Biomechanics of metastatic spine cancer

Progression toward Vertebral Collapse of Vertebral Metastases Treated with Percutaneous Vertebroplasty: Rate and Risk Factors

PURPOSE

To evaluate of the rate of and risks for progression toward collapse in vertebral metastases (VMs) treated with percutaneous vertebroplasty (PV).

MATERIALS AND METHODS

A total of 151 PVs were performed in 81 patients with vertebral metastases and were retrospectively analyzed. Follow-up imaging was performed at 12 months to measure vertebral body height and to report vertebral collapse at the level of the treated vertebrae. Vertebral characteristics (spine instability neoplastic score [SINS], number of lysed cortices, and prior radiotherapy) and procedural parameters (Saliou score, cortical contact with cement, and intradiscal cement leakage) were compared between the group of patients with and without collapse of the treated vertebrae.

RESULTS

Of the vertebrae treated with PV, 41 of 151 (27%) progressed toward collapse. Vertebral collapse was influenced by a high SINS (odds ratio [OR] = 1.27, P = .004), SINS value > 9 (OR = 2.96, P = .004), intradiscal cement leakage (OR = 2.18, P = .048), pre-existing spinal deformity (OR = 2.65, P = .020), and pre-existing vertebral fracture (OR = 3.93, P = .045). A high Saliou score (OR = 0.82, P = .011), more than 3 cortices in contact with the cement (OR = 0.38, P = .014), and preserved spinal alignment (OR = 0.38, P = .020) were associated with a lower incidence of collapse.

CONCLUSIONS

Rate of vertebral collapse despite PV was influenced by vertebra-specific characteristics and by cement injection quality. Vertebrae with a SINS of ≤9 and with homogeneous cement filling had a lower incidence of collapse.

Bone metastases with post-treatment intralesional fatty content of the spine: imaging features from T1-weighted imaging with CT finding correlations

BACKGROUND

Despite post-treatment intralesional fatty content (PIFAT) in bone metastases indicating a healing processes after treatment, the imaging features of PIFAT have not been studied in detail.

PURPOSE

To analyze imaging features from T1-weighted (T1W) imaging with computed tomography (CT) finding correlations in bone metastases with PIFAT of the spine.

MATERIAL AND METHODS

A total of 29 bone metastases with PIFAT were analyzed with T1W and CT images before and after treatment. On T1W imaging after treatment, the lesions were categorized into three types according to fat distribution patterns. CT attenuation changes after treatment were also evaluated. According to the MD Anderson (MDA) criteria, response types for all lesions were obtained on magnetic resonance (MR) and CT images.

RESULTS

The types from T1W imaging in bone metastases with PIFAT were as follows: 14 with a return to totally normal marrow signal intensity within the lesion; 13 with an inhomogeneous patchy pattern in the lesion; and two with a peripheral halo of fatty marrow or peripheral fat signal intensity foci in the lesion. Among bone metastases with PIFAT, 93.1% showed osteosclerotic changes in this study. According to the MDA criteria, the concordance between the response types of the MR and CT images was 57.2%.

CONCLUSION

Knowledge of imaging features from T1W imaging with CT correlation in bone metastases with PIFAT is important for the accurate interpretation of post-treatment MR and CT studies. Both MR and CT images have a complementary value regarding the post-treatment evaluation of bone metastases with PIFAT.

Large Lytic Defects Produce Kinematic Instability and Loss of Compressive Strength in Human Spines: An in Vitro Study

BACKGROUND

In patients with spinal metastases, kinematic instability is postulated to be a predictor of pathologic vertebral fractures. However, the relationship between this kinematic instability and the loss of spinal strength remains unknown.

METHODS

Twenty-four 3-level thoracic and lumbar segments from 8 cadaver spines from female donors aged 47 to 69 years were kinematically assessed in axial compression (180 N) and axial compression with a flexion or extension moment (7.5 Nm). Two patterns of lytic defects were mechanically simulated: (1) a vertebral body defect, corresponding to Taneichi model C (n = 13); and (2) the model-C defect plus destruction of the ipsilateral pedicle and facet joint, corresponding to Taneichi model E (n = 11). The kinematic response was retested, and compression strength was measured. Two-way repeated-measures analysis of variance was used to test the effect of each model on the kinematic response of the segment. Multivariable linear regression was used to test the association between the kinematic parameters and compressive strength of the segment.

RESULTS

Under a flexion moment, and for both models C and E, the lesioned spines exhibited greater flexion range of motion (ROM) and axial translation than the control spines. Both models C and E caused lower extension ROM and greater axial, sagittal, and transverse translation under an extension moment compared with the control spines. Two-way repeated-measures analysis revealed that model E, compared with model C, caused significantly greater changes in extension and torsional ROM under an extension moment, and greater sagittal translation under a flexion moment. For both models C and E, greater differences in flexion ROM and sagittal translation under a flexion moment, and greater differences in extension ROM and in axial and transverse translation under an extension moment, were associated with lower compressive strength of the lesioned spines.

CONCLUSIONS

Critical spinal lytic defects result in kinematic abnormalities and lower the compressive strength of the spine.

CLINICAL RELEVANCE

This experimental study demonstrates that lytic foci degrade the kinematic stability and compressive strength of the spine. Understanding the mechanisms for this degradation will help to guide treatment decisions that address inferred instability and fracture risk in patients with metastatic spinal disease.

Effect of metastatic lesion size and location on the load-bearing capacity of vertebrae using an optimized ash density-modulus equation

About 1.8 million new cancer cases are estimated in the US in 2019 from which 50-85% might metastasize to the thoracic and lumbar spines. Subject-specific quantitative computed tomography-based finite element analysis (QCT/FEA) is a promising used tool to predict vertebral fracture properties. The aims of this study were twofold: First, to develop an optimized equation for the elastic modulus accounting for all input parameters in FE modeling of fracture properties. Second, to assess the effect of lesion size and location on the predicted fracture loads. An inverse QCT/FEA method was implemented to determine optimal coefficients for the modulus equation as a function of ash density. Lesions of 16 and 20 mm were then virtually located at the center, off-centered, anterior, and posterior regions of the vertebrae. A total of 6426 QCT/FEA models were run to optimize the coefficients and evaluate the effect of lesions on fracture properties. QCT/FEA predicted stiffness showed high correlations (50%) with the experimentally measured values. Compared to a 16 mm lesion size, a 20 mm lesion had a reduction in failure load of 55%, 57%, 52%, and 44% at the center, off-centered, anterior cortex, and pedicle, respectively (p < 0.001). Lesions affecting mostly trabecular bone showed the largest reduction in predicted failure loads (about 55%), and females presented weaker outcomes than males. An optimal elastic modulus equation resulted in accurate vertebral stiffness predictions. A deterioration of the trabecular bone due to the presence of a lesion highly affected the predicted fracture loads, and this reduction was significantly higher in females compared to males.

Stent screw-assisted internal fixation (SAIF): clinical report of a novel approach to stabilizing and internally fixating vertebrae destroyed by malignancy

OBJECTIVE

Severe lytic cancerous lesions of the spine are associated with significant morbidity and treatment challenges. Stabilization and restoration of the axial load capability of the vertebral body (VB) are important to prevent or arrest vertebral collapse. Percutaneous stent screw-assisted internal fixation (SAIF), which anchors a VB stent/cement complex with pedicular screws to the posterior vertebral elements, is a minimally invasive, image-guided, 360° internal fixation technique that can be utilized in this patient cohort. The purpose of this study was to assess the feasibility, safety, and stabilization efficacy of VB reconstruction via the SAIF technique in a cohort of patients with extensive lytic vertebral lesions, who were considered to have an unstable or potentially unstable spine according to the Spinal Instability Neoplastic Score (SINS).

METHODS

This study was a retrospective assessment of a prospectively maintained database of a consecutive series of patients with neoplastic extensive extracompartmental osteolysis (Tomita type 4-6) of the VB treated with the SAIF technique. VB reconstruction was assessed on postprocedure plain radiographs and CT by two independent raters. Technical and clinical complications were recorded. Clinical and imaging follow-ups were assessed.

RESULTS

Thirty-five patients with extensive osteolytic metastatic lesions of the VB underwent 36 SAIF procedures. SAIF was performed as a stand-alone procedure in 31/36 cases and was associated with posterior surgical fixation in 5/36 (4/5 with decompressive laminectomy). In 1 case an epidural cement leak required surgical decompression. VB reconstruction was categorized as satisfactory (excellent or good rating) by the two raters in 34/36 cases (94.5%) with an interrater reliability of 94.4% (Cohen's kappa of 0.8). Follow-up, ranging from 1 to 30 months, was available for 30/36 levels. Long-term follow-up (6-30 months, mean 11.5 months) was available for 16/36 levels. Stability during follow-up was noted in 29/30 cases.

CONCLUSIONS

SAIF provides 360° nonfusion internal fixation that stabilizes the VB in patients with extensive lytic lesions that would otherwise be challenging to treat.

Instability and impending instability in patients with vertebral metastatic disease

Metastatic disease commonly involves the spine with an increasing incidence due to a worldwide rise of cancer incidence and a longer survival of patients with osseous metastases. Metastases compromise the mechanical integrity of the vertebra and make it susceptible to fracture. Patients with pathological vertebral fracture often become symptomatic, with mechanical pain generally due to intervertebral instability, and may develop spinal cord compression and neurological deficits. Advances in imaging, radiotherapy, as well as in spinal surgery techniques, have allowed the evolution from conventional palliative external beam radiotherapy to modern stereotactic radiosurgery and from traditional open surgery to less-invasive, and sometimes prophylactic stabilization surgical treatments. It is therefore clear that fracture risk prediction, and maintenance or restoration of intervertebral stability, are important objectives in the management of these patients. Correlation between imaging findings and clinical manifestations is crucial, and a common knowledge base for treatment team members rather than a compartmentalized view is very important. This article reviews the literature on the imaging and clinical diagnosis of intervertebral instability and impending instability in the setting of spine metastatic disease, including the spinal instability neoplastic score, which is a reliable tool for diagnosing unstable or potentially unstable metastatic spinal lesions, and on the different elements considered for treatment.

Spinal Radiosurgery for Metastatic Disease of the Spine

Background

Metastatic tumor in the spinal column is common, causing symptomatic spinal cord compression in approximately 25,000 patients annually. Although surgical treatment of spinal metastases has become safer, less invasive, and more efficacious in recent years, there remains a subset of patients for whom other treatment modalities are needed. Stereotactic radiosurgery, which has long been used in the treatment of intracranial lesions, has recently been applied to the spine and enables the effective treatment of metastatic lesions.

Methods

We review the evolution of stereotactic radiosurgery and its applications in the spine, including a description of two commercially available systems.

Results

Although a relatively new technique, the use of stereotactic radiosurgery in the spine has advanced rapidly in the past decade. Spinal stereotactic radiosurgery is an effective and safe modality for the treatment of spinal metastatic disease.

Conclusions

Future challenges involve the refinement of noninvasive fiducial tracking systems and the discernment of optimal doses needed to treat various lesions. Additionally, dose-tolerance limits of normal structures need to be further developed. Increased experience will likely make stereotactic radiosurgery of the spine an important treatment modality for a variety of metastatic lesions.

Current trends in mini-invasive management of spine metastases

The spine is a frequent localization of primary tumours or metastasis involving posterior arch, pedicles and vertebra body, and often causing unsustainable pain. The management of spinal metastasis remains complex, including medical therapy (corticosteroids, chemotherapy), radiotherapy and surgical treatment, or the recent percutaneous mini-invasive approach. The target of all these treatments is to improve the quality of life of patients affected by this type of lesion. Diagnosis of spinal metastasis and then its treatment should be based on the combination of different elements: clinical evaluation, CT, MRI and nuclear medicine patterns, considering the age of the patient, known primary tumour, location of the lesions, single/multiple lesions, pattern of morphology (border, matrix, expansile character, soft tissue extension), density or signal intensity, oncologic instability and expectancy of life. The percutaneous mini-invasive approach for patients affected by secondary lesions involving the spine has as treatment goal of: (1) pain relief improving the quality of life; (2) stability treatment re-establishing the spinal biomechanics, alterated by bone destruction or deformity, preventing pathological fracture; and (3) an anti-neoplastic effect. The aim of this paper is to provide a comprehensive diagnostic and percutaneous approach to the bone metastatic spine lesions, identifying which metamer should be treated to improve patient quality of life, showing the importance of a multi-disciplinary approach to this problem.

Hypofractionated stereotactic body radiotherapy in spinal metastasis - with or without epidural extension

AIMS

To evaluate clinical outcome and the effect of malignant epidural compression (MEC) in the treatment of spine metastasis with stereotactic body radiotherapy (SBRT).

MATERIALS AND METHODS

Seventy-six lesions in 52 patients with spinal metastasis received SBRT during the period July 2010 to December 2012. MEC was detected in 20 patients (38.4%) and was separately contoured. The median dose prescribed to involved vertebra (planning target volume) was 24 Gy (range 24-27 Gy) in a median of three fractions (range 1-3). Uninvolved elements were prescribed 21 Gy in three fractions. In 59 lesions (77.6%), the entire vertebra was treated and in 17 lesions (22.4%) only the anterior elements were treated. All patients were treated with volumetric modulated arc therapy with image guidance on a Novalis Tx linear accelerator with the ExacTrac system. Dosimetric and clinical outcomes were compared in patients with or without MEC.

RESULTS

At a median follow-up of 8.48 months (range 3-40 months), 1 year local control and overall survival was 94 and 68%, respectively. In patients with or without epidural extension, the median dose to the gross tumour volume (GTV; 95%) was 23.48 Gy (range 13.70-25.75) and 22.99 Gy (range 13.55-26.84), the median spinal cord Dmax was 17.36 Gy (range 8.47-21.63) and 15.71 Gy (range 8.39-23.33). The median GTV epidural (D95%) was 21.16 Gy (range 15.43-23.92). Complete pain relief was seen in 90% of patients with MEC and 93.75% without MEC (P=NS) and neurological improvement was seen in 60% of patients in both groups of patients.

CONCLUSION

It is feasible to deliver a high dose of radiation (∼90% of the prescription dose) to the epidural component with volumetric modulated arc therapy SBRT and image guidance. It yielded high rates of pain control and local control in patients with spine metastases with or without MEC.

Contemporary Treatment Strategy for Spinal Metastasis: The “LMNOP” System

The choice of treatment for spinal metastasis is complex because (1) it depends on several inter-related clinical and radiologic factors, and (2) a wide range of management options has evolved in recent years. While radiation therapy and surgery remain the cornerstones of treatment, radiosurgery and percutaneous vertebral augmentation have also established a role. Classification systems have been developed to aid in the decision-making process, and each has different strengths and weaknesses. The comprehensive scoring systems developed to date provide an estimate of life expectancy, but do not provide much advice on the choice of treatment. We propose a new decision model that describes the key factors in formulating the management plan, while recognizing that the care of each patient remains highly individualized. The system also incorporates the latest changes in technology. The LMNOP system evaluates the number of spinal Levels involved and the Location of disease in the spine (L), Mechanical instability (M), Neurology (N), Oncology (O), Patient fitness, Prognosis and response to Prior therapy (P).

Combining percutaneous pedicular and extrapedicular access for tumor ablation in a thoracic vertebral body

We present a percutaneous modified technique to access large thoracic vertebral body lytic lesions, to increase the volume of tumor accessible to ablation, prior to cement augmentation. Tumor ablation and cavity creation-assisted percutaneous vertebroplasty was considered a palliative measure for structural stabilization in plasmocytoma involvement of the entire T8 vertebral body. Given the extent of osteolysis bilateral combined transpedicular and extrapedicular access to the vertebral body was undertaken to maximize the volume of cavity creation within the tumor. The combined transpedicular and extrapedicular access was feasible, uncomplicated, and successful in reaching all the quadrants of the anterior two thirds of the vertebral body. Slow, fluoroscopically monitored injection of high-viscosity cement resulted in a successful, desired cement distribution into the anterior two thirds of the vertebral body, spanning superior to inferior endplates, providing structural stability, in the absence of venous or epidural leakage. The technical modification described in this case yielded positive results while overcoming some of the limitations of the existing coblation device. This approach may offer an option for cement augmentation of extensive vertebral body lytic lesions, at increased risk for tumor displacement and extra-vertebral cement leakage.

Vertebral augmentation for neoplastic lesions with posterior wall erosion and epidural mass

BACKGROUND AND PURPOSE

The presence of a cortical erosion of the posterior wall or an epidural mass is commonly considered a contraindication to performing a vertebral augmentation, considering the perceived increased risk of an epidural cement leak. Our aim was to assess technical and clinical complications of vertebral augmentation procedures performed for pain palliation and/or stabilization of neoplastic lytic vertebral body lesions, with cortical erosion of the posterior wall, often associated with a soft-tissue epidural mass.

MATERIALS AND METHODS

In 48 patients, we performed retrospective vertebral augmentation assessment on 70 consecutive levels with cortical erosion of the posterior wall, as demonstrated by preprocedural CT/MR imaging. An epidural mass was present in 31/70 (44.3%) levels. Cavity creation was performed with Coblation Wands before cement injection in 59/70 levels. Injection of high-viscosity polymethylmethacrylate was performed under real-time continuous fluoroscopic control. Postprocedural CT of the treated levels was performed in all cases. Clinical follow-up was performed at 1 and 4 weeks postprocedurally.

RESULTS

In 65/70 (92.8%) levels, the vertebral augmentation resulted in satisfactory polymethylmethacrylate filling of the lytic cavity and adjacent trabecular spaces in the anterior half of the vertebral body. An epidural leak of polymethylmethacrylate occurred in 10/70 (14.2%) levels, causing radicular pain in 3 patients, which spontaneously resolved within 1 week in 2 patients, while 1 patient with a T1-T2 foraminal leak developed severe weakness of the intrinsic hand muscles and a permanent motor deficit.

CONCLUSIONS

In our series of vertebral augmentation of neoplastic lytic vertebral lesions performed for palliation of pain and/or stabilization, we observed a polymethylmethacrylate epidural leak in only 14.2% of levels, despite the presence of cortical erosion of the posterior wall and an epidural mass, with an extremely low rate of clinical complications. Our data seem to justify use of vertebral augmentation in patients with intractable pain or those at risk for vertebral collapse.

Percutaneous cement augmentation of a lytic lesion of C1 via posterolateral approach under CT guidance

BACKGROUND CONTEXT

Percutaneous vertebroplasty (PV) can provide pain relief and biomechanical stabilization of lytic metastasis of the spine in selected patients. Percutaneous vertebroplasty of the atlas has been reported in only five cases and has been performed with different techniques and approaches.

PURPOSE

To describe the technique we used to perform PV of a lytic lesion of the lateral mass of C1 under computed tomography, computed tomography angiography, and computed tomography fluoroscopy guidance with a posterolateral approach, sparing the vertebral artery (VA).

STUDY DESIGN/SETTING

Technical note.

METHODS

A 36-year-old woman with a history of intestinal carcinoid tumor presented with neck pain refractory to medical treatment. Radiological evaluation showed osteolytic destruction of the left lateral mass of the atlas, at the risk of collapse, with erosion of the VA canal. Under computed tomography and computed tomography angiography guidance, a percutaneous posterolateral oblique approach to the C1 left lateral mass was performed followed by cement augmentation under computed tomography fluoroscopy control.

RESULTS

Complete cement filling of the osteolytic lesion was achieved. A cement leak was noted along the horizontal V3 segment of the left VA. Computed tomography angiography scan showed patency of the VA after the procedure. There were no clinical complications. The patient reported substantial pain relief and improved range of motion at 12 hours postprocedure, which remained stable at 2-month follow-up examination.

CONCLUSIONS

Computed tomography-guided PV of C1 lytic lesion with posterolateral approach was effective in the described case for pain control and stabilization, and it may be a therapeutic option in selected patients to avoid occipitocervical fusion. This procedure requires good understanding of the anatomy and rigorous technique to avoid potential complications.

Spine metastases: current treatments and future directions

Spinal metastases are the most frequently encountered spinal tumour and can affect up to 50% of cancer patients. Both the incidence and prevalence of metastases are thought to be rising due to better detection and treatment options of the systemic malignancy resulting in increased patient survival. Further, the development and access to newer imaging modalities have resulted in easier screening and diagnosis of spine metastases. Current evidence suggests that pain, neurological symptoms and quality of life are all improved if patients with spine metastases are treated early and aggressively. However, selection of the appropriate therapy depends on several factors including primary histology, extent of the systemic disease, existing co-morbidities, prior treatment modalities, patient age and performance status, predicted life expectancy and available resources. This article reviews the currently available therapeutic options for spinal metastases including conventional external beam radiation therapy, open surgical decompression and stabilisation, vertebral augmentation and other minimally invasive surgery (MIS) options, stereotactic spine radiosurgery, bisphosphonates, systemic radioisotopes and chemotherapy. An algorithm for the management of spine metastases is also proposed. It outlines a multidisciplinary and integrated approach to these patients and it is hoped that this along with future advances and research will result in improved patient care and outcomes.

Phase I trial of vertebral intracavitary cement and samarium (VICS): novel technique for treatment of painful vertebral metastasis

PURPOSE

Kyphoplasty is an effective procedure to alleviate pain in vertebral metastases. However, it has no proven anticancer activity. Samarium-153-ethylene diamine tetramethylene phosphonate ((153)Sm-EDTMP) is used for palliative treatment of bone metastases. A standard dose of 1 mCi/kg is administrated intravenously. The present study was conducted to determine the feasibility of intravertebral administration of (153)Sm with kyphoplasty.

METHODS AND MATERIALS

A total of 33 procedures were performed in 26 patients. Of these 26 patients, 7 underwent procedures performed at two vertebral levels. The mean age of the cohort was 64 years (range, 33-86). The kyphoplasty procedure was performed using a known protocol; 1-4 mCi of (153)Sm was admixed with the bone cement and administered under tight radiation safety measures. Serial nuclear body scans were obtained. Pain assessment was evaluated using a visual analog pain score.

RESULTS

All patients tolerated the procedure well. No procedure-related morbidities were noted. No significant change had occurred in the blood counts at 1 month after the procedure. One case was not technically satisfactory. Nuclear scans revealed clear radiotracer uptake in the other 32 vertebrae injected. Except for the first patient, no radiation leakage was encountered. The mean pain score using the visual analog scale improved from 8.6 before to 2.8 after the procedure (p < .0001). Follow-up bone scans demonstrated a 43% decrease in the tracer uptake.

CONCLUSION

The results of our study have shown that the combination of intravertebral administration of (153)Sm and kyphoplasty is well tolerated with adequate pain control. No hematologic adverse effects were found. A reduction of the bone scan tracer uptake was observed in the injected vertebrae. Longer follow-up is needed to study the antineoplastic effect of the procedure.

Lumbar tumor resections and management

More than one-third of patients with cancer have vertebral metastases found at autopsy. Primary and metastatic tumors to the spinal column can lead to pain, instability, and neurologic deficit. Symptomatic lesions are most prevalent in the thoracic spine (70%), followed by the lumbar spine (20%) and cervical spine (10%). Lesions in larger vertebral bodies tend to be asymptomatic given the increased ratio between the diameter of the spinal canal and the traversing nerve roots.

Preliminary experience of titanium mesh cages for pathological fracture of middle and lower cervical vertebrae

The advantages and disadvantages of titanium mesh cages (TMCs) assisted by anterior cervical plates (ACPs) for interbody fusion following cervical corpectomy were investigated. Between January 2002 and September 2006, 17 patients with cervical radiculomyelopathy caused by metastasis-induced pathologic fractures were selected for anterior corpectomy. TMCs were inserted into the post-corpectomy defect and stabilized by placement of ACPs filled with Triosite. Post-operative plain X-ray films indicated maintenance of spinal stability. No ceramic, donor site or surgery-related complications were observed. True trabeculation was observed in axial and reconstructive CT scans in all surviving patients one year after surgery. Neurological recovery, pain control, and good quality of life were achieved. Short hospital stays, minimal blood loss, short operation times and brief periods of bed confinement were also observed. We conclude that a TMC assisted by an ACP is safe and effective for interbody fusion following cervical corpectomy for pathological fractures resulting from cervical vertebral metastases.

Metastatic spinal lesions: state-of-the-art treatment options and future trends

The purpose of this article is to review the current state of the art for treating symptomatic spinal fractures associated with malignant lesions and to present potential future trends in treatments for this patient population. Epidemiology, clinical presentation, and biomechanical ramifications of these lesions are summarized and treatment regimes, clinical outcomes, and complications and technical issues associated with treatments are presented. Potential future trends and new technologies for performing vertebral body augmentation in patients with metastatic spinal lesions are also discussed.

Immediate biomechanical effects of lumbar posterior dynamic stabilization above a circumferential fusion

STUDY DESIGN

Biomechanical in vitro human cadaveric lumbar flexibility testing with 6 sequential treatments.

OBJECTIVE

To compare the range of motion (ROM) of dynamic one-level posterior stabilization constructs to one-level rigid rod fixation constructs and to study the effects of extending the posterior construct to the adjacent superior level.

SUMMARY OF BACKGROUND DATA

Patients experiencing pain and biomechanical instability at one level may also present with radiographic or other indicators of early degeneration at an adjacent level. Clearly, fusion would be warranted at the symptomatic level, but the treatment plan for the adjacent level remains controversial. Additionally, the effects on adjacent motion segments above a fusion level are currently not well understood.

METHODS

Thirteen fresh frozen human cadaveric lumbar spines (L1-L5) were tested in 6 modes of loading: 3 were randomized to dynamic posterior stabilization constructs and 7 to a rigid rod pedicle screw system. Each group was subjected to 6 treatments.

RESULTS

When comparing the instrumented treatments, only Treatment 6, two-level hybrid constructs, exhibited a statistically significant effect in flexion-extension bending at L2-L3 between the posterior dynamic system and rigid rod fixation (P = 0.014).

CONCLUSION

ROM at the superior adjacent level (L2-L3) demonstrated no significant difference between intact, destabilized, one-level posterior fixation, and one-level circumferential fusion at the index level (L3-L4) when comparing posterior dynamic stabilization to rigid rod fixation. However, ROM at the superior adjacent level (L2-L3) was significantly greater for lateral bending and axial rotation when both levels (L2-L3 and L3-L4) were stabilized with a dynamic stabilization system. When the functional spinal units were instrumented with a two-level hybrid construct, two-level posterior instrumentation (L2-L3 and L3-L4) with a cage at the index level (L3-L4), all bending modes generated significantly greater ROM for the dynamic stabilization group at L2-L3 compared with rigid rod fixation.

Trends in pathological vertebral fractures in the United States: 1993 to 2004

OBJECT

Pathological vertebral fractures (PVFs) are an increasingly important cause of disability and have many clinical and economic implications. The authors examined trends in epidemiology and surgical management of pathological vertebral fractures in the US between 1993 and 2004.

METHODS

The Nationwide Inpatient Sample database was used to analyze data collected from 1993 through 2004 to determine general trends in PVFs. Patients with PVFs were identified using the appropriate International Classification of Diseases, 9th Revision (ICD-9) diagnostic code (ICD-9 733.13). Trends in vertebral augmentation procedures and spinal fusions as well as comparison with incidences of other major pathological fractures, such as hip and upper limb, were also examined.

RESULTS

In 2004, there were more than 55,000 inpatient admissions for PVFs. The majority of patients admitted were women (78%) in the 65 to 84 year-age group (60%). Medicare accounted for greater than 80% of insurance, and nearly 50% of all patients were admitted from the emergency department. The mean duration of hospitalization has continued to decrease, from 8.1 days in 1993 to 5.4 days in 2004. The mortality rate has remained relatively constant at approximately 1.5%. The discharge disposition has continued to change with an increasing number of patients being discharged to other institutions such as nursing homes and rehabilitation facilities. There was a staggering increase in the number of vertebral augmentation procedures performed between 1993 and 2004. The "national bill" for inpatient hospitalizations for PVFs totaled $1.3 billion in 2004.

CONCLUSIONS

With the continued aging of the population, PVFs represent an important cause of disability and a significant source of healthcare resource utilization.

Radiosurgery for spinal metastases: clinical experience in 500 cases from a single institution

STUDY DESIGN

A prospective nonrandomized, longitudinal cohort study.

OBJECTIVE

To evaluate the clinical outcomes of single-fraction radiosurgery as part of the management of metastatic spine tumors.

SUMMARY OF BACKGROUND DATA

The role of stereotactic radiosurgery for the treatment of spinal lesions has previously been limited by the availability of effective target immobilization and target tracking devices. Large clinical experience with spinal radiosurgery to properly assess clinical experience has previously been limited.

METHODS

A cohort of 500 cases of spinal metastases underwent radiosurgery. Ages ranged from 18 to 85 years (mean 56). Lesion location included 73 cervical, 212 thoracic, 112 lumbar, and 103 sacral.

RESULTS

The maximum intratumoral dose ranged from 12.5 to 25 Gy (mean 20). Tumor volume ranged from 0.20 to 264 mL (mean 46). Long-term pain improvement occurred in 290 of 336 cases (86%). Long-term tumor control was demonstrated in 90% of lesions treated with radiosurgery as a primary treatment modality and in 88% of lesions treated for radiographic tumor progression. Twenty-seven of 32 cases (84%) with a progressive neurologic deficit before treatment experienced at least some clinical improvement.

CONCLUSIONS

The results indicate the potential of radiosurgery in the treatment of patients with spinal metastases, especially those with solitary sites of spine involvement, to improve long-term palliation.

Multiple myeloma of the cervical spine: treatment strategies for pain and spinal instability

OBJECT

Metastases of multiple myeloma often occur in the cervical spine. These metastases may cause pain and associated spinal instability. The authors report the results of radiotherapy and surgical treatment for myeloma involving the cervical spine. The results of radiation therapy for multiple myeloma metastases to the cervical spine that cause clinical or radiographically documented instability have not been reported previously.

METHODS

A retrospective chart review of patients with multiple myeloma metastases to the cervical spine was undertaken. Between 1993 and 2005, 35 patients were treated with external-beam radiation and/or surgical stabilization at the University of Texas M. D. Anderson Cancer Center in Houston, Texas. Nineteen of 20 patients with sufficient follow-up data experienced resolution of their pain when treated with radiation without surgical intervention. Twenty-three patients had evidence of spinal instability on radiographic images; 15 of these were treated with radiation alone. Of these, 10 had sufficient follow-up data, and none showed any clinical progression of instability. Radiographic follow-up images demonstrated an arrest of further progression of instability and, in some cases, healing of pathological fractures by means of radiation alone.

CONCLUSIONS

The results of this series suggest that, in selected cases, external-beam radiation for multiple myeloma metastases to the cervical spine is an effective palliative treatment, even in cases involving clinical or radiographically documented instability.

Radiosurgery for the treatment of spinal melanoma metastases

BACKGROUND

The role of stereotactic radiosurgery in treating metastatic melanoma involving the spine has previously been limited. Conventional external beam radiotherapy lacks the precision to allow delivery of large single-fraction doses of radiation and simultaneously to limit the dose delivered to radiosensitive structures such as the spinal cord. This study evaluated the clinical efficacy of radiosurgery for the treatment of melanoma spinal metastases in 28 patients.

METHODS

Thirty-six melanoma spine metastases were treated with a single-session radiosurgery technique (1 cervical, 11 thoracic, 13 lumbar, and 11 sacral) with a follow-up period of 3-43 months (median 13 months). Tumor volume ranged from 4.1 to 153 cm3 (mean 47.6 cm3). Twenty-three of the 36 lesions had received prior external beam irradiation.

RESULTS

Maximum tumor dose was maintained at 17.5-25 Gy (mean 21.7 Gy). Spinal cord volume receiving > 8 Gy ranged from 0.0 to 0.7 cm3 (mean 0.26 cm3); spinal canal volume at the cauda equina level receiving > 8 Gy ranged from 0.0 to 3.5 cm3 (mean 0.98 cm3). No radiation-induced toxicity occurred during the follow-up period. Axial and radicular pain improved in 27 of 28 patients (96%) who were treated primarily for pain. Long-term tumor control was seen in 3 of 4 cases treated primarily for radiographic tumor progression. Two patients went on to require open surgical intervention for tumor progression resulting in neurological deficit.

CONCLUSIONS

Spinal radiosurgery offers a therapeutic modality for the safe delivery of large dose fractions of radiation therapy in a single fraction for the management of spinal metastases in patients with advanced melanoma that are often poorly controlled with alternative conventional external beam radiation therapy, and is successful even in patients with previously irradiated lesions.

Radiosurgery for the treatment of spinal lung metastases

BACKGROUND

Spinal metastases are a common source of pain as well as neurologic deficit in patients with lung cancer. Metastases from lung cancer traditionally have been believed to be relatively responsive to radiation therapy. However, conventional external beam radiotherapy lacks the precision to allow delivery of large single-fraction doses of radiation and simultaneously limit the dose to radiosensitive structures such as the spinal cord. The current study evaluated the efficacy of single-fraction radiosurgery for the treatment of spinal lung cancer metastases.

METHODS

In the current prospective cohort evaluation, 87 lung cancer metastases to the spine in 77 patients were treated with a single-fraction radiosurgery technique with a follow-up period of 6 to 40 months (median, 12 months). The indication for radiosurgery treatment was pain in 73 cases, as a primary treatment modality in 7 cases, for radiographic tumor progression in 4 cases, and for progressive neurologic deficit in 3 cases.

RESULTS

Tumor volume ranged from 0.2 to 264 cm(3) (mean, 25.7 cm(3)). The maximum tumor dose was maintained at 15 to 25 grays (Gy) (mean, 20 Gy; median, 20 Gy). No radiation-induced toxicity occurred during the follow-up period. Long-term axial and radicular pain improvement occurred in 65 of 73 patients (89%) who were treated primarily for pain. Long-term radiographic tumor control was observed in all patients who underwent radiosurgery as their primary treatment modality or for radiographic tumor progression.

CONCLUSIONS

Spinal radiosurgery was found to be feasible, safe, and clinically effective for the treatment of spinal metastases from lung cancer. The results of the current study indicate the potential of radiosurgery in the treatment of patients with spinal lung metastases, especially those with solitary sites of spine involvement, to improve long-term palliation.

Single-fraction radiosurgery for the treatment of spinal breast metastases

BACKGROUND

The spine is the most common site of bony metastases in patients with osseous breast carcinoma metastases. Spine metastases are the source of significant pain and occasionally neurologic deficit in this patient population. Conventional external beam radiotherapy lacks the precision to allow delivery of large single-fraction doses of radiation and simultaneously limit the dose to radiosensitive structures such as the spinal cord. This study evaluated the clinical efficacy of the treatment of spinal breast carcinoma metastases with a single-fraction radiosurgical technique.

METHODS

In this prospective cohort evaluation, 68 breast carcinoma metastases to the spine in 50 patients were treated with a single-fraction radiosurgery technique with a follow-up period of 6-48 months, median 16 months. The most common indication for radiosurgery treatment was pain in 57 lesions, as a primary treatment modality in 8 patients, and for radiographic tumor progression, as a postsurgical boost, and for a progressive neurologic deficit in 1 patient each.

RESULTS

Tumor volume ranged from 0.8-197 cm3 (mean, 27.7 cm3). Maximum tumor dose was maintained at 15-22.5 Gy (mean, 19 Gy). No radiation-induced toxicity occurred during the follow-up period (6-48 mo). Long-term axial and radicular pain improvement occurred in 55 of 57 (96%) patients who were treated primarily for pain. Long-term radiographic tumor control was seen in all patients who underwent radiosurgery as their primary treatment modality, for radiographic tumor progression, or as a postsurgical treatment.

CONCLUSIONS

Spinal radiosurgery was found to be feasible, safe, and clinically effective for the treatment of spinal metastases from breast carcinoma. The results indicate the potential of radiosurgery in the treatment of patients with spinal breast metastases, especially those with solitary sites of spine involvement, to improve long-term palliation.