- Email: [email protected]
The problem of tissue deficiency in cleft palate: An experiment in mobilising the palatine bones of cleft dogs
British .7ournal ofPlastic Surgrr.v (19731, 26, 252-260
THE PROBLEM OF TISSUE PERIMENT IN MOBILISING
DEFICIENCY IN CLEFT PALATE: AN EXTHE PALATINE BONES OF CLEFT DOGS
By R. A. LATHAM, B.Sc., B.D.S., Ph.D., G. R. SMILEY,D.D.S., J. M. GREGG, D.D.S.,M.S., Ph.D.
M.Sc., and
Dental Research Center, The University of North Carolina, Chapel Hill, North Carolina 275I4, U.S.A.
CLEFT palate closure by surgery depends upon an adequacy of available palatal mucosal tissue. Insufficiency of such soft tissue is frequently a cause for concern in the closure of severe wide clefts of the secondary palate. While the need is primarily for soft tissue the value of supplying the deficiency of bone has also been stressed. Recently Reichert (1970) gave an account of the benefits obtained by placing in palatal clefts a triangular piece of the iliac bone. It would make an impressive list to name all the parts of the body which have been used as sources of both hard and soft tissues with which to eliminate clefts of the palate. However, the most abundant, and so far untapped, source of additional soft tissue and bone for this purpose is to be found in the normal growth processes of the oral cavity itself. The idea reported here was born out of a realisation of the normal function of the cranial sutures as lines of bone movement, adjustment and growth sites. The posterior one third of the hard palate is formed by the non-tooth-bearing palatine bones. These are connected to the medial surfaces of the maxillae by the palato-maxillary sutures. A section through the posterior part of the palate of a 17-week-old human foetus shows the crescent-shaped palatine bones lying in the lateral walls of the nasal cavities with short palatal processes inferiorly. A large fold of mucous membrane on the oral aspect of the palatal shelf has the appearance of having been displaced laterally by the tongue (Fig. I). It was hypothesised that if medial traction were to be applied to the palatal borders of the palatine bones, causing tension at the palato-maxillary sutures, it could result in their medial movement bodily towards the midline, together with oral and nasal mucous membranes and supporting tissues. It was expected that there would be little or no disturbance of the dental arch because adjustment and new growth should take place at the palato-maxillary suture. It appeared that by employing appropriate means the palatine bone region might yield sufficient additional palatal tissue to render severe wide clefts of the palate much more operable. An experiment was designed using young dogs in which it was proposed to reduce artificially created clefts in the palatine bone region by means of a pinned screw appliance. MATERIALSAND METHODS Ten mongrel dogs, 5-7 weeks old, were anaesthetised with sodium thiamylal and maintained with a Penthrane-oxygen mixture. A midline incision was made in the hard palate and the mucoperiosteum was elevated so as to preserve the greater palatine neurovascular bundles. An 8 mm. wide midline portion of the palatine bones extending from just anterior to the palatine bones posteriorly to the free border of the hard palate was then surgically removed (Fig. 2). The nasal mucosa was then divided and sutured to the edges of the oral mucous membrane to leave a localised artificial palatal cleft. After one week of post-operative healing an appliance consisting of lateral acrylic bases united by an expanded orthodontic screw1 (Figs. 3, 4 and 7), was secured to the remaining medial borders of the palatine bones using staples made from 0.029 inch stainless steel 1Rocky Mountain
No. A-655, 252
8.0 mm.
capacity.
THE
PROBLEM
OF TISSUE
DEFICIENCY
IN
CLEFT
PALATE
253
wire. The staples were driven into the bone using an orthodontic Eby band driver, and bonded to the appliance with rapid cold-cure acrylic resin. The screw was turned daily by one half a revolution, a reduction of approximately 0.40 mm.
FIG. I. Human foetus, IT-week with complete cleft of secondary palate. Coronal section showing the position of the palato-maxillary sutures and the palatine bones with short horizontal processes and closely related displaced fold of oral mucous membrane.
FIG. 2. Coronal
section of palate of S-week-old dog 3A showing palatine bones 12 hours after surgery.
artificial
cleft in
During the first week of appliance activation tetracycline hydrochloride (Tetrachel) or demethylchlortetracycline (Declomycin)l was given intravenously or intramuscularly 1 Lederle Laboratories,
Pearl River, N.Y.
10965
BRITISH
254
JOURNAL
OF PLASTIC
SURGERY
in the amount of 25 mg/Kg. A second dose was given about one week later. After an average experimental period of 14 days, g dogs were killed, the palates photographed, radiographed in some, and embedded in low viscosity nitrocellulose or Ward’s Bio-plast Undecalcilied sections were prepared with a hard tissue cutting prior to sectioning. machine using a diamond wheel, and these were then studied microscopically with an ultraviolet light source. Decalcified sections were cut at 30 microns thickness on a Leitz sledge microtome and stained by the Masson trichrome method.
FIG. 3. Photograph of the pinned screw appliance medial inclination given to the staple pins as used palatine bones.
FIG. 4. Diagram the palato-maxillary
showing the slight for fixation to the
showing the form and relationship of the palatine sutures and the manner in which the appliance palatine bones medially.
bones in the dog, acted to move the
&SULTS
In general the appliances worked smoothly with a steady approximation of the cleft edges. In all dogs the palatal defect was effectively closed after about 14 days (Figs. 5-9). The appliances were well tolerated and readily removed in most dogs by grasping with forceps and pulling downward. In several dogs the appliance was still tightly in place after the cleft had been closed. In some the appliance tended to embed
THE
PROBLEM
OF
TISSUE
DEFICIENCY
IN
CLEFT
PALATE
255
a little into the oral mucous membrane due to the medial inclination given to the securing staples. Although this caused some mucosal ulceration, healing was rapid following removal of the appliance. In some cases the initial turning of the screw to reduce the appliance met with resistance which lasted for several days after which the appliance worked smoothly and medial movement of the palatine bones occurred. Histological sections later showed that one or both of the anterior pins had been misplaced into maxillary bone instead of the palatine bone. The transmucosal pins were apparently well tolerated although lymphocytic concentrations were observed at their insertion sites and there had been some ingrowth of epithelium. Effects on the dental arch were minimal as comparison of initial stone models with the post-mortem specimens showed either no disturbance of the positions of the molar teeth, or that intermolar distance had decreased by less than one millimetre. 25
15 DAYS IO
IA
IC
2A
3A
3C
3D
3E
3F
3G
3H
DOG Half FIG.
5.
turn of screw
dally
A histogram
was carried
showing the number of days for which appliance activaout in each dog. Some clefts (IC, 2A and 3E) were just closed and some were overclosed (3A and 3~).
Transverse histological sections through the palatine bone region confirmed that both soft tissues and the palatine bones had been approximated in the elimination of the cleft (Fig. IO). In dog 3A, prolonged activation of the appliance resulted in excessive medial movement of the palatine bones and caused necrosis of soft tissue in the midline In general all tissues appeared normal in structure, and the palato(Figs. 5 and II). maxillary suture looked much the same as in the control sections with the exception of the presence of osteoclasts at points of tissue compression caused by the medial movement of the palatine bones. However the width of the nasopharynx had been narrowed as anticipated from the audibly forced breathing of some dogs towards the end of the experimental period. In one dog allowed to survive the experiment this obstruction rapidly cleared. Tetracycline marking of growth areas of the palatine bones in the experimental dogs was most conspicuous on the lateral surface of the vertical processes which bounded Evidence of growth was seen in parts of the the pterygo-palatine fossa (Fig. 12). palato-maxillary suture where its alignment tended to be at right angles to the direction For the most part the palato-maxillary suture was aligned of palatine bone movement.
BRITISH
FIG. 6
JOURNAL
OF
PLASTIC
SURGERY
FIG. 7
FIG. 6. Dog 3G, &week-old showing initial cleft in palatine bone region. FIG. 7. Dog 3G with pinned screw appliance after insertion, screw is fully expanded, acrylic plates touch molar teeth.
FIG. 8
FIG. 9
FIG. 8. Dog 3G after 15 days of appliance activation. Cleft has closed and acrylic plates have moved away from molar teeth which were not altered in position. Post-mortem photograph. FIG. g. Dog 3G. Photograph of palate after removal of appliance to show the cleft site where the borders of the cleft are now in contact.
THE
FIG.
PROBLEM
OF
TISSUE
DEFICIENCY
IN
CLEFT
PALATE
Dog 3~. Histological section of palate showing the palatine bone supthe soft tissue at the cleft borders. Narrowing of nasal cavity is due to the medial movement of the palatine bones, compare Fig. 2.
IO.
porting
Dog 3A. Unstained and undecalcified section embedded in clear plastic FIG. II. through closed cleft in which actual positions of cleft borders are accurately maintained. The black lines are pigment of oral mucosa and show that the cleft borders were overclosed by activating appliance longer than necessary.
26 3-E
257
258
BRITISH
JOURNAL
OF
PLASTIC
SURGERY
direction similar to that of the traction, and would have been a sliding piane along which the palatine bone moved in relation to the maxilla. In both control and experimental animals expected patterns of nasal resorption and oral deposition of bone were demonstrated.
in a
FIG. 12. Dog 3H. Photomicrograph of undecalcified coronal section through the palatine bone on left side showing fluorescence when illuminated by ultraviolet light. Tetrachel was given 3 days after appliance insertion and Declomycin 6 hours before death on 20th day. The tetrachel line of fluorescence has clearly demarcated the new bone formed on the lateral surface (right) of the palatine bone which was tending to remodel to its original position.
DISCUSSION
This work demonstrates that it is possible to develop from an artificial cleft palate additional tissue that is in all respects identical to the normal palate. There is no reason to think that palatine bone traction similarly applied to dogs with naturally occurring cleft palate would not have given the same results. The movement of the palatine bones was possible because of the presence of the palato-maxillary sutures. In cleft and noncleft animal alike these are situated laterally and presumably are not subject to the suspicion of lacking growth potential which attends the tissues bordering on clefts. It is necessary that the horizontal process of the palatine bones be of sufficient size to allow the securing of the appliance with the steel staples. Use of methods such as these tend to narrow the nasal cavities. However the growth of the nasal cavities is largely achieved by resorption of bone on the nasal walls and floor, possibly induced by the respiratory epithelium and there would be a tendency for any reduction of nasal cavity size to be restored in the normal process of subsequent growth. If the respiratory epithelium can be regarded as the “functional matrix” controlling growth of the nasal cavities, then one might well expect that normal dimensions would be restored over a period of time to satisfy functional criteria. The movement of the palatine bone by sliding at the palato-maxillary suture invokes a mechanism of skull growth quite different from that constantly used by the orthodontist in moving teeth (Latham, 1968). The sutural sliding mechanism is a function of the collagen fibres which hold the bones together. In response to sustained tension the
THE PROBLEM
OF TISSUE DEFICIENCY
IN CLEFT
PALATE
259
uniting collagen fibres relax, adjust and permit a physiological movement. Since this movement is a function of the rate of adjustment of collagen rather than of bone resorption and deposition, as in tooth movement, it may proceed at a faster rate. From a clinical point of view the amount of force necessary to obtain movement of facial bones at this faster rate and within the limits of physiological response should be determined. There is a tendency, however, to assume that more rapid results are to be obtained by increased forces. The danger is that once the optimum forces have been exceeded, and adjustment of collagen is expected to occur under ischaemic conditions, the results might not be those hoped for. Screw appliances are extensively used in orthodontics for rapid maxillary expansion which expands the midpalatal suture. The orthopaedic rather than orthodontic nature of the technique is well appreciated. Investigations of the forces involved in rapid maxillary expansion by Isaacson and Ingram (1964) showed that two one-fourth turns of an expansion screw daily resulted in a build up of forces to about IO pounds and in one IS&year-old patient a force of 22-5 pounds was recorded. Subsequently they advised a programme of screw activations to avoid such high forces so that additional loads would be added at close to the same rate that the facial skeleton can respond by physiological movement (Zimring and Isaacson, 1965). However in identifying the sites causing the resistance to maxillary expansion they concluded that the major resistance was not in the midpalatal suture but in the other maxillary and facial articulations in general (Isaacson and Ingram, 1964). It is necessary to understand the mechanical or physical effects produced at a facial joint which is to be subjected to force. The effect of the medial traction placed on the palatine bones in this experiment may be compared to that in the midpalatal suture undergoing expansion, other factors, such as age, being equal. Use of excessive medial forces on the palatine bones would have involved articulations other than the palato-maxillary sutures and would have initiated an undesirable movement of the maxillae and dental arches. Movement of the maxillae in relation to the zygomatic and palatine bones occurs as a normal feature of downward and forward facial growth (Latham, 1968). When, for therapeutic reasons, it is found desirable to augment this normal mechanism of the circum-maxillary sutures much lower forces than those necessary for other applications will probably be found adequate. The success of this experiment was assured because it was conceived within well recognised principles of skull growth. Further study of the applications of these principles in the treatment of cleft lip and palate may open the possibility that palatal orthopaedics, as distinct from maxillary orthopaedics, might become an important part of cleft palate management. Until the technique described here is used in an infant with a cleft palate the benefit to be derived from such medial movement of the palatine bones cannot be known. In its present form it does not apply to the maxillary part of a cleft palate because of the absence of suitable sutures. As a logical extension of this work the possibility of creating the necessary sutures artificially by osteotomy should now be examined. SUMMARY
AND
CONCLUSIONS
The potential of the cranial sutures for allowing movement of bones was used in an experiment designed to move the palatine bones medially for the reduction of cleft palate. Artificially created clefts of the palatine bone region in IO dogs were closed by means of daily activations of a pinned screw appliance. Thus additional palatal hard and soft tissue of optimal viability, growth and function was provided to minimise the surgeon’s difficulties and contribute to a more normal construction of the palate. Further development of the principle of using normal growth mechanisms within the
260
BRITISH
JOURNAL
OF
PLASTIC
SURGERY
oral cavity to provide additional tissue for cleft palate treatment may make an important contribution to the treatment of the cleft lip and palate condition in the future. The authors gratefully acknowledge the help of Drs J. R. Pick and J. L. Wagner in the care and anaesthesia of the dogs, Drs S. Yokeley and D. Schrum for invaluable technical help and Dr G. Bevin for his surgical help in the initial stages. Acknowledgment is made to Mrs K. McCaskill for the histotechnical work, to Mr R. Roberson for photography, to Mrs M. Crampton for illustration in Figs. 4 and 5, and to Mrs M. Mattocks for work with the manuscript. This investigation was supported by P.H.S. Research Grant No. DE 0.2668 from the National Institute of Dental Research and in part by General Research Support Grant No. RR 5333 from the General Research Support Branch of the National Institutes of Health. REFERENCES ISAACSON,R. J. and INGRAM,A. H. (1964). Forces produced by rapid maxillary expansion. II. Forces present during treatment. The Angle Orthodontist, 34, 261-270. LATHAM,R. A. (1968). A new concept of the early maxillary growth mechanism. Transactions of the European Orthodontic Society, 1968, 53-63.
LATHAM, R. A. (1968).
The sliding of cranial bones at sutural surfaces during growth.
Journal of Anatomy, 103, 593.
REICHERT, H. (1970). Journal
Osteoplasty
of Plastic Surgery,
in complete
clefts of the secondary
palate.
British
23, 45-59.
ZIMRING, J. E. and ISAACSON,R. J. (1965). III. Forces present during retention.
Forces produced by rapid maxillary expansion. The Angle Orthodontist, 35, 178-186.
THE PROBLEM OF TISSUE PERIMENT IN MOBILISING
DEFICIENCY IN CLEFT PALATE: AN EXTHE PALATINE BONES OF CLEFT DOGS
By R. A. LATHAM, B.Sc., B.D.S., Ph.D., G. R. SMILEY,D.D.S., J. M. GREGG, D.D.S.,M.S., Ph.D.
M.Sc., and
Dental Research Center, The University of North Carolina, Chapel Hill, North Carolina 275I4, U.S.A.
CLEFT palate closure by surgery depends upon an adequacy of available palatal mucosal tissue. Insufficiency of such soft tissue is frequently a cause for concern in the closure of severe wide clefts of the secondary palate. While the need is primarily for soft tissue the value of supplying the deficiency of bone has also been stressed. Recently Reichert (1970) gave an account of the benefits obtained by placing in palatal clefts a triangular piece of the iliac bone. It would make an impressive list to name all the parts of the body which have been used as sources of both hard and soft tissues with which to eliminate clefts of the palate. However, the most abundant, and so far untapped, source of additional soft tissue and bone for this purpose is to be found in the normal growth processes of the oral cavity itself. The idea reported here was born out of a realisation of the normal function of the cranial sutures as lines of bone movement, adjustment and growth sites. The posterior one third of the hard palate is formed by the non-tooth-bearing palatine bones. These are connected to the medial surfaces of the maxillae by the palato-maxillary sutures. A section through the posterior part of the palate of a 17-week-old human foetus shows the crescent-shaped palatine bones lying in the lateral walls of the nasal cavities with short palatal processes inferiorly. A large fold of mucous membrane on the oral aspect of the palatal shelf has the appearance of having been displaced laterally by the tongue (Fig. I). It was hypothesised that if medial traction were to be applied to the palatal borders of the palatine bones, causing tension at the palato-maxillary sutures, it could result in their medial movement bodily towards the midline, together with oral and nasal mucous membranes and supporting tissues. It was expected that there would be little or no disturbance of the dental arch because adjustment and new growth should take place at the palato-maxillary suture. It appeared that by employing appropriate means the palatine bone region might yield sufficient additional palatal tissue to render severe wide clefts of the palate much more operable. An experiment was designed using young dogs in which it was proposed to reduce artificially created clefts in the palatine bone region by means of a pinned screw appliance. MATERIALSAND METHODS Ten mongrel dogs, 5-7 weeks old, were anaesthetised with sodium thiamylal and maintained with a Penthrane-oxygen mixture. A midline incision was made in the hard palate and the mucoperiosteum was elevated so as to preserve the greater palatine neurovascular bundles. An 8 mm. wide midline portion of the palatine bones extending from just anterior to the palatine bones posteriorly to the free border of the hard palate was then surgically removed (Fig. 2). The nasal mucosa was then divided and sutured to the edges of the oral mucous membrane to leave a localised artificial palatal cleft. After one week of post-operative healing an appliance consisting of lateral acrylic bases united by an expanded orthodontic screw1 (Figs. 3, 4 and 7), was secured to the remaining medial borders of the palatine bones using staples made from 0.029 inch stainless steel 1Rocky Mountain
No. A-655, 252
8.0 mm.
capacity.
THE
PROBLEM
OF TISSUE
DEFICIENCY
IN
CLEFT
PALATE
253
wire. The staples were driven into the bone using an orthodontic Eby band driver, and bonded to the appliance with rapid cold-cure acrylic resin. The screw was turned daily by one half a revolution, a reduction of approximately 0.40 mm.
FIG. I. Human foetus, IT-week with complete cleft of secondary palate. Coronal section showing the position of the palato-maxillary sutures and the palatine bones with short horizontal processes and closely related displaced fold of oral mucous membrane.
FIG. 2. Coronal
section of palate of S-week-old dog 3A showing palatine bones 12 hours after surgery.
artificial
cleft in
During the first week of appliance activation tetracycline hydrochloride (Tetrachel) or demethylchlortetracycline (Declomycin)l was given intravenously or intramuscularly 1 Lederle Laboratories,
Pearl River, N.Y.
10965
BRITISH
254
JOURNAL
OF PLASTIC
SURGERY
in the amount of 25 mg/Kg. A second dose was given about one week later. After an average experimental period of 14 days, g dogs were killed, the palates photographed, radiographed in some, and embedded in low viscosity nitrocellulose or Ward’s Bio-plast Undecalcilied sections were prepared with a hard tissue cutting prior to sectioning. machine using a diamond wheel, and these were then studied microscopically with an ultraviolet light source. Decalcified sections were cut at 30 microns thickness on a Leitz sledge microtome and stained by the Masson trichrome method.
FIG. 3. Photograph of the pinned screw appliance medial inclination given to the staple pins as used palatine bones.
FIG. 4. Diagram the palato-maxillary
showing the slight for fixation to the
showing the form and relationship of the palatine sutures and the manner in which the appliance palatine bones medially.
bones in the dog, acted to move the
&SULTS
In general the appliances worked smoothly with a steady approximation of the cleft edges. In all dogs the palatal defect was effectively closed after about 14 days (Figs. 5-9). The appliances were well tolerated and readily removed in most dogs by grasping with forceps and pulling downward. In several dogs the appliance was still tightly in place after the cleft had been closed. In some the appliance tended to embed
THE
PROBLEM
OF
TISSUE
DEFICIENCY
IN
CLEFT
PALATE
255
a little into the oral mucous membrane due to the medial inclination given to the securing staples. Although this caused some mucosal ulceration, healing was rapid following removal of the appliance. In some cases the initial turning of the screw to reduce the appliance met with resistance which lasted for several days after which the appliance worked smoothly and medial movement of the palatine bones occurred. Histological sections later showed that one or both of the anterior pins had been misplaced into maxillary bone instead of the palatine bone. The transmucosal pins were apparently well tolerated although lymphocytic concentrations were observed at their insertion sites and there had been some ingrowth of epithelium. Effects on the dental arch were minimal as comparison of initial stone models with the post-mortem specimens showed either no disturbance of the positions of the molar teeth, or that intermolar distance had decreased by less than one millimetre. 25
15 DAYS IO
IA
IC
2A
3A
3C
3D
3E
3F
3G
3H
DOG Half FIG.
5.
turn of screw
dally
A histogram
was carried
showing the number of days for which appliance activaout in each dog. Some clefts (IC, 2A and 3E) were just closed and some were overclosed (3A and 3~).
Transverse histological sections through the palatine bone region confirmed that both soft tissues and the palatine bones had been approximated in the elimination of the cleft (Fig. IO). In dog 3A, prolonged activation of the appliance resulted in excessive medial movement of the palatine bones and caused necrosis of soft tissue in the midline In general all tissues appeared normal in structure, and the palato(Figs. 5 and II). maxillary suture looked much the same as in the control sections with the exception of the presence of osteoclasts at points of tissue compression caused by the medial movement of the palatine bones. However the width of the nasopharynx had been narrowed as anticipated from the audibly forced breathing of some dogs towards the end of the experimental period. In one dog allowed to survive the experiment this obstruction rapidly cleared. Tetracycline marking of growth areas of the palatine bones in the experimental dogs was most conspicuous on the lateral surface of the vertical processes which bounded Evidence of growth was seen in parts of the the pterygo-palatine fossa (Fig. 12). palato-maxillary suture where its alignment tended to be at right angles to the direction For the most part the palato-maxillary suture was aligned of palatine bone movement.
BRITISH
FIG. 6
JOURNAL
OF
PLASTIC
SURGERY
FIG. 7
FIG. 6. Dog 3G, &week-old showing initial cleft in palatine bone region. FIG. 7. Dog 3G with pinned screw appliance after insertion, screw is fully expanded, acrylic plates touch molar teeth.
FIG. 8
FIG. 9
FIG. 8. Dog 3G after 15 days of appliance activation. Cleft has closed and acrylic plates have moved away from molar teeth which were not altered in position. Post-mortem photograph. FIG. g. Dog 3G. Photograph of palate after removal of appliance to show the cleft site where the borders of the cleft are now in contact.
THE
FIG.
PROBLEM
OF
TISSUE
DEFICIENCY
IN
CLEFT
PALATE
Dog 3~. Histological section of palate showing the palatine bone supthe soft tissue at the cleft borders. Narrowing of nasal cavity is due to the medial movement of the palatine bones, compare Fig. 2.
IO.
porting
Dog 3A. Unstained and undecalcified section embedded in clear plastic FIG. II. through closed cleft in which actual positions of cleft borders are accurately maintained. The black lines are pigment of oral mucosa and show that the cleft borders were overclosed by activating appliance longer than necessary.
26 3-E
257
258
BRITISH
JOURNAL
OF
PLASTIC
SURGERY
direction similar to that of the traction, and would have been a sliding piane along which the palatine bone moved in relation to the maxilla. In both control and experimental animals expected patterns of nasal resorption and oral deposition of bone were demonstrated.
in a
FIG. 12. Dog 3H. Photomicrograph of undecalcified coronal section through the palatine bone on left side showing fluorescence when illuminated by ultraviolet light. Tetrachel was given 3 days after appliance insertion and Declomycin 6 hours before death on 20th day. The tetrachel line of fluorescence has clearly demarcated the new bone formed on the lateral surface (right) of the palatine bone which was tending to remodel to its original position.
DISCUSSION
This work demonstrates that it is possible to develop from an artificial cleft palate additional tissue that is in all respects identical to the normal palate. There is no reason to think that palatine bone traction similarly applied to dogs with naturally occurring cleft palate would not have given the same results. The movement of the palatine bones was possible because of the presence of the palato-maxillary sutures. In cleft and noncleft animal alike these are situated laterally and presumably are not subject to the suspicion of lacking growth potential which attends the tissues bordering on clefts. It is necessary that the horizontal process of the palatine bones be of sufficient size to allow the securing of the appliance with the steel staples. Use of methods such as these tend to narrow the nasal cavities. However the growth of the nasal cavities is largely achieved by resorption of bone on the nasal walls and floor, possibly induced by the respiratory epithelium and there would be a tendency for any reduction of nasal cavity size to be restored in the normal process of subsequent growth. If the respiratory epithelium can be regarded as the “functional matrix” controlling growth of the nasal cavities, then one might well expect that normal dimensions would be restored over a period of time to satisfy functional criteria. The movement of the palatine bone by sliding at the palato-maxillary suture invokes a mechanism of skull growth quite different from that constantly used by the orthodontist in moving teeth (Latham, 1968). The sutural sliding mechanism is a function of the collagen fibres which hold the bones together. In response to sustained tension the
THE PROBLEM
OF TISSUE DEFICIENCY
IN CLEFT
PALATE
259
uniting collagen fibres relax, adjust and permit a physiological movement. Since this movement is a function of the rate of adjustment of collagen rather than of bone resorption and deposition, as in tooth movement, it may proceed at a faster rate. From a clinical point of view the amount of force necessary to obtain movement of facial bones at this faster rate and within the limits of physiological response should be determined. There is a tendency, however, to assume that more rapid results are to be obtained by increased forces. The danger is that once the optimum forces have been exceeded, and adjustment of collagen is expected to occur under ischaemic conditions, the results might not be those hoped for. Screw appliances are extensively used in orthodontics for rapid maxillary expansion which expands the midpalatal suture. The orthopaedic rather than orthodontic nature of the technique is well appreciated. Investigations of the forces involved in rapid maxillary expansion by Isaacson and Ingram (1964) showed that two one-fourth turns of an expansion screw daily resulted in a build up of forces to about IO pounds and in one IS&year-old patient a force of 22-5 pounds was recorded. Subsequently they advised a programme of screw activations to avoid such high forces so that additional loads would be added at close to the same rate that the facial skeleton can respond by physiological movement (Zimring and Isaacson, 1965). However in identifying the sites causing the resistance to maxillary expansion they concluded that the major resistance was not in the midpalatal suture but in the other maxillary and facial articulations in general (Isaacson and Ingram, 1964). It is necessary to understand the mechanical or physical effects produced at a facial joint which is to be subjected to force. The effect of the medial traction placed on the palatine bones in this experiment may be compared to that in the midpalatal suture undergoing expansion, other factors, such as age, being equal. Use of excessive medial forces on the palatine bones would have involved articulations other than the palato-maxillary sutures and would have initiated an undesirable movement of the maxillae and dental arches. Movement of the maxillae in relation to the zygomatic and palatine bones occurs as a normal feature of downward and forward facial growth (Latham, 1968). When, for therapeutic reasons, it is found desirable to augment this normal mechanism of the circum-maxillary sutures much lower forces than those necessary for other applications will probably be found adequate. The success of this experiment was assured because it was conceived within well recognised principles of skull growth. Further study of the applications of these principles in the treatment of cleft lip and palate may open the possibility that palatal orthopaedics, as distinct from maxillary orthopaedics, might become an important part of cleft palate management. Until the technique described here is used in an infant with a cleft palate the benefit to be derived from such medial movement of the palatine bones cannot be known. In its present form it does not apply to the maxillary part of a cleft palate because of the absence of suitable sutures. As a logical extension of this work the possibility of creating the necessary sutures artificially by osteotomy should now be examined. SUMMARY
AND
CONCLUSIONS
The potential of the cranial sutures for allowing movement of bones was used in an experiment designed to move the palatine bones medially for the reduction of cleft palate. Artificially created clefts of the palatine bone region in IO dogs were closed by means of daily activations of a pinned screw appliance. Thus additional palatal hard and soft tissue of optimal viability, growth and function was provided to minimise the surgeon’s difficulties and contribute to a more normal construction of the palate. Further development of the principle of using normal growth mechanisms within the
260
BRITISH
JOURNAL
OF
PLASTIC
SURGERY
oral cavity to provide additional tissue for cleft palate treatment may make an important contribution to the treatment of the cleft lip and palate condition in the future. The authors gratefully acknowledge the help of Drs J. R. Pick and J. L. Wagner in the care and anaesthesia of the dogs, Drs S. Yokeley and D. Schrum for invaluable technical help and Dr G. Bevin for his surgical help in the initial stages. Acknowledgment is made to Mrs K. McCaskill for the histotechnical work, to Mr R. Roberson for photography, to Mrs M. Crampton for illustration in Figs. 4 and 5, and to Mrs M. Mattocks for work with the manuscript. This investigation was supported by P.H.S. Research Grant No. DE 0.2668 from the National Institute of Dental Research and in part by General Research Support Grant No. RR 5333 from the General Research Support Branch of the National Institutes of Health. REFERENCES ISAACSON,R. J. and INGRAM,A. H. (1964). Forces produced by rapid maxillary expansion. II. Forces present during treatment. The Angle Orthodontist, 34, 261-270. LATHAM,R. A. (1968). A new concept of the early maxillary growth mechanism. Transactions of the European Orthodontic Society, 1968, 53-63.
LATHAM, R. A. (1968).
The sliding of cranial bones at sutural surfaces during growth.
Journal of Anatomy, 103, 593.
REICHERT, H. (1970). Journal
Osteoplasty
of Plastic Surgery,
in complete
clefts of the secondary
palate.
British
23, 45-59.
ZIMRING, J. E. and ISAACSON,R. J. (1965). III. Forces present during retention.
Forces produced by rapid maxillary expansion. The Angle Orthodontist, 35, 178-186.