High precision minimally invasive hip prosthesis: Femur First and Osirix

Even in Italy, the protocol is starting to be appreciated Fast Track Surgery applied in minimally invasive surgery for the implantation of hip prosthesis e kneeThe 'fast track', the rapid intervention, incredibly reduces hospitalization times (from 7-8 days for traditional surgery to 2-3 days), rehabilitation, and recovery. Speed ​​aside, what are the innovative techniques that aim to achieve increasingly precise prostheses and customized?

In reference to minimally invasive hip replacement, the answer to this question is: let's talk about technique Femur First and software Osirix.

Minimally invasive hip replacement: the only solution for debilitating coxarthrosis

Before describing in detail the two techniques that allow the highly specialized surgeon to 'design' custom-made and extremely personalized hip prostheses, let us briefly recall what the advantages of minimally invasive prosthesis which solves the coxarthrosis (hip osteoarthritis) disabling.

Hip replacement is also necessary in cases of femoroacetabular impingement, rheumatoid arthritis, and avascular necrosis, all disabling conditions.

The possibility of implanting a hip prosthesis is evaluated when the conservative treatments (drug therapy, infiltration, physiotherapy, regenerative medicine) no longer have any effect on the symptoms of the patient who suffers from significant pain, stiffness, and severe limitations in joint movement.

In these cases, the only curative therapy involves replacing the cartilage and bone damaged by osteoarthritis with a minimally invasive prosthetic implant to relieve pain and restore joint function.

Before performing the surgery, the specialist will have to evaluate essential factors for choosing of the most suitable prosthesis: age, health status, daily activity, particular allergies to metals, etc.

The advantages of minimally invasive prosthetic surgery

It all comes down to thanks to the minimally invasive surgical technique:

• Times of intervention, hospitalization, rehabilitation, recovery;
• Trauma (swelling, pain, blood loss during and after surgery);
• Friction between the elements of the femoral head and the ceramic acetabulum;
• Incision and scarring thanks to the small size of the prosthesis;
• Administration of painkillers after surgery;
• Risk of infections and dislocations.

Minimally invasive surgery respects most the bodyHealthy tissue (muscle, bone, and soft tissue) is preserved as much as possible. The surgeon's goal is to preserve as much of the femoral neck, nerves, and periarticular structures as possible. Muscle, cartilage, and bone are not sectioned but rather separated with an incision margin of only 8 cm, also to minimize the risk of dislocation.

Thanks to minimally invasive surgery, the classic complications Post-surgery complications (infections, dislocations, joint stiffness, vascular complications) are reduced to the bone. They occur rarely (in 1-3% of cases).

These types of procedures are 95% successful. Patients generally resume normal daily activities 2-4 weeks after surgery.

Minimally invasive hip prosthesis lasts 20-25 years, sometimes even 30 years.

Long-lasting hip prosthesis: advanced materials and high-precision planning

With which materials is a hip prosthesis made? These are advanced materials, extremely resistant and biocompatible: titanium, ceramic, polyethylene with vitamin E, tantalum.

To make the minimally invasive biologically anchored hip prosthesis last as long as possible, it is necessary to follow a proper lifestyle, just as you should do for your natural hip: maintain a normal weight, practice physical activity, avoid excessive strain, etc.

Technically speaking, the duration of the prosthetic implant also depends a lot on the precision with which it is 'drawn' based on the patient's anatomy and the skill with which it is positioned during surgery.

We have arrived at the heart of our study: the two high-precision techniques for best designing the hip prosthesis.

Femur First Technique: the femur, first and foremost

Let's start with the Femur First technique that most experienced orthopedic surgeons use for hip replacement implantation.

Femur First, in English, means 'the femur, first'. The specialist works first on the femur, then on the acetabulum: all this serves to prepare a more targeted, precise operation, resistant to wear and tear and dislocation. The aim is to create a more anatomical hip prosthesis possible.

This is a 'navigation' technique that allows you to work more efficiently. precision and accuracy in reference to the working angle (between the femoral and acetabular portions). It allows for the final length of the limb to be calculated with maximum precision.

I advantages of the Femur First technique there are essentially two:

• Reduce the size of the prosthesis even further;
• Get the two legs to be the same length.

Digital hip replacement planning: OsiriX software

At the moment, the OsirisX software It is used to 'design' the minimally invasive hip prosthesis, not the knee prosthesis. It allows the surgeon to design a custom-made prosthetic implant as if he were a tailor of the human body. He performs the digital planning In the pre-operative phase, it allows for the precise reconstruction of the hip joint geometry, maximally customizing the prosthesis, shaping it based on the patient's unique joint structure and anatomy. Because each of us is unique. For once, it's the prosthesis that must adapt to the patient, not the other way around.

The digital program OsiriX Dicom Viewer uses different parameters to allow the prosthesis to be designed based on the patient's x-ray. It is wrong to think of using a single hip prosthesis model that can be adapted to anyone. Everyone has their own pathological and anatomical history.

With OsiriX the specialist can choose from a wide range of prosthetic models to focus on the one best suited to the anatomy of each patient.

How does OsiriX work?

OsiriX software displays X-ray images DICOM (CT, PEC, Magnetic Resonance, etc.) taken from CDs or hospital PACS systems. It interfaces with the GAP II, the patient clinical and surgical data archiving system.

By managing DICOM images, the surgeon has the possibility to perform 3D reconstructions very precise.

I templates (transparent transparencies) containing the graphics of the major prosthetic models are superimposed on the radiograph of the pelvis. Through accurate measurements a project is obtained that will be valuable for the surgeon in the operating room. From the OsiriX planning, the dimensions and alignments of the prosthetic components to be used will emerge, the hip prosthesis model to be adapted to the anatomical structure of the subject, any pelvic dismetries, etc.

Some more data on OsiriX

The initial version of the software dates back to 2014 while the official one is dated September 14th 2017.

OsiriX is a medical imaging software that 'runs' with the operating system MacOS and iOS: it is applied, specifically, by nuclear medicine experts. If it is true that it is compatible with the DICOM standards It is also true that it can view many other formats including JPEG, TIFF, PDF, AVI, MPEG, QuickTime.

This system functions as a DICOM imaging workstation and image processing software for nuclear, molecular, radiological, functional, 3D imaging research.

Il 3D viewer allows all the most modern modes of rendering (volume, surface, projection, multiplanar reconstruction) capable of merging two different series. OsiriX goes beyond 3D. It was developed to create, navigate and display highly detailed multidimensional images: not only 2D and 3D but also 4D (3D + time dimension), 5D (3D + temporal and functional dimension).

It is possible to apply selective filters To subtract anatomical portions such as bones or blood vessels from the three-dimensional image. The extracted images can be used to create useful animations, such as heartbeats, for accurate investigations of the patient's health.

edited by Dr. Michele Massaro