Kinematic analysis of pressing situations in female collegiate football games: New insight into anterior cruciate ligament injury causation.

The most common events during which anterior cruciate ligament (ACL) injuries occur in football are pressing situations. This study aimed to describe the knee and hip joint kinematics during pressing situations in football games to identify kinematic patterns in actions with a high risk for ACL injuries. We filmed 5 female collegiate football matches and identified 66 pressing situations. Five situations with a large distance between the trunk and foot placements in the sagittal plane were analyzed using a model-based image-matching technique. The mean knee flexion angle at initial contact (IC) was 13° (range, 8°-28°) and increased by 11° (95% confidence interval [CI], 3°-14°) at 40 ms after IC. As for knee adduction and rotation angles, the knee positions were close to neutral at IC, and only minor knee angular changes occurred later in the sequences. The mean hip flexion was 25° (range, 8°-43°) at IC and increased by 22° (95% CI, 11°-32°) after 100 ms. The hip was also externally rotated by 7° (range, -19° to 3°) at IC, and gradually rotated internally, reaching 10° of internal rotation (range, -5° to 27°) at 100 ms after IC. This study suggests that the observed knee valgus, internal hip and knee rotation, and static hip flexion previously reported in non-contact ACL injury events are unique to injury situations. In contrast, neither rapid knee valgus nor increased internal rotation was seen in non-injury pressing maneuvers.

Evaluation of hamstring muscle strength and morphology after anterior cruciate ligament reconstruction.

This study aimed to clarify the relationship between knee flexor strength and hamstring muscle morphology after anterior cruciate ligament (ACL) reconstruction using the semitendinosus (ST) tendon and to determine the causative factors of decreased knee flexor muscle strength. Fourteen male and ten female patients who resumed sports activities after surgery participated in the experiment. Isometric knee flexion torque was measured at 30°, 45°, 60°, 90°, and 105° of knee flexion. Magnetic resonance imaging (MRI) was used to calculate ST muscle length and hamstring muscle volume, and to confirm the status of ST tendon regeneration. The correlation between the MRI findings and flexor strength was analyzed. Regenerated ST tendon was confirmed in 21 of the 24 patients, but muscle volume (87.6%) and muscle length (74.5%) of the ST in the operated limb were significantly smaller than those in the normal limb. The percentage of the knee flexion torque of the operated limb compared with that of the normal was apparently lower at 105° (69.1%) and 90° (68.6%) than at 60° (84.4%). Tendon regeneration, ST muscle shortening, and ST muscle atrophy correlated with decreased knee flexion torque. These results indicated that preserving the morphology of the ST muscle-tendon complex is important.

Estimation of tensile force in the hamstring muscles during overground sprinting.

The purpose of this study was to identify the period of the gait cycle during which the hamstring muscles were likely injured by estimating the magnitude of tensile force in each muscle during overground sprinting. We conducted three-dimensional motion analysis of 12 male athletes performing overground sprinting at their maximal speed and calculated the hamstring muscle-tendon length and joint angles of the right limb throughout a gait cycle during which the ground reaction force was measured. Electromyographic activity during sprinting was recorded for the biceps femoris long head, semitendinosus, and semimembranosus muscles of ipsilateral limb. We estimated the magnitude of tensile force in each muscle by using the length change occurred in the musculotendon and normalized electromyographic activity value. The study found a quick increase of estimated tensile force in the biceps femoris long head during the early stance phase of the gait cycle during which the increased hip flexion angle and ground reaction force occurred at the same time. This study provides quantitative data of tensile force in the hamstring muscles suggesting that the biceps femoris long head muscle is susceptible to a strain injury during the early stance phase of the sprinting gait cycle.

Effect of cooling during inter-exercise periods on subsequent intramuscular water movement and muscle performance.

To evaluate the effects of cooling between exercise sessions on intramuscular water movement and muscle performance, the lower extremities of nine untrained men were assigned to either a cooling protocol (20-min water immersion, 15 °C) or a noncooling protocol. Each subject performed two exercise sessions involving maximal concentric knee extension and flexion (three repetitions, 60°/s; followed by 50 repetitions, 180°/s). The peak torque at 60°/s and total work, mean power, and decrease rate of torque value at 180°/s were evaluated. Axial magnetic resonance diffusion-weighted images of the mid-thigh were obtained before and after each exercise session. Apparent diffusion coefficient (ADC) values for the quadriceps and hamstrings were calculated for evaluating intramuscular water movement. Both groups exhibited significantly increased ADC values for the quadriceps and hamstrings after each exercise session. These ADC values returned to the pre-exercise level after water immersion. No significant difference was observed in muscle performance from first exercise session to the next in either group, except for increased total work and mean power in knee flexion in the cooled group. Cooling intervention between exercise sessions decreased exercise-induced elevation of intramuscular water movement and had some beneficial effects on muscle endurance of knee flexors, but not knee extensors.

Relationship between quadriceps femoris muscle volume and muscle torque at least 18 months after anterior cruciate ligament reconstruction.

The purpose of this study was to evaluate motor unit recruitment in the quadriceps femoris (QF) after anterior cruciate ligament (ACL) rupture and repair. Subjects included 24 patients at ≥ 18 months after ACL reconstruction and 22 control subjects with no history of knee injury. A series of cross-sectional magnetic resonance images were obtained to compare the QF of patients' injured side with that of their uninjured sides and that of uninjured control subjects. Muscle torque per muscle volume was calculated as isokinetic peak torque divided by QF muscle volume (cm(3)). The mean muscle torque per unit volume of the injured side of patients was not significantly different from that of the uninjured side or control subjects (one-way ANOVA) Results of the present study were contrary to the results of a previous study that evaluated patients at ≤ 12 months after ACL reconstruction. The present study found that high-threshold motor unit recruitment was restored at ≥ 18 months after ACL reconstruction. Thus, clinicians must develop techniques that increase the recruitment of high-threshold motor units in the QF from the period immediately after the injury until approximately 18 months after ACL reconstruction.

Evaluation of human muscle hardness after dynamic exercise with ultrasound real-time tissue elastography: a feasibility study.

AIM: To assess the feasibility of ultrasound real-time tissue elastography (RTE) for measuring exercise-induced changes in muscle hardness and to compare the findings of RTE with those of a tissue hardness meter for semi-quantitative assessment of the hardness of exercised muscles. MATERIALS AND METHODS: Nine male participants performed an arm-curl exercise. RTE measurements were performed by manually applying repetitive compression with the transducer on the scan position before exercise, immediately after exercise, and at 30 min after exercise; strain ratios between muscle and a reference material (hydrogel) were calculated (muscle strain/material strain). A tissue hardness meter was also used to evaluate muscle hardness. The intraclass correlation coefficients (ICCs) for the three repeated measurements at each measurement time were calculated to evaluate the intra-observer reproducibility of each technique. RESULTS: Immediately after exercise, the strain ratio and the value obtained using the tissue hardness meter significantly decreased (from 1.65 to 1.35) and increased (from 51.8 to 54.3), respectively. Both parameters returned to their pre-exercise value 30 min after exercise. The ICCs of the RTE (and the ICCs of the muscle hardness meter) were 0.971 (0.816) before exercise, 0.939 (0.776) immediately after exercise, and 0.959 (0.882) at 30 min after exercise. CONCLUSION: Similar to the muscle hardness meter, RTE revealed the exercise-induced changes of muscle hardness semi-quantitatively. The intra-observer reproducibility of RTE was very high at each measurement time. These findings suggest that RTE is a clinically useful technique for assessing hardness of specific exercised muscles.

Diffusion-weighted magnetic resonance imaging reveals the effects of different cooling temperatures on the diffusion of water molecules and perfusion within human skeletal muscle.

AIM: To evaluate the effect of local cooling on the diffusion of water molecules and perfusion within muscle at different cooling temperatures. MATERIALS AND METHODS: Magnetic resonance diffusion-weighted (DW) images of the leg (seven males) were obtained before and after 30 min cooling (0, 10, and 20°C), and after a 30 min recovery period. Two types of apparent diffusion coefficient (ADC; ADC1, reflecting both water diffusion and perfusion within muscle, and ADC2, approximating the true water diffusion coefficient) of the ankle dorsiflexors were calculated from DW images. T2-weighted images were also obtained to calculate T2 values of the ankle dorsiflexors. The skin temperature was measured before, during, and after cooling. RESULTS: Both ADC values significantly decreased after cooling under all cooling conditions; the rate of decrease depended on the cooling temperature used (ADC1: -36% at 0°C, -27.8% at 10°C, and -22.6% at 20°C; ADC2: -26% at 0°C, -21.1% at 10°C, and -14.6% at 20°C). These significant decreases were maintained during the recovery period. Conversely, the T2 value showed no significant changes. Under all cooling conditions, skin temperature significantly decreased during cooling; the rate of decrease depended on the cooling temperature used (-74.8% at 0°C, -51.1% at 10°C, and -26.8% at 20°C). Decreased skin temperatures were not restored to pre-cooling values during the recovery period under any cooling conditions. CONCLUSION: Local cooling decreased the water diffusion and perfusion within muscle with decreased skin temperature; the rates of decrease depended on the cooling temperature used. These decreases were maintained for 30 min after cooling.

Relationship between the MRI and EMG measurements.

The purpose of this study was to investigate the effect of intensive eccentric exercise on hamstring muscles by using magnetic resonance imaging (MRI) and to elucidate the relationships between the changes in the electromyographic (EMG) parameters and in the transverse relaxation time (T2) of the hamstring muscles. Seven male volunteers performed eccentric knee flexion exercise, and the EMG activity of the hamstring muscles was simultaneously measured. Before and immediately after the exercise, the maximum isometric knee flexion torque was measured and MR images of the hamstring muscles were obtained. For all hamstring muscles, the EMG activity of the fifth set was significantly lower than that of the first set. For each subject, a significant correlation was detected between the percentage change in the value of the post-exercise T2 value and those of EMG signals during the exercise only for the semitendinosus (ST) muscle and not for the biceps femoris (BF) and the semimembranosus (SM) muscles. These results suggested that the EMG-activity reductions in the BF, ST, and SM muscles were due to neuromuscular fatigue, and moreover the reduction in the ST muscle was due to a failure in the E-C coupling, which was caused by excessive muscle-fiber damage.

Effect of joint position on the electromyographic activity of the semitendinosus muscle.

The semitendinosus (ST) muscle has a tendinous intersection within the muscle belly that separates the ST muscle into distinct proximal and distal compartments. Thus far, no study has compared the electromyographic (EMG) activities between the proximal and distal compartments of the human ST muscle. This study aimed to investigate the intramuscular EMG activity patterns of the proximal and distal compartments of the ST muscle by altering the hip and knee joint positions. The study population comprised eight healthy male volunteers. They performed ramp isometric knee flexion tasks form the relaxed state to the maximal voluntary contraction (MVC) state with (1) the hip and knee at 90 degrees and 0 degrees, respectively (90-0 position), (2) both the hip and knee at 00 (0-0 position), and (3) the hip and knee at 0 degrees and 90 degrees, respectively (0-90 position). Fine-wire electrodes were inserted into the proximal and distal compartments of the ST muscle and the individual EMG activities were recorded. In the 90-0 position, the EMG activity of the distal compartment was higher than that of the proximal compartment at 60%, 80%, and 90% MVC. Moreover, in the 0-90 position, the EMG activity of the proximal compartment was higher than that of the distal compartment at 60% MVC. These results indicated that the lengthened or shortened muscle conditions induced regional differences in the EMG activity patterns, while the two compartments showed equivalent activity when the muscle length was moderate.

Non-contact ACL injuries in female athletes: an International Olympic Committee current concepts statement.

The incidence of anterior cruciate ligament (ACL) injury remains high in young athletes. Because female athletes have a much higher incidence of ACL injuries in sports such as basketball and team handball than male athletes, the IOC Medical Commission invited a multidisciplinary group of ACL expert clinicians and scientists to (1) review current evidence including data from the new Scandinavian ACL registries; (2) critically evaluate high-quality studies of injury mechanics; (3) consider the key elements of successful prevention programmes; (4) summarise clinical management including surgery and conservative management; and (5) identify areas for further research. Risk factors for female athletes suffering ACL injury include: (1) being in the preovulatory phase of the menstrual cycle compared with the postovulatory phase; (2) having decreased intercondylar notch width on plain radiography; and (3) developing increased knee abduction moment (a valgus intersegmental torque) during impact on landing. Well-designed injury prevention programmes reduce the risk of ACL for athletes, particularly women. These programmes attempt to alter dynamic loading of the tibiofemoral joint through neuromuscular and proprioceptive training. They emphasise proper landing and cutting techniques. This includes landing softly on the forefoot and rolling back to the rearfoot, engaging knee and hip flexion and, where possible, landing on two feet. Players are trained to avoid excessive dynamic valgus of the knee and to focus on the "knee over toe position" when cutting.

Statistical modelling of knee valgus during a continuous jump test.

Landing with the knee in a valgus position is recognized as a risk factor for anterior cruciate ligament (ACL) injury. Using linear and non-linear regression analyses, the purpose of this study was to examine the correlation between two-dimensional (2D) knee valgus and three-dimensional (3D) knee kinematics measured during a jump landing task. Twenty-eight female collegiate athletes participated. All participants were required to perform a continuous jump test. The average maximum angles of abduction and internal tibial rotation during landing were measured using the Point Cluster Technique. Average peak knee valgus angle was measured using a 2D approach. Linear and non-linear regression analyses between 2D valgus and 3D knee abduction, and between 2D valgus and 3D internal tibial rotation, were performed. The R2 value between 2D valgus and 3D knee abduction was significantly different from zero and had a moderate correlation for all models, whereas the R2 value between 2D valgus and 3D internal tibial rotation was not significantly different from zero. The 2D approach could be used to screen a specific group of individuals for risk of ACL injury; however, using frontal plane 2D analysis of valgus motion to evaluate internal tibial rotation is not advised.

Effect of resistance exercise training on bone formation and resorption in young male subjects assessed by biomarkers of bone metabolism.

We studied the effects of high intensity resistance exercise training on bone metabolism in 17 young adult Oriental males (23-31 years) by measuring sensitive biomarkers of bone formation and resorption. The subjects were assigned to a training group and a sedentary group. The training group followed a weight training program three times per week for 4 months. In the training group, serum osteocalcin concentration and serum bone-specific alkaline phosphatase activity were significantly increased within the first month after the beginning of resistance exercise training, and the elevated levels remained throughout the training period, while there was no significant change in plasma procollagen type-I C-terminal concentration. Urinary deoxypyridinoline excretion was transiently suppressed and returned to the initial value but was never stimulated during the 4 months. These results suggest that the resistance exercise training enhanced bone formation without prior bone resorption. In the sedentary group, there was no significant difference in bone metabolic markers except plasma procollagen type-I C-terminal, which continuously decreased during the experimental period. There were no significant changes in total and regional bone mineral density in either group. In conclusion, (1) resistance exercise training increased markers of bone formation, while it transiently suppressed a marker of bone resorption, and (2) such adaptive changes of bone metabolism to resistance exercise training occurred during the early period of the training, before changes in bone density were observable through densitometry.

An in vitro biomechanical evaluation of anterior-posterior motion of the knee. Tibial displacement, rotation, and torque.

We tested the anterior-posterior motion of nine normal cadaver knees in zero to 90 degrees of flexion using a specially designed apparatus. This apparatus applied a dynamic anterior-posterior force to each knee and measured the resulting tibial displacement, rotation, and torque. In the intact knee, an anterior force produced an internal tibial torque and internal tibial rotation, while a posterior force produced an external torque and external rotation. Anterior-posterior displacement increased by 30 per cent when the tibia was allowed to rotate freely about its neutral rotation position. Isolated section of the anterior cruciate ligament produced more than double the amount of anterior displacement without affecting posterior displacement. Isolated section of the posterior cruciate ligament produced almost triple the amount of posterior displacement without affecting anterior displacement. After cutting either the anterior or the posterior cruciate ligament, the resulting internal or external secondary tibial rotation disappeared. It appears, therefore, that the anterior and posterior cruciate ligaments are the primary restraints to motion in the anterior and posterior directions as well as the causes of internal and external tibial rotation during anterior and posterior motion.

Signal intensity changes in anterior cruciate ligament autografts: relation to magnetic field orientation.

RATIONALE AND OBJECTIVES: The purpose of this study was to use magnetic resonance (MR) imaging to investigate the contribution of graft alignment to changes in signal intensity in anterior cruciate ligament (ACL) autografts. MATERIALS AND METHODS: Forty patients who had undergone reconstruction of the ACL with an autograft underwent MR examinations of the knee in extension and flexion. The signal intensity of the intratibial bone tunnel and intraarticular portions of ACL graft were measured, and signal intensity ratios were defined by dividing the mean signal intensity of the graft by the mean signal intensity of the fatty marrow. The angles from the intraarticular and intratibial bone tunnel portions of the graft to the static magnetic field were measured for each signal intensity ratio. The Hotteling T2 test was used to evaluate the differences in signal intensity ratios to the differences in angles from flexion to extension for the intratibial bone tunnel and intraarticular portions of the graft. RESULTS: Significant increases occurred in the signal intensity of the graft and the angle with the change in position from flexion to extension for both the intratibial bone tunnel (P < .01) and intraarticular (P < .01) portions of the graft. Changes in signal intensity ratios were greater than zero, and these values differed significantly for the intraarticular and the intratibial bone tunnel (P < .01) portions of the graft. CONCLUSION: The signal intensity changes of the ACL graft related to changes in its alignment are likely a result of the magic-angle effect.

The prognosis of meniscectomy in athletes. The simple meniscus lesions without ligamentous instabilities.

This study analyzes patient participation in athletic activities after meniscectomy. Seventy simple meniscus lesions in 68 patients without ligamentous insufficiency were studied by means of a detailed questionnaire and clinical and radiological examinations. Follow-up ranged from 1 to 18.4 years, averaging 4.5 years. These cases are classified into two groups, depending on the intensity of athletic activities. Group 1 consisted of international class athletes and Group 2 consisted of both competitive and recreational athletes. None of those studied have given up sports following meniscectomy. Results were worse in Group 1 than in Group 2 in both clinical and subjective evaluation. In Group 1 volleyball players presented results worse than those of football (American style) players and wrestlers. In Group 2 there was no significant difference in results among athletes of various sports. We conclude that the results after meniscectomy are influenced by the quality and frequency of postoperative athletic activities.

Subtalar stress radiography using forced dorsiflexion and supination.

We investigated a new method of stress radiography of the subtalar joints using forced maximum dorsiflexion of the ankle in a supinated position. We measured transposition of the lateral process of the talus at the posterior subtalar joint in lateral views of normal amputated ankles, normal control subjects and patients with recurrent ankle sprains. The mean displacement in the control groups (n = 36) was 29.9%, significantly different from the 43.0% in patients with recurrent ankle sprains (n = 24). In the amputated specimens with intact ligaments movement was similar to that in normal subjects. Section of the calcaneofibular and the interosseous ligaments allowed much the same movement as in patients with recurrent ankle sprains. The new method is simple and useful for detecting subtalar instability.

Analysis of dystrophin in muscular diseases by two-dimensional gel electrophoresis using agarose gels in the first dimension.

We analyzed dystrophin in case of normal control, Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD) and infectious muscular disease using two-dimensional gel electrophoresis and immunoblotting with 3 monoclonal dystrophin antibodies: Dys 1, a mid-rod-domain antibody; Dys 2, a C-terminal-domain antibody; and Dys 3, an N-terminal-domain antibody. In cases of normal control, a clearly separated doublet of bands was observed for Dys 1 and 3 at molecular weights 400 and 420 kDa. The isoelectric point was between pH approximately 5.7-approximately 5.9, similar to that for the myosin heavy chain. In one DMD case, a single faint band was observed for Dys 2. BMD presented a single-band pattern for each antibody. Infectious diseases cases showed 3- to 5-band patterns for Dys 1 and single or no bands for Dys 2 and 3. The pI of the Dys 1 band was almost identical. These results suggest coexistence of normal dystrophin and its proteolytic products, both containing triple helical segment, and show that two-dimensional gel electrophoresis may be applicable in the analysis of dystrophin in muscular disease.

Follow-up study of Gore-Tex artificial ligament--special emphasis on tunnel osteolysis.

The Gore-Tex anterior cruciate ligament has been implanted in 123 patients at our institutions between 1984 and 1993. The Gore-Tex ligaments were totally ruptured in 26 cases. In the remaining 97 cases, 80 were followed up 5-11 years after operation. Graft loosening occurred in half of the cases, and osteoarthritic change was developed in 62% of the cases. Moreover, tibial and tunnel osteolysis was observed in most of the cases. Judging from these follow-up results, the Gore-Tex ligament should not be used for anterior cruciate ligament reconstruction.

[The study of washing operative wound with amikacin sulfate solution in the orthopedic surgery].

For the purpose of preventing postoperative orthopedic infections, investigation was carried out on effectiveness and safety of amikacin (AMK) after washing wound surface with its solution. 500 ml saline solution containing 400 mg AMK was used for washing. As the result, no postoperative infections were observed in all the 19 patients operated in our department. Neither abnormal findings to be regarded as abnormalities in blood test nor side-effects caused by washing were also observed. The blood samples obtained after washing did not show measurable AMK in all cases. It is said that use of antibiotics with 1) a wide-range of spectrum, 2) a bactericidal action and 3) low cross resistance against other antibiotics is preferable in washing wound surface in order to prevent postoperative infections. Under these circumstances, administration of aminoglycoside antibiotics is used frequently. Concerning the use of aminoglycoside antibiotics, however, it is necessary to pay attention to auditory and renal impairment. The previous study has revealed that AMK is lower in auditory and renal toxicity than other aminoglycoside antibiotics. AMK is thought, therefore, to be free from fear of auditory and renal impairment after washing and also to be one of effective antibiotics.

Gamma loop dysfunction in the quadriceps femoris of patients who underwent anterior cruciate ligament reconstruction remains bilaterally.

Purpose of this study was to investigate the effects of anterior cruciate ligament (ACL) repair on the gamma loop of the bilateral quadriceps femoris (QF). Maximal voluntary contraction (MVC) of knee extension and integrated electromyogram (I-EMG) of vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) were examined in uninjured and injured limbs of 18 patients and 10 normal subjects, before and after 20-min vibration applied to the QF. Mean percentage changes were calculated as: (pre-vibration value-post-vibration value)/pre-vibration value x 100. Patients were divided into two groups: short-term-group (tested /=18 months after ACL repair, n=10). Mean percentage changes of the four groups were compared with those of controls. Results indicated that changes of MVC and I-EMG on the uninjured and injured sides in short-term-group in response to vibration were significantly different from those of controls. There were no significant differences between uninjured sides in long-term and control groups. MVC and I-EMG of VM and RF of injured side in patients in the long-term-group in response to vibration were not different from those of controls. From these results, we concluded that this abnormality of the gamma loop in both injured and uninjured sides did not recover despite ACL reconstruction. However, the abnormality in uninjured side might recover >/=18 months after repair.