Download Knee Extensor Mechanism - Peggers Super Summaries

Peggers’ Super Summary of Knee Extensor Mechanism
Quadriceps Rupture:
EPIDEMIOLOGY:
 >40 yr old occurs at bone tendon junction
 <40 yr olds occurs at midsubstance
RF:
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Diabetes
Anabolic Steroids or steroid injections
Renal Failure
Inflammatory arthropathy
o
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FEATURES:
Clinically
NB: NEVER DIAGNOSE PARTIAL TEARS
 Within 2cm of superior pole
 Effusion
 Palpable gap
 Unable to SLR
Radiographically:
 Patella Baja <0.8 (range 0.8-1.2)
 Avulsion of superior patella
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FURTHER IMAGING:
 US – delineate between tear or not
 MRI – better for partial tears
MANAGEMENT:
Non-Operative
 Option for partial tears
Operative
 Ethibond number 5
 Posterior osseous tunnels to patella to avoid tilting
 Use dental wire to pull through the sutures through
osseous tunnels
 Techniques
o
Krackow
o
Scuderi – direct horizontal repair with
partial v flap
Codivilla V-Y plasty
 indicated for chronic
ruptures where the tendon
edges cannot be opposed
create a full thickness
inverted V flap which
ends 1.5 cm above the
rupture
The tendon edges are
repaired w/ heavy suture
The proximal portion of
the inverted V is closed
down (converting it to a
vertical line);
Post-Operative:
 Immediate vs delayed weight bearing
 A locked immobile knee offers no loading
 Immobilised until wound dry
 Hinged knee brace 0-450 at 3 weeks
 Increase by 150 every 1 week
 Benefits of early mobilation
o Prevent adhesions and stiffness
o Allow tenocytes to propagate under load
Patella Fracture:
EPIDEMIOLOGY
 Most commonly 20-50 yr olds
 Male to female 2:1 ratio
ANATOMY
 Largest seamoid bone in the body
 Bi-partite patella – superolateral corner
 Bone falls to lateral facet/articular surface
 Thickest articular surface in the human body
 Medial and lateral retinacula attach directly onto
tibia
o If retinacula intact CAN SLR
o To detect true extensor mechanism rupture
need to straighten knee from a FLEXED
position
 Blood supply is from geniculate arteries, which
anastomoses around circumferentially around entire
patella
MOMENT ARM
 Force is proportional to perpendicular distance
from moment arm
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Peggers’ Super Summary of Knee Extensor Mechanism
Patella increases mechanical advantage of
quadriceps. Excision will increase work of quads
by >30%
MANAGEMENT
Conservative
 When extensor mechanism intact
 3-6 weeks immobilised with increasing flexion
allowed
MANAGEMENT
Non-Operative
 <2mm gap and intact mechanism
 Low demanding patient
Operative: via longitudinal or horizontal incision
 Figure of 8 Tension band technique
 Circlage wires
 lag screw + circlage wire
 Canulated lag screw with wire going through it
 Partial or total patellectomy
Surgical
 Midline incision
o Saphenous and nerve branches come in
medially which cause neromas
 Frayed edges and haematoma debrided
o Heeling occurs in cortical & cancellous
bone ends
o No heeling potential from calcified
fibrocartilage and uncalcified
fibrocartilage
 Can use longitudinal bone tunnels for extra security
with the Krackow suture method
 Repair retinacula tears at the same time
 Test intra-operatively with knee flexion
 II good knee to see patella height
o Insalls ratio 0.8-1.2
o Blumensaats Line – roof
of supracondylar notch
>10mm = alta
COMPLICATIONS
 Reflex sympathetic dystrophy
 Hardware irritation or migration
POST-OPERTIVE REHABILITATION
 Immobilised until wound dry
 Partial weight bearing 0-45 degrees at 3 weeks
 Increase ROM every week
Patella Tendon Rupture:
EPIDEMIOLOGY
 Less common than quadriceps rupture
 <40 yr olds typically
COMPLICATIONS
 Stiffness
 Quadriceps weakness and
extensor lag
 Re-rupture
 Patella baja
RISK FACTORS
 RA / SLE
 Diabetes
 CRF
 Steroids
 Tendinitis
BIOMECHANICS
 3 x BW when going up stairs
 4 x BW when going down stairs
ANATOMY
 Posterior tendon blood supply via fat pad vessels
 Anterior blood supply via medial geniculate vessels
& recurrent tibial arteries
POST-OPERATIVE REHABILITATION
 (A locked knee offers no loading)
 TTWB for 6 weeks cricket pad splint
 Hinged knee brace 0-450 at 3 weeks
 Increase by 150 every 1 week
 Benefits of early mobilation
o Prevent adhesions and stiffness
o Allow tenocytes to propagate under load
 Full weight bearing at 6 weeks
 Can lift all restrictions when ROM and strength
90% of contralateral knee
HISTORY
 Audible pop and unable to mobalise
 Haemoarthrosis
 Defect
 Loss of active extension
DIAGNOSIS
 Patella alta
 +/- US
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