Ankle and Midfoot Power During Walking and Stair Ascent in Healthy Adults

Radiographic Measurements Associated With Ankle Power Generation During Gait in Patients With Cerebral Palsy

BACKGROUND

Pes planovalgus (PV) deformity accounts for lever arm dysfunction and compromises gait in patients with cerebral palsy (CP). However, the association between ankle power generation and radiographic indices is not yet understood. We aimed to investigate the association between ankle power and radiographic indices during gait in patients with CP concomitant with PV deformity.

METHODS

Patients older than 14 years with ambulatory CP and PV deformity were included. All the patients underwent 3-dimensional gait analysis and weight-bearing foot radiography. Gait data were collected, including foot progression angle, tibial rotation, hip rotation, and ankle power generation. Radiographic measurements included anteroposterior (AP) talo-first metatarsal angle, lateral talo-first metatarsal angle, and hindfoot angle. A linear mixed-effects model was performed to identify significant radiographic indices associated with ankle power generation.

RESULTS

Thirty-one limbs from 15 patients with spastic diplegia and 6 with spastic hemiplegia were included. Statistical analysis demonstrated that ankle power generation was significantly correlated with the CP type ( P =0.0068) and AP talo-1 st metatarsal angle ( P =0.0230).

CONCLUSION

Ankle power generation was significantly associated with the AP talo-first metatarsal angle. Surgeons might need to pay attention to correcting forefoot abduction to restore ankle power when planning surgeries for pes PV deformities in patients with CP.

LEVEL OF EVIDENCE

Prognostic Level III.

Ankle plantar flexor muscle performance and patient reported outcomes in people following total ankle arthroplasty

BACKGROUND

The purpose of this study was to prospectively evaluate ankle power generation during gait in people with total ankle arthroplasty, and examine the relationships between postoperative plantar flexor strength, ankle power, and patient outcomes.

METHODS

Nineteen people with end-stage ankle arthritis who received a total ankle arthroplasty and 19 healthy matched controls participated in this case-control study. Patient reported outcomes included a region specific measure of foot function and a generic measure of physical function. Gait speed was recorded with the 6-min walk test. Isokinetic plantar flexor strength was measured with an instrumented dynamometer. Motion capture and force plate data were used to calculate peak ankle power generation during walking. Paired or independent t-tests were used to compare ankle power across time and between groups, respectively. Bivariate correlations were performed to examine the interplay of postoperative strength, ankle power, gait speed, and patient reported outcomes.

FINDINGS

Ankle power was not different between the preoperative and 6-month postoperative time points (d = 0.20). Six-month postoperative ankle power was less than controls (d = 1.32). Strength, ankle power, and gait speed were directly correlated in the patient group 6-months postoperatively (r or ρ ≥ 0.47). Six-month postoperative strength and ankle power were directly correlated to select 2-year patient reported outcomes (both ρ = 0.54).

INTERPRETATION

Lower than normal 6-month postoperative ankle power, which was correlated to strength, gait speed, and longer-term patient reported outcomes, suggests efforts toward improving ankle plantar flexor muscle performance may improve patient outcomes.

The Keystone device as a clinical tool for measuring the supination resistance of the foot: A reliability study

BACKGROUND

The supination resistance test (SRT) is a kinetic test used in clinical and research contexts to estimate the amount of force required to supinate the foot. Previous studies either used a manual, less reliable version of this test or a more reliable instrumented version, but with devices inconvenient for clinical use. The clinically available Keystone device has been developed for the SRT, and could be better suited for clinical purposes. The objective of this study is to determine the intrarater and interrater reliability of the Keystone device for the SRT.

METHOD

Thirty young adults underwent two prospective experimental sessions, 1 week apart, during which SRT measures with the Keystone device were registered. Intrarater and interrater reliability were calculated using intraclass correlation coefficients (ICC), standard error of measurement (SEM), minimal detectable difference (MDD) and limits of agreements (LoA).

RESULTS

The intrarater reliability of the SRT was good (ICC = 0.86, p < 0.001). The SEM, MDD and 95% LoA were 7.3, 20.4 and -31.6-14.3 N, respectively. The interrater reliability of the SRT was good (ICC = 0.76, p < 0.001). The SEM, MDD and 95% LoA were 9.0, 24.9 and -36.6-24.9 N, respectively.

CONCLUSION

The Keystone device is a reliable tool that can be used in clinical and research contexts. Prospective studies aiming to determine if SRT measures are predictors of musculoskeletal injuries or if they can predict the effects of external supports on the biomechanics of the foot and ankle are warranted.

Midfoot Function Before and After Total Ankle Arthroplasty

BACKGROUND

Information regarding the effect of total ankle arthroplasty (TAA) on midfoot function is extremely limited. The purpose of this study was to characterize midfoot region motion and power during walking in people before and after TAA.

METHODS

This was a prospective cohort study of 19 patients with end-stage ankle arthritis who received a TAA and 19 healthy control group participants. A motion capture and force plate system was used to record sagittal and transverse plane first metatarsal and lateral forefoot with respect to hindfoot motion, as well as sagittal plane midfoot region positive and negative peak power during walking. Parametric or nonparametric tests to examine differences and equivalence across time were conducted. Comparisons to examine differences between postoperative TAA group and control group foot function were also performed.

RESULTS

Involved-limb midfoot function was not different between the preoperative and 6-month postoperative time point in the TAA group (all P ≥ .17). Equivalence testing revealed similarity in all midfoot function variables across time (all P < .05). Decreased first metatarsal and lateral forefoot motion, as well as positive peak power generation, were noted in the TAA group postoperative involved limb in comparison to the control group (all P ≤ .01).

CONCLUSION

The similarity of midfoot function across time, along with differences in midfoot function in comparison to controls, suggests that TAA does not change midfoot deficits by 6 months postoperation.

LEVEL OF EVIDENCE

Level II, prospective cohort study.

Effects of age and locomotor demand on foot mechanics during walking

Older adults exhibit reductions in push-off power that are often attributed to deficits in plantarflexor force-generating capacity. However, growing evidence suggests that the foot may also contribute to push-off power during walking. Thus, age-related changes in foot structure and function may contribute to altered foot mechanics and ultimately reduced push-off power. The purpose of this paper was to quantify age-related differences in foot mechanical work during walking across a range of speeds and at a single fixed speed with varied demands for push-off power. 9 young and 10 older adults walked at 1.0, 1.2, and 1.4 m/s, and at 1.2 m/s with an aiding or impeding horizontal pulling force equal to 5% BW. We calculated foot work in Visual3D using a unified deformable foot model, accounting for contributions of structures distal to the hindfoot's center-of-mass. Older adults walked while performing less positive foot work and more negative net foot work (p < 0.05). Further, we found that the effect of age on mechanical work performed by the foot and the ankle-foot complex increased with increased locomotor demand (p < 0.05). Our findings suggest that during walking, age-related differences in foot mechanics may contribute to reduced push-off intensity via greater energy loss from distal foot structures, particularly during walking tasks with a greater demand for foot power generation. These findings are the first step in understanding the role of the foot in push-off power deficits in older adults and may serve as a roadmap for developing future low-cost mobility interventions.

Total ankle arthroplasty: Strength, pain, and motion

BACKGROUND

While outcomes such as pain and ankle motion are well researched, information regarding the effect of total ankle arthroplasty on ankle plantarflexion strength is extraordinarily limited. The purpose of this study was to evaluate ankle plantarflexion strength before and after total ankle arthroplasty, and examine the interplay of pain, motion, and strength.

METHODS

This prospective case-control study included 19 patients with end-stage ankle arthritis who received a total ankle arthroplasty and 19 healthy control participants matched for age, sex, and body mass index. Pain was measured with a numeric pain rating scale. Passive sagittal plane ankle range of motion (°) and isokinetic ankle plantarflexion torque (Nm/kg) at 60 and 120°/s were measured with an instrumented dynamometer. t-tests or non-parametric tests were used to evaluate outcomes across time and between groups. Bivariate correlations were performed to evaluate the interplay of postoperative pain, motion, and torque.

FINDINGS

Patient pain and motion improved between the preoperative and six-month postoperative time points (d ≥ 0.7). Ankle plantarflexion torque was not different across time (d ≤ 0.5), but was lower than control group values postoperatively (d ≥ 1.4). Significant correlations between pain and motion (r = -0.48), but not torque (-0.11 ≤ r ≤ 0.13), were observed.

INTERPRETATION

Unchanged following surgery, impairments in muscle performance following total ankle arthroplasty do not appear to be changed by improved pain or motion. These findings provide impetus for postoperative strengthening interventions.

Ankle and Midfoot Power During Single-Limb Heel Rise in Healthy Adults

Although the midfoot is recognized to have an important role in the successful performance of a single-limb heel rise, healthy heel rise performance remains primarily characterized by ankle function. The purpose of this study was to examine the contribution of midfoot region power to single-limb heel rise in healthy adults. Participants (N = 12) performed 20 single-limb heel rises. An electromagnetic motion capture system and a force plate were used to record 3-segment foot motion and ground reaction forces. Inverse dynamic calculations were performed to obtain ankle and midfoot region powers. These data were evaluated with descriptive statistics. A correlation was performed to evaluate the contribution of midfoot region power to heel height, as heel height is a clinical measure of heel-rise performance. The midfoot contributed power during single-limb heel rise (peak positive power: 0.5 [0.2] W·kg-1). Furthermore, midfoot peak power accounted for 36% of the variance in heel height (P = .04). As energy generating internal mechanisms, such as muscle activity, are attributed to power generation, midfoot tissue loading and muscle performance should be considered during clinical and modeling applications of the heel-rise task.

The relationship between supination resistance and the kinetics and kinematics of the foot and ankle during gait

BACKGROUND

Clinical tests of foot posture and mobility are not strongly related to the dynamic kinematics of the foot during gait. These measures may be more directly related to foot and ankle kinetics. The supination resistance test (SRT) is a clinical test that may more directly measure forces acting on the weightbearing foot to provide clinicians with insight about the loading of foot structures.

RESEARCH QUESTION

What is the relationship between the SRT in relaxed calcaneal stance and in single-leg-stance and the kinetics and kinematics of the foot and ankle during gait?

METHODS

10 healthy adults between the ages of 18 and 65 were recruited to participate in this study. Three-dimensional motion analysis was performed using the Oxford Foot Model during gait. The results of the SRT were compared with peak midfoot and ankle joint moments, power generation and absorption, joint angles, and peak angular velocities and accelerations. Correlation coefficients were calculated to assess the strength of relationships between these variables and the SRT.

RESULTS

The SRT demonstrated significant relationships with several variables. In relaxed calcaneal stance, the SRT was inversely related to maximum midfoot pronation moments (r = -0.51), maximum midfoot plantarflexion moments (rho = -0.71), and peak midfoot power generation (r = -0.61). In single-leg-stance, the SRT was significantly related to maximum midfoot plantarflexion moments (rho = -0.55) and peak midfoot power generation (r = -0.47).

SIGNIFICANCE

The SRT is significantly associated to several kinetic variables that quantify midfoot loading during gait. Interventions that decrease supination resistance may have the potential to increase midfoot power generation.