Takanobu Abe

Analysis of strain distribution in the medial collateral ligament using a photoelastic coating method

The strain distribution over the entire medial collateral ligament (MCL) was measured using a photoelastic coating method. This new approach utilized a polyurethane monomer as a photoelastic coating film. The initial experiments investigating MCL strain measurement showed that this film had a high sensitivity for strain and good adhesion to the ligament. It was confirmed that strain distribution could be obtained qualitatively over the entire ligament using this method. The mechanism of MCL injury was studied by applying this polyurethane coating film to the entire MCL in a femur-MCL-tibia complex. When simple tension was applied to the complex, strain concentrations were centred at the tibial insertion site, and all the specimens ruptured at the MCL tibial insertion site. With application of a valgus bending moment, increased strain was seen in the MCL from the medial femoral condyle to the medial epicondyle. Histological analysis demonstrated midsubstance ligament ruptures in this same region. For both tests, rupture sites and increased strain concentration sites correlated. In addition, an impingement phenomenon of the MCL on the medial femoral condyle can be seen during application of valgus force, and this phenomenon may explain the higher incidence of MCL injuries on the femoral side seen in the clinical setting. This polyurethane coating method allows for direct and visual measurements, and can qualitatively measure the strain behaviour over the entire MCL surface. This new technique represents a significant improvement over previous point-by-point strain measurement methods.

Deterioration of the femoral articular surface after meniscal repair evaluated by second-look arthroscopy: comparison with partial meniscectomy

Abstract To evaluate whether meniscal repair can protect the cartilage deterioration, changes in articular cartilage of the involved compartment were evaluated by reviewing the videotapes recorded at the time of operations (33 meniscal repairs, 18 meniscectomies) and second-look arthroscopies. Meniscal repairs gave marginally better results than meniscectomies but the articular cartilage was often deteriorated in cases that had the incompletely healed meniscus or the unhealed meniscus. Although completely healed menisci restore the meniscal function and protect the articular damage, unsuccessful meniscal healings sometimes provoke degeneration of the articular cartilage.

Frequency analysis of surface EMG on knee extensors with anterior cruciate ligament insufficiency

Abstract The muscle strength of knees with an injured anterior cruciate ligament (ACL) is generally assessed by the peak of the isokinetic muscle contraction. However, assessment of the characteristics of muscle contraction, such as the contraction velocity and contraction endurance, has been largely ignored due to a lack of data. In this study, we have performed frequency analysis of the surface electromyograms during sustained isometric contraction of the quadriceps femoris muscle in 22 knees with ACL deficiency to evaluate the characteristics of muscle contraction. Concerning the time-related changes in the mean power frequency (MPF), the decrease with time was smaller than normal (reflecting a deficiency in the number of fast-twitch fibers) in the rectus femoris and vastus medialis muscles of the injured limb in many subjects. However, a slightly different pattern was observed in the vastus lateralis muscle, which showed little difference between the injured and intact limbs. Therefore the vastus lateralis muscle was considered to be less affected by an ACL deficiency than the other two muscles. The time-related changes in the MPF in the ACL deficient limb were clearly different from those in the intact limb and a deficiency in the fast-twitch fibers was suggested. Therefore a frequency analysis of the surface electromyograms was considered to allow detection of qualitative changes, such as of muscle fiber deficiency, as well as detection of changes in the simple muscle strength.

Frequency Analysis of Surface EMG on Knee Extensors in Cases with ACL Insufficiency. Per- and Post-operative Comparison.

Six cases (4 males, 2 females) with ACL insufficiency were evaluated by frequency analysis of surface EMG preoperatively and at 4 or 6 months after surgery. Patients ranged in age from 17 to 41 years (mean 27 years). The surface EMG was recorded from above the quadriceps muscle during sustained (30 sec.) isometric contraction. The recorded EMG was computerized by spectrum analyzer. Results were as follows. Mean power frequency showed a more sudden decrease post-operatively compared to per-operative values. In other words, the higher (>81Hz) frequency zone was increased post-operatively compared with pre-operation. We concluded that type II fibres on knee extensors were actived by reconstrution and rehabilitation.