Abstract
Background:
Hip arthroscopy can be performed with the patient in the lateral or supine position, but it remains technically demanding. We aimed to objectively quantify and compare learning curves between two groups of orthopaedic trainees randomized to learn simulated hip arthroscopy with the patient in either a lateral or a supine position. We also compared learning curves between senior and junior trainees.
Methods:
A hip arthroscopy simulator with anterolateral and anterior portals, a 70° arthroscope, and fixed distraction was used. Rotation of the simulator by 90° enabled arthroscopy with the patient in a supine or lateral position. Twenty orthopaedic trainees with minimal hip arthroscopy experience were randomized into lateral and supine position groups, and were asked to perform a diagnostic hip arthroscopy of the central compartment on twelve occasions. Each episode involved a change in the portal and repetition of the diagnostic round. A validated motion analysis system objectively measured surgical performance by recording time taken, total path-length of the hands, and number of hand movements.
Results:
Both groups demonstrated learning with objective improvement in all parameters (p < 0.001). Initially, the lateral group was significantly slower and more variable in their performance during the second diagnostic round, after portal exchange (p = 0.006). However, they achieved parity with the supine group in all parameters by nine episodes. During the first three episodes, the junior trainees performed significantly worse for the first diagnostic round (p = 0.005) but not for the second diagnostic round (p = 0.200), and they rapidly achieved parity with the senior trainees, performing at a similar level by the end of the study period.
Conclusions:
Trainees with minimal experience with hip arthroscopy progressively learn and objectively improve their performance when using a hip simulator. Orientation after portal exchange is difficult for all trainees but particularly for those learning with a simulated patient lateral position. Trainees are likely to benefit from simulator training to learn orientation and basic competence prior to performing hip arthroscopy on patients.
Level of Evidence:
Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.
Current surgical trainees face a learning environment that differs from that of previous generations of surgeons. Reductions in working hours and the drive for a specialist-led service limit opportunities to gain operative experience1,2. Modern surgical practice is subject to greater peer and public scrutiny3, and patient-reported outcome measures may be used to determine resource allocation between hospitals and within departments. Surgical training may suffer in the face of short-term cost savings.
These developments have stimulated the introduction of more structured training with an emphasis on skill acquisition4-6 and training that takes place outside the operating room. The use of surgical simulation is well established7-10. Numerous studies across specialties support the role of laboratory and virtual reality simulators for open and minimal access surgical procedures8,9,11-15. In orthopaedics, arthroscopy is particularly amenable to simulation16. Studies using knee14,17 and shoulder18,19 arthroscopy simulators have demonstrated validity and objective improvement in performance with training. Recent studies have demonstrated transfer validity of simulator-acquired skills to improved performance in the operating room, answering early criticisms regarding the clinical relevance of simulation17,20,21. Simulation is particularly advocated at the beginning of the learning curve, prior to operating on patients9.
Although not a new technique, hip arthroscopy has undergone a surge in popularity because of technical improvements in instrumentation and improved understanding of mechanisms of articular cartilage degeneration22. Achieving competence in hip arthroscopy as a trainee is difficult. In addition to a lack of familiarity with a 70° arthroscope, orientation is challenging because of the joint morphology and the need to change portals to gain satisfactory access to all areas. Limited limb distraction predisposes to iatrogenic articular cartilage injury. Portal loss (failure to maintain an open passage from the skin to the joint with use of an instrument) is difficult to recover; thus, a sequence of instrument exchange performed under direct vision is essential. Finally, the risk of neurapraxia limits the safe duration of limb traction. Hip arthroscopy is recognized as technically demanding, with additional skills required beyond those learned from arthroscopy of other joints, which is usually being performed by subspecialist surgeons, who may be less prepared to allow trainees to perform the surgery. Hip arthroscopy is performed with the patient in the lateral or supine position, with advanced techniques possible with either position22,23. The supine position allows arthroscopy on a standard fracture table, and dynamic impingement testing and fluoroscopic visualization of the femoral head-neck junction is straightforward. The lateral position is routine for open hip surgery and may enable easier access to the joint, particularly in obese patients, although the surgical setup is more complicated24. As training in hip arthroscopy is in its infancy, any information about teaching, learning, and competency in relation to simulation and these two patient positions will improve training efficiency.
The aim of this study was to objectively assess and quantify differences in learning curve patterns in two groups of orthopaedic trainees randomized to learn simulated hip arthroscopy with the patient in either the lateral or the supine position. We hypothesized that both groups would demonstrate improvements in performance over the course of training, that the lateral group would find the task harder to learn than the supine group, and that senior trainees with greater general experience with arthroscopy in other joints would find the task easier than more junior trainees, regardless of which group they were in.
Subjects
Between September 2010 and February 2011, orthopaedic trainees were recruited from a university hospital. To be eligible for inclusion, each trainee had to commit to four training sessions, each occurring one week apart. Trainees with fellowship training in arthroscopic surgery were excluded. A questionnaire concerning the year of training and logbook experience with arthroscopic surgery of the hip (number of procedures seen or performed as well as setup position), arthroscopic surgery of the knee and shoulder (number of procedures performed), and hip replacement surgery (number of total or hemiarthroplasties performed) in the supine and lateral positions was completed. Trainees in the first two years of training were considered “junior,” and those in year three or above were considered “senior.” Following stratification by seniority, the trainees were randomized, with use of sealed envelopes, into supine and lateral position groups.
Simulator Training
A hip arthroscopy benchtop simulator (Sawbones Europe, Malmö, Sweden) (Fig. 1) was set up in our dedicated skills laboratory, which has institutional review board approval for educational simulation studies. The modular outer skin, muscle, and capsular layers of the simulator were removed so that four points could be marked on the labrum with an indelible marker pen corresponding to the three, one, twelve, and nine o’clock positions. In addition to these points, three more landmarks were identified: two acetabular cartilage lesions (detached chondral flap lesions), already industrially present as pathological lesions on the model, located at two and twelve o’clock, and the ligamentum teres. The modular layers were then replaced. A fixed distraction of 1.0 cm was applied23, which remained in place throughout the study period. Optimum anterolateral and anterior portals were created. The anterolateral portal was placed 1 cm anterior to the proximal tip of the greater trochanter. The anterior portal was located at the intersection of a sagittal line drawn from 2 cm lateral to the anterior superior iliac spine and a transverse line level with the anterolateral portal. To ensure consistency of these portals throughout the experiment, they were reinforced by glued rubber rings to prevent tearing. Standard hip arthroscopy equipment (Access set; Smith & Nephew Endoscopy, Huntingdon, United Kingdom) was used, with a standard 70° arthroscope, arthroscopic camera, and display system (Dyonics; Smith & Nephew Endoscopy). The simulator was turned through 90° and clamped in place to simulate the lateral and supine positions.
Prior to commencing the first task on the simulator, each trainee viewed a standardized instructional PowerPoint presentation produced specifically for the study. This presentation included a video demonstration of the task incorporating a recording taken from the arthroscopic monitor together with a synchronized video of the operating surgeon’s hands and the simulator. It did not provide any specific “tips” on performing the task. Diagnostic rounds of the central compartment of the hip were performed from the anterolateral and anterior portals. The task commenced with the camera in the anterolateral portal and an arthroscopic probe within the joint via the anterior portal. Trainees were requested to probe labral points one through four, followed by the acetabular cartilage lesions, and finally the ligamentum teres. They then swapped portals, so that the camera was in the anterior portal and the probe was in the anterolateral portal, and identified the same landmarks in the same order. Probing of the ligamentum teres for the second time completed the task (Fig. 2 and Video 1 [see Appendix]). Each surgeon completed three episodes at each attendance over the four-week period (a total of twelve training episodes). No additional practice was permitted.
Motion Analysis
A validated customized motion tracking system (PATRIOT; Polhemus, Colchester, Vermont) was used to assess performance objectively. This tracking technology has been used previously, and its feasibility, reliability, and validity have been demonstrated9,11,17-19. The setup and analysis were identical to those in previous studies17-19. The outcome variables were the total path length of the subject’s hands (in centimeters), total number of hand movements, and time taken to complete the task (in seconds).
The arthroscopic video footage for each task was recorded and was time-synchronized to the motion analysis data. This enabled time-point analysis and segmentation into the three phases of the task (diagnostic round one, portal exchange, and diagnostic round two).
Each training episode was supervised. Two secondary outcomes were recorded in a prospective manner by the supervisor: (1) failure to complete the task, defined by loss of either portal, as the recording of data for that episode stopped as soon as portal loss was apparent, and (2) iatrogenic articular cartilage damage, defined as a scratch or creation of a flap tear of the simulator’s artificial cartilage layer.
Statistical Analysis
The primary outcome measure was the difference in the performances of the two groups as assessed with the motion analysis variables. Parameters during the first and last three episodes in each group were compared to identify differences in performance between the two groups at baseline and after training. A power analysis was performed to estimate the sample size required to detect a difference between the two groups over the initial learning curve (first three episodes). On the basis of trial runs by the authors, the total task time was estimated to be six minutes at the beginning of the learning curve. On the basis of a previous study19, the standard deviation during the first three episodes for a simulated arthroscopic task was estimated to be 40% of the task time, giving an estimated standard deviation of 144 seconds. A difference of two minutes (25%) was considered clinically relevant. Therefore, the standardized difference was calculated as 0.833 (120 of 144). To achieve 90% power25 (alpha = 0.05), the estimated sample size for detecting this difference was just under sixty episodes. Given three episodes per trainee in the initial learning curve, this equated to a total sample size of twenty trainees with ten in each group.
The Kolmogorov-Smirnov test indicated that the data distribution was non-Gaussian; therefore, nonparametric tests were used and medians and interquartile ranges are presented. Associations between the individual motion parameters were assessed with use of the Spearman rank correlation. The Mann-Whitney U test was used to compare each parameter during the first and last three attempts to identify any differences in performance between the two groups at baseline and after training. The paired Wilcoxon rank test was utilized to compare parameters within groups.
Statistically, failures were assigned a “failure score,” derived by addition of the worst score plus one standard deviation of the entire data set. This method provided continuous data for the failures and allowed their inclusion in the analyses. A p value of <0.05 was deemed to be significant.
Source of Funding
Funding support was received from the National Institute for Health Research (NIHR) Biomedical Research Unit and NHS Education South Central (NESC).
Cohort Demographics
Twenty orthopaedic trainees were recruited, stratified by seniority, and randomized into lateral and supine patient-position groups. The two groups were well matched (Table I). Only two trainees had performed a hip arthroscopy previously; one had performed one procedure and the other, two. Fourteen trainees had assisted with a procedure, with the individual maximum number of cases being fourteen. Of these trainees, six were in the lateral group (of whom four had experience with the lateral position and two, with the supine position) and eight were in the supine group (of whom two had experience with the lateral position and six, with the supine position).
Motion Analysis: Association of Between Parameters
All three parameters were strongly related statistically. The association between the total path length and the number of hand movements was very good26 (r = 0.881; 95% confidence interval [CI], 0.858 to 0.900; p < 0.0001). There was a good association between the time taken and the total path length (r = 0.783; 95% CI, 0.744 to 0.816; p < 0.0001) and between the time taken and the number of hand movements (r = 0.633; 95% CI, 0.574 to 0.686; p < 0.0001).
Analysis of Learning Curves Within Supine and Lateral Groups
In the supine group, the median time taken for completion of the entire task improved from 419 seconds per episode (interquartile range, 292 to 541) to 176 seconds (interquartile range, 157 to 228) (p < 0.0001). In the lateral group, the median time taken improved from 519 seconds (interquartile range, 374 to 892) to 188 seconds (interquartile range, 157 to 214) (p < 0.0001). The learning curve for both groups reached a plateau after nine episodes, with tight interquartile ranges (Fig. 3).
On the basis of the segmented data for each phase of the task, the trainees demonstrated substantial improvement in all three parameters during each phase (p < 0.005 for each parameter and phase; Tables II, III, and IV).
Comparison of Learning Curves Between Supine and Lateral Groups
The total task time did not differ significantly between the groups at either the beginning (p = 0.080) or the end of the study period (p = 0.739). However, the learning curves showed initial greater variability in performance in the lateral group (Fig. 3). The explanation for this is apparent from the segmented data for diagnostic rounds one and two (Table II). In the early episodes, the supine and lateral groups performed at a similar level in diagnostic round one, but the lateral group performed less well during diagnostic round two (Figs. 4, 5, and 6). While this difference was significant for the first three episodes in the time analysis (Table II, Fig. 4), there was a significant difference in the other parameters only over the first episode, with a median of 140 movements (interquartile range, fifty-three to 323) in the lateral group compared with fifty-one (interquartile range, twelve to 101) in the supine group (p = 0.011) and a median total path length of 2043 cm (interquartile range, 594 to 3765) in the lateral group compared with 566 cm (interquartile range, 0 to 959) in the supine group (p = 0.018). It was not until episode nine that the lateral group achieved parity, in terms of median and variability, with the supine group. By the end of the study period, the lateral group was significantly superior in terms of the movement parameters, but there was no difference in time (Tables II, III, and IV).
Task Failures and Iatrogenic Damage
Three failures occurred in the supine group (all different individuals), and seven occurred in the lateral group (five individuals). Eight of these failures occurred within the first four episodes, and there were no failures after episode seven. The failures in the supine group all occurred during portal exchange. Of the seven failures in the lateral group, two occurred during portal exchange and five occurred during diagnostic round two. There were six instances of iatrogenic articular cartilage damage in the supine group and seven in the lateral group.
Association of Performance with Previous Arthroscopic Surgical Experience
To assess the extent to which previous experience affected learning curve patterns and performance, the trainees were stratified by year of training. Twelve trainees were in year one or two (juniors), and eight were in year three or above (seniors). The proportions randomized to the lateral and supine groups were identical in these seniority groups (50%). The median year of training was one (interquartile range, one to two) for the juniors and 3.5 (interquartile range, three to 5.5) for the seniors (p = 0.0003). The juniors had performed a median of thirty knee and shoulder arthroscopies (interquartile range, thirteen to fifty-seven) and the seniors, 130 (interquartile range, seventy-eight to 202) (p = 0.0006). The juniors had participated in a median of one hip arthroscopy (interquartile range, zero to seven) and the seniors, 3.5 (interquartile range, 1.5 to 8.5) (p = 0.395).
Over the first three episodes, the seniors were superior in diagnostic round one with respect to all three parameters. They were quicker (102 versus 136 seconds, p = 0.0047), required fewer hand movements (fifty-three versus sixty-three, p = 0.125), and traveled less distance with their hands (752 versus 862 cm, p = 0.043). In diagnostic round two, the seniors remained marginally superior in all parameters, but the differences in time (143 versus 174 seconds, p = 0.200), movements (eighty-five versus ninety-seven, p = 0.195), and distance (1284 versus 1316 cm, p = 0.257) did not reach significance. During the last three episodes, there were no significant differences between the juniors and seniors with respect to any of the parameters (p values ranging from 0.170 to 0.769), except for distance traveled in diagnostic round one, during which the juniors were superior (467 versus 532 cm, p = 0.036).
The concept of the learning curve for surgical procedures is well described27. Learning curves for simulated and live surgical procedures have been demonstrated with use of various assessment methods17,28-30. Because surgeons with greater technical ability and experience perform tasks with greater efficiency and economy of movement, motion analysis is a sensitive, objective assessment tool and has been validated to differentiate surgeons of differing abilities11. Our study had three aims. First, we sought to objectively establish whether orthopaedic trainees learning a standardized task on a hip arthroscopy simulator would demonstrate learning curve patterns similar to those observed in knee and shoulder arthroscopy simulation studies16-19. All trainees demonstrated improvement, but performance plateaued after only nine episodes, with narrow interquartile ranges. To our knowledge, this is the first study to objectively demonstrate a learning curve for an arthroscopic hip procedure in a simulated environment. Our second aim was to determine whether there were differences in learning curve patterns among trainees matched with regard to general orthopaedic training and arthroscopic surgical experience, randomized to perform an identical task with either the lateral or the supine patient position. Our intention was not to demonstrate whether one position was better than the other, but merely to establish whether trainees learned more easily and effectively with either patient position. We observed a difference during the second diagnostic round, after portal exchange, with the lateral group initially having a worse and more variable level of performance. Our final aim was to determine whether senior trainees with more general surgical experience, and in particular more arthroscopic surgical experience, were objectively superior in performance to junior trainees. Initially, the senior trainees were marginally superior; however, the junior trainees achieved parity by nine episodes.
The initial performances of the lateral and supine groups in the first diagnostic round were similar. The learning curves for time taken to exchange portals were similar, as was the failure rate during portal exchange, suggesting that this skill is one where all trainees would benefit from simulator training. Both groups performed less well during the second diagnostic round, but these differences were greater in the lateral group, who also showed more variability. Failures tended to occur in the lateral group during the second diagnostic round. These results suggest that, early in the learning curve, portal exchange led to difficulties in the second diagnostic round, particularly in the lateral group. We suggest that this represents disorientation, leading to objective differences in the parameters and a higher rate of portal loss. After nine episodes, the lateral group performed equally, suggesting that they had caught up in this aspect of the task. Whether the statistical differences in individual motion parameters of time, number of hand movements, and total path length are clinically relevant is open to question. Motion analysis parameters should not be considered in isolation as authors of validation studies have recommended that they be used together as an assessment of surgical dexterity and performance18. Most important is the fact that both groups demonstrated significant improvement in all parameters over a short training period.
Regarding the level of experience, our findings suggest that hip arthroscopy has certain elements, particularly involving orientation after portal exchange, that require specific training beyond knee and shoulder arthroscopy. Both junior and senior trainees are likely to benefit from simulator training.
While caution is required in extrapolating these data to hip arthroscopy on patients, the results suggest that all trainees, regardless of the number of years of training, would benefit from at least nine episodes of a simulated task, such as that used in this study. If trainees start with sound basic skills, they are likely to progress to satisfactory performance of therapeutic and advanced procedures more quickly.
This study had limitations. The cohorts were small, but the sizes were similar to those in previous randomized studies17,20,21 and the power analysis estimated 90% power to detect clinically relevant differences during the initial learning curve. Several of the comparisons revealed highly significant p values. The procedure of hip arthroscopy consists of a number of distinct technical steps, each of which is important and would be desirable to simulate in order to create a more complete and realistic assessment of performance and learning curves. This simulation was not appropriate for assessing skill in achieving adequate joint distraction or establishing portals because of the lack of radiography and the risk of damaging the model, which may have biased later episodes. The portals were already established and optimally positioned. Accurate portal placement to enable adequate visualization while avoiding iatrogenic injury is a key competency that an inexperienced arthroscopist must achieve. The task was not extended to the peripheral compartment because of potential biases associated with the release and reapplication of lower-extremity traction. In hip arthroscopy terms, this was a more basic task; however, we consider it to be an essential competency for the trainee learning hip arthroscopy. In addition to these hip-specific limitations, and in common with all arthroscopy simulation studies, the ability to mimic real life is limited because of variations in the size and anatomy of individual patients, bleeding, the need to maintain strict sterile technique, and the inconsistent time interval between cases that may cause erosion of skills between cases. However, standardization of training protocols was mandatory for valid comparison between groups. The training duration was based on a previous study demonstrating that the learning curves reached a plateau by twelve episodes19. The difficulty of this task seemed appropriate for this duration of assessment. There was no early ceiling effect, suggesting that the complexity was appropriate. There was also no floor effect, as both groups achieved a similar level of competence and their learning curves plateaued toward the end of the study. Potentially, a more complicated task, such as labral repair, may have led to persisting differences, and it is also important to acknowledge that the finding that the learning reached a plateau at nine episodes applies only to the particular technical aspect examined in this study. The learning curve of the entire procedure is likely much longer.
In conclusion, this study objectively demonstrated an initial learning curve for a simulated hip arthroscopic procedure in a group of trainee surgeons. Trainees randomized to learning the task with the lateral patient position found field orientation more difficult than those learning it with the supine position, but they achieved similar competence after nine episodes. Junior trainees rapidly acquired skills and achieved a level of performance similar to that of more senior trainees within the study period. Trainers should be aware of these learning patterns, and trainees may benefit from simulator training to achieve basic competence prior to performing hip arthroscopy on patients.
A video of the arthroscopic monitor recording of the demonstration of the task protocol, as used in the instructional PowerPoint presentation, is available with the online version of this article as a data supplement at jbjs.org.
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Disclosure: One or more of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of an aspect of this work. In addition, one or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.