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Anatomic tibial graft fixation using a retrograde bio-interference screw for endoscopic anterior cruciate ligament reconstruction
Technical Note
Anatomic Tibial Graft Fixation Using a Retrograde Bio-interference Screw for Endoscopic Anterior Cruciate Ligament Reconstruction Craig D. Morgan, M.D., Drew A. Stein, M.D., Elliot H. Leitman, M.D., and Victor R. Kalman, D.O.
Abstract: The article describes a simple technique for anatomic anterior cruciate ligament (ACL) tibial graft fixation at the level of the intercondylar floor within a standard endoscopic tibial tunnel. Fixation is achieved with a retrograde positioned cannulated bio-interference screw delivered over a No. 5 permanent suture from a standard anteromedial portal. The screw is inserted into the tibial tunnel in an inside-out position, so that the head of the screw is flush with the intra-articular orifice of the tibial tunnel. Recent experimental, animal, and clinical studies have reported that the advantages of this type of anatomic graft fixation over nonanatomic tibial graft fixation include increased fixation strength, a more stable reconstruction through full knee range of motion, absence of postoperative tunnel expansion, and final biologic graft incorporation at or near the native ACL tibial insertion. Key Words: Anterior cruciate ligament reconstruction—Anatomic fixation—Retrograde screw.
T
he concept of anatomic graft fixation for anterior cruciate ligament (ACL) reconstruction is not new.1-6 In the past, positioning the anatomic graft within bone tunnels that avoid intercondylar roof and wall impingement was believed to be the major factor in achieving an optimum ACL reconstruction.7,8 Studies have documented anatomic landmarks to use for placing endoscopic tunnels that avoid graft impingement through full knee range of motion.9 However, several experimental and clinical studies have shown that both graft position and graft fixation at or near the origin and insertion of the native ACL will (1) minimize graft length change,1 (2) minimize graft tension,1 (3) avoid anterior
From the Morgan Kalman Clinic, Wilmington, Delaware, U.S.A. Address correspondence and reprint requests to Craig D. Morgan, M.D., 2501 Silverside Rd, Wilmington, DE 19810, U.S.A. E-mail: [email protected] © 2002 by the Arthroscopy Association of North America 1526-3231/02/1807-3429$35.00/0 doi:10.1053/jars.2002.35144
to posterior sagittal windshield-wiper type graft motion,4 and (4) produce a more stable reconstruction through full knee range of motion.1,3,4,6,10 In addition, follow-up studies of anatomic versus nonanatomic fixation for ACL reconstruction have shown absence of tunnel expansion up to 5 years with an anatomically fixed graft at the intra-articular tibial tunnel orifice.10-13 The all-inside technique for ACL reconstruction first described by Morgan et al.1 addressed these anatomic fixation issues. However, the procedure was technically demanding, which limited its popularity2,3,5,10 (Fig 1). The purpose of this technical note is to describe a simple technique for achieving apical anatomic tibial tunnel graft fixation for ACL reconstruction. This technique uses a retrograde-positioned bioabsorbable interference screw in an endoscopic approach. OPERATIVE TECHNIQUE After the soft-tissue graft to be used for ACL reconstruction is prepared and sized, a tibial tunnel and
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 18, No 7 (September), 2002: E38
1
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C. D. MORGAN ET AL.
FIGURE 1. (A) An all-inside ACL reconstruction with a quadriceps tendon autograft fixed anatomically at the intra-articular tibial and femoral socket orifices. Retrograde and antegrade headed titanium interference screws (Arthrex, Naples, FL) were used in the tibial and femoral sockets, respectively. (B) A lateral radiograph of the same case illustrating anatomic interference screw positioning. (C) A 2.5-year follow-up magnetic resonance image of an all-inside quadriceps tendon autograft ACL reconstruction using bioabsorbable interference screws. Graft and screw resorption up to the intercondylar floor where biologic graft incorporation appears similar to a native ACL without tunnel widening. (D) Radiograph 6 years after a quadriceps tendon autograft ACL reconstruction illustrates the absence of tunnel expansion on either the femoral or tibial side of the joint.
femoral socket with similar diameters to the graft are created. This is done using an endoscopic technique and based on landmarks previously reported.9 Graft choices include quadrupled hamstring autograft, quadriceps tendon autograft, Achilles allograft, hamstring allograft, and tibialis tendon allograft.
Once the appropriate anatomic bone tunnels have been established, a No. 5 Ethibond suture (Ethicon, Sommerville, NJ) with a large (3-mm) interference knot is threaded antegrade through the lumen of a cannulated 9 ⫻ 23 mm bioabsorbable biotenodesis screw (Arthrex, Naples, FL) (Fig 2). The interference
RETROGRADE BIO-INTERFERENCE SCREW FOR ACL RECONSTRUCTION
FIGURE 2. A 9 ⫻ 23 mm cannulated biotenodesis screw with a No. 5 Ethibond suture threaded through its lumen and a 3-mm diameter interference knot tied on the screw head side of the suture. (B) The screw-screw driver-suture construct: a cannulated Retroscrewdriver interfaces over the suture and into the biotenodesis screw from the tip of the screw toward the head of the screw. Interference of the taut proximal suture knot with the screw head keeps the screw engaged on the driver.
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FIGURE 4. (A) An outside view of a right knee with the No. 5 suture entering the knee from the medial portal and exiting the knee through the tibial tunnel. The biotenodesis screw and interference knot are outside the medial portal. (B) An intra-articular view of a right knee at the stage illustrated in panel A, with the graft passage sutures already placed from the tibial tunnel into the femoral socket and out the distal lateral thigh with a suture-passing pin.
FIGURE 3. (A) An outside view of the suture hand-off: the nonscrew end of the suture is delivered into the intercondylar notch with a grasping tool from the medial portal. The suture is then handed off to a second grasping tool brought up the tibial tunnel. (B) An intra-articular view of the suture hand-off in a right knee.
4
C. D. MORGAN ET AL. 4). At this point, tension is maintained on both the free end and the screw end of the suture to keep it positioned against the anterior wall of the tibial tunnel for its entire length. While the suture is kept as described, the graft is brought through the tibial tunnel and into the femoral socket using a standard endoscopic technique (Fig 5). Next, the femoral limb of the graft is fixed in the femoral socket with a bioabsorbable interference screw placed anterior to the graft. This screw is placed from the medial portal with the knee flexed to 120° (Fig 6). The head of the femoral screw should be flush with the intra-articular orifice of the femoral socket to produce anatomic fixation. Following femoral fixation, the graft is placed on tension and the knee is repeatedly cycled through full range of motion to confirm that no intercondylar roof or wall impingement occurs. Next, while graft tension is maintained, the biotenodesis screw is inserted in the knee through the medial portal (point end first) by placing tension on the free end of the suture exiting the tibial tunnel. This maneuver causes the screw tip to stay over the suture at the anterior margin of the tibial orifice in front of the graft (Fig 7). If the medial portal was not adequately cleared, the screw will occasionally “hang-up”
FIGURE 5. (A) An outside view of a right knee illustrates tension on the suture from both the medial portal and the tibial tunnel to keep the suture anterior in the tibial tunnel during graft passage. A suture-passing pin is used with standard endoscopic technique. (B) Intra-articular graft placement in a right knee.
knot consists of multiple knots tied to themselves on its distal end. Next, the medial portal is enlarged to 1 cm including the dermis, subcutaneous tissue, and capsule, which are visualized arthroscopically. Following medial portal enlargement, the free end of the No. 5 Ethibond suture (with the screw on the other end) is delivered into the intercondylar notch through the medial portal with a grasping tool. It is picked up with a second grasping tool brought up the tibial tunnel (Fig 3). The free end of the suture is brought down the tibial tunnel so that the suture exits the tibial tunnel anteriorly. The other end of the suture, with the screw attached, remains outside the medial portal (Fig
FIGURE 6. The femoral limb of the graft is fixed with a 9 ⫻ 23 mm Arthrex Biointerference Screw delivered from the medial portal and positioned anterior to the graft in the femoral socket. This is done with the knee flexed 120°. The screw is positioned so that the screw head is flush with the socket orifice, resulting in anatomic femoral fixation.
RETROGRADE BIO-INTERFERENCE SCREW FOR ACL RECONSTRUCTION
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FIGURE 7. (A) Screw delivery into the intercondylar notch from the medial portal. The surgeon applies tension to the tibial limb of the suture so that the screw enters the knee tip end first from the medial portal (shown in a right knee). (B) By increasing the tension on the suture distally, the surgeon flips the screw parallel to the graft over the suture. The screw tip then engages the graft at the interface of the anterior graft and the tibial tunnel orifice. It is directed by retrograde pressure from the proximal interference knot against the head of the screw.
in the portal. If this occurs, the screw can easily be pushed into the joint using a grasper attached to the head of the screw (Fig 8). Once the screw is positioned in the intercondylar notch, the free end of the suture that exits the tibial tunnel is threaded through a special cannulated hex-tipped Retro-screwdriver specifically designed for this purpose (Arthrex, Naples, FL) (Fig
9). The Retro-screwdriver is then delivered up the tibial tunnel anterior to the graft over the suture and into the biotenodesis screw under arthroscopic control (Fig 10). Final tibial graft fixation is then achieved by screwing the tenodesis screw counter-clockwise until the screw head is flush with the intercondylar floor (Fig 11). If additional tibial fixation is desired, a
FIGURE 8. Inadequate soft-tissue clearance for screw delivery through the medial portal may be overcome by “pushing” the screw through the portal with a grasping tool or large pituitary rongeur, as seen in this right knee.
FIGURE 9. The suture end exiting the tibial tunnel is threaded in a retrograde fashion from the tip toward the handle of a cannulated Retro-screwdriver specifically designed for this procedure.
FIGURE 10. (A) The Retro-screwdriver is threaded over the taut No. 5 suture up the tibial tunnel adjacent and anterior to the graft. It is then placed into the cannulated screw against interference resistance of the interference knot against the head of the screw. (B) An intra-articular view of the hexagonal tip of the Retro-screwdriver engaged within the hexagonal lumen of the cannulated biotenodesis screw.
FIGURE 11. (A) The screw is advanced from proximal to distal into the tibial tunnel by a counter-clockwise or reverse rotation of the Retro-screwdriver. Meanwhile, distal tension is applied on the suture, the screwdriver, and the graft, as is seen with this screw inserted approximately 75% in a retrograde fashion in a right knee. (B) Final retroscrew positioning for anatomic tibial graft fixation. The head of the screw is flush with the intercondylar floor anterior to the graft within the tibial tunnel (seen in a right knee). (C) A sagittal magnetic resonance image 1 week after ACL reconstruction illustrates retrograde screw positioning for anatomic tibial graft fixation.
RETROGRADE BIO-INTERFERENCE SCREW FOR ACL RECONSTRUCTION
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FIGURE 12. An early postoperative sagittal magnetic resonance image of a knee after ACL reconstruction. The image illustrates an anatomic tibial graft fixation with a 2-screw interlocking approach. Initial fixation is with a retoscrew as shown in Fig 11, which is then supplemented by a second interference screw placed antegrade posterior to the graft.
second interference screw may be placed from outside-in, in an antegrade fashion, posterior to the graft. This results in an interlocking screw-graft fixation construct (Fig 12).
structions without technical difficulty or short-term complications.
REFERENCES DISCUSSION This technical note describes a simple modification of an existing endoscopic technique for ACL reconstruction using any soft-tissue graft. The procedure provides anatomic tibial graft fixation at the level of the intercondylar floor. The advantages of anatomic graft fixation include improved stability, absence of tunnel expansion, decreased graft strain through full range of motion, and ultimate long-term biologic graft incorporation at the intra-articular tibial tunnel orifice similar to the native ACL. From a technical standpoint, final fixation with a retrograde screw tends to increase graft tension as the screw is advanced. Conversely, antegrade screw fixation tends to decrease graft tension with screw advancement, which is undesirable. Unpublished experimental data in matched cadaveric tibias (D.N.M. Caborn, personal communication, July 2001) revealed pullout to failure of 460 N for a single retroscrew and 662 N for the interlocking dual screw method with insertion torque values greater than 25 foot-pounds. Insertion torque values of 15 foot-pounds or greater have been shown by Brand et al.14 to clinically and experimentally correlate with pullout to failure strengths of greater than 400 N. This prevents clinical failure of fixation even with an aggressive postoperative rehabilitation protocol. We have used this technique in 35 successive ACL recon-
1. Morgan CD, Kalman VH, Grawl D. Isometry testing for anterior cruciate ligament reconstruction revisited. Arthroscopy 1995;11:647-659. 2. Palmeri M, Morgan CD. The all-inside anterior cruciate ligament reconstruction: A double socket approach. Operative Tech Orthop 1996;6:161-176. 3. Leitman EH, Morgan CD, Grawl DM. Quadriceps tendon anterior cruciate ligament reconstruction using the all-inside technique. Operative Tech Sports Med 1999;7:179-188. 4. Ishibashi Y, Rudy T, Livesay G, et al. The effect of anterior cruciate ligament graft fixation site at the tibia on knee stability: Evaluation using a robotic testing system. Arthroscopy 1997;13:177-182. 5. Stahelin A, Weiler A. All-inside anterior cruciate ligament reconstruction using semitendinosis tendon and soft threaded biodegradable interference screw fixation. Arthroscopy 1997; 13:773-779. 6. Barber FA. Flipped patellar tendon autograft anterior cruciate ligament reconstruction. Arthroscopy 2000;16:483-490. 7. Howell SM, Clark JA, Farley TE. A rationale for predicting anterior cruciate graft impingement by the intercondylar roof. A magnetic resonance imaging study. Am J Sports Med 1991; 19:276-281. 8. Howell SM, Clark JA. Tibial tunnel placement in ACL reconstructions and graft impingement. Clin Orthop 1992;283:187195. 9. Morgan CD, Kalman VR, Grawl DM. Definitive landmarks for reproducible tibial tunnel placement in anterior cruciate ligament reconstruction. Arthroscopy 1995;11:275-288. 10. Morgan CD. Quadriceps tendon autograft for ACL reconstruction. In: Jackson, D, ed. Master techniques in orthopaedic surgery ed 2. New York: Lippincott, 2002 (in press). 11. L’Insalata JC, Klatt B, Fu FH, Harner CD. Tunnel expansion following anterior cruciate ligament reconstruction: A comparison of hamstring and patellar tendon autografts. Knee Surg Sports Traumatol Arthrosc 1997;5:234-238.
8
C. D. MORGAN ET AL.
12. Weiler A, Peine R, Pashmineh-Azar A, et al. Tendon healing in a bone tunnel. Part I: Biomechanical results after biodegradable interference fit fixation in a model of anterior cruciate ligament reconstruction in sheep. Arthroscopy 2002; 18:113-123. 13. Weiler A, Hoffman RFG, Bail HJ, et al. Tendon healing in a bone tunnel. Part II: Histologic analyis after biodegrad-
able interference fit fixation in a model of anterior cruciate ligament reconstruction in sheep. Arthroscopy 2002;18:124135. 14. Brand JC Jr, Pienkowski D, Steenlage E, et al. Interference screw fixation: Strength of a quadrupled hamstring tendon graft is directly related to bone mineral density and insertion torque. Am J Sports Med 2000;28:705-710.
Anatomic Tibial Graft Fixation Using a Retrograde Bio-interference Screw for Endoscopic Anterior Cruciate Ligament Reconstruction Craig D. Morgan, M.D., Drew A. Stein, M.D., Elliot H. Leitman, M.D., and Victor R. Kalman, D.O.
Abstract: The article describes a simple technique for anatomic anterior cruciate ligament (ACL) tibial graft fixation at the level of the intercondylar floor within a standard endoscopic tibial tunnel. Fixation is achieved with a retrograde positioned cannulated bio-interference screw delivered over a No. 5 permanent suture from a standard anteromedial portal. The screw is inserted into the tibial tunnel in an inside-out position, so that the head of the screw is flush with the intra-articular orifice of the tibial tunnel. Recent experimental, animal, and clinical studies have reported that the advantages of this type of anatomic graft fixation over nonanatomic tibial graft fixation include increased fixation strength, a more stable reconstruction through full knee range of motion, absence of postoperative tunnel expansion, and final biologic graft incorporation at or near the native ACL tibial insertion. Key Words: Anterior cruciate ligament reconstruction—Anatomic fixation—Retrograde screw.
T
he concept of anatomic graft fixation for anterior cruciate ligament (ACL) reconstruction is not new.1-6 In the past, positioning the anatomic graft within bone tunnels that avoid intercondylar roof and wall impingement was believed to be the major factor in achieving an optimum ACL reconstruction.7,8 Studies have documented anatomic landmarks to use for placing endoscopic tunnels that avoid graft impingement through full knee range of motion.9 However, several experimental and clinical studies have shown that both graft position and graft fixation at or near the origin and insertion of the native ACL will (1) minimize graft length change,1 (2) minimize graft tension,1 (3) avoid anterior
From the Morgan Kalman Clinic, Wilmington, Delaware, U.S.A. Address correspondence and reprint requests to Craig D. Morgan, M.D., 2501 Silverside Rd, Wilmington, DE 19810, U.S.A. E-mail: [email protected] © 2002 by the Arthroscopy Association of North America 1526-3231/02/1807-3429$35.00/0 doi:10.1053/jars.2002.35144
to posterior sagittal windshield-wiper type graft motion,4 and (4) produce a more stable reconstruction through full knee range of motion.1,3,4,6,10 In addition, follow-up studies of anatomic versus nonanatomic fixation for ACL reconstruction have shown absence of tunnel expansion up to 5 years with an anatomically fixed graft at the intra-articular tibial tunnel orifice.10-13 The all-inside technique for ACL reconstruction first described by Morgan et al.1 addressed these anatomic fixation issues. However, the procedure was technically demanding, which limited its popularity2,3,5,10 (Fig 1). The purpose of this technical note is to describe a simple technique for achieving apical anatomic tibial tunnel graft fixation for ACL reconstruction. This technique uses a retrograde-positioned bioabsorbable interference screw in an endoscopic approach. OPERATIVE TECHNIQUE After the soft-tissue graft to be used for ACL reconstruction is prepared and sized, a tibial tunnel and
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 18, No 7 (September), 2002: E38
1
2
C. D. MORGAN ET AL.
FIGURE 1. (A) An all-inside ACL reconstruction with a quadriceps tendon autograft fixed anatomically at the intra-articular tibial and femoral socket orifices. Retrograde and antegrade headed titanium interference screws (Arthrex, Naples, FL) were used in the tibial and femoral sockets, respectively. (B) A lateral radiograph of the same case illustrating anatomic interference screw positioning. (C) A 2.5-year follow-up magnetic resonance image of an all-inside quadriceps tendon autograft ACL reconstruction using bioabsorbable interference screws. Graft and screw resorption up to the intercondylar floor where biologic graft incorporation appears similar to a native ACL without tunnel widening. (D) Radiograph 6 years after a quadriceps tendon autograft ACL reconstruction illustrates the absence of tunnel expansion on either the femoral or tibial side of the joint.
femoral socket with similar diameters to the graft are created. This is done using an endoscopic technique and based on landmarks previously reported.9 Graft choices include quadrupled hamstring autograft, quadriceps tendon autograft, Achilles allograft, hamstring allograft, and tibialis tendon allograft.
Once the appropriate anatomic bone tunnels have been established, a No. 5 Ethibond suture (Ethicon, Sommerville, NJ) with a large (3-mm) interference knot is threaded antegrade through the lumen of a cannulated 9 ⫻ 23 mm bioabsorbable biotenodesis screw (Arthrex, Naples, FL) (Fig 2). The interference
RETROGRADE BIO-INTERFERENCE SCREW FOR ACL RECONSTRUCTION
FIGURE 2. A 9 ⫻ 23 mm cannulated biotenodesis screw with a No. 5 Ethibond suture threaded through its lumen and a 3-mm diameter interference knot tied on the screw head side of the suture. (B) The screw-screw driver-suture construct: a cannulated Retroscrewdriver interfaces over the suture and into the biotenodesis screw from the tip of the screw toward the head of the screw. Interference of the taut proximal suture knot with the screw head keeps the screw engaged on the driver.
3
FIGURE 4. (A) An outside view of a right knee with the No. 5 suture entering the knee from the medial portal and exiting the knee through the tibial tunnel. The biotenodesis screw and interference knot are outside the medial portal. (B) An intra-articular view of a right knee at the stage illustrated in panel A, with the graft passage sutures already placed from the tibial tunnel into the femoral socket and out the distal lateral thigh with a suture-passing pin.
FIGURE 3. (A) An outside view of the suture hand-off: the nonscrew end of the suture is delivered into the intercondylar notch with a grasping tool from the medial portal. The suture is then handed off to a second grasping tool brought up the tibial tunnel. (B) An intra-articular view of the suture hand-off in a right knee.
4
C. D. MORGAN ET AL. 4). At this point, tension is maintained on both the free end and the screw end of the suture to keep it positioned against the anterior wall of the tibial tunnel for its entire length. While the suture is kept as described, the graft is brought through the tibial tunnel and into the femoral socket using a standard endoscopic technique (Fig 5). Next, the femoral limb of the graft is fixed in the femoral socket with a bioabsorbable interference screw placed anterior to the graft. This screw is placed from the medial portal with the knee flexed to 120° (Fig 6). The head of the femoral screw should be flush with the intra-articular orifice of the femoral socket to produce anatomic fixation. Following femoral fixation, the graft is placed on tension and the knee is repeatedly cycled through full range of motion to confirm that no intercondylar roof or wall impingement occurs. Next, while graft tension is maintained, the biotenodesis screw is inserted in the knee through the medial portal (point end first) by placing tension on the free end of the suture exiting the tibial tunnel. This maneuver causes the screw tip to stay over the suture at the anterior margin of the tibial orifice in front of the graft (Fig 7). If the medial portal was not adequately cleared, the screw will occasionally “hang-up”
FIGURE 5. (A) An outside view of a right knee illustrates tension on the suture from both the medial portal and the tibial tunnel to keep the suture anterior in the tibial tunnel during graft passage. A suture-passing pin is used with standard endoscopic technique. (B) Intra-articular graft placement in a right knee.
knot consists of multiple knots tied to themselves on its distal end. Next, the medial portal is enlarged to 1 cm including the dermis, subcutaneous tissue, and capsule, which are visualized arthroscopically. Following medial portal enlargement, the free end of the No. 5 Ethibond suture (with the screw on the other end) is delivered into the intercondylar notch through the medial portal with a grasping tool. It is picked up with a second grasping tool brought up the tibial tunnel (Fig 3). The free end of the suture is brought down the tibial tunnel so that the suture exits the tibial tunnel anteriorly. The other end of the suture, with the screw attached, remains outside the medial portal (Fig
FIGURE 6. The femoral limb of the graft is fixed with a 9 ⫻ 23 mm Arthrex Biointerference Screw delivered from the medial portal and positioned anterior to the graft in the femoral socket. This is done with the knee flexed 120°. The screw is positioned so that the screw head is flush with the socket orifice, resulting in anatomic femoral fixation.
RETROGRADE BIO-INTERFERENCE SCREW FOR ACL RECONSTRUCTION
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FIGURE 7. (A) Screw delivery into the intercondylar notch from the medial portal. The surgeon applies tension to the tibial limb of the suture so that the screw enters the knee tip end first from the medial portal (shown in a right knee). (B) By increasing the tension on the suture distally, the surgeon flips the screw parallel to the graft over the suture. The screw tip then engages the graft at the interface of the anterior graft and the tibial tunnel orifice. It is directed by retrograde pressure from the proximal interference knot against the head of the screw.
in the portal. If this occurs, the screw can easily be pushed into the joint using a grasper attached to the head of the screw (Fig 8). Once the screw is positioned in the intercondylar notch, the free end of the suture that exits the tibial tunnel is threaded through a special cannulated hex-tipped Retro-screwdriver specifically designed for this purpose (Arthrex, Naples, FL) (Fig
9). The Retro-screwdriver is then delivered up the tibial tunnel anterior to the graft over the suture and into the biotenodesis screw under arthroscopic control (Fig 10). Final tibial graft fixation is then achieved by screwing the tenodesis screw counter-clockwise until the screw head is flush with the intercondylar floor (Fig 11). If additional tibial fixation is desired, a
FIGURE 8. Inadequate soft-tissue clearance for screw delivery through the medial portal may be overcome by “pushing” the screw through the portal with a grasping tool or large pituitary rongeur, as seen in this right knee.
FIGURE 9. The suture end exiting the tibial tunnel is threaded in a retrograde fashion from the tip toward the handle of a cannulated Retro-screwdriver specifically designed for this procedure.
FIGURE 10. (A) The Retro-screwdriver is threaded over the taut No. 5 suture up the tibial tunnel adjacent and anterior to the graft. It is then placed into the cannulated screw against interference resistance of the interference knot against the head of the screw. (B) An intra-articular view of the hexagonal tip of the Retro-screwdriver engaged within the hexagonal lumen of the cannulated biotenodesis screw.
FIGURE 11. (A) The screw is advanced from proximal to distal into the tibial tunnel by a counter-clockwise or reverse rotation of the Retro-screwdriver. Meanwhile, distal tension is applied on the suture, the screwdriver, and the graft, as is seen with this screw inserted approximately 75% in a retrograde fashion in a right knee. (B) Final retroscrew positioning for anatomic tibial graft fixation. The head of the screw is flush with the intercondylar floor anterior to the graft within the tibial tunnel (seen in a right knee). (C) A sagittal magnetic resonance image 1 week after ACL reconstruction illustrates retrograde screw positioning for anatomic tibial graft fixation.
RETROGRADE BIO-INTERFERENCE SCREW FOR ACL RECONSTRUCTION
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FIGURE 12. An early postoperative sagittal magnetic resonance image of a knee after ACL reconstruction. The image illustrates an anatomic tibial graft fixation with a 2-screw interlocking approach. Initial fixation is with a retoscrew as shown in Fig 11, which is then supplemented by a second interference screw placed antegrade posterior to the graft.
second interference screw may be placed from outside-in, in an antegrade fashion, posterior to the graft. This results in an interlocking screw-graft fixation construct (Fig 12).
structions without technical difficulty or short-term complications.
REFERENCES DISCUSSION This technical note describes a simple modification of an existing endoscopic technique for ACL reconstruction using any soft-tissue graft. The procedure provides anatomic tibial graft fixation at the level of the intercondylar floor. The advantages of anatomic graft fixation include improved stability, absence of tunnel expansion, decreased graft strain through full range of motion, and ultimate long-term biologic graft incorporation at the intra-articular tibial tunnel orifice similar to the native ACL. From a technical standpoint, final fixation with a retrograde screw tends to increase graft tension as the screw is advanced. Conversely, antegrade screw fixation tends to decrease graft tension with screw advancement, which is undesirable. Unpublished experimental data in matched cadaveric tibias (D.N.M. Caborn, personal communication, July 2001) revealed pullout to failure of 460 N for a single retroscrew and 662 N for the interlocking dual screw method with insertion torque values greater than 25 foot-pounds. Insertion torque values of 15 foot-pounds or greater have been shown by Brand et al.14 to clinically and experimentally correlate with pullout to failure strengths of greater than 400 N. This prevents clinical failure of fixation even with an aggressive postoperative rehabilitation protocol. We have used this technique in 35 successive ACL recon-
1. Morgan CD, Kalman VH, Grawl D. Isometry testing for anterior cruciate ligament reconstruction revisited. Arthroscopy 1995;11:647-659. 2. Palmeri M, Morgan CD. The all-inside anterior cruciate ligament reconstruction: A double socket approach. Operative Tech Orthop 1996;6:161-176. 3. Leitman EH, Morgan CD, Grawl DM. Quadriceps tendon anterior cruciate ligament reconstruction using the all-inside technique. Operative Tech Sports Med 1999;7:179-188. 4. Ishibashi Y, Rudy T, Livesay G, et al. The effect of anterior cruciate ligament graft fixation site at the tibia on knee stability: Evaluation using a robotic testing system. Arthroscopy 1997;13:177-182. 5. Stahelin A, Weiler A. All-inside anterior cruciate ligament reconstruction using semitendinosis tendon and soft threaded biodegradable interference screw fixation. Arthroscopy 1997; 13:773-779. 6. Barber FA. Flipped patellar tendon autograft anterior cruciate ligament reconstruction. Arthroscopy 2000;16:483-490. 7. Howell SM, Clark JA, Farley TE. A rationale for predicting anterior cruciate graft impingement by the intercondylar roof. A magnetic resonance imaging study. Am J Sports Med 1991; 19:276-281. 8. Howell SM, Clark JA. Tibial tunnel placement in ACL reconstructions and graft impingement. Clin Orthop 1992;283:187195. 9. Morgan CD, Kalman VR, Grawl DM. Definitive landmarks for reproducible tibial tunnel placement in anterior cruciate ligament reconstruction. Arthroscopy 1995;11:275-288. 10. Morgan CD. Quadriceps tendon autograft for ACL reconstruction. In: Jackson, D, ed. Master techniques in orthopaedic surgery ed 2. New York: Lippincott, 2002 (in press). 11. L’Insalata JC, Klatt B, Fu FH, Harner CD. Tunnel expansion following anterior cruciate ligament reconstruction: A comparison of hamstring and patellar tendon autografts. Knee Surg Sports Traumatol Arthrosc 1997;5:234-238.
8
C. D. MORGAN ET AL.
12. Weiler A, Peine R, Pashmineh-Azar A, et al. Tendon healing in a bone tunnel. Part I: Biomechanical results after biodegradable interference fit fixation in a model of anterior cruciate ligament reconstruction in sheep. Arthroscopy 2002; 18:113-123. 13. Weiler A, Hoffman RFG, Bail HJ, et al. Tendon healing in a bone tunnel. Part II: Histologic analyis after biodegrad-
able interference fit fixation in a model of anterior cruciate ligament reconstruction in sheep. Arthroscopy 2002;18:124135. 14. Brand JC Jr, Pienkowski D, Steenlage E, et al. Interference screw fixation: Strength of a quadrupled hamstring tendon graft is directly related to bone mineral density and insertion torque. Am J Sports Med 2000;28:705-710.