134 ABSTRACTS

dried allografts, and Dacron have all been success- fully employed with this technique.

Isometric positioning of the ACL graft has been confirmed by cadaver studies, by arthroscopic vi- sualization and intraoperative testing of the graft, and on postoperative radiographs. The procedure has been performed on 102 patients, with the longest follow-up period being 42 months.

Postoperative radiographic analysis of the semi- tendinosis grafts in an initial series showed that 78% of the grafts were anatomically positioned. In a subsequent series of patients who were intraoper- atively tested for isometry, the graft placements were universally anatomic. In the initial series, the causes for the inappropriate femoral placement of the graft included the inexperience of the arthros- copist with the procedure, and failure to test the isometry of the graft at the time of surgery.

With the use of a single tunnel, graft insertion is facilitated, and because there are less bends in the graft, it appears to be better biomechanically than traditional two-tunnel techniques. It is recom- mended that the surgeon be familiar with the ab- normal arthroscopic anatomy of the anterior cru- ciate deficient knee, and that the ligament place- ment be tested for isometry prior to drilling the bony tibiofemoral tunnel.

Required Graft Prefixation Tension in Anterior Cru- ciate Ligament Reconstruction. Robert Leland and Robert T. Burks. Detroit, Michigan, U.S.A.

This study was undertaken to determine the tension that must be placed on an anterior cruciate ligament (ACL) graft prior to fixation to produce postopera- tive stability. Patellar tendon bone-tendon-bone (BTB), semitendinosis tendon, and fascia lata were evaluated.

Eight fresh cadaver knees had tibial and femoral intermedullary rods inserted and secured. The femur was secured and the tibia left unconstrained. The knee was flexed 25 ° and anterior stability was measured with the KT 1000 Knee Arthrometer. The ACL was demonstrated to be intact arthroscopic- ally, was transsected, and the knee was retested. Under arthroscopic control, guide pins were placed in the femur and tibia, and isometrically measured with a MedMetric Knee Isometer. Isometry was defined as ~2 mm excursion from 90-0 ° of knee flexion. Cannulated drill bits were used to develop osseous tunnels. Ten-mm-wide patellar tendon BTB, a doubled semitendinosis tendon, and fascia

lata 3-4 cm wide were separately passed, fixed at varying loads in the test position, and the knee was retested for anterior stability. Patellar tendon BTB was secured with interference screw fixation, and semitendinosis tendon and fascia lata were secured with AO soft tissue washers. Stability was defined as a 20-1b KT 1,000 postoperative measurement equal to the preoperative measurement.

The patel lar tendon BTB graft required an average 3-1b load with a range of 0-4 lb to produce stability, the semitendinosis tendon an average 8 lb with a range of 5 -9 lb, and the fascia lata an average of 13 lb with a range of 8-15 lb. The pa- tellar tendon BTB has been shown to be two to three times as stiff as the semitendinosis tendon and fascia lata, therefore requiring less tension to produce stability.

Although it has been noted that excessive loads produce necrosis in the grafts used, stability cannot be obtained using zero load. An intermediate load sufficient to produce knee stability immediately postoperatively may be most effective in ACL re- construction. By determining necessary load, it is hoped more uniformity in ACL reconstruction can be obtained.

Concurrent Injuries of the Anterior Cruciate Liga- ment and the Menisci of the Knee- -A Comprehen- sive Study of 426 Cases. Terry L. Whipple, Gary G. Poehling, and William C. Burns. Richmond, Vir- ginia, U.S.A.

Three thousand eight hundred and one consecu- tive trauma-related cases of arthroscopic knee examinations were recorded over a 2-year period in a standardized format from the experience of 10 surgeons specializing in disorders of the knee. This study was carried out to correlate patterns of injury to the anterior cruciate ligament (ACL), the medial and lateral menisci, and the articular surfaces of the knee. The series included 1,920 cases of torn me- niscus, 699 involved a torn ACL, and 426 were combined ACL and meniscal injuries. The inci- dence of an ACL injury having an associated me- niscus tear (60.9%) was greater than the incidence of a meniscal tear having some degree of ACL in- jury (22.2%), reflecting the fact that ACL injuries predispose the knee to meniscus injury. The risk to the lateral meniscus increases by 20-30% if the ACL tear is complete, indicating that lateral disper- sion of forces occurs in ACL-deficient knees. Ante- rior cruciate ligament deficiency concentra tes

Arthroscopy, Vol. 4, No. 2, 1988