Accuracy and Reliability of Single-Camera Measurements of Ankle Clonus and Quadriceps Hyperreflexia.

OBJECTIVE

To evaluate the accuracy and reliability of a simple, single-camera smartphone-based method, named the Reflex Tracker (RT) system, for measuring reflex threshold angles related to ankle clonus and quadriceps hyperreflexia.

DESIGN

A prospective comparison study using a high-fidelity reference standard was constructed employing a 2 × 2 × 2 factorial design, with factors of rater (tester) type (student and experienced physical therapist), joint (ankle and knee), and repetition (2 per condition).

SETTING

This multicenter study was conducted at 4 outpatient rehabilitation clinics.

PARTICIPANTS

A convenience sample of 14 individuals with a neurologic condition presented with 20 lower limbs that exhibited ankle clonus and/or quadriceps hyperreflexia and were included in the study. Also participating in the study were 8 student and 8 experienced physical therapist raters (testers) (N=16).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The plantar flexor reflex threshold angle (PFRTA) related to ankle clonus and the quadriceps reflex threshold angle (QRTA) related to quadriceps hyperreflexia were quantified.

RESULTS

PFRTA and QRTA results were compared between the smartphone RT method and synchronous 3-dimensional inertial measurement unit (IMU) sensor motion capture. Mean difference (bias) was minimal between RT and IMU measurements for PFRTA (bias≤0.2°) and QRTA (bias≤1.2°). Intrarater reliability for PFRTA ranged from 0.85-0.90 using RT and from 0.85-0.87 using IMU; QRTA ranged from 0.97-0.98 using RT and from 0.96-0.99 using IMU. Intersensor reliability for PFRTA and QRTA was 0.97 and 0.99, respectively. Minimum detectable change for PFRTA ranged from 7.1°- 8.7° and for QRTA ranged from 6.1°-8.3°.

CONCLUSIONS

RT performed comparable to IMU for accurate and reliable measurement of PFRTA and QRTA to quantify ankle clonus and quadriceps hyperreflexia in clinical settings.