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.

Combined effect of DBM, PRP, and bone marrow fluid on bone union in a rat posterolateral fusion model.

Platelet-rich plasma (PRP) promotes bone union through osteoinduction. We investigated whether adding demineralized bone matrix (DBM), derived naturally from biomaterial and with various growth factors, for osteoconductivity and bone marrow fluid for osteogenesis results in different bone unions. Eight-week-old male Sprague-Dawley rats were divided into four groups of five based on transplantation material: sham control (C group); DBM alone (D group); DBM + PRP (DP group); and DBM + PRP + bone marrow fluid (DPB group). After posterolateral fusion at L3-5, postoperative weekly CT imaging determined average number of bone union in facet joints (4 joints × 5 animals = 20 joints) and bone formation. Pathological evaluation and bone strength were assessed using 3-point bending two weeks postoperatively. Facet joint bone union at four weeks postoperatively was 4/20 (20%, DP group) and 8/20 (40%, DPB group) joints. Six weeks postoperatively, it was 7/20 (35%, D group), 12/20 (60%, DP group), and 16/20 (80%, DPB group). Eight weeks postoperatively, it was 13/20 (65%, D group), 17/20 (85%, DP group), and 20/20 (100%, DPB group), suggesting that DPB > DP > D > C. Bone formation and bone strength showed a similar DPB > DP > D > C group trend. Adding PRP and bone marrow fluid to DBM promotes bone union and strength.

Molecular design of a nylon-6 byproduct-degrading enzyme from a carboxylesterase with a beta-lactamase fold.

A carboxylesterase with a beta-lactamase fold from Arthrobacter possesses a low level of hydrolytic activity (0.023 mumol.min(-1).mg(-1)) when acting on a 6-aminohexanoate linear dimer byproduct of the nylon-6 industry (Ald). G181D/H266N/D370Y triple mutations in the parental esterase increased the Ald-hydrolytic activity 160-fold. Kinetic studies showed that the triple mutant possesses higher affinity for the substrate Ald (K(m) = 2.0 mm) than the wild-type Ald hydrolase from Arthrobacter (K(m) = 21 mm). In addition, the k(cat)/K(m) of the mutant (1.58 s(-1).mm(-1)) was superior to that of the wild-type enzyme (0.43 s(-1).mm(-1)), demonstrating that the mutant efficiently converts the unnatural amide compounds even at low substrate concentrations, and potentially possesses an advantage for biotechnological applications. X-ray crystallographic analyses of the G181D/H266N/D370Y enzyme and the inactive S112A-mutant-Ald complex revealed that Ald binding induces rotation of Tyr370/His375, movement of the loop region (N167-V177), and flip-flop of Tyr170, resulting in the transition from open to closed forms. From the comparison of the three-dimensional structures of various mutant enzymes and site-directed mutagenesis at positions 266 and 370, we now conclude that Asn266 makes suitable contacts with Ald and improves the electrostatic environment at the N-terminal region of Ald cooperatively with Asp181, and that Tyr370 stabilizes Ald binding by hydrogen-bonding/hydrophobic interactions at the C-terminal region of Ald.