Perthes lateral pillar classification: Definition, Uses, and Clinical Overview

Posted on February 28, 2026 | by drhip

Perthes lateral pillar classification Introduction (What it is)

Perthes lateral pillar classification is a way clinicians describe how much of the femoral head is affected in Legg–Calvé–Perthes disease.
It is based on what the hip looks like on an X-ray at a specific stage of the condition.
The system groups hips into categories that broadly reflect severity and expected shape during healing.
It is commonly used in pediatric orthopedics and in research to communicate prognosis in a standardized way.

Why Perthes lateral pillar classification used (Purpose / benefits)

Legg–Calvé–Perthes disease (often shortened to “Perthes disease”) is a childhood condition where blood supply to the femoral head (the “ball” of the ball-and-socket hip joint) is temporarily disrupted, leading to bone weakening and remodeling over time. Because the femoral head can change shape as it heals, clinicians need a consistent way to describe how much of the femoral head is structurally involved.

Perthes lateral pillar classification helps solve several practical problems:

Prognosis (expected outcome): It provides a structured estimate of how likely the femoral head is to maintain a round shape as the condition evolves. This matters because femoral head shape can influence hip motion and long-term joint mechanics.
Treatment planning framework: The grouping can help clinicians discuss overall management intensity (for example, closer monitoring versus more aggressive containment strategies). Specific choices vary by clinician and case.
Clear communication: The terms “Group A,” “Group B,” and so on allow orthopedic teams, radiologists, and therapists to speak the same language.
Follow-up consistency: It gives a reference point for tracking the disease course over time, especially when multiple clinicians are involved.
Research comparability: Studies often use standardized classifications so patients with similar imaging patterns can be compared.

Importantly, Perthes lateral pillar classification is descriptive and prognostic—it is not a treatment by itself, and it does not replace a full clinical evaluation.

Indications (When orthopedic clinicians use it)

Orthopedic clinicians typically use Perthes lateral pillar classification in scenarios such as:

A child with suspected or confirmed Legg–Calvé–Perthes disease based on symptoms (limp, hip/groin/thigh pain) and imaging
Baseline severity assessment after Perthes disease is diagnosed and staging is appropriate
Ongoing monitoring to document severity patterns consistently over time
Pre-treatment discussions when comparing general management pathways (nonoperative monitoring, bracing/containment concepts, or surgery—varies by clinician and case)
Second opinions or referrals, when standardized wording helps continuity of care
Clinical research or registry documentation where consistent categorization is required

Contraindications / when it’s NOT ideal

Perthes lateral pillar classification is not always suitable or may be less reliable in these situations:

Very early Perthes disease, before the characteristic stage used for this classification is visible on X-ray (classification depends on specific radiographic features)
Poor-quality or incomplete imaging, where key landmarks of the femoral head cannot be evaluated confidently
Atypical diagnoses, such as other causes of avascular necrosis or hip disorders where the lateral pillar concept does not apply
Prior hip surgery or major deformity that changes the anatomy and makes comparisons difficult
Nonstandard positioning during radiographs that distorts femoral head height and apparent collapse
Adult avascular necrosis, where different staging and classification systems are typically used

In such cases, clinicians may rely more on overall staging, alternative classification systems, or advanced imaging (varies by clinician and case).

How it works (Mechanism / physiology)

Perthes lateral pillar classification is grounded in a simple structural idea: how much of the outer (lateral) portion of the femoral head remains tall and supportive during the disease process.

The relevant hip anatomy (plain-language overview)

The femoral head is the “ball” at the top of the thigh bone.
The acetabulum is the “socket” in the pelvis.
The smooth movement of the hip depends on the femoral head remaining rounded and well-centered in the socket.
In Perthes disease, the femoral head goes through phases where bone becomes weaker, may flatten or collapse, and then gradually reforms.

What the “lateral pillar” means

On an AP (front-to-back) pelvic X-ray, clinicians conceptually divide the femoral head into vertical regions. The lateral pillar refers to the outer supporting column of the femoral head’s bony structure.

During the stage when the femoral head looks fragmented (often called the fragmentation stage), this outer column can appear:

Well preserved (maintaining height)
Partially collapsed
Severely collapsed

The amount of preserved height in this lateral portion is associated with how well the femoral head may maintain or regain a more spherical shape as healing continues.

Onset/duration or reversibility

Because Perthes lateral pillar classification is a classification system, not a treatment, it does not have an “onset” or “duration” in the way a medication or procedure would. Instead:

It is typically applied at a specific time in the disease course when the X-ray appearance supports reliable grouping.
The apparent category can change as the hip evolves, especially early on, which is one reason follow-up imaging and clinical context matter.

Perthes lateral pillar classification Procedure overview (How it’s applied)

Perthes lateral pillar classification is not a procedure performed on the body. It is a structured way to interpret imaging and document severity. A typical high-level workflow looks like this:

Evaluation / exam – A clinician assesses symptoms (often limp and hip or groin discomfort) and examines hip motion. – History and physical findings help decide whether imaging is needed and what other diagnoses should be considered.
Preparation – Standard hip radiographs are obtained, often including an AP pelvis view and other views depending on local practice. – Positioning matters because the classification relies on comparing relative heights and contours.
Testing / classification – The clinician (often with radiology input) determines whether the hip is in a stage where the lateral pillar assessment is considered reliable. – The lateral pillar height is visually assessed and compared with expected height/structure. – The hip is assigned to a lateral pillar group (commonly A, B, B/C borderline, or C).
Immediate checks – The clinician documents the group and may note any uncertainties (for example, borderline features or suboptimal imaging). – The classification is interpreted alongside age, range of motion, hip “containment” (how well the femoral head sits in the socket), and other imaging findings.
Follow-up – Repeat clinical visits and imaging may be used to track progression and adjust documentation as the disease evolves. – Any management plan is individualized and may change over time (varies by clinician and case).

Types / variations

Perthes lateral pillar classification is often associated with the Herring lateral pillar classification framework. The commonly described groupings include:

Group A
The lateral pillar is relatively preserved in height and structure.
This pattern is generally interpreted as less severe on radiographs.
Group B
The lateral pillar shows partial loss of height, suggesting moderate structural involvement.
Group B/C (borderline)
A “borderline” category used when findings fall between B and C.
This acknowledges that real-world X-rays do not always fit neatly into one box and that interpretation can vary.
Group C
The lateral pillar shows more substantial collapse, suggesting more extensive involvement.

Common practical variations in how it is used include:

Stage-aware application: Some clinicians emphasize that the classification is most informative at particular radiographic stages (often when fragmentation is clear).
Combined interpretation: The lateral pillar group is frequently considered alongside other factors (such as age at presentation and hip range of motion) rather than used alone.
Reporting style differences: Some reports include narrative descriptions (for example, “moderate lateral pillar loss”) in addition to a letter group, especially if imaging is borderline.

Pros and cons

Pros:

Provides a standardized language for describing radiographic severity in Perthes disease
Helps with broad prognosis discussions in a way that is easier to communicate than purely narrative descriptions
Supports care coordination among orthopedics, radiology, and therapy teams
Useful for research and comparison across studies and institutions
Can be applied using widely available X-rays, without requiring advanced imaging in every case

Cons:

Stage-dependent reliability: It may be harder to apply confidently very early in the disease course
Interpretation variability: Different readers may not always assign the same group, especially for borderline cases
Two-dimensional limitation: X-rays compress 3D anatomy into 2D images, which can hide or exaggerate deformity
Does not capture all clinically relevant factors (pain, function, hip motion, and containment still matter)
Not designed for other hip conditions (adult avascular necrosis and other pediatric hip disorders use different systems)
The category may change over time as radiographic features evolve, complicating “one-time” labeling

Aftercare & longevity

Because Perthes lateral pillar classification is an imaging-based label rather than a treatment, “aftercare” is best understood as what influences how the classification is used over time and how outcomes are assessed.

Factors that commonly affect overall interpretation and long-term hip outlook include:

Severity and extent of femoral head involvement, as reflected by the lateral pillar group and other imaging features
Timing in the disease course when the classification is assigned (earlier images may be less definitive)
Age at presentation, which clinicians often consider alongside imaging because growth and remodeling potential vary across childhood
Hip range of motion and function, which influence how the hip is managed and monitored
Follow-up consistency, since Perthes disease evolves over months to years and imaging findings can change
Rehabilitation and activity modification plans, when used, which are individualized and guided by the care team (varies by clinician and case)
Any bracing or surgical decisions, if pursued, as these depend on multiple clinical and imaging variables rather than the classification alone

In practical terms, the “longevity” of the classification is that it remains a useful reference point in the medical record, even though the hip’s radiographic appearance may evolve and the assigned group may be revisited.

Alternatives / comparisons

Perthes lateral pillar classification is one of several ways clinicians describe Perthes disease severity and expected outcomes. Alternatives and complements include:

Observation/monitoring without formal grouping
Some clinicians emphasize longitudinal clinical exams and serial imaging reports rather than a named classification.
This may be used when imaging is too early or unclear for confident lateral pillar assignment.
Other Perthes classification systems
Catterall classification: Another radiographic system that describes extent of femoral head involvement.
Salter–Thompson classification: Uses specific radiographic features (including subchondral fracture patterns) in certain stages.
Stulberg classification: Often used later to describe the final shape/outcome after healing rather than early severity.
These systems may be used alongside, instead of, or in addition to lateral pillar grouping, depending on clinician preference and case details.
Advanced imaging (MRI)
MRI can show bone and cartilage changes and may detect abnormalities earlier than plain X-ray in some cases.
MRI can be helpful when X-rays are nondiagnostic or when clinicians need more detail, but availability, cost, and the need for child cooperation vary.
Clinical-functional assessment tools
Range of motion, gait evaluation, and functional status are not “alternatives” to imaging classifications, but they are essential complements.
Many management decisions are based on the combined picture rather than any single imaging label.

Overall, Perthes lateral pillar classification is valued for being practical and widely understood, while other approaches may add detail, apply at different stages, or describe different endpoints.

Perthes lateral pillar classification Common questions (FAQ)

Q: What condition is Perthes lateral pillar classification used for?
It is used for Legg–Calvé–Perthes disease, a childhood condition involving temporary loss of blood supply to the femoral head. The classification describes how much of the outer supporting portion of the femoral head appears preserved on X-ray. It helps summarize radiographic severity in a standardized way.

Q: Does a lateral pillar group diagnose Perthes disease?
No. The classification is typically applied after Perthes disease is suspected or diagnosed based on symptoms, examination, and imaging. It is mainly used to describe severity and support prognosis discussions.

Q: What do Groups A, B, B/C, and C mean in plain language?
They broadly reflect how well the outer “support column” of the femoral head maintains its height during a key stage of the disease. Group A generally indicates more preserved structure, while Group C indicates more loss of structural height. Group B/C is used when findings fall between categories.

Q: Can the Perthes lateral pillar classification change over time?
Yes, it can. Perthes disease evolves through stages, and the X-ray appearance can change as the bone weakens and later heals. Clinicians may update or refine the classification as clearer imaging features appear.

Q: Is Perthes lateral pillar classification used to decide whether surgery is needed?
It can be one factor among many, but it is not the only factor. Age, hip motion, how well the femoral head is positioned in the socket, symptoms, and disease stage also matter. Specific decisions vary by clinician and case.

Q: Does the classification tell how much pain a child will have?
Not directly. The classification describes X-ray appearance, which does not perfectly predict pain levels or day-to-day function. Pain and limping can vary widely among children, even with similar imaging.

Q: Is it safe to get the X-rays needed for this classification?
Hip radiographs involve exposure to ionizing radiation, but they are commonly used in pediatric orthopedics when clinically indicated. Facilities generally aim to use the lowest exposure that still provides diagnostic quality. Questions about imaging frequency are best discussed with the treating team.

Q: How much does it cost to get a Perthes lateral pillar classification?
There is usually no separate “classification fee,” because it is part of interpreting imaging and the orthopedic visit. Total cost depends on the clinic setting, insurance coverage, region, and whether additional imaging is needed. For out-of-pocket estimates, costs vary by clinician and case.

Q: How long do the results “last”?
The label itself remains in the medical record, but the hip’s appearance can change as the condition progresses and heals. Follow-up imaging is often used to reassess the disease stage and overall alignment. The classification is best viewed as a snapshot at a point in time.

Q: Can a child go to school, play sports, drive, or work with Perthes disease?
Activity decisions are individualized and depend on symptoms, hip motion, disease stage, and clinician recommendations. Some children may continue many normal routines with modifications, while others may need more restrictions for a period. Guidance varies by clinician and case, and this classification alone does not determine what activities are appropriate.