Foot posture causes malocclusion!
Sometimes I come across papers that may seem to be just weird. This new paper looks at the association between foot posture and malocclusion.
The authors of this paper start by stating that functional disturbances of the masticatory muscles may be transmitted to other muscles along “muscle chains”. This may also be reversed and that the dental system may be influenced by imbalance in other areas of the body. They then suggest that early correction of malocclusion may minimise or eliminate the need for further treatment. As a result, we need to evaluate and correct foot posture early.
A team from Spain did this study. Medicine Journal published it.
Ana Marchena-Rodriguez et al.
Medicine: Doi http://dx.doi.org/10.1097/MD.0000000000010701
They did the study to answer this question;
“Is there a correlation between foot posture, footprint parameters and anteroposterior malocclusion”?
What did they do?
They did a cross sectional study of 189 6-9 years old children who they randomly selected from public schools in Malaga. They approached the parents of the children using a questionnaire that asked a range of questions about foot posture, breathing etc and these influenced the inclusion/exclusion criteria. These were extensive.
They then examined the children in their schools. They measured the following;
- Foot posture Index (FPI). This evaluates the nature of foot posture in 3 planes of space. An expert podiatrist measured this.
- The Clarke Angle. The expert podiatrist measured this from a tracing on a pedigraph.
- Angle’s classification: An orthodontist collected this data.
The orthodontist and the podiatrist were blinded to each others scores.
They chose the right foot only for the analysis and they measured association between the variables with the Pearson Correlation.
What did they find?
They found that 67% of the children had Class I, 21% Class II and 10% Class III molar relationships. They presented the data from the Clarke angle and FPI as parametric data and then did a non parametric test between the groups of Angle’s Classification (but this does not measure association). Here is the data as an imported table.
I looked up the normal values for FPI and in the child population this is 3.7 (SD=2.5). The values that they reported are within this range.
Their statistical analysis revealed that there was an association between the FPI, the Clarke Angle and dental classification. They then concluded;
“The Clarke angle decreased as the Angle classification increases from Class I to III, whereas the FPI is greater as the Angle Classification increases from Class I to III”.
This is an important statement as they suggest that the Angle Classification, which is a nominal scale, “increases”. This is an error because a nominal scale cannot increase.
In effect, I felt that their data presentation and statistical analysis was confusing and incorrect.
What did I think?
Over the last couple of years I have had many debates on this blog with the orthodontic “fringe”. I and others have consistently asked for evidence to underpin their theories. Some of the fringe practitioners flagged up and to be honest if this the best that can be done then there is no evidence to underpin the theories. This paper has the following major deficiencies;
- They do not provide sufficient details of the way that they selected the population of children
- The statistical analysis and data presentation is a complete muddle
- Association is not causation.
- The values of the FPI were within the range of a normal population.
- The use of Angle’s classification is a major error because this may be influenced by many co-founders, for example, missing teeth and dental caries. Unless foot posture influences caries!
- Importantly, the hypothesis that they were testing is not based on research data or even conventional wisdom. This is important because if we carry out a sufficiently large number of studies looking for something, then we will find it!
I know that my viewpoint will cause some discussion. Lets keep it scientific?
Finally, I have decided to review a few more of the “orthodontic fringe” papers over the summer. Next up is a paper by the London School of Orthotropics on the prevention of canine impaction with orthotropics.
Emeritus Professor of Orthodontics, University of Manchester, UK.