|Abstract / Summary
The physis is responsible for the longitudinal growth in the long bones in children. It is a fragile
area of the bone and is prone to injury. Physeal injuries in children, commonly due to fractures,
may result in formation of a bone bridge, with subsequent epiphysiodesis and post-traumatic
deformities due to the growth arrest. However, the physis can also be injured due to a surgical
intervention, such as insertion of an intramedullary nail. The use of intramedullary nails in
children is restricted due to the possible formation of a bone bridge in the empty physeal canal
when the nail is removed. The commonly used treatment option for consolidated bone bridges
is resection of the bridge with deposition of a fat graft in the empty gap. However, fat grafting is
reported to have a poor outcome and there is a need for a novel treatment technique.
The aim of this study is to evaluate the current fat grafting technique compared to allogeneic or
autologous cartilage graft in a standardised physeal gap. Furthermore, we wanted to assess
possible physeal growth and healing following the insertion and subsequent removal of an
intramedullary nail crossing the central physis.
Hence, three studies were carried out:
I. Autologous Cartilage and Fibrin Sealant are Superior to Conventional Fat Grafting in Preventing Physeal
Bone Bridge Formation in Porcines
II. Allogenic Cartilage in a Physeal Gap Suggests Cartilaginous Physeal Recovery with No Bone Bridge
III. Retrograde Femoral Nailing Through an Open Physis Does Not Impair Growth in a Porcine Model
Skeletally immature experimental porcine models where used for all three studies in a paired
design. A standardised physeal gap was created in the distal femoral physis in both hind legs in
Study I and II. The gaps were grafted with fat, autologous cartilage, allogenic cartilage, Tisseel®
or left empty. We evaluated the physeal healing using MRI and histology 14 weeks after grafting.
In Study III, a retrograde femoral nail was inserted unilaterally into the distal femur and removed
8 weeks upon insertion. The animals were followed for eight additional weeks after removal.
Interphyseal growth was assessed after eight and sixteen weeks. Physeal healing was additionally
A bone bridge model was presented. Fat grafting was found to be very inconsistent in preventing
bone bridges. Opposite, autologous cartilage was able to prevent bone bridges and showed
physeal regenerative potential with columnar cell arrangement in histology. Allogenic cartilage
possessed similar properties however with no columnar cell arrangement in histology.
Growth disturbances in the femur were not detected as a result of insertion or removal of the
femoral nail. Nor did we observe any bone bridge formation eight weeks after removal on MRI
or in histological tissue sections.
In conclusion, the conventional fat grafting after bone bridge resection is inconsistent in
preventing bone bridges whilst allogenic cartilage, autologous cartilage and Tisseel® appears to
be superior in preventing bone bridges. Injuring the distal femoral physis with an intramedullary
nail seems to be safe procedure with no subsequent bone bridge formation or growth disturbance.