Reliability of Power Spectral Analysis of Surface Electromyogram Recorded during Sustained Vastus Medialis Isometric Contraction in Assessment of Muscle Fatigability

The aim of this study was to determine the within-day and between-days reliability of surface electromyographic (EMG) power spectral analysis in assessing fatigability of the vastus medialis (VM) muscle during knee and hip flexion under constant load application. The subjects were 13 healthy adult men free of knee abnormalities. Surface EMG was recorded from vastus medialis obliquus (VMO) and vastus medialis longus (VML) during sustained isometric contractions at 60% of maximal voluntary contraction until exhaustion on the leg press machine (static leg press test). Linear regression analysis was applied to median frequency (MF) time series to calculate initial MF and MF slope. For VMO and VML, the initial MF showed moderate to high reliability, while the MF slope showed high reliability (Intraclass correlation coefficient (ICC) = initial MF: 0.63 - 0.92, MF slope: 0.70 - 0.86). The results demonstrated that spectral analysis of surface EMG recording during isometric VM muscle contraction has high within-day and between-days reliability in the assessment of fatigability of the VMO and VML.

Chronic training status affects muscle excitation of the vastus lateralis during repeated contractions

This study examined electromyographic amplitude(EMGRMS)-force relationships during repeated submaximal knee extensor muscle actions among chronic aerobically-(AT),resistance-trained(RT),and sedentary(SED)individuals.Fifteen adults(5/group)attempted 20 isometric trapezoidal muscle actions at 50%of maximal strength.Surface electromyography(EMG)was recorded from vastus lateralis(VL)during the muscle actions.For the first and last successfully completed contractions,linear regression models were fit to the log-transformed EMGRMS-force relationships during the linearly increasing and decreasing segments,and the b terms(slope)and a terms(antilog of y-intercept)were calculated.EMGRMS was averaged during steady force.Only the AT completed all 20 muscle actions.During the first contraction,the b terms for RT(1.3010.197)were greater than AT(0.9100.123;p?0.008)and SED(0.9120.162;p?0.008)during the linearly increasing segment,and in comparison to the linearly decreasing segment(1.0180.139;p?0.014),respectively.For the last contraction,the b terms for RT were greater than AT during the linearly increasing(RT?1.3730.353;AT?0.8830.129;p?0.018)and decreasing(RT?1.5260.328;AT?0.9700.223;p?0.010)segments.In addition,the b terms for SED increased from the linearly increasing(0.9680.144)to decreasing segment(1.2680.126;p?0.015).There were no training,segment,or contraction differences for the a terms.EMGRMS during steady force increased from the first-([64.0851.68]μV)to last-contraction([86.7349.55]μV;p?0.001)collapsed across training statuses.The b terms differentiated the rate of change for EMGRMS with increments in force among training groups,indicating greater muscle excitation to the motoneuron pool was necessary for the RT than AT during the linearly increasing and decreasing segments of a repetitive task.

Combination of medial patellofemoral ligament reconstruction with vastus medialis advancement for chronic patellar dislocation

Background The medial patellofemoral ligament （MPFL） reconstruction is popular in clinical practice for chronic patellar dislocation; however, the combination with vastus medialis advancement is rare. The aim of this study was to evaluate the clinical outcome of the combination of MPFL reconstruction with vastus medialis advancement.Methods We retrospectively analyzed 69 patients with chronic patellar dislocation between July 2004 and October 2008： twenty eight cases with isolated MPFL reconstruction （group Ⅰ）, forty one cases with the combination of MPFL reconstruction with vastus medialis advancement （group C）. All patients had CT scans available for review with knee flexion at 30 degree, on which the congruence angle, patellar tilt angle and patellar lateral shift were measured. Physical apprehension tests were examined and the redislocation was recorded. In addition, knee function was evaluated using the Kujala score and subjective questionnaires.Results Patients were followed up for a mean of 42 months （12-65 months） without a recurrent dislocation reported.Postoperatively, all indexes on CT scan were within the normal range without a statistical difference between the two groups. Results from the apprehension test showed eight patients in group Ⅰ and three in group Chad patellar lateral shift exceeding 1.5 cm with a hard end point （P 〈0.05）. The Kujala score improved significantly from 51.3±4.5 to 79.9±6.2 in group Ⅰ and from 53.7±5.2 to 83.9±6.5 in group C （P 〉0.05）. However, the subjective questionnaire revealed a significant difference （P 〈0.05）, including 12 excellent, seven good and nine fair in group Ⅰ and 30 excellent, six good and five fair in group C.Conclusion The combination of MPFL reconstruction with vastus medialis advancement is better than isolated reconstruction to improve the subjective effects and decrease the patellar instability rate for chronic patellar dislocation.

Significance of Diffusion Tensor Imaging of Vastus Medialis Oblique in Recurrent Patellar Dislocation

Background： Numerous studies have investigated the influence of osseous factors on patellofemoral joint instability, but research on the influence of dynamic muscle factors in vivo is still in the exploratory stage. This study aimed to use magnetic resonance imaging （MRI） and diffusion tensor imaging （DTI） to evaluate vastus medialis oblique （VMO） fiber bundles in patients with recurrent patellar dislocation to explore the changes in muscle morphology and function. Methods： This prospective study involved 30 patients （7 males and 23 females; average age, 21.4 ± 3.8 years） clinically diagnosed with recurrent patellar dislocation in Peking University Third Hospital and 30 healthy volunteers matched for age, sex, and body mass index in our medical school between January 2014 and October 2014. None of the patients had a recent history of traumatic patellar dislocation or transient patellar dislocation. All patients underwent conventional MRI and DTI of the knee. The cross-sectional area of the VMO on MRI and the fractional anisotropy （FA）, apparent diffusion coefficient （ADC）, and primary （λ1）, secondary （λ2）, and three-level characteristic （λ3） values on DTI were measured. The independent-samples t-test was used to compare these parameters between the two groups. Results： Compared with the control group, the patient group showed significantly higher FA values （0.39 ± 0.05 vs. 0.33 ± 0.03） and significantly lower ADC （1.51 ± 0.13 vs. 1.58± 0.07）, λ2 （4.96 ±0.13 vs. 5.04 ± 0.07）, and λ3 values （4.44 ± 0.14 vs. 4.58 ± 0.07; t = 5.99, t = -2.58, t = 3.02, and t = -4.88, respectively： all P 〈 0.05）. Cross-sectional VMO area and λ1 values did not differ between the two groups （t = 1.82 and t = 0.22, respectively; both P 〉 0.05）. Conclusions： The functional status of the VMO is closely associated with recurrent patellar dislocation. MRI, especially DTI （FA, ADC, λ2, and ,λ3）, can detect early changes in VMO function and might lhcilitate the noninvasive monitoring of the functional status of the VMO in patients with recurrent patellar dislocation.

Early electrical field stimulation prevents the loss of spinal cord anterior horn motoneurons and muscle atrophy following spinal cord injury

Our previous study revealed that early application of electrical field stimulation（EFS） with the anode at the lesion and the cathode distal to the lesion reduced injury potential, inhibited secondary injury and was neuroprotective in the dorsal corticospinal tract after spinal cord injury（SCI）. The objective of this study was to further evaluate the effect of EFS on protection of anterior horn motoneurons and their target musculature after SCI and its mechanism. Rats were randomized into three equal groups. The EFS group received EFS for 30 minutes immediately after injury at T_（10）. SCI group rats were only subjected to SCI and sham group rats were only subjected to laminectomy. Luxol fast blue staining demonstrated that spinal cord tissue in the injury center was better protected; cross-sectional area and perimeter of injured tissue were significantly smaller in the EFS group than in the SCI group. Immunofluorescence and transmission electron microscopy showed that the number of spinal cord anterior horn motoneurons was greater and the number of abnormal neurons reduced in the EFS group compared with the SCI group. Wet weight and cross-sectional area of vastus lateralis muscles were smaller in the SCI group to in the sham group. However, EFS improved muscle atrophy and behavioral examination showed that EFS significantly increased the angle in the inclined plane test and Tarlov＇s motor grading score. The above results confirm that early EFS can effectively impede spinal cord anterior horn motoneuron loss, promote motor function recovery and reduce muscle atrophy in rats after SCI.

Posterolateral dislocation of the knee:Recognizing an uncommon entity

Posterolateral dislocations of the knee are rare injuries.Early recognition and emergent open reduction is crucial.A 48-year-old Caucasian male presented with right knee pain and limb swelling 3 d after sustaining a twisting injury in the bathroom.Examination revealed the pathognomonic anteromedial "pucker" sign.Anklebrachial indices were greater than 1.0 and symmetrical.Radiographs showed a posterolateral dislocation of the right knee.He underwent emergency open reduction without an attempt at closed reduction.Attempts at closed reduction of posterolateral dislocations of the knee are usually impossible because of incarceration of medial soft tissue in the intercondylar notch and may only to delay surgical management and increase the risk of skin necrosis.Magnetic resonance imaging is not crucial in the preoperative period and can lead to delays of up to 24 h.Instead,open reduction should be performed once vascular compromise is excluded.