Abstract
Background
Few previous studies focused on plantar loading patterns in HV patients with metatarsalgia. Are there any differences in plantar pressure measurements in women with HV with and without metatarsalgia?
Methods
A prospective matched-cohort study was designed to analyze plantar pressure measurements in women with HV with and without metatarsalgia from January 2017 to December 2019. The inclusion criteria were age over 18 years old, women, diagnosis of HV with metatarsalgia. Control group had the same inclusion criteria, except metatarsalgia. Patient-reported outcomes scores included American Orthopedic Foot and Ankle Society Score (AOFAS), and Visual Analog Scale (VAS). Radiographic data were obtained according to the guidelines of the AOFAS Committee on Angular Measurements. Plantar pressure measurements were performed using a platform.
Results
Forty-seven patients met the inclusion criteria. An age-, BMI-, and hallux valgus angle-matched cohort of 47 patients were also selected. There were no statistically significant differences in demographic data and radiographic assessment. HV with metatarsalgia group showed greater values in peak and mean force, peak and mean pressure, and pressure–time integral under toes and metatarsal heads. These differences reached statistically significant in mean force (p = 0.009) and peak force (p = 0.003) under T1; mean pressure (p = 0.01) and peak pressure (p = 0.04) under T1; and mean force (p = 0.003) under MH1. The binary logistic regression analysis showed mean force under T1 as the most associated plantar pressure measurement with the presence of metatarsalgia. C-statistic was 0.66. Mean force > 35 N had a 70% of sensitivity and a 57% of specificity as a cut-off value for the presence of metatarsalgia.
Conclusion
HV patients with metatarsalgia had greater values in plantar pressure measurements. Mean force under T1 could be used as a plantar pressure measurement to predict metatarsalgia.
Keywords: Hallux valgus, Women, Metatarsalgia, Plantar pressure
Introduction
Metatarsalgia is a general term that refers to pain in the region of the metatarsal heads. Hallux valgus (HV) is one of the most common causes of primary metatarsalgia owing to first ray insufficiency. Another cause tested in the literature is the increase relative length of the second metatarsal [1, 2].
Previous studies reported plantar pressure measurements at the forefoot of HV patients [3–8]. However, few of them focused on plantar loading patterns in HV patients with metatarsalgia [9, 10]. Waldecker et al. reported the results of a pedographic analysis in HV patients with metatarsalgia compared with asymptomatic HV [9]. And Geng et al. analyzed differences in plantar pressures of postoperative HV patients with and without transfer metatarsalgia [10]. To our knowledge, matched-cohort studies have not been published before.
The purpose of our study was to assess differences in plantar pressure measurements in women with HV with and without metatarsalgia. We hypothesized that there would be significant differences between these groups. If there could be differences in the whole preoperative plantar pressure measurements or in some of them, plantar pressure technology might be a tool to use in orthopedic practice for a better understanding of the HV deformity associated with metatarsalgia.
Material and methods
Subjects
A prospective study was performed from January 2017 to December 2019 in the foot and ankle unit of a single hospital. Patients were chosen for the study according to the following inclusion criteria: age over 18 years old, women, diagnosis of HV with metatarsalgia. Patients reported pain in the region of metatarsal heads during the stance phase of gait. Criteria for exclusion were other forefoot deformities, gastrocnemius tightness, deformities of the hindfoot, arthrosis, systemic diseases, neurologic disorders, history of previous surgery of the foot and lower extremity, history of trauma or infection, and patients that were incapable of stepping correctly on the pressure platform during measurement.
Control group had the same inclusion and exclusion criteria, except metatarsalgia.
The match control group was selected on a 1:1 ratio to patients without metatarsalgia, based on age within 5 years, BMI within 2 kg/m2, and hallux valgus angle within 5°.
This study was performed in accordance with the ethical standards in the 1964 Declaration of Helsinki. The study was approved by our Institutional Review Board and informed written consent was obtained from all participants.
Functional assessment
The American Orthopaedic Foot and Ankle Society (AOFAS) hallux metatarsophalangeal interphalangeal score [11] and visual analogue scale (VAS) [12] were used for clinical evaluation. The orthopaedic surgeon, who did not know the plantar pressure data collection and the radiographic assessment, implemented these forms at one visit.
Radiographic assessments
Anteroposterior and lateral weight bearing radiographs were used by 2 orthopaedic surgeons, who did not know the plantar pressure data collection and functional assessment of the patients [13, 14].
On AP radiograph hallux valgus angle (HVA) [15], first–second intermetatarsal angle (IMA) [15], distal metatarsal articular angle (DMAA) [15], first and second metatarsal length [16], and first metatarsal protrusion distance [17] were measured. On the lateral radiograph, metatarsus primus elevatus (MPE) [18], and first metatarsal declination angle (MDA) [19] were assessed.
HVA was considered normal if value was 15 degrees or less, mild if it was less than 20 degrees, moderate if it was 20 to 40 degrees, and severe if it was 40° or more [15]. A normal value was defined as 9 degrees or less for IMA and 6 degrees or less for DMMA [15]. First metatarsal protrusion distance was evaluated with Hardy and Clapham´s arc method [17]. Values were measured and recorded in millimeters (mm); measurements within the range of + 1 to – 1 mm were considered to be equal length. Metatarsal index was classified as plus, plus minus, and minus index, whether the first metatarsal was longer, equal, or shorter than the second metatarsal, respectively [20]. MPE were measured and recorded in mm with a normal value of 8 mm or less [18]. A value between 19° and 25° was defined as normal for MDA [19].
Plantar pressure data collection
All patients underwent plantar pressure measurements by RunTime® (Diagnostic Support España S.L., Bormujos, Spain) platform with 9600 sensors (2 sensors/cm2 operating at 200 Hz). The total area was 130 × 45 cm, enclosing a 120 × 40 cm sensor area. The platform allowed a walking speed between 0.8 and 20 km per hour, and a maximum load of 130 kg. Patients were asked to walk in a relaxed way at a self-selected speed and did not look towards their feet [21]. Data collected started after feeling comfortable on the platform for a period of 15 s.
On the FreeStep® Software (Diagnostic Support España S.L., Bormujos, Spain) foot regions included (Fig. 1): great toe (T1), second to fifth toes (T2 to T5), first metatarsal head (MH1), second metatarsal head (MH2), third metatarsal head (MH3), fourth metatarsal head (MH4), fifth metatarsal head (MH5), medial midfoot (MMF), lateral midfoot (LMF), medial rearfoot (MRF), lateral rearfoot (LRF). For each region, peak pressure (Kpa), mean pressure (KPa), maximum force (N), mean force (N), and pressure–time integral (N/cm2s) were generated by the software. Three footprints were selected, the one in the middle of the trial, the anterior, and the posterior. The mean of these three footprints for plantar pressure measurements was calculated for further analysis. Previous research has supported this method to provide plantar pressure measurements [22, 23]. The podiatrist who conducted the analysis did not know the clinical and radiographic evaluation. Plantar pressure measurements were divided by the patient’s body weight to be normalized.
Fig. 1.
Plantar pressure map regions: T1 (great toe), T2-3–4-5 (second to fifth toe), MH1 (first metatarsal head), MH2 (second metatarsal head), MH3 (third metatarsal head), MH4 (fourth metatarsal head), MH5 (fifth metatarsal head), MMF (medial midfoot), LMF ( lateral midfoot), MRF (medial rearfoot), LRF (lateral rearfoot). Red color indicates the maximum pressure zone
Statistical analysis
Statistical analysis was conducted with IBM SPSS 18.0 software (IBM SPSS, Armonk, NY). Statistical significance was set at p < 0.05. All data were explored for normality prior to inferential analysis. Descriptive statistics were used to calculate the mean, standard deviation, and range for each estimate. Qualitative variables were showed with numbers and frequencies.
Parametric comparisons of continuous data were performed using the 2-tailed Student t test. The chi-square test was used for categorical data. Associations between continuous variables were determined using Pearson’s r correlation coefficient. Binary logistic analysis was used to determine the extent of these associations. The predictive accuracy of the plantar pressure data was assessed using the c-statistics, which is equivalent to the area under the receiver operating characteristic (ROC) curve. As a rule, c-statistics between 0.70 and 0.79 are considerable acceptable, and between 0.80 and 0.89 are considered excellent [24].
Results
During the period of study, 47 women with HV and metatarsalgia were chosen for the study. And they were matched with 47 women with HV without metatarsalgia based on age, BMI, and HVA.
There were no significant differences in mean age between groups: 53.5 years (SD 6.4; range 21–67) in HV with metatarsalgia group, and 56.4 years (SD 5.3; range 36–74) in HV without metatarsalgia group (p = 0.14); and mean BMI: 25.1 kg/m2 (SD 4.1; range 16.1–36.5), and 25.9 kg/m2 (SD 4.1; range 17.3–36), respectively. Lesser toe deformities were present in 32 patients (68.1%) in HV with metatarsalgia group, and 13 patients (27.7%) in HV without metatarsalgia group, and this difference was statistical significance (p < 0.001). They included 30 hammer toes and 2 claw toes in HV with metatarsalgia group, and 12 hammer toes and 1 claw toe in HV without metatarsalgia group (p = 0.86).
Functional assessment
Mean AOFAS score was statistically significantly lower in HV without metatarsalgia group 42.4 (SD 11.4; range 12–68) versus 55.0 (SD 12.7; range 27–72) in HV with metatarsalgia group (p < 0.001). Mean VAS pain was statistically significantly higher in HV without metatarsalgia group 7.8 (SD 1.3; range 5–10) versus 6.9 (SD 1.8; range 4–10) in HV with metatarsalgia group (p = 0.008).
Radiographic assessment
Radiographic assessments showed no statistically significant differences between groups (Table 1).
Table 1.
Radiographic assessments
| HV with metatarsalgia (n = 47) |
HV without metatarsalgia (n = 47) |
p-value | |
|---|---|---|---|
| HVA (°) | 29.2 ± 7.2 (20–43) | 31.2 ± 7.3 (16–44) | 0.18 |
| Hallux Valgus Categories | |||
| Mild | 5 (10.6) | 6 (12.8) | 0.88 |
| Moderate | 38 (80.9) | 36 (76.6) | |
| Severe | 4 (8.5) | 5 (10.6) | |
| IMA (°) | 13.0 ± 3.0 (7.6–22) | 12.4 ± 2.4 (8–19.7) | 0.25 |
| DMAA (°) | 11.9 ± 3.7 (1.6–20) | 12.3 ± 3.7 (5–20) | 0.58 |
| M1 (mm) | 6.5 ± 0.5 (5.8–7.8) | 6.4 ± 0.4 (5.5–7.6) | 0.57 |
| M2 (mm) | 7.6 ± 0.7 (6.4–9.6) | 7.8 ± 0.6 (6.1–9.0) | 0.32 |
| M1-M2 (mm) | 2.2 ± 2.2 (− 6.9 to 3.0) | 3.0 ± 1.7 (− 7.7 to 0) | 0.06 |
| Metatarsal index | |||
| Minus | 4 (8.5) | 0 | 0.05 |
| Plus/Plus minus | 43 (91.5) | 47 (100) | |
| MPE (mm) | 4.6 ± 1.9 (1.3–8.9) | 4.7 ± 2.1 (1.3–10.6) | 0.84 |
| MDA (°) | 21.6 ± 3.2 (14.4–27.8) | 21.7 ± 3.4 (14.2–30) | 0.86 |
Values are presented as mean ± standard deviation (range), n (%)
HVA hallux valgus angle, IMA first–second intermetatarsal angle, DMAA distal metatarsal articular angle, M1 absolute length of the first metatarsal, M1 absolute length of the second metatarsal, M1-M2 first metatarsal protrusion distance, MPE metatarsus primus elevates, MDA first metatarsal declination angle
HVA had a positive significant correlation with IMA (r = 0.334, p = 0.001) and DMAA (r = 0.442, p < 0.001), and a negative significant correlation with MPE (r = − 0.235, p = 0.02). IMA has a negative significant correlation with first metatarsal length (r = − 0.364, p < 0.001), and second metatarsal length (r = -0.339, p = 0.001). First metatarsal length had a positive significant correlation with second metatarsal length (r = 0.739, p < 0.001).
There was no significant correlation between radiographic measurements and AOFAS score or VAS pain.
Plantar pressure analysis
AOFAS scores did not correlate with any plantar pressure measurements. In patients with HV and metatarsalgia, we found a positive correlation between VAS pain and peak force (r = 0.293, p = 0.04), mean force (r = 0.329, p = 0.02), and mean pressure (r = 0.370, p = 0.01) under T1; and mean pressure (r = 0.296, p = 0.04) under T2 to T5. Conversely, in HV patients without metatarsalgia, VAS pain correlated positively with peak force (r = 0.439, p = 0.02), mean force (r = 0.311, p = 0.03), and pressure–time integral (r = 0.373, p = 0.10) under MH3.
Some significant correlations were found out between plantar pressures and radiographic variables. HVA showed a positive correlation with peak pressure under MMF, and a negative correlation with peak force and mean force under T1. DMAA presented a positive correlation with peak pressure and mean pressure under MH1, MH2, MH3 and MMF; peak force under MH2 and MMF, and mean force under MH2, MH3, and MMF. MDA displayed a positive correlation with peak pressure and mean pressure under T1, T2 to T5, MH1, MH2, MH3, MH4, and LRF; peak force under MH3, and MRF; and mean force under T1, MH3, MH4, and LRF. Length of the first and second metatarsal did not correlate with any plantar pressures data under the corresponding metatarsal head: peak pressure for M1 (r = − 0.002, p = 0.98) and M2 (r = − 0.009, p = 0.93), mean pressure for M1 (r = 0.07, p = 0.46) and M2 (r = 0.05, p = 0.60), peak force for M1 (r = 0.08, p = 0.42) and M2 (r = 0.19, p = 0.06), mean force for M1 (r = 0.10, p = 0.32) and M2 (r = 0.18, p = 0.07), and pressure–time integral for M1 (r = − 0.01, p = 0.88) and M2 (r = 0.09, p = 0.36). Pearson´s correlations coefficients (r) for HVA, DMAA, and MDA, ranged from 0.217 to 0.439.
In both groups, mean pressure and peak pressure values were highest under MH3 followed by MH2. For mean force and peak force, MRF had the highest value. Pressure–time integral arrived at its highest value under MH3. HV with metatarsalgia group showed greater values in peak and mean force, peak and mean pressure, and pressure–time integral under toes and metatarsal heads. These differences reached statistically significant in mean force (p = 0.009) and peak force (p = 0.003) under T1; mean pressure (p = 0.01) and peak pressure (p = 0.04) under T1; and mean force (p = 0.003) under MH1. With the numbers available, there were no significant differences in pressure–time integral between groups (Table 2).
Table 2.
Plantar pressure measurements in both groups
| Regions | HV with metatarsalgia (n = 47) |
HV without metatarsalgia (n = 47) |
p-value | |||
|---|---|---|---|---|---|---|
| Mean | SD | Mean | SD | |||
| Maximum Force (N) | T1 | 84.0 | 32.3 | 74.9 | 21.3 | 0.009 |
| T2-T5 | 37.2 | 22.2 | 32.6 | 16.3 | 0.25 | |
| MH1 | 90.7 | 27.2 | 74.7 | 28.3 | 0.007 | |
| MH2 | 95.4 | 21.3 | 89.2 | 25.6 | 0.20 | |
| MH3 | 109.5 | 25.0 | 102.4 | 25.0 | 0.17 | |
| MH4 | 91.0 | 27.8 | 83.3 | 22.0 | 0.14 | |
| MH5 | 40.6 | 16.7 | 37.0 | 11.8 | 0.23 | |
| MMF | 69.4 | 36.1 | 75.3 | 36.9 | 0.43 | |
| LMF | 122.7 | 44.8 | 119.8 | 34.9 | 0.39 | |
| MRF | 136.0 | 33.7 | 128.3 | 26.7 | 0.22 | |
| LRF | 123.8 | 46.0 | 113.2 | 40.5 | 0.24 | |
| Mean Force (N) | T1 | 42.3 | 17.5 | 33.1 | 10.4 | 0.003 |
| T2-T5 | 18.4 | 12.0 | 15.5 | 8.1 | 0.17 | |
| MH1 | 46.1 | 13.6 | 41.0 | 16.4 | 0.10 | |
| MH2 | 54.2 | 13.4 | 52.3 | 15.4 | 0.50 | |
| MH3 | 63.9 | 14.3 | 60.9 | 14.5 | 0.30 | |
| MH4 | 53.1 | 16.7 | 48.3 | 12.7 | 0.12 | |
| MH5 | 20.4 | 9.0 | 19.4 | 7.8 | 0.60 | |
| MMF | 35.2 | 22.8 | 39.5 | 20.6 | 0.33 | |
| LMF | 63.8 | 28.2 | 68.6 | 22.9 | 0.36 | |
| MRF | 88.6 | 21.9 | 83.6 | 19.6 | 0.24 | |
| LRF | 74.0 | 27.9 | 69.5 | 25.6 | 0.41 | |
| Peak pressure (KPa) | T1 | 783.2 | 198.7 | 682.0 | 184.8 | 0.01 |
| T2-T5 | 661.7 | 212.1 | 622.2 | 190.0 | 0.34 | |
| MH1 | 856.9 | 250.1 | 778.0 | 218.7 | 0.10 | |
| MH2 | 971.9 | 234.8 | 911.9 | 234.0 | 0.21 | |
| MH3 | 992.4 | 247.9 | 930.0 | 248.7 | 0.19 | |
| MH4 | 916.6 | 255.0 | 857.1 | 214.2 | 0.22 | |
| MH5 | 685.2 | 310.7 | 619.6 | 224.6 | 0.24 | |
| MMF | 732.2 | 155.3 | 754.3 | 168.0 | 0.50 | |
| LMF | 821.4 | 217.2 | 811.4 | 176.8 | 0.80 | |
| MRF | 799.2 | 230.6 | 762.0 | 220.0 | 0.42 | |
| LRF | 817.0 | 203.1 | 797.4 | 207.4 | 0.64 | |
| Mean pressure (KPa) | T1 | 328.4 | 91.1 | 296.0 | 71.3 | 0.04 |
| T2-T5 | 315.0 | 111.6 | 281.6 | 77.4 | 0.09 | |
| MH1 | 355.7 | 85.9 | 345.9 | 107.0 | 0.62 | |
| MH2 | 470.7 | 91.2 | 469.7 | 108.9 | 0.96 | |
| MH3 | 510.8 | 85.6 | 499.3 | 78.4 | 0.49 | |
| MH4 | 455.7 | 116.0 | 452.4 | 83.4 | 0.14 | |
| MH5 | 337.0 | 108.2 | 313.6 | 79.4 | 0.22 | |
| MMF | 322.8 | 60.3 | 332.0 | 72.4 | 0.50 | |
| LMF | 384.7 | 85.6 | 389.3 | 72.4 | 0.77 | |
| MRF | 394.5 | 80.6 | 386.3 | 85.3 | 0.63 | |
| LRF | 415.9 | 123.5 | 388.9 | 94.3 | 0.23 | |
| Pressure–time integral (N/cm2s) | T1 | 37.7 | 18.6 | 34.6 | 14.9 | 0.37 |
| T2-T5 | 17.3 | 12.8 | 16.6 | 9.2 | 0.77 | |
| MH1 | 57.0 | 19.1 | 50.1 | 21.3 | 0.10 | |
| MH2 | 65.5 | 16.7 | 64.7 | 20.1 | 0.84 | |
| MH3 | 77.4 | 16.3 | 75.9 | 20.9 | 0.68 | |
| MH4 | 63.2 | 20.0 | 60.3 | 16.8 | 0.45 | |
| MH5 | 25.7 | 10.4 | 24.1 | 12.7 | 0.87 | |
| MMF | 39.5 | 27.5 | 45.1 | 28.9 | 0.34 | |
| LMF | 62.4 | 26.9 | 74.5 | 38.5 | 0.08 | |
| MRF | 71.9 | 25.6 | 70.0 | 30.1 | 0.74 | |
| LRF | 63.5 | 26.1 | 64.1 | 36.8 | 0.93 | |
Values are presented as mean ± standard deviation
T1 great toe, T2—T5 second to fifth toes, MH1 first metatarsal head, MH2 second metatarsal head, MH3 third metatarsal head, MH4 fourth metatarsal head, MH5 fifth metatarsal head, MMF medial midfoot, LMF lateral midfoot, MRF medial rearfoot, LRF lateral rearfoot
Patients with lesser toe deformities had greater plantar pressures than patients without lesser toe deformities in both groups. However, these differences were not statistically significant.
The binary logistic regression analysis showed mean force under T1 as the most associated plantar pressure measurement with the presence of metatarsalgia (Table 3). The c-statistic was 0.66 (95% CI 0.55 to 0.77) (Fig. 2). Mean force under T1 higher than 35 N had a 70% of sensitivity and a 57% of specificity as a cut-off value for the presence of metatarsalgia, positive predictive value was 62% and negative predictive value was 66%; positive likelihood ratio was 1.63 and negative likelihood ratio was 0.53 (Table 4).
Table 3.
Binary logistic regression for plantar pressures predictor of the presence of metatarsalgia
| OR | 95% CI | p-value | |
|---|---|---|---|
| Peak pressure T1 | 1.004 | 0.998–1.010 | 0.15 |
| Mean pressure T1 | 0.988 | 0.974–1.002 | 0.08 |
| Peak force T1 | 0.972 | 0.926–1.021 | 0.26 |
| Peak force MH1 | 1.013 | 0.996–1.031 | 0.13 |
| Mean force T1 | 1.110 | 1.001–1.231 | 0.04 |
OR odds ratio
Fig. 2.
ROC curve for mean force under T1 higher than 35 N
Table 4.
Presence of metatarsalgia and mean force under T1
| Metatarsalgia | No metatarsalgia | n | |
|---|---|---|---|
| Mean force T1 > 35 N | 33 (62.3%) | 20 (37.7%) | 53 |
| Mean force T1 < 35 N | 14 (34.1%) | 27 (65.9%) | 41 |
| n | 47 | 47 | 94 |
p = 0.006
Power study
Power analysis compared mean force under T1 in both groups. For a sample size of 47 in each group, an alpha error of = 0.05 and a difference of 9.2 between groups, a Zβ value of 2.32 was computed. The power of this study was 98%.
Discussion
The main finding of this investigation was that HV with metatarsalgia patients showed a significantly higher value of mean pressure and peak pressure under T1, a significantly higher value of mean force and peak force under T1, and a significantly higher value of mean force under MH1. Mean force under T1 was the most associated variable with the presence of metatarsalgia.
Higher loading under central metatarsals had been reported previously in HV patients. Koller et al. referred in 55 HV patients that peak pressure and maximum force were greater under MH2 and MH3 [25]. Weng et al. compared plantar pressure measurements in 229 patients with self-reported pain in the forefoot and other 35 controls. They found increased loading under MH2 and MH3, and reduced force under T1 [4]. Martinez Nova et al. found that the highest mean pressure was under MH2 in 79 female patients with mild HV [3]. In our study, mean pressures and peak pressures were also higher under MH2 and MH3.
Few studies analyzed plantar loading patterns in HV patients with metatarsalgia. Waldecker et al. reported significantly higher loading patterns of the lateral forefoot (MH2 to MH5), and significant decrease of pressure variabilities under T1, in 50 patients with HV and metatarsalgia symptomatology compared with 50 asymptomatic HV. A peak pressure > 70 N/cm2 and a pressure–time integral > 28 N/cm2s at lateral forefoot was established in symptomatic HV feet as a critical threshold associated with symptomatology [9]. Geng et al. focused to determine specific differences in the loading patterns between 30 reconstructive HV feet with postoperative transfer metatarsalgia and 30 postoperative feet without pain. They did not find significant differences in peak force and force–time integral of MH2 and MH3 between groups. However, significantly higher cumulative load percentage and instant load percentage were higher in patients with transfer metatarsalgia [10]. As the magnitude of the HV increases, first ray malalignment and insufficiency arise, leading to a mechanical overloading of central metatarsals [26]. In our study, the positive correlation found between MDA and peak pressure and mean pressure under MH1, MH2, and MH3, showed this increase in pressure. Differences in plantar pressures under metatarsal heads between HV patients with and without metatarsalgia were small. Only pressure and force under T1, and maximum force under MH1 reached statistical significance. This increase loading related to the T1 region may be attributed to less pain and longer pressure–time integral. The hallux would load for a longer time, and more force would be applied. A mean force under T1 higher than 35 N as a critical threshold for the presence of metatatarsalgia a 70% of sensitivity and a 57% of specificity.
Previous research about toe deformities in diabetic patients referred that toe deformities increase metatarsal pressures. Mueller et al. published higher metatarsophalangeal joint angle in diabetic patients than non-diabetic patients. They referred that hammertoe deformity was the primary structural factor that predicted forefoot peak plantar pressure during walking in people with diabetes under great toe, MH2, MH3, MH4, and MH5. However, in non-diabetic patients hammertoe deformity only predicted forefoot peak plantar pressure under MH3 [27]. Yu et al. found higher in-shoe peak plantar pressures under MH1 to MH5 for diabetic patients with claw toes compared to controls [28]. In our study, the analysis of patients with toes deformities did not find statistically significant differences in plantar pressures under metatarsal heads. Our patients with toe deformities were more prone to have metatarsal pain, as Slullitel et al. reported before [29].
The effect of functional assessment on the foot pressure is less known. Martinez Nova et al. reported a negative correlation between AOFAS clinical score with mean pressure under T1 [3, 30]. In our study, AOFAS score did not correlate with any plantar pressure measurements. VAS pain had a different plantar pressure pattern behaviour between groups. HV patients with metatarsalgia showed a positive correlation with pressure variabilities under T1. Nevertheless, HV patients without metatarsalgia showed these positive correlations with pressure variabilities under MH3. Although these correlations were weak, they suggested that patients with greater pressure in these zones had more pain.
Maestro et al. referred a long second metatarsal as the most common cause of primary metatarsalgia [31]. However, other studies contradict this theory. Kaipel et al. studied peak pressure and maximal force in 51 feet with metatarsalgia and 51 feet without metatarsalgia. They did not find a correlation between the relative length of the first and third metatarsals and maximal peak pressure and maximal force. Maximal force under MH1 was significantly lower in the metatarsalgia group. The authors concluded that metatarsal length did not influence plantar loading [32]. Slullitel et al. referred an inverse relationship between metatarsal index and metatarsalgia, thereby patients with index minus were less likely to have metatarsal pain [29]. In our study, radiographic assessments showed no statistically significant differences between groups. We only measured first MDA, with no statistically significant differences between groups. However, second to five metatarsal declination angles were not taken into account, and maybe play a role in the development of metatarsal pain.
The study has limitations that ought to be addressed. First, we did not include a control group. The purpose of our study was to assess differences in dynamic plantar pressure measurements in women patients with HV with and without metatarsalgia. Maybe, it was not justifiable to expose healthy people to radiation exposure. Second, we did not assess first tarsometatarsal instability as a cause of HV. Third, a relatively small sample size in both groups, even though we were able to identify some statistically significant differences. Fourth, we did not address walking speed, and patients walked across the platform at a self-comfortable speed.
However, this study had also several strengths. First, this was a prospective study with well-established criteria and aims. Second, all radiographs were taken according to a strict protocol, which does eliminate the possibility of technical failure. Third, radiographs, functional assessment and plantar pressure analysis were blinded. Four, to our knowledge, this is the first marched cohort study focused on plantar pressure analysis in HV feet with metatarsalgia.
This study provides information about plantar pressure measurements in patients with HV and metatarsalgia. Mean force under T1 could be used as a plantar pressure measurement to predict metatarsalgia. Plantar pressure technology might be a tool to use for early screening in HV patients to predict metatarsalgia.
Funding
No funding to declare.
Declarations
Conflict of interest
All authors were fully involved in the study and preparation of the manuscript and declare that there is no conflict of interest.
Ethical approval
All the procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
Informed consent
Informed consent was obtained from the patient included in the case report.
Footnotes
Publisher's Note
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References
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