Extension of cephalo-photometric analysis

Extension of cephalo-photometric analysis

j. Cranio-Max.-Fac. Surg. 15 (1987) J. Cranio-Max.-Fac. Surg. 15 (1987) 75-78 © Georg Thieme Verlag Stuttgart - New York Extension of CephaloPhotomet...

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j. Cranio-Max.-Fac. Surg. 15 (1987) J. Cranio-Max.-Fac. Surg. 15 (1987) 75-78 © Georg Thieme Verlag Stuttgart - New York

Extension of CephaloPhotometric Analysis

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Summary Once specific anthropometric points have been determined more accurately, photometric analysis may now also be made from a cephalogram. The maxillo-zygomatic region, and especially its hypoplastic appearance, may be determined from additional geometrics based on the length of the facial thirds.

Kurt-W. Biitow DepartmentofMaxillo-Facialand OralSurgery(Head:Prof.K.-W.Bikow, MChD (MFOSurg),DMD).Universityof Pretoria,SouthAfrica. Submitted 19.6. 86; accepted 8.8.86

Introduction The "Lateral Photometric Analysis" for the evaluation of aesthetic-orthognathic deformity (Biitow, 1984) was developed as a third diagnostic aid - the other two being the well-known cephalometric analysis and model study. A more refined analysis, especially for the determination of certain anthropometric points, has been introduced in this paper. This analysis has now also been adapted for the cephalogram. Certain relevant points and circles of measurement can be more accurately established. The infraorbital margin of the face may now also be thus analysed.

Method of Analysis The various anatomical landmarks as determined for photometric analysis (Biitow, 1984) as well as for this newly-introduced analysis, are basically the same as the anthropometric landmarks defined by Farkas (1981). The relevant points, lines and circles of measurement as for lateral photometric analysis, as well as the defined measurements (Table 1), remain basically the same (Figs. i a and lb). Certain relevant points and circles which are difficult to determine from photometric analysis, are more accurately defined when the analysis is drawn from the more detailed cephalogram (Fig. i c). The relevant points and lines have been described in a previous publication (Bi;ttow, 1984).

Key-Words Photometric analysis - Cephalo-photometric analysis Cephalometric X-ray - Diagnostic aid in aesthetic and orthognathic surgery

the upper margin of the tragus; corresponds to the most postero-superior point of the glenoid fossa (a bony reference) (Fig. I b). Point B is accurately determined from the cephalogram as follows: A line (tangent) is drawn on the posterior border of the mandibular ramus and extended cranially. A second line, touching the superior margin of the condylar head, is drawn parallel to the Frankfort horizontal line. These two lines intersect to determine point B (Fig. 3). Y. Facial Circle: Three types of facial circle may be drawn. The individual facial circle which may be drawn, depends on the "normality" of the facial length (i. e. the superoinferior dimension). The BK distance is the radius of the facial circle (Y) and varies according to the superio-inferior dimensional length of the face. 1. BK° (norm) is the radius of the normal facial circle (Y norm). The facial third distance (Table I) is AE = GH = HJ °, i. e. jo is the "normal" facial third line at the pogoniongnathion area (Fig. 4). The facial circle (Y norm) is an essential reference for the determination of the infra-orbital margin (Z) (Fig. 5). 2. BK (max) is the radius of the "maxillary" facial circle (Y max) where the H line (AE = GH) is corrected to H' (the anthropometric landmark). The inferior facial third line (J), by using the real facial third distance for the mandible (AE = H'J) (Fig. 4), is thus established from the anthropometric

Redefined anatomical landmarks A. Glabella (originally on a lateral photograph (Bidtow, 1984) the most anterior point on the forehead; the starting point for photometric analysis; between one half to two units (Table 1) above the eyebrow (Fig. I b). When this analysis is made from the cephalogram, the following landmarks are important: 1. A "normal" skull base inclination - Point A is determined (Fig. 2): A line 90 ° to the extended line SN (SellaNasion) (Downs, 1948) touching the soft tissue of the Glabella. 2. In an "abnormal" i.e. a more horizontal skull base inclination,the angle SNPor (Sella-Nasion-Portion) (Downs, 1948) is greater than 10 °-. Thus point A is determined (Fig. 2): A line 90 ° to the extended line PorN touching the soft tissue Glabella. This determination is sNdom necessary. B. Pre-Tragion (originally on a lateral photograph (Biitow, 1984): 2-4 mm anterior and 2 mm superior to the notch on

Table 1

Standard measurement. Value

Angle C (at point B) 48 degreees Unit 5,5 millimetres

Positive (e. g. unit, triangle) Negative (e. g. unit, triangle) Facial third

drawn away from the face ( = away from point B) drawn towards the centre of the face (= towards point B) AE = B - = 1/2BD = IG = GH = HJ (1/2 the distance of the isometric lines of the "facial triangle")

Deviation _+ 1 degree + 0,5 millimetre (large face) - 1,0 millimetre (small face)

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J. Cranio-Max.-Fac. Surg. 15 (1987)

K.-W. Biitow

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Fig. 1 a Female with "normal features".

Fig. 1 b A photometric drawing of the same female with "normal features".

Fig. I c A cephalo-photometric drawing of the same female with "normal features".

Fig. 2 A cephalo-photometric drawing for point A.

Fig. 3

facial line ('). This maxillary facial circle (Y max) with the BK (max) radius is therefore adjusted according to the maxillary short face or long face syndrome and is essential for the determination of the nasal structure. (Biitow, 1984). 3. BK' (mand) is the radius of the "mandibular" facial circle (Y mand). The J linke (AE = HJ, for the normal midface length, or H'J) is adjusted to J', the mandibular anthropometric landmark - pogonioon-gnathion. This "mandibular" facial circle (Y mand) is for the determination of point L, the female chin position (Fig. 4). In a supero-inferior perfectly balanced face one will find only one facial circle, thus Y norm = Y max = Yomand. Z. Infra-orbital margin of the cephalogram: two points are established on lines G and H (not H') each one negative unit (Table 1) from the facial circle (Y norm). These points serve as the starting points of an isometric infra-orbital triangle,

with facial third distance (AE), and which joins at point Z (+ 0,60 unit) (Table 2) (Fig. 5). The accurate determination of the supero-inferior position, depends on the addition (for a maxillary short face) or the substraction (for the maxillary long face) at point Z, (thus the difference of H to H'). The range for "normal" cases is considerable. Thus all cases outside it may be considered as having a clearly abnormally situated infraorbital margin.

A cephalo-photometric drawing for point B.

Photometric Assessment Most of the various different types of orthognathic deformities have been demonstrated in the previous publication (Biitow, 1984). No soft tissue adjustments or definements are necessary for cephalo-photometric analysis.

Extension of Cephalo Photometric Analysis //

j. Cranio-Max.-Fac. Surg. 15 (1987)

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Fig. 4 A photometric drawing for the facial circle (Y) (see text for analysis).

Fig. 6a

A case: Maxillo-zygomatic "re-

trognathism".

Table 2

Fig. 5 A cephalo-photometric drawing forthe infra-orbital margin (Z) (see text for analysis).

Fig. 6 b The cephalogram of the case: maxillo-zygomatic "retrognathism".

Fig. 6 c The cephalo-photometric drawing of the case: Hypoplastic maxillo-zygomatic region, retrognathic maxilla, maxillary "longface", with a slight mandibular prognathism and mandibular "long face".

Standard deviation for point Z, as determined from 50 "normal" cases.

Point Z

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y. Cranio-Max.-Fac. Surg. i5 (1987)

The infra-orbital margin or maxillo-zygomatic insufficiency, is assessed according to the following patient example: Maxillo-zygomatic "'retrognathism" The patient (Figs. 6 a & 6 b) represents a typical maxillary retrognathism as well as a hypoplastic maxillo-zygomatic deformity. The cephalo-photometric analysis indicates the following aesthetic-orthognathic problems: a retrognathic maxilla (see the nasio-labial notch to line R) (Bidtow, 1984)), an increased midfacial length (H to H' and the stomion lies inferior to point), a hypoplastic maxillo-zygomatic region (point Z lies anterior to the infra-orbital region), a slight mandibular prognathism (the pogoniongnathion lies anterior to point K), a slightly increased mandibular face length (J to J'), and a descending mandibular plane (N to N') (Fig. 6 c). Final cephalo-photometric diagnosis: maxillary long-face with a retrognathic maxilla and a hypoplastic maxillozygomatic region, as well as a slightly prognathic and a slight long-face (the lower facial third).

K.-W. Biitow: Cephalo-Photometric Analysis posterior and supero-inferior dimensions. The posteriorly displaced infra-orbital margin is the most important distance to be calculated in any abnormal maxillo-zygomatic region. Photometric analysis (Bf~tow, 1984) has been adapted and slightly modified for the cephalogram. Two of the most important points, namely the Glabella (A) and Pre-Tragion (B) have been more accurately established. The facial circle (Y), especially in cases of a long or short face, has been defined in greater detail. Photometric analysis was introduced as a diagnostic aid in aesthetic-orthognathic surgery of the soft tissues. This adapted analysis is an improvement on the existing analysis of the lateral cephalogram. The cephalogram is more easily obtainable and more accurate than a life-size photograph of the patient. Thus cephalo-photometric analysis is a more accurately defined and expanded analysis than that previously used. The analysis is still determined from the facial profile, with only a few bony reference points added.

Discussion and Conclusions

Baud (1966) has made an attempt to use Leonardo da Vinci's (15th century) facial thirds and the facial circle, to establish some form of measurement of the face and nose. Photometric analysis (Biitow, 1984), which is also based on facial thirds and mathematically determined triangles and circles, is a diagnostic aid which may also be used in conjunction with standard cephalometric analysis and study model evaluation. Leonard and Walker (1977) established a cephalometric measurement of the infra-orbital margin. This has been applied to the hypoplastic maxillo-zygomatic region at the Le Fort II level. For those cases with an "abnormal" maxillo-zygornatic appearance, an infra-orbital margin analysis (Z) based on the facial third distance has been introduced here in this paper. The advantage of this specific type of cephalo-photometric analysis, is that the infraorbital margin may be determined in both the antero-

References Baud, C.: Une nouvelle mensuration du profil. Schweiz. Mschr. Zahn-

heilk. 76 (1966) 741 Biitow, K.-W.: A lateral photometric analysis for aesthetic-orthognathic treatment. J. Max. Fac. Surg. 12 (1984) 20 Downs, W. B.: Variation in facial relationships: their significancein treatment and prognosis. J. Orth. 34 (1948) 812 Farkas, I. G.: Anthropometry of the head and face in medicine. Elsevier, New York. Oxford (1981) p. 11 Leonard, M., Walker, G. F.: A cephalometricguide to the diagnosis of midface hypoplasia at the Le Fort II level.J. Oral Surg. 35 (1977) 21

Prof. K.-W. Biitow, DMD, MChD. Department Maxillo-Facial and Oral Surgery University of Pretoria P. O. Box1266 Pretoria 001, South Africa