Unicondylar Knee Arthroplasty Has Fewer Complications but Higher Revision Rates Than Total Knee Arthroplasty in a Study of Large United States Databases

Hybrid Oxford unicompartmental knee arthroplasty has lower residual cement extrusion than cemented arthroplasty in treating end-stage unicompartmental knee osteoarthritis

Background

Hybrid Oxford unicompartmental knee arthroplasty (OUKA) consists of cementless femoral prostheses and cemented tibial prostheses. Although a hybrid OUKA has been used in clinical practice, the clinical outcome has not been reported. The purpose of this study was to compare the short-term clinical outcomes and rate of residual bone cement extrusion between hybrid and cemented prostheses and analyse the possible reasons for differences between outcomes.

Methods

A total of 128 knees (118 patients) with end-stage osteoarthritis were included in this study, of which underwent consecutive operations using unicondylar Oxford phase 3 implants from July 2017 and September 2019 in our centre. Follow-up was performed at 6 weeks, 3 and 6 months, 1 year and every year after operation, and complications and changes in the Oxford knee score (OKS) were recorded. The OKS of the two groups was analysed by the generalized estimating equation approach. Prosthesis-based standard fluoroscopy was performed in a timely manner after each operation, and the rate of residual cement extrusion of the two groups was estimated using T-tests and a multivariate regression analysis.

Results

Excluding the cases that lost follow-up, a total of 120 knees (65 in hybrid group and 55 in cemented group) were included in the analysis. There was no statistically significant difference in patient characteristics between the two groups (p > 0.05). The average follow-up time was 23.4 months (and ranged from 12 to 38 months). As of the last follow-up, there were no complications, such as dislocation, fracture, prosthesis loosening and subsidence, but one patient in the cemented group experienced symptoms caused by residual loose cement. Postoperative OKS in both groups improved significantly (p < 0.001). There was no significant difference in the OKS at any point during the follow-up or in the improvement of the OKS between the two groups (p > 0.05). Residual cement was mainly extruded behind the tibial prosthesis. The rate of hybrid periprosthetic residual cement extrusion was significantly lower in the hybrid group than in the cemented group, and the difference was statistically significant (OR = 3.38; p = 0.014).

Conclusions

Hybrid OUKA is as effective as cemented OUKA in the short term after operation and can significantly reduce the residual cement extrusion rate around the tibial prosthesis.

Relevance of the Tibial Slope on Functional Outcomes in ACL-Deficient and ACL Intact Fixed-Bearing Medial Unicompartmental Knee Arthroplasty

BACKGROUND

Excessive posterior tibial slope in medial unicompartmental knee arthroplasty (UKA) has been implicated in early failure. The purpose of this study was to evaluate the relationship between preoperative posterior tibial slope and postoperative slope of the implant (PSI) on outcomes in patients with anterior cruciate ligament (ACL) intact and ACL-deficient knees after fixed-bearing medial UKA.

METHODS

Patients who underwent a medial UKA between 2002 and 2017 with a minimum 3-year follow-up were included. Preoperative posterior tibial slope and postoperative PSI were measured. Outcomes measures included Knee Injury and Osteoarthritis Outcomes Score (KOOS) subscales, Lysholm, and VR-12. Failure was defined as conversion to total knee arthroplasty.

RESULTS

Of 241 knees undergoing UKA, 131 patients (70 women, 61 men; average age of 65 ± 10 years (average BMI of 27.9 ± 4) were included. For all patients, survivorship was 98% at 5 years and 96% at 10 years with a mean survival time for UKA was 15.2 years [95% CI: 14.6-15.7]. No failure had a PSI >7°. There were no superficial or deep infections. There were no significant differences in outcome scores between the ACL intact and the ACL-deficient group; therefore, the data were combined for analysis. At mean 8-year follow-up, KOOS pain scores were better in patients with PSI ≤7° (87 ± 16) than those with PSI >7° (81 ± 15). 76% of patients with PSI ≤7° reached the Patient Acceptable Symptom State for KOOS pain; whereas, 59% of patients with PSI >7° reached PASS for KOOS pain (P = .015).

CONCLUSION

Patients with postoperative posterior slope of the tibial implant >7° had significantly worse postoperative pain, without conversion to TKA, and with maintenance of high function. In ACL deficient and intact knees, nonrobotically-assisted, fixed-bearing medial UKA had a 96% survivorship at 10 years.

Patient-acceptable symptom state for reporting outcomes following unicompartmental knee arthroplasty : a matched pair analysis comparing UKA in ACL-deficient versus ACL-intact knees

AIMS

The patient-acceptable symptom state (PASS) is a level of wellbeing, which is measured by the patient. The aim of this study was to determine if the proportion of patients who achieved an acceptable level of function (PASS) after medial unicompartmental knee arthroplasty (UKA) was different based on the status of the anterior cruciate ligament (ACL) at the time of surgery.

METHODS

A total of 114 patients who underwent UKA for isolated medial osteoarthritis (OA) of the knee were included in the study. Their mean age was 65 years (SD 10). No patient underwent a bilateral procedure. Those who had undergone ACL reconstruction during the previous five years were excluded. The Knee injury Osteoarthritis Outcome Score Activities of Daily Living (KOOS ADL) function score was used as the primary outcome measure with a PASS of 87.5, as described for total knee arthroplasty (TKA). Patients completed all other KOOS subscales, Lysholm score, the Western Ontario and McMaster Universities Osteoarthritis Index, and the Veterans Rand 12-item health survey score. Failure was defined as conversion to TKA.

RESULTS

Survivorship at ten years was 97% in both the ACL-deficient and ACL-intact groups. The mean survival was 16.1 years (95% confidence interval (CI) 15.3 to 16.8) for the ACL-deficient group and 15.6 years (95% CI 14.8 to 16.361) for the ACL-intact group (p = 0.878). At a mean of nine years (SD 3.5) in the ACL-deficient group, 32 patients (87%) reached the PASS for the KOOS ADL. In the ACL-intact group, at a mean of 8.6 years (SD 3) follow-up, 63 patients (85%) reached PASS for the KOOS ADL. There was no significant difference in the percentage of patients who reached PASS for all KOOS subscales and Lysholm between the two groups.

CONCLUSION

PASS was achieved in 85% of all UKAs for KOOS ADL, similar to reports for TKA. Fixed-bearing, medial, non-robotically-assisted UKA resulted in 97% survival at ten years in both the ACL-deficient and ACL-intact groups. There was no significant difference in all outcomes between the two groups. Understanding PASS will allow better communication between surgeons and patients to improve the surgical management of patients with single compartment OA of the knee. This study provides mid- to long-term data supporting the use of PASS to document outcomes following UKA. PASS was met in more than 85% of patients with no differences between ACL-deficient and ACL-intact knees at a mean follow-up of nine years. Cite this article: Bone Joint J 2021;103-B(8):1367-1372.

Robotic Assistance in Unicompartmental Knee Arthroplasty Results in Superior Early Functional Recovery and Is More Likely to Meet Patient Expectations

Robotic technology has reduced the errors of implant alignment in unicompartmental knee arthroplasty (UKA), but its impact on functional recovery after UKA is poorly defined. The purpose of this study was to compare early functional recovery, pain levels, and satisfaction in UKA performed with either robotic assistance or conventional methods. A retrospective analysis was performed on 89 matched consecutive patients who underwent outpatient UKA by a single physician using either conventional instruments (n = 39) or robotic methods (n = 50), with otherwise identical perioperative protocols. Outcomes studied included Lower Extremity Functional Score (LEFS), new Knee Society Score (KSS), Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS-JR.), VR/SF-12, Visual Analog Scale (VAS) pain scores, and perioperative opioid consumption. Patients in the robotic cohort had superior early functional outcomes, with greater LEFS (conventional = 23; robotic = 31) at 1 week post-op (p=0.015) and KOOS-JR (conventional = 74; robotic = 81) at up to 6 months post-op (p=0.037); these two values remained statistically significant after mixed-model regression analysis (p=0.010; p=0.023), respectively. At 1 year post-op, expectations were more likely to be met in those who received robotic assistance (p=0.06). No differences were reported with respect to postoperative opioid usage (p=0.320), reoperations (p=1.00), and complications (p=0.628). Robotic-assisted UKA resulted in more rapid recovery and less early postoperative pain and were more likely to meet expectations than conventional UKA, although functional differences equilibrated by 1 year postoperatively. Further follow-up is necessary to determine if implant durability is impacted by robotics.

Incidence, temporal trends and potential risk factors for aseptic loosening following primary unicompartmental knee arthroplasty: A meta-analysis of 96,294 knees

BACKGROUND

Aseptic loosening (AL) is among the major reasons for revision of failed primary unicompartmental knee arthroplasty (UKA). There is an ongoing temporal increase in the use of UKA with a resultant increase in the revision burden. We aimed to evaluate the incidence of, temporal trends and risk factors for AL.

METHODS

Longitudinal studies reporting the incidence of AL following primary UKA were sought from MEDLINE, Embase, Web of Science and Cochrane Library up to 6th April 2020. Incidence and relative risks (RR) (with 95% confidence intervals) were calculated.

RESULTS

We identified 62 studies for inclusion. Overall, 96,294 primary UKA procedures accounting for 1752 AL cases were included. AL incidence ranged from 0.00% to 22.70% over a 7.7 year weighted mean follow-up. The pooled random effects incidence (95% CI) was 1.77% (1.34-2.25) in the same follow-up period. The annual rate of AL was 0.10% (0.02-0.22). AL incidence increased with length of follow-up, but there was a temporal decrease from the 1970s onwards. Tibial loosening was more common than femoral component loosening: incidence (95% CI) of 1.63% (0.96-2.44) and 0.58% (0.20-1.09) respectively over a weighted follow-up of 6.6 years. Fixed bearing implant design and cemented fixation were both associated with increased AL risk, whereas robotic-assisted surgery was associated with decreased risk.

CONCLUSION

The overall incidence of AL following primary UKA is primarily driven by tibial component loosening and there is a temporal decline in rates. The use of mobile bearing, uncemented implants inserted with robotic assisted surgery may reduce the risk of AL.

Robot-Assisted versus Conventional Total and Unicompartmental Knee Arthroplasty: A Meta-analysis of Radiological and Functional Outcomes

The study aims to provide an up-to-date systematic review and meta-analysis comparing radiological and functional outcomes of total knee arthroplasty (TKA) and unicompartmental knee arthroplasty (UKA) using either robotic assistance or conventional methods from the latest assemblage of evidence. This study was conducted according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) and MOOSE (Meta-analysis of Observational Studies in Epidemiology) guidelines. All studies in PubMed, EMBASE, Medline, and Cochrane that reported radiological and functional outcomes after TKA or UKA with either robotic or conventional methods were included in the review. Selected endpoints for random effects, pairwise meta-analysis included operative details, radiological outcomes (mechanical axis, component angle deviation, and outliers), and functional outcomes (American Knee Society Score, Knee Society Function Score, revision and complication rate, range of motion (ROM), Hospital for Special Surgery score, and Western Ontario and McMaster Universities Osteoarthritis Index). A total of 23 studies comprising 2,765 knees were included from the initial search. Robot-assisted TKA and UKA were associated with significantly better component angle alignment accuracy (low-to-high quality evidence) at the cost of significantly greater operation time. Robot-assisted UKA was found to have significantly better short-term functional outcomes compared with conventional UKA (moderate-to-high quality evidence). Robot-assisted TKA, however, did not exhibit significantly better short- and midterm subjective knee outcome scores compared with its conventional counterpart (high-quality evidence). Robot-assisted TKA and UKA were associated with nonstatistically significant improved ROM and lesser rates of revision. Robot-assisted total and unicompartmental knee arthroplasty leads to better radiological outcomes, with no significant differences in mid- and long-term functional outcomes compared with conventional methods for the former. Larger prospective studies with mid- and long-term outcomes are required to further substantiate findings from the present study.

Total Versus Unicondylar Knee Arthroplasty: Does Race Play a Role in the Treatment Selection?

INTRODUCTION

Racial disparities have been well reported in the utilization and outcomes of knee arthroplasty, but it is unclear whether disparities also extend to the choice of surgical treatment. The primary objective of this study is to identify if race plays a role in the selection of unicondylar versus total knee arthroplasty (UKA, TKA) for isolated tibiofemoral osteoarthritis (OA). A secondary objective is to identify the differences in the complication rates for each procedure by racial identity.

METHODS

A retrospective review of the 2006-2018 American College of Surgeons National Surgical Quality Improvement Program was performed. Asian, Black, Hawaiian/Pacific Islander, Hispanic, Native American/Alaskan, and White individuals who underwent primary elective UKA or TKA were compared in terms of UKA vs. TKA utilization rates and outcomes.

RESULTS

A total of 308,715 patients were analyzed. After controlling for all baseline differences, Whites (3.5%), Asians (3.7%), and Hawaiian/Pacific Islanders (3.1%) had around twice the rate of UKA compared to Blacks (1.6%), while Hispanics (2.1%) and Native American/Alaskans (1.7%) were in between (p <0.001). TKA was associated with higher complications compared to UKA in all racial groups (p < 0.001).

CONCLUSION

Minority patients, especially Blacks, were less likely to receive UKA for treatment of isolated knee OA. This is significant because treatment selection in patients who are eligible for UKA can have a significant impact on postoperative recovery and complications rates.

Unicompartmental Knee Arthroplasty Is Associated With a Lower Rate of Periprosthetic Joint Infection Compared to Total Knee Arthroplasty

Background

Several studies have reported lower perioperative complications with unicompartmental knee arthroplasty (UKA) than with total knee arthroplasty (TKA). However, there is a paucity of data analyzing the incidence of periprosthetic joint infection (PJI) in similar patients undergoing UKA and TKA. As such, we sought to analyze the incidence of UKA and TKA PJI in a large matched population.

Material and Methods

The Mariner data set of the PearlDiver database was queried for all patients undergoing UKA or TKA during 2010-2017. Included patients were required to have at least 2 years of database inclusion after surgery. Patients were then matched at a 1:3 ratio (UKA:TKA) on age, gender, Elixhauser Comorbidity Index, tobacco use, and obesity. Rates of PJI requiring operative intervention within 90 days and 1 year were calculated.

Results

In total, 5636 patients having undergone UKA were matched to 16,890 patients having undergone TKA. Fifteen (0.27%) after UKA and 79 (0.47%) after TKA had a PJI surgically managed within 90 days (risk ratio = 0.57, 95% confidence interval = 0.33-0.99, P = .04). Thirty (0.53%) after UKA and 136 (0.81%) after TKA had a PJI surgically managed within 1 year (risk ratio = 0.66, 95% confidence interval = 0.45-0.98, P = .04).

Conclusions

In a large group of rigorously matched patients, UKA was associated with a significantly lower rate of surgically managed PJI than TKA at 90 days and 1 year; however, the rate of PJI in both groups remained low at <1% at 90 days and 1 year.

Length of Stay and 90-Day Readmission/Complication Rates in Unicompartmental Versus Total Knee Arthroplasty: A Propensity-Score-Matched Study of 10,494 Procedures Performed in a Fast-Track Setup

BACKGROUND

Whether to use unicompartmental knee arthroplasty (UKA) or total knee arthroplasty (TKA) for appropriate osteoarthritis cases is a subject of debate. UKA potentially offers faster recovery and fewer short-term complications. However, reported differences in preoperative comorbidity between TKA and UKA-treated patients could affect outcomes. The aim of this study was to investigate differences in the length of the postoperative hospital stay (LOS) as well as readmissions and complications within 90 days after surgery between matched UKA and TKA cohorts.

METHODS

Patients undergoing UKA or TKA in a fast-track setup at 9 orthopaedic centers from 2010 to 2017 were included in the study. Propensity score matching with exact matching for surgical year was used to address differences in demographics and comorbidity between the UKA and TKA groups, resulting in a matched cohort of 2,786 patients who underwent UKA and 7,708 who underwent TKA. Univariable linear or logistic regression models, multivariable mixed-effects models, and a chi-square test were used to investigate differences in LOS, readmissions, and complications between the UKA and TKA groups.

RESULTS

The UKA group had a shorter median LOS than the TKA group (1 compared with 2 days, p < 0.001). The UKA group was more likely to be discharged on the day of surgery (21.1% compared with 0.5%, odds ratio [OR] = 38.5, 95% confidence interval [CI] = 27.0 to 52.6) and less likely to have an LOS of >2 days (OR = 0.20, 95% CI = 0.17 to 0.24) compared with the TKA group. There was no difference in the 90-day readmission rate (p = 0.611) between the groups. The UKA group had fewer periprosthetic joint infections (OR = 0.50, 95% CI = 0.26 to 0.99) and reoperations (OR = 0.40, 95% CI = 0.20 to 0.81) compared with the TKA group. However, aseptic revisions were more frequent in the UKA group (OR = 2.5, 95% CI = 1.1 to 6.0).

CONCLUSIONS

The UKA group had shorter hospital stays, a higher rate of discharge on the day of surgery, and fewer periprosthetic joint infections and reoperations compared with the matched TKA group. However, the TKA group had fewer aseptic revisions. Our findings support the use of UKA in a fast-track setup when indicated.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Costs of unicompartmental compared with total knee arthroplasty : a matched cohort study over ten years

AIMS

The aim of this study was to compare ten-year longitudinal healthcare costs and revision rates for patients undergoing unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA).

METHODS

The Humana database was used to compare 2,383 patients undergoing UKA between 2007 and 2009, who were matched 1:1 from a cohort of 63,036 patients undergoing primary TKA based on age, sex, and Elixhauser Comorbidity Index. Medical and surgical complications were tracked longitudinally for one year following surgery. Rates of revision surgery and cumulative mean healthcare costs were recorded for this period of time and compared between the cohorts.

RESULTS

Patients undergoing TKA had significantly higher rates of manipulation under anaesthesia (3.9% vs 0.9%; p < 0.001), deep vein thrombosis (5.0% vs 3.1%; p < 0.001), pulmonary embolism (1.5% vs 0.8%; p = 0.001), and renal failure (4.2% vs 2.2%; p < 0.001). Revision rates, however, were significantly higher for UKA at five years (6.0% vs 4.2%; p = 0.007) and ten years postoperatively (6.5% vs 4.4%; p = 0.002). Longitudinal-related healthcare costs for patients undergoing TKA were greater than for those undergoing UKA at one year ($24,771 vs $22,071; p < 0.001) and five years following surgery ($26,549 vs $25,730; p < 0.001); however, the mean costs of TKA were comparable to UKA at ten years ($26,877 vs $26,891; p = 0.425).

CONCLUSION

Despite higher revision rates, patients undergoing UKA had lower mean healthcare costs than those undergoing TKA up to ten years following the procedure, at which time costs were comparable. In the era of value-based care, surgeons and policymakers should be aware of the costs involved with these procedures. UKA was associated with fewer complications at one year postoperatively but higher revision rates at five and ten years. While UKA was significantly less costly than TKA at one and five years, costs at ten years were comparable with a mean difference of only $14. Lowering the risk of revision surgery should be targeted as a source of cost savings for both UKA and TKA as the mean related healthcare costs were 2.5-fold higher in patients requiring revision surgery. Cite this article: Bone Joint J 2021;103-B(6 Supple A):23-31.

2021 Mark Coventry Award: Use of a smartphone-based care platform after primary partial and total knee arthroplasty: a prospective randomized controlled trial

AIMS

The purpose is to determine the non-inferiority of a smartphone-based exercise educational care management system after primary knee arthroplasty compared with a traditional in-person physiotherapy rehabilitation model.

METHODS

A multicentre prospective randomized controlled trial was conducted evaluating the use of a smartphone-based care management system for primary total knee arthroplasty (TKA) and partial knee arthroplasty (PKA). Patients in the control group (n = 244) received the respective institution's standard of care with formal physiotherapy. The treatment group (n = 208) were provided a smartwatch and smartphone application. Early outcomes assessed included 90-day knee range of movement, EuroQoL five-dimension five-level score, Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS JR) score, 30-day single leg stance (SLS) time, Time up and Go (TUG) time, and need for manipulation under anaesthesia (MUA).

RESULTS

Overall, 90-day mean flexion was not significantly different between the control (121° (SD 11.7°)) and treatment groups (121^o; p = 0.559); 90-day mean SLS was 22.7 seconds (SD 9.8) in controls and 24.3 seconds (SD 20.8) in treatment (p = 0.519); 90-day mean TUG times were 10.1 seconds (SD 4.8) in control and 9.3 seconds (SD 3.3) in treatment (p = 0.139). Mean KOOS JR scores were significantly different between control group (73.6 (SD 13.4)) and treatment group (70.4 (SD 12.6); p = 0.026). MUAs were performed in nine (3.7%) patients in the control group and four (1.9%) in the treatment group (p = 0.398). Physiotherapy was performed by 230 (94.4%) of control group and 123 (59.3%) of treatment group (p < 0.001). There were no significant differences between groups in postoperative urgent care visits, or readmissions within 90 days, with significantly fewer emergency department visits in the treatment group (16 (8.2%) vs five (2.5%), p = 0.014).

CONCLUSION

The use of the smartwatch/smartphone care platform demonstrated non-inferiority of clinically significant outcomes to traditional care models, while requiring significantly less postoperative physiotherapy and fewer emergency department visits. This platform could aid in decreasing postoperative costs, while improving patient engagement and communication with the healthcare team. Cite this article: Bone Joint J 2021;103-B(6 Supple A):3-12.

Pinless Navigation in Unicompartmental Knee Arthroplasty

Purpose: In contrast to total knee arthroplasty (TKA), unicompartmental knee arthroplasty (UKA) is a true resurfacing procedure, as none of the ligaments are replaced or released, and the pre-arthritic leg alignment is the major goal. As such, the alignment of the tibial component plays a crucial role in postoperative knee function and long-term survival. Pinless navigation has shown reliable results in total knee arthroplasty. To the best of our knowledge, the use of pinless navigation has not been investigated for UKA. Therefore, the present study investigated whether implantation of the tibial component in 3° varus, which is closer to the anatomical axis, is feasible with a pinless optical navigation system. Methods: 60 patients with the diagnosis of an unicompartmental arthritis, were eligible for UKA and treated with implantation in 3° varus alignment of the tibial component. Two groups were established. In the treatment group the tibial component was aligned using a pinless navigation technique. In the control group, a conventional extramedullary alignment guide was used. A clinical and radiographic follow up took place within 1 year of operation. Results: 57 Patients were eligible for analysis. No clinical incidents were noted in the follow up period. The desired target value, the position of the tibial component, was accurately achieved with an average of 3° medial inclination using the pinless navigation as well as using the conventional technique. Mean incision to suture time was negligible between the two techniques. The mean suture time was 43.2 min with pinless navigation and 42.7 min with the conventional technique. Conclusions: With pinless navigation in UKA, a method was presented that made it possible to achieve sled prosthesis alignment at the level of a high-volume surgeon. These results were achieved with an irrelevant increase of surgical time and without placement of pins.

Patient-specific musculoskeletal models as a framework for comparing ACL function in unicompartmental versus bicruciate retaining arthroplasty

Unicompartmental knee arthroplasty has been shown to provide superior functional outcomes compared to total knee arthroplasty and have motivated development of advanced implant designs including bicruciate retaining knee arthroplasty. However, few validated frameworks are available to directly compare the effect of implant design and surgical techniques on ligament function and joint kinematics. In the present study, the subject-specific lower extremity models were developed based on musculoskeletal modeling framework using force-dependent kinematics method, and validated against in vivo telemetric data. The experiment data of two subjects who underwent TKA were obtained from the SimTK "Grand Challenge Competition" repository, and integrated into the subject-specific lower extremity model. Five walking gait trials and three different knee implant models for each subject were used as partial inputs for the model to predict knee biomechanics for unicompartmental, bicruciate retaining, and total knee arthroplasty. The results showed no significant differences in the tibiofemoral contact forces or angular kinematic parameters between three groups. However, unicompartmental knee arthroplasty demonstrated significantly more posterior tibial location between 0% and 40% of the gait cycle (p < 0.017). Significant differences in range of tibiofemoral anterior/posterior translation and medial/lateral translation were also observed between unicompartmental and bicruciate retaining arthroplasty (p < 0.017). Peak values of anterior cruciate ligament forces differed between unicompartmental and bicruciate retaining arthroplasty from 10% to 30% of the gait cycle. Findings of this study indicate that unicompartmental and bicruciate retaining arthroplasty do not have identical biomechanics and point to the complementary role of anterior cruciate ligament and articular geometry in guiding knee function. Further, the patient-specific musculoskeletal model developed provides a reliable framework for assessing new implant designs, and effect of surgical techniques on knee biomechanics following arthroplasty.

Evaluation of Disease Severity and Health-Related Quality of Life in Patients with Rheumatoid Arthritis Undergoing Total Knee Arthroplasty

;Background: The Total Knee Arthroplasty (TKA) is one of the most common surgical intervention in patients with osteoarthritis (OA) and rheumatoid arthritis (RA). Previous studies suggested a significant improvement in health status after TKA surgery. But we have little data about the Iranian population undergone TKA. In the current clinical study, we evaluated postoperatively health status using reliable tools of MOS SF-36 and WOMAC in OA and RA patients undergoing TKA.

METHODS

In this cohort study, patients with OA and/or RA who were candidates for TKA surgery were included. Using two reliable questionnaires, i.e., WOMAC and SF-36, the quality of life of patients was examined during a period of six months (three monthly intervals) after the surgery. All data were analyzed using IBM SPSS Statistics. Kolmogrov-Smirnov, Kendall's tau, chi-square test and K-related Non-parametric tests were used.

RESULTS

Of the 2126 patients who underwent TKA, there were 2024 diagnosed osteoarthritis and 102 validated RA over one year. The mean ± SD of age and the average BMI were 68.0 ± 7.0 BMI 28.5 kg/m2, respectively. Regarding comorbidities and concurrent disorders, about 14% of cases were diabetic, 42% had cardiovascular diseases, 3% had respiratory diseases, and 12% involved with gastrointestinal diseases. The result of SF-36 dramatically increased during follow up. The central distributions of all domains in the SF-36 questionnaire indicated that most scores increased during the time after surgery. As a consequence, WOMAC and MOS FS-36 indicated statistically significant changes after TKA for those who are suffering from RA or OA.

CONCLUSION

TKA is an effective surgical process, which improves the quality of life in OA and/or RA. In addition, WOMAC and SF-36 examining tools are likely reliable tools with similar results to assess patients' quality of life after TKA surgery.

Rates and Causes of 90-day Complications and Readmissions Following Outpatient Hip and Knee Arthroplasty: A Retrospective Analysis of 525 Patients in a Single Institution

BACKGROUND

Outpatient joint arthroplasty (OJA) has gained increasing popularity and success in a well-defined population. Safety concerns, in terms of complications and readmissions, however still exist.

PATIENTS AND METHODS

This retrospective study included 525 patients (90 primary THAs, 277 primary TKAs, and 158 primary UKAs), initially planned for OJA. All complications and readmissions were evaluated for timing and cause (surgical vs medical) within a 90-day followup. Complications and readmissions were compared by the length of stay (LOS): same-day discharge (SDD) vs ≥1 day. Differences were assessed by the log-rank test. Complications and readmission risk were assessed using multivariable logistic regression analysis.

RESULTS

The complication rate was 9.9% at 30 days and 15% at 90 days. The readmission rate was 2.5% at 30 days and 4.2% at 90 days. The majority of surgical complications and readmissions were the result of wound discharge (43% and 56%, respectively). Overall, we did not observe different rates between SDD and LOS ≥1. Following THA, but not TKA or UKA, the 90-day complication rate was significantly lower in patients that underwent SDD compared with LOS ≥1. The risk of complications was positively associated with TKA (vs THA and UKA), ASA III (vs ASA I), and Charnley C (vs Charnley A). The risk of readmissions was negatively associated with a BMI ranging from 25-29.9 kg/m2 (vs BMI <25 kg/m2).

CONCLUSION

SDD following OJA did not result in more complications and hospital readmissions compared to a prolonged hospital stay. The majority of complications and readmissions were due to noninfected wound discharge.

Radiological outcomes following manual and robotic-assisted unicompartmental knee arthroplasty

Aims

The purpose of this study was to compare the radiological outcomes of manual versus robotic-assisted medial unicompartmental knee arthroplasty (UKA).

Methods

Postoperative radiological outcomes from 86 consecutive robotic-assisted UKAs (RAUKA group) from a single academic centre were retrospectively reviewed and compared to 253 manual UKAs (MUKA group) drawn from a prior study at our institution. Femoral coronal and sagittal angles (FCA, FSA), tibial coronal and sagittal angles (TCA, TSA), and implant overhang were radiologically measured to identify outliers.

Results

When assessing the accuracy of RAUKAs, 91.6% of all alignment measurements and 99.2% of all overhang measurements were within the target range. All alignment and overhang targets were simultaneously met in 68.6% of RAUKAs. When comparing radiological outcomes between the RAUKA and MUKA groups, statistically significant differences were identified for combined outliers in FCA (2.3% vs 12.6%; p = 0.006), FSA (17.4% vs 50.2%; p < 0.001), TCA (5.8% vs 41.5%; p < 0.001), and TSA (8.1% vs 18.6%; p = 0.023), as well as anterior (0.0% vs 4.7%; p = 0.042), posterior (1.2% vs 13.4%; p = 0.001), and medial (1.2% vs 14.2%; p < 0.001) overhang outliers.

Conclusion

Robotic system navigation decreases alignment and overhang outliers compared to manual UKA. Given the association between component placement errors and revision in UKA, this strong significant improvement in accuracy may improve implant survival.

Level of Evidence: III

Cite this article: Bone Jt Open 2021;2-3:191–197.

Coronal Alignment of Fixed-Bearing Unicompartmental Knee Arthroplasty Femoral Component May Affect Long-Term Clinical Outcomes

BACKGROUND

This study aims to investigate the clinical effects of femoral component coronal alignment in a cohort of fixed-bearing unicompartmental knee arthroplasty with clinical and radiological follow-up of 10 years.

METHODS

Prospectively collected registry data of 264 consecutive, cemented, primary fixed-bearing medial unicompartmental knee arthroplasties performed at a single institution from 2004 to 2007 were reviewed. Femoral component coronal angle (FCCA), tibial component coronal angle, and hip-knee-ankle angle were measured on postoperative radiographs. Patients were grouped into acceptable (AG ≤ 3°) and outlier (OG > 3°) groups according to absolute FCCA. Clinical assessment at 6-month, 2-year, and 10-year follow-up was performed using Knee Society Knee and Function Scores, Oxford Knee Score (OKS), and Short Form-36. Fulfillment of expectations, satisfaction, and implant survivorship was recorded.

RESULTS

There was no significant difference in demographics, tibial component coronal angle, hip-knee-ankle angle, and sagittal parameters in both groups. The OG had poorer OKS at 10 years and a larger deterioration from 2 to 10 years compared to AG (P = .02). Increase in FCCA was associated with deterioration in 2-year OKS (adjusted ß = 0.23, P = .01), 10-year OKS (adjusted ß = 0.26, P = .03), and 2-year Short Form-36 physical component score (adjusted ß = -0.44, P = .01). Expectation fulfillment at 2 years was lower in the OG vs the AG (88% vs 100%, P = .03). Both groups had similar 10-year survivorship (99% vs 98%, P = .65).

CONCLUSIONS

FCCA may affect long-term clinical outcomes, but not short-term clinical outcomes nor 10-year survivorship. Given similar limb alignment, coronal and sagittal component positioning, a larger FCCA was associated with poorer outcomes at 10-year follow-up.

Knee Arthroplasty and Gait: Effect on Level Walking-An Overview

BACKGROUND

Knee arthroplasty (KA) aims to restore normal gait, correct joint alignment, improve the quality of life and activities of daily living, and provide pain relief. Hence, the main purpose of this overview was to summarise data from published reviews exploring gait changes during unaided level walking post-KA, thereby providing for recommendations for future practice and research.

METHOD

A systematic review of review (RoR) for articles published in English and since 2010, was conducted online using PubMed and Google Scholar, as per Preferred Reporting Items for Systematic reviews and Metaanalyses guidelines. Predefined eligibility criteria were applied, and the data thus compiled were analysed. Study quality was assessed using AMSTAR-2 checklist.

RESULT

A total of 5 systematic reviews and meta-analysis consisting of 58 primary studies were included in the review. Based on the very limited evidence, it appears that though gait does not normalize post-KA, there seems to be an improvement in spatiotemporal gait parameters over mid to long term with some decline in gains over long term. Further reviews also suggest no benefits with unicompartmental KA in comparison to healthy controls or total KA patients. Further quality of the study was found to be of critically low confidence based on the AMSTAR-2 scale, suggesting that the results should be interpreted with great caution.

CONCLUSION

The overview highlights the knowledge gap and limitations in gait assessment research post-KA with existing heterogeneity in methods and reporting amidst other factors within primary studies, establishing the need for further research.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s43465-020-00342-w.

Bearing dislocation of mobile bearing unicompartmental knee arthroplasty in East Asian countries: a systematic review with meta-analysis

Background

Bearing dislocation is a common postoperative complication of mobile-bearing unicompartmental knee arthroplasty, and East Asian patients tend to be at higher risk. However, whether this high dislocation rate is common in all East Asian populations remains unclear. This meta-analysis was performed to explore this issue and describe various features of dislocation in East Asians, including the onset time, dislocation direction, and re-dislocation rate.

Methods

The literature was searched in PubMed, Embase, Ovid, and Cochrane Library up to May 2020. Studies were scrutinized by two independent authors, and the bearing dislocation rate, onset time, direction, and re-dislocation rate were specifically analyzed. RevMan 5.3 was used for the statistical analysis.

Results

Seven case series from Korea, China, and Japan were included. The pooled analysis showed that the total dislocation rate was 2.37%, while the subgroup analysis showed that the dislocation rate in Korea and other countries was 4.50% and 0.74%, respectively (P < 0.01). Another subgroup analysis of the onset time showed a significant difference before and after the first 5 years postoperatively (P < 0.01). Anterior and posterior dislocations were more frequent than medial and lateral dislocations (P < 0.01). The average re-dislocation rate was 32.45%, which was approximately seven times higher than the primary dislocation rate (P < 0.01).

Conclusion

Our meta-analysis demonstrated that Korea had a higher bearing dislocation rate among East Asian countries, especially in the first 5 years after primary UKA. Anterior and posterior dislocations were common. The most important finding is that the re-dislocation rate can be much higher than the initial dislocation rate.

The projected volume of primary and revision total knee arthroplasty will place an immense burden on future health care systems over the next 30 years

PURPOSE

Total knee arthroplasty (TKA) rates have increased substantially in the recent decades worldwide, with Germany being one of the leading countries in the prevalence of TKA. The aim of this study was to provide an overview of treatment changes during the last decade and to project the expected burden of primary and revision TKA (rTKA) for the next 30 years.

METHODS

Comprehensive nationwide data from Germany was used to quantify primary and revision TKA rates as a function of age and gender. Projections were performed with use of a Poisson regression models and a combination of exponential smoothing and autoregressive integrated moving average models on historical procedure rates in relation to official population projections from 2020 to 2050.

RESULTS

The incidence rate of primary TKAs is projected to increase by around 43% to 299 per 100,000 inhabitants [95% CI 231-368], leading to a projected total number of 225,957 primary TKAs in 2050 (95% CI 178,804-276,442). This increase has been related to a growing number of TKA performed in male patients, with the highest increase modelled in patients between 50 and 65 years of age. At the same time, the annual total number of revision procedures is forecast to increase even more rapidly by almost 90%, accounting for 47,313 (95% CI 15,741-78,885; IR = 62.7 per 100,000, 95% CI 20.8-104.5) procedures by 2050. Those numbers are primarily associated with a rising number of rTKAs secondary to periprosthetic joint infection (PJI).

CONCLUSIONS

Using this country- specific forecast approach, a rising number of primary TKA and an even more rapidly growing number of rTKA, especially for PJI, has been projected until 2050, which will inevitably provide a huge challenge for the future health care system. As many other industrialized nations will face similar demographic and procedure-specific developments, these forecasts should be alarming for many health care systems worldwide and emphasize the tremendous need for an appropriate financial and human resource management in the future.

LEVEL OF EVIDENCE

Level III, prognostic study, economic and decision analysis.

Unicondylar knee replacement versus total knee replacement for the treatment of medial knee osteoarthritis: a systematic review and meta-analysis

BACKGROUND

Since the optimal surgery for isolated medial knee osteoarthritis (OA) is unclear, this study aimed at comparing the effectiveness of unicondylar knee replacement (UKR) with total knee replacement (TKR) for simple medial knee OA.

METHODS

Literature searches of PubMed, Embase, Web of Science, and the Cochrane Library were searched up to 1th April 2020. Only studies comparing UKR with TKR for isolated medial knee OA were included. Data collection and extraction, quality assessment, and data analyses were performed according to the Cochrane standards.

RESULTS

A total of 13 articles with 1888 patients were included, among which, 944 and 944 underwent UKR and TKR, respectively. The analyzed postoperative outcomes were mostly within 5 years of follow-up. The meta-analysis showed that UKR improved knee general function (P < 0.00001) and health (P = 0.02), moreover, reduced post-operative pain (P = 0.01) and complications (P < 0.05) more than TKR. There were no significant differences in postoperative revision (P = 0.252), high-activity arthroplasty score (HAAS) (P = 0.307) and Oxford knee score (OKS) (P = 0.15) between the two techniques.

CONCLUSIONS

The patients of UKR could achieve better clinical results than that of TKR, moreover, there were negligible differences between the two techniques in postoperative revision in the early and mid-term follow-up and surgeons should be aware of the important reasons for revision of UKR. Thus, UKR instead of TKR should be performed in patients with late-stage isolated medial knee OA.

Unicompartmental knee arthroplasty has higher revisions than total knee arthroplasty at long term follow-up: a registry study on 6453 prostheses

PURPOSE

The purpose of this study is to analyse long-term unicompartmental knee arthroplasty (UKA) focusing on survivorship, causes of failure and revision strategy.

METHODS

This study is a retrospective analysis of data from a regional arthroplasty registry for cases performed between 2000 and 2017. A total of 6453 UKAs were identified and the following information was analysed: demographic data, diagnosis leading to primary implant, survivorship, complication rate, causes of failure, revision strategies. UKA registry data were compared with total knee arthroplasty (TKA) registry data of 54,012 prostheses, which were implanted in the same time period.

RESULTS

6453 UKAs were included in the study: the vast majority of them (84.4%) were implanted due to primary osteoarthritis followed by deformity (7.1%) and necrosis of the condyle (5.1%). When compared to TKA, UKA showed lower perioperative complication rate (0.3% compared to 0.6%) but higher revision rate (18.2% at 15 years, compared to 6.2% for TKA). No correlation was found between diagnosis leading to primary implant and prosthesis survival. The most frequent cause of failure was total aseptic loosening (37.4%), followed by pain without loosening (19.8%). Of the 620 UKAs requiring revision, 485 were revised with a TKA and 61 of them required a re-revision; on the other hand, of the 35 cases where another UKA was implanted, 16 required a re-revision.

CONCLUSION

UKA is associated with fewer perioperative complications but higher revision rates when compared to TKA. Its survivorship is not affected by the diagnosis leading to primary implant. Revision surgery of a failed UKA should be performed implanting a TKA, which is associated with a lower re-revision rate when compared to another UKA.

LEVEL OF EVIDENCE

Level 3, therapeutic study.

Excellent survival and outcomes with fixed-bearing medial UKA in young patients (≤ 60 years) at minimum 10-year follow-up

PURPOSE

To evaluate whether long-term (10-year minimum) patient outcomes and survival of fixed-bearing medial unicompartmental knee arthroplasty (UKA) in patients aged  ≤ 60 years were favorable despite non-conventional age criteria.

METHODS

The authors reviewed the records of 91 consecutive medial UKAs performed in patients aged ≤ 60 by a single surgeon. All patients received the same fixed-bearing M/G Unicompartmental Knee System. Patients records were updated, noting complications or revisions, and Oxford Knee Scores and overall satisfaction collected. If deceased, the general practitioner or next of kin provided data.

RESULTS

Of the initial 91 knees, 10 were revised, 6 were deceased, and 1 was lost to follow-up. The final cohort of 74 knees was aged 54.3 ± 4.3 years (range 41.8-60.6) at index surgery. Using revision of any component as endpoint, the present series had a KM survival of 92.9% (CI 84.8-96.7%) at 10 years, and 87.8% (CI 78.4-93.2%) at 15 years, and a single non-fatal DVT was reported. At final follow-up of 15 ± 1.3 years (range 11-18), OKS (available for all 74 knees) was 38.4 ± 8.4 (range 18-48). Overall patients were pleased or very pleased with 72 of the knees (97%).

CONCLUSION

Fixed-bearing medial UKA yields favorable results in the treatment of single compartment osteoarthritis of the knee in patients ≤ 60 years. The present study demonstrates low complication rates, good-to-excellent long-term patient outcomes, and satisfactory implant survival for this age group considering the advantages of UKA.

LEVEL OF EVIDENCE

Level IV, retrospective cohort study.

Unicompartmental knee arthroplasty and revision total knee arthroplasty have a lower risk of venous thromboembolism disease at 30 days than primary total knee arthroplasty

Background

While multiple studies have demonstrated a lower venous thromboembolism disease (VTED) risk for unicompartmental knee arthroplasty (UKA) compared to primary total knee arthroplasty (TKA), recent reports have shown that revision TKA also had a lower VTED risk compared to primary TKA, an unexpected finding because of its theoretical increased risk. Given the paucity of up-to-date comparative studies, our goal was to perform a high-powered VTED risk comparison study of UKA and revision TKA to primary TKA using recent data.

Methods

The National Surgical Quality Improvement Program (NSQIP) database was queried between 2011 and 2018, and we identified 213,234 patients for inclusion: 191,810 primary TKA, 9294 UKA, and 12,130 revision TKA. Demographics, medical comorbidities, and possible VTE risk factors were collected. Thirty-day outcomes, including deep vein thrombosis (DVT), pulmonary embolism (PE), and all-cause VTED were compared between knee arthroplasty types.

Results

On multivariate analysis, UKA was significantly associated with lower rates of DVT [OR 0.44 (0.31–0.61); P < 0.001], PE [OR 0.42 (0.28–0.65); P < 0.001], and all-cause VTED [OR 0.42 (0.32–0.55); P < 0.001] when compared to primary TKA. Revision TKA was significantly associated with lower rates of PE [OR 0.62 (0.47–0.83); P = 0.002], and all-cause VTED [OR 0.82 (0.70–0.98); P = 0.029] when compared to primary TKA.

Conclusions

Utilizing recent data from a nationwide patient cohort and controlling for confounding variables, our results showed that both revision TKA and UKA had a lower risk of VTED compared to primary TKA, corroborating the results of recent investigations. Additional prospective investigations are needed to explain this unexpected result.

Pain management of unicompartmental (UKA) vs. total knee arthroplasty (TKA) based on a matched pair analysis of 4144 cases

Unicompartmental knee arthroplasty and total knee arthroplasty are well established treatment options for end-stage osteoarthritis, UKA still remains infrequently used if you take all knee arthroplasties into account. An important factor following knee arthroplasty is pain control in the perioperative experience, as high postoperative pain level is associated with persistent postsurgical pain. There is little literature which describes pain values and the need for pain medication following UKA and/or TKA. So far, no significant difference in pain has been found between UKA and TKA. The aim of the study was to evaluate differences in the postoperative course in unicompartmental knee arthroplasty vs. total knee arthroplasty regarding the need for pain medication and patient-reported outcomes including pain scores and side effects. We hypothesized that unicompartmental knee arthroplasty is superior to total knee arthroplasty in terms of postoperative pain values and the need of pain medication. In this project, we evaluated 2117 patients who had unicompartmental knee arthroplasty and 3798 who had total knee arthroplasty performed, from 2015 to 2018. A total of 4144 patients could be compared after performing the matched pair analysis. A professional team was used for data collection and short patient interviews to achieve high data quality on the first postoperative day. Parameters were compared after performing a 1:1 matched pair analysis, multicenter-wide in 14 orthopedic departments. Pain scores were significantly lower for the UKA group than those of the TKA group (p < 0.001 respectively for activity pain, minimum and maximum pain). In the recovery unit, there was less need for pain medication in patients with UKA (p = 0.004 for non-opioids). The opiate consumption was similarly lower for the UKA group, but not statistically significant (p = 0.15). In the ward, the UKA group needed less opioids (p < 0.001). Patient subjective parameters were significantly better for UKA. After implantation of unicompartmental knee arthroplasty, patients showed lower pain scores, a reduced need for pain medication and better patient subjective parameters in the early postoperative course in this study.

The unicompartmental knee is the preferred side in individuals with both a unicompartmental and total knee arthroplasty

PURPOSE

To determine the preferred knee in patients with both one total and one unicompartmental knee arthroplasty.

METHOD

Patients simply with a unicompartmental (UKA) and total knee arthroplasty (TKA) on contralateral sides were retrospectively screened from three senior knee surgeon's logs over a 15 year period. Patients safe and free from other diseases to affect gait were approached. A total of 16 patients (mean age 70 ± 8) agreed to ground reaction force testing on an instrumented treadmill at a fair pace and incline. A gender-ratio identical group of 16 healthy control subjects (mean age 67 ± 10) and 16 patients with ipsilateral medial knee OA (mean age 66 ± 7) were analysed to compare.

RESULTS

Radiographically the mode preoperative Kellgren-Lawrence knee grade for each side was 3. Postoperatively, the TKA side had a mean coronal femoral component alignment of 7° and a mean tibial coronal alignment of 89° with a mean posterior slope of 5° in the sagittal plane. The UKA side had a mean coronal femoral component alignment of 7° and a mean tibial coronal alignment of 86° with a mean posterior slope of 4° in the sagittal plane. In 7 patients, the TKA was the first procedure, while 6 for the UKA and 3 done simultaneously. Gait analysis demonstrated in both walking conditions the UKA limb was the preferred side through all phases of loading (p < 0.05) and nearer to normal than the TKA limb when compared to healthy controls and patients with knee OA. The greatest difference was observed between the transition of weight acceptance and midstance (p = 0.008), when 22% more load was taken by the UKA side.

CONCLUSION

By using a dynamic metric of an everyday activity, a distinct gait difference between differing arthroplasty types were established. A more natural loading pattern can be achieved with unicompartmentals as compared to total knees.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.

Does new instrument for Oxford unicompartmental knee arthroplasty improve short-term clinical outcome and component alignment? A meta-analysis

Background

The Microplasty (MP) instrumentation designed for the Phase III Oxford mobile-bearing unicompartmental knee arthroplasty (UKA) system is considered a better option to achieve more accurate component positioning and alignment. In the present study, we focused on short-term clinical and radiological outcomes to determine whether the MP instrumentation can reduce the short-term revision rate and occurrence of outliers of metallic components.

Methods

The literature in PubMed, Embase, the Cochrane Library, and Web of Science was searched up to May 2020. Studies were scrutinized by two independent authors, and the revision rate, complication spectrum, and radiological assessment with outlier rates were specifically analyzed. RevMan 5.3 was used for the statistical analysis.

Results

Seven studies were included in the meta-analysis. Four studies reported both clinical and radiological outcomes, two reported only radiological outcomes, and one reported only clinical outcomes. The pooled analysis showed that the revision rate in the MP instrumentation group was 0.866 per 100 component years, while that in the control group was 1.124 (odds ratio, 0.77; p < 0.05). The subgroup analysis of the bearing dislocation rate showed a significantly greater reduction in the Korean population than in the populations of other countries (p < 0.05). The radiological assessment showed that the alignment of the femoral component was significantly improved (p < 0.05), while that of the tibial component was not (p > 0.05).

Conclusion

The newly developed MP instrumentation for Oxford UKA significantly reduced the revision rate of this treatment. The positioning of the femoral component was also proven to be better by radiological assessments.

Patient-specific instrument for unicompartmental knee arthroplasty does not reduce the outliers in alignment or improve postoperative function: a meta-analysis and systematic review

BACKGROUND

Unsatisfactory alignment in unicompartmental knee arthroplasty (UKA) is one potential cause of postoperative failure. Patient-specific instruments (PSIs) are designed to improve the alignment of the prostheses, but the effect of PSIs on the alignment or clinical outcome is controversial and lacks validated evidence. We conducted a meta-analysis and systematic review to determine the effect of PSIs on UKA outcomes for the first time.

MATERIALS AND METHODS

A systematic literature search in MEDLINE, EMBASE, CNKI (Chinese database) and Cochrane Central Register of Controlled Trials (up to June 2019) was performed to collect studies that compared PSIs with conventional instruments. Two reviewers independently screened all the records on the basis of inclusion and exclusion criteria. Quality assessments with Cochrane's quality assessment tool or Newcastle-Ottawa scale (NOS) were conducted, the data were extracted, and statistical analyses were completed.

RESULTS

Ten studies with 444 knees were included. The meta-analysis confirmed that PSIs contributed to reduced errors in the alignment of the femoral compartment in the sagittal plane (mean difference = - 2.53, CI [- 3.14, - 1.99], P < 0.01) and the tibial compartment in both the coronal (mean difference = - 0.97, CI [- 1.44, - 0.49], P < 0.01) and the sagittal plane (mean difference = - 1.29, CI [- 1.81, - 0.76], P < 0.01). One study supported that PSIs reduced outliers in inexperienced surgeons; however, all studies investigating PSIs among experienced surgeons suggested that PSIs cannot reduce the percentage of outliers. There was no significant difference in the postoperative score (mean difference = - 0.06, CI [- 0.36, 0.23], P = 0.68) or rate of complications (RR = 1.02, CI [0.15, 6.79], P = 0.99) between PSIs and conventional instruments.

CONCLUSION

The findings of this study suggest PSIs could not reduce the percentage of outliers in UKA patients for experts, and postoperative scores and complication rates are not improved by PSIs, compared with conventional instruments. Based on this meta-analysis and systematic review, no practical benefit to UKAs in experts was detected in PSIs. The findings of this study also suggest that PSIs improved alignment of UKA and might be beneficial to inexperienced surgeons, but it is still unclear whether this improvement is clinically significant and the evidence of inexperienced surgeons is limited. Therefore, more high-quality RCTs are need to be carried out in the future.

High Prevalence of Radiographic Outliers and Revisions with Unicompartmental Knee Arthroplasty

BACKGROUND

Alignment outcomes and their impact on implant survival following unicompartmental knee arthroplasty (UKA) are unclear. The purpose of this study was to assess the implant survival and radiographic outcomes after UKA as well as the impact of component alignment and overhang on implant survival.

METHODS

We performed a retrospective analysis of 253 primary fixed-bearing and mobile-bearing medial UKAs from a single academic center. All UKAs were performed by 2 high-volume fellowship-trained arthroplasty surgeons. UKAs comprised <10% of their knee arthroplasty practices, with an average of 14.2 medial UKAs per surgeon per year. Implant survival was assessed. Femoral coronal (FCA), femoral sagittal (FSA), tibial coronal (TCA), and tibial sagittal (TSA) angles as well as implant overhang were radiographically measured. Outliers were defined for FCA (>±10° deviation from neutral), FSA (>15° of flexion), TCA (>±5° deviation from neutral), and TSA (>±5° deviation from 7°). "Far outliers" were an additional >±2° of deviation. Outliers for overhang were identified as >3 mm for anterior overhang, >2 mm for posterior overhang, and >2 mm for medial overhang.

RESULTS

Among patients with a failed UKA, revision was performed at an average of 3.7 years (range, 0.03 to 8.7 years). The cumulative revision rate was 14.2%. Kaplan-Meier survival analysis demonstrated 5 and 10-year survival rates of 88.0% (95% confidence interval [CI] = 82.0% to 91.0%) and 70.0% (95% CI = 56.0% to 80.0%), respectively. Only 19.0% (48) of the UKAs met target alignment for all 4 alignment measures, and only 72.7% (184) met all 3 targets for overhang. Only 11.9% (30) fell within all alignment and overhang targets. The risk of implant failure was significantly impacted by outliers for FCA (failure rate = 15.4%, p = 0.036), FSA (16.2%, p = 0.028), TCA (17.9%, p = 0.020), and TSA (15.2%, p = 0.034) compared with implants with no alignment or overhang errors (0%); this was also true for far outliers (p < 0.05). Other risk factors for failure were posterior overhang (failure rate = 25.0%, p = 0.006) and medial overhang (38.2%, p < 0.001); anterior overhang was not a significant risk factor (10.0%, p = 0.090).

CONCLUSIONS

The proportions of UKA revisions and alignment outliers were greater than expected, even among high-volume arthroplasty surgeons performing an average of 14.2 UKAs per year (just below the high-volume UKA threshold of 15). Alignment and overhang outliers were significant risk factors for implant failure.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Treatment and Outcome of Periprosthetic Joint Infection in Unicompartmental Knee Arthroplasty

BACKGROUND

Periprosthetic joint infection (PJI) after unicompartmental knee arthroplasty (UKA) is a devastating but poorly understood complication, with a paucity of published data regarding treatment and outcomes. This study analyzes the largest cohort of UKA PJIs to date comparing treatment outcome, septic and aseptic reoperation rates, and risk factors for treatment failure.

METHODS

Twenty-one UKAs in 21 patients treated for PJI, as defined by Musculoskeletal Infection Society criteria, were retrospectively reviewed. Minimum and mean follow-up was 1 and 3.5 years, respectively. Fourteen (67%) patients had acute postoperative PJIs. Surgical treatment included 16 debridement, antibiotics, and implant retentions (DAIRs) (76%), 4 two-stage revisions (19%), and 1 one-stage revision (5%). Twenty (95%) PJIs were culture positive with Staphylococcus species identified in 15 cases (71%).

RESULTS

Survivorship free from reoperation for infection at 1 year was 76% (95% confidence interval, 58%-93%). Overall survival from all-cause reoperation was 57% (95% confidence interval, 27%-87%) at 5 years. Two additional patients (10%) underwent aseptic revision total knee arthroplasty for lateral compartment degeneration 1 year after DAIR and tibial aseptic loosening 2.5 years after 2-stage revision. All patients who initially failed PJI UKA treatment presented with acute postoperative PJIs (5 of 14; 36%).

CONCLUSION

Survivorship free from persistent PJI at 1 year is low at 76% but is consistent with similar reports of DAIRs for total knee arthroplasties. Furthermore, there is low survivorship free from all-cause reoperation of 71% and 57% at 2 and 5 years, respectively. Surgeons should be aware of these poorer outcomes and consider treating UKA PJI early and aggressively.

Unicompartmental Knee Arthroplasty: US and Global Perspectives

Unicompartmental knee arthroplasty (UKA) is a treatment option for anteromedial osteoarthritis. Compared with total knee arthroplasty (TKA), UKA offers improved knee range of motion, functional recovery and decreased medical complications. Revision rates continue to be higher with UKA compared with TKA. With current UKA implants, there is no significant difference in mobile bearing or fixed bearing, or between cemented and cementless implants. Enabling technology, such as robotic-assisted surgery, has demonstrated improvements in component positioning, but no long-term difference in survival compared with traditional manual instruments.

Mid-term functional, clinical, and radiological outcomes with factors affecting revision of mobile-bearing medial unicompartmental knee arthroplasty

BACKGROUND

To evaluate and compare the clinical and radiological outcomes of patients subjected to medial unicompartmental knee arthroplasty (UKA).

METHODS

The study included 146 knees of 115 consecutive medial UKAs patients with a minimum five-year follow-up. Pre- and postoperative functional and clinical outcomes were measured using the Visual Analog Scale (VAS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Oxford Knee Score (OKS), American Knee Society Score (AKSS-O), knee range of motion (ROM), and Short-Form Health Survey (SF-36). The Kellgren-Lawrence osteoarthritis (OA) grading system was used for the evaluation of the OA status. The joint line convergence angle (JLCA) of the operated and contralateral knee, the tibiofemoral coronal angle (TFCA), and the tibial slope angle were used in the radiological evaluation.

RESULTS

The mean age of patients was 58.8 ± 7.0 years. The mean follow-up period was 7.41 ± 1.54 years. Good to excellent functional outcomes were obtained according to VAS, WOMAC, OKS, AKSS-O, and SF-36 scores. Insert dislocation was the main reason for revision surgery (nine patients, 90%). Preoperative body mass index (BMI), postoperative BMI, American Society of Anesthesiologists (ASA) Score, postoperative knee flexion contracture, mean increase in postoperative medial joint space (PMJS) height, and OA progression were found to affect the revision status.

CONCLUSIONS

Good to excellent functional, clinical, and radiological outcomes were obtained with medial UKA at a minimum follow-up of five years. Differences in preoperative and postoperative radiological parameters except an increase in PMJS height had no impact on revision status.