Preoperative Bone Health Assessment in Spine Fusion Surgery
This presentation by Dr. Mark L. Prasarn focuses on the importance of assessing preoperative bone health in older patients undergoing spine fusion surgery. It covers the potential bone-related complications, osteogenesis process, osteoconduction, osteoinduction, and the favorable biomechanical environment required for successful fusion. The objectives include understanding spine fusion surgery, preoperative assessment techniques, and the impact of osteoporosis drugs on surgery outcomes.
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Presentation Transcript
Preoperative Bone Health Assesment Mark L Prasarn MD Professor and Chief Division of Spine Surgery Dept. of Orthopaedic Surgery University of Texas, Houston
Objectives At the end of the presentation the participant should: 1. Gain some understanding of spine fusion surgery and the potential bone related complications in older patients 2. Become comfortable with preoperative bone health assessment in patients undergoing spine fusion surgery 3. Be familiar with the literature of osteoporosis drugs and their impact on spine fusion success and complications
Three main properties for fusion Osteogenesis Ostoconduction Osteoinduction Favorable Biomechanical Environment
Spine Fusion: Definition Spine Fusion (arthrodesis): A surgical procedure to provide internal stability of the spine, by facilitating bony interconnection between two or more of the vertebra, leading to absence of motion between these segments. Indications: Degenerative diseases of the spine: Instability, neurologic compression, Deformity: scoliosis, kyphosis, spondylolisthesis Trauma or tumor
Osteogenesis Cells differentiating into osteogenic lineage Relies upon undifferentiated cells Mature osteoblasts can revert to less- differentiated cells Blood vessels important source perivascular origin of MSCs
Osteoinduction Molecules (GFs) induce MSCs to amplify And to differentiate into osteoprogenitor cells Most significant are TGF superfamily Include well-known BMPs
Osteoconduction Complementary to osteogenesis and osteoinduction Tridimensional scaffold structure of bone or bone substitute Scaffolding for cell population growth
Fusion Formation Combination of Intramembranous and Enchondral Ossification Three distinct phases Early (inflamation) phase Middle (reparative) phase Late (remodeling) phase Boden et al. Spine 1995
Bone grafts, extenders, osteobiologics Aid in fusion via: Osteogenesis Osteoinduction Osteoconduction Osteopromotion
Autograft Still the gold standard! First used in fusion by Hibbs 1911 Has all properties necessary Low cost No concern of disease transmission or compatibility High fusion rates (40-100%) Downside is complications
Donor site pain Often performed by the inexperienced Higher incidence in those with persistent pain Likely psychological component Summers and Eisenstein JBJS 1989 Greater incidence in lower fusion levels Delawi et al. Spine 2007 51% incidence of pain in those with no harvest Concordant pain only 19% Howard et al. TSJ 2011
Osteoinductive agents BMP-2 and BMP-7 BMP-2 on-label for ALIF w/ LT-cage BMP-7 on-label revision PLF in compromised host or those not feasible for bone harvest Myriad of problems and complications, in addition to high cost! DBMs
Stem cells for fusion Stem cells BMA, Fat, Muscle, PB, Amniotic All of which may or may not have MSCs May use as blood product w minimal manipulation Need osteodifferentiation Real stem cells need to be manipulated Not approved (even autologous) Clinical trial in progress
Spinal Stenosis Narrowing of the spinal canal DJ 4705 Rev 1
Spondylolisthesis Forward translation of one vertebral body with respect to another Most common in lower lumbar spine DJ 4705 Rev 1
Listhesis vs. Lysis Spondylolisthesis Slippage of one vertebral body on another Spondylolysis Defect of the pars interarticularis DJ 4705 Rev 1
Spondylolisthesis Operative Management In situNon instrumented posterolateral fusion 64% fusion rate Herkowitz et al. JBJS 1991 DJ 4705 Rev 1
Spondylolisthesis Operative Management Posterolateral fusion with pedicle screws 87% fusion rate Fritzell et al. Spine 2002 Fischgrund et al. Spine 1997 Mardjetko et al. Spine 1994 DJ 4705 Rev 1
Anterior Column Support Use anterior implant Restore/maintain integrity of anterior spinal column DJ 4705 Rev 1
Anterior / Middle Columns 80% compressive load through anterior and middle columns 90% surface area DJ 4705 Rev 1
Interbody Fusion: Biomechanical, Anatomic, Physiologic Restoration of disc space height Correction of alignment and balance Prevents progression of subluxation Provides load sharing Prolongs life of posterior instrumentation Higher fusion rate DJ 4705 Rev 1
Spondylolisthesis Operative Management Posterposterololateral fusion with pedicle screws and interbody fusion 91% fusion rate Lee et al. Clin Orthop Surg 2011 DJ 4705 Rev 1
Interbody Fusion Devices Anterior Posterior DJ 4705 Rev 1
ACRONYMS! PLF TLF ALIF XLIF What is the Difference???
Complications Fusion Failure (pseudoarthrosis) Construct/Device failure (pedicle screw loosening, interbody device subsistence) Proximal Junctional Kyphosis due to compression fracture of adjacent vertebral level
Risk factors for complications Old age Large spondylolisthesis slip angle Smoking Infection Excessive motion
Fusion Failure - Pseudarthrosis Screw loosening and interbody cage subsistence are potential complications that may be due in part to poor bone health leading to pseudarthrosis.
Pre-operative Bone Health Assessment Prior to Elective Spine Surgery Maybe women over 60? Men over 70? All with diagnosis of Osteoporosis Those with compression fxs from low energy All patients with chronic glucocorticoid exposure Smokers Major deformity surgery
Teriparatide What does it do? PTH is 84 AA protein Regulates Ca++ 1 alpha hydroxylation 25-hydroxyvitamin D Receptors on osteoblasts for PTH NF-kB (RANK) ligand RANK on osteoclasts Important for homeostasis and bone remodeling
The PTH paradox How does it work? PTH results in depletion of Ca++ from bone Pattern of exposure determines skeletal effects Sustained 1 Hyperparathyroidism Intermittent paradoxical effect Peak in 30 mins, and declines to non- detectable over 3 hrs
Bone Remodeling Osteoclasts - resorption cavity Osteoblasts Secrete osteod Osteoid Mineralized bone
Teriparatide Effects Normal Homeostasis
Teriparatide Effects When given as Forteo Intermittent dosing Preferential stimulation Osteoblasts Positive Balance
Forteo Fracture Prevention Trial Prospective, random, Double Blind Placebo (N=544), Forteo 20 mcg/day (N=541) Duration of 18 months Supplemental Ca++ and Vit D Endpoints vertebral fx, nonvertebral fx, BMD, safety Neer et al. NEJM 2001
Results Increased L-spine BMD (Anabolic) 9.7% Risk reduction Vertebral fx (RRR 65%) Non-vertebral new fx (RRR 53%) Neer et al. NEJM 2001
Anabolic Effect After 21 months of Forteo Neer et al. NEJM 2001
Who should get Forteo? On-label = Osteoporosis at high fx risk Failure on other anitresorptive tx Those who continue to lose bone mass or have very low T-scores despite tx Cannot tolerate bisphosphonates Glucocorticoid treated pts with fractures
Who should not get it? Open epiphyses Paget disease Prior XRT Hx of Osteosarcoma Increased Alk Phos Primary hyperparathyroidism Pregnant or breast feeding Renal impairment
102 women with colles fxs 20 or 40 g/kg dose 9.1, 7.4, 8.8 weeks to healing Shorter time to healing with 20 g/kg group versus control (p=0.006)
Prospective randomized every 1/3 21 elderly pts with pelvic fxs 100 g dose PTH 7.8 vs. 12.6 weeks (p<0.001) At 8 weeks (CT) healed in 100% vs. 9.1%
Retrospective review of 43 pts Very difficult to get to heal Good results with adjunctive Forteo Still need good biomechanical environment!
Spine Fusion Does it help? Is it cost effective? $1800-3200 per month Pedicle screws can be upwards of 4K each! What s the cost of failed back psuedarthrosis, nonunion, future fractures?
Posterolateral rabbit fusion model Intermittent PTH (10 g/kg) Fusion rate 81% vs 30% MicroCT 6.0 cc vs. 3.5 cc Histology twice the bone percentage area
Control vs. Teriparatide Control Teriparatide
