Complexity principles, highlighting the importance of interaction of agents, system history, start point and the potential for emergent events, may provide a better medical model. Our observation was of escalating clinical complexity, ie the interaction between the severity of primary condition and general status. We sought to quantify this.

Patients, methodology and summary of results

Over the past 8 years we have undertaken a number of clinical studies centred on clinical complexity which creates 4 groups: straightforward C0, locally complex C1, systemically complex C2 and most complex C3, which takes the form of a 2x2 table, with escalating complexity from C0 to C3.

We have undertaken studies for both elective and trauma conditions. We have found statistically significant differences between straightforward and most complex patient groups in a variety of parameters such as complication and mortality rates, recovery times and cost.

The future We are currently analysing results of a much larger cohort of knee replacement patients, and are aiming to apply the methodology to hip replacement and tibial plateau fractures. We hope to roll this methodology out to other Trusts and feel the methodology is suitable for any index condition.

Conclusions

• Patients’ clinical complexity is a key factor in determining treatment outcomes. This is currently not done adequately.

• It confirms summative interaction between local and general factors which is been under–represented in historic texts, literature and current registries.

• Complexity classification has increased the understanding of all the teams involved with patient care, improved patient counselling, surgical skillset and operating time allocation and cost awareness.

• The methodology fits with contemporary studies in other fields such as macro–economics.

• The methodology of application and use of this method of patient stratification is likely to have universal applicability.