The hip is the second support joint (after the knee) and is similar to a spherical joint. It is composed of the femoral head held by the portion of the pelvis called acetabulum. Thanks to its shape, it allows for a wide range of movement. Its stability is provided by the capsule, ligaments and robust muscle groups.
The most common hip disorders are constituted by degenerative joint diseases. The most common is osteoarthritis (coxarthrosis), which, through complex and still unclear biological mechanisms along with prolonged mechanical abuse, leads to the destruction of the cartilage and joint structures; this causes the loss of movement and progressively worsening pain.
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Dysplasia
Hip dysplasia is an anomaly in the development of the joint where the femoral head is not perfectly absorbed in the acetabular cavity. Heredity is a high risk factor. In recent decades, neonatal screening has allowed for treatment of dysplastic dysfunction in newborns with positive results, reducing the typical damage that otherwise occurs in adulthood.
There are several degrees of severity of dysplasia: from dislocation to minor morphological alterations that represent a cause of coxarthrosis.
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Femoro-acetabular impingement
Recent in-depth studies along with increasingly sophisticated diagnostic techniques have allowed for the identification of so-called “minor dysplasia”, as in the case of femoroacetabular impingement (FAI).
This is a condition in which the bones that make up the hip joint (femur and acetabulum) exhibit an abnormal shape and develop outgrowths or bone spurs around the femoral head and/or along the acetabulum. These, not being perfectly matched during movement, rub at one another; over time this can cause tears on the acetabular lip (the cartilage structure and degeneration of the articular cartilage leading up to confirmed arthrosis).
As athletes use their hip joints more violently and with extreme joint movements, they can develop symptoms before sedentary people.
The treatment of this disorder can be conservative (change in lifestyle to avoid movements or sports that cause pain, anti-inflammatory drugs and specific rehabilitation programs) or surgical.
In the case of surgery, arthroscopy allows, in selected cases, for treatment of the causes that provoke the degeneration, the cleaning of the injuries and, being minimally invasive, has very fast recovery periods.
Other causes for hip pain include rheumatoid arthritis or other specific arthritis, avascular necrosis of the femoral head, outcomes of fractures and age-related disorders such as dislocation, Perthes’ disease, epiphysis, etc.
As with the knee, the replacement of the hip with a prosthetic becomes necessary when the damage to the joints leads to such painful symptoms and functional limitations that the patient can no longer conduct a normal life.
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Cephalic necrosis
Hip osteonecrosis is a disease that occurs when the blood flowing to the femoral head is not sufficient. In the absence of blood, the bone tissue cells of the femoral head undergo necrosis (die) and the overlying cartilage collapses, ultimately leading to arthrosis and joint destruction.
Serious injuries such as femoral neck fractures or hip dislocations can lead to cephalic necrosis, however in most cases where the necrosis develops without trauma, the causes of the vascular crisis are still unknown. Some risk factors have been identified, such as diabetes, alcoholism, prolonged therapy with corticosteroid drugs (cortisone) or other diseases such as sickle cell anemia, myeloproliferative diseases, Gaucher’s disease, systemic lupus erythematosus, Crohn’s disease, thromboembolism and vasculitis.
Osteonecrosis develops in stages, whose progression varies from a few months to over a year. The first symptom is hip pain during use, which can worsen to the point of rendering walking impossible or even orthostatic dysregulation.
Early recognition of symptoms, before joint injuries develop, is fundamental for the prognosis of this disease: the earlier the treatment starts the better the results will be. Patients with osteonecrosis diagnosed in a very early stage (before the collapse of the femoral head), are good candidates for hip conservation procedures.
The so-called core decompression consists in the piercing of the femoral head through mini incisions and the removal of the part of bone tissue that has gone into necrosis and replacing it with autologous, homologous or bone substitute transplants. Stem cells and platelet concentrates can help promote revascularization of the area and thus bone and cartilage regeneration.
Another surgical option consists in the use of a vascularized fibular transplant. This is a more complex procedure, in which, using micro-surgical techniques, the fibula with the vascular pedicle is taken from the contralateral artery and subsequently grafted within the femoral head to facilitate healing of the area in necrosis.
When, however, the cephalic necrosis is in an advanced stage and the femoral head has collapsed, the most effective treatment is a prosthetic hip replacement.
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Hip replacement
The hip joint’s prosthetic replacement (total hip replacement – THR) includes both the acetabular side (the pelvis or cotyle portion) and the femoral side: it is referred to as arthroposthesis. In cases of fracture of the femoral neck, when the cartilage of the acetabulum is still good, it is possible to replace only the femoral component: this is called endoprosthesis.
There are different types of protheses, varying by design (neck conservation stems, straight and anatomical stems, hemispherical, truncated or modular stems) and type of fixation (cemented, non-cemented, press-fit or screwed).
The choice of implant type depends upon the morphology of the femur and cotyl, the specific disorder, general or localized conditions of the patient as well as upon the experience and philosophy of the surgeon
Preoperative planning is fundamental not only to prepare the measurements of the prosthetic components, but especially to define the morphological parameters through what is called coxometry in order to reproduce, where possible, normal articular physiology and prevent any intraoperative problems.
In general, the bone-preserving non-cemented protheses are utilized in young and active patients; cemented protheses are used, on the other hand, when the bone quality is not good (ex. elderly patients, osteoporosis, etc).
The new cementation techniques and the quality of modern cements guarantee optimal qualitative standards in terms of resistance, fixation of the prothesis to the bone and long-term survival of the implant.
The hip prosthesis is made up of a stem that is inserted into the femoral canal, from the cup that is implanted in the corresponding portion of the pelvis and the joint, consisting of a head, neck and a liner (cup insert).
The materials of which the prostheses are made are generally metal alloys in titanium (which is the material with the mechanical characteristics – the so-called elastic module – most like bone). The sliding surfaces, subject to friction, have to reduce wear as much as possible and are normally made of metal alloys (chromium – cobalt – molybdenum), ceramic and plastic (polyethylene) materials.
Before embarking on a hip replacement, the Orthopedic Surgeon will illustrate the technique to be used and will explain the pros and cons of the procedure. A careful evaluation of the general health conditions is indispensable for reducing the risk of severe complications.
Therefore, blood tests will be run as well as an electrocardiogram, a chest x-ray and any other specialist exams deemed necessary (ex. cardiology, vascular, etc.).
Any dental problems (especially abscesses), acute or chronic urinary tract or other infections will need to be carefully evaluated and treated in order to avoid the most pernicious complication: periprosthetic infection.
The access routes for implanting a hip prosthesis are varied; minimally invasive approach, where possible, can reduce recovery times.
Hip rehabilitation begins, if the general conditions allow it, immediately after surgery. A physiotherapist will teach you how to use a walker or crutches and will teach you exercises to strengthen your hip muscles. After a short stay in the hospital, rehabilitative care will continue at a rehabilitation center or at home.
Patient determination in following through with the muscle strengthening exercises and following the surgeon’s instructions is crucial to a good outcome. A return to normal life can normally be expected in 1-2 months, while a full functional recovery could require 5-6 months.
The rate of complications from total hip replacement surgery is low.
The majority of problems are negligible and easily treated. Larger complications occur in less than 2% of cases. It is still important to know and understand the risks before deciding to undergo the surgical procedure. Possible surgical complications include infections, thrombo-embolisms, dislocations and fractures around the prosthesis (peri-prosthetic).
MINIMALLY INVASIVE ANTERIOR APPROACH THR
The Direct Anterior Approach (DAA) to the hip is a minimally invasive surgical method, not widely used, which offers the advantage of saving the soft tissue, without dissecting or detaching muscles or tendons.
It was first described in the late 1800s by the German surgeon Heuter (from which it takes its name) and was taken up and utilized by Smith-Petersen and by Judet in the 20th century for the implantation of hip prostheses; modified in recent years by Matta, an American surgeon that, with the improvement and adjustment of surgical instruments, renewed interest in prosthetic implants by enhancing the characteristics of being minimally invasive.
It is a totally intermuscular and interstitial pathway that, unlike other access routes used for the implantation of hip prostheses, offers the undeniable benefits of complete tissue saving that is fundamental to early functional recovery and preservation, even after a long period of time, of the muscles that represent the engine of the joint.
Although the literature with regards to the benefits compared to other methods is discordant, cosmetic appearance, rapid functional recovery, and reduced risk of dislocation make it very appealing for both patients and surgeons.
This technique, apart from making the intervention more anatomical, allows for a faster and less painful functional recovery, reduced blood loss, fewer days of hospitalization and reduced risk of joint dislocation. The long-term benefits are those of allowing for a more natural return to normal functions and activities with respect to other surgical methods.