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Evaluation of autologous cancellous bone grafting of mandibular discontinuity defects in dogs using a Dacron-urethane prosthesis
J Oral Maxillofac
Surg
45.143-148,1987
Evaluation of Autologous Cancellous Bone Grafting of Mandibular Discontinuity Defects in Dogs Using a Dacron-Urethane Prosthesis HARRY C. SCHWARTZ, DMD, MD,*t DONALD L. LEAKE, DMD, MD,t AND ARTURO PIZZOFERRATO, MD* Reconstruction of 2 cm discontinuity defects using autologous cancellous bone chips and a Dacron-urethane prosthesis was evaluated in four canine mandibles. Histologic studies were performed on specimens taken six and 12 months after bone grafting. All four grafts were completely incorporated, producing a reconstruction that conformed precisely to the desired shape. Remodeling resulted in a trabecular pattern similar to that of the normal mandible. The prosthesis was well tolerated and did not elicit an inflammatory response. Cancellous bone chips often tend to seek a dependent position in a surgical wound. Therefore, they must be used in conjunction with a prosthesis in certain applications. The prosthesis confers shape and stability to the amorphous bone mass,
* Southern California Permanente Medical Group. Los Angeles, California. t Harbor-UCLA Medical Center, Torrance, California. $ Istituti Ortopedici Rizzoli. Bologna, Italy. Supported by a grant from the Kaiser Permanente Medical Care Program. Address correspondence and reprint requests to Dr. Schwartz: 4900 Sunset Boulevard, Los Angeles, CA 90027. 0278-2391187 $0.00 + .25
and provides fixation for the host bone on either side of the defect. The prosthesis must be perforated to permit diffusion of nutrients to the grafted tissue from the recipient bed, drainage of breakdown products from grafted cells that undergo necrosis, and ingrowth of capillary buds. Such a prosthesis is vital in grafting defects of the craniofacial skeleton, where the shape may be both critical and complex.’ Prostheses of stainless steel wire mesh, cast Vitallium, titanium, tantalum, and Dacron cloth mesh impregnated with urethane have been used for several years. In clinical application, Dacron-urethane* (Osteo-Mesh TM, Xomed Inc., Jacksonville, Florida) prostheses seem to offer some advantages over the metal prostheses.* The
FIGURE 1. Diagram showing 2 cm discontinuity defect bridged by a Dacron-urethane prosthesis. No other fixation is necessary. The defect is packed with autologous cancellous bone chips.
144
DACRON-URETHANE
PROSTHESIS
FOR MANDIBULAR
RECONSTRUCTION
FIGURE 2! (top). IIl diate po:stcJperative ri graph of a defect th at was reconstn Id.ed as she3urn in Figure 1. FIGURE ,3 (middle) I. Radiograph Of. the area sh[own in Figul -e 2 after t1hree months. FIGURE :4 (bottom) 1. Radiograph 01Ythe area sh in Figu lr(: 2 aft6 :r six
SCHWARTZETAL.
study evaluated the use of the Dacron-urethane prosthesis in the reconstruction of discontinuity defects in the dog mandible. Materials and Methods The posterior mandibular teeth were removed from four adult mongrel dogs. After a healing period of six weeks, a full-thickness 2 cm discontinuity defect was created in one horizontal mandibular ramus of each animal by an extraoral approach. The associated periosteum was excised in two animals. The defects were bridged with Dacron-urethane prostheses fixed with two intraosseous 24 gauge stainless steel wires on each side and immediately grafted with cancellous bone chips from the ilium (Fig. 1). No additional internal, external or maxillomandibular fixation was used. The animals were placed on a soft diet. The operative sites were radiographed immediately, postoperatively, and then every three months until the animals were sacrificed (Figs. 2-4). Two dogs were sacrificed at six months and two at 12 months, postoperatively. One month prior to sacrifice, intravital fluorochrome labeling (oxytetracycline 25 mg/kg) was performed. The mandibles were fixed in 10% buffered formalin, and the grafted regions were sectioned coronally and transversely. Some were embedded in methacrylate and sectioned at 40-100 km. These were stained with paragon and toluidine blue. Ultraviolet light was used to view unstained sections for the presence of tetracycline. Microradiographs were made from 100 km ground sections. Others were decalcified in EDTA, embedded in paraffin, and cut at 40 pm. These were stained with van Gieson stain and with hematoxylin and eosin. Results CLINICALANDRADIOGRAPHICOBSERVATIONS
There were no postoperative complications, and all four bone grafts developed solid clinical union. Radiographs revealed obliteration of the host-graft interface and development of a normal trabecular pattern in the grafted region within six months (Fig. 4). HISTOLOGICOBSERVATIONS
All four bone grafts were completely incorporated; there were no residual foci of nonviable bone. The bony contour was fairly regular, closely following the shape of the prosthesis (Fig. 5). Osteogenesis occurred from both endosteal and peri-
FIGURE 5. Coronal section at six months. The new bone formed in the defect follows the contour (arrows) of the prosthesis (P)closely. (Paragon. Original magnification. x I .)
osteal callus. Animals that had periosteum excised did not demonstrate periosteal callus; however, this did not affect the quantity or the character of the new bone in the grafted region. Periosteal callus generally incorporated the Dacron-urethane meshwork, and bridges of bone occasionally crossed the interstices (Fig. 6). When periosteum had been excised, a thin layer of fibrous connective tissue separated the meshwork from the newly-formed bone (Fig. 7). Inflammatory cells were not observed in association with the prosthesis. The newly-formed bone was richly vascularized. The trabeculae had regular margins along which were aligned numerous osteoblasts. Osteocytes occurred in all lacunae. A fatty marrow containing islands of hematopoietic cells was present. Thick trabeculae were present around the periphery of the grafted area whereas thinner trabeculae were were seen centrally (Fig. 8). The peripheral bone resembled the thick cortex of the resected mandible, and contained prominent osteons (Fig. 9). All four specimens showed identical fluorochrome uptake, with diffuse fluorescence throughout. The most striking fluorescence was noted in the osteoid seams along the trabecular margins and within osteons (Fig. 10).
146
DACRON-URETHANE
PROSTHESIS
FOR MANDIBULAR
RECONSTRUCTION
FIGURE 6 (fop). Photomicrograph showing periosteal callus (upper arrow) in area where periosteum was retained in the resection site. Endosteal callus (lower arrow) is also apparent. The callus envelops the Dacron-urethane prosthesis (P), and bridges of bone (small orrows) can be seen crossing the interstices in the prosthesis, (Paragon. Original magnification, x 4.) FIGURE 7 (bottom). Photomicrograph showing the Dacron-urethane prosthesis (P) enveloped by a thin, darkly-staining layer of fibrous connective tissue (small arrows) when periosteum was excised from the resection site. There are no bridges of bone in the interstices of the prosthesis and only endosteal callus (lower arrow) is present. (Paragon. Original magnification, x4.)
Discussion In many clinical situations autologous cancellous bone grafts may be superior to cortical bone grafts.3-8 Cortical bone autografts are subject to slow revascularization, irregular remodeling, and resorption.9-11 Much of the interior areas of such grafts are never revascularized or replaced by viable new bone, making them subject to stress fracture.12J3 Furthermore, the need for complex forms of fixation, compression and/or prolonged immobilization complicates the use of such grafts. Conversely, cancellous bone autografts are revascularized in days to weeks, and completely resorbed and replaced by viable new bone in weeks to months.9-1’,14 Many cells may survive transplantation to participate in osteogenesis. When cancellous bone chips are packed into an appropriate prosthesis, the new bone conforms precisely to the shape of that prosthesis. This makes the technique particularly useful in grafting highlycontoured defects of the craniofacial skeleton. The
prosthesis provides fixation. Immobilization, if required, need not be prolonged. External fixation must be used, however, when the technique is applied to defects of weight-bearing bones.’ The Dacron-urethane prosthesis has several advantages over the metal prostheses that are also in use.* It is lightweight and nonreactive, there are no sharp edges to injure the overlying soft tissues, it is easily modified and inserted in the operating room, and it does not require the use of specialized instruments. Perhaps most importantly, it is radiolucent, facilitating radiographic monitoring of the graft. Summary The use of a Dacron-urethane prosthesis and autologous cancellous bone was shown to be very effective for mandibular reconstruction in the current study. The grafts were completely incorporated. This occurred whether or not periosteum was retained in the recipient bed. The prostheses alone provided adequate skeletal fixation, and immobili-
SCHWARTZ ET AL.
FIGURE 8 (fop left). Microradiograph demonstrating that thick, compact trabeculae form at the margins of the reconstructed area, while thinner trabeculae form centrally. (Original magnification. x 2.5.) FIGURE 9 (top right). Prominent osteon formation at the outer margin of the reconstructed area. The prosthesis is at the bottom. (Paragon, polarized light. Original magnification, x 10.) FIGURE 10 (bottom right). Photomicrograph showing active fluorochrome uptake throughout the reconstructed area. (Fluorescent light. Original magnification, x 10.)
147
148
DACRON-URETHANE
zation of the mandible was not required. The grafted areas assumed a dense cortical outline, surrounding an open, cancellous medullary region, closely resembling the trabecular pattern of the normal mandible. These areas would be expected to withstand the stresses of normal function. Previously reported clinical results2 confirm these findings. References 1. Habal MB, Leake DL, Maniscalco JE, et al: Repair of major crania-orbital defects with an elastomer-coated mesh and autogenous bone paste. Plast Reconstr Surg 61:394. 1978 2. Schwartz HC: Mandibular reconstruction using the Dacronurethane prosthesis and autogenic cancellous bone: review of 32 cases. Plast Reconstr Surg 73:387, 1984 3. Mowlem R: Cancellous bone chip grafts. Lance1 2:746, 1944 4. Higgs SL: The use of cancellous chips in bone grafting. J Bone Joint Surg 28:15, 1946 5. Tuli SM: Bridging of bone defects by massive bone grafts in
PROSTHESIS
6.
7.
8. 9. 10.
11. 12.
13.
14.
FOR MANDIBULAR
RECONSTRUCTION
tumorous conditions and in osteomyelitis. Clin Orthop 87160, 1972 Lortat-Jacob A, Lelong P, Benoit J, et al: Complementary procedures following treatment of nonunion by Papineau’s method. Rev Chir Orthop 67:115, 1981 (French) Velasco RU, Habal MB, Spiegel PG. et al: A study of autologous cancellous bone particles in long bone discontinuity defects. Clin Orthop 177:264, 1983 Boyne PJ: Autogenous cancellous bone and marrow transplants. Clin Orthop 73: 199, 1970 Burchardt H, Enneking WF: Transplantation of bone. Surg Clin North Am 58:403, 1978 Urist MR: Bone transplants and implants. in Urist MR (ed): Fundamental and Clinical Bone Physiology. Philadelphia, JB Lippincott, 1980, pp 331-368 Burchardt H: The biology of bone graft repair. Clin Orthop 174:28, 1983 Enneking WF, Burchardt H, Puhl JJ, et al: Physical and biological aspects of repair in dog cortical-bone transplants. J Bone Joint Surg 57:237, 1975 Enneking WF, Eady JL, Burchardt H: Autogenous cortical bone grafts in the reconstruction of segmental skeletal defects. J Bone Joint Surg 62: 1039, 1980 Burwell RG: Studies in the transplantation of bone, part VII. J Bone Joint Surg 46: 110, 1964
Surg
45.143-148,1987
Evaluation of Autologous Cancellous Bone Grafting of Mandibular Discontinuity Defects in Dogs Using a Dacron-Urethane Prosthesis HARRY C. SCHWARTZ, DMD, MD,*t DONALD L. LEAKE, DMD, MD,t AND ARTURO PIZZOFERRATO, MD* Reconstruction of 2 cm discontinuity defects using autologous cancellous bone chips and a Dacron-urethane prosthesis was evaluated in four canine mandibles. Histologic studies were performed on specimens taken six and 12 months after bone grafting. All four grafts were completely incorporated, producing a reconstruction that conformed precisely to the desired shape. Remodeling resulted in a trabecular pattern similar to that of the normal mandible. The prosthesis was well tolerated and did not elicit an inflammatory response. Cancellous bone chips often tend to seek a dependent position in a surgical wound. Therefore, they must be used in conjunction with a prosthesis in certain applications. The prosthesis confers shape and stability to the amorphous bone mass,
* Southern California Permanente Medical Group. Los Angeles, California. t Harbor-UCLA Medical Center, Torrance, California. $ Istituti Ortopedici Rizzoli. Bologna, Italy. Supported by a grant from the Kaiser Permanente Medical Care Program. Address correspondence and reprint requests to Dr. Schwartz: 4900 Sunset Boulevard, Los Angeles, CA 90027. 0278-2391187 $0.00 + .25
and provides fixation for the host bone on either side of the defect. The prosthesis must be perforated to permit diffusion of nutrients to the grafted tissue from the recipient bed, drainage of breakdown products from grafted cells that undergo necrosis, and ingrowth of capillary buds. Such a prosthesis is vital in grafting defects of the craniofacial skeleton, where the shape may be both critical and complex.’ Prostheses of stainless steel wire mesh, cast Vitallium, titanium, tantalum, and Dacron cloth mesh impregnated with urethane have been used for several years. In clinical application, Dacron-urethane* (Osteo-Mesh TM, Xomed Inc., Jacksonville, Florida) prostheses seem to offer some advantages over the metal prostheses.* The
FIGURE 1. Diagram showing 2 cm discontinuity defect bridged by a Dacron-urethane prosthesis. No other fixation is necessary. The defect is packed with autologous cancellous bone chips.
144
DACRON-URETHANE
PROSTHESIS
FOR MANDIBULAR
RECONSTRUCTION
FIGURE 2! (top). IIl diate po:stcJperative ri graph of a defect th at was reconstn Id.ed as she3urn in Figure 1. FIGURE ,3 (middle) I. Radiograph Of. the area sh[own in Figul -e 2 after t1hree months. FIGURE :4 (bottom) 1. Radiograph 01Ythe area sh in Figu lr(: 2 aft6 :r six
SCHWARTZETAL.
study evaluated the use of the Dacron-urethane prosthesis in the reconstruction of discontinuity defects in the dog mandible. Materials and Methods The posterior mandibular teeth were removed from four adult mongrel dogs. After a healing period of six weeks, a full-thickness 2 cm discontinuity defect was created in one horizontal mandibular ramus of each animal by an extraoral approach. The associated periosteum was excised in two animals. The defects were bridged with Dacron-urethane prostheses fixed with two intraosseous 24 gauge stainless steel wires on each side and immediately grafted with cancellous bone chips from the ilium (Fig. 1). No additional internal, external or maxillomandibular fixation was used. The animals were placed on a soft diet. The operative sites were radiographed immediately, postoperatively, and then every three months until the animals were sacrificed (Figs. 2-4). Two dogs were sacrificed at six months and two at 12 months, postoperatively. One month prior to sacrifice, intravital fluorochrome labeling (oxytetracycline 25 mg/kg) was performed. The mandibles were fixed in 10% buffered formalin, and the grafted regions were sectioned coronally and transversely. Some were embedded in methacrylate and sectioned at 40-100 km. These were stained with paragon and toluidine blue. Ultraviolet light was used to view unstained sections for the presence of tetracycline. Microradiographs were made from 100 km ground sections. Others were decalcified in EDTA, embedded in paraffin, and cut at 40 pm. These were stained with van Gieson stain and with hematoxylin and eosin. Results CLINICALANDRADIOGRAPHICOBSERVATIONS
There were no postoperative complications, and all four bone grafts developed solid clinical union. Radiographs revealed obliteration of the host-graft interface and development of a normal trabecular pattern in the grafted region within six months (Fig. 4). HISTOLOGICOBSERVATIONS
All four bone grafts were completely incorporated; there were no residual foci of nonviable bone. The bony contour was fairly regular, closely following the shape of the prosthesis (Fig. 5). Osteogenesis occurred from both endosteal and peri-
FIGURE 5. Coronal section at six months. The new bone formed in the defect follows the contour (arrows) of the prosthesis (P)closely. (Paragon. Original magnification. x I .)
osteal callus. Animals that had periosteum excised did not demonstrate periosteal callus; however, this did not affect the quantity or the character of the new bone in the grafted region. Periosteal callus generally incorporated the Dacron-urethane meshwork, and bridges of bone occasionally crossed the interstices (Fig. 6). When periosteum had been excised, a thin layer of fibrous connective tissue separated the meshwork from the newly-formed bone (Fig. 7). Inflammatory cells were not observed in association with the prosthesis. The newly-formed bone was richly vascularized. The trabeculae had regular margins along which were aligned numerous osteoblasts. Osteocytes occurred in all lacunae. A fatty marrow containing islands of hematopoietic cells was present. Thick trabeculae were present around the periphery of the grafted area whereas thinner trabeculae were were seen centrally (Fig. 8). The peripheral bone resembled the thick cortex of the resected mandible, and contained prominent osteons (Fig. 9). All four specimens showed identical fluorochrome uptake, with diffuse fluorescence throughout. The most striking fluorescence was noted in the osteoid seams along the trabecular margins and within osteons (Fig. 10).
146
DACRON-URETHANE
PROSTHESIS
FOR MANDIBULAR
RECONSTRUCTION
FIGURE 6 (fop). Photomicrograph showing periosteal callus (upper arrow) in area where periosteum was retained in the resection site. Endosteal callus (lower arrow) is also apparent. The callus envelops the Dacron-urethane prosthesis (P), and bridges of bone (small orrows) can be seen crossing the interstices in the prosthesis, (Paragon. Original magnification, x 4.) FIGURE 7 (bottom). Photomicrograph showing the Dacron-urethane prosthesis (P) enveloped by a thin, darkly-staining layer of fibrous connective tissue (small arrows) when periosteum was excised from the resection site. There are no bridges of bone in the interstices of the prosthesis and only endosteal callus (lower arrow) is present. (Paragon. Original magnification, x4.)
Discussion In many clinical situations autologous cancellous bone grafts may be superior to cortical bone grafts.3-8 Cortical bone autografts are subject to slow revascularization, irregular remodeling, and resorption.9-11 Much of the interior areas of such grafts are never revascularized or replaced by viable new bone, making them subject to stress fracture.12J3 Furthermore, the need for complex forms of fixation, compression and/or prolonged immobilization complicates the use of such grafts. Conversely, cancellous bone autografts are revascularized in days to weeks, and completely resorbed and replaced by viable new bone in weeks to months.9-1’,14 Many cells may survive transplantation to participate in osteogenesis. When cancellous bone chips are packed into an appropriate prosthesis, the new bone conforms precisely to the shape of that prosthesis. This makes the technique particularly useful in grafting highlycontoured defects of the craniofacial skeleton. The
prosthesis provides fixation. Immobilization, if required, need not be prolonged. External fixation must be used, however, when the technique is applied to defects of weight-bearing bones.’ The Dacron-urethane prosthesis has several advantages over the metal prostheses that are also in use.* It is lightweight and nonreactive, there are no sharp edges to injure the overlying soft tissues, it is easily modified and inserted in the operating room, and it does not require the use of specialized instruments. Perhaps most importantly, it is radiolucent, facilitating radiographic monitoring of the graft. Summary The use of a Dacron-urethane prosthesis and autologous cancellous bone was shown to be very effective for mandibular reconstruction in the current study. The grafts were completely incorporated. This occurred whether or not periosteum was retained in the recipient bed. The prostheses alone provided adequate skeletal fixation, and immobili-
SCHWARTZ ET AL.
FIGURE 8 (fop left). Microradiograph demonstrating that thick, compact trabeculae form at the margins of the reconstructed area, while thinner trabeculae form centrally. (Original magnification. x 2.5.) FIGURE 9 (top right). Prominent osteon formation at the outer margin of the reconstructed area. The prosthesis is at the bottom. (Paragon, polarized light. Original magnification, x 10.) FIGURE 10 (bottom right). Photomicrograph showing active fluorochrome uptake throughout the reconstructed area. (Fluorescent light. Original magnification, x 10.)
147
148
DACRON-URETHANE
zation of the mandible was not required. The grafted areas assumed a dense cortical outline, surrounding an open, cancellous medullary region, closely resembling the trabecular pattern of the normal mandible. These areas would be expected to withstand the stresses of normal function. Previously reported clinical results2 confirm these findings. References 1. Habal MB, Leake DL, Maniscalco JE, et al: Repair of major crania-orbital defects with an elastomer-coated mesh and autogenous bone paste. Plast Reconstr Surg 61:394. 1978 2. Schwartz HC: Mandibular reconstruction using the Dacronurethane prosthesis and autogenic cancellous bone: review of 32 cases. Plast Reconstr Surg 73:387, 1984 3. Mowlem R: Cancellous bone chip grafts. Lance1 2:746, 1944 4. Higgs SL: The use of cancellous chips in bone grafting. J Bone Joint Surg 28:15, 1946 5. Tuli SM: Bridging of bone defects by massive bone grafts in
PROSTHESIS
6.
7.
8. 9. 10.
11. 12.
13.
14.
FOR MANDIBULAR
RECONSTRUCTION
tumorous conditions and in osteomyelitis. Clin Orthop 87160, 1972 Lortat-Jacob A, Lelong P, Benoit J, et al: Complementary procedures following treatment of nonunion by Papineau’s method. Rev Chir Orthop 67:115, 1981 (French) Velasco RU, Habal MB, Spiegel PG. et al: A study of autologous cancellous bone particles in long bone discontinuity defects. Clin Orthop 177:264, 1983 Boyne PJ: Autogenous cancellous bone and marrow transplants. Clin Orthop 73: 199, 1970 Burchardt H, Enneking WF: Transplantation of bone. Surg Clin North Am 58:403, 1978 Urist MR: Bone transplants and implants. in Urist MR (ed): Fundamental and Clinical Bone Physiology. Philadelphia, JB Lippincott, 1980, pp 331-368 Burchardt H: The biology of bone graft repair. Clin Orthop 174:28, 1983 Enneking WF, Burchardt H, Puhl JJ, et al: Physical and biological aspects of repair in dog cortical-bone transplants. J Bone Joint Surg 57:237, 1975 Enneking WF, Eady JL, Burchardt H: Autogenous cortical bone grafts in the reconstruction of segmental skeletal defects. J Bone Joint Surg 62: 1039, 1980 Burwell RG: Studies in the transplantation of bone, part VII. J Bone Joint Surg 46: 110, 1964