Below the Belt Ortho: Lower Extremity Injuries Missed in the ED

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

• Objectives:
  • 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

Knee Dislocation

Seroyer, et al. Management of the acute knee dislocation: the Pittsburgh experience. Injury. 2008;39:710–718.

• 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

Risk Factors

• Male
• High velocity injuries (high energy hyperextension)
• Obesity (for ultra low velocity dislocations, falls from standing or walking)

Classifying the injury:

1. Schenk: structures injured
2. Kennedy: direction of displacement
   • Anterior most common (40%)

Lachman, et al. Traumatic knee dislocatons: Evaluation, management, and surgical treatment. Orthop Clin N Am. 2015; 46:479-493.

Physical Exam

• 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
  • Paresthesias
  • 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

Imaging

Lachman, et al. Traumatic knee dislocatons: Evaluation, management, and surgical treatment. Orthop Clin N Am. 2015; 46:479-493.

Management

• 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:
  1. Quadriceps muscle and tendon
  2. Patella
  3. 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

Risk Factors

• M > F (8:1)
• > 40 years: peak 6-7th decade
• Systemic disease: RA, SLE, connective tissue disease, chronic steroids

Physical Exam

• Active straight leg raise (when supine, patient actively lifting leg up) – Extensor lag
• Audible crepitus
• Palpable gap or suprapatellar mass ^{8, 13}

Xray Findings

• 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

Ultrasound

• Quick and cost-effective
• Quadriceps tendon is superficial
• Varying sensitivity and specificity in the literature

Management

• Partial
  • Non-operative
  • Immobilized ~ 6 weeks
• Complete
  • 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.

Associated injuries

• Tibial plateau fracture
• Meniscal tear
• Intra-articular ligament ruptures ^{12, 15}

Risk Factors/Mechanism

• Unilateral
• < 40 years
• Knee flexed with quads contraction
• Steroid use, autoimmune disease ^{11, 16}

Physical exam

• Straight leg raise/knee extension – Extensor lag
• Feel for gap, mobile patella
• Assess for associated fracture ⁸

X-ray Findings

• 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}

Ultrasound

• Less sensitive and specific than quadriceps ultrasound
• False positives in obese and muscular patients
• Complete tear: Retracted, swelling, edge artefact, waviness ^{17, 19}

Management

• Surgical
• Risk of re-rupture is high!

Compartment Syndrome

• 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:

Von Keudell AG, Weaver M, Appleton PT, Bae DS, Syer GSM, Jupiter JB, Vrahas MS. Emergency surgery 3: Diagnosis and treatment of acute extremity compartment syndrome. The Lancet. 2015; 286: 1299-1310.

Tintinalli, et al. (2016). Emergency medicine: A comprehensive study guide (7th ed.) (p 1866). New York: McGraw-Hill, Medical Pub. Division.

Risk Factors

• 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

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

The numbers:

• 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

Management

• 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):

Maisonneuve Fracture. wikiRadiography. n. d. photograph, viewed February 15, 2017 http://www.wikiradiography.net/page/Maisonneuve+Fracture

• 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)
• 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

X-ray Interpretation

• 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
• Stress views (gravity or weighted) may be helpful to diagnose a syndesmotic injury ^{31, 33, 34}
  • High specificity but lower sensitivity

Tibiofibular overlap

Medical clear space

Tibiofibular clear space

Management

• No fracture, mild syndesmotic sprain (grade I)
  • Conservative management
• Severe injuries (grade II – III)
  • Surgical intervention
  • Considered unstable ^{31, 33, 34}

Summary

1. 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
2. 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
3. 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
4. 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)