Femoral insertions of the anteromedial and posterolateral bundles of the anterior cruciate ligament: morphometry and arthroscopic orientation models for double-bundle bone tunnel placement--a cadaver study.

PURPOSE: The purpose of this study was to analyze the femoral insertions of the anteromedial (AM) and posterolateral (PL) bundles of the anterior cruciate ligament (ACL) and to develop arthroscopic orientation models for double-bundle (DB) bone tunnel placement. METHODS: The femoral insertions of the AM and PL bundles were dissected in 50 human cadaveric knees, documented on digital photographs, and quantified with a digital image analysis system. RESULTS: The insertion areas of both bundles were significantly larger in men (53 mm(2) for AM and 45 mm(2) for PL) than in women (39 mm(2) for AM and 39 mm(2) for PL), and the average ACL insertion area was significantly larger in left knees than in right knees. According to the "femoral center angle model," the centers of the AM and PL bundles were horizontally aligned when the femoral shaft axis was lifted 12 degrees from the horizontal plane or when the knee was flexed to 102 degrees . In this position the center of the AM bundle was 3 to 4 mm "lower" (arthroscopic terminology) to the over-the-top position, and the distance of the PL bundle to the "shallow" articular cartilage of the lateral femoral condyle was 6 mm. According to the "modified femoral clock wall model," the average centers of the AM and PL bundles were both aligned at 1 o'clock for a left knee and at 11 o'clock for a right knee in 102 degrees of knee flexion. CONCLUSIONS: The average femoral insertion areas of the ACL and the AM and PL bundles were significantly larger in men compared with women and in left knees compared with right knees. According to the femoral center angle model, the AM and PL insertions are aligned horizontally in an average of 102 degrees of knee flexion, resulting in one commuted time for the AM and PL bundles in the modified femoral clock wall model. Both models support reproducible and reliable arthroscopic AM and PL bone tunnel placement. With regard to a mean anatomic anteroposterior length of the femoral ACL insertion of 14 to 15 mm, adequate DB bone tunnel placement should be possible in most cases. CLINICAL RELEVANCE: This study provides an anatomic description of the femoral AM and PL insertions including gender differences, landmarks, and arthroscopic orientation models for DB bone tunnel placement.

Prospective randomized comparison of double-bundle versus single-bundle anterior cruciate ligament reconstruction.

PURPOSE: Biomechanical studies show increased anterior and rotational stability with double-bundle (DB) compared to single-bundle (SB) anterior cruciate ligament (ACL) reconstruction. The aim of this study was to evaluate the clinical results of four-tunnel DB ACL reconstruction. METHODS: Seventy patients undergoing arthroscopic hamstring ACL reconstruction were prospectively randomized to DB (n = 35) or SB (n = 35) groups. Each bundle fixation was by means of a femoral EndoButton CL and a tibial biodegradable interference screw. Demographic data were comparable between groups, and the average age of all patients was 29 years. The average follow-up was 19 months for both groups and included a history, clinical evaluation with knee scores, and radiographs. RESULTS: The subjective results were similar in groups. The subjective International Knee Documentation Committee (IKDC) 2000 score was 88 P for DB versus 90 P for SB; the Lysholm score was 90 P for DB versus 93 P for SB; and the Cincinnati knee score was 91 P for DB versus 92 P for SB. The objective IKDC was significantly higher for DB: 78% "A" (P < .000) and 19% "B" compared to 24% "A" and 68% "B" for SB. The average KT-1000 side-to-side difference was 1.0 mm for DB and 1.6 mm for SB (P = .054) and the pivot shift test was negative in 97% for DB (P = .01) and 71% for SB. The range of motion was comparable for both groups. CONCLUSIONS: Our study shows a significant advantage in anterior and rotational stability as well as objective IKDC for four-tunnel DB ACL reconstruction compared to SB ACL reconstruction. The subjective Cincinnati knee score, the Lysholm score, and the subjective IKDC 2000 did not show any statistical difference for one or the other technique. LEVEL OF EVIDENCE: Level I, randomized controlled trial.

Tibial insertions of the anteromedial and posterolateral bundles of the anterior cruciate ligament: morphometry, arthroscopic landmarks, and orientation model for bone tunnel placement.

PURPOSE: For arthroscopic double-bundle (DB) anterior cruciate ligament (ACL) reconstruction, the size of the available area for tibial bone tunnel placement is crucial. Therefore, tibial insertions of the anteromedial (AM) and posterolateral (PL) bundles in the area intercondylaris anterior (AIA) of the tibia were quantified, landmarks were characterized, and an arthroscopic orientation model was developed. METHODS: The tibial insertions of the AM and PL bundles were dissected in 50 human cadaver knees. The footprints were documented on digital photographs and measured using a digital image analysis system. RESULTS: The average tibial ACL insertion area was 114 mm2 and varied considerably in size from 67 to 259 mm2. It was significantly smaller in female knees (P = .04) compared to male knees. The insertion area of the AM bundle was an average of 67 mm2 and that of the PL was 52 mm2. The centers of both bundles were an average of 5 mm apart near the middle of the ACL insertion. Important landmarks for arthroscopic DB bone tunnel placement were the ACL stump, respectively, its anterior and posterior borders; the rims of the articular surfaces of the medial and lateral tibial condyles, which border the AIA; and the posterior horn of the lateral meniscus. The new "tibial square model" indicates a minimum anteroposterior length of 14 to 15 mm for separate AM and PL bone tunnel placement. CONCLUSIONS: The prospective area for tibial bone tunnels varied from spacious to very small among the specimens, and the insertions and centers of the AM and PL bundles cannot be exactly anatomically reconstructed. For DB ACL reconstruction, an intraoperative hypothetical situation of 6 mm for the AM tunnel and 5 mm for the PL tunnel may be reasonable when considering an average length of the tibial ACL insertion area of 14 mm in women and 15 mm in men. Individual anatomic variations make it difficult to have general guidelines, but tibial landmarks and the "tibial square model" may assist in individualized bone tunnel placement. CLINICAL RELEVANCE: Anatomic description of morphology of tibial AM and PL insertions, landmarks, and orientation models for reproducible arthroscopic DB bone tunnel placement.