An overview on hip prosthesis

Everyone wants to get rid of pain. In our lives as humans, pain is one of the most impeding factors. Prosthetic replacement of the hip joint may resolve pain caused by wear and tear of the joint, and therefore it is currently an accepted method for improving quality of life. In Europe, about 800,000 hip replacement surgeries are performed annually, while in Hungary the number of hip prosthesis implantations is estimated to range between 12,000 and 15,000 per year. This number increases by 15 percent annually on average, and when evaluated by individual countries this growth rate is variable and shows a seasonal distribution. This is an extremely high number. Naturally, a proper professional reason is needed to recommend a prosthesis implantation as a solution for someone. Let us continue by examining the reasons that may result in wear and tear of the hip joint and collecting the available information on hip prostheses.

 

Hip osteoarthritis

Wear and tear of the hip joint is a complex condition causing typical symptoms that can be classified into two main types:

• Primary wear and tear, which actually develops as a result of the aging of cartilage. With aging, cartilage gradually loses its quality and function, and finally the hip joint may become completely deprived of cartilage
• Secondary wear and tear develops as a consequence of other factors. Reasons may include trauma, inflammation, tumours, metabolic disorders affecting the hip joint, consequences of childhood hip diseases, developmental malformations, incorrectly treated or untreated hip dislocation or hip impingement syndrome.

Symptoms

It typically presents as pain radiating into the folds of the groin, the buttocks and thighs. As it progresses, pain at night and pain related to activity increases and then becomes permanent. Walking becomes difficult and patients begin to limp. The range of motion of the hip joint becomes restricted. This restriction can be promptly assessed in one second, which makes differential diagnosis quite straightforward and easy for the specialist. The restriction in the range of motion found on rotating lower limbs accompanied by pain reveals the status of the hip joint.

Establishing the diagnosis

As I have already mentioned above, an adequate specialist can essentially establish the diagnosis of hip wear and tear (i.e. osteoarthritis) within a few seconds by physical examination. Knowledge of past medical history, previous diseases, medication, lifestyle and sports helps a lot with the diagnosis. These all reinforce that the examining physician is on the right track. Naturally, it seems proper to assess and confirm the diagnosis objectively, or in a manner that can be demonstrated to the lay patient. In this regard, X-ray scans play an important role, providing a clear picture of the expected stage of the disease while also providing assistance in planning the surgery. For more complex lesions, CT scanning may be warranted, and CT scans with 3D reconstruction may be of special assistance to the operating orthopaedist. I wish to emphasize that occasionally, from the point of view of differential diagnosis – which means differentiating from other diseases with similar symptoms – it may be difficult to establish the diagnosis of this condition. Disk herniation, lumbago, lower back pain, nerve inflammation, sciatica, osteoporosis, knee joint disease, ankylosing spondylitis and inflammation and other locomotor diseases accompanied by hip pain may also cause very similar symptoms, or conversely, wear and tear of the hip joint may lead to symptoms similar to the above conditions.

Treatment

The first step in the treatment of hip joint wear and tear is prevention. Unfortunately, a life style rich in adequate physical exercise and ensuring optimal load with a proper diet and body weight control only delays the development of wear and tear, however, it may do so quite efficiently.
Based on cartilage physiology, joint movements improve cartilage metabolism; moreover, moving a diseased joint has an analgesic effect.
Antiphlogistic creams, patches, physical therapy, physiotherapy exercises, as well as non-steroidal anti-inflammatory drugs and steroids should be chosen to control symptoms. However, you should certainly be aware that steroids may cause serious stomach, intestinal and liver issues and may adversely affect the body when taken over a long period of time.
The use of orthopaedic medical aids may help in easing the load and maintaining the ability to walk and thus to be self-sufficient.
Secondary hip wear and tear is prevented by treating the primary disease as adequately and completely as possible. It is essential to emphasize that all conditions that affect hips, whether they are acquired diseases or developmental malformations, will largely determine the "longevity” of hip joints, which means that it is expected that cartilage wear and tear will develop prematurely in the affected hip. Therefore essential steps for preventing further deterioration include adequate screening and treatment of hip dislocation, anatomical restoration of post traumatic lesions and proper therapy for inflammation.
Naturally, based on the above it is clear that conservative treatment is an option requiring prolonged and careful attention as well as great patience and perseverance both for the doctor and the patient, and which loses its efficiency after a while, becoming incapable of easing complaints as the disease progresses. For a large numbers of patients appearing at orthopaedic outpatient services with hip wear and tear, surgical intervention will be indicated sooner or later.
Hip prostheses, as with all medical procedures, have gone through an interesting, peculiar and sometimes strange development from the perspective of present-day expectations, but overall it can be stated that worldwide the large number of surgeries performed and the achievements prove that it is an effective procedure. A poor quality of life caused by the wear and tear on hips has raised the need for developing this procedure. Initially (at the turn of the century), attempts were actually made to place different materials between the worn joint surfaces by almost every method in order to ensure proper articular movement. Unfortunately, most of them did not succeed in part due to conditions that were not properly sterile in that era and in part the unsuitability of the materials used. From our modern perspective, these were in many respects scary attempts; however, without doubt, they led to the development of proper techniques and the use of proper materials.
Knowledge of prosthesis classification is important for the orthopaedic profession, while choosing and using the proper implant type is the orthopaedist’s job. A well trained orthopaedic surgeon cannot make major mistakes when choosing the proper prosthesis. In any case, the prosthesis is chosen for the patient, being – with a bit of exaggeration – tailored to the individual. Thus, the prosthesis chosen for an older patient in poor general health where hip replacement becomes indicated after a femoral neck fracture will be different from that chosen for a patient in good general health or of a younger age. For the former patient group, a technique requiring a shorter surgical period and representing a lower burden for the patient should be chosen, such as cervico-capital prostheses, where the main goal is for the patient to regain their capacity for self-sufficiency as soon as possible after surgery.

Nowadays, total hip endoprosthesis (TEP) has become an international standard for patients in suitable condition and of a proper age. Laypeople have become increasingly aware of the existence of cemented and uncemented prostheses. The essential part of the surgery takes place in the same way for both types: the place for the properly sized implant is created in the hip bone and the femur with special chisels, milling tools and rasps. The two techniques differ only after this point. For the cemented type, the prosthesis is embedded and fixed by a bonding material called bone cement, while for the uncemented type the surface of the prosthesis is coated with a material that gives it a porous surface structure and after implantation the bone will grow into these micro channels, and finally this bony connection will ensure proper attachment. A combination of the two techniques is called a hybrid method by the profession. It is a misconception among patients that the one or the other will be more beneficial for them. At a younger age and with a suitable bone structure and quality the cementless technique should be chosen, while for older patients with poor bone conditions the cemented type is a more professional choice. By all means, the method should be chosen individually after a proper assessment of the patient. The two types also differ regarding postoperative rehabilitation. According to the general principles of rehabilitation, the leg may bear loads 12 weeks after the implantation of a cementless prosthesis and 6–8 weeks for a cemented prosthesis. However, the most recent professional principles allow for a less strict protocol as well. In my opinion, it is the job of the operating surgeons to decide on the rate of rehabilitation, since they are the experts who saw, felt and palpated the quality of the bone during the surgery and due to their proper professional experience can decide on the degree and period for avoiding loads.

After learning the technique and gaining experience with it, the so-called muscle-sparing (without cutting the muscles) hip replacement technique performed using an anterior approach has become increasingly popular. It is also called a minimally invasive intervention, though, in my opinion this is not entirely true. I myself use this technique during a primary (first) implantation and during certain interventions indicated for prosthesis replacement. Anterior approach refers to a technique which is performed via an incision of about 8–10 cm made on the frontal part of the thigh at the level of the fold of the groin without cutting muscles.
Compared to the standard approaches, this is more advantageous since pain remains for a shorter period of time and often to a lesser degree, postoperative mobilisation can be initiated sooner, and thus rehabilitation time decreases, milder blood loss can be expected during surgery, and aesthetically the surgical scar is smaller and can be more easily hidden for patients sensitive to this issue. The probability for prosthesis dislocation can be reduced, and also the limb length can be more easily set. The surgery can be performed in almost all people regardless of their body type, though it should be added that for certain body types hip replacement surgery may be more difficult. During patient assessment (especially after viewing X-ray images), the surgeon is already considering the technical challenges that may be expected during surgery. This approach can be referred to as the so called "bikini incision" approach, which may be requested by ladies and should be asked for from the very beginning by the patient or discussed during patient information.
I would mention (not to deter you) that unfortunately in some cases a prosthesis cannot be implanted, or because of the loosening of the implanted prosthesis bone loss is so extensive that implantation of another prosthesis is not possible, and also in certain cases (such as a septic condition) the implant must be removed. In these cases (which nowadays are more and more infrequent) the affected hip remains in a "swinging" state (Girdlestone's position), which also can only bear loads with the support of a medical aid, but may ensure painlessness and thus a better quality of life. The occurrence of a final "stiffening" of the hip joint is considered a rarity nowadays.

Hip replacement surgery

Complications after hip prosthesis implantation

Dear Patients, please do not let the complications below deter you, but it would be silly to think that everything always goes perfectly. Nowadays, intraoperative (during surgery) and postoperative (after surgery) complications largely fall within an acceptable range. Proper preoperative assessment, well-established surgical techniques, well-trained operating room staff, professional skills of the orthopaedic surgeon and careful immediate and long-term postoperative care all contribute to better statistics. The most typical complications are discussed below:

Intraoperative complications

Development of a haematoma, cardiovascular complications, blood vessel injury, nerve injury, bone fracture, muscle injury and embolism. Overall, these complications do not occur at a high percentage, however, you should be aware of them and their risks when you undertake an intervention like this, since these complications may influence the outcome of the surgery and may lead to long term effects, poor quality of life or even severe consequences.

Infection

According to international literature, the occurrence of infections is about 1%, which is considered quite rare. Diabetes and liver diseases increase this risk, and infectious diseases occurring in other parts of the body also play a role in the development of infections around the prosthesis. These situations can be controlled by adequate antibiotic treatment, surgical exploration or by the removal of the prosthesis as a last resort. These days, reimplantation after purulent prosthesis loosening is not hopeless at all, though the indication for a new surgery must follow an extremely disciplined assessment and a strict protocol.

Dislocation

Prosthesis dislocation (or "popping out" as patients call it) occurs in about 4% of hip prostheses. This number increases to 20% for revision (prosthesis replacement) surgeries. Usually, this occurs within a couple of months after surgery. The most common reasons for dislocation include crossing the legs, improper positioning of the implant, loosening of the prosthesis, deep sitting-bending positions and accidents. After covered resetting, surgical exploration of the artificial joint and reconsideration of the adjustment of the joint tightness is warranted as well.

Loosening

The average lifespan of hip prostheses is 12–15 years. During this period – later if you are lucky or sooner if you are less lucky – the body begins to "push out" (reject) the prosthesis. Actually, this is a protective reaction of the body against the foreign material. Sterile loosening of prostheses is considered the most common long-term complication. New implantations after the removal of a prosthesis due to sterile loosening amount to around 25%. Signs of loosening may be revealed by nuclear medicine imaging or conventional X-ray scans, which also may help in planning the surgery.

Changes in limb length

The most important factor when implanting a hip prosthesis is to achieve stability of the artificial joint in the end. From this perspective, limb length may sometimes change and occasionally adequate stability may only be achieved using a prosthesis with a longer component. The risk of this complication may be reduced when using the anterior muscle-sparing technique.

Thrombosis

These days, prophylactic antithrombotic agents are used routinely at orthopaedic departments during lower limb surgeries; however, development of thrombosis may be still a real risk. Besides medicines or injections, appropriate exercises, bandaging and early mobilisation are extremely important. Embolisms may occur as a consequence of thrombosis, which may lead to various symptoms of varying severity, so avoiding embolisms is a common goal for the attending physician and the patient.

Periprosthetic fracture

The incidence of fractures adjacent to prostheses is about 1% for primary implantations and 4% for revision interventions. Such adverse fractures sometimes require large interventions and difficult professional solutions; however, effective healing may be achieved with a proper organisational, professional and technical background.

Metal allergy

Based on articles published in the international literature, it seems that there is no absolute position with regard to metal allergy and material choice for prosthesis. The following opinions are encountered in the literature: according to certain authors, no allergisation occurs from the deeper tissues, dermatological tests performed to confirm metal allergies may not necessarily help in implant selection and in asymptomatic cases routine allergy tests are not justified, while for known metal allergies the selection of an implant made of a suitable material may provide a sense of reassurance, even though deep tissue reactions to metal implants are rather rare. In the literature, it is recommended that symptoms that somehow may be linked to the implant should not be called allergies, but hypersensitive reactions (hypersensitivity).

Blood loss

Bleeding from large blood vessel injuries or following surgical exploration (given the nature of the intervention) may occasionally lead to severe blood loss that is demanding on the body. In such cases, haematopoietic drugs, transfusions of the patient’s own blood or matched donor blood transfusions are administered according to strict professional rules. Experience shows that blood products given when appropriate, considerably improve physical strength, promote the healing process and increase mobilisation capacity, while if refused all the above are adversely affected.