A novel technique for determining scapulohumeral translation: a case-control and inter-rater reliability study

Alterations in scapular and glenohumeral kinematics in patients with shoulder dysfunction have been recognized by this studies authors' and described in multiple other studies available in the literature. A reliability study was developed to assess a new technique for measuring scapulohumeral kinematics. Previous scapular position measuring techniques may require expensive equipment which decreases clinical utility. Other techniques require identification of multiple anatomic landmarks that may decrease accuracy, precision, and reliability.

A sample of asymptomatic controls and symptomatic study subjects were recruited. Each subject had markers placed on each acromion and stood at a standardized distance in front of a light. The shadow projected from the acromial marker onto a standardized, data collection board was measured during the resting, flexion, and scaption positions for bilateral shoulders. The horizontal and vertical translations of the shadows were measured compared to the resting point for both flexion and scaption.

The scapula translated superiorly and medially during both flexion and scaption movements in all subjects and controls. There was good inter-rater reliability for measuring scapular translation with scaption (ICC= 0.81) and moderate reliability for measuring scapular translation with flexion (ICC = 0.62). There was increased superior and medial scapular translation in the subjects with flexion (p= 0.004 and p=0.002) and scaption (p= 0.01 and p=0.007) in the symptomatic shoulder compared to the asymptomatic shoulder. Superior scapular translation with flexion (p=0.0003) and scaption (p=0.006) and medial scapular translation with flexion (p<0.0001) and scaption (p<0.0001) was greater in the symptomatic subjects compared to controls.

The scapula translates both superiorly and medially with flexion and scaption in asymptomatic and symptomatic subjects. After shoulder surgery, patients have increased superior and medial translation of the scapula compared to 1) their asymptomatic shoulder and 2) an asymptomatic control group. The current technique has good inter-rater reliability (ICC=0.81) when measuring scaption and moderate reliability when measuring flexion (ICC=0.62).

III Diagnostic Case-Control Study.