Posture, etiology of a syndrome - The case study

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Preface

Posture

Posturology

The case study

The backstage

Bibliography

Mechanics

The analysis of the Evidences provides consistence to the hypothesis that two simultaneous pathological postural strategies take place in the patient's physiology, the overlapping of which generates all the documented findings. The two postural strategies are well described by the classes:

Head forwarding postural strategy (HFPS): findings sensitive to regression events;
Mandible retruding postural strategy (MRPS): findings sensitive to orthodontic treatment.

Given the "dual" feature of the postural deviation and the uniqueness of the anatomy, we find:

physically, it is impossible to completely separate the action of either postural strategies on each anatomical district, resulting in partial physical independence,
logically, their reciprocal independence in onset and subsiding of symptoms and the different goal pursued allows a complete logical independence.

The strategy identification is done by:

Findings grouping: grouping the evidences according to their sensitivity to regression events and orthodontic treatment;
Strategy identification: within each findings group, analysis of the relationship to work out the global strategy and its pathologic goal.

MECHANICS: Head Forwarding Postural Strategy (HFPS)

Description

Mhfps01

Head forwarding postural strategy (HFPS)

Muscle map resulting from the evidences related to regression events

click to enlarge

Legend:

(1): weak muscles inducing upper airway patency loss,
(11-17): contracted muscles inducing cervical spine forward inclination,
(21-25): inhibited muscles for facilitation,
(31-33): contracted muscles inducing cervical spine forward inclination,
(41, 42): contracted muscles inducing cranial backward inclination,
(51, 52): contracted muscle for weight bearing overload and for implementing alternative motor pattern,
(61): contracted muscle for fighting forward body lean,

Mechanics-evidences relationship: the following list relates the map with the evidences

(1) weak genioglossus (GG), hyoglossus (HG), styloglossus (SL): Ecl20, Ese08, Ere04, Eot05;
(11) contracted anterior scalenus (AS): Ecl16, Ecl17, Ese07, Ere04;
(12) contracted anterior intracostalis (AI): Ese06;
(13) contracted internal oblique (IO): Ecl10, Ese06, Ese07, Ere04;
(14-15) contracted tensor fascia lata (TFL), rectus femoris (RF): Ecl04, Ecl05, Ese04, Ese06, Ere04;
(16) contracted hip adductor (HA): Ecl03;
(21) inhibited erector spinae (ES): Ecl100, Ecl12, Ecl16, Ecl17, Ese07, Esy07;
(22) inhibited posterior intercostalis (PI): Ese07;
(23) inhibited gluteus maximus (GM): Ecl05, Ecl07, Ecl08, Ecl12, Esy05, Ese04, Ese05, Ese06, Ere04;
(24) inhibited semimembranosus (SM), semitendinosus (ST), biceps femoris (BF): Ecl06, Ecl07, Ecl08, Ecl12, Esy04, Esy05, Ese04, Ese05, Ese06, Ere04;
(25) inhibited tibialis posterior (TP), flexor hallucis longus (FHL), flexor digitorum longus (FDL): Ecl01, Ecl02, Esy02, Ese01, Ese02, Ese03, Ese05, Ese06, Ere04;
(31) contracted upper trapezius (UT), only scapulo-cervical fibers (NO occipiral fibers): Ecl101, Ecl17, Esy100, Esy101;
(32-33) contracted pectoralis major (PMA), pectoralis minor (PMI): Ecl13, Ecl15, Esy08, Ese06, Ese07, Ere04;
(41-42) contracted splenius capiti (SPC), semispinalis capitis (SEC): Ecl101, Ecl17, Esy101;
(51) contracted soleus (S): Ecl02, Ese03, Ese05, Ese06, Ere04;
(52) contracted tibialis anterior (TA):Esy03;
(61) contracted multifidus (MF);

HFPS is present in the upright as well as in the prone and supine positions, its goal is supposed to be critical since its hyperactive actuator muscles fully inhibit antagonist contraction resulting in pathologic static muscle tone and disabling motor control; nevertheless its pathological action is way far from a randomly unbalanced muscles problem, it rather appears to be a well coordinated reflex, below are described strategy goal and mechanics:

Upper airway unilateral patency loss (1): GG, HG and SL (1) are not involved in the mechanics of the strategy, but, given the harmfulness of their weakness (airway patency loss), they are suspected to be involved in the pathomechanics, being closer to a cause rather than to an effect.
Cervical spine forward-ipsilateral inclination (11-17): AS (11) exerts direct pull on the spine but, as the first rib is not a solid pulling reference, requires AI, IO (12, 13) muscle chain to reach a steady bone (pelvis), which counter-pool is achieved by TFL, RF and HA (14-16) implementing unilateral pelvis anterior tilt. TA (17) scope is unclear, it is suspected not to be directly involved in cervical spine inclination.
Functional facilitation (21-25): ES and PI (21, 22) inhibition takes place to allow cervical spine forward inclination and the consequent modification of spine curves, furthermore, PI (22) inhibition is mandatory to allow left emithorax rear expansion during inspiration (frontal expansion is prevented by contracted AI (12)). Further inhibition of SM, ST, BF, GM (23, 24) takes place to facilitate pelvis forward inclination. TP, FHL and FDL (25) action in this context is unclear, it is suspected to facilitate ankle dorsiflexion by TA (52).
Cervical spine forward-ipsilateral inclination (31-33): UT (31) concur, together with (11-16), in exerting cervical spine forward inclination, UT (31) moment arm is further increased by forwarding the scapula by means of PMA and PMI (32, 33).
Cranial backward-ipsilateral inclination (41-42): SPC and SEC (41, 42) posterior neck muscles produces atlanto occipital joint (AOJ) hyperextension, therefore increasing craniocervical angle.
Weight bearing overload (51, 52): contracted S and TA (51, 52) function don't appear to be directly involved in the strategy, they're rather suspected to be either involved in sustaining the increased weight load owed to forward body lean and in implementing alternative motor patterns.
Thorax backward torque (61): function of the contracted MF (61) is to fight against the thorax forward lean force exerted by anterior hypertonic muscles (11-16), the action is performed by increasing lumbar lordosis.

Mhfps02

Joint displacement model

Anatomical displacement resulting from HFPS torques

click to enlarge

Legend:

Blu areas: anatomy physiologic position,
Blu lines: joint axis physiologic inclination,
Red Areas: displacements resulting from HFPS,
Red lines: joint axis inclination resulting from HFPS,
Black lines: HFPS muscle torques

Joints physiologic position in the erect station is harmfully affected by HFPS asymmetric torques, its result may be described as:

Pelvis left-side/forward inclination as consequence of anterior tilt under active TFL and RF (14, 15) torque and inhibition of SM, ST and BF (24),
Left femur medial rotation consequent RF torque (15) and concurrent GM (23) inhibition,
Left ankle pronation owed to tibia inclination, secondary to femur medial rotation,
Left shoulder forwarded, as consequence of PMA and PMI (32-33) torque, and aimed ad increasing UT (31) moment arm for cervical forward inclination,
Cervical spine forward inclination achieved by AS (11) and UT (31).

Mhfps03

Spine torsional model

click to enlarge

HFPS produces strong asymmetric and harmful torque on the spine inducing torsions, scoliosis, and exacerbated curves. The model describes the spine adaptation to HFPS.

Pathologic evidences:

lumbar spine scoliosis (back view), torsion (top view) and increased lordosis (lateral view) due to pelvis unilateral (left) forward tilt (14-16) (23, 24) and consequent sacroiliac joint axis inclination,
cervical spine torsion (top view) and forward inclination (lateral view) due to unilateral action of AS (11),
thoracic spine scoliosis (back view), torsion (top view) and increased chyphosis (lateral view) due to left emithorax expansion disorder (12-13) (21-22) and to connect exacerbated curves in 1) and 2),
spine shortening (back/lateral view) due to increased sagittal curves (lordosis, chyphosis, forwarding),
lumbar right-side nerve roots sufferance (back view) (Esy06, Esy07, Ere04) due to asymmetric disc degeneration consequent to 1),
thoracic right-side nerve roots sufferance (back view) (Ecl11) due to asymmetric disc degeneration consequent to 3).

MECHANICS: Mandible Retruding Postural Strategy (MRPS)

Description

Mmrps01

Mandibular retruding postural strategy (MRPS)

Muscle map resulting from the evidences related to orthodontic treatment

click to enlarge

Legend:

(11-15): contracted muscles inducing cervical spine forward inclination,
(21-24): inhibited muscles for facilitation,
(31-33): contracted muscles inducing cervical spine forward inclination,
(41, 42): contracted muscles inducing cranial backward inclination,
(61): contracted muscle for fighting forward body lean.

Given chronicity and symmetry features, mandible retruding postural strategy (MRPS) is a deviation that is difficult to be aware of, hence, is considered ordinary condition, moreover, the absence of regression events for this type of symptoms and the slowness of improvement during orthodontic treatment don't allow self evaluation to provide significant findings. Fortunately a lot of pre-post orthodontic treatment clues support the described mechanics, furthermore, an acceptable extent of agreement exists in clinic literature to confirm the mechanical hypothesis.

All the evidences of MRPS refer to the upright position, nevertheless, its presence in other context (eg. prone and supine) is suspected but this eventuality requires further resources to be investigated; the extent to which MRPS hyperactive actuator muscles inhibit antagonist contraction is lighter than HFPS, the overall result is pathologic static muscle tone but preserved motor control.

MRPS is aimed at mandible retrusion (mandible backward motion) for avoiding teeth conflicts, bilateral craniocervical extension (CCE) involvement is supposed to take place for limiting the effect of mandible retrusion (and consequent tongue backward motion) on airflow. Although some features of MRPS appear to be evident, the confidence of the author on all MRPS feature is not as solid as HFPS, hence, each feature is described together with its reliability extent, in other words, some features are evident, some other are uncertain.

Evident features:

(31) contracted upper trapezius (UT), only scapulo-cervical fibers (NO occipiral fibers): Ecl12, Ecl14, Ecl17;
(32-33) contracted pectoralis major (PMA), pectoralis minor (PMI): Ecl12, Ecl14, Ecl17;
(41-42) contracted splenius capiti (SPC), semispinalis capitis (SEC): Ecl12, Ecl14, Ecl17;

Uncertain features:

(11) contracted anterior scalenus (AS),
(12) contracted anterior intracostalis (AI),
(13) contracted internal oblique (IO),
(14-15) contracted tensor fascia lata (TFL), rectus femoris (RF),
(21) inhibited erector spinae (ES),
(22) inhibited posterior intercostalis (PI),
(23) inhibited gluteus maximus (GM),
(24) inhibited semimembranosus (SM), semitendinosus (ST), biceps femoris (BF);
(61) contracted multifidus (MF);

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