UKA: Alignment and Overhang Matter
(Reproduced, with permission, from Orthop Traumatol Surg Res. 2016 Apr;102[2]:183-7. Copyright © 2016 Elsevier Masson SAS. All rights reserved.)
These operations were performed by a group of fairly experienced surgeons who averaged >14 UKAs per year, although a commonly used threshold for a “high-volume” UKA surgeon is >15 procedures per year. The cumulative revision rate of 14.2% over 8.7 years, the 5-year Kaplan-Meier survival rate of 88%, and the 10-year survival rate of 70% found by Kazarian et al. are disturbing. Using revision as an endpoint may be problematic because some surgeons are quick to revise a UKA when the radiographic evaluation of component placement is not perfect. Still, this study demonstrates that radiographically determined alignment and overhang “outliers” and “far outliers” had a significantly increased risk of implant failure, compared with patients with good alignment and overhang.
This study did not include UKAs that used computer-assisted methods, but it seems safe to conclude that computer-assisted component placement would be more reliable than “eyeballing,” especially among surgeons with less-experienced eyes. Based on this and other recent studies, I think a controlled trial comparing the functional outcomes and revision rates of UKAs performed with and without computer assistance is warranted.
Marc Swiontkowski, MD
JBJS Editor-in-Chief
Editor’s Note: Click here to read the JBJS Clinical Summary on Unicompartmental Knee Arthroplasty.
What’s New in Adult Reconstructive Knee Surgery 2020
Every month, JBJS publishes a review of the most pertinent and impactful studies published in the orthopaedic literature during the previous year in 13 subspecialties. Click here for a collection of OrthoBuzz summaries of these “What’s New” articles. This month, author Michael J. Taunton, MD selected the 5 most clinically compelling findings from the more than 130 studies summarized in the January 15, 2020 “What’s New in Adult Reconstructive Knee Surgery.”
Unicompartmental Knee Arthroplasty (UKA)
—A prospective cohort study of 1,000 Oxford cementless UKAs indicated by standard Kozinn and Scott criteria found that revision-free survivorship at 10 years was 97%. Progression of lateral osteoarthritis and dislocation of the bearing were the most common reasons for revision.1
Pain Management
—Authors of a double-blinded, prospective, randomized study assigned 60 primary total knee arthroplasty (TKA) patients to receive either a continuous adductor canal block or a single-injection adductor canal block with adjuvant agents. They found no between-group differences in pain scores up to 42 hours postoperatively.2
Post-TKA Physical Therapy (PT)
—A prospective, randomized, noninferiority trial demonstrated that 290 post-TKA patients who were randomized to either outpatient PT, unsupervised web-based PT at home, or unsupervised printed-instruction-based PT at home had no difference in knee range of motion or in patient-reported outcomes at 4 to 6 weeks or 6 months postoperatively.3
Infection Prevention
—In a retrospective review of 29,695 total joint arthroplasties, preoperative penicillin allergy testing led to a 1.19% higher rate of infection-free survival at 10 years, principally by allowing more routine use of the prophylactic antibiotic cefazolin.4
Revision TKA
—A retrospective case series found that patients undergoing revision TKA at an age of < 50 years had a survivorship free of re-revision of 66% at 10 years. Regardless of the reason for revision, this population also had a higher risk of mortality than the general population at 10 years.5
References
- Campi S, Pandit H, Hooper G, Snell D, Jenkins C, Dodd CAF, et al. Ten-year survival and seven-year functional results of cementless Oxford unicompartmental knee replacement: A prospective consecutive series of our first 1000 cases. Knee. 2018 Dec;25(6):1231-7. Epub 2018/08/29.
- Turner JD, Dobson SW, Henshaw DS, Edwards CJ, Weller RS, Reynolds JW, et al. Single-Injection Adductor Canal Block With Multiple Adjuvants Provides Equivalent Analgesia When Compared With Continuous Adductor Canal Blockade for Primary Total Knee Arthroplasty: A Double-Blinded, Randomized, Controlled, Equivalency Trial. J Arthroplasty. 2018 Oct;33(10):3160-6 e1. Epub 2018/06/16.
- Fleischman AN, Crizer MP, Tarabichi M, Smith S, Rothman RH, Lonner JH, et al. 2018 John N. Insall Award: Recovery of Knee Flexion With Unsupervised Home Exercise Is Not Inferior to Outpatient Physical Therapy After TKA: A Randomized Trial. Clin Orthop Relat Res. 2019 Jan;477(1):60-9. Epub 2019/02/23.
- Wyles CC, Hevesi M, Osmon DR, Park MA, Habermann EB, Lewallen DG, et al. 2019 John Charnley Award: Increased risk of prosthetic joint infection following primary total knee and hip arthroplasty with the use of alternative antibiotics to cefazolin: the value of allergy testing for antibiotic prophylaxis. Bone Joint J. 2019 Jun;101-B(6_Supple_B):9-15. Epub 2019/05/31.
- Chalmers BP, Pallante GD, Sierra RJ, Lewallen DG, Pagnano MW, Trousdale RT. Contemporary Revision Total Knee Arthroplasty in Patients Younger Than 50 Years: 1 in 3 Risk of Re-Revision by 10 Years. J Arthroplasty. 2019 Jul;34(7S):S266-S70. Epub 2019/03/03.
Expanded Indications for Medial UKA?
Along with recently renewed interest in unicompartmental knee arthroplasty (UKA) has come debate as to whether the preoperative presence of patellofemoral osteoarthritis (OA) and/or abnormal patellofemoral alignment should be considered UKA contraindications. Findings from a retrospective review of 639 knees by Burger et al. in the September 18, 2019 issue of The Journal of Bone & Joint Surgery strongly suggest that the answer is “no.”
After examining preoperative radiographic OA and alignment characteristics and postoperative patient-reported outcomes among patients who underwent fixed-bearing medial UKA, the authors concluded that “neither the [radiographic] presence of preoperative mild to moderate [patellofemoral] osteoarthritis nor abnormal patellar tilt or congruence compromised [patient-reported knee and patellofemoral-specific] outcomes at intermediate-term follow-up [mean of 4.3 ±1.6 years].”
Expanding the surgical inclusion criteria for UKA based on these findings could increase the number of patients eligible for UKA by 20% to 40%, estimated Burger et al. In the practice of the senior author (Andrew D. Pearle, MD), patients with symptoms of patellofemoral OA (such as anterior knee pain with prolonged sitting or stair-climbing) are considered ineligible for UKA, prompting the authors to suggest that “the presence of such symptoms may be better than radiographic criteria for determining which patients are eligible for medial [UKA].”
Cost Analysis of Treatments for Unicompartmental Knee Arthritis: UKA Wins
Surgical treatment for knee osteoarthritis (OA) has become increasingly common. The many people who have damage to only one part of their joint (unicompartmental knee OA) are faced with three options—total knee arthroplasty (TKA), unicompartmental knee arthroplasty (UKA), or nonsurgical treatment. A study by Kazarian et al. in the October 3, 2018 issue of The Journal estimates the lifetime cost-effectiveness for those three options in patients from 40 to 90 years of age.
The authors used sophisticated computer modeling to estimate both direct costs (those related to medical/surgical care) and indirect costs (such as missed workdays) of the three options as a function of patient age at the time of treatment initiation. Here are the key findings:
- The surgical treatments were less expensive and provided patients from 40 to 69 years of age with a greater number of quality-adjusted life years (QALYs) than nonsurgical treatment.
- In patients 70 to 90 years of age, surgical treatments were still cost-effective compared with nonsurgical treatment, albeit less so than in younger patients. In this older age group, “cost-effectiveness ratios” of surgical treatment remained below a “willingness to-pay” threshold of $50,000 per QALY.
- When the two surgical treatments were compared to one another, UKA beat TKA decisively in cost-effectiveness among patients of any age.
After crunching more numbers, Kazarian et al. estimated that, by 2020, if all of the patients with unicompartmental knee OA who were candidates for UKA or TKA (a projected total of 120,000 to 210,000 people) received UKA, “it would lead to a lifetime cost savings of $987 million to $1.5 billion.
From these findings, the authors conclude that patients with unicompartmental knee OA should receive surgical treatment, preferably UKA, instead of nonsurgical treatment until the age of 70 years. After that age, all three options are reasonable from a cost-effectiveness perspective.
But perhaps the most important thing to remember about these findings is that they add information to—but should not replace—clinical decision-making based on complete and open communication between doctor and patient.
New Knee Content from JBJS
The recently launched JBJS Knee Spotlight offers highly relevant and potentially practice-changing knee content from the most trusted source of orthopaedic information.
Here are the five JBJS articles to which you will have full-text access through the Knee Spotlight during the month of March 2017:
- Improved Accuracy of Component Positioning with Robotic-Assisted Unicompartmental Knee Arthroplasty: Data from a Prospective, Randomized Controlled Study
- The Effect of Timing of Manipulation Under Anesthesia to Improve Range of Motion and Functional Outcomes Following Total Knee Arthroplasty
- Anatomic Single-Bundle ACL Reconstruction Is Possible with Use of the Modified Transtibial Technique: A Comparison with the Anteromedial Transportal Technique
- Autologous Chondrocyte Implantation in the Knee: Mid-Term to Long-Term Results
- Outcomes of Unicompartmental Knee Arthroplasty After Aseptic Revision to Total Knee Arthroplasty: A Comparative Study of 768 TKAs and 578 UKAs Revised to TKAs from the Norwegian Arthroplasty Register (1994 to 2011)
Knee studies offered on the JBJS Knee Spotlight will be updated monthly, so check the site often.
JBJS Editor’s Choice: Biomechanics Alone or Biomechanics + UKA for Painful Varus Knees?
In the January 18, 2017 issue of JBJS, Krych et al. report on early and mid-term results of the two most common surgical procedures to help patients 55 years old and younger with varus knees and medial compartment osteoarthritis: unicompartmental knee arthroplasty (UKA) and proximal tibial osteotomy (PTO). PTO realigns the knee’s biomechanics by moving the weight-bearing line laterally toward the more normal side of the knee. UKA corrects the biomechanical issue and removes and resurfaces damaged tissue.
In this comparative cohort study of 240 patients between 18 and 55 years old, patients receiving UKA had better functional scores and reached a higher activity level early after surgery. UKA survivorship (defined as avoiding revision to total knee arthroplasty [TKA]) was 94% at an average of 5.8 years, while PTO survivorship was 77% at an average of 7.2 years.
The functional outcomes should come as no surprise, seeing as arthroplasty replaces/denervates the subchondral bone in the medial compartment, while also correcting the alignment issue. A reasonable trauma-related analog to this can be seen with total hip arthroplasty providing generally better functional outcomes for displaced femoral neck fractures than internal fixation because the latter approach does not anatomically restore hip biomechanics. In both those cases, the mechanics of a weight-bearing joint are maintained/improved without relying on bone to heal. In contrast, with PTO and other bone and joint “preservation” approaches, the natural mechanics are altered.
However, I do not think we should extend this argument beyond what these data from Krych et al. provide. The mean length of follow-up in the UKA group was only 5.8 years. We need 20- to 30-year results in that group so we can truly understand the risk of further arthroplasty revision, polyethylene replacement, periprosthetic fracture, etc. I therefore truly hope to see follow-up reporting in a decade on this cohort of patients.
We must also recognize that these patients were selected for a surgical intervention based on their functional demand. The baseline characteristics of both groups suggest that those who had higher loading “habits” received an osteotomy.
Marc Swiontkowski, MD
JBJS Editor-in-Chief
UKA-to-TKA and TKA-to-TKA Revisions: Outcomes Same
Many surgeons recommend primary unilateral knee arthroplasty (UKA) over primary total knee arthroplasty (TKA) or tibial osteotomy for younger patients with unicompartmental knee osteoarthritis. Some do so believing that the results of any subsequent revision to TKA (UKA → TKA) will be better than a revision of a primary TKA to a second TKA (TKA → TKA).
A comparative, registry-based study by Leta et al. in the March 16, 2016 JBJS found that both revision categories yielded essentially the same outcomes. The authors found no significant differences between the two strategies in terms of overall implant survival rate or risk of re-revision, or in several patient-reported outcomes: the EuroQol EQ-5D, KOOS, and VAS pain and satisfaction scores. Two notable exceptions were as follows:
- The risk of re-revision was twice as high for TKA → TKA patients who were older than 70 years of age
- UKA → TKAs were more often re-revised because of a loose tibial component and pain alone, while TKA → TKAs were more often re-revised because of deep infection.
With few significant outcome differences, commentator Geoffrey Dervin, MD suggests that “patients facing the initial decision between UKA and TKA should focus more on differences in perioperative morbidity, clinical outcomes, and satisfaction” from the primary procedure rather than on the outcomes of revision should it be required.
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