Bone In-Growth by Michael Broder, M.D.
I am Radiologist, and have been a member of the Surface Hippy Message board since 2002. Over the years we have had numerous members, especially young active athletes, who have accidentally injured their prosthetic hip. Nuclear Medicine bone scans reveal metabolic activity (new bone growth) persisting for up to 2 years in adults over 30 who sustain fractures, or have had joint prosthetics. The reason is simple.
As the bone heals, new bone is produced by special cells, and tiny new blood vessels (neovasculature) which very slowly grow into the older bone, and the special surfaces of the prosthetic parts designed for that purpose. Over time, other special cells reshape the new bone, and eventually it is replaced with thicker stronger bone tissue. In fact, over time, ALL the bone in our body is being replaced slowly in response to various stress factors, and maintainance. This is true of many tissues in the body.
If we return to certain activities too soon, we will apply forces that will produce microscopic fractures in the new bone, and it may fail to completely heal. The complex process of bone healing is delayed or completely fails. This is a well known problem in treating fractures of any bone. That is why cast material is applied, or other methods of internal fixation (screws, plates, rods), or EXTERNAL FIXATION methods are used to hold fractured bones in place. Even slight mobility will result in mal-union, incomplete union, or even complete NON-UNION which is a very serious problem. Each person will heal at an individual rate controlled by complex factors.
Every surface hippy has already arrived at the point where the NATIVE HIP has failed.
New Hippys to be:
Don't put your new artifical hip at risk. Follow instructions. Exercising too forcefully, too soon can lead to failure of union of the new bone to the hip. This is especially true of the uncemented portion(s). There is no magic involved here. Once you have micro-fractured the new bone, it may never heal properly.
I waited 11 months at age 58 before returning to skiing.
Michael (MD in NC) (L) C+ 3/31/03