CORR Insights®: Chemotherapy Curtails Bone Formation From Compliant Compression Fixation of Distal Femoral Endoprostheses

Where Are We Now?

Orthopaedic surgeons have not made much progress in improving the results of endoprosthetic reconstruction of large tumor defects about the knee since the devices were first introduced in the 1980s. A variety of reasons exist for this, but the fact that such devices represent only a tiny portion of each manufacturer’s reconstructive portfolio means there is not much money invested in improving the design of these devices. The absence of a national Musculoskeletal Tumor Society database/registry for the past 40 years also has slowed the pace of discovery.

Recently, one study found 10-year implant survival to be only 26%, with failure of fixation being the dominant mode of failure both among cemented and cementless stems [7]. The search for the ideal method of fixation is ongoing, but compressive osseointegration seems promising [4, 8, 10]. Compressive osseointegration has many advantages, including preservation of bone, inducement of bone hypertrophy, effectiveness even in the presence of only a small amount of residual bone, and ease of revision if necessary. But there are many questions to be answered with this approach, and we are only slowly beginning to get robust data on it despite it being available for 20 years.

In the current study, Elalfy and colleagues [2] examine the effect of chemotherapy on bone formation with the use of compliant compression fixation. Those of us who use compression fixation have observed an inhibitory effect of chemotherapy on the development of bone hypertrophy, and tailor the postoperative care accordingly or avoid using the device entirely in that setting. The device obviously depends on osseointegration, hence the concerns about the effects of chemotherapy in patients reconstructed with devices that use this fixation approach. The authors confirmed that patients treated with chemotherapy had less bone formation compared with patients who did not receive chemotherapy. Fortunately, this effect did not result in any reduction in prosthesis survival at 10 years. This is an extremely important observation, which may result in expanded indications for this device among patients treated with chemotherapy.

However, other authors have reported a negative effect on bone ingrowth with other cementless implants in patients receiving chemotherapy and have recommended using a cemented stem in this situation [11]. In a multicenter study, Henderson and colleagues [5] described five main modes of failure of endoprosthetic reconstructions performed the majority being cemented. Aseptic loosening accounted for 19% of all the failure types and 7% of distal femoral replacement patients had loosening. Holm and colleagues [7] reported 16% of patients experiencing aseptic loosening.

All intramedullary cementless implants carry a risk of failure of biologic integration resulting in fibrous fixation, all carry a risk of stress shielding especially in children and adolescents, and some designs have an increased risk of stem fracture [3]. Improvements in the design of the Stanmore prosthesis with the addition of a hydroxyapatite collar aiming for a hybrid of cemented and cementless fixation has shown promising results [1].

Where Do We Need To Go?

We need to know more detail about the outcome of the devices we are implanting. We need to know the performance, durability, and complications of the specific device itself. If we do not have this information, and without a change in design or fixation method, we are not going to improve on the fact that a substantial percentage of survivors will experience fixation failure or loss of fixation [5, 6, 9] and will then undergo revision surgery. Thus far, there is no clear evidence supporting one method of fixation over another, but we cannot be satisfied with 7% to 16% risk of aseptic loosening with cemented stems [7, 9].

We need greater clarity as well about the impact of chemotherapy, if any, on the likelihood of aseptic loosening following knee reconstructions with implants that use compressive osseointegration fixation as well as other fixation approaches. The current study [2] seemed to suggest the risk may not be as great as we earlier believed [5, 7, 11]; given the frequency with which orthopaedic oncologists’ patients receive chemotherapy, such ambiguity risks harming our patients.

Reports about skeletal reconstructions above and below the knee all suffer from the same problems—including heterogeneity of patient populations, diagnoses, adjuvant treatments, stem lengths, and fixation approaches. Those issues, coupled with the rarity of these procedures, conspire to make conclusive statements regarding the results of any one method of reconstruction nearly impossible. It is simply very difficult for one center to amass enough data. The need for an implant registry has never been greater.

How Do We Get There?

While we are successful in limb preservation, we must strive to improve the long-term durability of the constructs we create. Orthopaedic oncologists should design, develop, and participate in a national/international registry to determine what is best for our patients. Unfortunately, a registry/database is still years away. Henderson and colleagues [9], in a multicenter retrospective review, provided us with valuable but incomplete information on the outcome of megaprosthetic reconstructions in our patients. A similar multicenter retrospective study aiming to obtain more specific data on the performance of various implants and the durability of stem fixation would provide much needed information regarding the outcomes of cemented stems, pressfit stems, extracortical fixation, and compressive osseointegration. We still need to determine the best choice for the reconstruction of the distal femur in an adolescent.