Study Design: A retrospective, cross-sectional study was conducted to analyze the implications of asymmetric baseball movements on the incidence of spondylolysis.Purpose: This study aimed to evaluate the relationship between asymmetric movements and the laterality of spondylolysis.Overview of Literature: Baseball, characterized by its asymmetric throwing and batting, may disproportionately stress one side. Lumbar spondylolysis is a frequent cause of lower back pain in young athletes, particularly those involved in activities with consistent unilateral rotations such as baseball. However, whether a link exists between the laterality in spondylolysis and the dominant throwing/ batting side or whether disparities exist between pitchers and fielders remains unclear.Methods: The study included 85 players. Participants were divided into two groups: pitchers and fielders. The association between the laterality of spondylolysis and the throwing/batting side in the overall cohort and between the two groups was evaluated.Results: Among pitchers, 16 lesions appeared on the throwing side and 32 on the nonthrowing side (p =0.029). For fielders, no notable difference was observed between the two sides (p =0.363). Furthermore, batting preference did not influence the laterality of spondylolysis in either group.Conclusions: Adolescent baseball players, particularly pitchers, exhibited a higher incidence of lumbar spondylolysis on the side opposite their throwing arm. The findings of this study highlight the significant effect of asymmetrical sporting activities on the development of spondylolysis, to which pitchers are particularly susceptible.

Study Design: A retrospective cohort study.Purpose: To determine whether the preoperative pars defect length predicts bone union following the modified smiley face rod (mSFR) technique for lumbar spondylolysis and to identify a threshold for clinical decision-making.Overview of Literature: Lumbar spondylolysis is a common cause of low back pain in young athletes, often leading to pseudarthrosis that requires surgical intervention. Various techniques, including mSFR, address pseudarthrosis; however, the effect of preoperative pars defect length on bone union remains unclear.Methods: This study analyzed 75 pars defects in 38 patients treated with mSFR between 2014 and 2022. Pre- and postoperative pars defect lengths were measured using computed tomography (CT). Patients were categorized into bone union and nonunion groups based on CT findings up to 24 months postoperatively. Group comparisons of defect lengths were performed using the Mann-Whitney U test. Logistic regression was used to examine the association between preoperative defect length and nonunion. Receiver operating characteristic (ROC) curve analysis was used to identify the optimal threshold for preoperative defect length.Results: Bone union was achieved in 65 of 75 defects (87%). The preoperative pars defect length was significantly shorter in the bone union group than in the nonunion group (3.0 mm vs. 5.6 mm, p <0.001). A strong correlation was observed between pre- and postoperative pars defect lengths (Spearman’s rho=0.76). Logistic regression analysis revealed a significant association between a longer preoperative defect and nonunion (odds ratio, 1.89; 95% confidence interval, 1.29–2.72; p =0.001). ROC analysis revealed a cut-off value of 3.8 mm (sensitivity, 89%; specificity, 75%; area under the curve=0.86).Conclusions: Bone union following the mSFR technique may be influenced by the pars defect length, with larger preoperative defects potentially hindering bone union. The technique is most effective when the preoperative defect length is ≤3.8 mm.

On-field screening for ‘elbow injury in baseball’, a condition commonly seen in youth baseball players, was conducted over two years on 160 elementary school students in Ibaraki Prefecture, Japan. This on-field screening was conducted in collaboration with the Ibaraki Prefecture High School Baseball Federation. Pitchers, catchers, symptomatic players, and players who had previously experienced elbow pain were given a comprehensive evaluation that included a physical exam and ultrasound. Out of the 135 students who were successfully screened, 10 were diagnosed with osteochondritis dissecans of the humeral capitellum (OCD). Notably, seven among these were asymptomatic. This assessment identified limited range of motion and pain when extending their elbow as significant risk factors for OCD. An attempt at on-field screening for baseball elbow injuries in collaboration with the local baseball federation was introduced. The risk factors for OCD were identified. Considering these factors, more efficient screening will be possible in the next attempt.

Background: Quantifying the reproducibility of ultrasound measurements of the medial elbow joint space is essential for interpreting changes over time and for comparing raters. However, measurement reliability under controlled, acquisition-independent conditions remains limited. Herein, we aimed to quantify the intra-rater repeatability and inter-rater agreement for static medial elbow ultrasound measurements exclusively focusing on the analytical (measurement) component in healthy elbows. Methods: In this cross-sectional reliability study, 130 high-quality static ultrasound images from healthy elbows (13 elbows × 10 images each) were acquired by a single experienced examiner using standardized limb positioning and evaluated twice by seven orthopedic surgeons with varying ultrasound experience. The medial elbow joint space width was defined as the narrowest distance between the distal medial edge of the humeral trochlea and the proximal edge of the ulnar trochlear notch. Measurements were blinded and repeated following a ≥ 2-week interval. Reliability was assessed using the following intraclass correlation coefficients: ICC(1,1) for intra-rater repeatability and ICC(2,1) for inter-rater agreement, with error metrics expressed as the standard error of measurement (SEM) and the minimal detectable change at 95% confidence (MDC95). In addition, the mean, standard deviation, and range were calculated to provide reference values. Results: Intra-rater ICC(1,1) spanned 0.860–0.973, with SEM 0.14–0.39 mm (MDC95 0.39–1.09 mm). Using two-session averages, inter-rater ICC(2,1) was found to be 0.872, with SEM 0.30 mm (MDC95 0.82 mm). Systematic measurement biases were observed, while more experienced raters showed narrower error ranges. The mean medial elbow joint space width in healthy elbows was 2.8 ± 0.8 mm (range 1.5–4.8 mm). Conclusions: In this study of static ultrasound images from healthy elbows, intra-rater variability was found to be small, while inter-rater agreement was good among seven orthopedic surgeons with varying experience. These findings reflect measurement reproducibility under standardized static image conditions, independent of image acquisition variability. For practical interpretation, an inter-rater threshold of approximately 0.8–0.9 mm was required to exceed the measurement noise in this dataset, supporting the use of two-session averaging when feasible. Because the present study only evaluated the measurement component, these results likely represent the upper limit of achievable reliability in clinical practice.

Purpose: Acromial and scapular spine fractures after reverse shoulder arthroplasty (RSA) can impair post-operative outcomes; however, quantitative assessment of pre-fracture cortical changes remains challenging. This study evaluated longitudinal changes in inferior acromial cortical thickness after RSA using a computed tomography-based (CT-based) acromial coronal view. Methods: This multicentre retrospective cohort study included 44 patients who underwent RSA. The acromion was divided into three zones: I (lateral acromion), II (acromial base), and III (scapular spine). Inferior cortical thickness was measured at the centre of each zone. Changes were analysed from immediately post-operatively to one year and from one to two years in shoulders with corresponding CT scans. Cortical area was assessed as a secondary outcome, and the fracture cases were described separately. Results: From immediately post-operatively to one year ( n = 41), cortical thickness was unchanged in Zone I but increased in Zone II from 2.0 ± 0.5 to 2.4 ± 0.7 mm and in Zone III from 3.8 ± 1.0 to 4.6 ± 1.6 mm. From one to two years ( n = 28), Zones II and III showed further increases, whereas Zone I remained unchanged. Thickness changes correlated with cortical area changes (Spearman’s ρ = 0.55). Five shoulders (11.4%) developed fractures within two years, and delayed Zone II and III fractures showed marked preceding cortical thickening. Conclusion: Inferior acromial cortical thickening after RSA progressed selectively in Zones II and III, suggesting region-specific post-operative acromial remodelling. These findings may help clarify the differences in fracture pathomechanisms according to the location.

Ultrasound imaging of the medial elbow is crucial for early detection of Ulnar Collateral Ligament (UCL) injuries. Specifically, measuring the elbow joint space on ultrasound images enables the assessment of valgus instability. Automating this measurement requires a precisely annotated dataset to leverage recent advances in deep neural networks; however, no publicly available dataset has been proposed to date. In this work, we introduce a novel medial elbow ultrasound dataset with landmark annotations, facilitating the development of deep neural networks for joint space measurement. The dataset comprises 4,109 medial elbow ultrasound images from 22 participants, with precise landmark annotations on the humerus and ulna, performed under the supervision of three orthopedic surgeons. We evaluate several landmark detection models on our dataset and demonstrate its effectiveness in training models. Additionally, we propose Shape Subspace Refinement (SSR) to refine landmark heatmap peaks, improving the accuracy of heatmap-based landmark detection models. Furthermore, we show that the detected landmarks can be utilized for point-based segmentation of the humerus and ulna. The dataset is publicly available at [dataset link].