A whole bunch of that decalcified bone is mixed with a gel that is bone inductive (it screams at bone to make bone). This widens the pelvic bone and makes an awning that is outside the capsule and right
on the rectus femoris reflected tendon (whose hollow spot on x-ray is a great landmark of real hip edge vs rebuilt. Remember, this bone derived material is not calcified and does not show up well on
x-ray. You can see it because it is riddled with air which looks dark speckled.
This mass, gets replaced with the patient's own solid bone. Then that does two things.
1. It takes the hit from dystonic spastic forces so that the cartilage does not deform. Reinforcement.
2. It is a contour that new hip growth beneath it must follow. We see the young
hips reverse loss of depth with deepening and more horizontal true socket growth following this shape. The reflected rectus femoris tendon hollow spot gives us a great guide so we are sure of this.
However, hip socket growth is a function of young children and not of older kids. We have pushed the "AGE" limit because many kids needing this surgery are bone age retarded which works in our favor. They
may be 7 years old but have the bone development of, say, three. Hey, we'll take any edge we can get.
So trying to prevent VRO -LATER- in dystonic kids who are horribly hard to position effectively and who can sometimes rip VRO fixation apart and even dislocate after VRO was the not so gentle prod that
got us into doing this.
So far no VROs after this. Oh, it will happen. But so far, not.
Helping to get a good outcome is the simultaneous handling of nasty muscle forces. The rectus femoris is recessed (taken off the pelvis to be just like the rest of the quadriceps. It looses nothing and
helps relax the reflex storm these kids have. One less thing to stretch and react. The psoas tendon is lengthened intramuscularly (inside the pelvis by sneaking in under the iliacus).
By performing this operation under local anesthesia in addition to general
anesthesia (yes BOTH) and implanting a temporary local anesthetic delivery filament we have - it seems - solved the problem of post operative ileus (where intestines shut down for days by protective reflex). Kids are much more comfortable as well with far less narcotic intervention and problems afterward.
No NSAIDS (aspirin, Motrin or ibuprofen etc.) are allowed as NSAIDS interfere with new bone formation! Tylenol is OK. Once bone is well established then it is OK to use whatever.
Hip range of motion begins on day 1 post op. With the operated hip kept abducted, we do flexion and extension movement. We sit the kids up as fast as they are able. The local anesthetic makes this a
breeze. Motion prevents new bone from obstructing later range. You maintain whatever range you exercise during healing.
A large to total replacement of the implant tissue by new native bone is seen by 4 weeks on x-ray when graduated weight bearing (abducted) is begun. If the bone shelf looks matured and dense on x-ray by
eight weeks we narrow the stance and begin walking (to the limits of the child's capability of course).