Faculty Bibliography

BACKGROUND:Modern polyethylene allows larger bearings in fixed-bearing total hip arthroplasty (THA), but any stability benefits of fully maximizing bearing diameter (e.g., 36-millimeter (mm) in 48/50-mm cups) are not well-established. We hypothesized that maximizing bearing diameter reduces odds of dislocation in primary fixed-bearing THA. METHODS:We retrospectively reviewed all patients who underwent fixed-bearing THA at a large, urban, academic institution between 2016 and 2022. We noted cases receiving the largest bearing available from any manufacturer for the acetabular diameter: 28 mm in 40/42 mm, 32 mm in 44/46-, 36- in 48/50-, or 40- in 52/54/56 mm. Larger cups were excluded because proportionately larger bearings were unavailable. Multivariate analyses using least-absolute-shrinkage-and-selection-operator (LASSO) logistic regression were performed to explore the association between maximized bearing diameter and dislocation risk while controlling for confounders. RESULTS:Bearing diameter was maximized in 835 (9.8%) of 8,607 patients, whereas 7,309 (84.9%) received the second-largest bearing available. There were 79 dislocations (0.9% overall); none occurred with maximized bearing diameters (P = 0.003). On univariate analyses, dislocation risk also varied with intraoperative technology use, surgical approach, and liner geometry (P = 0.017, P = 0.008, P = 0.007, respectively). In LASSO regression including these variables, maximized bearing diameters heavily protected against dislocation (odds ratio (OR) = 0.14). Robotic surgery (OR = 0.35), computer-navigation (OR = 0.90), lateral (OR = 0.48), and anterior (OR = 0.62) approaches were also protective. Lipped (OR = 1.2) and offset (OR = 1.4) liners, commonly used with posterior approaches and non-maximized bearing diameters, were associated with slightly higher odds of dislocation. Subanalysis of 4,185 patients who underwent posterior approach THA using non-maximized bearings revealed that liner geometry did not impact dislocation odds within this subgroup. CONCLUSION/CONCLUSIONS:Fully maximizing bearing diameter markedly reduced dislocation odds in primary fixed-bearing THA. The magnitude of this effect was substantially larger compared to other variables under surgeon control.

BACKGROUND:Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are widely used as screening tools for periprosthetic joint infection (PJI) following total knee and hip arthroplasty (TKA and THA, respectively). However, the significance of an isolated elevated ESR with a normal CRP, especially in cases with low clinical suspicion, remains unclear. METHODS:We retrospectively reviewed 19,872 primary TKAs and 12,143 primary THAs performed between March 2012 and March 2023 at a high-volume academic orthopaedic hospital. Of these, 656 TKA and 253 THA patients ≥ 18 years old who underwent elective TJA for osteoarthritis had an elevated ESR (higher than 30 millimeters/hour) and a normal CRP (less than or equal to 10 milligrams/liter) at least 90 days postoperatively. These cutoffs were chosen in concordance with the International Consensus Meeting (ICM) 2018 diagnostic criteria for PJI. Patients who were already undergoing PJI treatment were excluded, as it was inferred the serum biomarkers were not drawn for screening purposes. The final cohorts consisted of 641 TKA and 252 THA patients. Data collected through manual chart review of clinical progress notes included presenting symptoms, inflammatory markers, and PJI diagnoses. We calculated the incidence of PJI within the cohort of patients who had an isolated, elevated ESR. RESULTS:Of the 641 TKA patients who had an isolated, elevated ESR, seven (1.1%) were subsequently diagnosed with PJI. Of the 252 THA patients who had an isolated, elevated ESR, three (1.2%) were subsequently diagnosed with PJI. Of the seven TKA and three THA patients subsequently diagnosed with PJI, three (0.5%) TKA and two (0.8%) THA patients had clinical findings highly suspicious for PJI, such as a large effusion and severe, sudden-onset swelling. These patients did not represent cases where a surgeon would encounter true uncertainty regarding whether to pursue further workup and testing. This left four TKA (0.5%) and one THA (0.4%) patient who had an isolated, elevated ESR who were eventually diagnosed with PJI despite limited clinical concern beyond nonspecific pain. The positive predictive value (PPV) of an isolated, elevated ESR for the diagnosis of PJI was 1.1% in the TKA cohort and 1.2% in the THA cohort. CONCLUSION/CONCLUSIONS:Isolated, elevated ESR with a normal CRP should not automatically trigger a full PJI workup. The risk of PJI is low in this specific patient population, especially when only accompanied by nonspecific symptoms. Most PJI cases in this cohort were found in patients who also had relevant clinical symptoms like sudden-onset swelling or large effusions, suggesting that important weight should be given to the presence or absence of additional PJI symptoms when deciding whether to pursue further testing after an isolated, elevated ESR.

BACKGROUND:Management of severe acetabular bone loss during revision total hip arthroplasty (rTHA) remains challenging. Cup-cage constructs and custom triflange acetabular components are commonly used, but comparative outcomes remain poorly defined. METHODS:This meta-analysis was performed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. There were four electronic databases searched for studies published from 2015 to 2025 that reported outcomes of cup-cage or custom triflange reconstruction in patients who had Paprosky 2 to 3B acetabular defects. Indications for cup-cage and triflange constructs were recorded. Re-revision, periprosthetic joint infection (PJI), instability, and aseptic loosening were pooled using fixed- and random-effects models. Meta-regression was performed to adjust for acetabular defect severity. RESULTS:There were 18 studies comprising 808 revision THAs (293 cup-cage and 515 custom triflange) included. Across both reconstruction strategies, the most common indications were aseptic loosening and conversion after periprosthetic joint infection. The weighted mean follow-up was 5.8 years for cup-cage and 6.2 years for triflange reconstructions (P = 0.071). The cup-cage cohort had a higher proportion of Paprosky 3B defects than the triflange cohort (79.2 versus 71.8%, P < 0.001). After adjustment for acetabular defect severity, no differences in re-revision rates were observed between cup-cage and triflange constructs. Likewise, there were no differences in PJI, instability, or aseptic loosening between groups. CONCLUSIONS:Among patients undergoing rTHA with cup-cage or custom triflange reconstruction for Paprosky 2 to 3B defects, outcomes were equivalent across major failure modes after adjustment for bone loss severity. Neither construct demonstrated superior survivorship; therefore, implant selection should be individualized according to defect pattern, available resources, surgical goals, and surgeon preference rather than an expectation of differential clinical performance.

BACKGROUND:Nonmodular dual mobility (DM) articulations in total hip arthroplasty (THA) aim to reduce dislocations through a large outer bearing diameter while minimizing wear via a smaller inner bearing where most motion occurs. Although routine use remains uncommon in the United States, this construct may protect against dislocation. This study aimed to evaluate clinical outcomes of a cementless, nonmodular DM acetabular cup at a mean follow-up of two years. METHODS:We conducted a single-arm retrospective review of 604 primary, elective THAs using a cementless nonmodular DM acetabular cup between April 2017 and August 2024 at a single health system with at least 90 days of follow-up. All surgeries were performed by a single hip surgeon via posterior approach. Cases were planned using digital templating and performed with manual instruments without enabling technology. Clinical outcomes were collected, including 90-days readmission and revision rates, reasons for readmission and revision, and dislocation rates. RESULTS:At a mean follow-up of 2.0 years (range, 0.25 to 8.0), all-cause and aseptic acetabular cup implant survivorship was 99.8%. There were six revisions during the study period. There was one acetabular component (0.2%) that was revised due to cup dissociation from the pelvis. The remaining revisions included two for periprosthetic femoral fracture (0.3%), one for femoral loosening (0.2%), and two for acute periprosthetic joint infection (0.3%), none of which involved revision of the acetabular cup. There were no dislocations observed, and no patients required revision for instability. CONCLUSIONS:Cementless nonmodular DM acetabular cups offered excellent clinical outcomes in primary THA at a mean follow-up of 2.0 years, with no observed dislocations in 604 cases and high implant survivorship. These findings support the use of nonmodular DM implants as a viable option to achieve THA implant stability and durable fixation even when using a posterior approach without enabling technology.

BACKGROUND:Robotic-assisted total knee arthroplasty (RA-TKA) allows for intraoperative component positioning to personalize alignment and gaps. However, traditional trochlear designs not optimized for patellar tracking in kinematic alignment result in femoral internal rotation relative to the surgical transepicondylar axis (TEA). We sought to determine the femoral component alignment's effect on patellar tracking in RA-TKA. METHODS:We retrospectively reviewed 932 RA-TKA cases performed from January 2023 to August 2024 using a computed tomography (CT)-based robotic platform with a single radius femoral component with a 6° trochlear sulcus angle. Femoral rotation was defined as internal (IR) and external (ER) relative to TEA. Femoral coronal alignment was defined as varus (Var) or valgus (Val) relative to the mechanical axis. Patient-reported outcomes were collected at six weeks, three months, and one year postoperatively. Outcomes were analyzed using one-way analyses of variance and Chi-square tests. RESULTS:There were 445 (48%) Var-ER, 242 (26%) Val-ER, 105 (11%) Var-IR, and 141 (15%) Val-IR cases. Mean femoral component rotation (° external) was Var-ER: 2.8° (range, 0.2 to 6.5); Val-ER: 2.4° (range, 0.1 to 5.0); Var-IR: -0.6° (range, -3.4 to 0); and Val-IR: -1.0° (range, -4.2 to 0). There were three patella-related complications, two of which had further reoperations, all of which occurred in the Val-IR cohort (P < 0.001). Knee Injury and Osteoarthritis Outcome for Joint Replacement (KOOS, JR) at six weeks was lowest in the Var-ER cohort (52.3, P < 0.039). Planned femoral IR had no statistically significant impact on three-month and one-year KOOS, JR scores; there were no differences in Patient-Reported Outcomes Measurement Information System (PROMIS) scores at postoperative intervals studied. CONCLUSION/CONCLUSIONS:Planned femoral IR was not associated with statistically significant differences in patient-reported outcomes beyond six weeks postoperatively. However, all patella-related complications occurred in the Val-IR cohort. We caution surgeons against placing excessive combined valgus and IR with femoral implants designed with narrower trochlear sulcus angles.

BACKGROUND:Tranexamic acid (TXA) has reduced, but not eliminated, blood transfusions surrounding total knee arthroplasty (TKA). Identifying risk factors for transfusion remains important for risk reduction and type and screen (T and S) optimization. METHODS:We retrospectively reviewed 7,254 patients who underwent primary, unilateral TKA and 307 patients who underwent primary bilateral TKA between January 2014 and January 2023, who received perioperative TXA and had preoperative hemoglobin (Hgb) values. We compared demographics, baseline Hgb levels, and surgical details between patients who were and were not transfused. Data were analyzed utilizing multivariate regressions and receiver operating characteristic (ROC) analyses. A total of 172 unilateral TKA patients (2.4%) received perioperative transfusions, with 170 (2.3%) receiving postoperative transfusions and two (0.03%) receiving intraoperative transfusions. There were 26 bilateral TKA patients (8.5%) who received postoperative transfusions with no documented intraoperative transfusions. RESULTS:For unilateral TKA, the risk of transfusion demonstrated an inverse correlation with preoperative Hgb levels, a bimodal association with body mass index (BMI), and a direct correlation with American Society of Anesthesiologists (ASA) class and estimated blood loss (EBL) on multivariate testing. The ROC analyses demonstrated an optimal Hgb cutoff of 12.1 g/dL for predicting transfusion. The transfusion rate below Hgb of 12.1 g/dL was 6.6%, compared to a rate of 1.4% above this Hgb threshold. Below Hgb of 11 g/dL, the transfusion rate was 11.1%, while for Hgb between 11 and 12 g/dL, the transfusion rate was 4.6%. CONCLUSION/CONCLUSIONS:Transfusion is rare in unilateral TKA when TXA is used and preoperative Hgb is ≥ 12.1 g/dL, challenging universal T and S. Patients who have Hgb less than 11.0 g/dL and bilateral TKA patients remain at higher risk. Risk factors such as Hgb between 11 and 12 g/dL, BMI, ASA and EBL may predict transfusion risk and need for T and S.

BACKGROUND:The Coronal Plane Alignment of the Knee (CPAK) classification method describes knee phenotypes. The rise in robotic-assisted total knee arthroplasties (RA-TKA) has enabled surgeons to fine-tune bony cuts, minimizing soft tissue release while prioritizing balanced gaps rather than predetermined alignment targets, a technique known as functional alignment (FA). As a patient’s preoperative CPAK changes when using FA, our aim was to assess which preoperative CPAK phenotypes are maintained post-TKA and further define this change with a simplified classification. METHODS:We retrospectively reviewed 1,028 primary RA-TKA cases performed using functional alignment (FA) technique from 2023 to 2024. Arithmetic hip-knee-ankle (aHKA) and joint line obliquity (JLO) angles were obtained using robotic software, with boundaries in accordance with CPAK. Demographics, CPAK phenotypes, and planned resections were collected and analyzed. RESULTS: < 0.001). Based on results, we classified preoperative alignment according to final functional coronal alignment that would reflect tibia and aHKA angles and propose a new, simplified Functional Coronal Alignment (FCA) classification composing of four categories. CONCLUSION:This study highlighted the clinical usefulness of robotics for FA and described the FCA classification system to guide surgeons in optimizing kinematics using robotic assistance for FA.

Arthrofibrosis can be a major source of dissatisfaction for patients undergoing total knee arthroplasty (TKA). Manipulation under anesthesia (MUA) may be offered to improve motion in selected cases. Advancements in computer-navigated and robotic-assisted technology have been championed to improve component positioning with fewer soft tissue releases. We sought to investigate whether these technologies impact MUA rates. An institutional retrospective review was conducted on 18,815 patients who underwent a primary, elective, unilateral TKA between January 2010 and December 2022. Patients were stratified into conventional (n = 12,659), computer-navigated (n = 4,071), or robotic-assisted TKA (n = 2,085) cohorts. Patient demographics and implant data, including mode of fixation and level of constraint (cruciate-retaining [CR] vs. posterior-stabilized) were collected. MUA rates were the primary outcome. Data were analyzed using analysis of variance with Tukey post hoc testing and multivariate logistic regression analysis. We report a 1.7% overall MUA rate, with a rate of 1.6% for conventional and 1.5% for navigated TKA, which were significantly lower than robotic-assisted TKA at 3.2% (p < 0.001). However, on multivariate analysis, there was no difference in MUA rates for navigated and robotic-assisted when compared with conventional techniques. Cementless and hybrid fixation and CR implant designs were higher with robotic-assisted compared with conventional and navigated TKA. Multivariate regression revealed that TKA with fully cementless (odds ratio [OR]: 1.80 [95% confidence interval [CI]: 1.16-2.78]; p = 0.008) or hybrid fixation (OR: 2.92 [95% CI: 1.77-4.81]; p < 0.001) increased the risk for future MUA. Constraint also significantly influenced MUA rates, with CR designs yielding higher MUA rates (OR: 1.51 [95% CI: 1.16-1.96]; p = 0.002). When controlling for confounding factors, navigated and robotic-assisted TKA generated comparable odds for MUA when compared with conventional techniques. However, robotic-assisted TKA were more likely to utilize cementless or hybrid fixation and CR implant constraint, each of which were independently associated with increased odds of MUA. These operative factors should be considered when risk-stratifying and counseling patients on the likelihood of MUA. LEVEL OF EVIDENCE:  III.

BACKGROUND:Varying degrees of flexion contracture appear commonly in total knee arthroplasty (TKA) patients and can be corrected using increasing distal femoral bone resection. Robotic-assisted (RA) technology aims to avoid ligament release through optimized bony resections. This study evaluated the influence of preoperative flexion contracture on the magnitude of resections surgeons perform to balance knees in RA-TKA. MATERIALS AND METHODS/METHODS:We reviewed 789 primary RA-TKAs from 2023 to 2024 using cruciate-retaining (CR) implants. The cohort was divided by native flexion deformity into three groups: <0° flexion ("hyperextension", n = 157), 0-9.9° flexion ("minimal contracture", n = 457), and ≥ 10° flexion ("clinically important contracture", n = 175). Mean preoperative flexion contracture was - 3.8, 4.1, and 13.5° for the hyperextension, minimal contracture, and clinically important contracture cohorts, respectively. Demographics, implants, and intraoperative data were collected and analyzed. The arithmetic hip-knee-ankle (aHKA) angle was used to determine native deformity groups for additional subanalyses. RESULTS:Significant differences were found between cohorts for mean distal femur and proximal tibia resections, with the clinically important contracture group having the largest resections. After accounting for implanted polyethylene thickness, differences in mean tibia resections were quite small, varying by 0.9 millimeters (mm) laterally and 0.7 mm medially. Similarly, the mean distal femoral resection varied by only 1.4 mm laterally and 0.7 mm medially between the hyperextension and clinically important contracture cohorts. Indeed, 85% of cases with clinically important contractures were managed with less than 2 mm of additional distal femoral resection compared to the minimal contracture cohort. CONCLUSION/CONCLUSIONS:With robotic-assisted TKA, bone resections can be guided by collateral ligament tension in flexion and extension. Our data suggest that surgeons can follow this strategy and successfully address flexion contractures with very small increases in resection magnitudes, which may help to maintain the joint line.

(1) Introduction: Precise femoral component rotation is critical for achieving symmetric flexion-gap balance and physiologic patellofemoral tracking in mechanically aligned total knee arthroplasty (TKA). Surgeons often infer an appropriate rotational target from the patient's coronal limb alignment, yet the strength of this relationship remains uncertain. (2) Methods: We identified 695 consecutive patients undergoing primary TKA with a preoperative planning CT scan. The surgical transepicondylar axis (sTEA) and posterior condylar axis (PCAxis) were identified and the angle between them was measured. The angle between the mechanical axis of the femur and tibia was used to measure the coronal alignment of the limb. (3) Results: The mean sTEA was 3.0° externally rotated to the PCAxis (range 3.1° internal to 9.2° external). The mean coronal alignment was 4.3° varus (range -12.5° valgus to 24.5° varus). There were 465 patients with >2° varus and 101 patients with >2° valgus. The mean sTEA was 2.9 ± 1.9° externally rotated relative to the PCAxis in the valgus group and 2.8 ± 2.0° in the varus group, with no statistically significant difference (p = 0.7). (4) Conclusions: There is significant variation in the femoral rotation axes between patients, but no significant relationship between overall limb coronal alignment and the magnitude of femoral rotation axes variation. This reinforces the need for independent assessment of rotational landmarks when performing mechanically aligned TKA.