The effect of therapies for osteoporosis on spine fusion: a systematic review

Treatment Strategies in the Osteoporotic Spine

This article reviews the appropriate assessment and management of osteoporotic compression fractures and discusses the implications of osteoporosis on initial patient evaluation, medical optimization for surgery, selection of instrumentation, and surgical technique. Adverse outcomes associated with osteoporosis are discussed. Failure to appropriately evaluate, optimize, and treat spine patients with osteoporotic bone can lead to disastrous complications. Weakened bone can lead to implant failure through cage subsidence and screw pullout, as well as, peri-implant fractures, failure of deformity correction, and proximal kyphosis. These risks must be taken into account when considering operative interventions in these patients.

Biomechanical assessment of different transforaminal lumbar interbody fusion constructs in normal and osteoporotic condition: a finite element analysis

BACKGROUND CONTEXT

With the aging population, osteoporosis, which leads to poor fusion, has become a common challenge for lumbar surgery. In addition, most people with osteoporosis are elderly individuals with poor surgical tolerance, and poor bone quality can also weaken the stability of internal fixation.

PURPOSE

This study compared the fixation strength of the bilateral traditional trajectory screw structure (TT-TT), the bilateral cortical bone trajectory screw structure (CBT-CBT), and the hybrid CBT-TT (CBT screws at the cranial level and TT screws at the caudal level) structure under different bone mineral density conditions.

STUDY DESIGN

A finite element (FE) analysis study.

METHODS

Above all, we established a healthy adult lumbar spine model. Second, under normal and osteoporotic conditions, three transforaminal lumbar interbody fusion (TLIF) models were established: bilateral traditional trajectory (TT-TT) screw fixation, bilateral cortical bone trajectory (CBT-CBT) screw fixation, and hybrid cortical bone trajectory screw and traditional trajectory screw (CBT-TT) fixation. Finally, a 500-N compression load with a torque of 10 N/m was applied to simulate flexion, extension, lateral bending, and axial rotation. We compared the range of motion (ROM), adjacent disc stress, cage stress, and posterior fixation stress of the different fusion models.

RESULTS

Under different bone mineral density conditions, the range of motion of the fusion segment was significantly reduced. Compared to normal bone conditions, the ROM of the L4-L5 segment, the stress of the adjacent intervertebral disc, the surface stress of the cage, and the maximum stress of the posterior fixation system were all increased in osteoporosis. Under most loads, the ROM and surface stress of the cage and the maximum stress of the posterior fixation system of the TT-TT structure are the lowest under normal bone mineral density conditions. However, under osteoporotic conditions, the fixation strength of the CBT-CBT and CBT-TT structures are higher than that of the TT-TT structures under certain load conditions. At the same time, the surface stress of the intervertebral fusion cage and the maximum stress of the posterior fixation system for the two structures are lower than those of the TT-TT structure.

CONCLUSION

Under normal bone mineral density conditions, transforaminal lumbar interbody fusion combined with TT-TT fixation provides the best biomechanictability. However, under osteoporotic conditions, CBT-CBT and CBT-TT structures have higher fixed strength compared to TT-TT structures. The hybrid CBT-TT structure exhibits advantages in minimal trauma and fixation strength. Therefore, this seems to be an alternative fixation method for patients with osteoporosis and degenerative spinal diseases.

CLINICAL SIGNIFICANCE

This study provides biomechanical support for the clinical application of hybrid CBT-TT structure for osteoporotic patients undergoing TLIF surgery.

MRI-based central sarcopenia negatively impacts the therapeutic effectiveness of single-segment lumbar fusion surgery in the elderly

Central sarcopenia is associated with the prognosis of various orthopedic surgeries in the elderly. This study aims to investigate its impact on the outcomes of single-segment lumbar fusion surgery in elderly patients. Retrospective analysis was conducted on 314 patients aged 60 to 80 who underwent single-segment posterior lumbar fusion surgery due to degenerative lumbar diseases. Patients were categorized into high psoas and L4 vertebral index (PLVI) and low PLVI groups according to the MRI-measured PLVI for central sarcopenia. Basic patient data, surgery-related parameters, functional assessments at preoperative and postoperative 3, 6, and 12 months, and X-ray-based fusion status were compared. The basic data of the two groups showed no significant differences. Parameters including the operative segment, preoperative hemoglobin levels, surgical duration, and intraoperative blood loss exhibited no significant variances. However, notable differences were observed in postoperative initial hemoglobin levels, transfusion requirements, and length of hospital stay between the two groups. During the postoperative follow-ups at 3, 6, and 12 months, the VAS scores for lower back pain and ODI scores in the lower PLVI group were significantly higher compared to the high PLVI group. Additionally, the EuroQoL 5D scores were notably lower in the low PLVI group. There were no significant differences between the groups in terms of leg pain VAS scores at each time point and the fusion status at 12 months postoperatively. MRI-based central sarcopenia has a negative impact on the therapeutic effectiveness following single-segment lumbar fusion surgery in elderly patients.

Efficacy and safety of different anti-osteoporotic drugs for the spinal fusion surgery: A network meta-analysis

BACKGROUND

Administering anti-osteoporotic agents to patients perioperatively is a widely accepted approach for improving bone fusion rates and reducing the risk of complications. The best anti-osteoporotic agents for spinal fusion surgery remain unclear.

AIM

To investigate the efficacy and safety of different anti-osteoporotic agents in spinal fusion surgery via network meta-analysis.

METHODS

Searches were conducted in four electronic databases (PubMed, EMBASE, Web of Science, the Cochrane Library and China National Knowledge Infrastructure (CNKI) from inception to November 2022. Any studies that compared anti-osteoporotic agents vs placebo for spinal fusion surgery were included in this network meta-analysis. Outcomes included fusion rate, Oswestry disability index (ODI), and adverse events. Network meta-analysis was performed by R software with the gemtc package.

RESULTS

In total, 13 randomized controlled trials were included in this network meta-analysis. Only teriparatide (OR 3.2, 95%CI: 1.4 to 7.8) was more effective than placebo in increasing the fusion rate. The surface under the cumulative ranking curve (SUCRA) of teriparatide combined with denosumab was the highest (SUCRA, 90.9%), followed by teriparatide (SUCRA, 74.0%), zoledronic acid (SUCRA, 43.7%), alendronate (SUCRA, 41.1%) and risedronate (SUCRA, 35.0%). Teriparatide (MD -15, 95%CI: -28 to -2.7) and teriparatide combined with denosumab (MD -20, 95%CI: -40 to -0.43) were more effective than placebo in decreasing the ODI. The SUCRA of teriparatide combined with denosumab was highest (SUCRA, 90.8%), followed by teriparatide (SUCRA, 74.5%), alendronate (SURCA, 52.7), risedronate (SURCA, 52.1%), zoledronic acid (SURCA, 24.2%) and placebo (SURCA, 5.6%) for ODI. The adverse events were not different between groups.

CONCLUSION

This network meta-analysis suggests that teriparatide combined with denosumab and teriparatide alone significantly increase the fusion rate and decrease the ODI without increasing adverse events. Based on current evidence, teriparatide combined with denosumab or teriparatide alone is recommended to increase the fusion rate and to reduce ODI in spinal fusion patients.

Prevalence of osteoporosis in spinal surgery patients older than 50 years: A systematic review and meta-analysis

INTRODUCTION

In spine surgery, poor bone condition is associated with several complications like adjacent segment fractures, proximal junctional kyphosis, and screw loosening. Our study explored the prevalence of osteoporosis in spinal surgery patients older than 50 years through a systematic review and meta-analysis.

METHODS

This systematic review and meta-analysis were conducted according to the PRISMA criteria. Three electronic databases, including PubMed, EMBASE, and Web of Science, were searched from inception to August 2022. We used the random-effects model to calculate the overall estimates, and the heterogeneity was measured using Cochran's Q and I2 tests. Meta-regression and subgroup analyses were used to determine the source of the heterogeneity.

RESULTS

Based on the inclusion and criteria, we chose ten studies with 2958 individuals for our analysis. The prevalence of osteoporosis, osteopenia, and osteoporosis/osteopenia in the spinal surgery patients was 34.2% (95%CI: 24.5%-44.6%), 43.5% (95%CI: 39.8%-47.2%), and 78.7% (95%CI: 69.0%-87.0%), respectively. Regarding different diagnoses, the prevalence was highest in patients with lumbar scoliosis (55.8%; 95%CI: 46.8%-64.7%) and the lowest in patients with cervical disc herniation (12.9%; 95%CI: 8.1%-18.7%). In age groups 50-59, 50-69,70-79, the prevalence was 27.8%, 60.4%, 75.4% in females, and 18.9%, 17.4%, 26.1% in males.

CONCLUSIONS

This study showed a high prevalence of osteoporosis in patients undergoing spine surgery, especially in females, people of older age, and patients who received degenerative scoliosis and compression fractures. Current osteoporosis screening standards for patients undergoing spine surgery may not be adequate. Orthopedic specialists should make more efforts regarding preoperative osteoporosis screening and treatment.

Cortical bone trajectory screws in the treatment of lumbar degenerative disc disease in patients with osteoporosis

Lumbar degenerative disc disease (DDD) in the elderly population remains a global health problem, especially in patients with osteoporosis. Osteoporosis in the elderly can cause failure of internal fixation. Cortical bone trajectory (CBT) is an effective, safe and minimally invasive technique for the treatment of lumbar DDD in patients with osteoporosis. In this review, we analyzed the anatomy, biomechanics, and advantages of the CBT technique in lumbar DDD and revision surgery. Additionally, the clinical trials and case reports, indications, advancements and limitations of this technique were further discussed and reviewed. Finally, we concluded that the CBT technique can be a practical, effective and safe alternative to traditional pedicle screw fixation, especially in DDD patients with osteoporosis.

Blockade of Osteoclast-Mediated Bone Resorption With a RANKL-Inhibitor Enhances Bone Formation in a Rat Spinal Fusion Model

STUDY DESIGN

Rat spine fusion model.

OBJECTIVE

The present study aimed to determine whether administration of osteoprotegerin (OPG) in a rat model of spinal fusion increases bone volume, bone density, and decreases osteoclasts in the fusion mass.

SUMMARY OF BACKGROUND DATA

OPG is a soluble RANK-ligand inhibitor that blocks osteoclast differentiation and activation. This makes it a potential agent to control the remodeling process and enhance bone mass during spinal fusion.

MATERIALS AND METHODS

Forty-eight male Sprague-Dawley rats received a one-level spinal fusion of L4-L5 with bone allograft. Rats were then divided into four groups according to initiation of treatment: (1) saline on day 0 (saline), (2) OPG on day 0 (OPG D0), (3) OPG on day 10 (OPG D10), and (4) OPG on day 21 (OPG D21) postsurgery. After their initial injection, rats received weekly subcutaneous injections of OPG (10 mg/kg) and were euthanized six weeks postsurgery. MicroCT analysis of the fusion site and histological analysis of bone surface for quantification of osteoclast lining was performed.

RESULTS

Increased bone volume in the fusion site and around the spinous process was seen in OPG D0 and OPG D10 when compared with saline. Mean trabecular thickness was greater in all groups receiving OPG compared with saline, with OPG D0 and OPG D10 having significantly greater mean trabecular thickness than OPG D21. All OPG groups had less bone surface lined with osteoclasts when compared with Saline, with OPG D0 and OPG D10 having fewer than OPG D21.

CONCLUSIONS

This study indicates that OPG inhibited osteoclast bone resorption, which led to greater bone at the fusion site. Future studies investigating OPG on its own or in combination with an osteogenic factor to improve spinal fusion outcomes are warranted to further elucidate its potential therapeutic effect.

Impact of preoperative treatment of osteoporosis on re-operations, complications and health care utilization in patients undergoing thoraco-lumbar spine fusions. A 5-year national database analysis

OBJECTIVE

Identify the impact of preoperative treatment of Osteoporosis (OP) on reoperation rates, complications and healthcare utilization following thoraco-lumbar (TL) spine fusions.

MATERIALS AND METHODS

We used ICD9/10 and CPT codes to extract data from MarketScan (2000-2018). Patients were divided into two groups based on preoperative treatment of OP within one year prior to the index spinal fusion: medication (m-OP) cohort and non-medication (nm-OP) cohort. Outcomes (re-operation rates, re-admission, complications, healthcare utilization) were analyzed at 1-, 12-, 24- and 60-months.

RESULTS

Of 3606 patients, 65% (n = 2330) of patients did not receive OP medications (nm-OP). At index hospitalization, there were no difference in LOS (median nm-OP: 3 days vs. m-OP:4 days), discharge to home (nm-OP 80% vs. m-OP 75%) and complications (nm-OP 13% vs. m-OP 12%). Reoperation rates were not different among the cohorts at 1- (nm-OP 5.7% vs. m-OP 4.2%), 2- (nm-OP 9.4% vs. m-OP 7.8) and 5 years (nm-OP 16.9% vs. m-OP 14.8%). Patients in m-OP cohort incurred higher overall median payments at 1 year ($17,866 vs. $ 16,010), 2 years ($38,634 vs. $34,454) and 5 years ($94,797 vs. $91,072) compared to nm-OP cohort.

CONCLUSION

Preoperative treatment of OP had no impact on complications, LOS, discharge disposition following TL fusions at index hospitalization. Similarly, no impact of preoperative treatment was noted in terms of reoperation rates at 12-, 24- and 60 months following the index spine fusion. Patients who received preoperative treatment for OP incurred higher health care utilization at 12-, 24- and 60 months following surgery.

Antiresorptive and anabolic medications used in the perioperative period of patients with osteoporosis undergoing spine surgery: their impact on the biology of fusion and systematic review of the literature

OBJECTIVE

Osteoporosis represents the most common metabolic disease of the bone, with an estimated 10% of adults aged 50 years or older affected in the United States. This patient population is at increased risk for spine fracture and instrumentation-related complications after spine surgery. Surgeon knowledge of the available treatments for patients with low bone mineral density (BMD) and how they impact biology of fusion may help mitigate negative effects in the postoperative period. Recombinant parathyroid hormone, which is sold under the name teriparatide, is the most extensively studied bone-protecting agent in humans. Additionally, the success of the monoclonal antibody denosumab has led to further clinical investigations of human patients undergoing spine surgery. Another monoclonal antibody, romosozumab, was recently approved by the US FDA for human use in patients with osteoporosis. Although studies of romosozumab in patients undergoing spine surgery have not been conducted, this is a promising potential therapeutic agent based on its early success in preclinical and clinical trials. Here, the authors aimed to review the mechanisms of action and evidence of use of antiresorptive and anabolic agents in patients with osteoporosis undergoing spine surgery.

METHODS

In accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, a systematic review was conducted to explore the antiresorptive and anabolic agents used in the perioperative period in patients with osteoporosis undergoing spinal surgery. The search was performed by using the PubMed, Embase, and Cochrane Library databases. Titles and abstracts were screened and subsequently selected for full review.

RESULTS

The initial search returned 330 articles. Of these articles, 23 final articles were included and reviewed. Many of these articles reported that use of adjuvant agents in the perioperative period improved radiographic evidence of bony fusion and bone fusion rates. These agents tended to improve BMD postoperatively.

CONCLUSIONS

Although antiosteoporosis agents are effective to varying degrees as treatments of patients with low BMD, teriparatide and bisphosphonates have been the most extensively studied with respect to spinal instrumentation. The advent of newer agents represents an area for further exploration, especially due to the current paucity of controlled investigations. It is imperative for spine surgeons to understand the mechanisms of action of these drugs and their effects on biology of fusion.

Postoperative bisphosphonate do not significantly alter the fusion rate after lumbar spinal fusion: a meta-analysis

Background

To evaluate the effect of postoperative BP treatment on improving the fusion rate after lumbar spinal fusion surgery by performing a meta-analysis of randomized controlled trials (RCTs) and other comparative cohort studies.

Methods

A comprehensive search of PubMed, EMBASE, the Web of Science, and the Cochrane Central Register of Controlled Trials was performed for RCTs and other comparative cohort studies on the effect of BP treatment on improving the fusion rate after lumbar spinal fusion surgery. The primary outcome measures were the number of patients with bone formation grades A, B, and C at 12 months of follow-up; fusion rates at 12 and 24 months of follow-up; vertebral compression fracture (VCF) at 12 and 24 months of follow-up; pedicle screw loosening at 24 months of follow-up; and cage subsidence, the Oswestry disability index (ODI), and the visual analogue score (VAS) at 12 months of follow-up. The final search was performed in July 2020.

Results

Seven studies with 401 patients were included. Compared with the placebo, BP treatment did not significantly alter the number of patients with bone formation grades A, B, and C, or the VAS at the 12-month follow-up or the fusion rates at the 12- and 24-month follow-ups. In addition, compared with the placebo, BPs significantly reduced the risks of VCF at the 12- and 24-month follow-ups, pedicle screw loosening at the 24-month follow-up, and cage subsidence and the ODI at the 12-month follow-up.

Conclusions

Postoperative BPs do not clearly improve bone formation and the fusion rate, but they reduce VCF, cage subsidence, and loosening of pedicle screws after lumbar fusion surgery compared with the control treatment.

Osteoporosis: Recent Recommendations and Positions of the American Society for Bone and Mineral Research and the International Society for Clinical Densitometry

➤

Osteoporosis is common in orthopaedic patients, not only in those sustaining fragility fractures but also in patients ≥50 years old who are having elective orthopaedic surgery.

➤

The American Society for Bone and Mineral Research (ASBMR) has developed consensus-based recommendations for secondary fracture prevention for all patients who are ≥65 years old with a hip or spine fracture.

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The ASBMR encourages orthopaedic surgeons to "Own the Bone," by beginning prevention of a secondary fracture during hospitalization for a fragility fracture, if practicable, and arranging follow-up for continued bone health care after discharge.

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The International Society for Clinical Densitometry (ISCD) recognized that many poor outcomes and complications of elective orthopaedic surgery are related to osteoporosis.

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The ISCD used an evidence-based approach to create official positions to identify which patients ≥50 years old who are having elective orthopaedic surgery should undergo assessment of bone health and how this should be performed.

Effects of systemically administered abaloparatide, an osteoanabolic PTHrP analog, as an adjuvant therapy for spinal fusion in rats

BACKGROUND

Abaloparatide is a parathyroid hormone receptor agonist that increases bone formation and reduces vertebral and nonvertebral fracture risk in women with postmenopausal osteoporosis. Animal studies indicate abaloparatide stimulates vertebral bone formation and enhances bony bridging and biomechanical stability of fracture calluses.

AIMS

The current study is evaluating the potential utility for abaloparatide as an adjunct therapy for spinal fusions.

MATERIAL AND METHODS

The effects of 14 or 28 days of daily subcutaneous injections of abaloparatide (20 μg/kg/d) or vehicle were evaluated in 32 male Sprague-Dawley rats starting 1 day after noninstrumented posterolateral fusion (PLF) with bone autograft. Fusion mass microarchitecture was analyzed by micro-computed tomography (micro-CT) and serum markers of bone formation and bone resorption were evaluated. Motion segments were scored in a blinded manner as fused or unfused by postmortem radiography and manual palpation.

RESULTS

Abaloparatide-treated rats showed higher bone formation (serum osteocalcin) at day 14 and 28 compared with vehicle controls, without increases in the bone resorption marker serum TRACP-5b. Micro-CT showed greater trabecular number in fusion masses from the abaloparatide group vs vehicle controls at day 14. Manual palpation and radiography indicated no fusions in either group at day 14, whereas 25% of vehicle-treated rats and 50% of abaloparatide-treated rats had bilateral fusion at day 28.

DISCUSSION AND CONCLUSION

In summary, this rat PLF model showed that abaloparatide treatment was associated with higher levels of the bone formation marker osteocalcin, improved fusion mass architecture, and a non- significant 2-fold higher fusion rate compared with vehicle.

The impact of bisphosphonates on postoperative complication rates in osteoporotic patients undergoing posterior lumbar fusion

PURPOSE

To elucidate the effects of bisphosphonates on complications following posterior lumbar fusion (PLF) with a large database study.

METHODS

The PearlDiver Patient Record Database was queried to identify adult patients who had undergone posterior lumbar fusion (PLF). Those patient cohorts were divided based on a diagnosis of osteoporosis prior to surgery and bisphosphonate usage. This yielded three groups: Osteo+Bisph+, Osteo+Bisph-, and Osteo-Bisph-. The primary outcome of the present study was revision rates at 6 months and 1 year following surgery. Incidence of postoperative complications was analyzed, and statistical analysis was conducted using Pearson chi-square analysis.

RESULTS

Patients taking bisphosphonates did not have significantly different rates of revision surgery at 6 months and 1 year, instrumentation complications, or post-vertebral fractures than patients not taking bisphosphonates. Additionally, osteoporotic patients did not have significantly different rates of these complications than patients without osteoporosis.

CONCLUSION

Bisphosphonate usage did not significantly affect the rates of postoperative complications following posterior lumbar fusion. Further research is required to fully elucidate the effects of bisphosphonates on outcomes and complications following spine surgery.

The growth-friendly surgical treatment of scoliosis in children with osteogenesis imperfecta using distraction-based instrumentation

PURPOSE

The study was undertaken to determine the feasibility of growth-friendly distraction-based surgery in children with OI.

METHODS

Two multi-center databases were queried for children with OI who had undergone GR or VEPTR surgery. Inclusion criteria were a minimum 2-year follow-up and three lengthening procedures following the initial implantation. Details of the surgical techniques, surgical complications, and radiographic measurements of deformity correction, T1-T12 and T1-S1 elongation and growth were recorded.

RESULTS

Five patients were identified. There was one patient with type I OI and two patients each with type III and type IV. Four patients had GR constructs and one a VEPTR construct. The initial scoliosis deformity averaged 80° (70°-103°), and the subsequent corrections averaged 32% for initial correction, 48% at last follow-up, and 54% for the two patients that had a final fusion. The T1-T12 and T1-S1 growth averaged 31 mm and 44 mm respectively, and yearly growth averaged 4 mm and 6 mm, respectively. Growth was notably much less in those with more severe disease. There were 13 complications in 4 patients. Nine of the 10 surgical complications were anchor failures which were corrected in 7 planned and 2 un-planned procedures. Significant migration occurred in one patient with severe OI type III.

CONCLUSION

The results varied in this heterogeneous population. In general, satisfactory deformity corrections were obtained and maintained, modest growth was obtained, and complications were similar to those reported in other series of growth-friendly surgery. Limited growth and significant anchor migration are to be anticipated in this population.

LEVEL OF EVIDENCE

IV.

Teriparatide and bisphosphonate use in osteoporotic spinal fusion patients: a systematic review and meta-analysis

PURPOSE

Osteoporosis is one of the most common conditions among adults worldwide. It also presents a challenge among patients undergoing spinal surgery. Use of Teriparatide and bisphosphonates in such patients has been shown to improve outcomes after fusion surgery, including successful fusion, decreased risk of instrumentation failure, and patient-reported outcomes. Herein, we performed a systematic review and indirect meta-analysis of available literature on outcomes of fusion surgery after use of bisphosphonates or Teriparatide.

METHODS

We conducted a comprehensive search of all databases (Ovid MEDLINE(R) and Epub Ahead of Print, In-Process & Other Non-Indexed Citations, Ovid Embase, Ovid Cochrane Central Register of Controlled Trials, Ovid Cochrane Database of Systematic Reviews, and Scopus) to identify studies assessing outcomes of spinal fusion among osteoporotic patients after use of Teriparatide or bisphosphonate. Four authors independently screened electronic search results, and all four authors independently performed study selection. Two authors performed independent data extraction and assessed the studies' risk of bias assessment using standardized forms of Revised Cochrane risk-of-bias tool for randomized trials (RoB 2) and Risk Of Bias In Non-randomized Studies of Interventions (ROBINS-I).

RESULTS

Nineteen studies were included in the final analysis. A total of 13 studies evaluated the difference in fusion rate between bisphosphonates and Teriparatide or control group. Fusion rate was higher for bisphosphonates (effect size (ES) 83%, 95% CI 77-89%) compared with Teriparatide (ES 71%, 95% CI 57-85%), with the p value for heterogeneity between groups without statistical significance (p = 0.123). Five studies assessed the impact of using bisphosphonate or Teriparatide on screw loosening. The rate of screw loosening was higher for bisphosphonates (ES 19%, 95% CI 13-25%) compared with Teriparatide (ES 13%, 95% CI 9-16%) without statistical significance (p = 0.52).

CONCLUSION

Our results indicate that while both agents may be associated with positive outcomes, bisphosphonates may be associated with a higher fusion rate, while Teriparatide may be associated with lower screw loosening. The decision to treat with either agent should be tailored individually for each patient keeping in consideration the adverse effect and pharmacokinetic profiles.

Preoperative bone health assessment and optimization in spine surgery

OBJECTIVE

The purpose of this investigation was to characterize the bone health in preoperative spine surgery patients. This information will provide a framework to understand the needs and methods for providing bone health optimization in elective spine surgery patients.

METHODS

A retrospective study of 104 patients undergoing bone health optimization was performed. Patients were selected based on risk factors identified by the surgeon and suspected compromised bone health. Evaluation included history and examination, laboratory investigations, and bone mineral density (BMD) at 3 sites (femoral neck, lumbar spine, and radius). Patients' bone status was classified using WHO criteria and expanded criteria recommended by the National Osteoporosis Foundation (NOF). The 10-year Fracture Risk Assessment Tool (FRAX) scores of the hip and major osteoporotic fracture (MOF) were calculated with and without femoral neck BMD, with spine BMD, and with the trabecular bone score (TBS). Antiresorptive and anabolic agents were provided in accordance with meeting NOF criteria for treatment of osteoporosis.

RESULTS

The mean patient age was 69.0 years, and 81% of patients were female. The mean historical height loss was 5.6 cm, and 54% of patients had a history of fracture. Secondary osteoporosis due to chronic renal failure, inflammatory arthritis, diabetes, and steroid use was common (51%). The mean 25-hydroxy vitamin D was 42.4 ng/ml and was normal in 81% of patients, with only 4 patients being deficient. The mean T-scores were -2.09 (SD 0.71) of the femoral neck, -0.54 (1.71) of the lumbar spine, and -1.65 (1.38) of the distal radius. These were significantly different. The 10-year FRAX MOF score was 20.7%, and that for hip fracture was 6.9% using the femoral neck BMD and was not significantly different without the use of BMD. The FRAX risk-adjusted score using the lumbar spine BMD and TBS was significantly lower than that for the hip. Osteoporosis was present in 32.1% according to WHO criteria compared with 81.6% according to NOF criteria. Antiresorptive medications were recommended in 31 patients and anabolic medications in 44 patients.

CONCLUSIONS

Surgeons can reliably identify patients with poor bone health by using simple criteria, including historical height loss, history of fracture, comorbidities associated with osteoporosis, analysis of available imaging, and calculation of FRAX score without BMD. High-risk patients should have BMD testing and bone health assessment. In patients with osteoporosis, a comprehensive preoperative bone health assessment is recommended and, if warranted, pharmacological treatment should be started.

Does the use of preoperative bisphosphonates in patients with osteopenia and osteoporosis affect lumbar fusion rates? Analysis from a national spine registry

OBJECTIVE

Bisphosphonates are used to increase bone strength in treating osteopenia and osteoporosis, but their use for increasing lumbar fusion rates has been controversial. The objective of this study was to determine if preoperative treatment with bisphosphonates affects the reoperation rates for nonunions (operative nonunion rates) following lumbar fusions in patients with osteopenia or osteoporosis.

METHODS

The authors conducted a cohort study using data from the Kaiser Permanente Spine Registry. Patients (aged ≥ 50 years) with a diagnosis of osteopenia or osteoporosis who underwent primary elective lumbar fusions for degenerative disc disease, deformity, or spondylolisthesis were included in the cohort. Repeated spinal procedures at the index lumbar levels were noted through chart review. Reoperations for symptomatic nonunions (operative nonunions), time to nonunion, and the nonunion spine level(s) were also identified. The crude 2-year cumulative incidence of operative nonunions was calculated as 1 minus the Kaplan-Meier estimator. Cox proportional hazard regression was used to evaluate the association between preoperative bisphosphonate use and operative nonunion after adjustment for covariates. Analysis was stratified by osteopenia and osteoporosis diagnosis.

RESULTS

The cohort comprised 1040 primary elective lumbar fusion patients, 408 with osteopenia and 632 with osteoporosis. Ninety-seven (23.8%) patients with osteopenia and 370 (58.5%) patients with osteoporosis were preoperative bisphosphonate users. For the osteopenia group, no operative nonunions were observed in patients with preoperative bisphosphonate, while the crude 2-year incidence was 2.44% (95% CI 0.63–4.22) in the nonuser group. For the osteoporotic group, after adjustment for covariates, no difference was observed in risk for operative nonunions between the preoperative bisphosphonate users and nonusers (HR 0.96, 95% CI 0.20–4.55, p = 0.964).

CONCLUSIONS

To the authors’ knowledge, this study presents one of the largest series of patients with the diagnosis of osteopenia or osteoporosis in whom the effects of preoperative bisphosphonates on lumbar fusions were evaluated using operative nonunion rates as an outcome measure. The results indicate that preoperative bisphosphonate use had no effect on the operative nonunion rates for patients with osteoporosis. Similar indications were not confirmed in osteopenia patients because of the low nonunion frequency. Further studies are warranted to the determine if preoperative and postoperative timing of bisphosphonate use has any effect on lumbar fusion rates.

Abaloparatide and the Spine: A Narrative Review

Osteoporosis is a common and debilitating condition characterized by diminished bone mass and architecture leading to bone fragility. Antiresorptive medicines like bisphosphonates (and less commonly denosumab) are the typical first-line agents for the medical treatment of osteoporosis. However, newer anabolic agents have been shown to improve bone mass and architecture, as well as reduce fracture risk, to a greater degree than traditional antiresorptive therapies. Teriparatide (human recombinant parathyroid hormone (PTH) 1–34, Forteo, Ely Lilly, Indianapolis, IN), which was the first in class to be approved in the United States, is the most widely used anabolic osteoporosis medicine and has shown significant benefit over traditional antiresorptive therapies. However, abaloparatide (synthetic parathyroid-related peptide (PTHrP), Tymlos, Radius Health, Waltham, MA), the second drug in this family, has recently become available for use. In this narrative review, we review the mechanism, effects, and benefits of abaloparatide compared to alternative treatments as well as discuss the current literature in regard to its effect on osteoporosis-related complications in the spine.

Screw-Related Complications After Instrumentation of the Osteoporotic Spine: A Systematic Literature Review With Meta-Analysis

STUDY DESIGN

Systematic literature review with meta-analysis.

OBJECTIVE

Osteoporosis is common in elderly patients, who frequently suffer from spinal fractures or degenerative diseases and often require surgical treatment with spinal instrumentation. Diminished bone quality impairs primary screw purchase, which may lead to loosening and its sequelae, in the worst case, revision surgery. Information about the incidence of spinal instrumentation-related complications in osteoporotic patients is currently limited to individual reports. We conducted a systematic literature review with the aim of quantifying the incidence of screw loosening in osteoporotic spines.

METHODS

Publications on spinal instrumentation of osteoporotic patients reporting screw-related complications were identified in 3 databases. Data on screw loosening and other local complications was collected. Pooled risks of experiencing such complications were estimated with random effects models. Risk of bias in the individual studies was assessed with an adapted McHarm Scale.

RESULTS

From 1831 initial matches, 32 were eligible and 19 reported screw loosening rates. Studies were heterogeneous concerning procedures performed and risk of bias. Screw loosening incidences were variable with a pooled risk of 22.5% (95% CI 10.8%-36.6%, 95% prediction interval [PI] 0%-81.2%) in reports on nonaugmented screws and 2.2% (95% CI 0.0%-7.2%, 95% PI 0%-25.1%) in reports on augmented screws.

CONCLUSIONS

The findings of this meta-analysis suggest that screw loosening incidences may be considerably higher in osteoporotic spines than with normal bone mineral density. Screw augmentation may reduce loosening rates; however, this requires confirmation through clinical studies. Standardized reporting of prespecified complications should be enforced by publishers.

Effect of local zoledronic acid administration in a rat model of posterolateral spinal fusion

Study design

Randomized animal model study.

Purpose

Posterolateral spinal fusion represents a common surgical procedure in the United States. The effect of bisphosphonate administration in these patients is poorly understood. The purpose of this study is to determine whether local administration of bisphosphonate by soaking bone autograft would affect the apparent bone density or structural properties of the fusion mass in a rat model of posterolateral spinal fusion.

Methods

36 Spring Dawley rats underwent L4-5 posterolateral spinal fusion with bone autograft. These rats were divided into three groups, two experimental groups and one control group. Each of the experimental groups underwent spinal fusion with morselized vertebral cortical and cancellous autograft soaked in zoledronic acid solution; one group 20 mcg/mL, another 200 mcg/mL. The control group underwent L4-5 spinal fusion with cancellous allograft soaked with saline. At 8 weeks, the rats were euthanized for analysis. Evaluations consisted of micro-CT scanning, four-point bending biomechanical testing, histology, and radiographs.

Results

Both of the experimental groups showed statistically significant increase in apparent bone density and bone volume fraction at the fusion mass. Biomechanical measures revealed a trend for improvement in the experimental groups, but these did not reach statistical significance.

Conclusions

This data suggest that locally administered bisphosphonate medications result in increased apparent bone density and bone volume fraction at the fusion mass in posterolateral spinal fusion, and that there appear to be no deleterious consequences with regards to the stiffness or maximum load to failure of the fusion mass under flexion bending evaluation.

Radiographic and functional outcomes of bisphosphonate use in lumbar fusion: a systematic review and meta-analysis of comparative studies

PURPOSE

To date, there are conflicting reports with no consensus on the influence of bisphosphonates on lumbar fusion. The goal of this study was to compare the radiographic and functional outcomes of patients that had lumbar fusion with and without bisphosphonates.

METHODS

A systematic search of multiple medical reference databases was conducted for studies comparing bisphosphonate use to controls following spinal fusion. Meta-analysis was performed using the random-effects model for heterogeneity. Radiographic outcome measures included fusion rates and risk of screw loosening, cage subsidence and vertebral fracture. Functional outcomes measures included Oswestry Disability Index and visual analog scale score for back and leg pain.

RESULTS

Bisphosphonate use was statistically suggestive of a higher fusion rate compared to controls (OR 2.2, 95% CI 0.87-5.56, p = 0.09). There was no difference in screw loosening rates between the bisphosphonate group and controls (OR 0.45, 95% CI 0.14-1.48, p = 0.19). However, bisphosphonate use was associated with decreased odds of cage subsidence and vertebral fractures compared to controls (cage subsidence: OR 0.29, 95% CI 0.11-0.75, p = 0.01; vertebral fracture: OR 0.18, 95% CI 0.07-0.48, p = 0.0007).

CONCLUSION

Bisphosphonate use does not appear to impair successful lumbar fusion compared to controls. Additionally, bisphosphonate use was associated with decreased odds of cage subsidence and vertebral fractures compared to controls that had lumbar fusion. These slides can be retrieved under Electronic Supplementary Material.

Bone union after spinal fusion surgery using local bone in long-term bisphosphonate users: a prospective comparative study

Bisphosphonates are the most commonly used drugs for osteoporosis and long-term use of bisphosphonates may affect fusion rate after spinal fusion surgery. There was significant delayed union after 6 months in long-term bisphosphonates users; however, there were no significant difference in fusion rate of long-term bisphosphonate users. Therefore, spinal fusion surgery should not be hesitated in long-term bisphosphonates users.

PURPOSE

Bisphosphonates (BPs) are the most popular class of drugs for treatment of postmenopausal osteoporosis. Long-term use of BPs may also inhibit the spinal fusion process after posterior lumbar interbody fusion (PLIF). We compared bone fusion rates of long-term BPs users and non-users after undergoing spinal fusion surgery.

METHODS

A total of 97 postmenopausal women who were candidates for single-level PLIF were recruited from 2015 to 2016. Participants were divided into two groups, with 63 patients in a long-term BPs user group and 34 patients in a non-user group. Serum C-terminal cross-linking telopeptide (CTX) levels were checked for bone resorption markers. Bone fusion rates were calculated at 6 months and 1 and 2 years after the surgery. Clinical outcomes were measured using the Oswestry Disability Index (ODI) and visual analog scale (VAS).

RESULTS

Serum CTX level was dramatically decreased in the long-term BPs user group (p < 0.05). Fusion rates at 6 months after surgery were 42% in the non-user group and 26% in the long-term BPs user group (p = 0.035). However, fusion rates were 82% in the long-term BPs user group and 87% in the non-user group at 2 years after surgery (p > 0.05). There was no significant difference between the two groups in ODI or VAS.

CONCLUSIONS

Even though there was significant delayed union after 6 months in long-term BPs users, at the 2-year postoperative follow-up, there was no significant difference in bone fusion rate between the two groups. Long-term BPs users showed fusion rates greater than 80% and clinical outcome improvements that were comparable to those in non-users. No significant effect on fusion rate after PLIF was found in long-term BPs users.

Is Teriparatide Beneficial to Spinal Fusion Surgery in the Older Patient?: A Narrative Review

Since FDA approval in 2002, teriparatide has gained popularity as an anabolic therapy for the treatment of osteoporosis. Animal studies have suggested a role for teriparatide in spine surgery. Several recent studies have demonstrated adjunctive use of teriparatide in osteoporotic patients undergoing spine fusions improves fusion rates, decreases time to union, and decreases osteoporosis-related complications such as proximal junctional kyphosis. On the basis of the available literature, we outline an algorithm for the use of teriparatide in spine surgery.

Surgeon Management of Osteoporosis in Instrumented Spine Surgery: AOSpine Latin America Survey

STUDY DESIGN

Survey study.

OBJECTIVE

To determine the impact of osteoporosis (OP) in instrumented spine surgery among Latin American spine surgeons.

METHODS

An electronic survey on aspects of instrumented spine surgery and OP was sent electronically to all members of AOSpine Latin America (AOSLA): 16 multiple-choice questions included incidence and type of complications experienced, strategies to avoid intraoperative complications, on prevention of complications and OP assessment and treatment prior to surgery.

RESULTS

A total of 349 spine surgeons from a universe of 377 surgeons (230 orthopedic surgeons and 147 neurosurgeons), associated members of AOSLA answered the survey. About 80% recalled complications directly related to OP and 71% had revised instrumentation because of OP-related complications. Techniques for prevention of intraoperative complications varied; 65% extended instrumentation to additional segments, 63% performed vertebral body cement injection alone or associated with instrumentation. Preoperative screening was used by 19% but increased to 75% if patients had risk factors. A limit value of bone mineral density for delaying surgery was not established for 66.4% of respondents. Consultation for OP management was requested by 81%, mostly to endocrinology (56.3%). Interestingly, 19% personally managed their patient's OP.

CONCLUSION

This study provides a global perspective on how Latin American spine surgeons manage patients with OP undergoing instrumented spine surgery. Most have faced complications associated with OP and have had to resolve them surgically. Spine surgeons frequently participate partially in managing patients with OP. Most refer patients with OP for treatment to the endocrinology.

Does Systemic Administration of Parathyroid Hormone After Noninstrumented Spinal Fusion Surgery Improve Fusion Rates and Fusion Mass in Elderly Patients Compared to Placebo in Patients With Degenerative Lumbar Spondylolisthesis?

STUDY DESIGN

Prospective, randomized, double-blinded, placebo-controlled clinical trial.

OBJECTIVE

To evaluate whether 90-day subcutaneous injections with 20 μg teriparatide increases the volume and quality of the fusion mass compared to placebo based on 12-month postop fine cut computed tomography scans. The secondary objective is to evaluate whether parathyroid hormone (PTH) increases fusion rates compared to placebo.

SUMMARY OF BACKGROUND DATA

Few studies have investigated the effects of PTH on fusion in patients undergoing spinal arthrodesis. Early studies showed a more robust fusion mass with PTH after spinal fusion surgery. But the efficiency of PTH on noninstrumented spinal fusion surgery remains unclear.

METHODS

Patients with degenerative spondylolisthesis scheduled for noninstrumented posterolateral fusion were randomized to receive 90-day subcutaneous injections with 20 μg teriparatide (N = 41) or placebo (N = 46) in a 1:1 fashion. Fusion volume and quality was evaluated using 12-month postoperative fine cut computed tomography scans.

RESULTS

The two groups were comparable in terms of age, sex, and numbers of levels operated. PTH treatment was well tolerated but provided no additional benefit versus placebo. Fusion rates, the mean volume, and robustness of the fusion mass were similar between the PTH and placebo groups.

CONCLUSION

Ninety-day subcutaneous administration of 20 μg teriparatide did not increase fusion volume or improve the quality of the fusion mass in elderly patients compared to placebo after noninstrumented spinal fusion surgery for degenerative spondylolisthesis.

LEVEL OF EVIDENCE

1.

Effect of teriparatide use on bone mineral density and spinal fusion: a narrative review of animal models

Purpose of the study: Teriparatide (Human recombinant Parathyroid Hormone 1-34) is an anabolic agent that is frequently used in patients with osteoporosis and has been extensively investigated with animal model and clinical studies in current literature. The purpose of the study was to evaluate the impact of teriparatide on bone mineral density and fusion. Materials and methods: The findings from preclinical studies that have investigated the role of teriparatide in animal models are summarized in presented review. Results: Overall, the studies show an improvement in bone mineral density and increased fusion rates for osteoporotic animals undergoing spine fusion with teriparatide use. Conclusion: Further studies should be conducted for unanswered questions, such as teriparatide use before surgery, the effect on cervical fusion and surgery related complications.

The Biological Enhancement of Spinal Fusion for Spinal Degenerative Disease

In this era of aging societies, the number of elderly individuals who undergo spinal arthrodesis for various degenerative diseases is increasing. Poor bone quality and osteogenic ability in older patients, due to osteoporosis, often interfere with achieving bone fusion after spinal arthrodesis. Enhancement of bone fusion requires shifting bone homeostasis toward increased bone formation and reduced resorption. Several biological enhancement strategies of bone formation have been conducted in animal models of spinal arthrodesis and human clinical trials. Pharmacological agents for osteoporosis have also been shown to be effective in enhancing bone fusion. Cytokines, which activate bone formation, such as bone morphogenetic proteins, have already been clinically used to enhance bone fusion for spinal arthrodesis. Recently, stem cells have attracted considerable attention as a cell source of osteoblasts, promising effects in enhancing bone fusion. Drug delivery systems will also need to be further developed to assure the safe delivery of bone-enhancing agents to the site of spinal arthrodesis. Our aim in this review is to appraise the current state of knowledge and evidence regarding bone enhancement strategies for spinal fusion for degenerative spinal disorders, and to identify future directions for biological bone enhancement strategies, including pharmacological, cell and gene therapy approaches.

Clinical Management of Osteoporotic Fractures

PURPOSE OF REVIEW

This review examines recent literature regarding the clinical management of fragility fractures, provides insight into new practice patterns, and discusses controversies in current management.

RECENT FINDINGS

There are declining rates of osteoporosis management following initial fragility fracture. Management of osteoporotic fractures via a multidisciplinary team reduces secondary fracture incidence and improves overall osteoporotic care. Anabolic agents (abaloparatide and teriparatide) are effective adjuvants to fracture repair, and have shown positive results in cases of re-fracture in spite of medical management (i.e., bisphosphonates). For AO 31-A1 and A2 intertrochanteric hip fractures (non-reverse obliquity), no clinical advantage of intramedullary fixation over the sliding hip screw (SHS) has been proven; SHS is more cost-effective. As fragility fracture incidence continues to rise, orthopedic surgeons must play a more central role in the care of osteoporotic patients. Initiation of pharmacologic intervention is key to preventing subsequent fragility fractures, and may play a supportive role in initial fracture healing. While the media bombards patients with complications of medical therapy (atypical femur fractures, osteonecrosis of jaw, myocardial infarction), providers need to understand and communicate the low incidence of these complications compared with consequences of not initiating medical therapy.

A Systematic Review of Treatment Strategies for Degenerative Lumbar Spine Fusion Surgery in Patients With Osteoporosis

Purpose:

To evaluate the current evidence in the literature on treatment strategies for degenerative lumbar spine fusion in patients with osteoporosis.

Methods:

A systematic review of the literature from 1950 to 2015.

Results:

The review of the literature yielded 15 studies on the effect of treatment options for osteoporosis on lumbar fusion rates. This study evaluated only degenerative lumbar spine conditions and excluded deformity patients. One study demonstrated an association between low bone mass as measured by Hounsfield units and lower fusion rates. Six studies evaluated perioperative medical treatment of osteoporosis and showed higher fusion rates in patients treated with alendronate and teriparatide. The strongest evidence was for perioperative teriparatide. Eight studies evaluated surgical treatment strategies in patients with osteoporosis and showed that cement augmentation of pedicle screws and expandable pedicle screws demonstrated improved fusion rates than traditional pedicle screws. The strongest evidence was for expandable pedicle screws.

Conclusion:

There are 15 articles evaluating osteoporosis in patients undergoing lumbar fusion and the highest level of evidence is for perioperative use of teriparatide.

Proximal Junctional Kyphosis: Diagnosis, Pathogenesis, and Treatment

Proximal junctional kyphosis (PJK) is a common radiographic finding after long spinal fusion. A number of studies on the causes, risk factors, prevention, and treatment of PJK have been conducted. However, no clear definition of PJK has been established. In this paper, we aimed to clarify the diagnosis, prevention, and treatment of PJK by reviewing relevant papers that have been published to date. A literature search was conducted on PubMed using "proximal junctional", "proximal junctional kyphosis", and "proximal junctional failure" as search keywords. Only studies that were published in English were included in this study. The incidence of PJK ranges from 5% to 46%, and it has been reported that 66% of cases occur 3 months after surgery and approximately 80% occur within 18 months. A number of studies have reported that there is no significantly different clinical outcome between PJK patients and non-PJK patients. One study showed that PJK patients expressed more pain than non-PJK patients. However, recent studies focused on proximal junctional failure (PJF), which is accepted as a severe form of PJK. PJF showed significant adverse impact in clinical aspect such as pain, neurologic deficit, ambulatory difficulties, and social isolation. Numerous previous studies have identified various risk factors and reported on the treatment and prevention of PJK. Based on these studies, we determined the clinical significance and impact of PJK. In addition, it is important to find a strategic approach to the proper treatment of PJK.

Perioperative Medical Management of Spine Surgery Patients With Osteoporosis

Management of spine surgery patients with osteoporosis is challenging because of the difficulty of instrumenting and the potential complications, including nonunion and adjacent level fractures. Treatment of this patient population should involve a multidisciplinary approach including the spine surgeon, primary care physician, endocrinologist, and physical therapist. Indication for preoperative treatment before spinal fusion surgery is unclear. All patients should receive calcium and vitamin D. Hormone replacement therapy, including estrogen or selective estrogen receptor modulators, should be considered for elderly female patients with decreased bone mass. Bisphosphonates or intermittent parathyroid hormone are reserved for those with significant bone loss in the spine. Pretreatment with antiresorption medications affect bone remodeling, which is a vital part of graft incorporation and fusion. Although there have been numerous animal studies, there is limited clinical evidence. Accordingly, surgery should be delayed, if possible, to treat the osteoporosis before the intervention. Treatment may include bisphosphonates, as well as newer agents, such as recombinant parathyroid hormone. Further clinical data are needed to understand the relative advantages/disadvantage of antiresorptive vs anabolic agents, as well as the impact of administration of these medications before vs after fusion surgery. Future clinical studies will enable better understanding of the impact of current therapies on biomechanics and fusion outcomes in this unique and increasingly prevalent patient population.

Enhancement of Lumbar Fusion and Alleviation of Adjacent Segment Disc Degeneration by Intermittent PTH(1-34) in Ovariectomized Rats

Osteoporosis, which is prevalent in postmenopausal or aged populations, is thought to be a contributing factor to adjacent segment disc degeneration (ASDD), and the incidence and extent of ASDD may be augmented by osteopenia. Parathyroid hormone (PTH) (1-34) has already been shown to be beneficial in osteoporosis, lumbar fusion and matrix homeostasis of intervertebral discs. However, whether PTH(1-34) has a reversing or retarding effect on ASDD in osteopenia has not been confirmed. In the present study, we evaluated the effects of intermittent PTH(1-34) on ASDD in an ovariectomized (OVX) rat model. One hundred 3-month-old female Sprague-Dawley rats underwent L4 -L5 posterolateral lumbar fusion (PLF) with spinous-process wire fixation 4 weeks after OVX surgery. Control groups were established accordingly. PTH(1-34) was intermittently administered immediately after PLF surgery and lasted for 8 weeks using the following groups (n = 20) (V = vehicle): Sham+V, OVX+V, Sham+PLF+V, OVX+PLF+V, OVX+PLF+PTH. The fused segments showed clear evidence of eliminated motion on the fusion-segment based on manual palpation. Greater new bone formation in histology was observed in PTH-treated animals compared to the control group. The extent of ASDD was significantly increased by ovariotomy. Intermittent PTH(1-34) significantly alleviated ASDD by preserving disc height, microvessel density, relative area of vascular buds, endplate thickness and the relative area of endplate calcification. Moreover, protein expression results showed that PTH(1-34) not only inhibited matrix degradation by decreasing MMP-13, ADAMTS-4 and Col-I, but also promote matrix synthesis by increasing Col-II and Aggrecan. In conclusion, PTH(1-34), which effectively improves lumbar fusion and alleviates ASDD in ovariectomized rats, may be a potential candidate to ameliorate the prognosis of lumbar fusion in osteopenia.

Prevalence of Poor Bone Quality in Women Undergoing Spinal Fusion Using Biomechanical-CT Analysis

STUDY DESIGN

Retrospective, cross-sectional analysis of vertebral bone quality in spine-fusion patients at a single medical center.

OBJECTIVE

To characterize the prevalence of osteoporosis and fragile bone strength in a spine-fusion population of women with an age range of 50 years to 70 years. Fragile bone strength is defined as the level of vertebral strength below which a patient is at as high a risk of future vertebral fracture as a patient having bone density-defined osteoporosis.

SUMMARY OF BACKGROUND DATA

Poor bone quality--defined here as the presence of either osteoporosis or fragile bone strength--is a risk factor for spine-fusion patients that often goes undetected but can now be assessed preoperatively by additional postprocessing of computed tomography (CT) scans originally ordered for perioperative clinical assessment.

METHODS

Utilizing such perioperative CT scans for a cohort of 98 women (age range: 51-70 yr) about to undergo spine fusion, we retrospectively used a phantomless calibration technique and biomechanical-CT postprocessing analysis to measure vertebral trabecular bone mineral density (BMD) (in mg/cm³) and by nonlinear finite element analysis, vertebral compressive strength (in Newtons, N) in the L1 or L2 vertebra. Preestablished validated threshold values were used to define the presence of osteoporosis (trabecular BMD of 80 mg/cm³ or lower) and fragile bone strength (vertebral strength of 4500 N or lower).

RESULTS

Fourteen percent of the women tested positive for osteoporosis, 27% tested positive for fragile bone strength, and 29% were classified as having poor bone quality (either osteoporosis or fragile bone strength). Over this narrow age range, neither BMD nor vertebral strength were significantly correlated with age, weight, height, or body mass index (P values 0.14-0.97 for BMD; 0.13-0.51 for strength).

CONCLUSION

Poor bone quality appears to be common in women between ages 50 years and 70 years undergoing spinal fusion surgery.

LEVEL OF EVIDENCE

3.

Transforaminal Lumbar Interbody Fusion for Lumbar Degenerative Disorders: Mini-open TLIF and Corrective TLIF

Minimally invasive transforaminal lumbar interbody fusion (TLIF) as a short fusion is widely accepted among the spine surgeons. However in the long fusion for degenerative kyphoscoliosis, corrective spinal fixation by an open method is thought to be frequently selected. Our objective is to study whether the mini-open TLIF and corrective TLIF contribute to the improvement of the spinal segmental and global alignment. We divided the patients who performed lumbar fixation surgery into three groups. Group 1 (G1) consisted of mini-open TLIF procedures without complication. Group 2 (G2) consisted of corrective TLIF without complication. Group 3 (G3) consisted of corrective TLIF with instrumentation-related complication postoperatively. In all groups, the lumbar lordosis (LL) highly correlated with developing surgical complications. LL significantly changed postoperatively in all groups, but was not corrected in the normal range in G3. There were statistically significant differences in preoperative and postoperative LL and mean difference between the pelvic incidence (PI) and LL between G3 and other groups. The most important thing not to cause the instrumentation-related failure is proper correction of the sagittal balance. In the cases with minimal sagittal imbalance with or without coronal imbalance, short fusion by mini-open TLIF or long fusion by corrective TLIF contributes to good clinical results if the lesion is short or easily correctable. However, if the patients have apparent sagittal imbalance with or without coronal imbalance, we should perform proper correction of the sagittal spinal alignment introducing various technologies.

Management of osteoporosis in spine surgery

Osteoporosis is a burgeoning clinical problem that is characterized by decreased bone strength and density. It predisposes patients to fragility fractures and debilitating spine deformities. Several complications are associated with spine surgery in patients with osteoporosis, and there is currently no treatment algorithm to guide the spine surgeon. A multidisciplinary approach to treatment of patients with osteoporosis and spine deformity or fracture is encouraged, and preoperative planning is crucial for successful surgical outcomes. Several surgical techniques have been developed to treat osteoporosis-related deformities, including posterior instrumentation with fusion. However, achieving fixation and fusion in these patients can be difficult secondary to poor bone stock. Augmentation methods to improve pedicle screw fixation have evolved, including instrumentation at multiple levels, bioactive cement augmentation, and fenestrated or expandable pedicle screws, but their impact on clinical outcomes remains unknown. Management of osteoporosis in patients undergoing spine surgery is challenging, but with appropriate patient selection, medical optimization, and surgical techniques, these patients can experience pain relief, deformity correction, and improved function.

Commentary: Intermittent teriparatide enhancement of bone graft healing in a rat model of spinal glucocorticoid-induced osteoporosis

Sugiura T, Kashii M, Matsuo Y, Morimoto T, Honda H, Kaito T, et al. Intermittent administration of teriparatide enhances graft bone healing and accelerates spinal fusion in rats with glucocorticoid-induced osteoporosis. Spine J 2015;15:298-306 (in this issue).

Micro CT Analysis of Spine Architecture in a Mouse Model of Scoliosis

OBJECTIVE

Mice homozygous for targeted deletion of the gene encoding fibroblast growth factor receptor 3 (FGFR3(-/-)) develop kyphoscoliosis by 2 months of age. The first objective of this study was to use high resolution X-ray to characterize curve progression in vivo and micro CT to quantify spine architecture ex vivo in FGFR3(-/-) mice. The second objective was to determine if slow release of the bone anabolic peptide parathyroid hormone related protein (PTHrP-1-34) from a pellet placed adjacent to the thoracic spine could inhibit progressive kyphoscoliosis.

MATERIALS AND METHODS

Pellets loaded with placebo or PTHrP-1-34 were implanted adjacent to the thoracic spine of 1-month-old FGFR3(-/-) mice obtained from in house breeding. X rays were captured at monthly intervals up to 4 months to quantify curve progression using the Cobb method. High resolution post-mortem scans of FGFR3(-/-) and FGFR3(+/+) spines, from C5/6 to L4/5, were captured to evaluate the 3D structure, rotation, and micro-architecture of the affected vertebrae. Un-decalcified and decalcified histology were performed on the apical and adjacent vertebrae of FGFR3(-/-) spines, and the corresponding vertebrae from FGFR3(+/+) spines.

RESULTS

The mean Cobb angle was significantly greater at all ages in FGFR3(-/-) mice compared with wild type mice and appeared to stabilize around skeletal maturity at 4 months. 3D reconstructions of the thoracic spine of 4-month-old FGFR3(-/-) mice treated with PTHrP-1-34 revealed correction of left/right asymmetry, vertebral rotation, and lateral displacement compared with mice treated with placebo. Histologic analysis of the apical vertebrae confirmed correction of the asymmetry in PTHrP-1-34 treated mice, in the absence of any change in bone volume, and a significant reduction in the wedging of intervertebral disks (IVD) seen in placebo treated mice.

CONCLUSION

Local treatment of the thoracic spine of juvenile FGFR3(-/-) mice with a bone anabolic agent inhibited progression of scoliosis, but with little impact on kyphosis. The significant improvement in IVD integrity suggests PTHrP-1-34 might also be considered as a therapeutic agent for degenerative disk disorders.

Proximal junctional kyphosis following adult spinal deformity surgery

PURPOSE

Proximal junctional kyphosis (PJK) is a common radiographic finding following long spinal fusions. Whether PJK leads to negative clinical outcome is currently debatable. A systematic review was performed to assess the prevalence, risk factors, and treatments of PJK.

METHODS

Literature search was conducted on PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials using the terms 'proximal junctional kyphosis' and 'proximal junctional failure'. Excluding reviews, commentaries, and case reports, we analyzed 33 studies that reported the prevalence rate, risk factors, and discussions on PJK following spinal deformity surgery.

RESULTS

The prevalence rates varied widely from 6 to 61.7%. Numerous studies reported that clinical outcomes for patients with PJK were not significantly different from those without, except in one recent study in which adult patients with PJK experienced more pain. Risk factors for PJK included age at operation, low bone mineral density, shorter fusion constructs, upper instrumented vertebrae below L2, and inadequate restoration of global sagittal balance.

CONCLUSIONS

Prevalence of PJK following long spinal fusion for adult spinal deformity was high but not clinically significant. Careful and detailed preoperative planning and surgical execution may reduce PJK in adult spinal deformity patients.

Impact of initial conservative treatment interventions on the outcomes of patients with osteoporotic vertebral fractures

STUDY DESIGN

Prospective multicenter study.

OBJECTIVE

To examine whether initial conservative treatment interventions for osteoporotic vertebral fractures (OVF) influence patient outcomes.

SUMMARY OF BACKGROUND DATA

OVFs have been described as stable spinal injuries and, in most cases, are managed well with conservative treatment. However, systematic treatments for OVF have not been clearly established.

METHODS

A total of 362 patients with OVF (59 males and 303 females; mean age, 76.3 yr) from 25 institutes were enrolled in this clinical study. All the patients were treated conservatively without any surgical interventions. The patient outcomes were evaluated 6 months after the fractures on the basis of Short Form-36 (SF-36) physical component summary (PCS) and mental component summary (MCS), activities of daily living (the Japanese long-term care insurance system), back pain (visual analogue scale), cognitive status (mini-mental state examination), and vertebral collapse, which were used as response variables. Furthermore, brace type, hospitalization, bisphosphonates after injury, and painkillers after injury were explanatory variables for the treatment interventions. To evaluate the independent effects of treatment interventions on patient outcomes, we performed multivariate logistic regression analyses and obtained odds ratios that were adjusted for the potential confounding effects of age, sex, level of fracture, presence of middle-column injury, pain visual analogue scale at enrollment, mini-mental state examination score at enrollment, and previous use of steroids.

RESULTS

There was no significant difference for treatment intervention factors including brace type, hospitalization, bisphosphonates after injury, and painkillers after injury. For adjusting factors, the presence of middle-column injury was significantly associated with SF-36 PCS ≤ 40, reduced activities of daily living, prolonged back pain, and vertebral collapse. Female sex and advanced age were associated with SF-36 PCS ≤ 40. Low mini-mental state examination scores at enrollment were associated with SF-36 PCS ≤ 40 and reduced activities of daily living. The previous use of steroids was associated with SF-36 MCS ≤ 40, prolonged back pain, and vertebral collapse. No other examined variables were significant risk factors for patient outcomes.

CONCLUSION

These results showed that treatment intervention factors did not affect patient outcomes 6 months after OVF. Middle-column injury was a significant risk factor for both clinical and radiological outcomes. In the future, establishing systematic treatments for cases with middle-column injuries is needed.

LEVEL OF EVIDENCE

2.