Early complications after instrumentation of the lumbar spine using cortical bone trajectory technique

This retrospective chart review aimed to identify and report on a series of early complications that resulted from instrumentation of the lumbar spine using the cortical bone trajectory (CBT) technique. CBT technique is a novel method for fixation of the lumbar spine. Since it was first described in 2009 this technique has gained significant popularity. Here we report a series of early complications that have developed in patients who had lumbar spine fusion using the CBT technique. A retrospective chart review was performed in which all cases utilizing the CBT technique for instrumentation of the lumbar spine by two fellowship trained spine surgeons at our institution between July 2012 and May 2014 were reviewed. Medical records were reviewed to determine the number of patients who went on to develop an early complication after instrumentation with this technique. An early complication was defined as any of the following occurring within 3 months of surgery: (1) early screw loosening confirmed by post-operative CT scan, (2) evidence of fracture development confirmed by post-operative CT scan, (3) intra-operatively identified durotomy, (4) superficial or deep post-operative infection and (5) neurological injury. A total of 22 cases using the CBT technique were performed in our department. Of these cases two patients went onto develop early screw loosening, one developed an intra-operative pars fracture, one developed a dural tear and lastly, one patient developed both a pedicle fracture and early screw loosening. At our institution a total of five patients thus far have developed early complications after undergoing instrumentation of the lumbar spine using the CBT technique between 2012–2014.     

Accuracy and safety of cortical bone trajectory screw placement by an inexperienced surgeon using 3D patient-specific guides for transforaminal lumbar interbody fusion

Cortical bone trajectory (CBT) is an alternative method for pedicle screw insertion. However, identification of the optimal entry point and the direction of the CBT can be challenging for less-experienced surgeons. The purpose of this study was to evaluate the accuracy of the CBT screw placement by an inexperienced surgeon using a three-dimensional (3D) patient-specific guide for transforaminal lumbar interbody fusion (TLIF). Retrospective analysis of the data pertaining to 30 patients (128 screws) who underwent TLIF with CBT by an inexperienced surgeon using a 3D patient-specific guide (MySpine MC, Medacta) at a single center was performed. The accuracy of the CBT screw was graded into four groups (no perforation; Grade A, 0–2 mm; Grade B, 2–4 mm; and Grade C, > 4 mm). The accuracy of the CBT screw placement was 91% (116/128). Out of the 12 misplaced screws, Grade A was observed in 7 screws (5%), Grade B was observed in 3 screws (2%), and Grade C was observed in 2 screws (2%). There were no cases of medial pedicle wall perforation. The mean screw size was 5.95 ± 0.34 mm in diameter and 40.15 ± 2.83 mm in length. Note that, the accuracy of the CBT screws increased to 97% (83/86) over the first10 cases. Preoperative planning and 3D patient-specific guide enabled the use of longer and thicker screws and an optimal entry point. These results suggest the possibility of efficacy and safety in using 3D patient-specific guides for CBT screw placement by an inexperienced surgeon.     

Application study of three-dimensional printed navigation template between traditional and novel cortical bone trajectory on osteoporosis lumbar spine

To investigate the safety, accuracy and indications of traditional and novel cortical bone screws placement for osteoporosis lumbar spine, 4 lumbar vertebra specimens (2 males and 2 females) were used for this study. After the computed tomography scanning data of the above anatomical specimens were three-dimensional (3D) reconstructed, one side of each anatomical specimen was randomly chosen to place traditional cortical bone screws, and the other side received novel technical placement. The safety screw trajectory was designed, and a 3D navigation template complementary to the surface anatomical structure of lumbar isthmus lateral margin-vertebral plate-spinous process part was established. The designed supporting navigation template was substantialized, and the navigation template replicated different cortical bone screw trajectory at different sides of the same one lumbar vertebra. Forty cortical bone screws were firstly placed in 3D printed vertebra and then 40 were placed in real anatomical specimens. In 3D printed specimens, the success rates of screw placement with navigation template using traditional and novel techniques were both 100%. While in anatomical specimens, the success rate of screw placement using traditional and novel navigation template was 97.5% (one out of 40 went wrong). Therefore, it is safe, accurate and reliable to place traditional and novel cortical bone screws on osteoporosis lumbar spine using 3D printed navigation template. Traditional and novel screw placement methods should be flexibly applied or combined according to specific sequence and form of vertebra.