Dynamic evaluation of simulated leg length inequalities and their effects on the musculoskeletal apparatus
Introduction
Leg length inequality (LLI) is a condition in which paired limbs are noticeably unequal [1]. They can be found in 40–70% of the population and they may be greater than 2 cm in about 0.1% [1]. LLIs can be a predisposing factor for sacroiliac joint disorders, lumbar back pain, functional scoliosis as well as for symptoms in various joints due to the kinematic joint chain [2]. LLIs can affect all age groups and are categorized into anatomical and functional LLIs [1].
So far, the clinical diagnosis and treatment of LLIs is still performed mostly under static conditions, while patients are standing upright in front of the examiner. The amount of LLI is measured by palpating the height of the iliac crests and their position to each other. Larger LLIs lead to pelvic obliquity, which is then corrected by placing small blocks under the short leg until the pelvis is levelled. In multiple studies, the static effects of LLIs on the musculoskeletal system have been evaluated [[3], [4], [5]]. Hackenberg et al. [5] showed that there is a direct effect of simulated LLIs on the pelvic position and spinal posture [5]. Betsch et al. established a non-invasive method to simulate and examine LLIs and their effects on the musculoskeletal apparatus using a simulation platform [3,4]. The results of these studies confirmed a correlation between increasing LLIs and pelvic obliquity, torsion and changes of the spinal posture [3,4].
The human being is a dynamic individual [6] and therefore, we believe that the diagnosis and treatment of LLIs should also be carried out under dynamic conditions. With the development of surface topography there is a fast, reliable and radiation-free method available to diagnose and treat LLIs under dynamic conditions. In previous studies, the reliability and validity of this system under static and dynamic conditions was shown [[7], [8], [9], [10]].
Aim of this study was to develop a method for simulating and evaluating LLIs and their effects on the pelvis and spine under dynamic conditions.
Section snippets
Materials and methods
30 test subjects without pre-existing leg or spinal abnormalities were included in this study. Exclusion criteria of this first pilot study were a pelvic obliquity due to a functional or anatomical leg length discrepancy greater 10 mm and obesity with a body mass index (BMI) of greater 35 kg/m2, which could impede the detection of anatomical landmarks by the measuring system. Another exclusion criterion was back pain during the previous year lasting longer than 2 days. Mean age of the subjects
Static measurements (all results are presented in relation to the reference condition LLI = 0 mm)
Under static conditions a simulated LLI of 1 cm and greater led to a significant increase of the pelvic obliquity (p < 0.001) (Fig. 2).
The results also showed that with simulated LLIs of 1 cm and greater on the left and 2 cm and greater on the right side significant changes of the surface rotation occurred (left sided LLI: p = 0.0001–0.0229, right sided LLI: p = 0.0002–0.00016) (Fig. 3).
We also did find a significant increase under static conditions for the lateral deviation of the spine with
Discussion
Main goal of this study was to develop a method that allows the evaluation of LLIs under dynamic conditions. In order to be able to simulate and correct LLIs, we built three sets of sandals with insoles of varoius thickness (1–4 cm) that can accommodate most feet. We chose to use this model, instead of using regular shoe insoles with varying thickness, because we wanted to be able to simulate LLIs independent of the subjects anatomy, body weight and type of shoe wear.
The results of this study
Conclusion
LLIs can lead to multiple musculoskeletal disorders. The treatment and diagnosis of LLIs is still carried out under static conditions, although patients are moving and walking most of the time. We were able to develop and evaluate a novel method to simulate and examine the effects of LLIs on the musculoskeletal apparatus under dynamic conditions.
Conflict of interest
None
Declaration of interest
None.
Acknowledgments
All procedures performed in studies involving human participants were in accordance with the ethical standards of institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent was obtained from all individual participants included in the study. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for profit sectors.
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