4.1. Subjects and grafts

This research project was performed involving a total of 253 subjects in whom either bone was harvested or bony reconstruction was necessary in the cranio-maxillofacial skeleton. The work was divided into two main areas, which together combined five studies. The subject of bone graft harvesting comprised three studies (studies I, II and III) and the subject of coral-derived bone graft substitutes comprised two studies (studies IV and V). The number of subjects and their demographic data, are listed in Table 1.

The protocols were within the guidelines of the research ethics committees at the Hospital for Sick Children and University of Toronto, and the Department of Anatomy, University of Toronto, Toronto, Canada, that were in place prior to the commencement of the studies.

In study I, in order to assess the safety of the minimally invasive power driven trephine technique, a total of 25 adult cadavers were used to determine the volume and weight of bone that could be harvested using a motorized trephine (Osteocore^®, Straumann, A.G., Waldenburg, Switzerland). A total of 50 anterior iliac crests were sampled. Core samples of cancellous bone were measured, weighed, and their volumes were determined. The harvested sites were then dissected and evaluated for perforations of the medial and lateral walls of the ilium. These data were compared with the measurement of the first 40 consecutive in vivo cores trephined from 11 patients requiring bone grafts. The cadaver iliac sites were then intentionally perforated on the medial aspect of the ilium, towards the peritoneal cavity, to analyze the safety of the technique.

In study II, in order to asses the suitability of the minimally invasive technique in a clinical environment, a retrospective study analyzed 84 consecutively treated patients, requiring autogenous bone harvested using a motorized trephine (Osteocore^®, Straumann, A.G., Waldenburg, Switzerland) over a three-year period, from 86 trephined iliac crest sites. A total of 333 cancellous cores were harvested. The inclusion criteria were all patients who required elective cranio-maxillofacial surgery, those who were admitted on the same day of their procedure, a follow-up of at least six months, and completion of a telephone survey.

For each patient a chart review was performed and a survey questionnaire was completed. Intra-operative information regarding the number of trephined cores of bone harvested per iliac crest, as well as the bone volume obtained was recorded. Additionally, intra-operative complications including bleeding, perforation of the medial and lateral walls of the ilium, and quantity of bone were recorded. Post-operative reports of pain, bleeding, possible paresthesia and suitability for discharge were also recorded. All patients were followed one week post-operatively and examined for ambulatory gait deficits, wound complications including incision breakdown, infection, paresthesia, and pain.

All patients were then surveyed by a questionnaire examining their short-term (1–14 days), and long-term (greater than 6 months post-operative) deficits, pain or remarks.

In study III, in order to compare the morbidity of the minimally invasive power driven trephine with traditional open iliac crest bone graft harvesting, a total of 76 consecutive patients, requiring less than 30 ml of bone for maxillofacial grafting, were placed into two treatment groups. A prospective case-control format was applied. Group One consisted of the first 22 consecutive patients. These patients underwent corticocancellous block graft (CCBG) harvest in the traditional open medial approach to the anterior ilium. Group Two consisted of the next 54 consecutive patients. These patients had cancellous cores (CC) harvested in a closed fashion through a 0.5–1.0 cm incision with a motor-driven trephine (Osteocore^®, Straumann, A.G., Waldenburg, Switzerland).

ANOVA revealed no significant differences between Groups One and Two based on age: F(1,74) = 0.429 or gender: F(1,74) = .051, p > .05. The morbidity of the two groups was analyzed and compared. The following parameters were used to evaluate patient morbidity: number of days to unassisted ambulation, length of hospital stay, and pain scores for both the recipient and the donor sites. A visual analogue scale was used to grade the subjective hip and maxillofacial pain scores daily for the first three days following surgery.

In study IV, in order to assess the safety and applicability of coral-derived granules as a bone graft substitute in the cranio-maxillofacial skeleton, 36 patients with 54 craniofacial osseous contour defects received subperiosteal augmentations with natural coral-derived granules (CDG) made chiefly of calcium carbonate (Biocoral^® Granules, Socièté Inoteb, St. Gonnorey, France). The distribution of the location of these sites is depicted in Table 2.

The patients were followed for 12 to 36 months to describe post-operative complication rates and to develop a sense of post-operative morbidity from the use of this resorbable xenogenic bone graft substitute. Technical notes pertinent to the use of this material were also recorded and analyzed.

In study V, in order to assess the efficacy of coral-derived granules in the reconstruction of maxillomandibular, especially dento-alveolar defects in the growing patient, CDG (Biocoral® Granules, Socièté Inoteb, St. Gonnorey, France) were used in alveolar ridge preservation procedures in a growing population of 21 patients with a mean age of 13.8 years and with 48 dento-alveolar defects. These patients are detailed in Table 3.

Patients were grouped according to the aetiology of alveolar ridge defect. Group One comprised 17 alveolar ridge defects in the anterior maxilla resulting from trauma. The causes of tooth-loss in this group included complete avulsion, subluxation, root fracture and root resorption. In all 17 cases the labial and palatal plates of bone were present at the time of coral granule placement. Group Two comprised 31 alveolar ridge defects resulting from the careful conservative removal of ankylosed retained primary molars without succedaneous permanent premolars. ANOVA revealed no significant differences between Groups One and Two based on age: F(1,24) = 0.78 or gender: F(1,74) = .158, p > .05. In all 31 cases, the buccal and lingual plates of alveolar bone were intact at the time of coral granule placement. The aetiology of the tooth-loss and location of the augmented alveolar ridge sites are listed in Table 4.

Sites were augmented with 1 to 2 mls of Biocoral“ granules (Socièté Inoteb, Saint Gonnorey, France) placed into the otherwise intact avulsion or extraction sockets as inlay grafts. In all cases coral granules were placed the same day that the tooth was lost, either on the day of tooth avulsion or immediately following elective tooth removal.