The study included six dogs of Non-descript (n=3) breed, Labrador retriever (n=2) and Terrier (n=1) dog. The mean age of the dogs was 11.33±2.41 months (range 5 -18 months). The body weights of the dogs ranged from 8-32 kg with a mean of 15.83±3.67 kg. The cause of fractures was; automobile accident (n=4), fall from height (n=1) and physical trauma (n=1). The mean time gap between the time of fracture and treatment was 5.66±0.71 days (ranging from 3-8 days). The dogs were equally distributed based on gender.
The Collagen membrane used for guided bone regeneration was found to be satisfactory as it covered the bone defects and aided in proper placement of bone graft at bone loss site. Evaluation of immediate post-operative radiographs revealed proper placement of the plate and screws, good alignment and apposition of the fracture fragments (Fig 4). Immobilization was considered satisfactory with locking compression plating in five dogs. In one dog suture dehiscence with screw pullout from plate seen by 15
th postoperative day due to unrestricted activity of the dog and improper post operative care by the owner . The hydroxyapatite bone graft applied at the fracture site appeared as radio opaque granular structure at the fracture site in immediate post-operative radiographs which can be appreciated in Fig 4. Appearance of callus with adequate radio-density and radiolucent fracture line at the fracture site was observed on 45
th post-operative day. By 60
th post-operative day evidence of callus formation with reduced fracture gap was discernible and the graft had integrated with bridging callus and increased radio opacity. By 90
th post-operative day, fracture line disappeared and good radio dense callus was evident at fracture site and cortical continuity was established. The sequential postoperative radiographs revealed progressive bone healing (Fig 5).
Out of six dogs, one dog showed early bone healing by 60
th post operative day with cortico medullary continuity where as four dogs depicted slow healing as cortico medullary continuity was noticed by 90
th post operative day.The healing time of each bone was given in Table 1. In these four dogs the fracture gap along with distinct graft integrated with bridging callus was seen suggesting the slow resorption of the graft with slow bone healing by 90
th post-operative day. Slow bone healing was adduced to slow resorption of hydroxyapatite. Even though hydroxyapatite showed minimal resorbability it acted as a scaffold for bone ingrowth by providing a fixed structure for calcification to occur proving its osteoconductivity. In the present study a sterile hydroxyapatite bone graft (Sybograft) nano crystalline granules of particle size 200-300 microns was used. It provided a good surface for osteoconduction and biocompatibility. Similar findings were noticed by
Blokhuis et al., (2000) who stated that the biocompatibility of hydroxyapatite is attributed to its hexagonal crystal structure and similarity to the mineral phase of bone tissue. The porosity of the hydroxyapatite influences its osteoconductivity by serving as a framework for the migration of blood vessels and deposition of new bone. The similar views wereexpressed by
Wahl and Czernuszka, (2006),
Corinaldesi et al., (2009),
Anderud et al., (2014),
Bansal et al., (2009),
Basile et al., (2015) and
Santos et al., (2015).
One dog with femur fracture immobilized with LCP showed screw pull out by 15
th post-operative day. Plate removal was done in that dog and the fracture fragments were immobilized with intramedullary pining with adequate weight bearing noticed by 60
th post operative day.
The haematological and serum biochemical values fluctuated non significantly within the physiological limits through different post-operative days in all the dogs.
The Collagen membrane used for guided bone regeneration was satisfactory in all the six dogs. It is a bio-resorbable, bilayered,high purity type-I cross linked membrane with porosity lesser than the penetrable size of anepithelial cell . The porous and compact layers of collagen membrane not only enable osteogenic cell migration but also prevent the invasion of fibroblasts which helps in bone ingrowth. This was in correlation with
Jegoux et al., 2011 and
He et al., 2015. The study had a major limitationof controlled studies (with similar bone, almost similar age group, similar type of fractures) and larger sample size in clinical setting to validate the osteoconductive properties of hydroxyapatite bone graft along with bio-resorbable collagen membrane.