Background: It is commonly assumed that there is minimal variation between both hips bone mineral density (BMD). Until recently, screening was only done on one side, but due to technological development the study is now concurrently done on both hips. Dual-energy X-ray absorptiometry (DEXA) scan is routinely used to evaluate Bone Mineral Density (BMD) for the clinical diagnosis of osteoporosis. During standard BMD screening, we have noticed significant differences between hips in about 10% of the cases. The purpose of the current study was to determine whether asymmetrical femoral neck BMDs are also associated with asymmetrical gait.
Method: Study population included subjects with a difference higher than 0.5 SD in BMD between hips and normal control (less than 0.3 SD). All the participants performed gait tests. Exclusion criteria included any known neurological disease, leg operation, periheral neuropathy and orthopaedical problems. During the gait test subjects were asked to walk comfortably while outfitted with Pedar® pressure sensitive insole system (novel GmbH(. The subjects were also asked to walk at different speeds and while performing simple tasks. A number of gait parameters (for example foot pressure, step length) were recorded. For each gait parameter, we calculated an asymmetry index: GA (Gait Asymmetry)=|ln(XL/XR)|×100%. Values of 0.0 reflect perfect symmetry and higher values reflect greater degrees of asymmetry.
Results: The asymmetrical BMD group consisted of 36 participants (9 males; age 62.2±9.89 years; BMI: 25.86±5.28; Z scores between hips: 1.08±0.52). The symmetrical BMD group consisted of 9 participants (2 males; age 59.58±5.1 years; BMI: 25.54±4.31; Z scores between hips: 0.17±0.12). Most of the subjects were not aware of any difference between hips that could otherwise readily explain any gait asymmetries. The asymmetry indices of mean force, max force, step duration and swing time were significantly higher in the Asymm BMD group, compared with the Symm BMD group (p<0.01). Swing time difference (RSWT-LSWT) between left and right feet were correlated with BMD delta Z scores (Spearmans correlation=0.38, p=0.02.(There was no association between the side with lower BMD score and lower weight bearing (based on Ground reaction forces scores) according to preliminary results.
Conclusions: These preliminary findings may imply that asymmetries in BMD of the hips are associated with asymmetries in gait parameters and in the vertical ground reaction forces. These differences are naturally not the effect of nutrition, metabolism or lifestyle, which similarly affect both hips (significant left right differences were observed in particular group of our patients). Future work should aim to identify the mechanisms underlying the relationship between these asymmetries (e.g., does one cause the other?), if gait and balance testing can aid in the early detection of compromised bone health, and whether appropriate gait training and exercises that alleviate gait asymmetries may reduce BMD asymmetries.
Disclosure: The authors declared no competing interests.