This study examined the kinematics of the terminal swing phase in unilateral transfemoral amputees using microprocessor-controlled versus mechanical prosthetic knees. The researchers found that amputees had a latent period between knee extension and initial contact on the prosthetic limb that contributed to the lengthened swing phase. They also found that the latent period was reduced in amputees using microprocessor-controlled knees compared to mechanical knees. The latent period represents additional time needed for stability and confidence before initial contact.

1. Dr. Lakshmi Nair
Journal presentation

2. Kinematics in the Terminal Swing
Phase of Unilateral Transfemoral
Amputees: Microprocessor-Controlled
Versus Swing-Phase Control Prosthetic
Knees
Arch Phys Med Rehabil 2010;91:919-25

3. Introduction
the 3 most studied gait aspects are the compensation mechanisms
of the intact limb, the evolution of classic spatiotemporal
parameters, and energy costs.
 All the research studying these aspects has shown that,
compared with the intact limb, the stance phase duration,gait
speed, and stride length are reduced on the prosthetic side,while
the duration of swing phase is increased.
However, none of this research has examined the modifications
at the end of the swing phase of the prosthetic limb in TFAs

4. Aim of the study
 to compare the spatiotemporal parameters in the terminal
swing phase of TFAs in prosthetic and intact limbs with those
of able-bodied subjects.
At this sub phase of gait cycle, to identify a Latent period in
the TFA between the full extension of the prosthetic knee
and the initial ground contact of the ipsilateral foot.
 study the correlation between the LP and the duration of the
swing phase on the prosthetic side.
 evaluate the influence of the type of knee (microprocessor-
controlled prosthetic knees vs swing phase control prosthetic
knees), the time since amputation,and the amputation level
on this LP.

5. Study hypothesis
The latent period( LP) was important on the prosthetic limb
in TFAs and it contributed to the lengthening of the swing
phase on this side.
using a microprocessor-controlled prosthetic knee C-Leg
would reduce the LP.

6. Objective:
To analyze the spatiotemporal parameters in the terminal
swing phase of the prosthetic limb in unilateral transfemoral
amputees (TFAs) compared with a group of asymptomatic
subjects.
 to identify a latency period (LP) in the TFA between the full
extension of the prosthetic knee and the initial ground
contact of the ipsilateral foot.
 To study the correlation between the LP and the duration of
the swing phase.
 To evaluate the influence of the type of knee, the time since
amputation, and the amputation level on the latency period

7. Study design
This retrospective study used data recorded during the
3-dimensional gait analysis of TFAs examined between 1999
and 2007
Setting: Gait analysis laboratory of a re-education and
functional rehabilitation service.

8. sample
Participants: TransFemoralAmputees(n29) and able-
bodied (n15) subjects.
TRANS FEMORAL AMPUTEES
24 men ,4 women
11 right ,18 left
27 Traumatic, 2 tumoral
Prosthetic knee
1 Passive mechanical
11 Swing phase control
3 Stance and swing phase control
14 Microprocessor controlled (C-Leg)

9. Incusion criteria
21 -64 years
1-month acclimation period with their prosthetic knee.
exclusion criteria
 amputation because of vascular disease;
any osteo-articular, muscular, or neurologic pathology
(either of the residual limb or the intact limb) that would be
likely to modify their gait; and
 the use of walking supports (eg, canes)

10. The gait lab
This laboratory uses a 3-dimensional opto-electric motion
analysis system,
 a series of 7 infrared cameras that record the movement of
reflective markers,
and 3 forceplates.

11. Gait analysis
after warm-up exercises designed to insure that their gait
was relaxed and close to their usual gait,
the subjects were asked to walk at a freely chosen speed in
their regular shoes.
The 3 trials in which satisfactory pressure was applied on the
forceplates were retained.

12. Studied variables
Gait speed. the mean speed in the sagittal axis (x) of the
marker positioned on the sacrum,which represents the
body’s center of gravity.
Stride length. interval separating the position of the
marker placed on the the heel in 2 successive stance phases.
Stance phase duration. the evolution of the ground force
reaction obtained from the forceplates over time. interval
between the instant of initial ground contact and the instant
of terminal ground contact of a given foot

13. Studied variables contd..
Full knee extension instant. The knee joint angles were
the angle formed by the markers positioned on the thigh, the
lateral surface of the knee, and the external malleolus over
time. This variable was easily measured in able-bodied
subjects and in the TFA’s intact limb by examining the
characteristics of the knee’s flexion-extension curve in the
sagittal plane

15. In the prosthetic limb, however, measuring this variable is
made difficult by the absence or partial disappearance
(depending on the type of prosthesis) of knee flexion at the
beginning of the stance phase.
 On the curve, a plateau appears instead of the notch, which
corresponds to knee extension to insure stability during the
stance phase. The end of the prosthetic knee’s extension
appears on the curve as an abrupt reduction of the slope

17. Latency period. The LP is represented by the interval
situated between the end of the knee extension and the
ipsilateral heel’s initial ground contact. It is determined by
calculating the difference between those 2 events

18. Stastistical analysis
classic descriptive analysis (ie, mean and SDs) and 3 parametric
statistical tests:
an unpaired Student t test for comparing the control group with
the TFA group and TFAs with a swing-phase control prosthetic
knee to those with a microprocessor-controlled prosthetic knee;
 a paired Student t test for comparing the spatio-temporal
parameters of the prosthetic versus intact limb in the TFA group;
and
 Spearman correlation test for verifying the relationships between
the LP and the swing phase duration in the TFA group..

19. Results
There was a significant difference in gait speed
(P.0001),stride length (P.01), and cadence (P.0001), which
were lower in the TFA group than the control group.
The swing phase percentage for TFA prosthetic limbs was
significantly greater than in the intact limbs of the TFA group
(P.0001) and in the control group (P.0001).
The stance phase percentage in the intact limbs of the TFA
group was significantly greater than in the prosthetic limbs
(P.0001) and in the control group (P.0001).
LP- higher in the prosthetic limb than the intact limb in the
TFA group (P.0001) and than in the control group (P.0001)

21. Comparing swing phase control with
microprocessor controlled knee
Gait speed and cadence were significantly lower in the first
group compared with the second(P.048; P.02).
There was no significant difference between these 2 groups
in terms of swing phase percentage for the prosthetic limb
(P.34).

23. Factors influencing the LP.
● Age: The LP of the prosthetic limb of TFAs over 45 years of
age was greater compared with the others, but this difference
was not significant (P.26)
● Amputation level: The subjects with a long (n9) or
medium (n15) residual limb had an LP that was significantly
shorter than those of subjects with a short (n5)
residual limb, (P.046; P.029).
● Time since amputation: TFAs who had a limb amputated
quite some time ago (2y) (n16) had a shorter LP than those who had
an amputation relatively recently (2y) (n13), but this difference
was not significant (P.11)

24. Results

27. ● Type of knee: The LP measured for the prosthetic limb of
TFA with a swing phase control prosthetic knee was
significantly greater than the LP of those using a C-Leg
knee (P.021). On the intact limb, the LP was significantly
shorter in the first group compared with the second
(P.008),

29. DISCUSSION
Separating the subjects into 2 more homogeneous groups
according to age showed that those under 45 years of age
(n13) had a gait speed and a stride length (on both sides)
significantly higher than the others (n16).

31. Limitations
The TFA group was relatively heterogenous. Several factors
can explain this heterogeneity. These factors depend either on
the subject (age, amputation level, time since amputation) or
the prosthesis.

32. conclusions
Analyzing the end of the swing phase in unilateral transfemoral
amputees allowed to discover an LP, occurring between the end of
the full knee extension of the prosthetic limb and the initial ground
contact of the ipsilateral heel.
LF is of negligible duration in able-bodied subjects and in the intact
limbs of TFAs,
 the LP is significantly greater for the prosthetic limb. It seems to
be needed by TFAs to insure the stability of the prosthetic knee.
This LP can be qualified as “confidence time.”
It can explain the lengthened swing phase on the prosthetic side
based on the strong correlation between those 2 parameters.
Using a microprocessor-controlled prosthetic knee C-Leg allows
the confidence time to be reduced.