A modified standardized nine hole peg test for valid and reliable kinematic assessment of dexterity post-stroke

Abstract

Background: Impairments in dexterity after stroke are commonly assessed by the Nine Hole Peg Test (NHPT), where the only outcome variable is the time taken to complete the test. We aimed to kinematically quantify and to compare the motor performance of the NHPT in persons post-stroke and controls (discriminant validity), to compare kinematics to clinical assessments of upper extremity function (convergent validity), and to establish the within-session reliability.

Methods: The NHPT was modified and standardized (S-NHPT) by 1) replacing the original peg container with an additional identical nine hole pegboard, 2) adding a specific order of which peg to pick, and 3) specifying to insert the peg taken from the original pegboard into the corresponding hole of the target pegboard. Eight optical cameras registered upper body kinematics of 30 persons post-stroke and 41 controls during the S-NHPT. Four sequential phases of the task were identified and analyzed for kinematic group differences. Clinical assessments were performed.

Results: The stroke group performed the S-NHPT slower (total movement time; mean diff 9.8 s, SE diff 1.4), less smoothly (number of movement units; mean diff 0.4, SE diff 0.1) and less efficiently (path ratio; mean diff 0.05, SE diff 0.02), and used increased scapular/trunk movements (acromion displacement; mean diff 15.7 mm, SE diff 3.5) than controls (P < 0.000, r ≥ 0.32), indicating discriminant validity. The stroke group also spent a significantly longer time grasping and releasing pegs relative to the transfer phases of the task compared to controls. Within the stroke group, kinematics correlated with time to complete the S-NHPT and the Fugl-Meyer Assessment (rs 0.38-0.70), suggesting convergent validity. Within-session reliability for the S-NHPT was generally high to very high for both groups (ICCs 0.71-0.94).

Conclusions: The S-NHPT shows adequate discriminant validity, convergent validity and within-session reliability. Standardization of the test facilitates kinematic analysis of movement performance, which in turn enables identification of differences in movement control between persons post-stroke and controls that may otherwise not be captured through the traditional time-based NHPT. Future research should ascertain further psychometric properties, e.g. sensitivity, of the S-NHPT.

Keywords: Clinical laboratory techniques; Outcome assessment; Stroke; Upper extremity.

Conflict of interest statement

Ethics approval and consent to participate

All participants provided written informed consent and the study was approved by the Regional Ethical Review Board in Umeå, Sweden (dnr 2011–199-31 M).

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

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Figures

Fig. 1

Experimental setup and movement phases. a) Marker positions used for the calculations of the kinematic variables. Markers displayed with a dot in the center of the marker were positioned on the trunk. The enlarged pegboard shows the standardized order of which peg to pick and which hole to fill, referred to as the “vertical row strategy”. The S-NHPT consists of 9 pegs (3.8 cm long, 0.64 cm wide) and two pegboards (12.7 cm × 12.7 cm) with 9 holes (0.70 cm wide) spaced 3.2 cm apart. The two pegboards were attached to a wooden panel with a distance of 18 cm between the center holes of the pegboards. The arrow indicates the direction of the movement. b) The velocity of the index finger marker in the medial direction displays the events defining the transfer phases Peg Transfer (positive curve) and Hand Return (negative curve). The manipulative phases Peg Grip and Peg In Hole are between those transfer movements (see Methods)

Fig. 2

Movement paths from the stroke group and the control group. Examples of movement paths of the markers of the index finger in the frontal plane, and velocity profiles with marked number of movement units of one person post-stroke (left panel) and one control person (right panel) for the Peg Transfer Phase (a) and Hand Return Phase (b), respectively. The arrows indicate the direction of the movements