The clavicle DE CLAVICULA IN BEWEGING: BIOMECHANICA VAN AC EN SC GEWRICHT 1. 2. 3. 4. 5. Introduction Embryology Anatomy Biomechanics Function A Van Tongel MD PhD UZ Ghent AZ St Jan Brugge AZ St Lucas Brugge Zorgsaam Terneuzen Shouldergirdle = 3 joints 1. glenohumeral 2. acromioclavicular 3. sternoclavicular clavicle Not every animal has a clavicle Amphibia and reptiles à clavicle Mammals prehensile forelimbs (primates) and in bats à clavicle Cleidocranial dysplasia cleido = clavicle cranial = head dysplasia = abnormal forming 3 patient-based shoulder scores - American Shoulder and Elbow score (ASES) - Quick DASH - patient-based Constant Murley score (CS). 1
2. Embryology - Intramembranous ossification Results - 36 patients (27 female, 9 male) - mean age of 40 years - Bilateral absence (17), bilateral partial absence (16) and 3 patients had a total absence on one side and a partial absence on the other side. - The average patient-based CS at was 79, Quick DASH score was 11 and ASES score was 93. - no correlation between partial and total absences and the shoulder scores. the first bone in the body to ossify (5th week of fetal life) - Secundary ossification center - (medial and lateral) - Last bone to ossify in human body: medial clavicle (age of 22y) SC joint AC joint SC joint AC joint 2
Direct Motion: Bony framework for muscle insertions M Trapezius Retraction Indirect Motion: Bony framework for muscle insertions M Trapezius M Serratus anterior Bony framework for muscle insertions and origins Deltoid Pectoralis major Stenocleidomastoideus 3
Bony framework for muscle insertions and origins - The clavicular part pectoralis major à flexion, adduction - The anterior deltoid is weak in strict transverse flexion but assists the pectoralis major during shoulder transverse flexion / shoulder flexion (elbow slightly inferior to shoulders). Clavicle is working as a boom - maintain the appropriate length-tension relationship of the three muscles Clavicle is working as a crank à functionally increasing biomechanical lever arms à optimizing their strength. Prop: - The scapula has the tendency to go internal rotated, downward rotated and posterior tilted - The clavicle holds the scapula away from the body à Optimal position of the scapula Conclusion Prop: - Displaced fracture (shortening fracture) 1. The clavicle is not mandatory to move the arm 2. During evolution, changes in the anatomy of the clavicle allows humans to throw more accurately and harder: 1. Working as a prop 2. Workings as a boom 3. Workings as a crank 3. Disadvantage: two joints and a bone prone to pathology 4
Thank you www.terbruggen.be alexander.vantongel@uzgent.be UZ Ghent AZ St Jan Brugge AZ St Lucas Brugge Zorgsaam Terneuzen 5