The Ageing Foot

Feet suffer significant stress throughout a lifetime and undergo ageing-associated problems due to gradual tissue degeneration affecting the skin, connective tissue, and nerves. Oxygen supply to the tissues may be diminished. The skin gets dry and calluses, ulcers and fungal infections of the skin and nails are not uncommon. Ligaments and tendons degenerate and, without proper prevention, deformities including claw toes, hammer toes, tendonitis, and bursitis may occur. Skeletal toe deformities such as bunions, bony spurs, and hallux valgus may increase discomfort, while stress fractures may have an adverse impact on the patients' quality of life. The ageing foot pathology may add up to common age-related problems, such as crystal deposition arthropathies, diabetes mellitus, peripheral circulatory disorders, and peripheral edema, increasing morbidity. This review summarizes ageing-related feet problems, focusing on prevention and treatment. Foot health has a paramount role in overall wellbeing, therefore prevention, proper foot care, and prompt diagnosis and management of ageing-related changes are vital for maintaining a healthy, active status.

Three dimensional finite element analysis of biomechanics of osteotomy ends with three different fixation methods after hallux valgus minimally invasive osteotomy

PURPOSE

Biomechanical study of fixation methods post hallux valgus minimally invasive osteotomy using finite element technology hasn't been reported. This study aimed to compare maximum displacement and stress distribution of osteotomy ends after minimally invasive osteotomy fixed by bandage, Kirschner wire, Herbert screw.

METHODS

Foot CT images of a patient with mild-moderate hallux valgus were collected. Three-dimensional finite element model of hallux valgus was established through CT image. This study simulated bandage, Kirschner wire and Herbert screw fixation, and analyzed maximum displacement and stress distribution of osteotomy ends in plantar flexion position of foot after fixation.

RESULTS

Maximum equivalent stress of osteotomy end fixed with bandage, Kirschner wire, Herbert screw was 7.8615, 14.253, 8.3156 MPa, respectively. Total displacement of osteotomy end fixed by bandage, Kirschner wire, Herbert screw was 0.26,896, 0.022,779, 0.029,195 mm, respectively. Maximum stress of Kirschner wire and Herbert screw near osteotomy end was 154.7 and 46.404 MPa, respectively. Fixation strength and stability of Kirschner wire and Herber screw were better than bandage. Kirschner wire had stress concentration phenomenon, with potential fracture risk. Stress of Herbert screw was evenly distributed around osteotomy end, and there was a certain stress concentration, playing an important role in maintaining fracture end stability.

CONCLUSIONS

Herbert screw showed good fixation strength and stability, and stress distribution was uniform, which can well maintain stability of minimally invasive osteotomy ends. Findings of this study would provide a theoretical basis for selection of fixation methods after clinical minimally invasive osteotomy for hallux valgus.

[Biomechanics of the first metatarsophalangeal joint after replacement]

OBJECTIVE

Analysis of biomechanics of the first metatarsophalangeal joint after arthroplasty, interaction between bones and two implants of the first metatarsophalangeal joint using skeletal model of the foot.

MATERIAL AND METHODS

We developed anatomically adapted all-ceramic non-coupled endoprosthesis of proximal interphalangeal joint between 2016 and 2021. To create a model of the foot, we used diagnostic computed tomography whose images were applied in 3D sculpting system and computer-aided design system for final geometric modeling of the joint.

RESULTS

In dorsal flexion of the first metatarsophalangeal joint under 45° with the presence of implant, cortical bone tissue can withstand a load of up to 40 kg. Cortical bone tissue with implant can withstand a load of up to 305 kg without dorsal flexion. Strength of implant elements made of zirconium ceramics significantly exceeds strength of bone tissue within implant-bone tissue connection.

CONCLUSION

Postoperative axial load on the first metatarsophalangeal joint up to 35 kg with maximum dorsal flexion up to 45° is the most appropriate. Higher load and hyperextension over 45° may be followed by postoperative complications such as implant instability, dislocation and periprosthetic fracture.

Structural interaction between bone and implants due to arthroplasty of the first metatarsophalangeal joint

BACKGROUND

Currently, the metatarsophalangeal joint replacement through a restorative arthroplasty, where implants are used, is a viable invasive surgical medical procedure in the treatment of severe cases of osteoarthritis in this joint, better known as hallux rigidus. However, few things are known about the postoperative complications that implants can cause on the joint, like Swanson and Tornier implants.Research in this field can provide a valuable information that would help the specialist surgeon in the decision-making during the selection of the more suitable joint implant in each patient, as well as the redesign of the devices, to make them more efficient, durable and biocompatible with the human body.

METHODS

The aim of this work is to perform a structural biomechanical analysis of a restorative arthroplasty of the first metatarsophalangeal joint, and to analyze the interaction between bone and medical grade silicone implants. For that, a simulation of a foot with Swanson and Tornier joint implants were performed to evaluate the stress/strain distribution during a critical stage (toe-off).

RESULTS AND CONCLUSIONS

Principal stresses obtained for the first metatarsal with both implants suggest that failure is induced in this bone because, values exceed (up to 136.84% for Swanson model) the tensile strength reported for phalange trabecular bone, which may be related to osteolysis. Stress and strain values obtained in this work suggest that arthroplasty surgery with Swanson implant is more likely to cause postoperative complications versus Tornier implant.

Biomechanical study on surgical fixation methods for minimally invasive treatment of hallux valgus

Hallux valgus (HV) was one of the most frequent female foot deformities. The aim of this study was to evaluate mechanical responses and stabilities of the Kirschner, bandage and fiberglass fixations after the distal metatarsal osteotomy in HV treatment. Surface traction of different forefoot regions in bandage fixation and the biomechanical behavior of fiberglass bandage material were measured by a pressure sensor device and a mechanical testing, respectively. A three-dimensional foot finite element (FE) model was developed to simulate the three fixation methods (Kirschner, bandage and fiberglass fixations) in weight bearing. The model included 28 bones, sesamoids, ligaments, plantar fascia, cartilages and soft tissue. The peak Von Mises stress (MS) and compression stress (CS) of the distal fragment were predicted from the three fixation methods: Kirschner fixation (MS=6.71MPa, CS=1.232MPa); Bandage fixation (MS=14.90MPa, CS=9.642MPa); Fiberglass fixation (MS=15.83MPa, CS=19.70MPa). Compared with the Kirschner and bandage fixation, the fiberglass fixation reduced the relative movement of osteotomy fragments and obtained the maximum CS. We concluded that fiberglass fixation in HV treatment was helpful to the bone healing of distal fragment. The findings were expected to guide further therapeutic planning of HV patient.

Influence of first proximal phalanx geometry on hallux valgus deformity: a finite element analysis

Hallux abducto valgus (HAV), one of the most common forefoot deformities, occurs primarily in elderly women. HAV is a complex disease without a clearly identifiable cause for its higher prevalence in women compared with men. Several studies have reported various skeletal parameters related to HAV. This study examined the geometry of the proximal phalanx of the hallux (PPH) as a potential etiologic factor in this deformity. A total of 43 cadaver feet (22 males and 21 females) were examined by means of cadaveric dissection. From these data, ten representative PPHs for both genders were selected, corresponding to five percentiles for males (0, 25, 50, 75, and 100%) and five for females. These ten different PPHs were modeled and inserted in ten foot models. Stress distribution patterns within these ten PPH models were qualitatively compared using finite element analysis. In the ten cases analyzed, tensile stresses were larger on the lateral side, whereas compressive stresses were larger on the medial side. The bones of males were larger than female bones for each of the parameters examined; however, the mean difference between lateral and medial sides of the PPH (mean ± SD) was larger in women. Also the shallower the concavity at the base of the PPH, the larger the compressive stresses predicted. Internal forces on the PPH, due to differences in length between its medial and lateral sides, may force the PPH into a less-stressful position. The geometry of the PPH is a significant factor in HAV development influencing the other reported skeletal parameters and, thus, should be considered during preoperative evaluation. Clinical assessment should evaluate the first ray as a whole and not as isolated factors.

Biomechanics of first ray hypermobility: An investigation on joint force during walking using finite element analysis

Hypermobility of the first ray is suggested to contribute to hallux valgus. The investigation of first ray hypermobility focused on the mobility and range of motion that based on manual examination. The load transfer mechanism of the first ray is important to understand the development and pathomechanism of hallux valgus. In this study, we investigated the immediate effect of the joint hypermobility on the metatarsocuneiform and metatarsophalangeal joint loading through a reduction of the stiffness of the foot ligaments. A three-dimensional foot model was constructed from a female aged 28 via MRI. All foot and ankle bones, including two sesamoids and the encapsulated bulk tissue were modeled as 3D solid parts, linking with ligaments of shell elements and muscles connectors. The stance phase of walking was simulated by the boundary and loading conditions obtained from gait analysis of the same subject. Compared with the normal foot, the hypermobile foot had higher resultant metatarsocuneiform and metatarsophalangeal joint forces. The increases accounted for 18.6% and 3.9% body weight. There was also an abrupt change of metatarsocuneiform joint force in the medial-lateral direction. The predicted results represented possible risk of joint problems and metatarsus primus varus.

Stress at the second metatarsal bone after correction of hammertoe and claw toe deformity: a finite element analysis using an anatomical model

BACKGROUND

We used finite element analysis to evaluate three techniques for the correction of hammertoe and claw toe deformities: flexor digitorum longus tendon transfer (FDLT), flexor digitorum brevis tendon transfer (FDBT), and proximal interphalangeal joint arthrodesis (PIPJA).

METHODS

We performed a finite element analysis of FDLT and FDBT compared with PIPJA of the second toe using multislice computed tomography and 93 tomographic images of the foot obtained in a healthy 36-year-old man.

RESULTS

The PIPJA showed a significantly higher increase in traction and compressive stresses and strain at the medial aspect of the shaft of the second metatarsal bone compared with FDLT or FDBT (P < .01). Mean ± SD compressive stresses increased to -4.35 ± 7.05 MPa compared with the nonsurgical foot (-3.10 ± 4.90 MPa). It can, therefore, be hypothesized that if PIPJA is used to correct the hammertoe and claw toe deformities, it could also increase traction and compressive stresses and strain in the metatarsals during running and other vigorous activities.

CONCLUSIONS

There is a biomechanical advantage to performing FDLT or FDBT instead of PIPJA to surgically treat a hammertoe or claw toe deformity. In addition, tensile strain at the dorsal aspect of the second metatarsal bone when performing PIPJA increases the risk of metatarsalgia or stress fracture in patients at risk.

Master techniques in digital arthrodesis

This is a comprehensive review of various techniques of digital fusion. Evolution of the technique has afforded today's surgeons a valuable repertoire of surgical options. Ultimately, patient factors and surgeon preference determine the most appropriate method of fixation.

The use of flexor to extensor transfers for the correction of the flexible hammer toe deformity

Flexor to extensor transfer is a useful means for the correction of a flexible hammer toe deformity. Although satisfaction rates have varied in the literature, this technique remains a useful tool in the surgeon’s armamentarium to improve toe deformity, decrease pain, and aid in shoe wear.