Femoral Shaft Cortical Pathology associated with longterm Alendronate Therapy: A New Classification

• Published in: Malaysian Orthopaedic Journal Vol. 7; no. 2; pp. 12 - 17
• Main Authors: Kwan, MK, Chan, CK, Ng, WM, Merican, AM, Chung, WM, Chan, SP
• Format: Journal Article
• Language: English
• Published: Malaysian Orthopaedic Association 01-07-2013
• Subjects: Alendronate; Cortical Hypertrophy; Femur; Looser Zone
• ISSN: 1985-2533; 2232-111X
• DOI: 10.5704/MOJ.1307.008

There are reported cases of cortical reaction over the tension
side of the normal femoral shafts in patients on long term
treatment with alendronate, leading to subsequent femoral
shaft fractures. We performed a retrospective review of
patients with low-energy femoral shaft fracture on
alendronate, admitted to our institution during the period
2004 to May 2009. The presence of radiological changes of
cortical hypertrophy with or without Looser’s zone over the
tension side of the femoral bone (normal limb) was
determined and correlated with clinical symptoms. Thirteen
patients were identified. Average duration of alendronate use
was 6.5 ± 3.3 years (ranges, two to 10 years). These
radiological changes were noted in four patients. Average
duration of alendronate usage in these four patients was 6.5
± 2.4 years (ranges, 5 to10 years). Prodromal thigh pain was
present in a patient, who had cortical hypertrophy with the
presence of a Looser’s zone traversing the cortex on the
femoral shaft. One patient had Looser’s zone limited at the
lateral hypertrophied cortex without prodromal pain. The
interobserver kappa coefficient was 0.96. A femoral
radiograph should be performed in all patients who are on
long-term alendronate therapy who present with thigh pain.
We propose a new grading system based on our observation
of the radiological features in these four cases. This new
grading of the radiological spectrum of femoral shaft cortical
pathology has the potential to stratify the risk of low energy
femoral fracture for patients treated with long-term
alendronate therapy.