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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.
Fulltext Concomitant Ulnar Styloid Fractures in Distal Radius Osteosynthesis Does Not Impact Radiographic Outcomes, Ulnar Sided Symptoms and Patient Outcomes

Wong KC, Wu M, Zai Q, Wong MK, Howe TS, Koh S, et al.

Malays Orthop J, 2023 Mar;17(1):142-148.
PMID: 37064641 DOI: 10.5704/MOJ.2303.017

INTRODUCTION: Current literature reports varied significance of ulnar styloid fractures (USF) associated with distal radius fractures. Our study assesses the role of ulnar styloid fractures and fragment size in surgically managed distal radius fractures.
MATERIALS AND METHODS: We reviewed patients who underwent surgical fixation of distal radius fractures between January 2004 to June 2006. Patients were divided into those with (Group 1) and without (Group 0) USFs. Post-operative radiographic parameters, clinical outcomes and overall wrist function were analysed. Outcomes included ulnar-sided wrist pain, extensor carpi ulnaris (ECU) tendinitis, triangular fibrocartilage complex (TFCC) grind test, distal radioulnar joint (DRUJ) instability and pain. Overall wrist function was assessed with range of motion and Disabilities of the Arm, Shoulder and Hand (DASH) score.
RESULTS: Our study cohort included 31 males and 23 females, and 38.9% of these patients had concomitant USFs. There was no difference in terms of demographic data and fracture configuration between groups. Radiographic parameters were similar, except for palmar tilt, which was significantly higher in Group 1 (4.6º vs 9.4º, p=0.047). At 24 months, there were no differences in clinical outcomes and overall wrist function. A sub-group analysis showed that mean USF fragment size was larger in patients with a positive TFCC grind test (3.9mm vs 7.3mm, p=0.033).
CONCLUSION: The presence of USFs in surgically managed distal radius fractures does not compromise clinical and functional outcome. Similarly, the size of USFs does not impact clinical and functional outcome but is associated with the presence of a positive TFCC grind test.

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