Introducing new techniques
Surgical expertise is a relatively under-explored item in surgical trials. Often, results of surgical trials are reported without information on the participating surgeons expertise in a new treatment option [
1]. Critics used this argument against the utilization of randomized controlled trials (RCT) in surgery [
2]. When surgeons plan an RCT comparing a well established implant with a relatively low morbidity to a new, potential superior, implant; a surgeon has to weigh the additional benefits to possible morbidity the new implant may give. Using innovative implants possibly exposes a patient to risks due to the surgeon's inexperience introducing the new surgical technique, perhaps leading to an increase of complications or decreasing the functional result.
Through clinical trials, functional result as well as complications can be evaluated. Clinical trials however evaluate the outcome of the procedure as a whole and are therefore inadequate to determine which specific pitfalls are inherent in the operation itself. By determining these pitfalls within the operation, the surgeon can possibly anticipate them and thereby avoid them.
Moreover, random variation of surgical outcome is influenced both by number of cases included and the frequency with which the outcome occurs. In circumstances where the expected outcome is rare, outcome indicators will have only limited power to detect real differences in quality [
3]. A surgical technique with a low complication rate requires a high amount of surgical procedures with a long term follow-up for these complications to occur. This is particularly the case when evaluating the outcome of innovative prosthetic implants [
4‐
6]. However, when introducing a new innovative implant it is important to identify pitfalls and difficulties at an early stage, preferably during the first few cases, thereby minimising risk for subsequent patients in a planned RCT evaluating the new implant. Identifying pitfalls of a surgical technique during a learning curve therefore ideally requires a system which:
- is capable of analysing individual steps of a surgical procedure
- requires a small amount of procedures (small number of cases)
- does not require a long follow-up and provides immediate feedback
- is able to detect these pitfalls
- is reproducible
This calls for process instead of outcome measurement. Outcome measures are most relevant for the broader perspective since they reflect the inter-play of a wide variety of factors. With a narrow perspective, on individual learning curves, process measurements become relatively more useful. Process measurements are often only considered useful if they are assumed to correlate with clinical outcome [
3]. However, considering that errors within a process can have a synergistic effect it is important to focus on all errors not just those directly associated with a poor outcome [
7]. Errors can be categorised by active and latent errors. Active errors have an immediate effect on outcome, while latent errors are hidden within the system, until their synergistic effects will accumulate with resulting adverse events [
8,
9].
Process measurement can be performed by two methods: Implicit and explicit. Implicit methods require expert judgement, without predefined criteria. Explicit methods assess quality of care against predefined criteria or algorithms, thereby providing standardised comparative and reproducible data [
7]. In this study we aim to compare several surgeons and several procedures, necessitating an explicit reproducible measurement method. A previous pilot study performed at the Orthopaedic Research Centre Amsterdam by Veth and De Beer has shown an inter-observer reliability (expressed as IntraClass Correlation Coefficient) of 0.78 to 0.91 for anterolateral minimally invasive total hip arthroplasty, demonstrating it to be a reproducible tool to evaluate a perioperative process objectively.
Time-action analysis
Time-action analysis (TAA) is a tool to objectively determine the level of efficiency of individual steps of a surgical procedure [
10‐
13]. By analysing unedited video recordings of a surgical procedure the number and duration of the actions needed for a surgeon to achieve his goal and the efficiency of these actions is measured. In the past TAA has successfully been used to evaluate laparoscopic procedures and total shoulder arthroplasty procedures [
10‐
13]. Utilizing TAA a surgeon is able to recognise and anticipate specific pitfalls. It can also be used as a tool to evaluate the improvement of efficiency and the decrease of errors in time as a representation of the learning curve. By comparing the surgical technique of experienced surgeons with inexperienced surgeons, difficult steps which need further emphasis during the learning curve can be identified and errors possibly avoided. Furthermore it can provide feedback to manufacturers of surgical materials, consequently they can determine how improvements in surgical material can increase efficiency. Even though conducting a fully efficient procedure does not ensure good clinical outcome, improvements in surgical techniques is the most important way in which a surgeon can alter the outcome.
Femoral neck preserving hip arthroplasty
The Biodynamic cementless total hip prosthesis, introduced by Pipino in 1979, was designed with the aim to preserve maximum amount of bone stock for future revisions, to achieve physiological compression, tension and torsion forces and to minimise damage to vascular structures in the proximal femoral region [
14,
15]. The Biodynamic stem was replaced by the modified CFP prosthesis in 1996. The CFP prosthesis is made of titanium alloy with a hydroxyapatite porous coating, with longitudinal ribs to promote osseointegration. A seven year follow-up study of 353 CFP stem showed 99% good intergration, with only 2 cases of radiographically proven aseptic loosening [
16]. It has a built in anatomic anteversion and 117° and 126° CCD angles to closely resemble physiological anatomy. Clinical follow-up showed good functional recovery and DEXA analysis of 10 patients showed minimal periprosthetic bone loss [
14,
16,
17,
17]. The CFP stem is combined with a Trabeculae Oriented Pattern (TOP) cementless hemispheric cup. The TOP cup has a biequatorial dissociation with a medialcaudal recess to allow a wider range of motion and a cranial rim reaching over 180° to reduce the risk of dislocation [
14]. A clinical follow-up study of 301 TOP cups showed no detachement, migration, or osteolysis after 7 years [
16].
Currently the CFP stem has not been compared with conventional straight stems in an RCT, therefore additional benefits remain to be determined. Implantation of the CFP stem requires a major alteration of operating technique compared to conventional straight cementless stems and require specially designed instruments. Therefore a substantial learning curve is to be expected potentially compromising the validity of an RCT due to differential expertise based bias. Determining the minimum number of cases required before participating in an RCT is often arbitrary and for many complex procedures the learning curve has not reached a plateau after reaching the required number of procedures [
2]. Another potential for differential expertise bias is the influence of the number of years of clinical experience of participating surgeons [
2].
We aimed to evaluate the learning curve of experienced hip surgeons who will be participating in a future RCT evaluating the CFP stem. We hypothesized that using TAA could result in a clear understanding of a surgeon's learning curve and finally surgical expertise before embarking in an RCT comparing the CFP stem with a straight stem in total hip arthroplasty. By determining a surgeon's learning curve prior to initiating an RCT we aim to determine and possibly reduce the influence of differential expertise bias.