Influences on Interfragmentary Compression, Reduction and Stability of Simulated Equine Lateral Condylar Fracture

Research output: ThesisDoctoral Thesis

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Abstract

Fracture of the lateral condyle of the distal third metacarpal and metatarsal bone, commonly termed lateral condylar fracture, is among the most frequent catastrophic fracture encountered in racehorses world-wide. The standard of care for the treatment of complete lateral condylar fracture is internal fixation. A single proximodistal (linear configuration) column of 4.5 mm cortex screws placed across the fracture in lag fashion, is the most commonly employed method of internal fixation used to treat complete lateral condylar fracture. However, it has been suggested that two horizontally aligned screws (triangular configuration) positioned through the distal condyle, improves the stability of the repair. Lag screw fixation creates stability through interfragmentary compression. A greater number of screws, the addition of a washer and alternate tightening of screws are suggested methods to improve
interfragmentary compression. The overall aim of this work was to determine the influence of screw configuration on fracture reduction and repair stability of simulated complete lateral condylar fracture. In Study 1 our objectives were to compare the interfragmentary compression achieved by a linear (L) repair method, with a triangular (T) repair method, to assess the effect of a washer on interfragmentary compression in linear repairs (LW) and to evaluate the effect of tightening the dorsal screw of triangular configurations first (TD1). In study 2 our objective was to evaluate the stability of linear and triangular repairs under load using advanced imaging. In support of our objectives and Study 1, 63 lateral condylar fracture repairs were simulated in 21 cadaver limbs. Pressure sensitive film (Prescale®, Fuji Photo Film Co.) was placed in the osteotomy gap, then screws were placed in L, T, LW, TD1 configurations and tightened to 4 N m, using a randomized cross-over study design. Pressure prints were scanned using dedicated software (Fuji FPD-8010E, Fuji Photo Film Co.). A Bayesian network (BN) model was fitted to the data. In Study 2, a complete lateral condylar fracture was simulated in 18 cadaver fore limbs sourced from 9 horses, and the simulated fracture was repaired using either a triangular or linear screw configuration adopting a randomized cross-over study design. Limbs subsequently underwent computed tomography (CT) imaging in unloaded and loaded conditions, to evaluate repair stability. Osteotomy gaps were measured at dorsal, Influences on interfragmentary compression, reduction and stability of simulated equine lateral condylar fracture iii middle and palmar locations of the third metacarpal condyle. Fracture gaps were graded 0 – 4, based on voxels and a BN model was fitted to the data. In Study 1 (Chapter 4:), the BN predicted that the mean contact area was greatest in T repairs, followed by TD1, L and LW repairs. The BN model attributed a moderate effect of configuration on contact area for pressures > 10 MPa, while a weak effect was attributed to the addition of a washer, and screw tightening sequence. In study 2, the median fracture grade was the same for unloaded L and T repairs; however, when loaded, T repairs demonstrated lower median fracture grades than L repairs. But overall, the BN model indicated a weak effect of construct configuration on fracture
gap outcome. Overall, results indicate that triangular repair of simulated lateral condylar fracture creates greater interfragmentary compression when compared to linear repair and, therefore, this method should result in greater stability of condylar fracture repair. However, when triangular and linear repair were compared in ex vivo simulated complete lateral condylar fracture exposed to realistic post operative axial loads, linear repair was found to provide similar reduction and stability to triangular repair. These findings indicate that despite improved interfragmentary compression created by triangular repair, linear repair is likely to confer similar stability of complete lateral condylar fracture when the loading forces applied to repairs are axial in nature. However, clinical cases of repaired lateral condylar fractures are likely to sustain torsional forces which were not assessed in this research. Further research assessing the impact of triangular screw configuration, on the outcomes of clinical cases of lateral condylar fracture repair, are required.
Original languageEnglish
QualificationDoctor of Veterinary Studies
Awarding Institution
  • Charles Sturt University
Supervisors/Advisors
  • Labens, Raphael, Principal Supervisor
  • Hughes, Kris, Principal Supervisor
Place of PublicationAustralia
Publisher
Publication statusPublished - 06 Nov 2024

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