Custom Prosthesis for Patient with Femoral Chondrosarcoma (Slideshow)

By Nathan Mesko, MD and Joshua Lawrenz, MD

Complete resection is the gold standard for minimizing the chance of local recurrence in primary bone sarcoma. Sometimes, in an effort to resect without leaving behind any tumor cells, large voids can be created, making functionality impossible without reconstruction. But bone and soft tissue tumors often present ways that make routine resection and reconstruction impossible. Creative thinking can improve the chances of limb salvage over an amputation alternative, and can determine long- and short-term reconstruction success.

These slides demonstrate the case of a 70-year-old gentleman who presented with four years of progressively worsening left thigh cramping, with no specific history of trauma. Just prior to presentation, his pain progressed to the point where he stated the leg “felt like it was going to break.”

<p>Radiographs revealed a large and destructive lesion in his left femur, and subsequent MRI showed tumor extension from just above the knee joint to just below the lesser trochanter of the hip. This left distal femoral AP radiograph shows an aggressive bony process with a chondroid internal matrix, consistent with a chondrosarcoma.</p>

<p>He underwent an open biopsy at an outside institution, confirming the diagnosis of a Grade II chondrosarcoma, and then presented to Cleveland Clinic for definitive management. This left proximal femoral AP radiograph shows sparing of the hip joint and lesser peritrochanteric locations. He showed minimal arthritic changes in his left hip joint, and salvaging the joint was discussed.</p>

<p>Surgical excision of his femur was recommended, with plans to leave a short segment of his proximal femur remaining. Early loosening from a long endoprosthetic reconstruction was a major concern, given the long mechanical lever arm on the short segment of available bony fixation, and the short amount of proximal femur that would remain after resection of the tumor. Given these concerns, we planned initial design then sent to engineers to design and build with engineering software.</p>

<p>Working with the engineers from Stanmore (Stanmore Implants Worldwide, Ltd.; Elstree, UK), our team brainstormed an initial design and used it to develop a possible design solution. This blueprint features the implant engineers’ final design specifications. The entire femoral shaft was treated with silver, using the Agluna process.</p>

<p>Computer engineering technology allowed Stanmore to produce CT overlay designs to best mirror the anatomy we would resect. We obtained a compassionate use FDA approval for a single use of this customized implant in this specific situation, in order to streamline the process and expedite care. Nine weeks after we first saw the patient, we received the implant.</p>

<p>In a unique approach, the team added a cephalomedullary screw into the design to provide rotational and torsion stability and maximize bony fixation with the short remaining segment of proximal femur. We also added a hydroxyapatite coated collar and side plate to stimulate a hybrid biologic bony on-growth fixation with initial cement fixation, which we hoped would improve long-term survival.</p>

<p>Distal femoral custom implant, featuring silver-coated articulating surface of prosthetic knee joint. The proximal joint has been bolted together, showing the implant in its totality. The customized targeting guide is also visible. The silver coating enhances the implant’s antibacterial and antifungal properties.</p>

<p>During a seven-hour operation, we removed this 39.3 cm en bloc distal femoral resection, consisting of chondrosarcoma and wide-surgical margin. Final pathology was consistent with a Grade II chondrosarcoma.</p>

<p>We used intraoperative CT technology and computer navigation to allow us to accurately judge the exact level of bony resection and properly fit the custom-designed implant. A customized targeting guide allowed for placement of the cephalomedullary screw into the femoral head after cementation of the prosthesis.</p>

<p>At four months postop, the patient had resumed riding five miles daily on his stationary bicycle, ambulating without an assistive device, and lifting light weights in the gym. He remains free of distant disease, and continues to be followed regularly according to National Comprehensive Cancer Network guidelines for chondrosarcoma surveillance. This radiograph of left proximal femur shows the beginning of biologic bone on-growth onto the hydroxyapatite collar.</p>

<p>While standard reconstruction options following long bone sarcoma resection have led to a high rate of successful limb salvage surgery, some situations leave inadequate bony and soft tissue anchor points to pursue conventional means of reconstruction. Implant customization allows limb salvage opportunities for large pelvic defect reconstructions, pediatric “grower” prostheses, growth plate salvage in extremity tumors, or small segment fixation in long bones requiring improved fixation in the remaining bone. While customized implants aren’t often necessary, this form of technology has maximized functional outcomes and improved treatment of extremity and pelvis cancers.</p>

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Dr. Mesko is Director of the Musculoskeletal Tumor Center. Dr. Lawrenz is a resident in orthopaedic surgery.