Foot pressure in patients with chronic lumbar radicular pain (sciatica) caused by lumbar disc herniation: a case-control observational study

RESEARCH European Spine Journal https://doi.org/10.1007/s00586-025-08880-3 Introduction Radicular low back pain, also known as “sciatica,” occurs due to compression of the dorsal root of a spinal nerve, radiating to one or more dermatomes. It may be accompanied by additional radicular symptoms or functional deficits in the feet and lower extremities [1]. Sciatica is a major cause of chronic non-oncological pain in Europe, with a prevalence in the general population ranging from 3 to 25% [1–3]. Studies have indicated that lumbosacral radiculopathies contribute to 34.6% of neuropathic pain cases [4]. This condition is characterized by pain radiating along the lower limb, which may also extend to the foot. The sciatic nerve is comprised of the L4 through S3 nerve roots [5], which merge to form a large nerve running from the pelvis, passing along the posterior thigh, and dividing into the tibial and common peroneal nerves at the popliteal fossa, continuing to the foot. A functional relationship María Reina-Bueno [email protected] Pedro V. Munuera-Martínez [email protected] Carmen Vázquez-Bautista [email protected] Gabriel Domínguez-Maldonado [email protected] Ángel Martínez-Navas [email protected] María José García-Rodríguez [email protected] Inmaculada C. Palomo-Toucedo [email protected] 1 University of Seville, Seville, Spain 2 Universitary Valme Hospital, Seville, Spain Abstract Objective This study aimed to determine whether there are differences in plantar pressures during gait between patients with lumbar disc herniation -induced sciatica and healthy individuals. Methods This observational case–control study included 41 patients with sciatica due to lumbar disc herniation and 30 healthy controls. Plantar pressures were evaluated using the FootScan® platform in 10-foot zones during 3 gait phases, defined as rockers. After walking, body advancement with the supporting foot depends on stance–limb mobility, with the supporting foot acting as a pivot system. In a serial fashion, the heel, ankle, and forefoot serve as rockers that allow the body to advance smoothly. Data were also collected on quality of life, low back pain, lower limb pain, foot pain, foot pain-related disability, foot joint range of motion, and foot posture index. All variables were compared between the two groups. Results Patients with sciatica had a longer contact time and higher mean and peak pressures in all foot zones, except for the first metatarsal and toes. Pressures were higher in the third to fifth metatarsals, especially during push-off. Patients with sciatic arthritis experience not only low back pain, but also lower limb and foot pain, as well as higher foot pain-related disability. There were no significant differences in foot posture or joint ranges, except for decreased subtalar pronation in patients with sciatica. Conclusion Altered plantar pressure distribution in patients with sciatica may be associated with neuromuscular compensation mechanisms. Keywords Sciatica · Plantar pressure · Lumbar disc herniation · Lumbar radiculopathy. Received: 8 October 2024 / Revised: 25 February 2025 / Accepted: 18 April 2025 © The Author(s) 2025 Foot pressure in patients with chronic lumbar radicular pain (sciatica) caused by lumbar disc herniation: a case-control observational study Pedro V.Munuera-Martínez1· MaríaReina-Bueno1· CarmenVázquez-Bautista1· GabrielDomínguez-Maldonado1· ÁngelMartínez-Navas2· María JoséGarcía-Rodríguez2· Inmaculada C.Palomo-Toucedo1 1 3 European Spine Journal between the foot and lumbar region has been established, with one region influencing the development of pathologies in the other. A descending relationship is observed in which lumbar pathology, such as lumbar disc herniation (LDH) or lumbar spinal stenosis (LSS), leads to changes in the lower limb and foot [6–8]. These changes can include muscle weakness, pain, and neurological deficits. Conversely, an ascending relationship, in which foot support alterations contribute to lumbar dysfunctions, is also possible. Abnormal foot function, altered foot loading, and nonspecific low back pain are frequently associated with lumbar pathologies [9, 10]. Alterations in foot function during gait can affect pelvic position and mobility, increasing the risk of lumbar pathologies [11–16]. LDH-related nervous and muscular alterations can affect foot strength and motor control and alter foot loading during gait, resulting in changes in plantar pressure that increase the risk of lower extremity injuries. Lumbar radiculopathy affects sensory input and proprioceptive responses in the foot [17],, and the involvement of muscles innervated by the S1 and L5 roots further contributes to altered plantar pressure. Assessing plantar pressure may help evaluate lumbar root dysfunction severity [18]. Combining foot function assessments with neurological rehabilitation may help manage gait and pain in such patients. The identification of an association between specific plantar pressure patterns and sciatica could lead to improved clinical management. Lumbar intervertebral disc protrusion or herniation is a common cause of sciatica [2]. To the best of our knowledge, no study has directly established the relationship between plantar pressure and gait pressure. Therefore, this study elucidated plantar pressure patterns in patients with sciatica caused by LDH and compare them with those of healthy individuals. Materials and methods An observational case–control study was conducted with patients diagnosed with sciatica due to LDH and individuals of similar age, sex, and Body Mass Index (BMI) without the condition. The study was conducted at Valme University Hospital (Área de Gestión Sanitaria Sur de Sevilla) and the Clinical Podiatry Area of the University of Seville, Spain, between March 2022 and May 2024. The study was approved by the Clinical Research Ethics Committee of Valme University Hospital (Code 2449-N-21). All patients voluntarily participated but were informed of the study details and potential risks and provided signed informed consent. The inclusion criteria were a diagnosis of chronic (three months minimum duration) radicular low back pain (sciatica) with a minimum score of 5 using the Numeric Pain Rating Scale 11 (NPRS-11) caused by non-traumatic LDH. Patients with other spinal pathologies causing radicular pain, conditions affecting walking (e.g., neuromusculoskeletal, vestibular, and cardiopulmonary diseases), neuropathic pain related to diabetes or other conditions, pregnancy, cognitive impairment, prior foot surgery, inflammatory rheumatic disease, use of walking aids, or current foot orthoses were excluded. The control group included healthy individuals with similar demographics but without sciatica, LDH, lumbar pathology, trauma, surgery, musculoskeletal or neurological diseases, diabetes, or foot deformities. These individuals were companions of patients attending the Clinical Podiatry Area. Patients were recruited by two clinicians specializing in Anesthesiology, Resuscitation, and Pain Management. Eligible patients were invited to participate and were referred to the Clinical Podiatry Area at the University of Seville for data collection. (Fig. 1). The examinations were always conducted in the morning between 10:00 and 13:00 a.m. The pharmacological treatment was not altered so as not to interfere with the results. Clinical and demographic data, including age, sex, weight, and height, were collected. Pain in the foot, lower limb, or lower back was recorded and quantified using the Numeric Pain Rating Scale 11 (NPRS11). Disability was assessed using the Oswestry Disability Index (ODI), Manchester Foot Pain and Disability Index (MFPDI), and the SF-12 quality of life questionnaire. The foot joint range of motion was measured, including ankle dorsiflexion (knee extended and flexed), hindfoot and forefoot pronation and supination, first ray dorsiflexion and plantarflexion, and first toe dorsiflexion. Extrinsic foot muscle strength (dorsiflexors, plantarflexors, supinators, pronators) was evaluated using manual muscle testing, graded per the Medical Research Council classification (0–5 scale) [19], which assigns values between 0 and 5, where 0 represents no muscle activity and 5 represents normal muscle strength. The foot posture was assessed using the Foot Posture Index (FPI), a clinical tool, and the foot was classified as neutral, pronated, or supinated. Plantar pressure examination during gait was performed using the FootScan platform®(RSscan International, Olen, Bélgica), which has been proven to have good reliability and repeatability [20]. The platform dimensions were 2093 × 469 × 18 mm, with 16,384 resistive sensors arranged in a 256 × 64 matrix with a resolution of 4 sensors/cm², an active sensor area of 1950 mm × 325 mm, data acquisition frequency of 125 Hz, and pressure range of 1–200 N/cm². The platform was embedded flush with the ground on a 2-meter-wide by 10-meter-long wooden walkway to simulate walking on a regular, even surface and to prevent the 1 3 European Spine Journal targeting effect. Following the manufacturer’s instructions, the system was calibrated before each data collection. During calibration, the participant’s body weight and foot size were entered into the software, and then the participant was asked to walk over the platform. The analysis software then determined the recalibration factor for future measurements for the same participant. The platform is connected to a computer that transmits and processes all information using the Scientific FootScan® software. This system provides plantar pressure data by automatically dividing the foot image into 10 zones: medial heel (MH), lateral heel (LH), midfoot (MF), first metatarsal (M1), second metatarsal (M2), third metatarsal (M3), fourth metatarsal (M4), fifth metatarsal (M5), big toe (T1), and lesser toes (T2-5). For statistical analysis, the following plantar pressure variables were selected for each of these 10 zones: contact time (ms), mean pressure during total contact time (N/cm²), peak pressure (N/cm²), and time of peak pressure occurrence (% of the stance phase). These values were examined across the 3 functional rockers of the stance phase: [21] heel contact to forefoot contact (first rocker), forefoot contact to heel lift-off (second rocker), and heel lift-off to toe-off (third rocker). In addition, the foot-progression angle was also considered. In total, 121 Fig. 1 Image of the study laboratory 1 3 European Spine Journal during the gait cycle, potentially confounding the interpretation of results. Data analysis Statistical analysis was performed using IBM SPSS Statistics 27 (IBM, Armonk, NY, USA). For the descriptive analysis, absolute frequency (N), relative frequency (%), mean values, standard deviation (SD), 25th, 50th, and 75th percentiles, and interquartile ranges (IQR) were calculated. For the comparative analysis of qualitative variables, the chi-square test was used to determine whether there was any relationship (dependence) between the variables through cross-tabulations. To analyze the differences between the control and sciatica patient groups, normality tests were first performed using the Kolmogorov-Smirnov test. When the variable values followed a normal distribution, the independent samples T-test was used to compare the two groups; when the data did not follow a normal distribution, the Mann-Whitney U test for independent samples was used. For the inferential analysis, a 95% confidence level was considered by comparing the experimental p-value with a 5% significance level. Results The perceived low back pain and demographic characteristics are shown in Table 1. There were no statistically significant differences between the groups in any demographic characteristics. Participants with sciatica had a mean disease duration of 16.1 ± 3.4 years. No significant differences were found in the foot posture or range of motion (ROM) scores of the main foot joints between the control and sciatic groups, except for the pronation of the subtalar joint (Table 2). In the sciatic group, lower muscle strength was observed in the major extrinsic muscle groups of the foot (dorsiflexors, plantarflexors, pronators, and supinators) (Table 3). Additionally, participants with sciatica reported parameters were recorded for each foot (4 variables x 10 zones x 3 rockers + foot progression angle). Participants walked on the platform for 2 min at a comfortable speed for acclimatization. Data were then collected for five passages over the platform. The three most consistent footprints for each foot (complete footprints, heel-strike pattern, no adjustments) were selected by two experienced researchers. The average values of the pressure variables were used in the statistical analysis. The variable mean pressure was taken as a reference, and the sample size was calculated to compare two means. The formula used is as follows: n= 2 s 2( zα 2 + zβ )2 d 2 Here, s is the estimated standard deviation, α is the type I error, β is the type II error, and d is the minimum detectable difference. Thus, the final equation is as follows: n = 2 s 2( zα 2 + zβ )2 d2 = 2·42·(1,96 +0,84)2 2,52 =40,14 ≈41 A minimum of 41 cases per group was required to perform a comparison meeting these criteria. In this study, the unit of analysis was the foot, rather than the individual participants. In the control group, both feet were analyzed to determine the sample size required for statistical comparisons. However, in the sciatica group, only the affected limb was considered. Because plantar pressure variables were the primary outcome measures, the non-affected limb was excluded from the analysis to avoid potential bias.This decision was based on the premise that compensatory biomechanical and antalgic adaptation could alter the kinetics and kinematics of the unaffected foot Table 1 Participants’ demographic characteristics and perceived low back pain Control N = 30 Sciatic N = 41 p N%N% Sex Male 10 33.3 21 51.2 0.056 Female 20 66.7 20 48.8 Mean SD 95% CI Mean SD 95% CI AGE 47.0 9.4 46.5–43.0 47.5 10.0 46.9–44.0 0.771 BMI 25.5 3.5 24.2–26.8 27.1 4.5 26.0-28.5 0.500 Perceived Low Bak Pain 0.7 1.9 0.1–1.4 8.0 2.2 7.4–8.7 < 0.001 BMI: Body Mass Index. SD: Standard Desviation. IQR: Interquantil range 1 3 European Spine Journal times than controls in all zones except for the toes and first metatarsal, and they exhibited higher mean and peak pressures than controls in all zones except for the first toe. No significant between-group differences were observed in the timing of peak pressure or foot progression angle. worse scores on pain scales, disability related to foot, and quality of life (Table 4). Table 5 presents the variables related to plantar pressure divided into 10 zones of the foot, along with the p-values from the comparison between the control and sciatic groups. Participants in the sciatic group showed longer contact Table 2 Foot posture and range of motion of the main articular movements of the participants’ feet in the control and sciatic group (This table shows the comparison of foot variables; that is why the control group consisted of N = 60, as all variables were obtained from both feet) Control N = 60 Sciatic N = 41 p Mean SD 95%CI Median IQR Mean SD 95%CI Median IQR Foot Posture Index (FPI) 3.6 3.4 2.8–4.5 4 0–6 3 3.6 1.9–4.1 4 1.5–5.5 0.4372 Ankle dorsal flexion (KF) 19.6 5.9 18.1–21.1 20 16–24 18.0 6.3 16–20 18 14.5–22.0 0.1922 Ankle dorsal flexion (KE) 14.1 5.2 12.8–15.5 15 10.0-19.5 12.3 5.7 10.5–14.1 12 10–16 0.1482 Rearfoot pronation 11.2 5.2 9.8–12.5 10 8–14 9.4 4.5 7.9–10.9 9 7–10 0.0352 Rearfoot supination 27.4 9.3 25.0-29.8 28 20.0-33.8 28.1 6.4 26.0-30.2 28 22.0-32.5 0.6321 Forefoot pronation 14.2 7.9 12.2–16.2 15 8.0-19.8 12.3 6.6 10.3–14.4 10 7.0-16.5 0.2042 Forefoot supination 40.6 15.1 36.7–44.5 41.5 28.0-54.3 41.2 10.4 38.0-44.5 43 33.5–50.0 0.9472 First ray dorsiflexion 6.0 1.7 5.5–6.4 6 5–7 6.3 1.7 5.7–6.8 6 5.0-7.5 0.3732 First ray plantarflexion 4.5 1.0 4.2–4.8 5 4–5 4.8 1.4 4.3–5.2 5 4–6 0.5942 Hallux dorsiflexion 58.0 12.8 54.7–61.3 59 50.0-66.8 54.4 11.3 50.8–58.0 55 47.0-62.5 0.2582 1T test for independent samples 2 Mann-Whitney’s U test KF: Knee flexed; KE: Knee extended Table 3 Muscular strength of the participants’ feet in the control and sciatic group (This table shows the comparison of foot variables; that is why the control group consisted of N = 60, as all variables were obtained from both feet) Control N = 60 Sciatic N = 41 p Mean SD 95% CI Median IQR Mean SD 95% CI Median IQR Foot dorsal flexors#5.0 0 5–5 5 5–5 4.8 0.5 4.6-5.0 5 5–5 0.002 Foot plantar flexors#5.0 0 5–5 5 5–5 4.9 0.3 4.8-5.0 5 5–5 0.006 Foot pronators#4.9 0.3 4.8-5.0 5 5–5 4.6 0.6 4.5–4.8 5 4–5 0.002 Foot supinators#4.9 0.3 4.8-5.0 5 5–5 4.7 0.6 4.5–4.8 5 4–5 0.011 Comparisons were made using Mann-Whitney’s U test # Scores ranged from 0 to 5 (muscle strength quantified with the manual muscle test according to the Medical Research Council Scale of Muscle Strength) Table 4 Foot, lower limb and low back pain, disability related to foot pain and low back pain, and quality of life between the control and sciatic group Control N = 30 Sciatic N = 41 p Mean SD 95% CI Median IQR Mean SD 95% CI Median IQR Foot pain* 1.9 3.0 1.2–2.7 0 0–4 4.9 3.6 3.7-6.0 6 0.5-8.0 < 0.0012 Lower limb pain* 1.3 2.3 0.7–1.9 0 0–2 7.6 2.6 6.8–8.4 8 7–10 < 0.0012 Low back pain* 0.8 2.1 0.2–1.3 0 0–0 8.0 2.4 7.3–8.8 9 7–10 < 0.0012 MFPDI 3.5 6.3 1.9–5.2 0 0–5 16.9 10.3 13.7–20.2 20 9.5–23.5 < 0.0012 ODI 3.3 10.6 0.6–6.1 0 0–0 42.9 15.2 38.1–47.7 42 28–54 < 0.0012 SF-12 (Physical) 51.6 7.8 53.6–55.0 55 47.2–57.2 28.9 5.2 27.3–30.6 27.9 25.3–32.5 < 0.0012 SF-12 (Mental) 48.8 8.4 46.6–51.0 49.8 44.6–55.1 42.8 11.2 39.2–46.3 41.4 35.2–50.0 0.0031 1T test for independent samples 2 Mann-Whitney’s U test *Scores ranged from 0 to 10 (pain quantified with the Numeric Pain Rating Score 11) MFPDI: Manchester Foot Pain and Disability Index; ODI: Oswestry Disability Index 1 3 European Spine Journal Table 5 Contact time, mean pressure, peak pressure, and time when the peak pressure occurs in the 10 zones into which the foot is divided, and foot progression angle. Comparison between the control and sciatic groups Control N = 60 Sciatic N = 41 p Mean SD 95% CI Median IQR Mean SD 95% CI Median IQR Contact time (miliseconds) HM 67.2 5.8 65.7–68.7 67 63.4–71.4 70.3 6.4 68.3–72.3 71.5 68.3–74.8 0.0032 HL 67.2 5.5 65.8–68.7 66.9 63.6–70.9 73.5 22.3 66.5–80.5 71.5 68.2–74.6 0.0022 MF 67.4 5.8 65.9–68.9 68.1 63.9–71.0 72.1 4.9 70.6–73.7 72.5 69.4–75.6 < 0.0011 M1 80.3 5.7 78.8–81.8 80.4 77.7–83.8 81.8 4.5 80.3–83.2 82.4 79.2–85.0 0.1711 M2 84.0 4.0 82.9–85.0 84.3 81.5–86.2 86.1 3.9 84.8–87.3 86.4 83.5–88.4 0.0101 M3 86.0 3.0 85.2–86.8 86.1 83.89–87.5 87.4 4.1 86.1–88.7 87.8 85.4–89.5 0.0082 M4 84.8 2.9 84.0-85.5 86.1 83.9–87.5 86.5 4.3 85.2–87.9 87 84.8–88.7 0.0022 M5 78.7 4.7 77.5–79.9 79.1 75.4–81.6 81.2 5.1 79.6–82.8 82 78.8–84.6 0.0032 T1 68.5 11.0 65.6–71.3 68 61.6–77.4 71.7 8.5 69.0-74.3 72.5 65.3–78.0 0.1231 T2-5 66.3 13.0 62.9–69.6 67.1 57.6–76.8 69.4 12.4 65.5–73.3 73.3 60.8–77.5 0.1902 Mean pressure (n/cm2) HM 11.9 4.6 10.8–13.1 10.7 9.0-13.6 14.1 3.9 12.9–15.3 14 10.7–17.5 0.0022 HL 11.0 4.1 10.0-12.1 10.5 8.1–12.8 13.3 3.6 12.2–14.5 13.4 10–16 < 0.0012 MF 3.3 1.4 2.9–3.6 3 2.2–4.1 4.6 2.2 3.9–5.3 4.3 2.9–5.4 < 0.0012 M1 7.0 3.4 6.1–7.9 5.9 4.4–8.7 8.5 3.9 7.3–9.8 8.1 5.7–10.3 0.0202 M2 10.9 3.9 9.9–11.9 10 8.2–12.9 14.3 6.6 12.2–16.4 12.3 9.3–18.9 0.0132 M3 9.6 3.7 8.7–10.6 8.7 7.4–11.3 13.4 5.0 11.8–14.9 12.2 10.2–16.3 < 0.0012 M4 7.4 3.5 6.5–8.3 6.6 5.1–8.1 10.9 4.5 9.5–12.3 10 8.1–13.4 < 0.0012 M5 4.3 2.3 3.7–4.9 3.8 2.8–5.2 6.2 3.0 5.2–7.1 5.7 3.8–8.3 < 0.0012 T1 5.2 3.3 4.3-6.0 4.6 3.2–5.7 5.8 3.6 4.7–6.9 5.4 3.0-7.1 0.3282 T2-5 2.0 1.1 1.7–2.3 1.7 1.4–2.3 2.7 2.5 2.0-3.5 2.4 1.6–2.7 0.0152 Peak pressure (n/cm2) HM 19.3 7.5 17.3–21.2 17.4 14.8–21.6 23.3 6.4 21.3–25.3 22.4 17.5–27.4 < 0.0012 HL 18.4 7.4 16.5–20.4 17 13.8–20.5 22.6 6.6 20.5–24.7 22 16.7–27.4 < 0.0012 MF 6.0 2.5 5.3–6.6 5.7 4.1–7.2 8.7 3.7 7.5–9.8 8.4 5.9–10.5 < 0.0011 M1 15.5 6.8 13.8–17.3 13.9 10.7–18.6 17.5 6.4 15.5–19.5 16.6 12.1–21.0 0.0552 M2 23.5 8.2 21.4–25.6 22.1 18.2–26.4 29.3 13.6 25.0-33.6 24.9 18.3–38.5 0.0482 M3 20.3 7.8 18.3–22.3 18.4 15.3–23.4 27.5 10.3 24.3–30.8 25.5 20.1–35.6 < 0.0012 M4 15.0 7.0 13.2–16.8 13.3 10.4–17.5 22.6 9.2 19.7–25.5 20.4 15.8–29.2 < 0.0012 M5 9.1 4.8 7.9–10.3 7.6 6.2–11.1 13.8 6.7 11.7–15.9 12.3 9.4–17.3 < 0.0012 T1 12.0 6.9 10.2–13.7 9.7 6.8–15.8 12.5 6.6 10.4–14.6 11 7.3–15.7 0.5752 T2-5 4.8 2.4 4.1–5.4 4.2 3.2–6.2 6.5 5.7 4.7–8.3 5.1 4.3–6.6 0.0132 Peak pressure time (% stance phase) HM 30.8 6.1 29.2–32.4 31 26.5–34.0 33.1 7.9 30.6–35.6 31.8 27.8–36.9 0.2342 HL 29.8 4.5 29.8–28.7 29.4 27.5–32.6 31.0 6.5 29.0-33.1 30.8 27.4–33.1 0.5272 MF 47.7 8.5 45.5–49.9 47.5 41.2–53.5 49.8 10.2 46.6–53.1 51.1 42.4–58.3 0.2531 M1 74.9 4.9 73.6–76.1 76.1 72.8–78.0 74.1 7.7 71.7–76.6 75.9 71.4–79.4 0.7852 M2 77.5 4.0 76.5–78.5 78 76.1–78.9 78.3 3.9 77.1–79.6 78.9 76.3–80.7 0.1562 M3 75.9 4.1 74.8–77.0 76.3 74.3–79.0 77.0 3.7 75.8–78.1 77.4 75.6–79.6 0.0602 M4 71.7 5.4 70.4–73.1 71.6 69.1–75.9 73.6 5.1 71.9–75.2 74.8 71.7–77.0 0.0532 M5 67.4 8.2 65.3–69.6 69.6 63.3–73.8 68.8 8.0 66.2–71.3 71.7 63.3–74.8 0.2962 T1 83.5 6.2 81.9–85.1 85.3 82.3–86.7 81.9 9.0 79.0-84.7 84.1 77.5–88.4 0.6862 T2-5 81.5 6.7 79.7–83.2 83.7 77.8–86.0 82.1 6.4 80.1–84.1 82.9 79.1–86.2 0.7742 Foot progression angle 12.3 2.9 10.4–14.2 12.3 6.8–16.2 12.1 5.7 10.0–14.2 10.7 7.8–15.2 0.9141 1T test for independent samples 2 Mann-Whitney’s U test 1 3 European Spine Journal Discussion The main objective of our study was to analyze the differences in plantar pressure distribution between patients with and without sciatica.The results showed that patients with sciatica exhibited a significant increase in pressure during gait, as well as a longer contact time in all zones except The pressure values for the 10 zones during each of the 3 functional rockers (first rocker = heel rocker; second rocker = ankle rocker; third rocker = metatarsal rocker) are shown in Table 6. Table 6 Mean pressure in the 10 zones into which the foot is divided, in each of the 3 rockers separately. Comparison between the control and sciatic groups Control N = 60 Sciatic N = 41 p Mean SD 95% CI Median IQR Mean SD 95% CI Median IQR HM 1st rocker 5.9 2.8 5.2–6.7 5.6 4.1–7.2 5.7 2.5 4.9–6.4 5.9 3.6–7.2 0.6071 2nd rocker 12.7 5.0 11.4–14.0 11.3 9.4–14.6 15.0 4.1 13.7–16.3 14.6 11.6–18.3 0.0022 3rd rocker - - - - - - - - - - - HL 1st rocker 5.9 2.0 5.4–6.5 5.9 4.3–7.1 6.4 2.9 5.5–7.3 6.1 4.1-8.0 0.3881 2nd rocker 11.7 4.5 10.5–12.8 11.1 8.5–13.6 14.1 3.8 12.9–15.3 14.1 10.7–16.9 < 0.0012 3rd rocker - - - - - - - - - - - Mf 1st rocker 0.06 0.04 0.04–0.07 0.05 0.03–0.07 0.10 0.15 0.05–0.15 0.04 0.02–0.14 0.9382 2nd rocker 3.6 1.6 3.2-4.0 3.4 2.3–4.7 5.1 2.5 4.3–5.9 4.9 3.2–6.4 0.0022 3rd rocker 0.74 0.76 0.52–0.96 0.42 0.19–1.20 1.07 1.01 0.75–1.40 0.85 0.19–1.73 0.1882 M1 1st rocker - - - - - - - - - - - 2nd rocker 5.1 3.0 4.3–5.9 3.8 2.8–6.5 7.3 3.8 6.1–8.5 6.6 4.6–9.3 < 0.0012 3rd rocker 10.6 4.6 9.4–11.8 9.5 7.7–13.0 11.2 4.9 9.7–12.8 9.7 7.8–14.1 0.5682 M2 1st rocker - - - - - - - - - - - 2nd rocker 7.8 3.2 7.0-8.6 7.3 5.4–9.3 11.4 5.4 9.7–13.1 10 7.6–14.8 < 0.0012 3rd rocker 17.2 5.8 15.7–18.7 16 13.5–19.9 21.3 10.6 17.9–24.6 18.6 13.1–28.3 0.1122 M3 1st rocker - - - - - - - - - - - 2nd rocker 7.4 2.9 6.7–8.2 7 5.2–8.7 11.0 4.4 9.6–12.4 11 7.8–13.1 < 0.0012 3rd rocker 14.1 5.7 12.6–15.5 12.5 10.3–16.6 18.8 7.6 16.4–21.2 17.7 13.0-23.7 < 0.0012 M4 1st rocker - - - - - - - - - - - 2nd rocker 6.4 2.8 5.7–7.1 5.6 4.7–7.5 9.7 4.4 8.3–11.1 8.8 6.9–11.9 < 0.0012 3rd rocker 9.4 5.1 8.1–10.7 8.3 6.1–10.8 13.5 6.1 11.6–15.4 12.6 8.8–18.1 < 0.0012 M5 1st rocker - - - - - - - - - - - 2nd rocker 4.0 2.1 3.4–4.5 3.4 2.7–4.7 5.6 3.0 4.7–6.6 4.5 3.4–7.2 0.0022 3rd rocker 5.1 3.0 4.3–5.8 4.3 2.9–6.6 7.3 4.0 6.0-8.5 6.5 4.7–9.1 0.0032 t1 1st rocker - - - - - - - - - - - 2nd rocker 2.7 2.6 2.0-3.4 1.7 0.8–3.5 4.1 3.3 3.0-5.1 3.5 1.5–5.8 0.0162 3rd rocker 10.2 5.9 8.6–11.7 8.8 6.1–13.0 10.3 5.5 8.6–12.1 9.8 5.7–14.1 0.7332 t2-5 1st rocker - - - - - - - - - - - 2nd rocker 1.00 0.8 0.8–1.2 0.7 0.5–1.4 1.7 2.0 1.1–2.3 1.10 0.7–1.9 0.0142 3rd rocker 3.7 1.9 3.1–4.2 3.1 2.3–4.7 4.2 1.6 3.7–4.8 4.3 3.1–4.8 0.0402 1T test for independent samples 2 Mann-Whitney’s U test 1 3 European Spine Journal not find a characteristic gait pattern described in the literature for patients with LDH, the higher load observed in all foot zones except the first metatarsal and toes, especially during the push-off phase, could represent the first report of a characteristic gait pattern that helps reduce symptoms for these patients while walking. We believe that this difference in foot load distribution compared with normal feet was not due to differences in foot type between patients with LDH and controls, as neither the FPI nor the range of motion of the major foot joints showed significant differences between the two groups. Although patients with sciatica showed lower generalized strength in all four extrinsic foot muscle groups compared with controls, we believe that this difference was not clinically relevant enough to influence a postural change in the foot during gait (sciatica group median = 5, control group median = 5, in all muscle groups; small effect size for all muscle groups: dorsiflexors 0.30, plantarflexors 0.27, pronators 0.30, supinators 0.25). In our study, the only temporal parameter analyzed was foot contact time during gait, which was longer in patients with sciatica. This result is consistent with the findings of Bonab et al. [24] who observed that patients with LDH had longer step duration, shorter step length, and slower gait speed compared to healthy adults in the control group. The authors attributed these findings to a protective response in patients with LDH that minimizes forces acting on the body that could cause sciatic pain and to avoid wide ranges of motion in the spine and lower extremity. These findings are consistent with the reduced subtalar pronation observed in patients with sciatica in this study and in a previous study conducted by the same authors on another patient group [27]. Subtalar pronation is accompanied by internal rotation of the lower limb [13], which may alter lumbopelvic movement and contribute to degeneration and increased risk of low back pain [12, 28, 29]. By reducing pronation and internal rotation of the lower extremity, lumbopelvic mechanics may be normalized, which could contribute to decreased compression of the nerve roots forming the sciatic nerve, thereby slightly reducing pain during walking. Further research is required to confirm this hypothesis. Finally, regarding the pain reported by patients in the sciatica group, they showed higher values not only at the lumbar and lower limb levels, as expected, but also in the foot according to the NPRS-11 scale. However, compared with the control group, patients with sciatica demonstrated disability values related to foot pain similar to those seen in other systemic musculoskeletal conditions [27]. Therefore, we believe that foot pain associated with sciatica, although less intense than low back or lower limb pain, may also be related to the significantly lower quality of life reported by patients, affecting both physically and mentally [30]. for the first metatarsal and toes, compared with the control group. No differences were observed in foot posture or foot progression angle between the groups, suggesting that the observed changes in plantar pressure may be more related to neuromuscular compensation mechanisms than structural foot deformities. Neuromuscular compensation mechanisms are adaptive responses that the neuromuscular system employs to maintain functionality and movement efficiency during lumbar disc herniation. These compensation strategies reduce pain and preserve movement effectiveness, often at the expense of energy and mechanical efficiency. To the best of the authors’ knowledge, this is the first study to provide information on plantar pressure during the three functional rockers of gait in patients with chronic lumbar radicular pain due to lumbar disc herniation. Quantitative analysis of foot pressure during gait is increasingly used in both research and clinical practice. Previous studies have reported altered gait temporal parameters in patients with chronic low back pain [22, 23], including those with lumbar disc herniation [24]. However, the application of pedobarography during gait in patients with neurocompressive conditions has been reported in only a few studies [18, 25, 26]. Kanna et al. [18] investigated how lumbar radiculopathy affects plantar pressure distribution and found that peak and mean foot loads were significantly lower on the affected side during gait. Additionally, the load distribution was asymmetric, favoring the medial arch and the first metatarsal head on the affected side. Our study presents opposing results, as the affected side had a higher mean foot load than the control group. Moreover, the load was distributed differently, with participants in our study exhibiting higher pressure in all foot zones except for the first metatarsal and greater pressure on the lesser metatarsals, particularly during the push-off phase of gait. Participants in the sciatic group exhibited higher pressures than controls in the second rocker, from the heel through all five metatarsals, and significantly higher pressures in metatarsals 3 to 5 during the third rocker. This discrepancy may be attributed to different postural compensation patterns. Wei et al. [25]. analyzed plantar pressure distribution in patients with LSS before and after the onset of neurogenic intermittent claudication (NIC). Their results showed a significant increase in forefoot load and contact area after the onset of NIC, along with a decrease in the heel area. In another study, Wei et al. [26] reported that the mediallateral displacement of the center of pressure progressively increased with walking distance in patients with LSS, reflecting a balance dysfunction. These authors associated the asymmetric load distribution in the foot with a tendency toward forward lumbar flexion during gait to alleviate the symptoms of nerve root compression [25]. Although we did 1 3 European Spine Journal Data availability No datasets were generated or analysed during the current study. Declarations Competing interests Funding: This research was funded by the Sociedad Española de Biomecánica y Ortopodología-. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit h t t p : / / c r e a t i v e c o m m o n s . o r g / l i c e n s e s / b y / 4 . 0 /. References 1. Van Boxem K, Cheng J, Patijn J et al (2010) 11. Lumbosacral radicular pain. Pain Pract 10:339–358. h t t p s : / / d o i . o r g / 1 0 . 1 1 1 1 / j . 1 5 3 3 - 2 5 0 0 . 2 0 1 0 . 0 0 3 7 0 . x 2. Dower A, Davies MA, Ghahreman A (2019) Pathologic basis of lumbar radicular pain. World Neurosurg 128:114–121. h t t p s : / / d o i . o r g / 1 0 . 1 0 1 6 / j . w n e u . 2 0 1 9 . 0 4 . 1 4 7 3. Europe PA (2017) Survey on chronic pain 2017. Diagnosis, Treatment and Impact of Pain. Brussels 4. Rodríguez MJ, García AJ (2007) Costes Del Dolor neuropático Según etiología En Las unidades Del Dolor En España. Rev Soc Esp Dolor 14:404–415 5. Davis D, Maini K, Taqi M, Vasudevan A (2024) Sciatica. StatPearls [Internet]. StatPearls Publishing, Treasure Island (FL) 6. Abdalla M, Mostofi A, Shtaya A, Johnston FG (2022) Acute foot drop secondary to lumbar disc prolapse after seizure. Br J Neurosurg 36:524–526. h t t p s : / / d o i . o r g / 1 0 . 1 0 8 0 / 0 2 6 8 8 6 9 7 . 2 0 2 0 . 1 8 3 9 6 3 2 7. Ma J, He Y, Wang A et al (2018) Risk factors analysis for foot drop associated with lumbar disc herniation: an analysis of 236 patients. World Neurosurg 110:e1017–e1024. h t t p s : / / d o i . o r g / 1 0 . 1 0 1 6 / j . w n e u . 2 0 1 7 . 1 1 . 1 5 4 8. Marchesini N, Ricci UM, Soda C, Teli M (2023) Acute bilateral foot drop due to lumbar disc herniation treated by bilateral interlaminar approach: case report and literature review. Br J Neurosurg 37:899–901. h t t p s : / / d o i . o r g / 1 0 . 1 0 8 0 / 0 2 6 8 8 6 9 7 . 2 0 2 0 . 1 7 1 3 9 9 2 9. Deyo RA, Weinstein JN (2001) Low back pain. N Engl J Med 344:363–370. h t t p s : / / d o i . o r g / 1 0 . 1 0 5 6 / N E J M 2 0 0 1 0 2 0 1 3 4 4 0 5 0 8 10. Yazdani F, Razeghi M, Karimi MT et al (2018) The influence of foot hyperpronation on pelvic biomechanics during stance phase of the gait: A Biomechanical simulation study. Proc Inst Mech Eng [H] 232:708–717. h t t p s : / / d o i . o r g / 1 0 . 1 1 7 7 / 0 9 5 4 4 1 1 9 1 8 7 7 8 0 7 7 11. Cambron JA, Duarte M, Dexheimer J, Solecki T (2011) Shoe orthotics for the treatment of chronic low back pain: a randomized controlled pilot study. J Manipulative Physiol Ther 34:254– 260. h t t p s : / / d o i . o r g / 1 0 . 1 0 1 6 / j . j m p t . 2 0 1 1 . 0 4 . 0 0 4 12. Chou MC, Huang JY, Hung YM et al (2021) Flat foot and spinal degeneration: evidence from nationwide population-based cohort This study has some limitations. A potential limitation of this study is that the unit of analysis was the foot, rather than the individual participants; in the sciatica group, only the affected limb was analyzed, while the non-affected limb was excluded to avoid potential bias due to compensatory biomechanical and antalgic adaptations. In addition, we did not investigate limb predominance. Although this approach was intended to ensure that plantar pressure measurements reflected the direct impact of sciatic involvement, future studies should consider comparing both limbs to further explore interlimb compensatory mechanisms and their clinical implications. Another limitation is the study’s uniqueness, meaning that plantar pressure was not compared with that of patients with other neurocompressive pathologies, which would have contributed to testing the hypothesis of a potential specific foot load pattern in patients with LDH. The alterations found in the foot load distribution in patients with radiculopathy, as well as the related foot pain, are abnormalities that are not observed in a visual clinical examination of the patient. Therefore, we believe it is important to include the study of plantar pressures and foot pain in the evaluation of these patients. These measurements can be useful for assessing neuromuscular function in neurocompressive disorders related to LDH and may support a broader and more varied therapeutic approach that benefits patients. In addition, incorporating this type of assessment could help identify specific gait adaptations, allowing for targeted interventions to improve functional outcomes and patient comfort. Conclusions Patients with sciatica caused by LDH who participated in this study exhibited alterations in plantar pressure compared with healthy individuals. Overall, increased contact time and higher-than-normal mean pressure were observed in all foot areas except for the first toe, along with higher peak pressure in all foot zones except for the big toe and first metatarsal. Pressure was concentrated in the third, fourth, and fifth metatarsalsand in the lesser toes during push-off phase of gait. Author contributions Conceptualization, P.V.M.-M. and Á.V.-M; methodology, P.V.M.-M; software, C.V.-B; validation, I.C.P.-T.; formal analysis, P.V.M.-M.; investigation, M.R.-B. and C.V.-B. resources, P.V.M-M; data curation, M.JG.-R; writing—original draft preparation, P.V.M.-M; writing—review and editing, M.R.-B and M.J.G-R.;; supervision, P.V.M.-M; project administration, I.C.P.-T.; funding acquisition, G.D.-M. Funding Funding for open access publishing: Universidad de Sevilla/ CBUA 1 3