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Biomedical subjects

Joel A Finkelstein

Publications and source records attributed to Joel A Finkelstein.

8 recordsLinked to original sources
PubMed2006

Metastatic burst fracture risk assessment based on complex loading of the thoracic spine.

The mechanical integrity of vertebral bone is compromised when metastatic cancer cells migrate to the spine, rendering it susceptible to burst fracture under physiologic loading. Risk of burst fracture has been shown to be dependent on the magnitude of the applied load, however limited work has been conducted to determine the effect of load type on the stability of the metastatic spine. The objective of this study was to use biphasic finite element modeling to evaluate the effect of multiple loading conditions on a metastatically-involved thoracic spinal motion segment. Fifteen loading scenarios were analyzed, including axial compression, flexion, extension, lateral bending, torsion, and combined loads. Additional analyses were conducted to assess the impact of the ribcage on the stability of the thoracic spine. Results demonstrate that axial loading is the predominant load type leading to increased risk of burst fracture initiation, while rotational loading led to only moderate increases in risk. Inclusion of the ribcage was found to reduce the potential for burst fracture by 27%. These findings are important in developing a more comprehensive understanding of burst fracture mechanics and in directing future modeling efforts. The results in this study may also be useful in advising less harmful activities for patients affected by lytic spinal metastases.

Computer Simulation↗
PubMed2006

Biomechanics of vertebral level, geometry, and transcortical tumors in the metastatic spine.

Metastatic involvement can disrupt the mechanical integrity of the spine, rendering vertebrae susceptible to burst fracture and neurologic damage. Fracture risk assessment for patients with spinal metastases is important in considering prophylactic treatment options. Stability of thoracic vertebrae affected by metastatic disease has been shown to be dependent on tumor size and bone density, but additional structural and geometric factors may also play a role in fracture risk assessment. The objective of this study was to use parametric finite element modeling to determine the effects of vertebral level, geometry, and metastatic compromise to the cortical shell on the risk of burst fracture in the thoracic spine. Analysis of vertebral level and geometry was assessed by investigation of seven scenarios ranging in geometry from T2-T4 to T10-T12. The effects of cortical shell compromised were assessed by comparison of four transcortical scenarios to a fully contained central vertebral body tumor scenario. Results demonstrated that upper thoracic vertebrae are at greater risk of burst fracture and that kyphotic motion segments are at decreased risk of burst fracture. Vertebrae with transcortical lesions are up to 30% less likely to lead to burst fracture initiation. The findings of this study are important for improving the understanding of burst fracture mechanics in metastatically involved vertebrae and guiding future modeling efforts.

Biomechanical Phenomena↗
PubMed2006

Optimization of tumor volume reduction and cement augmentation in percutaneous vertebroplasty for prophylactic treatment of spinal metastases.

OBJECTIVE: Spinal metastatic disease occurs in up to one-third of all cancer patients. Metastasis can lead to vertebral burst fracture and consequent neurologic compromise. Percutaneous vertebroplasty (PV) is a minimally invasive procedure aimed at restoring vertebral stability by augmentation of weakened vertebrae with bone cement. PV is associated with a complication rate of 10% in treating vertebral metastases. Tumor ablation before cement injection has been suggested to improve PV outcome in the metastatic spine. The objectives of this study were to quantify the effects of volumetric tumor reduction and cement augmentation in the metastatic spine and to develop a protocol for recommended cement volume to achieve sufficient restoration of intact (nonpathologic) vertebral body stability. METHODS: A biphasic parametric finite element model of an L1 spinal motion segment was developed and validated against previously collected experimental data. Using this model, 12 scenarios were simulated to represent tumor volume reductions of up to 60% and cement augmentation from 1 to 8 mL. CONCLUSIONS: Restoration of intact vertebral stability is possible in metastatic vertebrae after 30% tumor ablation and 1 to 2 mL bone cement augmentation. A protocol was developed on the basis of the findings of this study suggesting recommended cement volume for injection as a function of remaining tumor volume after ablation. These findings may motivate refined methods of prophylactic treatment of metastatic vertebrae.

Bone Cements↗
PubMed2006

Response shift in outcome assessment in patients undergoing total knee arthroplasty.

BACKGROUND: A response shift is a psychological change in one's perception of the quality of life following a change in health status. This phenomenon initially was recognized in patients with terminal diseases who, despite a worsening of the physical condition, did not necessarily report deterioration in quality of life. The purpose of the present study was to examine the role of response shift in patients undergoing total knee replacement surgery. METHODS: Consecutive candidates undergoing total knee replacement for the treatment of degenerative arthritis completed a Western Ontario and McMaster Universities Osteoarthritis questionnaire preoperatively (Pre-Test). At six months postoperatively, the patients completed two questionnaires: one on how they felt currently (Post-Test), and one on how they perceived themselves to have been prior to surgery (Then-Test). The study cohort comprised 125 subjects, including ninety-one women and thirty-four men, with a mean age (and standard deviation) of 68+/-9.5 years. The impact of response shift was examined statistically. RESULTS: With use of the Then-Test methodology, a significant (p<0.05) response shift was observed in the domains of pain, physical function, and total Western Ontario and McMaster Universities Osteoarthritis score, indicating that patients perceived themselves as having been more disabled than what they had reported before surgery. In measuring outcome, this translates into the treatment effect being greater when adjusting for the presence of a response shift. With the numbers available, age, gender, comorbidity, and amount of recovery did not have a significant impact on response shift when adjusted for the preoperative level of disability. CONCLUSIONS: Patients who have undergone total knee replacement demonstrate a response shift in the measurement of their outcome at six months postoperatively. Although the response shift effect in the present study did not affect the interpretation of clinical results, we have highlighted the different patterns of individuals' psychological adaptation to a change in health status. This is an essential component of assessing the success or failure of surgical interventions as quantified with self-administered quality-of-life measures.

Adaptation, Psychological↗
PubMed2005

Patterns of collapse in thoracolumbar burst fractures.

OBJECTIVE: Functional outcomes of neurologically intact patients with burst fractures may be dependent on final kyphosis at the end of treatment. Conservative treatment is indicated if an acceptable sagittal alignment of the spine can be anticipated. Thoracolumbar burst fractures are often grouped as a single entity where, in fact, anatomically distinct areas of the spine may behave differently owing to different biomechanical factors. The goal of this work was to evaluate differential behavior in terms of final kyphosis in anatomically distinct regions of the spine following stable burst fractures. METHODS: Prospective analysis of kyphosis in 60 patients treated conservatively for traumatic thoracolumbar burst fracture was conducted. Initial trauma supine radiographs were measured for initial kyphosis (Ki). Final kyphosis (Kf) in the upright patient was measured at the end of treatment. The Ki and Kf were plotted on a scatter graph; with use of linear regression analysis, a mathematical model was created to define a relationship between Ki and Kf based on anatomic level of the spine. RESULTS: The thoracolumbar spine behaved in two independent patterns with respect to Kf. Kf at the thoracolumbar junction (T11-L1) had a collapse pattern that could be approximated most accurately with the equation Kf = Ki + 0.5 Ki. At the midlumbar spine, L2-L3 level, a best-fit model for collapse was Kf = Ki + 4 degrees . CONCLUSION: In this cohort of patients, fractures that were categorized as "stable" and not requiring surgery were studied for the purpose of determining differential collapse patterns in anatomically distinct areas of the lumbar spine. We have demonstrated that the thoracolumbar junction and the midlumbar spine behave differently biomechanically and recommend that these two anatomic levels be studied independently for research purposes.

Adult↗
PubMed2003

Quality of life in surgical treatment of metastatic spine disease.

STUDY DESIGN: Overall quality of life after surgical management of metastatic disease of the spine was prospectively assessed using a validated global health status quality-of-life instrument-the Edmonton Symptom Assessment Scale. OBJECTIVES: To prospectively evaluate the efficacy of surgery in patients with metastatic spinal disease with respect to quality of life. SUMMARY OF BACKGROUND DATA: Management of spinal metastases is palliative and is aimed at improving quality of life at an acceptable risk. Although previous studies have evaluated physical outcomes, improvements in pain, and neurologic function after surgery, a multidimensional assessment of quality of life is more relevant in the palliative patient. METHODS: Twenty-five consecutive patients undergoing surgery for spinal metastases were prospectively evaluated. Pre- and postoperative assessments were performed using the Edmonton Symptom Assessment Scale. The surgical procedure consisted of decompression and instrumented stabilization. RESULTS: After surgery, the largest improvement was noted in the domain of pain (P < 0.00001). There were also significant improvements noted in the domains of tiredness (P = 0.004), nausea (P = 0.01), anxiety (P = 0.006), drowsiness (P = 0.044), appetite (P = 0.02), and well-being (P = 0.004). CONCLUSIONS: The current study demonstrates that in the appropriate patient, surgical management brings about a positive effect on the overall quality of life in patients with spinal metastases. The greatest benefit occurred in the reduction of a patient's level of pain.

Adult↗
PubMed2003

Single-level fixation of flexion distraction injuries.

Flexion distraction injuries of the thoracic and lumbar spine can be stabilized with a short construct spanning one motion segment. This surgical technique has not been well accepted because of the paucity of published outcomes of patients treated in this manner. The current study is a cohort of patients who underwent a standardized posterior open reduction and single-level fixation for this injury pattern. Independent observation prospectively followed the cohort for a minimum of 20 months with functional and radiologic outcomes determined. A significant (p < 0.0001) correction of deformity was achieved, from a mean preoperative kyphosis of 10.1 degrees to a mean postoperative lordosis of 0.9 degrees. No loss of correction occurred. The mean Oswestry score was 11.5, with 88% of patients having minimal disability. This prospective study demonstrates the efficacy of posterior open reduction and single-level fixation of flexion distraction injuries.

Adolescent↗