A new standardized critical size bone defect model in the pig forehead for comparative testing of bone regeneration materials

Objectives The preclinical study aimed to establish a standardized preclinical model to investigate osseous graft consolidation in defect configurations of limited regenerative capacity. Material and methods Critical size defects (CSD) were prepared and titanium tubes inserted for defect separation from local bone in the forehead area of 18 pigs. Defects were filled with demineralized bovine bone mineral (DBBM) or served as empty controls and were covered with a resorbable collagen membrane (CM) or left untreated. Six randomly selected pigs were sacrificed after 4, 8 and 12 weeks. Specimens were histologically and histomorphometrically analysed focusing on newly formed bone (NFB), demineralized bovine bone mineral (DBBM) and soft tissue (ST) proportions. Results Four weeks after defect preparation, no statistically significant difference concerning NFB quantity could be detected within the groups. Defects covered with the CM showed lower amounts of DBBM. After 6 and 12 weeks, defects augmented with DBBM in combination with a CM (8 weeks: 43.12 ± 4.31; 12 weeks: 43.05 ± 3.01) showed a statistically significant higher NFB rate compared to empty control defects covered with 8 weeks: 7.66 ± 0.59; 12 weeks or without a CM; 8 weeks: 8.62 ± 2.66; 12 weeks: 18.40 ± 2.40. CM application showed no significant impact on osseous defect regeneration or soft tissue formation. Superior NFB could be detected for basal aspect for several evaluation time points. Conclusions The modification of CSD with titanium tubes represents a suitable model to imitate a one-wall defect regeneration situation. Clinical relevance The established model represents a promising method to evaluate graft consolidation in one-wall defect configuration.