Biomedical subjects

Serena S Hu

Publications and source records attributed to Serena S Hu.

15 recordsLinked to original sources

PubMed2006

Preparing the adult deformity patient for spinal surgery.

STUDY DESIGN: Review article of preoperative evaluation of surgical patients as relates to adult spine patients. OBJECTIVE: To determine which patients should undergo preoperative evaluation and review options for improved preoperative preparation for these patients. SUMMARY OF BACKGROUND DATA: There is increasing attention paid to preoperative preparation for surgical patients to decrease perioperative morbidity. Better preoperative evaluation may lead to decreased complication rates and may improve outcomes. METHODS: The literature to date, including surgical, hospitalist, and critical care, was reviewed and combined with the authors' experience. RESULTS: Suggestions for preoperative screening questions are summarized. CONCLUSION: Better recognition of preoperative risk factors may help spine surgeons improve preoperative preparation in their patients, leading to decreased complication rates.

Adult↗

PubMed2006

Intradiscal thermal therapy does not stimulate biologic remodeling in an in vivo sheep model.

STUDY DESIGN: Thermal energy was delivered in vivo to ovine cervical discs and the postheating response was monitored over time. OBJECTIVES: To determine the effects of two distinctly different thermal exposures on biologic remodeling: a "high-dose" regimen intended to produce both cellular necrosis and collagen denaturation and a "low-dose" regimen intended only to kill cells. SUMMARY OF BACKGROUND DATA: Thermal therapy is a minimally invasive technique that may ameliorate discogenic back pain. Potential therapeutic mechanisms include shrinkage of collagenous tissues, stimulation of biologic remodeling, and ablation of cytokine-producing cells and nociceptive fibers. METHODS: Intradiscal heating was performed using directional interstitial ultrasound applicators. Temperature and thermal dose distributions were characterized. The effects of high (>70 C, 10 minutes) and low (52 C-54 C, 10 minutes) temperature treatments on chronic biomechanical and architectural changes were compared with sham-treated and control discs at 7, 45, and 180 days. RESULTS: The high-dose treatment caused both an acute and chronic loss of proteoglycan staining and a degradation of biomechanical properties compared with low-dose and sham groups. Similar amounts of degradation were observed in the low-dose and sham-treated discs relative to the control discs at 180 days after treatment. CONCLUSIONS: While a high temperature thermal protocol had a detrimental effect on the disc, the effects of low temperature treatment were relatively minor. Thermal therapy did not stimulate significant biologic remodeling. Future studies should focus on the effects of low-dose therapy on tissue innervation and pro-inflammatory factor production.

Animals↗

PubMed2005

Risk factors for infection after spinal surgery.

STUDY DESIGN: A retrospective case control analysis of 48 cases of postoperative infection following spinal procedures. OBJECTIVES: Spinal procedures that became infected after surgery were analyzed to identify the significance of preoperative and intraoperative risk factors. Characterization of the nature and timing of the infections was also performed. SUMMARY OF BACKGROUND DATA: The rate of postoperative infection following spinal surgery varies widely depending on the nature of the procedure and the patient's diagnosis. Preoperative comorbidities and risk factors also influence the likelihood of infection. METHODS: A review of 1629 procedures performed on 1095 patients revealed that a postoperative infection developed in 48 patients (4.4%). Data regarding preoperative and intraoperative risk factors were gathered from patient charts for these and a randomly selected control group of 95 uninfected patients. For analysis, these patient groups were further divided into adult and pediatric subgroups, with an age cutoff of 18 years. Preoperative risk factors reviewed included smoking, diabetes, previous surgery, previous infection, steroid use, body mass index, and alcohol abuse. Intraoperative factors reviewed included staging of procedures, estimated blood loss, operating time, and use of allograft or instrumentation. RESULTS: The majority of infections occurred during the early postoperative period (less than 3 months). Age >60 years, smoking, diabetes, previous surgical infection, increased body mass index, and alcohol abuse were statistically significant preoperative risk factors. The most likely procedure to be complicated by an infection was a combined anterior/posterior spinal fusion performed in a staged manner under separate anesthesia. Infections were primarily monomicrobial, although 5 patients had more than 4 organisms identified. The most common organism cultured from the wounds was Staphylococcus aureus. All patients were treated with surgical irrigation and débridement, and appropriate antibiotics to treat the cultured organism. CONCLUSIONS: Aggressive treatment of patients undergoing complex or prolonged spinal procedures is essential to prevent and treat infections. Understanding a patient's preoperative risk factors may help the physician to optimize a patient's preoperative condition. Additionally, awareness of critical intraoperative parameters will help to optimize surgical treatment. It may be appropriate to increase the duration of prophylactic antibiotics or implement other measures to decrease the incidence of infection for high risk patients.

Adult↗

PubMed2004

Blood loss in adult spinal surgery.

Spinal surgery in adults can vary from simple to complex and can also have variable anticipated surgical blood loss. There are several factors that can put patients at increased risk for greater intraoperative blood loss. These factors, including a review of the literature, will be discussed.

Adult↗

PubMed2003

Studies in the modified Scoliosis Research Society Outcomes Instrument in adults: validation, reliability, and discriminatory capacity.

STUDY DESIGN: Observational study of patients with scoliosis and matched controls. OBJECTIVES: To determine the validity and reliability of the modified Scoliosis Research Society Outcomes Instrument (SRS-22) for use in the assessment of deformity in adults. To demonstrate the discriminate validity of the SRS-22 in differentiating between affected and unaffected adults. SUMMARY OF BACKGROUND DATA: Spinal deformity has an important impact on the general health status of adults. The magnitude of this impact has been difficult to measure and reported variably in the literature. The development of disease-specific outcomes tools permits improved sensitivity and specificity in measuring the patient's self-assessment of health status. An instrument for measuring disease-specific health status in adults with scoliosis has not been validated. MATERIALS AND METHODS: Observational study comparing the health status of adults affected by scoliosis and unaffected controls, matched for age, gender, and socioeconomic status. Pearson correlation analysis was used to determine the relationship of each domain within the SRS-22 and SF-36 with radiographic parameters including sagittal balance, coronal balance, and major curve correction. Discriminate validity of the modified SRS instrument was determined by a comparison of means between affected and unaffected cohorts. The validation of the SRS-22 was determined by criterion validity, using correlation analysis with comparable domains of the SF-36. The reliability of the SRS-22 was demonstrated using test-retest parity and Cronbach's alpha test for internal consistency. RESULTS: One hundred eighty adults were included in the study, 146 with scoliosis and 34 without. Adults with scoliosis scored significantly lower than unaffected controls on every domain of the SRS-22 and the SF-36. The floor and ceiling effect of the SRS-22 were less than observed in the SF-36 instrument. Pearson correlation analysis demonstrated no significant correlation between any radiographic process measure and any specific domain within the SRS-22 or the SF-36 (r < 0.25). Comparison of similar domains in the SRS-22 and the SF-36 demonstrates high correlation between the instruments. Test-retest analysis similarly demonstrates a high degree of reproducibility in each domain (r = 0.83-0.94). Cronbach's alpha test of internal consistency within each domain demonstrates intercorrelation values greater than 0.75 within each domain of the SRS-22. CONCLUSIONS: Adult scoliosis has a significant and measurable impact on affected patients compared with controls. There is a poor correlation between radiographic parameters of outcome and patient self-assessment of health status. The SRS-22 is a reliable instrument in adults as demonstrated by a high degree of internal consistency and reproducibility. The SRS-22 is a valid instrument for use in adult deformity as demonstrated by the criterion validity assessment with the SF-36. The study supports the use of the SRS-22 in the adult spinal deformity population.

Adolescent↗

PubMed2003

Burst fracture in the metastatically involved spine: development, validation, and parametric analysis of a three-dimensional poroelastic finite-element model.

STUDY DESIGN: A finite-element study and in vitro experimental validation was performed for a parametric investigation of features that contribute to burst fracture risk in the metastatically involved spine. OBJECTIVES: To develop and validate a three-dimensional poroelastic model of a metastatically compromised vertebral segment, to evaluate the effect of lytic lesions on vertebral strains and pressures, and to determine the influence of loading and motion segment status (bone density, pedicle involvement, disc degeneration, and tumor size) on the relative risk of burst fracture initiation. SUMMARY OF BACKGROUND DATA: Finite-element analysis has been used successfully to predict failure loads and fracture patterns for bone. Although models for vertebra affected with tumors have been presented, these have not been thoroughly validated experimentally. Consequently, their predictive capabilities remain uncertain. METHODS: A three-dimensional poroelastic finite-element model of the first lumbar vertebra and adjacent intervertebral discs, including a tumor of variable size, was developed. To validate the model, 12 cadaver spinal motion segments were tested in axial compression, in intact condition, and with simulated osteolytic defects. Features of the validated model were parametrically varied to investigate the effects of tumor size, trabecular bone density, pedicle involvement, applied loads, loading rates, and disc degeneration using outcome variables of vertebral bulge and vertebral axial deformation. RESULTS: Consistent trends between the experimental data and model predictions were observed. Overall, the model results suggest that tumor size contributes most toward the risk of initiating burst fracture, followed by the applied load magnitude and bone density. CONCLUSIONS: The parametric analysis suggests that the principal factors affecting the initiation of burst fracture in metastatically affected vertebrae are tumor size, magnitude of spinal loading, and bone density. Consequently, patient-specific measures of these factors should be factored into decisions regarding clinical prophylaxis. Pedicle involvement or disc degeneration was less important according to the outcome measures in this study.

Adult↗

PubMed2003

Biomechanically derived guideline equations for burst fracture risk prediction in the metastatically involved spine.

Methods to quantify burst fracture risk and neurologic deficit for patients with spinal metastases have not been well defined. This study aims to develop objective biomechanically based guidelines to quantify metastatic burst fracture risk. An experimentally validated finite element model of a human lumbar motion segment was used to simulate burst fracture. Through parametric analysis, the behavior of metastatically involved vertebrae was quantified and a formula to relate patient-specific variables to burst fracture risk defined. The equation-based guidelines were able to describe the mechanical behavior of the metastatically involved vertebral model (R2 = 0.97) reflecting the risk and mechanism of fracture. Vertebral density was found to influence the mechanism of burst fracture with respect to endplate failure. These analyses provide clinically feasible equation-based guidelines for burst fracture risk assessment in the metastatically involved spine.

Biomechanical Phenomena↗

PubMed2003

Lumbar end plate osteotomy in adult patients with scoliosis.

The maintenance of mobile segments in the lumbar spine may prevent complications associated with long fusions to the sacrum and permit improved postoperative patient function and mobility. The purpose of the current study was to describe the technique of end plate osteotomy for surgical treatment of fractional curves in the lumbosacral region. This technique serves to allow the end lumbar vertebra to become horizontal, to reduce lumbosacral fractional curves, and to create a stable end vertebra above the pelvis. A review of long-term clinical and radiographic outcomes in patients treated with the technique have been satisfactory. The authors show that the techniques of end plate osteotomy with concave osteophyte excision is a clinically valuable technique for the treatment of adults with fixed lumbosacral fractional curves.

Adult↗

PubMed2002

Predictors of flexibility and pain patterns in thoracolumbar and lumbar idiopathic scoliosis.

STUDY DESIGN: A retrospective evaluation of radiographs in patients with idiopathic scoliosis was undertaken to assess predictors of flexibility. OBJECTIVE: To evaluate potential predictors of flexibility in patients with thoracolumbar and lumbar scoliosis. SUMMARY OF BACKGROUND DATA: Curve flexibility is an important consideration in the operative management of idiopathic scoliosis. Flexibility of the major curve is a useful predictor of expected surgical correction, and flexibility of compensatory curves determines whether they are structural or nonstructural. An accurate assessment of curve flexibility has important implications on surgical approaches and planning for deformity correction. The role of age and curve magnitude in predicting curve flexibility has not been well defined. A quantitative assessment of changes in curve flexibility with age and progression of deformity may yield important insight into the change in surgical management options over time. METHODS: A retrospective review of 75 patients with idiopathic thoracolumbar and lumbar scoliosis (age range 13-78 years) was undertaken. Preoperative standing and side-bending radiographs of thoracolumbar and lumbar curves were evaluated. Cobb angles of structural and fractional curves, curve flexibility, presence of lateral listhesis, and axial and radicular pain were documented. Predictors of structural and fractional curve flexibility were evaluated with correlation and regression analysis. Correlation analysis was used to demonstrate an association between radiographic findings and the clinical presentation. RESULTS: Seventy-five patients had an average major curve magnitude of 56 degrees (range 34-82 degrees ) with flexibility averaging 55% (range 20-93%). Structural curve flexibility was highly inversely correlated with both curve magnitude (r = -0.7; P< 0.001) and with age (r = -0.6; P< 0.001). Lumbar fractional curve (L4-S1) flexibility showed a high inverse correlation with age (r = -0.65; P< 0.001) but did not show correlation with Cobb angle. Thoracic compensatory curves showed a moderate correlation with Cobb angle (r = 0.53). Structural and fractional curve flexibility showed high correlation with each other (r = 0.5-0.66). Regression analysis yielded a formula to predict the flexibility of the structural curve (FSC): FSC = 130 - (Cobb + Age/2). Axial pain was correlated with age (r = 0.63); however, it was not correlated with curve magnitude. CONCLUSION: We have shown that curve magnitude and patient age are the main predictors of structural flexibility. Every 10 degrees increase in curve magnitude over 40 degrees results in a 10% decrease in flexibility; every 10-year increase in age decreases flexibility of the structural curve by 5% and the lumbosacral fractional curve by 10%. Curve magnitude and age of the patients are significant predictors of curve flexibility. The demonstration of this association offers useful information in estimating how surgical options for deformity correction may change over time.

Adolescent↗

PubMed2002

Outcome and complications of long fusions to the sacrum in adult spine deformity: luque-galveston, combined iliac and sacral screws, and sacral fixation.

STUDY DESIGN: A retrospective study of adults with long fusion to the sacrum using three different fixations was performed. OBJECTIVE: To compare the long-term clinical results and complications associated with three methods of lumbosacral fixation for adult spine deformities: Luque-Galveston, combined iliac and sacral screws, and sacral screws. SUMMARY OF BACKGROUND DATA: The preferred technique for long fusion to the sacrum is controversial, and surgery for adult deformity is fraught with significant technical difficulties and high complication rates. No clinical study compares the long-term outcome of long fusion to the sacrum using these different methods of lumbosacral fixation. METHODS: This study included 54 consecutive patients who underwent elective combined anterior and posterior surgical reconstruction for adult spine deformity with a minimum follow-up period of 2 years. The patients were divided into three groups on the basis of the surgical method used for the posterior spine instrumentation. Group 1 consisted of 11 patients with smooth L-rod and segmental sublaminar wire instrumentation (Luque-Galveston technique). Group 2 consisted of 36 patients with posterior Isola segmental instrumentation and combined iliac and sacral screws. Group 3 consisted of 12 patients with Isola segmental instrumentation using bicortical sacral screws. Five patients were revised to another fixation group, giving a total of 59 cases. Radiographic, clinical results, and long-term outcome data were obtained using the modified Scoliosis Research Society (SRS) outcome instrument. RESULTS: There were 26 late complications. Pseudarthrosis developed in 10 patients, requiring revision surgery: 4 (36%) in the Group 1, 5 (14%) in Group 2, and 1 (8.5%) in Group 3. Comparison of the modified SRS outcomes showed no difference among the groups. The average SRS grand total score was 73.4% for Group 1, 70.9% for Group 2, and 62.6% for Group 3. Overall, 76% of the patients were satisfied with their outcome. The presence of perioperative complications or pseudarthrosis significantly correlated with a lower satisfaction score (P = 0.012 and P = 0.048, respectively). Sagittal plane decompensation significantly correlated with a higher pain score (P = 0.035). Patients with prior surgeries scored lower on the self-image questions than patients with no prior surgery (P = 0.007). CONCLUSIONS: Attention to sagittal balance is critical in these patients. Revision surgery is as safe and effective as primary surgery. According to the current findings, the Luque-Galveston fixation technique has an unacceptably high rate of pseudarthrosis, and this method is not recommended for adult deformities. Currently, the authors are using bicortical and triangulated sacral screws with an anterior interbody support in patients with good bone stock, but only when the spine balance is restored. Otherwise, they recommend using iliac fixation, although there is a higher rate of painful hardware, requiring removal.

Adult↗

PubMed2002

The lumbar zygapophyseal (facet) joints: a role in the pathogenesis of spinal pain syndromes and degenerative spondylolisthesis.

The zygapophyseal joints in the lumbar spine are important structural components contributing to the stability of the lumbar motion segments. Pathology of the zygapophyseal joints in the lumbar spine may be a significant cause of low back pain and segmental instability within the lumbar spine. Management of pathology related to the zygapophyseal joints remains a difficult challenge for the physician caring for patients with spinal disorders. Future investigations with tissue engineering, ligamentous reconstructions, and intervertebral disc replacement or regeneration may have useful applications in the treatment of zygapophyseal joint pathology.

Female↗

PubMed2002

Use of allograft femoral rings for spinal deformity in adults.

Anterior structural support plays an important role in spinal deformity surgery. Femoral ring allografts have been widely used for this purpose despite numerous alternative implants such as cages. The literature and the authors' experience support the use of femoral ring allograft as a structural and biologic compatible implant to reconstruct anterior column defects. Pseudarthrosis rates and the rate of subsidence and loss of correction are low. No long-term studies exist that show that cages are superior in correction of deformity. Femoral ring allograft remains a viable, cost-effective, and biologic sound alternative.

Biomechanical Phenomena↗

PubMedDate not supplied

Disc arthroplasty design influences intervertebral kinematics and facet forces.

BACKGROUND CONTEXT: Total disc replacement is a novel approach for dynamically stabilizing a painful intervertebral segment. While this approach is gaining popularity, and several types of implants are used, the effect of disc arthroplasty on lumbar biomechanics has not been widely reported. Consequently, beneficial or adverse effects of this procedure may not be fully realized, and data for kinematic optimization are unavailable. PURPOSE: To characterize kinematic and load transfer modifications at L5/S1 secondary to joint replacement. STUDY DESIGN: A human cadaveric biomechanical study in which the facet forces and instant axes of rotation (IAR) were measured for different spinal positions under simulated weightbearing conditions before and after total disc replacement at L5/S1 using semiconstrained (3 degrees of freedom [DOF]; Prodisc) and unconstrained (5 DOF; Charité) articulated implants. METHODS: Twelve radiographically normal human cadaveric L5/S1 joints (age range 45-64 years) were tested before and after disc replacement using Prodisc II implants (Spine Solutions, Paoli, PA) in six specimens and SB Charité III (Johnson & Johnson, New Brunswick, NJ) in six other specimens. Semiconstrained fixtures in combination with a servo-hydraulic materials testing system subjected the test specimens to a physiologic combination of compression and anterior shear. Multiple intervertebral positions were studied and included up to 6 degrees of flexion, extension, and lateral bending. The IAR was calculated for every 3-degree intervals, and the force through the facet joints was simultaneously measured using flexible intra-articular sensors. Data were analyzed using repeated-measures analysis of variance. RESULTS: During flexion/extension, the average IAR positions and directions were not significantly modified by implantation with the exception that the IAR was higher relative to S1 end plate with the Charité (p=.028). The IAR had a vertically oriented centrode throughout flexion/extension with the Prodisc (p<.001) and the Charité (p<.016). The centrode tended to be greater with the Prodisc. There was a trend that the facet force was decreased throughout flexion/extension for the Prodisc; however, this was statistically significant only at 6 degrees extension (27%, p=.013). In lateral bending, the IAR was significantly modified by Prodisc replacement, with a decreased inclination relative to S1 end plate, (ie, increased coupled axial rotation). While the IAR moved in the horizontal plane toward the side of bending, this effect was more pronounced with the Prodisc. The ipsilateral facet force was significantly increased in 6 degrees lateral bending with the Charité (85%; p=.001). CONCLUSIONS: The degree of constraint affects post-implantation kinematics and load transfer. With the Prodisc (3 DOF), the facets were partially unloaded, though the IAR did not match the fixed geometrical center of the UHMWPE. The latter observation suggests joint surface incongruence is developed during movement. With the Charité (5 DOF), the IAR was less variable, yet the facet forces tended to increase, particularly during lateral bending. These results highlight the important role the facets play in guiding movement, and that implant constraint influences facet/implant synergy. The long-term consequences of the differing kinematics on clinically important outcomes such as wear and facet arthritis have yet to be determined.

Arthroplasty, Replacement↗

PubMedDate not supplied

Percutaneous plasma decompression alters cytokine expression in injured porcine intervertebral discs.

BACKGROUND CONTEXT: Discectomy is a surgical technique commonly used to treat bulging or herniated discs causing nerve root compression. Clinical data suggest discectomy may also help patients with contained discs and no clear neural compromise. However, the mechanisms of clinical efficacy are uncertain, and consequently bases for treatment optimization are limited. PURPOSE: To determine the effect of percutaneous plasma decompression on the histologic, morphologic, biochemical and biomechanical features of degenerating intervertebral discs. STUDY DESIGN: An adult porcine model of disc degeneration was used to establish a degenerative baseline against which to evaluate discectomy efficacy. OUTCOME MEASURES: Cytokines interleukin (IL)-1, IL-6, IL-8, and tumor necrosis factor (TNF)-alpha were measured from tissue samples using enzyme-linked immunosorbent assay. Histology and morphology images were rated for degenerative findings (of cells and matrix) in both the nucleus and annulus. Proteoglycan content was determined, and intact specimen stiffness and flexibility were measured biomechanically. Magnetic resonance images were collected for biomechanical specimens. METHODS: Using a retroperitoneal surgical approach, stab incisions were made in four or five lumbar discs per spine in 12 minipigs. Animals were allocated into one of three groups: 6-week recovery, 12-week recovery and percutaneous plasma decompression using an electrosurgical device at 6 weeks with recovery for 6 additional weeks. Four additional animals served as controls. RESULTS: Discs treated with discectomy had a significant increase in IL-8 and a decrease in IL-1 as compared with the 12-week, nontreated discs. There were no significant differences in morphologic and biomechanical parameters or proteoglycan content between treated discs and time-matched, nontreated discs. CONCLUSIONS: Our results demonstrate that percutaneous plasma discectomy alters the expression of inflammatory cytokines in degenerated discs, leading to a decrease in IL-1 and an increase in IL-8. Whereas both IL-1 and IL-8 have hyperalgesic properties, IL-1 is likely to be a more important pathophysiologic factor in painful disc disorders than IL-8. Therefore, the alteration in cytokine expression that we observed is consistent with this effect as a mechanism of pain relief after discectomy. In addition, given that IL-1 is catabolic in injured tissue and IL-8 is anabolic, our results suggest that a percutaneous plasma discectomy may be capable of initiating a repair response in the disc.

Animals↗

PubMedDate not supplied

Spinal infections.

Spinal infections can occur in a variety of clinical situations. Their presentation ranges from the infant with diskitis who is unwilling to crawl or walk to the adult who develops an infection after a spinal procedure. The most common types of spinal infections are hematogenous bacterial or fungal infections, pediatric diskitis, epidural abscess, and postoperative infections. Prompt and accurate diagnosis of spinal infections, the cornerstone of treatment, requires a high index of suspicion in at-risk patients and the appropriate evaluation to identify the organism and determine the extent of infection. Neurologic function and spinal stability also should be carefully evaluated. The goals of therapy should include eradicating the infection, relieving pain, preserving or restoring neurologic function, improving nutrition, and maintaining spinal stability.

Adult↗