The Foot and Ankle Kinematics of a Simulated Progressive Collapsing Foot Deformity During Stance Phase: A Cadaveric Study

Abstract

Background: Progressive collapsing foot deformity (PCFD) is a complex pathology associated with tendon insufficiency, ligamentous failure, joint malalignment, and aberrant plantar force distribution. Existing knowledge of PCFD consists of static measurements, which provide information about structure but little about foot and ankle kinematics during gait. A model of PCFD was simulated in cadavers (sPCFD) to quantify the difference in joint kinematics and plantar pressure between the intact and sPCFD conditions during simulated stance phase of gait. Methods: In 12 cadaveric foot and ankle specimens, the sPCFD condition was created via sectioning of the spring ligament and the medial talonavicular joint capsule followed by cyclic axial compression. Specimens were then analyzed in intact and sPCFD conditions via a robotic gait simulator, using actuators to control the extrinsic tendons and a rotating force plate underneath the specimen to mimic the stance phase of walking. Force plate position and muscle forces were optimized using a fuzzy logic iterative process to converge and simulate in vivo ground reaction forces. An 8-camera motion capture system recorded the positions of markers fixed to bones, which were then used to calculate joint kinematics, and a plantar pressure mat collected pressure distribution data. Joint kinematics and plantar pressures were compared between intact and sPCFD conditions. Results: The sPCFD condition increased subtalar eversion in early, mid-, and late stance ( P < .05), increased talonavicular abduction in mid- and late stance ( P < .05), and increased ankle plantarflexion ( P < .05), adduction ( P < .05), and inversion ( P < .05). The center of plantar pressure was significantly ( P < .01) medialized in this model of sPCFD and simulated stance phase of gait. Discussion: Subtalar and talonavicular joint kinematics and plantar pressure distribution significantly changed with the sPCFD and in the directions expected from a PCFD foot. We also found that ankle joint kinematics changed with medial and plantar drift of the talar head, indicating abnormal talar rotation. Although comparison to an in vivo PCFD foot was not performed, this sPCFD model produced changes in foot kinematics and indicates that concomitant abnormal changes may occur at the ankle joint with PCFD. Clinical Relevance: This study describes the dynamic kinematic and plantar pressure changes in a cadaveric model of simulated progressive collapsing foot deformity during simulated stance phase.

Axial Plane Rotation of the Talus in Progressive Collapsing Foot Deformity: A Weightbearing Computed Tomography Analysis

“…A recent robotic cadaveric gait study by Henry et al 15 demonstrated this aberrant talar internal rotation in their simulated PCFD model. Although they confirmed the 3D talar motion within the mortise in PCFD, the authors did not provide an explanation for the aberrant internal rotation of the talus.…”

“…24 PCFD has been described as a 3-dimensional (3D) deformity centered around the talus, with eversion of the subtalar joint, lateral/dorsal translation of the navicular, and collapse of the medial longitudinal arch. 15,21,32 The motion of the talus itself in the mortise also has been described, such as narrowing of the posterior tibiotalar joint from talar sagging in the sagittal plane or valgus talar tilt in the coronal plane, 1,7,16,18 implying that multiplanar motion of the talus also occurs at the tibiotalar joint.…”

“…Given that numerous cadaveric studies have established that the spring ligament complex acts as a sling or hammock, preventing talar head plantarflexion and adduction, 6,17 it is reasonable to assume that axial rotation of the talus occurs in conjunction with talar sagging. A recent cadaveric gait study demonstrated that the talus internally rotates relative to the tibia in a simulated PCFD model 15 ; however, radiographic evidence in vivo demonstrating this phenomenon is scarce, possibly because plain radiographs have limited ability to display axial plane measurements of the talar rotation in the ankle mortise.…”

Modern Patellofemoral Arthroplasty

“…Future research should be aimed at incorporating robotic technologies into both surgical procedure and clinical practice, and assessing the impact on both implant position (particularly femoral component rotation) and patient outcome 114,115 . Ultimately, less-invasive, bone and soft tissue-sparing techniques will serve to benefit the patient, but only after they are vetted by extensive research and clinical practice.…”

Medium- to Long-term Results of Nonanatomic Spring Ligament Reconstruction Using an Allograft Tendon in Progressive Collapsing Foot Deformity With Severe Abduction Deformity

“…3,12,13,22 A tear of the spring ligament results in abduction deformity at the TN joint, which increases the stress on the tendons and ligaments of the medial foot which then leads to further foot collapse. 19,22 Recent cadaveric studies have demonstrated that the spring ligament maintains medial tibiotalar stability by forming a large confluent ligament (tibiospring ligament) with the superficial deltoid ligament, 7,11 highlighting its crucial role in preventing the peritalar instability observed in PCFD.…”