ABSTRACT
An alternative to the gold standard fourstrand hamstring tendon autograft for anterior cruciate ligament (ACL) reconstruction is the five-strand graft. The rationale for its use is to increase graft width to better restore the anatomical footprint and biomechanical properties of the native ACL when unable to create a four-strand graft of 8 mm in diameter. To date, there are no trials assessing the use of this wider graft and its effect on the kinematics of the knee. The aim of this study was to determine whether the use of a wider five-strand hamstring tendon autograft in ACL reconstructive surgery better replicated the kinematics of a normal non-injured knee than the gold standard four-strand graft. Forty-four patients (27 operative and 17 normal control) were recruited for this study over a 12-month period. Twenty patients underwent anterior cruciate ligament reconstruction with the four-strand hamstring tendon autograft construct and seven with the five-strand construct. All patients underwent kinematic testing using the KneeKG System (EMOVI, CA) according to a strict testing protocol. The operative group underwent testing at six (T1) and twelve (T2) weeks postoperatively. Analysis of variance was used to compare six degrees of freedom kinematic data across groups and correlations were made between kinematic data and intraoperatively measured graft width. Postoperative kinematic data revealed no statistically significant differences between graft types. At 12 weeks significant differences were seen between the four-strand and control group in the flexion/extension cycle in the preloading phase and at terminal stance. Significant correlations were seen between graft width and rotational stability at Preloading (Pearson's r=0.415) and Maximum Internal Rotation (Femoral Width Pearson's r=0.456 and Tibial Width Pearson's r=0.476) at 12 weeks regardless of graft type. This study demonstrated that to achieve anatomic knee kinematics in primary ACL reconstruction in the first 12 weeks postoperatively, a technique to optimise autograft width using a five-strand hamstring tendon autograft is useful. A relationship was found between graft width and more stable rotational kinematics of the knee during walking, regardless of graft type.
ABSTRACT
Using in situ X-ray photoelectron spectroscopy, reflection high-energy electron diffraction, and density functional theory, we analyzed the surface core level shifts and surface structure during the initial growth of ABO3 perovskites on Ge (001) by atomic layer deposition, where A = Ba, Sr and B = Ti, Hf, Zr. We find that the initial dosing of the barium- or strontium-bis(triisopropylcyclopentadienyl) precursors on a clean Ge surface produces a surface phase that has the same chemical and structural properties as the 0.5-monolayer Ba Zintl layer formed when depositing Ba by molecular beam epitaxy. Similar binding energy shifts are found for Ba, Sr, and Ge when using either chemical or elemental metal sources. The observed germanium surface core level shifts are consistent with the flattening of the initially tilted Ge surface dimers using both molecular and atomic metal sources. Similar binding energy shifts and changes in dimer tilting with alkaline earth metal adsorption are found with density functional theory calculations. High angle angular dark field scanning transmission microscopy images of BaTiO3, SrZrO3, SrHfO3, and SrHf0.55Ti0.45O3 reveal the location of the Ba (or Sr) atomic columns between the Ge dimers. The results imply that the organic ligands dissociate from the precursor after precursor adsorption on the Ge surface, producing the same Zintl template critical for perovskite growth on Group IV semiconductors during molecular beam epitaxy.
