In the absence of good evidence, we surgeons base decisions on what we were taught, our experience, and a sense of what we think is best for a particular patient. This is the case when we decide whether to resurface the patella during a distal femoral replacement. I go through this every time I get to the end of a case and the implant representative asks, “Do you want to do the patella?” More often than not I reply “No,” acknowledging that my decision is based not on evidence but on my opinion that it is unlikely to benefit the patient. I was therefore eager to read the paper by Etchebehere et al. and hoped that it would shed some light on this question.

The authors completed a very good study comparing the results of distal femoral replacement with and without patellar resurfacing. Interestingly, there was no difference in any of the radiographic or clinical outcomes between the two groups except for more patellar calcification after resurfacing, a finding that likely has no clinical bearing. These results are consistent with the impression among orthopaedic oncologists that resurfacing the patella has little impact on patient outcomes. The congruence between the results of the study and clinical experience adds validity to the authors’ conclusions and is the strength of this paper. However, this study brings to light the difficulties in conducting a clinical research project that is sufficiently rigorous in design and implementation to answer questions and/or change practice.

The research question in this paper is straightforward: Do you need to resurface the patella when doing a distal femoral replacement? However, when put into clinical context it becomes difficult to answer because of all of the variables at play. When operating on a patient with cancer, the surgeon’s goal is to remove the tumor in its entirety while providing a pain-free limb that functions as normally as possible. There are many variables that affect the outcome of this endeavor, including the extent of muscle and soft-tissue resection, technical factors such as joint line recreation and implant rotation, kinematics of a hinged knee prosthesis, rehabilitation protocols, patient motivation, and many others, some of which may not be readily apparent. Trying to figure out how patellar resurfacing affects the success of limb salvage surgery requires a study with a sufficient number of patients to be able to control for all of these variables and functional assessment tools that can accurately measure the desired outcomes. For example, the Musculoskeletal Tumor Society (MSTS) outcome measure is too broad to capture the specific benefits that resurfacing of the patella may offer (improved quadriceps strength, increased time to muscle fatigue, better stair climbing, less anterior knee pain, etc.). Collaborative efforts among institutions to obtain a sample of sufficient size and consensus on outcome measures are necessary but difficult to coordinate and realize.

The current study raises important questions regarding pain after distal femoral replacement. More than one-fourth of the patients in the resurfacing group experienced anterior knee pain and more than one-fifth of patients who did not have resurfacing had pain. A recent meta-analysis of patellar resurfacing in primary knee arthroplasty demonstrated no difference in outcomes with and without patellar resurfacing, although the patients without resurfacing underwent more additional procedures. This finding can be explained by the fact that, although both groups experienced anterior knee pain, the non-resurfaced group had the option of undergoing surgical treatment—hence, the higher rate of additional procedures. Schwab et al. reported a 33% prevalence of anterior knee pain in a series of forty-three patients who had undergone distal femoral replacement after bone tumor excision. They also found no difference in outcomes between patients who did and those who did not undergo patellar resurfacing. The logical question then is: What is the root cause of anterior knee pain? Does arthritis, soft-tissue contracture, patellar maltracking, surgical technique, impingement, implant design, or a combination of these influence pain? Are there interventions such as patellar denervation or targeted rehabilitation protocols that can help patients? With all of the variables, it is difficult to investigate these questions. On the basis of the current study and existing evidence, it seems that patellar resurfacing plays a minor role, if any, in preventing anterior knee pain.