Clinical outcomes and complications of pancarpal arthrodesis stabilised with 3.5†mm/2.7†mm locking compression plates with internal additional fixation in 12 dogs.

AIMS: To report the clinical outcomes and complications after the use of 3.5 mm/2.7 mm locking compression plates (LCP) with additional internal fixation for pancarpal arthrodesis (PCA) in dogs. METHODS: This was a retrospective study using medical records from a single orthopaedic referral hospital between December 2015 and April 2018. The inclusion criteria were the use of a dorsally applied LCP for PCA in dogs with a minimum follow-up period of 12 months. Additional crossed 2.7 or 3.5 mm cortical screws or Kirschner wires were placed in all limbs to further stabilise the joints. A light dressing without external coaptation was applied postoperatively to all limbs. Postoperative lameness assessment was recorded at the last clinical evaluation. RESULTS: Twelve dogs with 13 arthrodesed limbs were included, with carpal hyperextension injury being the most common indication for surgery (4/13; 31%). One dog was recorded with a minor complication, which was a metacarpal fracture distal to the bone plate. Major complications were observed in 4/13 (31%) limbs, with surgical site infection being recorded in all four limbs and screw loosening in one limb. No implant failure was reported. At the final clinical evaluation (43-437 days after surgery), none or mechanical lameness was recorded in 9/13 (69%) limbs, mild lameness in 3/13 (23%) limbs, and moderate lameness in one 1/13 (8%) limb. CONCLUSIONS AND CLINICAL RELEVANCE: Locking plate and screw fixation with additional internal fixation resulted in comparable complication and infection rates in canine PCA to previous published studies using hybrid dynamic compression plates. No implant failure was reported for any of the limbs despite the use of a light dressing without external coaptation.

Locked plate constructs are not necessarily stiffer than nonlocked constructs: A biomechanical investigation of locked versus nonlocked diaphyseal fixation in a human cadaveric model of nonosteoporotic and osteoporotic distal femoral fractures.

Objectives: The objective of this study was to compare the biomechanical properties of locked and nonlocked diaphyseal fixation in a model of distal femur fractures using osteoporotic and nonosteoporotic human cadaveric bone. Methods: A supracondylar osteotomy was created to mimic a fracture (OTA/AO 33A3) in osteoporotic (n = 4) and nonosteoporotic (n = 5) cadaveric distal femurs. The left and right femurs of each pair were instrumented with a distal femoral locking plate and randomly assigned to have diaphyseal fixation with either locked or nonlocked screws. The construct was cyclically axially loaded, and construct stiffness and load to failure were evaluated. Results: In osteoporotic bone, locked constructs were more stiff than nonlocked constructs (mean 143 vs. 98 N/mm when all time points combined, P < 0.001). However, in nonosteoporotic bone, locked constructs were less stiff than nonlocked constructs (mean 155 N/mm vs. 185 N/mm when all time points combined, P < 0.001). In osteoporotic bone, the average load to failure was greater in the locked group than in the nonlocked group (mean 1159 vs. 991 N, P = 0.01). In nonosteoporotic bone, the average load to failure was greater for the nonlocked group (mean 1348 N vs. 1214 N, P = 0.02). Bone mineral density was highly correlated with maximal load to failure (R2 = 0.92, P = 0.001) and stiffness (R2 = 0.78, P = 0.002) in nonlocked constructs but not in locked constructs. Conclusions: Contrary to popular belief, locked plating constructs are not necessarily stiffer than nonlocked constructs. In healthy nonosteoporotic bone, locked diaphyseal fixation does not provide a stiffer construct than nonlocked fixation. Bone quality has a profound influence on the stiffness of nonlocked (but not locked) constructs in distal femur fractures.

Biomechanical Testing of Additive Manufactured Proximal Humerus Fracture Fixation Plates.

Achieving satisfactory fracture fixation in osteoporotic patients with unstable proximal humerus fractures remains a major clinical challenge. Varus collapse is one of the more prominent complications that may lead to screw cutout. This aim of this study was to compare the fixation provided by conventional locking plates with novel design concepts that are only feasible through additive manufacturing (AM) techniques. In addition to reversed engineered implants, two novel implant designs with integrated struts were included in the study to provide medial support to humeral head. The medial strut was either solid or included a porous lattice structure intended to promote bone ingrowth. Biomechanical tests were performed using low density synthetic bones with simulated 3-part comminuted fractures. Nondestructive torsion and compression were performed, followed by increasing cyclic loading. The relative displacements between the bone fragments were determined using a 3D motion capture system. The AM manufactured implants with medial strut showed significant reduction of varus displacement during the increasing cyclic loading when compared to conventional designs. AM reversed-engineered locking plates showed similar mechanical behavior to conventional plates with identical geometry. This study demonstrates the feasibility and potential of employing alternative design via AM for fixation of unstable comminuted proximal humerus fractures to reduce fragment displacement.