Smaller External Fixator Tested for Elbow Injuries
Elbow dislocations are often accompanied by injuries to the ligaments. These ligaments support the joint so an injury can leave the elbow unstable. Sometimes an external fixator (frame with pins) is used to maintain joint stability while still allowing motion. The goal is to give the ligaments a chance to heal but prevent joint stiffness.
Fixators commonly used are large and rigid. They keep the elbow joint from sliding from side-to-side during motion. This is called varus and valgus motion. Normally the intact ligament would prevent this motion. But until the ligament heals, the joint is at risk. The unstable joint can't handle varus or valgus stresses.
In this study, six cadaver elbows are used to test a small, unilateral, articulated external fixator. Articulated means it has moving parts that allow joint motion. Patient using the larger, rigid frames often end up with a stiff elbow that doesn't move normally. The smaller fixator may work better.
The elbows were damaged to simulate a ligament injury on either side of the joint. Each elbow was tested for side-to-side motion under three loading conditions. The first test was with just the weight of the hand. The second was with a weight equal to a 12-oz drink. The third test doubled the load to 24 oz.
An electromagnetic tracking system recorded the elbow motion. Then the fixator was applied. Motion was tested again. Testing was done under the same three loading conditions.
The authors report the smaller, moveable fixator does protect the soft-tissue injury from both varus and valgus displacement loads. The fixator did give enough rigidity to decrease the force on healing tissue. The amount of load acceptable was still limited to 12 ounces. This restriction is the same as for the larger, bulkier fixators.
References: Srinath Kamineni, MD, et al. Effectiveness of the Lateral Unilateral Dynamic External Fixator After Elbow Ligament Injury. In The Journal of Bone and Joint Surgery. August 2007. Vol. 89-A. No. 8. Pp. 1802-1809.
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