Effect of bending direction on the mechanical behaviour of 3.5 mm String-of-Pearls and Limited Contact Dynamic Compression Plate constructs

Objective The aim of this study was to compare the locking compression plate (LCP) with polyaxial locking system (PLS) using single cycle to failure 4-point bending test and to investigate the behaviour of PLS with screws inserted mono- and polyaxially using cyclic fatigue test in two bending directions. Materials and Methods Tests were performed on bone surrogates in a fracture gap model. The 3.5 LCP and 3.5 PLS plates were tested in single cycle to failure. The 3.5 PLS plates with mono- and polyaxial screws were compared in a cyclic fatigue tests in two orthogonal directions. For both experiments, micro-computed tomography (CT) scans were performed pre- and post-testing to investigate the connections between the screw head and the plate hole. Means of forces and cycles needed to failure were statistically compared. Results The PLS plates were on average 30% weaker than LCP plates. Mode of failure was plate bending in the single cycle to failure tests, and plate breakage in the cyclic fatigue tests. Neither screw breakage nor loss of the screw–plate interface occurred. Mono- and polyaxial constructs performed similarly when loaded in the same direction. Micro-CT revealed no additional internal cracks in the plates or screws after testing. It also showed for both PLS and LCP that there was only partial contact of the screw head with the plate hole. Clinical Relevance PLS offers a durable locking system, even when the screws are placed polyaxially. The weaker bending properties of the PLS compared with LCP should be considered during preoperative planning.

Section: Discussionmentioning

confidence: 99%

Mechanical Performance of a Polyaxial Locking Plate and the Influence of Screw Angulation in a Fracture Gap Model

Kaczmarek¹,

Bartkowiak

Schuenemann³

et al. 2019

“…A caudally positioned plate is loaded via bending along its width in a cranial to caudal direction. 11 Applying the plate medially has a mechanical advantage over the same size plate placed caudally since the main force is craniocaudal bending. Applying the plate medially means the plate is 'edge loaded', increasing the area moment of inertia and therefore its relative bending stiffness.…”

Section: Discussionmentioning

confidence: 99%

“…Applying the plate medially means the plate is 'edge loaded', increasing the area moment of inertia and therefore its relative bending stiffness. 11,12 In addition, the plate used in 5/6 cases in this study (A version of the custom made plate used in these cases is now commercially available at Veterinary Instrumentation: Elbow arthrodesis plate) has been designed so that its width is increased in the mid-section in the region of greatest bending force.…”

Section: Discussionmentioning

confidence: 99%

“…Applying the plate medially is technically less challenging, requires less plate contouring, therefore minimizing surgical time, and theoretically offers the biomechanical advantage of 'edge loading' the plate. 11,12 To the authors' knowledge, there have been no previous reports where elbow arthrodesis was achieved via application of a medially positioned bone plate. The purpose of this case series is to report the surgical technique, associated complications and clinical outcomes.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Elbow Arthrodesis Using a Medially Positioned Plate in 6 Dogs

McCarthy

Comerford

Innes³

et al. 2019

Objective The aim of this study was to report the surgical technique, associated complications and clinical outcome of elbow arthrodesis using a medially positioned plate. Study Design This was a retrospective case series. Results Six cases met the inclusion criteria. In all cases, the elbow was approached medially without the requirement for ulnar osteotomy. A non-locking 2.7/3.5- mm pre-contoured elbow arthrodesis plate was applied in 5/6 cases and a 2.0-mm String of Pearls plate applied in one case. The mean angle of arthrodesis was 118° (range: 113–130°). One major intraoperative complication occurred. Three minor and 3 major postoperative complications occurred. Postoperative imaging was available for 5/6 cases. Complete arthrodesis was confirmed by imaging in 4/5 cases, partial progression of arthrodesis was documented in 1/5 cases and no further images were deemed necessary. Postoperative Liverpool Osteoarthritis in Dogs score was available for two cases with scores of 20/52 and 10/52, respectively. Subjective outcomes in the remaining three cases were rated as acceptable more than 1 year postoperatively. Conclusion Positioning the plate medially for elbow arthrodesis simplified the surgical approach, could be performed with a pre-contoured plate and allowed successful revision of an arthrodesis previously stabilized with a caudally positioned plate. The cases in this series had acceptable outcomes despite a high risk of complications.

“…To our knowledge, very little data are available in the literature on the biomechanical properties of the PAX and VetLOX systems. The bending properties of an implant depend on its material and its area moment of inertia (AMI) (17,18). Area moment of inertia is a mathematical representation of the distribution of area about an axis through the centre of an object's cross-section where the central plane is determined by the direction of bending (19).…”

Section: Single Cycle To Failure In Bending Of Three Titanium Polyaximentioning

confidence: 99%

Single cycle to failure in bending of three titanium polyaxial locking plates

Eid¹,

Martini²,

Bonardi³

et al. 2017