Table 1.
Study design.
Fig 1.
Pair housing of rabbits in floor pens of 3 m2.
Pens were provided with aspen bedding, autoclaved straw and hay, two plastic houses and a plastic tray with bedding. Pens were cleaned weekly.
Fig 2.
Single housing of rabbits in cages of 0.43 m2.
Cages were provided with autoclaved straw and hay and a shelf to hide under or sit on. Cages were cleaned weekly. A towel was provided in the cage until the rabbits were fully recovered from surgery.
Fig 3.
Picture of a bone replica of calcium phosphate cement (CPC) in place of a 20 mm mid-shaft radius defect in a NZW rabbit.
Fig 4.
Picture showing a collagenous membrane to be fitted around bone chips in place of a 20 mm mid-shaft radius defect in a NZW rabbit.
Fig 5.
Measurement of volume and density with μ-CT in a critical radius defect area 12 weeks after treatment with a synthetic material or bone.
Op 20 and 10 show the volume of measurement of the ulna and the radius defect area including any proliferation of bone. 20 mm encompasses the whole defect. 10 mm encompasses the centre of the defect.
Fig 6.
Radiographs of the radius and ulna sample from one rabbit, harvested 12 weeks after surgery.
The defect and the position of the defect have been measured and marked to guide the preparation of sections for histology.
Table 2.
Modified system for subjective scoring of radius defect area by histology [19].
Fig 7.
Outline of the distal part of the area of interest for the histomorphometric measurements.
The total area was outlined by the end (E) and the centre (C) of the defect. Longitudinal borders were the graft border (G) and the ulnar bone (U). The area that is coloured red represents the binary area (area with graft material and bone).
Fig 8.
Mean and individual body weights.
Means (SEM) pre op (0), 10 d and 12 weeks post creation of a critical radius defect in rabbits housed in cages or in floor pens. Mean body weights were lower at 10 d post op compared with pre op in group Floor (p = 0.029) and group Cage (p = 0.003), as well as compared with 12 w post op in group Floor (p = 0.0004) and group Cage (p = 0.0004).
Fig 9.
Rabbit CS activities in the M. quadriceps after 12 weeks of rehabilitation following a critical unilateral radius defect.
The animals were housed in floor pens of 3 m2 (n = 7) or cages of 0.43 m2 (n = 7). CS activity was higher in group Floor than in group Cage (p = 0.041, F = 4.64, one-way ANOVA). Data are mean + SEM.
Fig 10.
μ-CT image of the defect 12 weeks after surgery showing CPC implant with visible fractures and slight dislocation.
Fig 11.
The effect of Housing on the defect volume measured by micro-CT 12 weeks after creation of a critical radius defect treated with a calcium phosphate compound or augmented bone. The measurement was performed along the entire defect length (20 mm) and included the ulnar bone. There was an overall effect of Housing (p = 0.028, F = 6.59) that did not interact with Treatment (p = 0.18, F = 2.12). The volume was larger in group Floor (n = 7) than group Cage (n = 7), 95% CIs [355, 454], [436, 535], p = 0.028. Two-way ANOVA with Housing and Material as treatment factors followed by a comparison of the predicted means of the Housing factor. Data are individual values and mean ± SEM.
Fig 12.
The effect of Housing on the defect density measured by micro-CT 12 weeks after creation of a critical radius defect treated with a calcium phosphate compound or augmented bone. The measurement was performed along the entire defect length (20 mm) and included the ulnar bone. There was an overall effect of Housing (p = 0.044, F = 5.34) that did not interact with Treatment (p = 0.85, F = 0.04). The density was lower in floor housed rabbits (n = 7) than cage housed (n = 7), CIs [1.08, 1.15], [1.13, 1.21], p = 0.043 by two-way ANOVA with Housing and Material as treatment factors followed by a comparison of the predicted means of the Housing factor. Data are individual values and mean ± SEM.
Table 3.
Volume and density measured by μ-CT in the central area of the radius defect, 12 w after creation (Op 10), and of the contralateral uninjured side (Intact 10 and 20).
Measurements were made in the central part of the defect (10 mm), or the whole defect (20 mm). The measurements of the defect filling include the adjacent ulna and any surrounding new bone. There was no difference between group Floor and Cage in volume or density in the defect area or the intact area (two-way-ANOVA with factor Housing displayed).
Fig 13.
a-b. Rabbit in group AB-Floor: areas of complete reorganisation of trabecular bone. This represents a score 4 for category c (cancellous bone) and a score 3 for category e (filling of the defect). c-d. Rabbit in group AB-Cage: area of incomplete healing with fibrocartilage (arrows). This represents a score 2 (filling of the defect) for category e.
Fig 14.
a-b. Mean with SEM plots of total area and fraction of area filled with bone and material as measured by histomorphometry, 12 weeks after creation of a radius defect filled with calcium phosphate compound block or autologous bone. The area of measurement was outlined by the defect ends, the ulnar bone and the graft material + new bone. Rabbits were housed in pairs in floor pens of 3 m2 (n = 7) or singly in cages of 0.43 m2 (n = 7). NS by Mann-Whitney test.