Mario Lamontagne

Femoroacetabular impingement alters hip and pelvic biomechanics during gait Walking biomechanics of FAI.

Femoroacetabular impingement (FAI) has been reported to cause hip pain in a variety of daily activities including walking. However, the biomechanics of level gait has not been compared between FAI patients and a control group. This study quantified the affect of cam FAI on the three-dimensional (3-D) kinematics of the hip and pelvis, as well as the 3-D kinetics generated at the hip during walking. A unilateral cam impingement group (n=17) was compared to a matched control group (n=14) using between-group one-way ANOVAs. The FAI group had significantly lower peak hip abduction (p=0.009), frontal range of motion (ROM) (p=0.003), as well as attenuated pelvic frontal ROM (pelvic roll) (p=0.004) compared to the controls during level gait. There was also a trend of the impinged group having a lower sagittal ROM (p=0.047) than the controls. However, there were no kinetic differences between the two groups. Attenuated hip abduction, frontal ROM and sagittal ROM during gait in FAI individuals may be caused by soft tissue restriction, and decreased frontal pelvic ROM could result from limited mobility at the sacro-lumbar joint.

Reliability of EMG spectral parameters in repeated measurements of back muscle fatigue.

The change in median frequency of the power spectrum of the electromyographic (EMG) signal may be used as a measure of muscle fatigue. The reliability of the median frequency parameters was investigated for EMG-recording sites at L1 and L5 right and left on the erector spinae. The reliability of subjective fatigue ratings of the back muscles (Borg CR-10 scale) and of maximal trunk extension torque (MVC) was also investigated. Eleven subjects with healthy backs performed a 45-s isometric trunk extension at 80% of MVC twice a day, on three different days. Two-factor analysis of variance was made to obtain the different variances from which the standard error of measurement (SEM) and the intra class correlation coefficient (ICC) were calculated. The SEM within-day was somewhat lower than that between-days. Both were about the same at all four electrode sites. The 95% confidence interval for the studied variables was for the initial median frequency +/- 10 Hz, for the slope +/- 0.4-0.5%/s, for the MVC +/- 36 Nm and for the Borg ratings +/- 1.6. We conclude that, with the presently used method, changes or differences within these limits should be regarded as normal variability. The slope may be of limited value because of its large variability. Whether the low intraclass correlation coefficient for the EMG parameters in the presently studied test group implies a low potential in discriminating subjects with back pain can not be decisively concluded.

Passive knee muscle moment arms measured in vivo with MRI

OBJECTIVE: To determine moment arm lengths from seven knee muscles and the patellar tendon. The knee muscles were the biceps femoris, semitendinosus, semimembranosus, gracilis, sartorius, and the lateral and medial gastrocnemius muscles. DESIGN: The moment arms were calculated based on MRI measurements. BACKGROUND: Moment arm lengths of different muscles with respect to the joint centre of rotation (CR) or the centre of the contact point between joint surfaces are necessary basic data for biomechanical models predicting joint load. METHODS: Ten male and seven female subjects participated. Using a 1.5 Tesla magnetic resonance imaging system, 3-dimensional coordinates of relevant points were recorded from a 3-D volume reconstruction of the right knee at knee flexion angles of 0, 30 and 60 degrees. Muscular moment arms were calculated in both the sagittal and frontal planes. The recordings were all made during passive mode, which means that no muscular contraction was performed. RESULTS: All muscles except the lateral gastrocnemius showed statistically significant differences (P<0.05) of moment arm lengths between gender in the frontal plane. All muscles except biceps femoris and sartorius showed significant differences (P<0.05) of moment arm lengths between gender in the sagittal plane. Most muscles also showed a linear or quadratic trend of changing moment arms with varying knee angle. CONCLUSIONS: Our results indicate that for most biomechanical analyses involving knee muscles, gender- and angle-specific moment arms should be used.

Assessment of functional knee bracing: an in vivo three-dimensional kinematic analysis of the anterior cruciate deficient knee.

OBJECTIVE To describe three-dimensional tibial and femoral movements in vivo and examine the effect of a brace on knee kinematics during moderate to intense activity. DESIGN Skeletal kinematics of anterior cruciate ligament deficient knees was measured with and without braces during moderate to intense activity. BACKGROUND Invasive markers implanted into the tibia and femur are the most accurate means to directly measure skeletal motion and may provide a more sensitive measure of the differences between brace conditions. METHODS Steinmann traction pins were implanted into the femur and tibia of four subjects having a partial or complete anterior cruciate ligament rupture. Non-braced and braced conditions were randomly assigned and subjects jumped for maximal horizontal distance to sufficiently stress the anterior cruciate ligament. RESULTS Intra-subject peak vertical force and posterior shear force were generally consistent between conditions. Intra-subject kinematics was repeatable but linear displacements between brace conditions were small. Differences in angular and linear skeletal motion were observed across subjects. Bracing the anterior cruciate ligament deficient knee resulted in only minor kinematic changes in tibiofemoral joint motion. CONCLUSION In this study, no consistent reductions in anterior tibial translations were observed as a function of the knee brace tested. Relevance. Investigations have reported that knee braces fail when high loads are encountered or when load is applied in an unpredictable manner. Questions remain regarding tibiofemoral joint motion, in particular linear displacements. The pin technique is a means for direct skeletal measurement and may provide a more sensitive measure of the differences between brace conditions.

The clinical significance of electromyography normalisation techniques in subjects with anterior cruciate ligament injury during treadmill walking

This study investigated the clinical interpretation of three electromyographic (EMG) normalisation techniques to detect neuromuscular alterations in patients diagnosed with anterior cruciate ligament knee injury during treadmill walking. The EMG signal was normalised using the mean value during the gait cycles (MEA), the maximum value during the gait cycles (MAX), and a maximum voluntary isometric contraction (MVC) test in 16 male and female subjects. The MAX method detected an increase in total muscle activity in the injured limb rectus femoris (11.6%; P=0.02) while the MVC method detected decreased injured limb gastrocnemius medialis (GM) overall muscle activity (34.4%; P=0.02). The MAX method identified decreased GM activity in three portions of the gait cycle. This study indicates the importance of choosing the appropriate normalisation technique since its choice will change outcome measures and subsequent clinical interpretation.

In vivo knee kinematics during gait reveals new rotation profiles and smaller translations.

In order to identify abnormal or pathological motions associated with clinically relevant questions such as injury mechanisms or factors leading to joint degeneration, it is essential to determine the range of normal tibiofemoral motion of the healthy knee. In this study we measured in vivo 3D tibiofemoral motion of the knee during gait and characterized the nonsagittal plane rotations and translations in a group of six healthy young adults. The subjects were instrumented with markers placed on intracortical pins inserted into the tibia and femur as well as marker clusters placed on the skin of the thigh and shank. The secondary rotations and translation excursions of the knee were much smaller than those derived from skin markers and previously described in the literature. Also, for a given knee flexion angle, multiple combinations of transverse and frontal plane knee translation or rotation positions were found. This represents normal knee joint motions and ensemble averaging of gait data may mask this important subject-specific information.

Electromyographic and biomechanic analysis of anterior cruciate ligament deficiency and functional knee bracing

OBJECTIVE Examine the neuromuscular response to functional knee bracing relative to anterior tibial translations in vivo. DESIGN During randomised brace conditions, electromyographic data with simultaneous skeletal tibiofemoral kinematics were recorded from four anterior cruciate ligament deficient subjects to investigate the effect of the DonJoy Legend functional brace during activity. BACKGROUND Knee braces do not increase knee stability but may influence afferent inputs from proprioception and therefore one might expect changes in muscle firing patterns, amplitude and timing. METHODS Hoffman bone pins affixed with markers were implanted into the tibia and femur for kinematic measurement. The EMG data from the rectus femoris, semitendinosus, biceps femoris, and lateral head of the gastrocnemius were integrated for each subject in three separate time periods: 250 ms preceding footstrike and two consecutive 125 ms time intervals following footstrike. RESULTS With brace, semitendinosus activity significantly decreased 17% prior to footstrike whereas bicep femoris significantly decreased 44% during A2, (P<0.05). Rectus femoris activity significantly increased 21% in A2 (P<0.05). No consistent reductions in anterior translations were evident. CONCLUSION Our preliminary findings, based on a limited number of subjects, indicate joint stability may result from proprioceptive feedback rather than the mechanical stabilising effect of the brace. Despite a significant increase in rectus femoris activity upon landing, only one subject demonstrated an increase in anterior tibial drawer. RELEVANCE Studies have shown functional braces do not mechanically stabilise the anterior cruciate ligament deficient knee. Perhaps bracing alters proprioceptive feedback. It has been shown that bracing the anterior cruciate ligament deficient knee may affect hamstring and quadriceps activity. Our findings stresses the importance of functional knee bracing combined with proprioceptive and muscular coordination training in order to increase joint stability.

The effects of cam femoroacetabular impingement corrective surgery on lower-extremity gait biomechanics

Surgery to correct cam femoroacetabular impingement (FAI) is increasingly popular. Nevertheless, no known study has analyzed both the three-dimensional lower-extremity joint kinematics and kinetics to quantify FAI surgical outcomes. The purpose of this study was to determine the effects of FAI surgery on the affected lower-extremity joint mechanics during gait by comparing the three-dimensional hip, knee, ankle and pelvic angular displacements, as well as the hip, knee and ankle moments and powers of preoperative and postoperative FAI groups, and a healthy control group. Ten patients with unilateral symptomatic cam FAI, who underwent corrective surgery using an open or combined technique, participated in the biomechanical analysis of level walking preoperatively and postoperatively. Thirteen healthy control subjects provided normative data. Results showed that gait biomechanics of FAI patients did not return to normal after surgery. Postoperatively, patients had reduced hip frontal and sagittal plane ROM, smaller peak hip abduction and internal rotation moments, and decreased peak hip power generation compared to the control group. Despite reductions in hip pain, hip impairments and trends detected preoperatively, perhaps due to modified gait patterns, persisted postoperatively. Additional discrepancies in lower-extremity joint mechanics were observed postoperatively, which are believed to have resulted from partial muscle impairment caused by the surgical approaches. Further research is required to confirm the reasons for which lower-extremity gait mechanics of FAI patients do not return to normal following surgery. Clarifying these causes could help improve surgical techniques and rehabilitation programs for the treatment of FAI, and thus improve surgical outcomes.

Lower limb muscle activity and kinematics of an unanticipated cutting manoeuvre: a gender comparison

This investigation compared the amplitude and the timing of the muscle activity of the lower limb, as well as the three-dimensional kinematics of the hip, knee and ankle joints, of male and female elite soccer players performing an unanticipated cutting manoeuvre. These data were recorded for 15 female and 15 male participants for five successful cutting manoeuvres. For this manoeuvre to be performed in an unanticipated manner, the participants were instructed to execute one of three tasks, which were signalled to them with a target board composed of three different coloured lights. Female participants performed the cutting manoeuvre with greater lateral gastrocnemius activity in comparison with the male participants. It was also observed that they contracted their vastus lateralis to a greater extent than their vastus medialis, whereas the men adopted the opposite strategy. These neuromuscular control strategies adopted by the female athletes may elucidate the reasons for which women struck the ground with a more abducted knee during the cutting task. Given that this knee position places greater strain on the anterior cruciate ligament, a restoration of the medial/lateral activation balance of the lower limb muscles may reduce one’s risk of injury.

Preoperative and Postoperative Lower-Extremity Joint and Pelvic Kinematics During Maximal Squatting of Patients with Cam Femoro-Acetabular Impingement

BACKGROUND Understanding how the function of the lower extremity joints during everyday movements following surgery to treat cam femoro-acetabular impingement is essential to assess whether surgical intervention effectively restores the normal biomechanics of the hip. The purpose of this study was to compare preoperative and postoperative lower-extremity joint and pelvic angular displacements during maximal depth squatting of patients with unilateral symptomatic cam femoro-acetabular impingement. METHODS Ten participants were compared with respect to their preoperative and postoperative test results. The participants were between eighteen and fifty years of age and had a positive impingement test and visible cam deformity on anteroposterior and Dunn view radiographs. Postoperative testing for each participant occurred between eight and thirty-two months following surgical intervention. Three-dimensional lower-limb joint and pelvic kinematics of participants were collected during maximal depth squats. RESULTS Postoperatively, participants squatted to a greater mean maximal depth than they did preoperatively. Postoperative knee flexion and ankle dorsiflexion angles of the affected extremity at maximal depth were significantly greater than preoperative values. The postoperative sum of all joint angles of the affected limb at maximal squat depth was significantly larger than the preoperative sum. No significant differences were detected between the preoperative and postoperative measurements of the patients with cam impingement with respect to the kinematics of the affected hip at maximal squat depth, the pelvic angular displacements at maximal squat depth, or the overall pelvic range of motion during maximal deep squatting (p > 0.05). CONCLUSIONS The squat performance improved postoperatively, likely because of the combined effects of increased knee and ankle angles as well as a greater acetabular opening and thus reduced anterior femoral head coverage, allowing increased posterior pelvic pitch during the descent phase of the squat. LEVEL OF EVIDENCE Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.