Legg-Calve-Perthes disease is a pathological process that affects the development of the child’s hip. 1 Although doctors know that it is produced by aseptic necrosis of the femoral head, the causes that origin such necrosis is really unknown.
Conventional radiology does not allow an early diagnosis, so more advanced diagnostic techniques are needed for diagnosis of Legg-Calve-Perthes.
The moment in which the diagnosis of Legg-Calve-Perthes is made and, consequently, the degree of affectation in which the hip is at that moment, determines the treatment to be applied and the complications that the patient may develop in the future.
Radiographic images are the most common method to start the study of a painful presentation of the hip or pelvis, on suspicion of legg-calve-perthes or other pathology, as it is a simple, fairly accessible and easy to interpret method. In the study of legg-calve-perthes, anteroposterior and lateral images should be taken in the position of Lauenstein (“in a frog position”).
What Are The Stages Of Legg-Calve-Perthes Disease?
The Legg-Calve-Perthes consists of 4 stages: the first consists of lack of blood supply to the femoral head, then the body will remove the dead bone cells and replace them with new and healthier bone cells, in the next stage of Legg-Calve-Perthes the femoral head continues taking its rounded shape with new bone tissue. Finally, normal bone cells replace new bone cells.
From the radiological point of view, the process of ischemia and subsequent bone regeneration has been divided into several stages that reveal the anatomical changes of the femoral head and neck. The identification of the phase in which the process is located has therapeutic and prognostic importance.
Initial or Necrosis Phase or Stage of Legg-Calve-Perthes
The vascular supply and bone necrosis are interrupted. At this Legg-Calve-Perthes stage, the femoral head is very vulnerable to the forces acting on it.2
Fragmentation Phase or Stage of Legg-Calve-Perthes
A process of reabsorption of the necrotic bone begins in this stage of Legg-Calve-Perthes.2
Reossification Phase or Stage of Legg-Calve-Perthes
The density moves in the opposite direction. The epiphysis is invaded by vessels, the dense islets are reabsorbed and rarefaction (it means to the lessening of density) bone tissue is formed and then trabeculated. Repair begins with the disappearance of metaphyseal osteolysis. Osteolysis is defined as the process of attrition and reduction of one or more areas of a bone.
Final or Healing Phase or Stage of Legg-Calve-Perthes
The complete replacement of the necrotic bone with newly formed bone occurs in this stage of Legg-Calve-Perthes. The newly formed bone has a weaker consistency so it can be remodeled so that the morphology of the femoral head adapts to the shape of the cup or not. This process will not be definitive until the end of bone maturation. Since the final result can be that of a deformed femoral head, this phase can also be called the residual deformity phase.
The duration of each Legg-Calve-Perthes stage is very variable, but in general, the stage of necrosis and fragmentation lasts about 6 months, the period of reosification from 18 months to 3 years and the final or healing phase until bone maturation. For other experts, the fragmentation phase lasts approximately one year and the reossification phase lasts from 3 to 5 years.
The main drawback of conventional radiography is its ineffectiveness for the early diagnosis of bone necrosis. But once the osseous changes are visible, this will be very useful for classifying and monitoring the disease, focusing the type of treatment and establishing a prognosis.
Evolution and Prognosis of Legg-Calve-Perthes
Legg-Calve-Perthes is a self-limiting disease, because of its natural evolution is towards healing. In primary care, if doctors suspect that are facing a Legg-Calve-Perthes disease, they should do checkup every 3 or 4 months because some cases evolve unfavorably and leave severe sequelae in adulthood, mainly hip osteoarthritis, since the remodeling capacity of the femoral head with the acetabulum ends around 8 years and from this age there is hardly any power of remodeling.
Although 80% of patients affected by the Legg-Calve-Perthes have a good evolution until the fourth decade of life, between the fourth and fifth decade there is a significant risk of developing hip osteoarthritis, and in the sixth decade of life, half of the patients require the use of a hip prosthesis.