A mechanical equinometer to measure the range of motion of the ankle joint: interobserver and intraobserver reliability

Defining Equinus Foot in Cerebral Palsy

Background: Equinus foot is the deformity most frequently observed in patients with cerebral palsy (CP). While there is widespread agreement on the treatment of equinus foot, a clear clinical definition has been lacking. Therefore, we conducted this study to evaluate functional changes in gait analysis in relation to maximum possible dorsiflexion (0°, 5°, 10° and 15°) and in two subgroups of CP patients (unilateral and bilateral). Methods: In this retrospective study, CP patients with different degrees of clinically measured maximum dorsiflexion were included. We further subdivided patients into unilaterally and bilaterally affected individuals and also included a healthy control group. All participants underwent a 3D gait analysis. Our goal was to determine the degree of maximum clinical dorsiflexion where the functional changes in range of motion (ROM) and ankle moment and power during gait were most evident. Then, a subgroup analysis was performed according to the affected side. Results: In all, 71 and 84 limbs were analyzed in unilaterally and bilaterally affected subgroups. The clinically 0° dorsiflexion group barely reached a plantigrade position in the 3D gait analysis. Differences in ROM were observed between subgroups. Ankle moment was quite similar between different subgroups but to a lower extent in the unilateral group. All CP patients had reduced ankle power compared to controls. Conclusions: A cutoff value of clinical ≤ 5° dorsiflexion is the recommended value for defining a functionally relevant equinus foot in CP patients.

Validation of a new Equinometer device for measuring ankle range of motion in patients with cerebral palsy: An observational study

The goniometer is the gold-standard measurement tool of ankle range of motion (ROM). However, several studies have questioned its inter- and intra-rater reliability. Therefore, we conducted this validation study to assess the reliability of a different tool, named Equinometer, as a measurement device of ankle ROM in addition to comparing the reproducibility of their results.Sixteen healthy individuals were included. They underwent both goniometer and Equinometer measurements in knee extension and 90° knee flexion (Silfverskjöld Test). Three raters reported the values of dorsiflexion (DF) and plantarflexion (PF) in each session using both measurement tools. Intra-rater reliability was assessed between 2 raters on another study group of 24 participants. Intraclass correlation coefficients were used to determine the reliability of the used device.The age of study subjects ranged from 22 to 85 years. Fifty percent were males, and the right ankle joint was the most examined side (68.75%). In terms of DF and PF during knee extension and flexion, our analysis revealed that the measurements recorded by the Equinometer were equivalent to the goniometer. Of note, the intra-rater reliability of the Equinometer was excellent for both DF and PF assessment during both knee flexion and extension (Intraclass correlation coefficient ranged from 0.90 to 0.98), with minimal mean differences from goniometer measurements. Subgroup analysis based on age did not reveal any significant differences (P > .05).Given the high intra-rater correlations of the Equinometer, we suggest that it is reliable and precise in recording ankle ROM in outpatient clinics, particularly to obtain reproductive, comparable and unbiased data from different observers.

Is the Prevalence of Equinus Foot in Cerebral Palsy Overestimated? Results from a Meta-Analysis of 4814 Feet

Background: Equinus is a common foot deformity in patients with cerebral palsy (CP). However, its prevalence is scarcely reported in the literature. Therefore, we conducted this review to estimate the prevalence of equinus foot in CP. Methods: Eight databases were searched. Our primary outcome was the prevalence of equinus foot in CP patients. Subgroup analysis was conducted based on study design, the laterality of CP, and whether equinus foot was defined or not. Results: The prevalence of equinus foot in CP was 93% (95% CI: 71–99). The prevalence was 99% (95% CI: 55–100), 96% (95% CI: 57–100), and 65% (95% CI: 37–86) in unilateral, both, and bilateral CP, respectively. Based on study design, equinus foot prevalence was 92% (95% CI: 34–100) in case series and 62% (95% CI: 47–74) in cohort studies. Four studies reported definition criteria for equinus foot, with a pooled prevalence rate of equinus foot of 99% (95% CI: 36–100) compared to a rate of 89% (95% CI: 59–98) among studies that lacked a definition criterion. Conclusions: This is the first meta-analysis to address the prevalence of equinus foot in CP patients. Although its prevalence is very high, our findings should be interpreted with caution due to the presence of multiple limitations, such as the lack of standardized definition criteria for equinus foot, the inappropriate study design, the wide confidence interval of equinus foot rate, and the small number of studies investigating it as a primary outcome.

A Predictive Model for Gastrocnemius Tightness in Forefoot Pain and Intractable Plantar Keratosis of the Second Rocker

BACKGROUND

Many people experience gastrocnemius tightness. Few studies demonstrate the relationship between gastrocnemius tightness and forefoot pathology. This study aimed to define the association between intractable plantar keratosis of the second rocker (IPK2) (also known as well-localized IPK or discrete keratosis) and metatarsalgia.

METHODS

The Silfverskiöld (ST) and lunge (LT) tests, used for measuring ankle dorsiflexion, were applied to diagnose gastrocnemius tightness. An instrument for measuring accurate performance and the force to be applied (1.7-2.0 kg of force to the ankle dorsiflexion) complemented the ST for clinical diagnosis and to obtain repeatedly reliable results (the authors apply force manually, which is difficult to quantify accurately).

RESULTS

Of 122 patients studied, 74 were used to devise a prediction model from a logistic regression analysis that determines the probability of presenting gastrocnemius tightness in each test (LT and ST) with the following variables: metatarsalgia, IPK2, and maximum static pressure (baropodometry). The IPK2 plays the principal role in predicting this pathology, with the highest Wald values (6.611 for LT and 5.063 for ST). Metatarsalgia induces a somewhat lower change (66.7% LT and 64.3% ST). The maximum pressure of the forefoot is equally significant (P = .043 LT and P = .025 ST), taking α < .05 as the significance level.

CONCLUSIONS

The results of this validation report confirm that a model composed of metatarsalgia, IPK2, and maximum pressure in static acts as a predictive method for gastrocnemius tightness.

Use of an Instrumented Ankle Arthrometer and External Strain Gauge to Assess Ankle Dorsiflexion Motion and Plantarflexor Stiffness

BACKGROUND

Ankle dorsiflexion motion and plantarflexor stiffness measurement offer clinical insight into the assessment and treatment of musculoskeletal and neurologic disorders. We aimed to determine reliability and concurrent validity of an ankle arthrometer in quantifying dorsiflexion motion and plantarflexor stiffness.

METHODS

Ten healthy individuals were assessed for dorsiflexion motion and plantarflexor stiffness using an ankle arthrometer with a 6 degree-of-freedom kinematic linkage system and external strain gauge to apply dorsiflexion torque. Two investigators each performed five loads to the ankle at different combinations of loads (10 or 20 Nm), rates (2.5 or 5 Nm/sec), and knee angles (10° or 20°). Anteroposterior displacement and inversion-eversion rotation were also assessed with arthrometry, and functional dorsiflexion motion was assessed with the weightbearing lunge (WBL) test.

RESULTS

Good-to-excellent intrarater reliability was observed for peak dorsiflexion (intraclass correlation coefficient [ICC][2,k] = 0.949-0.988) and plantarflexor stiffness (ICC[2,k] = 0.761-0.984). Interrater reliability was good to excellent for peak dorsiflexion (ICC[2,1] = 0.766-0.910) and poor to excellent for plantarflexor stiffness (ICC[2,1] = 0.275-0.914). Reliability was best for 20-Nm loads at 5 Nm/sec. Strong correlations were observed between peak dorsiflexion and anteroposterior displacement (r = 0.666; P = 0.035) and WBL distance (r = -0.681; P = 0.036).

CONCLUSIONS

Using an ankle arthrometer to assess peak dorsiflexion and plantarflexor stiffness seems reliable when performed to greater torques with faster speeds; and offers consistency with functional measures. Use of this readily available tool may benefit clinicians attempting to quantify equinus and dorsiflexion deficits in pathological populations.

Effect of Syndesmotic Implant Removal on Dorsiflexion

BACKGROUND

There is limited evidence that syndesmotic implant removal (SIR) is beneficial. However, many surgeons advocate removal based on studies suggesting improved motion. Methodologic difficulties make the validity and applicability of previous works questionable. The purpose of this study was to examine the effect of ankle dorsiflexion after SIR using radiographically measured motion before and after screw removal utilizing a standardized load.

METHODS

All patients undergoing isolated SIR were candidates for inclusion. Dorsiflexion was measured radiographically: (1) immediately before implant removal intraoperatively, (2) immediately after removal intraoperatively, and (3) 3 months after removal. A standardized torque force was applied to the ankle and a perfect lateral radiograph of the ankle was obtained. Four reviewers independently measured dorsiflexion on randomized, deidentified images. A total of 29 patients met inclusion criteria. All syndesmotic injuries were associated with rotational ankle fractures. There were 11 men (38%) and 18 women (62%). The mean, and standard deviation, age was 50.3 ± 16.9 years (range 19-80).

RESULTS

The mean ankle dorsiflexion pre-operatively, post-operatively, and at a 3-month follow-up was 13.7 ± 6.6 degrees, 13.3 ± 7.3 degrees and 11.8 ± 11.3 degrees, respectively ( P = .466). For subsequent analysis, 5 patients were excluded because of the potential confounding effect of retained suture button devices. Analysis of the remaining 24 patients (and final analysis of 21 patients who had complete 3-month follow-up) demonstrated similar results with no statistically significant difference in ankle dorsiflexion at all 3 time points.

CONCLUSION

Removal of syndesmotic screws may not improve ankle dorsiflexion motion and should not be used as the sole indication for screw removal.

LEVEL OF EVIDENCE

Level II, prospective cohort study.

The Design, Development, and Reliability Testing of a New Innovative Device to Measure Ankle Joint Dorsiflexion

BACKGROUND

In clinical and research settings, ankle joint dorsiflexion needs to be reliably measured. Dorsiflexion is often measured by goniometry, but the intrarater and interrater reliability of this technique have been reported to be poor. Many devices to measure dorsiflexion have been developed for clinical and research use. An evaluation of 12 current tools showed that none met all of the desirable criteria. The purpose of this study was to design and develop a device that rates highly in all of the criteria and that can be proved to be highly reliable.

METHODS

While supine on a treatment table, 14 participants had a foot placed in the Charles device and ankle joint dorsiflexion measured and recorded three times with a digital inclinometer. The mean of the three readings was determined to be the ankle joint dorsiflexion.

RESULTS

The analysis used was intraclass correlation coefficient (ICC). There was very little difference in ICC single or average measures between left and right feet, so data were pooled (N = 28). The single-measure ICC was 0.998 (95% confidence interval, 0.996-0.998). The average-measure ICC was 0.998 (95% confidence interval, 0.995-0.999). Limits of agreement for the average measure were also very good: -1.30° to 1.65°.

CONCLUSIONS

The Charles device meets all of the desirable criteria and has many innovative features, increasing its appropriateness for clinical and research applications. It has a suitable design for measuring dorsiflexion and high intrarater and interrater reliability.

The effect of the gastrocnemius on the plantar fascia

Although anatomic and functional relationship has been established between the gastrocnemius muscle, via the Achilles tendon, and the plantar fascia, the exact role of gastrocnemius tightness in foot and plantar fascia problems is not completely understood. This article summarizes past and current literature linking these 2 structures and gives a mechanical explanation based on functional models of the relationship between gastrocnemius tightness and plantar fascia. The effect of gastrocnemius tightness on the sagittal behavior of the foot is also discussed.

Sagittal plane kinematics of passive dorsiflexion of the foot in adolescent athletes

BACKGROUND

Although assessment of passive maximum foot dorsiflexion angle is performed routinely, there is a paucity of information regarding adolescents' foot and foot segment motion during this procedure. There are currently no trials investigating the kinematics of the adolescent foot during passive foot dorsiflexion.

METHODS

A six-camera optoelectronic motion capture system was used to collect kinematic data using the Oxford Foot Model. Eight female amateur gymnasts 11 to 16 years old (mean age, 13.2 years; mean height, 1.5 m) participated in the study. A dorsiflexing force was applied to the forefoot until reaching maximum resistance with the foot placed in the neutral, pronated, and supinated positions in random order. The maximum foot dorsiflexion angle and the range of movement of the forefoot to hindfoot, tibia to forefoot, and tibia to hindfoot angles were computed.

RESULTS

Mean ± SD maximum foot dorsiflexion angles were 36.3° ± 7.2° for pronated, 36.9° ± 4.0° for neutral, and 33.0° ± 4.9° for supinated postures. One-way repeated-measures analysis of variance results were nonsignificant among the 3 groups (P = .70), as were the forefoot to tibia angle and hindfoot to tibia angle variations (P = .091 and P = .188, respectively). Forefoot to hindfoot angle increased with the application of force, indicating that in adolescents, the forefoot does not lock at any particular posture as portrayed by the traditional Rootian paradigm.

CONCLUSIONS

Participants had very flexible foot dorsiflexion, unlike those in another study assessing adolescent athletes. This finding, together with nonsignificant statistical results, implies that foot dorsiflexion measurement may be performed at any foot posture without notably affecting results.

Reproducibility of an instrumented measure for passive ankle dorsiflexion in conscious and anaesthetized children with cerebral palsy

AIM

The aims of this study were to (1) determine whether an instrumented measure will reduce measurement error to less than 5° in children with cerebral palsy (CP), (2) determine agreement and reliability of this instrumented measure in both conscious and anaesthetized participants, and (3) compare the method with previously reported measures.

METHOD

Thirty-four ambulant children (15 males, 19 females), aged 3 to 9 years, with spastic CP were studied in a tertiary-care paediatric hospital (21 with hemiplegia, 11 with diplegia, and two with quadriplegia). The majority of children functioned at Gross Motor Function Classification System level I (n=11) or II (n=18), with five children at level III. Ankle dorsiflexion at 50% bodyweight was photographed and measured. Each child was measured when conscious and when under mask anaesthesia by two experienced assessors.

RESULTS

The standard error of measurement (SEM) ranged from 3.9° (anaesthetized; 95% confidence interval [CI] 3.3-4.0°) to 6.7° (conscious; 95% CI 5.3-8.0°). This compared favourably with previously reported dorsiflexion measures (SEM range 6.5-7.8°) in conscious children with CP. Intrarater reliability was good in both conditions (intraclass correlation coefficient [ICC]: range 0.95 [anaesthetized; 95% CI 0.92-0.98] to 0.86 [conscious; 95% CI 0.76-0.95]). The ICC for interrater reliability ranged from 0.87 (anaesthetized; 95% CI 0.81-0.93) to 0.65 (conscious; 95% CI 0.50-0.81).

INTERPRETATION

Passive ankle dorsiflexion using an instrumented measure has face validity and may assist in the improvement of reproducibility under anaesthesia for clinical research. When an individual is conscious, this technique is not better than trained assessors using conventional goniometry reported in the literature and is not recommended for routine clinical use.

Validity and reliability of a new ankle dorsiflexion measurement device

BACKGROUND

The assessment of the maximum ankle dorsiflexion angle is an important clinical examination procedure. Evidence shows that the traditional goniometer is highly unreliable, and various designs of goniometers to measure the maximum ankle dorsiflexion angle rely on the application of a known force to obtain reliable results. Hence, an innovative ankle dorsiflexion measurement device was designed to make this measurement more reliable by holding the foot in a selected posture without the application of a known moment.

OBJECTIVES

To report on the comprehensive validity and reliability testing carried out on the new device.

METHODS

Following validity testing, four different trials to test reliability of the ankle dorsiflexion measurement device were performed. These trials included inter-rater and intra-rater testings with a controlled moment, intra-rater reliability testing with knees flexed and extended without a controlled moment, intra-rater testing with a patient population, and inter-rater reliability testing between four raters of varying experience without controlling moment. All raters were blinded.

STUDY DESIGN

A series of trials to test intra-rater and inter-rater reliabilities.

RESULTS

Intra-rater reliability intraclass correlation coefficient was 0.98 and inter-rater reliability intraclass correlation coefficient (2,1) was 0.953 with a controlled moment. With uncontrolled moment, very high reliability for intra-tester was also achieved (intraclass correlation coefficient = 0.94 with knees extended and intraclass correlation coefficient = 0.95 with knees flexed). For the trial investigating test-retest reliability with actual patients, intraclass correlation coefficient of 0.99 was obtained. In the trial investigating four different raters with uncontrolled moment, intraclass correlation coefficient of 0.91 was achieved.

CONCLUSIONS

The new ankle dorsiflexion measurement device is a valid and reliable device for measuring ankle dorsiflexion in both healthy subjects and patients, with both controlled and uncontrolled moments, even by multiple raters of varying experience when the foot is dorsiflexed to its end of range of motion.

CLINICAL RELEVANCE

An ankle dorsiflexion measuring device has been designed to increase the reliability of ankle dorsiflexion measurement and replace the traditional goniometer. While the majority of similar devices rely on application of a known moment to perform this measurement, it has been shown that this is not required with the new ankle dorsiflexion measurement device and, rather, foot posture should be taken into consideration as this affects the maximum ankle dorsiflexion angle.

The effect of uncontrolled moment and short-term, repeated passive stretching on maximum ankle joint dorsiflexion angle

BACKGROUND

Trials investigating ankle joint measurement normally apply a known moment. Maximum ankle angle is affected by foot posture and stretching characteristics of the calf muscles.

OBJECTIVES

To investigate whether consistent maximum ankle angles could be achieved without applying a constant moment to all subjects, and whether short, repetitive stretching of the calf muscle tendon unit would produce a difference in the maximum ankle angle.

METHOD

Passive dorsiflexion in 14 healthy participants was captured using an optoelectronic motion analysis system, with the foot placed in 3 postures.

RESULTS

The maximum ankle angles for both the neutral and supinated positions did not differ significantly. In general, the majority of subjects (92.8%) showed no increase in the maximum ankle dorsiflexion angle following repetitive brief passive stretching. Only one subject exhibited a significant increase in maximum ankle angle at the neutral position.

CONCLUSION

Since the range of motion of the ankle joint is clearly determined by other physical factors, the maximum ankle dorsiflexion angle can be assessed at both neutral and supinated positions without moment being controlled.