Ligament strain and ankle joint opening during ankle distraction.

To determine the efficacy of ankle distraction and to investigate possible complications of the procedure, the strain on four ankle ligaments and the tibiotalar joint opening resulting from distraction force and various foot positions were studied. We mounted strain gauges on the deltoid, calcaneofibular, tibiofibular, and anterior talofibular ligaments of six fresh human cadaver ankles. An Acufex ankle distractor was used to apply forces of 45, 90, 135, and 180 N at 20 degrees dorsiflexion, neutral, and 10 degrees plantar flexion. The ankle distractor proved to be effective in opening the joint space for better visualization, but complications of pin bending, excessive ligament strain, and bony destruction did occur within the clinically recommended range. Based on the observed results, the safest method of distraction was to use forces < 135 N in the neutral position.

Basilar crescentic osteotomy. A three-dimensional computer simulation.

A three-dimensional computer simulation of the basilar crescentic osteotomy has been presented. The bunion deformity consists of hallux valgus, an increased first and second intermetatarsal angle, pronation of the great toe, and elevation of the first metatarsal head. Every foot is different and some may have more or less of each of the above noted components. Because the deformity is multiplanar, at least two roentgenograms are needed to evaluate the deformity. The weight-bearing, anterior-posterior roentgenogram is the principle radiograph used in preoperative planning. The use of a weight-bearing, sesamoid roentgenogram is recommended to quantify the anterior-posterior deflection and rotation of the first metatarsal head. A computer model (based on a cylinder) of the first metatarsal has been formulated. The osteotomy then was performed in a variety of scenarios in order to simulate the surgical correction. A great deal of flexibility is afforded by this osteotomy. The surgeon needs to be aware of the coupled motions that occur. That is, closure of the intermetatarsal angle may also cause head rotation, depression, or elevation. If the osteotomy is performed in an oblique multiplanar direction, then it is possible for the metatarsal head to elevate, pronate, and significantly shorten as the intermetatarsal angle is closed. If this scenario should occur, a poor surgical outcome will result. Excision of the medial eminence is recommended after the osteotomy has been completed and secured with stable fixation because of these rotational changes. The basilar crescentic osteotomy is an excellent method for correction of a marked metatarsus primus varus. It is important to pay close attention to a variety of anatomic considerations. The osteotomy must not be made in the diaphysis because of potential nonunion. There should be little dissection of the periosteum because of possible delayed union. As in any bunion surgery, it is essential to perform an adequate, distal, soft-tissue repair. Three dimensional preoperative planning is essential in obtaining correction of all components of a bunion. Specific guidelines, based on a three-dimensional computer model, are now available. An interactive computer program also is available to aid the surgeon in preoperative planning. We hope there will be better understanding of this technically difficult but highly versatile osteotomy.