Impingement pressure in the anatomical and nonanatomical anterior cruciate ligament reconstruction: a cadaver study.
ABSTRACT Although the literature has extensively discussed impingement after anterior cruciate ligament (ACL) reconstruction, the definition of impingement is vague, and impingement pressure has not been well investigated as a function of tunnel position.
To determine the amount of impingement pressure between the ACL and posterior cruciate ligament (PCL) and between the ACL and notch roof in the native ACL, the single-bundle ACL reconstruction with different tunnel placements, and the anatomical double-bundle ACL reconstruction.
Controlled laboratory study.
Fifteen fresh-frozen nonpaired human cadaver knees were used. In each knee, different femoral and tibial tunnels were created, which allowed different graft placements. A single graft was placed in 3 positions: tibial anteromedial (AM) to femoral AM (anatomical), tibial posterolateral (PL) to femoral high AM (nonanatomical/mismatch), and tibial AM to femoral high AM. Double grafts were placed in an anatomical fashion (AM to AM and PL to PL). In each case, pressure-measuring films were inserted between the ACL and roof, the ACL and PCL, and the AM and PL bundles (for double-bundle group only). Knees were then moved with 40 N of force and from full flexion to full extension, and the pressure pattern on the film was analyzed.
Compared with other groups, only the AM-high AM group showed significantly higher roof impingement pressure (P < .05). There was no significant difference in PCL impingement pressure between the intact ACL group and any of the reconstructed groups. No impingement pressure was observed between the grafts in the anatomical double-bundle ACL reconstruction.
This study evaluated the effect of different tunnel placements on the impingement pressure after ACL reconstruction. Anatomical single- or double-bundle ACL reconstruction and nonanatomical tibial PL-femoral high AM ACL reconstruction do not cause roof, PCL, and interbundle impingement.
Surgeons can perform the anatomical double-bundle ACL, anatomical single-bundle, and nonanatomical tibial PL-femoral high AM reconstructions as impingement-free reconstructions.
Conference Paper: Oxide Defect Density, Failue Rate and Screen Yield[Show abstract] [Hide abstract]
ABSTRACT: The concepts of "weakness factor", w, and defect density, D(w), are introduced for thin oxide study. The defect density is sensitive to silicon material qualities and process conditions and can be characterized by simple time-to-breakdown or ramp-breakdown field measurements (see Figure 1). We present an experimentally verified method of predicting the time-dependent dielectric breakdown (TDDB) behavior for different oxide area and field using D(w). We also demonstrate a method for determining the stress time and stress field required for screening to meet a given failure rate for any oxide area and operating field, and the yield loss due to screening. Based on this study, there appears to be a large window between adequate screen and over-screen.VLSI Technology, 1986. Digest of Technical Papers. Symposium on; 06/1986
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ABSTRACT: To reveal the relationship between anatomically placed anterior cruciate ligament (ACL) graft and the intercondylar roof using three-dimensional computed tomography (3D-CT). Twenty-four patients undergoing anatomical double-bundle ACL reconstruction were included in this study. Anatomical double-bundle ACL reconstruction was performed with two femoral tunnels (antero-medial; AM and postero-lateral; PL) and two tibial tunnels. Hamstring autograft was used in all cases. Six to eight weeks after operation and when the subjects had obtained full extension of the knee, 3D-CT was performed with full knee extension. In the 3D-CT, the ACL graft was also reconstructed and visualized three dimensionally. Tunnel placement was evaluated with 3D-CT and intra-operative radiographs. The extension angle of the knee was also evaluated with 3D-CT. No intercondylar roof impingement was observed. In 12 subjects, the ACL graft touched the roof (Touch group) but no graft deformation was observed. In 12 subjects, no roof-graft contact was observed (Non-touch group). No significant difference in femoral and tibial tunnel placement was observed between the Touch and Non-touch groups. All subjects attained full knee extension. We believe that 3D-CT is an effective means of evaluating impingement after ACL reconstruction. For the clinical relevance, when the grafts are positioned in an anatomical fashion, there is no risk of impingement, and surgeons can perform anatomical double-bundle ACL as an impingement-free reconstruction. Level of evidence: III (Case control study).Knee Surgery Sports Traumatology Arthroscopy 12/2010; 19(4):674-9. DOI:10.1007/s00167-010-1331-x · 2.84 Impact Factor
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ABSTRACT: Background: Minimal attention has been directed toward tibial tunnel position and the native tibial anterior cruciate ligament (ACL) footprint. Purpose: To evaluate the effect of tibial tunnel position on restoration of knee kinematics and stability after ACL reconstruction. Study Design: Controlled laboratory study. Methods: Ten paired cadaveric knees were subjected to biomechanical testing (standardized Lachman and mechanized pivot-shift examination). With each maneuver, a computer-assisted navigation system recorded the 3-dimensional motion path of a tracked point at the center of the tibia, medial tibial plateau, and lateral tibial plateau. The testing protocol consisted of evaluation in the intact state and after complete ACL transection, after ACL transection with bilateral meniscectomy, and after ACL reconstruction using 3 tibial tunnel positions-over the top (OTT), anterior footprint (AT), and posterior footprint (PT)-with a standard femoral socket placed in the center of the femoral footprint. Repeated-measures analysis of variance with a post hoc Tukey test compared measured translations with each condition. Results: A significant difference in anterior translation was seen with Lachman examination between the ACL-deficient condition and both the OTT and AT reconstructions, but no significant difference was observed between the ACL-deficient and PT reconstruction. The OTT and AT constructs were significantly better in limiting anterior translation of the lateral compartment compared with the PT ACL reconstruction during a pivot-shift maneuver in the ACL- and meniscal-deficient knee. However, anteriorizing the tibial position was accompanied by a correspondingly greater risk and magnitude of graft impingement in extension.The American Journal of Sports Medicine 02/2011; 39(2):366-73. DOI:10.1177/0363546510388157 · 4.70 Impact Factor