Lower extremity dexterity is associated with agility in adolescent soccer athletes

Agility is important for sport performance and potentially injury risk; however, factors affecting this motor skill remain unclear. Here, we evaluated the extent to which lower extremity dexterity (LED) and muscle performance were associated with agility. Fourteen male and 14 female soccer athletes participated. Agility was evaluated using a hopping sequence separately with both limbs and with the dominant limb only. The LED test evaluated the athletes' ability to dynamically regulate foot-ground interactions by compressing a spring prone to buckling with the lower limb. Muscle performance included hip and knee isometric strength and vertical jump height. Correlation analyses were used to assess the associations between muscle performance, LED, and agility. Multiple regression models were used to determine whether linear associations differed between sexes. On average, the female athletes took longer to complete the agility tasks than the male athletes. This difference could not be explained by muscle performance. Conversely, LED was found to be the primary determinant of agility (double limb: R(2) = 0.61, P < 0.001; single limb: R(2) = 0.63, P < 0.001). Our findings suggest that the sensorimotor ability to dynamically regulate foot-ground interactions as assessed by the LED test is predictive of agility in soccer athletes. We propose that LED may have implications for sport performance, injury risk, and rehabilitation.

The influence of sex and maturation on landing biomechanics: implications for anterior cruciate ligament injury

During landing and cutting, females exhibit greater frontal plane moments at the knee (internal knee adductor moments or external knee abduction moments) and favor the use of the knee extensors over the hip extensors to attenuate impact forces when compared with males. However, it is not known when this biomechanical profile emerges. The purpose of this study was to compare landing biomechanics between sexes across maturation levels. One hundred and nineteen male and female soccer players (9-22 years) participated. Subjects were grouped based on maturational development. Lower extremity kinematics and kinetics were obtained during a drop-land task. Dependent variables included the average internal knee adductor moment and sagittal plane knee/hip moment and energy absorption ratios during the deceleration phase of landing. When averaged across maturation levels, females demonstrated greater internal knee adductor moments (0.06±0.03 vs 0.01±0.02 N m/kg m; P<0.005), knee/hip extensor moment ratios (2.0±0.1 vs 1.4±0.1 N m/kg m; P<0.001) and knee/hip energy absorption ratios (2.9±0.1 vs 1.96±0.1 N m/kg m; P<0.001) compared with males. Higher knee adductor moments combined with disproportionate use of knee extensors relative to hip extensors observed in females reflect a biomechanical pattern that increases anterior cruciate ligament loading. This biomechanical strategy already was established in pre-pubertal female athletes.

Association between patella alta and the prevalence and worsening of structural features of patellofemoral joint osteoarthritis: the multicenter osteoarthritis study

OBJECTIVE

To examine the relationship between patella alta and the prevalence and worsening at followup of structural features of patellofemoral joint (PFJ) osteoarthritis (OA) on magnetic resonance imaging (MRI).

METHODS

The Multicenter Osteoarthritis Study is a cohort study of persons ages 50-79 years with or at risk for knee OA. Patella alta was measured using the Insall-Salvati ratio (ISR) on the baseline lateral radiograph, and cartilage damage, bone marrow lesions (BMLs), and subchondral bone attrition (SBA) were graded on MRI at baseline and at 30 months of followup in the PFJ. We examined the association of the ISR with the prevalence and worsening of cartilage damage, BMLs, and SBA in the PFJ using logistic regression.

RESULTS

A total of 907 knees were studied (mean age 62 years, body mass index 30 kg/m(2), ISR 1.10), 63% from female subjects. Compared with knees in the lowest ISR quartile at baseline, those in the highest quartile had 2.4 (95% confidence interval [95% CI] 1.7-3.3), 2.9 (95% CI 2.0-4.3), and 3.5 (95% CI 2.3-5.5) times the odds of having lateral PFJ cartilage damage, BMLs, and SBA, respectively, and 1.5 (95% CI 1.1-2.0), 1.3 (95% CI 0.9-1.8), and 2.2 (95% CI 1.4-3.4) times the odds of having medial PFJ cartilage damage, BMLs, and SBA, respectively. Similarly, those with high ISRs were also at risk for worsening of cartilage damage and BMLs over time than those with low ISRs.

CONCLUSION

A high ISR, indicative of patella alta, is associated with structural features of OA in the PFJ. Additionally, the same knees have an increased risk of worsening of these same features over time.

Prediction of slips: an evaluation of utilized coefficient of friction and available slip resistance

The purpose of this study was to investigate the relationship between measures of floor surface slip resistance and an individual's peak utilized coefficient of friction (COFU) on the probability of a slip occurring during level walking. Video, kinematic and ground reaction force data were recorded simultaneously as subjects walked at a self-selected speed during conditions of normal and reduced floor surface slip resistance. Peak COFU during weight acceptance was calculated and the available floor surface slip resistance was measured using the variable incidence tribometer (VIT). Separate logistic regression analyses identified that knowledge of the available slip resistance (as measured by the VIT) in combination with an individual's peak COFU allowed for greater accuracy in classifying slip outcomes (89.5%; p = 0.004), while knowledge of only the available slip resistance reduced the accuracy of categorization to 78.9% (p = 0.021).

Lower extremity kinetics during stair ambulation in patients with and without patellofemoral pain

OBJECTIVE

To compare lower extremity kinetics during stair ascent and descent in subjects with and without patellofemoral pain.

DESIGN

A cross-sectional study utilizing a control group.

BACKGROUND

The patellofemoral joint reaction force (the resultant force between the quadriceps muscle force and patellar ligament force) increases with quadriceps force and knee flexion angle. Consequently, patients with patellofemoral pain may employ compensatory strategies to minimize pain and reduce patellofemoral joint reaction forces during activity.

METHODS

10 individuals with a diagnosis of patellofemoral pain and 10 individuals without pain participated. Subject groups were matched on sex, age, height, and body mass. Anthropometric data, three dimensional kinematics, and ground reaction forces were used to calculate lower extremity sagittal plane moments (inverse dynamics) while subjects ascended and descended stairs at a self-selected pace. Differences in kinetic variables between groups were assessed using 2x2 (group x stair condition) analysis of variance.

RESULTS

Subjects with patellofemoral pain had decreased peak knee extensor moments during stair ascent and descent. There were no group differences in peak hip, ankle, or support moments, however, subjects with patellofemoral pain had decreased cadence (descent) compared to controls.

CONCLUSION

Subjects with patellofemoral pain had reduced peak knee extensor moments, suggesting that quadriceps avoidance was employed to reduce patellofemoral joint reaction forces. The lack of group differences in peak moments at the hip and ankle suggests that secondary compensation did not occur exclusively at the hip or ankle in this group of subjects with patellofemoral pain. RELEVANCE STATEMENT: Because stair ambulation is often used to evaluate the reproducibility of symptoms and to identify abnormal movement patterns indicative of patellofemoral pain, knowledge of lower extremity mechanics during stair negotiation is necessary to better characterize compensatory behavior in this population.

Electromyographic activity of selected trunk muscles during dynamic spine stabilization exercises

OBJECTIVES

To compare the electromyographic activity of the trunk flexors and extensors during 2 spine stabilization exercises and to evaluate the changes in muscle activity with increasing levels of exercise difficulty.

DESIGN

Descriptive study.

SETTING

Research laboratory.

PARTICIPANTS

Twelve healthy subjects without history of lower back pain.

INTERVENTION

Subjects were instructed how to perform the Dying Bug and the Quadruped exercises. Electromyographic and motion data were recorded from each muscle group during maximum voluntary isometric contraction (MVIC).

MAIN OUTCOME MEASURES

Surface electromyographic recordings of the erector spinae, rectus abdominus, abdominal oblique, and gluteus maximus muscles.

RESULTS

During the Dying Bug exercise, the trunk flexors (rectus abdominus, abdominal oblique) were equally active and demonstrated proportional increases in electromyographic activity with increasing level of exercise difficulty. In the Quadruped exercise, significantly greater electromyographic activity was observed in the abdominal oblique compared with the rectus abdominus; however, abdominal oblique activity did not change with increasing level of difficulty. The erector spinae and gluteus maximus demonstrated a significant level effect and were most active during elevation of the ipsilateral leg. At no point did activity of any of the muscles studied exceed 41% of the MVIC.

CONCLUSIONS

Results indicated the Dying Bug exercise predominantly recruited the abdominal musculature, while greater activity was observed in the trunk and hip extensors during the Quadruped exercise. The relatively low levels of electromyographic activity observed in both exercises suggests that the intensity of muscle recruitment is not likely sufficient to provide a strengthening effect in healthy subjects.

Patellofemoral joint kinetics during squatting in collegiate women athletes

OBJECTIVE

To characterize the biomechanics of the patellofemoral joint during squatting in collegiate women athletes.

DESIGN

Repeated measures experimental design.

BACKGROUND

Although squatting exercises are required components of most intercollegiate resistance-training programs and are commonly performed during rehabilitation, the effects of various squatting depths on patellofemoral joint stress have not been quantified.

METHODS

Anthropometric data, three-dimensional knee kinematics, and ground reaction forces were used to calculate the knee extensor moment (inverse dynamics approach) in five intercollegiate female athletes during squatting exercise at three different depths (approximately 70 degrees, 90 degrees and 110 degrees of knee flexion). A biomechanical model of the patellofemoral joint was used to quantify the patellofemoral joint reaction force and patellofemoral joint stress during each trial.

RESULTS

Peak knee extensor moment, patellofemoral joint reaction force and patellofemoral joint stress did not vary significantly between the three squatting trials.

CONCLUSIONS

Squatting from 70 degrees to 110 degrees of knee flexion had little effect on patellofemoral joint kinetics. The relative constancy of the patellofemoral joint reaction force and joint stress appeared to be related to a consistent knee extensor moment produced across the three squatting depths.

RELEVANCE

The results of this study do not support the premise that squatting to 110 degrees places greater stress on the patellofemoral joint than squatting to 70 degrees. These findings may have implications with respect to the safe design of athletic training regimens and rehabilitation programs.

The effects of eccentric velocity on activation of elbow flexors: evaluation by magnetic resonance imaging

PURPOSE

To compare magnetic resonance imaging (MRI) signal intensity changes in the primary elbow flexors during two isotonic exercise protocols varying in eccentric velocity and the ratio of eccentric to concentric activity.

METHODS

Twelve men performed two exercise protocols. The right and left arms were randomly assigned to one of two protocols that had the same workload (60% 1RM) and same total time of exercise (144 s) but differed in the velocity and ratio of eccentric to concentric activity (1:1 and 5:1 for the fast and slow protocols, respectively). MRI signal intensity changes were quantified pre- and post-exercises using an inversion recovery sequence with a 1.5T MRI system (TR = 2500 ms, TE = 90 ms, TI = 140 ms). Percent change in MRI signal intensity, rate of perceived exertion (RPE), and delayed onset muscle soreness (DOMS) were recorded and analyzed.

RESULTS

The biceps brachii was found to be preferentially recruited during the fast protocol compared with the brachialis, whereas the brachialis was found to be preferentially recruited during the slow protocol (P < 0.05). The fast exercise protocol was perceived as being more strenuous (RPE = 8.3 +/- 2.1) than the slow (RPE = 5.4 +/- 1.5, P < 0.05) and produced DOMS in 58% of the tested subjects.

CONCLUSIONS

These results suggest that agonists respond to various loading conditions nonhomogeneously. These findings may have implications with respect to exercise prescriptions for specific muscles.

Patellar kinematics, part I: the influence of vastus muscle activity in subjects with and without patellofemoral pain

BACKGROUND AND PURPOSE

Reduced motor unit activity of the vastus medialis muscle relative to the vastus lateralis muscle has been implicated as a cause of lateral patellar subluxation. The purpose of this study was to assess the influence of vastus muscle motor unit activity on patellar kinematics.

SUBJECTS

Twenty-three women (mean age=26.8 years, SD=8.5, range=14-46) with a diagnosis of patellofemoral pain and 12 women (mean age=29.1 years, SD=5.0, range=24-38) without patellofemoral pain participated. Only female subjects were studied because of potential biomechanical differences between sexes.

METHODS

Patellar kinematics (kinematic magnetic resonance imaging) and vastus muscle electromyographic (EMG) activity using indwelling electrodes were measured during resisted knee extension. Measurements of medial and lateral patellar displacement and tilt obtained from magnetic resonance images were correlated with normalized vastus lateralis:vastus medialis oblique muscle and vastus lateralis:vastus medialis longus muscle EMG ratios at 45, 36, 27, 18, 9, and 0 degrees of knee flexion using a stepwise regression procedure.

RESULTS

The vastus lateralis:vastus medialis longus muscle EMG ratio contributed to the prediction of lateral patellar glide at 27 degrees of knee flexion (r=-.48), with increased vastus medialis longus muscle activity being associated with greater lateral patellar displacement. A similar inverse relationship was evident with lateral patellar tilt at 36, 27, 18, and 9 degrees of knee flexion.

CONCLUSION AND DISCUSSION

These results suggest that increased motor unit activity of the vastus medialis muscle appears to be associated with abnormal patellar kinematics in women, but it is not necessarily a cause of abnormal patellar kinematics.

Patellar kinematics, part II: the influence of the depth of the trochlear groove in subjects with and without patellofemoral pain

BACKGROUND AND PURPOSE

A shallow intercondylar groove has been implicated as being contributory to abnormal patellar alignment. The purpose of this study was to assess the influence of the depth of the intercondylar groove on patellar kinematics.

SUBJECTS

Twenty-three women (mean age=26.8 years, SD=8.5, range=14-46) with a diagnosis of patellofemoral pain and 12 women (mean age=29.1 years, SD=5.0, range=24-38) without patellofemoral pain participated. Only female subjects were studied because of potential biomechanical differences between sexes.

METHODS

Patellar kinematics were assessed during resisted knee extension using kinematic magnetic resonance imaging. Measurements of medial and lateral patellar displacement and tilt were correlated with the depth of the trochlear groove (sulcus angle) at 45, 36, 27, 18, 9, and 0 degrees of knee flexion using regression analysis.

RESULTS

The depth of the trochlear groove was found to be correlated with patellar kinematics, with increased shallowness being predictive of lateral patellar tilt at 27, 18, 9, and 0 degrees of flexion and of lateral patellar displacement at 9 and 0 degrees of flexion (r=.51-.76).

CONCLUSION AND DISCUSSION

The results of this study indicate that bony structure is an important determinant of patellar kinematics at end-range knee extension (0(-30().

The influence of lower extremity joint torque on gait characteristics in elderly men

OBJECTIVE

To examine the relation between certain lower extremity isokinetic muscle torque capabilities and selected stride characteristics for a group of elderly, sedentary men.

STUDY DESIGN

Descriptive analysis of convenience sample.

SETTING

Veterans Administration (VA) ambulatory care center.

SUBJECTS

Eighty-one elderly men, capable of independent ambulation, were recruited from outpatient clinics and the local community (mean age, 74.7yr).

MAIN OUTCOME MEASURES

Maximal isokinetic torque in the sagittal plane of hip, knee, and ankle muscles; stride characteristics of speed, stride length, and cadence recorded during walking at a self-selected velocity.

RESULTS

Stepwise regression analysis revealed that hip extension torque was the only significant independent predictor for free walking speed, stride length, and cadence, and accounted for 37% (r = .611), 35% (r = .590), and 12% (r = .341) of the total variance, respectively. Other joint torques correlated with gait parameters but did not add significantly to the multivariate model.

CONCLUSIONS

Hip extension torque was the only significant independent predictor for free walking velocity, stride length, and cadence in this group. These results support the idea that strengthening the hip extensors may improve stride characteristics in elderly individuals.

The influence of patellofemoral pain on lower limb loading during gait

OBJECTIVE

To determine if subjects with patellofemoral pain demonstrate excessive lower limb loading during gait.

DESIGN

Prospective study utilizing a group of patients with patellofemoral pain and a control group.

BACKGROUND

Increased rate of lower limb loading has been hypothesized as being contributory to knee osteoarthritis and may be the result of decreased knee flexion during weight acceptance. Since patients with patellofemoral pain have been reported to limit knee flexion during gait, these individuals may be at risk for the adverse effects of impulse loading.

METHODS

Force plate parameters, lower extremity kinematics and stride characteristics were recorded in 15 females with patellofemoral pain and 10 pain-free controls during self-selected free and fast walking velocities.

RESULTS

Individuals in the patellofemoral pain group demonstrated a significantly slower gait velocity during the free and fast trials as well as decreased stance phase knee flexion during fast walking. The average peak loading rate for the patellofemoral pain group was significantly less than the control group during both free (P=0.004) and fast walking (P=0. 03).

CONCLUSIONS

Despite diminished stance phase knee flexion during fast walking, subjects with patellofemoral pain did not demonstrate increased lower limb loading. During gait, the ground reaction forces appeared to be minimized by adopting a slower walking velocity.

RELEVANCE

These results indicate that altered knee kinematics as a result of patellofemoral pain do not place these individuals at risk for the adverse effects of impulse loading.

Effect of bracing on patellar kinematics in patients with patellofemoral joint pain

PURPOSE

Bracing is commonly used to correct patellar malalignment syndromes. However, there are little objective data documenting the effect of such supports on patellofemoral joint relationships. The purpose of this study was to assess the effectiveness of an elastic patellofemoral sleeve brace in altering patellar tracking in subjects with patellofemoral pain.

METHODS

Ten female subjects (12 patellofemoral joints) between the ages of 17 and 46 participated in this study. All subjects had a diagnosis of patellofemoral pain and demonstrated lateral patellar tracking based on magnetic resonance imaging (MRI) assessment. Each subject underwent kinematic MRI of the patellofemoral joint through a range of 45 to 0 degrees of knee flexion against a resistance of 15% body weight. Imaging was performed with and without a patellofemoral joint brace (Bauerfeind Genutrain P3 brace, Atlanta, GA). Measurement of medial/lateral patellar displacement, medial/lateral patellar tilt, and the depth of the trochlear groove (sulcus angle) were obtained with midpatellar image sections at 45, 36, 27, 18, 9 and 0 degrees of knee flexion.

RESULTS

No statistically significant differences in medial/lateral patellar displacement or tilt were found between braced and unbraced trials across all knee flexion angles (P < 0.05). A small but statistically significant increase in sulcus angle was found across all knee flexion angles with the braced trials (P > 0.05).

CONCLUSIONS

These results do not support the hypothesis that the brace used in this study corrects patellar tracking patterns in subjects with patellofemoral pain. However, the increased sulcus angle indicates a change in patella position within the trochlea. It is possible that the clinical improvements seen with bracing may be the result of subtle differences in joint mechanics and not gross changes in alignment.

Relationship between foot pronation and rotation of the tibia and femur during walking

The purpose of this study was to test the hypothesis that the magnitude and timing of peak foot pronation would be predictive of the magnitude and timing of peak rotation of tibia and femur. Thirty subjects who demonstrated a wide range of pronation participated. Three-dimensional kinematics of the foot, tibia, and femur segments were recorded during self-selected free walking trials using a six-camera VICON motion analysis system. Regression analysis demonstrated that the magnitude and timing of peak pronation was not predictive of the magnitude and timing of tibial and femoral rotation. The lack of a relationship between peak foot pronation and the rotation of the tibia and femur is contrary to the clinical hypothesis that increased pronation results in greater lower extremity rotation. It would seem, therefore, that the relationship between foot pronation and rotation of the lower extremity segments should be assessed on a patient-by-patient basis.

Criterion-related validity of a clinical measurement to determine the medial/lateral component of patellar orientation

STUDY DESIGN

Repeated measures design using a sample of convenience.

OBJECTIVE

To assess the criterion-related validity and intrarater reliability of a clinical measurement used for determining the medial/lateral position of the patella.

BACKGROUND

Patellar taping is a common treatment for patellofemoral pain. Application of this intervention requires accurate assessment of patellar orientation; however, the validity of this clinical procedure has not been documented.

METHODS AND MEASURES

Fourteen subjects (10 women, 4 men; average age, 41 +/- 16 years) were evaluated. Clinical assessment of medial/lateral patellar orientation using the technique described by McConnell was compared with the actual position of the patella as determined through magnetic resonance imaging (MRI). Imaging was done on 7 knees of 4 subjects who were asymptomatic and 11 knees of 10 subjects who were symptomatic. Both clinical and MRI assessments were made with the subjects supine, the knee extended, and the quadriceps relaxed. Agreement between the 2 techniques and the intrarater reliability of each measurement were quantified by means of the intraclass correlation coefficient (ICC).

RESULTS

Both the clinical and MRI measures of medial/lateral patellar displacement were found to demonstrate good intrarater reliability (ICC = 0.91 and 0.85, respectively). The agreement between the clinical and MRI determinations of medial/lateral patellar position was poor (ICC = 0.44). The average amount of lateral patellar displacement as determined by the clinical method was more than twice that established through MRI.

CONCLUSIONS

The clinical assessment of the medial/lateral position of the patella overestimates the true amount of lateral patellar displacement. A more valid clinical method of assessing the medial/lateral component of patellar orientation is necessary.

Rehabilitation of patellofemoral joint disorders: a critical review

Patellofemoral pain is one of the most common knee disorders seen in orthopaedic practice. Despite its high incidence, treatment of this disorder remains controversial. Traditionally, nonoperative management of patellofemoral pain has focused on restoring normal patellar tracking by improving dynamic stability. Of particular interest to clinicians has been the vastus medialis oblique, which has been implicated as being the primary medial stabilizer of the patella. Although emphasis on the vastus medialis oblique continues to be the mainstay of conservative care of patellofemoral pain, there exists considerable disagreement between research outcomes and clinical practice. This article critically reviews the current literature concerning the treatment of patellofemoral pain with respect to the vastus medialis oblique, taping, and bracing, as well as various forms of therapeutic exercise, and relates these findings to the prevailing views regarding the management of this disorder.

Effects of distal cement voids on cement stress in total hip arthroplasty

The purpose of this study was to determine whether voids in the distal cement mantle created during total hip arthroplasty increase cement stress at the distal tip of the femoral component. Using a three-dimensional finite element model of an idealized, cylindrical femoral shaft with implanted prosthesis, peak von Mises stress in the cement mantle was evaluated for five different air-bubble configurations and two cement mantle thicknesses, 2 mm and 5 mm. Results indicated that voids in the cement mantle increased peak cement stress at the medial tip of the prosthesis by 2% to 57%, with greater increases in stress being evident with larger bubble sizes. On the average, peak stresses were 53% greater in the models with the thinner cement mantle. Clinicians are encouraged to use a thicker cement mantle and to avoid bubble formation during total hip arthroplasty.

Quantification of patellar tracking using kinematic MRI

The purpose of this study was to describe a method to quantify dynamic patellar tracking using kinematic MRI (KMRI). Twelve normal females and three patients with patellofemoral pain participated. Imaging was performed with a 1.5-T/64-MHz MR system using a fast spoiled gradient-recalled acquisition in the steady state (GRASS) pulse sequence. A nonferromagnetic positioning device permitted active, bilateral knee extension against resistance (15% bwt) from 45 degrees knee flexion to full extension. Subjects were instructed to extend their knees at a rate of 9 degrees per second, which allowed images to be obtained at 45 degrees, 36 degrees, 27 degrees, 18 degrees, 9 degrees, and 0 degrees. All images were assessed for medial/lateral patellar displacement, patellar tilt, and sulcus angle using a computer-aided system. Normal patellar motion was characterized by medial movement from 45 degrees to 18 degrees, followed by a reversal toward lateral displacement from 18 degrees to full extension. The results for patellar tilt revealed a tendency toward decreasing lateral tilt as the knee extended. Sulcus angle measurements indicated that the patella was moving to a more shallow portion of the trochlear groove (superiorly) during extension.

The effects of patellar taping on stride characteristics and joint motion in subjects with patellofemoral pain

Although patellar taping has been reported to be effective in reducing pain, the effects of this procedure on functional outcomes, such as ambulation, have not been documented. The purpose of this study was to compare stride characteristics and joint motion in subjects with patellofemoral pain, with and without the application of patellar taping using the McConnell technique. Fifteen female subjects between the ages of 14 and 41 years with diagnosis of patellofemoral pain participated in this study. Stride characteristics (Stride Analyzer) and sagittal plane joint motion (VICON) were recorded simultaneously during taped and untaped trials of free walking, fast walking, and ascending and descending a ramp and stairs. A repeated measures analysis of variance was used to determine differences between taped and untaped trials. Although subjects reported an average pain reduction of 78% using a visual analogue scale, the only significant change in stride characteristics was an increase in stride length during ramp ascent. Patellar taping did, however, result in a small but significant increase in loading response knee flexion across all conditions tested. We believe this finding demonstrates more willingness by the patellofemoral pain subjects to load the knee joint, thus permitting increased shock absorption, increased quadriceps activity, and tolerance of increased patellofemoral joint reaction force.

Are patellofemoral pain and quadriceps femoris muscle torque associated with locomotor function?

BACKGROUND AND PURPOSE

The purpose of this investigation was to determine the influence of pain and muscle weakness on gait variables in subjects with patellofemoral pain (PFP).

SUBJECTS

Nineteen female subjects with a diagnosis of PFP and 19 female subjects without PFP participated in the study.

METHODS

Subjects underwent gait analysis (stride characteristics and joint motion) during level walking, ascending and descending stairs, and ascending and descending ramps, in addition to isometric torque testing of the knee extensors of the involved limb. Pain and functional status also were assessed.

RESULTS

Compared with the comparison group, the primary gait compensation in the PFP group was a reduced walking speed, which was a function of both a reduced stride length and cadence. Knee extensor torque was the only predictor of gait function, with increased torque correlating with improved stride characteristics. In addition, PFP was not associated with locomotor function.

CONCLUSION AND DISCUSSION

These findings suggest that functional ability in persons with PFP is associated with increased quadriceps femoris muscle torque. Future research is needed to determine whether function improves with quadriceps femoris muscle strengthening.

Stair ambulation in persons with transtibial amputation: an analysis of the Seattle LightFoot

The purpose of this study was to document gait patterns in a group of individuals with transtibial amputations (TTA) during stair ambulation, and to identify the functional limitations associated with this task. Ten persons with TTA fitted with a Seattle LightFoot prosthetic component, and 14 nondisabled subjects participated in this study. Electromyographic activity (EMG) of the vastus lateralis (VL), rectus femoris (RF), gluteus maximus (GMAX), semimembranosus (SMEMB), biceps femoris long head (BFLH), and biceps femoris short head (BFSH) was assessed using indwelling wire electrodes during ascending and descending stairs. Lower limb kinematics (VICON) and stride characteristics (Footswitch Stride Analyzer System) also were collected. Stride characteristics revealed that those with TTA had a significantly slower rate of stair ambulation and demonstrated stance phase asymmetry between limbs compared to the nondisabled. Kinematic analysis determined significant limitations in prosthetic ankle motion, which necessitated compensatory functions at the hip and knee to accomplish stair ascent and descent and resulted in significantly greater muscular effort (increased EMG intensity and duration) compared to nondisabled.

Timing and intensity of vastus muscle activity during functional activities in subjects with and without patellofemoral pain

BACKGROUND AND PURPOSE

Differences in intensity and timing of muscle activity between the vastus medialis and vastus lateralis muscles have been hypothesized as contributing to lateral patellar tracking and patellofemoral pain (PFP). The purpose of this study was to ascertain whether there were differences in the activity of the vastus muscles that would be suggestive of patellar instability in subjects with PFP.

SUBJECTS

Twenty-six subjects with PFP and 19 subjects without PFP participated in the study.

METHODS

Fine-wire electromyography was used to record activity of the vastus medialis oblique, vastus medialis longus, vastus lateralis, and vastus intermedius muscles during level walking, stair climbing, and walking on ramps. Knee motion was assessed using a six-camera motion analysis system.

RESULTS

No differences in onset or cessation of muscle activity was found among the vastus muscles for either group, regardless of condition. Subjects with PFP demonstrated less activity of all vastus muscles for level walking and ramp walking than did subjects without PFP.

CONCLUSIONS AND DISCUSSION

These results do not support the hypothesis that timing or intensity differences between the vastus medialis and vastus lateralis muscles are associated with PFP.

The influence of lower-extremity muscle force on gait characteristics in individuals with below-knee amputations secondary to vascular disease

BACKGROUND AND PURPOSE

The purpose of this study was to establish the relationship between isometric muscle force and temporal-spatial gait characteristics for individuals who have had a below-knee amputation secondary to vascular disease.

SUBJECTS

Twenty-two individuals (15 male, 7 female) with dysvascular below-knee amputations participated. The male subjects were aged 35 to 72 years (x=59.6, SD=11.1), and the female subjects were aged 54 to 68 years (x=60.5, SD=5.1). Methods. The subjects underwent stride analysis during free-speed and fast walking, as well as bilateral isometric force testing of their remaining hip, knee, and ankle muscles.

RESULTS

Stepwise regression analysis revealed that hip extensor force on the amputated side was the only predictor of both free speed (gamma=.50) and fast speed (gamma=.72). Hip abduction force of the sound++ limb was correlated with cadence for both free-speed trials (gamma=.57) and fast-speed trials (gamma=.57). Sound-side knee extensor force was related to free-speed stride length (gamma=.44), whereas residual-limb knee extensor force predicted stride length during fast walking (gamma=.67).

CONCLUSION AND DISCUSSION

These results indicate that adequate force is necessary in both residual and sound limbs to improve functional gait ability and that ther hip extensors and abductors and the knee extensors should be emphasized in the rehabilitation of individuals with below-knee amputations.

The effect of five prosthetic feet on the gait and loading of the sound limb in dysvascular below-knee amputees

The purpose of this study was to determine the effects of prosthetic foot design on the vertical ground reaction forces experienced by the sound and amputated limbs in a group of persons with dysvascular below-knee amputations. Stride characteristics, joint motion, and ground reaction forces were recorded simultaneously during a self-selected free walking velocity in seven subjects wearing five different prosthetic feet (SACH, Flex-Foot, Carbon Copy II, Seattle, Quantum). Subjects used each foot for one month prior to testing. Results indicated that the sound limb was exposed to higher vertical ground reaction forces than normal despite a reduced walking velocity. Use of the Flex-Foot resulted in the lowest sound limb vertical forces, which appears to be related to its large arc of dorsiflexion motion. In addition, there was increased loading response knee flexion of the sound limb indicating an attempt by these subjects to modulate floor impact. These results suggest that the intact lower extremity is susceptible to excessive floor impact, and that prosthetic foot design can have an effect on the magnitude of the vertical forces experienced by the limb.

Rearfoot posture in subjects with patellofemoral pain

The relationship between structural foot deformities and excessive subtalar joint pronation as being contributory to patellofemoral pain has not been well documented. It was the purpose of this study to assess the rearfoot posture in patients diagnosed with patellofemoral pain compared with a normal population. In addition, the intratester reliability in obtaining rearfoot measurements was assessed for right and left sides in 21 normal subjects. A goniometer was used to measure rearfoot posture in 30 female subjects (15 with patellofemoral pain and 15 controls). Measurements were taken with the subjects prone and the subtalar joint in neutral. Intraclass correlation coefficients were good for both the right and left measurements (.87 and .86, respectively). A small but significant increase in rearfoot varus was found in the patellofemoral pain group compared with the control group (8.9 vs. 6.8 degrees; p = .0002). These results suggest that increased rearfoot varus may be a contributing factor in patellofemoral pain and should be assessed when evaluating the events at the subtalar joint and the lower extremity. In addition, it has been demonstrated that consistent rearfoot measurements can be obtained by an individual clinician.

Energy expenditure during ambulation in dysvascular and traumatic below-knee amputees: a comparison of five prosthetic feet

Recent advancement in prosthetic technology has led to the development of dynamic elastic response feet (DER), which are reported to store and release energy to facilitate gait. To date, there has been no objective evidence to suggest energy conservation while using these foot designs. The purpose of this study was to compare the energy expenditure of five commercially available prosthetic feet (SACH and four DER feet) in both the traumatic and dysvascular populations during level walking. Seventeen male subjects with below-knee amputation (nine traumatic and seven dysvascular) were tested for energy expenditure (Douglas Bag technique) during a 20-min walk while wearing each of the prosthetic feet. The DER prosthetic foot designs were not shown to reduce the energy cost (ml O2/kg-m) or rate of energy expenditure (ml O2/kg-min) compared to the SACH foot. Overall, the traumatic amputees had a similar oxygen consumption per meter traveled compared to the dysvascular amputees; however, the rate of energy consumption was much higher in the traumatic group. This increased rate was a function of the greater walking velocity employed by the traumatic subjects, made possible by their better physical fitness.

Single mRNAs visualized by ultrastructural in situ hybridization are principally localized at actin filament intersections in fibroblasts

Considerable evidence indicates that mRNA associates with structural filaments in the cell (cytoskeleton). This relationship would be an important mechanism to effect mRNA sorting since specific mRNAs could be sequestered at sites within the cell. In addition, it can provide a mechanism for spatial regulation of mRNA expression. However, the precise structural interactions between mRNA and the cytoskeleton have yet to be defined. An objective of this work was to visualize "individual" poly(A) mRNA molecules in situ by electron microscopy to identify their relationship to individual filaments. Poly(A) RNA and filaments were identified simultaneously using antibodies to detect hybridized probe and filaments or actin-binding proteins. In human fibroblasts, most of the poly(A) mRNA (72%) was localized within 5 nm of orthogonal networks of F-actin filaments. Poly(A) mRNA also colocalized with vimentin filaments (29%) and microtubules (< 10%). The sites of mRNA localization were predominantly at filament intersections. The majority of poly(A) mRNA and polysomes colocalized with the actin crosslinking proteins, filamin, and alpha-actinin, and the elongation factor, EF-1 alpha (actin-binding protein; ABP-50). Evidence that intersections contained single mRNA molecules was provided by using a labeled oligo dT probe to prime the synthesis of cDNA in situ using reverse transcriptase. Both the poly(A) and cis sequences of the same mRNA molecule could then be visualized independently. We propose that the cytoskeletal intersection is a mRNA receptor and serves as a "microdomain" where mRNA is attached and functionally expressed.

Influence of prosthetic foot design on sound limb loading in adults with unilateral below-knee amputations

Altered gait patterns resulting from amputation has been implicated as a possible mechanism for early degenerative changes in the sound limb of unilateral amputees. The purpose of this study was to examine the ground reaction force characteristics and joint motion in this population. Ground reaction forces, joint motion, and stride characteristics of 10 traumatic below-knee amputees were analyzed while wearing five different prosthetic feet (SACH, Flex-foot, Carbon Copy II, Seattle, and Quantum). Subjects used each foot for 1 month prior to testing. Results indicated that the Flex-foot significantly reduced the initial peak of the vertical ground reaction force on the sound limb compared to all other feet tested (p < .0001). The SACH foot consistently produced the greatest ground reaction forces on the sound limb; however, this was not statistically significant. The effective factor of the Flex-foot appears to be minimization of the center of gravity elevation, which was accomplished through a significant increase in terminal stance dorsiflexion compared to the other feet tested (p < .0001).

Isometric shoulder torque in subjects with spinal cord injury

The etiology of shoulder pain in spinal cord injured (SCI) patients has been attributed to overuse, with dysfunction being more prevalent as the time since injury increases. Impingement syndrome, the most common diagnosis in this population, may be related to weakness of the rotator cuff and shoulder girdle musculature. Shoulder dysfunction is greater in subjects with SCI than in able-bodied patients; consequently, this study compares isometric strength of quadriplegic and paraplegic subjects to able-bodied controls. Peak isometric torque for internal rotation, external rotation, and scapular elevation was assessed using a Lido isokinetic dynamometer. The strength (torque) values of the quadriplegic group were significantly lower than the control group and paraplegic group for all motions tested (p < .0005). The only significant difference between the paraplegic and able-bodied groups was found with internal rotation (p < .0001). These results indicate that quadriplegic patients may be at greater risk for shoulder pathology because of both muscular limitation and increased functional demand.

Below-knee amputee gait in stair ambulation. A comparison of stride characteristics using five different prosthetic feet

The purpose of this study was to compare the stride characteristics provided by four of the new dynamic elastic response prosthetic feet and the SACH foot to determine if any of them provided an increased performance during stair ambulation. Ten traumatic below-knee amputees were studied; each of them tested all five prosthetic feet (Flex-Foot, Carbon Copy II, Seattle, Quantum, and SACH). Compression closing footswitches were used to calculate stride characteristics while ascending and descending a four-step staircase. The only significant difference between feet was found during the initial double-limb support (IDLS) phase of stair ascent, with the Flex-Foot providing a more symmetrical amputated:sound limb IDLS ratio compared with the SACH foot (1.03 versus 1.30). The increased IDLS time seen with the SACH foot reflects the inability to adequately advance the tibia and body weight over the prosthetic foot to achieve progression. This lack of progression and symmetrical gait pattern between limbs may be a function of the limited dorsiflexion range inherent with the SACH foot.