Upper Body Gait Deviation in Duchenne Muscular Dystrophy Depends on Numerous Factors that must be Included in the Gait Analysis

We read with interest the article by Romkes et al. on a retrospective study of upper body gait deviation (UBGD) in 12 patients with Duchenne muscular dystrophy (DMD) using three-dimensional whole-body gait analysis [1] .In the sagittal plane, the thoracic segment was tilted posteriorly in DMD compared to control subjects, and the relative angle between the pelvis and thoracic segment showed a greater backward tilt with increased shoulder extension [1] .In the frontal plane, patients walked with increased shoulder abduction and took larger steps [1] .The range of motion of the thorax was increased in all three planes [1] .The study is excellent, but some points should be discussed.The first point refers to the retrospective design of the study [1] .Retrospective designs have several disadvantages [2] .A retrospective design allows only limited control over the sample of the population and only limited control over the type and quality of the predictor variables.In addition, the relevant predictors may not have been recorded in the medical record, and it may be difficult or impossible to establish confounding variables and causality.It is also inevitable that some information will be missing as the data are based on the review of medical records that were not originally intended for the collection of data for research purposes.Selection and recall errors further influence the results [2] .The second point is that UBGD may depend strongly not only on the stage of the disease but also on the underlying mutation.Therefore, we should know in how many of the patients DMD is due to point mutations, deletions or duplications in the dystrophin gene.Since orthopaedic complications are directly related to muscle weakness, UBGD will also depend on the type and extent of the mutation.Was there a difference in UBGD between patients with deletions/duplications and those with point mutations?The third issue is that it was not stated how many of the 12 patients had scoliosis, what type of scoliosis and what severity.As DMD is often complicated by scoliosis [3] , this information is essential as it can strongly influence the results of the gait analysis.It is also important to know whether or not a patient has already undergone spinal stabilization surgery for scoliosis.The fourth point is that DMD often affects the myocardium [4] .Since cardiac function strongly affects mobility and kinetics due to poor oxygen supply to the muscle, it is important to know how many of the included patients had cardiomyopathy.Cardiomyopathy in DMD patients can manifest as either dilated or hypertrophic cardiomyopathy.Rarely, patients are also found with left ventricular noncompaction, also known as left ventricular hypertrabeculation [5] .In summary, this interesting study has limitations that put the results and their interpretation into perspective.By removing these limitations, the conclusions could be more stringent and the message of the study could be more strongly supported.All open questions need to be clarified before readers uncritically accept the conclusions of the study.UBGD in DMD is highly dependent on the underlying genetic defect, disease duration, degree of cardiac involvement and degree of scoliosis, so these parameters should be included in any gait analysis of DMD patients.