- Email: [email protected]
Anatomic double-bundle anterior cruciate ligament reconstruction using tibialis anterior tendon allografts
Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction Using Tibialis Anterior Tendon Allografts Armando F. Vidal, MD, Peter U. Brucker, MD, MS, and Freddie H. Fu, MD, DSc (Hon), DPs (Hon) The anterior cruciate ligament (ACL) is a complex structure consisting of 2 functionally independent anatomic bundles, the anteromedial and posterolateral bundles. Anatomic and biomechanical studies have demonstrated distinctive functions for each of these bundles at various degrees of flexion. ACL reconstructions have traditionally focused solely on the reconstruction of the anteromedial bundle, with little consideration for the posterolateral bundle. Recent reports have appeared describing various techniques for anatomic ACL reconstruction in an attempt to recreate the native anatomy. We present an arthroscopic technique of anatomic, double-bundle ACL reconstruction using tibialis anterior tendon allografts. This technique restores the anatomic footprint of the native ACL on both the tibia and the femur. We believe that focusing reconstructive techniques on recreating both bundles of the ACL more closely recreates the biomechanical function of the native ligament. Oper Tech Orthop 15:140-145 © 2005 Elsevier Inc. All rights reserved. KEYWORDS anterior cruciate ligament, anatomic reconstruction, double bundle, allograft, arthroscopy
R
econstruction of the injured anterior cruciate ligament (ACL) has been the subject of considerable scrutiny for the past 3 decades. Modern ACL reconstructive procedures have focused on endoscopic reconstruction of the anteromedial (AM) bundle of the ACL using a variety of graft choices and fixation options. Clinical success rates of modern techniques have varied between 69% and 95% in various series.1-3 The explanation for these less than satisfactory results remains elusive but may be the consequence of a failure of modern techniques to fully restore normal kinematics to the knee. Recent biomechanical studies have revealed some interesting insight regarding the role that the posterolateral (PL) bundle may have in restoring knee stability. Biomechanical studies in our research center have shown that standard ACL reconstructions using either quadruple-loop hamstring or
Department of Orthopaedic Surgery, Center for Sports Medicine, University of Pittsburgh Medical Center, Pittsburgh, PA. Address reprint requests to Armando F. Vidal, MD, Department of Orthopaedic Surgery, Center for Sports Medicine, University of Pittsburgh Medical Center, 3471 Fifth Avenue, Suite 1011, Pittsburgh, PA 15213. E-mail: [email protected]
140
1048-6666/05/$-see front matter © 2005 Elsevier Inc. All rights reserved. doi:10.1053/j.oto.2004.11.006
bone-patellar tendon-bone grafts are successful at restoring anterior stability to the knee. However, these standard techniques are deficient at restoring stability in response to a combined rotatory and internal rotation force with valgus torque, as one would see with a pivot shift.4 Current reconstructive procedures place the graft to close to the central axis of the tibia and femur, making them inadequate to resist these rotational moments. This concept was further illustrated recently when Loh and coworkers5 examined the biomechanical implications of femoral tunnel placement at either a 10 o’clock or 11 o’clock position. They discovered that both positions were able to effectively resist anterior tibial translation; however, the 10 o’clock position, which is closer to the footprint of the PL bundle, was far superior at resisting rotatory loads. As one would expect, neither single bundle reconstruction was successful at fully restoring knee stability back to the level of the intact knee. Further investigations in our laboratory examined the biomechanical differences between standard single-bundle and anatomic double-bundle ACL constructs in a cadaveric model.6 Anatomic double-bundle reconstructions were able to more closely restore normal kinematics to the knee when compared with a single-bundle technique. Both anterior tib-
Double-bundle ACL reconstruction using tibialis anterior tendon allografts
Figure 1 Operating room setup for double-bundle ACL reconstruction
ial translation and coupled rotatory translation were significantly less in the specimens with double-bundle ACL reconstructions. Furthermore, the in situ loads experienced by the experimental double-bundle ACL grafts were closer to the values experienced by the native ligament in both anterior translation and coupled rotation. The findings in this study suggested that a more anatomic reconstruction is necessary to completely restore knee stability. We therefore developed a technique of double-bundle, anatomic ACL reconstruction using 2 separate tibialis anterior tendon allografts which function as the biomechanically independent bundles of the native ACL. It is our feeling that an anatomically based reconstruction will be better at restoring normal kinematics to the ACL deficient knee and this will ultimately translate into improved clinical outcomes.
141 placed into the arthroscopic leg holder and locked into position (Fig. 1). While one assistant sterilizes and drapes the knee, a second assistant prepares the 2 anterior tibial tendon allografts. Alternatively, a posterior tibial tendon allograft can be used for one of the grafts. The posterior tibial tendon allograft tends to be smaller in both diameter and length, which often is well suited for reconstruction of the PL bundle. Each graft is individually fashioned as a double loop. The anterior tibial tendon and posterior tibial tendon allografts generally range from 24 to 30 mm in total length. When doubled over, these provide more than sufficient tissue for the reconstruction. The AM graft generally is made slightly larger than the PL graft. We use an 8- to 9-mm graft for the AM bundle and a 7to 8-mm graft to recreate the PL bundle (Fig. 2). Standard anterolateral and anteromedial arthroscopic portals are established. For ACL reconstruction surgery, we place these portals immediately adjacent to the lateral and medial patella tendon borders at the level of the inferior pole of the patella. A complete diagnostic arthroscopy is performed and any intraarticular pathology (ie, meniscal or chondral injury) is addressed at this time. Any interfering fat pad or ligamentum mucosum is removed using a motorized full-radius shaver to allow for an unobstructed view of the notch and ACL. The injured ACL is examined with an arthroscopic probe, dissected and debrided. We leave the tibial footprint of the ACL intact for its proprioceptive and vascular contributions. The anatomic footprints of the AM and PL bundles of the ACL on the lateral wall of the intercondylar notch are identified. When introducing the arthroscope into the medial and lateral infrapatellar portals in combination, the 3-dimensional visualization of the ACL femoral footprint on the wall of the intercondylar notch is enhanced when compared with the view from only a single portal. The PL femoral tunnel is drilled first. This is performed via an accessory AM portal. This portal is established under di-
Surgical Technique The patient is identified in the preoperative holding area and the operative limb is signed by the operative surgeon. General or regional anesthesia can be used. In addition, supplementation with femoral nerve blocks is generally performed at our institution to aid in postoperative pain control. The patient is positioned supine on the operating room table with the nonoperative limb positioned in a well-leg holder in a flexed and abducted position. A pneumatic tourniquet is applied to the operative leg and insufflated to 300 to 350 mm Hg after the limb is exsanguinated. The leg is then promptly
Figure 2 Anterior tibialis tendon allograft preparation for doublebundle reconstruction. The AM graft (top) is 8 mm in diameter and longer than the PL graft (bottom). The PL graft pictured is 7 mm in diameter.
142
Figure 3 Drilling of the femoral tunnel of PL bundle via the accessory AM portal (view from the standard AM portal: right knee).
rect visualization. The arthroscope is placed into the AM portal to allow a direct view of the PL femoral origin. An 18-gauge spinal needle is then inserted medial and distal to the AM portal just above the medial meniscus. The placement of this accessory AM portal is critical in obtaining the correct trajectory and entry point for the PL femoral tunnel. A 3.2-mm guide wire is passed into the posterior and distal portion of the lateral wall of the intercondylar notch. The guide wire is placed adjacent to the articular surface of the medial femoral condyle just above the medial meniscus. Adequate distance is needed such that the drill will not damage either of these surfaces. The knee is flexed approximately 110°. Once the pin is in an acceptable position, the tunnel is drilled with an acorn drill over the guide wire to a depth of approximately 25 to 30 mm (Fig. 3). The tunnel is drilled to a diameter that is 1 mm smaller than the actual diameter of the graft and expanded using serial dilators in 0.5 mm increments to the desired size. The far cortex is then breached with a 4.5-mm EndoButton™ drill (Smith & Nephew, Andover, MA) and the depth gauge is used to assess the distance to the far cortex. This tunnel typically requires an EndoButton loop of approximately 15 to 20 mm. A 4-cm skin incision is made over the anteromedial surface of the tibia for creation of the tibial tunnels and passage of the grafts. This is made at the level of the tibial tubercle midway between the tubercle and the posteromedial border of the tibia. First, the tibial tunnel for the PL bundle is drilled. An ACL tibial drill guide is placed on the PL aspect of the ACL tibial footprint with the angle set to 55° (Fig. 4). This tunnel has a more medial starting point on the tibial cortex than a standard ACL tibial tunnel. This position is typically just anterior to the superficial medial collateral ligament fibers. Once acceptable placement of the PL tibial pin is obtained, the AM tibial guide wire is placed. The guide wire for the tunnel of the AM bundle is positioned in a more AM position on the tibial footprint using the tibial drill guide set at an angle of 45°. The starting point of the AM pin on the tibial cortex is more anterior and central than the PL pin. An osse-
A.F. Vidal, P.U. Brucker, and F.H. Fu
Figure 4 Placement of the tibial drill guide for the PL bundle in the PL aspect of ACL footprint.
ous bridge of approximately 1 to 2 cm should remain on the tibial cortex between the 2 tunnels. The PL tibial tunnel is drilled first followed by the AM tunnel. To preserve bone and prevent collapse of the tunnel into each other, the tunnels are drilled to a diameter that is 1 mm less than the diameter of the graft and then expanded using serial dilators. The dilators for both the AM and PL tunnels are placed into the joint simultaneously and visualized to ensure that the grafts will pass concomitantly. The femoral tunnel of the AM bundle is the last tunnel to be addressed. A transtibial technique is used in the same fashion that a single bundle reconstruction would be performed. A 6- or 7-mm over-the-top guide is placed on the posterior cortex of the notch between the 10:30- and 11:00o’clock positions (Fig. 5). The guide wire is passed to a depth of 10 to 15 mm, and the tunnel is drilled over the guide wire to a depth of 30 to 35 mm. The tunnel is underdrilled by 1 mm and serially dilated to the desired diameter. The far cortex is then breached with the EndoButton drill and a depth
Figure 5 Placement of the femoral tunnels for the AM and PL bundle on the lateral femoral condyle (view from AM portal).
Double-bundle ACL reconstruction using tibialis anterior tendon allografts
143 extension. CPM is started immediately from 0° to 45° of flexion, and increased by 10° per day. The brace is unlocked at 1 week, and crutches are maintained until quadriceps control is reestablished, typically 4 to 6 weeks. The accelerated rehabilitation protocol described by Irrgang is utilized.7
Discussion
Figure 6 PL bundle in situ and preparation of AM bundle passage.
gauge is used to measure the tunnel length. This tunnel usually requires a longer EndoButton loop of approximately 30 to 40 mm. Once the tunnel lengths are determined, final graft preparation is completed. Each allograft is doubled over a closedloop EndoButton of appropriate length. Ideally at least 20 to 30 mm of the tendon graft rests within each respective femoral tunnel. The graft for PL bundle is passed first. A Beath pin with a long looped suture attached to the eyelet is passed via the accessory AM portal and out through the PL femoral tunnel. The knee is flexed approximately 110° to ensure that the Beath pin exits anterior to the biceps femoris, thus protecting the peroneal nerve. The looped suture is visualized within the joint and retrieved with an arthroscopic suture grasper through the PL tibial tunnel. The graft is passed in a routine fashion and the EndoButton loop is flipped to establish femoral fixation. The trajectory of the PL femoral tunnel is primarily through metaphyseal bone. If there is any concern regarding the quality of the bone or the strength of the metaphyseal cortex, we supplement the femoral fixation of the PL bundle with a 5.5-mm bioabsorbable interference screw. The graft for the AM bundle is then passed in a standard fashion using a transtibial technique via a Beath pin with a loaded looped suture (Fig. 6). The EndoButton is flipped and the fixation is tested. The knee is then cycled through a full range of motion from 0° to 120° approximately 20 to 30 times. The PL bundle is tensioned and fixed first in 45° of flexion, followed by the AM bundle at 10° of flexion. Tibial fixation is achieved with bioabsorbable interference screws which are the same diameter as the corresponding tunnel. One or two staples typically are used as adjunctive fixation on the tibial side. The knee is then taken through a final full range of motion and the graft is examined arthroscopically to exclude graft impingement. If correct placement of the tunnels was achieved, almost the entire PL bundle is hidden behind the AM bundle and is “peaking” behind the AM graft (Fig. 7). Postoperatively, the patient is placed in a hinged knee brace. Full weight-bearing is allowed with the knee locked in
Countless techniques of ACL reconstruction have been described in the literature. Until recently, these techniques have focused primarily on recreating the AM bundle with little regard for the PL bundle. The combination of average clinical results and compelling biomechanical data, has prompted us and others6,8-17 to develop techniques that are more anatomically accurate and enhance the ability of the graft to restore normal kinematics to the knee. Initial reports of anatomic ACL reconstruction first appeared in the literature approximately 20 years ago.13,17 The past few decades, however, have been dominated by countless descriptions of various single-bundle techniques. In recent years, several reports have begun to surface describing anatomic ACL reconstructions with 2 bundles. Takeuchi and
Figure 7 AM and PL bundle in situ. (A) The PL bundle is almost completely hidden behind the AM bundle (PCL, posterior cruciate ligament) and (B) only visible in its trajectory by lifting the AM bundle.
A.F. Vidal, P.U. Brucker, and F.H. Fu
144 coworkers16 described double-bundle ACL reconstruction using a bone-hamstring-bone composite autograft. Their technique uses a single femoral and single tibial tunnel. In this technique, the 2 bundles are created by separating the hamstring strands with a bone block and rotating the graft 90° in an attempt to align them separately in the desired position for restoration of the PL and the AM bundles. Marcacci and coworkers12 described a technique in which a gracilis and semitendinosus autograft is routed through a tibial tunnel and looped back into the knee through a femoral tunnel from the over-the-top position. The graft is then rerouted through a common tibial tunnel and fixed to the anterior tibial cortex with sutures. Pederzini and coworkers15 reported their technique of a double tibial tunnel ACL reconstruction using a quadriceps autograft. They split the quadriceps graft into a 2-tailed soft tissue graft with a single bone plug. The bone plug portion of the graft is placed into the femoral tunnel and fixed with a metal interference screw, while the two-tailed soft tissue portion is passed into two separate tibial tunnels and fixed with bioabsorbable interference screws. Hara and coworkers10 used a hybrid hamstring and patellar tendon autograft for double bundle ACL reconstruction. Their technique places the bone-patellar tendon-bone graft in the traditional AM tunnel position and places the hamstring tendon graft in the over-the-top position to recreate the PL bundle. Muneta and coworkers14 reported their preliminary results of 2-bundle ACL reconstruction with double-looped hamstring autograft. Their technique use 2 separate tunnels on the femur and the tibia with EndoButton fixation on the femur and post fixation on the tibia. They reviewed 54 consecutive patients at 2 years follow-up and compared these preliminary results with their previous hamstring ACL reconstructions. Their 2-bundle procedure trended toward less anterior instability and fewer patients with greater than 5 mm differences on KT-1000 testing. The presented technique is unique in that it involves precise reconstruction of the AM and PL bundles of the ACL according to their anatomic footprints on the femur and tibia. The foundation for this technique is based on previous biomechanical work, which strongly demonstrates the importance of the PL bundle in restoring rotatory stability to the knee.4-6 To recreate the native anatomic footprints and fiber orientation of the respective bundles, we strongly recommend two separate tunnels on both the femur and tibia. Because our technique of anatomic ACL reconstruction requires a separate graft for each tunnel, choice of graft and fixation method are important decisions. Various different configurations have been described. As noted, hamstring autografts,8,9,12 hybrid combinations of autogenous bone-tendon-bone and hamstring grafts,10,11,16 and quadriceps tendon autografts15 have been reported. Initially, our experience with anatomic double-bundle ACL reconstruction employed 2 separate quadrupled hamstring autografts.18 Because of graft length limitations, this technique required that a shorter length of tendon graft reside within each bone tunnel when compared with a standard single bundle ACL reconstruction. Often, only 15 mm of tendon graft was positioned within one
of the femoral tunnels. The implications of limited tendon length within the bone tunnel became a significant concern. Greis and coworkers19 demonstrated that the pullout strength of a soft tissue graft within a bone tunnel after 6 weeks in vivo is greatly influenced by the tendon length and fit within the tunnel. Modern aggressive rehabilitation protocols demand stable and reliable fixation during the healing period.7 Subsequently, our technique evolved to using 2 doubled tibialis anterior tendon allografts to address this issue. This allows for approximately 25 to 30 mm of graft to reside within each respective femoral tunnel. The use of allografts in ACL reconstruction has the advantage of unrestricted size, widespread availability, decreased operative time, and a lack of donor site morbidity. Specifically in regards to length, anterior tibial tendon allografts have a great advantage when compared with autogenous hamstring tendons for double-bundle reconstructions. Additionally, the biomechanical properties of doubled tibialis anterior and posterior tendon are superb. In fact, the material and viscoelastic properties of a single loop of anterior tibialis or posterior tibialis tendon are comparable to a quadrupled hamstring graft.20 The use of allograft in primary ACL reconstruction surgery is controversial. Allografts tendons have been shown in numerous studies to be an acceptable alternative to autograft tissue in regards to clinical outcome.21,22 The cited advantages of allograft implantation, however, must be weighed against the potential disadvantages which include slower graft incorporation,23 potential bacterial contamination,24,25 and most importantly the possibility of disease transmission.21,26-28 The current risk of HIV transmission from a musculoskeletal allograft in the United States is estimated at approximately 1 in 1.7 million.26 Thus, frank and open discussion with the patient and thorough informed consent is essential before proceeding with allograft implantation. In conclusion, ACL reconstructive techniques have evolved dramatically during the course of the past few decades. Current single-bundle techniques have been relatively successful at restoring stability to the injured knee; however, there remains considerable room for improvement. It is our opinion that double-bundle ACL reconstruction techniques are more anatomically accurate and more successful at restoring normal kinematics. We feel that our approach using 2 tibialis anterior tendon allografts to recreate the AM and PL bundles best reproduces the normal anatomy. Additionally, the use of allogeneic tendon offers a more favorable tendonbone interface within the bony tunnels for this technique. However, clinical studies investigating residual laxity in vivo and patient outcomes are necessary to assess the long term results of this procedure.
References 1. Harter RA, Osternig LR, Singer KM, et al: Long-term evaluation of knee stability and function following surgical reconstruction for anterior cruciate ligament insufficiency. Am J Sports Med 16:434-443, 1988 2. Freedman KB, D’Amato MJ, Nedeff DD, et al: Arthroscopic anterior cruciate ligament reconstruction: A metaanalysis comparing patellar tendon and hamstring tendon autografts. Am J Sports Med 31:2-11, 2003
Double-bundle ACL reconstruction using tibialis anterior tendon allografts 3. Johnson RJ, Eriksson E, Haggmark T, et al: Five- to ten-year follow-up evaluation after reconstruction of the anterior cruciate ligament. Clin Orthop 183:122-140, 1984 4. Woo SL, Kanamori A, Zeminski J, et al: 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 84-A:907-914, 2002 5. Loh JC, Fukuda Y, Tsuda E, et al: Knee stability and graft function following anterior cruciate ligament reconstruction: Comparison between 11 o’clock and 10 o’clock femoral tunnel placement. Arthroscopy 19:297-304, 2003 6. Yagi M, Wong EK, Kanamori A, et al: Biomechanical analysis of an anatomic anterior cruciate ligament reconstruction. Am J Sports Med 30:660-666, 2002 7. Irrgang JJ: Modern trends in anterior cruciate ligament rehabilitation: nonoperative and postoperative management. Clin Sports Med 12:797813, 1993 8. Adachi N, Ochi M, Uchio Y, et al: Reconstruction of the anterior cruciate ligament. Single- versus double-bundle multistranded hamstring tendons. J Bone Joint Surg Br 86:515-520, 2004 9. 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 17:801-807, 2001 10. Hara K, Kubo T, Suginoshita T, et al: Reconstruction of the anterior cruciate ligament using a double bundle. Arthroscopy 16:860-864, 2000 11. Kubo T, Hara K, Suginoshita T, et al: Anterior cruciate ligament reconstruction using the double bundle method. J Orthop Surg (Hong Kong) 8:59-63, 2000 12. Marcacci M, Molgora AP, Zaffagnini S, et al: Anatomic double-bundle anterior cruciate ligament reconstruction with hamstrings. Arthroscopy 19:536-540, 2003 13. Mott HW: Semitendinosus anatomic reconstruction for cruciate ligament insufficiency. Clin Orthop 172:90-92, 1983 14. Muneta T, Sekiya I, Yagishita K, et al: Two-bundle reconstruction of the anterior cruciate ligament using semitendinosus tendon with Endobuttons: Operative technique and preliminary results. Arthroscopy 15: 618-624, 1999
145 15. Pederzini L, Adriani E, Botticella C, et al: Technical note: Double tibial tunnel using quadriceps tendon in anterior cruciate ligament reconstruction. Arthroscopy 16:E9, 2000 16. Takeuchi R, Saito T, Mituhashi S, et al: Double-bundle anatomic anterior cruciate ligament reconstruction using bone-hamstring-bone composite graft. Arthroscopy 18:550-555, 2002 17. Zaricznyj B: Reconstruction of the anterior cruciate ligament of the knee using a doubled tendon graft. Clin Orthop 220:162-175, 1987 18. Cha P, Brucker P, West R, et al: Arthroscopic double bundle anterior cruciate ligament reconstruction: An anatomic approach. Arthroscopy (in press) 19. Greis PE, Burks RT, Bachus K, et al: The influence of tendon length and fit on the strength of a tendon-bone tunnel complex. A biomechanical and histologic study in the dog. Am J Sports Med 29:493-497, 2001 20. Haut Donahue TL, Howell SM, Hull ML, et al: A biomechanical evaluation of anterior and posterior tibialis tendons as suitable single-loop anterior cruciate ligament grafts. Arthroscopy 18:589-597, 2002 21. Strickland SM, MacGillivray JD, Warren RF: Anterior cruciate ligament reconstruction with allograft tendons. Orthop Clin North Am 34:4147, 2003 22. Harner CD, Olson E, Irrgang JJ, et al: Allograft versus autograft anterior cruciate ligament reconstruction: 3- to 5-year outcome. Clin Orthop 324:134-144, 1996 23. Jackson DW, Corsetti J, Simon TM: Biologic incorporation of allograft anterior cruciate ligament replacements. Clin Orthop 324:126-133, 1996 24. Barbour SA, King W: The safe and effective use of allograft tissue—an update. Am J Sports Med 31:791-797, 2003 25. Kainer MA, Linden JV, Whaley DN, et al: Clostridium infections associated with musculoskeletal-tissue allografts. N Engl J Med 350:25642571, 2004 26. Buck BE, Malinin TI, Brown MD: Bone transplantation and human immunodeficiency virus. An estimate of risk of acquired immunodeficiency syndrome (AIDS). Clin Orthop 240:129-136, 1989 27. Buck BE, Malinin TI: Human bone and tissue allografts. Preparation and safety. Clin Orthop 303:8-17, 1994 28. Miller SL, Gladstone JN: Graft selection in anterior cruciate ligament reconstruction. Orthop Clin North Am 33:675-683, 2002
R
econstruction of the injured anterior cruciate ligament (ACL) has been the subject of considerable scrutiny for the past 3 decades. Modern ACL reconstructive procedures have focused on endoscopic reconstruction of the anteromedial (AM) bundle of the ACL using a variety of graft choices and fixation options. Clinical success rates of modern techniques have varied between 69% and 95% in various series.1-3 The explanation for these less than satisfactory results remains elusive but may be the consequence of a failure of modern techniques to fully restore normal kinematics to the knee. Recent biomechanical studies have revealed some interesting insight regarding the role that the posterolateral (PL) bundle may have in restoring knee stability. Biomechanical studies in our research center have shown that standard ACL reconstructions using either quadruple-loop hamstring or
Department of Orthopaedic Surgery, Center for Sports Medicine, University of Pittsburgh Medical Center, Pittsburgh, PA. Address reprint requests to Armando F. Vidal, MD, Department of Orthopaedic Surgery, Center for Sports Medicine, University of Pittsburgh Medical Center, 3471 Fifth Avenue, Suite 1011, Pittsburgh, PA 15213. E-mail: [email protected]
140
1048-6666/05/$-see front matter © 2005 Elsevier Inc. All rights reserved. doi:10.1053/j.oto.2004.11.006
bone-patellar tendon-bone grafts are successful at restoring anterior stability to the knee. However, these standard techniques are deficient at restoring stability in response to a combined rotatory and internal rotation force with valgus torque, as one would see with a pivot shift.4 Current reconstructive procedures place the graft to close to the central axis of the tibia and femur, making them inadequate to resist these rotational moments. This concept was further illustrated recently when Loh and coworkers5 examined the biomechanical implications of femoral tunnel placement at either a 10 o’clock or 11 o’clock position. They discovered that both positions were able to effectively resist anterior tibial translation; however, the 10 o’clock position, which is closer to the footprint of the PL bundle, was far superior at resisting rotatory loads. As one would expect, neither single bundle reconstruction was successful at fully restoring knee stability back to the level of the intact knee. Further investigations in our laboratory examined the biomechanical differences between standard single-bundle and anatomic double-bundle ACL constructs in a cadaveric model.6 Anatomic double-bundle reconstructions were able to more closely restore normal kinematics to the knee when compared with a single-bundle technique. Both anterior tib-
Double-bundle ACL reconstruction using tibialis anterior tendon allografts
Figure 1 Operating room setup for double-bundle ACL reconstruction
ial translation and coupled rotatory translation were significantly less in the specimens with double-bundle ACL reconstructions. Furthermore, the in situ loads experienced by the experimental double-bundle ACL grafts were closer to the values experienced by the native ligament in both anterior translation and coupled rotation. The findings in this study suggested that a more anatomic reconstruction is necessary to completely restore knee stability. We therefore developed a technique of double-bundle, anatomic ACL reconstruction using 2 separate tibialis anterior tendon allografts which function as the biomechanically independent bundles of the native ACL. It is our feeling that an anatomically based reconstruction will be better at restoring normal kinematics to the ACL deficient knee and this will ultimately translate into improved clinical outcomes.
141 placed into the arthroscopic leg holder and locked into position (Fig. 1). While one assistant sterilizes and drapes the knee, a second assistant prepares the 2 anterior tibial tendon allografts. Alternatively, a posterior tibial tendon allograft can be used for one of the grafts. The posterior tibial tendon allograft tends to be smaller in both diameter and length, which often is well suited for reconstruction of the PL bundle. Each graft is individually fashioned as a double loop. The anterior tibial tendon and posterior tibial tendon allografts generally range from 24 to 30 mm in total length. When doubled over, these provide more than sufficient tissue for the reconstruction. The AM graft generally is made slightly larger than the PL graft. We use an 8- to 9-mm graft for the AM bundle and a 7to 8-mm graft to recreate the PL bundle (Fig. 2). Standard anterolateral and anteromedial arthroscopic portals are established. For ACL reconstruction surgery, we place these portals immediately adjacent to the lateral and medial patella tendon borders at the level of the inferior pole of the patella. A complete diagnostic arthroscopy is performed and any intraarticular pathology (ie, meniscal or chondral injury) is addressed at this time. Any interfering fat pad or ligamentum mucosum is removed using a motorized full-radius shaver to allow for an unobstructed view of the notch and ACL. The injured ACL is examined with an arthroscopic probe, dissected and debrided. We leave the tibial footprint of the ACL intact for its proprioceptive and vascular contributions. The anatomic footprints of the AM and PL bundles of the ACL on the lateral wall of the intercondylar notch are identified. When introducing the arthroscope into the medial and lateral infrapatellar portals in combination, the 3-dimensional visualization of the ACL femoral footprint on the wall of the intercondylar notch is enhanced when compared with the view from only a single portal. The PL femoral tunnel is drilled first. This is performed via an accessory AM portal. This portal is established under di-
Surgical Technique The patient is identified in the preoperative holding area and the operative limb is signed by the operative surgeon. General or regional anesthesia can be used. In addition, supplementation with femoral nerve blocks is generally performed at our institution to aid in postoperative pain control. The patient is positioned supine on the operating room table with the nonoperative limb positioned in a well-leg holder in a flexed and abducted position. A pneumatic tourniquet is applied to the operative leg and insufflated to 300 to 350 mm Hg after the limb is exsanguinated. The leg is then promptly
Figure 2 Anterior tibialis tendon allograft preparation for doublebundle reconstruction. The AM graft (top) is 8 mm in diameter and longer than the PL graft (bottom). The PL graft pictured is 7 mm in diameter.
142
Figure 3 Drilling of the femoral tunnel of PL bundle via the accessory AM portal (view from the standard AM portal: right knee).
rect visualization. The arthroscope is placed into the AM portal to allow a direct view of the PL femoral origin. An 18-gauge spinal needle is then inserted medial and distal to the AM portal just above the medial meniscus. The placement of this accessory AM portal is critical in obtaining the correct trajectory and entry point for the PL femoral tunnel. A 3.2-mm guide wire is passed into the posterior and distal portion of the lateral wall of the intercondylar notch. The guide wire is placed adjacent to the articular surface of the medial femoral condyle just above the medial meniscus. Adequate distance is needed such that the drill will not damage either of these surfaces. The knee is flexed approximately 110°. Once the pin is in an acceptable position, the tunnel is drilled with an acorn drill over the guide wire to a depth of approximately 25 to 30 mm (Fig. 3). The tunnel is drilled to a diameter that is 1 mm smaller than the actual diameter of the graft and expanded using serial dilators in 0.5 mm increments to the desired size. The far cortex is then breached with a 4.5-mm EndoButton™ drill (Smith & Nephew, Andover, MA) and the depth gauge is used to assess the distance to the far cortex. This tunnel typically requires an EndoButton loop of approximately 15 to 20 mm. A 4-cm skin incision is made over the anteromedial surface of the tibia for creation of the tibial tunnels and passage of the grafts. This is made at the level of the tibial tubercle midway between the tubercle and the posteromedial border of the tibia. First, the tibial tunnel for the PL bundle is drilled. An ACL tibial drill guide is placed on the PL aspect of the ACL tibial footprint with the angle set to 55° (Fig. 4). This tunnel has a more medial starting point on the tibial cortex than a standard ACL tibial tunnel. This position is typically just anterior to the superficial medial collateral ligament fibers. Once acceptable placement of the PL tibial pin is obtained, the AM tibial guide wire is placed. The guide wire for the tunnel of the AM bundle is positioned in a more AM position on the tibial footprint using the tibial drill guide set at an angle of 45°. The starting point of the AM pin on the tibial cortex is more anterior and central than the PL pin. An osse-
A.F. Vidal, P.U. Brucker, and F.H. Fu
Figure 4 Placement of the tibial drill guide for the PL bundle in the PL aspect of ACL footprint.
ous bridge of approximately 1 to 2 cm should remain on the tibial cortex between the 2 tunnels. The PL tibial tunnel is drilled first followed by the AM tunnel. To preserve bone and prevent collapse of the tunnel into each other, the tunnels are drilled to a diameter that is 1 mm less than the diameter of the graft and then expanded using serial dilators. The dilators for both the AM and PL tunnels are placed into the joint simultaneously and visualized to ensure that the grafts will pass concomitantly. The femoral tunnel of the AM bundle is the last tunnel to be addressed. A transtibial technique is used in the same fashion that a single bundle reconstruction would be performed. A 6- or 7-mm over-the-top guide is placed on the posterior cortex of the notch between the 10:30- and 11:00o’clock positions (Fig. 5). The guide wire is passed to a depth of 10 to 15 mm, and the tunnel is drilled over the guide wire to a depth of 30 to 35 mm. The tunnel is underdrilled by 1 mm and serially dilated to the desired diameter. The far cortex is then breached with the EndoButton drill and a depth
Figure 5 Placement of the femoral tunnels for the AM and PL bundle on the lateral femoral condyle (view from AM portal).
Double-bundle ACL reconstruction using tibialis anterior tendon allografts
143 extension. CPM is started immediately from 0° to 45° of flexion, and increased by 10° per day. The brace is unlocked at 1 week, and crutches are maintained until quadriceps control is reestablished, typically 4 to 6 weeks. The accelerated rehabilitation protocol described by Irrgang is utilized.7
Discussion
Figure 6 PL bundle in situ and preparation of AM bundle passage.
gauge is used to measure the tunnel length. This tunnel usually requires a longer EndoButton loop of approximately 30 to 40 mm. Once the tunnel lengths are determined, final graft preparation is completed. Each allograft is doubled over a closedloop EndoButton of appropriate length. Ideally at least 20 to 30 mm of the tendon graft rests within each respective femoral tunnel. The graft for PL bundle is passed first. A Beath pin with a long looped suture attached to the eyelet is passed via the accessory AM portal and out through the PL femoral tunnel. The knee is flexed approximately 110° to ensure that the Beath pin exits anterior to the biceps femoris, thus protecting the peroneal nerve. The looped suture is visualized within the joint and retrieved with an arthroscopic suture grasper through the PL tibial tunnel. The graft is passed in a routine fashion and the EndoButton loop is flipped to establish femoral fixation. The trajectory of the PL femoral tunnel is primarily through metaphyseal bone. If there is any concern regarding the quality of the bone or the strength of the metaphyseal cortex, we supplement the femoral fixation of the PL bundle with a 5.5-mm bioabsorbable interference screw. The graft for the AM bundle is then passed in a standard fashion using a transtibial technique via a Beath pin with a loaded looped suture (Fig. 6). The EndoButton is flipped and the fixation is tested. The knee is then cycled through a full range of motion from 0° to 120° approximately 20 to 30 times. The PL bundle is tensioned and fixed first in 45° of flexion, followed by the AM bundle at 10° of flexion. Tibial fixation is achieved with bioabsorbable interference screws which are the same diameter as the corresponding tunnel. One or two staples typically are used as adjunctive fixation on the tibial side. The knee is then taken through a final full range of motion and the graft is examined arthroscopically to exclude graft impingement. If correct placement of the tunnels was achieved, almost the entire PL bundle is hidden behind the AM bundle and is “peaking” behind the AM graft (Fig. 7). Postoperatively, the patient is placed in a hinged knee brace. Full weight-bearing is allowed with the knee locked in
Countless techniques of ACL reconstruction have been described in the literature. Until recently, these techniques have focused primarily on recreating the AM bundle with little regard for the PL bundle. The combination of average clinical results and compelling biomechanical data, has prompted us and others6,8-17 to develop techniques that are more anatomically accurate and enhance the ability of the graft to restore normal kinematics to the knee. Initial reports of anatomic ACL reconstruction first appeared in the literature approximately 20 years ago.13,17 The past few decades, however, have been dominated by countless descriptions of various single-bundle techniques. In recent years, several reports have begun to surface describing anatomic ACL reconstructions with 2 bundles. Takeuchi and
Figure 7 AM and PL bundle in situ. (A) The PL bundle is almost completely hidden behind the AM bundle (PCL, posterior cruciate ligament) and (B) only visible in its trajectory by lifting the AM bundle.
A.F. Vidal, P.U. Brucker, and F.H. Fu
144 coworkers16 described double-bundle ACL reconstruction using a bone-hamstring-bone composite autograft. Their technique uses a single femoral and single tibial tunnel. In this technique, the 2 bundles are created by separating the hamstring strands with a bone block and rotating the graft 90° in an attempt to align them separately in the desired position for restoration of the PL and the AM bundles. Marcacci and coworkers12 described a technique in which a gracilis and semitendinosus autograft is routed through a tibial tunnel and looped back into the knee through a femoral tunnel from the over-the-top position. The graft is then rerouted through a common tibial tunnel and fixed to the anterior tibial cortex with sutures. Pederzini and coworkers15 reported their technique of a double tibial tunnel ACL reconstruction using a quadriceps autograft. They split the quadriceps graft into a 2-tailed soft tissue graft with a single bone plug. The bone plug portion of the graft is placed into the femoral tunnel and fixed with a metal interference screw, while the two-tailed soft tissue portion is passed into two separate tibial tunnels and fixed with bioabsorbable interference screws. Hara and coworkers10 used a hybrid hamstring and patellar tendon autograft for double bundle ACL reconstruction. Their technique places the bone-patellar tendon-bone graft in the traditional AM tunnel position and places the hamstring tendon graft in the over-the-top position to recreate the PL bundle. Muneta and coworkers14 reported their preliminary results of 2-bundle ACL reconstruction with double-looped hamstring autograft. Their technique use 2 separate tunnels on the femur and the tibia with EndoButton fixation on the femur and post fixation on the tibia. They reviewed 54 consecutive patients at 2 years follow-up and compared these preliminary results with their previous hamstring ACL reconstructions. Their 2-bundle procedure trended toward less anterior instability and fewer patients with greater than 5 mm differences on KT-1000 testing. The presented technique is unique in that it involves precise reconstruction of the AM and PL bundles of the ACL according to their anatomic footprints on the femur and tibia. The foundation for this technique is based on previous biomechanical work, which strongly demonstrates the importance of the PL bundle in restoring rotatory stability to the knee.4-6 To recreate the native anatomic footprints and fiber orientation of the respective bundles, we strongly recommend two separate tunnels on both the femur and tibia. Because our technique of anatomic ACL reconstruction requires a separate graft for each tunnel, choice of graft and fixation method are important decisions. Various different configurations have been described. As noted, hamstring autografts,8,9,12 hybrid combinations of autogenous bone-tendon-bone and hamstring grafts,10,11,16 and quadriceps tendon autografts15 have been reported. Initially, our experience with anatomic double-bundle ACL reconstruction employed 2 separate quadrupled hamstring autografts.18 Because of graft length limitations, this technique required that a shorter length of tendon graft reside within each bone tunnel when compared with a standard single bundle ACL reconstruction. Often, only 15 mm of tendon graft was positioned within one
of the femoral tunnels. The implications of limited tendon length within the bone tunnel became a significant concern. Greis and coworkers19 demonstrated that the pullout strength of a soft tissue graft within a bone tunnel after 6 weeks in vivo is greatly influenced by the tendon length and fit within the tunnel. Modern aggressive rehabilitation protocols demand stable and reliable fixation during the healing period.7 Subsequently, our technique evolved to using 2 doubled tibialis anterior tendon allografts to address this issue. This allows for approximately 25 to 30 mm of graft to reside within each respective femoral tunnel. The use of allografts in ACL reconstruction has the advantage of unrestricted size, widespread availability, decreased operative time, and a lack of donor site morbidity. Specifically in regards to length, anterior tibial tendon allografts have a great advantage when compared with autogenous hamstring tendons for double-bundle reconstructions. Additionally, the biomechanical properties of doubled tibialis anterior and posterior tendon are superb. In fact, the material and viscoelastic properties of a single loop of anterior tibialis or posterior tibialis tendon are comparable to a quadrupled hamstring graft.20 The use of allograft in primary ACL reconstruction surgery is controversial. Allografts tendons have been shown in numerous studies to be an acceptable alternative to autograft tissue in regards to clinical outcome.21,22 The cited advantages of allograft implantation, however, must be weighed against the potential disadvantages which include slower graft incorporation,23 potential bacterial contamination,24,25 and most importantly the possibility of disease transmission.21,26-28 The current risk of HIV transmission from a musculoskeletal allograft in the United States is estimated at approximately 1 in 1.7 million.26 Thus, frank and open discussion with the patient and thorough informed consent is essential before proceeding with allograft implantation. In conclusion, ACL reconstructive techniques have evolved dramatically during the course of the past few decades. Current single-bundle techniques have been relatively successful at restoring stability to the injured knee; however, there remains considerable room for improvement. It is our opinion that double-bundle ACL reconstruction techniques are more anatomically accurate and more successful at restoring normal kinematics. We feel that our approach using 2 tibialis anterior tendon allografts to recreate the AM and PL bundles best reproduces the normal anatomy. Additionally, the use of allogeneic tendon offers a more favorable tendonbone interface within the bony tunnels for this technique. However, clinical studies investigating residual laxity in vivo and patient outcomes are necessary to assess the long term results of this procedure.
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