Takashi Hasegawa

Lumbar lordosis influences load transmission in the lumbar spine, but its effects on stress in the anterior cortical bone of the vertebral bodies remain unclear. This study investigated how lumbar lordosis angle (LL) affects vertebral stress. A finite element model from T12 to the sacrum was constructed from computed tomography images of a cadaver from a 66-year-old male donor. Three models with identical bone geometry and material properties but LL values of 50°, 30°, and 15° were analyzed under a 300 N compressive load and the same load combined with a 5 N·m flexion moment. Mean von Mises stress and the 95th percentile of von Mises stress were evaluated in the anterior cortical bone of L1–L5, and vertebral-level distributions were normalized to L1. Under both loading conditions, the LL15° model showed higher von Mises stress than the LL50° and LL30° models at all vertebral levels. Adding the flexion moment further increased stress in all models. Normalized stress was lowest at L3 in the LL50° and LL30° models, whereas values in the LL15° model remained relatively close to L1 across L2–L5. These findings suggest that models with lower LL exhibit higher anterior cortical bone stress and altered vertebral-level stress distributions.

Approaches to preserve corticomotor excitability (CE) are attracting interest as a treatment for pain-induced changes in neural plasticity. We determined the effects of mirror therapy (MT) on skeletal muscle pain. Fifteen healthy adults who received hypertonic saline injections (5.8% NaCl, 0.2 mL) into the first dorsal interosseous (FDI) muscle of the right hand to induce experimental skeletal muscle pain were assigned to either the “MT and injection” or “injection only” group. Post-injection, the “MT and injection” group observed their left index finger abducting and adducting for 4 min, creating the illusion that the right index finger was moving. The “injection only” group remained at rest. CE and pain were assessed by measuring motor-evoked potentials (MEPs) of the right FDI triggered by transcranial magnetic stimulation and the numerical rating scale (NRS), respectively. MEP amplitudes were significantly higher in the “MT and injection” group, a trend that persisted post-MT intervention (MT intervention; p < 0.01, post-1; p < 0.05). The time for the NRS score to reach 0 was notably shorter in the “MT and injection” group (p < 0.05). Our preliminary results suggested that MT decreases CE and pain in skeletal muscles, potentially preventing neural plasticity changes associated with skeletal muscle pain and providing early pain relief.

[Purpose] This study aimed to determine the relationship between preoperative and discharge assessments in patients undergoing around-the-knee osteotomy. [Participants and Methods] We enrolled patients admitted to our hospital who underwent around-the-knee osteotomy. We measured knee joint range of motion, pain numeric rating scale, pain catastrophizing scale, hospital anxiety and depression scale, and 10-m walk time were measured preoperatively and before discharge. Pre-post comparisons and correlation testing were performed. [Results] A total of 18 patients were analyzed. Resting and exercise pain numeric rating scale, knee flexion and extension range of motion, and pain catastrophizing scale were significantly better during discharge. A significant correlation was observed between the preoperative pain catastrophizing scale total score and 10-m walking time, knee flexion and extension range of motion, pain catastrophizing scale total score, and hospital anxiety and depression scale-depression subscale preoperatively. [Conclusion] Appropriate postoperative rehabilitation after around-the-knee osteotomy improved physical function and cognitive/psychological evaluation at discharge. The correlation between the preoperative pain catastrophizing scale total score and 10-m walking time at discharge suggests that the prolonged walking pain that occurred preoperatively may have affected the cognitive and psychological evaluation of pain.

Continuous repetition of motor imagery leads to mental fatigue. This study aimed to examine whether fatigue caused by motor imagery training affects improvement in performance and the change in corticospinal excitability. The participants were divided into “physical practice training” and “motor imagery training” groups, and a visuomotor task (set at 50% of maximal voluntary contraction in participants) was performed to assess the training effect on fatigue. The measurements were recorded before and after training. Corticospinal excitability at rest was measured by transcranial magnetic stimulation according to the Neurophysiological Index. Subjective mental fatigue and muscle fatigue were assessed by using the visual analog scale and by measuring the pinch force, respectively. Additionally, the error area was evaluated and calculated at pre-, mid-, and post-terms after training, using a visuomotor task. After training, muscle fatigue, subjective mental fatigue, and decreased corticospinal excitability were noted in both of the groups. Moreover, the visuomotor task decreased the error area by training; however, there was no difference in the error area between the mid- and post-terms. In conclusion, motor imagery training resulted in central fatigue by continuous repetition, which influenced the improvement in performance in the same manner as physical practice training.