Displaying publications 1 - 20 of 57 in total

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  1. Kwan MK, Chan CY
    Eur Spine J, 2016 10;25(10):3065-3074.
    PMID: 27021616
    PURPOSE: To investigate whether an optimal upper instrumented vertebra (UIV) tilt angle would prevent 'lateral' shoulder imbalance or neck tilt (with 'medial' shoulder imbalance) post-operatively.

    METHODS: The mean follow-up for 60 AIS (Lenke 1 and Lenke 2) patients was 49.3 ± 8.4 months. Optimal UIV tilt angle was calculated from the cervical supine side bending radiographs. Lateral shoulder imbalance was graded using the clinical shoulder grading. The clinical neck tilt grading was as follows: Grade 0: no neck tilt, Grade 1: actively correctable neck tilt, Grade 2: neck tilt that cannot be corrected by active contraction and Grade 3: severe neck tilt with trapezial asymmetry >1 cm. T1 tilt, clavicle angle and cervical axis were measured. UIVDiff (difference between post-operative UIV tilt and pre-operative Optimal UIV tilt) and the reserve motion of the UIV were correlated with the outcome measures. Patients were assessed at 6 weeks and at final follow-up with a minimum follow-up duration of 24 months.

    RESULTS: Among patients with grade 0 neck tilt, 88.2 % of patients had the UIV tilt angle within the reserve motion range. This percentage dropped to 75.0 % in patients with grade 1 neck tilt whereas in patients with grade 2 and grade 3 neck tilt, the percentage dropped further to 22.2 and 20.0 % (p = 0.000). The occurrence of grade 2 and 3 neck tilt when UIVDiff was <5°, 5-10° and >10° was 9.5, 50.0 and 100.0 %, respectively (p = 0.005). UIVDiff and T1 tilt had a positive and strong correlation (r2 = 0.618). However, UIVDiff had poor correlation with clavicle angle and the lateral shoulder imbalance.

    CONCLUSION: An optimal UIV tilt might prevent neck tilt with 'medial' shoulder imbalance due to trapezial prominence and but not 'lateral' shoulder imbalance.

  2. Kwan MK, Chan CY
    Spine J, 2017 02;17(2):224-229.
    PMID: 27609611 DOI: 10.1016/j.spinee.2016.09.005
    BACKGROUND CONTEXT: With an increased cost of adolescent idiopathic scoliosis (AIS) surgery over the past 10 years, improvement of patient safety and optimization of the surgical management of AIS has become an important need. A dual attending surgeon strategy resulted in reduction of blood loss and complication rate.
    PURPOSE: This study aimed to investigate the perioperative outcome of posterior selective thoracic fusion in Lenke 1 and 2 AIS patients comparing a single versus a dual attending surgeon strategy.
    STUDY DESIGN: A prospective cohort study was carried out.
    PATIENT SAMPLE: The study sample comprised 60 patients
    OUTCOME MEASURE: Operative duration, blood loss, postoperative hemoglobin, need for transfusion, morphine usage, and duration of hospital stay were the outcome measures.
    METHODS: A total of 116 patients who underwent posterior selective thoracic fusion from two centers were prospectively recruited. The patients were grouped into Group 1 (single surgeon) and Group 2 (two surgeons). One-to-one matching analysis using "propensity score-matched cohort patient sampling method" was done for age, gender, height, weight, preoperative Cobb angle, number of fusion level, and Lenke classification. The outcome measures included operative duration, blood loss, postoperative hemoglobin, need for transfusion, morphine usage, and duration of hospital stay. This study was self-funded with no conflict of interest.
    RESULTS: From 86 patients who were operated by the two surgeons (Group 2), 30 patients were matched with 30 patients who were operated by a single surgeon (Group 1). Group 2 (164.0±25.7 min) has a significantly shorter operation duration (p=.000) compared with Group 1 (257.3±51.4 min). The total blood loss was significantly more (p=.009) in Group 1 (1254.7±521.5 mL) compared with Group 2 (893.7±518.4 mL). There were seven patients (23.3%) in Group 1 who received allogenic blood transfusion (p
  3. Lee CK, Chan CY, Kwan MK
    Asian Spine J, 2015 Dec;9(6):962-5.
    PMID: 26713131 DOI: 10.4184/asj.2015.9.6.962
    Managing multiple level spinal metastases is challenging. We report the case of a 58-year-old female with advanced lung cancer who presented with multiple pathological fractures of the thoracic spine (T5, T6, T7, and T8 vertebrae). She was treated with palliative radiotherapy. Her resting pain improved, but the instability pain persisted. One month later, she had a trivial fall leading to a pathological fracture of the L2 vertebra with cauda equine syndrome. The patient was treated surgically with minimally invasive decompression of the L2 and with percutaneous instrumented stabilization using an ultra-long construct from T3 to L5 (15 spinal levels), spanning the previously radiated zone and the decompression site. Postoperatively, she had significant improvements in pain and neurology. There were no surgical complications. Ultra long construct minimally invasive spinal stabilization is the ideal approach for symptomatic multicentric spinal metastasis with poor prognostic scores. Using this technique, the goals of spinal stabilization and direct neural decompression can be achieved with minimal morbidity.
  4. Chan CY, Kwan MK, Saw LB, Hussin P
    Clin Spine Surg, 2016 May 26.
    PMID: 24141340
    The clinical application of recombinant bone morphogenetic protein in spinal surgery has been shown to be safe and effective. However, its use in minimally invasive spine surgery has been limited to anterior interbody fusion procedures. To date, no study has evaluated the feasibility of percutaneous posterolateral fusion in the spine utilizing rhBMP-2.
  5. Kwan MK, Jeffry A, Chan CY, Saw LB
    Surg Radiol Anat, 2012 Apr;34(3):217-27.
    PMID: 22194086 DOI: 10.1007/s00276-011-0919-2
    Studies of sacral pedicle anatomy have been reported in the European population. However, the feasibility for the use of S1, S2 and S2-ilium screws has not been fully investigated in the Asian population.
  6. Chan CY, Kwan MK, Saw LB
    Surg Radiol Anat, 2011 Jan;33(1):19-25.
    PMID: 20848102 DOI: 10.1007/s00276-010-0726-1
    Pedicle screw instrumentation has superior biomechanical as well as clinical outcome. Thoracic pedicles show great variation in different population groups, particularly in Asians who have been shown to have smaller pedicle dimensions. Although plain radiographs are widely performed prior to spine surgery, no studies have been done so far to investigate whether the thoracic pedicle profile on plain radiographs affect thoracic pedicle screw insertion. Therefore, this is a cadaveric study aimed to determine the relationship between plain radiographic thoracic pedicle profile in Asians and the outcome of pedicle screw insertion in the thoracic spine.
  7. Chiu CK, Chan CY, Singh VA
    Med J Malaysia, 2009 Mar;64(1):22-6.
    PMID: 19852315
    Issues that had been encountered during proximal femoral fracture fixation using proximal femoral nail include (i) the adequacy of the femoral neck width in the local population and (ii) the potential difficulty encountered during fixation in certain prefixed angles as determined by the implant. This was a retrospective, descriptive study evaluating the anterior-posterior pelvic radiographs of 100 consecutive patients, from January to August 2007, managed at University Malaya Medical Centre, Kuala Lumpur. The femoral neck width in the population studied was adequate for placement of femoral neck screw and anti-rotation pin or hip pin using the proximal femoral nail implant. (mean = 34.0 +/- 3.7 mm, min = 24.6 mm). There was no significant difference between the working area using an implant angled at 130 degrees or 135 degrees (P = 0.91). Both femoral neck width and neck shaft angle of the Malaysian population studied were not a factor influencing the placement of femoral neck lag screws and anti-rotation pin.
  8. Chan CY, Kwan MK, Saw LB
    Eur Spine J, 2010 Jan;19(1):78-84.
    PMID: 19763636 DOI: 10.1007/s00586-009-1157-8
    The objective of this cadaveric study is to determine the safety and outcome of thoracic pedicle screw placement in Asians using the funnel technique. Pedicle screws have superior biomechanical as well as clinical data when compared to other methods of instrumentation. However, misplacement in the thoracic spine can result in major neurological implications. There is great variability of the thoracic pedicle morphometry between the Western and the Asian population. The feasibility of thoracic pedicle screw insertion in Asians has not been fully elucidated yet. A pre-insertion radiograph was performed and surgeons were blinded to the morphometry of the thoracic pedicles. 240 pedicle screws were inserted in ten Asian cadavers from T1 to T12 using the funnel technique. 5.0 mm screws were used from T1 to T6 while 6.0 mm screws were used from T7 to T12. Perforations were detected by direct visualization via a wide laminectomy. The narrowest pedicles are found between T3 and T6. T5 pedicle width is smallest measuring 4.1 +/- 1.3 mm. There were 24 (10.0%) Grade 1 perforations and only 1 (0.4%) Grade 2 perforation. Grade 2 or worse perforation is considered significant perforation which would threaten the neural structures. There were twice as many lateral and inferior perforations compared to medial perforations. 48.0% of the perforations occurred at T1, T2 and T3 pedicles. Pedicle fracture occurred in 10.4% of pedicles. Intra-operatively, the absence of funnel was found in 24.5% of pedicles. In conclusion, thoracic pedicle screws using 5.0 mm at T1-T6 and 6.0 mm at T7-T12 can be inserted safely in Asian cadavers using the funnel technique despite having smaller thoracic pedicle morphometry.
  9. Hussin P, Chan CY, Saw LB, Kwan MK
    Emerg Med J, 2009 Sep;26(9):677-8.
    PMID: 19700594 DOI: 10.1136/emj.2008.064972
    U-shaped sacral fracture is a very rare injury. This injury is easily missed and the diagnosis is often delayed as it is difficult to detect on the anteroposterior view of the pelvic radiograph. It is highly unstable and neurological injury is common. Two cases of U-shaped sacral fractures are reported here in which the diagnosis was delayed resulting in the late development of cauda equina syndrome. In these two cases, full recoveries were achieved following surgical decompression. A high index of suspicion with proper clinical and radiographic assessments will decrease the incidence of missed diagnosis and prevent the occurrence of delayed neurological deficits.
  10. Cheong ML, Chan CY, Saw LB, Kwan MK
    Eur Spine J, 2009 Jul;18 Suppl 2:269-71.
    PMID: 19390875 DOI: 10.1007/s00586-009-1004-y
    We present a case report of a patient with pneumocranium secondary to halo vest pin penetration and a review of literature. The objectives of this study are to report a rare complication of halo vest pin insertion and to discuss methods of prevention of this complication. Halo vest orthosis is a commonly used and well-tolerated upper cervical spinal stabilizing device. Reports of complications related to pin penetration is rare and from our review, there has been no reports of pneumocranium occurring from insertion of pins following standard anatomical landmarks. A 57-year-old male sustained a type 1 traumatic spondylolisthesis of C2/C3 following a motor vehicle accident. During application of the halo vest, penetration of the left anterior pin through the abnormally enlarged frontal sinus occurred. The patient developed headache, vomiting and CSF rhinorrhoea over his left nostril. He was treated with intravenous Ceftriaxone for 1 week. This resulted in resolution of his symptoms as well as the pneumocranium. In conclusion, complications of halo vest pin penetration are rare and need immediate recognition. Despite the use of anatomical landmarks, pin penetration is still possible due to aberrant anatomy. All patients should have a skull X-ray with a radio-opaque marker done prior to placement of the halo vest pins and halo vest pins have to be inserted by experienced personnel to enable early detection of pin penetration.
  11. Kwan MK, Chiu CK, Lee CK, Chan CY
    Bone Joint J, 2015 Nov;97-B(11):1555-61.
    PMID: 26530660 DOI: 10.1302/0301-620X.97B11.35789
    Percutaneous placement of pedicle screws is a well-established technique, however, no studies have compared percutaneous and open placement of screws in the thoracic spine. The aim of this cadaveric study was to compare the accuracy and safety of these techniques at the thoracic spinal level. A total of 288 screws were inserted in 16 (eight cadavers, 144 screws in percutaneous and eight cadavers, 144 screws in open). Pedicle perforations and fractures were documented subsequent to wide laminectomy followed by skeletalisation of the vertebrae. The perforations were classified as grade 0: no perforation, grade 1: < 2 mm perforation, grade 2: 2 mm to 4 mm perforation and grade 3: > 4 mm perforation. In the percutaneous group, the perforation rate was 11.1% with 15 (10.4%) grade 1 and one (0.7%) grade 2 perforations. In the open group, the perforation rate was 8.3% (12 screws) and all were grade 1. This difference was not significant (p = 0.45). There were 19 (13.2%) pedicle fractures in the percutaneous group and 21 (14.6%) in the open group (p = 0.73). In summary, the safety of percutaneous fluoroscopy-guided pedicle screw placement in the thoracic spine between T4 and T12 is similar to that of the conventional open technique.
  12. Chan CY, Lim CY, Shahnaz Hasan M, Kwan MK
    Eur Spine J, 2016 05;25 Suppl 1:245-50.
    PMID: 27028615 DOI: 10.1007/s00586-016-4538-9
    PURPOSE: Patients with Fontan circulation have increased cardio-respiratory risk during major spinal surgery. We report a case of severe scoliosis with a Cobb angle of 123.3° in a 16-year-old boy with Fontan circulation treated with single stage posterior segmental pedicle screw instrumentation and fusion.

    METHODS: Case report.

    RESULTS: The use pre-operative halo-ring traction for a duration of 6 weeks in this case lead to improvement in cobb angle from 123.3°, kyphotic angle 87.1° to cobb angle of 78.0°, kyphotic angle 57.2° (on bending and stress films). The operation was completed in 150 min, blood loss 1050 ml (25 ml/kg), and cell salvage of 490 ml. He was immediately extubated post correction, but monitored in ICU for a day. Total length of stay was 8 days without any perioperative morbidity or allogeneic blood transfusion. Final post-operative radiograph showed a cobb angle of 44.2°, kyphotic angle 22.8°. Follow up at 27 months showed solid union with no significant loss of correction.

    CONCLUSION: From this case experience, pre-operative halo traction is a useful surgical strategy in patients with Fontan circulation with severe kyposcoliosis to achieve adequate correction without additional osteotomies to minimize the risk of surgical correction.

  13. Kwan MK, Lee CK, Chan CY
    Asian Spine J, 2016 Feb;10(1):99-110.
    PMID: 26949465 DOI: 10.4184/asj.2016.10.1.99
    STUDY DESIGN: Prospective cohort study.

    PURPOSE: To report the outcome of 50 patients with spinal metastases treated with minimally invasive stabilization (MISt) using fluoroscopic guided percutaneous pedicle screws with/without minimally invasive decompression.

    OVERVIEW OF LITERATURE: The advent of minimally invasive percutaneous pedicle screw stabilization system has revolutionized the treatment of spinal metastasis.

    METHODS: Between 2008 and 2013, 50 cases of spinal metastasis with pathological fracture(s) with/without neurology deficit were treated by MISt at our institution. The patients were assessed by Tomita score, pain score, operation time, blood loss, neurological recovery, time to ambulation and survival.

    RESULTS: The mean Tomita score was 6.3±2.4. Thirty seven patients (74.0%) required minimally invasive decompression in addition to MISt. The mean operating time was 2.3±0.5 hours for MISt alone and 3.4±1.2 hours for MISt with decompression. Mean blood loss for MISt alone and MISt with decompression was 0.4±0.2 L and 1.7±0.9 L, respectively. MISt provided a statistically significant reduction in visual analog scale pain score with mean preoperative score of 7.9±1.4 that was significantly decreased to 2.5±1.2 postoperatively (p=0.000). For patients with neurological deficit, 70% displayed improvement of one Frankel grade and 5% had an improvement of 2 Frankel grades. No patient was bed-ridden postoperatively, with the average time to ambulation of 3.4±1.8 days. The mean overall survival time was 11.3 months (range, 2-51 months). Those with a Tomita score <8 survived significantly longer than those a Tomita score ≥8 with a mean survival of 14.1±12.5 months and 6.8±4.9 months, respectively (p=0.019). There were no surgical complications, except one case of implant failure.

    CONCLUSIONS: MISt is an acceptable treatment option for spinal metastatic patients, providing good relief of instability back pain with no major complications.

  14. Chiu CK, Kwan MK, Chan CY, Schaefer C, Hansen-Algenstaedt N
    Bone Joint J, 2015 Aug;97-B(8):1111-7.
    PMID: 26224830 DOI: 10.1302/0301-620X.97B8.35330
    We undertook a retrospective study investigating the accuracy and safety of percutaneous pedicle screws placed under fluoroscopic guidance in the lumbosacral junction and lumbar spine. The CT scans of patients were chosen from two centres: European patients from University Medical Center Hamburg-Eppendorf, Germany, and Asian patients from the University of Malaya, Malaysia. Screw perforations were classified into grades 0, 1, 2 and 3. A total of 880 percutaneous pedicle screws from 203 patients were analysed: 614 screws from 144 European patients and 266 screws from 59 Asian patients. The mean age of the patients was 58.8 years (16 to 91) and there were 103 men and 100 women. The total rate of perforation was 9.9% (87 screws) with 7.4% grade 1, 2.0% grade 2 and 0.5% grade 3 perforations. The rate of perforation in Europeans was 10.4% and in Asians was 8.6%, with no significant difference between the two (p = 0.42). The rate of perforation was the highest in S1 (19.4%) followed by L5 (14.9%). The accuracy and safety of percutaneous pedicle screw placement are comparable to those cited in the literature for the open method of pedicle screw placement. Greater caution must be taken during the insertion of L5 and S1 percutaneous pedicle screws owing to their more angulated pedicles, the anatomical variations in their vertebral bodies and the morphology of the spinal canal at this location.
  15. Kwan MK, Wong KA, Lee CK, Chan CY
    Eur Spine J, 2016 Feb;25(2):401-8.
    PMID: 25962815 DOI: 10.1007/s00586-015-4016-9
    PURPOSE: To introduce a new clinical neck tilt grading and to investigate clinically and radiologically whether neck tilt and shoulder imbalance is the same phenomenon in AIS patients.

    METHODS: 89 AIS Lenke 1 and 2 cases were assessed prospectively using the new clinical neck tilt grading. Shoulder imbalance and neck tilt were correlated with coracoid height difference (CHD), clavicle\rib intersection distance (CRID), clavicle angle (CA), radiographic shoulder height (RSH), T1 tilt and cervical axis.

    RESULTS: Mean age was 17.2 ± 3.8 years old. 66.3 % were Lenke type 1 and 33.7 % were type 2 curves. Strong intraobserver (0.79) and interobserver (0.75) agreement of the clinical neck tilt grading was noted. No significant correlation was observed between clinical neck tilt and shoulder imbalance (0.936). 56.3 % of grade 3 neck tilt, 50.0 % grade 2 neck tilt patients had grade 0 shoulder imbalance. In patients with grade 2 shoulder imbalance, 42.9 % had grade 0, 35.7 % grade 1, 14.3 % grade 2 and only 7.1 % had grade 3 neck tilt. CHD, CRID, CA and RSH correlated with shoulder imbalance. T1 tilt and cervical axis measurements correlated with neck tilt.

    CONCLUSIONS: In conclusion, neck tilt is distinct from shoulder imbalance. Clinical neck tilt has poor correlation with clinical shoulder imbalance. Clinical neck tilt grading correlated with cervical axis and T1 tilt whereas clinical shoulder grading correlated with CHD, RSH CRID and CA.

  16. Tan BB, Chan CY, Saw LB, Kwan MK
    Indian J Orthop, 2012 Nov;46(6):710-3.
    PMID: 23325978 DOI: 10.4103/0019-5413.104235
    Unstable spine fractures commonly occur in the setting of a polytraumatized patient. The aim of management is to balance the need for early operative stabilization and prevent additional trauma due to the surgery. Recent published literature has demonstrated the benefits of early stabilization of an unstable spine fracture particularly in patients with higher injury severity score (ISS). We report two cases of polytrauma with unstable spine fractures stabilized with a minimally invasive percutaneous pedicle screw instrumentation system as a form of damage control surgery. The patients had good recovery from the polytrauma injuries. These two cases illustrate the role of minimally invasive stabilization, its limitations and technical pitfalls in the management of unstable spine fractures in the polytrauma setting as a form of damage control surgery.
  17. Chung WH, Chiu CK, Wei Chan CY, Kwan MK
    Acta Orthop Traumatol Turc, 2020 Sep;54(5):561-564.
    PMID: 33155569 DOI: 10.5152/j.aott.2020.19144
    Growth hormone secreting pituitary tumor or gigantism has not been previously reported to be associated with rapid progression of scoliosis in the literature. However, there are some reports indicating scoliosis can be worsened by growth hormone therapy in children and adolescents. A 19-year-old boy was referred to our institution for the treatment of a right thoracolumbar scoliosis. The Cobb angle had worsened from 29° to 83° over two years' duration. He attained puberty at the age of 13. He had a previous history of slipped upper femoral epiphysis (SUFE), which was operated in 2015, with no clinical features of gigantism. Preoperative assessment was performed. He was diagnosed with growth hormone secreting pituitary macroadenoma by magnetic resonance imaging with a high serum level of insulin-like growth factor-I (IGF-I). Computed tomography (CT) of the pancreas showed a pancreatic endocrine tumor. The patient was later diagnosed with multiple endocrine neoplasia type 1 (MEN 1). He underwent endoscopic endonasal excision of the pituitary mass and distal pancreatectomy. This case indicates that growth hormone secreting pituitary macroadenoma could result in rapid progression of scoliosis.
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