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Daniel J. Blizzard, Michael A. Gallizzi, Robert E. Isaacs and Christopher R. Brown

Lateral interbody fusion (LIF) via the retroperitoneal transpsoas approach is an increasingly popular, minimally invasive technique for interbody fusion in the thoracolumbar spine that avoids many of the complications of traditional anterior and transforaminal approaches. Renal vascular injury has been cited as a potential risk in LIF, but little has been documented in the literature regarding the etiology of this injury. The authors discuss a case of an intraoperative complication of renal artery injury during LIF. A 42-year-old woman underwent staged T12–L5 LIF in the left lateral decubitus position, and L5–S1 anterior lumbar interbody fusion, followed 3 days later by T12–S1 posterior instrumentation for idiopathic scoliosis with radiculopathy refractory to conservative management. After placement of the T12–L1 cage, the retractor was released and significant bleeding was encountered during its removal. Immediate consultation with the vascular team was obtained, and hemostasis was achieved with vascular clips. The patient was stabilized, and the remainder of the procedure was performed without complication. On postoperative CT imaging, the patient was found to have a supernumerary left renal artery with complete occlusion of the superior left renal artery, causing infarction of approximately 75% of the kidney. There was no increase in creatinine level immediately postoperatively or at the 3-month follow-up. Renal visceral and vascular injuries are known risks with LIF, with potentially devastating consequences. The retroperitoneal transpsoas approach for LIF in the superior lumbar spine requires a thorough knowledge of renal visceral and vascular anatomy. Supernumerary renal arteries occur in 25%–40% of the population and occur most frequently on the left and superior to the usual renal artery trunk. These arteries can vary in number, position, and course from the aorta and position relative to the usual renal artery trunk. Understanding of renal anatomy and the potential variability of the renal vasculature is essential to prevent iatrogenic injury.

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Gautam Nayar, Daniel J. Blizzard, Timothy Y. Wang, Steven Cook, Adam G. Back, David Vincent and Isaac O. Karikari

OBJECTIVE

A previous study found that ultra-low radiation imaging (ULRI) with image enhancement significantly decreases radiation exposure by roughly 75% for both the patient and operating room personnel during minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) (p < 0.001). However, no clinical data exist on whether this imaging modality negatively impacts patient outcomes. Thus, the goal of this randomized controlled trial was to assess pedicle screw placement accuracy with ULRI with image enhancement compared with conventional, standard-dose fluoroscopy for patients undergoing single-level MIS-TLIF.

METHODS

An institutional review board–approved, prospective internally randomized controlled trial was performed to compare breach rates for pedicle screw placement performed using ULRI with image enhancement versus conventional fluoroscopy. For cannulation and pedicle screw placement, surgery on 1 side (left vs right) was randomly assigned to be performed under ULRI. Screws on the opposite side were placed under conventional fluoroscopy, thereby allowing each patient to serve as his/her own control. In addition to standard intraoperative images to check screw placement, each patient underwent postoperative CT. Three experienced neurosurgeons independently analyzed the images and were blinded as to which imaging modality was used to assist with each screw placement. Screw placement was analyzed for pedicle breach (lateral vs medial and Grade 0 [< 2.0 mm], Grade 1 [2.0–4.0 mm], or Grade 2 [> 4.0 mm]), appropriate screw depth (50%–75% of the vertebral body’s anteroposterior dimension), and appropriate screw angle (within 10° of the pedicle angle). The effective breach rate was calculated as the percentage of screws evaluated as breached > 2.0 mm medially or postoperatively symptomatic.

RESULTS

Twenty-three consecutive patients underwent single-level MIS-TLIF, and their sides were randomly assigned to receive ULRI. No patient had immediate postoperative complications (e.g., neurological decline, need for hardware repositioning). On CT confirmation, 4 screws that had K-wire placement and cannulation under ULRI and screw placement under conventional fluoroscopy showed deviations. There were 2 breaches that deviated medially but both were Grade 0 (< 2.0 mm). Similarly, 2 breaches occurred that were Grade 1 (> 2.0 mm) but both deviated laterally. Therefore, the effective breach rate (breach > 2.0 mm deviated medially) was unchanged in both imaging groups (0% using either ULRI or conventional fluoroscopy; p = 1.00).

CONCLUSIONS

ULRI with image enhancement does not compromise accuracy during pedicle screw placement compared with conventional fluoroscopy while it significantly decreases radiation exposure to both the patient and operating room personnel.