VERSÃO EM PORTUGUÊS

 

Nuno Craveiro Lopes M.D. 

Head of Orthopedic and Traumatologic Department
 Garcia de Orta Hospital, Almada - Portugal

Any comment, suggestion or contact can be done to: nuno.lopes@netvisao.pt

 

PAPER PRESENTATION

The effect of transphyseal neck to head femoral drilling. An experimental model for a preventive method of Legg-Calvé-Perthes disease.(1993)

 

            We developed an experimental model in the hip of the White New Zealand rabbit, so that we could study the hemodynamic effect of the transphyseal drilling of the femoral neck and head and its consequences for the growth of the proximal femur. 

 

Guide and drill developed to perform neck head drilling on the rabbit experimental model.

 

 

            We concluded that the drilling induces a marked increase of epiphyseal micro-vascularisation, due to the passage and anastomosis of small blood vessels between metaphysis and epiphysis.

            We found that to be efficient and get blood vessels crossing the growth plate, it must be big enough to create a bone bridge. Thin holes are rapidly closed by the growth plate borders.

 

Arteriographic aspect of increased micro-vascularisation of the femoral head, after TNHD at left, comparing with control hip at right.

Anastomosis between the metaphyseal and epiphyseal vascular network,  through the growth plate.

  Oblique cut to the growth plate. A) Growth plate. B) Bone bridge. E) Epiphysis. 

M) Metaphysis. Arterial vessels crossing the growth plate (Arrows)

 

            The perforation of less than 10% of the growth plate area, utilizing a smooth technique, did not interfere with the normal growth and development of the proximal femur.

            We found that, what concerns growth arrest or slowing by the bone bridge, it is a mater of forces. If the growth force of the remaining growth plate is bigger than the resistance of the bone bridge, there are no growth arrest or growth slowing. We found on our experimental work that if the drilled area is less than 10% of the whole area of the growth plate, there are no growth disturbance. If it is more than 20%, there are growth arrest. In between, there are some growth slowing. 

            Those numbers were lately confirmed by the studies about traumatic bone bridges on distal femur by Peterson.

 

Drilling less than 10% of the growth plate area of the hip at left. At right, control hip. No growth disturbance.

Drilling more than 20% of the growth plate area of the hip at left. At right, control hip. Growth arrest.

 

            CLINICAL RELEVANCE: Transphyseal neck to head drilling (TNHD) may have a relevant  importance in the prevention of Legg-Calvé-Perthes disease, if applied in the repetitive ischemic period that precedes LCPD, called "ischemic disease of the growing hip" (IDGH). It can have also a favorable application on the early necrotic stage of LCPD, as it increased micro-vascularisation and blood flow to the necrotic epiphyseal sequestrum, permitting a faster re-absorption and reconstruction with better vascular conditions. 

 

Nuclide bone scan with a image of IDGH stage III (left) and II (right), on a 6 yo boy

T1 weighted MRI bone scan image of the same case.

Xr of the IDGH stage III. Note the epiphyseal porosis that precedes the sub-chondral fracture.

One month after TNHD. Epiphyseal ischemic bone was remodeled by primary bone substitution and evolution to LCPD was aborted.

Xr 6 years after TNHD. No  growth disturbance.

        

        Data from this experimental researsh permitted us to develop a surgical procedure that can prevent the onset of LCPD, when associated to a screening protocol of IDGH, entity that precedes LCPD. 

        The protocol can be seen at  http://www.geocities.com/craveiro01/pagedlcp/index.html

        The experimental model in which the screening protocol was based can be seen at http://www.geocities.com/craveiro01/lcpd01.htm

 

        Actually we have done more than 200 TNHD procedures in children aged more than 5 years old, for IDGH and LCPD, half of then as already reached the end of growth, and none presented growth disturbances. None of the 78 IDGH cases progressed to LCPD and on the 44 LCPD cases where TNHD was done, we found that fragmentation stage was reached  in half the usual time ( mean 5 months ) and only 41% needed to be subjected to a surgical containment. 

 

Above: Evolution without TNHT

Bellow. Evolution with TNHT