PMC8655870_01
Radiographic progression of bone non-union. (A) At the first visit, radiographs of the right hind limb show a diaphyseal comminuted fracture of the right femur with active bone callus formation and implant failure. (B) Three months after the first revision surgery, the radiographs of the right femur show implant loosening, bone shortening, and no new callus formation in the fracture gap. (C) Four months after the second revision surgery, although autogenous cancellous bone graft was applied during the surgery, implant loosening and non-union are still noted. (D) After 11 months and multiple surgical revisions, significant atrophic non-union and bone shortening are noted.
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F1
Radiographic examination revealed a closed, comminuted, mid-diaphyseal fracture of the right femur with notable bone callus formation and implant failure (Figure 1A). Radiographic examination indicated 30% femoral shortening and loosening of the four distal screws (Figure 1B). However, 4 months later, the lameness remained unimproved, and radiographs showed delayed union with screw loosening (Figure 1C). At presentation 11 months later, atrophic non-union of the affected femur was noted (Figure 1D).
A brief timeline of the surgeries performed on the cat. The initial surgery was performed 3 weeks prior to the first revision surgery. The second and third revision surgeries were performed 2 months and 6 months after the first revision surgery, respectively. The final surgery applying rhBMP-2 and autografts was performed 11 months after the first revision surgery.
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F2
The surgical events of this case are shown in the timeline (Figure 2).
Surgical procedures. (A) Debridement of the diaphyseal fracture site of the right femur using a harmonic scalpel. (B) Medullary recanalization using a 2.8-mm pin. (C) Autograft harvested from the ipsilateral seventh rib. (D) Fixation using a locking plate system followed by transplantation of the autologous rib; the asterisk indicates the rib autograft. (E) Autograft harvested from the ipsilateral iliac crest. (F) Application of the rhBMP-2-soaked collagen sponge onto the site of defect; the arrow indicates the soaked sponge surrounding the bone defect, and the arrowhead indicates the corticocancellous iliac autograft.
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F3
Tokyo, Japan) (Figure 3A). The medullary canal was recanalized by drilling a 2.8-mm pin into the canal from the fracture site (Figure 3B). The fractured edges were maximally distracted using bone-holding forceps, although the original bone length could not be restored due to excessive soft tissue tension. Tokyo, Japan) (Figure 3C). The intercostal muscles were then apposed over the cut edge of the rib with 3-0 polydioxanone suture in a simple interrupted pattern. The length of the graft was chosen to be the length of the fracture gap plus 0.5 mm. The graft was then positioned at the center of the fracture gap with gentle manual impaction (Figure 3D). Several pieces of corticocancellous iliac autograft were obtained with a rongeur (Figure 3E) and placed to fill the residual space around the rib graft. Finally, a 3 x5 cm absorbable collagen sponge (SavPet, Oriental Co., Taipei, Taiwan) was soaked in 100 mug of rhBMP-2 (10426-HNAE, Sino Biological, Beijing, China) reconstituted in 0.5 mL of normal saline and wrapped around the bone defect (Figure 3F).
Radiographic progression of bone fracture repair. (A) Immediately after the final revision surgery, rib (arrow) and iliac crest autografts are implanted into the bone defect, and a locking plate is applied to stabilize the fracture. Mild distal femoral varus is noted. (B) At 2 months postoperatively, bridging of the callus and resorption of the rib graft are noted. (C) At 5 months postoperatively, the bone defect shows new bone formation, and the transplanted rib graft is indiscernible. (D) At 12 months postoperatively, remodeling and maturity of the regenerated bone are seen.
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F4
Postoperative radiographs were obtained to confirm the position of the graft (Figure 4A). Mild distal femoral varus was also noted (Figure 4A). Radiographs showed bridging callus formation with new bone formation and incorporation of the transplanted rib graft (Figure 4B). On radiographs taken 5 months postoperatively, bony union at the fracture gap was evident and the transplanted rib graft was indiscernible (Figure 4C). Moreover, at the last recheck examination 12 months postoperatively, successful bone remodeling and apparent maturity of the generated bone were noted (Figure 4D).