External fixation overview and princibles

basic principles of Ex. Fix

1. External Fixation Overview and Principles Dr. Ahmed AbdelGhani Alkhateeb M.SC. (ORTHO.) , M.R.C.S. ( GLASGOW - U.K.) C.P.H.Q. , L.R.S. – P.D.

2. Objectives: Identify the indications and contraindications of external fixation. Describe the equipment, biomechanics, and technique in regards to external fixation. Review appropriate evaluation of the potential complications and clinical significance of external fixation. Explain interprofessional team strategies for improving care coordination and communication to advance external fixation treatment and improve outcomes.

3. Introduction: External fixation used to treat fractures for more than 2000 years as a way to immobilize the fracture while preserving soft tissue integrity. The fixator design and biomechanics have changed dramatically over the years, but the principles remain the same. The primary goal of external fixation is to maintain the length, alignment, and rotation of the fracture.

4. Introduction: External fixation can serve as provisional fixation or definitive fixation purposes. Both methods can be performed in conjunction with partial internal fixation if necessary. It is important for orthopedic surgeons at a trauma center to be familiar with the techniques and principles of external fixation for various fractures of the upper extremity, lower extremity, and pelvis.

5. Factors Affect Construct Stiffness and Stability: One method of changing the stability is to alter the pin configuration. Placing pins closer to the fracture site, adding more pins and increasing the spread of the pins will all add to the stiffness of the construct. However, one must also place the pins out of the field of future surgical approaches during definitive fixation.

6. Factors Affect Construct Stiffness and Stability: Any increases in pin diameter will strengthen the construct to the fourth power and reduce the stress at the bone-pin interface. Increasing pin diameter has the greatest influence on the stability of unilateral frames. Larger pins increase the risk of a potential stress riser and can ultimately lead to fracture. For example; a 5 mm pin is 144% stiffer than a 4 mm pin.

7. Factors Affect Construct Stiffness and Stability: Another way to change the strength of the construct is to increase the diameter of the rods or secure it closer in proximity to the bone. One can also add multiple bars to the same pins to enhance stability. Bars get secured to the pins by clamps. The most common material for bars today is carbon fiber, which is 15 % stiffer than stainless steel bars.

8. Types of External Fixator: External fixator types divide into several different subcategories, including uniplanar, multiplanar , unilateral, bilateral, and circular fixators. By adding pins in different planes (i.e., placed perpendicular to each other), one can create a multiplanar construct. Uniplanar fixation devices are fast and easy to apply. Bilateral frames are created when the pins are on both sides of the bone and can also add additional stability.

9. Types of External Fixator: Circular fixators have gained popularity with limb lengthening procedures but are especially effective at allowing the patient to weight bear and maintain some joint motion during the treatment. They are more difficult to apply and use smaller gauge pins and more of them to distribute the weight.

10. Types of External Fixator: There are many different ways to change and enhance the external fixation construct. To complicate things further, there are also hybrid frames which are a combination of any of the previous constructs described. The surgeon must create a level of stability that is appropriate for optimal healing. It is essential also to have a good understanding of basic fracture principals because stiffer is not always better when it comes to external fixation.

11. Clinical Significance: External fixation plays a vital role in fracture care today. Not only can it temporarily stabilize fractures, but it can provide definitive fixation as well. The use of external fixation in a damage control setting can prevent the so-called “second hit” phenomenon because of the quick application, decreased blood loss, and minimally invasive application. Furthermore, by giving time for the soft tissues swelling to subside in severe injuries, the risk of infection and wound complication proportionally decreases.

12. Biomechanics :   Maximizing pin size, pin number, pin separation, pin proximity to the fracture, bone to clamp/bar proximity, and the diameter of the pins/connecting rod optimizes frame stability. The ideal position for pin placement is a near-far construct with a pin placed close to the fracture site on both sides and a pin placed as far away as possible on each side of the fracture. Stiffness is also increased by double stacking the connecting rods.

13. Pin Care :   Up to 10% of external fixation pins develop signs of infection. Care must be taken to avoid pin site infection or loosening. Loose pins should be removed and replaced, if necessary, to maintain fixator stability.

14. Indications: Clinicians use external fixation in orthopedic trauma, pediatric orthopedics, and plastic surgery for an array of different pathology. Below are a few of the indications for external fixation devices: Unstable pelvic ring injuries. Comminuted periarticular fractures such as pilon, distal femur, tibial plateau, elbow, and distal radius fractures. Fractures with large amounts of soft tissue swelling. Fractures in a patient that is hemodynamically unstable or cannot undergo an open procedure.

15. Indications: Comminuted long bone fractures. Fractures with significant bone loss. Open fractures with soft tissue loss. Limb deformity and limb lengthening. Osteomyelitis with bone loss.

16. Indications: Immobilization of joint after soft tissue flap. Arthrodesis. Nonunion. Malunion. Infection. Traction to aid in intraoperative fracture reduction.

17. Contraindications: External fixation is a relatively safe minimally invasive procedure and can provide significant benefit to the patient when used in the correct setting. There are limited contraindications for its use in orthopedics. Relative contraindications include an obese patient where safely placing pins would be difficult.

18. Contraindications: A non-compliant patient is a relative contraindication because he or she may not follow up for the removal of the device. Peri-prosthetic fractures can limit the bone stock available to place the pins. General contraindications include patient refusal, unable to withstand the procedure physiologically.

19. Complications: The following list includes complications that can occur with external fixation treatment: Pin site infection. Osteomyelitis. Frame or pin/wire failure or loosening. Malunion. Non-union. Neurovascular injury. Compartment syndrome. Refracture around pin.

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