CHAPTER 44 Surgical Options for Femoral Reconstruction Impaction Grafting

Femoral impaction grafting is a technique that uses milled allograft bone impacted into a deficient femur to create a new medullary canal for the femur. A collarless double-tapered polished stem is then cemented into this new medullary canal to create a prosthesis ensheathed in cement and bone that can subsequently incorporate into the host femur.

The technique was first performed in 1987 in Exeter, United Kingdom ¹ and has been used extensively since. The development of specialized instruments (Fig. 44-2) and refinement of the surgical technique have made the impaction process more reproducible and allow better compaction of the chips for stability and more consistent alignment of the prosthesis.² The idea for the technique is an adaptation of impaction grafting of the acetabulum, a procedure that was pioneered in Nijmegen, Netherlands. In vitro work, along with retrieval specimens, shows that bone is often incorporated and remodeled, recreating a trabecular structure very similar to native bone, thus facilitating any revision procedure that subsequently needs to be performed.³

FIGURE 44-2 Cannulated instruments for distal and proximal packing of femur.

Femoral impaction grafting is a technically demanding procedure requiring attention to the details of the technique. Reinforcement of the femur on its periosteal surface using mesh or strut allograft is often required. Bypass of any deficient areas or stress risers with a long stem prosthesis has been found to be important, but when the rules for reconstruction have been adhered to, the technique has resulted in impressive clinical results at 15-year follow-up.⁴

CONTRAINDICATIONS

Contraindications to the procedure include the following:

Presence of >10 cm of proximal femoral bone loss

Where age or infirmity preclude lengthy surgery if significant reconstruction of the femur is necessary

PREOPERATIVE PLANNING

Exclusion of Infection

Screening of patients for infection is carried out along conventional lines. When there is a clinical suspicion of infection or when anti-inflammatory markers are raised, aspiration of the joint is carried out before the definitive revision procedure. If the infection is proven or if there remains a high index of suspicion for infection, then a two-stage procedure is carried out with appropriate use of high-dosage antibiotics in cement spacers at the first stage. Antibiotic powder is added to the graft and cement at the subsequent impaction grafting procedure.

Analysis of Bone Deficiencies

Pre-revision radiographs are analyzed in detail. Anteroposterior (AP) pelvic radiographs, AP femur films extending to well below the tip of the existing implant, and lateral radiographs are taken to detect endosteal and cortical femoral bone deficiencies. A careful comparison with older follow-up films is made in order to identify the mode of failure of the existing implant. Donor allograft femoral heads or condyles and strut grafts, if necessary, are ordered from a bone bank. Femoral reconstruction metal meshes must be available for reconstruction of the femoral tube where preoperative x-ray films indicate cortical deficiencies or where there is loss of medial femoral neck.

Templating

Femoral Component

From the radiographs the size, length, and offset of the stem required for revision are determined with the appropriate translucent revision templates (Fig. 44-3). The stem must bypass the most distal significant femoral defect—for example, a cortical defect or a significant lytic lesion (involving 50% or more of the cortex seen on two views)—by at least one, and preferably two, cortical diameters. The stems allow for 35.5 to 50 mm of offset and from 125 to 260 mm of length. The definitive stem offset and size are determined intraoperatively.