High Yield Overview

ISOLATED ULNA FRACTURES

Nightstick Fracture | Direct Blow | Nonoperative vs ORIF

DirectBlow mechanism

50%Distal third location

10mmDisplacement threshold for ORIF

HighUnion rate nonoperative

TREATMENT DECISION

Minimally displaced

PatternLess than 50% displacement, less than 10° angulation

TreatmentFunctional bracing

Moderately displaced

Pattern50% displacement or 10-15° angulation

TreatmentConsider ORIF

Significantly displaced

PatternGreater than 50% or greater than 15° angulation

TreatmentORIF recommended

Open fracture

PatternAny displacement

TreatmentSurgical debridement + ORIF

Critical Must-Knows

Nightstick fracture = isolated ulna shaft from direct blow (defensive mechanism)
EXCLUDE Monteggia (check radial head position on all views)
Nonoperative threshold: less than 50% displacement, less than 10° angulation
ORIF with 3.5mm DCP plate - 6+ cortices each side
High union rate both operative and nonoperative

Examiner's Pearls

"
ALWAYS check PRUJ - rule out Monteggia lesion
"
Functional bracing allows early motion
"
Plate fixation is gold standard for displaced
"
Refracture risk higher with plate removal

Critical Exam Concepts

Rule Out Monteggia

ALWAYS check radial head. An isolated ulna fracture is NOT Monteggia. Get proper views including elbow. A line through radial neck should bisect capitellum on ALL views (radiocapitellar line).

Direct Blow History

Classic mechanism. Patient raises arm to defend against blow (assault, fall onto object). The subcutaneous position of the ulna makes it vulnerable. Ask about mechanism carefully.

Nonoperative Criteria

Strict criteria. Less than 50% displacement, less than 10° angulation in proximal 2/3 or less than 15° in distal 1/3. Middle/distal third location. Functional brace allows early motion.

ORIF Threshold

Greater than 50% displacement or significant angulation. Use 3.5mm DCP plate with 6+ cortices each side. Compression plating standard technique.

Isolated Ulna Fracture Quick Decision

Displacement	Angulation	Location	Treatment
Less than 50%	Less than 10°	Middle/distal	Functional brace
50%	10-15°	Any	Borderline - consider ORIF
Greater than 50%	Greater than 15°	Proximal	ORIF recommended
Any	Any	Open fracture	ORIF + debridement

Mnemonic

NIGHTNightstick Fracture Features

Not Monteggia

Confirm radial head located

Isolated ulna

Single bone injury

Guard position

Defensive arm raised

Hit directly

Direct blow mechanism

Treatment by displacement

Brace or ORIF

Memory Hook:NIGHT stick fracture from a NIGHT time assault!

Mnemonic

PLATEORIF Indications

Proximal third

Higher union issues

Large displacement (greater than 50%)

Unstable pattern

Angulation greater than 15°

Malunion risk

Two bone involvement

Not truly isolated

Expected compliance poor

Brace won't work

Memory Hook:PLATE the ulna when criteria met!

Mnemonic

SAFENonoperative Criteria

Stable pattern

Less than 50% displacement

Angulation minimal

Less than 10-15 degrees

Functional brace compliant

Patient can manage

Exclude Monteggia

Radial head in joint

Memory Hook:SAFE for functional bracing!

Overview and Epidemiology

Why 'Nightstick' Fracture?

Historical name. Called nightstick fracture because the mechanism is typically a direct blow to the raised forearm, as when defending against an assault with a nightstick (baton). The subcutaneous ulna border is vulnerable to direct impact.

Epidemiology

2-5% of forearm fractures
Bimodal: young males (assault), elderly (falls)
More common in males
Middle to distal third most common

Mechanism

Direct blow to subcutaneous ulna border
Defensive arm position (guard)
Fall onto hard edge
Sports (hockey stick, bat)

Anatomy and Biomechanics

Ulna Shaft

Position: The posterior border is subcutaneous throughout its length, making it vulnerable to direct trauma.

Cross-section: Triangular proximally, becomes more rounded distally.

Interosseous membrane: Connects ulna to radius. Important for load transfer and forearm stability. Disruption creates longitudinal instability (Essex-Lopresti).

Classification

OTA/AO Classification

22-A1: Simple fracture of ulna only.

22-B1: Wedge fracture of ulna only.

22-C1: Complex fracture of ulna only.

The classification guides complexity but treatment is primarily based on displacement and angulation.

Clinical Assessment

History

Mechanism (direct blow vs fall)
Assault or accident
Location and timing of impact
Previous forearm injury
Hand dominance

Examination

Inspect for deformity, swelling
Palpate entire ulna and radius
Check DRUJ and PRUJ
Test forearm rotation
Neurovascular exam

Must Exclude Monteggia

An isolated ulna fracture is NOT a Monteggia lesion. Always check the proximal radioulnar joint (PRUJ). The radiocapitellar line (line through radial shaft/neck) should bisect the capitellum on ALL views. If the radial head is dislocated, it is a Monteggia fracture-dislocation, not an isolated ulna fracture.

Investigations

Essential Views

Forearm AP and Lateral: Both bones, full length.

Include elbow: Essential to assess radiocapitellar alignment and exclude Monteggia.

Include wrist: Assess DRUJ for longitudinal instability.

Measurements: Displacement as percentage of bone width, angulation in degrees.

Management

Functional Bracing

Indications: Less than 50% displacement, less than 10° angulation (proximal/middle), less than 15° angulation (distal), intact radiocapitellar joint.

Protocol: Initial long-arm splint 1-2 weeks. Convert to functional brace. Allow elbow and wrist motion. Serial X-rays at 2, 4, 6 weeks.

Expected outcomes: Union in 8-12 weeks. Good functional results if criteria met.

Failure: If displacement increases or patient non-compliant, convert to ORIF.

Functional Bracing Rationale

Why functional bracing works: The interosseous membrane and surrounding soft tissues provide stability. Early motion prevents stiffness while allowing fracture healing through micromotion. The ulna is primarily a stabilizer (not weight-bearing like radius), so moderate displacement is tolerated.

Advantages

Avoids surgery complications
Lower infection risk
Early joint motion
Cost-effective
No hardware removal needed

Requirements

Patient compliance critical
Regular follow-up essential
Serial radiographs needed
Accept some residual deformity
Longer time to union

Plate Removal Consideration

Refracture after plate removal is a recognized complication (up to 20% in some series). Counsel patients about this risk. If removing plate, protect arm for 6-12 weeks after removal.

Surgical Technique

Posterior Approach to Ulna

Position: Supine with arm across chest, or lateral with arm on table.

Incision: Direct posterior over subcutaneous ulna border.

Internervous plane: Between ECU (posterior interosseous) and FCU (ulnar nerve). The ulna is subcutaneous - minimal dissection needed.

Key structure: Ulnar nerve is anterior and does not need to be identified for shaft fractures.

Complications

Complication	Incidence	Management
Nonunion	5-10% (nonoperative)	ORIF with bone graft
Malunion	Variable	Osteotomy if symptomatic
Refracture post plate removal	Up to 20%	Protect arm, consider leaving plate
Infection	1-2% (operative)	Antibiotics, debridement
Hardware prominence	Common	Plate removal after union

Postoperative Care

Rehabilitation Protocol

Week 0-2Immobilization

Splint or brace. Wound care. Finger and shoulder ROM.

Week 2-6Early Motion

Begin elbow and wrist ROM. Gentle forearm rotation. Sling for comfort.

Week 6-12Progressive ROM

Full ROM goal. Light strengthening. X-ray to confirm healing.

Month 3-6Return to Activity

Progressive strengthening. Return to work based on healing. Sports at 4-6 months.

Outcomes and Prognosis

Outcome Factors

Favorable: Distal third, minimal displacement, good compliance, anatomic reduction.

Unfavorable: Proximal third, comminution, delayed treatment, smoking.

Evidence Base and Key Studies

Functional Bracing - Sarmiento

Sarmiento A et al. • J Bone Joint Surg Am (1998)

Key Findings:

Functional bracing for isolated ulna fractures
High union rate with less than 50% displacement
Good functional outcomes
Established nonoperative criteria

Clinical Implication: Functional bracing is effective for minimally displaced isolated ulna fractures.

Limitation: Retrospective series.

ORIF Outcomes

Mackay D et al. • Injury (2000)

Key Findings:

Plate fixation outcomes for displaced fractures
High union rate with compression plating
6+ cortices recommended each side
Low complication rate

Clinical Implication: ORIF with compression plating is reliable for displaced fractures.

Limitation: Single center.

Refracture After Plate Removal

Hidaka S, Gustilo RB. • J Bone Joint Surg Am (1984)

Key Findings:

Refracture rate up to 22% after plate removal
Higher risk with early removal
Recommend waiting 18-24 months if removing
Consider leaving plate in situ

Clinical Implication: Counsel patients about refracture risk if plate removal planned.

Limitation: Historical series.

Proximal Third Outcomes

Wright RR et al. • Clin Orthop (1997)

Key Findings:

Proximal third fractures have higher nonunion rate
Consider lower threshold for ORIF in proximal third
Muscle pull creates deforming forces
Better outcomes with operative treatment proximally

Clinical Implication: Consider ORIF for proximal third fractures even with less displacement.

Limitation: Small numbers.

Nonoperative vs Operative Meta-Analysis

Atkin DM et al. • J Orthop Trauma (1995)

Key Findings:

Compared nonoperative and operative treatment
Similar outcomes if appropriate selection
Key is following displacement criteria
Operative preferred for greater than 50% displacement

Clinical Implication: Selection based on displacement criteria determines success of either treatment.

Limitation: Heterogeneous studies.

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

Scenario 1: Nightstick Fracture

EXAMINER

"A 28-year-old man presents after an altercation where he raised his arm to defend himself. X-rays show an isolated mid-shaft ulna fracture with 30% displacement and 5 degrees of angulation. How would you manage this?"

EXCEPTIONAL ANSWER

This is a classic nightstick fracture - an isolated ulna shaft fracture from a direct blow in a defensive position. Before making a treatment decision, I must confirm this is truly an isolated ulna fracture by verifying the radial head is located on all views - a line through the radial shaft should bisect the capitellum to exclude Monteggia. Assuming the PRUJ and DRUJ are intact, this fracture meets criteria for nonoperative management: 30% displacement is less than the 50% threshold, and 5 degrees angulation is less than 10 degrees. My treatment would be initial immobilization in a long-arm splint for 1-2 weeks for comfort, then transition to a functional brace that allows elbow and wrist motion while supporting the fracture. I would obtain serial X-rays at 2, 4, and 6 weeks to monitor for displacement. Expected union is 8-12 weeks. I would counsel the patient about the importance of compliance with the brace and follow-up, as well as avoiding further trauma. The prognosis is excellent with approximately 90% union rate for fractures meeting these criteria.

KEY POINTS TO SCORE

Confirm radial head located - exclude Monteggia

30% displacement and 5° angulation = nonoperative criteria met

Functional bracing after initial splint

Serial X-rays to monitor

90% union rate expected

COMMON TRAPS

✗Not checking radiocapitellar line

✗Operating on a minimally displaced fracture

✗Not counseling about compliance

✗Missing DRUJ injury

LIKELY FOLLOW-UPS

"What if displacement was 60%?"

"What if the radial head was dislocated?"

"What if the fracture was proximal third?"

VIVA SCENARIOStandard

Scenario 2: Displaced Fracture

EXAMINER

"A 35-year-old woman falls onto a metal railing, striking her forearm. X-rays show an isolated ulna fracture with 75% displacement and 20 degrees of angulation. How would you treat this?"

EXCEPTIONAL ANSWER

This isolated ulna fracture exceeds the nonoperative thresholds considerably - 75% displacement is greater than 50% and 20 degrees angulation is greater than 15 degrees. I would recommend ORIF. Again, I must first confirm this is isolated by checking the radiocapitellar line on all views and assessing the DRUJ. My surgical approach would be direct posterior over the subcutaneous ulna border. I would use a 3.5mm narrow DCP or LCP, typically 8-10 holes in length. Fixation goals are minimum 6 cortices (3 screws) on each side of the fracture. For this oblique/displaced pattern, I would use a lag screw through the plate if the fracture geometry allows, then neutralization/compression mode. Post-operatively, she would be in a removable splint for comfort, with early ROM exercises starting at 2 weeks. I would obtain X-rays at 2, 6, and 12 weeks. Expected union is 10-14 weeks. I would counsel her about possible hardware prominence given the subcutaneous position, and discuss that if plate removal is desired, it should wait until at least 18-24 months and carries a refracture risk.

KEY POINTS TO SCORE

75% displacement and 20° = exceeds nonoperative criteria

ORIF recommended

3.5mm DCP or LCP, 6+ cortices each side

Lag screw if fracture pattern allows

Counsel about hardware prominence and refracture risk

COMMON TRAPS

✗Attempting nonoperative for significantly displaced fracture

✗Inadequate fixation (fewer than 6 cortices)

✗Not checking radiocapitellar alignment

✗Removing plate too early

LIKELY FOLLOW-UPS

"How would you approach the ulna surgically?"

"What if the fracture was comminuted?"

"When would you consider plate removal?"

VIVA SCENARIOChallenging

Scenario 3: Proximal Third Fracture

EXAMINER

"An isolated ulna fracture in the proximal third with 40% displacement. The radial head is confirmed located. How would your management differ from a mid-shaft fracture?"

EXCEPTIONAL ANSWER

This is an important distinction. Although 40% displacement is technically less than the 50% threshold for nonoperative treatment, I would have a lower threshold for ORIF in a proximal third fracture. There are several reasons: First, the proximal ulna has deforming forces from muscle attachments that make maintaining alignment more difficult. Second, studies have shown higher nonunion rates with nonoperative treatment of proximal third fractures. Third, the functional implications of malunion are greater proximally due to effects on the elbow and pronation-supination arc. I would discuss both options with the patient - nonoperative with very close monitoring and strict brace compliance, versus ORIF which provides reliable alignment and allows early motion. Given the borderline displacement and proximal location, I would lean toward recommending ORIF for this patient, especially if they are young and active or have high functional demands. If the patient strongly prefers nonoperative treatment, I would accept that with understanding of the higher risk of complications and need for very close follow-up with low threshold to convert to surgery if alignment is lost.

KEY POINTS TO SCORE

Proximal third = lower threshold for ORIF

Higher nonunion rate with nonoperative proximally

Deforming muscle forces

40% displacement is borderline - location tips decision

Shared decision-making with patient

COMMON TRAPS

✗Treating all isolated ulna fractures the same regardless of location

✗Being too rigid with 50% threshold

✗Not discussing treatment options

✗Ignoring prognostic factors

LIKELY FOLLOW-UPS

"What muscles attach to the proximal ulna?"

"What is the nonunion rate for proximal third fractures?"

"How would you approach proximal ulna surgically?"

VIVA SCENARIOCritical

Scenario 4: Open Fracture

EXAMINER

"A 42-year-old motorcyclist presents with a Gustilo grade II open isolated ulna fracture. The radial head is confirmed located. How would you manage this injury?"

EXCEPTIONAL ANSWER

This is an open isolated ulna fracture requiring urgent surgical management regardless of displacement. My priorities follow ATLS principles first, then addressing the open fracture. Immediate management includes IV antibiotics - cefazolin 2g as first line, adding gentamicin if contamination significant. Tetanus prophylaxis if needed. The wound needs thorough irrigation and debridement in theatre ideally within 6 hours. After debridement, I would perform definitive fixation with ORIF using a 3.5mm DCP or LCP. The approach would be through or adjacent to the wound, extending as needed for adequate exposure. I would achieve rigid fixation with 6+ cortices each side. The wound would be managed based on its condition - if clean after debridement and good soft tissue coverage, primary closure or delayed primary closure. If contaminated or significant soft tissue loss, leave open with planned second look at 48-72 hours. Post-operatively, IV antibiotics for 24-48 hours (grade II), regular wound inspections, and early motion once soft tissues allow. I would counsel about higher infection risk, possible need for further surgery, and longer healing time compared to closed fractures.

KEY POINTS TO SCORE

Open fracture = operative regardless of displacement

Antibiotics, debridement, tetanus within 6 hours

ORIF with adequate fixation

Wound management based on grade and contamination

Higher complication rate counseling

COMMON TRAPS

✗Delaying surgery for 'minimally displaced' pattern

✗Inadequate debridement

✗Primary closure of contaminated wound

✗Not considering soft tissue coverage

LIKELY FOLLOW-UPS

"What antibiotics for a grade IIIB fracture?"

"When would you consider external fixation?"

"How do you manage soft tissue loss over ulna?"

MCQ Practice Points

Displacement Threshold

Q: What is the displacement threshold for nonoperative treatment of isolated ulna fractures? A: Less than 50% of bone width. Beyond this, ORIF is recommended.

Angulation Threshold

Q: What angulation is acceptable for nonoperative treatment? A: Less than 10 degrees in proximal/middle third, up to 15 degrees in distal third.

Monteggia Exclusion

Q: What must be confirmed before diagnosing an isolated ulna fracture? A: Radial head is located. Check radiocapitellar line on all views to exclude Monteggia lesion.

Plate Fixation

Q: What is the minimum fixation required for ulna shaft ORIF? A: 6 cortices (3 screws) on each side of the fracture with a 3.5mm DCP or LCP.

Refracture Risk

Q: What is a significant risk after plate removal from the ulna? A: Refracture (up to 20%). Recommend waiting 18-24 months before removal if indicated.

Nightstick Mechanism

Q: What is the mechanism of a nightstick fracture? A: Direct blow to the subcutaneous ulna border, typically when arm is raised in defense.

Australian Context

Clinical Practice

Common ED presentation
Assault and falls common mechanisms
Functional bracing widely available
ORIF for displaced fractures standard

Medicolegal

Document mechanism carefully
Rule out NAI in children
Assault cases may involve police
Photography of injuries important