Inclusion criteria All patients who were diagnosed and treated for idiopathic clubfoot at BCCH between January 1984 and present are eligible for the study. Patients whose clubfoot is a secondary diagnosis to another disorder (mal-position, neuromuscular disorder and chromosomal abnormality) are excluded from this study.

Database design Using information gathered from literature review and interviews with several of the orthopaedic surgeons at BCCH the most common treatment methods for clubfoot and the ones that are and have been in use in BCCH were identified. Six treatment methods were then described in detail. These treatment methods are: comprehensive release, posterio-medial release, posterior release, Kite-method, Ponseti-method and BCCH-method. From all different treatment-steps possible "units" were designed. The units that were designed are: initial consult, clinic visit, consult physiotherapist, consult occupational therapist, OT-splint, consult orthotist, X-ray, Boots and Bars, AFO by orthotist, custom orthotic, shoes, surgery, cast applied during surgery, surgery second foot, surgery extra, anaesthesia extra 1-3, daycare surgery, overnight stay in hospital, gastrosoleus defunctioning using Botox, Botox, gait analysis and non-clubfoot related hospital encounter. Per unit there are more treatment "options" available. For example in the unit "clinic visit", there are 18 options, such as clinic visit, clinic visit with manipulation and casting using plaster of paris below knee, clinic visit with manipulation and casting using plaster of paris above knee, clinic visit with manipulation and casting using 3-M soft cast below knee. Within the unit "X-ray" there are 3 options such as unilateral X-ray of the foot, bilateral X-ray of the foot, X-ray of the pelvis. For a complete list of all units and options see Appendix 2.

More units were designed that are not part of the treatment, but do have their impact on the costs concerning the treatment and therefore have to be considered. These units are: number of persons traveling, days away form home, lost wages, air transportation, ground transport, mileage, accommodation and meals.

All these units, together with patient demographics ( patient ID, last name, first name, gender, hometown and distance to BCCH) and intervention type ( one of the 6 treatment-regimes that the patient fits in) formed the database, which was set up in the Microsoft Excel program.

Patient Data collection All patients that are eligible for this study were identified using the hospital data retrieval system. The patient's hospital medical records will be collected and chart review will be performed. Patient data will be entered into the database, using one line for every visit (either as an inpatient or as an outpatient) to the hospital.

Costing Data collection Direct costs A detailed breakdown of all "parts" constituting the units was performed Costing information on all these parts was then obtained using a great variety of sources, including the MSP- billing book, personal communication with a pharmacy- representative and interviews with nursing representatives, an expert in the financial department and experts in the decision support department. Appendix 3 gives a detailed description where and how all costing information was obtained.

General overhead costs The general overhead costs will be determined using information from the decision support services and from the Orthopaedic department.

Data analysis It is a cost-analysis between the different methods of orthopaedic treatment for clubfoot. Statistical analysis will be completed on all continuous variables. Statistical analysis will be completed using SAS Statistical Software (SAS Institute, Cary, NC).