High Yield Overview

AC JOINT INJURIES - CLASSIFICATION and MANAGEMENT

Rockwood Classification Guides Treatment | CC Ligaments Key | Type III Controversial

9-12%All shoulder injuries

Type IIIMost controversial

IV-VISurgical types

5:1Male:Female ratio

ROCKWOOD CLASSIFICATION

Type I

PatternAC ligament sprain (intact)

TreatmentConservative - sling 1-2 weeks

Type II

PatternAC ligament torn, CC sprain

TreatmentConservative - sling 2-4 weeks

Type III

PatternCC ligaments torn, 25-100% displacement

TreatmentCONTROVERSIAL - mostly conservative

Type IV

PatternPosterior displacement into trapezius

TreatmentSurgical reconstruction

Type V

PatternGreater than 100% superior displacement

TreatmentSurgical reconstruction

Type VI

PatternInferior (subacromial/subcoracoid)

TreatmentSurgical - very rare

Critical Must-Knows

CC ligaments (conoid + trapezoid) provide vertical stability - torn in Type III+
AC ligaments (superior most important) provide horizontal stability
Type III is controversial - most now treated conservatively unless high-demand athlete/laborer
Type IV posterior displacement may look like Type III on AP - need axillary view
Hook plate requires removal at 3-4 months - mandatory second surgery

Examiner's Pearls

"
Rockwood classification expanded Tossy (I-III) to include Types IV-VI
"
CC distance greater than 13mm or greater than 50% increase compared to contralateral = Grade III+
"
AC ligament superior portion provides 56% of horizontal stability
"
Type VI inferior dislocation extremely rare - associated with severe trauma

Clinical Imaging

Imaging Gallery

AP shoulder X-ray showing right AC joint separation with blue arrow indicating widened joint and superior clavicle displacementCredit: Wikimedia Commons - James Heilman, MD via Wikimedia Commons (CC-BY 2.5)

Bilateral panoramic shoulder X-ray with 10kg stress weights showing Type III AC separation on left side with increased coracoclavicular distanceCredit: Wikimedia Commons - Hellerhoff via Wikimedia Commons (CC-BY-SA 3.0)

2-panel image: (a) Pre-operative AP showing severe AC dislocation, (b) Post-operative showing hook plate fixation with anatomic reductionCredit: Huang et al., J Orthop Surg Res 2018 via PMC5956760 (CC-BY 4.0)

3-panel image: (a) Pre-op AC dislocation, (b) Post-op reduction with CC fixation, (c) Schematic diagram of CC suture techniqueCredit: Huang et al., J Orthop Surg Res 2018 via PMC5956760 (CC-BY 4.0)

AP shoulder X-ray showing AC joint separation with arrow indicating widened joint — AC Joint Separation: AP radiograph demonstrating widening of the acromioclavicular joint with superior displacement of the lateral clavicle. The blue arrow indicates the pathological separation characteristic of AC joint dislocation.Credit: Wikimedia Commons - James Heilman, MD (CC-BY 2.5)

Critical AC Joint Injury Exam Points

Type III Controversy

Most examiners want conservative first for Type III. Consider surgery in: throwing athletes, heavy laborers, failed conservative 3-6 months. Don't reflexively operate!

Imaging Essentials

Axillary view is MANDATORY - Type IV posterior displacement looks like Type III on AP. Weighted views controversial but may help quantify displacement.

CC vs AC Ligaments

CC ligaments = vertical stability (torn III+). AC ligaments = horizontal stability (superior portion 56%, posterior 25%). Know their anatomic insertions.

Surgical Options

Hook plate: temporary fixation, MUST remove 3-4 months, acute only. CC reconstruction: anatomic (both ligaments) better than Weaver-Dunn. Know indications for each.

Quick Decision Guide

Rockwood Type	CC Ligaments	Displacement	Treatment
Type I	Intact (sprained)	None - tenderness only	Sling 1-2 weeks, ice, early ROM
Type II	Sprained (intact)	AC widened, slight step	Sling 2-4 weeks, conservative
Type III	TORN	25-100% superior	CONTROVERSIAL - conservative first
Type IV	Torn	Posterior into trapezius	Surgical - needs axillary view to diagnose
Type V	Torn + deltotrapezial	Greater than 100-300% superior	Surgical - severe soft tissue injury
Type VI	Torn	Inferior (subcoracoid)	Surgical - extremely rare, high-energy

Mnemonic

ROCK - Rockwood Type III Decision

Re-evaluate at 3-6 months

Most improve with conservative care

Occupation matters

Heavy laborers/overhead workers may need surgery

Conservative first

Current consensus for most Type III

Know the athlete

Throwing athletes/contact sports may benefit from surgery

Memory Hook:ROCK solid conservative management first for Type III

Mnemonic

CC Ligaments - TACO

Trapezoid

LATERAL - quadrilateral shape, 20mm from AC joint

AND

Both required for vertical stability

Conoid

MEDIAL - conical shape, 45mm from AC joint, stronger

On the coracoid

Both insert on coracoid process base

Memory Hook:TACO - Trapezoid And Conoid On coracoid - Trapezoid lateral, Conoid medial

Mnemonic

AC Ligaments - SAPI

Superior

56% of horizontal stability - MOST IMPORTANT

Minor contribution

Posterior

25% of horizontal stability - second most important

Inferior

Minor contribution

Memory Hook:SAPI - Superior and Posterior most Important for AP stability

Mnemonic

HOOK - Hook Plate Rules

Hardware removal mandatory

Remove at 3-4 months or complications

Only for acute injuries

Not suitable for chronic (greater than 6 weeks)

On lateral acromion

Hook sits 10-15mm medial to lateral edge

Know the complications

50% impingement if too long/medial

Memory Hook:HOOK plate requires HOOK removal - plan the second surgery

Mnemonic

SPATIRockwood Classification

Sprain

Type I (AC sprain)

Partial

Type II (AC torn, CC sprain/partial)

All

Type III (All ligaments torn)

Through

Type IV (Posterior - 'Through' trapezius)

Inferior/High

Type VI (Inferior) / Type V (High)

Memory Hook:SPATIal orientation of the clavicle!

Mnemonic

COFSurgical Complications

Coracoid fracture

Fracture during drilling

Ossification

Heterotopic ossification common

Failure

Hardware failure / loss of reduction

Memory Hook:Watch out for the COF (Cough) when operating!

Overview and Epidemiology

AC joint injuries are common shoulder injuries, particularly in young active males participating in contact sports. They result from disruption of the ligamentous structures stabilizing the acromioclavicular joint.

Mechanism of injury:

Direct blow - fall onto point of shoulder with arm adducted (most common)
Indirect - fall onto outstretched hand with transmitted force
Contact sports - rugby, AFL, ice hockey, cycling crashes

Risk factors:

Contact sports participation
Male gender
High-velocity activities (cycling, motorcycling)
Previous AC joint injury

Historical Classification

Tossy classification (1963) described Types I-III. Rockwood expanded this to include Types IV-VI, recognizing different displacement patterns that require surgical intervention.

Anatomy and Biomechanics

Gray's Anatomy illustration of shoulder ligaments including coracoclavicular ligaments — Shoulder Ligament Anatomy (Gray's Anatomy): Anterior view of the left shoulder showing key stabilizing structures. Note the coracoclavicular ligaments (conoid - medial, trapezoid - lateral) providing vertical stability, and the superior acromioclavicular ligament providing horizontal stability.Credit: Gray's Anatomy Plate 326 - Henry Vandyke Carter (Public Domain)

AC Joint anatomy:

Synovial diarthrodial joint between lateral clavicle and medial acromion
Contains fibrocartilaginous intra-articular disc (degenerates with age)
Joint capsule reinforced by AC ligaments
Small contact area with high stress concentration

AC Ligaments (horizontal stability):

Ligament	Contribution	Function
Superior	56%	Most important for AP stability
Posterior	25%	Second most important
Anterior	Minor	Weak contribution
Inferior	Minor	Least important

Superior AC Ligament

The superior AC ligament is the most important for horizontal (AP) stability, contributing 56%. It blends with the deltotrapezial fascia to form a strong superior stabilizer.

CC Ligaments (vertical stability):

Ligament	Position	Distance from AC	Shape	Strength
Trapezoid	Lateral	20mm	Quadrilateral	Weaker
Conoid	Medial	45mm	Conical	Stronger

CC Ligament Anatomy

Trapezoid is LATERAL, Conoid is MEDIAL. The conoid is the stronger ligament. Both insert on the undersurface of the clavicle and the base of the coracoid process. Anatomic reconstruction must address BOTH ligaments.

Muscular attachments:

Deltoid - originates from lateral clavicle and acromion anteriorly
Trapezius - inserts on clavicle and acromion posteriorly
Deltotrapezial fascia - critical for stability and surgical repair

Normal radiographic parameters:

CC distance: 11-13mm (normal)
AC joint width: 1-3mm (normal)
Side-to-side CC difference: less than 50% variation is normal

Classification Systems

Type I - AC Ligament Sprain

AC ligaments sprained but intact
CC ligaments intact
No displacement on X-ray
Tenderness over AC joint only

Treatment: Sling 1-2 weeks, ice, early ROM Prognosis: Excellent - full recovery expected

Rockwood Classification Summary

Type	AC Ligaments	CC Ligaments	Displacement	Surgery?
I	Sprained	Intact	None	No
II	Torn	Sprained	Slight (AC widened)	No
III	Torn	TORN	25-100% superior	Controversial
IV	Torn	Torn	Posterior	Yes
V	Torn	Torn	Over 100% superior	Yes
VI	Torn	Torn	Inferior	Yes

Clinical Presentation and Assessment

History:

Mechanism: fall onto point of shoulder, direct blow
Time since injury
Sport/occupation
Hand dominance
Overhead requirements (throwing athlete, laborer)
Previous AC joint problems

Physical examination:

Physical Examination Findings by Grade

Finding	Type I	Type II	Type III+	Significance
AC joint tenderness	Present	Present	Present	Non-specific
Visible step-off	None	Slight	Obvious	Indicates severity
Piano key sign	Negative	May be positive	Positive	CC ligament integrity
Cross-body adduction pain	Positive	Positive	Positive	AC joint pathology
Horizontal instability	None	Present	Present	AC ligament tear

Specific tests:

1. Cross-body adduction test (Scarf test):

Patient reaches hand to opposite shoulder
Positive: pain at AC joint
Sensitive but not specific for AC injury

2. O'Brien test (Active compression):

Arm 90° flexion, 10° adduction, internally rotated (thumb down)
Resist downward force
Positive: pain at AC joint relieved with supination
May also be positive for SLAP lesions

3. Piano key sign:

Examiner presses lateral clavicle inferiorly
Positive: clavicle depresses then springs back
Indicates CC ligament compromise

4. Horizontal instability:

Stabilize acromion, translate clavicle AP
Increased translation = AC ligament tear

Examination Pearls

Always examine for associated injuries: scapula fracture (floating shoulder), clavicle shaft fracture, rotator cuff pathology. Examine neurovascular status and check for skin tenting (relative surgical indication).

Investigations

Standard imaging:

AP Shoulder/Zanca View:

Zanca view: 10-15° cephalic tilt, centered on AC joint
Compare CC distance bilaterally
Measure AC joint width
Assess displacement percentage

Zanca View

The Zanca view (10-15° cephalic tilt) is optimal for AC joint assessment. It angles the beam perpendicular to the AC joint plane, reducing overlap from spine and scapula.

Axillary Lateral View (ESSENTIAL):

MUST obtain in all AC joint injuries
Only view to identify Type IV (posterior displacement)
Shows hook of acromion, coracoid, glenoid
Type IV: clavicle posterior to acromion

Axillary View Mandatory

Never diagnose or treat an AC joint injury without an axillary view. Type IV posterior displacement looks identical to Type III on AP view. Missing Type IV leads to failed conservative treatment.

Stress Views (Controversial):

Weighted views (5-10kg weights in hands)
May help differentiate Type II from III
Most centers no longer routinely use
Pain limits utility in acute setting

Radiographic measurements:

Parameter	Normal	Type III+
CC distance	11-13mm	Over 13mm or over 50% increase
AC joint width	1-3mm	Over 5mm widening
Bilateral CC difference	Under 50%	Over 50%

When to order CT:

Suspected fracture (clavicle, acromion, coracoid)
Failed conservative treatment (evaluate for occult fracture)
Preoperative planning for complex reconstruction

When to order MRI:

Suspected associated rotator cuff injury
Chronic AC joint pain (evaluate disc, OA)
Preoperative assessment in delayed reconstruction

Management

Conservative management (Types I-II, most Type III):

Acute Phase (0-2 weeks)

Ice, analgesia, NSAIDs
Sling for comfort
Avoid aggravating activities
Gentle pendulum exercises

Mobilization Phase (2-6 weeks)

Wean sling as pain allows
Active ROM exercises
Avoid cross-body movements initially
No heavy lifting

Strengthening Phase (6-12 weeks)

Progressive strengthening
Rotator cuff and scapular exercises
Sport-specific rehabilitation
Return to non-contact sport when pain-free

Return to Activity (12+ weeks)

Return to contact sport when full strength
Some persistent cosmetic deformity acceptable
Protective padding if returning to collision sports

Conservative Success

80-90% of Type III injuries treated conservatively achieve satisfactory outcomes. Persistent symptoms at 3-6 months warrant reconsidering surgery, but this is uncommon.

Surgical Technique

Clavicle Hook Plate Fixation

Pre-operative and post-operative X-rays showing hook plate fixation for AC dislocation — Hook Plate Fixation: (a) Pre-operative AP radiograph showing Type V AC joint dislocation with severe superior displacement of the lateral clavicle. (b) Post-operative radiograph demonstrating anatomic reduction with clavicle hook plate in situ. Note the hook extending under the acromion into the subacromial space.Credit: Huang et al., J Orthop Surg Res 2018 - PMC5956760 (CC-BY 4.0)

Mechanism: Hook extends under acromion into subacromial space, plate secures to clavicle, pulls clavicle down to reduce AC joint

Indications:

Acute injuries only (less than 3 weeks)
Type III-V where rapid rigid fixation desired

Advantages:

Technically simpler
Rigid fixation
No graft harvest required

Disadvantages:

MUST be removed at 3-4 months (mandatory second surgery)
High complication rate if not removed (50% impingement)
Subacromial impingement/rotator cuff irritation
Acromion fracture or erosion (5-10%)
Not suitable for chronic injuries

Hook Plate Removal

Hook plates MUST be removed at 3-4 months. Complications if left include: subacromial impingement (50%), acromion fracture, rotator cuff damage, plate breakage. Always plan the second surgery.

Complications

Complications by Treatment Type

Complication	Conservative	Hook Plate	CC Reconstruction
Persistent pain	10-20%	10-20%	10-15%
Cosmetic deformity	Common (accepted)	Low (while in)	Low
Loss of reduction/instability	N/A	10-15% (after removal)	10-15%
Impingement	N/A	Up to 50% if not removed	Rare
Hardware complications	N/A	Common (requires removal)	5-10%
Fracture	N/A	Acromion 5-10%	Coracoid/clavicle 2-5%
Second surgery needed	Rare (under 10%)	100% (mandatory)	10-20%

Conservative treatment complications:

Persistent pain (10-20% - usually mild)
Cosmetic deformity (common - usually well-tolerated)
AC joint arthritis (long-term)
Failed conservative requiring delayed surgery (5-10%)

Hook plate specific complications:

Subacromial impingement (up to 50% if hook too long/medial)
Acromion fracture or erosion (5-10%)
Mandatory hardware removal (100% - second surgery)
Recurrent instability after removal (10-15%)
Rotator cuff irritation/damage

CC reconstruction complications:

Loss of reduction/failure (10-15%)
Coracoid fracture (2-5%)
Clavicle fracture through tunnels
Graft site morbidity (if autograft)
Infection (1-2%)
Nerve injury (rare - musculocutaneous, suprascapular)

Distal Clavicle Excision

Distal clavicle excision (Mumford procedure) can address AC joint arthritis but does NOT treat instability. In chronic AC separations with arthritis, combine CC reconstruction with limited (5-7mm) distal clavicle excision if needed.

Postoperative Care and Rehabilitation

Post-operative protocol (CC reconstruction):

Week 0-2

Sling full time
Pendulum exercises only
Ice, wound care
No active shoulder movement

Week 2-6

Sling when walking/out
Passive ROM to 90° elevation, neutral rotation
Active elbow and wrist ROM
No lifting

Week 6-12

Wean sling
Active-assisted then active ROM
Progressive strengthening begins at 8 weeks
No heavy lifting

Week 12+

Full active ROM
Progressive strengthening
Sport-specific training
Return to contact sport 6-9 months

Hook plate specific protocol:

Similar early protocol to above
Hardware removal at 3-4 months (mandatory)
After removal: 2-4 weeks protected, then progressive activity
Some loss of reduction after removal is normal (usually asymptomatic)

Deltotrapezial Repair

Robust deltotrapezial fascia repair is critical for success. This layer shares load with the CC reconstruction and prevents superior instability. Failure of this repair leads to persistent pain and weakness.

Outcomes and Prognosis

Conservative treatment outcomes:

Type I-II: Excellent outcomes, full recovery expected
Type III: 80-90% satisfactory, may have cosmetic deformity
Most patients return to full sport/activity

Surgical outcomes:

Type IV-VI: Good outcomes with surgery (90% satisfaction)
Type III (delayed surgery): Similar outcomes to early surgery
Anatomic reconstruction superior to Weaver-Dunn

Cosmetic Deformity

Cosmetic deformity (persistent bump) is common after conservative or surgical treatment. This is usually well-tolerated and does NOT correlate with functional outcome. Counsel patients preoperatively.

Factors affecting outcome:

Accuracy of diagnosis (don't miss Type IV)
Patient selection (appropriate conservative vs surgical)
Surgical technique (anatomic reconstruction preferred)
Rehabilitation compliance
Associated injuries (rotator cuff, fractures)

Evidence Base

Level I

📚 CRAC Study (Canadian Randomized AC)

Key Findings:

No significant difference in DASH scores at 2 years between operative and non-operative treatment for acute Type III AC separations.

Clinical Implication: Conservative management is appropriate initial treatment for most Type III injuries.

Source: J Bone Joint Surg Am 2015

Level I

📚 Smith et al. Meta-analysis

Key Findings:

Pooled analysis showed no significant difference in outcomes between operative and non-operative treatment for Type III AC separations. Surgery associated with higher complication rates.

Clinical Implication: Conservative treatment first for Type III; surgery for those who fail conservative or specific high-demand patients.

Source: Am J Sports Med 2011

Level II

📚 Beitzel et al. Systematic Review

Key Findings:

Anatomic CC ligament reconstruction demonstrated superior clinical outcomes compared to non-anatomic techniques (Weaver-Dunn). Failure rates 10-15% vs 20-30%.

Clinical Implication: When surgery is indicated, anatomic CC reconstruction is preferred over Weaver-Dunn.

Source: Am J Sports Med 2013

Level III

📚 Hook Plate Complications (Salem et al.)

Key Findings:

Hook plate complications include subacromial impingement (50% if not removed), acromion fracture (8%), and loss of reduction after removal (15%).

Clinical Implication: Hook plates require mandatory removal at 3-4 months. Consider CC reconstruction for chronic injuries.

Source: J Shoulder Elbow Surg 2018

Basic Science

📚 AC Joint Biomechanics (Klimkiewicz)

Key Findings:

Superior AC ligament provides 56% of resistance to posterior translation. CC ligaments provide majority of vertical stability with conoid being stronger than trapezoid.

Clinical Implication: Anatomic reconstruction should address both vertical (CC) and horizontal (AC) stability when possible.

Source: Am J Sports Med 1999

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

EXAMINER

"A 25-year-old rugby player presents after a tackle onto his right shoulder. X-rays show a Type III AC joint separation with CC distance 15mm (contralateral 11mm). He wants to return to professional rugby. How would you manage this patient?"

EXCEPTIONAL ANSWER

This is a Type III AC joint separation in a young professional athlete - an important clinical scenario given the controversy around Type III management. I would take a systematic approach: First, confirm the classification with AP plus Zanca view AND axillary lateral to exclude Type IV posterior displacement. The CC distance of 15mm versus 11mm (36% increase) confirms Type III. For most patients, I would recommend conservative management as multiple RCTs show equivalent outcomes to surgery at 2 years. However, for a professional rugby player, I would have a detailed discussion about the trade-offs: conservative treatment has 80-90% success but may result in cosmetic deformity; surgery offers faster return and anatomic reduction but has complications including infection, hardware issues, and recurrence. Given his professional status and the demands of rugby, early surgery with anatomic CC reconstruction is a reasonable option, though I would still counsel that conservative treatment remains appropriate. I would involve him in shared decision-making.

KEY POINTS TO SCORE

History: hand dominance, position played, time of season, professional vs amateur

Examination: assess displacement, skin integrity, neurovascular status, associated injuries

Imaging: AP + AXILLARY view (essential), compare CC distances bilaterally

Classification: Type III - CC distance increased by over 50% but not over 100%

Type III is CONTROVERSIAL - discuss conservative vs operative options

Conservative: sling, physio, 80-90% success rate, cosmetic deformity expected

Surgery considerations: professional athlete, high-demand, early return desired

If surgery: anatomic CC reconstruction preferred, discuss hook plate pros/cons

Counsel: similar outcomes at 1-2 years, surgery has complications, shared decision

COMMON TRAPS

✗Not getting axillary view (missing Type IV)

✗Reflexively recommending surgery for Type III without discussion

✗Not acknowledging the controversy around Type III management

✗Forgetting to discuss hook plate mandatory removal

VIVA SCENARIOChallenging

EXAMINER

"A 40-year-old manual laborer presents 3 months after a cycling accident. He was treated conservatively for an AC joint injury but has persistent pain and cosmetic deformity. X-rays show 100% superior displacement with AC joint arthritis. What is your assessment and management?"

EXCEPTIONAL ANSWER

This is a chronic, symptomatic AC joint separation with secondary arthritic changes - a common and challenging scenario. The key points are: First, this represents failed conservative treatment after 3 months, which is an appropriate time to consider surgical intervention. Second, the 100% displacement suggests this was originally a Type V (or high-grade III) injury. Third, the presence of AC arthritis complicates the treatment. For investigation, I would get AP and axillary views, and consider MRI to assess the rotator cuff given the chronic nature. For treatment, this patient requires surgery given failed conservative treatment in a manual laborer. The key principle is that hook plate is NOT suitable for chronic injuries (greater than 6 weeks) - it only works in acute settings. He needs anatomic CC ligament reconstruction using either autograft (semitendinosus), allograft, or synthetic. Given the AC arthritis, I would combine this with a limited (5-7mm) distal clavicle excision (Mumford procedure) to address the arthritic component. I would counsel him that some loss of reduction may occur over time but usually remains asymptomatic.

KEY POINTS TO SCORE

This is a chronic Type V (or high-grade III) AC separation

Need to assess: pain pattern, functional limitation, overhead work requirements

Imaging: check for AC arthritis (common in chronic), clavicle/coracoid morphology

MRI if needed to assess rotator cuff status

Treatment options for chronic symptomatic separation:

Option 1: Anatomic CC reconstruction (NOT hook plate - chronic injury)

Option 2: May combine with limited distal clavicle excision if arthritic

Hook plate is NOT suitable for chronic injuries (over 6 weeks)

Graft options: autograft (semitendinosus), allograft, synthetic

Counsel: some loss of reduction over time is normal but usually asymptomatic

COMMON TRAPS

✗Recommending hook plate for chronic injury (not indicated)

✗Not recognizing this as symptomatic failure of conservative treatment

✗Forgetting to address the AC arthritis component

✗Not assessing rotator cuff before surgery

VIVA SCENARIOCritical

EXAMINER

"A 30-year-old presents after a motorcycle accident with severe shoulder deformity. The AP X-ray shows what appears to be a Type III AC separation with significant superior displacement. On examination, the lateral clavicle cannot be palpated anteriorly and there is fullness posteriorly. What is your concern and management?"

EXCEPTIONAL ANSWER

This presentation is highly concerning for a Type IV AC joint separation with posterior clavicle displacement - a commonly missed injury. The clinical signs are classic: on examination the lateral clavicle is not palpable anteriorly and there is posterior fullness because the clavicle is displaced into or through the trapezius muscle. The critical point is that Type IV looks IDENTICAL to Type III on AP X-ray, but the management is completely different. I would immediately obtain an axillary lateral view which will show the clavicle displaced posterior to the acromion. Type IV is an absolute surgical indication because it cannot be reduced closed - the clavicle buttonholes through the trapezius fascia. Given the high-energy mechanism (motorcycle accident), I would complete a full trauma workup including chest X-ray for rib fractures and pneumothorax, and assess neurovascular status. Surgery involves a superior incision, open reduction through the trapezius, and stabilization either with hook plate acutely or anatomic CC reconstruction. I would operate within 1-2 weeks ideally before soft tissue scarring makes reduction difficult.

KEY POINTS TO SCORE

HIGH SUSPICION for Type IV (posterior displacement)

Clavicle displaced posteriorly INTO or THROUGH trapezius

AP X-ray cannot differentiate Type III from Type IV

AXILLARY VIEW is ESSENTIAL and will show posterior displacement

Type IV is SURGICAL indication - cannot be reduced closed

Clavicle buttonholed through trapezius = needs open reduction

Associated injuries common: rib fractures, pneumothorax, neurovascular

Full trauma workup indicated given high-energy mechanism

Surgical approach: superior incision, open reduction, CC reconstruction

May use hook plate acutely or anatomic reconstruction

COMMON TRAPS

✗Treating as Type III conservatively without axillary view

✗Not recognizing the clinical signs of posterior displacement

✗Missing associated injuries in high-energy trauma

✗Attempting closed reduction of Type IV

MCQ Practice Points

Anatomy Question

Q: Which AC ligament provides the majority of resistance to horizontal translation? A: Superior AC ligament (56%). The posterior AC ligament contributes 25%. The CC ligaments provide vertical (superior-inferior) stability, not horizontal.

Classification Question

Q: What distinguishes Type V from Type III AC joint separation? A: Deltotrapezial fascia detachment in Type V leads to greater than 100-300% superior displacement (vs 25-100% in Type III). Type V represents more severe soft tissue disruption.

Imaging Question

Q: Which view is essential to differentiate Type III from Type IV AC separation? A: Axillary lateral view. Type IV has posterior clavicle displacement that cannot be seen on AP view. Missing Type IV leads to failed conservative treatment.

Treatment Question

Q: What is the current consensus for treatment of Type III AC separations? A: Conservative management first for most patients. Surgery considered in: throwing athletes, heavy laborers, or after failed conservative treatment at 3-6 months. Multiple RCTs show no significant difference in outcomes.

Surgical Question

Q: Why is the hook plate not suitable for chronic AC joint injuries? A: Hook plate provides temporary rigid fixation only (must be removed at 3-4 months). In chronic injuries, soft tissue healing has already occurred and anatomic CC ligament reconstruction is needed to address persistent instability.

CC Ligament Question

Q: What is the anatomic position of the trapezoid vs conoid ligament? A: Trapezoid is LATERAL (20mm from AC joint), Conoid is MEDIAL (45mm from AC joint). Remember: TACO - Trapezoid And Conoid On coracoid, with Trapezoid lateral.

Australian Context

Epidemiology:

Common injury in contact sports (AFL, rugby league, rugby union)
Cycling accidents significant mechanism in Australia
Predominantly male, young adult population

Management considerations:

Day surgery possible for hook plate in straightforward cases
Public hospital waiting lists may influence treatment decisions

Return to work considerations:

Clerical work: 1-2 weeks (Type I-II), 4-6 weeks (Type III+)
Light manual: 6-8 weeks
Heavy manual/overhead work: 12-16 weeks post-surgery
WorkCover implications for occupational injuries

Return to sport:

Non-contact sport: 6-8 weeks (conservative), 12 weeks (surgery)
Contact sport: 12+ weeks (conservative), 6-9 months (surgery)
Protective padding may be used when returning to collision sports

Exam Context

Know the Australian perspective on AC joint management. The trend is toward conservative treatment for Type III, with surgery reserved for specific populations. Be prepared to discuss WorkCover implications for occupational injuries.

AC JOINT INJURIES

High-Yield Exam Summary

ROCKWOOD CLASSIFICATION

•Type I: AC sprain, intact CC - conservative
•Type II: AC torn, CC sprain - conservative
•Type III: CC torn, 25-100% - CONTROVERSIAL (mostly conservative)
•Type IV: Posterior displacement - SURGICAL (need axillary view!)
•Type V: Over 100% superior, deltotrapezial detached - SURGICAL
•Type VI: Inferior (rare) - SURGICAL

KEY ANATOMY

•CC ligaments = VERTICAL stability (conoid medial, trapezoid lateral)
•AC ligaments = HORIZONTAL stability (superior 56%, posterior 25%)
•Normal CC distance: 11-13mm
•Trapezoid: 20mm from AC joint (lateral)
•Conoid: 45mm from AC joint (medial)

TYPE III CONTROVERSY

•Multiple RCTs show NO difference operative vs conservative
•Current consensus: CONSERVATIVE FIRST
•Consider surgery: throwing athletes, heavy laborers, failed conservative
•80-90% satisfactory outcome with conservative treatment

IMAGING ESSENTIALS

•ALWAYS get AXILLARY VIEW (Type IV looks like III on AP)
•Zanca view: 10-15° cephalic tilt for AC joint
•CC distance increased over 50% or over 13mm = Type III+
•Weighted views controversial - rarely change management

SURGICAL OPTIONS

•Hook plate: ACUTE only, MUST remove at 3-4 months
•Anatomic CC reconstruction: Both ligaments, 10-15% failure
•Weaver-Dunn: Non-anatomic, 20-30% failure (historical)
•CC screw: Must remove 6-8 weeks (breakage risk)

TRAPS AND PEARLS

•Missing Type IV (no axillary view) = failed conservative
•Hook plate in chronic injury = wrong indication
•Forgetting hook plate mandatory removal = complications
•K-wire migration = unacceptable complication rate
•Cosmetic deformity doesn't predict function

Rockwood Type

CC Ligaments

Displacement

Treatment

Type I

Intact (sprained)

None - tenderness only

Sling 1-2 weeks, ice, early ROM

Type II

Sprained (intact)

AC widened, slight step

Sling 2-4 weeks, conservative

Type III

TORN

25-100% superior

CONTROVERSIAL - conservative first

Type IV

Torn

Posterior into trapezius

Surgical - needs axillary view to diagnose

Type V

Torn + deltotrapezial

Greater than 100-300% superior

Surgical - severe soft tissue injury

Type VI

Torn

Inferior (subcoracoid)

Surgical - extremely rare, high-energy

Ligament

Contribution

Function

Superior

56%

Most important for AP stability

Posterior

25%

Second most important

Minor

Weak contribution

Inferior

Minor

Least important

Ligament

Position

Distance from AC

Shape

Strength

Trapezoid

Lateral

20mm

Quadrilateral

Weaker

Conoid

Medial

45mm

Conical

Stronger

Type

AC Ligaments

CC Ligaments

Displacement

Surgery?

Sprained

Intact

None

Torn

Sprained

Slight (AC widened)

III

Torn

TORN

25-100% superior

Controversial

Torn

Posterior

Yes

Torn

Over 100% superior

Yes

Torn

Inferior

Yes

Finding

Type I

Type II

Type III+

Significance

AC joint tenderness

Present

Non-specific

Visible step-off

None

Slight

Obvious

Indicates severity

Piano key sign

Negative

May be positive

Positive

CC ligament integrity

Cross-body adduction pain

Positive

AC joint pathology

Horizontal instability

None

Present

AC ligament tear

Parameter

Normal

Type III+

CC distance

11-13mm

Over 13mm or over 50% increase

AC joint width

1-3mm

Over 5mm widening

Bilateral CC difference

Under 50%

Over 50%

Clavicle Hook Plate Fixation

Mechanism: Hook extends under acromion into subacromial space, plate secures to clavicle, pulls clavicle down to reduce AC joint

Indications:

Acute injuries only (less than 3 weeks)
Type III-V where rapid rigid fixation desired

Advantages:

Technically simpler
Rigid fixation
No graft harvest required

Disadvantages:

MUST be removed at 3-4 months (mandatory second surgery)
High complication rate if not removed (50% impingement)
Subacromial impingement/rotator cuff irritation
Acromion fracture or erosion (5-10%)
Not suitable for chronic injuries

Hook Plate Removal

Hook plates MUST be removed at 3-4 months. Complications if left include: subacromial impingement (50%), acromion fracture, rotator cuff damage, plate breakage. Always plan the second surgery.

Complication

Conservative

Hook Plate

CC Reconstruction

Persistent pain

10-20%

10-15%

Cosmetic deformity

Common (accepted)

Low (while in)

Low

Loss of reduction/instability

N/A

10-15% (after removal)

10-15%

Impingement

N/A

Up to 50% if not removed

Rare

Hardware complications

N/A

Common (requires removal)

5-10%

Fracture

N/A

Acromion 5-10%

Coracoid/clavicle 2-5%

Second surgery needed

Rare (under 10%)

100% (mandatory)

10-20%

Type	Indication
Absolute	Type IV (posterior displacement)
Absolute	Type V (severe displacement over 100%)
Absolute	Type VI (inferior displacement)
Absolute	Open injury
Relative	Skin tenting/threatened
Relative	Type III in throwing athlete
Relative	Type III in heavy laborer/overhead worker
Relative	Type III failed conservative (3-6 months)
Relative	Associated displaced clavicle fracture

Type	Indication
Absolute	Type IV (posterior displacement)
Absolute	Type V (severe displacement over 100%)
Absolute	Type VI (inferior displacement)
Absolute	Open injury
Relative	Skin tenting/threatened
Relative	Type III in throwing athlete
Relative	Type III in heavy laborer/overhead worker
Relative	Type III failed conservative (3-6 months)
Relative	Associated displaced clavicle fracture