High-yield overview
Deltoid split · Axillary-nerve safe zone · Greater tuberosity access · Mini-open rotator cuff
about 5cmConservative deltoid-split safe zone — axillary nerve as close as 5.2cm (Traver 2016)
6.3cmMean axillary-nerve distance from the anterolateral acromion, range 5.2-7.6cm (Traver 2016)
30°Deltoid fibre obliquity (anterior to coronal) — split parallel, not perpendicular
greater than 5mmGreater-tuberosity displacement threshold for ORIF — the impingement line
Critical Must-Knows
- The lateral approach is a deltoid-splitting (anterolateral acromial) exposure giving direct access to the greater tuberosity, rotator cuff and lateral humeral head while avoiding deltopectoral dissection — so less postoperative stiffness.
- The axillary nerve (anterior branch) crosses the deep deltoid a mean 6.3cm from the anterolateral acromion (Traver 2016, range 5.2-7.6cm). Because the closest cadaveric distance was 5.2cm, a conservative working limit of about 5cm is used, the nerve is identified and protected before extending, and sustained retraction is avoided (mean 51% nerve strain, Traver 2016). Injury causes deltoid paralysis.
- Deltoid fibres run obliquely about 30° anterior to the coronal plane — split PARALLEL to the fibres with blunt dissection. Splitting perpendicular transects the fibres and causes permanent weakness.
- Landmarks: acromion lateral edge (start of the split), greater tuberosity 0.5cm lateral to the bicipital groove. The GT carries three facets — superior for supraspinatus, middle for infraspinatus, inferior for teres minor.
- Indications: isolated greater tuberosity fractures displaced greater than 5mm, selected 2-part surgical neck fractures, mini-open rotator cuff repair, and subacromial decompression. Contraindicated for 3-4 part fractures and arthroplasty, which need the deltopectoral approach.
When & Why
What it exposes. The lateral approach delivers the greater tuberosity, the rotator cuff insertion, and the lateral humeral head and surgical neck through a deltoid-splitting window. It is the workhorse exposure for isolated greater tuberosity fractures (15-20% of proximal humerus fractures), selected 2-part surgical neck fractures amenable to lateral plating or nailing, mini-open rotator cuff repair, and subacromial decompression. Why lateral (and not deltopectoral). The lateral approach preserves the deltopectoral interval and works a true muscle-splitting plane, so there is less dissection, faster deltoid healing and less postoperative stiffness. It also gives a perpendicular, on-axis view of the greater tuberosity — ideal for lag-screw or suture fixation. The trade-off is limited exposure: it cannot reach the lesser tuberosity, subscapularis or anterior capsule, so 3-4 part fractures, fracture-dislocations and arthroplasty still require the deltopectoral approach. Three scenarios where the lateral approach excels:
- Isolated greater tuberosity fractures displaced greater than 5mm — the displaced fragment would otherwise impinge under the acromion. The lateral approach gives direct access and perpendicular fixation.
- Mini-open rotator cuff repair — a 3-4cm deltoid split reaches the supraspinatus and infraspinatus footprint with less morbidity than an open deltopectoral exposure, and combines naturally with arthroscopy.
- 2-part surgical neck fractures (head-shaft only, tuberosities intact) — fixable with a lateral PHILOS locking plate or an antegrade nail through the same window. Position & landmarks. Beach chair is standard: semi-recumbent 30-40°, torso rotated 20-30° toward the operative side to open the shoulder laterally, head in a horseshoe rest, and the arm free-draped for full range of motion. The surgeon works from a natural lateral orientation and can extend anteriorly to convert to a deltopectoral approach if needed. Watch for beach-chair hypotension — maintain mean arterial pressure greater than 70mmHg and consider an arterial line in patients over 70 or with cardiac history. Lateral decubitus with the arm suspended from a boom is the alternative: no hypotension risk and gravity distracts the head from the acromion, but it is disorienting and slower to set up. Palpate and mark the acromion lateral edge (the start point), the greater tuberosity (2cm distal to the acromion, 0.5cm lateral to the bicipital groove), the long head of biceps tendon in the groove (the anterior reference), and the line of the deltoid fibres running obliquely down from the acromion. Pre-operative imaging. A trauma series (AP, scapular Y, and a mandatory axillary lateral) defines tuberosity displacement and head position. CT with 3D reconstruction clarifies fracture pattern, fragment size and head-shaft angulation for surgical planning. For cuff work, MRI sizes the tear (small under 1cm, medium 1-3cm, large 3-5cm, massive greater than 5cm) and grades fatty infiltration (Goutallier 0-4; grade 3-4 predicts poor healing).
The Exposure
Work down through the deltoid in the line of its fibres, respecting the axillary-nerve safe zone, to open the subacromial space and the greater tuberosity.
Exposure sequence
Step 1Skin incision along the deltoid fibres
- Start at the acromion lateral edge and extend distally 5-7cm for a fracture, 3-5cm for a mini-open cuff repair.
- Run the incision parallel to the deltoid fibres — oblique, about 30° anterior to the pure vertical / coronal plane.
- Carry a 15-blade through skin and subcutaneous tissue to the deltoid fascia.
Step 2Split the deltoid PARALLEL to its fibres
- Incise the fascia longitudinally, then split the muscle by blunt dissection (spreading scissors or a finger) in the fibre direction.
- The split opens easily when parallel to the fibres; resistance means you are crossing fibres — stop and re-align.
- Carry the split through the full thickness of deltoid down to the lateral humeral surface.
Step 3Respect the axillary-nerve safe zone
- Before extending distally, measure from the acromion lateral edge with a sterile ruler and respect a conservative 5cm safe zone.
- The axillary nerve lies on the deep deltoid a mean 6.3cm from the acromion (range 5.2-7.6cm, Traver 2016) — the closest cadaveric distance was 5.2cm, so 5cm is a margin, not a fixed constant.
- Palpate for the nerve on the deep deltoid surface and protect it before going further; insert a self-retaining deltoid retractor with gentle tension only.
Step 4Open the subacromial space and find the greater tuberosity
- The split opens into the subacromial bursa — incise it longitudinally and debride inflamed tissue to expose the rotator cuff and greater tuberosity.
- Use the long head of biceps tendon in the bicipital groove as the anterior landmark; the greater tuberosity is 0.5cm lateral to it.
- For a fracture, identify the fracture line and assess fragment size, displacement and comminution; for cuff work, visualise the supraspinatus footprint (superior facet).
Step 5Elevate the deltoid origin if more width is needed
- If exposure is inadequate, do not push the split distally past the safe zone. Instead, elevate the deltoid origin 1-2cm off the lateral acromion subperiosteally with a Cobb elevator.
- Tag the freed origin with heavy suture for later repair; this gains 2-3cm of width without threatening the nerve.
- The third option is to convert to a deltopectoral approach — the right move for a 3-4 part fracture discovered intraoperatively.
Step 6Perform the target procedure
- Greater tuberosity fracture: grasp the fragment, reduce it flush with the head (not proud), hold with 2.0mm K-wires, confirm on AP and axillary fluoroscopy, then fix with 2-3 parallel 4.0mm partially-threaded cannulated screws placed perpendicular to the fracture line (lag compression), countersunk into the tuberosity. For osteoporotic bone or a small fragment, use heavy #5 FiberWire in a figure-8 through drill holes in the shaft.
- Surgical neck fracture: apply a PHILOS locking plate just posterior to the bicipital groove, 5-8mm distal to the tuberosity, with subchondral proximal locking screws and bicortical shaft screws; or insert an antegrade nail lateral to the greater tuberosity.
- Rotator cuff: debride the supraspinatus footprint to bleeding bone and place 5.5mm double-loaded suture anchors at the medial footprint, passing mattress sutures through the tendon edge.
Step 7Closure
- Release the self-retaining retractor and close the deltoid split side-to-side with 0 or 2-0 Vicryl interrupted sutures placed parallel to the fibres (4-6 sutures, no excess tension).
- If the origin was elevated, re-attach it to the acromion with transosseous sutures or suture anchors — critical for restoring deltoid power.
- Close the fascia (2-0 Vicryl), subcutaneous tissue (3-0 Vicryl) and skin (4-0 Monocryl subcuticular). Immobilise in a sling for fractures, or an abduction pillow after a massive cuff repair.
The axillary nerve is the highest-risk structure — measure, protect, retract gently
The deltoid-splitting approach's feared complication is axillary nerve injury, which causes deltoid paralysis. The nerve is variable (mean 6.3cm from the acromion, range 5.2-7.6cm; Traver 2016), so keep the split within about 5cm, identify and protect the nerve before extending, and retract gently and intermittently — Traver showed sustained retraction produced a mean 51% nerve strain with microscopic myelin and axonal damage even without transection. With careful technique the deficit rate is near zero (Gardner 2008: no axillary nerve deficits in 52 fractures).
If exposure is inadequate, gain width — not length
Do not push the split blindly distally past the safe zone. The correct moves are: (1) identify and protect the nerve, then extend gently; (2) elevate the deltoid origin off the acromion for width; or (3) convert to a deltopectoral approach. Splitting perpendicular to the fibres is always wrong — split parallel, by blunt dissection.
Dangers & Extensions
Structures at risk, by layer
Axillary nerve (anterior branch on deep deltoid)
- Why it is at risk
- Mean 6.3cm from the anterolateral acromion, range 5.2-7.6cm (Traver 2016); also injured by sustained retraction (mean 51% strain)
- How to protect it
- Keep the split within about 5cm, measure with a ruler, identify and protect the nerve before extending, retract gently and intermittently
Deltoid muscle fibres
- Why it is at risk
- Fibres run oblique about 30° anterior to coronal — a perpendicular split transects them
- How to protect it
- Split parallel to the fibres by blunt dissection; repair the split securely at closure
Anterior circumflex humeral artery
- Why it is at risk
- Runs deep to the deltoid at the level of the surgical neck
- How to protect it
- Bipolar haemostasis; safe to ligate via the posterior circumflex collateral
Rotator cuff (supraspinatus footprint)
- Why it is at risk
- Wrong plane risks inadvertent cuff entry; a nail entry point can damage supraspinatus
- How to protect it
- Use the long head of biceps as a landmark; enter a nail just off the cuff insertion
Humeral head blood supply (arcuate artery)
- Why it is at risk
- At risk with anterior dissection around the head
- How to protect it
- The lateral approach deliberately avoids it (Gardner 2008)
Extensile options. The lateral window does not extend far. For more width, elevate the deltoid origin off the acromion (see Step 5). For more versatility and anterior reach (lesser tuberosity, subscapularis, rotator interval, arthroplasty), convert to the deltopectoral approach, which is fully extensile. Neither direction should be gained by forcing the deltoid split distally past the axillary-nerve safe zone. Common complications
Axillary nerve injury
- Rate / note
- Highest-risk structure; near-zero with careful technique (Gardner 2008: no deficits in 52)
- Prevention and management
- Measure the split, identify and protect the nerve, retract gently; if transected repair primarily, if neuropraxia observe with EMG at about 3 months
Deltoid detachment
- Rate / note
- Reported around 5%
- Prevention and management
- Split parallel to fibres; securely repair the split and any elevated origin
Rotator cuff injury
- Rate / note
- 2-5%
- Prevention and management
- Stay in the correct plane; repair if recognised
Stiffness
- Rate / note
- 10-15%
- Prevention and management
- Early physiotherapy — PROM at 2 weeks; a deltoid split stiffens less than a deltopectoral exposure
Hardware prominence
- Rate / note
- About 10% (lateral plate or proud screws)
- Prevention and management
- Countersink greater-tuberosity screws; remove a prominent plate after union
Infection
- Rate / note
- 2-5%
- Prevention and management
- Standard — superficial: oral antibiotics; deep: debridement with hardware retention if stable
Procedures Through This Approach
- Proximal humerus fracture plating vs hemiarthroplasty — the related fixation-vs-arthroplasty decision for proximal humerus fractures.
- Isolated greater tuberosity fracture ORIF — 2-3 parallel 4.0mm partially-threaded cannulated screws perpendicular to the fracture (lag compression, countersunk), or heavy #5 FiberWire figure-8 for small fragments or osteoporotic bone.
- Selected 2-part surgical neck fractures — lateral PHILOS locking plate (subchondral proximal locking screws plus bicortical shaft screws) or antegrade intramedullary nail.
- Mini-open rotator cuff repair — small-to-medium tears via a 3-4cm split with 5.5mm double-loaded suture anchors into the greater-tuberosity footprint.
- Subacromial decompression / acromioplasty and excision of calcific tendinitis of the supraspinatus.
- Greater tuberosity malunion osteotomy and proximal humerus non-union revision with bone graft.
Viva & Exam Focus
Mnemonic
LATERAL SPLITLATERAL SPLIT — the deltoid-splitting technique
L
Landmarks
Acromion lateral edge to start; stop at about 5cm (axillary-nerve safe zone)
A
Axillary nerve
Mean 6.3cm, closest 5.2cm from the acromion (Traver 2016) — protect it
T
Trace fibres
Fibres oblique about 30° anterior — split parallel, not perpendicular
E
Elevate origin
For more width, elevate the deltoid off the acromion — do not extend distally
R
Ruler
Measure the split intraoperatively with a sterile ruler — never guess
A
Atraumatic
Blunt scissors or finger dissection parallel to the fibres — it opens easily
L
Longitudinal fascia
Incise the deltoid fascia in line with the skin incision
S
Self-retaining retractor
Maintains the split with gentle tension only
P
Perpendicular is wrong
Splitting across the fibres transects them — poor healing, weakness
L
Look for the GT
Greater tuberosity is 0.5cm lateral to the bicipital groove
I
Inspect subacromial space
Open the bursa to expose the rotator cuff
T
Tie the split
Close the deltoid side-to-side with Vicryl parallel to the fibres
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
Viva scenarioCritical
Clinical prompt
“Where is the axillary nerve in the lateral approach, and how do you protect it?”
Viva scenarioAdvanced
Clinical prompt
“A 65-year-old has a 3-part proximal humerus fracture involving the lesser tuberosity. Do you use a lateral or deltopectoral approach, and why?”
Viva scenarioChallenging
Clinical prompt
“You have exposed an isolated greater tuberosity fracture displaced 8mm superiorly. How do you fix it, and what happens if you leave it displaced?”
Exam day cheat sheet
Lateral approach to the proximal humerus — exam-day essentials
High-yield anatomy
- Axillary nerve anterior branch: mean 6.3cm from the anterolateral acromion, range 5.2-7.6cm (Traver 2016) — variable, not a fixed number
- Conservative safe zone: keep the split within about 5cm and protect the nerve before extending — injury causes deltoid paralysis
- Deltoid fibres oblique about 30° anterior to coronal — split parallel (blunt), never perpendicular
- Greater tuberosity 0.5cm lateral to the bicipital groove; three facets — superior supraspinatus, middle infraspinatus, inferior teres minor
- GT displacement greater than 5mm is the surgical indication (impingement threshold)
Critical technique
- Measure with a sterile ruler: mark an about 5cm safe zone and identify the nerve before extending
- Split parallel to the fibres by blunt dissection — it opens easily; resistance means you are crossing fibres
- For more exposure: protect the nerve and elevate the deltoid origin, or convert to deltopectoral — never extend blindly distally
- GT fixation: 2-3 cannulated 4.0mm screws perpendicular to the fracture, lag compression, countersunk heads
- Fluoroscopy: AP and axillary — confirm the GT is flush, no superior displacement, screws not intra-articular
Lateral vs deltopectoral
- Lateral for: isolated GT fractures, 2-part surgical neck (tuberosities intact), mini-open cuff repair
- Lateral inadequate for: 3-4 part fractures, lesser-tuberosity involvement, arthroplasty
- Deltopectoral mandatory for: 3-4 part fractures, lesser-tuberosity fractures, arthroplasty, revision
- Lateral advantages: minimally invasive, direct lateral plating access, deltoid split heals with less stiffness
- Lateral caveat: the axillary nerve is the highest-risk structure — identify and protect it; retract gently (Traver 2016)
GT fracture fixation
- Indication: displacement greater than 5mm (impingement if left — painful arc, cuff dysfunction)
- Reduction: flush with the head, less than 2mm acceptable, no superior prominence
- Standard: 2-3 cannulated 4.0mm screws, partially threaded for lag compression, countersunk
- Osteoporotic bone: heavy #5 FiberWire figure-8 through drill holes in the shaft
- Fluoroscopy mandatory: AP for superior displacement, axillary for posterior displacement, screws not intra-articular
Complications & prevention
- Axillary nerve injury: measure the split, protect the nerve, retract gently — near-zero with care (Gardner 2008)
- Deltoid weakness: split parallel, repair the split securely, re-attach any elevated origin
- GT malunion: fluoroscopy to keep the GT flush; countersink screw heads
- Stiffness (10-15%): early PT — PROM at 2 weeks; a deltoid split stiffens less than deltopectoral
- Hardware prominence (about 10%): countersink GT screws; remove a prominent plate after union
Evidence you must know
- Traver 2016 (J Orthop Trauma): nerve mean 6.3cm, range 5.2-7.6cm; sustained retraction causes mean 51% strain
- Samart 2014 (J Med Assoc Thai): nerve distance correlates with arm length and shortens with abduction — no fixed safe number
- Gardner 2008 (J Orthop Trauma): anterolateral acromial approach — lateral plating access, no nerve deficits in 52 fractures
- Platzer 2008 (J Trauma): 52 operative GT fractures all united; operative better than non-operative
- Kasten 2011 (Int Orthop) RCT: mini-open vs arthroscopic supraspinatus repair — equivalent Constant and ROM at 6 months
References
Evidence
Is the Axillary Nerve at Risk During a Deltoid-Splitting Approach for Proximal Humerus Fractures?
Traver JL, Guzman MA, Cannada LK, Kaar SG • J Orthop Trauma (2016)
Key Findings:
- Cadaveric study (10 fresh-frozen specimens) defining the axillary nerve relationship to the lateral deltoid-splitting approach
- Axillary nerve located a mean 6.32cm (range 5.20-7.60cm) from the anterolateral acromion
- Progressive Kolbel retraction produced a mean final nerve strain of 51% (range 28-99%) and a mean length increase of 8.42mm
- Histology confirmed myelin sheath disruption and axonal retraction — structural damage occurred even without transection
Clinical implication: The nerve position is variable and can be as close as about 5.2cm, justifying a conservative working safe zone of around 5cm. The injury mechanism is not only direct laceration but sustained traction — keep retraction gentle and intermittent, and identify and protect the nerve before extending.
Evidence
The Anterolateral Acromial Approach for Fractures of the Proximal Humerus
Gardner MJ, Boraiah S, Helfet DL, Lorich DG • J Orthop Trauma (2008)
Key Findings:
- Technique paper plus case series of 52 acute displaced proximal humerus fractures treated through the anterolateral acromial (deltoid-splitting) approach with a locking plate or intramedullary nail
- Uses the plane of the avascular anterior deltoid raphe; the axillary nerve is positively identified and protected
- No postoperative axillary nerve deficits related to the approach (23 patients assessed at minimum 1 year, average 28 months)
- Mean QuickDASH 25.2; the approach gave direct access to the lateral plating zone while avoiding anterior dissection near the humeral head blood supply
Clinical implication: The lateral / anterolateral acromial approach gives direct access to the lateral plating zone with low nerve morbidity when the axillary nerve is identified and protected. It suits lateral-zone pathology (greater tuberosity, selected 2-part necks); complex 3-4 part fractures needing subscapularis or anterior access are still best managed deltopectorally.
Evidence
Displaced Fractures of the Greater Tuberosity: Operative vs Nonoperative Treatment
Platzer P, Thalhammer G, Oberleitner G, et al • J Trauma (2008)
Key Findings:
- 52 displaced greater tuberosity fractures treated operatively (30 ORIF, 22 closed reduction and percutaneous fixation), compared with 9 nonoperative, mean 5.5-year follow-up
- All fractures healed with no nonunion; minimal loss of reduction (under 5mm superior) in 9 patients (17%) without significant effect on function
- Operatively treated patients had significantly better shoulder scores than the nonoperative control group (p less than 0.05)
- ORIF gave slightly better results than percutaneous fixation, but the difference was not statistically significant
Clinical implication: Displaced greater tuberosity fractures should be reduced and fixed — operative treatment significantly outperformed nonoperative. Anatomic reduction matters because residual superior displacement causes subacromial impingement; confirm on intraoperative fluoroscopy that the tuberosity is not left proud.
Evidence
Prospective Randomised Comparison of Arthroscopic vs Mini-Open Rotator Cuff Repair of the Supraspinatus
Kasten P, Keil C, Grieser T, et al • Int Orthop (2011)
Key Findings:
- RCT, 17 patients per group (arthroscopic double-row anchor repair vs mini-open transosseous repair) for supraspinatus tears with limited retraction and minor fatty degeneration
- Arthroscopic group used fewer NSAID tablets in the first postoperative week; mini-open group had less pain from weeks four to eight (p less than 0.05)
- At six months the Constant-Murley score and range of motion were equivalent between groups
- Postoperative MRI showed tendon discontinuity in 3 of 16 in each group; more tendon thinning in the arthroscopic group
Clinical implication: For repairable supraspinatus tears, mini-open and all-arthroscopic repair give equivalent functional outcomes and structural integrity at six months. The mini-open lateral approach remains a valid, lower-cost option and a reasonable choice earlier on the arthroscopic learning curve.
Evidence
Correlation Between Acromion-Axillary Nerve Distance and Upper Arm Length: A Cadaveric Study
Samart S, Apivatgaroon A, Lakchayapakorn K, Chemchujit B • J Med Assoc Thai (2014)
Key Findings:
- 70 cadaveric shoulders measured from the lateral acromial edge to the axillary nerve in three arm positions
- Mean distance 57.9mm in 30° adduction, 57.1mm at 45° abduction and 52.9mm at 90° abduction — the nerve moved closer to the acromion with increasing abduction
- The acromion-to-nerve distance correlated linearly with upper arm length, allowing prediction of the anterior-branch danger zone
- Confirms there is no single fixed safe distance — the nerve position depends on individual arm length and arm position
Clinical implication: The axillary nerve danger zone is patient-specific and shortens with shoulder abduction. Rather than relying on a fixed number, position the arm in adduction during the split, scale expectations to patient size, measure intraoperatively and protect the nerve before extending distally.