Knock and Drill Technique: A Simple Tips for the Instrumentation in Complex Craniovertebral Junction Anomalies without using Fluoroscopy

Abstract

Context:Existence of complex variable bony and vertebral artery (VA) anomalies at craniovertebral junction (CVJ) in subset of complex CVJ anomalies demands individualized instrumentation policy and placing screws in each bone requires strategic preoperative planning and intraoperative skills.Aim:To evaluate the clinical accuracy of knock and drill (K and D) technique for the screw placement in complex CVJ anomalies.Settings and Design:Prospective study and operative technical note.Materials and Methods:Totally 36 consecutive patients (16 - pediatrics, 20 - adult patients) of complex CVJ: Complete/partial occipitalized C1 vertebra; at least one hypoplastic (C1/C2) articular mass, rotational component, and variations in the third part of VA were included in this study. Preoperative detail computed tomography (CT) CT CVJ with three-dimensional reconstruction was done for the assessment of CVJ anatomy and facet joint orientation. The accuracy of novel technique was assessed with postoperative CT to evaluate cortical breach in between 5th and 7th postoperative day in all the patients. All patients were underwent clinico-radiological evaluation at 6-month follow-up.Results:Totally 144 screws were placed using K and D technique (pediatric group - 64 screws, adult patients - 80 screws). Total of 12 screws were placed in C1 lateral mass in both age group without any bony cortical breach and complication. Sixteen C2 pedicle screws and 12 C2 pars screw in pediatrics and 18 C2 pedicle screws in adult patients were placed without any bony breach or VA injury. Out of thirty subaxial lateral mass screws in pediatric group, the bony breach was encountered with one screw (3.3%). Total of 38 C2 pars screws was placed in adult group in which bony breach along with VA injury was encounter with 1screw (2.6%).Conclusion:A simple technique of K and D for placing a screw increases the accuracy and spectrum of bony purchase and has the potential to reduce the complication in patients with complex CVJ anomalies.

C3 segmental vertebral artery and its surgical implication in craniovertebral junction anomalies

“…The V3 segment of the VA is intimately related with C1/2 area and the anatomy of this segment, with its variations, do have great implications during the surgical exposure and instrumentation for CVJ anomalies, particularly from a posterior approach. [ 1 7 8 ] Normally, the V3 segment is divisible into 3 parts: the vertical part between C1 and C2 transverse processes, a horizontal part on the upper surface of C1 (the sulcus arteriosus) and an oblique part after leaving the sulcus arteriosus before entering the dura between the occiput and the C1.…”

“…This was in contrast to the C2 segmental artery, which lies on the C1/2 joint and limits proper exposure of the joint and joint remodeling. [ 1 7 ] It, however, posed challenges with respect to the choice of instrumentation. The fact that the artery was taking a course right beneath the C2 pars with thinning of the overlying pars, neither the pars interarticularis nor a transarticular screw placement was considered a safe option.…”

A Prospective, Single-Blinded, Bicentric Study, and Literature Review to Assess the Need of C2-Ganglion Preservation - SAVIOUR’s Criteria

“…All the surgeries were performed under general anaesthesia, in prone position, with neck fixed in extended position and traction (according to weight of patient) applied. We followed standard free-hand technique of knock-and-drill [ 8 ]. The incision was standardized starting 1 cm below inion to C3 spinous process and technique of fascia-muscle opening and closing was kept similar among all the patients.…”

“…We followed standard freehand technique of knock-and-drill. 8 The incision was standardized starting 1-centimetres below inion to C3 spinous process and technique of fascia-muscle opening and closing was kept similar among all the patients. After skin incision, the fascia was split in 'Y' shaped manner (so as to have advantage in closure), muscles were split (rather than cauterized) using sharp-knife and bi-polar cautery.…”