Prospective randomized controlled trial of The Stabilis Stand Alone Cage (SAC) versus Bagby and Kuslich (BAK) implants for anterior lumbar interbody fusion.

BACKGROUND: Degenerative disc disease is common and debilitating for many patients. If conservative extensive care fails, anterior lumbar interbody fusion has proven to be an alternative form of surgical management. The Stabilis Stand Alone Cage(SAC) was introduced as a method to obtain stability and fusion. The purpose of this study was to determine whether the Stabilis Stand Alone Cage (SAC) is comparable in safety and efficacy to the Bagby and Kuslich (BAK) device. METHODS: As part of a prospective, randomized, controlled FDA trial, 73 patients underwent anterior interbody fusion using either the SAC(56%) or the BAK device (44%). RESULTS: Background characteristics were similar between the two groups. There was no significant difference between the SAC and BAK groups in mean operative time or mean blood loss during surgery. Adverse event rates did not differ between the groups. Assessment of plain radiographs could not confirm solid fusion in 63% of control and 71% of study patients. Functional scores from Owestry and SF-36 improved in both groups by the two-year follow-up. There were no significant differences between the SAC and BAK patients with respect to outcome. CONCLUSIONS: Both the Stabilis Stand Alone Cage and the BAK Cage provided satisfactory improvement in function and pain relief, despite less than expected radiographic fusion rates. The apparent incongruency between fusion rates and functional outcomes suggests that either radiographs underestimate the true incidence of fusion, or that patients are obtaining good pain relief and improved function despite a lower rate of fusion than previously reported. This was a Level III study.

Transpedicular aspiration of osteoprogenitor cells from the vertebral body: progenitor cell concentrations affected by serial aspiration.

BACKGROUND CONTEXT: Spinal fusion is facilitated when the fusion site is augmented with autograft bone. Iliac crest, long the preferred source of autograft material, is the site of frequent complications and pain. Connective tissue progenitor cells (CTPs) aspirated from marrow provide a promising alternative to traditional autograft harvest. The vertebral body represents an even larger potential reservoir of progenitor cells than the ilium. PURPOSE: To test the hypothesis that a suitable concentration of osteoprogenitor cells can be aspirated from different depths of the vertebral body, maintaining progenitor cell concentrations comparable to the "gold standard," the iliac crest, even after sequential aspirations along the same transpedicular axis. STUDY DESIGN: Prospective clinical investigation quantifying CTP concentrations within the vertebral body relative to depth of sequential aspirations. PATIENT SAMPLE: Adult men and women undergoing elective posterior lumbar fusion and pedicle screw instrumentation (six men and seven women, mean age 56 years [range 40-74 years]). OUTCOME MEASURES: Cell count, CTP concentration (CTPs/cc marrow), and CTP prevalence (CTPs/million cells) were calculated for both individual and pooled aspirate samples. METHODS: Thirteen patients were enrolled into an institutional review board-approved protocol studying transpedicular aspiration of marrow progenitor cells. Connective tissue progenitor cells were aspirated from four depths along the transpedicular axis of the vertebral body and quantified according to cell concentration and CTP prevalence. Histochemical analysis of alkaline phosphatase-positive colony-forming units (CFUs) provided the prevalence of vertebral CTPs relative to depth of aspiration, vertebral level, age, and gender. RESULTS: Four 2.0cc aspirations were obtained from each pedicle of lumbar vertebrae selected for pedicle screw fixation (four 2.0cc aspirates from each of four pedicles). Aspirates of vertebral marrow demonstrated comparable or greater concentrations of CFUs compared with standards previously established for the iliac crest. Overall, the 208 aspirations from 26 vertebral bodies provided a mean CTP concentration of 741.5+/-976.2 CTPs per cubic centimeter of marrow, ranging from a mean concentration of 1316+/-1473 CTPs per cubic centimeter of marrow at superficial (30mm) aspirations to 439+/-557 CTPs per cubic centimeter marrow at deepest (45mm) aspiration depths (p<.00002). There were no significant differences relative to vertebral body level, side aspirated, or gender. An age-related decline in cellularity was suggested for vertebral body aspirates. CONCLUSIONS: The vertebral body is a potential marrow reservoir for aspiration of autograft osteogenic CTPs that can be used to augment spinal fusion. The cancellous bone within that portion of the vertebral body routinely cannulated during pedicle screw placement allows serial aspirations with only modest depletion of progenitor cell concentrations or dilution with peripheral blood. Connective tissue progenitor cell concentrations from all depths were comparable to the mean levels previously established for the iliac crest. The ability to simultaneously harvest progenitor cells for graft augmentation while preparing the pilot hole for pedicle screw fixation will expand the potential for cell harvest techniques for fusion augmentation and reduce the need for iliac crest harvest.

Spinal surgery in patients with Parkinson's disease: construct failure and progressive deformity.

STUDY DESIGN: Retrospective case series review of patients with Parkinson's disease undergoing elective spine surgery at a single tertiary referral center. OBJECTIVES: To assess the rate of complications of spine surgery in the population with Parkinson's disease and characterize the causes of failure and special needs of this unique population. SUMMARY OF BACKGROUND DATA: Patients with Parkinson's disease experience a combination of poor bone quality and a severe neuromuscular disorder. There is little information in the literature about outcomes of spine surgery in this population. Preliminary review suggests that these patients have a high rate of instrument-related complications that has not been reported previously. METHODS: A computerized search using diagnostic and procedural codes identified 14 patients with Parkinson's disease who underwent spine surgery from January 1993 through December 2000. Their charts and radiographs were reviewed, and those not examined within twelve months were invited for follow-up review. The remaining patients were being followed on a regular basis by their spine surgeon, the Movement Disorders Clinic, or both and were seen and examined during their routine follow-up observation. INDICATIONS AND EXTENT OF INDEX SURGERY VARIED: Complications, revisions, and radiographic evidence of loosening were assessed. Causes of failure were sought with respect to surgical and clinical factors. All patients underwent surgical care by a fellowship-trained spine surgeon. RESULTS: The mean follow-up period from index procedure was 66.8 months; the median follow-up period was 38 months. Of 14 patients, 12 (86%) required additional surgery, undergoing a total of 31 reoperations. Eleven patients (79%) underwent 22 additional procedures at the same or adjacent level for instability, including four patients (29%) who had hardware failure or pullout, necessitating 10 reoperations. The one other patient who required additional surgery had a successful index procedure but underwent another operation to address instability at a remote spinal segment. Of five patients whose index procedure involved only one spinal level, three (60%) required additional procedures, all at that level. Two patients (14%) developed wound infections during the course of treatment but not as the cause of initial treatment failure. The primary mechanisms of failure were relentless kyphosis or segmental instability at the operated-on or adjacent levels. CONCLUSION: Patients with Parkinson's disease undergoing spine surgery in a single tertiary referral center had a very high reoperation rate associated with technical complications. Patients should be appropriately counseled regarding the increased risk of operative complications and closely followed for incipient failure.