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Anatomic Single-Bundle Anterior Cruciate Ligament Reconstruction With a Rounded Rectangular Femoral Dilator

March 01, 2019

Contributors: Junsuke Nakase, MD; Takeshi Oshima, MD; Kengo Shimozaki; Yasushi Takata, MD; Hiroyuki Tsuchiya, MD; Kazuki Asai, MD; Kazuki Asai, MD

In the past 10 years, anterior cruciate ligament (ACL) reconstruction has shifted toward anatomic reconstruction, regardless whether a single- or double-bundle technique is used. The use of a smaller hamstring autograft is a predictor of poor clinical outcomes in patients who undergo conventional single-bundle ACL reconstruction. To improve the surgical methods for anatomic single-bundle ACL reconstruction, surgeons must use a larger graft without the risk of roof impingement in smaller patients. Several anatomic studies have reported that the femoral insertion of the ACL has a rounded rectangular shape. Our studies revealed that the cross-sectional shape of the fourfold semitendinosus tendon graft was oval rather than round. In addition, the fourfold semitendinosus graft is more suitable for a rounded rectangular femoral tunnel than a round femoral tunnel. Our technique involves the use of a rounded rectangular femoral dilator that was designed to be more anatomic and to create a wider tendon-bone junction. This video demonstrates ACL reconstruction with the a rounded rectangular femoral dilator and discusses the clinical results of the procedure. We compared the femoral tunnel size, anteroposterior knee laxity, negative pivot-shift test results, and Lysholm Knee Scale scores of patients who underwent conventional anatomic single-bundle ACL reconstruction and patients who underwent rounded rectangular femoral tunnel ACL reconstruction. The minimum follow up was 2 years. All ACL reconstruction procedures were performed by a single surgeon with the use of a semitendinosus graft. We used three-dimensional CT and the quadrant method to evaluate the femoral tunnel position of rounded rectangular femoral tunnel ACL reconstruction. Femoral height and femoral length were expressed as percentages to describe the femoral tunnel position. An oblique incision is made approximately 4 cm above the pes anserinus. The vessel tape is passed to the semitendinosus tendon, and two branches of semitendinosus tendon are cut. The semitendinosus tendon is harvested using an open tendon stripper. We use two sizing blocks for the femoral and tibial tunnels. The rounded rectangular sizing block is used for the femoral side, and the rounded sizing block is used for the tibial side. The fourfold semitendinosus graft for the femoral side is measured using a rounded rectangular sizing block from 6 × 12 mm to 6 × 9 mm. The smallest size that allows the graft to pass smoothly through the sizing block is selected. If the graft is less than 6 × 10 mm, we harvest the gracilis tendon. Similarly, the graft for the tibial side is measured using a rounded sizing block from a larger to a smaller size. The ACL insertion on the femur is confirmed through the medial portal. A mark is made at the center of the ACL insertion using a 3.5-mm drill pin through the low anteromedial portal and penetrating the lateral side of the thigh using a freehand technique with the knee in in greater than 120° of flexion. After the wire is placed centrally in the femoral insertion, the femoral tunnel is drilled to a length of 15 mm using a 6.0-mm drill tip. To create the rounded rectangular aperture, we used the original rounded rectangle dilators through a guide pin, which is available in various sizes. The tunnel is dilated based on the graft size, and the rotation angle of the dilator is confirmed to mimic the ACL insertion via intraoperative imaging. In all the patients, the femoral tunnel was manually dilated the full 15 mm with a hammer. The tibial tunnel is drilled using a tibial guide set to a 50° angle with the knee in 90° of flexion. The tip of the aimer is positioned 3 to 4 mm anterior to the posterior border of the anterior horn of the lateral meniscus and directly anteromedial to the center of the tibial attachment of the ACL. The graft is inserted through the tibial tunnel and looped over an adjustable fixation device for femoral fixation. The other end of the graft is fixed, and initial graft tension is set to 40 N with the knee in 20° of flexion. The femoral tunnel area in the patients who underwent rounded rectangular femoral tunnel ACL reconstruction was larger than that in the patients who underwent anatomic rounded single-bundle ACL reconstruction (52.7 mm2 ± 4.8 mm2 versus 47.0 mm2 ± 7.3 mm2, respectively). In addition, anteroposterior stability, rotational laxity, and Lysholm Knee Scale scores were substantially better in the patients who underwent rounded rectangular femoral tunnel ACL reconstruction than in the patients who underwent anatomic rounded single-bundle ACL reconstruction (0.8 mm ± 1.1 mm versus 1.8 mm ± 1.2 mm, respectively, for anteroposterior knee laxity; 93.3% versus 82.5%, respectively, for rotational laxity; and 98.9 ± 2.4 versus 97.6 ± 3.3, respectively, for Lysholm Knee Scale score). Partial posterior tunnel wall blowout occurred in one patient a result of lack of knee flexion angle; however, the damage was minimal, and the graft was corrected using the standard technique. In the rounded rectangular femoral tunnel ACL reconstruction cohort, iatrogenic injury to the medial femoral condyle occurred in three patients and difficulty with graft passage occurred in two patients. Using the positioning ratios that we calculated, the femoral tunnel was located 24.8% from the deepest subchondral contour of the lateral femoral condyle and 32.1% from the Blumensaat line. Rounded rectangular femoral tunnel ACL reconstruction is more anatomic and fits the cross-sectional shape of the hamstring graft, resulting in improved anteroposterior and rotatory stability and clinical outcomes as well as providing a larger tunnel and graft size for smaller patients. We did not experience any serious intraoperative complications during rounded rectangular femoral tunnel ACL reconstruction. The femoral tunnels were located within the anatomic ACL footprint. This technique, which is simple, addresses the shortcomings of conventional single-bundle ACL reconstruction.

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