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Bernard J.1, Beldame J.2, Lecuyer M.1, Brunel H.1, Van Driessche S.3, Masse M.2, Matsoukis J.4, Billuart F.1
1IFMK Saint-Michel, Paris, France, 2Clinique Mégival, Saint-Aubin-sur-Scie, France, 3Clinique de Montargis, Montargis, France, 4Hopital J Monod, Montivilliers, France
Background: Total hip arthroplasty (THA) is the second most commonly performed surgical procedure. Although surgery relieves pain and improves health-related quality of life, literature reveals that despite the post-operative improvements, gait and posturographic parameters of the patients undergoing THA do not reach those of the general population, especially for the anterior approach for THA. In addition, the rehabilitation of static postural balance conducted on a force platform or at home does not standardize postural parameters. An electromyographic study of the hip muscles involved in the surgery (Gluteus Maximus, Gluteus Medius, TFL, Sartorius) may provide information on the functioning of the hip joint after THA.
Purpose: The aim of this study was to analyze muscle activity during different tasks of postural stability. We hypothesized that among patients who underwent THA muscle activity explains the postural stability.
Methods: 11 asymptomatic participants and 11 THA patients (anterior surgical approach) participated in the study. Each participant realized 4 postural tasks: bipedal eyes opened and closed, and unipedal stance on the operated and non-operated limb. EMG activity during the postural tasks was expressed as a normalized value of the EMG activity observed during a maximal voluntary contraction (MVC). Data were recorded with four bipolar surface electrodes (SX-230, Biometrics Ltd), placed over the muscle bellies of Gluteus Maximus (GMax), Gluteus Medius (GMed), TFL and Sartorius (S) using SENIAM recommendations.
Results: THA patients presented a greater EMG activity compared to asymptomatic participants for the operated and non-operated limbs. In bipedal eyes closed GMax and GMed activity was greater on the operated limb and non-operated limb (15.3%±11.9 and 12.5%±5.7 vs 7.3%±5.8 for GMax, 13.3%±8.4 and 13.3%±5.9 vs 8.0%±4.7 for GMed, p 0.05). In unipedal, GMed activity was greater on the operated limb and non-operated limb (51.1%±29.7 and 47.6%±26.9 vs 28.1%±13.2, p 0.05) and TFL activity was greater only for the operated limb (22.8%±16.9 vs 11.9%±15.8, p 0.05).
Conclusion(s): GMax and GMed muscles are the main hip stabilizers in the medio-lateral plan. A greater EMG activity of these 2 muscles shows higher energy consumption in THA patients than in asymptomatic participants for maintaining balance in both bipedal and unipedal stance. This result is consistent with previous studies on postural stability on force platform, where it is shown that postural parameters suffer a degradation among THA patients, particularly on those operated with the anterior approach. This postural perturbation could result from a mechanoreceptor damage in the joint capsule or in the TFL and S muscles during the surgery. As TFL activity is greater in THA patients compared to asymptomatic participants for the unipedal stance on the operated limb, we can assume TFL muscle regulates hip muscles activity for the postural stability.
Implications: Even though total hip arthroplasty with minimally invasive approaches lead to excellent clinical and functional results, static postural perturbations persist several weeks after surgery. It is known that a functional rehabilitation of static balance on a force platform or self-rehabilitation at home is not sufficient. We suggest a precocious and specific rehabilitation with a neuromuscular approach.
Funding acknowledgements: IFMK Saint-Michel, Paris, France.
Topic: Orthopaedics
Ethics approval: Ethics approval obtained from GHH Hôpital J Monod Ethics Committee, Montivilliers, on April 1st 2014.
All authors, affiliations and abstracts have been published as submitted.
