Stiffness and arthroscopic rotator cuff repair: a literature review

Introduction

The prevalence of rotator cuff tears has been estimated to be 20–30% in the general population (1-3) rising to 51–62% in populations over 80 (4,5). Rotator cuff tears are often repaired arthroscopically using sutures and anchors to reattach the torn tendon to its footprint (6). A recent Italian study noted a linear increase in the number of rotator cuff repairs performed each year since 2001 and estimated an increase of 170% by 2025 (7).

Tendon retear or failure to heal following rotator cuff repair is the most common complication occurring at rates of 11–94% (8), with the primary mode of failure due to tendon pulling through sutures (9). Retear usually occurs in the first 6 months following surgery (10,11). Postoperative stiffness is the second most common complication with an estimated incidence of up to 20% of patients (12), although recent evidence suggest that it may be an important factor associated with improved healing post rotator cuff repair surgery.

There has been extensive research into the factors associated with tendon retear, with many published reviews detailing predictors of retear such as preoperative tear size, age and fatty degeneration amongst others (13,14). Although, management options for concomitant shoulder stiffness and rotator cuff tear, or postoperative stiffness following rotator cuff repair has been explored to an extent in the literature (15,16), there remains a paucity in the literature regarding the relationship between stiffness and rotator cuff repair integrity.

Thus, this review aims to evaluate known factors associated with retear and the effect of shoulder stiffness on rotator cuff integrity. We present the following article in accordance with the Narrative Review reporting checklist (available at https://aoj.amegroups.com/article/view/10.21037/aoj-22-26/rc).

Methods

A literature review was conducted using online databases from the dates of inception to February 2021. The included databases were EMBASE, Ovid MEDLINE and all EBM Reviews. Search terms included (“rotator cuff” or “rotator cuff injuries” or “rotator cuff tear*”) and (“stiff*” or “rigid”) and (“tear*” or “tear size”) as either Medical Subject Headings of keywords. Reference lists of all retrieved full texts were screened for further identification of potentially relevant studies.

Selected studies included those with patients that had undergone rotator cuff repair and reported on the factors associated with rotator cuff retear. The timing of retear varied depending on the study. Case studies, conference abstracts and posters were excluded. After screening title, abstract and full texts, a total of 41 studies comprised the comprehensive summary of information included in this review (Table 1).

Discussion

Factors associated with retear rates

A number of factors have been found to be associated with an increased incidence of repair failure following arthroscopic rotator cuff repair.

Fatty degeneration

Goutallier et al. (17) conducted a seminal study (n=220) that identified a positive association between the global fatty degeneration index (GFDI) in the supraspinatus muscle belly and retear rate; rotator cuffs with a lower GFDI (<0.25) had a 19% retear rate, which then followed a linearly increasing trend up to a 100% retear rate in shoulders with GFDI ≥2. Interestingly, increased tear size, another important factor predictive of retear rates, has been demonstrated to be predictive of supraspinatus fatty degeneration (R²=0.43), which suggests tear size plays a significant role in determining the degree of fatty degeneration (18).

Age

Advancing age has been consistently identified as an independent predictor of rotator cuff retears (19-31). This relationship has been documented reliably in studies ranging from retrospective analyses to cadaveric studies (31). A large recent study (n=1,600) conducted at our institution by Diebold et al. (22) reported that the rate of retears in patients below the age of 50 was 5%, the rate then consistently increased with age between ages 50 to >80 years up to a rate of 34%. The most substantial increase in retear rate was noted between ages 60 to 69 and 70 to 79 (OR =1.89) (22).

Tear size

Thirty four studies were identified that utilised multivariate logistic regression to investigate whether tear size was associated with repair integrity (19-27) following rotator cuff repair (32-56) (Table 2). There was a general consensus that tear size is an independent predictor of rotator cuff repair integrity.

The first publication by our institution in this area was by Wu et al. (25) in 2012. In this retrospective study (n=500) that assessed 6 month repair integrity, the authors reported patients with <2 cm² rotator cuff tears as least likely to have a failed repair (10%) and that retear rate increased linearly with tear size: 2 to 4 cm² (16%), 4 to 6 cm² (31%), 6 to 8 cm² (50%), >8 cm² (57%) (25). Through multivariate regression analysis, tear area was found to be the most significant independent predictor of retear on forward (F-to-enter value =45) and backward (F-to-enter value =23.5) stepwise regression (25). A subsequent study by Le et al. (24) (n=1,000) in 2014 supported these findings and identified anteroposterior tear length as the strongest independent predictor of retear (Wald Statistic =33) followed by age (Wald Statistic =5) and operative time (Wald Statistic =4). The largest and most recent study in 2020 (n=1,962) by Duong et al. (19) noted a 4-fold increase in retear rate as anteroposterior tear length increased from 1 to 3 cm, after controlling for age and surgeon experience (Figure 1). Again, anteroposterior tear size was the most significant independent predictor of rotator cuff retear at 6 months (Wald Statistic =90) followed by surgeon case number (Wald Statistic =59), age (Wald Statistics =30) and hospital type (Wald Statistic =17) (19).

Figure 1 Retear rates according to varying anteroposterior tear size, patient ages, case numbers and hospital types. (A) Case number 1,000 in a private hospital; (B) case number 1,000 in a public hospital; (C) case number 3,000 in a private hospital; (D) case number 3,000 in a public hospital. Retear rates increased 4-fold when anteroposterior tear length increased from 1 to 3 cm, when other factors were controlled. Figure reproduced from (19).

A study from Korea evaluated 339 patients with a minimum 1 year follow-up post arthroscopic rotator cuff repair using either a single row or double row technique (23). The authors also reported significantly higher failure rates in patients with a tear >2 cm (34%) compared to patients with a tear <2 cm (11%) and identified the anteroposterior tear dimension to be an independent predictor that affected rotator cuff healing (OR =2.913) (23). This study was limited to full-thickness rotator cuff tear <3 cm in size (23). A later study (n=603) at the same institution reported that mediolateral tear length ≥3 cm (OR =4.56) had the greatest effect size as an independent predictor of rotator cuff healing followed by age (OR =2.71) and GFDI ≥2 (OR =2.91) (20). A subsequent study (n=531) by the same group also noted mediolateral tear length (OR =1.065), infraspinatus fatty degeneration (OR =1.913) and age (OR =1.038) as independent predictors of retear (41). At another Korean institution, Lee et al. (n=693) determined tear size (OR =0.38) and supraspinatus fatty degeneration (OR =0.59) to be independent risk factors for retear (21).

None of the above studies performed at our institution or elsewhere incorporated measures of stiffness into their regression analyses.

Stiffness

As outlined above, stiffness is the second most common complication following rotator cuff repair (57). Postoperative stiffness is typically characterised by limited passive shoulder range of motion (57). For many years, stiffness was considered a significant negative issue that required a delay in surgery if noted preoperatively or additional surgery if noted postoperatively (58). Recent evidence seems to suggest, however, that preoperative and/or postoperative stiffness may be a manifestation of a more robust healing response that is ultimately of benefit to the patient, and eventually resolves without requiring further surgery (46,57,59,60). These studies demonstrate that patients with preoperative and early postoperative stiffness appear to have lower retear rates when compared to their counterparts without stiffness (Table 3).

Preoperative stiffness

In 2016, our group conducted a study (n=195) that compared the outcomes of patients who had undergone rotator cuff repair and manipulation under anaesthesia with concomitant glenohumeral capsular release for severe preoperative stiffness (n=25) with chronologically matched rotator cuff repair patients (n=170) (60). At 6 months and 2-year follow-up, the authors noted higher retear rates in the non-stiff group [14% (P=0.047) and 20% (P=0.009) respectively] compared to 0% retear rate in the stiffness group (Figure 2) (60). A similar study (n=359) at another institution also reported a lower retear rate in their stiff group (2.6%) (n=39) compared to a non-stiff group (15%) (n=320) (46). Neither study was able to discern if the improved rotator cuff integrity was a result of the concomitant capsular release or stiffness. Both studies identified an association between preoperative stiffness and early postoperative stiffness [P<0.0001 (60); P=0.04 (61)].

Figure 2 Comparison of retear rates between stiff and non-stiff groups. Lower retear rates seen in group with preoperative stiffness compared to group without at 6 months and 2 years follow-up. Figure reproduced from (60). RCR, rotator cuff repair; MUA, manipulation under anaesthesia; CR, capsular release.

Tendon healing and stiffness

A prospective study (n=57) at our institution evaluated ultrasound changes after rotator cuff repair and found significantly increased bursal thickness, tendon vascularity and posterior capsular thickness in the repaired shoulder early on (at 1 and 6 weeks), as compared to the contralateral shoulder, with resolution by 6 months (64) (Figure 3A,3B). The increase in capsular thickness was associated with increased patient reported shoulder stiffness (64). This may suggest early postoperative shoulder stiffness is in fact associated with a more exuberant healing response.

Figure 3 Ultrasound changes after rotator cuff repair. A (A) pictorial representation and (B) graphical representation of changes in bursal thickness, capsule thickness, tendon vascularity and shoulder stiffness over 6 months after operation. ***, P<0.001. Figure reproduced from (64).

Postoperative stiffness

None of the earlier studies identified a significant difference in retear rates between groups that developed postoperative stiffness and those that did not, although there were several limitations. In 2010, a retrospective cohort study (n=43) by Parsons et al. (63) reported no statistically significant difference (P=0.079) for retear rate in the stiff group (30%) compared to the non-stiff group (64%), where stiffness was defined as external rotation <30° at 6 weeks postoperatively. In 2013, Chung et al. (61) performed a retrospective analysis (n=288) and identified patients as stiff or not at 1 year follow-up. Stiffness was defined as having any 1 of 3 criteria (external rotation <30°, forward flexion <120°, internal rotation <L3) (61). The authors observed a significantly higher retear rate in patients with postoperative stiffness at 1 year (90%) compared to patients without (18%) (61). An important consideration with this study is that postoperative stiffness was assessed at 1 year (61). More recently in 2017, a retrospective 10 year follow-up of rotator cuff repairs (n=210) found that retears were not significantly more frequent in the group with shoulder stiffness at 6 months (24%) compared to the group that did not report stiffness (19%) (62). Here, stiffness was defined as a deficit of >30^o in external rotation and forward flexion compared with the intact, contralateral shoulder (62). However, this study lost a substantial proportion of their patients to follow-up (37%) and also analysed patients operated on by 15 different surgeons with a mixture of open or arthroscopic repair, which may have adversely influenced the outcome (62).

Conversely, recent evidence that specifically investigated the effects of early postoperative stiffness found that it had a protective effect on rotator cuff retears at 6 months following surgical repair. In 2016, our institution conducted the largest study to date (n=1,533) to evaluate the relationship between stiffness and retears at 6 months follow-up (57). McNamara et al. (57) reported on multivariate analysis that patients with decreased passive shoulder range of motion at 6 and 12 weeks had significantly lower retear rates at 6 months (P<0.001). Specifically, patients with external rotation less than 20° had a significantly lower retear rate of 7%, compared to a rate of 15% in those with external rotation greater than 20° (57). Patient ranked shoulder stiffness postoperatively at 6 weeks was an independent predictor of rotator cuff integrity (Wald Statistic =11) (57).

A long-term follow-up was performed on the same cohort of patients from the aforementioned study, 69 with stiff and 63 with non-stiff shoulders (59). The stiff group were selected as the bottom 15^th percentile for external rotation at 6 weeks after surgery for each calendar year of surgery, whereas the non-stiff group was selected as the upper 15^th percentile (59). Patients in the stiff group experienced a significantly lower retear rate (10%) than patients without postoperative stiffness (30%) at a mean follow-up of 5 years after surgery (P=0.005) (59) (Figure 4). However, there was no statistically significant difference between rotator cuff retear rates in the stiff and non-stiff groups beyond 6 months after surgery (P=0.359) (59). Tear size was included as a variable in statistical analysis but did not differ significantly between the stiff and non-stiff groups (59).

Figure 4 Long term rotator cuff repair integrity. Intact rotator cuff repair survival in patients with postoperative stiff vs. non-stiff shoulders over 9 years follow-up. Figure reproduced from (59).

Resolution of stiffness

Our studies have shown that postoperative stiffness is typically most evident at 6 weeks and gradually improves over the first 6 months following rotator cuff repair. In the study by McNamara et al. (57), the stiff group reported significantly greater patient ranked shoulder stiffness and reduced passive range of motion as compared to the non-stiff group (P<0.001) at 6, 12 and 24 weeks following the operation. However, Millican et al. (59) found that by follow-up at 5 years there was no significant difference between the stiff and non-stiff groups for passive range of motion in internal rotation, abduction and forward flexion. The stiff group did have a significantly lower mean external rotation (50° vs. 61°), but all range of motion measurements returned to preoperative levels or better for both groups (59). The fact that there was no significant difference found in the long term between stiff and non-stiff groups for most measures of passive range of motion suggests that early postoperative shoulder stiffness has no lasting effects for patients.

Interactions between factors

Tear size and stiffness

There is some evidence that patients with smaller tears experience greater postoperative pain and are more likely to develop stiffness post rotator cuff repair prompting the question as to whether tear size and stiffness have an interaction that affects retear rates. McNamara et al. (57) reported greater patient ranked stiffness was associated with smaller anteroposterior tear size. Yeo et al. (65) (n=1,624) performed a retrospective cohort study with a primary focus on pain outcomes and identified that smaller tears were correlated with greater pain (r=0.14, P<0.0001) and difficulty with behind-the-head (r=0.09–0.15, P<0.0001) and overhead activities (r=0.11–0.16, P<0.0001) at 6 weeks. Rizvi et al. (66) (n=2,172) reported similar results with the mean tear size of those experiencing very severe pain being 191 mm² compared to 378 mm² in patients that experienced no pain. They also noted that stiffer shoulders preoperatively were more painful postoperatively at 6 weeks (r=0.2, P<0.001) (66). These findings suggest that smaller tears are associated with greater postoperative stiffness. However, none of these studies investigated the association between tear size and examiner-assessed passive range of motion after surgery, a question that requires further research.

Kim et al. (46) (n=359) reported a significant difference (P=0.002) between the mean mediolateral tear size of the stiff (18.9 mm) and non-stiff group (24.1 mm) for preoperatively stiff patients. This study performed multiple logistic regression analysis and identified mediolateral tear size (OR =1.043, P=0.014), but not preoperative stiffness (OR =0.229, P=0.164) as an independent predictor of retear (46). However, they did not evaluate the effect of postoperative stiffness in their analysis.

Other interactions

An understanding of the interactions between independent risk factors is likely to be of assistance to surgeons and patients when considering surgery (and the type of surgery) following rotator cuff repair. At our institution Duong et al. (19) recently found that anteroposterior tear length had no interaction effect with age at surgery (P=0.245) upon multiple logistic regression analysis—each was important, but the effect of each factor was additive, rather than compound. Further studies to identify and quantify potential interactions between these factors may provide patients and surgeons better prognostic information.

Conclusions

There is a substantial amount of high-quality evidence in the literature that indicates larger tear sizes are important independent predictors of higher retear rates following arthroscopic rotator cuff repair. There is some, often circumstantial evidence, that stiffness, either preoperative, or postoperative is associated with a more vigorous healing response and more intact repairs, and that these effects are more pronounced in younger patients. This seems to suggest that early postoperative shoulder stiffness is an indicator of beneficial healing and is in fact a positive “complication” (67). Smaller tears are associated with more pain and stiffness. It is possible that tear size per se is not important, but rather the more vigorous healing response that occurs following repair of a small tear.

Acknowledgments

Funding: None.

Footnote

Reporting Checklist: The authors have completed the Narrative Review reporting checklist. Available at https://aoj.amegroups.com/article/view/10.21037/aoj-22-26/rc

Peer Review File: Available at https://aoj.amegroups.com/article/view/10.21037/aoj-22-26/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://aoj.amegroups.com/article/view/10.21037/aoj-22-26/coif). GACM is on the editorial board of both Journal of Shoulder and Elbow Surgery, and Shoulder & Elbow (UK) and is a paid consultant for Smith and Nephew. Siemens and General Electric provide ultrasound equipment to be used to collect data in the study. The other authors have no conflicts of interest to declare.

Ethical Statement:The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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