Multi-radius posterior-stabilized mobile-bearing total knee arthroplasty partially produces in-vivo medial pivot during activity of daily living and high demanding motor task

Abstract

PurposeThe purpose of the present study was to assess the kinematical behavior of a multi-radius posterior-stabilized (PS) mobile-bearing (MB) total knee arthroplasty (TKA) during an activity of daily living (Sit-To-Stand-STS) and a high demanding motor task (Deep-Knee-Lunge-DKL) using model-based dynamic RSA. We hypothesized the achievement of medial pivoting movement in both motor tasks due to the congruent geometry of the inlay with the femoral component, which should allow good stability of the medial compartment, and to the high magnitude of rotations guaranteed by the MB on the tibial side. Methods Twenty-two randomly selected patients were recruited and prospectively evaluated. The PS MB cemented TKA was implanted with the standard technique (medial parapatellar approach, adjusted mechanical alignment). At minimum 9-month follow-up, patients were examined with model based Dynamic RSA developed in our Institute (BI-STAND DRX 2) during the execution of two motor tasks: STS and DKL. The motion parameters were evaluated using the Grood and Suntay decomposition and the low-point kinematics methods. ResultsIn the extension phase of DKL femur performed a greater antero posterior translation of 3.8 mm compared to STS between 0° and 20° of knee lexion (p < 0.05). Low-point analysis showed a medial pivoting movement in both motor tasks: in 62% of patients during STS and 48% during DKL. Varus-valgus rotations were lower than 1° during all the range-of-motion in both motor tasks without diferences. Conclusions Medial pivot was partially produced by this multi-radius PS MB TKA with some diferences during activity of daily living (STS) and high demanding motor task (DKL). Level of evidence IV.

Over-constrained kinematic of the medial compartment leads to lower clinical outcomes after total knee arthroplasty

“…In particular, the "medial pivot" kinematics (i.e., larger anterior-posterior translation of the lateral femorotibial compartment with respect to the medial one) is associated with native knee joint motion [12]. Such a pattern has already been described in previous works either intraoperatively (through surgical navigation systems) or under weight-bearing conditions (through radiographic/luoroscopic techniques) [2,3,16,23]. Nevertheless, there is no substantial evidence of the association between this specific kinematic pattern and either better postoperative outcomes or patients' satisfaction.…”

“…Patients were evaluated after a minimum of 9-month follow-up by model-based dynamic radiostereometric analysis (RSA). The RSA setup was analogous to those already published in previous articles from the same study group [7][8][9]16]. Two radiographic tubes and two digital panels were positioned perpendicularly with respect to each other and synchronized to acquire two contemporary sets of images (Fig.…”

In vivo kinematic comparison between an ultra-congruent and a posterior-stabilized total knee arthroplasty design by RSA

“…This was due to the strict inclusion criteria and the radiographic setup of the study. Moreover, the sample size was in line with previous studies conducted using the same technology [8,21,16]. The RSA evaluation was conducted at minimum 9 months after surgery.…”

“…The sample size was based on a power analysis consistent with previous studies performed with identical methodology and evaluated tasks [13,8,[6][7][8][9][10][11][12][13][14][15][16]. The two-sample t test was used, with a true diference in AP translations of 5 mm, a standard deviation of 3 mm, and a p < 0.05.…”

Letter to the Editor on “Prediction of Knee Kinematics at Time of Noncontact Anterior Cruciate Ligament Injuries Based on Bone Bruises”

“…This position, which significantly differed from the “resting” MRI position, is extremely consistent with the findings reported in a study with a similar methodology presented by our group at the Italian Congress of Orthopaedics and Traumatology (SIOT) in 2019 6 and scheduled as a free paper presentation at the 2020 European Society of Sports traumatology, Knee and Arthroscopy (ESSKA) Congress, which was not however presented due to the COVID-19 pandemic. According to our model, which included patients with both medial and lateral bone bruises (to increase matching accuracy) and that used the in vivo weightbearing condition (acquired through a Dynamic Roentgen-Stereophotogrammetric Analysis 1 – 4 , 13 ) as reference baseline position, we found that bone bruises occur with a knee flexion above 30°, and with an average anterior tibial translation of 28.4 mm, external rotation of 13.7° and knee valgus of 10.6°.

Figure 1 Knee position obtained in our research study 6 through MRI-based model-matching of the bone bruises (red for femur, blue for tibia) on medial and lateral compartments (top); knee position obtained in the study of Shi et al .

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