Figure 1.
The one-stage bone-transport procedure [20]–[22] harnesses the regenerative potential of the periosteum and cells therein, e.g. for treatment of a critical sized long bone defect after tumor resection.
(a) The tumor is first identified and (b) then resected in toto, leaving a critical sized defect. The periosteum is scored (dashed line, b) and (c) gently peeled back off the proximal bone, leaving denuded bone below. (d) The denuded bone is osteotomized and transported distally to fill the defect zone. It is docked to the distal, healthy femur using ligament sutures. A limiting factor in implementation of this technique is the availability of periosteum in areas easily accessible to the surgical site. This is particularly problematic in high impact trauma injuries such as blast wounds or high speed sports or traffic injuries. Images used with permission [21].
Figure 2.
A periosteal substitute, novel directed delivery device cum implant was developed and implemented to mimic structure-function relationships intrinisic to the periosteum and to enable vectorial delivery, i.e. control of delivery direction and magnitude or concentration, of periosteal factors.
In the current study we tested the efficacy of directional delivery of periosteal factors to enhance defect healing. (A) The implant comprises an outer elastomeric membrane (FDA approved material), an inner elastomeric membrane with a gradient of perforations of highest concentration furthest from the proximal and distal edges of the defect zone. The layers are sewn together with suture material, creating four pockets into which periosteal factors can be tucked. (B) Collagen membranes (FDA approved) were cut and tucked into the pockets of Group 1 implants. (c) Cells were isolated from periosteum of the bone removed to create the defect, seeded on the collagen membranes (FDA approved), and tucked into the pockets of Group 2 implants. (D) Strips of periosteum were resected from bone removed to create the defect and tucked into the pockets of Group 3 implants. Bony bridging of defects sheathed by each respective periosteum substitute was compared between groups and with a Control group implementing an isotropic, simple elastomeric membrane (FDA approved). (E) The periosteum substitute implant was then sutured to the proximal and distal edges of periosteum lifted along the edges of the defect and sutured close along the longitudinal axis of the lateral aspect. Refer to Fig. 3 for intraoperative photo.
Table 1.
Defect bridging was scaled to assess objectively defect bridging without the ability to measure volume of bone generated quantitatively due to the presence of the intramedullary nail.
Figure 3.
Intraoperative photo showing a periosteal substitute in situ, enveloping a critical sized defect in the middiaphysis of the ovine femur.
Figure 4.
High resolution micro-computed tomography (μ-CT) of bone regenerate in Group 1 at 3 weeks and in all groups at 16 weeks after surgery.
The intramedullary nail is present along the longitudinal axis of all specimens. Each group comprised five sheep and the sample images showing the least and most amount of new bone are depicted for each group.
Figure 5.
Mean area of de novo bone regenerate in defect zone, measured in histological sections through the defect zone.
Error bars represent standard error of the mean. Statistical significance of differences between groups was tested using the Mann-Whitney (Wilcoxon) test, with significance defined as p<0.05. p = 0.0003,
p = 0.0459,
p = 0.037.
Figure 6.
Histological cross-sections for Giemsa and eosin-stained specimens showing representative areas of tissue regeneration for each control and experimental group.
(A) Stained and unprocessed specimen for the Control Group. (B) Stained and unprocessed specimen for Group 1 incorporating collagen sheets. (C) Stained and unprocessed specimen for Group 2 incorporating periosteum derived cells seeded on collagen sheets. (D) Stained and unprocessed specimen for Group 3 incorporating periosteal strips. (E) Segmented image from Group 3 (D) highlighting mineralized tissue. (F) Demonstration of collage resolution, as shown in a single field-of-view (acquired from D). Scale bar for (A–E) is 5 mm.
Figure 7.
Proliferation of seeded cells derived from ovine periosteum.
Error bars depict standard deviations.
Figure 8.
High resolution micro-computed tomograph (μ-CT) images of healing 16 weeks after critical sized defect from the previous study [21] (used with permission).
(A) Baseline, untreated control defect, confirming critical size of defects (does not heal without treatment). Defect is completely healed in experimental groups, e.g. (B) including group treated with periosteum, left in situ with small cortical bone chips adherent to inner surface, around defect.