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around endoprostheses, nor resorption of grafts, while this is an important issue in larger biological reconstructions98, 127. Fourth, the classi cation system did not distinguish breakage of implants from breakage of supportive hardware (i.e., a supportive screw), while the clinical implications of the two are materially di erent. We present a modi ed version of the Henderson classi cation (tables 1 and 2), aiming to further improve reporting of complications and failures and comparability of di erent surgical strategies and reconstructive techniques. Future collaborative studies are indicated to optimize the classi cation system based on factors that are relevant for clinical outcome.
Careful evaluation of functional outcome, not just complications and failures, should be included in future studies to o er further insight in clinical outcome of various reconstructive techniques. Currently, two systems are widely accepted for assessment of functional outcome. The MSTS (MusculoSkeletal Tumor Society) score was developed in the 1980s and is currently the most commonly used132. The system is a physician-reported outcome that assigns numerical values (0-5) for six domains, producing an overall numerical score that can be used to calculate a percentage rating. The TESS (Toronto Extremity Salvage Score), on the other hand, is a patient-reported questionnaire that was developed in the 1990s133. The TESS questionnaire assigns numerical values (1-5) for 30 activities of daily living. Although the questionnaires demonstrate reasonable agreement, the subjective satisfaction and acceptance of physical impairment are generally higher than the objective score134. In addition, we are of the opinion that the scoring systems o er little discriminative value. Data of large cohort studies should be used to develop a novel, easy-to-use system for assessment of functional outcome. A recent study concluded that the vast majority of functional improvement can be expected during the rst two years after surgery, suggesting that long-term follow-up studies are not necessarily needed to assess functional outcome135.
Apart from evaluating functional outcomes, we are of the opinion that innovative surgical techniques should be introduced in a regulated manner, ensuring the safety and e ectiveness of novel techniques. The IDEAL consortium proposed a ve-stage model that was based on the phased approach for drug development136. It should be taken into account, however, that well-regulated introduction of novel treatment strategies and implants in orthopaedic oncology is complicated. Because of the rarity of disease, combined with the heterogeneity in localizations, disease extent, use of co-treatments, and patient characteristics, it is extremely di cult to adequately compare the outcomes of di erent techniques.
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General discussion
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