Classification system
Crowe Classification
Crowe Classification of Developmental Dysplasia of the Hip
The Crowe classification grades developmental dysplasia of the hip in adults by how far the femoral head has migrated proximally, expressed as a percentage of the femoral head height and estimated from the pelvic height, giving four types: under 50%, 50–75%, 75–100% and over 100% subluxation.
What the Crowe category means
Crowe scores run from 1 to 4, where a lower score is better. The bands below are conventional reporting categories, not diagnostic cut-offs.
- Low dislocation (types I–II)1–2
The femoral head still articulates at least partly with the true acetabulum. Reconstruction at the anatomic centre of rotation is usually achievable.
- High dislocation (types III–IV)3–4
A separate false acetabulum, a deficient superolateral rim, a narrow femoral canal and shortened abductors. Small cups, structural grafting and femoral shortening osteotomy come into the plan.
Published criteria and reliability
The published cut-offs that define this instrument, and the measured agreement between observers using it. Each is reported with the population it was derived in.
| Type | Value | Subscale | Population | Follow-up | Source |
|---|---|---|---|---|---|
| Criterion | Subluxation less than 50% of femoral head height — type I | — | Adults with developmental dysplasia of the hip on an anteroposterior pelvic radiograph | — | Crowe JF 1979 |
| Criterion | Subluxation 50% to 75% — type II; 75% to 100% — type III; more than 100% — type IV | — | Adults with developmental dysplasia of the hip on an anteroposterior pelvic radiograph | — | Crowe JF 1979 |
| Criterion | Femoral head height is taken as 20% of pelvic height, measured from the iliac crest to the ischial tuberosity | — | Adult pelvic radiographs, as the denominator of the subluxation percentage | — | Crowe JF 1979 |
Criterion is a published cut-off, definition or performance figure belonging to a classification or decision rule — it is not a change score and should not be read as one.
How the score is calculated
Stated in full so the calculation can be independently checked, and reproduced by hand if needed.
Two distances are measured on a standardised anteroposterior pelvic radiograph: the vertical migration of the hip, taken from the interteardrop line to the medial head–neck junction, and the pelvic height, taken from the highest point of the iliac crest to the lowest point of the ischial tuberosity. The femoral head height is taken to be 20% of the pelvic height, a substitution Crowe adopted because a dysplastic femoral head is often too deformed to measure directly. The subluxation percentage is the migration divided by that estimated head height, expressed as a percentage — equivalently, migration divided by 0.2 times the pelvic height. Type I is less than 50% subluxation, type II is 50% to less than 75%, type III is 75% to less than 100% and type IV is 100% or more, which represents complete dislocation. Because both distances come from the same film the ratio is unaffected by magnification, but it is affected by pelvic rotation and tilt, which change the apparent position of the teardrops and the crest.
Missing data
Both measurements are required; there is no imputation. Where the teardrop is obscured or the iliac crest is not included on the film, obtain an adequate radiograph rather than estimating — an error of a few millimetres in either measurement can move a hip across a type boundary.
Instrument profile
- Developer
- John F. Crowe, Henry J. Mankin and Chitranjan S. Ranawat
- Institution
- Hospital for Special Surgery, New York, United States
- First published
- 1979
- Items
- 2
- Response format
- Two radiographic measurements in millimetres
- Score range
- 1 to 4
- Direction
- Lower score = better
- Completion time
- About 2 minutes
- Age range
- Adults
- Regions
- Hip
- Conditions
- Developmental dysplasia of the hip, Congenital hip dislocation, Hip dysplasia, Secondary hip osteoarthritis
- Procedures
- Total hip arthroplasty, Subtrochanteric shortening osteotomy, Acetabular bone grafting
- Validity
- The type correlates with the technical demands of hip replacement — the need for a small cup, for structural graft and for femoral shortening all rise with it — which is why it has remained the standard preoperative shorthand.
- Reliability
- Agreement is generally good because the method is a measurement rather than a judgement, but it depends on a well-centred film: pelvic rotation and tilt shift the teardrops and the crest and can move a hip between adjacent types.
When to use the Crowe
Well suited to
- Planning total hip arthroplasty in an adult with dysplasia, where the degree of proximal migration drives the choice of cup, the need for graft and the need for femoral shortening.
- Reporting dysplastic hip series, where Crowe type is the expected stratification.
- Communicating case complexity before surgery in a way that transfers between units.
Limitations and poor fits
- Children and infants, where dysplasia is assessed with the acetabular index, Graf ultrasound grading and the Tönnis grade of dislocation instead.
- As a description of the acetabulum: it says nothing about version, the size of the superolateral defect or the presence of a false acetabulum — the Hartofilakidis classification addresses those directly.
- Measuring on a rotated, tilted or coned-down film, or on films where the iliac crest or the teardrops are not visible.
- Grading acetabular dysplasia without dislocation, where the lateral centre-edge angle and the Tönnis (acetabular roof) angle are the relevant measurements.
Crowe compared with other instruments
Instruments measuring a related construct, with the practical difference between them.
| Instrument | Items | Range | What it adds |
|---|---|---|---|
| LCEA | 1 | 0–60 | The lateral centre-edge angle measures how far the acetabulum covers the femoral head laterally on an anteroposterior pelvis radiograph, where below 18 degrees indicates frank dysplasia, 18 to 25 degrees is borderline, 25 to 39 degrees is normal, and 40 degrees or more indicates overcoverage. |
| Tönnis Angle | 1 | -10–30 | The Tönnis angle measures the slope of the acetabular weight-bearing zone on an anteroposterior pelvis radiograph, where 0 to 10 degrees is normal, above 10 degrees indicates a steep upsloping roof associated with dysplasia and instability, and a negative angle indicates overcoverage. |
| Harris Hip Score | — | 0–100 | The Harris Hip Score is a 100-point clinician-administered hip assessment combining 44 points for pain, 47 for function, 4 for absence of deformity and 5 for range of motion, where 90 or above is graded excellent and below 70 poor. |
| Kellgren-Lawrence | 1 | 0–4 | The Kellgren-Lawrence classification grades radiographic osteoarthritis from 0 to 4 based on osteophyte formation, joint space narrowing, subchondral sclerosis and bone contour deformity, with grade 2 conventionally taken as the threshold for definite radiographic osteoarthritis. |
Copyright and permitted use
Published openly because it is the question every clinician and researcher asks before using an instrument, and almost nobody answers it.
A published radiographic measurement and classification method. No licence is required.
References
- Crowe JF, Mankin HJ, Ranawat CS. Total hip replacement in congenital dislocation and dysplasia of the hip. Journal of Bone and Joint Surgery (American Volume). 1979.
- Hartofilakidis G, Stamos K, Karachalios T, Ioannidis TT, Zacharakis N. Congenital hip disease in adults: classification of acetabular deficiencies and operative treatment with acetabuloplasty combined with total hip arthroplasty. Journal of Bone and Joint Surgery (American Volume). 1996.
Editorial status
This page has not yet been signed off by a named clinical reviewer. The scoring logic is stated in full above so it can be independently verified, and every threshold is traceable to its source. See our editorial methodology.