S. Rajasekaran

ISSLS prize winner: A study of diffusion in human lumbar discs: a serial magnetic resonance imaging study documenting the influence of the endplate on diffusion in normal and degenerate discs.

Study Design. An in vivo serial magnetic resonance imaging study of diffusion characteristics in human lumbar discs over 24 hours in healthy volunteers and patients with low back pain. Objectives. To document the temporal pattern of diffusion in normal human lumbar discs and to study the influence of the vascularity of bone and the status of endplate on diffusion in the normal and degenerate discs. Summary of Background Data. Diffusion is the only source of nutrition to the discs, but no firm data are available on pattern of diffusion in humans. More data on this important subject are required to improve our understanding of disc degeneration and to probe research possibilities for preventing the same. Methods. The diffusion pattern over 24 hours following gadodiamide injection was studied in 150 discs (96 normal and 54 degenerate). Signal intensity values for three regions of interest in bone (i.e., vertebral body, subchondral bone, and endplate zone) and seven in the disc were calculated, and normal percentiles of diffusion were derived for these regions. Enhancement percentage for each time period, peak enhancement percentage for each region, and the time taken to achieve peak enhancement percentage (Tmax) were used to define and compare diffusion characteristics and plot a time-intensity curve to document the 24-hour temporal pattern. The correlation of blood flow of the bone as measured by peak enhancement percentage of vertebral body, the status of the endplate zone as measured by the peak enhancement percentage, and Tmax of the endplate zone were correlated with the diffusion of the disc. Univariate analysis of variance, multiple comparisons, appropriate tests for significance, and stepwise linear regression analysis were used for analysis of the data using SPSS software. Results. In normal discs, a “diffusion march” from the vertebral body to the center of disc was noted with the SImax being observed at 5 min in the vertebral body and subchondral bone, at 2 hours in the endplate zone, and at 6 hours in the nucleus pulposus. A significant difference in mean peak enhancement percentage was observed between that of the body and the discs in those less than 10 years and those above the age of 20 years (P < 0.001). Alterations in endplate zone produced distinct magnetic resonance imaging signs of disturbance in diffusion, which offered a reliable noninvasive method of identifying endplate cartilage damage. Stepwise linear regression analysis showed that the significant variable influencing diffusion to the center of the nucleus pulposus of the total sample was peak enhancement percentage of endplate zone (R2 = 0.216; P < 0.001), that of degenerate discs was peak enhancement percentage of endplate zone (R2 = 0.322; P < 0.001), and that of normal discs (R2 = 0.324; P < 0.001) was age. Conclusions. Serial postcontrast magnetic resonance imaging studies offer a reliable method of assessing the diffusion of the discs and the functional status of the endplate cartilage. Endplate cartilage damage increases with age and produces considerable changes in diffusion. The present study has described reliable signs by which these damages can be identified in vivo. Aging and degeneration have been shown to be two separate processes by documenting clear-cut differences in diffusion. The present data encourage use of diffusion studies as a noninvasive method to assess the physiologic status of the disc and endplate and to study the effect of drugs, smoking, mechanical loading, exercises, etc. on the physiology of the disc.

Randomized clinical study to compare the accuracy of navigated and non-navigated thoracic pedicle screws in deformity correction surgeries.

Study Design. Randomized clinical trial (level I evidence). Objective. To compare the accuracy of non-navigation and Iso-C based navigation in pedicle screw fixation in thoracic spine deformities. Summary of Background Data. Thoracic pedicle screw insertion for spinal deformity correction can be associated with increased pedicle breaches. Iso-C based navigation has been reported to improve the accuracy of pedicle screw placement, but its use in the presence of deformity has not been reported. Methods. Twenty-seven patients with scoliosis and 6 patients with kyphosis had a total of 478 thoracic pedicle screws. The average Cobb angle was 58.4° ± 8° (range 50°–80°), and the mean kyphotic angle was 54.6° ± 4° (range 51°–76°). By random allocation, 17 patients had screw insertion under navigation (242 screws) and 16 under fluoroscopic control (236 screws). The 2 groups were compared for accuracy of screw placement, time for screw insertion, and the number of times the C-arm had to be brought into the field. Two independent blinded observers determined accuracy using postoperative computed tomography assessments. Results. There were 54 (23%) pedicle breaches in the non-navigation group as compared to only 5 (2%) in the navigation group (P < 0.001). Thirty-eight screws (16%) in the non-navigation group had penetrated the anterior or lateral cortex compared to 2 screws (0.8%) in the navigation group. Average screw insertion time in the non-navigation group was 4.61 ± 1.05 minutes (range 1.8–6.5) compared to 2.37 ± 0.72 minutes (range 1.16–4.5) in navigation group (P < 0.01). The C-arm had to be moved into the operation field on an average of 1.5 ± 0.25 times (range 1–3) per screw. With single screening data, an average of 11.4 pedicles (range 9–14) could be visualized without necessity to bring the C-arm into operating field again. Conclusions. Iso-C navigation increases accuracy, and reduces surgical time and radiation in thoracic deformity correction surgeries.

Effects of using intravenous antibiotic only versus local intrawound vancomycin antibiotic powder application in addition to intravenous antibiotics on postoperative infection in spine surgery in 907 patients.

Study Design. A prospective randomized controlled trial. Objective. To assess the ability of local vancomycin powder in controlling postoperative infection in spine surgery. Summary of Background Data. Despite improvements through the use of prophylactic systemic antibiotics, surgical site infections remain a significant problem in spine surgical procedures. Various retrospective and prospective studies have reported the efficacy of local application of vancomycin powder in reducing the infection in animal and human studies. However, there were no randomized control trials that reported on its efficacy. Methods. Prospective randomized controls of 907 patients with various spinal pathologies were treated surgically during a period of 18 months. The control group received standard systemic prophylaxis only, whereas the treatment group received vancomycin powder in the surgical wound in addition to systemic prophylaxis. Patient demographics, comorbidities, level of spinal pathology, estimated blood loss, nutritional status, and hemoglobin were recorded. Incidence of infection was the primary outcome evaluated. Results. There were 8 infections (1.68%) in the control group (6 instrumented and 2 noninstrumented, 6 deep and 2 superficial) with bacteria cultured in 3 (1 Escherichia coli and 2 Staphylococcus aureus). In the treatment group, 7 infections (1.61%) were observed (6 instrumented and 1 noninstrumented surgical procedures, 6 deep and 1 superficial) with bacteria cultured in 3 (1 Staphylococcus aureus and 2 Klebsiella). No adverse effects were observed from the use of vancomycin powder. Statistically no significant difference was seen in infection rate between the treatment group and control group. Conclusion. The local application of vancomycin powder in surgical wounds did not significantly reduce the incidence of infection in patients with surgically treated spinal pathologies. The use of vancomycin powder may not be effective when incidence of infection is low. Level of Evidence: 2

Tuberculous lesions of the lumbosacral region. A 15-year follow-up of patients treated by ambulant chemotherapy.

Study Design. A 15‐year clinical follow‐up of tuberculous lesions of the lumbosacral region. Objectives. To verify the hypothesis that the lumbar lordosis and the specific biomechanics of the lumbosacral region influence and alter the healing pattern and progress of the disease when compared with their effects in other regions of the spine. Summary of Background Data. An estimated 2 million or more patients have active spinal tuberculosis, and the global incidence of the disease is increasing. The involvement of the lower lumbar region and the lumbosacral junction is relatively rare, with few reports in English literature. Methods. Of a total of 304 patients forming a part of a controlled clinical trial comparing two forms of therapy in spinal tuberculosis, 53 patients had involvement of L3 and below. The following data were studied in these patients: age at start of treatment, number of vertebra involved, vertebral body loss, progress of the angle of kyphosis, and anterior and posterior growth of the involved segment during a period of 15 years. Students t test for independent samples was used for statistical analysis. Results. The fourth lumbar vertebra was the most common vertebral segment involved, and the lumbosacral junction was affected in 12 patients. The average pretreatment kyphosis was 6.4° and increased to 10.2° at the end of 15 years. The average kyphotic angle per vertebral body loss was 4.9°, far less than in the dorsolumbar region in which kyphotic angles of 27‐30° have been reported. Children younger than 10 years old differed in clinical appearance and progress compared with those older than 17 years. They not only showed more extensive involvement but also had more deformity with the same vertebral loss. Twelve patients less than 10 years old had an average involvement of 3.1 vertebral bodies and an average vertebral loss of 2.2 bodies. In comparison, the average number of vertebrae involved was 1.9 (P < 0.01) and the vertebral body loss was only 0.87 (P < 0.01) in patients older than 17 years. Also, the average kyphosis was 6.4° compared with only 4.2° (P < 0.01) in adults. In patients older than 17 years, there was no change after 2 years, by which time the collapse was complete. Four of 12 patients less than 10 years old, showed progressive kyphosis caused by continued growth of posterior parts of the body (i.e., sequestrated hemivertebrae). Conclusions. In tuberculosis of the lumbosacral region, the development of kyphosis is minimal in patients older than 17 years, when growth has already stopped, and deformity is expressed more as foreshortening of the trunk. Children younger than 10 years old have more severe involvement with increased tendency toward greater kyphosis. They are also prone to progressive deformity through the years when the anterior growth plates are destroyed. Surgery is indicated in this group to prevent greater deformity.

Comparison of prognostic value of different MRI classifications of signal intensity change in cervical spondylotic myelopathy

BACKGROUND CONTEXT Signal intensity (SI) changes of the spinal cord on magnetic resonance imaging (MRI) in cervical spondylotic myelopathy (CSM) are thought to be a predictor of surgical outcome. However, the clinical significance of SI change remains controversial. Although several classifications exist for SI change, there are no previous studies comparing their prognostic significance. PURPOSE To determine the MRI classification of SI changes in patients with CSM that is useful for prognostication of surgical outcome. STUDY DESIGN Retrospective case study. PATIENT SAMPLE Patients who underwent cervical laminectomy for CSM between the time period of January 2000 and December 2005. OUTCOME MEASURE Clinical outcome was measured by the recovery rate (RR) and the postoperative Nurick grade. METHODS We retrospectively studied 35 of the 77 CSM patients (mean age, 57.8 years; range, 30-69; preoperative symptom duration, 9.3 months) who underwent cervical laminectomy and who met the inclusion criteria. Postoperative MRIs were performed at a mean of 51.3 months postsurgery to assess for resolution of preoperative signal changes. The pattern of spinal cord SI was classified in three different ways: based on high SI on T2-weighted images (T2WI) (Grade 0-absent, Grade 1-obscure, and Grade 2-intense); based on the extent of SI change on T2WI into focal (confined to one disc level) and multisegmental (more than one disc level); and based on T1-weighted image (T1WI) and T2WI changes into Group A (MRI normal/normal), no intramedullary SI abnormality on T1WI or T2WI; Group B (MRI normal/high SI), no intramedullary SI abnormality on T1WI and high intramedullary SI on T2WI; Group C (MRI low/high SI changes), low-intensity intramedullary signal abnormality on T1WI and high-intensity intramedullary signal abnormality on T2WI. Preoperative clinical findings and MRI abnormalities were correlated with outcomes (Nurick scores, RR) after surgical intervention. RESULTS Preoperative MRI studies demonstrated the following: Grade 0=1, Grade 1=13, Grade 2=13; focal=18, multisegmental=16; Group A=1; Group B=29; and Group C=5. Resolution of signal changes in T2WI was seen in most patients; however, four patients developed low SI in T1WI in the postoperative MRI. There was no significant difference in the RRs of patients with different grades in the T2WI or with focal or multisegmental SI changes (p=.47 and .28, respectively). In contrast, patients with low SI changes in T1WI were associated with a poor surgical outcome (p<.001). The linear regression model performed using low-intensity signal changes as a dependent variable and the RR as an independent variable confirmed the significance (p<.001) of low SI changes on T1WI as a predictor for surgical outcome. CONCLUSIONS A classification system of MRI signal changes that accommodates both T1WI and T2WI is more predictive of surgical outcome than those that include T2W SI changes alone. Postoperative MRI is useful to identify late onset of low T1W intensity changes in patients with poor neurological recovery.

ISSLS Prize Winner: The Anatomy of Failure in Lumbar Disc Herniation An In Vivo, Multimodal, Prospective Study of 181 Subjects

Study Design. A prospective multimodal study including clinical, radiological, serial postcontrast magnetic resonance imaging, intraoperative findings, and histopathological study. Objective. To document in vivo, the site of anatomical failure in lumbar disc herniation (LDH). Summary of Background Data. Although in vitro mechanical disruption studies have implicated both the endplate junction (EPJ) and the annulus fibrosus (AF) as the site of failure in LDH, there are no in vivo human studies to document the exact anatomy of failure. Methods. One hundred eighty-one consecutive patients requiring microdiscectomy at a single level formed the study group. The status of the endplate and AF in the operated level (study discs) and the other discs (control) were evaluated by plain radiograph, thin slice computed tomographic scan, plain and contrast magnetic resonance imaging, intraoperative examination, and histopathological analysis. Results. LDH due to EPJ failure (EPJF- type I herniation) was more common (117; 65%) than annulus fibrosis rupture. Herniated discs had a significantly higher incidence of EPJF than control discs (P < 0.0001). The EPJF was evident radiologically as vertebral corner defect in 30 patients, rim avulsion in 46, frank bony avulsions in 24, and avulsion at both upper and lower EP in 4. Thirteen discs with normal EP radiologically had cartilage or bone avulsion intraoperatively. Sixty-four discs (35%) had intact EP of which annular high intensity zone was found in 21 (11%), suggesting a disruption of AF (type II herniation). Postcontrast magnetic resonance image of 20 patients showed dye leak at the EPJ proving EPJF as main cause of LDH. Conclusion. Our study provides the first in vivo evidence that LDH in humans is more commonly the result of EPJF than AF rupture and offers clinical validation of previous in vitro mechanical disruption studies. Future research must focus on the EPJ as a primary area of interest in LDH. Level of Evidence: N/A

Intraoperative Iso-C three-dimensional navigation in excision of spinal osteoid osteomas.

Study Design. A prospective observational study on the use of Iso-C 3-dimensional navigated surgery in treating 4 patients with spinal osteoid osteomas by a minimally invasive approach. Objective. To report on the efficacy of Iso-C 3-dimensional intraoperative spinal navigation in excising osteoid osteomas. Summary of Background Data. Curative treatment of osteoid osteomas entails complete intralesional excision of the nidus. However, intraoperative localization of the nidus can be difficult, and may involve wide resection of the surrounding normal bony structure resulting in instability requiring fusion or inadvertent neurovascular injury. Computer navigation provides real-time multiplanar images of the vertebral anatomy, and has been used extensively to increase the accuracy of pedicle screw placement. However, the efficacy of this technology in intraoperative localization and excision of spinal tumors is still largely unknown. Method. Iso-C 3-dimensional intraoperative navigation was used to localize osteoid osteomas of the spine in 4 patients. A minimally invasive reflective array, tool navigator, and a registered burr were used for localization and deroofing of the lesion, followed by curettage and high-speed burring of the cavity. Complete removal of the nidus was confirmed intraoperatively by reacquisition of data. Results. In all 4 patients, Iso-C 3-dimensional computer navigation was successful in accurate localization of the osteoid osteomas. The tool navigator was helpful to localize and deroof the lesion. The ability to register the burr was useful to clear the lesion without removal of any excess bone. Reregistration allowed intraoperative confirmation of adequacy of excision. Conservation of bone allowed early mobilization and also removed the need for reconstruction. Postoperative computer tomography scan done in 2 patients confirmed complete extirpation of the nidus. Histopathology confirmed the clinical diagnosis in all cases. All patients had immediate relief of the characteristic pain after surgery and were asymptomatic at 2 years follow-up. Conclusion. Intraoperative Iso-C 3-dimensional navigation is useful in accurately localizing and guiding complete excision of spinal osteoid osteomas through a minimally invasive approach without compromising spinal stability.

Iso-C3D fluoroscopy-based navigation in direct pedicle screw fixation of Hangman fracture: a case report.

Direct pedicle screw fixation of the C2 is rarely performed in trauma owing to the risk of damage to the neurovascular structures. Computed tomography-based navigation has the problem of change in intersegmental anatomy after positioning for surgery. Iso-C3D–based computer navigation acquires the intraoperative real-time images after patient positioning and thus avoids registration errors and improves accuracy. A Hangman fracture treated by posterior direct pedicle screw fixation using Iso-C3D computer navigation guidance is reported. Postoperative computed tomographic images confirmed the accurate placement of pedicular screws. Intraoperative fluoroscopy-based computer navigation is advantageous especially in an unstable upper cervical spine injury where the likelihood of change in the intersegmental relationship is maximal before and after positioning for surgery. The Iso-C3D navigation has the advantages of clarity and accuracy, making safe pedicle fixation of C1 and C2 possible despite fractured posterior elements. To our knowledge, this is the first reported case of displaced Hangman fracture treated successfully using Iso-C3D fluoroscopic navigation assisted direct pedicle screw osteosynthesis in the literature. Intraoperative acquisition of fluoroscopic images avoids registration-related problems. Three-dimensional fluoroscopic navigation gives excellent accuracy and safety in screw instrumentation of Hangman fracture.

ISSLS Prize Winner: A Study of Effects of In Vivo Mechanical Forces on Human Lumbar Discs With Scoliotic Disc as a Biological Model: Results From Serial Postcontrast Diffusion Studies, Histopathology and Biochemical Analysis of Twenty-One Human Lumbar Scoliotic Discs

Study Design. A comprehensive study of 21 lumbar scoliotic discs by in vivo serial post contrast diffusion magnetic resonance imaging (MRI), histopathological, and biochemical analysis. Objective. To investigate the in vivo effects of compressive and tensile mechanical stress on the lumbar discs with scoliotic disc as the biologic model. Summary of Background Data. Most studies implicating mechanical stress in degenerative disc disease (DDD) are on animals, in vitro conditions and cadavers. They are also restricted to histopathological or biochemical evaluation without analyzing the endplate (EP) and nucleus pulposus (NP) separately. The few human studies have not analyzed diffusion changes which is the final pathway for DDD. Adolescent scoliotic disc offer a perfect model to study the effects of mechanical stress. Methods. Twenty-one discs from 6 patients with adolescent idiopathic scoliosis undergoing anterior corrective surgery were assessed before surgery by postcontrast MRI to document the EP diffusion patterns. The same discs harvested during surgery were analyzed histologically and biochemically. The results were correlated to clinical and radiologic parameters. Results. Altered diffusion patterns was seen in all discs with site specific breaks in 2, double peak pattern in 3, high intensity pattern in 14, and frank contrast leak in 2. There was marked decrease in cell density and viability in all discs on both convex and concave sides compared to the control disc (P = 0.001). Neovascularization, calcification, and matrix degeneration were observed to varying extent in different regions of NP and EP. There was a decrease in water content with increasing severity of curves with significant difference between mild and severe curves (NP: P = 0.000, EP: P = 0.002). Lactate was significantly higher in caudal EP (P = 0.035) and discs with coronal migration of more than 15 mm (P = 0.007). Regression analysis showed that truncal decompensation was a main factor for decrease in cell density, matrix degeneration, calcification, and water content. Conclusion. The study documents widespread changes in the EP and NP even in discs with minimal wedging. EP damage and alterations in diffusion were observed earlier than MRI changes and could indicate nutritional factors as the primary mechanism of degeneration induced by mechanical stress. Degeneration was more severe in caudal discs and those with truncal decompensation. Its implications on the timing and choice of surgery in scoliosis are discussed.

Intraspinal anomalies in scoliosis: An MRI analysis of 177 consecutive scoliosis patients

Background: The association of intraspinal neural anomalies with scoliosis is known for more than six decades. However, there are no studies documenting the incidence of association of intraspinal anomalies in scoliotic patients in the Indian population. The guide lines to obtain an magnetic resonance imaging (MRI) scan to rule out neuro-axial abnormalities in presumed adolescent idiopathic scoliosis are also not clear. We conducted a prospective study (a) to document and analyze the incidence and types of intraspinal anomalies in different types of scoliosis in Indian patients. (b) to identify clinico-radiological ‘indicators’ that best predict the findings of neuro-axial abnormalities in patients with presumed adolescent idiopathic scoliosis, which will alert the physician to the possible presence of intraspinal anomalies and optimize the use of MRI in this sub group of patients. Materials and Methods: The data from 177 consecutive scoliotic patients aged less than 21 years were analyzed. Patients were categorized into three groups; Group A - congenital scoliosis (n=60), group B -presumed idiopathic scoliosis (n=94) and group C - scoliosis secondary to neurofibromatosis, neuromuscular and connective tissue disorders (n=23). The presence and type of anomaly in the MRI was correlated to patient symptoms, clinical signs and curve characteristics. Results: The incidence of intraspinal anomalies in congenital scoliosis was 35% (21/60), with tethered cord due to filum terminale being the commonest anomaly (10/21). Patients with multiple vertebral anomalies had the highest incidence (48%) of neural anomalies and isolated hemi vertebrae had none. In presumed ‘idiopathic’ scoliosis patients the incidence was higher (16%) than previously reported. Arnold Chiari-I malformation (AC-I) with syringomyelia was the most common neural anomaly (9/15) and the incidence was higher in the presence of neurological findings (100%), apical kyphosis (66.6%) and early onset scoliosis. Isolated lumbar curves had no anomalies. In group-C, incidence was 22% and most of the anomalies were in curves with connective tissue disorders. Conclusion: The high incidence of intraspinal anomalies in presumed idiopathic scoliosis in our study group emphasizes the need for detailed examination for subtle neurological signs that accompany neuro-axial anomalies. Preoperative MRI screening is recommended in patients with presumed ‘idiopathic’ scoliosis who present at young age, with neurological findings and in curves with apical thoracic kyphosis.