P32. Minimally Invasive Surgery for Degenerative Scoliosis

Proceedings of the NASS 24th Annual Meeting / The Spine Journal 9 (2009) 1S-205S

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constructs. Past biomechanical studies have reported on plate and dual rod implants, but to date no study has evaluated hybrid systems. PURPOSE: To investigate and compare the biomechanical performance and properties of three modern anterior spinal implants. STUDY DESIGN/SETTING: Biomechanical in vitro study PATIENT SAMPLE: 27 fresh-frozen, human thoracolumbar spines (T12L2) were extracted with intact discoligamentous complexes. OUTCOME MEASURES: Implant rigidity in flexion-extension, lateral bending and axial rotation, ultimate strength, load-to-failure analysis METHODS: In a custom MTS frame, each spine had pure moments applied in flexion-extension(66 Nm), lateral bending (66 Nm), and axial rotation (66 Nm) under a continuous 50 N axial load. Specimens were tested intact and after an L1 corpectomy, interbody graft and instrumentation. The three constructs were tested with nine spines in each group. Neutral zone and stiffness values were recorded and calculated. Following non-destructive testing, each instrumented sample was tested to failure in flexion with a ramped load of 2.5 Nm/sec. Ultimate strength and failure analysis was recorded. Descriptive statistics compared the intact and three instrumentation groups with all tests performed at the 0.05 level of significance. RESULTS: There were no significant differences in age, sex or bone mineral density between the three instrumented groups. In flexion and extension, stiffness values for intact (I), locking plate (LP), dual rods (DR) and hybrid (H) constructs showed no statistical difference (pO0.05). In lateral bending, the three instrumentation system stiffness values did not differ between groups (pO0.05); but were significantly greater than intact specimens (I:0.60 N/mm, LP:0.73 N/mm, DR:0.76 N/mm, H:0.75 N/mm; p!0.05). In axial rotation, the instrumentation systems demonstrated no difference between groups (pO0.05), but had significantly lower stiffness values compared to the intact specimens (I:20.8 Nm/deg, LP:8.0 Nm/ deg, DR:10.0 Nm/deg, H:11.3 Nm/deg; p!0.05). Load-to-failure testing revealed that each instrumentation failed through vertebral body screw ‘‘plow-through,’’ endplate fractures and posterior ligamentous rupture. Ultimate strength did not correlate with age, BMD, or implant type (pO0.05). CONCLUSIONS: This is the first study to evaluate and compare the biomechanical performance of ‘‘hybrid’’ plate/rod constructs. Our results suggest that all three systems share similar biomechanical properties. The three constructs reliably restore rigidity of the spine to pre-injury levels, except in the axial rotation plane. Clinically, our results suggest caution against the use of anterior-only instrumentation in axial rotation injuries. We recommend ideal implant selection be based on surgeon preference and patient profile. FDA DEVICE/DRUG STATUS: Synthes TSLP Locking Plate: Approved for this indication; Depuy Expedium Dual Rods: Approved for this indication; Globus Gateway hybrid plate/rod: Approved for this indication.

OUTCOME MEASURES: Overall and disease specific survival, independence in activities of daily living. METHODS: Retrospective review of 30 patients undergoing spinopelvic resection. RESULTS: Tumors included osteosarcoma (n59), chondrosarcoma (n56), chordoma (n55), other sarcomas (n55), neurogenic tumors (n54), and local extension of carcinoma (n51). Resections could be divided into 4 types. Type 1 resections included a total sacrectomy with lower lumbar spine and bilateral medial iliac resections. Type 2 resections included hemisacrectomy, partial lumbar spine excision, and iliac wing resection. Type 3 resections encompassed external hemipelvectomy with hemisacrectomy and partial lumbar spine excision. Type 4 resections encompassed external hemipelvectomy, total sacrectomy, and lumbar spine excision. For each resection type, we have developed staged surgical approaches to allow resection with wide margins and reconstruction of spinopelvic continuity. Tumor free margins were achieved in all cases. Perioperative mortality was 3/30. 7 additional patients have died of disease, 2 died of other causes, 2 are alive with disease, and 16 have no evidence of disease. 13/18 surviving patients are independent in their activities of daily living. CONCLUSIONS: En bloc excision and reconstruction of spinopelvic neoplasms may be classified into four types. For each type, we have devised surgical treatment guidelines to allow for wide resection and reconstruction of spinopelvic continuity. Long term survival and independent function can be achieved in this challenging patient population. This represents the first standardized classification of oncologic spinopelvic resections and reconstructions.

doi: 10.1016/j.spinee.2009.08.288

doi: 10.1016/j.spinee.2009.08.289

P31. Classification of Spinopelvic Resections: Oncologic and Reconstructive Implications Mark Dekutoski, MD, Michael Yaszemski, MD, PhD, Peter Rose, MD, Bradford Currier, MD, Paul Huddleston, MD, Ahmad Nassr, MD, Mark Pichelmann, MD, Franklin Sim, MD; Mayo Clinic, Rochester, MN, USA BACKGROUND CONTEXT: Curative treatment of malignancies in the sacrum and lower lumbar spine frequently requires en bloc spinopelvic resection. There is no standard classification of these procedures. We present outcomes and a classification scheme with oncologic and reconstructive guidelines for spinopelvic tumors based on an analysis of 30 cases. PURPOSE: We sought to assess outcomes of oncologic spinopelvic resections and provide a framework to guide resections and reconstructions. STUDY DESIGN/SETTING: Retrospective review of patients treated at a major oncology referral center. PATIENT SAMPLE: Thirty patients undergoing en bloc oncologic resections which disrupted spinopelvic continuity. Patients with sacral resections at or below the S1 neuroforamina (without disruption of spinopelvic continuity) were not included.

Resection Type 1 (n=12) 2 (n=6) 3 (n=9) 4 (n=3)

Spinal Resection

Pelvic Resection

Total Sacrectomy +/- lumbar spine

Bilateral iliac wings

Hemisacrectomy +/- lumbar hemivertebrectomy

Unilateral medial ilium

Hemisacrectomy +/- lumbar hemivertebrectomy Total Sacrectomy +/- lumbar spine

External hemipelvectomy

External hemipelvectomy +/- medial ilium on retained side

Reconstruction PSF L-spine to pelvis; fibular struts L-spine to pelvis PSF L-spine to pelvis with unilateral strut L-spine to pelvis None vs. PSF remaining L spine to remaining hemipelvis Femur of amputated leg used to connect L spine to remaining hemipelvis

Table. Classification of spinopeivic resections.

FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.

P32. Minimally Invasive Surgery for Degenerative Scoliosis Luiz Pimenta, MD, PhD1, Leonardo Oliveira1, Etevaldo Coutinho1, Behrooz Akbarnia, MD2; 1Instituto de Patologia de Coluna, Sao Paulo, Brazil; 2La Jolla, CA, USA BACKGROUND CONTEXT: Symptomatic adult scoliosis deformity presents as a difficult problem to solve. Traditional treatments include anterior and posterior open approaches. The purpose of this paper is to present a lateral retroperitoneal minimally invasive approach (eXtreme Lateral Interbody Fusion – XLIF) for the treatment of adult scoliosis requiring more than four levels of arthrodesis without the morbidity of an open procedure. PURPOSE: The purpose of the study is to show reasonable coronal and sagittal alignment and clinical improvement in patients with degenerative scolisis corrected by a minimal invasive lateral approach (XLIF). STUDY DESIGN/SETTING: A prospective, non-randomized, single center study. PATIENT SAMPLE: 14 patients, mean age 69.64 (51-87 years) with two year follow up, diagnosed with degenerative scoliosis. OUTCOME MEASURES: Dynamics X-ray, neurological examination and clinical outcome assessments using Oswestry and VAS scores.

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Proceedings of the NASS 24th Annual Meeting / The Spine Journal 9 (2009) 1S-205S

METHODS: Lateral, A-P, flexion-extension X-rays, neurological examination and clinical outcome assessments using Oswestry and VAS scores were performed at the preoperative, 1, 6 week, 3, 6, 12 and 24 months postoperative intervals. The extreme lateral approach was done through the retroperitoneal space and through psoas muscle avoiding vascular lesions. A partial discectomy was done and the end-plate cleaned preserving ALL, keeping the spine more stable than the traditional anterior surgery. The operated levels ranged from four to seven levels, including T10-T11 to L4-L5. RESULTS: The procedures were performed without complication in an average 121 minutes and with less than 50 cc blood loss. Ten patients had four levels of fusion; two patients had five levels and two patients with seven levels of arthrodesis. VAS pain scores improved from an average 8.33 at pre-op to 3.16 at 2 years, standard deviation 1.49 and 1.06 respectively. Oswestry scores improved from an average 51.2 at pre-op to 27.33 at 2 years with standard deviation of 13.42 and 13.09 respectively. Coronal and sagittal alignments improved from average Cobb angles of 16.4 degrees at pre-op and 7.8 degrees at 2 years, and average lordosis angles of 35.7 degrees at pre-op to 46.5 degrees at 2 years. CONCLUSIONS: Using the XLIF approach we were able to treat long thoracolumbar deformities in a minimally invasive way targeting the pain improvement after surgery without the risks and morbidity associated with big corrections. Our intent was pain improvement and stabilization. We found reasonable coronal and sagittal correction in addition to successful clinical improvements in pain and function in long thoracolumbar reconstructions. FDA DEVICE/DRUG STATUS: XLIF: Approved for this indication. doi: 10.1016/j.spinee.2009.08.290

P33. A Study of the Enzymatic Action of Chymopapain Using a Pluronic Based Nano-Carrier System on Cadaveric Nucleus Pulposus Tissue Sang-Heon Lee, MD, PhD1, Young-Ki Hong, MD2, Gi-Yoong Tae, PhD3, Won-Il Choi3, Dong-Geun Sul, PhD2, Sun-Wook Hwang, PhD2, Min Lee2, Seok Kang, MD2, Jeong-Eun Lee, PT2; 1Stanford University, Stanford, CA, USA; 2Korea University, Seoul, South Korea; 3Gwangju Institute of Science and Technology, Gwanju, Jeollanam-do, South Korea BACKGROUND CONTEXT: Chemonucleolysis via chymopapain is an effective therapy for some types of the intervertebral disc herniation. However, a high possibility of the degenerative spondylotic change including excessive destruction of the intervertebral disc after chymopapain treatment has been a demerit of this treatment. At present, there is no method to control the enzymatic field of chymopapain in the intervertebral disc. Drug delivery using a pluronic based nano-carrier has a biochemical property that modifies the enzymatic action of loaded drugs in some ways. Therefore we designed a pluronic based nano-carrier system to control the extent of the enzymatic action of chymopapain. PURPOSE: To evaluate the efficacy of newly a designed chymopapain solution compared to an ordinary chymopapain solution using a pluronicbased nano-carrier system on cadaveric intervertebral discs. STUDY DESIGN/SETTING: An enzymatic action of the chymopapain using pluronic- based nano-carrier system on the cadaveric nucleus pulposus was investigated. PATIENT SAMPLE: Nine cadaveric intervertebral discs OUTCOME MEASURES: Estimation of the cross-sectioned cheonulcelolyitic areas of each chymopapain injected intervertebral discs METHODS: Pluonic-based nano-carriers were prepared by photo crosslinkng of diluted diacrylated pluronic F127 (DA-PF127) and DA-PF68 solutions. Nine intervertebral discs were taken from one cadaver. The discs were divided into three subgroups according to the type of injected chymopapain solution. Each group consisted of three discs. Three types of chymopapain solution (ordinary chymopapain, DA-PF 127 based nanocarrier and DA-PF 68 based nano-carrier loaded cymopapains) were used. Discs were bisected in the transverse plane 1week after chymopapain injection and each of the cross sectioned specimens was examined.

RESULTS: The average chemonucleolytic area of the ordinary chymopapain group was 2.4060.43cm2. The DA-PF 127 based nano-carrier group and DA-PF 68 based nano-carrrier group were 9860.25 cm2 and 0.7860.19 cm2, respectively. CONCLUSIONS: Enzymatic action of chymopapain using a pluronicbased nano-carrier system on nucleus pulposus appears to be localized around the center of the injection site instead of spreading broadly. Therefore, chymopapain delivery by a pluronic- based nano-carrier system is assumed to become an effective method for locally acting selective chemonucleolysis in the future. FDA DEVICE/DRUG STATUS: Chymopapain using a pluronic based nano-carrier system: Investigational/Not approved. doi: 10.1016/j.spinee.2009.08.291

P34. 5-Lipoxygenase Inhibition and a Novel Rat Posterolateral Lumbar Spinal Fusion Model Using Homologous Rat Demineralized Bone Matrix Praveen Yalamanchili, MD1, Michael Vives, MD1, J. Patrick O’Connor, PhD1, Mitchell Reiter, MD2, Catherine Cunningham, BS1, Colin Harris, MD1; 1 UMDNJ - New Jersey Medical School, Newark, NJ, USA; 2Overlook Hospital, Summit, NJ, USA BACKGROUND CONTEXT: Previous studies in fracture healing models have shown increased healing rates with 5-lipoxygenase (5-LO) inhibition, which is thought to be related to increased prostaglandin formation through the arachidonic acid pathway. More recently, 5-LO inhibition in a rat posterolateral lumbar fusion model using iliac crest autograft has demonstrated a positive effect. No studies have been previously done to evaluate the ability of 5-LO inhibition to improve fusion rates using allograft. PURPOSE: To determine if local application of a 5-LO inhibitor to the posterolateral fusion bed can improve the fusion rate of rats undergoing posterolateral fusion with allograft (homologous) demineralized bone matrix (DBM). STUDY DESIGN/SETTING: Animal study of posterolateral lumbar fusion in rats. PATIENT SAMPLE: Thirty-six adult male Sprague-Dawley rats. OUTCOME MEASURES: The lumbar fusion masses were evaluated with radiographs and manual palpation testing of the intact harvested spines, and micro-CT imaging of selected specimens. METHODS: Thirty-six adult male Sprague-Dawley rats (approximate weight 450 grams) underwent posterolateral intertransverse lumbar fusions from L4-L5 utilizing Wiltse approaches. After exposure of the transverse processes and high-speed burr decortication, allograft homologous rat DBM with a glycerol carrier was implanted in the fusion bed with either of two 5-LO inhibitors (AA861 or zileuton) on a calcium sulfate carrier pellet (experimental groups), or homologous rat DBM plus calcium sulfate pellet alone (control group). Spines were harvested en bloc between postoperative days 28 and 42. Manual palpation testing was performed and graded as per Dimar et al (1). Plain radiographs of the intact specimens were performed and graded as per Lenke et al (2) . The groups were compared with Mann-Whitney-U testing. Selected specimens from each group underwent micro-CT imaging. RESULTS: Eleven of 12 control animals, 10 of 11 animals in the AA861 group and 13 of 13 animals in the zileuton group survived to study completion. At sacrifice, manual palpation revealed 11/11 control spines with solid or moderate fusion; 10/10 AA861 spines with solid or moderate fusion; and 10/13 zileuton spines with solid or moderate fusion. Radiographic review of the control spines revealed 64% definite or probable fusion rate compared to 80% in the AA861 group and 85% in the zileuton group. This trend toward increased fusion rates in the experimental groups was not statistically significant with the numbers available. Radiographic appearance of the fusion masses and micro-CT imaging of selected specimens, however, suggests more robust new bone formation in the experimental groups. CONCLUSIONS: This study suggests that a 5-lipoxygenase inhibitor applied locally to the spinal fusion bed may have a positive effect on fusion