Generally bones heal in about 6-8 weeks, but healing depends on location of the bone. Healing is fastest in the phalanges (around 3 weeks), and slowest in the tibia (around 2-3 months)

Delayed Union= Fracture not healed within the expected time period

Non-Union = Fracture is not going to heal without intervention. Some sources will say “6-9 months.” The classic locations are the scaphoid, anterior tibia, and lateral femoral neck.

Mal-Union= Union in poor anatomic position.  

Risk Factors

  • Vitamin D Deficiency is associated with Non-Union.
  • Gastric Bypass Patients have altered calcium absorption (causes secondary hyperparathyroidism and stripping of calcium from bones) and therefore higher rates of nonunion. 

Fractures of hand/wrist

Scaphoid Fracture

Most common carpal bone fracture

  • 70% at the wrist (adults)
  • Blood supply is distal to proximal; with the proximal pole most susceptible to AVN. 
  • The first sign of AVN= Scleiosis (the dead bone can’t turn over/ recycle)
  • Proximal fractures are most susceptible to AVN and non-union 
  • Avulsion fractures occur at distal pole
  • AVN on MRI – This is controversial. Probably the most reliable is sign is DARK ON Tl.

Scapho-Lunate Ligament Tear

The Terry Thomas look (gap between the scaphoid and lunate) on plain film.  

There are actually 3 parts (volar, dorsal, and middle), with the dorsal band being the most important for carpal stability (opposite of luno-triquetral which is volar). Disruption of the ligament predisposes for DISI deformity. 

SLAC Vs SNAC wrists 

  • SLAC Wrist (Scaphoid-Lunate Advanced Collapse) occurs with injury (or degeneration via CPPD) to the S-L ligament 
  • SNAC Wrist (Scaphoid Non-Union Advanced Collapse) occurs with a scaphoid fracture. 

scaphoid always wants to rotate in flexion – the scaphoid-lunate ligament is the only thing holding it back. If this ligament breaks it will tilt into flexion, messing up the dynamics of the wrist.

The radial scaphoid space will narrow, and the capitate will migrate proximally. 

Treatment depends on the occupation/needs of the wrist. Wrist fusion will maximize strength, but cause a loss of motion. Proximal row carpectomy will maximize ROM, but cause a loss of strength.

Carpal Dislocations

Scapho-Lunate

Dissociation

Peri-Lunate

Dislocation

Mid-Carpal

Dislocation

Lunate

Dislocation

SL- Wider Than 3mm 

Clenched Fist View can worsen it (would make a good next step question) 

Chronic SL dissociation can result in a SLAG wrist

60% associated with Scaphoid fractures

Lunate stays put – the capitate (and radius move back)

  

Associated with triquetro-lunate interosseous ligament disruption

Associated with a triquetral fracture

Happens with dorsal-radiolunate ligament injury

‘The most severe form’

 

 

Vulnerable Zones Theory

Dislocations around the lunate are described in two flavors.

  • LesserArc: Pure Ligament Injury (No Fractures)
  • GreaterArc: Associated with fractures.

Described by saying “trans” the name of the fracture then the dislocation.Example “Trans-scaphoid, peri-lunate dislocation”

 

DISI vs VISI

This is a very confusing topic – thus high yield. If you have carpal ligament disruption, the carpal bones will
rotate the way they naturally do. The reasons for their rotational desires are complex but basically have to do with the shape of the fossa they sit on.

 Just remember the scaphoid wants to flex (rock volar) and the lunate wants to extend (rock dorsal). The only thing holding them back is their ligamentous attachment to each other.

 DISI (dorsal intercalated segmental instability) – We will call this dorsiflexion instability because it helps me remember what is going on. After a radial sided injury (scapholunate

side) the lunate becomes free of the stabilizing force of the scaphoid and rocks dorsally.

Remember SL ligament injury is common, so this is common.

 VISI (volar intercalated segmental instability)

I like to call this volar flexion (palmar flexion) instability because it helps me remember what is going on. After an ulnar sided

injury (lunotriquetral side) the lunate no longer has the stabilizing force of the lunotriquetral ligament and gets ripped volar with the scaphoid (remember the scaphoid stays up late every night dreaming of tilting volar). Remember LT ligament injury is not common, so this is not common. It’s so uncommon in fact that if you see it – it’s probably a normal variant due to wrist laxity

  • Phalanges= Heal Fast (3 Weeks)
  • Tibia= Heal Slow (10 Weeks)
  • Everything Else = 6-8 weeks


 

-The Terry Thomas look-

-SNAC-


-SLAC-