Tag Archive | total hip arthroplasty

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

JBJS Classics: Porous-Coated Hip Components

JBJS Classics Logo.pngOrthoBuzz regularly brings you a current commentary on a “classic” article from The Journal of Bone & Joint Surgery. These articles have been selected by the Editor-in-Chief and Deputy Editors of The Journal because of their long-standing significance to the orthopaedic community and the many citations they receive in the literature. Our OrthoBuzz commentators highlight the impact that these articles have had on the practice of orthopaedics. Please feel free to join the conversation by clicking on the “Leave a Comment” button in the box to the left.

In their classic 1987 publication, Drs. Charles Engh, Dennis Bobyn, and Andrew Glassman described clinical and radiographic results of a series of 307 hips with 2-year follow-up, and 89 hips with 5-year follow-up after total hip arthroplasty in which the patients had received an extensively porous-coated femoral stem. The authors also described histologic evaluation of 11 hips retrieved at autopsy or revision.

By 1987 the same authors as well as other investigators had already published observations concerning the influence of femoral stem size, shape, stiffness, and porosity on clinical and radiographic evidence of fixation and stress shielding in humans and animal models.1,2 But this study, which so far has been cited more than 1500 times, goes “above and beyond” by carefully correlating previous observations with histologic sections obtained through human femora.

Among other achievements, Engh et al. described radiographic criteria for categorizing a femoral implant as either stable by bone ingrowth, stable by fibrous tissue ingrowth, or unstable. Implants thought to be stable by fibrous ingrowth had a prominent radio-opaque line around the stem, separated from the implant by a radiolucent space up to 1 mm in thickness. This line was thought to represent a shell of bone with load-carrying capability. However, histology demonstrated that the space between the shell and the implant was composed of dense fibrous tissue. When the shell was present, there tended to be little hypertrophy or atrophy of the adjacent femoral cortex.

Engh et al. noted that radiographs and histology of hips with extensive ingrowth from the endosteum often showed parallel increased porosity of the adjacent cortex – an early manifestation of stress shielding. Overall, 259 (84%) of the femoral stems had radiographic findings suggestive of bone ingrowth, 42 (13%) had findings interpreted as stable fibrous ingrowth, and 2% were thought to be unstable (but not yet revised at the time of the study). Stress shielding was much more common in larger-diameter stems and those with good bone ingrowth compared to smaller implants or those with stable fibrous fixation.

Why do we consider this manuscript a classic? First, the authors include a careful correlation of histology with radiographic and clinical findings, helping illustrate the importance of tight press fit at the isthmus to achieve proximal fixation. The authors also document intracortical porosity as the morphologic manifestation of stress shielding and emphasize the impact of a small increase in stem diameter on axial rigidity.

Designs of femoral stems have evolved considerably since the 1980s,3 and the findings described in this paper helped validate fundamental principles related to load transmission and bone remodeling4-6 and thus helped advance that evolutionary process.

Thomas W. Bauer, MD, PhD
JBJS Deputy Editor

References

  1. Bobyn JD, Pilliar RM, Binnington AG, Szivek JA. The effect of proximally and fully porous-coated canine hip stem design on bone modeling. Journal of orthopaedic research : official publication of the Orthopaedic Research Society 1987;5:393-408.
  2. Bobyn JD, Pilliar RM, Cameron HU, Weatherly GC. The optimum pore size for the fixation of porous-surfaced metal implants by the ingrowth of bone. Clinical orthopaedics and related research 1980:263-70.
  3. McAuley JP, Culpepper WJ, Engh CA. Total hip arthroplasty. Concerns with extensively porous coated femoral components. Clinical orthopaedics and related research 1998:182-8.
  4. Huiskes R. Validation of adaptive bone-remodeling simulation models. Stud Health Technol Inform 1997;40:33-48.
  5. Huiskes R, Weinans H, Dalstra M. Adaptive bone remodeling and biomechanical design considerations for noncemented total hip arthroplasty. Orthopedics 1989;12:1255-67.
  6. Weinans H, Huiskes R, Grootenboer HJ. Effects of fit and bonding characteristics of femoral stems on adaptive bone remodeling. J Biomech Eng 1994;116:393-400.

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.

JBJS Case Connections—Preventing and Managing Post-THA Hip Dislocations

CCX OBuzz Image.gifHip dislocation is one of the most common perioperative complications of total hip arthroplasty (THA). The latest “Case Connections” article examines an often-overlooked spinal basis for THA dislocations, 2 cases of dual-mobility hip-bearing dissociations during attempted closed reduction for post-THA dislocations, and a unique application of Ilizarov distraction to treat a chronic post-THA dislocation.

The springboard case report, from the February 22, 2017, edition of JBJS Case Connector, describes the case of a 63-year-old woman who had experienced 4 anterior dislocations in less than 3 years after having her left hip replaced. Each dislocation was accompanied by lower back pain, and the patient also reported substantial pain in the contralateral hip. The authors emphasize the importance of recognizing pelvic retroversion and sagittal spinal imbalance before performing total hip arthroplasty.

Two additional JBJS Case Connector case reports summarized in the article focus on:

While closed reduction with the patient under sedation is a frequently employed first-line tactic that is often successful for dislocated THAs, these 3 cases show that creative surgical interventions may be necessary for optimal outcomes in patients with “complicated” hips and/or recurrent dislocations.

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

The Most-Read JBJS Articles of 2016

11-2016_VCR_II_Template-Final.jpgAs an end-of-year thank-you to the orthopaedic community, we’re offering limited-time full-text access to the five most-read JBJS articles of 2016. The fact that several of these most-read articles were published prior to 2016 is testament to the durable utility of orthopaedic research published in The Journal of Bone & Joint Surgery.