Back height is measured from the seat to the floor of the axilla with the shoulder flexed to 90 degrees. What adjustment is made to place the back below the inferior angles of the scapulae?

Back height is measured from the seat to the floor of the axilla with the shoulder flexed to 90 degrees. What adjustment is made to place the back below the inferior angles of the scapulae?

• A. Subtract 4 inches
• B. Add 4 inches
• C. Subtract 2 inches
• D. Add 2 inches

Answer: (A)

The measurement from seat to axilla with the shoulder at 90 degrees is used to size the back height of seating. To place the back below the inferior angles of the scapulae, you lower that height by about 4 inches. Subtracting 4 inches moves the backrest down enough so the inferior angles don’t press against it, allowing the scapulae to rest against the back without impingement and preserving comfortable shoulder movement. If you subtracted less than 4 inches, the backrest might still contact the inferior angles; adding height would place the backrest higher and risk pressing into that area.

The measurement from seat to axilla with the shoulder at 90 degrees is used to size the back height of seating. To place the back below the inferior angles of the scapulae, you lower that height by about 4 inches. Subtracting 4 inches moves the backrest down enough so the inferior angles don’t press against it, allowing the scapulae to rest against the back without impingement and preserving comfortable shoulder movement. If you subtracted less than 4 inches, the backrest might still contact the inferior angles; adding height would place the backrest higher and risk pressing into that area.