1.Scanning Electron Microscopy Study of Retrieved Implants Suggests a Ratcheting Mechanism Behind Medial Migration in Cephalomedullary Nailing of Hip Fractures
Law GW, MRCS ; Koh JSB, FRCS ; Yew AKS, PhD ; Howe TS, FRCS
Malaysian Orthopaedic Journal 2020;14(No.1):7-17
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 antigravity 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.
2.The Painful Anterior Apprehension Test – an Indication of Occult Shoulder Instability
Law GW ; Ng ZD ; Tan JH ; Wong KLF ; Ng YH
Malaysian Orthopaedic Journal 2022;16(No.1):97-102
Introduction: To evaluate the clinical relevance of the
painful anterior apprehension test in shoulder instability.
Materials and methods: We performed a retrospective
study of 155 patients that underwent arthroscopic anterior
Bankart repair between 2014–2016. Exclusion criteria were
previous ipsilateral shoulder surgery, bony Bankart lesions,
glenohumeral osteoarthritis and concomitant surgery
involving rotator cuff tears, biceps tendon pathology and
superior labrum from anterior to posterior (SLAP) lesions.
The study cohort was divided into three groups:
apprehension test with apprehension only, apprehension test
with pain only, and apprehension test with both apprehension
and pain. Patient demographics, clinical characteristics,
radiological imaging, arthroscopy findings and surgical
outcomes (Constant, American Shoulder and Elbow
Surgeons (ASES), SF-36 scores) were evaluated.
Results: A total of 115 (74.2%) had apprehension only, 26
(16.8%) had pain only and 14 (9.0%) had pain and
apprehension with the apprehension test. Univariate analysis
showed significant differences between the groups in
patients with traumatic shoulder dislocation (p=0.028),
patients presenting with pain (p=0.014) and patients
presenting with recurrent dislocations (p=0.046). Patients
with a purely painful apprehension test were more likely to
have a traumatic shoulder dislocation, more likely to present
only with pain, and less likely to present with recurrent
shoulder dislocations. Multivariate analysis showed that
none of these factors alone were significant as single
predictors for shoulder instability. All three groups were
otherwise similar in patient profile, MRI and arthroscopic
assessments, and clinical outcomes of surgery. Excellent
clinical outcomes were achieved in all groups with no
difference in pre-operative and post-operative scores across
all groups at all time points.
Conclusion: The painful apprehension test may suggest
underlying shoulder instability.