MRI at the six-month postoperatively follow-up. Tendon healing was classified using the Sugaya system, which graded tendon healing based on T2-weighted oblique coronal and sagittal MR images [35]. Retear was defined as Sugaya classification Types Ⅳ and V. Additionally, tendon thickness at the tendon-bone interface was quantitatively measured at the freshly prepared bone surface (created intraoperatively by burr debridement of the greater tuberosity) to evaluate structural healing. The measurement site was defined as the intraoperatively prepared bone surface at the supraspinatus footprint, which was identified on MRI by correlating with surgical records and localized bone marrow edema signals (hyperintensity on T2-weighted images). On oblique coronal T2-weighted images, the maximum tendon thickness was measured perpendicular to the tendon’s longitudinal axis at the center of the freshly prepared bone surface. To ensure specificity, measurements were restricted to the burr-treated bone bed and excluded adjacent non-debrided regions. All MRI scans were evaluated independently by two blinded musculoskeletal radiologists (each with over 5 years of experience in musculoskeletal imaging), who were unaware of the patient’s treatment group assignment. In cases of disagreement between the two radiologists regarding the Sugaya classification, a consensus reading was conducted to determine the final grade with a third radiologists.

Statistical analysis

Data were analyzed using SPSS v.22.0. Descriptive statistics were presented as mean ± standard deviation (SD) for continuous variables and as frequencies (percentages) for categorical variables. Between-group differences in baseline characteristics were assessed using independent t-tests for continuous variables and chi-square tests for categorical variables.

For the primary outcome measures (CMS, ASES, SSV, VAS), preoperative and 6-month postoperative values were compared within and between the groups using paired t-tests (for within-group comparison) and independent t-tests (for between-group comparison). The level of significance was set at p < 0.05. With a significance level of 0.05, a power value of 0.8, and an effect size of 0.5d, the estimated required sample size should be 64 cases per group. A Bonferroni correction for 4 comparisons was used, with statistical significance defined as p < 0.0125. Effect sizes (Cohen’s d) and statistical power (1-β) were also calculated for between-group comparisons.

For tendon healing (Sugaya classification), categorical data were analyzed using the chi-square test to compare the distribution of healing grades between groups. Post-hoc analysis of clinically relevant categories (favorable healing: Grades Ⅰ/Ⅱ; retears: Grades Ⅳ/Ⅴ) was performed using Fisher’s exact test. The maximum tendon thickness at the prepared bone surface was compared between the PRP gel-augmented and control groups using independent t-tests.

Results

General data of patients

This study evaluated the effects of PRP gel injection at the tendon-bone interface during arthroscopic rotator cuff repair on postoperative pain, functional recovery, and tendon healing. A total of 152 patients were included in the analysis, with 91 patients in the PRP group and 61 patients in the control group. Demographic factors, including gender, age, BMI, and the side of surgery, were comparable between the two groups (Table 1).

Functional and pain outcomes

At the 6-month follow-up, patients in both groups showed substantial functional recovery and pain reduction compared to their preoperative status. However, the PRP group demonstrated significantly better outcomes compared to the control group: CMS (79.88 ± 11.81 vs. 73.92 ± 8.85, effect size d = 0.59, p < 0.001, power = 0.924), ASES (86.11 ± 9.77 vs. 80.39 ± 9.59, effect size d = 0.59, p < 0.001, power = 0.944), VAS (1.07 ± 0.93 vs. 1.72 ± 1.07, effect size d = 0.66, p < 0.001, power = 0.975), and SSV (82.97 ± 8.03 vs. 78.85 ± 9.28, effect size d = 0.48, p = 0.006, power = 0.812) (Table 2).

Table 2.

Functional, pain, and tendon healing outcomes at 6-months

Outcomes	Control group (n = 61)	PRP Group (n = 91)	Effect size	p	power
CMS	73.92 ± 8.85	79.88 ± 11.81	0.537	<0.001	0.924
ASES	80.39 ± 9.59	86.11 ± 9.77	0.566	<0.001	0.944
VAS	1.72 ± 1.07	1.07 ± 0.93	0.631	<0.001	0.975
SSV	78.85 ± 9.28	82.97 ± 8.03	0.470	0.006	0.812
Tendon Healing				<0.001
Grade I	4 (6.6%)	14 (15.4%)
Grade II	29 (47.5%)	67 (73.6%)
Grade III	20 (32.8%)	8 (8.8%)
Grade IV	6 (9.8%)	2 (2.2%)
Grade V	2 (3.3%)	0 (0%)
Favorable healing (I/II), n (%)	33 (54.1%)	81 (89.0%)		<0.001	0.998
Retears (IV/V), n (%)	8 (13.1%)	2 (2.2%)		0.007	0.718
Maximum tendon thickness	0.50 ± 0.06	0.63 ± 0.08		<0.001	0.999

Tendon healing and the maximum tendon thickness

At the six-month postoperatively follow-up using MRI, tendon healing was evaluated employing the Sugaya classification. The interclass correlation coefficient (ICC) between the two observers was 0.956 (95% CI, 0.920–0.976), indicating good inter-rater reliability. The distribution of Sugaya grades significantly differed between groups (p < 0.001, chi-square test). The PRP group had a significantly higher proportion of favorable healing (Sugaya grades Ⅰ and Ⅱ: 81/91 [89.0%]) compared to the control group (33/61 [54.1%]). Conversely, the retear rate (Sugaya grades Ⅳ and V) was significantly lower in the PRP group (2/91 [2.2%]) than in the control group (8/61 [13.1%]) (p < 0.01). Additionally, the maximum tendon thickness at the prepared bone surface was significantly greater in the PRP group (0.63 ± 0.08 cm) compared to the control group (0.50 ± 0.06 cm) (p < 0.001) (Table 2).

Age-stratified subgroup analysis

To further evaluate the impact of age on PRP efficacy, patients were stratified into subgroups aged < 70 years (n = 78) and ≥ 70 years (n = 13). Postoperative functional outcomes revealed statistically significant differences between subgroups. The younger cohort (< 70 years) demonstrated higher CMS scores (80.76 ± 12.02 vs. 74.62 ± 9.22, p = 0.047) and ASES scores (86.86 ± 9.88 vs. 81.62 ± 8.06, p = 0.050) compared to the older cohort (≥ 70 years). However, VAS pain scores (1.06 ± 0.96 vs. 1.08 ± 0.76, p = 0.957) and SSV (83.46 ± 7.74 vs. 80.00 ± 9.35, p = 0.226) showed no significant intergroup differences (Table 3). Though not statistically significant, trend was observed in structural tendon healing. The distribution of Sugaya classification grades between the age subgroups was not significantly different (p = 0.484). Nonetheless, the younger subgroup (< 70 years) exhibited a numerically higher proportion of favorable healing (Sugaya Grades Ⅰ/Ⅱ) compared to the older subgroup. The retear rate (Sugaya Grades Ⅳ/V) was lower in the younger subgroup than in the older subgroup. The detailed distribution of Sugaya grades is presented in Table 3.

Table 3.

Age-stratified subgroup analysis

	Aged < 70 years(n = 78)	Aged ≥ 70 years(n = 13)	Effect size	p value	Effect size	power
CMS	80.76 ± 12.02	74.62 ± 9.22	0.520	0.047	0.520	0.405
ASES	86.86 ± 9.88	81.62 ± 8.06	0.536	0.050	0.536	0.425
VAS	1.06 ± 0.96	1.08 ± 0.76	0.022	0.957	0.022	0.051
SSV	83.46 ± 7.74	80.00 ± 9.35	0.431	0.226	0.431	0.296
Tendon Healing				0.484
Grade I	13(16.7%)	1(7.7%)
Grade II	58(74.3%)	9(69.2%)
Grade III	6(7.7%)	2(15.4%)
Grade IV	1(1.3%)	1(7.7%)
Grade V	0	0
Favorable healing (I/II), n (%)	71(91.0%)	10(76.9%)		0.132		0.286
Retears (IV/V), n (%)	1(1.3%)	1(7.7%)		0.144		0.141

Discussion

PRP’s role in tendon-bone healing

The rotator cuff is a complex structure comprising bone, tendon, and muscle units, with injuries to this system potentially leading to significant functional impairments, pain, and reduced quality of life [36]. Rotator cuff tears are common musculoskeletal injuries that often result in ongoing pain and dysfunction, and their healing process is frequently complicated by the formation of fibrous tissue at the tendon-bone interface. This tissue can hinder proper tendon-bone integration, impairing mechanical function and increasing the risk of re-injury [37]. Despite advancements in surgical techniques, many patients continue to experience delayed recovery and prolonged pain after rotator cuff repair [38].

PRP potentiates rotator cuff repair through its rich reservoir of growth factors, including platelet-derived growth factor (PDGF), transforming growth factor-beta (TGF-β), and vascular endothelial growth factor (VEGF) [39–41]. These mediators orchestrate a triphasic healing response: initially dampening inflammation via interleukin inhibitors, subsequently stimulating angiogenesis and tenocyte proliferation, and ultimately promoting collagen maturation at the tendon-bone interface. The kinetics of growth factor release from PRP gels is a critical factor influencing their therapeutic efficacy. Innovative approaches to modulate the release kinetics of growth factors from PRP gels have been explored. For instance, the development of dual-responsive hydrogels, as described by Zhang et al. offers a promising solution. These hydrogels, which respond to reactive oxygen species and pH changes, provide controlled and sustained release of growth factors, thereby enhancing the healing of skin wounds by promoting epithelialization, collagen deposition, and angiogenesis [42]. Similarly, the use of photoactivated PRP, as investigated by Karimi et al. demonstrates that photostimulation can achieve sustained growth factor release over an extended period, further expanding the therapeutic applications of PRP [41]. This biological cascade addresses the fundamental challenge of fibrous non-union that frequently compromises conventional repairs. By creating a regenerative microenvironment, PRP shifts the balance from scar formation toward functional tissue restoration. A rat model demonstrated that autologous PRP injections could enhance the biomechanical properties of the tendon-bone junction at two weeks post-surgery, suggesting improved early-phase healing [43]. A rabbit study found that combining PRP with bioactive glass resulted in significantly stronger tendon-bone integration, with higher mechanical load-to-failure values compared to controls [44].

In contrast, clinical studies on PRP’s role in rotator cuff repair have yielded mixed results. One study on arthroscopic supraspinatus repair found that while repeated PRP injections improved patient satisfaction and clinical outcomes, there were no additional benefits to tendon integrity as measured by MRI scores or retear rates [45]. Another study concluded that PRP did not significantly improve clinical or structural outcomes in patients with isolated supraspinatus tears, suggesting that the role of PRP in tendon healing remains uncertain [22]. This discrepancy could be attributed to variations in PRP preparation [46], activation methods [47], and the timing of application [48], all of which can influence its therapeutic effects.

Advantages of Gel-Based PRP delivery

Our study utilized a PRP gel injected directly at the tendon-bone interface under arthroscopic visualization, a method that differs from prior studies that typically used liquid PRP injections without controlled gel formation [22] or precise delivery to the treatment area under direct arthroscopic guidance [45]. Research has demonstrated that combining calcium gluconate with thrombin enhances platelet activation and promotes a higher release of growth factors, thereby improving the healing process [49–51]. Unlike traditional injections prone to rapid dispersion in synovial fluid, arthroscopically guided gel deposition achieves spatial confinement to the repair site. Furthermore, studies have explored the use of burr techniques to freshen the greater tubercle of the humerus to enhance tendon-bone healing. This method stimulates bone marrow release, which may complement the effects of PRP gel by further improving tendon-bone integration [52–55].

It is important to contextualize our positive findings within the broader literature, which includes studies with negative results. For instance, a randomized controlled trial by Rodeo et al. found that the application of a thrombin-activated platelet-rich fibrin matrix did not significantly improve healing rates or functional outcomes after rotator cuff repair compared to controls [56]. The divergence in outcomes between our study and that of Rodeo et al. may be attributed to key methodological differences. Our PRP gel, activated with a combination of thrombin and calcium gluconate, likely forms a more robust and adherent fibrin scaffold than the preparation used in the earlier study. This scaffold may provide superior retention and a more sustained release of growth factors. Additionally, the precise, arthroscopically guided delivery of the gel in a liquid state before polymerization, ensuring complete coverage of the footprint, may offer a delivery advantage. These technical refinements in both formulation and application may explain the enhanced structural healing observed in our cohort.

Clinical significance of early functional gains

The selection of the 6-month postoperative interval for functional and structural assessment aligns strategically with critical biological, clinical, and socioeconomic benchmarks. Biologically, this period represents the peak window for retear risk and early tendon-bone maturation, enabling timely detection of healing integrity through Sugaya classification—a validated predictor of long-term structural outcomes [57]. Clinically, the 6-month window is critical as it aligns with the time frame in which achieving accelerated functional reinstatement—a central tenet of the ERAS paradigm—holds the greatest socioeconomic value. Our data demonstrate that PRP gel augmentation was associated with a significantly accelerated recovery within this pivotal window, evidenced by superior CMS improvement (Δ = 23.33 vs. 13.08, p < 0.01) and pain reduction (ΔVAS = 3.97 vs. 3.51, p < 0.01). These gains translate directly to socioeconomic value: earlier restoration of shoulder function (SSV: 82.97% vs. 78.85%) and pain control enable expedited return to occupational demands [58]. PRP gel was associated with significantly improved structural healing, with 89.0% achieving favorable Sugaya Ⅰ/Ⅱ grades versus 54.1% in controls (p < 0.001) and reduced retear rates (Ⅳ/Ⅴ: 2.2% vs. 13.1%, p < 0.01), alongside greater tendon thickness (0.63 ± 0.08 cm vs. 0.50 ± 0.06 cm, p < 0.001). This structural improvement may diminish compensatory strain on the contralateral shoulder, lowering secondary injury risks associated with unresolved dysfunction [59]. Furthermore, it not only enhances the quality of life for patients but also effectively reduces the economic burden on social health insurance. From a healthcare systems perspective, this 6-month checkpoint provides insurers with objective evidence (e.g., MRI-based healing metrics, functional scores) to justify coverage of adjunctive therapies like PRP gel, which may reduce long-term revision costs and disability claims.

Age-stratified subgroup analysis

Our subgroup analysis suggests that age may influence functional outcomes following PRP-augmented rotator cuff repair. While younger patients (< 70 years) achieved statistically superior CMS and ASES scores compared to older patients (≥ 70 years), the observed differences (ΔCMS = 6.14; ΔASES = 5.24) fell below established minimal clinically important differences (MCID) for these scales (CMS MCID = 10.4; ASES MCID = 6.5–17). This implies that while statistical significance was detected, the clinical relevance of these differences remains uncertain.

Importantly, a parallel trend was observed in structural healing. Although the distribution of Sugaya classification grades did not reach statistical significance between age subgroups (p = 0.484), the younger cohort exhibited a numerically higher rate of favorable healing (Grades Ⅰ/Ⅱ: 91.0% vs. 76.9%) and a lower retear rate (Grades Ⅳ/V: 1.3% vs. 7.7%). This consistent pattern across both functional and structural outcomes reinforces the notion that age is a factor in the healing response, even if the study was underpowered to detect statistically significant differences in structural endpoints within this subgroup.

Several factors may explain this age-dependent trend: (1) Biological Healing Capacity: Diminished cellular responsiveness to growth factors in elderly patients may attenuate PRP-driven tendon regeneration. (2) Comorbidities: Older adults often exhibit comorbidities (e.g., microvascular disease, sarcopenia) that impede tendon-bone healing. 3.Rehabilitation Adherence: Younger patients may engage more rigorously in postoperative therapy, amplifying functional gains. This observed age-dependent efficacy is consistent with previous research by Murrell et al. [60], which also highlighted age as a significant factor influencing outcomes in rotator cuff healing. These findings highlight the need for age-specific rehabilitation protocols and larger studies validating PRP’s role in elderly populations.

Limitations and future research directions

Despite promising outcomes, this study has notable constraints. First, its retrospective and non-randomized design introduces the potential for selection bias. The assignment of patients to the PRP and control groups was based on surgical time periods rather than randomization. Although the two groups were well-balanced in terms of baseline demographic and clinical characteristics (Table 1), unmeasured confounding factors could still influence the outcomes. Second, the 6-month follow-up precludes assessment of Sugaya grade progression and re-tear rates peaking at 12–24 months. Third, the statistically significant functional improvements in the PRP group should be interpreted with caution. The absolute score differences, while detectable due to the study’s adequate sample size and power, are modest and may fall below established thresholds for minimal clinically important difference (MCID), limiting their immediate clinical relevance. Additionally, although the PRP group demonstrated a statistically significant increase in maximum tendon thickness at the repair site compared to the control group (0.63 ± 0.08 cm vs. 0.50 ± 0.06 cm, p < 0.001), the absolute difference is modest. The clinical relevance of this incremental increase remains uncertain, and its repeatability and functional correlation warrant further investigation in larger studies.

Larger clinical trials with longer follow-up periods and more comprehensive outcome measures, such as re-tear rates and quality of life, are essential to fully evaluate the long-term benefits and limitations of PRP gel therapy. Standardization of PRP parameters (platelet concentration > 1,000 × 10⁹/L; thrombin-calcium activation ratios) and combinatorial approaches with microfracture or mesenchymal stem cells warrant investigation to optimize age-specific protocols. Additionally, the exact mechanism by which PRP gel accelerates tendon-bone healing remains unclear. While growth factors in PRP have been shown to improve healing, the precise role of the gel’s physical properties (such as its viscosity and scaffold-like structure) in promoting cellular behavior at the tendon-bone interface requires further investigation. Further studies with histological analyses could help elucidate the cellular and molecular mechanisms underlying the observed improvements in tendon healing.

Conclusion

By focusing on this pivotal recovery phase, our research aligns with ERAS objectives to bridge the gap between surgical success and timely return to productivity, addressing both biological healing and socioeconomic implications. By addressing these questions, we seek to advance the paradigm of accelerated rehabilitation in rotator cuff surgery, offering insights into optimizing PRP-based therapies for clinical practice. In conclusion, intraoperative arthroscopic delivery of thrombin-activated PRP gel to the tendon-bone interface was associated with significant improvements in functional outcomes (CMS, ASES, SSV), reductions in pain (VAS), and enhancement of structural healing (improved Sugaya healing grades, reduced retear rates, increased tendon thickness) at the 6-month follow-up compared to standard repair alone. The 6-month window—strategically selected for its biological significance (peak retear risk), relevance to accelerated functional reinstatement, and socioeconomic impact (earlier return to work)—serves as a critical benchmark for evaluating adjunctive therapies. Our findings demonstrate that the use of PRP gel was associated with a reduction in compensatory contralateral strain and productivity losses, addressing both clinical and health-economic priorities in rotator cuff rehabilitation. Future prospective studies with extended follow-up are warranted to validate long-term benefits, optimize PRP standardization, and refine age-specific protocols.

Authors' contributions

JZ and LY wrote the main manuscript text and both YY, LY, YY, XZ, and QZ participated in the study. All seven authors read and approved the final manuscript.

Funding

This work was supported by the Medical and Health Research Project of Zhejiang Province (No.2025KY1819).

Data availability

The datasets used and analyzed during the current study are available from the corresponding author, as a supplementary file, on reasonable request.

Declarations

Ethics approval and consent to participate

The study was approved by Ethics Committee of Zhejiang Taizhou Hospital (No. K20221219), and all methods were performed in accordance with the relevant guidelines and regulations. All procedures performed in this study involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. Due to the retrospective study design, the need for individual informed consent was waived by the Ethics Committee of Zhejiang Taizhou Hospital.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.