John C. Y. Leong

Prevalence and Pattern of Lumbar Magnetic Resonance Imaging Changes in a Population Study of One Thousand Forty-Three Individuals

Study Design. A cross-sectional population study of magnetic resonance imaging (MRI) changes. Objective. To examine the pattern and prevalence of lumbar spine MRI changes within a southern Chinese population and their relationship with back pain. Summary of Background Data. Previous studies on MRI changes and back pain have used populations of asymptomatic individuals or patients presenting with back pain and sciatica. Thus, the prevalence and pattern of intervertebral disc degeneration within the population is not known. Methods. Lumbar spine MRIs were obtained in 1043 volunteers between 18 to 55 years of age. MRI changes including disc degeneration, herniation, anular tears (HIZ), and Schmorl’s nodes were noted by 2 independent observers. Differences were settled by consensus. Disc degeneration was graded using Schneiderman’s classification, and a total score (DDD score) was calculated by the summation of the Schneiderman’s score for each lumbar level. A K-mean clustering program was used to group individuals into different patterns of degeneration. Results. Forty percent of individuals under 30 years of age had lumbar intervertebral disc degeneration (LDD), the prevalence of LDD increasing progressively to over 90% by 50 to 55 years of age. There was a positive correlation between the DDD score and low back pain. L5–S1 and L4–L5 were the most commonly affected levels. Apart from the usual patterns of degeneration, some uncommon patternsof degeneration were identified, comprising of subjects with skip level lesions (intervening normal levels) and isolated upper or mid lumbar degeneration. Conclusion. LDD is common, and its incidence increases with age. In a population setting, there is a significant association of LDD on MRI with back pain.

Effects of short anterior lumbar interbody fusion on biomechanics of neighboring unfused segments

Study Design Segmental mobility and intradiscal pressure were measured and the data compared in six cadaveric lumbar spine specimens before and after in vitro simulated single level L4‐5 and double level L4‐5‐S1 anterior interbody fusions. Objective The experimental objective was to study the biomechanical effects of single level L4‐5 and double level L4‐5‐S1 anterior interbody fusions on the neighboring unfused segments. Summary of Background Data The relationship between the local rigidity created by fusion mass and accelerated degeneration reported at the neighboring unfused intervertebral discs is not clear. Methods Six cadaveric lumbar spine specimens were biomechanically tested in flexion and extension. Segmental mobility and intradiscal pressure of the specimens were measured before and after in vitro simulation of single level L4‐5 and double level L4‐5‐S1 anterior interbody fusions. Results The mobility of the motion segments immediately above and below an L4‐5 fusion was increased in flexion. When the L5‐S1 segment was also fused, the loss of segmental motion in both flexion and extension at the L4‐5 and L5‐S1 were compensated for by increased motion in all levels above the fusion. In both flexion and extension, the intradiscal pressures of all unfused intervertebral discs were increased after a single level L4‐5 fusion and this increase was even more marked after a double level L4‐5‐S1 fusion. Conclusions There is no evidence that the neighboring unfused segments are loaded beyond their physiological limits due to the fusion. However, the neighboring unfused segments have to work more frequently toward the extremes of their functional ranges of motion after fusion and these effects will be more marked after a double level L4‐5‐S1 fusion.

The TRP2 Allele of COL9A2 is an Age-Dependent Risk Factor for the Development and Severity of Intervertebral Disc Degeneration

Study Design. Low back pain (LBP) and sciatica are usually caused by degenerative disc disease (DDD). Although they are common, the etiology of these conditions is poorly understood. A large population case-control study in the Southern Chinese was performed to study genetic risk factors to DDD. Objectives. To gain a better understanding of the etiology of DDD in relation to structural defects of the intervertebral disc. Summary of Background Data. A Finnish study found an association between LBP and sciatica with two variants of the α-chains of collagen IX, encoded by the Trp2 and Trp3 alleles, representing Gln326Trp and Arg103Trp amino acid substitutions in the COL9A2 and COL9A3 genes, respectively. Trp2 was found only in affected individuals (4%), whereas Trp3 was present in both affected (24%) and unaffected (9%) individuals. Because of the low frequency of the Trp2 allele in whites, the significance and contribution of this allele to DDD are not known. Using more objective criteria to define the disease by magnetic resonance imaging (MRI), we tested these alleles for association with DDD in a large population study. Methods. Lumbar DDD, the presence of anular tears, and disc and endplate herniations were defined by MRI in 804 Southern Chinese volunteers 18 to 55 years of age. These were correlated with the frequencies of the Trp2 and Trp3 alleles. Results. The Trp2 allele was present in 20% of the population and was associated with a fourfold increase in the risk of developing anular tears at 30 to 39 years and a 2.4-fold increase in the risk of developing DDD and endplate herniations at 40 to 49 years. Affected Trp2 individuals had more severe degeneration. The Trp3 allele was absent from the Southern Chinese population. Conclusion. This largest-ever population study using MRI to define DDD demonstrates for the first time that the Trp2 allele is a significant risk factor for the development and severity of degeneration. The association is age- dependent as it is more prevalent in some age groups than in others. The contrasting Trp allele frequencies between the Finns and the Chinese are the first indication that the genetic risk factors for DDD varies between ethnic groups.

Continuous dynamic spinal motion analysis.

Study Design. Continuous dynamic lumbar intervertebral flexion-extension is assessed by a videofluoroscopy with a new auto-tracking system. Objectives. To develop and validate a new method for the continuous assessment of lumbar kinematics. Summary of Background Data. Instability of the lumbar spine is thought to be associated with low back pain, but the diagnosis remains difficult. Functional radiographs have been used for diagnosis of spinal instability but error and limitation exist, whereas videofluoroscopy provides a cost-effective way for such analysis. However, common approaches of image analysis of videofluoroscopic video are tedious and time-consuming because of the low quality of the images. Physicians have to extract the vertebrae manually in most cases; thus, continuous motion analysis is hardly achieved. Methods. A new system that can perform automatic vertebrae segmentation and tracking is developed. In vitro and in vivo validity were evaluated. Intervertebral flexion and extension was assessed in 30 healthy volunteers. Results. In vitro and in vivo validity tests have been conducted with good results. A linear-liked pattern of the intervertebral flexion-extension (IVFE) curves in different levels was found, and the IVFE decreased in descending order from L1–L5 at different points of range of motion in flexion. Conversely, extension is evenly contributed at different levels, and the concavity of lumbar lordosis increases steadily in backward movement. Conclusions. The newly developed technique in assessing the dynamic lumbar motion is reliable and able to analyze the lumbar intervertebral movement from videofluoroscopic images automatically and accurately. The proposed system requires less human intervention than common approaches. It may have a potential value in the evaluation of spinal “instability” in clinical practice.

Development and validation of a new technique for assessing lumbar spine motion.

Study Design. Dynamic lumbar flexion–extension motions were assessed by an electrogoniometer and a videofluoroscopy unit simultaneously. Objective. To develop and validate a new technique for the assessment of lumbar spine motion. Summary of Background Data. Spine instability, a clinical condition that is common but difficult to diagnose, has been suggested to involve a characteristic change in the relation between vertebrae during motion. Assessment of lumbar instability using functional radiographs is controversial. Information regarding dynamic spine kinematics in vivo is limited. Methods. A lumbar spine motion analysis system was developed, and its reliability was assessed. Simultaneous total flexion range of motion and segmental motion of the lumbar spine were assessed in 30 healthy volunteers. Lumbar images were captured in 10° intervals during flexion–extension. Intervertebral flexion–extension of each vertebral level was calculated. Results. In flexion, the lumbar vertebrae flexed with a descending order from L1 to L5 throughout the motion. Conversely, the concavity of lumbar lordosis increased steadily in extension. No statistically significant difference in the pattern of motion was found between genders. Conclusions. The results from this study showed that the newly developed technique is reliable. It may have potential value for evaluating spine instability in clinical practice.

Assessment of scoliosis correction in relation to flexibility using the fulcrum bending correction index

Study Design. A prospective study on adolescent idiopathic scoliosis to assess a new method of describing frontal plane correction. Objective. To assess the difference between using the correction rate and using the new fulcrum bending correction index when describing scoliosis correction. Summary of Background Data. A description of the outcome of scoliosis surgery based on the correction rate does not take into account the curves flexibility. Methods. The fulcrum bending correction index is calculated by dividing the correction rate by the fulcrum flexibility (based on the fulcrum bending radiograph) and is expressed as a percentage. The fulcrum bending correction index was compared with the correction rate in 35 patients with adolescent idiopathic scoliosis undergoing surgical correction. These patients were divided into a stiff and a flexible group based on a fulcrum flexibility of 50% to show the advantage of the fulcrum bending correction index over the correction rate. Results. The difference in correction rate between the flexible (66%) and the stiff group (45%) was significant (P < 0.05). The difference in the fulcrum bending correction index between the flexible (96%) and the stiff group (107%) was not significant (P = 0.2). Conclusions. The fulcrum bending correction index takes into account the curve flexibility and is therefore better than the correction rate for comparing curve correction and use of instrumentation systems between different series of patients. A fulcrum bending correction index of close to 100% suggests that the instrumentation has taken up all the flexibility revealed by the fulcrum bending radiograph. It is recommended that the fulcrum bending correction index be used in the future as part of the postoperative assessment of frontal plane correction in cases of thoracic scoliosis.

The biomechanical functions of the iliolumbar ligament in maintaining stability of the lumbosacral junction

The iliolumbar ligament is one of the three lumbopelvic ligaments. Recent study has shown that the ligament is not present at birth and is formed from metaplasia of the quadratus lumborum muscle at the end of the first decade. To study the biomechanical functions of this ligament, an apparatus was developed using linear variable differential transformers. Twenty fresh cadaveric specimens of the lumbosacral pelvis were tested. The flexibility of the intact lumbar segment was studied before and after the ligaments were divided. Flexion of L5 on S1 was mainly controlled by the posterior band and lateral bending by the anterior band of the ligament. When the L5–S1 disc was degenerated, total division of the ligaments reduced extension during loading. Its effect on torsion was not evident from this study.

The effect on the lumbosacral spine of long spinal fusion for idiopathic scoliosis. A minimum 10-year follow-up

The effect on the lumbosacral spine of long spinal fusion in adolescent idiopathic scoliosis was studied in 22 patients. The average duration of follow-up was 12.8 years. Corrections of the coronal curves through instrumentations were satisfactory. However, a kyphosis was produced at the fused segment of the lumbar spine in more than half of the cases. The unfused intervertebral spaces distally were hypermobile in extension, which probably indicated early disc degeneration. The incidences of back pain and radiological degeneration were found to be low. There was no relationship between back symptoms and type of employment, pregnancies or radiological degeneration. Preservation of normal lumbar lordosis during spinal fusions was emphasized.

The flexion-extension profile of lumbar spine in 100 healthy volunteers.

Study Design. Dynamic lumbar flexion–extension motions were assessed by an electrogoniometer and a videofluoroscopy unit simultaneously. Objectives. The aims of this study were to assess the motion profile of lumbar spine in different genders and age groups and to assess their differences. Summary of Backgrounds Data. The dynamic lumbar flexion–extension motions analysis method has been developed and validated. However, data profile of the spinal motions of healthy volunteers has not been established. Methods. A total of 100 healthy volunteers, including 50 men and 50 women, were recruited. They were then divided into four equal groups, following their age ranges of 21 to 30 years, 31 to 40 years, 41 to 50 years, and 51 years and older. Lumbar flexion–extension motion was assessed with an electrogoniometer and videofluoroscopy simultaneously. Radiologic images of the lumbar spine were captured during flexion–extension in 10° intervals. Intervertebral flexion–extension (IVFE) of each vertebral level was calculated. The spinal motion of different genders was compared segment by segment with independent t test. The spinal motion of different age groups was compared with one-way analysis of variance. Results. A linear-liked pattern of the IVFE curves was observed in different genders and age groups. No statistically significant difference in the pattern of motion was found between genders. However, statistically significant difference in the slope of IVFE curves was found at all lumbar levels in subjects whose age was 51 years or older (P < 0.05). Conclusions. Assessment of motion profile was found to be helpful for the identification of spinal disorders in clinical practice. Because of the normal variation of spinal motion of subjects in different age ranges, interpretation of spinal motion disorders should be careful. Although the sample size in this study was limited, the database generated might be useful to assist the diagnosis of spinal “instability” in the future.

The effect of pinealectomy on scoliosis development in young nonhuman primates.

Study Design. Prospective study on pinealectomy in primates. Objective. To evaluate whether pinealectomy in a bipedal nonhuman primate model will result in the development of scoliosis. Summary of Background Data. Pinealectomy in newborn chickens consistently resulted in scoliosis development. Published data suggest that the surgical removal of the pineal, loss of melatonin secretion, and a bipedal posture are important elements in the development of scoliosis in lower animal models. Method. There were 18 rhesus monkeys between 8 and 11 months old that underwent pineal excision. All monkeys were kept in a regulated 12-hour light-dark cycle. Monthly radiographs assessed scoliosis development. Completeness of pineal excision was assessed by measurement of a major metabolite of melatonin in the urine, 6-sulfatoxymelatonin, using an enzyme-linked immunosorbent assay assessed. Results. Mean follow-up was 28 months (range 10− 41). Seven monkeys died prematurely, and 11 survived to date; the data from those that died could still be used, although follow-up was shortened. At the latest follow-up or death, scoliosis did not develop in any of the monkeys. Urinary 6-sulfatoxymelatonin measurements revealed 3 patterns. Group 1 consisted of 10 monkeys, which showed definite evidence of complete pineal excision. Group 2 consisted of an uncertain group of 2 monkeys in which the nighttime melatonin level is slightly high. Group 3 consisted of 6 monkeys that had incomplete pineal excision or ectopic melatonin production. Conclusions. To our knowledge, this is the first report of pinealectomy in nonhuman primates. Of the 18 monkeys, 10 had a loss of melatonin secretion, for a mean of 29 months after surgery. Because none of the monkeys had scoliosis develop, this study strongly suggests that the possible etiologic factors producing idiopathic scoliosis in lower animals are different from primates, and findings in lower animals cannot necessarily be extrapolated to human beings.