Nicola C. Casartelli

Hip muscle weakness in patients with symptomatic femoroacetabular impingement

OBJECTIVE Femoroacetabular impingement (FAI) is a pathomechanical process, which may cause hip pain, disability and early development of hip osteoarthritis (OA) in young and active adults. Patients with FAI experience functional disability during dynamic weight-bearing activities, which could originate from weakness of the hip muscles. The objective of this study was to compare hip muscle strength between patients with symptomatic FAI and healthy controls. It was hypothesized that patients would present overall hip muscle weakness compared to controls. METHODS A total of 22 FAI patients and 22 controls matched for gender, age, and body mass participated in the study. We evaluated isometric maximal voluntary contraction (MVC) strength of all hip muscle groups using hand-held and isokinetic dynamometry, and electromyographic (EMG) activity of the rectus femoris (RF) and tensor fasciae latae (TFL) muscles during active flexion of the hip. RESULTS FAI patients had significantly lower MVC strength than controls for hip adduction (28%), flexion (26%), external rotation (18%) and abduction (11%). TFL EMG activity was significantly lower in FAI patients compared with controls (P=0.048), while RF EMG activity did not differ significantly between the two groups (P=0.056). CONCLUSIONS Patients with symptomatic FAI presented muscle weakness for all hip muscle groups, except for internal rotators and extensors. Based on EMG recordings, it was demonstrated that patients with symptomatic FAI have a reduced ability to activate TFL muscle during hip flexion. These findings provide orthopedic surgeons with objective information about the amount and specificity of hip muscle weakness in patients with FAI. Future research should investigate the relationship between hip muscle weakness, functional disability and overuse injury risks, as well as the effects of hip muscle strengthening on clinical outcomes in individuals with symptomatic FAI.

Validity and reliability of the Myotest accelerometric system for the assessment of vertical jump height.

Casartelli, N, Müller, R, and Maffiuletti, NA. Validity and reliability of the Myotest accelerometric system for the assessment of vertical jump height. J Strength Cond Res 24(11): 3186-3193, 2010-The aim of the present study was to verify the validity and reliability of the Myotest accelerometric system (Myotest SA, Sion, Switzerland) for the assessment of vertical jump height. Forty-four male basketball players (age range: 9-25 years) performed series of squat, countermovement and repeated jumps during 2 identical test sessions separated by 2-15 days. Flight height was simultaneously quantified with the Myotest system and validated photoelectric cells (Optojump). Two calculation methods were used to estimate the jump height from Myotest recordings: flight time (Myotest-T) and vertical takeoff velocity (Myotest-V). Concurrent validity was investigated comparing Myotest-T and Myotest-V to the criterion method (Optojump), and test-retest reliability was also examined. As regards validity, Myotest-T overestimated jumping height compared to Optojump (p < 0.001) with a systematic bias of approximately 7 cm, even though random errors were low (2.7 cm) and intraclass correlation coefficients (ICCs) where high (>0.98), that is, excellent validity. Myotest-V overestimated jumping height compared to Optojump (p < 0.001), with high random errors (>12 cm), high limits of agreement ratios (>36%), and low ICCs (<0.75), that is, poor validity. As regards reliability, Myotest-T showed high ICCs (range: 0.92-0.96), whereas Myotest-V showed low ICCs (range: 0.56-0.89), and high random errors (>9 cm). In conclusion, Myotest-T is a valid and reliable method for the assessment of vertical jump height, and its use is legitimate for field-based evaluations, whereas Myotest-V is neither valid nor reliable.

Return to sport after hip surgery for femoroacetabular impingement: a systematic review

Background We aimed to appraise (1) the rate of return to sport of athletes after hip surgery for femoroacetabular impingement (FAI) and (2) some aspects that may influence the return to sport. Methods Four databases (EMBASE, PubMed, Web of Science, Cochrane Library) were searched until 21 October 2014. Studies evaluated return to sport of athletes who underwent hip surgery for the treatment of symptomatic FAI. A validated tool was used for quality evaluation of the studies. Results A total of 18 case series (level of evidence IV) with moderate-to-high methodological quality were included. On average, 87% of athletes returned to sport after hip surgery for FAI and 82% returned to the same sport level as before the occurrence of the symptoms. Professional athletes seem to return to sport at a higher rate compared with recreational and collegiate athletes. Sport participation after hip arthroscopy tends to decrease for professional athletes at short-term and mid-term follow-ups. Diffuse hip osteoarthritis at the time of surgery may not allow athletes to return to sport. Conclusions Most athletes return to sport after hip surgery for the treatment of symptomatic FAI. The level of competition, time of evaluation after hip surgery and presence of articular cartilage lesions at the time of surgery may influence return to sport. Future studies with higher levels of evidence should describe and evaluate return to sport protocols after hip surgery for FAI.

Comparison of quadriceps inactivation between nerve and muscle stimulation

We evaluated the use of direct muscle stimulation for quantifying quadriceps inactivation at different contraction levels as opposed to conventional twitch interpolation using nerve stimulation. Fourteen healthy volunteers were tested. Paired stimuli were delivered to the femoral nerve or to the quadriceps muscle belly during voluntary contractions ranging from 20% to 100% of maximum, and the amplitude of the superimposed doublet was quantified to investigate inactivation. Superimposed doublet for muscle and nerve stimulation, respectively between the range of 60% to 100% of maximum (e.g., at 100%, muscle stimulation was 14 ± 5 Nm and nerve stimulation was 15 ± 6 Nm). Despite higher current doses, muscle stimulation was associated with less discomfort than nerve stimulation (P < 0.05). Collectively, our data suggest that direct muscle stimulation could be used to assess quadriceps inactivation at maximal and quasi‐maximal contraction levels as a valid alternative to motor nerve stimulation. Muscle Nerve, 2010

Test-retest reliability of quadriceps muscle function outcomes in patients with knee osteoarthritis.

Quadriceps muscle weakness and the underlying neuromuscular deficits have been increasingly studied over the last few years in patients with knee osteoarthritis, but the applied methodologies have never been validated for this specific population. The aim of this study was to investigate test-retest reliability of several quadriceps muscle function outcomes in patients with knee osteoarthritis both before and after knee arthroplasty surgery. Ten preoperative and 20 postoperative patients participated in two identical testing sessions. A series of voluntary and/or electrically stimulated contractions of the involved quadriceps with concomitant torque and electromyographic recordings were used to characterize muscle strength, muscle activation and muscle contraction properties. Vastus lateralis morphology (thickness and fascicle pennation angle) was also assessed using ultrasonography. Overall, good reliability scores were observed for the majority of the 13 assessed variables (nine variables with intraclass correlation coefficients >0.75, 12 variables with coefficients of variation <15%). The most reliable testing protocol for patients with knee osteoarthritis would entail the assessment of (1) isometric maximal voluntary torque for evaluating muscle strength, with (2) simultaneous vastus lateralis electromyographic activity for evaluating muscle activation, (3) potentiated (resting) doublet peak torque for evaluating muscle contractility, and (4) vastus lateralis thickness for evaluating muscle size.

Differences in gait characteristics between total hip, knee, and ankle arthroplasty patients: a six-month postoperative comparison

BackgroundThe recovery of gait ability is one of the primary goals for patients following total arthroplasty of lower-limb joints. The aim of this study was to objectively compare gait differences of patients after unilateral total hip arthroplasty (THA), total knee arthroplasty (TKA) and total ankle arthroplasty (TAA) with a group of healthy controls.MethodsA total of 26 TAA, 26 TKA and 26 THA patients with a mean (± SD) age of 64 (± 9) years were evaluated six months after surgery and compared with 26 matched healthy controls. Subjects were asked to walk at self-selected normal and fast speeds on a validated pressure mat. The following spatiotemporal gait parameters were measured: walking velocity, cadence, single-limb support (SLS) time, double-limb support (DLS) time, stance time, step length and step width.ResultsTAA and TKA patients walked slower than controls at normal (p<0.05) and fast speeds (p<0.01). The involved side of TAA and TKA patients showed shorter SLS compared to controls at both normal and fast speeds (p<0.01). Regardless of walking speed, the uninvolved side of TAA and TKA patients demonstrated longer stance time and shorter step length than controls (p<0.01). TAA patients showed shorter SLS of the involved side, longer stance time and shorter step length of the uninvolved side compared to the contralateral side at both normal and fast speeds (p<0.001).ConclusionsGait disability after unilateral lower-limb joint arthroplasty was more marked for distal than for proximal joints at six months after surgery, with a proximal-to-distal progression in the impairment (TAA>TKA>THA). THA patients demonstrated no gait differences compared with controls. In contrast, TAA and TKA patients still demonstrated gait differences compared to controls, with slower walking velocity and reduced SLS in the involved limb. In addition, TAA patients presented marked side-to-side asymmetries in gait characteristics.

Hip flexor muscle fatigue in patients with symptomatic femoroacetabular impingement

PurposePatients with symptomatic femoroacetabular impingement (FAI) have considerable hip muscle weakness, in particular, hip flexion and hip adduction. In addition, they experience disabilities while performing prolonged dynamic tasks. It was therefore postulated that, besides hip flexor muscle weakness, patients with symptomatic FAI would show greater hip flexor fatigue compared with healthy controls.MethodsHip flexor fatigue was evaluated in two different experiments. Fifteen patients with symptomatic FAI and 15 age-matched healthy controls were tested in each experiment. In the first one, changes in hip flexor torque fluctuations and electromyographic (EMG) activity were measured during a sustained submaximal isometric contraction. In the second experiment, hip flexor torque decline was measured during a series of 20 maximal dynamic contractions.ResultsPatients with FAI exhibited hip flexor weakness under both isometric (P = 0.02) and isokinetic conditions (P = 0.03). Fatigue-induced changes in isometric hip flexor torque fluctuations, EMG root mean square and median frequency did not differ significantly between patients and controls (P > 0.05). Similarly, isokinetic hip flexor torque decline was comparable in patients with FAI and controls (P > 0.05).ConclusionsNone of the hip flexor fatigue outcomes considered here differed between patients with symptomatic FAI and controls. Therefore, the disabilities that patients experience while performing prolonged dynamic tasks do not seem to be caused by exaggerated hip flexor muscle fatigue.

Validity of resting myotonometric assessment of lower extremity muscles in chronic stroke patients with limited hypertonia: A preliminary study

The aim of this preliminary study was to examine the validity of a recently-introduced tool (MyotonPRO) for the assessment of mechanical parameters of the main lower extremity muscles in patients with chronic stroke. Thigh and shank muscles of 20 stroke patients with limited hypertonia (11 men and 9 women; mean age: 52±11yrs) and 20 healthy controls (11 men and 9 women; mean age: 53±10yrs) were bilaterally evaluated with (i) MyotonPRO for muscle stiffness, tone and elasticity, (ii) ultrasonography for muscle and subcutaneous thickness, and (iii) dynamometry for isometric muscle strength. MyotonPRO parameters of stroke patients were reassessed a week later (inter-day test-retest design). For all the investigated muscles, MyotonPRO variables did not differ between the more affected and the less affected side of patients (P>0.05 for main side effect), and neither differed between patients and controls (P>0.05 for main group effect), except for gastrocnemius medialis stiffness that was higher in patients (300±51N/m) than in controls (281±29N/m; P<0.05). Thigh muscle stiffness was negatively correlated to subcutaneous thickness (r=-0.84 for the vastus lateralis; P<0.001), while only tibialis anterior stiffness and tone correlated positively with muscle thickness (both r=0.46; P<0.01). Test-retest reliability of MyotonPRO parameters was adequate, except for muscle elasticity. The validity of MyotonPRO for the evaluation of thigh muscles in chronic stroke patients is partially challenged by the poor discriminant ability and by the considerable impact of subcutaneous tissue thickness (sex-dependent) on mechanical parameters. The potential validity of MyotonPRO for the assessment of shank muscles requires further investigation.

Validity and reliability of isometric, isokinetic and isoinertial modalities for the assessment of quadriceps muscle strength in patients with total knee arthroplasty.

Reliability of isometric, isokinetic and isoinertial modalities for quadriceps strength evaluation, and the relation between quadriceps strength and physical function was investigated in 29 total knee arthroplasty (TKA) patients, with an average age of 63 years. Isometric maximal voluntary contraction torque, isokinetic peak torque, and isoinertial one-repetition maximum load of the involved and uninvolved quadriceps were evaluated as well as objective (walking parameters) and subjective physical function (WOMAC). Reliability was good and comparable for the isometric, isokinetic, and isoinertial strength outcomes on both sides (intraclass correlation coefficient range: 0.947-0.966; standard error of measurement range: 5.1-9.3%). Involved quadriceps strength was significantly correlated to walking speed (r range: 0.641-0.710), step length (r range: 0.685-0.820) and WOMAC function (r range: 0.575-0.663), independent from the modality (P < 0.05). Uninvolved quadriceps strength was also significantly correlated to walking speed (r range: 0.413-0.539), step length (r range: 0.514-0.608) and WOMAC function (r range: 0.374-0.554) (P < 0.05), except for WOMAC function/isokinetic peak torque (P > 0.05). In conclusion, isometric, isokinetic, and isoinertial modalities ensure valid and reliable assessment of quadriceps muscle strength in TKA patients.

Prevalence and Functional Consequences of Femoroacetabular Impingement in Young Male Ice Hockey Players.

Background: Femoroacetabular impingement (FAI), which is highly prevalent in adult ice hockey players, is often associated with negative clinical and functional outcomes. It is unclear, however, whether FAI-related bony deformities and symptoms may lead to functional alterations as reflected in hip muscle strength, range of motion (ROM), and on-ice physical performance in youth ice hockey players. Hypothesis: Compared with players with neither structural signs nor symptoms related to FAI, players with symptomatic FAI would show hip muscle weakness and reduced hip ROM, which would in turn affect ice hockey physical performance. Study Design: Controlled laboratory study. Methods: A total of 74 young male ice hockey players were evaluated bilaterally for passive hip internal rotation ROM by use of a hip examination chair. Only the side with less internal rotation ROM was further investigated. FAI-related bony deformities were evaluated with magnetic resonance imaging (MRI). The involved hip was classified as symptomatic or asymptomatic based on the presence of hip pain during exercise and results from the flexion/adduction/internal rotation (FADIR) provocation test. Hip muscle strength, passive hip ROM, and on-ice physical performance were compared between players with no FAI, players with asymptomatic MRI-positive FAI, and players with symptomatic FAI. Results: Fifty of 74 players (68%) had FAI-related bony deformities, of whom 16 (22%) were symptomatic. Hip muscle strength, hip ROM, and on-ice physical performance did not differ significantly between players with no FAI and those with asymptomatic or symptomatic FAI. Conclusion: Despite a high prevalence of FAI-related bony deformities, youth ice hockey players with asymptomatic or symptomatic FAI did not show functional impairments in terms of hip muscle strength, hip ROM, or on-ice physical performance. Clinical Relevance: Hip muscle strength, passive hip ROM, and on-ice physical performance do not seem to discriminate for FAI-related signs and symptoms in young male ice hockey players.