Background Safely performing instrumented spinal fusion requires an intimate knowledge of anatomy and variations. Pedicle screw position and size have implications on intraoperative and post-operative complications. While pre-operative planning with Computed Tomography (CT) scan measurements may be the safest way to judge trajectory and maximal screw size, it is not standard practice for many spine surgeons. We investigated how height and weight correlated with PD. We hypothesized that these routinely obtained, non-invasive measurements would provide an easily referenced data point to aid in perioperative estimation of maximum safe pedicle screw diameter (MSPSD). Methods Coronal cuts of the lumbar spine were assessed to obtain transverse outer cortical PD as measured through the isthmus at lumbar vertebrae one through five. We assessed whether height, weight, and BMI significantly correlated with PD in our diverse population. Results Height and weight were found to significantly correlate with PD. Height explained roughly 10% of the variance in PD, weight explained only 3-4%, and BMI nearly 0%. There were significant differences in this theoretical safety profiles between the "Taller Height" and "Shorter Height" groups for the majority of pedicle screw sizes at L1 through L3. Significant differences between the populations at L4 and L5 were only seen for 8.0 mm screws at the L4 level. At L5, 100% of the "Taller Height" and "Shorter Height" subjects' pedicles could safely accommodate pedicle screws up to 8.0 mm in diameter. Conclusions We previously reported on the significant difference in PD between different races. The results of this study provide yet another variable to be considered when making radiographic assessments of pedicle diameter.

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BackgroundSpinal surgery requires an intimate understanding of pedicle morphology to provide safe and effective outcomes. Although current research has attempted to identify morphological vertebral pedicle trends, no study has utilized computed tomography (CT) scans to compare the lumbar transverse pedicle angle (TPA) with patient demographics factors in a diverse population throughout multiple hospital centers.MethodsAnalysis of randomly selected CT scans from L1-L5 of 97 individuals who underwent imaging over a two-week period for non-back pain related complaints was conducted. Measuring 970 TPAs in total allowed for comparison of each patients’ pedicle angle with important patient specific demographics including ethnicity, age, gender, height and weight. Statistical analysis utilized multiple comparisons of demographics at each level with post-hoc Bonferroni correction analysis to compare demographics at each level.ResultsWith relation to gender, age, height or weight, no statistically significant differences were identified for TPAs at any vertebral level. However, when stratified by ethnicity, the differences in transverse pedicle angles averages (TPA –Avg) at L2 and L3 were found to be statistically significant (p < 0.05).ConclusionWe have identified a previously unknown and significant relationship between ethnicity and TPA at lumbar vertebral levels. These findings provide critical information that may be added to the operating surgeons’ knowledge of pedicle morphology. We hope this novel information can assist in preoperative planning of pedicle screw placement and potentially help improve surgical outcomes.

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Minimally invasive percutaneous pedicle screws (PPS) are placed through muscle sparing paramedian incisions and provide rigid 3 column fixation to promote stability and fusion. Percutaneous pedicle instrumentation is generally performed as adjunctive posterior stabilization after anterior lumbar interbody fusion or lateral lumbar interbody fusion procedures. In these instances, arthrodesis is often achieved through the interbody fusion rather than posterior column fusion. In some cases, the surgeon may choose to perform posterior facet fusion in addition to PPS and anterior interbody. The addition of a minimally invasive facet fusion to PPS and anterior column interbody fusion creates more fusion surface and enables a truly circumferential fusion. While robotic-guided facet decortication has been suggested, there are currently no published techniques. Here, we describe a novel minimally invasive technique to perform percutaneous robotic facet decortication in conjunction with PPS following anterior lumbar interbody fusion or lateral lumbar interbody fusion.