LETTERS TO THE EDITOR Discovering the uniqueness of the individual To the Editor:
A recent article published in the JOURNAL entitled "Skeletal Maturation and Craniofacial Growth"' has prompted me to make some comments about the need for a more comprehensive approach toward this type of research and about the essential task confronting us in identifying the nature of maturational development on an individual patient basis• Unless this is accomplished, the proper evaluation of unique personal craniofacial growth patterns cannot be identified, and the initiation of treatment modalities cannot be advantageously implemented and timed. The authors of the article outlined it well by stating: "Maturational status can have considerable influence on diagnosis, treatment goals, treatment planning, and the eventual outcome of orthodontic treatment. • . . Prediction of t'-'h the times and the amounts of active growth, especiall~ in the craniofacial complex, would be useful to the orthodontist." I do want to make it clear that I am not in any way singularly selecting the work of Drs. Moore, Moyer, and DuBois to criticize. It just represents a very recent study of maturational research that serves as an example for the following discussion. Their underlying thesis is sound, to investigate whether craniofacial growth demonstrates the same growth spurts characteristic of that seen with sta' Jral height as identified On hand-wrist radiographs. They went about it methodically and in a very clear and concise fashion. The problem is that practically all investigations of this type have failed to take into account some very significant maturational factors that are esse,atial for a more valid interpretation of growth using hand-wrist radiographs. We know that normal children express similar stages of adolescent maturational development at widely varying chronologic ages?" To not initially identify and separate the sample subjects in whom maturation is delayed and those in whom it is accelerated from the average maturers is to inject into the sample a very wide-ranging variable that cannot be subsequently controlled. For instance, peak velocity of adolescent growth varies greatly in both time and intensity between delayed and average maturers. Accelerated maturers demonstrate earlier timing of peak growth acceleration and more intensity of incremental growth per unit of time. Delayed maturers take longer to express the same percentage amounts of completed growth, continually attempting to catch up with the average maturers. As a result, delayed maturers, as a group, eventually demonstrate more incremental growth than accelerated maturers, an example being that delayed maturers usually become taller than accelerated maturers. This is a classic example of the law of biologic regression, growth continually expressing itself toward mean values.' Very few investigators have acknowledged the significance of these maturational variations by incorporating this factor into their study methods. 20A
Burstone ~ properly demonstrated the significance of the variations .in adolescent growth curves relative to accelerated, average, and delayed levels of maturation and demonstrated how a maturational event, such as menarche, varies in relationship to this. Moore, Moyer, and DuBois concluded: "The results of this study do not show conclusively that an actual growth spurt exists in any of the facial dimensions that were examined . . . . The unresolved issues are whether a 2- to 3-year acceleration is a 'spurt.'" I feel confident that the extended timeframe associated with peak velocity of growth in this study would have been very significantly narrowed if the variable of maturation level, accelerated versus average versus delayed, was initially taken into account dudng the sample selection• The time difference between the periods of peak growth velocity of delayed and accelerated maturers, in itself, can account for the 2- to 3-year period seen in this study. Different levels of maturation need to be studied separately in an investigation such as this. In all probability, the study would have revealed conclusions opposite what was found, that craniofacial growth did express growth "spurts" that were positively associated with that seen with statural height. Other investigators have demonstrated this positive association. ".~,' A very important maturational consideration concerns the clarification and proper interpretation of skeletal age. Pediatricians, radiologists, orthodontists, and other specialists investigating growth and development continue to use hand-wrist radiographs in varying ways with varying degrees of success. A very basic and common mistake is the expression of maturational (skeletal) age in terms of chronologic age. This is often done with the hand-wrist atlas and other methods of interpretation? ,9 The underlying inference in doing this is that a "normal" relationship is supposed to exist between chronologic age and specific stages of maturation. A handwrist radiograph is thereby tagged with a specific skeletal chronologic age, which may or may not concur with the child's actual chronologic age. Could this possibly be true? Except for very rare instances, all the children we see as orthodontic patients are healthy and normal; yet they all express their maturational growth in varying patterns of time. Very few adolescents, if any, actually display growth velocity curves in statural height that concur with growth curves that are representative of the female or male populations. It is commonly presented that most girls start adolescence at approximately the age of 10 years, demonstrate peak velocity of growth at the age of 12 years, and terminate adolescence just beyond the age of 14 years• Boys are depicted as demonstrating similar general skeletal growth curves, although of more intensity, approximately 2 years la.ter. It is a mistake to assume any child treated by an orthodontist will actually demonstrate such a similar pattern, as these curves are only representative of statistical compilations of large numbers of persons; they are valid only for each sex group as a whole and not necessarily for the individual person. it is partly for these reasons that a different approach
Volume 99 Number 3
was taken and the system of Skeletal Maturation Assessment (SMA) was developed2." The underlying premise that serves as the foundation for this method is that every normally healthy child will express his or her own individual and unique pattern of maturational development at widely varying chronologic ages. All of the maturational variation is considered to be normal. Maturational (skeletal) age is designated in maturational terms and not in units of chronologic age. The SMA is easily learned and applied both clinically, on a routine basis, and investigatively. Eleven clearly designated and reliable adolescent Skeletal Maturity Indicators (SMIs) are identified from hand-wrist radiographs. These stages are subsequently related to existing maturation levels (accelerated, average, and delayed) for purposes of individualized growth evaluation.Since the identifiable maturational stages (SMIs) represent specific percentage levels of total completed growth, although different for the varying levels of maturation, accelerated versus average versus delayed, evaluation of both past and future growth can be undertaken. After many years of investigation in this area of interest, I am convinced more than ever that hand-wrist radiographs, if used and interpreted properly, will provide us with the best of means to identify and interpret individualized patterns related to the timing of growth. Hand-wrist radiographs represent a very low radiologic risk and should become a part of the routine diagnostic record in every practitioner's office. In regard to research investigations, every growthrelated study should, as part of its method, initially include a maturational distribution of the sample material (Fig. 1). Whether the SMA or some other scheme is used for this purpose, it is the only way that the results can be interpreted with confidence. First, the sample must be outlined on the basis of levels of maturation-accelerated versus average versus delayed. Second, a specific maturational stage must be appropriately assigned to each sample unit. Only in this way can a homogeneous sample be selected for the task at hand. By doing this, the basic purpose of the investigation can be better isolated and identified and not be subject to unwanted variability and confusion. A brief example of the value of doing this would be a study of the best time to use high-pull maxillary headgear mechanics on children who demonstrate excessive vertical mandibular development. If the sample was sorted by chronologic age, rather than by maturational age, the results of the investigation would always be in question, as there would be no reliable way of interpreting what growth periods were actually involved to achieve the best results. The sample needed to be initially selected by maturational age since children demonstrate widely varying chronologic patterns of development. Unfortunately, much of our literature is subject to this type of doubt and important studies need to be repeated for verification. One of the most important challenges facing our profession at this time is the need to discover the unique developmental characteristics associated with each of our patients. Our specialty has led the way in developing
Letters to t/re editor
21A
MATURATIONAL DISTRIBUTION OF A SAMPLE :3.4 MATURATION MATURATI ON LEVELS STAGES A- accelerated
4/~7
B
ca"erage D -delayed II SKELITAL I E x l m p l e s of m a t u r a t l o u
MATURITY
INDICATORS
use:
l l A -- ( S M I 9. a¢¢elersted
level A)
3C -- ( S A i l 3, s v e r l l e
level C |
very sophisticated means of analyzing craniofacial growth, especially relative to directional patterns within skeletal types. The information has been clinically used to the best advantage and has served tJs well. We also need to understand as much about the timing of growth, as growth direction, magnitude, and timing are all closely interrelated. Individualized evaluation of maturational development will provide this knowledge if hand-wrist radiographs are properly used. Leonard S. Fishman, DDS, PC 550 E. Genese St. Syracttse, N.Y. 13202 REFERENCES 1. Moore RN, Moyer BA, DuBois LM. Skeletal maturation and craniofacial growth. AMJ ORTHODDENTOFACORT}tOP 1990;98:3340. 2. Fishman LS. Chronologic versus skeletal age, an evaluation of craniofacial growth. Angle Orthod 1979;49:181-9. 3. Fishman LS. Radiographic evaluation of skeletal maturation. Angle Orthod 1982;52:88-I 12. 4. Fishman LS. Maturational patterns and prediction during adolescence. Angle Orthod 1987;57:178-93. 5. Burstone CJ. Process of maturation and growth prediction. AM J OR'roOD 1963;49:907-19. 6. Bergersen EO. The male adolescent growth spurt: its prediction and relation to skeletal maturation. Angle Orthod 1972;42:31938. 7. Nanda RS. The rates of growth of several facial components measured from serial cephalometric roentgenograms. AM J OR"nXOD1955;41:658-73. 8. Greulich WW, PyleSI. Radiographic atlas ofskeletal development of the hand wrist. Stanford:Stanford University Press, 1959. 9. Tanner JM, Whitehouse RH, Marshall WA, Healy MJ, Goldstein H. Assessment of skeletal maturity and prediction of adult height (TW2 method). London: Academic Press, 1975.
Reply To tile Editor: W e would like to t h a n k Dr. F i s h m a n for c o m m e n t i n g
on our article on skeletal maturity and craniofacial growth and for focusing on the problem of sorting the sample by maturity levels before analysis.' He suggests that the sample should be divided into groups according to accelerated, average, and delayed skeletal maturation. We agree that it would be beneficial to study the different levels of maturation separately in a study such as ours. However, the problem with this approach lies in defining
A recent article published in the JOURNAL entitled "Skeletal Maturation and Craniofacial Growth"' has prompted me to make some comments about the need for a more comprehensive approach toward this type of research and about the essential task confronting us in identifying the nature of maturational development on an individual patient basis• Unless this is accomplished, the proper evaluation of unique personal craniofacial growth patterns cannot be identified, and the initiation of treatment modalities cannot be advantageously implemented and timed. The authors of the article outlined it well by stating: "Maturational status can have considerable influence on diagnosis, treatment goals, treatment planning, and the eventual outcome of orthodontic treatment. • . . Prediction of t'-'h the times and the amounts of active growth, especiall~ in the craniofacial complex, would be useful to the orthodontist." I do want to make it clear that I am not in any way singularly selecting the work of Drs. Moore, Moyer, and DuBois to criticize. It just represents a very recent study of maturational research that serves as an example for the following discussion. Their underlying thesis is sound, to investigate whether craniofacial growth demonstrates the same growth spurts characteristic of that seen with sta' Jral height as identified On hand-wrist radiographs. They went about it methodically and in a very clear and concise fashion. The problem is that practically all investigations of this type have failed to take into account some very significant maturational factors that are esse,atial for a more valid interpretation of growth using hand-wrist radiographs. We know that normal children express similar stages of adolescent maturational development at widely varying chronologic ages?" To not initially identify and separate the sample subjects in whom maturation is delayed and those in whom it is accelerated from the average maturers is to inject into the sample a very wide-ranging variable that cannot be subsequently controlled. For instance, peak velocity of adolescent growth varies greatly in both time and intensity between delayed and average maturers. Accelerated maturers demonstrate earlier timing of peak growth acceleration and more intensity of incremental growth per unit of time. Delayed maturers take longer to express the same percentage amounts of completed growth, continually attempting to catch up with the average maturers. As a result, delayed maturers, as a group, eventually demonstrate more incremental growth than accelerated maturers, an example being that delayed maturers usually become taller than accelerated maturers. This is a classic example of the law of biologic regression, growth continually expressing itself toward mean values.' Very few investigators have acknowledged the significance of these maturational variations by incorporating this factor into their study methods. 20A
Burstone ~ properly demonstrated the significance of the variations .in adolescent growth curves relative to accelerated, average, and delayed levels of maturation and demonstrated how a maturational event, such as menarche, varies in relationship to this. Moore, Moyer, and DuBois concluded: "The results of this study do not show conclusively that an actual growth spurt exists in any of the facial dimensions that were examined . . . . The unresolved issues are whether a 2- to 3-year acceleration is a 'spurt.'" I feel confident that the extended timeframe associated with peak velocity of growth in this study would have been very significantly narrowed if the variable of maturation level, accelerated versus average versus delayed, was initially taken into account dudng the sample selection• The time difference between the periods of peak growth velocity of delayed and accelerated maturers, in itself, can account for the 2- to 3-year period seen in this study. Different levels of maturation need to be studied separately in an investigation such as this. In all probability, the study would have revealed conclusions opposite what was found, that craniofacial growth did express growth "spurts" that were positively associated with that seen with statural height. Other investigators have demonstrated this positive association. ".~,' A very important maturational consideration concerns the clarification and proper interpretation of skeletal age. Pediatricians, radiologists, orthodontists, and other specialists investigating growth and development continue to use hand-wrist radiographs in varying ways with varying degrees of success. A very basic and common mistake is the expression of maturational (skeletal) age in terms of chronologic age. This is often done with the hand-wrist atlas and other methods of interpretation? ,9 The underlying inference in doing this is that a "normal" relationship is supposed to exist between chronologic age and specific stages of maturation. A handwrist radiograph is thereby tagged with a specific skeletal chronologic age, which may or may not concur with the child's actual chronologic age. Could this possibly be true? Except for very rare instances, all the children we see as orthodontic patients are healthy and normal; yet they all express their maturational growth in varying patterns of time. Very few adolescents, if any, actually display growth velocity curves in statural height that concur with growth curves that are representative of the female or male populations. It is commonly presented that most girls start adolescence at approximately the age of 10 years, demonstrate peak velocity of growth at the age of 12 years, and terminate adolescence just beyond the age of 14 years• Boys are depicted as demonstrating similar general skeletal growth curves, although of more intensity, approximately 2 years la.ter. It is a mistake to assume any child treated by an orthodontist will actually demonstrate such a similar pattern, as these curves are only representative of statistical compilations of large numbers of persons; they are valid only for each sex group as a whole and not necessarily for the individual person. it is partly for these reasons that a different approach
Volume 99 Number 3
was taken and the system of Skeletal Maturation Assessment (SMA) was developed2." The underlying premise that serves as the foundation for this method is that every normally healthy child will express his or her own individual and unique pattern of maturational development at widely varying chronologic ages. All of the maturational variation is considered to be normal. Maturational (skeletal) age is designated in maturational terms and not in units of chronologic age. The SMA is easily learned and applied both clinically, on a routine basis, and investigatively. Eleven clearly designated and reliable adolescent Skeletal Maturity Indicators (SMIs) are identified from hand-wrist radiographs. These stages are subsequently related to existing maturation levels (accelerated, average, and delayed) for purposes of individualized growth evaluation.Since the identifiable maturational stages (SMIs) represent specific percentage levels of total completed growth, although different for the varying levels of maturation, accelerated versus average versus delayed, evaluation of both past and future growth can be undertaken. After many years of investigation in this area of interest, I am convinced more than ever that hand-wrist radiographs, if used and interpreted properly, will provide us with the best of means to identify and interpret individualized patterns related to the timing of growth. Hand-wrist radiographs represent a very low radiologic risk and should become a part of the routine diagnostic record in every practitioner's office. In regard to research investigations, every growthrelated study should, as part of its method, initially include a maturational distribution of the sample material (Fig. 1). Whether the SMA or some other scheme is used for this purpose, it is the only way that the results can be interpreted with confidence. First, the sample must be outlined on the basis of levels of maturation-accelerated versus average versus delayed. Second, a specific maturational stage must be appropriately assigned to each sample unit. Only in this way can a homogeneous sample be selected for the task at hand. By doing this, the basic purpose of the investigation can be better isolated and identified and not be subject to unwanted variability and confusion. A brief example of the value of doing this would be a study of the best time to use high-pull maxillary headgear mechanics on children who demonstrate excessive vertical mandibular development. If the sample was sorted by chronologic age, rather than by maturational age, the results of the investigation would always be in question, as there would be no reliable way of interpreting what growth periods were actually involved to achieve the best results. The sample needed to be initially selected by maturational age since children demonstrate widely varying chronologic patterns of development. Unfortunately, much of our literature is subject to this type of doubt and important studies need to be repeated for verification. One of the most important challenges facing our profession at this time is the need to discover the unique developmental characteristics associated with each of our patients. Our specialty has led the way in developing
Letters to t/re editor
21A
MATURATIONAL DISTRIBUTION OF A SAMPLE :3.4 MATURATION MATURATI ON LEVELS STAGES A- accelerated
4/~7
B
ca"erage D -delayed II SKELITAL I E x l m p l e s of m a t u r a t l o u
MATURITY
INDICATORS
use:
l l A -- ( S M I 9. a¢¢elersted
level A)
3C -- ( S A i l 3, s v e r l l e
level C |
very sophisticated means of analyzing craniofacial growth, especially relative to directional patterns within skeletal types. The information has been clinically used to the best advantage and has served tJs well. We also need to understand as much about the timing of growth, as growth direction, magnitude, and timing are all closely interrelated. Individualized evaluation of maturational development will provide this knowledge if hand-wrist radiographs are properly used. Leonard S. Fishman, DDS, PC 550 E. Genese St. Syracttse, N.Y. 13202 REFERENCES 1. Moore RN, Moyer BA, DuBois LM. Skeletal maturation and craniofacial growth. AMJ ORTHODDENTOFACORT}tOP 1990;98:3340. 2. Fishman LS. Chronologic versus skeletal age, an evaluation of craniofacial growth. Angle Orthod 1979;49:181-9. 3. Fishman LS. Radiographic evaluation of skeletal maturation. Angle Orthod 1982;52:88-I 12. 4. Fishman LS. Maturational patterns and prediction during adolescence. Angle Orthod 1987;57:178-93. 5. Burstone CJ. Process of maturation and growth prediction. AM J OR'roOD 1963;49:907-19. 6. Bergersen EO. The male adolescent growth spurt: its prediction and relation to skeletal maturation. Angle Orthod 1972;42:31938. 7. Nanda RS. The rates of growth of several facial components measured from serial cephalometric roentgenograms. AM J OR"nXOD1955;41:658-73. 8. Greulich WW, PyleSI. Radiographic atlas ofskeletal development of the hand wrist. Stanford:Stanford University Press, 1959. 9. Tanner JM, Whitehouse RH, Marshall WA, Healy MJ, Goldstein H. Assessment of skeletal maturity and prediction of adult height (TW2 method). London: Academic Press, 1975.
Reply To tile Editor: W e would like to t h a n k Dr. F i s h m a n for c o m m e n t i n g
on our article on skeletal maturity and craniofacial growth and for focusing on the problem of sorting the sample by maturity levels before analysis.' He suggests that the sample should be divided into groups according to accelerated, average, and delayed skeletal maturation. We agree that it would be beneficial to study the different levels of maturation separately in a study such as ours. However, the problem with this approach lies in defining
