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Evaluation of the Dislocated Knee

Dr Alan GetgoodMD MPhil FRCS(Tr&Orth) DipSEM

Assistant ProfessorComplex Knee and Sport MedicineOrthopaedic Sport Medicine Fellowship DirectorThe Fowler Kennedy Sport Medicine ClinicUniversity of Western OntarioLondon, OntarioCanada

• Research Support– ISAKOS/OREF – Musculoskeletal Transplant 

Foundation– Canadian Institute for 

Health Research– Arthritis Society– Ontario Research Fund– Smith & Nephew Inc.– Arthrex Inc.– Conmed Inc. – Depuy Synthes Inc.– Eupraxia Inc.– SBM Inc.

• Editorial Board– AJSM Social Media

• Consultant– Smith & Nephew Inc.

– Conmed Inc.

– Depuy Synthes Inc.

– Ferring Inc.

– 3D4 Medical Inc.

– Ossur Inc.

Disclosures

• Epidemiology

• Classification of MLKI

• Presentation

• Assessment

• Decision making

Overview

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Epidemiology

• MLKI ‐ 0.02‐0.2% of all orthopedic injuries– Male:Female = 4:1– Bilateral cases rare <5%

• Mechanism of Injury– High energy – MVA, fall from height, sports trauma– Low energy – sports trauma, obese– Ultra‐low velocity MLKI

• BMI 49 vs 34 in main cohort• Female preponderance 

– 69% vs 24%• CPN injury 

– 39% vs 8%• Vascular injury 

– 28% vs 4.7%

• Schenk Classification

• Pattern of injury– Anterior 40%– Posterior 33%– Medial 4%– Lateral 18%– Rotatory

Classification

Presentation

• History/Mechanism of injury– Acute vs. chronic

• Physical Exam– ATLS– Reduce knee– Secondary survey

• Haemarthrosis• Gross laxity• Recurvatum

– Neurovascular status– Ligament exam

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Vascular Exam – selective arteriography

ABPI = Ankle Brachial Pressure Index

Neurological Exam

• Common Peroneal nerve– 25‐36% CPN palsy in knee dislocation– PCL/PLC – up to 45% of cases– Higher in ULV‐MLKI

• Generally carry poor prognosis– < 40% patients have full functional recovery– Dependent on injury pattern and severity

• Deep and Superficial branches

• Tinel Test – good to gauge recovery

• No place for NCS/EMG until 3 months (at least)

Peroneal nerve injured

Nerve contused

Observe ‐ 18 mths Skeletally immatureSkeletally mature

Nerve severely stretched

Nerve disrupted

Nerve GraftingTibialis Posterior TendonTransferNerve Recovery

Simplified Algorithm – Dr. Bruce Twaddle

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Clinical Examination: Gait

Clinical Examination

Clinical Examination

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Clinical Examination:  18 yr old elite level cheerleader

Imaging

• Plain Radiographs– AP/Lat/Rosenberg

– Stress Radiographs

– Hip to ankle alignment views (chronic)

• MRI

• CT– Associated fracture

– CT arteriogram

PCL Kneeling Stress Views

• Uninjured PCL

– 0‐4 mm SSD

• Isolated PCL

– 5‐12 mm SSD

• Complex Grade III PCL +

– >12mm SSD

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PCL Kneeling Stress Views

PCL Kneeling Stress Views

(LaPrade, Bernhardson, AJSM, 2010)

• Side-to-Side change• 3.2 mm =

complete sMCLtear

• 9.8 mm = complete medial knee injury

Right knee preop 6 months postop

Valgus Stress X-rays

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Side–to–side difference > 2.7 mm – FCL tear > 4 mm – complete posterolateral tear

(LaPrade, JBJS, 2008)

Varus Stress X‐rays

ND, 18 yr old elite level cheerleader

ND, 18 yr old elite level cheerleader

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Decision Making

• Operative vs. non operative?

• Early vs. delayed surgery?

• External fixator?

• Single or multi stage?

• Repair vs. reconstruct?

• Graft options?

• Technique?

• Tensioning pattern?

• Osteotomy?

• Rehabilitation?

• Early operative treatment

– Improved patient reported outcome (IKDC)

– Higher rates of return to work

– Higher rates of return to sport

Operative vs. non operative

• Vascular compromise

• Compartment syndrome

• Irreducible knee with ‘dimple’ sign

• External fixator

– Unable to hold reduction

– Obese

– Vascular injury

– MRI compatible implants

Absolute indications for early surgery……

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Summary

• High suspicion in multi injured patient

• ATLS – life and limb

• Thorough vascular and neurological exam

• Use stress views

• Try to avoid external fixator

Thank you