Differences in macrophage expression in induced membranes by fixation method - Masquelet technique using a mouse's femur critical-sized bone defect model.

INTRODUCTION: Masquelet's induced membrane technique (MIMT) is an emerging method for reconstructing critical-sized bone defects. However, an incomplete understanding of the underlying biological and physical processes hinders further optimization. This study investigated the effect of different bone-defect fixation methods on macrophage expression in an induced membrane using a novel mouse plate-fixed Masquelet model. METHODS: Mice were divided into Plate-fixed Masquelet (P-M), Intramedullary-fixed Masquelet (IM-M), Plate-fixed Control (P-C), and Back subfascial (B) groups. In the P-M and IM-M groups, a polymethylmethacrylate (PMMA) spacer was implanted into a 3 mm bone defect, while the defect in the P-C group remained unfilled. In group B, a spacer was inserted under the back fascia to examine membrane formation caused by a simple foreign body reaction. Tissues were collected at 1, 2, and 4 weeks postoperatively. Hematoxylin and eosin (H&E) staining and immunohistochemistry (CD68 and CD163: macrophage markers) were performed to assess macrophage expression within the membrane. qPCR was performed to measure the expression of CD68, CD163, and fibroblast growth factor 2 (FGF2). RESULTS: Four weeks post-operation, the P-M group presented with minimal callus growth, whereas the IM-M group exhibited vigorous growth. The P-M and IM-M groups displayed a tri-layered membrane structure, which is consistent with the results of previous studies. The IM-M group had significantly thicker membranes, whereas the P-M group exhibited higher expression levels of CD68, CD163, and FGF2. Group P-C showed no osteogenesis, whereas group B maintained a thin, cell-dense membrane structure. The P-M group consistently showed higher gene expression levels than the P-C and P-B groups. CONCLUSION: This study introduced a mouse plate fixation model for MIMT. The induced membranes could be adequately evaluated in this model. Induced membranes are formed by foreign body reactions to PMMA spacers; however, their properties are clearly different from those of simple foreign body reaction capsules and granulation tissues that infiltrate bone defects, suggesting that they are more complex tissues. The characteristics and expression of macrophages within these induced membranes varied according to the bone defect fixation method.

Age-Related Differences in the Limited Range of Motion of the Lower Extremity and Their Relation to Low Back Pain in Young Baseball Players: A Cross-Sectional Study of 1215 Players.

BACKGROUND: Age-related differences in the limited range of motion of the lower extremities and their relationship with low back pain in juvenile athletes have not been well assessed. This study investigated the relationship between low back pain and limited range of motion of the hip and knee in young baseball players during the baseball season. RESULTS: Participants comprised 1215 baseball players (216 pitchers, 999 fielders) aged 6-16 years who underwent medical checkups (self-completed questionnaire and physical examination). Of the 1215 players, 255 (21.0%) experienced seasonal low back pain requiring rest during the previous year. The prevalence of low back pain and a positive Thomas test, straight-leg-raising test, and heel-to-buttock test increased with age. Univariate analysis revealed that a positive heel-to-buttock test in both the throwing and non-throwing arm sides in the 11-12 age group and a positive Thomas test in the throwing arm side in the 13-14 age group were associated with seasonal low back pain (P = 0.0051, P = 0.021, and P = 0.048, respectively). Multivariate analysis, adjusted for factors associated with low back pain, showed significant associations between the positive heel-to-buttock test (odds ratio 1.75, 95% confidence interval 1.11-2.79; P = 0.016) and low back pain in players aged 11-14 years. CONCLUSIONS: A positive heel-to-buttock test is potentially associated with low back pain among juvenile baseball players. Particular attention should be paid to the limited range of motion of the knee joint and tightness of the quadriceps femoris muscle among baseball players with low back pain aged 11-14 years.

Impact of low back pain experience on future occurrence of shoulder pain in adolescent baseball players: A 1-year prospective cohort study.

BACKGROUND: Low back pain can affect musculoskeletal problems of the upper limb in adolescent overhead athletes. However, few epidemiological studies have examined this causal relationship. This prospective cohort study aimed to investigate the relationship between baseline low back pain experience and the occurrence of future shoulder and elbow pain among high school baseball players. METHODS: Participants comprised 383 high school baseball players from 43 high school baseball teams who had undergone baseline medical evaluations (a self-completed questionnaire and physical examination). The occurrence of shoulder and elbow pain during a 1-year follow-up and associations with baseline low back pain (positive subjective symptom during the last year at baseline) adjusted for flexibility of the scapulo-thoracic region, shoulder, and lower extremities, such as straight-leg raise angle (hamstring tightness), Thomas test (iliopsoas tightness), heel-buttock-distance (quadriceps tightness) and passive range of motion of the hip were investigated using multivariable analysis. RESULTS: A total of 307 players (80.2%) participated in the 1-year follow-up survey, with shoulder and elbow pain reported in 75 players (24.4%) and 119 players (38.8%), respectively, during follow-up. After adjusting for factors associated with shoulder pain using logistic regression modeling, significant associations between LBP experienced during the last year at baseline (odds ratio, 2.18; 95% confidence interval, 1.23-3.87; P = 0.0078) and new-onset of shoulder pain were noted. CONCLUSIONS: Baseline low back pain impacted future shoulder pain in high school baseball players during the 1-year follow-up. Management of shoulder pain warrants careful attention to low back pain.

Clinical characteristics of early-stage lumbar spondylolysis detected by magnetic resonance imaging in male adolescent baseball players.

BACKGROUND: Many adolescent athletes experience low back pain; the most common cause is lumbar spondylolysis. Although early identification of lumbar spondylolysis in adolescent athletes is critical, few studies have focused on identifying the early stages of spondylolysis in baseball players. This study aimed to investigate the clinical characteristics of early-stage spondylolysis in male adolescent baseball players. METHODS: The participants comprised male junior and high school baseball players. Before magnetic resonance imaging, we recorded their demographic data, low back pain characteristics, and physical findings (lumbar flexion, extension, Kemp's test and the provocative tenderness of a spinous process). After the imaging evaluation, the association among low back pain characteristics, physical findings and the final diagnosis (early-stage spondylolysis or not) were investigated using univariate and multivariable analyses. RESULTS: A total of 171 players were included in this study. Univariate analyses indicated that the characteristics associated with early-stage spondylolysis were longer duration of low back pain (P = 0.0085), low back pain-related interference while running (P = 0.0022), low back pain starting with laterality (P = 0.0001), lumbar extension (P = 0.022), positive Kemp's test (P = 0.020), and the tenderness of a spinous process (P = 0.0003). After adjusting for confounding factors (age and position), we found that early-stage spondylolysis was significantly associated with low back pain duration ≥4 weeks (odds ratio 3.13, 95% confidence interval 1.42-6.92; P = 0.0048), low back pain-related interference while running (odds ratio 2.89, 95% confidence interval 1.30-6.46; P = 0.0094), low back pain starting with laterality (odds ratio 2.78, 95% confidence interval 1.24-6.27; P = 0.0133), and the tenderness of a spinous process (odds ratio 3.00, 95% confidence interval 1.36-6.57; P = 0.0062). CONCLUSIONS: Male adolescent baseball players with early-stage spondylolysis might have low back pain duration of more than four weeks, low back pain-related interference while running, and a history of low back pain starting with laterality. The tenderness of a spinous process might be helpful in the diagnosis of early-stage spondylolysis in male adolescent baseball players.

The Relationship between Exercise-Induced Low Back Pain, the Fat Infiltration Rate of Paraspinal Muscles, and Lumbar Sagittal Balance.

Introduction: Exercise-induced low back pain (EILBP) is induced during anterior trunk tilting when walking or prolonged standing. In some elderly with chronic LBP, the pain is induced by EILBP. The paraspinal muscles play an important role in supporting the spine; therefore, a dysfunction of back muscles and kyphotic alignment are considered to be associated with EILBP. However, few reports are showing the relationship between EILBP and degenerative muscle changes. This study aimed to clarify the relationship between EILBP, degenerative changes of paraspinal muscles, and spinal alignment in an epidemiological study. Methods: A total of 324 subjects were included in the analysis. The presence of EILBP was determined through a medical interview and physical examination. The subjects underwent lumbar spine magnetic resonance image (MRI) and X-ray. The fat infiltration rate (FIR) of the multifidus, erector spinae, and psoas major were analyzed using MRI. For lumbar sagittal balance, L1 axis S1 distance (LASD) was measured using X-ray images. Multivariate logistic regression analysis was used to analyze the association between the presence of EILBP and FIR or LASD. Results: The prevalence of EILBP was 21% and it increased with age. The subjects with EILBP had statistically higher FIR of the multifidus, erector spinae, and psoas major than those without EILBP. There was a significant association between the presence of EILBP and higher FIR of the erector spinae at L1-2 and L5-S1 (p<0.05). However, there were no significant associations between EILBP and LASD. Conclusions: According to the results in this study, EILBP is not rare and the FIR of the erector spinae is associated with the presence of EILBP.

The influence of chronic medial epicondylar apophysitis on medial ulnar collateral ligament insufficiency-: a retrospective cohort study.

Background: This study aimed to investigate the effect of chronic traction apophysitis of the medial epicondyle (MEC) on medial ulnar collateral ligament (MUCL) insufficiency in high school baseball players. Methods: In this retrospective cohort study, 3034 of 6069 high school baseball players were enrolled. A self-reported questionnaire was distributed to investigate past history of elbow pain and elbow pain during the previous season. Physical examinations to assess tenderness on the MUCL and the elbow valgus stress test (EVST) were performed. Ultrasonography was performed to determine the presence of morphological abnormalities of the anteroinferior aspect of the MEC (MEC lesions). Results: Participants with MEC lesions had a significantly higher prevalence of past history of elbow pain, elbow pain during the previous season, MUCL tenderness, and positive EVST than those without MEC lesions (P < .05). Multivariate logistic regression analysis revealed that the participants with the fragmented type had the highest risk of past history of elbow pain (odds ratio [OR] = 3.94), elbow pain during the previous season (OR = 2.27), positive EVST (OR = 3.49), and the second highest risk of MUCL tenderness (OR = 2.01) followed by the irregular type (OR = 2.31). Participants with the hypertrophic type had the lowest risk of past history of elbow pain (OR = 2.08), elbow pain during the previous season (OR = 1.42), MUCL tenderness (OR = 1.09), and positive EVST (OR = 1.47). Conclusion: The presence of chronic non-healed traction apophysitis of the MEC in high school baseball players presented a significantly high risk of elbow pain and MUCL insufficiency.

The role of the flexor pronator muscles as dynamic stabilizers against elbow valgus stress in patients with medial ulnar collateral ligament insufficiency.

BACKGROUND: The flexor pronator muscles (FPMs) have been reported to act as dynamic stabilizers against valgus forces in overhead-throwing athletes. Several studies have demonstrated the anatomic, biomechanical, and clinical effects of the FPMs. However, no studies have investigated the in vivo kinematics of the FPMs against the valgus forces on the elbow. This study aimed to clarify the clinical contribution of the FPMs as dynamic stabilizers in medial ulnar collateral ligament (MUCL) insufficiency. METHODS: Eighteen baseball players with MUCL injury participated in this study. The elbow was flexed to 90°, and the forearm was placed in the supinated position. Manual valgus stress was applied to the elbow joint until maximal shoulder external rotation was achieved. The width of the ulnohumeral joint space was measured using ultrasonography, and any changes in medial elbow pain were recorded before and after isometric forearm pronation. RESULTS: All the subjects had MUCL tenderness and felt medial elbow pain when elbow valgus stress was applied. The width of the medial joint space was significantly larger on the injured side than on the healthy side (5.1 ± 1.0 mm vs. 3.2 ± 1.0 mm) with elbow valgus stress. During isometric forearm pronation, the width of the medial joint space was significantly decreased (3.1 ± 0.9 mm vs. 2.6 ± 1.0 mm) and medial elbow pain had completely diminished. CONCLUSION: Isometric forearm pronation reduces valgus stress-induced widening of the medial joint space and medial elbow pain in patients with MUCL insufficiency.

Sufficient duration of off-season decreases elbow disorders in elementary school-aged baseball players.

BACKGROUND: Several guidelines for the prevention of throwing injuries recommend a sufficiently long off-season; however, few studies providing scientific evidence to support these recommendations exist. Our study aimed to clarify the association between off-season duration and throwing elbow injuries among elementary school-aged baseball players. METHODS: This study enrolled 680 elementary school-aged baseball players who underwent medical checkups. The experience with elbow pain and the off-season duration were investigated via the administration of a self-completed questionnaire. Ultrasonographic assessment of the elbow joint was performed on the day of the medical checkup to assess for morphologic abnormalities. RESULTS: The prevalence of elbow pain and morphologic abnormalities of the medial epicondyle (medial epicondyle lesions) was significantly decreased when the subjects' off-season duration was longer. Multivariate analysis revealed that the risk of elbow pain was significantly lower in the group whose off-season lasted 1 to 2 months (odds ratio [OR], 0.32; 95% confidence interval [CI], 0.15-0.62; P = .0006) and in the group whose off-season lasted longer than 2 months (OR, 0.59; 95% CI, 0.37-0.95; P = .0316). The risk of medial epicondyle lesions was also significantly lower in the group whose off-season lasted 1 to 2 months (OR, 0.39; 95% CI, 0.22-0.67; P = .0005) and in the group whose off-season lasted longer than 2 months (OR, 0.36; 95% CI, 0.23-0.56; P < .0001). On the contrary, no significant correlation was found between capitellar osteochondritis dissecans and off-season duration. CONCLUSION: Off-season duration has a significant correlation with elbow pain and morphologic abnormalities of the medial elbow joint in elementary school-aged baseball players.