Spinal locking is necessary for long-lever, high-velocity low-amplitude (HVLA) techniques to localize forces and achieve cavitation at a specific vertebral segment.'-7 Short-lever HVLA techniques do not require locking of adjacent spinal segments.
Locking can be achieved by either facet apposition or the utilization of ligamentous myofascial tension, or a combination of both. '-5-7 The principle used in these approaches is to position the spine in such a way that leverage is localized to one joint without undue strain being placed upon adjacent segments.
The osteopathic profession developed a nomenclature to classify spinal motion based upon the coupling of sidebending and rotation movements, This coupling behaviour will vary depending upon spinal positioning:
• Type 1 movement — sidebending and rotation occur in opposite directions (see Fig. A.4,1)
• Type 2 movement — sidebending and rotation occur in the same direction (see Fig, A.4,2).
The principle of facet apposition locking is to apply leverages to the spine that cause the facet joints of uninvolved segments to be apposed and consequently locked. To achieve locking by facet apposition, the spine is placed in a position opposite to that of normal coupling behaviour. The vertebral segment at
which you wish to produce cavitation should never be locked.
CERVICAL SPINE (see Table A.4.1)
Greenman7 describes the normal coupled motion of sidebending and rotation at the occipitoatlantal (CO-Cl) segment as being type 1. The principle of facet apposition locking does not apply to HVLA thrust techniques directed to the CO-Cl segment. However, facet apposition locking of the CO-Cl segment can be utilized for HVLA thrust techniques directed to other cervical levels.
The type of coupled movement available at the Cl-2 segment is complex. This segment has a predominant role in total cervical rotation.8-" Up to 77% of total cervical rotation occurs at the atlantoaxial joint, with a mean rotation range of 40.5° to either side.8-"1 The great range of rotation at the atlantoaxial joint can be attributed to facet plane, the loose nature of the ligamentous fibrous capsule and the absence of ligamentum flavum above C2,11 Only a small amount of rotation occurs at the joints above and below the atlantoaxial joint.12 Ij
Below C2, normal coupling behaviour in the cervical spine is type 2, i,e, sidebending and rotation occur to the same side,7-'5-'* To generate facet apposition locking, the operator must introduce a type 1 movement, which is sidebending of the cervical spine in one direction and rotation in the opposite direction, e,g. sidebending right with rotation left. This positioning locks the segments above the joint to be cavitated and enables a thrust to be applied to one vertebral segment. The amount or degree of sidebending and rotation can be varied to obtain facet locking, The intent should be to have a primary and secondary leverage, The principal or primary leverage can be either sidebending or rotation (see Fig, A.4.3).
CO-Cl (occipitoatlantal) Cl-2 (atlantoaxial) C2-T4
Coupled motion Type 1
Complex — primary rotation Type 2
Facet apposition locking Type 2
Not applicable Type 1
The principles of facet apposition locking that apply to the cervical spine are also utilized for HVLA techniques to the cervicotho-racic junction (C7-T4). If cervicothoracic region techniques require locking via the cervical spine, this is achieved by introducing type 1 movements to the cervical spine.
Current research relating to coupled movements of sidebending and rotation in the thoracic and lumbar spine is inconsistent. Although research does not validate any single model for spinal positioning and locking in the thoracic and lumbar spine, the model in Table A.4.2 is useful for teaching HVLA techniques.
Evidence supports the view that spinal posture and positioning alter coupling behaviour. I7-19 This has implications for joint locking in the thoracic and lumbar spine. In relation to patient positioning, the locking procedures will be different depending on whether the patient's spine is placed in a flexed or a neutral/ extended position.
There is some evidence to support the view that, in the flexed position, the coupling of sidebending and rotation is to the same side,17-19 whereas in the neutral/ extended position, the coupling of sidebending and rotation occurs to opposite sides.'718 The model outlined in Table A.4.2 incorporates the available evidence and is useful in the teaching and application of HVLA techniques. Because the evidence for coupling behaviour is inconsistent, it must be understood that this is a model for facet apposition locking which cannot be relied upon in all circumstances.
The patient's lumbar and thoracic spine is positioned in a neutral/extended posture (Fig. A.4.4). Using the model outlined, the normal coupling behaviour of sidebending and
Facet apposition locking
Position of spine T4-L5
Type 1 or type 2 Type 1 or type 2
Type 2 Type 1
Type 2 or type 1 Type 2 or type 1
Type 1 — sidebending and rotation to the opposite side Type 2 — sidebending and rotation to the same side
rotation in the neutral/extension position is type 1 movement. Facet apposition locking will be achieved by introducing a type 2 movement, i.e. sidebending a.nd rotation to the same side.
The spine in the neutral/ extension position is slung between the pelvis and shoulder girdle and creates a long C curve with the trunk sidebending to the patient's right when the patient lies on the left side.
Tnmk rotation to the right is introduced by gently pushing the patient's upper shoulder away from the operator. Rotation and sidebending to the same side achieve facet apposition locking in the neutral or extended position, in this instance with sidebending and rotation to the right (Fig, A.4.5).
The patient's lumbar and thoracic spine is positioned in a flexed posture (Fig, A.4.6). The normal coupling behaviour of sidebending
and rotation in the flexed position is type 2 movement. Facet apposition locking will be achieved by introducing a type 1 movement, i.e. sidebending and rotation to opposite sides.
To achieve facet apposition locking of the spine, in the Hexed posture, the trunk must be rotated and sidebent to opposite sides (Fig. A.4.7). The operator introduces trunk sidebending to the left by placing a pillow under the patient's thoracolumbar spine. Trunk rotation to the right is introduced by gently pushing the patient's upper shoulder away from the operator (Fig. A.4.7).
Many factors, such as facet tropism, vertebral level, intervertebral disc height, back pain and spinal position, can affect coupling behaviour and there will be occasions when the model outlined needs to be modified to suit an individual patient. In such circumstances, the operator will need to adjust patient positioning to facilitate effective localization of forces. To achieve this, the operator must develop the palpatory skills necessary to sense appropriate pre-thrust tension and leverage prior to delivering the HVLA thrust.
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