Clustering of shoulder movement patterns using K-means algorithm based on the shoulder range of motion

Context Categorization in medicine is used to enhance understanding of a disease or syndrome and apply it to treatment and is based on human clinical experience or theory. Cluster analysis using the K-means algorithm is an unsupervised machine learning method that classifies clusters based on numerical data. The purpose of this study was to classify subjects into clusters using K-means algorithm based on shoulder range of motion (ROM) and identify the characteristics of the clusters. Design Cross-sectional study Methods 551 data samples measured in the 5th Size Korea Anthropometric Survey (2003∼2004) were used. Clustering was performed using the K-means algorithm, and the appropriate number of clusters was determined using the elbow curve and silhouette score. The characteristics of the clusters were analyzed by comparing the average values of shoulder ROM in the clusters. Results The appropriate number of classifications of clusters according to the shoulder ROM was 8. Clusters 1 and 5 had the lowest flexion range, and clusters 7 and 8 had low internal rotation and shoulder horizontal adduction ranges. Clusters 2 and 6 exhibited the highest flexion and overall high flexibility. Clusters 3 and 4 showed moderate flexion ranges but low horizontal adduction ranges. Shoulder movement patterns were classified into a total of 8 clusters according to the shoulder ROM. Conclusion Based on this clustering system, it was possible to identify the pattern of shoulder movement in ordinary people, and it could be used as basic data to identify and treat diseases or syndromes according to the pattern. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study did not receive any funding ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: This study was approved by the Public Institutional Review Board Designated by Ministry of Health and Welfare I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes This study used data samples obtained from the 5th anthropometric survey (2003-2004) of the Size Korea (Korean anthropometric survey) project of the Korean Agency for Technology and Standards.