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Fulltext A Biomechanical Comparison between Taylor's Spatial Frame and Ilizarov External Fixator

Tan B, Shanmugam R, Gunalan R, Chua Y, Hossain G, Saw A

Malays Orthop J, 2014 Jul;8(2):35-9.
PMID: 25279090 DOI: 10.5704/MOJ.1407.012

Taylor's spatial frame (TSF) and Ilizarov external fixators (IEF) are two circular external fixator commonly used to address complex deformity and fractures. There is currently no data available comparing the biomechanical properties of these two external fixators. This study looks into the mechanical characteristics of each system. TSF rings with 6 oblique struts, 4 tube connectors, 4 threaded rods, and 6 threaded rods were compared to a standard IEF rings with 4 threaded rods. Compression and torsional loading was performed to the frame as well as construct with Polyvinylchloride tubes. TSF rings with 4 tube connectors had the highest stiffness (3288 N/mm) while TSF rings with 6 struts was the least stiff. The situation was reversed for torsion where TSF rings with 6 oblique struts had the highest torsional stiffness (82.01 Nm/Degree) and frame Ilizarov rings with 4 threaded rods the least. Standard TSF construct of two ring with 6 oblique struts have better torsional stiffness and lower axial stiffness compared to the standard IEF.
Fulltext Percutaneous pedicle screw for unstable spine fractures in polytraumatized patients: A report of two cases

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.
Fulltext Post-implantation Deformation of Titanium Rod and Cobalt Chrome Rod in Adolescent Idiopathic Scoliosis

Sia U, Tan BB, Teo YY, Wong CC

Malays Orthop J, 2019 Mar;13(1):14-19.
PMID: 31001378 DOI: 10.5704/MOJ.1903.002

Introduction: Post-implantation rod deformation is anticipated in scoliosis surgery but the difference in rod deformation between titanium and cobalt chrome rod has not been elucidated. This study aims to compare the difference in rod deformation between two groups. Materials and Methods: Twenty-one adolescent idiopathic scoliosis (AIS) patients were recruited from a single center. The over-contoured concave rods were traced prior to insertion. Post-operative sagittal rod shape was determined from lateral radiographs. Rod deformation was determined using maximal rod deflection and angle of the tangents to rod end points. The differences between pre- and post-operative rod contour were analysed statistically. Rod deformation and thoracic kyphosis between two types of implants were analysed. Results: Both rods exhibited significant change of rod angle and deflection post-operatively. Curvature of the titanium rod and cobalt chrome rod decreased from 60.5° to 37°, and 51° to 28° respectively. Deflection of titanium rod and cobalt chrome rod reduced from 28mm to 23.5mm and 30mm to 17mm respectively. There was no significant difference between titanium and cobalt chrome groups with regard to rod angle (p=0.173) and deflection (p=0.654). Thoracic kyphosis was increased from 20° to 26° in titanium group but a reduction from 25° to 23° was noticed in cobalt chrome group, but these findings were not statistically significant. Conclusion: There was no statistical difference in rod deformation between the two groups. Thus, the use of titanium rod in correction of sagittal profile is not inferior in outcome compared with cobalt chrome but with lower cost.
Fulltext A Rare Incidence of Breakage of tip of Micropituitary Forceps during Percutaneous Discectomy - How to Remove it: A Case Report

Sureisen M, Tan BB, Teo YY, Wong CC

Malays Orthop J, 2015 Nov;9(3):58-60.
PMID: 28611913 MyJurnal DOI: 10.5704/MOJ.1511.009

Breakage of the tip of the micropituitary forceps during spine surgery is a rare occurrence. Retrieval of the broken tip could be a challenge in minimally invasive surgeries due to limitation of access and retrieval instruments. We describe our experience in handling such a situation during percutaneous radiofrequency discectomy. The removal was attempted, without converting into open surgery, by utilising percutaneous endoscopic lumbar discectomy working cannula and guided by image intensifier. We were able to remove the fragment without any significant morbidity to the patient. This technique for removal has not been reported previously in the literature.
Fulltext A rare cause of back pain and radiculopathy - spinal tophi: a case report

Wan SA, Teh CL, Jobli AT, Cheong YK, Chin WV, Tan BB

J Med Case Rep, 2019 Jan 08;13(1):8.
PMID: 30626451 DOI: 10.1186/s13256-018-1940-4

BACKGROUND: Gout is a monosodium urate deposition disease which is prevalent worldwide. The usual manifestations are crystal arthropathy and tophi deposition in the soft tissues. Spinal tophi may also occur and are rarely reported, resulting in various clinical manifestations such as back pain, spinal cord compression, radiculopathy, and even mimicking epidural abscess and spondylodiscitis.

CASE PRESENTATION: We report a case of a 42-year-old Chinese man with underlying gout who presented with back pain and radiculopathy. The diagnosis of spinal tophi was unsuspected and he was initially treated for epidural abscess and spondylodiscitis. He underwent a laminectomy and posterolateral fusion during which tophus material was discovered. He recovered and medications for gout were started.

CONCLUSION: Spinal tophi are rare. The diagnosis is difficult and spinal tophi may be mistaken for epidural abscess, spondylodiscitis, or neoplasm.
Rod Lengthening With the Magnetically Controlled Growing Rod: Factors Influencing Rod Slippage and Reduced Gains During Distractions

Cheung JPY, Yiu KKL, Samartzis D, Kwan K, Tan BB, Cheung KMC

Spine (Phila Pa 1976), 2018 04 01;43(7):E399-E405.
PMID: 28767632 DOI: 10.1097/BRS.0000000000002358

STUDY DESIGN: Prospective study.
OBJECTIVE: To identify the factors that are associated with rod slippage and to study the pattern of achieved length gain with a standard distraction methodology.
SUMMARY OF BACKGROUND DATA: Ability to achieve successful magnetically controlled growing rod (MCGR) distraction is crucial for gradual spine lengthening. Rod slippage has been described as a failure of internal magnet rotation leading to a slippage and an inability to distract the rod. However, its onset, significance, and risk factors are currently unknown. In addition, how this phenomenon pertains to actual distracted lengths is also unknown.
METHODS: A total of 22 patients with MCGR and at least six distraction episodes were prospectively studied. Patients with rod slippage occurring less than six distraction episodes were considered early rod slippage whereas those with more than six episodes or have yet to slip were grouped as late rod slippage. The association of parameters including body habitus, maturity status, age of implantation, total number of distractions, months of distraction from initial implantation, initial and postoperative Cobb angle, T1-T12, T1-S1, T5-T12 kyphosis, curve flexibility, instrumented length, and distance between magnets in dual rods and between the magnets and apex of the curve with early or late onset of rod slippage were studied. Differences between expected and achieved distraction lengths were assessed with reference to rod slippage episodes and rod exchanges to determine any patterns of diminishing returns.
RESULTS: Patients had mean age of 7.1 years at diagnosis with mean follow-up of 49.8 months. A mean 32.4 distractions were performed per patient. Early rod slippage occurred in 14 patients and late rod slippage occurred in eight patients. Increased height, weight, body mass index, older age, increased T1-12 and T1-S1 lengths, and less distance between magnets were significantly associated with early rod slippage. Expected distraction lengths did not translate to achieve distraction lengths and reduced gains were only observed after achieving one-third of the allowable distracted length in the MCGR. Length gains return to baseline after rod exchange.
CONCLUSION: This is the first study to specifically analyze the impact of rod slippage on distraction lengths and the risk factors associated with its onset and frequency. Increased body habitus and reduced distance between internal magnets significantly influenced rod slippage events. Diminishing returns in distracted length gains were only observed after a period of usage.
LEVEL OF EVIDENCE: 3.