Azevedo D.1, Paiva E.2, Lopes A.3, Santos H.1, Carneiro R.1,2, Rodrigues A.2, Andrade M.A.2, Novais E.4, Van Dillen L.5
1Pontificia Universidade Catolica de Minas Gerais, Physical Therapy Department, Belo Horizonte, Brazil, 2Universidade Federal de Minas Gerais, Belo Horizonte, Brazil, 3Axial Medicina Diagnostica, Belo Horizonte, Brazil, 4Boston Children's Hospital, Department of Orthopaedic Surgery, Boston, United States, 5Washington University School of Medicine, Program in Physical Therapy, Saint Louis, United States
Background: Hip morphologic abnormalities are considered a fundamental part of femoroacetabular impingement (FAI). However, it is common to find similar abnormalities in asymptomatic populations as those seen in people with FAI. Pelvic movement has been considered a possible discriminating parameter associated with FAI symptom onset. Decreased pelvic rotation has been found during squatting in people with FAI when compared to hip-healthy people with and without morphologic changes associated with FAI. However, it is possible that changes in pelvic movement may occur in other hip conditions because of pain and may not be specific to FAI.
Purpose: To compare sagittal pelvic rotation during hip flexion and in sitting between people with symptomatic FAI, people with other symptomatic hip conditions, and hip-healthy people.
Methods: The current study was a cross-sectional, case-control design. There were 2 independent variables. The first variable was hip condition with three levels, people with a symptomatic hip associated with FAI, people with a symptomatic hip associated with other hip conditions, and people with healthy hips. The second variable was hip position with 3 levels, standing hip flexion to 45°, standing hip flexion to 90°, and sitting. The dependent variable was the amount of sagittal plane pelvic rotation movement. Thirty people with symptomatic FAI with cam deformity, 30 people with other symptomatic hip conditions, and 20 hip-healthy people participated in the study. Sagittal pelvic rotation was calculated based on measures of pelvic alignment in standing, hip flexion to 45° and 90°, and sitting. Sagittal pelvic position was assessed using the Palpation Meter device - PALM. A digital inclinometer was used to measure hip flexion. The examiner responsible for performing the pelvic rotation measures was blinded to group assignment.
Results: The mixed model ANOVA test revealed a significant interaction between hip condition and hip position (F2.2,85.5= 3.2, P= 0.039). The one-way ANOVA tests revealed significant differences in sagittal pelvic rotation among the three groups in all conditions (Ps 0.05). Post-hoc analyses revealed that participants in the symptomatic FAI group had less pelvic rotation during hip flexion to 45° and 90° compared to participants in the other symptomatic hip conditions group and hip-healthy group (mean difference= 1.2° to 1.9°). In sitting, participants in the other symptomatic hip conditions group had less posterior pelvic rotation compared to the hip-healthy group (mean difference= 3.9°).
Conclusion(s): Results from this study suggest that people with symptomatic FAI with cam deformity have decreased posterior pelvic rotation during active hip flexion when compared to people with other symptomatic hip conditions and hip-healthy people. Limited posterior pelvic rotation during hip flexion may be an underlying mechanism of symptom onset in people with FAI with cam deformity.
Implications: Decreased posterior pelvic rotation appears to be a specific pathomechanism related to people with symptomatic FAI with cam deformity that is not seen in other symptomatic hip conditions. It is possible that increasing posterior pelvic rotation during hip flexion activities in people with FAI with cam deformity would attenuate impingement of hip tissues.
Funding acknowledgements: The authors would like to thank Axial Medicina Diagnostica for providing magnetic resonance imaging examinations for the hip-healthy participant group.
Topic: Musculoskeletal: lower limb
Ethics approval: This study was approved by the ethics committee of Pontificia Universidade Catolica de Minas Gerais, PUC-Minas, MG, Brazil
All authors, affiliations and abstracts have been published as submitted.
