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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

D-Dimer Levels May Help with PJI Diagnoses

D-dimer for OBuzzThe percentage of periprosthetic joint infections (PJIs) among patients requiring revision arthroplasty of the hip and knee is increasing. PJIs have important clinical implications both for revision surgical procedures as well as pre- and postoperative management. Any extra help we can get making a PJI diagnosis outside of the obvious (where the patient presents with a draining wound) would be most welcome.

In the September 6, 2017 issue of The Journal, Shahi et al. present compelling data from a prospective study suggesting that serum D-dimer levels may help diagnose PJI—and thereby help determine the optimal timing of component reimplantation. The authors determined that 850 ng/mL was the optimal threshold value for D-dimer in diagnosing PJI. Moreover, with sensitivity of 89% and specificity of 93%, this test outperformed the widely used ESR and CRP tests, which until now have proven to be the “best” tools we have at our disposal.

Ideally, after these results are confirmed in larger populations of patients undergoing revision arthroplasty, the serum D-dimer test—inexpensive and almost universally available—will be used in all high-volume joint replacement centers. The continued pursuit of diagnostic and treatment methodologies for patients with suspected PJI is definitely warranted, given the increasing number of patients requiring arthroplasty and combined lifetime knee- and hip-replacement revision rates hovering around 10% to 12%. The identification of D-Dimer elevation as a potentially more accurate diagnostic tool than our currently available tests is a welcome contribution.

Marc Swiontkowski, MD
JBJS Editor-in-Chief

Longer Surgeries, Lengths of Stay Associated with More Adverse Events

Trauma Image for OBuzzThe phrase “adverse event” has been defined variably in the orthopaedic literature, which is one reason identifying the factors associated with such events can be tricky. In the August 16, 2017 edition of The Journal of Bone & Joint Surgery, Millstone et al. go a long way toward pinpointing modifiable factors that boost the risk of adverse events.

Using an institution-wide adverse-event reporting system called OrthoSAVES, the authors analyzed adverse events among 2,146 patients who underwent one of three elective orthopaedic procedures: knee replacement, hip replacement, or spinal fusion. They found an overall adverse event rate of 27%, broken down by surgical site as follows:

  • 29% for spine
  • 27% for knee
  • 25% for hip

The most common adverse events had a low severity grade (1 or 2); the authors suggest that including events typically not viewed as severe (such as urinary retention) is one reason the overall adverse event rate in this study was higher than most previously reported.

The unique finding from this study was that two modifiable factors—length of stay and increasing operative duration—were independently associated with a greater risk of an adverse event. More specifically, the authors found that, regardless of surgical site, each additional 30 minutes of surgery increased the adjusted odds for an adverse event by 13%.

The authors were quick to point out that their findings should not be interpreted as an admonition for surgeons to hurry up. “While operative duration may be a modifiable factor, operating more quickly for spinal or any other procedures may, itself, lead to increased complications,” they wrote. Rather, Millstone et al. suggest that the multiple factors comprising “procedural efficiency” during a surgical hospitalization warrant further investigation.

Where Does the Blood Flow in the Femoral Head?

Femoral Head Vasculature.jpegOsseous vascular anatomy has always been clinically relevant to orthopaedists, but its importance is sometimes overlooked. In the July 19, 2017 issue of The Journal, Rego et al. provide a precise topographic map of arterial anatomy in and around the femoral head.

Ever since Trueta’s classic work published in the British volume of JBJS in 1953, we’ve known that the terminal branches of the medial femoral circumflex system (also known as the lateral epiphyseal artery complex) supply blood to the majority of the femoral head. This information has proved critical in supporting treatment decisions for the management of femoral head and neck fractures. In those cases, surgeons typically perform ORIF through an anterior approach because it is remote from this posterior vascular supply.

The details in the Rego et al. study will help today’s and tomorrow’s arthroscopists more safely manage acetabular labral tears associated with cam deformities. In those settings, when increasing the “offset” across the femoral neck to decrease impingement, surgeons should limit the depth of bone removal to avoid injury to this important vascular network. Thanks to this study, operating surgeons now have precise anatomic information (albeit derived from non-deformed cadaver hips) with which to limit the risks of increasing the femoral head offset.

Marc Swiontkowski, MD
JBJS Editor-in-Chief

Centenarians Fare Pretty Well After Hip Fracture Treatment

Centenarian.jpgPeople 100 years old and older—centenarians—make up only 0.02% of the current US population. Nevertheless, the number of centenarians is expected to increase five-fold by 2060. That is in part what prompted Manoli III et al. to analyze a large New York State database to determine whether patients ≥100 years old who sustained a hip fracture fared worse in the hospital than younger hip-fracture patients. The study appears in the July 5, 2017 issue of The Journal of Bone & Joint Surgery.

Only 0.7% of the more than 168,000 patients ≥65 years old included in the analysis sustained a hip fracture when they were ≥100 years old. Somewhat surprisingly, centenarians incurred costs and had lengths of stay that were similar to those of the younger patients. However, despite those similarities, centenarians had a significantly higher in-hospital mortality rate than the younger patients. Male sex and an increasing number of comorbidities were found to predict in-hospital mortality for centenarians with hip fractures.

Manoli III et al. also found that, relative to other age groups, centenarians were managed nonoperatively at a slightly higher frequency when treated for extracapsular hip fractures. For intracapsular fractures, an increasing proportion of patients >80 years were managed with hemiarthroplasty and nonoperative treatment. Finally, among centenarians, time to surgery did not affect short-term mortality rates, suggesting a potential benefit to preoperative optimization.

The Acetabulum’s Role in SCFE: Cause or Consequence?

Acetabular Version for O'Buzz.jpegThe multifactorial pathogenesis of slipped capital femoral epiphysis (SCFE) almost certainly involves the acetabulum, but previous studies about that relationship have been inconclusive. In the June 21, 2017 issue of JBJS, Hesper et al. report on a matched-cohort study that used precise measurements gleaned from CT to determine that acetabular retroversion—not acetabular depth or overcoverage of the femoral head—is associated with SCFE.

The authors carefully measured acetabular depth, head coverage, and retroversion in three groups of hips: the affected hips of 36 patients with unilateral SCFE, the unaffected contralateral hips of those same patients, and healthy hips of 36 age- and sex-matched controls. They observed no deep acetabula or acetabular overcoverage in the SCFE-affected hips, but they did find a lower mean value for acetabular version (i.e., retroversion) at the level of the femoral-head center in the SCFE-affected hips, relative to contralateral and control hips.  The acetabulum was retroverted cranially in cases of severe SCFE compared with mild and moderate cases.

These findings support the hypothesis that SCFE-affected hips have reduced acetabular version, but the authors note that “additional studies will be necessary to determine whether acetabular retroversion is a primary morphological abnormality associated with the mechanical etiology of SCFE, or if it is an adaptive response to the acetabulum after the slip.” Either way, Hesper et al. conclude that their data “may help with planning treatment for patients with residual pain and limited motion related to femoroacetabular impingement after SCFE.

Does Hip Arthroscopy Really Help?

Menge_Image_for_O'Buzz.pngOver the past 15 to 20 years, the use of arthroscopic procedures for hip pathologies has rapidly increased. Leaders in sports medicine have standardized many arthroscopic techniques, including methods of joint distraction, portal location, approaches to labral repair or debridement, and management of cartilage lesions.

Many in the orthopaedic community have wondered whether this expansive  use of  hip arthroscopy is justified by significant improvement in patient function or is simply a first (and perhaps overused) step toward inevitable hip arthroplasty. To help answer that question, in the June 21, 2017 issue of The Journal, Menge et al. document the 10-year outcomes of arthroscopic labral repair or debridement in 145 patients who originally presented with femoroacetabular impingement (FAI).

Whether these patients were treated with debridement or repair, their functional outcomes and improvement in symptoms were excellent over the 10-year time frame, and the median satisfaction score (10) indicates that these patients were very satisfied overall. However, as seen in other similar studies in the peer-reviewed literature, the results in older patients with significant cartilage injury or radiographic joint space narrowing were inferior, and most of the patients with these characteristics ended up with a hip replacement.

The Menge et al. study helps confirm that arthroscopic repair or debridement in well-selected FAI patients yields excellent longer-term outcomes, and it provides concrete criteria for patient selection.

Marc Swiontkowski, MD
JBJS Editor-in-Chief

Good Outcomes with After-Hours Hip Fracture Surgery

marc-swiontkowski-2In the June 7, 2017 issue of The Journal of Bone & Joint Surgery, Pincus et al. report on a careful analysis comparing outcomes from hip fracture surgery occurring “after hours” (defined by the authors as weekday evenings between 5 PM and 12 AM) with surgeries occurring during “normal hours” (weekdays from 7 AM to 5 PM). In the busy Ontario trauma center where this study was performed, it is common for patients with blunt trauma to take precedence over seniors who are relatively stable but in need of hip fracture care.

Pincus et al. found that adverse outcomes, in terms of surgical and medical complications, were similar whether the hip surgery occurred during normal hours or after hours.  Interestingly, there was a higher rate of inpatient complications in the normal-hours group, and fewer patients in the after-hours group were discharged to a rehab after surgery than in the normal-hours group.

It has been my impression that highly skilled professional surgeons and their teams are going to put forward their best efforts for all patients—no matter what time of day or night they operate. Concentration, focus, and high standards can generally overcome fatigue. However, the Pincus et al. study should not be viewed as justification for hospital decision makers to forget their commitment to optimize management of all resources, including surgical teams. After-hours care should never become “routine,” and there should be continuous attention on developing alternative solutions, such as moving elective surgery to other facilities or true shift scheduling that provides all members of the team with occasional daytime hours off for rest and management of personal lives.

The authors note that in their Canadian jurisdiction, there are hospital and surgeon-reimbursement incentives that may work to promote after-hours surgery, but the long-term focus must always put patient outcomes first. And we must always remember that good patient outcomes rely on maintaining surgical teams who are experienced and not burnt out.

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.