- Email: [email protected]
Frozen femoral head allogeneic bone grafts for orthognathic surgery
J Oral Maxdlofac Surg 40.6355639. 1962
Frozen Femoral Head Allogeneic Bone Grafts for Orthognathic Surgery JAMES M. CHRISTIAN,
DDS,* AND LARRY J. PETERSON,
DDSt
Bone grafts are occasionally required in orthognathic surgery procedures. Allogeneic grafts are desirable because they decrease patient morbidity. Fresh frozen bone obtained during total hip replacement has been used in 12 orthognathic operations. Observations for one to three years have
showed
very good results.
Materials
Bone grafting is commonly used in orthognathic procedures such as mandibular advancements with C-osteotomy, total maxillary advancements, and segmental alveolar osteotomies that leave significant intrabony spaces.‘-x Bone grafts are useful in these situations because they promote bony healing and provide mechanical stability.‘.” Autogenous bone is the most desirable graft but carries definite operative morbidity, including pain, scarring, and decreased ability to ambulate in the immediate postoperative period. The use of allogeneic bone circumvents these problems. Cryogenically preserved allogeneic bone is preferred, because treating bone with harsh chemicals or by autoclaving it damages the graft and delays its incorporation with host bone.“.“’ Lyophilized bone has enjoyed popularity because of its long shelf life and easy storage, but it requires extensive preparation with specialized equipment, rendering it expensive and difficult to obtain.‘,” An alternative is frozen bone. With the recent increase in frequency of prosthetic hip replacement procedures, femoral head bone has become readily available. We have used this source of bone for three years. The purpose of this paper is to describe a technique for procurement and use of frozen femoral head bone and to report the results of long-term follow-up of such grafts in orthognathic surgery.
CLINICAL MATERIAL
Twelve patients who were treated at the University of Connecticut were included in this study (Table 1). Two of the patients underwent ramus procedures: three, alveolar segmental procedures; and seven, a variety of maxillary procedures. Follow-up periods ranged from 12 to 36 months. Routine diagnosis and treatment planning, using radiographs. models of the teeth, and a thorough clinical examination, were accomplished for each patient. Postoperative radiographs were obtained immediately after surgery and at appropriate intervals in the postoperative course in order to evaluate (1) position of the graft, (2) inflammatory resorption of the graft, (3) replacement of the graft by host bone, and (4) relapse of surgically repositioned segments. Clinical examinations were conducted to
* Formerly Chief Resident; currently in private practice in Hadley, Massachusetts. i Professor and Program Director. Received from the School of Dental Medicine. University of Connecticut. Farmington, CT 06032. Address correspondence and reprint requests to Dr. Peterson. 0278-23911821100010635
$01 .OO Q American
and Methods
FIGURE I. Cut surface of the femoral cortex and dense cancellous bone. Association
635
of Oral and Maxillofacial
Surgeons
head,
showing
a thin
636
FEMORAL
HEAD
BONE
GRAFTS
FIGURE 2. A, C-osteotomy for mandibular advancement with corticocancellous bone graft in vertical position and cancellous bone graft in horizontal position. B, Immediate postoperative panoramic radiograph of patient. C, One-year postoperative panoramic radiograph at time of mesh removal. There is complete incorporation of the grafts by host bone. D, Surgical site one year after graft insertion. There is complete replacement of graft by host bone.
evaluate the occlusion and adequacy of the union of the segments. Postoperative complications were also noted. FROZEN ALLOGENEIC
BONE PREPARATION
Femoral head bone was removed under sterile conditions during total hip replacement procedures in patients whose ages ranged from 57 to 76 years. The specimens were between 3.5 and 7 cm in diameter. A small fragment of each specimen was submitted to culture to assess sterility. The bone was packaged in a double glass container, the outer container being labeled with the donor’s name and hospital number, reason for removal, date, and name of operating surgeon. The bone was then stored at -2 C for at least two weeks before use. When the bone was removed from the bank, it was allowed to thaw for at least one hour before grafting. The bone was then shaped as necessary by use of saws and rongeurs (Fig. 1). Before the bone was inserted, it was vigorously and thoroughly irrigated with sterile saline to remove as much soft tissue as possible.12,13 Femoral head bone used for grafting consists of a thin outer cortex and a rather dense cancellous
medullary portion. As the cancellous dense, the strength is satisfactory.
bone is quite
OPERATIVE TECHNIQUE
The size and shape of the graft varied depending on the particular procedure involved and the size and shape of the recipient site (Figs. 2, 3, and 4). Fixation of the graft was similar to that which would be employed with autogenous bone. Systemic antibiotics, usually penicillin G, l,OOO,OOOunits intravenously immediately preoperatively and every two hours during the procedure, with the last dose in the recovery room, were used for prevention of wound infection.14 Systemic steroids, usually methylprednisolone, 125 mg every six hours for two days, were given intravenously to minimize postoperative edema. Results CLINICAL
EVALUATION
All patients recovered uneventfully, had a normal postoperative course, and were discharged from the hospital on the first or second day after surgery to be followed up as outpatients. Primary Healing Phase. This phase correspond-
CHRISTIAN AND PETERSON
637
ed to the postoperative maxillomandibular fixation period (6 to 8 weeks). Patients were examined closely for possible signs of graft rejection, which would have been manifested as an increase in erythema and/or edema following the period after which initial edema would be expected to resolve, allergic skin reaction, soft tissue wound dehiscence, or accelerated resorption of the graft itself.15,16 None of these occurred, and soft tissue healing proceeded normally. Union und Relapse. The interval required to achieve union of the mobile segments was comparable with that expected after similar procedures in which autogenous bone is used.1*3 Relapse of repositioned segments was considered a minor problem. In 11 of 12 cases, no relapse was seen. One patient, who had a maxillary disimpaction of 7 mm, experienced a 2 mm vertical relapse of the anterior maxilla at 18 months. Complete host bone replacement was seen by direct visualization of the operative sites in a patient who had undergone C-osteotomies for mandibular advancement when titanium mesh splints, which were placed bilaterally at the inferior borders for fixation, were removed one year postoperatively (Fig. 2). Postoperative infection was seen Complicutions. in one of the 12 cases. The infection was managed conservatively with daily irrigations and antibiotics. Graft removal because of infection was not necessary. RADIOGRAPHIC
EVALUATION
Standard radiographs were obtained at regular postoperative intervals. The first important information afforded by radiography was determination of the rate and amount of graft resorption and the rate of replacement by host bone. Early, rapid resorption of the grafted bone did not occur in any of
FIGURE 3.
Right lateral orbital rim in patient
modified LeFort III advancement, holding zygoma forward.
with cancellous
undergoing bone graft
FIGURE 4. Above, Right posterior mandibular segmental procedure with cancellous bone graft holding the segment with the third molar forward. Center, Immediate postoperative panoramic radiograph showing bone graft in place posterior to the mandibular third molar. Belong, One year postoperative radiograph showing no evidence of bone graft. There has been complete incorporation by host bone.
the patients. Long-term radiographs showed that there was simultaneous resorption of the graft and replacement by host bone, with no loss of overall size of the original graft (Figs. 2 and 4). The other important information afforded by cephalometric radiography was determination of skeletal relapse. In this manner, relapse was noted in only one case-that of a maxillary disimpaction, where the initial gain in maxillary height of 7 mm relapsed to 5 mm. This patient’s maxilla has remained stable since the relapse occurred.
638
FEMORAL HEAD BONE GRAFTS
Table 1.
Outcome of Bone Grafting with Frozen Femoral Head Allogeneic Bone in 12 Patients
2 3 4 5 6 I 8 9 10
11 12
Amount of Defect (mm)
Complications
Relapse
I advancement midline split I with midline
36
4
-
No
23
4
-
No
I with midline
35
3
-
No
I I disimpaction
38 18
8 7
-
20
8
-
20
8
-
12 34 12
5 5 5
13
10
16
4
Operation
Patient 1
Length of Follow-up (mo)
LeFort with LeFort split LeFort split LeFort LeFort
Zygomatico-maxillary (LeFort III) advancement Zygomatico-maxillary (LeFort III) advancement C-osteotomy C-osteotomy Mandibular posterior segmental osteotomy Mandibular posterior segmental osteotomy Maxillary anterior segmental osteotomy midline split
Fracture of right body of mandible Postoperative infection -
No 2mmfatANS 3mmfatPNS 1 mmfatANS No No No No
No No
with
Discussion
Bone grafts are necessary for certain orthognathic procedures. In some situations the osteogenic potential of autogenous bone is essential for the success of the procedure, e.g., osteotomies involving residual clefts that require grafts. There are other procedures in which allogeneic bone may be preferred because a second operative procedure is not required. An allogeneic graft is defined as tissue taken from a donor who belongs to the same species but is not genetically related to the recipient. The process of freezing allogeneic bone significantly reduces the immunogenic response compared with the response to fresh allogeneic bone.17 Frozen allogeneic bone grafting establishes a matrix for the ingrowth of host bone that will promote bony union, provide mechanical stability between the segments during healing, and stimulate formation of bone. Allogeneic transfer of any tissue, including blood and bone, may risk transmission of disease. To reduce this possibility, all donors are screened for hepatitis B, syphilis, active infection, malignant disease, autoimmune disease (including rheumatoid arthritis), and chronic parenteral drug abuse. If the potential donor has had any of these, the bone is unacceptable. Therefore, only patients with histories of chronic degenerative joint disease or osteoarthritis or who have had a fracture of the femoral neck are accepted. At this time, we have used frozen femoral head in 28 patients (the follow-up is not of sufficient length to report on the other 16 patients at this time). We are unaware of any trans-
mission of disease in these patients; this is similar to other published reports.‘* In this study, the grafted sites underwent normal bony healing with the incorporation and eventual replacement of the graft by host bone. The grafted maxillae and mandibles usually showed no evidence of relapse (except in one case) by cephalometric radiographic comparisons and by careful clinical follow-up examinations. There was an obvious lack of complications. Those that did occur were mainly caused by surgical technique and not by the use of allogeneic bone. One postoperative infection was seen, but it was easily managed in a conservative manner.
Conclusions Four conclusions about the use of frozen femoral head bone grafts can be made from this study. (1) It is readily available and relatively inexpensive compared with other sources of allogeneic bone. (2) A normal progression of healing, with eventual incorporation and replacement by host bone, occurs. (3) Skeletal relapse is generally avoided. (4) There is absence of clinically immunologic recognizable response. References 1. Epker B et al: The use of freeze-dried bone in middle-third advancements. Oral Surg 42:278, 1976 2. Constantinides .I, Zachariades N: Homogenous bone grafts to the mandible. J Oral Surg 36:599, 1978
CHRISTIAN
AND PETERSON
3. Bays R: Anterior mandibular dentoalveolar advancement utilizing lyophilized bone. lnt J Oral Surg 8:283, 1979 4. Byrne R, Hinds E: The ramus “C” osteotomy with body saggital split. J Oral Surg 32:259, 1974 5. Bell W: LeFort 1 osteotomy for correction of maxillary deformities. J Oral Surg 33:412, 1975 6. Peterson LJ: Posterior mandibular segmental alveolar osteotomy. J Oral Surg 36:454. 1978 7. Kent J. Hinds E: Management of dental facial deformities by anterior alveolar surgery. J Oral Surg 29:13, 1971 8. Epker B, Wolford L: Middle-third facial osteotomies: Their use in the correction of acquired and developmental dentofacial and craniofacial deformities. J Oral Surg 33:491. 1975 9. Boyne PJ: Implants and transplants: Review of recent research in this area of oral surgery. J Am Dent Assoc (Special Issue) 87: 1074, 1973 10. Boyne PJ: Review of the literature on cryopreservation of bone. Cryobiology 4:341, 1968
639
11. Gresham R: Freeze-drying of human tissue for clinical use. Cryobiology 1: 150, 1964 12. Pappas AM: Current methods of bone storage by freezing and freeze-drying. Cryobiology 4:358. 1968 13. Friedlander G, Mankin H: Guidelines for banking of musculoskeletal tissues. Am Assoc Tissue Banks Newsletter 4(SUPPl). 1980 14. Peterson LJ: Principles of antibiotic therapy. III Topazian RG, Goldberg MH (Eds): Management of Infections of Oral and Maxillofacial Regions. Philadelphia, WB Saunders, 1981, pp 159-165 15. Billingham RE: The immunobiology of tissue transplantation, Int Dent J 21:478, 1971 16. Friedlander GE: The antigenicity of preserved allografts. Transplant Proc 8 (Suppl 1):195, 1976 17. Langer F, Gross A: The clinical and immunological assessment offrozen bone allogmfts. Acta Med Pal 19271. 1978 18. Marx R et al: The use of freeze-dried allogeneic bone in oral and maxillofacial surgery. J Oral Surg 39:264. 1981
Frozen Femoral Head Allogeneic Bone Grafts for Orthognathic Surgery JAMES M. CHRISTIAN,
DDS,* AND LARRY J. PETERSON,
DDSt
Bone grafts are occasionally required in orthognathic surgery procedures. Allogeneic grafts are desirable because they decrease patient morbidity. Fresh frozen bone obtained during total hip replacement has been used in 12 orthognathic operations. Observations for one to three years have
showed
very good results.
Materials
Bone grafting is commonly used in orthognathic procedures such as mandibular advancements with C-osteotomy, total maxillary advancements, and segmental alveolar osteotomies that leave significant intrabony spaces.‘-x Bone grafts are useful in these situations because they promote bony healing and provide mechanical stability.‘.” Autogenous bone is the most desirable graft but carries definite operative morbidity, including pain, scarring, and decreased ability to ambulate in the immediate postoperative period. The use of allogeneic bone circumvents these problems. Cryogenically preserved allogeneic bone is preferred, because treating bone with harsh chemicals or by autoclaving it damages the graft and delays its incorporation with host bone.“.“’ Lyophilized bone has enjoyed popularity because of its long shelf life and easy storage, but it requires extensive preparation with specialized equipment, rendering it expensive and difficult to obtain.‘,” An alternative is frozen bone. With the recent increase in frequency of prosthetic hip replacement procedures, femoral head bone has become readily available. We have used this source of bone for three years. The purpose of this paper is to describe a technique for procurement and use of frozen femoral head bone and to report the results of long-term follow-up of such grafts in orthognathic surgery.
CLINICAL MATERIAL
Twelve patients who were treated at the University of Connecticut were included in this study (Table 1). Two of the patients underwent ramus procedures: three, alveolar segmental procedures; and seven, a variety of maxillary procedures. Follow-up periods ranged from 12 to 36 months. Routine diagnosis and treatment planning, using radiographs. models of the teeth, and a thorough clinical examination, were accomplished for each patient. Postoperative radiographs were obtained immediately after surgery and at appropriate intervals in the postoperative course in order to evaluate (1) position of the graft, (2) inflammatory resorption of the graft, (3) replacement of the graft by host bone, and (4) relapse of surgically repositioned segments. Clinical examinations were conducted to
* Formerly Chief Resident; currently in private practice in Hadley, Massachusetts. i Professor and Program Director. Received from the School of Dental Medicine. University of Connecticut. Farmington, CT 06032. Address correspondence and reprint requests to Dr. Peterson. 0278-23911821100010635
$01 .OO Q American
and Methods
FIGURE I. Cut surface of the femoral cortex and dense cancellous bone. Association
635
of Oral and Maxillofacial
Surgeons
head,
showing
a thin
636
FEMORAL
HEAD
BONE
GRAFTS
FIGURE 2. A, C-osteotomy for mandibular advancement with corticocancellous bone graft in vertical position and cancellous bone graft in horizontal position. B, Immediate postoperative panoramic radiograph of patient. C, One-year postoperative panoramic radiograph at time of mesh removal. There is complete incorporation of the grafts by host bone. D, Surgical site one year after graft insertion. There is complete replacement of graft by host bone.
evaluate the occlusion and adequacy of the union of the segments. Postoperative complications were also noted. FROZEN ALLOGENEIC
BONE PREPARATION
Femoral head bone was removed under sterile conditions during total hip replacement procedures in patients whose ages ranged from 57 to 76 years. The specimens were between 3.5 and 7 cm in diameter. A small fragment of each specimen was submitted to culture to assess sterility. The bone was packaged in a double glass container, the outer container being labeled with the donor’s name and hospital number, reason for removal, date, and name of operating surgeon. The bone was then stored at -2 C for at least two weeks before use. When the bone was removed from the bank, it was allowed to thaw for at least one hour before grafting. The bone was then shaped as necessary by use of saws and rongeurs (Fig. 1). Before the bone was inserted, it was vigorously and thoroughly irrigated with sterile saline to remove as much soft tissue as possible.12,13 Femoral head bone used for grafting consists of a thin outer cortex and a rather dense cancellous
medullary portion. As the cancellous dense, the strength is satisfactory.
bone is quite
OPERATIVE TECHNIQUE
The size and shape of the graft varied depending on the particular procedure involved and the size and shape of the recipient site (Figs. 2, 3, and 4). Fixation of the graft was similar to that which would be employed with autogenous bone. Systemic antibiotics, usually penicillin G, l,OOO,OOOunits intravenously immediately preoperatively and every two hours during the procedure, with the last dose in the recovery room, were used for prevention of wound infection.14 Systemic steroids, usually methylprednisolone, 125 mg every six hours for two days, were given intravenously to minimize postoperative edema. Results CLINICAL
EVALUATION
All patients recovered uneventfully, had a normal postoperative course, and were discharged from the hospital on the first or second day after surgery to be followed up as outpatients. Primary Healing Phase. This phase correspond-
CHRISTIAN AND PETERSON
637
ed to the postoperative maxillomandibular fixation period (6 to 8 weeks). Patients were examined closely for possible signs of graft rejection, which would have been manifested as an increase in erythema and/or edema following the period after which initial edema would be expected to resolve, allergic skin reaction, soft tissue wound dehiscence, or accelerated resorption of the graft itself.15,16 None of these occurred, and soft tissue healing proceeded normally. Union und Relapse. The interval required to achieve union of the mobile segments was comparable with that expected after similar procedures in which autogenous bone is used.1*3 Relapse of repositioned segments was considered a minor problem. In 11 of 12 cases, no relapse was seen. One patient, who had a maxillary disimpaction of 7 mm, experienced a 2 mm vertical relapse of the anterior maxilla at 18 months. Complete host bone replacement was seen by direct visualization of the operative sites in a patient who had undergone C-osteotomies for mandibular advancement when titanium mesh splints, which were placed bilaterally at the inferior borders for fixation, were removed one year postoperatively (Fig. 2). Postoperative infection was seen Complicutions. in one of the 12 cases. The infection was managed conservatively with daily irrigations and antibiotics. Graft removal because of infection was not necessary. RADIOGRAPHIC
EVALUATION
Standard radiographs were obtained at regular postoperative intervals. The first important information afforded by radiography was determination of the rate and amount of graft resorption and the rate of replacement by host bone. Early, rapid resorption of the grafted bone did not occur in any of
FIGURE 3.
Right lateral orbital rim in patient
modified LeFort III advancement, holding zygoma forward.
with cancellous
undergoing bone graft
FIGURE 4. Above, Right posterior mandibular segmental procedure with cancellous bone graft holding the segment with the third molar forward. Center, Immediate postoperative panoramic radiograph showing bone graft in place posterior to the mandibular third molar. Belong, One year postoperative radiograph showing no evidence of bone graft. There has been complete incorporation by host bone.
the patients. Long-term radiographs showed that there was simultaneous resorption of the graft and replacement by host bone, with no loss of overall size of the original graft (Figs. 2 and 4). The other important information afforded by cephalometric radiography was determination of skeletal relapse. In this manner, relapse was noted in only one case-that of a maxillary disimpaction, where the initial gain in maxillary height of 7 mm relapsed to 5 mm. This patient’s maxilla has remained stable since the relapse occurred.
638
FEMORAL HEAD BONE GRAFTS
Table 1.
Outcome of Bone Grafting with Frozen Femoral Head Allogeneic Bone in 12 Patients
2 3 4 5 6 I 8 9 10
11 12
Amount of Defect (mm)
Complications
Relapse
I advancement midline split I with midline
36
4
-
No
23
4
-
No
I with midline
35
3
-
No
I I disimpaction
38 18
8 7
-
20
8
-
20
8
-
12 34 12
5 5 5
13
10
16
4
Operation
Patient 1
Length of Follow-up (mo)
LeFort with LeFort split LeFort split LeFort LeFort
Zygomatico-maxillary (LeFort III) advancement Zygomatico-maxillary (LeFort III) advancement C-osteotomy C-osteotomy Mandibular posterior segmental osteotomy Mandibular posterior segmental osteotomy Maxillary anterior segmental osteotomy midline split
Fracture of right body of mandible Postoperative infection -
No 2mmfatANS 3mmfatPNS 1 mmfatANS No No No No
No No
with
Discussion
Bone grafts are necessary for certain orthognathic procedures. In some situations the osteogenic potential of autogenous bone is essential for the success of the procedure, e.g., osteotomies involving residual clefts that require grafts. There are other procedures in which allogeneic bone may be preferred because a second operative procedure is not required. An allogeneic graft is defined as tissue taken from a donor who belongs to the same species but is not genetically related to the recipient. The process of freezing allogeneic bone significantly reduces the immunogenic response compared with the response to fresh allogeneic bone.17 Frozen allogeneic bone grafting establishes a matrix for the ingrowth of host bone that will promote bony union, provide mechanical stability between the segments during healing, and stimulate formation of bone. Allogeneic transfer of any tissue, including blood and bone, may risk transmission of disease. To reduce this possibility, all donors are screened for hepatitis B, syphilis, active infection, malignant disease, autoimmune disease (including rheumatoid arthritis), and chronic parenteral drug abuse. If the potential donor has had any of these, the bone is unacceptable. Therefore, only patients with histories of chronic degenerative joint disease or osteoarthritis or who have had a fracture of the femoral neck are accepted. At this time, we have used frozen femoral head in 28 patients (the follow-up is not of sufficient length to report on the other 16 patients at this time). We are unaware of any trans-
mission of disease in these patients; this is similar to other published reports.‘* In this study, the grafted sites underwent normal bony healing with the incorporation and eventual replacement of the graft by host bone. The grafted maxillae and mandibles usually showed no evidence of relapse (except in one case) by cephalometric radiographic comparisons and by careful clinical follow-up examinations. There was an obvious lack of complications. Those that did occur were mainly caused by surgical technique and not by the use of allogeneic bone. One postoperative infection was seen, but it was easily managed in a conservative manner.
Conclusions Four conclusions about the use of frozen femoral head bone grafts can be made from this study. (1) It is readily available and relatively inexpensive compared with other sources of allogeneic bone. (2) A normal progression of healing, with eventual incorporation and replacement by host bone, occurs. (3) Skeletal relapse is generally avoided. (4) There is absence of clinically immunologic recognizable response. References 1. Epker B et al: The use of freeze-dried bone in middle-third advancements. Oral Surg 42:278, 1976 2. Constantinides .I, Zachariades N: Homogenous bone grafts to the mandible. J Oral Surg 36:599, 1978
CHRISTIAN
AND PETERSON
3. Bays R: Anterior mandibular dentoalveolar advancement utilizing lyophilized bone. lnt J Oral Surg 8:283, 1979 4. Byrne R, Hinds E: The ramus “C” osteotomy with body saggital split. J Oral Surg 32:259, 1974 5. Bell W: LeFort 1 osteotomy for correction of maxillary deformities. J Oral Surg 33:412, 1975 6. Peterson LJ: Posterior mandibular segmental alveolar osteotomy. J Oral Surg 36:454. 1978 7. Kent J. Hinds E: Management of dental facial deformities by anterior alveolar surgery. J Oral Surg 29:13, 1971 8. Epker B, Wolford L: Middle-third facial osteotomies: Their use in the correction of acquired and developmental dentofacial and craniofacial deformities. J Oral Surg 33:491. 1975 9. Boyne PJ: Implants and transplants: Review of recent research in this area of oral surgery. J Am Dent Assoc (Special Issue) 87: 1074, 1973 10. Boyne PJ: Review of the literature on cryopreservation of bone. Cryobiology 4:341, 1968
639
11. Gresham R: Freeze-drying of human tissue for clinical use. Cryobiology 1: 150, 1964 12. Pappas AM: Current methods of bone storage by freezing and freeze-drying. Cryobiology 4:358. 1968 13. Friedlander G, Mankin H: Guidelines for banking of musculoskeletal tissues. Am Assoc Tissue Banks Newsletter 4(SUPPl). 1980 14. Peterson LJ: Principles of antibiotic therapy. III Topazian RG, Goldberg MH (Eds): Management of Infections of Oral and Maxillofacial Regions. Philadelphia, WB Saunders, 1981, pp 159-165 15. Billingham RE: The immunobiology of tissue transplantation, Int Dent J 21:478, 1971 16. Friedlander GE: The antigenicity of preserved allografts. Transplant Proc 8 (Suppl 1):195, 1976 17. Langer F, Gross A: The clinical and immunological assessment offrozen bone allogmfts. Acta Med Pal 19271. 1978 18. Marx R et al: The use of freeze-dried allogeneic bone in oral and maxillofacial surgery. J Oral Surg 39:264. 1981