- Email: [email protected]
The Importance of Tibial Tunnel Placement in Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction
The Importance of Tibial Tunnel Placement in Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction Kazuhisa Hatayama, M.D., Ph.D., Masanori Terauchi, M.D., Ph.D., Kenichi Saito, M.D., Hiroshi Higuchi, M.D., Ph.D., Shinya Yanagisawa, M.D., and Kenji Takagishi, M.D., Ph.D.
Purpose: The purposes of this study were to measure the anterior edge of the tibial tunnel after anatomic anterior cruciate ligament (ACL) reconstruction on lateral radiographs and to determine whether the difference in tibial tunnel placement affects postoperative outcomes. Methods: For 60 patients who underwent anatomic double-bundle ACL reconstruction with semitendinosus tendon, we evaluated the side-to-side difference in anterior tibial translation on stress radiographs, as well as rotational stability by the pivot-shift test, 2 years after surgery. Loss of extension (LOE) was evaluated on lateral radiographs of both knees in full extension, and graft integrity was assessed during second-look arthroscopy 1 to 2 years after surgery. On true lateral radiographs, we measured the anterior placement percentage of the tibial tunnel using the method described by Amis and Jakob. The cutoff value was set at 25% of the mean value of the anterior edge of the ACL that Amis and Jakob reported, and patients were divided into 2 groups (27 in the anterior group and 33 in the posterior group). Postoperative clinical results were compared between the groups. Results: The mean anterior placement percentage was 26.0% 4.1%. The postoperative mean side-to-side difference was 1.4 2.7 mm for the anterior group and 3.0 2.7 mm for the posterior group, a significant difference (P < .05). The positive ratio of the pivot-shift test was not significantly different between groups (P > .05). Mean LOE in the anterior and posterior groups was 0.9 3.0 and 0.8 4.0 , respectively; the difference was not significant (P > .05). Five of 27 knees in the anterior group and 5 of 33 knees in the posterior group had superficial graft laceration or elongation, which was not significantly different (P > .05). Conclusions: Anterior placement of the tibial tunnel in anatomic double-bundle ACL reconstruction leads to better anterior knee stability than posterior placement does. Anterior tibial tunnel placement inside the footprint did not increase the incidence of LOE and graft failure. Level of Evidence: Level IV, therapeutic case series.
N
umerous studies of the anatomic femoral and tibial attachment area of the anterior cruciate ligament (ACL) have been reported that have clarified that the anatomic tunnel position is different from the traditional nonanatomic tunnel position.1-4 This recognition led to increasing interest in anatomic ACL reconstruction in which the tunnels were placed in the
From the Department of Orthopaedic Surgery, Social Insurance Gunma Chuo General Hospital (K.H., M.T.); the Department of Orthopaedic Surgery, Gunma University Graduate School of Medicine (K.S., S.Y., K.T.); and the Department of Orthopaedic Sports Surgery, Asakura Sports Rehabilitation Clinic (H.H.), Maebashi, Japan. The authors report that they have no conflicts of interest in the authorship and publication of this article. Received April 9, 2012; accepted February 6, 2013. Address correspondence to Kazuhisa Hatayama, M.D., Ph.D., Department of Orthopaedic Surgery, Social Insurance Gunma Chuo General Hospital, 1-7-13 Koun, Maebashi, Gunma, 371-0025, Japan. E-mail: [email protected] Ó 2013 by the Arthroscopy Association of North America 0749-8063/12223/$36.00 http://dx.doi.org/10.1016/j.arthro.2013.02.003
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center of the native femoral and tibial insertion sites. The femoral attachment area of the ACL is located just posterior to the lateral intercondylar ridge and extends to the posterior cartilage margin of the lateral femoral condyle.1,3 It has been reported that anatomic femoral tunnels are located lower (more posterior) than the traditional positions.2 Yet it has been clarified that the ACL tibial attachment is located widely in the anteroposterior direction in the tibial plateau and that the anteromedial tunnel begins anterior to the traditional position.2,4 Bedi et al.5 evaluated the effect of tibial tunnel position on restoration of knee kinematics and stability after ACL reconstruction with cadaveric knees. They showed that the anterior placement of the tibial tunnel results in significantly reduced anterior tibial translation, as shown on the Lachman and pivot-shift examinations, compared with placement of an ACL graft in the posterior aspect of the tibial footprint. However, Howell et al.6,7 have reported that anterior placement of the tibial tunnel causes intercondylar roof impingement of the ACL graft, resulting in graft failure and loss of
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 29, No 6 (June), 2013: pp 1072-1078
IMPORTANCE OF TIBIAL TUNNEL PLACEMENT
extension (LOE), and they pointed out the importance of avoiding impingement. Their caution is relevant to traditional nonanatomic reconstruction, but it is unknown whether it is applicable to anatomic ACL reconstruction. Jagodzinski et al.8 analyzed the interaction between the ACL and the roof of the intercondylar notch in the uninjured knee, using magnetic resonance cinematography, and found that all ACLs made contact with the intercondylar roof in hyperextension of the knee. In view of this result, it may be that anatomic ACL reconstruction causes physiologic roof impingement. However, it remains unclear how much impingement is tolerated after ACL reconstruction. In anatomic ACL reconstruction, the effects of anterior placement of the tibial tunnel on LOE and graft integrity have not been thoroughly investigated. The purposes of this study were to measure the anterior edge of the tibial tunnel after anatomic ACL reconstruction on lateral radiographs and to determine whether the difference in tibial tunnel placement affects postoperative outcomes. We hypothesized that anterior tibial tunnel placement in anatomic ACL reconstruction does not cause graft roof impingement and leads to better knee stability after surgery than posterior placement does, without either postoperative LOE or graft failure.
Methods Patients Between January 2008 and April 2010, 76 consecutive patients underwent primary anatomic doublebundle ACL reconstruction with semitendinosus tendon at our institute. Patients who had unilateral ACL injury were included in our study, and patients were excluded from our study if they had bilateral ACL injuries, multiple ligamentous injuries, fractures around the knee, or previous injury or surgery. Of those 76 patients, 7 had bilateral ACL injuries, 2 had multiple ligamentous injury, and 1 had a proximal tibial fracture. Four were lost to follow-up monitoring because they moved to another location, and 2 declined to undergo second-look arthroscopy. Thus we enrolled 60 patients in our study, 26 male and 34 female patients, with a mean age of 26.4 10.7 years (range, 13 to 49 years) at the time of surgery. This study was approved by our institutional review board. Surgical Technique for Anatomic ACL Reconstruction A single surgical team performed all operations. All patients underwent arthroscopic ACL reconstruction under general anesthesia. An oblique incision approximately 5 cm long was made in the anteromedial portion of the proximal tibia. The semitendinosus tendon was harvested with a tendon stripper. The harvested
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tendon was cut in half to create both an anteromedial bundle (AMB) graft and a posterolateral bundle (PLB) graft; each tendon was doubled. An EndoButton CL (Smith & Nephew, Andover, MA) was attached at the looped end of each graft, and a Telos artificial ligament (Telos, Marburg, Germany) was sutured with the other end by a gloved suture technique.9,10 After the ACL remnant was resected around the femoral attachment area, the lateral intercondylar ridge was visualized on the wall. We created femoral tunnels through an accessory anteromedial portal. While keeping the knee at maximum flexion, we inserted a 2.4-mm Kirschner wire at the center of the AMB footprint, which is located anterior to the posterior cartilage margin of the lateral femoral condyle and behind the ridge at 90 of knee flexion. Using this wire as a guide, we made a tunnel through the femur with a 4.5-mm cannulated drill and then measured the length of the tunnel with a depth gauge. Then we created a tunnel matched to the diameter of the AMB graft, using a cannulated drill. Similarly, we created a femoral tunnel for the PLB graft while keeping the knee at maximum flexion, at the center of the PLB footprint, which is located at the most peripheral position of the lateral femoral condyle and behind the ridge at 90 of knee flexion (Figs 1A and 2). We created femoral tunnels for both the AMB and PLB inside the crescent-shaped area at the ACL insertion in every knee while viewing the ridge. If we could identify the lateral bifurcate ridge,1 this also was used as a landmark. We did not perform a notchplasty in any knee. Next, we created tibial tunnels using an ACL drill guide. Tibial tunnels for AMB and PLB grafts were created to fill up the tibial attachment point of the ACL. In other words, a tunnel for the AMB graft was created at a position anteromedial to the ACL attachment and lateral to the medial tibial spine. A tunnel for the PLB graft was created anterior to the intertubercular ridge between the medial and lateral tibial intercondylar tubercles (Fig 1B). To correctly create the tibial tunnel inside the anatomic footprint, we checked the position of the guidewire in near extension. In near extension of the knee, the transverse ligament moves forward, making visible the anterior edge of the tibial footprint. The grafts were passed through each tunnel, the femoral side was secured by flipping the EndoButton devices, and the tibial fixation was accomplished with 2 spiked staples (Ai-Medic, Tokyo, Japan). Because biomechanical study has shown that average strains in both bundles were equal at 15 of knee flexion,11 we tensioned each bundle at 30 N with the knee at 15 of flexion, using a ligament tensioner. Postoperative Rehabilitation The postoperative rehabilitation protocol was the same for all patients. Partial weight bearing was started 1 week after surgery, progressing to full weight bearing
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K. HATAYAMA ET AL. Fig 1. Arthroscopic view of left knee. (A) Femoral tunnels at 90 of knee flexion viewing from anteromedial portal and (B) tibial tunnel positions viewing from anterolateral portal in double-bundle reconstruction. We carefully created bone tunnels not to connect each tunnel for the AMB and PLB in the femoral and tibial tunnels. The width of the bony bridge between each tunnel is approximately 1 to 2 mm. (GAM, guidewire for AMB; GPL, guidewire for PLB; TAM, tunnel for AMB; TPL, tunnel for PLB.)
at 3 weeks. Range-of-motion exercises were initiated 1 week after surgery, and full range of motion was allowed 3 weeks. Jogging was started at 3 months. With regard to the schedule for return to sports, many authors reported that full sports activity was allowed 8 to 12 months after ACL reconstruction with hamstring tendon.12-14 We allowed jumping-andcutting exercises, as used in basketball, volleyball, and soccer, at 6 months and allowed full contact sports participation at 8 months. Clinical Evaluations All patients underwent clinical examinations before and 2 years after surgery by 2 of the authors (K.H. and M.T.). At those examinations, we measured the side-toside difference (SSD) in anterior tibial translation on
Fig 2. Three-dimensional computed tomography showing femoral tunnel position.
stress radiographs using a Telos Stress Device (type SE 2000; Telos, Hungen-Obbornhofen, Germany) at 20 of knee flexion under an anterior drawer force of 150 N and evaluated anterior knee stability. Rotational stability was assessed by the manual pivot shift 2 years after surgery. We evaluated pivot-shift test findings according to the method described by Yasuda et al.10 and categorized them as negative, þ, and þþ. Clinical results were determined by the Lysholm score 2 years after surgery. All patients provided informed consent, and secondlook arthroscopy at the time of staple removal was performed to assess ACL graft integrity independently of postoperative symptoms at a mean of 15.5 months (range, 12 to 23 months) (the timing was determined by each patient) after the initial operation. Synovial coverage and the presence of graft laceration or elongation were assessed during second-look arthroscopy. At the same time, to detect subtle LOE quantitatively, we obtained a lateral radiograph, with the patient under general or lumbar anesthesia, of the reconstructed and contralateral healthy knees in full extension while the patient’s heels were elevated above the table. For reproducibility, both posterior condyles of the femur were superimposed under fluoroscopy in every knee. Because there is an issue regarding exposure to radiation, we planned to use a protector covering the patient’s trunk during exposure; this was approved by the institutional review board. We measured the extension angleddefined as the angle between the anterior cortex of the femur and the posterior cortex of the tibiadof both knees (Fig 3). LOE was defined as the difference in angles between the reconstructed and contralateral healthy knees. Radiographic Evaluation of Tibial Tunnel Position The first author (K.H.) performed radiographic evaluation. A true lateral radiograph was taken to evaluate the tibial tunnel position 1 year after surgery. We measured the anterior placement percentage of the tibial tunnel using the method reported by Amis and
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IMPORTANCE OF TIBIAL TUNNEL PLACEMENT
Fig 3. Lateral radiograph with reconstructed knee in full extension. The (A) maximal extension angle was measured as the angle between (B) the anterior cortex of the femur and the (C) posterior cortex of the tibia. (D, line parallel to line C.)
Jakob15 (Fig 4). We measured both the length from the tibial anterior margin to the anterior edge of the tibial tunnel (A) and the anteroposterior length of the tibial plateau (TP) by measuring the line that is parallel to the medial tibial plateau and passes through the anterior and posterior margins of the proximal end of the tibia.
The sagittal percentage of the tibial tunnel was calculated as follows: Anterior placement percentage of tibial tunnel ¼ A/TP 100 (%). The cutoff value was set at 25% of the mean value of the anterior edge of the ACL footprint that Amis and Jakob15 previously reported, and our patients were divided into 2 groups: the anterior group, in whom the tibial tunnel was created more anterior, and the posterior group, in whom the tunnel was more posterior. Postoperative clinical outcomes were compared between the groups. All radiographic measurements were performed with an iRad-IA viewer (Infocom, Tokyo, Japan). Statistics All statistical analyses were performed by the first author (K.H.) using StatView software (SAS Institute, Cary, NC). The Student t test was used to compare the SSD in anterior tibial translation and the LOE between the groups. The Mann-Whitney U test was used to compare pivot-shift test results and Lysholm scores between the groups. The c2 test was used to compare the incidence of LOE greater than 5 and second-look findings between the groups. The Pearson correlation coefficient was used to investigate the relation between the LOE and tibial tunnel position. P < .05 was considered significant.
Results
Fig 4. The anterior placement percentage of the tibial tunnel was calculated from true lateral radiographs as the distance from the anterior margin of the tibia to the anterior edge of the tibial tunnel (A) divided by the anteroposterior length of the tibial plateau (TP) and multiplied by 100.
The preoperative and postoperative mean SSDs in anterior translation were 7.3 4.1 mm and 2.2 2.9 mm, respectively, and the anterior translation was significantly reduced after surgery (P < .001). On the postoperative pivot-shift test, 7 of 60 patients (11.7%) had scores of grade þ and 3 patients (5%) had a score of grade þþ. The mean postoperative Lysholm score was 96.8 (range, 85 to 100). The mean LOE was 0.1 3.7 , and 4 knees had LOE greater than 5 . There was no LOE greater than 10 in any knee. The mean anterior placement percentage of the tibial tunnel was 26.0% 4.1% (range, 16.5% to 34.3%). We assigned 27 knees to the anterior group and 33 knees to the posterior group (Table 1). The distributions of age and sex were not significantly different between the groups (Table 1). The mean postoperative SSD in anterior tibial translation on stress radiographs was 1.4 2.7 mm for the anterior group and 3.0 2.7 mm for the posterior group, a significant difference (P ¼ .03). Positive ratios were found on the pivot-shift test in the anterior and posterior groups in 4 of 27 knees (14.8%) and 6 of 33 knees (18.2%), respectively; this was not significantly different (P ¼ .71). The mean postoperative Lysholm scores in the anterior and posterior groups were 96.1 (range, 85 to 100) and 97.6 (range, 90 to 100), respectively, which was not significantly different (P ¼ .23) (Table 1).
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Table 1. Demographic Data and Clinical Outcomes After Surgery Parameter
Anterior Group (n ¼ 27)
Posterior Group (n ¼ 33)
P Value
Age (range) (yr) Sex (M/F) SSD of anterior tibial translation (mm) Pivot-shift test (no. of cases) Negative þ þþ Lysholm score LOE ( ) LOE <5 (no. of cases) Graft integrity at second-look arthroscopy: superficial laceration or elongation of graft (no. of cases)
26.8 (13-49) 12/15 1.4 2.7
26.1 (13-42) 14/19 3.0 2.7
.79 .88 .03 .71
23 3 1 96.1 (85-100) 0.9 3.0 2 5
27 4 2 97.6 (90-100) 0.8 4.0 2 5
The LOE in the anterior and posterior groups was 0.9 3.0 and 0.8 4.0 , respectively, with no significant difference (P ¼ .08) (Table 1). LOE greater than 5 was found in 2 of 27 knees in the anterior group and 2 of 33 knees in the posterior group, with no significant difference (P ¼ .84). There was no significant correlation between the LOE and the anterior placement percentage of the tibial tunnel (r ¼ 0.21, P ¼ .12). With respect to ACL graft integrity at second-look arthroscopy, 5 of 27 knees (18.5%) in the anterior group versus 5 of 33 knees (15.2%) in the posterior group had laceration of the superficial fibers, graft elongation, or partial synovial coverage, which was not significantly different (P ¼ .73) (Table 1). Three patients (2 in the anterior group and 1 in the posterior group) had cyclops lesions that were resected.
Discussion Our study showed that anterior placement of the tibial tunnel results in significantly more reduced postoperative anterior tibial translation after anatomic ACL reconstruction than posterior placement does without increasing the risk of postoperative LOE and graft failure. Bedi et al.5 also showed that positioning the tibial tunnel in the anterior aspect of the footprint results in significantly less anterior tibial translation than posterior tibial footprint positioning in a cadaveric study. They suggested that anterior placement of the tibial tunnel results in correspondingly greater sagittal graft obliquity and improved control of anterior tibial translation after ACL reconstruction.5 To minimize the risk of roof impingement, posterior placement of the tibial tunnel was historically recommended with traditional transtibial ACL reconstruction.6,7 However, it has been pointed out that posterior placement of the tibial tunnel results in nonanatomic vertical graft placement16 and inferior postoperative stability.17,18 Even if the tibial tunnel in anatomic ACL reconstruction is located more anteriorly, roof impingement of the graft may be unlikely to occur because the femoral tunnel is created at a lower position than in traditional ACL reconstruction. Iriuchishima et al.19
.23 .08 .84 .73
reported no significant difference in roof impingement pressure between the intact ACL and anatomic ACL reconstruction in a cadaveric study. However, no in vivo studies have investigated whether anterior placement of the tibial tunnel causes postoperative LOE and graft failure resulting from roof impingement after anatomic double-bundle ACL reconstruction. The tibial insertion site is larger than the midsubstance of the ACL, which results in its classic fanned-out shape.20 That fanned-out shape makes it difficult to completely restore normal ACL anatomy during ACL reconstruction and may result in theoretic roof impingement and LOE if the graft is placed in the anterior aspect of the tibial insertion. We found that LOE in the anterior group was a little greater than that in the posterior group; however, the difference was not statistically significant. The incidence of LOE greater than 5 was also not significantly different between our groups. In addition, there was no significant correlation between LOE and the anterior placement percentage of the tibial tunnel. Furthermore, graft integrity at secondlook arthroscopy was not significantly different between our 2 groups. Jagodzinski et al.8 showed that a certain degree of roof impingement in hyperextension is physiologic for the uninjured knee. Therefore an anatomically reconstructed graft may tolerate physiologic roof impingement without damage. Our study showed no significant difference in postoperative rotational stability between anterior and posterior tibial tunnel placement. However, Bedi et al.5 showed that anterior tunnel placement significantly reduced anterior translation of the lateral compartment during the mechanized pivot shift compared with posterior tunnel placement. The assessment of rotational stability in our study was not quantitative but rather was qualitative, which may be why our results differ from those of the cadaveric study by Bedi et al. Furthermore, several authors have reported that coronal graft obliquity is more important to restore rotational stability and that it depends on the femoral tunnel position.18 The anatomic femoral tunnel position is lower and may improve coronal graft obliquity
IMPORTANCE OF TIBIAL TUNNEL PLACEMENT
and rotational control of the knee. Therefore it may be that the difference in anteroposterior position of the tibial tunnel in our study did not affect coronal obliquity, and postoperative rotational stability might not be significantly different between groups. Limitations Our study had some limitations. First, we had a relatively small sample size and short duration of followup. Second, the assessment of rotational stability was not quantitative. Third, investigator blinding was not used. Fourth, it is impossible to assess where the tibial tunnel was created inside the tibial footprint in each case. There are some reports of sagittal radiographic studies of the tibial footprint of the ACL.20,21 Doi et al.21 reported that the anterior edge of the ACL was located 25.1% 4.2% (range, 15.6% to 33.9%) from the anterior margin of the tibia in the anteroposterior direction. In our study the anterior edge of the tibial tunnel was located 26.0% 4.1% (range, 16.5% to 34.3%) from the margin, and the mean value was similar to that in the cadaveric study of Doi et al. However, variation of the tibial footprint morphology in the individual knee must be taken into account. We create the tibial tunnel with reference to the ACL remnant during surgery because on the tibial side, bony landmarks are less defined. Our study suggested that for better postoperative anterior stability, it is important to create the tibial tunnel in a more anterior position inside the anatomic footprint.
Conclusions Our study showed that anterior placement of the tibial tunnel in anatomic double-bundle ACL reconstruction leads to better anterior knee stability than posterior placement does. Anterior tibial tunnel placement inside the footprint did not increase the incidence of LOE and graft failure.
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Acknowledgment Katharine O’Moore-Klopf, E.L.S., East Setauket, New York, provided professional English-language editing of the manuscript.
References 1. Ferretti M, Ekdahl M, Shen W, Fu FH. Osseous landmarks of the femoral attachment of the anterior cruciate ligament: An anatomic study. Arthroscopy 2007;23:1218-1225. 2. Kopf S, Forsythe B, Wong AK, et al. Nonanatomic tunnel position in traditional transtibial single-bundle anterior cruciate ligament reconstruction evaluated by threedimensional computed tomography. J Bone Joint Surg Am 2010;92:1427-1431. 3. Purnell ML, Larson AI, Clancy WG. Anterior cruciate ligament insertions on the tibia and femur and their relationships to critical bony landmarks using
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high-resolution volume-rendering computed tomography. Am J Sports Med 2008;36:2083-2090. Zantop T, Wellmann M, Fu FH, Petersen W. Tunnel positioning of anteromedial and posterolateral bundles in anatomic anterior cruciate ligament reconstruction: Anatomic and radiographic finding. Am J Sports Med 2008;36:65-72. Bedi A, Maak T, Musahl V, et al. Effect of tibial tunnel position on stability of the knee after anterior cruciate ligament reconstruction: Is the tibial tunnel position most important? Am J Sports Med 2011;39:366-373. Howell SM, Taylor MA. Failure of reconstruction of the anterior cruciate ligament due to impingement by the intercondylar roof. J Bone Joint Surg Am 1993;75:1044-1055. Howell SM, Barad SJ. Knee extension and its relationship to the slope of the intercondylar roof. Implications for positioning the tibial tunnel in anterior cruciate ligament reconstructions. Am J Sports Med 1995;23:288-294. Jagodzinski M, Richter GM, Pässler HH. Biomechanical analysis of knee hyperextension and of the impingement of the anterior cruciate ligament: A cinematographic MRI study with impact on tibial tunnel positioning in anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc 2000;8:11-19. Asagumo H, Kimura M, Kobayashi Y, Taki M, Takagishi K. Anatomic reconstruction of the anterior cruciate ligament using double-bundle hamstring tendons: Surgical techniques, clinical outcomes, and complications. Arthroscopy 2007;23:602-609. Yasuda K, Kondo E, Ichiyama H, Tanabe Y, Tohyama H. Clinical evaluation of anatomic double-bundle anterior cruciate ligament reconstruction procedure using hamstring tendon graft: Comparisons among 3 different procedures. Arthroscopy 2006;22:240-251. Bach JM, Hull ML, Patterson HA. Direct measurement of strain in the posterolateral bundle of the anterior cruciate ligament. J Biomech 1997;30:281-283. Ardern CL, Taylor NF, Feller JA, Webster KE. Return-tosport outcomes at 2 to 7 years after anterior cruciate ligament reconstruction surgery. Am J Sports Med 2012;40:41-48. Kinugasa K, Mae T, Matsumoto N, Nakagawa S, Yoneda M, Shino K. Effect of patient age on morphology of anterior cruciate ligament grafts at second-look arthroscopy. Arthroscopy 2011;27:38-45. Tohyama H, Kondo E, Hayashi R, Kitamura N, Yasuda K. Gender-based differences in outcome after anatomic double-bundle anterior cruciate ligament reconstruction with hamstring tendon autografts. Am J Sports Med 2011;39:1849-1857. Amis AA, Jakob RP. Anterior cruciate ligament graft positioning, tensioning and twisting. Knee Surg Sports Traumatol Arthrosc 1998;6(suppl 1):S2-S12. Ayerza MA, Muscolo DL, Costa-Paz M, Makino A, Rondon L. Comparison of sagittal obliquity of the reconstructed anterior cruciate ligament with native anterior cruciate ligament using magnetic resonance imaging. Arthroscopy 2003;19:257-261. Lee MC, Seong SC, Lee S, et al. Vertical femoral tunnel placement results in rotational knee laxity after anterior cruciate ligament reconstruction. Arthroscopy 2007;23: 771-778.
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18. Loh JC, Fukuda Y, Tsuda E, Steadman RJ, Fu FH, Woo LY. Knee stability and graft function following anterior cruciate ligament reconstruction: Comparison between 11 o’clock and 10 o’clock femoral tunnel placement. Arthroscopy 2003;19:297-304. 19. Iriuchishima T, Tajima G, Ingham SJ, Shen W, Smolinski P, Fu HF. Impingement pressure in the anatomical and nonanatomical anterior cruciate ligament reconstruction: A cadaver study. Am J Sports Med 2010;38: 1611-1617.
20. Stäubli HU, Rauschning W. Tibial attachment area of the anterior cruciate ligament in the extended knee position: Anatomy and cryosections in vitro complemented by magnetic resonance arthrography in vivo. Knee Surg Sports Traumatol Arthrosc 1994;2:138-146. 21. Doi M, Takahashi M, Abe M, Suzuki D, Nagano A. Lateral radiographic study of the tibial sagittal insertions of the anteromedial and posterolateral bundles of human anterior cruciate ligament. Knee Surg Sports Traumatol Arthrosc 2009;17:347-351.
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Purpose: The purposes of this study were to measure the anterior edge of the tibial tunnel after anatomic anterior cruciate ligament (ACL) reconstruction on lateral radiographs and to determine whether the difference in tibial tunnel placement affects postoperative outcomes. Methods: For 60 patients who underwent anatomic double-bundle ACL reconstruction with semitendinosus tendon, we evaluated the side-to-side difference in anterior tibial translation on stress radiographs, as well as rotational stability by the pivot-shift test, 2 years after surgery. Loss of extension (LOE) was evaluated on lateral radiographs of both knees in full extension, and graft integrity was assessed during second-look arthroscopy 1 to 2 years after surgery. On true lateral radiographs, we measured the anterior placement percentage of the tibial tunnel using the method described by Amis and Jakob. The cutoff value was set at 25% of the mean value of the anterior edge of the ACL that Amis and Jakob reported, and patients were divided into 2 groups (27 in the anterior group and 33 in the posterior group). Postoperative clinical results were compared between the groups. Results: The mean anterior placement percentage was 26.0% 4.1%. The postoperative mean side-to-side difference was 1.4 2.7 mm for the anterior group and 3.0 2.7 mm for the posterior group, a significant difference (P < .05). The positive ratio of the pivot-shift test was not significantly different between groups (P > .05). Mean LOE in the anterior and posterior groups was 0.9 3.0 and 0.8 4.0 , respectively; the difference was not significant (P > .05). Five of 27 knees in the anterior group and 5 of 33 knees in the posterior group had superficial graft laceration or elongation, which was not significantly different (P > .05). Conclusions: Anterior placement of the tibial tunnel in anatomic double-bundle ACL reconstruction leads to better anterior knee stability than posterior placement does. Anterior tibial tunnel placement inside the footprint did not increase the incidence of LOE and graft failure. Level of Evidence: Level IV, therapeutic case series.
N
umerous studies of the anatomic femoral and tibial attachment area of the anterior cruciate ligament (ACL) have been reported that have clarified that the anatomic tunnel position is different from the traditional nonanatomic tunnel position.1-4 This recognition led to increasing interest in anatomic ACL reconstruction in which the tunnels were placed in the
From the Department of Orthopaedic Surgery, Social Insurance Gunma Chuo General Hospital (K.H., M.T.); the Department of Orthopaedic Surgery, Gunma University Graduate School of Medicine (K.S., S.Y., K.T.); and the Department of Orthopaedic Sports Surgery, Asakura Sports Rehabilitation Clinic (H.H.), Maebashi, Japan. The authors report that they have no conflicts of interest in the authorship and publication of this article. Received April 9, 2012; accepted February 6, 2013. Address correspondence to Kazuhisa Hatayama, M.D., Ph.D., Department of Orthopaedic Surgery, Social Insurance Gunma Chuo General Hospital, 1-7-13 Koun, Maebashi, Gunma, 371-0025, Japan. E-mail: [email protected] Ó 2013 by the Arthroscopy Association of North America 0749-8063/12223/$36.00 http://dx.doi.org/10.1016/j.arthro.2013.02.003
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center of the native femoral and tibial insertion sites. The femoral attachment area of the ACL is located just posterior to the lateral intercondylar ridge and extends to the posterior cartilage margin of the lateral femoral condyle.1,3 It has been reported that anatomic femoral tunnels are located lower (more posterior) than the traditional positions.2 Yet it has been clarified that the ACL tibial attachment is located widely in the anteroposterior direction in the tibial plateau and that the anteromedial tunnel begins anterior to the traditional position.2,4 Bedi et al.5 evaluated the effect of tibial tunnel position on restoration of knee kinematics and stability after ACL reconstruction with cadaveric knees. They showed that the anterior placement of the tibial tunnel results in significantly reduced anterior tibial translation, as shown on the Lachman and pivot-shift examinations, compared with placement of an ACL graft in the posterior aspect of the tibial footprint. However, Howell et al.6,7 have reported that anterior placement of the tibial tunnel causes intercondylar roof impingement of the ACL graft, resulting in graft failure and loss of
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 29, No 6 (June), 2013: pp 1072-1078
IMPORTANCE OF TIBIAL TUNNEL PLACEMENT
extension (LOE), and they pointed out the importance of avoiding impingement. Their caution is relevant to traditional nonanatomic reconstruction, but it is unknown whether it is applicable to anatomic ACL reconstruction. Jagodzinski et al.8 analyzed the interaction between the ACL and the roof of the intercondylar notch in the uninjured knee, using magnetic resonance cinematography, and found that all ACLs made contact with the intercondylar roof in hyperextension of the knee. In view of this result, it may be that anatomic ACL reconstruction causes physiologic roof impingement. However, it remains unclear how much impingement is tolerated after ACL reconstruction. In anatomic ACL reconstruction, the effects of anterior placement of the tibial tunnel on LOE and graft integrity have not been thoroughly investigated. The purposes of this study were to measure the anterior edge of the tibial tunnel after anatomic ACL reconstruction on lateral radiographs and to determine whether the difference in tibial tunnel placement affects postoperative outcomes. We hypothesized that anterior tibial tunnel placement in anatomic ACL reconstruction does not cause graft roof impingement and leads to better knee stability after surgery than posterior placement does, without either postoperative LOE or graft failure.
Methods Patients Between January 2008 and April 2010, 76 consecutive patients underwent primary anatomic doublebundle ACL reconstruction with semitendinosus tendon at our institute. Patients who had unilateral ACL injury were included in our study, and patients were excluded from our study if they had bilateral ACL injuries, multiple ligamentous injuries, fractures around the knee, or previous injury or surgery. Of those 76 patients, 7 had bilateral ACL injuries, 2 had multiple ligamentous injury, and 1 had a proximal tibial fracture. Four were lost to follow-up monitoring because they moved to another location, and 2 declined to undergo second-look arthroscopy. Thus we enrolled 60 patients in our study, 26 male and 34 female patients, with a mean age of 26.4 10.7 years (range, 13 to 49 years) at the time of surgery. This study was approved by our institutional review board. Surgical Technique for Anatomic ACL Reconstruction A single surgical team performed all operations. All patients underwent arthroscopic ACL reconstruction under general anesthesia. An oblique incision approximately 5 cm long was made in the anteromedial portion of the proximal tibia. The semitendinosus tendon was harvested with a tendon stripper. The harvested
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tendon was cut in half to create both an anteromedial bundle (AMB) graft and a posterolateral bundle (PLB) graft; each tendon was doubled. An EndoButton CL (Smith & Nephew, Andover, MA) was attached at the looped end of each graft, and a Telos artificial ligament (Telos, Marburg, Germany) was sutured with the other end by a gloved suture technique.9,10 After the ACL remnant was resected around the femoral attachment area, the lateral intercondylar ridge was visualized on the wall. We created femoral tunnels through an accessory anteromedial portal. While keeping the knee at maximum flexion, we inserted a 2.4-mm Kirschner wire at the center of the AMB footprint, which is located anterior to the posterior cartilage margin of the lateral femoral condyle and behind the ridge at 90 of knee flexion. Using this wire as a guide, we made a tunnel through the femur with a 4.5-mm cannulated drill and then measured the length of the tunnel with a depth gauge. Then we created a tunnel matched to the diameter of the AMB graft, using a cannulated drill. Similarly, we created a femoral tunnel for the PLB graft while keeping the knee at maximum flexion, at the center of the PLB footprint, which is located at the most peripheral position of the lateral femoral condyle and behind the ridge at 90 of knee flexion (Figs 1A and 2). We created femoral tunnels for both the AMB and PLB inside the crescent-shaped area at the ACL insertion in every knee while viewing the ridge. If we could identify the lateral bifurcate ridge,1 this also was used as a landmark. We did not perform a notchplasty in any knee. Next, we created tibial tunnels using an ACL drill guide. Tibial tunnels for AMB and PLB grafts were created to fill up the tibial attachment point of the ACL. In other words, a tunnel for the AMB graft was created at a position anteromedial to the ACL attachment and lateral to the medial tibial spine. A tunnel for the PLB graft was created anterior to the intertubercular ridge between the medial and lateral tibial intercondylar tubercles (Fig 1B). To correctly create the tibial tunnel inside the anatomic footprint, we checked the position of the guidewire in near extension. In near extension of the knee, the transverse ligament moves forward, making visible the anterior edge of the tibial footprint. The grafts were passed through each tunnel, the femoral side was secured by flipping the EndoButton devices, and the tibial fixation was accomplished with 2 spiked staples (Ai-Medic, Tokyo, Japan). Because biomechanical study has shown that average strains in both bundles were equal at 15 of knee flexion,11 we tensioned each bundle at 30 N with the knee at 15 of flexion, using a ligament tensioner. Postoperative Rehabilitation The postoperative rehabilitation protocol was the same for all patients. Partial weight bearing was started 1 week after surgery, progressing to full weight bearing
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K. HATAYAMA ET AL. Fig 1. Arthroscopic view of left knee. (A) Femoral tunnels at 90 of knee flexion viewing from anteromedial portal and (B) tibial tunnel positions viewing from anterolateral portal in double-bundle reconstruction. We carefully created bone tunnels not to connect each tunnel for the AMB and PLB in the femoral and tibial tunnels. The width of the bony bridge between each tunnel is approximately 1 to 2 mm. (GAM, guidewire for AMB; GPL, guidewire for PLB; TAM, tunnel for AMB; TPL, tunnel for PLB.)
at 3 weeks. Range-of-motion exercises were initiated 1 week after surgery, and full range of motion was allowed 3 weeks. Jogging was started at 3 months. With regard to the schedule for return to sports, many authors reported that full sports activity was allowed 8 to 12 months after ACL reconstruction with hamstring tendon.12-14 We allowed jumping-andcutting exercises, as used in basketball, volleyball, and soccer, at 6 months and allowed full contact sports participation at 8 months. Clinical Evaluations All patients underwent clinical examinations before and 2 years after surgery by 2 of the authors (K.H. and M.T.). At those examinations, we measured the side-toside difference (SSD) in anterior tibial translation on
Fig 2. Three-dimensional computed tomography showing femoral tunnel position.
stress radiographs using a Telos Stress Device (type SE 2000; Telos, Hungen-Obbornhofen, Germany) at 20 of knee flexion under an anterior drawer force of 150 N and evaluated anterior knee stability. Rotational stability was assessed by the manual pivot shift 2 years after surgery. We evaluated pivot-shift test findings according to the method described by Yasuda et al.10 and categorized them as negative, þ, and þþ. Clinical results were determined by the Lysholm score 2 years after surgery. All patients provided informed consent, and secondlook arthroscopy at the time of staple removal was performed to assess ACL graft integrity independently of postoperative symptoms at a mean of 15.5 months (range, 12 to 23 months) (the timing was determined by each patient) after the initial operation. Synovial coverage and the presence of graft laceration or elongation were assessed during second-look arthroscopy. At the same time, to detect subtle LOE quantitatively, we obtained a lateral radiograph, with the patient under general or lumbar anesthesia, of the reconstructed and contralateral healthy knees in full extension while the patient’s heels were elevated above the table. For reproducibility, both posterior condyles of the femur were superimposed under fluoroscopy in every knee. Because there is an issue regarding exposure to radiation, we planned to use a protector covering the patient’s trunk during exposure; this was approved by the institutional review board. We measured the extension angleddefined as the angle between the anterior cortex of the femur and the posterior cortex of the tibiadof both knees (Fig 3). LOE was defined as the difference in angles between the reconstructed and contralateral healthy knees. Radiographic Evaluation of Tibial Tunnel Position The first author (K.H.) performed radiographic evaluation. A true lateral radiograph was taken to evaluate the tibial tunnel position 1 year after surgery. We measured the anterior placement percentage of the tibial tunnel using the method reported by Amis and
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IMPORTANCE OF TIBIAL TUNNEL PLACEMENT
Fig 3. Lateral radiograph with reconstructed knee in full extension. The (A) maximal extension angle was measured as the angle between (B) the anterior cortex of the femur and the (C) posterior cortex of the tibia. (D, line parallel to line C.)
Jakob15 (Fig 4). We measured both the length from the tibial anterior margin to the anterior edge of the tibial tunnel (A) and the anteroposterior length of the tibial plateau (TP) by measuring the line that is parallel to the medial tibial plateau and passes through the anterior and posterior margins of the proximal end of the tibia.
The sagittal percentage of the tibial tunnel was calculated as follows: Anterior placement percentage of tibial tunnel ¼ A/TP 100 (%). The cutoff value was set at 25% of the mean value of the anterior edge of the ACL footprint that Amis and Jakob15 previously reported, and our patients were divided into 2 groups: the anterior group, in whom the tibial tunnel was created more anterior, and the posterior group, in whom the tunnel was more posterior. Postoperative clinical outcomes were compared between the groups. All radiographic measurements were performed with an iRad-IA viewer (Infocom, Tokyo, Japan). Statistics All statistical analyses were performed by the first author (K.H.) using StatView software (SAS Institute, Cary, NC). The Student t test was used to compare the SSD in anterior tibial translation and the LOE between the groups. The Mann-Whitney U test was used to compare pivot-shift test results and Lysholm scores between the groups. The c2 test was used to compare the incidence of LOE greater than 5 and second-look findings between the groups. The Pearson correlation coefficient was used to investigate the relation between the LOE and tibial tunnel position. P < .05 was considered significant.
Results
Fig 4. The anterior placement percentage of the tibial tunnel was calculated from true lateral radiographs as the distance from the anterior margin of the tibia to the anterior edge of the tibial tunnel (A) divided by the anteroposterior length of the tibial plateau (TP) and multiplied by 100.
The preoperative and postoperative mean SSDs in anterior translation were 7.3 4.1 mm and 2.2 2.9 mm, respectively, and the anterior translation was significantly reduced after surgery (P < .001). On the postoperative pivot-shift test, 7 of 60 patients (11.7%) had scores of grade þ and 3 patients (5%) had a score of grade þþ. The mean postoperative Lysholm score was 96.8 (range, 85 to 100). The mean LOE was 0.1 3.7 , and 4 knees had LOE greater than 5 . There was no LOE greater than 10 in any knee. The mean anterior placement percentage of the tibial tunnel was 26.0% 4.1% (range, 16.5% to 34.3%). We assigned 27 knees to the anterior group and 33 knees to the posterior group (Table 1). The distributions of age and sex were not significantly different between the groups (Table 1). The mean postoperative SSD in anterior tibial translation on stress radiographs was 1.4 2.7 mm for the anterior group and 3.0 2.7 mm for the posterior group, a significant difference (P ¼ .03). Positive ratios were found on the pivot-shift test in the anterior and posterior groups in 4 of 27 knees (14.8%) and 6 of 33 knees (18.2%), respectively; this was not significantly different (P ¼ .71). The mean postoperative Lysholm scores in the anterior and posterior groups were 96.1 (range, 85 to 100) and 97.6 (range, 90 to 100), respectively, which was not significantly different (P ¼ .23) (Table 1).
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Table 1. Demographic Data and Clinical Outcomes After Surgery Parameter
Anterior Group (n ¼ 27)
Posterior Group (n ¼ 33)
P Value
Age (range) (yr) Sex (M/F) SSD of anterior tibial translation (mm) Pivot-shift test (no. of cases) Negative þ þþ Lysholm score LOE ( ) LOE <5 (no. of cases) Graft integrity at second-look arthroscopy: superficial laceration or elongation of graft (no. of cases)
26.8 (13-49) 12/15 1.4 2.7
26.1 (13-42) 14/19 3.0 2.7
.79 .88 .03 .71
23 3 1 96.1 (85-100) 0.9 3.0 2 5
27 4 2 97.6 (90-100) 0.8 4.0 2 5
The LOE in the anterior and posterior groups was 0.9 3.0 and 0.8 4.0 , respectively, with no significant difference (P ¼ .08) (Table 1). LOE greater than 5 was found in 2 of 27 knees in the anterior group and 2 of 33 knees in the posterior group, with no significant difference (P ¼ .84). There was no significant correlation between the LOE and the anterior placement percentage of the tibial tunnel (r ¼ 0.21, P ¼ .12). With respect to ACL graft integrity at second-look arthroscopy, 5 of 27 knees (18.5%) in the anterior group versus 5 of 33 knees (15.2%) in the posterior group had laceration of the superficial fibers, graft elongation, or partial synovial coverage, which was not significantly different (P ¼ .73) (Table 1). Three patients (2 in the anterior group and 1 in the posterior group) had cyclops lesions that were resected.
Discussion Our study showed that anterior placement of the tibial tunnel results in significantly more reduced postoperative anterior tibial translation after anatomic ACL reconstruction than posterior placement does without increasing the risk of postoperative LOE and graft failure. Bedi et al.5 also showed that positioning the tibial tunnel in the anterior aspect of the footprint results in significantly less anterior tibial translation than posterior tibial footprint positioning in a cadaveric study. They suggested that anterior placement of the tibial tunnel results in correspondingly greater sagittal graft obliquity and improved control of anterior tibial translation after ACL reconstruction.5 To minimize the risk of roof impingement, posterior placement of the tibial tunnel was historically recommended with traditional transtibial ACL reconstruction.6,7 However, it has been pointed out that posterior placement of the tibial tunnel results in nonanatomic vertical graft placement16 and inferior postoperative stability.17,18 Even if the tibial tunnel in anatomic ACL reconstruction is located more anteriorly, roof impingement of the graft may be unlikely to occur because the femoral tunnel is created at a lower position than in traditional ACL reconstruction. Iriuchishima et al.19
.23 .08 .84 .73
reported no significant difference in roof impingement pressure between the intact ACL and anatomic ACL reconstruction in a cadaveric study. However, no in vivo studies have investigated whether anterior placement of the tibial tunnel causes postoperative LOE and graft failure resulting from roof impingement after anatomic double-bundle ACL reconstruction. The tibial insertion site is larger than the midsubstance of the ACL, which results in its classic fanned-out shape.20 That fanned-out shape makes it difficult to completely restore normal ACL anatomy during ACL reconstruction and may result in theoretic roof impingement and LOE if the graft is placed in the anterior aspect of the tibial insertion. We found that LOE in the anterior group was a little greater than that in the posterior group; however, the difference was not statistically significant. The incidence of LOE greater than 5 was also not significantly different between our groups. In addition, there was no significant correlation between LOE and the anterior placement percentage of the tibial tunnel. Furthermore, graft integrity at secondlook arthroscopy was not significantly different between our 2 groups. Jagodzinski et al.8 showed that a certain degree of roof impingement in hyperextension is physiologic for the uninjured knee. Therefore an anatomically reconstructed graft may tolerate physiologic roof impingement without damage. Our study showed no significant difference in postoperative rotational stability between anterior and posterior tibial tunnel placement. However, Bedi et al.5 showed that anterior tunnel placement significantly reduced anterior translation of the lateral compartment during the mechanized pivot shift compared with posterior tunnel placement. The assessment of rotational stability in our study was not quantitative but rather was qualitative, which may be why our results differ from those of the cadaveric study by Bedi et al. Furthermore, several authors have reported that coronal graft obliquity is more important to restore rotational stability and that it depends on the femoral tunnel position.18 The anatomic femoral tunnel position is lower and may improve coronal graft obliquity
IMPORTANCE OF TIBIAL TUNNEL PLACEMENT
and rotational control of the knee. Therefore it may be that the difference in anteroposterior position of the tibial tunnel in our study did not affect coronal obliquity, and postoperative rotational stability might not be significantly different between groups. Limitations Our study had some limitations. First, we had a relatively small sample size and short duration of followup. Second, the assessment of rotational stability was not quantitative. Third, investigator blinding was not used. Fourth, it is impossible to assess where the tibial tunnel was created inside the tibial footprint in each case. There are some reports of sagittal radiographic studies of the tibial footprint of the ACL.20,21 Doi et al.21 reported that the anterior edge of the ACL was located 25.1% 4.2% (range, 15.6% to 33.9%) from the anterior margin of the tibia in the anteroposterior direction. In our study the anterior edge of the tibial tunnel was located 26.0% 4.1% (range, 16.5% to 34.3%) from the margin, and the mean value was similar to that in the cadaveric study of Doi et al. However, variation of the tibial footprint morphology in the individual knee must be taken into account. We create the tibial tunnel with reference to the ACL remnant during surgery because on the tibial side, bony landmarks are less defined. Our study suggested that for better postoperative anterior stability, it is important to create the tibial tunnel in a more anterior position inside the anatomic footprint.
Conclusions Our study showed that anterior placement of the tibial tunnel in anatomic double-bundle ACL reconstruction leads to better anterior knee stability than posterior placement does. Anterior tibial tunnel placement inside the footprint did not increase the incidence of LOE and graft failure.
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Acknowledgment Katharine O’Moore-Klopf, E.L.S., East Setauket, New York, provided professional English-language editing of the manuscript.
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18. Loh JC, Fukuda Y, Tsuda E, Steadman RJ, Fu FH, Woo LY. Knee stability and graft function following anterior cruciate ligament reconstruction: Comparison between 11 o’clock and 10 o’clock femoral tunnel placement. Arthroscopy 2003;19:297-304. 19. Iriuchishima T, Tajima G, Ingham SJ, Shen W, Smolinski P, Fu HF. Impingement pressure in the anatomical and nonanatomical anterior cruciate ligament reconstruction: A cadaver study. Am J Sports Med 2010;38: 1611-1617.
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