Failure Of Segmentation Research Articles

Goldenhar-Associated Conditions (hemifacial microsomia) and Congenital Deformities of the Spine

We performed a retrospective study of 668 consecutive patients with congenital spine deformities. To determine the prevalence of Goldenhar conditions in patients with congenital spine deformities, and describe the types of vertebral abnormalities and their treatment. The craniofacial malformations described by Goldenhar can be associated with congenital vertebral anomalies. This nonrandom association represents unilateral errors in the morphogenesis of the spine, the first and second branchial arches. The medical records were reviewed, and patients with Goldenhar conditions were identified. The vertebral anomalies causing spine deformity were detected on radiographs. The type and site of the craniofacial abnormalities, other musculoskeletal deformities, and systemic anomalies were recorded. There were 14 patients, including 7 males and 7 females, who had Goldenhar conditions. Thoracic scoliosis was the most common deformity, occurring in 10 patients (71.5%). Of these patients, 8 had an isolated hemivertebra, and the remaining 2 had a unilateral unsegmented bar with contralateral hemivertebra at the same level. There was only 1 patient with lumbar scoliosis caused by a hemivertebra. The side of vertebral anomaly correlated with that of hemifacial microsomia in 5 of 11 patients with scoliosis or kyphoscoliosis. Thoracolumbar kyphosis occurred in 4 patients, including 2 who had posterior hemivertebrae, 1 who had wedge vertebrae, and the remaining who had an anterior unsegmented bar. Thoracolumbar kyphoscoliosis occurred in only 1 patient because of a posterolateral quadrant vertebra. Klippel-Feil syndrome occurred in 6 patients (42.8%). There were 8 patients (57%) who underwent surgical treatment at a mean age of 9.8 years (range 2.9-19). Four patients had undergone a combined anterior-posterior, and 4 had a posterior-only spine arthrodesis. The prevalence of Goldenhar-associated conditions in patients with congenital spine deformities was 2%. Failures of vertebral segmentation were the most frequent abnormality in the cervical spine, whereas failures of vertebral formation most commonly occurred in the thoracic or thoracolumbar spine.

Spinal Neurenteric Cysts in the Magnetic Resonance Imaging Era

Neurenteric cysts are derived from displaced entodermal tissue. They are infrequently found in the ventral spinal canal with varying degrees of success in their removal. Experience with 10 such individuals is critically analyzed to aid in the diagnosis and management. Ten patients, ages 4 through 55 years, with neurenteric cysts were encountered in the last 20 years. This series included three females and seven males; seven children and three adults. The follow-up periods ranged from 3 to 18 years. Three cysts were located at the ventral cervicomedullary junction, five in the midventral cervical spine, and one thoracic and one lumbosacral. The symptoms reflected the location. Six of the 10 patients had associated bony abnormalities such as bifid clivus, hemivertebrae, segmentation failures at the site of the lesion, and blocked vertebra. The patient with the thoracic spinal lesion (age, 55 yr) had symptoms from early childhood. A diplomyelia at the site of the lesion was seen in one individual and tethered spinal cord in the same adult and in a young child. Two patients had undergone laminectomy for aspiration and partial resection before referral to our institution at the time of recurrence. Cervicomedullary junction lesions were approached via the far lateral transcondylar approach; two of the cervical intramedullary lesions were resected via a ventral corpectomy with radical resection and interbody fusion. The goal in each case was complete resection to avoid recurrences. Spinal neurenteric cysts are ventrally located, usually intradural and extramedullary, but may insinuate into the spinal cord. They are isointense on T1 images and hyperintense on T2-weighted images on magnetic resonance imaging without true enhancement. These lesions may be associated with block and hemivertebrae with a predisposition to the craniocervical region. Partial resections have led to recurrence and arachnoiditis.

Aortoiliac endarterectomy: An 11-year review

Fifty-seven patients underwent aortoiliac endarterectomy over an 11-year period, the majority (86 per cent) for disabling claudication. No patient died within 30 days of surgery, but nine patients suffered significant complications. The cumulative survival rate was 98 per cent at 1 year, and was 94 and 78 per cent at 5 and 10 years respectively. Cumulative operated segment patency rates were 92 per cent at 5 years and 68 per cent at 10 years. There was no significant difference in survival rates between patients who smoked after surgery and those who did not, but smokers had significantly worse rates for cumulative patency, limb failure and symptom status than non-smokers. Twenty-seven patients developed worsening symptoms during follow-up and 24 patients required secondary vascular intervention. Fourteen patients subsequently required aortofemoral bypass and the largest single cause of operated segment failure was recurrent disease in the external iliac artery. Our evidence suggests that, while aortoiliac endarterectomy should be considered in young patients with localized disease not involving the external iliac artery, those who do not fit these criteria should be considered for primary aortofemoral bypass. Regardless of the choice of operation, the chance of success is jeopardized if the patient continues to smoke.

An exploratory study of loading and morphometric factors associated with specific failure modes in fatigue testing of lumbar motion segments

There is currently little information regarding factors associated with specific modes of motion segment failure using a fatigue failure model. Thirty-six human lumbar motion segments were fatigue tested using spinal compressive and shear loads that simulated lifting a 9 kg weight in three torso flexion angles (0 degrees, 22.5 degrees, and 45 degrees). Twenty-five segments failed via fatigue prior to the 10,000 cycle maximum. These specimens were visually inspected and dissected so that the mode(s) of failure could be determined. Failure modes included endplate fractures (classified into nine varieties), vertebral body fractures, and/or zygapophysial joint disruption. Logistic regression analyses were performed to determine whether certain morphometric variables, amount of motion segment flexion, disk degeneration scores, and/or loading characteristics were associated with the occurrence of specific failure modes. Results indicated that stellate endplate fractures were associated with increased posterior shear forces (P < 0.05) and less degenerated discs (P < 0.01). Fractures running laterally across the endplate were associated with motion segments having larger volumes (P < 0.01). Endplate depression was more common in smaller specimens (P < 0.01), as well as those experiencing increased posterior shear force (P < 0.05). Zygapophysial joint damage was more likely to occur in a neutral posture (P < 0.01). These results suggest that prediction of failure modes (e.g., specific endplate fracture patterns) may be possible (at least for older specimens) given knowledge of the spinal loads along with certain characteristics of the lumbar spine.

Congenital Anomalies of the Ribs and Chest Wall Associated with Congenital Deformities of the Spine

Congenital anomalies of the ribs and chest wall as well as Sprengel deformity of the shoulder are often associated with congenital deformities of the spine. It has been suggested that rib anomalies may adversely affect the progression of the spinal deformity. We conducted a retrospective study of the medical records and spine radiographs of 620 consecutive patients with congenital deformities of the spine; 497 patients (80%) had scoliosis; eighty-eight patients (14%), kyphoscoliosis; and thirty-five patients (6%), kyphosis. The rib anomalies were classified into simple and complex, and the presence of a Sprengel deformity of the shoulder was recorded. The rate of scoliosis deterioration without treatment before the age of eleven years, as well as the patient age and curve size at the time of surgery, was compared for different types of vertebral abnormalities in patients with and without rib anomalies. A total of 119 patients (19.2%) had rib anomalies, which were most commonly associated with congenital scoliosis (111 patients; 93%) and were much less frequently associated with congenital kyphoscoliosis or kyphosis (eight patients). The rib anomalies were simple in ninety-five patients and complex in twenty-four. Eighty-five patients (71%) with rib abnormalities had a scoliosis due to a unilateral failure of vertebral segmentation, and seven patients had mixed or unclassifiable vertebral anomalies. In contrast, only sixteen of 203 patients with a scoliosis due to a hemivertebra alone had rib anomalies. The rib anomalies were most frequently associated with a thoracic or thoracolumbar scoliosis (102 patients; 92%) and occurred on the concavity in eighty-two patients (74%), the convexity in twenty-two patients (20%), and were bilateral in seven patients. The Sprengel deformity occurred in forty-five patients and most frequently in association with a thoracic scoliosis due to a unilateral failure of vertebral segmentation (twenty-seven patients). No significant difference was detected in the rate of curve progression without treatment in patients with and without rib anomalies. The only exception was the mean age at the time of surgery, which was higher for patients with a unilateral unsegmented bar without rib anomalies (p = 0.005). In addition, no significant difference was found with regard to any tethering effect due to the site of the rib fusions on the concavity of the scoliosis, i.e., whether they were in close approximation to the spine or were more lateral (p > 0.05). Congenital rib anomalies occur most commonly on the concavity of a thoracic or thoracolumbar congenital scoliosis that is due to a unilateral failure of vertebral segmentation, and they do not appear to have an adverse effect on curve size or rate of progression.

CONGENITAL ANOMALIES OF THE RIBS AND CHEST WALL ASSOCIATED WITH CONGENITAL DEFORMITIES OF THE SPINE

Background: Congenital anomalies of the ribs and chest wall as well as Sprengel deformity of the shoulder are often associated with congenital deformities of the spine. It has been suggested that rib anomalies may adversely affect the progression of the spinal deformity. Methods: We conducted a retrospective study of the medical records and spine radiographs of 620 consecutive patients with congenital deformities of the spine; 497 patients (80%) had scoliosis; eighty-eight patients (14%), kyphoscoliosis; and thirty-five patients (6%), kyphosis. The rib anomalies were classified into simple and complex, and the presence of a Sprengel deformity of the shoulder was recorded. The rate of scoliosis deterioration without treatment before the age of eleven years, as well as the patient age and curve size at the time of surgery, was compared for different types of vertebral abnormalities in patients with and without rib anomalies. Results: A total of 119 patients (19.2%) had rib anomalies, which were most commonly associated with congenital scoliosis (111 patients; 93%) and were much less frequently associated with congenital kyphoscoliosis or kyphosis (eight patients). The rib anomalies were simple in ninety-five patients and complex in twenty-four. Eighty-five patients (71%) with rib abnormalities had a scoliosis due to a unilateral failure of vertebral segmentation, and seven patients had mixed or unclassifiable vertebral anomalies. In contrast, only sixteen of 203 patients with a scoliosis due to a hemivertebra alone had rib anomalies. The rib anomalies were most frequently associated with a thoracic or thoracolumbar scoliosis (102 patients; 92%) and occurred on the concavity in eighty-two patients (74%), the convexity in twenty-two patients (20%), and were bilateral in seven patients. The Sprengel deformity occurred in forty-five patients and most frequently in association with a thoracic scoliosis due to a unilateral failure of vertebral segmentation (twenty-seven patients). No significant difference was detected in the rate of curve progression without treatment in patients with and without rib anomalies. The only exception was the mean age at the time of surgery, which was higher for patients with a unilateral unsegmented bar without rib anomalies (p = 0.005). In addition, no significant difference was found with regard to any tethering effect due to the site of the rib fusions on the concavity of the scoliosis, i.e., whether they were in close approximation to the spine or were more lateral (p > 0.05). Conclusions: Congenital rib anomalies occur most commonly on the concavity of a thoracic or thoracolumbar congenital scoliosis that is due to a unilateral failure of vertebral segmentation, and they do not appear to have an adverse effect on curve size or rate of progression. Level of Evidence: Prognostic Level II. See Instructions to Authors for a complete description of levels of evidence.

Interactive Object Recognition System for a Helper Robot Using Photometric Invariance

We are developing a helper robot that carries out tasks ordered by the user through speech. The robot needs a vision system to recognize the objects appearing in the orders. It is, however, difficult to realize vision systems that can work in various conditions. Thus, we have proposed to use the human user's assistance through speech. When the vision system cannot achieve a task, the robot makes a speech to the user so that the natural response by the user can give helpful information for its vision system. Our previous system assumes that it can segment images without failure. However, if there are occluded objects and/or objects composed of multicolor parts, segmentation failures cannot be avoided. This paper presents an extended system that tries to recover from segmentation failures using photometric invariance. If the system is not sure about segmentation results, the system asks the user by appropriate expressions depending on the invariant values. Experimental results show the usefulness of the system.

Bone Mineral Content and Fatigue Failure of Lumbar Motion Segments in Simulated Flexed Lifting: Does Specimen Age Influence the Relationship?

This paper describes a comparison of the fatigue failure responses of older versus younger lumbar spine cadaver motion segment specimens. These specimens were repeatedly subjected to loads simulating those experienced by the spine in lifting a 9 kg load in different torso flexion postures (0, 22.5, and 45 degrees of flexion). An older sample of 36 motion segments (average age 81 years + 8 SD) is compared with a younger sample of 18 motion segments (average age: 47 years + 9 SD) with respect to the number of cycles to failure and results of survival analyses evaluating the effects of flexion and bone mineral content with and without the younger data set. Compared to the older sample of spines, the younger sample exhibited many more cycles to fatigue failure in all the torso flexion conditions (10020 versus 8267 average cycles to failure in 0 degrees flexion, 7124 versus 3262 in 22.5 degrees flexion, and 3229 versus 263 cycles to failure in 45 degrees flexion). The increased cycles to failure in young specimens is likely due to the increased bone mineral content (BMC) in younger motion segments (30.7 g + 11.1 g per motion segment versus 27.8 + 9.4 g). Cox regression analyses modeling both flexion effects and BMC indicate that betas are similar when just older spines are modeled and when younger specimens are included in the analysis. Betas for survival analysis models with and without younger specimens generally show little change for flexion (2.716 versus 2.756 for 22.5 degrees [0 degrees referent], 3.926 versus 3.380 for 45 degrees [0 degrees referent]). Bone mineral content shows a similar protective effect in both models (Betas: −0.127 versus −0.087). Overall, comparison of the models indicate that risk ratios are similar for 22.5 degrees flexion, slightly increased for 45 degrees flexion and slightly more protective influence predicted for BMC in the combined sample versus the older sample alone.

Sacral Insufficiency Fractures Following Multilevel Instrumented Spinal Fusion

Case series. To report a series of patients in whom sacral insufficiency fractures developed following multilevel spinal fusion with instrumentation. Rigid spinal fusion with instrumentation results in abnormal distribution of forces in the spine. These forces have the potential to cause failure of adjacent segments, especially in older, osteopenic individuals. Sacral insufficiency fractures following lumbar-sacral fusion may be the result of these abnormal forces. However, this complication is not well described in the literature. Three patients who sustained sacral fractures after instrumented lumbar-sacral fusion performed for degenerative disease of the spine are discussed. History, physical examination findings, and radiographic features are presented, along with a brief review of the pertinent literature. All 3 patients in our series started complaining of new-onset buttock pain a few weeks after their operative procedure. Radiographic examination revealed that they had transverse sacral fractures just below the fusion instrumentation. Nonoperative, conservative treatment was performed. At final follow-up, the fractures had healed completely and the patients' complaints had resolved. Patients who complain of new-onset buttock pain following multilevel lumbar-sacral fusion with instrumentation should be evaluated for sacral insufficiency fractures, especially if they have been sitting for prolonged periods. Conservative treatment seems to be sufficient.

Planispheric multiplanar reformatted CT: a new method for evaluation of paediatric congenital spine abnormalities

We describe an original reconstruction method for spine CT performed in four patients with single or multiple congenital spine abnormalities. Conventional radiographic imaging is at the forefront of diagnosis and follow-up of congenital scoliosis, but is frequently difficult to interpret. Three-dimensional CT reconstruction facilitates visualization of complex anatomic structures, but does not give a reliable assessment of failures of segmentation. Mental three-dimensional reconstruction of the information displayed by classical multiplanar reformatted CT remains difficult. Planispheric reformatted imaging allows the visualization of all deformities in a single plane.

Adjacent Segment failure after Lumbar Spine Fusion: Controlled Study for Risk Factors

Purpose: To verify the risk factors associated with adjacent segment failure after lumbar spine fusion using pedicle screws. Materials and Methods: The study group consisted of 35 patients who underwent lumbar spine fusion using pedicle screws and required revision surgery due to adjacent segment failure. These were compared with 73 control patients who were stratified according to the aspect of the surgical method and period. Gender, age, surgical procedures, the number of fusion segments, the fixation of the sacrum, initial instability and degeneration of the adjacent segments, lumbar lordosis, whole lumbar spondylosis, placement of most proximal screws, habitat, the demand of physical work, physical exercise, smoking, life style and BMI were reviewed retrospectively. Results: Multivariate logistic regression showed that insufficient lumbar lordosis (odds ratio=3.041), instability of the distal adjacent segment (odds ratio=17.196), physically demanding jobs (odds ratio=2.462), delinquent exercise (odds ratio=2.534) and rural habitat (odds ratio=46.729) were associated with an increased incidence of adjacent segment failure. Conclusion: Insufficient lordosis, instability of the distal adjacent segment, physically demanding jobs, delinquent exercise and rural habitat were found to be risk factors. The postoperative life style has a large impact on adjacent segment failure. The extension of fusion to an unstable distal segment should be deliberated even though it is not attributable to the current symptoms. A reconstruction of the proper lordosis far outweights the other methodological factors.

Adaptive output feedback actuator failure compensation for a class of non‐linear systems

AbstractAn adaptive compensation control scheme using output feedback is designed and analysed for a class of non‐linear systems with state‐dependent non‐linearities in the presence of unknown actuator failures. For a linearly parameterized model of actuator failures with unknown failure values, time instants and pattern, a robust backstepping‐based adaptive non‐linear controller is employed to handle the system failure, parameter and dynamics uncertainties. Robust adaptive parameter update laws are derived to ensure closed‐loop signal boundedness and small tracking errors, in general, and asymptotic regulation, in particular. An application to controlling the angle of attack of a non‐linear hypersonic aircraft dynamic model in the presence of elevator segment failures is studied and simulation results show that the developed adaptive control scheme has desired actuator failure compensation performance. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Time-dependent drift degradation due to the progressive failure of rock bridges along discontinuities

An important element of time-dependent drift degradation is the progressive failure of intact segments along discontinuities, referred to as rock bridges. A fracture mechanics model is developed to simulate the time-dependent failure of rock bridges along discontinuities. The time dependence of the rock bridge failure process is modeled utilizing subcritical crack growth. The rock bridges give an effective cohesion to the discontinuities, and this cohesion is time-dependent due to the time-dependent failure of the rock bridges. The resulting first-order differential equation for joint cohesion is implemented into the UDEC distinct element numerical code to model time-dependent drift degradation. The model and its implementation into UDEC are validated using several simple examples, including a direct shear test and a rigid block on a slope. Two time-dependent drift degradation examples are then shown, one with and one without thermal loading. These examples used similar geometry, material parameters and in situ stresses as for the proposed underground drifts for the storage of nuclear waste at Yucca Mountain. Both with and without thermal loading, a large zone develops around the excavation where the joint cohesion and tensile strength drop to zero due to the failure of rock bridges. This in turn results in an excavation that is significantly less stable than if time dependence was not included. The results demonstrate the importance of time-dependence on the stability of underground excavations in hard rock.

Determinants and heterogeneity of mechanical competence throughout the thoracolumbar spine of elderly women and men

Vertebral fractures represent the hallmark of osteoporosis. Here, we test the hypotheses that (sub)cortical bone strength and density predict failure better than trabecular core strength and density, and that elderly women display lower failure stress of thoracic vertebrae than men. We examined the vertebral bodies T3 to L5 in 39 spines from elderly donors (23 women; 16 men; age 79 ± 11 years). Peripheral quantitative computed tomography was used to measure total, trabecular, and (sub)cortical bone density. Mechanical tests were performed in functional spinal units, planoparallel sections of vertebrae, trabecular cores, and (sub)cortical ring specimens. The failure stress decreased with descending vertebral level. Failure stress was highest for the (sub)cortical rings and planoparallel sections and lowest for the trabecular core. The failure stress did not differ significantly between men and women. Mechanical strength of the functional unit was more strongly correlated with the strength of the (sub)cortical ring ( r = 0.78) than with that of the trabecular core ( r = 0.62). However, total density was more highly correlated with mechanical strength of the same and remote vertebrae ( r = 0.63) than trabecular ( r = 0.50) or (sub)cortical density ( r = 0.36), respectively. The results show that vertebral strength is similar in elderly women and men. Strength of (sub)cortical bone provides significantly better prediction of strength of functional spinal units than that of the trabecular core. However, total density predicts functional segment failure stress with higher accuracy than (sub)cortical or trabecular density and is thus recommended for predicting fracture strength clinically.

Compression and Shear Loads on Lumbar Spine Motion Segments in Neutral and Flexed Postures

An analysis was performed to estimate compression and shear loads on three motion segments of the lumbosacral spine in neutral and flexed torso postures. 87 lifting tasks were evaluated using a biodynamic lifting model for lifts starting at 0, 22.5 and 45 degrees torso flexion. Results indicated that the compressive loading on the L5-S1 disk in the 22.5 and 45 degree torso flexion conditions were approximately double and triple those observed in the 0 degree condition. Shear reaction forces acted anteriorly in neutral and moderate flexion, but acted posteriorly in full flexion. Load rates were also dramatically affected by posture, with the load rate in the fully flexed posture being seven times greater than in the neutral posture. Analysis of the upper lumbar levels (L1–L2 and L3–L4) suggested significant shear forces; however, shear forces at L5-S1 remained moderate in all conditions. Results of this analysis will be used in a study examining the fatigue failure of lumbar motion segments when subjected to loads experienced at different angles of torso flexion.

Congenital scoliosis

Congenital scoliosis is the most frequent congenital deformity of the spine. Congenital curvatures are due to anomalous development of the vertebrae (failure of formation and/or segmentation). Congenital scoliosis is believed to be related to an insult to the fetus during spine embryological development, and associated malformations (heart, spinal cord, kidney.) are frequently observed. A perfect understanding of the natural history of the deformity and the treatment principles will allow best management of these complex spine deformities. New imaging techniques like three-dimensional computed tomography (CT) and magnetic resonance imaging (MRI) are important tools for analyzing the underlying deformity and understanding the evolution of the complex deformities. The mainstay of treatment is either observation or, in case of curve progression (>10 degrees /year), surgery. Different surgeries are described with two main principles: (1) prophylactic surgeries like hemiepiphysiodesis or in situ fusions that will prevent worsening or allow progressive correction over time, and (2) corrective surgeries, with spinal fusion with or without spinal resection. Exceptional procedures (e.g. spinal column resection or halo distraction) can be attempted in cases of very severe deformity. Congenital curves must be carefully observed to choose the least invasive procedure at the right time and to minimize spinal cord risks.

Cervical spine instability in children with Goldenhar’s syndrome: D. Healey, M. Letts, JG Jarvis. Can J Surg 45:341–344, (October), 2002

To study the vertebral involvement of the cervical spine, in particular the stability of C1-C2, in children with proven Goldenhar's syndrome.A case review.The Children's Hospital of Eastern Ontario, Ottawa.Eight children who had a minimum of 2 out of 3 Goldenhar criteria plus other strong associations with the syndrome and for whom detailed radiographic spinal assessment, including flexion-extension views of the cervical spine and computed tomography of the congenital anomalies, were available.Radiographic findings.Seven children demonstrated cervical spine anomalies. Of particular concern was the high incidence of C1-C2 instability in 3 children, 2 of whom required occiput to C2 fusion. The presence of hemivertebrae and failures of segmentation were most common and resulted in thoracic scoliosis, leading to spinal fusion in 2 children.In patients with Goldenhar's syndrome the cervical spines must be monitored carefully for C1-C2 subluxation before any proposed surgery for other malformations associated with the syndrome, so that any instability can be identified to avoid cord impingement during a general anesthetic.

The use of poly-L-lactic acid in lumbar interbody cages: design and biomechanical evaluation in vitro.

Cage design and cage material may play a crucial role in the incidence of postoperative complications reported with current non-absorbable interbody cage devices. Bioabsorbable poly-L-lactic acid cage devices may have potential benefits. The purpose of this study was to determine the required strength of poly-L-lactic acid cages for use in experimental goat studies and to evaluate the mechanical properties of different cage designs in situ. The yield and ultimate strength of native goat motion segments (L1-L6) were determined; the yield strength was used as a design parameter for the cages. The mechanical behaviour of two types of poly-L-lactic acid cages, the influence of endplate perforation, differences between toothed and smooth cages, and the influence of cage filling were biomechanically tested and compared to native motion segments. Only axial compression until failure of the motion segments was performed. Dual energy X-ray absorptiometry was used to determine bone mineral content. The yield and ultimate strength of the native motion segments were 3.5 and 7.0 kN, respectively. Based on these data, flexible and stiff poly-L-lactic acid cages were designed with strengths of 3.5 and 7 kN, respectively. Poly-L-lactic acid cages, whether with or without bone graft and perforating the endplates, did not reduce the compressive strength of motion segments as compared to native segments. However, toothed titanium cages, with the same geometry, negatively influenced the segments' compressive strength, which effect was reduced using smooth titanium cages.

Wednesday, October 30, 2001 4:42–5:25 pm Concurrent Session 2A: Cervical Spine Surgery Complications: 4:42 Anterior discectomy and plating for traumatic unilateral cervical jumped facet: an analysis of failures in a single-institution series of 56 cases

Purpose of study: Significant controversy persists regarding the ideal treatment of an isolated unilateral jumped or locked facet after cervical spine trauma. The purpose of this study was to examine the efficacy and outcomes of such a purely anterior technique for the treatment of a unilateral jumped facet.Methods used: Between 1994 and 2002, a retrospective review was conducted at the Los Angeles County General Hospital to identify a total of 56 patients with cervical spine trauma and unilateral jumped facet syndrome who were subsequently treated by anterior cervical discectomy and fusion. Demographic data, initial neurological examinations, surgical data, radiographic findings and follow-up records were reviewed. The mean follow-up was 14.5 months with greater than 6-month follow-up available in 95% of patients. Treatment failure was identified as progression of cervical deformity, graft or hardware migration, or new neurological deficit. Time to failure was divided arbitrarily into immediate (0 to 4 weeks), early (4 weeks to 3 months), middle (3 to 6 months) and late (longer than 6 months).of findings: We identified a total of 13 treatment failures (23%) documented on delayed radiographic imaging. Within the failure group, the following variables were identified as carrying a negative prognosis as compared with the overall cohort: high-speed mechanisms of trauma (eg, motor vehicle accident vs. simple assault), presence of a motor deficit or numbness, reflex changes, loss of consciousness and/or intracranial bleed, smoking, other systemic diseases, lesions of the cervicothoracic junction (C6–T1), evidence of increased T2-signal or disc changes on the initial magnetic resonance imaging scan, presence of kyphosis or disc height loss at the injured level and successful preoperative halo reduction at a low weight. Of these, high-speed mechanisms, neurological deficit, intracranial bleeding and the presence of kyphosis were statistically significant (p<.005). Radiographic failure of the motion segment was most commonly seen in the early period (8 weeks to 3 months; seven cases) followed by the middle period (3 to 6 months; four cases). Average time to diagnosis of failure was 11.2 weeks after surgery. At the time of failure, the most common physical examination findings were new numbness (6 of 13) and new or worsening pain (11 of 13). Of the failures, seven were treated with posterior surgery only and five underwent revision anteriorly followed by posterior surgery. At a mean follow-up of 8.3 months, all 13 cases have subsequently done well.Relationship between findings and existing knowledge: Our observation of a 23% failure rate at a mean interval of 11.2 weeks after anterior reconstruction for unilateral jumped facet syndrome is slightly higher than that previously reported in the literature. This study represents one of the largest single-institution studies from a major trauma center and may reflect a higher proportion of high-impact type injuries. The other negative prognostic variables suggest that a more serious injury was likely initially present in the patients whose anterior construct failed.Overall significance of findings: Careful analysis of the exact injury is needed for cases of cervical unilateral jumped facets. Whereas anterior discectomy and plating may prove adequate for low-impact type injuries, it may be inadequate for more serious cases with higher force injuries. Identification of features suggestive of more serious injury, including the ones listed above, may help guide treating surgeons to identify which patients require circumferential stabilization.Disclosures: No disclosures.Conflict of interest: No conflicts.

7:58 Adjacent segment failure above lumbosacral fusions instrumented to L1 or L2

Purpose of study: Adjacent segment degeneration has been recognized as a problem in lumbar fusion surgery. Several studies have evaluated the radiographic changes adjacent to fusions, but very little has been reported on adjacent segment degeneration as it relates to the level of lumbar fusion. During routine follow-up of adult patients with long instrumented lumbar fusions, we noticed an unexpectedly high number of complications at the cephalad end of the fusion construct. This review was designed to evaluate the rate of adjacent segment problems in patients with instrumented lumbar fusions from the sacrum to L1 or L2.Methods used: From 1994 to 2000, 20 adult patients, with an average age of 56 years, who underwent lumbosacral fusions from the sacrum to L1 or L2 for a variety of spinal pathologies, including degenerative spinal stenosis, scoliosis, postlaminectomy syndrome, pseudarthrosis and spondylolisthesis, were retrospectively reviewed from a prospectively gathered computerized database. Clinical outcomes, pain scores, Short Form (SF)-36 scores, satisfaction scores, reoperation rates and radiographic analysis were performed for all patients at a minimum 2-year follow-up.of findings: Overall, the clinical results for these patients after their index surgery were poor with only two patients having a good or excellent clinical result. Nine patients had adjacent segment failure, usually within the first 2 years postoperatively. Reoperations were required in seven patients, four for fracture at or above the most superior instrumented vertebra, two for adjacent segment degeneration and spinal stenosis and one for infection. One other patient had a pedicle fracture above his fusion treated nonperatively, and two more patients have developed symptomatic adjacent segment degeneration requiring further nonoperative care and are being considered for reoperation.Relationship between findings and existing knowledge: Although the effects of fusion on the acceleration of degenerative changes at levels adjacent to lumbar fusions have been recognized, little has been published about the need for reoperations for symptomatic degeneration, and very few publications have evaluated the effects of number of fusion levels on adjacent segment failure. This study supported the initial clinical observation that instrumented lumbosacral fusions in the adult degenerative population that included the L1 or L2 vertebra resulted in high incidence of adjacent segment failure.Overall significance of findings: Fractures or rapid disc degeneration with subsequent stenosis occurred in half of the patients within the first 2 years of surgery. Because of this unacceptably high rate of early adjacent segment failure, we cannot recommend to L1 or L2 in the adult degenerative population.Disclosures: Device or drug: lumbar pedicle screws. Status: approved.Conflict of interest: No conflicts.