One of my residency mentors always stressed that orthopaedic surgeons should be “masters of musculoskeletal anatomy.” During his first lecture each July, he would grill the junior residents on muscle origins and insertions, along with innervations. Knowing safe surgical planes helps us avoid complications from neural or vascular injury and increases the likelihood of a successful orthopaedic procedure. With the increased popularity of the direct anterior approach (DAA) for total hip arthroplasty (THA), it is crucial that orthopaedists understand the anatomical implications of that technique.
One key to a successful DAA hip replacement is adequate visualization, which is aided by retractors. However, malpositioned retractors can cause femoral nerve palsy, a potentially serious neurological complication that can delay postoperative rehabilitation. In the January 15, 2020 issue of The Journal, Yoshino et al. report on a cadaveric study that quantifies the distance between the femoral nerve and the acetabular rim at varying points along the rim. Knowing these precise distances could help surgeons make safer decisions about where—and where not—to place retractors.
The authors dissected 84 cadaveric hips from 44 formalin-embalmed cadavers and measured the distance from the femoral nerve to various points along the acetabular rim by using a reference line drawn from the anterior superior iliac spine (ASIS) to the center of the acetabulum. They found the femoral nerve was closest to the rim (only 16.6 mm away) at the 90° point.
In addition, at 90°, the thickness of the iliopsoas muscle and the femoral length (a probable proxy for size of the patient) were positively associated with increased distance to the nerve. Other anatomic factors such as inguinal ligament length, femoral head diameter, and thickness of the capsule were not associated with the nerve-rim distance.
The degree nomenclature used by Yoshino et al. can be correlated to a clock-face representation of the acetabulum, with the 60° point at the 3 o’clock (anterior) position; the 30° point represents a relatively safe location for placement of the anterior inferior iliac spine retractor (see Figure above).
This important anatomic study can help us improve our mastery of musculoskeletal anatomy—and avoid, if possible, placement of retractors at 90° relative to a line drawn from the ASIS to the center of the acetabulum.
Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media
In March 2019, OrthoBuzz covered a JBJS study by Rudasill et al. that found a progressively increasing risk of bleeding requiring transfusion among total knee arthroplasty (TKA) patients who had a preoperative International Normalized Ratio (INR) >1. (INR is a standardized measure of how long it takes blood to clot—the higher the number, the longer the clotting time.) These authors also found a significantly increased risk of infection in TKA patients with INR >1.5. and an increased risk of mortality within 30 days of surgery among those with an INR >1.25 to 1.5.
In the January 2, 2020 issue of JBJS, the same team of researchers report findings from a similarly designed NSQIP-based study of patients undergoing total hip arthroplasty (THA). The authors evaluated data from >17,500 patients who underwent a primary THA between 2005 and 2016 and who also had an INR value documented within 2 days prior to joint replacement. Rudasill et al. stratified these patients into 4 groups based on preoperative INRs: ≤1, >1 to <1.25, 1.25 to <1.5, and ≥1.5).
After adjustment, the authors found a significant, independent effect between increased preoperative INR and increased bleeding requiring transfusion and mortality. Specifically, bleeding risk became evident at INR ≥1.25, and patients with INR ≥1.5 were at a significantly increased risk of mortality. The length of hospital stay also increased significantly as INR class increased.
The authors suggest that “current INR targeting [INR <1.5 for elective orthopaedic surgery] may not be strict enough to minimize adverse outcomes for patients undergoing primary total hip arthroplasty.” While admitting that these findings are not likely to change the day-to-day practice of orthopaedic surgeons, the authors say they “may influence preoperative risk stratification for those patients with elevated INR.”
Pediatric orthopaedists have long been searching for anatomic, mechanical, and metabolic causes of slipped capital femoral epiphysis (SCFE). Adolescent obesity has been a recognized SCFE risk factor for 50 years. (Interestingly, high BMI is a consistent risk factor in males, but females who experience SCFE are often thin.) Possible racial risk factors have been examined as well, with no clear conclusions.
Because the incidence of SCFE is relatively low (1 in 10,000 children according to this JBJS Clinical Summary) and the risk of bilaterality is high (in the range of 30% to 40%), it seems likely that anatomic risk factors are at play. In the January 2, 2020 issue of The Journal, Novias et al. home in on the 3-D anatomy of the epiphyseal tubercle (a small, round protuberance thought to stabilize the epiphysis) and peripheral “cupping” of the epiphysis in patients with and without SCFE.
They found a smaller epiphyseal tubercle and more extensive epiphyseal cupping in patients with SCFE compared with normal hips. The authors encourage further investigation of the first finding to determine whether smaller tubercles are a consequence of the slip process or an anatomic variant that predisposes the epiphysis to slip.
A major strength of this study is that all measurements were made by a single observer blinded to the diagnosis of SCFE and other potentially confounding clinical and demographic data. Also, the measurement processes used in this study have been previously validated.
Investigation into the anatomic features of this disease should continue, along with development of minimally invasive, safe, and inexpensive ways to screen for possible anatomic risk factors. The most pertinent clinical goals are to continue evolving minimally invasive methods of epiphyseal stabilization to prevent and/or treat SCFE and to more accurately identify hips at risk of SCFE.
Marc Swiontkowski, MD
Based on ample published data and experience, today’s hip surgeons can give patients who are considering total hip arthroplasty (THA) a good general idea of outcomes to expect. But what if orthopaedists could provide more tailored predictions of THA outcome, and thus help patients more realistically manage expectations?
That is essentially what Hesseling et al. set out to do in their database analysis of 6,030 THA patients gleaned from the Dutch Arthroplasty Register; the findings appear in the December 18, 2019 issue of JBJS. Using the patients’ Oxford Hip Scores (OHS) collected up to 1 year postoperatively and a sophisticated statistical technique called latent class growth modeling, the authors categorized outcome trajectories into 3 categories:
- Fast Starters (n = 5,290)—steep improvement in OHS during the first 3 postoperative months, after which the OHS leveled out
- Late Dippers (n = 463)—more modest improvement in OHS initially, followed by subsequent decline toward the 1-year mark
- Slow Starters (n = 277)—virtually no change at the 3-month mark, followed by an improvement in OHS at 1 year postoperatively
Although the authors were unable to tease out factors that clearly distinguished between late dippers and slow starters, they did identify several factors associated with less-than-fast-starter outcomes:
- Female sex
- Age >75 years
- Anxiety and depression
- American Society of Anesthesiologist (ASA) grade III or IV
- Hybrid fixation (cemented acetabular implant)
- Direct lateral surgical approach
Emphasizing that all 3 subgroups experienced functional improvement after THA, Hesseling et al. nevertheless provide useful information that can help surgeons more accurately estimate which patients might be at risk of a less favorable recovery.
Surgical skills education in orthopaedics has changed dramatically from the “see one, do one, teach one” process of 30 years ago. These changes have come with a greater degree of supervision and formal skills assessments, and they have been aided by the visionary leadership at the Accreditation Council for Graduate Medical Education (ACGME) and our own orthopaedic Residency Review Committee. These skill-acquisition enhancements have benefited both our trainees and the patients we collectively care for.
A decade ago, we entered a new phase of skill development and enhancement with computer-based surgical simulators. With advances in software and widespread interest across North America in goal-driven learning through simulation, great progress has been made. In the November 20, 2019 issue of JBJS, Weber et al. report on the further validation of a surgical simulator focused specifically on percutaneous, fluoroscopically guided pin placement for femoral neck fractures. The simulator was developed in partnership between the AAOS and OTA.
This study sought to determine whether novice practitioners (medical students, in this case) who completed 9 training modules before using the simulator (the “trained” group) would perform the simulated pinning task better than peers who did not complete the presimulation training (the “untrained” group). It was no surprise to me that the trained group had a significantly higher overall performance score on the simulator. In addition, relative to the untrained group, the trained students also showed improved performance on 4 specific measures—3 of which were related to the angle between the placed pins.
These findings are clearly supportive of continued development of this and additional simulation environments. But at the same time, we need to move forward with improved documentation of surgical skill acquisition among orthopaedic residents and fellows. As simulator technology continues to improve, the next decade should yield even more positive results in skills acquisition than we saw in the last decade. We are clearly on the right path with the use of advanced technology for surgical skill development among orthopaedic trainees.
Marc Swiontkowski, MD
According to the orthopaedic literature, the risk of vascular injury during internal fixation of a proximal femoral fracture is low. But applying the findings from an anatomical analysis by Jaipurwala et al. in the November 6, 2019 issue of The Journal of Bone & Joint Surgery could help minimize that risk even further.
The authors examined lower-limb CT angiograms of 47 patients (mean age 69) who had the scans performed for reasons other than a femoral fracture. They then measured the distance from the tip of the greater trochanter to the profunda femoris artery and its perforators within 5 mm of the medial femoral shaft, along the length of typical placement of dynamic hip screws used for fixation of proximal femoral fractures. (The authors assumed the use of a 4-hole, 78 mm plate or a 6-hole, 110 mm plate.)
All 47 patients had 2 vessels within 5 mm of the medial femoral shaft along the line of presumed dynamic hip screw insertion. Noting that these vessels could be damaged by reduction instruments or during drilling and plate-screw insertion during actual cases of femoral-fracture fixation, Jaipurwala et al. make the following suggestions:
- Avoid or take special care when drilling or inserting screws along the femoral shaft from 110 to 120 mm from the tip of the greater trochanter in women and from 120 to 130 mm in men.
- If possible, avoid inserting a screw in the fourth hole of a 4-hole dynamic hip screw plate or inserting a screw in the fourth and fifth holes of a 6-hole plate.
The authors emphasize that these suggestions are based on measurements taken from patients who did not have a hip fracture and that “a femoral fracture may potentially alter local anatomy because of swelling and damage to surrounding structures.” But they conclude that the risk of vascular injuries in patients with a proximal femoral fracture would be further reduced if surgeons took these findings into account during operative planning and execution of hip-fracture fixation.
OrthoBuzz occasionally receives posts from guest bloggers. In response to a recent study in The New England Journal of Medicine, the following commentary comes from Paul E. Matuszewski, MD.
A recent issue of The New England Journal of Medicine published the results from a large, multicenter randomized trial comparing the outcomes of hemiarthroplasty versus total hip arthroplasty (THA) to treat displaced femoral neck fractures in ambulatory adults.
The HEALTH investigators enrolled 1,495 patients in the study, and 85.1% of those patients had complete data for analysis after 2 years. The researchers found no significant differences between the groups with regard to the primary outcome—secondary hip procedures (7.9% in the THA group vs 8.3% in the hemi group). The risk of secondary hip procedures during the first year was higher in the THA group, but the hemiarthroplasty group had a higher risk of secondary procedures in the second year. Open/closed reductions of hip dislocations were the most common secondary procedures among the THA group, and revision to THA was the most common secondary procedure in the hemiarthroplasty group. The THA group had slightly better WOMAC scores, but the difference was not within a clinically significant range. There were no between-group differences noted in other patient-reported outcomes.
The HEALTH investigators followed these patients for only two years, which is notably the standard for many orthopaedic studies, but this short follow-up limits the practical application of these findings. The authors note that after the first year, primary THA was favorable with regard to secondary hip procedures. It is reasonable to think that this difference may become more compelling beyond 2 years, as more patients who received hemiarthroplasty are likely to be converted to THA.
The suggestion that there may not be an early benefit of THA over hemiarthroplasty in the ambulatory adult with a displaced femoral neck fracture contrasts with current recommendations from the American Academy of Orthopaedic Surgeons. However, the 2-year follow-up of this trial represents only a “snapshot” of the continuum of outcomes from these two hip-fracture treatments. The findings may add to our understanding of what our patients can expect during the first 2 years following these procedures, but I would caution surgeons against making any drastic changes to their current practice in response to this data.
Paul E. Matuszewski, MD is the Director of Orthopaedic Trauma Research and Assistant Professor of Orthopaedic Traumatology at the University of Kentucky.
Manufacturing, farming, and shopping…These are just 3 diverse examples of how technology is advancing daily and automating tedious tasks, decreasing costs, and improving efficiencies. Orthopaedics and orthopaedic research are not being left behind in this progression. In the November 6, 2019 edition of JBJS, Wyles et al. evaluate the accuracy of natural language processing (NLP) tools in automating the extraction of orthopaedic data from electronic health records (EHRs) and registries. The findings suggest that NLP-generated algorithms can indeed reliably extract data without the labor-intensive and costly process of manual chart reviews.
First, using an open-source NLP “engine,” the researchers developed NLP algorithms focused on 3 elements of >1,500 total hip arthroplasty (THA) procedures captured in the Mayo Total Joint Registry: (1) operative approach, (2) fixation technique, and (3) bearing surface. They then applied the algorithm to operative notes from THAs performed at Mayo and to THA-specific EHR data from outside facilities to determine external validity.
Relative to the current “gold-standard” of manual chart reviews, the algorithm had an accuracy of 99.2% in identifying the operative approach, 90.7% in identifying the fixation technique, and 95.8% in identifying the bearing surface. The researchers found similar accuracy rates when they applied the algorithm to external operative notes.
The findings from this study strongly suggest that properly “trained” NLP algorithms may someday eliminate the need for manual data extraction. That, in turn, could substantially streamline future research, policy, and surveillance tasks within orthopaedics. As Gwo-Chin Lee, MD predicts in his Commentary on this study, “When perfected, NLP will become the gold standard in the initial data mining of patient records for research, billing, and quality-improvement initiatives.” Dr. Lee is quick to add, however, that “no machine learning can occur…without the integral and indispensable input of the human element.”
Orthopaedic surgeons are already using robots to assist them in performing total joint arthroplasties. Wyles et al. show how we can use technology to reliably expedite research on that same subject. I believe the future holds much promise for the use of ever-advancing technologies in orthopaedic surgery and research.
Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media
A recent report in Radiology citing possible complications from injecting steroids into painful joints with osteoarthritis (OA) has received lots of attention in the mainstream media. Radiologists from Boston, Germany, and France reviewed the existing literature and found an association between intra-articular steroid injections and a small increased risk of four adverse joint findings: accelerated OA progression, subchondral insufficiency fracture, complications from osteonecrosis, and bone loss. However, the study did not include a control group that did not receive injections, and therefore it cannot be used to assess whether injections are associated causally with the adverse joint findings.
In an interview with Boston radio station WBUR, lead author Ali Guermazi, MD stressed the point that readers should not conclude from this report that steroid injections cause these complications, adding that additional research in this area is “urgently needed.” In the same radio coverage, Jeffrey Katz, MD, a professor of orthopaedic surgery at Boston’s Brigham & Women’s Hospital and a Deputy Editor at JBJS, said patients who have received such injections or plan to should not be overly worried. However, he added that “for clinicians and patients who’ve been doing injections for several years, it’s worth it to pause and say, ‘Do we want to discuss [again] what we think are the benefits and risks of this.’”