Complications of bioabsorbable suture anchors in the shoulder

The development of the suture anchor has played a pivotal role in the transition from open to arthroscopic techniques of the shoulder. Various suture anchors have been manufactured that help facilitate the ability to create a soft tissue to bone repair. Because of reported complications of loosening, migration, and chondral injury with metallic anchors, bioabsorbable anchors have become increasingly used among orthopaedic surgeons. In this review, the authors sought to evaluate complications associated with bioabsorbable anchors in or about the shoulder and understand these in the context of the total number of bioabsorbable anchors placed. In 2008, 10 bioabsorbable anchor-related complications were reported to the US Food and Drug Administration. The reported literature complications of bioabsorbable anchors implanted about the shoulder include glenoid osteolysis, synovitis, and chondrolysis. These potential complications should be kept in mind when forming a differential diagnosis in a patient in whom a bioabsorbable anchor has been previously used. These literature reports, which amount to but a fraction of the total bioabsorbable anchors implanted in the shoulder on a yearly basis, underscore the relative safety and successful clinical results with use of bioabsorbable suture anchors. Product development continues with newer composites such as PEEK (polyetheretherketone) and calcium ceramics (tricalcium phosphate) in an effort to hypothetically create a mechanically stable construct with and improve biocompatibility of the implant. Bioabsorbable anchors remain a safe, reproducible, and consistent implant to secure soft tissue to bone in and about the shoulder. Meticulous insertion technique must be followed in using bioabsorbable anchors and may obviate many of the reported complications found in the literature. The purpose of this review is to provide an overview of the existing literature as it relates to the rare complications seen with use of bioabsorbable suture anchors in the shoulder.     

Pullout strength of suture anchors in comparison with transosseous sutures for rotator cuff repair

Suture anchors are increasingly gaining importance in rotator cuff surgery. This means they will be gradually replacing transosseous sutures. The purpose of this study was to compare the stability of transosseous sutures with different suture anchors with regard to their pullout strength depending on bone density. By means of bone densitometry (CT scans), two groups of human humeral head specimens were determined: a healthy and a osteopenic bone group. Following anchor systems were being tested: SPIRALOK™ 5.0 mm (resorbable, DePuy Mitek), Super Revo 5 mm (titanium, Linvatec), UltraSorb (resorbable, Linvatec) and the double U-sutures with Orthocord™ USP 2 (partly resorbable, DePuy Mitek) and Ethibond Excel 2 (non-resorbable, Ethicon). The suture anchors/double U-sutures were inserted in the greater tuberosity 12 times. An electromechanical testing machine was used for cyclic loading with power increasing in stages. We recorded the ultimate failure loads, the system displacements and the modes of failure. The suture anchors tended to bring about higher ultimate failure loads than the transosseous double U-sutures. This difference was significant in the comparison of the Ethibond suture and the SPIRALOK 5.0 mm—both in healthy and osteopenic bone. Both the suture materials and the SPIRALOK 5.0 mm showed a significant difference in pullout strength on either healthy or osteopenic bone; the titanium anchor SuperRevo 5 mm and the tilting anchor UltraSorb did not show any significant difference in healthy or osteopenic bone. There was no significant difference concerning system displacement (healthy and osteopenic bone) between the five anchor systems tested. The pullout strength of transosseous sutures is neither on healthy nor on osteopenic bone higher than that of suture anchors. Therefore, even osteopenic bone does not constitute a valid reason for the surgeon to perform open surgery by means of transosseous sutures. The choice of sutures in osteopenic bone is of little consequence anyway since it is mostly the bone itself which is the limiting factor.     

Contact area and pressure in suture bridge rotator cuff repair using knotless lateral anchors

Purpose

To evaluate whether the use of knotless lateral anchors in a suture bridge construct produces better contact area and pressure parameters than a suture bridge construct with standard lateral anchors that require knots or a double-row repair. The hypothesis was that knotless lateral anchors would produce better contact area and pressure parameters than the other two constructs.

Methods

A total of fifteen matched pairs of cadaveric shoulders were divided into three groups. In Group 1, a suture bridge using knotless anchors for the lateral row was performed on five shoulders. A suture bridge using standard lateral row anchors that require knots was performed on the contralateral shoulders. In Group 2, suture bridge with knotless lateral row anchors was compared with double-row repair. In Group 3, suture bridge using standard lateral row anchors was compared with double-row repair. The contact conditions of the rotator cuff footprint were measured using pressure-sensitive film.

Results

There were no statistically significant differences between any of the techniques regarding contact area F(2, 15.7) = 3.09, P = 0.07 or mean contact pressure F(2, 15.1) = 2.35, P = 0.12. A post hoc power analysis suggests differences between techniques are likely less than 91–113 mm² for area and 0.071-0.089 N for pressure.

Conclusions

The use of knotless anchors in the lateral row of a suture bridge repair did not increase the footprint contact area or contact pressure when compared to a suture bridge repair requiring knots laterally or to a double-row repair.     

Neoinnervation in rotator cuff tendinopathy

The aim of this study was to determine whether there are more nerves in tendinopathic human tendon, and if so, where are they located. Tendon biopsies were collected from normal, tendinopathic, and torn human rotator cuff tendons and then analyzed using immunohistochemistry and antibodies against a general nerve marker (protein gene product 9.5, PGP9.5), a nerve regeneration marker (growth-associated protein 43, GAP43), and an endothelial cell marker (CD34). Nerve fibers exhibiting PGP9.5 or GAP43 immunoreactivity were often observed intimately in association with tiny blood vessels in the endotendineum of tendinopathic tendons. The expression of PGP9.5 and GAP43 were significantly higher in tendinopathic tendon compared with control tendon and torn tendon. These data support the hypothesis that early tendinopathy is associated with increases of newly grown nerve fibers and blood vessels inside and around tendinopathic tendon, and these may be the source of pain in tendinopathy.     

Ultrasonography of the rotator cuff

The authors suggest that sonography may be the best screening study for the diagnosis of rotator cuff tears.     

Imaging of the rotator cuff

The imaging evaluation of the rotator cuff augments the clinical evaluation. Radiography, computed tomography, and magnetic resonance imaging all have various roles in the assessment of the rotator cuff, which can be combined with arthrography for added detail. Furthermore, ultrasound is a very useful technique that provides functional information that is not offered by simple anatomic imaging.     

Arthroscopic double-row repair of the rotator cuff: a comparison of bio-absorbable and non-resorbable anchors regarding osseous reaction

Purpose

The aim of this study was to analyse the osseous reaction after arthroscopic double-row rotator cuff repair using bio-absorbable poly-l-lactic acid (PLLA) and non-absorbable polyetheretherketone (PEEK) suture anchors. Focus of interest was the appearance of peri-implant fluid and anchor tunnel widening.

Methods

Thirty-six patients were evaluated at final follow-up (16 PLLA and 20 PEEK). Clinical results were acquired by use of the subjective shoulder value, the Constant score and the Western Ontario Rotator Cuff Index. Radiological results were analysed by supraspinatus tendon integrity, footprint coverage, muscular atrophy and fatty infiltration. Furthermore, anchor tunnel expansion was measured, anchor structure and peri-implant fluids graduated.

Results

At 28.4 ± 8.9-month follow-up, clinical outcome was similar (n.s.). MRI investigation revealed osseous reaction in both groups; tunnel widening was 0.9 ± 0.7 mm in PLLA and 0.8 ± 0.6 mm in PEEK anchors (n.s.). Peri-implant fluid was pronounced in PLLA anchors (p < 0.05). Tunnel widening was significantly higher in lateral anchors irrespectively of the material used. Tendon integrity, muscular atrophy, fatty infiltration and footprint coverage were not significantly different (n.s.).

Conclusion

Both materials lead to osseous reaction in this study, whereas consequences of pronounced fluid in PLLA patients remain unclear. Pronounced tunnel widening in lateral anchors leads to the assumption that other causes such as mechanical stress potentially have to be considered when analysing osseous reaction.

Level of evidence

III.     

Rehabilitation of rotator cuff tendinopathy

Rehabilitation of the dysfunction that is associated with rotator cuff tendinopathy should be based on the evidence known about the pathoetiology of the tendinopathy, what is known about the extent of the local anatomic injury, the local and distant physiological and biomechanical alterations, and on the knowledge developed regarding progressive loading of the injured or altered structures. Prehabilitation, or prospective exercises to minimize future rotator cuff loading stresses, should be included at the end of rehabilitation as part of the return to function.     

Histopathology of rotator cuff tears

The pathogenesis of rotator cuff tears is multifactorial. Tendon abnormalities of the rotator cuff include alteration of collagen fiber structure, tenocytes, cellularity, and vascularity. Ruptured tendons show marked collagen degeneration and disordered arrangement of collagen fibers. Fibroblast population decreases as the size of the tear in the rotator cuff increases. The larger fibroblast population seen in the smaller tears is also actively proliferating and is part of an active reparative process. Inflammatory cell infiltrate correlates inversely to rotator cuff tear size in the torn supraspinatus tendon samples, with larger tears showing a marked reduction in all cell types. As tear size increase, there is also a progressive decrease in the number of blood vessels. Whether rotator cuff tear heals spontaneously is an important pathologic and clinical question. Histologic changes indicative of repair and inflammation lead to consider biological options in addition to biomechanical treatment of the rotator cuff tears.     

Pitfalls of rotator cuff sonography

Experience with rotator cuff sonography in 106 patients was analyzed to identify the causes of scan misinterpretation. Possible interpretive errors may be classified into four categories: those from failure to recognize normal anatomy, those caused by soft-tissue abnormalities, those caused by bony abnormalities, and those caused by technical limitations of the study. Errors in recognition of normal anatomy are easily overcome by experience and comparison to the normal, contralateral rotator cuff. Errors resulting from soft-tissue abnormalities were seen in two patients with calcific tendinitis simulating rotator cuff tears. Problems in interpretation resulting from fractures in two patients and inferior glenohumeral subluxation in two other patients could have been avoided by review of the plain films before performing sonography. The major technical limitation of the study arises from the inability to image the rotator cuff beneath the acromion. Fortunately, rotator cuff tears are rarely isolated in this location, and passive maneuvers often allow otherwise hidden parts of the cuff to be imaged.     

Ultrasonography of symptomatic rotator cuff tears compared with MR imaging and surgery

Purpose

To compare the accuracy of ultrasonography and magnetic resonance imaging in the detection of rotator cuff tears.

Materials and methods

Ninety-six patients with clinically suspected rotator cuff pathology underwent ultrasonography and magnetic resonance imaging of the shoulder. The findings in 88 patients were compared with arthroscopy or open surgery.

Results

Full-thickness tear was confirmed in 57 cases, partial-thickness tear in 30 cases and degenerative changes without tear in 1. In all 57 cases of full-thickness tear and in 28 out of 30 cases of partial-thickness tear the supraspinatus tendon was involved. The accuracy in the detection of full-thickness tears was 98 and 100% for ultrasonography and magnetic resonance imaging, respectively. The accuracy in the detection of bursal or articular partial-thickness tears was 87 and 90% for ultrasonography and magnetic resonance imaging, respectively.

Conclusions

In experienced hands ultrasonography should be considered as an accurate modality for the initial investigation of rotator cuff, especially supraspinatus, tears.     

Biomechanical factors in rotator cuff pathology

The rotator cuff provides dynamic stability and is critical to normal shoulder function. Forces generated by the rotator cuff facilitate the motions involved in activities of daily living and the more demanding movements of athletics and manual labor. Injury and pathology of the rotator cuff are common and the unique anatomical and biomechanical characteristics of the cuff contribute to the etiology of its injury. This review provides a biomechanical and anatomic context to understanding normal rotator cuff function and summarizes recent work describing biomechanical implications of cuff pathology.     

Role of metalloproteinases in rotator cuff tear

The role of matrix metalloproteinases (MMPs) and their inhibitors (TIMPS) in the pathophysiology of rotator cuff tears has not been established yet. Recent advances empathize about the role of MMPs and TIMPS in extracellular matrix (ECM) remodeling and degradation in rotator cuff tears pathogenesis and healing after surgical repair. An increase in MMPs synthesis and the resulting MMPs mediated alterations in the ECM of tendons have been implicated in the etiopathogenesis of tendinopathy, and there is an increase in the expression of MMPs and a decrease in TIMP messenger ribonucleic acid expression in tenocytes from degenerative or ruptured tendons. Importantly, MMPs are amenable to inhibition by cheap, safe, and widely available drugs such as the tetracycline antibiotics and bisphosphonates. A better understanding of relationship and activity of these molecules could provide better strategies to optimize outcomes of rotator cuff therapy.