The MAC (Multi-Axial Correcting) Monolateral External Fixation System (Biomet/EBI) Technique: An Easier Way to Correct Deformity

The MAC (Multi-Axial Correcting) Monolateral External Fixation System (Biomet, Warsaw, IN) permits simplified acute or gradual deformity correction by applying a mechanical hinge directly to the center of rotation of angulation (CORA) with stable fixation above and below the CORA. Although application of the hinge on the CORA should correct deformity completely, failure to apply the hinge correctly may lead to residual deformity, which can be corrected by use of the MAC fixation system's 2 planes of angulation, 2 planes of translation, compression, distraction, and rotation without returning to the operating room, making time-consuming adjustments, or using computer-based systems. The MAC can be applied anywhere on the extremities from the shoulder to the hand and the hip to the foot. Office visits are similarly simple. Each visit requires only measurement of length and angular deformity on the anteroposterior and lateral x-rays. Correction is accomplished by sequentially turning one screw to lengthen 0.25 mm 4 times per day (1 mm per d), then turning another screw to correct angulation 1° 4 times per day (4°/d). Complex computer calculations are not needed for deformity correction. In this work the simple application technique and the concepts of application of the MAC are explained. It also provides some examples of application, including Blount's syndrome, femur varus, and shortness correcting length and angulation simultaneously, and 2-level correction of clubfoot.