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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.

What Is a “High-Priority” Knee Replacement?

This post comes from Fred Nelson, MD, an orthopaedic surgeon in the Department of Orthopedics at Henry Ford Hospital and a clinical associate professor at Wayne State Medical School. Some of Dr. Nelson’s tips go out weekly to more than 3,000 members of the Orthopaedic Research Society (ORS), and all are distributed to more than 30 orthopaedic residency programs. Those not sent to the ORS are periodically reposted in OrthoBuzz with the permission of Dr. Nelson.

The coronavirus epidemic has caused all of us to “rethink” many things. Several days ago, a radiologist asked me whether 3 of my requested imaging studies were high priority in light of the pandemic. My response was, “God bless you. No, none of those is urgent.”

I am 79 years old and think back to my first year of orthopaedic residency, 1968. In 2020, the expectation among many patients is for immediate relief, and many orthopaedists try to deliver that. Whatever “new normal” emerges after the COVID-19 surge subsides, how will patients and physicians work together to arrive at a decision when to proceed to a knee replacement? Although knee replacement can result in pain and function salvation for patients with end-stage knee osteoarthritis, as many as 20% of patients report “unsatisfactory” results.

A recent “appropriateness” analysis of data from 2 multicenter cohort studies classified 3,417 potential knee replacements as follows:

  • Timely—total knee replacement took place within 2 years after the procedure had met “potentially appropriate” criteria
  • Potentially Appropriate but Not Replaced (for >2 years after the procedure had met appropriateness criteria)
  • Premature—a replacement that the authors deemed inappropriate but was performed anyway.

The authors found that surgery for 9% of the knees for which replacement was potentially appropriate took place in a “timely” manner. But overall, there was a high prevalence of both delayed and premature surgery. Specifically, 91% of the knees for which replacement was potentially appropriate were not replaced, and 26% of the 1,114 total knee replacements that were performed were considered to be “likely inappropriate” and therefore “premature.”

The likelihood of a knee being classified as potentially appropriate but not undergoing replacement was greater among black patients, and the likelihood of having premature total knee replacement was lower among participants with a body mass index of >25 kg/m2 and those with depression.

In a Commentary on this study, Michael G. Zywiel, MD noted that the Escobar appropriateness criteria used in the analysis focuses predominantly on physician-assessed rather than patient-assessed factors. This all begs the question: Now that we have joint-replacement tools that we could not even dream of in 1968, how do we as responsible surgeons help guide our patients in deciding when the time is right to use them?

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

Osteoarthritis Progression: Our Current Understanding

This post comes from Fred Nelson, MD, an orthopaedic surgeon in the Department of Orthopedics at Henry Ford Hospital and a clinical associate professor at Wayne State Medical School. Some of Dr. Nelson’s tips go out weekly to more than 3,000 members of the Orthopaedic Research Society (ORS), and all are distributed to more than 30 orthopaedic residency programs. Those not sent to the ORS are periodically reposted in OrthoBuzz with the permission of Dr. Nelson.

Our understating of the progression pathways in knee osteoarthritis (OA) has evolved dramatically in recent years, as described in a recent review article.1 Over the past 2 decades, we have come to view the knee joint as an organ unto itself (with cartilage, synovium, bone, ligaments, and capsule). In the knee, we add to the mix the meniscus, which not only guides motion but is responsible for weight distribution on articular cartilage. Investigations into the etiology and progression of knee OA have merged joint mechanics with insights from studies of inflammation and immunology.

Woodell-May and Sommerfeld examine the process of knee OA as a wound-healing response. Triggered by damage-associated molecular patterns, the innate immune system is typically the first responder to this process. The acute phase in wound healing is short and involves infiltration of neutrophils. In response to neutrophil signals, monocytes migrate from the vessels and differentiate into macrophages, initially type I (inflammatory), which help form the granulation tissue seen in wound healing.

One take-home from the review article is that OA progression may be driven by the chronic inflammation associated with continuing efforts to heal. The back-and-forth between stimulating inflammation (M1 macrophages) and modulating inflammation (M2 macrophages) seems to be predominately driven from the synovium. In addition, specific receptors and intracellular kinases (such as toll-like receptors and mitogen-activated protein kinase) are upregulated in many OA samples.

M1 macrophages promote the elaboration of TNFα and IL-1 by synovial cells. Both cytokines are also active in rheumatoid arthritis (RA). Biologic treatment directed at either one of those cytokines can be effective in RA, but such treatment does not appear to be effective in OA. Over the past decade, the use of autologous conditioned serum (serum drawn off after blood is exposed to glass beads and incubated) has been studied in an attempt to reduce IL-1 activity. The conditioned serum also seems to affect TNFα and has shown some early promise in OA cases.

This burgeoning basic-science knowledge about OA has the potential to lead to disease-modifying treatments, which would revolutionize how orthopaedists approach OA treatment.

Reference
1. Woodell-May JE, Sommerfeld SD. Role of Inflammation and the Immune System in the Progression of Osteoarthritis. J Orthop Res. 2020 Feb;38(2):253-257. doi: 10.1002/jor.24457. Epub 2019 Sep 12. Review. PMID: 31469192

Risk of Repeat Complications after Staged Bilateral TKA

Sometimes the findings of well-designed orthopaedic studies are unexpected and counterintuitive—and sometimes they are not. In the latter category are the important but unsurprising results from the Grace et al. database study in the February 19, 2020 issue of The Journal of Bone & Joint Surgery.

The authors set out to determine whether having a specific medical complication after a first total knee arthroplasty (TKA) increased the chance that the same complication would occur after a second TKA performed 90 to 365 days after the first one. Among the specific complications investigated were myocardial infarction (MI), ischemic stroke, respiratory complications, urinary complications, digestive complications, hematoma, deep vein thrombosis (DVT), and pulmonary embolism (PE).

Overall complications after either procedure were low—>90% of the >36,200 patients who underwent bilateral TKAs did not experience any complications during the study period. However, those who had a complication after the first TKA had a significantly higher likelihood of having the same complication after the subsequent, contralateral procedure. Expressed as odds ratios (ORs), the increased probabilities of the same complication recurring after the second procedure were as follows:

  • Myocardial infarction—OR, 56.63
  • Ischemic stroke—OR, 41.38
  • Hematoma—OR, 15.05
  • Urinary complications—OR, 11.19
  • PE—OR, 11.00
  • Respiratory complications—OR, 8.58
  • Non-MI cardiac complications—OR, 7.73
  • DVT—OR, 7.40

Noting that these findings do not imply causality, the authors nevertheless surmise that “the occurrence of complications after the first replacement likely reflects a burden of comorbidity that predisposes patients to a recurrence of the same complications after the second replacement.” Consequently, Grace et al. suggest that this data could be used to help guide shared decision-making with patients considering staged bilateral TKAs, and that these findings could help identify “a subgroup of patients who may benefit from…targeted optimization strategies prior to the second surgical procedure.”

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

Precise Pivot-Shift Data Shines New Light on Partial ACL Tears

Concern, conversations, and controversy still exist around the optimal treatment for a partial anterior cruciate ligament (ACL) tear. Many surgeons recommend nonoperative treatment, despite evidence that up to 40% of those patients progress to a complete tear. Then again, surgical management comes with an ample array of possible complications. In the February 5, 2020 issue of The Journal of Bone & Joint Surgery, Lian et al. add insight into how best to treat partial ACL tears with their study of rotatory knee laxity in >300 patients with varying severities of ACL injury.

As part of the research undertaken by the PIVOT Study Group, Lian et al. made precise measurements of lateral knee compartment translation (measured with image-based iPad software; see Figure) and lateral compartment acceleration (measured with a surface-mounted accelerometer) during preoperative pivot-shift testing of affected and healthy knees in patients under anesthesia who had the following ACL problems:

  • A partial ACL tear (n=20)
  • A complete ACL tear (n=257)
  • A failed ACL reconstruction (n=27)

With each increasing grade of injury, the authors found  progressively increased rotatory laxity, defined as an increased difference in affected-knee-versus-healthy-knee lateral translation and acceleration. They also found a progressive, injury grade-related increase in lateral knee compartment translation in the healthy knees of these patients. In addition, the data suggest that patients who experience a failed ACL reconstruction exhibit increased rotatory knee laxity prior to the event that precipitated the failure.

From these findings and previous evidence that persistent rotatory knee laxity correlates with reduced patient-reported outcome scores and increased rates of meniscal and cartilage damage among patients with ACL injuries, Lian et al. conclude that “an elevated quantitative pivot shift in the case of a partial ACL tear might be an indication for bundle augmentation or ACL reconstruction.”

More Work, Less Pay for Revision TKAs

Time is a valuable commodity for everyone. Most physicians have spent long hours in the clinic or hospital, away from our families, sometimes missing important life events. We accept those aspects of our chosen profession. But everyone, including surgeons, wants to be appropriately reimbursed for their time. It’s logical that more complex surgical cases take more time to perform correctly and safely. But does Medicare (and the private insurers who base their physician payments on Medicare rates) adequately reimburse for that extra time?

The short answer is “no,” at least in terms of revision surgery for infected total knee arthroplasties (TKAs). Samuel et al. tackle that topic in the February 5, 2020 issue of The Journal. The authors reviewed records from the NSQIP database to identify cases of aseptic revision TKA, 1-stage septic revision TKA, and 2-stage septic revision TKA. Using propensity-score matching that controlled for age, sex, race, BMI, and ASA classification, the authors established 4 cohorts that allowed for comparison of the following types of revision TKA:

  • 1-stage, 2-component aseptic revisions (n=1,096)
  • 1 stage, 2-component septic revisions (n=274)
  • First stage of a 2-stage septic revision (n=274)
  • Second stage of a 2-stage septic revision (n=274)

The authors then compared the relative value units (RVUs) for each type of revision TKA. (Medicare uses RVU-based algorithms to reimburse physicians for their services.) The authors also identified operative times for the surgery types and made RVU-per-minute and dollars-per-minute calculations.

The mean operative times were statistically different between each cohort (149 minutes for the aseptic group, 160 minutes for the 1-stage septic group, 138 minutes for the first-stage of the 2-stage septic group, and 170 minutes for the second-stage of the 2-stage septic group). The dollar-per-minute calculation in the “easiest case” of aseptic revision was $7.74 per minute, while in the “hardest case” of a 2-stage septic revision, reimbursement was $5.66 per minute for the first stage and $5.19 per minute for the second stage.

The fact that Medicare’s current reimbursement system does not account for the complexity of treating an infected TKA harms not only surgeons. Financially discouraging physicians from taking complex cases could lead to patients having a difficult time finding a doctor to treat their infected knee replacement. This entire predicament warrants further investigation, possible adjustments to the RVU system, and more realistic valuations of time in the OR.

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

Virtual PT Noninferior to and Less Expensive than Usual Care

OrthoBuzz occasionally receives posts from guest bloggers. In response to a recent study in The Journal of Bone & Joint Surgerythe following commentary comes from Jaime L Bellamy, DO.

The most common complication arthroplasty surgeons worry about after total knee arthroplasty (TKA) is stiffness, which occurs in a reported 15.98% of cases.1 The notion of TKA patients doing their postoperative physical therapy (PT) on their own at home with a “virtual avatar” gives me pause because it might increase the risk of stiffness. However, if patients could save money, make satisfactory progress in the comfort of their own home, and not experience undue knee stiffness, virtual PT technology would be worth it.

In the January 15, 2020 issue of The Journal, Bettger et al. report on a randomized controlled trial that compared virtual to traditional PT after TKA. The authors hypothesized that virtual PT would cost less and would be clinically noninferior to traditional PT. The  FDA-approved Virtual Exercise Rehabilitation Assistant (VERA) studied in this trial uses 3-D technology to track patient movement and an avatar (digitally simulated coach) to assist patients through PT exercises. Virtual PT technology like this not only has the potential to reduce costs (particularly travel costs incurred by patients who live in rural areas), but also to help address current and expected therapist shortages.

There were 143 patients in the virtual PT group and 144 in the traditional PT group. Patients randomized to virtual PT had the technology set up in their home prior to surgery. In addition to avatar-assisted home exercises, virtual PT patients had weekly “video visits” with a human therapist.

Bettger et al. found the median 12-week costs for virtual and traditional PT to be $1,050 and $2,805, respectively. Additionally, at 6 weeks, virtual PT was found to be noninferior to traditional PT in terms of patient outcome measures, knee range of motion, and gait speed. At 12 weeks, virtual PT was found to be noninferior to usual care in terms of pain and hospital readmissions.

I am relieved that virtual PT has the potential to provide cost savings, without apparently increasing the risk of knee stiffness. The cost savings and at-home convenience may be especially important for elderly TKA patients who are living on a fixed income and for whom transportation issues are often vexing. I hope technology like VERA continues to contribute to improved patient satisfaction and easier access to PT.

Jaime L. Bellamy, DO (@jaimelbellamyDO) is an orthopaedic surgeon specializing in hip and knee reconstruction in Fort Bragg, NC and a member of the JBJS Social Media Advisory Board.

Reference

  1. Can administrative data be used to analyze complications following total joint arthroplasty? Clair AJ, et al. J Arthroplasty, 2015;30(9 Suppl):17-20. http://dx.doi.org/10.1016/j.arth.2015.01.060

Highly Cross-Linked Poly Adds No Benefit to Most TKAs

The preponderance of published orthopaedic evidence supports the use of highly cross-linked polyethylene (HXLPE) in acetabular components for patients undergoing total hip arthroplasty (THA). (See related OrthoBuzz post.) But the literature is filled with conflicting findings about the benefits of HXLPE for those undergoing total knee arthroplasty (TKA). Seeking clarity, in the January 15, 2020 issue of The Journal of Bone & Joint Surgery, Partridge et al. report findings from a registry-based cohort analysis of more than a half-million TKAs, comparing revision rates among those using conventional polyethylene (CPE) with those using HXLPE.

The authors analyzed TKA data captured by the National Joint Registry for England, Wales, and Northern Ireland during the period from 2003 to 2014. Of the >550,000 procedures examined, only about 10% utilized HXLPE. When the authors compared adjusted aseptic revision rates per 100 years observed within the three most common TKA systems in the database (NexGen by Zimmer, PFC Sigma by DePuy, and Triathlon by Stryker), they found no significant differences between HXLPE and CPE after a maximum follow-up of 12 years.

The only notable difference between the two polyethylene types was found in patients <60 years old and/or those with BMI >35 kg/m2, in whom the second-generation Stryker X3 HXLPE showed significantly better survival than its CPE counterpart. In explaining why the benefits of HXLPE seen in THA might not translate to TKA, Partridge et al. contrast the “ball and socket” hip joint with the wear mechanisms in TKA, which involve “rolling, sliding, and rotational motion that potentially put the polyethylene insert at greater risk of wear by delamination, pitting, and fatigue failure.”

The authors conclude that the extra costs of HXLPE bearings for TKA may not be justified for most TKA patients in the intermediate term, but commentator Remy Simon Nizard, MD notes that “other uncontrolled or insufficiently controlled parameters [such as quality of component positioning] may have had an influence on the results.”  While Partridge et al. call for “additional follow-up,” Dr. Nizard questions whether full-blown clinical trials investigating alternative bearings in TKA are justified, “given the emerging subject of the burden of research waste.”

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