Hip(I)

10.1055/b-0034-92242

Hip(I)

Radiographic Landmarks of the Hip

The following radiographic landmarks and their interrelationships are helpful in diagnosing congenital and acquired abnormalities of the acetabulum ( Fig. 2.1 ):

Iliopectineal line (arcuate line, linea terminalis): The iliopectineal line is the radiographic reference line for the anterior column.
Ilioischial line: The upper portion of this line is formed by the posterior part of the quadrilateral plate, its lower portion by the ischium (medial boundary). The ilioischial line is the landmark for the posterior column.
Acetabular roof line.
Acetabular teardrop: This is a teardrop-shaped figure formed laterally by the medial portion of the acetabulum and medially by the antero-inferior portion of the quadrilateral plate. The quadrilateral plate is the posterior wall of the acetabulum, which faces inward on the pelvic inlet and presents an approximately square, flat surface.
Anterior rim of the acetabulum.
Posterior rim of the acetabulum.

Armbuster TG, Guerra J Jr, Resnick D, et al. The adult hip: an anatomic study. Part I: the bony landmarks. Radiology 1978;128(1):1–10

Femoral Neck–Shaft Angle and Anteversion Angle

Projected Neck–Shaft Angle

The projected femoral neck–shaft angle (NSA, called also the caput–collum–diaphyseal (CCD) angle; Fig. 2.2 ) is determined on the anteroposterior (AP) pelvic radiograph or the AP radiograph of the hip and femur. It is the angle formed by the longitudinal axes of the neck and shaft of the femur.

Anatomic landmarks for evaluating the hip in the anteroposterior pelvic radiograph. 1 = Iliopectineal line 2 = Ilioischial line 3 = Acetabular roof line 4 = Acetabular teardrop 5 = Posterior rim of acetabulum 6 = Anterior rim of acetabulum a Schematic drawing. b Anteroposterior pelvic radiograph.

The femoral neck axis can be determined as follows ( Fig. 2.3 ): first the center of the femoral head is located with a circle template or computer-assisted technique at a workstation. Next a line is drawn connecting the points where the circle intersects the medial and lateral borders of the femoral neck. A line drawn perpendicular to that line through the center of the femoral head represents the femoral neck axis.

M.E. Müller uses the following method for an accurate reconstruction of the NSA:

The center of the femoral head is located with a circle template or a computer-assisted technique. Reference points for the circular arc are the lateral portion (outermost point) of the epiphysis and the medial corner of the femoral neck.
The point of deepest concavity on the lateral border of the femoral neck is marked.
Another arc through that point using the center of the femoral head as the center is drawn.
The points where the circle intersects the femoral neck are connected.
A line is drawn perpendicular to that line through the center of the femoral head. That line represents the femoral neck axis.
The femoral shaft axis is drawn midway between the lateral and medial borders of the femoral shaft.

Projected NSA


• Normal values in adults:	~ 120–130°
• Coxa valga:	> 130°
• Coxa vara:	< 120°

The anteversion of the proximal femur causes the NSA to appear larger on radiographs than it really is.

Determining the femoral neck axis on an anteroposterior radiograph of the hip or pelvis. a Approximate determination of the femoral neck axis.

M = Center of the femoral head

A = Point where the circle intersects the lateral cortex of the femoral neck

B = Point where the circle intersects the medial cortex of the femoral neck

1 = Femoral neck axis (line perpendicular to AB through M)

b M. E. Müller method for accurate reconstruction of the femoral neck axis.

M = Center of the femoral head

A = Deepest point in lateral concavity of the femoral neck

B = Point on medial border of the femoral neck defined by the second arc

1 = Femoral neck axis (line perpendicular to AB through M)

2 = Femoral shaft axis

Dunn–Rippstein– Müller method of determining the anteversion angle on conventional radiographs. Schematic illustration. a View from the foot of the table. b Side view.

Dunn-Rippstein-Müller method of reconstructing the anteversion angle. M = Center of the femoral head A = Deepest point in lateral concavity of the femoral neck B = Point where the second arc intersects the medial femoral neck

1 = Femoral neck axis (line perpendicular to AB through M)

2 = Horizontal plane (defined by the positioning frame)

3 = Projected anteversion angle

Müller ME. Die hüftnahen Femurosteotomien. 1st ed. Stuttgart: Thieme; 1957

Projected Anteversion Angle (Dunn–Rippstein–Müller Method)

Today the Dunn–Rippstein–Müller method is widely used to assess rotational deformity by calculating the true NSA and femoral anteversion (AV) angle. The projected AV angle is measured on a radiograph in the Rippstein projection (called also the Rippstein II view). This projection is standardized by using a positioning frame that holds the hip in 90° of flexion and 20° of abduction ( Fig. 2.4 ).

The AV angle is measured between the horizontal plane (defined by the positioning frame) and the femoral neck axis ( Fig. 2.5 ). The Müller method (see p. 11) is best for determining the femoral neck axis. When calculated in this way, the AV angle is determined relative to the transverse axis of the femoral condyles.

True Neck–Shaft Angle and Anteversion Angle

Geometric formulae are available for converting the projected NSA and AV angle to the true angles.

Calculation of the true AV angle:

Calculation of the true NSA:

cot β = cot β₂ • cot α

where:

α = true AV angle

α₂ = projected AV angle

β₂ = projected NSA

γ = abduction angle of the femur = 20°

The use of conversion charts will facilitate the rapid calculation of values in everyday practice. The chart published by Müller in 1957 is a well-established clinical tool ( Table 2.1 ). Another current option is the use of computer software.

Both the NSA and AV angle change with aging and show a large range of variation. Tables 2.2 and 2.3 list age-adjusted normal values and analytic criteria proposed by the Commission for the Study of Developmental Dysplasia of the Hip of the German Society for Orthopedics and Traumatology. These tables can be helpful in routine clinical decision-making. Prognostic assessments are difficult, however, because spontaneous normalization often occurs during growth and cannot be predicted with certainty.

Chart for finding the true values of the anteversion (AV) angle (horizontal numbers) and neck–shaft angle (NSA) (vertical numbers) based on the projected angles (source: Müller 1957)
Projected AV angle (°)
		5	10	15	20	25	30	35	40	45	50	55	60	65	70	75	80
Projected NSA (°)	100	4	9	15	20	25	30	35	40	45	50	55	60	65	70	75	80
	100	101	100	100	100	100	99	99	98	97	96	95	94	94	93	92	91
	105	5	9	15	20	25	31	35	41	46	51	56	60	65	70	75	80
	105	105	105	104	104	103	103	102	100	100	99	98	97	96	95	94	92
	110	5	10	16	21	27	32	36	42	47	52	56	61	66	71	76	80
	110	110	110	109	108	108	106	106	105	104	103	101	99	98	97	95	93
	115	5	10	16	21	27	32	37	43	48	52	57	62	67	71	76	81
	115	115	115	114	112	112	111	110	109	107	105	104	102	101	99	96	94
	120	6	11	16	22	28	33	38	44	49	53	58	63	68	72	77	81
	120	120	119	118	117	116	115	114	112	110	108	106	104	103	101	98	95
	125	6	11	17	23	28	34	39	44	50	54	58	63	68	72	77	81
	125	125	124	123	121	120	119	118	116	114	112	109	107	105	103	100	95
	130	6	12	18	24	29	35	40	46	51	55	60	64	69	73	78	82
	130	130	129	127	126	125	124	122	120	117	116	112	109	107	104	101	96
	135	7	13	19	25	31	36	42	47	52	56	61	65	70	74	78	82
	135	135	133	132	131	130	129	126	124	120	118	114	112	109	105	102	96
	140	7	13	20	27	32	38	44	49	53	58	63	67	71	75	79	83
	140	139	138	137	135	134	132	130	127	124	120	117	114	111	107	103	97
	145	8	14	21	28	34	40	45	50	55	59	64	68	72	75	79	83
	145	144	142	141	139	138	136	134	131	128	124	120	117	114	110	104	98
	150	8	15	22	29	35	42	47	52	56	61	65	69	73	76	80	84
	150	149	147	146	144	143	141	138	136	134	129	124	120	116	112	105	100
	155	9	17	24	32	38	44	50	54	58	63	67	71	74	77	81	84
	155	154	152	151	149	148	145	142	139	137	132	128	124	119	115	108	103
	160	10	18	27	34	44	46	52	57	61	65	69	73	76	79	82	82
	160	159	158	157	155	153	151	147	144	141	134	132	128	122	116	111	105
	165	13	23	33	40	47	53	57	62	67	69	73	76	78	81	83	86
	165	164	162	160	159	158	156	153	148	144	140	135	130	122	119	113	106
	170	15	27	37	46	53	58	63	67	70	73	76	78	80	83	84	87
	170	169	167	166	164	163	159	157	154	150	145	142	134	130	122	118	113

Dunn DM. Anteversion of the neck of the femur; a method of measurement. J Bone Joint Surg Br 1952;34-B (2):181–186 Müller ME. Die hüftnahen Femurosteotomien. 1st ed. Stuttgart: Thieme; 1957 Rippstein J. Determination of the antetorsion of the femur neck by means of two x-ray pictures. [Article in German] Z Orthop Ihre Grenzgeb 1955;86(3):345–360 Tönnis D. Die angeborene Hüftdysplasie und Hüftluxation im Kindes- und Erwachsenenalter. Chapter 9: Allgemeine Röntgendiagnostik des Hüftgelenks. Berlin: Springer; 1984; 129–134

Classification of true neck–shaft angles (NSAs) (Commission for the Study of DDH, German Society for Orthopedics and Traumatology; MV = mean value; source: Tönnis 1984)
Age (years)	Grade –4 (extremely abnormal)	Grade –3 (severely abnormal)	Grade –2 (slightly abnormal)	Grade 1 (normal to borderline)	Grade +2 (slightly abnormal)	Grade +3 (severely abnormal)	Grade +4 (extremely abnormal)
> 1 to < 3	< 105	≥ 105 to < 115	≥ 115 to < 125	≥ 125 to < 150 (MV 140)	≥ 150 to < 155	≥ 155 to < 160	≥ 160
> 3 to < 5	< 105	≥ 105 to < 115	≥ 115 to < 125	≥ 125 to < 145 (MV 135)	≥ 145 to < 150	≥ 150 to < 155	≥ 155
> 5 to < 10	< 100	≥ 100 to < 110	≥ 110 to < 120	≥ 120 to < 145 (MV 132)	≥ 145 to < 150	≥ 150 to < 155	≥ 155
> 10 to < 14	< 100	≥ 100 to < 110	≥ 110 to < 120	≥ 120 to < 140 (MV 130)	≥ 140 to < 145	≥ 145 to < 155	≥ 155
14 or more	< 100	≥ 100 to < 110	≥ 110 to < 120	≥ 120 to < 135 (MV 128)	≥ 135 to < 140	≥ 140 to < 150	≥ 150

Classification of true anteversion (AV) angles (Commission for the Study of DDH, German Society for Orthopedics and Traumatology; MV = mean value; source: Tönnis 1984)
Age (years)	Grade –4 (extremely abnormal)	Grade –3 (severely abnormal)	Grade –2 (slightly abnormal, borderline)	Grade 1 (normal)	Grade +2 (slightly abnormal, borderline)	Grade +3 (severely abnormal)	Grade +4 (extremely abnormal)
> 1 to < 3	< 20	≥ 20 to < 25	≥ 25 to < 35	≥ 35 to < 55 (MV 45)	≥ 55 to < 60	≥ 60 to < 75	≥ 75
≥ 3 to < 7	< 15	≥ 15 to < 20	≥ 20 to < 30	≥ 30 to < 50 (MV 40)	≥ 50 to < 55	≥ 55 to < 70	≥ 70
≥ 7 to < 9	< 10	≥ 10 to < 15	≥ 15 to < 25	≥ 25 to < 45 (MV 35)	≥ 45 to < 50	≥ 50 to < 65	≥ 65
≥ 9 to < 11	< 5	≥ 5 to < 10	≥ 10 to < 20	≥ 20 to < 40 (MV 30)	≥ 40 to < 45	≥ 45 to < 60	≥ 60
≥ 11 to < 13	< 5	≥ 5 to < 10	≥ 10 to < 15	≥ 15 to < 35 (MV 25)	≥ 35 to < 40	≥ 40 to < 55	≥ 55
≥ 13 to <15	< 0	≥ 0 to < 5	≥ 5 to < 10	≥ 10 to < 30 (MV 20)	≥ 30 to < 35	≥ 35 to < 50	≥ 50
≥ 15	< 0	≥ 0 to < 5	≥ 5 to < 10	≥ 10 to < 25 (MV 15)	≥ 25 to < 30	≥ 30 to < 45	≥ 45