Physiological kinematics is very difficult to restore after total knee arthroplasty (TKA). A new model of medial stabilized (MS) TKA prosthesis has a high spherical congruence of the internal compartment, which guarantees anteroposterior (AP) stability associated with a flat surface of the insert in the lateral compartment, that allows a greater AP translation of the external condyle during knee flexion. The aim of our study is to evaluate, by dynamic radiostereometric analysis (RSA), the knee A cohort of 18 patients (72.1 ± 7.4 years old) was evaluated by dynamic RSA 9 months after TKA. The kinematic evaluation was carried out using the dynamic RSA tool (BI-STAND DRX 2), developed at our Institute, during the execution of sit to stand and lunge movements. The kinematic data were processed using the Grood and Suntay decomposition and the Low Point method. The patients performed two motor tasks: a sit-to-stand and a lunge. Data were related to the flexion angle versus internal-external, varus-valgus rotations and antero-posterior translations of the femur with respect to the tibia. During the sit to stand, the kinematic analysis showed the presence of a medial pivot, with a significantly greater (p=0.0216) anterior translation of the lateral condyle (3.9 ± 0.8 mm) than the medial one (1.6 ± 0.8 mm) associated with a femoral internal rotation (4.5 ± 0.9 deg). During the lunge, in the flexion phase, the lateral condyle showed a larger posterior translation than the medial one (6.2 ± 0.8 mm vs 5.3 ± 0.8 mm) associated with a femoral external rotation (3.1 ± 0.9 deg). In the extension phase, there is a larger anterior translation of the lateral condyle than the medial one (5.8 ± 0.8 mm vs 4.6 ± 0.8 mm) associated with femoral internal rotation (6.2 ± 0.9 deg). Analysing individual kinematics, we also found a negative correlation between clinical scores and VV laxity during sit to stand (R= −0.61) and that the higher femoral extra-rotation, the poorer clinical scores (R= 0.65). The finding of outliers in the VV and IE rotations analysis highlights the importance of a correct soft tissue balancing in order to allow the prosthetic design to manifest its innovative features.
Anterior cruciate ligament (acl) reconstruction is one of the most commonly performed procedures in orthopedics for acl injury. While literature suggest short-term good-to-excellent functional results, a significant number of long-term studies report unexplained early oa development, regardless type of reconstruction. The present study reports the feasibility analysis and development of a clinical protocol, integrating different methodologies, able to determine which acl reconstruction technique could have the best chance to prevent oa. It gives also clinicians an effective tool to minimize the incidence of early oa. A prospective clinical trial was defined to evaluate clinical outcome, biochemical changes in cartilage, biomechanical parameters and possible development of oa. The most common reconstruction techniques were selected for this study, including hamstring single-bundle, single-bundle with extraarticular tenodesis and anatomical double-bundle. Power analysis was performed in terms of changes at cartilage level measurable by mri with t2 mapping. A sample size of 42 patients with isolated traumatic acl injury were therefore identified, considering a possible 10% to follow-up. Subjects presenting skeletal immaturity, degenerative tear of acl, other potential risk factors of oa and previous knee surgery were excluded. Included patients were randomized and underwent one of the 3 specified reconstruction techniques. The patients were evaluated pre-operatively, intra-operatively and post-operatively at 4 and 18 months of follow-up. Clinical evaluation were performed at each time using subjective scores (koos) and generic health status (sf-12). The activity level were documented (marx) as well as objective function (ikdc). Preliminary results allow to verify kinematic patterns during active tasks, including level walking, stair descending and squatting using dynamic roentgen sterephotogrammetric analysis (rsa) methodology before and after the injured ligament reconstruction. Intra-operative kinematics was also available by using a dedicated navigation system, thus to verify knee laxity at the time of surgery. Additionally, non-invasive assessment was possible both before the reconstruction and during the whole follow-up period by using inertial sensors. Integrating 3d models with kinematic data, estimation of contact areas of stress patterns on cartilage was also possible. The presented integrate protocol allowed to acquired different types of information concerning clinical assessment, biochemical changes in cartilage and biomechanical parameters to identify which acl reconstruction could present the most chondroprotective behavior. Preliminary data showed all the potential of the proposed workflow. The study is on-going and final results will be shortly provided.
