Tag Archive | THA

Has Conventional Polyethylene Become Obsolete in THA?

XLPE for OBuzzHighly cross-linked polyethylene (XLPE) has been in clinical use for nearly 15 years. In acetabular components for total hip arthroplasty (THA), XLPE’s superior wear characteristics and lower revision rates, relative to conventional polyethylene (PE), have been demonstrated in numerous studies. Here is one more: a 10-year Level I study in the October 18, 2017 issue of The Journal of Bone & Joint Surgery by Devane et al.

In this double-blinded, randomized trial, authors measured 2-D, 3-D, and volumetric wear (in mm or mm2), along with wear rates (mm/year), presence or absence of osteolysis, and revision rates in 91 patients at specified time intervals, up to a minimum of 10 years. The following results corroborate the general findings from most other studies on this topic:

  • The mean 3-D wear rate among patients with the XLPE acetabular liner was 0.03 mm/yr, versus 0.27 mm/yr among patients with conventional PE.
  • Eight percent of patients in the XLPE group showed radiographic evidence of osteolysis, versus 38% of patients in the PE group.
  • Patients with the conventional PE liner had a significantly higher revision rate (14.6%) than those with the XLPE liner (1.9%).

There were no significant between-group differences in clinical outcome scores, including the Oxford Hip Score and SF-12 physical well-being score.

The authors note that “the longer-term implications of these findings are unclear,” but their calculations indicated that, through 20 years, none of the XLPE liners would wear through, but 6 of the conventional PE liners would require revision due to wear-through.

Long-term Results Show No Advantage to “Minimalist” THA

Minimal Incision THA for OBuzzThe debate regarding minimally invasive/minimal incision total hip arthroplasty (THA) has been simmering for a decade and a half. When assessing the impact of adult reconstruction procedures, patients and treating physicians alike are most interested in longer-term results. Improved return of function in the first 3 to 6 weeks is of some value to all patients—and perhaps of great value to younger patients—and that has been one of the purported advantages of the “minimalist” approach. But it is the long-term results that really matter.

In the October 18, 2017 issue of The Journal, Stevenson et al. provide 10-year results from a 2005 randomized trial of small-incision posterior hip arthroplasty, and they confirm it adds no clinical, radiographic, or implant-survivorship benefit when compared with a standard posterior approach. An extra caveat here is that these procedures, originally done in 2003-2004, were undertaken by a highly experienced surgeon who had performed >300 minimal-incision THAs. In the hands of surgeons with less experience, smaller incisions may result in suboptimal component positioning and other complications, a point emphasized by Stevenson et al. and by Daniel Berry in his JBJS editorial accompanying the original study.

This long-term data is of great value to patients and surgeons alike. It is my hope that such high-quality evidence will temper the claims used in marketing materials that hype minimally invasive approaches, to which hip surgeons are routinely subjected.

Marc Swiontkowski, MD
JBJS Editor-in-Chief

More Comparative Data on Surgical Approaches to THA

Implant Survival and THA Approach.jpegThe May 17, 2017 edition of The Journal of Bone & Joint Surgery features a registry-based study by Mjaaland et al. comparing implant-survival/revision outcomes in total hip arthroplasty (THA) among four different surgical approaches:

  • Minimally Invasive (MI) Anterior (n=2017)
  • MI Anterolateral (n=2087)
  • Conventional Posterior (n=5961)
  • Conventional Direct Lateral (n=11,795)

Although the authors analyzed a whopping 21,860 THAs from 2008 to 2013, the findings are limited by the fact that all of those procedures used an uncemented stem.

Overall, the revision rates and risk of revision with the MI approaches were similar to those of the conventional approaches. There was a higher risk of revision due to infection in THAs that used the direct lateral approach than in THAs using the other three approaches. “To our knowledge,” the authors write, “this finding has not been previously described in the literature, and we do not have an explanation for it.” The authors also found a reduced risk of revision due to dislocation in THAs that used the MI anterior, MI anterolateral, and direct lateral approaches, relative to those using the posterior approach.

While the authors found all-cause risk of revision to be similar among all four approaches, they note that the follow-up in the study was relatively short (mean of 4.3 years) and that “additional studies are needed to determine whether there are long-term differences in implant survival.”

After THA, Self-Directed Home Exercise Yielded Same Benefits as Formal PT

THA3 for OBuzz.jpegAn estimated 40% of total costs from a total hip arthroplasty (THA) episode are accrued from post-discharge services.  With that in mind, Austin et al. embarked on a randomized controlled trial comparing outcomes among two groups of primary THA patients: those who followed a 10-week self-directed home exercise regimen (n=54) and those who received a combination of in-home and outpatient physical therapy (PT) for 10 weeks (n=54). The results were published in the April 19, 2017 edition of The Journal of Bone & Joint Surgery.

At 1 month and 6 to 12 months after surgery, patients in both groups showed significant preoperative-to-postoperative improvements in function as measured by all administered instruments (Harris Hip Score, WOMAC Index, and SF-36 Physical Health Survey). However, there was no difference in any of the measured functional outcomes between the two groups.

In addition, a total of 30 patients (28%) crossed over between groups: 20 (37%) from the formal physical therapy group and 10 (19%) from the home exercise group.  The 10 patients who crossed over from home exercise to formal PT were not meeting progress goals; they tended to be older and had worse preoperative function than those in that cohort who did not cross over.

So, while this study provides evidence that unsupervised home exercise can be as effective as a structured rehabilitation program for most patients, the authors say the following patient characteristics might be indications for a referral to formal PT:

  • Older age
  • Poorer preoperative function
  • Severe preoperative gait imbalance
  • Postoperative neurological complications
  • Expectations for quick return to high-level activity

Total Joint Arthroplasty: Does One Lead to Another?

TJA and Second TJA.jpegAn estimated 7 million people living in the US have undergone a total joint arthroplasty (TJA), and the demand for total hip arthroplasty (THA) and total knee arthroplasty (TKA) will almost certainly increase during the next 15 years.  But how many people can expect to have an additional TJA after having a first one?

That’s the question Sanders et al. address in their historical cohort study, published in the March 1, 2017 edition of The Journal of Bone & Joint Surgery. They followed more than 4,000 patients who underwent either THA or TKA between 1969 and 2008 to assess the likelihood of those patients undergoing a subsequent, non-revision TJA.

Here’s what they found:

  • Twenty years after an initial THA, the likelihood of a contralateral hip replacement was 29%.
  • Ten years after an initial THA, the likelihood of a contralateral knee replacement was 6%, and the likelihood of an ipsilateral knee replacement was 2% at 20 years.
  • Twenty years after an initial TKA, the likelihood of a contralateral knee replacement was 45%.
  • After an initial TKA, the likelihood of a contralateral hip replacement was 3% at 20 years, and the likelihood of an ipsilateral hip replacement was 2% at 20 years.

In those undergoing an initial THA, younger age was a significant predictor of contralateral hip replacement, and in those undergoing an initial TKA, older age was a predictor of ipsilateral or contralateral hip replacement.

The authors conclude that “patients undergoing [THA] or [TKA] can be informed of a 30% to 45% chance of a surgical procedure in a contralateral cognate joint and about a 5% chance of a surgical procedure in noncognate joints within 20 years of initial arthroplasty.” They caution, however, that these findings may not be generalizable to populations with more racial or socioeconomic diversity than the predominantly Caucasian population they studied.

Single-Anesthetic Bilateral THA as Complication-Free as Staged Procedures

Single_Anesth_vs_Staged_Bilateral_THA.pngSingle-anesthetic bilateral total hip arthroplasty (THA) has had a historically high perioperative complication profile. However, a matched cohort study by Houdek et al. in the January 4, 2017 edition of JBJS comparing single-anesthetic versus staged bilateral THA over four years found no significant differences between the two procedures in terms of:

  • Risks of revision, reoperation, or complications (including DVT/PE, dislocation, periprosthetic fracture, and infection; see graph, where blue line represents single-anesthetic and red line indicates staged)
  • Perioperative mortality
  • Discharge to home versus rehab

The single-anesthetic group (94 patients, 188 hips) experienced shorter total operating room time and hospital length of stay than the matched cohort, and consequently the single-anesthetic approach lowered the relative total cost of care by 27%.

While the Mayo Clinic authors concede the potential for selection bias in this study (e.g., there was no standardized protocol for determining eligibility for inclusion in either group), they say that they currently consider single-anesthetic bilateral THA for patients with bilateral coxarthrosis who are <70 years of age, relatively healthy, and/or have bilateral hip contractures that would make rehabilitation difficult.

JBJS Editor’s Choice: How Best to Treat Femoral Neck Fractures in Younger Adults

ORIF or THA for Femoral Neck Fx.gifIn the January 4, 2017 issue of The Journal, Swart et al. provide a well-done Markov decision analysis on the cost effectiveness of three treatment options for femoral neck fractures in patients between the age of 40 and 65: open reduction and internal fixation (ORIF), total hip arthroplasty (THA), and hemiarthroplasty. Plugging the best data available from the current orthopaedic literature into their model, the authors estimated the threshold age above which THA would be the superior strategy in this relatively young population.

For patients in this age group, traditional thinking has been to perform ORIF in order to “save” the patient’s native hip and avoid the likelihood of later revision arthroplasty. However, in this analysis THA emerges as a cost-effective option in otherwise healthy patients >54 years old, in patients >47 years old with mild comorbidity, and in patients >44 years old with multiple comorbidities.

On average, both THA and ORIF have similar outcomes across the age range analyzed. But ORIF with successful fracture healing yields slightly better outcomes and considerably lower costs than THA, whereas patients whose fracture does not heal with ORIF have notably worse outcomes than THA patients. This finding supports my personal bias that anatomical reduction and biomechanically sound fixation must be achieved in this younger population with displaced femoral neck fractures. The analysis confirmed that, because of poor functional outcomes with hemiarthroplasty in this population, hemiarthroplasty should not be considered. Poor hemiarthroplasty outcomes are likely related to the mismatch between the metal femoral head and the native acetabular cartilage, leading to fairly rapid loss of the articular cartilage and subsequent need for revision.

This analysis by Swart et al. provides very valuable data to discuss with younger patients and families when engaging in shared decision making about treating an acute femoral neck fracture. In my experience, most patients in this age group prefer to “keep” their own hip whenever possible, which puts the onus on the surgeon to gain anatomic reduction and biomechanically sound fixation with ORIF.

Marc Swiontkowski, MD
JBJS Editor-in-Chief

JBJS Reviews Editor’s Choice—Trunnion Wear After THA

Modular NeckTotal hip arthroplasty made its debut about 60 years ago. As with most new technologies, it was anticipated that advances and improvements would occur. However, the improvements have been incremental and in some cases have led to problems, particularly with regard to interchangeable parts, modularity, and the materials used for articulating surfaces. Some still believe that total hip arthroplasty was close to being optimized at the time that it was introduced.

Some may view these comments as somewhat provocative, but I would not be surprised if a lot of surgeons agree. The issue of trunnion wear is one example of these problems. One of the main contributing factors is the fact that each implant manufacturer uses tapers with their own specifications, which vary in terms of angle, diameter, straightness, roundness, and surface properties. Therefore, most femoral neck implant tapers are not necessarily compatible with each other. It is important to note that femoral heads should not be used interchangeably between designs as the cone angle may differ. ?If this is done, trunnionosis will be a likely outcome.

In the August 2016 issue of JBJS Reviews, Lanting et al. provide an important and very worthwhile discussion of the risk factors for trunnionosis. Trunnionosis may be enabled by the disruption of the protective oxidative layer on the metal by fretting, potentiating the corrosion of the exposed metal beneath the oxidative layer through an active combination of biochemical and electrochemical processes. Time in vivo consistently has been shown to be a risk factor for trunnionosis. Flexural rigidity of the trunnion has been demonstrated to have an important role in the development of trunnionosis. A flexible trunnion may allow fretting as well as point loading. Edge loading is known to make tribocorrosion more likely to occur. In the presence of any degree of angular mismatch, the effect of trunnionosis may be increased.

The role of design and manufacturing variables in the development of trunnion problems continues to be debated. Surgeon-related factors, especially the greater variability and taper assembly with smaller-incision surgery, also may contribute to this phenomenon. Patients presenting with unexplained pain who have modular neck-body implants should be considered to have an adverse local tissue reaction resulting from corrosion of the neck-stem interface as potential cause of the pain.

In most cases, I suspect that removal of the femoral head, cleaning of the taper, and replacement with a different femoral head (usually a ceramic head with a titanium adapter sleeve) represents adequate treatment based on care recommendations. In contrast, in cases involving adverse local tissue reactions associated with the modular neck designs, removal of the modular stem and neck may be required.

Thomas A. Einhorn, MD
Editor, JBJS Reviews

Metal-on-Metal Hip Arthroplasty: Where Do We Go From Here?

OrthoBuzz occasionally receives posts from guest bloggers. This guest post comes from Richard S. Yoon, MD.

We’re entering the “midterm” follow-up period for the metal-on-metal (MoM) hip devices implanted in the early 2000s, and recent reports from around the world are confirming early concerns. Several studies published during the first few months of 2016 report unacceptably high failure rates.

In the Open Orthopaedics Journal, Mogensen et al. reported an 18.4% revision rate in more than 100 CONSERVE MoM hips, at a mean follow-up of 4.5 years. These results led the Danish authors to terminate the use of MoM at their centers.

In the BMJ Open, Langton et al. reported a 16% failure rate among more than 350 Pinnacle MoM hips after about nine years of follow-up. Greiner et al. published a follow-up of prior research in a recent edition of the Journal of Arthroplasty. Among more than 150 MoM modular acetabular components with 5- to 12-year follow-ups, the results related to adverse local tissue reactions and revisions were inferior when compared with those of metal-on-polyethylene articulations. Dhotare et al., in Hip International, reported an alarming failure-rate increase from 7% at six years to 29% at ten years for the Birmingham MoM cup and large metal head.

While we cannot turn back the clock on the past use of MoM devices, we have some information about surveillance and treatment that may help us prevent catastrophic failure.

Data regarding the effects of increasing serum metal ions are mixed. Some studies have found a direct correlation between high metal ion levels and the incidence of adverse tissue reactions (and the need for subsequent revision), while other studies have not.  A recent JBJS study identified cobalt-ion thresholds that could help stratify patients with Birmingham and Corail-Pinnacle hips who are at low risk of metal-debris adverse reactions.

The systemic effects of increased serum metal ions are also being debated. Some case reports have cited neurotoxicity presenting as tinnitus, gait imbalance, and other issues, while a more recent, larger longitudinal study published in the Journal of Arthroplasty did not confirm this correlation. Those authors surmised that increased serum ion levels may cause neurotoxicity-associated symptoms primarily in MoM patients with metal hypersensitivity.

Metal artifact reduction sequence (MARS) MRI has been helpful in early identification of adverse soft tissue reactions. However, there is no general consensus or guideline as to when and how often this technology should be utilized in order to provide consistent surveillance and/or indications for revision.

While we are still trying to understand the finer points of the many variables related to MoM, there is an obvious need to forge consensus. Recently, in the Bone and Joint Journal, Berber et al., representing the International Specialist Centre Collaboration on MoM Hips (ISCCoMH), conducted a survey among six international tertiary referral centers to assess the overall consensus in surveillance and treatment practices. Only a moderate agreement value (kappa = 0.6) was found. This inconsistent agreement led the group to call for international coordination to help set forth guidelines that would standardize and improve surveillance of and treatment for those with MoM hips.

Richard S Yoon, MD is executive chief resident at the NYU Hospital for Joint Diseases.

Cup-Placement Precision Declines as Obesity Increases

Obesity can negatively affect outcomes after total hip arthroplasty (THA), and an inadvertent reduction in cup anteversion may be one reason why, according to findings from Brodt et al. in the May 4, 2016 edition of The Journal of Bone & Joint Surgery.

Cup Anteversion Obesity.gifThe authors retrospectively analyzed postoperative radiographs from 790 THA patients (all of whom were operated on via a direct lateral approach) within three BMI ranges: normal weight (BMI <25 kg/m2), moderately obese (BMI between 25 and 34 kg/m2), and morbidly obese (BMI of ≥35 kg/m2). Reduced cup anteversion significantly correlated with increasing BMI and younger patient age, with the morbidly obese group demonstrating a 3.4° anteversion reduction compared with the normal-weight group. The authors attribute the reduced anteversion to increased pressure applied to dorsal and ventral acetabular rim retractors to ensure adequate visualization during THA surgery in obese patients.

When the authors applied their findings to the Lewinnek “safe zone” for acetabular positioning, only 59% of the morbidly obese patients were in that zone.  While this study was not designed to track subsequent dislocations (a common consequence of incorrect cup positioning), the authors claim that these findings are nevertheless clinically important. “Knowledge of a systemic error in obese patients should raise surgeons’ awareness of the need to perform cup implantation with greater attention,” they conclude.