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Reproducibility of aimed-at profiles
Journal of Cranio-MaxillofacialSurgety (1998) 26, 22-28 © 1998 European Association for Cranio-Maxillofacial Surgery
Reproducibility of aimed-at profiles Robert E. C. M. Mooren, Hans Peter M. Freihofer, Wilfred A. Borstlap
Department of Oral and Maxillofacial Surgery (Head." Prof. H. P. M. Freihofer), University Hospital Nijmegen, The Netherlands SUMMARY. Would a surgeon always draw the same aimed-at profile when planning the correction of a face with evidently malpositioned jaws? The same 10 profile lines were given to seven maxillofacial surgeons on two occasions at intervals of 6 months. The differences in absolute and proportional vertical measurements were compared. It is shown that the variations between first and second drawing were quite large for individual values. However, even the mean differences per measurement vary between surgeons from 0 to 10%. The drawings for the whole group corresponded reasonably well with the ratios given by Farkas and Munro (1987) but were rather divergent from the 'golden dimensions' proposed by Brons and Muli~ (1993). Considering the sometimes significant differences, one is advised not to draw profiles 'off the cuff' but to use a construction system for planning osteotomies.
INTRODUCTION
and the inclination of the tangent to upper lip and chin with a precision of 0.5 °. The middle third, i.e. the nasal height, was measured between soft tissue nasion and subnasale. Ratios were calculated and the data were compared with the first series. The mean error of measurement was 0.7 mm for linear measurements, being less for the upper and more for the lower jaw, 0.5 ° for angles and 0.01 for ratios. As points of orientation, deviations of 5% and 10%, 4 ° and for ratios 0.04, which also corresponds to 5%, were used.
An earlier study (Freihofer and Mooren, 1996, 1997) has shown that there is some variability amongst surgeons then they are asked to draw the ideal profile line of any given line for a case with obviously malpositioned jaws. It was observed simultaneously that different surgeons handled a series of aberrant profile lines differently. Some drew similar profiles for all the profiles submitted while others demonstrated considerable differences between the various propositions. The next question to answer was whether the surgeons were consistent in their plans. Would a second drawing for the same patient differ from the first? In other words, are the drawings reproducible or done on the spur of the moment?
RESULTS
Upper lip The differences in height of the upper lip varied only slightly in absolute numbers. The range was in most cases quite similar to the first series, and only one mean differed a little more than 5% from the first value (Fig. 1). Nevertheless, almost 30% of the individual values differed between 5 and 10%; 15% were even more than 10%.
M A T E R I A L S AND M E T H O D S The same 10 profile lines as previously produced (Freihofer and Mooren, 1996, 1997) were given to the same seven senior maxillofacial surgeons of the department 6 months later. They were again asked to draw the profile lines o f the lower third of the face which they wished to give to these patients. No changes to the forehead or the nose should be considered. They were permitted to draw them 'artistically' off the cuff, or to use some construction or other with reference lines. The drawing was not to be based on the facial analysis of Brons (Brons and Mulid, 1993). The height of the upper lip between subnasale and stomion and the lower jaw between stomion and gnathion was measured with a precision of 0.5 mm
Height of the lower jaw The findings were considerably less uniform for the lower jaw. Ranges shortened by up to 40% or increased up to 65% and only four means varied by 5% or less (Fig. 2). For two surgeons, the second range was found completely within the first range, for two it was the other way round. The variations per case were quite marked and were found between 5 and 10% in 25%. Changes of more than 10% were even more frequent 22
Reproducibility of aimed-at profiles 23 50
45
40
35
llMean
,7
20
t0
la
lb
2a
2b
3a
3b
411
4b
5~
5b
6a
6b
7=
7b
surgeons
Fig. 1 - Ranges and means of the height of the upper lip in the two consecutiveindentical series drawn by the seven surgeons. The differences in the sevenpairs of means were 4%, -1%, -7%, 2%, 2%, 2% and -2%.
75
70
'-=
IIMean
lg
lb
2a
2b
3a
3b
4~
4b
5a
5b
6~
eb
7a
?b
Surgeons
Fig. 2 - Ranges and means of the height of the lowerjaw in the two indentical series. The differencesin the seven pairs of means were-2%, -11%, -1%, 5%, -2%, 8% and -9%. (one third), one surgeon having not less than six in that area and all had at least one case outside that margin.
Overall height of the lower third Considering the variations of its parts, it is not surprising that the variations in the total height of the lower third were also marked (Fig. 3). The smallest change in range was 15%, while the most important were 55% narrower, and 130% broader. The variations in the means were still rather small, four being less than 5% and all of them less than 10%. However, 30% of the second values differed by 5% to 10% from the first, 15% by more than 10%. One surgeon had just one and two had seven values outside the 5% margin (Fig. 6).
Angulation The angulation of the tangent from the upper lip to the chin did not seem to vary too much. A general trend to have the profile lines more retroclined was seen in the second series. The difference of the mean was, in most series, 2 ° or less. However, there was clear evidence of coincidental compensation since 40% of the single measurements showed changes o f more than 4 ° .
Ratio of upper lip to lower jaw The range of ratios did not show spectacular changes. They were evenly distributed between 3% and 10% (Fig. 4). However, of the single values, 25% were
24 Journalof Cranio-Maxillofacial Surgery
95.
90, gs.
8o
75
p
°]
55
50 la
lb
2tl
2b
3a
3b
4a
4b
5a
5b
Sa
6b
7a
7b
Surgeons
Fig. 3 Rangesand means of the total height of the lower third of the face. The differencesin the sevenpairs of means were -1%, -8%, -3%, 4%, 1%, 6% and -7%.
0,70.
0,60, T
O,56
O,30-
0,20.
0,I0 •
0,00 la
lb
2a
2b
3a
3b
4a
4b
5a
5b
6a
5b
7a
7b
Surgeons
Fig. 4 - Ranges and means of the ratios of upper lip to lowerjaw height. The differencesin the sevenpairs of means were 5%, 6%, 7%, 4%, 3%, 8% and 10%. between the 5% and the 10% limits and another 15% even outside the 10% margin (Fig. 7). It is noteworthy that five surgeons together drew 11 profiles with a ratio of 0.50 or more in total in the two series, i.e. only about 10% of all their profile lines, while the two remaining planned 19 profiles this way, which amounts to about 50%.
difficult profile lines. In case 8, all variations except one were less than 3%, in case 6 five were outside and two just within the 5% limit. Cases with ratios of 0.62 or less were uncommon, only about 20%, and distributed rather regularly over the surgeons. Most means were between 0.70 and 0.80.
Ratio of nasal height to lower third
DISCUSSION
The ranges look quite similar but only two surgeons had a difference of the means of 1%, while the others had changes between 6% and 8% (Fig. 5). The differences for individual profiles were considerable, almost 30% between 5% and 10% and another 10% outside the 10% margin (Fig. 8). There seem to be easy and
The study was planned to give information about the consistency of profile line drawing. These drawings are quite an important instrument in planning the correction of profiles by osteotomies of the jaws, since they represent the 'ideal' profile line at which the surgeon aims in his treatment.
Reproducibility of aimed-at profiles 25 1,10
1,00
+
O,SO.
!
i 0,00 -
I
I 0,78 0,70 0,74
I 0,7~
0,71
I
0,70 -
0,60.
0,50 •
0~40 la
lb
2a
2b
3a
3b
4a
4b
5a
5b
Oa
6b
7a
7b
Surgeons
Fig. 5 - Ranges and means of the ratios of the nasal height to the lower third of the face. The differences in the sevenpairs of means were 1%, 7%, 7%, 6%, 1%, -7% and 8%.
o21
t
X4 ¸
Io01 +7 i
--
1
2
3
4
5
0
7
i
0
9
10
Ca~s
Differencesin the total height of the lower facial third in mm between first and second drawingper profile for the seven surgeons (3.5 mm = 5%).
Fig. 6 -
A rather simple set-up was chosen, asking surgeons, at an interval of 6 months, to draw the same 10 profile lines. The deviations of these profiles were chosen to represent a rather broad spectrum, i.e. Angle classes II and III, with or without open bite. A measurement error had to be accepted. Since the height of the middle third was not changed, the same values were used for all calculations. The point Sn was chosen once for all profiles. Since the lower border of the upper lip is well defined, it is not surprising that the inter-observer measurement error was small (0.5 mm). On the other hand, the soft tissue contour below the chin was often drawn more or less obliquely; that is, not horizontally. Consequently, the level of the submental tissues and, with that, the caudal point of measurement of the lower third was open to discussion. As
it was also unique for each drawing, it is not surprising, that the error was greater (1.5 mm). Of course, the most important question is whether variations are tolerable. They are almost unavoidable and the margin is probably a value between 5% and 10%. In our opinion, a 5% change of one part does not influence the profile markedly (Figs. 9-11). However, a 10% difference is visible. Since one has to consider that a 5% reduction in one part and a 5% addition to the other part also induce a 10% difference in total, resulting in a change of the ratio of 0.04, it indicates where a reasonable limit could be placed approximately. In this example, the total height of the lower third would change only 2% and the ratio nasale height to lower third only 0.02. Based on such calculations, we are inclined to allow only for rather
26
Journalof Cranio-MaxillofacialSurgery 0,25 •
o,2
i
0,15
0,1 ~
- - = ' 1
-0,1 ,
-0,2 • -0,25 1
Fig. 7
-
2
3
4
5
6 Case=
7
0
9
10
Differences in the ratios of the upper lip to the lower jaw per profile for the seven surgeons (0.004 = 5%).
0,25, 0,2, 0,15, 0,~,
0,05,
-i l -
.0,0
~2 A3 X4 e5
+7
-0,1,
-0,25 1
2
3
4
5
6
7
8
10
9
Cases
Fig. 8
-
Differences in the ratios of the nasal height to the total height of the lower third of the face (0.05 = 5%).
.io,(
.5,(
+5
+
P
J
_
0.41
0.43
0,45
0.47
0.50
Fig. 9 - Variations of a profile line by reducing respectively augmenting the upper lip by 5% and 10%. The corresponding ratios are given
for upper lip to lower jaw (upper row) and nasal height to lower third of the face (lower row). In the middle as a reference is the mean of all values measured.
Reproducibility of aimed-at profiles
27
( < -5%
_) 0.50 0.76
0.47 0.75
0.45
0.43
0.41
0.73
0.70
0.68
Fig. 10 - Variations of a profile line by reducing respectively augmenting the lower jaw by 5% and 10%. The corresponding ratios and the same reference are given.
- 10
- 5%
+5
+10
0.45
0.45
0.45
0.45
0.45
0.80
0.76
O.73
0.69
0,66
Fig. 11 - Variations in the profile line by reducing respectively augmenting both upper lip and lower jaw by 5% and 10%. The corresponding ratios and the same reference are given.
restricted variations. In our view, one should be even more careful with changes in the inclination of the lower third. The differences were surprising and were mainly due to the height of the mandible. This seems to be the critical area for changes. It is evident that with the constancy of the values in the upper lip (which can be explained by the fact that important modifications were seldom considered necessary there) and the variations in the mandible, the ratios also had to change
quite a bit, One would expect that there are changes of 5% to 10% now and then, but it came as a surprise that the means changed so much for most surgeons and that the differences did not compensate. With a lot of reservations, one could assume that a surgeon one day favours drawing deep high mandibles and at other times prefers short ones. Furthermore, there are apparently easy and difficult profiles. Some seem to dictate a correction, as is shown by a small range of ratios for cases 2 and 10 for
28 Journalof Cranio-MaxillofacialSurgery upper lip to lower jaw (Fig. 7) or case 9 for middle to lower third (Fig. 8), while others stimulate free ranging fantasy. This can also be seen by the position of the profile line. About 20% profiles of the average type ('Mittelwertsgesicht' according to Schwarz, 1951) were drawn, the others were all more or less markedly straightforward. Everybody had at least one average type profile, and it was the profile of the same patient for all. If one had a second, again it was the same patient for all of them. Of course, one can go further and add up all six individual differences under Figures 6-8. This shows that there are surgeons with rather small differences (e.g. number l) while number 7 had more than twice as much, the others being more or less grouped together in-between. For the ratios, three surgeons (numbers 1, 4 and 5) have mean differences around 0.03, which is below the 5% limit (i.e. 0.04), three others have about 0.05, which is just above the limit, and number 7 has 0.08. Looking at the ratios in comparison with existing advice reveals the following. Only 20% of all the lower thirds have ratios of upper lip to lower jaw of more than 1:2 (the value proposed by da Vinci) and only two are below 1:3 (as proposed by Diirer). Four profiles only, all drawn by the same surgeon, are above 0.62, which is the golden range utilized by Brons (Brons and MuliO, 1993). It seems that, for our group, a ratio of 0.4 to 0.5 is aesthetically acceptable and most natural. Our mean of all values together perfectly fits the 0.45, which is given by Farkas and Munro (1987) for the normal young adult face. The ratio of nasal height to lower third cannot be compared reliably with the 1:1 advocated by the famous painters da Vinci and Dfirer because of different measurement points. However, it can be compared with the advice of the golden range (Brons and MuliO, 1993). Only 15% are below 0.62 and the great majority between 0.7 and 0.9. Assuming that another centimetre should be added to the middle third (up to glabella point) to make comparison with Diirer possible, it would bring the ratios in the vicinity of 1.0. Again, the recommendation of the two artists seems to suggest a profile line which appear to us more natural than the theoretically based, more attractive golden range. The mean of all our ratios also corresponds to 0.75, almost perfectly to the value of 0.73 of the Caucasian young adult (Farkas and Munro, 1987).
CONCLUSION The present study confirms the conclusions drawn, based on the first series, that there is considerable variation between surgeons when drawing aimed-at profile lines. It is further shown that, without any additional guidelines, the profile lines are not very reproducible in the lower third of the face. Furthermore, quite impressive differences can be noted when comparing reproducibility between surgeons. This indicates very clearly that aimed-at profiles should not be drawn 'artistically,' even by experienced surgeons. Which construction system should be used remains open to discussion. In any case, it seems necessary that the guidelines of facial harmony as elaborated by Brons and Mulid (1993) are carefully evaluated with respect to the broad spectrum of profiles which fulfil their conditions. Although their basal guideline is the golden range, (which is without doubt very harmonious as a mathematical principle) ratios with or in proximity to this value were exceptional in this study, suggesting that other facial proportions are more accepted. References
Brons, R., R. 3/[. Mulid: Faciale harmonie. Smits, Den Haag 1993 Da Vinci, L. : In: Gonzal6s:Transact. Int. Conf. Oral Surg.
Churchill Livingstone,Edinburgh 1970 Diirer, A.: In: Brons and Muli& Faciale harmonie. Smit, Den Haag
1993 Farkas, L. G, ~ R. Munro. Anthropometricfacial proportions in
medicine. Thomas, Springfield1987 Freihofer, H. P. M., R. E. C. M. Mooren." Correctingprofiles.The
Goal. Abstr. Congress EACMFS, Zfirich,J. CranioMaxillofac. Surg. 24 (1996) Suppl. 1, 43 Freihofer, H. P M., R. E. C. M. Mooren: Profiloplasty: Variations in personal views. J. Cranio-Maxillofac.Surg. 25 (1997) 249-253 Schwarz, A. M.: Lehrgangder Gebissregutierung.Urban and Schwarzenberg,Wien-Innsbruck 1961 R. E. C. M. Mooren MD, DMD
Dept. OraI and MaxillofacialSurgery UniversityHospital Nijmegen EB. Box 9101 NL-6500 HB Nijmegen The Netherlands Paper received28 September. 1997 Accepted 22 December. 1997
Reproducibility of aimed-at profiles Robert E. C. M. Mooren, Hans Peter M. Freihofer, Wilfred A. Borstlap
Department of Oral and Maxillofacial Surgery (Head." Prof. H. P. M. Freihofer), University Hospital Nijmegen, The Netherlands SUMMARY. Would a surgeon always draw the same aimed-at profile when planning the correction of a face with evidently malpositioned jaws? The same 10 profile lines were given to seven maxillofacial surgeons on two occasions at intervals of 6 months. The differences in absolute and proportional vertical measurements were compared. It is shown that the variations between first and second drawing were quite large for individual values. However, even the mean differences per measurement vary between surgeons from 0 to 10%. The drawings for the whole group corresponded reasonably well with the ratios given by Farkas and Munro (1987) but were rather divergent from the 'golden dimensions' proposed by Brons and Muli~ (1993). Considering the sometimes significant differences, one is advised not to draw profiles 'off the cuff' but to use a construction system for planning osteotomies.
INTRODUCTION
and the inclination of the tangent to upper lip and chin with a precision of 0.5 °. The middle third, i.e. the nasal height, was measured between soft tissue nasion and subnasale. Ratios were calculated and the data were compared with the first series. The mean error of measurement was 0.7 mm for linear measurements, being less for the upper and more for the lower jaw, 0.5 ° for angles and 0.01 for ratios. As points of orientation, deviations of 5% and 10%, 4 ° and for ratios 0.04, which also corresponds to 5%, were used.
An earlier study (Freihofer and Mooren, 1996, 1997) has shown that there is some variability amongst surgeons then they are asked to draw the ideal profile line of any given line for a case with obviously malpositioned jaws. It was observed simultaneously that different surgeons handled a series of aberrant profile lines differently. Some drew similar profiles for all the profiles submitted while others demonstrated considerable differences between the various propositions. The next question to answer was whether the surgeons were consistent in their plans. Would a second drawing for the same patient differ from the first? In other words, are the drawings reproducible or done on the spur of the moment?
RESULTS
Upper lip The differences in height of the upper lip varied only slightly in absolute numbers. The range was in most cases quite similar to the first series, and only one mean differed a little more than 5% from the first value (Fig. 1). Nevertheless, almost 30% of the individual values differed between 5 and 10%; 15% were even more than 10%.
M A T E R I A L S AND M E T H O D S The same 10 profile lines as previously produced (Freihofer and Mooren, 1996, 1997) were given to the same seven senior maxillofacial surgeons of the department 6 months later. They were again asked to draw the profile lines o f the lower third of the face which they wished to give to these patients. No changes to the forehead or the nose should be considered. They were permitted to draw them 'artistically' off the cuff, or to use some construction or other with reference lines. The drawing was not to be based on the facial analysis of Brons (Brons and Mulid, 1993). The height of the upper lip between subnasale and stomion and the lower jaw between stomion and gnathion was measured with a precision of 0.5 mm
Height of the lower jaw The findings were considerably less uniform for the lower jaw. Ranges shortened by up to 40% or increased up to 65% and only four means varied by 5% or less (Fig. 2). For two surgeons, the second range was found completely within the first range, for two it was the other way round. The variations per case were quite marked and were found between 5 and 10% in 25%. Changes of more than 10% were even more frequent 22
Reproducibility of aimed-at profiles 23 50
45
40
35
llMean
,7
20
t0
la
lb
2a
2b
3a
3b
411
4b
5~
5b
6a
6b
7=
7b
surgeons
Fig. 1 - Ranges and means of the height of the upper lip in the two consecutiveindentical series drawn by the seven surgeons. The differences in the sevenpairs of means were 4%, -1%, -7%, 2%, 2%, 2% and -2%.
75
70
'-=
IIMean
lg
lb
2a
2b
3a
3b
4~
4b
5a
5b
6~
eb
7a
?b
Surgeons
Fig. 2 - Ranges and means of the height of the lowerjaw in the two indentical series. The differencesin the seven pairs of means were-2%, -11%, -1%, 5%, -2%, 8% and -9%. (one third), one surgeon having not less than six in that area and all had at least one case outside that margin.
Overall height of the lower third Considering the variations of its parts, it is not surprising that the variations in the total height of the lower third were also marked (Fig. 3). The smallest change in range was 15%, while the most important were 55% narrower, and 130% broader. The variations in the means were still rather small, four being less than 5% and all of them less than 10%. However, 30% of the second values differed by 5% to 10% from the first, 15% by more than 10%. One surgeon had just one and two had seven values outside the 5% margin (Fig. 6).
Angulation The angulation of the tangent from the upper lip to the chin did not seem to vary too much. A general trend to have the profile lines more retroclined was seen in the second series. The difference of the mean was, in most series, 2 ° or less. However, there was clear evidence of coincidental compensation since 40% of the single measurements showed changes o f more than 4 ° .
Ratio of upper lip to lower jaw The range of ratios did not show spectacular changes. They were evenly distributed between 3% and 10% (Fig. 4). However, of the single values, 25% were
24 Journalof Cranio-Maxillofacial Surgery
95.
90, gs.
8o
75
p
°]
55
50 la
lb
2tl
2b
3a
3b
4a
4b
5a
5b
Sa
6b
7a
7b
Surgeons
Fig. 3 Rangesand means of the total height of the lower third of the face. The differencesin the sevenpairs of means were -1%, -8%, -3%, 4%, 1%, 6% and -7%.
0,70.
0,60, T
O,56
O,30-
0,20.
0,I0 •
0,00 la
lb
2a
2b
3a
3b
4a
4b
5a
5b
6a
5b
7a
7b
Surgeons
Fig. 4 - Ranges and means of the ratios of upper lip to lowerjaw height. The differencesin the sevenpairs of means were 5%, 6%, 7%, 4%, 3%, 8% and 10%. between the 5% and the 10% limits and another 15% even outside the 10% margin (Fig. 7). It is noteworthy that five surgeons together drew 11 profiles with a ratio of 0.50 or more in total in the two series, i.e. only about 10% of all their profile lines, while the two remaining planned 19 profiles this way, which amounts to about 50%.
difficult profile lines. In case 8, all variations except one were less than 3%, in case 6 five were outside and two just within the 5% limit. Cases with ratios of 0.62 or less were uncommon, only about 20%, and distributed rather regularly over the surgeons. Most means were between 0.70 and 0.80.
Ratio of nasal height to lower third
DISCUSSION
The ranges look quite similar but only two surgeons had a difference of the means of 1%, while the others had changes between 6% and 8% (Fig. 5). The differences for individual profiles were considerable, almost 30% between 5% and 10% and another 10% outside the 10% margin (Fig. 8). There seem to be easy and
The study was planned to give information about the consistency of profile line drawing. These drawings are quite an important instrument in planning the correction of profiles by osteotomies of the jaws, since they represent the 'ideal' profile line at which the surgeon aims in his treatment.
Reproducibility of aimed-at profiles 25 1,10
1,00
+
O,SO.
!
i 0,00 -
I
I 0,78 0,70 0,74
I 0,7~
0,71
I
0,70 -
0,60.
0,50 •
0~40 la
lb
2a
2b
3a
3b
4a
4b
5a
5b
Oa
6b
7a
7b
Surgeons
Fig. 5 - Ranges and means of the ratios of the nasal height to the lower third of the face. The differences in the sevenpairs of means were 1%, 7%, 7%, 6%, 1%, -7% and 8%.
o21
t
X4 ¸
Io01 +7 i
--
1
2
3
4
5
0
7
i
0
9
10
Ca~s
Differencesin the total height of the lower facial third in mm between first and second drawingper profile for the seven surgeons (3.5 mm = 5%).
Fig. 6 -
A rather simple set-up was chosen, asking surgeons, at an interval of 6 months, to draw the same 10 profile lines. The deviations of these profiles were chosen to represent a rather broad spectrum, i.e. Angle classes II and III, with or without open bite. A measurement error had to be accepted. Since the height of the middle third was not changed, the same values were used for all calculations. The point Sn was chosen once for all profiles. Since the lower border of the upper lip is well defined, it is not surprising that the inter-observer measurement error was small (0.5 mm). On the other hand, the soft tissue contour below the chin was often drawn more or less obliquely; that is, not horizontally. Consequently, the level of the submental tissues and, with that, the caudal point of measurement of the lower third was open to discussion. As
it was also unique for each drawing, it is not surprising, that the error was greater (1.5 mm). Of course, the most important question is whether variations are tolerable. They are almost unavoidable and the margin is probably a value between 5% and 10%. In our opinion, a 5% change of one part does not influence the profile markedly (Figs. 9-11). However, a 10% difference is visible. Since one has to consider that a 5% reduction in one part and a 5% addition to the other part also induce a 10% difference in total, resulting in a change of the ratio of 0.04, it indicates where a reasonable limit could be placed approximately. In this example, the total height of the lower third would change only 2% and the ratio nasale height to lower third only 0.02. Based on such calculations, we are inclined to allow only for rather
26
Journalof Cranio-MaxillofacialSurgery 0,25 •
o,2
i
0,15
0,1 ~
- - = ' 1
-0,1 ,
-0,2 • -0,25 1
Fig. 7
-
2
3
4
5
6 Case=
7
0
9
10
Differences in the ratios of the upper lip to the lower jaw per profile for the seven surgeons (0.004 = 5%).
0,25, 0,2, 0,15, 0,~,
0,05,
-i l -
.0,0
~2 A3 X4 e5
+7
-0,1,
-0,25 1
2
3
4
5
6
7
8
10
9
Cases
Fig. 8
-
Differences in the ratios of the nasal height to the total height of the lower third of the face (0.05 = 5%).
.io,(
.5,(
+5
+
P
J
_
0.41
0.43
0,45
0.47
0.50
Fig. 9 - Variations of a profile line by reducing respectively augmenting the upper lip by 5% and 10%. The corresponding ratios are given
for upper lip to lower jaw (upper row) and nasal height to lower third of the face (lower row). In the middle as a reference is the mean of all values measured.
Reproducibility of aimed-at profiles
27
( < -5%
_) 0.50 0.76
0.47 0.75
0.45
0.43
0.41
0.73
0.70
0.68
Fig. 10 - Variations of a profile line by reducing respectively augmenting the lower jaw by 5% and 10%. The corresponding ratios and the same reference are given.
- 10
- 5%
+5
+10
0.45
0.45
0.45
0.45
0.45
0.80
0.76
O.73
0.69
0,66
Fig. 11 - Variations in the profile line by reducing respectively augmenting both upper lip and lower jaw by 5% and 10%. The corresponding ratios and the same reference are given.
restricted variations. In our view, one should be even more careful with changes in the inclination of the lower third. The differences were surprising and were mainly due to the height of the mandible. This seems to be the critical area for changes. It is evident that with the constancy of the values in the upper lip (which can be explained by the fact that important modifications were seldom considered necessary there) and the variations in the mandible, the ratios also had to change
quite a bit, One would expect that there are changes of 5% to 10% now and then, but it came as a surprise that the means changed so much for most surgeons and that the differences did not compensate. With a lot of reservations, one could assume that a surgeon one day favours drawing deep high mandibles and at other times prefers short ones. Furthermore, there are apparently easy and difficult profiles. Some seem to dictate a correction, as is shown by a small range of ratios for cases 2 and 10 for
28 Journalof Cranio-MaxillofacialSurgery upper lip to lower jaw (Fig. 7) or case 9 for middle to lower third (Fig. 8), while others stimulate free ranging fantasy. This can also be seen by the position of the profile line. About 20% profiles of the average type ('Mittelwertsgesicht' according to Schwarz, 1951) were drawn, the others were all more or less markedly straightforward. Everybody had at least one average type profile, and it was the profile of the same patient for all. If one had a second, again it was the same patient for all of them. Of course, one can go further and add up all six individual differences under Figures 6-8. This shows that there are surgeons with rather small differences (e.g. number l) while number 7 had more than twice as much, the others being more or less grouped together in-between. For the ratios, three surgeons (numbers 1, 4 and 5) have mean differences around 0.03, which is below the 5% limit (i.e. 0.04), three others have about 0.05, which is just above the limit, and number 7 has 0.08. Looking at the ratios in comparison with existing advice reveals the following. Only 20% of all the lower thirds have ratios of upper lip to lower jaw of more than 1:2 (the value proposed by da Vinci) and only two are below 1:3 (as proposed by Diirer). Four profiles only, all drawn by the same surgeon, are above 0.62, which is the golden range utilized by Brons (Brons and MuliO, 1993). It seems that, for our group, a ratio of 0.4 to 0.5 is aesthetically acceptable and most natural. Our mean of all values together perfectly fits the 0.45, which is given by Farkas and Munro (1987) for the normal young adult face. The ratio of nasal height to lower third cannot be compared reliably with the 1:1 advocated by the famous painters da Vinci and Dfirer because of different measurement points. However, it can be compared with the advice of the golden range (Brons and MuliO, 1993). Only 15% are below 0.62 and the great majority between 0.7 and 0.9. Assuming that another centimetre should be added to the middle third (up to glabella point) to make comparison with Diirer possible, it would bring the ratios in the vicinity of 1.0. Again, the recommendation of the two artists seems to suggest a profile line which appear to us more natural than the theoretically based, more attractive golden range. The mean of all our ratios also corresponds to 0.75, almost perfectly to the value of 0.73 of the Caucasian young adult (Farkas and Munro, 1987).
CONCLUSION The present study confirms the conclusions drawn, based on the first series, that there is considerable variation between surgeons when drawing aimed-at profile lines. It is further shown that, without any additional guidelines, the profile lines are not very reproducible in the lower third of the face. Furthermore, quite impressive differences can be noted when comparing reproducibility between surgeons. This indicates very clearly that aimed-at profiles should not be drawn 'artistically,' even by experienced surgeons. Which construction system should be used remains open to discussion. In any case, it seems necessary that the guidelines of facial harmony as elaborated by Brons and Mulid (1993) are carefully evaluated with respect to the broad spectrum of profiles which fulfil their conditions. Although their basal guideline is the golden range, (which is without doubt very harmonious as a mathematical principle) ratios with or in proximity to this value were exceptional in this study, suggesting that other facial proportions are more accepted. References
Brons, R., R. 3/[. Mulid: Faciale harmonie. Smits, Den Haag 1993 Da Vinci, L. : In: Gonzal6s:Transact. Int. Conf. Oral Surg.
Churchill Livingstone,Edinburgh 1970 Diirer, A.: In: Brons and Muli& Faciale harmonie. Smit, Den Haag
1993 Farkas, L. G, ~ R. Munro. Anthropometricfacial proportions in
medicine. Thomas, Springfield1987 Freihofer, H. P. M., R. E. C. M. Mooren." Correctingprofiles.The
Goal. Abstr. Congress EACMFS, Zfirich,J. CranioMaxillofac. Surg. 24 (1996) Suppl. 1, 43 Freihofer, H. P M., R. E. C. M. Mooren: Profiloplasty: Variations in personal views. J. Cranio-Maxillofac.Surg. 25 (1997) 249-253 Schwarz, A. M.: Lehrgangder Gebissregutierung.Urban and Schwarzenberg,Wien-Innsbruck 1961 R. E. C. M. Mooren MD, DMD
Dept. OraI and MaxillofacialSurgery UniversityHospital Nijmegen EB. Box 9101 NL-6500 HB Nijmegen The Netherlands Paper received28 September. 1997 Accepted 22 December. 1997