Plantar measurements to determine success of surgical correction of Stage IIb adult acquired flatfoot deformity

Effect of foot orthoses on balance among individuals with flatfoot: A systematic review and meta-analysis

Individuals with flatfoot have impaired proprioception owing to ligament laxity and impaired tendons, which can result in poor balance. Foot orthoses (FOs) have been reported to stimulate plantar mechanical receptors and are used to manage foot overpronation in individuals with flatfoot. However, the results of the use of FOs to improve balance are inconsistent. In this systematic review and meta-analysis, we aimed to identify and investigate the effects of FOs on balance in individuals with flatfoot. Electronic databases were searched for articles published before March 2023. Peer-reviewed journal studies that included adult participants with flexible flatfoot and reported the effects of FOs on balance were included and classified based on the study design: randomized control trials (RCT) and non-RCTs. Four RCT studies were retained, and their methodological quality was assessed (mean, 63.2%; range 47.3%-73.1%: high), as were three non-RCT studies (mean, 54.1%; range, 42.1%-68.4%: high). Meta-analysis was performed by calculating the effect size using the standardized mean differences between the control and FO conditions. Transverse-arch insoles immediately improved static balance after use. However, no immediate significant effect was found for medial archsupport FOs, cuboid-posting FOs, or University of California Berkeley Laboratory FOs during the study period (2-5 weeks) when compared with the controls. The transverse-arch insole is the most effective FO feature for improving static balance. However, the high heterogeneity between study protocols contributes to the lack of evidence for the effects of FO on balance in people with flatfoot.

A novel implantable mechanism-based tendon transfer surgery for adult acquired flatfoot deformity: Evaluating feasibility in biomechanical simulation

Adult acquired flatfoot deformity becomes permanent with stage III posterior tibialis tendon dysfunction and results in foot pain and difficulty walking and balancing. To prevent progression to stage III posterior tibialis tendon dysfunction when conservative treatment fails, a flexor digitorum longus to posterior tibialis tendon transfer is often conducted. However, since the flexor digitorum longus only has one-third the force-capability of the posterior tibialis, an osteotomy is typically also required. We propose the use of a novel implantable mechanism to replace the direct attachment of the tendon transfer with a sliding pulley to amplify the force transferred from the donor flexor digitorum longus to the foot arch. In this work, we created four OpenSim models of an arched foot, a flatfoot, a flatfoot with traditional tendon transfer, and a flatfoot with implant-modified tendon transfer. Paired with these models, we developed a forward dynamic simulation of the stance phase of gait that reproduces the medial/lateral distribution of vertical ground reaction forces. The simulation couples the use of a fixed tibia, moving ground plane methodology with simultaneous activation of nine extrinsic lower limb muscles. The arched foot and flatfoot models produced vertical ground reaction forces with the characteristic double-peak profile of gait, and the medial/lateral distribution of these forces compared well with the literature. The flatfoot model with implant-modified tendon transfer produced a 94.2% restoration of the medial/lateral distribution of vertical ground reaction forces generated by our arched foot model, which also represents a 2.1X improvement upon our tendon transfer model. This result demonstrates the feasibility of a pulley-like implant to improve functional outcomes for surgical treatment of adult acquired flatfoot deformity with ideal biomechanics in simulation. The real-world efficacy and feasibility of such a device will require further exploration of factors such as surgical variability, soft tissue interactions and healing response.

In Vivo Plantar Pressures in Adult-Acquired Flatfoot Compared to Control Using an Intraoperative Pedobarographic Device

BACKGROUND

Intraoperative pedobarography has the potential to aid surgical decisions, but no parameters exist to guide its use.

QUESTIONS/PURPOSES

This study compared supine plantar pressures between flatfoot patients and controls using a previously validated intraoperative pedobarographic device and examined associations between supine, walking, and standing plantar pressures.

METHODS

Ten preoperative patients with stage II adult-acquired flatfoot deformity (AAFD) were compared to ten healthy controls. Supine plantar pressures were assessed using the pedobarographic device. Standing and walking plantar pressures were assessed with an EMED-XT sensor array (Novel). Maximum force (MF) and peak pressure (PP) were calculated for nine anatomical foot regions adjusting for age and BMI.

RESULTS

No differences in plantar pressures were found between flatfoot patients and controls in the supine or standing positions. During walking, flatfoot patients had greater MF of the first, second, and third metatarsals (p ≤ 0.018) and greater PP of the first and second metatarsals than controls (p ≤ 0.010). Supine MF and PP were both strongly positively correlated with their respective pressure measurements for both standing and walking in multiple foot regions (p ≤ 0.05, all analyses). Correlations in the first metatarsal region were generally weak and not statistically significant.

CONCLUSION

This device did not show differences in supine plantar pressures of flatfoot patients and healthy subjects, highlighting the limitations of intraoperative devices in guiding flatfoot correction. The differences between flatfoot and controls during walking and the correlations between supine and walking conditions suggest that dynamic plantar pressures are a more useful parameter in guiding flatfoot reconstruction.

A population of patient-specific adult acquired flatfoot deformity models before and after surgery

Following IRB approval, a cohort of 3-D rigid-body computational models was created from submillimeter MRIs of clinically diagnosed Adult Acquired Flatfoot Deformity patients and employed to investigate postoperative foot/ankle function and surgical effect during single-leg stance. Models were constrained through physiologic joint contact, passive soft-tissue tension, active muscle force, full body weight, and without idealized joints. Models were validated against patient-matched controls using clinically utilized radiographic angle and distance measures and plantar force distributions in the medial forefoot, lateral forefoot, and hindfoot. Each model further predicted changes in strain for the spring ligament, deltoid ligament, and plantar fascia, as well as joint contact loads for three midfoot joints, the talonavicular, navicular-1st cuneiform, and calcaneocuboid. Radiographic agreement ranged across measures, with average absolute deviations of <5° and <4 mm indicating generally good agreement. Postoperative plantar force loading in patients and models was reduced for the medial forefoot and hindfoot concomitant with increases in the lateral forefoot. Model predicted reductions in medial soft-tissue strain and increases in lateral joint contact load were consistent with in vitro observations and elucidate the biomechanical mechanisms of repair. Thus, validated rigid-body models offer promise for the investigation of foot/ankle kinematics and biomechanical behaviors that are difficult to measure in vivo.