Extra-articular distal-third shaft | radial nerve at the septum | anterior plating
- Indication: Extra-articular fractures of the distal third of the humeral shaft (and some non-unions or lesions) where anterior plate placement is desired and the radial nerve must be safely managed as it crosses anteriorly.
- The radial nerve is the defining structure: unlike the mid-shaft anterolateral approach (nerve out of field), here the radial nerve IS in the field — it has pierced the lateral intermuscular septum about 10 cm above the lateral epicondyle and lies anterior to it, dividing distally into the posterior interosseous nerve (PIN) and the superficial radial nerve at the level of the lateral epicondyle or radiocapitellar joint.
- Interval: superficially lateral to biceps and brachialis; the deep working interval distally is between brachialis (medially) and brachioradialis (laterally). Brachialis is split or retracted medially to reach the anterior cortex; brachioradialis is retracted laterally with the radial nerve protected.
- Internervous plane caveat: as with the more proximal anterior approach there is no single clean internervous interval — brachialis is dual-innervated and brachioradialis is radial-innervated, so safety comes from POSITIVELY IDENTIFYING the radial nerve, not from a safe plane.
- Technique discipline: find the radial nerve PROXIMAL to the fracture or lesion first, trace it distally to where it divides, protect it on a vessel loop, then plate the anterior or anterolateral cortex. Avoid posterolaterally directed bicortical screws near the nerve.
- Alternatives: the posterior approach gives the widest distal exposure and direct nerve visualisation; a combined anterolateral (proximal) plus lateral (distal) bimodal approach (Lee 2013) is a described way to protect the nerve while plating distal-third shaft fractures.
When & Why
What it exposes. The anterolateral approach to the distal humerus gives access to the anterior and anterolateral surfaces of the distal-third metadiaphysis for extra-articular shaft fractures, with controlled, anterior management of the radial nerve. It is the workhorse exposure when anterior or anterolateral plating of a distal-third shaft fracture is desired and the surgeon wants to keep the patient supine. Why anterolateral (and not posterior). 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 plate is applied, avoiding the prone or lateral positioning of the posterior approach. It does, however, provide less wide exposure than the posterior approach for very distal or comminuted patterns, and it is not for intra-articular distal humeral fractures (those need a posterior, olecranon-osteotomy or paratricipital exposure of the articular surface). Position & landmarks. Supine, arm on a radiolucent arm board (or across the chest), with a tourniquet high on the arm if used and an image intensifier available. Landmarks are the lateral border of biceps and brachialis proximally and the lateral epicondyle distally; the incision follows the anterolateral aspect of the distal arm, curving toward the lateral epicondyle as needed.
Open reduction and internal fixation of extra-articular distal-third humeral shaft fractures by anterior or anterolateral plating; non-union or malunion of the distal shaft; excision or biopsy of distal anterior diaphyseal lesions; situations where the radial nerve needs controlled anterior management.
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 or anterolateral plate is applied, avoiding the prone or lateral positioning of the posterior approach.
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).
Posterior approach (widest exposure, direct radial nerve visualisation); combined anterolateral plus lateral bimodal approach (Lee 2013) for nerve protection across the distal shaft; minimally invasive plate osteosynthesis (MIPO) through anterior windows for selected patterns.
- Anterolateral
- Good anterior/anterolateral cortex; nerve anterior
- Posterior
- Widest; direct nerve visualisation in groove
- Combined bimodal (Lee 2013)
- Anterolateral proximally plus lateral distally
- Anterolateral
- Identified anterior to septum
- Posterior
- Directly visualised
- Combined bimodal (Lee 2013)
- Protected by bimodal dissection — 0 palsies reported
- Anterolateral
- Supine
- Posterior
- Lateral/prone
- Combined bimodal (Lee 2013)
- Supine
- Anterolateral
- Anterior plating preferred; distal shaft
- Posterior
- Maximal exposure / nerve repair
- Combined bimodal (Lee 2013)
- Distal-third shaft needing nerve protection
- Anterolateral
- Comparable union (Saracco 2020)
- Posterior
- Comparable union; superior exposure (Saracco 2020)
- Combined bimodal (Lee 2013)
- Union ~11.2 wk, MEPI over 97% (Lee 2013)
The Exposure
The radial nerve is the anatomy that defines this whole approach, so the dissection is built around finding and protecting it. The nerve leaves the posterior compartment by piercing the lateral intermuscular septum on average about 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 or lateral epicondyle it divides into the posterior interosseous nerve (PIN) — which passes between the two heads of supinator and is motor to the extensors — and the superficial radial nerve, which runs distally deep to brachioradialis as a sensory nerve to the dorsoradial hand. In layers: superficially lie biceps brachii (retracted medially with the musculocutaneous nerve) and, distally, the mobile wad or brachioradialis laterally; deep, brachialis covers the anterior distal cortex (split or retracted medially) while brachioradialis is retracted laterally to open the interval housing the radial nerve; the bone exposed is the anterior and anterolateral surface of the distal humeral metadiaphysis, with the supracondylar ridges defining the distal limit of safe extra-articular fixation.
Exposure sequence
- Supine, arm on a radiolucent arm board (or across the chest); tourniquet high on the arm if used. Image intensifier available.
- Landmarks: the lateral border of biceps and brachialis proximally and the lateral epicondyle distally.
- The incision follows the anterolateral aspect of the distal arm, curving as needed toward the lateral epicondyle.
- Incise skin and fascia along the anterolateral distal arm.
- Identify and protect the lateral antebrachial cutaneous nerve (the sensory continuation of the musculocutaneous nerve) in the subcutaneous plane lateral to biceps.
- Before approaching the fracture, identify the radial nerve PROXIMALLY where it pierces the lateral intermuscular septum, about 10 cm above the lateral epicondyle.
- Place the nerve on a vessel loop. This is the non-negotiable step that makes the rest of the dissection safe.
- Open the interval between brachialis (medial) and brachioradialis (lateral), following the radial nerve distally toward its bifurcation.
- Retract brachioradialis and the radial nerve laterally; split or retract brachialis medially to reach the anterior or anterolateral cortex.
- Be cautious distally where the PIN dives into supinator — limit distal dissection and avoid forceful retraction across the nerve.
- With the radial nerve protected and retracted laterally with brachioradialis, reduce the fracture and apply an anterior or anterolateral plate to the distal-third cortex.
- Keep the radial nerve clear of the plate and avoid posterolaterally directed bicortical screws adjacent to it.
- Confirm radial nerve continuity and that the nerve is free of the plate at the end of the procedure.
- Loosely reapproximate brachialis, repair the fascia, and close subcutaneous tissue and skin.
- Document radial, PIN and superficial radial nerve function in recovery.
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 (about 10 cm above the lateral epicondyle), proximal to the pathology, before any deep dissection or fixation.
In the distal third the radial nerve is no longer posterior — it has pierced the lateral intermuscular septum and lies anteriorly between brachialis and brachioradialis. Assuming it is still posterior, or relying on a safe internervous plane, is the classic error.
Dangers & Extensions
Structures at risk, by layer
- Where it is at risk
- Anterior to the septum, between brachialis and brachioradialis
- Protection strategy
- Identify proximal to the fracture first; vessel-loop control; trace distally
- Where it is at risk
- Distally as it enters supinator near the radiocapitellar joint
- Protection strategy
- Limit distal dissection; gentle retraction; keep the forearm pronated to move the PIN away when working laterally near the proximal radius
- Where it is at risk
- Deep to brachioradialis distally
- Protection strategy
- Avoid over-distal exposure; protect under brachioradialis
- Where it is at risk
- Subcutaneous, lateral to biceps
- Protection strategy
- Identify and protect during superficial dissection
There is no single clean internervous plane in the distal arm — brachialis is dual-innervated (musculocutaneous and radial) and brachioradialis is radial-innervated. Safety in this approach depends entirely on positively identifying the radial nerve, not on working a theoretical safe interval.
Extensile options. The incision can be extended proximally along the lateral border of biceps and brachialis to expose more of the anterolateral shaft, and distally toward the lateral epicondyle and into the brachialis–brachioradialis interval — but distal extension brings the PIN and superficial radial nerve into increasing danger as they form and diverge, so it should be deliberate and gentle. For patterns that need wider exposure or direct nerve work, convert to a posterior approach; for distal-third shaft fractures where the nerve needs protection across its whole anterior course, consider the combined anterolateral plus lateral bimodal approach (Lee 2013). Closure. Loosely reapproximate brachialis over the plate, repair the fascia, and close subcutaneous tissue and skin. Confirm radial nerve continuity and freedom from the plate before closure, and document radial, PIN and superficial radial nerve function in recovery.
Procedures Through This Approach
- Humeral shaft fractures and distal humerus fractures — the clinical conditions this approach addresses (extra-articular distal-third shaft patterns).
- Open reduction and internal fixation of extra-articular distal-third humeral shaft fractures by anterior or anterolateral plating.
- Non-union and malunion reconstruction of the distal shaft; excision or biopsy of distal anterior diaphyseal lesions.
- Controlled anterior management of the radial nerve where it must be mobilised or protected across the distal shaft.
- Related exposures: anterolateral approach to the humerus, posterior approach to the humerus and radial nerve exploration.
Viva & Exam Focus
SPLITDistal radial nerve danger
Viva Scenarios
Practise clinical reasoning and management decisions out loud
“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?'”
“The examiner asks whether the anterolateral or posterior approach gives better outcomes for an extra-articular distal-third shaft fracture.”
Anatomy
- Radial nerve pierces the lateral intermuscular septum about 10 cm above the lateral epicondyle
- Lies between brachialis and brachioradialis anteriorly
- Divides into the PIN (into supinator) and the superficial radial nerve near the radiocapitellar joint
Technique
- Supine; identify the nerve proximal to the fracture first
- Interval: brachialis (medial) over brachioradialis (lateral)
- Retract brachioradialis and the nerve laterally; plate the anterolateral cortex
- Avoid posterolateral bicortical screws near the nerve
Evidence
- No superiority of anterolateral versus posterior for union (Saracco 2020)
- Posterior gives the widest exposure plus a direct nerve view
- Bimodal approach: union about 11.2 weeks, MEPI over 97%, 0 palsies (Lee 2013)
Pitfalls
- The radial nerve IS in the field here — positively identify it
- About 10 cm above the lateral epicondyle is where it pierces the lateral intermuscular septum
- This is for EXTRA-articular distal-shaft fractures only, not intra-articular distal humeral fractures
References
Combined anterolateral plus lateral (bimodal) approach protects the radial nerve
- A combined anterolateral (proximal) and lateral (distal) approach was devised specifically to protect the radial nerve while fixing mid-to-distal humeral shaft fractures.
- Radiological union at a mean 11.2 weeks (range 8-20); all four pre-operative incomplete radial nerve palsies recovered.
- No post-operative radial nerve palsy, non-union, malunion or infection; over 97% excellent or good Mayo Elbow Performance Index scores.
Distal humerus shaft: lateral or anterolateral versus posterior approach — comparable outcomes
- No significant difference between posterior and lateral or anterolateral approaches for extra-articular distal humeral shaft fractures in the pooled literature.
- The posterior approach offers advantages in fracture exposure and direct visualisation of the radial nerve, favoured for complex or multifragmentary patterns.
- Approach choice should be individualised to fracture pattern, nerve status and surgeon familiarity.
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 about 10 cm above the lateral epicondyle, then dividing into the PIN and the superficial radial nerve — reflects standard, well-established surgical-anatomy teaching.