Daniel H. K. Chow

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 effect of backpack load on the gait of normal adolescent girls

Concerns regarding the effects of load carriage have led to recommendations that backpacks be limited to 10 – 15% of body weight, based on significant changes in physical performance. However, gait responses to backpack loads are not entirely consistent and there is a particular lack of data regarding load-bearing gait in adolescent females. Gait patterns of 22 normal adolescent girls were recorded at backpack loads of 0, 7.5, 10.0, 12.5 and 15.0% body weight. Temporal-distance, ground reaction force and joint kinematic, moment and power parameters were analysed by repeated measures ANOVA with factors of backpack load and side (left or right). Walking speed and cadence decreased significantly with increasing backpack load, while double support time increased. Kinematic changes were most marked at the proximal joints, with a decreased pelvic motion but a significant increase in the hip sagittal plane motion. Increased moments and power at the hip, knee and ankle showed increasing demand with backpack load. Parameters showed different responses to increasing load, and those that suggested a critical load indicated this to be approximately 10% body weight. While this may be due to a change in gait due to increased demand, further work is required to verify this and also to examine the cumulative effects of backpack load on the musculoskeletal system, which may be more appropriate in determining recommended load limits.

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 of rigid versus flexible spinal orthosis on the clinical efficacy and acceptance of the patients with adolescent idiopathic scoliosis.

Study Design. A prospective study on the comparison of the clinical efficacy and patient’s acceptance of the 2 orthotic management methods. Objective. To compare the treatment effectiveness and patients’ acceptance of the flexible spinal orthosis, SpineCor with that of the rigid spinal orthosis for the patients with moderate adolescent idiopathic scoliosis. Summary of Background Data. The patients’ acceptance to the rigid spinal orthoses is always a concern as it could greatly affect the clinical outcome. SpineCor is a relatively new design for tackling those inevitable drawbacks found in rigid orthosis. However, there was no study to compare this design with the conventional method regarding their treatment efficacy and the patient’s acceptance. Methods. Forty-three subjects with moderate adolescent idiopathic scoliosis were randomly assigned to the SpineCor group (S group, n = 22) and rigid orthosis group (R group, n = 21). Their survival rate in the first 45 months of intervention was studied. The subjects’ acceptance to the orthoses was evaluated by a purpose-designed questionnaire, which was administered in the 3rd, 9th, and 18th months of intervention. Results. In the study period, there were 68% of the subjects in the S group and 95% of the subjects in the R group did not show curve progression. Significant difference (P = 0.046, by Fisher exact test) in failure rate between the 2 subject groups was found although the 2 groups had similar responses to the questionnaire. Conclusion. The current study showed that the failure rate of the SpineCor was significantly higher than that of the rigid spinal orthosis, and the patients’ acceptance to the SpineCor was comparable to the conventional rigid spinal orthosis.

The use of electro-acupuncture in conjunction with exercise for the treatment of chronic low-back pain.

OBJECTIVES To determine the effect of a series of electro-acupuncture (EA) treatment in conjunction with exercise on the pain, disability, and functional improvement scores of patients with chronic low-back pain (LBP). DESIGN A blinded prospective randomized controlled study. SUBJECTS AND INTERVENTIONS A total of 52 patients were randomly allocated to an exercise group (n = 26) or an exercise plus EA group (n = 26) and treated for 12 sessions. OUTCOME MEASURES Numerical Rating Scale (NRS), Aberdeen LBP scale, lumbar spinal active range of movement (AROM), and the isokinetic strength were assessed by a blinded observer. Repeated measures analysis of variance (R-ANOVA) with factors of group and time was used to compare the outcomes between the two groups at baseline (before treatment), immediately after treatment, 1-month follow-up, and 3-month follow-up. The level of significance was set at p = 0.05. RESULTS Significantly better scores in the NRS and Aberdeen LBP scale were found in the exercise plus EA group immediately after treatment and at 1-month follow-up. Higher scores were also seen at 3-month follow-up. No significant differences were observed in spinal AROM and isokinetic trunk concentric strength between the two groups at any stage of follow-up. CONCLUSIONS This study provides additional data on the potential role of EA in the treatment of LBP, and indicates that the combination of EA and back exercise might be an effective option in the treatment of pain and disability associated with chronic LBP.

The effect of prosthesis alignment on the symmetry of gait in subjects with unilateral transtibial amputation

A high degree of gait symmetry is characteristic of healthy gait. The aim of this study is to examine the symmetry of various gait parameters in subjects with unilateral trans-tibial amputation over a range of acceptable anteroposterior translational and tilt alignments, and further to examine if a consistent alignment of highest symmetry can be found. Acceptable alignments were determined by bench, static and dynamic testing on level and non-level surfaces. A total of 15 kinetic and kinematic parameters were then measured in the seven subjects participating in this study. Results indicate that some parameters show consistently higher symmetries, particularly the vertical ground reaction force parameters and the stance duration, step length and time to full knee flexion during the swing phase. Symmetries in other parameters such as knee flexion at loading response, acceleration impulse, and peak anteroposterior propulsive force seem to have little relevance in determining whether the gait pattern for that prosthetic alignment is acceptable or not. While analysis of the symmetry of more relevant gait parameters may assist the prosthetist in consistently and objectively identifying a most symmetrical alignment within the acceptable range, further clinical study is required before any conclusions can be drawn regarding evaluation of symmetry as a tool in defining any optimum alignment.

Lumbar spinal mobility after short anterior interbody fusion.

Study Design Segmental deformations of the lumbar spine in asymptomatic volunteers measured radiologically were compared with those in patients who underwent anterior interbody fusion. Objective To determine the effects of anterior lumbar interbody fusion on the juxta-fused segments. Summary of Background Data. Stiffness of a spinal segment after fusion was thought to be the cause of the degeneration process at the juxta-fused segments. Methods Segmental deformations of the lumbar spine, from maximum extension to maximum flexion, in 30 asymptomatic volunteers and 52 pain-free patients who had single-level L4-L5 or double-level L4-S1 fusion were measured and compared. Results The total flexibility of the lumbar spine was decreased after a single-level fusion and further decreased after double-level fusions. The segmental deformations of the juxta-fused segments also were decreased after either a single-or double-level fusion. Conclusions During normal flexion and extension of the lumbar spine, the juxta-fused segments were not deformed beyond their physiological limits after fusion. Thus, accelerated degeneration observed at a juxta-fused segment is unlikely to be attributable to hypermobility.

Intervertebral disc autografting in a bipedal animal model.

Fusion of the spine while restoring stability of the spinal segment, fails to preserve spinal mobility. Long term complications of accelerated degeneration in the neighboring segments have been reported. The present study explores the possibility of intervertebral disc autografting in a bipedal animal model by isolating a lumbar disc together with the adjacent end plates and repositioning it with minimal internal fixation. Fourteen Rhesus monkeys were sacrificed at 2, 4, 6, and 12 months after surgery and the grafted discs were examined radiologically, biochemically, pathologically, and biomechanically. Healing of the bony end plate was seen between 2 to 4 months postoperatively. There was early loss of disc height at 2 and 4 months but there was a suggestion of some reconstitution up to 12 months. There was minimal evidence of gross degeneration at all stages. Gradual loss of water content was found in the annulus and the nucleus. The nucleus pulposus seemed to be able to reaccumulate proteoglycan after an initial drop in the first 4 months. There was significant increase in hydroxyproline content in the annulus fibrosus and the nucleus pulposus. Biomechanically, the grafted disc showed hypermobility in the first 4 months but gradually became stabilized with time. Results from this study suggested that a fresh intervertebral disc autograft could survive a period of ischemia. Although the physiology of the disc was deranged, it was able to preserve a certain degree of segmental mobility without sacrificing stability. Further studies are required to validate these results and the field of disc allografting should be explored.

An image feature approach for computer-aided detection of ischemic stroke

We present a computer-aided detection (CAD) scheme for early detection of ischemic stroke with small lesions using image feature characteristics. A novel Circular Adaptive Region of Interest (CAROI) method is proposed to analyze the Computed Tomography (CT) images of the brain. Our result indicates that for the emergency physicians and radiology residents, there is a significant improvement in sensitivity and specificity when using CAD (P < 0.005). A mathematical model is established incorporating the weighting of the feature changes. Our CAD scheme is promising for early detection of ischemic stroke and helps improve the efficiency and accuracy of clinical practice.

Impaired dynamic balance control in adolescents with idiopathic scoliosis and abnormal somatosensory evoked potentials.

Background: Both balance control dysfunction and dysfunction of the central nervous system have been proposed as being causative factors in adolescent idiopathic scoliosis (AIS), yet the relationship between these factors has not been investigated in detail. An intergroup comparative study was conducted to investigate the effect of abnormal somatosensory function on the dynamic balance parameters of girls with AIS. Methods: The relationship between dynamic balance control and abnormal somatosensory function seen in AIS patients was examined by studying the dynamic balance parameters in normal controls, in AIS patients with normal posterior tibial nerve somatosensory cortical evoked potentials (PTN-SCEPs), and in AIS patients with abnormal PTN-SCEPs. Gait parameters were recorded in 18 AIS girls (8 showing abnormal PTN-SCEPs and 10 showing normal PTN-SCEPs). Eight healthy age-matched volunteers served as a control group. Results: No significant left-right asymmetry of gait parameters was found for the controls or the AIS patients with normal PTN-SCEPs, whereas significantly higher gait parameters were found on the side of the curvature in the AIS patients with abnormal PTN-SCEPs. Conclusions: Somatosensory dysfunction in AIS patients shows to have an impact on dynamic balance control. Further studies to examine the association between somatosensory dysfunction and balance control and how they may be related to the etiology of AIS are recommended. Level of Evidence: Diagnostic study, level IV (case-control study).