Genetic susceptibility to orthopaedic conditions is of interest to clinicians and patients alike. While the link between genetics and certain pediatric conditions is known, studies of sets of twins are providing new insights into adult issues, such as osteoarthritis, and the impact that genetics may have.
In the current issue of JBJS, Hailer et al. report on an investigation in Sweden in which they analyzed genetic susceptibility to hip and knee osteoarthritis necessitating total hip arthroplasty (THA) or total knee arthroplasty (TKA), and whether body mass index (BMI) moderates the heritability of these outcomes. They linked nearly 30,000 twin pairs with BMI information in the Swedish Twin Registry with the Swedish National Patient Register to identify twins who had undergone THA or TKA with a primary diagnosis of osteoarthritis. Structural equation modeling was then used to calculate the heritability of osteoarthritis treated with THA or TKA and how it related to BMI, age, and sex.
The authors note that, for radiographically defined knee osteoarthritis, previous twin studies have shown that the genetic susceptibility (“the proportion of the variation of a trait that can be attributed to the variation of genetic factors”) is between 0.4 to 0.8. In twin studies using total joint replacement as the outcome, heritability has been estimated to be 0.2 for TKA and 0.5 for THA.
Hailer et al. found that, on average in their cohort, approximately half of the susceptibility to undergo THA or TKA for osteoarthritis was explained by heritability, with similar estimates demonstrated for the 2 procedures: THA, 0.65 (95% CI, 0.59 to 0.70) and TKA, 0.57 (95% CI, 0.50 to 0.64). Of note, heritability decreased with higher BMI in both men and women for THA and in men for TKA. But in women, heritability for TKA increased with higher BMI (0.37 for a BMI of 20 kg/m2 and 0.87 for a BMI of 35 kg/m2).
Although the need for THA or TKA is not a perfect indicator of osteoarthritis (plenty of osteoarthritis does not become symptomatic enough to warrant total joint arthroplasty), this large study offers further data on the question of genetic susceptibility to the development of osteoarthritis. Understanding the influence of obesity (a modifiable risk factor) becomes increasingly important and warrants continued investigation in studies exploring heritability in relation to orthopaedic conditions.
Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media
Changes in 24-Hour Physical Activity Patterns and Walking Gait Biomechanics After Primary Total Hip Arthroplasty
Together with improvements in self-reported pain and perceived physical function, patients had significantly improved gait function postoperatively.
Read the full article here.
In a prospective case-control study reported in JBJS, Ohmori et al. evaluated factors related to postoperative gait speed in patients with osteoarthritis undergoing total hip arthroplasty. They found that the preoperative, contralateral-side OLST (one-leg standing time) was a significant factor (p < 0.001) for postoperative comfortable gait speed. They also found that preoperative, contralateral-side knee extensor strength was a significant factor (p = 0.018) for postoperative maximum gait speed.
Reflecting on their findings, the authors note:
THA is a procedure that typically has a good a postoperative prognosis. However, some patients do not have sufficient satisfaction. Investigating reasons for this, we found that the functional status of the nonoperative lower limb is an important factor.
Surgical intervention before lower-limb function on the contralateral side declines, or a preoperative rehabilitation intervention on the contralateral side, may improve the THA outcome.”
Click here for the full JBJS report.
As the volume of total hip arthroplasty (THA) cases continues to rise, so too will the need for revision surgery. Revision THA can be complicated by insufficient bone stock on either the femoral or acetabular side, and researchers are gaining further insight into bone loss potentially related to implant design, such as loss that may occur through stress-shielding from press-fit implants.
In a randomized controlled trial recently reported in JBJS, Brodt et al. evaluated reduction in bone mineral density (BMD), primarily periacetabular BMD, as measured in 2 groups: patients who received a press-fit isoelastic monoblock cup (24 patients analyzed) and those who received a modular titanium press-fit cup (23 patients analyzed). At question was whether an isoelastic monoblock cup, with an elastic modulus similar to that of bone, would lead to less stress-shielding and thus less bone loss compared with a conventional modular titanium cup.
Periprosthetic BMD was assessed at 1 week postoperatively (baseline) and at 4 years postoperatively using dual x-ray absorptiometry (DXA). The authors evaluated 4 regions of interest (ROIs) around the acetabular component and 7 ROIs around the femoral component based on regions previously described in the literature for assessing periprosthetic bone loss.
Baseline patient characteristics, operative time, and improvement in clinical outcome scores did not differ between the groups. A decrease in overall periacetabular BMD was found in both groups, but the difference between the groups was not significant.
However, the researchers found a significant difference between the groups in BMD changes in certain periprosthetic regions. On the acetabular side, the group with the modular titanium cup had a 15.9% decrease in BMD in zone 2 (the superior pole of the acetabulum) compared with a decrease of 4.9% in the group with the isoelastic monoblock cup. And on the femoral side, the group with the modular titanium cup had a 15.4% decrease in BMD in zone 1 (along the greater trochanter) compared with a loss of 7% in the group with the isoelastic monoblock cup. None of the other regions differed significantly between the groups.
Despite the relatively short follow-up and small (but adequately powered) numbers, these results are worthy of our consideration. I agree with the authors that longer follow-up is needed before conclusions can be drawn. As implant design can impact component longevity, it is critical that we evaluate differences to better understand the long-term implications.
Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media
Consulting with their patients, orthopaedic surgeons make many decisions each day by weighing the best evidence available. One frequent—and controversial—decision is how best to treat displaced femoral neck fractures, a common injury among elderly patients.
Often this choice comes down to hemiarthroplasty (HA) or total hip arthroplasty (THA). The preponderance of evidence suggests that outcomes from both procedures are nearly equivalent. On Monday, June 28, 2021 at 8 pm EDT, JBJS will host a complimentary 1-hour webinar delving into the most recent findings about this dilemma.
Mohit Bhandari, MD, PhD will present findings from a 2020 Level-I meta-analysis of 16 randomized controlled trials. Functional outcomes and 5-year rates of revision and dislocation were similar between groups. THA eked out a small advantage in health-related quality of life, and HA yielded minor reductions in operative time.
Bheeshma Ravi, MD, PhD will discuss data comparing the 2 procedures in terms of complications and costs. Based on findings from this propensity score-matched analysis, the nod goes to THA, with lower 1-year rates of revision surgery and lower health-care costs.
Moderated by Bassam A. Masri, MD, FRCSC, the webinar will feature expert commentaries on these “neck-and-neck” findings. Pierre Guy, MD will comment on Dr. Bhandari’s paper, and Kelly Lefaivre, MD will weigh in on Dr. Ravi’s paper.
The webinar will conclude with a 15-minute live Q&A session during which attendees can ask questions of all the panelists.
Seats are limited–so Register Today!
CME credit will be available for surgeons and PAs attending this event live for a minimum of 50 minutes. Directions to claim your CME credit will be sent out within 48 hours of the broadcast.
The National Surgical Quality Improvement Program (NSQIP) database contains more than a half-million records of patients who received a total knee arthroplasty (TKA), unicompartmental knee arthroplasty (UKA), or total hip arthroplasty (THA) from 2009 through 2018. Fewer than 4% of those procedures were done in an outpatient setting, but patient demand for outpatient arthroplasty is rising rapidly.
With retrospective data like that from NSQIP, the most meaningful comparisons between inpatient and outpatient procedures come through a propensity score-matched analysis. Propensity score matching pairs up patients in each group according to multiple factors thought to influence outcome. In a recent study in The Journal of Bone & Joint Surgery, Lan et al. used propensity score matching to compare inpatient and outpatient arthroplasty in terms of adverse events and readmissions.
What the Researchers Did:
- Matched each outpatient case of TKA, UKA, and THA from the database with 4 unique inpatient cases based on age, sex, ASA class, race, BMI, type of anesthesia, and history of hypertension, smoking, congestive heart failure, and diabetes
- Compared inpatient vs outpatient rates of 30-day adverse events (both minor and severe) and readmissions
- Identified risk factors for adverse events and readmissions
What the Researchers Found:
- For all 3 arthroplasty types, patients who underwent an outpatient procedure were less likely to experience any adverse event, when compared with those who underwent an inpatient procedure.
- The above adverse-event findings held true when TKAs, UKAs, and THAs were analyzed separately.
- Outpatient procedure status was an independent protective factor against the risk of adverse events.
- For all 3 procedures, readmission rates were similar among inpatients and outpatients. (The 2 most common reasons for readmission were infections and thromboembolic events.)
- Clinicians are probably (and reasonably) selecting healthier patients to undergo outpatient procedures, but 42% of the outpatient cohort had an ASA class ≥3, and 55% had a BMI ≥30 kg/m2.
In their abstract, the authors cited “increased case throughput” as one rationale for outpatient arthroplasty, but this study provides convincing evidence that adverse-event reduction is another compelling reason for certain patients to consider outpatient knee and hip procedures.
Total hip arthroplasty (THA) with ceramic-on-ceramic (CoC) bearings has become popular, especially in younger patients, largely because of the material’s durability. However, CoC bearings are susceptible to catastrophic failure through fracture. Although the definitive mechanistic pathway for ceramic fracture has not been elucidated, one of the proposed mechanisms is impingement between the ceramic acetabular liner and the metal neck of the femoral stem. In the January 20, 2021 issue of The Journal, Lee et al. take an illuminating radiographic dive into the patterns of impingement in CoC THA.
The authors analyzed 244 cases of CoC THAs that had ≥15 years of radiographic follow-up. They found impingement-related notches at 77 sites in 57 (23.4%) of the cases. The notches were seen either on the neck (28 cases) or on the shoulder (29 cases) of the stem. In 8 cases, notches were found in multiple locations.
All of the neck notches were found when either a medium-neck or long-neck head was used. Shoulder notches were found on the stem only when a short-neck head was used. Lee et al. observed that the use of medium-neck or long-neck heads prevents the ceramic liner from contacting the stem shoulder because the liner impinges on the neck first. The authors also noted that the mean cup inclination was significantly lower in the cases with notched stems compared to stems without notches (36.9° vs 39.8°), and that mean anteversion was higher in the cases with notches (19.9° vs 17.3°).
We have known that impingement can occur between the ceramic liner and metal stem in CoC THA, but this study suggests that it may happen in a significant proportion of patients, both along the neck and shoulder of the stem. Manufacturers should consider these findings when designing implants, and patients and surgeons considering CoC implants may want to avoid short-neck heads, if possible. Also, because impingement-related stem notching appears to occur more frequently with lower cup inclination and higher anteversion, surgical technique remains vitally important in these cases, independent of implant design and selection.
Finally, we should note that the patients in this study were young (mean age of 43 years) and Asian. Asian culture and lifestyle include frequent squatting and sitting cross-legged, which Lee et al. say “induces more impingement between the stem and liner.”
Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media
Total hip arthroplasty (THA) is a tried-and-true treatment for debilitating hip osteoarthritis. But as the number of patients undergoing THA continues to rise, so does the incidence of periprosthetic femoral fractures and the need for revision surgery. The increasing burden of periprosthetic fractures has led to the development of shorter-stemmed femoral components that theoretically preserve bone, decrease fracture risk, and make revision surgery easier if it is required. In the January 6, 2021 issue of The Journal, Slullitel et al. report on a randomized controlled trial that determined whether bone loss differed between patients who received a conventional stem and those who received a short, bone-preserving stem over 2 years following THA.
Forty-six patients received the short, proximally porous-coated stem (Depuy Synthes Tri-Lock bone-preservation stem), and 40 received the conventional stem (Depuy Synthes collarless Corail stem). The primary outcome–bone mineral density (BMD)–was analyzed at 12, 26, 52, and 104 weeks after surgery with dual x-ray absorptiometry region-free analysis (DXA-RFA), which revealed pixel-level resolution of BMD at the bone-implant interface.
Immediately after surgery, researchers found a similar amount of bone loss in both groups in the calcar region and the cancellous portion of the distal greater trochanter. But at all other subsequent time points, bone loss was significantly greater in patients with the bone-preserving stem (analysis of variance [ANOVA] p < 0.0001). In addition, over the full study period the small areas of bone gain that the researchers found were statistically greater in the conventional-stem group than in the Tri-Lock group. Notably, patient-reported outcomes and adverse events did not differ between the 2 groups at the 2-year follow-up.
These early results cast a shadow of doubt over whether a stem that is marketed to preserve bone actually accomplishes that objective. However, 2 years is a very short follow-up when looking at the lifetime of a hip arthroplasty, and the clinical implications of these findings will become clearer with longer-duration analysis.
Click here to read a JBJS Clinical Summary titled “Short-Stem Femoral Components in THA” by Tad Mabry, MD.
Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media
There are many more “types” of diabetes than the pathophysiologic designations of Type 1 and Type 2. In the December 16, 2020 issue of The Journal of Bone & Joint Surgery, Na et al. delineate 4 different diabetes categories and determine their impact on 90-day complications and readmission rates after elective total joint arthroplasty (TJA) among Medicare patients. One premise for this investigation was that, although diabetes is a known risk factor for arthroplasty complications, alternative payment models such as the federally run Comprehensive Care for Joint Replacement (CJR) program adjust their payments only in diabetes cases where the comorbidity is coded as severe.
The authors stratified diabetes into 4 groups as follows:
- No diabetes
- Controlled-uncomplicated diabetes
- Controlled-complicated diabetes
- Uncontrolled diabetes
Among the >500,000 total knee arthroplasties (TKAs) and total hip arthroplasties (THAs) analyzed, the authors found the following when comparing data from the 3 diabetes groups with the no-diabetes group:
- The odds of TKA complications were significantly higher for those with uncontrolled diabetes (odds ratio [OR] = 1.29).
- The odds of THA complications were significantly higher for those with controlled-complicated diabetes (OR = 1.45).
- The odds of readmission were significantly higher in all diabetes groups for both TKA (ORs = 1.21 to 1.48) and THA (ORs = 1.20 to 1.70).
The authors come to 3 basic conclusions based on these findings:
- The odds of hospital readmission and complications following an elective TKA or THA are increased for Medicare beneficiaries who have diabetes.
- It would be reasonable to defer arthroplasty surgery for those with uncontrolled diabetes to allow them to achieve glycemic control.
- The Centers for Medicare & Medicaid Services should include less-severe diabetes and associated systemic complications in alternative-payment model adjustments.
Click here for an “Author Insight” video about this study from co-author Annalisa Na, PhD, DPT.
No consensus has emerged yet regarding the best prosthetic construct with which to manage patients who require revision surgery for dislocation after a total hip arthroplasty (THA). But in the December 2, 2020 issue of The Journal of Bone & Joint Surgery, Hoskins et al. add insight into that question by tapping the Australian Orthopaedic Association Total Joint Replacement Registry to analyze which of 4 first-revision component constructs led to the fewest second revisions.
Among the 1,275 THAs that were revised once for prosthesis dislocation, 203 hips went on to have a second revision, with dislocation being the most common cause for re-revision. The authors studied the second-revision THAs in 4 prosthetic categories: standard-sized femoral heads, large-sized femoral heads, dual-mobility heads, and constrained acetabular liners. The rate of all-cause second revision was significantly higher in the standard-head group when compared with the constrained-liner group. But in the 91 cases of second revisions for dislocation, the standard head showed significantly higher second-revision rates than any of the other 3 constructs. There was no statistically significant difference in rates of second revision between those 3 non-standard articulations
The authors discuss dual-mobility heads at some length, asserting that “caution should be exercised in their routine use, particularly in younger and active patients.” They note that the constrained liner was the “only articulation to show a difference when compared with standard-head THA for both all-cause revision and revision for a subsequent diagnosis of dislocation,” but they observe that impingement and acetabular component loosening are common concerns with constrained liners.
Despite these caveats, it seems clear from this data that the choice of articulating surface for either a first or second revision THA due to dislocation should probably exclude standard head sizes. Calling for longer-term data on all 3 alternative constructs studied here (the follow-up periods were different for all 4 articulations), the authors emphasize that “surgeons should [also] look beyond articulating surfaces”—to surgical approach, component orientation, and patient factors such as soft-tissue quality—in the effort to reduce the burden of THA dislocations.