Subsequent projects

Dr. Alexander Nedopil
University of Würzburg
Orthopädische Klinik - König-Ludwig-Haus

Prof. Dr. Stephen Howell
University of California, Davis
Biomedical Engineering

Is deviation from the native joint lines associated with necessity of soft tissue releases and decreased patient function after total knee arthroplasty?


Mechanical alignment (MA) strives to position the femoral and tibial component perpendicular to the mechanical axes of the corresponding bone which mal-aligns most the femoral and tibial components from the native femoral and tibial joint lines during total knee arthroplasty (TKA). Measuring the femoral resections and ensuring that the thickness of the femoral resection equal the thickness of the femoral component after compensating for wear and kerf of the saw blade aligns the femoral component parallel to the native joint lines. In MA the bone resections are usually not measured. The goal of this study is to measure bone resections after MA to evaluate whether deviations from the native joint line affect the necessity of soft tissue releases and patient function.


One hundred consecutive patients treated with MA TKA will be prospectively followed. Intraoperatively, the thickness of the distal and posterior femoral resections and the thickness of the tibial resection will be measured. The difference between the recommended resection thickness to restore the orientation of the native joint line and the measured resection thickness will be calculated. The necessity of soft tissue releases will be recorded. Six months after the surgery the Oxford Knee Score (OKS) and the Forgotten Joint Score (FJS) will be obtained. The correlations between the difference of the recommended and measured resection thickness and the necessity of soft tissue releases, and the postoperative function scores will be analyzed.


Primary project: Dynamic-MRI assessment of knee kinematics and validation of rotational axes

Final Report

BaCaTeC’s continuous funding has enabled us to delve into two practical topics. The first focuses on tibial rotation measurement during total knee arthroplasty (TKA). Tibial rotation is the soft-tissue-driven axial rotation of the tibia during a flexion cycle. In a healthy knee, the tibia rotates on average 18° internally during a knee flexion from 0° to 90°. By using an insert goniometer, which measures tibial internal/external orientation relative to the femur, we have found that when a surgeon restores the patient’s pre-arthritic tibial slope, preserves the posterior cruciate ligament and implants a medial ball-in-socket with a flat-lateral insert design, the insert goniometer can guide the surgeon in selecting the insert thickness, thereby enhancing tibial rotation and facilitating coronal and patellofemoral stability. The second topic explores the consequences of mechanical aligned (MA) TKA. MA TKA intentionally changes the patient’s presurgical functional phenotype more than one category and over-resects the medial condyle more than 1 mm relative to the pre-arthritic articular surface, which significantly lowers the patient’s functional outcome and thus should be avoided. 


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