Periprosthetic Fractures: A Rising Tide of Hip Arthroplasty Failure Noted in the American Joint Replacement Registry and the Preventative Role of Cemented Stems.

BACKGROUND: This investigation examined cemented femoral component use in total hip arthroplasty (THA) and its impact on the incidence of periprosthetic fractures (PPFx), a common failure mode in THA. The study leverages data from the American Joint Replacement Registry (AJRR) to assess trends in cemented femoral component usage over time, its association with PPFx rates, and compares the survivorship and 90-day complication rates between cemented and cementless femoral component THAs. METHODS: Primary THAs, captured in the AJRR, in patients aged 65 years and older from 2012 to 2021 were analyzed. Variables considered included age, sex, race, region, teaching status, year, Charlson Comorbidity Index (CCI), and institution bed size. Analysis compared fixation types for THA on all-cause linked revision and PPFx. Logistic regression models analyzed the odds ratios for all-cause linked revision and PPFx for any follow-up time as well as for 90-day revision. The models were adjusted for the listed variables. RESULTS: During the study period, the rate of cement utilization as a percentage of primary THAs performed and reported to the AJRR increased from 4.4 to 8.3%. The rate of THA failure from PPFx increased from 11.4 to 33.3%. When both fixation groups were compared in the univariate analysis, there was a statistically significant difference in all demographic variables (P < 0.001). To account for this, multivariable logistic regression models were applied. In our models, cemented stems showed a 54.4% (OR [odds ratio]: 0.456, 95% CI [confidence interval]: 0.347 to 0.599, P < 0.0001) and 65.8% (OR: 0.342, 95% CI: 0.237 to 0.493, P < 0.0001) lower risk of PPFx linked and PPFx early linked revision, respectively. CONCLUSION: Periprosthetic fractures are becoming a leading failure mode for THAs in the AJRR. Given cemented fixation's relative resistance to this failure mode compared to cementless fixation, we should consider increasing the utilization of this technique.

Lower Associated Risk of Revision with All-Polyethylene Tibial Components in Total Knee Arthroplasty: An Analysis of the American Joint Replacement Registry.

BACKGROUND: Despite the potential advantage of all-polyethylene tibial components, modular metal-backed component use predominates the market in the United States for total knee arthroplasty (TKA). This is partially driven by concerns about the associated revision risk due to the lack of modularity with all-polyethylene components. This study utilized the American Joint Replacement Registry (AJRR) to compare the associated risk of all-cause revision and revision for infection for all-polyethylene versus modular metal-backed tibial components. METHODS: An analysis of primary TKA cases in patients aged 65 years and older was performed with AJRR data linked to Centers for Medicare and Medicaid Services data from 2012 to 2019. Analyses compared all-polyethylene to modular metal-backed tibial components. We identified 485,024 primary TKA cases, consisting of 479,465 (98.9%) metal-backed and 5,559 (1.1%) all-polyethylene. Cox proportional hazard regression analyses created hazard ratios (HRs) to evaluate the association of design and the risk of all-cause revision while adjusting for sex, age and the competing risk of mortality. Event-free survival curves evaluate time to revision. RESULTS: The all-polyethylene tibia group demonstrated a decreased risk for all-cause revision (HR = 0.37, 95% CI [confidence interval]: 0.24 to 0.55, P < 0.0001) and revision for infection (HR = 0.41, 95% CI: 0.22 to 0.77, P < 0.0001). Event-free survival curves demonstrated a decreased risk of all-cause revision that persisted across time points until 8 years post-TKA. CONCLUSION: In the United States, all-polyethylene tibial component use for TKA remains low compared to modular metal-backed designs. A decreased associated risk for revision should ease concerns about the use of all-polyethylene components in patients aged 65 years or older, and future investigations should investigate the potential cost and value savings associated with expanded use in this population.

Antibiotic calcium sulphate beads lower the bacterial burden and prevent infection in a mouse model of periprosthetic joint infection.

Aims: Delayed postoperative inoculation of orthopaedic implants with persistent wound drainage or bacterial seeding of a haematoma can result in periprosthetic joint infection (PJI). The aim of this in vivo study was to compare the efficacy of vancomycin powder with vancomycin-eluting calcium sulphate beads in preventing PJI due to delayed inoculation. Methods: A mouse model of PJI of the knee was used. Mice were randomized into groups with intervention at the time of surgery (postoperative day (POD) 0): a sterile control (SC; n = 6); infected control (IC; n = 15); systemic vancomycin (SV; n = 9); vancomycin powder (VP; n = 21); and vancomycin bead (VB; n = 19) groups. Delayed inoculation was introduced during an arthrotomy on POD 7 with 1 × 105 colony-forming units (CFUs) of a bioluminescent strain of Staphylococcus aureus. The bacterial burden was monitored using bioluminescence in vivo. All mice were killed on POD 21. Implants and soft-tissue were harvested and sonicated for analysis of the CFUs. Results: The mean in vivo bioluminescence in the VB group was significantly lower on POD 8 and POD 10 compared with the other groups. There was a significant 1.3-log10 (95%) and 1.5-log10 (97%) reduction in mean soft-tissue CFUs in the VB group compared with the VP and IC groups (3.6 × 103 vs 7.0 × 104; p = 0.022; 3.6 × 103 vs 1.0 × 105; p = 0.007, respectively) at POD 21. There was a significant 1.6-log10 (98%) reduction in mean implant CFUs in the VB group compared with the IC group (1.3 × 100 vs 4.7 × 101, respectively; p = 0.038). Combined soft-tissue and implant infection was prevented in 10 of 19 mice (53%) in the VB group as opposed to 5 of 21 (24%) in the VP group, 3 of 15 (20%) in the IC group, and 0% in the SV group. Conclusion: In our in vivo mouse model, antibiotic-releasing calcium sulphate beads appeared to outperform vancomycin powder alone in lowering the bacterial burden and preventing soft-tissue and implant infections.

The Role of Revision Total Joint Arthroplasty for Periprosthetic Fractures With Unstable Implants.

The management of periprosthetic fractures with unstable prosthetic implants is a challenging and commonly encountered problem. It is important to address the many current issues and controversies regarding the treatment of periprosthetic fractures with revision total joint arthroplasty. Key strategies to optimize surgical decision making around the use of arthroplasty and management of complications following these complex injuries will be addressed.

Reducing the Burden of Disease Associated With Periprosthetic Fractures: Prevention and the Need for Improved Perioperative Care.

The management of periprosthetic fractures remains challenging and controversial. There continues to be a significant burden of disease and substantial resource implications associated with fractures following total joint arthroplasty. Achieving consensus opinions regarding the prevention and treatment of this problem has important implications given the profound effect on patient outcomes. Multidisciplinary care in the preoperative and postoperative settings is critical, with a specific focus on bone health.

Fixation Strategies for Periprosthetic Fractures With Stable Implants.

The fixation of periprosthetic fractures remains challenging and controversial. It is important to achieve consensus opinions regarding the management of stable periprosthetic fractures with internal fixation. Key strategies to optimize surgical decision making and fixation and manage complications following these difficult injuries are addressed.

A Comparative Evaluation of Conventional Instrumentation and Accelerometer-Based Navigation in the Practice of a High-Volume Unicompartmental Knee Arthroplasty (UKA) Surgeon.

Background: Component malpositioning and joint malalignment following unicompartmental knee arthroplasty (UKA) increase the risk for revision. This study investigates whether accelerometer-based navigation (NAV) decreases radiographic outliers with respect to component placement and joint alignment in comparison to conventional instrumentation in UKA. Methods: A radiographic review of UKAs was performed by a single surgeon following adoption of an accelerometry-guided navigation system (OrthAlign, Aliso Viejo, CA). This cohort was then compared to previous patients undergoing UKA with conventional instrumentation. Six-week postoperative radiographs were used to compare femoral coronal and sagittal angles, tibial coronal and sagittal angles, the net coronal angle, tibial component rotation, and medial tibial overhang. Outliers in implant positioning were compared between groups. Patient variables including age, gender, body mass index, American Society of Anesthesiology, and surgical time (incision until the start of closure) were also compared between groups. Results: Eighty-eight UKA's were reviewed (49 conventional instrumentation [CI] patients; 39 NAV patients). Using 2-sample t-tests, no significant differences were found in patient demographics, radiographic parameters, and operative times between the CI and NAV cohorts. Using chi-squared tests, no significant difference was found in the number of radiographic outliers between the CI and NAV cohorts. Conclusions: Our study found that a high-volume UKA surgeon achieved a low rate of radiographic outliers in both NAV and CI cohorts. This data suggests that NAV is no different from conventional instrumentation with respect to implant positioning, overall joint alignment, and operative time when used by a high-volume UKA surgeon.

The Effect of Prosthetic Joint Infection on Work Status and Quality of Life: A Multicenter, International Study.

BACKGROUND: Periprosthetic joint infection (PJI) and subsequent revision surgeries may affect patients' social and physical health, ability to complete daily activities, and disability status. This study sought to determine how PJI affects patients' quality of life through patient-reported outcome measures with minimum 1-year follow-up. METHODS: Patients who suffered PJI following primary total joint arthroplasty (TJA) from 2012 to 2021 were retrospectively reviewed. Patients met Musculoskeletal Infection Society criteria for acute or chronic PJI, underwent revision TJA surgery, and had at least 1 year of follow-up. Patients were surveyed regarding how PJI affected their work and disability status, as well as their mental and physical health. Outcome measures were compared between acute and chronic PJIs. In total, 318 patients (48.4% total knee arthroplasty and 51.6% total hip arthroplasty) met inclusion criteria. RESULTS: Following surgical treatment for knee and hip PJI, a substantial proportion of patients reported that they were unable to negotiate stairs (20.5%), had worse physical health (39.6%), and suffered worse mental health (25.2%). A high proportion of patients reported worse quality of life (38.5%) and social satisfaction (35.3%) following PJI. Worse reported patient-reported outcome measures including patients' ability to complete daily physical activities were found among patients undergoing treatment for chronic PJI, and also, 23% of patients regretted their initial decision to pursue primary TJA. CONCLUSIONS: A PJI negatively affects patients' ability to carry out everyday activities. This patient population is prone to report challenges overcoming disability and returning to work. Patients should be adequately educated regarding the risk of PJI to decrease later potential regrets. LEVEL OF EVIDENCE: Case series (IV).

Spondylolisthesis and mismatch deformity affect outcomes after total knee arthroplasty.

BACKGROUND: Little published data currently exist regarding the potential relationships between spondylolisthesis, mismatch deformity, and clinical outcomes following total knee arthroplasty (TKA). We hypothesize that preexisting spondylolisthesis will result in decreased functional outcomes after TKA. METHODS: This retrospective cohort comparison of 933 TKAs was performed between January 2017 and 2020. TKAs were excluded if they were not performed for primary osteoarthritis (OA) or if preoperative lumbar radiographs were unavailable/inadequate to measure the degree of spondylolisthesis. Ninety-five TKAs were subsequently available for inclusion and divided into two groups: those with spondylolisthesis and those without. Within the spondylolisthesis cohort, pelvic incidence (PI) and lumbar lordosis (LL) were calculated on lateral radiographs to determine the difference (PI-LL). Radiographs with PI-LL > 10° were then categorized as having mismatch deformity (MD). The following clinical outcomes were compared between the groups: need for manipulation under anesthesia (MUA), total postoperative arc of motion (AOM) both pre-MUA or post-MUA/revision, incidence of flexion contracture, and a need for later revision. RESULTS: Forty-nine TKAs met the spondylolisthesis criteria, while 44 did not have spondylolisthesis. There were no significant differences in gender, body mass index, preoperative knee range of motion (ROM), preoperative AOM, or opiate use between the groups. TKAs with spondylolisthesis and concomitant MD were more likely to have MUA (p = 0.016), ROM < 0-120 (p < 0.014), and a decreased AOM (p < 0.02) without interventions. CONCLUSION: Preexisting spondylolisthesis by itself may not have adverse effect clinical results following TKA. However, spondylolisthesis increases the likelihood of developing MD. In those with both spondylolisthesis and concomitant mismatch deformities, patients had statistically and clinically significantly decreased in postoperative ROM/AOM and increased need for MUA. Surgeons should consider clinical/radiographic assessments of patients with chronic back pain who present for total joint arthroplasty. LEVEL OF EVIDENCE: Level 3.

Short-term outcomes of periprosthetic compared to native distal femur fractures, a national database study.

BACKGROUND: Distal femur fractures (DFFx) are highly morbid injuries with a complication rate comparable to hip fractures. Rising rates of total knee arthroplasty (TKA) have led to increasing rates of periprosthetic DFFx (pDFFx). We sought to determine how pDFFx complication rates differed from native DFFx (nDFFx). METHODS: The American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) was used to identify patients who sustained pDFFx or nDFFx between 2012 and 2018. Patients were further stratified by operative treatment: open reduction internal fixation (ORIF) or distal femur replacement (DFR). Multivariate logistic regression was used to compare 30-day complication rates between pDFFx versus nDFFx and, among pDFFx patients, ORIF versus DFR or revision TKA (rTKA). RESULTS: 563 patients with pDFFx and 2259 patients with nDFFx were identified between 2012 and 2018. pDFFx patients had significantly lower rates of ORIF than nDFFx patients (36.4 vs 95.4%, p < 0.001). On multivariate analysis, pDFFx were associated with a higher rate of surgical site complications (OR 2.48, p = 0.009) compared to nDFFx. There were no differences in mortality, reoperations, major complications, rate of blood transfusion, venous thromboembolism and disposition. In patients with pDFFx, patients undergoing DFR/rTKA were more likely to be discharged home versus a rehab facility, compared to those undergoing ORIF (OR 2.62, p < 0.001). CONCLUSIONS: In this first large registry study comparing pDFFx and nDFFx, we find similar outcomes between these groups in the first 30 days after surgery. Patients with pDFFx did have higher rates of surgical site complications, including infection and dehiscence. In pDFFx patients, those undergoing DFR were more likely to return home post-operatively.

Distal Femoral Replacement for Fractures Allows for Early Mobilization with Low Complication Rates: A Multicenter Review.

Periprosthetic fractures around a total knee arthroplasty (TKA), comminuted and intra-articular femur fractures, or fracture nonunions in osteoporotic bone represent technically challenging problems. This is particularly true when the fracture involves a loose femoral component or the pattern results in suboptimal fixation potential. These clinical indications often arise in an older and comorbid patient population in whom a principal goal of treatment includes allowing for early mobilization. Limited data indicate that arthroplasty via distal femoral replacement (DFR) is a reasonable alternative to open reduction and internal fixation, allowing for early ambulation with low complication rates. We performed a retrospective review of trauma and arthroplasty surgeries at three tertiary referral institutions. Adult patients treated for the above with a DFR were included. Patients with active infection, open and/or high-energy injuries and revisions unrelated to fracture were excluded. Patient demographics, treatment details, and outcomes were assessed. Between 2002 and 2017, 90 DFR's were performed for the above indications with a mean follow-up of 24 months. Postoperatively, 80 patients (88%) were allowed to weight bear as tolerated, and at final follow-up, 9 patients (10%) remained dependent on a wheelchair. The average arc of motion at final follow-up was 95 degrees. There were seven (8%) implant-related complications requiring secondary surgeries: two infections, one with associated component loosening; one fracture of the hinge mechanism and one femoral component failure in conjunction with a patellofemoral dislocation (both requiring revision); one case of patellofemoral arthrosis in a patient with an unresurfaced patella; one periprosthetic fracture with associated wound dehiscence; and one case of arthrofibrosis. In each of these cases, only modular components of the DFR were exchanged. All nonmodular components cemented into the femur or tibia were retained. DFR provides a viable reconstruction option in the treatment of acute distal femur fractures, periprosthetic femur fractures, and fracture nonunions. We noted that in an elderly patient population with high comorbidities, the complication and secondary surgery rates remained relatively low, while allowing for immediate weight bearing.

Comparison of complication profiles for femoral neck, intertrochanteric, and subtrochanteric geriatric hip fractures.

INTRODUCTION: Most geriatric hip fractures occur in the femoral neck (FN) and intertrochanteric (IT) regions of the femur, while a minority occur in the subtrochanteric (ST) region. Relative outcomes based on the anatomical subtype of fracture are not well studied. This study characterizes postoperative complications and outcomes of hip fractures distinguished by anatomic region. MATERIALS AND METHODS: The targeted hip fracture series of the American College of Surgeons National Surgical Quality Improvement Program database was queried to identify geriatric (≥ 65 years) patients who sustained operative FN, IT, and ST hip fractures. Primary patient demographic and perioperative data were collected and correlated with 30-day postoperative complications and outcomes. Multivariate regression was used to calculate relative risks of adverse events (AEs) between groups. RESULTS: In total, 8220 geriatric hip fracture patients were identified. Risk-adjusted 30-day mortality was not significantly different between patients with ST (5.8%, p = 0.735) and IT (7.3%, p = 0.169) femur fractures relative to those with FN fractures (6.6%). The overall risk-adjusted rate of minor and major medical AEs within 30 days and risk-adjusted rate of wound complications was not significantly different between FN, IT, and ST fractures. Patients with IT [34.4%, OR 2.35 (2.35-3.08), p < 0.001] and ST fractures [49.8%, OR 5.94 (4.58-7.70), p < 0.00] had higher risk-adjusted incidence of postoperative blood transfusion relative to FN fractures (18.5%). Furthermore, patients with IT fractures had a slightly lower risk-adjusted incidence of unplanned reoperation [2.1 vs. 2.7%, OR 0.69 (0.47-0.99), p = 0.046] and hospital readmission (7.8 vs. 9.2%, OR 0.76 [0.63-0.91], p = 0.003) than patients with FN fractures. CONCLUSIONS: With respect to anatomic region, geriatric hip fractures have similar short-term mortality and medical AE profiles with differences in transfusion, reoperation, and readmission rates. Knowledge of these short-term outcomes may guide surgeons in counseling hip fracture patients peri-operatively.

Racial disparities in post-operative complications and discharge destination following total joints arthroplasty: a national database study.

INTRODUCTION: The objective of this study was to explore race-based differences in 30-day complication rates following total joint arthroplasty (TJA) using a large national database. METHODS: Patients undergoing primary, elective THA and TKA between 2012 and 2018 were retrospectively reviewed using the ACS-NSQIP. We compared Black and Hispanic patients with non-Hispanic White patients using multivariate statistical models adjusting for demographic, operative, and medical characteristics. RESULTS: A total of 324,795 and 200,023 patients undergoing THA and TKA, respectively, were identified. After THA, compared to White patients, Black and Hispanic patients were more likely to be diagnosed with VTE (p < 0.001), receive a blood transfusion (p < 0.001), and to be discharged to an inpatient facility (p < 0.001). After TKA, compared to White patients, Black and Hispanic patients were more likely to experience a major complication (p < 0.001 and p = 0.008, respectively), be diagnosed with VTE (p < 0.001), and be discharged to a facility (p < 0.001). CONCLUSIONS: Our findings indicate higher rates of VTE, blood transfusions, and discharge to an inpatient facility for Black and Hispanic patients when compared to White patients following TJA, though we are unable to comment on the etiology of these disparities. These results may contribute to a growing divide with respect to outcomes and access to TJA for these at-risk patient populations.

Racial Disparities in Rates of Revision and use of Modern Features in Total Knee Arthroplasty, a National Registry Study.

BACKGROUND: The purpose of our study was to investigate the association of race and ethnicity with rates of modern implant use and postoperative outcomes in total knee arthroplasty (TKA) using the American Academy of Orthopaedic Surgeons American Joint Replacement Registry. METHODS: Adult TKAs from 2012 to 2020 were queried from the American Joint Replacement Registry. A total of 1,121,457 patients were available for analysis for surgical features and 1,068,210 patients for analysis of outcomes. Mixed-effects multivariable logistic regression models were used to examine the association of race with each individual surgical feature (unicompartmental knee arthroplasty (UKA) and robotic-assisted TKA (RA-TKA)) and 30- and 90-day readmission. A proportional subdistribution hazard model was used to model the risk of revision TKA. RESULTS: On multivariate analyses, compared to White patients, Black (odds ratio (OR): 0.52 P < .0001), Hispanic (OR 0.75 P < .001), and Native American (OR: 0.69 P = .0011) patients had lower rates of UKA, while only Black patients had lower rates of RA-TKA (OR = 0.76 P < .001). White (hazard ratio (HR) = 0.8, P < .001), Asian (HR = 0.51, P < .001), and Hispanic-White (HR = 0.73, P = .001) patients had a lower risk of revision TKA than Black patients. Asian patients had a lower revision risk than White (HR = 0.64, P < .001) and Hispanic-White (HR = 0.69, P = .011) patients. No significant differences existed between groups for 30- or 90-day readmissions. CONCLUSION: Black, Hispanic, and Native American patients had lower rates of UKA compared to White patients, while Black patients had lower rates of RA-TKA compared to White, Asian, and Hispanic patients. Black patients also had higher rates of revision TKA than other races.

Lower Rates of Ceramic Femoral Head Use in Non-White Patients in the United States, a National Registry Study.

BACKGROUND: The purpose of our study was to investigate the association of race and ethnicity with the use of the newest technology and postoperative outcomes in total hip arthroplasty (THA) using the American Academy of Orthopaedic Surgeons (AAOS) American Joint Replacement Registry (AJRR). METHODS: Adult THA procedures were queried from the AJRR from 2012 to 2020. A mixed-effects multivariate regression model was used to evaluate the association of race and ethnicity with the use of the newest technology (ceramic femoral head, dual-mobility implant, and robotic assist) at 30-day, and 90-day readmission. A proportional subdistribution hazard model was used to model a risk of revision THA. RESULTS: There were 85,188 THAs with complete data for an analysis of outcomes and 103,218 for an analysis of ceramic head usage. The median length of follow-up was 37.9 months (interquartile range [IQR] 21.6 to 56.3 months). In multivariate models, compared to White non-Hispanic patients, Black (odds ratio [OR] 0.79, 95% confidence interval [CI] 0.69-0.92, P < .001), Hispanic (OR 0.76, CI 0.59-0.99, P = .037), Asian (OR 0.74, CI 0.55-1.00, P = .045), and Native American (OR 0.52, CI 0.30-0.87, P = .004) patients all had significantly lower rates of ceramic head use in THA. Compared to White non-Hispanic patients, Asian (hazard ratio [HR] 0.39, CI 0.18-0.86, P = .008) and Hispanic (HR 0.43, CI 0.19-0.98, P = .043) patients had significantly lower rates of revision. No differences in 30-day or 90-day readmission rates were seen. CONCLUSION: Black, Hispanic, Native American, and Asian patients had lower rates of ceramic head use in THA when compared to White patients. These differences did not translate into worse clinical outcomes on a short-term follow-up. In fact, Asian patients had lower revision rates compared to non-Hispanic White patients. Additional study is necessary to evaluate the long-term consequence of lower ceramic head use in non-White patients in the United States.

Modular Metal-Backed Tibial Components Provide Minimal Mid-Term Survivorship Benefits Despite Increased Cost and Frequency of Use: A Retrospective Review of the American Joint Replacement Registry Database.

BACKGROUND: Previous studies have demonstrated equivalent survivorship of modular metal-backed tibial (MBT) and all-polyethylene tibial (APT) components. The purpose of this study is to compare the utilization and outcomes of APT and MBT components in a large US database. METHODS: The American Joint Replacement Registry was queried to identify all patients undergoing primary total knee arthroplasty (TKA) during the study period from 2012 to 2019. These patients were divided into cohorts based on tibial component (APT or MBT). Cohort demographics including gender, hospital size, hospital teaching status, region, age, and Charlson Comorbidity Index were reported with descriptive statistics. Overall reoperation rates and revisions for infection, aseptic loosening, periprosthetic fracture, manipulation under anesthesia, and revision for other reasons were identified using International Classification of Diseases, Ninth Revision and Current Procedural Terminology codes and compared across APT and MBT cohorts. Kaplan-Meir survival analysis was performed based on reason for reoperation for APT and MBT. RESULTS: During the study period, 703,007 TKAs were reported with 97.8% utilizing MBT and 2.2% utilizing APT components. Despite the introduction of alternative payment models during the study period, the utilization of APT decreased from 5.8% in 2012 to 1.7% in 2019. The survival of APT and MBT TKAs were similar across the study period: 98.1% vs 98.6% at 8 years. The rate of reoperation for all-causes was higher for APT compared to MBT (1.36% vs 1.00%; odds ratio 1.52). CONCLUSION: Despite their paucity of use and lower cost APT remained within a 0.4% margin of survivorship when compared to MBT implants for up to 8 years. LEVEL OF EVIDENCE: Level III, retrospective.

Lumbar Spine Sagittal Mismatch Deformity Negatively Affects Total Knee Arthroplasty Outcomes.

There is currently a paucity of data regarding the potential relationships between preexisting spinal deformity and clinical outcomes following total knee arthroplasty (TKA). We sought to expand upon this deficit. We hypothesize that lumbar sagittal mismatch deformity (MD) will correlate with a decrease in functional outcomes after TKA. This retrospective cohort comparison of 933 TKAs was performed between January 2017 and 2020. TKAs were excluded if they were not performed for primary osteoarthritis (OA) or if preoperative lumbar radiographs were unavailable/inadequate to measure sagittal parameters of interest: pelvic incidence, sacral slope, pelvic tilt, lumbar lordosis, and deformity mismatch. Ninety-four TKAs were subsequently available for inclusion and divided into two groups: those with MD as defined by |PI-LL| > 10 degrees and those without MD. The following clinical outcomes were compared between the groups: total postoperative arc of motion (AOM), incidence of flexion contracture, and need for manipulation under anesthesia (MUA). In total, 53 TKAs met the MD criteria, while 41 did not have MD. There were no significant differences in demographics, body mass index, preoperative knee range of motion (ROM), preoperative AOM, or opiate use between the groups. TKAs with MD were more likely to have MUA (p = 0.026), ROM <0 to 120 (p < 0.001), a decreased AOM by 16 degrees (p < 0.001), and a flexion contracture postoperatively (p = 0.01). Preexisting MD may adversely affect clinical results following TKA. Statistically and clinically significant decreases in postoperative ROM/AOM, increased likelihood of flexion contracture, and increased need for MUA were all noted in those with MD. This is a Level 3 study.

Severity and location of lumbar spine stenosis affects the outcome of total knee arthroplasty.

BACKGROUND: Recent studies have noted that patients with pre-existing lumbar spinal stenosis (LSS) have lower functional outcomes after total knee arthroplasty (TKA). Given that LSS manifests heterogeneously in location and severity, its influence on knee replacement merits a radiographically targeted analysis. We hypothesize that patients with more severe LSS will have diminished knee mobility before and after TKA. METHODS: This retrospective case series assessed all TKAs performed at our institution for primary osteoarthritis from 2017-2020. Preoperative lumbar magnetic resonance image (MRI) with no prior lumbar spine surgery was necessary for inclusion. Stenosis severity was demonstrated by (1) anterior-posterior (AP) diameter of the thecal sac and (2) morphological grade. TKA outcomes in 103 cases (94 patients) were assessed by measuring preoperative and postoperative arc of motion (AOM), postoperative flexion contracture, and need for manipulation under anesthesia. RESULTS: Patients with mild stenosis did significantly better in terms of postoperative knee AOM. As AP diameter decreased at levels L1-2, L2-3, L3-4, and L4-5, there was a significant reduction in preoperative-AOM (p < 0.001 for each), with a 16 degree decrease when using patients' most stenotic level (p < 0.001). The same was noted with respect to increased morphological grade (p < 0.001), with a 5 degree decrease for patients' most stenotic level (p < 0.001). CONCLUSION: Severe LSS, which is readily demonstrated by a reduction in the AP diameter of the thecal sac or increased morphological grade on MRI, correlated with a significant reduction in preoperative AOM that was not improved after TKA. Persistent postoperative reductions in AOM may contribute to reduced patient satisfaction and recovery. LEVEL OF EVIDENCE: Level 4.

Active rheumatoid arthritis in a mouse model is not an independent risk factor for periprosthetic joint infection.

INTRODUCTION: Periprosthetic joint infection (PJI) represents a devastating complication of total joint arthroplasty associated with significant morbidity and mortality. Literature suggests a possible higher incidence of periprosthetic joint infection (PJI) in patients with rheumatoid arthritis (RA). There is, however, no consensus on this purported risk nor a well-defined mechanism. This study investigates how collagen-induced arthritis (CIA), a validated animal model of RA, impacts infectious burden in a well-established model of PJI. METHODS: Control mice were compared against CIA mice. Whole blood samples were collected to quantify systemic IgG levels via ELISA. Ex vivo respiratory burst function was measured via dihydrorhodamine assay. Ex vivo Staphylococcus aureus Xen36 burden was measured directly via colony forming unit (CFU) counts and crystal violet assay to assess biofilm formation. In vivo, surgical placement of a titanium implant through the knee joint and inoculation with S. aureus Xen36 was performed. Bacterial burden was then quantified by longitudinal bioluminescent imaging. RESULTS: Mice with CIA demonstrated significantly higher levels of systemic IgG compared with control mice (p = 0.003). Ex vivo, there was no significant difference in respiratory burst function (p = 0.89) or S. aureus bacterial burden as measured by CFU counts (p = 0.91) and crystal violet assay (p = 0.96). In vivo, no significant difference in bacterial bioluminescence between groups was found at all postoperative time points. CFU counts of both the implant and the peri-implant tissue were not significantly different between groups (p = 0.82 and 0.80, respectively). CONCLUSION: This study demonstrated no significant difference in S. aureus infectious burden between mice with CIA and control mice. These results suggest that untreated, active RA may not represent a significant intrinsic risk factor for PJI, however further mechanistic translational and clinical studies are warranted.