Vertebral Somatic Dysfunction

Osteopathic literature identifies two types of vertebral somatic dysfunction that are based on Laws I and II.

Vertebral somatic dysfunction is classified as Type I when a positional asymmetry is identified with the spine in a neutral sagittal plane position. Type I somatic dysfunction is multi-segmental and adaptive in nature. Its positional asymmetry presents in accordance with Law I, therefore, side bending and rotation of the motion segment occur to opposite sides. With positional testing, a neutral (Type I) dysfunction is identified when multiple segments have posterior transverse processes on the same side in all three testing positions. The positional asymmetry of the transverse processes is decreased in the flexed and extended test positions. A scoliotic spinal curve is an example of this type of dysfunction. Groups of vertebra are treated as a functional unit when addressing neutral (Type I) vertebral somatic dysfunction.

Type II vertebral somatic dysfunction reveals a positional asymmetry when the spine is in a non-neutral (flexed or extended) sagittal plane position. Type II dysfunction is usually found at a single spinal segment and is traumatic in origin. Its positional asymmetry presents in accordance with Law II, therefore, side bending and rotation of the motion segment occurs to the same side. With positional testing, a non-neutral (Type II) dysfunction is identified if one transverse process is more posterior in the flexed position (revealing an asymmetry) and then becomes more symmetrical in the extended position. A non-neutral (Type II) dysfunction is also identified if one transverse process is more posterior in the extended position (revealing an asymmetry) and then becomes more symmetrical in the flexed position.

Type II vertebral somatic dysfunction is commonly found in the athletic setting. It typically involves a limitation of motion into only one quadrant (i.e. flexion, right side bending and right rotation). A single zygapophyseal joint is hypothesized to be the site of limited motion. Muscle hypertonus, joint subluxation or loose bodies are proposed causes of this single quadrant limitation of segmental motion. The normalization of muscle tone of intersegmental muscles (e.g. multifidus) is the aim of muscle energy techniques used to treat Type II dysfunction. Restoring normal muscle tone to intersegmental muscles is thought to allow normal motion the vertebral segment. Treatment is directed at a single vertebral motion segment when addressing non-neutral (Type II) vertebral somatic dysfunction.