Clinical acceptance and accuracy assessment of spinal implants guided with SpineAssist surgical robot: retrospective study.

STUDY DESIGN: Retrospective, multicenter study of robotically-guided spinal implant insertions. Clinical acceptance of the implants was assessed by intraoperative radiograph, and when available, postoperative computed tomography (CT) scans were used to determine placement accuracy. OBJECTIVE: To verify the clinical acceptance and accuracy of robotically-guided spinal implants and compare to those of unguided free-hand procedures. SUMMARY OF BACKGROUND DATA: SpineAssist surgical robot has been used to guide implants and guide-wires to predefined locations in the spine. SpineAssist which, to the best of the authors' knowledge, is currently the sole robot providing surgical assistance in positioning tools in the spine, guided over 840 cases in 14 hospitals, between June 2005 and June 2009. METHODS: Clinical acceptance of 3271 pedicle screws and guide-wires inserted in 635 reported cases was assessed by intraoperative fluoroscopy, where placement accuracy of 646 pedicle screws inserted in 139 patients was measured using postoperative CT scans. RESULTS: Screw placements were found to be clinically acceptable in 98% of the cases when intraoperatively assessed by fluoroscopic images. Measurements derived from postoperative CT scans demonstrated that 98.3% of the screws fell within the safe zone, where 89.3% were completely within the pedicle and 9% breached the pedicle by up to 2 mm. The remaining 1.4% of the screws breached between 2 and 4 mm, while only 2 screws (0.3%) deviated by more than 4 mm from the pedicle wall. Neurologic deficits were observed in 4 cases yet, following revisions, no permanent nerve damage was encountered, in contrast to the 0.6% to 5% of neurologic damage reported in the literature. CONCLUSION: SpineAssist offers enhanced performance in spinal surgery when compared to free-hand surgeries, by increasing placement accuracy and reducing neurologic risks. In addition, 49% of the cases reported herein used a percutaneous approach, highlighting the contribution of SpineAssist in procedures without anatomic landmarks.

Early failure of lumbar disc replacement: case report and review of the literature.

We report a case of a patient who underwent two-level lumbar total disc replacement at L4-L5 and L5-S1 with the ProDisc II prosthesis, who was diagnosed with early anterior migration of the caudally placed device with partial occlusion of the left common iliac vein. The device was explanted and revised to an anterior lumbar interbody fusion with posterior instrumented fusion. Despite the substantial experience with lumbar disc arthroplasty in Europe and the United States, there exist few reports of device explantation or revision. To our knowledge, early postoperative vascular complications, while discussed hypothetically, have not been reported. With implantation of the total disc replacement in proximity to the great vessels, the potential for vascular complications is clearly substantial. The technical aspects of the device explantation are discussed as well as issues pertinent to early failure. A literature review of device complications associated with lumbar total disc replacement is also presented.

Anterior cervical decompression and fusion with plate fixation as an outpatient procedure.

BACKGROUND CONTEXT: Outpatient cervical spine surgery has previously been described for posterior laminoforaminotomy and anterior microdiscectomy with allograft fusion. Anterior cervical discectomy and fusion (ACDF) with plate fixation has not, to our knowledge, been described as an outpatient procedure. PURPOSE: The objective of this study was to evaluate the safety and feasibility of ACDF with instrumentation when performed as an outpatient in a free-standing ambulatory surgical center. Additionally, the authors sought to determine any patient selection bias and its effect on outcome. STUDY DESIGN: This study is a retrospective medical record review. PATIENT SAMPLE: The sample included all patients who underwent one or two level ACDF with plate fixation at levels C4-5 or below as an adjunct to autogenous iliac crest bone graft or structural allograft from 1998 to 2002 by the two senior authors. OUTCOME MEASURES: Complications were assessed clinically with special attention to dysphagia and respiratory complications. Inpatient lengths of stay and postoperative hospital admission or readmission were also measured. METHODS: Thirty consecutive patients were treated at a free-standing ambulatory surgery center, whereas two control groups, each of 30 consecutive patients, had surgery performed in the hospital and were admitted overnight for observation. The first control group consisted of admitted patients before the commencement of patient selection for the outpatient group; the second control group was comprised of admitted patients who had surgery performed concurrently with the outpatient group. The study group was evaluated on the first postoperative day and 3 weeks after surgery. RESULTS: Ninety patients underwent ACDF plate fixation at 140 different levels. Forty patients were treated at one level, and 50 were treated at two levels. The three groups were comparable in age, sex, and body mass index. There were no major complications. Seven patients (13%) had minor postoperative complications among the controls: transient dysphagia in three (5%) and graft donor site pain in four (14%). Three patients (10%) in the outpatient group had minor complications (all had dysphagia). Among the controls, four patients (7%) had increased length of stay owing to complications. Four patients (7%) in the combined control group were readmitted for early complications; no patient was admitted for a complication after outpatient surgery. CONCLUSIONS: In the present study, selection criteria for outpatient surgery included one or two level involvement C4-5 or lower, absence of myelopathy, subjective neck size, and estimated operative time. The data did not otherwise suggest a difference in the surgical populations. The outpatient group had a lower complication rate compared with the controls. This was likely the result of selection bias. Transient dysphagia was the most prevalent complication in the outpatient group.

Intradiscal pressure monitoring in the cervical spine.

BACKGROUND: Discography has been widely used in the lumbar and cervical spine as a diagnostic tool to identify sources of discogenic pain that may be amenable to surgical treatment. Discography in the cervical spine is currently performed without the benefit of pressure monitoring, and corresponding pressure parameters have not been determined. OBJECTIVE: The purpose of this study was to develop the framework for intradiscal pressure monitoring in the cervical spine and the basis for a pressure curve that will reflect clinically significant cervical internal disc disruption. We also sought to determine whether there is any pressure increase in adjacent discs during cervical discography that might result in false-positive diagnosis during in-vivo discography. An additional goal was to establish safe upper parameters for infusion volume and intradiscal pressure in the cervical spine. DESIGN: Investigation of fresh-frozen discs in the cervical spine. METHODS: Investigated were 26 discs in 5 fresh-frozen cadaveric cervical spines aged 45 to 68 with no prior history of cervical spine disease. A T2 MRI was performed on each specimen and radiographically abnormal discs were noted. Pressure-controlled, fluoroscopically guided discography was performed on each level using a right lateral approach. Opening pressure, rupture pressure, volume infused, and location of rupture were recorded. Pressures were simultaneously recorded at each adjacent disc level using additional pressure monitors and identical needle placement. Immediately following discography, CT was performed on each specimen according to the discography protocol. RESULTS: Twenty-six discs C2-3 to C7-T1 were grossly intact for evaluation. The median opening pressure was 30 psi (range 14-101 psi). Two discs did not rupture and were pressurized to 367 psi. In 24 discs, the median intradiscal rupture pressure was 40 psi (range 14-171 psi). The median volume infused at rupture was 0.5 ml (range 0.25-1.0 ml). When grouped, the median intradiscal rupture pressure in the C2-3, C3-4, and C7-T1 discs was 53 psi (range 16-171 psi) compared to 36.5 psi (range 14-150 psi) in the C4-5, C5-6, and C6-7 discs (p=0.18). There was no measurable pressure change in any of the 30 adjacent disc levels evaluated. CONCLUSION: In the cervical spine, iatrogenic disc injury may be caused at significantly lower pressures and volumes infused than in the lumbar spine. There was no measurable pressure change in any of the adjacent disc levels evaluated at maximum intradiscal pressurization. Further cadaveric testing will be necessary to develop parameters for intradiscal pressure monitoring in the cervical spine.