Table 1.

A list of operations passing both criteria for inclusion in this study

Operation codes (OPCS-4)	Specific operation type	Generic operation type
F091	Surgical removal of impacted wisdom tooth	Wisdom tooth
F093	Surgical removal of wisdom tooth NEC
J183	Total cholecystectomy NEC	Cholecystectomy
M653	Endoscopic resection of prostate NEC	Prostate resection
Q074	Total abdominal hysterectomy NEC	Hysterectomy
T212	Repair of recurrent inguinal hernia using insert of prosthetic material	Inguinal hernia (IH) repair
T242	Repair of umbilical hernia using insert of prosthetic material	Umbilical hernia (UH) repair
T243	Repair of umbilical hernia using sutures
T272	Repair of ventral hernia using insert of prosthetic material	Ventral hernia (VH) repair
V255	Primary posterior decompression of lumbar spinal cord NEC	Lumbar decompression
W371	Primary total prosthetic replacement of hip joint using cement	Total hip replacement (THR)
W381	Primary total prosthetic replacement of hip joint not using cement
W391	Primary total prosthetic replacement of hip joint NEC
W931	Primary hybrid prosthetic replacement of hip joint using cemented acetabular component
W941	Primary hybrid prosthetic replacement of hip joint using cemented femoral component
W401	Primary total prosthetic replacement of knee joint using cement	Total knee replacement (TKR)
W411	Primary total prosthetic replacement of knee joint not using cement
W421	Primary total prosthetic replacement of knee joint NEC

Frequency of these operation types is specified in table 2.

NEC, not elsewhere classified;OPCS-4, OPCS Classification of Interventions and Procedures version 4.