Letter to the Editor: No Difference Between Trabecular Metal Cones and Femoral Head Allografts in Revision TKA: Minimum 5-year Followup.

To the Editor,

We read the article by Sandiford and colleagues [3] with great interest. Although this is a valuable study, we have some queries for the authors.

In the Patients and Methods section, the authors noted that 45 TKA revisions were performed using augmentation of host bone. Of those 45, surgeons used “femoral head allograft in 30 (75%) and trabecular metal cones in 15 (25%).” Shouldn’t the percentages be 66.7% and 33.3%, respectively?

In the Trabecular Metal Cone Technique section, the authors stated: “Nine Type 2A and two Type 2B femoral defects and 13 Type 2A and six Type 2B tibial defects were treated with femoral head allografts. Four Type 2B and two Type 3 femoral defects and two Type 2A and seven Type 2B tibial defects were treated using trabecular metal cones.” However, the second sentence does not match up with the data in Table 1. Are the data in the text or in Table 1 correct?

In the Conclusions section, the authors state that both techniques are viable options for the management of Anderson Orthopaedic Research Institute (AORI) Type 2 and 3 defects. But in the study, no patients with Type 3 bone defects were treated with femoral head allografts. Because of this, we believe that that the study’s conclusions may be overstated as published.

Finally, the authors used the Oxford Knee Score, WOMAC, SF-12, and the UCLA activity score to assess knee function and quality of life, and additionally, radiographs were assessed for signs of loosening. But radiostereometric analysis (RSA) is also important because the AORI classification referenced in the article is based on radiological images. In fact, in a study by Jensen and colleagues [2], the difference between the mean maximum total point motion of the trabecular metal cone group and the no trabecular metal cone group was almost 2 mm, but they could not detect this as a significant difference. However, in Sandiford and colleagues, perhaps there is a significant difference between the trabecular metal cone and femoral head allograft groups. If Sandiford and colleagues compared outcomes of the two groups’ images at 3 weeks, 6 weeks, 3 months, and 1 year using RSA [1], and then annually after 1 year, using the methods they used, perhaps their conclusions would have been more convincing.