Mechanical properties of heel pads reconstructed with flaps

The Treatment Experience of Different Types of Flaps for Repairing Soft Tissue Defects of the Heel

Objective

To summarize the clinical application effects of three different types of flaps for repairing soft tissue defects of the heel, and to discuss the importance of tissue repair and heel reconstruction.

Methods

A total of 46 cases with skin tissue defects of the heel with deep tissue exposure were treated. The reasons for the defect were trauma (n = 26), burns and electric shocks (n = 12), chronic ulcers (n = 2), postoperative infection of the calcaneus and Achilles tendon (n = 5), and tumor resection (n = 1). The scope of wound defect was 2.0×2.5 to approximately 15.0×20.0 cm. The flaps used were medial plantar island flaps (n = 9), distal pedicled sural neurovascular island flaps (n = 23), and free anterolateral thigh (perforator) flaps (n = 14). The flap cutting range was 3.0×3.5 to approximately 16.0×22.0 cm.

Results

After surgery, all 46 flaps survived. In two cases, patients experienced partial epidermal necrosis at the distal end of the flap that healed after local dressing exchange, and after this treatment, the complete skin grafts survived. Follow-up was conducted in 40 cases, with an average follow-up duration of 8.2 months (3-44 months) and the two-point discrimination of 5-14 mm. The average American Orthopaedic Foot and Ankle Society scale was 89.2 points with good flap color and texture, satisfactory appearance, and normal gait.

Conclusion

The repair method should be selected according to the"5-zone method": The plantar medial island flap is suitable for small area (<5 cm) of medial, posterior and plantar defects. The distal pedicled sural neurovascular flap is suitable for lateral, posterior, and medium-range (6-10 cm) joint area defects. The free anterolateral thigh perforator flap is suitable for large-scale (>10 cm) joint area defects.

Reconstruction of a Complex Foot Injury With Free Remodeled Fibular Osteocutaneous Flap: A Case Report and Literature Review

Management of complex foot injuries, which involve open fractures and severe trauma to soft tissues, represent a challenge to orthopedic clinicians. In the present case report, we treated a complex foot injury with a remodeled fibular osteocutaneous free flap to reconstruct the anterior and lateral areas of the foot. The flap survived completely. At the 9-month follow-up examination, bony union of the graft bone was identified by radiographic examination. The reconstructed foot could bear body weight, and the patient could maintain a bipedal gait without discomfort. The remodeled fibular osteocutaneous free flap provides an option for functional reconstruction of foot defects.

Material properties of the heel fat pad across strain rates

The complex structural and material behaviour of the human heel fat pad determines the transmission of plantar loading to the lower limb across a wide range of loading scenarios; from locomotion to injurious incidents. The aim of this study was to quantify the hyper-viscoelastic material properties of the human heel fat pad across strains and strain rates. An inverse finite element (FE) optimisation algorithm was developed and used, in conjunction with quasi-static and dynamic tests performed to five cadaveric heel specimens, to derive specimen-specific and mean hyper-viscoelastic material models able to predict accurately the response of the tissue at compressive loading of strain rates up to 150 s⁻¹. The mean behaviour was expressed by the quasi-linear viscoelastic (QLV) material formulation, combining the Yeoh material model (C10=0.1MPa, C30=7MPa, K=2GPa) and Prony׳s terms (A1=0.06, A2=0.77, A3=0.02 for τ1=1ms, τ2=10ms, τ3=10s). These new data help to understand better the functional anatomy and pathophysiology of the foot and ankle, develop biomimetic materials for tissue reconstruction, design of shoe, insole, and foot and ankle orthoses, and improve the predictive ability of computational models of the foot and ankle used to simulate daily activities or predict injuries at high rate injurious incidents such as road traffic accidents and underbody blast.

Heel Pad Stiffness in Plantar Heel Pain by Shear Wave Elastography

The goal of the study was to evaluate the reliability of supersonic shear wave elastography in measuring heel pad stiffness and the change in heel pad stiffness in patients with plantar heel pain. In the reliability test involving 12 normal participants, each heel pad was tested six times in succession, and adequate reliability was reflected in the intraclass correlation coefficients (0.95, 0.93 and 0.96 for the microchambers, macrochambers and bulk heel pad, respectively). In the clinical assessment involving 20 normal participants and 16 unilateral plantar heel pain patients, diseased heel pads (86.8 ± 22.9, 36.8 ± 7.7 and 46.6 ± 10.9 kPa for the microchambers, macrochambers and bulk heel pad, respectively) were significantly stiffer than unaffected heel pads (66.8 ± 14.1, 25.2 ± 5.7, 34.2 ± 6.6 kPa) and those of normal participants (60.9 ± 11.4, 26.3 ± 6.1, 31.8 ± 6.3 kPa), suggesting that the heel pad with plantar heel pain was associated with loss of elasticity.

The effects of heel-elevated total contact insole on rearfoot pressure reduction in heel injury patients who had neurosensory impairment after receiving reconstructive flap operations

OBJECTIVE

To evaluate the effects of a custom-molded heel-elevated total contact insole (TCI) on rearfoot pressure reduction and heel cushion for patients with heel-reconstruction.

METHODS

Eleven patients with unilateral heel-reconstruction were recruited in this study. Maximal force and plantar pressures (peak pressure and pressure-time integral) at three different areas (heel Midfoot and forefoot) were measured under 3 randomized conditions (shoe-only flat insole and heel- elevated TCI) after wearing a heel-elevated TCI for 3 months. Ulceration inspection and pain intensity were evaluated before and 3 months after wearing a heel-elevated TCI Results: Pain intensity was decreased and walking velocity was improved in all patients (p<0.01), and ulcerations were completely healed in all of the five patients who had heel ulcers 3 months after wearing heel-elevated TCIs. Compared to shoe-only condition, the heel-elevated TCI was effectively reduced maximal force and plantar pressures in heel area (p<0.01) while part of the body weight was shifted from heel to midfoot and forefoot. Plantar pressures in heel area were more effectively reduced in the heel-elevated TCI than in the flat insole (p<0.05).

CONCLUSION

These findings suggested that heel-elevated TCI provided more effective heel pressure reduction and shock absorption, and resulted in improvement of clinical symptoms.

Effect of the posterior tibial and peroneal longus on the mechanical properties of the foot arch

BACKGROUND

The mechanical properties of the foot are controlled by many structures including muscles, tendons, ligaments, tarsal joints and bones. Among them, muscles make the dynamic changes of foot alignment, especially the posterior tibial (PT) and peroneal longus (PL) which contribute to maintaining the foot arch. The purpose of this study was to quantify the effect of PT and PL on the foot mechanical properties.

METHODS

The mechanical properties with a longitudinal load to the tibia was measured in eight cadaveric feet. The measurement was carried out with absence of tendon traction (control), the presence of isolated traction of each tendon of the PT or PL, and finally after simultaneous traction of both tendons.

RESULTS

The bone displacement significantly decreased with tendon traction. The stiffness significantly increased with PT traction compared to control, and significantly decreased with PL traction and with traction of both tendons. Among the four testing conditions, the energy during loading was least with isolated PT traction. The energy dissipation rate was significantly increased with PL traction and with traction on both tendons, whereas no significant difference existed with PT traction compared to control.

CONCLUSIONS

The PT increased the stiffness and reduces the energy stored in the foot. The PT acted to improve the energy efficiency of the load transmission. The PL decreased the stiffness and increased the energy stored.

CLINICAL RELEVANCE

PT and PL muscles affect the foot arch. Excessive or insufficient traction may cause some foot disorders.

Three-dimensional morphology of heel fat pad: an in vivo computed tomography study

Heel fat pad cushioning efficiency is the result of its structure, shape and thickness. However, while a number of studies have investigated heel fat pad (HFP) anatomy, structural behavior and material properties, no previous study has described its three-dimensional morphology in situ. The assessment of the healthy, unloaded, three-dimensional morphology of heel pad may contribute to deepen the understanding of its role and behavior during locomotion. It is the basis for the assessment of possible HFP morphological modifications due to changes in the amount or distribution of the loads normally sustained by the foot. It may also help in guiding the surgical reconstruction of the pad and in improving footwear design, as well as in developing a correct heel pad geometry for finite element models of the foot. Therefore the purpose of this study was to obtain a complete analysis of HFP three-dimensional morphology in situ. The right foot of nine healthy volunteers was scanned with computed tomography. A methodological approach that maximizes reliability and repeatability of the data was developed by building a device to lock the foot in a neutral position with respect to the scan planes during image acquisition. Scan data were used to reconstruct virtual three-dimensional models for both the calcaneus and HFP. A set of virtual coronal and axial sections were extracted from the three-dimensional model of each HFP and processed to extract a set of one- and two-dimensional morphometrical measurements for a detailed description of heel pad morphology. The tissue exhibited a consistent and sophisticated morphology that may reflect the biomechanics of the foot support. HFP was found to be have a crest on its anterior dorsal surface, flanges on the sides and posteriorly, and a thick portion that reached and covered the posterior surface of the calcaneus and the achilles tendon insertion. Its anterior internal portion was thinner and a lump of fat was consistently present in this region. Finally, HFP was found to be thicker in males than in females.

Longitudinal outcomes and application of the subunit principle to 165 foot and ankle free tissue transfers

BACKGROUND

Free tissue transfer to the lower extremity has become a well-established reconstructive modality. The purpose of this study was to develop a "subunit" approach to patients undergoing free tissue transfer for foot and ankle wounds to help further define subunit-specific functional and aesthetic operative goals.

METHODS

The institutional review board approved this retrospective review of 161 patients who underwent free tissue transplantation for foot and ankle wounds between March 1, 1997, and February 28, 2007, at a single institution. Endpoints included flap-related complications, secondary surgery, time to ambulation, flap stability, and limb salvage.

RESULTS

The most common types of wounds treated were trauma-related [n = 120 (75 percent)], diabetes-related [n = 24 (15 percent)], and oncologic defects [n = 8 (5 percent)]. Ten different donor sites were used for reconstruction, with the latissimus dorsi flap being the most common. The mean follow-up time was 26.9 months (range, 0.5 to 130 months). Mean time to ambulation was 3.1 months (range, 0.75 to 14 months). Overall, 11 percent of patients required revision surgery for flap instability at a mean time of 25.3 months after flap surgery. Wounds located over the heel (subunit 5) were most likely to develop instability (Fisher's exact test, p < 0.05). The overall 5-year limb salvage rate as determined by Kaplan-Meier analysis was 89 percent.

CONCLUSIONS

The use of free tissue transplantation for treatment of foot and ankle wounds is associated with a high rate of limb salvage. Although a variety of flaps may be used, the application of the subunit principle can assist surgeons in designing flaps that will address subunit-specific functional and aesthetic concerns.

Microchambers and macrochambers in heel pads: are they functionally different?

The heel pad consists of a superficial microchamber layer and a deep macrochamber layer. This study highlights the different biomechanical behaviors between the microchamber and macrochamber layers using ultrasonography. The heel pad in each left foot of six healthy volunteers aged ∼25 yr old was measured with a device consisting of a 10-MHz linear-array ultrasound transducer and a load cell. The testing heels were loaded on the ultrasound transducer with a loading velocity of ∼0.5 cm/s and were withdrawn when the specified maximum stress (158 kPa) was reached. Unloaded tissue thickness, end-loaded thickness, deformation proportion, average deformation, and rebound rates and elastic modulus of the microchamber and macrochamber layers were assessed. The unloaded thickness of the microchamber layer was ∼30% of the macrochamber layer. The microchamber layer also had significantly less unloaded thickness, end-loaded thickness, mean deformation rate, mean rebound rate, and deformation proportion than the macrochamber layer. A significant difference between the unloaded and end-loaded thickness in the macrochamber layer was observed. The average soft tissue deformation rate was significantly different from the rebound rate in the microchamber layer. A similar trend was detected in the macrochamber layer. The elastic modulus of the microchamber layer was 450 kPa (SD 240), which was nearly 10 times of that in the macrochamber layer. In conclusion, ultrasound can identify the heterogeneous tissue properties of the heel pad. The macrochamber layer responds to loading with large deformation, and the microchamber layer has a high degree of tissue stiffness.

Altered energy dissipation ratio of the plantar soft tissues under the metatarsal heads in patients with type 2 diabetes mellitus: a pilot study

BACKGROUND

Foot ulceration occurs frequently on the plantar aspect of the metatarsal head region, in which the altered foot biomechanics has been mentioned as a contributor. This study attempted to compare the energy dissipation in the plantar soft tissue under the metatarsal head between type 2 diabetic patients and age-matched healthy subjects in vivo.

METHODS

The plantar soft tissues under the metatarsal heads in each left foot of 13 patients with type 2 diabetes mellitus and eight age-matched healthy subjects were measured with a loading-unloading device. The system comprised a 5-12 MHz linear-array ultrasound transducer and a load cell that operated at an impact velocity of about 5 cm/s. The stress-strain plot was derived by simultaneously recording the stress response and tissue deformation during a loading-unloading cycle. The energy dissipation ratio in all subjects could then be analyzed.

FINDINGS

Although only the plantar soft tissue under the fourth metatarsal head in the diabetic patients endured significantly greater energy (P=0.035) than the healthy subjects, a trend of an increased energy dissipation ratio for the metatarsals in the diabetic patients was observed.

INTERPRETATION

The plantar soft tissue under the metatarsal head in the diabetic patients endures high dissipated energy during a simulating walking status in the study. The increased dissipated energy in the tissue may be responsible for the tissue breakdown in the diabetic patients.

Hindfoot containment orthosis for management of bone and soft-tissue defects of the heel

BACKGROUND

Bone, soft-tissue, and nerve deficits of the weightbearing surface of the foot are frequent sequelae from foot trauma or diabetes mellitus and present challenging treatment issues. Injury to the specialized, shock-absorbing, heel-pad tissue containing spirally arranged fat chambers is particularly difficult to manage. Appropriate footwear modifications and shoe inserts for protection of this skin are essential to the long-term management of bone and soft-tissue defects of the heel. This study evaluated the performance of a new custom total contact foot orthosis (Hindfoot Containment Orthosis, HCO) which was designed to contain the soft tissues of the heel, reduce shear forces, redistribute weightbearing load, and accommodate bone or soft-tissue deformity of the heel.

METHODS

Twenty-two patients treated with HCO were retrospectively reviewed. Followup averaged 26 months. The effectiveness of the orthosis was assessed by how well the integrity of the soft tissue was maintained (e.g. the number of ulcerations since dispensing the orthosis), the number of refabrications of the orthosis that were required, and whether or not revision surgery was required.

RESULTS

Ten patients had superficial ulcerations. No patient required revision surgery. A total of 62 refabrications of the orthoses in 22 patients were required over a 2-year period. Overall results were good in 17 (77%) patients, fair in four (18%), and poor in one.

CONCLUSIONS

The HCO is effective for preservation of soft-tissue integrity of the heel pad after bony or soft-tissue injury. Important factors in achieving success with the HCO are patient compliance and periodic monitoring for refabrication of the orthosis to accommodate skeletal growth, change in foot size or shape, and compression or wear of insert materials.

Improvement of gait by using orthotic insoles in patients with heel injury who received reconstructive flap operations

OBJECTIVE

To investigate the effect of orthotic insoles in heel injury patients who received reconstructive flap operations.

DESIGN

Motion analysis and force platform data were collected in able-bodied subjects and patients with heel injuries during walking without and with the use of the total contact insole. Gait kinetics were collected for the hip, knee, and ankle joints and then compared with Student's t tests.

RESULTS

Walking velocity and step length were decreased (P < 0.014 and P < 0.005) for patients not wearing the total contact insole. The affected limbs had longer double-support duration (14.8% of gait cycle, P < 0.037) and shorter single-support duration (34.5% of gait cycle, P < 0.045). Less hip power generation was noted for the affected limbs during both initial contact and preswing phases, 0.17 +/- 0.10 N-m/kg-m and 0.45 +/- 0.20 N-m/kg-m, as compared with that of the able-bodied subjects, 0.36 +/- 0.08 N-m/kg-m and 0.89 +/- 0.22 N-m/kg-m, respectively. Decreased ankle power generation was noted for the affected limbs (1.08 +/- 0.38 N-m/kg-m) during preswing phase as compared with the able-bodied subjects (2.24 +/- 0.33 N-m/kg-m). After fitting of the total contact insole, the affected limbs recovered to a gait pattern similar to that of the able-bodied subjects (P < 0.05).

CONCLUSION

Asymmetry of gait pattern after heel injury resulted in altered gait kinetics. Gait symmetry could be recovered in these patients as the total contact insole provides weight acceptance, shock absorption, and cushioning effect for the reconstructed heels.

Biomechanics of the heel pad for type 2 diabetic patients

OBJECTIVES

To quantify the dynamic behavior of the heel pad in type 2 diabetic patients and age-matched healthy individuals using mathematical modeling.

BACKGROUND

No single parameter can fully describe the heel-pad biomechanical properties during the loading-unloading process.

DESIGN

A descriptive study using pseudoelastic modeling was conducted to simulate the heel-pad stress-strain relationship in the loaded and unloaded states. Transmission electron microscope was used to examine six heel specimens taken from amputated legs in diabetic and non-diabetic patients.

METHODS

Energy dissipation ratio, loading curvature, and unloading curvature were calculated from the stress-strain curve-fits. Differences in ultrastructure between the heel pad of healthy subjects and those with diabetes were described.

RESULTS

The diabetic patients had a significantly higher mean energy dissipation ratio (mean 36.1% (SD, 8.7%) vs mean 27.9% (SD, 6.1%); P<0.001) and mean unloaded curvatures (mean 11.8 (SD, 5.1) vs mean 8.46 (SD, 2.6); P<0.001) than those of the control group. The collagen fibrils in diabetic heel samples were ruptured with unclear striation and uneven distribution.

CONCLUSIONS

The curvature parameters may explain the poor rebound phenomenon resulting in the high impact energy in diabetic heel pads. Breakdown in collagen fibrils may be responsible for this observation.

RELEVANCE

These findings can be integrated into the fabrication of orthotics that dissipate excessive heel impact energy and protect against injury.

Altered heel-pad mechanical properties in patients with Type 2 diabetes mellitus

AIMS

To compare the heel-pad mechanical properties in patients with Type 2 diabetes mellitus with forefoot ulceration, without forefoot ulceration and age-matched healthy subjects.

METHODS

Heel-pad mechanical properties in 40 heels of 20 healthy subjects (group I) age-matched with the other groups, 42 heels of 21 diabetic patients without forefoot ulceration (group II), and 14 heels of 12 diabetic patients with active forefoot ulceration (group III) were assessed using a self-constructed loading-unloading device and a 10-MHz linear-array ultrasound transducer.

RESULTS

There were no differences in the unloaded heel-pad thickness, compressibility index and elastic modulus between the three groups. When compared with group I subjects (mean +/- SD, 27.9 +/- 6.1%), a significant increase (P < 0.001) was found in both group II (36.1 +/- 8.7%) and group III patients (43.2 +/- 6.6%) for the energy dissipation ratio. This ratio was also significantly different (P = 0.003) between groups II and III.

CONCLUSIONS

The higher impact energy dissipated in the heel-pad may put patients with Type 2 diabetes at higher risk for developing foot ulceration.

Treatment of proximal plantar fasciitis with ultrasound-guided steroid injection

OBJECTIVE

To investigate the efficacy of ultrasound-guided steroid injection for the treatment of proximal plantar fasciitis and to evaluate mechanical properties of the heel pad after steroid injection.

DESIGN

Proximal plantar fascia and heel pad were assessed with a 10-MHz linear array ultrasound transducer. Pain intensity was quantified with a tenderness threshold (TT) and visual analog scale (VAS). The transducer was incorporated into a specially designed device to measure mechanical properties of the heel pad. Evaluations were performed before injection and at 2 weeks and 3 months after injection.

SETTING

An outpatient clinic of a tertiary care center.

PATIENTS

Fourteen consecutive patients with unilateral proximal plantar fasciitis.

INTERVENTION

Ultrasound-guided injection of 7 mg betamethasone and 0.5 mL of 1% lidocaine into the inflamed proximal plantar fascia.

MAIN OUTCOME MEASURES

VAS, TT, heel pad and plantar fascia thickness, and echogenicity of the proximal plantar fascia on sonogram were assessed. Mechanical properties included unloaded heel pad thickness, compressibility index, and energy dissipation ratio.

RESULTS

Both VAS score +/- standard deviation (SD; 5.43 +/- 2.03, 1.39 +/- 2.19, 0.57 +/- 1.40 at the 3 measurements, respectively) and TT +/- SD (5.05 +/- 1.42, 9.34 +/- 1.84, 9.93 +/- 1.98 kg/cm2 at the 3 measurements, respectively) improved significantly (p < .001) after steroid injection. The mean thickness of the plantar fascia was greater in the symptomatic side than in the asymptomatic side before treatment (0.58 +/- 0.13 cm vs 0.40 +/- 0.11 cm, p < .001). The thickness had decreased significantly 3 months after injection (0.46 +/- 0.12 cm at 2 weeks, 0.42 +/- 0.10 cm at 3 months, p < .001). The hypoechogenicity at the proximal plantar fascia disappeared after steroid injection (p < .001). Mechanical properties of the heel pad did not change 3 months after steroid injection (p > .05).

CONCLUSION

Ultrasound offers an objective measurement of the therapeutic effect on proximal plantar fasciitis. Accurate steroid injection under ultrasound guidance can effectively treat proximal plantar fasciitis without significant deterioration of the mechanical properties of the heel pads.