Perkins line

In the normally located hip, the ossified femoral-head epiphysis should lie below Hilgenreiner line and medial to Perkin line, within the inferomedial quadrant. When the femoral head is not yet ossified, the position of the proximal femur relative to these landmarks remains useful. Modern descriptions specifically define Perkin line as perpendicular to Hilgenreiner line at the lateral acetabular roof.

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History of the Perkins line

1925 – Heinrich Hilgenreiner (1870–1953) described a horizontal baseline connecting the two Y-shaped (triradiate) cartilages as part of a wider radiographic measurement system for congenital hip dislocation. He extended this line laterally and used perpendicular measurements from the proximal femora to quantify superior displacement, together with measurements of lateral displacement and acetabular inclination.

My procedure is to draw a horizontal line connecting the two Y-shaped cartilages.

Importantly, Hilgenreiner’s perpendiculars arose from the proximal femora. They were therefore not the modern Perkin lines.

1928 – George Perkins (1892–1979) published Signs by which to diagnose congenital dislocation of the hip in The Lancet. His aim was to provide a simple radiographic method that could show whether the femoral head was displaced upwards or outwards. Perkins first drew his own transverse reference:

Draw a horizontal line joining A to A; A is the innermost part of the ilium at the Y-shaped cartilage of the acetabulum.

He then drew a perpendicular through the lateral pelvic landmark B. The femoral-head ossification centre should lie below the horizontal line and medial to the perpendicular; superior or lateral displacement suggested congenital dislocation

These two lines will show whether the head of the femur is further up or further out than it should be

1980 – Jørgen Reimer incorporated Perkin lines perpendicular to Hilgenreiner line into his radiographic assessment of hip migration in children with cerebral palsy. The resulting migration percentage quantified the proportion of the femoral head lying lateral to the acetabular boundary. This embedded the Hilgenreiner–Perkin construction in paediatric hip assessment.

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Associated Persons

• Heinrich Hilgenreiner (1870-1953) and the Hilgenreiner line
• Edward Warren Hine Shenton (1872–1955) and the Shenton line
• George Perkins (1892-1979) and the Perkins line
• Dietrich Tönnis (1927-2010) and the Tönnis angle

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Alternative names

• Perkin’s line
• Perkin line
• Perkins’ line

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Eponymythology

Hilgenreiner’s vertical lines are not Perkin lines.

Hilgenreiner starts with the femur. He drops a perpendicular from the centre of the proximal femur onto his horizontal Y-cartilage baseline. The position of that perpendicular therefore changes when the femur moves. He then derives h and d from that construction.

Perkins starts his vertical from the pelvis. Point B is a fixed pelvic landmark — explicitly the anterior inferior iliac spine / prominent outer lower iliac angle on the radiograph — and he drops a vertical from B to intersect his A–A transverse line. The femoral head is then judged relative to that fixed boundary.g represents a later synthesis of two closely related but not identical historical constructions.

Feature	Hilgenreiner, 1925	Perkins, 1928	Modern terms
Horizontal reference	A “connecting line of the two Y-cartilages extended laterally.“	“Draw a horizontal line joining A to A”; A = “the innermost part of the ilium at the Y-shaped cartilage of the acetabulum.”	Hilgenreiner line: horizontal through the superior aspects of the two triradiate cartilages.
Vertical reference	A perpendicular is dropped from the centre of the proximal/central end of each femur to the horizontal baseline. The vertical moves with the femur; it is a measurement line, not a fixed pelvic landmark.	A vertical is drawn from B, which Perkins identifies as the anterior inferior iliac spine, “the prominent outer lower angle of the ilium as seen on the radiogram”, meeting A–A at right angles.	Perkin linne: perpendicular to Hilgenreiner line through the lateral-most acetabular roof / lateral acetabular margin.
Superior displacement	Quantified as h: perpendicular distance between the proximal femur and Hilgenreiner’s baseline. h decreases as the femur migrates superiorly.	Femoral-head ossification centre should lie below A–A; above it indicates superior displacement.	Epiphysis should lie below Hilgenreiner line.
Lateral displacement	Quantified as d: distance along the horizontal baseline from the perpendicular footpoint to the acetabulum/Y-cartilage. d increases with lateral displacement.	Femoral-head ossification centre should lie medial/internal to the B vertical; lateral position indicates displacement.	Epiphysis should lie medial to Perkin line, (in the inferomedial quadrant)
Additional measurement	α, the acetabular roof angle relative to the Y-cartilage baseline.	No equivalent angular measurement in this paper.	Hilgenreiner line remains the reference baseline for the acetabular index.
Aim	Quantitative measurement of height, lateral distance and acetabular inclination, especially before femoral-head ossification.	Simple categorical test: Is the head too high or too far out?	Combined system used for DDH assessment and hip-surveillance methods.

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References

Historical references

• Hilgenreiner H. Zur Frühdiagnose und Frühbehandlung der angeborenen Hüftgelenkverrenkung. Medizinische Klinik 1925; 21: 1385-1388, 1425-1429
• Perkins G. Signs by which to diagnose congenital dislocation of the hip. Lancet 1928: 648-650
• Perkins G. Signs by which to diagnose congenital dislocation of the hip. 1928. Clin Orthop Relat Res. 1992 Jan;(274):3-5

Eponymous term review

• Campbell SE. Radiography of the hip: lines, signs, and patterns of disease. Semin Roentgenol. 2005 Jul;40(3):290-319.
• Yeap PM, Budak MJ. The pelvic radiograph: lines, arcs and stripes. Singapore Med J. 2021 Jul;62(7):333-340.
• Bi AS, Carter C, Price AE, Litrenta J, Karamitopoulos M, Castañeda PG. A history of eponym usage in hip and pelvis radiography part 1: the paediatric hip. Hip Int. 2023 Mar;33(2):136-143.
• Bi AS, Ryan MK, Castañeda PG, Youm T. A history of eponym usage in hip and pelvis radiography part 2: the adult hip. Hip Int. 2023 Mar;33(2):144-151