A comparison of ultra-high-molecular weight polyethylene cable and stainless steel wire using two fixation techniques for repair of equine midbody sesamoid fractures: an in vitro biomechanical study.
OBJECTIVE
To compare the monotonic tensile and fatigue strength of 16-gauge stainless steel wire (SSW) to ultra-high-molecular weight polyethylene (UHMWPE) cable using a transfixed cerclage technique in an in vitro midbody sesamoid osteotomy model. Endoscopic modifications to Martins transfixed cerclage technique were developed. A new suture technique of fixation was compared with the transfixed cerclage technique by measuring gap formation after cyclic testing.


METHODS
An in vitro biomechanical paired equine cadaver limb study.


METHODS
Twenty-one paired cadaveric adult equine forelimbs.


METHODS
Uniaxial medial midbody sesamoid osteotomies were created in paired adult equine forelimbs. Monotonic tensile strength was measured on 10 forelimbs repaired by a transfixed cerclage technique using wire or cable. Fatigue testing to failure was performed on 4 forelimbs repaired using the transfixed cerclage technique by cycling the limbs between 500 N and 2,000 N. The limbs were initially repaired with wire, cycled until the wire broke, then repaired with cable and cycled again to failure. Fatigue testing for gap displacement was performed on 8 limbs repaired with either the transfixed cerclage technique or the suture technique. Limbs were cycled between 500 N and 2,000 N for 10,000 cycles. The limbs were repaired with wire initially, tested, and then repaired with cable and tested again. Twenty-two limbs were used for mechanical testing. The remaining limbs (20) were used to develop and practice the endoscopic transfixed cerclage (10 limbs) and suture (10 limbs) techniques.


RESULTS
Ultimate tensile strength (UTS) of UHMWPE cable constructs was 34% greater than the UTS of SSW constructs. Fatigue strength was 2 to 20 times greater for UHMWPE cable constructs than SSW constructs. Separation of fragments was 153% less for limbs repaired by the suture technique compared with those repaired by the transfixed cerclage technique.


CONCLUSIONS
UHMWPE cable shows promise for this clinical application because of its greater tensile and fatigue strength. The newly described suture technique significantly reduced gap formation compared with the transfixed cerclage technique. Osteotomy gap formation occurred early in cycling, suggesting that rigid support in the form of a cast may be needed during the early postoperative period for wiring techniques.


CONCLUSIONS
Clinical testing of UHMWPE cable should eliminate problems of wire breakage seen with SSW. The endoscopic transfixed cerclage technique can be used by surgeons familiar with arthroscopic surgery. However, the suture technique needs to be tested in vivo to determine whether there is a clinical advantage compared with the transfixed cerclage technique.
Rothaug
Paul G
PG
Richard S. Reynolds, Jr, Comparative Orthopedic Research Laboratory, New Bolton Center, Department of Clinical Studies, College of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA, USA.
Boston
Ray C
RC
Richardson
Dean W
DW
Nunamaker
David M
DM
D000818:Animals; D001696:Biomechanical Phenomena; D001863:Bone Screws / Q000662:veterinary; D001864:Bone Wires / Q000662:veterinary*; D002102:Cadaver; D005592:Fracture Fixation / Q000295:instrumentation / Q000379:methods / Q000662:veterinary*; D050723:Fractures, Bone / Q000000981:diagnostic imaging / Q000601:surgery / Q000662:veterinary*; D006736:Horses / Q000293:injuries* / Q000601:surgery; D020959:Polyethylene; D011859:Radiography; D012716:Sesamoid Bones / Q000293:injuries* / Q000503:physiopathology / Q000601:surgery; D013193:Stainless Steel; D013536:Suture Techniques / Q000662:veterinary; D013718:Tensile Strength
D013193:Stainless Steel; D020959:Polyethylene