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Department of Physical Therapy NEW YORK UNIVERSITY

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1 Department of Physical Therapy NEW YORK UNIVERSITY
Abnormal Gait Department of Physical Therapy NEW YORK UNIVERSITY

2 Historical Perspective
Tendency to classify gait according to disease or injury state Hemiplegic gait Parkinsonian gait Spastic gait Quadra- or paraplegic gait Amputee gait, etc.

3 Rationale A specific disease or injury state manifested as a discrete and clinically describable problem with the mechanics of gait

4 Our Starting Point We’ll take a deficit-oriented vs. disease- oriented approach to abnormal gait analysis Example: “How might a spastic hamstring on one side, secondary to hemiplegia caused by a CVA, affect gait mechanics?”

5 Answer A spastic hamstring may limit step or stride excursion and/or pelvic transverse rotation

6 Preferred Rate of Ambulation
Free or comfortable walking speed Self-selected pace Rate at which the normal individual is most energy efficient Range: ~ mph (cadence of ~ steps per minute) Will vary from individual-to-individual

7 Walking Rates - Historical Perspective
Historically walking rates classified as: Slow: ~ steps per minute Medium: ~ steps per minute Fast: ~ steps per minute

8 Energy Cost vs. Rate

9 Summary & Interpretation
Oxygen expenditure is least while walking at a rate somewhere between ~85 to 110 steps per minute irrespective of stride (or step) length Individuals tend to gravitate toward a self-selected pace which is most energy efficient for that individual

10 Enter - The Idea of a ‘Preferred Rate’
A preferred rate of ambulation is a self-selected walking pace that an individual assumes that is most energy efficient

11 Clinical Implication Since there is apparently a rate-dependent issue that drives gait efficiency the PT should understand that going slower than and faster than the preferred rate will lead to inefficiency and potential stress on the cardiovascular and motor control systems

12 Why is Gait More Efficient at Preferred Rate?
What is the relationship between energy efficiency and a preferred rate of ambulation?

13 The Center of Gravity (COG)
COG located at S1 - S2 During preferred rate walking the COG approximates a sinusoidal curve from the: Sagittal perspective - no greater than a 2” peak-to-valley excursion Frontal perspective - no greater than a 2” medial-to-lateral excursion

14 Path of the COG

15 Distortion of the Path of the COG
A distorted path of the COG will require mechanical and motor control compensations that will: Disrupt normal timing of events Over-ride normal gait control Change from ‘automatic’ to ‘manua’l control strategies Lead to over-correction of gait mechanics

16 The Result Increased energy expenditure

17 A Simple Example Walking with a stiff-knee (“stiff-knee gait”) with a cylinder cast During stance the HAT will vault over the fixed foot (especially during mid-stance) COG will be deflected higher than the usual 2” upward vertical displacement with increased energy cost

18 Who Walks with a Stiff Knee?
Transient knee injury patient (e.g., surgical repair of a ligament Hemiplegic with loss of knee control The AK amputee with a locked-knee prosthesis The BK amputee with poor knee control Should we consider each case the SAME?

19 The Control of Gait Motor control options:
‘Manual’ control theory - thinking about having to take a step each time you want to advance the foot forward ‘Automatic control theory - an automatic control system that accounts for gait mechanics without having to think about foot placement and other metrical details

20 Which one is it? Think about this...

21 An Everyday Occurrence
You’re walking along 23rd Street, heading west toward your bus stop You’re thinking about what was discussed in Kinesiology class today You’re also thinking that there is a lot a traffic and it’s going to take you forever to get home tonight...

22 Questions Are you thinking about foot placement?
Are you thinking about how long each step should be? Are you thinking about trunk and pelvic rotation in the transverse plane and maintaining reciprocal arm-swing? Are you thinking about...

23 Answer Probably NOT! Why? Your gait control is on ‘automatic pilot’
When do you have to think about gait control? When there’s a perturbation

24 Central Pattern Generator (CPG)
CPG - a group of synaptic connections probably at the spinal cord level which are triggered by an event or condition When a threshold is met via a triggering mechanism the CPG appears to be activated and takes over automatic control of gait metrics - i.e., you don’t have to think about it

25 Evidence Spinalized (cord transected) cats suspended over a treadmill will walk with an alternating, striding quadripedal gait Human quadriplegics have also “walked” this way

26 CPG and Supraspinal Influence
Gait perturbations Example: Someone walks across your path from the side that you didn’t see There’s a need to take immediate corrective action to avoid a collision Supraspinal centers appear to over-ride the CPG and switch to a ‘manual control’ strategy

27 What Triggers a CPG? There seems to be a close relationship between activating a CPG for gait control and preferred rate of ambulation In other words, there is a rate-dependent relationship between normal gait mechanics and its control mechanism

28 So... It appears we maintain the path of the COG within very tight limits and therefore expend the least amount of energy by assuming a preferred rate which in turn leads to an activation of a CPG

29 Think About This... What’s one of the most common things heard during gait training in a PT clinic?

30 “Mr. Jones, while you’re walking, I want to go…”

31 “...very slow!”

32 What are some possible implications of this?
Mr. Jones will be safe - probably won’t fall and break his hip (good news). Mr. Jones won’t sue you (good news). The path of the COG may be distorted (bad news). Energy cost may increase (bad news) Suppose Mr. Jones has a cardiac condition?

33 What are some possible implications of this?
Mr. Jones may never reach his pre-injury/disease preferred rate of ambulation and therefore never trigger a CPG that automates gait (bad news). Mr. Jones’ gait may never look ‘normal’ (bad news).

34 Is it possible that... …going very slow might actually cause Mr. Jones to lose his balance and fall? Why?

35 Factors That Lead to the Initiation of Gait
Assume right LE will advance first: Weight shift to left LE (unloads right hip) Left hip moves into (hyper-) extension and precedes right hip flexion Right side of pelvis rotates medially preceding right hip flexion COG moves over right foot after it’s advanced

36 Factors That Lead to the Initiation of Gait
Successful completion of these events probably leads to a triggering of a CPG as preferred rate is attained

37 Gait Training Scenario
Mrs. Flanagan is standing in the parallel bars with her physical therapist, Dudley Doright, getting ready to take a left step to start walking. We hear the PT say, “Now, Mrs. Flanagan, I want you to put your left foot forward and take a step…”

38 What wrong with this picture?
Where is the patient’s COG relative to her base-of-support? What is probably the size of the left step (step length) relative to the right? What impact will this likely have on her forward velocity? What are the chances of attaining her pre-injury/disease preferred rate?

39 Deficit-Oriented Gait Analysis
Questions: Do diseases/injuries specifically manifest as a stereotypical gait pattern? or Does the disease/injury lead to a deterioration of control parameters which cause gait deficits?

40 Response If you believe the latter…it shouldn’t matter what the patient’s problem is If you understand the consequence of the disease or injury (loss of motor control, weakness, damaged supportive structures, loss of a part of or an entire limb, etc.)...

41 …you should be able to anticipate or predict what impact a deficit has on gait irrespective of their state of injury or disease.

42 Hip Extensors - Stance

43 Analysis of Deficits Hip Extensors - Stance
Early stance HS) Prevent hip flexion (jack-knifing) Early stance (HS - FF) Guide hip into flexion eccentrically Early stance HS) weakness/absence Hip/trunk collapses into flexion Early stance (HS - FF) Trunk falls forward

44 Hip Abductors - Stance

45 Hip Abductors Prevent contra-lateral hip from dipping greater than Stance-side abductors active Loss of abductors: Static analysis - + Trendelenburg sign Dynamic analysis - weakness o f abductors manifests as ‘lurching gait’ (toward stance- side)

46 Analysis of Deficits Abductors - Stance
Early stance COG shifts away from stance side LE Increases moment arm of COG relative to stance side hip Stance side abductors generate counter-rotational torque to prevent contra-lateral from dropping > 5-80 Early stance weakness/absence Contra-lateral hip drops > 5-80 Compensation is to lean (‘lurch’) over stance-side LE

47 Quadriceps - Stance

48 Analysis of Deficits Quadriceps - Stance
Early stance (HS - FF) Guides knee into 200 of flexion eccentrically (controls unlocking of the knee) Late stance (HR - TO) Controls for knee flexion (~400 at TO) Early stance weakness/absence Inability to absorb energy Buckling Late stance weakness/absence Knee collapse into flexion -premature flexion into early swing - ‘rubber knee’

49 Pre-Tibial Group - Stance

50 Analysis of Deficits Pre-tibial Group - Stance
Early stance (HS - FF) Lowers forefoot to floor eccentrically After forefoot contacts floor- pull tibia forward over foot Early stance weakness/absence Forefoot slaps to the floor - ‘drop-foot’ gait Loss of forward pull of tibia

51 Plantar Flexors - Stance

52 Analysis of Deficits Plantar Flexors - Stance
Late mid-stance Concentrically pulls tibia forward Late stance (HR - TO) Provides propulsive thrust during push off Early stance weakness/absence Loss of forward pull of tibia Loss of forward thrust - poor transition to early swing

53 Ankle Stability - Late Stance
Ankle less stable and subject to injury (e.g., sprains) in plantar flexion vs.dorsiflexion Posterior trochlea in mortise Collateral ligaments swing out of collateral position Position of ankle during push-off (late stance) = plantar flexed

54 Analysis of Deficits Peroneals - Stance
Late stance (HR - TO) Dynamically provide collateral stability to ankle when plantar flexed Secondary plantar flexor for forward thrust Late stance weakness/absence Ankle instability causing medial-lateral movement Potential for ankle injury - sprains Poor transition from late stance to early swing

55 Analysis of Deficits Plantar Intrinsics - Stance
Late stance (HR - TO) Provide medial - lateral stability to MTP joints (especially nos. 1 & 2) - cancels second degree of freedom Improves forward propulsion and transition to early swing Late stance weakness/absence Excessive medial - lateral ‘shimmy’ of hindfoot during HR Inefficient forward thrust

56 Paraspinals -Stance

57 Analysis of Deficits Paraspinals - Stance
Early stance (HS - FF) & late stance (HR - TO) Prevent forward flexion of trunk acting on pelvis Early & late stance weakness/absence Trunk falls forward Loss of head and neck control

58 Analysis of Deficits Hip Flexors - Swing
Late stance - early swing (acceleration) Forward flexion of femur working with plantar flexors to accelerate LE in early swing Functionally shortens LE (with eccentric action of quadriceps and dorsiflexors) to prevent ‘toe-drag’ Late stance - early swing weakness/absence of forward acceleration after TO Toe may not clear the floor during swing through Compensate with circumduction at hip

59 Dorsiflexors - Swing

60 Analysis of Deficits Dorsiflexors - Swing
Mid-to-late swing (deceleration) Affects ‘toe-up’ concentrically Functionally shortens LE during swing through Mid-to-late swing weakness/absence Loss of ‘toe-up’ Compensation Increased hip flexion - ‘steppage gait’ Circumduction at hip

61 Hamstrings - Swing

62 Analysis of Deficits Hamstrings - Swing
Late swing (deceleration) Decelerates tibial shank Provides for smooth transition between late stance and early swing Late swing weakness/absence ‘Impact on terminal extension’ - knee slapped into extension or hyperextension

63 Gait in the Elderly Men - Murray, Kory & Clarkson
Gait did not appear vigorous or labored Gait pattern did not resemble that of patients with CNS damage Gait was guarded and restrained - attempt to maximal stability and security

64 Gait in the Elderly Men - Murray, Kory & Clarkson
Gait resembled someone walking on a slippery surface decreased step & stride legnth wider dynamic BOS increased lateral head movement decreased rotation of pelvis

65 Gait in the Elderly Men - Murray, Kory & Clarkson
toe/floor clearance distance slightly decreased lower stance-to-swing ratio decreased reciprocal arm swing more from elbow than shoulder

66 Spasticity and its Impact on Gait
Spasticity - resistance to passive stretch Results from CNS (UMN) injury/disease Increased source of uncontrolled/poorly controlled tension Probably due to loss of inhibiting action of the CNS While tension production may be significant the time-rate-of-tension development may be delayed

67 Spasticity & Gait Spastic response may be caused by: Effects:
Unexpected quick stretch of muscles Foot contact with floor Supraspinal overlay Effects: Restrict joint excursion Delay transition from one gait phase to the next

68 Spasticity & Gait Dubo et al. showed that EMG activity of spastic muscles increased during mid-stance i.e., there was a loss of phasic control of muscles

69 Spasticity & Gait Examples
Quadcriceps May prevent knee from unlocking during interim between HS and FF Knee maintained in extension leading to a ‘vaulting’ over stance limb or circumduction of hip Disrupts (timing) transition to mid- and late stance May prevent LE bending during swing phase

70 Spasticity & Gait Examples
Plantar flexors Increase in spastic tone may limit forward rotation of tibia between MS and PO May locate ground reaction force well behind knee causing significant flexion moment during late MS and knee buckling tendency Ankle may be locked up during PO decreasing propulsive thrust forward - inefficient transition from TO to early swing

71 Spasticity & Gait Examples
Hamstrings May limit forward swing of LE - decreasing step length May prevent knee from reaching a terminally extended position just prior to HS

72 Gait Training - Questions
If gait is controlled by a rate-dependent chain of synaptic connections at the spinal cord level (i.e., a CPG), is it possible for a PT to effect (physiological) changes in the gait control system?

73 Gait Training - Questions
If gait is initiated (and sustained) as described previously (e.g., unloading of hip, pelvis rotates medially, COG loads over stance foot, etc.), how do we train patients to start walking?

74 Gait Training - Questions
What impact will ‘assistive devices’ have on gait performance? Parallel bars Walkers Bilateral & unilateral crutches and canes PTs using contact guarding from the side or behind

75 Gait Training - Questions
If the rhythmic, symmetrical alternating characteristics of gait are triggered when a patient assumes their preferred rate, will gait symmetry and a ‘normal’ appearing gait be possible if the patient walks substantially slower than her preferred rate?

76 Gait Training - Questions
Are all patients’ objectives concerning walking the same? Are your objectives for Ms. Walksalot, a 39 year old healthy female who broke her ankle two weeks ago in an intensive tennis match, the same as for Mr. Livesinathirdstorywalkup, a frail 87 year old male, with emphysema and a fractured, pinned hip?

77 Gait Training - Questions
What’s the best thing a PT can say to their patient while gait training?...

78 ...Probably very little!


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