Functional evaluation of hip abductor muscles with use of magnetic resonance imaging

Influence of motor imagery training on hip abductor muscle strength and bilateral transfer effect

Motor imagery training could be an important treatment of reduced muscle function in patients and injured athletes. In this study, we investigated the efficacy of imagery training on maximal force production in a larger muscle group (hip abductors) and potential bilateral transfer effects. Healthy participants (n = 77) took part in two experimental studies using two imagery protocols (∼30 min/day, 5 days/week for 2 weeks) compared either with no practice (study 1), or with isometric exercise training (study 2). Maximal hip abduction isometric torque, electromyography amplitudes (trained and untrained limbs), handgrip strength, right shoulder abduction (strength and electromyography), and imagery capability were measured before and after the intervention. Post intervention, motor imagery groups of both studies exhibited significant increase in hip abductors strength (∼8%, trained side) and improved imagery capability. Further results showed that imagery training induced bilateral transfer effects on muscle strength and electromyography amplitude of hip abductors. Motor imagery training was effective in creating functional improvements in limb muscles of trained and untrained sides.

The relationship between gluteus medius and minimus muscle volumes and hip development in developmental dysplasia of the hip

BACKGROUND

Several studies in adult hips have revealed the role of the gluteus medius (Gmed) and gluteus minimus (Gmin) muscles in maintaining the stability and centripetal force of the hip joint. Hip centripetality in developmental dysplasia of the hip (DDH) patients contributes to subsequent healthy hip development later in life. The purpose of this study is to investigate the relationship between Gmed and Gmin volume and centripetality of the hip in infant DDH patients.

METHODS

We retrospectively enrolled 41 unilateral DDH patients (4 males, 37 females) who were treated by closed reduction from 2006 to 2016 and underwent magnetic resonance imaging at around 2 years old. Gmed, and Gmin volume was measured in magnetic resonance imaging. We defined both Gmin and Gmed together as hip abductor gluteus muscles (GMs; Gmed + Gmin). The muscle volume ratio of the affected side was calculated by dividing the GMs volume of the affected side by the contralateral side. Relationships between center-head distance discrepancy (CHDD) at 2 years old, and at 4-6 years old and GMs volume ratio were investigated by Pearson's correlation coefficient within the same patients.

RESULTS

Mean age of closed reduction was 0.8 years old and mean age at MRI was 2.2 years old with a mean follow-up period of 3.7 years. Mean GMs volume in the affected side, contralateral side, and muscle volume ratio were 25.3 cm³, 27.0 cm³, and 0.94, respectively. GMs volumes were significantly higher in the contralateral side (p < 0.001). GMs volume ratio at 2 years old significantly correlated with CHDD at 4-6 years old (p < 0.05).

CONCLUSION

GMs volume at 2 years old was found to be associated with later hip afferents. Promoting the healthy development of GMs by properly maintaining the infant's natural hip movement is important for the healthy hip development.

LEVEL OF EVIDENCE

Level III.

Sexual Dimorphism Impact on the Ground Reaction Force Acting on the Mediolateral Direction During Level Walking: Hip Abductor Muscle Biomechanics and Its Correlation to GRF Moment Arm

The female pelvis morphology represents an evolved compensation between two opposing needs: a broad pelvis enough to deliver a sizeable brained offspring while remaining narrow enough to allow for effective bipedal gait. The precise expectation of hip abductor force generation is critical in anthropological studies and experimental practice of human stride mechanics. Hip implants and surgical procedures for hip anatomy reconstruction are based on the static single-leg stance paradigm. The current work investigated the impact of sexual dimorphism on the ground reaction force (GRF) acting on the mediolateral direction during level walking, emphasizing the difference in hip abductor muscle biomechanics and its correlation to ground reaction force moment arm, R. The ground reaction force in the mediolateral direction, hip abduction and adduction moments during the gait cycle and ground reaction force moment arm, R were measured. The current study concludes that the male individuals exhibit significantly higher mass-specific mediolateral ground reaction force during level walking. In contrast, hip abductor moments/kg body weight, medialization of the trochanter, R, and hip coronal were more significant in female individuals. We conclude that increased abductor moment and medialization of the greater trochanter will increase R, hip coronal and decrease abductor moment arm, r, in female individuals, affecting the effective mechanical advantage (EMA) of hip abductors in single-limb stance during level walking.

FABREX: A NEW CLINICAL TEST FOR DIAGNOSIS GLUTEAL TENDINOPATHY

Objective:

This study aims to describe a simple and accurate semiological method executing a specific maneuver with the lower limb to direct the semiological investigation towards the tendinopathies in the gluteus medius and minimus.

Methods:

Fifty patients participated in the study, with a mean age of 44.1 ± 13 years, with persistent pain on the side of the hip for more than three months. To compare the FABREX (proposed test) and Lequesne semiological tests, in the diagnosis of tendinopathies in the gluteus medius and minimus, Magnetic Resonance Imaging (MRI) was adopted as the gold standard.

Results:

FABREX presented high sensitivity and moderate specificity for tendinopathy in the gluteus medius and high sensitivity and specificity for tendinopathy in the gluteus minimus.

Conclusion:

The proposed test, when positive, can be used to determine the diagnosis of gluteal tendinopathies (high specificity). Moreover, it has high sensitivity, excluding the diagnosis when negative. This study represents the initial step for validating the FABREX test, and can therefore be considered a simple and accurate procedure to identify patients with or without gluteal tendinopathies. Level of Evidence III, Case Control Study.

Rehabilitation After Gluteus Medius and Minimus Treatment

We reviewed the current literature regarding rehabilitation after gluteus medius and minimus tears as part of a conservative management or postoperative protocol. The greater trochanteric pain syndrome includes a constellation of pathologies that generate pain in the greater trochanteric region and may be accompanied by varying degrees of hip abductor disfunction. It may be related to tendinitis of the gluteus medius and minimus, greater trochanteric bursitis, or even formal tears of the hip abductor tendons. The initial management strategy of the hip abductor tears is conservative, including different anti-inflammatory therapies such as physical therapy and cortisone and platelet-rich plasma injections. The clearest indication for surgical management is failure of conservative management and loss of abductor muscle power. Surgical management has been performed both open and endoscopic with good reported clinical results. More severe tears typically require a more rigid and complex type of fixation. Exorcise intervention seem to improve symptoms after 4 months to a year of therapy therefore a very close supervision of the rehabilitation protocol is mandatory. Gluteus medius and minimus tears are frequent and may be not diagnosed timely. Treatment of these of lesions is based on the knowledge of pathomechanics involved and the extent of injury to the tendon and muscle tissue. Conservative management is based on protecting the hip abductor tendons from excessive tensile and compression stresses while applying progressive load in conjunction with physical and medical anti-inflammatory measures. Surgical treatment is indicated when conservative management fails or an abductor power deficit is associated with pain. Similar physical therapy protocols to those used in conservative management are used postoperatively.

Level of Evidence

Level V, expert opinion.

Magnetic Resonance Imaging Assessment of Abductor Muscles Shortly After Curved Periacetabular Osteotomy

BACKGROUND

Curved periacetabular osteotomy (CPO) is performed via an anterior approach without detachment of the hip abductor muscles. This study aimed to evaluate the abductor muscle status shortly after CPO on magnetic resonance imaging (MRI).

METHODS

We prospectively evaluated 38 hips in 38 patients 1 week and 3 months after CPO between October 2017 and July 2019. The status of the abductor muscles was assessed on MRI using the following criteria: grade 0, normal; grade I, strain/edema; grade II, partial tear; and grade III, complete tear. We also evaluated associations between muscle status and patients' characteristics.

RESULTS

One week after CPO, the gluteus maximus was classified as grade 0 in all patients. The gluteus medius was grade 0 in 84.2% of patients and grade I in 15.8%. The gluteus minimus was grade I in 55.3% of patients and grade II in 44.7%. Three months after CPO, both the gluteus maximus and gluteus medius were grade 0 in all patients, while the gluteus minimus was still grade I in 47.4%. There were no significant differences between patients with a grade 0 and grade I gluteus minimus at 3 months after CPO in patients' characteristics (age and body mass index) or clinical scores (Harris Hip Score and Japanese Orthopedics Association score).

CONCLUSION

Both the gluteus minimus and medius showed abnormal appearances on MRI 1 week after CPO, whereas only the gluteus minimus showed abnormalities 3 months after CPO. This abductor muscle status did not affect the postoperative Harris Hip Score or Japanese Orthopedics Association score.

The pathological features of hip abductor tendon tears - a cadaveric study

Background

The hip abductors are crucial in maintaining pelvic stability. Tears in these tendons are common and often debilitating. There is uncertainty regarding both the histological and macroscopic features of hip abductor tears. This study aims to clarify both the macroscopic and microscopic features of the tendon and enthesis in hip abductor tendon tears.

Methods

Thirty-six cadavers with an average age of 81 were dissected, and the hip abductor mechanisms removed en-bloc. The presence, location and size of the tears were recorded and analysed. The samples were processed into histological blocks and viewed using both transmitted and polarised light. Tendon histology was graded using the modified Movin’s score in three sections (deep, middle and superficial layers) and the enthesis graded separately using 5-point criteria. Analysis of variance was used to confirm histological features associated with tears.

Results

Tears were found in 24 of 36 samples (67%). The most common finding was an isolated tear in the gluteus minimus (46%), followed by concurrent gluteus medius and gluteus minimus tears (33%). Histology revealed significantly more degeneration in both the tendon (p = 0.0005) and enthesis (p = 0.0011) when tears were present. Furthermore, these changes were concentrated in the deeper layers of the tendon (p = 0.0002) and enthesis (p = 0.003).

Conclusion

This study demonstrated degeneration as the primary pathology underlying hip abductor tendon tears. Degenerative changes occur in both the tendon and enthesis, with the deeper layers predominantly affected. These findings are important for guiding surgical repair techniques and to aid the development of novel materials and biologics.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-020-03784-3.

Towards a Simplified Estimation of Muscle Activation Pattern from MRI and EMG Using Electrical Network and Graph Theory

Muscle functional MRI (mfMRI) is an imaging technique that assess muscles’ activity, exploiting a shift in the T2-relaxation time between resting and active state on muscles. It is accompanied by the use of electromyography (EMG) to have a better understanding of the muscle electrophysiology; however, a technique merging MRI and EMG information has not been defined yet. In this paper, we present an anatomical and quantitative evaluation of a method our group recently introduced to quantify its validity in terms of muscle pattern estimation for four subjects during four isometric tasks. Muscle activation pattern are estimated using a resistive network to model the morphology in the MRI. An inverse problem is solved from sEMG data to assess muscle activation. The results have been validated with a comparison with physiological information and with the fitting on the electrodes space. On average, over 90% of the input sEMG information was able to be explained with the estimated muscle patterns. There is a match with anatomical information, even if a strong subjectivity is observed among subjects. With this paper we want to proof the method’s validity showing its potential in diagnostic and rehabilitation fields.

Rehabilitation Exercises for the Gluteus Minimus Muscle Segments: An Electromyography Study

CONTEXT

The gluteus minimus (GMin) muscle consists of 2 uniquely oriented segments that have potential for independent function and have different responses to pathology and aging. For healthy young adults, it is unknown that which rehabilitation exercises specifically target the individual segments.

OBJECTIVE

To quantify segmental GMin activity for 6 common lower-limb rehabilitation exercises in healthy young adults and determine if significant differences exist in segmental activity levels between the exercises.

METHOD

Six common lower-limb rehabilitation exercises were performed by 10 healthy young adults with fine-wire electromyography (EMG) electrodes inserted into the anterior and posterior segments of the GMin muscle.

MAIN OUTCOME MEASURES

Electromyography signals were recorded, and median normalized exercise activity levels were reported and compared for each GMin segment across the 6 exercises.

RESULTS

High activity levels were generated in the anterior segment by the resisted hip abduction-extension exercise (51% maximum voluntary isometric contraction [MVIC]), whereas for the posterior segment, high activity levels were produced by the single-leg bridge (49% MVIC), the side-lie hip abduction (43% MVIC), the resisted hip abduction-extension exercise (43% MVIC), and the single-leg squat (40% MVIC). There were significant differences (P < .05) in the median electromyography activity levels for the anterior GMin segment but not for the posterior GMin segment across some of the exercises with large effect sizes.

CONCLUSION

Targeted rehabilitation exercises graded by exercise intensity can be prescribed specifically for the anterior and posterior GMin segments to aid in restoration of hip function following injury or aging.

Hip abductor muscle volumes are smaller in individuals affected by patellofemoral joint osteoarthritis

OBJECTIVE

The aims of this study were twofold: firstly, to compare hip abductor muscle volumes in individuals with patellofemoral joint (PFJ) osteoarthritis (PFJ OA) against those of healthy controls; and secondly, to determine whether hip muscle volumes and hip kinematics during walking are related in individuals with PFJ OA and healthy controls.

METHODS

Fifty-one individuals with PFJ OA and thirteen asymptomatic, age-matched healthy controls ≥40 years were recruited. Volumes of the gluteus medius, gluteus minimus and tensor fasciae latae were obtained from magnetic resonance (MR) images. Video motion capture was used to measure three-dimensional hip joint kinematics during overground walking.

RESULTS

Significantly smaller gluteus medius (P = 0.017), gluteus minimus (P = 0.001) and tensor fasciae latae (P = 0.027) muscle volumes were observed in PFJ OA participants compared to controls. Weak correlations were observed between smaller gluteus minimus volume and larger hip flexion angle at contralateral heel strike (CHS) (r = -0.279, P = 0.038) as well as between smaller gluteus minimus volume and increased hip adduction angle at CHS (r = -0.286, P = 0.046).

CONCLUSION

Reduced hip abductor muscle volume is a feature of PFJ OA and is associated with increased hip flexion and adduction angles during the late stance phase of walking for PFJ OA participants and healthy controls.

Fat infiltration in the gluteus minimus muscle in older adults

Purpose

Fat infiltration (FI) in the gluteus minimus muscle (GMin) has been reported as being restricted to the anterior part. The aim of this study was to verify whether FI is localized only to the anterior part of the GMin through the dissection of large number of elderly cadavers and to clarify the underlying mechanism of FI localized to a specific region.

Materials and methods

Thirty-eight hips from 20 embalmed elder cadavers were dissected for verification of FI localization. The samples of three regions – the fat infiltrated region of the anterior part (FI), the region without FI (non-FI), and the posterior region – were harvested from nine hips for the histological fiber type assessment.

Results

The FI area was distributed at 2.6°–38° from the anterior border within the anterior part, of which function is responsible for hip extension and internal rotation and is likely reduced by disuse following aging. The number of type I fibers was lowest in FI, followed by non-FI, while the number of type I fibers was highest in the posterior. Meanwhile, the number of type II fibers was equivalent across the three regions. Atrophic type II fibers were observed in overall samples of the three regions, and grouped atrophy, which is evidence of denervation, was observed in FI and non-FI samples. Type grouping, which suggests to be reinnervated, was found in the non-FI and posterior samples but very little in the FI samples.

Conclusion

FI in the GMin in older adults restricted to deep within the anterior part is secondary to disuse and is strongly related to impaired denervation–reinnervation process.

Hip rotation during standing and dynamic activities and the compensatory effect of femoral anteversion: An in-vivo analysis of asymptomatic young adults using three-dimensional computed tomography models and dual fluoroscopy

BACKGROUND

Individuals are thought to compensate for femoral anteversion by altering hip rotation. However, the relationship between hip rotation in a neutral position (i.e. static rotation) and dynamic hip rotation is poorly understood, as is the relationship between anteversion and hip rotation.

RESEARCH OBJECTIVE

Herein, anteversion and in-vivo hip rotation during standing, walking, and pivoting were measured in eleven asymptomatic, morphologically normal, young adults using three-dimensional computed tomography models and dual fluoroscopy.

METHODS

Using correlation analyses, we: 1) determined the relationship between hip rotation in the static position to that measured during dynamic activities, and 2) evaluated the association between femoral anteversion and hip rotation during dynamic activities. Hip rotation was calculated while standing (static-rotation), throughout gait, as a mean during gait (mean gait rotation), and as a mean (mid-pivot rotation), maximum (max-rotation) and minimum (min-rotation) during pivoting.

RESULTS

Static-rotation (mean ± standard deviation; 11.3° ± 7.3°) and mean gait rotation (7.8° ± 4.7°) were positively correlated (r = 0.679, p = 0.022). Likewise, static-rotation was strongly correlated with mid-pivot rotation (r = 0.837, p = 0.001), max-rotation (r = 0.754, p = 0.007), and min-rotation (r = 0.835, p = 0.001). Strong positive correlations were found between anteversion and hip internal rotation during all of the stance phase (0-60% gait) and during mid- and terminal-swing (86-100% gait) (all r > 0.607, p < 0.05).

CONCLUSIONS

Our results suggest that the static position may be used cautiously to express the neutral rotational position of the femur for dynamic movements. Further, our results indicate that femoral anteversion is compensated for by altering hip rotation. As such, both anteversion and hip rotation may be important to consider when diagnosing hip pathology and planning for surgical procedures.

Can Anatomic Measurements of Stem Anteversion Angle Be Considered as the Functional Anteversion Angle?

BACKGROUND

Stem anteversion angle is important in the combined anteversion theory to avoid implant impingement after total hip arthroplasty (THA). However, anatomic measurements of stem anteversion angle may not represent functional anteversion of the femur if the femur undergoes axial rotation. Herein, the femoral rotational angle (FRA) was measured in supine and standing positions before and after THA to evaluate the difference between anatomic and functional measurements.

METHODS

A total of 191 hips (174 patients) treated with THA for osteoarthritis were analyzed in this retrospective, case-controlled study. The FRA was measured as the angle between the posterior condylar line and the line through the bilateral anterior superior iliac spines (positive for external rotation) and was measured preoperatively and postoperatively in supine and standing positions with computed tomography segmentation and landmark localization of the pelvis and the femur followed by intensity-based 2D-3D registration. The number of cases in which the absolute FRA remained <15° in both positions was also calculated.

RESULTS

The average ± standard deviation preoperative FRA was 0.3° ± 8.3° in the supine position and -4.5° ± 8.8° during standing; the postoperative FRA was -3.8° ± 9.0° in supine and -14.3° ± 8.3° during standing. There were 134 cases (70%) in which the preoperative absolute FRA remained <15° in both positions while only 85 hips (45%) remained <15°, postoperatively.

CONCLUSION

Substantial variability was seen in the FRA, especially during the postoperative period. These results suggest that the anatomic stem anteversion angle may not represent the functional anteversion of the femur.

Volume Increases of the Gluteus Maximus, Gluteus Medius, and Thigh Muscles After Hip Arthroplasty

BACKGROUND

Muscle atrophy in osteoarthritis (OA) patients is expected to recover after total hip arthroplasty (THA) because of the increase in activity levels. Although some reports have shown an increase in the thigh muscles (Th) after THA, no reports of increases in the gluteal muscles and of analyses of the factors related to muscle recovery have been published. In this study, the changes in the gluteal and Th volumes after THA were quantitatively evaluated using computed tomography (CT) images, and the factors related to muscle recovery were analyzed.

METHODS

The subjects were 40 OA hips with CT images taken 3 weeks after THA (first postoperative [postop] CT) and more than 2 years after THA (second postop CT). The cross-sectional areas of gluteus maximus (G-max), gluteus medius (G-med), and Th were measured in both CT images. The factors related to muscle recovery that were measured and evaluated were age, gender, days from operation, surgical approach, Kellgren-Lawrence grades, and hip functional score (Japanese Orthopaedics Association hip score).

RESULTS

All measured cross-sectional areas of the operated side increased significantly from the first postop CT to the second postop CT (G-max, 40%; G-med, 11%; and Th, 20%). In the analysis of the factors related to muscle recovery, the increase rate of G-max correlated significantly with patient age, and the increase rate of G-med correlated significantly with the increase in Japanese Orthopaedics Association hip score.

CONCLUSIONS

Hip OA can lead to atrophy of the gluteal and Th, but the muscle volume can recover more than 2 years after THA.

M-Mode Ultrasound Reveals Earlier Gluteus Minimus Activity in Individuals With Chronic Hip Pain During a Step-down Task

STUDY DESIGN

Controlled laboratory study.

BACKGROUND

The hip abductor muscles are important hip joint stabilizers. Hip joint pain may alter muscle recruitment. Motion-mode (M-mode) ultrasound enables noninvasive measurements of the onset of deep and superficial muscle motion, which is associated with activation onset.

OBJECTIVES

To compare (1) the onset of superficial and deep gluteus medius and gluteus minimus muscle motion relative to the instant of peak ground reaction force and (2) the level of swing-phase muscle motion during step-down between subjects with chronic hip pain and controls using M-mode ultrasound.

METHODS

Thirty-five subjects with anterior, nontraumatic hip pain for more than 6 months (mean ± SD age, 54 ± 9 years) and 35 controls (age, 57 ± 7 years) were scanned on the lateral hip of the leading leg during frontal step-down onto a force platform using M-mode ultrasound. Computerized motion detection with the Teager-Kaiser energy operator was applied on the gluteus minimus and the deep and superficial gluteus medius to determine the time lag between muscle motion onset and instant of peak ground reaction force and the level of gluteus minimus motion during the swing phase. Time lags and motion levels were averaged per subject, and t tests were used to determine between-group differences.

RESULTS

In participants with hip pain, gluteus minimus motion onset was 103 milliseconds earlier (P = .002) and superficial gluteus medius motion was 70 milliseconds earlier (P = .047) than those in healthy control participants. The level of gluteus minimus swing-phase motion was higher with pain (P = .006).

CONCLUSION

Increased gluteus minimus motion during the swing phase and earlier gluteus minimus and superficial gluteus medius motion in individuals with hip pain suggest an overall increase of muscle activity, possibly a protective behavior.

Gluteal Tendinopathy: Integrating Pathomechanics and Clinical Features in Its Management

Synopsis Gluteal tendinopathy is now believed to be the primary local source of lateral hip pain, or greater trochanteric pain syndrome, previously referred to as trochanteric bursitis. This condition is prevalent, particularly among postmenopausal women, and has a considerable negative influence on quality of life. Improved prognosis and outcomes in the future for those with gluteal tendinopathy will be underpinned by advances in diagnostic testing, a clearer understanding of risk factors and comorbidities, and evidence-based management programs. High-quality studies that meet these requirements are still lacking. This clinical commentary provides direction to assist the clinician with assessment and management of the patient with gluteal tendinopathy, based on currently limited available evidence on this condition and the wider tendon literature and on the combined clinical experience of the authors. J Orthop Sports Phys Ther 2015;45(11):910-922. Epub 17 Sep 2015. doi:10.2519/jospt.2015.5829.

An evidence-based review of hip-focused neuromuscular exercise interventions to address dynamic lower extremity valgus

Deficits in proximal hip strength or neuromuscular control may lead to dynamic lower extremity valgus. Measures of dynamic lower extremity valgus have been previously shown to relate to increased risk of several knee pathologies, specifically anterior cruciate ligament ruptures and patellofemoral pain. Therefore, hip-focused interventions have gained considerable attention and been successful in addressing these knee pathologies. The purpose of the review was to identify and discuss hip-focused exercise interventions that aim to address dynamic lower extremity valgus. Previous electromyography, kinematics, and kinetics research support the use of targeted hip exercises with non-weight-bearing, controlled weight-bearing, functional exercise, and, to a lesser extent, dynamic exercises in reducing dynamic lower extremity valgus. Further studies should be developed to identify and understand the mechanistic relationship between optimized biomechanics during sports and hip-focused neuromuscular exercise interventions.

Effects of the Indoor Horseback Riding Exercise on Electromyographic Activity and Balance in One-leg Standing

[Purpose] This study investigated the influence of the indoor horseback riding exercise on the electromyographic activity of the lower extremity and balance during one-leg standing. [Subjects] Twenty normal adults were divided into an indoor horseback riding exercise group (IHREG, n=10), which performed the indoor horseback riding exercise using equipment 3 times a week for 3 weeks, and a control group (CG, n=10), which performed no exercise. [Methods] For comparitive analysis, an electromyographic test was performed to measure the electromyographic activities of the rectus femoris (RF), adductor longus (AL), and gluteus medius and the Biodex Balance System was used to measure the anteroposterior stability index (APSI), mediolateral stability index, and overall stability index (OSI). [Results] The electromyographic activities of RF and AL significantly increased and the balance abilities of APSI and OSI decreased significantly in the IHREG compared to the CG. [Conclusion] We consider indoor horseback riding exercise is an effective intervention for increasing electromyographic activities of the RF and AL, and the balance abilities of APSI and OSI of normal adults.

Separate assessment of gluteus medius and minimus: B-mode or M-mode ultrasound?

The hip abductors gluteus medius (Gmed) and minimus (Gmin) differ slightly in function and how they are affected by hip joint pathology. A separate assessment of Gmed and Gmin is feasible by ultrasound (US) imaging. B-mode and M-mode US can be used to measure muscle thickness. Two B- and two M-mode scans of Gmed and Gmin thickness were taken in relaxation on 16 asymptomatic volunteers, repeated within 4 days on 11 subjects. Three types of intra-rater reliability of muscle thickness measurements were examined: (1) within-session reliability comparing two scans from the same session, (2) between-days reliability comparing thickness from two scanning occasion within 4 days and (3) reliability of taking thickness measurements by re-measuring the same US scans after 1 week. Thickness measurements on B- and M-mode images provided ICC3,1 >0.96 for within-session reliability. ICC3,k >0.89 for between-days reliability and ICC3,1 >0.85 for re-reading the same scans were estimated. Minimal detectable changes >1.0 mm within-session, >2.4 mm between-days and >1.7 mm for re-reading scans indicated that small thickness changes are not detectable. The investigation suggests a slight advantage for fascia recognition in B-mode and the advantage of visual control of muscle relaxation in M-mode.

Abductor tendon tears are associated with hypertrophy of the tensor fasciae latae muscle

OBJECTIVE

To evaluate the association between hypertrophy of the tensor fasciae latae muscle and abductor tendon tears.

MATERIALS AND METHODS

Thirty-five patients who underwent MRI of the abductor tendons of the hip were included in this retrospective study. A subgroup of 18 patients was examined bilaterally. The area of the tensor fasciae latae muscle and the area of the sartorius muscle (size reference) were quantified at the level of the femoral head, and a ratio was calculated. Two radiologists assessed the integrity of the gluteus medius and minimus tendon in consensus. Data were analyzed with a Mann-Whitney U test.

RESULTS

Sixteen out of 35 patients (46 %) had a tear of the gluteus medius or minimus tendon. The ratio of the area of the tensor fasciae latae to the sartorius muscle was significantly higher (p = .028) in the group with an abductor tendon tear (median 2.25; Interquartile Range [IQR] = 1.97-3.21) compared to the group without any tears (median 1.91; IQR = 1.52-2.26). The bilateral subanalysis showed that in patients without a tear, the ratio of the two areas did not differ between each side (p = .966), with a median of 1.54 (primary side) and 1.76 (contralateral side). In patients with an abductor tendon tear the ratio was significantly higher (p = .031) on the side with a tear (median 2.81) compared to the contralateral healthy side (1.67).

CONCLUSION

Patients with abductor tendon tears showed hypertrophy of the tensor fasciae latae muscle when compared to the contralateral healthy side and to patients without a tear.

[More muscle mass in men: explanatory model for superior outcome after total hip arthroplasty]

BACKGROUND

Men show better functional results after total hip arthroplasty (THA). The aim of this study was a patient-specific analysis of the hip joint muscles in comparison to the joint geometry.

METHODS

In this study 93 computed tomography (CT) scans of the pelvis (45 men, 48 women) were analyzed to determine hip joint geometry and the volume of the gluteus medius (GMV), gluteus maximus (GXV) and tensor fasciae latae (TFL) muscles. The abduction muscle volumes were analyzed with respect to patient-specific adduction moments.

RESULTS

The absolute total volume of the hip muscular system (TMV) was larger in men than in women (1913 ccm vs. 1479 ccm; p <0.0001). Men exhibited a more progressive increase of muscle volume as the adduction moment increases.

CONCLUSIONS

Men have a greater abduction muscle mass in order to balance adduction moments occurring in the hip joint and therefore have more muscle mass to compensate the inevitable intraoperative muscle damage during THA. This argument supports the extraordinary importance of muscle sparing surgical techniques in women.

[Repair of chronic ruptures of the gluteus medius muscle using a nonresorbable patch]

OBJECTIVE

Repair of a chronic rupture with a defect of the gluteus medius muscle with or without a total hip replacement. Improvement of gait and limping by functional stabilization of the pelvis. Reduction of pain in the region of the greater trochanter.

INDICATIONS

Chronic rupture with a defect of the gluteus medius.

CONTRAINDICATIONS

Complete bony defect and absence of the greater trochanter and hip infection.

OPERATIVE TECHNIQUE

Lateral positioning of the patient. Longitudinal incision of 12-15 cm over the greater trochanter. Preparation to the fascia and longitudinal incision slightly dorsal to the greater trochanter. Preparation and mobilization of the ruptured parts of the gluteal muscles. Smoothening of the insertion of the gluteal muscle. Transosseus fixation of the ventral part of the ruptured gluteal muscles using fiber wires (Arthrex, Munich, Germany) with a Mason-Allen technique. Suturing of the mobilized posterior part of the ruptured gluteal muscle on the resutured ventral gluteal part. Securing of the readaptation by suturing a nonresorbable collagen patch (Zimmer, Winterthur, Switzerland) in a rhomboid direction with nonresorbable sutures (Ethibond, Ethicon, Norderstedt, Germany). Wound closure. POSTOPERATIVE TREATMENT: Prophylaxis of deep venous thrombosis. Early functional mobilization. Continuous increase of weight bearing over a period of 6 weeks and 6 weeks no adduction or active abduction.

RESULTS

Ten patients (9 women, 1 man; age 73.4 ± 12.3 years) showed significant improvement of their symptoms after 1 year. All were pain free and did not need crutches anymore. Four could walk without any limping and in 6 slight limping was observed. The Harris Hip Score increased from 47.5 ± 9.5 points preoperative to 85.2 ± 7.6 points 1 year postoperative. Complications were not observed.

Quantitative MRI of vastus medialis, vastus lateralis and gluteus medius muscle workload after squat exercise: comparison between squatting with hip adduction and hip abduction

The aim of the present study was to evaluate the use MRI to quantify the workload of gluteus medius (GM), vastus medialis (VM) and vastus lateralis (VL) muscles in different types of squat exercises. Fourteen female volunteers were evaluated, average age of 22 ± 2 years, sedentary, without clinical symptoms, and without history of previous lower limb injuries. Quantitative MRI was used to analyze VM, VL and GM muscles before and after squat exercise, squat associated with isometric hip adduction and squat associated with isometric hip abduction. Multi echo images were acquired to calculate the transversal relaxation times (T2) before and after exercise. Mixed Effects Model statistical analysis was used to compare images before and after the exercise (ΔT2) to normalize the variability between subjects. Imaging post processing was performed in Matlab software. GM muscle was the least active during the squat associated with isometric hip adduction and VM the least active during the squat associated with isometric hip abduction, while VL was the most active during squat associated with isometric hip adduction. Our data suggests that isometric hip adduction during the squat does not increase the workload of VM, but decreases the GM muscle workload. Squat associated with isometric hip abduction does not increase VL workload.

Changes of gluteus medius muscle in the adult patients with unilateral developmental dysplasia of the hip

Background

The gluteus medius muscle is essential for gait and hip stability. Changes that occur in the gluteus medius muscles in patients with developmental dysplasia of the hip (DDH) are not well understood. A better understanding of DDH related changes will have positive repercussions toward hip soft tissue reconstruction.

Methods

19 adult patients with unilateral DDH scheduled for total hip arthroplasty were assessed for: cross-sectional area (CSA), radiological density (RD) and the length of gluteus medius using computed tomograhpy(CT) (scanned before THA). Hip abductor moment arm and gluteus medius activation angle were also measured via hip anteroposterior radiographs.

Results

Both CSA and RD of gluteus medius muscle were significantly reduced (p < 0.05) in the affected hip compared to the control. In the affected hip, the length of the gluteus medius muscle was reduced by 8-11 % (p < 0.05) while the gluteus medius activation angle was significantly increased (p < 0.05) and the hip abductor moment arm was decreased (p < 0.05).

Conclusions

The gluteus medius showed substantial loss of CSA, RD as well as decreased length in patients with DDH in the affected hip. These changes should be considered in both hip reconstruction and postoperative rehabilitation training in patients with DDH.

A preliminary multifactorial approach describing the relationships among lower extremity alignment, hip muscle activation, and lower extremity joint excursion

CONTEXT

Multiple factors have been suggested to increase the risk of faulty dynamic alignments that predict noncontact anterior cruciate ligament injury. Few researchers have examined this relationship using an integrated, multifactorial approach.

OBJECTIVE

To describe the relationship among static lower extremity alignment (LEA), hip muscle activation, and hip and knee motion during a single-leg squat.

DESIGN

Descriptive laboratory study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Thirty men (age= 23.9± 3.6 years, height =178.5± 9.9 cm, mass= 82.0± 14.1 kg) and 30 women (age= 22.2± 2.6 years, height= 162.4± 6.3 cm, mass= 60.3± 8.1 kg).

MAIN OUTCOME MEASURE(S)

Pelvic angle, femoral anteversion, quadriceps angle, tibiofemoral angle, and genu recurvatum were measured to the nearest degree; navicular drop was measured to the nearest millimeter. The average root mean square amplitude of the gluteus medius and maximus muscles was assessed during the single-leg squat and normalized to the peak root mean square value during maximal contractions for each muscle. Kinematic data of hip and knee were also assessed during the single-leg squat. Structural equation modeling was used to describe the relationships among static LEA, hip muscle activation, and joint kinematics, while also accounting for an individual's sex and hip strength.

RESULTS

Smaller pelvic angle and greater femoral anteversion, tibiofemoral angle, and navicular drop predicted greater hip internal-rotation excursion and knee external-rotation excursion. Decreased gluteus maximus activation predicted greater hip internal-rotation excursion but decreased knee valgus excursion. No LEA characteristic predicted gluteus medius or gluteus maximus muscle activation during the single-leg squat.

CONCLUSIONS

Static LEA, characterized by a more internally rotated hip and valgus knee alignment and less gluteus maximus activation, was related to commonly observed components of functional valgus collapse during the single-leg squat. This exploratory analysis suggests that LEA does not influence hip muscle activation in controlling joint motion during a single-leg squat.

MRI findings of gluteus minimus muscle damage in primary total hip arthroplasty and the influence on clinical outcome

INTRODUCTION

The influence of surgical trauma on gluteus minimus muscle in total hip arthroplasty (THA) and the impact on functional outcome has been hardly investigated up to now. Potential risks of minimus damage during the approach or femoral preparation is due to its attachment to the anterior facet of the greater trochanter. Possible trauma-associated functional deficits of minimus muscle may result in reduced abduction force or in an unstable hip joint. The aim of the present study was to assess the pre- and post-operative gluteus minimus muscle (tendon defects and fatty atrophy) in patient with anterolateral minimally invasive and modified lateral approach by means of magnetic resonance imaging (MRI) and to investigate the associated impact on functional outcome.

MATERIALS AND METHODS

Thirty-eight patients [average age, 64 years (35-80); BMI, 28 kg/m(2) (19-35)] with primary coxarthrosis were prospectively enrolled in the study. A cementless hip prosthesis was implanted either via a minimally invasive anterolateral or a modified direct lateral approach. Patients were clinically and radiologically (MRI) examined preoperatively, 3, and 12 months postoperatively. Additionally, the Harris hip score, a pain score (NRS 0-10) and a satisfaction score (1-6) were recorded. To test the function of the abductor muscles the Trendelenburg's sign and the abductor muscle strength were evaluated. MRI evaluation includes the assessment of tendon defects and fatty atrophy of the minimus muscle.

RESULTS

Tendon defects and fatty atrophy were seen in nearly 50% of the patients after THA. Harris hip-, pain-, and satisfaction scores did not correlate with the MR findings. There was also no impact on the abduction strength or the Trendelenburg's sign. Furthermore, the frequency of minimus damage was neither influenced by age, gender, BMI nor by the applied approach.

CONCLUSION

Muscle atrophy and tendon defects of the minimus muscle appear frequently after THA without any favored relation to the lateral or anterolateral approach. The extent of injured minimus muscle has a minor impact on the clinical outcome particularly not on the abduction strength within the first postoperative year. The main function of the gluteus minimus is rather the centralization of the femoral head in the joint during the gait cycle than hip abduction and stabilization of the pelvis. The use of a straight stem with the associated need for lateral femoral preparation may be a risk factor for minimus tendon damage. Therefore, the surgeon should pay special attention to the prevention of surgical trauma to the gluteus minimus muscle during femoral preparation.

Kinesiology of the hip: a focus on muscular actions

The 21 muscles that cross the hip provide both triplanar movement and stability between the femur and acetabulum. The primary intent of this clinical commentary is to review and discuss the current understanding of the specific actions of the hip muscles. Analysis of their actions is based primarily on the spatial orientation of the muscles relative to the axes of rotation at the hip. The discussion of muscle actions is organized according to the 3 cardinal planes of motion. Actions are considered from both femoral-on-pelvic and pelvic-on-femoral perspectives, with particular attention to the role of coactivation of trunk muscles. Additional attention is paid to the biomechanical variables that alter the effectiveness, force, and torque of a given muscle action. The role of certain muscles in generating compression force at the hip is also presented. Throughout the commentary, the kinesiology of the muscles of the hip are considered primarily from normal but also pathological perspectives, supplemented with several clinically relevant scenarios. This overview should serve as a foundation for understanding the assessment and treatment of musculoskeletal impairments that involve not only the hip, but also the adjacent low back and knee regions.

The association between degenerative hip joint pathology and size of the gluteus medius, gluteus minimus and piriformis muscles

This study aimed to investigate changes in the deep abductor muscles, gluteus medius (GMED), piriformis (PIRI), and gluteus minimus (GMIN), occurring in association with differing stages of unilateral degenerative hip joint pathology (mild: n=6, and advanced: n=6). Muscle volume assessed via magnetic resonance imaging was compared for each muscle between sides, and between groups (mild, advanced, control (n=12)). GMED and PIRI muscle volume was smaller around the affected hip in subjects with advanced pathology (p<0.01, p<0.05) while no significant asymmetry was present in the mild and control groups. GMIN showed a trend towards asymmetry in the advanced group (p=0.1) and the control group (p=0.076) which appears to have been associated with leg dominance. Between group differences revealed a significant difference for the GMED muscle reflecting larger muscle volumes on the affected side in subjects with mild pathology, compared to matched control hips. This information suggests that while GMED appears to atrophy in subjects with advanced hip joint pathology, it may be predisposed to hypertrophy in early stages of pathology. Assessment and exercise prescription methods should consider that the response of muscles of the abductor synergy to joint pathology is not homogenous between muscles or across stages of pathology.

Results of surgical repair of abductor avulsion after primary total hip arthroplasty

Abductor avulsion after primary total hip arthroplasty (THA) is an uncommon event and is associated with the lateral approach. Results of surgical repair have only been reported in one previous study. In a retrospective review of 2657 primary THAs, we identified 19 (0.7%) patients operated upon for repair of abductor avulsion on average 19 months after primary THA. The study's aim was to assess improvement in pain and limp, patient satisfaction, and functional outcome (Harris Hip Score) after surgical repair. Eighteen patients were evaluated at a mean follow-up of 38 months. Overall, only half of the patients had substantial improvement of both limp and pain. Limping and functional outcome markedly improved with early repair (<15 months), whereas obesity was associated with worse functional results.

Femoral neck shortening after fracture fixation with multiple cancellous screws: incidence and effect on function

BACKGROUND

Shortening of the femoral neck after fracture fixation with multiple parallel screws decreases the moment arm for the abductor muscles of the hip. This study aimed to assess the incidence of femoral neck shortening quantitatively and qualitatively in patients with femoral neck fractures treated with multiple cannulated screws, and to investigate its influence on functional outcome.

METHODS

We conducted an observational study in a consecutive series of 56 patients with united fractures of the femoral neck treated with multiple cancellous screws. The latest anterior-posterior radiograph of the fractured hip was compared with that of the contralateral uninjured hip. After scanning and electronically overlapping those radiographs, femoral neck shortening was assessed. All identified patients were contacted and the Short Form-36 (SF-36) functional outcome questionnaire was administered.

RESULTS

The shortening rate was 31% for undisplaced (14 of 45) and 27% for displaced fractures (3 of 11). The average abductor moment arm shortening was 10 +/- 4 mm. The average femur length decrease was 8 +/- 5 mm. In all other patients, abductor moment arm as well as femur length measurements were within 3 mm of the contralateral side and considered not to be shortened. Thirteen patients completed the SF-36 questionnaire (12 of 13 undisplaced fractures; all 13 with good fracture reduction). Patients with shortened fractures (8 of 13) had significantly lower Physical Functioning (p = 0.01) and Role Physical (p = 0.04) SF-36 subscores.

CONCLUSIONS

Femoral neck shortening after femoral neck fracture fixation with multiple cancellous screws is common and it has a significant negative impact on physical functioning.

Hip pain in renal transplant recipients: symptomatic gluteus minimus and gluteus medius tendon abnormality as an alternative MRI diagnosis to avascular necrosis

OBJECTIVE

The purpose of this study was to review the diagnosis on MRI and radiography of 24 renal transplant recipients with hip pain suspicious for avascular necrosis and to investigate whether there is an association between kidney transplant patients with end-stage renal disease and symptomatic gluteus minimus and medius tendon abnormality.

CONCLUSION

Symptomatic gluteus minimus and medius tendon lesions and abnormalities can occur in renal allograft recipients. The MRI findings of this entity allow an alternative diagnosis in this patient population.

Altered mitochondrial apparent affinity for ADP and impaired function of mitochondrial creatine kinase in gluteus medius of patients with hip osteoarthritis

The cellular energy metabolism in human musculus gluteus medius (MGM) under normal conditions and hip osteoarthritis (OA) was explored. The functions of oxidative phosphorylation and energy transport systems were analyzed in permeabilized (skinned) muscle fibers by oxygraphy, in relation to myosin heavy chain (MHC) isoform distribution profile analyzed by SDS-PAGE, and to creatine kinase (CK) and adenylate kinase (AK) activities measured spectrophotometrically in the intact muscle. The results revealed high apparent Km for ADP in regulation of respiration that decreased after addition of creatine in MGM of traumatic patients (controls). OA was associated with increased sensitivity of mitochondrial respiration to ADP, decreased total activities of AK and CK with major reduction in mi-CK fraction, and attenuated effect of creatine on apparent Km for ADP compared with control group. It also included a complete loss of type II fibers in a subgroup of patients with the severest disease grade. It is concluded that energy metabolism in MGM cells is organized into functional complexes of mitochondria and ATPases. It is suggested that because of degenerative remodeling occurring during development of OA, these complexes become structurally and functionally impaired, which results in increased access of exogenous ADP to mitochondria and dysfunction of CK-phosphotransfer system.

Effects of a home program on strength, walking speed, and function after total hip replacement

OBJECTIVE

To assess the efficacy of a home exercise program in increasing hip muscle strength, walking speed, and function in patients more than 1.5 years after total hip replacement (THR).

DESIGN

Randomized controlled trial.

SETTING

Kinesiology laboratory.

PARTICIPANTS

Fifty-three patients with unilateral THR were randomly assigned to the training (n=26) and control (n=27) groups. Patients in the training group were further divided into exercise-high (n=13) and exercise-low (n=13) compliance groups according to their practice ratio (high, > or =50%).

INTERVENTION

The training group underwent a 12-week home program that included hip flexion range of motion exercises for both hip joints; strengthening exercises for bilateral hip flexors, extensors, and abductors; and a 30-minute walk every day. The control group did not receive any training.

MAIN OUTCOME MEASURES

Strength of bilateral hip muscles, free and fast walking speeds while walking over 3 different terrains, and functional performance were assessed by using a dynamometer, videotape analysis, and the functional activity part of the Harris Hip Score, respectively, before and after the 12-week period.

RESULTS

Subjects in the exercise-high compliance group showed significantly (P <.05) greater improvement in muscle strength for the operated hip, fast walking speed, and functional score than those in the exercise-low compliance and control groups.

CONCLUSIONS

The designed home program was effective in improving hip muscle strength, walking speed, and function in patients after THR who practiced the program at least 3 times a week, but adherence to this home program may be a problem.