Optimization of Portal Placement for Endoscopic Calcaneoplasty in Valgus, Cavus and Normal Feet

In the AMC, patients with a chronic retrocalcaneal bursitis are treated through
a technique called 'endoscopic calcaneoplasty'. In this procedure the
posterosuperior calcaneal prominence and the bursa will be removed. For this
endoscopic procedure the surgeon uses two entrance points called 'portals'.
These portals are right above the posterosuperior part of the calcaneus,
lateral and medial from the Achilles tendon. For the experienced orthopaedic
surgeon it may be easier to palpate this superior part of the calcaneus, but it
happens that a less experienced surgeon places the portal too far proximal.
Especially when the bursitis changes the outside appearance of the soft tissue
around the Achilles tendon, it is harder to identify the posterosuperior part
of the calcaneus. Standardizing portal placement in endoscopic calcaneoplasty
therefore would be useful. In posterior ankle arthroscopy, the distal tip op
the fibula is an important landmark for portal placement. The portals in
posterior ankle arthoscopy differ from the portals in endoscopic
calcaneoplasty. We feel that the fibula tip is a useful landmark for endoscopic
calcaneoplasty, and that maybe the distance between this tip and the
posterosuperior calcaneus could be a useful tool for portal placement. The
three different foottypes (cavus, valgus, normal), however, should be taken
into account since tilting the calcaneus causes differences in this distance.
We would use a conventional lateral radiograph of the foot to accurately
measure the distance between fibula tip and posterosuperior calcaneus. A fibula
is not visible on conventional x-rays; herefore we developed a device, which we
named the FOPP- device (For Optimization of Portal Placement). This device
needs to be validated.

The objective of the study is to standardize portal placement in endoscopic
calcaneoplasty, thereby taken into account the three different foot shapes,
cavus, valgus and normal feet. Primarily the FOPP- device needs to be
validated. If found valid, the measurements can be used.

This study is designed as a validation study of the FOPP- device for
standardizing portal placement in volunteers. 30 volunteers will receive 3
X-rays.
In two X-rays, the FOPP-device is used, which means that a metal bar will be
put against the lateral malleolus. This way the fibulatip is visible on the
X-ray, so we can measure the distance between the fibulatip and the
posterosuperior part of the calcaneus. When the device is valid, we can use the
measurements for further analysis.
We will look for difference in distance between the three different foot types.
If the radiological measurements of the distance between top of the bar and
calcaneus in the first 5 volunteers show low association within each volunteer
(difference between measurements within one subject > 3 mm), measurements are
not reproducible and the device needs revision before continuing the study.
One X-ray is to determine the exact foot deformity.

Manufacturing 3 X-rays has a trivial radiation risk. An additional visit to the
hospital is will not be necessary. It will take 30 minutes time for the
volunteers to co-operate.