Total hip replacement
The goal of a total hip replacement is to eliminate pain, restore function, and improve the quality of life for patients suffering from osteoarthritis or other hip-related problems. This goal was originally achieved in the 1960s, and significant progress has been made since then.
Hip replacement is now a very common surgical procedure with exceptional clinical results. In an arthritic hip, the femoral head is replaced with a ceramic ball placed on a stem (cemented or not) in the femur and articulated with a cup containing a ceramic or polyethylene insert. The system is secured with a press-fit (interlocking) on the acetabular aspect.
CERAMIC-ON-CERAMIC PROSTHESIS
Ceramics were introduced in 1970 in hip surgery. The first to use was Pierre Boutin, in France, and after him Mittelmeyer in Germany. The aim was to reduce the production of wear particles in order to achieve better results with young patients. Since then, more than 300,000 ceramic prostheses have been implanted worldwide. Initially, numerous problems were encountered due to both ceramic fractures and osteolysis in the bone/prosthesis interface. However, other large-scale scientific studies reported more optimistic results. The first plants of this type failed, not only because of the poor quality of ceramic (oxidized aluminum), but also for the shape of the implants and surgical techniques, perhaps still too rudimentary. The most significant feature of ceramic coupling on ceramics is its biocompatibility as well as its inert nature. Under normal circumstances (ideal biomechanical circumstances after implantation), the wear of the prosthetic components is minimal. The biological reaction is minimized and consists of the presence of fibrous tissues with a very small number of macrophages and giant cells. However, when mechanical conditions are impaired, such as in cases of fracture or mobilization of prosthetic components, there will be a more important biological reaction caused by a larger number of wear particles. Thanks to the progress made in terms of the mechanical properties of ceramics, to more suitable forms of today’s prostheses and to more advanced surgical techniques, the old problems encountered with ceramics have been overcome, so the choice of ceramic coupling on ceramics is the most advantageous. What’s more, this mating is one that boasts the longest survival rate with young patients (50 years). Currently, the risk of rupture of a pottery prosthesis is less than 1 in 200,000, compared with an initial risk of 1%. Squeaking in total hip prostheses is a described phenomenon and is a characteristic of the tribology of this type of material. It becomes audible to the human ear as a complication only in the medium to long term from the system implantation. Although very rare, it is attributable, in most cases, to an optimal sub-positioning of the acetabular component, concomitant with a lubrication defect of the prosthetic components and a particular design of the femoral stem. The latter component is the one that causes a tuning fork effect on the system that produces audible noise frequency to the human ear. Using a correct surgical technique in component positioning and a choice of implants with an adequate design, the risk of the development of this phenomenon stands at around 0.1%.
Hip resurfacing
Hip resurfacing surgery is the closest approach to the natural hip:
– greater bone saving
– better recovery in biomechanics
– more natural feeling
– greater opportunities to practice impact sports
– normal recovery of gait
Hip resurfacing is a hip resurfacing procedure consisting of two hemispherical steel plates that cover the joint. The difference with traditional hip replacement surgery is that it is non-invasive, meaning it doesn't affect bone tissue. Degenerative hip problems, in most cases, affect the cartilage. Therefore, hip resurfacing replaces the cartilage, both on the acetabular and femoral sides, creating a new load-bearing surface.
I PRO 1) Pattern di camminata più normale Gli studi hanno dimostrato che i modelli di deambulazione sono più naturali dopo il rivestimento dell'anca rispetto alla tradizionale sostituzione dell'anca. Nell'analisi dell'andatura sono stati osservati anche un aumento del carico sull'anca e un miglioramento della spinta. I pazienti riferiscono inoltre che il rivestimento dell'anca risulta molto naturale. 2) Maggiore stabilità e maggiore attività Poiché la dimensione della sfera e dell'incavo è simile a quella dell'anca originale, il rischio di lussazione è molto più basso per il rivestimento dell'anca rispetto alla sostituzione totale dell'anca convenzionale, anche nelle attività che richiedono un'ampia gamma di movimenti come il surf, il tennis e il calcio . Il rivestimento dell'anca utilizza superfici portanti resistenti agli urti e all'usura che sono più adatte a richieste di attività più elevate. Questo vale per il tradizionale impianto di rivestimento metallo su metallo e per il nuovo impianto ceramica su ceramica. Questo, insieme alla preservazione dell'osso, fa sì che i pazienti con rivestimento dell'anca siano più in grado di tornare ad attività come la corsa e gli sport d'impatto. 3) Conservazione e revisione dell'anca The PROs 1) More normal walking pattern Studies have shown that walking patterns are more natural after hip lining than traditional hip replacement. In the gait analysis, an increase in the load on the hip and an improvement in the thrust were also observed. Patients also report that the hip lining is very natural. 2) Greater stability and more activity Since the size of the sphere and socket is similar to that of the original hip, the risk of dislocation is much lower for hip lining than the total replacement of the conventional hip, even in activities that require a wide range of movements such as surfing, tennis and football. The hip coating uses shock and wear-resistant load-bearing surfaces that are more suitable for higher task demands. This applies to the traditional metal coating system on metal and the new ceramic plant on ceramics. This, along with bone preservation, causes patients with hip coating to be better able to return to activities such as running and impact sports. 3) Hand preservation and revision A hip lining preserves a greater part of your natural bone. Because the components (called implants) used in hip replacements and hip lining are mechanical parts, they can wear or loose over time and require a second operation called overhaul. If you need to review a hip prosthesis in the future, preserving this bone makes the procedure much easier and is similar to performing a standard total hip replacement.
THE AGAINST If the surgery is performed by an experienced surgeon, the cons are slim. There is a possibility of hypersensitivity or allergic reactions to the components of the metal alloy, and to a possible suffering of the head of the encapsulated femur. The risks are around 1% globally. The abnormal wear caused by a malposition of all the prosthetic systems involves complications: in the case of polyethylene (currently the one most used in the world) the polyethylene disease can be verified, in the case of ceramics it can be had the rupture of the device and in the case of the metal you can face metaly. The substantial difference is that only with the latter system there are measurable markers (dosage of chromium and cobalt in the blood) to intercept an abnormal wear and tear early, in the other systems the problem is detected clinically only when the damage has already been established.
The patient suitable for resurfacing:
Until recently, hip resurfacing was reserved for young, active men with femoral heads greater than 50 mm in diameter. This was due to the high failure rates observed with metal-on-metal resurfacing in women and patients with small femoral heads.
With the introduction of ReCerf, a ceramic-on-ceramic implant, these limitations can be removed and the resurfacing can be offered to all active patients. The only remaining limitations are patients with very severe dysplastic hips (abnormal shape) or severe avascular necrosis, in which the femoral head bone is dead and cannot support the resurfacing implant.
The patient suitable for resurfacing:
Until recently, hip resurfacing was reserved for young, active men with femoral heads greater than 50 mm in diameter. This was due to the high failure rates observed with metal-on-metal resurfacing in women and patients with small femoral heads.
With the introduction of ReCerf, a ceramic-on-ceramic implant, these limitations can be removed and the resurfacing can be offered to all active patients. The only remaining limitations are patients with very severe dysplastic hips (abnormal shape) or severe avascular necrosis, in which the femoral head bone is dead and cannot support the resurfacing implant.
Resurfacing ceramica su ceramica
Hip replacement revision
When one or both of the prosthetic components are worn or loose, they need to be replaced. This is called an implant revision.
There are various reasons for the loosening of prostheses:
– osteolysis (bone resorption) induced by polyethylene particulates;
– infection (septic);
– fracture (for example from a fall).
Revision surgery involves a longer and more difficult surgery with higher complication rates than an initial prosthesis implant.
Triplanar acetabular osteotomy
Hip dysplasia is a disease that develops at birth or in the first few years of life, most commonly in females.
Hip dysplasia can therefore be of genetic origin but can also develop as a consequence of other hip joint diseases, such as Legg-Calvé-Perthes syndrome.
This condition is bilateral in 50% of patients. In most cases, the disease is diagnosed between the ages of 15 and 30, but symptoms can appear earlier or later in life.
In patients with hip dysplasia, the acetabulum does not develop a matrix over the femoral component and therefore will subsequently not provide adequate coverage for the femoral head to correctly distribute loads during walking.
When in these patients, dysplasia in the absence of advanced coxarthrosis causes painful symptoms and constant discomfort in daily life and further increases the functional demand, it is possible to resort to the intervention called PAO (periacetabular osteotomy), also known as Ganz triplanar osteotomy.
During the operation, the acetabulum is partially detached from the pelvis so that it can be reoriented and thus create greater congruence/coverage of the femoral head.