In vivo dynamic migration of the posterior interosseous nerve across various elbow and forearm positions

Article information

J Korean Shoulder Elbow Soc. 2024;.cise.2024.00213
Publication date (electronic) : 2024 September 27
doi : https://doi.org/10.5397/cise.2024.00213
Department of Orthopedic Surgery, Teikyo University School of Medicine, Tokyo, Japan
Corresponding author: Hideaki Miyamoto Department of Orthopedic Surgery, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-0003, Japan Tel: +81-3-3964-4097 Fax: +81-3-5375-6864 Email: miyamotoh@med.teikyo-u.ac.jp
Received 2024 March 11; Revised 2024 June 20; Accepted 2024 June 20.

Abstract

Background

The posterior interosseous nerve (PIN) is at risk of iatrogenic nerve injury during elbow surgery when using a lateral or posterolateral approach. Results of cadaveric studies indicated that maintaining forearm pronation throughout the surgery can help move the PIN away from the surgical window. However, in vivo dynamic migration of the PIN in response to changes in the elbow and forearm position is unclear. This study aimed to clarify the in vivo dynamic migration pattern of the PIN in response to changes in the elbow and forearm position using ultrasound imaging.

Methods

This study included 43 upper extremities of 22 healthy volunteers (16 females; mean age, 29 years). Using ultrasound imaging, we measured the shortest distance from the radial head (RH) to the point where the PIN crossed the lateral aspect of the radial axis in six positions of the elbow and forearm: 90° forearm supination, 90° pronation, and neutral forearm position, each at 135° of elbow flexion and 0° of elbow extension.

Results

The RH-to-nerve distance was greater during elbow extension than during elbow flexion regardless of the forearm position. However, the maximum migration distance was 3.5 mm when transitioning from elbow extension and forearm pronation (25.1 mm) to elbow flexion and forearm supination (21.6 mm).

Conclusions

Although forearm pronation may help move the PIN away from the surgical window, care should be taken not to injure the nerve when performing elbow surgery using a lateral or posterolateral approach.

Level of evidence

III.

INTRODUCTION

Lateral and posterolateral approaches to the elbow are often used to expose the proximal radius during surgical management of elbow fractures or arthritis. The posterior interosseous nerve (PIN) crosses the lateral aspect of the radius from proximal and anterior to distal and posterior directions and is at risk of iatrogenic nerve injury during elbow surgery [1-3]. In the literature, forearm pronation is the reason for distal PIN movement from the radial head (RH) and out of the surgical window [1,4]. Therefore, the recommendation is to maintain the forearm in a pronated position during elbow surgery when lateral or posterolateral approaches are used. Previous studies were conducted on cadavers [1,4-7], with dissection of soft tissue surrounding the PIN; however, in vivo migration of the PIN across elbow and forearm positions is unclear. We hypothesized that the PIN moves away from the RH during forearm pronation. The purpose of this study was to clarify the in vivo dynamic migration of the PIN across elbow and forearm positions using ultrasound imaging.

METHODS

The Institutional Review Board of Teikyo University reviewed and approved the study protocol (No. 20-133) and waived the requirement for written informed consent. This study included 43 upper extremities with a full range of motion in 22 healthy vol­unteers (16 females; mean age, 29 years). The exclusion criteria were subjective or objective muscle weakness, sensory distur­bance, or history of extremity trauma, which was the case for one extremity. The subjects were asked to sit in front of an examination table with their shoulder slightly flexed in an internal rotation with the lateral epicondyle on top. The examiner was an orthopedic surgeon with 15 years of experience in musculoskeletal ultrasound. We measured the shortest distance from the RH to the point where the PIN crossed the lateral aspect of the radial axis in six positions of the elbow and forearm (90° forearm supination, neutral, or 90° forearm pronation, each at 135° of elbow flexion and 0° of elbow extension). All included extremities met the range of motion criteria of 0° to 135° and achieved 90° of supination/pronation. The measurements were obtained using ultrasound imaging with an 18 MHz linear-array transducer (HI VISION Preirus, Hitachi Aloka Medical) (Figs. 1 and 2). Continuous variables are shown as means±standard errors. The distances at each elbow and forearm position were compared using paired t-tests. Statistical significance was set at P-value <0.05. Basic demographic data are presented in Table 1.

Fig. 1.

Distance between the radial head (RH) and posterior interosseous nerve (PIN). Position of the ultrasound imaging probe. Ultrasound images revealed a change of shape at the lower edge of the RH. Distance was measured as indicated by the double-headed arrow. The PIN is outlined with a dotted white circle.

Fig. 2.

Ultrasound images in six positions.

Basic demographic data of the participants

RESULTS

The RH-to-nerve distance was greater during elbow extension than flexion in each forearm rotation position (Fig. 3). At elbow flexion, the head-to-nerve distance was significantly greater during forearm pronation (23.4±0.84 mm) than during supination (21.6±0.76 mm, P=0.010). In contrast, the head-to-nerve distance was not significantly different between forearm pronation (25.1±0.68 mm) and forearm supination (25.1±0.79 mm) during elbow extension (P=0.980). The maximum migration distance was 3.5 mm and occurred when transitioning from elbow extension and forearm pronation (25.1±0.68 mm) to elbow flexion and forearm supination (21.6±0.76 mm). All relevant data and the differences between the dominant and non-dominant arms are presented in Table 2.

Fig. 3.

Box and whisker diagram illustrating the distance between the radial head and posterior interosseous nerve at each upper extremity position. NS: not significant.

All relevant data of the participants

DISCUSSION

The main finding of our study was that the RH-to-nerve distance associated with the elbow extension position was greater than the distance associated with elbow flexion, independent of forearm rotation. In general, the elbow and forearm positions in which the RH-to-nerve distance was longer appeared safer because of reduced risk of injury resulting from the nerve emerging in the surgical window. However, when examining the RH-to-nerve distance changes by position, the difference between the extended pronation position and flexion supination position was the largest at 3.5 mm but may be inconsequential to surgical risk.

In the literature, forearm pronation resulted in distal movement of the PIN from the RH, excluding it from the surgical field. Hackl et al. [1] examined the location of the PIN in neutral rotation, supination, and pronation using three-dimensional x-ray scans in six upper extremities of fresh-frozen cadavers. In the sagittal view, the PIN crossed the proximal radius 61.8 mm and 41.1 mm below the RH in pronation and supination, respectively. Diliberti et al. [4] showed in a study of 32 fresh cadavers that the PIN crossed the proximal radius 52.0 mm and 34.4 mm from the radiocapitellar articulation in pronation and supination, respectively. However, flexion and extension of the elbow did not affect these distances. Calfee et al. [5] reported that the PIN crossed the radius at a mean of 5.6 cm distal to the radiocapitellar joint in pronation, and supination decreased this distance to 3.2 cm in 20 fresh-frozen cadaveric upper extremities. Overall, the evidence indicates that pronation increased the proximal safe zone to approximately 2 cm in the lateral approach. In contrast, our in vivo study indicated that PIN migration during the same movement was 3.5 mm, which is significantly less than that reported in cadaveric studies.

The PIN branches separate from the radial nerve at the arcade of Frohse and continue along the supinator muscle of the forearm, under the brachioradialis muscle. Therefore, full extension may exert tension on the PIN, while elbow flexion may relieve this tension. Full flexion, which contracts the anterior muscles, may push the PIN further toward the radiocapitellar joint. However, in our vivo study, PIN migration was minimal in each forearm position. This finding may be due to the supinator and brachioradialis muscles ensuring a constant position of the PIN in vivo. In contrast, in cadaveric studies of PIN migration, sufficient dissection of the soft tissue and muscles is performed to clearly visualize the position of the PIN. Soft tissue dissection may allow the PIN to move more freely than it does in vivo.

This study has some limitations. First, the PIN originates from the posterior humerus and travels to the anterolateral forearm. The angle of the PIN along the proximal radial shaft results in a significant deviation of the RH-to-nerve distance depending on ultrasound probe placement. We did not consider intra- or inter-examiner errors or individual differences in sex, age, or body size, which may have affected the presented estimates. Second, most elbow surgeries are performed in the midrange of flexion at approximately 90°. However, in our study, measurements were performed only in full extension and near-full flexion, in which range the PIN distance is unclear. Third, the potential effects of muscle tension cannot be ignored because the measurements were obtained in an awake patient. In addition, the effects of injury could not be assessed due to the in vivo nature of this study.

CONCLUSIONS

We found that the PIN moved farther from the RH during elbow extension than during elbow flexion and farther during forearm pronation than during forearm supination. However, distal migration of the PIN was minimal, indicating that a difference of just 3.5 mm may not guarantee safety during surgery. Thus, care should be taken to ensure that the PIN is not within the surgical window even when the forearm is in the pronated position.

Notes

Author contributions

Conceptualization: HM, HK. Data curation: KI. Formal analysis: KI, TI. Methodology: HM, TI.

Project administration: KI. Supervision: HM, HK. Writing – original draft: KI. Writing – review & editing: HM, HK.

Conflict of interest

None.

Funding

None.

Data availability

Contact the corresponding author for data availability.

Acknowledgments

None.

References

1. Hackl M, Wegmann K, Lappen S, Helf C, Burkhart KJ, Müller LP. The course of the posterior interosseous nerve in relation to the proximal radius: is there a reliable landmark? Injury 2015;46:687–92.
2. Kelly EW, Morrey BF, O'Driscoll SW. Complications of repair of the distal biceps tendon with the modified two-incision technique. J Bone Joint Surg Am 2000;82:1575–81.
3. Strauch RJ, Rosenwasser MP, Glazer PA. Surgical exposure of the dorsal proximal third of the radius: how vulnerable is the posterior interosseous nerve? J Shoulder Elbow Surg 1996;5:342–6.
4. Diliberti T, Botte MJ, Abrams RA. Anatomical considerations regarding the posterior interosseous nerve during posterolateral approaches to the proximal part of the radius. J Bone Joint Surg Am 2000;82:809–13.
5. Calfee RP, Wilson JM, Wong AH. Variations in the anatomic relations of the posterior interosseous nerve associated with proximal forearm trauma. J Bone Joint Surg Am 2011;93:81–90.
6. Hohenberger GM, Schwarz AM, Maier MJ, et al. Safe zone for the posterior interosseous nerve with regard to the lateral and posterior approaches to the proximal radius. Surg Radiol Anat 2018;40:1025–30.
7. Schwarz AM, Hohenberger GM, Weiglein AH, Riedl R, Staresinic M, Grechenig S. Avoiding radial nerve palsy in proximal radius shaft plating: a cadaver study. Injury 2017;48 Suppl 5:S34–7.

Article information Continued

Fig. 1.

Distance between the radial head (RH) and posterior interosseous nerve (PIN). Position of the ultrasound imaging probe. Ultrasound images revealed a change of shape at the lower edge of the RH. Distance was measured as indicated by the double-headed arrow. The PIN is outlined with a dotted white circle.

Fig. 2.

Ultrasound images in six positions.

Fig. 3.

Box and whisker diagram illustrating the distance between the radial head and posterior interosseous nerve at each upper extremity position. NS: not significant.

Table 1.

Basic demographic data of the participants

Variable Value
Age (yr) 29±1 (23–44)
Sex
 Male 6 Cases (12 elbows)
 Female 16 Cases (31 elbows)
 Total 22 Cases (43 elbows)

Values are presented as mean±standard deviation (range) or number.

Table 2.

All relevant data of the participants

Case Age (yr) Sex Dominant side Side The radial head-to-nerve distance in six positions of the elbow and forearm (mm)
Flexion, pronation Flexion, neutral Flexion, supination Extension, pronation Extension, neutral Extension, supination
1 28 Female Right Right 24.2 24.7 22.7 21.9 20.7 29.4
Left 12.0 12.0 15.7 26.1 19.9 24.1
2 27 Female Right Right 23.4 24.7 20.6 23.9 21.4 20.6
Left 15.7 15.3 17.2 27.0 23.4 14.8
3 25 Female Right Right 13.2 14.0 12.4 27.9 23.8 30.1
Left 16.9 15.5 11.9 18.1 22.1 23.3
4 26 Female Left Right 16.2 22.6 19.0 25.1 22.0 27.6
Left 23.5 22.5 19.6 27.7 27.3 24.1
5 24 Female Right Right 13.0 12.7 13.4 13.8 16.8 18.5
Left 18.4 15.4 14.6 18.2 18.4 13.8
6 31 Male Right Right 28.5 26.8 15.2 25.1 23.9 24.5
Left 28.7 22.7 16.8 30.0 23.1 22.6
7 42 Male Left Right 28.6 22.3 21.8 32.3 29.0 29.8
Left 29.5 26.7 19.2 28.2 25.8 28.7
8 25 Female Right Right 23.1 16.2 25.1 25.6 27.1 26.8
Left 32.5 26.5 28.1 30.3 24.8 25.7
9 28 Male Right Right 25.7 25.8 25.5 26.6 25.4 29.2
Left 26.5 24.2 23.7 25.1 29.1 25.5
10 23 Female Right Right 23.0 19.8 20.4 25.7 22.4 29.5
Left 22.4 23.6 24.4 24.2 22.6 25.6
11 32 Female Right Right 21.5 22.4 22.2 31.0 30.1 28.9
Left 26.6 28.7 28.2 30.7 31.2 27.2
12 30 Male Right Right 24.9 24.7 20.8 20.8 29.7 23.8
Left 24.9 22.3 24.0 21.0 23.0 27.8
13 44 Female Right Right 20.5 19.4 20.0 21.8 21.9 23.1
Left 19.4 19.2 21.4 22.8 18.3 18.5
14 30 Female Right Right 21.5 20.3 26.7 23.0 20.6 21.0
Left 30.5 30.7 31.4 24.0 19.9 22.1
15 31 Female Right Right 28.6 25.7 24.5 23.5 23.1 23.4
Left 28.8 22.1 23.3 29.0 22.1 30.1
16 30 Female Left Right 15.8 12.4 12.4 15.8 12.8 12.8
Left 12.0 13.6 14.0 23.0 23.1 25.4
17 26 Female Right Right 22.1 24.0 16.4 20.0 23.4 21.5
Left 24.7 14.6 14.8 23.6 20.4 15.4
18 31 Female Right Right 28.7 28.6 26.5 31.7 31.3 33.6
Left 25.2 23.8 26.1 29.5 28.6 31.7
19 28 Male Right Right 32.7 29.9 30.6 21.7 31.5 28.5
Left 27.7 21.7 23.0 28.7 25.1 23.2
20 26 Male Right Right 28.3 29.1 30.3 32.0 33.6 32.6
Left 27.5 34.2 34.0 31.9 35.6 33.1
21 25 Female Right Right 21.7 28.2 25.4 25.6 32.1 32.6
Left 22.1 26.1 22.3 25.4 21.1 25.4
22 27 Female Left Left 24.6 25.5 21.6 21.6 24.2 24.3
Dominant vs. non-dominant for case 1-21, P-value 0.896 0.410 0.876 0.248 0.034 0.013