Evaluation of the Risk Factors for a Rotator Cuff Retear After Repair Surgery

Abstract

Background:

A retear is a significant clinical problem after rotator cuff repair. However, no study has evaluated the retear rate with regard to the extent of footprint coverage.

Purpose:

To evaluate the preoperative and intraoperative factors for a retear after rotator cuff repair, and to confirm the relationship with the extent of footprint coverage.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Data were retrospectively collected from 693 patients who underwent arthroscopic rotator cuff repair between January 2006 and December 2014. All repairs were classified into 4 types of completeness of repair according to the amount of footprint coverage at the end of surgery. All patients underwent magnetic resonance imaging (MRI) after a mean postoperative duration of 5.4 months. Preoperative demographic data, functional scores, range of motion, and global fatty degeneration on preoperative MRI and intraoperative variables including the tear size, completeness of rotator cuff repair, concomitant subscapularis repair, number of suture anchors used, repair technique (single-row or transosseous-equivalent double-row repair), and surgical duration were evaluated. Furthermore, the factors associated with failure using the single-row technique and transosseous-equivalent double-row technique were analyzed separately.

Results:

The retear rate was 7.22%. Univariate analysis revealed that rotator cuff retears were affected by age; the presence of inflammatory arthritis; the completeness of rotator cuff repair; the initial tear size; the number of suture anchors; mean operative time; functional visual analog scale scores; Simple Shoulder Test findings; American Shoulder and Elbow Surgeons scores; and fatty degeneration of the supraspinatus, infraspinatus, and subscapularis. Multivariate logistic regression analysis revealed patient age, initial tear size, and fatty degeneration of the supraspinatus as independent risk factors for a rotator cuff retear. Multivariate logistic regression analysis of the single-row group revealed patient age and fatty degeneration of the supraspinatus as independent risk factors for a rotator cuff retear. Multivariate logistic regression analysis of the transosseous-equivalent double-row group revealed a frozen shoulder as an independent risk factor for a rotator cuff retear.

Conclusion:

Our results suggest that patient age, initial tear size, and fatty degeneration of the supraspinatus are independent risk factors for a rotator cuff retear, whereas the completeness of rotator cuff repair based on the extent of footprint coverage and repair technique are not.

Keywords

shoulder rotator cuff tear arthroscopic rotator cuff repair retear extent of footprint coverage

A rotator cuff tear is one of the most important causes of shoulder problems, and its prevalence increases with age.^10,50 Full-thickness tears and partial-thickness tears that involve >50% of the tendon thickness are indications for surgical rotator cuff repair.³⁵ Arthroscopic repair is widely performed, with good outcomes reported in several studies.^15,16

A retear of the repaired tendon is a significant clinical problem after rotator cuff repair. Historical estimates of the retear rate range from 11% to 94%,^15,23,30 while more recent estimates range from 11% to 57%.^{2,12,24,46,47,54} However, the factors affecting a rotator cuff retear remain unclear, although patient age, preoperative tear size, degree of muscular atrophy, degree of fatty infiltration, surgical technique, and inappropriate postoperative rehabilitation have been implicated.^{2,11,15,20,33,48}

To date, no study has evaluated the retear rate with regard to the completeness of rotator cuff repair based on the extent of footprint coverage. It is often difficult to cover the entire length (both medial-lateral and anterior-posterior) of the supraspinatus-infraspinatus footprint because of retraction, atrophy, and tendon loss. We believe that the retear rate should differ between patients with complete and incomplete footprint coverage. However, no valid conclusion can be drawn in this regard from the findings of available studies.

The purpose of the present study was to evaluate the preoperative and intraoperative factors for a retear after rotator cuff repair, with particular focus on the influence of the footprint coverage and repair technique. The tested hypothesis was that greater footprint coverage would result in a better healing rate while the repair technique would not affect the retear rate.

Methods

This cohort study was approved by the Institutional Review Board of our hospital. Between January 2006 and December 2014, a total of 1633 arthroscopic rotator cuff repairs were performed by a single surgeon.

The inclusion criteria were as follows: repair of arthroscopically confirmed rotator cuff tears at our institution, availability of preoperative and 5- to 6-month postoperative magnetic resonance imaging (MRI) findings, and a follow-up duration of more than 1 year. A total of 417 patients (60.2%) were followed up for more than 24 months. Surgical indications included full-thickness rotator cuff tears or partial-thickness tears involving >80% of the thickness of the tendon, with more than a 1.5-cm tear of the anteroposterior diameter and persistent pain and functional disability after nonsurgical treatments lasting at least 3 months. Because partial-thickness tears were nearly full-thickness tears, we did not evaluate the difference between partial-thickness tears and full-thickness tears. Rotator cuff tears were diagnosed by preoperative MRI.

The exclusion criteria were as follows: type IV partial repair (n = 64)^29,53; no record of the type of repair (n = 105); massive tears (n = 148); revision surgery (n = 37); main tear of the subscapularis tendon (n = 28); calcific tendinitis, fracture, or infection (n = 92); open repair (n = 1); and missing preoperative and postoperative MRI data (n = 465). Eventually, a total of 693 patients were enrolled in this study.

Iannotti et al²⁵ reported that retears primarily occur between 6 and 26 weeks after arthroscopic rotator cuff repair. Khazzam et al²⁷ reported that intact rotator cuff repairs or full-thickness retears can be identified with moderate reliability when evaluating MRI scans after rotator cuff repair. Therefore, a retear was evaluated on postoperative MRI performed at a mean postoperative duration of 5.4 months (range, 2-48 months). In total, 665 patients (96.0%) underwent shoulder MRI between 4 and 7 months. The classification for tendon integrity proposed by Sugaya et al⁴⁵ was used as follows: type I, a repaired rotator cuff with sufficient thickness and homogeneous low intensity on each image; type II, sufficient thickness associated with a partial high-intensity area; type III, insufficient thickness without discontinuity; type IV, presence of a minor discontinuity in more than one slice of each image, suggesting a small tear; and type V, presence of a major discontinuity on each image, suggesting a medium or large tear. Thus, types I, II, and III represent healed rotator cuffs, while types IV and V represent retears.

Preoperative Factors

We reviewed the medical records of all patients. Preoperative demographic data included sex; age; involvement of the dominant arm; time from symptom onset to surgery; and a history of a contralateral shoulder problem, shoulder dislocation, trauma, thyroid disease (hyperthyroidism, hypothyroidism), inflammatory arthritis (rheumatic arthritis, systemic lupus erythematosus, ankylosing spondylitis), frozen shoulder, diabetes, and smoking.

A frozen shoulder was defined as follows: insidious onset of shoulder pain; global limitation of both active and passive ranges of motion (forward flexion <100°, external rotation at the side of 0°-20°, and internal rotation below the thoracic vertebral level)⁵²; and no history of major trauma, infection, or surgery around the affected shoulder.

Visual analog scale (VAS) pain scores, functional VAS (FVAS) scores, American Shoulder and Elbow Surgeons (ASES) scores,⁴⁴ and Constant scores⁷ were computed for all patients. The Simple Shoulder Test (SST) was also performed, along with examinations of the ranges of motion, including forward flexion, abduction, external rotation with the arm at the side, and internal rotation behind the back. Internal rotation was measured by the ability to reach the vertebral spinous process with the tip of the thumb and was based on contiguously numbered groups: T1-T12 to 1-12, L1-L5 to 13-17, buttock to 18, and greater tubercle of the proximal femur to 19.⁴¹

The supraspinatus, infraspinatus, and subscapularis muscles were evaluated on preoperative MRI using the Goutallier fatty infiltration staging system adapted by Fuchs et al.^14,19 The global fatty degeneration index (GFDI), which is the mean value of fatty infiltration indices for the supraspinatus, infraspinatus, and subscapularis, was then calculated.²⁰ Interobserver reliability was evaluated by asking 2 independent orthopaedic surgeons with fellowships in shoulder injuries to evaluate global fatty degeneration using the same image cuts. Both surgeons performed single evaluations because of the large sample size. Reliability was considered excellent, fair to good, and poor if the intraclass correlation coefficient (ICC) was >0.75, 0.4 to 0.75, and <0.4, respectively.³¹

Intraoperative Factors

Surgical Technique

All operations were performed by the senior author (J.C.Y.) and with patients in the lateral decubitus position. After the routine creation of posterior and anterior portals, intra-articular injuries, including those involving the long head of the biceps tendon, superior labrum, and subscapularis tendon, were addressed. The arthroscope was inserted into the subacromial space from the posterior portal. Posterolateral viewing and lateral working portals were created, and the subacromial space was evaluated. If required, acromioplasty was performed. After bursectomy and debridement of pathological rotator cuff tissue, the tear size was determined by a 5-mm calibrated probe. Mobility of the tendon was evaluated. In partial-thickness tears, we used the full-thickness tear conversion technique. After examination of the partially torn rotator cuff tear, we repaired it as a full-thickness rotator cuff tear.

With the single-row technique, the torn rotator cuff tendon was repaired in a single row. With the transosseous-equivalent double-row technique, double-loaded suture anchors were placed at the far lateral end of the greater tuberosity (Figure 1). In case of a subscapularis tendon tear, the footprint was prepared using a shaver, bur, and microfracturing. The suture anchor was placed, and the subscapularis tear was repaired using mattress sutures.

Before 2010, we performed all repairs using the single-row technique. Since 2010, we have repaired using the double-row technique. The single-row technique was compared with the transosseous-equivalent double-row technique.

Intraoperative Measurements

After the completion of rotator cuff repair, the completeness of repair according to the footprint coverage achieved was evaluated. All repairs were classified into 4 types according to the amount of footprint coverage at the end of surgery. Type I repair was defined as complete repair up to the lateral end of the greater tuberosity footprint. Type II repair was repair up to the medial half or less of the footprint. Types III and IV were incomplete repairs with either small exposure of the humeral head (<10 mm) or moderate exposure of the head with force-couple repair.^29,53 The tear size was classified as follows: small (<1 cm), medium (1 to <3 cm), large (3 to <5 cm), and massive (≥5 cm).^9,17 Additional parameters documented included the surgical duration, defined as the time from the first skin incision and visualization of the glenohumeral joint through the posterior portal until skin closure, and the number of suture anchors used to achieve fixation.

Postoperative Factors

Postoperative Rehabilitation

The postoperative rehabilitation protocol was identical for all patients. An abduction brace was applied for protection for 4 weeks, with an allowance for elbow and finger exercises. Passive range of motion exercises were initiated in the fourth week after surgery, and active range of motion exercises and rehabilitation were initiated after complete passive range of motion had been acquired. Strengthening exercises with elastic bands were initiated at 3 months after surgery. At a mean of 5.4 months after rotator cuff repair, all patients underwent shoulder MRI.

Statistical Analysis

All statistical analyses were performed with SAS version 9.4 (SAS Institute). A P value of <.05 was considered statistically significant. In univariate analysis, a generalized linear mixed model was used for continuous and categorical variables. In multivariate analysis, logistic regression with a forward stepwise technique was performed using variables that showed statistical significance in univariate analysis.

Preoperative variables included sex; age; involvement of the dominant arm; time from symptom onset to surgery; and a history of a contralateral shoulder problem, shoulder dislocation, trauma, thyroid disease (hyperthyroidism, hypothyroidism), inflammatory arthritis (rheumatic arthritis, systemic lupus erythematosus, ankylosing spondylitis), frozen shoulder, diabetes, and smoking. Intraoperative variables included the tear size, extent of footprint coverage, concomitant subscapularis repair, number of suture anchors used, repair technique (single-row or transosseous-equivalent double-row repair), and surgical duration. A t test and Fisher exact test were used to compare factors between the intact and retear groups.

In the absence of previously established risk factors with a particular focus on the influence of footprint coverage, the sample size calculation was based on previously reported retear rates for small-, medium-, and large-sized rotator cuff tears.⁴⁹ That study showed that the retear rate increased in a linear fashion with the size of the rotator cuff tear: the retear rate was 10% for 2-cm² tears, 16% for 2- to 4-cm² tears, and 31% for 4- to 6-cm² tears.⁴⁹ We surmised that a small-sized rotator cuff tear could be repaired with type I repair, a medium-sized rotator cuff tear with type I or type II repair, and a large-sized rotator cuff tear with type II or type III repair. Thus, the sample size calculation was based on the previously reported retear rates for small-, medium-, and large-sized rotator cuff tears. In this study, the retear rates that were type I (10%), type II (15%), and type III (30%) were interpreted as clinically meaningful. Therefore, for a P value of <.05 and a power of 0.8, 207 patients were required.

Results

Demographic Information

In total, 311 men and 382 women with a mean age of 59.5 years (range, 36-87 years) were evaluated. Of these, 501 showed right shoulder involvement, and 192 showed left shoulder involvement. The dominant arm was involved in 514 of 693 patients. Of the total, 120 patients reported a history of a contralateral shoulder problem, including rotator cuff tears, impingement syndrome, calcific tendinitis, and adhesive capsulitis. Twelve patients reported a previous dislocation of the involved shoulder, and 102 and 48 patients reported a history of diabetes mellitus and thyroid disease, respectively. The mean duration of symptoms (time from onset of shoulder symptoms until rotator cuff repair) was 27.5 months (range, 0-420 months). A total of 533 full-thickness tears and 160 partial-thickness tears were noted. The tear was small in 74 patients, medium in 348, and large in 111. A mean of 3 suture anchors (range, 1-7 anchors) were used, and the mean surgical duration was 91.2 minutes (range, 31-265 minutes). The mean follow-up duration was 31.2 months (range, 12-101 months). The single-row technique was used to treat 214 patients, and the transosseous-equivalent double-row technique was used to treat 479 patients. In terms of footprint coverage, 568 patients had type I, 83 had type II, and 42 had type III.

Patients with retears were older than those without. The rate of type III and the frequency of large full-thickness tears were higher in the retear group than in the intact group (Table 1).

Table 1

Comparison of Patients in the Intact and Retear Groups^a

	Intact Group (n = 643)	Retear Group (n = 50)	P Value
Age at surgery, y	59.1 (36-87)	64.6 (49-80)	<.0001
Completeness of rotator cuff repair			.05
I	533 (82.9)	35 (70.0)
II	74 (11.5)	9 (18.0)
III	36 (5.6)	6 (12.0)
Tear size			.0003
Partial	154 (24.0)	6 (12.0)
Small	73 (11.4)	1 (2.0)
Medium	323 (50.2)	25 (50.0)
Large	93 (14.5)	18 (36.0)
Repair technique			.4117
Single row	198 (30.8)	16 (32.0)
Transosseous-equivalent double row	445 (69.2)	34 (68.0)
No. of suture anchors	3.1 (1-7)	3.4 (1-5)	.02
Frozen shoulder, n	113	8	>.99
Operative time, min	90.6 (31-265)	98.5 (61-200)	.03
Fatty degeneration
Supraspinatus	1.24 (0-4)	1.80 (0-3)	<.0001
Infraspinatus	0.88 (0-4)	1.36 (0-3)	.0006
Subscapularis	0.75 (0-4)	1.04 (0-4)	.02

Values are presented as mean (range) or n (%).

Rotator Cuff Retear Rate

There were 50 patients with type IV or V tendon integrity and an additional 47 with type III tendon integrity. Accordingly, the retear rate was 7.22%.

Results of Univariate and Multivariate Analyses

Univariate analysis revealed that rotator cuff repair was affected by age; the presence of inflammatory arthritis; the completeness of rotator cuff repair; initial tear size; number of suture anchors; mean operative time; FVAS scores; SST findings; ASES scores; and fatty degeneration of the supraspinatus, infraspinatus, and subscapularis. The repair technique did not affect the retear rate (Table 2).

Table 2

Univariate Analysis Showing Variables Affecting Retears^a

	P Value	Beta
Age	<0.0001	0.06872
Completeness of rotator cuff repair	0.0153
II vs I		0.7154
III vs I		1.0621
Inflammatory arthritis	0.0268	2.3173
No. of suture anchors	0.0332	0.2576
Operative time	0.0078	0.01332
Repair technique (transosseous- equivalent double row vs single row)	0.4117	−0.2254
Tear size	<0.0001	0.6601
FVAS score	0.0295	−0.097
ASES score	0.0567	−0.01157
SST score	0.0132	−0.1017
Fatty degeneration
Supraspinatus	<0.0001	0.8728
Infraspinatus	<0.0001	0.701
Subscapularis	0.0339	0.3111

ASES, American Shoulder and Elbow Surgeons; FVAS, functional visual analog scale; SST, Simple Shoulder Test.

Multivariate logistic regression analysis revealed patient age, initial tear size, and fatty degeneration of the supraspinatus as independent risk factors for a rotator cuff retear. The completeness of rotator cuff repair based on the extent of footprint coverage and repair technique were not independent risk factors for a retear (Table 3).

Table 3

Factors for a Rotator Cuff Retear in Multivariate Analysis Using Logistic Regression

Variable	Exp (B)	P Value
Age	0.0415	.0266
Tear size	0.3785	.05
Fatty degeneration of supraspinatus	0.5903	.01

Analysis by Repair Technique

Univariate analysis of the single-row repair technique group revealed that rotator cuff repair was affected by age; the extent of footprint coverage; the initial tear size; the number of suture anchors; mean operative time; the presence of subscapularis tendon repair; and fatty degeneration of the supraspinatus, infraspinatus, and subscapularis. Multivariate logistic regression analysis revealed patient age and fatty degeneration of the supraspinatus as independent risk factors for a rotator cuff retear.

Univariate analysis of the transosseous-equivalent double-row technique group revealed that rotator cuff repair was affected by age, initial tear size, a frozen shoulder, FVAS scores, SST scores, and fatty degeneration of the supraspinatus and infraspinatus. Multivariate logistic regression analysis revealed a frozen shoulder as an independent risk factor for a rotator cuff retear (Table 4). However, the repair technique was not an independent risk factor for a rotator cuff retear.

Table 4

Comparison With Repair Technique in Multivariate Analysis Using Logistic Regression

Variable	Exp (B)	P Value
Single row repair technique
Age	0.08305	.05
Fatty degeneration of supraspinatus	1.2849	.0211
Double row repair technique
Frozen shoulder	0.202	.046

Interobserver Reproducibility

Reproducibility for the GFDI on sagittal oblique sections was good (Y-view; ICC, 0.73).

Subgroup Analysis

In general, type IV or V represents a retear as per the classification of Sugaya et al.⁴⁵ However, the status of type III tendons, whether healed or retorn, remains controversial. We conducted a subgroup analysis by adding patients with type III tendon integrity to those with type IV or V and found surgical duration, initial tear size, presence of a frozen shoulder, and fatty degeneration of the supraspinatus and infraspinatus as independent factors.

Discussion

The results of the present study suggest that age, initial tear size, and fatty degeneration of the supraspinatus are significant factors for a retear after arthroscopic rotator cuff repair, whereas the completeness of repair based on the extent of footprint coverage is not.

Some studies have shown a significant correlation between retears and rotator cuff tendon quality with regard to fatty degeneration and supraspinatus atrophy,^{2-5,18,20,24,39} while others have been unable to replicate these results.^4,13,21,40 Furthermore, limited studies have shown that other more general measures of tissue quality, such as biceps and acromioclavicular joint lesions, were correlated with retears.^6,39,54 The size of the initial tear is often implicated,^{1,3,5,22,24,28,38,39} although it is not always considered significant.^{2,4,12,13,23,34,40,54} The sample size in most studies evaluating the factors for a rotator cuff retear has ranged from 18 to 272 shoulders. As an exception, Wu et al⁴⁹ evaluated the effects of intraoperative variables on retears in 500 patients and found the initial tear size to be the best predictor, followed by patient age, while Le et al³² evaluated preoperative and intraoperative factors for 1000 consecutive rotator cuff repairs and found that the rotator cuff tear size (tear dimensions, tear size area, and tear thickness) was strongly associated with retears at 6 months after surgery. However, both these large-scale studies did not evaluate the effects of the completeness of rotator cuff repair based on the extent of footprint coverage.

The rate of retears in the present study was 7.22%, which was comparable or lesser than previously reported rates of 11% to 57%.^{2,12,24,46,47,54} Peters et al⁴³ and Kamath et al²⁶ showed that partial-thickness tears converted to full-thickness tears are less susceptible to retearing compared with full-thickness tears. There were 23.1% of partial-thickness tears in the present study, which may have influenced the slightly better retear rate.

Advancing age has been associated with retears because of its association with fatty degeneration, decreased resiliency of tissue to trauma, poorer tissue perfusion, and depleted stores of growth factors pivotal to tendon healing.^2,6,23,37,42 Cummins and Murrell⁸ and Mazzocca et al³⁶ reported that the most common mechanism underlying a retear is the pullout of intact sutures through the tendon. Therefore, the suture-tendon interface is a weak point, making it reasonable to suspect that tendon quality may be a key factor in retears.³² In the present study, the findings were consistent with previously documented results.

We found that the diabetic status of patients was not associated with retears, as reported by Le et al.³² The presence of a frozen shoulder also was not an independent factor for the single-row repair technique.

The number of suture anchors was not an independent factor. The number of suture anchors, however, was strongly correlated with the initial tear size. Therefore, multivariate logistic regression analysis did not reveal it to be an independent factor.

One of the purposes of this study was to determine the relative importance of factors associated with retears. We can conclude that factors related to patient age, initial tear size, and fatty degeneration of the supraspinatus are strongly correlated with a retear. Although numerous previous studies have shown a significant effect for the initial tear size,^{1,3,5,22,24,28,38,39} to our knowledge, Gladstone et al¹⁸ and Wu et al⁴⁹ published the only previous studies identifying the initial tear size as an independent predictor of retears. Gladstone et al¹⁸ found that while muscle degeneration significantly affected retears when analyzed in isolation, the initial tear size was the only independent predictor of healing in multivariate analysis; these results were consistent with our own.

The other major aim of this study was to evaluate whether the completeness of repair based on the extent of footprint coverage is associated with retears. However, this was not found to be an independent factor for either group. We speculate that the completeness of repair is highly dependent on other variables, particularly the initial tear size and fatty degeneration of the supraspinatus and infraspinatus. Any effort to maximize the extent of footprint coverage is likely to affect the above results. Yoo et al⁵¹ reported that arthroscopic repair of large to massive rotator cuff tears was found to be associated with a relatively high retear rate (45.5%). In the present study, the patients with large-size tears (111 patients, 16.0%) were fewer than those with partial-thickness, small-size, and medium-size tears (582 patients, 84.0%). The proportion of large-size tears to medium-size tears or smaller was not even. Therefore, this distribution is also likely to affect the above results.

The difference between the single-row technique and transosseous-equivalent double-row technique was evaluated. We divided the patients into 2 groups. Univariate analysis of the 2 different techniques revealed that rotator cuff repair was affected by age, initial tear size, and fatty degeneration of the supraspinatus and infraspinatus. Multivariate logistic regression analysis of the 2 different techniques revealed that rotator cuff repair was affected by age and fatty degeneration of the supraspinatus with the single-row technique and a frozen shoulder with the transosseous-equivalent double-row technique. The completeness of repair based on the extent of footprint coverage was not associated with retears as an independent factor for either group.

To our knowledge, this is the second largest study performing radiological evaluations of structural integrity after rotator cuff repair. However, there are several limitations. First, the study has the inherent weaknesses of a retrospective study. We did not obtain preoperative and postoperative MRI data in many patients (n = 465), which could cause selection bias. We were often missing the postoperative MRI scans because patients frequently did not comply with this follow-up study, often for economic reasons (ie, the expensive charge). Second, a single surgeon performed all surgeries using the single-row repair technique until 2009 and the transosseous-equivalent double-row repair technique since 2010. Therefore, the results may not be applicable to other surgeons and/or other rotator cuff repair techniques. Third, although MRI measurements were obtained by 2 surgeons, measurement bias is inevitable. Fourth, a minimum 1-year follow-up duration was short. However, 417 patients (60.2%) were followed for more than 24 months. Because most retears occur between 12 and 26 weeks after repair, a follow-up duration of more than 1 year is sufficient to evaluate retear risk factors. Fifth, there was imprecision in the measurements of footprint coverage.

Conclusion

In conclusion, the results of this study suggest that age, initial tear size, and fatty degeneration of the supraspinatus are independent risk factors for a rotator cuff retear, whereas the completeness of rotator cuff repair based on the extent of footprint coverage and repair technique are not.

Footnotes

Acknowledgements

The authors thank Ye Ji Lim, PhD, for statistical analysis.

The authors declared that they have no conflicts of interest in the authorship and publication of this contribution.

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