SLOB (Summit Shelf) Details
P.O. Home Innominate Summit Shelf Overview Summit Shelf Details Acetabuloplasty Hip Bones
DystonicForcesiliac wing - iliumlabrumfemoral necklesser trochanter - psoas attachment pointshaft of femurgreater trochanterthis is where most dislocations happenhip capsule line of attachment - a sleeve from socket edge to here

In neurologic syndromes with spasticity, dystonia, rigidity or any sustained high muscle activity unrelenting, the cylinder of muscles running up the thigh produce a net force parallel to the femur. When that force is directed laterally by adduction (cross leg posture)  then the ball of the femur comes to press on the socket EDGE (here shown in yellow). In children that edge is growing and soft being made of cartilage and certain growth tissues.


Here, for example above, is the rectus femoris. It has two attachments to the pelvis, one straight to the pubis and the 'reflected' portion that arcs over the hip socket like an eyebrow on the eye socket (small yellow arrow). If the legs were spread wide, then this muscle's tension would tend to seat the ball into the depth of the socket - backed by bone. But in this position that force focuses on soft cartilage which can and does deform over time like a boxer's nose. Notice the 'hip capsule' which envelops the  articulation and keeps those slippery and nutrient juices bathing the joint.


ShowSaucerreflected tendon of rectus femoris outside capsulestraight portion of rectus femoris tendon to anterior inferior spine on pubisrectus common tendon leading to pelvis attachments (this has to go)capsule window removed to look (but not in surgery)

That capsule is blocking our view so we will cut a window in it and remove the upper femur from view also. See the socket within? That rim of LABRUM (in yellow) is the growing soft edge. Looks a bit flattened. The socket also, from here, looks a wee bit flat, more like a disk than a cup. Is that real?


LabrumFlattenssoft lip fails

Yes. The labrum no longer overhangs the ball as an awning, but looks like an excited puppy ear perked up. Growth is no longer pointed down and out but now straight up.


LabrumFlattens2cartilage here is backed by boneunsupported soft growing edgewill continue to grow in wrong direction if this stays upoutside capsule this takes the 'hit' of dystonic thruststamped filler starts herefiller made wider herefinal filler made widest here

So growth give a taller and taller socked lacking depth and worse it is more and more vertical. The shallow vertical socket is called "paralytic hip dysplasia". This last term is apt. Plastic means formable and dys means not the right way.

Conceptually, we need to reorient that growing edge - maybe deepen the socket while doing that. If only we had . . . a chisel... (we call them osteotomes - bone cutters).

Concept-Geometry750the starting bone cutwe want the back half of this support cup

If Froot-of-the-Loom can make a bra out of flat cloth, possessed doctors with chisels ought to be able to shape the saucer into a cup . Cutting into the bone around the saucer edge we need to bend the top down and the back surface forward like that. With the right tools we can do that.

PelvicShorteningreflected head of rectus femoris

If the hip has migrated upward too far for too long, even with muscle lengthening it may resist moving back down to recenter. Shortening the pelvis by trimming a strip off the top and easing the muscles off both sides of the iliac bone can do this (to a degree) and gives up a nifty hunk of bone to put in that gap we just chiseled (typically make three wedges placed at 12, 1, and 3 o'clock positions in that right opening.

For the younger kids, who are the prime group for this, we don't need to do all that. Just cubes of decalcified cancellous bone are stepwise tamped into this gap crushing them and interlocking them quite solidly. Pretty much eliminates the space. Firm and needs no metal.

IliopsoasTDseq_SSrectus femoris tendonship capsule usually left intact

So imagine this space packed solidly with a material that is quite firm when so  placed and tamped.



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).