Technical Notes
Applying Cross-Pin System in Both Femoral and Tibial Fixation in Anterior Cruciate Ligament Reconstruction Using Hamstring Tendons Wei Qi, M.D., Yujie Liu, M.D., Jing Xue, M.D., Haifeng Li, M.D., Junliang Wang, M.D., and Feng Qu, M.D.
Abstract: Use of the RigidFix Cross Pin System (DePuy Mitek, Raynham, MA) is a popular technique for femoral fixation of grafts in anterior cruciate ligament reconstruction (ACLR). However, tibial fixation is still limited to the use of interference screws and post fixation, and few surgeons apply the femoral RigidFix system in tibial fixation. Meanwhile, tunnel enlargement is still a problem that affects the outcome of ACLR with hamstring grafts. We have used the femoral RigidFix system in femoral and tibial fixation. The rod top of the guide frame should be placed under the level of the subchondral bone at the proximal end of the tibial tunnel to ensure that the pins will not be inserted into the joint. The pins are inserted through the center of the lateral tibia. Using our technique, the fixation points of the femur and tibia are close to the anterior cruciate ligament insertions, and full contact of the graft with the tunnel wall can be accomplished. On the basis of our preliminary observations and investigation, we are optimistic about the prospect of performing ACLR using the RigidFix system in femoral and tibial fixation.
D
uring the past decade, given the lower anteroposterior laxity as measured with the KT-1000 arthrometer (MEDmetric, San Diego, CA) and sufficient mechanical strength,1,2 more and more cross-pin fixation systems were used in anterior cruciate ligament reconstruction (ACLR) with hamstring tendon grafts. One such device, the RigidFix Cross Pin System (DePuy Mitek, Raynham, MA), uses 2 parallel pins across the graft and femoral tunnel.2 The pins are composed of polylactic acid, and they are fully absorbed in the human body by hydrolysis. However, various interference screws and suture posts are still the primary applications in tibial fixation in ACLR. Meanwhile, the tibial RigidFix Cross Pin System is hardly used, and few investigators have reported the use of the femoral fixation system in tibial fixation.
From the Orthopedics Department, Chinese PLA General Hospital (W.Q., Y.L., H.L., J.W., F.Q.); and Orthopedics Department, Air Force General Hospital of Chinese PLA (J.X.), Beijing, China. The authors report that they have no conflicts of interest in the authorship and publication of this article. Received January 19, 2015; accepted March 17, 2015. Address correspondence to Yujie Liu, M.D., Orthopedics Department, Chinese PLA General Hospital, 28 Fuxing Road, Haidian District, Beijing 100853, China. E-mail: [email protected] Ó 2015 by the Arthroscopy Association of North America 2212-6287/1560/$36.00 http://dx.doi.org/10.1016/j.eats.2015.03.018
We have applied the femoral RigidFix Cross Pin System in femoral and tibial fixation in more than 300 cases with semitendinosus and gracilis grafts since 2007. No fixation failure or knee instability has been observed postoperatively. The purpose of this study is to present a standard surgical procedure using the femoral RigidFix Cross Pin System in both the femur and tibia during arthroscopic ACLR.
Surgical Technique Preparation and Graft Harvest The patient is placed in the supine position, under general or spinal anesthesia. A routine diagnostic arthroscopy is performed. Meniscal injury and articular cartilage lesions are evaluated, and if necessary, meniscectomy or meniscal repair and treatment for cartilage lesions (chondroplasty or microfracture) are performed. Then, the arthroscope is withdrawn. Routinely, the semitendinosus and gracilis are harvested to obtain a length of at least 18 cm. The tendons are made into 4 or 6 strands. Usually, the diameter of the tendon graft is 7 to 9 mm, and the length is about 90 to 100 mm. The tibial and femoral portions of the tendon are sutured to achieve 30 to 35 mm prospectively under pretensioning with whipstitches (Fig 1, Video 1) using No. 2 Ethibond suture (Ethicon, Somerville, NJ). The surgeon marks a position 30 mm from the end of the
Arthroscopy Techniques, Vol 4, No 5 (October), 2015: pp e397-e402
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Fig 1. Care is taken to pretension the 4 or 6 strands uniformly, and the tibial and femoral portions of the tendon graft are both sutured together to achieve 30 to 35 mm under pre-tensioning.
femur where the tendon is planned to be transplanted and threads a No. 5 Ethibond thread through the tendon for later traction. Femoral Tunnel Preparation With the knee positioned in 120 of flexion, a transportal ACL Femoral Guide (Smith & Nephew Endoscopy, Andover, MA) is brought through the anteromedial portal and seated at the 10:30 clock-face position to 11-o’clock position for a right knee or 1o’clock position to 1:30 clock-face position for a left knee. Then, while keeping the knee in a hyperflexion position (120 ), the surgeon drills a straight 2.4-mm guide pin (Smith & Nephew Endoscopy) through the transportal ACL Femoral Guide into the rear part of the anterior cruciate ligament (ACL) femoral footprint, exiting on the lateral side of the knee. The length of the femoral tunnel is measured from the lateral exit by using a “minus method” with another 2.4-mm guide pin, whose length is equal to that of the original guide pin (Fig 2, Video 1). After the precise placement of the mark is confirmed by arthroscopy, a femoral reamer (Smith & Nephew Endoscopy) with a diameter equal to the graft diameter is introduced, and the femoral tunnel
is made with a depth of 30 mm and at 1 to 2 mm anteriorly to the posterior cortex. Tibial Tunnel Preparation From the anteromedial portal, the tibial guide (Smith & Nephew Endoscopy) is positioned at 50 and is maintained 20 to 25 medially with respect to the longitudinal axis of the tibia. After the exit point is positioned at the center of the intercondylar ACL remnant of the tibia, the 2.4-mm guide pin is positioned on which a cannulated drill (Smith & Nephew Endoscopy) whose diameter is equal to the diameter of graft is run. Femoral Cross-Pin Hole Preparation The RigidFix Cross Pin guide frame is inserted in the femoral tunnel. The lateral femoral condyle is then identified, and the sleeves are checked so that they lie in the center of the condyle. Stab incisions are made, and the sleeve-trocar assembly is inserted through the jig. Drilling should be performed slowly and firmly without pushing too hard because the trocar could easily miss the locking aperture in the jig. The femoral sleeve-trocar assembly is not removed to check that the pins will be placed in the center of the tunnel (Fig 3A,
Fig 2. (A) The end of the 2.4-mm guide pin (GP) is parallel to the articular entrance (AE) at the lateral condyle (LC) of the femur. (B) The minus method is used for measurement of the femoral tunnel length. Another 2.4-mm guide pin (GP0 ), whose length is equal to that of GP, is inserted to touch the cortex (white arrow) of the LC by the side of GP, and the length between the tip of GP and the end of GP’ (yellow double-headed arrow) is the length of the femoral tunnel.
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Fig 3. (A) To determine whether the position of the cross pin in the tunnel is correct, the guide pins (arrows) are inserted into the holes for the cross pin, and the surgeon observes whether they are located in the center of the cross section of the tunnel with an arthroscope inserted into the tunnel. (B) The arrows show that the cross pins have missed the center of the tunnel.
Video 1); otherwise, the tunnel of the cross pins should be re-created (Fig 3B). Tibial Cross-Pin Hole Preparation The RigidFix Cross Pin guide frame is inserted in the tibial tunnel, and the top of the guide should be parallel to the level of the subchondral bone of the proximal entrance of the tibial tunnel (Fig 4A, Video 1). The sleeve-trocar assembly is inserted through the jig in the center of the lateral tibia. The insertion points should be a little more anterior to the center of the lateral tibia to protect the peroneal nerve (Fig 4B). The surgeon should make sure that the pins are placed in the center of the tibial tunnel by the same method used to check the femoral side (Video 1). Graft Passage and Fixation The tendon is drawn from the tibial tunnel to the femoral tunnel until the pre-marked 30-mm position is reached. The surgeon performs a final check to determine whether the graft is in the correct position
by using a guide pin to feel the “soft touch” (Video 1). The surgeon then punches in 2 cross pins from the proximal to distal end of the femur with the knee in 90 of flexion. Tension is applied to the tendon sutures outside the tibial tunnel after the tendon is firmly fixed at the femoral end. With the knee in 30 of flexion, the surgeon punches in 2 RigidFix cross pins for the tibial end from the proximal to distal end; he or she then inspects the tension of the reconstructed ACL under arthroscopy and checks whether there is intercondylar collision with flexion and extension of the knee joint. The treatment algorithm is presented in the flow diagram (Fig 5). Advantages, indications, contraindications, tips and pearls, pitfalls and risks, key points, and limitations of the procedure are described in Table 1.
Discussion Selection of the graft fixation technique for ACLR should be such that it has sufficient strength, is
Fig 4. (A) To make the cross-pin holes a little lower than the tibial plateau (TP), the top of the guide is paralleled to the level of the subchondral bone (SCB) at the proximal entrance of the tibial tunnel (about 5 mm below the articular surface of the tibial plateau). The double-headed arrow shows the thickness of the subchondral bone. (B) The jig of the guide frame is placed on the anterolateral side of the right tibia (arrow) to create the tibial tunnel.
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Fig 5. Flow diagram showing steps of tibial and femoral RigidFix Cross Pin fixation technique using semitendinosus (SMT) and gracilis (G) tendon graft for anterior cruciate ligament (ACL) reconstruction. Symbols with a solid arrow indicate activity performed by the surgeon; symbols with a dashed arrow indicate activity optionally performed by the assistant.
capable of overcoming the displacement under cyclic loads, and is helpful for the healing of the tendon and bone tunnel to achieve permanent fixation. The press-in fixation of interference screws has a serious drawback in that it incises the graft and, in turn, reduces the strength of the tendon. Fixations with the EndoButton device (Ethicon) or suture post are all far from the anatomic insertion of the ACL.
Consequently, the graft in the bone tunnel is subject to longitudinal movement, which causes the bungee effect, and transverse movement, which causes the windshield-wiper effect, and, hence, creep of the tendon graft, enlargement of the bone tunnel, and ingression of synovial fluid; eventually, the healing of the tendon is affected. These problems have induced strong concerns among researchers for a long time.
FEMORAL AND TIBIAL CROSS-PIN FIXATION IN ACLR Table 1. Advantages, Indications, Contraindications, Tips and Pearls, Pitfalls and Risks, Key Points, and Limitations of Tibial and Femoral RigidFix Cross Pin Fixation Technique for ACL Reconstruction Advantages The fixation points are closer to the anatomic insertions on both the femoral and tibial sides compared with EndoButton or suture post fixation. There is less interference with the tendon-bone interface in the tunnel than when using interference screws. The distance between the femoral and tibial fixation points is shortened, preventing the bungee effect of the graft. Indications Soft-tissue graft including hamstring autograft tendon, Achilles allograft tendon, or quadriceps allograft tendon is available for ACL reconstruction. Contraindications ACL-deficient knee complicated by inflammatory arthritis or joint stiffness Acute injury in which popliteal neurovascular complications are yet to be ruled out Tips and pearls The femoral tunnel should be drilled through the anteromedial portal to obtain a more oblique and shorter tunnel that could allow a 6-strand graft to be made. The top of the guide rod should be placed 5 mm below the articular facet, and the cross-pin holes should be made with a 15 -45 slope angle to the coronal plane of the tibia. After the guide frame is detached and removed, the arthroscope is inserted into the femoral or tibial tunnel, and the guide pin is then inserted through each sleeve in turn to check if the cross pins will be in the center, indicating correct placement. Pitfalls and risks Drilling the femoral tunnel through the anteromedial portal may result in fracture of the posterior cortex of the femoral tunnel. Metal micro-debris will be made between the cross-pin sleeves and the drills when the cross-pin holes are being drilled. This wear debris will affect the imaging quality of the postoperative MRI examination. Key points The tendon graft should be no shorter than 9 cm; otherwise, one of the cross pins may not cross the graft. The length of the whipstitches should be sutured as long as the length of the tunnel so that all 4 cross pins can fix the graft. The surgeon should double check if the cross-pin holes are placed in the center of the tunnel during the operation. Achieving the correct insertion depth of the guide rod in the tibial tunnel is very important; otherwise, the cross pins may cross over the articular surface of the tibial plateau. Limitations The technique may be difficult to apply to double-bundle ACL reconstruction. ACL, anterior cruciate ligament; MRI, magnetic resonance imaging.
The farther the fixation points relative to the anatomic point of the ACL, the greater the enlargement of the bone tunnel, and conversely, the closer the fixation point, the more stable the anatomic point of the ACL. By applying the RigidFix Cross Pin System in femoral and tibial fixation in ACLR, the distance between the fixation points of the femur and tibia is shortened. Choi et al.3 investigated whether
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hamstring ACLR using RigidFix and IntraFix (DePuy Mitek) fixation showed less widening of the tibial tunnels than observed in previously published studies, and they showed tibial tunnel widening in 25% of patients after hamstring ACLR using IntraFix tibial fixation. Among our patients, there has been no femoral or tibial tunnel widening after hamstring ACLR using RigidFix femoral and tibial fixation. To make the cross-pin holes a little lower than the tibial plateau, the 2 holes with guide pins on the side of the tibia for the cross pins should be drilled with the RigidFix guide device inserted into the tibial tunnel with the end tip of it aligned with the subchondral bone at the inner socket of the tibial tunnel. The distance between the first hole for cross-pin insertion and the end tip of the RigidFix guide device is only 9 mm; if the end tip of the RigidFix guide device is aligned with the inner socket of the tibial tunnel, the first hole for cross-pin insertion will be too close to the tibial plateau, so it is risky to drill the sleeve-trocar assembly into the joint and the strength of the first cross pin will be affected. The guide pins should be placed through the center hole of the guide rod; otherwise, if it slips over the surface of the guide rod, the cross pin will deviate from the center of the cross section of the tunnel and may miss the tendon, consequently affecting the stability of the fixation. The following methods can help to determine whether the position of the cross pin in the tunnel is correct. First, the surgeon keeps the drill bit in the tunnel after the hole for the cross pin has been drilled; then, he or she inserts the guide pin following the center hole of the guide device. If impact between the guide pin and the bit is felt, then the positioning of the cross-pin hole is correct. Alternatively, to check the cross-pin hole position, the surgeon can insert the guide pin into the hole for the cross pin and observe whether it is located in the center of the cross section of the tunnel with an arthroscope inserted into the tunnel (Fig 3A). If the pin track is deviated (Fig 3B), an alternative cross-pin hole should be redesigned and redrilled. The action should be gentle when punching the RigidFix Cross Pin, and the surgeon should avoid punching the cross pin too deep to penerate the medial condyle of the femur. The limitation of our technique is that it only has been applied in single-bundle ACLR so far. To determine whether the technique could be used in doublebundle or anatomic ACLR, more basic research and practice are needed. More basic research, such as kinematic and biomechanical studies, should be performed to support the use of this technique. Furthermore, long-term follow-up is needed to evaluate the outcome of the technique.
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Acknowledgment The authors thank Juanli Zhu, the scrub nurse, for assisting with the surgical procedure, and Yang Liu, the technician, for recording the video.
References 1. Frosch S, Rittstieg A, Balcarek P, et al. Bioabsorbable interference screw versus bioabsorbable cross pins: Influence of femoral graft fixation on the clinical outcome after
ACL reconstruction. Knee Surg Sports Traumatol Arthrosc 2012;20:2251-2256. 2. Tirmik U, Mahirogullari M, Kuskucu M. The results of reconstruction of the ACL using the cross-pin femoral system and four-strand hamstring tendon autografts. Acta Orthop Traumatol Turc 2011;45:233-239. 3. Choi NH, Lee JH, Son KM, Victoroff BN. Tibial tunnel widening after anterior cruciate ligament reconstructions with hamstring tendons using Rigidfix femoral fixation and Intrafix tibial fixation. Knee Surg Sports Traumatol Arthrosc 2010;18:92-97.
Applying Cross-Pin System in Both Femoral and Tibial Fixation in Anterior Cruciate Ligament Reconstruction Using Hamstring Tendons Wei Qi, M.D., Yujie Liu, M.D., Jing Xue, M.D., Haifeng Li, M.D., Junliang Wang, M.D., and Feng Qu, M.D.
Abstract: Use of the RigidFix Cross Pin System (DePuy Mitek, Raynham, MA) is a popular technique for femoral fixation of grafts in anterior cruciate ligament reconstruction (ACLR). However, tibial fixation is still limited to the use of interference screws and post fixation, and few surgeons apply the femoral RigidFix system in tibial fixation. Meanwhile, tunnel enlargement is still a problem that affects the outcome of ACLR with hamstring grafts. We have used the femoral RigidFix system in femoral and tibial fixation. The rod top of the guide frame should be placed under the level of the subchondral bone at the proximal end of the tibial tunnel to ensure that the pins will not be inserted into the joint. The pins are inserted through the center of the lateral tibia. Using our technique, the fixation points of the femur and tibia are close to the anterior cruciate ligament insertions, and full contact of the graft with the tunnel wall can be accomplished. On the basis of our preliminary observations and investigation, we are optimistic about the prospect of performing ACLR using the RigidFix system in femoral and tibial fixation.
D
uring the past decade, given the lower anteroposterior laxity as measured with the KT-1000 arthrometer (MEDmetric, San Diego, CA) and sufficient mechanical strength,1,2 more and more cross-pin fixation systems were used in anterior cruciate ligament reconstruction (ACLR) with hamstring tendon grafts. One such device, the RigidFix Cross Pin System (DePuy Mitek, Raynham, MA), uses 2 parallel pins across the graft and femoral tunnel.2 The pins are composed of polylactic acid, and they are fully absorbed in the human body by hydrolysis. However, various interference screws and suture posts are still the primary applications in tibial fixation in ACLR. Meanwhile, the tibial RigidFix Cross Pin System is hardly used, and few investigators have reported the use of the femoral fixation system in tibial fixation.
From the Orthopedics Department, Chinese PLA General Hospital (W.Q., Y.L., H.L., J.W., F.Q.); and Orthopedics Department, Air Force General Hospital of Chinese PLA (J.X.), Beijing, China. The authors report that they have no conflicts of interest in the authorship and publication of this article. Received January 19, 2015; accepted March 17, 2015. Address correspondence to Yujie Liu, M.D., Orthopedics Department, Chinese PLA General Hospital, 28 Fuxing Road, Haidian District, Beijing 100853, China. E-mail: [email protected] Ó 2015 by the Arthroscopy Association of North America 2212-6287/1560/$36.00 http://dx.doi.org/10.1016/j.eats.2015.03.018
We have applied the femoral RigidFix Cross Pin System in femoral and tibial fixation in more than 300 cases with semitendinosus and gracilis grafts since 2007. No fixation failure or knee instability has been observed postoperatively. The purpose of this study is to present a standard surgical procedure using the femoral RigidFix Cross Pin System in both the femur and tibia during arthroscopic ACLR.
Surgical Technique Preparation and Graft Harvest The patient is placed in the supine position, under general or spinal anesthesia. A routine diagnostic arthroscopy is performed. Meniscal injury and articular cartilage lesions are evaluated, and if necessary, meniscectomy or meniscal repair and treatment for cartilage lesions (chondroplasty or microfracture) are performed. Then, the arthroscope is withdrawn. Routinely, the semitendinosus and gracilis are harvested to obtain a length of at least 18 cm. The tendons are made into 4 or 6 strands. Usually, the diameter of the tendon graft is 7 to 9 mm, and the length is about 90 to 100 mm. The tibial and femoral portions of the tendon are sutured to achieve 30 to 35 mm prospectively under pretensioning with whipstitches (Fig 1, Video 1) using No. 2 Ethibond suture (Ethicon, Somerville, NJ). The surgeon marks a position 30 mm from the end of the
Arthroscopy Techniques, Vol 4, No 5 (October), 2015: pp e397-e402
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W. QI ET AL.
Fig 1. Care is taken to pretension the 4 or 6 strands uniformly, and the tibial and femoral portions of the tendon graft are both sutured together to achieve 30 to 35 mm under pre-tensioning.
femur where the tendon is planned to be transplanted and threads a No. 5 Ethibond thread through the tendon for later traction. Femoral Tunnel Preparation With the knee positioned in 120 of flexion, a transportal ACL Femoral Guide (Smith & Nephew Endoscopy, Andover, MA) is brought through the anteromedial portal and seated at the 10:30 clock-face position to 11-o’clock position for a right knee or 1o’clock position to 1:30 clock-face position for a left knee. Then, while keeping the knee in a hyperflexion position (120 ), the surgeon drills a straight 2.4-mm guide pin (Smith & Nephew Endoscopy) through the transportal ACL Femoral Guide into the rear part of the anterior cruciate ligament (ACL) femoral footprint, exiting on the lateral side of the knee. The length of the femoral tunnel is measured from the lateral exit by using a “minus method” with another 2.4-mm guide pin, whose length is equal to that of the original guide pin (Fig 2, Video 1). After the precise placement of the mark is confirmed by arthroscopy, a femoral reamer (Smith & Nephew Endoscopy) with a diameter equal to the graft diameter is introduced, and the femoral tunnel
is made with a depth of 30 mm and at 1 to 2 mm anteriorly to the posterior cortex. Tibial Tunnel Preparation From the anteromedial portal, the tibial guide (Smith & Nephew Endoscopy) is positioned at 50 and is maintained 20 to 25 medially with respect to the longitudinal axis of the tibia. After the exit point is positioned at the center of the intercondylar ACL remnant of the tibia, the 2.4-mm guide pin is positioned on which a cannulated drill (Smith & Nephew Endoscopy) whose diameter is equal to the diameter of graft is run. Femoral Cross-Pin Hole Preparation The RigidFix Cross Pin guide frame is inserted in the femoral tunnel. The lateral femoral condyle is then identified, and the sleeves are checked so that they lie in the center of the condyle. Stab incisions are made, and the sleeve-trocar assembly is inserted through the jig. Drilling should be performed slowly and firmly without pushing too hard because the trocar could easily miss the locking aperture in the jig. The femoral sleeve-trocar assembly is not removed to check that the pins will be placed in the center of the tunnel (Fig 3A,
Fig 2. (A) The end of the 2.4-mm guide pin (GP) is parallel to the articular entrance (AE) at the lateral condyle (LC) of the femur. (B) The minus method is used for measurement of the femoral tunnel length. Another 2.4-mm guide pin (GP0 ), whose length is equal to that of GP, is inserted to touch the cortex (white arrow) of the LC by the side of GP, and the length between the tip of GP and the end of GP’ (yellow double-headed arrow) is the length of the femoral tunnel.
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Fig 3. (A) To determine whether the position of the cross pin in the tunnel is correct, the guide pins (arrows) are inserted into the holes for the cross pin, and the surgeon observes whether they are located in the center of the cross section of the tunnel with an arthroscope inserted into the tunnel. (B) The arrows show that the cross pins have missed the center of the tunnel.
Video 1); otherwise, the tunnel of the cross pins should be re-created (Fig 3B). Tibial Cross-Pin Hole Preparation The RigidFix Cross Pin guide frame is inserted in the tibial tunnel, and the top of the guide should be parallel to the level of the subchondral bone of the proximal entrance of the tibial tunnel (Fig 4A, Video 1). The sleeve-trocar assembly is inserted through the jig in the center of the lateral tibia. The insertion points should be a little more anterior to the center of the lateral tibia to protect the peroneal nerve (Fig 4B). The surgeon should make sure that the pins are placed in the center of the tibial tunnel by the same method used to check the femoral side (Video 1). Graft Passage and Fixation The tendon is drawn from the tibial tunnel to the femoral tunnel until the pre-marked 30-mm position is reached. The surgeon performs a final check to determine whether the graft is in the correct position
by using a guide pin to feel the “soft touch” (Video 1). The surgeon then punches in 2 cross pins from the proximal to distal end of the femur with the knee in 90 of flexion. Tension is applied to the tendon sutures outside the tibial tunnel after the tendon is firmly fixed at the femoral end. With the knee in 30 of flexion, the surgeon punches in 2 RigidFix cross pins for the tibial end from the proximal to distal end; he or she then inspects the tension of the reconstructed ACL under arthroscopy and checks whether there is intercondylar collision with flexion and extension of the knee joint. The treatment algorithm is presented in the flow diagram (Fig 5). Advantages, indications, contraindications, tips and pearls, pitfalls and risks, key points, and limitations of the procedure are described in Table 1.
Discussion Selection of the graft fixation technique for ACLR should be such that it has sufficient strength, is
Fig 4. (A) To make the cross-pin holes a little lower than the tibial plateau (TP), the top of the guide is paralleled to the level of the subchondral bone (SCB) at the proximal entrance of the tibial tunnel (about 5 mm below the articular surface of the tibial plateau). The double-headed arrow shows the thickness of the subchondral bone. (B) The jig of the guide frame is placed on the anterolateral side of the right tibia (arrow) to create the tibial tunnel.
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Fig 5. Flow diagram showing steps of tibial and femoral RigidFix Cross Pin fixation technique using semitendinosus (SMT) and gracilis (G) tendon graft for anterior cruciate ligament (ACL) reconstruction. Symbols with a solid arrow indicate activity performed by the surgeon; symbols with a dashed arrow indicate activity optionally performed by the assistant.
capable of overcoming the displacement under cyclic loads, and is helpful for the healing of the tendon and bone tunnel to achieve permanent fixation. The press-in fixation of interference screws has a serious drawback in that it incises the graft and, in turn, reduces the strength of the tendon. Fixations with the EndoButton device (Ethicon) or suture post are all far from the anatomic insertion of the ACL.
Consequently, the graft in the bone tunnel is subject to longitudinal movement, which causes the bungee effect, and transverse movement, which causes the windshield-wiper effect, and, hence, creep of the tendon graft, enlargement of the bone tunnel, and ingression of synovial fluid; eventually, the healing of the tendon is affected. These problems have induced strong concerns among researchers for a long time.
FEMORAL AND TIBIAL CROSS-PIN FIXATION IN ACLR Table 1. Advantages, Indications, Contraindications, Tips and Pearls, Pitfalls and Risks, Key Points, and Limitations of Tibial and Femoral RigidFix Cross Pin Fixation Technique for ACL Reconstruction Advantages The fixation points are closer to the anatomic insertions on both the femoral and tibial sides compared with EndoButton or suture post fixation. There is less interference with the tendon-bone interface in the tunnel than when using interference screws. The distance between the femoral and tibial fixation points is shortened, preventing the bungee effect of the graft. Indications Soft-tissue graft including hamstring autograft tendon, Achilles allograft tendon, or quadriceps allograft tendon is available for ACL reconstruction. Contraindications ACL-deficient knee complicated by inflammatory arthritis or joint stiffness Acute injury in which popliteal neurovascular complications are yet to be ruled out Tips and pearls The femoral tunnel should be drilled through the anteromedial portal to obtain a more oblique and shorter tunnel that could allow a 6-strand graft to be made. The top of the guide rod should be placed 5 mm below the articular facet, and the cross-pin holes should be made with a 15 -45 slope angle to the coronal plane of the tibia. After the guide frame is detached and removed, the arthroscope is inserted into the femoral or tibial tunnel, and the guide pin is then inserted through each sleeve in turn to check if the cross pins will be in the center, indicating correct placement. Pitfalls and risks Drilling the femoral tunnel through the anteromedial portal may result in fracture of the posterior cortex of the femoral tunnel. Metal micro-debris will be made between the cross-pin sleeves and the drills when the cross-pin holes are being drilled. This wear debris will affect the imaging quality of the postoperative MRI examination. Key points The tendon graft should be no shorter than 9 cm; otherwise, one of the cross pins may not cross the graft. The length of the whipstitches should be sutured as long as the length of the tunnel so that all 4 cross pins can fix the graft. The surgeon should double check if the cross-pin holes are placed in the center of the tunnel during the operation. Achieving the correct insertion depth of the guide rod in the tibial tunnel is very important; otherwise, the cross pins may cross over the articular surface of the tibial plateau. Limitations The technique may be difficult to apply to double-bundle ACL reconstruction. ACL, anterior cruciate ligament; MRI, magnetic resonance imaging.
The farther the fixation points relative to the anatomic point of the ACL, the greater the enlargement of the bone tunnel, and conversely, the closer the fixation point, the more stable the anatomic point of the ACL. By applying the RigidFix Cross Pin System in femoral and tibial fixation in ACLR, the distance between the fixation points of the femur and tibia is shortened. Choi et al.3 investigated whether
e401
hamstring ACLR using RigidFix and IntraFix (DePuy Mitek) fixation showed less widening of the tibial tunnels than observed in previously published studies, and they showed tibial tunnel widening in 25% of patients after hamstring ACLR using IntraFix tibial fixation. Among our patients, there has been no femoral or tibial tunnel widening after hamstring ACLR using RigidFix femoral and tibial fixation. To make the cross-pin holes a little lower than the tibial plateau, the 2 holes with guide pins on the side of the tibia for the cross pins should be drilled with the RigidFix guide device inserted into the tibial tunnel with the end tip of it aligned with the subchondral bone at the inner socket of the tibial tunnel. The distance between the first hole for cross-pin insertion and the end tip of the RigidFix guide device is only 9 mm; if the end tip of the RigidFix guide device is aligned with the inner socket of the tibial tunnel, the first hole for cross-pin insertion will be too close to the tibial plateau, so it is risky to drill the sleeve-trocar assembly into the joint and the strength of the first cross pin will be affected. The guide pins should be placed through the center hole of the guide rod; otherwise, if it slips over the surface of the guide rod, the cross pin will deviate from the center of the cross section of the tunnel and may miss the tendon, consequently affecting the stability of the fixation. The following methods can help to determine whether the position of the cross pin in the tunnel is correct. First, the surgeon keeps the drill bit in the tunnel after the hole for the cross pin has been drilled; then, he or she inserts the guide pin following the center hole of the guide device. If impact between the guide pin and the bit is felt, then the positioning of the cross-pin hole is correct. Alternatively, to check the cross-pin hole position, the surgeon can insert the guide pin into the hole for the cross pin and observe whether it is located in the center of the cross section of the tunnel with an arthroscope inserted into the tunnel (Fig 3A). If the pin track is deviated (Fig 3B), an alternative cross-pin hole should be redesigned and redrilled. The action should be gentle when punching the RigidFix Cross Pin, and the surgeon should avoid punching the cross pin too deep to penerate the medial condyle of the femur. The limitation of our technique is that it only has been applied in single-bundle ACLR so far. To determine whether the technique could be used in doublebundle or anatomic ACLR, more basic research and practice are needed. More basic research, such as kinematic and biomechanical studies, should be performed to support the use of this technique. Furthermore, long-term follow-up is needed to evaluate the outcome of the technique.
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Acknowledgment The authors thank Juanli Zhu, the scrub nurse, for assisting with the surgical procedure, and Yang Liu, the technician, for recording the video.
References 1. Frosch S, Rittstieg A, Balcarek P, et al. Bioabsorbable interference screw versus bioabsorbable cross pins: Influence of femoral graft fixation on the clinical outcome after
ACL reconstruction. Knee Surg Sports Traumatol Arthrosc 2012;20:2251-2256. 2. Tirmik U, Mahirogullari M, Kuskucu M. The results of reconstruction of the ACL using the cross-pin femoral system and four-strand hamstring tendon autografts. Acta Orthop Traumatol Turc 2011;45:233-239. 3. Choi NH, Lee JH, Son KM, Victoroff BN. Tibial tunnel widening after anterior cruciate ligament reconstructions with hamstring tendons using Rigidfix femoral fixation and Intrafix tibial fixation. Knee Surg Sports Traumatol Arthrosc 2010;18:92-97.
