Mortality and perioperative complications after unicompartmental knee arthroplasty

The Relationship Between Age and 30-day Outcomes Following Unicompartmental versus Total Knee Arthroplasty

BACKGROUND

An enhanced understanding of the short-term complication profile following unicompartmental knee arthroplasty (UKA) versus total knee arthroplasty (TKA) can improve surgical decision-making and subsequent patient outcomes. This study aimed to determine if the difference in risk of 30-day morbidity and mortality between UKA and TKA varied as a function of patient age.

METHODS

This retrospective study of a national quality improvement database using data from 2014 to 2020 included 403,342 patients undergoing UKA (n = 12,324) or TKA (n = 391,018). A generalized additive model (GAM) evaluated non-linear relationships between primary outcome and predictors (age, procedure type, and procedure type x age interaction) using a 1:5 UKA to TKA matched sample. Probabilities and odds ratios (95% CI [confidence interval]) estimated the relative risk of complications across the age spectrum.

RESULTS

In the GAM, TKA patients relative to UKA had 1.30 higher odds (95% CI 1.19 to 1.43, P < 0.001) of 30-day morbidity and mortality. There was a significant, non-linear relationship between age and the primary outcome (P = 0.02), such that the odds were lowest at younger ages. They increased slowly until about age 65 years, at which point the slope became steeper. The interaction terms for age and procedure type were not significant (P = 0.30). The 30-day probability for short-term complications of a 65-, 75-, and 85-year-old undergoing UKA was 2.1% (95% CI, 1.8 to 2.3), 2.4% (95% CI, 2.0 to 2.8), and 3.2% (95% CI, 2.3 to 4.1), respectively. Conversely, the probability of a 65-, 75-, and 85-year-old undergoing TKA was 2.9% (95% CI, 2.7 to 3.0), 3.6% (95% CI, 3.3 to 3.8), and 5.5% (95% CI, 4.7 to 6.3).

CONCLUSIONS

Patients undergoing UKA had a quantifiable lower likelihood of morbidity or mortality than TKA at all ages. These data can provide individualized risk for UKA and TKA across the age spectrum and could be helpful in counseling patients regarding their risk for perioperative complications.

Preoperative Corticosteroid Injections Are Not Associated with Deep Infection after Unicompartmental Knee Arthroplasty

Prior to unicompartmental knee arthroplasty (UKA), corticosteroid injections (CSI) are a common nonoperative treatment for arthritis. It is unclear whether CSI prior to UKA impacts the likelihood of postoperative infection. This study sought to determine if there is a time- and/or dose-dependent relationship between preoperative CSI and postoperative infection. An administrative claims database was queried for patients undergoing UKA with more than 1 year of pre-enrollment and follow-up. Of 31,676 patients with a UKA who met enrollment criteria, 8,628 patients had a CSI 0 to 3 months prior to surgery, 111 had a CSI 3 to 12 months prior to surgery, and 22,937 never received an injection. Overall, 246 postoperative deep infections were reported (0.8%). Time-dependent and dose-dependent relationships were modeled using multivariable logistic regressions. Postoperative deep infections occurred in 64 patients with CSI 0 to 3 months prior to surgery (0.7%), compared with 0 patients with CSI 3 to 12 months before surgery (0.0%) and 182 controls (0.8%, p = 0.58). CSI within 1 month prior to UKA was not statistically associated with postoperative infection (p = 0.66). Two or more CSI within 3 months prior to UKA were associated with a twofold elevated odds of infection, compared with receiving a single injection (odds ratio [OR]: 2.08, p = 0.03). Univariable predictors of infection included younger age, increasing Charlson Comorbidity Index, smoking, asthma, chronic obstructive pulmonary disease, chronic kidney disease, diabetes, liver disease, and obesity. Multivariable analysis controlling for these characteristics elicited no relationship between recent CSI administration and postoperative infection. CSI within 3 months of surgery (1.5%) or 3 to 12 months (1.8%) were associated with increased conversion to total knee arthroplasty (TKA) compared with those who did not receive an injection (1.1%, p = 0.01), although TKA for indication of periprosthetic joint infection was not statistically different (p = 0.72). Preoperative CSI within 3 months of UKA is not associated with postoperative infection, although significant medical comorbidity does show an association. Preoperative CSI is associated with increased conversion from UKA to TKA for noninfectious indications.

Can single-stage bilateral unicompartmental knee arthroplasty be safely performed in patients over 70?

Background

For patients with bilateral, symptomatic unicompartmental knee arthritis, single-stage bilateral unicompartmental knee arthroplasty (ssBUKA) presents an attractive option. However, most studies have examined younger patient cohorts and the safety of ssBUKA remains controversial for older individuals. Therefore, the purpose of this study was to compare complication rates following ssBUKA for patients ≤70 and > 70 years old.

Methods

A retrospective chart review of 238 patients having undergone ssBUKA was performed, including 134 patients ≤70 and 104 patients >70. Post-operative complications were recorded at the six-week post-operative visit, along with emergency room visits and hospital readmissions within 90 days.

Results

Compared to patients ≤70, patients >70 were more frequently female (43.3% and 55.8%, respectively) (p = 0.037) and had significantly lower body mass index (30.41 ± 4.64 and 27.30 ± 3.68, respectively) (p < 0.001). Patients >70 were discharged home (50%) less commonly than patients ≤70 (73.1%) (p < 0.001). Two patients ≤70 (1.5%) and two patients >70 (1.9%) sought emergency room treatment (p = 0.589), with respiratory complications most common. There were no differences regarding any postoperative complications between patients ≤70 and > 70 years old.

Conclusion

These results suggest that patients >70 can safely undergo ssBUKA, as it does not appear to increase the incidence of early post-operative complications compared to patients ≤70. However, 50% of patients >70 were not able to discharge directly home following surgery.

Hybrid fixation of unicompartmental knee arthroplasty shows equivalent short-term implant survivorship and clinical scores compared to standard fixation techniques

INTRODUCTION

There is a paucity of data regarding hybrid-fixated unicompartmental knee arthroplasty (UKA), and no study directly compared all three available fixation techniques (cementless, cemented, and hybrid). The hypothesis was that hybrid fixation might have a lower incidence of radiolucent lines (RLL) than cemented UKA, with equivalent outcomes to uncemented UKA.

MATERIALS AND METHODS

A total of 104 UKA with a minimal follow-up of 1 year were retrospectively included, of which 40 were cemented, 41 cementless, and 23 hybrid prostheses. The functional outcomes scores included the Oxford Knee (OKS), Subjective Knee (SKS), and Forgotten Joint scores (FJS). RLLs, subsidence, and component positioning were assessed on radiographs.

RESULTS

At a mean follow-up of 28 months, the survival rate was 95% for cemented UKA and 100% for the cementless and hybrid UKA (n.s.), respectively. Postoperative FJS (93 vs. 82 points, p = 0.007) and SKS (4.7 vs. 4.1 points, p = 0.001) were better in cementless than cemented UKA, with hybrid-fixated UKA in between the two (90 and 4.4 points, n.s.). Improvement of OKS preoperatively to postoperatively did not differ between the groups (n.s.). RLLs were more frequent in cemented (23%) compared to cementless (5%, p = 0.021) and hybrid UKA (9%, n.s.). With an incidence of 12%, subsidence occurred more commonly in cementless UKA compared to cemented (5%) and hybrid (0%) (n.s.) UKA.

CONCLUSION

Hybrid fixation achieves equivalent results to standard UKA fixation techniques regarding implant survival and functional and radiological outcomes. Therefore, the hybrid fixation technique seems to be a valuable alternative as it combines the advantages of cemented tibial components with those of uncemented femoral components.

LEVEL OF EVIDENCE

III.

Readmissions and mortality after outpatient vs inpatient unicompartmental knee arthroplasty in Denmark - A propensity score matched study of 5,384 procedures

BACKGROUND

Limited nationwide data on the development of outpatient unicompartmental knee arthroplasty (UKA) practice and patient safety exist. The primary objective of this study on patients receiving a medial or lateral UKA was to investigate 7-, 30- and 90-day readmission risk and 90-day mortality in outpatient vs inpatient surgeries. Secondary to investigate the nationwide development of outpatient UKA surgery in 2014-2018.

METHODS

Included patients received a medial or lateral UKA in the period January 1, 2014 to December 31, 2018 in any Danish hospital. Data were collected from the Danish National Patient Register. The cohort consisted of 1,059 outpatient and 4,325 inpatient surgeries, hereof 5,182 medial and 202 lateral UKA. After propensity score matching (1:1) 1,057 patients were included in each group.

RESULTS

We found a 7-day readmission risk of 1.5 % vs 1.4 % (p = 0.8), 30-day readmission risk of 2.6 % vs 3.2 % (p = 0.3), and 90-day readmission risk of 4.2 % vs 4.8 % (p = 0.4) after outpatient vs inpatient UKA. Similar results were found after matching. We found no significant differences in 90-day mortality for the unmatched or matched cohorts. The amount of outpatient UKA surgeries in Denmark increased from 86 in 2014 to 214 in 2018.

CONCLUSION

Outpatient medial or lateral UKA seem to be as safe as inpatient UKA on a nationwide basis.

Disease Progression After Unicompartmental Arthroplasty: Add a Compartment or Revise to Total Knee Arthroplasty?

BACKGROUND

Five percent to 7% of unicompartmental knee arthroplasties (UKA) require revision for disease progression in untreated compartment(s), most commonly to total knee arthroplasty (TKA). TKA requires removal of bone and usually the anterior cruciate ligament. Preserving the UKA and converting to a bicompartmental arthroplasty (BCA) by performing a second UKA is an alternative.

METHODS

The results of 73 UKA-BCA patients were compared to 75 patients treated by UKA-TKA revision. Knee Society, Knee Osteoarthritis Outcome Score Joint Replacement, and patient satisfaction scores were collected by a blinded therapist. Patients were asked about their implant preference and recovery. Twenty-two UKA-BCA revision patients had a UKA (6) or TKA (16) in the contralateral knee; thus, a direct comparison of UKA-BCA to both UKA and TKA was possible.

RESULTS

Of the UKA-BCA patients, 69 (94%) had excellent or good, 2 (3%) fair, and 2 (3%) poor outcomes with 1 patient requiring revision to TKA. Of patients with a TKA in the contralateral knee, 13 (81%) preferred the UKA-BCA replacement and 3 (19%) preferred the TKA. All patients said the UKA-BCA revision recovery was similar or easier than their initial UKA. Of UKA-TKA revisions, 59 (79%) had excellent or good, 9 (12%) fair, and 7 (9%) poor outcomes. There was 1 wound infection and 1 re-revision in the UKA-BCA group and 1 wound infection and 3 re-revisions in the UKA-TKA group. The Knee Osteoarthritis Outcome Score Joint Replacement and Knee Society Scores were better for UKA-BCA compared to UKA-TKA.

CONCLUSION

UKA-BCA is a successful treatment for disease progression following UKA.

Association of alignment variables, posteromedial tibial cartilage wear and anterior cruciate ligament insufficiency in participants with varus knee osteoarthritis: a cross-sectional study

PURPOSE

Total knee arthroplasty (TKA) and unicompartment knee arthroplasty (UKA) are among the most important treatment options for end-stage knee osteoarthritis. Previous papers have noted the importance of knowing the type of medial tibial wear in deciding to manage varus knee osteoarthritis patients with TKA vs UKA. But few studies have delineated the pre-operative variables predicting the type of tibia wear.

METHODS

This study assessed individuals with varus knee osteoarthritis planned for knee arthroplasty. After recording the demographic variables, hip-knee-ankle joint alignment views were taken from all patients. Finally, the type of tibial wear encountered during the surgery (posteromedial, non-posteromedial) was documented.

RESULTS

A total of 325 knees and 301 participants were evaluated in the study. Participants aged 67.12 (± SD 8.14) and the male to female ratio was 0.20. Between either non-posteromedial/posteromedial wear or insufficient/sufficient ACL cases, there was a statistically significant difference with regard to MPTA, LDFA, VA, and JCA (P value < 0.05). Sixty-three percent of knees had non-posteromedial wear in the tibia plateau and 37% had posteromedial wear. Posteromedial wear was associated with 95% chance of ACL tear. Non-posteromedial knee had nearly 50% chance of having ACL insufficiency. Among non-posteromedial cases, VA of 14.5 as cut-off value had 65% sensitivity, 90% specificity, 73% negative predictive value, 87% positive predictive value, and 78% accuracy in detecting ACL insufficiency.

CONCLUSION

Posteromedial tibial wear is associated with ACL insufficiency. However, regarding non-posteromedial cases, varus angle > 14.5 is highly predictive of ACL tear (87% positive predictive value).

Periprosthetic joint infection after primary TKA in the medicare population: How frequently are patients revised at a different hospital?

BACKGROUND

Periprosthetic infection (PJI) after total knee arthroplasty (TKA) places a significant burden on hospitals. We sought to describe the proportion of patients undergoing revision for PJI at a different hospital within one year of primary TKA and whether patient characteristics or hospital volume were associated with this change.

METHODS

Medicare data from 2005 to 2014 was retrospectively reviewed using PearlDiver. All patients over 64 years undergoing revision for PJI within one year of primary TKA were stratified by the revision occurring within 90 days. Hospitals were grouped by annual TKA volume as Low (<50), Medium (51-100), High (101-200), and Very High (>200). Associations of patient characteristics and hospital volume with revision at a different hospital were assessed using Chi-squared tests and Somers' D.

RESULTS

Of 8,337 patients undergoing revision within 90 days of TKA, 1,370 (16%) were revised at a different hospital. Changing hospitals was associated with having primary TKA at a lower volume hospital (24% for low, 15% medium, 12% high, and 12% very high; P < 0.001). Of 7,608 patients undergoing revision between 91 and 365 days, 1,110 (15%) were revised at a different hospital. Changing hospitals was associated with having primary TKA at a lower volume hospital (26% for low, 14% medium, 10% high, and 9% very high; P < 0.001). Changing hospitals was not associated with sex or age.

CONCLUSION

Patients frequently undergo revision for PJI at a different hospital, even within 90 days of TKA. Further research is needed to understand these implications of this care pathway shift.

Application of unicompartmental knee arthroplasty in the treatment of knee osteoarthritis

OBJECTIVE

For the treatment of medial compartment knee osteoarthritis, unicompartmental knee arthroplasty was chosen on the basis of the clinical effects and the rate of prosthesis survival. A retrospective analysis was performed on 500 patients with osteoarthritis of the medial compartment knee treated by unicompartmental knee arthroplasty between April 2007 and April 2017. The cohort was comprised of 176 males and 324 females, aged (61.12 ± 8.0) years old. The clinical treatment was evaluated in terms of the range of movement (ROM), the Knee Society score (KSS), and the Oxford knee score.

RESULTS

The follow-up lasted 1.59-11.60 years. Grouped in terms of age, 133 cases were in the middle-age, 295 were in the old-age group, and 72 in the advanced-age group. Against the Iwano classification of the patellofemoral joint, 104 cases were graded 0-1; 179 were graded 2; 182 were graded 3 and 35 were graded 4. The KSS score improved from (59 ± 5.6) points before the operation to (93 ± 3.5) points after the operation. The OKS score increased from (24 ± 2.4) points before the operation to (45 ± 3.8) points after the operation. The ROM of knee joint was (111 ± 6.8)° before the operation and was (117 ± 9.7)° after the operation. The 10-year survival rate of the prosthesis was 96%.

CONCLUSION

UKA is one of the treatments for medial compartmental knee osteoarthritis. The issues, such as age and patellofemoral joint degeneration, can be addressed by careful selection of patients and precise operational manipulation.

Meniscal bearing dislocation following minimally invasive Oxford medial unicompartmental knee arthroplasty treated with simple open reduction: Case report

INTRODUCTION

Dislocation of polyethylene insert is one of the most common complications of mobile bearing-medial unicompartmental knee arthroplasty (MUKA). Bearing dislocation was diagnosed by radiograph examination in these cases upon trivial injury.

CASE PRESENTATION

We reported one case of meniscal bearing dislocation after an Oxford MUKA treated with a simple open reduction technique.

CLINICAL DISCUSSION

Simple open reduction surgery without change of the bearing and the use of knee brace for 6 months was effective in preventing re-dislocation.

CONCLUSION

Mobile bearing dislocation is one of the most common complications in mobile-bearing MUKA. Besides the prevention of technical errors, usage of UKA with a frequency of 10-15 per year is recommended to increase the surgeon's learning curve.

Medial femoral condyle fracture during an Oxford unicompartmental knee replacement surgery: case report

Oxford unicompartmental knee arthroplasty has been used as a good alternative for medial unicompartmental osteoarthritis due to its association with early rehabilitation and a low rate of intraoperative complications. This case describes a rare complication during the procedure of an intraoperative fracture of the medial condyle that was treated with osteosynthesis with 6.5 mm cannulated screws and a compression technique. The patient followed a non-weight-bearing protocol for 6 weeks and reached full range of motion at 3 months. Complete radiological fusion and good functional outcome were observed. Intraoperative fractures can benefit from stable osteosynthesis that allows free range of motion and does not jeopardise the final surgical result.

Accuracy of tibial component placement in unicompartmental knee arthroplasty performed using an accelerometer-based portable navigation system

PURPOSE

There is a need for new devices to improve the accuracy of implantation in unicompartmental knee arthroplasties (UKAs). The accelerometer-based portable navigation system is expected to improve this accuracy. This study aimed to compare the accuracy of UKAs performed by the portable navigation system with that of the conventional method, and to investigate whether the portable navigation system can complement the surgeon's experience.

METHODS

The study comprised of 80 Oxford UKAs. Knees were divided into two groups based on the method of tibial osteotomy: the conventional group (37 UKAs performed by an experienced surgeon using the extra-medullary guide) and the portable navigation group (43 UKAs performed by 2 unaccustomed surgeons using the navigation system). The absolute error from the target angle on the coronal and sagittal plane was measured on whole lower leg X-ray. The incidence of outliers (> 3°) was compared between the groups using Fisher's exact probability test.

RESULTS

The incidences of outliers on the coronal plane were 41.0% (15 of 37 knees) in the conventional group and 9.3% (4 of 43 knees) in the portable navigation group (p < 0.0001). The incidences of outliers on the sagittal plane were 13.5% (5 of 37 knees) in the conventional group and 14.0% (6 of 43 knees) in the portable navigation group (p = 0.3772).

CONCLUSION

This is the first report on the usefulness of an accelerometer-based portable navigation system in UKA. The use of this system improves the accuracy of implantation of the tibial component beyond the experience of the surgeon.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.

Age stratified, matched comparison of unicompartmental and total knee replacement

BACKGROUND

Unicompartmental knee replacement (UKR) tends to provide better function but has a higher revision rate than total knee replacement (TKR). The aim was to determine if this occurred in all age groups.

METHODS

Two large, non-registry, prospective cohorts with median 10-year follow-up (2252 TKR, 1000 medial UKR) were identified. All UKR met recommended indications. TKR with an inappropriate disease pattern for medial UKR were excluded. Knees were propensity score-matched within age-strata (<60 years at operation, 60 to <75, 75+) and compared using Oxford Knee Score (OKS), Kaplan-Meier revision rates and a composite failure, defined as any of revision, reoperation or no improvement in OKS.

RESULTS

One thousand five hundred and eighty-two TKR and UKR were matched. Results are reported TKR vs UKR for ages <60, 60 to <75 and 75+. Median 10-year OKS were 33 vs 45 (p < 0.001), 36 vs 42 (p < 0.001) and 36 vs 38 (p = 0.25). Ten-year revision rates were 11% vs 7%, 5% vs 5%, and 5% vs 10%, (none significant). The composite failures occurred 8%, 5% and 5% more frequently with TKR than UKR (none significant).

CONCLUSIONS

In this matched study UKR provided better functional outcomes in all age groups, particularly the young, and provided substantially more excellent outcomes. Although in older groups TKR tended to have a lower revision rate, in the young UKR had a lower revision rate. This was surprising and was perhaps because in this study UKR was, as recommended, only used for bone-on-bone arthritis, whereas in young patients it is widely used for early arthritis, which is associated with a high failure rate. This study supports the use of UKR with recommended indications, in all age groups.

Patient outcomes in Anteromedial osteoarthritis patients over 80 years old undergoing Oxford Unicompartmental knee Arthroplasty in China

Background

The use of Oxford Unicompartmental Knee Arthroplasty (UKA) has increased rapidly in both Western and Asian populations, with excellent functional outcomes and high patient satisfaction. While previous evidence regarding clinical outcomes and survival rates after Oxford UKA was based on studies in Western populations, the results may be different in Asian patients. The relevance of age for postoperative function after Oxford UKA also remains unclear. Hence, the aim of our study was to clarify the effectiveness and safety of Oxford UKA in Asian patients aged over 80 years.

Methods

A retrospective review was performed and included 195 patients (209 knees) who underwent an Oxford UKA between June 2015 and July 2018. We divided the patients into three groups by age: Group 1, 60–69 years; Group 2, 70–79 years; and Group 3, over 80 years. We used the Hospital for Special Surgery (HSS) score and Western Ontario and McMaster (WOMAC) Universities Osteoarthritis Index score to evaluate the general condition of the patients’ knees before surgery and at last follow-up. We also recorded perioperative and short-term complications.

Result

Group 1 consisted of 60 patients (60 knees); Group 2, 70 patients (79 knees); and Group 3, 65 patients (70 knees). The mean follow-up was 21.34 ± 12.04, 22.08 ± 11.38, and 21.76 ± 10.20 months in groups 1, 2, and 3, respectively. At last follow-up, the patients in Group 3 showed lower function scores compared to groups 1 and 2 (P < 0.05), but the HSS scores and the WOMAC scores were significantly improved in all three groups. In terms of perioperative and other complications, the three age groups did not differ significantly.

Conclusion

Oxford UKA is an effective and safe treatment for osteoarthritis, even in elderly patients in China. Elderly patients have lower knee function scores than younger patients. However, the knee joint pain of the elderly patients was relieved and function improved compared to the preoperative condition.

Clinical validation and accuracy testing of a radiographic decision aid for unicondylar knee arthroplasty patient selection in midterm follow-up

PURPOSE

The purpose of this study was to examine the predictive value concerning clinical outcome and implant survival, as well as the accuracy of individual tests of a recently published radiographic decision aid for unicondylar knee arthroplasty indication findings.

METHODS

In the retrospective part of the study, 98 consecutive patients who had undergone unicondylar knee arthroplasty (Phase 3 Oxford medial UKA) were included, using revision questionnaires, as well as the Forgotten Joint Score-12 (FJS-12) and Knee Osteoarthritis Outcome Score (KOOS) and analysed for suitability of the radiographic decision aid. Inappropriate and appropriate indications were then compared concerning the clinical outcome and implant survival. The prospective part of the study assessed the accuracy of the decision aid's radiographic tests (varus and valgus stress views, true lateral view and skyline view), and included 90 patients. Definition as appropriate for UKA procedure included medial bone-on-bone situation in varus stress views, full-thickness lateral cartilage and functional medial collateral ligament in valgus stress views, functional anterior cruciate ligament (ACL) in true lateral views and absence of lateral facet osteoarthritis with bone loss in skyline views. Pre-operative radiographic assessment with respect to the decision aid was then compared with intraoperative articular conditions. The clinical outcome was analysed using non-parametric tests (Mann-Whitney U), and revision rates were compared using the Fisher's exact test. Accuracy assessment included calculations of the sensitivity, specificity, negative predictive value and positive predictive value. A p value < 0.05 was considered statistically significant.

RESULTS

Appropriate unicondylar knee arthroplasty with respect to the decision aid showed a significantly lower revision rate compared to inappropriate unicondylar knee arthroplasty (7.3% vs. 50.0%, p < 0.0001), as well as higher clinical outcome scores (FJS-12: 53.13 vs. 31.25, p = 0.041 and KOOS-QDL: 68.75 vs. 50.0, p = 0.036). The overall sensitivity (70.1%) and specificity (76.2%) for the radiographic decision aid was comparably low, which was essentially based on false negative cases (22.7%) regarding medial bone-to-bone conditions.

CONCLUSION

The radiographic decision aid is a helpful tool to predict clinical outcome and implant survival of mobile-bearing unicondylar knee arthroplasty. Strict use of the radiographic decision aid may lead to increased exclusion of appropriate patients with unicondylar knee arthroplasty implantation.

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.

Ten-Year Survivorship, Patient-Reported Outcomes, and Satisfaction of a Fixed-Bearing Unicompartmental Knee Arthroplasty

BACKGROUND

We sought to determine the 10-year survivorship and reasons for revision for a fixed-bearing unicompartmental knee arthroplasty (UKA) design. In addition, we report on patient-reported outcomes and satisfaction and compare results of medial vs lateral compartment UKA and cemented vs cementless UKA with the same design.

METHODS

We performed a retrospective cohort study on a single-surgeon case series using a single fixed-bearing UKA design in 158 consecutive patients who underwent 177 UKA procedures between July 2000 and December 2010. Cases missing follow-up within the last year, clinically or via telephone, were excluded (n = 17, 10%). A cumulative incidence competing risk model was used to evaluate the cumulative incidence of failure.

RESULTS

Cumulative incidence of revision at a mean follow-up of 10 years was 13%. The majority of revisions (43%, 10/23) were for aseptic tibial component loosening, followed by progression of osteoarthritis (5/23, 22%). All Patient Reported Outcomes Measurement Information System measures demonstrated mean T-scores within one standard deviation from the US population norm. The mean Knee Injury and Osteoarthritis Outcome Score for Joint Replacement was 96.9 (range, 40-100). The mean pain score was 3.8 (range, 0-8). Eighty-six percent of patients were satisfied with the UKA.

CONCLUSIONS

At 10-year follow-up, the most common causes for revision were aseptic tibial loosening and adjacent compartment knee arthroplasty, and similar results were found for medial vs lateral compartment and for cemented vs cementless UKA. Surgeons should consider these findings for future UKA designs, and this represents the first study reporting on survivorship and outcomes of this specific UKA design.

Influence of patient selection, component positioning and surgeon's caseload on the outcome of unicompartmental knee arthroplasty

BACKGROUND

Implant malpositioning, low surgical caseload, and improper patient selection have been identified as essential factors, which could negatively affect the longevity of unicompartmental knee arthroplasty (UKA). The aim of the current study was to evaluate the impact of the surgeon's caseload on patient selection, component positioning, as well as component survivorship and functional outcomes following a PSI-UKA.

METHODS

A total of 125 patient-specific instrumented (PSI) UKA were included. One hundred and two cases were treated by a high-volume surgeon (usage 40%) and 23 cases by a low-volume surgeon (< 10 cases/year, usage 34%). Preoperative UIS, as well as the postoperative clinical and radiologic outcome, were assessed retrospectively.

RESULTS

Irrespective of the surgeon's UKA caseload, PSI allowed good accuracy in component positioning (p > 0.05). The high-volume surgeon had a more strict indication for UKA with 89% showing a UIS > 25 (considered a good indication) compared to 70% for the low-volume surgeon (p = 0.016). The low-volume surgeon achieved worse results regarding functional outcome (p < 0.05) and a tendency toward an increased risk for UKA failure (p = 0.11) compared to the high-volume surgeon.

CONCLUSION

Due to potential selection errors, mostly connected to a low UKA-caseload, low-volume UKA surgeons might achieve worse outcomes. Very strict indications for UKA might be recommended in low-volume surgeons to achieve excellent clinical outcomes following a UKA.

Most unicompartmental knee replacement revisions could be avoided: a radiographic evaluation of revised Oxford knees in the National Joint Registry

PURPOSE

The purpose of this study was to understand why the revision rate of unicompartmental knee replacement (UKR) in the National Joint Registry (NJR) is so high. Using radiographs, the appropriateness of patient selection for primary surgery, surgical technique, and indications for revision were determined. In addition, the alignment of the radiographs was assessed.

METHODS

Oxford UKR registered with the NJR between 2006 and 2010 and subsequently revised were identified by the NJR. A blinded review was undertaken of pre-primary, post-primary, and pre-revision anteroposterior and lateral radiographs of a sample of 107 cases from multiple centres.

RESULTS

The recommended indications were satisfied in 70%, with 29% not demonstrating bone-on-bone arthritis. Major technical errors, likely leading to revision, were seen in 6%. Pre-revision radiographs were malaligned and, therefore, difficult to interpret in 53%. No reason for revision was seen in 67%. Reasons for revision included lateral compartment arthritis (10%), tibial loosening (7%), bearing dislocation (7%), infection (6%), femoral loosening (3%), and peri-prosthetic fracture (2%, one femoral, one tibial).

CONCLUSIONS

Only 20% of the revised UKR were implanted for the recommended indications, using appropriate surgical technique and had a mechanical problem necessitating revision. One-third of primary surgeries were undertaken in patients with early arthritis, which is contraindicated. Two-thirds were presumably revised for unexplained pain, which is not advised as it tends not to help the pain. This study suggests that variable and inappropriate indications for primary and revision surgery are responsible for the high rates of revision seen in registries.

LEVEL OF EVIDENCE

III, Therapeutic study.

Posterior Bearing Overhang Following Medial and Lateral Mobile Bearing Unicompartmental Knee Replacements

This study explores the extent of bearing overhang following mobile bearing Oxford unicompartmental knee replacement (OUKR) (Oxford Phase 3, Zimmer Biomet). The Oxford components are designed to be fully congruent, however knee movements involve femoral rollback, which may result in bearing overhang at the posterior margin of the tibial implant, with potential implications for; pain, wear, and dislocation. Movement is known to be greater, and therefore posterior overhang more likely to occur, with; lateral compared to medial implants, anterior cruciate ligament (ACL) deficiency (ACLD) compared to ACL intact (ALCI), and at extremes of movement. Twenty-four medial, and 20 domed lateral, OUKRs underwent sagittal plane knee fluoroscopy during step-up and forward lunge exercises. The bearing position was inferred from the relative position of the femoral and tibial components. On the basis of the individual component sizes and geometry the extent the posterior part of the bearing which overhung the posterior part of the tibial component was calculated. There was no significant posterior overhang in knees with medial implants. Knees with lateral domed implants exhibited overhang at flexion angles beyond 60°, the magnitude of which increased with increasing flexion angle, reaching a maximum of 50% of the bearing length at 140° (range 0-140°). This demonstrates a clear difference between the kinematics, and prevalence and extent of posterior bearing overhang between medial and lateral OUKRs. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1938-1945, 2019.

Midterm clinical and radiographic outcomes of 115 consecutive patient-specific unicompartmental knee arthroplasties

BACKGROUND

Poor implant positioning has been identified as a factor in early failure of unicompartmental knee arthroplasty. The aim of this study was to report the accuracy of component positioning, and midterm clinical, functional and radiological outcomes following patient-specific instrumented (PSI) unicompartmental knee arthroplasty (UKA).

METHODS

A total of 115 PSI-UKA were included. The primary outcomes were UKA survival, complication, and failure rates. Tibial implant positioning was determined using plain radiographs. Functional assessment included Oxford Knee Score (OKS), Forgotten Joint Score (FJS), patient satisfaction, and range of motion (ROM).

RESULTS

The survival rate of PSI-UKA was 92% after a mean follow-up of 55 months. The complication and failure rate was 13% and eight percent, respectively. The tibial component was accurately implanted in the desired frontal and sagittal alignment with a minor deviation of 0.3° (SD 1.9°) and 0.4° (SD 2.6°) to the preoperative planning. OKS increased from 24 (SD eight) points to 44 (SD six). FJS was 87 (SD 23) and 89.6% of all patients reported to be satisfied at the final follow-up. Patient satisfaction was negatively correlated with patients' age (p < 0.05).

CONCLUSION

Excellent accuracy regarding component placement in UKA can be achieved with PSI. However, despite excellent survivorship and clinical outcomes, these data indicate that the PSI system is not superior to conventional UKA implantation methods.

No Differences in Outcomes Scores or Survivorship of Unicompartmental Knee Arthroplasty Between Patients Younger or Older than 55 Years of Age at Minimum 10-Year Followup

BACKGROUND

Although patients who have undergone unicompartmental knee arthroplasty (UKA) report improvements in functional outcomes, orthopaedic surgeons tend to avoid UKA in younger patients due to implant survivorship concerns. As a result, few studies specifically have examined the outcomes of patients 55 years and younger.

QUESTIONS/PURPOSES

Is there a difference between two cohorts of patients: those 55 years and younger and those 56 years and older who underwent UKA in terms of: (1) functional outcomes scores, (2) quality-of-life scores, and (3) implant survivorship free from all-cause revision.

METHODS

Between 2004 and 2007, 100 patients 55 years and younger underwent UKA at one institution. Of those, three (3%) died, and 13 (13%) were lost to followup before the 10-year minimum required for this study, leaving 84 patients available for propensity score matching. During that same period, 343 patients older than 56 years underwent UKA; 48 (14%) died, and 59 (17%) were lost to followup before 10 years, leaving 236 patients available in that group for potential inclusion. After propensity score matching to account for confounding preoperative variables (surgeon, patient's body mass index, and sex), the patients were divided into two groups based on age: (1) 55 years and younger, (2) 56 years and older. There were 71 patients in each group, with minimum followup of 10 years. The mean age in the group of patients 55 years and younger was 52 years (range, 45-55 years) and that of the older patients was 64 years (range, 56-80 years). The mean (range) followup in both groups was 13 years (range, 11-15 years). Patient functional outcomes, quality of life scores, and implant survivorship were assessed for both groups of patients. To detect a minimum clinically important difference of 5 points in the Oxford Knee Score (OKS), a sample size of at least 68 patients in each group would be required to achieve a power of 0.95.

RESULTS

With the numbers available, there were no differences between patients 55 years and younger and those 56 years and older in terms of OKS (18 ± 6 versus 20 ± 8, mean difference -1.8; 95% CI, -4.1 to 0.5; p = 0.133) and Knee Society Knee Score (84 ± 16 versus 79 ± 21, mean difference 4.7; 95% CI, -1.8 to 11.2; p = 0.157) at 10 years postoperatively. With the numbers available, there were no differences between patients 55 years and younger and those 56 years and older in terms of the physical component summary (PCS) (47 ± 10 versus 48 ± 11, mean difference -0.4; 95% CI, -4.0 to 3.2; p = 0.827) and the mental component summary (MCS) (52 ± 12 versus 51 ± 12, mean difference 1.4; 95% CI, -2.6 to 5.4; p = 0.491) of the SF-36 at 10 years postoperatively. Finally, we found no differences with the numbers available between patients 55 years and younger and those 56 years and older in terms of survivorship free from all-cause revision at a minimum of 10 years followup (both groups had the same 10-year revision-free rate of 0.96; 95% CI, 0.91-1.00).

CONCLUSIONS

Because we found few differences between patients 55 years and younger and those older than that in terms of functional outcomes, quality of life, and implant survivorship after UKA, we believe that appropriately selected younger patients should not be excluded from the potential benefits of undergoing UKA, especially in the hands of high-volume surgeons.

LEVEL OF EVIDENCE

Level III, therapeutic study.

A novel preoperative scoring system for the indication of unicompartmental knee arthroplasty, as predictor of clinical outcome and satisfaction

INTRODUCTION

Proper patient selection is a crucial factor for the outcome of the unicompartmental knee arthroplasty (UKA). However, there is still not a clear consensus on which patients could benefit the utmost from a UKA. The purpose of this prospective study was to introduce a novel, preoperative, predictive score (Unicompartmental Indication Score, UIS) to aid proper patient selection in UKA.

MATERIALS AND METHODS

A total of 152 patients with an average age of 68 years and a mean follow-up of 27 months were evaluated preoperatively with the UIS and postoperative at every follow-up. Correlation analysis was applied to identify potential relationships between the UIS, functional outcomes, pain relief, patient satisfaction, and range of motion. The ROC analysis was used to identify the best cutoff value of the UIS, which would have predicted an optimal outcome following UKA.

RESULTS

The majority of the patients (91%) were satisfied with the operation, with 61% reporting excellent and 30% good satisfaction. The UIS was positively correlated to the postoperative Knee Society Score (KSS) for both pain (r = 0.26, p < 0.001) and function (r = 0.31, p < 0.001). The UIS was also positively correlated to the patient satisfaction (p = 0.46, p < 0.001) and maximum postoperative flexion (r = 0.25, p < 0.001). The ROC analysis provided an ideal cutoff for UIS at 25 points (sensitivity: 75%, sensibility: 93%, area under the curve: 86%). At a mean follow-up of 27 months (range 24-37), we observed three revisions in 152 consecutive UKA with a mean UIS of 27 points (range 20-30).

CONCLUSIONS

The newly introduced UIS score might be a reliable preoperative scoring system to predict patients with excellent satisfaction, functional outcome, pain relief and possibly implant survivorship following UKA, and therefore, could help the proper patient selection and decision-making in UKA.

LEVEL-OF-EVIDENCE

Prospective study, II.

Cost-Effectiveness of Surgical and Nonsurgical Treatments for Unicompartmental Knee Arthritis: A Markov Model

BACKGROUND

There has been increased utilization of surgical options for the treatment of end-stage unicompartmental arthritis in patients at both extremes of the age spectrum. The purpose of this study was to determine how these changing paradigms affected the lifetime cost-effectiveness of total knee arthroplasty (TKA), unicompartmental knee arthroplasty (UKA), and nonsurgical treatment (NST).

METHODS

Using a Markov decision analytic model, we assessed how lifetime costs and quality-adjusted life years (QALYs) vary as a function of age at the time of initial treatment (ATIT) of patients with end-stage unicompartmental knee osteoarthritis undergoing TKA, UKA, and NST. Separate models were estimated for ATITs at 5-year intervals from 40 through 90 years. Direct medical costs, QALYs, and transition probabilities were determined from the published literature. Indirect costs (lost wages, Social Security disability collections, and value of missed workdays) were calculated. Cost-effectiveness and incremental cost-effectiveness ratios (ICERs) were calculated for each treatment at each ATIT. The model assumed no crossover from NST to UKA or TKA. ICERs were compared with a willingness-to-pay threshold of 50,000 U.S. dollars, and a 1-way sensitivity analysis was used to assess the robustness of ICER-based treatment decisions. Societal savings were estimated.

RESULTS

In the base-case model, surgical treatments were less expensive and provided a greater number of QALYs than NST from 40 to 69 years of age. From 70 years of age and onward, surgical treatments remained cost-effective compared with NST, with ICERs remaining below the societal willingness-to-pay threshold. When surgical treatments were compared, UKA dominated TKA for all ATITs. The preferential use of UKA in all U.S. patients with unicompartmental osteoarthritis would result in an estimated lifetime societal savings of 987 million to 1.5 billion U.S. dollars per annual wave of patients undergoing treatment.

CONCLUSIONS

In this preliminary assessment, recent expansion of surgical treatments into younger and older age demographics appears to be cost-effective in the setting of unicompartmental knee osteoarthritis. Our findings suggest that NST should be used sparingly in patients below the age of 70 years and UKA should be chosen over TKA in order to maximize cost-effectiveness.

LEVEL OF EVIDENCE

Economic and decision analysis Level IV. See Instructions for Authors for a complete description of levels of evidence.

Age and Outcomes of Medial Meniscal-Bearing Unicompartmental Knee Arthroplasty

BACKGROUND

National joint registries report increasing revision rates with decreasing patient age for all types of joint arthroplasty. This study aimed to explore the effect of age on function and revision risk in patients undergoing medial meniscal-bearing UKA.

METHODS

A prospectively followed cohort of 1000 consecutive medial meniscal-bearing UKAs at a designer center was analyzed. All knees were implanted for recommended indications and had mean 10-year follow-up. Patients were grouped by age at surgery (<55, 55 to <65, 65 to <75, 75+). Oxford Knee Scores (OKS) were assessed at 5 and 10 years. Component-time revision incidence rates and Kaplan-Meier implant survival were calculated.

RESULTS

Mean patient age at surgery was 66.6 years (range, 33-88). All age-groups had significant (P < .001) improvement in OKS over time, and at 5 years achieved a median OKS of 44. At 10 years, median OKS, from youngest group to eldest, were 44, 45, 42, and 39, with the eldest group having a significantly lower OKS (P < .01). Ten-year implant survival rates were 97%, 94%, 94%, and 93%, respectively, and was not significantly associated with age at UKA.

CONCLUSION

Medial meniscal-bearing UKA provides good functional outcomes in all age-groups; however, in older patients (75+), the functional outcome deteriorated at 10 years presumably due to deteriorating health. Contrary to registry observations, the revision rate was not higher in younger patients. These results suggest that, with correct indications, patient age should not be considered a contraindication to medial meniscal-bearing UKA.

Should Medicare Remove Total Knee Arthroplasty From Its Inpatient Only List? A Total Knee Arthroplasty Is Not a Partial Knee Arthroplasty

BACKGROUND

The Centers for Medicare and Medicaid Services have solicited comments to consider removing total knee arthroplasty (TKA) from the Inpatient Only list, as it has done for unicompartmental knee arthroplasty (UKA). The purpose of this study is to determine whether Medicare-aged patients undergoing TKA had comparable outcomes to those undergoing UKA.

METHODS

We queried the American College of Surgeons-National Surgical Quality Improvement Program database for all patients aged 65 years or older who underwent elective TKA or UKA from 2014 and 2015. Demographic variables, comorbidities, length of stay (LOS), 30-day complication, and readmission rates were compared between UKA and TKA patients. A multivariate regression analysis was then performed to identify independent risk factors for complications and hospital LOS greater than 1 day.

RESULTS

Of the 50,487 patients in the study, there were 49,136 (97%) TKA patients and 1351 UKA patients (3%). Medicare-aged TKA patients had a longer mean LOS (2.97 vs 1.57 days, P < .001), had a higher complication rate (9% vs 3%, P < .001), and were more likely to be discharged to a rehabilitation facility (31% vs 9%, P < .001) than Medicare-aged UKA patients. When controlling for other variables, TKA patients were more likely to experience a complication (odds ratio, 2.562; P < .001) and require LOS >1 day (odds ratio, 14.679; P < .001) than UKA patients.

CONCLUSION

TKA procedure in the Medicare population is an independent risk factor for increased complications and LOS compared to UKA. Policymakers should use caution extrapolating UKA data to TKA patients and recognize the inherent disparities between the 2 procedures.

Unicompartmental knee replacement in patients aged 70 years and older

Introduction

The management of isolated unicompartmental osteoarthritis in the patient aged 70 years and older is an issue of debate. The purpose of the present study was to retrospectively evaluate the outcomes of patients aged over 70 years who underwent unicompartmental knee replacement (UKR) for the treatment of isolated unicompartmental osteoarthritis. The hypothesis was that this represents a safe and viable procedure leading to improved functional outcome in elderly patients affected by isolated unicompartmental osteoarthritis.

Methods

22 consecutive medial compartment UKRs performed between 1998 and 2008 were retrospectively evaluated. Mean age was 74 years (range 70-93 years). Patients were evaluated preoperatively and after an average follow-up of 6.2 years (range 2 to 8). Assessment included KOOS score, WOMAC score, Knee Society Score. Standard X-rays were performed prior to surgery and at follow-up.

Results

Twenty patients showed a statistically significant improvement in all parameters. One patient who was 93 years old at the time of surgery died for unrelated causes. One patient required conversion to a total knee arthroplasty.

Discussion

UKR is a safe and clinically effective procedure, which has been proven valuable for the treatment of elderly patients with isolated unicompartmental osteoarthritis and with initial degenerative signs in the other compartments.

Conclusion

Age more than 70 does not appear to be a contraindication to the procedure.

Level of evidence

IV (case series).

Changes in Markers of Thrombin Generation and Interleukin-6 During Unicondylar Knee and Total Knee Arthroplasty

BACKGROUND

Total knee arthroplasty (TKA) is associated with a risk of thromboembolism requiring routine thromboprophylaxis, but there is debate about the risk with unicondylar knee arthroplasty (UKA) as it is a more minor procedure. We sought to investigate the relative risk of thromboembolism with UKA compared to TKA and one-staged bilateral TKA (BTKA) by measuring the increase in circulating biochemical markers of thrombin generation during the procedures. Degree of surgical trauma was also assessed by measuring interleukin-6, a marker of metabolic injury.

METHODS

We prospectively studied a total of 75 patients: 25 patients undergoing UKA, unilateral TKA, and BTKA, respectively. All patients had surgery performed with tourniquet and received no tranexamic acid. Blood samples were taken during surgery and assayed for circulating markers of thrombin generation: prothrombin fragment 1+2 (F1+2) and thrombin-antithrombin complexes plus interleukin-6.

RESULTS

Thrombin-antithrombin complexes, increased during all time points (P < .001) but was not significantly different between surgical treatment groups. F1+2 also rose significantly during surgery, with no significant difference between UKA and TKA. There was, however, a significant difference in F1+2 between BTKA and UKA or TKA (P < .02). Interleukin-6 rose minimally with UKA but rose significantly with TKA and BTKA (P < .001).

CONCLUSION

Based on these data of circulating biochemical markers, patients undergoing UKA are at similar risk of thromboembolism with respect to TKA despite a lower index of metabolic injury. We believe that UKA patients should receive thromboprophylaxis comparable to TKA patients.

Predictors of Midterm Outcomes after Medial Unicompartmental Knee Arthroplasty in Asians

Background

This study was designed to evaluate predictors of good outcomes following medial unicompartmental knee arthroplasty (UKA) in Asian patients.

Methods

Registry data of patients who underwent primary unilateral medial UKA from 2006 to 2011 were collected. Outcomes studied were the Oxford Knee Score (OKS) and the Physical Component Score (PCS) of the Short Form 36 (SF-36) questionnaire. These outcome scores were collected prospectively, pre- and postoperatively up to 5 years. Good outcome was defined as an overall improvement in score greater than or equal to the minimal clinically important difference (MCID). The MCID for the OKS was 5 while the MCID for the PCS was 10. Regression analysis was used to identify predictors of good outcomes following medial UKA.

Results

Primary medial UKA was performed in 1,075 patients. Higher (poorer) preoperative OKS (odds ratio [OR], 1.27; p < 0.001), lower (poorer) preoperative PCS (OR, 1.08; p < 0.001), lower (poorer) preoperative Knee Society Knee Score (KSKS; OR, 1.02; p < 0.001) and higher (better) preoperative SF-36 Mental Component Score (MCS; OR, 1.02; p < 0.001) were significant predictors of good outcomes.

Conclusions

Patients with poorer OKS, PCS and KSKS and better SF-36 MCS preoperatively tended to achieve good outcomes by the MCID criterion at 5 years following the index surgery.

Early outcomes of twin-peg mobile-bearing unicompartmental knee arthroplasty compared with primary total knee arthroplasty

Aims

Since redesign of the Oxford phase III mobile-bearing unicompartmental knee arthroplasty (UKA) femoral component to a twin-peg design, there has not been a direct comparison to total knee arthroplasty (TKA). Thus, we explored differences between the two cohorts.

Patients and Methods

A total of 168 patients (201 knees) underwent medial UKA with the Oxford Partial Knee Twin-Peg. These patients were compared with a randomly selected group of 177 patients (189 knees) with primary Vanguard TKA. Patient demographics, Knee Society (KS) scores and range of movement (ROM) were compared between the two cohorts. Additionally, revision, re-operation and manipulation under anaesthesia rates were analysed.

Results

The mean follow-up for UKA and TKA groups was 5.4 and 5.5 years, respectively. Six TKA (3.2%) versus three UKAs (1.5%) were revised which was not significant (p = 0.269). Manipulation was more frequent after TKA (16; 8.5%) versus none in the UKA group (p < 0.001). UKA patients had higher post-operative KS function scores versus TKA patients (78 versus 66, p < 0.001) with a trend toward greater improvement, but there was no difference in ROM and KS clinical improvement (p = 0.382 and 0.420, respectively).

Conclusion

We found fewer manipulations, and higher functional outcomes for patients treated with medial mobile-bearing UKA compared with TKA. TKA had twice the revision rate as UKA although this did not reach statistical significance with the numbers available.

Cite this article: Bone Joint J 2016;98-B(10 Suppl B):28–33.

Survivorship and clinical outcome of the minimally invasive Uniglide medial fixed bearing, all-polyethylene tibia, unicompartmental knee arthroplasty at a mean follow-up of 7.3years

BACKGROUND

Medial UKA performed in England and Wales represents seven to 11% of all knee arthroplasty procedures, and is most commonly performed using mobile-bearing designs. Fixed bearing eliminates the risk of bearing dislocation, however some studies have shown higher revision rates for all-polyethylene tibial components compared to those that utilize metal-backed implants. The aim of the study is to analyse survivorship and maximum eight-year clinical outcome of medial fixed bearing, Uniglide unicompartmental knee arthroplasty performed using an all-polyethylene tibial component with a minimal invasive approach.

METHODS

Between 2002 and 2009, 270 medial fixed UKAs were performed in our unit. Patients were reviewed pre-operatively, five and eight years post-operatively. Clinical and radiographic reviews were carried out. Patients' outcome scores (Oxford, WOMAC and American Knee Score) were documented in our database and analysed.

RESULTS

Survival and clinical outcome data of 236 knees with a mean of 7.3years follow-up are reported. Every patient with less than 4.93years of follow-up underwent a revision. The patients' average age at the time of surgery was 69.5years. The American Knee Society Pain and Function scores, the Oxford Knee Score and the WOMAC score all improved significantly. The five-year survival rate was 94.1% with implant revision surgery as an end point. The estimated 10years of survival rate is 91.3%. Fourteen patients were revised before the five-year follow-up.

CONCLUSION

Fixed bearing Uniglide UKA with an all-polyethylene tibial component is a valuable tool in the management of a medial compartment osteoarthritis, affording good short-term survivorship. Level of evidence IV.

Medial femoral condyle fracture as an intraoperative complication of Oxford unicompartmental knee replacement

Oxford unicompartmental knee replacement (OUKR) is associated with a low perioperative complication rate. This case report describes a periprosthetic fracture of the medial femoral condyle that occurred during an OUKR. The patient was treated with a non-weight-bearing long leg cast for 6 weeks. Afterwards, the fracture had healed, and 3 months postoperatively, there was a full range of motion. Factors leading to this complication could be the impaction force or direction, or a diminished load resistance of the distal femur. Minimally displaced coronal periprosthetic fractures after OUKR can be managed conservatively without residual functional impairment.

LEVEL OF EVIDENCE

Case report, Level IV.

Predicting Satisfaction for Unicompartmental Knee Arthroplasty Patients in an Asian Population

BACKGROUND

Despite renewed interest in unicompartmental knee arthroplasty (UKA), there is a paucity of published literature with regard to patient satisfaction after UKA within Asian populations. The purpose of this study is to identify characteristics and factors which may contribute to patient dissatisfaction after UKA in a multiracial Asian population.

METHODS

Seven hundred twenty-four UKAs were performed between January 2007 and April 2013. Preoperative and postoperative variables were prospectively captured, such as standardized knee scores, knee range of motion, and patient satisfaction scores. These variables were then analyzed with a multiple logistic regression model to determine statistically significant factors contributing to patients' satisfaction.

RESULTS

Minimum duration of follow-up was 2 years, with an overall patient satisfaction rate of 92.2%. There was improvement in mean knee range of motion and across various standardized knee scores. Preoperative variables associated with patient dissatisfaction included a poorer preoperative Mental Component Summary, better preoperative knee extension, and better preoperative Oxford Knee Scores. Significant postoperative variables included better Oxford Knee Score at 6 months and Mental Component Summary at 2 years.

CONCLUSION

Despite the impressive patient satisfaction rate of UKA in this Asian population, these findings suggest that there is a targeted group of patients with select preoperative factors who would benefit from preoperative counseling.

Analysis and Treatment of Complications after Unicompartmental Knee Arthroplasty

Purpose

To analyze the causes and types of complications after unicompartmental knee arthroplasty (UKA) and determine proper prevention and treatment methods.

Materials and Methods

A total of 1,576 UKAs were performed for osteoarthritis of the knee from January 2002 to December 2014 at one institution. We analyzed complications after UKA retrospectively and investigated proper methods of treatment.

Results

A total of 89 complications (5.6%) occurred after UKA. Regarding the type of complications after UKA, there were 42 cases of dislocation of the mobile bearing, 23 cases of loosening of the prosthesis, 6 cases of periprosthetic fracture, 3 cases of polyethylene wear, 3 cases of progression of arthritis in the contralateral compartment, 2 cases of medial collateral ligament injury, 2 cases of impingement, 5 cases of infection, 1 case of arthrofibrosis, and 2 cases of failure due to unexplained pain. The most common complication after UKA was mobile bearing dislocation in the mobile-bearing knees and loosening of the prosthesis in the fixed-bearing knees, but polyethylene wear and progression of arthritis were relatively rare. The complications were treated with conversion to total knee arthroplasty in 58 cases and simple bearing change in 21 cases.

Conclusions

The most common complication after UKA was dislocation of the mobile bearing. When a complication occurs after UKA, appropriate treatment should be performed after accurate analysis of the cause of complication.

Downhill walking gait pattern discriminates between types of knee arthroplasty: improved physiological knee functionality in UKA versus TKA

PURPOSE

To determine whether downhill walking gait pattern discriminates between different types of knee arthroplasty.

METHODS

Nineteen unicompartmental knee arthroplasty (UKA) and fourteen total knee arthroplasty (TKA) patients who were well matched demographically and with high Oxford knee scores (OKS) for their operation type were evaluated at a minimum 1 year after their operation with downhill gait analysis. Nineteen healthy young subjects were used as controls. Downhill gait analysis was carried out on an instrumented treadmill that was ramped at the rear to produce a declination of 7°. All subjects after a period of habituation were tested for preferred and top downhill walking speed with associated ground reaction and temporospatial measurements.

RESULTS

The UKA group had higher mean OKS (44.8 ± 2.9 vs 41.9 ± 4.7, p = 0.03) as predicted. The UKA group walked downhill 15% faster than the TKA group (1.75 ± 0.14 vs 1.52 ± 0.13 m/s, p < 0.0001) despite having the same cadence (134.9 ± 8.0 vs 133.9 ± 9.6 steps/min). This 15% difference in speed appeared largely due to a 15% increase in stride length (173 ± 14 vs 150 ± 17 cm, p = 0.0007) and normal weight acceptance, both of which were similar to the controls.

CONCLUSION

Using an instrumented treadmill to test a commonly performed task, stride length when walking downhill highlights the functional differences between arthroplasty groups. Near normal restoration of physiological gait pattern was found in unicompartmentals as compared to total knee replacements.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.

Effect of age on cost-effectiveness of unicompartmental knee arthroplasty compared with total knee arthroplasty in the U.S

BACKGROUND

Trade-offs between upfront benefits and later risk of revision of unicompartmental knee arthroplasty compared with those of total knee arthroplasty are poorly understood. The purpose of our study was to compare the cost-effectiveness of unicompartmental knee arthroplasty with that of total knee arthroplasty across the age spectrum of patients undergoing knee replacement.

METHODS

Using a Markov decision analytic model, we compared unicompartmental knee arthroplasty with total knee arthroplasty with regard to lifetime costs, quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratios (ICERs) from a societal perspective for patients undergoing surgery at forty-five, fifty-five, sixty-five, seventy-five, or eighty-five years of age. Transition probabilities were estimated from the literature; survival, from the Swedish Knee Arthroplasty Register; and costs, from the literature and the Healthcare Cost and Utilization Project (HCUP) database. Costs and QALYs were discounted at 3.0% annually. We conducted sensitivity analyses to test the robustness of model estimates and threshold analyses.

RESULTS

For patients sixty-five years of age and older, unicompartmental knee arthroplasty dominated total knee arthroplasty, with lower lifetime costs and higher QALYs. Unicompartmental knee arthroplasty was no longer cost-effective at a $100,000/QALY threshold when total knee arthroplasty rehabilitation costs were reduced by two-thirds or more for these older patients. Lifetime societal savings from utilizing unicompartmental knee arthroplasty in all older patients (sixty-five or older) in 2015 and 2020 were $56 to $336 million and $84 to $544 million, respectively. In the forty-five and fifty-five-year-old age cohorts, total knee arthroplasty had an ICER of $30,300/QALY and $63,000/QALY, respectively. Unicompartmental knee arthroplasty became cost-effective when its twenty-year revision rate dropped from 27.8% to 25.7% for the forty-five-year age group and from 27.9% to 26.7% for the fifty-five-year age group.

CONCLUSIONS

Unicompartmental knee arthroplasty is an economically attractive alternative in patients sixty-five years of age or older, and modest improvements in implant survivorship could make it a cost-effective alternative in younger patients.

Mobile-bearing unicondylar knee arthroplasty: the Oxford experience

With the recent increase in medial unicompartmental arthroplasty, this article reviews the design history, indications, results, and modern technique for the implantation of the Oxford mobile-bearing unicompartmental arthroplasty. The article also discusses how the indications for the Oxford differ from the historical indications for medial unicompartmental arthroplasty and supports this paradigm shift with review of the recent data. A detailed series of surgical pearls is also presented to help surgeons with the surgical nuances of the Oxford partial knee.

45-day mortality after 467,779 knee replacements for osteoarthritis from the National Joint Registry for England and Wales: an observational study

BACKGROUND

Understanding the risk factors for early death after knee replacement could help to reduce the risk of mortality after this procedure. We assessed secular trends in death within 45 days of knee replacement for osteoarthritis in England and Wales, with the aim of investigating whether any change that we recorded could be explained by alterations in modifiable perioperative factors.

METHODS

We took data for knee replacements done for osteoarthritis in England and Wales between April 1, 2003, and Dec 31, 2011, from the National Joint Registry for England and Wales. Patient identifiers were used to link these data to the national mortality database and the Hospital Episode Statistics database to obtain details of death, sociodemographics, and comorbidity. We assessed mortality within 45 days by Kaplan-Meier analysis and assessed the role of patient and treatment factors by Cox proportional hazards models.

FINDINGS

467,779 primary knee replacements were done to treat osteoarthritis during 9 years. 1183 patients died within 45 days of surgery, with a substantial secular decrease in mortality from 0·37% in 2003 to 0·20% in 2011, even after adjustment for age, sex, and comorbidity. The use of unicompartmental knee replacement was associated with substantially lower mortality than was total knee replacement (hazard ratio [HR] 0·32, 95% CI 0·19–0·54, p<0·0005). Several comorbidities were associated with increased mortality: myocardial infarction (HR 3·46, 95% CI 2·81–4·14, p<0·0005), cerebrovascular disease (3·35, 2·7–4·14, p<0·0005), moderate/severe liver disease (7·2, 3·93–13·21, p<0·0005), and renal disease (2·18, 1·76–2·69, p<0·0005). Modifiable perioperative risk factors, including surgical approach and thromboprophylaxis were not associated with mortality.

INTERPRETATION

Postoperative mortality after knee replacement has fallen substantially between 2003 and 2011. Efforts to further reduce mortality should concentrate more on older patients, those who are male and those with specific comorbidities, such as myocardial infarction, cerebrovascular disease, liver disease, and renal disease.

FUNDING

National Joint Registry for England and Wales.

Adverse outcomes after total and unicompartmental knee replacement in 101,330 matched patients: a study of data from the National Joint Registry for England and Wales

BACKGROUND

Total knee replacement (TKR) or unicompartmental knee replacement (UKR) are options for end-stage osteoarthritis. However, comparisons between the two procedures are confounded by differences in baseline characteristics of patients undergoing either procedure and by insufficient reporting of endpoints other than revision. We aimed to compare adverse outcomes for each procedure in matched patients.

METHODS

With propensity score techniques, we compared matched patients undergoing TKR and UKR in the National Joint Registry for England and Wales. The National Joint Registry started collecting data in April 1, 2003, and is continuing. The last operation date in the extract of data used in our study was Aug 28, 2012. We linked data for multiple potential confounders from the National Health Service Hospital Episode Statistics database. We used regression models to compare outcomes including rates of revision, revision/reoperation, complications, readmission, mortality, and length of stay.

FINDINGS

25,334 UKRs were matched to 75,996 TKRs on the basis of propensity score. UKRs had worse implant survival both for revision (subhazard ratio [SHR] 2·12, 95% CI 1·99–2·26) and for revision/reoperation (1·38, 1·31–1·44) than TKRs at 8 years. Mortality was significantly higher for TKR at all timepoints than for UKR (30 day: hazard ratio 0·23, 95% CI 0·11–0·50; 8 year: 0·85, 0·79–0·92). Length of stay, complications (including thromboembolism, myocardial infarction, and stroke), and rate of readmission were all higher for TKR than for UKR.

INTERPRETATION

In decisions about which procedure to offer, the higher revision/reoperation rate of UKR than of TKR should be balanced against a lower occurrence of complications, readmission, and mortality, together with known benefits for UKR in terms of postoperative function. If 100 patients receiving TKR received UKR instead, the result would be around one fewer death and three more reoperations in the first 4 years after surgery.

FUNDING

Royal College of Surgeons of England and Arthritis Research UK.

Efficacy of autologous bone marrow concentrate for knee osteoarthritis with and without adipose graft

Introduction. We investigated the use of autologous bone marrow concentrate (BMC) with and without an adipose graft, for treatment of knee osteoarthritis (OA). Methods. Treatment registry data for patients who underwent BMC procedures with and without an adipose graft were analyzed. Pre- and posttreatment outcomes of interest included the lower extremity functional scale (LEFS), the numerical pain scale (NPS), and a subjective percentage improvement rating. Multivariate analyses were performed to examine the effects of treatment type adjusting for potential confounding factors. The frequency and type of adverse events (AE) were also examined. Results. 840 procedures were performed, 616 without and 224 with adipose graft. The mean LEFS score increased by 7.9 and 9.8 in the two groups (out of 80), respectively, and the mean NPS score decreased from 4 to 2.6 and from 4.3 to 3 in the two groups, respectively. AE rates were 6% and 8.9% in the two groups, respectively. Although pre- and posttreatment improvements were statistically significant, the differences between the groups were not. Conclusion. BMC injections for knee OA showed encouraging outcomes and a low rate of AEs. Addition of an adipose graft to the BMC did not provide a detectible benefit over BMC alone.

Differences in short-term complications between unicompartmental and total knee arthroplasty: a propensity score matched analysis

BACKGROUND

Knee arthroplasty has emerged as an effective treatment for end-stage gonarthrosis. Although total knee arthroplasty remains the gold standard, unicompartmental knee arthroplasty is an appropriate alternative for select patients. We sought to use a large, heterogeneous national database to identify differences in thirty-day complication rates between unicompartmental and total knee arthroplasty as well as to identify risk factors for complications.

METHODS

Patients in the ACS NSQIP (American College of Surgeons National Surgical Quality Improvement Program) database who had undergone total or unicompartmental knee arthroplasty from 2005 to 2011 were identified. CPT (Current Procedural Terminology) codes were used to select cases of elective primary knee arthroplasty. Statistical models employing univariate and multivariate logistic regression identified risk factors associated with the thirty-day incidence of morbidity and mortality after total and unicompartmental knee arthroplasty. Propensity score matching addressed demographic differences between the total and unicompartmental knee arthroplasty cohorts.

RESULTS

A total of 29,333 patients were identified; 27,745 (94.6%) underwent total knee arthroplasty and 1588 (5.41%) underwent unicompartmental knee arthroplasty. Prior to matching, the total knee arthroplasty cohort was 63.7% female and had a mean BMI of 32.8 ± 7.3 kg/m(2), whereas the values for the unicompartmental cohort were 55.3% and 31.5 ± 6.5 kg/m(2) (p < 0.0001). The mean ages of these cohorts were 67.2 ± 10.1 and 64.0 ± 10.7 years, respectively (p < 0.0001). A previously developed and implemented propensity score matching algorithm was used to address the demographic differences. Following matching, the total complication rate did not differ significantly between the total and unicompartmental knee arthroplasty cohorts (5.29% compared with 4.16%, p = 0.35), whereas the rate of deep venous thrombosis (1.50% compared with 0.50%, p = 0.02) and the duration of hospital stay (3.4 compared with 2.2 days, p < 0.0001) were significantly higher in the total knee arthroplasty cohort.

CONCLUSIONS

Comparison of total and unicompartmental knee arthroplasty revealed no differences in overall short-term (thirty-day) morbidity and mortality. Although this study does not address long-term subjective outcomes or implant survival, these findings should provide helpful information for surgeons counseling patients considering total and/or unicompartmental knee arthroplasty.

LEVEL OF EVIDENCE

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

Mid-term survivorship of minimally invasive unicompartmental arthroplasty with a fixed-bearing implant: revision rate and mechanisms of failure

Minimally invasive unicondylar arthroplasty (UKA) continues to gain popularity for the management of patients with degenerative arthritis limited to one compartment of the knee. In this study, we examine a series of 517 fixed-bearing, cemented unicompartmental knee components implanted in patients to manage degenerative arthritis in the medial compartment of their knee. All UKAs were performed at a single institution using the same fixed-bearing design. In this study we sought to examine the survivorship of the UKA components and the mechanisms of failure for the knees that were revised. The survivorship and revision rate with this implant were similar to those found in other published reports of fixed-bearing unicompartmental arthroplasties performed through minimally invasive surgical techniques.

Cost-effectiveness of unicondylar versus total knee arthroplasty: a Markov model analysis

BACKGROUND

Unicondylar knee arthroplasty (UKA) is believed to lead to less morbidity and enhanced functional outcomes when compared with total knee arthroplasty (TKA). Conversely, UKA is also associated with a higher revision risk than TKA. In order to further clarify the key differences between these separate procedures, the current study assessing the cost-effectiveness of UKA versus TKA was undertaken.

METHODS

A state-transition Markov model was developed to compare the cost-effectiveness of UKA versus TKA for unicondylar osteoarthritis using a Belgian payer's perspective. The model was designed to include the possibility of two revision procedures. Model estimates were obtained through literature review and revision rates were based on registry data. Threshold analysis and probabilistic sensitivity analysis were performed to assess the model's robustness.

RESULTS

UKA was associated with a cost reduction of €2,807 and a utility gain of 0.04 quality-adjusted life years in comparison with TKA. Analysis determined that the model is sensitive to clinical effectiveness, and that a marginal reduction in the clinical performance of UKA would lead to TKA being the more cost-effective solution.

CONCLUSION

UKA yields clear advantages in terms of costs and marginal advantages in terms of health effects, in comparison with TKA.

Uncertainties surrounding the choice of surgical treatment for 'bone on bone' medial compartment osteoarthritis of the knee

A number of different surgical interventions can be used for treating antero-medial osteoarthritis (AMOA) of the knee and this choice can present challenges for patient's decision-making. Patients with AMOA can undergo Total Knee Replacement (TKR), Unicompartmental Knee Replacement (UKR) or High Tibial Osteotomy (HTO) for the same pathology. However many uncertainties still exist as to deciding which operation is best for individual patients and the Orthopaedic community has failed to systematically compare treatment options. The relative lack of scientifically based evidence has impacted on the ability to provide clear guidelines on treatment choice, patient suitability and direct patient preference for treatment. This paper, using available evidence, discusses the issue and offers some suggestions for future development.