# Nondestructive, fatigue cyclic, and ramped cyclic biomechanical testing of surgical techniques for stabilization of the lumbosacral junction in dogs

## TL;DR

This study compares three surgical techniques for stabilizing the lumbosacral junction in dogs and finds they all provide similar biomechanical stability.

## Contribution

The study introduces a direct comparison of three stabilization methods using nondestructive and cyclic biomechanical testing in canine spines.

## Key findings

- All three stabilization methods reduced range of motion equally in flexion/extension.
- Fatigue and ramped cyclic testing showed similar performance across all groups.
- Progressive screw loosening was the main failure mode for all techniques.

## Abstract

To compare transarticular screw fixation (TSF), pedicle screw‐rod fixation (PSRF), and screws and polymethylmethacrylate (SPMMA) for stabilization of the canine lumbosacral junction (LSJ).

Ex vivo biomechanical study.

Twenty‐one L7‐S1 canine spine specimens collected from adult, large‐breed dogs.

Specimens were subjected to nondestructive biomechanical testing in flexion/extension (FE), lateral bending (LB), and axial rotation (AR). Subsequently, the L7‐S1 joint was destabilized by dorsal laminectomy and partial discectomy of L7‐S1 and then stabilized by (1) TSF, (2) PSRF, or (3) SPMMA (n = 7 specimens/group). Stabilized specimens were subjected to nondestructive biomechanical testing, fatigue cyclic testing, and ramped cyclic testing. For nondestructive and fatigue cyclic testing, range of motion (ROM) was calculated for each testing condition/stabilization method, while for ramped cyclic testing the bending moment necessary to reach a ROM of 5.0°, 7.5° and 10.0° and failure mode were recorded. Linear mixed models and Fisher's exact test were used to analyze continuous parameters and failure modes, respectively.

All stabilization methods resulted in an equal reduction in ROM in FE. Fatigue cyclic testing resulted in minor increases in ROM compared to baseline for all groups. Ramped cyclic testing resulted in failure of all groups, with no differences between groups for the bending moment necessary to reach 5.0°/7.5°/10.0° of ROM. The main failure mode for each method was progressive screw loosening.

Transarticular screw fixation, PSRF and SPMMA provided immediate biomechanical stability to the LSJ and were similar when subjected to fatigue and ramped cyclic testing.

Transarticular screw fixation, PSRF, and SPMMA are biomechanically effective options for stabilizing the canine LSJ. This study supports clinical use of these procedures.