Hip or spine surgery first?: a survey of treatment order for patients with concurrent degenerative hip and spinal disorders

AIMS: Patients may present with concurrent symptomatic osteoarthritis (OA) of the hip and degenerative disorders of the lumbar spine, with surgical treatment being indicated for both. Whether arthroplasty of the hip or spinal surgery should be performed first remains uncertain. MATERIALS AND METHODS: Clinical scenarios were devised for a survey asking the preferred order of surgery and the rationale for this decision for five fictional patients with both OA of the hip and degenerative lumbar disorders. These were symptomatic OA of the hip and: 1) lumbar spinal stenosis with neurological claudication; 2) lumbar degenerative spondylolisthesis with leg pain; 3) lumbar disc herniation with leg weakness; 4) lumbar scoliosis with back pain; and 5) thoracolumbar disc herniation with myelopathy. This survey was sent to 110 members of The Hip Society and 101 members of the Scoliosis Research Society. The choices of the surgeons were compared among scenarios and between surgical specialties using the chi-squared test. The free-text comments were analyzed using text-mining. RESULTS: Responses were received from 51 hip surgeons (46%) and 37 spine surgeons (37%). The percentages of hip surgeons recommending 'hip first' differed significantly among scenarios: 59% for scenario 1; 73% for scenario 2; 47% for scenario 3; 47% for scenario 4; and 10% for scenario 5 (p < 0.001). The percentages of spine surgeons recommending 'hip first' were 49% for scenario 1; 70% for scenario 2; 19% for scenario 3; 78% for scenario 4; and 0% for scenario 5. There were significant differences between the groups for scenarios 3 (more hip surgeons recommended 'hip first'; p = 0.012) and 4 (more hip surgeons recommended 'spine first'; p = 0.006). CONCLUSION: In patients with coexistent OA of the hip and degenerative disorders of the spine, the question of 'hip or spinal surgery first' elicits relatively consistent answers in some clinical scenarios, but remains controversial in others, even for experienced surgeons. The nature of neurological symptoms can influence surgeons' decision-making. Cite this article: Bone Joint J 2019;101-B(6 Supple B):37-44.

Effect of the intra-abdominal pressure and the center of segmental body mass on the lumbar spine mechanics - a computational parametric study.

Determination of physiological loads in human lumbar spine is critical for understanding the mechanisms of lumbar diseases and for designing surgical treatments. Computational models have been used widely to estimate the physiological loads of the spine during simulated functional activities. However, various assumptions on physiological factors such as the intra-abdominal pressure (IAP), centers of mass (COMs) of the upper body and lumbar segments, and vertebral centers of rotation (CORs) have been made in modeling techniques. Systematic knowledge of how these assumptions will affect the predicted spinal biomechanics is important for improving the simulation accuracy. In this paper, we developed a 3D subject-specific numerical model of the lumbosacral spine including T12 and 90 muscles. The effects of the IAP magnitude and COMs locations on the COR of each motion segment and on the joint/muscle forces were investigated using a global convergence optimization procedure when the subject was in a weight bearing standing position. The data indicated that the line connecting the CORs showed a smaller curvature than the lordosis of the lumbar spine in standing posture when the IAP was 0 kPa and the COMs were 10 mm anterior to the geometric center of the T12 vertebra. Increasing the IAP from 0 kPa to 10 kPa shifted the location of CORs toward the posterior direction (from 1.4 ± 8.9 mm anterior to intervertebral disc (IVD) centers to 40.5 ± 3.1 mm posterior to the IVD centers) and reduced the average joint force (from 0.78 ± 0.11 Body weight (BW) to 0.31 ± 0.07 BW) and overall muscle force (from 349.3 ± 57.7 N to 221.5 ± 84.2 N). Anterior movement of the COMs from -30 mm to 70 mm relative to the geometric center of T12 vertebra caused an anterior shift of the CORs (from 25.1 ± 8.3 mm posterior to IVD centers to 7.8 ± 6.2 mm anterior to IVD centers) and increases of average joint forces (from 0.78 ± 0.1 BW to 0.93 ± 0.1 BW) and muscle force (from 348.9 ± 47.7 N to 452.9 ± 58.6 N). Therefore, it is important to consider the IAP and correct COMs in order to accurately simulate human spine biomechanics. The method and results of this study could be useful for designing prevention strategies of spinal injuries and recurrences, and for enhancing rehabilitation efficiency.

Postoperative deep wound infections in adults after spinal fusion: management with vacuum-assisted wound closure.

OBJECTIVE: Vacuum-assisted wound closure (VAC) exposes the wound bed to negative pressure, resulting in removal of edema fluid, improvement of blood supply, and stimulation of cellular proliferation of reparative granulation tissue. It has been used to treat open wounds in the extremities, open sternal wounds, pressure ulcers, and abdominal wall wounds. This study retrospectively reviewed instrumented spine fusions complicated by surgical wound infection and managed by a protocol including the use of VAC in order to evaluate the efficacy of applying vacuum therapy on patients with deep spine infections and exposed instrumentation. METHODS: Twenty consecutive patients with deep wound infections after undergoing spinal fusion procedures were studied. There were 12 men and 8 women with an average age of 55 years (31-81 years). Eight patients had undergone concomitant anterior and posterior arthrodesis, nine patients had a posterior spinal fusion, and three patients had a transforaminal lumbar interbody fusion. Seven patients had a decompression with exposed dura. Sixteen patients presented with a draining wound within the first 6 weeks postoperatively (average 24 days). There were four patients who presented with back pain and temperature after 1 year postoperatively (average 3 years). All patients were taken to the operating room for irrigation and debridement followed by placement of the VAC with subsequent delayed closure of the wound. RESULTS: There was an average of 1.8 (1-8) irrigation and debridement procedures prior to placement of the VAC. Once the VAC was initiated, there was an average of 2.2 (2-3) procedures until and including closure of the wound. The wound was closed an average of 7 days (5-14 days) after the placement of the initial VAC in the wound. All patients tolerated the VAC without adverse effects. All patients were kept on a 6-week course of intravenous antibiotic therapy. The average follow-up was 10 months (6-24 months). There were no cases of uncontrolled sepsis once the VAC was initiated. All patients achieved a clean closed wound without removal of instrumentation at a minimum follow-up of 6 months. CONCLUSION: VAC therapy is an effective adjunct in closing complex deep spinal wounds with exposed instrumentation.

Anterior versus posterior treatment of stable thoracolumbar burst fractures without neurologic deficit: a prospective, randomized study.

OBJECTIVE: A prospective randomized study was conducted to determine whether there exist any differences in radiographic, clinical, or functional outcomes when individuals with stable burst fractures of the thoracolumbar junction without neurologic deficit are treated with either a posterior fusion with instrumentation or anterior reconstruction, fusion, and instrumentation. There exists relatively little literature evaluating the outcomes of individuals treated with anterior surgery, and no prospective randomized studies exist comparing the two treatment approaches. METHODS: From May 1995 to March 2001, a consecutive series of subjects with acute isolated burst fractures of the thoracolumbar junction (T10-L2) without neurologic deficit were randomized to receive either an anterior fusion with instrumentation or a posterior fusion with instrumentation. Radiographs including computed tomography (CT) were obtained. Radiographs were repeated at 2, 4, 6, 12, and 24 months. The CT scan was also repeated at 24 months. Hospital stay, cost, operating time, blood loss, complications, and patient-related functional outcomes were measured. RESULTS: Of 43 enrolled, 38 completed a minimum of 2-year follow-up (average: 43 months; range: 24-108 months). Eighteen received a posterior spine fusion and 20 an anterior approach. Hospital stay and operating time were similar. Blood loss was higher in the group treated anteriorly; however, the incidence of transfusion was the same. There were 17 "complications" including instrumentation removal for pain in 18 patients treated posteriorly, but only 3 minor complications in 3 patients treated anteriorly. Patient-related functional outcomes were similar for the two groups. CONCLUSIONS: Although patient outcomes are similar, anterior fusion and instrumentation for thoracolumbar burst fractures may present fewer complications or additional surgeries.

Pathologic mechanism of experimental scoliosis in pinealectomized chickens.

STUDY DESIGN: This study was designed to investigate the pathologic mechanisms of idiopathic scoliosis using experimentally induced scoliosis in chickens. OBJECTIVE: To understand the process of producing a scoliotic deformity in pinealectomized chickens. SUMMARY OF BACKGROUND DATA: Pinealectomy in chickens consistently produces scoliosis with anatomic characteristics similar to those of human idiopathic scoliosis. Pinealectomized chickens are an important animal model for the study of idiopathic scoliosis. METHODS: In this study, 40 chickens were divided into two groups; 20 chickens treated with pinealectomy and 20 with a sham operation as control subjects on the second after hatching. The chickens in both groups then were killed at intervals ranging from 1 to 20 weeks after surgery. Their spines were examined visually and radiologically for the presence of a scoliotic curve and vertebral deformities. RESULTS: Rotational lordoscoliosis developed in pinealectomized chickens. The chickens with severe scoliosis were characterized by apically wedge-shaped vertebrae. In contrast, no scoliosis with any vertebral deformity developed in any of the chickens that received a sham operation. CONCLUSIONS: Because there normally is evidence of lordosis in the thoracic spine of chickens, the rotational instability of the spine induced by pinealectomy may produce a scoliotic deformity as a secondary phenomenon. Pinealectomy in chickens consistently produces scoliosis with anatomic characteristics similar to those of human idiopathic scoliosis. The authors believe that disturbance of the equilibrium and the posture mechanism associated with a defect in melatonin synthesis after pinealectomy may promote the development of rotational lordoscoliosis.

Extension of fusions to the pelvis in idiopathic scoliosis.

STUDY DESIGN: Retrospective study of patients after extension of previous scoliosis fusions to the pelvis. OBJECTIVE: To determine whether modern instrumentation and surgical techniques provide for increased fusion rates with fewer complications. SUMMARY OF BACKGROUND DATA: Traditionally, long fusions to the pelvis in adults with idiopathic scoliosis have resulted in high complication rates, including pseudarthrosis. METHODS: The hospital and clinic charts of 41 patients (40 female, 1 male) were reviewed 41 months (range: 24-116) after surgery for extension to the pelvis of previous scoliosis fusions. Thirty-nine of 41 had a combined anteroposterior fusion extension; two had posterior extension only. In 37 of 41 patients, Cotrel-Dubousset (CD) instrumentation was used; in two, Isola (Acromed Corp., Cleveland, OH), in one, TSRH; (Sofamor-Danek, Memphis, TN), and in one, Synergy (Cross Medical Products, Columbus, OH). Parameters analyzed were fusion rate, sagittal and coronal balance, lumbar lordosis, length of fusion extension, and distal fixation method. RESULTS: Complications were seen in 30 of 41 patients. The pseudarthrosis rate was 37% (15/41) and was significantly related to the method of distal posterior fixation. With sacral fixation only, the rate was 53% (8/15), with iliac fixation only 42% (3/7), and with both iliac and sacral fixation 21% (4/19; P < 0.05). This was not correlated with fusion rate, and the length of fusion extension did not affect the pseudarthrosis rate or sagittal balance. CONCLUSION: When fixed to the ilium and sacrum, modern instrumentation appears capable of maintaining sagittal balance with lower rates of pseudarthrosis when previous scoliosis fusions are extended to the pelvis. The complication rate remains significant.

Torsional rigidity of scoliosis constructs.

STUDY DESIGN: A biomechanical study of the rigidity of various scoliosis constructs instrumented with and without caudal pedicle screw anchors and with none, one, or two cross-link devices. OBJECTIVES: To determine whether the increased torsional rigidity provided by distal pedicle screw fixation might make cross-linking unnecessary. SUMMARY OF BACKGROUND DATA: Pedicle screws and cross-linking devices have been shown to increase the structural rigidity of spinal constructs. Their relative contributions to scoliosis construct rigidity has not been determined. METHODS: "Short" (T2-T11) and "long" (T2-L3) scoliosis constructs were mounted on an industrially fabricated spine model and tested in a hydraulic testing machine. Four different short and four different long constructs were tested: hooks only, hooks with concave side thoracic sublaminar wires, hooks with distal pedicle screw anchors, and hooks, distal pedicle screw anchors, and concave thoracic sublaminar wires. There were four iterations for each construct tested: no cross-links, one superior cross-link at T4-T5, one inferior cross-link at T9-T10, and two cross-links. Torsional rigidity was tested by applying a rotational torque at T2. Vertebral body motion was recorded with a three-dimensional video analysis system. RESULTS: Constructs with distal pedicle screws were statistically more rigid in torsion than those with hooks as distal anchors. The additional torsional rigidity from one or more cross-links was negligible compared with that provided by pedicle screws. CONCLUSIONS: With pedicle screws as distal anchors in scoliosis constructs, cross-linking with one or two devices adds very little additional rotational stiffness and may be unnecessary in many cases.

Thoracic discography in healthy individuals. A controlled prospective study of magnetic resonance imaging and discography in asymptomatic and symptomatic individuals.

STUDY DESIGN: A prospective case-control investigation. OBJECTIVES: To determine the responses to thoracic discography of asymptomatic individuals. SUMMARY OF BACKGROUND DATA: Literature regarding lumbar and cervical discography reveals that even morphologically abnormal discs often are not painful, whereas painful discs typically exhibit anular or endplate disruption. METHODS: Ten adult lifelong asymptomatic volunteers, ages 23 to 45 years, underwent magnetic resonance imaging of the thoracic spine, followed by four-level discography. Provocative responses were graded on a scale of 0 (no sensation) to 10 (extreme pain or pressure), and filmed discs were graded using a modified Dallas scheme. Concomitantly, 10 nonlitigious adults (6 men and 4 women, ages 31 to 55 years) experiencing chronic thoracic pain were similarly studied as a control group. RESULTS: The mean pain response in the asymptomatic volunteers was 2.4/10. Three discs were intensely painful (scores of 7/10, 8/10, 10/10), with all three exhibiting prominent endplate irregularities and anular tears typical of thoracolumbar Scheuermann's disease. On discography, 27 of 40 discs were abnormal, with endplate irregularities, anular tears, and/or herniations. Ten discs read as normal on magnetic resonance imaging showed anular pathology on discography. In the group with chronic thoracic pain, the average pain response was 6.3/10 (P < 0.05). Of the 48 discs studied, 24 were concordantly painful, with a pain response of 8.5/10 (P < 0.05); 17 had nonconcordant pain/pressure, with an average pain of 4.8/10 (P < 0.05); and 5 had no response. On magnetic resonance imaging 21 of the 48 discs appeared normal. However, on discography, only 10 were judged as normal. CONCLUSIONS: On discography, thoracic discs with prominent Schmorl's nodes may be intensely painful, even in lifelong asymptomatic individuals, but the pain is unfamiliar or nonconcordant. Thoracic discography may-demonstrate disc pathology not seen on magnetic resonance imaging.

Prevention of deep-vein thrombosis after major spinal surgery: a comparison study of external devices.

We studied the difference in postoperative thrombotic complications after major spinal surgery between two commonly used external compression devices. Our 136 subjects were prospectively randomized to receive either thigh-high sequential pneumatic compression wraps or pneumatic foot-compression wraps. All were studied postoperatively with duplex ultrasonography and analyzed for leg swelling, the rate of thrombotic events, and overall subjective patient comfort. The rate of postoperative thrombosis was 1.5%. The one pulmonary embolism was successfully treated with heparin. One other patient had a small asymptomatic thrombus of the saphenous vein. Both subjects wore foot wraps. Subjectively, the devices were rated as being equally comfortable. We believe that external compression for thrombosis prophylaxis after major spinal surgery is effective. The particular device chosen may be driven by other factors such as cost, physician or nursing preference, and ease of application.

The natural history of asymptomatic thoracic disc herniations.

STUDY DESIGN: Magnetic resonance imaging was used to determine the natural history of asymptomatic thoracic disc herniations. OBJECTIVES: To determine whether thoracic disc herniations change in size over time. SUMMARY OF BACKGROUND DATA: Based on previous work by the authors of the present study, the incidence of asymptomatic thoracic disc herniations is approximately 37%. The natural history of thoracic disc herniations is unknown. The natural history of lumbar and cervical disc herniations in symptomatic individuals who become asymptomatic has been shown in multiple studies frequently to result in a decrease in size of the herniation. METHODS: Twenty patients with 48 asymptomatic thoracic herniations previously diagnosed with magnetic resonance imaging underwent repeat magnetic resonance imaging using sagittal T1-weighted spine echo and axial multiplanar gradient refocused images at each thoracic disc level from T1 to T12 for a mean follow-up period of 26 months. Midsagittal canal diameter was recorded, and disc herniation square area was measured using a computer-assisted digitizing program. Disc herniations were categorized according to percentage of canal compromise. The change in size of the disc herniations over time was analyzed. RESULTS: All patients remained asymptomatic during the follow-up period. A total of 48 disc herniations were identified from the original magnetic resonance images. There were 21 small (0-10% canal compromise) disc herniations, 20 medium (> 10-20%) disc herniations, and seven large (> 20%) disc herniations. Of the 21 small disc herniations, 18 showed no significant change in size, whereas three showed a measurable increase in size. Of the 20 medium-sized disc herniations, 16 showed either a small or no change in size, one showed a significant increase in size, and three showed a significant decrease in size. Of the seven large disc herniations, three demonstrated no change in size, and four demonstrated a significant decrease in size. In addition, five new disc herniations were detected in four patients; one was small, and four were moderate in size. CONCLUSIONS: Based on the results of this study, the authors believe that asymptomatic disc herniations may well exist in a state of relative flux, yet exhibit little change in size and remain asymptomatic. There was a trend, however, for small disc herniations either to remain unchanged or increase in size and for large disc herniations often to decrease in size.

Rotational changes of the vertebral pelvic axis after sublaminar instrumentation in adolescent idiopathic scoliosis.

STUDY DESIGN: The authors studied the rotational effect of sublaminar wiring on the spinal pelvic axis on 20 patients who were being treated for adolescent idiopathic scoliosis. OBJECTIVES: To determine if sublaminar wiring effectively derotates the scoliotic spine. SUMMARY OF BACKGROUND DATA: The correction of the rotational deformity in adolescent scoliosis via sublaminar wiring is not well quantified in the literature. The derotation maneuver of Cotrel-Dubousset has been shown to produce variable and unpredictable amounts of axial derotation. METHODS: Twenty patients who underwent posterior spine fusion for adolescent idiopathic scoliosis were evaluated using computed tomography scans and plain radiography before and after surgery and at a subsequent follow-up examination (average time of follow-up examination, 35 months after surgery). The degree of angle of vertebral rotation about the sagittal plane and that relative to the pelvis were measured before and after surgery and at a follow-up examination. RESULTS: The primary thoracic curves were not derotated significantly relative to the pelvis with sublaminar wiring. Primary thoracolumbar curves instrumented on the convexity with pedicle screws were derotated significantly relative to the pelvis (P = .001). The average initial correction was 57%. On final follow-up examination, the correction was 24% (18 of 20 twenty individuals lost axial correction by an average of 34%). In nine of 20 patients the spine was more rotated, relative to the pelvis, than it had been before surgery. No coronal or sagittal decompensation was seen in any curve type. CONCLUSIONS: Coronal and sagittal plane correction of scoliotic curves may be achieved with sublaminar instrumentation. The ability to derotate axially the scoliotic spine appears to be variable, however, and, in most cases, curve-type dependent. Over time, much correction appears to be lost, and in many patients the scoliosis actually becomes worse than it was before surgery. Nonetheless, the apical derotation that takes place appears to be reasonably true: the percent correction of angle of rotation about the sagittal plane and the percent correction of angle of rotation about the sagittal plain relative to the pelvis were closely correlated. Derotation forces applied to the instrumented spine do not appear to be transmitted to more distal segments.

Pelvic fractures after long lumbosacral spine fusions.

STUDY DESIGN: A retrospective review of late pelvic ring fractures after long spine fusions to the lumbosacral spine. OBJECTIVES: To review the clinical course and predisposing features of late fractures of the pelvic ring, usually atraumatic, in patients with long fusions to the lumbosacral spine. SUMMARY OF BACKGROUND DATA: Fractures of the pelvic ring after long fusions to the lumbosacral spine is a heretofore rarely reported complication. METHODS: Records from the authors' institution from 1985 to 1994 were reviewed retrospectively. Two hundred sixty-eight patients with long fusions to the lumbosacrum were identified. RESULTS: Between 1985-1994, five patients suffered late atraumatic fractures of the pelvic ring after long instrumented fusions to L5 or the sacrum. All fractures were on the left side of the pelvic ring, primarily the public rami. All patients were women, and at the time of fracture, all were aged 50 years or older. Fractures occurred from 4 months to 7 years after the last surgery (mean, 28 months). All were treated with protected weightbearing until comfortable. At average 27 months' follow-up evaluation, four patients reported no pain; the fifth had become pain-free at 31 months, but 2 months later, the patient spontaneously fractured the contralateral public rami. CONCLUSION: Stress-type fractures of the pelvic ring are a potential source of late pain after long fusions to the lumbosacral spine. Orthopedic surgeons should be aware of this possibility, especially in older, potentially osteoporotic women. Early treatment with simple protected weightbearing appears satisfactory and can prevent significant morbidity.

Effect of sacral and iliac instrumentation on strains in the pelvis. A biomechanical study.

STUDY DESIGN: This study is a biomechanical study on human cadaver pelves using strain gauges to measure strains at different locations in response to different load states. OBJECTIVES: To examine the changes in strains, at different sites on the pelvis, and after instrumentation of the lumbosacral joint and the lumbosacroiliac joint. SUMMARY OF BACKGROUND DATA: Pelvic girdle pain after long instrumented fusions to the sacrum has been described and studied along with sacroiliac and pubic instability. Fractures of the pelvic rami or the iliac wing have been reported in patients after surgical fusions that incorporated the sacrum and sacroiliac joint. METHODS: Pelves with lumbar spine attached had three axis rosette strain gauges cemented to specific sites on the pelves (ilium [correction of ileum] and rami). Specimens were tested in different configurations involving lumbosacral and sacroiliac instrumentation. Iliac bone harvest was also tested. Strain values were computed and compared for each configuration. RESULTS: The "Galveston" and "sacral" instrumentation configurations caused significant stress shielding in pelves under all compression loads applied. Axial rotations on the instrumented specimens caused higher strains at all sites. Harvesting of bone from the ilium did not alter the strains seen at the different sites. CONCLUSIONS: This study suggests significant stress shielding provided by sacro and sacroiliac instrumentation systems, supporting the possibility of development of device-related osteopenia that may predispose patients to late, insufficiency-type fractures as their activity increases. The rigid instrumentation of the lumbosacral spine was found to increase the stress during torsion, which may lead to failure during activity.

Complications and long-term outcome of upper cervical spine arthrodesis in patients with Down syndrome.

STUDY DESIGN: A retrospective review of 15 patients with Down syndrome who had undergone arthrodesis of the upper cervical spine for instability. OBJECTIVES: To determine the complication rate and long-term outcome after posterior cervical arthrodesis for upper cervical instability in patients with Down syndrome. SUMMARY OF BACKGROUND DATA: Atlantoaxial instability is common in patients with Down syndrome, and fusion of the upper cervical spine has been recommended for patients who have instability, with or without myelopathy. Unfortunately, the results of posterior cervical arthrodesis are not well reported, and the natural history of this condition is unknown. METHODS: Fifteen patients with an average follow-up period of 74.6 months (range, 24-142 months) were reviewed after posterior arthrodesis of the upper cervical spine. Twelve patients were reexamined by the investigators specifically for the purpose of this study, and three patients had long-term follow-up results available from chart review. RESULTS: Eleven of 15 patients (73%) sustained 23 major complications including nonunion, loss of reduction, neurologic deterioration, late subaxial instability, infection, and wound dehiscence. Six patients (40%) required seven reoperations to address a complication. Ultimately, 12 patients (80%) obtained osseous union, but a definite clinical improvement was identifiable in only three patients, whereas two others had worsened neurologically at latest follow-up evaluation. CONCLUSIONS: A high complication rate should be anticipated after posterior arthrodesis of the upper cervical spine in patients with Down syndrome. A cautious approach to asymptomatic instability in this condition is advocated.

Effect of patient position on the sagittal-plane profile of the thoracolumbar spine.

Although the normal sagittal profile of the thoracolumbar spine has been described, this has been obtained primarily by using young individuals standing. We sought to describe the sagittal profile of the thoracolumbar spine in an older population in the supine cross-table lateral position compared with that standing. We enrolled 50 volunteers with no history of back pain or spine deformity and 50 matched subjects with mechanical back pain (LBP) only. Lateral radiographs of the thoracolumbar spine (T10-S1) in both standing and cross-table supine positions were obtained. Lordosis from L1 to S1, kyphosis from T10 to L1, and the changes seen moving from the supine position to standing were calculated. There were few differences comparing the two groups in either the standing or cross-table supine position, or when changing positions. Within each group, however, there were small, but significant, differences in the midlumbar and thoracolumbar spine when comparing supine versus standing. Both asymptomatic individuals and those with a history of LBP demonstrated similar small but statistically significant increases in lumbar lordosis and thoracolumbar kyphosis when standing versus supine. The clinical significance of these findings remains to be determined.

Thoracic volume changes in scoliosis surgery.

STUDY DESIGN: Eighteen patients with adolescent idiopathic scoliosis treated with ISOLA instrumentation and 13 treated with Cotrel-Dubousset instrumentation were studied before and after surgery with computed tomography scans. OBJECTIVES: To analyze and compare the immediate change in chest volume of patients treated with the derotation method of Cotrel-Dubousset versus the sublaminar wire translational technique of ISOLA. SUMMARY OF BACKGROUND DATA: Previous literature suggests a small but variable improvement in pulmonary function with the use of Harrington instrumentation when treating adolescent idiopathic scoliosis. The effect of modern instrumentation techniques on chest volume and ultimately pulmonary function has not been determined. METHODS: An axial computed tomography slice was made through each vertebral body from T3 to T10. Using a technique of spine curve measurements, the cross-sectional area at each level was computed, and from the height measured, the volume of the thoracic cage was computed. RESULTS: Single thoracic curves (King-Moe Type III) managed with ISOLA sublaminar instrumentation showed a statistically significant increase in chest volume when compared with other curve types and when compared with all curves managed with Cotrel-Dubousset. Seventeen of 18 patients treated with ISOLA instrumentation gained chest volume, whereas half of those treated with Cotrel-Dubousset actually lost volume. CONCLUSIONS: ISOLA instrumentation and sublaminar wiring appears to increase the chest volume in patients with adolescent idiopathic scoliosis. Its clinical significance remains to be determined.

Magnetic resonance imaging of the thoracic spine. Evaluation of asymptomatic individuals.

We reviewed magnetic resonance imaging studies of the thoracic spines of ninety asymptomatic individuals to determine the prevalence of abnormal anatomical findings. This group included sixty individuals who had no history of any thoracic or lumbar pain and thirty individuals who had a history of low-back pain only. In addition, we reviewed imaging studies of eighteen patients who had an operatively proved herniation of a thoracic disc and studies of thirty-one patients who had been seen with thoracic pain. Sagittal T1-weighted spin-echo and axial multiplanar gradient refocused images at each disc level were interpreted by us (two neuroradiologists and two orthopaedic spine surgeons); we had no clinical information about the patients. Sixty-six (73 percent) of the ninety asymptomatic individuals had positive anatomical findings at one level or more. These findings included herniation of a disc in thirty-three subjects (37 percent), bulging of a disc in forty-eight (53 percent), an annular tear in fifty-two (58 percent), deformation of the spinal cord in twenty-six (29 percent), and Scheuermann end-plate irregularities or kyphosis in thirty-four (38 percent). This study documents the high prevalence of anatomical irregularities, including herniation of a disc and deformation of the spinal cord, on the magnetic resonance images of the thoracic spine in asymptomatic individuals. We emphasize that these findings represent roentgenographic abnormalities only, and any clinical decisions concerning the treatment of pain in the thoracic spine usually require additional studies.

The morbidity of heparin therapy after development of pulmonary embolus in patients undergoing thoracolumbar or lumbar spinal fusion.

STUDY DESIGN: The postoperative course of patients who developed a pulmonary embolus after thoracolumbar or lumbar spinal fusion treated with heparin was studied to quantify the morbidity risk of anticoagulation. OBJECTIVE: To compare the morbidity risk of heparinization with that of an alternative form of therapy--inferior vena cava filter placement. SUMMARY OF BACKGROUND DATA: Therapeutic heparinization was the current treatment of choice for patients who develop thromboembolic disease after surgery. Although heparin usage was reported to be associated with a number of complications after other orthopedic and general surgical procedures, no information was available to identify complications of heparinization after lumbar or thoracolumbar spine surgery or to define the risk of such complications. METHODS: Twenty-two members of the Scoliosis Research Society were polled to determine their experiences with the anticoagulation of this subset of patients. Surgeons polled had a combined experience of 250 man-years and had performed more than 13000 thoracolumbar and lumbar spinal fusions. The MEDLINE database was used to review pertinent English language publications describing inferior vena cava filter complications, effectiveness, safety, and indications for use. RESULTS: Nine patients were located who fit the inclusion criteria of this study. Six (67%) had complications attributable to heparinization. Clinically significant complications of filter placement ranged from 0.12% to 10.1%. CONCLUSIONS: Heparinization after the development of pulmonary embolus in patients recently undergoing spinal fusion is associated with a high complication rate. The morbidity of vena cava filter placement is low and should be considered a treatment alternative in the treatment of patients who experience pulmonary embolus after surgery.

An improved technique for measuring in vivo intervertebral motion in the canine.

STUDY DESIGN: An experimental animal study using an established technique for measuring in vivo motion in canines was designed to improve measurement techniques and to eliminate the effects of the instrument mounting technique on the tissue and subsequently on the motion being measured. OBJECTIVES: The purpose of this study was to improve a technique for measuring in vivo intervertebral motion in canines, so that the measuring technique did not affect the motion being measured. SUMMARY OF BACKGROUND DATA: Biplanar radiography has been used to measure in vivo intervertebral motion, but involves radiation exposure and expensive equipment. Electromechanical devices have been used more recently but have had significant effects on the motion over extended time periods. METHODS: Intervertebral motion was measured using an instrumented spatial linkage in eight adult canines divided into two groups that differed regarding the method of "mounting pin" placement. Group I had open surgical placement of the pins and Group II had pins placed into the spinous processes. After pin implantation, the instrumented spatial linkage was attached and motion data were recorded during walking. This testing sequence was repeated 3 weeks later. Animals were killed and intervertebral and facet motion were calculated from the experimental data and compared statistically. RESULTS: Facet motion decreased 1 to 3 weeks after pin implantation for animals of group I (3.4 +/- 0.2 mm to 1.1 +/- 0.3 mm), whereas the facet excursion of animals in Group II showed no change (3.0 +/- 0.2 mm and 3.1 +/- 0.3 mm). CONCLUSIONS: A new method of measuring in vivo intervertebral motion in canines has been developed and shown to have no significant affect on the segment mechanics.

Radiographic evaluation of instability in spondylolisthesis.

STUDY DESIGN: The amount of intervertebral motion seen during dynamic radiography when imaged with the patient in the standing position was compared with that obtained with the patient in the lateral decubitus position. SUMMARY OF BACKGROUND DATA: Regarding analysis of spondylolisthesis, whether flexion/extension radiographs should be obtained with the patient in the lateral decubitus or standing position has been anecdotal. METHODS: Fifty consecutive adult patients with spondylolisthesis underwent flexion/extension lumbar spine radiographs in both positions. Abnormal motion was considered above 12 degrees dynamic angulation or 8% translation. RESULTS: Thirty-one of 50 patients displayed abnormal translation. Of these, 18 had abnormal motion only when they were examined in the lateral decubitus position and not when standing. Nine displayed excessive motion in both positions. Only four displayed more translation while standing. There was no statistical difference in the evaluation of dynamic angulation based on patient position. Neither age, degree of slip, listhetic level, nor type of spondylolisthesis correlated with abnormal motion. CONCLUSIONS: When spondylolisthesis is being analyzed, to maximize motion, flexion/extension radiographs should be obtained in the lateral decubitus position.