Abstract
An inclusive classification system is required if valid comparisons are to be made between the various types of implants used for total elbow replacement (TER). The aim of the study was to consider the characteristics of the prostheses developed for TER in order to classify these into clearly defined categories.
A descriptive term such as ‘surface replacement’ is unhelpful as this would embrace every design.A classification based solely upon degree of resistance to movement –‘constraint’-is untenable. ‘Constrained’ or ‘fully constrained’ accurately describes a uni-axial hinge, but the term ‘semi-constrained’ defies description.
The terms ‘unconstrained’ or ‘non-constrained’ applied to a joint defy understanding. If articulating surfaces offer no resistance to movement as these terms imply, then there can be no contact between those articulating surfaces.
A definable, inclusive classification can be formulated by considering the mechanical characteristics of the articulating surfaces of each design.
Every design of TER can be classified into one of two broad groups, Linked or Unlinked. We define linked components as those offering resistance to distraction which includes snap-fit designs. Each of these two groups can then be sub-divided into ‘congruous’ or ‘non-congruous’ designs depending upon the shape of the articulating surfaces.
This classification can therefore be summarised as: Linked Congruous – original uni-axial hinge, snap fit designs; Linked Non-congruous – ‘sloppy hinge’; Unlinked Congruous – eg. Capitellocondylar,Souter/ Strathclyde,Roper-Tuke etc; and Unlinked Non-congruous – Kudo, iBP
The abstracts were prepared by Mr Roger Emery. Correspondence should be addressed to him at the British Orthopaedic Association, Royal College of Surgeons, 35-43 Lincoln’s Inn Fields, London WC2A 3PN
