Posterior Spinal Elements Research Articles

Destructive Cervical Spine Osteoblastoma at C5 in a Young Patient Initially Presenting with Quadriparesis: Case Report and Review of the Literature

BackgroundOsteoblastomas are rare benign bone tumors that are mostly found in the posterior spinal elements; about 20% are located in the cervical spine. ObjectiveThe case of a destructive cervical osteoblastoma at C5 is reported in a 19-year-old man who initially presented with spastic quadriparesis. Case ReportA 19-year-old man was self-referred, reporting symptoms in keeping with a progressive spastic quadriparesis, which had suddenly developed 6 days earlier. Preceding symptoms included mild non-specific neck pain for 3 weeks. The patient was afebrile, and no ambulatory X-ray study had been performed until the time of referral. A cervical spine computed tomography (CT) scan revealed a lytic lesion involving the spinal process and the pedicles of the C5 vertebra. Cervical spine magnetic resonance imaging performed on an inpatient basis revealed a well-circumscribed, destructive lesion of the C5 vertebra, measuring approximately 3 cm. The spinal cord was significantly compressed. The patient underwent open surgical resection of the tumor through a midline posterior approach. Histopathology of the tumor specimen was in keeping with a diagnosis of osteoblastoma. ConclusionNeuroimaging should be performed with either conventional plain X-ray study, which seems to be sufficient in patients presenting with non-specific symptomatology related to cervical spine damage, or with advanced techniques in the case of patients with persistent neck pain or neurological deficit.

Multilevel Magnetic Resonance Imaging Analysis of Multifidus-Longissimus Cleavage Planes in the Lumbar Spine and Potential Clinical Applications to Wiltseʼs Paraspinal Approach

Retrospective magnetic resonance imaging (MRI)-based study. Our goal was to develop Wiltse's paraspinal surgical approach by determining the precise anatomic locations of the intermuscular cleavage planes formed by the multifidus and longissimus muscles. The primary objective was to measure the distances between the midline and the intermuscular planes, bilaterally, on MRI scans at each of the five disc levels between L1 and S1. Secondary objectives included identifying the existence of any correlations between patient demographics and the measured outcomes. In 1968, Wiltse described an approach to the spine using the natural cleavage plane of the multifidus and longissimus muscles as an entry to the posterior spinal elements. The small direct incisions lessened bleeding, tissue violation, and muscle retraction, which popularized Wiltse's approach among surgeons. A detailed description of the locations of the intermuscular cleavage planes at each lumbar disc level, however, is not available. MRI scans of 200 patients taken during routine care (2007-2009) were retrospectively reviewed to gather measurements of the distances from the intermuscular cleavage planes to the midline, bilaterally, at each disc level from L1 to S1. Age, sex, and BMI (body mass index) were obtained to determine correlations. Mean measurements significantly differed between all disc levels. At L5-S1, the mean distance was 37.8 mm; at L4-L5, 28.4 mm; at L3-L4, 16.2 mm; at L2-L3, 10.4 mm; and at L1-L2, 7.9 mm. The mean female distances were significantly greater than males (2 mm) on both sides of L5-S1 only. No correlation was discovered between BMI, age, height (N = 50), or weight (N = 50) with respect to measured distances. In the absence of any significant clinical correlation between patient demographics and the entry site in Wiltse's approach, the spine surgeon may use distances described in this paper to apply to a broad base of spine patients regardless of BMI, sex, or age.

US summit: neonatal spine – how to do it

Sonography of the spine is performed as a screening examination in neonates with cutaneous lesions associated with spinal cord abnormalities, such as deep sacral dimples, dorsal midline masses, hemangiomas, skin tags, hairy tufts, skin discoloration and sinus tracts; congenital anomalies with a high incidence of occult spinal dysraphism, including imperforate anus, caudal regression syndrome, cloacal malformation and cloacal exstrophy; vertebral body anomalies; and tumors located near the vertebral canal such as neuroblastoma, sacrococcygeal teratoma and presacral masses in patients with Currarino triad. Additional indications include assessment of hemorrhage following birth injury or lumbar puncture, and in the detection of epidural abscesses. Infants are usually examined in the prone position. A small bolster or pillow placed under the pelvis accentuates the lumbar lordosis and thereby aids in the sonographic delineation of the lumbosacral junction. If prone positioning is not possible, the study can also be performed with the infant lying on his or her side. A neonate who is fed immediately prior to or during the examination will usually lie quietly as scanning is performed. The neonatal spinal cord can be assessed with US due to a lack of ossification of the predominantly cartilaginous posterior arches of the spine. As the posterior spinal elements progressively ossify, the quality of the US images declines and, in most cases, is inadequate by 6 months of age. In patients with spinal dysraphism, however, the persisting acoustic window permits US scanning at any age. Most studies are limited to an evaluation of the lumbosacral spine, as, for example, in the investigation of a sacral dimple or to determine the presence of a hematoma after a traumatic or unsuccessful lumbar puncture. However, in selected patients, an examination of the entire spinal canal is performed, from the craniocervical junction to the coccyx. Scanning is generally accomplished with high-frequency linear-array transducers with images obtained in transverse and longitudinal planes. The craniocervical junction is best imaged with a smaller footprint sector transducer to permit optimal imaging through the foramen magnum. The normal neonatal spinal cord appears as a tubular, hypoechoic structure with hyperechoic walls. The central canal is hyperechoic, and the surrounding subarachnoid space is anechoic. The vertebral bodies located anterior to the spinal canal appear as discrete, echogenic structures. In the axial plane, the spinal cord is round or oval in shape. Echogenic dentate ligaments can be seen extending laterally from the spinal cord to attach to the arachnoid and dura mater. The cord gradually tapers at the level of the first or second lumbar vertebral body to form the conus medullaris. The fibrous filum terminale arises from the tip of the conus medullaris and extends into the sacral canal. The filum appears echogenic and is surrounded by the echogenic nerve roots of the cauda equina. A cystic structure is occasionally noted at the tip of the conus medullaris. This terminal ventricle, or filar cyst, is a normal developmental variant. The level of the conus medullaris must be determined in every patient. It usually lies above the level of the L2 vertebral body, although it can extend as low as the upper third of the L3 vertebral body. A low-lying cord can result from tethering and requires further evaluation with MRI. Determination of vertebral level can be accomplished in a Disclaimer Dr. Paltiel has no financial interests, investigational or offlabel uses to disclose.

Langerhans′ cell histiocytosis involving posterior elements of the dorsal spine: An unusual cause of extradural spinal mass in an adult

Langerhans cell histiocytosis (LCH) is a clonal proliferation of Langerhans cells occurring as an isolated lesion or as part of a systemic proliferation. It is commoner in children younger than 10 years of age with sparing of the posterior elements in more than 95% of cases. We describe a case of LCH in an adult female presenting with paraplegia. MRI revealed a well-defined extradural contrast enhancing mass at D2-D4 vertebral level involving the posterior elements of spine. D2-5 laminectomy with excision of lesion was performed which lead to marked improvement of patients neurological status. Histopathology was suggestive of eosinophilic granuloma. We describe the case, discuss its uniqueness and review the literature on this rare tumor presentation.

Huge thoracolumbar extradural arachnoid cyst excised by recapping T-saw laminoplasty

Background context Spinal extradural arachnoid cysts are rare expanding lesions in the spinal canal. Total removal of the cyst and repair of the dural defect is the primary treatment for symptomatic spinal extradural arachnoid cysts. Purpose To report the usefulness of recapping T-saw laminoplasty in treating huge extradural arachnoid cyst. Study design Case report. Methods We report the case of a 43-year-old man who presented with a 2-year history of progressive muscle weakness and numbness of the lower extremities. Magnetic resonance imaging (MRI) showed a huge extradural arachnoid cyst at the T12–L3 level extending into bilateral neural foramina and severe posterior compression of the spinal cord and cauda equina. Results The patient underwent total resection of the cyst and closure of the communication. En bloc recapping T-saw laminoplasty of T12–L2 including the T12–L1 and L1–L2 facet joints was performed to obtain extensive exposure and preserve posterior stability. Postoperatively, the patient achieved complete recovery of neurologic functions. Follow-up MRI demonstrated no recurrence of the cyst. Bone union after laminoplasty was obtained within 6 months. Conclusion Total resection of the cyst and closure of the communication is curative for this rare lesion. Recapping T-saw laminoplasty provides extensive exposure for removal of a large cyst while allowing complete preservation of the posterior spinal elements.

Erosion of the spinous process: a potential cause of interspinous process spacer failure

Interspinous process spacers have recently become available for treatment of symptomatic lumbar spinal stenosis. To date, there have been few data regarding the causes of failure. The authors present 2 cases in which there was erosion of the spinous processes adjacent to the interspinous process spacers. In 1 patient, the recurrence of symptoms was likely related to the erosive changes. Such abnormal changes allow settling of the posterior spinal elements and probably results from continued motion at the treated levels.

Single-level bilateral facet joint hypertrophy causing thoracic spinal canal stenosis

Thoracic canal stenosis caused by hypertrophy of the posterior spinal elements is rare. We report an unusual case of bilateral zygapophyseal joint hypertrophy occurring solely at thoracic levels T10–11, producing bilateral leg weakness and numbness. The diagnosis was established using CT scans and MRI. A wide decompressive laminectomy and posterolateral bone fusion was performed. Postoperatively there was a marked improvement in symptoms and signs. We present a literature review on bilateral single-level facet joint hypertrophy producing canal stenosis and report our experience.

Spinal Tuberculosis

Pedicle involvement in spinal tuberculosis (TB), the prevertebral abscess formation, severity of vertebral body, and disc collapse were evaluated from magnetic resonance imaging (MRI) of the patients. To study the pedicle involvement in spine TB in relation to the degree of vertebral body and disc collapse, prevertebral abscess collection, and degree of kyphosis; and to correlate the occurrence of pedicle involvement and the degree of spinal deformity. There are a few reports describing the posterior element involvement in spinal TB. Typically, the infection resides in the anterior part of the vertebral body endplates and rarely involved the pedicles. There were 31 patients, who had been diagnosed and treated for spinal TB from 2003 to 2007 at our center. Critical evaluation of each patient's MRI was carried out for the pedicle involvement, prevertebral abscess formation, severity of vertebral body, and disc collapse. Spinal TB mostly involved the thoracic level (48.4%). Pedicle involvement was noted in 64.5% of patients, and the highest involvement was at thoracic level. The mean vertebral body, disc collapse, prevertebral abscess, and kyphosis were more severe in pedicle involved group. The posterior spinal element, specifically the pedicle is not uncommonly involved in spinal TB. Pedicle involvement is part of the disease process and usually associated with relatively severe vertebral body and disc destruction, wide prevertebral abscess, and severe kyphosis. Pedicle involvement can be detected early from MRI and need to be documented as it may influence the treatment strategy.

A Biomechanical Evaluation of Graded Posterior Element Removal for Treatment of Lumbar Stenosis

A validated finite element model of the intact lumbar spine (L1-S1) was modified to study the biomechanical changes as a result of surgical alteration for treatment of stenosis at L3-L4 and L4-L5 using 2 established techniques and 1 new minimally invasive technique. To investigate the impact of graded posterior element removal associated with new surgical techniques on postoperative segmental motion and loading in the annulus. Several studies have shown that laminectomy increases and produces segmental instability unless fusion is performed. However, no data exist comparing the biomechanical impact of completely preserving the contralateral anatomy and what effect this has compared to traditional approaches. The effect of graded removal of posterior elements because of iatrogenic change associated with the 3 approaches was investigated using an 800 N compressive preload using the follower load technique and application of 8 Nm flexion, 6 Nm extension, 4 Nm torsion, and 6 Nm lateral bending moments. This study shows that removal of posterior elements for treatment of stenosis at L3-L4 and L4-L5 results in increased flexion-extension and axial rotation at the surgical site. This study also shows that the segmental motion following a traditional laminectomy is greater than the minimally invasive approach in flexion, extension, left and right axial rotation. Moderate preservation of the posterior elements which occurs in the intralaminar approach generates greater segmental motion that the minimally invasive approach in extension, left and right axial rotation. Minimization of bone and ligament removal associated with minimally invasive procedures results in greater preservation of the normal motion of the lumbar spine after surgery. This study suggests that preservation of the posterior spinal elements associated with minimally invasive surgery could minimize the risk of developing de novo postoperative changes in spinal alignment and/or acceleration of facet and disc degeneration.

Comparison of the load-sharing characteristics between pedicle-based dynamic and rigid rod devices

Recently, numerous types of posterior dynamic stabilization (PDS) devices have been introduced as an alternative to the fusion devices for the surgical treatment of degenerative lumbar spine. It is hypothesized that the use of ‘compliant’ materials such as Nitinol (Ni–Ti alloy, elastic modulus = 75 GPa) or polyether-etherketone (PEEK, elastic modulus = 3.2 GPa) in PDS can restore stability of the lumbar spine without adverse stress-shielding effects that have often been found with ‘rigid’ fusion devices made of ‘rigid’ Ti alloys (elastic modulus = 114 GPa). Previous studies have shown that suitably designed PDS devices made of more compliant material may be able to help retain kinematic behavior of the normal spine with optimal load sharing between the anterior and posterior spinal elements. However, only a few studies on their biomechanical efficacies are available. In this study, we conducted a finite-element (FE) study to investigate changes in load-sharing characteristics of PDS devices. The implanted models were constructed after modifying the previously validated intact model of L3-4 spine. Posterior lumbar fusion with three different types of pedicle screw systems was simulated: a conventional rigid fixation system (Ti6Al4V, Φ = 6.0 mm) and two kinds of PDS devices (one with Nitinol rod with a three-coiled turn manner, Φ = 4.0 mm; the other with PEEK rod with a uniform cylindrical shape, Φ = 6.0 mm). To simulate the load on the lumbar spine in a neutral posture, an axial compressive load (400 N) was applied. Subsequently, the changes in load-sharing characteristics and stresses were investigated. When the compressive load was applied on the implanted models (Nitinol rod, PEEK rod, Ti-alloy rod), the predicted axial compressive loads transmitted through the devices were 141.8 N, 109.8 N and 266.8 N, respectively. Axial forces across the PDS devices (Nitinol rod, PEEK rod) and rigid system (Ti-alloy rod) with facet joints were predicted to take over 41%, 33% and 71% of the applied compression load, respectively. Our results confirmed the hypothesis on the PDS devices by showing the substantial reduction in stress-shielding characteristics. Higher axial load was noted across the anterior structure with the PDS devices, which could slow the degeneration process of bony structures and lower the possibility of implant failure.

Spine inflammatory changes in patients with ankylosing spondylitis assessed by magnetic resonance image

Objective. To develop the optimal mode of spine evaluation with magnetic resonance image (MRl) in pts with ankylosing spondylitis (AS) and to study relationship between MR! signs of spinal inflammatory lesions (IL), spondylitis duration and clinical features of AS activity. Material and methods. MRl was performed in 36 pts (22 male, 14 female) fulfilling the modified NY criteria of AS. Median age of pis was 26 years (range 19 - 55), Median AS duration - 8 years (range 1,8 - 24). 34 (97%) pts were HLA-B27 positive. 21 (64%) pts had high AS activity - median BASDAI 40 (range 10 - 77). 92% of pts had inflammatory spine pain (VAS>20 mm) and 61% of pts had night pain. Median inflammatory pain duration had been defined separately for every part of the spine assessed by MRl. Median duration of axial pain was 36 months (range: 1-240). MR-scanning (Magnetom Symphony, Siemens, 1.5 T) was performed inTl, T2 and T2-FS (fat signal suppression) modes. IL scoring was done only in 29 pts evaluated in both sagittal and axial planes. We used two scoring methods: 1) individual IL score of the each spine element (vertebral bodies, processes, arches, zygapophyseai, costovertebral and costotransverse joints, ligaments), and 2) separate IL scoring in the vertebral bodies and posterior spinal elements in order yes/no”. Results. 50 MRl images of different parts of the spine (8 cervical, 30 thoracic and 12 lumbar) have been obtained in 36 pts. Spine IL were found in 35 pts. 26% of all IL were revealed in axial planes. 3 pts with short AS duration had IL only on axial slices (zygapophyseai lumbar joints, costotransverse joints, processes). IL were revealed more often in thoracic (average score: 7.1), than in lumbar (3.7) and cervical (2.1) spine. In most (26 from 29 pts, 90%) pts IL were found in painful parts of spine. There was no IL score difference between pts(n=12) with low (BASDAI 40; n=17) AS activity. Me and range were 4 (1.8-10.3) and 6 (4-16), respectively; p=0.35. There was also no difference in percent of images with IL between pts with short (Me: 4 months, range: 1-18; n= 10) and prolonged (Me: 54 months, range: 24-180; n=16) duration of spondylitis (100% and 94% of images, respectively). However, pts with early spondylitis had significantly more IL in posterior spinal structures than in vertebral bodies (92.3% and 23.1% images, respectively; p<0,001). Conclusion. Inflammatory MRl lesions are frequently observed in pts with active AS, more often in thoracic spine, and independently of spondylitis duration. Inflammatory MRl lesions in early spondylitis are revealed more often in posterior structures of spine. These results show the necessity to obtain MRl scans for early diagnosis of AS not only in sagittal but also in axial plane.

P104. Biomechanical Changes Due to Graded Removal of Posterior Elements in the Lumbar Spine

BACKGROUND CONTEXT: Lumbar stenosis is one of the most common diseases of the spine in the geriatric population and has become the leading indication for spinal surgery in patients over the age of 65. The standard surgical treatment for lumbar stenosis is a wide midline decompressive laminectomy. The disadvantages associated with this procedure have led to the development of alternatives to wide laminectomies. These alternative approaches provide varying degrees of posterior spinal element preservation.

Comparison of the effect of 3 different approaches to the lumbar spinal canal on postoperative paraspinal muscle damage

Background To assess the effect of 3 different surgical approaches on paraspinal muscle atrophy in patients undergoing lumbar back surgery, we compared their pre- and postoperative CT scans and their serum Hb, CRP, and CPK levels. Methods The study population consisted of 71 patients who had undergone lumbar back surgery with microscopic posterior decompression without fusion. We examined the effect on paraspinal muscle atrophy of 3 different approaches to the spinal canal. Group 1 (n = 19) underwent unilateral paraspinal dissection from the spinous process with cutting of the spinous process. In group 2 (n = 24), we used modified bilateral decompression via hemilaminectomy, and group 3 (n = 28) was treated by modified bilateral decompression via spinous process splitting. We measured the levels of CPK, Hb, and CRP preoperatively and on the first postoperative day, and compared the preoperative volume of the paraspinal muscle with the volume measured 1 year after the operation. Results Age, sex, operative time, and CRP and Hb levels were not statistically different among the 3 groups. The postoperative elevation of CPK was significantly lower in groups 2 and 3 than in group 1. Group 3 manifested a significantly lower degree of atrophic changes of the paraspinal muscle than groups 1 and 2. Conclusions We found that among the 3 approaches evaluated, modified bilateral decompression via spinous process splitting is less invasive, facilitates preservation of the paraspinal muscle, and is a useful approach to posterior spinal elements resulting in decreased muscle damage.

Distinctive spinal changes in two patients with unusual forms of autosomal dominant endosteal hyperostosis: a case series

Endosteal hyperostosis was encountered in a 26-year-old-man and his 6-month-old daughter. Both the father and his daughter presented with fractures. Odontoid process hyperplasia, and progressive sclerosis of the posterior spinal elements, was the other significant features. To the best of our knowledge, this is the first clinical report describing distinctive spinal changes in association with fractures and endosteal hyperostosis.

Change in Lordosis at the Occipitocervical Junction Following Posterior Occipitocervical Fusion in Skeletally Immature Children

Retrospective case series. Evaluate the change in lordosis at the occipitocervical junction occurring during growth in skeletally immature children treated with posterior occipitocervical arthrodesis versus patients skeletally mature at arthrodesis. Posterior occipitocervical arthrodesis is often indicated for children who have instability of the upper cervical spine develop. Theoretically, in skeletally immature children, this approach retards the growth of the posterior spinal elements but allows the anterior spinal column to continue to grow with the risk of excessive lordosis of the cervical spine developing. There were 21 children, younger than 11 years (range 1.9-10.9) at surgery and expected to have normal spinal growth, followed radiographically for an average of 6.3 years (range 2.0-12.4). Postoperative lateral neutral radiographs were compared to those at most recent follow-up to measure the change in occipitocervical angle. These results were then compared to a series of control patients who were skeletally mature at surgery. Average overall change in lordosis at the occipitocervical junction was -4.6 degrees (range -12.8 degrees to +6.5 degrees). Average annualized change was -0.28 degrees per vertebral level per year (range -1.13 degrees to +0.67 degrees). This annualized change in angle was statistically significant compared to the average change of +0.01 degrees (range -0.09 degrees to +0.11 degrees) measured in the control series of patients skeletally mature at surgery (P = 0.01). Increasing lordosis occurs at the occipitocervical junction following fusion in skeletally immature children. If occipitocervical arthrodesis is indicated in a skeletally immature child, fusion in excessive extension and overtightening of posterior wires should be avoided.

Anterior Posterior Fusion and the Management of Lumbar Instability

Anterior-posterior surgery is indicated for the treatment of lumbar instability in the presence of simultaneous compromise of both the anterior and the posterior spinal elements or to augment the stability and rigidity of a fusion construct. The addition of an anterior interbody fusion to a posterior instrumented fusion serves to more successfully restore sagittal balance, effect indirect neural decompression, and to decrease pedicle screw strain by reconstituting the load-sharing ability of the anterior column. A variety of posterior fixation and minimally invasive techniques has been demonstrated to increase circumferential construct stiffness and rates of fusion.

Nucleus pulposus replacement: an emerging technology

Debilitating low back pain as a result of symptomatic lumbar disc degeneration places a significant burden on an industrial society. Traditionally surgical treatment involving fusion of the anterior and posterior spinal elements has resulted in unpredictable and frequently irreproducible results, especially with regard to return to work rates. A new surgical method of managing symptomatic disc degeneration recalcitrant to nonoperative measures involves the partial or complete removal of the intervertebral disc with replacement with a motion-sparing device. A review of the English-speaking literature will be discussed evaluating the historical development, design considerations, animal models, basic science studies, cadaveric research, and clinical outcomes of the partial removal of the intervertebral disc (nucleus pulposus) and replacement with a motion-sparing implant. An overview of traditional methods of surgical management of lumbar degenerative disc disease will then be followed by an introduction to the concept of motion-sparing implants (nucleus pulposus replacement) intended to remove the pain generator without the associated morbidity of a surgical fusion.

5:20 109. Comparison of autograft to DBX demineralized bone matrix putty combined with autograft used in posterolateral lumbar spinal fusion

BACKGROUND CONTEXT: The quantitiy of autograft obtained through direct decortication of of the posterior spinal elements if often inadequate to promote solid spinal fusion. The amount of autograft obtained from the iliac crest is often a large quantity resulting in a high donor site morbidity. The use of demineralized bone matrix (DBM) as an autograft “extender” for the limited supply of autologous bone eliminates or reduces the need to harvest large quantities from a secondary surgical site, and thus reduces donor site morbidity.

An Investigational Study on the Healing Process of Anterior Spinal Arthrodesis Using a Bioactive Ceramic Spacer and the Change in Load-Sharing of Spinal Instrumentation

Ceramic anterior lumbar interbody arthrodesis was performed using an in vivo sheep model. Observations of fusion status and the load-sharing of spinal instrumentation were studied at sequential intervals for 1 year after surgery. To elucidate the healing process of spinal arthrodesis performed with a bioactive ceramic spacer and the change in load-sharing of anterior spinal instrumentation. With the improved development of spinal instrumentation, anterior spinal arthrodesis has become a standard spinal reconstruction technique; however, the mechanistic basis underlying the healing process is not well documented. Moreover, it remains unclear how load-distribution through the fusion mass and spinal instrumentation change throughout the healing process. Using 24 sheep, a two-level anterior lumbar interbody fusion (L2-L3, L4-L5) was performed using a smooth surface and a porous surface-modified bioactive ceramic, with each segment instrumented using a one-rod anterior spinal instrumentation system. Four animals each were killed at 2, 4, 8, 12, 24, and 52 weeks after surgery. Postmortem analysis included quantification of anterior rod strain under multidirectional flexibility testing and radiographic and histologic analyses of the arthrodesed segments. From 0 to 8 weeks after surgery, the bending strain of the rod gradually decreased despite no obvious bone formation. From 8 to 24 weeks after surgery, the rod strain markedly decreased with the development of bridging trabeculated bone formation between vertebral bodies. After 24 weeks after surgery, minimal changes were observed in rod strain; however, the fusion mass volumetrically increased with corresponding facet joint atrophy. The porous surface-modification of ceramic did not influence the histologic healing process, despite the improvement of interface osseous union rate. In anterior spinal arthrodesis, spinal instrumentation is mainly exposed to bending stress, with decreased load-sharing with corresponding development of the spinal fusion. Continuous bone remodeling of the anterior fusion mass results in concurrent decreases in spinal instrumentation and posterior spinal element load-transmission. The principal healing mechanism of ceramic anterior interbody spinal fusion is not an osseous union between the ceramic and vertebral body, but bridging bone formation around the ceramic, which directly connects the vertebral bodies above and below the disc.

Role of SPECT imaging in symptomatic posterior element lumbar stress injuries

Background : Diagnosis of stress injuries of spine is very difficult with conventional radiography. Methods : In a observational study, 132 subjects were recruited (between 8 and 38 years of age), who had lumbar spondylolysis or posterior element stress injuries. All these patients underwent clinical examination followed by plain X-rays, planar bone scintigraphy and SPECT (single photon emission computerised tomography). SPECT scans can identify the posterior element lumbar stress injuries earlier than other imaging modalities. As the lesions evolve and the completed spondylolysis becomes chronic, the SPECT scans tend to revert to normal even though healing of the defect has not occurred. The aim of the study was to determine the time lag after which SPECT imaging tends to be negative. We divided the patients into two groups, one SPECT positive group and the other SPECT negative group. Pre treatment background variables such as age, gender, back pain in extension or flexion, sporting activities, time of onset of symptoms, Oswestry Disability Index (ODI) were used in a univariate logistic regression model to find the strong predictors of positive SPECT imaging results. Determinants of positivity versus negativity of SPECT were identified by discriminant analysis using multivariate logistic regression. Results : Seventy nine patients had positive SPECT scans whereas 53 patients had negative SPECT scans. Bilateral increased uptake was more common than unilateral uptake. Increased uptake at the L 5 lumbar spine was more common (70%) in SPECT positive group. Low back pain in extension was significantly more common in SPECT positive subjects. Active sporting individuals had higher probability of having a positive SPECT scan. The mean time lag from the onset of low back pain to SPECT imaging was 7 months in SPECT positive group and 25 months in the SPECT negative group. Multivariate analysis predicted that there is a significant difference in positivity of SPECT scans (reduced number of positive results) in subjects who had onset of pain more than six months. Conclusion : SPECT imaging performed within the first six months following the onset of symptoms could predict the mode of treatment in patients with lumbar spondylolysis or posterior lumbar spinal element stress injuries.