Arthrofibrosis and stiffness are challenging complications after total knee arthroplasty (TKA), often treated with Manipulation Under Anesthesia (MUA). Robotic-assisted TKA (RA-TKA) aims to enhance surgical precision, though its impact on stiffness remains unclear. This study examined the association between surgical technologies and MUA rates using propensity score matching (PSM) and assessed whether surgeon experience affects MUA risk. We conducted a retrospective case-control study of 25,611 primary unilateral TKAs (2016–2024), stratified by manual, computer-assisted (CA), or RA techniques. MUA cases within 90 days were matched 1:2 to controls using PSM. Conditional logistic regression assessed the association between surgical technologies and MUA risk. A learning curve analysis of each surgeon’s first 100 RA-TKAs assessed surgical proficiency progression. Odds ratios were compared before and after the learning phase to evaluate its impact on MUA rates. Both CA-TKA (OR = 1.11, P = 0.33) and RA-TKA (OR = 1.24, P = 0.12) revealed a higher trend in MUA risk compared to manual. Learning curve analysis of 10 surgeons demonstrated a distinct learning breakpoint at case 11.8 (95

BACKGROUND:The coronal plane alignment of the knee (CPAK) classification provides an objective framework for describing coronal alignment in total knee arthroplasty (TKA). Mechanical alignment (MA) traditionally aims to achieve CPAK type V, defined by neutral arithmetic hip-knee-ankle angle (aHKA) and neutral joint line obliquity (JLO). However, inconsistency in achieving this target has been reported, and the clinical value of postoperative neutral alignment remains uncertain. This study sought to (1) characterize the postoperative distribution of CPAK phenotypes following MA-TKA across three surgical technologies and (2) determine whether achieving MA targets is associated with improved outcomes. METHODS:A retrospective review was performed of 636 primary TKAs conducted at a single high-volume institution. All procedures followed an MA strategy using manual instrumentation, computer navigation, or robotic-assisted techniques. Full-length standing radiographs were analyzed to determine preoperative and postoperative CPAK phenotypes. Patient-reported outcomes were assessed preoperatively and at two years. Alignment targets were defined as CPAK type V, neutral JLO, and neutral aHKA. Multivariable logistic regression analyses identified predictors of achieving alignment targets and evaluated whether alignment achievement independently increased the odds of attaining clinically meaningful outcome thresholds. RESULTS:Postoperative CPAK distribution was significantly different between the three techniques, with multivariable regression analysis outlining robotic-assisted as a significant positive predictor for achieving both postoperative CPAK type V (odds ratio: 2.3, P < 0.001) and neutral JLO (odds ratio: 4.3, P < 0.001). Achieving the neutral targets conferred no significant advantage in clinical outcome. Regression analyses confirmed that none of the alignment targets independently increased the odds of meeting clinical thresholds (all P > 0.26). CONCLUSIONS:Despite the same alignment philosophy, postoperative CPAK phenotype distribution varies significantly by surgical technology, underscoring the value of an objective alignment classification. However, achieving postoperative neutral alignment was not associated with improved outcomes in this cohort.

➢ Adherence to accepted definitions of the various alternative total knee arthroplasty alignment strategies is important for research and communication between surgeons.➢ Technological advances, including robotics and navigation-assisted systems, have made precise execution of alternative alignment strategies feasible.➢ Modern studies have suggested that minor deviations (±3°) from neutral mechanical alignment do not significantly impact long-term total knee arthroplasty implant survivorship.➢ Individualized alignment strategies, such as kinematic, restricted kinematic, and functional alignment, aim to respect native anatomy and soft-tissue balance.➢ The majority of studies comparing intermediate-term outcomes of kinematic and mechanical alignment suggest noninferior outcomes with kinematic alignment; however, some studies have suggested superior outcomes with kinematic alignment.

BACKGROUND:Dislocation remains one of the most challenging complications after total hip arthroplasty (THA). Previous studies suggested that three or more dislocations were a threshold for revision; however, these data predate contemporary implants and modern surgical approaches. We used a contemporary cohort of primary THA patients to evaluate the relationship between dislocation recurrence, timing of instability, and subsequent revision for instability. METHODS:There were 40,315 patients who underwent primary THA at our institution from 2016 to 2024. Among these patients, those who sustained a dislocation event were included. Keyword and diagnosis code search were performed to identify patients, and charts were reviewed to confirm dislocation. A total of 285 patients (0.7%) were included at a mean 5.7-year follow-up, of whom 242 (84.9%) ultimately underwent revision for instability. Instability was categorized by recurrence (one, two, or ≥ three dislocations) and timing ([early ≤ 90] versus late [greater than 90 days)]). Multivariable logistic regressions were performed to identify factors independently associated with risk of revision. RESULTS:Revision risk increased sharply with recurrence, rising from 69.1% after one dislocation to 93.9% after two and 98.5% after three or more. Patients who had two dislocations had significantly greater odds of revision than those who had one (odds ratio 7.70, 95% confidence interval 3.28 to 20.49, P < 0.001), while risk did not significantly increase beyond the second dislocation. Late dislocations were more likely to result in revision than early events (97.0 versus 74.9%, P < 0.001) and remained independently associated with revision (odds ratio 7.76, 95% confidence interval 2.46 to 35.10, P = 0.002). The association between recurrence, timing, and revision risk was consistent across both approaches. CONCLUSIONS:In contemporary THA practice, revision frequently occurred after a second dislocation, and late dislocations were more likely to require revision than early events. Future multicenter studies are needed to further refine instability management strategies.

BACKGROUND:The coronal plane alignment of the knee (CPAK) classification proposes nine knee phenotypes based on constitutional limb alignment and joint line obliquity. However, there is considerable confusion and variability in defining types, and its impact on surgical decision-making is unclear. A simple modified CPAK system is proposed to improve accuracy and facilitate decision-making. Herein, we applied a deep learning model to automate knee phenotyping and analyzed modified CPAK distributions in a large cohort. METHODS:We included 972 patients (1,944 healthy and arthritic knees) who had full-limb radiographs from a large publicly available dataset. A previously validated deep learning model was used to measure the lateral distal femoral angle and the medial proximal tibial angle. Knee phenotypes were determined using a two-level classification framework designed to capture both overall limb alignment, as measured by arithmetic hip-knee-ankle, and femoral and tibial joint-line contribution, as measured by lateral distal femoral angle and medial proximal tibial angle. RESULTS:There were seven phenotypic patterns identified, with five accounting for 99.2% of knees. The most frequent phenotypes were varus knees with valgus femur/varus tibia (26.9%), followed by neutral knees (25.6%), and valgus knees with valgus femur/varus tibia (24.2%). Less common were valgus knees with valgus femur/valgus tibia (12.2%) and varus femur/varus tibia in varus knees (10.3%). Varus phenotypes were predominantly tibial-driven (99.2%), while valgus phenotypes were femoral-driven (98.9%). Among neutral knees, 95% demonstrated a valgus femur with varus tibia configuration, while perfectly neutral combinations accounted for fewer than 2% of the total cohort. CONCLUSIONS:The Modifed CPAK offers a simplified and precise framework for knee phenotyping. Knee alignment demostrates a consistent pattern, with varus primarly driven by the tibia and valgus by the femur. This system provides a surgically relevant assessment of the knee, supporting alignment-based surgical planning.

BACKGROUND:Cementless fixation is increasingly popular for total knee arthroplasty (TKA). Prior research suggested that volumetric bone mineral density (vBMD) measured in preoperative computerized tomography (CT) scans could be useful to identify suitable candidates for cementless TKA with sufficient bone strength to avoid aseptic loosening. However, the clinically relevant thresholds of vBMD for cementless knees have not been defined. As a step toward defining such thresholds, we sought to relate the preoperative vBMD to the migration of tibial baseplates after TKA as a marker of aseptic loosening. METHODS:We prospectively enrolled 15 patients undergoing unilateral primary TKA with cementless tibial baseplates and cruciate-retaining inserts. Patients received a preoperative CT scan as standard of care, including a BMD reference phantom, and postoperative CT scans the day of surgery, at 6 weeks postoperatively, and at 6 months postoperatively. We calculated the implant motion relative to the day of surgery scan and related it to the vBMD in the four mm immediately under the baseplate. RESULTS:The maximum total point motion (MTPM) ranged from 0.1 to 0.9 mm at 6 weeks and between 0.2 and 1.1 mm at 6 months. The largest motion occurred vertically and, on average, was consistent with the posterior tilt of the baseplate. The preoperative vBMD was highest under the posterior-medial quadrant (mean: 229.8 mg/cm3 range, 113 to 329.2), and the medial-to-lateral vBMD ratio was proportional to the preoperative arithmetic hip-knee-ankle angle. However, neither the vBMD under the implant nor the limb alignment was related to any metric of implant motion at any time point. CONCLUSIONS:This is, to our knowledge, the first study to characterize the postoperative implant motion relative to a pre-weight-bearing CT scan and relate such motion to the vBMD directly under the tibial baseplate. Our results suggest that BMD alone cannot predict early migration of tibial baseplates.

Purpose:Offset measurement is critical in total hip arthroplasty (THA) for guiding restoration of native anatomy. However, measurements are time-consuming and measurer-dependent, creating obstacles for large cohort analyses. We aim to create an objective and reliable offset measurement algorithm using deep learning. Materials and Methods:Five hundred radiographs from the Osteoarthritis Initiative (OAI) were segmented with identification of the teardrop, femoral head, implant head, and femoral diaphysis. A U-Net convolutional neural network was trained to identify these landmarks and optimized using the multi-class Dice coefficient metric. Femoral axis and femoral/implant head center of rotation were calculated with the model predictions, and measurements of offset were compared against two trained readers on an independent testing cohort. Results:The optimized model had a Dice coefficient of 0.96 and a foreground mask accuracy of 96.2%. The model measured femoral, acetabular, and global offset on both limbs at a rate of 1.67 sec/image. On an independent cohort (n=90), the intraclass correlation coefficient between readers and the algorithm was 0.86 (95% confidence interval [CI] 0.80-0.91) for femoral offset, 0.87 (95% CI 0.78-0.91) for acetabular offset, and 0.94 (95% CI 0.91-0.96) for global offset. When applied to the entire OAI cohort (n=4,188), all relevant anatomical features (femoral axis, implant/femoral center of rotation, inter-teardrop line) were correctly calculated in 83.0% of images. Conclusion:We report the development of an accurate and rapid offset measurement model using deep learning that can be applied before and after THA. Future work will involve external model validation.

BACKGROUND:Patient dual eligibility status for Medicare and Medicaid is known to be a well-established proxy for socioeconomic vulnerability. Many studies have examined the impact that dual eligibility status has on patient outcomes after total joint arthroplasty (TJA), but its association with surgeon-level reimbursement after TJA remains insufficiently characterized. This study evaluated whether surgeon dual eligibility proportion was independently associated with standardized Medicare reimbursement per procedure for primary total hip arthroplasty (THA) and total knee arthroplasty (TKA) in 2023. METHODS:A cross-sectional retrospective analysis of a Medicare database was performed for 2023. A total of 4,506 THA surgeons performing 161,221 procedures and 6,618 TKA surgeons performing 297,919 procedures were identified. Surgeons performing primary THA and primary TKA in 2023 were identified and stratified into quartiles based on the proportion of their patient panel that was dual-eligible. The primary outcome was mean standardized Medicare reimbursement per procedure. Multivariable linear regressions were used to evaluate independent associations. Surgeon panel covariates included Hierarchical Condition Category (HCC) risk score, minority beneficiary proportion, and practice rurality. RESULTS:For THA, mean standardized reimbursement declined from $1,002 in Q1 to $971 in Q4 (P < 0.001). For TKA, mean reimbursement declined from $1,005 in Q1 to $981 in Q4 (P < 0.001). A higher dual eligibility proportion was independently associated with lower reimbursement for both THA (β = -1.58, P < 0.001) and TKA (β = -1.04, P < 0.001) after adjustment for rurality, HCC risk score, and minority beneficiary proportion per surgeon. CONCLUSIONS:Among surgeons performing primary TJA, a higher dual-eligible patient proportion was associated with reduced standardized reimbursement, despite the greater medical comorbidity and psychosocial complexity characterizing this population. These findings suggest that existing reimbursement frameworks may be associated with lower reimbursement for surgeons who disproportionately serve socioeconomically disadvantaged patients, with potential implications for equitable access to total joint arthroplasty. LEVEL OF EVIDENCE:Level III, retrospective cross-sectional study.

Aims:The choice of fixation for total knee arthroplasty (TKA) remains controversial. Cementless designs incorporating highly porous titanium surfaces may achieve durable biological fixation and mitigate cement-related complications. However, little has been written comparing the methods of fixation for robotic-assisted (RA) TKA. The aim of this study was to compare the implant survival and complication rates between cemented and cementless RA-TKA using a single robotic system and uniform implant design. Methods:This retrospective review involved 2,647 consecutive primary RA-TKAs undertaken by 27 surgeons at a high-volume academic centre, between 2016 and 2024, using a single CT-based robotic platform and implant design (Triathlon). Patients aged > 18 years with primary osteoarthritis and at least one year of follow-up were included. The method of fixation was determined by the operating surgeon. This resulted in 1,289 cemented and 1,358 cementless RA-TKAs. The mean follow-up was 3.5 years (SD 2.1). Outcomes included Kaplan-Meier survival free from revision (overall, septic, and aseptic), all-cause further surgery, and 90-day readmissions and nonoperative complications. Multivariable Cox regression analysis adjusted for age, BMI, sex, race, ethnicity, and operating time was performed to identify independent predictors. Results:The five-year revision-free survival was 98.0% (95% CI 97.1 to 98.9) and 98.5% (95% CI 97.4 to 99.6) for cemented and cementless fixation, respectively (p = 0.137, log-rank test). Cementless fixation was associated with a significantly decreased risk of septic revision (hazard ratio 0.21 (95% CI 0.03 to 0.71); p = 0.021), whereas there were no differences between the groups for aseptic revision. The five-year survival free from any reoperation was 96.6% (95% CI 95.5 to 97.7) in the cemented group and 97.1% (95% CI 95.9 to 98.4) in the cementless group (p = 0.472, log-rank test). The most common indication for reoperation was stiffness, followed by periprosthetic joint infection. The 90-day readmission and nonoperative complication rates were similar between the groups (p = 0.999 and p = 0.290, respectively). Conclusion:Cementless RA-TKA showed excellent five-year survival with a significantly decreased risk of septic revision compared with cemented RA-TKA. These findings suggest a decreased infection-related risk of failure with cementless fixation, without compromising the short-term implant survival.

BACKGROUND:The direct anterior approach (DAA) is a widely used muscle-sparing technique for total hip arthroplasty (THA) designed to minimize soft-tissue injury and support early recovery. The Superior Transverse Anatomic Reconstruction (STAR) approach is a piriformis-preserving modification of the postero-lateral approach that aims to combine the visualization advantages of posterior access with the muscle-sparing benefits of DAA. This study evaluated whether piriformis preservation through the STAR approach achieves early postoperative gait symmetry and spatio-temporal recovery comparable to DAA THA. METHODS:In this prospective cohort study, 47 patients undergoing primary, unilateral THA were enrolled at a single high-volume academic center between November 2024 and September 2025. Of these, 31 underwent STAR approach and 16 underwent DAA. In-office gait analysis was conducted preoperatively and at six weeks postoperatively. The primary outcomes were step-length and single-limb support symmetry ratios; secondary outcomes included spatio-temporal gait parameters, Timed Up and Go, and Forgotten Joint Score. Between-group differences were evaluated using analysis of covariance, adjusted for confounders. RESULTS:Baseline demographics and preoperative gait were similar. At six weeks, both STAR and DAA achieved symmetric gait, with postoperative step-length symmetry measured as 1.03 (range 0.87 to 1.34) in STAR and 1.02 (0.96 to 1.10) in DAA and single-limb support symmetry measured as 0.99 (0.83 to 1.16) and 1.01 (0.88 to 1.09), respectively. Nearly all patients achieved near-normal symmetry, with greater than 96.8% meeting step-length thresholds and greater than 93.5% achieving single-limb support symmetry. Adjusted analyses demonstrated no statistically significant between-group differences in step-length symmetry (+0.03, P = 0.15) and single-limb support symmetry (-0.01, P = 0.78). Similarly, spatio-temporal gait parameters and other functional outcomes showed no statistical differences (P > 0.05). CONCLUSION:Both piriformis-preserving approaches yielded comparable early postoperative gait symmetry and spatio-temporal parameters, supporting the hypothesis that muscle preservation through STAR can achieve similar gait recovery to DAA. Further studies with larger cohorts and extended follow-up are needed to confirm these findings.

BACKGROUND:Total hip (THA) and total knee arthroplasty (TKA) utilization has increased substantially over the past decade, highlighting the importance of understanding how operative volume is distributed among surgeons. While prior studies have focused on consolidation at the health-system level, surgeon-level procedural concentration remains incompletely characterized. METHODS:A retrospective analysis of Medicare fee-for-service claims from 2013 to 2023 was performed using a national Medicare administrative claims dataset. The primary and revision THAs and TKAs were identified using Current Procedural Terminology codes, including surgeons performing ≥ 11 procedures annually. Surgeon-level case concentration was assessed using the Herfindahl-Hirschman Index (HHI), with state-level variation evaluated using change in HHI (2023 to 2013). Entrant surgeons were defined as those who had no cases in the prior two years. Temporal trends were assessed using linear regressions. RESULTS:Primary THA volume increased from 166,730 to 274,801 and TKA from 390,710 to 526,893 between 2013 and 2023, with corresponding increases in median annual surgeon volume (THA: 21 to 26; TKA: 27 to 31). Surgeon-level HHI declined for primary THA (2.7 to 2.0; β = -0.064/year, P < 0.001) and TKA (1.7 to 1.5; β = -0.016/year, P = 0.022), indicating decentralization. Revision THA volume decreased (5,667 to 1,814) with increasing HHI (42.4 to 132.8; β = +8.37/year, P < 0.001), while revision TKA remained persistently concentrated. Entrant surgeons accounted for 12 to 18% of annual primary arthroplasty volume. CONCLUSIONS:The primary THAs and TKAs have become increasingly dispersed over the last decade, whereas revision arthroplasty remained concentrated among specialist high-volume surgeons, indicating contrasting workforce patterns.

BACKGROUND:Precise acetabular component positioning depends heavily on accurately recreating pelvic tilt (PT) during total hip arthroplasty (THA). The direct anterior approach (DAA) facilitates intraoperative fluoroscopy for real-time assessment, yet the accuracy of recreating preoperative standing PT intraoperatively remains unexplored. This study evaluated the precision of intraoperative PT recreation between pre- and intra-operative antero-posterior (AP) radiographic images during DAA THA. METHODS:This retrospective cohort included 325 patients undergoing primary unilateral DAA THA by a single surgeon between July 2022 and July 2024. Sagittal PT was measured on preoperative EOS radiographs in both standing and sitting positions. There were two validated parameters, anteroposterior PT and the sacro-femoral-pubic (SFP) angle, that were then calculated for both standing as well as intraoperative fluoroscopic images. There were two blinded observers who independently performed all measurements using the intraclass correlation coefficient (ICC greater than 0.80). The primary outcome was the proportion of patients in whom intraoperative PT was reproduced within ± 7.0 and ± 14.0° of standing values, thresholds corresponding to approximately 5.0 and 10.0° of anteversion inaccuracy. The secondary outcomes assessed correlations between pre- and intra-operative alignment parameters. RESULTS:Both AP PT and the Delta SFP (standing-to-sitting) angle demonstrated moderate-to-strong correlations with sagittal standing PT and Delta PT, confirming measurement accuracy before intraoperative analysis. Intraoperative fluoroscopy reproduced standing PT within ± 7.0° in 76% of patients and within ± 13.0° in 95%. However, preoperative standing and intraoperative AP PT demonstrated low correlation (r = 0.294), indicating substantial variability. The change in SFP (standing to supine) demonstrated moderate correlation with the change in AP PT (r = 0.422), further reflecting the limited precision of the PT recreation. CONCLUSION:Visual fluoroscopic recreation of standing PT during DAA THA demonstrated moderate accuracy, with three-quarters of patients achieving clinically relevant precision. Variability in reproducing functional PT suggests that visual assessment alone may benefit from adjunctive verification to improve consistency in acetabular positioning.

BACKGROUND:Larger femoral heads have been proposed to reduce dislocation risk following total hip arthroplasty (THA). While the benefit of increasing head size from 28 or 32 mm to ≥ 36 mm is well established, it remains unclear whether jumbo (40 or 44 mm) femoral heads confer additional stability over traditional large (36 mm) heads. This study aimed to determine whether jumbo heads improve stability or alter early complication rates. METHODS:We identified 6,413 primary THAs with large-diameter femoral heads (36-, 40-, or 44-mm) implanted at a single institution between February 1, 2016, and December 31, 2022. Cases were stratified by femoral head diameter into the traditional large-head (36 mm, n = 5,897) and jumbo-head (40 or 44 mm, n = 516) groups. The median follow-up was 2.4 years (range, 0.1 to 9.8; interquartile range [IQR], 1.3 to 4.1). The primary outcome was prosthetic hip dislocation at the last clinical follow-up. Time-to-event analyses were performed using multivariable Cox models with surgeon-level random effects, adjusting for patient-specific factors, year of surgery, surgical approach, and robotic assistance. RESULTS:In the full follow-up period, jumbo heads were not associated with a lower adjusted dislocation risk (hazard ratio (HR): 0.55 [95% confidence interval (CI): 0.13 to 2.34], P = 0.139) when compared with 36 mm heads. When analysis was truncated to the first postoperative year, 40 or 44 mm heads were associated with a lower dislocation risk compared with 36 mm heads (HR: 0.20 [95% CI: 0.05 to 0.79], P = 0.032). There were no significant differences in dislocation risk observed at 90 days. Rates of postoperative complications (periprosthetic joint infection and fracture) were similar between groups at 90 days, one year, and last follow-up. CONCLUSION:Compared with traditional large heads (36 mm), jumbo heads (40 or 44 mm) provided a modest, transient reduction in dislocation risk during the first postoperative year, most evident following the posterior approach THA, but did not confer additional long-term protection. Jumbo heads were not associated with increased rates of early surgical complications. Longer-term studies are warranted to address historical concerns.

Aims The Superior Transverse Anatomic Reconstruction (STAR) approach for total hip arthroplasty (THA) is a modified posterior approach that preserves the piriformis and the quadratus femoris. This approach provides improved short-term outcomes, but few studies compare patients undergoing THA with STAR to the posterolateral approach (PA). The goal of this study is to compare the short-term perioperative outcomes of STAR with PA and evaluate the learning curve associated with the STAR approach. Methods A total of 561 consecutive patients who underwent primary THA from 1 August 2023 to 30 April 2024 were included in the STAR approach cohort. Patients in the PA cohort underwent primary THA from 1 January 2017 to 31 July 2023 and were matched 1:1 with STAR patients by age, sex, BMI, and surgeon. Continuous outcomes (change in Hip disability and Osteoarthritis Outcome Score for Joint Replacement (HOOS, JR), estimated blood loss (EBL), length of stay (LOS), operating time, opioid use, morphine milligram equivalents, and binary outcomes (transfusion, readmission, complications) were assessed with multiple linear regression at six weeks post operation. Results STAR cohort patients used less postoperative opiods in the immediate postoperative period and at six weeks (MME 65 (SD 58) vs 107 (SD 126); p < 0.001, and 258 (SD 273) vs 364 (SD 308); p < 0.001, respectively) and experienced less EBL (127 ml (SD 55) vs 162 ml (SD 87); p < 0.001), lower operating time (82 minutes (SD 24) vs 90 minutes (SD 27); p < 0.001), and shorter LOS (0.9 days (SD 1.2) vs 1.7 days (SD 1.3); p < 0.001). There were no differences in the change in HOOS, JR score from pre- to postoperative, the rate of blood transfusion, readmission, or postoperative complications requiring revision. Conclusion The STAR approach is a piriformis and quadratus preserving approach that can be used for primary THA and without a learning curve. The benefits of the STAR approach may include a shorter operating time, less EBL, shorter LOS, and less postoperative pain requiring opioids. Longer-term follow-up in necessary to determine if the STAR approach continues to be associated with a lower overall revision rate compared with the conventional posterior approach.

BACKGROUND:Conventional educational materials for total joint arthroplasty frequently exhibit deficiencies in readability and personalization. This investigation assessed a custom-tailored artificial intelligence (CTAI) platform to evaluate its efficacy in enhancing preoperative patient education within arthroplasty surgery. METHODS:This prospective, observational pilot study employed a two-phase sequential design: a 10-patient a priori cohort followed by implementation with 30 additional participants undergoing primary total hip or knee arthroplasty. Participants accessed the platform during the preoperative period and early postoperative recovery. There were 32 patients (50.0% knee, 50.0% hip) who completed the preoperative survey. Outcomes were captured using structured surveys administered at the presurgical screening visit and again at the 6-week follow-up using a phase-specific postoperative instrument that retained core items and incorporated recovery-focused domains. Measures included feasibility (e.g., platform access and engagement) and patient-reported experience, including usefulness, understandability of responses, perceived completeness of answers, and perceived preparedness/readiness. RESULTS:The majority (84.8%) successfully engaged with the CTAI; 59.4% submitted one to four queries, while 25.1% submitted five or more. Surgeon-provided educational materials constituted the predominant information source (84.4%), followed by CTAI engagement (56.3%). The platform was deemed clinically valuable (≥ 4 rating) by 66.7% of users, with 84.4% reporting high comprehensibility of responses and 75.1% indicating satisfactory resolution of surgical inquiries. Furthermore, 75.0% reported enhanced preparedness, and 80.4% expressed intention to recommend the platform. Predominant query domains included perioperative logistics (22.8%), postoperative concerns (22.0%), and activity parameters (12.9%). At six weeks postoperatively, 24 of 32 (75.0%) completed the postoperative survey, and 22 of 24 (91.7%) reported successful platform access. Engagement was heterogeneous, with seven of 24 (29.2%) submitting zero questions and five of 24 (20.8%) submitting greater than 10. For postoperative question resolution, seven of 24 (29.2%) reported all questions were answered clearly (score 5), whereas seven of 24 (29.2%) reported the CTAI did not answer their questions (score 1). Recovery instruction comprehensibility remained high, with 14 of 24 (58.3%) reporting the instructions were very easy to understand (score 5). CONCLUSIONS:Preliminary findings demonstrate that the CTAI platform is feasible to deploy as an efficacious adjunctive tool for preoperative total joint arthroplasty education. Most participants who accessed the platform reported favorable understandability and perceived completeness of responses and reported increased preparedness for surgery. The diversity of inquiry domains underscores the platform's capacity for addressing varied patient concerns. Larger comparative studies with appropriate control groups are needed to determine the platform's impact relative to standard education and to evaluate downstream clinical outcomes.

BACKGROUND:The coronal plane alignment of the knee (CPAK) classification provides an objective framework to describe alignment changes after total knee arthroplasty (TKA). Although preserving the native phenotype improves intraoperative soft-tissue balance in varus and neutral knees, its functional benefits remain uncertain. We therefore evaluated whether preserving the preoperative CPAK phenotype in varus and neutral knees is associated with superior early postoperative gait patterns following TKA. METHODS:We prospectively enrolled 44 patients who had varus and neutral coronal alignment who underwent robotic-assisted TKA performed by five fellowship-trained surgeons. Spatiotemporal gait parameters were evaluated preoperatively and at six weeks postoperatively using a pressure mat that captured velocity, cadence, step length, and support time. Patients were grouped according to whether their postoperative alignment preserved or altered their native CPAK phenotype, as measured in long-leg biplane radiographs. Between-group differences were assessed using analysis of covariance adjusted for confounding and baseline gait values. RESULTS:Of the 44 patients, 21 (47.7%) had their native CPAK phenotype preserved, and 23 (52.3%) experienced a phenotype change. Preserving CPAK was associated with significantly faster postoperative walking velocity (+11.7 cm/s, P = 0.01), higher cadence (+7.0 steps/minute, P = 0.02), longer single-limb support (+1.5%, P = 0.003), and shorter step time (P = 0.02) compared with patients whose CPAK phenotype changed. Preoperative-to-postoperative gait changes analysis further confirmed this pattern: the changed group demonstrated significant reductions in walking velocity (P = 0.04) and cadence (P = 0.01), along with increased step time (P = 0.02), whereas the unchanged group showed significant improvements in step length (P = 0.02), greater single-limb support (P < 0.01), and reduced double-limb support (P < 0.01). CONCLUSIONS:Preserving the native CPAK phenotype after TKA is associated with improved early gait metrics, suggesting a potential biomechanical advantage of restoring constitutional alignment. These findings should be confirmed in larger cohorts with longer-term follow-up.

Robotic-assisted total knee arthroplasty (RA-TKA) is increasingly used to improve implant positioning, soft-tissue balance, and procedural reproducibility. Yet, little is known about how different components of the operation independently contribute to the overall learning curve. This study aimed to characterize the learning curve of MAKO-assisted TKA by separately evaluating these components and assessing their differential impact on operative workflow. A retrospective observational study included 92 consecutive patients who underwent image-based RA-TKA (MAKO, Stryker) for primary knee osteoarthritis. All procedures were performed by a single experienced arthroplasty surgeon with no prior robotic or computer-assisted surgery background. Cumulative sum (CUSUM) analysis with piecewise linear regression was applied to total surgical time, pin placement time, and composite robotic workflow time to identify inflection points and define learning curve phases. Piecewise regression of the CUSUM plot for total surgical time revealed two breakpoints at cases 11 and 51, defining three phases of the learning curve: (1) initial learning (cases 1–11), (2) competence (cases 12–51), and (3) optimized performance (cases 52–90). Mean surgical time was 68.9 ± 20.1 min, stabilizing around 65 min after 50 cases. Along with total surgical time, the initial learning phase ended around cases 10–11 for both robotic workflow and pin placement. However, subsequent performance patterns differed: pin placement reached optimized performance by case 52 (mean 8.4 ± 4.3 min), whereas robotic workflow time improved more gradually, without clear stabilization until the end of the series (mean 37.8 ± 10.8 min). RA-TKA with the MAKO system follows a structured learning curve with early achievement of proficiency after 11 cases. Total surgical time and pin placement reached optimized performance by mid-series, whereas robotic workflow tasks required a longer consolidation period, likely influenced by patient-specific anatomical variability. These findings support RA-TKA as a safe and effective tool, offering rapid surgeon adaptation. IV.

Background Robotic platforms can provide increased information and accuracy to the procedure of total knee arthroplasty (TKA). However, it is unclear whether these advantages translate to decreased failures over time. Therefore, the purpose of this study was to describe aseptic failures following robotic TKA by examining (1) types of failure and (2) subsequent procedures/reoperations. Methods We retrospectively reviewed 2,648 robotic TKAs with a single robotic platform performed at our institution between January 1, 2016, and May 31, 2024. There were 1,303 men and 1,345 women who had a mean age of 64 years (range, 20 to 93). Patients were excluded if they had a prior history of infection, posttraumatic arthritis, or hardware other than a prior anterior cruciate ligament reconstruction. Patients who had less than 12-month follow-up were also excluded from the final analyses. Results At a mean follow-up of 42 months (range, 14 to 95), 203 patients (7.7%) who underwent robotic primary TKA experienced at least one complication. There were 163 patients (6.2%) who required at least one additional intervention, and 39 knees (1.5%) required a revision TKA. There were 21 patients (0.8%) who developed infections (14 periprosthetic joint infections and seven surgical site infections). Aseptic complications occurred in the following order of decreasing frequency: stiffness (5.5%); chronic pain (0.7%); instability (0.2%); and aseptic loosening (0.1%). There were two cases each of patellar maltracking, patellar clunk, and popliteus/iliotibial band syndrome. Also, there were three periprosthetic fractures and one case of a quadriceps tendon rupture. Conclusions Failures can still occur following robotic TKA. Stiffness requiring manipulation was the most common complication. Traditional early failures such as instability and aseptic loosening were infrequent. Comparative clinical trials with defined targets are necessary to confirm these observations and determine the advantages and disadvantages of robotic TKA systems.

BACKGROUND:Changing from standing to sitting positions requires rotation of the femur from an almost vertical plane to the horizontal plane. Osteoarthritis of the hip limits hip extension, resulting in less ability to recruit spinopelvic tilt (SPT) while standing and requiring increased SPT while sitting to compensate for the loss of hip range of motion. To date, the effect of total hip arthroplasty (THA) on spinopelvic sitting and standing mechanics has not been reported, particularly in the setting of patients with coexistent sagittal plane spinal deformity. METHODS:A retrospective review was performed of patients ≥18 years of age undergoing unilateral THA for hip osteoarthritis with sitting and standing radiographs made before and after THA. Alignment was analyzed at baseline and follow-up after THA in both standing and sitting positions in a relaxed posture with the fingers resting on top of the clavicles. Patients were grouped according to the presence or absence of sagittal plane deformity preoperatively into 3 groups: no sagittal plane deformity (normal), thoracolumbar (TL) deformity (pelvic incidence-lumbar lordosis [PI-LL] mismatch > 10° and/or T1-pelvic angle [TPA] > 20°), or apparent deformity (PI-LL ≤ 10° and TPA ≤ 20°, but sagittal vertical axis [SVA] > 50 mm). RESULTS:In this study, 192 patients were assessed: 64 had TL deformity, 39 had apparent deformity, and 89 had normal alignment. Overall, patients demonstrated a reduction in standing SVA (45 to 34.1 mm; p < 0.001) and an increase in SPT (14.6° to 15.7°; p = 0.03) after THA. There was a greater change in standing SVA (p < 0.001) among patients with apparent deformity (-29.0 mm) compared with patients with normal alignment (0.9 mm) and patients with TL deformity (-16.3 mm). Those with apparent deformity also experienced the greatest difference (p = 0.03) in postural SPT change (moving from standing to sitting) (-10.1°) from before to after THA when compared with those with normal alignment (-3.6°) and TL deformity (-1.2°). The difference in postural SVA change from before to after THA was also greatest (p < 0.001) in those with apparent deformity (32.1 mm) compared with those with normal alignment (6.5 mm) and TL deformity (17.3 mm). CONCLUSIONS:Postural changes in spinopelvic alignment vary after THA depending on the presence of TL deformity or apparent deformity due to hip flexion contracture. Patients with apparent deformity had larger changes in standing and sitting alignment than patients with TL deformity or patients with normal alignment. The assessment of global sagittal alignment findings can be used to predict the likelihood of improvement in sagittal alignment after THA. LEVEL OF EVIDENCE:Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Background Robotic arm assisted total knee arthroplasty (RA-TKA) aims to improve accuracy in bone resection, implant positioning, and joint alignment compared to manual TKA (M-TKA). However, the learning curve of RA-TKA can disrupt operating room efficiency, increase complications, and raise costs. This study examines the operative time learning curve of RA-TKA using a single robotic system. Methods The study analyzed the first 80 RA-TKA and the last 80 M-TKA cases performed by a single surgeon using the VELYS robotic system after transitioning from M-TKA. Cases were subdivided into groups of 20 and compared to M-TKA cases. A cumulative summation analysis identified the learning curve phases. Results Three phases were identified: Phase 1 (initial learning, cases 1-9), Phase 2 (increased competence, plateau from cases 10-52), and Phase 3 (post-learning, optimized performance from cases 53-80). Mean surgical time for RA-TKA was 42.4 ± 8.7 minutes, compared to 35.3 ± 7.0 minutes for M-TKA (P < .001). Early RA-TKA cases (1-20) had significantly longer times than late RA-TKA cases (61-80) and M-TKA cases (P < .05). Late RA-TKA times were comparable to M-TKA (P = .06). Conclusions RA-TKA is an enabling surgical tool that can be integrated efficiently into a surgical workflow with a rapid learning curve of 9 cases.