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A calendar of facial growth
A C A L E N D A R O F FACIAL G R O W T H By D. G~ErR WALKER, M.D., F.D.S.R.C.S.(Eng.)
Stoke Mandeville Hospital, Aylesbury IT has been a pleasant task to contribute to a number of the ffournal produced in honour of Professor Kilner, the more so since we shared an interest in malformations of the face for twenty-five years. It is interesting to look back over that period to the days when anresthesia was not the skilled performance it is to-day, when bone grafts of the jaw suffered the fate of infection, and when cleft palates were the domain of the general surgeon. The period has seen many changes and perhaps the most vivid in my mind is the large collection of untreated facial malformations of the earlier days in contrast to the few that are seen to-day. There can be little doubt that introduction of the antibiotics has allowed tremendous advances. It can further be said that the various operative techniques have to a large extent been worked out and that the particular method of choice is a matter of personal preference. The next big advance will be in the field of the transplantation of tissue and this will end some of the problems that confront us to-day. One of Professor Kilner's main interests was, of course, cleft lip and palate lesions. The efforts of the plastic surgeons over the past quarter of a century to place the treatment of these cases on a rational basis stands out in great contrast to the remainder of facial and jaw surgery in which, to say the least, there appears to be no scientific basis. In the case of the cleft lip, the repair is carried out shortly after birth so that the child may suck. In a similar way the palate is restored before the child begins to speak. Anyone associated with Professor Kilner was well aware of the timing basis for these operations ; and also in the cases of bat ears and of hypospadias where corrections were performed before the child went to school with the object of preventing psychological trauma. The above reasons for justifying the time of operations are important considerations in attempting to formulate a calendar for the particular child so that all operations can be placed in a rational order. It is unfortunate that there are many other malformations of the face that are placed in the category with the object of waiting until growth is completed. No longer can surgery be based on the personal opinion of the particular surgeon who all too frequently is apt to have no basis for his argument. The day of the empirical approach to these problems is past. All facial and jaw operations for congenital and acquired malformations need a more scientific approach to the timing of the operation. Twenty years ago at Stoke Mandeville valuable discussions began with the object of establishing earlier treatment for many facial malformations. It was then that certain seeds were sown such as the desire to treat prognathism during the growing period, and if needs be by more than one operation. Correspondingly the unilateral or bilateral micrognathic jaw was lengthened at an early age. Since Professor Kilner was actively interested in these problems it is proposed to outline briefly certain of these procedures which it might be added are not the general practice of many other units. The conditions that will be described are : I. Mierognathism. (a) Associated with condylar agenesis. (b) Associated with ankylosis. (c) The genetic small jaw. 424
A CALENDAR
OF
FACIAL
GROWTH
425
2. Prognathism. (a) Without open bite. (b) With open bite. I. M i c r o g n a t h i s m . - - ( a ) Associated with Condylar Agenesis.--Some years ago I reported some fifty cases o f unilateral and bilateral condylar agenesis that resulted from either trauma or infection. Previously these cases, mostly of the unilateral variety, had been left until adult life when they were treated by an extensive buccal inlay. T h e r e was no doubt that the external appearance, as the result of this operation, was greatly improved. T h e r e was, however, the disadvantage that the patients were committed to wear a prosthesis for the remainder o f their lives and, furthermore, as they became edentulous so the stability of the appliance suffered. T h e issue that arose was simply how early could these cases be treated, and since we knew about condylar cartilage growth surely all that was needed was simply to supply the length by way of an interstitial bone graft. T h e history of these cases and the treatment is interesting, and since the major n u m b e r were treated by M r R. P. Osborne and myself it is interesting to record a few observations. Having decided that the shortened jaw should be elongated the next step was to decide how early. T h e first case treated in the younger group of patients was aged I I years, and while the correction of the deviation was rectified it was immediately obvious that at this stage the jaw was already flattened and distorted. It was further obvious that the articulation of the teeth was becoming stabilised and little could be done in the way o f orthodontia. For these reasons it was decided to operate earlier and one of the most successful results shortly afterwards was a child where the jaw was elongated at 4 years o f age. It is difficult to define an exact time for the best period of operation since so much depends on the degree o f condylar growth failure and the time of the initial infection or trauma. Broadly speaking, the cases fall into two categories. T h e first the severe type that shows facial asymmetry requires early elongation (4 to 6 years) and may need a second operation. T h e second is the group needing correction between the ages of 6 and 9 years. T h e indication for the need for operation can be judged by the degree of shortening of the ramus and the corresponding asymmetry of the jaw. I f treatment is carried out at these ages orthodontic treatment can correct any minor dental irregularities. (b) Associated with Ankylosis.--There is no doubt that this is the most severe type of malformation and the one that demands the greatest care in treatment planning. In the past, and indeed at the present time, the old dictum of performing a condylectomy holds sway. T h e surgeon is imbued with the idea of freeing the temporo-mandibular joint. A recent tour of the Commonwealth countries gave me an opportunity to see a n u m b e r of these young children, and in all cases the question asked was, what is the next step in treatment ? We found this so difficult at Stoke Mandeville that many years ago we decided that the fundamental principle should be to elongate the jaw before performing an excision. Whether the case was unilateral or bilateral an osteotomy was performed in the ramus and the jaw elongated even to the point of over-correction. I f at all possible the freeing o f the ankylosis is delayed, and if needs be no hesitation should prevent successive elongations because a number of these children are brought for treatment at a very early age° (c) The Genetic Small ffaw.--There is a type of case where to all intents and 4G
426
BRITISH
JOURNAL
OF P L A S T I C
SURGERY
purposes the a~tiology is still unexplained. There is no ankylosis and no history of trauma or infection. The child presents an extremely small jaw out of all proportion to the size of the rest of the face. The problem here is the same as with the ankylosed jaw, but the elongation of the ramus does not really give the complete answer. It appears that the body of the jaw is the part at fault, and it may well be that in the future some method of elongating this part of the mandible may prove to be preferable. One of the interesting aspects about elongating the small jaw is the prevention of the sloping or receding chin. Whenever there is defective condylar growth the chin becomes more and more retroposed and the teeth further proclined forwards. This has presented many problems in the adult and the difficulty of onlay bone grafts or the old-fashioned buccal inlay still leave a lot to be desired. The chin can be kept vertical if there is adequate elongation early enough. 2. Prognathism.--(a) Without Open Bite.--Just as one has been advocating elongating the small jaw, so, in reverse, the plan of treatment in these cases is serial reduction. In the cases not associated with an open bite the jaw is shortened, on an average, at about the age of 12. The object is to keep the parts in harmony. On the cases undertaken at this age it has been found that a second operation is necessary in the late teenage. The purpose of this article is not to discuss technical operative procedures but rather to present the point of view that the derangement in skeletal growth ought to be treated earlier and by serial operations. Each individual surgeon will have his own ideas as to the best operative method, and this does not affect the basic principles. One cannot, however, fail to observe that the first operation calls for a shortening of the body of the mandible. The observation was made that ill certain micrognathism this part of the jaw was unduly small and the converse in prognathism suggests that in certain instances the body rather than the ramus is too big. (b) With Open Bite.--If any case demands an early operation it is the open bite. Many have experienced the great difficulty of treating these cases in the adult. The explanation of how these cases occur has so far baffled all experts. There appear to be many factors involved, but it is difficult to pin-point the particular one for each case. More recently we have been treating these cases surgically at the age of 12 years, and the final assessment cannot yet be given. So far, just as with micrognathism or prognathism, it would appear that some demand earlier treatment, while others can be postponed to 14 years of age when it is unlikely that any further operations wilt be needed. These operations gave hope for further efforts, but it became all too obvious as time went on that it ought to be possible by means of a carefully compiled calendar to state the best and correct times for operations. There is, however, one major difficulty. It is simple enough to work out the average and produce a growth table, but there is such variation around the normal that it required an actual analysis for each particular individual. The problem is therefore one of estimating the predetermined shape for the individual child. It will be appreciated that in the rather rare case of congenital absence, or defective growth of the nose, there are considerable differences in size of the face in any cross-section of the population. If therefore in the particular instance, we can estimate the eventual vertical height of the face for an individual the reconstruction can be not only accurate in length, but the times of operation can be based on a known growing period.
A CALENDAR
OF F A C I A L
GROWTH
427
T h e r e are many obstacles to be overcome, because while the length of the nose based on the distance between the nasion and the nasal spine is a comparatively easy problem, the same cannot be said about the abnormal mandible. It was for this reason that some work was undertaken not only to verify some of the lines of thought concerning skull and facial growth but with a view also to seek a means of predicting the final form of a child's skull and facial structures. T h e r e can be little disagreement about the rigidity with which the form o f bone is controlled. Possibly one of the best examples is seen in orthodontia where
A
FIG. I T h e g r o w t h of the forebrain. A, T h e relative anteroposterior size o f t h e skull at b i r t h is c o m p a r e d with t h e B adult. Placed in b e t w e e n t h e small skull o f a child to d e m o n s t r a t e d i a g r a m matically a half-way stage. As t h e forebrain a d v a n c e s it carries with it the facial structures. B, A similar c o m p a r i s o n was m a d e of t h e cranial base a n d palate. T h e circles in front of a n d lateral to t h e f o r a m e n m a g n u m are the external auditory m e a d and t h e glenoid foss~e.
the limitations of treatment are well recognised. I f the part is genetically determined it becomes obvious that in a collection such as in the skull it would be of immense value to decide if the individual differential of the part was determined early, and with this ratio established, we were confronted with an increase of the w h o l e - - t h e ratio of the parts remaining unaltered. In order to elucidate certain points the interesting experiment of comparing the skull at birth with the adult one was undertaken. In the first instance the skull at birth was superimposed upon the adult so that the centre of the foramen magnum was taken as a fixed point and the nasion of the small skull was placed on the line joining the foramen magnum with the nasion in the adult. This immediately suggested that there was tremendous forward growth of the face, and one could not refrain from drawing the conclusion that it was the growth of the anterior part of the brain that was responsible for this forward thrust (Fig. I). Further investigation of cephalometric radiographs suggested that at
428
BRITISH
JOURNAL
OF P L A S T I C
SURGERY
about 4 years this growth of the brain ended. The value of this deduction is that a date can be placed on the point of the nasion--there are further changes with the formation of the frontal sinus but further clinical growth studies are needed. Another point worthy of mention was that if the skull at birth was enlarged and superimposed in a similar manner on the adult, the increase in size being such that the nasion foramen magnum length was equal in both cases--there was a remarkable
.'
?.-.:.,~
. .......
::( "
)2
\
A
,,
!
,
B FIG. 2 T h e predetermined disposinon of the parts.
A, T h e skull at birth was enlarged up to the size of the adult. It will be noted that the calvarium of the y o u n g skull is bigger, and this can be explained by the fact that it stops growing before the facial structures. T h e greatest discrepancy is in the alveolar growth of the maxilla, but it will be noted that there is no great difference between the positions of the nasal spine. It is obvious that the major factor in facial growth is the vertical dimension (the mandible has been retracted to demonstrate this point). B, T h e young skulls in Figure 2, B have been enlarged to the size of the adult to confirm the findings in the horizontal plane.
~:ommon pattern suggesting that the differential of the parts is decided early and there then follows a uniform expansion maintaining the early established ratio (Fig. 2). The only failure in this respect in the facial bones was the maxillary alveolar area. This, of course, can be accounted for by the fact that at birth the development of the teeth and alveolar bone has not been completed. If this suggestion can be confirmed on a clinical growth series of cases it establishes that, with the exception of the vertical alveolar growth, it is possible to predict the final form in the facial structures. Similar studies of the cranial base supported comparable findings. So much for understanding the cranial base, calvarium, and facial bones, but the problem becomes very complicated in the attempt to estimate the alveolar
A CALENDAR OF FACIAL GROWTH
429 `
growth in the maxilla on account of the change that takes place in the direction of growth of the condylar cartilage (Fig. 3). The angle of the mandible is obtuse in the newborn. The reason for this is that in the first four years of life the lower jaw must keep pace with the rapid early forward growth of the face mentioned above. When the forward growth commences to slow down the mandible is changing its direction of growth so that it can take part in the vertical increase in the height of the face. At the moment there is no easy solution to the problem of estimating the
A
B FIG. 3 T h e change in the mandibular angle.
A, T h e relative position of the mandible at birth and 6 years of age is compared with the adult. I n the early stages the open angle allows the lower jaw to keep pace with the fast-growing forebrain. There is a gradual change so that the vertical growth of the maxilla can be accommodated. B, T h e same series of mandibles is enlarged to illustrate more clearly the change that takes place in condylar growth direction.
predetermined shape of the jaw. Nevertheless, it may be possible at a later date to predict the final form of the mandible. Following this rather crude estimation carried out on skull specimens it appeared that a case could be made for the early differential in the parts and that thereafter the process, with a few exceptions, was a smooth growth maintaining the early established ratios. These are only preliminary observations, and before definite statements can be made a carefully controlled growth study in clinical material must be undertaken. When work has advanced on these lines further information ought to be available, and particularly so if a careful survey of the growing child can be included in the study. On superficial examination it seems as if a carefully compiled calendar of growth will form the basis of surgical operations upon the facial structures. It is only in such a way that the rational will supersede the empirical approach. Figures I, 2, and 3 are reproduced by kind permission of the " British Dental Journal."
Stoke Mandeville Hospital, Aylesbury IT has been a pleasant task to contribute to a number of the ffournal produced in honour of Professor Kilner, the more so since we shared an interest in malformations of the face for twenty-five years. It is interesting to look back over that period to the days when anresthesia was not the skilled performance it is to-day, when bone grafts of the jaw suffered the fate of infection, and when cleft palates were the domain of the general surgeon. The period has seen many changes and perhaps the most vivid in my mind is the large collection of untreated facial malformations of the earlier days in contrast to the few that are seen to-day. There can be little doubt that introduction of the antibiotics has allowed tremendous advances. It can further be said that the various operative techniques have to a large extent been worked out and that the particular method of choice is a matter of personal preference. The next big advance will be in the field of the transplantation of tissue and this will end some of the problems that confront us to-day. One of Professor Kilner's main interests was, of course, cleft lip and palate lesions. The efforts of the plastic surgeons over the past quarter of a century to place the treatment of these cases on a rational basis stands out in great contrast to the remainder of facial and jaw surgery in which, to say the least, there appears to be no scientific basis. In the case of the cleft lip, the repair is carried out shortly after birth so that the child may suck. In a similar way the palate is restored before the child begins to speak. Anyone associated with Professor Kilner was well aware of the timing basis for these operations ; and also in the cases of bat ears and of hypospadias where corrections were performed before the child went to school with the object of preventing psychological trauma. The above reasons for justifying the time of operations are important considerations in attempting to formulate a calendar for the particular child so that all operations can be placed in a rational order. It is unfortunate that there are many other malformations of the face that are placed in the category with the object of waiting until growth is completed. No longer can surgery be based on the personal opinion of the particular surgeon who all too frequently is apt to have no basis for his argument. The day of the empirical approach to these problems is past. All facial and jaw operations for congenital and acquired malformations need a more scientific approach to the timing of the operation. Twenty years ago at Stoke Mandeville valuable discussions began with the object of establishing earlier treatment for many facial malformations. It was then that certain seeds were sown such as the desire to treat prognathism during the growing period, and if needs be by more than one operation. Correspondingly the unilateral or bilateral micrognathic jaw was lengthened at an early age. Since Professor Kilner was actively interested in these problems it is proposed to outline briefly certain of these procedures which it might be added are not the general practice of many other units. The conditions that will be described are : I. Mierognathism. (a) Associated with condylar agenesis. (b) Associated with ankylosis. (c) The genetic small jaw. 424
A CALENDAR
OF
FACIAL
GROWTH
425
2. Prognathism. (a) Without open bite. (b) With open bite. I. M i c r o g n a t h i s m . - - ( a ) Associated with Condylar Agenesis.--Some years ago I reported some fifty cases o f unilateral and bilateral condylar agenesis that resulted from either trauma or infection. Previously these cases, mostly of the unilateral variety, had been left until adult life when they were treated by an extensive buccal inlay. T h e r e was no doubt that the external appearance, as the result of this operation, was greatly improved. T h e r e was, however, the disadvantage that the patients were committed to wear a prosthesis for the remainder o f their lives and, furthermore, as they became edentulous so the stability of the appliance suffered. T h e issue that arose was simply how early could these cases be treated, and since we knew about condylar cartilage growth surely all that was needed was simply to supply the length by way of an interstitial bone graft. T h e history of these cases and the treatment is interesting, and since the major n u m b e r were treated by M r R. P. Osborne and myself it is interesting to record a few observations. Having decided that the shortened jaw should be elongated the next step was to decide how early. T h e first case treated in the younger group of patients was aged I I years, and while the correction of the deviation was rectified it was immediately obvious that at this stage the jaw was already flattened and distorted. It was further obvious that the articulation of the teeth was becoming stabilised and little could be done in the way o f orthodontia. For these reasons it was decided to operate earlier and one of the most successful results shortly afterwards was a child where the jaw was elongated at 4 years o f age. It is difficult to define an exact time for the best period of operation since so much depends on the degree o f condylar growth failure and the time of the initial infection or trauma. Broadly speaking, the cases fall into two categories. T h e first the severe type that shows facial asymmetry requires early elongation (4 to 6 years) and may need a second operation. T h e second is the group needing correction between the ages of 6 and 9 years. T h e indication for the need for operation can be judged by the degree of shortening of the ramus and the corresponding asymmetry of the jaw. I f treatment is carried out at these ages orthodontic treatment can correct any minor dental irregularities. (b) Associated with Ankylosis.--There is no doubt that this is the most severe type of malformation and the one that demands the greatest care in treatment planning. In the past, and indeed at the present time, the old dictum of performing a condylectomy holds sway. T h e surgeon is imbued with the idea of freeing the temporo-mandibular joint. A recent tour of the Commonwealth countries gave me an opportunity to see a n u m b e r of these young children, and in all cases the question asked was, what is the next step in treatment ? We found this so difficult at Stoke Mandeville that many years ago we decided that the fundamental principle should be to elongate the jaw before performing an excision. Whether the case was unilateral or bilateral an osteotomy was performed in the ramus and the jaw elongated even to the point of over-correction. I f at all possible the freeing o f the ankylosis is delayed, and if needs be no hesitation should prevent successive elongations because a number of these children are brought for treatment at a very early age° (c) The Genetic Small ffaw.--There is a type of case where to all intents and 4G
426
BRITISH
JOURNAL
OF P L A S T I C
SURGERY
purposes the a~tiology is still unexplained. There is no ankylosis and no history of trauma or infection. The child presents an extremely small jaw out of all proportion to the size of the rest of the face. The problem here is the same as with the ankylosed jaw, but the elongation of the ramus does not really give the complete answer. It appears that the body of the jaw is the part at fault, and it may well be that in the future some method of elongating this part of the mandible may prove to be preferable. One of the interesting aspects about elongating the small jaw is the prevention of the sloping or receding chin. Whenever there is defective condylar growth the chin becomes more and more retroposed and the teeth further proclined forwards. This has presented many problems in the adult and the difficulty of onlay bone grafts or the old-fashioned buccal inlay still leave a lot to be desired. The chin can be kept vertical if there is adequate elongation early enough. 2. Prognathism.--(a) Without Open Bite.--Just as one has been advocating elongating the small jaw, so, in reverse, the plan of treatment in these cases is serial reduction. In the cases not associated with an open bite the jaw is shortened, on an average, at about the age of 12. The object is to keep the parts in harmony. On the cases undertaken at this age it has been found that a second operation is necessary in the late teenage. The purpose of this article is not to discuss technical operative procedures but rather to present the point of view that the derangement in skeletal growth ought to be treated earlier and by serial operations. Each individual surgeon will have his own ideas as to the best operative method, and this does not affect the basic principles. One cannot, however, fail to observe that the first operation calls for a shortening of the body of the mandible. The observation was made that ill certain micrognathism this part of the jaw was unduly small and the converse in prognathism suggests that in certain instances the body rather than the ramus is too big. (b) With Open Bite.--If any case demands an early operation it is the open bite. Many have experienced the great difficulty of treating these cases in the adult. The explanation of how these cases occur has so far baffled all experts. There appear to be many factors involved, but it is difficult to pin-point the particular one for each case. More recently we have been treating these cases surgically at the age of 12 years, and the final assessment cannot yet be given. So far, just as with micrognathism or prognathism, it would appear that some demand earlier treatment, while others can be postponed to 14 years of age when it is unlikely that any further operations wilt be needed. These operations gave hope for further efforts, but it became all too obvious as time went on that it ought to be possible by means of a carefully compiled calendar to state the best and correct times for operations. There is, however, one major difficulty. It is simple enough to work out the average and produce a growth table, but there is such variation around the normal that it required an actual analysis for each particular individual. The problem is therefore one of estimating the predetermined shape for the individual child. It will be appreciated that in the rather rare case of congenital absence, or defective growth of the nose, there are considerable differences in size of the face in any cross-section of the population. If therefore in the particular instance, we can estimate the eventual vertical height of the face for an individual the reconstruction can be not only accurate in length, but the times of operation can be based on a known growing period.
A CALENDAR
OF F A C I A L
GROWTH
427
T h e r e are many obstacles to be overcome, because while the length of the nose based on the distance between the nasion and the nasal spine is a comparatively easy problem, the same cannot be said about the abnormal mandible. It was for this reason that some work was undertaken not only to verify some of the lines of thought concerning skull and facial growth but with a view also to seek a means of predicting the final form of a child's skull and facial structures. T h e r e can be little disagreement about the rigidity with which the form o f bone is controlled. Possibly one of the best examples is seen in orthodontia where
A
FIG. I T h e g r o w t h of the forebrain. A, T h e relative anteroposterior size o f t h e skull at b i r t h is c o m p a r e d with t h e B adult. Placed in b e t w e e n t h e small skull o f a child to d e m o n s t r a t e d i a g r a m matically a half-way stage. As t h e forebrain a d v a n c e s it carries with it the facial structures. B, A similar c o m p a r i s o n was m a d e of t h e cranial base a n d palate. T h e circles in front of a n d lateral to t h e f o r a m e n m a g n u m are the external auditory m e a d and t h e glenoid foss~e.
the limitations of treatment are well recognised. I f the part is genetically determined it becomes obvious that in a collection such as in the skull it would be of immense value to decide if the individual differential of the part was determined early, and with this ratio established, we were confronted with an increase of the w h o l e - - t h e ratio of the parts remaining unaltered. In order to elucidate certain points the interesting experiment of comparing the skull at birth with the adult one was undertaken. In the first instance the skull at birth was superimposed upon the adult so that the centre of the foramen magnum was taken as a fixed point and the nasion of the small skull was placed on the line joining the foramen magnum with the nasion in the adult. This immediately suggested that there was tremendous forward growth of the face, and one could not refrain from drawing the conclusion that it was the growth of the anterior part of the brain that was responsible for this forward thrust (Fig. I). Further investigation of cephalometric radiographs suggested that at
428
BRITISH
JOURNAL
OF P L A S T I C
SURGERY
about 4 years this growth of the brain ended. The value of this deduction is that a date can be placed on the point of the nasion--there are further changes with the formation of the frontal sinus but further clinical growth studies are needed. Another point worthy of mention was that if the skull at birth was enlarged and superimposed in a similar manner on the adult, the increase in size being such that the nasion foramen magnum length was equal in both cases--there was a remarkable
.'
?.-.:.,~
. .......
::( "
)2
\
A
,,
!
,
B FIG. 2 T h e predetermined disposinon of the parts.
A, T h e skull at birth was enlarged up to the size of the adult. It will be noted that the calvarium of the y o u n g skull is bigger, and this can be explained by the fact that it stops growing before the facial structures. T h e greatest discrepancy is in the alveolar growth of the maxilla, but it will be noted that there is no great difference between the positions of the nasal spine. It is obvious that the major factor in facial growth is the vertical dimension (the mandible has been retracted to demonstrate this point). B, T h e young skulls in Figure 2, B have been enlarged to the size of the adult to confirm the findings in the horizontal plane.
~:ommon pattern suggesting that the differential of the parts is decided early and there then follows a uniform expansion maintaining the early established ratio (Fig. 2). The only failure in this respect in the facial bones was the maxillary alveolar area. This, of course, can be accounted for by the fact that at birth the development of the teeth and alveolar bone has not been completed. If this suggestion can be confirmed on a clinical growth series of cases it establishes that, with the exception of the vertical alveolar growth, it is possible to predict the final form in the facial structures. Similar studies of the cranial base supported comparable findings. So much for understanding the cranial base, calvarium, and facial bones, but the problem becomes very complicated in the attempt to estimate the alveolar
A CALENDAR OF FACIAL GROWTH
429 `
growth in the maxilla on account of the change that takes place in the direction of growth of the condylar cartilage (Fig. 3). The angle of the mandible is obtuse in the newborn. The reason for this is that in the first four years of life the lower jaw must keep pace with the rapid early forward growth of the face mentioned above. When the forward growth commences to slow down the mandible is changing its direction of growth so that it can take part in the vertical increase in the height of the face. At the moment there is no easy solution to the problem of estimating the
A
B FIG. 3 T h e change in the mandibular angle.
A, T h e relative position of the mandible at birth and 6 years of age is compared with the adult. I n the early stages the open angle allows the lower jaw to keep pace with the fast-growing forebrain. There is a gradual change so that the vertical growth of the maxilla can be accommodated. B, T h e same series of mandibles is enlarged to illustrate more clearly the change that takes place in condylar growth direction.
predetermined shape of the jaw. Nevertheless, it may be possible at a later date to predict the final form of the mandible. Following this rather crude estimation carried out on skull specimens it appeared that a case could be made for the early differential in the parts and that thereafter the process, with a few exceptions, was a smooth growth maintaining the early established ratios. These are only preliminary observations, and before definite statements can be made a carefully controlled growth study in clinical material must be undertaken. When work has advanced on these lines further information ought to be available, and particularly so if a careful survey of the growing child can be included in the study. On superficial examination it seems as if a carefully compiled calendar of growth will form the basis of surgical operations upon the facial structures. It is only in such a way that the rational will supersede the empirical approach. Figures I, 2, and 3 are reproduced by kind permission of the " British Dental Journal."