2.1 Preoperative planning and devices

Defining the osteotomy level and identifying the best graft based on patient characteristics are essential during preoperative planning. The osteotomy level should be defined according to the extent of bone disease assessed on magnetic resonance imaging (MRI) at the time of diagnosis. The planning involves cutting the bone 2 cm from the tumor to achieve an adequate oncologic radicality (Fig. 1). Computer assistance was not considered necessary in this specific case. A length in centimeters (cm) from the femoral calcar should then be planned to achieve disease-free margins. The femoral calcar is also used as an anatomic reference for graft preparation, preferred to the greater trochanter because it is subject to less interindividual variability as a reference for the proximal osteotomy required for implantation of the prosthetic stem. The proximal femur allograft choice is dictated by some characteristics of the native bone as assessed by a preoperative computerized tomography (CT) scan. In particular, the diaphyseal diameter at the level of the osteotomy should be as close as possible to that of the patient's native femur, allowing for a proper interface.

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Fig. 1 A coronal MRI image shows the tumor mass extent, and measurements are taken for subsequent bone resection to achieve adequate oncologic radicality.

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Furthermore, an allograft with intact tendon insertions should be used to reinsert the major hip muscles, and this is an essential advantage over mega-prostheses, which do not allow anatomic reinsertion of periarticular muscles along their force vectors. The cephalic portion of the femoral allograft is replaced with a partial hip prosthesis with a short, cemented stem (LIMA® Friendly Short cemented stem) and a BIOLOX®delta ceramic femoral head.

The cemented stem is chosen to provide good primary stability in allograft bone. At the same time, its short design allows the prosthesis not to over-extend at the distal femoral diaphysis of the still-growing patient, thus reducing the risk of fracture or prosthetic loosening. The plate used for allograft synthesis with the residual distal femur is the Depuy Synthes® VA-LCP PPFx proximal femur Hook Plate 3.5/4.5/5.0 mm with its dedicated tensioner; osteosynthesis is performed according to the principles of absolute stability. Hip muscle tenodesis is performed with Ethibond Excel® non-resorbable polyester suture.

2.2 Graft preparation

Allograft preparation is performed on a workstation, where the cemented prosthetic stem and plate are placed on the graft. At first, tissue debris must be removed; then, a proximal osteotomy is performed approximately 1 cm from the lesser trochanter to allow insertion of the curved rasps to prepare the femoral canal (Fig. 2). Next, the Depuy Synthes® VA-LCP PPFx proximal femur Hook Plate 3.5/4.5/5.0 mm is synthesized on the graft, leaving the correct sized rasp in place to avoid impingement between the screws and prosthetic stem and bone perforation with the cement in place, in case the prosthesis is implanted before plate synthesis, which increases the risk of implant loosening due to alteration of the bone-cement interface (Fig. 3).

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Fig. 2 Tissue debris is removed from the allograft, and a proximal osteotomy is performed about 1 cm from the lesser trochanter.

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Fig. 3 The correctly sized rasp is left in place to avoid impingement between the screws and prosthetic stem, as well as to prevent perforation of the bone with the cement in place in case the prosthesis is implanted before plate synthesis.

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Finally, with the plate and screws positioned in the correct direction, the LIMA® Friendly Short stem is cemented inside the allograft placed on the workstation (Fig. 4). No cement is applied distally to the allograft at the interface with the patient's bone to promote repopulation of the graft and possibly, achieve good osseointegration.

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Fig. 4 After the plate and screws are placed in the correct direction, the LIMA® Friendly Short stem is cemented inside the allograft placed on the workstation.

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2.3 Surgical approach

The patient should be placed in a lateral position to access the hip and femoral diaphysis, with landmarks on the contralateral limb for length and axis checking. A posterolateral approach to the hip is performed to access the proximal femur, with distal lateral extension along the diaphysis for plate synthesis. The tendon insertions of the major muscle groups (gluteus, ileopsoas, and vastus lateralis) and the joint capsule must be dissected and protected for subsequent reinsertion into the graft. Next, as planned preoperatively and performed on the allograft, an osteotomy is performed with manual measurement from the calcar along the femoral diaphysis, with en bloc excision of the proximal femur. The margins should appear macroscopically free of disease. Finally, the femoral diaphysis will be prepared up to the distal third for plate synthesis, limiting deperiostization.

2.4 Osteosynthesis of the graft

The allograft previously prepared on the workstation is placed at the host site and temporarily clamped with reduction forceps once proper anteversion and osteotomy surface correspondence is achieved. Synthesis is then performed according to the principles of absolute stability with at least six proximal and six distal cortices to the osteotomy site. The plate tensioner and two non-locking eccentric screws achieve compression between the contact surfaces. The capsule and major tendon structures are reinserted and sutured with Ethibond Excel®. A fluoroscopic examination is used throughout the procedure, and an anteroposterior (AP) and Lateral View X-ray are performed at the end of the surgical procedure to confirm successful prosthetic implantation and successive synthesis (Fig. 5). Finally, a pelvic-condylar spica must be made to protect osteosynthesis, tenodesis, and hip stability.

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Fig. 5 An anteroposterior (AP) and Lateral View X-ray are performed at the end of the surgical procedure to confirm successful prosthetic implantation and successive synthesis.

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2.5 Follow-up

Pelvic-condylar spica is maintained for 30 days postoperatively, with subsequent removal, and progressive weight-bearing is allowed to be started only when there is good proximal femoral osseointegration on radiographic evaluation. No weight-bearing is recommended until 60 postoperative days, then partial loading with crutches until 90 postoperative days. Clinical and radiographic follow-ups are scheduled 30, 60, and 90 days after the surgical procedure.