Biomechanical analysis of ulnar nerve gliding and elongation: implications for nonsurgical ulnar nerve release in cubital tunnel syndrome

Teruhisa Mihata; Masaki Akeda; Michael Künzler; Michelle H. McGarry; Thay Q. Lee

doi:10.5397/cise.2024.00934

Clin Shoulder Elb > Volume 28(2); 2025 > Article

Mihata, Akeda, Künzler, McGarry, and Lee: Biomechanical analysis of ulnar nerve gliding and elongation: implications for nonsurgical ulnar nerve release in cubital tunnel syndrome

Original Article

Clinics in Shoulder and Elbow 2025; 28(2): 137-145.

Published online: April 25, 2025

DOI: https://doi.org/10.5397/cise.2024.00934

Biomechanical analysis of ulnar nerve gliding and elongation: implications for nonsurgical ulnar nerve release in cubital tunnel syndrome

Teruhisa Mihata^1,^2,³

, Masaki Akeda¹

, Michael Künzler¹

, Michelle H. McGarry¹

, Thay Q. Lee¹

¹Orthopedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA, USA

²Department of Orthopedic Surgery, Osaka Medical and Pharmaceutical University, Osaka, Japan

³Department of Orthopedic Surgery, Katsuragi Hospital, Osaka, Japan

Corresponding author: Teruhisa Mihata Department of Orthopedic Surgery, Osaka Medical and Pharmaceutical University, 2-7 Daigaku-machi, Takatsuki, Osaka 569-8686, Japan
Tel: +81-72-683-1221 Fax: +81-72-683-6265 Email: tmihata@ompu.ac.jp

Received: November 14, 2024 Revised: January 13, 2025 Accepted: February 4, 2025

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background

Nonsurgical ulnar nerve release was developed for conservative treatment of cubital tunnel syndrome. Our objective in this study was to investigate the amount of ulnar nerve gliding and elongation during passive wrist, forearm, or elbow movements to determine the most effective nonsurgical ulnar nerve release technique.

Methods

Seven fresh-frozen cadaveric upper limbs were tested in an elbow-testing system. Ulnar nerve gliding (mobility) and elongation (stretching) were measured around the elbow joint using a three-dimensional digitizing system. Data were compared between arm positions (elbow extension vs. 90° flexion, wrist extension vs. flexion, or forearm pronation vs. supination).

Results

Passive wrist movement from flexion to extension caused the ulnar nerve to glide. The largest amount of glide during passive wrist movement was found at 90° elbow flexion and maximum forearm supination position (5.4±1.1 mm). Ulnar nerve gliding during passive forearm movement was subtle. The ulnar nerve tightened with elbow flexion. Maximum elongation of the ulnar nerve was 5.6±0.6 mm from extension to 90° flexion in the elbow.

Conclusions

Ulnar nerve gliding was most severe during passive wrist movement in elbow flexion and forearm supination. This result suggests that passive wrist movement from flexion to extension with the elbow flexed and forearm supinated may be the most effective nonsurgical ulnar nerve release position to treat cubital tunnel syndrome. Attention should be paid to the elbow flexion angle during nonsurgical ulnar nerve release to not exacerbate cubital tunnel symptoms.

Level of evidence

III.

Key Words: Cubital tunnel; Elongation; Gliding; Nerve release; Ulnar nerve

INTRODUCTION

Ulnar nerve entrapment at the elbow—cubital tunnel syndrome—is the second most frequent peripheral neuropathy in the arm after carpal tunnel syndrome [1,2]. Entrapment implies nerve dysfunction as a result of pressure from surrounding anatomic structures, but the term also includes other causes of nerve dysfunction such as local friction or traction. Symptoms consist primarily of paresthesia and numbness distal to the elbow and may be worsened by repetitive flexion of the elbow or external pressure at the ulnar aspect of the elbow [3]. Nonoperative treatment is primarily recommended for cubital tunnel syndrome, although surgical intervention is indicated when nonoperative treatment fails to provide adequate relief of symptoms [1,4].

Inflammation of nerve trunks plays a major role in widespread painful conditions such as carpal tunnel syndrome, cubital tunnel syndrome, and chronic back pain from nerve root irritation [5,6] even though nerve lesions may not be apparent. When a peripheral nerve is inflamed, minimal elongation (3%) can cause it to become mechanosensitive, and this may provoke pain and other symptoms [6]. Moreover, nerve elongation of 5% to 10% impairs intraneural blood flow [7], axonal transport [8], and nerve conduction [9].

Nerve gliding prevents excessive elongation and tension of the nerve during joint movements [10]. When nerve gliding is inhibited due to any adhesion to the surrounding soft tissues or any injurious change in anatomy caused by aging or trauma, the nerve may elongate at the inhibited area during joint movement rather than glide [10]. Nonsurgical nerve release, which is achieved by nerve gliding exercises, has been developed to improve physiological nerve gliding as these exercises decrease or eliminate the deleterious effects of peripheral nerve elongation [10-12]. For cubital tunnel syndrome, repetitive forearm or wrist movement is recommended to improve physiological gliding of the ulnar nerve [2,13,14]. Large glide with proper nerve tension, which depends on elbow flexion, is thought to be the most effective nerve release exercise [15].

Coppieters et al. [2] reported that nonsurgical ulnar nerve release completely resolved the pain and disability of cubital tunnel syndrome. Oskay et al. [13] investigated the clinical results of nonsurgical ulnar nerve release for cubital tunnel syndrome. All of their seven patients experienced a decrease in pain and an increase in grip and pinch strength at final follow-up. However, Svernlöv et al. [16] concluded that nonsurgical ulnar nerve release was superfluous for cubital tunnel syndrome. One of the reasons why the clinical results of these exercises have not been consistent across studies is the use of various applied passive movement and elbow flexion positions for nonsurgical ulnar nerve release. Our objective in this study was to investigate the amounts of ulnar nerve glide and elongation during passive wrist, forearm, or elbow movements. Measurements were obtained using cadaveric upper extremities, in which ulnar nerve movement and stretching can be measured precisely. Our hypothesis was that ulnar nerve glide would be greatest during passive wrist movement as described in a previous clinical study that detailed good outcomes [2].

METHODS

This study did not require ethical approval or informed consent because it was conducted using cadaveric specimens.

Preparation of Specimens

Seven fresh-frozen cadaveric upper extremities from the scapula to the fingers (2 females and 5 males; mean age at death, 66.4±1.6 years) were used to test nerve elongation and gliding in a custom elbow-testing system (Fig. 1). The hand was fixed to the elbow testing system with sutures; the forearm was fixed with two threaded cross pins in the distal radius; the upper arm was fixed with two screws through the midshaft of the humerus; and the scapula was fixed to a mounting plate using three screws with 60° glenohumeral abduction in the scapular plane.

The three major elbow flexor-extensors (biceps brachii, brachialis, and triceps) were loaded via cables sutured to all tendons with polyester sutures and a long-chain polyethylene core to apply a compressive load across the elbow. Loads were determined by muscle cross-sectional area ratios to a total of 40 N [17], such that the loads were as follows: biceps brachii, 6 N; brachialis, 9.2 N; and triceps, 24.8 N.

A muscle-splitting approach was used to access the ulnar nerve in the intermuscular septum 3 cm proximal to the arcade of Struthers, leaving the epineurium intact. The nerve was then exposed in a distal direction along the septum to the point where it traversed the cubital tunnel entering the forearm. Osborne’s fascia was left intact. All specimens were confirmed to be free of preexisting pathology.

Measurements

The nerve was marked with seven metallic beads sutured to the nerve tissue in 1-cm increments along its anatomical course beneath the epineurium, starting in the intermuscular septum distal to the arcade of Struthers at 45° elbow flexion, neutral forearm rotation, and neutral wrist flexion (Fig. 2A). The marks extended to the entrance to the cubital tunnel. To define the position of the nerve relative to bony anatomical landmarks, a reference screw was inserted in the medial epicondyle (Fig. 2A). The reference screw defined the three-dimensional grid for digitizing the metallic bead markers and the screw marks [18]. The positions of the screw and the nerve marks were digitized using a three-dimensional digitizing system (Microscribe 3DLX, Revware Inc.; accuracy, 0.3 mm). After completion of the tests, the entire nerve segment was dissected, and the nerve markers were digitized with the nerve at rest. The length of the ulnar nerve at rest was defined as the “resting” length (Fig. 2B).

Ulnar nerve strain (positive values represent elongation of the nerve) was calculated by dividing the ulnar nerve length in each position by the “resting” length of the ulnar nerve, as measured after harvest. Also, ulnar nerve gliding at each segment between two adjacent suture markers (from segment 1 at the proximal end to segment 6 at the distal end) was measured by calculating the change in location of each segment during passive elbow, wrist, or forearm movement.

Ulnar Nerve Gliding

Ulnar nerve gliding was calculated on the basis of the displacement of a suture from the point of intersection of the epicondylar reference line with the longitudinal axis of the nerve [18]. The vector of every segment was extended to cross the x-plane of the reference grid defined by the reference screw (X=0). The total distance from the segment midpoint to the point of intersection with the x-plane was calculated and used to determine differences in nerve excursion between wrist or forearm positions. Differences were calculated for wrist flexion–extension and pronation–supination. As a first step, the steepness “t” of the vector was determined using a linear function, with “A” being the point farthest from the x-plane and AM→ the vector from this point to the segment midpoint (M):

(1)

X=A+t⋅AM→ | X=0

(2)

t=−A→AM→

The calculated t was then used to define the intersection point of the vector with the x-plane:

(3)

xiyizi=xAyAzA+t⋅vxvyvz

These values were used to calculate the distance (d) from the midpoint (M) to the intersection point (I) by calculating the magnitude of the vector:

(4)

d=xI−xM2+yI−yM2+zI−zM2

Different arm positions were compared by calculating ∆d between the two positions. To correct for nerve strain, ∆l between the two positions was subtracted. The gliding of each segment, either from wrist flexion to extension or from pronation to supination, was measured, and the average was used for analysis.

Ulnar nerve gliding during wrist movement over the full range from flexion to extension was calculated in the four arm position combinations of elbow extension or 90° flexion and forearm supination or pronation. Ulnar nerve gliding during forearm movement over the full range from pronation to supination was calculated at elbow extension or elbow 90° flexion with the wrist flexed at 0° (neutral position).

Ulnar Nerve Length and Strain

The segment length of the ulnar nerve was defined as the length of the vector between the two nerve marks of a segment. Total nerve length was calculated by summing the lengths of all individual segments. Nerve strain was calculated using the formula.

(5)

e= l−l0l0=Δll0

where e is the relative strain, “l” is the nerve length at each position, “l₀” is the resting nerve length, and “∆l” is the difference between the two lengths.

Length and strain of the ulnar nerve were calculated in six arm positions: elbow 90° flexion or extension with the forearm supinated and wrist extended, wrist flexion or extension with the elbow flexed and forearm supinated, and forearm supination or pronation with the elbow flexed at 90° and wrist extended.

Data Analysis

All measurements were performed twice, and the average value was used for data analyses. Statistical analyses were performed using Statistica version 6.0 (StatSoft). Nerve gliding and strain were compared between positions (elbow extension vs. 90° flexion, wrist extension vs. flexion, or forearm pronation vs. supination) using paired t-tests after confirming that the data had a normal distribution. The maximum nerve gliding during wrist movement occurred with the forearm supinated and the elbow flexed at 90°. This measurement was compared among the six segments using Fisher’s least significant difference post-hoc test. The significance level was set at 0.05; data are reported as means±standard errors of the mean. Given the average of the first four specimens, six specimens were determined to be needed to achieve 80% power on the basis of differences in nerve gliding and strain between positions. In light of these considerations, we tested seven specimens.

RESULTS

Ulnar Nerve Gliding

Effect of passive wrist movement

Passive wrist movement over the full range from flexion to extension caused the ulnar nerve to glide (Table 1). The amount of ulnar nerve gliding differed with elbow and forearm positions. The largest gliding during passive wrist movement was found at 90° elbow flexion and forearm supination (Table 1). In segments 2 through 6, the amount of ulnar nerve gliding during passive wrist movement at 90° elbow flexion was significantly greater than that at elbow extension (P<0.05) (Table 1). In segment 3, forearm supination during passive wrist movement with the elbow in flexion allowed significantly longer gliding than did pronation (P=0.03). In segment 5, forearm supination during passive wrist movement with the elbow in either extension (P=008) or 90° flexion (P=007) resulted in significantly longer gliding than did pronation (Table 1). Furthermore, the amount of ulnar nerve gliding differed with location along the ulnar nerve. At 90° elbow flexion and forearm supination, segment 5 had significantly longer gliding than segments 1 and 2, and segment 6 had significantly longer gliding than segments 1, 2, 3, and 4 (Fig. 3).

Effect of passive forearm movement

Ulnar nerve gliding was subtle during passive forearm movement over the full range from supination to pronation (Table 2). Maximum gliding was only 1.2±0.3 mm in segment 1 in elbow extension (Table 2).

Ulnar Nerve Elongation

Effect of passive elbow movement

Ulnar nerve tightened with elbow flexion. The total length of the ulnar nerve increased by 5.6±0.6 mm from extension to 90° flexion (Table 3). In elbow extension, with the forearm supinated and the wrist extended, strain of the ulnar nerve in all segments had a negative value relative to the resting length (–1.9% to –9.2%), representing absence of elongation. In contrast, strain of the ulnar nerve was positive in all segments at 90° elbow flexion (1.0% to 8.9%), representing elongation in all segments (Table 3). Length and strain were significantly greater in elbow flexion than in elbow extension in segments 1 (P=0.004), 4 (P=0.002), 5 (P=0.006), and 6 (P=0.003) and in all segments combined (P<0.001).

Effect of passive wrist movement

Passive wrist extension increased the tension of the ulnar nerve. The total length of the ulnar nerve increased by 1.6±0.4 mm over the full range from flexion to extension (Table 4). Wrist extension led to significantly greater length and strain of the ulnar nerve than did wrist flexion in segments 2 (P=0.009) and 6 (P=0.007) and in all segments combined (P=0.006) (Table 4).

Effect of passive forearm movement

Length and strain of the ulnar nerve did not differ between forearm supination and pronation (P=0.27 to P=0.82) (Table 5).

DISCUSSION

This is the first cadaveric biomechanical study to investigate ulnar nerve gliding and elongation in the cubital tunnel. We demonstrated that ulnar nerve gliding was longest during passive wrist movement in elbow flexion and forearm supination, suggesting that passive wrist flexion/extension movements may induce physiological gliding of the ulnar nerve and are appropriate to recommend as nonsurgical ulnar nerve release exercises for conservative treatment of mild or moderate cubital tunnel syndrome.

The ulnar nerve originates in the brachial plexus from nerve roots C8 and T1. It passes through the axilla into the anterior compartment of the arm and then pierces the intermuscular septum and travels in the posterior compartment. Next, it passes posterior to the medial epicondyle into the cubital tunnel. The nerve then continues along the forearm between the flexor carpi ulnaris and flexor digitorum profundus, innervating the flexor carpi ulnaris and flexor digitorum profundus of the ring and small fingers. A dorsal cutaneous branch of the ulnar nerve innervates the dorsoulnar side of the hand proximal to the ulnar tunnel. Therefore, the ulnar nerve extends continuously from the cervical region to the hand, passing through the shoulder, elbow, and wrist joints, and must glide during joint movements, specifically wrist movement, to prevent non-physiological nerve elongation.

Non-surgical ulnar nerve release, which is achieved using nerve gliding exercises, is a conservative treatment for cubital tunnel syndrome. Although the clinical findings of previous studies that have investigated nerve gliding exercise have not been consistent, Coppieters et al. [2] reported nerve gliding exercises including wrist movements that completely resolved the pain and disability of subjects suffering from cubital tunnel syndrome. In the current study, we found that the greatest ulnar nerve gliding occurred during passive wrist movement. Therefore, passive wrist movements should be included in the nerve gliding exercises prescribed to release the ulnar nerve.

In cubital tunnel syndrome, the main sites of compression of the ulnar nerve are the arcade of Struthers, the medial intermuscular septum, and Osborne’s fascia. We found that segments 5 and 6 at the distal end of the cubital tunnel experienced the largest translation during passive wrist movement (extension–flexion) in elbow flexion with forearm supination. On the one hand, for mild or moderate cubital tunnel syndrome, physiological gliding of the ulnar nerve can be induced mainly at the distal end of the cubital tunnel by nerve gliding exercises involving wrist movement. On the other hand, nonsurgical ulnar nerve release may worsen the symptoms for severe cubital tunnel syndrome, specifically in the presence of bony deformity or ulnar nerve subluxation.

Excessive nerve elongation produces electrophysiological impairment [19-21] and a reduction or cessation of epineural blood flow [7,9,22]. Wall et al. [9] investigated the effect of nerve elongation on nerve conduction. After nerve elongation at 6% strain, the amplitude of the action potential decreased by 70% in 1 hour but returned to normal during the recovery period. Nerve elongation at 12% strain completely and irreversibly blocked conduction within 1 hour. Our study showed that the maximum strain on the ulnar nerve with no pathological lesion was 4.7% over its total length in 90° elbow flexion, maximum forearm supination, and maximum wrist extension. When nerve gliding is inhibited due to any adhesion to the surrounding soft tissues or any pathological lesion related to aging or trauma, the increased strain during wrist movement may exceed the threshold elongation at excessive elbow flexion. Therefore, the elbow flexion angle during nonsurgical ulnar nerve release must be controlled to not exacerbate cubital tunnel symptoms.

The elbow flexion test is a method of physical examination to assess for cubital tunnel syndrome [23]. This test is performed at maximum elbow flexion with a fully extended wrist. In this position, patients with cubital tunnel syndrome experience the onset of, or an increase in, one or more of the symptoms of pain, numbness, or tingling. We found here that the position used for the elbow flexion test (elbow flexion, wrist extension, and forearm supination) resulted in maximum elongation of the ulnar nerve. However, the maximum strain in this position was only 4.7%. Therefore, without additional entrapment by other pathologies, such as osteophytes or ligament and fascial hypertrophy, an increase in strain on the ulnar nerve may not provoke symptoms, resulting in a negative result on the elbow flexion test. However, when a peripheral nerve is inflamed, a mere 3% elongation is thought to cause mechanosensitivity [6]. Therefore, patients with inflammation of the ulnar nerve may have a positive elbow flexion test even though the maximum strain of the ulnar nerve is only 4.7%.

Strengths of our study include our direct measurement of ulnar nerve gliding and strain in cadaveric specimens as such measurements cannot be accurately investigated in living subjects. In addition, we precisely determined ulnar nerve elongation or slackening based on strain measurements because dissection of the nerve after testing allowed accurate determination of nerve length in the absence of force.

Our study also had several limitations. First, none of our specimens had elbow pathology on macroscopic observation. In contrast, patients with cubital tunnel syndrome may experience shorter gliding and greater elongation near the area of entrapment. A second limitation is that only limited muscle forces were applied in our study. Activation and tension in some muscles and tendons may affect nerve gliding and strain. However, when nonsurgical ulnar nerve release is performed by passive movement of the elbow, forearm, and wrist, most muscles should be at rest. Therefore, our results are likely indicative of those obtainable in living patients by passive movement. Third, we measured only superficial length and strain of the ulnar nerve.

CONCLUSIONS

Ulnar nerve gliding during wrist flexion–extension was greatest at the distal end of the cubital tunnel and with the elbow flexed and forearm supinated. This result suggests that passive wrist movement from flexion to extension with the elbow flexed and forearm supinated may be the most effective nonsurgical ulnar nerve release exercise for cubital tunnel syndrome. Attention should be paid to the elbow flexion angle so as not to exacerbate current symptoms during nonsurgical ulnar nerve release because the increased strain of the ulnar nerve at excessive elbow flexion positions may exceed the elongation threshold.

NOTES

Author contributions

Conceptualization: TM, TQL. Data curation: MHM. Formal analysis: MK, TM. Investigation: MA, TM. Methodology: MA, TM. Project administration: TM, MHM, TQL. Resources: MHM. Software: MHM. Supervision: TM, TQL. Validation: MHM, TM. Visualization: MHM, TM. Writing – original draft: TM. Writing – review & editing: TM, MHM, TQL. All authors read and agreed to the published version of the manuscript.

Conflict of interest

None.

Funding

None.

Data availability

Contact the corresponding author for data availability.

Acknowledgments

None.

Fig. 1.

Elbow testing system. (A) 90° Elbow flexion and (B) elbow extension positions with the forearm supinated and the wrist extended.

Fig. 2.

Suture marking on the ulnar nerve during testing (A) and after harvest (B).

Fig. 3.

Ulnar nerve gliding during passive wrist movement (from full flexion to full extension). *Indicates a significantly greater value than for the segments listed in parentheses (P<0.05).

Table 1.

Ulnar nerve gliding during passive wrist movement (from full extension to full flexion, mm)

	Forearm position		P-value (supination vs. pronation)
	Supination	Pronation	P-value (supination vs. pronation)
Segment 1
Elbow position
Extension	1.4±0.4	1.2±0.4	0.70
90° Flexion	1.9±0.4	1.4±0.3	0.12
P-value (extension vs. flexion)	0.34	0.75
Segment 2
Elbow position
Extension	0.7±0.2	0.4±0.1	0.17
90° Flexion	2.0±0.4	1.7±0.3	0.24
P-value (extension vs. flexion)	0.004	0.006
Segment 3
Elbow position
Extension	0.4±0.1	0.3±0.1	0.75
90° Flexion	2.6±0.3	1.8±0.3	0.03
P-value (extension vs. flexion)	<0.001	<0.001
Segment 4
Elbow position
Extension	0.9±0.2	0.3±0.1	0.07
90° Flexion	2.3±0.5	1.9±0.4	0.44
P-value (extension vs. flexion)	0.02	0.01
Segment 5
Elbow position
Extension	0.8±0.1	0.3±0.1	0.008
90° Flexion	3.8±0.6	2.9±0.6	0.007
P-value (extension vs. flexion)	0.003	0.003
Segment 6
Elbow position
Extension	1.1±0.2	0.7±0.2	0.18
90° Flexion	5.4±1.1	4.0±0.7	0.10
P-value (extension vs. flexion)	0.004	0.003

Values are presented as mean±standard error of the mean.

Table 2.

Ulnar nerve gliding during passive forearm movement (from full supination to full pronation, mm)

Segment	Elbow position		P-value (extension vs. flexion)
Segment	Extension	90° Flexion	P-value (extension vs. flexion)
1	1.2±0.3	0.3±0.1	0.02
2	0.9±0.2	0.3±0.1	0.07
3	0.9±0.4	0.4±0.1	0.24
4	0.4±0.1	0.4±0.1	0.87
5	0.5±0.2	0.3±0.1	0.56
6	0.5±0.2	0.6±0.2	0.66

Values are presented as mean±standard error of the mean. These values measured at wrist neutral position.

Table 3.

Ulnar nerve length and strain during passive elbow movement

Segment	Length (mm)		Change in length (mm)	Strain (%)		Change in strain (%)	P-value (extension vs. flexion)
Segment	Elbow extension	90° Elbow flexion	Flexion–extension	Elbow extension	90° Elbow flexion	Flexion–extension	P-value (extension vs. flexion)
1	9.5±0.3	10.2±0.4	0.7±0.1	–5.5±2.4	1.0±3.0	6.4±1.4	0.004
2	9.8±0.2	10.4±0.3	0.6±0.3	–2.2±4.0	3.5±1.9	5.7±2.8	0.08
3	9.5±0.2	10.3±0.3	0.8±0.4	–3.8±2.0	3.4±1.6	7.2±3.1	0.07
4	10.4±0.2	11.6±0.3	1.2±0.2	–1.9±1.7	8.9±1.2	10.8±2.2	0.002
5	9.2±0.6	10.2±0.4	1.0±0.2	–3.6±3.2	7.6±4.3	11.2±2.6	0.006
6	8.8±0.4	10.2±0.5	1.4±0.4	–9.2±3.7	4.9±2.2	14.1±3.1	0.003
Total	57.3±0.5	62.8±0.7	5.6±0.6	–4.6±1.5	4.7±1.2	9.3±1.0	<0.001

Values are presented as mean±standard error of the mean. These values were obtained with the forearm supinated and wrist extended. A positive value for strain represents nerve elongation.

Table 4.

Ulnar nerve length and strain during wrist movement

Segment	Length (mm)		Change in length (mm)	Strain (%)		Change in strain (%)	P-value (flexion vs. extension)
Segment	Flexion	Extension	Extension–flexion	Flexion	Extension	Extension–flexion	P-value (flexion vs. extension)
1	10.1±0.4	10.2±0.4	0.1±0.1	0.0±2.9	1.0±3.0	0.9±0.6	0.13
2	10.1±0.3	10.4±0.3	0.4±0.1	0.0±2.1	3.5±1.9	3.5±0.9	0.009
3	10.0±0.4	10.3±0.4	0.3±0.2	0.5±1.4	3.4±1.6	2.8±1.8	0.16
4	11.2±0.3	11.6±0.3	0.3±0.2	6.0±1.6	8.9±1.2	2.9±1.7	0.15
5	10.0±0.6	10.2±0.4	0.1±0.3	5.5±2.9	7.6±4.3	2.1±3.1	0.54
6	9.7±0.4	10.2±0.5	0.5±0.1	0.1±2.6	4.9±2.2	4.7±1.2	0.007
Total	61.2±0.8	62.8±0.7	1.6±0.4	1.9±0.8	4.7±1.2	2.8±0.7	0.006

Values are presented as mean±standard error of the mean. These values were obtained with the elbow flexed and forearm supinated. A positive value for strain represents nerve elongation.

Table 5.

Ulnar nerve length and strain during passive forearm movement

Segment	Length (mm)		Change in length (mm)	Strain (%)		Change in strain (%)	P-value (supination vs. pronation)
Segment	Forearm supination	Forearm pronation	Pronation– supination	Forearm supination	Forearm pronation	Pronation– supination	P-value (supination vs. pronation)
1	10.2±0.4	10.2±0.4	0.0±0.1	1.0±3.0	1.5±3.2	1.5±1.3	0.72
2	10.4±0.3	10.3±0.3	–0.1±0.1	3.5±1.9	2.0±1.4	–1.5±1.4	0.31
3	10.3±0.4	10.3±0.4	0.0±0.1	3.4±1.6	3.8±1.9	0.4±1.5	0.82
4	11.6±0.3	11.5±0.3	–0.1±0.1	8.9±1.2	8.6±2.0	–0.4±1.3	0.82
5	10.2±0.4	10.3±0.5	0.1±0.1	7.6±4.3	8.5±3.9	0.9±1.2	0.50
6	10.2±0.5	10.1±0.5	–0.1±0.1	4.9±2.2	4.1±2.3	–0.8±0.6	0.27
Total	62.8±0.7	62.8±0.7	–0.1±0.1	4.7±1.2	4.6±1.1	–0.1±0.2	0.27

Values are presented as mean±standard error of the mean. These values were obtained with the elbow flexed at 90° and wrist extended. A positive value for strain represents nerve elongation.

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