Diffusion-weighted magnetic resonance (DW-MR) neurography of the lumbar plexus in the preoperative planning of lateral access lumbar surgery.

PURPOSE: Magnetic resonance (MR) neurography has been used to evaluate entire nerves and nerve bundles by providing better contrast between the nerves and the surrounding tissues. The purpose of the study was to validate diffusion-weighted MR (DW-MR) neurography in visualizing the lumbar plexus during preoperative planning of lateral transpsoas surgery. METHODS: Ninety-four (188 lumbar plexuses) spine patients underwent a DW-MR examination of the lumbar plexus in relation to the L3-4 and L4-5 disc spaces and superior third of the L5 vertebral body. Images were reconstructed in the axial plane using high-resolution Maximum Intensity projection (MIP) overlay templates at the disc space and L3-4 and L4-5 interspaces. 10 and 22 mm MIP templates were chosen to mimic the working zone of standard lateral access retractors. The positions of the L4 nerve root and femoral nerve were analyzed relative to the L4-5 disc in axial and sagittal planes. Third-party radiologists and a senior spine surgeon performed the evaluations, with inter- and intraobserver testing performed. RESULTS: In all subjects, the plexus was successfully mapped. At L3-4, in all but one case, the components of the plexus (except the genitofemoral nerve) were located in the most posterior quadrant (zone IV). The L3 and L4 roots coalesced into the femoral nerve below the L4-5 disc space in all subjects. Side-to-side variation was noted, with the plexus occurring in zone IV in 86.2 % right and only 78.7 % of left sides. At the superior third of L5, the plexus was found in zone III in 27.7 % of right and 36.2 % of left sides; and in zone II in 4.3 % right and 2.1 % left sides. Significant inter- and intraobserver agreement was found. CONCLUSIONS: By providing the surgeon with a preoperative roadmap of the lumbar plexus, DW-MR may improve the safety profile of lateral access procedures.

Adult degenerative scoliosis treated with XLIF: clinical and radiographical results of a prospective multicenter study with 24-month follow-up.

STUDY DESIGN: Prospective, multicenter, single-arm study. OBJECTIVE: The objective of this study was to evaluate the clinical and radiographical results of patients undergoing extreme lateral interbody fusion (XLIF), a minimally disruptive lateral transpsoas retroperitoneal surgical approach for the treatment of degenerative scoliosis (DS). SUMMARY OF BACKGROUND DATA: Surgery for the treatment of DS has been reported to have acceptable results but is traditionally associated with high morbidity and complication rates. A minimally disruptive lateral transpsoas retroperitoneal surgical approach (XLIF) has become popular for the treatment of DS. This is the first prospective, multicenter study to quantify outcomes after XLIF in this patient population. METHODS: A total of 107 patients with DS who underwent the XLIF procedure with or without supplemental posterior fixation at one or more intervertebral levels were enrolled in this study. Clinical and radiographical results were evaluated up to 24 months after surgery. RESULTS: Mean patient age was 68 years; 73% of patients were female. A mean of 3.0 (range, 1-6) levels were treated with XLIF per patient. Overall complication rate was low compared with traditional surgical treatment of DS. Significant improvement was seen in all clinical outcome measures at 24 months: Oswestry Disability Index, visual analogue scale for back pain and leg pain, and 36-Item Short Form Health Survey mental and physical component summaries (P < 0.001). Eighty-five percent of patients were satisfied with their outcome and would undergo the procedure again. In patients with hypolordosis, lumbar lordosis was corrected from a mean of 27.7° to 33.6° at 24 months (P < 0.001). Overall Cobb angle was corrected from 20.9° to 15.2°, with the greatest correction observed in patients supplemented with bilateral pedicle screws. CONCLUSION: This study demonstrates the use of the XLIF procedure in the treatment of DS. XLIF is associated with good clinical and radiographical outcomes, with a substantially lower complication rate than has been reported with traditional surgical procedures. LEVEL OF EVIDENCE: 3.

Dynamically evoked, discrete-threshold electromyography in the extreme lateral interbody fusion approach.

OBJECT: because the psoas muscle, which contains nerves of the lumbar plexus, is traversed during the extreme lateral interbody fusion (XLIF) approach, appropriate nerve monitoring is needed to avoid nerve injury during surgery and prevent approach-related neural deficit. This study was performed to assess the effectiveness of dynamically evoked electromyography (EMG) to detect and prevent neural injury during the XLIF approach. METHODS: one hundred two patients undergoing XLIF at L3-4 and/or L4-5 were enrolled in a prospective, multicenter, nonrandomized clinical study. The EMG threshold values for each of the 3 successive dilators were recorded at the surface of the psoas muscle, mid-psoas, and on the spine. At each location, the dilators were rotated 360°, taking recordings immediately posterior, superior, anterior, and inferior. For each dilator, the authors noted the rotational position (the angle in degrees) at which the lowest threshold was found. Findings of pre- and postoperative neurological examinations were also recorded. RESULTS: nerves were identified within proximity of the dilators (alert-level EMG feedback) in 55.7% of all cases during the XLIF approach. Although nerves were more commonly identified in the posterior margin (63%), there was significant variability in the location of nerves identified. Despite the fact that the posterior half of the disc space was targeted in 90% of cases, no significant long-lasting neural deficits were identified in any case; 27.5% experienced new iliopsoas/hip flexion weakness and 17.6% experienced new postoperative upper medial thigh sensory loss. Transient motor deficits were identified in 3 patients (2.9%), and all had resolved by the 6-month follow-up visit. CONCLUSIONS: the ability to identify and report a discrete, real-time EMG threshold during the transpsoas approach helps to avoid nerve injury and is required for the safe performance of the XLIF procedure. Additionally, nerve location is variable, thus reinforcing the need for real-time directional and proximity information.

A prospective, nonrandomized, multicenter evaluation of extreme lateral interbody fusion for the treatment of adult degenerative scoliosis: perioperative outcomes and complications.

STUDY DESIGN: Prospective multicenter nonrandomized institutional review board-approved observational study of clinical and radiographic outcomes of the extreme lateral interbody fusion (XLIF) procedure in adult scoliosis. OBJECTIVE: Perioperative measures from this longitudinal study were compiled to identify the short-term results and complications of the procedure. SUMMARY OF BACKGROUND DATA: The surgical treatment of adult scoliosis presents a treatment challenge. Neural decompression with combined anterior/posterior instrumented fusion is often performed. These procedures have been reported to carry a high risk of complication, particularly in the elderly patient population. Over the past decade, less invasive surgical approaches to neural decompression and fusion have been popularized and have recently been applied in the treatment of degenerative scoliosis. To date, there has been little published data evaluating these treatment approaches. METHODS: A total of 107 patients who underwent the XLIF procedure with or without supplemental posterior fusion for the treatment of degenerative scoliosis were prospectively studied. Intraoperative data collection included surgical procedural details, operative time, estimated blood loss, and surgical complications. Postoperative complications, length of hospital stay, and neurologic status were recorded. For this report, perioperative data (inclusive of outcomes through the 6-week postoperative clinic visit) were evaluated. RESULTS: In all, 107 patients (mean age, 68 years; range, 45-87) were treated with XLIF; 28% had at least 1 comorbidity. A mean of 4.4 levels (range, 1-9) were treated per patient. Supplemental pedicle screw fixation was used in 75.7% of patients, 5.6% had lateral fixation, and 18.7% had stand-alone XLIF. Mean operative time and blood loss were 178 minutes (58 minutes/level) and 50 to 100 mL. Mean hospital stay was 2.9 days (unstaged), 8.1 day (staged, 16.5%), 3.8 days overall. Five patients (4.7%) received a transfusion, 3 (2.8%) required intensive care unit admission, and 1 (0.9%) required rehabilitation services. Major complications occurred in 13 patients (12.1%): 2 (1.9%) medical, 12 (11.2%) surgical. Of procedures that involved only less invasive techniques (XLIF stand-alone or with percutaneous instrumentation), 9.0% had one or more major complications. In those with supplemental open posterior instrumentation, 20.7% had one or more major complication. Early reoperations (3) (all for deep wound infections) were associated with open posterior instrumentation procedures. CONCLUSION: The morbidity in adult scoliosis surgery is minimized with less invasive techniques. The rate of major complications in this study (12.1%) compares favorably to that reported from other studies of surgery for degenerative deformity.

Lumbar fusion in octogenarians: the promise of minimally invasive surgery.

STUDY DESIGN: Retrospective chart review of prospectively collected data from 2 nonrandomized, nonconcurrent cohorts. OBJECTIVE: Early results of 2 lumbar interbody fusion procedures-open posterior lumbar interbody fusion (PLIF) and minimally invasive (extreme lateral interbody fusion [XLIF])-were compared in octogenarians to demonstrate the safety of each in the extreme elderly populations. SUMMARY OF BACKGROUND DATA: Although spinal pathologies are common in the elderly patients, additional health conditions often preclude operative treatment because anesthesia, blood loss, and recovery are too demanding. Minimally invasive approaches reduce procedure-related morbidity and recovery time. METHODS: In our single-site prospective series of XLIF patients, 40 were identified as those aged ≥80 years with a minimum of 3-month follow-up. A complete, retrospective review of surgical patients treated in the same practice with traditional open posterior (PLIF) approach found 20 patients aged ≥80 years. Comparisons were made between groups to identify differences in morbidity and mortality rates. RESULTS: No clinically significant differences in demographics, diagnoses, or comorbidities were found between groups. Complication rate, blood loss/transfusion rate, and hospital stay were significantly lower in the minimally invasive surgery (MIS) group (P < 0.0001). MIS patients left the hospital an average of 4 days earlier than the open PLIF patients, most discharged home (92.5% XLIF vs. 0% PLIF) rather than to skilled nursing facilities. Six deaths occurred in the PLIF follow-up, 3 within 3 months postoperatively; there was 1 death at 6 months postoperatively XLIF. CONCLUSION: Surgical treatment need not be withheld on the basis of age; elderly patients can successfully be treated using MIS techniques, and are-in our experience-among the most satisfied with their outcomes, enjoying significant improvements in pain, mobility, and quality of life.