Vascular Injury
WHAT IS THE NORMAL ABI CUTOFF?
0.9
HOW MANY LIGAMENTS MUST BE DISRUPTED FOR A KNEE TO DISLOCATE?
At least 2
Therefore a knee dislocation by definition is a multi-lig knee injury
WHAT PERCENT OF KD’S HAVE ASSOCIATED FRACTURE?
10-20%
WHICH GENDER IS MOST AFFECTED? and ratio (for bonus 100)
4:1 M:F
WHAT TYPES OF VASCULAR INJURY CAN OCCUR (List at least 3)
Occlusion
Thrombosis
Transection
Intimal flap
Intimal tear
WHICH IS THE MOST COMMON MULTI-LIG INJURY PATTERN?
Both cruciates and MCL
or ACL/MCL
What complication can occur especially post vascular intervention?
Compartment syndrome
LIST 3 COMPLICATIONS FROM KD
Vascular injury
Nerve injury
Compartment syndrome
DVT
WHAT IS THE RATE OF POPLITEAL ARTERY INJURY?
16%
WHAT STRUCTURE IS USUALLY SPARED IN A ROTATORY KD?
PCL
WHICH RESULTS IN HIGHER NERVE INJURY, ULTRA-LOW, LOW, OR HIGH ENERGY MX?
Ultra low
WHAT IS THE MOST COMMON POSTERIOR DISLOCATION MX?
caused by significant posteriorly directed force across the proximal tibia
Classically the “dashboard” injury
HOW MUCH WARM ISCHEMIA TIME LINKED TO HIGHER AMPUTATION RATE (and what percent)?
Delay in blood flow greater than 8 hours lead to 85% amputation rate
LIST FROM MOST COMMON TO LEAST FOR EACH DISLOCATION DIRECTION
Anterior
Posterior
Lateral
Rotatory
Medial
WHERE IS THE CPN MOST COMMONLY INJURED AND WHY?
At fibular neck
CPN tethered there
No intraneural vessels in that region
WHAT DEGREE DO YOU SPLINT OR APPLY A NON-HINGED SPANNING EX-FIX AT AND WHY?
20 degrees
This decreases tension on posterior NV structures
WHY COULD YOU HAVE A PALPABLE DISTAL PULSE IN THE PRESENCE OF POPLITEAL INJURY?
May have an intimal injury and early on will continue to provide flow until it clots off.
Or, in young patients, collateral flow about the knee is robust enough to possibly sustain a normal pulse in the foot for a short time
Note, the distal flow is TEMPORARY
WHAT IS THE SEQUENCE OF FAILURE OF STRUCTURES IN AN ANTERIOR DISLOCATION AND BY WHAT MECHANISM?
hyperextension mechanism
sequential failure of:
posterior capsule
then posterior cruciate ligament (PCL)
and sometimes anterior cruciate ligament (ACL)
WHAT IS THE PROGNOSIS FOR NERVE INJURY? (% for full, partial and no motor recovery)
21% full neurologic recovery
29% partial recovery
Remaining 50% had no useful motor recovery
DESCRIBE 2 KNEE DISLOCATION CLASSIFICATIONS
Kennedy (A. ant, B. post, C. Med/Lat D. Rotational) and Schenk (KD I-V, I=1 cruciate plus collateral, II=both cruciates injured, both cruciates + 1 collateral, IV=all 4, V= associated fracture)