Biomechanical Effects of Graft Shape for the Evans Lateral Column Lengthening Procedure: A Patient-Specific Finite Element Investigation

A modified lateral column lengthening for the treatment of flexible flatfoot: From clinical applications to finite element analysis

BACKGROUND

Finite element (FE) analysis and clinical follow-up were used to evaluate the efficacy of a modified lateral column lengthening (H-LCL) for treating flexible flatfoot.

METHODS

By applying inclusion and exclusion criteria, we selected patients who underwent H-LCL surgery at our institution from January 2019 to January 2023. We compared the Visual Analog Scale (VAS) scores, American Orthopaedic Foot and Ankle Society (AOFAS) scores, Pain Interference (PI), and Physical Function (PF) scores in Patient-Reported Outcomes Measurement Information System (PROMIS) between preoperative and final follow-up assessments of patients, as well as FE submodels. Furthermore, evaluate the H-LCL's biomechanical characteristics and clinical outcome before and after surgery.

RESULTS

A total of 66 patients met the criteria. The average surgery time was 69.47 ± 13.22 min, and the follow-up duration was 15.18 ± 6.40 months. In the last follow-up, VAS and PI decreased compared to before surgery, while AOFAS and PF increased compared to before surgery. Meary's angle (dorsoplantar image and lateral image), calcaneal valgus angle, and talonavicular coverage angle decreased compared to before surgery, while the pitch angle increased compared to before surgery. In FE analysis, postoperative tension on the plantar fascia (PF), spring ligament (SL), and posterior tibial tendon (PTT) decreased compared to before surgery, pressure on the talonavicular joint and subtalar joints also decreased compared to before surgery, and there was no significant change in pressure on the calcaneocuboid joint.

CONCLUSION

H-LCL in correcting flexible flatfoot resulted in a significant improvement of clinical outcome scores and led to good radiological correction of flatfoot deformities. It can reduce the soft tissue and interosseous pressure in maintaining the foot arch.

Biomechanical effects of Evans versus Hintermann osteotomy for treating adult acquired flatfoot deformity: a patient-specific finite element investigation

BACKGROUND

Evans and Hintermann lateral column lengthening (LCL) procedures are both widely used to correct adult acquired flatfoot deformity (AAFD), and have both shown good clinical results. The aim of this study was to compare these two procedures in terms of corrective ability and biomechanics influence on the Chopart and subtalar joints through finite element (FE) analysis.

METHODS

Twelve patient-specific FE models were established and validated. The Hintermann osteotomy was performed between the medial and posterior facets of the subtalar joint; while, the Evans osteotomy was performed on the anterior neck of the calcaneus around 10 mm from the calcaneocuboid joint surface. In each procedure, a triangular wedge of varying size was inserted at the lateral edge. The two procedures were then compared based on the measured strains of superomedial calcaneonavicular ligaments and planter facia, the talus-first metatarsal angle, and the contact characteristics of talonavicular, calcaneocuboid and subtalar joints.

RESULTS

The Hintermann procedure achieved a greater correction of the talus-first metatarsal angle than Evans when using grafts of the same size, indicating that Hintermann had stronger corrective ability. However, its distributions of von-Mises stress in the subtalar, talonavicular and calcaneocuboid joints were less homogeneous than those of Evans. In addition, the strains of superomedial calcaneonavicular ligaments and planter facia of Hintermann were also greater than those of Evans, but both generally within the safe range (less than 6%).

CONCLUSION

This FE analysis study indicates that both Evans and Hintermann procedures have good corrective ability for AAFD. Compared to Evans, Hintermann procedure can provide a stronger corrective effect while causing greater disturbance to the biomechanics of Chopart joints, which may be an important mechanism of arthritis. Nevertheless, it yields a better protection to the subtalar joint than Evans osteotomy.

CLINICAL RELEVANCE

Both Evans and Hintermann LCL surgeries have a considerable impact on adjacent joints and ligament tissues. Such effects alongside the overcorrection problem should be cautiously considered when choosing the specific surgical method.

LEVEL OF EVIDENCE

Level III, case-control study.

In silico comparative biomechanical analysis of oblique and chevron medial displacement calcaneal osteotomies for pes planus deformity

BACKGROUND

Medializing displacement calcaneal osteotomy is commonly performed as part of reconstructive surgery for patients with valgus hindfoot and progressive pes planus deformity. Among several types of calcaneal osteotomies, the oblique and Chevron osteotomy patterns have been commonly described in the literature and gained popularity as they are easily reproducible through percutaneous techniques. Currently, there is scarce evidence in the literature on which cut pattern is superior in terms of stability. To investigate the impact of cut pattern and posterior fragment medialization level on foot biomechanics, computational methods are employed.

METHODS

Ankle weightbearing computer tomography (CT) scans of seven patients diagnosed with stage II pes planus deformity are segmented and converted into 3D computational models. Oblique and Chevron osteotomy patterns are modeled independently for each patient. The posterior fragments are medially translated by 8-, 10- and 12-mm and subsequently fixated to the anterior calcaneus with two screws. A total of 42 models are exported to finite element software for biomechanical simulations. Among the investigated parameters, the higher stiffness and lower von Mises stress at the osteotomy interface and the screw site are assumed to be precursors of better stability.

RESULTS

It is recorded that as the medialization level increases, the stiffness decreases, and overall stresses increase. Also, it is observed that the Chevron cut produces a stiffer construct while the overall stresses are lower, indicating better stability when compared to the oblique cut. The statistical comparisons of the relevant groups that support these trends are found to be significant (p < 0.05).

CONCLUSION

Chevron osteotomy showed superior stability compared to the oblique osteotomy while underscoring the negative impact of increased medialization of the posterior fragment.

CLINICAL RELEVANCE

Opting for a lower medialization level and implementing the Chevron technique may facilitate union and earlier weightbearing.

An Update on Pediatric Flatfoot

The pediatric flatfoot can include multiple planes of deformity and concomitant concerns such as metatarsus adductus and equinus. Each aspect of the deformity must be carefully evaluated before any surgical planning. The goal of surgery should be an improvement in symptoms by creating a controllable foot with a reduction of deforming forces. There are multiple procedures that can be used for the pediatric flatfoot, including the Evans calcaneal osteotomy, the Cotton medial cuneiform osteotomy, the medial calcaneal slide osteotomy, and arthroereisis implants. Each contributes in a specific way to the overall deformity correction. Multiple options exist for grafts and hardware.

Disease-Specific Finite element Analysis of the Foot and Ankle

Finite-element analysis is a computational modeling technique that can be used to quantify parameters that are difficult or impossible to measure externally in a geometrically complex structure such as the foot and ankle. It has been used to improve our understanding of pathomechanics and to evaluate proposed treatments for several disorders, including progressive collapsing foot deformity, ankle arthritis, syndesmotic injury, ankle fracture, plantar fasciitis, diabetic foot ulceration, hallux valgus, and lesser toe deformities. Parameters calculated from finite-element models have been widely used to make predictions about their biomechanical correlates.

Lateral column lengthening (LCL) using a rectangular shape graft for managing symptomatic flexible flatfoot showed acceptable early functional and radiological outcomes

PURPOSE

We aimed to report the results of performing lateral column lengthening (LCL) using a rectangular-shaped graft to correct the flat foot deformity.

METHODS

A total of 28 feet of 19 patients (10 males, 9 females) having an average age of 10 ± 3.2 years who were unresponsive to conservative management underwent flat foot deformity correction through LCL procedure supplemented with rectangular-shaped graft harvested from the fibula. Functional assessment was performed according to the American Orthopedic Foot and Ankle Society (AOFAS) scale. The radiographic assessment consisted of four parameters, Meary's angle in both anteroposterior (AP) and lateral (Lat.) views, calcaneal inclination angle (CIA), and calcaneocuboid angle (CCA).

RESULTS

After an average of 30.2 ± 8.1 months, the AOFAS improved significantly from 46.7 ± 10.2 preoperatively to 86.7 ± 9.5 at the last follow up (P < 0.05). All the osteotomies showed healing at an average of 10.3 ± 2.7 weeks. All the radiological parameters showed significant improvement at the last follow up compared to the preoperative measurements, CIA from 6.3 ± 2.8-19.3 ± 3.5, Lat. Meary's angle from 19.3 ± 4.9-5.8 ± 2.5, AP Meary's Angle from 19.3 ± 5.8-6.1 ± 3.1, and CCA from 23.9 ± 8.2-6.8 ± 4.5, (P < 0.05). No pain at the site of the fibular osteotomy was reported in any of the patients.

CONCLUSION

Lateral column lengthening using a rectangular graft effectively restores bony alignment with good radiological and clinical results, high patient satisfaction, and acceptable complications.