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.

Stiffness of individual quadriceps muscle assessed using ultrasound shear wave elastography during passive stretching

Background: Until recently it has not been possible to isolate the mechanical behavior of individual muscles during passive stretching. Muscle shear modulus(an index of muscle stiffness) measured using ultrasound shear wave elastography can be used to estimate changes in stiffness of an individual muscle. The aims of the present study were(1) to determine the shear modulus—knee angle relationship and the slack angle of the vastus medialis oblique(VMO), rectus femoris(RF), and vastus lateralis(VL) muscles;(2) to determine whether this differs between the muscles.Methods: Nine male rowers took part in the study. The shear modulus of VMO, RF, and VL muscles was measured while the quadriceps was passively stretched at 3°/s. The relationship between the muscle shear modulus and knee angle was plotted as shear modulus—knee angle curve through which the slack angle of each muscle was determined.Results: The shear modulus of RF was higher than that of VMO and VL when the muscles were stretched over 54°(all p < 0.01). No significant difference was found between the VMO and VL(all p > 0.05). The slack angle was similar among the muscles: 41.3°± 10.6°, 44.3°± 9.1°, and 44.3°± 5.6° of knee flexion for VMO, RF, and VL, respectively(p = 0.626).Conclusion: This is the first study to experimentally determine the muscle mechanical behavior of individual heads of the quadriceps during passive stretching. Different pattern of passive tension was observed between mono-and bi-articular muscles. Further research is needed to determine whether changes in muscle stiffness are muscle-specific in pathological conditions or after interventions such as stretching protocols.