- Email: [email protected]
Posterior cruciate ligament tibial attachment anatomy and radiographic landmarks for tibial tunnel placement in PCL reconstruction
Arthroscopy: The Journal of Arthroscopic and Related Surgery 10(5):546-549
Published by Raven Press, Ltd, O 1994ArthroscopyAssociationof North America
Posterior Cruciate Ligament Tibial Attachment Anatomy and Radiographic Landmarks for Tibial Tunnel Placement in PCL Reconstruction John A. Racanelli, M.D., and David Drez, Jr., M.D.
Summary: The posterior cruciate ligament (PCL) was dissected in 12 frozen human cadaver knees. The tibial attachment was radiographicaUy mapped and guide wires placed on the distal-lateral bulk of the ligament's tibial attachment. Radiographic landmarks were then described on the anteroposterior and lateral radiographs to assist in tibial tunnel guide wire placement in PCL reconstruction. The radiographic site corresponding to the posterior ridge of the tibiat plateau - t c m below the joint line and a few millimeters lateral to the center of the lateral tibial tubercle will reliably confirm tibial tunnels in PCL reconstruction. Key Words: Posterior cruciate ligament--Tibial tunnel--Radiographic verification,
debrided and a tibial capsular insertion is elevated. Visualization of this PCL insertion is always recommended during PCL reconstruction. The purpose of this current study was to dissect frozen human cadaver knees and place retrograde guide wires through the tibia for the most isometric tibial site. Radiographs were then taken to provide radiographic landmarks to be used in antegrade guide wire placement in PCL reconstruction.
Posterior cruciate ligament (PCL) reconstruction has evolved into a viable form of knee ligament reconstruction in selected patients. Arthroscopically assisted intraarticular reconstruction is one method of performing PCL reconstruction. Numerous studies have focused on the anatomy and surgical reconstruction of the PCL (1-5). It appears that the large anterolateral bundle, which becomes taut in flexion, provides the most stability to the posterior displacement of the tibia on the femur. Therefore, in surgical reconstruction of the PCL, placing the tibial tunnel nearest the lateral insertion of the ligament would most recreate the anterolateral bundle. During PCL reconstruction, a guide wire is placed from anterior to posterior in the tibia under radiographic control. It is important to place the tibial tunnel close to the most isometric distallateral point on the posterior tibia. This portion of the tibia is usually not visible intraarticularly during the procedure unless the ruptured PCL stump is
MATERIALS AND METHODS Twelve frozen human cadaveric knees of unknown age, but with intact anterior cruciate ligaments and PCLs, were dissected from a posterior approach in order to isolate the tibial attachment and the PCL. A 3/32 in guide wire was then drilled retrograde from a point that was the most distal lateral attachment of the bulk of the PCL to a point slightly distal and lateral to the tibial tubercle. This tibial site corresponds to a point 5 mm inferior lateral to the center of the tibial attachment of the PCL as described by Clancy (2). This allows for the most isometric tibial placement with a 10-mm tunnel as described by Grood (4). This tunnel will recreate the anterolateral bundle of the PCL. Once the guide
From the Department of Orthopaedics, Louisiana State University, Lake Charles, Louisiana, U.S.A. Address correspondence and reprint requests to Dr. David Drez, Jr., 2615 Enterprise Boulevard, Lake Charles, LA 70601, U.S.A.
546
TIBIAL TUNNEL PLACEMENT I N PCL RECONSTRUCTION
wires were in place and the tip of the guide wire was flush with the posterior cortical surface of the tibia, radiographs were taken in the anteroposterior (AP) and lateral planes with the knee in full extension. Radiographic landmarks were then described to assist in antegrade placement of the tibial tunnel guide wire. One cadaveric knee had the footprint of the PCL tibial attachment radiographically mapped by placing radiodense tacks around the tibial attachment site of the ligament. AP and lateral radiographs were taken of this knee with the tacks in place. All radiographs were taken from a distance of 40 inches, and measurements were adjusted for magnification.
547
FIG. 2. Radiographic map of bulk of PCL attachment on lateral view.
RESULTS The radiographic footprint of the tibial attachment of the PCL is depicted in Figs. 1 and 2. The shaded areas represent the attachment of the tibial portion of the PCL. The most distal attachment of the PCL coincides with a rough ridge found in all of the cadaveric dissections. This ridge is rarely depicted in PCL dissections or drawings (6,7). The ridge proceeds from distal medial to proximal lateral (Fig. 3). This ridge coincides with the superior border of the popliteus muscle and tendon (6). The size of the ridge is variable in all specimens, but its location is consistent, coinciding with the most distal attachment of the PCL. The guide wire placement in all specimens was started at the area of the distal lateral attachment of the PCL on the posterior tibial ridge (Fig. 4). It was aimed free hand fashion anterolaterally at an angle of 45 ° off the tibial plateau to allow for soft tissue coverage of screw heads
used in graph fixation. All guide wires exited lateral to the distal end of the tibial tubercle. The radiographic maps of all 12 guide wire placements in the AP and lateral planes are depicted in Figs. 5 and 6. A representative radiograph of one of the cadaver specimens is present in Figs. 7 and 8. The AP film had perpendicular lines drawn across the tibial plateau and through the center of the lateral tibial tubercle of the tibial eminence. The lateral radiograph had a line drawn parallel to the tibial plateau. The centermost point of the guide wire was used as a reference point in mapping the 12 cadaveric knees. Once all the guide wire points were mapped, a circle of the smallest possible diameter was drawn around them. A parallel line referenced
FIG. 1. Radiographic map of bulk of PCL attachment on AP view.
FIG. 3. Posterior tibial ridge of distal attachment of PCL. Arthroscopy, Vol, 10, No, 5, 1994
548
J. A RACANELL1 A N D D. DREZ, JR.
FIG. 6. Variability of radiographic guide wire insertions on the lateral projection.
FIG. 4. Starting site for retrograde guide wires at distal lateral attachment of PCL.
from a line drawn across the tibial plateau was drawn through the center of the circle on the lateral radiograph. From an AP radiographic map, a parallel line from one drawn through the center of the lateral tibial tubercle was also made through the center of the map circle. There were no radiographic variations of >2.5 mm from the center of the circle. The center of the circle on the AP radiograph was 8 mm below a line drawn parallel across
the tibial plateau. This corresponds to the posterior tibial ridge visualized in the cadaveric dissections. This ridge is easily visualized on the lateral radiograph of a knee. On the AP radiograph, the line drawn through the center of the radiographic mappings was 3 mm lateral to the perpendicular line drawn through the lateral tubercle of the tibia.
J
J L
FIG. 5. Variability of radiographic guide wire insertions on the AP projection. Arthroscopy, Vol. I0, No. 5, 1994
FIG. 7. AP radiograph of guide pin in place in cadaver tibia.
TIBIAL TUNNEL P L A C E M E N T I N PCL RECONSTRUCTION
549
work, it is important to reconstruct the anterolateral bundle of the PCL to achieve best reconstruction results. To our knowledge, there have been no radiographic landmarks given to verify guide wire placement that corresponds to the appropriate anatomic site of the PCL. This anatomic study of the PCL tibial attachment has shown the ligament attached superior to and onto the consistent posterior tibial ridge. A point on the posterior tibial ridge ~8 mm below the joint line and - 3 mm lateral to the mid-line of the lateral tibial tubercle has been shown to be consistent with reconstruction of the anterolateral bundle of the PCL. We feel that these radiographic landmarks will aid in future PCL reconstructions and can be used to verify tibial tunnel placement. Again, we stress that radiographic verification of tibial tunnel placement should be used as an adjunct to direct visualization of the tibial attachment of the PCL. CONCLUSION A reproducible anatomic and radiographic point coinciding with the posterior tibial ridge on the lateral radiograph and 2-3 mm lateral to the center of the lateral tibial tubercle on the AP radiograph will allow for proper tibial tunnel placement in PCL reconstruction. FIG. 8. Lateral radiograph of guide pin in place in cadaver tibia.
REFERENCES DISCUSSION PCL reconstruction is an accepted form of knee reconstruction in selected patients. Review of the literature and instructional tapes shows that in PCL reconstruction, the tibial tunnel should be placed in its most distal lateral attachment site and verified under radiographic control. We believe that the tibial attachment site of the PCL should be visualized under direct control during the reconstruction of this ligament and that radiographic verification of the PCL tunnel should be used as an adjunct to this direct visualization. Even though femoral attachment sites of the PCL are more important in isometric reconstruction, as evidenced by Grood's
1. Bomberg BC, Acker JH, et al. The effect of posterior cruciate ligament loss and reconstruction of the knee. A m J Knee Surg 1990;3(2):85-96. 2. Clancy WG, Shelbourne KC, Zoellner GB, et al. Treatment of knee joint instability secondary to rupture of the posterior cruciate ligament. J Bone Joint Surg 1983;65A:310-22. 3. Girgis FG, Marshal JL, AI Monajem ARS. The cruciate ligaments of the knee joint, anatomical, functional and experimental analysis. Clin Orthop Rel Res 1975;106:216-31. 4. Grood E., Hefzy M. Lindenfield T. Factors affecting the region of most isometric femoral attachments. Part 1: The posterior cruciate ligament. A m J Sports M e d 1989;17:197207. 5. Vandommelen BA, Fowler PJ. Anatomy of the posterior cruciate ligament. A review. A m J Sports M e d 1989;17:24-9. 6. Guyot J. Atlas of human limb joints, New York; SpringerVerlag, 1981, pp. 46--9. 7. Netter FH. Atlas of human anatomy; New Jersey, CibaGeigy Corporation, 1989, Plate 479.
Arthroscopy, Vol. 10, No. 5, 1994
Published by Raven Press, Ltd, O 1994ArthroscopyAssociationof North America
Posterior Cruciate Ligament Tibial Attachment Anatomy and Radiographic Landmarks for Tibial Tunnel Placement in PCL Reconstruction John A. Racanelli, M.D., and David Drez, Jr., M.D.
Summary: The posterior cruciate ligament (PCL) was dissected in 12 frozen human cadaver knees. The tibial attachment was radiographicaUy mapped and guide wires placed on the distal-lateral bulk of the ligament's tibial attachment. Radiographic landmarks were then described on the anteroposterior and lateral radiographs to assist in tibial tunnel guide wire placement in PCL reconstruction. The radiographic site corresponding to the posterior ridge of the tibiat plateau - t c m below the joint line and a few millimeters lateral to the center of the lateral tibial tubercle will reliably confirm tibial tunnels in PCL reconstruction. Key Words: Posterior cruciate ligament--Tibial tunnel--Radiographic verification,
debrided and a tibial capsular insertion is elevated. Visualization of this PCL insertion is always recommended during PCL reconstruction. The purpose of this current study was to dissect frozen human cadaver knees and place retrograde guide wires through the tibia for the most isometric tibial site. Radiographs were then taken to provide radiographic landmarks to be used in antegrade guide wire placement in PCL reconstruction.
Posterior cruciate ligament (PCL) reconstruction has evolved into a viable form of knee ligament reconstruction in selected patients. Arthroscopically assisted intraarticular reconstruction is one method of performing PCL reconstruction. Numerous studies have focused on the anatomy and surgical reconstruction of the PCL (1-5). It appears that the large anterolateral bundle, which becomes taut in flexion, provides the most stability to the posterior displacement of the tibia on the femur. Therefore, in surgical reconstruction of the PCL, placing the tibial tunnel nearest the lateral insertion of the ligament would most recreate the anterolateral bundle. During PCL reconstruction, a guide wire is placed from anterior to posterior in the tibia under radiographic control. It is important to place the tibial tunnel close to the most isometric distallateral point on the posterior tibia. This portion of the tibia is usually not visible intraarticularly during the procedure unless the ruptured PCL stump is
MATERIALS AND METHODS Twelve frozen human cadaveric knees of unknown age, but with intact anterior cruciate ligaments and PCLs, were dissected from a posterior approach in order to isolate the tibial attachment and the PCL. A 3/32 in guide wire was then drilled retrograde from a point that was the most distal lateral attachment of the bulk of the PCL to a point slightly distal and lateral to the tibial tubercle. This tibial site corresponds to a point 5 mm inferior lateral to the center of the tibial attachment of the PCL as described by Clancy (2). This allows for the most isometric tibial placement with a 10-mm tunnel as described by Grood (4). This tunnel will recreate the anterolateral bundle of the PCL. Once the guide
From the Department of Orthopaedics, Louisiana State University, Lake Charles, Louisiana, U.S.A. Address correspondence and reprint requests to Dr. David Drez, Jr., 2615 Enterprise Boulevard, Lake Charles, LA 70601, U.S.A.
546
TIBIAL TUNNEL PLACEMENT I N PCL RECONSTRUCTION
wires were in place and the tip of the guide wire was flush with the posterior cortical surface of the tibia, radiographs were taken in the anteroposterior (AP) and lateral planes with the knee in full extension. Radiographic landmarks were then described to assist in antegrade placement of the tibial tunnel guide wire. One cadaveric knee had the footprint of the PCL tibial attachment radiographically mapped by placing radiodense tacks around the tibial attachment site of the ligament. AP and lateral radiographs were taken of this knee with the tacks in place. All radiographs were taken from a distance of 40 inches, and measurements were adjusted for magnification.
547
FIG. 2. Radiographic map of bulk of PCL attachment on lateral view.
RESULTS The radiographic footprint of the tibial attachment of the PCL is depicted in Figs. 1 and 2. The shaded areas represent the attachment of the tibial portion of the PCL. The most distal attachment of the PCL coincides with a rough ridge found in all of the cadaveric dissections. This ridge is rarely depicted in PCL dissections or drawings (6,7). The ridge proceeds from distal medial to proximal lateral (Fig. 3). This ridge coincides with the superior border of the popliteus muscle and tendon (6). The size of the ridge is variable in all specimens, but its location is consistent, coinciding with the most distal attachment of the PCL. The guide wire placement in all specimens was started at the area of the distal lateral attachment of the PCL on the posterior tibial ridge (Fig. 4). It was aimed free hand fashion anterolaterally at an angle of 45 ° off the tibial plateau to allow for soft tissue coverage of screw heads
used in graph fixation. All guide wires exited lateral to the distal end of the tibial tubercle. The radiographic maps of all 12 guide wire placements in the AP and lateral planes are depicted in Figs. 5 and 6. A representative radiograph of one of the cadaver specimens is present in Figs. 7 and 8. The AP film had perpendicular lines drawn across the tibial plateau and through the center of the lateral tibial tubercle of the tibial eminence. The lateral radiograph had a line drawn parallel to the tibial plateau. The centermost point of the guide wire was used as a reference point in mapping the 12 cadaveric knees. Once all the guide wire points were mapped, a circle of the smallest possible diameter was drawn around them. A parallel line referenced
FIG. 1. Radiographic map of bulk of PCL attachment on AP view.
FIG. 3. Posterior tibial ridge of distal attachment of PCL. Arthroscopy, Vol, 10, No, 5, 1994
548
J. A RACANELL1 A N D D. DREZ, JR.
FIG. 6. Variability of radiographic guide wire insertions on the lateral projection.
FIG. 4. Starting site for retrograde guide wires at distal lateral attachment of PCL.
from a line drawn across the tibial plateau was drawn through the center of the circle on the lateral radiograph. From an AP radiographic map, a parallel line from one drawn through the center of the lateral tibial tubercle was also made through the center of the map circle. There were no radiographic variations of >2.5 mm from the center of the circle. The center of the circle on the AP radiograph was 8 mm below a line drawn parallel across
the tibial plateau. This corresponds to the posterior tibial ridge visualized in the cadaveric dissections. This ridge is easily visualized on the lateral radiograph of a knee. On the AP radiograph, the line drawn through the center of the radiographic mappings was 3 mm lateral to the perpendicular line drawn through the lateral tubercle of the tibia.
J
J L
FIG. 5. Variability of radiographic guide wire insertions on the AP projection. Arthroscopy, Vol. I0, No. 5, 1994
FIG. 7. AP radiograph of guide pin in place in cadaver tibia.
TIBIAL TUNNEL P L A C E M E N T I N PCL RECONSTRUCTION
549
work, it is important to reconstruct the anterolateral bundle of the PCL to achieve best reconstruction results. To our knowledge, there have been no radiographic landmarks given to verify guide wire placement that corresponds to the appropriate anatomic site of the PCL. This anatomic study of the PCL tibial attachment has shown the ligament attached superior to and onto the consistent posterior tibial ridge. A point on the posterior tibial ridge ~8 mm below the joint line and - 3 mm lateral to the mid-line of the lateral tibial tubercle has been shown to be consistent with reconstruction of the anterolateral bundle of the PCL. We feel that these radiographic landmarks will aid in future PCL reconstructions and can be used to verify tibial tunnel placement. Again, we stress that radiographic verification of tibial tunnel placement should be used as an adjunct to direct visualization of the tibial attachment of the PCL. CONCLUSION A reproducible anatomic and radiographic point coinciding with the posterior tibial ridge on the lateral radiograph and 2-3 mm lateral to the center of the lateral tibial tubercle on the AP radiograph will allow for proper tibial tunnel placement in PCL reconstruction. FIG. 8. Lateral radiograph of guide pin in place in cadaver tibia.
REFERENCES DISCUSSION PCL reconstruction is an accepted form of knee reconstruction in selected patients. Review of the literature and instructional tapes shows that in PCL reconstruction, the tibial tunnel should be placed in its most distal lateral attachment site and verified under radiographic control. We believe that the tibial attachment site of the PCL should be visualized under direct control during the reconstruction of this ligament and that radiographic verification of the PCL tunnel should be used as an adjunct to this direct visualization. Even though femoral attachment sites of the PCL are more important in isometric reconstruction, as evidenced by Grood's
1. Bomberg BC, Acker JH, et al. The effect of posterior cruciate ligament loss and reconstruction of the knee. A m J Knee Surg 1990;3(2):85-96. 2. Clancy WG, Shelbourne KC, Zoellner GB, et al. Treatment of knee joint instability secondary to rupture of the posterior cruciate ligament. J Bone Joint Surg 1983;65A:310-22. 3. Girgis FG, Marshal JL, AI Monajem ARS. The cruciate ligaments of the knee joint, anatomical, functional and experimental analysis. Clin Orthop Rel Res 1975;106:216-31. 4. Grood E., Hefzy M. Lindenfield T. Factors affecting the region of most isometric femoral attachments. Part 1: The posterior cruciate ligament. A m J Sports M e d 1989;17:197207. 5. Vandommelen BA, Fowler PJ. Anatomy of the posterior cruciate ligament. A review. A m J Sports M e d 1989;17:24-9. 6. Guyot J. Atlas of human limb joints, New York; SpringerVerlag, 1981, pp. 46--9. 7. Netter FH. Atlas of human anatomy; New Jersey, CibaGeigy Corporation, 1989, Plate 479.
Arthroscopy, Vol. 10, No. 5, 1994