Arthroscopic Rotator Cuff Repair With Metal and Biodegradable Suture Anchors: A Prospective Randomized Study

Arthroscopic Rotator Cuff Repair With Metal and Biodegradable Suture Anchors: A Prospective Randomized Study Giuseppe Milano, M.D., Andrea Grasso, M.D., Matteo Salvatore, M.D., Maristella F. Saccomanno, M.D., Laura Deriu, M.D., and Carlo Fabbriciani, M.D.

Purpose: The purpose of this study was to compare the clinical outcome of arthroscopic rotator cuff repair with metal and biodegradable suture anchors. Methods: Arthroscopic rotator cuff repair was performed in 110 patients with a full-thickness rotator cuff tear. They were divided into 2 groups of 55 patients each, according to suture anchors used: metal anchors in group 1 and biodegradable anchors in group 2. Results were evaluated by use of the Disabilities of the Arm, Shoulder and Hand (DASH) and Work-DASH self-administered questionnaires, as well as the Constant score normalized for age and sex. On analyzing the results at 2 years’ follow-up, we considered the following independent variables: baseline scores; age; sex; arm dominance; location, shape, and retraction of cuff tear; fatty degeneration; treatment of biceps tendon; rotator cuff repair technique (anchors or anchors and side to side); and number of anchors. Univariate and multivariate statistical analyses were performed to determine which variables were independently associated with the outcome. Significance was set at P ⬍ .05. Results: Of the patients, 9 (8.2%) were lost to follow-up. Comparison between groups did not show significant differences for each variable considered. Overall, according to the results, the mean DASH scores were 17.6 ⫾ 17.2 points in group 1 and 22.8 ⫾ 19.9 points in group 2; the mean Work-DASH scores were 24.9 ⫾ 28.1 points and 22.5 ⫾ 24.1 points, respectively; and the mean Constant scores were 104 ⫾ 20.5 points and 98.6 ⫾ 14.3 points, respectively. Differences between groups 1 and 2 were not significant. Univariate and multivariate analysis showed that only baseline score, age, tear location, and fatty degeneration significantly and independently influenced the outcome. Conclusions: At a short-term follow-up, differences between arthroscopic repair of full-thickness rotator cuff tears with metal and biodegradable suture anchors were not significant. Level of Evidence: Level I, high-quality randomized controlled trial with no statistically significant differences but narrow confidence intervals.

T

he use of biodegradable materials in orthopaedic surgery has progressively increased during the last decades, with a wide application in reparative and reconstructive arthroscopic procedures. Theoretic advantages of biodegradable over metal implants include

From the Department of Orthopaedics and Traumatology, Catholic University (G.M., M.F.S., L.D., C.F.), Rome, Italy; and Villa Valeria Clinic (A.G., M.S.), Rome, Italy. The authors report no conflict of interest. Received August 10, 2009; accepted January 28, 2010. Address correspondence and reprint requests to Giuseppe Milano, M.D., Department of Orthopaedics and Traumatology, Catholic University, Largo A. Gemelli, 8-00168 Rome (RM), Italy. E-mail: [email protected] © 2010 by the Arthroscopy Association of North America 0749-8063/9480/$36.00 doi:10.1016/j.arthro.2010.01.030

easier revision, less postoperative imaging alteration, and eventual hardware resorption. The use of biodegradable implants in rotator cuff surgery has been introduced in recent times. Several ex vivo studies focused on the mechanical behavior of biodegradable devices for rotator cuff repair1-8; however, few articles have reported on the efficacy of these implants in clinical practice, and they have shown disagreement in their results when compared with metal suture anchors.9,10 One of the major concerns about the use of biodegradable devices in rotator cuff surgery is related to the potential risk of bone resorption around the implant and consequent implant dislodgement.11,12 The purpose of this study was to compare the clinical outcome of arthroscopic rotator cuff repair by use

S112 Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 26, No 9 (September, Suppl 1), 2010: pp S112-S119

CUFF REPAIR WITH METAL AND BIODEGRADABLE ANCHORS of metal and biodegradable suture anchors in patients with a full-thickness rotator cuff tear. The null hypothesis of the study was that differences in clinical outcome between the 2 types of suture anchors would not be significant. METHODS For this study, we enlisted 110 patients with a full-thickness rotator cuff tear who accepted our invitation to enter the study and who signed an agreement disclosure form. In all cases the lesion was investigated preoperatively with a magnetic resonance imaging (MRI) study. Inclusion criteria for the study group were patients with a repairable full-thickness tear of the supraspinatus or the posterior-superior rotator cuff. Reparability of the tendon tear was defined as the possibility to reattach the tendon edge at least on the medial side of the tendon footprint without excessive tension or extensive releases, such as interval slides. Patients with biceps pathology were included. We also excluded patients with a partial-thickness or irreparable full-thickness tear, extension of the tear to the subscapularis tendon, an isolated subscapularis tear, labral pathology amenable to surgical repair, degenerative arthritis of the glenohumeral joint, symptomatic arthritis of the acromioclavicular joint, rotator cuff arthropathy, previous surgery on the same shoulder, or Workers’ Compensation claims. We confirmed patient inclusion at the time of arthroscopy, after verifying that the tear pattern matched the inclusion criteria. An arthroscopic rotator cuff repair was performed in all patients with a single-row technique. Patients were divided into 2 groups including 55 cases each. In group 1 rotator cuff repair was performed with metal suture anchors (Corkscrew FT II, 5.5 mm; Arthrex, Naples, FL); in group 2 we used biodegradable suture anchors (Bio-Corkscrew FT, 5.5 mm; Arthrex). All the anchors were preloaded with 2 No. 2 FiberWire sutures (Arthrex). Patients were randomly assigned to 1 of the 2 groups. Randomization was performed with a random sequence generator (www.random.org), and the randomization list was kept by an independent researcher (not involved in the study). Allocation concealment was performed by use of a closed-envelope procedure, and the assignment code of each patient to 1 of the 2 groups was shown to the surgeon only at the time of surgery. A single surgeon (G.M.) performed all the operations. During surgery, we documented the pattern of rotator cuff tear, according to the following criteria: location, shape, and retraction. The location of the tear

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was classified into 6 segments, according to Patte,13 as follows: 1, subscapularis; 2, rotator interval; 3, supraspinatus; 4, supraspinatus and part of infraspinatus; 5, supraspinatus and infraspinatus; or 6, massive rupture (extending to subscapularis). We included in the study only patients with tears located in segments 3, 4, and 5. The tear shape was classified as crescent shaped, L shaped, inverse L shaped, V shaped, or U shaped. Retraction was graded according to Patte (1, not retracted; 2, retracted to humeral head; or 3, retracted to glenoid). Fatty degeneration of rotator cuff muscles was documented on MRI and classified according to Fuchs et al.14 (grade 0, no fatty infiltration; grade 1, some fatty streaks; grade 2, more muscle than fat; grade 3, as much muscle as fat; or grade 4, less muscle than fat). Surgical Technique After induction of regional anesthesia by interscalene block, the patient was assessed in the beachchair position. The operated limb was held by use of a Star Sleeve (Arthrex) with 3 kg of traction. After diagnostic arthroscopy and debridement of tendon edges, the greater tuberosity was decorticated with a motorized shaver. The rotator cuff was repaired with 2 different techniques, according to tear pattern. We used a tendon-to-bone repair technique with suture anchors when possible. In more retracted and larger tears, we used a combined technique consisting of tendon-to-bone repair with suture anchors and side-toside repair with No. 2 FiberWire sutures. Suture anchors were placed at the medial edge of the tendon footprint. The number of anchors varied from 1 to 4 according to the size of the cuff tear. Each suture was passed through the tendon approximately 15 mm medial to the tear margin and tied in a simple configuration with a sliding Duncan knot, followed by 3 alternating half-hitches. Pathology of the long head of the biceps was treated by shaving when the lesion involved approximately less than 25% of the tendon; biceps instability or severe tendon lesions (involving approximately ⬎25% of tendon) were treated depending on the patient’s age. In patients aged over 50 years, we performed a biceps tenotomy; in the other cases we performed a tenodesis with 2 metal suture anchors (Corkscrew FT II, 5.5 mm) placed in the proximal part of the bicipital groove.15 Postoperative Rehabilitation After surgery, a sling was applied to the operated limb and was maintained for 3 weeks; after this pe-

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riod, all patients underwent the following rehabilitation program adapted from principles of shoulder rehabilitation of Kibler et al.16: ●

First phase (weeks 4-8 after surgery)—range-ofmotion exercise program (passive, active assisted, and active) ● Second phase (weeks 9-12 after surgery)—muscle strengthening program by closed kinetic chain exercises for rotator cuff, subscapularis, biceps, deltoid, pectoralis major, and scapular stabilizers ● Third phase (weeks 13-16 after surgery)— open kinetic chain exercises, proprioceptive and plyometric exercises, and postural rehabilitation of the kinetic chain (lumbo-pelvic, thoracolumbar, and scapulothoracic regions) No differences in the rehabilitation program were considered between the 2 groups or according to the extent of rotator cuff tear. Patients were examined every 2 weeks for the first 3 months and then once a month until the sixth month after surgery. Outcome Measurements Patients were evaluated preoperatively and at followup by use of subjective and objective questionnaires. Subjective outcome was analyzed with the national validated version of the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire, together with the optional module for working capacity (Work-DASH).17 These self-administered questionnaires grade the disease-related disability and are based on a metric scale, ranging from 0 points (minimum disability, best result) to 100 points (maximum disability, poorest result). Objective evaluation was performed with the scoring system of Constant and Murley.18 Assessors who performed both baseline and follow-up objective evaluations were blind to allocation. Sample Size Calculation Sample size was calculated according to the primary outcome measure selected (DASH score). We performed a previous pilot study on a series of 30 patients with a full-thickness rotator cuff tear who matched the inclusion and exclusion criteria of the present study. In these patients we performed the control treatment (arthroscopic rotator cuff repair with metal suture anchors). The pilot sample showed a normal distribution for all the variables considered, and the mean DASH score at 1-year follow-up was 18.2 ⫾ 16.4 points. On considering 10 points as the minimal clinically important difference detectable

with the DASH score,19 we determined sample size with dedicated statistical software (G*Power, version 3.0.5, Heinrich Heine University, Dusseldoerf, Germany) for sample size calculation using an a priori model of power analysis and a 2-sided alternative hypothesis, given ␣ (the probability of yielding a type I error) equal to .05, 1 ⫺ ␤ (the power to detect a difference if one truly exists) equal to .80, ␴ as the SD reported in the pilot TABLE 1.

Comparison Between Groups for Variables Considered

Variable DASH score at baseline (0-100) Work-DASH score at baseline (0-100) Constant score at baseline (0-100) Mean age (yr) Sex Male Female Arm dominance Yes No Location Segment 3 Segment 4 Segment 5 Shape Crescent L Inverse L V U Retraction Grade 1 Grade 2 Grade 3 Fatty degeneration Grade 1 Grade 2 Grade 3 Grade 4 LHB treatment No (or shaving) Tenotomy Tenodesis Repair technique Anchors Combined No. of anchors 1 2 3 4

Group 1

Group 2

P Value

52.5 ⫾ 21.9

52.3 ⫾ 23

.961

69.2 ⫾ 23

66.2 ⫾ 26.9

.543

50.5 ⫾ 14.9 62.8 ⫾ 7.9

50.3 ⫾ 14.9 60.4 ⫾ 8.6

.957 .146 .212

31 21

35 14

33 19

37 12

16 19 17

13 22 14

26 4 6 2 14

20 5 10 5 9

15 23 14

11 26 12

13 15 16 8

10 19 13 7

32 12 8

23 15 11

32 23

20 26

12 18 20 2

10 25 14 0

.189

.694

.382

.649

.765

.334

.141

.231

Abbreviation: LHB, long head of biceps.

CUFF REPAIR WITH METAL AND BIODEGRADABLE ANCHORS study (16.4), and ⌬ as the minimal clinically important difference of the DASH score (10 points). The sample size calculated was 44 cases per group. We increased this value to 55 per group to compensate for an eventual 20% maximum loss of patients at follow-up.

The confidence level was assumed to be 95%, and significance was set at P ⬍ .05. RESULTS The mean follow-up was 24.4 ⫾ 2.6 months. We lost 9 patient (8.2%) to follow-up, 3 from group 1 and 6 from group 2. We did not determine the causes for their lack of follow-up participation. The final evaluation was thus carried out in 101 patients. There were 66 men and 35 women. The age ranged between 46 and 80 years (mean age, 61.6 ⫾ 8.3 years). Comparison between groups did not show significant differences between them for each independent variable (Table 1). Comparison between groups showed that the metal anchor group had better DASH and Constant scores than the biodegradable anchor group, although the differences were not significant for each outcome considered (Table 2). Univariate analysis (Table 3) showed that among continuous variables, baseline score had a significant positive correlation with outcome for DASH and Constant scores, whereas age had a significant positive correlation with the DASH score and a significant negative correlation with the Constant score. For ordinal variables, tear retraction and fatty degeneration showed a significant positive correlation with the DASH and Work-DASH scores and a significant negative correlation with the Constant score. Among dichotomous variables, sex was significantly associated with the DASH score and repair technique was significantly associated with the Constant score. For nominal variables, tear location was significantly associated with the Work-DASH score, tear shape was significantly associated with all the outcomes, and number of anchors was significantly associated with the Constant score. All other variables did not show significant associations with the outcomes. On multivariate analysis (Table 4), baseline score and

Statistical Analysis Statistical analysis was performed with SPSS statistical software, version 10.1.3 (SPSS, Chicago, IL). We considered the following outcomes: total DASH score, total Work-DASH score, and total Constant score normalized for age and sex.20 The independent variables analyzed were baseline scores; age; sex; arm dominance; location, shape, and retraction of cuff tear; fatty degeneration; treatment of the biceps tendon; repair technique (tendon to bone v combined [tendon to bone and side to side]); and number of suture anchors. Comparison between the 2 groups for each independent variable was carried out with the Student t test for continuous variables and the ␹2 test for categorical variables. Comparison between the 2 groups for each outcome considered was performed by use of a 1-way analysis of covariance model with adjustment for baseline values. DASH and WorkDASH comparisons were also adjusted for age and sex. A univariate analysis was performed to determine which independent variables were significantly associated with the outcomes. We used Pearson linear correlation for continuous variables (baseline scores and age), Spearman linear correlation for ordinal variables (retraction and fatty degeneration), the Student t test for dichotomous variables (sex, dominance, and repair technique), and the analysis of variance test for nominal variables (location and shape of lesion, biceps treatment, and number of anchors). A multivariate analysis with linear regression by use of a stepwise selection model was performed to determine which variables were independently associated with the outcome.

TABLE 2.

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Univariate Analysis of Outcomes According to Treatment Group Mean ⫾ SD

95% CI

Outcome

Group 1

Group 2

P Value

Lower

Upper

DASH score (0-100)* Work-DASH score (0-100)* Constant score (0-100)†

17.6 ⫾ 17.2 24.9 ⫾ 28.1 104 ⫾ 20.5

22.8 ⫾ 19.9 22.5 ⫾ 24.1 98.6 ⫾ 14.3

.064 .690 .123

⫺13.792 ⫺8.525 ⫺1.480

0.401 12.820 12.271

Abbreviation: CI, confidence interval. *Adjusted for baseline score, age, and sex. †Adjusted for baseline score only.

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Univariate Analysis of Outcomes According to Variables Considered

DASH Score Variable Baseline score Age (yr) Sex Male Female Arm dominance Yes No Location Segment 3 Segment 4 Segment 5 Shape Crescent L Inverse L V U Retraction Grade 1 Grade 2 Grade 3 Fatty degeneration Grade 1 Grade 2 Grade 3 Grade 4 LHB treatment No (or shaving) Tenotomy Tenodesis Repair technique Anchors Combined No. of anchors 1 2 3 4

Mean ⫾ SD

Linear Correlation 0.222 0.285

Work-DASH Score P Value

Mean ⫾ SD

⫺0.80 0.096

.025* .004* .043*

17.1 ⫾ 16.1 25.8 ⫾ 22

Linear Correlation

Constant Score P Value .426 .339 .356

.892 102.1 ⫾ 15.7 99.8 ⫾ 22.2

.220

.015*

.315

25 ⫾ 26.3 15.5 ⫾ 22.9 33.3 ⫾ 27.3

104.1 ⫾ 14.2 102.5 ⫾ 21.1 97.4 ⫾ 16.2

.031*

.034*

.006*

16.2 ⫾ 24.8 17.4 ⫾ 21.1 34.4 ⫾ 26.2 25 33.4 ⫹ 29.9 0.247

.013*

14.7 ⫾ 16.5 20.2 ⫾ 19.1 25.4 ⫾ 19

107.1 ⫾ 11.2 97.2 ⫾ 9.2 102.3 ⫾ 10.1 103.5 ⫾ 7.2 90.4 ⫾ 29.7 0.253

.011*

14.9 ⫾ 23.9 22.8 ⫾ 24.1 34.1 ⫾ 29.2 0.487

.0001*

10.3 ⫾ 14.3 14.6 ⫾ 14.1 28.9 ⫾ 19.4 30.7 ⫾ 21.1

0.545

.209

.0001* 110.5 ⫾ 9.5 104.4 ⫾ 12.5 91.3 ⫾ 25.3 100.3 ⫾ 11.2 .151

22.7 ⫾ 23.6 31 ⫾ 31.6 16.1 ⫾ 23.3 .262

18.2 ⫾ 19.1 22.4 ⫾ 18

⫺0.258

.009*

⫺0.368

.0001*

.152 100.4 ⫾ 20.6 96.6 ⫾ 16.1 108.4 ⫾ 8.3

.085 19.5 ⫾ 24 28.7 ⫾ 28

.015* 105.6 ⫾ 11.8 96.4 ⫾ 22.3

.405 24.6 ⫾ 24.4 17.2 ⫾ 18.7 20.2 ⫾ 14.2 30.8

102.7 ⫾ 26.9 102.8 ⫾ 10.8 97.6 ⫾ 17.6

7.9 ⫾ 17.9 16.5 ⫾ 18.8 32.8 ⫾ 31.2 46.7 ⫾ 18

20.4 ⫾ 20.1 23.9 ⫾ 17.4 14 ⫾ 15.3

.008* .014* .450

.596

23.9 ⫾ 27 23.2 ⫾ 24.4

16.5 ⫾ 19.8 19.3 ⫾ 17.3 17.3 ⫾ 10.2 15.2 ⫾ 6.6 31 ⫾ 20.6

P Value

102.7 ⫾ 9.6 99 ⫾ 27.5

.550

18.8 ⫾ 17.1 17.4 ⫾ 15.5 24.9 ⫾ 18.6

Linear Correlation 0.263 ⫺0.244

21.9 ⫾ 25.1 27.1 ⫾ 28.1

20.8 ⫾ 19.9 18.6 ⫾ 15.8

Mean ⫾ SD

.133 26.4 ⫾ 31.7 17.6 ⫾ 20.8 28.1 ⫾ 27.7 50

.008* 90.5 ⫾ 31 103.6 ⫾ 8.5 104.8 ⫾ 11.7 116

Abbreviation: LHB, long head of biceps. *Statistically significant.

age were independently associated with the outcome only for DASH score, location was significantly associated with the Work-DASH score, and fatty degeneration was confirmed to be independently associated with the 3 outcomes measured: DASH, Work-DASH, and Constant scores. All the other significant associations observed on univariate analysis were not confirmed. Multivariate analysis confirmed that treatment (metal v biodegradable suture anchors) was not significantly associated with the outcomes. Given that the mean dif-

ference between the 2 groups in the primary outcome (DASH score) was less than 10 points, the null hypothesis of the study was accepted. DISCUSSION The use of biodegradable materials in shoulder arthroscopy started in the 1990s with polyglyconate tacks to treat glenohumeral instability.21,22 The clinical outcome of this treatment was shown to be

CUFF REPAIR WITH METAL AND BIODEGRADABLE ANCHORS TABLE 4.

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Multivariate Analysis by Linear Regression of Variables Significantly Associated With Outcomes DASH Score

Work-DASH Score

95% CI

Constant Score

95% CI

95% CI

Variable

P Value

Lower

Upper

P Value

Lower

Upper

P Value

Lower

Upper

Baseline score Age Sex Location Shape Retraction Fatty degeneration Repair technique No. of anchors Treatment group

.017 .046 † ⴱ † † .0001 ⴱ ⴱ †

0.032 0.007 — — — — 4.273 — — —

0.327 0.807 — — — — 10.799 — — —

* ⴱ ⴱ .010 † † .0001 ⴱ ⴱ †

— — — ⫺16.355 — — 11.973 — — —

— — — ⫺2.244 — — 22.856 — — —

† † * * † † .002 † † †

— — — — — — ⫺8.857 — — —

— — — — — — ⫺1.982 — — —

Abbreviation: CI, confidence interval. *Not analyzed because it was not significantly associated with the outcome on univariate analysis. †Excluded on multivariate analysis.

significantly worse than that with traditional open treatments23; furthermore, some authors reported complications associated with the intra-articular use of biodegradable tacks, such as synovitis, foreign body reaction, and chondral damage.24,25 These complications seemed to be related to the rapid degradation and fragmentation of the implants with formation of loose bodies, which can determine immune response and mechanical injuries to the joint.24,25 These phenomena caused a progressive decrease in the application of biodegradable tacks to address shoulder instability. On the contrary, increasing evidence of successful results with the use of suture anchors for the arthroscopic treatment of shoulder instability26,27 led many companies to produce biodegradable suture anchors to address shoulder instability, which yielded experimental and clinical results similar to those reported for metal suture anchors.28-30 Theoretic advantages of biodegradable suture anchors over tacks can be related to differences in implant design. Tacks have a prominent profile that is susceptible to breakage, with consequent risks of synovitis and mechanical injuries. On the contrary, suture anchors are completely recessed into bone; this implies a lower risk of migration and soft-tissue reaction. Application of biodegradable implants for rotator cuff repair is more recent, and there are not yet consistent results in the literature about their effectiveness. Recent biomechanical and clinical studies reported satisfactory results with the use of biodegradable tacks for rotator cuff repair.1,4,10 However, some other biomechanical studies showed that fixation

strength of biodegradable tacks was significantly lower than that of metal suture anchors.5,6 Moreover, Cummins et al.9 reported significantly worse clinical results using biodegradable tacks in comparison with metal suture anchors. Biodegradable suture anchors for rotator cuff repair seem to offer lower fixation strength than metal anchors.31 In particular, biomechanical studies have shown that biodegradable suture anchors are particularly sensitive to permanent load, because they creep under static tension,2,3 and their structural properties significantly reduce when mechanical tests are performed at body temperature instead of room temperature.3 However, a recent biomechanical study reported that pullout strength of biodegradable suture anchors was not lower than that of metal anchors, even in osteopenic bone.8 From a clinical viewpoint, there is a lack of information about the effectiveness of biodegradable suture anchors for addressing rotator cuff tears, although some authors reported complications with the use of these devices. Magee et al.32 reported on 30 patients with pain after rotator cuff repair with biodegradable anchors. On MRI, 13 of these patients showed a dislodgement of suture anchors. Recently, 2 case reports were published about failure of rotator cuff repair with biodegradable anchors by anchor disintegration and osteolysis.11,12 To our knowledge, this study is the first prospective randomized trial that compared clinical outcome of arthroscopic rotator cuff repair with metal and biodegradable suture anchors. We used the DASH outcome

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measure as the primary clinical outcome. The DASH outcome measure is a self-report questionnaire for specific disability-related quality-of-life assessment jointly developed by the Institute for Work & Health and the American Academy of Orthopaedic Surgeons. Different from other instruments, such as the American Shoulder and Elbow Surgeons score and the Simple Shoulder Test, a validated version of the DASH outcome measure exists in the Italian language. Because cross-cultural adaptation is crucial for a selfreport questionnaire, the DASH questionnaire probably represents the most reliable tool to evaluate subjective outcomes of shoulder diseases in Italy. On analyzing our results, we observed that the clinical outcome of arthroscopic rotator cuff repair was significantly associated with some independent variables, most of which were strictly related to the baseline conditions. On multivariate analysis, we observed that baseline score and age were independently associated with the primary outcome, tear location was independently associated with the working capacity of the patients, and fatty degeneration of rotator cuff muscles was independently associated with all the outcomes considered. These results confirmed those reported in recent outcome studies on rotator cuff repair.33-35 On considering the hypothesis of this study, we observed on univariate analysis that the metal anchor group had slightly better results than the biodegradable anchor group for the DASH and Constant scores. Although the differences between the 2 groups were not significant for all the outcomes considered, the difference in DASH score trended toward significance (P ⫽ .064). Multivariate analysis confirmed these data, and therefore we can affirm that the clinical outcome of rotator cuff repair was not significantly affected by the type of suture anchors used. Unquestionably, it is necessary to remark that our results refer to a single type of biodegradable anchor and that they cannot be considered definitive for all biodegradable implants. Barber et al.,7 in a recent biomechanical study, showed that design differences can affect the mechanical behavior of biodegradable suture anchors and that Bio-Corkscrew FT, which we used in our study, had the lowest displacement after 500 loading cycles in comparison to other biodegradable anchors. We want to point out that this study has important limitations. First, we did not consider bone quality of patients, which can significantly affect the fixation strength of biodegradable anchors.7 Second, we did

not perform a postoperative imaging study, so we were not able to compare functional results with anatomic integrity of cuff repair or to find out the eventual role of suture anchors in determining failure of repair and poor clinical outcome (inflammatory reaction, osteolysis, anchor migration, or breakage). Third, the follow-up was short, although the effectiveness of suture anchor repair has clinical relevance in the first period after surgery, before tendon healing has occurred, because late failures are supposed to depend on tissue quality (tendon degeneration, tension, healing capability) rather than fixation implants used for tendon repair.

CONCLUSIONS Our results showed that, at a short-term follow-up and with the numbers available, differences between arthroscopic repair of full-thickness rotator cuff tears with metal and biodegradable suture anchors were not significant for the 3 outcomes measured—DASH score, Work-DASH score, and Constant score—although there was a trend toward improved DASH score with metal suture anchors.

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