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Dental epidemiological surveys of Sarawak school children

Yim KS, Loh SM, Koh JT

Dent J Malaysia Singapore, 1973 May;13(1):23-39.
PMID: 4149371
Fulltext Scanning Electron Microscopy Study of Retrieved Implants Suggests a Ratcheting Mechanism Behind Medial Migration in Cephalomedullary Nailing of Hip Fractures

Law GW, Koh J, Yew A, Howe TS

Malays Orthop J, 2020 Mar;14(1):7-17.
PMID: 32296476 DOI: 10.5704/MOJ.2003.002

Introduction: Medial migration is the paradoxical migration of the femoral neck element (FNE) superomedially against gravity with respect to the intramedullary component of the cephalomedullary device, increasingly seen in the management of pertrochanteric hip fractures with the intramedullary nail. We postulate that the peculiar anti-gravity movement of the FNE in the medial migration phenomenon stems from a ratcheting mechanism at the intramedullary nail-FNE interface, which should inadvertently produce unique wear patterns on the FNE that can be seen with high-powered microscopy. By examining the wear patterns on retrieved implants from patients with medial migration, our study aims to draw clinical correlations to the ratcheting mechanism hypothesis.
Material and Methods: Four FNEs were retrieved from revision surgeries of four patients with prior intramedullary nail fixation of their pertrochanteric hip fractures complicated by femoral head perforation. The FNEs were divided into two groups based on whether or not there was radiographic evidence of medial migration prior to the revisions. Wear patterns on the FNEs were then assessed using both scanning electron microscopy and light microscopy.
Results: Repetitive, linearly-arranged, regularly-spaced, unique transverse scratch marks were found only in the group with medial migration, corresponding to the specific segment of the FNE that passed through the intramedullary component of the PFNA during medial migration. These scratch marks were absent in the group without medial migration.
Conclusion: Our findings are in support of a ratcheting mechanism behind the medial migration phenomenon with repetitive toggling at the intramedullary nail-FNE interface and progressive propagation of the FNE against gravity.
Periprosthetic Fractures after Total Knee Arthroplasty: the Influence of Pre-Operative Mechanical Factors versus Intraoperative Factors

Zainul-Abidin S, Lim B, Bin-Abd-Razak HR, Gatot C, Allen JC, Koh J, et al.

Malays Orthop J, 2019 Jul;13(2):28-34.
PMID: 31467648 DOI: 10.5704/MOJ.1907.005

Introduction: Periprosthetic fractures are a devastating complication following total knee arthroplasty. Little is known about the effect of mechanical factors on the incidence of periprosthetic fractures. The aim of this study was to examine the correlation between pre-operative mechanical factors, like side of surgery, coronal alignment and pre-operative range of motion and intra-operative factors, and the incidence of a periprosthetic fracture, following primary total knee arthroplasty (TKA). Materials and Methods: Forty-two patients with periprosthetic fractures (PPF) after primary TKA were identified from our hospital arthroplasty registry. These patients were matched two-to-one for gender and age at primary knee arthroplasty to 84 patients without PPF. The incidence of periprosthetic fracture with regards to laterality, coronal alignment and pre-operative range of motion was analysed. Intra-operative factors like implant type, patellar resurfacing and notching were also analysed using logistic regression. Results: Coronal alignment, pre-operative range of motion and patella resurfacing were not significant predictors of periprosthetic fractures. Anterior femoral notching was found to be significantly higher in the fracture group with an odds ratio of 17. Left sided surgery was also significantly higher in the periprosthetic fracture group. Conclusion: Periprosthetic fractures are 17 times more likely to occur in a knee with anterior femoral notching. Preoperative factors like coronal alignment and poor preoperative range of motion do not seem to increase the risk of periprosthetic fractures after TKA.
Behavioural responses of anxiety in aversive and non-aversive conditions between young and aged Sprague-Dawley rats

Hiew LF, Khairuddin S, Aquili L, Koh J, Fung ML, Lim WL, et al.

Behav Brain Res, 2020 05 15;385:112559.
PMID: 32097707 DOI: 10.1016/j.bbr.2020.112559

Measures of anxiety in behavioural tests remain largely unclear even decades after their establishment. Differences in the severity of anxiety measured by anxiety tests is an important issue that must be addressed. To test the hypothesis that the addition of light as an aversive stimulus will elicit a difference in behaviour between aged and young animals, we compared the responses of aged and young animals in the home cage emergence test (HCET) and elevated plus maze (EPM), in high aversive bright light and low aversive dim light conditions. In the HCET, our results demonstrated that young animals escaped with shorter latency and greater frequency than aged animals in both bright and dim light conditions, indicating that young animals display greater exploratory tendencies than aged animals. In the EPM, bright light conditions induced anxiogenic effects in both age groups. Interestingly, two-way ANOVA showed a significant interaction effect of age and light on the number of entries into the open arms of the EPM as well as frequency of escape in the HCET. These results show that the addition of light as an aversive stimulus in the EPM and HCET produced different responses in aged versus young animals in each test. In conclusion, significant interactions between age and light affected aged and young animals differently in the HCET and EPM, indicating that the two tests measure different aspects of anxiety.