Skip to main content
NCBI home page
NIHPA Author Manuscripts logoLink to NIHPA Author Manuscripts
. Author manuscript; available in PMC: 2013 Aug 12.
Published in final edited form as: Am J Sports Med. 2009 Mar 4;37(5):962–969. doi: 10.1177/0363546508330145

Biomechanical Comparison of Single-Tunnel–Double-Bundle and Single-Bundle Anterior Cruciate Ligament Reconstructions

Hemanth R Gadikota *, Jong Keun Seon *,†, Michal Kozanek *, Luke S Oh *, Thomas J Gill *, Kenneth D Montgomery ‡, Guoan Li *,§
PMCID: PMC3740372  NIHMSID: NIHMS496680  PMID: 19261901

Abstract

Background

Anatomic double-bundle reconstruction has been thought to better simulate the anterior cruciate ligament anatomy. It is, however, a technically challenging procedure, associated with longer operation time and higher cost.

Hypothesis

Double-bundle anterior cruciate ligament reconstruction using a single femoral and tibial tunnel can closely reproduce intact knee kinematics.

Study Design

Controlled laboratory study.

Methods

Eight fresh-frozen human cadaveric knee specimens were tested using a robotic testing system to investigate the kinematic response of the knee joint under an anterior tibial load (130 N), simulated quadriceps load (400 N), and combined torques (5 N·m valgus and 5 N·m internal tibial torques) at 0°, 15°, 30°, 60°, and 90° of flexion. Each knee was tested sequentially under 4 conditions: (1) anterior cruciate ligament intact, (2) anterior cruciate ligament deficient, (3) single-bundle anterior cruciate ligament reconstruction using quadrupled hamstring tendon, and (4) single-tunnel–double-bundle anterior cruciate ligament reconstruction using the same tunnels and quadrupled hamstring tendon graft as in the single-bundle anterior cruciate ligament reconstruction.

Results

Single-tunnel–double-bundle anterior cruciate ligament reconstruction more closely restored the intact knee kinematics than single-bundle anterior cruciate ligament reconstruction at low flexion angles (≤30°) under the anterior tibial load and simulated muscle load (P < .05). However, single-tunnel–double-bundle anterior cruciate ligament reconstruction overconstrained the knee joint at high flexion angles (≥60°) under the anterior tibial load and at 0° and 30° of flexion under combined torques.

Conclusion

This double-bundle anterior cruciate ligament reconstruction using a single tunnel can better restore anterior tibial translations to the intact level compared with single-bundle anterior cruciate ligament reconstruction at low flexion angles, but it overconstrained the knee joint at high flexion angles.

Clinical Relevance

This technique could be an alternative for both single-bundle and double-tunnel–double-bundle anterior cruciate ligament reconstructions to reproduce intact knee kinematics and native anterior cruciate ligament anatomy.

Keywords: anterior cruciate ligament (ACL), knee kinematics, single-tunnel–double-bundle ACL reconstruction, robotic testing

Many clinical outcome studies have demonstrated satisfactory stability of the knee joint after a single-bundle anterior cruciate ligament (ACL) reconstruction.7,29,35 However, long-term clinical studies have reported a high incidence of osteoarthritis and knee pain in the ACL-reconstructed knee.3,7,17,18,30,33 Several prospective studies have reported no differences in the rate of osteoarthritis between patients treated operatively or nonoperatively.12,24,41 Improving ACL reconstruction techniques that may restore normal knee kinematics and prevent joint degeneration remains a subject of continuing debate in sports medicine research.

Double-bundle ACL reconstruction was introduced to reconstruct the 2 functional bundles (anteromedial [AM] and posterolateral [PL]) of the ACL.10,45 The 2 functional bundles were reconstructed by creating different numbers of femoral and tibial tunnels (2 tibial/2 femoral, 2 tibial/1 femoral, 1 tibial/2 femoral, and 1 tibial/1 femoral).11,25,31,32,45,46 There are clinical and biomechanical studies that have reported that double-bundle ACL reconstruction restores the knee joint stability more closely to the intact level than single-bundle ACL reconstruction.13,26,27,37,43,44,46 On the contrary, there are also clinical and biomechanical studies showing no significant advantage of the double-bundle ACL reconstruction over the conventional single-bundle ACL reconstruction.|| Several factors, such as the tunnel position for single-bundle and double-bundle ACL reconstruction techniques, initial graft tension, angle of graft fixation, fixation devices, and clinical examinations, may have contributed to the discrepancies found in these studies that compared single-bundle and double-bundle ACL reconstruction techniques. Accepted standards for these factors are yet to be established. There is no consensus in the literature showing a significant advantage of the double-bundle ACL reconstruction over the single-bundle ACL reconstruction.

Recently, a few authors have proposed surgical techniques to reconstruct both the functional bundles using a single femoral and tibial tunnel.11,36,39 Using these techniques, the ACL reconstruction could reproduce the 2 functional bundles by separating the bundles in a single femoral and tibial tunnel. Furthermore, such a reconstruction adheres to a more familiar tunnel placement than a technically challenging double-tunnel ACL reconstruction. To our knowledge, there are no biomechanical studies that have investigated the kinematics of a double-bundle ACL-reconstructed knee using a single tunnel. The purpose of this study was to quantitatively measure the kinematics of the knee joint under 3 external loading conditions after single-tunnel–double-bundle ACL reconstruction and to compare these kinematics with those obtained after a single-bundle ACL reconstruction using a robotic testing system. We hypothesized that single-tunnel–double-bundle ACL reconstruction can restore the anterior-posterior and rotational stabilities to the intact level more closely than the single-bundle ACL reconstruction.

MATERIALS AND METHODS

Eight fresh-frozen human cadaveric knee specimens (age range, 59–64 years) were used in this study. Fluoroscopy and manual stability tests were performed to examine the specimens for osteoarthritis and ACL injuries. If the specimen had either of these conditions, they were eliminated from the study. Each specimen was thawed at room temperature for 24 hours before the testing. The femur and the tibia were truncated approximately 25 cm from the joint line without damaging the soft tissues around the knee. The fibula was fixed in its anatomic position to the tibia by using a bone screw. The musculature around the shafts of the femur and tibia was removed to facilitate the installation of the specimen on the robotic testing system.

The robotic testing system consists of a robotic manipulator (Kawasaki UZ150, Kawasaki Robotics USA Inc, Wixom, Michigan) and a 6 degrees of freedom load cell (JR3 Inc, Woodland, California). This system can be used to study the biomechanics of the knee joint. Several studies have been published to describe the operation of this robotic testing system.21–23,47 To simulate muscle function, quadriceps muscles were sutured to a rope that was passed through a pulley system on the femoral clamp. Quadriceps muscle loading was simulated by hanging weights on the free end of the ropes. Each specimen was manually flexed 10 times, from full extension to full flexion, to precondition the specimen before it was installed on the robotic testing system.

After the specimen was installed on the robotic testing system, the robotic testing system was used to determine a passive flexion path in the unloaded knee. The passive flexion path was determined by finding the passive positions from full extension to 90° of flexion in 1° increments. The passive position is described as a position of the knee at which all resultant forces and moments at the knee center were minimal (<5 N and <0.5 N·m, respectively).

In this study, each knee was tested under 3 different external loading conditions (anterior tibial load [130 N], simulated quadriceps load [400 N], and combined torques [5-N·m valgus and 5-N·m internal tibial torques]) at selected flexion angles of 0°, 15°, 30°, 60°, and 90° along the passive path. The anterior tibial load was used to simulate clinical examinations such as Lachman and anterior drawer tests. The quadriceps load (applied parallel to the femoral shaft) was used to simulate an isometric extension of the knee. The knees were also subjected to combined torques (5-N·m valgus and 5-N·m internal tibial torques) at 0° and 30° of knee flexion. Under each load, the robot manipulated the knee joint in 5 degrees of freedom until the applied load was balanced by the knee at a selected flexion angle. This position of the knee represents the kinematic response of the knee to the applied load. In this article, the anterior-posterior tibial translations and internal-external tibial rotations of the knee are reported under each external loading condition mentioned above at all selected flexion angles.

After the knee was tested in the intact condition, the knee was tested in 3 different conditions sequentially. First, the ACL was resected through a small medial arthrotomy with the knee flexed to 30° to simulate an ACL-deficient knee condition. The arthrotomy and the skin were repaired in layers by sutures. The ACL-deficient knee kinematics were determined under the same external loading conditions used for the intact knee. Second, single-bundle ACL reconstruction (Figure 1A) was then performed using a quadrupled hamstring (semitendinosus and gracilis tendons) graft. Single-bundle ACL-reconstructed knee kinematics were determined under the 3 external loading conditions. Finally, single-tunnel–double-bundle ACL reconstruction (Figure 1B) was then performed using the same quadrupled hamstring (semitendinosus and gracilis tendons) graft and tunnels that were used for the single-bundle ACL reconstruction. The kinematic responses of the single-tunnel–double-bundle ACL-reconstructed knee under the 3 external loading conditions were determined.

Figure 1.

Figure 1

Open in a new tab

Schematic representation of single-bundle (A) and single-tunnel–double-bundle (B) ACL reconstructions. AMB, anteromedial bundle; PLB, posterolateral bundle.

For testing the knee under the 4 different conditions (intact, ACL-deficient, single-bundle ACL-reconstructed, and single-tunnel–double-bundle ACL-reconstructed), the passive path determined under the intact knee condition was used as the reference position to measure the knee kinematics in response to the external loads. This procedure eliminated any variability in the starting positions before the external loads were applied and facilitated a repeated-measures analysis of the data.

Surgical Techniques

Single-Bundle ACL Reconstruction

The surgery was performed with the specimen installed on the robotic system. All the surgeries were performed by a single surgeon. The surgery began by harvesting the semitendinosus and gracilis tendons used as the graft material for both ACL reconstructions. The tibial tunnel was reamed through the anteromedial surface of the tibia at the level of the tibial tubercle, passing through the landmarks of the center of the ACL remnant. A Kirschner wire was inserted through the tibial tunnel, aimed at the 2- or 10-o’clock position and 7 mm anterior from the posterior bony edge of the intercondylar wall of the femur. The femoral tunnel was reamed through the tibial tunnel with the knee flexed to 90° using a 4.5-mm– diameter EndoButton drill (Smith & Nephew Endoscopy, Andover, Massachusetts) to the lateral cortex of the distal femur. A final 35-mm–long femoral socket was then created by a cannulated reamer that matched the prepared graft diameter (8–8.5 mm). For the single-bundle ACL reconstruction, the graft was passed though the tibial tunnel into the joint and finally through the femoral socket and was secured with an EndoButton CL (Smith & Nephew Endoscopy). The tibia was then loaded posteriorly with a 40-N load at 0° and the graft was secured at the tibial end by a metallic interference screw (Arthrex, Naples, Florida) with 40 N of axial graft tension. The arthrotomy and the skin were repaired using sutures.

Single-Tunnel–Double-Bundle ACL Reconstruction

The femoral and tibial tunnels used for single-bundle ACL reconstruction were dilated to 10 mm and were reused for single-tunnel–double-bundle ACL reconstruction. The graft used in single-bundle ACL reconstruction was reused for the single-tunnel–double-bundle ACL reconstruction. If there was any significant damage noticed to the graft after the single-bundle ACL reconstruction, the specimen was excluded from the study. The semitendinosus tendon and the gracilis tendon were passed through the AperFix femoral implant (Cayenne Medical, Scottsdale, Arizona) separately (Figure 1B) and looped to form 4 strands. Two strands of the semitendinosus tendon were used to represent the AM bundle, while the 2 gracilis tendon strands represented the PL bundle. The design of the AperFix femoral implant facilitates the separation of the AM and PL bundles (Figure 2A). This implant was passed through the tibial tunnel into the femoral tunnel and deployed in standard fashion. Before deployment, the 2 bundles were positioned inside the femoral tunnel in the native ACL bundle positions. After the graft was secured at the femoral end, the distal end of the graft was rotated by 90° in a clockwise direction for the left knee (counterclockwise for the right knee), giving rise to the AM and PL bundles (Figure 2B). The AperFix tibial implant (Figure 1B) was used to fix the tibial end of the graft at the same knee position and posterior load as used for the single-bundle ACL reconstruction. A 40-N graft tension was simultaneously applied to the 2 bundles during the graft fixation.

Figure 2.

Figure 2

Open in a new tab

Schematic illustration of the femoral implant and the separation of the 2 bundles in the femoral tunnel (A) and the tibial implant and the separation of the 2 bundles in the tibial tunnel (B). AMB, anteromedial bundle; PLB, posterolateral bundle.

Data Analysis

The study was designed to evaluate the kinematic (anterior tibial translation and internal tibial rotation) response of the same knee under 4 different conditions (ACL intact, ACL deficient, single-bundle ACL reconstructed, and single-tunnel–double-bundle ACL reconstructed). This facilitated a within-subjects analysis of knee kinematics. Repeated-measures analysis of variance was used to detect statistically significant differences in kinematics of the knee under the 4 different conditions. If significant differences were detected, post hoc comparisons were made among the 4 groups using the Student-Newman-Keuls test. Differences were considered statistically significant at P < .05.

RESULTS

Kinematic Response Under Anterior Tibial Load (130 N)

Under the anterior tibial load, the largest anterior tibial translations of the ACL-intact knee were observed at 15° and 30° of flexion as 7.4 ± 0.8 mm and 7.8 ± 1.2 mm, respectively (Figure 3). After the ACL was resected, the anterior tibial translations of the knee increased by 157.6% and by 162.9% at 15° and 30° of flexion, respectively, compared with the intact knee. The anterior tibial translations of the ACL-deficient knee were significantly greater than the ACL-intact knee at all flexion angles (P < .05). The anterior tibial translations after the single-bundle ACL reconstruction were greater than the intact knee by 22.9% at 15° and by 20.1% at 30° of flexion. These translations for the single-bundle ACL reconstruction were significantly greater than those of the ACL-intact knee at 15° and 30° of flexion (P < .05). No significant differences were observed between the intact knee and single-bundle ACL reconstruction at 0°, 60°, and 90° of flexion (P > .05). Anterior tibial translations of the ACL-intact knee were closely reproduced after the single-tunnel–double-bundle ACL reconstruction at 0°, 15° and 30° of flexion (P > .05). Anterior tibial translations of the single-tunnel–double-bundle ACL reconstruction were significantly lower than the intact knee by 33.67% and by 50.0% at 60° and 90° of flexion (P < .05). Anterior tibial translations for the single-tunnel–double-bundle ACL reconstruction were significantly lower than the single-bundle ACL reconstruction at 15°, 30°, 60°, and 90° of flexion (P < .05).

Figure 3.

Figure 3

Open in a new tab

Anterior tibial translation under anterior tibial load in the 4 different knee conditions. Anterior tibial translations of the ACL-deficient knee were significantly different from the intact, single-bundle ACL-reconstructed, and single-tunnel–double-bundle ACL-reconstructed knee at all flexion angles. Error bars represent standard deviation. *P < .05. Recon, reconstruction.

Kinematic Response Under Simulated Quadriceps Load (400 N)

In response to the quadriceps load, anterior tibial translations of the ACL-intact knee were 4.9 ± 0.8 mm at 15° and 5.1 ± 1.1 mm at 30° of flexion (Figure 4). Anterior tibial translations of the ACL-deficient knee increased by 91.4% at 15° and by 88.8% at 30° of flexion compared with the intact knee. At 0°, 15°, and 30° of flexion, anterior tibial translations of the ACL-deficient knee were significantly greater than the ACL-intact knee (P < .05). After single-bundle ACL reconstruction, the anterior tibial translations were significantly greater than the intact knee by 35.3% and by 23.7% at 15° and 30° of flexion (P < .05). The tibia of the single-tunnel–double-bundle ACL-reconstructed knee translated 3.4% less than the intact knee at 15° and 10.40% less than the intact knee at 30° of flexion. These translations after single-tunnel–double-bundle ACL reconstruction were statistically similar to the ACL-intact knee at 0°, 15°, and 30° of flexion (P > .05). Anterior tibial translations for the single-tunnel–double-bundle ACL reconstruction were significantly lower than those of the single-bundle ACL reconstruction at 0°, 15°, 30°, and 60° of flexion (P < .05). Anterior tibial translations of both the ACL reconstructions were significantly different from the intact knee at 60° and 90° of flexion (P < .05). There were no significant differences (P > .05) in tibial rotations among the 4 different knee conditions at all flexion angles (Figure 5).

Figure 4.

Figure 4

Open in a new tab

Tibial translation under quadriceps load in the 4 different knee conditions. Tibial translations of the ACL-deficient knee were significantly different from the intact, single-bundle ACL-reconstructed and the single-tunnel–double-bundle ACL-reconstructed knee at all flexion angles. +Anterior tibial translation; −posterior tibial translation; *P <.05. Error bars represent standard deviation. Recon, reconstruction.

Figure 5.

Figure 5

Open in a new tab

Tibial rotations under the simulated quadriceps load in the 4 different knee conditions. +Internal tibial rotations; −external tibial rotations. Error bars represent standard deviation. Recon, reconstruction.

Kinematic Response Under Combined Torques (5-N·m Valgus and 5-N·m Internal Tibial Torques)

In response to the combined torques, the tibia of the ACL-intact knee translated anteriorly by 1.3 ± 1.2 mm at 0° and 3.3 ± 1.6 mm at 30° of flexion. The anterior tibial translations of the ACL-deficient knee were significantly increased, by 196.9% at 0° and by 58.2% at 30° of flexion, compared with the ACL-intact knee (P < .05). The anterior tibial translations of the single-bundle ACL-reconstructed knee were 33.9% and 22.2% greater than the intact knee at 0° and 30° of flexion, respectively. The anterior tibial translations of the single-tunnel–double-bundle ACL reconstruction were significantly lower than those of the ACL-intact, ACL-deficient, and single-bundle ACL-reconstructed knee at 0° and 30° of flexion (P < .05) (Table 1).

TABLE 1.

Tibial Translation (Mean ± Standard Deviation [mm]) Under Combined Torquesa

Flexion Angle ACL Intact ACL Deficient Single-Bundle ACL Reconstruction Single-Tunnel–Double-Bundle ACL Reconstruction
0° +1.3 ± 1.2 +3.8 ± 1.9b +1.7 ± 1.2cd −0.2 ± 1.4bc
30° +3.3 ± 1.6 +5.2 ± 2.2b +4.0 ± 2.1cd +2.1 ± 1.4bc
Open in a new tab
a

+Anterior translation; –posterior translation; ACL, anterior cruciate ligament.

b

P < .05; significantly different from ACL-intact knee.

c

P < .05; significantly different from ACL-deficient knee.

d

P < .05; significantly different from single-tunnel–double-bundle ACL reconstruction.

The internal tibial rotations of the ACL-intact knee were not significantly different (P > .05) from both the single-bundle and single-tunnel–double-bundle ACL-reconstructed knee (Figure 6).

Figure 6.

Figure 6

Open in a new tab

Internal tibial rotations under combined torques in the 4 different knee conditions. Error bars represent standard deviation. *P < .05. Recon, reconstruction.

DISCUSSION

Extensive biomechanical studies have been conducted to evaluate the efficiency of single-bundle and double-bundle ACL reconstructions.34,40,42,44 In this study, we investigated the effectiveness of a single-tunnel–double-bundle ACL reconstruction technique that uses a single femoral and tibial tunnel to restore the knee joint stability to the intact level by using a robotic testing system. Our results demonstrated that the single-tunnel–double-bundle ACL reconstruction was able to closely restore the intact knee kinematics under an anterior tibial load and simulated quadriceps load at low flexion angles (≤30°), but overconstrained the knee joint at high flexion angles (≥60°) under anterior tibial load and under combined torques.

We found that ACL deficiency resulted in increased anterior tibial translations compared with the ACL-intact knee at all flexion angles under the anterior tibial load and simulated quadriceps load. Single-bundle ACL reconstruction reduced these increased anterior tibial translations significantly but could not restore them to the intact level at low flexion angles. These results are consistent with previous biomechanical studies that used similar loading conditions.42,44,47

The single-tunnel–double-bundle ACL reconstruction significantly reduced the anterior tibial translations of the ACL-deficient knee at all flexion angles under anterior tibial load and simulated quadriceps load. No significant differences between the anterior tibial translations of the single-tunnel–double-bundle ACL reconstruction and ACL-intact knee were observed at low flexion angles under both the loading conditions. In a biomechanical study conducted by Yagi et al,44 it was reported that the anatomic double-tunnel–double-bundle ACL reconstruction resulted in significantly greater anterior tibial translations compared with the ACL-intact knee at full extension and 30° of flexion in response to an anterior tibial load of 134 N. In other biomechanical studies, Petersen et al32 and Zantop et al48 reported no significant difference in anterior tibial translations between the ACL-intact knee and anatomic double-tunnel–double-bundle ACL-reconstructed knee under the anterior tibial load of 134 N. Our results showed that the single-tunnel–double-bundle ACL reconstruction resulted in a slightly overconstrained knee at 60° and 90° of flexion under the anterior tibial load and simulated quadriceps load. However, the maximum difference in anterior tibial translation between the ACL-intact knee and the single-tunnel–double-bundle ACL-reconstructed knee in response to the 2 loading conditions was less than 3 mm at high flexion angles (≥60°). These results suggest that this single-tunnel–double-bundle ACL reconstruction could produce clinically satisfactory anterior stability.

The internal tibial rotations of the single-bundle ACL-reconstructed and the single-tunnel–double-bundle ACL-reconstructed knee were decreased compared with the intact knee, although no significant differences at all the selected flexion angles under simulated quadriceps load were observed (P > .05). Recently, Yoo et al47 reported significantly reduced internal tibial rotations after bone–patellar tendon–bone reconstruction compared with the intact knee at low flexion angles. These data indicate that ACL reconstruction might result in overconstraining the tibial rotation.

Previously, biomechanical studies have shown that single-bundle ACL reconstruction could not restore the anterior stability under combined torques (10-N·m valgus torque and 5-N·m or 10-N·m internal tibial torque).42,44 In this study, anterior tibial translations under combined torques (5-N·m valgus and 5-N·m internal tibial torques) showed no significant difference between single-bundle ACL reconstruction and the ACL intact knee at 0° and 30° of flexion, whereas, the single-tunnel–double-bundle ACL reconstruction resulted in an overconstrained knee at 0° and 30° of flexion under the same loading condition. In a recent biomechanical study, Zantop et al48 reported no significant difference in anterior tibial translation between the ACL-intact and anatomic double-tunnel–double-bundle ACL-reconstructed knee under combined torques, while other biomechanical studies showed that anatomic double-tunnel–double-bundle ACL reconstruction resulted in greater anterior tibial translations than the ACL-intact knee at low flexion angles (≤30°) under combined torques.32,44 This discrepancy in the anterior tibial translations under combined torques may be due to the different loading conditions and surgical techniques used among these studies.

No significant differences were observed in the internal tibial rotations between ACL-intact, single-bundle ACL-reconstructed, and the single-tunnel–double-bundle ACL-reconstructed knee in this study under combined torques. These results may suggest that combined internal and valgus torques are an inefficient loading condition for investigating the rotational stability in cadaveric specimens. Comprehensive loading conditions are required to truly assess the ability of ACL and ACL graft to restrain tibial rotations.

It should be noted that, in this study, both ACL graft bundles were fixed at 0° with an axial graft tension of 40 N. This was done to simulate widely used operative procedures for single-bundle ACL reconstruction. However, the 2 bundles of the ACL do not function in the same manner along the flexion path.6,14,19,20 To achieve the native tension pattern in the AM bundle and PL bundle along the flexion path of the knee, different tensioning strategies for the 2 graft bundles and the graft fixation angle may be needed, as practiced in various double-tunnel–double-bundle ACL reconstruction techniques.4,13,27,46 This study showed that the single-tunnel–double-bundle ACL reconstruction resulted in an overconstrained knee at high flexion angles (≥60°). This may be because both the bundles were tensioned and fixed at 0°, which may have resulted in over-tightening of the AM bundle at high flexion angles. However, it is important to understand that these results represent the time-zero responses of the knee joint. It is known that there is a significant decrease in the initial graft tension with cyclic loading after ACL reconstruction, which results in increased laxity of the knee joint.1,9,28 A long-term clinical follow-up study is required to truly assess the ability of this single-tunnel–double-bundle ACL reconstruction technique to restore the normal knee joint kinematics postoperatively.

The single-tunnel–double-bundle ACL reconstruction technique introduced in this study has distinct differences compared with the double-tunnel–double-bundle ACL reconstruction. Although the double-tunnel–double-bundle ACL reconstruction technique is designed to reproduce the 2 functional bundles, it is a technically challenging procedure. The double-tunnel–double-bundle ACL reconstruction is also associated with an increase in the duration of surgery and higher cost as compared with the traditional single-bundle ACL reconstruction.11,16,34,45 In addition, the double-tunnel–double-bundle ACL reconstruction makes a revision surgery difficult. The single-tunnel–double-bundle technique introduced in this study is aimed to reproduce both the functional bundles of the ACL by creating a single femoral and tibial tunnel as opposed to creating 2 tunnels in the tibia and femur. The surgical procedure is more familiar to surgeons and a revision could be performed as performed for a single-bundle ACL reconstruction. However, the double-tunnel–double-bundle technique has the advantage of being able to tension the 2 graft bundles at different flexion angles while using different initial graft tensions, whereas in the single-tunnel–double-bundle technique, these various combinations of graft bundle fixation angles and different graft bundle tensions are difficult to perform. The kinematic results observed from this study and the ease of the surgical procedure demonstrate that the single-tunnel–double-bundle technique may be a potential alternative to single-bundle and double-tunnel–double-bundle ACL reconstruction techniques.

There are some limitations to the current study. The study was designed to investigate the combined effect of the 2 bundles and the fixation device in single-tunnel–double-bundle ACL reconstruction on the kinematics of the knee joint. Therefore, the current data do not provide information on the amount of stability provided by the individual bundles of the reconstructed ACL. Because this was a cadaveric study, we cannot speculate on how much of the improvement in the kinematics observed in single-tunnel–double-bundle ACL reconstruction of this study would carry over to clinical outcomes. However, our design facilitated a controlled repeated-measures analysis of kinematics using the same specimen under different loading conditions. The order for testing the 2 surgical techniques was not randomized because the single-tunnel–double-bundle ACL reconstruction required a larger femoral tunnel than that required for single-bundle ACL reconstruction. A 7-mm offset aimer was used for both single-bundle and single-tunnel–double-bundle ACL reconstructions. The femoral tunnel diameter for the single-bundle ACL reconstruction ranged from 8 to 8.5 mm. Hence, a 7-mm offset aimer might have influenced the kinematic outcomes of the single-bundle ACL reconstruction. These limitations indicate that a patient follow-up study might be necessary to further evaluate the efficacy of the single-tunnel–double-bundle ACL reconstruction technique in restoration of normal knee kinematics and prevention of degenerative changes.

CONCLUSION

On the basis of this investigation, we conclude that the single-tunnel–double-bundle ACL reconstruction is capable of restoring the knee stability more closely to the ACL-intact knee at low flexion angles (≤30°) compared with the single-bundle ACL reconstruction. However, the single-tunnel–double-bundle ACL reconstruction overconstrained the knee joint at high flexion angles (≥60°). Although we cannot speculate on how this overconstrained pattern may affect the clinical outcomes, this technique is similar to the more familiar single-bundle ACL reconstruction and could be an alternative to the technically demanding double-tunnel–double-bundle ACL reconstruction. Clinical follow-up studies need to be performed in the future to analyze the potential benefits of single-tunnel–double-bundle ACL reconstruction.

Acknowledgments

The authors gratefully acknowledge the support of the Department of Orthopaedic Surgery of Massachusetts General Hospital and the National Institutes of Health (AR055612). Cayenne Medical (Scottsdale, Arizona) donated the implants used in this study.

Footnotes

||

References 2, 5, 8, 15, 16, 25, 27, 34, 38, 46.

One or more of the authors has declared a potential conflict of interest: Dr Montgomery is on the Clinical Advisory Board for and owns stocks in Cayenne Medical.

References

  • 1.Abramowitch SD, Papageorgiou CD, Withrow JD, Gilbert TW, Woo SL. The effect of initial graft tension on the biomechanical properties of a healing ACL replacement graft: a study in goats. J Orthop Res. 2003;21:708–715. doi: 10.1016/S0736-0266(02)00265-6. [DOI] [PubMed] [Google Scholar]
  • 2.Adachi N, Ochi M, Uchio Y, Iwasa J, Kuriwaka M, Ito Y. Reconstruction of the anterior cruciate ligament: single- versus double-bundle multi-stranded hamstring tendons. J Bone Joint Surg Br. 2004;86:515–520. [PubMed] [Google Scholar]
  • 3.Aglietti P, Buzzi R, D’Andria S, Zaccherotti G. Long-term study of anterior cruciate ligament reconstruction for chronic instability using the central one-third patellar tendon and a lateral extraarticular teno-desis. Am J Sports Med. 1992;20:38–45. doi: 10.1177/036354659202000111. [DOI] [PubMed] [Google Scholar]
  • 4.Aglietti P, Giron F, Cuomo P, Losco M, Mondanelli N. Single- and double-incision double-bundle ACL reconstruction. Clin Orthop Relat Res. 2007;454:108–113. doi: 10.1097/BLO.0b013e31802baaf4. [DOI] [PubMed] [Google Scholar]
  • 5.Albuquerque RFM, Sasaki SU, Amatuzzi MM, Angelini FJ. Anterior cruciate ligament reconstruction with double bundle versus single bundle: experimental study. Acta Ortop Bras. 2007;3:335–344. doi: 10.1590/s1807-59322007000300020. [DOI] [PubMed] [Google Scholar]
  • 6.Amis AA, Dawkins GP. Functional anatomy of the anterior cruciate ligament. Fibre bundle actions related to ligament replacements and injuries. J Bone Joint Surg Br. 1991;73:260–267. doi: 10.1302/0301-620X.73B2.2005151. [DOI] [PubMed] [Google Scholar]
  • 7.Anderson AF, Snyder RB, Lipscomb AB., Jr Anterior cruciate ligament reconstruction. A prospective randomized study of three surgical methods. Am J Sports Med. 2001;29:272–279. doi: 10.1177/03635465010290030201. [DOI] [PubMed] [Google Scholar]
  • 8.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. doi: 10.1016/j.arthro.2007.01.009. [DOI] [PubMed] [Google Scholar]
  • 9.Boylan D, Greis PE, West JR, Bachus KN, Burks RT. Effects of initial graft tension on knee stability after anterior cruciate ligament reconstruction using hamstring tendons: a cadaver study. Arthroscopy. 2003;19:700–705. doi: 10.1016/s0749-8063(03)00400-6. [DOI] [PubMed] [Google Scholar]
  • 10.Buoncristiani AM, Tjoumakaris FP, Starman JS, Ferretti M, Fu FH. Anatomic double-bundle anterior cruciate ligament reconstruction. Arthroscopy. 2006;22:1000–1006. doi: 10.1016/j.arthro.2006.06.005. [DOI] [PubMed] [Google Scholar]
  • 11.Caborn DN, Chang HC. Single femoral socket double-bundle anterior cruciate ligament reconstruction using tibialis anterior tendon: description of a new technique. Arthroscopy. 2005;(21):1273.e1–e8. doi: 10.1016/j.arthro.2005.07.015. [DOI] [PubMed] [Google Scholar]
  • 12.Fink C, Hoser C, Hackl W, Navarro RA, Benedetto KP. Long-term outcome of operative or nonoperative treatment of anterior cruciate ligament rupture—is sports activity a determining variable? Int J Sports Med. 2001;22:304–309. doi: 10.1055/s-2001-13823. [DOI] [PubMed] [Google Scholar]
  • 13.Fu FH, Shen W, Starman JS, Okeke N, Irrgang JJ. Primary anatomic double-bundle anterior cruciate ligament reconstruction: a preliminary 2-year prospective study. Am J Sports Med. 2008;36:1263–1274. doi: 10.1177/0363546508314428. [DOI] [PubMed] [Google Scholar]
  • 14.Girgis FG, Marshall JL, Monajem A. The cruciate ligaments of the knee joint: anatomical, functional, and experimental analysis. Clin Orthop Relat Res. 1975;106:216–231. doi: 10.1097/00003086-197501000-00033. [DOI] [PubMed] [Google Scholar]
  • 15.Gudas R, Smailys A, Vostrugina K, Tamosinas R, Simonaitis D, Kalesinskas RJ. A prospective comparison of double- and single-bundle anterior cruciate ligament reconstructions. Medicina (Kaunas) 2008;44:110–118. [PubMed] [Google Scholar]
  • 16.Hamada M, Shino K, Horibe S, et al. Single- versus bi-socket anterior cruciate ligament reconstruction using autogenous multiple-stranded hamstring tendons with EndoButton femoral fixation: a prospective study. Arthroscopy. 2001;17:801–807. doi: 10.1016/s0749-8063(01)90002-7. [DOI] [PubMed] [Google Scholar]
  • 17.Howe JG, Johnson RJ, Kaplan MJ, Fleming B, Jarvinen M. Anterior cruciate ligament reconstruction using quadriceps patellar tendon graft: part 1, long-term followup. Am J Sports Med. 1991;19:447–457. doi: 10.1177/036354659101900505. [DOI] [PubMed] [Google Scholar]
  • 18.Jomha NM, Borton DC, Clingeleffer AJ, Pinczewski LA. Long-term osteoarthritic changes in anterior cruciate ligament reconstructed knees. Clin Orthop Relat Res. 1999;358:188–193. [PubMed] [Google Scholar]
  • 19.Jordan SS, DeFrate LE, Nha KW, Papannagari R, Gill TJ, Li G. The in vivo kinematics of the anteromedial and posterolateral bundles of the anterior cruciate ligament during weightbearing knee flexion. Am J Sports Med. 2007;35:547–554. doi: 10.1177/0363546506295941. [DOI] [PubMed] [Google Scholar]
  • 20.Li G, DeFrate LE, Sun H, Gill TJ. In vivo elongation of the anterior cruciate ligament and posterior cruciate ligament during knee flexion. Am J Sports Med. 2004;32:1415–1420. doi: 10.1177/0363546503262175. [DOI] [PubMed] [Google Scholar]
  • 21.Li G, Gill TJ, DeFrate LE, Zayontz S, Glatt V, Zarins B. Biomechanical consequences of PCL deficiency in the knee under simulated muscle loads—an in vitro experimental study. J Orthop Res. 2002;20:887–892. doi: 10.1016/S0736-0266(01)00184-X. [DOI] [PubMed] [Google Scholar]
  • 22.Li G, Rudy TW, Sakane M, Kanamori A, Ma CB, Woo SL. The importance of quadriceps and hamstring muscle loading on knee kinematics and in-situ forces in the ACL. J Biomech. 1999;32:395–400. doi: 10.1016/s0021-9290(98)00181-x. [DOI] [PubMed] [Google Scholar]
  • 23.Li G, Zayontz S, DeFrate LE, Most E, Suggs JF, Rubash HE. Kinematics of the knee at high flexion angles: an in vitro investigation. J Orthop Res. 2004;22:90–95. doi: 10.1016/S0736-0266(03)00118-9. [DOI] [PubMed] [Google Scholar]
  • 24.Lohmander LS, Ostenberg A, Englund M, Roos H. High prevalence of knee osteoarthritis, pain, and functional limitations in female soccer players twelve years after anterior cruciate ligament injury. Arthritis Rheum. 2004;50:3145–3152. doi: 10.1002/art.20589. [DOI] [PubMed] [Google Scholar]
  • 25.Mae T, Shino K, Miyama T, Shinjo H, Ochi T, Yoshikawa H, Fujie H. Single- versus two-femoral socket anterior cruciate ligament reconstruction technique: biomechanical analysis using a robotic simulator. Arthroscopy. 2001;17:708–716. doi: 10.1053/jars.2001.25250. [DOI] [PubMed] [Google Scholar]
  • 26.Muneta T, Koga H, Morito T, Yagishita K, Sekiya I. A retrospective study of the midterm outcome of two-bundle anterior cruciate ligament reconstruction using quadrupled semitendinosus tendon in comparison with one-bundle reconstruction. Arthroscopy. 2006;22:252–258. doi: 10.1016/j.arthro.2005.12.008. [DOI] [PubMed] [Google Scholar]
  • 27.Muneta T, Sekiya I, Yagishita K, Ogiuchi T, Yamamoto H, Shinomiya K. Two-bundle reconstruction of the anterior cruciate ligament using semitendinosus tendon with EndoButtons: operative technique and preliminary results. Arthroscopy. 1999;15:618–624. doi: 10.1053/ar.1999.v15.0150611. [DOI] [PubMed] [Google Scholar]
  • 28.Numazaki H, Tohyama H, Nakano H, Kikuchi S, Yasuda K. The effect of initial graft tension in anterior cruciate ligament reconstruction on the mechanical behaviors of the femur-graft-tibia complex during cyclic loading. Am J Sports Med. 2002;30:800–805. doi: 10.1177/03635465020300060801. [DOI] [PubMed] [Google Scholar]
  • 29.O’Neill DB. Arthroscopically assisted reconstruction of the anterior cruciate ligament: a prospective randomized analysis of three techniques. J Bone Joint Surg Am. 1996;78:803–813. [PubMed] [Google Scholar]
  • 30.Otto D, Pinczewski LA, Clingeleffer A, Odell R. Five-year results of single-incision arthroscopic anterior cruciate ligament reconstruction with patellar tendon autograft. Am J Sports Med. 1998;26:181–188. doi: 10.1177/03635465980260020601. [DOI] [PubMed] [Google Scholar]
  • 31.Pederzini L, Adriani E, Botticella C, Tosi M. Technical note: double tibial tunnel using quadriceps tendon in anterior cruciate ligament reconstruction. Arthroscopy. 2000;16:E9. doi: 10.1053/jars.2000.7551. [DOI] [PubMed] [Google Scholar]
  • 32.Petersen W, Tretow H, Weimann A, et al. Biomechanical evaluation of two techniques for double-bundle anterior cruciate ligament reconstruction: one tibial tunnel versus two tibial tunnels. Am J Sports Med. 2007;35:228–234. doi: 10.1177/0363546506294468. [DOI] [PubMed] [Google Scholar]
  • 33.Pinczewski LA, Deehan DJ, Salmon LJ, Russell VJ, Clingeleffer A. A five-year comparison of patellar tendon versus four-strand hamstring tendon autograft for arthroscopic reconstruction of the anterior cruciate ligament. Am J Sports Med. 2002;30:523–536. doi: 10.1177/03635465020300041201. [DOI] [PubMed] [Google Scholar]
  • 34.Sasaki SU, da Mota e Albuquerque RF, Pereira CA, Gouveia GS, Vilela JC, de Alcarás FL. An in vitro biomechanical comparison of anterior cruciate ligament reconstruction: single bundle versus anatomical double bundle techniques. Clinics. 2008;63:71–76. doi: 10.1590/s1807-59322008000100013. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 35.Shaieb MD, Kan DM, Chang SK, Marumoto JM, Richardson AB. A prospective randomized comparison of patellar tendon versus semi-tendinosus and gracilis tendon autografts for anterior cruciate ligament reconstruction. Am J Sports Med. 2002;30:214–220. doi: 10.1177/03635465020300021201. [DOI] [PubMed] [Google Scholar]
  • 36.Shino K, Nakata K, Nakamura N, Toritsuka Y, Nakagawa S, Horibe S. Anatomically oriented anterior cruciate ligament reconstruction with a bone-patellar tendon-bone graft via rectangular socket and tunnel: a snug-fit and impingement-free grafting technique. Arthroscopy. 2005;21:1402. doi: 10.1016/j.arthro.2005.08.017. [DOI] [PubMed] [Google Scholar]
  • 37.Siebold R, Dehler C, Ellert T. Prospective randomized comparison of double-bundle versus single-bundle anterior cruciate ligament reconstruction. Arthroscopy. 2008;24:137–145. doi: 10.1016/j.arthro.2007.11.013. [DOI] [PubMed] [Google Scholar]
  • 38.Streich NA, Friedrich K, Gotterbarm T, Schmitt H. Reconstruction of the ACL with a semitendinosus tendon graft: a prospective randomized single blinded comparison of double-bundle versus single-bundle technique in male athletes. Knee Surg Sports Traumatol Arthrosc. 2008;16:232–238. doi: 10.1007/s00167-007-0480-z. [DOI] [PubMed] [Google Scholar]
  • 39.Takeuchi R, Saito T, Mituhashi S, Suzuki E, Yamada I, Koshino T. Double-bundle anatomic anterior cruciate ligament reconstruction using bone-hamstring-bone composite graft. Arthroscopy. 2002;18:550–555. doi: 10.1053/jars.2002.30680. [DOI] [PubMed] [Google Scholar]
  • 40.Tashman S, Collon D, Anderson K, Kolowich P, Anderst W. Abnormal rotational knee motion during running after anterior cruciate ligament reconstruction. Am J Sports Med. 2004;32:975–983. doi: 10.1177/0363546503261709. [DOI] [PubMed] [Google Scholar]
  • 41.Von Porat A, Roos EM, Roos H. High prevalence of osteoarthritis 14 years after an anterior cruciate ligament tear in male soccer players: a study of radiographic and patient relevant outcomes. Ann Rheum Dis. 2004;63:269–273. doi: 10.1136/ard.2003.008136. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 42.Woo SL, Kanamori A, Zeminski J, Yagi M, Papageorgiou C, Fu FH. The effectiveness of reconstruction of the anterior cruciate ligament with hamstrings and patellar tendon: a cadaveric study comparing anterior tibial and rotational loads. J Bone Joint Surg Am. 2002;84:907–914. doi: 10.2106/00004623-200206000-00003. [DOI] [PubMed] [Google Scholar]
  • 43.Yagi M, Wong EK, Kanamori A, Debski RE, Fu FH, Woo SL. Biomechanical analysis of an anatomic anterior cruciate ligament reconstruction. Am J Sports Med. 2002;30:660–666. doi: 10.1177/03635465020300050501. [DOI] [PubMed] [Google Scholar]
  • 44.Yagi M, Kuroda R, Nagamune K, Yoshiya S, Kurosaka M. Double-bundle ACL reconstruction can improve rotational stability. Clin Orthop Relat Res. 2007;454:100–107. doi: 10.1097/BLO.0b013e31802ba45c. [DOI] [PubMed] [Google Scholar]
  • 45.Yasuda K, Kondo E, Ichiyama H, et al. Anatomic reconstruction of the anteromedial and posterolateral bundles of the anterior cruciate ligament using hamstring tendon grafts. Arthroscopy. 2004;20:1015–1025. doi: 10.1016/j.arthro.2004.08.010. [DOI] [PubMed] [Google Scholar]
  • 46.Yasuda K, Kondo E, Ichiyama H, Tanabe Y, Tohyama H. Clinical evaluation of anatomic double-bundle anterior cruciate ligament reconstruction procedure using hamstring tendon grafts: comparisons among 3 different procedures. Arthroscopy. 2006;22:240–251. doi: 10.1016/j.arthro.2005.12.017. [DOI] [PubMed] [Google Scholar]
  • 47.Yoo JD, Papannagari R, Park SE, DeFrate LE, Gill TJ, Li G. The effect of anterior cruciate ligament reconstruction on knee joint kinematics under simulated muscle loads. Am J Sports Med. 2005;33:240–246. doi: 10.1177/0363546504267806. [DOI] [PubMed] [Google Scholar]
  • 48.Zantop T, Diermann N, Schumacher T, Schanz S, Fu FH, Petersen W. Anatomical and nonanatomical double-bundle anterior cruciate ligament reconstruction: importance of femoral tunnel location on knee kinematics. Am J Sports Med. 2008;36:678–685. doi: 10.1177/0363546508314414. [DOI] [PubMed] [Google Scholar]

RESOURCES