Subacromial bursal preservation can enhance rotator cuff tendon regeneration: a comparative rat supraspinatus tendon defect model study

Histological and biochemical changes in a rat rotator cuff tear model with or without the subacromial bursa

The subacromial bursa (SAB) plays an important role in the tendon healing process. Based on previous reports, co-culture of the rotator cuff (RC) and SAB have been shown to increase the tendon-related gene expressions, inflammatory cytokines, and tensile strength. However, the nature of the specific biochemical alterations during the inflammatory and repair phases of tendon healing with or without the SAB remain unknown. Using a full-thickness RC tear rat model, we determined how the presence or absence of the SAB alters the histological characteristics and gene expressions. After 3 and 6 weeks, tissues were collected for histological and real-time quantitative polymerase chain reaction (RT-qPCR) evaluations. Results showed greater cell density at 3 weeks, neovascularization and tendon thickening at 6 weeks with SAB preservation. Immunostaining revealed significant increases in type 3 collagen (COL3) expression at 6 weeks with SAB preservation. The RT-qPCR results showed that SAB preservation induced significant increases in the expression of scleraxis, matrix metalloproteinase-13 (MMP-13), interleukin-1β (IL-1β), and inducible nitric oxide synthase (iNOS) at 3 weeks and significant increases in COL3, IL-10, and arginase-1 (Arg-1) at 6 weeks. An RC tear undergoes more appropriate inflammatory and repair phases during the tendon healing process when the SAB is retained.

Human Rotator Cuff Tears Reveal an Age-Dependent Increase in Markers of Cellular Senescence and Selective Removal of Senescent Cells With Dasatinib + Quercetin Increases Genetic Expression of COL1A1 In Vitro

PURPOSE

To quantify cellular senescence in supraspinatus tendon and subacromial bursa of humans with rotator cuff tears and to investigate the in vitro efficacy of the senolytic dasatinib + quercetin (D+Q) to eliminate senescent cells and alter tenogenic differentiation.

METHODS

Tissue was harvested from 41 patients (mean age, 62 years) undergoing arthroscopic rotator cuff repairs. In part 1 (n = 35), senescence was quantified using immunohistochemistry and gene expression for senescent cell markers (p16 and p21) and the senescence-associated secretory phenotype (SASP) (interleukin [IL] 6, IL-8, matrix metalloproteinase [MMP] 3, monocyte chemoattractant protein [MCP] 1). Senescence was compared between patients <60 and ≥60 years old. In part 2 (n = 6) , an in vitro model of rotator cuff tears was treated with D+Q or control. D+Q, a chemotherapeutic and plant flavanol, respectively, kill senescent cells. Gene expression analysis assessed the ability of D+Q to kill senescent cells and alter markers of tenogenic differentiation.

RESULTS

Part 1 revealed an age-dependent significant increase in the relative expression of p21, IL-6, and IL-8 in tendon and p21, p16, IL-6, IL-8, and MMP-3 in bursa (P < .05). A significant increase was seen in immunohistochemical staining of bursa p21 (P = .028). In part 2, D+Q significantly decreased expression of p21, IL-6, and IL-8 in tendon and p21 and IL-8 in bursa (P < .05). Enzyme-linked immunosorbent assay analysis showed decreased release of the SASP (IL-6, MMP-3, MCP-1; P = .002, P = .024, P < .001, respectively). Tendon (P = .022) and bursa (P = .027) treated with D+Q increased the expression of COL1A1.

CONCLUSIONS

While there was an age-dependent increase in markers of cellular senescence, this relationship was not consistently seen across all markers and tissues. Dasatinib + quercetin had moderate efficacy in decreasing senescence in these tissues and increasing COL1A1 expression.

CLINICAL RELEVANCE

This study reveals that cellular senescence may be a therapeutic target to alter the biological aging of rotator cuffs and identifies D+Q as a potential therapy.

Investigation of the effects of subacromial bursal tissue preservation and microfracture procedure on healing after rotator cuff repair in a rat model

INTRODUCTION

The aim of this study is to compare the preservation of bursal tissue and microfracture techniques and to examine the effectiveness of the combination of the two methods in rotator cuff tear healing in the rat shoulder.

HYPOTHESIS

Bursal tissue preservation combined with microfracture is more effective in the rotator cuff repair.

MATERIALS AND METHODS

Twenty-three male Sprague-Dawley rats were randomly divided into two groups. The bursal tissue was preserved in group 1 (n=11) and excised in group 2 (n=12). Groups were categorized into subgroups as L (left) and R (right) based on the shoulder side receiving microfracture (L received microfracture, R did not). Histopathological examination was performed using modified Bonar Score System.

RESULTS

Cell morphology grades of group 1 were lower than group 2 (p<0.05). In terms of collagen measurements, the grade of group 1L (bursa preservation+microfracture) was lower than groups 1R, 2L, and 2R, and the grade of group 1R was lower than groups 2L and 2R. Cellularity grades of group 2 were higher than group 1 (p<0.05). Extracellular matrix grades of group 1 were lower than group 2 (p<0.05). The overall grades were lower in group 1 than in group 2 (p<0.05).

DISCUSSION

Combined treatment of bursal tissue preservation and microfracture was the most efficient method as determined by healing findings in histopathological specimens. Preservation of bursal tissue was a more effective option in tendon healing than performing only microfracture.

LEVEL OF PROOF

II, animal research.

Increased operative time has a negative impact on clinical outcome in arthroscopic rotator cuff repair

BACKGROUND

Few data are available about the impact of operative time on outcome of rotator cuff repair.

AIM

The aim of this study was to evaluate the impact of operative time on clinical outcome and tendon healing after arthroscopic rotator cuff repair.

METHODS

Patients operated on for distal supraspinatus tear in our institution between 2012 and 2018 were included retrospectively. Operative time, from skin incision until skin closure, was extracted from medical files. For statistical analysis, operative time was treated as a quantitative variable. Endpoints were clinical outcome (Constant score, range of motion), tendon healing (on CT or MRI) and complications at 1 year. The significance threshold was set at p = 0.05.

RESULTS

A total of 219 Patients, with a mean age of 54.6 years (range 40-70 years), were included. Mean operative time 44.9 min (range 14-140 min). Significant correlations (p < 0.05) were found for Constant score and external rotation at 1 year: increasing operative time by 1 min led to a decrease in Constant score of 0.115 points, or 6.9 points for a 60-min increase (p = 0.0167) and a decrease in external rotation of 0.134°, or 8.04° for a 60-min increase (p = 0.0214). No significant correlations were found for anterior elevation at 1 year (p = 0.2577), tendon healing at 1 year (p = 0.295) or onset of complications during follow-up (p = 0.193).

DISCUSSION

The minimal clinically important difference in Constant score in patients undergoing rotator cuff surgery is between 6 and 10 points. An increase of more than 60 min in operative time significantly impacted clinical outcome of arthroscopic distal supraspinatus repair, but not tendon healing.

LEVEL OF EVIDENCE

Level III: Retrospective Cohort Design. Therapeutic Study.

Microfracture Lateral to the Greater Tuberosity of the Humerus Enhances Tendon-to-Bone Healing in a Rat Rotator Cuff Model

BACKGROUND

Microfracture at the rotator cuff insertion is an established surgical marrow-stimulation technique for enhancing rotator cuff healing. However, the effect of lateralized or medialized microfracture on the insertion is unknown.

PURPOSE

To compare the biomechanical and histologic effects of microfracture at 3 different regions for rotator cuff repair in a rat model.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 72 Sprague-Dawley rats with bilateral supraspinatus tendon insertion detachment were allocated into 4 groups with 4 different interventions: no microfracture at the humeral head as a control group (Con), traditional microfracture at the footprint area (MFA), and medialized microfracture to the footprint area (MMFA) on the articular surface of the humerus or lateralized microfracture to the footprint area at the greater tuberosity (LMFA). All underwent immediate repair. Tendon-to-bone healing was assessed by biomechanical and histologic tests 4 and 8 weeks postoperation.

RESULTS

At 4 weeks, the LMFA group showed a significantly superior failure load compared with the other groups (all P < .05). The LMFA and MFA groups showed significantly superior stiffness compared with the Con and MMFA groups (all P < .01). At 8 weeks, superior failure load and stiffness were observed in the LMFA group compared with the control group (all P < .05). Histologic examination revealed that the LMFA group had superior collagen composition and tendon-to-bone maturation at the interface at 4 and 8 weeks compared with the Con group (all P < .05).

CONCLUSION

Lateralized microfracture at the greater tuberosity improved the histologic quality of repair tissue and biomechanical strength at the tendon-to-bone insertion after rotator cuff repair in a rat model.

CLINICAL RELEVANCE

Microfracture lateral to the footprint area might be a better way to enhance rotator cuff healing clinically.

Outcomes After Superior Capsular Reconstruction With an Achilles Tendon-Bone Allograft Using the Modified Keyhole Technique: A 2-Year Follow-up of a Novel Technique for Irreparable Rotator Cuff Tears

Background

Despite improved outcomes, failure or nonhealing of graft materials has been reported after superior capsular reconstruction (SCR) for massive irreparable rotator cuff tears.

Purpose

To evaluate the short-term clinical and radiological outcomes of a novel technique for SCR using an Achilles tendon-bone allograft.

Study Design

Case series; Level of evidence, 4.

Methods

We performed a retrospective review of patients who underwent SCR using an Achilles tendon-bone allograft with the modified keyhole technique and who had a minimum follow-up of 2 years. The visual analog scale score for pain, American Shoulder and Elbow Surgeons score, and Constant score were evaluated as subjective outcomes, while range of motion of the shoulder joint and isokinetic strength were evaluated as objective outcomes. The acromiohumeral interval (AHI), bone-to-bone healing of the allograft and humeral head on computed tomography, and graft integrity on magnetic resonance imaging were evaluated as radiological outcomes.

Results

This study included 32 patients with a mean age of 56.8 ± 4.2 years and a mean follow-up of 28.4 ± 6.2 months. A significant improvement from preoperatively to the last follow-up was seen in the mean visual analog scale score for pain (from 6.7 to 1.8), American Shoulder and Elbow Surgeons score (from 42.7 to 83.8), Constant score (from 47.2 to 78.5), and AHI (from 4.8 to 8.2 mm) (P < .001 for all) as well as range of motion in forward elevation and internal rotation (P < .001 for both). Medial-to-lateral graft integrity was good in all patients. Nonunion at the fitting zone of the keyhole on the greater tuberosity was diagnosed in 1 case (3.1%), and failure of incorporation between the allograft and remnant tendon at the site of posterior margin convergence was observed in 4 cases (12.5%).

Conclusion

The outcomes after SCR using an Achilles tendon-bone allograft and the keyhole technique improved, with an increased AHI and excellent integrity in the medial and lateral directions compared with preoperatively. This technique is a reasonable option for the surgical treatment of irreparable rotator cuff tears.

Anatomical and Interpositional Bursa Preservation Showed Similar Improved Tendon to Bone Healing Compared With the Bursa Removal in a Rat Rotator Cuff Tear Model

PURPOSE

To compare the effects of anatomical preservation (AP) and interpositional preservation (IP) of subacromial bursa tissue on tendon-to-bone healing in a rat model of rotator cuff tear.

METHODS

In this study, 48 male Sprague-Dawley rats (average weight 283 g) underwent bilateral supraspinatus tendons severed by sharp incision and repaired immediately. The subacromial bursa tissues were completely removed in 16 rats, who served as the control (CON) group. The other 32 rats were randomly divided into 2 groups AP and IP between tendon and bone. Eight rats of each group were sacrificed for bilateral shoulders at 3 and 9 weeks after the operation, including 5 rats for biomechanical tests and 3 for histologic analysis.

RESULTS

No significant differences in terms of biomechanical properties were observed among the groups 3 weeks after surgery. At 9 weeks, the maximum load and stiffness of the AP (32.95 ± 6.33 N, P = .029; 12.49 ± 3.17 N/mm, P < .001; respectively) and IP (33.58 ± 8.47 N, P = .015; 11.63 ± 2.84 N/mm, P = .010, respectively) groups were significantly superior to that of the CON group (26.59 ± 4.47 N; 8.42 ± 2.33 N/mm, respectively). More organized collagen and more mature tendon insertion were observed in AP and IP groups at the interface at 9 weeks, which means better tendon-to-bone healing compared with the CON group.

CONCLUSIONS

The subacromial bursa plays a positive role in tendon-bone healing. Either anatomical preservation or interpositional preservation between tendon and bone can similarly facilitate the process of healing.

CLINICAL RELEVANCE

Considering the additional surgical time and surgical manipulation, preserving the subacromial bursa at the anatomical position seems to be a better way to promote rotator cuff healing.

Cancellous bone should not be exposed during medialized rotator cuff repair based on bone-to-tendon healing in a rat mode

PURPOSE

To compare the biological bone-to-tendon healing using three different medialized bone bed preparation techniques (i.e. cortical bone exposure, cancellous bone exposure, and no cartilage removal) in a rat model of medialized rotator cuff repair.

METHODS

Twenty-one male Sprague-Dawley rats with 42 shoulders were subjected to bilateral supraspinatus tenotomy from the greater tuberosity. The rotator cuff was repaired using medialized anchoring with the cortical bone exposed, the cancellous bone exposed, or no cartilage removed. Four and three rats in each group were killed for biomechanical testing and histological evaluation, respectively, at postoperative 6 weeks.

RESULTS

All rats survived until the end of the study, but one infected shoulder in the cancellous bone exposure group was excluded from further analysis. Compared with the cortical bone exposure and no cartilage removal groups, the rotator cuff healing of the cancellous bone exposure group showed significantly lower maximum load (cancellous bone exposure group: 26.2 ± 2.3 N, cortical bone exposure group: 37.6 ± 7.9 N, no cartilage removal group: 34.6 ± 7.2 N, P = 0.005 and 0.029) and less stiffness (cancellous bone exposure group: 10.5 ± 2.4 N/mm, cortical bone exposure group: 17.4 ± 6.7 N, no cartilage removal group: 16.0 ± 3.9 N, P = 0.015 and 0.050) at postoperative 6 weeks. In all three groups, the repaired supraspinatus tendon healed towards the original insertion rather than the medialized insertion. The cancellous bone exposure group showed inferior fibrocartilage formation and insertion healing.

CONCLUSIONS

The medialized bone-to-tendon repair strategy does not guarantee complete histological healing, and the removal of excessive bony structure impairs bone-to-tendon healing. This study concludes that surgeons should not expose the cancellous bone during the medialized rotator cuff repair.

Absorbable suture knots on the supraspinatus tendon prevent adverse effects of nonabsorbable suture knots in a rat model

PURPOSE

To compare the absorbable and nonabsorbable suture knots on the tendon on bone-to-tendon healing during the early phase in a rat rotator cuff tear (RCT) model.

METHODS

Fifty-two male Sprague-Dawley rats (10 weeks old; mean weight, 380 g) were used in this study, and 51 of them were randomly assigned into three groups: absorbable suture group (ASG, n = 22), nonabsorbable suture group (NSG, n = 22), and sham surgery group (SSG, n = 7), and the remaining rat was used to take surgical pictures. Bilateral supraspinatus tendon tears were created and repaired immediately in ASG and NSG. Three rats from ASG and NSG were killed for Western blot and histological evaluation at 3 days, 1 week, and 4 weeks after surgery. At 4 weeks, four rats from each group were killed for biomechanical test, and three rats from SSG were used for histological evaluation.

RESULTS

Absorbable suture knots on the tendon completely degraded at 4 weeks. However, nonabsorbable suture knots remained intact between the tendon and articular side. ASG showed a stronger inflammatory reaction at 3 days and 1 week, but a weaker reaction at 4 weeks as confirmed by gross observation and Western blot. Besides, ASG showed superior biomechanical properties in terms of maximum load to failure and stiffness at 4 weeks. Modified Bonar score revealed superior maturity for tissue healing in ASG to that in NSG at 4 weeks. Furthermore, inferior bone-to-tendon interface and weakest link formation were observed in NSG on histologic images.

CONCLUSION

Absorbable suture knots on the tendon contributed to better mechanical properties compared with the nonabsorbable one after rotator cuff repair.

The Subacromial Bursa: Current Concepts Review

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The subacromial bursa is a distinct anatomic structure with distinct histologic features; it plays a critical role in the symptoms of the painful shoulder and in the local healing capacity of the rotator cuff tendon.

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Treatment of pain from bursitis of the subacromial bursa largely involves nonoperative interventions; however, operative treatment may be considered in certain instances.

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Preservation of the subacromial bursa should occur whenever possible given its intrinsic trophic and pluripotent factors, which have been shown to play important roles in rotator cuff tendon pathology.

Failure Rate After Superior Capsular Reconstruction With Achilles Tendon-Bone Allograft for Irreparable Rotator Cuff Tears

Background

Superior capsular reconstruction (SCR) is an alternative to reverse shoulder arthroplasty for irreparable rotator cuff tears (IRCTs). The reconstructed capsule acts as a static restraint to prevent superior migration of the humeral head. Traditional SCR uses a fascia lata autograft, which has shown failure at the greater tuberosity. An Achilles tendon-bone allograft has been proposed to improve the failure rate.

Purpose

To evaluate the surgical outcomes of SCR using an Achilles tendon-bone allograft for the treatment of IRCTs.

Study Design

Case series; Level of evidence, 4.

Methods

We retrospectively evaluated 6 patients with massive IRCTs who underwent SCR using an Achilles tendon-bone allograft between January 2017 and January 2018. Clinical outcomes were assessed using range of motion, the American Shoulder and Elbow Surgeons score, and the visual analog scale for pain. The acromiohumeral distance and the status of graft integrity were evaluated using serial magnetic resonance imaging. Second-look arthroscopy surgery was performed to evaluate graft integrity at the mean of 7.5 months postoperative.

Results

The mean ± SD clinical follow-up period was 14.5 months (range, 12-17 months). The American Shoulder and Elbow Surgeons and visual analog scale scores improved from 42.8 ± 11.9 and 4.0 ± 1.2 to 62.1 ± 14.7 and 2.8 ± 1.4, respectively. Forward flexion and external rotation improved from 98° ± 36° and 58° ± 4° to 123° ± 20° and 39° ± 8°, respectively. The acromiohumeral distance improved from 3.9 ± 0.8 mm to 6.4 ± 2.2 mm at final follow-up. However, second-look arthroscopy at a mean of 7.6 months postoperatively confirmed a graft failure rate of 83.3%.

Conclusion

SCR using an Achilles tendon-bone allograft for the treatment of IRCTs had a high graft failure rate among patients in this case series.