FEMORAL OSTEOTOMIES FOR DDH IN THE ADULT

Abstract

In early secondary arthritis due to femoral dysplasia, varus osteotomy achieves a control of arthritis for two decades in 80 % of cases : it is therefore a very reliable conservative treatment. Moreover, in carefully selected cases of severe arthritis in young active patients, a valgus osteotomy can achieve pain relief for a decade in 70 % of cases.

THE VARUS OSTEOTOMY is recommended when the arthritis is due to a coxa valga ≥ 140°. By reducing the inclination angle to 125° the abductors level of arm is optimized, and their contracture is decreased. Therefore, the osteotomy reduces the surface strains, but it does not improve the extent of articular surfaces.

A – INDICATIONS

1) Four factors are mandatory to achieve long term improvement:

• The arthritis must be the consequence of the dysplasia, with degenerative changes localized at the supero lateral part of the head and of the acetabulum. This can be confirmed by isotope scanning. If the arthritic changes are not localised the desease is rather a primary arthritis, or an inflammatory or a metabolic disease, which are not an indication for a biomecanical treatment.

• There must be a real coxa valga, evidenced by coxometry. Anteversion is mesured by CT scan, and the inclinaison is mesured on a X ray of the pelvis with the hips in internal rotation equal to the ante-version. If there is a shortened femoral neck (such as a post reduction osteonecrosis), the modification of the glutei lever of arm may not change significantly the articular strains, and therefore osteotomy is no indicated.

• The articular congruency must not be impaired by the reduced inclination angle. Pre operative X rays with the hips in an abduction equal to the planned varisation must not reveal any lateral narrowing of the joint space, which would mean incongruity, and lead to failure.

• The possibility of articular healing must be important : varus osteotomy is recommended before 45 years, and if the joint space remains ≥ 50 % of normal.

2) Therefore varus osteotomy is not recommended

• in a non symptomatic dysplasia (as some of them may not lead to arthritis), or if the symptoms are those of a labrum syndrom, with suddent pain, instead of a progressive and mechanical arthritic pain.

• if the dysplasia is only acetabular : then only the acetabulum has to be treated.

• if the anatomic abnormality is not an increase of the inclinaison (neck-shaft) angle, but a modification of the head-neck angle, which causes impigement with the labrum, and which is not improved by inter-tro-chanteric osteotomy.

3) The assosciated dysplasia have to be taken into consideration

• If there is a femoral hyperanteversion there are two different conditions in the adult :

• if the patient walks with internal rotation of knees (convergent strabismus of patella), realising a dynamic correction of hyperanteversion, the association an external rotation of the femur to the varisation is recommended.

• but if, despite hyperanteversion, walking is without abnormal rotations of the knees, this means that the optimum congruity of the hip is in that position. An ostotomy is no advocated as, instead of retroversing the femoral neck, it would rotate externally the femoral shaft.

• If there are both an acetabular and a femoral dysplasia, they both have to be treated :

• if an augmentation is recommended for an anterolateral defect, the shelf osteoplasty can be performed in the same operation that the varus osteotomy.

• if a medialisation is necessary (Chiari), both osteotomies can be assosciated in one stage.

• but if a complex reorientation osteotomy is necessary (either periacetabular –Giacometti-,

• or pelvic –Ganz-), it could be hazardous to perform a varus osteotomy at the same time.

B – SURGICAL TECHNIC

• The importance of the varisation depends on that of the coxa valga. The final inclinaison angle must be 125°, as the lever of arm of the abductors is impaired for a lower angle. Moreover there is a post operative limping due to the ajustement of the glutei length, the duration of which is function of the varisation (one year per 10°). To reduce this limping, only the necessary varisation has to be made.

• The technic has several important points :

• non union is avoided by non dissection of the medial metaphysis or removal of a wedge :

• we use a subperiosteal osteotomy, leaving in contact the medial cortex, with a lateral opening, fixed by a nail plate as a tension band. This technique gives a minimum limb shortening (12 mm for 15° varisation).

• respect of the articulation and soft tissues. There is no arthrotomy as the nail plate is inserted on a guide pin. Later implantation of the THR will not be complicated by the previous osteotomy.

• precise, « automatic » correction, depends only on the nailplate angle.

• the resistance of the osteosynthesis allows immediate rehabilitation (this extra articular operation does not reduce ROM), and 10 to 20 kilos weight bearing. Full weight bearing is authorized at three months.

C – RESULTS

There are less thant 5 % mechanical complications. An antalgic effect is obtained within some weeks. In 80 % of cases, painlessness and absence of radiological deterioration for two decades is achieved, a THR becoming necessary in the third decade. In 20 % of cases, only a temporary effect is obtained, leading to a THR after 5 to 10 years.

THE VALGUS OSTEOTOMY is at present used in only seldom cases of young patients with a severely damaged articulation, but who prefer an antalgic conservative surgery than a THR, because they wish to continue for a decade a strenuous activity not compatible with an arthroplasty. This can be made only when there are two large osteophytic drops of the acetabulum and of the femoral head, which can be put into contact by the valgisation, and facilitate healing of the superior lesions. In carefully selected cases, a relief of pain is achieved for a decade in 70 % of patients.

IN CONCLUSIONS

The femoral varus osteotomy remains one of the most reliable conservative operations in osteoarthritis due to DDH. However to achieve these good results, a clear understanding of the indications and biomechanical demands of this operation is required.

In seldom and selected cases of severe arthritis, a palliative valgus osteotomy can achieve a decade of pain relief.