With the protocols and time constraints of our ED environment, it is fairly easy to fall into the trap of imaging prior to examining our orthopedic patients. This may result in missed injuries, as we tend to base our diagnosis on the X-ray, rather than the patient assessment. In today’s post, we will review relatively common but frequently missed lower extremity orthopedic injuries including a general approach, focused assessment, and management of these injuries.
Introduction: Commonly Missed Lower Extremity Injuries
- “Orthopedic injuries are among the most likely conditions to be missed in the ED” 1
- The extremity injuries discussed in this post are mostly clinical diagnoses and include:
- Knee Dislocation
- Extensor Mechanism Injury
- Compartment Syndrome
- Tibiofibular Syndesmosis Injuries
- Increase awareness of 4 lower extremity injuries that are seen and sometimes missed in our EDs
- Develop an ED approach to these less common but serious MSK injuries
- Review the mechanism of injury, risk factors, physical examination, and management of these injuries with some clinical pearls
- Tibiofemoral dislocation leads to tremendous ligamentous disruption 2
- Rare: 0.5% of joint dislocations, but potentially limb-threatening:
- Amputation rate 11 – 86 % 3
- Nerve injury 14 – 35 % 4
- Popliteal artery injury 5 – 65% 5
Review of the Literature
Medina, et al. Vascular and neve injury after knee dislocation: A sytematic review. Clin Ortho Relat Res. 2014;472:2621-2629.
- 862 patients with knee dislocations
- 171 sustained vascular injury
- Weighted frequency of 18%.
- 80% (134 of 160) of vascular injuries underwent repair
- 12% (22 of 134) of vascular injuries resulted in amputation
Natsuhara, et al. What is the frequency of vascular injury after knee dislocation. Clin Orthop Relat Res. 2014;472:2615–2620.
- 11 million orthopaedic patients (ICD-9 diagnostic codes for all knee dislocation 2004 to 2009)
- 8050 limbs with knee dislocation identified
- 267 had a concomitant vascular injury for an overall frequency of 3.3%
- 34 of the 267 cases (13%) underwent surgical treatment
- Largest study to date, with data suggesting lower frequencies of vascular injury associated with knee dislocation and a lower proportion undergoing surgical management
- High velocity injuries (high energy hyperextension)
- Obesity (for ultra low velocity dislocations, falls from standing or walking)
Classifying the injury:
- Schenk: structures injured
- Kennedy: direction of displacement
- Anterior most common (40%)
- Examination is key, ½ spontaneously reduce prior to ED arrival
- +/- Knee swelling
- Knee capsule is usually torn with injury, which allows an associated hemarthrosis to dissipate into surrounding tissues
- Buckling knee with foot drop
- Loose knee on exam
- Absent/asymmetric distal pulses
- Posterior sag sign
- Knee hyper-extends when examiner lifts the foot by the heel
- Dimple sign 7, 8
- Ankle-Brachial Index (ABI)
- < 0.9 100 % PPV
- > 0.9 100 % NPV
- +/- Knee swelling
- Serial physical exams and ABI in ED are key
- Vascular will decide further imaging modalities, such as angiography
- IF the knee has not reduced spontaneously, early reduction is key
Extensor Mechanism Injury
- Extensor mechanism:
- Quadriceps muscle and tendon
- Patellar tendon
- Injury to any of these disrupts the extensor mechanism
- Highly disabling injury 11, 12
(1) Quadriceps Tendon Rupture
- 50% missed in ED 12
- ~ 1/3 of all extensor mechanism injuries 11
- M > F (8:1)
- > 40 years: peak 6-7th decade
- Systemic disease: RA, SLE, connective tissue disease, chronic steroids
- Active straight leg raise (when supine, patient actively lifting leg up) – Extensor lag
- Audible crepitus
- Palpable gap or suprapatellar mass 8, 13
- The Low Patella = Patella Baja
- From joint line to patella should be approximately 1 finger breadth, lower than this, think baja
- Check contralateral side, may be a variant of normal
- Avulsion patellar fragment
- Patellar spur
- Suprapatellar calcification
- Quick and cost-effective
- Quadriceps tendon is superficial
- Varying sensitivity and specificity in the literature
- Immobilized ~ 6 weeks
- Knee immobilizer
- Surgical management (timely) 8, 12, 14
(2) Patellar Tendon Rupture
The patellar tendon is the second strongest tendon in the human body, requiring a force of ~17.5 x body weight to rupture.
- Tibial plateau fracture
- Meniscal tear
- Intra-articular ligament ruptures 12, 15
- < 40 years
- Knee flexed with quads contraction
- Steroid use, autoimmune disease 11, 16
- Straight leg raise/knee extension – Extensor lag
- Feel for gap, mobile patella
- Assess for associated fracture 8
- The High Patella = Patella Alta
- Patella should be approximately 1 finger breadth from joint line, above this = alta
- Focal intratendinous radiolucency (FIR)
- Sens 82.5, spec 95.2%
- Avulsion inferior pole patella
- Avulsion tibial tuberosity
- Infrapatellar fat pad disruption 15, 17, 18
- Less sensitive and specific than quadriceps ultrasound
- False positives in obese and muscular patients
- Complete tear: Retracted, swelling, edge artefact, waviness 17, 19
- Risk of re-rupture is high!
- Definition: Increased pressure in a confined space 20
- 3 categories:
- More contents in the compartment
- Less volume within the compartment
- External pressure 2
- The lower leg is the most common location of acute extremity compartment syndrome, with the anterior and lateral compartments more frequently affected.
- ~31-36% of acute extremity compartment syndrome = from tibial diaphysis fractures 21
- Compartment locations/contents:
- M > F (10x if trauma)
- Young > old 21
Signs and Symptoms:
- “6 Ps”= pain, paralysis, paresthesia, pallor, pulselessness, poikilothermia
- “pain, pain, pain, …” – most important symptom
- Pain out of proportion
- Pain requiring increased analgesia
- Pain with passive stretch
- Paresthesias, hypoesthesias 24
- “pain, pain, pain, …” – most important symptom
Pressure Monitoring: General Principles
- Within 5 cm of fracture site
- Pain control
- Check all compartments involved
- Do not raise the affected limb above level of heart 22
- Normal pressures < 8 mm Hg (adults)
- First symptoms of ischemia 20 – 30 mm Hg
- Differential pressure: △P = Diastolic BP – intracompartmental BP ≤ 30 mm Hg 21, 22
Compartmental Pressure Monitoring
- High false positives associated with single measurement of pressure
- Continuous compartmental pressure monitoring not validated, not used frequently in Canada in lieu of clinical monitoring and serial physical exams
- In the awake, mentating patient:
- History and clinical exam
- Early ortho involvement
- Indications for compartmental pressure monitoring:
- Unresponsive/uncooperative patient
- Multiple distracting injuries 25, 26
Tibiofibular Syndesmosis Injuries (the High Ankle Sprain):
- A fibrous joint; complex between distal tibia and fibula
- Two bones plus 4 ligaments:
- Anterior tibiofibular ligament
- Interosseous ligament (IOL)
- Posterior inferior tibiofibular ligament (PITFL)
- Transverse tibiofibular ligament (TTL)
- Two bones plus 4 ligaments:
- Mechanism of Injury: External rotation + dorsiflexion ankle + eversion of talus 29
- ~20 % missed in ED 28
- 1-18% ankle sprains are high ankle sprains 30
Signs and Symptoms:
- ‘High ankle pain’ and anterolateral ankle pain
- Inability to weight bear or pain at push off
- Swelling proximal to ankle joint
- Pain with dorsiflex, external rotation 30, 31
Physical Examination: Special Tests
- Measurements = 1 cm above tibial plafond
- Tibiofibular overlap
- Normal > 1 mm mortise
- Normal > 6 mm AP 30, 31
- Medial clear space
- Normal ≤ 4 mm 28, 30, 31
- Tibiofibular clear space
- Distance between lateral border of posterior tibial prominence and medial border of the fibula
- Normal < 5 – 6 mm
- Tibiofibular overlap
- Stress views (gravity or weighted) may be helpful to diagnose a syndesmotic injury 31, 33, 34
- High specificity but lower sensitivity
- No fracture, mild syndesmotic sprain (grade I)
- Conservative management
- Severe injuries (grade II – III)
- Surgical intervention
- Considered unstable 31, 33, 34
- Knee Dislocations:
- Beware the ultra-low velocity
- Perform physical exam including ABI + pulses
- Some X-ray associated features such as medial joint space widening, segond fracture, and an arcuate fragment may be present
- Extensor Mechanism Injuries:
- Perform an active straight leg raise in every patient with knee injury
- Assess gaps in the extensor mechanism
- Assess whether the patella is high or low riding
- Ultrasound is a good adjunct
- Compartment Syndrome:
- PAIN is the key feature
- Fractures are a common cause(tibial fractures 36%)
- Measuring compartment pressures:
- One-time use is associated with high false positives
- Continuous use is not validated
- Indications for use: unresponsive/uncooperative patient or multiple distracting injuries
- Key value with pressure monitoring is delta pressure: △P = Diastolic BP – intracompartmental BP ≤ 30 mm Hg
- Syndesmotic Disruption:
- Consider with EVERSION mechanism or if patient has Weber B or C fracture
- A combination of special tests can be helpful in physical examination and x=X-ray measurements are key:
- Tibiofibular overlap > 6 mm AP
- Medial clear space < 4 mm
- Tibiofibular clear space < 5-6 mm (AP & mortise)
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- Natsuhara, K.M., Yeranosian, M.G., Cohen, J.R. et al, What is the frequency of vascular injury after knee dislocation. Clin Orthop Relat Res. 2014;472:2615–2620.
- Medina O, Arom GA, Yeranosian MG, Petrigliano FA, McAllister DR. Vascular and neve injury after knee dislocation: A sytematic review. Clin Ortho Relat Res. 2014;472:2621-2629.
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