Thank you for giving us the opportunity to comment on the letter.
Firstly, it is important to state that dislocations that were not reducible by closed method (thus openly reduced/revised) were accounted for in the paper and are included into the analysis as a revision. As such, six dislocations were observed of which three were managed by open reduction and revision surgery and the remaining three managed by brief anesthesia and closed reduction only.
The reason for not including the closed reductions in the statistical analysis of revision surgery was an attempt to homogenize the term revision, and as a closed reduction does not involve incision of the skin and the patient is discharged briefly after the reduction, we do not find it to be comparable to other procedures included into the category “revision”, such as exchange of bone anchored implant parts, debridement etc. We believe it is a complication and not a revision. We do, however, strongly advocate the reporting of dislocation risk, whether reduced by an open or closed procedure, so that in future meta-analyses, data can be pooled addressing the different risk of dislocation between endoprostheses.
Secondly, we very much share your concern regarding loss to follow-up for functional outcome in the internal fixation group and therefore we chose not to conclude on functional outcome between the groups. However, as we find a tendency towards increased revision risk using these implants, we considered it reasonable to make a rather weak conclusion regarding revision risk. As our study shows, those selected to receive internal fixation were more likely to not attend clinical follow-up. We speculate that surgeons tend to select patients with the poorest survival probabilities for internal fixation, which probably also means that this group had a worse performance status and/or functional status prior to surgery and thus are most likely to also have a poor outcome after surgery, potentially irrespective of the performance of the surgical implant. Randomized controlled trials are essential to robustly address functional outcomes between endoprosthesis and internal fixation; no statistical analysis can correct/adjust for the inherent selection bias.
It is important to underline that we concluded that the use of an endoprosthesis results in rapid rehabilitation, but cannot say how this compares to internal fixation we cannot say. We advocate caution when selecting internal fixation due to a possible increased risk of implant failure and creating a need for major revision surgery.
At our institution we aim to treat our patients only once—one metastasis, one implant. In our experience, we find that the use of endoprosthesis achieves just that and the rehabilitation period is relatively short. As for internal fixation, we do not know how long time it takes to rehabilitate, but have a feeling that the risk of implant failure is vastly increased compared to endoprosthesis. The question we have to ask is, how much is a patient approaching the end of life willing to trade off the uncertain but potentially increased rehabilitation time against an increased risk of needing two operations for one metastasis?
Sincerely,
Michala Skovlund Sørensen on behalf of the co-authors.