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Research Reports |
KR Archer, PT, MS, DPT, is a PhD candidate, Center for Injury Research and Policy, Bloomberg School of Public Health, Johns Hopkins University, 624 North Broadway, Room 545, Baltimore, MD 21205 (USA).
RC Castillo, MS, is Assistant Scientist, Center for Injury Research and Policy, Department of Health Policy and Management, Bloomberg School of Public Health, Johns Hopkins University
EJ MacKenzie, PhD, is Fred and Julie Soper Professor and Chair, Department of Health Policy and Management, Bloomberg School of Public Health, Johns Hopkins University
MJ Bosse, MD, is Director and Clinical Research and Orthopaedic Traumatologist, Department of Orthopaedic Surgery, Carolinas Medical Center, Charlotte, NC
The LEAP Study Group is: Ellen J MacKenzie, PhD; Michael J Bosse, MD; James F Kellam, MD; Andrew R Burgess, MD; Lawrence X Webb, MD; Marc F Swiontkowski, MD; Roy Sanders, MD; Alan L Jones, MD; Mark P McAndrew, MD; Brendan Patterson, MD; Melissa L McCarthy, ScD; Thomas G Travison, PhD; and Renan C Castillo, MS.
Address all correspondence to Dr Archer at: karcher5{at}comcast.net
Submitted January 31, 2006;
Accepted July 25, 2006
| Abstract |
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Key Words: Clinical decision making Leg injuries Rehabilitation
| Introduction |
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Rehabilitation of people with lower-extremity reconstruction typically ranges from 12 to 72 months, with a median recovery time of 30 months.11 Smaller studies (<40 subjects) that have examined the recovery of gait have demonstrated that a slower preferred walking speed, a lengthened stride time, a deterioration of balance control, and an involvement of the knee joint are associated with longer salvage recovery times.4,11,12 One study6 showed that poor muscle strength (force-generating capacity) was correlated with abnormal gait, as well as the significant prognostic factors of increasing age and female sex. In salvages from bone tumors, decreased knee extensor strength was associated with a step-to-step (nonreciprocal) stair-climbing pattern, decreased locomotion, and compensatory hip and ankle movement strategies.5 Research suggests that muscle power is a primary determinant of gait,6,13,14 and manual muscle testing is a common clinical assessment tool for patients with lower-extremity trauma. The functional role, optimal strength, and optimal range of motion (ROM) of the hip, knee, and ankle have been well documented for normal gait, but the association of these measures with the recovery of gait among patients with limb salvage remains questionable.
The purpose of this study was to identify clinical measures associated with gait asymmetry and impaired walking speed in patients with lower-extremity reconstruction. The attainment of independent and unimpaired ambulation is an essential element of rehabilitation for lower-extremity trauma. Based on prior limb-salvage research, we hypothesized that increasing age, nonreciprocal stair-climbing ability, poor single-leg balance, and a manual muscle test (MMT) grade of less than 4 for hip extension, knee extension, ankle dorsiflexion (DF), and ankle plantar flexion (PF) would be statistically associated with gait deviation and walking speeds of less than 4 ft/s (1 ft/s=0.30 m/s). Understanding the association of strength, ROM, and functional measurements with impaired physical mobility in patients with lower-limb reconstruction will assist clinicians with establishing effective plans of care and help inform treatment decision making and prioritization of interventions.
| Method |
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The current analysis excluded 32 patients with bilateral injuries and 161 patients treated by amputation. An additional 27 patients were lost to follow-up at 24 months, resulting in 381 subjects with lower-limb reconstruction. Patients lost to follow-up were more likely to be of lower socioeconomic status than those with complete follow-up.17 Lower-extremity reconstruction surgery was performed primarily as a result of complex tibia fractures (51%), with the remaining 30% performed following severe foot and ankle injuries (Gustilo grade IIIB ankle fractures, all grade III intra-articular fractures of the distal tibia) and 18% following dysvascular injuries (knee dislocations, closed fractures of the tibia, or penetrating wounds with vascular injury).15,17 Injury characteristics included articular involvement (35%), nerve damage (6%), moderate-to-severe muscle damage (48%), and bone loss greater than 2 cm (21%). The mean age of the primarily male (75%) subjects was 35.6 years (SD=12.3). The majority of the participants were white (71%) and had less than a grade 12 education (69%).
Outcome
This study was primarily interested in the recovery of functional gait, as measured by gait speed and symmetry. Walking speed of
4 ft/s and gait deviation were combined into one primary outcome measure. This combined measure was used not only to provide an indication of impaired physical mobility,18 but to reflect a subjects poor quality of movement.19 Below we describe how walking speed and gait deviation were evaluated in the LEAP study and how these evaluations were combined into one primary outcome measure.
Walking speed.
Subjects were asked to walk 150 ft (45.7 m) on a level surface "as fast as they can" without an assistive device. The time it took for subjects to complete the task was measured with a stopwatch and recorded as feet per second. The use of a stopwatch has been found to yield data with excellent concurrent validity with the gold standard of infrared timing gates and an intraclass correlation coefficient (ICC) of at least .998 for tests of walking speed.20 No other reliability testing was conducted on this measure.
Gait deviation.
Subjects who participated in the 150-ft independent walking test also were visually monitored for gait deviations. Physical therapists were provided with a detailed description of each deviation. Participants were found to have gait asymmetry if they had one or more of the following common deviations: Trendelenburg gait, trunk asymmetry, leg circumduction, hip hike (increased hip abduction on the unaffected stance limb, with simultaneous pelvic elevation on the affected side during swing), knee hyperextension, no heel-strike, toe drag, uneven step length, or a limp not accounted for by the other listed deviations. Observational techniques have been found to yield data with moderate reliability,21–23 while instrumented gait analysis is the criterion standard.24 However, a 3-dimensional technique was impractical and too costly for the present study.
Walking speed and gait deviation.
A walking speed of 4 ft/s or less was considered an appropriate cutoff for impaired speed because the literature recognizes acceptable walking speeds of 3.2 ft/s for patients with lower-limb salvage 15 months postinjury and speeds ranging from 4.07 to 4.2 ft/s for fully recovered patients with transtibial and below-knee amputations.3,25,26 Mean walking speeds for individuals without gait impairments range from 4.4 to 4.9 ft/s, depending on age, sex, and location of ambulation.27–29 A walking speed cutoff of 5 ft/s also was examined to confirm associations between selected clinical variables and the primary outcome measure.
Potential Clinical Factors Associated With Abnormal Gait
A number of common impairment and functional measures were used as assessment tools to examine the factors associated with abnormal gait. We will describe these measures along with their scales and scoring systems.
Self-report pain scale.
Pain level was assessed with a visual analog scale (VAS), using a 0- to 100-mm horizontal line. Participants were asked to rate their average daily leg pain by placing a mark on the line between "no pain" on the left and "unbearable pain" on the right. The VAS score was recorded by measuring the distance from the "no pain" end of the line to the participants mark of personal pain intensity. A distance of 5 to 44 mm was considered mild pain, 45 to 74 mm was considered moderate pain, and 75 to 100 mm was considered severe pain.30
Stair-climbing and balance performance.
Gait capacity can be estimated by a persons ability to go up and down stairs with a step-by-step (reciprocal) maneuver.5 Participants were asked to climb 12 steps and then descend the same 12 steps at their preferred speed. A physical therapist noted whether the subject displayed a step-by-step pattern or a nonreciprocal, step-to-step pattern for both ascending and descending tasks.
Two parameters were used for standing balance: unilateral (single-leg) and tandem stance. For unilateral stance, subjects were asked to stand on one leg with their eyes open and arms crossed across their chest for 30 seconds. The number of seconds that the subject was able to stand before dropping the other leg was recorded for both the involved and uninvolved legs. Subjects were scored from 0 to 30 seconds. They then were asked to stand unsupported for 10 seconds with their eyes closed, arms crossed across their chest, and their injured foot touching the heel of their other foot. A score of less than 30 seconds for the unilateral stance and less than 10 seconds for the tandem stance was defined as functionally poor.31–33 A score of 0 seconds was attributed to subjects being unable to perform either of the 2 balance tasks.
Girth measurements.
Thigh and calf girth measurements were used to assess muscle atrophy.34 Circumferential measurements have been found to have high intrarater reliability and interrater reliability, with ICCs of .82 and .72, respectively.35 Data were recorded with a tape measure using the following landmarks: 8 cm proximal to the superior patella with knee in extension and 8 cm distal to the tibial tuberosity. Muscle atrophy of 0 cm, 1 to 2 cm, or 3 cm or greater was determined by comparing each subjects data for the involved leg with data for the uninvolved leg.
Range of motion.
Hip flexion and extension, knee flexion, and ankle DF and PF were measured using a standard goniometric technique.36 Subjects were asked to remove their shoes and socks and actively move the joint through the desired range. Physical therapists recorded the active range of motion (AROM) with the subjects positioned supine and then prone using a universal goniometer; measurements were rounded up to 5 for 3s and 4s and rounded down to 0 for 1s and 2s. Studies of the universal goniometer have shown high intrarater reliability for knee and ankle ROM, with ICCs for knee flexion and extension ranging from .97 to .99 and ICCs for ankle PF and DF ranging from .82 to .86.37,38 Starting and ending positions of each joint, as recommended by the American Academy of Orthopaedic Surgeons (AAOS),39 were used to record measurements. Norms were determined based on the averages published by the AAOS; ROMs below 120 degrees of hip flexion, 30 degrees of hip extension, 135 degrees of knee flexion, 20 degrees of ankle DF, and 50 degrees of ankle PF were considered restricted.
Strength.
Hip flexion, extension, and abduction; knee flexion and extension; and ankle DF and PF strength were measured by a patented device for exercising and measuring strength of a persons limb.40 The strength apparatus includes a pair of pivot clamps that were used to connect it to a physical therapy table. The pivot clamps enabled rotational and translational movement of the frame, which allowed the frame to be positioned in a desired location and orientation relative to the limb being tested. Subjects were asked to apply maximal force against the force plates in the direction of the desired movement. A force transducer produced an output that represented each subjects force, and the output was displayed on a digital panel meter. A force gauge has been found to measure strength more reliably and accurately than manual muscle testing.
Three measurements of each motion were recorded for both the involved and uninvolved limbs. The maximum effort was selected, and the ratio of the injured limb to the uninjured limb for each motion was calculated. The ratio scores were separated into 2 categories: less than 50% and greater than 50%. Because manual muscle testing41 is a more widely used measure and the MMT scale of 0 to 5 is clinically meaningful,42 the ratio categories were translated into MMT grades with the use of the percentage scores of Kendall and McCreary.43 Normal strength or an MMT grade of 5 corresponds to a joint motion ratio of greater than 81%, a ratio of 51% to 80% is considered grade 4, a ratio of 21% to 50% is considered grade 3, and a ratio of 20% or less is considered grade 2.43,44 An MMT grade of 4 is considered an average or good score, and an MMT grade of less than 4 indicates fair or even poor strength.41 Because a good score is considered a necessity for fast walking,45 subjects in this study with an MMT grade of less than 4 were considered to have impaired strength.
An additional variable of toe raises was used to measure functional ankle PF strength of the involved and uninvolved legs.41 The number of times a subject performed full-excursion toe raises within 15 seconds, while keeping the knee straight and using one hand for support, was recorded.41,46 If a subject was unable to perform a toe raise, then a score of zero was recorded for that subject. A normal score was 10; a score of less than 10 was considered functionally impaired.33
Data Analysis
Data analysis and interpretation of results were performed using Stata statistical software, version 8.0.* Bivariate relationships between demographic and clinical variables and outcome measures were assessed using chi-square tests for binomial data and Student t tests for continuous data.
The main goal was to develop a multivariate logistic regression model of clinical measures correlating with gait deviation and impaired walking speed 2 years following major lower-extremity trauma treated by reconstruction. Separate analyses were conducted for gait deviation and walking speed at
4 ft/s and for gait deviation and walking speed at
5 ft/s. Each analysis was conducted in 4 phases. First, a bivariate logistic regression analysis was performed to assess the relationship between potential variables and the combined outcome of gait deviation and decreased walking speed. Second, an initial multivariate logistic regression analysis was conducted with all baseline sociodemographic characteristics and clinical variables. The results of the multivariate and bivariate logistic regression analyses were compared to ensure that no covariates had been incorrectly dropped from the analysis, and the presence of interactions and correlations between impairment and functional measures was investigated. Third, clinical factors with P values less than or equal to .10 using the Wald test were selected for additional analysis. These variables were confirmed with stepwise regression and goodness-of-fit techniques. Fourth, a final multivariate logistic regression analysis was performed with variables that were statistically significant at the P<.10 level or if removal of the variable resulted in substantial changes in the magnitude of other variables in the model. Data for subjects who were missing specific data points were kept in the analysis by using missing data categories, but these categories are not presented.
| Results |
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The distributions of demographic and injury characteristics and clinical variables by outcome are presented in Tables 1 and 2. The bivariate associations between the primary outcome and these clinical measures 24 months after reconstruction are shown in Table 3. Nonreciprocal stair-climbing pattern, <30 seconds of unilateral stance, <10 seconds of tandem standing balance, <10 toe raises,
3 cm of calf atrophy, <120 degrees of hip flexion ROM of the involved limb, <50 degrees of ankle PF ROM of the involved limb, <20 degrees of ankle DF ROM of the involved limb, and all strength measures with an MMT grade of <4, except hip abduction, were independently related to gait deviation and decreased walking speed at P<.05. After adjusting for age, insurance, and injury, only a nonreciprocal stair-climbing pattern, impaired unilateral stance, decreased hip extension and knee flexion strength, and limited ankle PF ROM of the involved limb remained significantly associated with impaired physical mobility (P<.10).
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4 ft/s for subjects with lower-limb reconstruction were <50 degrees of PF ROM of the involved ankle, nonreciprocal stair climbing, and knee flexion strength with an MMT grade of <4 at P<.05 (Tab. 4). In addition, these associations were further confirmed with a multivariate logistic regression of gait deviation and walking speed of
5 ft/s.
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| Discussion |
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Studies of gait recovery after limb-saving surgery secondary to malignant bone tumors and trauma have consistently shown an association between decreased knee extension strength and increased asymmetry and decreased walking speed.3,5,11 The association between knee extensor strength and impaired gait directly relates to the extent of quadriceps femoris muscle excision during the tissue and bone resection process of tumor surgery3,48 and the resulting quadriceps femoris muscle atrophy in patients with traumatic reconstruction.11 In this study of patients with traumatic lower-extremity reconstruction, decreased knee extension strength and thigh atrophy were not significantly associated with gait deviation and decreased walking speed. We found that only 24% of the subjects had a knee extension MMT grade of <4 and 18% had thigh atrophy of
3 cm. The limited quadriceps femoris muscle involvement in this patient population can be attributed to their distribution of injury characteristics. The majority of the reconstruction surgeries were due to tibia fractures (51%) and severe foot and ankle injuries (40%), where excision of the quadriceps femoris muscle is not common.
Instead, impaired knee flexion strength was found to be significantly associated with pathological gait. Approximately, 72% of the subjects with impaired knee flexion strength had a gait deviation, and 50% had a gait deviation and a walking speed of
4 ft/s. This high percentage of gait deviation is consistent with the functional role of the knee during ambulation. The knee absorbs energy during the stance phase of gait and is mainly involved with smoothing the gait pattern.49 A smaller contribution is made to walking speed by the biceps femoris muscle, which flexes the knee during the swing phase to assist with flexion velocity as well as smooth foot clearance.4
Hip extension strength also was found to correlate with gait pattern and speed. Although the knee flexors are involved mostly with energy absorption, the hip extensors are responsible for propulsion and forward acceleration of the trunk. In normal gait, propulsion is initiated after heel-strike and is maintained during mid-stance though eccentric activation of the hip extensor muscles.13 The hip extensors also lengthen the supporting limb and reduce excessive drop of the bodys center of mass.14 Propulsion is an essential component of gait speed, while control of the stance limb allows for a smooth transition into the swing phase of gait. A study by Sadeghi et al26 of patients with amputation showed that increased hip extensor strength and early activation during the stance phase is needed to control perturbations and normalize walking speed in order to compensate for the lack of ankle function on the amputated leg.
An unexpected finding was the strong contribution of decreased ankle PF ROM to gait deviation and walking speed of
4 ft/s. Other researchers50,51 have found ankle stiffness among patients with lower-extremity reconstruction and proposed that diminished ankle ROM contributes to impaired gait and stair-climbing ability, but a statistical association has not been reported in the literature.
The objective of our study was not only to identify factors significantly associated with gait deviation and decreased walking speed, but also to provide measurement guidelines that would assist clinicians with treatment planning and goal setting for patients with lower-limb reconstruction. The independent associations with gait deviation and impaired walking speed suggest that treatment plans of care should consider strategies to address the following impairments of the involved lower extremity: calf atrophy greater than 3 cm, hip flexion ROM below 120 degrees, ankle PF ROM below 50 degrees, ankle DF ROM below 20 degrees, and an MMT grade of less than 4 for hip and knee extension and flexion strength and ankle PF and DF strength. In addition, functional goal setting should consider: a reciprocal stair-climbing pattern, unilateral stance of the involved and uninvolved lower extremities for greater than 30 seconds, tandem standing balance for greater than 10 seconds, and the ability to perform more than 10 toe raises on the involved and uninvolved limbs.
Results from the multivariate analysis help inform treatment priorities, which appear to be improving ankle PF ROM to greater than 50 degrees, improving knee flexion strength to an MMT grade of greater than 4, and improving a patients ability to ascend and descend stairs with a reciprocal stair-climbing pattern. Additionally, we believe that priority consideration should be given to improving hip extension strength and single-leg stance of the involved and uninvolved limbs. Recommendations for future research include examining the predictive ability of these impairment and functional measures on impaired mobility and physical disability. Further investigation is needed to determine the timing of treatment strategies and to support the inclusion of ankle PF ROM, knee flexion and hip extension strengthening, stair climbing, and single-leg-stance balance training in goal setting for patients with lower-extremity reconstruction.
A number of limitations of our study must be acknowledged. Information on the primary outcome and the functional variables was available on 73% to 75% of the eligible subjects. Subjects who were lost to follow-up at 24 months were more likely to be of low socioeconomic status than those who completed the study. Thus, the results may be an underestimation of the samples level of abnormal gait and the associative ability of the significant clinical predictors. However, data on strength and ROM were available for only 31% to 40% of our sample. Even though the missing data were accounted for in the analysis, the small amount of impairment data may have contributed to the insignificant findings of knee extension strength and ankle involvement. In addition, the reliability of visual observations of gait deviation was not determined in this study and also should be considered in the interpretation of results.
The generalizability of our results is limited due to the focus of the study on patients from level I trauma centers. Limb-salvage outcomes may be influenced by the expertise of the staff from these level I sites. Moreover, the clinical variables were measured after 24 months, a period that may not be representative of full salvage recovery. Resolution of functional limitations and changes in gait may occur during the 24- to 36-month recovery period.
| Conclusion |
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| Footnotes |
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This study was approved by the institutional review boards at the coordinating center (Johns Hopkins University, Bloomberg School of Public Health) and each LEAP study site.
This research was supported with funds from the Johns Hopkins Center for Injury Research and Policy and National Center for Injury Prevention and Control, Centers for Disease Control and Prevention (grant no. CE000198-03), and the National Institute of Arthritis, Musculoskeletal and Skin Diseases, National Institutes of Health (grant no. RO1-AR42659).
* Stata Corp, 4905 Lakeway Dr, College Station, TX 77845. ![]()
| References |
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