Keith Dip-Kei Luk

A meta-analysis of the clinical effectiveness of school scoliosis screening

Study Design. A meta-analysis that systematically reviewed the evaluation studies of a scoliosis screening program reported in the literature. Objective. To evaluate the best current evidence on the clinical effectiveness of school screening for adolescent idiopathic scoliosis. Summary of Background Data. The use of school scoliosis screening is controversial, and its clinical effectiveness has been diversely reported. Methods. Data sources included 3 databases, namely, PubMed, Google scholar, CINAHL database, and the references from identified reviews and studies. Studies were included if: (1) they adopted a retrospective cohort design; (2) were screened using either the forward bending test (FBT), angle of trunk rotation, or Moiré topography; (3) reported results of screening tests and radiographic assessments; (4) screened adolescents only; (5) reported the incidence of curves with a minimum Cobb angle of 10° or greater; and (6) reported the number of referrals for radiography. Reviews, comments, case studies, and editorials were excluded. Results. Thirty-six studies, including 34 from the 775 initially identified studies and 2 from the references, met the selection criteria. The pooled referral rate for radiography was 5.0%, and the pooled positive predictive values for detecting curves ≥10°, curves ≥20°, and treatment were 28.0%, 5.6%, and 2.6%, respectively. There was substantial heterogeneity across studies. Meta-regression showed that programs using the FBT alone reported a higher referral rate (odds ratio [OR] = 2.91) and lower positive predictive values for curves ≥10° (OR = 0.49) and curves ≥20° (OR = 0.34) than programs using other tests. Only one small study followed students until skeletal maturity and reported the sensitivity of screening; however, the specificity was not reported. No severe publication bias was noted. Conclusion. The use of the FBT alone in school scoliosis screening is insufficient. We need large, retrospective cohort studies with sufficient follow-up to properly assess the clinical effectiveness of school scoliosis screening.

Abnormal diffusion tensor in nonsymptomatic familial amyotrophic lateral sclerosis with a causative superoxide dismutase 1 mutation

To determine whether diffusion abnormalities can be observed in nonsymptomatic family members with a known causative Cu/Zn superoxide dismutase mutation (asymptomatic familial amyotrophic lateral sclerosis; AFALS+SOD1) in a family with autosomal dominant familial amyotrophic lateral sclerosis (ALS) using diffusion tensor imaging (DTI).

Strontium–calcium coadministration stimulates bone matrix osteogenic factor expression and new bone formation in a large animal model

Strontium (Sr) has become increasingly attractive for use in the prevention and treatment of osteoporosis by concomitantly inhibiting bone resorption and enhancing bone formation. Strontium shares similar chemical, physical, and biological characteristics with calcium (Ca), which has been widely used as a dietary supplement in osteoporosis. However, the effects of Sr–Ca coadministration on bone growth and remodeling are yet to be extensively reported. In this study, 18 ovariectomized goats were divided into four groups: three groups of five goats each treated with 100 mg/kg/day Ca, Ca plus 24 mg/kg/day Sr (Ca + 24Sr), or Ca plus 40 mg/kg/day Sr (Ca + 40Sr), and three untreated goats fed low calcium feed. Serum Sr levels increased 6‐ and 10‐fold in the Ca + 24Sr and Ca + 40Sr groups, respectively. Similarly, Sr in the bone increased four‐ and sixfold in these two groups. Sr–Ca coadministration considerably increased bone mineral apposition rate (MAR). The expression of insulin‐like growth factor (IGF)‐1 and runt‐related transcription factor 2 (Runx2) was significantly upregulated within the Ca + 40Sr treatment group; tumor necrosis factor (TNF)‐agr; expression was significantly downregulated in the Ca and Ca + 40Sr groups. The results indicate that Sr–Ca coadministration increases osteogenic gene expression and stimulates new bone formation.

Somatosensory-evoked potentials as an indicator for the extent of ultrastructural damage of the spinal cord after chronic compressive injuries in a rat model

OBJECTIVE Somatosensory-evoked potentials (SEPs) were found to correlate well with the disability and postoperative recovery in patients with cervical spondylotic myelopathy. Yet the exact pathophysiology behind it remains to be elucidated. This study aims to characterise the ultrastructural changes of a chronically compressive spinal cord with various SEP responses in a rat model. METHODS A total of 15 rats were used with surgical implantation of a water-absorbing polymer sheet into the cervical spinal canal on the postero-lateral side, which expanded over time to induce chronic compression in the cord. At postoperative 6 months, the functional integrity of the cords was recorded by SEP responses by comparing injured and non-injured sides, and the ultrastructural integrity was assessed by 7-T magnetic resonance (MR) diffusion imaging, contrast-enhanced micro-computed tomography (μCT) and histological evaluations. RESULTS Six rats showed unchanged SEP, and the other nine showed decreased amplitude only (n=5) or delayed latency (n=4). The circulation insults of the cords were found among all the rats, showing central canal enlargement, intra-tissue bleeding or increased blood vessels in the central grey matter. Ultrastructural damage was noted in the rats with changed SEP responses, which was suggested by lower fractional anisotropy and higher contrast intensity radiologically and echoed by less myelin stain and cavitation changes histologically. In the animals with delayed latency, the cord showed significant loss of motoneurons as well as gross appearance distortion. CONCLUSIONS The categorised SEP responses by amplitude and latency could be an indicator for the extent of ultrastructural damage of the spinal cord after chronic compressive injuries. SIGNIFICANCE The findings built a solid foundation for SEP application in clinical diagnosis and prognostication of spinal cord injuries.

Cervical spinal cord BOLD fMRI study: modulation of functional activation by dexterity of dominant and non-dominant hands.

The objective of this study was to investigate the effect of dexterity on the magnitude of signal changes in functional magnetic resonance imaging (fMRI) in the cervical spinal cord with unilateral finger-tapping. Right-handed healthy volunteers were investigated with blood oxygenation level-dependent (BOLD) fMRI. Spinal cord BOLD functional MR images were acquired from 10 healthy right-handed volunteers who performed four sessions of unilateral finger-tapping tasks: left sequential (LS), right sequential (RS), left interleaved (LI), and right interleaved (RI) tasks. Our results from the difficulty measurement test showed that finger-tapping in interleaved order was more difficult than in sequential order. For the functional activation, seven out of 10 subjects had activation in all four fMRI sessions (two of the subjects who showed no detectable activation had problems in volume registration). The mean contrast value of the activation area inside the entire cervical spinal cord was significantly higher in performing LS than RS tasks. The increase in the mean contrast value was because the less skilled and competent right hemisphere required additional processing power for doing the left hand task than the left hemisphere required in doing the right hand task. The analysis of the interleaved finger-tapping tasks did not show any significant difference in the results. This was probably because the interleaved task was similarly challenging for both hands, and required high dexterity. Therefore, differences in activity between the left and right hands were less apparent. Our results showed the modulation of activation intensity in the spinal cord by the dexterity.

A Multidisciplinary Rehabilitation Programme for Patients with Chronic Low Back Pain: A Prospective Study

Purpose. To examine the effectiveness of a multidisciplinary rehabilitation programme for patients with chronic low back pain in Hong Kong, and to identify factors associated with work resumption. Methods. 57 men and 8 women aged 20 to 56 (mean, 39) years who had a >3-month history of low back pain and were unresponsive to >6 months of conventional treatment participated in a 14-week multidisciplinary rehabilitation programme involving physical conditioning, work conditioning, and work readiness. Training protocols entailed flexibility and endurance training, hydrotherapy, weight lifting, and work stimulation. Patients were assessed at baseline (week 1), week 7, week 14, and month 6 with regard to the intensity of low back pain, self-perceived disability, range of lumbar motion, isoinertial performance of the trunk muscles, and depression level. Patient demographics that influenced work resumption were identified using a prediction model. Patients who did and did not return to work were compared. Results. Of the 54 patients who completed all follow-up assessments, 28 returned to work and 26 did not. The latter was significantly older (37 vs. 42 years, p=0.038) and absent from work longer (11 vs. 22 months, p=0.029) than the former. The rehabilitation programme helped patients regain physical function and the ability to work. Patients who returned to work showed greater improvement in self-perceived disability and physical function. Conclusion. This rehabilitation programme facilitated regain of physical functioning and the ability to return to work. The pre-programme employment status, duration of absence from work, and patient age were the most important predictors for work resumption.

Comparison of time-frequency analysis techniques in intraoperative somatosensory evoked potential (SEP) monitoring

Somatosensory evoked potentials (SEPs) can be monitored during spinal surgery to prevent possible spinal cord injury. In order to improve the reliability of SEP monitoring, an investigation of the application of various time-frequency analysis (TFA) techniques to detect both temporal and spectral changes in SEP waveforms was conducted. SEP signals from 15 scoliosis patients were analysed using various methods. The time-frequency distributions (TFDs) computed using these methods were assessed and compared. The most appropriate TFA technique may depend on the type of SEP signal, Short term Fourier transform (STFT) with a 20 point length Hanning window probably provides the best result for SEP signals.

In Vitro characterization of low modulus linoleic acid coated strontium-substituted hydroxyapatite containing PMMA bone cement

Poly (methyl methacrylate) (PMMA) bone cement is widely used in vertebral body augmentation procedures such as vertebroplasty and balloon kyphoplasty. Filling high modulus PMMA increases the modulus of filled verterbra, increasing the risk of fracture in the adjacent vertebra. On the other hand, in porous PMMA bone cements, wear particle generation and deterioration of mechanical performance are the major drawbacks. This study adopts a new approach by utilizing linoleic acid coated strontium substituted hydroxyapatite nanoparticle (Sr-5 HA) and linoleic acid as plasticizer reducing bone cements modulus with minimal impact on its strength. We determined the compressive strength (UCS) and modulus (Ec), hydrophobicity, injectability, in vitro bioactivity and biocompatibility of this bone cement at different filler and linoleic acid loading. At 20 wt % Sr5-HA incorporation, UCS and Ec were reduced from 63 ± 2 MPa, 2142 ± 129 MPa to 58 ± 2 MPa, 1785 ± 64 MPa, respectively. UCS and Ec were further reduced to 49 ± 2 MPa and 774 ± 70 MPa respectively when 15 v/v of linoleic acid was incorporated. After 7 days of incubation, pre-osteoblast cells (MC3T3-E1) attached on 20 wt % Sr5-HA and 20 wt % Sr5-HA with 15 v/v of linoleic acid group were higher (3.73 ± 0.01 x 10⁴, 2.27 ± 0.02 x 10⁴) than their PMMA counterpart (1.83 ± 0.04 x 10⁴). Incorporation of Sr5-HA with linoleic acid in monomer phase is more effective in reducing the bone cements stiffness than Sr5-HA alone. Combination of low stiffness and high mechanical strength gives the novel bone cement the potential for use in vertebroplasty cement applications.

Time-frequency component analysis of somatosensory evoked potentials in rats.

BackgroundSomatosensory evoked potential (SEP) signal usually contains a set of detailed temporal components measured and identified in a time domain, giving meaningful information on physiological mechanisms of the nervous system. The purpose of this study is to measure and identify detailed time-frequency components in normal SEP using time-frequency analysis (TFA) methods and to obtain their distribution pattern in the time-frequency domain.MethodsThis paper proposes to apply a high-resolution time-frequency analysis algorithm, the matching pursuit (MP), to extract detailed time-frequency components of SEP signals. The MP algorithm decomposes a SEP signal into a number of elementary time-frequency components and provides a time-frequency parameter description of the components. A clustering by estimation of the probability density function in parameter space is followed to identify stable SEP time-frequency components.ResultsExperimental results on cortical SEP signals of 28 mature rats show that a series of stable SEP time-frequency components can be identified using the MP decomposition algorithm. Based on the statistical properties of the component parameters, an approximated distribution of these components in time-frequency domain is suggested to describe the complex SEP response.ConclusionThis study shows that there is a set of stable and minute time-frequency components in SEP signals, which are revealed by the MP decomposition and clustering. These stable SEP components have specific localizations in the time-frequency domain.

Potential use of diffusion tensor imaging in level diagnosis of multilevel cervical spondylotic myelopathy.

Study Design. A prospective study on a series of consecutive patients. Objective. To investigate the use of diffusion tensor imaging (DTI) and orientation entropy in level localization in patients diagnosed with multilevel cervical spondylotic myelopathy (CSM). Summary of Background Data. Multilevel CSM presents complex neurological signs that make level localization difficult. DTI is recently found to be able to assess the microstructural changes of the white matter caused by cord compression. Methods. Sixteen patients with CSM with multilevel compression were recruited. The level(s) responsible for the clinical symptoms were determined by detailed neurological examination, T2-weighted (T2W) magnetic resonance imaging (MRI), and DTI. On T2W MRI, anterior–posterior compression ratio and increased signal intensities were used to determine the affected level(s). The level diagnosis results from T2W MRI, increased signal intensities, DTI, and combination method were correlated to that of neurological examination on a level-to-level basis, respectively. The accuracy, sensitivity, and specificity were calculated. Results. When correlated with the clinical level determination, the weighted orientation entropy–based DTI analysis was found to have higher accuracy (82.76% vs. 75.86%) and sensitivity (84.62% vs. 76.92%) than those of the anterior–posterior compression ratio. The increased signal intensities have the highest specificity (100.00%) but the lowest accuracy (58.62%) and sensitivity (53.85%). When combined with the level diagnosis result of wOE with that of anterior–posterior compression ratio, it demonstrated the highest accuracy and sensitivity that were 93.10% and 96.15%, respectively, and equal specificity (66.67%) with using them individually. Conclusion. DTI can be a useful tool to determine the pathological spinal cord levels in multilevel CSM. This information from orientation entropy–based DTI analysis, in addition to conventional MRI and clinical neurological assessment, should help spine surgeons in deciding the optimal surgical strategy. Level of Evidence: 4