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Case Report

Spatiotemporal Parameters and Step Activity of a Specialized Stepping Pattern Used by a Transtibial Amputee During a Denali Mountaineering Expedition

Highsmith, M. Jason DPT, CP, FAAOP; Kahle, Jason T. CPO, FAAOP; Quillen, William S. DPT, PhD, FACSM; Mengelkoch, Larry J. PT, PhD

Author Information
JPO Journal of Prosthetics and Orthotics: July 2012 - Volume 24 - Issue 3 - p 153-157
doi: 10.1097/JPO.0b013e31825f7ad9
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There are numerous mountain climbing techniques and stepping patterns, such as the French technique.1 The French technique is described as easing the ability to traverse ice, snow, and gentle to steep mountain grades (0°–60° pitch). The French technique is also known as flat footing because one of this pattern’s goals is to keep the sole of the footwear parallel to the snow/ice.

Specialized gait patterns and their potential benefit or detriment for mountaineering expeditions have not been studied in persons with transtibial amputation (TTA). Therefore, the purpose of this case report was to 1) describe spatiotemporal differences between the French technique and typical walking patterns of an individual with TTA in a laboratory setting and 2) report the qualitative and quantitative step activity of a US military veteran with TTA during a climbing expedition on Mt. McKinley in Denali, AK, USA.

METHODS

SUBJECT AND PROSTHESIS

The subject was a mesomorphic man, aged 51 years (height, 183 cm; and weight, 96 kg) with right TTA. He was a functional level 4 ambulator with a 45/47 score on the Amputee Mobility Predictor.2 During medical evaluation, he was found to have comorbid but pharmacologically controlled hypertension, gastroesophageal reflux disease, and phantom limb pain. The subject’s primary care physician cleared him to participate in an expeditionary summit attempt on Mt. McKinley. His amputation was of traumatic etiology 4 years before this report. His cylindrically shaped residual limb was 28 cm long (53% length of sound tibia; Figure 1), with bone bridging procedure,3 posterior flap closure, and its characteristic anterior-distal scar. The subject had 5/5 extensor and flexor strength (manual muscle test)4 bilaterally in the hips, knees, and sound-side ankle. The subject’s range of motion was normal for age at all lower limb joints.5 The subject’s prosthesis included a carbon fiber–laminated total surface bearing socket with a uniform Alps cushion liner (St Petersburg, FL, USA), an Otto Bock Derma ProFlex suspension sleeve (Duderstadt, Germany), and an Ossur Vertical Shock Pylon foot component (Reykjavik, Iceland). The subject reported having his current socket for 2 years and his foot component for 4 years, with no modifications, repairs, or adjustments. He further reported that he routinely fluctuates between 10 sock plies (achieved via two five-ply socks) and 12 sock plies (achieved by adding two additional one-ply socks) in a given day. His weekly activity was self-described as “highly active,” including 6 days per week of circuit training exercise with primary emphasis on large muscle groups of the lower limb (such as the quadriceps femoris, gluteal group, hamstrings, and sound plantar flexors). In preparation for the Denali expedition, this training routine was highly consistent for 7 months. Before this time, the subject’s exercise preference was biased toward upper limb strengthening. In addition, the subject self-reported an estimated daily 2500 to 3000 kcal diet consistent with caloric output, paying attention to avoid caloric deficit given the increased metabolic demands for the aforementioned circuit training. The subject specifically increased protein and reduced carbohydrate intake while maintaining a variety of fruit and vegetable intake.

Figure 1
Figure 1:
A, Anterior view of case climber’s residual limb. B, Posterior view of case climber’s residual limb. C, Case climber wearing prosthesis used during his summit attempt on Mt. McKinley.

DATA FORM AND STEP ACTIVITY MONITORING

A daily data journal was developed to include the day of the week/date, daily step count, peak daily altitude, duration spent climbing, an overall daily rating of perceived exertion (0–10 scale),6 and notes for freeform comments. In addition to the daily journal, an event log was provided that prompted the subject to capture any event of consequence (such as dermatologic, prosthetic, musculoskeletal issues), the pedometry count and time at the instance such an event was recognized, the day of the climb, a description of both the problem and solution, and a prompt to take a photo of the issue. Step count was monitored both daily and at events (as previously described) using a Sportline ThinQ XA Model 305 Pedometer (Yonkers, New York, NY, USA). The pedometer was hung on a lanyard around the climber’s neck such that the climber’s core temperature would keep the instrument within its described operating temperature range and such that clothing and gear strapping would minimize extraneous instrument movement that could erroneously be counted as steps.

MT. MCKINLEY MOUNTAINEERING PLAN

The 15-member expedition team included professionally trained mountaineering guides and emergency medical personnel. The team planned to traverse the 26.7-km trail along Mt. McKinley’s West Buttress route. Once on the trail, the expedition was scheduled to take approximately 17 days to reach the summit, notwithstanding inclement weather. The planned ascent would start at 2195 m and elevate to 6194 m of altitude at the summit. The team planned to encounter perilous crevasses and thus was trained and equipped to rescue fallen climbers. Because the snow-covered ground would soften during the daylight hours because of increased temperature and ground thaw, the team planned to travel at night. Specific training immediately preceding and during the climb occurred daily and included vital topics ranging from knot tying, crevasse rescue, acute mountain sickness symptom recognition, and varied gait patterns to accomplish such goals as team stepping synchrony.

SPATIOTEMPORAL GAIT DATA COLLECTION

Two weeks after the climbing expedition, the climber with TTA reported to the University of South Florida’s Human Functional Performance Laboratory for a debriefing interview and to demonstrate the French technique, self-selected walking speed (SSWS) (and gait pattern), and fastest possible walking speed (FPWS) (and gait pattern). At debriefing, investigators and the climber reviewed the daily climbing journal and event log. After debriefing, the subject traversed a 7.92-m GAITRite portable walkway (Havertown, PA, USA) three times each with the stepping patterns and velocities previously described. The GAITRite portable walkway is a valid and reliable instrument for recording spatiotemporal parameters of gait that has been used in the amputee population.7 While all of the spatiotemporal gait parameters captured by the GAITRite walkway were collected, the following variables were selected a priori for analysis:

  1. velocity
  2. stride time
  3. step time
  4. double support time (time with both feet on the ground)
  5. stride length
  6. step length
  7. base of support (BOS) width

It is known that side-to-side asymmetry exists with unilateral TTA.7 However, the purpose of this report was to gain a preliminary understanding of spatiotemporal differences between these particular gait patterns. Therefore, left and right side data (i.e., unilaterally recorded data) were averaged together to describe the given stepping pattern’s bilaterally averaged parameter (e.g., stride time, stride length, etc). Between-pattern differences were compared with a repeated-measures analysis of variance, and statistical significance was set at p ≤ 0.05. Statistical analyses were performed using SPSS 2011 (Armonk, New York, NY, USA).

RESULTS

DAILY STEP ACTIVITY AND EVENT JOURNAL

The daily step count revealed 8 days on the trail (Table 1), two of which were predominated by rest (day 2) or inclement weather (day 7). The subject reported three crevasse falls through ice (days 2 and 3). The total step count on the trail was 62,421 steps (days 2 and 7 not included). The average daily step count for the six active climbing days was 10,404 steps (range, 6,640–12,540 steps). Of the active climbing days, the climber estimated that 27% of steps (17,095 steps) were taken with the French technique. The event log documents five total events (Table 2). Of these, one was dermatologic in nature, three musculoskeletal events were documented, and the culminating event was cardiovascular in nature, in which the TTA climber reported overheating, exertion, and ultimately “hitting the wall” or “bonking,” requiring cessation of his climb and evacuation from the summit attempt. The climb terminated at 4115 m of altitude, which is greater than half of the total planned trek.

Table 1
Table 1:
Daily step activity
Table 2
Table 2:
Event log

SPATIOTEMPORAL GAIT DATA

Figure 2 demonstrates that gait velocity was 185 ± 1.1 cm/second for FPWS, 140 ± 5.4 cm/second for SSWS, and 20 ± 9.8 cm/second for the French technique, and each value was significantly different from both others (p ≤ 0.01). A priori selected temporal parameters were also all significantly different (p ≤ 0.05) from the respective measures from the other stepping patterns (Figure 3). These measures included stride time (SSWS, 1.1 ± 0.0 seconds; FPWS, 1.0 ± 0.0 seconds; and French technique, 4.7 ± 1.7 seconds), step time (SSWS, 0.6 ± 0.0 seconds; FPWS, 0.5 ± 0.0 seconds; and French technique, 2.4 ± 0.8 seconds), and double support time (SSWS, 0.3 ± 0.0 seconds; FPWS, 0.2 ± 0.0 seconds; and French technique, 3.7 ± 1.9 seconds). Two of the three selected spatial parameters (stride and step length) were also all significantly different (p ≤ 0.01) from the respective measures from the other stepping patterns (Figure 4). Stride lengths were 157.9 ± 2.3 cm for SSWS, 176.1 ± 0.9 cm for FPWS, and 81.7 ± 5.1 cm for the French technique. Step lengths were 79.0 ± 1.1 cm for SSWS, 88.0 ± 0.6 cm for FPWS, and 40.4 ± 2.6 cm for the French technique. The width of the BOS was significantly wider in the French technique (24.9 ± 1.9 cm) than in both SSWS (13.2 ± 0.6 cm) and FPWS (12.9 ± 1.7 cm) typical walking. The BOSs in SSWS and FPWS typical walking patterns were not different.

Figure 2
Figure 2:
Fastest possible walking speed (FPWS) and self-selected walking speed (SSWS): gait velocity by stepping pattern. *p ≤ 0.01 vs. French technique. †p ≤ 0.01 vs. SSWS. ‡p ≤ 0.01 vs. FPWS.
Figure 3
Figure 3:
Fastest possible walking speed (FPWS) and self-selected walking speed (SSWS): temporal parameters. *p ≤ 0.05 vs. French technique. †p ≤ 0.05 vs. SSWS. ‡p ≤ 0.05 vs. FPWS.
Figure 4
Figure 4:
Fastest possible walking speed (FPWS) and self-selected walking speed (SSWS): spatial parameters. *p ≤ 0.01 vs. French technique. †p ≤ 0.01 vs. SSWS. ‡p ≤ 0.01 vs. FPWS.

DISCUSSION

We hypothesized that spatiotemporal parameters would be different between a typical walking pattern at both SSWS and FPWS and the specialized French technique mountaineering stepping pattern. We further hypothesized that dermatological and prosthetic issues would be the most representative events during the trek. In fact, spatiotemporal differences were observed across the three stepping patterns; however, musculoskeletal events were the most representative problem during the climb and the culminating event was cardiopulmonary in nature.

Based on laboratory-measured step length of traditional stepping at SSWS (79 cm) and the French technique (40 cm), we estimate that with a step count of 62,421 steps, where 27% were taken with the French technique and 73% with traditional stepping, approximately 46.9 km were covered in total. This is clearly an overestimation, because the total trail length is 26.7 km and the climb was terminated at approximately halfway to the summit. In our opinion, this difference occurred because simulated stepping in the laboratory was done under ideal conditions on flat ground, allowing for optimally long step/stride lengths despite attempts and instruction to recreate field step/stride lengths. While on the climb, it is likely that traditional and French technique step/stride lengths were shorter because of a number of factors, including ground inclination, depth of snow, pack load, adverse weather, and others.

The daily step count averaged 10,404 steps on active climbing days. This is greater than the typical daily step count measured in community ambulating lower limb amputees, which is 6,000 steps.8,9 This is of course expected given the nature of the expedition, where destinations must be reached for critical reasons such as safety. Interestingly, however, the average daily step count on the trail is only slightly greater than the 10,000 daily steps recommended for a healthy lifestyle.10 This highlights a considerable limitation with step counting. That is, step counting provides no information about the intensity of stepping (i.e., the step rate).9 Therefore, to understand the difficulty of stepping, choices would be journaling, rating exertion, or using more sophisticated instruments to capture step rate, bout duration, and other parameters associated with ambulation. In this case, more sophisticated instrumentation was cost prohibitive and presented potential reliability challenges in terms of thermal effects regarding equipment function. Therefore, we opted for both journaling and rating exertion.

It is obvious that stepping in this environment is more challenging regardless of step count, but it is important to gain an understanding of what the stepping demands are in terms of volume of activity so that appropriate prosthetic components can be selected to minimize potential durability issues. In the case of this climber, a durable foot was selected, which, by the event log, presented no issues. Conversely, the climber “hit the wall” and was evacuated. It is therefore attractive to speculate if a foot component with less mass could meet the durability challenge while simultaneously being less fatiguing, thus allowing for greater distance on the climb to be achieved. Although this is a difficult environment in which to conduct such a study, the information is vital for select populations. For instance, military personnel who have sustained service-related amputations may need to perform with minimal impairment in comparable environments to continue service. Ecologically valid data such as these provide some insight into human performance under these circumstances.

Finally, we presented spatiotemporal differences between traditional stepping and the French technique. The French technique incorporates decreased velocity, step, and stride length and an increased BOS relative to traditional stepping at comfortable and fast speeds. Relative to temporal differences, the French technique uses increased stride, step, and double support time. Ultimately, the French technique is a slower, more deliberate gait that takes on similarities to that of populations that use more stable stepping patterns, such as the gait observed in toddlers, geriatric persons, and bilaterally involved amputees of dysvascular etiology.7,11,12 Each of these groups has the tendency to walk slower, increase step width, and double support time, which are all parameters that decrease mobility, to improve the stability profile of their gait pattern. Cumulatively, in the laboratory setting, the distance traversed by the French technique is approximately half that covered by traditional SSWS. Furthermore, the duration required to complete steps and/or strides was four to five times greater in the French technique than in the traditional stepping. Finally, the velocity was also four to five times slower in the French technique. Taken in total, this quantitative spatiotemporal profile of the French technique agrees with aspects of the qualitatively outlined description that describes a stepping pattern that favors stability and optimizes rest.1 Other means of study are necessary to determine if ground reaction forces approximate joint centers minimizing environmental influence on joints and whether muscles are less active using the French technique relative to other stepping patterns.

LIMITATIONS

This project had several limitations that must be considered. To begin with, data were collected on a single subject, which creates issues with generalizing. In addition, data collected on an expedition such as this are justifiably at risk of being a secondary responsibility and thus at risk of being of suboptimal quality and incomplete. Potential sources of such error include the journal and exertion ratings. Step counters as an instrument have potential error associated with extraneous movement despite attempts to minimize them. Finally, making field inferences from laboratory-collected data will have obvious limitations in terms of precision. For instance, precision of laboratory estimates can be improved if the actual mountain climb slope(s) is (are) simulated in the gait analysis measures.

CONCLUSION

We hypothesized that dermatological and prosthetic component issues would predominate in the case climber’s event log. In fact, musculoskeletal issues predominated, and the only skin issue was not associated directly with the prosthesis. Similarly, the prosthesis presented no failure issues. However, a fatigue issue ultimately concluded the climb, which warrants further investigation into balancing component durability and mass in terms of prosthetic foot selection. In terms of stepping techniques, as the altitude became progressively higher, the French technique was selected by the climber as the strategy of choice. The French technique is ultimately a slower stepping technique, with qualities suggestive of heightened stepping stability as opposed to mobility.

REFERENCES

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12. Su PF, Gard SA, Lipschutz RD, Kuiken TA. Differences in gait characteristics between persons with bilateral transtibial amputations, due to peripheral vascular disease and trauma, and able-bodied ambulators. Arch Phys Med Rehabil 2008; 89 (7): 1386–1394.
Keywords:

extreme athletics; gait; leg amputation; prosthesis; rehabilitation; physical therapy

© 2012 by the American Academy of Orthotists and Prosthetists.