BME 240

Clinical Medicine

As part of the graduate program at UC Irvine, not only do we participate in observing surgeries but we also gain insight from clinical medical professions. This website if part of an ongoing effort to expand the knowledge base and have a good reference for others to use.

Long Bone Orthopedics

This webpage will provide background on long bone orthopedics specifically Ilizarov Apparatus, and Taylor Spatial Frame and accompanying software. It is our hope that by surfing through these pages you will gain an understanding in the biology of broken bones and how these devices work and why they are needed to help repair human bodies.

 

Bone:

Bone is not necessarily a living part of our bodies, but is performs essential function aside from support. There are many parts of bone, this section will discuss the biological background of bone and why we need to maintain bone within our bodies. With 206 bones in our bodies, it is sometimes hard to prevent injury. The following sections discuss bone and different problems that can arise.

 

Components of Bone:

Cortical Bone: This is the hard outer shell of the bone that acts as a shield and adds strength to the structure of bone. Cortical bone is very dense but also brittle, this means that if our bone was pure cortical, it would be very heavy and easily damaged.

Trebecular Bone: This is the internal load bearing and shock absorption structure of bone. This mesh-like structure has the ability to "give" and slightly deform to better allow for shock absorption.

Marrow: This is the nurtient rich section of the bone that makes new red-blood cells consisting of 4% of the overall human weight. This structure is laced with blood vessels to help with transportation of these components.

Cellular components:

Osteocytes: Mature cells located within cortical bone that have the ability to sense the enviornment and send signals to osteoblasts to build new bone in a specific density and structure.

Osteoclasts: Cells that have the ability to break down bone. These cells "eat" broken or old bone that will eventually be replaced with osteoblasts.

Osteoblasts: The main cells in building new bone structures. These cells lay down new bone that is better adapted to the environment or activity of the individual.

 

Bone problems:

Aside from breaks bones can be bruised and damaged on the inside. Weakness can occur is proper nutrients are not consumed, the big one is calcium. This is called osteoporosis. If you are diagnosed with this disorder you have a higher likely hood of bone fracture due to a reduced bone mineral density. Different types of cancers (prostate or breast) can spread into the bone causing severe pain and possible fractures due to extreme weakness.

Ilizarov Apparatus:

The Ilizarov apparatus was first constructed by Dr. Gavril Ilizarov. The goal was to create a device that could lengthen or reshape limb (long) bones, and help complex break to heal more smoothly. It was first performed in the 1950's in Siberia and came to the West (Italy) in the 1980's and around the world by the 1990's.

The device was designed around a shaft bow harness, originally built from bicycle parts.

This modular device is constructed from stainless steel rings. These rings are affixed to the bone above and below the break. The rings are connected together through tension wire and rods. This allows force to be transferred through the outer rings as opposed through the damaged bone.

This device allows for the correction of broken bone but allows bone to be straightened by rebreaking a poorly healed site. Aside from fixing breaks, this device allows for the lengthening of limbs at roughly 1 mm a day.

This device is not very easy to work with but still allows the patient to remain active. As you can see in the image below, screws and nuts are used to provide the support. These are not easy to manipulate to fix and straighten the bone.

http://upload.wikimedia.org/wikipedia/en/f/f6/Ilizarov2.jpg

Taylor Spatial Frame:

The Taylor Spatial Frame is a device created by Dr. Charles Taylor and presently produced by Smith and Nephew. This is a stream line version of the Ilizarov Apparatus that has many benefits in terms of use and functionality.

The Taylor Spatial Frame is a hexagonal ring system that still requires screws to be implanted above and below the injured area. This device requires only 2 screws at each site but doctors prefer to insert 3 for added stability.

From the picture below, it is easy to see how this device has become the for runner over the Ilizarov Apparatus. There are only two rings instead of 4 or more rings. The struts are the key to making this new design even stronger. 6 struts allow the device to cover basically all degrees of freedom. This is the same technology that is used on flight simulators (patent holder, US Air force).

Smith and Nephew's could not patent the device so instead they patented the software that goes with the device. The doctor enters the patient information, the position of the bone and what components of the Taylor spatial frame were used. The initial settings of the struts are entered. The end goal is also entered whether it is straightening or lengthening to a specific dimension. The software links to a supercomputer that is able to compute an individual treatment plan for the patient. The images below show how powerful this software is and the reason why people pay to be able to use this advanced device. It is also why Smith & Nephew are leading in terms of providing orthopedic care for long bone injuries.

This image shows the entering of the initial deformation.

This image shows the selection of components used on the patient. The rings are selected at the top and then each of the six strut sizes are selected, from 91 mm to 311 mm. There are two styles of struts that can be used, the "Fast Fix" struts have a sliding and self locking mechanism that allows for quick easy placement to the proper length.

This images shows where the doctor enters in the frame position in relation to the leg. The more perpendicular to the bone, the easier it is for the computer to compute.

This image shows the computed placement of the Taylor Spatial Frame on the patients leg. Notice the deformity and how the device can conform to it.

Once the initial settings are confirmed against CT and x-ray, the final outcome is computed. This is a check to make sure that the rings and struts do not make contact with the limb.

This is where the doctor enters the prescription for the patient. The key entry is in blue, the "Correction Time." Once this is selected, the supercomputer will compute the most efficient way to reach the end goal.

The treatment plan above shows what each strut should be set to each day. This is an example of a 10 day treatment plan which requires strut 3 to change to another size (medium to long). This treatment is very easy to follow. The patient makes the required adjustment at home and is only required to enter the clinic if a strut change is required.

A final report is generated that summarizes the whole procedure from initial settings to treatment plan. It tells which parts were used and when changes need to be made.

 

Future Applications:

A device has been published (not commercial yet) that shows a motorized version of the Taylor Spatial Frame. This device is connected to a computer that controls the motors and 1:100 gear ratio that allows for micro movements, specifically 156 sequential steps daily.

The old way of fixing badly broken bones.

The upgraded versions that has 6 motors and allows the patient some mobility. Once the computer is minimized, this will be a great addition to long bone orthopedics.

K Seide, M Faschingbauer, M E Wenzl, N Weinrich, C Juergens. A hexapod robot external fixator for computer assisted fracture reduction and deformity correction. Int J. Medical Robotics and Computer Assisted Surgery 2004;1(1):64–69

Image Gallery:

The following are images of Taylor Spatial Frame Orthopedics:

Taylor spatial frame adapted for long bone and ankle alignment. (http://www.nationalreviewofmedicine.com/images/issue/2006/issue07_apr15/3_leg_lengthen_7.jpg)

A comparison between the actual device and the x-ray image, notice the broken bone in the x-ray and the wound area on the skin. Even with a severe break, the device holds the bone in proper alignment. (http://www.informaworld.com/ampp/image?path=/713400243/757972022/sort_a_000772_o_f0001g)

This device has the ability to straighten out extremely crooked bone. (http://www.boneguru.com/Site/Welcome_files/IMG_1856.jpg)

 

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