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Hip diseases

Hip joint : the hip joint consists of two anatomical parts. The acetabular side (cup) and femoral side (head). The capsule, ligaments and strong muscles link both sides of the joint.

Medullar cavity : central part of the femur that is having the femoral implant. The medullar cavity has a complex shape, it is borded by the cortical bone. Anatomical variations of the medullar cavity are at the origin of adequacy issues with the design of the implant. The customized femoral implant follows a design very similar to the actual medullar cavity.

Cortical bone : the femur is similar to an empty tube whose wall is the cortical bone. Depending on the thickness of the femur cortices, the medullar cavity is more or less wide which requires an adaptation of the rod's design. Thickness of femoral cortices differ according to age, bone metabolism and femoral neck tilt.

Neck/Shaft angle : the angle made by the femur's main axis (femoral shaft) and the femoral neck varies from one person to another. If the implanted femoral rod shows a different angulation from the femoral anatomy, it will generate an alteration of both the hip's muscle balance and the length of the lower limb.

Femoral anteversion : the femoral neck goes frontward, at an angle of 20°. However, anatomical variations are frequent, between -5° (retroversion) and +50°(hyper anteversion). 3D planning enables to measure the femoral anteversion and plan the femoral rod anteversion. If the implant anteversion is not well adapted to the hip anatomy, it will result in a rotation impairment.

Coxarthrosis : Mechanical deterioration of the hip joint caused by cartilage degeneration, bone spurs (ostheophytes), adjacent bone condensation and minor focal degeneration (geodes). Treating coxarthrotis is based on the whole hip implant.

Anatomical variations : The hip morphology, shown in 3D, is complex and varies from one individual to another. Since the beginning of hip implant history, surgeons and implant makers have always tried to adapt the shape and the position of implants to the patients' needs. Today, different responses to this demand are possible: either by multiplying implant types and sizes or by designing a customized implant if the situation requires it.

Malformation : hip malformations represent a risk factor of early ostheoarthritis. The risk is increased in case of intensive sports training. The hip malformation makes the implant insertion even more complicated, which can lead to the use of a customized implant.

Dysplasia : still called insufficient coverage, dysplasia is a general malformation of the hip that is often related to femoral morphological abnormalities such as coxa valga (femoral neck put into vertical position) or torsion disorders (anteversion excess of the femoral neck). The customized implant is the answer to such malformations.

Dysplasia : still called insufficient coverage, dysplasia is a general malformation of the hip that is often related to femoral morphological abnormalities such as coxa valga (femoral neck put into vertical position) or torsion disorders (anteversion excess of the femoral neck). The customized implant is the answer to such malformations.

Coxa Vara : lack of femoral neck tilt compared to the main femur axis (neck horizontal straightening)

Genetics : there's a genetic component to coxarthrosis. Some families are subject to early joint degeneration, especially in the hip area.

Sport : intensive practice of some sports increases the risk of early hip athrosis. Martial arts, football, rugby, dancing and many other sports inlvolving wide moves, pivots and impacts are concerned.

Operative indication : choosing to insert a hip implant is the result of a dialogue between the surgeon and patient, after clinical and radiological tests. The implant is a radical solution that is chosen when medical or conservative solutions are not satisfying enough.

Fracture : after a femoral fracture, the medullar cavity morphology can be much impaired. Fixing a standard implant can be complex and risky. Designing a customized rod is a good solution in case of femoral malunion.

Femoral implant : metal rod made of an intraosseous main axis (tail) and a secondary extraosseous axis (neck) which is surmounted by the femoral head.

Acetabular implant : semicircular cup to be fixed on the pelvis. Synonyms: cotyloidal implant, cotyloidal cup, prosthetic joint.

Modularity : use of several elements to constitute the femoral rod making sure it matches the anatomy of the operated hip. Historically, the first femoral rods were in on piece, then modularity concerned the head (rod in two pieces), then the neck (rod in 3 pieces).

Standard implant : every hip implant maker offers a catalogue that includes different sizes and sometimes different implant types. It is up to the surgeon to plan the implant the most adapted to the patient's morphology and foresee the implant placement in conformance with the pre-operation objectives. In case of inadequacy to the patient's morphology, the customized implant is a good way to restore the anatomy.

Pre-operation planning : before placing a hip implant, planning enables to figure out the implants' size and position.

2D Planning : use of X-rays and layout tracing to choose the right implants for the hip. 2D planning has its limits: lack of knowledge in the actual size of bone structures (X-rays is the projection of an image with unpredictable magnification ). Also, 2D planning does not enable the measurement of the hip rotational component (anteversion or retroversion). At last, 2D planning does not provide information about bone volume and more particularly the exact shape of the medullar cavity.

3D Planning : use of a scanner to choose implants adapted to the hip. Like industrial engineering techniques, 3D planning use the implants' volume models. 3D planning is conducted at real scale while taking into account the hip rotational component (anteversion or retroversion) and the actual intraosseous anatomy.

Risk : every implant placement is associated with risks of different nature: mechanical risk, infectuous risk, anaesthetic risk... "zero risk" does not exist. 3D planning associated with a customized implant enables to reduce the risk of mechanical complication in case of unusual coxo-femoral morphology.

Extension : Placing a hip implant enables to change the length of the lower limb. The hip extension can be planned to compensate the joint deterioration caused by arthrosis. The extension is sometimes unintentional, which turns up to be a surgery complication. 3D planning associated with a customized implant placement increases the acuracy of the implant placement.

Shortening : while placing the hip implant, shortening the hip can generate a muscle impulse and a risk of dislocation. 3D planning associated with a customized implant placement increases the acuracy of the implant placement and reduces the risk of mechanical complication.

Medialisation : while placing the hip implant, the unintentional reduction of the femoral neck lever arm (offset) generates a muscle impulse and a risk of dislocation. 3D planning associated with a customized implant placement enables to assess the pre-operation offset acurately and respect the joint anatomy restoration objectives.

Lateralisation : while placing the hip implant, the unintentional increase of the femoral neck lever arm (offset) generates a muscle impulse and a risk of post-operation pains. 3D planning associated with a customized implant placement enables to assess the pre-operation offset acurately and respect the joint anatomy restoration objectives.

Research office : all engineers working with the hip surgeon to design and make a customized femoral implant that suits the patient's anatomy and meets his/her needs.

Offer : technical file related to customized implant, designed by the research office and then modified or approved by the hip surgeon.

Approval : hip surgeon's decision to start the making of the customized implant, according to the design provided by the research office.

Cost : a customized femoral implant represents an extra cost that is only justified if the medical service provided is superior to the one of a standard implant. This is particularly true in the case of a complex hip with unusual morphology, where the customized implant can reduce the risk of mechanical failure. The professional social and financial overcharge when confronted to a hip implant mechanical failure is very important, especially when a second surgical operation is needed.

Life cycle : every implant fixed in the hip shows signs of wear that increase with time. This wear is more important among young sporty people. The customized implant does not prevent this wear but it limits the risk of early surgical operation due to inadequacy between the implant and the original hip.

Supervision : a hip implant must be continuously watched via specialised clinical and radiological checks.

3D Scanner

Implants evolution

Manufacturing stages

Life cycle of an implant

A unique object My customized hip implant Directed by Jérôme Bourdon See the video

Introduction

Chapter 1

My life before surgery Continue story with...

Hip diseases Know moreSee
3D Scanner Know moreSee

The making of the implant

Chapter 2
Implants evolution Know moreSee
Manufacturing stages Know moreSee

The operation

Chapter 3
Life cycle of an implant Know moreSee

My life after surgery Continue story with...

Bonus