Failed vascularized fibular graft in treatment of osteonecrosis of the femoral head. A histopathological analysis

Abstract

Purpose: vascularized fibular grafting has been used to treat osteonecrosis of the femoral head in younger patients. Although the results described in the literature are promising, the failure rate is still significant, especially in steroid users. This study was undertaken to learn more, on a histopathological level, about the mechanism of vascularized fibular graft failure.

Methods: fifteen femoral heads removed at conversion to total hip arthroplasty were analyzed. The case load comprised 10 men and 5 women. They ranged in age from 28 to 39 years and had a median age of 35 years. The interval between the vascularized fibular implant procedure and the conversion to total hip arthroplasty ranged from 22 months to 30 months; the median interval was 26 months. All the patients were steroid users. The heads were sectioned and axial and coronal sections were taken and stained using the WHO method (hematoxylin, phloxine, saffron and Alcian green). A quantitative and qualitative analysis of graft-host interaction at the head (zone 1), neck (zone 2) and epiphysis (zone 3) was performed.

Results: all the specimens showed recognizable collapse of the articular surface over the area of necrosis. Thirteen femoral heads showed the presence of an osteochondral flap attached only at the margins of the area of avascular necrosis, and 10 of these 13 femoral heads also showed loss of the articulating surface with an ulcer crater corresponding to the exposed area of avascular necrosis.

Conclusions: vascularized fibular graft failure seems to be related to a negative effect of creeping substitution: the revascularization becomes a negative force as it supports unbalanced bone resorption, which, as is well known, is enhanced by corticosteroids.

Clinical relevance: creeping substitution is an undermining force in the repair and revascularization of the necrotic area in the femoral head.

Keywords: corticosteroid; creeping substitution; femoral head; osteonecrosis; vascularized fibular graft.

Fig. 1

Diagrammatic view of the anatomical features of the implanted graft and its relationship with the host. The length of the graft was divided into three zones: zone 3, the femoral neck; zone 2, the lower femoral head or “metaphysis”; zone 1, the more apical or epiphyseal component of the femoral head. The intention was to track the vascularization of the pedicle and the changes in the three different areas of the specimen.

Fig. 2

Low energy slab imaging showing the gap at the implant tip.

Fig. 3

Low energy slab imaging showing a flap and cysts at the implant tip.

Fig. 4

Low energy slab imaging showing sclerotic bone on growth on the implant.

Fig. 5

Pattern of recanalization of an artery in the pedicle.

Fig. 6

Fibrous tissue (top) and fibrovascular tissue (bottom) in the pedicle space.

Fig. 7

Lysis of the tip of the graft in zone 1.

Fig. 8

Presence of nuclei, indicating graft viability.