This post could be also titled “Why we dichotomize: Part XXIXCM”, but I´ll focus on the subject matter. Gu et al. investigated how prior knee arthroscopy affects the subsequent total knee replacement surgery. They concluded:
This study suggests that an interval of at least 36 weeks should be maintained between the 2 procedures to minimize risks of PJI and revision surgery.
Although authors did completely arbitrary categorization of a continuous variable, namely time from arthroscopy to the TKR surgery, this is an interesting finding. Authors propose that reason why a short time from prior surgery increases the risk for complications after TKR, is some sort of capsular violation or bacterial seed from the arthroscopy.
I postulate that this finding may be related to the patient-related factors. Arthroscopic treatment of knee osteoarthritis has no clinically relevant benefits. So question is why did these patients had arthroscopic surgery in the first place? Were they unable to cope with the pain and arthroscopy was done “as a last resort”? Are these patients different to those who have not undergone a prior arthroscopy? Maybe these intrinsic patient-related factors also explain why they eventually have higher a risk of complication after TKR surgery? And further, maybe these patient-related factors have stronger influence when patient undergoes TKR surgery quickly after arthroscopic surgery. Orthopaedic surgery is mainly about improving quality of life. This means patient related factors have huge relevance in our practice. Self-efficacy, life satisfaction and other intrinsic factors remain underinvestigated in orthopaedics.