Epiphyseal Angulation and Related Spatial Orientation in Slipped Capital Femoral Epiphysis: Theoretical Model and Biomechanical Explanation of Varus and Valgus Slip.

The management of slipped capital femoral epiphysis (SCFE) is controversial. Surgical decision-making is based regularly on the chronicity, stability, and severity of the slip. The purpose of this study was to determine the true angulation and spatial orientation of the epiphysis in hips with SCFE and contralateral hips.
METHODS: Eighteen hips in 18 patients with SCFE were included in the analysis. Trigonometric calculations, based on angle measurements using 2 conventional radiographs in planes that are perpendicular to each other, were used to determine the angulation of the epiphysis and its orientation in space.
RESULTS: The mean absolute epiphyseal obliquity of the SCFE hips was 56.2° and the spatial orientation was 36.5°. The mean obliquity of the contralateral side was 34.0°, with a related spatial orientation of 16.8°. The maximum error can reach up to 9.9° (or 41%) when comparing the calculated angles with the angle measurements on radiographs.
CONCLUSIONS: On standard radiographs, the epiphyseal angulation in SCFE is consistently underestimated. As a consequence, the assigned classification of some patients may be 1 severity group too low, which impacts the value of traditional severity classification for surgical decision-making. The analysis of the spatial orientation of the slip with the concomitant direction of the resultant shear can partially explain varus and valgus slip in SCFE. LEVEL OF EVIDENCE: Diagnostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

For patients with slipped capital femoral epiphysis (SCFE), treatment options vary. Surgical procedures include in situ pinning without[1-3] or with an open or arthroscopic offset correction[4,5], in situ fixation and later intertrochanteric corrective osteotomy[6,7], differing techniques of compensatory wedge osteotomy[8], and the Dunn procedure[9-12] or modified Dunn procedure[13-26]. Performing the modified Dunn procedure with a trochanteric slide approach and surgical hip dislocation facilitates correct reduction of the epiphysis and safe positioning of the hardware in the treatment of SCFE with, for experienced surgeons, lower than historical rates of osteonecrosis of the femoral head[27-29].

Three classification systems of SCFE are used. The chronological classification[30] divides SCFE into the temporally based categories of “chronic,” “acute,” and “acute-on-chronic.” The stability-based classification is related to walking ability and defines SCFE as “unstable” when the patient is unable to walk[31]. The severity-based classification defines SCFE on the basis of the extent of epiphyseal displacement. A slip angle of <30° is classified as a “minor” slip; 30° to 50°, “moderate”; and >50°, “severe”[32]. Routine radiographs may underestimate the extent of the displacement and potentially influence the choice of management between in situ pinning and newer methods of anatomic reconstruction with capital realignment[33]. Minor slips and post-slip deformity of the proximal part of the femur have a high risk of early damage of the acetabular cartilage and the development of osteoarthritis[3,34-41]. Thus, the precise analysis of the true slip angle, together with other considerations, is an important factor in surgical decision-making[33]. The direction of the slip is only roughly described as a posterior slip or rotation[42-44]. We are aware of no previous study in which the angle of epiphyseal obliquity and its precise spatial orientation based on 2 radiographs perpendicular to each other have been calculated. This uncertainty may be a reason why a consensus is missing concerning the best treatment for SCFE[45].

In this study, we aimed to determine the true angles of rotational displacement and the spatial orientation of the epiphysis in hips with SCFE. The spatial position of the epiphysis of the contralateral hips served for comparison. The corresponding trigonometric calculations based on angle measurements on 2 radiographs made in 2 planes perpendicular each other were performed for a series of patients who presented to our department with SCFE.

Materials and Methods

On the anteroposterior view, the epidiaphyseal angle was measured[32,46,47]. When using the originally described method of the angle measurement[32], the epidiaphyseal angle decreases with increasing rotational displacement of the epiphysis in the frontal plane. To avoid this phenomenon, the Southwick supplementary angle corresponding to the epiphyseal inclination was used for the calculations (Fig. 1, left panel). On the lateral view, the angle between a perpendicular to the growth plate and the femoral neck axis was measured (Fig. 1, right panel).

Fig. 1

Illustrations showing the method of measuring epiphyseal obliquity on anteroposterior (left panel) and lateral (right panel) radiographic views. On the anteroposterior radiograph, the medial and lateral end points of the epiphysis are connected by a line. The angle between a line corresponding to the femoral shaft axis and a line perpendicular to the epiphyseal line indicates the obliquity or inclination of the growth plate in the frontal plane. The originally used method of Southwick uses the obtuse angle between these 2 lines, with the disadvantage being that the Southwick angle decreases with increasing epiphyseal obliquity. To overcome this, the acute angle α corresponding to the supplement of the Southwick angle is used for the measurements. On the lateral radiograph, the anterior and posterior end points of the epiphysis are connected by a line. Posterior obliquity is assessed by the angle β between a perpendicular to the epiphyseal line and the femoral neck axis.

The calculations of the real epiphyseal rotational displacement and the epiphyseal orientation in space were performed as follows (Fig. 2): the measured angle on the anteroposterior radiograph (angle α) is drawn into the X-Z coordinate system, and the angle on the lateral radiograph (angle β), into the Y-Z coordinate system. The adjacents on the Z axis are set to the radius of the unit circle (= 1). The opposite side a corresponds to tanα, and the opposite side b, to tanβ. Using the Pythagorean theorem, the hypotenuse c is calculated as the square root of the sum of the squares of a and b (c = ). The absolute epiphyseal obliquity (angle η) is given as arctan(c). The spatial orientation (angle θ) of the epiphyseal obliquity is given as arctan(b/a)[48]. Calculations were performed using the absolute angles as measured on the anteroposterior and lateral radiographs for both the hips with SCFE and the contralateral hips and also using the relative angles by subtracting the angles of the contralateral side from the SCFE side in both planes. Appendix 1 provides an Excel (Microsoft) calculation sheet that can be used for assessing the real epiphyseal obliquity, spatial orientation, and the absolute and relative errors between measured and calculated angles. Please be aware that calculations are only possible in the first quadrant from 0° to 90°, where the angles have positive values. Appendix 2 provides instructions for using the Excel sheet.

Fig. 2

Assessment of the real epiphyseal obliquity and related spatial orientation. In the frontal and sagittal planes, the diaphysis is oriented parallel to the corresponding X and Y axes. The angles of epiphyseal obliquity on the anteroposterior and lateral views are drawn into the X-Z and Y-Z coordinate systems. The adjacents of the triangles on the Z axis are set to the value 1, corresponding to the radius of the unit circle (for easier calculations). Having measured the epiphyseal obliquity on the anteroposterior radiograph (frontal plane, angle α) and on the lateral view (sagittal plane, angle β), the opposite sides of the triangles a and b are defined as tanα and tanβ, respectively. Using the Pythagorean theorem, the hypotenuse c is calculated as the square root of the sum of the squares of a and b. The maximum slip angle η is given by the formula: η = arctan(c). The orientation in space (angle θ) of the maximum slip angle can be calculated by the formula: θ = arctan(b/a).

To illustrate the impact of this theoretical model on the severity classification, the series of patients presenting with SCFE in our department were included in the analysis. The study was approved by the Cantonal Ethics Commission.

The angles as measured on the radiographs were compared with the calculated angles using the previously described mathematical functions. In addition, absolute (in degrees) and relative (in percent) error calculations as a function of the measured angles in the frontal and sagittal planes were performed. All measurements and calculations are based on the assumption that all radiographs were made correctly in 2 planes perpendicular to each other using the technique described by Hafner and Meuli[49].

Statistical analysis was performed using WinSTAT (R. Fitch Software). The level of significance was set to p < 0.05. Normal distribution of all parameters was tested with the Kolmogorov-Smirnov test. Because most parameters were not normally distributed, we only used the nonparametric Mann-Whitney U test for independent variables.

Results

Eighteen patients who had unilateral SCFE were included in the mathematical analysis. The mean age was 12.9 years (range, 6.8 to 17 years). There were 2 female and 16 male patients. In 14 patients, the left hip was involved, and in 4, the right hip. Fourteen hips were classified as stable, and 4, unstable; 1 slip was acute, 15 were acute-on-chronic, and 2 were chronic.

In the frontal plane, the mean angle of epiphyseal inclination was 49.0° on the side with SCFE and was 32.7° on the contralateral side. In the sagittal plane, the mean angle of posterior epiphyseal angulation was 42.6° and 11.2° for the hips with SCFE and contralateral hips, respectively (Fig. 3-A). According to the originally described method[32], slip angles are not defined as absolute but as relative angles, by subtracting the angle of the normal, contralateral side from that of the slipped side. The relative slip was 16.3° in the frontal plane and 31.4° in the sagittal plane (Fig. 3-B). Using the presented trigonometric formula, the calculated real angles were quite different: the absolute epiphyseal obliquity angle (angle η) was, on average, 56.2° for the hips with SCFE and 34.0° for the contralateral hips. The spatial orientation angle (angle θ) of this maximum epiphyseal obliquity was 36.5° and 16.8° for the SCFE and contralateral hips, respectively (Fig. 4-A). Taking the relative angles as the basis for the calculations, the mean relative slip angle (ηSlip) can reach 34.1°, and the related spatial orientation (θSlip) of the slip can reach 67.0° (Fig. 4-B). See Table I for additional details.

Fig. 3-A

Measurements of epiphyseal obliquity of the hips with SCFE (red circles) and contralateral hips (blue circles) in the frontal and sagittal planes. The lines with corresponding colors indicate the mean obliquity measurements in each plane.

Fig. 3-B

The relative slip angles of the hips with SCFE (red circles), after subtraction of the angle of the contralateral hip from that of the SCFE side, are shown. The red lines indicate the mean for each plane. Geometrically, this arithmetic subtraction procedure repositions all contralateral hips to the 0°/0° position of the coordinate system of the figure (blue circle).

Fig. 4-A

The absolute epiphyseal position of the SCFE hips and of the contralateral sides. A risk line for epiphyseal slip can be hypothesized, with a critical value of about 25° in the sagittal plane and 45° in the frontal plane.

Fig. 4-B

The relative epiphyseal position after subtraction of the angles of the contralateral side from the SCFE side. Geometrically, such subtraction indicates that all contralateral hips have a 0°/0° position (North Pole position).

Figs. 3-A and 3-B Absolute and relative angles of epiphyseal obliquity in the frontal and sagittal planes.

Figs. 4-A and 4-B A 3-dimensional coordinate system allows visualization of the position in space of the epiphyses of the hips with SCFE (red circles) and the contralateral hips (yellow circles). The calculated epiphyseal obliquity (angle η) can be read on the latitude (blue), and its related spatial orientation (angle θ) can be read on the longitude (brown). 0° means an obliquity purely in the frontal plane, and 90°, purely in the sagittal plane.

Using the traditional severity score, 7 hips presented with a mild slip; 9, moderate; and 2, severe. After having calculated the real relative slip angle, 1 hip in the SCFE group was reclassified, from moderate to severe slip (Table II).

Error calculations taking into account combinations of caudal and posterior obliquity angles showed that the maximum error occurs when the caudal obliquity (angle α) equals the posterior obliquity (angle β). The error reaches up to 9.9°, or 41.1% (Figs. 5-A and 5-B). In our cohort of patients, the absolute slip angles were underestimated, on average, by 2.6° (range, 0.1° to 9.2°) or, on average, 8.8% (range, 0.4% to 30.7%).

Figs. 5-A

Calculated epiphyseal obliquity (in degrees) as a function of the measured angles on the anteroposterior (angle α) and lateral radiographs (angle β). The maximum error is 9.9°, in a case of combined frontal and sagittal plane obliquity of 40° each.

Figs. 5-B

Percentage errors made when angles are not corrected by trigonometric calculations. As an example, an epiphyseal obliquity on the anteroposterior radiograph (angle α) of 30° combined with an obliquity of 25° in the lateral projection (angle β) corresponds in reality to an obliquity (angle η) of 36.6° (blue square, Fig. 5-A), and thus to a relative error of 21.9% (blue square, Fig. 5-B). This means that a hip with SCFE having slipped distally as well as posteriorly can change the category of the severity of slip classification from mild to moderate, or from moderate to severe.

Error calculations with respect to the measured angles of the epiphyseal obliquity in the frontal and sagittal planes. Yellow to red shadings of the squares indicate an increasingly large error between measured and calculated angles.

Discussion

The aim of our analysis was to assess the real absolute epiphyseal obliquity angles and the relative slip angles and related spatial orientation in hips with SCFE and contralateral hips using 2 radiographs perpendicular to each other. To perform the calculations, the methodology used for the analysis of posttraumatic deformities in long bones was adopted[48].

Our analysis revealed that the epiphyseal slip angles in SCFE hips and the epiphyseal angulation in the contralateral hips were underestimated compared with the values as measured on standard radiographs. Error calculations showed that that the maximum error can reach up to 10°, or 41.1%.

SCFE can be classified using 3 systems. The chronological classification divides SCFE into the categories of chronic, acute, and acute-on-chronic SCFE[30]. However, the history of the patient is difficult to assess because the patient and the parents often do not remember the exact date of the onset of hip symptoms. The stability-based classification is related to the ability to walk[31]. According to Ziebarth et al., epiphyseal stability as reported preoperatively is not correlated with the stability of the epiphysis found during surgery[50]. Thus, this classification is only of relative value for the choice of treatment. The severity-based classification is based on the slip angles as measured on radiographs. Arbitrarily, an angle of <30° is classified as a minor slip; 30° to 50°, as a moderate slip; and >50°, as a severe slip[32].

The threshold angle of 30° differentiates only hips presenting with a minor slip from hips with a moderate slip; we are aware of no information in the literature providing a definitive threshold angle for differentiating between a normally positioned hip and a hip with a minor slip. However, this seems to be an important factor for the decision-making concerning prophylactic pinning of the contralateral hip. It is recommended that stabilization of the contralateral hip be performed when, in the lateral view, the absolute angle of posterior tilt exceeds 20°[51,52]. Thus, this proposal relies only on the lateral radiograph without taking into account the 3-dimensional nature of epiphyseal slipping. We are convinced that, in this context, the spatial orientation of the epiphyseal obliquity is also important. In our series, the mean spatial orientation of the epiphyseal obliquity was 36.5° for the hips with SCFE but only 16.8° for the contralateral hips. More longitudinal, long-term outcome studies with a precise definition of the epiphyseal position of the contralateral hip are needed to be able to differentiate between normally positioned hips, “silent slip” hips, and hips with late femoroacetabular impingement due to an undiagnosed or underestimated minor slip.

Our data showed that epiphyseal slip and angulation are underestimated when taking measurements on radiographs. Thus, the severity classification is not precise. When the calculated real angles are taken in consideration, some patients may change from one severity group to the next-higher severity group.

In addition, the severity classification relies on relative angles, because the measured angles of the contralateral side are subtracted from those on the SCFE side for both the anteroposterior and the lateral radiograph. It remains debatable whether these conventionally reported relative slip angles are reliable for a classification system. Subtracting the angles of the contralateral side from those of the affected side indirectly assumes that the contralateral side is completely normal. Given that a high percentage of SCFE cases present with a bilateral pathology[53-61] and prophylactic stabilization of the contralateral hip is commonly recommended to avoid progressive deformity of the contralateral side[53,55,56,60,62-68], the contralateral, asymptomatic hip may not then be classified as normal and thus, should not serve as reference to define the severity of the slip. In addition, other long-term studies show a high prevalence of proximal femoral deformity in the contralateral hip in patients treated for unilateral SCFE[36,55,56,68]. The contralateral asymptomatic hip should be classified as potentially being a pre-slip or silent hip[69,70].

To overcome some of the problems with the present classifications, a novel staging system[71] of SCFE was proposed, relying on the so-called epiphyseal tubercle situated on the posterosuperior quadrant of the growth plate and playing the role of the major stabilizer or keystone of the epiphysis[72]. This staging shows a high correlation with the severity of the slip, but moderate and negligible correlation with the stability and chronicity classification, respectively[71]. A more recent analysis revealed that hips with SCFE have a smaller epiphyseal tubercle and larger peripheral epiphyseal cupping compared with healthy hips. The authors concluded that a smaller epiphyseal tubercle may be either a predisposing morphologic factor or a consequence of the increased shearing stress across the physis secondary to the slip[73].

Biomechanical forces at the hip may cause separation of the growth plate due to shear overload[74]. There is a competition between forces trying to displace the epiphysis and forces trying to stabilize it. The displacing force is the shear force acting parallel to the obliquely oriented plane of the growth plate. The stabilizing force is the compressive force, being perpendicular to the epiphyseal growth plate, creating compression and friction at the interface. In the single-leg standing position, the resultant force acting on the hip joint in the frontal plane is 16° divergent with respect to the vertical axis[75]. The absolute obliquity of the growth plate and the spatial orientation of compression and shear forces are probably the most important mechanical factors causing the epiphyseal slip. In this context, only the shear force and the direction of its action line are of interest. The action line of the shear force on the growth plate points, in most SCFE hips, much more toward the posterior direction than the caudal direction, explaining why epiphyseal slipping is mainly toward the posterior direction (Fig. 6-A). However, with the 3-dimensional vector diagram, the valgus slip in SCFE can be at least partially explained. With a valgus slip, the epiphyseal inclination in the frontal plane is regularly very low[76-80], and thus the shear component of the resultant force points toward the posterolateral direction; this is interpreted on an anteroposterior radiograph as a valgus slip (Fig. 6-B).

Fig. 6-A

Figs. 6-A and 6-B The amount and direction of the shear force acting on the growth plate. Fig. 6-A With increasing obliquity of the growth plate, the shear force on the epiphysis increases and the compressive force decreases. The resultant force acting on the femoral head is divided in its components of shear and compression. In the frontal plane, the resultant force (FRf), and thus its action line on the hip joint, is 16° divergent (angle γ) with respect to the vertical axis (V)75. Angle α is the measured absolute obliquity of the epiphysis, angle δ is the angle between the resultant force and the direction of its compressive-force component (FCf), and perpendicular to FCf the amount of shear force acting on the growth plate (FSf) is visualized—using the method of the parallelogram of forces. In the sagittal plane, the resultant force (FRs) is parallel to the vertical axis. When the posterior obliquity angle β equals the caudal obliquity angle α, the amount of shear force toward the posterior direction is clearly much higher than in the frontal plane. Angle ε, which is defined as the angle between the resultant force (FRs) and its compressive-force component (FCs), equals angle β. No divergence of the resultant force in this plane is present, and thus, angle ε does not need to be corrected by subtracting 16°. The resultant shear force points with its action line much more toward the posterior direction than the caudal direction, explaining why the epiphysis in SCFE slips mainly toward the posterior direction.

Fig. 6-B

A valgus slip in a case of a hypervalgus hip is illustrated. In the frontal plane, the growth plate is oriented close to 0°, and in the sagittal plane, a posterior slip is present. The resultant vector of the shear force points in the posterolateral direction, which is interpreted in the anteroposterior radiograph as a valgus slip. Depending on the epiphyseal obliquity in space, anteromedial and anterolateral slips can also be imagined. α = the angle of caudal obliquity (inclination) of the growth plate; γ = the angle of divergence of the resultant force of the hip with respect to the vertical axis (16°); δ = the angle between the resultant force and the force component perpendicular to the growth plate (= α – γ); F = the resultant force on the hip in the frontal plane; F = the compressive-force component in the frontal plane (= FRf cosδ); F = the shear-force component in the frontal plane (= FRf sinδ); β = the angle of posterior obliquity of the growth plate; ε = the angle between the resultant force and the force component perpendicular to the growth plate in the sagittal plane (= β); F = the resultant force on the hip in the sagittal plane; F = the compressive-force component in the sagittal plane (= FRs cosε); and F = the shear-force component in the sagittal plane (= FRs sinε).

We are convinced that a measurement system not relying on the contralateral hip but indicating the absolute angle of epiphyseal slip and the absolute angle of the spatial orientation of this maximum slip would be more useful and reliable.

Our data as well as biomechanical reflections suggest that the risk for epiphyseal slipping depends on the absolute amount of epiphyseal obliquity as well as its spatial orientation. Because of the 16° divergence of the resulting force with respect to the vertical axis, epiphyseal obliquity in the sagittal plane is more susceptible to slipping than in the frontal plane. The critical angle in the sagittal plane must be around 25°, and in the frontal plane, around 45°. Depending on the spatial orientation of the slip, the critical values are situated between 25° and 45°.

Our study had limitations. First, the number of involved patients was relatively small, but they serve only to illustrate the methodology of calculations. Second, all patients with SCFE were included regardless of the chronicity and stability of the slip. Third, correct calculations require a perfect exposure of the femoral neck in 2 planes perpendicular to each other, which may be difficult to obtain for some patients. And fourth, to our knowledge, there are no normative data available regarding the epiphyseal angulation of normal hips to support the hypothesis of a critical angle for the occurrence of a slip.

Strengths of this study include the following: first, trigonometric calculations are precise when based on perfect radiographs made in 2 planes perpendicular to each other. Second, to our knowledge, this is the first time that data showing the exact amount and 3-dimensional direction of the slip and epiphyseal obliquity have been presented. Third, accurate assessment of epiphyseal obliquity of the contralateral hip can help to discriminate between a normally positioned hip and a minor slip of the asymptomatic, contralateral side. And fourth, the presented theoretical model allows assessment of the amount and direction of the shear force acting on the epiphysis, which can at least partially explain the phenomenon of the valgus slip.

Conclusions

Generally, classification systems should inform the appropriate treatment and the prognosis of a distinct pathology as well as allow for scientific comparison of the obtained results. All 3 of the traditionally used classification systems for SCFE have a major drawback: difficulty in assessment (chronological classification), classification that may differ from intraoperative findings (stability classification), or underestimation of the real deformity of the proximal part of the femur (severity classification). Newer surgical techniques allow a complete analysis of hip joint pathology and mechanics under direct visualization. Even minor slips can lead to early damage of the articular cartilage and the adjacent labrum in the weight-bearing area of the joint due to femoroacetabular impingement caused by the slip or post-slip deformity of the proximal part of the femur[81,82]. Accurate analysis of the contralateral hip is needed to discriminate between a truly healthy hip from a hip presenting with an asymptomatic “silent slip” needing prophylactic stabilization. Even when the morphology of the SCFE hip may not be the only factor for surgical decision-making, a more precise analysis of the deformity caused by the epiphyseal slip seems to be needed[40,83] to take into account not only the real angle of the epiphyseal obliquity or the relative angle of the slip but also the spatial orientation of the slip.

Appendix

Supporting material provided by the authors is posted with the online version of this article as data supplements at jbjs.org (http://links.lww.com/JBJSOA/A227) (http://links.lww.com/JBJSOA/A228).

TABLE I

Radiographic Measurements and Calculated Absolute and Relative Angles*

Parameter	Side	Mean Angle ± SD (°)	Range (°)	95% CI (°)	P Value (SCFE Vs. Contralateral)
Absolute value
Frontal angle α	SCFE	49.0 ± 16.7	33-92	41.3-56.7	<0.001
	Contralateral	32.7 ± 5.7	23-49	30.1-35.3
Sagittal angle β	SCFE	42.6 ± 16.6	16-70	34.9-50.3	<0.001
	Contralateral	11.2 ± 4.7	2-20	9.0-13.4
Calculated angle η	SCFE	56.2 ± 14.5	38.6-89.8	49.5-62.9	<0.001
	Contralateral	34.0 ± 5.6	25.4-50.3	31.4-36.6
Spatial orientation θ	SCFE	36.5 ± 15.9	0.4-63.1	29.2-43.9	<0.001
	Contralateral	16.8 ± 6.7	3.8-26.6	13.7-19.9
Relative value: ΔSCFE−contralateral
Frontal slip angle α		16.3 ± 13.3	1-45	10.2-22.5
Sagittal slip angle β		31.4 ± 14.1	9-56	24.9-37.9
Calculated slip angle η		34.1 ± 15.2	9.1-60.8	27.1-41.1
Spatial orientation of slip θ		67.0 ± 12.5	45-83.9	61.2-72.8

SD = standard deviation, and CI = confidence interval.

TABLE II

Influence of the Calculated Angles on the Severity Classification

Patient	Absolute Angles (°)						Relative Angles* (°)		Calculated Angle η Using Relative Angles	Severity Classification						Error
	Contralateral Side			SCFE Side						Traditional Angles†			Calculated Angles†
	Frontal Angle α	Sagittal Angle β	Calculated Angle η	Frontal Angle α	Sagittal Angle β	Calculated Angle η	Frontal Angle α	Sagittal Angle β		<30°	30-50°	>50°	<30°	30-50°	>50°	Absolute Error (°)	Relative Error (%)
1	32	14	33.9	77	70	79.0	45	56	60.8			56			60.8	4.8	8.6
2	31	4	31.2	40	16	41.6	9	12	14.8	12			14.8			2.8	23.3
3	32	12	33.4	52	46	58.7	20	34	37.5		34			37.5		3.5	10.3
4	33	16	35.4	34	25	39.4	1	9	9.1	9			9.1			0.1	1.1
5	23	12	25.4	35	45	50.7	12	33	34.3		33			34.3		1.3	3.9
6	49	20	50.3	92	68	89.8	43	48	55.4		48				55.4	7.4	15.4
7	29	15	31.6	34	53	56.1	5	38	38.2		38			38.2		0.2	0.5
8	30	9	30.9	33	27	38.6	3	18	18.1	18			18.1			0.1	0.6
9	32	8	32.6	62	38	63.8	30	30	39.2		30			39.2		9.2	30.7
10	30	12	31.6	50	57	62.8	20	45	46.8		45			46.8		1.8	4.0
11	31	3	31.1	36	24	40.4	5	21	21.5	21			21.5			0.5	2.4
12	40	12	40.9	70	52	71.7	30	40	45.5		40			45.5		5.5	13.8
13	28	2	28.1	38	18	40.2	10	16	18.6	16			18.6			2.6	16.3
14	32	10	33.0	56	51	62.6	24	41	44.3		41			44.3		3.3	8.0
15	32	14	33.9	40	42	50.9	8	28	28.8	28			28.8			0.8	2.9
16	29	11	30.4	42	41	51.4	13	30	31.9		30			31.9		1.9	6.3
17	39	11	39.8	47	63	65.9	8	52	52.2			52			52.2	0.2	0.4
18	37	16	38.9	44	31	48.7	7	15	16.4	15			16.4			1.4	9.3
Total no.										7	9	2	7	8	3	** Expression is faulty **

SCFE minus contralateral.

Bolded values demonstrate the change in classification, from moderate to severe.