Prediction of osteoporotic spinal deformity

The influence of osteoporosis on mechanical complications in lumbar fusion surgery: a systematic review

Background

Adults undergoing spine surgery often have underlying osteoporosis, which may be a risk factor for postoperative complications. Although these associations have been described, osteoporosis remains profoundly underdiagnosed and undertreated in the spine surgery population. A thorough, comprehensive systematic review summarizing the relationships between bone mineral density (BMD) and specific complications of lumbar fusion surgery could be a valuable resource for raising awareness and supporting clinical practice changes.

Methods

PubMed, Embase, and Web of Science databases were searched for original clinical research articles reporting on BMD, or surrogate measure, as a predictor of complications in adults undergoing elective lumbar fusion for degenerative disease or deformity. Endpoints included cage subsidence, screw loosening, pseudarthrosis, vertebral fracture, junctional complications, and reoperation.

Results

A total of 71 studies comprising 12,278 patients were included. Overall, considerable heterogeneity in study populations, methods of bone health assessment, and definition and evaluation of clinical endpoints precluded meta-analysis. Nevertheless, low BMD was associated with higher rates of implant failures like cage subsidence and screw loosening, which were often diagnosed with concomitant pseudarthrosis. Osteoporosis was also a significant risk factor for proximal junctional kyphosis, particularly due to fracture. Many studies found surgical site-specific BMD to best predict focal complications. Functional outcomes were inconsistently addressed.

Conclusions

Our findings suggest osteoporosis is a significant risk factor for mechanical complications of lumbar fusion. These results emphasize the importance of preoperative osteoporosis screening, which allows for medical and surgical optimization of high-risk patients. This review also highlights current practical challenges facing bone health evaluation in patients undergoing elective surgery. Future prospective studies using standardized methods are necessary to strengthen existing evidence, identify optimal predictive thresholds, and establish specialty-specific practice guidelines. In the meantime, an awareness of the surgical implications of osteoporosis and utility of preoperative screening can provide for more informed, effective patient care.

Comparison of the predictive values of MRI-based vertebral bone quality scores for the determination of osteoporosis in different diseases

PURPOSE

The study aimed to examine the consistency of vertebral bone quality (VBQ) scores for assessing osteoporosis across different etiologies and explore the predictive value of various VBQ scores for fragility vertebral fractures.

METHODS

Patients with fragility fractures were matched by age and sex to patients with lumbar degeneration. VBQ scores were calculated in T1- and T2-weighted magnetic resonance imaging. Differential analysis of bone quality was performed based on etiology.

RESULTS

A total of 96 inpatients were retrospectively enrolled. VBQT1 scores were only sensitive to osteoporotic bone in degenerative group (p < 0.01), failing to identify osteoporosis in fractured group (p > 0.05). For the degenerative group, the area under the curve (AUC) using the VBQT1 scores to differentiate osteoporosis was 0.72. After controlling the confounding variables, only VBQT2 scores were significantly higher in fractured group than degenerative group, with a greater AUC of 0.82 predicting fragility fractures. VBQT1 scores moderately correlated with femoral neck T-scores in degenerative group (r = -0.45, p < 0.01) but not in fractured group (r = -0.24, p > 0.05). VBQT2 scores were not associated with femoral neck T-scores (p > 0.05).

CONCLUSION

This study is the first to evaluate the effectiveness of VBQs scores in assessing osteoporosis post-fracture. Only non-fractured patients' bone quality is fully susceptible to VBQT1 scores. While VBQT1 scores may not correlate with fragility fractures, VBQT2 scores present a viable alternative.

Osteoporosis and Vertebral Column

Background

Osteoporosis is an age-related metabolic disease which has a significant impact on bone health and overall quality of life. It is gaining importance as a major medical consideration with the rapid increase in geriatric population globally. It increases the risk of vertebral fractures, progressive spinal deformities and neurological complications, contributing significantly to morbidity and mortality. Increase in life expectancy and advancement of medical technology has led to an increase in the proportion of geriatric patients undergoing orthopaedic procedures. It is becoming vital to adequately evaluate, investigate and treat osteoporosis before planning spinal surgery, especially spinal fusions and instrumentation.

Content

Historically, osteoporosis was considered a contraindication to spine surgery adding to the burden of Disability Adjusted Life Years (DALYs) and mortality. Conversely, osteoporotic patients who underwent spine surgery were not adequately optimized, leading to an increase in failure and complication rates. Better understanding of the pathophysiology of osteoporosis and the biomechanics of an osteoporotic spine with knowledge of current standards of treatment of osteoporosis facilitate the timely and adequate management of this disease. Advances in surgical and anaesthetic techniques facilitate successful surgeries on high-risk elderly and osteoporotic patients with multiple comorbidities allowing for a significantly high predictability for long-term positive outcomes.This article discusses the biomechanics of the osteoporotic spine, the diagnosis and management of osteoporotic patients with spinal disease, and the new treatments, recommendations, surgical indications, strategies and advances in instrumentation in patients with osteoporosis who require spinal surgery.

Implications

In this article, the authors aim to provide a generalized overview for better understanding of the pathophysiological processes underlying osteoporosis in the vertebral column. This review provides a comprehensive set of guidelines for overall health and management of spine patients with pathologies, either caused by or compounded with osteoporosis. An overview of current techniques, strategies and technologies designed to address the challenges associated with spine surgery in osteoporotic patients is also outlined.

Sources

Content for this article has been sourced from routinely cited articles available via PubMed, from National Institute of Health consensus development conference, from the recommendations by World Health Organization technical report series, from previous articles by the authors and from the protocols established by the authors in their clinical practice based on experience and detailed case reviews.

Type 2 diabetes alters the viscoelastic behavior and macromolecular composition of vertebra

Type 2 diabetes (T2D) affects the functional behavior of vertebra bone by altering its structural and mechanical properties. The vertebral bones are responsible to carry the body weight and it remains under prolonged constant load which results to viscoelastic deformation. The effect of T2D on the viscoelastic behavior of vertebral bone is not well explored yet. In this study, the effects of T2D on the creep and stress relaxation behavior of vertebral bone are investigated. Also, this study established a correlation between T2D associated alteration in macromolecular structure and viscoelastic behavior of vertebra. In this study T2D female rat SD model was used. The obtained results demonstrated a significant reduction in the amount of creep strain (p ≤ 0.05) and stress relaxation (p ≤ 0.01) in T2D specimens than the control. Also, the creep rate was found significantly lower in T2D specimens. On the other hand, molecular structural parameters such as mineral-to-matrix ratio (control vs T2D: 2.93 ± 0.78 vs 3.72 ± 0.53; p = 0.02), and non-enzymatic cross link ratio (NE-xL) (control vs T2D: 1.53 ± 0.07 vs 3.84 ± 0.20; p = 0.01) were found significantly altered in T2D specimens. Pearson linear correlation tests show a significant correlation; between creep rate and NE-xL (r = -0.94, p < 0.01), and between stress relaxation and NE-xL (r = -0.946, p < 0.01). Overall this study explored the understanding about the disease associated alteration in viscoelastic response of vertebra and its correlation with macromolecular composition which can help to understand the disease related impaired functioning of the vertebrae body.

The role of bone metastases on the mechanical competence of human vertebrae

Spine is the most common site for bone metastases. The evaluation of the mechanical competence and failure location in metastatic vertebrae is a biomechanical and clinical challenge. Little is known about the failure behaviour of vertebrae with metastatic lesions. The aim of this study was to use combined micro-Computed Tomography (microCT) and time-lapsed mechanical testing to reveal the failure location in metastatic vertebrae. Fifteen spine segments, each including a metastatic and a radiologically healthy vertebra, were tested in compression up to failure within a microCT. Volumetric strains were measured using Digital Volume Correlation. The images of undeformed and deformed specimens were overlapped to identify the failure location. Vertebrae with lytic metastases experienced the largest average compressive strains (median ± standard deviation: -8506 ± 4748microstrain), followed by the vertebrae with mixed metastases (-7035 ± 15605microstrain), the radiologically healthy vertebrae (-5743 ± 5697microstrain), and the vertebrae with blastic metastases (-3150 ± 4641microstrain). Strain peaks were localised within and nearby the lytic lesions or around the blastic tissue. Failure between the endplate and the metastasis was identified in vertebrae with lytic metastases, whereas failure localised around the metastasis in vertebrae with blastic lesions. This study showed for the first time the role of metastases on the vertebral internal deformations. While lytic lesions lead to failure of the metastatic vertebra, vertebrae with blastic metastases are more likely to induce failure in the adjacent vertebrae. Nevertheless, every metastatic lesion affects the vertebral deformation differently, making it essential to assess how the lesion affects the bone microstructure. These results suggest that the properties of the lesion (type, size, location within the vertebral body) should be considered when developing clinical tools to predict the risk of fracture in patients with metastatic lesions.

An Investigation of the Association between 3D Spinal Alignment and Fibromyalgia

Fibromyalgia syndrome (FMS) is a common condition lacking strong diagnostic criteria; these criteria continue to evolve as more and more studies are performed to explore it. This investigation sought to identify whether participants with FMS have more frequent and larger postural/spinal displacements in comparison to a matched control group without the condition of FMS. A total of 67 adults (55 females) out of 380 participants with FMS were recruited. Participants with FMS were sex- and age-matched with 67 asymptomatic participants (controls) without FMS. We used a three-dimensional (3D) postural assessment device (Formetric system) to analyze five posture variables in each participant in both groups: (1) thoracic kyphotic angle, (2) trunk imbalance, (3) trunk inclination, (4) lumbar lordotic angle, and (5) vertebral rotation. In order to determine whether 3D postural measures could predict the likelihood of a participant having FMS, we applied the matched-pairs binary logistic regression analysis. The 3D posture measures identified statistically and clinically significant differences between the FMS and control groups for each of the five posture variables measured (p < 0.001). For three out of five posture measurements assessed, the binary logistic regression identified there was an increased probability of having FMS with an increased: (1) thoracic kyphotic angle proportional odds ratio [Prop OR] = 1.76 (95% CI = 1.03, 3.02); (2) sagittal imbalance Prop OR = 1.54 (95% CI = 0.973, 2.459); and (3) surface rotation Prop OR = 7.9 (95% CI = 1.494, 41.97). We identified no significant probability of having FMS for the following two postural measurements: (1) coronal balance (p = 0.50) and (2) lumbar lordotic angle (p = 0.10). Our study’s findings suggest there is a strong relationship between 3D spinal misalignment and the diagnosis of FMS. In fact, our results support that thoracic kyphotic angle, sagittal imbalance, and surface rotation are predictors of having FMS.

Osteoporosis in Indian Patients Undergoing Elective Arthroplasty and Spinal Procedures: An Observational Study

Background This is an observational study conducted to determine the prevalence of osteoporosis and osteopenia in patients undergoing elective arthroplasty and spinal procedures in India. Methods This observational, multicentre study included both male and female patients. Their bone mineral density and fracture risk were measured using dual-energy x-ray absorptiometry (DEXA) and Fracture Risk Assessment Tool (FRAX®: Centre for Metabolic Bone Diseases, University of Sheffield, UK), respectively, in compliance with the guidelines for Good Epidemiological Practice (ISRCTN: 14543098). Results The study revealed that majority (76.4%; 97/127) of the patients had low BMD; over one-third had osteoporosis (39.4%; 50/127) or osteopenia (37%; 47/127). Among those undergoing total knee replacement (TKR)/total hip replacement (THR), majority (75.6%; 59/78) had low BMD (osteoporosis: 38.5% {30/78}; osteopenia: 37.2% {29/78}). Among the patients undergoing spinal procedures, all except two (93.10%; 27/29) had low BMD, two-thirds had osteoporosis (65.5%; 19/29), and around one-fourth had osteopenia (27.6%; 8/29). Radial BMD measurements showed higher prevalence of osteoporosis and osteopenia. Based on FRAX score, nearly 30% of patients were at a high risk of hip fracture in the next 10 years. As per National Osteoporosis Foundation (NOF) guidelines, most (59.79%; 58/97) patients with osteoporosis/osteopenia met criteria for pharmacological treatment. Conclusions Regular preoperative bone health evaluation should be adopted and osteoporosis/osteopenia patients should be adequately managed pharmacologically in India.

Monitoring scoliosis and other spinal deformity surgeries

Surgery to correct a spinal deformity incurs a risk of injury to the spinal cord and roots. Injuries include postoperative paraplegia. Surgery for cervical myelopathy also incurs risk for postoperative motor deficits, as well as nerve injury most commonly at the C5 root. Risks can be mitigated by monitoring the nervous system during surgery. Ideally, monitoring detects an impending injury in time to intervene and correct the impairment before it becomes permanent. Monitoring includes several modalities of testing. Somatosensory evoked potentials measure axonal conduction in the spinal cord posterior columns. This can be checked almost continuously during surgery. Motor evoked potentials measure conduction along the lateral corticospinal tracts. Because motor pathway stimulation often produces a patient movement on the table, these often are tested periodically rather than continuously. Electromyography observes for spontaneous discharges accompanying injuries, and is useful to assess misplacement of pedicle screws. Literature demonstrates the usefulness of these techniques, their association with reducing motor adverse outcomes, and the relative value of the techniques. Neurophysiologic monitoring for scoliosis, kyphosis, and cervical myelopathy surgery are addressed, along with background information about those conditions.

A Progressive Paraplegic Patient with Thalassemia Because of Extramedullary Hematopoiesis and Vertebral Fracture: A Case Report

CASE

We present a case of progressive paraplegia because of extramedullary hematopoiesis and pathological vertebral fracture in thalassemia patient. The various surgical techniques including larger pedicle screws, bicortical fixation, and convergent direction to improve pullout strength had been used secondary to osteoporotic bone and kyphotic deformity.

CONCLUSION

Prompt diagnosis and awareness of the compromised bone quality of the thalassemic patient is essential to guide the proper management and produce the desire outcomes.

Diagnostic, Surgical, and Technical Considerations for Lumbar Interbody Fusion in Patients with Osteopenia and Osteoporosis: A Systematic Review

Objective: Osteoporosis is increasing in incidence as the ageing population continues to grow. Decreased bone mineral density poses a challenge for the spine surgeon. In patients requiring lumbar interbody fusion, differences in diagnostics and surgical approaches may be warranted. In this systematic review, the authors examine studies performing lumbar interbody fusion in patients with osteopenia or osteoporosis and suggest avenues for future study. Methods: A systematic literature review of the PubMed and MEDLINE databases was performed for studies published between 1986 and 2020. Studies evaluating diagnostics, surgical approaches, and other technical considerations were included. Results: A total of 13 articles were ultimately selected for qualitative analysis. This includes studies demonstrating the utility of Hounsfield units in diagnosis, a survey of surgical approaches, as well as exploring the use of vertebral augmentation and cortical bone screw trajectory. Conclusions: This systematic review provides a summary of preliminary findings with respect to the use of Hounsfield units as a diagnostic tool, the benefit or lack thereof with respect to minimally invasive approaches, and the question of whether or not cement augmentation or cortical bone trajectory confers benefit in osteoporotic patients undergoing lumbar interbody fusion. While the findings of these studies are promising, the current state of the literature is limited in scope and, for this reason, definitive conclusions cannot be drawn from these data. The authors highlight gaps in the literature and the need for further exploration and study of lumbar interbody fusion in the osteoporotic spine.

Risk factors for subsequent vertebral fracture after acute osteoporotic vertebral fractures

PURPOSE

To investigate the incidence and characteristics of subsequent vertebral fracture after osteoporotic vertebral fractures (OVFs) and identify risk factors for subsequent vertebral fractures.

METHODS

This post-hoc analysis from a prospective randomized multicenter trial included 225 patients with a 48-week follow-up period. Differences between the subsequent and non-subsequent fracture groups were analyzed.

RESULTS

Of the 225 patients, 15 (6.7%) had a subsequent fracture during the 48-week follow-up. The annual incidence of subsequent vertebral fracture after fresh OVFs in women aged 65-85 years was 68.8 per 1000 person-years. Most patients (73.3%) experienced subsequent vertebral fractures within 6 months. At 48 weeks, European Quality of Life-5 Dimensions, the Japanese Orthopedic Association Back Pain Evaluation Questionnaire pain-related disorder, walking ability, social life function, and lumbar function scores were significantly lower, while the visual analog scale (VAS) for low back pain was higher in patients with subsequent fracture. Cox proportional hazards analysis showed that a VAS score ≥ 70 at 0 weeks was an independent predictor of subsequent vertebral fracture. After adjustment for history of previous fracture, there was a ~ 67% reduction in the risk of subsequent vertebral fracture at the rigid-brace treatment.

CONCLUSION

Women with a fresh OVF were at higher risk for subsequent vertebral fracture within the next year. Severe low back pain and use of soft braces were associated with higher risk of subsequent vertebral fractures. Therefore, when treating patients after OVFs with these risk factors, more attention may be needed for the occurrence of subsequent vertebral fractures.

LEVEL OF EVIDENCE

III.

The methods for inserting lumbar bicortical pedicle screws from the anatomical perspective of the prevertebral great vessels

BACKGROUND

At present, bicortical pedicle screws (BPSs) are not used clinically because they carry the potential risk of damaging the prevertebral great vessels (PGVs). The authors observed the anatomical relationship between the PGVs and simulated BPSs at different transverse screw angles (TSAs), exploring the insertion method of the BPS.

METHODS

Computed tomography angiography (CTA) images from 65 adults were collected. A total of 4-5 TSAs of the BPSs were simulated on the left and right sides of L1-L5 (L1-L3: 0°, 5°, 10°, 15°; L4-L5: 0°, 5°, 10°, 15°, 20°). There were three types of distances from the anterior vertebral cortex (AVC) to the PGVs (D_AVC-PGV); D_{AVC-PGV < 0.50 cm}, D_{AVC-PGV ≥ 0.50 cm}, and D_AVC-PGV↑; these distances represented close, distant, and noncontact PGV, respectively.

RESULTS

The ratio of every type of PGV was calculated, and the appropriate TSA of the BPS was recommended. In L1, the recommended left TSA of the BPS was 0°, and the ratio of the close PGV was 7.69%, while the recommended right TSA was 0°-10°, and the ratio of the close PGV was 1.54-4.62%. In L2, the recommended left TSA of the BPS was 0° and the ratio of the close PGV was 1.54%, while the recommended right TSA was 0°-15° and the ratio of the close PGV was 3.08-9.23%. In L3, the recommended left TSA was 0°-5°, and the ratio of the close PGV was 1.54-4.62%. In L4, the recommended left TSA was 0°, and the ratio of the close PGV was 4.62%. BPS use was not recommended on the right side of either L3 or L4 or on the either side of L5.

CONCLUSIONS

From the anatomical perspective of the PGVs, BPSs were not suitable for insertion into every lumbar vertebra. Furthermore, the recommended methods for inserting BPSs were different in L1-L4.

Finite Element Method Analysis of Compression Fractures on Whole-Spine Models Including the Rib Cage

Spinal compression fractures commonly occur at the thoracolumbar junction. We have previously constructed a 3-dimensional whole-spine model from medical images by using the finite element method (FEM) and then used this model to develop a compression fracture model. However, these models lacked the rib cage. No previous study has used whole-spine models including the rib cage constructed from medical images to analyze compression fractures. Therefore, in this study, we added the rib cage to whole-spine models. We constructed the models, including a normal spine model without the rib cage, a whole-spine model with the rib cage, and whole-spine models with compression fractures, using FEM analysis. Then, we simulated a person falling on the buttocks to perform stress analysis on the models and to examine to what extent the rib cage affects the analysis of compression fractures. The results showed that the intensity of strain and the vertebral body with minimum principle strain differed between the spine model including the rib cage and that excluding the rib cage. The strain on the spine model excluding the rib cage had approximately twice the intensity of the strain on the spine model including the rib cage. Therefore, the rib cage contributed to the stability of the thoracic spine, thus preventing deformation of the upper thoracic spine. However, the presence of the rib cage increased the strain around the site of compression fracture, thus increasing the possibilities of a refracture and fractures of adjacent vertebral bodies. Our study suggests that the analysis using spine models including the rib cage should be considered in future investigations of disorders of the spine and internal fracture fixation. The development of improved models may contribute to the improvement of prognosis and treatment of individual patients with disorders of the spine.

The CBP® mirror image® approach to reducing thoracic hyperkyphosis: a retrospective case series of 10 patients

[Purpose] To present a case series demonstrating the reduction of thoracic hyperkyphosis by the Chiropractic BioPhysics^® multimodal rehabilitation program. [Participants and Methods] Ten randomly selected files and corresponding radiographs were chosen from recent clinic archives of patients who were treated for thoracic hyperkyphosis. All patients were treated by CBP mirror image^® thoracic extension traction and exercises, as well as spinal manipulative therapy. [Results] Results demonstrated an average reduction in hyperkyphosis of 11.3° over an average of 25 treatments, over an average of 9 weeks. Patients also experienced a reduction in pain levels and disability ratings. [Conclusion] Postural hyperkyphosis is a serious progressive deformity that is related to a plethora of symptoms, syndromes, and early death. Thoracic hyperkyphosis may be reduced/corrected by posture-specific, thoracic extension protocols including mirror image extension traction and exercises, as well as spinal manipulation as part of the CBP multi-modal rehabilitation program.

X-Ray Imaging is Essential for Contemporary Chiropractic and Manual Therapy Spinal Rehabilitation: Radiography Increases Benefits and Reduces Risks

To remedy spine-related problems, assessments of X-ray images are essential to determine the spine and postural parameters. Chiropractic/manual therapy realignment of the structure of the spine can address a wide range of pain, muscle weakness, and functional impairments. Alternate methods to assess such spine problems are often indirect and do not reveal the root cause and could result in a significant misdiagnosis, leading to inappropriate treatment and harmful consequences for the patient. Radiography reveals the true condition and alignment of the spine; it eliminates guesswork. Contemporary approaches to spinal rehabilitation, guided by accurate imaging, have demonstrated superiority over primitive treatments. Unfortunately, there are well-meaning but misguided activists who advocate elimination or minimization of exposures in spine radiography. The radiation dose employed for a plain radiograph is very low, about 100 times below the threshold dose for harmful effects. Rather than increasing risk, such exposures would likely stimulate the patient’s own protection systems and result in beneficial health effects. Spine care guidelines need to be revised to reflect the potential benefits of modern treatments and the lack of health risks from low X-ray doses. This would encourage routine use of radiography in manual spine therapy, which differs from common pharmacologic pain relief practice.

A retrospective analysis of bone mineral status in patients requiring spinal surgery

Background

Impaired bone quality is associated with poor outcome of spinal surgery. The aim of the study was to assess the bone mineral status of patients scheduled to undergo spinal surgery and to report frequencies of bone mineral disorders.

Methods

We retrospectively analyzed the bone mineral status of 144 patients requiring spinal surgery including bone mineral density by dual-energy X-ray absorptiometry (DXA) as well as laboratory data with serum levels of 25-hydroxyvitamin D (25-OH-D), parathyroid hormone, calcium, bone specific alkaline phosphate, osteocalcin, and gastrin. High-resolution peripheral quantitative computed tomography (HR-pQCT) was additionally performed in a subgroup of 67 patients with T-Score below − 1.5 or history of vertebral fracture.

Results

Among 144 patients, 126 patients (87.5%) were older than 60 years. Mean age was 70.1 years. 42 patients (29.1%) had suffered from a vertebral compression fracture. 12 previously undiagnosed vertebral deformities were detected in 12 patients by vertebral fracture assessment (VFA). Osteoporosis was present in 39 patients (27.1%) and osteopenia in 63 patients (43.8%). Only 16 patients (11.1%) had received anti-osteoporotic therapy, while 54 patients (37.5%) had an indication for specific anti-osteoporotic therapy but had not received it yet. The majority of patients had inadequate vitamin D status (73.6%) and 34.7% of patients showed secondary hyperparathyroidism as a sign for a significant disturbed calcium homeostasis. In a subgroup of 67 patients, severe vertebral deformities were associated with stronger deficits in bone microarchitecture at the distal radius compared to the distal tibia.

Conclusions

This study shows that bone metabolism disorders are highly prevalent in elderly patients scheduled for spinal surgery. Vertebral deformities are associated with a predominant deterioration of bone microstructure at the distal radius. As impaired bone quality can compromise surgical outcome, we strongly recommend an evaluation of bone mineral status prior to operation and anti-osteoporotic therapy if necessary.

A model-based approach for estimation of changes in lumbar segmental kinematics associated with alterations in trunk muscle forces

The kinematics information from imaging, if combined with optimization-based biomechanical models, may provide a unique platform for personalized assessment of trunk muscle forces (TMFs). Such a method, however, is feasible only if differences in lumbar spine kinematics due to differences in TMFs can be captured by the current imaging techniques. A finite element model of the spine within an optimization procedure was used to estimate segmental kinematics of lumbar spine associated with five different sets of TMFs. Each set of TMFs was associated with a hypothetical trunk neuromuscular strategy that optimized one aspect of lower back biomechanics. For each set of TMFs, the segmental kinematics of lumbar spine was estimated for a single static trunk flexed posture involving, respectively, 40° and 10° of thoracic and pelvic rotations. Minimum changes in the angular and translational deformations of a motion segment with alterations in TMFs ranged from 0° to 0.7° and 0 mm to 0.04 mm, respectively. Maximum changes in the angular and translational deformations of a motion segment with alterations in TMFs ranged from 2.4° to 7.6° and 0.11 mm to 0.39 mm, respectively. The differences in kinematics of lumbar segments between each combination of two sets of TMFs in 97% of cases for angular deformation and 55% of cases for translational deformation were within the reported accuracy of current imaging techniques. Therefore, it might be possible to use image-based kinematics of lumbar segments along with computational modeling for personalized assessment of TMFs.

Biomechanical Evaluation of Cross Trajectory Technique for Pedicle Screw Insertion: Combined Use of Traditional Trajectory and Cortical Bone Trajectory

OBJECTIVE

To introduce a novel double-screw (cross trajectory) technique that combines use of the traditional trajectory (TT) and cortical bone trajectory (CBT) and to investigate its fixation strength quantitatively by finite element (FE) analysis.

METHODS

Three-dimensional FE models of 30 osteoporotic L4 vertebrae (patients' mean age: 77.3 ± 7.4 years, 11 men and 19 women) were computationally created. Each vertebral model was implanted with bilateral pedicle screws by TT (using 7.5 mm × 40 mm screws), CBT (using 5.5 mm × 35 mm screws) and cross trajectory (combined use of TT screws of 5.5 mm × 40 mm and CBT screws of 5.5 mm × 35 mm) and compared among three groups. The vertebral fixation strength of a bilateral-screw construct was examined by applying forces simulating flexion, extension, lateral bending, and axial rotation to the vertebrae by non-linear FE analyses.

RESULTS

Fixation strength using the cross trajectory was the highest among the three different techniques (P < 0.01). The cross trajectory construct demonstrated 320% higher strength than the TT construct in flexion, 293% higher in extension, 102% higher in lateral bending, and 40% higher in axial rotation (P < 0.01). Similarly, the cross trajectory construct showed 268% higher strength than the CBT construct in flexion, 269% higher in extension, 210% higher in lateral bending, and 178% in axial rotation (P < 0.01).

CONCLUSIONS

The cross trajectory technique offered superior fixation strength over the TT and CBT techniques in each plane of motion. This technique may be a valid option for posterior fusion, especially in osteoporotic spine.

Feasibility for Measuring Transverse Area Ratios and Asymmetry of Lumbosacral Region Paraspinal Muscles in Working Dogs Using Computed Tomography

OBJECTIVES

Describe computed tomographic (CT) anatomy of canine lumbosacral (LS) paraspinal muscles, a method for measuring paraspinal muscle transverse area ratios and asymmetry using CT, and application of this method in a small sample of working dogs with versus without LS pain.

METHODS

Published anatomy references and atlases were reviewed and discrepancies were resolved by examination of anatomic specimens and multiplanar reformatted images to describe transverse CT anatomy of LS region paraspinal muscles. Sixteen Belgian malinois military working dogs were retrospectively recruited and assigned to LS pain positive versus negative groups based on medical record entries. A single observer unaware of dog group measured CT transverse areas of paraspinal muscles and adjacent vertebral bodies, in triplicate, for L5-S1 vertebral locations. A statistician compared muscle transverse area ratios and asymmetry at each vertebral location between groups.

RESULTS

The relative coefficient of variation for triplicate CT area measurements averaged 2.15% (N = 16). Multifidus lumborum (L6-7), psoas/iliopsoas (L5-6, L6-7), and sacrocaudalis dorsalis lateralis (L6-7, L7-S1) transverse area ratios were significantly smaller in dogs with LS pain (n = 11) versus without LS pain (n = 5) (p ≤ 0.05). Muscle asymmetry values were not significantly greater in dogs with versus without LS pain.

CLINICAL RELEVANCE

Computed tomographic morphometry of LS region paraspinal muscles is a feasible objective method for use in future evidence-based research studies in working dogs. Potential future research applications include determining whether decreased paraspinal muscle area ratios and/or increased paraspinal muscle asymmetry could be used as markers for preclinical LS pain in stoic dogs or risk factors for other injuries in high performance canine athletes, or determining whether core muscle strengthening exercise prescriptions for dogs with LS pain have an effect on paraspinal muscle area ratios and asymmetry.

Quantitative, 3D Visualization of the Initiation and Progression of Vertebral Fractures Under Compression and Anterior Flexion

The biomechanical mechanisms leading to vertebral fractures are not well understood. Clinical and laboratory evidence suggests that the vertebral endplate plays a key role in failure of the vertebra as a whole, but how this role differs for different types of vertebral loading is not known. Mechanical testing of human thoracic spine segments, in conjunction with time-lapsed micro-computed tomography, enabled quantitative assessment of deformations occurring throughout the entire vertebral body under axial compression combined with anterior flexion ("combined loading") and under axial compression only ("compression loading"). The resulting deformation maps indicated that endplate deflection was a principal feature of vertebral failure for both loading modes. Specifically, the onset of endplate deflection was temporally coincident with a pronounced drop in the vertebra's ability to support loads. The location of endplate deflection, and also vertebral strength, were associated with the porosity of the endplate and the microstructure of the underlying trabecular bone. However, the location of endplate deflection and the involvement of the cortex differed between the two types of loading. Under the combined loading, deflection initiated, and remained the largest, at the anterior central endplate or the anterior ring apophysis, depending in part on health of the adjacent intervertebral disc. This deflection was accompanied by outward bulging of the anterior cortex. In contrast, the location of endplate deflection was more varied in compression loading. For both loading types, the earliest progression to a mild fracture according to a quantitative morphometric criterion occurred only after much of the failure process had occurred. The outcomes of this work indicate that for two physiological loading modes, the vertebral endplate and underlying trabecular bone are critically involved in vertebral fracture. These outcomes provide a strong biomechanical rationale for clinical methods, such as algorithm-based qualitative (ABQ) assessment, that diagnose vertebral fracture on the basis of endplate depression. © 2015 American Society for Bone and Mineral Research.

Development and Validation of a Musculoskeletal Model of the Fully Articulated Thoracolumbar Spine and Rib Cage

We developed and validated a fully articulated model of the thoracolumbar spine in opensim that includes the individual vertebrae, ribs, and sternum. To ensure trunk muscles in the model accurately represent muscles in vivo, we used a novel approach to adjust muscle cross-sectional area (CSA) and position using computed tomography (CT) scans of the trunk sampled from a community-based cohort. Model predictions of vertebral compressive loading and trunk muscle tension were highly correlated to previous in vivo measures of intradiscal pressure (IDP), vertebral loading from telemeterized implants and trunk muscle myoelectric activity recorded by electromyography (EMG).

Creating physiologically realistic vertebral fractures in a cervine model

Approximately 50% of women and 25% of men will have an osteoporosis-related fracture after the age of 50, yet the micromechanical origin of these fractures remains unclear. Preventing these fractures requires an understanding of compression fracture formation in vertebral cancellous bone. The immediate research goal was to create clinically relevant (midvertebral body and endplate) fractures in three-vertebrae motion segments subject to physiologically realistic compressional loading conditions. Six three-vertebrae motion segments (five cervine, one cadaver) were potted to ensure physiologic alignment with the compressive load. A 3D microcomputed tomography (microCT) image of each motion segment was generated. The motion segments were then preconditioned and monotonically compressed until failure, as identified by a notable load drop (48-66% of peak load in this study). A second microCT image was then generated. These three-dimensional images of the cancellous bone structure were inspected after loading to qualitatively identify fracture location and type. The microCT images show that the trabeculae in the cervine specimens are oriented similarly to those in the cadaver specimen. In the cervine specimens, the peak load prior to failure is highest for the L4-L6 motion segment, and decreases for each cranially adjacent motion segment. Three motion segments formed endplate fractures and three formed midvertebral body fractures; these two fracture types correspond to clinically observed fracture modes. Examination of normalized-load versus normalized-displacement curves suggests that the size (e.g., cross-sectional area) of a vertebra is not the only factor in the mechanical response in healthy vertebral specimens. Furthermore, these normalized-load versus normalized-displacement data appear to be grouped by the fracture type. Taken together, these results show that (1) the loading protocol creates fractures that appear physiologically realistic in vertebrae, (2) cervine vertebrae fracture similarly to the cadaver specimen under these loading conditions, and (3) that the prefracture load response may predict the impending fracture mode under the loading conditions used in this study.

Changes of paraspinal muscles in postmenopausal osteoporotic spinal compression fractures: magnetic resonance imaging study

Background

To investigate the changes of cross sectional area (CSA) in paraspinal muscles upon magnetic resonance imaging (MRI) and bone mineral density (BMD) in postmenopausal osteoporotic spinal compression fractures.

Methods

We reviewed 81 postmenopausal women with osteoporosis, who had underwent MRI examination. The patients were divided into 51 patients who had osteoporotic spinal compression fractures (group I), and 30 patients who without fractures (group II). Group I were subdivided into IA and IB, based on whether they were younger (IA) of older (IB) than 70 years of age. We additionally measured body mass index and BMD. The CSA of multifidus, erector spinae, paraspinal muscles, psoas major (PT), and intervertebral (IV) discs were measured. The degree of fatty atrophy was estimated using three grades.

Results

The BMD and T-score of group I were significantly lower than those of group II. The CSA of erector spinae, paraspinal muscles, and PT in the group I was significantly smaller than that of group II. The CSA of paraspinal muscles in group IB were significantly smaller than those of group IA. The CSA of erector spinae, mutifidus, and PT in group IB were smaller than those of group IA, but the difference was not statistically significant. Group 1 exhibited greater fat infiltration in the paraspinal muscle than group II.

Conclusions

Postmenopausal osteoporotic spinal compression fracture is associated with profound changes of the lumbar paraspinal muscle, reduction of CSA, increased CSA of IV disc, and increased intramuscular fat infiltration.

Influence of sagittal balance on spinal lumbar loads: a numerical approach

BACKGROUND

Pathological deformities involving the sagittal alignment of the spine may lead to loss of spine stability and imbalance. The effect of different patterns of sagittal balance on the loads acting in the spine was only marginally investigated, although it would be of critical importance in the clinical management of spinal disorders.

METHODS

Optimization-based finite element models of the human spine in the standing position able to predict the loads acting in the lumbar spine and the activation of the spinal muscles were developed and used to explore a wide range of sagittal balance conditions, covering both inter-subject variability and pathological imbalance. 1000 two-dimensional randomized spine models with simplified geometry were generated by varying anatomical parameters such as lumbar lordosis, sacral slope, and C7 plumb line. Muscular loads were calculated by means of an optimization procedure aimed to minimize total muscular stress.

FINDINGS

The simulation of a physiological spine in the standing position predicted average disk stresses ranging from 0.38 to 0.5MPa, in good agreement with in vivo measurements. The C7 plumb line and the parameters describing the lumbar spine were found to be the strongest determinants of the lumbar loads and muscle activity. Marginal relevance was found concerning the thoracic and cervical parameters.

INTERPRETATION

The present modeling approach was found to be able to capture correlations between sagittal parameters and the loads acting in the lumbar spine. The method represents a good platform for future improvements aimed at patient-specific modeling to support pre-operative surgical planning.

Increased variability of bone tissue mineral density resulting from estrogen deficiency influences creep behavior in a rat vertebral body

Progressive vertebral deformation increases the fracture risk of a vertebral body in the postmenopausal patient. Many studies have observed that bone can demonstrate creep behavior, defined as continued time-dependent deformation even when mechanical loading is held constant. Creep is a characteristic of viscoelastic behavior, which is common in biological materials. We hypothesized that estrogen deficiency-dependent alteration of the mineral distribution of bone at the tissue level could influence the progressive postmenopausal vertebral deformity that is observed as the creep response at the organ level. The objective of this study was thus to examine whether the creep behavior of vertebral bone is changed by estrogen deficiency, and to determine which bone property parameters are responsible for the creep response of vertebral bone at physiological loading levels using an ovariectomized (OVX) rat model. Correlations of creep parameters with bone mineral density (BMD), tissue mineral density (TMD) and architectural parameters of both OVX and sham surgery vertebral bone were tested. As the vertebral creep was not fully recovered during the post-creep unloading period, there was substantial residual displacement for both the sham and OVX groups. A strong positive correlation between loading creep and residual displacement was found (r=0.868, p<0.001). Of the various parameters studied, TMD variability was the parameter that best predicted the creep behavior of the OVX group (p<0.038). The current results indicated that creep caused progressive, permanent reduction in vertebral height for both the sham and OVX groups. In addition, estrogen deficiency-induced active bone remodeling increased variability of trabecular TMD in the OVX group. Taken together, these results suggest that increased variability of trabecular TMD resulting from high bone turnover influences creep behavior of the OVX vertebrae.

Postmenopausal women with osteoporosis and musculoskeletal status: a comparative cross-sectional study

Background

With increased life expectancy of the world's population that has taken place in recent decades, there has been growth in the incidence of illnesses of the most advanced ages, including osteoporosis. However, changes in musculoskeletal disorders are not yet so clear. This study proposes to evaluate musculoskeletal alterations in osteoporotic postmenopausal women and healthy and correlate with bone mineral density of the lumbar spine.

Methods

Randomized, examiner-blinded, comparative cross-sectional study was designed with two groups of women attending the Menopause Clinic in the UNICAMP, 30 women with osteoporosis, while 33 women without osteoporosis comprised the second group. Diagnosis of the presence or absence of osteoporosis was based on bone densitometry performed on the lumbar spine. Volunteers were interviewed and underwent a physical examination with the same examiner, including the muscle strength and amplitude of movement of back flexion and extension, angles of thoracic kyphosis and lumbar lordosis, as well as static and dynamic balance.

Results

Mean back flexors and extensors strength was significantly lower in women with osteoporosis (P < 0.01). Flexion spinal range of motion was similar in both groups (P = 0.91). However, movement amplitude of spine extension was 20.5^o in women with osteoporosis and 28.4^o in women without osteoporosis. Thoracic kyphosis angles from T1 to T4 (P < 0.01) and lumbar lordosis angles (P = 0.02) were greater in women with osteoporosis. Seventy-three point three percent of women with osteoporosis and 78.8% of women without osteoporosis had good reply to static balance. Women in both groups had poor results to dynamic balance. No significant differences were observed in static or dynamic balance between women with and without osteoporosis. Vertebral fractures were present in 20% of women with osteoporosis and absent in women without osteoporosis.

Conclusions

Women with osteoporosis in the study population had poorer musculoskeletal status than women without osteoporosis. Further studies are necessary to evaluate whether correction of these alterations would be related to preventing falls and reducing fracture risk.

Keywords

Balance; Kyphosis; Mobility; Muscle strength; Osteoporosis; Postmenopausal

Newly developed compression fractures after percutaneous vertebroplasty: comparison with conservative treatment

PURPOSE

The aim of this study was to investigate the incidence and timing of subsequent fractures in patients treated with and without percutaneous vertebroplasty (PVP).

MATERIALS AND METHODS

We reviewed 794 patients who underwent 1500 PVPs with polymethylmethacrylate (PMMA) at our institution between January 1999 and December 2009. We also reviewed 349 patients with vertebral fractures who underwent conservative treatment without PVP between October 1999 and December 2009 and compared the incidence and timing of subsequent fractures in the two groups.

RESULTS

Among the 794 patients treated by PVP, 171 (21.5%) suffered 336 new vertebral fractures. Among the patients not treated by PVP, 82 (23.5%) presented with 154 new fractures. There was no statistically significant difference (P = 0.46). Among the PVP-treated patients, one-half of new fractures occurred at a level adjacent to the treated level, and they occurred significantly sooner than nonadjacent level fractures (log-rank test, P < 0.01).

CONCLUSION

PVP did not increase the incidence of new compression fractures compared with conservative treatment, but half of the new fractures at the adjacent vertebral bodies occurred sooner.

Variability of tissue mineral density can determine physiological creep of human vertebral cancellous bone

Creep is a time-dependent viscoelastic deformation observed under a constant prolonged load. It has been indicated that progressive vertebral deformation due to creep may increase the risk of vertebral fracture in the long-term. The objective of this study was to examine the relationships of creep with trabecular architecture and tissue mineral density (TMD) parameters in human vertebral cancellous bone at a physiological static strain level. Architecture and TMD parameters of cancellous bone were analyzed using microcomputerized tomography (micro-CT) in specimens cored out of human vertebrae. Then, creep and residual strains of the specimens were measured after a two-hour physiological compressive constant static loading and unloading cycle. Creep developed (3877 ± 2158 με) resulting in substantial levels of non-recoverable post-creep residual strain (1797 ± 1391 με). A strong positive linear correlation was found between creep and residual strain (r = 0.94, p < 0.001). The current results showed that smaller thickness, larger surface area, greater connectivity of trabeculae, less mean tissue mineral density (TMD, represented by gray levels) and higher variability of TMD are associated with increasing logarithmic creep rate. The TMD variability (GL(COV)) was the strongest correlate of creep rate (r = 0.79, p < 0.001). This result suggests that TMD variability may be a useful parameter for estimating the long-term deformation of a whole vertebral body. The results further suggest that the changes in TMD variability resulting from bone remodeling are of importance and may provide an insight into the understanding of the mechanisms underlying progressive failure of vertebral bodies and development of a clinical fracture.

Vulnerability of healthy vertebrae in patients with and without previous vertebral fracture

Vertebral deformities are associated with a marked increase in morbidity, mortality, and burden in terms of sanitary expenditures. Patients with vertebral fractures have a negative impact in their health, less quality of life, and loss of functional capacity and independence. The purpose of this study was to explore the vulnerability of healthy vertebrae in patients who have sustained already a compression fracture and in patients who do not have prevalent fractures in the thoracic spine; and to explore the association of the deformity in healthy vertebrae with different variables, such as bone mineral density (BMD), body mass index, age, loss of height, presence of clinical kyphosis, history of other osteoporotic fractures, and falls occurring during the last year. Clinical data and complementary studies from 175 postmenopausal outpatients were analyzed. These women (age: 69.7±11.1 years) had not received any treatment for osteoporosis. Anteroposterior and lateral radiographs of the thoracic spine and bone densitometry of the hip were obtained; morphometry was performed in 1575 thoracic vertebrae from T4 to T12. The angle of wedging of each vertebral body was calculated using a trigonometric formula. Then, the sum of wedge angles of vertebral bodies (SWA) was determined, and Cobb angle was measured. In patients with vertebral fractures, after excluding the angles of fractured vertebral bodies, the mean wedge angle of the remaining vertebrae (MWAhealthy) was calculated. The same procedure was followed in patients without vertebral fractures. MWAhealthy was considered as an indicator of the structural vulnerability of non-fractured vertebrae. Patients with prevalent fractures had lower BMD, wider Cobb angle, and higher sum of wedge angles than patients without vertebral fractures. The proportion of patients with accentuation of clinical kyphosis was higher in the group with prevalent vertebral fractures. A highly significant difference was found in the MWAhealthy, which was higher in patients with prevalent fractures (4.1±1.3° vs. 3.0±1.1°; p<0.001). Patients showing vertebral fractures had 7.1±4.2 cm height loss in average, significantly superior than that found among non-fractured women (3.6±3.2 cm; p<0.01). In multivariate analysis, the increase of MWAhealthy was associated with advancing age (p<0.02), lower femoral neck BMD (p<0.005), presence of clinical kyphosis (p<0.01) and vertebral fractures (p<0.02). This study presents evidence that a series of factors independently influence the increase in wedging deformity of vertebral bodies that are not fractured yet. These factors could contribute to an increased vulnerability of the vertebrae, making them more susceptible to fracture.

Spinous process fractures in osteoporotic thoracolumbar vertebral fractures

OBJECTIVES

To evaluate the incidence and pattern of spinous process fractures (SPFs) in patients with osteoporotic compression fractures (OCFs) of the thoracolumbar spine.

METHODS

Spinal MRI or CT of 398 female patients (age range 50-89 years, mean age 70 years) who had OCFs in the thoracolumbar spine were retrospectively reviewed. The incidence, location and imaging results for the SPFs were evaluated.

RESULTS

Of the 398 patients who had thoracolumbar OCFs, 14 (3.5%) had SPF. In six patients with single compression fractures, the SPF occurred at the level just above the vertebral compression fracture. In six out of seven patients with multiple continuous compression fractures, the SPF occurred just one level above the uppermost level of the compression fracture. The remaining one patient who had thoracolumbar spinal fixation at T12-L2 with continuous compression fractures in T12-L5 had a SPF in L2. In one patient who had multiple compression fractures in discontinuous levels (fractures at T10 and L1, respectively), the SPF occurred at T12. The directions of the fractures were vertical or oblique vertical (perpendicular to the long axis of the spinous process) in all cases.

CONCLUSION

In the presence of an OCF in the thoracolumbar spine, a SPF was found in 3.5% of cases, and most of the fractures were located just one level above the compression fracture. Therefore, in patients who have OCF, the possibility of a SPF in the level just above the compression fracture should be considered.

Vertebroplasty and Kyphoplasty Can Restore Normal Spine Mechanics following Osteoporotic Vertebral Fracture

Osteoporotic vertebral fractures often lead to pain and disability. They can be successfully treated, and possibly prevented, by injecting cement into the vertebral body, a procedure known as vertebroplasty. Kyphoplasty is similar, except that an inflatable balloon is used to restore vertebral body height before cement is injected. These techniques are growing rapidly in popularity, and a great deal of recent research, reviewed in this paper, has examined their ability to restore normal mechanical function to fractured vertebrae. Fracture reduces the height and stiffness of a vertebral body, causing the spine to assume a kyphotic deformity, and transferring load bearing to the neural arch. Vertebroplasty and kyphoplasty are equally able to restore vertebral stiffness, and restore load sharing towards normal values, although kyphoplasty is better at restoring vertebral body height. Future research should optimise these techniques to individual patients in order to maximise their beneficial effects, while minimising the problems of cement leakage and adjacent level fracture.

Age-related hyperkyphosis: its causes, consequences, and management

SYNOPSIS

Age-related hyperkyphosis is an exaggerated anterior curvature in the thoracic spine that occurs commonly with advanced age. This condition is associated with low bone mass, vertebral compression fractures, and degenerative disc disease, and contributes to difficulty performing activities of daily living and decline in physical performance. While there are effective treatments, currently there are no public health approaches to prevent hyperkyphosis among older adults. Our objective is to review the prevalence and natural history of hyperkyphosis, associated health implications, measurement tools, and treatments to prevent this debilitating condition.

LEVEL OF EVIDENCE

Diagnosis/prognosis/therapy, level 5.J Orthop Sports Phys Ther 2010;40(6):352-360, Epub 15 April 2010. doi:10.2519/jospt.2010.3099.

Effects of an exercise and manual therapy program on physical impairments, function and quality-of-life in people with osteoporotic vertebral fracture: a randomised, single-blind controlled pilot trial

BACKGROUND

This randomised, single-blind controlled pilot trial aimed to determine the effectiveness of a physiotherapy program, including exercise and manual therapy, in reducing impairments and improving physical function and health-related quality of life in people with a history of painful osteoporotic vertebral fracture.

METHODS

20 participants were randomly allocated to an intervention (n = 11) or control (n = 9) group. The intervention group attended individual sessions with an experienced clinician once a week for 10 weeks and performed daily home exercises with adherence monitored by a self-report diary. The control group received no treatment. Blinded assessment was conducted at baseline and 11 weeks. Questionnaires assessed self-reported changes in back pain, physical function, and health-related quality of life. Objective measures of thoracic kyphosis, back and shoulder muscle endurance (Timed Loaded Standing Test), and function (Timed Up and Go test) were also taken.

RESULTS

Compared with the control group, the intervention group showed significant reductions in pain during movement (mean difference (95% CI) -1.8 (-3.5 to -0.1)) and at rest (-2.0 (-3.8 to -0.2)) and significantly greater improvements in Qualeffo physical function (-4.8 (-9.2 to -0.5)) and the Timed Loaded Standing test (46.7 (16.1 to 77.3) secs). For the perceived change in back pain over the 10 weeks, 9/11 (82%) participants in the intervention group rated their pain as 'much better' compared with only 1/9 (11%) participants in the control group.

CONCLUSION

Despite the modest sample size, these results support the benefits of exercise and manual therapy in the clinical management of patients with osteoporotic vertebral fractures, but need to be confirmed in a larger sample.

TRIAL REGISTRATION

NCT00638768.

Segment-by-segment stabilization for degenerative disc disease: a hybrid technique

Patients with multisegmental degenerative disc disease (DDD) resistant to conservative therapy are typically treated with either fusion or non-fusion surgical techniques. The two techniques can be applied at adjacent levels using Dynesys (Zimmer GmbH, Winterthur, Switzerland) implants in a segment-by-segment treatment of multiple level DDD. The objective of this study was to evaluate the clinical and radiological outcome of patients treated using this segment-by-segment application of Dynesys in some levels as a non-fusion device and in other segments in combination with a PLIF as a fusion device. A consecutive case series is reported. The sample included 16 females and 15 males with a mean age of 53.6 years (range 26.3-76.4 years). Mean follow-up time was 39 months (range 24-90 months). Preoperative Oswestry disability index (ODI), back- and leg-pain scores (VAS) were compared to postoperative status. Fusion success and system failure were assessed by an independent reviewer who analyzed AP and lateral X-rays. Back pain improved from 7.3 +/- 1.7 to 3.4 +/- 2.7 (p < 0.000002), leg pain from 6.0 +/- 2.9 to 2.3 +/- 2.9 (p < 0.00006), and ODI from 51.6 +/- 13.2% to 28.7 +/- 18.0% (p < 0.00001). Screw loosening occurred in one of a total of 222 implanted screws (0.45%). The results indicate that segment-by-segment treatment with Dynesys in combination with interbody fusion is technically feasible, safe, and effective for the surgical treatment of multilevel DDD.

High weight or body mass index increase the risk of vertebral fractures in postmenopausal osteoporotic women

In the general population, low body weight and body mass index (BMI) are significant risk factors for any fracture, but the specific association between body weight, BMI, and prevalence of vertebral fractures in osteoporotic women is not fully recognized. Hence, the association between body weight, BMI, and prevalent vertebral fractures was investigated in 362 women with never-treated postmenopausal osteoporosis. All participants underwent measurement of BMI, bone mineral density (BMD), and semiquantitative assessment of vertebral fractures. Thirty percent of participants had > or =1 vertebral fracture. Body weight and BMI were associated with L1-L4 BMD (R = 0.29, P < 0.001 and R = 0.17, P = 0.009, respectively). In logistic regression analysis, BMI was positively associated with the presence of vertebral fractures independent of age and other traditional risk factors for fractures. Including weight and height instead of BMI in the multivariate model, showed weight as a positive and significant covariate of the presence of vertebral fractures (OR = 1.045; P = 0.016; 95% CI 1.008-1.084). BMI was associated with the number of vertebral fractures (rho = 0.18; P = 0.001), this association being confirmed also in the multivariate analysis (beta = 0.14; P = 0.03) after correction for smoking, early menopause, family history of fragility fractures and BMD. In conclusion, among postmenopausal women with osteoporosis, body weight and BMI are associated with a higher likelihood of having a vertebral fracture, irrespective of the positive association between weight and BMD.

Bone creep can cause progressive vertebral deformity

INTRODUCTION

Vertebral deformities in elderly people are conventionally termed "fractures", but their onset is often insidious, suggesting that time-dependent (creep) processes may also be involved. Creep has been studied in small samples of bone, but nothing is known about creep deformity of whole vertebrae, or how it might be influenced by bone mineral density (BMD). We hypothesise that sustained compressive loading can cause progressive and measurable creep deformity in elderly human vertebrae.

METHODS

27 thoracolumbar "motion segments" (two vertebrae and the intervening disc and ligaments) were dissected from 20 human cadavers aged 42-91 yrs. A constant compressive force of approximately 1.0 kN was applied to each specimen for either 0.5 h or 2 h, while the anterior, middle and posterior heights of each of the 54 vertebral bodies were measured at 1 Hz using a MacReflex 2D optical tracking system. This located 6 reflective markers attached to the lateral cortex of each vertebral body, with resolution better than 10 microm. Experiments were at laboratory temperature, and polythene film was used to minimise water loss. Volumetric BMD was calculated for each vertebral body, using DXA to measure mineral content, and water immersion for volume.

RESULTS

In the 0.5 h tests, creep deformation in the anterior, middle and posterior vertebral cortex averaged 4331, 1629 and 614 micro-strains respectively, where 10,000 micro-strains represents 1% loss in height. Anterior creep strains exceeded posterior (P<0.01) so that anterior wedging of the vertebral bodies increased, by an average 0.08 degrees (STD 0.14 degrees ). Similar results were obtained after 2 h, indicating that creep rate slowed considerably with time. Less than 40% of the creep strain was recovered after 2 h. Increases in anterior wedging during the 0.5 h creep test were inversely proportional to BMD, but only in a selected sub-set of 20 specimens with average BMD<0.15 g/cm3 (P=0.042). Creep deformation caused more than 5% height loss in four vertebrae, three of which had radiographic signs of pre-existing damage.

CONCLUSION

Sustained loading can cause progressive anterior wedge deformity in elderly human vertebrae, even in the absence of fracture.

The prognosis for pain, disability, activities of daily living and quality of life after an acute osteoporotic vertebral body fracture: its relation to fracture level, type of fracture and grade of fracture deformation

The level of the acute osteoporotic vertebral fracture, fracture type and grade of fracture deformation were determined in 107 consecutive patients and related to pain, disability, activities of daily living (ADL) and quality of life (QoL) after 3 weeks, 3, 6 and 12 months. Two-thirds of the fractured patients were women and with a similar average age, around 75 years, as the men. Fifty-eight of the acute fractures were located in the thoracic spine and 49 in the lumbar spine and predominantly at the Th12 and L1 levels. Sixty-nine percent of the fractures were wedge, 19% concave and 12% crush fractures. There were 22 mildly, 50 moderately and 35 severely deformed vertebrae. The grade of fracture deformation was not related to gender, age or fracture location. Severely deformed vertebrae predominantly (92%) occurred among the crush fracture type. One year after the fracture, irrespective of fracture level, fracture type or grade of fracture deformation, 4/5 still had pronounced pain and deteriorated QoL. Initial severe fracture deformation by far was the worst prognostic factor for severe lasting pain and disability, and deterioration of ADL and QoL. Factors like fracture level, lumbar fractures tended to improve steadily while thoracic deteriorated, type of fracture, the wedge and concave resulting in less pain and better QoL than the crush fracture type and gender influenced to a lesser extent the outcomes during the year after the acute fracture.

Segmental deformity correction after balloon kyphoplasty in the osteoporotic vertebral compression fracture

OBJECTIVE

Balloon kyphoplasty can effectively relieve the symptomatic pain and correct the segmental deformity of osteoporotic vertebral compression fractures. While many articles have reported on the effectiveness of the procedure, there has not been any research on the factors affecting the deformity correction. Here, we evaluated both the relationship between postoperative pain relief and restoration of the vertebral height, and segmental kyphosis, as well as the various factors affecting segmental deformity correction after balloon kyphoplasty.

METHODS

Between January 2004 and December 2006, 137 patients (158 vertebral levels) underwent balloon kyphoplasty. We analyzed various factors such as the age and sex of the patient, preoperative compression ratio, kyphotic angle of compressed segment, injected PMMA volume, configuration of compression, preoperative bone mineral density (BMD) score, time interval between onset of symptom and the procedure, visual analogue scale (VAS) score for pain rating and surgery-related complications.

RESULTS

The mean postoperative VAS score improvement was 4.93+/-0.17. The mean postoperative height restoration rate was 17.8+/-1.57% and the kyphotic angle reduction was 1.94+/-0.38 degrees . However, there were no significant statistical correlations among VAS score improvement, height restoration rate, and kyphotic angle reduction. Among the various factors, the configuration of the compressed vertebral body (p=0.002) was related to the height restoration rate and the direction of the compression (p=0.006) was related with the kyphotic angle reduction. The preoperative compression ratio (p=0.023, p=0.006) and injected PMMA volume (p<0.001, p=0.035) affected both the height restoration and kyphotic angle reduction. Only the preoperative compression ratio was found to be as an independent affecting factor (95% CI : 1.064-5.068).

CONCLUSION

The two major benefits of balloon kyphoplasty are immediate pain relief and local deformity correction, but segmental deformity correction achieved by balloon kyphoplasty does not result in additional pain relief. Among the factors that were shown to affect the segmental deformity correction, configuration of the compressed vertebral body, direction of the most compressed area, and preoperative compression ratio were not modifiable. However, careful preoperative consideration about the modifiable factor, the PMMA volume to inject, may contribute to the dynamic correction of the segmental deformity.

Gravitational forces and sagittal shape of the spine. Clinical estimation of their relations

The sagittal morphology of the pelvis determines the amount of lordosis needed for each individual. The proper harmony of the sagittal spinal curves allows a stable balance, economical in terms of mechanical effects and muscular energy. A previous barycentremetrical laboratory study allowed us to demonstrate that the axis of gravity of the upper body segment was located behind the lumbar vertebrae and the femoral heads, thus ensuring economy and stability. The determination of the anatomical connection of the individual gravity is thus of primary importance for the evaluation of sagittal balance. Data for 42 patients without spinal pathology, previously evaluated by barycentremetry, were used to establish a predictive equation for the application point of the gravity at the level of the third lumbar vertebra (L3). This equation, using anthropometric and radiographic pelvic and spinal parameters, was integrated into a software program called Similibary. It was applied to the same 42 subjects. These results were compared in order to validate the method. No significant difference was observed between the two techniques. This easy-to-use tool allows a personalised evaluation of the sagittal balance of the spine, both through the evaluation of the harmonious relationship between the spinal curves and the pelvis, and through the location of gravity supported by the vertebral structures in L3.

Finite-element analysis on closing-opening correction osteotomy for angular kyphosis of osteoporotic vertebral fractures

BACKGROUND

Closing-opening correction (COC) osteotomy is a useful procedure for severe angular kyphosis. However, there is no previous research on the reconstructed vertebrae with kyphotic malalignment in the presence of osteoporosis. Finite-element (FE) analysis was performed to estimate the biomechanical stress with both osteoporotic grades and corrective kyphotic angles during COC osteotomy for osteoporotic angular kyphosis.

METHODS

FE models of COC osteotomy were created by changing three major parameters: (1) grade of osteoporosis; (2) kyphotic angle; and (3) compensated posture when standing still. Osteoporosis was graded at four levels: A, normal (nonosteoporotic); B, low-grade osteoporosis; C, middle-grade osteoporosis; D, high-grade osteoporosis. The kyphotic angle ranged from 0 degrees as normal to 15 degrees and 30 degrees as moderate and severe kyphosis, respectively. FE analyses were performed with and without assumed compensated posture in kyphotic models of 15 degrees and 30 degrees . Along each calculated axis of gravity, a 427.4-N load was applied to evaluate the maximum compressive principal stress (CPS) for each model.

RESULTS

The CPS values for the vertebral element were the highest at the anterior element of T10 in all FE models. The maximum CPS at T10 increased based on the increases in both the grade of osteoporosis and the kyphotic angle. Compensated posture made the maximum CPS value decrease in the 15 degrees and 30 degrees kyphotic models. The highest CPS value was 40.6 MPa in the high-grade osteoporosis (group D) model with a kyphotic angle of 30 degrees . With the normal (nonosteoporotic) group A, the maximum CPS at T10 was relatively low. With middle- and high-grade osteoporosis (groups C and D, respectively), the maximum CPS at T10 was relatively high with or without compensated posture, except for the 0 degrees model.

CONCLUSIONS

Lack of correction in osteoporotic kyphosis leads to an increase in CPS. This biomechanical study proved the advantage of correcting the kyphotic angle to as close as possible to physiological alignment in the thoracolumbar spine, especially in patients with high-grade osteoporosis.

Thoracic kyphosis affects spinal loads and trunk muscle force

BACKGROUND AND PURPOSE

Patients with increased thoracic curvature often come to physical therapists for management of spinal pain and disorders. Although treatment approaches are aimed at normalizing or minimizing progression of kyphosis, the biomechanical rationales remain unsubstantiated.

SUBJECTS

Forty-four subjects (mean age [+/-SD]=62.3+/-7.1 years) were dichotomized into high kyphosis and low kyphosis groups.

METHODS

Lateral standing radiographs and photographs were captured and then digitized. These data were input into biomechanical models to estimate net segmental loading from T2-L5 as well as trunk muscle forces.

RESULTS

The high kyphosis group demonstrated significantly greater normalized flexion moments and net compression and shear forces. Trunk muscle forces also were significantly greater in the high kyphosis group. A strong relationship existed between thoracic curvature and net segmental loads (r =.85-.93) and between thoracic curvature and muscle forces (r =.70-.82).

DISCUSSION AND CONCLUSION

This study provides biomechanical evidence that increases in thoracic kyphosis are associated with significantly higher multisegmental spinal loads and trunk muscle forces in upright stance. These factors are likely to accelerate degenerative processes in spinal motion segments and contribute to the development of dysfunction and pain.

Postural taping decreases thoracic kyphosis but does not influence trunk muscle electromyographic activity or balance in women with osteoporosis

BACKGROUND

Greater thoracic kyphosis is associated with increased biomechanical loading of the spine which is potentially problematic in individuals with osteoporotic vertebral fractures. Conservative interventions that reduce thoracic kyphosis warrant further investigation. This study aimed to investigate the effects of therapeutic postural taping on thoracic posture. Secondary aims explored the effects of taping on trunk muscle activity and balance.

METHODS

Fifteen women with osteoporotic vertebral fractures participated in this within-participant design study. Three taping conditions were randomly applied: therapeutic taping, control taping and no taping. Angle of thoracic kyphosis was measured after each condition. Force plate-derived balance parameters and trunk muscle electromyographic activity (EMG) were recorded during three static standing tasks of 40s duration.

RESULTS

There was a significant main effect of postural taping on thoracic kyphosis (p=0.026), with a greater reduction in thoracic kyphosis after taping compared with both control tape and no tape. There were no effects of taping on EMG or balance parameters.

CONCLUSIONS

The results of this study demonstrate that the application of postural therapeutic tape in a population with osteoporotic vertebral fractures induced an immediate reduction in thoracic kyphosis. Further research is needed to investigate the underlying mechanisms associated with this decrease in kyphosis.

Intervertebral disc degeneration can predispose to anterior vertebral fractures in the thoracolumbar spine

Mechanical experiments on cadaveric thoracolumbar spine specimens showed that intervertebral disc degeneration was associated with reduced loading of the anterior vertebral body in upright postures. Reduced load bearing corresponded to locally reduced BMD and inferior trabecular architecture as measured by histomorphometry. Flexed postures concentrated loading on the weakened anterior vertebral body, leading to compressive failure at reduced load.

INTRODUCTION

Osteoporotic fractures are usually attributed to age-related hormonal changes and inactivity. However, why should the anterior vertebral body be affected so often? We hypothesized that degenerative changes in the adjacent intervertebral discs can alter load bearing by the anterior vertebral body in a manner that makes it vulnerable to fracture.

MATERIALS AND METHODS

Forty-one thoracolumbar spine "motion segments" (two vertebrae and the intervertebral disc) were obtained from cadavers 62-94 years of age. Specimens were loaded to simulate upright standing and flexed postures. A pressure transducer was used to measure the distribution of compressive "stress" inside the disc, and stress data were used to calculate how compressive loading was distributed between the anterior and posterior halves of the vertebral body and the neural arch. The compressive strength of each specimen was measured in flexed posture. Regional volumetric BMD and histomorphometric parameters were measured.

RESULTS

In the upright posture, compressive load bearing by the neural arch increased with disc degeneration, averaging 63 +/- 22% (SD) of applied load in specimens with severely degenerated discs. In these specimens, the anterior half of the vertebral body resisted only 10 +/- 8%. The anterior third of the vertebral body had a 20% lower trabecular volume fraction, 16% fewer trabeculae, and 28% greater intertrabecular spacing compared with the posterior third (p < 0.001). In the flexed posture, flexion transferred 53-59% of compressive load bearing to the anterior half of the vertebral body, regardless of disc degeneration. Compressive strength measured in this posture was proportional to BMD in the anterior vertebral body (r2 = 0.51, p < 0.001) and inversely proportional to neural arch load bearing in the upright posture (r2 = 0.28, p < 0.001).

CONCLUSIONS

Disc degeneration transfers compressive load bearing from the anterior vertebral body to the neural arch in upright postures, reducing BMD and trabecular architecture anteriorly. This predisposes to anterior fracture when the spine is flexed.

Validation of a computer analysis to determine 3-D rotations and translations of the rib cage in upright posture from three 2-D digital images

Since thoracic cage posture affects lumbar spine coupling and loads on the spinal tissues and extremities, a scientific analysis of upright posture is needed. Common posture analyzers measure human posture as displacements from a plumb line, while the PosturePrint claims to measure head, rib cage, and pelvic postures as rotations and translations. In this study, it was decided to evaluate the validity of the PosturePrint Internet computer system's analysis of thoracic cage postures. In a university biomechanics laboratory, photographs of a mannequin thoracic cage were obtained in different postures on a stand in front of a digital camera. For each mannequin posture, three photographs were obtained (left lateral, right lateral, and AP). The mannequin thoracic cage was placed in 68 different single and combined postures (requiring 204 photographs) in five degrees of freedom: lateral translation (Tx), lateral flexion (Rz), axial rotation (Ry), flexion-extension (Rx), and anterior-posterior translation (Tz). The PosturePrint system requires 13 reflective markers to be placed on the subject (mannequin) during photography and 16 additional "click-on" markers via computer mouse before a set of three photographs is analyzed by the PosturePrint computer system over the Internet. Errors were the differences between the positioned mannequin and the calculated positions from the computer system. Average absolute value errors were obtained by comparing the exact inputted posture to the PosturePrint computed values. Mean and standard deviation of computational errors for sagittal displacements of the thoracic cage were Rx=0.3+/-0.1 degrees , Tz=1.6+/-0.7 mm, and for frontal view displacements were Ry=1.2+/-1.0 degrees , Rz=0.6+/-0.4 degrees , and Tx=1.5+/-0.6 mm. The PosturePrint system is sufficiently accurate in measuring thoracic cage postures in five degrees of freedom on a mannequin indicating the need for a further study on human subjects.

Correction of osteoporotic fracture deformities with global sagittal imbalance

Osteoporotic spinal deformities with global sagittal imbalance have devastating effects on patients. However, treatment is difficult and there is a high risk of perioperative medical and mechanical complications. Patients with osteoporotic spinal deformities are not ideal candidates for posterior pedicle subtraction osteotomy; the condition necessitates combined anterior-posterior for corrections of the deformity. We ascertained the complication rates and efficacy of the anterior-posterior surgery and determined the factors influencing the results. To determine complication rates we analyzed a series of patients (n = 32). To evaluate overall results, we analyzed 18 patients with more than 2-years followup. A total of 18 complications occurred in 12 of 32 patients (37.5%) with seven early complications occurring in five patients and 11 delayed complications occurring in seven patients. Three patients needed additional surgery to treat the complications. At 2 years postoperatively, 17 of 18 patients (94%) reported subjective improvement with 54% decrement of Oswestry Disability Index and 70% decrement of the visual analogue scale pain score. The factors associated with clinical improvement was restoration of total lumbopelvic lordosis, C7 plumb, and control of T4-12 thoracic kyphosis. Prevention and aggressive treatment of junctional fractures were important in achieving favorable results.

LEVEL OF EVIDENCE

Therapeutic study, Level IV (case series, [patients treated one way with no comparison group of patients treated in another way]). See the Guidelines for Authors for a complete description of the levels of evidence.

Does vertebral height restoration achieved at vertebroplasty matter?

PURPOSE

Altered vertebral and spinal configuration after osteoporotic vertebral compression fracture (VCF) is believed to contribute to postfracture morbidity. The objective of this study was to determine whether patients in whom partial vertebral height restoration (VHR) was achieved at percutaneous vertebroplasty had greater pain relief or improved quality of life compared with patients in whom no anatomic restoration was achieved.

MATERIALS AND METHODS

Consecutive subjects undergoing percutaneous vertebroplasty for painful osteoporotic VCFs completed the Osteoporosis Quality of Life Questionnaire (OQLQ) a validated, disease specific instrument that measures health related quality of life in women with osteoporosis with back pain caused by VCF. At postoperative week 2, month 2, and month 6, all subjects completed the mini-OQLQ, a validated extraction of OQLQ. Pain was rated with a standard visual analogue scale (VAS). Radiographs were manually digitized and evaluated for the presence of dynamic mobility and VHR. The relationship between VHR achieved at percutaneous vertebroplasty and postoperative pain relief and quality of life outcome was examined by multivariate analysis.

RESULTS

Forty-six subjects (32 women) underwent 49 percutaneous vertebroplasty procedures to treat 66 painful VCFs. Mean patient age was 74.3 years+/-10.9. Mean fracture age was 2.5 months+/-2.1. Pain rating fell from 7.7+/-1.8 to 2.8+/-1.8 within 1 day of percutaneous vertebroplasty and remained improved through month 6 (P<.001). All OQLQ domains improved substantially at week 2 (P<.02) and remained improved through month 6 (P<or=.007). Preoperative dynamic mobility ranged -2.9 to 19.9 mm (average, 5.5 mm). Postoperative VHR in mobile VCFs ranged -2.1 to 9.6 mm (average, 2.9 mm). At all postoperative time points up to 6 months, pain and OQLQ domain scores were similar in patients who achieved partial VHR at percutaneous vertebroplasty compared with those in whom no VHR was achieved.

CONCLUSION

Partial vertebral height restoration achieved at percutaneous vertebroplasty did not result in additional pain relief or improved quality of life beyond cement fixation alone.

Influence of spine morphology on intervertebral disc loads and stresses in asymptomatic adults: implications for the ideal spine

BACKGROUND CONTEXT

Sagittal profiles of the spine have been hypothesized to influence spinal coupling and loads on spinal tissues.

PURPOSE

To assess the relationship between thoracolumbar spine sagittal morphology and intervertebral disc loads and stresses.

STUDY DESIGN

A cross-sectional study evaluating sagittal X-ray geometry and postural loading in asymptomatic men and women.

PATIENT SAMPLE

Sixty-seven young and asymptomatic subjects (chiropractic students) formed the study group.

OUTCOME MEASURES

Morphological data derived from radiographs (anatomic angles and sagittal balance parameters) and biomechanical parameters (intervertebral disc loads and stresses) derived from a postural loading model.

METHODS

An anatomically accurate, sagittal plane, upright posture, quadrilateral element model of the anterior spinal column (C2-S1) was created by digitizing lateral full-spine X-rays of 67 human subjects (51 males, 16 females). Morphological measurements of sagittal curvature and balance were compared with intervertebral disc loads and stresses obtained using a quadrilateral element postural loading model.

RESULTS

In this young (mean 26.7, SD 4.8 years), asymptomatic male and female population, the neutral posture spine was characterized by an average thoracic angle (T1-T12) = +43.7 degrees (SD 11.4 degrees ), lumbar angle (T12-S1) = -63.2 degrees (SD 10.0 degrees ), and pelvic angle = +49.4 degrees (SD 9.9 degrees ). Sagittal curvatures exhibited relatively broad frequency distributions, with the pelvic angle showing the least variance and the thoracic angle showing the greatest variance. Sagittal balance parameters, C7-S1 and T1-T12, showed the best average vertical alignment (5.3 mm and -0.04 mm, respectively). Anterior and posterior disc postural loads were balanced at T8-T9 and showed the greatest difference at L5-S1. Disc compressive stresses were greatest in the mid-thoracic region of the spine, whereas shear stresses were highest at L5-S1. Significant linear correlations (p < .001) were found between a number of biomechanical and morphological parameters. Notably, thoracic shear stresses and compressive stresses were correlated to T1-T12 and T4-hip axis (HA) sagittal balance, respectively, but not to sagittal angles. Lumbar shear stresses and body weight (BW) normalized shear loads were correlated with T12-S1 balance, lumbar angle, and sacral angle. BW normalized lumbar compressive loads were correlated with T12-S1 balance and sacral angle. BW normalized lumbar disc shear (compressive) loads increased (decreased) significantly with decreasing lumbar lordosis. Cervical compressive stresses and loads were correlated with all sagittal balance parameters except S1-HA and T12-S1. A neutral spine sagittal model was constructed from the 67 subjects.

CONCLUSIONS

The analyses suggest that sagittal spine balance and curvature are important parameters for postural load balance in healthy male and female subjects. Morphological predictors of altered disc load outcomes were sagittal balance parameters in the thoracic spine and anatomic angles in the lumbar spine.