Biologic Augmentation of Arthroscopic Rotator Cuff Repair Using Minced Autologous Subacromial Bursa

Editorial Commentary: Meniscal Posterior Root to Bone Postoperative Healing Appears Incomplete at 24 Weeks in a Goat Model

The goal of many orthopaedic surgeries is to mechanically stabilize the tissue long enough for biological healing to occur. The healed tissue should be able to bear the load before the mechanical device (screw, suture, anchor, etc.) eventually fails. Recent research shows that in a goat model, meniscus posterior root repair to bone is not fully healed at 24 weeks postoperatively (after the suture is removed and under biomechanical and histologic testing). In addition, magnetic resonance imaging at 24 months postoperatively showed persistent meniscal extrusion but only under mechanical loading. Of course, in clinical practice, repair sutures are not removed and continue to provide mechanical stability until they either fail, the tissue-suture interface fails, or the meniscus root is healed enough to resist the load. Nevertheless, we need to be mindful of time to healing, weightbearing, and return to activity in human patients.

Optimizing Tissue Engineering for Clinical Relevance in Rotator Cuff Repair

Rotator cuff tear (RCT) is the most common cause of disability in the upper extremity. It results in 4.5 million physician visits in the United States every year and is the most common etiology of shoulder conditions evaluated by orthopedic surgeons. Over 460,000 RCT repair surgeries are performed in the United States annually. Rotator cuff (RC) retear and failure to heal remain significant postoperative complications. Literature suggests that the retear rates can range from 29.5% to as high as 94%. Weakened and irregular enthesis regeneration is a crucial factor in postsurgical failure. Although commercially available RC repair grafts have been introduced to augment RC enthesis repair, they have been associated with mixed clinical outcomes. These grafts lack appropriate biological cues such as stem cells and signaling molecules at the bone-tendon interface. In addition, they do little to prevent fibrovascular scar tissue formation, which causes the RC to be susceptible to retear. Advances in tissue engineering have demonstrated that mesenchymal stem cells (MSCs) and growth factors (GFs) enhance RC enthesis regeneration in animal models. These models show that delivering MSCs and GFs to the site of RCT enhances native enthesis repair and leads to greater mechanical strength. In addition, these models demonstrate that MSCs and GFs may be delivered through a variety of methods including direct injection, saturation of repair materials, and loaded microspheres. Grafts that incorporate MSCs and GFs enhance anti-inflammation, osteogenesis, angiogenesis, and chondrogenesis in the RC repair process. It is crucial that the techniques that have shown success in animal models are incorporated into the clinical setting. A gap currently exists between the promising biological factors that have been investigated in animal models and the RC repair grafts that can be used in the clinical setting. Future RC repair grafts must allow for stable implantation and fixation, be compatible with current arthroscopic techniques, and have the capability to deliver MSCs and/or GFs.

Biologic augmentation of rotator cuff repair with microfragmented autologous subacromial bursal tissue enveloped in a patch of compressed autologous long head of biceps tendon tissue: the Bio-Ravioli technique

Background

Rotator cuff repair is one of the most frequently performed procedures in orthopedic surgery. However, considering the limited healing potential of rotator cuff tendons, several augmentation strategies have evolved to enhance tendon healing. The purpose of this article was to present a new surgical technique called Bio-Ravioli.

Methods

Patients with repairable full-thickness posterosuperior rotator cuff tear and a moderate-to-high risk of healing failure were chosen as candidates for the Bio-Ravioli procedure. It is a biologic augmentation strategy to increase healing potential of arthroscopic rotator cuff repair by use of a biologic graft fixed at the bone-tendon interface. The Bio-Ravioli consists of microfragmented autologous subacromial bursal tissue enveloped in a patch of compressed autologous long head of biceps tendon tissue. The rotator cuff is then repaired to the bone and over the graft using a transosseus equivalent configuration.

Conclusion

The Bio-Ravioli technique represents an easy and reliable way to increase the healing potential at the bone-tendon interface by using autologous mesenchymal stem cells from different sources: subacromial bursa and long head of the biceps tendon.

Bursal Tissue Harvested During Rotator Cuff Repair Contains Viable Mesenchymal Stem Cells

Purpose

To evaluate the effect of intraoperative ablation on the viability, distribution, phenotype, and potential for culture expansion of bursal cells harvested during arthroscopic rotator cuff surgery.

Methods

Tissue was collected during primary arthroscopic rotator cuff repair on 6 healthy, randomly selected patients from a fellowship-trained surgeon's practice between September 2020 and January 2021. There were 3 women (aged 60 ± 8 years) and 3 men (aged 61 ± 10 years). At the time of surgery, subacromial bursal tissue was subjected to no ablation, 1 second of ablation, or 3 seconds of ablation. Tissues were collected by an autograft harvesting system connected to an arthroscopic shaver and a pituitary grasper. Tissue fragments from each condition were sampled for viability testing or cell isolation. A viability kit with confocal microscopy was used to assess live and dead cells. Cell isolation consisted of collagenase digestion or placing tissue fragments onto tissue culture-treated plates that induced migration of cells out of the tissue. Cell proliferation rates were monitored and surface markers for mesenchymal stem cells (MSC) and pericytes were analyzed via multicolor flow cytometry.

Results

Increased ablation time significantly reduced cell viability. The mean percentage of live cells was 55.2% ± 27.2% (range, 26%-90% live) in the control group, 46.8% ± 23.8% (range, 9.6%-69.6%, P = .045) in the short-ablation group, and 35.5% ± 19% (range, 11%-54%, P = .03) in the long-ablation group. No significant differences in population doubling level (1.6 ± 0.5 days) and population doubling time (6.7 ± 2.4 days) were observed in cells from any treatment. The surface marker profile indicated an MSC phenotype with absence of a pericyte population. Ablation or cell isolation procedure had no significant effect on the surface marker profile of isolated cells.

Conclusions

Radiofrequency ablation significantly reduced the overall tissue viability but had no significant effect on cell proliferation or expression of surface markers on isolated subacromial bursal cells harvested arthroscopically.

Clinical Relevance

Analysis of the viability and performance of cells harvested after the use of ablation devices using mechanical surgical collection during rotator cuff repair surgery could further our understanding of subacromial bursal tissue and its potential role in augmenting rotator cuff repair healing.

The effect of augmenting suture material with magnesium and platelet-rich plasma on the in vitro adhesion and proliferation potential of subacromial bursa-derived progenitor cells

Background

Connective tissue subacromial bursa-derived progenitor cells (SBDCs) have been suggested as a potent biologic augment to promote healing of the repaired rotator cuff tendon. Maximizing the amount of retained progenitor cells at the tendon repair site is essential for ensuring an optimal healing environment, warranting a search for proadhesive and proliferative adjuvants. The purpose was to evaluate the effect of magnesium (Mg), platelet-rich plasma (PRP), and a combination of both adjuvants on the in vitro cellular adhesion and proliferation potential of SBDCs on suture material commonly used in rotator cuff surgery.

Methods

SBDCs were isolated from subacromial bursa samples harvested during rotator cuff repair and cultured in growth media. Commercially available collagen-coated nonabsorbable flat-braided suture was cut into 1-inch pieces, placed into 48-well culture dishes, and sterilized under ultraviolet light. Either a one-time dose of 5 mM sterile Mg, 0.2 mL of PRP, or a combination of both adjuvants was added, while a group without treatment served as a negative control. Cellular proliferation and adhesion assays on suture material were performed for each treatment condition.

Results

Augmenting the suture with Mg resulted in a significantly increased cellular adhesion (total number of attached cells) of SBDCs compared to PRP alone (31,527 ± 19,884 vs. 13,619 ± 8808; P < .001), no treatment (31,527 ± 19,884 vs. 21,643 ± 8194; P = .016), and combination of both adjuvants (31,527 ± 19,884 vs. 17,121 ± 11,935; P < .001). Further, augmentation with Mg achieved a significant increase in cellular proliferation (absorbance) of SBDCs on suture material when compared to the PRP (0.516 ± 0.207 vs. 0.424 ± 0.131; P = .001) and no treatment (0.516 ± 0.207 vs. 0.383 ± 0.094; P < .001) group. The combination of Mg and PRP showed a significantly higher proliferation potential compared to PRP alone (0.512 ± 0.194 vs. 0.424 ± 0.131; P = .001) and no treatment (0.512 ± 0.194 vs. 0.383 ± 0.094; P < .001). There were no significant differences in the remaining intergroup comparisons (P > .05, respectively).

Conclusion

Augmenting suture material with Mg resulted in a significantly increased cellular adhesion of SBDCs compared to untreated suture material, as well as augmentation with PRP alone or a combination of both adjuvants. Further, Mg with or without PRP augmentation achieved a significant increase in the cellular proliferation of SBDCs on suture material compared to untreated sutures and augmentation with PRP alone. Application of Mg may be a clinically feasible approach to optimizing the use of SBDCs as a biological augment in rotator cuff repair, while combined augmentation with PRP may harness the full potential for optimized tissue recovery due to the high concentration of PRP-derived growth factors.

Clinical outcomes of rotator cuff repair with subacromial bursa reimplantation: a retrospective cohort study

Background

The subacromial bursa has been found to be a rich, local, source of mesenchymal stem cells but is removed for visualization during rotator cuff repair. Reimplantation of this tissue may improve rotator cuff healing. The purpose of this study is to evaluate clinical outcomes of rotator cuff repair with and without subacromial bursa reimplantation.

Methods

Patients aged 37-77 with a full-thickness or near full-thickness supraspinatus tears underwent arthroscopic transosseous-equivalent double row rotator cuff repair. In patients prior to July 2019, the subacromial bursa was resected for visualization, and discarded. In patients after July 2019, the subacromial bursa was collected using a filtration device connected to an arthroscopic shaver and reapplied to the bursal surface of the tendon at the completion of the rotator cuff repair. Rotator cuff integrity was evaluated via magnetic resonance imaging on bursa patients at 6 months postoperatively. Minimum 18-month clinical outcomes (Single Assessment Numeric Evaluation, American Shoulder and Elbow Surgeons, patient satisfaction) were compared between bursa and nonbursa cohorts.

Results

A total of 136 patients were included in the study (control n = 110, bursa n = 26). Preoperative demographics and tear characteristics were not different between groups. Average follow-up was significantly longer in the control group (control: 3.2 ± 0.7 years; bursa: 1.8 ± 0.3 years; P < .001). The control group showed a significantly higher Single Assessment Numeric Evaluation score (control: 87.9 ± 15.8, bursa: 83.6 ± 15.1, P = .037) that did not meet minimum clinically important difference. The American Shoulder and Elbow Surgeons and patient satisfaction scores were similar between the groups. Symptomatic retears were not significantly different between groups (control: 9.1%, bursa 7.7%, P = .86). Seven patients in the control group underwent reoperation (6.4%), compared to 0 patients in the bursa group (0%, P = .2). Six-month postoperative magnetic resonance images obtained on bursa patients demonstrated 85% rotator cuff continuity (n = 17/20) as defined via Sugaya classification.

Conclusion

Augmentation of rotator cuff repair with bursal tissue does not appear to have negative effects, and given the accessibility and ease of harvest of this tissue, further research should be performed to evaluate its potential for improved tendon healing or clinical outcomes.

Arthroscopic Biological Augmentation With Subacromial Bursa for Bursal-Sided Partial-Thickness Rotator Cuff Tears

Background

Augmentation with subacromial bursa has not been fully established in bursal-sided partial-thickness rotator cuff tears (PT-RCTs).

Purpose

To compare the results of acromioplasty + arthroscopic debridement versus acromioplasty + augmentation with subacromial bursa for Ellman type 2 PT-RCTs involving 25% to 50% of the tendon surface area.

Study Design

Cohort study; Level of evidence, 3.

Methods

Included were 40 patients (mean age, 47.8 years) with Ellman type 2 PT-RCTs whose symptoms did not regress despite 3 months of nonoperative treatment. The patients underwent either acromioplasty + debridement (group A; n = 18) or acromioplasty + augmentation (group B; n = 22). Outcome scores (visual analog scale [VAS] pain score, Constant-Murley score [CMS], and American Shoulder and Elbow Surgeons [ASES] score) were obtained preoperatively and at 6, 12, and 18 months postoperatively. Magnetic resonance imaging (MRI) scans performed at 6 months postoperatively were used to determine the integrity and state of healing.

Results

There were no significant differences between groups A and B in preoperative VAS, CMS, or ASES scores, and patients in both groups saw significant improvement at each follow-up time point on all 3 outcome scores (P = .001 for all). Scores on all 3 outcome measures were significantly better in group B than group A at each postoperative time point (P < .05 for all). Postoperative MRI scans revealed persistent partial tears in 5 of 18 patients in group A compared with 2 of 22 patients in group B (P < .05). Conversion to full-thickness tear (3/18 patients) was seen only in group A.

Conclusion

Patients who underwent biological augmentation of their PT-RCTs had improved outcome scores compared with those treated with acromioplasty and debridement alone.

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.

Irreparable Massive Rotator Cuff Tears: Subacromial Balloon Surgical Technique

Massive irreparable rotator cuff tears pose a significant challenge for both the treating orthopedic surgeon and patient. Surgical treatment options for massive rotator cuff tears include arthroscopic debridement, biceps tenotomy or tenodesis, arthroscopic rotator cuff repair, partial rotator cuff repair, cuff augmentation, tendon transfers, superior capsular reconstruction, subacromial balloon spacer, and ultimately reverse shoulder arthroplasty. The present study will provide a brief overview of these treatment options along with a description of the surgical technique for subacromial balloon spacer placement.

Subacromial Bursa: A Neglected Tissue Is Gaining More and More Attention in Clinical and Experimental Research

The subacromial bursa has long been demolded as friction-reducing tissue, which is often linked to shoulder pain and, therefore, partially removed during shoulder surgery. Currently, the discovery of the stem cell potential of resident bursa-derived cells shed a new light on the subacromial bursa. In the meanwhile, this neglected tissue is gaining more attention as to how it can augment the regenerative properties of adjacent tissues such as rotator cuff tendons. Specifically, the tight fibrovascular network, a high growth factor content, and the large progenitor potential of bursa-derived cells could complement the deficits that a nearby rotator cuff injury might experience due to the fact of its low endogenous regeneration potential. This review deals with the question of whether bursal inflammation is only a pain generator or could also be an initiator of healing. Furthermore, several experimental models highlight potential therapeutic targets to overcome bursal inflammation and, thus, pain. More evidence is needed to fully elucidate a direct interplay between subacromial bursa and rotator cuff tendons. Increasing attention to tendon repair will help to guide future research and answer open questions such that novel treatment strategies could harvest the subacromial bursa's potential to support healing of nearby rotator cuff injuries.

Histological and molecular features of the subacromial bursa of rotator cuff tears compared to non-tendon defects: a pilot study

Background

The role of the subacromial bursa in the development or healing of shoulder pathologies is unclear. Due to this limited knowledge, we aimed to understand specific reactions of the subacromial bursa according to rotator cuff (RC) pathologies compared to non-tendon defects of the shoulder. We hypothesized that the tissue composition and inflammatory status of the bursa are likely to vary between shoulder pathologies depending on the presence and the extent of RC lesion.

Method

Bursa samples from patients with either 1) shoulder instability with intact RC (healthy bursa, control), 2) osteochondral pathology with intact RC, 3) partial supraspinatus (SSP) tendon tear, or 4) full-thickness SSP tear were investigated histologically and on gene expression level.

Result

Bursae from SSP tears differed from non-tendon pathologies by exhibiting increased chondral metaplasia and TGFβ1 expression. MMP1 was not expressed in healthy bursa controls, but strongly increased with full-thickness SSP tears. Additionally, the expression of the inflammatory mediators IL1β, IL6, and COX2 increased with the extent of SSP tear as shown by correlation analysis. In contrast, increased angiogenesis and nerve fibers as well as significantly upregulated IL6 and COX2 expression were features of bursae from patients with osteochondral pathology. Using immunohistochemistry, CD45+ leukocytes were observed in all examined groups, which were identified in particular as CD68+ monocytes/macrophages.

Conclusion

In summary, besides the strong increase in MMP1 expression with SSP tear, molecular changes were minor between the investigated groups. However, expression of pro-inflammatory cytokines correlated with the severity of the SSP tear. Most pronounced tissue alterations occurred for the osteochondral pathology and full-thickness SSP tear group, which demonstrates that the bursal reaction is not exclusively dependent on the occurrence of an SSP tear rather than longstanding degenerative changes. The present bursa characterization contributes to the understanding of specific tissue alterations related to RC tears or non-tendon shoulder pathologies. This pilot study provides the basis for future studies elucidating the role of the subacromial bursa in the development or healing of shoulder pathologies.