Faculty Bibliography

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: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.

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.

INTRODUCTION/BACKGROUND:The integration of computer-assisted navigation systems (CASs) in total knee arthroplasty (TKA) procedures has gained popularity in recent years. However, additional validation of the accuracy of CAS feedback is necessary. We used short-length and full-length postoperative radiographs to quantify the differences between alignment parameters measured by a novel imageless CAS and alignment outcomes as evidenced on postoperative radiographs. MATERIALS AND METHODS/METHODS:A retrospective analysis was conducted on prospectively collected data from a cohort of patients undergoing navigated primary TKA. Fifty-eight patients had met inclusion criteria, and intraoperative CAS measurements were obtained from device recordings. Alignment parameters were measured digitally and included femorotibial angle on short-length films and hip-knee-ankle axis, mechanical lateral distal femoral angle (mLDFA), and mechanical medial proximal tibial angle (mMPTA) on full-length films. These were compared between CAS and radiograph measurements using a 2-tailed t test. RESULTS:The mean mLDFA measured by the CAS was 0.7° ± 1.1°, compared with 1.3° ± 1.4° as measured on full-body radiographs (P = .1). The mean mMPTA measured by the CAS was 0.2° ± 1.0°, compared with 0.9° ± 1.4° as measured on full-body radiographs (P = .06). On average, radiograph and CAS measurements differed by 0.5° ± 1.5° for mLDFA and 0.7° ± 1.5° for mMPTA. The average postoperative hip-knee-ankle axis was 177.6° ± 2.1°, and the average femorotibial angle was 176.0° ± 9.6° as measured on radiographs. CONCLUSION/CONCLUSIONS:No significant differences in either average or individual measured values for mLDFA or mMPTA were observed between the intraoperative CAS measurements and alignment outcomes postoperatively. Our data highlight the clinical utility of CASs to accurately achieve intended TKA alignment objectives.

BACKGROUND:Historically, total knee arthroplasty (TKA) used resection and balancing techniques to target symmetric medial and lateral gaps throughout range of motion (ROM). With modern awareness on alternate alignment concepts, one area of ongoing debate is whether asymmetric medial and lateral compartment gaps improve outcomes. Proponents of an asymmetric looser lateral compartment gap philosophy postulate that this phenotype recreates native knee kinematics with lateral femoral condylar rollback pivoting through a tighter medial compartment during knee flexion. The purpose of this study was to compare patient-reported outcomes (PROs) and ROM with respect to symmetric or asymmetric gaps. METHODS:We performed a systematic review and random-effects meta-analysis of prospective and retrospective studies. We compiled all comparative studies reporting symmetric and asymmetric gaps, irrespective of directional or nondirectional gap asymmetry. However, we performed a meta-analysis only between a cohort of directional asymmetric gaps (looser lateral than medial gap) and symmetric gaps (equal medial and lateral gaps). Gaps were compared in flexion and extension. ROM and PROs were evaluated through standardized mean difference (SMD), with statistical significance defined by 95% confidence interval (CI). RESULTS:A total of 17 studies with 3,319 knees were included. Four studies reported nondirectional gap asymmetry, whereas 13 studies reported directional gap asymmetry, of which 8 shared common outcome variables and were therefore included in the meta-analysis. Analysis of gaps in flexion revealed significantly increased ROM favoring asymmetric looser lateral gaps over symmetric gaps (SMD -0.19, 95% CI -0.29 to -0.09). Analysis of gaps in extension also revealed increased ROM favoring asymmetric looser lateral gaps (SMD -0.10, 95% CI -0.36 to 0.16). Finally, the Forgotten Joint Score (FJS) favored looser lateral gaps in flexion over symmetric gaps (SMD -0.13, 95% CI -0.41 to 0.15). However, differences in the latter 2 were nonsignificant. CONCLUSION/CONCLUSIONS:This is the first meta-analysis evaluating the postoperative outcomes as a function of symmetric vs. asymmetric mediolateral gaps. We report improved FJS and ROM favoring asymmetric looser lateral gaps in flexion. LEVEL OF EVIDENCE/METHODS:Therapeutic Level II, systematic review of Level II and III and IV studies. See Instructions for Authors for a complete description of levels of evidence.

(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.

BACKGROUND:A tourniquet is commonly used during total knee arthroplasty (TKA) to improve surgical field visibility and minimize blood loss. While the short-term effects of tourniquet use on postoperative outcomes have been studied extensively and found to be minimal, its influence on longer-term outcomes remains underexplored. This study examined tourniquet use in TKA with up to five-year follow-up. METHODS:In this post hoc analysis of a randomized controlled trial, 227 patients who underwent primary TKA in the tourniquet (T) group (n = 112) or no tourniquet (NT) group (n = 115) were evaluated. Clinical outcomes and patient-reported outcome measures (PROMs) were compared between the two groups. RESULTS:The T group had non-significant trends toward reduced blood loss (131.8 versus 116.7 ml, P = 0.098) and shorter operative time (97.8 versus 95.7 minutes, P = 0.264), with slightly higher postoperative day-one Visual Analog Scale (VAS) pain scores (3.1 versus 3.6, P = 0.197). Length of stay (2.0 versus 2.1 days, P = 0.837) and home discharge rate (88.7 versus 92.0%, P = 0.340) were comparable. The NT group had three 90-day readmissions, while none occurred in the T group (2.7 versus 0%, P = 0.081). The active range of motion at the final follow-up was similar between groups (108.3 versus 106.5 degrees, P = 0.457). All-cause revision rates at five years were comparable between the NT and T groups (5.2 versus 3.6%, P = 0.546). Kaplan-Meier survivorship analysis revealed comparable aseptic implant survival at five years (P = 0.769). There were no significant differences in Knee injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS, JR), Patient-Reported Outcomes Measurement Information System (PROMIS) pain intensity, PROMIS pain interference, or PROMIS physical health scores at three months, one year, and five years postoperatively. CONCLUSION/CONCLUSIONS:Using a tourniquet during primary TKA was not associated with differences in clinical or patient-reported outcomes at up to five-year follow-up. These findings suggest that tourniquet use in TKA can be left to the surgeon's discretion.

BACKGROUND:Tranexamic acid (TXA) is a renally-excreted antifibrinolytic commonly utilized in total joint arthroplasty (TJA). This study examined whether TXA administration affected clinical outcomes and kidney function in patients who had end-stage renal disease (ESRD) undergoing TJA or hemiarthroplasty. METHODS:Through a retrospective chart review, we identified 123 patients: 40 who underwent primary elective total knee arthroplasty (TKA; 65% received TXA), 34 who underwent primary elective total hip arthroplasty (THA; 52.9% TXA), and 49 who underwent nonelective THA or hemiarthroplasty (44.9% TXA) from January 2011 to February 2024. All patients had ESRD and/or were on dialysis, with no difference in percentage on dialysis between TXA groups (TKA: 65.4 versus 64.3%; THA: 55.6 versus 50.0%; nonelective/hemiarthroplasty: 86.4 versus 85.2%, P values ≥ 0.586). Demographic and perioperative characteristics, including preoperative hemoglobin, TXA administration, dose, and route of administration (ROA; intravenous, topical), were extracted. Pre- and postoperative (≤ 7 days) creatinine, perioperative transfusions, revisions, and 90-day emergency department (ED) visits, readmissions, and mortalities were recorded and compared between TXA groups. RESULTS:In the total sample and all cohorts, change in pre- to postoperative creatinine and incidence of postoperative acute kidney injury (AKI), per Kidney Disease Improving Global Outcomes (KDIGO) guidelines, did not significantly differ based on receiving TXA (P values ≥ 0.159). Among patients receiving TXA, change in creatinine did not significantly differ by dose (P values ≥ 0.428) or ROA (P values ≥ 0.256). There were no statistically significant differences in 90-day ED visits, readmissions, or mortalities based on receiving TXA (P values ≥ 0.055). Thromboembolic events occurred in four patients (one TXA, three no TXA, P = 0.617), and perioperative transfusions occurred in two patients (one TXA, one no TXA, P = 0.882) in the nonelective/hemiarthroplasty cohort, with none in the elective cohorts. CONCLUSIONS:The administration of TXA does not portend a significant increase in complications for patients who have ESRD undergoing TJA or hemiarthroplasty for fracture, suggesting TXA should not be contraindicated in this population.

BACKGROUND:Robotic assistance (RA) is increasingly used in total knee arthroplasty (TKA) for more accurate bony resection and balancing. However, the impact of robotic TKA (RATKA) on clinical outcomes and patient-reported measures (PROMs) remains unclear. This study aims to compare RATKA and conventional TKA (CTKA) using a novel robotic system. METHODS:A retrospective review was conducted on 10,031 patients who underwent TKA from February 2021 to October 2024. 289 RATKAs were performed with a hand-held robotic system. These RATKA cases were 1:1 propensity-score matched to CTKA for patient demographics, surgeon, implant system, and articulation design. Postoperative and clinical outcomes including surgical time, length of stay (LOS), discharge disposition, 90-day emergency department (ED) visits, manipulation under anesthesia (MUA), debridement, reoperations and revisions were collected and analyzed. Patient-reported outcomes measures (PROMs) included Knee Injury and Osteoarthritis Outcome Scores (KOOS, JR) and Patient Reported Outcome Measurement Information System (PROMIS) scores. RESULTS:RATKA demonstrated significantly shorter LOS (30.04 vs. 51.91 hours, p < 0.001, respectively) compared to CTKA. There was no difference in surgical time (107.18 vs. 106.22 minutes, p = 0.349). Although there was no statistical difference in 90-day ED visits, the majority of the CTKA revisits were due to surgery-related causes when compared to the RATKAs (1.38% vs. 0.34%, p = 0.239). While RATKAs had higher incidence of MUAs (2.07% vs. 0.34%, p = 0.201), CTKAs had more reoperations (1 vs. 0, p = 0.369) and more revisions than the RATKAs (6 vs. 0, p = 0.117). In terms of PROMs, both RATKAs and CTKAs showed similar improvements in KOOS, JR and PROMIS pain scores following TKA, with no significant differences in the magnitude of improvement at early postoperative timepoints. However, at the one-year follow-up, RATKA demonstrated significantly greater reduction in PROMIS pain intensity (Δ-9.12, p = 0.032) compared to CTKAs. CONCLUSIONS:This retrospective analysis showed that the novel RATKA resulted in reduced length of stay, fewer reoperations, and greater reduction in one-year PROMIS pain intensity compared to CTKAs, despite having a higher incidence of MUA rates. Further research is needed to clarify these differences clinically and enhance patient outcomes.

INTRODUCTION/BACKGROUND:Robotic-assisted technologies provide the ability to avoid soft tissue release by utilizing more accurate bony cuts during total knee arthroplasty (TKA). However, the ideal limb alignment is not yet established. The aim of this study was to predict postoperative Coronal Plane Alignment of the Knee (CPAK) using corresponding native bony measurements. METHODS:This study analyzed a retrospective cohort of 530 primary robotic-assisted TKAs. Machine learning was utilized to predict appropriate target lateral distal femoral angles (LDFA) and medial proximal tibial angles (MPTA). Normalization of LDFA and MPTA alignments was performed using the min-max scaler operation on the training set with feature range [-1, 1] and repeated separately for the input and target distributions. A neural network of hidden dimensions (16, 8, 4) was trained via supervised learning to predict planned LDFA and MPTA values from preoperative LDFA and MPTA measurements. RESULTS:The model converged after 104 epochs and batch size 4 with mean squared error ±1.82°. The model's regression agrees with the hypothesized change in preoperative to planned coronal alignment: valgus measurements are translated to neutral/aligned targets while varus alignments are translated to varus alignment of lesser severity. Evaluative statistics demonstrate this method for planning knee morphologies is significantly more accurate than making predictions about the mean (RMSE 1.440; R-squared 0.444; Nash Sutcliffe 0.579). CONCLUSION/CONCLUSIONS:This study's model provides accurate predictions for target knee alignment morphologies. Future work is warranted to evaluate this method's usefulness for planning robotic TKA.