S S R T I A ANALYSIS & TRAINING OF AMPUTEES ON

Outline Normal Biomechanics Differences with Below-Knee Stair Patterns Implications Video Brainstorming! **Consider what muscles / segments are affected in amputee clients during discussion

Normal Characteristics Cadence – Ascent = steps/min – Descent = steps/min – Shorter women go faster! Proportions: – Ascent = stance 50-65% – Descent = stance 19-68% – 31% double support

Trans-Tibial Amputees Slower velocity (Powers et al, 1997) – Ascent: 80% of normal (29.6m/min vs 33.4m/min) – Descent: 84% of normal (29.6m/min vs 35.2m/min) Significant stance phase asymmetry, especially single support (decreased 12% ascending, 13% descending).

Trans-tibial Amputees Powers et al (1997) Decreased velocity indicative of – Limited ability to elevate body mass. – Diminished ability to maintain forward progression. Diminished single support time is an indication of instability, and difficulty controlling balance.

Normals Large amount of intra-subject variability, but high correlations of certain characteristics between subjects. Higher the activity in certain muscles, the lower the variability. Indicates the inherent instability of this task.

Stair Ascent McFadyen & Winter (1988) Stance – Weight Acceptance (WA) – Pull Up (PU) – Forward Continuance (FCN) Swing – Foot Clearance (FC) – Foot Placement (FP)

Weight Acceptance Moves body into optimal position to be pulled up onto the step. Initiated by contralateral plantarflexors. Involves strong concentric activity of hip & knee extensors. Ankle moves into ~13 0 dorsiflexion, with soleus working eccentrically to stop too much knee flexion.

Weight Acceptance – BKA’s Powers et al (1997) – Lengthened “initial double limb support”. – Indicates difficulty transferring weight forwards onto prosthesis. – “Prosthetic DF only capable of ~7 0 Yack et al (1999) – Passive properties of prosthesis cannot limit excessive knee flexion like soleus would.

Weight Acceptance – BKA’s Torburn et al (1994) – Increased hip flexion (trunk flexion) to assist moving weight forward over the foot.

Pull Up Most unstable portion – body supported on one limb, while all joints are flexed. Support moment twice normal gait. Concentric power generation by VL and plantarflexors (mainly soleus). Hip moments & power are variable – must control Head/Arms/trunk segment. Gluteus medius active at beginning of PU, keeping pelvis level during single support.

Pull Up – BKA’s Powers (1997), Yack (1999) & Torburn (1994) – Amputees used a “hip dominant” strategy to raise body weight, rather than “knee strategy”. – Decreased joint moments & powers at knee & ankle. – Increased joint moments, powers, and total work at hip 20% inc hip extensor work; 40% inc VL work; Increased & prolonged hamstring contractions – Assist hip extension – Protect distal tibial remnant from pressure on anterior socket. RF recruited to assist VL.

Forward Continuance The subject has ascended the step, & is moving forward to the next. Mainly horizontal – no vertical shift of CoM until just prior to toe-off. Support moment remains extensor, with burst of gatrocs/soleus activity at the end to produce vertical thrust.

Forward Continuance – BKA’s Decreased hip extension range / increased trunk flexion. No plantarflexion for vertical thrust.

Foot Clearance Involves lifting the leg & clearing the intermediate step. Involves concentric dorsiflexor activity, then concentric hamstring activity. Forward & up movement produced by hip flexors (not RF) & contralateral vertical thrust. Some RF activity to reverse knee flexion & limit heel rise.

Foot Clearance – BKA’s Decreased dorsiflexion range: ~5 0 Knee motion not significantly different (Powers et al 1997).

Foot Placement Hamstrings work eccentrically to lower the foot, with simultaneous concentric DF activity. Final foot position is controlled by hip extensors. Preparatory activity prior to foot contact in RF, VL, Glut max & glut med.

RF VL Gmax Gmed McFadyen & Winter (1988)

Other points Differences from ground to step 1 compared to step1 to step 3. Two peaks in GRF’s – Start of single limb support = 107%BW – End of FCN corresponding to vertical thrust = 115%BW No periods of vertical movement without concurrent horizontal movement. Support moment needing to be generated is 2-3 times that for level walking.

Other Points Need up to of knee flexion.

Points for BKA’s More prolonged & intense EMG (Powers et al 1997) through stance. – Total combined power generation avg 32% of isometric MMT, vs 23% in normals. Increased energy expenditure. Moment & power calculations may be decreased around the knee, as calculations do not account for co-contraction with hamstrings.

Descent McFadyen & Winter (1988) Stance – Weight Acceptance (WA) – Forward Continuance (FCN) – Controlled Lowering (CL) Swing – Leg Pull-Through (LP) – Foot Placement (FP)

Weight Acceptance Usually a toe-strike Dominated by eccentric activity of RF, VL, gastrocs & soleus. Most energy is absorbed by plantarflexors.

Weight Acceptance – BKA’s Powers et al (1997) – Foot contact in ~ 3 0 DF, thus no toe-strike, and no energy absorption through PF’s. – Increased Gmax & hamstrings activity to assist weight shift. ? Softer contact = no momentum, & therefore must actively extend to shift weight. Decreased knee flexion during WA.

Forward Continuance Extensor moment at all 3 lower limb joints. Knee extends slightly while moving forwards. Movement controlled by eccentric plantarflexor activity.

Forward Continuance –BKA’s Prolonged & more intense hip extensor activity.

Controlled Lowering Involves descent to the next step. Power absorbed by eccentric quads, less so from soleus. Burst of concentric soleus activity at the end, to relieve the extreme dorsiflexed position. Hip flexors working concentrically – suggests working to control Head/Arms/Trunk segment rather than assist in the lowering of the body

Controlled Lowering – BKA’s Powers et al (1997) – Decreased knee flexion (17 0 vs 25 0 ). – Decreased ankle DF (10 0 vs 23 0 ). – Increased hip flexion (29 0 vs 17 0 ). – Greater anterior pelvic tilt. Significant Gmax activity, & prolonged hams activity: Hip involved in lowering body mass Hams co-contraction to protect distal tibia from excessive pressure against socket (Yack et al 1999). RF recruited earlier (late swing) and earlier cessation of activity (16% cycle vs 47% cycle).

Leg Pull Through Hip continues to flex concentrically. Knee flexion required to clear intermediate step (but not as much as ascent ~100 0 ). Ankle dorsiflexes concentrically.

Foot Placement Reversal of movement – hip & knee extend, ankle plantarflexes. Hamstrings decelerate knee extension. Glut med active just prior to contact – may have been involved in keeping limb abducted as well as preparing for WA. Tib-Ant contraction just prior to contact to move impact point to outer border of foot. Gastrocs co-contraction in preparation for impact.

Foot placement – BKA’s No active plantarflexion in preparation for impact.

Figure 4: EMG During Descent (McFadyen & Winter, 1988) McFadyen & Winter 1988)

Other Points Differences from step 3 to 1 compared to step 2 to floor. No vertical movements without concurrent horizontal movements. Descent speed correlated significantly with cross-sectional area of knee extensors & psoas major – suggests muscle mass plays a role.

Other Points Evidence of preparatory actions in Gmed, Gmax, VL, & gastrocs. Two peaks in GRF’s: – First at start of WA = 120%BW – Second at end of FCN / start CL = 100%BW Greater Centre-of-Mass / Centre-of-pressure divergence indicates greater inherent instability in descent – “controlled fall” (Zachazewski et al 1993).

Other Points Use of handrail “in the usual fashion” did not influence flexion/extension moments (Andriacchi et al 1980). Joint ROM required: – Up to knee flexion. – Up to 25 0 ankle dorsiflexion.

IMPLICATIONS 1. Ascent & descent requires up to knee flexion & 25 0 dorsiflexion. Uh oh. Reduce bulk in popliteal area. Foot placement in descent – toes over edge to allow foot to roll over.

2. Large power bursts are required in the stance hip & knee, and in a greater range than level walking. Train through required ranges concentric & eccentric. Vary tread depth & riser height to alter intensity. “Power”, not strength. Consider speed & timing, esp as hip & knee extend together in ascent. Consider: – Part practice – part range -> full range. – Double support -> single support. – Practice step to same level -> 2 steps. – Minimise use of hand for pulling up or weight bearing. – Maximal extension in ascent occurs before contralateral foot placement.

3. In ascent, 2 nd peak in GRF occurs at end of stance (vertical thrust), produced by PF’s. No PF’s on amputated side – increased demand on extensors on intact side. Older / frail vascular amputees may have difficulty ascending on intact limb as contribution from contralateral PF’s is absent -> need to train bilaterally. Older / frail vascular amputees have weakness of intact PF’s (Winter et al 1990) -> increased demand on amputated side quads when ascending step over step.

4. Hip & Knee flexion occur simultaneously during swing in ascent. Train as a unit. Make use of motion-dependent characteristics of swing (momentum/inertia) to assist. Specific strategies to increase strength & recruitment of psoas & hamstrings. How much circumduction is allowed?

5. Activity in RF, VL, Gmax & Gmed is evident before foot contact. Specificity of practice includes stages prior to targeted component to allow learning of preparatory actions.

6. At no time is there a vertical shift of CoM without a concurrent horizontal shift. Clients must be trained to move forward & up, or forward & down. Consider what muscles / prosthetic components should be involved in assisting or limiting this movement. Eg plantarflexors normally control forward movement during FCN in descent. – What has to compensate? – Will the client avoid forward movement as they feel they have no control?

7. During descent, the largest GRF occurs at weight acceptance – 120%BW – and most energy is usually absorbed by PF’s. Implications even in “bad leg to hell” patterns. Landing is more stressful than lowering. Eccentric control of quads/hip extensors/abductors must be trained during landing, including proper forward shift during WA, to assist in shock absorption and control forward shift in place of PF’s. Increased demand on contralateral limb during it’s CL phase.

8. No toe-strike during descent on prosthetic side. Contralateral limb may have greater demands on – Knee joint flexion – Eccentric quads strength through that increased range. – Ankle dorsiflexion range. Energy absorption through eccentric quads control -> train “impact” / knee flexion (no greater than ~23 0 )

9. Differences in kinematics & kinetics observed with Floor step vs step step. Also need to include approach – planning step lengths appropriately, & different ranges / powers on different steps. Training on 1 step does not always carry over to a flight of steps.

10. Incorrect use of handrail is the most common compensation. Pulling or weight bearing on rail masks kinematic or kinetic deviations. Structure environment to minimise hand use but maintain safety: – Which side holds rail? Suggest ipsilateral. – Grip – Rail vs aid vs standby assist – Height of rail (or other hand support) – Step heights in part practice to allow practice of correct activation patterns. Use of rail in normal fashion did not influence flexion / extension moments.

11. Improve power in muscles that compensate for loss of ankle mechanism. Ipsilateral VL, RF, (conc & ecc), hams as hip extensor Contralateral PF’s, VL, RF, hams as hip extensor. Ipsilateral hip flexors (no vertical thrust).

12. Remember to train Core Stability for trunk control. Increased “hip dominance”, but they will need a stable base to work off.

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