Roof Impingement Revisited

Transcription

1 Roof Impingement Revisited John A Tanksley MD, Evan J Conte MD, Brian C Werner MD, F Winston Gwathmey MD, Stephen F Brockmeier MD, Mark D Miller MD, University of Virginia, Charlottesville, VA

2 Introduction Contact between an ACL graft and the intercondylar roof can cause graft failure and poor outcomes Howell et al. 1,2 noted roof impingement in grafts placed too anterior using a transtibial technique. Requires hyperextension lateral radiographs Line extended from Blumenstaat s The risk of roof impingement with independent femoral tunnel drilling in single-bundle ACLR has not been established Tibial tunnel placement in the anterior portion of the native ACL may provide superior stability based on Clinical study 3 showing improved stability and no loss of extension Biomechanical study 4 showing improved Lachman and Pivot Shift Anatomic study 5 indicating that anterior fibers of the native ACL may be more functional 1. Howell SM, et al Clin Orthop Relat Res Oct;(283): Howell SM and Taylor MA JBJS 1993; 75A : Hatayama, et al. Arthroscopy Jun;29(6): Bedi A, et al. Am J Sports Med Feb;39(2): Amis, et al. J Bone Joint Surg Br Mar;73(2):260-7

3 Introduction Where is the native ACL tibial footprint? Staubli, et al. 1 landmark paper Midsagittal measurement A 24.6% B 43.3% C 62.1% Roof inclination angle Avg 39.8 Conclusion: We advocate placing the center of the tibial tunnel at 44% of the tibia diameter posterior and parallel to the individual intercondylar roof inclination angle. A B C 1. Staubli HU, et al. Knee Surg Sports Traumatol Arthrosc. 1994;2(3):138-46

4 Objectives 1. To determine if tibial tunnels centered in the very anterior aspect of the native ACL insertion are at risk for intercondylar roof impingement. 2. To compare independent femoral tunnel (IF) drilling with transtibial femoral tunnel (TT) drilling with regards to impingement risk. Hypotheses 1. The risk of roof impingement is substantial with the TT technique in the setting of a far-anterior tibial tunnel due to its inherent technical restraints. 2. The risk of roof impingement is low with the IF technique regardless of a far-anterior tibial tunnel due to the improved accuracy in placing anatomic femoral tunnels.

5 Methods Design: Controlled laboratory study 12 fresh frozen knees (6 matched pairs) Randomized to TT or IF Technique ACL tunnels drilled Tibial tunnel drilled far-anterior (Staubli 35%) 8 mm Goretex smoother introduced as a surrogate graft % Staubli % calculated prior to reaming to permit wire repositioning if necessary

6 Methods 8 mm Goretex Smoother

7 Methods Imaging CT performed Goretex in place Maximal extension 3D-reformatting Volume subtraction allows visualization of graft course CT sagittal and coronal reformats raw 3D images volume subtraction graft evaluation

8 Primary outcome measure Methods Impingement Review Index (IRI) 1 Independent variables Drilling technique Knee extension angle Plateau diameter Intercondylar Roof Inclination Angle (RIA) Initial guidepin position Dependent variables CT-measured Staubli % Sagittal graft angle (SGA) Tunnel lengths Impingement Review Index (IRI) Type 1. Impingement: The ACL graft touches the roof and the graft shape is deformed (pathological impingement) Type 2. Touch: The ACL graft touches the roof and the graft shape is not deformed (physiological impingement) Type 3. Non-touch: The ACL graft does not touch the roof 1. Iriuchishima T, et al. Evaluation of the intercondylar roof impingement after anatomical double-bundle ACL reconstruction using 3D-CT. Knee Surg Sports Traumatol Arthrosc (2011) 19:

9 Results Impingement Review Index Type 1 Type 2 Type 3 (Impinge) (Touch) (No touch) IF technique TT technique 2 0 4* +2* *Two Migrated Posteriorly because of expanded Tibial Tunnel

10 N=12 Guidepin Staubli CT Staubli Results RIA (roof inclination⁰ ) Knee Flexion⁰ Plateau length (mm) Tibial Tunnel (mm) Femoral Tunnel (mm) SGA (Sagittal Graft⁰) Group (n=12) 27.6 ( ) 31.6 ( ) 39.6 ( ) 1.1 ( ) 51.6 ( ) 35.3 ( ) 40.8 ( ) 38.2 ( ) IF (n=6) 27.2 ( ) 28.7 ( ) 39.9 ( ) 0.1 ( ) 51.4 ( ) 34.3 ( ) 34.9 ( ) 47.3 ( ) TT (n=6) 27.9 ( ) 34.6 ( ) 39.3 ( ) 2.1 ( ) 51.8 ( ) 36.4 ( ) 46.6 ( ) 29.1 ( ) ρ-value

11 Results Sagittal Graft Angle (SGA) Roof Inclination Angle (RIA) RIA minus SGA IF Graft 47.3⁰ TT Grafts 29.1⁰ ρ-value IF trajectory TT trajectory

12 Results Matched Cadaver Pair TT graft impinges (IRI type 1) Angular deformity with roof contact IF graft touches (IRI type 2) No angular deformity Staubli 29.3% Staubli 23%

13 Discussion Consistent with prior studies, roof impingement is a concern when tibial tunnels are placed in the anterior portion of the native ACL. However, this risk appears to be high only for the transtibial (TT) technique, and low with the independent femoral (IF) technique. IF technique: no roof impingement, 0/6 specimens Transtibial technique: 2/6 (33.3%) specimens impinged In full extension, the sagittal trajectory of the graft is dictated by tunnel location. Intuitively, graft trajectories that converged with Blumensaat s line were at increased risk for impingement, while divergence and posterior enlargement of the tibial tunnel were protective. Significant differences were found with respect to intraarticular sagittal graft trajectory. IF grafts were universally divergent (by avg 7 ) from Blumensaat s line; TT grafts universally converged (avg 10 ).

14 Discussion The majority of roof impingement literature focuses on the transtibial technique exclusively, and may not apply to anatomic techniques. Published studies of double-bundle ACL reconstruction support our findings 1 for grafts centered in the anterior fibers of native ACL AM bundle grafts avg Staubli 33% 0/24 impinging grafts (IRI type 1) 12/24 AM grafts touched the roof (IRI type 2). 1. Iriuchishima T, et al. Evaluation of the intercondylar roof impingement after anatomical double-bundle ACL reconstruction using 3D-CT. Knee Surg Sports Traumatol Arthrosc (2011) 19:

15 Power Limitations N=12, Small sample size Generalizability Cadaver design Technical limitations Properties of Goretex surrogate graft Full extension not possible in 3 specimens (all TT) Would likely serve to decrease impingement risk, which, if anything, may have strengthened conclusions

16 Conclusions The risk of roof impingement with a far-anterior tibial tunnel (Staubli% 35) appears low with an independent femoral (IF) tunnel drilling technique, but high with a transtibial (TT) technique. One plausible explanation for this is a graft trajectory that is divergent from the intercondylar roof with an IF technique, but convergent with a TT technique. A far-anterior tibial tunnel position is achievable with either drilling technique, but it may induce posterior enlargement of the tibial tunnel during transtibial drilling. Further studies are needed in the era of anatomic ACL reconstruction.

17 Bibliography 1. Howell SM, Clark JA. Tibial tunnel placement in anterior cruciate ligament reconstructions and graft impingement. Clin Orthop Relat Res. 1992;283: Howell SM, Taylor MA. J Bone Joint Surg. 1993; 75A : Hatayama, et al. Arthroscopy Jun;29(6): Bedi A, Maak TG, Musahl V, et al. Effect of tibial tunnel position on stability of the knee after anterior cruciate ligament reconstruction: is the tibial tunnel position most important? Am J Sports Med. 2011; 39: Amis AA, Dawkins GP. J Bone Joint Surg Br Mar;73(2): Staubli HU, Rauschning W. Tibial attachment area of the anterior cruciate ligament in the extended knee positionknee Surg Sports Traumatol Arthrosc. 1994;2(3): Iriuchishima T, et al. Evaluation of the intercondylar roof impingement after anatomical double-bundle ACL reconstruction using 3D-CT. Knee Surg Sports Traumatol Arthrosc (2011) 19: