Surgical Technique for Reconstruction of Diaphyseal Defect with Endoprosthesis following Intercalary Resection in Femoral Shaft

Introduction

The options for reconstruction of diaphyseal skeletal defects after excision of bone tumors in the shaft of long bones include the use of autogenous vascularized fibular grafts1, autogenous extracorporeally inactivated bone2, massive allografts3, a combination of autogenous fibular grafts and allografts4, 5 and intercalary endoprostheses6, 7, 8.

Reconstruction with an intercalary massive allograft is currently the most frequently used type of diaphyseal reconstruction; it has a survival rate of more than 80% on long‐term follow‐up9, 10, 11. It allows restoration of bone stock, soft tissue reconstruction of ligaments, preservation of the juxta‐articular bone and joint, fewer long‐term mechanical problems and preservation of the epiphysis in children. However, disadvantages include the risk of disease transfer to the host, a long period of non‐weight bearing or immobility of the limb to allow union, relatively high risk of early infection, fracture and graft failure12, 13.

The long bone most commonly affected by primary and secondary malignant disease is the femur. Primary bone sarcomas usually occur in the proximal or distal ends of the bone; some types of tumor, including lymphoma, myeloma, osteosarcoma and chondrosarcoma, may be confined to the diaphysis14, 15, 16. The incidence of metastatic tumors in the femoral shaft from organs such as the lung, liver, and kidney has increased significantly because of the long life expectancy that has accompanied improvements in chemotherapy, radiotherapy and biological therapy17, 18, 19. Limb salvage by segmental resection allows preservation of the hip and knee joints as well as the epiphyseal plate in children, making it an attractive option with clear functional benefits. Use of a segmental prosthesis to reconstruct an intercalary defect is far less popular than other methods20, 21, 22. The purpose of this study was to describe the surgical technique for reconstructing a diaphyseal skeletal defect with an intercalary endoprosthesis after resection of a tumor in the femoral shaft.

Case Presentation

A 67‐year‐old woman had sustained a pathological fracture of the left femoral shaft two months prior to her presentation to our clinic. She had undergone left nephrectomy for renal cancer 3 years previously. She had subsequently undergone gamma knife radiotherapy for a lung mass, which had not been definitively diagnosed as metastatic cancer or primary lung cancer. While she was receiving lung radiotherapy, she had sustained a pathological fracture of the left femoral shaft. This was immobilized with a splint and skin traction while she completed her course of lung radiotherapy. The response to radiotherapy was evaluated as good. The patient was then referred to our department for surgical management of her fracture.

An X‐ray film revealed a fracture with widely separated fragments in the midshaft of the left femur with an osteolytic lesion extending 5 cm proximally and distally from the fracture site. A computed tomography (CT) scan showed osteolysis with “moth‐eaten” destruction of cortical bone in the femur adjacent to the fracture. Preoperative magnetic resonance imaging (MRI) to assess the extent of the intramedullary tumor showed that the lesion measured about 13 cm based on signal transformation of bone marrow on T1WI images; a soft tumor mass of 5 cm × 10 cm was also observed on the anterolateral aspect of the femur and there was extensive edema of soft tissue around the mass and the femur.

Anteroposterior and lateral radiographs were taken with a size marker placed at the level of the bone to determine magnification. The titanium intercalary endoprosthesis used has two components that are connected with a lap tap and fixed using two locking bolts; the other end of each of these components has a fluted intramedullary stem that is cemented into the corresponding canal.

Surgical Technique

After induction of general anesthesia, the patient was placed in a lateral position. A 20 cm longitudinal femoral incision was made on the lateral thigh, 3 cm above and below the lesion of the bone. The fascia lata was split and the insertion of the vastus lateralis on the lateral femoral intermuscular septum and the lateral aspect of the femur dissected out, after which the vastus lateralis was reflected anteriorly. If the tumor mass had been too large to permit this, the vastus lateralis would have been split sharply and reflected anteriorly and posteriorly. Four Hoffmann retractors were used, two being placed on either side of the incision proximally and two distally to hold the muscles, thus exposing the affected bone. Taking care to ensure that the tumor itself was never penetrated, the vastus intermedius was dissected proximally and distally and then left over the tumor‐bearing bone. The bony transection points, as identified on preoperative imaging, were then accurately imprinted. The two osteotomies were carried out with an oscillating saw. Two specific extractors were then installed into each end of the involved intramedullary cavity and the bone lifted to facilitate dissection of the medial and posterior muscles and fascia, including the vastus medialis, medial femoral intermuscular septum and the attachments of the adductor muscles on the femoral linea aspera. Several perforating arteries deriving from the femoral artery were carefully managed while dissecting the posterior muscles. The segment of involved bone was then removed from the operative field.

Hemostasis was achieved and normal saline pulsatile lavage performed, after which hot distilled water at about 60 °C was used to clean the operative field for about 15 min to kill any residual tumor cells. The proximal and distal ends of the femur were then reamed to accomodate the prosthesis. Rigid intramedullary reamers were used to prepare the intramedullary spaces proximally and distally beginning with a small size and reaming to at least 2 mm diameter greater than the diameter of the stem to be implanted. The aim was to achieve a 2 mm mantle of polymethyl methacrylate around the stem. Trial implants were used to determine the appropriate combination of stem lengths, diameters and body sizes. When the final implant had been selected, a standard cement gun was used to introduce cement into the prepared intramedullary canal.

The two stems were simultaneously cemented in situ in the proximal and distal canals. Half of the lap tap was then placed on to each stem, the orientation and rotation being carefully adjusted. Paying special attention to rotation of the limb, the correct rotational alignment was achieved purely by visual inspection. The lap tap was then assembled and connected using two locking bolts. A torque‐limiting screwdriver was then used to seat the two locking bolts fully. Once the cement had fully hardened, the length and alignment of the leg were checked. After performing a last wash, the soft tissues and skin were closed in layers and the resected specimen sent for histological examination.

Intravenous antibiotics were administered for three days postoperatively. Active physiotherapy was commenced as pain permitted and full weight‐bearing allowed immediately after drainage had been removed once the output had diminished to <50 mL per day. The patient was then followed up clinically and radiologically until the wound had healed.

Discussion

Intercalary resection can be performed for both primary and metastatic tumors provided oncological principles have been adhered to; the expectancy of patients with metastatic disease should be no less than 3 months. Intercalary endoprosthesis with cementation technique for diaphyseal defect is a stable, feasible reconstructive option that allows immediate weight‐bearing and achieves reconstructions comparable with those of allografts. The following should be considered when using intercalary endoprosthesis:

1. En bloc excision of the tumor should be carried out according to the principles defined by Enneking et al.23; the surgeon should endeavor to achieve a safe margin resection with a surrounding cuff of normal tissue. The extent of an intramedullary tumor should be accurately assessed preoperatively by MRI24, 25, 26.

2. Take must be taken to achieve the appropriate rotational alignment. If the affected femoral shaft is intact, a longitudinal imprint on each transection site is marked on the bone surface with a marker pen or osteotome to guide the rotational alignment while seating portion of the body of the prosthesis; However, if the affected femoral shaft is fractured, rotational alignment must be corrected by visual inspection only by keeping the lower leg in a neutral position.

3. The femoral isthmus is an important anatomical mark when resecting a segment of the femoral shaft. If the lesion involves the mid shaft, the isthmus will be removed with the lesion and the diameters of the proximal and distal parts of the femur will be similar to each other. However, when the lesion is located proximal or distal to the isthmus, there is a large discrepancy between the diameters of the proximal and distal parts of the femoral bone. It is therefore crucial to consider the relationship of the lesion to the isthmus when selecting the stem sizes of the endoprosthesis to be implanted.

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Supporting information

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