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Hi guy's

Was wondering if anyone could help clarify whether on the RS scan, if a patient was using high gear propulsion would you expect the COP line to travel through the 1st MTPJ?

Thanks for your help,

Paul.

 

Paul:

The theory is that "high-gear propulsion" involves having the center of pressure (COP) go through the 1st metatarsal head rather than the more lateral metatarsal heads. Whether this is a good or bad thing for the patient, we really don't know since as patients pronate more in late midstance, they will have more "high-gear propulsion".

Personally, I don't like the terms "high-gear" or "low-gear" propulsion and don't use it in my lectures and writing since these terms tend to imply that using "high-gear" propulsion will make you a faster walker and "low-gear" propulsion will make you slower walker, which, in fact, may not be the the case in most individuals.

 

I believe the ideal high gear is with the centre of pressure advancing through the fist and second metatarsal as the heel lifts from the ground. This is not pure pronation as the ankle is plantar flexing and is required,imho, to relay efficient motion towards the swing leg as it comes into heel contact.

Maintaining low gear propulsion for "too long" is never ideal and results in the need for the "abductory twist" into propulsion eg. late mid stance - propulsion "pronation".

Regards

 

Kevin and Graham,

Thanks for your replies!

Paul

 

The CoP is an average point of force. If the CoP were to go through the first met head, it would mean that there was no force on the other metatarsals. This would indicate a foot that had pronated to the point where the lesser mets were off of the ground. This would put a high stress on the first ray. I would not want this as a therapeutic goal.

In other threads, I described the problem with ascribing high and low gear propulsion. The short version is that this assumes constant angular velocity and this may not be the case.

Cheers,

Eric

 

Graham,

Could you explain that further? To maintain a "low gear" the foot has to be supinating to keep the lateral metatarsals on the ground. I don't often see an abductory twist with a foot that is supinating in late stance phase.


Regards,

Eric