Knee varus alters three-dimensional ankle alignment in standing- a study with upright computed tomography

Varus knee osteoarthritis with ankle osteoarthritis demonstrates greater hindfoot inversion and larger ankle inversion loading during gait following total knee arthroplasty compared to varus knee osteoarthritis alone

PURPOSE

Although patients with varus knee osteoarthritis (KOA) and concurrent ankle osteoarthritis (AOA) may experience increased ankle joint pain after total knee arthroplasty (TKA), the underlying mechanism remains unclear. This study aimed to investigate the effects of concurrent AOA on ankle and hindfoot alignment, frontal plane ankle and hindfoot biomechanics during gait following TKA and the clinical outcomes.

METHODS

Twenty-four patients with varus KOA who underwent TKA were included in this retrospective cohort study. Patients were categorized into two groups: with and without AOA. Radiographic evaluations of lower-limb, ankle and hindfoot alignment, and knee and ankle clinical outcomes were conducted preoperatively and 6 months postoperatively. In addition, gait analyses were performed to investigate knee, ankle and hindfoot kinematics and kinetics. Each data was compared between patients with and without AOA.

RESULTS

Concomitant AOA was found in eight ankles. The AOA group exhibited greater postoperative hindfoot varus and increased postoperative ankle pain than the non-AOA group. Gait analysis showed no significant differences in knee varus alignment or tibial tilt after TKA between the groups. However, the AOA group demonstrated significantly greater hindfoot inversion and larger ankle inversion loading.

CONCLUSION

One third of patients who underwent TKA had concurrent AOA associated with hindfoot varus. Despite achieving proper coronal knee alignment postoperatively, these patients experienced greater hindfoot and ankle joint inversion load during gait. Surgeons should consider the inability to evert the hindfoot and the possibility of increased ankle joint pain when planning and performing TKA.

LEVEL OF EVIDENCE

Level III.

Extra-articular location of the three-dimensional mechanical axis in advanced knee osteoarthritis: an upright computed tomography study

PURPOSE

One of the most widely used benchmarks of lower-limb alignment is the mechanical axis (MA), which passes through the centers of the femoral head and the ankle in the weight-bearing position. However, where the MA passes through three-dimensionally (3D) is unclear. We investigated the MA in 3D (3D-MA) in knee osteoarthritis (OA) using upright computed tomography (CT).

MATERIALS AND METHODS

This study included 66 varus OA knees from 38 patients [age 70.0 (64.8-77.0) years; median (interquartile range)]. The 3D-MA was determined using upright CT data and compared among Kellgren-Lawrence (KL) grades. Further, correlations between the 3D-MA and other parameters were evaluated.

RESULTS

The 3D-MA was located at 5.3 (1.3-14.4)% medially and 7.1 (0.7-15.3)% posteriorly on the tibial plateau in KL-1, and was translated medioposteriorly with increased KL grade. The 3D-MA in KL-3 [30.6 (22.6-42.6)% medially and 50.9 (45.8-80.2)% posteriorly] and KL-4 [56.7 (48.5-62.9)% medially and 92.3 (50.2-127.1)% posteriorly] was located extra-articularly. The mediolateral position of the 3D-MA correlated with the femorotibial angle [correlation coefficient (CC) = - 0.85, p < 0.001], and the anteroposterior position of the 3D-MA correlated with the knee flexion angle (CC = - 0.93, p < 0.001).

CONCLUSION

Our analysis demonstrated that the 3D-MA in low-grade OA knees passes slightly medial and posterior to the knee center, and the 3D-MA is translated medioposteriorly with the progression of knee OA. Further, the 3D-MA is translated medially with varus progression and posteriorly with the progression of knee flexion contracture.

CT in osteoarthritis: its clinical role and recent advances

Computed tomography (CT) is a widely available imaging method and considered as one of the most reliable techniques in bone assessment. Although CT has limited tissue contrast and needs radiation exposure, it has several advantages like fast scanning time and high spatial resolution. In this regard, CT has unique roles in osteoarthritis (OA) and its variable utilities have been reported. Hence, this review highlights the clinical role of CT in OA of representative joints. In addition, CT showed the several technical advancements recently, for example, acquiring the CT image with standing, obtaining the dual-energy data, and novel photon-counting detector development. Therefore, the recent studies and potential utility of these new CT systems in OA are also discussed.

Lateral wedge insoles and their use in ankle instability

The aim of the present study is to assess the immediate effects of applying lateral wedge insoles of different heights (0.00, 0.3, 0.4, and 0.6 cm) in patients with chronic ankle instability (CAI) in normal and supinated feet during a Star Excursion Balance Test (SEBT) and in the reflex response of Peroneus Longus (PL), Peroneus Brevis (PB), and Tibialis Anterior (TA) over a 30° inversion of the feet. The effects of the height of the wedges were assessed using a double-blind, crossover design. In total, 25 participants were allocated into two groups, depending on the foot posture (Normal = 12, Supinated = 13) and performed the tests in a random fashion. Reaction time (RT) of stabilizing muscles of the ankle was measured using superficial electromyography (EMG) and postural balance with the SEBT. Foot posture did not show any significant effects on the analyzed variables. Nonetheless, the use of a 0.3 cm external rearfoot wedge (PB p = 0.002; PL p = 0.066 and TA p = 0.006) and 0.6 cm (PB p = 0.043; PL p = 0.058 and TA p = 0.071) reduces RT in stabilizing muscles of the ankle and improves results in SEBT, except for the anterolateral direction, in subjects with CAI. Therefore, our results suggest that the use of lateral wedge insoles could reduce RT and improve dynamic balance in chronic ankle instability.