Reconstruction of the flexor tendon sheath. An experimental study in rabbits

[Application of medical biomaterials in prevention and treatment of tendon adhesion]

Objective

To review the research progress of medicine biomaterials in prevention and treatment of adhesion after tendon injury, and to provide reference for clinical treatment.

Methods

The literature on the application of medical biomaterials in the prevention and treatment of tendon adhesions in recent years was reviewed, and the biological process, treatment methods, and current status of tendon adhesions were summarized.

Results

Tendon adhesion as part of the healing process of the tendon is the biological response of the tendon to the injury and is also a common complication of joint dysfunction. Application of medical biomaterials can achieve better biological function of postoperative tendon by reducing the adhesion of peritendon tissues as far as possible without adversely affecting the tendon healing process.

Conclusion

The use of medical biomaterials is conducive to reduce the adhesion of tendon after operation, and the appropriate anti-adhesion material should be selected according to the patients' condition and surgical needs.

Cross-linked cartilage acellular matrix film decreases postsurgical peritendinous adhesions

Cartilage extracellular matrix contains antiadhesive and antiangiogenic molecules such as chondromodulin-1, thrombospondin-1, and endostatin. We have aimed to develop a cross-linked cartilage acellular matrix (CAM) barrier for peritendinous adhesion prevention. CAM film was fabricated using decellularized porcine cartilage tissue powder and chemical cross-linking. Biochemical analysis of the film showed retention of collagen and glycosaminoglycans after the fabrication process. Physical characterization of the film showed denser collagen microstructure, increased water contact angle, and higher tensile strength after cross-linking. The degradation time in vivo was 14 d after cross-linking. The film extract and film surface showed similar cell proliferation, while inhibiting cell migration and cell adhesion compared to standard media and culture plate, respectively. Application of the film after repair resulted in similar tendon healing and significantly less peritendinous adhesions in a rabbit Achilles tendon injury model compared to repair only group, demonstrated by histology, ultrasonography, and biomechanical testing. In conclusion, the current study developed a CAM film having biological properties of antiadhesion, together with biomechanical properties and degradation profile suitable for prevention of peritendinous adhesions.

History and performance of implant materials applied as peritendinous antiadhesives

Peritendinous fibrotic adhesions after tendon surgery are still a problem up-to-date. Approaches to overcome or at least minimize adhesion formation include implantation of barrier materials, application of lubricants or combinations of materials and functionalized drugs that are controllably released and support the healing tendon to glide and achieve the full range of motion after regeneration. Although a huge amount of different materials have been experimentally tested, the optimal strategy with respect to material and method has not yet been determined. In this review, we present a historical overview of physical barriers as well as liquid agents that have been used in order to prevent peritendinous adhesion formation. The materials are divided according to their first publication into two time frames; before and after 1980. There is no claim to include all materials tested neither will the "best" material be chosen; however, we present several materials that were experimentally tested in different animal trials as well as in clinical trials in contrast to other materials that were only tested once and disappeared from the assortment of anti-adhesives; which as such is a valuable information about its applicability for this purpose.

Surgical reconstruction and mobilization therapy for a retracted extensor hallucis longus laceration and tendon defect repaired by split extensor hallucis longus tendon lengthening and dermal scaffold augmentation

A reconstructive technique and physical therapy protocol is presented for the treatment of extensor hallucis longus (EHL) lacerations with critical size defects caused by tendon retraction. The primary goal of treatment was to restore EHL structure and function without the use of a bridging allograft or tendon transfer. The technique is performed by split lengthening the distal segment of the lacerated EHL and rotating the lengthened segment proximally 180° to bridge the tendon defect. The lengthened tendon is then sutured to the proximal segment of the EHL. The EHL is then tubularized with an acellular dermal scaffold at the region of tendon rotation to improve tendon strength, minimize the probability of tendon overlengthening or re-rupture, and improve the tendon gliding motion, which can be compromised by the tendon irregularity caused by rotation of the tendon. Postoperative range of motion therapy should be initiated at 3 weeks postoperatively. A case report of this technique and postoperative mobilization protocol is presented. The American Orthopaedic Foot and Ankle Society midfoot score at 3 and 6 months postoperatively was 90 of 100. The patient regained active dorsiflexion motion of the hallux without functional limitations, deformity, or contracture of the hallux. The advantages of this technique include that a large cadaveric allograft is not needed to bridge a critical size tendon defect and tendon lengthening provides a biologically active tendon graft without the secondary comorbidities and dysfunction commonly associated with tendon transfer procedures.

Effects of antisense transforming growth factor-beta1 gene transfer on the biological activities of tendon sheath fibroblasts

Recent studies have shown the importance of transforming growth factor-beta (TGF-beta) in flexor tendon wound healing. Decreased adhesion formation and increased range of motion after the administration of TGF-beta antibodies after tendon repair have been shown. But TGF-beta antibodies have a short biologic half-life, and continuous supplementation of exogenous TGF-beta antibodies is not practical. Transfer of growth factor genes to tenocytes provides an alternative to protein therapeutics, and a gene therapy approach will prolong the availability of therapeutic proteins.We investigated the biological activities effects of rabbit tendon sheath fibroblasts transfected by antisense TGF-beta1 gene. Tendon sheath fibroblasts were isolated from New Zealand white rabbits and transfected by antisense TGF-beta1 gene with Lipofectin (Invitrogen, Carlsbad, California). Reverse transcription polymerase chain reaction was used to measure collagen I, collagen III, and TGF-beta1 expression, and Western blot was used to measure collagen protein I expression in tendon sheath fibroblasts after being transfected by antisense TGF-beta1 gene. Reverse transcription polymerase chain reaction displayed that tendon sheath fibroblasts transfected with antisense TGF-beta1 gene showed marked decrease collagen I, collagen III, and TGF-beta1 mRNA expression. Western blot showed that tendon sheath fibroblasts transfected with antisense TGF-beta1 gene showed marked decrease expression of collagen I protein, and there was significant difference compared with the untransfected and empty transfected groups (P<.01). Tendon sheath fibroblasts can transfect with antisense TGF-beta1 gene successfully and can decrease production of collagen I, collagen III, and TGF-beta1, which were factors of tendon adhere formation.

Porcine peritoneum as source of biocompatible collagen in mice

PURPOSE: To investigate the biocompatibility and biodegradability of a membrane made from porcine peritoneum. METHODS: The membrane (5x5 mm) was inserted in the subcutaneous tissue on the back of 15 mice, which were killed after 1, 3 and 9 weeks (ISO 10993-6). The cellular components of the inflammatory response and degradation of the membrane were analyzed in hematoxylin-eosin-stained histological sections. RESULTS: After one week, mononuclear cells were observed inside the membrane. After three weeks, the material was almost completely absorbed. After nine weeks, there was no presence of material and there were signs of tissue remodeling. There was neither a foreign body reaction nor signs of tissue necrosis. CONCLUSION: The collagen membrane derived from porcine peritoneum is biocompatible and bioabsorbable when implanted in the subcutaneous tissue of mice.

The Use of a Hydrogel Sealant on Flexor Tendon Repairs to Prevent Adhesion Formation

The prevention of peritendinous adhesions after zone II flexor tendon repair poses a significant challenge to hand surgeons. This study evaluates a hydrogel sealant (FocalSeal-L) as a barrier to peritendinous adhesion formation. The deep flexors of toes 2 through 4 were divided and repaired in 30 chickens. Chickens were randomized to tendon repair with (n = 15) or without (n = 15) FocalSeal-L. Each group was further randomized to have their tendons studied postoperatively at 3 (n = 10), 6 (n = 10), or 12 (n = 10) weeks. Histologic evaluation revealed decreased peritendinous adhesion formation in the FocalSeal-L group. Biomechanical analysis demonstrated a decrease in work of flexion in the FocalSeal-L group that was most pronounced at 6 weeks (P = 0.0020). There was no significant difference in breaking strength. Apparently, an effective barrier to peritendinous adhesion formation, this sealant system is easy to use, biocompatible, and bioresorbable. In addition, it is not bulky or restrictive to tendon glide.

The scientific basis for advances in flexor tendon surgery

During the last 40 years, there has been an enormous amount of basic scientific research designed to improve our knowledge of the structure of tendons, the biomechanics of their action, their biologic response to injury and repair, the mechanical characteristics of various tendon suture methods, and the effect of postrepair motion stress on tendon strength and healing. These investigative efforts have given rise to improved methods of tendon repair and protocols for the early application of passive and active wrist and digital motion as a means to more rapidly increase the strength and gliding of repaired tendons. The surgical techniques of hand surgeons and the rehabilitation protocols of hand therapists have improved enormously from these scientific efforts and the results of flexor tendon repair have become much more reliable. This article attempts to review many of the important scientific reports dealing with flexor tendons that have been published during the last three-plus decades and indicate how those works have improved our management of these difficult injuries.

Chondroitin sulfate-coated polyhydroxyethyl methacrylate membrane prevents adhesion in full-thickness tendon tears of rabbits

Polyhydroxyethyl methacrylate (pHEMA) membranes coated on one side with chondroitin sulfate (CS) were used to block adhesion physically and to reduce friction between healing flexor tendons and the surrounding tissue in rabbit forepaws after surgical repair. Digits with pHEMA-only, standard tendon sheath repair, and with no sheath repair were the controls. Over 12 weeks the CS-coated membranes were evaluated for joint flexion, adhesion limitation, and tendon healing progress. The membranes initially allowed for better flexion (ie, for 6 weeks), but their relative superior effectiveness faded afterward. Histology showed that adhesions were less severe and healing was better in the CS-pHEMA membranes at 3 and 6 weeks. If further studies determine precise amounts or thicknesses of CS coats that will maximize its healing properties, CS-pHEMA should prove useful in clinical settings in which restoration of tendon sheath integrity with a minimum of adhesions is not possible.

Studies in flexor tendon wound healing: neutralizing antibody to TGF-beta1 increases postoperative range of motion

The postoperative outcome of hand flexor tendon repair remains limited by tendon adhesions that prevent normal range of motion. Recent studies using in situ hybridization techniques have implicated transforming growth factor beta-1 (TGF-beta1) in both intrinsic and extrinsic mechanisms of repair. TGF-beta1 is a growth factor that plays multiple roles in wound healing and has also been implicated in the pathogenesis of excessive scar formation. The purpose of this study was to examine the effect of neutralizing antibody to TGF-beta1 in a rabbit zone II flexor tendon wound-healing model. Twenty-two adult New Zealand White rabbits underwent complete transection of the middle digit flexor digitorum profundus tendon in zone II. The tendons were immediately repaired and received intraoperative infiltration of one of the following substances: (1) control phosphate-buffered saline; (2) 50 microg neutralizing antibody to TGF-beta1; (3) 50 microg each of neutralizing antibody to TGF-beta1 and to TGF-beta2. Eight rabbits that had not been operated on underwent analysis for determination of normal flexion range of motion at their proximal and distal interphalangeal joints, using a 1.2-N axial load applied to the flexor digitorum profundus tendon. All rabbits that had been operated on were placed in casts for 8 weeks to allow maximal tendon adhesion and were then killed to determine their flexion range of motion. Statistical analysis was performed using the Student's unpaired t test. When a 1.2-N load was used on rabbit forepaws that had not been operated on, normal combined flexion range of motion at the proximal and distal interphalangeal joints was 93+/-6 degrees. Previous immobilization in casts did not reduce the range of motion in these forepaws (93+/-4 degrees). In the experimental groups, complete transection and repair of the flexor digitorum profundus tendon with infiltration of control phosphate-buffered saline solution resulted in significantly decreased range of motion between the proximal and distal phalanges [15+/-6 degrees (n = 8)]. However, in the tendon repairs infiltrated with neutralizing antibody to TGF-beta1, flexion range of motion increased to 32+/-9 degrees (n = 7; p = 0.002). Interestingly, a combination of neutralizing antibody to TGF-beta1 and that to TGF-beta2 did not improve postoperative range of motion [18+/-4 degrees (n = 7; p = 0.234)]. These data demonstrate that (1) the rabbit flexor tendon repair model is useful for quantifying tendon scar formation on the basis of degrees of flexion between proximal and distal phalanges; (2) intraoperative infiltration of neutralizing antibody to TGF-beta1 improves flexor tendon excursion; and (3) simultaneous infiltration of neutralizing antibody to TGF-beta2 nullifies this effect. Because TGF-beta1 is thought to contribute to the pathogenesis of excessive scar formation, the findings presented here suggest that intraoperative biochemical modulation of TGF-beta1 levels limits flexor tendon adhesion formation.