Download Imaging of Anatomy and Pathology of the Popliteal fossa: A Pictorial

Imaging of Anatomy and Pathology of the Popliteal fossa: A
Pictorial review
Poster No.:
C-2643
Congress:
ECR 2015
Type:
Educational Exhibit
Authors:
D. Santosh , R. White ; Newport/UK, Cardiff/UK
Keywords:
Embolism / Thrombosis, Cysts, Aneurysms, Diagnostic procedure,
MR, CT-Angiography, Musculoskeletal system, Anatomy
DOI:
10.1594/ecr2015/C-2643
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Learning objectives
1.
2.
3.
Illustrates normal anatomy of the popliteal fossa using schematic illustrations
and cross-sectional and angiographic imaging, highlighting important
variants.
Provides an overview of imaging modalities to investigate popliteal
pathologies.
Depicts a range of common and esoteric pathologies of the popliteal
fossa on multimodality imaging, with reference to clinical relevance and
subsequent management (endovascular or otherwise).
Background
Anatomy
The popliteal fossa is a quadrilateral structure situated at the posterior aspect of the knee.
Boundaries Fig. 1 on page 5
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•
Superior: Semimembranosus/semitendinosus and biceps femoris
Inferior: Medial and lateral heads of gastrocnemius
Contents Fig. 2 on page 8
•
•
•
•
•
Popliteal artery (PA) Fig. 3 on page 8
Popliteal vein (PV) Fig. 8 on page 12
Tibial nerve and Common peroneal nerve
Fat
Lymphnodes
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Fig. 8: Line diagram illustrates the PV. (1) Deep femoral vein; (2) Femoral vein; (3)
PV; (4) Anterior tibial vein; (5) Fibular vein; (6) Posterior tibial vein. Modified from [2]
References: Modified from [2]
Anatomical Variants of Popliteal artery
Incidence is 10%.
Knowledge of the normal variants of PA is essential for surgical approach and planning
bypass procedures.
There are 3 main types of variation in PA branching with further subtypes (Kim et al).[1]
•
•
•
Normal level of branching Fig. 4 on page 6
High division of the popliteal artery Fig. 5 on page 9
Hypoplastic or aplastic branching with altered distal supply Fig. 6 on page
10
Anatomical Variants of Popliteal vein
High origin of the popliteal vein from two or three tributaries is the common anatomical
variant (19%). Fig. 7 on page 12
True duplication of the popliteal vein is rare (5.1%) anatomical variant, but their presence
is considered as risk factor for deep vein thrombosis. [2]
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Fig. 7: Fig.8: Line diagram (A) & (B) shows high origin of the PV.(C) Illustrates true
duplication of the PV. Modifies from [2]
References: Modifies from [2]
Images for this section:
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Fig. 1: Popliteal fossa.(a)Semitendinosus;(b)Semimembranosus;(C)Medial head of
Gastrocnemius;(d)Long head of Biceps femoris;(e)Lateral head of Gastrocnemius.
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Fig. 4: Line diagram demonstrates High origin of the Trifurcation - Type IB. A common
anatomical variant of PA branching. Modified from [1]
Fig. 2: Axial MRI Image demonstrates the contents of the popliteal fossa and the inferior
margins.(a)PA ;(b)PV ;(c)Lateral Head of Gastrocnemius Muscle (LGHM);(d)Medial
Head of Gastrocnemius Muscle (MHGM);(e)Patella.
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Fig. 3: Coronal MRI image demonstrates both the popliteal artery and its branches. PA is
a continuation of superfical femoral artery beyond adductor hiatus. The PA divides in to
anterior tibial artery (AT) and tibial-peroneal trunk (TP) at the lower border of the popliteus
muscle.PT - Posterior tibial artery;PeR - Peroneal artery.
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Fig. 5: Line diagram illustrates high branching of PA - Type 2A; AT arises at or above
the knee joint. Modified from [1]
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Fig. 6: Line diagram illustrates Hypoplastic posterior tibial artery. Modified from [1]
Fig. 7: Fig.8: Line diagram (A) & (B) shows high origin of the PV.(C) Illustrates true
duplication of the PV. Modifies from [2]
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Fig. 8: Line diagram illustrates the PV. (1) Deep femoral vein; (2) Femoral vein; (3) PV;
(4) Anterior tibial vein; (5) Fibular vein; (6) Posterior tibial vein. Modified from [2]
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Findings and procedure details
Imaging techniques - Brief Review
Ultrasonography (USG)
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First line of imaging - Evaluation of swelling in the popliteal region
Doppler - Excellent for diagnosing venous thrombosis
Advantages - Easily available.No radiation/Iodinated contrast
Disadvantages - Operator dependant
Computed Tomography (CT)
•
•
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CT Angiogram Lower Limbs - Accurate diagnosis, imaging anatomy, surgical
planning
Non-contrast CT - Surgical planning for musculoskeletal pathology
Advantage - Quick & Multiplanar capability
Disadvantage - Radiation & IV contrast
Magnetic Resonance Imaging (MRI)
•
•
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MR Angiogram - Accurate diagnosis
Advantages - Multiplanar & Excellent spatial resolution
Disadvantage - Not easily available, IV contrast
Conventional Angiography
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Gold Standard for vascular assessment
Image acquisition - Early rapid phase (arterial anatomy) & delayed phase
(venous anatomy)
Imaging pathology
Overview of Common and Uncommon pathologies of the popliteal fossa described below
(Table -1)
Vascular
1.
2.
3.
4.
5.
PA atherosclerosis
PA embolus
PA aneurysm
PA adventitial cyst
PA entrapment syndrome
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6.
7.
PV Deep Vein Thrombosis
Superficial thrombophlebitis
Musculoskeletal
1.
2.
3.
Popliteal cyst or Baker's cyst
Lipoma
Necrotising fasciitis
Vascular Pathologies of the Popliteal fossa
Popliteal artery atherosclerosis
Atherosclerosis is the most common cause of popliteal artery occlusion.[9]
The clinical symptom varies depending on the degree of the disease ranging from single
vessel stenosis to complete occlusion. Fig. 9 on page 19 Fig. 10 on page 20 Fig.
11 on page 21 Fig. 12 on page 23 Fig. 13 on page 25
Conventional angiography is performed when endovascular or surgical intervention is
required.
Popliteal artery embolus
The source for the embolus in the PA are cardiac, aortic aneurysms and proximal arterial
plaque or ulceration. The macroemboli have a tendency to lodge in the lower popliteal
artery at the bifurcation. Fig. 14 on page 27
Popliteal artery aneurysm (PAA)
The PA measuring 7mm or more constitutes PAA (incidence - <0.1%). They are
associated with aneurysms in other locations including Abdominal Aortic Aneurysm in
30%-50%, contralateral PAA in 30% - 50% patients Fig. 15 on page 27 . The large
PAA's are at risk of thrombosis, distal embolus and rarely rupture. The complication rate
is 18% - 31%. [9, 10] Fig. 16 on page 27 Fig. 17 on page 29 Fig. 18 on page 31
Fig. 19 on page 32 Fig. 20 on page 34
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PA Adventitial Cyst Disease (ACD)
ACD is a rare vascular disease (0.1%) and occurs when mucoid cysts are formed within
the adventitia of the peripheral vessels. These adventitial cysts (AC) cause endoluminal
compression and eventually complete occlusion of the artery. The popliteal artery is the
most common location for ACD (85%).[3-5]
The diminished or loss of popliteal and foot pulses during the flexion of the knee (Ishizawa
sign) is a classical clinical sign.
Imaging findings: Doppler assessment shows avascular, anechogenic cyst in the wall of
the vessel. Fig. 21 on page 34 Fig. 22 on page 35 Fig. 23 on page 36 Fig. 24
on page 37
Angiography: depending on the position of the AC (concentric or eccenteric) the arterial
stenosis will demonstrate hourglass appearance or Schimitar sign. Although conventional
arteriography has been considered gold standard, it is non-specific and can be normal.
Popliteal artery entrapment syndrome (PAES)
PAES is a developmental abnormality described as popliteal artery compression due to
abnormal anatomical relation between the vessel and the surrounding muculotendinous
structures. [6-8]
I
PA medially displaced,Normal MHGM
#
II
Normal PA, laterally displaced MHGM
III
Compression of PA by abnormal slip of
gastrocnemius muscle
IV
The PA is entrapped by abnormal slip of
gastrocnemius muscle
V
Compression of PV
VI
Functional entrapment of PA. No aberrant
anatomy
#Medial Head of Gastrocnemius Muscle
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Imaging findings:
Stress Angiography: Occlusion of the popliteal artery during flexion or extension and nonocclusion in neutral position. Fig. 25 on page 39 Fig. 26 on page 39
MR Imaging and MRA: is excellent in evaluating both the vascular lumen and the
surrounding anatomy. Fig. 27 on page 40 Fig. 28 on page 41
PV deep vein thrombosis
DVT is a common clinical problem.
Imaging findings: The distended veins with limited or no compressibility and absent
Doppler flow with filling defect are characteristic sonographic features of acute DVT Fig.
29 on page 41
Superficial thrombophlebitis
Superficial thrombophlebitis refers to thrombus located in the superficial varicosities or
great or small saphenous vein. Fig. 30 on page 42 Fig. 31 on page 43
Musculoskeletal Pathologies of the Popliteal Fossa
Popliteal/Baker's cyst
Baker's cyst was first described in 1840 by Adams. They are a distension of the
gastrocnemius-semimembranosus bursa Fig. 32 on page 44 A communication with
the adjacent knee joint is found in most cases in adults but rarely seen in children.[11,
12] Fig. 34 on page 46 Fig. 33 on page 45
Lipoma
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It is the most common soft tissue tumour seen in the extremity. It can be catagorised in
to superficial and deep. Fig. 35 on page 47
Necrotising fasciitis (NF)
NF is a rapidly progressive infection of the soft tissue compartment including skin,
subcutaneous tissue, superficial fascia and muscle.
It is commonly a polymicrobial infection, but in 15% of cases a single pathogen, Group
A streptococci (flesh-eating bacteria) has been isolated.[13]
Imaging finding: On a CT the hallmark is the presence of air in the soft tissue with fluid
collections in the deep fascia. Fig. 36 on page 47 Fig. 37 on page 48
Images for this section:
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Fig. 9: Axial CT shows complete occlusion of the popliteal artery.
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Fig. 10: The volume rendered images of the CT Lower Limb Angiography, shows a short
right PA complete occlusion.
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Fig. 11: (a) Angiography confirmed the short right popliteal occlusion.
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Fig. 12: (b) & (c) The patient underwent balloon angioplasty with satisfactory post
dilatation angiographic results.
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Fig. 13: (b) & (c) The patient underwent balloon angioplasty with satisfactory post
dilatation angiographic results.
Fig. 14: A 71yr old female, known to have atrial fibrillation, presented with acute pain
in both the legs. Axial image of the CT angiogram lower limbs demonstrates complete
occlusion of bilateral popliteal artery.
Fig. 15: Axial CT angiogram lower limbs shows bilateral popliteal artery aneurysm, larger
on the right side.
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Fig. 16: 60yr man complained of right leg pain following right PAA repair. Selective right
lower limb angiogram was performed.
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Fig. 17: Selective right lower limb angiogram shows distal right popliteal bypass graft
stenosis. There is a bilobed aneurysm just distal to the distal graft anastamoses.
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Fig. 18: Subtracted right lower limb angiogram images shows distal right popliteal bypass
graft stenosis, a bilobed aneurysm just distal to the distal graft anastamoses and PTA
arterio-venous malformation(AVM) with early venous filling.
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Fig. 19: The distal graft stenosis was dilated with a 5x40mm balloon with initial wasting
being abolished. Satisfactory post-dilatation angiography results.
Fig. 20: Transverse colour Doppler USG image of the popliteal fossa shows thrombosed
popliteal artery aneurysm.
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Fig. 21: A 45yr male patient presented with symptoms of claudication in the left leg during
exercise. The colour Doppler axial image shows eccentric anechogenic adventitial cyst
adjacent to the popliteal artery. No vascular flow within the cyst.
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Fig. 22: Sagittal colour Doppler image demonstrates the popliteal artery and anechoic
adventitial cyst(arrow) with no vascular flow.
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Fig. 23: Axial CT section shows a well-defined eccentric hypodensity within the wall of
the PA consistent with adventitial cyst (Ac).
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Fig. 24: Coronal CT section demonstrates Adventitial Cyst.
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Fig. 25: Subtracted stress angiography demonstrating the patent popliteal artery(arrow)
in neutral position.
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Fig. 26: Subtracted stress angiography demonstrating the popliteal artery occlusion
(arrow) on flexion.
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Fig. 27: 40yr old male non-smoker presents with bilateral claudication. A strip of tissue
(arrow) passes inferomedially from the lateral aspect of the distal femur to abut the
popliteal vessels - Bilateral PAES (Type 4).
Fig. 28: 35yr old male presented with bilateral calf pain. Axial MRI images show lateral
displacement of the MHGM with normal popliteal artery - Bilateral PAES (Type 2).
Incidence of bilateral PAES is 30%.
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Fig. 29: Sagittal USG image of popliteal fossa shows popliteal vein thrombosis.
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Fig. 30: USG of the popliteal fossa shows an enlarged superficial vein containing some
low echogenic debris. This is suggestive of superficial thrombophlebitis. Popliteal vein
was normal.
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Fig. 31: There is an enlarged superficial vein with sluggish blood flow suggestive of
superficial thrombophlebitis.
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Fig. 32: USG of right popliteal fossa shows anechoic cystic structure between the
Gastrocnemius and Semimembranosus. This is consistent with uncomplicated Baker's
cyst.
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Fig. 33: USG of the popliteal fossa shows multiple mobile calcified bodies within the
Baker's cyst.
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Fig. 34: Longitudinal USG image demonstrates large multiloculated Baker's cyst.
Fig. 35: Sagittal image of the USG shows an isoechogenic well-defined lipoma.
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Fig. 36: A 60yr old diabetic man presented to the emergency department with pain,
redness and swelling of the right leg. Non-contrast axial image of the CT knee (soft tissue
window) demonstrates thickening of the skin, increased density of the subcutaneous
tissue and air (arrow)consistent with necrotising fasciitis.
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Fig. 37: A 60yr old diabetic man presented to the emergency department with pain,
redness and swelling of the right leg. Non-contrast sagittal image of the CT knee shows
air in the subcutaneous tissue.
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Conclusion
This exhibit will highlight the normal anatomy on multilodality imaging. In addition,
reminds the reader of the usual and also aid better understanding of the estoric vascular
and musculoskeletal pathologies seen in the popliteal fossa on imaging.
Personal information
References
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