The Prevalence of Lumbosacral Transitional Vertebrae in an American Population

Proceedings of the NASS 26th Annual Meeting / The Spine Journal 11 (2011) 1S–173S removed at a rate of 5.0 mm/min per ASTM F 543-07 and load-displacement data was collected at 50 Hz. The maximum axial force applied during each test was determined based on the load-displacement curve. RESULTS: 56 fixation points were available for evaluation. For Test A, the Screw Sock TM increased pullout strength compared with the stripped screw by 49.5% (102.3 vs.152.9 N, Figure 1). For Test B, Screw Sock TM achieved 84% of the pullout force of a larger 4.0 mm rescue screw (86.6 N vs 103.3 N). When the data from Test A and B were pooled, however, Screw Sock TM increased pullout forces compared with the rescue screw by 15.8% (119.8 N vs 103.3 N). In Test C, Screw Sock TM increased pullout forces compared with the intact 3.5 mm screw by 14.7% (229.0 N vs 199.6 N, Figure 2). CONCLUSIONS: Without using a larger screw, the Screw Sock TM increased stripped lateral mass screw pullout by 49.5%, demonstrated a similar performance profile (range: 84–115%) compared with the larger 4.0 mm rescue screw, and increased intact screw pullout by 14.7%. This simple, efficient device warrants further study as a cost-effective and highly versatile means to salvage stripped screws in the spine without needing to convert to a larger screw, or potentially as a primary screw augmentation device in patients with compromised local host bone (i.e. osteoporosis). FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. doi: 10.1016/j.spinee.2011.08.402

P101. The Prevalence of Lumbosacral Transitional Vertebrae in an American Population Pedro Ricart-Hoffiz, MD1, Alexios Apazidis, MD, MBA2, Christopher Diefenbach1, Jeffrey Spivak, MD3; 1New York, NY, USA; 2 Brookhaven Memorial Hospital, East Patchogue, NY, USA; 3Scarsdale, NY, USA BACKGROUND CONTEXT: Lumbosacral transitional vertebrae (LSTV) is a congenital vertebral anomaly of the L5-S1 junction in the spine. This alteration may contribute to incorrect identification of a vertebral segment, leading to wrong-level spine surgery and poor correlation with clinical symptoms. Though several studies describe the occurrence of this anomaly in back pain populations, investigation of the prevalence in an American non-back pain population is lacking. PURPOSE: To establish the prevalence rates for lumbosacral transitional vertebrae in non-back pain subjects. STUDY DESIGN/SETTING: Retrospective review. PATIENT SAMPLE: Consecutive kidney-urinary-bladder (KUB) radiographs of non-back pain related subjects from the past two years (2008–09) OUTCOME MEASURES: Clinical demographics, number of lumbar vertebrae, L5-S1 transverse process height, and rib length. METHODS: Consecutive adult kidney-urinary-bladder (KUB) studies of adult subjects were queried with clear visibility of the last rib’s vertebral body articulation, all lumbar transverse processes, and complete sacral wings. Exclusion criteria consisted of any radiologic evidence of previous lumbosacral surgery. A total of 1100 abdominal films were reviewed, and 211 were identified as being adequate for the measurement of the desired parameters. RESULTS: 211 subjects were identified as eligible for the study and 75 (35.6%) were classified as positive for a transitional lumbosacral vertebra. The average age at the time of the KUB study was 59.8 years (18–95 years). The most common anatomical variant was the Castellvi type IA (14.7%), followed by type IB (8.53%). Gender distribution was significant between the normal group and type IB (p5.03). 197 subjects (93.4%) presented five lumbar (non-ribbed) vertebrae, and only fourteen (6.6%) had six lumbar vertebrae. The longest TP was present 55% at L3. The mean length of last rib for the sample was 12.11 cm (2–23 cm). CONCLUSIONS: The significance of lumbosacral transitional level changes to the establishment of pain, degenerative changes, stenosis, and disc disease have been well documented in symptomatic patients. Though

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LSTV’s role in low back pain remains controversial, our study has shown that, when the same criteria are used for classification, prevalence amongst the general population and symptomatic patients is similar. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. doi: 10.1016/j.spinee.2011.08.403

P102. Reduced Dose of rhBMP-2 with Demineralized Bone Matrix-Based Product for Spinal Fusion Yalda Safai1, Michael Kropf, MD2, Hyun Bae, MD3, Li Zhao4, Lea Kanim4, Christine Thang5, Justin Houman6, Rick Delamarter, MD2; 1Cedars Sinai Medical Center, Los Angeles, CA, USA; 2Los Angeles, CA, USA; 3Spine Institute St. John’s Health Center, Los Angeles, CA, USA; 4Spine Research Foundation, Santa Monica, CA, USA; 5Glendale, CA, USA; 6Anaheim, CA, USA BACKGROUND CONTEXT: Each year there are more demineralized bone matrix-based products (DBMs) commercially available as allograft bone graft extenders for fusion procedures. DBM-based products are most commonly used with autograft, allografts, and possibly BMPs. Very few of these DBM-based products have been systematically evaluated in vivo. Even fewer of these DBM-based products have been experimentally evaluated when combined with autografts, allografts, or rhBMPs. Previously we have reported fusion variability across different production Lots of these DBM-based products. Recent studies have shown both intra product variability (lot-to-lot variability due to production lots) and inter product variability (product formulations). PURPOSE: The purpose of this study was to assess the benefit of adding DBM-based product to a subefficacious dose of rhBMP-2, or autogeneous bone. STUDY DESIGN/SETTING: Followup of reduced dosing and performance testing of grafting materials after implantation using posterolateral fusion surgical procedure challenge in a skeletally mature animal model (Athymic Rats). PATIENT SAMPLE: Athymic Rats. OUTCOME MEASURES: Manual testing fusion; radiographic fusion. METHODS: A L4-5 posterolateral lumbar spinal fusion was performed on athymic rats with implantation of 3 unique Lots of DBM-based product (EquivaBone, Etex Co., Cambridge, MA) with and without subefficacious dose of 0.006 mg/ml rhBMP2þDBM-based product. Positive controls were included (0.32 mg/ml, 0.16 rhBMP-2). Each combination graft (total volume 0.3 cc/side) was tested on 4 rats total. Fusion success was determined at eight weeks (short-term endpoint) and 6 months (long-term endpoint) with use of radiographs and manual palpation of the vertebral segments. Histology was completed. Fisher’s exact test and Logistic regression were used to determine the difference and predictive abilities of assayed and added rhBMPs. RESULTS: All segments implanted with 0.006 mg/ml rhBMP2/ACS only were not fused; however all segments implanted with the same dose of 0.006 mg/ml rhBMP2/ACS combined with DBM-based product had bone formation. Positive controls of 0.032 mg/ml and abover were fused. Also, when 25% DBM and 25%CP was used with 50% ICBG, well remodeled fusion was observed by 6 months. CONCLUSIONS: Fusion was not observed with the low dose rhBMP2/ ACS only. The higher the quantity of DBM to CP base in the product, the more rapid the bone formation. The optimal ratio between DBM and CP was 75% DBM to 25% CP. Very low doses of rhBMP-2 added to DBM-based product enhanced remodeling and rapid bone formation at all ratios of DBM to base. As is clinically practiced, autogeneous bone added to the DBM-based product also enhanced rapid bone formation. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. doi: 10.1016/j.spinee.2011.08.404

All referenced figures and tables will be available at the Annual Meeting and will be included with the post-meeting online content.