Tenotomies of the iliopsoas and adductor longus are important steps during open reduction of a developmental dislocated hip that have a direct impact on obtaining and maintaining a stable, concentrically reduced hip joint. Nonetheless, the literature remains scarce and inconsistent as to whether these tenotomies cause negative effects on gait patterns at the long-term following MOR in the management of children with DDH [7, 12, 13, 15]. The main findings of the current study are that there are notable deviations in the gait patterns of children with DDH treated by MOR at long-term follow-up compared to healthy children’s gait patterns.

When analyzing the results of this study, all the spatiotemporal gait parameters differed significantly among the groups except for the swing time. The stance and double support times of the unilateral and bilateral DDH groups were comparable based on pair-wise comparisons, but those were shorter in both DDH groups compared to the healthy group. Additionally, both DDH groups exhibited shorter strides and step lengths along with faster cadence. Of note, the differences in length and cadence values only reached statistical significance for the bilateral group, not the unilateral group. However, the trend favored the decrease in these values of children with unilateral DDH. It can be assumed that the reduction in stance and support times result from the decrease in stride and step lengths. Given the similar gait velocity of all groups, children with DDH seems to increase the cadence to tolerate these alterations. These spatiotemporal gait deviations could be attributed to the long-term negative effect of impaired functions of the iliopsoas and adductor muscles following MOR. Particularly, these alterations are more pronounced in children undergoing bilateral DDH, reinforcing our first hypothesis that children with DDH treated by MOR could develop significant gait deviations at the long-term compared to healthy controls due to impaired functions of the iliopsoas and adductor muscles.

Other important findings of the current study supporting the first hypothesis include detectable changes in kinematic and kinetic gait parameters. At normal walking velocity, both DDH groups exhibited decreased anterior pelvic tilt compared to the healthy controls, and children with unilateral DDH demonstrated the highest amount of pelvic obliquity. Impaired functions of the iliopsoas and adductor muscles following MOR may have resulted in a posterior pelvic tilt in a similar pelvic tilt range, regardless of unilateral or bilateral application. Furthermore, it is well-known that bilateral control of the hip abductor and adductor muscles is essential for pelvic stability [21]. Thus, the increased pelvic obliquity in children with unilateral DDH could be caused by unilateral adductor muscle weakness since there is no compensatory force on the contralateral side. In addition, there were no significant changes in the range of pelvic rotation between groups, as pelvic rotation occurs primarily in the horizontal plane, whereas the iliopsoas and adductor muscles produce movements predominantly in the sagittal and frontal planes, respectively. Therefore, these findings can be interpreted as supporting the second hypothesis that MOR could negatively affect pelvic motion during the gait cycle of the affected extremity due to impaired functions of the iliopsoas and adductor muscles.

An interesting result from the study included SKG analyses of the study participants. SKG is a common gait disorder in ambulatory children with cerebral palsy, characterized by diminished PKF and total knee ROM as well as delayed time to the PKF [22]. The main cause of SKG is the over-activity of the rectus femoris muscle in the swing or pre-swing phase of gait, resulting in tripping during the swing phase and a greater expenditure of energy when walking [11, 19]. Moreover, in a recent study by Akalan et al. investigating the relationship between iliopsoas muscle weakness and SKG during walking in healthy participants, the authors suggested that any treatment approach that lessens hip flexion during gait by weakening the iliopsoas muscle could produce a SKG pattern along with a slower gait velocity [11]. Based on the existing literature, we hypothesized that iliopsoas tenotomy could influence swing-phase knee flexion and contribute to SKG in children treated by MOR. Our results supported this hypothesis, as four children undergoing bilateral MOR exhibited SKG pattern based on the definition of Goldberg et al. Nonetheless, no SKG was observed in the long-term following unilateral MOR. Suppose unilateral iliopsoas tenotomy does not result in a stiff knee gait pattern in the long term. In that case, it might be due to preserving some degree of balance in muscle function and joint dynamics. Unilateral procedures allow for better compensation and adaptation by the musculoskeletal system, reducing the likelihood of gait abnormalities.

According to our literature review, very little research has been conducted on long-term residual gait changes in children with DDH who underwent MOR. In one study, Ömeroğlu et al. (2008) [15] investigated the long-term effects of posteromedial soft tissue release, including sectioning of the adductor longus and iliopsoas tendons, on 3-D quantitative gait analysis of ten patients (mean age, 8.1 years) with unilateral DDH surgically treated under the age of 18 months. Similar to our study design, the authors compared those data with healthy controls. They concluded that despite mild gait deviations compared to healthy ones, the posteromedial soft tissue surgery did not cause significant alterations in the gait analysis at midterm follow-up in DDH. In another study, Chang et al. (2012) [13] performed quantitative gait analysis on eleven females (mean age: 10.6 ± 1.0 years) in whom open reduction with Pemberton’s osteotomy was applied for unilateral DDH at 1.6 ± 0.5 years of age and eleven age-matched healthy controls. In the Pemberton group, an asymmetrical gait pattern was identified, including increased knee flexion and ankle dorsiflexion in the affected limb, hiking at the affected side, and rotation towards the unaffected side of the pelvis. The authors inferred that those gait deviations could be due to the altered pelvic motions to reduce loads of those muscles in the affected hip often involved during the surgery, despite the possibility of increasing harmful loading rates at both hip joints. Findings from the present study supported the previous studies, indicating that MOR could adversely affect pelvic motion during gait, secondary to impaired functions of the iliopsoas and adductor muscle. Unlike previous research [13, 15], the current study contributes to the existing literature by examining the relationship between MOR and SKG, comparing bilateral DDH to healthy controls in addition to unilateral cases, with a longer follow-up period.

The present study has several limitations, and the study results and conclusions should be interpreted keeping these in perspective. The main limitation was the small sample size, which reduced the generalizability of the findings. Another limitation was its retrospective design, which contributed to selection bias. It’s also important to note that this is a nonrandomized, observational study, meaning there might be several hidden, confounding factors and potential selection biases in the data. Finally, the study has solely focused on analyzing gait data to test hypotheses. However, there is a dearth of clinical data in this investigation, which includes objective assessments such as muscular strength and electromyography, as well as radiological evaluations like magnetic resonance imaging findings. Future prospective studies are needed to validate our findings in a larger cohort for better generalization. Nevertheless, the current study is one of the few studies dealing with gait patterns and deviations at long-term follow-up in children who underwent MOR. Furthermore, this is the first study to focus on the development of SKG in this specific cohort.