Abstract
The clinical success of revision THA combined with impaction morcelised bone graft is completely dependent on healing of the bone graft. Both the platelets inside a fibrin clot contained in the graft bed, and the row bone surfaces of bone graft pieces leak bone morpogenetic proteins essential for healing.
Pre operatively in the state of aseptically loosening when osteolysis is the predominant metabolism, there are also a bone healing activity present in the endosteum, as could be visualised studying Flouride-uptake in a Positron Emission Tomography scan.
One day after revision THA using a Lubinus SP II stem with impacted morcelised fresh frozen and fat reduced allografts, no bone healing activity could be detected using PET.
8 days after the same kind of surgery an intense bone healing activity detected as an elevated Flouride-PET uptake was seen.
3 weeks after the same kind of surgery, histological analyses of human biopsies from the graft beds surrounding femoral stems revealed an intense state of healing. A fibrin clot, invaded by inflammatory cells, predominantly granulocytes, was surrounded the necrotic graft pieces. Fibroblasts creating a granulation tissue with newly formed capillaries were also seen in the graft bed. This is the healing scenario normally seen at periostal callus formation. Occasionally bone formation with osteoide was seen in the periphery of the graft beds at this early stage.
3–4 months after surgery histological analyses showed the fibrous healing to have reached 3–5 mm inside the graft beds. Bone healing was somewhat slower; it had reached 2–4 mm.
At this stage a continuously high bone healing activity could be confirmed using PET.
6 months post operatively the fibrous and bone healing had advanced further 2–3 mm.
10 months after surgery, the superficial 3-mm of the graft beds were mainly bone healed as seen by histology. Also the deeper layers of the graft beds were now in an intense state of bone healing. The secondary stage of bone healing, creating new Haversian canals and trabeculares in the direction of load, visible in plain radiographs, is not yet present at this time.
1 year compared to 1 week after surgery PET scans revealed the maximal bone forming activity to have advanced from the surface of the graft beds (which is in the interface to the endosteum) to the deep graft area close to the cement mantle surrounding the stem.
1 1/2 year after surgery is the earliest stage, to my knowledge, when new trabecular formation inside the graft bed can be detected at plain radiographs. Predominantly first visible in the most loaded Gruen zones. If new trabecular formation is not detected after 3 years it is unlikely to become present at al. Cortical repair however may be detected after half a year.
The course of healing described here is to my knowledge predominant. Less good healing scenarios do however occur. Whole or parts of the graft bed may remain necrotic, as has been described in the literature. In case of non-healing, the stem and the cement mantle is bound to a slow but continuos subsidence. Pain is not likely to occur until the tip of such a stem is in contact with the cortex.
Theses abstracts were prepared by Professor Dr. Frantz Langlais. Correspondence should be addressed to him at EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
