Research Article: Positioning the femoral bone socket and the tibial bone tunnel using a rectangular retro-dilator in anterior cruciate ligament reconstruction

Date Published: May 2, 2019

Publisher: Public Library of Science

Author(s): Hiroteru Hayashi, Daisaburo Kurosaka, Mitsuru Saito, Ryo Ikeda, Daisuke Kubota, Tomohiro Kayama, Takashi Hyakutake, Keishi Marumo, Brandon J Erickson.


The purpose of this study was to evaluate the positions of femoral bone sockets and tibial bone tunnels made with the rectangular retro-dilator (RRD), which we manufactured for anterior cruciate ligament reconstruction (ACLR) with a bone-patella tendon-bone (BPTB) graft which is fixed into the rectangular bone socket and tunnel made at anatomical ACL insertion sites.

42 patients who had undergone ACLR with BPTB using the RRD were evaluated to assess bone socket and tunnel positions by the quadrant method and Magnussen classification using three-dimensional (3-D) CT. Intra-operative complications were also investigated in all patients.

3-D CT of the operated knee joints using the RRD showed that the bone socket and tunnel were placed in anatomical positions. In the quadrant method, the mean position of the femoral bone socket aperture was located at 22.0 ± 4.2% along the Blumensaat’s line, and 37.4 ± 7.2% across the posterior condylar rim. The mean positions of the tibial bone tunnel aperture were 37.7 ± 5.2% and 46.1 ± 2.2% antero-posteriorly and medio-laterally, respectively. In addition, according to the Magnussen classification, 39 cases were evaluated as type 1, and almost all were located behind the lateral intercondylar ridge (also known as the resident’s ridge). 3 cases were classified as type 2, which overlapped with the resident’s ridge. A partial fracture of BPTB bone fragment was observed in 2 patients, but no serious complications including neurovascular injury were observed.

The study indicates that the use of RRD achieves a safe anatomical reconstruction of the ACL.

Partial Text

In recent years, there have been reports that the locations of the femoral bone socket and the tibial bone tunnel aperture affect the clinical outcome in ACLR, and its importance has been increasingly recognized [1,2]. Until recently, the trans-tibial technique was mainstream, but there have also been reports of the antero-medial portal technique and also the outside-in technique, which is a method to create a tunnel from the outside. The outside-in retrograde drilling technique in which a guide pin is inserted from the outside, but the tunnel is created from the within the joint with a retrograde drill has also demonstrated good clinical results [3]. Recently it has been reported that ACLR using BPTB replicates the fibrous arrangement of healthy ligaments [4,5]. Furthermore, a rectangular tunnel at the anatomical insertion site, or the anatomical rectangular tunnel (ART), recreates the biomechanics of a healthy ACL, yielding good clinical results [6,7]. In BPTB ACLR incorporating the anatomical rectangular tunnel (ART BPTB ACLR) technique, the pattern of force sharing was similar to that in the normal ACL in response to anterior tibial load and during passive knee extension motion [8]. We previously reported a safe, minimally invasive method of ART BPTB ACLR technique by using a rectangular retro-dilator (RRD) (Ario Medical, Osaka, Japan) [9]. The RRD method enables easier bone socket and tunnel creation at the intended target positions whilst minimizing bone drilling. In this study, we evaluated the femoral bone socket and tibial bone tunnel aperture positions made with the RRD, which we manufactured specifically for ART BPTB ACLR.

Primary ACLR with BPTB grafts using RRD were performed in 56 patients from April 2015 to August 2017. Bone socket and tunnel aperture positions were evaluated in 42 patients (all male, with a mean age of 29 years, range: 17–51 years), who agreed to undergo a CT evaluation post-operatively. At 3 weeks after surgery, a 3-D CT of the operated knee joint was taken. The centers of the femoral bone socket and the tibial bone tunnel apertures were measured where the diagonal lines of the rectangle crossed and then evaluated using the quadrant method [10,11]. The aperture centers of the femoral bone socket and the tibial bone tunnel were measured using Image J software (National Institute of Health, Bethesda, Maryland) 12] with the average of two independent readings measured by two orthopaedic surgeons used for analysis. Regarding the femoral bone socket, in order to clarify the positional relationship with the resident’s ridge, evaluation was carried out by the method suggested by Magnussen et al [13]. In addition, surgical complications were also investigated in all cases. Written informed consent was obtained from all participants prior to surgery. Consent was obtained for both medical treatment and for participation in this study. This reconstruction technique was considered standard of care at our institution, and its outcome was investigated in this study. All protocols in this study are under approval by the ethics committee for clinical research at The Jikei University School of Medicine [Permission no. 30–458 (9479)].

Mean patient characteristics were 172.3 cm in height, and 72.1 kg in weight with a BMI of 24.3 kg/m2. The mean patellar tendon length measured with the picture archiving and communication system (PACS) measurement tool on the MRI was 47.7 mm (Table 1).

Recently, good clinical results of ART BPTB ACLR have been reported [4–7]. Rectangular femoral ACL fixation constructs and grafts may prove more efficacious at restoring in vivo ACL kinematics than round femoral tunnels [7]. Some studies [3,15,16] indicated that bone tunnels can be safely and accurately created with an outside-in technique using retrograde drills, namely: AI drill (Aimedic MMT (Telos Japan), Tokyo, Japan) 17], O-drill (Meira Co., Aichi, Japan), Endobutton retro drill (Smith&Nephew, Andover, MA) [18] and FlipCutter (Arthrex, Naples, FL) [17–20]. We reported a technique of minimally invasive ART BTB ACLR, which utilized the outside-in method and in which a rectangular pull-type dilator (rectangular retro-dilator) was used [9]. In this study, a guide pin was inserted into the anatomical position taking into account the shape of the RRD, and it was confirmed that rectangular socket and tunnel were created at the anatomical position with high probability without complications of posterior wall damage. The 3-D CT evaluation of BPTB ACLR using the RDD confirmed that both the femoral socket and the tibial tunnel were placed in their appropriate anatomical positions as shown in similar studies reported previously [21–29] (Table 2).

BPTB ACLR using the RRD is a safe technique that enables bone socket and tunnel creation at the anatomical positions.




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