Outcome
Primary outcome parameters
• Nett Goal Oriented Action Time = time spend on Goal Oriented Actions (GOAs) – delay
• Delay = time spend on repetitions, additional actions and waiting
• Efficiency = percentage of nett Goal Oriented Action Time during each procedure
• Level of difficulty = Nett Goal Oriented Action Time of a specific GOA + time spend on repeating that GOA during subsequent GOAs
Secondary outcome parameters
Functional outome
As part of current clinical protocol, functional outcome will be measured using the Dutch version of the Hip disability and Osteoarthritis Outcome Score (HOOS), validated by De Groot et al [18]. Functional score will be recorded pre-operatively and at 6 weeks, 3 months and one year follow-up, as part of standard follow-up protocol [18]. Follow-up protocol is not affected by this study.
Position of the prosthesis
position of the prosthesis will be measured on AP-pelvis x-rays by two independend assessors blinded for the case number and level of experience.
Complication rate
complications: peri-operative and post-operative will be recorded by independent nurse practitioners blinded for the case number.
Participating centres
The study will be a cooperation between the Academic Medical Centre Amsterdam, the Onze Lieve Vrouwe Gasthuis (OLVG) Amsterdam, The Isala Hospital Zwolle and McMaster University Hamilton, Canada. Surgical procedures will be performed by several surgeons at the OLVG Hospital in Amsterdam and the Isala Hospital in Zwolle. The learning of each individual surgeon will be analysed. Analysis will be performed at the Academic Medical Centre in Amsterdam by an independent assessment committee.
Variables
Independent variable
Level of experience
We aim to compare 4 surgeons with different levels of experience in implanting non-cemented stems. Experience will be defined in years post board registration and number of arthroplasties performed per year.
Dependent variables
Four types of actions are analysed:
1. Goal Oriented Actions (GOA)
2. Repetitions
3. Additional Actions (AA)
4. waiting
Controlled variables
• Interval between operations
For valid comparison of the learning curve, time between procedures cannot exceed more than 1 month.
• Patient population
Inclusion criteria of patients
Adult patients with disabling degenerative arthritis of the hip or (avascular) head necrosis.
Maximum age is determined by the current clinical protocol of each participating hospital.
Exclusion criteria of patients
Patients not eligible for CFP arthroplasty in this study are:
Patients with a BMI of more than 40
Patients with skeletal immaturity
Patients with a life expectancy of less than 3 years
Patients with altered anatomy resulting in impossibility for the CFP procedure, according to the surgeon e.g.:
- hip dysplasia with high dislocation
- post traumatic severe anatomy change
Patients with extremity amputation
Patients with an active malignant disease or current cytostatic treatment
• Surgical technique
Predefined in the taxonomy
Sample size
Since there is currently no data on the learning curve of the CFP stem, sample size is estimated by reviewing the learning curve of other implants or techniques in current literature. Previous literature on learning curves in total hip and total knee arthroplasty determine the learning curve on the amount of complications, clinical outcome, implant position or mean operative time [6, 19].
Archibeck et al. analysed the first experience of 159 surgeons with the 2-incision minimally invasive THA. He found a significant reduction in the mean operative time in the first ten cases. The amount of complications did not show any reduction as a function of the case number [19].
Flamme et al. studied the learning curve in total hip arthroplasty of three surgeons with different levels of experience operating on a total of 168 patients. They found no association between functional outcome as determined by the Merle d'Aubigné score and case number. However considering intraoperative complication rate, all three surgeons ended their learning curve after a maximum of 20 cases [6]. Based on these studies, we estimate the efficiency to reach a plateau between 10 and 20 cases. Therefore the first 20 cases of each surgeon will be analysed.
A learning curve can however differ between individual surgeons. It is therefore important to study multiple surgeons with different levels of experience and to define a stopping rule. The stopping rule defines whether the estimated number of 20 cases is sufficient to study an individuals learning curve and terminate the task analysis or whether additional cases are needed. The criterion for terminating the task analysis was previously determined through the probability of failure (P) multiplied by the cost of failure (C) to an acceptable level – the P × C rule [20]. The role of the P × C rule is to save the analyst time in analysing tasks where the error variance would be inconsequential and to guide more exploration where the error variance would be intolerable [20]. The cost of failure is inherent to the clinical consequence of a peri-operative complication which requires clinical interpretation. We defined three major peri-operative complications during total hip arthroplasty which determined C:
1. massive bleeding
2. fracture (femoral or acetabular)
3. evident neurological damage
This resulted in the following definition of the stopping rule: if a surgeon encounters a major complication (C) within the last five consecutive surgical procedures (P), the stopping rule is considered unacceptable and an additional five surgical procedures have to be analysed.
To facilitate comparison of different levels of expertise we suggest one surgeon less than five years board certification, two surgeons 5 to 15 years and 1 surgeons more than 15 years board certification. This justifies our total sample of 4 surgeons each performing 20 cases, resulting in a total of between 80 surgical interventions to be analysed.
Data acquisition
With the use of three cameras and a microphone, video-recordings are made of abovementioned procedures. One wide-angle (or fish eye) camera is positioned proximally 1,5 meters above the operating table, to record an overview-image of the operating theatre. A second camera is situated on the head of the surgeon to record a clear view of the actions performed by the surgeon. An additional portable camcorder is used to film any actions that are missed by the previously mentioned cameras. Sound is recorded with use of the camcorder. The total number of persons required to be present in the operating room during the operation is limited to only one.
A Quad unit combines four signals, 3 video and 1 sound, into one signal. This way, all images can be analysed simultaneously on one laptop on a split-screen (see Figure 1 and see Additional file 1: movie sample TAA).
Equipment
Theatre setup
• 3 camera's
◦ One camcorder camera on a stand
◦ One camera to be placed on the head of the surgeon
◦ One fish eye camera to be placed above the operating theatre
• Quad unit
• AV-converter
• Software for video analysis and image conversion
• Laptop with digital video portal.
The Taxonomy
Time-action analysis is a quantitative method which can be used to objectively analyse the course of a surgical procedure. The analysis is done by scoring strictly defined actions in time. This way a procedure can be observed in detail and knowledge can be obtained about the difficulty and efficiency of a procedure and the comparison of two procedures can be performed objectively.
In performing a time-action analysis a taxonomy is used; a list of predefined Goal-Oriented Actions (GOA) which; taken together, describe the total procedure. The concept of time-action analysis described by Minekus [12] served as a template for the design of this taxonomy and has been modified for the CFP stem surgical technique. A GOA is defined as an action which contributes directly to the progress of the procedure [12]. The GOA's can then be divided in a number of Separate Actions (SA). For example, in the GOA skin incision, the SA's are: skin incision and positioning retractors. By formulating the GOA's as accurate as possible, almost every recorded action can be defined. This way of grouping separate actions into GOA's was chosen, since it would not have been feasible or efficient to separately score every action seen in a 90 minute film. Eventually the operative procedure is divided in Goal Oriented Phases (GOP);
1- Incision phase,
2- Prosthesis phase, subdivided in
a. femoral phase
b. acetabulum phase
c. stem phase
3- Closure phase.
These GOP's are divided in GOA's and at last, the GOA's are subdivided in SA's. All essential actions of the procedure are defined, e.g. sawing, cutting, suction, coagulating, placing of retractors. Extra sections are added for 'waiting' and 'additional actions' to be able to eventually account for every second of film.
Apart from formulating this list of pre-defined steps it is very important to come to good general agreements on the methods of scoring so that the inter-observer variation is limited to a minimum (see Table 1 in Additional file 2).
Construction of the taxonomy
Using a method similar to Sarker et al. a template taxonomy is constructed using currently available literature on CFP stem surgical techniques [21, 21]. The template taxonomy is discussed with participating surgeons and adjusted to represent individual surgical technique. This results in the final taxonomy, which is defined prior to analysis. During the course of the analysis the structure of the taxonomy is fixed.
Task analysis
After scoring the video, a task analysis will be performed using the predefined taxonomy. This results in an hierarchical (studying procedural sequences) task analysis.
The duration and number of all actions are categorised in (Figure 2):
1. Goal Oriented Actions (GOA's)
2. Repetitions
3. Additional actions (AA's)
4. Waiting
GOA's are actions which contribute directly to the advancement of the procedure. Furthermore they are performed in consecutive order during each fase corresponding with the pre-defined taxonomy.
A GOA inadequately executed may require a Repetitions. Repetitions are Separate Actions (SA's), which are repeated due to insufficient progress of the procedure. An example of a Repetition is inadequate exposure, which causes insufficient progress and necessitates extending the incision, or repositioning the retractors.
A surgeon may encounter difficulties requiring actions not defined in the taxonomy. These actions are defined as AA's. This may be either due to abnormal anatomy, unexpected pathology, instrument failure or an inadequately executed goal-oriented action. Since we merely describe the External Mode of Malfunction, instead of the mechanisms or causes of malfunction we do not subcategorise additional actions by their cause. As Rassmussen put it: "For performance in unfamiliar situations requiring proper problem solving, a cognitive task analysis, if at all possible, requires interviews and discussions with the performer [22]." This results in a subjective analysis of an opinion. To obtain objective data additional actions will be categorised irrespective of their cause.
Waiting is the amount of time between two actions, with a minimum of 5 seconds.
While the amount and duration of GOA's is an expression of the level progress during the operation, delay is defined by the amount of time spend on Reptitions, AA's and waiting. The level of efficiency is an expression of the level of progress and delay.
Outcome measurements
If the outcome is unacceptable, despite having a perfectly efficient procedure, the procedure has still failed to reach its goal. In task analysis it is therefore important to have an objective method to verify that the goal of the procedure has been met. Goal of the operation is determined by functional outcome as perceived by the patient and position of the prosthesis.
Functional outcome
To measure postoperative functional outcome the validated Dutch version of the Hip disability and Osteoarthritis Outcome Score (HOOS) taken pre-operative, within one week before the operation and postoperative at 6 weeks and one year follow-up [18]. Questionnaires will be collected by local surgical staff and send to the trial committee.
Position of the prosthesis
AP pelvis roentgenograms are taken pre-operatively, postoperatively and during follow-up visits after 6 weeks and one year follow-up as part of the standard care.
Cup inclination
The radiological cup inclination as described by Murray [23] defined as the angle between the longitudinal axis and the acetabular axis when this is projected on to the coronal plane. It is measured by measuring the angle between the teardrop line and the line which divides the cup inner ellipse in halve. If the teardrop line is not clearly visible, alternatively the line between the two SI joint or the lower border of the ramus inferior can be used.
Femoral shaft alignment is measured on AP pelvis roentgenogram.
Leg length discrepancy
pre- and postoperative leg length discrepancy is determined on a standing weight-bearing AP pelvis roentgenogram after calibration. A horizontal line is drawn through the inferior aspect of the acetabular teardrop. Two other lines parallel to the teardrop line are drawn through the centre of the lesser trochanter of each femur. Leg length discrepancy is defined as the difference between distances from the teardrop line to the lines through the lesser trochanters of each femur. All radiographs will be analyzed by two independent surgeons, blinded to the case sequence and surgeon's expertise.
Complications
Postoperative complications during the follow-up will be recorded by an independent nurse practitioner.
Assessor
Task analysis will be performed by an independent observer.
Data analysis
A regression analysis will be performed to reveal any significant increase of efficiency or decrease of the errors rate as a function of the case number.
Patient safety
Interventions
The TAASTIC trial is strictly an observational study, therefore the study must not interfere with clinical decision making. Allocation of the CFP stem to a patient is not influenced by this trial. No additional interventions will be performed to facilitate this trial.
Privacy
Video recordings will only be made after written informed consent by the patient. The identity of the patients is concealed in all recordings.
Ethical approval
Since the TAASTIC trial is an observational study, a formal ethical approval was waived for this study by the OLVG Medical Ethics Committee. The OLVG Medical Ethics Committee declared to have no objections to the TAASTIC trial.
Operating theatre protocol
Cameras must not compromise sterility in the operating theatre. The minimum additional person to be present during surgery is restricted to only one. Local theatre protocols apply.
Trial management
Organisation
Coordination
Responsible for coordination of the study is the Surgical Learning Curve and Expertise committee consisting of the following members:
Jakob van Oldenrijk, Academic Medical Centre, Amsterdam
Matthias Schafroth, Academic Medical Centre, Amsterdam
Rudolf Poolman, Onze Lieve Vrouwe Gasthuis (Principal Investigator), Amsterdam
Mohit Bhandari, McMaster University, Hamilton, Canada
Operating surgeons
During the course of the CFP TAASTIC trial The Surgical Learning curve and Expertise Working Group consist of the following surgeons:
R.W. Poolman, Onze Lieve Vrouwe Gasthuis, Amsterdam
W.C. Runne, Onze Lieve Vrouwe Gasthuis. Amsterdam
C.C.P.M. Verheyen, Isala Kliniek Zwolle
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C.
van Egmond, Isala Kliniek Zwolle