P30. Lumbar microdiscectomy comparing minimally invasive tubular retractors versus standard retractors

Proceedings of the NASS 19th Annual Meeting / The Spine Journal 4 (2004) 3S–119S DISCLOSURES: No disclosures. CONFLICT OF INTEREST: No Conflicts. doi: 10.1016/j.spinee.2004.05.233

P85. Anterior cervical fusion using dense cancellous allografts and dynamic plating Daniel Kim1, Hoang Le1, Raju Balabhadra1, Ho-Yeol Zhang2; 1Stanford University, Stanford, CA, USA; 2CA, USA BACKGROUND CONTEXT: Dense cancellous allografts (DCAs), which have become available in recent years, present several distinct biological advantages over cortical or corticocancellous allografts for anterior cervical fusion (ACF). The large surface area available due to trabecular structure of the dense cancellous grafts greatly facilitates early and more complete fusion by early vascularization and cellular penetration. Thus, DCAs tend to integrate with the host bone earlier than cortical or corticocancellous grafts. Clinical efficacy of DCA spacers for ACDF have not been previously reported. PURPOSE: The aim of this study is to evaluate the efficacy of the dense cancellous allografts as a substrate for anterior cervical fusion along with instrumentation. STUDY DESIGN/SETTING: This is a retrospective clinical study PATIENT SAMPLE: Between January 2001 and March 2002, 98 patients underwent anterior cervical discectomy, fusion using dense cancellous allograft bone with instrumentation using dynamic plating. Of these procedures, 60 involved single-level and 38 involved two-level fusions. OUTCOME MEASURES: Clinical symptoms and neurological findings were reviewed from the patient’s charts. Radiographs were evaluated for subsidence and fusion by an experienced spine surgeon who was not involved in the care of these patients. METHODS: Subsidence was assessed at 1, 3, 6, and 12 months and fusion was assessed at 3, 6, and 12 months post-operatively by plain radiographs. Fusion was defined as appearance of bridging trabecular bone and absence of motion in flexion-extension films. RESULTS: The mean follow-up period was 15 (range 12–25) months. Successful fusion was observed in 70%, 84%, and 96% of the cases at 3, 6, and 12 months respectively. The average subsidence for single-level and two fusions were 2.0 mm and 3.2 mm respectively. No allograft or hardware related complications were encountered in our series. CONCLUSIONS: Dense cancellous allografts are very effective as bone graft substitutes for achieving anterior cervical fusion along with instrumentation. Successful fusion was observed in 70% of our cases at 3 months with a fusion rate of 96% at one year. These allografts provide an effective replacement for autologous grafts in cervical interbody fusion. DISCLOSURES: Device or drug: dense cancellous bone. Status: Approved for this indication. CONFLICT OF INTEREST: No Conflicts.

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PATIENT SAMPLE: A series of 182 patients since 1997 having had total lumbar disc replacement with the Charite´ artificial disc, performed by a single surgeon. Of the 182 cases, 5 (2.7%) required surgical revision. OUTCOME MEASURES: Back and leg VAS, Oswestry Disability Index (ODI), Roland-Morris Disability Questionnaire (R-MD), and patient selfassessment of outcome. METHODS: Over the course of 6 years, 182 patients presented with severe discogenic pain with or without sciatica. Failing non-operative treatment they were indicated for total lumbar disc replacement at 1 or 2 levels. A total of 263 Charite´ prostheses were implanted. Five (5) cases of surgical revision were identified. The complications that led to the surgical revision and the techniques employed were documented. Clinical follow-up was documented. RESULTS: Patient #1 had TDR at L3–4 and L4–5 and developed an early anterior subluxation at L3–4. This patient was revised with removal of the original device and received a new Charite´ disc prosthesis. Patient #2 had TDR at L4–5 and L5-S1 and experienced a core dislocation at L5-S1 resulting in a left iliac vein obstruction. This patient had an inferior vena cava umbrella with removal of the prosthesis and conversion to ALIF. Patient #3 had TDR at L4–5 and L5-S1 and experienced increased L5 radicular pain due to over distraction at L5-S1. This patient underwent removal of the prosthesis and conversion to instrumented circumferential fusion. Patient #4 had TDR at L5-S1 and experienced a core dislocation. The prosthesis was removed and a conversion to ALIF was performed. Patient #5 had TDR at L5-S1 and developed a spondylolisthesis secondary to progression of facet arthropathy. The prosthesis remained in situ and was supplemented with an instrumented posterolateral fusion. Mean back VAS was 4.2 (0–7). Mean leg VAS was 2.1 (0–7). Mean ODI was 32.4 (0–58). Mean R-MD was 11.4 (1–18). Patients were asked to rate their satisfaction with their outcome following surgical revision with choices of excellent, good, satisfactory, or poor. In these 5 cases, 4 rated their outcome as excellent and 1 as good. Two patients suffer from the significant comorbidity of rheumatoid arthritis, and 1 is in early postoperative phase. CONCLUSIONS: Considerable scepticism exists regarding the advantages of lumbar disc replacement and significant attention has been given to revision procedures and complications that may arise. 1 A surgical revision rate of 2.7% from a single surgeon’s experience was reported. This rate is well below the rate suggested in the literature with respect to lumbar fusion procedures. 2 Careful patient selection and preoperative planning remain paramount in avoiding the need for revision in the future. As with other types of spinal surgery, a reliable and predictable surgical revision strategy is necessary to manage complications. DISCLOSURES: Device or drug: Charite Artificial Disc. Status: Investigational/Not approved. CONFLICT OF INTEREST: Author (MS) Consultant: Author has a consulting agreement with DePuy Spine; Author (MS) Other: participates as part of DePuy Spine’s product development team. doi: 10.1016/j.spinee.2004.05.235

doi: 10.1016/j.spinee.2004.05.234

P35. Revision strategies for total lumbar disc replacement Matthew Scott-Young, MBBS, FRACS; Pacific Private Clinic, Southport, Queensland, Australia BACKGROUND CONTEXT: Prosthetic devices have been developed to partially or totally replace symptomatic discs. Potential postoperative complications include infection, mechanical failure, loss of fixation, and neurological irritation or deficit. In the event of a complication, a sound surgical salvage strategy can result in a satisfactory outcome for the patient. PURPOSE: To describe the rate of complications requiring surgical revision and the strategy employed in each case resulting in satisfactory patient outcome. STUDY DESIGN/SETTING: Retrospective review of 5 surgical revision cases in patients implanted with the third-generation Charite´ artificial disc prosthesis.

P30. Lumbar microdiscectomy comparing minimally invasive tubular retractors versus standard retractors Arya Nick Shamie, Assistant Professor1, Saman Aboudi2, Larry Khoo1, Jeffrey Wang1; 1University of California, Los Angeles, Santa Monica, CA, USA; 2Chicago Medical School, IL, USA BACKGROUND CONTEXT: Microdiscectomy is typically performed via a small incision utilizing a microscope for enhanced visualization. With the recent interest in minimally invasive surgery, tubular retractors which dilate the muscle fibers have become popular in order to minimize the incision length, while achieving the same surgical goals. The purpose of this study was to compare the results of lumbar microdiscectomy using minimally invasive tubular retractors and standard “open” retractors (standard microdiscectomy vs. MetRx Tube retractors). PURPOSE: To compare the two methods of Microdiscectomy utilizing two different retractors, MetRx tube and the standard (McCullough) retractors.

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Proceedings of the NASS 19th Annual Meeting / The Spine Journal 4 (2004) 3S–119S

STUDY DESIGN/SETTING: Patients undergoing single level microdiscectomy procedures from 2001 to 2003 were reviewed. Patients with prior lumbar surgeries were excluded. Retrospective review of surgical complications, hospital stay, estimated blood loss, relief of symptoms, and need for reoperation was performed. PATIENT SAMPLE: Sixty-two consecutive patients who underwent a total of sixty five procedures over a 3-year period were retrospectively reviewed. OUTCOME MEASURES: Review of patient charts for recurrence of symptoms was performed. VAS scores pre- and postoperatively was also reviewed. METHODS: All patients had single-level disc herniations confirmed with MRI studies and had failed a proper course of conservative care including NSAIDs, physical therapy, and epidural injections. The data used for comparison of these two procedures include the duration of hospital stay, blood loss, surgical complications, persistence of symptoms, need for revision surgery, and clinical results. RESULTS: Of the total sixty-two patients, a standard microdiscectomy utilizing standard “open” retractors were performed on 39 patients, while 24 had surgery using the MetRx Tubular retractors. For the patients who underwent the classical approach, two dural tears and one patient recurrent radiculopathy were noted. Of the 24 patients who underwent discectomy using the tubular retractors, one dural tear and five recurrent radiculopathies were noted. None of the patients suffered nerve injury or infection during or following the procedures. There was no statistically significant difference between the two groups as far as intraoperative complications, postoperative complications, total procedure time, or hospital stay. The average estimated blood loss was 57.7cc for the patients who underwent the classical approach versus 53.9cc for the patients who underwent the tubular approach. The average hospital stay was 1.42 days for patients who underwent the classical approach and 0.75 days for patients who underwent the tubular approach. CONCLUSIONS: There appears to be no significant difference between the minimally invasive tubular retractors or standard retractors for patients undergoing single-level lumbar microdiscectomy procedures. There may be a trend towards a shorter hospital stay and perhaps a higher rate of recurrent symptoms with the use of the tubular retractors, however, it appears that both methods are successful and provide similar clinical results. DISCLOSURES: No disclosures. CONFLICT OF INTEREST: No Conflicts. doi: 10.1016/j.spinee.2004.05.236

P80. Restoration in osteoporotic vertebral fracture: kyphoplasty is superior to postural correction Joseph Lane, MD1, Jason Koob1, Michael Shindle, MD2, Susan Bukata, MD1, Margaret Peterson, PhD1; 1Hospital for Special Surgery, New York, NY, USA; 2Johns Hopkins University, Baltimore, MD, USA BACKGROUND CONTEXT: It has recently been demonstrated that many vertebral compression fractures (VCF’s) are mobile and positional correction can lead to clinically significant height restoration. PURPOSE: The purpose of this report was to test the hypothesis that positional maneuvers are statistically inferior to kyphoplastic balloon tamps for the reduction of low energy vertebral compression fractures. STUDY DESIGN/SETTING: Retrospective review, Hospital for Special Surgery. PATIENT SAMPLE: 25 consecutive patients with 43 vertebral compression fractures. OUTCOME MEASURES: Radiographs were evaluated for percent height restoration related to positioning and balloon kyphoplasty. METHODS: Preoperative standing lateral radiographs of the fractured vertebrae were compared with prone cross-table lateral radiographs with the patient in a hyper-extension position on pelvic and sternal rolls. Following positional manipulation patients underwent a unilateral balloon kyphoplasty. Postoperative standing radiographs were evaluated for percent of height restoration related to positioning and balloon kyphoplasty.

RESULTS: In the central portion of the vertebrae, the average preoperative fractured vertebral body height compared to a “normal vertebral body” was 60.12%. Postural maneuvering and kyphoplasty increased central height to 66.16% (p⬍0.005) and 82.95% (p⬍0.001) respectively. The percent restoration of the central portion of the vertebral body with extension positioning was 10.44%, median=11.11%, and after balloon kyphoplasty was 59.31%, median=62.18%, (p⬍0.001). Thus, while positioning provided an average of 10.44% restoration, kyphoplasty provided an additional 48.87% restoration in the central portion. With operative positioning, 51.16% of VCF’s had ⬎10% restoration of the central portion of the vertebral body as compared with 90.7% after balloon kyphoplasty (p⫽0.0014). CONCLUSIONS: Proponents of vertebroplasty advocate that placing the patient in the prone position in extension should lead to adequate reduction of the fracture due to dynamic mobility. Although this study supports the concept that many VCF’s can be moved with positioning, balloon kyphoplasty enhanced the height reduction ⬎5 fold over the positioning maneuver alone and accounted for over 75% of the ultimate reduction. Even in these patients with marked positional improvement, kyphoplasty provided significant additional height restoration. If height restoration is the goal, kyphoplasty is clearly superior in most cases to the positioning maneuver alone. DISCLOSURES: Device or drug: Kyphon inflatable balloon tamp. Status: Approved for this indication. Device or drug: Polymethylmethacrylate cement (PMMA). Status: Not approved for this indication. CONFLICT OF INTEREST: Author (jl) Consultant: Kyphon; Author (jl) Speaker’s Bureau Member: Kyphon; Author (jl) Grant Research Support: Kyphon. doi: 10.1016/j.spinee.2004.05.237

P25. Evaluation of pedicle screw placement in the deformed spine using intraoperative plain radiographs: a comparison with CT scans Yong-Jung Kim1, Lawrence Lenke1*, Gene Cheh, MD2, K. Daniel Riew1; 1Washington University in St. Louis, St. Louis, MO, USA; 2MO, USA BACKGROUND CONTEXT: Is it possible to predict malpositioned screws on plain intraoperative radiographs? PURPOSE: To evaluate the sensitivity of intraoperative plain radiographs to detect malpositioned pedicle screws in the deformed thoracic and lumbar spine. STUDY DESIGN/SETTING: A retrospective radiographs and CT scan review. PATIENT SAMPLE: 49 patients. OUTCOME MEASURES: Radiographs and CT scans. METHODS: A total of 776 pedicle screws (618 thoracic pedicle screws and 158 lumbar pedicle screws) inserted from T1 to L4 in 49 patients with postoperative CT scan data were investigated. According to the diagnoses, the number of screws placed were: 692 for scoliosis (45 patients), and 84 for Scheuermann’s kyphosis (4 patients). The position of the pedicle screw inserted was graded as an accurate screw (n=711) with acceptable position vs inaccurate screw (n=65) with significant violation, defined as the central line of the inserted pedicle screw was out of the outer cortex of the pedicle wall with CT scans taken after operation. Comparative analysis of these 65 inaccurate screws (15 medial violations and 50 lateral violations) using postoperative CT scan and intraoperative plain radiographs was done. All CT scan evaluations were performed independently by three different spine surgeons who had not been part of the operation. Three plain radiographic criteria were used to judge the accuracy of screw position: 1) violation of the harmonious segmental change of the tips of the inserted screws (medial or lateral out), 2) no crossing of medial pedicle wall by the pedicle screw inserted (lateral out), and 3) violation of the imaginary midline of the vertebral body using the posterior upper spinolaminar junction in the plain PA x-ray by the absolute position of the tip of the inserted pedicular screw