Analysis of Spinal Rod Deformation After Cutting with a Surgical Rod Cutter

Abstract

Scoliosis, a deformity characterized by an abnormal curvature of the spine, requires various treatment approaches depending on the severity of the condition, including surgical or non-surgical options. Surgical procedures, often involving the use of spinal fusion rods, play a crucial role in correcting spinal deformities. However, the process of cutting these rods with a surgical rod cutter may introduce deformations at the cut ends, potentially leading to complications and compromised treatment outcomes.This paper presents an analysis of the deformation observed in scoliosis rods after they have been cut using a surgical rod cutter. Identification of the extent and characteristics of deformations that occur during the cutting process will be assessed, as well as determining the point at which deformation ceases along the length of the rods.To achieve this objective, photogrammetry and three-dimensional modeling techniques were employed. Photogrammetry was used to create accurate three-dimensional models of these rods from two-dimensional photographs, providing a detailed representation of the deformed rod ends. Precise measurements and analysis were then performed to quantify and characterize the deformations.Three different diameters (4.75mm, 5.5mm, and 6.0mm) of two different types of metal rods (Titanium and Cobalt Chrome) resulting in six different experimental groups, were analyzed. Analysis of the deformed rod ends involved assessing the deviating angle of the plasticly deformed region of the rod and the roundness of the deformed cross sections. The higher diameter the rod, the more deformation was experienced. Cobalt chrome also experienced more angular deviation and lower roundness compared to its Titanium counterpart. Once all angular deviations reached 0 degrees and roundness values reached above 0.985, there was confidence there was minimal deformation at that spot. For the 4.75 mm and 5.5 mm Ti rods, 4 mm of space is required between the edge of the cut to where there is minimal deformation. For the 6.0 mm Ti, and all CoCr rods, 5 mm of space is needed. These data remain consistent with metal deformation studies, which show larger diameter rods deforming more than smaller ones, as well as CoCr deforming more than Ti. It is crucial to leave the required room to decrease the chances of instrument failure.This study contributes to the ongoing improvement of surgical techniques and treatment outcomes in scoliosis management. The analysis of deformation in scoliosis rods after cutting provides important information for optimizing surgical procedures and enhancing the long-term success of spinal fusion treatments.