Papers by Hamed Malakoutikhah
Foot & Ankle Orthopaedics, Sep 30, 2023
Clinical biomechanics, Jul 1, 2024
Journal of Orthopaedic Research, Jan 3, 2022
The contribution of each of the ligaments in preventing the arch loss, hindfoot valgus, and foref... more The contribution of each of the ligaments in preventing the arch loss, hindfoot valgus, and forefoot abduction seen in progressive collapsing foot deformity (PCFD) has not been well characterized. An improved understanding of the individual ligament contributions to the deformity would aid in selecting among available treatments, optimizing current surgical techniques, and developing new ones. In this study, we evaluated the contribution of each ligament to the maintenance of foot alignment using a finite element model of the foot reconstructed from computed tomography scan images. The collapsed foot was modeled by simulating the failure of all the ligaments involved in PCFD. The ligaments were removed one at a time to determine the impact of each ligament on foot alignment, and then restored one at a time to simulate isolated reconstruction. Our findings show that the failure of any one ligament did not immediately lead to deformity, but that combined failure of only a few (the plantar fascia, long plantar, short plantar, deltoid, and spring ligaments) could lead to significant deformity. The plantar fascia, deltoid, and spring ligaments were primarily responsible for the prevention of arch collapse, hindfoot valgus, and forefoot abduction, respectively. Moreover, to produce deformity, a considerable amount of attenuation in the spring, tibiocalcaneal, interosseous talocalcaneal, plantar naviculocuneiform, and first plantar tarsometatarsal ligaments, but only a small amount in the plantar fascia, long plantar, and short plantar ligaments was needed. The results of this study suggest that the ability of a ligament to prevent deformity may not correlate with its attenuation in a collapsed foot.
Journal of Orthopaedic Research, Jun 2, 2022
Background: Progressive collapsing foot deformity results from degeneration of the ligaments and ... more Background: Progressive collapsing foot deformity results from degeneration of the ligaments and the posterior tibial tendon (PTT). Our understanding of the relationship between the failures of them remains incomplete. We sought to improve this understanding through computational modeling of force in these soft tissues. Methods: The impact of PTT and ligament tears on force changes in the remaining ligaments was investigated by quantifying ligament force changes during simulated ligament and tendon cutting in a previously validated finite element model of the foot. The ability of the PTT to restore foot alignment in a collapsed foot was evaluated by increasing the PTT force in a foot with attenuated ligaments and comparing the alignment angles to the intact foot. Results: Rupture of any one of the ligaments led to overloading the remaining ligaments, except for the plantar naviculocuneiform, first plantar tarsometatarsal, and spring ligaments, where removing one led to unloading the other two. The attenuation of the plantar fascia, long plantar, short plantar, and spring ligaments significantly overloaded the deltoid and talocalcaneal ligaments. Isolated PTT rupture had no effect on foot alignment, but did increase the force in the deltoid and spring ligaments. Increasing the force within the PTT to 30% of body weight was effective at restoring foot alignment during quiet stance, primarily through reducing hindfoot valgus and forefoot abduction as opposed to improving arch height. Conclusion: The attenuation of any one ligament often leads to overload of the remaining ligaments which may lead to progressive degeneration. The PTT can maintain alignment in the collapsing foot, but at an increased load which could lead to its injury. Early intervention, in the form of ligament repair or reconstruction, might be used to prevent the progression of deformity. Moreover, strengthening the PTT through therapeutic exercise might improve its ability to restore foot alignment.
Foot & Ankle Orthopaedics, Oct 1, 2022
Category: Hindfoot; Ankle; Ankle Arthritis Introduction/Purpose: Patients with longstanding progr... more Category: Hindfoot; Ankle; Ankle Arthritis Introduction/Purpose: Patients with longstanding progressive collapsing foot deformity (PCFD) often develop osteoarthritis of the peritalar (tibiotalar, subtalar, and talonavicular) joints, which can be symptomatic or can lead to fixed deformities that further complicate the treatment of other sequalae of the deformity (Mann, 1992). Degeneration and subsequent tearing of the arch supporting ligaments leads to altered joint contact mechanics which is a likely causative factor in the development of arthrosis (Hauser and Dolan, 2011). However, the initial effect of ligament tears on changes in joint contact mechanics in the collapsing foot has not been well characterized. The goal of this work was to compare the joint contact mechanics between the neutrally aligned and the flexible flatfoot (collapsed foot). Methods: A validated finite element model of the foot (Malakoutikhah et al., 2022a) was used to compare joint contact pressures between the normally aligned and the collapsed foot. The model of the foot constructed from CT scan images of a female cadaveric foot weighing 60 kg included all 28 bones, 72 ligaments, cartilage, and an encapsulating soft tissue. The model was loaded with 0.5 body weight applied at the center of mass and 0.25 body weight applied to the Achilles tendon simulating quiet stance. The collapsed foot model was created by simulated transection of the plantar fascia, long plantar, short plantar, deltoid, and spring ligaments and unloading of the posterior tibial tendon (Malakoutikhah et al., 2022b). The joint contact pressure maps were determined for both the neutrally aligned and collapsed foot models. The average and peak contact pressures were compared. Results: The peak contact pressures were increased in the tibiotalar and subtalar joints, but paradoxically were decreased in the talonavicular joint in the collapsed as compared to the neutrally aligned foot (Figure 1). The center of pressure was markedly different in all three joints between the neutral and collapsed foot conditions. Specifically, collapsing the foot caused two centers of the talonavicular joint peak pressure to shift towards the central region of the navicular bone, which were evenly distributed in the lateral and medial regions in the neutrally aligned foot. In the subtalar joint, the peak pressure that was uniformly distributed in the lateral and medial regions of the posterior facet in the neutrally aligned foot shifted towards the lateral region in the collapsed foot. Similarly, the peak contact pressure across the tibiotalar joint moved from the center to the lateral region when the foot collapsed. Conclusion: Degenerative tearing of the arch supporting ligaments in PCFD leads to an increase and laterization of the contact pressure in the tibiotalar and subtalar joints with a decrease of the pressure in the talonavicular joint. The paradoxical unloading of the talonavicular joint may be a result of the inability of the malaligned medial column to transmit force from the hindfoot to the forefoot. One implication of this work is that future treatments of PCFD might be directed towards normalizing contact pressure within the peritalar joints to prevent the progression of disease and the development of arthrosis.
Clinical Biomechanics, Apr 1, 2022
BACKGROUND Patients with longstanding progressive collapsing foot deformity often develop osteoar... more BACKGROUND Patients with longstanding progressive collapsing foot deformity often develop osteoarthritis of the ankle, midfoot, or hindfoot joints, which can be symptomatic or lead to fixed deformities that complicate treatment. The development of deformity is likely caused by ligament degeneration and tears. However, the effect of individual ligament tears on changes in joint contact mechanics has not been investigated. METHODS A validated finite element model of the foot was used to compare joint contact areas, forces, and pressures between the intact and collapsed foot, and to evaluate the effect of individual ligament tears on joint contact mechanics. FINDINGS Collapsing the foot resulted in an increase in contact pressure in the subtalar, calcaneocuboid, tibiotalar, medial naviculocuneiform, and first tarsometatarsal joints but a decrease in contact pressure in the talonavicular joint. Rupture of the spring ligament was the main contributor to increased calcaneocuboid and subtalar joint contact pressures and decreased medial naviculocuneiform and first tarsometatarsal joint contact pressures, as well as talonavicular subluxation. Deltoid ligament rupture was the primary source of increased contact pressure in the medial naviculocuneiform, first tarsometatarsal, and tibiotalar joints. INTERPRETATION Degenerative tearing of the ligaments in flatfoot deformity leads to increased joint contact pressures, primarily in the calcaneocuboid, subtalar, and tibiotalar joints, which has been implicated in the development of osteoarthritis in these joints. An improved understanding of the relationship between ligament tears and joint contact pressures could provide support for the use of ligament reconstructions to prevent the development of arthrosis.
Foot & Ankle Orthopaedics, Apr 1, 2022
Category:Ankle; Midfoot/Forefoot; OtherIntroduction/Purpose:Progressive collapsing foot deformity... more Category:Ankle; Midfoot/Forefoot; OtherIntroduction/Purpose:Progressive collapsing foot deformity (PCFD) is a degenerative disorder of ligaments and tendons that encompasses a wide range of deformities, including arch height loss, hindfoot valgus, and forefoot abduction. The posterior tibial tendon (PTT) is the main active stabilizer of the arch. We hypothesize that it may become injured secondarily as it attempts to maintain foot stability when the ligaments, passive stabilizers, are attenuated. Several cadaveric studies have been conducted on the role of the PTT in PCFD, but the ability of the PTT to compensate for the loss of the ligamentous stabilizers has not been clearly characterized. We developed a high-fidelity finite element model of the foot to determine the PTT's ability to maintain foot stability when the principle ligamentous stabilizers are attenuated.Methods:The encapsulating soft tissue (EST), cartilage, and cortical and trabecular bones were reconstructed in Mimics from CT scan images of a female cadaveric foot weighing 60 kg. Tension-only spring elements were used to reflect all the ligaments in ANSYS. Bodyweight and tendon forces were applied using force vectors in the direction of their lines of action. The proximal tibia was fixed only in the vertical direction, allowing it to translate and rotate in all other degrees of freedom. Nonlinear frictional contacts were used between the EST and the ground, and between the cartilages. The flatfoot was simulated by removing all of the ligaments. We measured the foot alignment angles for the flatfoot and the foot with ruptured spring/deltoid ligament, while we gradually increased the force within the PTT. The measured angles were then compared to the intact foot to evaluate the ability of the PTT to restore foot alignment.Results:The models were validated by comparing the Meary's (MA), calcaneal pitch (CPA), hindfoot alignment (HAA), and talonavicular coverage angles (TCA) to clinically-derived values. In the flatfoot, an increase of the PTT force to approximately 700% of normal ('7 ×25.71 N=180 N') led to a nearly complete restoration of foot alignment (Fig. 1). The angles associated with arch height (MA/CPA) were restored to a lesser extent than those associated with hindfoot and forefoot alignment (HAA/TCA). For the foot with ruptured deltoid ligament, increasing force within the PTT by 500% led to a restoration of near normal hindfoot alignment (Fig. 1c). For the foot with ruptured spring ligament, the forefoot abduction was completely compensated only when the PTT force was increased to 1100% of normal (Fig. 1d).Conclusion:Almost seven times the normal PTT force is required to restore the foot to neutral alignment. Augmentation of PTT force to this extent is unrealistic. However, a lesser increase in PTT force provides partial alignment compensation.Furthermore, the restoration achieved by overloading the PTT primarily impacts the alignment of the hindfoot and forefoot rather than the arch. Because the PTT can partially restore foot alignment, it may become secondarily injured when the ligaments are torn. Strengthening of the PTT through therapeutic exercise can improve its ability to restore foot alignment and should be a cornerstone of non-operative treatment of PCFD.Open in a separate window
Foot & Ankle Orthopaedics
Category: Hindfoot; Ankle; Ankle Arthritis Introduction/Purpose: Patients with longstanding progr... more Category: Hindfoot; Ankle; Ankle Arthritis Introduction/Purpose: Patients with longstanding progressive collapsing foot deformity (PCFD) often develop osteoarthritis of the peritalar (tibiotalar, subtalar, and talonavicular) joints, which can be symptomatic or can lead to fixed deformities that further complicate the treatment of other sequalae of the deformity (Mann, 1992). Degeneration and subsequent tearing of the arch supporting ligaments leads to altered joint contact mechanics which is a likely causative factor in the development of arthrosis (Hauser and Dolan, 2011). However, the initial effect of ligament tears on changes in joint contact mechanics in the collapsing foot has not been well characterized. The goal of this work was to compare the joint contact mechanics between the neutrally aligned and the flexible flatfoot (collapsed foot). Methods: A validated finite element model of the foot (Malakoutikhah et al., 2022a) was used to compare joint contact pressures between t...
Foot & Ankle Orthopaedics
Category: Ankle; Midfoot/Forefoot; Other Introduction/Purpose: Progressive collapsing foot deform... more Category: Ankle; Midfoot/Forefoot; Other Introduction/Purpose: Progressive collapsing foot deformity (PCFD) is a degenerative disorder of ligaments and tendons that encompasses a wide range of deformities, including arch height loss, hindfoot valgus, and forefoot abduction. The posterior tibial tendon (PTT) is the main active stabilizer of the arch. We hypothesize that it may become injured secondarily as it attempts to maintain foot stability when the ligaments, passive stabilizers, are attenuated. Several cadaveric studies have been conducted on the role of the PTT in PCFD, but the ability of the PTT to compensate for the loss of the ligamentous stabilizers has not been clearly characterized. We developed a high-fidelity finite element model of the foot to determine the PTT's ability to maintain foot stability when the principle ligamentous stabilizers are attenuated. Methods: The encapsulating soft tissue (EST), cartilage, and cortical and trabecular bones were reconstructed ...
Clinical Biomechanics, 2022
Background: Progressive collapsing foot deformity results from degeneration of the ligaments and ... more Background: Progressive collapsing foot deformity results from degeneration of the ligaments and the posterior tibial tendon (PTT). Our understanding of the relationship between the failures of them remains incomplete. We sought to improve this understanding through computational modeling of force in these soft tissues. Methods: The impact of PTT and ligament tears on force changes in the remaining ligaments was investigated by quantifying ligament force changes during simulated ligament and tendon cutting in a previously validated finite element model of the foot. The ability of the PTT to restore foot alignment in a collapsed foot was evaluated by increasing the PTT force in a foot with attenuated ligaments and comparing the alignment angles to the intact foot. Results: Rupture of any one of the ligaments led to overloading the remaining ligaments, except for the plantar naviculocuneiform, first plantar tarsometatarsal, and spring ligaments, where removing one led to unloading the...
Journal of Orthopaedic Research
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Papers by Hamed Malakoutikhah