The Effect of 1-Ethyl-3-(3-Dimethylaminopropyl) Carbodiimide Suture Coating on Tendon Repair Strength and Cell Viability in a Canine Model.

PURPOSE: To determine if impregnating a suture with a cross-linking agent, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC), improved suture pull-out strength and cell viability. METHODS: Canine flexor digitorum profundus tendons were cut in canine zone D, and a single suture loop was placed in each end, with sutures soaked in either saline or an EDC solution with a concentration of 1%, 10%, or 50%. Suture pull-out strength, stiffness, and elongation to failure was determined by pulling the loop until failure. Cytotoxicity of the EDC treatment was evaluated by suspending treated sutures over cultured tenocytes. RESULTS: Mechanical properties for the EDC-treated side were improved over controls when treated with the 10% and 50% EDC solutions. The ratio of dead to live cells was significantly increased at all distances from the suture for the 50% EDC-treated group. CONCLUSIONS: Suture treated with a 10% EDC solution provided the best combination of mechanical reinforcement and limited toxicity. CLINICAL RELEVANCE: Sutures so treated may improve the ability of a tendon repair to sustain early mobilization.

Biomechanical Study of the Digital Flexor Tendon Sliding Lengthening Technique.

PURPOSE: To compare the mechanical properties of sliding lengthening (SL) and Z-lengthening (ZL) for flexor tendon elongation used for conditions such as Volkmann contracture, cerebral palsy, and poststroke spasticity. METHODS: We harvested 56 flexor tendons, including flexor pollicis longus tendons, flexor digitorum superficialis tendons (zones II to IV), and flexor digitorum profundus tendons (zones II to V) from 24 upper limbs of 12 fresh cadavers. Each tendon was harvested together with its homonymous tendon from the opposite side of the cadaver and paired. We used 28 pairs of tendons and divided them randomly into 4 groups depending on the lengthening distance (20 or 30 mm) and type of stitching (single or double mattress sutures). Then we divided each pair into either the SL or ZL group. Each group was composed of 7 specimens. The same surgeon lengthened all tendons and stitched them with 2-0 polyester sutures. We tested biomechanical tensile strength immediately after completing lengthening and suturing in each group. RESULTS: Ultimate tensile strengths were: 23 N for the SL 20-mm lengthening and single mattress suture and 7 N for the ZL; 25 N for the SL 20-mm lengthening and double mattress suture and 10 N for the ZL; 15 N for the SL 30-mm lengthening and single mattress suture and 8 N for the ZL; and 18 N for the SL 30-mm lengthening and double mattress suture and 10 N for the ZL. CONCLUSIONS: The SL technique may be a good alternative to the ZL technique because it provides higher ultimate tensile strength. CLINICAL RELEVANCE: Because of its higher ultimate tensile strength, the SL technique may allow for earlier rehabilitation and reduced risk of postoperative complications.

The effect of Anti-NGF receptor (p75 Neurotrophin Receptor) antibodies on nociceptive behavior and activation of spinal microglia in the rat brachial plexus avulsion model.

STUDY DESIGN: We measured the response of the behavior and spinal glial activation to anti-nerve growth factor receptor (p75 neurotrophin receptor [p75NTR]) antibodies in the rat brachial plexus avulsion (BPA) model. OBJECTIVE: The aim of this study was to investigate the effect of anti-p75NTR antibodies on nociceptive behavior and activation of spinal microglia in the rat BPA model. SUMMARY OF BACKGROUND DATA: Tanezumab (anti-nerve growth factor antibody) treatment is associated with pain reduction and improvement in function, but with several complications. METHODS: Thirty male Wistar rats were used. In the BPA group, the C8-T1 roots were avulsed from the spinal cord with forceps at the lower trunk level and 10 µL of saline was applied locally (n = 10). In the anti-p75NTR group, the C8-T1 roots were avulsed and 10 µL of anti-p75NTR antibody was applied locally (n = 10). In a sham-operated group, the lower trunk was simply exposed (n = 10). Mechanical hyperalgesia and pain-induced walking patterns were measured using von Frey filaments (Stoelting, Wood Dale, IL) and the CatWalk gait analysis (Noldus Information Technology, the Netherlands) system every third day for 3 weeks. Activation of astrocytes and microglia was immunohistochemically examined in the spinal cord using anti-glial fibrillary acidic protein (GFAP) and anti-Iba1 antibodies both 7 and 21 days after surgery. RESULTS: Animals in the BPA group displayed significant mechanical hyperalgesia that continued through day 21 compared with animals in the sham-operated group, and mechanical hyperalgesia in the anti-p75NTR group was significantly improved 6 days after the operation. Regarding pain-induced gait analysis via CatWalk, animals in the BPA group displayed a significantly greater pain-like gait pattern than the p75 group for up to 3 weeks. Levels of GFAP-immunoreactive astrocytes and Iba1-immunoreactive microglia in the anti-p75NTR group were significantly reduced compared with the BPA group. CONCLUSION: Our results suggest that p75NTR contributes to neuropathic pain associated with BPA, and that inhibition of p75NTR reduces neuropathic pain. LEVEL OF EVIDENCE: N/A.

Fractional Fowler tenotomy for chronic mallet finger: a cadaveric biomechanical study.

PURPOSE: The Fowler tenotomy, adjusting the balance of the extensor mechanism by central slip and lateral band detachment, is a common surgical technique for chronic mallet finger. The purpose of this study was to determine how much tendon to detach from the middle phalanx by measuring the extensor lag of the distal interphalangeal (DIP) joint following the procedure and to quantify how often a boutonniere deformity occurred as a consequence of the procedure. METHODS: Sixteen fingers were obtained from 8 fresh-frozen cadaver hands. We made mallet finger deformity models by terminal tendon elongation. We detached the central slip and lateral band from the middle phalanx by one-third, one-half, and two-thirds of the phalangeal length and measured extensor lag of the DIP and proximal interphalangeal joints before and after this procedure. RESULTS: In these models, the average extensor lag of the DIP joint was 44° (range, 40° to 50°). After central slip and lateral band detachment over one-third of the phalangeal length, the average residual extensor lag of the DIP joint was 19° (range, 0° to 40°). With one-half detachment, the average lag was 13° (range, 0° to 35°), and with two-thirds detachment, the average lag was 6° (range, 0° to 15°). Extensor lag at the proximal interphalangeal joint occurred in 4 fingers, with an average lag of 8° (range, 5° to 15°). CONCLUSIONS: In the Fowler tenotomy models, detachment of the central slip and lateral band from the middle phalanx reduced extensor lag of the DIP joint. Detachment of up to two-thirds of the phalangeal length was effective in this model and did not cause any boutonniere deformity. CLINICAL RELEVANCE: Controlled clinical application of our cadaveric results might yield improved active motion for chronic mallet extensor lag.

Evaluation of behavior and neuropeptide markers of pain in a simple, sciatic nerve-pinch pain model in rats.

Pathomechanisms of injured-nerve pain have not been fully elucidated. Radicular pain and chronic constriction injury models have been established; however, producing these models is complicated. A sciatic nerve-pinch injury is easy to produce but the reliability of this model for evaluating pain behavior has not been examined. The current study evaluated pain-related behavior and change in pain markers in the dorsal root ganglion (DRG) of rats in a simple, sciatic nerve-pinch injury model. In the model, the sciatic nerve was pinched for 2 s using forceps (n = 20), but not injured in sham-operated animals (n = 20). Mechanical and thermal hyperalgesia were measured every second day for 2 weeks using von Frey filaments and a Hargreaves device. Calcitonin gene-related peptide (CGRP), activating transcription factor-3 (ATF-3), phosphorylated p38 mitogen activated protein (Map) kinase (p-p38), and nuclear factor-kappa B (NF-κB; p65) expression in L5 DRGs were examined at 4 and 7 days after surgery using immunohistochemistry. The proportion of neurons immunoreactive for these markers was compared between the two groups. Mechanical (during 8 days) and thermal hyperalgesia (during 6 days) were found in the pinch group rats, but not in the sham-operated animals (p < 0.05); however, hyperalgesia was not significant from days 10 to 14. CGRP, ATF-3, p-p38, and NF-κB expression in L5 DRGs was upregulated in the nerve-injured rats compared with the sham-operated rats (p < 0.01). Our results indicate that a simple sciatic nerve pinch produced pain-related behavior. Upregulation of the pain-marker expression in the nerve-injury model suggested it could be used as a model of pain. However, it was not considered as suitable for long-term studies.