High-yield overview

Extra-articular Distal-Third Shaft | Radial Nerve at the Septum | Anterior Plating

Surgical Imaging

Anterior view of the distal humerus (coronoid fossa highlighted) — the anterior metadiaphyseal surface exposed for plating in the anterolateral approach to the distal third.Credit: Doctor Jana via Wikimedia Commons (CC BY-SA 4.0)

Posterior view of the distal humerus showing the deltoid tuberosity, the radial (spiral) groove and the lateral border of the shaft. The radial nerve runs in this groove before crossing the lateral boCredit: Doctor Jana via Wikimedia Commons (CC BY-SA 4.0)

Indications & Rationale

Primary indications

Open reduction and internal fixation of extra-articular distal-third humeral shaft fractures by anterior/anterolateral plating; non-union or malunion of the distal shaft; excision/biopsy of distal anterior diaphyseal lesions; situations where the radial nerve needs controlled anterior management.

Rationale

The distal third is the transition zone where the radial nerve crosses to the anterior compartment. An anterolateral exposure allows the nerve to be found, traced and protected anteriorly while an anterior/anterolateral plate is applied — avoiding the prone/lateral positioning of the posterior approach.

Limitations

Provides less wide exposure than the posterior approach for very distal or comminuted patterns; intra-articular distal humeral fractures are NOT an indication (these need a posterior, olecranon-osteotomy or paratricipital exposure of the articular surface).

Alternatives

Posterior approach (widest exposure, direct radial nerve visualisation); combined anterolateral + lateral bimodal approach (Lee 2013) for nerve protection across the distal shaft; MIPO through anterior windows for selected patterns.

Surgical Anatomy

The radial nerve in the distal arm — the key relationships

The radial nerve leaves the posterior compartment by piercing the lateral intermuscular septum on average ~10 cm proximal to the lateral epicondyle.
Anterior to the septum it lies in the groove between brachialis (medial) and brachioradialis (lateral), accompanied by branches to brachioradialis and ECRL.
Near the radiocapitellar joint / lateral epicondyle it divides into:
- Posterior interosseous nerve (PIN) — passes between the two heads of supinator (motor to the extensors); at risk with distal dissection and retraction.
- Superficial radial nerve — runs distally deep to brachioradialis (sensory to the dorsoradial hand).

Muscle layers

Superficial: biceps brachii (retracted medially with the musculocutaneous nerve) and, distally, the mobile wad/brachioradialis laterally.
Deep: brachialis covering the anterior distal cortex (split or retracted medially); brachioradialis retracted laterally to open the interval housing the radial nerve.
Bone: the anterior and anterolateral surfaces of the distal humeral metadiaphysis are exposed for plate application; the supracondylar ridges define the distal limit of safe extra-articular fixation.

The Approach — Step by Step

Supine, arm on a radiolucent arm board (or across the chest); tourniquet high on the arm if used. Image intensifier available.
Landmarks: lateral border of biceps/brachialis proximally and the lateral epicondyle distally; the incision follows the anterolateral aspect of the distal arm, curving as needed toward the lateral epicondyle.

Dangers & How to Avoid Them

Structures at risk

Non-negotiable

In this approach the radial nerve is IN the field and must be POSITIVELY IDENTIFIED — there is no internervous plane to hide behind. Find the nerve where it pierces the lateral intermuscular septum (~10 cm above the lateral epicondyle), proximal to the pathology, before any deep dissection or fixation.

Anterolateral vs Posterior vs Bimodal — Distal Shaft

Approach selection for extra-articular distal-third shaft fractures

Outcomes & Evidence

Evidence

Combined anterolateral + lateral (bimodal) approach protects the radial nerve

Level IV (prospective case series, 35 patients)

Lee TJ, Kwon DG, Na SI, Cha SD • Clinics in Orthopedic Surgery (2013)

Verify on PubMed (PMID 24009907)

Evidence

Distal humerus shaft: lateral/anterolateral vs posterior approach — comparable outcomes

Systematic review (265 patients)

Saracco M, Smimmo A, De Marco D, et al. • Orthopedic Reviews (Pavia) (2020)

Verify on PubMed (PMID 32913599)

Evidence attribution

Based on articles retrieved from PubMed: Lee et al. (DOI) and Saracco et al. (DOI). The radial nerve's course (piercing the lateral intermuscular septum ~10 cm above the lateral epicondyle, division into PIN and superficial radial nerve) reflects standard, well-established surgical-anatomy teaching.

Viva Scenarios

Practise clinical reasoning and management decisions out loud

Viva scenarioStandard

Clinical prompt

“You are exposing an extra-articular distal-third humeral shaft fracture anterolaterally. The examiner asks: 'Where is the radial nerve and how do you keep it safe?'”

Practical approach

The radial nerve has left the posterior compartment by piercing the lateral intermuscular septum about 10 cm proximal to the lateral epicondyle, so it now lies anteriorly in the interval between brachialis and brachioradialis. I identify it PROXIMAL to the fracture first — at the septum — and place it on a vessel loop, then trace it distally toward where it divides into the PIN (into supinator) and the superficial radial nerve (under brachioradialis). I retract brachioradialis and the nerve laterally, work along the anterolateral cortex, and avoid posterolaterally directed bicortical screws. There is no internervous plane here, so safety depends on positively identifying the nerve.

Viva scenarioStandard

Clinical prompt

“The examiner asks whether the anterolateral or posterior approach gives better outcomes for an extra-articular distal-third shaft fracture.”

Practical approach

The pooled evidence shows no significant difference in union or complication rates between lateral/anterolateral and posterior approaches for extra-articular distal-third shaft fractures (Saracco 2020). The posterior approach offers wider exposure and direct radial nerve visualisation, so it is favoured for complex/multifragmentary patterns; the anterolateral approach is supine and keeps anterior plating options open. A combined anterolateral + lateral bimodal technique reported union at ~11 weeks with no radial palsies (Lee 2013). I individualise to fracture pattern, nerve status and my own familiarity.

Viva & Exam Focus

Mnemonic

SPLITDistal radial nerve danger

Hook:In the distal humerus the radial nerve has crossed to the front — you must SPLIT your attention to it: find it at the septum, follow it past the PIN.

High-yield exam points

The radial nerve IS in the field here (unlike the mid-shaft anterolateral approach) — positively identify it.
~10 cm above the lateral epicondyle = where it pierces the lateral intermuscular septum.
This approach is for EXTRA-ARTICULAR distal-shaft fractures, not intra-articular distal humeral fractures.

Exam day cheat sheet