Obesity, morbid obesity and their related medical comorbidities are associated with increased complications and revision rates after unicompartmental knee arthroplasty

Is There Variation in Time to and Type of Treatment for Hip Osteoarthritis Based on Insurance?

BACKGROUND

Disparities in care access based on insurance exist for total hip arthroplasty (THA), but it is unclear if these lead to longer times to surgery. We evaluated whether rates of THA versus nonoperative interventions (NOI) and time to THA from initial hip osteoarthritis (OA) diagnosis vary by insurance type.

METHODS

Using a national claims database, patients who had hip OA undergoing THA or NOI from 2011 to 2019 were identified and divided by insurance type: Medicaid-managed care; Medicare Advantage; and commercial insurance. The primary outcome was THA incidence within 3 years after hip OA diagnosis. Multivariable logistic regression models were created to assess the association between THA and insurance type, adjusting for age, sex, region, and comorbidities.

RESULTS

Medicaid patients had lower rates of THA within 3 years of initial diagnosis (7.4 versus 10.9 or 12.0%, respectively; P < .0001) and longer times to surgery (297 versus 215 or 261 days, respectively; P < .0001) compared to Medicare Advantage and commercially-insured patients. In multivariable analyses, Medicaid patients were also less likely to receive THA (odds ratio (OR) = 0.62 [95% confidence intervals (CI): 0.60 to 0.64] versus Medicare Advantage, OR = 0.63 [95% CI: 0.61 to 0.64] versus commercial) or NOI (OR = 0.92 [95% CI: 0.91 to 0.94] versus Medicare Advantage, OR = 0.81 [95% CI: 0.79 to 0.82] versus commercial).

CONCLUSIONS

Medicaid patients experienced lower rates of and longer times to THA than Medicare Advantage or commercially-insured patients. Further investigation into causes of these disparities, such as costs or access barriers, is necessary to ensure equitable care.

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.

Is unicompartmental knee arthroplasty truly contraindicated in an obese patient? A meta-analysis

BACKGROUND

Obesity has long been considered a relative contraindication to unicompartmental knee arthroplasty (UKA). However, with improved implants and techniques, the criteria for UKAs have been challenged. This paper aims to assess the impact of body mass index (BMI) on revision rates and functional outcomes in UKAs.

METHODS

Databases of Pubmed, EMBASE, MEDLINE, CINHL and the Cochrane registries were systematically searched following the PROSPERO protocol. Studies comparing implant survival and functional outcome scores between obese and non-obese patients after a UKA were included.

RESULTS

Twenty-five articles reported revision rates or functional outcomes in 42,434 UKA surgeries. There was a trend to higher revision rates in patients with BMI > 30 kg/m2 (odds ratio [OR] 0.91 [0.79-1.05]), BMI >35 kg/m2 (OR 0.70 [0.48, 1.01]) or BMI >40 kg/m2 (OR 0.66 [0.41, 1.07]), although the difference was not significant. There was a significant larger improvement in Oxford Knee Scores in obese patients after a UKA (OR 2.68 [1.79, 3.57], p < 0.00001), but no difference in Knee Society Scores or Visual Analogue Scale scores.

CONCLUSION

With no significant increase in revision rates after a UKA, a significantly greater improvement in Oxford Knee Scores and no differences Knee Society Scores or Visual Analogue Scales, obesity should no longer be viewed as a relative contraindication when performing unicompartmental knee replacements.

Obese Patients Achieve Good Improvements in Patient-Reported Outcome Measures After Medial Unicompartmental Knee Arthroplasty Despite a Lower Preoperative Score

BACKGROUND

In this study, we examined the association between obesity and patient-reported outcome measures after medial unicompartmental knee arthroplasty (MUKA), assessed through score changes, Patient Acceptable Symptom State (PASS), and minimal important change (MIC). Second, the association between obesity and early readmissions was examined.

METHODS

A total of 450 MUKAs (mean body mass index [BMI] 30.3, range, 19.6-53.1), performed from February 2016 to December 2020, were grouped using BMI: <30, 30-34.9, and >34.9. Oxford Knee Score (OKS), Forgotten Joint Score (FJS), and Activity and Participation Questionnaire (APQ) were assessed preoperatively and at 3, 12, and 24 months, postoperatively. The 12-month PASS and MIC were also assessed, defining PASS as OKS = 30, MIC-OKS as change in OKS = 8, and MIC-FJS as change in FJS = 14.

RESULTS

No significant differences in OKS change were found between BMI groups. After 12 months, patients who had a BMI of 30-34.9 had lower change in FJS (estimate -8.1, 95% CI -14.9 to -1.4) and were less likely to reach PASS (odds ratio 0.4, 95% CI 0.2-0.7) as well as MIC-FJS (odds ratio 0.5, 95% CI 0.2-0.9). Both obese groups had lower change in APQ after 12 months. Differences in 90-day readmission rates were nonsignificant between groups.

CONCLUSION

Our findings of no differences in OKS improvement between BMI groups and achieving MIC for BMI > 34.9 suggest good improvements in obese patients despite lower preoperative scores, supporting contemporary indications for MUKA. Lower APQ development and achievement of 12-month PASS may be used when addressing expectations of recovery.

All-polyethylene unicompartmental knee arthroplasty is associated with increased risks of poorer knee society knee score and lower satisfaction in obese patients

BACKGROUND

Although metal-backed tibial component (MB) is biomechanically superior to all-polyethylene (AP) implants in fixed-bearing unicompartmental knee arthroplasty (UKA), recent studies have shown comparable functional outcomes between the two. However, no study has examined this comparison in obese patients (BMI ≥ 30 kg/m²). We investigated whether functional outcomes between the two implants differ among obese patients, and whether the extent of obesity influences these outcomes.

PATIENTS AND METHODS

Four hundred twenty-two UKA implants from 347 obese patients were reviewed retrospectively. Patients were assessed using the Knee Society Knee Score (KSKS) and Function Score (KSFS), the original Oxford Knee Score (OKS), and SF-36 Physical Component Summary (PCS) and Mental Component Summary (MCS). Minimal clinically important difference (MCID) attainment was recorded. Patients' fulfillment of expectations and satisfaction with the surgery outcome was also graded. Patients were further divided into lower obesity (BMI 30-34.9 kg/m²) and higher obesity (BMI ≥ 35 kg/m²) to examine effect modification.

RESULTS

There were no differences in functional outcomes and quality-of-life scores, MCID attainment of functional scores, as well as satisfaction and expectation fulfillment between AP and MB. Among higher obesity patients, AP was associated with a poorer KSKS (p = 0.031) and lower proportion of satisfaction fulfillment (p = 0.041) 2 years postoperatively compared to MB.

CONCLUSION

We found no differences in functional and quality-of-life outcomes between fixed-bearing AP and MB tibial components among obese patients who underwent UKA. However, among higher obesity patients (BMI ≥ 35 kg/m²), patients with AP tibial component were associated with lower KSKS score and a lower proportion of attaining satisfaction fulfillment 2 years postoperatively.

Obesity increases the risk of conversion to total knee arthroplasty after unicompartimental knee arthroplasty: a meta-analysis

PURPOSE

The aim of this meta-analysis was to to determine the influence of obesity on patient outcome and implant survivorship after primary unicompartmental knee arthroplasty (UKA).

METHODS

A PRISMA systematic review was conducted by searching the Medline (PubMed), EMBASE, and Cochrane electronic databases to identify clinical studies investigating the effect of obesity on outcomes after UKA. Data were collected on aspecifically designed extraction form. Methodological quality was assessed using the Methodological Index for Nonrandomized Studies score. Quantitative meta-analysis was carried out using RevMan 5.4 software.

RESULTS

A total of 17 studies were included; 43,845 primary UKA patients were classified by their BMI: on-obese (BMI 25 to < 30 kg/m²); obese (BMI 30 to < 35 kg/m²); severely obese (BMI > 35 kg/m²). Pooled analysis showed no statistically significant difference in Knee Society Score (KSS) pain in the obese (n.s.) and the severely obese (n.s.) group compared to the non-obese group, while the KSS function score was lower in the severely obese (P = 0.0002) compared to the obese (P = 0.06) and the non-obese group. Postoperative Oxford Knee Score (OKS) was lower in the obese group (P = 0.01) but not in the severely obese group (P = 0.16). Postoperative Range of Motion (ROM) was comparable in the obese and non-obese group (P = 0.16). Implant survival at 10 years follow-up was significantly lower in the obese (82.5-95.3%; P < 0.0001) and the severely obese group (87.5-93.8%; P < 0.0001) thanthe non-obese group (83.6-98.6%).

CONCLUSION

Obesity and severe obesity were associated with significantly higher revision and lower implant survival rates. Obesity did not influence clinical and most functional outcomes after UKA, whereas KSS function score was significantly lower only for the severely obese patient group.

LEVEL OF EVIDENCE

III, meta-analysis.

Fewer Adverse Events Following Outpatient Compared with Inpatient Unicompartmental Knee Arthroplasty

BACKGROUND

Unicompartmental knee arthroplasty (UKA) is a common procedure for unicompartmental knee arthritis, often resulting in pain relief and improved function. The demand for total knee arthroplasty in the U.S. is projected to grow 85% between 2014 and 2030, and the volume of UKA procedures is growing 3 to 6 times faster than that of total knee arthroplasty. The purpose of the present study was to examine the safety of outpatient and inpatient UKA and to investigate changes over time as outpatient procedures were performed more frequently.

METHODS

Patients who underwent UKA from 2005 to 2018 as part of the National Surgical Quality Improvement Program were identified. Patients were divided into an early cohort (5,555 patients from 2005 to 2015) and late cohort (5,627 patients from 2016 to 2018). Outpatient status was defined as discharge on the day of surgery. Adverse events within 30 days postoperatively were compared, with adjustment for baseline characteristics with use of standard multivariate regression and propensity-score-matching techniques.

RESULTS

Among the 5,555 cases in the early cohort, the rate of surgical-site infection was lower for inpatient (0.84%) compared with outpatient UKA (1.69%; adjusted relative risk [RR] for inpatient, 0.5; 95% confidence interval [CI], 0.2 to 1.0; p = 0.045); no other significant differences were identified. Among the 5,627 cases in the late cohort, inpatient UKA had higher rates of any complication (2.53% compared with 0.95% for outpatient UKA; adjusted RR for inpatient, 2.5; 95% CI, 1.4 to 4.3; p = 0.001) and readmission (1.81% compared with 0.88% for outpatient UKA; adjusted RR for inpatient, 2.0; 95% CI, 1.1 to 3.5; p = 0.023). In the propensity-score-matched comparison for the late cohort, inpatient UKA had a higher rate of any complication (RR for inpatient, 2.0; 95% CI, 1.0 to 4.0; p = 0.049) and return to the operating room (RR for inpatient, 4.3; 95% CI, 1.4 to 12.6; p = 0.009). Although the rate of readmission was almost twice as high among inpatients (1.67% compared with 0.84% for outpatients; RR for inpatient, 2.0; 95% CI, 1.0 to 4.1; p = 0.059), this difference did not reach significance with the sample size studied. There was a significant reduction in the overall rate of complications over time (3.44% in the early cohort compared with 2.11% in the late cohort; adjusted RR for late cohort, 0.7; 95% CI, 0.5 to 0.8; p = 0.001), with a more than fourfold reduction among outpatients (3.95% in the early cohort compared with 0.95% in the late cohort; adjusted RR for late cohort, 0.3; 95% CI, 0.1 to 0.5; p < 0.001).

CONCLUSIONS

Outpatient UKA was associated with a lower risk of complications compared with inpatient UKA when contemporary data are examined. We identified a dramatic reduction in complications across the early and late cohorts, suggesting an improvement in quality over time, with the largest improvements seen among outpatients. This shift may represent changes in patient selection or improvements in perioperative protocols.

LEVEL OF EVIDENCE

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

Application of Personalized Navigation Templates to Oxford Single Condylar Replacement in a Chinese Population

The purpose of this study is to develop and validate a novel patient-specific navigational template for unicompartmental knee arthroplasty (UKA). A total of 120 patients who underwent UKA were randomized and divided into the conventional method and navigational template groups. In the navigational template group, patient-specific navigational templates were designed and used intraoperatively to assist 60 patients with UKA. Information on operation time and blood loss was recorded by an independent operating room nurse. After surgery, the positions of the prostheses were evaluated using X-rays. All navigation templates were found to fit its corresponding biomodel appropriately without any free movement. The navigational template exhibited significantly better accuracy than the conventional method. Statistically significant differences in the femoral prosthesis flip angle, femoral prosthesis flexion angle, and tibial plateau varus and valgus angle were observed between the two groups (p = 0.022, 0.042, 0.043, respectively). In addition, the mean operation time was statistically and significantly lower in the navigational template group than in the conventional group (p = 0.035). This study introduces a novel navigational template to UKA, the accuracy of which is proven by clinical operation. This is a Level III, therapeutic study.

Unicompartmental Knee Replacement in Obese Patients: A Systematic Review and Meta-Analysis

Thanks to modern surgical techniques and implants, traditional exclusion criteria for unicompartmental knee arthroplasty (UKA) are no longer considered contraindications. The aim of this study is to clarify the impact of obesity on functional outcomes and revision rates of UKA. We performed a comprehensive systematic review using PubMed–Medline, Google Scholar and Cochrane Central. Then, we extracted data related to body mass index (BMI), age and follow-up, functional outcome scores and rate of revisions (all-cause, aseptic and septic). Patients were stratified according to BMI into two groups: non-obese (BMI < 30) and obese (BMI ≥ 30). We identified 22 eligible studies, of which 13 were included in the meta-analysis. Patients with a BMI > 30 had a significantly higher likelihood for revision (p = 0.02), while the risk of septic revision was similar (p = 0.79). The clinical outcome measures showed a significant difference in favor of patients with a BMI < 30 (p < 0.0001). The improvements in Oxford Knee Score and Knee Society Score were significant in both obese and non-obese patients, although the latter showed inferior results. The results of this systematic review and meta-analysis show that BMI is not a contraindication to UKA. However, obese patients have a higher risk for aseptic failure and lower improvement in clinical scores compared to non-obese patients.

Mid-Term Evaluation of the Unicompartmental Knee Arthroplasty in Patients with BMI of 40 or Greater

Limited evidence is available on mid-term follow-up for patients with body mass index (BMI) ≥ 40 receiving a unicompartmental knee arthroplasty (UKA). The primary objective of this study was to investigate survival of the UKA in patients with BMI ≥ 40. Secondary objectives were to assess functional and patient reported outcome measures (PROMs). Survival analysis with endpoint revision of any component for any reason was conducted using Kaplan-Meier technique on 121 knees (103 patients) that underwent UKA with Oxford Phase 3 implant (Oxford Knee, Biomet, Swindon, United Kingdom) between September 2001 and March 2014 by seven surgeons. Survivorship differences were compared using Log Rank (Mantel-Cox) tests, and Cox Proportional Hazard Model was used to assess predictors of failure. Preoperative PROMs were compared at 2 and 5 years postoperatively using paired t-tests. Mean age of patients was 58 years (43-75), mean BMI 43 kg/m² (40-51), and mean follow-up 7 years (2 months to 15 years). Survival rate for the whole cohort was 92% at 2 years and 86% at 5 years. Females had a significantly higher revision rate than males (p = 0.043). A total of 19 knees required revision (16 to TKA, 2 polyethylene liner exchanges, and 1 femoral component and liner revision). With respect to PROMs, there was a significant improvement at 2 and 5 years (p < 0.001) on 4 of 5 knee injury and osteoarthritis outcome score subscales. The mid-term survival rate for the Oxford UKA in patients with morbid obesity is similar to that of other nondesigner patient series with BMI ≥ 30, which provides further evidence for the safety of the implant in this patient population with significant improvements on PROMs at short and mid-term follow-up.

[Recommendations for unicondylar knee replacement in the course of time : A current inventory]

BACKGROUND

A higher patient satisfaction stands in contrast to higher revision rates of unicondylar knee joint endoprosthetics (UKE) compared to total knee joint endoprosthetics (TKE). Furthermore, old "dogmas" regarding indications and contraindications persist, which is still reflected in the significantly different case numbers.

AIM

The aim of this article is to provide an overview of the current literature regarding 1. indication and contraindication (BMI, age, sport, arthrosis of other compartments, ligament status) and 2. the "eternal rival" fixed or mobile bearing for UKE.

RESULTS

The choice of the right patient remains essential, even if all the old "dogmas" of contraindications have been relativized or even outdated. Arthroses of the contralateral (in medial UKE correspondingly lateral) compartment and advanced arthroses of the lateral patella facet remain the only persistent contraindications. In contrast, a high BMI, age, chondrocalcinosis, medial patella facet and a defective (but particularly functionally stable) ACL are not contraindications; however, severe obesity is responsible for a significantly higher complication rate and probably a higher rate of loosening. Rather, the experience and thus the number of UKEs of the individual surgeon is decisive for the outcome, to which the discussion about mobile or fixed inlays must also be completely subordinated.

CONCLUSION

The indications for UKE can, therefore, be extended with a clear conscience on the basis of literature, and the current 1:10 UKE:TKE ratio in Germany can be shifted significantly.

The effect of obesity on revision rate in unicompartmental knee arthroplasty: a systematic review and meta-analysis

The number of patients with knee osteoarthritis, the proportion that is obese and the number undergoing unicompartmental knee arthroplasty (UKA) are all increasing. The primary aim of this systematic review was to determine the effects of obesity on outcomes in UKA. A systematic review was performed using PRISMA guidelines and the primary outcome was revision rate per 100 observed component years, with a BMI of ≥ 30 used to define obesity. The MINORS criteria and OCEBM criteria were used to assess risk of bias and level of evidence, respectively. 9 studies were included in the analysis. In total there were 4621 knees that underwent UKA. The mean age in included studies was reported to be 63 years (mean range 59.5-72 years old)) and range of follow up was 2-18 years. Four studies were OCEBM level 2b and the average MINORS score was 13. The mean revision rate in obese patients (BMI > 30) was 0.33% pa (95% CI - 3.16 to 2.5) higher than in non-obese patients, however this was not statistically significant (p = 0.82). This meta-analysis concludes that there is no significant difference in outcomes between obese and non-obese patients undergoing UKA. There is currently no evidence that obesity should be considered a definite contraindication to UKA. Further studies are needed to increase the numbers in meta-analysis to explore activity levels, surgeon's operative data, implant design and perioperative complications and revision in more depth.Level of evidence Level III.

Obesity does not adversely impact the outcome of unicompartmental knee arthroplasty for osteoarthritis: a meta-analysis of 80,798 subjects

BACKGROUND

Patients with end-stage single compartment osteoarthritis benefit from the less invasive unicompartmental knee arthroplasty (UKA). With increasing financial restraints, some healthcare services have set specific BMI cut-offs when determining patient eligibility for knee arthroplasty due to perceived obesity-related complications. The aim of this systematic review is to determine the effect obesity has on outcomes following UKA, and thus elucidate whether obesity should be a contraindication for UKA.

METHODS

A PRISMA systematic review was conducted using five databases (MEDLINE, EMBASE, Cochrane, PubMed and Web of Science) to identify all clinical studies that examined the effect of obesity on outcomes following UKA. Quantitative meta-analysis was carried out using RevMan 5.3 software. Quality assessment was carried out using the Critical Appraisal Skills Programme (CASP) checklist.

RESULTS

Thirty studies, including a total of 80 798 patients were analysed. The mean follow- up duration was 5.42 years. Subgroup meta-analyses showed no statistically significant difference following UKA between patients cohorts with and without obesity in overall complication rates (95% CI, P = 0.52), infection rates (95% CI, P = 0.81), and revision surgeries (95% CI, P = 0.06). When further analysing complications, no differences were identified in minor (95% CI, P = 0.23) and major complications (95% CI, P = 0.68), or venous thromboembolism rates (95% CI, P = 0.06). When further analysing revision surgeries, no differences were identified for revisions specifically for infection (95% CI, P = 0.71) or aseptic loosening (95% CI, P = 0.75).

CONCLUSIONS

This meta-analysis shows that obesity does not result in poorer post-operative outcomes following UKA and should not be considered a contraindication for UKA. Future studies, including long-term follow-up RCTs and registry-level analyses, should examine factors associated with obesity and consider stratifying obesity to better delineate any potential differences in outcomes.

Revision Following Cemented and Uncemented Oxford-III Primary Medial Unicompartmental Knee Replacements: A 19-Year Analysis from the New Zealand Joint Registry

BACKGROUND

Oxford-III unicompartmental knee replacements (UKRs) are among the most commonly used prostheses to treat isolated medial compartment osteoarthritis (OA). However, the best mode of implant fixation for primary UKRs remains a source of debate. The hypothesis of this study was that the biologically superior fixation of uncemented Oxford-III primary UKRs would translate into a lower revision rate when compared with cemented Oxford-III primary UKRs used to treat isolated medial compartment OA.

METHODS

Data on all Oxford-III primary UKRs (n = 8,733) completed for isolated medial compartment OA from January 2000 to December 2018 were obtained from the New Zealand Joint Registry (NZJR). Revision rates were documented for each fixation type and analyzed for associations with patient sex and age at surgery. A multivariate Cox proportional-hazards analysis was completed to determine if type of fixation was an independent risk factor for revision of Oxford-III UKRs.

RESULTS

Statistical analysis revealed a >1.8-fold greater revision risk for cemented Oxford-III UKRs compared with uncemented Oxford-III UKRs (p = 0.001) when considered independently of other risk factors. Furthermore, compared with uncemented fixation, cemented fixation was associated with a 2.9-fold (p < 0.001) increase in revision risk for women <65 years old and a 1.7-fold (p = 0.008) increase in revision risk for men 55 to 74 years old. There was no significant difference in the risk of revision between fixation methods for women ≥65 years old and men ≥75 years old.

CONCLUSIONS

We found that the type of fixation was an independent risk factor for revision of Oxford-III UKRs used in the treatment of isolated medial compartment OA. Uncemented Oxford-III primary UKRs had superior implant survivorship in women <65 years old and men 55 to 74 years old. Age and sex are important factors to consider when determining the type of fixation for Oxford-III primary UKRs used to treat isolated medial compartment OA.

LEVEL OF EVIDENCE

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

Therapeutic Effects Comparison and Revision Case Analysis of Unicompartmental Knee Arthroplasty and Open Wedge High Tibial Osteotomy in Treating Medial Knee Osteoarthritis in Patients Under 60 years: A 2-6-year Follow-up Study

Objective

To evaluate the therapeutic effects and revision cases of unicompartmental knee arthroplasty (UKA) and open wedge high tibial osteotomy (OWHTO) in treating medial knee osteoarthritis (MKOA) in patients under 60 years.

Methods

The present retrospective study included a total of 192 patients who were diagnosed with MKOA and treated by UKA or OWHTO in the Second Affiliated hospital of Xi'an Jiaotong University and Xi'an Honghui Hospital between December 2012 and December 2016. Among these patients, 83 were treated by UKA (17 men and 66 women, aged 53.7 ± 5.2 years) and 109 were treated by OWHTO (23 men and 86 women, aged 51.8 ± 6.9 years). Patients were followed up at 1, 3, 6, and 12 months for the first year postoperation, and every 6 months from the second year postoperation. Basic data, perioperative data, hospital for special surgery (HSS) score, visual analogue pain score (VAS), low‐impact recovery, and revision cases of the patients were evaluated.

Results

The average follow‐up periods of the UKA group and the OWHTO group were 39.3 ± 11.2 months and 40.2 ± 13.5 months, respectively. No significant difference was found in the basic data of the two groups (P ≥ 0.05). The operative time, incision length, and dominant blood loss of the UKA group was less than those of OWHTO group by 19.6%, 10.7%, and 35.1%, respectively, and the differences were significant (P < 0.05), while no significant difference was found in postoperative in‐bed time (P ≥ 0.05). The HSS scores of the UKA group at 1 and 3 months postoperation were higher than those of the OWHTO group by 5.1% and 3.9% (P < 0.05), while no differences were found from 6 months postoperation (P ≥ 0.05). The VAS score of the UKA group 1 month postoperation was lower than that of the OWHTO group by 12.2% (P < 0.05), while no differences were found from 3 months postoperation (P ≥ 0.05). One year after the operation, most patients in both groups could not achieve ideal recovery in low‐impact sports, and no significant differences were found (P < 0.05). The sport in which most patients could not achieve ideal recovery was mountain climbing. No revision cases occurred in the OWHTO group, while two revisions occurred in the UKA group.

Conclusion

Candidates for UKA should be chosen carefully and the current indications and contraindications raised by Goodfellow should be modified.

Clinical results and short-term survivorship of robotic-arm-assisted medial and lateral unicompartmental knee arthroplasty

PURPOSE

The aim of this multicentre, retrospective, observational study was to determine the incidence of revision and clinical results of a large cohort of robotic-arm-assisted medial and lateral UKAs at short-term follow-up. It was hypothesized that patients who receive robotic-arm-assisted UKA will have high survivorship rates and satisfactory clinical results.

METHODS

Between 2013 and 2016, 437 patients (470 knees) underwent robotic-arm-assisted medial and lateral UKAs at two centres. Knee Injury and Osteoarthritis Outcome Score (KOOS), Forgotten Joint Score 12 (FJS-12) and Short-Form Physical and Mental Health Summary Scales (SF-12) were administered to estimate patients' overall health status pre- and post-operatively. Results were dichotomized as 'excellent' and 'poor' if KOOS/FJS-12 were more than or equal to 90 and SF-12 was more or equal to 45. Associations between patients' demographic characteristics and clinical outcomes were investigated. Post-operative complications and pain persistence were recorded.

RESULTS

Following exclusions and losses to follow-up, 338 medial and 67 lateral robotic-arm-assisted UKAs were assessed at a mean follow-up of 33.5 and 36.3 months, respectively. Three medial UKAs were revised, resulting in a survivorship of 99.0%. No lateral implants underwent revision (survivorship 100%). On average, significant improvement in all clinical scores was reported in both medial and lateral UKA patients. In medial UKA patients, male gender was associated with higher probability of better scores in overall KOOS, FJS-12 and in specific KOOS subscales. No other associations were reported between biometric parameters and outcome for either medial or lateral UKA.

CONCLUSIONS

Robotic-assisted medial and lateral UKAs demonstrated satisfactory clinical outcomes and excellent survivorship at 3-year follow-up. Continued patient follow-up is needed to determine the long-term device performance and clinical satisfaction.

LEVEL OF EVIDENCE

Retrospective cohort study, Level IV.

[Effect of body mass index on short- and medium-term effectiveness of unicompartmental knee arthroplasty]

Objective

To investigate the effect of body mass index (BMI) on the short- and medium-term effectiveness of unicompartmental knee arthroplasty (UKA) in the treatment of anterior medial compartmental osteoarthritis of knee joint.

Methods

The clinical data of 55 patients (61 knees) with anterior medial compartmental osteoarthritis of knee joint treated with minimally invasive UKA between May 2014 and May 2019 were retrospectively analyzed. According to BMI, the patients were divided into 3 groups: normal body mass group [group A, BMI 18.50-24.99 kg/m ², 23 cases (25 knees)], overweight group [group B, BMI 25.00-29.99 kg/m ², 23 cases (25 knees)], obesity group [group C, BMI 30.00-39.99 kg/m ², 9 cases (11 knees)]. There was no significant difference in gender, age, sides, disease duration, and preoperative American Special Surgery Hospital (HSS) score, pain visual analogue scale (VAS) score, and knee range of motion (ROM) among 3 groups ( P>0.05). The operation time, intraoperative dominant blood loss, and the postoperative decreased amount of hemoglobin at 1 week were recorded and compared among 3 groups. The HSS score, VAS score, and ROM were used to evaluate the knee function and pain improvement.

Results

There was no significant difference in the operation time, the intraoperative dominant blood loss, and the postoperative decreased amount of hemoglobin at 1 week among 3 groups ( P>0.05). All the 55 patients were followed up 5-60 months, with an average of 24 months. No complication such as infection, fat embolism, or deep venous thrombosis of lower extremity occurred after operation. The anteroposterior and lateral X-ray films of the knee joint showed that no dislocation or loosening of the prosthesis occurred and the position of the prosthesis was good. At last follow-up, the HSS score, VAS score, and ROM of the 3 groups were significantly improved when compared with preoperative ones ( P<0.05); but there was no significant difference among 3 groups ( P>0.05).

Conclusion

For obese and overweight patients with anterior medial compartmental osteoarthritis of the knee joint, the use of minimally invasive UKA can achieve satisfactory short- and medium-term effectiveness, and the long-term effectiveness needs further follow-up.

High Failure Rates for Unicompartmental Knee Arthroplasty in Morbidly Obese Patients: A Two-Year Minimum Follow-Up Study

BACKGROUND

Several recent studies have recommended offering unicompartmental knee arthroplasty (UKA) to all patients regardless of body mass index (BMI). The aim of this investigation was to evaluate the proposition that UKA can indeed be offered to the morbidly-obese and super-obese (morbidly-obese, BMI ≥ 40 kg/m²) without compromising results or survivorship.

METHODS

We retrospectively reviewed mobile-bearing medial UKA procedures performed at our facility from January 2012 to May 2015 with a minimum of 2-year follow-up. The study cohort was divided into patients with morbid obesity (BMI ≥ 40 kg/m²) and those without morbid obesity (BMI < 40 kg/m²). A detailed medical record review was performed. Extracted outcome data included the frequency of (1) major revision procedures (components revised), (2) minor secondary procedures (components not revised), (3) infection procedures, and (4) recommendations for revision.

RESULTS

We found 152 patients (190 knees) who met criteria for inclusion. Mean follow-up duration was 3.4 years (range: 2.0-6.8 years). Major revision surgery occurred more frequently in the morbid-obesity UKA group (15.7% vs 3.0%, P < .01). Rates of minor secondary surgery and infection were comparable for both groups. Most failures in the morbid-obesity UKA group (85.7%) were due to disease progression involving other compartments or mobile-bearing instability.

CONCLUSION

We found the rate of early major revision surgery in morbidly-obese patients undergoing UKA to be over 5-times greater than that of other patients. Failure was predominantly due to disease progression in other compartments or mobile-bearing instability. Further study is warranted and needed before expanding UKA indications to the morbidly-obese population.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Corrective osteotomies of femur and tibia: which factors influence bone healing?

INTRODUCTION

Corrective osteotomies of the lower limb are standard procedures in orthopedic surgery. Still, there is only limited research on factors affecting bone healing after osteotomies. We hypothesize that especially the location of the osteotomy, smoking status and BMI affect bone healing.

MATERIAL AND METHODS

The healing process of 547 patients who underwent osteotomies of the lower limb (259 female, 288 male; average 40.6 years, range 14-77) was evaluated. To assess bone healing, participants were divided into three groups by bone healing duration ( < 5/5-8/ > 8 months). Differences in healing duration related to the anatomic level of the osteotomy (diaphysis vs. metaphysis), age, gender, smoking status, BMI, and modus of the osteotomy (open vs. closed wedge) were tested for significance using an ordinal regression analysis.

RESULTS

A significant correlation between bone healing and the anatomical level of the osteotomy on femur and tibia and the patients' smoking status was found. The odds of the diaphysis considering bone healing was 0.187 (95% CI, 0.08-0.44) times that of the metaphysis (Wald χ²(1) = 14.597, p < 0.000). The odds ratio of smokers considering bone healing was 0.192 (95% CI, 0.11-0.33) times that of non-smokers (Wald χ²(1) = 35.420, p < 0.000). All other analyzed factors did not show a significant correlation with bone healing.

CONCLUSIONS

Smoking status and the localization of the osteotomy on femur and tibia (diaphysis vs. metaphysis) are significantly correlated with bone healing duration. In line with current literature emphasizing the detrimental effect of smoking on bone healing, our findings should encourage surgeons to think twice about the indication to perform osteotomies on smokers. Furthermore, if applicable, osteotomies should be performed in the metaphyseal areas of femur and tibia.

Mid-term survivorship and patient-reported outcomes of robotic-arm assisted partial knee arthroplasty

Aims

Limited evidence is available on mid-term outcomes of robotic-arm assisted (RA) partial knee arthroplasty (PKA). Therefore, the purpose of this study was to evaluate mid-term survivorship, modes of failure, and patient-reported outcomes of RA PKA.

Methods

A retrospective review of patients who underwent RA PKA between June 2007 and August 2016 was performed. Patients received a fixed-bearing medial or lateral unicompartmental knee arthroplasty (UKA), patellofemoral arthroplasty (PFA), or bicompartmental knee arthroplasty (BiKA; PFA plus medial UKA). All patients completed a questionnaire regarding revision surgery, reoperations, and level of satisfaction. Knee Injury and Osteoarthritis Outcome Scores (KOOS) were assessed using the KOOS for Joint Replacement Junior survey.

Results

Mean follow-up was 4.7 years (2.0 to 10.8). Five-year survivorship of medial UKA (n = 802), lateral UKA (n = 171), and PFA/BiKA (n = 35/10) was 97.8%, 97.7%, and 93.3%, respectively. Component loosening and progression of osteoarthritis (OA) were the most common reasons for revision. Mean KOOS scores after medial UKA, lateral UKA, and PFA/BiKA were 84.3 (SD 15.9), 85.6 (SD 14.3), and 78.2 (SD 14.2), respectively. The vast majority of the patients reported high satisfaction levels after RA PKA. Subgroup analyses suggested tibial component design, body mass index (BMI), and age affects RA PKA outcomes. Five-year survivorship was 98.4% (95% confidence interval (CI) 97.2 to 99.5) for onlay medial UKA (n = 742) and 99.1% (95% CI 97.9 to 100) for onlay medial UKA in patients with a BMI < 30 kg/m2 (n = 479).

Conclusion

This large single-surgeon study showed high mid-term survivorship, satisfaction levels, and functional outcomes in RA UKA using metal-backed tibial onlay components. In addition, favourable results were reported in RA PFA and BiKA. Cite this article: Bone Joint J 2020;102-B(1):108–116

Unicondylar Tibiofemoral Arthroplasty - Opinions of the Members of the German Knee Society (DKG) and the German Professional Association of Orthopaedic and Trauma Specialists (BVOU)

BACKGROUND

The number of implanted unicondylar tibiofemoral knee arthroplasties (UKA) is despite the potential advantages in comparison to total knee arthroplasties (TKA) in Germany relatively low. Goal of this survey, initiated by the Small Implants Group of the German Knee Society, was to gather opinions and put them into context of the current literature.

METHODS

Based on the Delphi method and the AWMF rules and standards, 19 statements were developed, which were presented to the members of the DKG and BVOU in an anonymous online survey using "SurveyMonkey". Overall, 410 colleagues participated.

RESULTS

The biggest detected controversies were the determination of indications with respect to the body mass index and the existence of a patellofemoral arthrosis. A general consent was determined that a contralateral tibiofemoral arthrosis grade III - IV and meniscal deficiency in the contralateral compartment are an absolute contraindication. There was a consent that age is not a limitation for the implantation of an UKA. If a personal minimum volume of 15 implantations/year should be implemented was seen controversial.

CONCLUSION

The personal opinion, eventually built by personal experiences, appears to be in conflict with the knowledge of scientific literature in many instances. Intensive training and education appears necessary.

The effect of morbid obesity (BMI ≥ 35 kg/m2) on functional outcome and complication rate following unicompartmental knee arthroplasty: a case-control study

Background

The aim of this study was to evaluate and compare the functional outcomes and complication rates of patients in short-term and midterm follow-up period when medial unicompartmental knee arthroplasty (UKA)-applied patients were grouped according to BMI values.

Methods

One hundred four patients (mean age 60.2 ± 7.4 (range, 49–80)) to whom medial UKA was applied between 2011 to 2016 with a minimum of 2 years follow-up were grouped as normal and overweight (less than 30 kg/m²), obese (30–34.9 kg/m²) and morbidly obese (BMI ≥ 35 kg/m²) according to their BMI. The postoperative Knee Society Scores (KSS), functional Knee Society Scores (fKSS), Oxford Knee Scores (OKS), visual analogue scale (VAS) and range of motion (ROM) results and complication rate of these groups were compared statistically. The implant positioning of the patients requiring revision was analysed according to the Oxford radiological criteria.

Results

The average BMI of 104 patients was 34.4 (range, 22–56.9). Twenty-six (25%) of these were normal or overweight, 40 (38.5%) were obese and 38 (36.5%) were morbidly obese. However, in these BMI groups, there was no significant difference between the preoperative VAS, postoperative VAS and VAS score changes among these three groups (p > 0.05). The postop KSS, f KSS and OKS were significantly poorer in the morbidly obese group by 75.2, 70.5 and 33.1, respectively. Furthermore, amount of ROM changes (4.2°) were significantly poorer in the morbidly obese group (p < 0.05). Complications including eminence fractures, insert dislocations, tibial component collapses and superficial infections developed in 10 patients (9.6%). Six of them (60%) were morbidly obese, and four of them (40%) were obese. Furthermore, 11 (10.6%) of the patients required revision. Eight (72.7%) of the patients were morbidly obese, and three (27.3%) of them were obese.

Conclusions

We concluded that morbid obesity is an independent risk factor for functional outcomes and implant survival after UKA. However, it is possible to obtain excellent results for obese and overweight patients with good planning and correct surgical technique. Morbid obese patients should be preoperatively informed about poor functional outcome and high complication rate. Treatment of morbid obesity before UKA surgery may be a good option.

An increased body mass index was not associated with higher rates of 30-day postoperative complications after unicompartmental knee arthroplasty

BACKGROUND

The association of postoperative complications and obesity after total knee arthroplasty (TKA) has been well described. However, the effect of an increased body-mass index (BMI) on postoperative complications after unicompartmental knee arthroplasty (UKA) is controversial. Therefore, our aim was to assess the influence of BMI on 30-day postoperative complications after UKA when analyzed as both a categorical and continuous variable.

METHODS

The American College of Surgeons National Quality Improvement Program (NSQIP) database was used to identify a total of 8029 patients who underwent UKA from January 1, 2008, to December 31, 2016. The database was queried for over 30 unique complications occurring within 30 days. The impact of BMI on short-term outcomes was assessed as a categorical variable using univariate and multivariate regression. Additionally, BMI was assessed as a continuous variable using spline regressions.

RESULTS

Univariate regression analysis revealed that compared to normal weight patients, overweight patients had a lower risk of major complication (odds ratio [OR], 0.506; 95% confidence interval [CI], 0.279-0.918; p = 0.025), and any complication ([OR] 0.632; 95% CI, 0.423-0.944; p = 0.025) Multivariate regression analysis found no statistically significant relationship between categorical BMI and complications or outcomes, except for morbidly obese patients who had a greater risk of superficial SSI (p = 0.026). Spline regression found no statistically significant non-linear relationships between BMI and any complication (p = 0.4687), major complications (p = 0.1567), or minor complications (p = 0.4071).

CONCLUSION

Overweight and obese individuals who undergo UKA may not have an increased risk of 30-day postoperative complications compared to normal weight individuals.

Variations in Utilization of Carpal Tunnel Release Among Medicaid Beneficiaries

PURPOSE

To evaluate the null hypothesis that Medicaid patients receive carpal tunnel release (CTR) at the same time interval from diagnosis as do patients with Medicare Advantage or private insurance.

METHODS

We conducted a retrospective review using a database containing claims records from 2007 to 2016. The cohort consisted of patient records with a diagnosis code of carpal tunnel syndrome (CTS) and a procedural code for CTR within 3 years of diagnosis. We stratified patients into 3 groups by insurance type (Medicaid managed care, Medicare Advantage, and private) for an analysis of the time from diagnosis until surgery and use of preoperative electrodiagnostic testing.

RESULTS

Of all patients who received CTR within 3 years of diagnosis, Medicaid patients experienced longer intervals from CTS diagnosis to CTR compared with Medicare Advantage and privately insured patients (median, 99 days vs 65 and 62 days, respectively). The Medicaid cohort was significantly less likely to receive CTR within 1 year of diagnosis compared with the Medicare Advantage cohort (adjusted odds ratio [OR] = 0.54) or within 6 months of diagnosis compared with the privately insured cohort (adjusted OR = 0.61). Those in the Medicaid cohort were less likely to receive electromyography and nerve conduction studies within 9 months before surgery compared with their Medicare Advantage (adjusted OR = 0.43) and privately insured (adjusted OR = 0.41) counterparts. These effects were statistically significant after accounting for age, sex, region, and Charlson comorbidity index.

CONCLUSIONS

Medicaid managed care patients experience longer times from diagnosis to surgery compared with Medicare Advantage or privately insured patients in this large administrative claims database. Similar variation exists in the use of electrodiagnostic testing based on insurance type.

CLINICAL RELEVANCE

Medicaid patients may experience barriers to CTS care, such as delays from diagnosis to surgery and reduced use of electrodiagnostic testing.

Long-Term Results of Medial Unicompartmental Knee Arthroplasty for Knee Avascular Necrosis

BACKGROUND

Numerous series have documented short and mid-term successes with cemented, metal-backed modern unicompartmental knee arthroplasty (UKA) for avascular osteonecrosis of the knee (AVN). However, data are lacking regarding long-term implant fixation and patient function. The aim of this study is therefore to evaluate the long-term clinical outcome and implant survivorship of patients who underwent UKA for medial knee osteonecrosis (ON).

METHODS

Twenty-nine consecutive UKAs performed by 2 senior surgeons (>50 UKAs a year) in 28 patients (19 women and 9 men with a mean age of 67 years) with medial unicompartmental AVN of the knee between 1989 and 2001 were retrospectively reviewed. AVN was diagnosed using X-ray, magnetic resonance imaging scan, and finally confirmed by postoperative sample analysis. The mean patient body mass index was 27 kg/m². Etiologies were spontaneous/idiopathic AVN in 19 knees (66%) and secondary AVN in 10 knees (33%). The mean follow-up was 21 years (range 15-26).

RESULTS

At 15 years, survivorship of the components free of revision for any cause was 92% (95% confidence interval 87-97). At latest follow-up, 26 years, survivorship of the components free of revision for any reason was 83% (95% confidence interval 74-95). No survivorship difference was found between the patients suffering from spontaneous or secondary ON of the knee (83% vs 90%, P = .6). At latest follow-up, the mean Knee Society Scoring system Knee was 89 points (range 68-100) and 83 (range 66-96) for Knee Society Scoring system Function.

CONCLUSION

In the longest series to date, medial UKA for treatment of AVN was associated with high survival rates and stable clinical improvement. UKA is a durable and efficient option to treat patients with unicompartmental ON of the knee.

LEVEL OF EVIDENCE

IV.

The association of under-weight and obesity with mortality after hip arthroplasty

Background

although many studies have demonstrated the association between body mass index (BMI) and many diseases, there is little evidence of postoperative mortality after hip arthroplasty. The aim of this study was to evaluate the association between BMI and mortality after hip arthroplasty in the older population.

Methods

a total of 3,627 older patients who underwent hip arthroplasty from 2010 to 2013 were included. We used Cox regression analysis to evaluate the association between BMI and mortality after hip arthroplasty. The hazard ratios (HRs) was calculated from 30 days, 31-365 days, and from the first day of surgery to the day of death during the study.

Results

under-weight (BMI under 18.5 kg/m2) is significantly associated with increased mortality (HR:1.423; 95% Confidence Interval (CI): 1.023-1.981) after hip arthroplasty compared to the normal range. However, in the short-term mortality within 30 days after surgery, both under-weight (HR: 2.368; 95%CI: 1.130-4.960) and obesity (25-29.9 kg/m2, HR: 2.023; 95%CI: 1.008-4.059) are associated with increased mortality.

Conclusion

our study suggested that under-weight is associated with increased risk of mortality after hip arthroplasty. Further, in a short-term outcome, obesity appear to be associated with increased mortality after hip arthroplasty within 30 days.

The Influence of Obesity on Total Elbow Arthroplasty

Total elbow arthroplasty (TEA) has undergone a significant evolution in indications and outcomes in the past decade. Although rheumatoid patients once had the overwhelming number of TEAs, now TEAs for the sequelae of trauma predominate. Furthermore, as obesity has mirrored the increase in the posttraumatic population, TEA complications have increased whereas the durability of implants under these loads has decreased. Solutions are urgently needed to address the complications and revision burden related to posttraumatic deformity and obesity.

Body mass index changes after unicompartmental knee arthroplasty do not adversely influence patient outcomes

PURPOSE

The objective of this study is to evaluate the prevalence of patients who lost or gained weight following unicompartmental knee arthroplasty (UKA), the effect of post-operative body mass index (BMI) changes on functional outcomes and quality of life (QoL), and predictive factors associated with BMI changes.

METHODS

Prospectively collected data of 1043 patients who underwent UKA between 2000 and 2014 were reviewed. BMI, Knee Society Knee Score and Function Score, Oxford Knee Score (OKS), Short-Form 36 (SF-36) Physical Component Score (PCS) and Mental Component Score and proportion of patients attaining OKS/SF-36 minimal clinically important differences (MCID) were recorded preoperatively and at 2 years post-operatively. The patients were stratified into three groups based on weight changes for further analysis.

RESULTS

Following UKA, 138 (13.3%) patients had lost weight, 695 (66.6%) maintained their weight, and 210 (20.1%) gained weight. Patients in all groups demonstrated significant improvements in functional and SF-36 PCS scores at 2 years post-operatively. There were no significant differences in functional outcomes, QoL or revision rate between the groups. Post-operative BMI changes were not correlated with any outcome scores or attainment of MCID (n.s.).

CONCLUSIONS

This is the first study that evaluates change in BMI following UKA. It demonstrated a higher proportion of patients who gained weight as compared to those who lost weight. Post-operative BMI changes did not appear to affect outcomes of UKA. These findings will provide important information to surgeons when counselling patients regarding BMI change and its effect on outcomes after UKA.

LEVELS OF EVIDENCE

Level III.

Development and Evaluation of a Preoperative Risk Calculator for Periprosthetic Joint Infection Following Total Joint Arthroplasty

BACKGROUND

Preoperative identification of patients at risk for periprosthetic joint infection (PJI) following total hip arthroplasty (THA) or total knee arthroplasty (TKA) is important for patient optimization and targeted prevention. The purpose of this study was to create a preoperative PJI risk calculator for assessing a patient's individual risk of developing (1) any PJI, (2) PJI caused by Staphylococcus aureus, and (3) PJI caused by antibiotic-resistant organisms.

METHODS

A retrospective review was performed of 27,717 patients (12,086 TKAs and 31,167 THAs), including 1,035 with confirmed PJI, who were treated at a single institution from 2000 to 2014. A total of 42 risk factors, including patient characteristics and surgical variables, were evaluated with a multivariate analysis in which coefficients were scaled to produce integer scores. External validation was performed with use of data on 29,252 patients who had undergone total joint arthroplasty (TJA) at an independent institution.

RESULTS

Of the 42 risk factors studied, 25 were found not to be significant risk factors for PJI. The most influential of the remaining 17 included a previous open surgical procedure, drug abuse, a revision procedure, and human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS). The areas under the curves were 0.83 and 0.84 for any PJI, 0.86 and 0.83 for antibiotic-resistant PJI, and 0.86 and 0.73 for S. aureus PJI in the internal and external validation models, respectively. The rates of PJI were 0.56% and 0.61% in the lowest decile of risk scores and 15.85% and 20.63% in the highest decile.

CONCLUSIONS

In this large-cohort study, we were able to identify and validate risk factors and their relative weights for predicting PJI. Factors such as prior surgical procedures and high-risk comorbidities should be considered when determining whether TJA is indicated and when counseling patients.

LEVEL OF EVIDENCE

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

Can obesity and physical activity predict outcomes of elective knee or hip surgery due to osteoarthritis? A meta-analysis of cohort studies

OBJECTIVE

The aim of this study was to systematically review the literature to identify whether obesity or the regular practice of physical activity are predictors of clinical outcomes in patients undergoing elective hip and knee arthroplasty due to osteoarthritis.

DESIGN

Systematic review and meta-analysis.

DATA SOURCE AND ELIGIBILITY CRITERIA

A systematic search was performed on the Medline, CINAHL, EMBASE and Web of Science electronic databases. Longitudinal cohort studies were included in the review. To be included, studies needed to have assessed the association between obesity or physical activity participation measured at baseline and clinical outcomes (ie, pain, disability and adverse events) following hip or knee arthroplasty.

DATA EXTRACTION

Two independent reviewers extracted data on pain, disability, quality of life, obesity, physical activity and any postsurgical complications.

RESULTS

62 full papers were included in this systematic review. From these, 31 were included in the meta-analyses. Our meta-analysis showed that compared to obese participants, non-obese participants report less pain at both short term (standardised mean difference (SMD) -0.43; 95% CI -0.67 to -0.19; P<0.001) and long term post-surgery (SMD -0.36; 95% CI -0.47 to -0.24; P<0.001), as well as less disability at long term post-surgery (SMD -0.32; 95% CI -0.36 to -0.28; P<0.001). They also report fewer postsurgical complications at short term (OR 0.48; 95% CI 0.25 to 0.91; P<0.001) and long term (OR 0.55; 95% CI 0.41 to 0.74; P<0.001) along with less postsurgical infections after hip arthroplasty (OR 0.33; 95% CI 0.18 to 0.59; P<0.001), and knee arthroplasty (OR 0.42; 95% CI 0.23 to 0.78; P=0.006).

CONCLUSIONS

Presurgical obesity is associated with worse clinical outcomes of hip or knee arthroplasty in terms of pain, disability and complications in patients with osteoarthritis. No impact of physical activity participation has been observed.

PROSPERO REGISTRATION NUMBER

CRD42016032711.

Early comparative outcomes of unicompartmental and total knee arthroplasty in severely obese patients

BACKGROUND

Medial unicompartmental knee arthroplasty (UKA) may have advantages over total knee arthroplasty (TKA) in the setting of obesity. There has been no direct comparison between the two cohorts. This study compares outcomes and complications of severely obese patients undergoing medial UKA versus TKA.

METHODS

Six hundred and fifty medial UKA and 1300 TKA were performed in patients with BMI >35kg/m² (mean 41kg/m²) between 2007 and 2012. Pre- and postoperative ROM, Knee Society scores, perioperative factors, complications and reoperations were compared.

RESULTS

UKA patients had higher preoperative ROM, and Knee Society pain (KSP), functional (KSF), and clinical (KSC) scores (p<0.001, p=0.0008, p=0.0003, p=0.051 respectively). Mean tourniquet times, operative times, and lengths of stay were lower after UKA. Four TKA patients required transfusion. Mean follow-up was 2.3years. The frequency of manipulation under anesthesia was higher in TKA patients (p<0.001), while the rate of component revision was similar between the two groups (1.2% vs. 1.7%, p=0.328). Frequency of deep infection was lower in the UKA group (p=0.016). Postoperative KSF, change in KSF, and ROM were higher (p<0.0001) after UKA, but KSP and KSC were equivalent.

CONCLUSIONS

Severely obese patients who underwent medial UKA demonstrated equal survivorship with substantially fewer reoperations, reduced deep infection, and less perioperative complications at short term follow-up. Severely obese patients had improved KSF scores and maintenance of ROM after UKA compared with TKA.

Morbid Obesity in Total Knee Arthroplasty: Joint-Specific Variance in Outcomes for Operative Time, Length of Stay, and Readmission

BACKGROUND

It is increasingly apparent that the effect of obesity in arthroplasty is joint-specific. This study evaluates the effects of morbid obesity on primary total knee arthroplasty by comparing short-term outcomes between a morbidly obese (body mass index ≥40 kg/m²) and a normal weight (body mass index 18.5-<25 kg/m²) cohort at our institution between January 2003 and December 2010.

METHODS

One hundred seventeen morbidly obese patients were compared with 94 normal weight patients. Operative time, length of stay, complications, 30-day readmission, and readmission length were compared.

RESULTS

Morbid obesity conveyed no significant increase in 30-day readmission. Operative time was increased at 100 minutes in the morbidly obese group, compared with 90.5 minutes (P = .026).

CONCLUSION

Morbid obesity conveyed no increased risk of length of stay or readmission in this cohort.

Medial vs lateral unicompartmental knee arthrroplasty: clinical results

Unicompartmental Knee Arthroplasty (UKA) is a common procedure for the management of isolated osteoarthritis. UKA is considered less invasive compared to total knee arthroplasty, associated with less operative time, blood loss and faster recovery. Isolated lateral osteoarthritis is a relatively uncommon clinical problem, with an incidence about ten times lower than the medial compartment. In fact, lateral UKA are about 5-10% of the total amount of the UKAs. In addition, it's historically considered more challenging and with poorer results. The aim of this paper was to compare current indications, modes of failure, survivorship and clinical results of medial and lateral UKA by a narrative review of the latest literature.

Survivorship and patient satisfaction of robotic-assisted medial unicompartmental knee arthroplasty at a minimum two-year follow-up

BACKGROUND

Successful clinical outcomes following unicompartmental knee arthroplasty (UKA) depend on lower limb alignment, soft tissue balance and component positioning, which can be difficult to control using manual instrumentation. Although robotic-assisted surgery more reliably controls these surgical factors, studies assessing outcomes of robotic-assisted UKA are lacking. Therefore, a prospective multicenter study was performed to assess outcomes of robotic-assisted UKA.

METHODS

A total of 1007 consecutive patients (1135 knees) underwent robotic-assisted medial UKA surgery from six surgeons at separate institutions between March 2009 and December 2011. All patients received a fixed-bearing metal-backed onlay implant as tibial component. Each patient was contacted at minimum two-year follow-up and asked a series of five questions to determine survivorship and patient satisfaction. Worst-case scenario analysis was performed whereby all patients were considered as revision when they declined participation in the study.

RESULTS

Data was collected for 797 patients (909 knees) with average follow-up of 29.6months (range: 22-52months). At 2.5-years of follow-up, 11 knees were reported as revised, which resulted in a survivorship of 98.8%. Thirty-five patients declined participation in the study yielding a worst-case survivorship of 96.0%. Of all patients without revision, 92% was either very satisfied or satisfied with their knee function.

CONCLUSION

In this multicenter study, robotic-assisted UKA was found to have high survivorship and satisfaction rate at short-term follow-up. Prospective comparison studies with longer follow-up are necessary in order to compare survivorship and satisfaction rates of robotic-assisted UKA to conventional UKA and total knee arthroplasty.

Early functional outcome after lateral UKA is sensitive to postoperative lower limb alignment

PURPOSE

The predictive role of patient-specific characteristics and radiographic parameters on medial unicompartmental knee arthroplasty (UKA) outcomes is well known, but knowledge of these predictors is lacking in lateral UKA. Therefore, purpose of this study was to assess the predictive role of these parameters on short-term functional outcomes of lateral UKA.

METHODS

In this retrospective cohort study, Western Ontario and McMaster Universities Arthritis Index scores were collected at 2-year follow-up (median 2.2 years, range 2.0-4.0 years) in 39 patients who underwent lateral UKA. Patient-specific characteristics included age, BMI and gender, while radiographic parameters included osteoarthritis severity of all three compartments and both preoperative and postoperative hip-knee-ankle alignment.

RESULTS

BMI, gender, age and preoperative valgus alignment were not correlated with functional outcomes, while postoperative valgus alignment was correlated with functional outcomes (0.561; p = 0.001). Postoperative valgus of 3°-7° was correlated with better outcomes than more neutral (-2° to 3° valgus) alignment (96.7 vs. 85.6; p = 0.011). Postoperative alignment was a predictor when corrected for patient-specific characteristics (regression coefficient 4.1; p < 0.001) and radiological parameters (regression coefficient 3.8; p = 0.002).

CONCLUSIONS

Postoperative valgus alignment of 3°-7° was correlated with the best short-term functional outcomes in lateral UKA surgery, while patient-specific parameters and preoperative alignment were not correlated with functional outcomes. Based on these findings, a surgeon should aim for valgus alignment of 3°-7° when performing lateral UKA surgery for optimal functional outcomes.

LEVEL OF EVIDENCE

Prognostic study, Level II.

The Role of Patient Characteristics on the Choice of Unicompartmental versus Total Knee Arthroplasty in Patients With Medial Osteoarthritis

BACKGROUND

Medial unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) are both viable treatment options for medial osteoarthritis (OA). However, it remains unclear when to choose for which arthroplasty treatment. Goals of this study were therefore to (1) compare outcomes after both treatments and (2) assess which treatment has superior outcomes in different patient subgroups.

METHODS

In this retrospective cohort study, 166 patients received the RESTORIS MCK Medial UKA and 63 patients the Vanguard TKA and were radiographically matched on isolated medial OA. Western Ontario and McMaster Universities Arthritis Index scores were collected preoperatively and postoperatively (mean: 3.0 years, range: 2.0-5.0 years).

RESULTS

Preoperatively, no differences were observed, but medial UKA patients reported better functional outcomes than TKA (89.7 ± 13.6 vs 81.2 ± 18.0, P = .001) at follow-up.Better functional outcomes were noted after medial UKA in patients younger than age 70 years (89.5 ± 14.2 vs 78.6 ± 20.0, P = .001), with body mass index below 30 (90.3 ± 11.4 vs 83.6 ± 14.9, P = .005), with body mass index above 30 (88.3 ± 17.5 vs 78.8 ± 21.0, P = .034) and in females (90.6 ± 11.0 vs 78.1 ± 19.4, P = .001) when compared with TKA. No differences were found in males and older patients between both arthroplasties.

CONCLUSION

Superior functional outcomes were noted after medial UKA over TKA in patients presenting with medial OA with these prostheses. Subgroup analyses suggest that medial UKA is the preferred treatment in younger patients and females while no differences were noted in older patients and males after medial UKA and TKA. This might help the orthopedic surgeon in individualizing arthroplasty treatment for patients with medial OA.

Morbid Obesity and Total Knee Arthroplasty: A Growing Problem

Obesity is an epidemic, with approximately 35% of the US population affected. This rate is unlikely to decline and may increase the demand for total knee arthroplasty (TKA). Data regarding the risks, benefits, and potential complications of TKA in this patient population are conflicting. Preoperative considerations are optimization of nutritional status, safe weight loss strategies, and bariatric surgery. Intraoperative concerns unique to this population include inadequate exposure, implant alignment, and durable implant fixation; postoperative issues include tibial loosening, wound complications, cardiovascular events, and respiratory complications. A thorough understanding of the medical and surgical complications associated with TKA in the obese patient will facilitate research efforts and improve outcomes.

Obesity has no effect on outcomes following unicompartmental knee arthroplasty

PURPOSE

Although obesity has historically been described as a contraindication to UKA, improved outcomes with modern UKA implant designs have challenged this perception. The purpose of this study was to assess the influence of obesity on the outcomes of UKA with a robotic-assisted system at a minimum follow-up of 24 months with the hypothesis that obesity has no effect on robotic-assisted UKA outcomes.

METHODS

There were 746 medial robotic-assisted UKAs (672 patients) with a mean age of 64 years (SD 11) and a mean follow-up time of 34.6 months (SD 7.8). Mean overall body mass index (BMI) was 32.1 kg/m² (SD 6.5), and patients were stratified into seven weight categories according to the World Health Organization classification.

RESULTS

Patient BMI did not influence the rate of revision surgery to TKA (5.8 %) or conversion from InLay to OnLay design (1.7 %, n.s.). Mean postoperative Oxford knee score was 37 (SD 11) without correlation with BMI (n.s.). The type of prosthesis (InLay/OnLay) regardless of BMI had no influence on revision rate (n.s.). BMI did not influence 90-day readmissions (4.4 %, n.s.), but showed significant correlation with higher opioid medication requirements and a higher number of physical therapy session needed to reach discharge goals (p = 0.031).

CONCLUSION

These findings suggest that BMI does not influence clinical outcomes and readmission rates of robotic-assisted UKA at mid-term. The classic contraindication of BMI >30 kg/m² may not be justified with the use of modern UKA designs or techniques.

LEVEL OF EVIDENCE

IV.

[Fixed bearing unicondylar arthroplasty in medial osteoarthritis of the knee]

OBJECTIVE

The unicondylar prosthesis replaces the medial femerotibial compartment only, the part presenting with osteoarthritic changes. The remaining compartments of the knee present less osteoarthritic changes and thus can be preserved.

INDICATIONS

Osteoarthritis of the medial femorotibial compartment is the ideal indication for unicondylar arthroplasty. The knee should show an intraarticular deformity, which means the malalignment is caused by the osteoarthritic changes of the medial compartment.

CONTRAINDICATIONS

Malalignment of >5°, flexion contracture of >10°, mediolateral instability and symptomatic osteoarthritis of a second compartment should be considered as contraindications for unicondylar arthroplasty.

SURGICAL TECHNIQUE

In the current article, implantation of the BalanSys® system is presented. Femoral bony resection is solely ligament balanced. The technique allows creation of an optimal extension and flexion gap. Bone cuts were performed using a soft tissue tension device for measuring the extension and flexion gap.

POSTOPERATIVE MANAGEMENT

Full weight bearing on crutches is allowed immediately after surgery without restriction in flexion. Crutches are recommended for 4 weeks in order to compensate for neuromuscular deficits. Anticoagulation is recommended for 11-14 days according to the AWMF guidelines (S3 guidelines, Release:15 October 2015).

RESULTS

The clinical follow-up after 2 years showed 87 ± 13 points in the knee score and 80 ± 10 points in the function score. The mean range of motion increased from 113°±24° prior to surgery to 122°±23° after surgery. A preoperative extension deficit of 10° was observed in 9 patients and reduced postoperatively in 3 patients.

Trigger digit release: rates of surgery and complications as indicated by a United States Medicare database

A United States insurance database was examined for trigger digit release using International Classification of Diseases, 9th Revision diagnoses and procedures or Current Procedural Terminology codes. Complications after trigger digit release, including stiffness, infection and revision surgery, were assessed. A total of 209,634 patients who underwent trigger digit release were included. The rate of trigger digit release increased significantly from 2005 to 2012, with the middle finger the most frequently released. The rate of postoperative stiffness was low, ranging from 0.8% to 1.6% depending on the operated digit. The rate of postoperative infection was lower, ranging from 0.5% to 0.6%. The need for revision within 3 years of initial trigger digit release was also low, ranging from 0.3% to 0.8%. Complications, including infection, stiffness and revision surgery, occur infrequently, but certain factors, including diabetes, Dupuytren's disease, smoking, rheumatoid arthritis, obesity and age, increase risk.

LEVEL OF EVIDENCE

Therapeutic Level III, Retrospective comparative study.

The Role of Preoperative Patient Characteristics on Outcomes of Unicompartmental Knee Arthroplasty: A Meta-Analysis Critique

BACKGROUND

In 1989, Kozinn and Scott introduced strict exclusion criteria for unicompartmental knee arthroplasty (UKA). Because outcomes have improved with modern techniques and implants, these criteria have now been challenged. Therefore, the goal was to assess the role of these criteria on (1) functional outcomes and (2) revision rates of medial UKA. The hypothesis was that, with modern surgical techniques and implants, these traditional exclusion criteria are no longer strict contraindications for UKA.

METHODS

Databases of PubMed, EMBASE, and Cochrane and annual registries were searched for studies comparing UKA results in subgroups: age (young vs old), gender (male vs female), body mass index (obese vs nonobese), present vs absent patellofemoral osteoarthritis, and intact vs deficient anterior cruciate ligament.

RESULTS

Thirty-one comparative cohort studies (7 level II and 24 level III/IV studies) and 6 registries reported outcomes in 17,147 patients and revision rates in 285,472 patients. Females had inferior functional outcomes compared to males (odds ratio [OR], 4.03; 95% CI, 1.77-6.30). Furthermore, younger patients (in studies: OR, 1.52; 95% CI, 1.06-2.19; in registries: OR, 2.09; 95% CI, 1.70-2.57) and females (OR, 1.13; 95% CI, 1.06-1.21) had increased likelihood for revision. No increased likelihood for inferior outcomes or revisions was detected in patients with obesity, preoperative patellofemoral osteoarthritis, or anterior cruciate ligament deficiency.

CONCLUSION

Findings of increased revision risk in younger patients and increased revision risk with inferior outcomes in females give a more nuanced perspective on historical criteria, such that surgical decision-making may be based on UKA outcome data for subgroups rather than strict exclusion criteria.

Five-Year Survival of 20,946 Unicondylar Knee Replacements and Patient Risk Factors for Failure: An Analysis of German Insurance Data

BACKGROUND

Improvements in implant design and surgical technique of unicondylar knee arthroplasty have led to reduced revision rates, but patient selection seems to be crucial for success of such arthroplasties. The purpose of the present study was to analyze the 5-year implant survival rate of unicondylar knee replacements in Germany and to identify patient factors associated with an increased risk of revision, including >30 comorbid conditions.

METHODS

Using nationwide billing data of the largest German health-care insurance for inpatient hospital treatment, we identified patients who underwent unicondylar knee arthroplasty between 2006 and 2012. Kaplan-Meier survival curves with revision as the end point and log-rank tests were used to evaluate 5-year implant survival. A multivariable Cox regression model was used to determine factors associated with revision. The risk factors of age, sex, diagnosis, comorbidities, type of implant fixation, and hospital volume were analyzed. Hazard ratios (HRs) and 95% confidence intervals (95% CIs) were calculated.

RESULTS

During the study period, a total of 20,946 unicondylar knee arthroplasties were included. The number of unicondylar knee arthroplasties per year increased during the study period from 2,527 in 2006 to 4,036 in 2012. The median patient age was 64 years (interquartile range, 56 to 72 years), and 60.4% of patients were female. During the time evaluated, the 1-year revision rate decreased from 14.3% in 2006 to 8.7% in 2011. The 5-year survival rate was 87.8% (95% CI, 87.3% to 88.3%). Significant risk factors (p < 0.05) for unicondylar knee arthroplasty revision were younger age (the HR was 2.93 [95% CI, 2.48 to 3.46] for patient age of <55 years, 1.86 [95% CI, 1.58 to 2.19] for 55 to 64 years, and 1.52 [95% CI, 1.29 to 1.79] for 65 to 74 years; patient age of >74 years was used as the reference); female sex (HR, 1.18 [95% CI, 1.07 to 1.29]); complicated diabetes (HR, 1.47 [95% CI, 1.03 to 2.12]); depression (HR, 1.29 [95% CI, 1.06 to 1.57]); obesity, defined as a body mass index of ≥30 kg/m² (HR, 1.13 [95% CI, 1.02 to 1.26]); and low-volume hospitals, denoted as an annual hospital volume of ≤10 cases (HR, 1.60 [95% CI, 1.39 to 1.84]), 11 to 20 cases (HR, 1.47 [95% CI, 1.27 to 1.70]), and 21 to 40 cases (HR, 1.31 [95% CI, 1.14 to 1.51]) (>40 cases was used as the reference).

CONCLUSIONS

Apart from known risk factors, this study showed a significant negative influence of obesity, depression, and complicated diabetes on the 5-year unicondylar knee replacement survival rate. Surgical indications and preoperative patient counseling should consider these findings.

LEVEL OF EVIDENCE

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

The Timing of Total Hip Arthroplasty After Intraarticular Hip Injection Affects Postoperative Infection Risk

BACKGROUND

The data regarding any association between preoperative intraarticular steroid injection and risk ofperiprosthetic joint infection (PJI) after total hip arthroplasty (THA) are conflicting. The goal of the present study is to evaluate the association of preoperative intraarticular hip injection before THA on the incidence of postoperative PJI.

METHODS

A national database was queried for patients who underwent THA and those patients who underwent prior ipsilateral hip injection. Three cohorts were created: THA within 3 months of ipsilateral hip injection (n = 829), THA between 3 and 6 months after ipsilateral hip injection (n= 1379), and THA between 6 and 12months after ipsilateral hip injection (n=1160). A control group of THAwithout prior injectionwas created for comparison purposes (n=31,229). The rate of postoperative infectionwas compared between injection cohorts and controls.

RESULTS

The incidence of infection after THA at 3 months (2.41%; odds ratio, 1.9; P = .004) and 6 months (3.74%; odds ratio, 1.5; P < .019) was significantly higher in the patients who underwent hip injection within 3months before THA comparedwith controls. Therewas no significant difference in infection rates in patients who underwent THA between 3 and 6months or 6 and 12months after ipsilateral hip injection compared with controls.

CONCLUSIONS

The present study demonstrates a significant increase in PJI in patients who underwent intraarticular hip injection within 3 months before THA. This association was not noted when THA was more than 3 months after injection.