OBJECTIVE To investigate the relationship between multiple cryoprobes was investigated to determine whether they work in an additive or synergistic fashion in an in vivo animal model because 1.47 mm (17-gauge) cryoprobes have been introduced to the armamentarium for renal cryotherapy. METHODS Laparoscopic-guided percutaneous cryoablation was performed in both renal poles of 3 pigs using 3 IceRod cryoprobes. These 12 cryolesions were compared with 12 cryolesions using a single IceRod cryoprobe. Each cycle consisted of two 10-minute freeze cycles separated by a 5-minute thaw. The iceball volume was measured using intraoperative ultrasonography. The kidneys were harvested, and cryolesion surface area was calculated. The lesions were fixed and excised to obtain a volume measurement. Statistical analysis was used to compare the single probe results multiplied by 3 to the multiple probe group for iceball volume, cryolesion surface area, and cryolesion volume. RESULTS The iceball volume for the first freeze cycle for the single cryoprobe multiplied by 3 was 8.55 cm3 compared with 9.79 cm3 for the multiple cryoprobe group (P = .44) and 10.01 cm3 versus 16.58 cm3 for the second freeze (P =.03). The cryolesion volume for the single cryoprobe multiplied by 3 was 11.29 cm3 versus 14.75 cm3 for the multiple cyroprobe group (P =.06). The gross cryolesion surface area for the single cryoprobe multiplied by 3 was 13.14 cm2 versus 13.89 cm2 for the multiple probe group (P =.52). CONCLUSION The cryolesion created by 3 simultaneously activated 1.47-mm probes appears to be larger than that of an additive effect. The lesions were significantly larger as measured by ultrasonography and nearly so (P =.06) as measured by the gross cryolesion volume.

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Study Design.: Retrospective cohort study. Objectives: To clinically evaluate saphenous nerve somatosensory-evoked potentials (SSEPs) as a reliable and predictable way to detect upper lumbar plexus injury intraoperatively during lateral lumbar trans-psoas interbody fusion (LLIF). Methods: Saphenous nerve SSEPs were obtained by stimulation of inferior medial thigh with needle electrodes and recording from transcranial potentials. The primary outcome was measured by testing reproducibility of SSEPs at baseline, changes during the procedure, and relevance to standard modalities. Significant SSEP changes were compared with actual postoperative nerve complications. The sensitivity and specificity of saphenous SSEPs to detect postoperative lumbar plexus nerve injury was calculated. Results: A total of 62 patients were included in the study. Reliable saphenous SSEPs were recorded on the LLIF approach side in 52/62 patients. Persistent saphenous SSEP reduction of amplitude of >50% in 6 cases was observed during expansion of the tubular retractor or during the procedure. Two of 6 patients postoperatively had femoral nerve sensory deficits, and 5 of 6 patients had mild femoral nerve motor weakness, all of which resolved at an average of 12 weeks postoperatively (range 2-24 weeks). One patient had saphenous SSEP changes but demonstrated intraoperative recovery and had no postoperative clinical deficits. Saphenous SSEPs demonstrated 52% to 100% sensitivity and 90% to 100% specificity for detecting postoperative femoral nerve complications. Conclusion: Saphenous SSEPs can be used to detect electrophysiological changes to prevent femoral nerve injury during LLIF. Intraoperative SSEP recovery after amplitude reduction or loss may be a prognostic factor for final clinical outcome.

Introduction Pedicle screw instrumentation in revision spinal surgery can be challenging because of the altered anatomy and existing instrumentation. Malpositioned pedicle screws can result in surgical complications that may lead to persistent pain, dysfunction, and morbidity. Robotic-guided screw placement has been shown to be accurate in the setting of primary surgery, however, less is known about its accuracy in revision situations. The purpose of this study was to identify the accuracy rate of pedicle screws placed via robotic guidance in revision spine surgery. Patients and Methods Patients who underwent revision spinal instrumentation with robotic guidance during a 3-year period (2011–2014) at our institution were identified and included in the study if they had postoperative CT scans of the operated levels. Screw insertion was identified in revision levels and included for analysis if they were categorized as screw redirection, prior fusion without instrumentation, prior laminectomy, or a spinal level adjacent to a previously operated level. Postoperative CT scans were reviewed for pedicle screw accuracy by independent radiologists. Results A total of 36 patients met inclusion criteria (average age 61.6 years, 13 males and 26 females). Of the 682 total pedicle screws placed, 229 were placed in revision levels. Overall, 220 (96.1%) of the 229 revision screws were confirmed to be accurate by postoperative CT. Of the nine screws that were malpositioned, none were clinically significant nor required revision surgery. Of the nine malpositioned screws, there were five lateral breaches, and four medial breaches. One patient required revision surgery for cage migration at a similar level as a misplaced screw, however, pedicle screws were not revised. Conclusion Robotic-assisted pedicle screw placement in revision spinal surgery provides accuracy similar to other techniques in primary cases. In cases of previous laminectomy or fusion, robotic guidance can provide benefit to surgeons in navigating altered bony anatomy. Larger studies are needed to confirm these findings.