The International Documentation and Evaluation System IDES: a single center observational case series for development of an ankle prosthesis documentation questionnaire and study of its feasibility and face validity

The International Documentation and Evaluation System was first introduced in 1993 by Sir Dennis Paterson [1]. Its precursors, however, were already used by Prof. Maurice E. Müller since 1984 for documentation of total hip arthroplasties (THA). Several years later a module for total knee arthroplasties was developed. Thousands of THA and TKA were recorded by this means including primary interventions, revision surgeries and scientific followups. The IDES data sets are still stored at the Institute for Evaluative Research in Orthopedic Surgery, formerly called the Department of Education and Documentation (MEM-CED) of the Maurice E. Müller foundation in Bern, Switzerland [2].

Joint arthroplasty has meanwhile been expanded to smaller joints like shoulder, elbow and ankle. Early total ankle arthroplasty designs (TAA) of the 70's were of constrained nature and had a multitude of problems like poor instrumentation, consequent implant malpositioning, lack of soft tissue balance and insufficient and negatively influencing cement fixation as well. Modern three-component designs with porous-coating for uncemented fixation show good-to excellent mid- and even long-term results and thus have led to increasing use in foot and ankle practice [3, 4].

Meanwhile, it is justified to consider TAA a non-experimental surgical intervention with promising and long-lasting positive results. However, no prosthesis can be evaluated without a followup time of at least five years [3]. In order to provide the community of TAA users with a standardized tool for proper and uniform documentation and reporting of interventions and outcomes, we have developed a new set of questionnaires, which conform to the principles of IDES. The current article represents a detailed report of the variables and parameters that make up the new IDES ankle module. A series of 74 primary Hintegra^© ankle prosthesis, 28 revisions and 92 followups were documented for studying the feasibility of the new system.

The IDES hip and knee questionnaires were used as templates for developing the ankle module. Hence, an A-form for primary interventions (figure 1), a B-form for revisions (figure 2) and a C-form for followup (figure 3) examinations were implemented. Each form was divided into so-called subforms, for better structuring the content and in order to allow for real-time documentation at source in a team effort. All IDES forms are usually available in English, German, French, Spanish and Italian [2]. The English and German versions of the IDES ankle series are available under http://​www.​memdoc.​org, the translations into French, Spanish and Italian are still in progress.

The A-form is composed of the following subforms:

The B-form has an additional subform for pre-revision radiology

The C-form is composed of different subforms:

A surgeon-administered clinical rating system is an important part of the IDES forms. While the Harris Hip Score and the Knee Society Knee Score and Function Score are integrated into Clinical Evaluation subforms of the hip and knee modules, the AOFAS ankle score was chosen for the ankle module [5]. Its validity and responsiveness were assessed by SooHoon [6, 7]. He found increased responsiveness compared to the SF-36 as general quality of life instrument and a moderate correlation in patients with ankle-hindfoot disorders. In addition, the users can optionally choose to use patient based disease-specific and general quality of life instruments such as the Foot Function Index (FFI) [8, 9]. In order to allow an ubiquitary use of the IDES forms for academic centers, smaller hospitals and even private practices, there is the possibility to choose between a minimal dataset (implant registry), a scientific dataset, and optional add-on subforms. Moreover, the forms are available as scanable OMR (optical mark reader) forms and in an online version via the documentation portal http://​www.​memdoc.​org[10].

The primary subforms deal with the following topics:

Admission: date of admission, height, weight, diagnosis, previous surgeries, detailed clinical status of the operated ankle joint, status of the opposite ankle joint.

Admission add-on: subdiagnosis, status of knee joints, comorbidities.

Clinical Evaluation: ASA status, pain assessment, activity levels, mobility assessment, walking, motion, alignment (AOFAS score).

Clinical Evaluation add-on: walking aids, range of motion, pain and other medication, scars and skin status.

Surgery: date of operation, type of prosthesis, fixation, intraoperative complications and their therapies, duration of procedure, additional procedures, intraoperative motion.

Surgery add-on: qualification of surgeon, bone status, narcosis, and blood loss.

Radiology: angles and radiolucent lines.

Discharge: date of discharge, local and systemic complications, therapy of complications.

The revision subforms are of similar structure and the additional subform pre-revision radiology deals with angles, radiolucent lines, and radiographic abnormalities like cysts and component subsidence.

The followup forms allow a very brief followup summary in their minimal version. Thereby only the first subform "Followup" is completed. It mainly deals with followup date, - interval, a radiographic summary, and patients' satisfaction. It is followed by other subforms like:

Followup add-on: patient height/weight, detailed status of operated foot, status of opposite ankle joint, status of knees, systemic diseases, social and work situation.

Clinical Evaluation: ASA status, pain assessment, activity levels, mobility assessment, walking, motion, alignment (AOFAS score).

Clinical evaluation add-on: gait, walking and orthopaedic aids, pain and additional medication for operated joint.

Complications: systemic and local postoperative complications and their consequences.

Radiology: angles and radiolucent lines, cysts, wear, component subsidence, osteophytes.

The current article presents results of a retro-/prospective single surgeon series of 74 primary and 28 revision TAA interventions as well as 92 followups. Its purpose was the content development of the new IDES ankle module and a demonstration of the possibilities of data collection and reporting. The number of total ankle replacements has been increasing in the last years but compared to hip or knee replacements the implantation rates still remain much lower. Most publications present short- and medium-term results. Long-term outcomes are still very rarely reported.

Traditional studies and the resulting articles are not usable as early warning systems for poorly performing total ankle replacements, because of the long time periods needed for collecting adequate numbers of patients, conducting followup examinations and publishing the outcomes [14]. A well known problem is the lack of motivation for reporting poor results which is referred to as publication bias.

For solving these problems we developed the first international documentation and evaluation system for total ankle replacements. Following the well approved principles of the IDES in presentation and structure of the primary and secondary parameters, the system is compatible with the existing database of knee and hip replacements. Its implementation on the MEMdoc documentation portal http://​www.​memdoc.​org of the Institute for Evaluative Research in Orthopaedic Surgery at the University of Bern, Switzerland, allows online and offline data entry. All information is sent in an encrypted fashion and in those cases where national filter modules are in place, the patient and user related information is stored in the national database and does not even leave the country, i.e. only anonymized clinical datasets reach the central database [10]. Nevertheless, informed written consent by the patient is always recommended for the documentation.

Thanks to numerous user tools every participating surgeon can export his raw data or monitor his proper outcomes and compare them to the cumulated data pool with online statistics. The online statistics do, however, not allow comparisons with other surgeons or access to their raw data [10]. Use of IDES is free of charge since each user contributes his cases to the data pool owned by the University institute. Thanks to the exporting function, the users are in full control and ownership of all the cases they themselves stored in the database. User groups or specialist societies that want to make use of IDES ankle but also keep possession of the pooled data of their group will be charged based on participant number and case load.

The IDES-forms provide a structured and standardized data collection that is feasible in a research orientated but also purely clinical setting; this because of the modularity how data can be recorded. The consistent use of the system assures a stringent internal quality assurance, and more interesting, an external quality assurance by means of comparisons and benchmarking with other users feeding the data pool with the exact same variables and outcomes.

As opposed to the frequently practised retrospective followup studies with cumbersome and error prone work-up of patient histories and radiographs, the IDES system allows overviews of primary and followup records, data exports, statistical frequency analyses and viewing of radiographs 24/7 from any computer with internet connection. Since primary interventions, postoperative complications and revisions are clearly assignable to the respective patient, implant related problems in design, material, fabrication, patient selection or surgical technique can be evaluated.

In a time where the patients' views about the outcome of surgery have an increasing weight, the physician based assessment with the AOFAS ankle score can be complemented with validated patient assessment instruments such as the FFI. That way, both, the surgeon's and the patient's perspectives about the pre- to postoperative improvement can be described and compared as composite score results (AOFAS) or visual analogue scale scores (FFI).