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Biomedical subjects

Stephen L Ondra

Publications and source records attributed to Stephen L Ondra.

At least 19 recordsLinked to original sources
PubMed2007

The selection of operative versus nonoperative treatment in patients with adult scoliosis.

STUDY DESIGN: Retrospective case-control matched series. OBJECTIVE: The purpose of this study is to define factors that influence the patient and surgeon in the selection of surgical versus nonsurgical treatment for adult scoliosis. SUMMARY OF BACKGROUND DATA: There is no literature that specifically examines why adult scoliosis patients and/or their surgeons choose surgical versus nonsurgical treatment. METHODS: This study analyzes a prospective multicentered database for adult spinal deformity. A logistic regression technique was used to perform case-control matching. A total of 161 matched pairs were compared for radiographic characteristics, questionnaire responses, and standardized outcome measures. RESULTS: Nonsurgical patients had greater preoperative medical risk factors. Surgical patients had larger thoracic (51 degrees vs. 44 degrees, P = 0.006) and thoracolumbar/lumbar curves (55 degrees vs. 43 degrees, P = 0.000). Surgical patients had more frequent leg pain (47% vs. 35%, P = 0.04). They reported a higher mean level of daily back pain (P = 0.008) and more frequent moderate-to-severe back pain over the past 6 months (P = 0.03). There were also significant differences in perception of appearance and social function between the cohorts. CONCLUSIONS: This study emphasizes the complexity of surgical decision making for adult scoliosis patients. It also underscores the importance of patient-based health status measures in evaluating the adult scoliosis patient.

Adolescent↗
PubMed2006

Mathematical calculation of pedicle subtraction osteotomy size to allow precision correction of fixed sagittal deformity.

STUDY DESIGN: This is a retrospective review of 15 consecutive fixed sagittal plane deformity patients who have undergone pedicle subtraction osteotomies. The focus of this article is the application of a trigonometric equation that calculates the degree of correction needed to achieve sagittal balance. The intraoperative predictive accuracy and clinical radiographic results of using this mathematical equation are discussed. OBJECTIVE: The need for a precise and reproducible planning tool for the correction of sagittal imbalance prompted us to apply a simple trigonometric equation to achieve the desired sagittal alignment of the spine. SUMMARY OF BACKGROUND DATA: Establishing sagittal balance has been widely recognized as one of the most important parameters in optimizing outcomes for spinal reconstruction patients. Preoperative planning for sagittal plane correction in adult spinal deformity has traditionally been done by estimation or with cumbersome film cutouts. To our knowledge, there has not been a consistent method of calculating the exact number of degrees needed to reestablish spinal balance. METHODS: Patients' C7 plumb lines are measured on a 36-inch radiograph to assess the degree of sagittal imbalance and determine how many degrees of correction (and subsequent millimeters of wedge resection) are needed. Applying a basic trigonometric formula for the tangent to the sagittal alignment is used to do this. RESULTS: We have used this technique reliably in a series of 15 consecutive patients to reestablish sagittal balance. The predicted degree of correction was compared to the achieved degree of correction at the site of the osteotomy. This comparison was accurate to within 3 degrees (the standard error of measurement for the method of Cobb) in all cases except 2. CONCLUSIONS: By using a simple mathematical equation, one can reliably determine the degree of pedicle subtraction osteotomy needed for correction of sagittal deformity. This technique is reproducible and has led to successful clinical outcomes.

Adult↗
PubMed2006

A kinematic model to assess spinal motion during walking.

STUDY DESIGN AND OBJECTIVES: A 3-dimensional multi-segment kinematic spine model was developed for noninvasive analysis of spinal motion during walking. Preliminary data from able-bodied ambulators were collected and analyzed using the model. SUMMARY OF BACKGROUND DATA: Neither the spine's role during walking nor the effect of surgical spinal stabilization on gait is fully understood. Typically, gait analysis models disregard the spine entirely or regard it as a single rigid structure. Data on regional spinal movements, in conjunction with lower limb data, associated with walking are scarce. METHODS: KinTrak software (Motion Analysis Corp., Santa Rosa, CA) was used to create a biomechanical model for analysis of 3-dimensional regional spinal movements. Measuring known angles from a mechanical model and comparing them to the calculated angles validated the kinematic model. Spine motion data were collected from 10 able-bodied adults walking at 5 self-selected speeds. These results were compared to data reported in the literature. RESULTS: The uniaxial angles measured on the mechanical model were within 5 degrees of the calculated kinematic model angles, and the coupled angles were within 2 degrees. Regional spine kinematics from able-bodied subjects calculated with this model compared well to data reported by other authors. CONCLUSIONS: A multi-segment kinematic spine model has been developed and validated for analysis of spinal motion during walking. By understanding the spine's role during ambulation and the cause-and-effect relationship between spine motion and lower limb motion, preoperative planning may be augmented to restore normal alignment and balance with minimal negative effects on walking.

Adult↗
PubMed2006

Anterior thoracic spine reconstruction using a titanium mesh cage and pedicled rib flap.

STUDY DESIGN: A retrospective clinical study. OBJECTIVES: To evaluate the safety and efficacy of using an integrated titanium mesh cage and pedicled rib flap for thoracic spine reconstruction in patients at high risk of pseudarthrosis. SUMMARY OF BACKGROUND DATA: A variety of materials are available for interbody thoracic reconstruction; however, the optimal treatment of patients at high risk of pseudarthrosis remains a challenging problem. Free or pedicled bone flaps have been shown to be highly effective in terms of promoting fusion and titanium mesh cages provide excellent structural support. METHODS: Eleven patients who underwent anterior thoracic corpectomy and spinal reconstruction using an integrated titanium mesh cage and pedicled rib flap were analyzed with a mean follow-up of 37 months (range, 25-55 months). The etiology of spinal disease was infection in 7 (64%) patients and tumor in the remaining 4 (36%) patients. Seven (64%) patients were treated with only an anterior approach while the remaining 4 (36%) patients underwent circumferential spinal reconstruction. RESULTS: All patients demonstrated clinical and radiographic evidence of spinal fusion at the time of follow-up. All patients had stable or improved Frankel grades after surgery. There was a mean kyphosis correction of 7 degrees for both the focal and regional thoracic kyphosis. There were three significant postoperative complications: bilateral pleural effusion, gram-negative bacteremia, and transient right lower extremity weakness requiring reoperation and pedicle screw revision. Two patients died after surgery: one from aneurysmal subarachnoid hemorrhage and the other from complications of breast cancer. CONCLUSIONS: The use of an integrated rib flap and titanium mesh cage construct appears to be a safe and effective means of providing immediate and substantial anterior column support as well as achieving arthrodesis in challenging fusion candidates.

Adult↗
PubMed2006

Safety and efficacy of C2 pedicle screws placed with anatomic and lateral C-arm guidance.

STUDY DESIGN: This is a retrospective review of 150 C2 pedicle screw placements. Candidates had their C2 pedicle morphology assessed through three-dimensional imaging, including preoperative image guidance. After surgery, the patients were serially CT scanned. Follow-up, with fusion assessment, ranged from 1 to 12 years. OBJECTIVE: We will show that an open technique combined with lateral C-arm guidance provides rapid placement of C2 pedicle screws. SUMMARY OF BACKGROUND DATA: C2 pedicle screws can be successful anchors for a variety of cervical problems. Standard intraoperative image guidance, biplane fluoroscopy, or free hand techniques all have their drawbacks. METHODS: After adequate C2 exposure, the C2 pedicle is palpated. The dissector remains stationary to provide coronal orientation while a lateral C-arm radiograph is obtained for sagittal orientation. The drill trajectory is set, the C2 pedicle cannulated, and a cancellous screw placed. RESULTS: A total of 71 patients had bilateral screws placed and 8 patients had unilateral screws placed. The overall complication rate was 2.7%. CONCLUSIONS: In our series, we have found a consistent way to cannulate the C2 pedicle. C2 fixation serves as an integral part of cervical reconstruction. Preoperative planning, anatomic knowledge, and lateral C-arm orientation create a low morbidity method for C2 screw placement.

Adolescent↗
PubMed2006

Revision deformity surgery.

Revision deformity surgery may be necessary for several reasons. Symptomatic pseudarthrosis, implant failure or pull-out, or loss of correction may mandate reoperation. The keys to a successful revision procedure are a careful analysis of the problem, particularly the mode of failure and the contributing biomechanical factors, and the development of an appropriate surgical plan.

Humans↗
PubMed2006

Salvage technique of posterior iliac bolt placement in long-segment spinal constructs with a previous posterior iliac crest harvest: technical note.

OBJECTIVE AND IMPORTANCE: Fusion between the lumbar spine and sacrum has been used to treat deformity, degenerative disease, trauma, and tumor. These constructs have a higher failure rate when a long construct is designed, in patients with poor bone quality, and in patients with previous irradiation or with significant osteoporosis. CLINICAL PRESENTATION: Extending the construct to the pelvis has been shown to increase the fusion rate of these patients and to reduce the risk of hardware failure before fusion has occurred. INTERVENTION: We extend the constructs with the use of iliac bolts placed within the posterior iliac crests. Placement of these bolts can be challenging after the posterior iliac crest has been harvested for autologous bone in a previous operation. CONCLUSION: The purpose of this technical note is to describe our salvage technique of iliac bolt placement as an adjunct to lumbar-sacral fusions in a previously harvested iliac crest.

Bone Screws↗
PubMed2006

A method for calculating the exact angle required during pedicle subtraction osteotomy for fixed sagittal deformity: comparison with the trigonometric method.

OBJECTIVE: Pedicle subtraction osteotomy (PSO) has emerged as a powerful procedure for correcting fixed sagittal deformity. There has only been one attempt to quantify the magnitude of correction needed to restore sagittal balance; the trigonometric method for calculating the desired PSO angle is an approximation. We propose a method for calculating the exact angle required for PSO and explore how this angle differs from that obtained via the trigonometric method in illustrative cases. METHODS: We conducted a mathematical analysis of the spine with application in illustrative cases. The trigonometric method calculates the necessary angular correction at the axial level of the PSO, but along the sacral vertical line. However, the angular measurement should take place at the true axis of rotation, the apex of the PSO. Measurements were taken from full-length standing x-rays, and both methods were explored. RESULTS: The trigonometric method for calculating PSO angle is an exact measurement only if the apex of the PSO site lies on the sacral vertical line. As the apex of the PSO site moves anterior to that line, the trigonometric approximation underestimates the actual angle. As the apex of the PSO moves posterior to that line, the trigonometric approximation overestimates the actual angle. CONCLUSION: The trigonometric method for calculating the PSO angle required for surgical deformity correction is an approximation, but its validity in clinical practice was confirmed by this study. The exact angle is obtained by a method centered on the apex of the PSO site. Although the difference between these angles is small, it is an important conceptual point for spine surgeons. Measurement of the exact angle is easily performed and should replace the trigonometric method for calculating the required PSO angle when standard digital measurement tools are available.

Aged↗
PubMed2006

Clinical and radiographic outcomes of thoracic and lumbar pedicle subtraction osteotomy for fixed sagittal imbalance.

OBJECT: The authors conducted a study to evaluate the radiographically documented and functional outcomes obtained in patients who underwent pedicle subtraction osteotomy (PSO). They also compared outcomes after classification of cases into thoracic and lumbar PSO subgroups. METHODS: The authors analyzed data obtained in 35 consecutive PSO-treated patients with sagittal imbalance. One surgeon performed all surgeries. The minimal follow-up period was 2 years. Events during the perioperative course and complications were noted. Standing long-film radiographs of the spine were obtained and measurements were made preoperatively, immediately postoperatively, and at most recent follow-up examination. The modified Prolo Scale and the 22-item Scoliosis Research Society (SRS-22) Outcomes Questionnaire were administered. Early complications after PSO included neurological injury, wound-related problems, and nosocomial infections. Late complications were limited to pseudarthrosis and attendant instrumentation failure. Early and late complication rates ranged from 10 to 30% for both thoracic and lumbar PSO cohorts. Lumbar PSO was associated with improvements in local, segmental, and global measures of sagittal balance, whereas thoracic PSO was only associated with local improvement. Most patients rated their functional status as fair to good according to the modified Prolo Scale and reported, according to the SRS-22 Outcomes Questionnaire, that they were satisfied with the overall treatment of their back condition. CONCLUSIONS: The ability to perform a PSO at both lumbar and thoracic levels is a powerful asset for the spine surgeon treating spinal deformity. In the present study radiographic and clinical outcomes were superior when PSO was used to treat lumbar deformity rather than thoracic deformity because of several anatomical and technical obstacles that hindered the thoracic procedure. Nevertheless, the thoracic PSO proved a useful addition with which to produce regional improvement in sagittal balance for patients with a fixed thoracic kyphosis.

Adult↗
PubMed2005

The prophylactic use of inferior vena cava filters in patients undergoing high-risk spinal surgery.

Prophylactic inferior vena cava filter (IVCF) placement is advocated in some high-risk groups. We sought data regarding safety and efficacy for prophylactic IVCF placement in patients at high risk for venous thromboembolism (VTE) following major spinal reconstruction. Seventy-four spine surgery patients with contraindication to anticoagulation (44 females, 30 males; mean age 56.2) received prophylactic IVCFs. Criteria were (1) history of thromboembolism, (2) diagnosed thrombophilia, (3) malignancy, (4) bedridden >2 weeks prior to surgery, (5) staged procedures or multiple levels, (6) combined anterior/posterior approaches, (7) expected need for significant iliocaval manipulation during exposure, and (8) single-stage anesthetic time >8 hr. Seventy patients had at least two risk factors. All received IVCFs prior to the first stage of spine reconstruction. Patients were evaluated for filter complications, deep vein thrombosis (DVT), and pulmonary embolism (PE). Patients' lower extremity veins from groin to ankle were imaged weekly until discharge using duplex ultrasound (DUS). One-third also underwent thoracic and pelvic computed tomography scans, and the pelvic veins, IVC, and pulmonary vasculature were evaluated for VTE. Multiple DUS (n = 198, mean 2.6 studies per patient) were performed in 68 patients. At a mean follow-up of 11 months, one of the patients developed PE. Twenty-seven limbs in 23 patients developed DVT. Five limbs had isolated calf DVT, and 22 had proximal vein involvement. Insertion site DVT accounted for nearly one-third of the DVTs. Six patients died from unrelated complications. There was one technical error with an IVCF deployed in the iliac vein. Despite a high incidence of DVT following high-risk spinal surgery, prophylactic IVCF placement appears to protect patients from PE.

Adolescent↗
PubMed2004

Surgical strategies for vertebral osteomyelitis and epidural abscess.

Pyogenic vertebral discitis and osteomyelitis (PVDO) has become an increasing problem for the spine surgeon. Despite recent advances in medical care and improved diagnostic neuroimaging, PVDO remains a major cause of illness and death in the elderly population. Infection of the spinal column often presents insidiously; however, if not treated appropriately and in a timely manner it can lead to severe neurological impairment, systemic septicemia, and progressive spinal deformity. In this paper the authors review the epidemiological and pathophysiological features and the clinical presentation of PVDO. Conventional medical therapy is described, with a particular focus on the methods of diagnosis. Surgical strategies for PVDO are then presented based on the literature and according to the practice of the senior author (S.L.O.), with an emphasis placed on structural considerations, implant selection, and techniques for augmenting vascular tissue to the site of infection.

Bacterial Infections↗
PubMed2004

Prophylactic placement of an inferior vena cava filter in high-risk patients undergoing spinal reconstruction.

OBJECT: The purpose of this study was to evaluate the safety and efficacy of prophylactic inferior vena cava (IVC) filter placement in high-risk patients who undergo major spine reconstruction. METHODS: In the pilot study, 22 patients undergoing major spine reconstruction received prophylactic IVC filters. These patients were prospectively followed to evaluate complications related to the filter, the rate of deep venous thrombosis (DVT) formation, and the rate of pulmonary embolism (PE). These data were compared with those obtained in a retrospective review for PE in a matched cohort treated at the same institution. At a second institution the treatment guidelines were implemented in 17 patients undergoing complex spine surgery with the same follow-up criteria. In the pilot study, no patient experienced PE (0%), whereas two had DVT (9%). Bilateral DVT developed postoperatively in one patient (associated morbidity rate 4.5%), who required thrombolytic therapy. One patient died of unrelated surgical complications. The PE rate in the matched cohort at the same institution was 12%. At the second institution, no patient had PE, and no complications were noted. CONCLUSIONS: In this patient population, prophylactic IVC filter placement appears to decrease the PE rate substantially, from 12 to 0%. The placement of IVC filters appears to be a safe and efficacious intervention for prevention of PE in high-risk patients.

Adult↗
PubMed2004

Transforaminal lumbar interbody fusion: surgical technique and results in 24 patients.

OBJECTIVE: The advantage of anterior column support and fusion in addition to pedicle fixation in patients with degenerative spinal disorders has become increasingly clear. With the increase in popularity of this treatment, a variety of techniques have been used to achieve the goal of anterior column support, fusion, and segmental instrumentation. Posterior lumbar interbody fusion has been used since the late 1940s in the treatment of degenerative lumbar spine. We evaluated a modification to posterior lumbar interbody fusion called transforaminal lumbar interbody fusion (TLIF). METHODS: A retrospective analysis was performed on 24 patients (9 women, 15 men) who underwent TLIF. The approach involved a unilateral laminectomy and inferior facetectomy at the level of fusion. The interbody fusion was achieved from this unilateral approach by performing discectomy, arthrodesis, and insertion of one or two titanium cages packed with autologous bone. The average age of the patients in this study was 42.6 +/- 12.5 years. Five patients were smokers. Five cases were related to workmen's compensation. Seventeen patients' original symptoms were a combination of low back pain and radiculopathy. Ten patients had had a previous spine operation. RESULTS: Eleven patients had L4-S1 TLIFs. The rest of the patients had a single-level TLIF (L2-S1). Average intensive care unit and floor days were 1.1 +/- 1.0 and 5.8 +/- 2.2 days, respectively. The number of days to ambulation was 2.8 +/- 1.6 days. There were a total of six self-limited complications in 24 patients (including one transient neurological complication). The average follow-up time was 16.9 +/- 9.1 months. Twenty-two patients had solid fusions. A modified Prolo scale (4 worst, 20 best) was used to evaluate the clinical outcome. The average score was 16.1 +/- 4.1. CONCLUSION: TLIF is a reliable and safe technique for interbody support that can be performed with excellent clinical outcome. In the authors' experience, TLIF offers excellent exposure with minimal risk. This applies particularly in cases of repeat spine surgery, in which the presence of scar tissue makes traditional posterior lumbar interbody fusion techniques difficult or impossible. In addition, TLIF seems to be a viable alternative to anteroposterior circumferential fusion and/or anterior lumbar interbody fusion.

Adult↗
PubMed2004

Improved repair of cervical esophageal fistula complicating anterior spinal fusion: free omental flap compared with pectoralis major flap. Report of four cases.

Esophageal injury is a serious complication of anterior cervical fusion. A team approach to the management of these cases is described. The authors performed spinal assessment, control of the fistula, and interposition of a vascularized flap between the spine and the esophagus. They compared the overall efficacy of the pectoralis major flap (pedicled; two cases) and omental flap (free; two cases).

Adolescent↗
PubMed2003

Management of iatrogenic flat-back syndrome.

Iatrogenic loss of lordosis is now frequently recognized as a complication following placement of thoracolumbar instrumentation, especially with distraction instrumentation. Flat-back syndrome is characterized by forward inclination of the trunk, inability to stand upright, and back pain. Evaluation of the deformity should include a full-length lateral radiograph obtained with the patient's knees and hips fully extended. The most common cause of the deformity includes the use of distraction instrumentation in the lumbar spine and pseudarthrosis. Surgical treatment described in the literature includes opening (Smith-Petersen) osteotomy, polysegmental osteotomy, and closing wedge osteotomy. The authors will review the literature, cause, clinical presentation, prevention, and surgical management of flat-back syndrome.

Back Pain↗