McLaughlin Procedure (Locked Posterior Shoulder Dislocation)

Surgical Indications

Primary Indication

• Engaging reverse Hill-Sachs defect involving approximately 20 to 40 percent of the humeral head articular surface after a chronic locked posterior dislocation (greater than 3 weeks duration)
• The defect is the impaction created on the ANTEROMEDIAL humeral head when the head is locked against the posterior glenoid rim
• The McLaughlin procedure (or its modifications) blocks re-engagement of the defect on the posterior glenoid rim in functional positions

Classic Mechanism Triad

The index injury is almost always one of three:

• Seizure (ictal phase): violent contraction of the stronger internal rotators (subscapularis, latissimus, pectoralis) overcomes the external rotators and drives the head posteriorly; the anteromedial head impacts the posterior glenoid rim
• Electrocution: similar mechanism - tetanic internal rotator contraction against a fixed thorax
• High-energy trauma: fall on the flexed, adducted, internally-rotated arm; motor vehicle accident with axially-loaded flexed arm

Absolute Indications

• Chronic locked posterior dislocation (greater than 3 weeks) with an engaging reverse Hill-Sachs defect
• Acute locked posterior dislocation that fails closed reduction attempts (e.g. buttonhole engagement of the head through a posterior capsular tear)
• Recurrent posterior instability with a documented engaging reverse Hill-Sachs defect on CT (less common - most posterior instability is atraumatic and treated with soft-tissue procedures, but the McLaughlin / modified Neer is the bony answer for a structural engaging defect)

Relative Indications

• Acute locked posterior dislocation with a 20 to 40 percent defect - McLaughlin transfer as a primary procedure to address the bone defect
• Failed nonoperative management of a smaller defect with persistent symptoms and documented engagement
• Combined bony (reverse Hill-Sachs) and soft-tissue (posterior Bankart) pathology

Contraindications

Absolute:

• Humeral head AVN with collapse - reverse total shoulder arthroplasty is the answer, not the McLaughlin transfer
• Established glenohumeral arthritis with loss of joint space - arthroplasty indicated
• Defect greater than 40 to 50 percent without sufficient articular surface for transfer - allograft reconstruction or arthroplasty

Relative:

• Acute dislocation with small defect (less than 20 percent) - trial nonoperative management
• Patient unable to comply with 6-week subscapularis protection protocol
• Active infection
• Neuropathic joint (Charcot) - arthrodesis or reverse total shoulder arthroplasty

Evidence for the McLaughlin Procedure

Original McLaughlin (1952)

• McLaughlin HL described the original technique in 1952: open reduction of the chronic posterior dislocation through a deltopectoral approach, followed by transposition of the subscapularis tendon into the reverse Hill-Sachs defect
• Series of 22 patients reported; 18 had satisfactory outcomes with the subscapularis transfer acting as a 'check-rein' against re-engagement
• Established the principle: address the BONE defect by filling it with the attached subscapularis, not just by soft-tissue capsular repair

Modified Neer / Hawkins

• Hawkins RJ and colleagues (Hughes and Neer 1975) modified the procedure to include osteotomy of the LESSER TUBEROSITY with the attached subscapularis, transferring both bone and tendon into the defect
• Rationale: bony block provides more robust engagement against the posterior glenoid rim; cancellous bone surface on the tuberosity heals to the prepared defect with biological union; fixation is stronger (screws vs tendon sutures alone)
• The modified Neer has largely superseded the original McLaughlin in current practice

Outcomes Literature

• Hawkins (1985, J Bone Joint Surg Am) reported 17 of 17 patients with a satisfactory result after open reduction and lesser tuberosity transfer for chronic posterior dislocations; recurrent instability in 1 patient
• Several smaller series report 80 to 90 percent good-to-excellent results with the modified Neer / Hawkins procedure at mid-term follow-up
• Recurrent instability rates after McLaughlin / modified Neer: 5 to 15 percent in most series (lower than soft-tissue-only repairs for engaging defects)
• Conversion to arthroplasty: 10 to 25 percent at 10 to 15 years, driven by progressive arthritis and AVN

Comparison: McLaughlin vs Allograft vs Arthroplasty

Key Evidence

Posterior Shoulder Anatomy and the Reverse Hill-Sachs Defect

The Reverse Hill-Sachs Defect

• An IMPACTION FRACTURE of the ANTEROMEDIAL humeral head, created when the head is driven posteriorly against the posterior glenoid rim during a posterior dislocation
• The opposite of the (anterolateral) Hill-Sachs defect, which is created on the POSTEROLATERAL head during an ANTERIOR dislocation
• Size: usually 20 to 50 percent of the articular surface in chronic locked dislocations; can be measured on CT (best modality) or on axillary MRI
• Engagement: the defect engages the posterior glenoid rim in positions of flexion, adduction, and INTERNAL rotation - these are functional positions and so the joint is unstable in everyday use

Posterior Glenohumeral Anatomy

• The glenoid is a shallow, dish-shaped socket; the posterior rim is the third of the glenoid that contacts the anteromedial head during posterior dislocation
• The posterior capsule inserts on the posterior glenoid rim and the labrum (posterior labrum is the anchor of the posterior band of the inferior glenohumeral ligament - the key static restraint against posterior translation in functional positions)
• The posterior capsule is THICKER and less compliant than the anterior capsule; this is why posterior dislocations tend to be locked rather than reducible

Subscapularis Insertion and the Modified Neer Osteotomy

• The subscapularis inserts on the LESSER TUBEROSITY of the humerus, with a footprint approximately 2.5 cm in the superoinferior direction and 1.5 cm wide
• The footprint lies just lateral to the bicipital groove (where the long head of biceps runs); the medial border of the lesser tuberosity is the landmark for the medial dissection
• The axillary nerve runs along the INFERIOR border of the subscapularis, approximately 3 to 7 mm medial to its musculotendinous junction - IDENTIFY and PROTECT before any tenotomy or osteotomy
• The modified Neer osteotomy is a planar cut through the lesser tuberosity, just lateral to the bicipital groove, freeing a wafer of bone (roughly 2 x 1.5 cm) with the subscapularis attached
• The wafer is mobilised medially and transferred into the prepared reverse Hill-Sachs defect

Vascular Anatomy of the Humeral Head

• Arcuate artery: branch of the anterior circumflex humeral artery; runs along the lateral border of the bicipital groove and enters the head at the proximal end of the groove - the dominant blood supply in 80 percent of cadaveric studies
• Posteromedial vessels: branches of the posterior circumflex humeral artery; supply the posteromedial humeral head - these are the vessels at risk in a chronic posterior dislocation
• AVN risk: 9 to 30 percent in chronic locked posterior dislocations; increases with duration of dislocation greater than 6 months and with attempted closed reduction of long-standing dislocations

Deltopectoral Approach - Anatomy

Surface Anatomy

• Coracoid process: palpable bony landmark at the superolateral aspect of the anterior shoulder; origin of the coracobrachialis, short head of biceps, and pectoralis minor
• Deltopectoral groove: the palpable depression between the lateral border of the pectoralis major and the anterior border of the deltoid
• Cephalic vein: runs in the deltopectoral groove, ascending from the forearm to the infraclavicular fossa; the AV of the deltopectoral approach

Incision and Superficial Dissection

• Skin incision from the tip of the coracoid extending 10 to 12 cm distally along the deltopectoral groove
• Identify and ligate (or preserve - surgeon preference) the cephalic vein; retract laterally with the deltoid to preserve the venous drainage of the deltoid
• Develop the deltopectoral interval; retract the deltoid laterally and the pectoralis major medially with a self-retaining retractor

Deep Dissection - The Subscapularis Window

• Identify the conjoint tendon (coracobrachialis + short head of biceps) descending from the coracoid tip; retract it medially (or release the coracoid tip for further exposure - reattach at closure)
• Identify the anterior humeral circumflex vessels ('three sisters') running along the inferior border of the subscapularis; LIGATE these to expose the inferior border of the subscapularis
• The axillary nerve is palpable as a cord along the inferior border of the subscapularis; confirm by digital palpation and gentle tug (the nerve moves the digit)
• The musculocutaneous nerve enters the coracobrachialis 2 to 8 cm distal to the coracoid tip; excessive medial retraction stretches it - release at intervals

SubsCapularis Tenotomy vs Lesser Tuberosity Osteotomy

• Tenotomy (original McLaughlin): divide the subscapularis 1 cm medial to its insertion; tag with heavy sutures for later repair. Faster, simpler, but the tendon-to-bone repair is the structural weak link
• Lesser tuberosity osteotomy (modified Neer / Hawkins): use an osteotome to create a wafer of bone at the lesser tuberosity, leaving the bone attached to the subscapularis. The bone-to-bone healing is more robust; the wafer can be fixed with screws or heavy transosseous sutures into the defect
• Modern practice favours the osteotomy for the McLaughlin modification; the tenotomy remains valid when the defect is small and the surgeon prefers a less extensive procedure

Positioning and Preparation

Patient position: Beach-chair position with the back at approximately 45 degrees of elevation. The shoulder is positioned slightly off the edge of the table to allow arm mobility. A sterile arm holder or Mayo stand draped free is used so the arm can be positioned through the full range of motion during the procedure.

Anaesthesia: General anaesthesia with endotracheal intubation. Interscalene brachial plexus block for postoperative analgesia (single-shot or continuous catheter). Avoid long-acting paralytics - the surgeon needs to stimulate nerves (axillary, musculocutaneous) during dissection to confirm their location and integrity.

Preoperative imaging checklist:

• True AP, axillary lateral, scapular Y radiographs (or equivalent CT reconstructions)
• CT scan to quantify the reverse Hill-Sachs defect size (axial cuts are most accurate)
• MRI to assess humeral head viability (look for AVN), posterior labral / capsular pathology, and rotator cuff integrity
• Document axillary nerve function preoperatively (deltoid contour, sensation over the lateral shoulder) - this is the most commonly injured nerve and a baseline exam is medicolegally essential

Consent: Specifically counsel regarding risk of recurrent posterior instability (5 to 15 percent), subscapularis dysfunction or failure (5 to 10 percent), axillary or musculocutaneous nerve injury (1 to 3 percent), avascular necrosis of the humeral head (10 to 30 percent in chronic dislocations), and progression to arthritis (20 to 50 percent at 10 to 15 years) requiring conversion to arthroplasty.

Step-by-Step Modified Neer (Lesser Tuberosity Osteotomy) Procedure

Step 1: Skin Incision and Deltopectoral Approach

Make a 10 to 12 cm skin incision from the tip of the coracoid extending distally along the deltopectoral groove. Identify the cephalic vein; ligate or preserve per surgeon preference. Develop the deltopectoral interval and place a self-retaining retractor (Charnley or similar) with the deltoid retracted laterally and the pectoralis medially.

Step 2: Conjoint Tendon Management

Identify the conjoint tendon (coracobrachialis and short head of biceps) descending from the coracoid tip. Retract it medially with a blunt retractor. If exposure is limited, an in-situ release of the coracoid tip (with later repair) or a partial release of the conjoint tendon (off its lateral half) can be performed - but most modified Neer procedures do not require conjoint release.

Step 3: Anterior Circumflex Vessels and Axillary Nerve Identification

Identify and ligate the 'three sisters' (anterior humeral circumflex artery and its venae comitantes) running along the inferior border of the subscapularis. This exposes the inferior border of the subscapularis, where the AXILLARY NERVE runs. Confirm the axillary nerve by palpation and by gentle neurostimulation if available.

Step 4: Lesser Tuberosity Osteotomy

Identify the bicipital groove (the long head of biceps is a useful landmark). The lesser tuberosity is just MEDIAL to the bicipital groove. Plan an osteotomy that creates a wafer of bone approximately 2 cm long (superoinferior) x 1.5 cm wide (mediolateral), incorporating the entire subscapularis footprint.

Use a sharp osteotome (curved or straight depending on surgeon preference) and a mallet. The osteotomy is performed parallel to the articular surface, cutting through the lesser tuberosity to a depth of approximately 1 cm. The wafer of bone is left attached to the subscapularis.

Alternatively, the wafer can be predrilled and tapped for later screw fixation. The bone is mobilised medially with the subscapularis still attached. The axillary nerve is protected by keeping the dissection SUPERIOR to it.

Step 5: Open Reduction of the Chronic Posterior Dislocation

With the subscapularis / lesser tuberosity mobilised medially, expose the anterior glenohumeral joint. The humeral head is typically impacted against the posterior glenoid rim. Use a blunt Hohmann retractor or bone hook to lever the head back into the reduced position. Gentle internal rotation of the arm, combined with anterior translation of the proximal humerus, will usually reduce the dislocation.

Inspect the articular surface for the reverse Hill-Sachs defect - the impaction is on the ANTEROMEDIAL head. Note the size of the defect as a percentage of the articular surface (a ruler or the CT scan is helpful for comparison).

Step 6: Prepare the Reverse Hill-Sachs Defect

Using a curette or small osteotome, elevate the impaction fragment subchondrally to recreate the contour of the humeral head. Take care NOT to violate the overlying articular cartilage. Fill the metaphyseal defect with cancellous autograft (harvested from the bicipital groove, the proximal humerus, or the iliac crest if needed).

The cancellous graft provides:

• A bone stock surface for the lesser tuberosity wafer to heal to
• Mechanical support for the elevated subchondral fragment
• Biological substrate for the subscapularis tendon / lesser tuberosity integration

Step 7: Transfer the Lesser Tuberosity / Subscapularis into the Defect

Position the lesser tuberosity wafer (or the subscapularis tendon in the original McLaughlin) into the prepared reverse Hill-Sachs defect. The cancellous undersurface of the wafer sits on the cancellous graft in the defect.

Fix the wafer with one of the following techniques:

• Screw fixation: one or two 3.5 mm cortical or 4.0 mm cancellous lag screws placed through the wafer into the head (predrill and tap if the wafer is soft)
• Heavy transosseous sutures: number 5 braided non-absorbable sutures placed through drill holes in the wafer and out through the lateral humeral cortex, tied over a bone bridge
• Suture anchors: double- or triple-loaded suture anchors in the defect, with the sutures passed through the wafer (or through the tendon in the tenotomy technique) in Mason-Allen or mattress configuration

Step 8: Verify Stability and Range of Motion

Test the shoulder through a full range of motion in the scapular plane:

• Forward flexion - check that the head does not subluxate or re-dislocate posteriorly
• External rotation in abduction - should reach 30 to 45 degrees without subluxation
• Internal rotation in adduction (the position of original engagement) - should NOT subluxate; this is the test of the transfer
• The transferred lesser tuberosity / subscapularis should block the engagement of the prepared defect on the posterior glenoid rim

Document the final range of motion and the stability in each position. The transferred wafer / tendon should be visible in the depth of the defect, with no residual gap.

Step 9: Closure

Irrigate the joint. Place a drain deep to the deltopectoral interval (remove at 24 to 48 hours). Close the deltopectoral interval with 1-0 absorbable sutures. Close the subcutaneous layer with 2-0 absorbable sutures. Close the skin with 3-0 non-absorbable monofilament (nylon or Prolene) in a running or interrupted fashion, or with staples.

Apply a sterile dressing and an arm sling in slight abduction (15 to 20 degrees) and NEUTRAL rotation - the sling supports the arm WITHOUT tensioning the subscapularis repair.

Step 10: Postoperative Imaging

Obtain AP and axillary lateral radiographs (or intraoperative imaging) to confirm:

• The humeral head is reduced
• The lesser tuberosity wafer is in the prepared defect
• The screw (if used) is not intra-articular
• No new fracture or screw penetration

Post-operative Protocol

Sling and Early Protection (Day 0 to 6 weeks)

• Sling immobilisation in slight abduction (15 to 20 degrees) and NEUTRAL rotation for 4 to 6 weeks
• The sling supports the arm WITHOUT tensioning the subscapularis repair - do not allow external rotation past neutral in the sling
• No active internal rotation against resistance for 6 weeks
• Pendulum exercises and passive forward flexion in the scapular plane from day 1
• Hand, wrist, and elbow active range of motion from day 1
• Cryotherapy for swelling control
• Analgesia: paracetamol, NSAIDs, opioid supplementation as needed for the first 1 to 2 weeks

Intermediate Phase (Weeks 6 to 12)

• Wean from sling
• Begin ACTIVE-ASSISTED forward flexion and abduction in the scapular plane
• Begin ACTIVE range of motion - including internal rotation - with light resistance
• External rotation stretching - aim to reach 30 to 45 degrees of external rotation in abduction by 12 weeks
• Scapular stabilisation exercises begin
• No resisted internal rotation until 12 weeks
• Formal physiotherapy 2 to 3 times per week

Strengthening Phase (Weeks 12 to 24)

• Begin progressive strengthening of the rotator cuff (external rotators, abductors)
• Begin progressive strengthening of the subscapularis - light resistance internal rotation
• Closed chain and proprioceptive exercises
• Sport-specific or work-specific conditioning from 16 to 20 weeks
• Return to heavy labour: 4 to 6 months
• Return to overhead sport: 6 to 9 months
• Return to contact sport: 9 to 12 months

Long-term Monitoring

• AVN surveillance: MRI at 3 to 6 months and again at 12 to 18 months in high-risk patients (chronic dislocation greater than 6 months, large initial defect)
• Arthritis surveillance: annual radiographs (AP, axillary lateral); counsel about the high rate of long-term arthritic conversion
• Functional outcomes: serial Constant or ASES scores; document return to work and sport

Special Case: Acute vs Chronic Locked Posterior Dislocation

Acute Locked Posterior Dislocation (less than 3 weeks)

• Usually the result of a high-energy injury (seizure in an alcoholic patient, electrocution, fall)
• Closed reduction is often possible UNDER ANAESTHESIA with gentle internal rotation and anterior translation - DO NOT use force
• After closed reduction, assess the reverse Hill-Sachs defect with CT
• If the defect is less than 20 percent: trial of immobilisation in slight external rotation (10 to 20 degrees) for 4 to 6 weeks
• If the defect is 20 to 40 percent and engages: proceed to McLaughlin / modified Neer transfer (open approach) as a primary procedure
• If the defect is greater than 40 to 50 percent: allograft reconstruction or arthroplasty

Chronic Locked Posterior Dislocation (greater than 3 weeks)

• Diagnosis usually delayed - the patient presents weeks to months after the index event
• Open reduction is the rule - closed reduction is rarely successful and risks iatrogenic fracture or humeral shaft fracture
• The McLaughlin / modified Neer transfer is the workhorse for 20 to 40 percent defects
• The delay matters: AVN rates increase substantially when the dislocation has been present for greater than 6 months; warn patient about this
• CT and MRI before surgery to assess head viability and defect size
• Posterior capsular release is often required for reduction; the chronically contracted posterior capsule is a key reason the head cannot be reduced closed

Special Case: Locked Posterior Dislocation in Seizure Patients

Why the Diagnosis Is Missed

• The seizure is the obvious clinical event; the shoulder injury is often overlooked
• Post-ictal patients may be obtunded or unable to give a clear history
• The classic finding of a 'stiff, internally-rotated shoulder' may be misdiagnosed as a 'frozen shoulder' or 'rotator cuff tear'
• The lightbulb sign is not sought on a standard shoulder radiograph if the axillary view is not obtained

Algorithm for Post-Ictal Shoulder

• Always obtain axillary lateral and scapular Y radiographs in any post-ictal or post-electrocution patient with shoulder pain or stiffness
• A normal axillary view rules out posterior dislocation
• If the lightbulb sign is present on AP and the axillary confirms posterior dislocation: classify as acute (less than 3 weeks), subacute (3 weeks to 3 months), or chronic (greater than 3 months)
• CT scan to assess the reverse Hill-Sachs defect size; MRI to assess head viability and rule out AVN
• Treat according to the algorithm: closed vs open reduction, McLaughlin vs allograft vs arthroplasty

Anaesthesia Considerations

• Continue the patient's usual anticonvulsant medications
• Avoid long-acting paralytics (as in any shoulder case where nerve identification is required)
• Bispectral index (BIS) monitoring to confirm adequate depth of anaesthesia during the procedure
• Increased risk of post-operative seizure if anticonvulsant levels are subtherapeutic - monitor and adjust

Special Case: Elderly Patients with Chronic Locked Poslocation

Why Elderly Patients Are Different

• Higher prevalence of osteoporotic bone - greater risk of iatrogenic fracture
• Higher prevalence of rotator cuff disease - the rotator cuff may be deficient
• Higher prevalence of glenohumeral arthritis at presentation
• Lower functional demand - the threshold for arthroplasty is lower
• Higher anaesthetic risk - shorter, less invasive procedures are preferred

When to Consider Reverse Total Shoulder Arthroplasty as the Primary Procedure

• Patient age greater than 70 years with a chronic locked posterior dislocation
• Defect greater than 40 to 50 percent of the articular surface
• Established AVN or arthritis
• Rotator cuff deficiency (fatty infiltration grade 3 or 4 on MRI)
• Failed prior McLaughlin / modified Neer procedure
• Lower functional demand (does not require the durability of a hemiarthroplasty in a young patient)

Surgical Pearls for Reverse TSA in This Setting

• The humeral head is often severely deformed - use a humeral cutting guide based on the residual anatomy
• The glenoid may be eroded posteriorly - consider a posteriorly-augmented glenoid baseplate
• Address any bone defects with structural allograft or augments
• A standard reverse TSA baseplate and a humeral stem of appropriate size are used; the surgical technique is otherwise identical to primary reverse TSA

Outcomes and Prognosis

Short-term (less than 2 years)

• 80 to 90 percent good-to-excellent results after the McLaughlin / modified Neer procedure for 20 to 40 percent defects
• Recurrent instability: 5 to 15 percent (lower than soft-tissue-only repairs for engaging defects)
• Return to most activities of daily living by 3 to 6 months
• Return to heavy labour: 4 to 6 months
• Return to overhead sport: 6 to 9 months

Mid-term (2 to 10 years)

• Recurrent instability remains low (less than 10 percent) in compliant patients
• Arthritic progression begins to be clinically apparent in 20 to 30 percent of patients
• Functional scores (Constant, ASES) remain good but slowly decline
• AVN becomes clinically apparent in 9 to 30 percent of patients with chronic dislocations

Long-term (greater than 10 years)

• Arthritic conversion to arthroplasty: 20 to 50 percent at 10 to 15 years
• Once arthroplasty is performed, the outcomes are similar to primary arthroplasty in matched patients
• Patient satisfaction remains high if expectations are set correctly preoperatively
• The McLaughlin / modified Neer is a 'buy-time' procedure for younger patients - it reliably restores stability and delays arthroplasty for a decade or more in most patients