WHAT IS IT?

A Hinged Crank Arm is a specialized cycling device which allows an individual with limited knee flexion the ability to a complete a full pedal rotation cycle.

Fig. 1 - A Hinged Crank Arm

It has been reported that some people with limited knee flexion in past have engaged in cycling in the past by using a peg for balance. The disadvantage of this solution lies in its inability to generate torque. The other alternative has been to hike the hip up very high on the limited side and then return to the seat as the pedal descends. Others may choose to avoid the activity altogether. These alternatives are now grouped with a new one, the hinged crank arm.

The HCA allows the rider to generate some torque, while accommodating the knee flexion by providing the appropriate clearance. We customize each one to the required amount of clearance to ensure the maximum mechanical advantage possible is gained.

The pathway of the pedal rotation cycle when riding with a hinged crank arm fabricated at a 50:50 ration is illustrated below (Fig.2):

Fig.2 - PRC tracking

WHO MIGHT BENEFIT FROM AN HCA?

Until this point the people who have returned to cycling as a result of riding with the HCA have all had a Van Nes Rotationplasty. Due to the nature of this procedure, limitations in knee flexion range resulted. We feel that the HCA may allow cycling opportunities to the following orthopaedic clients with knee flexion limitations such as:

§Trauma§
§Arthritic Changes
Post-surgical Healing
Total Knee Replacement Clients
Van Nes Clients
Knee Disarticulation Clients

There are some important advantages to consider for the amputee population with limited knee flexion specifically, and they include:

§Normal ambulation without modifications to the day to day prosthesis
Remains independent of the prosthesis
Improved comfort during the activity

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