Sensory Neurography and S2PD, a Test-Retest Study

Sensory Neurography and S2PD: A Test-Retest Study in Ten Healthy Individuals to Assess Method Reliability

This study was conducted as a test-retest investigation to assess the reliability of the methods prior to a planned study on the same topic. Ten volunteer participants were recruited from among employees at Sodersjukhuset (South General Hospital). The radial aspects of the second and fourth digits on both hands were examined using static two-point discrimination (S2PD) and sensory neurography on two separate occasions. The results from the two separate measurements will be analysed with an Intra Class Coefficient analysis and a Bland-Altman test.

Study Overview

• Status: Active, not recruiting
• Conditions: Reliability of Sensory Neurography and S2PD
• Intervention / Treatment: Diagnostic test: S2PD; Diagnostic test: Sensory neurography

Detailed Description

A neurophysiological examination can objectively measure remaining function in an injured digital nerve. Using this method, axons that are still able to conduct an action potential are assessed.

The response can be measured as the amplitude (the summed action potentials from the nerve's axons) and as the area (the amount of functioning axons). The area is a somewhat more precise measurement method, as it includes all axons, both those with low and high conduction velocities. Amplitude measurements may give falsely low values if nerves with poorer degrees of myelination are included in the measurement. Amplitude is measured in µV (microvolt) and area in µV/ms (microvolt per millisecond).

The method currently used to assess discriminative sensation is the S2PD-test. In this test two pins are pressed perpendicular and longitudinally on each side of the fingertip. The pins can consist of an unfolded paper clip or a factory-made discriminator. The distance between the two pins, where it is possible to discriminate between one or two pins, is the S2PD. The test is influenced by many external factors, such as the clinician's level of experience, the patient's desire to give the correct answer, language barriers, and similar issues. Furthermore, this examination method does not clarify what is actually being measured beyond the patient's subjective discriminative sensation.

If neurophysiological assessment is used as a complement to S2PD and can provide an objective measurement tool with high reliability and reproducibility, it could become an important addition to the clinical arsenal for follow-up after nerve injury. Such knowledge would make it easier to clinically evaluate, understand, and monitor the healing process of the injured nerve. It would also facilitate the assessment and systematic follow-up of treatment outcomes.

The participants will be examined at the Hand Surgery Clinic at South General Hospital at two separate occasions separated. Each visit is estimated to last approximately 60 minutes. It will include assessment using S2PD and neurophysiological examination of the radial side of the second and fourth fingers on both hands.

Finger temperature will be measured using an infrared thermometer (Testo 826-T2), and, if necessary, the fingers will be warmed (using a water bath, heating pad or something similar) to a target temperature of a minimum of 32 °C. The hands will then be gently abraded using a preparation gel (NuPrep). Conductive gel (Ten20) will be applied to the electrodes.

A recording electrode will be placed volarly over the wrist, a ground electrode in the palm, and the stimulating electrode on the radial side of the finger (digits II and IV). Electrical stimulation will be delivered in an orthodromic direction, from the finger toward the wrist. The stimulus intensity will be gradually increased until no further increase in amplitude is observed/amplitude is stable. At the first visit, the examination begins with S2PD followed by sensory neurography. At the second visit, the order of the assessments is reversed to minimize potential crossover effects.

• Study Type: Interventional
• Enrollment (Actual): 10
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Sweden
  • Stockholm, Sweden
    • Department of Hand Surgery, Södersjukhuset Hospital, Stockholm, Sweden

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Age >20
• Age <60

Exclusion Criteria:

• Neurologic disease
• Dementia
• Cognitive disability
• Severe psychiatric disorder (not be able to participate)
• Ongoing drug abuse
• Not understanding swedish language
• History of carpal tunnel syndrome
• Negative experience of electric stimulation

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Device Feasibility
• Allocation: Non-Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: S2PD and sensory neurography; Radial digital nerve of second and fourth finger on both hands, are first examined with S2PD, secondly with Sensory neurography.	Diagnostic test: S2PD; see section "study description"; Diagnostic test: Sensory neurography; see section "study description"
Active Comparator: Sensory neurography and S2PD; Radial digital nerve of second and fourth finger on both hands, are first examined with Sensory neurography, secondly with S2PD	Diagnostic test: S2PD; see section "study description"; Diagnostic test: Sensory neurography; see section "study description"

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Reliability of method: Sensory neurography measurements (AREA) performed on two separate occasions.	ICC (Intraclass correlation coefficient) will be used to assess correlation between measurements at baseline and 2 weeks	Measures will be assessed at baseline and 2 weeks.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Assessment of agreement AREA	The Bland-Altman method will be used to assess whether the measurement method demonstrates sufficient agreement to be considered reliable. The predefined limit for acceptable differences between measurements is 50%.	Measurements will be performed at baseline and at 2 weeks.
Reliability of method: Sensory neurography measurements (SNAP) performed on two separate occasions	ICC (Intraclass correlation coefficient) will be used to assess whether the measurement method demonstrates sufficient correlation to be considered reliable.	Measures will be assessed at baseline and 2 weeks.
Assessment of agreement SNAP	The Bland-Altman method will be used to assess whether the measurement method demonstrates sufficient agreement to be considered reliable. The predefined limit for acceptable differences between measurements is 50%.	Measurements at baseline and 2 weeks

Collaborators and Investigators

• Sponsor: Karolinska Institutet
• Collaborators: Stockholm South General Hospital; AFA Insurance
• Investigators: Principal Investigator: Cecilia Mellstrand Navarrro, Associate professor, Department of Clinical Science and Education, Karolinska Institutet, Södersjukhuset, Stockholm, Sweden

Publications and helpful links

General Publications

• Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet. 1986 Feb 8;1(8476):307-10.
• Bland JM, Altman DG. Measuring agreement in method comparison studies. Stat Methods Med Res. 1999 Jun;8(2):135-60. doi: 10.1177/096228029900800204.
• Bland JM, Altman DG. Comparing methods of measurement: why plotting difference against standard method is misleading. Lancet. 1995 Oct 21;346(8982):1085-7. doi: 10.1016/s0140-6736(95)91748-9.
• Pan D, Patel AU, Patterson JM, Johnson AR, Gordon T, Mackinnon SE. Surgeons, physiatrists and neurologists speaking "EDX and nerve surgery": A paradigm shift for nerve injured patients. JPRAS Open. 2025 Nov 12;47:3-20. doi: 10.1016/j.jpra.2025.11.004. eCollection 2025.

Study record dates

Study Major Dates

• Study Start (Actual): December 4, 2025
• Primary Completion (Actual): January 20, 2026
• Study Completion (Estimated): May 1, 2026

Study Registration Dates

• First Submitted: February 2, 2026
• First Submitted That Met QC Criteria: May 18, 2026
• First Posted (Actual): May 26, 2026

Study Record Updates

• Last Update Posted (Actual): May 26, 2026
• Last Update Submitted That Met QC Criteria: May 18, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: S2PD; Digital nerve injury; Sensory neurography; Sensory nerve action potentials
• Other Study ID Numbers: 2024-08365-02

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: All data will be shared, in pseudonymised form.
• IPD Sharing Time Frame: Supporting information will be available upon study completion and retained for ten years.
• IPD Sharing Access Criteria: All data will be available from corresponding author upon reasonable request.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF; ANALYTIC_CODE; CSR

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No