Fractures, joint injuries & instability Flashcards
What happens to external fixator rigidity if you increase the distance between rods and bone in distal radius fractures?
Rigidity decreases.
Increasing distance reduces mechanical stability.
Optimal position for distal pin placement in external fixation of index metacarpal?
Insert pins with MCP joint flexed at 90° to avoid extensor tendon tethering.
Optimal positioning prevents tendon injury during fixation.
Where should proximal pins in radial shaft be placed during external fixation?
Between ECRB and ECRL or between ECRB and EDC, avoiding the superficial radial nerve.
Precise placement prevents nerve irritation or injury.
According to Lafontaine criteria, which radiographic feature indicates instability of distal radius fractures?
Dorsal comminution.
Predictive of secondary displacement post-reduction.
Does radial shortening greater than 5mm define instability according to Lafontaine criteria?
No, radial shortening is not a criterion defined by Lafontaine.
It is considered by some authors, but not by Lafontaine.
List 3 features from Lafontaine criteria that indicate an unstable distal radius fracture.
- Age >60
- Dorsal angulation >20°
- Intra-articular radiocarpal fracture
Presence of 3+ indicates instability.
Which distal radius fracture type most commonly associates with scapholunate ligament injuries?
Chauffeur fracture (radial styloid fracture).
Injury extends distally into ligament insertion.
What defines a Barton fracture of distal radius?
Intra-articular fracture with dorsal or volar subluxation of the carpus.
Associated carpal instability differentiates Barton fractures.
Which fracture historically described as a “reverse Colles” fracture?
Smith fracture (volar angulation fracture).
Contrasts the dorsal displacement typical of Colles fracture.
True or false: Non-displaced distal radius fractures have lower EPL tendon rupture risk compared to displaced fractures.
False, non-displaced fractures have a higher EPL rupture risk.
Non-displaced fractures increase pressure at EPL watershed zone.
Does wrist immobilization in full palmar flexion decrease risk of carpal tunnel syndrome after distal radius fracture?
No, it increases risk due to higher intracarpal pressure.
Extended wrist positions are preferred to reduce pressure.
Which distal radius fracture classification is based on the mechanism of injury?
Fernandez classification.
What is the key feature distinguishing the Melone classification for distal radius fractures?
It classifies fractures based on four major fragments: radial styloid, dorso-ulnar, volar-ulnar, radial shaft.
Emphasizes fragment-specific management.
What does Frykman classification primarily focus on in distal radius fractures?
Radiocarpal and distal radioulnar joint involvement, and ulnar styloid presence or absence.
Highlights joint involvement and ulnar injury.
Through which anatomical space does the lunate displace volarly in perilunate dislocations?
Space of Poirier (weak volar area of capsule between radiocapitate and long radiolunate ligaments).
Describe Stage 2 of the Mayfield classification for perilunate injuries.
Stage 2 involves disruption of the lunocapitate articulation (progression from radial to ulnar side).
What differentiates greater arc from lesser arc perilunate injuries?
Greater arc injuries involve fractures of radius, carpus, or ulna; lesser arc injuries involve purely ligamentous disruptions.
Which ligament is the primary stabilizer of the scapholunate joint?
Dorsal component of the scapholunate ligament.
Is the dorsal or volar component of the lunotriquetral ligament stronger?
The volar component of the lunotriquetral ligament is stronger (300N strength vs. dorsal component).
Name two secondary stabilizers of the scapholunate joint.
Dorsal radiocarpal ligament and scaphotrapezial ligament.
At what displacement (in mm) is a scaphoid fracture considered unstable?
Displacement greater than 1mm.
How does delay in treatment (>4 weeks) influence scaphoid non-union risk?
Increases non-union rate significantly, from ~5% up to 45%.
Recommended definitive treatment for a Gustilo-Anderson type II open distal radius fracture with a 2mm intra-articular step-off?
Internal fixation using a volar locking plate.
Why is K-wire fixation insufficient for an intra-articular step-off in an open distal radius fracture?
K-wire fixation doesn’t reliably maintain reduction of intra-articular fragments, leading to poor outcomes.
What advantage does volar locking plate fixation offer in open distal radius fractures?
Stable internal fixation, better fracture alignment, and lower infection risk after adequate debridement.
Optimal management of a displaced fracture-dislocation of ring and little finger CMCJs diagnosed at 5 weeks post-injury?
Open reduction and internal fixation (due to chronicity and complexity of injury).
Why is buddy-splinting insufficient at 5 weeks for CMCJ fracture-dislocation?
Because malalignment is already established, closed techniques are unlikely to restore proper anatomy.
When might arthrodesis of ring and little finger CMCJs be considered after a fracture-dislocation?
If severe articular cartilage damage is present, making functional restoration impossible.
Why is remanipulation with casting alone insufficient for re-displaced intra-articular distal radius fractures?
High risk of further displacement and poor anatomical restoration.
When is open reduction with a volar locking plate indicated in distal radius fractures?
For severely displaced fractures or those failing closed reduction or pinning.
Typical MRI appearance of occult scaphoid fracture on T1-weighted sequences?
Low signal (dark) on T1 images.
On STIR MRI sequences, how does an acute scaphoid fracture typically appear?
High signal (bright) on STIR due to bone marrow edema.
Why is MRI superior to X-ray in early scaphoid fracture detection?
MRI has higher sensitivity (>90%) detecting fractures invisible on X-rays.
What is the primary purpose of pre-bending a compression plate before fixation?
To prevent volar gapping at the fracture site.
What happens if a straight compression plate is applied without pre-bending?
Tension develops on the far cortex, leading to asymmetric compression and instability.
How does pre-bending the plate enhance stability in transverse fractures?
It creates uniform compression across the entire fracture site, minimizing gapping.
Which cells predominate early in the inflammatory stage of fracture healing?
Monocytes (which differentiate into macrophages).
Name two cytokines crucial for early inflammatory response in fracture healing.
TNF-α and IL-1.
During secondary bone healing, what is the role of the fibrin matrix?
Acts as a scaffold for inflammatory cell influx and subsequent cell differentiation.
How does a lag screw fixation promote fracture healing?
It achieves interfragmentary compression, facilitating primary bone healing without callus.
Why is a countersink used during lag screw fixation?
To ensure even load distribution, preventing stress concentration and screw head prominence.
What happens to the proximal phalanx in an ulnar collateral ligament (UCL) tear of the thumb MCP joint?
It rotates by volar supination on the side of the UCL tear.
In a Stener lesion, what prevents the UCL from healing spontaneously?
The torn UCL lies superficial to (trapped above) the adductor aponeurosis.
What is the most common site for avulsion fractures associated with thumb MCP UCL injuries?
At the proximal phalanx insertion of the UCL.
What intra-operative maneuver determines the need to fix an ulnar styloid fracture associated with distal radius fractures?
Ballottement test for DRUJ instability.
When does an ulnar styloid fracture require fixation during distal radius fracture surgery?
Only if the DRUJ is unstable after distal radius fixation.
Does ulnar styloid fracture size correlate with DRUJ instability in distal radius fractures?
No, stability is related to the integrity of the foveal attachment, not fracture size.
What indicates surgical treatment for collateral ligament avulsion fractures of the proximal phalanx base in fingers?
Fragment involving ≥25% of articular surface with joint instability.
Preferred surgical approach for unstable avulsion fractures at the proximal phalanx base?
Volar approach (avoids violating extensor mechanisms).
When is ligament reconstruction required for proximal phalanx collateral ligament injuries?
Rarely, typically only in chronic injuries with persistent instability.
First-line treatment for a type 1A TFCC tear presenting with clicking and ulnar wrist pain?
Arthroscopic synovectomy and TFCC debridement.
Which TFCC tear type involves central perforation of the disc?
Palmer type 1A.
What clinical test is most sensitive for DRUJ instability assessment in TFCC injuries?
Ballottement test.
In Mayfield classification of perilunate injuries, what causes lunotriquetral dissociation in stage III?
Ulnar arcuate ligament pulling the triquetrum dorsally.
In which stage of Mayfield classification do you see disruption of the lunocapitate articulation?
Stage III.
What ligament remains intact until Mayfield stage IV perilunate dislocation?
Radioscaphocapitate (RSC) ligament.
What type of carpal instability involves ligament injury within a single carpal row?
Carpal instability dissociative (CID)
How is carpal instability non-dissociative (CIND) defined?
Instability due to injury of extrinsic ligaments, affecting stability between carpal rows.
What best describes a radiocarpal joint dislocation in terms of carpal instability patterns?
Carpal instability non-dissociative (CIND)
What is the Eaton-Belsky technique?
Transarticular fixation using antegrade k-wires through the MCP joint into the proximal phalanx.
What is the advantage of lateral plating via mid-axial approach for proximal phalangeal fractures?
It avoids plate irritation and tendon adherence compared to dorsal plating.
What deformity occurs commonly with proximal phalangeal base fractures due to intrinsic muscle pull?
Apex angulation deformity.
What imaging is the gold standard to assess scaphoid vascularity intra-operatively?
Punctate bleeding assessment during surgery.
Describe a Zaidemberg graft.
Vascularized graft from dorsal distal radius using the 1,2 intercompartmental supraretinacular artery.
How is stage I SNAC wrist treated?
Cancellous bone grafting and radial styloidectomy.
What factor determines surgical indication for a bony mallet injury?
Volar subluxation of DIP joint rather than fracture fragment size alone.
Describe the Ishiguro extension-blocking technique.
The DIP joint is hyperflexed; k-wire blocks dorsal fragment migration and stabilizes the joint.
What is the standard non-operative treatment duration for bony mallet injuries?
Mallet splint for 6-8 weeks, followed by 2 weeks night splinting.
Which method is preferred for a dorsal fracture-dislocation involving 30% of the volar articular surface?
Extension-block pinning.
When is hemi-hamate arthroplasty indicated for PIP fracture-dislocations?
For unstable injuries involving 30–50% of joint surface with non-reconstructable fragments.
Why is static external fixation less desirable in PIP fracture-dislocations?
It does not allow early mobilization, increasing stiffness risk.
Identify the fracture type described: “Intra-articular dorsal shear fracture of distal radius with dorsal subluxation of the carpus.”
Barton fracture
• Involves dorsal or volar rim of radius
• Associated with carpal subluxation
• Often requires buttress plate fixation
Identify the fracture type described: “Fracture of distal third of radius with distal radio-ulnar joint (DRUJ) dislocation.”
Galeazzi fracture
• Needs ORIF of radius and stabilization of DRUJ
Identify the fracture type described: “Fracture of ulna shaft with proximal radial head dislocation.”
Monteggia fracture
• Typically requires ORIF of ulna
Identify the fracture type described: “Extra-articular distal radius fracture with volar angulation.”
Smith fracture
• Reverse deformity of Colles
• Usually treated with volar plating if unstable
Identify the fracture type described: “Isolated intra-articular radial styloid fracture.”
Chauffeur fracture
• From rotational or shear trauma (historically crank handle injuries)
• May require surgical fixation
Which fixation method is described by: “Converts tensile forces into compression at fracture site.”
Tension band wiring
• Common in olecranon and phalangeal avulsion fractures
Which fixation principle is defined by: “Achieving fracture stability through three cortical points of fixation?”
Intramedullary wiring (three-point fixation)
• Common in metacarpal fractures
Which fixation type is ideal for: “Providing stability against shear forces at metaphyseal fractures, e.g., volar Barton fracture?”
Buttress plate fixation
• Prevents fragment displacement under axial/shear loads
Which fixation device achieves maximal compression when placed perpendicular to the fracture line?
Lag screw fixation
• Ideal for oblique/spiral fractures
Which fixation method bridges comminuted fracture segments without directly fixing intermediate fragments?
Bridging plate
• Maintains alignment and length
Which hand radiograph view best demonstrates thumb CMC arthritis?
Robert view
• True AP projection of thumb
Which radiographic view demonstrates proximal migration of the capitate and scapholunate diastasis?
Clenched fist view
• Highlights subtle instability
Which radiographic view identifies subtle impaction fractures at metacarpal heads (fight-bite injuries)?
Brewerton view
• Tangential view of metacarpal heads
Which wrist view clearly identifies scaphoid fractures?
Ziter view
• PA, ulnar deviation, angled 20° towards elbow
Which view is best for identifying fractures of the trapezial ridge or hook of hamate?
Carpal tunnel view
• Axial view with maximal wrist dorsiflexion
Which wrist test is used to detect scapholunate ligament instability?
Watson’s scaphoid shift test
• Positive if painful clunk occurs
Which wrist maneuver identifies midcarpal instability through a “catch-up” clunk?
Lichtman pivot shift test
Which test assesses lunotriquetral joint instability?
Kleinman shear test
• Radially/ulnarly deviates wrist
Which test helps identify ulnar-sided wrist pathology (e.g., TFCC injury)?
Ulnocarpal stress test
• Pain indicates positive test
Which clinical test identifies lunotriquetral ligament instability?
Reagan shuck test
• Positive if painful click or laxity present
What surgical technique is ideal for irreparable scapholunate ligament injury with reducible malalignment and no arthritis?
3-ligament tenodesis (Brunelli)
• Stabilizes scapholunate dissociation
What treatment is best for complete yet reparable scapholunate ligament injury with normal alignment?
Open repair + K-wire stabilization
• Direct ligament repair, healing potential intact
Which surgical procedure addresses incomplete scapholunate ligament injuries?
Blatt capsulodesis/Berger
- Uses dorsal capsule for wrist stabilization
Which fusion is optimal for irreparable scapholunate ligament injury with irreducible malalignment but intact cartilage?
Scapho-trapezium-trapezoid (STT) arthrodesis
• Stabilizes scaphoid; preserves wrist function
