Osseointegration

Introduction

Osseointegration, also known as direct skeletal fixation, is a surgical procedure that involves fitting a metal implant directly into the residual bone of an amputee and connecting an external prosthesis to it, thereby avoiding the necessity for a conventional socket-mounted prosthesis. Surgery can be performed in one or two stages, depending on the type of implant system involved. Osseointegration aims to provide improved mobility and function and quality of life to individuals who have undergone amputation.

Types

The 2 types of commonly used osseointegration systems include:

• Screw Shape Prosthesis or OPRA Implant System: In this type of osseointegration system, the titanium prosthesis has a screw design and a relatively short length and is basically derived from dental implants. The titanium screws need a fairly long time for solid osseointegration, and the rehabilitation period until full weight-bearing is usually long, consisting of 6 to 12 months. Another drawback of this system is that the distal abutment is relatively weak, and the implant may become loose, resulting in breakage or bending during daily activities.
• Press-Fit Prosthesis or ILP Implant System: The design and implantation technique of this type of osseointegration system was derived from orthopedic hip prostheses. This prosthesis comprises a 3D tripod surface structure with a chrome cobalt molybdenum alloy rod. The osseointegration capacity of this type of prosthesis is good and can bear more load than the screw shape prosthesis. The latest generation press-fit prostheses are made of titanium alloy rods with a rough surface. This titanium prosthesis has similar qualities to current orthopedic implants; solid and strong. The osseointegration period is quicker, lasting about 6 weeks, and the rehabilitation period is brief.

Who is a Good Candidate for Osseointegration?

You are a good candidate for osseointegration if you:

• Are uncomfortable with the use of conventional socket prostheses due to pain, skin problems, and perspiration
• Have difficulty with sitting, standing, or walking with the use of a prosthetic socket
• Have fitting issues with the use of prosthetic sockets
• Have obtained full skeletal maturity
• Have normal skeletal anatomy
• Are between 18 years old and  70 years old
• Have met the criteria for surgery based on your medical history and physical examination
• Are willing to comply with the treatment recommendation and subsequent follow-up

Who is Not a Good Candidate for Osseointegration?

You are not a good candidate for osseointegration if you:

• Are diabetic
• Have severe peripheral vascular disease
• Are pregnant
• Have exposed your legs to radiation
• Have osteoporosis
• Have a bodyweight of more than 100 kg, about 220 pounds
• Are a smoker
• Have skin disorders involving the amputated leg
• Have a mental illness or psychotic disorder
• Are satisfied with conventional prosthetic sockets

Preparation

Preoperative preparation for osseointegration may involve the following:

• A thorough history and physical examination
• Routine blood work and imaging
• Refraining from blood thinners, aspirin, or NSAIDs
• Informing your doctor of any allergies to medications, anesthesia, or latex
• Refraining from solids or liquids at least 8 hours prior to surgery
• Arranging for someone to drive you home following surgery
• Signing a consent form after the risks and benefits of the surgery have been explained

Procedure

Osseointegration is performed under anesthesia and involves the following steps:

• X-rays and CT scans of the limb are taken to determine exact measurements  for a custom-made implant built to fit inside the bone.
• The implant is created and placed into the residual limb bone through an incision.
• Any adjustments that need to be made to the bone length and soft tissue are addressed.
• The wound is closed after implantation.
• A small surgical cut is then made and a connecting adapter of the osseointegration prosthesis is placed through this incision into the implant. This point of skin penetration is called a stoma.
• The skin is then closed with sutures.

Postoperative Instructions

Following surgery, you will be transferred to the recovery area where you will be observed for 3 to 5 days and then discharged. Your doctor will provide you with instructions on how to clean the stoma site. The prosthesis will be arranged for connection with the osseointegrated implant by your prosthetist. One week after surgery a rehabilitation protocol is started daily in the rehab department. You will be taught how to load the prosthesis and how to walk with the crutches. The rehabilitation protocol will last anywhere from 3 to 5 weeks based on whether the individual is a below-knee or above-knee amputee. You need to continue doing exercises daily at home before you can fully bear weight on the osseointegration prosthesis without crutches.

Benefits

Some of the potential benefits of osseointegration include:

• Eliminates the need for prosthetic sockets
• Reduced pain or irritation when compared with prosthetic sockets
• Enhanced stability with standing or walking
• Able to walk long distances
• Enhanced sitting comfort
• Minimal skin complications
• Osseoperception - a more natural feeling with the ability to feel or sense the prosthesis
• Improved quality of life

Risks and Complications

Some of the potential complications of osseointegration include:

• Skin or deep tissue infection
• Soft tissue impingement
• Periprosthetic fractures
• Failure of osseointegration, needing implant revision
• The need for regular maintenance
• Limitations on participation in high impact sports

Summary

Osseointegration represents a significant change from the traditional method of fitting a prosthetic socket to a residual limb, which has been the traditional approach for hundreds of years. Once an option for only those with above-knee amputations, the osseointegration technique is now being increasingly used to treat below the knee as well as upper limb patients.