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This article presents a mechanical model that can be used to understand the foot, to help develop methods of treatment of foot pathology, and to provide direction for future research in foot mechanics and pathology. The anatomy and mechanical function of the windlass mechanism of the foot are analyzed using principles of mechanical engineering. The principles of force couples and free-body diagrams are explained and then applied to the foot. The relationship of the windlass mechanism to plantar fasciitis or heel spur syndrome, hallux abducto valgus, and hallux limitus is discussed.
BACKGROUND: Normative studies on the Arch Height Index (AHI), Arch Rigidity Index (ARI), and arch stiffness have primarily focused on healthy populations, with little consideration of pathology. The purpose of this study was to create a normative sample of the aforementioned measurements in a pathological sample and to identify relationships between arch structure measurements and pathology. METHODS: AHI was obtained bilaterally at 10% and 90% weightbearing conditions using the Arch Height Index Measurement System (AHIMS). ARI and arch stiffness were calculated using AHI measurements. Dependent t-tests compared right and left, dominant and non-dominant, and injured and non-injured limbs. Measurements of the dominant foot were compared between sexes using independent t-tests. Relationships between arch stiffness and age, sex, and AHI were examined using the coefficient of determination (R2). One-way ANOVAs were used to determine differences between arch structure measurements and number of pathologies or BMI. RESULTS: A total of 110 participants reported either one (n=55), two (n=38), or three or more (n=17) pathologies. Plantar fasciitis (n=31) and hallux valgus (n=28) were the most commonly reported primary concerns. AHI, ARI, and arch stiffness did not differ between limbs for any comparisons, nor between sexes. Between subgroups of BMI and number of pathologies, no differences exist in AHI or ARI; however, BMI was found to have an impact on AHI (10%WB) and arch stiffness (p<.05). Arch stiffness showed a weak relationship to AHI, where a higher AHI was associated with a stiffer arch (R2=0.06). CONCLUSIONS: Normative AHI, ARI and arch stiffness values were established in a pathological sample with a large incidence of plantar fasciitis and hallux valgus. Findings suggest relationships between arch stiffness and both BMI and arch height; however, few trends were noted in AHI and ARI. Determining relationships between arch structure and pathology is helpful for both clinicians and researchers.
Normal Values of the Foot Posture Index in a Young Adult Spanish Population
A Cross-Sectional Study
Background
Although the appearance of foot or lower-limb pathologies is etiologically multifactorial, foot postures in pronation or supination have been related to certain diseases such as patellofemoral syndrome and plantar fasciitis. The objective of the present study was to determine the normal values of foot posture in a healthy young adult Spanish sample, and to identify individuals at risk of developing some foot pathology.
Methods
The Foot Posture Index (FPI) was determined in a sample of 635 (304 men, 331 women) healthy young adults (ages 18–30 years). The FPI raw score was transformed into a logit score, and a new classification was obtained with the mean ± 2 SD to identify the 5% of the sample with potentially pathologic feet.
Results
The normal range of the FPI was −1 to +6, and FPI values from +10 to +12 and −6 to −12 could be classified as indicating potentially pathologic feet. The women's logit FPI (0.50 ± 1.4, raw FPI +3) was higher than the men's (0.25 ± 1.6, raw FPI +2), with the difference being significant (P = 0.038). No statistically significant differences were found between body mass index groups (P = 0.141).
Conclusions
The normal FPI range goes from just one point of supination to a certain degree of pronation (+6). The identification of 35 individuals with potentially pathologic feet may help in the implementation of a preventive plan to avoid the appearance of foot disorders.
Background: Human amniotic membrane contains growth factors and cytokines, which promote epithelial cell migration and proliferation, stimulate metabolic processes leading to collagen synthesis, and attract fibroblasts, while also reducing pain and inflammation. Randomized studies have shown that micronized dehydrated human amnion chorion membrane (mdHACM) allograft injection is an effective treatment for plantar fasciitis. Our objective is to present our experience with using mdHACM injection as a treatment for Achilles tendinopathy and report short term treatment outcomes. Methods: Included in this retrospective case series were patients diagnosed with Achilles tendinopathy treated with mdHACM by a single physician were identified from an electronic medical record system. Included for analysis were those with at least 2 follow up visits within 45 days of mdHACM injection. Outcomes examined included change in reported level of pain during the 45-day observation period and adverse events associated with treatment. Results: Follow-up data were available for 32 mdHACM-treated patients and abstracted from the electronic medical record. At treatment initiation 97% of patients reported severe (66%) or moderate (31%) pain. At first follow-up visit (mean 8.1 {plus minus} 2.7 days after injection), 84% (27/32) had reported improvement in pain levels, although 37% of patients continued to report severe (6%) or moderate (31%) pain. At the second follow-up visit (mean 23.1 {plus minus} 6.2 days after injection), no patients reported severe pain and one reported moderate pain. Within 45 days of mdHACM injection complete resolution of symptoms was reported by 66% of treated patients (n=21) with the remaining 34% reporting improvement but not complete resolution (n=11) of their symptoms. Two patients reported calf or quadricep pain or tightness post-injection. Conclusions: In a single practice mdHACM injection reduced or eliminated pain in all patients where follow-up data was available.
Letters to the Editor
Effectiveness of Extracorporeal Shockwave Treatment in 353 Patients with Chronic Plantar Fasciitis
Background
The definition of equinus varies from less than 0° to less than 25° of dorsiflexion with the foot at 90° to the leg. Despite its pervasive nature and broad association with many lower-extremity conditions, the prevalence of ankle equinus is unclear. Furthermore, there are few data to suggest whether equinus is predominantly a bilateral finding or isolated to the affected limb only.
Methods
We conducted a prospective cohort study examining consecutive patients attending a single foot and ankle specialty practice. Participation involved an assessment of ankle joint range of motion by a single rater with more than 25 years of clinical experience. We defined ankle equinus as ankle joint dorsiflexion range of motion less than or equal to 0° and severe equinus as less than or equal to –5°. Patients who had previously experienced an Achilles tendon rupture, undergone posterior group lengthening (ie, Achilles tendon or gastrocnemius muscle lengthening), or had conservative or surgical treatment of equinus previously were excluded.
Results
Of 249 included patients, 61% were female and 79% nondiabetic. The prevalence of ankle equinus was 73% [183 of 249], and nearly all of these patients had bilateral restriction of ankle joint range of motion (prevalence of bilateral ankle equinus was 98.4% [180 of 183] among those with equinus). We also found that ankle equinus was more common in patients with diabetes, higher body mass indexes (BMIs), or overuse symptoms.
Conclusions
The prevalence of ankle equinus in this sample was higher than previously reported, and nearly all of these patients had bilateral involvement. These data suggest that many people attending foot/ankle specialty clinics will have ankle equinus, and select groups (diabetes, increased BMI, overuse symptoms) are increasingly likely.
Letters to the Editor
Effectiveness of Extracorporeal Shockwave Treatment in 353 Patients with Chronic Plantar Fasciitis
We report the case of a 40-year-old female patient presenting with resistant heel pain attributable to plantar fascia rupture. She was treated with ultrasound-guided platelet-rich plasma injection, and her pain was decreased. Additionally, ultrasound was useful for diagnosis, intervention and follow-up of the patient.
Ultrasound-guided Plantar Fascia Release Technique
A Retrospective Study of 46 Feet
Background: Ultrasound-guided plantar fascia release offers the surgeon clear visualization of anatomy at the surgical site. This technique uses small arthroscopic dissecting instruments through a 0.5-cm incision, allowing the surgeon to avoid the larger and more tissue-disruptive incision that is traditionally used for plantar heel spur resection and plantar fascia releases.
Methods: Forty-one patients (46 feet) were selected for the study. The mean patient age was 47 years. Twenty-nine were considered obese with a body mass index greater than 30 kg/m2. Patients were functionally and subjectively evaluated 4 weeks after surgery using the American Orthopedic Foot and Ankle Society Ankle and Hindfoot Rating Scale.
Results: Results from the study show a significant improvement (P = .05 confidence level) 4 weeks postoperatively for the 41 patients (46 feet), compared to their preoperative condition. The mean pretest score was 33.6 (range 10–52); this score improved to 88.0 (range 50–100), 4 weeks postoperatively. There were no postoperative infections or complications.
Conclusions: The ultrasound-guided plantar fascia release technique is a practical surgical procedure for the relief of chronic plantar fascia pain because the surgeon is able to clearly visualize the plantar fascia by ultrasound. In addition, there is minimal disruption to surrounding tissue because small instruments are passed through a small 0.5-cm incision. The traditional open method of heel spur surgery, in contrast, uses a larger skin incision of 3 to 5 cm, followed by larger instruments to dissect to the plantar fascia. (J Am Podiatr Med Assoc 99(3): 183–190, 2009)
