Stan Andrzejewski, PT

A basic vertebra is comprised of a bony block, called a vertebral body, and a bony ring. The disk is sandwiched between two blocks. The ring houses the precious spinal cord. The ring consists of 2 pedicles, 2 lamina, 1 spinous process, and 2 transverse processes. Processes are levers that attach to muscles. Each vertebra has 4 facets [joints], 2 superior, 2 inferior attached on the lateral posterior side of the vertebral body. A thoracic vertebra has 4 more facets attaching to the ribs. Facets are the synovial joints of the spine. This means they have a synovial membrane, that secrete synovial fluid, and a capsular ligament that holds the synovial fluid. The angle of orientation of the facets change with each vertebra. The angle influences the direction of movement.

The spine is segmental, consisting of 7 cervical, 12 thoracic, 5 lumbar, 5 sacral [fused], and 4 coccygeal [fused] vertebras. We must consider that each vertebrae has any direction of movement. The image of vertebra floating in all directions is useful. We categorize each vertebra movement as flexion, extension, rotation, and side bending. Some vertebras move less, some more. This is called the relative flexibilities or inflexibilities of the spine.

Lumbar vertebras are massive for weight bearing. The facets have a sagittal orientation allowing little rotation, but a lot of flexion, extension.

Thoracic vertebras are medium size with ribs attached. Ribs are the armor of our vital organs. We have 4 more facets per vertebrae. Since there are more facets to become hypomobile, thoracic movement is more likely to be restricted. The spinous processes are sharply angled down to prevent excessive backbending.

Cervical vertebras are the smallest, designed for mobility of our head. They are the easiest to wear away because of their size and mobility. Facets are angled at 45 ° from the horizontal. The cervical vertebras have 2 additional atypical joints called the lateral interbody joints or the uncovertebral joints of Luschka. These joints are on the posterior lateral vertebral bodies of the cervical spine. They have no articular cartilage or synovial components. Cervical disks are shaped with the anterior part of the disk, 2 times higher than posterior part.

The shoulder girdle consists of the scapula, humerus, and clavicle. The scapula [shoulder blade] is a broad flat bone that consists of a spine, acromium process, coricoid process, and an inferior angle. The glenoid fossa is shallow pear shaped socket about the size of a quarter.

The humerus [upper arm bone] has a head, 45 ° neck angle, a greater and a lesser tubercle, as well as a deltoid tuberosity.

The clavicle [collar bone] is "S" shaped.

Spinal ligaments allow efficient passive joint stabilization. They limit and direct vertebral movement. These ligaments have many pain receptors. The anterior longitudinal ligament [ALL] is thin, stretching from the occiput to the sacrum. The ALL stretches with backbends. The posterior longitudinal ligament [PLL] is thick, but tapers from the lumbar to the sacrum. The PLL stretches in forward bends. There many more spinal ligaments connecting vertebras to each other in every imaginable direction.

Disks are fluid-filled cylinders. Their water content decreases with age. Most disk surgery is performed on people in their 30s to 50s, when the water content is enough to make them bulge. Normal spinal curves allow even disk compression. There is 3x more interdiscal pressure in sitting than in standing.

Muscles are divided into 2 types. Deeper, postural muscles, such as the multifudus and scaleni, sustain posture with lower energy. Surface, phasic, 2 joint muscles, such as the erector spinae and the sternocleidomastoid are quick and explosive. The muscle contractions can be concentric [shortening], isometric [same muscle length], or eccentric [lengthening] contractions.

Normal weight bearing through the spine is a tripod design. The 2 facets in the back and the disk to the front. The disk / facet weight bearing is [80 / 20] through the lumbar spine and [50 / 50] in the cervical spine.

Joint of the Shoulder Girdle

The shoulder is considered to have 4 joints : gleno humeral, acromio- clavicular, sterno clavicular, and the scapulothoric.

The gleno humeral joint is a shallow ball and socket synovial joint. The congruent area where the humerus and fossa meet is the size of quarter.

The acromio- clavicular joint [AC] is more prone to fracture and dislocations than the SC. The coracoclavicular ligament is considered both the conoid and trapezoid ligaments. These ligaments allow the clavicle to move in first 30 degrees of elevation, then become taut, The AC joint is stable through the rest of elevation.

The sterno clavicular [SC] joint is highly mobile and allows 30 ° of elevation and protraction, 50 ° of backward rotation. The articular disk of the SC provides mobility and shock absorption.

The scapulothoracic joint is not a synovial joint, but essentially muscles attached from the rib cage and spine to the scapula. The scapula literally slides upon the rib cage.

Normal Biomechanics

The plumb line in stance runs vertically down through the ear lobe through cervical spine through shoulder through greater trochanter through knee through front ankle. Vertical alignment allows for efficient posture because of the reliance on the bony structures. There is a tripod support of disk / lateral interbodies and both facets in the cervical spine. More bony support means less muscular work.

Normal cervical and thoracic posture shows capital flexion with cervical and thoracic extension. Facets take 50%, disks / lateral interbodies take 50% of the weight. Lumbar facets take only 20% and lumbar disks take 80%.

Ideal scapular posture on the back ribs is down, in and in. But the scapula should not retract in towards each.

ö down - depression
ö into back ribs - inner edge of scapula
ö bottom tip in - posterior tipping

Ideal vertebral movement is segmental, each vertebrae moves slightly, but total range is considerable.

Vertebral movement is rotational [3D] movement in all directions. Cervical vertebral movement is much more than thoracic. Cervical facet orientation of horizontal plane allows rotation and sidebending as well as flexion and extension.

Occipital - C1

ö nodding "yes"
ö 10 ° capital flexion
ö 25 ° capital extension

C1 - C2

ö shaking head "no"
ö 90 ° from right to left
ö 5 ° flexion

C2-C7

ö gliding in all directions
ö most flexion at C4-5, C5-6
ö most extension at C4-5

Thoracic vertebral movement is restricted by rib cage and downward facing spinous processes. There is more less thoracic than cervical movement in all directions. The thoracic spine has more rotation but less flexion and extension than the lumbar spine.

The entire spine allows

ö 75° of cervical flexion
ö 25° of thoracic flexion
ö 60° lumbar flexion.

This movement pinches the anterior disk, as well as bulges the posterior disk. The inferior facets of cepheid body slide up and forward, gap, pull on capsule and tendons.

The entire spine has

ö 75° of cervical extension
ö 25° of thoracic extension
ö 35° of lumbar extension.

This movement pinches the posterior disk and bulges anterior disk. The inferior facets of cepheid body slide down and back compressing facet.

Spinal rotation compresses the disk with torque. The facet, rotating toward, flexes [back and down], other facet extends [forward and up.]

Movements of the scapula sliding upon the rib cage are considered scapular thoracic movement.

ö protraction - retraction
ö elevation - depression
ö internal rotation - external rotation
ö winging [inner edge moves away from ribs] - inner edges move into ribs
ö posterior tipping [top of scapula moves posterior, while bottom tip moves into ribs]

Both posterior tipping and inner edges moving into ribs are synergistic with thoracic extension.

The clavicle moves relate to the sternum at the SC joint. The clavicle moves relative to the scapula at the acromium at the AC joint.

Clavicular movements are called :

ö elevation - depression
ö backwards [external] rotation - forwards [internal] rotation

Glenohumeral movement is that of the humerus moving in the glenoid fossa of the scapula. The movement is in all possible directions. We categorize this movement in the cardinal planes of flexion, extension, horizontal adduction, horizontal abduction, external rotation, internal rotation. But the movement of the arm must be considered as the combination of scapular thoracic, sterno clavicular, acromial clavicular, and glenohumeral movement.

Elevation in plane of scapula [POS] is about 45° between the sagittal and frontal planes, 45° in-between flexion and abduction. In the plane of the scapula the humerus and glenoid fossa joint surfaces have the most contact [most congruent] in surface area with each other. The initial 30° of elevation of the arm is initiated by the supraspinatus muscle. The scapula is still stabilized on the ribs. The scapula first moves relative to the clavicle at the AC joint with protraction, elevation, and external rotation. Then the AC joint close packs. Then the scapular- clavicular unit moves relative to the sternum at the SC joint with backwards rotation and elevation. After first 30 ° of elevation, humerus [90 - 110°] moves on the scapula [60°] in a 2:1 ratio. This is called scapular humeral rhythm. The distal end of the clavicle lifts and backward rotates once the AC joint closes and the movement is at the SC joint. The rotator cuff and long head of biceps stabilizes and glides head of humerus inferiorly [cinches] in glenoid fossa as humerus elevates. The humerus externally rotates to avoid greater tubercle into AC shelf especially in abduction, less in flexion. But in the last 30° of elevation, the humerus internally rotates to 180°. The last 20 ° to elevation needs thoracic extension and side bend.

Faulty Biomechanics

The common thread of all neck and shoulder faulty mechanics is the forward head posture.

ö capital extension - tension at occipital ridge
ö lower cervical flexion
ö puffiness at C7
ö thoracic flexion [kyphosis]
ö upper neck and top shoulder muscle tension
        muscles chronically holding head up with muscles not designed for postural work chronic tension leads to trigger points
        and adaptive shortening

ö unstable scapulae winging and premature elevation
ö dull heavy spine
  

ö pelvis out of neutral
  

ö ungrounding lower extremities
   legs and pelvis not a base of support for the spine in standing
  

The joints of the mid cervical spine [C 4,5,6] are typically compressed due to a lack of skill of lightness or lengthening. The relative inflexibilities commonly show little movement in the lower cervical and upper thoracic spine [ C 6 - T 3], combined with relative excessive movement at C 4,5,6.

Shoulder impingement is a common injury of the rotator cuff due to poor upper quarter biomechanics. The rotator cuff cannot do its job on gliding head of humerus downwards because of the thoracic spine, scapula, and clavicles don’t do theirs.

ö the rotator cuff does not cinch head of humerus downwards for elevation
ö the levator scapula overly active in premature and excessive scapular elevation
ö the thoracic spine does not extend [backbend] in elevation
ö the lack of humeral rotation hits greater tubercle against AC shelf
ö the supraspinatus compresses into AC shelf because of lack of inferior glide

The supraspinatus stress can result in its tear or calcification. The joint surfaces involved can develop bony spurs, refereed pain is expressed in the front shoulder.

Musculoskeletal Tissue Strain

ö The bent finger syndrome is the simple deformation of normal tissue which causes sensation or pain. If you remove the strain, the sensation or pain stops. When you read in slumped position, your neck or back may ache, then just by laying on floor, the pain will stop.

ö Trigger point formation can be caused by phasic muscles contracting too long. They are not designed for such sustained contractions. They rather were designed for quick short term activity such as when you orient your head to a sound. The problem is that lactic acid builds up, irritating muscle. The levator scapula and upper trapezius were not designed to hold your head forward for a long time in forward head posture. The inner edge of scapula muscles can knot up from being asked to stabilize scapula from a winged position.

ö Adaptive shortening is the process where tissue eventually becomes shortened, fibrotic, inextensible by the inflammatory process. Now attempts of normal movement cause adaptively shortened tissues to strain further for more neck inflammation and pain.

ö Osteoarthrosis [OA] is the acquired joint degeneration through poor biomechanics. Uneven weight bearing and abnormal pulls from tendons can degenerate facets. Excessive facet compression during spinal extension can aggravate joint lining, cause joint inflammation and pain. Bone tissue can respond to compression by forming more bone tissue, that is, an osteophyte or commonly called a spur. Chronic pulls of tendons of tense muscles can cause the formation of osteophytes at the site of the tendon’s attachment in the periosteum of the bone. Abnormal pull of the disk attachment to vertebral body results from poor alignment of spine. Snap, crackle, and pop sounds can be caused by neck movement, sometimes painful, sometimes not. But these sounds are probably caused by OA. The lateral interbodies are joints between disk and nerve root susceptible to OA. Capsular ligaments can be caught between a spur and bone, irritating pain sensitive tissues. Facets can lock up causing compression pain and compensatory movement. OA can cause nerve root irritation through impingement. This leads to inflammation, pain, muscle guarding, or radiculopathy.

ö Cervical spondylosis is osteoarthritis of the cervical spine. Osteophytes form around the foramen, allowing normal movements of the neck to impinge nerve roots. Forward head causes these spurs to form from the mechanical stress at the joint surface. Not only do facets develop facets, but uneven compression on lateral interbodies cause this osteoarthritis. These spurs narrow the space of the foramen therefore press on the nerve root. Spinal extension, side bend, rotation normally narrows foramen space. But with spurs, the space is too narrow and the nerve root is compressed with these normal movements. 75% of people over 65 have cervical spondylosis without symptoms. Many do have symptoms.

ö Cervical disk herniation is the bulging of the disk into its posterior lateral wall. Forward head flexion of lower cervical vertebrae places uneven mechanical pressure at this posterior lateral wall of the cervical disks. Bulging disks can possibly cause soft tissue irritation, muscle tension, or worse nerve root impingement. There is less likely herniation in cervical as compared to lumbar spine. Posterior longitudinal ligament [PLL] covers entire posterior wall of the cervical spine [unlike the lumbar spine.] Cervical disks wider in front/ narrower in back; less likely to bulge posteriorly. But still nerve roots can be irritated by impingement of the disk bulge. This inflames peripheral nerve, causing numbness, tingle, sensory involvement, motor weakness in the arm.

ö Whiplash is the acute trauma from sudden acceleration / deacceleration of the head causing neck hyperflexion and or hyperextension. Muscles, ligaments, and tendons strain or tear. Muscles then begin to spasm as a result of these injuries to the soft tissue. A rear end auto accident causes a hyperextension injury. The ALL tears, anterior disk herniates, facets encroach on nerve roots. A head on collision causes a hyperflexion injury. The PLL tears, facets sublux, capsular ligament tears. After hyperflexion, a head may rebound into hyperextension.

ö Thoracic Inlet Syndrome is the compression of brachial plexus and subclavian artery
        between anterior and medial scaleni
        between clavicle and first ribs with scapular depression
        between pectoralis minor and ribs with humeral abduction/ flexion.

First we need to develop awareness of how we are perpetuating mechanical stress by our poor biomechanics. This culture seems to facilitate forward head posture. We are all stimulated visually by orienting of heads forward in TVs, monitors, over steering wheels, across the dining room table. We do many activities with our arms forward. The thoracic flexion, scapula tension and weakness culminate into these structural changes.