Total knee arthroplasty in valgus knee deformities continues to be a challenge for a surgeon. Approximately 10% of patients who undergo total knee arthroplasty have a valgus deformity. While performing total knee arthroplasty in a severe valgus knee, one should aware with the technical aspects of surgical exposure, bone cuts of the distal femur and proximal tibia, medial and lateral ligament balancing, flexion and extension gap balancing, creating an appropriate tibiofemoral joint line, balancing the patellofemoral joint, preserving peroneal nerve function, and selection of the implant regarding constraint. Restoration of neutral mechanical axis and correct ligament balance are important factors for stability and longevity of the prosthesis and for good functional outcome. Thus, our review aims to provide step by step comprehensive knowledge about different surgical techniques for the correction of severe valgus deformity in total knee arthroplasty.

Purpose To evaluate if there was a correlation between in vivo kinematics of a medial-stabilized (MS) total knee arthroplasty (TKA) and post-operative clinical scores. We hypothesized that (1) a MS-TKA would produce a medial pivot movement and that (2) this speciic pattern would be correlated with higher clinical scores. Methods 18 patients were evaluated through clinical and functional scores evaluation (Knee Society Score clinical and functional, Womac, Oxford), and kinematically through dynamic radiostereometric analysis (RSA) at 9 months after MS-TKA, during the execution of a sit-to-stand and a lunge motor task. The anteroposterior (AP) Low Point translation of medial and lateral femoral compartments was compared through Student's t test (p < 0.05). A correlation analysis between scores and kinematics was performed through the Pearson's correlation coeicient r. Results A signiicantly greater (p < 0.0001) anterior translation of the lateral compartment with respect to the medial one was found in both sit-to-stand (medial 2.9 mm ± 0.7 mm, lateral 7.1 mm ± 0.6 mm) and lunge (medial 5.3 mm ± 0.9 mm, lateral 10.9 mm ± 0.7 mm) motor tasks, thus resulting in a medial pivot pattern in about 70% of patients. Signiicant positive correlation in sit-to-stand was found between the peak of AP translation in the lateral compartment and clinical scores (r = 0.59 for Knee Society Score clinical and r = 0.61 for Oxford). Moreover, we found that the higher peak of AP translation of the medial compartment correlated with lower clinical scores (r = − 0.55 for Knee Society Score clinical, r = − 0.61 for Womac and r = − 0.53 for Oxford) in the lunge. A negative correlation was found between Knee Society Score clinical and VV laxity during sit-to-stand (r = − 0.56) and peak of external rotation in the lunge motor task (r = − 0.66). Conclusions The MS-TKA investigated produced in vivo a medial pivot movement in about 70% of patients in both examined motor tasks. There was a correlation between the presence of medial pivot and higher post-operative scores. Level of evidence IV.

Functional outcome of elderly patients treated for odontoid fracture. A multicenter study.

PurposeThe aim of the present study was to compare the in vivo under weight‐bearing kinematic behavior of a posterior‐stabilized (PS) and an ultra‐congruent (UC) total knee arthroplasty (TKA) model during a sit‐to‐stand motor task, a common activity of daily life. MethodsA cohort of 16 randomly selected patients (8 PS Persona Zimmer, 8 UC Persona Zimmer) was evaluated through dynamic radiostereometric analysis (RSA) at a minimum of 9 months after TKA, during the execution of a sit‐to‐stand. The anteroposterior (AP) translation of the femoral component and the AP translation of the low point of medial and lateral femoral compartments were compared through Student’s t test (p < 0.05). ResultsA significantly greater anterior translation of the femoral component was found for the PS group compared to the UC group. The flexion interval where statistical significance was found was between 30° and 0° (p = 0.017). Both groups showed a significantly greater anterior translation of the low point of the lateral compartment with respect to the medial one (PS: p = 0.012, UC: p = 0.018). This was consistent with a medial‐pivot pattern. Furthermore, a significantly greater anterior translation of the medial compartment was found in the PS group compared to the UC group (p = 0.001). The same pattern was observed for the lateral compartment (p = 0.006). ConclusionsThe TKA designs evaluated in the present study showed comparable in‐vivo kinematics with regards to medial pivot pattern but differences in absolute AP translation. Specifically, the UC design showed greater AP stability than the PS design. This finding could be positive in terms of implant stability, but negative in terms of premature polyethylene wear and thus implant failure. This remains to be verified in studies with a larger sample size and longer follow‐up. Level of evidenceIV.

Purpose To assess, using model‐based dynamic radiostereometric analysis (RSA), the biomechanical behaviour of a new design posterior‐stabilized (PS) fixed‐bearing (FB) total knee arthroplasty (TKA) in vivo while patients performing two common motor tasks. The hypothesis was that model‐based dynamic RSA is able to detect different behaviour of the implant under weight‐bearing and non‐weight‐bearing conditions. Methods A cohort of 15 non‐consecutive patients was evaluated by dynamic RSA 9 months after TKA implantation. The mean age of patients was 73.4 (65–72) years. The kinematic evaluations were performed using an RSA device (BI‐STAND DRX 2) developed in our Institute. The patients were asked to perform two active motor tasks: sit‐to‐stand in weight‐bearing condition; range of motion (ROM) while sitting on the chair. The motion parameters were evaluated using the Grood and Suntay decomposition and the low‐point kinematics methods. Results The dynamic RSA evaluation showed a significant difference (p < 0.05) between the biomechanical behaviour of the prosthesis during the two motor tasks. When subjected to the patient weight (in the sit‐to‐stand) the low point of the medial compartment had a shorter motion (5.7 ± 0.2 mm) than the lateral (11.0 ± 0.2 mm). This realizes a medial pivot motion as in the normal knee. In the ROM task, where the patient had no weight on the prosthesis, this difference was not present: the medial compartment had a displacement of 12.7 ± 0.2 mm, while the lateral had 17.3 ± 0.2 mm. Conclusions Model‐based RSA proved to be an effective tool for the evaluation of TKA biomechanics. In particular, it was able to determine that the fixed‐bearing posterior‐stabilized TKA design evaluated in this study showed a medial pivoting movement under weight‐bearing conditions that was not present when load was not applied. Under loading conditions what drives the pattern of movement is the prosthetic design itself. By the systematic use of this study protocol future comparisons among different implants could be performed, thus contributing significantly to the improvement of TKA design. Level of evidence IV.