W Y Cheung

The University of Hong Kong, Hong Kong, Hong Kong

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Publications (14)25.38 Total impact

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    ABSTRACT: Purpose:To explore the value of diffusion-tensor (DT) imaging in addressing the severity of cervical spondylotic myelopathy (CSM) and predicting the outcome of surgical treatment.Materials and Methods:From July 2009 to May 2012, 65 volunteers were recruited for this institutional review board-approved study, and all gave informed consent; 20 volunteers were healthy subjects (age range, 41-62 years), and 45 were patients with CSM (age range, 43-86 years). Anatomic and DT 3.0-T magnetic resonance images were obtained. Surgical decompression was performed in 22 patients with CSM, and patients were followed up for 6 months to 2 years. The clinical severity of myelopathy and postoperative recovery were assessed by using the modified Japanese Orthopaedic Association (mJOA) score. A recovery ratio (comparison of postoperative with preoperative mJOA score) of more than 50% indicated a good clinical outcome of surgery. DT findings, patient age, T2 high signal intensity (HSI), and somatosensory evoked potential (SEP) were analyzed by using a logistic regression model to predict the surgical outcome of patients with CSM.Results:A significant difference in cervical cord mean fractional anisotropy (FA) was found between healthy subjects and patients with CSM (0.65 ± 0.05 [standard deviation] vs 0.52 ± 0.13, P < .001). FA values were significantly correlated with the severity of neurologic dysfunction indicated by mJOA score (r(2) = 0.327, P = .016). Logistic regression analysis showed that mean FA (P = .030) and FA at the C2 vertebra (P = .035) enabled prediction of good surgical outcome; however, preoperative mJOA (P = .927), T2 HSI (P = .176), SEP amplitude (P = .154), and latency (P = .260) did not.Conclusion:FA is a biomarker for the severity of myelopathy and for subsequent surgical outcome.© RSNA, 2013Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13121885/-/DC1.
    Radiology 08/2013; 270(1). DOI:10.1148/radiol.13121885 · 6.21 Impact Factor
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    ABSTRACT: Transarticular screw fixation with autograft is an established procedure for the surgical treatment of atlantoaxial instability. Removal of the posterior arch of C1 may affect the rate of fusion. This study assessed the rate of atlantoaxial fusion using transarticular screws with or without removal of the posterior arch of C1. We reviewed 30 consecutive patients who underwent atlantoaxial fusion with a minimum follow-up of two years. In 25 patients (group A) the posterior arch of C1 was not excised (group A) and in five it was (group B). Fusion was assessed on static and dynamic radiographs. In selected patients CT imaging was also used to assess fusion and the position of the screws. There were 15 men and 15 women with a mean age of 51.2 years (23 to 77) and a mean follow-up of 7.7 years (2 to 11.6). Stable union with a solid fusion or a stable fibrous union was achieved in 29 patients (97%). In Group A, 20 patients (80%) achieved a solid fusion, four (16%) a stable fibrous union and one (4%) a nonunion. In Group B, stable union was achieved in all patients, three having a solid fusion and two a stable fibrous union. There was no statistically significant difference between the status of fusion in the two groups. Complications were noted in 12 patients (40%); these were mainly related to the screws, and included malpositioning and breakage. The presence of an intact or removed posterior arch of C1 did not affect the rate of fusion in patients with atlantoaxial instability undergoing C1/C2 fusion using transarticular screws and autograft. Cite this article: Bone Joint J 2013;95-B:972-6.
    07/2013; 95-B(7):972-976. DOI:10.1302/0301-620X.95B7.30598
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    W Y Cheung, Keith D K Luk
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    ABSTRACT: Introduction Tuberculosis of the spine is a still a common disease entity, not only in developing countries but is also returning in developed countries especially in the immune-compromised patients. Conservative treatment with chemotherapy is still the main stay of treatment. This article focuses on the clinical and radiological outcomes, and problems with conservative treatment. Method The available literature of anti-tuberculosis chemotherapy in managing spinal tuberculosis was reviewed. Data sources included relevant literature of the English language identified through Medline search from 1946 to 2011. Personal experience and unpublished reviews from the authors’ institution were also included. Results Although majority of patients respond well to anti-tuberculosis chemotherapy, about 15 % of them develop paradoxical response. The Medical Research Council (MRC) studies have shown that for patients without significant neurological deficits, operative and conservative treatment could produce the same clinical outcome at 15 years follow-up. Patients treated operatively with debridement and spinal fusion with strut graft had faster bony fusion and less kyphotic deformity. In contrast, those treated with drugs alone or with simple debridement without fusion may result in disease reactivation, severe kyphosis or late instability, which in turn may lead to late-onset Pott’s paraplegia, back pain, sagittal imbalance and compromised pulmonary function that are difficult or risky to treat. Conclusion Recognition of the clinical and radiologic features of these late sequels is important for the management. Prevention of deformity in the early disease has been added to the modern standard of treatment of TB spine.
    European Spine Journal 05/2012; 22(Suppl 4). DOI:10.1007/s00586-012-2332-x · 2.47 Impact Factor
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    ABSTRACT: Genitopatellar syndrome is one of the syndromes described in the last decade. It is characterized by agenesis of the corpus callosum, absent or hypoplastic patellae, extremity contractures, skeletal anomalies, urogenital anomalies, and facial dysmorphic features. While writing this report, only 15 cases have been reported in the literature. The etiology, clinical features, management, and natural history of this syndrome are not yet well established. Past reports in the literature have not been able to identify the exact genetic etiology but it somewhat coincides with nail patella syndrome and short patella syndrome. We would like to introduce this terminology to the orthopedic community and highlight the clinical features of the genitopatellar syndrome. To the best of our knowledge, this is a single case report with the longest follow-up of 11 years in the literature.
    Journal of pediatric orthopaedics. Part B / European Paediatric Orthopaedic Society, Pediatric Orthopaedic Society of North America 05/2012; 22(4). DOI:10.1097/BPB.0b013e3283528d40 · 0.66 Impact Factor
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    W Y Cheung, Keith D K Luk
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    ABSTRACT: Pyogenic spondylitis is a neurological and life threatening condition. It encompasses a broad range of clinical entities, including pyogenic spondylodiscitis, septic discitis, vertebral osteomyelitis, and epidural abscess. The incidence though low appears to be on the rise. The diagnosis is based on clinical, radiological, blood and tissue cultures and histopathological findings. Most of the cases can be treated non-operatively. Surgical treatment is required in 10-20% of patients. Anterior decompression, debridement and fusion are generally recommended and instrumentation is acceptable after good surgical debridement with postoperative antibiotic cover.
    International Orthopaedics 02/2012; 36(2):397-404. DOI:10.1007/s00264-011-1384-6 · 2.02 Impact Factor
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    ABSTRACT: Current randomized controlled trials (RCTs) for assessing the efficacy of bracing in patients with adolescent idiopathic scoliosis (AIS) suffer from poor recruitment. Additionally, patients who consent for randomization may be a highly selected group of individuals who have no preference on treatment; thus may limit the assessment of effectiveness. Therefore, we aimed to determine the feasibility of an alternative study design, "the comprehensive cohort study" that can overcome the concerns of conventional RCTs. AIS patients aged ≥10 years, had Risser sign between 0-II, and had a Cobb angle of 25° to <30° or 20° to <25° with 5° deterioration over the past 4 months were invited to join a RCT. Those who declined were given an option to stay in the study, but choose whether they wish to be braced or observed. A randomization schedule was generated for all patients whether or not they joined the RCT; thus patients who made their own choice may also fit with the randomized choices. For those without brace but had ≥6° curve progression or reached 30° were considered failures, and braces were offered. Patients were followed every 4 months. Over 1 year, there were 87 eligible patients, 68 (78%) patients with mean age of 12.5 years consented to participate with a median follow-up of 57 weeks. Of which, 19 (28%) patients accepted randomization with respectively 13 and 6 patients allotted to brace and observation. For others who declined randomization, 18 (37%) chose brace and 28 (57%) patients had their choice of treatment the same as that on the randomization schedule. This Comprehensive Cohort Study design has the potential to improve the rate of recruitment such that both efficacy and effectiveness of bracing in AIS can be assessed. Our preliminary study showed that it can be feasibly conducted with less recruitment burden.
    Studies in health technology and informatics 01/2012; 176:493.
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    ABSTRACT: Spring-back complication after open-door laminoplasty as described by Hirabayashi is a well-known risk, but its definition, incidence, and associated neurologic outcome remain unclear. To investigate the incidence and the neurologic consequence of spring-back closure after open-door laminoplasty. A retrospective radiographic and clinical review. Lateral cervical spine X-rays were evaluated. Anteroposterior diameters (APD) of the vertebral canal of C3-C7 were measured. Spring-back was defined as loss of APD on follow-up in comparison to immediate postoperative canal expansion. The loss of the end-on lamina silhouette with consequent reappearance of the lateral profile of the spinous processes was also assessed to verify the presence of spring-back. Spring-back closure was classified based on whether the collapse was total or partial, and whether all the operated levels or only a subset had collapsed (ie, complete vs. partial closure, segmental closure vs. total-construct closure). Neurologic status was documented using the Japanese Orthopaedic Association (JOA) score. Thirty consecutive patients who underwent open-door laminoplasty from 1995 to 2005 at a single institution with a minimum follow-up of 2 years were assessed. They were all operated on using the classic Hirabayashi technique. Radiographic outcomes were assessed independently by two individuals. Sixteen men and 14 women with an average follow-up of 5 years (range, 2-12 years) were included. Of these patients, 24 had cervical spondylotic myelopathy and six had ossification of the posterior longitudinal ligament. Spring-back closure was found in three patients (10%) and 7 of 117 laminae (6%) within 6 months of the operation, which was further confirmed by computed tomography and magnetic resonance imaging. All spring-back closures were partial segmental closures. Gender and age were not significant factors related to spring back (p>.05). The mean JOA score on follow-up was 12.5, with a recovery rate of 40%. All patients with spring back and available JOA data exhibited postoperative neurologic deterioration. Of the three patients with spring back, two patients underwent revision surgery, whereas one declined. Spring-back closure occurred in 10% of our patients at or before 6 months after surgery. The incidence of spring-back by level (ie, 117 laminae) was 6%, mainly occurring at the lower cervical spine. All spring-back closures were partial segmental closures, most commonly involving C5 and C6. Postoperative neurologic deficit was associated with spring-back closure; therefore, surgeons should adopt preemptive surgical measures to prevent the occurrence of such a complication.
    The spine journal: official journal of the North American Spine Society 09/2011; 11(9):832-8. DOI:10.1016/j.spinee.2011.07.026 · 2.80 Impact Factor
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    ABSTRACT: At present, individual techniques, including intraoperative acute normovolemic hemodilution, use of tranexamic acid, use of intrathecal morphine, proper positioning, and modification of operative techniques, seem most promising for reducing perioperative blood loss and allogeneic blood transfusion in patients undergoing major spine surgery. Other techniques including preoperative autologous predonation; mandatory discontinuation of use of antiplatelet agents; intraoperative and postoperative red-blood-cell salvage; use of aprotinin, epsilon-aminocaproic acid, recombinant factor VIIa, or desmopressin; induced hypotension; avoidance of hypothermia; and minimally invasive operative techniques require additional studies to either establish their effectiveness or address safety considerations.
    The Journal of Bone and Joint Surgery 07/2011; 93(13):1268-77. DOI:10.2106/JBJS.J.01293 · 4.31 Impact Factor
  • W. Y. Cheung, Keith D. K. Luk
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    ABSTRACT: The incidence of spinal tuberculosis, which may lead to severe spinal deformity, early and late neurological complications, is increasing. This paper reviews its pathophysiology, clinical presentation, diagnosis and management.
    Orthopaedics and Trauma 06/2011; 25(3):161-167. DOI:10.1016/j.mporth.2011.02.002
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    ABSTRACT: Introduction The cause of adolescent idiopathic scoliosis (AIS) is still not known. Although several candidate gene studies and linkage analyses have been done, no causal relationship has yet been established. To our knowledge, we report the first case-control based genome-wide association study (GWAS) for this trait. Methods The study was undertaken in a set of 196 cases with a specific AIS phenotype (based on Lenke's classification) in southern China, and in 401 controls without radiological evidence of scoliosis. Results Two single-nucleotide polymorphisms (SNPs) on one particular chromosome showed marginal significant association (snp1: p=1·32×10–6, odds ratio=0·52; snp2: p=1·23×10–5, odds ratio=0·55). Imputation results suggested that three more SNPs in this region showed significant association (snp3: p=2·47×10–7, odds ratio=0·49; snp4 and snp5: p=1·68×10–6, odds ratio=0·53). Conclusions Despite the small number of cases and controls, the strength of this study is in the use of a specific phenotype and that all controls were mature individuals with radiological confirmation of straight spines. We believe that these factors have contributed to the success of the GWAS. Our findings offer the potential to explore the pathogenesis of AIS with GWAS.
    12th International Phillip Zorab Symposium, London, UK, J Bone Joint Surg Br; 03/2011
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    ABSTRACT: Prospective clinical-radiographic study. To investigate the natural coupling behavior between frontal deformity correction and the simultaneous changes in thoracic kyphosis, and to examine how the postoperative thoracic sagittal realignment relates to this natural coupling behavior. Restoration of the sagittal alignment is one of the fundamental goals in scoliosis correction surgery. It is generally achieved by rod precontouring intraoperatively. However, clinical studies suggested that postoperative sagittal realignment seems to be more affected by the inherent properties of the spine rather than the instrumentation or the surgical maneuver. Ninety-eight idiopathic scoliosis patients with thoracic curves treated with one-stage posterior spinal fusion, using corrective segmental spinal instrumentation (hook-rod or pedicle screw-rod constructs) were investigated. Pre- and postoperative frontal and sagittal alignments were measured by standing anteroposterior and lateral radiographs. Preoperative frontal plane flexibility was assessed by the fulcrum bending radiograph in the standard manner, an additional radiograph was taken in the lateral plane, to assess how this frontal correction force affects sagittal plane alignment (lateral fulcrum bending radiograph). When thoracic frontal deformity was corrected under fulcrum bending, coupled changes in the thoracic kyphosis demonstrated 3 different patterns: thoracic kyphosis increased in 25 patients with a mean kyphosis of 9 degrees to 19 degrees, decreased in 45 with a mean of 34 degrees to 21 degrees and remained unchanged (within 3 degrees ) in 28 with a mean of 19 degrees to 18 degrees. After surgery, the direction of correction of thoracic kyphosis significantly correlated with the coupling patterns demonstrated on fulcrum bending radiographs (r = 0.579, P < 0.001). However, the actual postoperative thoracic kyphosis angle cannot be predicted by the preoperative lateral fulcrum bending radiograph. There was no statistically significant difference (P = 0.263) between using pedicle screws and hooks in achieving the additional correction beyond what was demonstrated on the lateral fulcrum bending radiographs. Changes in thoracic kyphosis on fulcrum bending due to natural coupling of deformities are directed towards "self-normalization." There is no difference in the sagittal plane deformity correction with the use of hook-rod system or pedicle screw-rod constructs. This can be used as a guideline for exact preoperative rod contouring to reduce the stress on the bone-implant interface and the rate of postoperative failures. The findings also suggest that it is not how big or strong the implants are, but rather the natural curve behavior will at least partially determine the final sagittal outcome.
    Spine 05/2010; 35(11):1158-64. DOI:10.1097/BRS.0b013e3181bb49f3 · 2.45 Impact Factor
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    Wai Yuen Cheung, Lawrence G Lenke, Keith D K Luk
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    ABSTRACT: A retrospective series of 35 idiopathic scoliosis patients underwent spinal fusion with a segmental thoracic pedicle screw system. To evaluate the amount of scoliosis correction with segmental pedicle screw constructs, and assess whether the fulcrum bending radiograph can predict surgical correction. The fulcrum bending radiograph is highly predictive of actual curve correction based on hook or hybrid systems. However, its predictive value in segmental pedicle screw fixation systems has not been reported. Patients diagnosed with Lenke type 1A and 1B thoracic idiopathic scoliosis who underwent posterior spinal fusion with segmental pedicle screw constructs by single surgeon from January 2000 to December 2005 were reviewed. The fulcrum flexibility rate (FFR) and correction rate were compared. Stepwise linear regression analysis was done and a prediction equation for the postoperative Cobb angle was developed. Thirty-five consecutive patients were included. Age at surgery was 14.8 years. Twenty scoliosis deformities were flexible, 15 were rigid. All patients had at least 2-year follow-up. The average preoperative Cobb angle was 58 degrees , fulcrum bending Cobb angle was 28 degrees , and postoperative Cobb angle 15 degrees and 16 degrees at 1 month and 2 years, respectively, after surgery. There was significant difference between FFR (51%) and correction rate at 1 month (72%) and 2 year (70%) after surgery. The difference between fulcrum bending corrective index of flexible (122%) and rigid (203%) curves was statistically significant. Stepwise linear regression analysis showed: Predicted postoperative Cobb angle = 0.012 + 1.75 x age - 0.212 x FFR (R = 0.69, P < 0.01). Thoracic pedicle screw constructs achieved better scoliosis correction compared with fulcrum bending radiographs. The fulcrum bending corrective index achieved was significantly greater in rigid than flexible curves. The postoperative Cobb angles could be calculated with a predictive equation.
    Spine 03/2010; 35(5):557-61. DOI:10.1097/BRS.0b013e3181b9cfa9 · 2.45 Impact Factor
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    ABSTRACT: Cervical spondylotic myelopathy is a common clinical problem. No study has examined the pattern of neurological recovery after surgical decompression. We conducted a prospective study on the pattern of neurological recovery after surgical decompression in patients with cervical spondylotic myelopathy. Patients suffering from cervical spondylotic myelopathy and requiring surgical decompression from January 1995 to December 2000 were prospectively included. Upper limbs, lower limbs and sphincter functions were assessed using the Japanese Orthopaedic Association (JOA) score. Assessment was done before the operation, at 1 week, 2 weeks, 1 month, 3 months, 6 months, 1 year and then yearly after surgery. Results were analysed with the t-test. Differences with P-values less than 0.05 were regarded as statistically significant. Fifty-five patients were included. The average follow-up period was 53 months. Thirty-nine patients (71%) had neurological improvement after the operation with a mean recovery rate of 55%. The JOA score improved after surgery, reaching statistical significance at 3 months and a plateau at 6 months. Thirty-six patients (65%) had improvement of upper limb function. Twenty-four patients (44%) had improvement of lower limb function. Eleven patients (20%) had improvement of sphincter function. The recovery rate of upper limb function was 37%, of lower limb function was 23% and of sphincter function was 17%. Surgical decompression worked well in patients with cervical spondylotic myelopathy. Seventy-one percent of patients had neurological improvement after the operation. The neurological recovery reached a plateau at 6 months after the operation. The upper limb function had the best recovery, followed by lower limb and sphincter functions.
    International Orthopaedics 05/2008; 32(2):273-8. DOI:10.1007/s00264-006-0315-4 · 2.02 Impact Factor
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    ABSTRACT: To determine whether right hip adduction deficit is associated with adolescent idiopathic scoliosis. 102 adolescents (mean age, 14 years) with idiopathic scoliosis were prospectively studied. Their spinal curve pattern (according to Lenke's classification), curve severity (by Cobb's angle), and hip adduction ranges of both sides were recorded. Additional factors that may affect hip adduction range including the preferred leg during standing, the presence of hip flexor tightness, and the side of the dominant leg were also assessed. The mean Cobb's angle was 27 degrees. The difference in hip adduction range between the right and left hips was 5 degrees (p<0.05). Of 102 patients, 64 had an adduction range deficit of the right hip, 4 of the left hip, and 34 had no difference. Patients with >10 degrees of right hip adduction deficit were associated with a higher proportion of left leg dominance than those with less than or equal to 10 degrees of right hip adduction deficit (18% vs 4%). Left leg dominance may play a role in right hip adduction deficit and scoliosis.
    Journal of orthopaedic surgery (Hong Kong) 04/2008; 16(1):24-6.

Publication Stats

92 Citations
25.38 Total Impact Points

Institutions

  • 2010–2013
    • The University of Hong Kong
      • • Department of Orthopaedics and Traumatology
      • • Department of Anaesthesiology
      Hong Kong, Hong Kong
  • 2008–2011
    • Queen Mary Hospital
      Hong Kong, Hong Kong