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Femoral Tunnel Position in Anterior Cruciate Ligament Reconstruction Using Three Techniques. A Cadaver Study
Femoral Tunnel Position in Anterior Cruciate Ligament Reconstruction Using Three Techniques. A Cadaver Study Francesco Giron, M.D., Roberto Buzzi, M.D., and Paolo Aglietti, M.D.
Summary: The possibility of achieving correct deep femoral tunnel positioning during anterior cruciate ligament (ACL) reconstruction with the double incision technique (DI), the transtibial technique (TT), and the anteromedial technique (AM) was evaluated in 30 cadaver knees. A reference hole was made just deep to the insertion of the anteromedial bundle of the ACL through an anteromedial arthrotomy. In the DI technique, a Kirshner wire was inserted outside-in using a rear entry C guide. In the TT and AM techniques, the K-wire was inserted inside-out through the tibial tunnel and through the arthrotomy, respectively. The reference hole could be achieved with each technique. Using lateral radiographs, the superficial aspect of the intra-articular exit of the femoral tunnel was found to be located on average at 36%, 36%, and 34% of the width of the condyles from the posterior margin (NS). None of the holes was more anterior than 40%. In conclusion, a deep femoral tunnel positioning could be achieved with each technique. The choice of technique must be based on the surgeon’s preference and clinical results. Key Words: Anterior cruciate ligament—Reconstruction— Femoral tunnel—Cadaver study.
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correct femoral tunnel position during intraarticular anterior cruciate ligament (ACL) reconstruction is critical to achieve a successful result. Displacements along the line of the roof of the notch, described as superficial and deep,1 are particularly significant. In a minimum 5-year follow-up of 89 arthroscopic-assisted ACL reconstructions, we have found that 88% of knees with a correct deep placement of the femoral tunnel showed satisfactory stability. A superficial placement of the femoral tunnel was associated with graft failure in 62.5% of the cases.2 Present surgical techniques are insufficient to duplicate the complex geometry or fiber-tensioning patterns of the ACL. The surgeon’s purpose is limited to duplicate the global function of the deficient ligament.3,4 The ACL is not isometric and only few fibers From the First Orthopaedic Clinic of the University of Florence, Florence, Italy. Address correspondence and reprint requests to Paolo Aglietti, M.D., Prima Clinica Orthopedica, Universita` di Firenze, Largo P. Palagi 1, 50139 Firenze, Italy. r 1999 by the Arthroscopy Association of North America 0749-8063/99/1507-1949$3.00/0
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are nearly isometric over the range of motion. However, a nearly isometric behavior of the ACL substitute is desirable, with a 2 to 3 mm lengthening of the graft toward extension.1,3-7 Length changes in the distance between the insertion points are widely influenced by the femoral tunnel positioning. Most investigators have found that tunnel positioning close to the insertion of anteromedial fibers would be desirable.1,3,5,6,8-14 After the introduction of arthroscopic-assisted ACL reconstructions, three major surgical techniques have been developed to produce the femoral tunnel: the double-incision technique (DI),15-17 the single-incision transtibial technique (TT),18,19 and the single-incision technique through the anteromedial portal (AM).20,21 The DI technique requires an anteromedial incision for the tibial work and a lateral approach for the femoral metaphysis. Front-entry or rear-entry C guides are used to introduce a Kirshner wire outside-in into the lateral femoral metaphysis. In the TT technique, the femoral tunnel is drilled inside-out through the tibial tunnel, using special atraumatic reamers, with the knee in 70° to 80° of flexion. Using the AM technique, the
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 15, No 7 (October), 1999: pp 750–756
FEMORAL TUNNEL POSITION IN ACL RECONSTRUCTION femoral tunnel is produced inside-out trough a low anteromedial portal, using atraumatic reamers with the knee in maximum flexion. The purpose of this study was to experimentally verify in the cadaver model if the a correct deep position of the femoral tunnel could be obtained equally with the three different techniques. MATERIALS AND METHODS Fifteen fresh male cadavers were used for this study for a total of 30 knees. Each technique was employed in a group of 5 cadavers for a total of 10 knees. The average age was 64 years (range, 45 to 81 years). All the joints were free of degenerative changes and showed intact menisci, and cruciate and collateral ligaments. The lower limbs were not amputated to more closely reproduce the operating conditions. The knee was approached through an anteromedial arthrotomy. The ACL fiber bundles were defined by removing the overlying synovium. The femoral insertion area of the anteromedial bundle was identified. A small reference hole was produced just deep to this area (Fig 1) using a 60° curved awl (Linvatec, Largo, FL). In this report, the position of a point into the notch is described in relationship to the line of the roof of the notch.1 Anterior and posterior positions along the roof of the notch are described as superficial and deep. Displacement along a direction perpendicular to the roof line are described as superior and inferior. This nomenclature was introduced to describe positions from the arthroscopist’s point of view, who looks into the knee when it is flexed while the standard anatomical nomenclature relates to the fully extended knee.1
FIGURE 1. The ACL femoral insertion area is outlined in blue. The insertion area of the anteromedial bundle is colored in red. The black point identifies the reference hole. It was produced just deep to anteromedial bundle insertion area. In this report, the position of a point into the notch is described in relationship to the roof of the notch. Displacements along the roof of the notch are defined as superficial and deep. Displacement along a direction perpendicular to the roof line are defined as superior and inferior.
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The ACL was cut and removed and the reference hole was clearly visualized. In the DI technique, the Rear Entry guide (Acufex, Mansfield, MA) was used. The guide was introduced into the joint using a curved hook passed over the top of the lateral femoral condyle. The K-wire was drilled outside-in to reach the reference hole in the lateral wall of the notch. The tip of the K-wire was left flush with the wall of the notch. A lateral radiograph with superimposition of the femoral condyles was obtained. The K-wire was then overdrilled with a 10-mm cannulated reamer. The intra-articular tunnel exit was marked using a bariumsulphate paste (Mixbar Esofago, Bracco, Milan, Italy) and a second lateral radiographic view was obtained. In the TT technique the tibial K-wire was inserted using the Concept Pin guide (Linvatec). We aimed in the tibia at a point located along a line connecting the anteromedial spine and the posterior edge of the anterior horn of the lateral meniscus, one third of the distance from the spine.22 A 10-mm tibial tunnel was drilled using a cannulated reamer. The femoral K-wire was introduced through the tibial tunnel aiming to the reference hole in the lateral wall of the notch. The K-wire was drilled into the femur and withdrawn from the thigh until its tip was flush with the wall of the notch. A lateral view was obtained. The K-wire was reintroduced into the tibial tunnel. A 10-mm femoral half tunnel was drilled using an atraumatic reamer (Acufex). The barium-sulphate paste was applied at the intra-articular end of the tunnel and a second lateral radiograph was obtained. Using the AM technique, a K-wire was introduced into the joint through the anteromedial arthrotomy
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FIGURE 2. (A) In a lateral view, the position of the tip of the K-wire is measured in relationship to Blumensaat’s line. CW is the width of the condyles along the Blumensaat’s line and A is the distance between the tip of the K-wire and the posterior condyles. ␣ is the angle between the K-wire and Blumensaat’sline. (B) Radiographic example.
aiming at the reference hole in the lateral wall of the notch. The knee was gently taken to maximum flexion and the K-wire was drilled through the femur and withdrawn from the thigh until its tip was flush with the wall of the notch. A lateral view was obtained. The K-wire was reintroduced into the joint and overdrilled with a 10-mm atraumatic reamer. The barium-sulphate paste was applied at the intra-articular tunnel exit and a second lateral radiograph was obtained. In every radiograph, the following parameters were defined: Angle ␣. This is the angle between the femoral K-wire and the Blumensaat’s line (Fig 2). Distance CW. This represents the condylar width measured in millimeters along Blumensaat’s line (Fig 2).
Distance A. The distance between the tip of the K-wire and a line tangent to the posterior contour of the femoral condyles, perpendicular to Blumensaat’s line (Fig 2). Distance A’. The distance between two lines perpendicular to Blumensaat’s line, the first one tangent to the superficial margin of the femoral tunnel exit and the second tangent to the posterior contour of the femoral condyles (Fig 3). Distance CH. The condylar height measured as the distance between Blumensaat’s line and a second line, parallel to the first one and tangent to the contour of the condyles (Fig 4). Distance B. The perpendicular distance between the tip of the K wire and the Blumensaat’s line (Fig 4).
FIGURE 3. (A) In a lateral view of the knee, A’ is the distance between two lines perpendicular to Blumensaat’s line, the first one tangent the superficial margin of the femoral hole, the second tangent the posterior contour of the condyles. (B) Radiographic example.
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FIGURE 4. (A) In a lateral view, B represents the distance of the tip of the K-wire from Blumensaat’s line and CH the height of the condyles. (B) Radiographic example.
Distance B8. The perpendicular distance between the Blumensaat’s line and a second line parallel to the Blumensaat’s line and tangent to the inferior margin of the femoral tunnel exit (Fig 5). Ratios A/CW (Fig 2) and B/CH (Fig 4) define the position of the tip of the K-wire. Ratios A8/CW (Fig 3) and B8/CH (Fig 5) define the position of the intra-articular femoral tunnel exit. In order to assess intraobserver variability, the measurements A/CW, B/CH, A8/CW, and B8/CH, were repeated by the first author twice in the same day (intraobserver same-day variability) and again the
following day (intraobserver day-to-day variability). To study the interobserver variability, the measurements performed by the first author were repeated by the second author. Statistical Analysis Statistical analysis was performed using unpaired Student t test and the significance was set at P ⫽ .05. The statistical significance of intraobserver same-day, day-to-day, and interobserver variability was evaluated using a single regression analysis.
FIGURE 5. (A) In a lateral view, B8 represents the distance between the inferior margin of the femoral tunnel and Blumensaat’s line. CH is the condyle height. (B) Radiographic example.
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RESULTS The ratio A/CW was, on average, 27.5% for the DI technique and 25% for both the TT and the AM techniques. The ratio B/CH was, on average, 14% with the DI technique, 11% with the TT technique, and 15% with the AM technique. The angle ␣ between K-wire and Blumensaat’s line was 86°, 98°, and 100° with the DI, TT, and AM techniques, respectively. The differences between the three techniques were not significant (Table 1). The ratio A8/CW was, on average, 36% in the DI technique, 36% for the TT technique, and 34% for the AM technique. The ratio B8/CH was, on average, 27% in the DI technique, 26.5% in the TT technique, and 28% for the AM technique. The differences between the three techniques were statistically insignificant (Table 2). The superficial margin of the femoral tunnel (distance A8) was never more superficial than 40% of the condyle width. Comparison of the two measurements performed by the same author in the same day (intraobserver sameday variability) showed good agreement for the A/CW ( ⫽ .783, P ⫽ .001), B/CH ( ⫽ .734, P ⫽ .001), A8/CW ( ⫽ .693, P ⫽ .001) and B8/CH measurements ( ⫽ .717, P ⫽ .001). A good agreement was also present between the two measurements performed by the same author in different days (intraobserver day-today variability) for A/CW ( ⫽ .755, P ⫽ .001), B/CH ( ⫽ .710, P ⫽ .001), A8/CW ( ⫽ .689, P ⫽ .001) and B8/CH measurements ( ⫽ .697, P ⫽ .001). The same applies to interobserver variability with A/CW ( ⫽ .803, P ⫽ .001), B/CH ( ⫽ .781, P ⫽ .001), A8/CW ( ⫽ .746, P ⫽ .001) and B8/CH ( ⫽ .694, P ⫽ .001). DISCUSSION The importance of accurate femoral tunnel positioning in ACL reconstruction cannot be overemphasized. Errors in femoral tunnel positioning in a direction TABLE 1. Surgical Techniques
A/CW ⫻ 100 B/CH ⫻ 100 ␣
DI
TT
AM
27.5% SD ⫾ 3.9% (21%-33%) 14% SD ⫾ 4.7% (7%-21%) 86° SD ⫾ 8° (70°-96°)
25% SD ⫾ 3.6% (21%-30%) 11% SD ⫾ 4.4% (4%-18%) 98° SD ⫾ 7° (87°-110°)
25% SD ⫾ 3.6% (21%-31%) 15% SD ⫾ 3% (11%-21%) 100° SD ⫾ 9° (87°-116°)
A8/CW ⫻ 100 B8/CH ⫻ 100
DI
TT
AM
36% SD ⫾ 4.5% (28%-40%) 27% SD ⫾ 4.8% (21%-33%)
36% SD ⫾ 2.6% (33%-40%) 26.5% SD ⫾ 4.1% (19%-37%)
34% SD ⫾ 3.9% (26%-40%) 28% SD ⫾ 6% (19%-37%)
along Blumensaat’s line lead to greater length changes than errors in a direction perpendicular to it.1,12,13 In a 7-year follow-up study of 44 open ACL reconstructions using the central third patellar tendon and a lateral extra-articular tenodesis,23 knees with a superficial femoral hole, at 45% to 50% of the posteroanterior width of the condyles, showed a greater anterior tibial displacement (4.7 mm on average) than knees with a deeper femoral hole, located at 30% to 40% (2 mm on average). The importance of femoral tunnel placement was confirmed in a 7-year follow-up study of 89 arthroscopic-assisted ACL reconstructions using the central third patellar tendon2; 88% of the knees with a correct deep placement of the femoral tunnel showed satisfactory stability. A superficial placement of the femoral tunnel, in the anterior 50% of the width of the condyles, was associated with graft failure in 62.5% of the knees. Using a method of measurement similar to ours, Good et al.24 reported the 2-year results of 24 consecutive ACL reconstructions. The knees with a superficial femoral exit hole (⬎38% of the posteroanterior length of the condyles) had less objective stability than knees with a deeper femoral exit hole. Khalfayan et al.25 prospectively studied 128 arthroscopic-assisted ACL reconstructions. When the femoral tunnel was placed within the posterior 40% of the femoral condyles and tibial tunnel was posterior to the 20% of the width of the tibial plateau, 79% of knees had KT-1000 arthrometer measurements within 3 mm. Thus, several studies2,23-25 from different institutions have confirmed that a deep placement of the femoral tunnel, within the posterior 35% to 40% of the width of the condyles, is associated with an improved objective stability. A point just deep to the insertion of the anteromedial fibers of the ACL was chosen in our study as the ideal landmark for K-wire placement for two reasons: first, the anteromedial fibers are the most isometric1,3,5,8-14; second, these fibers are easily identified during a knee dissection. Our experience in this study was that the ‘‘ideal’’ reference point on the femur, deep into the notch, can
FEMORAL TUNNEL POSITION IN ACL RECONSTRUCTION be equally reached either outside-in using a rear-entry C guide (DI technique), drilling inside-out through the tibial tunnel (TT technique), or through an anteromedial approach (AM technique). On a lateral radiograph, the tip of the K-wire was located, on average, at 25% to 27.5% of the width of the condyles along the Blumensaat’s line and at 11% to 15% of the height of the condyles (perpendicular to the Blumensaat’s line). The differences between the three techniques were not statistically significant. The radiographic projection of the center of the ACL insertion area has been previously found to be located at 24.8% of the posteroanterior width of the condyles,26 which is consistent with our results. Overdrilling the K-wire with a 10-mm drill bit causes some superficial and inferior displacement of the femoral insertion. The superficial margin of the intra-articular exit hole was located, on average, at 34% to 36% of the width of the condyles along the Blumensaat’s line. None of the femoral holes was more superficial than 40%. The inferior margin of the intra-articular exit hole was located, on average, at 26.5% to 28% of the height of the condyles. Again the differences between the three techniques were not significant. In this anatomic study, we were able to reach with the tip of the K-wire a point located deep into the notch, close to the insertion of the anteromedial fibers, using the three techniques. However this is not to say that there are not differences in the orientation of the femoral tunnel. In a previous study, the orientation of the femoral tunnel in the frontal plane was measured in 25 knees operated on with a DI technique and 25 with a TT technique.27 More recently, the study has been expanded to include 50 knees operated with the AM technique.28 The inclination of the femoral and tibial tunnels was measured in relationship to the joint line (Fig 6). The angulation of the tibial tunnel was similar for the three techniques ranging from 67° to 72° on average. Significant differences were found between the angulation of the femoral tunnel for the DI technique (37°), the TT (68°), and the AM (50°). Therefore, divergence between femoral and tibial tunnels was minimal using a TT technique, as could be expected. A wide divergence between the tunnels was present after the DI technique, 35° on average, due to the more horizontal angulation of the femoral tunnel. The divergence was intermediate in the AM technique (17°). The superficial margin of the femoral intraarticular exit hole was well deep into the notch with the three techniques, ranging from 37% to 31% on average.
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FIGURE 6. The inclination of the femoral and tibial tunnels performed with the DI, the TT, and the AM techinique was measured in relationship to the joint line.28
Based on the results of this study, each one of the three techniques can be used to produce a suitable, deep femoral tunnel position. The choice of the technique is up to the surgeon. Each technique has advantages and disadvantages. The DI is the oldest, and perhaps easiest technique but a second lateral incision is required. The use of a rear-entry guide decreases the risk of a superficial femoral tunnel placement. The single-incision TT approach is more demanding. The location of the femoral tunnel is constrained by the correct angulation of the tibial tunnel. There is a tendency for the K-wire to be more toward the roof of the notch, near 11 o’clock or 11:30 for the right knee. Recently endoscopic femoral guides introduced through the tibial tunnel, have become popular. These guides are size specific and have a tongue that is placed in the over-the-top position, thereby standardizing the placement of the tunnel entrance. Using the TT technique, the femoral and tibial tunnels have minimal divergence. This theoreti-
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cally avoids the wear-related damage that has been shown in laboratory studies.29 The single-incision AM technique is also a demanding technique. The femoral tunnel is drilled in full flexion. Visibility is limited and the surgeon must have good confidence with arthroscope. Drilling the femoral tunnel is not constrained by the orientation of the tibial tunnel and the angulation of the femoral tunnel, almost at right angle to the Blumensaat’s line, prevents blowing-out the posterior wall. The position that is achieved tends to be more toward the wall of the notch than using the TT technique, at around 10:30 for the right knee. In conclusion, this experimental study has shown that a correct deep placement of the femoral tunnel could be achieved drilling the K-wire outside-in with a rear entry guide or inside-out through the tibial tunnel or the anteromedial portal. Therefore, the choice of technique for producing the femoral tunnel—DI, TT, or AM—should be based on other issues, such as surgeon’s preference and experience, clinical results, patient acceptance, and cosmesis. REFERENCES 1. Amis AA, Beynnon B, Blankevoort L, et al. Proceedings of the ESSKA scientific workshop on reconstruction of the anterior and posterior cruciate ligaments. Knee Surg Sports Traumatol Arthrosc 1994;2:124-132. 2. Aglietti P, Buzzi R, Giron F, Simeone AJV, Zaccherotti G. Arthroscopic-assisted anterior cruciate ligament reconstruction with the central third patellar tendon. A 5-8-year follow-up. Knee Surg Sports Traumatol Arthrosc 1997;5:138-144. 3. Friederich NF, O’Brien WR. Functional anatomy of the cruciate ligaments. In: Jakob RP, Staubli HU, eds.The knee and the cruciate ligaments. Berlin: Springer Verlag, 1992;78-91. 4. O’Brien WR, Friederich NF. Isometric placement of cruciate ligament substitutes. In: Feagin JA, ed. The crucial ligaments. Ed 2. New York: Churchill Livingstone, 1994; 595-604. 5. Sapega AA, Moyer RA, Schneck C, Komalahiranya M. Testing for isometry during reconstruction of the anterior cruciate ligament: Anatomical and biomechanical considerations. J Bone Joint Surg Am 1990;72:259-267. 6. Amis AA, Dawkins GPC. Functional anatomy of the anterior cruciate ligament: Fiber bundle actions related to ligament replacements and injuries. J Bone Joint Surg Br 1991;73:260267. 7. Markolf KL, Burchfield DM, Shapiro MM, Davis BR, Finerman GAM, Slauterbeck JL. Biomechanical consequences of replacement of the anterior cruciate ligament with a patellar ligament allograft. J Bone Joint Surg Am 1996;78:1720-1727. 8. Arms SW, Pope MH., Johnson RJ, Fisher RA, Arvidsson I, Eriksson E. The biomechanics of the anterior cruciate ligament rehabilitation and reconstruction. Am J Sports Med 1984;12: 8-18. 9. Hoogland T, Hillen B. Intra-articular reconstruction of the anterior cruciate ligament: An experimental study of lenght changes in different ligament reconstructions. Clin Orthop 1984;185:197-202. 10. Melhorn JM, Henning CE. The relationship of the femoral attachment site to the isometric tracking of the anterior cruciate ligament graft. Am J Sports Med 1987;15:539-542.
11. Graf B. Isometric placement of the substitutes for anterior cruciate ligament. In: Jackson DW, Drez D, eds. The anterior cruciate deficient knee: new concept in ligament repair. St. Louis: CV Mosby, 1987;102-113. 12. Bradley J, Fitzpatrick D, Daniel DM, Schercliff T, O’Connor J. Orientation of the cruciate ligament in the sagittal plane: a method of predicting its lenght change with flexion. J Bone Joint Surg Br 1988;70:94-99. 13. Hefzy MS, Grood ES, Noyes FR. Factors affecting the region of most isometric femoral femoral attachments. Part II. The anterior cruciate ligament. Am J Sports Med 1989;17:208-216. 14. Schutzer SF, Christen S, Jakob RP. Further observations on the isometricity of the anterior cruciate ligament: an anatomical study using a 6 mm diameter replacement. Clin Orthop 1989;242:247-255. 15. Hewson GF. Drill guides for improving accurancy in anterior cruciate ligament repair and reconstruction. Clin Orthop 1983; 172:119-124. 16. Daniel DM. Principles of knee ligament surgery In: Daniel DM, Akeson WH, O’Connor JJ, eds. Knee ligaments. Structure, function, injury and repair. New York, Raven, 1990; 11-29. 17. Nogalsky MP., Bach BR. Acute anterior cruciate ligament injuries. In: Fu FH, Harner CD, Vince KG, eds. Knee surgery. Baltimore: Williams & Wilkins, 1994;679-730. 18. Hardin GT, Bach BR, Bush-Joseph CA, Farr J. Endoscopic single-incision ACL reconstruction using patellar tendon autograft; surgical technique. Am J Knee Surg 1992;5:144-155. 19. Rosemberg TD, Paulos LE, Victoroff BN, Abbott PJ. Arthroscopic cruciate repair and reconstruction: An overview and descriptions of technique. In: Feagin JA, ed. The crucial ligaments. Ed 2. New York: Churchill Livingstone, 1994;528553. 20. O’Donnell JB, Scerpella TA. Endoscopic anterior cruciate ligament reconstruction: Modified technique and radiographic review. Arthroscopy 1995;11:577-584. 21. Scranton PE, Pinczewski L, Auld KM, Khalfayan EE. Outpatient endoscopic quadruple Hamstring anterior cruciate ligament reconstruction. Oper Tech Orthop 1996;6:177-180. 22. Jackson DW, Gasser SI. Tibial tunnel placement in ACL reconstruction. Arthroscopy 1994;10:124-131. 23. Aglietti P, Buzzi R, D’Andria S, Zaccherotti G. Long-term study of anterior cruciate ligament reconstruction for chronic instability using the central one-third patellar tendon and a lateral extraarticular tenodesis. Am J Sports Med 1992;20: 38-45. 24. Good L, Odensten M, Gillquist J. Sagittal knee stability after anterior cruciate ligament reconstruction with patellar tendon strip. A two year follow-up study. Am J Sports Med 1994;22: 518-523. 25. Khalfayan EE, Sharkey PF, Alexander AH, Bruckner JD, Bynum EB. The relationship between tunnel placement and clinical results after anterior cruciate ligament reconstruction. Am J Sports Med 1996;24:335-341. 26. Bernard M, Hertel P, Hornung H, Cierpinsky T. Femoral insertion of the ACL. Radiographic quadrant method. Am J Knee Surg 1997;10:14-22. 27. Aglietti P, Zaccherotti G, Menchetti PPM, De Biase P. A comparison of clinical and radiological parameters with two arthroscopic techniques for anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc 1995;3:2-8. 28. Aglietti P. Patellar ligament versus hamstring graft for ACL. Instructional Course Lecture, Combined Congress of the International Arthroscopy Association and the International Society of the Knee, Hong Kong, 1995. 29. Graf B, Vanderby R Jr. Autograft reconstruction of the anterior cruciate ligament. Placement, tensioning and preconditioning. In: DW Jackson, et al. eds. The anterior cruciate ligament: Current and future concepts. New York: Raven, 1993;281-290.
Summary: The possibility of achieving correct deep femoral tunnel positioning during anterior cruciate ligament (ACL) reconstruction with the double incision technique (DI), the transtibial technique (TT), and the anteromedial technique (AM) was evaluated in 30 cadaver knees. A reference hole was made just deep to the insertion of the anteromedial bundle of the ACL through an anteromedial arthrotomy. In the DI technique, a Kirshner wire was inserted outside-in using a rear entry C guide. In the TT and AM techniques, the K-wire was inserted inside-out through the tibial tunnel and through the arthrotomy, respectively. The reference hole could be achieved with each technique. Using lateral radiographs, the superficial aspect of the intra-articular exit of the femoral tunnel was found to be located on average at 36%, 36%, and 34% of the width of the condyles from the posterior margin (NS). None of the holes was more anterior than 40%. In conclusion, a deep femoral tunnel positioning could be achieved with each technique. The choice of technique must be based on the surgeon’s preference and clinical results. Key Words: Anterior cruciate ligament—Reconstruction— Femoral tunnel—Cadaver study.
A
correct femoral tunnel position during intraarticular anterior cruciate ligament (ACL) reconstruction is critical to achieve a successful result. Displacements along the line of the roof of the notch, described as superficial and deep,1 are particularly significant. In a minimum 5-year follow-up of 89 arthroscopic-assisted ACL reconstructions, we have found that 88% of knees with a correct deep placement of the femoral tunnel showed satisfactory stability. A superficial placement of the femoral tunnel was associated with graft failure in 62.5% of the cases.2 Present surgical techniques are insufficient to duplicate the complex geometry or fiber-tensioning patterns of the ACL. The surgeon’s purpose is limited to duplicate the global function of the deficient ligament.3,4 The ACL is not isometric and only few fibers From the First Orthopaedic Clinic of the University of Florence, Florence, Italy. Address correspondence and reprint requests to Paolo Aglietti, M.D., Prima Clinica Orthopedica, Universita` di Firenze, Largo P. Palagi 1, 50139 Firenze, Italy. r 1999 by the Arthroscopy Association of North America 0749-8063/99/1507-1949$3.00/0
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are nearly isometric over the range of motion. However, a nearly isometric behavior of the ACL substitute is desirable, with a 2 to 3 mm lengthening of the graft toward extension.1,3-7 Length changes in the distance between the insertion points are widely influenced by the femoral tunnel positioning. Most investigators have found that tunnel positioning close to the insertion of anteromedial fibers would be desirable.1,3,5,6,8-14 After the introduction of arthroscopic-assisted ACL reconstructions, three major surgical techniques have been developed to produce the femoral tunnel: the double-incision technique (DI),15-17 the single-incision transtibial technique (TT),18,19 and the single-incision technique through the anteromedial portal (AM).20,21 The DI technique requires an anteromedial incision for the tibial work and a lateral approach for the femoral metaphysis. Front-entry or rear-entry C guides are used to introduce a Kirshner wire outside-in into the lateral femoral metaphysis. In the TT technique, the femoral tunnel is drilled inside-out through the tibial tunnel, using special atraumatic reamers, with the knee in 70° to 80° of flexion. Using the AM technique, the
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 15, No 7 (October), 1999: pp 750–756
FEMORAL TUNNEL POSITION IN ACL RECONSTRUCTION femoral tunnel is produced inside-out trough a low anteromedial portal, using atraumatic reamers with the knee in maximum flexion. The purpose of this study was to experimentally verify in the cadaver model if the a correct deep position of the femoral tunnel could be obtained equally with the three different techniques. MATERIALS AND METHODS Fifteen fresh male cadavers were used for this study for a total of 30 knees. Each technique was employed in a group of 5 cadavers for a total of 10 knees. The average age was 64 years (range, 45 to 81 years). All the joints were free of degenerative changes and showed intact menisci, and cruciate and collateral ligaments. The lower limbs were not amputated to more closely reproduce the operating conditions. The knee was approached through an anteromedial arthrotomy. The ACL fiber bundles were defined by removing the overlying synovium. The femoral insertion area of the anteromedial bundle was identified. A small reference hole was produced just deep to this area (Fig 1) using a 60° curved awl (Linvatec, Largo, FL). In this report, the position of a point into the notch is described in relationship to the line of the roof of the notch.1 Anterior and posterior positions along the roof of the notch are described as superficial and deep. Displacement along a direction perpendicular to the roof line are described as superior and inferior. This nomenclature was introduced to describe positions from the arthroscopist’s point of view, who looks into the knee when it is flexed while the standard anatomical nomenclature relates to the fully extended knee.1
FIGURE 1. The ACL femoral insertion area is outlined in blue. The insertion area of the anteromedial bundle is colored in red. The black point identifies the reference hole. It was produced just deep to anteromedial bundle insertion area. In this report, the position of a point into the notch is described in relationship to the roof of the notch. Displacements along the roof of the notch are defined as superficial and deep. Displacement along a direction perpendicular to the roof line are defined as superior and inferior.
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The ACL was cut and removed and the reference hole was clearly visualized. In the DI technique, the Rear Entry guide (Acufex, Mansfield, MA) was used. The guide was introduced into the joint using a curved hook passed over the top of the lateral femoral condyle. The K-wire was drilled outside-in to reach the reference hole in the lateral wall of the notch. The tip of the K-wire was left flush with the wall of the notch. A lateral radiograph with superimposition of the femoral condyles was obtained. The K-wire was then overdrilled with a 10-mm cannulated reamer. The intra-articular tunnel exit was marked using a bariumsulphate paste (Mixbar Esofago, Bracco, Milan, Italy) and a second lateral radiographic view was obtained. In the TT technique the tibial K-wire was inserted using the Concept Pin guide (Linvatec). We aimed in the tibia at a point located along a line connecting the anteromedial spine and the posterior edge of the anterior horn of the lateral meniscus, one third of the distance from the spine.22 A 10-mm tibial tunnel was drilled using a cannulated reamer. The femoral K-wire was introduced through the tibial tunnel aiming to the reference hole in the lateral wall of the notch. The K-wire was drilled into the femur and withdrawn from the thigh until its tip was flush with the wall of the notch. A lateral view was obtained. The K-wire was reintroduced into the tibial tunnel. A 10-mm femoral half tunnel was drilled using an atraumatic reamer (Acufex). The barium-sulphate paste was applied at the intra-articular end of the tunnel and a second lateral radiograph was obtained. Using the AM technique, a K-wire was introduced into the joint through the anteromedial arthrotomy
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FIGURE 2. (A) In a lateral view, the position of the tip of the K-wire is measured in relationship to Blumensaat’s line. CW is the width of the condyles along the Blumensaat’s line and A is the distance between the tip of the K-wire and the posterior condyles. ␣ is the angle between the K-wire and Blumensaat’sline. (B) Radiographic example.
aiming at the reference hole in the lateral wall of the notch. The knee was gently taken to maximum flexion and the K-wire was drilled through the femur and withdrawn from the thigh until its tip was flush with the wall of the notch. A lateral view was obtained. The K-wire was reintroduced into the joint and overdrilled with a 10-mm atraumatic reamer. The barium-sulphate paste was applied at the intra-articular tunnel exit and a second lateral radiograph was obtained. In every radiograph, the following parameters were defined: Angle ␣. This is the angle between the femoral K-wire and the Blumensaat’s line (Fig 2). Distance CW. This represents the condylar width measured in millimeters along Blumensaat’s line (Fig 2).
Distance A. The distance between the tip of the K-wire and a line tangent to the posterior contour of the femoral condyles, perpendicular to Blumensaat’s line (Fig 2). Distance A’. The distance between two lines perpendicular to Blumensaat’s line, the first one tangent to the superficial margin of the femoral tunnel exit and the second tangent to the posterior contour of the femoral condyles (Fig 3). Distance CH. The condylar height measured as the distance between Blumensaat’s line and a second line, parallel to the first one and tangent to the contour of the condyles (Fig 4). Distance B. The perpendicular distance between the tip of the K wire and the Blumensaat’s line (Fig 4).
FIGURE 3. (A) In a lateral view of the knee, A’ is the distance between two lines perpendicular to Blumensaat’s line, the first one tangent the superficial margin of the femoral hole, the second tangent the posterior contour of the condyles. (B) Radiographic example.
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FIGURE 4. (A) In a lateral view, B represents the distance of the tip of the K-wire from Blumensaat’s line and CH the height of the condyles. (B) Radiographic example.
Distance B8. The perpendicular distance between the Blumensaat’s line and a second line parallel to the Blumensaat’s line and tangent to the inferior margin of the femoral tunnel exit (Fig 5). Ratios A/CW (Fig 2) and B/CH (Fig 4) define the position of the tip of the K-wire. Ratios A8/CW (Fig 3) and B8/CH (Fig 5) define the position of the intra-articular femoral tunnel exit. In order to assess intraobserver variability, the measurements A/CW, B/CH, A8/CW, and B8/CH, were repeated by the first author twice in the same day (intraobserver same-day variability) and again the
following day (intraobserver day-to-day variability). To study the interobserver variability, the measurements performed by the first author were repeated by the second author. Statistical Analysis Statistical analysis was performed using unpaired Student t test and the significance was set at P ⫽ .05. The statistical significance of intraobserver same-day, day-to-day, and interobserver variability was evaluated using a single regression analysis.
FIGURE 5. (A) In a lateral view, B8 represents the distance between the inferior margin of the femoral tunnel and Blumensaat’s line. CH is the condyle height. (B) Radiographic example.
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RESULTS The ratio A/CW was, on average, 27.5% for the DI technique and 25% for both the TT and the AM techniques. The ratio B/CH was, on average, 14% with the DI technique, 11% with the TT technique, and 15% with the AM technique. The angle ␣ between K-wire and Blumensaat’s line was 86°, 98°, and 100° with the DI, TT, and AM techniques, respectively. The differences between the three techniques were not significant (Table 1). The ratio A8/CW was, on average, 36% in the DI technique, 36% for the TT technique, and 34% for the AM technique. The ratio B8/CH was, on average, 27% in the DI technique, 26.5% in the TT technique, and 28% for the AM technique. The differences between the three techniques were statistically insignificant (Table 2). The superficial margin of the femoral tunnel (distance A8) was never more superficial than 40% of the condyle width. Comparison of the two measurements performed by the same author in the same day (intraobserver sameday variability) showed good agreement for the A/CW ( ⫽ .783, P ⫽ .001), B/CH ( ⫽ .734, P ⫽ .001), A8/CW ( ⫽ .693, P ⫽ .001) and B8/CH measurements ( ⫽ .717, P ⫽ .001). A good agreement was also present between the two measurements performed by the same author in different days (intraobserver day-today variability) for A/CW ( ⫽ .755, P ⫽ .001), B/CH ( ⫽ .710, P ⫽ .001), A8/CW ( ⫽ .689, P ⫽ .001) and B8/CH measurements ( ⫽ .697, P ⫽ .001). The same applies to interobserver variability with A/CW ( ⫽ .803, P ⫽ .001), B/CH ( ⫽ .781, P ⫽ .001), A8/CW ( ⫽ .746, P ⫽ .001) and B8/CH ( ⫽ .694, P ⫽ .001). DISCUSSION The importance of accurate femoral tunnel positioning in ACL reconstruction cannot be overemphasized. Errors in femoral tunnel positioning in a direction TABLE 1. Surgical Techniques
A/CW ⫻ 100 B/CH ⫻ 100 ␣
DI
TT
AM
27.5% SD ⫾ 3.9% (21%-33%) 14% SD ⫾ 4.7% (7%-21%) 86° SD ⫾ 8° (70°-96°)
25% SD ⫾ 3.6% (21%-30%) 11% SD ⫾ 4.4% (4%-18%) 98° SD ⫾ 7° (87°-110°)
25% SD ⫾ 3.6% (21%-31%) 15% SD ⫾ 3% (11%-21%) 100° SD ⫾ 9° (87°-116°)
A8/CW ⫻ 100 B8/CH ⫻ 100
DI
TT
AM
36% SD ⫾ 4.5% (28%-40%) 27% SD ⫾ 4.8% (21%-33%)
36% SD ⫾ 2.6% (33%-40%) 26.5% SD ⫾ 4.1% (19%-37%)
34% SD ⫾ 3.9% (26%-40%) 28% SD ⫾ 6% (19%-37%)
along Blumensaat’s line lead to greater length changes than errors in a direction perpendicular to it.1,12,13 In a 7-year follow-up study of 44 open ACL reconstructions using the central third patellar tendon and a lateral extra-articular tenodesis,23 knees with a superficial femoral hole, at 45% to 50% of the posteroanterior width of the condyles, showed a greater anterior tibial displacement (4.7 mm on average) than knees with a deeper femoral hole, located at 30% to 40% (2 mm on average). The importance of femoral tunnel placement was confirmed in a 7-year follow-up study of 89 arthroscopic-assisted ACL reconstructions using the central third patellar tendon2; 88% of the knees with a correct deep placement of the femoral tunnel showed satisfactory stability. A superficial placement of the femoral tunnel, in the anterior 50% of the width of the condyles, was associated with graft failure in 62.5% of the knees. Using a method of measurement similar to ours, Good et al.24 reported the 2-year results of 24 consecutive ACL reconstructions. The knees with a superficial femoral exit hole (⬎38% of the posteroanterior length of the condyles) had less objective stability than knees with a deeper femoral exit hole. Khalfayan et al.25 prospectively studied 128 arthroscopic-assisted ACL reconstructions. When the femoral tunnel was placed within the posterior 40% of the femoral condyles and tibial tunnel was posterior to the 20% of the width of the tibial plateau, 79% of knees had KT-1000 arthrometer measurements within 3 mm. Thus, several studies2,23-25 from different institutions have confirmed that a deep placement of the femoral tunnel, within the posterior 35% to 40% of the width of the condyles, is associated with an improved objective stability. A point just deep to the insertion of the anteromedial fibers of the ACL was chosen in our study as the ideal landmark for K-wire placement for two reasons: first, the anteromedial fibers are the most isometric1,3,5,8-14; second, these fibers are easily identified during a knee dissection. Our experience in this study was that the ‘‘ideal’’ reference point on the femur, deep into the notch, can
FEMORAL TUNNEL POSITION IN ACL RECONSTRUCTION be equally reached either outside-in using a rear-entry C guide (DI technique), drilling inside-out through the tibial tunnel (TT technique), or through an anteromedial approach (AM technique). On a lateral radiograph, the tip of the K-wire was located, on average, at 25% to 27.5% of the width of the condyles along the Blumensaat’s line and at 11% to 15% of the height of the condyles (perpendicular to the Blumensaat’s line). The differences between the three techniques were not statistically significant. The radiographic projection of the center of the ACL insertion area has been previously found to be located at 24.8% of the posteroanterior width of the condyles,26 which is consistent with our results. Overdrilling the K-wire with a 10-mm drill bit causes some superficial and inferior displacement of the femoral insertion. The superficial margin of the intra-articular exit hole was located, on average, at 34% to 36% of the width of the condyles along the Blumensaat’s line. None of the femoral holes was more superficial than 40%. The inferior margin of the intra-articular exit hole was located, on average, at 26.5% to 28% of the height of the condyles. Again the differences between the three techniques were not significant. In this anatomic study, we were able to reach with the tip of the K-wire a point located deep into the notch, close to the insertion of the anteromedial fibers, using the three techniques. However this is not to say that there are not differences in the orientation of the femoral tunnel. In a previous study, the orientation of the femoral tunnel in the frontal plane was measured in 25 knees operated on with a DI technique and 25 with a TT technique.27 More recently, the study has been expanded to include 50 knees operated with the AM technique.28 The inclination of the femoral and tibial tunnels was measured in relationship to the joint line (Fig 6). The angulation of the tibial tunnel was similar for the three techniques ranging from 67° to 72° on average. Significant differences were found between the angulation of the femoral tunnel for the DI technique (37°), the TT (68°), and the AM (50°). Therefore, divergence between femoral and tibial tunnels was minimal using a TT technique, as could be expected. A wide divergence between the tunnels was present after the DI technique, 35° on average, due to the more horizontal angulation of the femoral tunnel. The divergence was intermediate in the AM technique (17°). The superficial margin of the femoral intraarticular exit hole was well deep into the notch with the three techniques, ranging from 37% to 31% on average.
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FIGURE 6. The inclination of the femoral and tibial tunnels performed with the DI, the TT, and the AM techinique was measured in relationship to the joint line.28
Based on the results of this study, each one of the three techniques can be used to produce a suitable, deep femoral tunnel position. The choice of the technique is up to the surgeon. Each technique has advantages and disadvantages. The DI is the oldest, and perhaps easiest technique but a second lateral incision is required. The use of a rear-entry guide decreases the risk of a superficial femoral tunnel placement. The single-incision TT approach is more demanding. The location of the femoral tunnel is constrained by the correct angulation of the tibial tunnel. There is a tendency for the K-wire to be more toward the roof of the notch, near 11 o’clock or 11:30 for the right knee. Recently endoscopic femoral guides introduced through the tibial tunnel, have become popular. These guides are size specific and have a tongue that is placed in the over-the-top position, thereby standardizing the placement of the tunnel entrance. Using the TT technique, the femoral and tibial tunnels have minimal divergence. This theoreti-
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cally avoids the wear-related damage that has been shown in laboratory studies.29 The single-incision AM technique is also a demanding technique. The femoral tunnel is drilled in full flexion. Visibility is limited and the surgeon must have good confidence with arthroscope. Drilling the femoral tunnel is not constrained by the orientation of the tibial tunnel and the angulation of the femoral tunnel, almost at right angle to the Blumensaat’s line, prevents blowing-out the posterior wall. The position that is achieved tends to be more toward the wall of the notch than using the TT technique, at around 10:30 for the right knee. In conclusion, this experimental study has shown that a correct deep placement of the femoral tunnel could be achieved drilling the K-wire outside-in with a rear entry guide or inside-out through the tibial tunnel or the anteromedial portal. Therefore, the choice of technique for producing the femoral tunnel—DI, TT, or AM—should be based on other issues, such as surgeon’s preference and experience, clinical results, patient acceptance, and cosmesis. REFERENCES 1. Amis AA, Beynnon B, Blankevoort L, et al. Proceedings of the ESSKA scientific workshop on reconstruction of the anterior and posterior cruciate ligaments. Knee Surg Sports Traumatol Arthrosc 1994;2:124-132. 2. Aglietti P, Buzzi R, Giron F, Simeone AJV, Zaccherotti G. Arthroscopic-assisted anterior cruciate ligament reconstruction with the central third patellar tendon. A 5-8-year follow-up. Knee Surg Sports Traumatol Arthrosc 1997;5:138-144. 3. Friederich NF, O’Brien WR. Functional anatomy of the cruciate ligaments. In: Jakob RP, Staubli HU, eds.The knee and the cruciate ligaments. Berlin: Springer Verlag, 1992;78-91. 4. O’Brien WR, Friederich NF. Isometric placement of cruciate ligament substitutes. In: Feagin JA, ed. The crucial ligaments. Ed 2. New York: Churchill Livingstone, 1994; 595-604. 5. Sapega AA, Moyer RA, Schneck C, Komalahiranya M. Testing for isometry during reconstruction of the anterior cruciate ligament: Anatomical and biomechanical considerations. J Bone Joint Surg Am 1990;72:259-267. 6. Amis AA, Dawkins GPC. Functional anatomy of the anterior cruciate ligament: Fiber bundle actions related to ligament replacements and injuries. J Bone Joint Surg Br 1991;73:260267. 7. Markolf KL, Burchfield DM, Shapiro MM, Davis BR, Finerman GAM, Slauterbeck JL. Biomechanical consequences of replacement of the anterior cruciate ligament with a patellar ligament allograft. J Bone Joint Surg Am 1996;78:1720-1727. 8. Arms SW, Pope MH., Johnson RJ, Fisher RA, Arvidsson I, Eriksson E. The biomechanics of the anterior cruciate ligament rehabilitation and reconstruction. Am J Sports Med 1984;12: 8-18. 9. Hoogland T, Hillen B. Intra-articular reconstruction of the anterior cruciate ligament: An experimental study of lenght changes in different ligament reconstructions. Clin Orthop 1984;185:197-202. 10. Melhorn JM, Henning CE. The relationship of the femoral attachment site to the isometric tracking of the anterior cruciate ligament graft. Am J Sports Med 1987;15:539-542.
11. Graf B. Isometric placement of the substitutes for anterior cruciate ligament. In: Jackson DW, Drez D, eds. The anterior cruciate deficient knee: new concept in ligament repair. St. Louis: CV Mosby, 1987;102-113. 12. Bradley J, Fitzpatrick D, Daniel DM, Schercliff T, O’Connor J. Orientation of the cruciate ligament in the sagittal plane: a method of predicting its lenght change with flexion. J Bone Joint Surg Br 1988;70:94-99. 13. Hefzy MS, Grood ES, Noyes FR. Factors affecting the region of most isometric femoral femoral attachments. Part II. The anterior cruciate ligament. Am J Sports Med 1989;17:208-216. 14. Schutzer SF, Christen S, Jakob RP. Further observations on the isometricity of the anterior cruciate ligament: an anatomical study using a 6 mm diameter replacement. Clin Orthop 1989;242:247-255. 15. Hewson GF. Drill guides for improving accurancy in anterior cruciate ligament repair and reconstruction. Clin Orthop 1983; 172:119-124. 16. Daniel DM. Principles of knee ligament surgery In: Daniel DM, Akeson WH, O’Connor JJ, eds. Knee ligaments. Structure, function, injury and repair. New York, Raven, 1990; 11-29. 17. Nogalsky MP., Bach BR. Acute anterior cruciate ligament injuries. In: Fu FH, Harner CD, Vince KG, eds. Knee surgery. Baltimore: Williams & Wilkins, 1994;679-730. 18. Hardin GT, Bach BR, Bush-Joseph CA, Farr J. Endoscopic single-incision ACL reconstruction using patellar tendon autograft; surgical technique. Am J Knee Surg 1992;5:144-155. 19. Rosemberg TD, Paulos LE, Victoroff BN, Abbott PJ. Arthroscopic cruciate repair and reconstruction: An overview and descriptions of technique. In: Feagin JA, ed. The crucial ligaments. Ed 2. New York: Churchill Livingstone, 1994;528553. 20. O’Donnell JB, Scerpella TA. Endoscopic anterior cruciate ligament reconstruction: Modified technique and radiographic review. Arthroscopy 1995;11:577-584. 21. Scranton PE, Pinczewski L, Auld KM, Khalfayan EE. Outpatient endoscopic quadruple Hamstring anterior cruciate ligament reconstruction. Oper Tech Orthop 1996;6:177-180. 22. Jackson DW, Gasser SI. Tibial tunnel placement in ACL reconstruction. Arthroscopy 1994;10:124-131. 23. Aglietti P, Buzzi R, D’Andria S, Zaccherotti G. Long-term study of anterior cruciate ligament reconstruction for chronic instability using the central one-third patellar tendon and a lateral extraarticular tenodesis. Am J Sports Med 1992;20: 38-45. 24. Good L, Odensten M, Gillquist J. Sagittal knee stability after anterior cruciate ligament reconstruction with patellar tendon strip. A two year follow-up study. Am J Sports Med 1994;22: 518-523. 25. Khalfayan EE, Sharkey PF, Alexander AH, Bruckner JD, Bynum EB. The relationship between tunnel placement and clinical results after anterior cruciate ligament reconstruction. Am J Sports Med 1996;24:335-341. 26. Bernard M, Hertel P, Hornung H, Cierpinsky T. Femoral insertion of the ACL. Radiographic quadrant method. Am J Knee Surg 1997;10:14-22. 27. Aglietti P, Zaccherotti G, Menchetti PPM, De Biase P. A comparison of clinical and radiological parameters with two arthroscopic techniques for anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc 1995;3:2-8. 28. Aglietti P. Patellar ligament versus hamstring graft for ACL. Instructional Course Lecture, Combined Congress of the International Arthroscopy Association and the International Society of the Knee, Hong Kong, 1995. 29. Graf B, Vanderby R Jr. Autograft reconstruction of the anterior cruciate ligament. Placement, tensioning and preconditioning. In: DW Jackson, et al. eds. The anterior cruciate ligament: Current and future concepts. New York: Raven, 1993;281-290.