Cervical spondylolysis in a judo player: a case report and biomechanical analysis.

STUDY DESIGN: A case report and a biomechanical study using a finite element method. OBJECTIVES: To report a case with the cervical spondylolysis and to understand the biomechanics of the cervical spine with spondylolysis at C6. Cervical spondylolysis, although not a common spinal disorder, can occur in athletes. Presently, the exact pathology, natural history and biomechanics are not known. Thus, treatment strategies for this disorder in athletes are in controversy. To treat and/or advise patients with cervical spondylolysis, the cervical spine biomechanics regarding this disorder should be understood. METHODS: A case of a 12-year-old male judo player is presented. The patient presented with occipital and upper neck pain. Plain radiographs, reconstructed CT scan and MRIs of this patient were reviewed. Biomechanically, stress distributions were analyzed in response to 73.6 N axial compression and 1.5-Nm moment in flexion, extension, lateral bending, and axial rotation using a FE model of the intact ligamentous C3 to C7 segment. Bilateral spondylolysis was created in the model at C6. The stress results from the bilateral defect model were compared to the intact model predictions. RESULTS: Plain radiographs showed bilateral C6 spondylolysis, and grade I spondylolisthesis. MRI showed mild disc degeneration at C6/7. With conservative treatment, the symptoms disappeared. In the spondylolysis model, the maximum Von Mises Stresses at C6/7 increased in all cervical spine motions, as compared to the intact case. Specifically, in axial rotation, the stress increase was 3.7-fold as compared to the intact model. The range of motion at C6/7 increased in the spondylolysis model as well. Again, during axial rotation, the increase in motion was 2.3-fold when compared to the intact model. CONCLUSIONS: Cervical spondylolysis can cause biomechanical alterations, especially in axial rotation, leading to increased disc stresses and range of motion. The increased stresses in the disc and the hypermobility would be a dangerous condition for athletes participating in contact sports such as judo. Thus, we recommended that judo players with cervical spondylolysis should change to non-contact sports, such as jogging.

Cyclooxygenase-2 inhibitor delays fracture healing in rats.

BACKGROUND: Cyclooxigenase-2 (COX-2) inhibitors have been reported to delay fracture healing. To investigate the major inhibitory period of COX-2 inhibitors in fracture healing, we administrated etodolac, a COX-2-specific inhibitor, to a rat fracture model by altering the period of administration from early to late. METHOD: After closed fractures had been created at the middle of the femoral shafts in 12-week-old Wister rats, a standardized dose of etodolac was administrated in three ways: group I received it for 3 weeks, group II for just the first week after operation, and group III for just the third (final) week. Group IV was the vehicle control group. Bone maturation was estimated by radiographic scoring system, and mechanically by a three-point bending test. RESULTS AND INTERPRETATION: In both the radiographic and mechanical studies, groups I and II showed lower scores than group IV, indicating that even a short period of administration of a COX-2-specific inhibitor in the early phase of fracture healing creates a risk of delayed healing. blacksquare, square, filled.

Athletes with unilateral spondylolysis are at risk of stress fracture at the contralateral pedicle and pars interarticularis: a clinical and biomechanical study.

BACKGROUND: Unilateral spondylolysis is common in youths; its clinical and biomechanical features, especially effects on the contralateral side, are not fully understood. HYPOTHESIS: Unilateral spondylolysis predisposes the contralateral side to stress fracture, especially in athletes actively engaged in sporting activities involving torsion of the trunk. STUDY DESIGN: Case series and descriptive laboratory study. METHODS: Thirteen athletes younger than age 20 with unilateral spondylolysis were included. The contralateral pedicle and pars of spondylolytic vertebrae were examined using computed tomography and magnetic resonance imaging. Using a finite element model of the intact ligamentous L3-S1 segment, stress distributions were analyzed in response to 400-N axial compression and 10.6-N.m moment in flexion, extension, lateral bending, and axial rotation. Unilateral spondylolysis was created in the model at L5. The stress results from the unilateral defect model were compared to the intact model predictions and correlated to the contralateral defects seen in patients. RESULTS: Among 13 patients, there were 6 early-, 2 progressive-, and 5 terminal-stage defects. Three (23.1%) showed contralateral stress fracture. Among them, 2 belonged to the progressive-stage and 1 to the terminal-stage spondylolysis group. The remaining 4 patients in the terminal defect group showed stress reactions, such as sclerosis at the contralateral pedicle. In the finite element analysis model with an L5 left spondylolysis, the stresses at the contralateral and pars interarticularis were found to increase in all loading modes, with increases as high as 12.6-fold compared to the intact spine. CONCLUSIONS: Unilateral spondylolysis could lead to stress fracture or sclerosis at the contralateral side due to an increase in stresses in the region. CLINICAL RELEVANCE: Surgeons should be aware of possibility of contralateral stress fractures in cases in which patients, especially athletes engaged in active sports, show unilateral spondylolysis and persistent low back pain complaints.

Continuous muscle stretch prevents disuse muscle atrophy and deterioration of its oxidative capacity in rat tail-suspension models.

OBJECTIVE: The purpose of this study was to evaluate the effect of continuous muscle stretch on disuse-atrophied muscles. DESIGN: Sprague-Dawley rats were used and divided into five groups: control group, hind limb suspended for 3 and 7 days, and hind-limb suspension plus strenuous continuous muscle stretch for 3 and 7 days. In the hind-limb suspension plus strenuous continuous muscle stretch groups, the gastrocnemius-plantaris-soleus muscles were stretched using a plastic plate that immobilized the ankle joint at the maximum dorsal flexed position during the hind-limb suspension period. The intracellular energy metabolism of the working muscle during electric stimulation was evaluated by phosphorus-31 magnetic resonance spectroscopy in vivo. Changes in phosphocreatine, inorganic phosphate, and the intracellular pH were monitored to evaluate intramuscular oxidative capacity. Maximum tension and muscle wet mass were also measured. RESULTS: The oxidative capacity, muscle wet weight, and maximum tension decreased after hind-limb suspension. The muscle oxidative capacity at control levels was maintained during the first 3 days in muscles subjected to continuous strenuous stretch. It was also effective to prevent the decrease in muscle mass and maximum twitch tension during the initial 3 days. However, the effects did not persist. CONCLUSION: Continuous strenuous stretch was effective to prevent disuse muscle atrophy and its functional deterioration; however, its effects did not last long.

Muscular oxidative capacity in ovariectomized rats discussion on the endurance performance of female athletes with sports-related-amenorrhea.

The purpose of this study was to evaluate the effects of ovariectomy on intramuscular energy metabolism in adult rats. Based on the results, we discussed the skeletal muscle metabolism in female athlete with sports related amenorrhea. Twenty-five adult (20-week-old) Sprague-Dawley female rats were used. Fifteen rats underwent ovariectomy (OVX group), and the other ten rats were sham-operated (Sham group). One and four weeks after surgery, muscular oxidative capacity was measured using (31)P-MR spectra of the gastrocnemius-plantaris-soleus (GPS) muscles group at rest and during electric stimulation. Wet weight and maximum tension of the whole GPS muscles group were also measured. From the MRS measurements, the muscle oxidative capacity in the OVX group was significantly lower than that in the Sham group (p < 0.05) at both one and four weeks after surgery. The muscle's wet weight one week after surgery in the OVX group was the same as the Sham group, while four weeks after surgery it was significantly greater than that in the Sham group (p < 0.05). There were no significant differences in maximum tension among the groups. In conclusion, in adult rats the oxidative capacity decreased due to ovariectomy despite the increase in muscle weight. It is suggested that the muscular endurance capacity in female adult athletes with sports related amenorrhea may deteriorate. Key PointsIn vivo measurement of muscular energy metabolism.Effects of ovariectomy on muscle function and volume.Muscle function of sports-related amenorrhea.

Electrical stimulation prevents deterioration of the oxidative capacity of disuse-atrophied muscles in rats.

INTRODUCTION: The purpose of this study was to evaluate the effects of electrical stimulation on disuse-atrophied muscles. METHODS: Sprague-Dawley rats were used and divided into three groups: control (C), hind-limb suspended for 7 d (HS), and HS plus transcutaneous electrical stimulation for 7 d (ES). In the ES group, transcutaneous electrical stimulation was induced at 1 Hz for 1 h every day to condition the gastrocnemius-plantaris-soleus muscles. Muscle oxidative capacity was evaluated by 31P-MRS in vivo. Maximum tension and muscle wet mass were also measured. RESULTS: Muscle oxidative capacity decreased within 1 wk in HS; however, it was maintained when electric stimulation was applied to the suspended limb. The maximum twitch tension in HS was significantly smaller than that in C (p < 0.05), while in ES it did not differ from that in C. The muscle mass was significantly smaller in the HS and ES groups compared to C (p < 0.05). CONCLUSION: These data indicated that twitch electrical stimulation was effective in preventing deterioration of muscle functions, such as maximum tension and oxidative capacity, induced by 1 wk of disuse.

Cyclooxygenase-2 inhibitor inhibits the fracture healing.

We investigated the effects of cyclooxigenase-2 (cox-2) on fracture healing. After closed non-displaced fractures were created at the middle of both femoral shafts in 12-week-old Wister rats, a cox-2 specific inhibitor, etodolac (20 mg/day; intra-peritoneal) was administered every day for three weeks (E group). Bone union and callus formation were evaluated by weekly radiographs. Three weeks after surgery, the mechanical strength of the fractured femur was evaluated by a three-point-bending test. These results were compared with those of a vehicle control group (V group). The fracture healing score on radiographs in the E group three weeks after the surgery was 3.3 +/- 0.9, and in the V group it was 5.8 +/- 1.5, indicating that fracture healing was significantly poorer in the E than the V group (p < 0.05). From the three point bending test, the ultimate strength and stiffness of etodolac-treated fractured femurs were shown to be significantly lower than those in vehicle control group (p < 0.05). Mechanically, femurs of etodolac treated rats were weaker than those of control rats. Thus, it was concluded that etodolac, a cox-2 specific inhibitor, inhibited fracture healing.

A relative high dose of vitamin E does not attenuate unweighting-induced oxidative stress and ubiquitination in rat skeletal muscle.

We previously reported that intragastric administration of cysteine could be beneficial to prevent unweighting-induced ubiquitination and degradation of muscle protein in association with redox regulation [Ikemoto et al., Biol. Chem., 383 (2002), 715-721]. In this study, we investigated whether vitamin E, another potent antioxidative nutrient, also had beneficial effects on the muscle protein catabolism. However, daily intragastric supplementation of 1.5 or 15 mg/rat of alpha-tocopherol did not prevent weight loss of hindlimb skeletal muscle in tail-suspended rats. To elucidate the reason for the non-effectiveness of vitamin E, we further examined concentrations of oxidative stress markers, ubiquitination of muscle proteins and fragmentation of myosin heavy chain in gastrocnemius muscle of rats daily treated with 15 mg of alpha-tocopherol. Unexpectedly, vitamin E increased concentrations of glutathione disulfide and thiobarbituric acid-reactive substance and decreased glutathione level in the muscle, compared with those of vehicle treatment, indicating that vitamin E enhanced unweighting-induced oxidative stress in skeletal muscle. The vitamin E supplementation did not suppress the ubiquitination of muscle proteins and fragmentation of myosin heavy chain caused by tail-suspension. Our results suggest that supplementation of a relative high dose of vitamin E could not inhibit ubiquitin-dependent degradation of muscle protein in tail-suspended rats possibly due to its prooxidant action.

The most effective exercise for strengthening the supraspinatus muscle: evaluation by magnetic resonance imaging.

BACKGROUND: Electromyography has been used to determine the best exercise for strengthening the supraspinatus muscle, but conflicting results have been reported. Magnetic resonance imaging T2 relaxation time appears to be more accurate in determining muscle activation. PURPOSE: To determine the best exercises for strengthening the supraspinatus muscle. STUDY DESIGN: Criterion standard. METHODS: Six male volunteers performed three exercises: the empty can, the full can, and horizontal abduction. Immediately before and after each exercise, magnetic resonance imaging examinations were performed and changes in relaxation time for the subscapularis, supraspinatus, infraspinatus, teres minor, and deltoid muscles were recorded. RESULTS: The supraspinatus muscle had the greatest change among the studied muscles in relaxation time for the empty can (10.5 ms) and full can (10.5 ms) exercises. After the horizontal abduction exercise the change in relaxation time for the supraspinatus muscle (3.6 ms) was significantly smaller than that for the posterior deltoid muscle (11.5 ms) and not significantly different from that of the other muscles studied. CONCLUSION: The empty can and full can exercises were most effective in activating the supraspinatus muscle.