Prosthetic reconstructive surgery

When changes to cartilage are very significant, there may be no indication for preserving surgery. Measures such as weight loss, moderate physical activity, analgesic medications and physiotherapy can help control the symptoms at an early stage.

When the disability becomes significant, the alternative is placement of an artificial hip prosthesis.

The prosthesis can replace a hip with simple arthrosis (fig. 5), a deformed hip (fig. 6) or other prosthesis in surgical revision (fig.7).

Primary prosthesis of the hip (total hip arthroplasty)

During a total hip replacement, both parts of the joint are removed and replaced. Typically, a metal component with an inner high-density plastic or ceramic replaces the articular cavity of the pelvis and a metallic sphere or ceramic replaces the femoral head (fig.1 and 3). A metallic stem is placed to join the sphere to the rest of the femur (fig. 2).

The surgical approach carried out can be lateral or anterior depending on the case and the surgeon's experience. During surgery all structures (muscles and tendons) should be preserved to the maximum to ensure the proper functioning of the prosthesis.

The components can be fixed to the bone by means of a pasty substance which solidifies (cement) or be fitted and screwed to the bone, according to the quality of the same.

The main indications for total hip arthroplasty are:

• Degenerative changes – coxarthrosis – with limited mobility and pain, that in other surgical procedures do not exhibit good results;
• Fractures of the femoral neck with interruption of blood supply to the femoral head;
• Treatment of benign or malignant tumors of the hip or proximal thigh.

The contact interface between the two components of the prosthesis, always results wear (regardless of the type of material used) requiring their replacement after some time. The durability of implants is related to the type of physical activity to which the prosthesis is subjected throughout life, with its composition and the way it is placed.

The results of surgery are good, particularly when the indication is coxarthrosis. The patient substantially improves from pain and can resume his / her normal activities excluding impact sports. When surgery is conducted due to fracture of the femoral neck, the duration of the implants seems to be less by greater wear of the contact surfaces, but quality of life is also improved.

Prosthesis in hip revision

The hip revision surgery is becoming increasingly common by the fact that many implants are placed in younger individuals, with more physical activity which determines an increased wear of the implants. Other causes which motivate the revision are infections (related to surgery or later complications) and instability of the prosthesis (in certain positions disengages).

In the revision of total hip prosthesis, one or both parts of the joint are removed and / or replaced. New components are usually different, larger (fig. 4) so that they can be fixed in the bone which has already undergone previous surgery. The prosthesis revision surgery may be technically much more complicated than the primary prosthesis and usually results from surgery that they are not as good as that of the primary prosthesis.
 

fig. 1: Various types of materials used in the sphere replacing the femoral head: different ceramics and metal.

 

fig. 2: Two different types of cemented stem: one polished another with striations.

 

fig. 3: Two different types of stem acetabular component: cemented on the right and cementless on the left.

 

fig. 4: Femoral stem revision, with striations and longer than a primary.

 

fig. 5: radiograph of a patient with simple bilateral coxarthrosis in which it was made a surgical placement of a prosthesis.

 

fig. 6: radiograph of a patient aged 40 with coxarthrosis secondary to dysplasia and with a history of previous surgery. The procedure for placing the prosthesis in such cases is technically more complex. Normally in order to achieve implant of the prosthesis in the proper position is necessary to use bone graft harvested in the patient's own femoral head. This procedure is more biologic than the use of prostheses which compensate dysplasia since it preserves more bone and prepares for future revisions of the implanted prosthesis.

 

fig. 7: radiograph of a patient with a placed prosthesis in mechanical failure. Revision surgery consists in the reconstruction of the reabsorbed bone using bone graft and special implants, different from those used in the primary surgeries.