• Skip to primary navigation
  • Skip to main content
  • Skip to primary sidebar
  • Home
  • TeleConsult
  • About
  • Newsletter/Updates
  • Contact Us
  • Policies

Bone and Spine

Orthopedic health, conditions and treatment

  • General Ortho
  • Procedures
  • Spine
  • Upper Limb
  • Lower Limb
  • Pain
  • Trauma
  • Tumors

Trochlear Dysplasia of Femur

By Dr Arun Pal Singh

In this article
    • Biomechanics of the Proximal Trochlea
    • Diagnosis of Trochlear Dysplasia
      • Xrays
      • Crossing Sign
      • Trochlear Depth
      • Trochlear Bump
      • Double Contour Sign
      • Trochlear Angle or Sulcus Angle
    • Classification of Trochlear Dysplasia
      • Type A
      • Type B
      • Type C
      • Type D
    • Findings in Different Types of Trochlear Dysplasia
      • Type A
      • Type B
      • Type C
      • Type D
    • MRI in Trochlear Dysplasia
      • Lateral Trochlear Inclination
      • Trochlear facet asymmetry
      • Trochlear depth
    • Treatment of Trochlear Dysplasia
      • Albee trochleoplasty
      • Deepening Trochleoplasty
      • Wedge Resection Trochleoplasty
    • References
      • Related

Trochlear dysplasia refers to a pathologic alteration in the shape of the femoral trochlea. Trochlea is also called facies patellaris, intercondylar groove, or intercondylar sulcus.

Normal trochlea is sufficiently concave to guide and retain the patella throughout the normal range of movement.

However trochlear dysplasia may cause the groove to be shallower than normal or even flat or convex.

This predisposes the patient to patellar instability or even dislocation.

The primary contributors to patellar instability are trochlear dysplasia, quadriceps dysplasia/patellar tilt, patella alta and tibial tuberosity–trochlear groove distance.

In trochlear dysplasia, the trochlear joint surface is flattened proximally, and the concavity is less pronounced distally or the trochlear surface may even become convex with increasing hypoplasia of the medial joint surface.

As trochlear dysplasia is frequently bilateral, it is said to be a developmental anomaly.

The criteria for diagnosing trochlear dysplasia were first defined for x-rays but MRI has shown its superiority over conventional x-rays and is the procedure of choice for diagnosis of trochlear dysplasia.

Biomechanics of the Proximal Trochlea

In full knee extension, the patella lies just superolateral to the most superior portion of the trochlea. The patella starts moving at approximately 10° of flexion downward from this position to enter the trochlea.

And this explains from another angle

The most proximal part of the is the shallowest and it is the part that patella encounters in very early flexion.

Being shallow this part offers the least stability to the patella and here the patella is most susceptible to dislocation. [Hence the reason that patellar dislocation often occurs in the presence of patella alta as it articulates with the proximal shallow portion of the trochlea for a longer time]

With further flexion, the trochlear floor deepens and is able to provide greater stability.

provides increased patellar stability. Thus, it is rare for the patella to dislocate from the distal, or more inferior, portions of the trochlear groove. Consequently, any trochlear measurements that are relevant to patellar stability must be made proximally, that is, in the early stages of knee flexion.

Diagnosis of Trochlear Dysplasia

Xrays

Crossing Sign

Crossing sign is seen in about 96% of abnormal cases and is seen in the lateral view of knee x-ray. The crossing sign is positive when the contours of the trochlear floor and of the lateral femoral condyle intersect at any level.

This indicates that, at that level, the lateral side of the trochlea is flat or, equivalently, the trochlear floor is flush with the lateral condyle.

Trochlear Depth

Measurement of trochlear depth for trochlear dysplasia
Image 1 -Measurement of Trochlear Depth

For trocheal depth draw lines as follow

  • A vertical line is along the posterior cortex of the femoral diaphysis (Green dotted line)
  • Draw a second horizontal line (dashed green line) is drawn at the vertical level of the most proximal point of the posterior contour of the femoral condyles [Shown by blue arrow]. This marks the concavity of the femoral metaphysis giving way to the convexity of the posterior femoral condyles.
  • Draw third line anteroinferiorly[beginning at the intersection of above two lines] and angled 15° from the horizontal line (solid green line).
  • Measure distance between the osseous trochlear floor and lateral condyle(red line).

A value of 4 mm or less is abnormal. Trochlear depth is shallow in 85% of abnormal cases.

Trochlear Bump

trochlear bump measurement

For measuring the trochlear bump draw a line along the most distal 10 cm of the anterior cortex of the femoral diaphysis. [green line]

Measure the distance from this line at the most anterior extent of the trochlear floor(red line).

A value of +3 mm or greater is considered pathological.

[Trochlear beak/spur or spur is an angular projection of the most proximal portion of the trochlea and should not be confused with bump].

Double Contour Sign

The double contour sign indicates that the contour of the medial femoral condyle is significantly smaller than that of the lateral femoral condyle.

Trochlear Angle or Sulcus Angle

The trochlear angle refers to the opening angle of the trochlea as visualized on a 30° flexion axial radiograph. The normal value is >145 degrees.

It is shallow in 65% of abnormal cases.

Classification of Trochlear Dysplasia

Signs of trochlear dysplasia are found in more than 85% of patients with patellar dislocation.

Following classification by Dejour describes four types of trochlear dysplasia

Type A

type A trochlear dysplasia
Type A trochlear dysplasia

The normal shape of the trochlea preserved but a shallow trochlear groove.

Type B

Markedly flattened or even convex trochlea

Type B trochlear dysplasia
Type B trochlear dysplasia

Type C

type C trochlear dysplasia
type C trochlear dysplasia

Asymmetric trochlear facets, with the lateral facet being too high and the medial facet being hypoplastic, which results in the flattened joint surface forming an oblique plane

Type D

Type D trochlear dysplasia
Type D trochlear dysplasia

Findings in Different Types of Trochlear Dysplasia

Type A

  •  Crossing sign
  • Axial CT shows shallow trochlea [but not flat.]

Type B

  • Trochlear spur
  • On axial images trochlea is flat.

Type C

  • No trochlear spur
  • Double contour sign
  • On axial images, these trochlea is convex, with a hypoplastic medial condyle.

Type D

  • Double contour sign
  • Crossing sign
  • Trochlear spur
  • On axial images, these trochleae have a sharp convex “cliff” separating the medial and lateral facets.

In addition to the features of type C, a vertical link between the medial and lateral facets (cliff pattern on parasagittal images).

MRI in Trochlear Dysplasia

Axial and sagittal MR images allow better and accurate identification of the type of trochlear anomaly.

Trochlear dysplasia can be evaluated at MR imaging by determining lateral trochlear inclination, trochlear facet asymmetry, or trochlear depth.

Lateral Trochlear Inclination

Trochlear Inclination Measurement
Trochlear Inclination Measurement

 

It is the angle formed between the plane of the lateral trochlear facet subchondral bone and a tangential line through posterior femoral condyles. An angle of <11º is considered abnormal.

Trochlear facet asymmetry

This is the ratio of a width of the medial trochlear facet width to lateral trochlear facet width and measured in the axial plane. A ratio of <0.4 is considered abnormal [that means the medial facet is <40% the width of the lateral facet].

Trochlear depth

This measures the inset depth of the trochlear groove or sulcus relative to the mean of the medial and lateral femoral condyle outsets.  It is determined by axial imaging at the same level as the trochlear facet asymmetry. A trochlear depth of <3 mm is considered abnormal.

Treatment of Trochlear Dysplasia

Trochlear dysplasia can be corrected using surgery.

 

Albee trochleoplasty

Albee Trochleoplasty

It involves a  coronally-oriented opening osteotomy of the lateral femoral condyle which steepens the inclination of the lateral trochlea.

But it does not address the apparent cause i.e. elevated trochlear floor. The procedure tends to lift the patella further away from the femur, narrowing the angle between the vectors of the quadriceps and patellar tendons and causing more cartilage loading.

Deepening Trochleoplasty

 

This procedure involves removing a near full-width coronal slab of cancellous bone from the anterior femur and then bluntly depressing the central trochlear surface into the surgical defect to create the new trochlear floor (Figure 15). A procedure described by Bereiter et al.29 is similar but involves a thinner flap of the trochlear surface.

Deepening Trochleoplasty
Deepening Trochleoplasty

 

Wedge Resection Trochleoplasty

Wedge resection trochleoplasty
Wedge resection trochleoplasty

For those trochleae that contain a prominent bump. A wedge of cancellous bone is removed from the anterior femur, and the superior aspect of the trochlea is tilted posteriorly into the surgical defect to make it flush with the anterior diaphyseal cortex.

References

  • Fulkerson JP. Disorders of the Patellofemoral Joint. 4th ed. Philadelphia, PA: Lippincott, Williams, & Wilkins; 2004.
  • Rémy F, Chantelot C, Fontaine C, Demondion X, Migaud H, Gougeon F. Inter- and intraobserver reproducibility in radiographic diagnosis and classification of femoral trochlear dysplasia. Surg Radiol Anat. 1998;20(4):285–9.
  • Dejour D, Saggin P. The sulcus deepening trochleoplasty—the Lyon’s procedure. Int Orthop. 2010 Feb;34(2):311–6.
  • Pfirrmann CW, Zanetti M, Romero J, Hodler J. Femoral trochlear dysplasia: MR findings. Radiology. 2000 Sep;216(3):858–64.

All Images in the article are courtesy of Radsource.us

Related

Spread the Knowledge
7
Shares
 
7
Shares
 7   

Filed Under: Knee

About Dr Arun Pal Singh

Arun Pal Singh is an orthopedic and trauma surgeon, founder and chief editor of this website. He works in Kanwar Bone and Spine Clinic, Dasuya, Hoshiarpur, Punjab.

This website is an effort to educate and support people and medical personnel on orthopedic issues and musculoskeletal health.

You can follow him on Facebook, Linkedin and Twitter

Primary Sidebar

Browse Articles

Fluoroscopic Image of Nuceloplasty

What Is Nucleoplasty?

Nucleoplasty is a percutaneus procedure where a catheter is percutaneously inserted into the intervertebral disc under fluoroscopy. The catheter has low-temperature resister probe to disintegrate and evacuate disc material causing disc decompression. The nucleoplasty is percutaneous and does not require any incision. Indications for Nucleoplasty It is most useful in patients with nerve root irritation […]

Elbow joint bones

Elbow Joint Anatomy and Significance

The elbow joint is made up of three bones, the humerus, ulna, and radius. Elbow joint connects the proper arm to the forearm. It is a  synovial joint structurally but functionally is a hinge joint. Elbow joint allows flexion and extension. There are actually three joints at the elbow. Humeroulnar joint – Hinge joint formed […]

complex-regional pain syndrome lower limb

Complex Regional Pain Syndrome or CRPS

Complex regional pain syndrome or CRPS is a chronic painful condition causing intense pain, usually in the arms, hands, legs, or feet. The cause of condition is poorly understood and there is no cure. The management involves control of symptoms by various modalities. The condition It may happen after an injury to a nerve or […]

Enchondromatosis or ollier disease upper limb

Ollier Disease – Causes, Presentation and Treatment

Ollier’s disease is a rare, nonhereditary skeletal disorder characterized by a multifocal intramedullary proliferation of hypercellular dysplastic cartilage. It is a type of enchondromatosis. Maffucci’s syndrome is another type of enchondromatosis where the skeletal lesions are accompanied by hemangiomas of skin, soft tissu, and viscera. Enchondromatosis represents a distinct developmental disorder of enchondral ossification and […]

Layer by layer dissection of tissues of forearm

Dynamic Compression Plate Fixation Procedure for Forearm

A patient with fracture proximal radius and ulna was treated by dynamic compression Plate fixation. Fractures of forearm bones [radius or ulna or both] require open reduction and internal fixation in most of the adult cases. While ulna is subcutaneous bone which you can palpate from elbow to wrist,the radius is deep situated. The radius can […]

L3 Compression Fracture

Thoracolumbar Spine Injuries Presentation and Treatment

Thoracolumbar spine injuries refer to injuries of the thoracic and lumbar spine. Thoracic spine has 12 vertebrae from T1 to T12 whereas lumbar vertebrae are five in number are mostly caused by two-wheeler accidents. Injuries to both these regions are considered together because the pattern of injury and their treatment is similar. Thoracolumbar spine injuries are […]

Leg Length Measurement with Tape

True and Apparent Leg Length Measurement

True and apparent leg length refer to limb lengths in absolute terms and in compensated forms. The limb length measurement is used to find leg length discrepancy if any. When there is a shortening of the limb, the body compensates by tilting the pelvis down, equinus position of the foot and flexion of the opposite […]

© Copyright: BoneAndSpine.com
Manage Cookie Consent
The site uses cookies. Please accept cookies for a better visiting experience.
Functional Always active
The technical storage or access is strictly necessary for the legitimate purpose of enabling the use of a specific service explicitly requested by the subscriber or user, or for the sole purpose of carrying out the transmission of a communication over an electronic communications network.
Preferences
The technical storage or access is necessary for the legitimate purpose of storing preferences that are not requested by the subscriber or user.
Statistics
The technical storage or access that is used exclusively for statistical purposes. The technical storage or access that is used exclusively for anonymous statistical purposes. Without a subpoena, voluntary compliance on the part of your Internet Service Provider, or additional records from a third party, information stored or retrieved for this purpose alone cannot usually be used to identify you.
Marketing
The technical storage or access is required to create user profiles to send advertising, or to track the user on a website or across several websites for similar marketing purposes.
Manage options Manage services Manage vendors Read more about these purposes
View preferences
{title} {title} {title}
 

Loading Comments...