Cam Deformity

What is it?

A cam deformity is an eccentricity at the junction between the head of the femur and the neck. The head of the femur should be virtually spherical and should sit on the neck like a lollipop on a (broad) stick: quite symmetrically: if it doesn’t sit symmetrically, the range of hip flexion (knee to chest movement) will be restricted or uncomfortable.

What are the Symptoms of Cam Deformity

Most typically patients have pain or discomfort sitting in a car for a long time; as the journey goes on, if it is the left hip, lifting the leg to press on the clutch to change gear.

How does it develop?

Cam deformity most probably develops in adolescence. In our experience cam deformity in 80% of cases co-exists with relative femoral retroversion (less than 10degrees anteversion). This is exactly the same pattern of bone deformity which children’s Orthopaedic Surgeons see in adolescent Slipped Upper Femoral Epiphysis(SUFE). Most probably, Cam Deformity represents a subtle, unrecognised, ” forme fruste”version of SUFE:

A small proportion may result from unrecognised childhood Perthes’ Disease.

Why does it develop?

We don’t really know, but its almost certainly in the genes, so blame your parents!

There is a tendency for patients to mistakenly blame their hip pathology on their sporting activities; this is wrong; their sporting activities bring underlying problems to light earlier than would happen if they were couch potatoes!

The Natural History; (it gets worse…)

nvestigations involving a group of a symptomatic volunteers followed up for five years in Ottawa has shown that the presence of a cam discovered on scans five years ago, leads to a 4.3 times increased risk of developing hip pain. Hip pain developed 3.1 times more commonly over five years, where internal rotation in 90 degrees flexion was less than 20 degrees.

It is commonly believed by knowledgeable joint preserving hip surgeons that cam deformity and femoral retroversion is one of the most potent causes of hip arthritis, especially in males.