Superficial surgical landmarks for identifying the posterior interosseous nerve

Radial nerve compression: anatomical perspective and clinical consequences

The radial nerve is the biggest branch of the posterior cord of the brachial plexus and one of its five terminal branches. Entrapment of the radial nerve at the elbow is the third most common compressive neuropathy of the upper limb after carpal tunnel and cubital tunnel syndromes. Because the incidence is relatively low and many agents can compress it along its whole course, entrapment of the radial nerve or its branches can pose a considerable clinical challenge. Several of these agents are related to normal or variant anatomy. The most common of the compressive neuropathies related to the radial nerve is the posterior interosseus nerve syndrome. Appropriate treatment requires familiarity with the anatomical traits influencing the presenting symptoms and the related prognoses. The aim of this study is to describe the compressive neuropathies of the radial nerve, emphasizing the anatomical perspective and highlighting the traps awaiting physicians evaluating these entrapments.

Posterior Interosseous Nerve Graft: Utilizing External Landmarks and Anthropometric Ratios to Predict Available Length for Digital Nerve Reconstruction in a Cadaveric Study

Objective:

In digital nerve defects that require grafting, autografts remain the efficacious option. The sensory posterior interosseous nerve (PIN) is an ideal choice as it is of similar caliber to digital nerves and leaves no donor morbidity upon resection. However, a finite length of harvestable PIN exists, and considerable variations of this length have been reported in the literature. There exists no predictive model to estimate this length. We sought to determine a method to accurately predict the available length of PIN based on individual patient anthropometry.

Methods:

A cadaveric dissection study was performed in a fresh tissue laboratory. The length of the sensory branch of the PIN and various anthropometric measurements were made in respect to surface anatomy of the ulna to develop a predictable ratio for available PIN donor graft.

Results:

A total of 16 specimens were obtained. On average the length of the PIN was 5.7 cm (range: 3.3-9. cm) and the length of the ulna was 25.7 cm (range: 23.5-30.6 cm). The ratio of PIN to ulnar length was 0.222 ( r = 0.4651). Using one-fifth the length of the ulna, the mean predicted length of the PIN was 5.14 cm (range: 4.7-6.1 cm). On univariate analysis, there was no significant difference between the measured and predicted PIN length ( P = .249).

Conclusion:

An anthropometric ratio predicated on reproducible surface anatomy of the ulna is a useful tool in predicting the sensory PIN length. Such a prediction may be a useful in guiding patient discussions concerning surgical options for digital nerve reconstruction.

Optimization of Anterior Incision Placement for Distal Biceps Repair

Introduction

Damage to the posterior interosseous nerve (PIN) is a known complication when using a cortical button during distal biceps tendon repair. Prior studies show that the trajectory of the drill through the biceps tuberosity can affect the distance from the PIN. We develop a mathematical model to predict the location of the tuberosity based on a palpable bony landmark and patient demographic factors.

Methods

The medical charts and elbow radiographs of (n = 82) adult patients were retrospectively reviewed. Using standard radiographic software, two observers measured the distance from the olecranon tip to the center of the biceps tuberosity. Multivariate regression analysis was used to build a linear model. The model was cross-validated with five arms from three distinct cadavers. A surgical wire was guided into the volar aspect of each forearm using the model, and a dissection was then performed to assess the proximity of the surgical wire to the insertion of the biceps tendon on the radial tuberosity.

Results

Olecranon-tuberosity distance (OTD) ranged from 52.3 mm to 77.2 mm (mean 66.5 mm). Univariate analyses revealed males had significantly longer OTD (mean 69.3 mm) compared to females (mean 61.2 mm, t-test, p < 0.001). Increased body mass index (BMI) weakly correlated with increased distance (Pearson’s r = 0.22, p = 0.048). Height showed strong positive correlation with increased distance (r = 0.77, p < 0.001). Multivariate regression revealed that significant predictive factors for olecranon-tuberosity distance were height (coefficient = 35.8, p < 0.001), BMI (coefficient = 0.14, p = 0.032), and male sex (coefficient = 3.17, p = 0.0039). The average error in the cadaveric validation, measured as distance from the surgical wire to the distal biceps insertion was 1.8 mm.

Conclusion

A highly accurate mathematical model can be used to predict the location of the biceps tuberosity in relation to the palpable tip of the olecranon, based only on height, BMI, and sex of the patient. Knowledge of this distance can guide accurate placement of the skin incision when a transverse single-incision approach is utilized for repair of the distal biceps tendon using a cortical button. Diagnostics showed the model to be less accurate near the extremes of the measurement. Since patients with a target incision point far removed from average would most benefit from such a model, we will continue by identifying and enrolling patients at the low and high ends of the range. We further hypothesize that the technique described above could be similarly applied to benefit other procedures.

Posterior interosseous nerve localization within the proximal forearm - a patient normalized parameter

AIM

To provide a “patient-normalized” parameter in the proximal forearm.

METHODS

Sixty-three cadaveric upper extremities from thirty-five cadavers were studied. A muscle splitting approach was utilized to locate the posterior interosseous nerve (PIN) at the point where it emerges from beneath the supinator. The supinator was carefully incised to expose the midpoint length of the nerve as it passes into the forearm while preserving the associated fascial connections, thereby preserving the relationship of the nerve with the muscle. We measured the transepicondylar distance (TED), PIN distance in the forearm’s neutral rotation position, pronation position, supination position, and the nerve width. Two individuals performed measurements using a digital caliper with inter-observer and intra-observer blinding. The results were analyzed with the Wilcoxon-Mann-Whitney test for paired samples.

RESULTS

In pronation, the PIN was within two confidence intervals of 1.0 TED in 95% of cases (range 0.7-1.3 TED); in neutral, within two confidence intervals of 0.84 TED in 95% of cases (range 0.5-1.1 TED); in supination, within two confidence intervals of 0.72 TED in 95% of cases (range 0.5-0.9 TED). The mean PIN distance from the lateral epicondyle was 100% of TED in a pronated forearm, 84% in neutral, and 72% in supination. Predictive accuracy was highest in supination; in all cases the majority of specimens (90.47%-95.23%) are within 2 cm of the forearm position-specific percentage of TED. When comparing right to left sides for TEDs with the signed Wilcoxon-Mann-Whitney test for paired samples as well as a significance test (with normal distribution), the P-value was 0.0357 (significance - 0.05) indicating a significant difference between the two sides.

CONCLUSION

This “patient normalized” parameter localizes the PIN crossing a line drawn between the lateral epicondyle and the radial styloid. Accurate PIN localization will aid in diagnosis, injections, and surgical approaches.

Anatomic cadaveric study of the extensile extensor digitorum communis splitting approach for exposing the ulnar coronoid process

BACKGROUND

The extensile extensor digitorum communis (EDC) splitting approach can access the ulnar coronoid process (UCP), which can be used to treat terrible triad injuries. The present study anatomically examined the extensile EDC splitting approach for exposing the UCP.

METHODS

Twenty fresh frozen cadaveric upper limbs were dissected. The splitting length of the EDC and detachment length of the extensor carpi radialis brevis (ECRB)-extensor carpi radialis longus (ECRL)-brachioradialis (BR) origin were measured to expose the UCP. The distance between the most distal site of the EDC splitting and the point at which the posterior interosseous nerve (PIN) crosses the anterior aspect of the radial shaft, and the distance between the most proximal site of the ECRB-ECRL-BR origin detachment and the point at which the radial nerve crosses the anterior aspect of the humeral shaft were measured.

RESULTS

The splitting length of the EDC was 45.4 ± 4.8 mm, the detachment length of the ECRB-ECRL-BR origin was 30.2 ± 4.7 mm, the distance between the distal site of the EDC splitting and PIN was 10.6 ± 6.1 mm (minimum distance, 1.1 mm), and the distance between the proximal site of the ECRB-ECRL-BR origin detachment and the radial nerve was 49.5 ± 9.7 mm (minimum distance, 31.7 mm).

CONCLUSIONS

The extensile EDC splitting approach can sufficiently expose the UCP. However, splitting must be performed carefully because the most distal site of the EDC splitting is close to the point at which the PIN crosses the anterior aspect of the radial shaft (average distance, 10 mm; minimum distance, 1 mm).

Vascular anatomy relevant to distal biceps tendon repair

BACKGROUND

Avoiding bleeding and vascular complications in open repair of distal biceps tendon rupture requires knowledge of the local vascular anatomy. This study examined the vascular anatomy relevant to distal biceps tendon repair.

METHODS

The antecubital regions of 17 cadaveric upper extremities were dissected using ×2.5 loupe magnification to identify the brachial artery, the radial artery and its recurrent branches, and venous branches crossing the distal biceps tendon. With the elbow in full extension and supination, the position of each vascular structure was measured relative to the most proximal aspect of the bicipital tuberosity.

RESULTS

The most common pattern (13 of 17 specimens) was a single radial recurrent artery (RRA) crossing volar to the tendon at a mean of 4 mm proximal to the tuberosity and positioned 15.4 mm volar to the tuberosity. The RRA bifurcated 2 to 9 mm from its origin in 6 arms and demonstrated a single bifurcation. In 8 of 17 specimens, an additional recurrent branch off the brachial artery traveled dorsal to the intact biceps tendon 16 mm proximal to the RRA. Two arms demonstrated a high brachial artery bifurcation. The crossing veins were venae comitantes of the RRAs and radial and ulnar arteries. They connected to the superficial veins by way of a perforating branch. Most often, 3 transverse veins positioned on average 0.2 mm proximal and 16 mm volar to the tuberosity were seen.

CONCLUSIONS

The vascular anatomy encountered during distal biceps repair is variable, and RRAs occasionally travel dorsal to the biceps tendon. Most often, a single RRA on average 4 mm proximal to the tuberosity will branch once.

Effect of elbow flexion on the proximity of the PIN during 2-incision distal biceps repair

The posterior interosseous nerve (PIN) is at risk for injury during surgical dissection for distal biceps repair, yet the optimal position of elbow flexion to avoid a PIN injury has never been established for the 2-incision approach. The purpose of this study was to determine the proximity of the PIN to the radial tuberosity during surgical dissection in different degrees of elbow flexion. Ten cadaveric specimens with an intact elbow and forearm were dissected in full pronation using a modified Boyd-Anderson approach. Half of the dissections were completed in 90° of flexion and the other half were completed in maximal flexion. To simulate the location of the PIN during a single-incision biceps repair, the distance of the PIN to the radial tuberosity was recorded in full extension and supination. Results from these measurements were assessed for differences using paired t tests, with differences deemed significant for P values less than .05. The PIN was not identified in any of the 2-incision surgical dissections. Based on these findings, the proximity of the PIN to the radial tuberosity is not significantly affected by the degree of elbow flexion in the muscle-splitting 2-incision approach. In addition, a safe zone exists for avoiding PIN injury in a single-incision technique for distal biceps repair because a drill bit exiting the radial tuberosity greater than 1 cm in a distal-radial direction would place the PIN at risk.

Posterior interosseous nerve palsy in a child associated with recurrent dislocation of the head of the radius

Injuries to the posterior interosseous nerve (PIN) appear to be very uncommon in children. In this paper, the authors describe a 9-year-old boy with a radial malunion and radial head instability that resulted in PIN compression. Surgical decompression via transection of the overlying supinator muscle with correction of the radial deformity and instability resulted in complete return of PIN function. The clinician should be aware of anterior dislocation of the radial head as a cause of PIN injury. Based on the authors' experience, nerve decompression and correction of the bone deformity result in return of normal PIN function.

Comparison of dorsal and volar approaches to the proximal radius

Proximal radius exposure may be acquired by either the dorsal or volar approach depending on surgical requirements. The dorsal approach is traditionally recommended for fracture fixation of the proximal radius because of theoretically improved exposure and because the dorsal aspect of the bone is the tensile surface. The posterior interosseous nerve can be visualized and protected using this approach. The volar approach is preferred for biceps repair and boasts a distal extensile approach with adequate soft tissue coverage. Impingement on the bicipital tuberosity and biceps tendon, in addition to positioning on the compression side of the bone, makes the anterior or anterolateral position for plate placement less desirable. The goal of this study was to quantify and compare in a cadaver model the area of bone exposed using both approaches. We hypothesized that equivalent exposures can be obtained and the posterior interosseous nerve can be identified with either the Thompson or Henry approach. Standard dorsal and volar approaches were performed on 10 fresh-frozen adult cadaveric upper-limb specimens. Cross-sectional area of exposure was quantified from digital photographs using software. The 2 approaches did not result in a significant difference in area exposed. Depending on case requirements, either the dorsal or volar approach will provide adequate exposure to the proximal radius.

Median nerve branches to the pronator teres: cadaveric study with potential use in neurotization procedures to the radial nerve at the elbow

Object

Various donor nerves have been used for brachial plexus neurotization procedures. To the authors' knowledge, neurotization of median nerve branches to the pronator teres to the radial nerve at the elbow have not been explored.

Methods

In an attempt to identify an additional nerve donor candidate for neurotization procedures of the upper limb, 20 cadaveric upper limbs underwent dissection of the cubital fossa and identification of branches of the median nerve to the pronator teres. Measurements were made of such branches, and distal transection was then performed to determine the appropriate length so that the structure could be brought to the laterally positioned radial nerve via tunneling deep to the biceps brachii muscle.

Results

All specimens were found to have a median nerve branch to the pronator teres that was long enough to reach the radial nerve in the cubital fossa. Neural connections remained tension free with full pronation and supination. The mean length of these branches to the pronator teres was 3.6 cm. The overall mean diameter of these nerves was 1.5 mm. The mean proximal, midpoint, and distal diameters were 2.0, 1.8, and 1.5 mm, respectively. The mean distance between the origin of these branches to the pronator teres and the medial epicondyle of the humerus was 4.1 cm.

Conclusions

Based on the results of our cadaveric study, the use of the branch of the median nerve to the pronator teres muscle may be considered for neurotization of the radial nerve in the cubital fossa.

Innervation of the supinator muscle and its relationship to two-incision distal biceps tendon repair: an anatomic study

Reinsertion of the ruptured distal biceps tendon has been performed using either a single-anterior incision or a two-incision approach. A systematic review of these two repair methods has identified a higher incidence of supination weakness following the two-incision approach. The objective of this study was to describe the innervation of the supinator muscle and its implications regarding a two-incision distal biceps repair. Twelve fresh upper extremity specimens from 12 males were dissected with the forearm in full pronation. The number of branches of the posterior interosseous nerve (PIN) to the supinator, their site of exit from the PIN trunk, and their distance from a variety of known anatomic landmarks were recorded. Specimens were characterized as high (<5 mm), moderate (6-10 mm), or low (>10 mm) risk of nerve branch injury depending on the proximity of nerve branches to the bicipital tuberosity. In general, we found the innervation of the supinator to be highly variable. There were from two to nine branches of the PIN which supplied the supinator, with 0-3 arising from the ulnar side of the nerve. Four specimens were at low, five at moderate, and three at high risk of nerve branch injury during dorsal exposure of the bicipital tuberosity. We conclude that there is a substantial amount of variability in the innervation of the supinator, with certain patterns being at higher risk of nerve branch injury if dissection of the supinator is carried out over the bicipital tuberosity.

The course and branching pattern of the deep branch of the radial nerve in relation to the supinator muscle in fetus elbow

We aimed to make first demonstration of the course and branching pattern of deep branch of the radial nerve (DBRN) in relation to the supinator muscle in the forearms of fetuses and make morphological measurements in both fetuses and adults. We carried out dissection on 80 radial nerves from 20 adult cadavers (16 males and 4 females), ranging from 30 to 56 years old and 20 formalin-fixed, spontaneously aborted fetuses (10 males and 10 females) without detectable malformations, ranging from 20 to 37 weeks of gestation. There were three different branching patterns of the DBRN in fetuses. It divided its terminal branches at entrance of the supinator in 2 (5%), after entry of the supinator in 4 (10%) and after the supinator in 34 (85%) forearms. The course was bilaterally same in fetuses. Dividing pattern at the entrance of the supinator was not seen in adults. Only 4 (10%) were seen at after entering to the supinator and 36 (90%) were seen at after the supinator. We saw in fetuses neither fibrous band deep from the extensor carpi radialis longus nor upper border of the supinator. We assume that these fibrous structures appear after birth, perhaps favored by physical exercise, such as repeated pronation-supination movements. We think that it is one of the reasons why DBRN compression has never been reported in children. This is the first fetal study about the course and branching pattern of the DBRN and there is a constant ratio (mean 4.3) between the measurements of the fetuses and adults.