Introduction

As early as 1867 the French surgeon Louis Ollier described his experience with free bone grafts after exhaustive experimental research. His observations prompted a surge of new experiments investigating their clinical use, but it was not until 1931 that the Swiss surgeon Hermann Matti—based on his clinical experience and histological findings—pointed out the great value of autogenous cancellous bone for transplantation. Despite his impressive results in the treatment of pseudarthrosis, autogenous cancellous bone grafts did not become popular until modern osteosynthesis techniques were developed. These techniques facilitated adequate fixation and mechanical stabilization of and around the bone graft—important prerequisites for its undisturbed incorporation.

Autogenous bone grafting and nonunion

The most important factors leading to a nonunion are disturbed vascularity and instability with or without locoregional infection and/or bone defect as major complicating factors.

The range of indications for autogenous bone transplantation, and more specifically for cancellous bone grafting, is very wide. The emphasis is on its use in atrophic nonunions as a strong stimulus to bone healing by enhancement of biological responses. Bone defects can be filled or bridged with a bone graft but in an infected environment, autogenous cancellous bone is the only material which, by virtue of its rapid revascularization, can cope with the destructive effect of a progressive infection.

Pathophysiology

Autogenous (cortico-)cancellous bone grafts are the gold standard for both biological and mechanical purposes (Fig 1.4.2-1). They combine three properties that all contribute to enhancement of bone healing:

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  Osteogenic—a source of vital cells

  
  
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  Osteoinductive—for recruitment of local mesenchymal cells that differentiate into osteoblast-like cells

  
  
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  Osteoconductive—a scaffold for creeping substitution with ingrowth of new bone and remodeling by functional adaptation

The osteoblast phase encompasses the direct effect of surviving bone cells that show massive proliferation from the third to fourth postoperative day and in interaction with osteoblasts, complete breakdown and remodeling of the graft. On the other hand, there is the indirect effect of osteogenic induction by a variety of bone morphogenic proteins and mono polysaccharides that are localized in the intercellular matrix.

The proper incorporation of a bone graft requires three crucial prerequisites:

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  Mechanical stability

  
  
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  Good vascularization of the graft bed

  
  
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  Close contact between graft and environment

In anatomical terms, cancellous bone is nothing but “loosely packed” bone. Its honeycomb structure facilitates the nutrition, revascularization, resorption and remodeling of the graft. Massive corticocancellous bone grafts which can be obtained from the pelvis combine the good properties of cancellous bone with the mechanical firmness afforded by the (relatively thin) cortical layers.

Clinical application

The pelvis is the most suitable donor site for autogenous bone grafts. Large amounts of graft material can be removed from the anterior (Fig 1.4.2-2) and even more from the posterior iliac crests with low morbidity and without reducing the mechanical properties of the pelvis (Fig 1.4.2-3). Other sources are the greater trochanter and to a lesser extent the head of the tibia, the olecranon and the distal radius, femur, and tibia. Removal of larger amounts of cancellous bone from the trochanteric complex entails some risk of fracture as a result of local skeletal weakening.

An alternative is the use of the bone debris after intramedullary nailing and a large amount of osteogenetic material can be obtained by reaming the healthy femur (Fig 1.4.2-4, Fig 1.4.2-5).

The technique for iliac-crest cancellous bone and corticocancellous bone-graft harvesting is as follows: the anterior iliac crest is approached by a curved medial skin incision and the periosteum is dissected sharply. Using a curved periosteal elevator, a musculotendinous flap of the iliac and abdominal muscles can be created.

By this technique the inside of the pelvis can be approached in a rather atraumatic way. Gauzes are inserted to stop possible bleeding and one or two broad, pointed Hohmann retractors are inserted to allow free access to the inside of the pelvis, if necessary down to the sacroiliac joint.

No exposure of the sensory nerves is necessary. The cutaneus femoris lateralis and ilioinguinal nerves are well-protected in the musculotendinous flap. This approach allows for harvesting of the types of grafts needed for reconstructive surgery: elevation of the internal lamina of the pelvis with chisels gives free access to the pure cancellous bone. A large corticocancellous piece of bone can be resected without disturbing the external shape of the pelvis (Fig 1.4.2-6). Finally, bicortical wedged grafts can be taken by resection of the inside of the iliac crest leaving the outside intact (see Fig 1.4.2-7).

Transosseous reinsertion of the musculo-tendinous flap with resorbable sutures will restore the shape of the iliac crest and the function of the abdominal muscles (Fig 1.4.2-6b–e).

Autogenous cancellous bone grafting is as a rule the cornerstone of treatment of infected nonunions. Resistance is stimulated biologically, osteogenesis is enhanced, dead spaces are filled and bone defects are bridged. As mentioned previously, it is also the only transplant material that is infection resistant, given the conditions of mechanical stability. Even in such unfavorable conditions, the great osteogenic capacity of autogenous cancellous bone grafting ensures the rapid formation of new bone.

Bone grafting in hypertrophic nonunions is not necessary, compression and stable internal fixation will lead to union—this type of nonunion is a pure mechanical problem.

Atrophic nonunions represent a combination of missing mechanical stability and disturbed biology. Internal or external fixation will lead to stability, but healing can only be achieved by stimulation of the biology by autogenous bone grafts.

Obvious indications for bone grafting are defect nonunions but also sclerotic, avascular nonunions. Compression of the sclerotic nonunion surfaces will create stability but remaining gaps after full compression of the avascular bone ends will not be bridged, implants inserted for fixation will finally fail. Healing has to occur by the formation of a bridging callus. This callus will occur after decortication and cancellous bone grafting.

The sclerotic bone is slightly decorticated, small bone pieces are chiselled away from the exterior aspect of the cortex, while preserving their vascular supply, thus creating a well-vascularized transplant bed for a cancellous bone graft. The bone graft improves the local vascularization and will strongly enhance osteogenesis. As a result the sclerotic bone of the nonunion site will be bridged by the formation of a well-vascularized callus (see Fig 1.4.2-8).

Pure cancellous bone grafts can be taken out of the iliac crest or out of the metaphyseal area of the same bone.

The indication to use corticocancellous bone grafts are metaphyseal nonunions with unilateral defects. Impaction of bicortical anterior iliac bone grafts will correct a malalignment and create intrinsic stability. Those grafts have a mechanical and biological function, minimal internal fixation is necessary to secure the achieved stability (Fig 1.4.2-9).

In contrast, pure impacted cancellous bone grafts can only be used if the stability of the internal fixation is assured during the ingrowth process of the graft. These types of grafts have no primary mechanical function and are used as already mentioned in diaphyseal nonunions where mainly biological stimulation is needed and full stability is achieved with compression plating or nailing.