Functionally Graded, Bone- and Tendon-Like Polyurethane for Rotator Cuff Repair.
ABSTRACT: Critical considerations in engineering biomaterials for rotator cuff repair include bone-tendon-like mechanical properties to support physiological loading and biophysicochemical attributes that stabilize the repair site over the long-term. In this study, UV-crosslinkable polyurethane based on quadrol (Q), hexamethylene diisocyante (H), and methacrylic anhydride (M; QHM polymers), which are free of solvent, catalyst, and photoinitiator, is developed. Mechanical characterization studies demonstrate that QHM polymers possesses phototunable bone- and tendon-like tensile and compressive properties (12-74 MPa tensile strength, 0.6-2.7 GPa tensile modulus, 58-121 MPa compressive strength, and 1.5-3.0 GPa compressive modulus), including the capability to withstand 10 000 cycles of physiological tensile loading and reduce stress concentrations via stiffness gradients. Biophysicochemical studies demonstrate that QHM polymers have clinically favorable attributes vital to rotator cuff repair stability, including slow degradation profiles (5-30% mass loss after 8 weeks) with little-to-no cytotoxicity in vitro, exceptional suture retention ex vivo (2.79-3.56-fold less suture migration relative to a clinically available graft), and competent tensile properties (similar ultimate load but higher normalized tensile stiffness relative to a clinically available graft) as well as good biocompatibility for augmenting rat supraspinatus tendon repair in vivo. This work demonstrates functionally graded, bone-tendon-like biomaterials for interfacial tissue engineering.
Project description:The principle of margin convergence can be applied to rotator cuff repair to enhance the security of fixation by decreasing the mechanical strain at the margins of the tear. We describe a suture technique, over-under lacing, that reproduces the same margin convergence, with equal tissue tension across the entire surface area of the cuff. A consecutive series of patients affected by massive U-shaped rotator cuff tears were treated by this repair technique. Preoperative diagnosis, tear assessment, and grading of fatty infiltration of the cuff muscles were based on arthro-computed tomography evaluation. The technique passes 2 sutures from the medial to lateral margin of the tear, with a knotless suture anchor for tendon-to-bone fixation. The proposed technique seems to reduce tensile strain on the repaired tendon, can reconstruct the rotator cuff cable, and can attain the balanced pull of the tendon in a medial-to-lateral fashion. The over-under lacing suture technique is both simple and reproducible. This technique may achieve the goals of margin convergence with satisfactory preliminary clinical results for patients with massive rotator cuff tears.
Project description:<h4>Purpose</h4>To assess the mechanical properties, tendon resistance to suture cutout, and knot size of a broad variety of high-strength sutures and tapes available for arthroscopic rotator cuff repair.<h4>Methods</h4>Nine different types of high-strength sutures and tapes for arthroscopic rotator cuff repair were studied: 6 were tapes (FiberTape, Hi-Fi Tape, Permatape, SutureTape, UltraTape, and XBraid TT), and 3 were sutures (Dynacord, FiberWire, and Ultrabraid). First, mechanical tensile testing of suture loops (n = 6) was performed. Second, the suture material was passed through an intact human cadaveric rotator cuff tendon (supraspinatus or infraspinatus), and cyclic as well as load-to-failure testing was performed, 8 times for each suture or tape. Statistical analysis of groups (tapes vs sutures) and between each suture and each tape was performed.<h4>Results</h4>Material testing revealed significant differences with superior mechanical properties of tapes compared with sutures regarding load for 3 mm of displacement (201 N vs 84 N, <i>P</i> < .0001), displacement at 200 N (3.6 mm vs 6.6 mm, <i>P</i> < .0001), stiffness (46 N/mm vs 25 N/mm, <i>P</i> < .0001), and ultimate load to failure (509 N vs 288 N, <i>P</i> < .0001). FiberTape showed the highest ultimate load to failure (805.5 ± 36.1 N), the highest load necessary for 3 mm of displacement (376.2 ± 19.1 N), and the lowest displacement at a 200-N load (2 ± 0.1 mm). Permatape had the highest stiffness (58.5 ± 5.3 N/mm). FiberTape had the highest knot height (9.5 ± 1.3 mm) and knot width (3.8 ± 0.7 mm) of a suture loop with 7 square knots. The typical failure mode in the cadaveric study part was tendon cut through.<h4>Conclusions</h4>Biomechanical in vitro testing showed that high-strength suture tapes compared with regular high-strength sutures have significantly better mechanical properties in both dry-laboratory testing and human cadaveric rotator cuff tendon pullout testing. FiberTape outperformed the other tapes and the sutures used in this analysis. Nonetheless, differences in tendon testing appeared to be less substantial than in dry-laboratory testing, and FiberTape had the highest knot height and width.<h4>Clinical relevance</h4>FiberTape revealed the most favorable biomechanical performance in dry-laboratory and rotator cuff tendon testing. It may provide the best repair strength in vivo; however, it also has the largest knot size.
Project description:Despite advancements in arthroscopic rotator cuff repair techniques, achieving tendon-to-bone healing can be difficult in the setting of poor-quality tendon. Moreover, medial tendon tears or tears with lateral tendon loss may preclude standard techniques. Rip-stop suture configurations have been shown to improve load to failure compared with simple or mattress stitch patterns and may be particularly valuable in these settings. The purpose of this report is to describe a technical modification of a rip-stop rotator cuff repair that combines the advantages of a rip-stop suture (by providing resistance to tissue cutout) and a double row of load-sharing suture anchors (minimizing the load per anchor and therefore the load per suture within each anchor).
Project description:Articular surface partial rotator cuff tendon tears are a common source of shoulder pain and dysfunction, and there is no consensus regarding the optimal arthroscopic treatment. Commonly accepted techniques, such as transtendinous repair or tear takedown with primary repair, may violate healthy tendon tissue and increase the suture anchor density. In this note, we describe an outside-in double row-equivalent technique for repair of partial articular-sided rotator cuff tears. A medial row of inverted horizontal mattress stitches is placed percutaneously using spinal needles to shuttle partially absorbable braided sutures into the joint. The technique may incorporate a soft tissue biceps tenodesis into the rotator cuff with a second, oblique medial row mattress stitch. Suture limbs are retrieved and tied in the subacromial space and then secured to a lateral anchor. The result is a side-to-side double row-equivalent rotator cuff repair, anatomically reproducing the footprint of the rotator cuff without removing healthy tissue. We believe this is an efficient and reproducible technique that preserves intact bursal tissue, limits implant costs, and produces reliable healing in partial articular-sided tears of the rotator cuff.
Project description:The subscapularis tendon plays an essential role in shoulder function. Although subscapularis tendon tears are less common than other rotator cuff tears, tears of the subscapularis tendon have increasingly been recognized with the advent of magnetic resonance imaging and arthroscopy. A suture bridge technique for the treatment of posterosuperior rotator cuff tears has provided the opportunity to improve the pressurized contact area and mean footprint pressure. However, suture bridge fixation of subscapularis tendon tears appears to be technically challenging. We describe an arthroscopic surgical technique for suture bridge repair of subscapularis tendon tears that obtains ideal cuff integrity and footprint restoration. Surgery using such a suture bridge technique is indicated for large tears, such as tears involving the entire first facet or more, tears with a disrupted lateral sling, and combined medium to large supraspinatus/infraspinatus tears.
Project description:Recent advances to improve outcomes in rotator cuff repair include using arthroscopic double-row suture-bridge techniques in an effort to reconstruct the rotator cuff footprint and improve fixation. However, when using this technique for larger tears, it can be difficult to get the lateral portion of the rotator cuff into an anatomic position. This report describes a triple-row modification of the suture-bridge technique that results in significantly more footprint contact area and contact pressure compared with the double-row and standard suture-bridge techniques. Maximizing the rotator cuff footprint contact area exposes more of the tendon to bone and may improve the healing potential.
Project description:Partial-thickness articular-sided rotator cuff tears are a common cause of shoulder pain in adults. Although partial rotator cuff tears have a high prevalence, there is still controversy over their proper surgical treatment. Different surgical procedures have been suggested when partial tears involve the articular side of the rotator cuff, such as arthroscopic debridement of the tear with or without acromioplasty, tear completion and repair, and transtendinous in situ repair. Although multiple repair techniques have been described, significant clinical data to definitively support one technique over the others are currently lacking. We describe an arthroscopic technique for repair of a partial articular supraspinatus tendon avulsion that avoids the transtendinous insertion of suture anchors to preserve the tendon integrity.
Project description:This article aims to describe a modification of the arthroscopic suture bridge technique for repair of a massive (>3 cm) rotator cuff tear. The method uses 2 medial anchors and 2 lateral anchors for rotator cuff repair, as well as double-row biceps tenodesis. This operative modification may impart better tendon healing and fewer rupture complications than the traditional double-row repair techniques.
Project description:The double-row suture technique and the suture-bridge technique have been used for rotator cuff repair to decrease the occurrence of retears. However, when only the degenerated tendon end is sutured, the risk of retear remains. The augmentation suture technique is a new procedure that connects the intact medial tendon to the lateral greater tuberosity, and this approach may protect the initial repair site. The procedures for this technique are as follows: 2 sutures are placed through the medial intact tendon, the cuff tear is repaired by the single-row technique, 2 sutures are pulled laterally over the single-row repair site, and 2 sutures are fixed at the lateral greater tuberosity with a push-in-type anchor. This technique is simple and easy and does not require special equipment. Moreover, this approach can augment the single-row repair technique without creating high tension at the cuff end.
Project description:Rotator cuff repair is a widely performed surgery. Its purpose is to improve shoulder function, fix tendons to bones, restore anatomical structure, and prevent the progression of rotator cuff tear arthropathy and associated muscle degeneration. However, in large and massive tears, the tension imposed during repair becomes too high. Medialized repairs have been reported for cases of rotator cuff tear, but they are difficult to perform. We report on ex-medialization that used common portals and instruments to remove the osteochondral and subchondral bone, reduce humeral head volume, and suture the tendon extremely medially. Compared to a common medialized repair, this procedure reduces tension on the rotator cuff to be sutured. The goal of this technique is to restore functional anatomy, reduce the rate of retear, prevent the progression of rotator cuff muscle atrophy and fatty degeneration, and to improve muscle strength by allowing the repair of rotator cuff tears (Goutallier grade 2 or higher) to the humeral head, which have conventionally been challenging.