• Ralph J Mobbs, Wen Jie Choy, Telvinderjit Singh, Lachlan Cassar, Chris Davidoff, Leigh Harris, Kevin Phan, and Meinrad Fiechter.
• University of New South Wales, Sydney, New South Wales, Australia; NeuroSpine Surgery Research Group, Sydney, New South Wales, Australia; Prince of Wales Private Hospital, Randwick, New South Wales, Australia; NeuroSpine Clinic, Prince of Wales Private Hospital, Randwick, New South Wales, Australia. Electronic address: r.mobbs@unsw.edu.au.
• World Neurosurg. 2019 Dec 1; 132: 75-80.

BackgroundIncomplete ossification of the pars interarticularis will result in a pars defect, a common cause of low back pain in youth and strongly associated with participation in high-impact sports. If left untreated, it can result in spondylolisthesis, causing dynamic canal stenosis, low back pain, and radiculopathy. The treatment of pars defect was first described by Bucks in 1970, who used screws in the lamina placed through an upward and outward direction. However, because of the multiple inclusion and exclusion criteria and narrow margin of error, the Bucks pars repair technique is not commonly performed.MethodsA 28-year-old woman had with low back pain that she had been experiencing since mid-adolescence. Computed tomography revealed a bilateral L5 pars defect without spondylolisthesis. Her L5 vertebra was reconstructed virtually. The screw trajectories, a 3-dimensional (3D) model of the vertebra, and a patient-specific drill guide (PSDG) were designed and printed using positioning guide software (MySpine MC Guides [Medacta International SA, Castel San Petro, Switzerland]). A modified Bucks procedure using cannulated compression screws and the PSDG was performed.ResultsFollow-up computed tomography revealed accurate placement of the compression screws, mirroring the planned trajectory. The patient was pain free at 3 months postoperatively, and early union across the defect was visualized on the 5-month radiographic imaging study.ConclusionUsing 3D planning software, complex surgical procedures can be planned using the patient's anatomy and computed tomography. With the aid of 3D-printed PSDGs, screw placement in narrow corridors, such as was shown in our case, is safe, efficient, and achievable.Copyright © 2019 Elsevier Inc. All rights reserved.

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