Posterior Tibial Slope Increases Anterior Cruciate Ligament Stress in Bi-Cruciate Retaining Total Knee Arthroplasty: In Vivo Kinematic Analysis

The study design involved here is experimental in nature. The resection of the anterior cruciate ligament (ACL) during conventional total knee arthroplasty (TKA) has been considered a potential factor leading to abnormal in vivo knee kinematics. Bi-cruciate retaining (BCR) TKA designs allow the preservation of the ACL with the potential to restore native knee kinematics. This study aimed to investigate the effect of posterior tibial slope (PTS) on stress experienced by the ACL during weight bearing sit-to-stand (STS) and single-leg deep lunge. The ACL elongation patterns were measured in 30 unilateral BCR TKA patients during weight-bearing STS and single-leg deep lunge using a validated dual fluoroscopic tracking technique. The minimum normalized stress within the anteromedial (AM) and posterolateral (PL) bundle of the ACL during weight-bearing STS and single-leg deep lunge was found at a PTS of 3.7 degrees. The maximum AM and PL bundle stresses were observed at a PTS of 8.5 and 9.3 degrees, respectively during STS and at 8.4, and 9.1 degrees, respectively during single-leg deep lunge. There was a significant positive correlation between PTS and stress observed within the AM and PL bundle of the ACL during weight-bearing STS (R 2 = 0.37; p < 0.01; R2 = 0.36; p = 0.01) and single-leg deep lunge (R 2 = 0.42; p < 0.01; R 2 = 0.40; p < 0.01). The study demonstrates that PTS of operated BCR TKA knees has a significant impact on the stress experienced by the preserved ACL during weight-bearing STS and single-leg deep lunge. This suggests that avoiding excessive PTS may be one of the surgical implant alignment factors to consider during surgery to minimize increased loading of the preserved ACL.

ACL partial tears: Is it possible to define which bundle is compromised using magnetic resonance?

Objective: Anterior Cruciate Ligament (ACL) tears are diagnosed through a clinical examination and imaging confirmation. Magnetic Resonance Imaging (MRI) is the diagnostic image method of choice; however the sensitivity is variable for the different kind of partial injuries. The objective of this study is to evaluate the effectiveness of the MRI in the diagnosis of clinically unstable partial ACL tears that already underwent surgical treatment and define which bundle was compromised. Methods: A retrospective review of the preoperative MRI of 40 patients who were surgically operated because of ACL tears was executed. In all cases, arthroscopic findings defined one bundle was intact. All MRI were reviewed by a single osteo-articular specialist staff of the Image Department. All injuries were classified according to which bundle was involved (anteromedial (AM) or posterolateral (PL)). Results were compared with the surgical findings. Results: Concordance between MRI and arthroscopic findings was 42.5% (17/40 patients). If we analyze AM and PL tears separately we found that the concordance was 51.5% for AM bundle tears (17/33) and 0% for PL bundle tears (0/7). Conclusion: Definitive diagnosis and surgical indication for ACL tears requires both, clinical examination and image diagnosis. Over 65% of partial tears are misdiagnosed by MRI only.

ANATOMICAL STUDY OF THE MORPHOMETRY OF THE ANTERIOR CRUCIATE LIGAMENT ATTACHMENT SITES. Estudio anatómico de la morfometría de los sitios de fijación del ligamento cruzado anterior

Incidence of anterior cruciate ligament (ACL) rupture and its consequent reconstruction is on the rise. In contributing to the achievement of anatomic reconstruction this study seek to provide information regarding the position and variability of the tibial attachment sites, dimensions of femoral insertions and compare these measurements in males and females, and in right and left knees. Thirty one cadaveric knees (15 right and 16 left from 9 females and 7 males, mean age 77 years) were dissected. Various ACL footprint dimensions were taken. The mean length and width of the tibial anteromedial (AM) bundle footprint were 8.9 and 9.8 mm while that of the posterolateral (PL) bundle were 9.3 and 8.0 mm respectively. The mean length and width of the tibial AM and PL bundles in males were 8.5 and 9.8 mm, and 9.1 and 8.3 mm while corresponding values in females were and 9.2 and 9.7 mm, and 9.4 and 7.8 mm respectively. Males had larger femoral footprints (P=0.020) and tibial plateau (P<0.001). No significant difference between the right and left knees were observed. The mean anatomical positions of the AM and PL bundles were 46.0% and 50.0% of the mediolateral diameter of the tibial plateau. The mean length and width of the ACL femoral insertion sites were 8.3 and 7.7 mm for the AM bundle and 7.8 and 6.9 mm for the PL bundle respectively. The smaller ACL attachment parameters in females could be a contributing factor to the higher incidence of ACL rupture in female athletes. La incidencia de la rotura del ligamento cruzado anterior (LCA) y su consiguiente reconstrucción está en aumento. Para contribuir a la actualización de la reconstrucción anatómica del ligamento cruzado anterior, este estudio proporciona información sobre la posición y la variabilidad de los sitios de fijación en la tibia, las dimensiones de las inserciones femorales, así como las relaciones de estas mediciones en hombres y mujeres y en las rodillas derecha e izquierda. Se disecaron treinta y un (15 rodillas de cadáver derecha, 16 izquierda, de 9 mujeres y 7 hombres, con una edad media de 77 años). Se tomaron diversas dimensiones de la huella del LCA. La longitud media y la anchura de la huella del haz tibial anteromedial (AM) eran 8,9 mm y 9,8 mm mientras que la del haz posterolateral (PL) eran 9,3 mm y 8 mm respectivamente. La longitud media y la anchura de la AM tibial y paquetes PL en los varones eran 8,5 y 9,8 mm, y 9,1 y 8,3 mm, mientras que los valores correspondientes en las mujeres eran 9,2 y 9,7 mm, y 9,4 y 7,8 mm, respectivamente. Los varones tenían huellas femorales (P = 0,045 para AM, P = 0,043 para PL) y la meseta tibial (P <0,001) más grandes. No se observó ninguna diferencia significativa entre la rodilla derecha e izquierda. Las posiciones anatómicas medias de los haces de AM y PL fueron 46% y 50% del diámetro mediolateral de la meseta tibial. La longitud media y la anchura de los sitios de inserción femoral del LCA fueron 8,3 y 7,7 mm para el paquete de AM y 7,8 y 6,9 mm para el paquete PL respectivamente. Los parámetros más pequeños de fijación del LCA en las mujeres podría ser un factor que contribuye a la mayor incidencia de rotura del LCA en mujeres atletas.

Locally flat PL submanifolds with codimension two

We refer the reader to the IHES notes of Zeeman (14) for basic facts about PL (or piecewise-linear) manifolds. If Mm is a locally flat PL-submanifold of Qm+2, our object will be to study the normal structure of M in Q: one of our main results is:There exists a PL-bundle over M, with fibre a 2-simplex, which is PL-homeomorphic to a neighbourhood of M in Q; moreover, the bundle and homeomorphism are unique up to equivalence. We also make an application to smoothing theory.