Types of hip prosthesis

• There are several classifications of types of hip prostheses depending on technique, materials, etc.
• In some types of hip prostheses only one of the components, the femoral component, is implanted.
• Hip replacement surgery aims to relieve pain and restore the functionality of the joint.

It should be borne in mind that the hip is responsible for our upright posture as well as our movement, so it is one of the structures that suffers the most wear and tear over the years.

The hip is one of the most important joints in the human body, both in terms of function and size.

Within the hip joint we find the following components:

• Acetabulum or pelvic cup: which is the bony component that forms part of the human pelvis and which houses the other bony component of the joint, the head of the femur.

Both parts of the joint are concave and convex with respect to each other so that the union of the two allows movement at virtually all possible angles.

• Joint capsule and a synovial membrane: which are responsible for generating the synovial fluid that covers both bony components and serves to lubricate the hip joint to prevent premature wear and tear due to friction.
• Ligaments that support it and a muscular apparatus: which allows movement and fixation of the joint.

A prosthesis is an object made of synthetic material that replaces the absence of an organ to restore the function of the affected organ.

A hip prosthesis is an artificial medical device that replaces the natural structure when it has been damaged.

We call hip prosthesis the replacement of all the components that form part of the hip joint with others made of synthetic material that will perform the function of the dysfunctional or broken organic part. 

In the specific case of the hip and when we talk about a total hip prosthesis, the 2 fundamental elements involved in the hip joint are usually exchanged: the femoral head and the pelvic cup.

It is often necessary to operate on a hip joint and replace it with a type of prosthesis when it is altered and/or when the affected hip has been fractured:

Hip fracture, generally, is the breakage of the upper part of the femur, being usual the use of a partial prosthesis:

• Fractured, traumatically or otherwise.
• When the affected hip suffers from some type of pathology in its structure: necrosis of the femoral head, intense osteoporosis, degenerative arthrosis in an advanced stage, etc.
• When there has been an alteration in the hip socket or acetabulum of the pelvis that prevents the femoral head from resting inside it and being able to exercise its joint function naturally.

At what ages is a hip fracture requiring a hip replacement most common?

Epidemiological studies studying the prevalence and epidemiology of hip fractures always agree that there are 2 important stages in the life of a human being where hip fractures can become a health problem.

The most important of all is the age group over 70, people in the third stage of life with an associated comorbidity that makes them more prone to hip fractures, and another much less important one is the age group between 20 and 30 years of age in which traffic accidents and hip fractures of traumatic origin are the most frequent.

Causes of hip fracture in older adults (over 70 years of age)

In the stage of life in which people are over 70 years of age, the main incidence of hip fracture is the existence of moderate to severe osteoporosis that precipitates, generally through a minor fall, a fracture in the hip joint.

For this type of fracture it is not necessary for the blow to have been very strong, but rather the existence of pathologies that affect the hip and weaken it to favour the fracture. On many occasions it is not enough to fix the fractured part for its consolidation and it is necessary to choose a type of hip prosthesis to replace the fractured part.

Another very prevalent pathology in elderly patients is arthrosis of the large joints. When osteoarthritis is very advanced, the ability to stand and walk becomes impossible and pain accompanies the patient 24 hours a day.

Almost 60% of adults over the age of 80 suffer from osteoarthritis to a greater or lesser extent in the hip.

At that time, it would be advisable for specialists to assess the possibility of the need for hip replacement surgery in order to restore the functionality of the joint and the disappearance of pain.

Depending on the pathology affecting the patient, several different tests may be necessary, although, in general terms, a simple anterior-posterior hip X-ray, an axial or angle X-ray or a lateral X-ray is usually sufficient for a definitive diagnosis, especially if the origin is a pathological or traumatic fracture.

If the process suffered by the patient is a degenerative disease such as osteoarthritis, the X-ray will give us very important initial information, although it may be necessary to carry out an X-ray:

• Magnetic resonance imaging (MRI): is an imaging test that uses magnetic fields to align the hydrogen nuclei of water in the body, allowing us to see organs and structures inside the body. These images help diagnose various conditions such as torn ligaments or the presence of tumours.
• Computed tomography (CT) scan: this is a diagnostic imaging test that uses x-rays to create cross-sectional images of the body and, in some cases, the patient ingests a contrast dye that helps some parts of the body to be seen better.

These tests allow us to visualise more accurately the characteristics of the injury and to be able to choose one or another treatment that will determine the type of hip prosthesis most necessary for the patient.

Are you thinking of solving the problems caused by a hip fracture or wear and tear as soon as possible? Meet our specialists in Traumatology and assess the treatment that best suits your case by clicking below:

Hip prosthesis according to the type of surgery to be performed

Depending on the type of surgery to be performed for the replacement of the hip joint with a hip prosthesis, there are two types of prosthesis: 

• Primary prosthesis, which are those in which the joint or some of its original components are replaced by a prosthesis.
• Revision prosthesis, which is surgery in which a worn or old prosthesis is replaced by a new one.

Hip prosthesis according to the size of its components

Depending on the size of the components with which the hip prosthesis operation is to be carried out, there are three different types:

• Conventional prosthesis replacement, in which the size of the components is usually the usual size, consisting of an artificial femoral condyle with a stem that joins the femoral head and is inserted inside the femur, of normal length and a pelvic component or usual artificial cup.
• Replacement of short stem prosthesis, which are hip prostheses in which the rest of the components are the same as usual but the stem or rod that serves as an anchor in the femur is shorter than usual, so that the damage caused by pressure on the femur is less and the bone can be preserved for longer and the prosthesis can be re-intervened more times if necessary. This type of hip replacement is usually performed on young adults who are more likely to have to be reoperated.
• Replacement of surface hip prosthesis, in which the stem that comes out of the femoral condyle is very small, this is a variant of the previous one that is usually performed on young people with a great integrity of the femoral bone.

Hip prosthesis according to the anchorage of its components to the bone

It is also possible to classify the hip prosthesis replacement procedure according to the type of anchorage of the components to each other and to other bone structures that serve as support, in this sense we find 4 types of hip prosthesis replacement:

• Cemented hip prosthesis, in which the femoral condyle and pelvic cup are glued and attached to their bony parts with a cement mixture. 
• Uncemented hip prosthesis in which the components are not cemented to their respective supports; hybrid prostheses in which the femoral condyle and femoral stem are cemented to the inside of the bone but the pelvic cup is not. 
• Reverse hybrid hip replacements in which the pelvic cup is cemented to the pelvis and the femoral condyle and its stem are not.

Types of hip prostheses according to the amount of prosthesis replaced

Depending on the amount of prosthesis implanted, we can classify the types of hip prostheses into two fundamental interventions: 

• Total hip prosthesis, in which both components of the hip prosthesis joint (cup and femoral condyle with the stem) are replaced.
• Partial hip replacement, in which only the femoral condyle component with the stem is replaced.

If we talk about the materials used to make each of the parts that make up the hip joint, we have to divide them into 3 different groups: metallic mixtures, ceramics and polymer mixtures.

Hip prosthesis made of mixed metals

The metal mixtures which are included in the classification of hip prosthesis types according to the composition of their materials can be divided into several groups: iron components, cobalt components and titanium components.

The fundamental differences between them is that cobalt is the most resistant, iron is the best tolerated as it offers hardly any rejection or allergic reactions of the human body towards the foreign objects that are the prostheses.

Hip prosthesis made of polymer blends

Polymer blends are an artificial mixture of components with a high molecular mass, which makes them very suitable materials for use in the acetabulum or socket of the pelvis as they allow very good gliding and self-lubrication. 

The main problem lies in the high wear they suffer and in the fact that they tend to be somewhat fragile in the event of direct blows.

Ceramic hip prosthesis

Ceramics are very resistant to friction but quite weak to direct trauma, a similar case to polymers, however their high resistance to displacement on them makes them very good candidates for use. 

Attempts have been made to mix them with carbon sheets to increase their resistance to impact, but the tests have not been very beneficial.

At Operarme, each of our specialists decides together with the patient which type of hip prosthesis is suitable for the case, as in the field of medicine it is very important to carry out specific diagnoses and treatments for each patient. 

Despite this, it is important to mention that all the hip prostheses (and also knee prostheses) that we use at Operarme are made by market leaders in prosthetic and orthopaedic material.

If you would like to request a free consultation with one of our Specialists in Orthopaedic Surgery and Traumatology and get a surgery date, you can make an appointment by calling at +34 91 141 33 56, or by clicking in the following banner: