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SPINAL BIOMECHANICS

This post discusses the importance of spinal biomechanics and posture analysis in understanding the effects of axial compressive forces on the body. It covers the key factors that contribute to postural imbalances and provides an overview of the role of muscles, joints, and ligaments. Additionally, it highlights the impact of foot, knee, and hip alignment on posture.

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SPINAL BIOMECHANICS

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  1. SPINAL BIOMECHANICS POSTURE ANALYSIS

  2. POSTURE • Keep in mind the spine is found at the posterior aspect of the body, behind the center of gravity • Center of gravity lies: • Through the atlanto-occipital joint • Tragus of the ear • Anterior humeral head • Anterior-inferior edge of T11 • Greater trochanter • Just behind the patella • Through the lateral malleoli

  3. DURING POSTURAL ANALYSIS… • Usually stance is asymmetrical if not intentional. • The weight of the body is borne by the skeleton aided by the action of intrinsic back muscles • Sway occurs during stance. • Postural sway of the vertebral column on the pelvis is controlled by the erector spinae, and the rectus abdominis. • 80% of the contraction occurs in the E.S., whereas only 20% of contraction occurs in the abdominals, as confirmed by EMG studies. • In scoliosis, E.S. contraction is higher on the convexside.

  4. AFFECTS OF AXIAL COMPRESSIVE FORCES • Increases from the C/S to the L/S • Lumbar problems are common--#1 reason to see a Chiropractor

  5. HOW DO MUSCLES BECOME IMBALANCED? • Skeletal misalignment- triggers other muscles to be recruited to restore normal posture • Joint pain or malformation- imbalance in stance and gait • Ligamentous injury/instability- recruits muscles to support the joint • Muscle fatigue- recruits other muscles to contract to accomplish the same movement, often resulting in myofascial trigger points

  6. BEGINNING POSTURE ANALYSIS • Work from the “ground-up”: • Check for any lower extremity deformity that may be creating imbalance above

  7. EXAMINE THE FEET • LONGITUDINAL ARCH • PRONATION • SUPINATION • MEDIAL MALLEOLI LEVELS • ACHILLES TENDON POSITION • SIGNS OF LIGAMENTOUS LAXITY

  8. Pes Planus Pes Cavus

  9. REASONS BEHIND TOE-IN & TOE-OUT • TOE-IN • INTERNAL TIBIAL ROTATION • TIBIA VARUS • INCREASED INTERNAL ROTATION of FEMUR —often due to muscular contraction/imbalance • TOE-OUT • BILATERAL- SACRAL ANTERIORITY • UNILATERAL- PELVIC ANTERIORITY • INCREASED EXTERNAL ROTATION of FEMUR—often due to muscular contraction/imbalance Blount's disease

  10. EXAMINE THE KNEES • FLEXED • Hamstring spasm • Quad weakness • Acute low back pain • HYPEREXTENDED • Ligamentous • Anterior compression fracture

  11. KNEES GENU VALGUS GENU VARUS

  12. An abnormally high Q-Angle can cause stress on the entire kinetic chain of the lower extremity causing many conditions from low back pain to foot pain. D. Robert Kuhn, DC, Terry R. Yochum, DC, Anton R. Cherry, Sean S.Rodgers Q – ANGLE(Quadriceps) Wide Hips (female runners) Knock Knees (·Genu valgum) Pronation of the feet Subluxating Patella High riding patella (patella alta) Weak Vastus Medialis

  13. Imbalance of Hip Rotators • Leg length discrepancies and foot pronation may lead to: • Iliotibial band syndrome • Piriformis syndrome • Recurrent muscle strains (hamstring and groin pulls) can be an indicator of asymmetry in structural alignment.

  14. HIP MUSCLES… • Transfer ground-reaction forces from legs to trunk during gait • Supply coordinated propulsion • Provide balanced stability for the pelvis and spine • Through repetitive use patterns and after injuries, hip muscles may become shortened and/or weak [1] Kim D. Christensen, DC, CCSP, DACRB

  15. THIGH AND PELVIS • BULK OF HAMSTRINGS • GREATER TROCHANTERS • PELVIC TILT, SWAY (antalgia), TORTION- AS or PI • ILIAC CREST LEVELS • PSIS LEVELS • SACRAL ROTATION (S2—PSIS distance) • GLUTEAL MUSCLES- Deeper Dimpling

  16. POSTURAL ANALYSIS P-A View • Sacral Base- • Level • Held in place by innominate bones • Dependant upon equal leg lengths • What can go wrong? • Sacral deformity- • Transitional segment • Plateau base • Anatomical short leg • Congenital • Acquired • Functional • Due to muscle imbalance • Due to pelvic distortion

  17. BODY RESPONDS IN A PREDICTABLE MANNER • Attempts to restore balance: • Eyes on horizontal plane “Righting Reflex” • Equally distributing weight to center of gravity

  18. VERTICAL PLANE of LUMBAR SPINE • SPINOUS ALIGNMENT • SECTIONAL TOWERING • CURVATURE • LORDOSIS • PARASPINAL MUSCLE TONICITY • SKIN DISCOLORATION

  19. THORACIC OBSERVATIONS • SPINOUS ALIGNMENT • SECTIONAL TOWERING • CONVEXITY or SCOLIOSIS • + ADAM’S SIGN • KYPHOSIS • RIB HUMP • SCAPULAR WINGING (myopathies, shoulder instability, Serratus anterior weakness) • POSTERIOR SCAPULA (scoliosis) • HIGH SHOULDER/TRAP • INTERNAL ROTATION HUMEROUS

  20. NECK and HEAD OBSERVATIONS • C2 SPINOUS ALIGNS WITH S2 TUBERCLE? • MASTOID PROCESS LEVELS • HEAD TILT OR ROTATION • ANTERIOR HEAD CARRIAGE • LORDOSIS • MUSCLE TONE

  21. LATERAL VIEW • SACRUM: Inclines from 26-56º from horizontal • LUMBAR: Levels off at L4 superior body surface (Apex), continues posteriorly in upper L/S • THORACIC: Gradual reversal of curve: body wedging to create kyphosis at apex (T4-T6) • CERVICAL: Curve reverses again: apex (C4) • What constitutes postural abnormality? • Any Variation in the AP or Lat • Pelvic unleveling • Spinal segment unleveling • Produces imbalance & altered weight imposition

  22. Kendall, et. al.

  23. FROM THE SIDE KYPHOSIS LORDOSIS

  24. NORMAL RANGES of MOTION • Varies • Age • Activity • EVALUATE: As a total unit; comparing symmetry more than degrees • Break it down by section—if blocked in one section may lead to hypermobility in another • Look for: • Abnormal coupling of motion (rotation with flexion) • Bilateral symmetry; smoothness & ease of motion

  25. SACROILIAC KINETICS

  26. THE SACROILIAC JOINTA Controversial Topic • Complicated Anatomy • and Biomechanics: • Small ROM • 2. Passive movement • 3. Stress-relieving joint

  27. MOTION IN THE S/I JOINT • No gross excursion (except due to severe trauma) • Movement: Normal physiological effect of shock absorption • Obvious movement during ambulation-Sacral nutation • Clear osseous limitation- • Interlocking ridges & grooves • Strong reinforcing ligaments • Key-stone in arch stability • Age Factors in degree of motion: • Flexible—to—Ankylosis

  28. Gillett’s test … Demonstrates pelvic motion by comparing PSIS motion B/L: • Fixation • Pseudo-ankylosis • Fusion • Lumbar or hip muscle hypertonicity

  29. Pelvis Tips and Rotates in Accommodation…Aresponse to dysfunction above or below • Leads to: • Abnormal: unequal weight into each S/I joint leading to… • Pelvic distortion • Eccentric weight imposition into each S/I joint • Abnormal posture • Abnormal gait

  30. PELVIC DISTORTION IS PREDICTABLE… • Predictable patterns of accommodation have been demonstrated as a response to imbalance both above and below. • Therefore, pelvic distortion is often not a primary subluxation, but a compensatory, secondary distortion

  31. PRIMARY SUBLUXATION IN THE LUMBAR SPINE (Secondary S/I Dysfunction) IVD HERNIATION CURVATURE OR SCOLIOSIS TRANSITIONAL SEGMENT ALTERED SAGITTAL CURVE FUNCTIONAL: GROSS MUSCULAR

  32. PRIMARY DISTORTION DUE TO LOWER LIMB DEFICIENCY(Secondary S/I Dysfunction) • ANATOMICALLY SHORT FEMUR OR TIBIA • GENU VARUM OR VALGUS • PRONATION • FLAT FOOT • HIP, KNEE, ANKLE OR FOOT PAIN

  33. PRIMARY Sacroiliac Fixation • Chronic stress to the S/I joints leads to: • Repetitive microtraumas • Gross muscular compensation—holding joint in the fixed malposition • May eventually lead to : • Sclerotic changes

  34. PRIMARY Sacroiliac Instability • Sprain • Pregnancy & Child Birth • Pubic Symphysis Dysfunction

  35. CHARACTERISTICS OF S/I PAIN • Painful to walk • Ascending or descending stairs • Standing from a sitting position • Hopping or standing on involved leg • Sharp pain that awakens the patient from sleep upon turning in bed

  36. What Research Has Shown • L/S may refer pain to S/I • S/I ROM: • Decreases with age • Minimal compared to spine • Pain can= • 1° Fixation, Instability or • 2° Accommodation

  37. CONTINUED S/I JOINT STRESS… • May lead to true fixation in its misalignment—becoming a primary subluxation • Prolonged accommodation to chronic spinal subluxation and postural abnormality or leg deficiency may lead to • Fixation • Gross muscular change • Sclerosis

  38. OTHER ENTITIES CAUSING S/I JOINT PAIN • Pelvic disorders-Prostatitis, Interstitial Cystitis, or breast, lung or prostate metastasis • Enteric disorders-Iliopsoas abscess(Diabetes, UTI) • Inflammatory arthrotides or “Spondyloarthropathies”-A.S, Lupus, Reactive Arthritis (“Reiter’s”), Crohn’s disease

  39. EXAMINATION • Observation • Primary Stress Tests • Leg Length Tests • Weight Bearing Kinetic Tests • Secondary Stress Tests • Orthopedic Tests

  40. OBSERVATIONI. OBSERVATION Pages 88-90 • Postural Analysis: • Pelvic tilt (Anterior or Posterior) • Lateral pelvic tilt • Any structural asymmetry • Check for landmark: • Alignment • Tenderness • Belt Test: Test to R/O lumbar involvement

  41. REINERT SPECIFIC LISTINGS FOR PELVIC DISTORTIONS AS RELATED TO THE SACROILIAC JOINT • POSTERIOR • POSTERO-INFERIOR • INFERIOR • ANTERIOR • ANTERO-SUPERIOR • SUPERIOR

  42. PRIMARY STRESS TESTS

  43. LEG LENGTH

  44. WEIGHT-BEARING KINETIC TESTS

  45. Sacral Compression Test Forced Counternutation

  46. GAENSLEN’S TEST

  47. YEOMAN’S TEST

  48. FABER PATRICK’S TEST

  49. HIBB’S TEST

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