pISSN 1598-298X
J Vet Clin 31(5) :417-420 (2014)
417
Use of Synthetic Bone Material with
Osteoinductive Proteins to Promote Bone Healing in Dogs
Sung-jin Choi†, In-seong Jung*†,Yong-kyu Yoo*, Beom-seok Seo**, Gab-chol Choi*** and Nam-soo Kim**1 Chois animal hospital, Seoul 142-882, Korea
*Royal Animal Medical Center, Seoul 131-878, Korea
**Department of Veterinary Surgery, Chonbuk National University, Jeonju 561-756, Korea
***College of Veterinary Medicine and Veterinary Science Research Institute, Konkuk University, Seoul 143-701, Korea (Accepted: September 29, 2014)
Abstract : Bone grafts are essential for promoting bone healing in some orthopedic cases, and synthetic bone materials have been widely used for bone defects. In addition, osteoinductive proteins such as bone morphogenetic protein and fibroblast growth factor promote osteoblast differentiation and proliferation. The combination of these factors is very useful clinically for promoting bone healing. In this study, we report the use of synthetic bone materials and osteoinductive proteins to repair bone defects in two dogs.
Key words : Bone graft, biphasic calcium phosphates, collagen, BMP-2, bFGF.
Introduction
Bone grafts are essential to promote healing of some ortho- pedic diseases. An ideal bone graft material should have osteo- conduction, osteoinduction, osteogenesis, and osseointegration activities. However, synthetic bone materials possess only osseointegration and osteoconduction activities. Among them, calcium phosphates such as hydroxyapatite (HA), tricalcium phosphate (TCP) and biphasic calcium phosphate have been used in clinical practice due to their excellent biocompatibil- ity and osteoconductive activity (13,17).
Many osteoinductive proteins are available such as bone morphogenetic protein (BMP), fibroblast growth factor, insu- lin like growth factor, and platelet derived growth factor.
BMP is a member of the transforming growth factor-β super- family that promotes bone regeneration in vivo and has been widely used in veterinary clinical practice (12,15). Fibroblast growth factors are a family of polypeptides and are subdi- vided into 1-23. They control proliferation and differentiation of various cell types (1). Basic fibroblast growth factor (bFGF) plays an important role in skeletal development and fracture repair (7,14). In the skeletal system, bFGF promotes osteo- blast differentiation and proliferation in vitro and bone regen- eration in vivo (2,3,10). These proteins require adequate scaffolds to enhance their biological activities.
Composite bone materials have been developed to improve osteoconductivity. A novel synthetic bone material, OSTEON II collagen, is a composite of HA and β-TCP and its surface is coated with bovine collagen. It has a porous structure sim- ilar to cancelleous bone.
In this study, we introduce treatment of delayed union and severe arthritis cases using OSTEON II collagen with BMP-2 or bFGF in two dogs.
Case
Case 1
A 3-year-old intact male mixed dog weighing 14 kg was presented with left tibial fracture. The dog had been adminis- tered anti-inflammatory drugs for 10 days and had undergone surgery with intramedullar pinning at a local animal hospital 1 day ago. General condition and the physical examination were normal except for the fracture site. Complete blood count and serum chemistry were within normal ranges. No abnormal findings were detected on thoracic radiography. The transar- ticular pin was placed insufficiently and a metaphyseal frac- ture and delayed union were found in the tibia on radiography (Fig 1). The pin was removed under sedation to prevent bone infection. The limb was stabilized with a Robert-Johnson bandage, and the dog was given an antibiotic (cefazolin 20 mg/kg IV BID) for 10 days.
Tibial fixation and tarsocrural joint arthrodesis were con- ducted. The aseptic surgical field was prepared under anes- thesia with isoflurane and propofol (6 mg/kg IV). The dog was administered antibiotic (cefazolin 20 mg/kg IV) and analgesic (tramadol 5 mg/kg IM), and the tibial and tarsal joints were exposed with a cranial incision of the joint.
The bone fragments were removed manually, and the frac- ture surfaces were trimmed until normal bone marrow was exposed. The articular surfaces of the tarsal bones were removed with a round burr and the distal tibial articular sur- face was removed with a sagittal saw. The cancellous bones were collected from the humeral head and implanted between the tarsal bones. However, their volume was not enough to
†These authors contribute equally to this work
1Corresponding author.
E-mail: namsoo@jbnu.ac.kr
418 Sung-jin Choi, In-seong Jung, Yong-kyu Yoo, Beom-seok Seo, Gab-chol Choi and Nam-soo Kim
fill the defect, so synthetic bone material implantation was conducted. Granule type Osteon II collagen (bovine type 1 collagen coated biphasic calcium phosphate; HA 30% +β- TCP 70%; pore size 250µm; 70% porosity, Genoss, Suwon, Korea) was prepared and implanted into the defect. After the bone grafts, the tibial, tarsal, and metatarsal bones were fixed using a 2.7 mm reconstruction plate and screws. The gran- ules were soaked in 200µg/ml bFGF solution using a syringe.
The surgical field was closed routinely, and antibiotic (ceph- azolin 20 mg/kg IV BID) and analgesic (tramadol 5 mg/kg IM BID) were administered for 7 days.
The dog was presented for follow-up radiography. The tibia was united well after 6 weeks of the surgery, and there were no clinical signs and abnormal findings on radiography 12 weeks after the surgery (Fig 2).
Case 2
A 3-year-old intact male mixed dog weighing 4.6 kg was presented with lameness of the left stifle joint. No abnormal signs were observed on a physical examination, and general condition was normal except non-weight bearing lameness of the left hind limb. Complete blood count and serum chemis- try were within normal ranges. The stifle joint showed severe arthritis with osteolytic and sclerotic changes in the distal femur and proximal tibia on radiography.
Arthrodesis of the stifle joint was conducted. The anesthe- sia protocol and surgical preparation were the same as for case 1. The stifle joint was exposed with a craniolateral approach.
The distal femur and the proximal tibia were removed using a sagittal saw, and a large bone defect was created. Osteon II collagen was trimmed to the same size as the bone defect.
Gaps between the bone and bone material were filled with granular type Osteon II collagen. The femur and the tibia were fixed with a 2.0 mm reconstruction plate and screws.
The surgical field was closed routinely. Antibiotic (cephazo- lin 20 mg/kg IV BID) and analgesic (tramadol 5 mg/kg IM BID) were administered for 5 days.
Six weeks after the surgery, we confirmed a broken plate at the region of the femur fracture line on radiography (Fig 3).
A second surgery was performed to remove and replace the plate. The stifle joint was exposed under anesthesia using the Fig 1. Preoperative radiographs of case 1.
Fig 2. Postoperative radiographs of case 1 after pantarsal arthrodesis.
Fig 3. Implantation of synthetic bone material in case 2 (left: trimmed bone material, middle: implantation, right: postoperative radio- graphs).
Use of Synthetic Bone Material with Osteoinductive Proteins to Promote Bone Healing in Dogs 419
protocol described above. The broken plate and screws were removed carefully to avoid damage to the implanted materi- als, and a 2.7 mm plate and screws were applied. One ml of BMP-2 (250µg) solution was injected into the implanted materials.
The dog was presented for follow-up 8 weeks after the sec- ond surgery for radiography and physical examination. The implanted materials were calcified 4 weeks after the second surgery and united well with the femur and tibia (Fig 4). No abnormal findings were detected on radiography.
Discussion
Nonunion of long bones occurs in impairment of blood sup- ply, infection, bone fragments loss, inadequate reduction and inadequate fixation. Among them, inadequate fixation is the most common cause (11). In case 1, the surgical procedure was performed incorrectly, and the intramedullary pin was not inserted completely. The intramedullary pin damaged the articular surfaces of the tarsal joints. We found that the artic- ular surfaces sustained irreversible damage, and conducted pantarsal arthrodesis for tibial fixation and tarsal joint stabili- zation. Case 2 also underwent stifle joint arthrodesis for the same reason.
OSTEON II collagen has a porous structure (pore size 250 µm, 70% porosity) and it has been suggested to be similar to cancellous bone. A pore size of about 100-1000µm is ade- quate for bone regeneration (4,5,8). These pores size and connectivity provide space for cell and blood vessel inva- sion. Although we could not confirm new bone tissue in the pore structures by histomorphology, we believe that this pore structure facilitated osteoblast and blood vessel invasion into the defects. In addition, the implant became elastic after being soaked because it was coated with collagen. This elas- ticity makes the manipulation convenient during surgery and can shorten surgery time.
The effective dose of BMP-2 and bFGF for osteoinductive function is dose-dependent (9,18). Larger mammals tend to need larger doses to promote bone regeneration than those of rodents. We determined dose by referring to previous studies (2,6,16). However, an excessive dose of bFGF can induce ectopic bone formation. Choi et al reported that supersatu- rated bFGF flows out and forms new bone tissues in the het- erotopic region in a canine skull defect model (2). In this study, both cases showed a callus on radiography in the early
stage after the surgery without ectopic bone formation during the follow-up period. Therefore, the dose of BMP and bFGF may have been adequate for bone healing in both cases.
The implant failure in case 2 may have been caused by inadequate plate size, bending, or positioning. The screw hole of the plate was laid on the fracture line of the femur. In addi- tion, an angularly curved plate causes unbalanced mechanical stress. We bent and located the plate on the femur carefully during the second surgery. The principles of bone plate appli- cation in orthopedic surgery should be followed.
We injected BMP-2 and bFGF into the implants after implanting synthetic bone material. This method does not provide enough time to bind the scaffolds. Although collagen and biphasic calcium phosphate have excellent binding affin- ity to the proteins, some of the BMP-2 or bFGF can be washed away by body fluids or blood. The surgeon should make an adequate surgical plan and prepare the implant soaked with osteoinductive proteins before the surgery to reduce protein loss.
Various kinds of synthetic bone material have been intro- duced. In this study, we treated nonunion cases with Osteon II collagen, bBMP, or bFGF, and the results were successful.
This combination may provide other alternates for treatment of severe orthopedic diseases.
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개에서 골형성 촉진을 위한 합성 골물질과 골유도 단백질의 사용
최성진†·정인성*†·유용규*·서범석*·최갑철*·김남수**1
초이스 동물병원, *로얄 애니멀 메디칼센터, **전북대학교 수의과대학
요 약 : 몇몇의 정형외과 질환에서 골이식은 필수적이며, 합성 골물질은 골이식물로서 널리 쓰여지고 있다. 한편, 골 형성 단백질과 섬유아세포 성장 인자와 같은 골 유도 단백질은 골아세포의 분화 및 증식을 촉진시킬 수 있다. 이러한 물질들의 조합은 조기에 골형성을 촉진시킬 수 있어 수의임상에서 널리 사용되고 있다. 이번 증례보고에서는 합성 골 물질과 골유도 단백질을 조합하여 대형 골결손부를 성공적으로 치료한 개의 2 증례를 보고하고자 한다.
주요어 : 골이식, 이상성 인산칼슘, 콜라겐, BMP-2, bFGF
