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Weight-Bearing CT: An Incremental Step in Addressing Posttraumatic Ankle Arthritis

Orthopaedic surgeons recognize that an intra-articular fracture of the distal tibia (pilon fracture) is the worst actor when it comes to the sequela of posttraumatic ankle osteoarthritis. Despite decades of focusing on surgical techniques that yield the best-looking postoperative radiographs, we have come to realize that, to reduce the risk of subsequent arthritis, limiting the extent of the surgical approach may be as important as achieving the “perfect” articular reduction. Slowly we have come to understand that articular cartilage damage from the injury (and in some instances exacerbated by overaggressive surgical dissection) is as big a factor as the bone injury in terms of postoperative joint-space narrowing and its associated ankle stiffness and pain.

Thankfully, the orthopaedic trauma community is making strides toward new biologic, mechanical, and rehabilitative interventions that have the potential to limit this articular narrowing. But to meaningfully evaluate the effectiveness of these strategies, we need not only validated patient-oriented functional outcome measures, but also more reliable and reproducible ways to assess the joint-space narrowing.

In the May 6, 2020 issue of The Journal, Willey et al. report on a standardized technique using weight-bearing computed tomography (WBCT), which yields a 3D assessment of the postoperative joint space with the ankle in a loaded, functional position (see Figure above). When this technique was applied to 20 patients (mean age of 44 years) with a partial or complete articular pilon fracture 6 months after surgical treatment, the authors found significantly less tibiotalar joint space in the injured ankle compared with the uninjured ankle. Interrater correlation and test-retest data indicated that this method has good measurement reliability and reproducibility.

Any safe, reliable, and reproducible measure of early joint-space narrowing after pilon fracture surgery is an important incremental step in designing clinical trials that will assess new interventions designed to preserve postoperative joint space—and hopefully reduce the incidence of posttraumatic ankle arthritis. Willey et al. have demonstrated the usefulness of WBCT as such a modality.

Marc Swiontkowski, MD
JBJS Editor-in-Chief

Romosozumab for Hip Fractures: All That Glitters Is Not Gold

We have all come to realize that promising results from lab studies or preclinical trials in animal models do not always translate into meaningful clinical benefits in humans. Yet it is vitally important to perform those human trials to ascertain that knowledge. This is demonstrated by Schemitsch et al. in the April 15, 2020 edition of The Journal. The authors performed a Level I, double-blinded, randomized controlled trial comparing varying doses of romosozumab to placebo in the treatment of older patients with a hip fracture.

Romosozumab is a sclerostin-inhibiting antibody that helps increase bone formation while decreasing resorption. It is indicated to treat osteoporosis in postmenopausal women, in whom the drug has been shown to increase bone mineral density and reduce the risk of fragility fractures. In multiple preclinical studies, romosozumab has increased bone mass and bone strength in rodent osteotomy models, suggesting it might possibly promote fracture healing in people.

In the current study, Schemitsch et al. randomized patients between 55 and 95 years old who had a low-energy hip fracture amenable to internal fixation to receive 3 postsurgical subcutaneous injections of romosozumab at doses of either 70 mg (60 patients), 140 mg (93 patients), or 210 mg (90 patients), or to receive 3 placebo injections (89 patients). The primary end point was the validated “timed Up and Go” (TUG) score. The authors also measured the Radiographic Union Scale for Hip (RUSH) score, and hip pain on a visual analog scale (VAS).

The authors enrolled 325 patients, with 263 (79.2%) reaching the 24-week follow up and 229 (69.0%) reaching the 52-week follow up. They found no statistically significant between-group differences in the TUG, with all patients improving and plateauing at week 20. Similarly, there were no differences between any of the treatment arms in time to radiographic healing, RUSH scores, or VAS. The safety profile of the medication was similar between the 3 romosozumab doses and the placebo.

Romosozumab may increase bone mineral density and reduce the risk of fragility fracture in patients with osteoporosis, but when it comes to helping heal hip fractures, it did not prove to be more advantageous than placebo. This shows, yet again, that what may glitter in animal studies may not necessarily shine like gold in clinical trials with people.

Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media

Treating Transitional Ankle Fractures: Best Evidence Yet

Transitional fractures of the ankle in adolescents are related to torsional injuries that occur around the time that the distal tibial physis begins to close. In recent years, treatment has moved toward screw fixation when the intra-articular fracture gap in Salter type III (Tillaux) and type IV (triplane) fractures is  between 1 mm and 2 mm. The rationale for operative treatment has been that intra-articular fracture gaps should be completely reduced, particularly in younger patients, to limit the long-term risk of post-traumatic osteoarthroses. However, evidence supporting the wisdom of surgical intervention has been thin at best. (See Clinical Summary on Triplane Ankle Fractures.)

In the April 15, 2020 issue of The Journal, Lurie et al. report on a retrospective analysis of 34 patients with a triplane fracture and 23 patients with a Tillaux fracture, all of which had 2 mm to 5 mm of articular displacement. Among those 57 patients, 34 were treated with surgery and 23 with closed reduction and casting.

Based on regression analysis, nonoperative treatment, a larger intra-articular gap after closed reduction, and the presence of a grade-III complication were associated with worse functional outcomes at a mean follow-up of 4.5 years. Patients who were treated nonoperatively and had a gap ≤2.5 mm had significantly better functional scores than similar patients with a gap >2.5 mm. From this data, the authors conclude that “surgical management of these injuries likely conveys the greatest functional benefit when the intra-articular gap exceeds 2.5 mm.”

This study has the usual issues of treatment and detection bias inherent in retrospective reviews, and the measurement of fracture gaps, even with the CT scans these authors used, is not always reliable at this level of precision. Nevertheless, this data from Lurie et al. is the best we have to date to indicate that the so-called “2-mm rule” of nonoperative management of transitional ankle-fracture gaps  ≤2 mm probably makes sense in most clinical situations.

Marc Swiontkowski, MD
JBJS Editor-in-Chief

Does Computer-Assisted Surgery Drive Better TKA Outcomes?

Computer-assisted surgery (CAS) for total knee arthroplasty (TKA) has become popular largely based on claims that the technology improves accuracy of component positioning and alignment. Theoretically, that leads to superior patient-reported outcomes. However, the use of CSA has not reliably yielded improvements in implant survival or clinical outcomes. A large registry study by Roberts et al. in the April 1, 2020 issue of The Journal sheds additional light on this perplexing question.

An earlier study by the same author group used data from the same New Zealand Joint Registry and showed no difference in functional outcomes or implant survival between TKAs performed with and without CAS.1 However, that study did not account for the potential bias introduced by surgeons who use CAS only for complex cases.

In this study, Roberts et al. analyzed data from 2 carefully selected groups of surgeons: those who used CAS in 90% of their TKAs (“routine CAS” surgeons) and those who used CAS in <10% of their TKAs (“routine conventional” surgeons). Further limiting their analysis to surgeons with >50 TKAs recorded in the registry between 2006 and 2018, Roberts et al. identified 25 “routine CAS” surgeons and 22 “routine conventional” surgeons. This allowed a comparison between 9,501 TKAs performed by routine CAS surgeons and 7,672 TKAs performed by routine conventional surgeons.  While analyzing revision rates and Oxford Knee Scores (OKS) at 6 months, 5 years, and 10 years, the authors also controlled for confounding variables such as age, body-mass index, and implant type.

With a mean follow-up of 4.5 years, the authors found a revision rate per 100 component-years of 0.437 in the group operated on by routine CAS surgeons, compared to a mean 4.9-year revision rate of 0.440 in the group operated on by routine conventional surgeons (p=0.724).  When stratifying outcomes of patients <65 years old, the authors again found no statistical difference in revision rates. They also found no between-group differences in OKS within the full and <65 cohorts at 6 months, 5 years, or 10 years.

The findings prompt the authors (and I) to wonder whether continually improving design and durability of modern implants make it difficult to discern any advantage from computer assistance in implant positioning.

Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media

Reference

  1. Roberts TD, Clatworthy MG, Frampton CM, Young SW. Does computer assisted navigation improve functional outcomes and implant survivability after total knee arthroplasty? J Arthroplasty. 2015 Sep; 30(9)Suppl: 59-63.

Subtalar Joint Compensation after Ankle Fusion

Ankle fusion continues to be a predictable treatment for degenerative tibiotalar arthritis. It improves both pain and function from primary osteoarthritis and degeneration related to chronic instability or trauma. JBJS has published several recent studies demonstrating that the outcomes of fusion compare favorably with those of total ankle replacement, particularly in higher-demand patients. (See, for example, Effectiveness and Safety of Ankle Arthrodesis Versus Arthroplasty and Outcomes of Total Ankle Replacement, Arthroscopic Ankle Arthrodesis, and Open Ankle Arthrodesis for Isolated Non-Deformed End-Stage Ankle Arthritis.)

Many clinicians have wondered why outcomes after ankle arthrodesis are typically so much better than those after arthrodesis of other mobile joints. In the April 1, 2020 issue of The Journal, Lenz et al. provide an answer. Using dual fluoroscopy integrated with 3-D CT, the authors compared the subtalar motion of the surgically fused ankle in 10 patients with the motion of the untreated, asymptomatic side. The findings strongly suggest that compensatory increased plantar flexion of the subtalar joint allows improved function following successful arthrodesis. The authors found that this increased motion occurred during both normal plantigrade ambulation and bilateral heel raises.

Clinicians can use this important information to explain to patients who are deciding between ankle arthrodesis and arthroplasty how fusion can not only improve pain, but can also result in good functional range of motion. On the other hand, the authors surmise that the compensatory increase in subtalar joint plantar flexion may explain the reported increased risk of future subtalar osteoarthritis in surgically fused ankles. However, to answer that question, we’ll need larger, longitudinal clinical studies that evaluate the relationship between the compensatory post-fusion subtalar kinematics discovered by Lenz et al. and radiographic findings and patient-reported pain and function.

Marc Swiontkowski, MD
JBJS Editor-in-Chief

Displaced Proximal Humeral Fractures: Fix or Replace?

Nonoperative management of proximal humerus fractures in the elderly used to be fairly common, but multiple studies have shown poor outcomes. Open reduction and internal fixation (ORIF) with locked-plate constructs has shown some promise, but it has been fraught with complications. Most recently, reverse total shoulder arthroplasty (rTSA) has emerged as a possible surgical solution, but this is a complicated procedure, and questions have arisen about long-term outcomes.  Compounding this conundrum are the varying degrees of severity of proximal humeral fractures.

In the March 18, 2020 issue of The Journal, Fraser et al. share 2-year results from a multicenter, single-blinded randomized trial that compared rTSA to ORIF for severely displaced proximal humeral fractures in patients 65 to 85 years of age. Included patients (n=124) had OTA/AO 11-B2 or 11-C2 fractures with >45° valgus or >30° varus in the anteroposterior view, or >50% displacement of the humeral head. Using the Constant shoulder score as the primary outcome measure, the authors demonstrated both a statistically significant and clinically meaningful difference favoring rTSA in this cohort.

The mean Constant score was 68.0 points for the rTSA group compared to 54.6 points for the ORIF group. The mean between-group difference, 13.4 points, was significant (p<0.001) and exceeded the minimal clinically important difference of 10 points.  The Constant-score difference between ORIF and rTSA was most pronounced (18.7 points) in patients with C2 fractures, but there was no significant score difference in those with B2 fractures. Secondary outcomes (Oxford Shoulder Scores) showed a consistent trend of the rTSA group scoring higher than the ORIF group at 2 years.

Although this study indicates an advantage for rTSA, one must consider that only severely displaced fractures were investigated and that 2-year follow-up for joint arthroplasty is considered short term. In a Commentary about this article, Peter A. Cole, MD points out that “if there was a 25% revision rate for reverse TSA at 5 to 10 years, then the superior results would be reversed, and we would be reinventing another wheel in orthopaedics.”

Clearly, longer-term studies in this population are a necessity, and Fraser et al. say they plan to follow these patients in 5-year intervals.

Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media

THA in the Very Young: Midterm Results

Orthopaedic surgeons work hard to find good alternatives to total hip arthroplasty (THA) in patients <50 years old. That’s because the high functional demands and longer remaining lifespan in these patients can result in excessive wear of the bearing surfaces and loosening of the components—both of which have been documented in multiple publications. But what happens when THA is the most viable solution for a posttraumatic or congenital hip problem in a very young patient because arthrodesis or other osteotomies are not feasible?

In the March 18, 2020 issue of The Journal, Pallante et al. report medium-term outcomes of THA in 78 patients who were ≤20 years of age at the time of surgery, with follow-ups ranging from 2 to 18 years. The findings included the following:

  • 10-year survivorship for reoperation of 95.0%
  • 10-year survivorship for revision of 97.2%
  • 10-year survivorship for complications of 89.5%

Overall, the linear articular wear averaged 0.019 mm/yr in the ceramic-on-ceramic, ceramic-on-highly cross-linked polyethylene, and metal-on-highly cross-linked polyethylene bearings studied, and the average modified Harris hip score in the cohort was 92.

However, despite these impressive clinical and survivorship outcomes, I advise orthopaedists not to lower their resistance to performing THA on these very young patients, many of whom present with hip problems caused by deforming conditions such as Legg-Calve-Perthes disease. We really need 30 to 40 years of outcome data to truly  understand what happens with function, revision rates, and wear characteristics in this population. Having said that, I am confident that this group from Mayo will continue reporting on this patient cohort at 5- to 10-year intervals, so that the worldwide orthopaedic community can keep learning from this experience.

Marc Swiontkowski, MD
JBJS Editor-in-Chief

Are Tantalum Hip Implants Safe?

I have been told that daytime TV is punctuated by a continual stream of ads for personal-injury lawyers asking if you have been injured by a particular medication or medical device.  Since 2002, billions of dollars have been paid out in lawsuits over metal-on-metal hip replacements containing cobalt and/or chromium, the “loose” ions of which increase the risk for aseptic lymphocyte-dominated vasculitis-associated lesions (ALVAL)—which are sometimes referred to as “pseudotumors.” So orthopaedic surgeons understandably want to know more about the potential long-term implications of newer metal technologies such as tantalum.

“Trabecular Metal” is a trade name for tantalum-based bone-ingrowth material that is now quite common in acetabular cups and revision shells used for total hip arthroplasty (THA). In the March 4, 2020 issue of the The Journal, Brüggemann et al. investigated the safety of these tantalum components. They retrospectively reviewed blood tantalum levels in 30 patients who underwent primary THA with no tantalum components, 30 patients who received a tantalum cup during a primary THA, and 84 patients who received a tantalum shell during a revision. Tantalum levels in 59 blood-donor volunteers served as controls. The authors also measured subsets of lymphocytes (CD8+ and CD4+ T-cells) that are thought to be associated with the immunologic cascade causing ALVAL.

At an average follow-up of 4 years, Brüggemann et al. found that median tantalum concentrations were 0.051 µg/L  in those receiving primary tantalum implants and 0.05 µg/L in those receiving primary implants without tantalum. (The “detection limit” for tantalum used in this study was 0.05 µg/L.) Patients receiving revision tantalum shells had median serum tantalum levels of 0.091 µg/L.  Time since surgery did not affect tantalum levels.

The authors also found a weak negative correlation between increased tantalum concentration and lower concentrations of CD8+ T-cells. Clinically, none of the hips in this series was deemed loose, and the Harris hip scores among all subjects were good to excellent.

It seems that with stable tantalum implants, any increase in serum concentrations of tantalum is small, but we don’t yet know the longer-term implications of these small increases. While it’s also reassuring that the lymphocyte activation associated with ALVAL does not seem to occur with these tantalum implants, I agree with the authors’ conclusion that this study “cannot exclude the possibility that even low tantalum concentrations confer a risk to patients’ health.”  Clearly, longer-term studies are needed.

Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media

Implant Prices are Main Cost Driver in Joint Replacements

Orthopaedic surgeons have long been aware of the role that implant prices play in the total cost of care for arthroplasty procedures, but methodical breakdowns of implant costs in relation to the cost of other aspects of care have generally been lacking. In the March 4, 2020 issue of The Journal, Carducci et al. detail the impact of implant costs on the total cost of care in a study of 6 lower- and upper-extremity arthroplasty types performed at a single, high-volume orthopaedic specialty hospital.

Using a uniform method called time-driven activity-based costing, the authors calculated the total costs of >22,200 inpatient primary total joint arthroplasties, and then broke down those total costs by categories, including implant price and personnel costs. It was no surprise that, as a percentage of total cost, implant costs were highest for low-volume surgeries (as high as 65% for total ankle arthroplasty) and lowest for high-volume procedures (e.g., 40% for total knee arthroplasty). Nevertheless, across the board, implant price was the most expensive component of total cost.

Implant prices are individually negotiated between a hospital and an implant supplier and are usually protected by nondisclosure agreements, so the data from this investigation may not match up with data from any other institution. Unfortunately, the future of implant-cost research will be tied to the complex issue of return-on-investment for implant-manufacturer stockholders as it relates to negotiations with individual hospitals and health systems.

The profound impact of implant price on the total cost of all the joint arthroplasties studied by Carducci et al. also begs the questions as to how “generic” implants (those not manufactured by the major orthopaedic producers) will ultimately influence the market—and whether “branded” implants, with their 30% to 50% markups, provide any functional benefit for patients. We will need further well-designed research to address those questions.

Marc Swiontkowski, MD
JBJS Editor-in-Chief

So Far, Bundled Payments Not Affecting Patient Selection for Joint Replacement

Many people predicted that the mandatory “bundling” of payments for knee and hip arthroplasty by the Centers for Medicare and Medicaid Services (CMS) that began on April 1, 2016 in several US metropolitan areas would lead to  “cherry-picking” and ”lemon-dropping.” In other words, hospitals and surgeons wouldn’t take on more complex and sicker patients for joint replacement for fear that the bundled payment would be insufficient (lemon-dropping), and would instead select the healthier patients (cherry-picking). See related OrthoBuzz post.

In the February 19, 2020 issue of The Journal, Humbyrd et al. compare the characteristics of patients who underwent hip and knee replacement (HKR) from April to December 2015 with those of HKR patients during the same period in 2016, after CMS mandated the bundled-payment program in 67 metropolitan statistical areas (MSAs). The patients were matched so that those treated in bundled and non-bundled settings had similar socioeconomic backgrounds.

The matched groups included 12,388 HKR episodes in 40 bundled MSAs and 20,288 HKRs in 115 nonbundled MSAs. The authors also evaluated pre- and post-policy case-mix changes among 1,549 hip hemiarthroplasties, which are not subject to bundling, in the bundled MSAs.

Among patients who underwent HKR, Humbyrd et al. found no significant differences in patient characteristics—including race, dual Medicare-Medicaid eligibility, tobacco use, obesity, diabetes, and Charlson Comorbidity Index (CCI)—after the bundled-payment policy was implemented. Also, they found that patients in bundled MSAs undergoing hemiarthroplasty had significantly higher CCI values and were more likely to have diabetes than those who underwent HKR. This suggests that some surgeons opt for hemiarthroplasty over total hip replacement in less-healthy patients to avoid treating such patients under a bundled program.

From the MSA perspective, these results suggest that cherry picking and lemon dropping are not occurring in the short term. But we would do well as a profession to ensure that those controversial patient-selection practices are not happening at the individual surgeon level, and that the short-term results demonstrated here by Humbyrd et al. persist over the longer term. Even our sickest joint replacement patients deserve the best surgical care.

Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media