All patients should have the usual preoperative evaluations including medical history, functional history, and physical examinations. The standard standing anteroposterior X rays may be misleading
because of the posturing of the knee with a flexion contracture. This contracture will alter the apparent remaining joint space, because the X-ray beams may not be parallel to the joint line, and the joint space will appear to be obliterated (Fig. 5.3). In addition, if there is external rotation of the knees when the X ray is taken, the apparent alignment will be misleading. Therefore, care should
be taken to have the X rays taken parallel to the tibial plateau surface and with a true anteroposterior position. In addition to alignment and joint-space aberration there will also be increased magnification from X-ray beam parallax making the templating inaccurate. These variations should be recognized during preoper-ative planning.
Accurate preoperative anteroposterior X rays are important because a tangential X ray, which shows absence of joint space, is misleading and may suggest that an arthroplasty is required. If joint space remains and the principal abnormality is soft tissue contracture, then this knee could potentially be handled by soft tissue release alone. This would be particularly important in patients who have quiescent juvenile rheumatoid arthritis or immobility contractures with preservation of articular cartilage surface.
Some surgeons have recommended preoperative casting to reduce the contracture. This can potentially make the surgical procedures easier and avoid postoperative skin and nerve complications. If the contracture is of relative recent onset and there is a soft spring to the extension endpoint, indicating potential improvement in extension, then there may be some benefit from repeated preoperative casting to reduce the contracture.
Preoperative casting can be initiated with a knee manipulation under anesthesia and casting in the extended position. The cast must be very carefully applied with padding over the patella, achilles tendon, and posterior thigh. Pressure sores must be assiduously avoided.
In one study by Convrey and associates4 46 knees in 23 patients were treated with casts with an average correction of 60%. At follow-up averaging 41 months the patients showed a general tendency for the deformity to recur. However, the original deformity was maintained with a mean loss of only 5 to 11 degrees. The amount of correction that was obtained did not appear to be directly effected by the severity of joint destruction, precast deformity, or ambulatory status. The total degree of flexion was unchanged with the casting technique. The overall functional status was dependent on the deformity. The study acknowledged the difficulty in a retrospective review for multiple uncontrolled variables.
A variety of casting techniques have been described. These have included (1) serial casts with anesthesia; (2) removing a long anterior window from the foot, anterior tibia, and knee, with subsequently placing thicker soft padding behind the heel and calf; (3) hinges with turnbuckle extenders; and (4) traction. Most of these techniques have been described but not scientifically validated. They may or may not be appropriate for arthroplasty surgery.
There is very little written on casting for flexion contractures prior to joint arthroplasty. The number of patients that may require casting is relatively small, and there are a variety of disease processes with variable amounts of joint destruction. Therefore, it is difficult to make firm recommendations in this regard. However, our own preference is to consider casting for younger patients with recent contractures but not to utilize casting in patients who are older with fixed deformities and significant joint destruction.
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