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Comparison of Tibial Tunnel Techniques in Posterior Cruciate Ligament Reconstruction: C-Arm Versus Anatomic Fovea Landmark
Original Article with Video Illustration
Comparison of Tibial Tunnel Techniques in Posterior Cruciate Ligament Reconstruction: C-Arm Versus Anatomic Fovea Landmark Yong Seuk Lee, M.D., Ph.D., Taeg Su Ko, M.D., Jin Hwan Ahn, M.D., Ph.D., Seo Goo Kang, M.D., Uk Hyun Choi, M.D., Ashraf Elazab, M.D., and Hyung Rae Lee, M.D.
Purpose: To evaluate the accuracy of the posterior cruciate ligament (PCL) fovea landmark against conventional fluoroscopic pin placement retrospectively using 3-dimensional computed tomography (3D CT). Methods: This retrospective comparison focused on the tibial tunnel locations determined in consecutive 26 patients using the fluoroscopic imaging technique (group I) and in consecutive 23 patients using the PCL fovea landmark technique without the help of the fluoroscopy (group II) for tibial tunnel formation. The 3D surface-modeled CT images that appropriately located the position of the PCL fovea on the tibial plateau were used. Ratios between total length of the fovea and length of the tunnel center from the medial border (coronal) and posterior edge (sagittal) were evaluated. Results: The ratios between sagittal tunnel length and total sagittal length for groups I and II were 35.4% 12.2% and 44.1% 23.1%, respectively (P ¼ .07). The ratios between the coronal tunnel lengths and total coronal lengths for groups I and II were 47.3% 9.2% and 57.3% 18.1%, respectively: group II showed a more laterally positioned tibial tunnel than did group I (P ¼ .03). Conclusions: A more laterally located tibial tunnel was produced using the PCL fovea landmark technique. However, the differences in centers were small and probably not clinically relevant. Therefore, the PCL fovea landmark technique might be an alternative method to the fluoroscopic imaging technique for locating the anatomic tibial tunnel during transtibial PCL reconstruction. Level of Evidence: Level III, retrospective comparative study.
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ibial insertion of the posterior cruciate ligament (PCL) is in the posterior half of the PCL fovea, or the center of the PCL working fibers is 7 mm anterior to the posterior cortex.1,2 Intraoperative fluoroscopic images are usually used for the creation of the tibial tunnel during transtibial PCL reconstruction. However, intraoperative fluoroscopic identification of the tibial
From the Department of Orthopaedic Surgery, Bundang Hospital, Seoul National University College of Medicine (Y.S.L., S.G.K., U.H.C., A.E., H.R.L.), Seoul; and the Department of Orthopaedic Surgery, Kangbuk Samsung Hospital, Sungkyunkwan University College of Medicine (T.S.K., J.H.A.), Seoul, Republic of Korea. The authors report the following potential conflict of interest or source of funding: This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2014R1A1A2053356; Y.S.L.). Received November 18, 2014; accepted August 25, 2015. Address correspondence to Yong Seuk Lee, M.D., Ph.D., Department of Orthopaedic Surgery, Seoul National University College of Medicine, Bundang Hospital, 166 Gumi-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 463-707, Republic of Korea. E-mail: [email protected] or [email protected] Ó 2015 by the Arthroscopy Association of North America 0749-8063/14973/$36.00 http://dx.doi.org/10.1016/j.arthro.2015.08.036
insertion area of the PCL is often impaired by tibial rotation and overlapping anatomic structures (Fig 1).1 Therefore, the definition of reliable, arthroscopically identifiable anatomic landmarks would be of great value for proper positioning of the tibial guide pin in arthroscopic transtibial PCL reconstruction. During our transtibial PCL reconstruction, a trans-septal portal is made just behind the PCL fibers, and the margin of the PCL fovea can be palpated with the tip of the tibial guide.3-5 The posterior cortex and the medial and lateral borders of the PCL fovea are landmarks for the anatomic positioning of the tibial tunnel, allowing the guide pin to be inserted approximately 7 mm anterior to the posterior cortex and central area of the mediolateral plane (Fig 2).1,2 These landmarks are time saving and not affected by tibial rotation and overlapping anatomic structures. Furthermore, additional equipment is required for the intraoperative fluoroscopic images, and this could increase the risk of the contamination and radiation exposure. The purpose of this study was to evaluate the accuracy of the PCL fovea landmark against conventional fluoroscopic pin placement retrospectively using 3-dimensional computed tomography (3D CT). Our
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Fig 1. Different views after rotation of the tibia: (A) internal rotation, (B) neutral, and (C) external rotation.
hypothesis was that accurate tibial tunnel preparation would be possible without intraoperative fluoroscopic imaging using the reliable anatomic landmarks of the PCL fovea.
the tunnel, which could be helpful for postoperative management. Institutional Review Board approval was obtained before initiation of the retrospective analysis (B-1408/262-115).
Methods
Fluoroscopic Imaging Technique A posterior trans-septal portal was made to prepare the tibial tunnel.3-5 The anteromedial (AM) and anterolateral (AL) portals were made immediately adjacent to the lateral and medial borders of the patellar tendon and 1 cm above the joint line to allow an easy passage of an arthroscope through the intercondylar notch into the posterior compartment of the knee joint. As the first step of the posterior trans-septal portal, the posteromedial (PM) portal was made under direct arthroscopic visualization using a transillumination technique. The posterolateral (PL) portal was made in a similar fashion. To create the trans-septal portal, a PM approach of the arthroscope was made, and a switching stick was inserted through the PL portal to push the septum medially. A motorized shaver was inserted through the AM portal and reached the PM compartment. Without disrupting the remnant PCL, a small hole was made at the central portion of the posterior septum behind the PCL with the shaver. The posterior capsule was detached from its attachment, and frayed soft tissue was removed through the PM and PL portals using the trans-septal portal. A PCL tibial drill guide (Acufex, Smith & Nephew, Andover, MA, USA) was introduced through the AM portal, with viewing via the PM portal, and a guide pin was introduced by placing the drill guide at an angle of 50 to 55 , with a fluoroscopic image assistance. The tip of the guide was aimed at the distal-central portion of the PCL tibial attachment site. Fluoroscopic images are only used for the sagittal location of the tibial tunnel, and an
Study Design and Materials This retrospective comparison focused on the tibial tunnel locations determined in consecutive 26 patients using the fluoroscopic imaging technique (group I) and in consecutive 23 patients using the PCL fovea landmark technique (group II) between 2012 and 2014. The mean patient ages for groups I (23 male patients, 3 female patients) and II (22 male patients, 2 female patients) were 34.5 13.9 years and 36.9 15.6 years, respectively. Each patient had a unilateral isolated PCL or combined PCL-posterolateral rotatory instability deficient knee and underwent PCL or PCLposterolateral corner sling (PLCS) reconstruction. Each technique was performed at different institutes (Y.S.L., J.H.A.), and each surgeon used only one technique because of the different style of the PCL reconstruction. The patient inclusion criteria were (1) available 3D CT data, (2) primary isolated PCL or PCLPLCS reconstruction, and (3) no history of bony surgery around proximal tibia. Our exclusion criteria were (1) PCL reconstruction without an available CT scan (4 patients in group I and 3 patients in the group II) and (2) revision reconstructions (5 patients in group I and 2 patients in group II). CT of the operated knees was performed within 2 weeks after surgery. In this period, all patients who underwent PCL reconstruction were recommended to have a CT scan. Each patient provided informed consent for the CT scan for the evaluation of the tunnel position and breakage of
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Fig 2. Viewing from posteromedial portal in the right knee. (A) Medial border, (B) lateral border, and (C) posterior edge of the posterior cruciate ligament fovea are palpated, and (D) the guide pin is inserted approximately 7 mm anterior to the posterior cortex and the central area of the mediolateral plane.
arthroscope is used for location of the coronal plane. The diameter of the tunnel was determined based on the graft diameter (9 to 10 mm), and the tunnel was made using a reamer. PCL Fovea Landmark Technique The trans-septal portal formation was similar to the technique described above.3 A 1-cm, longitudinal skin incision was made at the medial side to the tibial tuberosity after the confirmation of the incision site after insertion of the guide sleeve. Viewing through the trans-septal portal via the PM portal, the drill guide (RetroConstruction Drill Guide Set, Arthrex, FL, USA) was angled at 50 to the tibia and inserted via the AM portal.1,5 To confirm the exit point of the guide pin, the medial, lateral, and posterior edges of the PCL fovea were palpated using a guide tip (Fig 2). For the exact palpation of the PCL fovea, the septum that exists just
behind the portion of the PCL remnant should be removed during the trans-septal portal formation. The tip portion was positioned at the midpoint of the PCL fovea (medial-lateral direction), approximately 7 mm anterior to the posterior edge (Video 1). The guide sheath was changed to a FlipCutter (FlipCutter, Arthrex, FL, USA) sheath, and the FlipCutter was inserted to perform the retroreaming. Evaluation Methods A continuous scan was obtained from 10 cm above to 10 cm below the joint line. Coronal reconstructions were performed at a level parallel to a line joining the posterior femoral condyles, and sagittal reconstructions were performed at a level parallel to the outer rim of the lateral femoral condyle. The 128-channel iCT SP and 64-channel Brilliance 64 (Philips, Amsterdam, Netherlands) were used for 3D reconstruction of the CT
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images. The 3D surface models were reconstructed, scanning with a 0.5 mm interval, to obtain sagittal, coronal, and transverse plane views with a 2-mm interval, using the Extended Brilliance Workstation (EBW, Philips). A 3D reconstructed surface model using 2D sliced images from with the viewed image that appropriately show the whole area of the PCL fovea on the tibial plateau and the PCL fovea parallel to the plane was used for the evaluation of the tunnel position. Sagittal images that show the whole tunnel were evaluated for the bone bridge and the tunnel breakage. Five different parameters were measured, and 2 parameters were calculated, including the sagittal distance from the posterior border of the tibial spine to the posterior edge of the PCL fovea (total sagittal length; Fig 3A), sagittal distance from the center of the tibial tunnel to the posterior edge of the PCL fovea (sagittal tunnel length; Fig 3B), ratio between the sagittal tunnel length and the total sagittal length, coronal dimension of the PCL fovea from the medial edge to the lateral edge (total coronal length; Fig 3C), coronal distance from the medial edge of the PCL fovea to the center of the tibial tunnel (coronal tunnel length; Fig 3D), ratio between the coronal tunnel length and the total coronal length, and the nearest distance from the posterior border of the tibial tunnel to the posterior cortex (length of the posterior bone bridge; Fig 3E). In this measurement, “-” was used to indicate that the cortex was blown out and was regarded as “cortical breakage.” To reduce intraand interobserver bias, the measurements were made each twice by 2 orthopaedic sports medicine fellows for all patients. The second measurement was performed 2 weeks after the first measurement. Statistical Methods Measurement reliability was assessed through an examination of intrarater and inter-rater reliability using the intraclass correlation coefficient, and post hoc power analysis was also performed. Post hoc power analysis was performed with G-power 3.1 (Copyright 2010-2013 Heinrich-Heine-Universität Düsseldorf) for the Mann-Whitney U-test with the following values: effect size, 0.8; a error, 0.05; sample size of group I, 26; and sample size of group II, 23; the power was 0.85. For the sagittal ratio, the effect size was calculated with the mean and standard deviation of each group, and the power with the following valuesdeffect size, 0.66; a error, 0.05; sample size of group I, 26; and sample size of group II, 23dwas 0.94. On the coronal ratio, effect size was also calculated with mean and standard deviation of each group, and the power with the following valuesdeffect size, 0.98; a error, 0.05; sample size of group I, 26; and sample size of group II, 23dwas 0.99. The SPSS statistical package, version 18.0 (SPSS, Chicago, IL, USA) was used. P < .05 was considered statistically significant. Comparisons of the tibial tunnel
position and the length of the posterior bone bridges between groups I and II were performed using a MannWhitney U-test.
Results The inter- and intraobserver reliabilities for tunnel measurement were satisfactory, with mean values of 0.85 (range, 0.63 to 0.99) and 0.84 (range, 0.65 to 0.98), respectively. Detailed measurement data are listed in the Table 1. The total sagittal lengths in group I and II were 19.2 2 mm and 17.7 5 mm, respectively (P ¼ .55). The sagittal tunnel lengths in groups I and II were 6.8 2.5 mm and 7.4 3.7 mm, respectively (P ¼ .21). Therefore, the ratios between sagittal tunnel length and total sagittal length for groups I and II were 35.4% 12.2% and 44.1% 23.1%, respectively (P ¼ .07). Group II showed a slightly more proximal tunnel without statistical significance. Similarly, the total coronal lengths in groups I and II were 15.7 1.5 mm and 14.9 1.5 mm, respectively (P ¼ .08). The coronal tunnel lengths in groups I and II were 7.4 1.5 mm and 8.4 2.6 mm, respectively (P ¼ .07). Thus, the ratios between the coronal tunnel lengths and total coronal lengths for groups I and II were 47.3% 9.2% and 57.3% 18.1%, respectively; group II showed a more laterally positioned tibial tunnel than did group I (P ¼ .03). The lengths of the posterior bone bridge in groups I and II were 0.6 1.1 mm and 0.8 0.9 mm, respectively (P ¼ .51). There were cortical breakages in 2 patients in group I and in 3 patients in group II. However, the breakages were <2 mm, and all portions of the tunnel exits were located within the PCL fovea. All of the cortical breakages in group I were in medially positioned tibial tunnels, and all of them in group II were in tibial tunnels laterally positioned to the center of the PCL fovea.
Discussion The principal finding of this study was that the PCL fovea landmark technique provided a more laterally located tibial tunnel with statistical significance and a more proximally located tibial tunnel without statistical significance. However, both groups showed that the tibial tunnels were made in the PCL fovea, and they showed less than 1 mm of difference, which might not be clinically relevant. The posterior aspect of the proximal tibia has a unique 3D anatomy compared with the mid- or distal tibia because multiple structures, including the tibial plateau, PCL fovea, and posterior cortex, abruptly change.1 The sloping central depression between the medial and lateral portions of the tibial plateau has been called PCL fovea, facet, or fossa.2,6 Anatomically, this insertion is distinct from the vertical cortex of the
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Fig 3. Sagittal distance from the posterior border of the tibial spine to the posterior edge of the posterior cruciate ligament (PCL) fovea (total sagittal length; Fig 3A), sagittal distance from the center of the tibial tunnel to the posterior edge of the PCL fovea (sagittal tunnel length; Fig 3B), coronal dimension of the PCL fovea from the medial edge to the lateral edge (total coronal length; Fig 3C), coronal distance from the medial edge of the PCL fovea to the center of the tibial tunnel (coronal tunnel length; Fig 3D), and nearest distance from the posterior border of the tibial tunnel to the posterior cortex (length of the posterior bone bridge; Fig 3E).
tibia and appears as a consistent radiographic landmark for pin placement in PCL reconstruction.2 On the coronal plane, the PCL inserts at points within the whole area of the PCL fovea, and it could imply a large insertional area with a wide acceptable range.7-9
However, slightly higher graft forces have been recorded when the tunnel is positioned too medially beyond 65 during passive knee flexion and may impinge the medial femoral condyle.10 In our study, a more laterally located tibial tunnel with statistical significance was
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Table 1. Comparison of the Measurement Data Between Groups TS, mm S, mm Ratio (S/TS) TC, mm C, mm Ratio (C/TC)
Group I 19.2 2 6.8 2.5 35.4 12.2% 15.7 1.5 7.4 1.5 47.3 9.2%
Group II 17.7 5 7.4 3.7 44.1 23.1% 14.9 1.5 8.4 2.6 57.3 18.1%
P Value .55 .21 .07 .08 .07 .03*
NOTE. Data presented as mean standard deviation unless otherwise indicated. C, coronal tunnel length; S, sagittal tunnel length; TC, total coronal length; TS, total sagittal length. *Statistically significant.
observed using the PCL fovea landmark technique. However, both groups showed that the tibial tunnels were made in the PCL fovea and located around the center of the coronal plane with less than 1 mm difference, which might not be clinically relevant. On the sagittal plane, several studies have examined the anatomy of the PCL insertion.2,7-9 Moorman et al.2 reported that the more posterior fibers, which insert up to 20 mm down the posterior cortex of the tibia, posterior and inferior to the PCL facet, are 0.5 mm thick. They emphasized that in the sagittal plane, the center of the working fibers of the PCL was 7 mm anterior to the posterior cortex of the tibia, as measured along the PCL fovea. Lee et al.1 reported that the PCL insertion was in the posterior 48% of the area of the PCL fovea, to the posterior cortex, consistent with Moorman et al.2 In our study, group II showed a tibial tunnel that was slightly anteriorly positioned, without statistical significance, however, the patients in both groups I and II showed tibial tunnels that were located approximately 7 mm anterior to the posterior tibial cortex. Identifying the PCL fovea and the real posterior cortex that is aligned with the PCL fovea is important during transtibial PCL reconstruction to prevent breakage of the posterior cortex. The posterior cortex of the plateau area curves posteriorly to the tibial plateau, whereas the posterior cortex of the PCL fovea area is depressed anteriorly. Thus, this area overlaps in lateral radiographs. Lee et al.1 reported that the longest distance between the real posterior cortex and the most posteriorly positioned cortical line is 10.8 2.2 mm. Limitations Our study has several limitations. First, this was a retrospective series and 2 surgeons were involved.
Therefore, selection and performance biases could exist in this study. Second, the PCL fovea landmark technique is technically demanding because it requires complete access to the posterior compartment, and skill is necessary for the palpation of the margin of the PCL fovea. Third, only post hoc power analysis was performed.
Conclusions A more laterally located tibial tunnel was produced using a PCL fovea landmark technique. However, the differences in centers were small and probably not clinically relevant. Therefore, the PCL fovea landmark technique might be an alternative method to the fluoroscopic imaging technique for locating the anatomic tibial tunnel during transtibial PCL reconstruction.
References 1. Lee YS, Ra HJ, Ahn JH, Ha JK, Kim JG. Posterior cruciate ligament tibial insertion anatomy and implications for tibial tunnel placement. Arthroscopy 2011;27:182-187. 2. Moorman CT 3rd, Murphy Zane MS, Bansai S, et al. Tibial insertion of the posterior cruciate ligament: A sagittal plane analysis using gross, histologic, and radiographic methods. Arthroscopy 2008;24:269-275. 3. Ahn JH, Chung YS, Oh I. Arthroscopic posterior cruciate ligament reconstruction using the posterior trans-septal portal. Arthroscopy 2003;19:101-107. 4. Ahn JH, Lee YS, Choi SH, Chang MJ, Lee do K. Singlebundle transtibial posterior cruciate ligament reconstruction using a bioabsorbable cross-pin tibial back side fixation. Knee Surg Sports Traumatol Arthrosc 2013;21:1023-1028. 5. Lee YS, Ahn JH, Jung YB, et al. Transtibial double bundle posterior cruciate ligament reconstruction using TransFix tibial fixation. Knee Surg Sports Traumatol Arthrosc 2007;15: 973-977. 6. Girgis FG, Marshall JL, Monajem A. The cruciate ligaments of the knee joint. Anatomical, functional and experimental analysis. Clin Orthop Relat Res 1975:216-231. 7. Edwards A, Bull AM, Amis AA. The attachments of the fiber bundles of the posterior cruciate ligament: An anatomic study. Arthroscopy 2007;23:284-290. 8. Tajima G, Nozaki M, Iriuchishima T, et al. Morphology of the tibial insertion of the posterior cruciate ligament. J Bone Joint Surg Am 2009;91:859-866. 9. Takahashi M, Matsubara T, Doi M, Suzuki D, Nagano A. Anatomical study of the femoral and tibial insertions of the anterolateral and posteromedial bundles of human posterior cruciate ligament. Knee Surg Sports Traumatol Arthrosc 2006;14:1055-1059. 10. Markolf KL, McAllister DR, Young CR, McWilliams J, Oakes DA. Biomechanical effects of medial-lateral tibial tunnel placement in posterior cruciate ligament reconstruction. J Orthop Res 2003;21:177-182.
Comparison of Tibial Tunnel Techniques in Posterior Cruciate Ligament Reconstruction: C-Arm Versus Anatomic Fovea Landmark Yong Seuk Lee, M.D., Ph.D., Taeg Su Ko, M.D., Jin Hwan Ahn, M.D., Ph.D., Seo Goo Kang, M.D., Uk Hyun Choi, M.D., Ashraf Elazab, M.D., and Hyung Rae Lee, M.D.
Purpose: To evaluate the accuracy of the posterior cruciate ligament (PCL) fovea landmark against conventional fluoroscopic pin placement retrospectively using 3-dimensional computed tomography (3D CT). Methods: This retrospective comparison focused on the tibial tunnel locations determined in consecutive 26 patients using the fluoroscopic imaging technique (group I) and in consecutive 23 patients using the PCL fovea landmark technique without the help of the fluoroscopy (group II) for tibial tunnel formation. The 3D surface-modeled CT images that appropriately located the position of the PCL fovea on the tibial plateau were used. Ratios between total length of the fovea and length of the tunnel center from the medial border (coronal) and posterior edge (sagittal) were evaluated. Results: The ratios between sagittal tunnel length and total sagittal length for groups I and II were 35.4% 12.2% and 44.1% 23.1%, respectively (P ¼ .07). The ratios between the coronal tunnel lengths and total coronal lengths for groups I and II were 47.3% 9.2% and 57.3% 18.1%, respectively: group II showed a more laterally positioned tibial tunnel than did group I (P ¼ .03). Conclusions: A more laterally located tibial tunnel was produced using the PCL fovea landmark technique. However, the differences in centers were small and probably not clinically relevant. Therefore, the PCL fovea landmark technique might be an alternative method to the fluoroscopic imaging technique for locating the anatomic tibial tunnel during transtibial PCL reconstruction. Level of Evidence: Level III, retrospective comparative study.
T
ibial insertion of the posterior cruciate ligament (PCL) is in the posterior half of the PCL fovea, or the center of the PCL working fibers is 7 mm anterior to the posterior cortex.1,2 Intraoperative fluoroscopic images are usually used for the creation of the tibial tunnel during transtibial PCL reconstruction. However, intraoperative fluoroscopic identification of the tibial
From the Department of Orthopaedic Surgery, Bundang Hospital, Seoul National University College of Medicine (Y.S.L., S.G.K., U.H.C., A.E., H.R.L.), Seoul; and the Department of Orthopaedic Surgery, Kangbuk Samsung Hospital, Sungkyunkwan University College of Medicine (T.S.K., J.H.A.), Seoul, Republic of Korea. The authors report the following potential conflict of interest or source of funding: This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2014R1A1A2053356; Y.S.L.). Received November 18, 2014; accepted August 25, 2015. Address correspondence to Yong Seuk Lee, M.D., Ph.D., Department of Orthopaedic Surgery, Seoul National University College of Medicine, Bundang Hospital, 166 Gumi-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 463-707, Republic of Korea. E-mail: [email protected] or [email protected] Ó 2015 by the Arthroscopy Association of North America 0749-8063/14973/$36.00 http://dx.doi.org/10.1016/j.arthro.2015.08.036
insertion area of the PCL is often impaired by tibial rotation and overlapping anatomic structures (Fig 1).1 Therefore, the definition of reliable, arthroscopically identifiable anatomic landmarks would be of great value for proper positioning of the tibial guide pin in arthroscopic transtibial PCL reconstruction. During our transtibial PCL reconstruction, a trans-septal portal is made just behind the PCL fibers, and the margin of the PCL fovea can be palpated with the tip of the tibial guide.3-5 The posterior cortex and the medial and lateral borders of the PCL fovea are landmarks for the anatomic positioning of the tibial tunnel, allowing the guide pin to be inserted approximately 7 mm anterior to the posterior cortex and central area of the mediolateral plane (Fig 2).1,2 These landmarks are time saving and not affected by tibial rotation and overlapping anatomic structures. Furthermore, additional equipment is required for the intraoperative fluoroscopic images, and this could increase the risk of the contamination and radiation exposure. The purpose of this study was to evaluate the accuracy of the PCL fovea landmark against conventional fluoroscopic pin placement retrospectively using 3-dimensional computed tomography (3D CT). Our
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol
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Fig 1. Different views after rotation of the tibia: (A) internal rotation, (B) neutral, and (C) external rotation.
hypothesis was that accurate tibial tunnel preparation would be possible without intraoperative fluoroscopic imaging using the reliable anatomic landmarks of the PCL fovea.
the tunnel, which could be helpful for postoperative management. Institutional Review Board approval was obtained before initiation of the retrospective analysis (B-1408/262-115).
Methods
Fluoroscopic Imaging Technique A posterior trans-septal portal was made to prepare the tibial tunnel.3-5 The anteromedial (AM) and anterolateral (AL) portals were made immediately adjacent to the lateral and medial borders of the patellar tendon and 1 cm above the joint line to allow an easy passage of an arthroscope through the intercondylar notch into the posterior compartment of the knee joint. As the first step of the posterior trans-septal portal, the posteromedial (PM) portal was made under direct arthroscopic visualization using a transillumination technique. The posterolateral (PL) portal was made in a similar fashion. To create the trans-septal portal, a PM approach of the arthroscope was made, and a switching stick was inserted through the PL portal to push the septum medially. A motorized shaver was inserted through the AM portal and reached the PM compartment. Without disrupting the remnant PCL, a small hole was made at the central portion of the posterior septum behind the PCL with the shaver. The posterior capsule was detached from its attachment, and frayed soft tissue was removed through the PM and PL portals using the trans-septal portal. A PCL tibial drill guide (Acufex, Smith & Nephew, Andover, MA, USA) was introduced through the AM portal, with viewing via the PM portal, and a guide pin was introduced by placing the drill guide at an angle of 50 to 55 , with a fluoroscopic image assistance. The tip of the guide was aimed at the distal-central portion of the PCL tibial attachment site. Fluoroscopic images are only used for the sagittal location of the tibial tunnel, and an
Study Design and Materials This retrospective comparison focused on the tibial tunnel locations determined in consecutive 26 patients using the fluoroscopic imaging technique (group I) and in consecutive 23 patients using the PCL fovea landmark technique (group II) between 2012 and 2014. The mean patient ages for groups I (23 male patients, 3 female patients) and II (22 male patients, 2 female patients) were 34.5 13.9 years and 36.9 15.6 years, respectively. Each patient had a unilateral isolated PCL or combined PCL-posterolateral rotatory instability deficient knee and underwent PCL or PCLposterolateral corner sling (PLCS) reconstruction. Each technique was performed at different institutes (Y.S.L., J.H.A.), and each surgeon used only one technique because of the different style of the PCL reconstruction. The patient inclusion criteria were (1) available 3D CT data, (2) primary isolated PCL or PCLPLCS reconstruction, and (3) no history of bony surgery around proximal tibia. Our exclusion criteria were (1) PCL reconstruction without an available CT scan (4 patients in group I and 3 patients in the group II) and (2) revision reconstructions (5 patients in group I and 2 patients in group II). CT of the operated knees was performed within 2 weeks after surgery. In this period, all patients who underwent PCL reconstruction were recommended to have a CT scan. Each patient provided informed consent for the CT scan for the evaluation of the tunnel position and breakage of
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Fig 2. Viewing from posteromedial portal in the right knee. (A) Medial border, (B) lateral border, and (C) posterior edge of the posterior cruciate ligament fovea are palpated, and (D) the guide pin is inserted approximately 7 mm anterior to the posterior cortex and the central area of the mediolateral plane.
arthroscope is used for location of the coronal plane. The diameter of the tunnel was determined based on the graft diameter (9 to 10 mm), and the tunnel was made using a reamer. PCL Fovea Landmark Technique The trans-septal portal formation was similar to the technique described above.3 A 1-cm, longitudinal skin incision was made at the medial side to the tibial tuberosity after the confirmation of the incision site after insertion of the guide sleeve. Viewing through the trans-septal portal via the PM portal, the drill guide (RetroConstruction Drill Guide Set, Arthrex, FL, USA) was angled at 50 to the tibia and inserted via the AM portal.1,5 To confirm the exit point of the guide pin, the medial, lateral, and posterior edges of the PCL fovea were palpated using a guide tip (Fig 2). For the exact palpation of the PCL fovea, the septum that exists just
behind the portion of the PCL remnant should be removed during the trans-septal portal formation. The tip portion was positioned at the midpoint of the PCL fovea (medial-lateral direction), approximately 7 mm anterior to the posterior edge (Video 1). The guide sheath was changed to a FlipCutter (FlipCutter, Arthrex, FL, USA) sheath, and the FlipCutter was inserted to perform the retroreaming. Evaluation Methods A continuous scan was obtained from 10 cm above to 10 cm below the joint line. Coronal reconstructions were performed at a level parallel to a line joining the posterior femoral condyles, and sagittal reconstructions were performed at a level parallel to the outer rim of the lateral femoral condyle. The 128-channel iCT SP and 64-channel Brilliance 64 (Philips, Amsterdam, Netherlands) were used for 3D reconstruction of the CT
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images. The 3D surface models were reconstructed, scanning with a 0.5 mm interval, to obtain sagittal, coronal, and transverse plane views with a 2-mm interval, using the Extended Brilliance Workstation (EBW, Philips). A 3D reconstructed surface model using 2D sliced images from with the viewed image that appropriately show the whole area of the PCL fovea on the tibial plateau and the PCL fovea parallel to the plane was used for the evaluation of the tunnel position. Sagittal images that show the whole tunnel were evaluated for the bone bridge and the tunnel breakage. Five different parameters were measured, and 2 parameters were calculated, including the sagittal distance from the posterior border of the tibial spine to the posterior edge of the PCL fovea (total sagittal length; Fig 3A), sagittal distance from the center of the tibial tunnel to the posterior edge of the PCL fovea (sagittal tunnel length; Fig 3B), ratio between the sagittal tunnel length and the total sagittal length, coronal dimension of the PCL fovea from the medial edge to the lateral edge (total coronal length; Fig 3C), coronal distance from the medial edge of the PCL fovea to the center of the tibial tunnel (coronal tunnel length; Fig 3D), ratio between the coronal tunnel length and the total coronal length, and the nearest distance from the posterior border of the tibial tunnel to the posterior cortex (length of the posterior bone bridge; Fig 3E). In this measurement, “-” was used to indicate that the cortex was blown out and was regarded as “cortical breakage.” To reduce intraand interobserver bias, the measurements were made each twice by 2 orthopaedic sports medicine fellows for all patients. The second measurement was performed 2 weeks after the first measurement. Statistical Methods Measurement reliability was assessed through an examination of intrarater and inter-rater reliability using the intraclass correlation coefficient, and post hoc power analysis was also performed. Post hoc power analysis was performed with G-power 3.1 (Copyright 2010-2013 Heinrich-Heine-Universität Düsseldorf) for the Mann-Whitney U-test with the following values: effect size, 0.8; a error, 0.05; sample size of group I, 26; and sample size of group II, 23; the power was 0.85. For the sagittal ratio, the effect size was calculated with the mean and standard deviation of each group, and the power with the following valuesdeffect size, 0.66; a error, 0.05; sample size of group I, 26; and sample size of group II, 23dwas 0.94. On the coronal ratio, effect size was also calculated with mean and standard deviation of each group, and the power with the following valuesdeffect size, 0.98; a error, 0.05; sample size of group I, 26; and sample size of group II, 23dwas 0.99. The SPSS statistical package, version 18.0 (SPSS, Chicago, IL, USA) was used. P < .05 was considered statistically significant. Comparisons of the tibial tunnel
position and the length of the posterior bone bridges between groups I and II were performed using a MannWhitney U-test.
Results The inter- and intraobserver reliabilities for tunnel measurement were satisfactory, with mean values of 0.85 (range, 0.63 to 0.99) and 0.84 (range, 0.65 to 0.98), respectively. Detailed measurement data are listed in the Table 1. The total sagittal lengths in group I and II were 19.2 2 mm and 17.7 5 mm, respectively (P ¼ .55). The sagittal tunnel lengths in groups I and II were 6.8 2.5 mm and 7.4 3.7 mm, respectively (P ¼ .21). Therefore, the ratios between sagittal tunnel length and total sagittal length for groups I and II were 35.4% 12.2% and 44.1% 23.1%, respectively (P ¼ .07). Group II showed a slightly more proximal tunnel without statistical significance. Similarly, the total coronal lengths in groups I and II were 15.7 1.5 mm and 14.9 1.5 mm, respectively (P ¼ .08). The coronal tunnel lengths in groups I and II were 7.4 1.5 mm and 8.4 2.6 mm, respectively (P ¼ .07). Thus, the ratios between the coronal tunnel lengths and total coronal lengths for groups I and II were 47.3% 9.2% and 57.3% 18.1%, respectively; group II showed a more laterally positioned tibial tunnel than did group I (P ¼ .03). The lengths of the posterior bone bridge in groups I and II were 0.6 1.1 mm and 0.8 0.9 mm, respectively (P ¼ .51). There were cortical breakages in 2 patients in group I and in 3 patients in group II. However, the breakages were <2 mm, and all portions of the tunnel exits were located within the PCL fovea. All of the cortical breakages in group I were in medially positioned tibial tunnels, and all of them in group II were in tibial tunnels laterally positioned to the center of the PCL fovea.
Discussion The principal finding of this study was that the PCL fovea landmark technique provided a more laterally located tibial tunnel with statistical significance and a more proximally located tibial tunnel without statistical significance. However, both groups showed that the tibial tunnels were made in the PCL fovea, and they showed less than 1 mm of difference, which might not be clinically relevant. The posterior aspect of the proximal tibia has a unique 3D anatomy compared with the mid- or distal tibia because multiple structures, including the tibial plateau, PCL fovea, and posterior cortex, abruptly change.1 The sloping central depression between the medial and lateral portions of the tibial plateau has been called PCL fovea, facet, or fossa.2,6 Anatomically, this insertion is distinct from the vertical cortex of the
TIBIAL TUNNEL TECHNIQUES IN PCL RECONSTRUCTION
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Fig 3. Sagittal distance from the posterior border of the tibial spine to the posterior edge of the posterior cruciate ligament (PCL) fovea (total sagittal length; Fig 3A), sagittal distance from the center of the tibial tunnel to the posterior edge of the PCL fovea (sagittal tunnel length; Fig 3B), coronal dimension of the PCL fovea from the medial edge to the lateral edge (total coronal length; Fig 3C), coronal distance from the medial edge of the PCL fovea to the center of the tibial tunnel (coronal tunnel length; Fig 3D), and nearest distance from the posterior border of the tibial tunnel to the posterior cortex (length of the posterior bone bridge; Fig 3E).
tibia and appears as a consistent radiographic landmark for pin placement in PCL reconstruction.2 On the coronal plane, the PCL inserts at points within the whole area of the PCL fovea, and it could imply a large insertional area with a wide acceptable range.7-9
However, slightly higher graft forces have been recorded when the tunnel is positioned too medially beyond 65 during passive knee flexion and may impinge the medial femoral condyle.10 In our study, a more laterally located tibial tunnel with statistical significance was
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Table 1. Comparison of the Measurement Data Between Groups TS, mm S, mm Ratio (S/TS) TC, mm C, mm Ratio (C/TC)
Group I 19.2 2 6.8 2.5 35.4 12.2% 15.7 1.5 7.4 1.5 47.3 9.2%
Group II 17.7 5 7.4 3.7 44.1 23.1% 14.9 1.5 8.4 2.6 57.3 18.1%
P Value .55 .21 .07 .08 .07 .03*
NOTE. Data presented as mean standard deviation unless otherwise indicated. C, coronal tunnel length; S, sagittal tunnel length; TC, total coronal length; TS, total sagittal length. *Statistically significant.
observed using the PCL fovea landmark technique. However, both groups showed that the tibial tunnels were made in the PCL fovea and located around the center of the coronal plane with less than 1 mm difference, which might not be clinically relevant. On the sagittal plane, several studies have examined the anatomy of the PCL insertion.2,7-9 Moorman et al.2 reported that the more posterior fibers, which insert up to 20 mm down the posterior cortex of the tibia, posterior and inferior to the PCL facet, are 0.5 mm thick. They emphasized that in the sagittal plane, the center of the working fibers of the PCL was 7 mm anterior to the posterior cortex of the tibia, as measured along the PCL fovea. Lee et al.1 reported that the PCL insertion was in the posterior 48% of the area of the PCL fovea, to the posterior cortex, consistent with Moorman et al.2 In our study, group II showed a tibial tunnel that was slightly anteriorly positioned, without statistical significance, however, the patients in both groups I and II showed tibial tunnels that were located approximately 7 mm anterior to the posterior tibial cortex. Identifying the PCL fovea and the real posterior cortex that is aligned with the PCL fovea is important during transtibial PCL reconstruction to prevent breakage of the posterior cortex. The posterior cortex of the plateau area curves posteriorly to the tibial plateau, whereas the posterior cortex of the PCL fovea area is depressed anteriorly. Thus, this area overlaps in lateral radiographs. Lee et al.1 reported that the longest distance between the real posterior cortex and the most posteriorly positioned cortical line is 10.8 2.2 mm. Limitations Our study has several limitations. First, this was a retrospective series and 2 surgeons were involved.
Therefore, selection and performance biases could exist in this study. Second, the PCL fovea landmark technique is technically demanding because it requires complete access to the posterior compartment, and skill is necessary for the palpation of the margin of the PCL fovea. Third, only post hoc power analysis was performed.
Conclusions A more laterally located tibial tunnel was produced using a PCL fovea landmark technique. However, the differences in centers were small and probably not clinically relevant. Therefore, the PCL fovea landmark technique might be an alternative method to the fluoroscopic imaging technique for locating the anatomic tibial tunnel during transtibial PCL reconstruction.
References 1. Lee YS, Ra HJ, Ahn JH, Ha JK, Kim JG. Posterior cruciate ligament tibial insertion anatomy and implications for tibial tunnel placement. Arthroscopy 2011;27:182-187. 2. Moorman CT 3rd, Murphy Zane MS, Bansai S, et al. Tibial insertion of the posterior cruciate ligament: A sagittal plane analysis using gross, histologic, and radiographic methods. Arthroscopy 2008;24:269-275. 3. Ahn JH, Chung YS, Oh I. Arthroscopic posterior cruciate ligament reconstruction using the posterior trans-septal portal. Arthroscopy 2003;19:101-107. 4. Ahn JH, Lee YS, Choi SH, Chang MJ, Lee do K. Singlebundle transtibial posterior cruciate ligament reconstruction using a bioabsorbable cross-pin tibial back side fixation. Knee Surg Sports Traumatol Arthrosc 2013;21:1023-1028. 5. Lee YS, Ahn JH, Jung YB, et al. Transtibial double bundle posterior cruciate ligament reconstruction using TransFix tibial fixation. Knee Surg Sports Traumatol Arthrosc 2007;15: 973-977. 6. Girgis FG, Marshall JL, Monajem A. The cruciate ligaments of the knee joint. Anatomical, functional and experimental analysis. Clin Orthop Relat Res 1975:216-231. 7. Edwards A, Bull AM, Amis AA. The attachments of the fiber bundles of the posterior cruciate ligament: An anatomic study. Arthroscopy 2007;23:284-290. 8. Tajima G, Nozaki M, Iriuchishima T, et al. Morphology of the tibial insertion of the posterior cruciate ligament. J Bone Joint Surg Am 2009;91:859-866. 9. Takahashi M, Matsubara T, Doi M, Suzuki D, Nagano A. Anatomical study of the femoral and tibial insertions of the anterolateral and posteromedial bundles of human posterior cruciate ligament. Knee Surg Sports Traumatol Arthrosc 2006;14:1055-1059. 10. Markolf KL, McAllister DR, Young CR, McWilliams J, Oakes DA. Biomechanical effects of medial-lateral tibial tunnel placement in posterior cruciate ligament reconstruction. J Orthop Res 2003;21:177-182.