Hips that are discovered to be dislocated or unstable at this time can usually be helped return to the joint by soft tissue release. The simplest soft tissue release is a release of a muscle on the inside of the thigh next to the groin – adductor tenotomy. This procedure needs to be carried out under a brief general anaesthetic. Some contrast material needs to be put in to the joint in order that the treating surgeon can observe the proper seating together of the two parts of the hip joint. It is usually necessary for a plaster to be applied for approximately 3 months. The plaster will probably need changing once during that period. The plaster involved, a hip spica, is a particularly inconvenient type of plaster because of difficulties in keeping it clean at the tail end, but at the present time there is no alternative.
The purpose of relocating the hip is to facilitate remodeling of the hip and socket to one another, ideally to produce a normal hip once this remodeling is complete. For children who have received treatment during this period, approximately 25% of them will need a later operation to deepen the socket because the socket’s remodeling remains inadequate despite several years of observation. Unfortunately, the time at which such a subsequent operation is required varies from child to child according to the rate of remodeling seen on the follow-up x-rays.
Every attempt to relocate a hip by this method is attended by a 10% risk of avascular necrosis. This is where the blood supply of the head of the femur (the ball in the socket) is compromised as a result of treatment. Whereas avascular necrosis in later childhood is a very serious problem, at this age it is not always the case.
Medial approach open reduction is a more extensive soft tissue release operation performed through a wound on the upper inner side of the leg. The operation consists of adductor tenotomy, when required, release of the psoas muscle and release of the tight soft tissues on the inner and underside of the hip joint. This is a very successful operation when used as the first operation to put the hip back in joint. The operation has been criticised because of a high rate of avascular necrosis (as high as 25% or 30%), but this only occurs where there have been other unsuccessful attempts to put the hip back in joint. Each unsuccessful attempt contributes an approximate risk of 10% to the risk of avascular necrosis. It is tempting for critics to attribute avascular necrosis following medial approach open reduction to this operation, whereas in fact in the vast majority of such cases this risk is in fact attributable to other earlier attempts to relocate the joint.
The operation wound is relatively short – perhaps 3-4cm (1.5″). It is usually sewn up with invisible mending. As with adductor tenotomy, a hip spica is applied for 3 months. Some night time splintage is occasionally necessary following both of these treatments. In general it would be best to budget for perhaps 3-6 months of night time splintage after removal of the plaster.
There are at least three well respected studies of several scores of children treated by medial approach open reduction in the literature, which indicate that there is a 6% risk of avascular necrosis, and a similar risk of re-dislocation or need for subsequent bony procedure to stabilise the hip socket.
Beyond the age of 8 months, an increasing proportion of children who present with dislocated hips need more than a simple or extended soft tissue release to allow the head to return to the socket.
A proportion of them, increasing with age, require an operation to deepen the socket, as the amount of re-modelling that can be expected after 8 months of age is not usually enough to produce a normal hip at maturity.
The “industry standard” operation to deepen the socket is the Salter osteotomy. The designer of the operation, Professor Bob Salter from Toronto, has demonstrated that approximately 90% of children treated by this operation, combined with open reduction to get the hip back in joint, between the ages of 18 and 48 months have a good or excellent result rate at 30 or more years’ follow-up.
The second patient mentioned, also bled a great deal during the course of the operation and it is possible that damage was caused to one of the nerve cables whilst trying to stop the bleeding.
Attempts to perform an open reduction and a Salter osteotomy below the age of approximately 18 months are fraught with complications which are largely avoidable if the operation is deferred until the bones are of a sufficient size and strength that they can be crafted accurately.
Therefore, it is not my policy to treat any children between the age of 8 and 18 months for congenital dislocation of the hip, except in exceptional circumstances.
In such cases, as advised elsewhere in this section, the usual treatment is an open reduction accompanied by a Salter osteotomy.
A hip spica plaster is worn for 6 weeks. This is then usually changed to broomstick plasters for a further 4-6 weeks. At the time the plaster is changed, the hip is tested for stability. Occasionally children need napping splints thereafter if the result on the x-ray is less than ideal.
The Salter osteotomy involves a cut immediately above the hip socket in the pelvic bone, with the insertion of a wedge of bone taken from the adjacent pelvis.
The wedge of bone turns down the roof of the hip socket and stabilises it. It is usually held with one or two absorbable screws that do not need later removal.
The wound, approximately 6 cm long, is sewn up with invisible mending and there are no sutures to remove. The wound of a Salter osteotomy is particularly cosmetically pleasing and is described as “a bikini incision” as it can be easily sited to be completely obscured by a bikini.
Children who are diagnosed at more than 2 ½ years of age need an open reduction through a Salter type wound. Depending on the hip configuration, as indicated by scans, it may be advisable to carry out a Salter osteotomy. Alternatively, the deformity of the hip socket may require an acetabuloplasty to be performed. An acetabuloplasty is an operation slightly different from a Salter osteotomy, and is specifically used to re-direct and slightly re-shape the hip socket where the correction provided by a Salter osteotomy would be inappropriate.
The choice between a Salter osteotomy and an acetabuloplasty is substantially dependent upon the configuration of the hip socket as indicated by CT scans.
As a child gets older, and as the shortening of the leg is more longstanding, there is a much greater risk of avascular necrosis of the femoral head occurring as a result of the compressive forces caused to it after relocation.
As a result of this appreciation, approximately 12 or 15 years ago Orthopaedic Surgeons started doing femoral shortening. This is where a section of the femur (thigh bone) perhaps 2-3cm (1″) long is removed. The femur is then plated up slightly short. The hip is then relocated and the roof of the hip socket is turned down and held using the bone taken from the femur.
Parents are sometimes concerned that this combination of operations can result in some shortening, but at worst this is usually a matter of only a few millimetres. In any case, it would be better for a child to have a slightly short and perfectly stable joint, than a leg of the correct length with the hip unstable.
Shortening of the femur requires a second wound to be made on the outer part of the thigh in the upper third. The plate used to hold the bones together needs to be removed approximately one year later.
Using the combination of open reduction, acetabuloplasty and femoral shortening, it is possible to reconstruct to near normal x-ray appearances, complete dislocations up to the age of approximately 10 years.
When a child is skeletally mature (12 in a girl and 14 in a boy) it is rarely practical, safe or effective to relocate a hip using any method that preserves the original joint surfaces.
The hip does not re-model at all at this age. The two parts never fit together properly and it is certain that the original bearing surfaces in the joint will not function in the longer term. Accordingly, it is necessary to do an additional procedure, a hip resurfacing.
This is a relatively new procedure and I have performed about 10 of these over the last 4 or 5 years. The majority of patients treated have suffered from severe cerebral palsy, but the operation has also been used occasionally in normal, young adults who have presented with completely dislocated hips.
The operation consists of a metal-on-metal chrome cobalt hip resurfacing performed through a posterior approach (the ordinary approach used for a hip replacement).
Because of shallowness of the hip socket, it is frequently necessary to use specially adapted components to stabilise the socket part with supplementary screws. There is usually a large defect in the bony socket above the metal prosthetic socket component and this is filled with bone graft taken at the time of the operation.
After the resurfacing has been implanted, it is impossible to put the hip back in joint because the soft tissue tension is too great.
A femoral shortening operation is then performed. This consists of a 7-hole heavy fracture plate applied to the upper femur (thigh bone) immediately below the hip joint. Approximately 3cm (1.25″) of thigh bone is removed and the surgical fracture (osteotomy) is plated up in the usual way.
The shortening of the femur does not usually result in shortening of the leg compared with the original leg length because the hip joint has been brought down to its correct level. The hip resurfacing can then be relocated and the wound is closed.
It is usually advisable to apply broomstick plasters, particularly in disabled or uncooperative patients, either short cuffs of plaster on the thigh only, or the whole way from the groin to the ankles, with a broomstick holding the legs apart to hold the hip in joint during the healing period, i.e. the first 6 weeks.
The outcome of this operation so far has been promising. The very first patient, who had particularly soft bone, suffered two plate cut-outs which have been treated successfully, and where the outcome has not been compromised. All the remainder of the patients have had satisfactory outcomes without any such complications. One patient with cerebral palsy who was uncontrollable in the very short-term after the operation did suffer a dislocation, but this was managed successfully by the application of long broomstick plasters.
Informal audit of the parents and carers of these patients has indicated a significant improvement in the quality of life, better seating, better toileting, more comfortable transfers, as well as an ability to sit up and take in the world better than before because the leg is soundly connected to the body, and the overall trunk balance is better.
It is noteworthy in the same context, that if a hip dislocation in cerebral palsy is associated with severe or rigid scoliosis, it is advisable that the scoliosis is corrected first so that the hip does not re-dislocate after the resurfacing with femoral shortening.