Outcomes of fixed versus mobile-bearing medial unicompartmental knee arthroplasty.

Aims: The optimal bearing surface design for medial unicompartmental knee arthroplasty (UKA) remains controversial. The aim of this study was to compare outcomes of fixed-bearing (FB) and mobile-bearing (MB) UKAs from a single high-volume institution. Methods: Prospectively collected data were reviewed for all primary cemented medial UKAs performed by seven surgeons from January 2006 to December 2022. A total of 2,999 UKAs were identified, including 2,315 FB and 684 MB cases. The primary outcome measure was implant survival. Secondary outcomes included 90-day and cumulative complications, reoperations, component revisions, conversion arthroplasties, range of motion, and patient-reported outcome measures. Overall mean age at surgery was 65.7 years (32.9 to 94.3), 53.1% (1,593/2,999) of UKAs were implanted in female patients, and demographics between groups were similar (p > 0.05). The mean follow-up for all UKAs was 3.7 years (0.0 to 15.6). Results: Using revision for any reason as an endpoint, five-year survival for FB UKAs was 97.2% (95% CI 96.4 to 98.1) compared to 96.0% for MB (95% CI 94.1 to 97.9; p = 0.008). The FB group experienced fewer component revisions (14/2,315, 0.6% vs 12/684, 1.8%; p < 0.001) and conversion arthroplasties (38/2315, 1.6% vs 24/684, 3.5%; p < 0.001). A greater number of MB UKAs underwent revision due to osteoarthritis progression (FB = 21/2,315, 0.9% vs MB = 16/684, 2.3%; p = 0.003). In the MB group, 12 (1.8%) subjects experienced bearing dislocations which required revision surgery. There were 15 early periprosthetic tibia fractures (0.6%) in the FB group compared to 0 for MB (p = 0.035). Conclusion: In similar patient populations, FB UKAs demonstrated slightly higher survival than a commonly used MB design. Adverse event profiles differed by bearing type, with an increased risk of bearing dislocation and OA progression with MB designs, and early periprosthetic tibia fractures for FB designs.

Outpatient Total Joint Arthroplasty in the "Unhealthy": Staying Safe Using Institutional Protocols.

BACKGROUND: Recent expansion in the indications for outpatient total joint arthroplasty has led to debates over patient selection. The purpose of this study was to compare early clinical outcomes and complications of same-day discharge (SDD) hip and knee arthroplasties from a high-volume institution based on the American Society of Anesthesiologists (ASA) physical status classification. METHODS: Prospectively collected data were reviewed for all SDD primary joint arthroplasties between January 2013 and August 2023. There were 8 surgeons who performed 7,258 cases at hospital outpatient (n = 4,288) or ambulatory surgery centers (n = 2,970). This included 3,239 total hip arthroplasties, 1,503 total knee arthroplasties, and 2,516 unicompartmental knee arthroplasties. The ASA 1 group comprised 506 subjects, compared to 5,005 for ASA 2 and 1,736 for ASA 3. The primary outcomes included emergency department (ED) visits, readmissions, complications, and revisions within 24 hours and 90 days of surgery. The ASA 3 group was older (ASA 1 = 55 versus ASA 2 = 63 versus ASA 3 = 66 years; P < .01) and had a higher body mass index (ASA 1 = 25.4 versus ASA 2 = 28.5 versus ASA 3 = 32.7; P < .01). RESULTS: There were no differences between ASA groups in joint-related ED visits, readmissions, and complications within 24 h and 90 days of surgery (P > .05). Subjects in the ASA 3 group experienced greater 90-day revisions compared to the other groups (ASA 1 = 1 of 506, 0.2% versus ASA 2 = 15 of 5,005, 0.3% versus ASA 3 = 15 of 1,736, 0.9%; P = .01). Regarding systemic events, ASA 1 subjects experienced significantly greater 24-hour complications (8 of 506, 1.6%) and ED visits (5 of 506, 1.0%), and the ASA 3 subjects had a higher incidence of 90-day readmissions (19 of 1,736, 1.1%) compared to the other groups (P < .05). Within 24 hours of discharge, urinary retention and syncope were the most frequent complications that required additional health care utilization. CONCLUSIONS: Medically optimized patients categorized as ASA 3 can safely undergo SDD hip and knee arthroplasty without increased risk of 24-hour or 90-day complications. Patient preference for outpatient care, reliable social support, and independent functional status are imperative for a successful outpatient program.

The Effect of the COVID Pandemic on the Rate of Same-Day Discharge in Primary Hip and Knee Arthroplasty.

BACKGROUND: Same-day discharge (SDD) following primary total hip arthroplasty (THA) and total knee arthroplasty (TKA) started increasing prior to 2020. The purpose of this study was to evaluate the change in the rate of SDD after the pandemic and determine whether those changes became permanent. METHODS: The annual rate of SDD for 15,208 primary THA and TKA cases performed between January 1, 2015, and September 9, 2022, at a single institution was determined. We also examined changes in SDD patient demographics as well as differences in the 90-day complication rates of SDD and overnight patients. RESULTS: In 2015, the rate of SDD for primary arthroplasty was 24%, which grew annually to 29% in 2019. Postpandemic, the rate of SDD jumped above 50% and continued up to 64% by 2022. The biggest increase was in TKA, which went from under 10% SDD prepandemic to 50% by 2022. The average age and body mass index of SDD cases prepandemic increased significantly to 62 ± 9 years and 29.4 ± 5.3 (P < .01). Overnight patients had higher rates of 90-day postoperative complications (8.4 versus 4.2%, P < .00001). CONCLUSIONS: The pandemic caused major changes in the rate of SDD for primary THA and TKA, increasing in subsequent years. The SDD patients became older and heavier due to the expanded criteria for SDD cases. The 90-day postoperative complication rate was lower for SDD patients since higher risk patients were kept overnight. At the prepandemic rate, 29% of patients currently being sent home would have stayed overnight.

Debridement, Antibiotics, and Implant Retention in Unicompartmental Knee Arthroplasty Infection.

BACKGROUND: This multicenter study sought to further investigate the method and outcome of debridement, antibiotics, and implant retention (DAIR) for the management of unicompartmental knee periprosthetic joint infection (PJI). METHODS: This retrospective study was performed on 52 patients who underwent DAIR for PJI of a unicompartmental knee arthroplasty (UKA) across 4 academic medical centers, all performed by fellowship-trained arthroplasty surgeons. Patient demographics, American Society of Anesthesiologists score, infecting organism, operative data, antibiotic data, and success in infection control at 1 year were collected. RESULTS: The average time from index surgery to diagnosis of PJI was 11.1 weeks (range, 1.4 to 48). There was no correlation between time of diagnosis and success at 1 year (R = 0.09, P = .46). There was an association between surgical synovectomy and the eradication of infection (R = 0.28, P = .04). Overall, there was an 80.8% (42 of 52) infection-controlled success rate at 1 year from the DAIR procedure. All DAIR failures went on to require another procedure, either 1-stage (2 of 10) or 2-stage (8 of 10) revision to total knee arthroplasty (TKA). Of the DAIR successes, 6 (14.3%) went on to require conversion to TKA for progression of arthritis within 5 years. CONCLUSIONS: This study demonstrates that DAIR is a safe and moderately effective procedure in the setting of acute PJI of UKA across institutions, with a success rate consistent with DAIR for TKA. The data suggest that a wide exposure and thorough synovectomy be incorporated during the DAIR UKA to improve the likelihood of successful eradication of PJI at the 1-year mark. LEVEL OF EVIDENCE: Level III.

The CCJR® Charles A. Engh, Sr, MD. Excellence in Hip Research Award: The Evolution of Revision Hip Arthroplasty and Impact on the Trainee's Experience.

BACKGROUND: Advances in total hip arthroplasty (THA) have resulted in evolving revision indications and intraoperative techniques, which can influence the exposure of trainees to complex cases. We report 3 decades of revision experience from a tertiary referral center that trains fellows, comparing the reasons for revision and the complexity of revisions over time. METHODS: We retrospectively reviewed all revision THAs performed at our institution from 1990 to 2022. Revision diagnoses, components revised, types of revision implants used, and exposure techniques were collected. A "complex" revision was defined as a case that involved an extended trochanteric osteotomy, triflange and cup-cage construct, or acetabular augment. RESULTS: A total of 3,556 THA revisions were identified (108 revisions/year). Aseptic loosening was the most common indication in 1990 to 1999 (45 per year), but decreased to 28.3/year in 2010 to 2019. From 1990 to 1999 and 2010 to 2019, fracture increased from 3.1 to 7.3 per year, infection from 2.9/year to 16.9/year, and metallosis from 0.1 to 13.2 per year. Both component revision were common from 1990 to 1994 (42.6 per year), while polyethylene exchange was most common in 2010 to 2019 (43.3 per year). A decrease was observed in "complex" cases over time: 14.8 extended trochanteric osteotomies/year in 2000 to 2004 compared to 5.4 per year in 2018 to 2022, 4.5 triflange and cup-cage constructs/year in 2004 to 2007 compared to 0.8 per year in 2018 to 2022, and 4 acetabular augments per year in 2009 to 2012 compared to 1 per year in 2018 to 2022. CONCLUSIONS: Indications for revision have changed over the decades, while the number of "complex" revisions has gradually decreased, presumably due to advances in implants and materials. If this trend extends to other training institutions, the next generation of arthroplasty surgeons will have less exposure to complex revisions during their training.

Cementless Total Knee Arthroplasty: A Resurgence-Who, When, Where, and How?

BACKGROUND: Total knee arthroplasty (TKA) is one of the most common procedures in orthopaedics, but there is still debate over the optimal fixation method for long-term durability: cement versus cementless bone ingrowth. Recent improvements in implant materials and technology have offered the possibility of cementless TKA to change clinical practice with durable, stable biological fixation of the implants, improved operative efficiency, and optimal long-term results, particularly in younger and more active patients. METHODS: This symposium evaluated the history of cementless TKA, the recent resurgence, and appropriate patient selection, as well as the historical and modern-generation outcomes of each implant (tibia, femur, and patella). Additionally, surgical technique pearls to assist in reliable, reproducible outcomes were detailed. RESULTS: Historically, cemented fixation has been the gold standard for TKA. However, cementless fixation is increasing in prevalence in the United States and globally, with equivalent or improved results demonstrated in appropriately selected patients. CONCLUSIONS: Cementless TKA provides durable biologic fixation and successful long-term results with improved operating room efficiency. Cementless TKA may be broadly utilized in appropriately selected patients, with intraoperative care taken to perform meticulous bone cuts to promote appropriate bony contact and biologic fixation.

Outcomes Following Intraoperative Calcar Fractures During Cementless Total Hip Arthroplasty.

BACKGROUND: Intraoperative calcar fractures (IOCFs) are an established complication of cementless total hip arthroplasty (THA). Prompt recognition and management may prevent subsequent postoperative complications. This study aimed to evaluate the outcomes and revision rates of THAs with IOCFs identified and managed intraoperatively. METHODS: There were 11,438 primary cementless THAs performed at a single institution from 2009 to 2022. Prospectively collected data on cases with an IOCF was compared to cases without the complication. The fracture group had a lower body mass index (26.9 versus 28.9 kg/m2; P = .01). Patient age, sex, and mean follow-up (3.2 (0 to 12.8) versus 3.5 years (0 to 14); P = .45) were similar between groups. RESULTS: An IOCF occurred in 62 of 11,438 (0.54%) cases. The THAs done via a direct anterior approach experienced the lowest rate of fractures (31 of 7,505, 0.4%) compared to postero-lateral (27 of 3,759, 0.7%; P = .03) and lateral (4 of 165, 2.4%; P < .01) approaches. Of the IOCFs, 48 of 62 (77%) were managed with cerclage cabling, 4 of 62 (6.5%) with intraoperative stem design change and cabling, 4 of 62 (6.5%) with restricted weight-bearing, and 6 of 62 (9.7%) with no modification to the standard postoperative protocol. The IOCF group experienced one case of postoperative component subsidence. No subjects in the IOCF cohort required revision, and rates were similar between groups (0 of 62, 0% versus 215 of 11,376, 1.9%; P = .63). Postoperative Hip dysfunction and Osteoarthritis Outcome Score for Joint Replacement scores were comparable (85.7 versus 86.4; P = .80). CONCLUSIONS: Cementless THA complicated by IOCF had similar postoperative revision rates and patient-reported outcome measures at early follow-up when compared to patients not experiencing this complication. Surgeons may use these data to provide postoperative counseling on expectations and outcomes following these rare intraoperative events.

Outpatient Total Knee Arthroplasty From a Stand-Alone Surgery Center: Safe as the Hospital?

BACKGROUND: Literature suggests that outpatient arthroplasty may result in low rates of complications and readmissions. There is, however, a dearth of information on the relative safety of total knee arthroplasty (TKA) performed at stand-alone ambulatory surgery centers (ASCs) versus hospital outpatient (HOP) settings. We aimed to compare safety profiles and 90-day adverse events of these 2 cohorts. METHODS: Prospectively collected data were reviewed on all patients who underwent outpatient TKA from 2015 to 2022. The ASC and HOP groups were compared, and differences in demographics, complications, reoperations, revisions, readmissions, and emergency department (ED) visits within 90 days of surgery were analyzed. There were 4 surgeons who performed 4,307 TKAs during the study period, including 740 outpatient cases (ASC = 157; HOP = 583). The ASC patients were younger than HOP patients (ASC = 61 versus HOP = 65; P < .001). Body mass index and sex did not differ significantly between groups. RESULTS: Within 90 days, 44 (6%) complications occurred. No differences were observed between groups in rates of 90-day complications (ASC = 9 of 157, 5.7% versus HOP = 35 of 583, 6.0%; P = .899), reoperations (ASC = 2 of 157, 1.3% versus HOP = 3 of 583, 0.5%; P = .303), revisions (ASC = 0 of 157 versus HOP = 3 of 583, 0.5%; P = 1), readmissions (ASC = 3 of 157, 1.9% versus HOP = 8 of 583, 1.4%; P = .625), and ED visits (ASC = 1 of 157, 0.6% versus HOP = 3 of 583, 0.5%; P = .853). CONCLUSION: These results suggest that in appropriately selected patients, outpatient TKA can be safely performed in both ASC and HOP settings with similar low rates of 90-day complications, reoperations, revisions, readmissions, and ED visits.

Early Practice All-Cause Complications for Fellowship-Trained Anterior Hip Surgeons Are Not Increased When Compared to "Gold Standard" Experienced Posterior Approach Surgeons.

BACKGROUND: Increased complication rates have been reported during the learning curve for direct anterior approach (DAA) total hip arthroplasty (THA). However, emerging literature suggests that complications associated with the learning curve may be substantially reduced with fellowship training. METHODS: Our institutional database was queried to identify 2 groups: (1) 600 THAs comprised of the first 300 consecutive cases performed by 2 DAA fellowship-trained surgeons; and (2) 600 posterolateral approach (PA) THAs, including the most recent 300 primary cases performed by 2 experienced PA surgeons. All-cause complications, revision rates, reoperations, operative times, and transfusion rates were evaluated. RESULTS: Comparing DAA and PA cases, there were no significant differences in rates of all-cause complications (DAA = 18, 3.0% versus PA = 23, 3.8%; P = .43), periprosthetic fractures (DAA = 5, 0.8% versus PA = 10, 1.7%; P = .19), wound complications (DAA = 7, 1.2% versus PA = 2, 0.3%; P = .09), dislocations (DAA = 2, 0.3% versus PA = 8, 1.3%, P = .06), or revisions (DAA = 2, 0.3% versus PL = 5, 0.8%; P = .45) at 120 days postoperatively. There were 4 patients who required reoperation for wound complications, all within the DAA group (DAA = 4, 0.67% versus PA = 0; P = .045). Operative times were shorter in the DAA group (DAA <1.5 hours = 93% versus PA <1.5 hours = 86%; P < .01). No blood transfusions were given in either group. CONCLUSION: In this retrospective study, DAA THAs performed by fellowship-trained surgeons early in practice were not associated with higher complication rates compared to THAs performed by experienced PA surgeons. These results suggest that fellowship training may allow DAA surgeons to complete their learning curve period with complication rates similar to experienced PA surgeons.

Motor Nerve Palsy After Direct Anterior Versus Posterior Total Hip Arthroplasty: Incidence, Risk Factors, and Recovery.

BACKGROUND: There is limited literature on motor nerve palsy in modern total hip arthroplasty (THA). The purpose of this study was to establish the incidence of nerve palsy following THA using the direct anterior (DA) and postero-lateral (PL) approaches, identify risk factors, and describe the extent of recovery. METHODS: Using our institutional database, we examined 10,047 primary THAs performed between 2009 and 2021 using the DA (6,592; 65.6%) or PL (3,455; 34.4%) approach. Postoperative femoral (FNP) and sciatic/peroneal nerve palsies (PNP) were identified. Incidence and time to recovery was calculated, and association between surgical and patient risk factors and nerve palsy were evaluated using Chi-square tests. RESULTS: The overall rate of nerve palsy was 0.34% (34/10,047) and was lower with the DA approach (0.24%) than the PL approach (0.52%), P = .02. The rate of FNPs in the DA group (0.20%) was 4.3 times more than the rate of PNPs (0.05%), while in the PL group the rate of PNPs (0.46%) was 8 times more than that of FNPs (0.06%). Higher rates of nerve palsy were observed with women, shorter patients, and nonosteoarthritis preoperative diagnoses. Full recovery of motor strength occurred in 60% of cases with FNP and 58% of cases with PNP. CONCLUSION: Nerve palsy is rare after contemporary THA through the PL and DA approaches. The PL approach was associated with a higher rate of PNP, whereas the DA approach was associated with a higher rate of FNP. Femoral and sciatic/peroneal palsies had similar rates of complete recovery.

Timing and Factors Associated With Revision for Infection After Primary Total Knee Arthroplasty Based on American Joint Replacement Registry Data.

BACKGROUND: Infection following total knee arthroplasty (TKA) remains a challenging clinical problem. Using American Joint Replacement Registry data, this study examined factors related to the incidence and timing of infection. METHODS: Primary TKAs performed from January 2012 through December 2018 among patients ≥65 years of age at surgery were queried from the American Joint Replacement Registry and merged with Medicare data to enhance capture of revisions for infection. Multivariate Cox regressions incorporating patient, surgical, and institutional factors were used to produce hazard ratios (HRs) associated with revision for infection and mortality after revision for infection. RESULTS: Among 525,887 TKAs, 2,821 (0.54%) were revised for infection. Men had an increased risk of revision for infection at all-time intervals (≤90 days, HR = 2.06, 95% CI: 1.75-2.43, P < .0001; >90 days to 1 year, HR = 1.90, 95% CI: 1.58-2.28, P < .0001; >1 year, HR = 1.57, 95% CI: 1.37-1.79, P < .0001). TKAs performed for osteoarthritis had an increased risk of revision for infection at ≤90 days (HR = 2.01, 95% CI: 1.45-2.78, P < .0001) but not at later times. Mortality was more likely among patients who had a Charlson Comorbidity Index (CCI) ≥ 5 compared to those who had a CCI ≤ 2 (HR = 3.21, 95% CI: 1.35-7.63, P = .008). Mortality was also more likely among older patients (HR = 1.61 for each decade, 95% CI: 1.04-2.49, P = .03). CONCLUSION: Based on primary TKAs performed in the United States, men were found to have a persistently higher risk of revision for infection, while a diagnosis of osteoarthritis was associated with a significantly higher risk only during the first 90 days after surgery.

Spinal Anesthesia for Primary Hip and Knee Arthroplasty: Comparative Rates of Transient Neurological Symptoms and Urinary Retention Using Lidocaine, Mepivacaine, and Bupivacaine.

BACKGROUND: Short-acting spinal anesthetics enable rapid recovery after hip and knee arthroplasty; however, concerns with transient neurological symptoms (TNS) cause some to avoid using lidocaine. Postoperative urinary retention (POUR) is also a concern with spinal anesthesia. We sought to study the comparative rates of TNS and POUR between lidocaine, mepivacaine, and bupivacaine in a high-volume hip and knee arthroplasty setting. METHODS: Data for 1,217 primary THA, TKA, and unicompartmental knee arthroplasty cases were reviewed and grouped by spinal anesthetic agent (lidocaine, mepivacaine, or bupivacaine). Of the 1,217 cases, utilization was 523 lidocaine, 573 mepivacaine, and 121 bupivacaine. The incidence of TNS and POUR requiring catheterization was measured both by clinical evaluation as well as a questionnaire sent to patients 14 days postoperatively. RESULTS: The overall rate of TNS was 8%. With the numbers available, there was no difference in rates of TNS between groups (6.9% lidocaine, 9.2% mepivacaine, and 4.1% bupivacaine; P = .297). There was no difference in rates of TNS or POUR between THA and TKA/unicompartmental knee arthroplasty. Bupivacaine had a significantly higher rate of urinary retention (9.1%; P < .001) than mepivacaine (2.8%) or lidocaine (1.5%). CONCLUSION: This study showed no difference in the rate of TNS between the 3 common agents used in spinal anesthesia. Short-acting spinal anesthetics such as lidocaine and mepivacaine can lower the rate of POUR requiring catheterization, helping to enable rapid recovery after hip and knee arthroplasty.

Early Results of a Randomized Controlled Trial of Partial Versus Total Knee Arthroplasty.

BACKGROUND: Debate still exists regarding the benefits of unicompartmental (UKA) versus total knee arthroplasty (TKA) for the treatment of medial compartment osteoarthritis. The purpose of this randomized trial is to compare the early outcomes of UKA versus TKA. METHODS: One-hundred and seven candidates for UKA were randomized at two centers; 57 candidates received UKA and 50 received TKA. Six-week and 6-month outcome measures including Knee Injury and Osteoarthritis Outcome Score, Joint Replacement (KOOS, JR), Knee Society Score (KSS), Forgotten Joint Score (FJS), and VR-12 global health scores were obtained. No demographic or baseline patient reported outcome (PRO) differences were present suggesting successful randomization (P > .05). RESULTS: UKA demonstrated shorter operative times (UKA = 65 minutes, TKA = 74 minutes; P < .001) and length of stay (UKA = 0.7 nights, TKA = 1.2 nights; P < .01). At 6 weeks, there were no differences in KOOS, JR (P = .755), KSS (P = .754), FJS (P = .664), or PRO change from preoperative scores (P = .468). There were three surgical complications within 90 days in each group. The duration of opioid consumption (UKA = 33.8 days, TKA = 28.5 days; P = .290) and return to work (UKA = 57.1 days, TKA = 47.3 days; P = .346) did not differ between groups. CONCLUSION: Data suggest no clinically significant differences between UKA and TKA in the early postoperative period in regards to patient-reported outcome measures, duration of opioid use, or return to work. Patients undergoing UKA can anticipate a shorter length of stay and greater early range of motion. All-cause short-term complications may be more prevalent with TKA.

Prior Anterior Cruciate Ligament Reconstruction Does Not Compromise the Functional Outcomes of Medial Unicompartmental Knee Arthroplasty Although Revision for Progressive Arthritis May Occur Earlier.

BACKGROUND: Anterior cruciate ligament (ACL) deficiency is commonly considered a contraindication for unicompartmental knee arthroplasty (UKA). The purpose of this study is to compare the outcomes of UKA after prior ACL reconstruction (rACL cohort) to UKA with an intact native ACL (nACL cohort). METHODS: Forty-five patients from 3 institutions who underwent medial UKA after prior rACL were matched by age, gender, preoperative function scores, and body mass index to 90 patients who underwent UKA with an intact nACL. Primary outcomes were Knee Injury and Osteoarthritis Outcome Score for Joint Replacement, Oxford Knee Scores, Knee Society Functional Scores, and Kellgren-Lawrence scores in the unresurfaced, lateral tibiofemoral compartment. Secondary outcomes were postoperative complications and the need for revision to TKA. RESULTS: At a mean of 3.6 years, all PROMs improved significantly with no differences identified between groups. The incidence of revision TKA was similar between cohorts (P = 1.00); however, the mean time to revision for progressive osteoarthritis was 4.0 years in the nACL group and 2.2 years in the rACL group. Twenty percent of rACL patients had a postoperative complication compared to 8% in the nACL group. Despite presenting with a similar degree of lateral arthritis, a greater percentage of patients developed Kellgren-Lawrence scores of ≥3 in the rACL cohort (9%) than in the nACL cohort (0%). CONCLUSION: A previously reconstructed ACL does not appear to compromise the short-term functional outcomes of UKA; however, there is a higher rate of minor complications and progression of lateral compartment arthritis, which should be considered with patients in the shared decision process.

Alignment in Medial Fixed-Bearing Unicompartmental Knee Arthroplasty: The Limb Has a Leg Up on the Component.

BACKGROUND: To assess how implant alignment affects unicompartmental knee arthroplasty (UKA) outcome, we compared tibial component alignment of well-functioning UKAs against 2 groups of failed UKAs, revised for progression of lateral compartment arthritis ("Progression") and aseptic loosening ("Loosening"). METHODS: We identified 37 revisions for Progression and 61 revisions for Loosening from our prospective institutional database of 3351 medial fixed-bearing UKAs performed since 2000. Revision cohorts were matched on age, gender, body mass index, and postoperative range of motion with "Successful" unrevised UKAs with minimum 10-year follow-up and Knee Society Score ≥70. Tibial component coronal (TCA) and sagittal (TSA) plane alignment was measured on postoperative radiographs. Limb alignment was quantified by hip-knee-ankle (HKA) angle on long-leg radiographs. In addition to directly comparing groups, a multivariate logistic regression examined how limb and component alignments were associated with UKA revision. RESULTS: In the Progression group, component alignment was similar to the matched successes (TCA 3.6° ± 3.5° varus vs 5.1° ± 3.5° varus, P = .07; TSA 8.4° ± 4.4° vs 8.8° ± 3.6°, P = .67), whereas HKA angle was significantly more valgus (0.3° ± 3.6° valgus vs 4.4° ± 2.6° varus, P < .001). Loosening group component alignment was also similar to the matched successes (TCA 6.1° ± 3.7° varus vs 5.9° ± 3.1° varus, P = .72; TSA 8.4° ± 4.6° vs 8.1° ± 3.9°, P = .68), and HKA was significantly more varus (6.1° ± 3.1° varus vs 4.0° ± 2.7° varus, P < .001). Using a multivariate logistic regression, HKA angle was the most significant factor associated with revision (P < .001). CONCLUSION: In this population of revised UKAs and long-term successes, limb alignment was a more important determinant of outcome than tibial component alignment. LEVEL OF EVIDENCE: Level III case-control study.

A lower threshold for revision of aseptic unicompartmental vs total knee arthroplasty.

AIMS: It has been hypothesized that a unicompartmental knee arthroplasty (UKA) is more likely to be revised than a total knee arthroplasty (TKA) because conversion surgery to a primary TKA is a less complicated procedure. The purpose of this study was to determine if there is a lower threshold for revising a UKA compared with TKA based on Oxford Knee Scores (OKSs) and range of movement (ROM) at the time of revision. METHODS: We retrospectively reviewed 619 aseptic revision cases performed between December 1998 and October 2018. This included 138 UKAs that underwent conversion to TKA and 481 initial TKA revisions. Age, body mass index (BMI), time in situ, OKS, and ROM were available for all patients. RESULTS: There were no differences between the two groups based on demographics or time to revision. The top reasons for aseptic TKA revision were loosening in 212 (44%), instability in 88 (18%), and wear in 69 (14%). UKA revision diagnoses were primarily for loosening in 50 (36%), progression of osteoarthritis (OA) in 50 (36%), and wear in 17 (12%). Out of a maximum 48 points, the mean OKS of the UKAs before revision was 23 (SD 9.3), which was significantly higher than the TKAs at 19.2 (SD 9.8; p < 0.001). UKA patients scored statistically better on nine of the 12 individual OKS questions. The UKA cases also had a larger pre-revision mean ROM (114°, SD 14.3°) than TKAs (98°, SD 25°) ; p < 0.001). CONCLUSION: At revision, the mean UKA OKSs and ROM were significantly better than those of TKA cases. This study suggests that at our institution there is a difference in preoperative OKS between UKA and TKA at the time of revision, demonstrating a revision bias. Cite this article: Bone Joint J 2020;102-B(6 Supple A):91-95.

The Impact of Coronal Alignment on Revision in Medial Fixed-Bearing Unicompartmental Knee Arthroplasty.

BACKGROUND: To better define the optimal alignment target for medial fixed-bearing unicompartmental knee arthroplasty (UKA), this study compares the postoperative mechanical alignment of well-functioning UKAs against 2 groups of failed UKAs, including revisions for progression of lateral compartment osteoarthritis ("Progression") and revisions for aseptic loosening or subsidence ("Loosening"). METHODS: From our prospective institutional database of 3351 medial fixed-bearing UKAs performed since 2000, we identified 37 UKAs revised for Progression and 61 UKAs revised for Loosening. Each of these revision cohorts was matched based on age at surgery, gender, body mass index, and postoperative range of motion with unrevised UKAs that had at least 10 years of follow-up and a Knee Society Score of 70 or greater without subtracting points for alignment ("Success" groups). Postoperative alignment was quantified by the hip-knee-ankle (HKA) angle measured on long-leg alignment radiographs. RESULTS: The mean HKA angle at 4-month follow-up for the Progression group was 0.3° ± 3.6° of valgus compared to 4.4° ± 2.6° of varus for the matched Success group (P < 0.001). For the Loosening group, the mean HKA angle was 6.1° ± 3.1° of varus versus 4.0° ± 2.7° of varus for the matched Success group (P < 0.001). CONCLUSIONS: Patients with well-functioning UKAs at 10 years exhibited mild varus mechanical alignment of approximately 4°, whereas patients revised for progression of osteoarthritis averaged more valgus and those revised for loosening or subsidence averaged more varus. The optimal mechanical alignment for medial fixed-bearing UKA survival with contemporary polyethylene is likely slight varus.

To Cement or Not? Five-Year Results of a Prospective, Randomized Study Comparing Cemented vs Cementless Total Knee Arthroplasty.

BACKGROUND: The optimal mode of fixation in total knee arthroplasty is a continuing subject of debate. METHODS: Previously, we reported 2-year results for this prospective, randomized trial. Knee Society Scores, Oxford scores, and pain visual analog scales were collected pre-operatively and post-operatively. Minimum 5-year follow-up has been obtained with radiographic analysis for 85 patients. RESULTS: Mean Knee Society Scores and Oxford scores and patient-reported outcomes were similar in both groups. Each group had 1 additional revision, but neither was related to implant fixation. Survivorship with revision as an endpoint was equivalent (95.9% and 95.3%, P = .98). There was no significant difference in radiolucencies observed between groups (P = .10), all were non-progressive. CONCLUSION: Cementless and cemented total knee arthroplasty had equivalent patient-reported outcomes and survivorship at midterm follow-up. Updates are planned at 10 and 15-year intervals to observe long-term modes of failure between these 2 methods of fixation.

The Lawrence D. Dorr Surgical Techniques & Technologies Award: "Running Two Rooms" Does Not Compromise Outcomes or Patient Safety in Joint Arthroplasty.

BACKGROUND: Scrutiny from the federal government and the media regarding the safety of 1 surgeon doing cases in 2 operating rooms (ORs) on the same day, prompted us to examine our own institutional data. Over the past 11 years, surgeons at our facility have operated consecutively in 1 OR on a given day or used 2 alternating ORs. This study compares these cases with a focus on revisions and complications in both groups. METHODS: Six surgeons performed a total of 16,916 primary hip and knee arthroplasties from 2006-2016. 7002 cases (41%) were consecutive cases (CCs) and 9914 cases (59%) were overlapping cases (OCs). Intraoperative complications, component revisions, and postoperative complications within 90 days of surgery were compared between the CC and OC groups. RESULTS: There was no difference in intraoperative complication rates between the two groups (CC 1.6% vs. OC 1.7%, relative risk 1.082, 95% confidence interval 0.852 to 1.375, P = .52). There was no difference in 90-day component revision rates among the CC and OC groups (0.66% vs. 0.85% respectively, relative risk = 1.290, 95% confidence interval 0.901 to 1.845, P = .19). There was also no difference in 90-day complication rates among the CC and OC groups (1.33% vs. 1.45% respectively, relative risk = 1.094, 95% confidence interval 0.844 to 1.417, P = .54). CONCLUSION: This large study of a single institution with multiple surgeons over an 11-year period shows no compromise in patient safety or outcomes when comparing cases done in either consecutive or overlapping rooms.

Is Outpatient Unicompartmental Knee Arthroplasty Safe to Perform at an Ambulatory Surgery Center? A Comparative Study of Early Post-Operative Complications.

BACKGROUND: Unicompartmental knee arthroplasty (UKA) lends itself to the outpatient surgical setting. Prior literature has established a low rate of readmission and post-operative complications when performed in a hospital outpatient setting (HOP). To our knowledge, there have been no studies comparing complications of UKA performed at an ambulatory surgery center (ASC) and those in a HOP. METHODS: We retrospectively reviewed all patients who underwent outpatient UKA by a single surgeon from 2012 to 2016. In all 569 outpatient UKAs were performed: 288 in the ASC group and 281 in the HOP group. We compared the groups with regard to all complications within the first 90 days after surgery. RESULTS: Thirty minor and major complications occurred within 90 days (5.3%). There was no difference in the overall complication rate between groups (ASC 12, 4.2%; HOP 18, 6.4%) (P = .26). Day of surgery admission occurred once in the HOP group (0.4%) and did not occur in the ASC group (P = .49). There was 1 visit to the emergency department (ED) <24 hours from surgery in each group (ASC 0.3%, HOP 0.4%) (P = 1.0). ED visits occurred within 7 days in 3 ASC cases (1.0%) and 4 HOP cases (1.4%) (P = .72). Re-admissions in the first 90 days occurred in 5 ASC cases (1.7%) and 8 HOP cases (2.8%) (P = .41). CONCLUSION: UKA at an ASC has a low early postoperative complication rate without increased risk of re-admission or ED evaluation when compared to UKAs performed at a HOP.