February 2021

Orthotic Insoles Improve Gait and Pain in Lower Limb Discrepancy

Orthotic insoles significantly improved gait symmetry in the pelvis in the frontal plane and the ankle in the sagittal plane in participants with lower leg discrepancies (LLD) of both ≤ 1 cm and > 1 cm but > 3 cm, suggesting that it may be appropriate to treat even mild leg length discrepancy.

Leg length discrepancy can be either caused by anatomical deformities originating from true differences in the bony structures of the lower limb, or it may be functional, resulting from abnormal lower limb movements. The diagnosis, classification, and treatment of LLD remain controversial among both researchers and clinicians. Some authors classify discrepancies ≤2.0 cm as mild, while others consider discrepancies of up to 3.0 cm as mild. These classifications are intended to guide practitioners in the treatment of LLD, but there is much disagreement in the literature as to the magnitude at which LLD requires treatment. It has been suggested that orthotic insoles (OIs), shoe lifts, or other clinical interventions to equalize leg length should be considered for LLD ≥ 1.0 cm, or even between 0.5 and 1.0 cm. However, other authors are more conservative, suggesting that below 2 cm, no treatment is required.

The lack of consensus regarding the need to treat mild LLD stems from the fact that there is no real agreement as to the biomechanical effects of a mild LLD on lower limb and spinal joints during walking. Many studies have reported that even mild LLD can cause lower limb biomechanical disorders, including one study which found that compensatory strategies and asymmetrical gait occurred from 1.0 cm of LLD induced by foot lifts (from 1 to 5 cm high).

Mild LLD, including LLD ≤ 1 cm, has been associated with an increased risk of knee osteoarthritis and scoliosis, both of which are frequently associated with low back pain. Mild LLD is therefore frequently treated with the aim of preventing the development of such secondary pathologies. OIs are the most frequently used treatment likely because they are noninvasive, inexpensive, and readily available. Despite the widespread use of OI, their impact on gait kinematics and pain has been little studied in patients with mild anatomical LLD. Recently, Menez et al. (2020) evaluated the effect of OI on gait kinematics and low back pain in subjects with mild LLD. They found that changes in gait symmetry varied and was specific across individuals; however, low back pain decreased in all patients after the use of OI. However, mild LLD is commonly not treated in patients with low back pain. Moreover, mild LLD is frequently found in the adult population, and the correction of LLD ≤ 1 cm remains insufficiently incorporated into the treatment of low back pain, with many clinicians continuing to overlook the potential impact of mild LLD. There is disagreement about the correct treatment and the magnitude of LLD. Indeed, for White et al. (2004), OIs to equalize leg length should be considered in patients with LLD ≥ 1 cm, whereas Khamis and Carmeli (2018) suggest that even mild LLD between 0.5 and 1 cm should be treated.

It seems that LLD causes asymmetry in the locomotion of the lower limbs, leading to pain, with a disruption of normal biomechanical function. The functional alterations increase biomechanical disorders, asymmetrical gait, low back pain, and/or other pain, and may even promote the development of associated pathologies such as osteoarthritis of the hip or knee. OI is a treatment often used in podiatry to try to reduce biomechanical asymmetries and pain, leading to the hypothesis that OI can reduce the asymmetries and associated pain in patients with mild and very mild LLD during walking.

The primary aim of this study was therefore to evaluate the immediate effects of OI on gait symmetry and pain according to the degree of mild LLD (i.e., LLD ≤ 1 cm vs. LLD > 1 cm <3 cm). The secondary aim was to analyze the specific effects of OI on lower limb joint kinematics.

Methods: Forty-six adults with mild leg length discrepancy were retrospectively included and classified into two groups (GLLD≤1cm or GLLD>1cm). All subjects underwent routine 3D gait analysis with and without orthotic insoles. The symmetry index was calculated to assess changes in gait symmetry between the right and left limbs. Pain was rated without (in standing) and with the orthotic insoles (after 30 min of use) on a visual analog scale.

Results: There was a significant improvement in the symmetry index of the pelvis in the frontal plane (p = 0.001) and the ankle in the sagittal plane (p = 0.010) in the stance with the orthotic insoles independent from the group. Pain reduced significantly with the orthotic insoles independently from the group (p < 0.001).

Discussion: The results of this study demonstrated that gait symmetry improved with the OI, particularly at the pelvis (frontal plane) and ankle (sagittal plane) during the stance phase of gait. Moreover, there was a significant reduction in pain with the OI. The kinematic results support the findings of a few studies that showed that even mild LLD can alter the kinematics of gait and cause pain. The results of this study add to this body of knowledge by showing that even LLD <1 cm can alter symmetry and cause pain, and that both symmetry and pain can be improved with OI.

The present results showed that OIs have a similar effect in mild LLD ≤ 1 and >1 cm. The increase in ankle dorsiflexion on the longer leg and the increase in the plantar flexion on the shorter leg during stance phase are also in line with the results of previous studies. These results showed that use of an OI significantly increased peak dorsiflexion in the shorter leg and decreased both peak dorsiflexion and peak plantar flexion in the longer leg (independently from the group). These changes likely contributed to the improvement in ankle gait symmetry shown by the SI.

The positive effect of the OI on symmetry found in the present study for both mild and very mild LLD was further supported by the significant reduction in pain: use of the OI immediately and significantly reduced pain in both groups, with no between-group differences. These results are clinically important since the biomechanical, postural, and functional changes caused by LLD have been shown to alter joint angles, leading to low back pain, scoliosis, pelvic and sacral misalignments, hip and knee osteoarthritis, and even stress fractures of the lower limbs.

Therefore, we can recommend treatment of mild LLD with OI, even when LLD ≤ 1 cm.

Source: Menez C, L’Hermette M, Coquart J. Orthotic insoles improve gait symmetry and reduce immediate pain in subjects with mild leg length discrepancy. Front Sports Act Living. 2020;2:579152. Use is per Creative Commons License 4.0. To read the full article, visit https://www.frontiersin.org/articles/10.3389/fspor.2020.579152/full

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