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Physiological Gait Analysis of Type IIIC Tibial Limb Salvage Patients Versus Traumatic Transtibial Amputees

David H. Nielsen, PhD, PT
Donald G. Shurr, PT, CPO
Pamela A. Macfarlane, PhD
Lisa M. Marco, MPT
Julie K. Mills, MPT
Lisa L. Padgett, MPT
Jennifer J. Randall, MPT
James V. Nepola, MD

ABSTRACT

The purpose of this study was to examine the physiological responses to overground (OG) versus treadmill (TM) walking in tibial limb salvage (TLS) patients with comparisons to transtibial (below-knee) amputees. The participants included five TLS (age = 39.2 + 10.2 yrs, weight 91.4 +/- 11.6 lbs) and five transtibial (age 37.6 +/- 14.1 yrs, weight 99.2 +/- 11.8 lbs) subjects. A multiple-speed (53.6, 67.1, 80.5 and 93.9 m/min = 2.0, 2.5, 3.0 and 3.5 mph) repeated-measures design was used. Results showed mean increases in exercise intensity (a 3.1-percent increase in APMHR) and energy cost (an 11.7-percent VO₂ increase) and a decrease in gait efficiency (an 11-percent Geff decrease) for TM versus OG walking.

Although comparisons between groups were not statistically significant, trends suggested a more impaired gait for TLS subjects than for transtibial subjects. The question of whether severe tibial fracture patients should undergo lengthy limb salvage procedures, which may involve multiple surgeries, long hospital stays and prolonged rehabilitation periods, remains unresolved. Additional research in this area will further assist the prosthetist and surgeon in answering questions involved in decisions surrounding elective amputation.

Introduction

Tibial limb salvage procedures can provide an alternative to transtibial (below-knee) amputation in patients who have sustained severe (type IIIC) tibial fractures (1-3). However, only a limited number of comparisons between tibial limb salvage (TLS) patients and transtibial amputees have been conducted. Numerous research studies have been conducted on physiological and descriptive gait parameters of transtibial amputees (4-12) and the normal population (5,13-22). One of the first investigations involving TLS versus transtibial gait comparisons (23) demonstrated no significant between group differences in energy cost and gait efficiency, but the conclusions are limited because only two relatively slow walking velocities were examined.

Prosthetists are routinely consulted when IIIC tibial fractures are evaluated for definitive care. Following discussions about elective amputation, information is often included on orthoses, shoes, shoe modifications and elevations, custom inserts, and artificial limbs. During these discussions, questions often arise concerning outcomes with prostheses, including queries about walking speed. A comparison between TLS and transtibial gait would be helpful in answering questions about amputation versus salvage.

For practical reasons past studies involving patient groups as well as normal subjects have commonly used treadmill (TM) ambulation for data collection (6,9,10,13-15,21-25). Because it has been found that transtibial amputees use significantly shorter step lengths with both feet during TM walking compared to overground (OG) walking, it is unclear whether TM results are directly transferable to functional OG ambulation.

The primary focus of this research was to study the gait of TLS subjects during ambulation over a functional range of walking velocities. Specifically, the study was designed to assess the relative exercise intensity, energy cost, gait efficiency and gait symmetry during multiple-graded speed ambulation. In this context the study has three objectives:

• To investigate differences in gait performance between OG versus TM walking in TLS subjects
• To compare the gait performance of TM walking for TLS subjects to a group of previously tested transtibial patients (9)
• To compare OG self-selected walking velocity (SSW-V) gait performance of TLS subjects to previously tested transtibial patients (9)

Methods

Outcome Variables

As previously defined (14), the percent of age-predicted maximum heart rate (%APMHR = 100-HR exercise/220 - age) served as the criterion measure of relative exercise intensity. Energy cost (VO₂) was assessed by direct measurement of oxygen uptake (VO₂ = mlO₂/Kg-min). Gait efficiency (Geff), the energy cost per distance traveled, was calculated from the ratio of energy cost to walking velocity [Geff = (mlO₂/Kg-min)/(m/min) = mlO₂/Kg-m]. The more efficient the gait, the smaller the Geff value. Gait symmetry (Gsym) was computed from step-length ratios (Gsym = involved/uninvolved step length). SSW-V was determined from the mean of repeated time trials of steady-state walking.

Experimental Design

A two-factor repeated-measures design was used to evaluate %APMHR, VO₂ and Geff responses in the TLS subjects. The two factors observed were walking mode (OG versus TM) and walking speed (53.6, 67.1, 80.5 and 93.9 in/mm = 2.0, 2.5, 3.0 and 3.5 mph.) A between-group (TLS versus transtibial) repeated-measures (multiple speeds) design was used to evaluate %APMHR, VO₂ and Geff responses for TM walking. Between-group differences in S-SWV and Gsym during OG ambulation also were tested. The data on the transtibial subjects were collected from patients walking with dynamic response prosthetic feet (Flex-Foot Inc., Irvine, Calif.).

Subjects

The TLS subjects in this study consisted of five healthy adult males who had sustained type IIIC fractures of the tibia. All subjects had undergone limb salvage procedures by the same orthopedist. The following were used as inclusion criteria for entry into the study: no head injury, independent ambulation without assistive devices, no contralateral limb involvement and at least one-year post-injury status. Each subject was fully informed of the test procedures and gave written consent to enroll in the study.

Prior to testing, the subjects were screened to assess their general health and ability to perform the walking tests. During testing the subjects wore comfortable clothing and their normal walking footwear. All subjects were compensated monetarily for their participation in the study.

The descriptive data on the TLS subjects were compared to the transtibial data from the previous study (9). By design the groups were of the same gender (males) and statistically similar in age and weight (see Table 1 ). Sample sizes were the same (n=5).

Procedures

Participation involved three one-hour sessions separated by at least one hour of rest. An initial orientation session was followed by two test sessions (one TM and one OG walking) with a randomized test order. During the first session, all necessary paperwork was completed, and each subject was familiarized with the general testing procedures and equipment and allowed to practice walking on the OG 60-rn continuous walking course and treadmill. The subject's S-SWV was determined during the initial session according to a standardized protocol (9). Following three minutes of free-paced walking, five time measurements were taken over a 5-in segment of the OG walking course. These measurements were collected with an electronic timer, portable lights and photoconductive switches and were used to calculate S-SWV.

The subsequent test sessions involved walking at speeds of 53.6, 67.1, 80.5 and 93.9 in/mm, and S-SWV. Overground speed was measured using an electronic speedometer cane (17) held by the investigator who walked with the subject during the OG test. The speedometer cane was used to check the TM speed during TM testing. Each test consisted of a three-minute warm-up at the appointed speed, immediately followed by approximately two to three additional minutes of data collection at that speed. Data collection included VO₂ and HR measurements at all speeds and step-length measurements for the subject's individually determined S-SWV.

During the walking tests, Douglas bags were used for timed collection of the subject's steady-state expired air. The procedure required the subject to wear a lightweight adjustable head harness that supported a small respiratory valve and rubber mouthpiece. A nose clip was worn to prevent nasal breathing. Lightweight, large-diameter flexible tubing connected the respiratory valve to the Douglas bags. The Douglas bags were carried by the investigator during OG ambulation and suspended for TM walking. Final calculation of VO₂ was determined by the open-circuit method using a semiautomated on-line computer system (9).

Heart rate was monitored by EGG radio-telemetry. Three electrodes were placed on the subject's chest using a modified chest manubrium V electrode lead system. Lightweight electrode cables connected the electrodes to a miniature radio transmitter worn around the subject's waist. The transmitted EGG signals were picked up by an FM receiver that was connected to a standard electrocardiograph. Minute HR values were based on six-second EGG strips. Heart rate measurements at minutes four and five of each trial were compared to verify steady-state conditions. The final HR measurement was used in the calculation of %APMHR, which served as the index of relative exercise intensity.

Step-length measurements were determined using a previously reported method (9) for the S-SWV trials during OG walking. Mean values based on three to five walking trials were used in the final calculations of the involved to uninvolved step-length ratio for the Gsym measurement.

Statistical Analysis

Descriptive statistics were computed on all variables. Student t-tests were used to test for between-group differences in the demographic data and the measurement of S-SWV. Repeated measures two-way ANOVA was used to test for interactions and main effects for mode of walking (OG versus TM) and speed of walking for the TLS ambulation data. A mixed model repeated-measures, two-way ANOVA was used to test for interactions and the main between-group (TLS versus transtibial) and speed effects for the FM walking data. Bonferroni-adjusted-tests were used for pairwise follow-up contrasts. To limit the number of pairwise comparisons, only differences at adjacent velocities were contrasted. Between-group Gsym differences at 5WV were tested with ANCOVA. An alpha level of 0.05 was selected as the criterion for statistical significance.

Results

In OG versus TM comparisons, %APMHR systematically increased with velocity in both modes of ambulation (see Figure 1). Analysis of variance showed no significant velocity by mode interaction. Additionally, the main effect for velocity was significant, whereas the main effect for mode was not significant (OG = 58.9 %APMHR, TM = 60.7 %APMHR). Follow-up analysis produced significant pairwise contrasts for all adjacent velocities except 67.1 to 80.5 in/mm.

As indicated in Figure 2 , VO₂ also increased systematically with velocity in both modes of walking. Once again, no significant velocity by mode interaction was indicated. In this case, however, both the main effect for velocity and the main effect for mode were significant (OG = 13.7 ml O₂/kg-min, TM = 15.3 ml O₂/kg~min). Follow-up analysis showed significant contrasts for all velocities.

Between-walking-mode comparisons for Geff are illustrated in Figure 3 . The means for Geff revealed a descending parabolic response with the highest numerical values (low efficiency) at the slowest velocities and the lowest numerical values (optimal efficiency) at the middle velocities. The trends for OG versus TM paralleled each other with values for TM appearing higher (less efficient) than those for 0G. The velocity versus mode interaction was non-significant. Additionally, the main effect for velocity was nonsignificant, but the main effect for mode was significant (OG = 0.19 ml O₂/kg~m,TM = 0.21 ml O₂/kg~m). Follow-up analysis showed no significant differences between adjacent velocities.

Between-group comparisons (TLS versus transtibial) for %APMHR are graphically presented in Figure 4 . As indicated, %APMHR systematically increased with velocity in a parallel manner for both groups. In all cases, %APMHR was higher for the TLS compared to the transtibial group. Analysis of variance revealed no significant main effect for velocity but a non-significant main effect for group (TLS = 60.7 %APMHR, transtibial = 57.1 %APMHR). Follow-up analysis produced significant pairwise contrasts for all adjacent walking velocities.

As indicated in Figure 5 , similar responses were seen for VO₂. Walking velocity produced systematic increases in VO₂; however, the between-group differences were more pronounced. Analysis of variance revealed no significant group by velocity interaction. As before, the main effect for walking velocity was significant, and the main effect for group was nonsignificant (TLS = 15.3 ml O₂/kg~min, transtibial = 13.9 ml O₂/kg~min). Again, follow-up analyses produced significant pairwise contrasts for all adjacent walking velocities.

Between-group comparisons for Geff are shown in Figure 6 . The response curves demonstrated a descending parabolic relationship between Geff and velocity with TLS appearing higher (less efficient) than transtibial. Again, the highest values (least efficient) appeared at the lowest velocities, and the lowest values (most efficient) at the middle velocities. Analysis of variance revealed no significant differences between Geff for TLS versus transtibial subjects (TLS = .21 ml O₂/kg~m, transtibial = .19 ml O₂/kg~m).

To make between-group comparisons at the nonstandardized S-SWV, ANCOVA was used with velocity as the covariable. As indicated in Table 2 , S-SWV for the transtibial group was higher than for the TLS group (TLS = 67.7 m/min, transtibial = 80.0 m/min); however, the difference was not statistically significant. Based on ANCOVA, the adjusted S-SWV for the two groups was 73.8 in/mm. The ANCOVA adjusted means and standard errors for the %APMHR, VO₂, Geff and Gsym are presented in Table 3 . As indicated, the between-group differences appeared negligible and were found to be nonsignificant.

Discussion

Numerous studies have used both OG and TM walking for gait analysis in normals as well as selected patient groups (4,5,27,28). Treadmill walking has the advantages of convenience and ease of standardization and data collection. In general, VO₂ and HR responses have shown an ascending curvilinear relationship with increases in walking velocity (9,19,21,29). In patients with nonpathological gait, Rohrig found no differences in VO₂ and HR measurements for continuous OG versus TM walking from speeds of 1.0-4.0 mph (21) yet other research with normal subjects has produced conflicting results (1).

Little research has been conducted examining these parameters with pathological populations. However, one study suggested HR and VO₂ differences between modes of walking in TLS patients (23), and another study found transtibial subjects took significantly shorter steps on the TM than OG (26).

The current study's results on TLS patients indicated systematic increases in HR and VO₂ as expected with increases in walking velocities for both OG and TM walking. At all velocities tested, %APMHR and VO₂ results were higher on the treadmill. The overall mean for %APMHR was 3.1 percent higher for TM walking whereas the mean for VO₂ was 11.67 percent higher for TM walking.

Traditionally, %APMHR has been used as a criterion measure of relative exercise intensity, and in the context of the present study indicated the relative cardiovascular stress of walking. The general guideline for continuous aerobic exercise is that %APMHR should not exceed 85 percent (30). Mean %APMHR for both modes of walking ranged from 52.7 to 68.8 %APMHR for the TLS subjects. These results suggest that the subjects were working at an acceptable level of exercise intensity.

Gait efficiency, defined as the energy cost per distance traveled, has been used by numerous researchers (11,12,14,22,31,32). Previous studies (9,19) demonstrated a parabolic relationship between Geff and walking velocity, with the most efficient Geff seen at the individual's S-SWV. Increases or decreases in velocity varying from the S-SWV resulted in less efficient, elevated Geff values. Gait efficiency for OG and TM modes in TLS subjects exhibited the expected parabolic relationship. Again, TM values were higher than OG at all velocities, resulting in a mean l0.5-percent less efficient gait.

The increases in %APMHR, VO₂ and Geff in the TLS treadmill ambulation imply that the exercise workload of walking was greater on the TM than 0G. A possible explanation for this difference may be a tendency for this patient group to use shorter step-lengths and increased cadence during TM walking as was previously reported in transtibial subjects (26). Further investigation in this area is recommended.

The data collected on the TLS subjects were compared to transtibial data (9). Statistically, the two groups were similar based on age, weight and gender (see Table 1 ). Although none of the between-group differences was statistically significant, TLS subjects exhibited a 6.3-percent higher mean %APMHR, l0.l-percent higher VO₂ and an average l0.5-percent less efficient gait than transtibial subjects. Based on step-length ratios Gsym was slightly better (2.5 percent) in the TLS subjects than the transtibial subjects.

Self-selected walking velocity can be used as a general measure of overall walking performance. It has been shown by several investigators that people select an optimally efficient walking speed, referred to as the self-selected or free-paced walking velocity (10,12,19,27,31,33). Persons with abnormal gait patterns typically walk at slower speeds but still choose the most efficient walking velocity (9). Gait efficiency of TLS subjects was therefore compared to that of transtibial subjects at S-SWV for its functional implications, The most S-SWV v in normal subjects was deters mined to be 74-83 in/mm (5). For TLS s subjects, the average S-SWV was 67.7 -in/mm and for transtibial subjects, 80.0 -in/mm.

Although the difference between the TLS and transtibial subjects was statistically nonsignificant, the TLS subjects walked on average 15.4 percent slower than the transtibial subjects, which may be clinically relevant. Further study, including expanding the sample size, may reveal statistically significant betweengroup comparisons that were not found in this study due to its small sample size and inherently large between-subject variability.

Conclusion

Knowledge of energy cost (VO₂), relative exercise intensity (%APMHR), gait efficiency (Geff = VO₂/velocity) and gait symmetry (Gsym = involved/uninvolved step length) provides quantitative information regarding the evaluation of walking performance. Whether type IIIC tibial fracture patients should undergo lengthy limb salvage procedures-often consisting of 15-40 separate surgeries, long hospital stays and rehabilitation-remains a challenging clinical question. Based on the select sample of subjects tested in this study, the following conclusions appear to be warranted:

• TM walking in TLS subjects produced a nonsignificant difference in %APMHR compared to OG walking.
• TM walking in TLS subjects produced significantly higher VO₂ (11.7 percent) values compared to OG walking.
• TM walking in TLS subjects produced a significant difference in Geff (TM 11 percent less efficient compared to OG walking).
• TLS versus transtibial comparison of %APMHR revealed a statistically nonsignificant difference (TLS = 6 percent higher than transtibial).
• TLS versus transtibial comparison of VO₂ revealed a statistically nonsignificant difference (TLS = 10 percent higher than transtibial).
• TLS versus transtibial comparison of Geff revealed a statistically non significant difference (TLS = 11 percent less efficient than transtibial).
• TLS versus transtibial ANOVA comparison of S-SWV revealed a statistically nonsignificant difference (TLS = 15 percent slower than transtibial).
• TLS versus transtibial at an ANCOVA-adjusted common S-SWV revealed nonsignificant differences in %APMHR, VO₂, Geff and Gsym.

The results of this study indicate that values obtained during TM ambulation in populations with pathological gait (TLS) are not necessarily transferable to more functional OG ambulation. Thus, caution should be used when making generalizations about gait parameters in these populations based or data collected on the TM. Although TLS versus transtibial comparisons revealed statistically nonsignificant differences, trends suggested that walking performance in TLS subjects may be more deviate/pathologic (more energy-consuming and less efficient, with a slower S-SWV) when compared to transtibial subjects. Further studies incorporating larger sample sizes could confirm these findings.

DONALD G. SHURR, PT CPO, is with American Prosthetics Inc. in Iowa City, Iowa. He is also an adjunct lecturer for the Physical Therapy Graduate Program in the Division of Associated Medical Sciences! College of Medicine at The University of Iowa, Iowa City, Iowa.

PAMELA A. MACFARLANE, PHD, is assistant professor of physical education at Northern Illinois University, DeKalb, Ill.

LISA M. MARCO, MPT; during the conduct of this study were graduate students in the Physical Therapy Graduate Program in the Division of Associated Medical Sciences/College of Medicine at The University of Iowa, Iowa City, Iowa.

JULIE K. MILLS, MPT; during the conduct of this study were graduate students in the Physical Therapy Graduate Program in the Division of Associated Medical Sciences/College of Medicine at The University of Iowa, Iowa City, Iowa.

LISA L. PADGETT MPT during the conduct of this study were graduate students in the Physical Therapy Graduate Program in the Division of Associated Medical Sciences/College of Medicine at The University of Iowa, Iowa City, Iowa.

JENNIFER I. RANDALL, MPT during the conduct of this study were graduate students in the Physical Therapy Graduate Program in the Division of Associated Medical Sciences/College of Medicine at The University of Iowa, Iowa City, Iowa.

JAMES V NEPOLA, MD, is a professor of orthopedic surgery at the College of Medicine at The University of iowa, Iowa City, Iowa.

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