Cell lineage in vascularized bone transplantation

Pedicled iliac crest bone flap transfer for the treatment of upper femoral shaft fracture nonunion: An anatomic study and clinical applications

PURPOSE

We present the results of a study on the anatomy of the ascending branch of the lateral circumflex femoral artery (AB-LCFA) and the use of the pedicled iliac bone flap transfer perfused by AB-LCFA combined with external fixation for the treatment of the nonunion of upper femoral shaft fractures.

METHODS

The orientation, diameter, length, and distribution of the AB-LCFA from 40 lower limbs of adult cadavers were dissected and measured. From 2000 to 2012, 13 patients with nonunion of upper femoral shaft fractures underwent pedicled iliac bone flap transfer perfused by the AB-LCFA combined with external fixation. The time of bone fracture union was recorded based on X-ray examination. The functional results of the femoral shaft were evaluated by the Klemm classification.

RESULTS

The lateral circumflex femoral artery (LCFA) divided into ascending, transverse, and descending branches in 32 specimens (80%). The diameter of the AB-LCFA at the origin was 3.15 ± 0.9 mm and the length of the AB-LCFA was 8.51 ± 3.06 cm. The postoperative course of the procedure was uneventful in all 13 patients. The average follow-up was 15 months. Bone union was achieved in all patients and the average union time was 5.3 months. 12 patients achieved excellent or good functional results based on the Klemm classification.

CONCLUSION

The AB-LCFA has a consistent orientation and abundant blood flow. The transfer of the iliac crest bone flap perfused by the AB-LCFA while combined with external fixation could be an option for treating the nonunion of upper femoral shaft fractures.

Vascularized bone transplant chimerism mediated by vascular endothelial growth factor

BACKGROUND

Vascular endothelial growth factor (VEGF) induces angiogenesis and osteogenesis in bone allotransplants. We aim to determine whether bone remodeling in VEGF-treated bone allotransplants results from repopulation with circulation-derived autogenous cells or survival of allogenic transplant-derived cells.

METHODS

Vascularized femoral bone transplants were transplanted from female Dark Agouti rats (DA;RT1(a) ) to male Piebald Viral Glaxo (PVG;RT1(c) ). Arteriovenous bundle implantation and short-term immunosuppression were used to maintain cellular viability. VEGF was encapsulated in biodegradable microspheres and delivered intramedullary in the experimental group (n = 22). In the control group (n = 22), no VEGF was delivered. Rats were sacrificed at 4 or 18 weeks. Laser capture microdissection of bone remodeling areas was performed at the inner and outer cortex. Sex-mismatched genes were quantified with reverse transcription-polymerase chain reaction to determine the amount of male cells to total cells, defined as the relative expression ratio (rER).

RESULTS

At 4 weeks, rER was significantly higher at the inner cortex in VEGF-treated transplants as compared to untreated transplants (0.622 ± 0.225 vs. 0.362 ± 0.081, P = 0.043). At 4 weeks, the outer cortex in the control group had a significantly higher rER (P = 0.038), whereas in the VEGF group, the inner cortex had a higher rER (P = 0.015). Over time, in the outer cortex the rER significantly increased to 0.634 ± 0.106 at 18 weeks in VEGF-treated rats (P = 0.049). At 18 weeks, the rER was >0.5 at all cortical areas in both groups.

CONCLUSIONS

These in vivo findings suggest a chemotactic effect of intramedullary applied VEGF on recipient-derived bone and could imply that more rapid angiogenesis of vascularized allotransplants can be established with microencapsulated VEGF.