In vivo blood flow after rotator cuff reconstruction in a sheep model: comparison of single versus double row

Animal Models of Rotator Cuff Injury and Repair: A Systematic Review

There are a large number of animal studies on rotator cuff injury and repair, but a lack of detailed research and evaluation on the animal models. This systematic review aims to provide a framework for animal studies and repair patches for rotator cuff injury. Four hundred nine animal studies were included, of which the most common animal model of rotator cuff injury is rat (53.56%), the most common site of rotator cuff injury is the supraspinatus tendon (62.10%), and the most common injury type (degree) is acute tear (full thickness) (48.41%). The most common research purpose is to evaluate the repair effect of the patch (24.94%), followed by the observation of pathophysiological changes after rotator cuff injury (20.87%). Among the five types of repair patch materials including nondegradable and degradable synthetic materials, autologous and allogeneic tissues, and naturally derived biomaterial, the last one is the mostly used (52.74%). For different animal models, the rodent models (rat and mouse) are the most commonly used and probably the most suitable species for preliminary studies of rotator cuff injury; the rabbit, canine, sheep, and goat models are more suitable for biomechanical performance testing, rehabilitation training, and validation of surgical methods; and the nonhuman primate models (monkey and baboon) are the closest to human, but it is more difficult to carry out the animal studies on them because of ethical issues, high feeding cost, and management difficulties.

Excessively High Repair Tension Decreases Microvascular Blood Flow Within the Rotator Cuff

BACKGROUND

Repair tension and microvascular blood flow within the rotator cuff has a critical impact on tendon healing after rotator cuff repair. However, the relationship between repair tension and microvascular blood flow within the rotator cuff remains unclear.

PURPOSE/HYPOTHESIS

The purpose of this study was to determine how much tension adversely affects microvascular blood flow within the rotator cuff. The hypothesis was that as the repair tension increases, the microvascular blood flow within the rotator cuff decreases.

STUDY DESIGN

Controlled laboratory study.

METHODS

Repair tension and microvascular blood flow within the rotator cuff of 30 patients with full-thickness rotator cuff tears were simultaneously measured using a digital tension meter and a contact-type laser Doppler flowmeter, respectively. Microvascular blood flow was measured under 4 levels of tension (0, 10, 20, and 30 N) at 5 points on the rotator cuff. The obtained values were statistically analyzed by a linear mixed-effects model to clarify the effect of tension on microvascular blood flow within the rotator cuff.

RESULTS

There was no statistically significant difference in microvascular blood flow (mL/min/100 g) within the rotator cuff between 0 N (mean, 3.51; 95% CI, 3.0-4.0) and 10 N (mean, 3.74; 95% CI, 3.2-4.3) of tension (P = .716). However, there were statistically significant differences in microvascular blood flow within the rotator cuff between 0 and 20 N of tension (mean, 2.84; 95% CI, 2.3-3.4) (P = .002) and between 0 and 30 N of tension (mean, 2.45; 95% CI, 1.9-3.0) (P < .001).

CONCLUSION/CLINICAL RELEVANCE

Our findings indicate that tension of ≥10 N during rotator cuff repair significantly decreases the microvascular blood flow within the rotator cuff. These data will contribute to determining the optimal repair tension during rotator cuff repair.

Biomechanical evaluation of a novel double rip-stop technique with medial row knots for rotator cuff repair: an in vitro study

Aims

Many biomechanical studies have shown that the weakest biomechanical point of a rotator cuff repair is the suture-tendon interface at the medial row. We developed a novel double rip-stop (DRS) technique to enhance the strength at the medial row for rotator cuff repair. The objective of this study was to evaluate the biomechanical properties of the DRS technique with the conventional suture-bridge (SB) technique and to evaluate the biomechanical performance of the DRS technique with medial row knots.

Methods

A total of 24 fresh-frozen porcine shoulders were used. The infraspinatus tendons were sharply dissected and randomly repaired by one of three techniques: SB repair (SB group), DRS repair (DRS group), and DRS with medial row knots repair (DRSK group). Specimens were tested to failure. In addition, 3 mm gap formation was measured and ultimate failure load, stiffness, and failure modes were recorded.

Results

The mean load to create a 3 mm gap formation in the DRSK and DRS groups was significantly higher than in the SB group. The DRSK group had the highest load to failure with a mean ultimate failure load of 395.0 N (SD 56.8) compared to the SB and DRS groups, which recorded 147.1 N (SD 34.3) and 285.9 N (SD 89.8), respectively (p < 0.001 for both). The DRS group showed a significantly higher mean failure load than the SB group (p = 0.006). Both the DRS and DRSK groups showed significantly higher mean stiffness than the SB group.

Conclusion

The biomechanical properties of the DRS technique were significantly improved compared to the SB technique. The DRS technique with medial row knots showed superior biomechanical performance than the DRS technique alone.

Does the Dog-Ear or Bird-Beak Deformity Remodel After Rotator Cuff Repair?

BACKGROUND

Dog-ear and bird-beak deformities are common after transosseous-equivalent repair (suture bridge technique). The natural course of deformities after rotator cuff (RC) repair using the suture bridge technique is unclear. The remodeling potential of these deformities has not been investigated.

PURPOSE

To evaluate remodeling and retear rates associated with deformities after RC repair.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Between November 2011 and February 2012, we studied 99 consecutive shoulders. All patients underwent arthroscopic RC repair via the suture bridge technique with or without additional sutures. Two groups were formed: no deformity (n= 46) and deformity (n = 53). Deformity was defined as marginal detachment and protrusion of the RC after repair, involving inappropriate compression of the suture limbs from the anchors. Tendon height was measured from the highest point of the most protruding portion of the cuff to the cortex on semi-coronal magnetic resonance imaging (MRI) scan. Change in tendon height was evaluated on MRI scan at 1 week and 6 months postoperatively. Clinical assessment at every patient visit included the American Shoulder and Elbow Surgeons (ASES) score, Constant shoulder score, and visual analog scale for pain (pVAS) score.

RESULTS

No significant differences were found in age, sex, symptom duration, tear size, and preoperative ASES, Constant, and pVAS scores (P > .05) between the 2 groups. The initial tendon height was 7.4 ± 1.5 mm in the no-deformity group and 9.3 ± 2.0 mm in the deformity group. Follow-up height was 6.3 ± 2.1 mm in the no-deformity group and 6.4 ± 1.6 mm in the deformity group. Mean postoperative tendon heights were 90.1% ± 23.8% of the initial height in the no-deformity group and 73.2% ± 15.1% in the deformity group. Clinical scores (ASES, Constant, and pVAS) were not significantly different between the groups at 6 months. There were 4 shoulders in each group that experienced retearing (types 4 and 5 according to the Sugaya classification) at 6 months postoperatively. There was no difference in retear rate (P > .999).

CONCLUSION

Most deformities after RC repair were remodeled with no effect on retears. Clinical outcomes were not affected by deformities.

Tendon Healing Progression Evaluated With Magnetic Resonance Imaging Signal Intensity and Its Correlation With Clinical Outcomes Within 1 Year After Rotator Cuff Repair With the Suture-Bridge Technique

BACKGROUND

After a rotator cuff (RC) is repaired, its signal intensity (SI) on magnetic resonance imaging (MRI) gradually changes to normal and could reflect the degree of RC healing. Nevertheless, it remains unclear how long it takes for SI to recover to normal and whether the SI progression correlates with clinical outcomes after RC repair (RCR).

PURPOSE

To serially evaluate the SIs of the repaired RC tendon on MRI and the postoperative clinical outcomes and then analyze the correlation between them.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

This study prospectively included 25 patients who underwent arthroscopic RCR with the suture-bridge technique between June 2016 and July 2017. Twenty-three patients accepted full follow-ups at 1, 3, 6, 9, and 12 months. Before surgery and at each follow-up, visual analog scale (VAS) for pain and 4 functional scores were evaluated: Constant-Murley score, American Shoulder and Elbow Surgeons shoulder evaluation form, modified University of California at Los Angeles score, and Fudan University shoulder score. The patients underwent MRI examinations at every follow-up. The values of the signal/noise quotient at the distal (SNQd) and proximal (SNQp) areas were calculated to evaluate the SI of the repaired tendon. The correlations of clinical outcomes with SNQd and SNQp values were analyzed, and subgroup analyses were performed.

RESULTS

Overall, the mean postoperative VAS score significantly decreased at postoperative 1 month (P < .001), and the functional scores were all significantly higher than the preoperative values at 6 months (all P < .001). SNQd and SNQp values were both significantly higher than normal at 1 and 3 months (all P < .001) and reduced to normal after 9 and 6 months, respectively. Correlation analyses showed that the SNQp value significantly correlated with VAS score (positive) and all functional scores (negative) at 1 and 3 months postoperatively. Further comparison indicated that the patients with VAS score >3 had higher SNQp values than patients with VAS score ≤3 at 1 and 3 months postoperatively (both P = .01).

CONCLUSION

After RCR with the suture-bridge technique, it took longer for SI to become relatively normal than it did to have a significant clinical improvement. Early after surgery (1-3 months), worse clinical outcome correlated with higher SI on proximal cuff tendon.

Biomechanics of an interlinked suture anchor rotator cuff repair in a human cadaveric model

Background

The purpose of this study was to evaluate the initial fixation of a transosseous-equivalent rotator cuff repair and an interlinked medial repair, quantifying the cyclic and failure loading properties of each construct.

Methods

Twenty-four human cadaveric shoulders from 12 matched pairs were dissected, and full-thickness supraspinatus tears were created. In each pair, 1 side was repaired with a transosseous-equivalent repair (control) and the other, with an interlinked repair. All specimens were cycled to 1 MPa of effective stress at 1 Hz for 500 cycles, and gap formation was recorded with a digital video system. All samples were then loaded to failure, and the ultimate load and displacement and modes of failure were recorded.

Results

The interlinked repair showed a decrease in the amount of construct gapping after cycle 50 and in peak construct gapping compared with the control group (control, 3.4 ± 0.9 mm; interlinked, 2.5 ± 0.8 mm; P = .048). The interlinked repair also showed a higher ultimate load to failure (control, 318.7 ± 77.9 N; interlinked, 420.6 ± 93.7 N; P = .007). No other significant differences were detected between constructs for preparation or testing metrics.

Conclusions

The interlinked repair, in which 1 continuous suture linked the medial anchors, showed decreased construct gapping and increased ultimate load to failure compared with the control construct. This study establishes the biomechanical validity of the new interlinked repair construct compared with a previously validated construct.

Does Medial-Row Fixation Technique Affect the Retear Rate and Functional Outcomes After Double-Row Transosseous-Equivalent Rotator Cuff Repair?

Background:

Double-row transosseous-equivalent (TOE) rotator cuff repair techniques have been widely accepted because of their superior biomechanical properties when compared with arthroscopic single-row repair. Concerns regarding repair overtensioning with medial-row knot tying have led to increased interest in knotless repair techniques; however, there is a paucity of clinical data to guide the choice of technique.

Hypothesis:

Arthroscopic TOE repair techniques using knotless medial-row fixation will demonstrate lower retear rates and greater improvements in the Constant score relative to conventional knot-tying TOE techniques.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

A systematic review of 3 databases (PubMed, Cochrane, and Embase) was performed using PRISMA (Preferred Reporting Items for Systematic Meta-Analyses) guidelines. Inclusion criteria were English-language studies that examined repair integrity or Constant scores after arthroscopic rotator cuff repair with TOE techniques. Two investigators independently screened results for relevant articles. Data regarding the study design, surgical technique, retear rate, and Constant shoulder score were extracted from eligible studies. A quality assessment of all articles was performed using the Methodological Index for Non-Randomized Studies (MINORS) criteria.

Results:

The systematic review identified a total of 32 studies (level of evidence, 1-4) that met inclusion and exclusion criteria. Of the 32 studies, 5 reported on knotless TOE techniques, 25 reported on knot-tying TOE techniques, and 2 reported on both. In the knotless group, retear rates ranged from 6% to 36%, and Constant scores ranged from 38-65 (preoperative) to 73-83 (postoperative). In the knot-tying group, retear rates ranged from 0% to 48%, and Constant scores ranged from 42-64 (preoperative) to 55-96 (postoperative).

Conclusion:

Despite several theoretical advantages of knotless TOE repair, both knotless and knot-tying techniques reported considerable improvement in functional outcomes after rotator cuff repair. Although tendon failure rates showed a downward trend in knotless studies, additional prospective studies are warranted to better understand the role of medial-row fixation on tendon repair integrity and postoperative clinical outcomes.

Clinical and structural outcomes after arthroscopic rotator cuff repair: a comparison between suture bridge techniques with or without medial knot tying

Purpose

To compare arthroscopic suture bridge (SB) techniques with medial tying to those without tying, considering clinical and structural outcomes.

Methods

We included 124 patients with rotator cuff tears after arthroscopic rotator cuff repair (ARCR). Fifty-three patients with clinical and structural evaluations 3, 12, and 24 months postoperatively were included and divided into 29 patients with medial tying (WMT group) and 24 without tying (WOMT group). Clinical outcomes comprised the University of California Los Angeles (UCLA) and Japanese Orthopaedic Association (JOA) scores. Structural outcomes were evaluated with magnetic resonance images (MRI) using Sugaya classifications.

Results

JOA and UCLA scores in the WMT and WOMT groups improved significantly from before surgery to 24 months after surgery (P < 0.01, respectively). No significant difference was noted between groups. No significant postoperative retears (Sugaya types 4 and 5) between WMT and WOMT groups were noted at 3 months (5 vs 3 cases), 12 months (6 vs 5 cases), and 24 months (7 vs 6 cases) postoperatively. Complete healing (Sugaya type 1) was noted at 3 months (8 vs 11 cases), 12 months (10 vs 10 cases), and 24 months (8 vs 13 cases, P = 0.024) postoperatively. Incomplete healing (Sugaya types 2 and 3) were noted at 3 months (16 vs 10 cases), 12 months (13 vs 9 cases), and 24 months (14 vs 5 cases, P = 0.024) postoperatively.

Conclusion

Clinical outcomes for both techniques were comparable, but the number of incompletely healed tendons in SB with medial tying was significantly larger at 24 months after surgery.

Level of evidence

This study is a level III, case-control study.

Clinical relevance

This study revealed the influence of medial tying in rotator cuff repair.

Double row equivalent for rotator cuff repair: A biomechanical analysis of a new technique

Introduction

There are numerous configurations of double row fixation for rotator cuff tears however, there remains to be a consensus on the best method. In this study, we evaluated three different double-row configurations, including a new method. Our primary question is whether the new anchor and technique compares in biomechanical strength to standard double row techniques.

Methods

Eighteen prepared fresh frozen bovine infraspinatus tendons were randomized to one of three groups including the New Double Row Equivalent, Arthrex Speedbridge and a transosseous equivalent using standard Stabilynx anchors. Biomechanical testing was performed on humeri sawbones and ultimate load, strain, yield strength, contact area, contact pressure, and a survival plots were evaluated.

Results

The new double row equivalent method demonstrated increased survival as well as ultimate strength at 415N compared to the remainder testing groups as well as equivalent contact area and pressure to standard double row techniques.

Conclusions

This new anchor system and technique demonstrated higher survival rates and loads to failure than standard double row techniques. This data provides us with a new method of rotator cuff fixation which should be further evaluated in the clinical setting.

Level of Evidence

Basic science biomechanical study.

[Arthroscopic rotator cuff surgery : New and established methods]

This present article summarizes established and current developments and aspects of rotator cuff surgery. Achieved milestones as well as current approaches are presented and assessed with respect to their clinical and radiographic impact. Despite biomechanical and technical improvements in modern rotator cuff repair techniques, re-defect and re-tearing rates could not be fully eliminated. Meanwhile, the importance of biological processes around successful tendon-bone reintegration has been increasingly recognized. Hence, this article presents the current scientific standing regarding biological growth factors, platelet-rich plasma and rotator cuff augmentation techniques (with allogenic/autologous grafts). In summary, there are clear biomechanical advantages as well as many promising approaches to biological augmentation; however, the latter have not yet been transferred into regular clinical application.

Perfusion of the Rotator Cuff Tendon According to the Repair Configuration Using an Indocyanine Green Fluorescence Arthroscope: A Preliminary Report

BACKGROUND

The disturbance of rotator cuff tendon perfusion has been connected with the suture-bridge configuration repair (SBCR) technique; however, in vivo assessments of the tendon blood supply have been problematic with other modalities. An evaluation of tissue perfusion by an indocyanine green (ICG) fluorescence arthroscope has been developed to counteract this difficulty.

PURPOSE

To verify the hindrance of perfusion in SBCR, we used an ICG fluorescence camera to compare parallel-type transosseous repair (PTR) and SBCR in rabbits immediately and at 3 days after rotator cuff repair.

STUDY DESIGN

Controlled laboratory study.

METHODS

Acute rotator cuff repair was performed on the shoulders of 10 rabbits. Both shoulders were repaired using either PTR or SBCR. For PTR, simple repair was performed through 2 parallel transosseous tunnels created using a microdrill. For SBCR, 2 additional crisscross transosseous tunnels were added to mimic arthroscopic SBCR. Immediately after repair, ICG was injected through the ear vein, and images were recorded using an ICG fluorescence camera. Tendon perfusion was compared by measuring fluorescence intensity using ImageJ software in both methods. At 3 days after rotator cuff repair, a reassessment of ICG fluorescence was performed. In addition, as a subsidiary study, a comparison of each repair method and a healthy tendon was performed (PTR vs healthy tendon and SBCR vs healthy tendon). Six rabbits (3 for each comparison) were included.

RESULTS

Immediately after rotator cuff repair, the mean (±SD) grayscale intensity of ICG fluorescence was weaker in SBCR than PTR in 10 specimens (65.9 ± 47.6 vs 84.3 ± 53.4 per pixel, respectively; P = .003). At 3 days after repair, 8 specimens were included in the analysis because suture strands failed in 2 specimens in SBCR. The mean intensity of fluorescence was still weaker in SBCR compared with PTR (52.5 ± 13.7 vs 60.2 ± 22.7 per pixel, respectively; P = .077). The mean fluorescence intensity compared with a healthy tendon was 83.2% ± 9.5% in PTR and 63.2% ± 13.2% in SBCR.

CONCLUSION

Our ICG fluorescence camera system was able to detect ICG fluorescence in an acute rabbit rotator cuff repair model. SBCR showed inferior tendon perfusion immediately after repair. At 3 days after repair, SBCR still showed inferior fluorescence intensity, although it did not reach statistical significance.

CLINICAL RELEVANCE

In this study, SBCR hindered perfusion at the tendon in the compressed area. This finding may affect rotator cuff tendon healing and failure mode.

Healing disturbance with suture bridge configuration repair in rabbit rotator cuff tear

BACKGROUND

Medial row failure has been reported in the suture bridge technique of rotator cuff repair. This study compared the healing response of suture bridge configuration repair (SBCR) and parallel type transosseous repair (PTR).

METHODS

Acute rotator cuff repair was performed in 32 rabbits. Both shoulders were repaired using PTR or SBCR. In PTR, simple PTR was performed through 2 parallel transosseous tunnels created using a microdrill. In SBCR, 2 additional crisscross transosseous tunnels were added to mimic arthroscopic SBCR. At 1, 2, and 5 weeks postoperatively, comparative biomechanical testing was performed in 8 rabbits, and histologic analysis, including immunohistochemical staining for CD31, was performed in 4 rabbits.

RESULTS

Failure loads at 1 week (38.12 ± 20.43 N vs 52.00 ± 27.23 N; P = .284) and 5 weeks (97.93 ± 48.35 N vs 119.60 ± 60.81 N; P = .218) were not statistically different between the SBCR and PTR groups, respectively, but were significantly lower in the SBCR group than in the PTR group (23.56 ± 13.56 N vs. 44.25 ± 12.53 N; P = .009), respectively, at 2 weeks. Markedly greater fibrinoid deposition was observed in the SBCR group than in the PTR group at 2 weeks. For vascularization, there was a tendency that more vessels could be observed in PTR than in SBCR at 2 weeks (15.9 vs 5.6, P = .068).

CONCLUSIONS

In a rabbit acute rotator cuff repair model, SBCR exhibited inferior mechanical strength, and fewer blood vessels were observed at the healing site at 2 weeks postoperatively. Medial row tendon failure was more common in SBCR. Surgeons should consider the clinical effect of SBCR when performing rotator cuff repair.

The optimum tension for bridging sutures in transosseous-equivalent rotator cuff repair: a cadaveric biomechanical study

BACKGROUND

Transosseous-equivalent (TOE) rotator cuff repair can increase contact area and contact pressure between the repaired cuff tendon and bony footprint and can show higher ultimate loads to failure and smaller gap formation compared with other repair techniques. However, it has been suggested that medial rotator cuff failure after TOE repair may result from increased bridging suture tension.

PURPOSE

To determine optimum bridging suture tension in TOE repair by evaluating footprint contact and construct failure characteristics at different tensions.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 18 fresh-frozen cadaveric shoulders, randomly divided into 3 groups, were constructed with a TOE configuration using the same medial suture anchor and placing a Tekscan sensing pad between the repaired rotator cuff tendon and footprint. Nine of the 18 shoulders were used to measure footprint contact characteristics. With use of the Tekscan measurement system, the contact pressure and area between the rotator cuff tendon and greater tuberosity were quantified for bridging suture tensions of 60, 90, and 120 N with glenohumeral abduction angles of 0° and 30° and humeral rotation angles of 30° (internal), 0°, and 30° (external). TOE constructs of all 18 shoulders then underwent construct failure testing (cyclic loading and load to failure) to determine the yield load, ultimate load, stiffness, hysteresis, strain, and failure mode at 60 and 120 N of tension.

RESULTS

As bridging suture tension increased, contact force, contact pressure, and peak pressure increased significantly at all positions (P < .05 for all). Regarding contact area, no significant differences were found between 90 and 120 N at all positions, although there were significant differences between 60 and 90 N. The construct failure test demonstrated no significant differences in any parameters according to various tensions (P > .05 for all).

CONCLUSION

Increasing bridging suture tension to over 90 N did not improve contact area but did increase contact force and pressure. Bridging suture tension did not significantly affect ultimate failure loads.

CLINICAL RELEVANCE

Considering the risks of overtensioning bridging sutures, it may be clinically more beneficial to keep bridging suture tension below 90 N.