Influence of a customized three‐dimensionally printed drill guide on the accuracy of pedicle screw placement in lumbosacral vertebrae: An ex vivo study

Abstract

ObjectiveTo compare the accuracy of pedicle screw insertion (PSI) into canine lumbosacral vertebrae with custom‐made three‐dimensionally (3D)‐printed drill guides or freehand insertion.Study designEx vivo study.Sample populationNineteen canine lumbosacral specimens.MethodsDrill guides for PSI were designed on the basis of safe screw insertion trajectories by using preoperative computed tomography (CT) and produced by 3D printing of templates. Right and left sides of the specimens were randomly allocated to two groups; 4‐mm pedicle screws were inserted in L5‐L6 and L7‐S1 spinal segments either freehand (control group) or with custom‐made drill guides (guide group). Sixty‐six screws were inserted with each method. Insertion angles (α, β), bone stock, and vertebral canal breach were assessed according to postoperative CT. χ2 Tests were used to compare vertebral canal breach between groups and vertebrae.ResultsBreaches in the vertebral canal were less common (P < .001) when screws were placed with a guide in the guide group (9/66, 14%) than without a guide (30/66, 45%). The rate of vertebral canal breach differed at L5 (P = .021) but not at L6 (P = .05), L7 (P = .075) or S1 (P = .658). The angle of insertion (α) did not differ between specimens with and without breaches (guide, P = .068; control, P = .394).ConclusionThe use of a customized 3D‐printed guide generally improved the accuracy of PSI in canine lumbosacral vertebrae, although statistical significance was reached only at L5.Clinical significanceThe use of customized drill guides may be considered as an alternative to freehand PSI in the lumbosacral area, especially for L5‐L6 vertebrae.

Accuracy of Placement of Pedicle Screws in the Lumbosacral Region of Dogs Using 3D-Printed Patient-Specific Drill Guides

“…These findings compare favourably with a similar recent cadaveric study where the vertebral canal breach was 14% in the lumbosacral region when screws were placed with the aid of a drill guide. 2 The number of screws placed (66) was higher compared with our study, which may explain the slightly different results. Previously reported clinical studies in the veterinary literature report similar rates of vertebral canal penetration of 3%, 9% and 21% using similar 3D-printed patient-specific guides.…”

“…1 Degenerative lumbosacral stenosis is a common cause of cauda equina syndrome and mainly affects working and large breed dogs. 2,3 The pathophysiology of this disease is not completely understood, although a multifactorial aetiology is suspected. Key features of the syndrome include degeneration and protrusion of the seventh lumbar (L7) to osteomyelitis of the adjacent vertebrae with a predisposition in male, large breed, older and pedigree dogs.…”

“…12 In both of these conditions the aim of the surgery is to achieve decompression at the level of the cauda equina (via laminectomy with or without discectomy) and to provide an adequate stability. 2,9 Different techniques have been described for stabilization of the lumbosacral region including the use of pins or screws with polymethylmethacrylate (PMMA), dorsal laminectomy and transarticular facet screws, a distraction-stabilization system (with an intervertebral distraction bolt, connecting rods and polyaxial screws), a minimally invasive transilial vertebral blocking procedure and pedicle screw with rod fixation. 4,9,[13][14][15][16] Safe and accurate screw or pin placement is challenging, as, especially in L7, available bone stock can be limited and safe corridors narrow.…”

“…17,18 A cadaveric study reported that 42.6% of screws placed freehand penetrated the vertebral canal versus 14% placed using three-dimensional (3D)printed drill guides. 2 The selection and use of smaller implants in situations where there are narrow safe implant corridors or where there is sub-optimal screw positioning will increase the risk of implant failure. 19 Recently the use of 3D-printed patient-specific drill guides to facilitate implant placement has been reported to be more accurate and safe compared with freehand technique.…”

Accuracy of three‐dimensionally printed animal‐specific drill guides for implant placement in canine thoracic vertebrae: A cadaveric study

“…This discrepancy results in a difficult choice for clinicians attempting to employ best clinical practices. The error rate of freehand placement of pedicle implants into animals has been poorly documented, although it is likely substantial 23,32,33 . Results of studies in man provide evidence that the use of 3‐D printed guides can improve the accuracy of placement of such implants compared with freehand techniques, and this improvement is described as dramatic in some reports 34‐44 .…”