Clinical outcomes of cemented distal femur replacements with all-polyethylene tibial components for oncologic indications

Abstract

Background: Endoprosthetic distal femoral replacement (DFR) is a well-established salvage procedure following resection of malignant tumors within the distal femur. Use of an all-polyethylene tibial (APT) component is cost-effective and avoids failure due to locking-mechanism issues and backside wear, but limits modularity and the option for late liner exchange. Due to a paucity of literature we sought to answer three questions: (1) What are the most common modes of implant failure for patients undergoing cemented DFR with APT for oncologic indications? (2) What is the survivorship, rate of all-cause reoperation, and rate of revision for aseptic loosening of these implants? And (3) Is there a difference in implant survivorship or patient demographics between cemented DFRs with APT performed as a primary reconstruction vs those performed as a revision procedure?

Aim: To assess outcomes of cemented DFRs with APT components used for oncologic indications.

Methods: After Institutional Review Board approval, a retrospective review of consecutive patients who underwent DFR between December 2000 to September 2020 was performed using a single-institutional database. Inclusion criteria consisted of all patients who underwent DFR with a GMRS^® (Global Modular Replacement System, Stryker, Kalamazoo, MI, United States) cemented distal femoral endoprosthesis and APT component for an oncologic indication. Patients undergoing DFR for non-oncologic indications and patients with metal-backed tibial components were excluded. Implant failure was recorded using Henderson's classification and survivorship was reported using a competing risks analysis.

Results: 55 DFRs (55 patients) with an average age of 50.9 ± 20.7 years and average body mass index of 29.7 ± 8.3 kg/m² were followed for 38.8 ± 54.9 mo (range 0.2-208.4). Of these, 60.0% were female and 52.7% were white. The majority of DFRs with APT in this cohort were indicated for oncologic diagnoses of osteogenic sarcoma (n = 22, 40.0%), giant cell tumor (n = 9, 16.4%), and metastatic carcinoma (n = 8, 14.6%). DFR with APT implantation was performed as a primary procedure in 29 patients (52.7%) and a revision procedure in 26 patients (47.3%). Overall, twenty patients (36.4%) experienced a postoperative complication requiring reoperation. The primary modes of implant failure included Henderson Type 1 (soft tissue failure, n = 6, 10.9%), Type 2 (aseptic loosening, n = 5, 9.1%), and Type 4 (infection, n = 6, 10.9%). There were no significant differences in patient demographics or rates of postoperative complications between the primary procedure and revision procedure subgroups. In total, 12 patients (21.8%) required a revision while 20 patients (36.4%) required a reoperation, resulting in three-year cumulative incidences of 24.0% (95%CI 9.9%-41.4%) and 47.2% (95%CI 27.5%-64.5%), respectively.

Conclusion: This study demonstrates modest short-term survivorship following cemented DFR with APT components for oncologic indications. Soft tissue failure and endoprosthetic infection were the most common postoperative complications in our cohort.

Keywords: Dislocation; Distal femoral replacement; Modular; Oncologic; Revision.

Figure 1

Radiographs of a 28-year-old male patient demonstrating a pathologic fracture of the distal third of the left femoral diaphysis. A: Preoperative anteroposterior and lateral radiographs prior to reconstruction; B: Following left distal femoral replacement with use of an all-polyethylene tibial component.

Figure 2

Competing risk analysis for cemented distal femoral replacement with all-polyethylene tibial component constructs for oncologic indications with all-cause revision (femoral or tibial component) and all-cause reoperation as the primary endpoints. One- and three-year cumulative incidences were 14.6% (95%CI 5.7%-27.4%) and 24.0% (95%CI 9.9%-41.4%), respectively, with all-cause revision as the endpoint. One- and three-year cumulative incidences were 26.1% (95%CI 14.2%-39.7%) and 47.2% (95%CI 27.5%-64.5%), respectively, with all-cause reoperation as the endpoint. DFR: Distal femoral replacement.

Figure 3

Competing risk analysis for cemented distal femoral replacement with all-polyethylene tibial components for oncologic indications with all-cause revision of the all-polyethylene tibial component (APT) and revision of the APT due to periprosthetic joint infection as the primary endpoints. One- and three-year cumulative incidences were 18.2% (95%CI 2.5%-45.5%) and 47.0% (95%CI 15.1%-74.0%), respectively, with all-cause revision of the APT as the endpoint. One- and three-year cumulative incidences were 10.0% (95%CI 0.5%-37.4%) and 44.0% (95%CI 6.3%-59.3%), respectively, with revision of APT due to periprosthetic joint infection as the endpoint. APT: All-polyethylene tibial; PJI: Periprosthetic joint infection.

Figure 4

Radiographs of a 58-year-old male patient showing increased lucency surrounding the proximal femoral stem with abutment of the lateral cortex. A: Anteroposterior radiographs of the loosened distal femoral replacement; B: Interval explantation of the prior distal femoral replacement and placement of an intercalary cemented modular antibiotic spacer.