Bone Grafting around an Articular Joint

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Chapter 15 Bone Grafting around an Articular Joint

Marcus Head, James B. Richardson

Introduction

No substitute has been proven to be better than autograft. Bone is formed by stem cells, and most arrive in the circulation and migrate to an injured surface of bone, attach, and begin to form bone.

The contribution of stem cells in the graft is thought to be small, but the scaffold of bone and its contained growth factors is ideal for the formation of new bone. William Macewen of Glasgow proved the ability of bone graft to regenerate a humerus, and this followed an exemplary series of studies and research.¹

Circulating monocytes also migrate through the endothelium of adjacent capillaries and become either alternatively activated (AA) macrophages or, under the influence of receptor activator of nuclear factor-кβ (RANK), osteoclasts. These three cell types are the basis of repair, bone regeneration, and remodeling.

The early hematoma forming around an injured bone surface (whether the result of your osteotomy or a fracture) immediately contains stem cells.² These multiply rapidly in the hematoma and are in the right place to contribute to healing.

Of note, only the first bleeding from an injured bony surface provides these cells, so the initial hematoma is particularly precious; it should not be thrown away but should be used to amalgamate your bone graft or mix into bone graft substitutes.

The osteoblasts are particularly sensitive to the mechanical environment.

Stability is defined as the maintenance of reduction and correlates with strength. Stiffness is a distinctly different parameter from strength and in fracture or osteotomy fixation is defined as the rigidity of the construct.

Osteoblasts are evolved for a rigid environment with cyclic strains of less than 1% to 2% of their length.

It is particularly useful for graft to be packed tight, for early callus to be bulky, and to limit cyclic movements or a rigid plate be applied while an osteotomy or cancellous fracture is healing.

Weight bearing is good for the maintenance of bone and muscle and the prevention of deep vein thrombosis, but the biological plate of callus or the internal or external fixation must be able to sustain these loads, otherwise weight-bearing loads will need to be limited.

Flexible fixation and early cyclic movements are appropriate for the bulky callus formation needed in diaphyseal fractures.³

This external callus is rarely needed in the metaphysic or epiphysis where there is sufficient bulk and well vascularized cancellous bone that will allow rapid union. John Charnley took biopsies at 6 weeks following knee arthrodesis to prove that union is achieved in this time.⁴

Taking Autograft

Cancellous Graft

Before surgery, and even if the possibility is remote, explain to your patient that he or she may need a bone graft and that this will be taken from the iliac crest.

It is useful to know if the patient always sleeps on one side, as you should warn the patient that the donor site will be tender for some time.

When possible, a small sandbag behind the hip is useful.

Prepare the area of the iliac crest with antiseptic, and use adherent paper drapes with an adherent plastic sheet to prevent the drapes from moving around while you are operating on the knee.

Use a skin incision that ends 2 cm from the anterior superior iliac spine to avoid cutting the lateral cutaneous nerve of the thigh. This happens in 10% of cases, and it is of note that in 10% of cases the nerve passes through the bone of the iliac crest.

If there is no spinal anesthetic, it is useful to infiltrate bupivacaine or a similar long-acting anesthetic in the tissues around your incision at this time to prevent painful stimuli reaching the brain.

Cut the fibers of gluteus maximus as they arise from the lip of the iliac crest.

Hemostasis will be needed at the posterior part of your incision.

Use a saw to cut the outer table of the iliac crest and then a broad osteotome to lift a lid. This exposes the cancellous layer (see Fig. 15-1, A-C).

FIGURE 15-1 A, Exposure of the iliac crest. A slice of the iliac crest has been raised by an oscillating saw, although a sharp osteotome is an alternative. B, Exposure of the iliac crest. Cadaver image. C, Section through A-A’. Skin and deep fascia have been incised and the iliac crest osteotomized to expose the internal cancellous bone.

Use a sharp, long-handled curette to remove cancellous bone from between the cortical sheets (Fig. 15-2).

FIGURE 15-2 The cancellous bone has been removed in scoops using a suitable sharp spoon.

Keep the hematoma that gathers in the wound with your graft.

Corticocancellous Strips

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