Effect of knee flexion contracture on sagittal alignment in patients with cerebral palsy

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Introduction

Cerebral palsy (CP) remains the leading cause of childhood disability, affecting 1.5 to 4.0 per 1000 live births [1, 2]. As the child grows, secondary musculoskeletal complications develop and accumulate, manifesting as persistent muscle contractures and subsequently as bony deformities.

One of the most clinically significant lower extremity pathologies is knee flexion contracture (KFC), with a reported prevalence of up to 50% of cases [3, 4]. The development of KFC is primarily driven by muscle spasticity, which causes a persistent imbalance between knee flexors and extensors, leading to impaired lower limb biomechanics [5, 6]. The knee joint functions as a key component of a unified kinematic chain, and its extension deficit provokes the development of a pathological gait pattern — crouch gait. This movement pattern is functionally disadvantageous: it is associated with a marked increase in energy expenditure, overload of the extensor mechanism, and progressive loss of independent ambulation [7]. Crouch gait is the most common pathological gait pattern in CP; however, the effect of isolated KFC on sagittal balance remains insufficiently studied [8].

Of particular relevance is the investigation of the effect of KFC on the overlying segments — the pelvis and spine. The maintenance of an upright posture is ensured by the coordinated interaction of all segments of the musculoskeletal system. Impaired knee extension causes a shift in the center of mass and triggers a cascade of compensatory responses: changes in pelvic tilt, flattening of lumbar lordosis, and increased thoracic kyphosis [9, 10]. Any disturbance of the sagittal profile impairs postural stability and reduces the child's motor capabilities [11].

Despite the apparent relationship between knee joint status, pelvic position, and sagittal spinal profile, the mechanisms of age-related adaptation of spinopelvic relationships in response to KFC remain insufficiently understood. The elucidation of these patterns is essential for understanding the pathogenesis of biomechanical disturbances and optimizing surgical treatment strategies [12]. Establishing clear correlations will enable the prediction of functional outcomes and improve the efficacy of treatment in patients with CP.

The aim of the study — to evaluate the impact of knee flexion contracture on sagittal spinopelvic parameters in children with cerebral palsy.

Methods

Study design

The study included 89 children with spastic diplegia and KFC who were treated at the H. Turner National Medical Research Center for Сhildren's Orthopedics and Trauma Surgery between 2022 and 2026. Patient age ranged from 4 to 17 years.

Inclusion criteria:

– presence of KFC of at least 5°;

– Gross Motor Function Classification System (GMFCS) levels II-III.

Exclusion criteria:

– congenital and acquired spinal deformities;

– equinus deformities of the feet, subluxation or dislocation of the hip;

– history of orthopedic surgery on the lower extremities, hips, or spine.

All patients were divided into two age groups: the first group comprised 34 patients under 12 years of age, and the second group comprised 55 patients aged 12 years and older.

To assess the effect of KFC on sagittal spinal and pelvic parameters, data from our previous study, which included 44 patients with CP at GMFCS levels I-III aged 3 to 18 years, were used as a control group [12]. In that study, patients were not selected based on the presence or absence of KFC, allowing the sample to be considered as a general population of children with CP. The comparison of the control group with the main groups of the present study (patients with verified KFC) allows for assessment of the additional contribution of KFC to the formation of sagittal spinopelvic relationships beyond the changes characteristic of CP in general. Patient examination in both cohorts was performed at a single center using unified radiological parameters and measurement protocols, ensuring comparability of the obtained data.

All patients underwent clinical and radiological examinations. Clinical assessment included the measurement of KFC magnitude, determination of the popliteal angle, and deficit of active knee extension. The popliteal angle was considered as an additional indicator of the functional status of the hamstring muscles and a potential marker of crouch gait pattern progression [8].

Radiological examination was performed in the standing position using panoramic lateral radiography of the spine and pelvis. The analysis of sagittal profile parameters was performed using Surgimap v. 2.3.2.1 software. The following sagittal spinopelvic balance parameters were assessed: pelvic tilt (PT), pelvic incidence (PI), sacral slope (SS), lumbar lordosis (LL), thoracic kyphosis (TK), and sagittal vertical axis (SVA).

Statistical analysis

Statistical data processing was performed using MS Office 365 Excel and IBM SPSS Statis-tics 27. Quantitative variables were described using the arithmetic mean (M), standard deviation (SD), and range (min-max). To ensure comparability with the historical control group, Table 1 presents mean values and standard deviations. Intergroup differences were assessed using nonparametric methods (Mann-Whitney U test) based on median values [12]. Normality of distribution was evaluated using the Shapiro-Wilk test. Given the non-normal distribution of the data, nonparametric statistical methods were applied. The Mann-Whitney U test was used to compare quantitative variables between groups. To quantify the effect of motor function level (according to GMFCS) on sagittal balance parameters, linear regression analysis was performed with GMFCS as the independent variable. Correlation analysis was conducted using Spearman's rank correlation coefficient (ρ).

To assess the independent effect of the magnitude of KFC on sagittal balance parameters (PT, SS, LL, TK, SVA) while accounting for GMFCS level, partial correlation analysis was employed. Given the hypothesis of age-related changes in compensatory mechanisms, statistical analyses were performed separately for two age groups (under 12 years and 12 years and older). Statistical significance was set at p < 0.05. In view of the multiple correlations tested, the interpretation of individually significant associations was performed with consideration of the potential type I error risk, without formal correction for multiple comparisons. To assess the robustness of the partial correlation results, bootstrap analysis was performed (1000 resamples, 95% confidence intervals with bias-corrected and accelerated [BCa] adjustment).

Results

The mean age of patients in the first group was 8±2 years, and in the second group — 14±2 years. The magnitude of KFC in the first group was 13±5° (range, 5-30°), and in the second group — 15±9° (range, 5-45°); the popliteal angle was 105±7° (range, 90-120°) and 103±12° (range, 90-125°), respectively. The deficit in active knee extension in the first group was 16±9° (range, 5-30°), and in the second group — 23±10° (range, 5-45°).

The distribution of patients by motor function level according to the GMFCS was uneven: in the younger age group, patients at GMFCS level III predominated (21 patients and 13 patients), whereas in the older group, level II predominated (36 patients and 19 patients), which necessitated additional assessment of the effect of this factor on sagittal balance parameters.

Comparison of sagittal balance parameters between patients at GMFCS levels II and III showed that in patients under 12 years of age, statistically significant differences were found only for lumbar lordosis (LL) (p = 0.018), whereas no significant differences were observed for the remaining parameters: PT (p = 0.261), PI (p = 0.506), SS (p = 0.065), TK (p = 0.727), and SVA (p = 0.169). In patients older than 12 years, differences were observed for pelvic incidence (PI) (p = 0.030) and thoracic kyphosis (TK) (p = 0.025); no differences were found for the other parameters: PT (p = 0.155), SS (p = 0.779), LL (p = 0.128), and SVA (p = 0.593).

These findings may suggest that the effect of motor function level on sagittal balance parameters increases with age; however, it does not appear to be a determining factor in the formation of compensatory mechanisms.

To quantitatively assess the effect of GMFCS level on parameter variability, linear regression analysis was performed. In the younger age group, GMFCS level had a statistically significant effect on PT (β = 0.348; p = 0.044) and LL (β = -0.406; p = 0.017). In the older age group, the effect of GMFCS level was retained only for PI (β = 0.269; p = 0.047) and TK (β = 0.311; p = 0.021). Thus, motor function level affects only selected parameters of the sagittal profile and does not determine the formation of its systemic reorganization.

To exclude the effect of GMFCS level on sagittal balance parameters, partial correlation analysis was performed. In the first group (children under 12 years of age), no statistically significant correlations were found between the magnitude of KFC and sagittal spinopelvic balance parameters (p > 0.05), which may indicate the local nature of biomechanical changes. In the second group (children older than 12 years), by contrast, statistically significant correlations were revealed bet-ween the magnitude of KFC and sagittal balance parameters: SS (r = 0.306; p = 0.024), LL (r = 0.369; p = 0.006), and SVA (r = -0.372; p = 0.006). The persistence of these correlations after controlling for GMFCS indicates that the association between the magnitude of KFC and sagittal spinopelvic balance parameters is not explained solely by differences in patients' motor function level. Bootstrap analysis of partial correlations confirmed the robustness of the identified correlations in the older age group after controlling for GMFCS: for SS (95% CI 0.065-0.563), LL (95% CI 0.062-0.593), and SVA (95% CI -0.584 to -0.064). In the younger age group, the CI crossed zero, which is consistent with the absence of stable correlations. Additionally, comparison with a control population group of patients with CP showed that PI values were comparable across all study groups, confirming its anatomical stability (Table 1). In the younger age group, minor changes in pelvic complex parameters were observed, manifested by an increase in PT (posterior pelvic tilt) and a decrease in SS, which may reflect early adaptive changes of the musculoskeletal system in response to KFC. In contrast, older patients demonstrated increased spinal parameters (TK and LL), indicating spinal involvement in compensatory mechanisms.

 

Table 1

Comparison of sagittal spinopelvic balance parameters between patients with KFC and a population-based group of patients with CP, M±SD (min-max)

Parameter	First group	Second group	Control group
Age, years	8±2.3 (4-11)	14.2±1.8 (12-17)	10.25±3.7 (5-18)
Pelvic incidence (PI), deg.	41.5±8.7 (23.4-58)	41.6±11.3 (16.3-61)	42.4±12.1 (16-72)
Pelvic tilt (PT), deg.	12.6±13.7 (-25.2-38.4)	6.23±12.7 (-17.8-37.4)	7.6±15.6 (-23.5-59.8)
Sacral slope (SS), deg.	27.4±10.9 (0-53.1)	35.4±9.81 (15.5-57.7)	36.8±12.3 (-3.2-60.1)
Thoracic kyphosis (TK), deg.	45.8±14.2 (16.9-72.4)	47.7±14.4 (17.6-80.6)	35.7±12.6 (11.2-61.4)
Lumbar lordosis (LL), deg.	37.5±15.9 (1.8-68.3)	48.4±17.3 (9.6-91.4)	44.2±19.3 (2.4-80.4)

Note: to ensure comparability with the control group data [12], the table presents mean values and standard deviations. The control group was used as a reference population for descriptive comparison of sagittal spinopelvic balance parameters. Statistical analysis of intergroup differences was performed between age groups of patients with KFC using nonparametric methods (Mann-Whitney U test) based on median values.

 

Comparison with the control group suggests that the observed changes are attributable to the effect of KFC on sagittal spinopelvic relation-ships. In this regard, an analysis of the nature of compensatory changes in the musculoskeletal system depending on age was performed.

Compensation types

The analysis of sagittal spinopelvic parameters demonstrated that the pattern of bio-mechanical changes in patients with KFC differed according to age. The findings allowed for the identification of distinct patterns of compensatory changes, conventionally designated as local, spinal, and pelvic types, reflecting the predominant nature of relationships between knee joint parameters (magnitude of KFC, deficit of active extension, popliteal angle), spinal, and pelvic parameters.

Local compensation type

In the younger age group, no statistically significant correlations were found between the magnitude of KFC and sagittal spinopelvic balance parameters (PT, SS, LL, SVA) (p > 0.05).

A weak negative correlation with PT (ρ = -0.29; p = 0.119) and a moderate negative correlation with TK (ρ = -0.31; p = 0.096) were noted; however, these associations did not reach statistical significance.

The only statistically significant correlation was a moderate negative correlation between the deficit of active knee extension and PI (ρ = -0.47; p = 0.008). Since PI is an anatomically fixed parameter, this relationship cannot be regarded as a compensatory change. Nevertheless, it may suggest that individual pelvic morphology could serve as a predisposing factor for the development of secondary deformities.

Overall, the spinopelvic parameters maintained relationships typical for physiological sagittal balance. These findings suggest that at this stage, the effect of KFC is predominantly local and confined to the knee joint level.

Systemic compensation types

In the older age group, two types of systemic compensation were identified, reflecting different mechanisms of musculoskeletal adaptation to the presence of KFC.

Spinal compensation type

A moderate negative correlation was found between the deficit of active knee extension and LL (ρ = -0.42; p = 0.013), as well as a moderate positive correlation between the extension deficit and SVA (ρ = 0.36; p = 0.039). These findings indicate an anterior shift of the center of gravity and a decrease in lumbar lordosis, reflecting the formation of the spinal compensation type.

At the same time, no statistically significant correlations were found between knee joint parameters and pelvic complex parameters (PI, PT, SS) (p > 0.05), which may suggest predominant involvement of the spine in compensatory adaptation mechanisms.

A key local manifestation of the deformity was the change in patellar position. Statistically significant correlations were revealed between the Insall-Salvati index and knee joint parameters: a positive correlation with KFC (ρ = 0.36; p = 0.049) and with the deficit of active extension (ρ = 0.38; p = 0.037), as well as a negative correlation with the popliteal angle (ρ = -0.39; p = 0.029). These findings suggest that the development of patella alta may be considered a consequence of long-standing KFC.

Pelvic compensation type

A strong negative correlation was found between the magnitude of KFC and SS (ρ = 0.66; p = 0.004), as well as a moderate negative correlation between the deficit of active knee extension and SS (ρ = -0.54; p = 0.027). These findings indicate the formation of the pelvic compensation type, in which the adaptation of the musculoskeletal system is achieved through pelvic retroversion.

In this group, a strong negative correlation was also revealed between the magnitude of KFC and the femorotibial angle (ρ = -0.63; p = 0.005), which may suggest the likelihood of developing secondary bony deformities of the lower extremity with long-standing contracture. Furthermore, a strong positive correlation was established between the deficit of active knee extension and internal rotation of the hip (ρ = 0.61; p = 0.034), reflecting the formation of complex compensatory motor patterns.

The analysis of the sagittal spinal profile revealed two types of posture according to the P. Roussouly classification [13]. In patients from the first group and in those with the spinal compensation type, type II posture (flat back) was more commonly observed, characterized by decreased lumbar lordosis and anterior displacement of the sagittal vertical axis. In patients with the pelvic compensation type, parameters corresponding to type III posture (balanced posture) were identified. However, the maintenance of global sagittal balance was achieved through the formation of pronounced lumbar hyperlordosis (61.0±14.7°), exceeding the calculated values. Across different compensation types, SVA values ranged from 10.7±66.9 to 65.4±66.7 mm, reflecting different stages of musculoskeletal adaptation to KFC.

The obtained results allowed us to construct a model of sequential compensation, encompassing local, spinal, and pelvic levels, which is presented as a diagram (Figure 1) and supported by radiographic examples (Figure 2).

 

Figure 1. Schematic representation of compensation levels in knee flexion contracture, demonstrating the sequential involvement of the knee, spine, and pelvis in the maintenance of sagittal balance

 

Figure 2. Panoramic sagittal X-rays of the spine and pelvis illustrating different types of compensatory changes in knee flexion contracture:

a — local type;

b — spinal type;

c — pelvic type

 

The obtained results indicate the presence of an association between KFC and parameters of the sagittal spinal and pelvic profile in patients with CP, as well as the age-dependent nature of compensatory mechanisms.

Discussion

The data obtained in our study indicate the presence of an association between KFC and parameters of sagittal spinopelvic balance, as well as the age-dependent nature of the observed changes. The identified patterns are consistent with biomechanical concepts previously outlined by V.V. Umnov, who noted that shortening of the biarticular hamstring muscles, which participate in both knee flexion and hip extension, leads to approximation of their attachment points [14]. Under such conditions, an attempt at knee extension is ac-companied by posterior pelvic tilt, flattening of lumbar lordosis, and compensatory increase in thoracic kyphosis. Our findings demonstrating an association between the deficit of knee extension and decreased lumbar lordosis are in agreement with this described mechanism.

At the same time, the results of some studies indicate a less pronounced relationship between KFC and sagittal profile parameters. For instance, S.I. Wolf et al., in a study of 375 patients with CP, did not find an association between KFC and pelvic tilt angle [15]. Such discrepancies may be attributable to differences in study methodology, as in that work, sagittal profile assessment was performed primarily on the basis of clinical gait analysis.

Contrasting data are reported by L. Abbasi et al., who identified a significant effect of KFC on spinopelvic relationships, manifested by forward trunk inclination [16]. Similar results were obtained by A. Szopa et al., who found a statistically significant association between knee flexion and impaired sagittal trunk balance [10]. These findings are consistent with the results of our study, in which changes in spinal and pelvic alignment were observed in older patients, reflecting the formation of systemic compensatory mechanisms.

In our previous publication, a significant correlation between KFC and sagittal spinopelvic balance parameters was found only in patients with GMFCS level III [17]. This result was interpreted as a possible effect of assistive device use, accompanied by anterior displacement of the center of gravity to maintain sagittal balance. However, in the present study, after controlling for the effect of GMFCS level using partial correlation ana-lysis, statistically significant associations between KFC and sagittal balance parameters (LL, SS, SVA) persisted in the older age group regardless of motor level. This suggests that the observed patterns are attributable to long-standing KFC itself, rather than being a consequence of assistive device use.

11. Kiernan et al. demonstrated that crouch gait is not always accompanied by a pronounced compensatory trunk response, and that spinopelvic parameters may remain within physiological ranges [18]. Based on their findings, the authors concluded that crouch gait does not have a significant effect on spinal status in patients with CP. These observations are partially consistent with the results of our study in the younger age group, where no statistically significant associations between KFC and sagittal balance parameters were found after controlling for GMFCS level. At the same time, in the older age group, we identified stable associations between KFC and sagittal profile parameters. These discrepancies may be attributable to several factors. First, the study by D. Kiernan et al. analyzed the crouch gait pattern itself in a dynamic context (mean patient age, 11.3 years), whereas the present study assessed static KFC. Second, according to our data, systemic changes in spinopelvic relationships develop with long-stan-ding contracture and become statistically significant specifically during adolescence, an age group that was not represented in the study by D. Kiernan et al. Thus, our findings do not contradict the authors' conclusions but rather complement them, demonstrating that long-standing KFC — not merely the gait pattern — can lead to systemic reorganization of sagittal balance.

A systematic review by R. O'Sullivan et al. confirms that crouch gait in CP has a progressive natural history [19]. The authors describe the pathogenetic mechanism as a vicious cycle, in which knee flexion resulting from increased activity of the hamstring muscles leads to compensatory increased activity of the quadriceps femoris muscle to maintain knee extension. Increased quadriceps activity, in turn, places an increased demand on the hip extensors, including the same hamstring muscles, which participate in both knee flexion and hip extension. This leads to their overload and further progression of the flexion deformity.

The findings of the present study allow us to expand this concept by demonstrating that the spine and pelvis are also involved in the aforementioned vicious cycle. In the older age group, stable associations were identified between KFC and lumbar lordosis, sagittal vertical axis, and sacral slope. This suggests that long-standing KFC not only worsens through the mechanism described by R. O'Sullivan et al., but also triggers systemic reorganization of the overlying segments, which in turn may sustain and exacerbate the flexed knee posture, closing the vicious cycle at a new, higher level.

The study by H. Böhm et al. demonstrated that in some patients, surgical correction of KFC was followed by an increase in PT and compensatory enhancement of LL [20]. This indicates that changes in knee joint biomechanics can affect pelvic position and the lumbar spine. The correlations between KFC and PT and LL parameters identified in our study in the older age group are consistent with these observations and likely reflect similar biomechanical mechanisms operating in the setting of long-standing contracture.

J.C. Bernard et al. showed that in ambulatory patients with CP, changes predominantly affect pelvic orientation (PT and SS) while the anatomical parameter PI remains preserved [21]. This indicates the presence of compensatory mechanisms involving the pelvic complex that are not related to congenital pelvic morphological features. The authors also noted a dependence of pelvic parameters on the level of motor impairment: with increasing GMFCS level, an increase in posterior pelvic tilt and a decrease in sacral slope were observed. These findings are consistent with the pelvic type of compensation identified in our study, in which adaptation to long-standing KFC is achieved through changes in spatial pelvic orientation.

1. Attias et al. demonstrated that in patients with CP, the range of trunk motion increases with greater severity of motor impairment, reflecting the complexity of compensatory processes involving the overlying segments of the musculoskeletal system [22]. Our data complement these observations by demonstrating that compensatory changes in CP are not limited to increased trunk mobility but also affect static sagittal balance parameters. Taken together, this indicates that compensatory processes in CP are systemic in nature and consistently involve the spine and pelvis, with the magnitude and pattern of these changes depending on age and the duration of contracture.

The data obtained in our study indicate an age-related dynamics of compensatory changes in the musculoskeletal system in KFC. The absence of statistically significant associations between the magnitude of KFC and sagittal balance parameters in patients under 12 years of age after controlling for GMFCS influence suggests that at early stages, compensatory mechanisms are implemented predominantly at the local level, without involving the spinopelvic complex.

In patients older than 12 years, by contrast, stable associations were identified between KFC and LL, SVA, and SS after controlling for GMFCS level. This suggests that long-standing contracture leads to the sequential involvement of overlying segments of the kinematic chain: initially the spine (changes in LL and SVA), followed by the pelvic complex (changes in SS).

The identified age-related dynamics are consistent with the three sequential compensation levels (local, spinal, and pelvic) distinguished in the present study and may have clinical implications for determining the optimal timing of surgical intervention.

Study limitations

This study has several methodological limitations. First, the cross-sectional design does not allow definitive confirmation of the sequential (evolutionary) nature of the identified compensatory changes or establishment of causal relationships between KFC and sagittal spinopelvic balance parameters. Therefore, the obtained results should be interpreted as reflecting age-related associations that require confirmation in longitudinal studies. Second, the control group served as a reference population and was used primarily for descriptive com-parison of sagittal spinopelvic profile parameters rather than for direct statistical comparison, which does not allow complete exclusion of the influence of baseline differences between samples. Third, the distribution of patients by motor function level (GMFCS) was uneven, which could potentially affect sagittal balance parameters. To minimize this influence, regression analysis and partial correlation ana-lysis with GMFCS control were additionally performed. Fourth, the study was limited to the analysis of static clinical and radiological parameters and did not include instrumented three-dimensional gait analysis, which limits the ability to comprehensively assess the relationship between static sagittal profile changes and dynamic features of crouch gait.

Conclusion

The results of this study allow the changes in spinopelvic relationships in patients with knee flexion contracture and cerebral palsy to be considered as a sequential adaptation of the musculoskeletal system aimed at maintaining sagittal balance. Comparison of the obtained data after controlling for GMFCS level enabled the identification of three sequential types of compensatory changes in knee flexion contracture: local, spinal, and pelvic. The identified compensation types reflect the evolution of adaptive mechanisms of the musculoskeletal system in long-standing knee flexion contracture and suggest the sequential involvement of different components of the knee-spine-pelvis kinematic chain.

Disclaimers

Author contribution

Novikov V.A. — study design, drafting the manuscript, literature search and review.

Umnov V.V. — editing the manuscript.

Mustafaeva A.R. — data acquisition, statistical data processing, editing the manuscript literature search and review.

Zharkov D.S. — data acquisition, literature search and review.

Umnov D.V. — data acquisition, literature search and review.

All authors have read and approved the final version of the manuscript of the article. All authors agree to bear responsibility for all aspects of the study to ensure proper consideration and resolution of all possible issues related to the correctness and reliability of any part of the work.

Funding source. This study was not supported by any external sources of funding.

Disclosure competing interests. The authors declare that they have no competing interests.

Ethics approval. Not applicable.

Consent for publication. Written consent was obtained from legal representatives of children for publication of relevant medical information and all of accompanying images within the manuscript.

Use of artificial intelligence. In the preparation of this manuscript, the artificial intelligence tool ChatGPT (GPT-5, OpenAI, https://chat.openai.com) was used to generate the initial draft of Figure 1. The final version of the illustration was prepared by the authors independently. Artificial intelligence was not used for data analysis, interpretation of results, or manuscript writing. The authors confirmed the accuracy and appropriateness of all final materials by manually verifying the results.

About the authors

Vladimir А. Novikov

H. Turner National Medical Research Center for Сhildren’s Orthopedics and Trauma Surgery

Author for correspondence.
Email: novikov.turner@gmail.com
ORCID iD: 0000-0002-3754-4090
SPIN-code: 2773-1027

Cand. Sci. (Med.)

Russian Federation, St. Petersburg

Valery V. Umnov

H. Turner National Medical Research Center for Сhildren’s Orthopedics and Trauma Surgery

Email: umnovvv@gmail.com
ORCID iD: 0000-0002-5721-8575
SPIN-code: 6824-5853

Dr. Sci. (Med.)

Russian Federation, St. Petersburg

Alina R. Mustafaeva

H. Turner National Medical Research Center for Сhildren’s Orthopedics and Trauma Surgery

Email: alina.mys23@yandex.ru
ORCID iD: 0009-0003-4108-7317
SPIN-code: 1099-7340

научный сотрудник отдела нейроортопедии, системных и орфанных заболеваний, аспирант 

Russian Federation, St. Petersburg

Dmitry S. Zharkov

H. Turner National Medical Research Center for Сhildren’s Orthopedics and Trauma Surgery

Email: striker5621@gmail.com
ORCID iD: 0000-0002-8027-1593
SPIN-code: 5908-7774
Russian Federation, St. Petersburg

Dmitry V. Umnov

H. Turner National Medical Research Center for Сhildren’s Orthopedics and Trauma Surgery

Email: dmitry.umnov@gmail.com
ORCID iD: 0000-0003-4293-1607
SPIN-code: 1376-7998

Cand. Sci. (Med.)

Russian Federation, St. Petersburg

References

Supplementary files