The effects of bi-functional anti-adhesion scaffolds on flexor tendon healing in a rabbit model.

Progressive tendon adhesion is a major challenge in flexor tendon repair. The authors developed a bifunctional anti-adhesion scaffold and hypothesized that its application would reduce adhesion formation and deliver mesenchymal stem cells (MSCs) to enhance tendon healing. The scaffold was fabricated by an electrospinning machine before surface modification. The flexor tendons of 29 New Zealand rabbits underwent surgical repair and randomized to control, scaffold and scaffold loaded with MSC group. At 3 and 8 weeks post-surgery, range of motion (ROM), biomechanical properties, and histology were examined. There was no significant increase in ROM and biomechanical properties between the three groups. The histology showed successful delivery of MSCs but no significant difference in nuclear morphometry. This barrier delivers and retains MSCs within the tendon repair site. However, its sheet form and wrapping around the repair site may not be optimal for tendon healing. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2605-2614, 2018.

The Effects of Autologous Platelet-Rich Fibrin on Flexor Tendon Healing in a Rabbit Model.

PURPOSE: Platelet-rich plasma containing large amounts of growth factors is purported to increase repaired flexor tendon strength. However, the use of bovine thrombin has the risk of antibody formation. We evaluated the effects of the newer generation autologous platelet-rich fibrin (PRF) on flexor tendon healing. METHODS: We performed surgical repair of 32 flexor tendons from the index and ring digits of the hind paws of 8 New Zealand white rabbits. In the PRF group, the PRF membrane was either wrapped around or interposed between the repair sites. At 3 weeks after surgery, the tested tendons were subjected to range of motion analysis, cross-sectional area measurement, biomechanics testing, and histological analysis. RESULTS: The results showed no significant increase in range of motion in the PRF group compared with the control group, but there was a significant increase in cross-sectional area of the tendons in the PRF group. The biomechanical testing suggested that the control had a higher load to failure and stress to failure but similar stiffness and modulus to the PRF group. CONCLUSIONS: The PRF did not have a major influence on cellular organization. It also had an undesirable effect on the biomechanical properties of repaired flexor tendons. CLINICAL RELEVANCE: The findings of this study suggest PRF may, in certain situations, hinder rather than enhance, the healing for repaired flexor tendons.

Biomechanical comparison of different suturing techniques in rabbit medial gastrocnemius muscle laceration repair.

INTRODUCTION: Skeletal muscle laceration is a common injury. Repair of disrupted delicate tissue is still a clinical challenge for surgeons. A few different muscle repair techniques have been reported. However, the best muscle repair technique has not been identified. The aim of the present study is to compare the biomechanical features of different repair techniques in muscles to identify the most effective one. MATERIAL AND METHODS: New Zealand white rabbits (2.5-3 kg) were euthanized and medial gastrocnemius muscles were isolated. The muscles were completely transected with scalpels and then repaired by 3 different techniques, namely, (1) 2-strand mattress, (2) 4-strand Kessler (with epitendinous suture), and (3) Mason-Allen. To measure suture performance, the repaired specimens were mounted onto a mechanical testing machine Instron 5543. The muscles were loaded to failure at a constant speed of 60 mm/min. Data collected from Merlin v5.31 software were used to compute the biomechanical properties of each specimen. RESULTS: There was no significant difference in the mean maximum load of Kessler group (15.5 N) and Mason-Allen group (13.2 N), whereas the mean maximum load of the control (Mattress) group (4.4 N) was significantly smaller than the other 2 groups. Moreover, Kessler stitches were the stiffest among the 3. It is noteworthy that the mechanisms of failure were different: Kessler stitches were all pulled out longitudinally, whereas Mason-Allen stitches transmitted load across the laceration and ruptures occur at areas adjacent to the stitches, indicating that muscle is the weakest element in the biomechanical testing. CONCLUSIONS: Both Kessler and Mason-Allen stitches have shown better biomechanical features compared with the control group. Further study has to be done to compare the effect of these 2 techniques on muscle regeneration and scar formation in an in vivo model.

Mechanical failure of the distal radius volar locking plate.

PURPOSE: To review 9 cases of mechanical failure of the volar locking plate for distal radial fractures. METHODS: Records of 374 consecutive patients who underwent volar locking plating for distal radial fractures were reviewed. Mechanical failures of the volar locking plate were defined as plate breakage or bending, screw breakage or loosening, or collapse of articular fragments resulting in intra-articular screw extrusion. RESULTS: Nine mechanical failures occurred between 2 weeks and 3 months in 8 (2.4%) of the patients aged 25 to 82 (median, 74) years with AO fracture types of A3 (n=4), C1 (n=1), C2 (n=1), and C3 (n=3). Mechanical failures included screw pullout (n=5), locking plate bending (n=2), locking screws breakage (n=1), and loosening of locked variable angle screws (n=1). One patient underwent revision of fixation and 2 underwent implant removal. The remainder were treated conservatively. All patients were followed up for a minimum of 12 months; their mean flexion arc was 87 degrees (standard deviation [SD], 17) and the mean rotation arc was 136 degrees (SD, 29 degrees). According to the Green and O'Brien score, their outcomes were good (n=1), fair (n=4), and poor (n=3). CONCLUSION: Although mechanical failure of volar locking plate is uncommon, some are potentially preventable.

The effect of fibrin glue on tendon healing and adhesion formation in a rabbit model of flexor tendon injury and repair.

Fibrin glue has been widely used in a variety of surgical procedures to promote haemostasis and tissue bonding. It can also be used as a cell carrier for stem cells on tendons. However, the data about the effect of fibrin glue on flexor tendon healing is very limited. The present study examined the role of fibrin glue TISSEEL® in a rabbit model of flexor tendon injury. The rabbits were killed 3 or 8 weeks after the operation. The range-of-motion of the fingers and biomechanical properties of tendons were measured and compared between the control group and TISSEEL-treated group. The findings have shown that the range-of-motion in the TISSEEL-treated group was significantly different from that of the control group at 3 weeks after the operation. However, there is no significant difference in range-of-motion at 8 weeks after the operation. Moreover, there is no significant difference in biomechanical properties between the control group and TISSEEL-treated group. The results indicate that TISSEEL may attenuate adhesion formation at the early stage of flexor tendon repair. However, there is no significant effect on biomechanical features during tendon repair. In conclusion, this study has shown that it may be safe to use TISSEEL in tissue engineering applications for tendon regeneration and healing.

The reconstruction of large bone defects in the upper limb.

Large bone defects in the upper limb pose many challenges in reconstructive surgery. Conventional and innovative methods have been described, employing the use of microsurgical and non-microsurgical techniques to overcome both bony and soft tissue defects. This article reviews the success and pitfalls of different techniques of reconstruction of large bone defects in the upper limb, including microsurgical transfer of the free vascularised fibula graft as a diaphyseal bone replacement and as a hemivascularised joint transplant, and non-microsurgical options using conventional bone grafting, the induced membrane technique and the role of callotatic distraction-lengthening procedures.

Pulmonary artery re-thrombosis following interruption of anti-thrombotic therapy for bilateral carpal tunnel release surgery: an update of current protocols.

In the perioperative period, patients who are under anti-thrombotic therapy should be managed with care, although there is no clear consensus on this matter. For hand surgery, several authors have advocated no interruption of the anti-thrombotic therapy, but the choice differs between institutes according to protocols and surgeons' preference. We report a case of massive pulmonary embolism after stopping warfarin for carpal tunnel release in a patient with a previous history of pulmonary embolism. Although the patient recovered after thrombolytic therapy and intensive care unit (ICU) care, this case has struck the authors as a valuable lesson. In managing anti-thrombotic therapy, we should weigh the risks and benefits of the patients carefully before making a decision.

A biomechanical comparison of 3 loop suture materials in a 6-strand flexor tendon repair technique.

PURPOSE: The braided polyblend (FiberWire) suture is recognized for its superiority in tensile strength in flexor tendon repair. The purpose of this study was to compare the biomechanical performance of 3 loop-suture materials used in a locking 6-strand flexor tendon repair configuration: braided polyblend (FiberLoop 4-0), cable nylon (Supramid Extra II 4-0), and braided polyester (Tendo-Loop 4-0). We hypothesized that, using this technique, the braided polyblend suture would give superior tensile strength compared with the other 2 suture materials. METHODS: We divided 30 fresh porcine flexor tendons transversely and repaired each with 1 of the 3 suture materials using a modified Lim-Tsai 6-strand suture technique. We loaded the repaired tendons to failure using a materials testing machine and collected data on the mechanism of failure, ultimate tensile strength, gap strength, and stiffness. RESULTS: Failure mechanisms for the repaired specimens were as follows: the braided polyblend had 50% suture breakage and 50% suture pullout; the cable nylon had 100% suture breakage; and the braided polyester had 80% suture breakage and 20% suture pullout. Specimens repaired with the braided polyblend suture had the highest mean ultimate tensile strength (97 N; standard deviation, 22) and the highest mean gap force (35 N; standard deviation, 7). CONCLUSIONS: This study supports the findings of previous studies showing superior strength of the braided polyblend suture. CLINICAL RELEVANCE: We were able to achieve up to 124 N in ultimate tensile strength and 48 N of gap force with this suture in porcine tendons. This gives greater confidence in starting immediate controlled passive or active rehabilitation after repair of flexor tendon injuries.

Mycobacterium abscessus Hand Infections in Immunocompetent Fish Handlers: Case Report.

Mycobacterium abscessus hand infections are rare and usually occur in immunocompromised patients or after injection with contaminated injectables. This article describes 2 cases of M abscessus infection of the hand in otherwise healthy fish handlers. Mycobacterium abscessus can cause severe chronic tenosynovitis even in immunocompetent patients and should be suspected alongside the more common M marinum as a cause of nontuberculous mycobacterial hand infections in patients with aquatic and fish exposure.