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Introduction/Purpose: There is a paucity of literature investigating the association of operative time and postoperative outcomes following total ankle arthroplasty (TAA). Thus, this study seeks to evaluate the relationship between total operative time and postoperative outcomes following TAA. Methods: The American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) database was queried from 2007-2020 to identify 2133 TAA patients. Demographics, medical comorbidities, concomitant procedures, hospital length of stay (LOS), and 30-day complication, readmission, and reoperation rates were compared between groups. Patients were excluded based on an operative time greater than 290 minutes to limit the influence of extreme outliers. The cohort was predominantly male (53.8%) and mean patient age was 64.10 (range 19-87) years with a mean BMI of 31.00 (range 17.14-57.78) m/kg2. The mean operative time of the cohort was 149.56 (standard deviation [SD]=49.60) minutes. Results: Demographic characteristics associated with increased operative time were decreased age (p 1 SD above the mean), independently predicted were readmission (OR=2.817; 95%CI=1.334-5.951; p=0.007), urinary tract infection (OR=6.410; 95%CI=1.384-29.6866; p=0.018), wound dehiscence (OR=5.127; 95%CI=1.282-20.508; p=0.021), and bleeding requiring transfusion (OR=18.364; 95%CI=1.846-182.682; p=0.013). Conclusion: The study found longer operative time during TAA is associated with a statistically significant increase in wound dehiscence, urinary tract infection, readmission, reoperation, and increased length of stay. Therefore, surgeons should prioritize measures to reduce operative time when appropriate while optimizing implant placement, deformity correction, and implant stability in TAA.

Introduction/Purpose: Charcot arthropathy is a debilitating and challenging clinical problem for patients and providers. Patient reported outcome measures (PROMs) are an effective tool for gauging a patient’s quality of life and daily functioning, but they have not been reported in the setting of Charcot arthropathy. Our goal is to assess PROMs severity in midfoot Charcot arthropathy (Brodsky Type 1), alongside linked demographics and comorbidities. We will compare these values with PROMs from conditions like ESRD, knee and hip arthritis, highlighting Charcot arthropathy's comparable debilitation. Methods: A retrospective chart review identified 67 patients with Brodsky Type 1 Charcot arthropathy by one of two fellowship- trained foot and ankle surgeons at a single academic medical center between years 2015 and 2023. ICD-10 CM codes E11.610, M14.671, and M14.672 were used to identify diagnosis of Charcot arthropathy and radiological interpretation determined Brodsky type. Data collected from patient charts included demographics, medical history, presence of ulcers, and preoperative Visual Analog Scale (VAS), 12-Item Short Form Health Survey (SF-12), Pain Catastrophizing Scale (PCS), Pain Disability Index (PDI), SSS- 8, Foot and Ankle Outcome Score (FAOS), and Foot and Ankle Ability Measure (FAAM) scores and postoperative FAOS and FAAM scores. A One-Way ANOVA was performed to evaluate statistical significance. Averages of preoperative PROM scores were compared to literature values for other diseases. Results: Our cohort was mostly male (58.2%), with mean age 61.73 years, BMI 32.9, and A1C 6.9. Initial presentation revealed 50.7% had ulcers. Brodsky type 1 (midfoot) had notably the lowest pre-op PROM scores when compared to other Brodsky types: PDI Recreation (p=.033), FAOS Symptoms and Stiffness (p=.044), and FAOS Recreation (p=.027). Ulcer presence yielded significantly lower FAAM-ADL scores (p=.038), while other PROMs showed no statistical difference. Our mean VAS score was 53.34 which was higher than hip arthritis VAS (43.0) but lower than ESRD VAS (60.0) and knee arthritis VAS (64.2). Our SF-12 PCS scores (29.4) exceeded prior reports (hip 28.5, knee 28.6), while SF-12 MCS scores were higher in earlier studies (hip 49.6, knee 51.5) than our 43.8. Conclusion: Patients with Charcot arthropathy struggle in daily tasks, reflected in lowered FAOS ADL scores. Brodsky type 1 patients also face challenges in higher-level activities, evident in reduced PDI recreation and FAOS recreation scores. Those with ulcers similarly encounter issues in daily tasks, seen in lower FAAM ADL scores. Brodsky type 1 patients also experience debilitating pain as noted by higher VAS scores when compared to known debilitating conditions such as hip and knee arthritis. Comparatively minor differences in knee and hip arthritis SF-12 PCS scores indicate significant physical limitations for these patients.

Introduction/Purpose: With increasing total ankle arthroplasty (TAA) being performed and a plethora of new survivorship data available, an updated literature review is needed to better understand the impact of different types of implants on the outcomes of TAA. The purpose of this study is to compare the outcomes of fixed vs mobile bearing TAAs in the literature. Methods: A comprehensive search of MEDLINE for all articles published between 2004 and 2023 was conducted with a minimum two-year mean follow-up. Two reviewers evaluated each study to determine whether it was eligible for inclusion and abstracted the data of interest. Meta-analytic pooling of group results across studies was performed, examining implant survival and component failure. Seventy-three implant groups met inclusion criteria (only 3rd and 4th generation implants), composed of STAR (20), Salto (mobile bearing) (10), Salto Talaris (11), Hintegra (8), Zimmer (6), INBONE II (6), INBONE I (4), Infinity (4), Cadence (4). 41 groups (56.2%) were implanted with mobile bearing devices, and 32 (43.8%) with fixed bearing implants. In total, 6498 subjects were included, with a mean age of 61.77 years and a mean BMI of 28.5 kg/m 2 . At a mean follow-up of 62.2 months, the overall reoperation rate was 21.13% and the metal component revision rate was 10.16%. Results: The mean follow-up of mobile bearing TAA studies (N =41) was 77.8 (range 24-188.4) months, and that of fixed bearing studies (N =32) was 45.3 (range 24-85.2) months. Multivariate analysis of bearing type, controlling for follow-up duration, found fixed bearing implants had statistically significantly higher metal component survival rates (fixed=96.1%, mobile=87.9%, p=.001); however, there were no statistically significant differences in rates of reoperation (fixed=17.0%, mobile=24.8%, p=.768). When examining specifically tibial and talar component failure rates, there was no statistically significant difference between bearing type (fixed tibial=1.46%, mobile tibial=2.95%, p=.472) (fixed talar=2.19%, mobile talar=2.79%, p=.966). Overall implant survival rates at one, two, five, and ten years were 96.4%, 96.0%, 92.7%, and 79.4%, respectively, and did not differ by bearing type (Table 1). Conclusion: Implant survival was statistically significantly better for 3rd and 4th generation fixed bearing TAAs as compared to mobile bearing TAAs, controlling for length of follow-up. There was no statistically significant difference in total reoperation rate. This suggests that fixed bearing implants may offer improved implant survival compared to mobile bearing implants, though further research is needed to confirm these findings.

Introduction/Purpose: Diabetes mellitus (DM) is known to negatively impact outcomes following surgical operations and increase the susceptibility of affected individuals to higher rates of nonunion, surgical site infection, ulceration, increased risk of amputation of the extremities, and various other perioperative complications. A number of in vitro studies suggest that the increase in undesired outcomes is largely secondary to the effects of diabetes-induced prolonged inflammation and advanced glycation end products (AGEs) on these patients' vascular systems and skeletal microarchitecture. However, there is a paucity of literature investigating the effects of blood glucose-regulating medications on the clinical outcomes of diabetic patients following fusion procedures. This study aims to determine the impact of commonly prescribed diabetic medications on bone health and bone healing following foot and ankle operations. Methods: A retrospective review was conducted of 114 diabetic patients undergoing ankle, hindfoot, or midfoot arthrodesis by one of two fellowship-trained foot and ankle orthopaedic surgeons from 2015-2022. Patients were identified by having undergone surgery via 27870, 27815, 27825, or 27835 CPT codes, as well as having been diagnosed with diabetes mellitus prior to or at time of surgery. Joints fused included the tibiotalar joint (n=45; 39.5%), subtalar joint (n=62; 54.4%), talonavicular joint (n=31; 27.2%), and calcaneocuboid (n=14; 12.3%). Data collected included demographics, medical history, diabetic medication, postoperative complications, readmission rates, and reoperation rates. 36 patient cases were noted to not have concurrent medications prescribed to control their diabetes, while the other 78 patient cases were concurrently prescribed either metformin (33 cases; 28.9%), insulin (19 cases; 16.7%), both metformin and insulin (18 cases; 15.8%), glipizides (11 cases; 9.6%), dulaglutides (7 cases; 6.1%), semaglutides (9 cases; 7.9%), and sitagliptins (8 cases; 7.0%). Results: The overall cohort was majority male (62.3%) with mean age 60.38 (range 31-76) years, mean BMI 34.00 (range 21.47- 61.38) kg/m 2 and mean follow-up 1.90 (range .50-6.25) years. The cohort had a 27.2% superficial infection rate, 28.9% deep infection rate, 41.2% non-union rate, 47.4% reoperation rate, and a 14% 90-day readmission rate. Except for insulin-treated patients, who had significantly higher infection (insulin=45.9%, non-insulin=18.2%; p=.003) and deep infection rates (insulin=45.9%, non-insulin=18.2%; p=.003), there was no statistically significant difference in any outcomes by specific medication or any diabetic medication use. Patients with Charcot arthropathy (n=42) had significantly higher superficial infection (charcot=42.9%, non- Charcot=18.1%; p=.005), deep infection (Charcot=52.4%, non-Charcot=15.3%; p

Introduction/Purpose: Orthopaedic, vascular, and general surgeons all perform lower extremity amputations. Previous studies have indicated that outcomes may be related surgeon experience or skill, with a similar study indicating that general surgeons experience worst postoperative outcomes than vascular surgeons. In spite of these studies, there is a paucity of literature investigating the difference in outcomes between amputations performed by orthopaedic and vascular surgeons. This study aims to analyze the effect of surgeon specialty on 30-day complication, readmission, reoperation, and mortality rates following below-knee amputation (BKA) procedures between orthopaedic and vascular surgeons. Methods: The American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) database was queried from 2010-2019 to identify 28,776 patients undergoing BKA by either orthopaedic, general, or vascular surgeons using Current Procedural Terminology (CPT) codes 27880, 27881, and 27882. Patients were stratified into groups based on surgeon specialty with 18,935 (66.4%) cases performed by vascular surgeons, 6,146 (21.6%) cases by general surgeons, and 3,429 (15.3%) cases were performed by orthopaedic surgeons. Demographics, comorbid conditions, hospital length of stay (LOS), and 30-day complications, readmission, reoperation, and mortality rates were compared between groups. Univariate and multivariate analysis were performed to examine the associations between outcomes and surgical specialty, while controlling for comorbid conditions as measured by ASA score and 5-factor modified frailty index (mFI-5) score. Results: The cohort was predominantly male (68.4%), white (61.9%), and the mean age was 63.54 (range, 18-90) years. The cohort of patients treated by vascular and general surgeons had significantly higher rates of numerous comorbidities, including mFI-5 score (p

Introduction/Purpose: Fixation of fourth-generation ankle replacements is evolving. Given the concern for tibial tray loosening or radiolucencies, three-dimensional (3-D) printing has been suggested as a solution. Additive manufacturing allows for the creation of an optimal implant surface for improved initial stability and bony on growth. To date, there are no reported data concerning survivorship and clinical improvement following a 3-D printed ankle replacement. Documentation of implant survivability and comparison studies of the latest generation implants are limited. The purpose of this study is report on prospectively-collected patient reported outcome measures (PROMs) in a multi-institutional study of a 3-D printed fourth-generation total ankle. Methods: Patients presenting for a total ankle replacement at 12 institutions were prospectively enrolled and implanted in both academic and private settings. Patients had demographics and PROMs recorded pre-operatively and at 6 month and 12-month intervals. The following PROMs were collected: Ankle Osteoarthritis Score (AOS), PROMIS Global Physical Health, Foot and Ankle Outcome Score (FAOS), and satisfaction scores. The preoperative and latest follow-up scores for patients with two years of follow-up were analyzed. Results: 91 of 177 subjects enrolled have reached one-year in follow-up currently. From the 177 enrolled (52.5% male) with an average age of 64.0±10.3 years old with an average BMI of 30.8±6.2. The pre-operative diagnosis for arthritis type was degenerative arthritis (27.7%), rheumatoid arthritis (1.7), post-traumatic arthritis (70.1%), and other (0.50%). There were 3 (1.69%) clinical failures:1 early infection: at 2 months, 1 tibial subsidence at 7 months, and 1 deep infection associated with trauma at 8 months post-operatively. The patients improved in all PROMs domains at one year including: Mean Total AOS (19.0. ± 17.5) p

Category: Ankle; Basic Sciences/Biologics Introduction/Purpose: Next-generation DNA sequencing (NGS) technologies have increased the sensitivity of bacterial cultures and has been used in other areas of orthopaedics to better understand the native microbiome of various joints. This study uses NGS to determine whether (1) a unique microbiome exists in human ankle tissues, (2) if components of the ankle microbiome impact patient outcomes, and (3) whether microbes found on the skin are a normal part of the ankle microbiome. Methods: A prospective study recruited 32 patients undergoing total ankle arthroplasty (TAA, n=23) or ankle arthrodesis via an anterior approach (n=9) during 2020-2021 with one of two fellowship-trained foot and ankle surgeons at an academic medical center. During the operation, the surgeon would swab five layers of the ankle for analysis at a CLIA-licensed molecular diagnostic laboratory: skin (n=32), retinaculum (n=31), tibialis anterior tendon (n=31), joint capsule (n=31), and distal tibia (n=32). Demographics, medical comorbidities, surgical indication, postoperative complications, and readmission and reoperation rates were collected from patient records. Results: Of the 157 swabs sent for NGS, 19 (12.1%) indicated 27 bacteria were present (positive), while the remaining 138 (87.9%) had no bacteria present (negative). The most common organisms were Cutibacterium acnes, present in 11 ankles (34.4%), and Staphylococcus epidermidis, present in 3 ankles (9.4%). The most bacteria were found in the retinaculum (29.6%). No PROM nor follow-up duration was associated with the presence of bacteria, or the number of bacteria or affected layers. Similarly, complication (positive=18.2%, negative=23.8%; p=1.000), nonunion (positive=0.0%, negative=28.6%; p=1.000), infection (positive=0.0%, negative=4.8%; p=1.000), 90-day readmission (positive=0.0%, negative=4.8%; p=1.000), and reoperation (positive=0.0%, negative=4.8%; p=1.000) rates did not differ if a subject’s NGS profile was positive or negative. Conclusion: This study found that C. acnes and S. epidermidis were most commonly found in the ankle microbiome, with C. acnes being present in 34% of ankles. There was no difference in complication rates between patient with and without positive bacterial cultures following TAA or ankle arthrodesis.

Category: Ankle; Other Introduction/Purpose: The American Society of Anesthesiologist (ASA) physical status classification system serves as a useful measure of patient comorbidities. Multiple studies have found an increased risk of readmission in patients undergoing total knee or hip arthroplasty with elevated ASA scores. There is a paucity of literature investigating the association of ASA score and postoperative outcomes following total ankle arthroplasty (TAA). Thus, this study seeks to evaluate the relationship between ASA score and postoperative outcomes following TAA. Methods: The American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) database was queried from 2007-2020 to identify 2210 TAA patients. Patients were stratified based on preoperative ASA score, 1-normal healthy patient (n=101), 2-mild systemic disease (n=1228), 3-severe systemic disease (n=855), 4-severe, life-threatening systemic disease (n=26). Demographics, medical comorbidities, concomitant procedures, hospital length of stay (LOS), and 30-day complication, readmission, and reoperation rates were compared between groups. The cohort was predominantly male (54.0%) and mean patient age was 63.99 (range 19-87) years with a mean BMI of 31.01 (range 17.14-57.78) m/kg2. Results: Patients with an ASA score ≥3 were significantly older (≤2 =62.78, ≥3 =65.81%; p

Category: Ankle Arthritis Introduction/Purpose: With the increasing total ankle arthroplasty (TAA) literature, there is a need to further examine the outcomes across a wide variety of implants. The purpose of this study is to review the existing literature and identify trends among current individual TAA implants. Methods: A comprehensive search of MEDLINE for all articles published between 1996 and 2021 was conducted with a minimum two-year mean follow-up. Two reviewers evaluated each study to determine whether it was eligible for inclusion and abstracted the data of interest. Meta-analytic pooling of group results across studies was performed, examining for individual implant survival and component failure. Seventy-three implant groups met inclusion criteria (3rd and 4th generation implants only), composed of STAR (20), Salto (mobile bearing) (10), Salto Talaris (11), Hintegra (8), Zimmer (6), INBONE II (6), INBONE I (4), Infinity (4), Cadence (4). 41 groups (56.2%) were implanted with mobile bearing devices and 32 (43.8%) with fixed bearing implants. In total, 6498 subjects were included with a mean age of 61.77 years and mean BMI of 28.5 kg/m 2 . At mean follow-up of 62.2 months, the overall reoperation rate was 21.13% and metal component revision rate was 10.16%. Results: Multivariate analysis of all implants, controlling for follow-up duration, found a statistically significant difference in the metal component survival rate (p=.036) and reoperation rate (p=.007) with the STARs TAAs surviving significantly worse and undergoing reoperation at a significantly higher rate than all other implants. There was no statistically significant difference in the rate of metal component revision (p=.768), tibial component failure rate (p=.095), or talar component failure rate (p=.089). Analysis of the Salto Talaris vs Salto found a significant difference in metal component survival rate (Salto=90.68%, Salto Talaris=97.81%; p=.002). Lastly, analysis of the INBONE I vs II implants found INBONE I had a significantly greater rate of revision due to metal component failure (INBONE I=9.8%, INBONE II=3.4%; p=.002). Conclusion: Based on current literature, it appears that the STAR total ankle implant has a statistically significantly lower rate of metal component survival and higher rate of reoperation than the other 3rd and 4th generation implants examined, even when controlling for study follow-up duration. The fixed bearing Salto Talaris had statistically significantly better survival rate than the mobile bearing Salto. These findings are important to physicians when considering implants for total ankle arthroplasty.

Category: Ankle; Hindfoot Introduction/Purpose: A nonunion is a challenging clinic problem following foot and ankle arthrodeses. There is great interest in orthobiologics as surgical adjuvants. The purpose of this study is to compare three orthobiologics (PDGF-B agonist [PDGF-B], allograft bone morphogenetic protein [ABMP], crushed cancellous allograft [CC]) to determine if there is a difference in union rates following foot and ankle arthrodeses. Methods: A retrospective review was conducted of 258 feet (255 patients) with minimum 3-month follow-up, undergoing arthrodesis by a single fellowship-trained foot and ankle orthopaedic surgeon from 2016-2022. Patients underwent ankle, pantalar, triple, subtalar (ST), midfoot, or talonavicular fusion. Data collected included demographics, medical history, orthobiologics used, postoperative complications, readmission and reoperation rates. 83 (34.0%) cases used PDGF-B with CC, 32 (13.1%) used solely ABMP, 66 (27.0%) used ABMP with CC, and 63 (25.8%) used solely CC. Union was defined as bridging bone on three joint quadrants on AP and lateral radiographs, or greater than 50% bridging bone of the joint space on computed tomography (CT). Results: Of the 258 cases, the ST joint was most commonly fused (53.7%). Cases using ABMP had statistically significantly shorter mean time to fusion (ABMP=120.81 days, no ABMP=162.04 days). Patients treated with ABMP were also significantly less likely to undergo reoperation or removal of hardware. Between PDGF-B+CC and ABMP+CC groups, only reoperation rates differed significantly (PDGF-B+CC=26.5%, ABMP+CC=7.6%,). Multivariate regression modeling for time to fusion found ABMP usage to be the only statistically significant predictor of time to fusion, predicting patients will achieve fusion nearly 40.7 days quicker with the use of ABMP. Conclusion: Joints treated with PDGF-B and ABMP demonstrated equivalent fusion rates. Treatments using ABMP and CC achieved quicker time to fusion and lower rates of reoperation when compared to treatments using PDGF-B and CC.

Category: Basic Sciences/Biologics; Ankle Introduction/Purpose: Next-generation DNA sequencing (NGS) technologies have increased the sensitivity of bacterial cultures and helped to better understand the normal flora of different joints. Researchers have utilized NGS to identify organisms associated with reoperations in shoulder surgery, but there is very little data on the field of foot and ankle. This study uses NGS to determine whether there is a unique microbiome that exists on orthopaedic hardware in the foot and ankle. Methods: A prospective study recruited 34 patients undergoing hardware removal surgery from the foot or ankle during 2020- 2023 with one of two fellowship-trained foot and ankle surgeons at an academic medical center. Patients were excluded based on the diagnosis or suspicion of infection prior to surgery. Explanted hardware was sent for analysis at a CLIA-licensed molecular diagnostic laboratory. Demographics, medical comorbidities, surgical indication, postoperative complications, readmission, and reoperation rates were collected from patient records. The majority of patients underwent surgery for diagnosis with painful orthopaedic hardware (70.6%). The cohort was majority female (67.6%) and average age was 53.15 (range 18-78) years. Results: Of the 34 samples sent for NGS, 5 (14.7%) indicated 9 bacteria were present (positive), while the remaining 29 (85.3%) had no bacteria present (negative). The most common organisms were of the genus Staphylococcus, representing 4 bacteria (44.4%), and Corynebacterium, representing 2 bacteria (22.2%). C. acnes was only present in one sample. There was no relationship between bacterial presence and patients undergoing hardware removal for diagnosis of painful orthopaedic hardware. No demographics nor postoperative outcomes were statistically associated with the presence of bacteria on removed hardware samples. The overall rate of complication, reoperation, and readmission were 8.8%, 2.9%, and 2.9%, respectively. Conclusion: This study found that there is no common microbial community present in patients undergoing hardware removal surgery. The most commonly present bacteria were of the genus Staphylococcus, bacteria overall were isolated in 14.7% of specimens. C acnes appeared to be uncommon. Further research should be done with a larger sample to support these findings.

Category: Ankle Arthritis Introduction/Purpose: With increasing numbers of total ankle arthroplasty (TAA) procedures being performed and a plethora of new survivorship data available, an updated literature review is needed to better understand the impact of different types of implants on outcomes of TAA. The purpose of this study is to compare the outcomes of fixed vs mobile bearing TAAs in the literature. Methods: A comprehensive search of MEDLINE for all articles published between 2004 and 2021 was conducted with a minimum two-year mean follow-up. Two reviewers evaluated each study to determine whether it was eligible for inclusion and abstracted the data of interest. Meta-analytic pooling of group results across studies was performed, examining implant survival and component failure. Seventy-three implant groups met inclusion criteria (only 3rd and 4th generation implants), composed of STAR (20), Salto (mobile bearing) (10), Salto Talaris (11 ), Hintegra (8), Zimmer (6), INBONE II (6), INBONE I (4), Infinity (4), Cadence (4). 41 groups (56.2%) were implanted with mobile bearing devices and 32 (43.8%) with fixed bearing implants. In total, 6498 subjects were included with a mean age of 61.77 years and mean BMI of 28.5 kg/m 2 . At mean follow-up of 62.2 months, the overall reoperation rate was 21.13% and metal component revision rate was 10.16%. Results: The mean follow-up of mobile bearing TAA studies (N=41) was 77.8 (range 24-188.4) months and fixed bearing studies (N=32) was 45.3 (range 24-85.2) months. Multivariate analysis of bearing type, controlling for follow-up duration, found fixed bearing implants had statistically significantly higher metal component survival rates (fixed=96.1%, mobile=87.9%, p=.001) ; however, there were no statistically significant differences in rates of reoperation (fixed=17.0%, mobile=24.8%, p=.768). When examining specifically tibial and talar component failure rates, there was no statistically significant difference between bearing type (fixed tibial=1.46%, mobile tibial=2.95%, p=.472) (fixed talar=2.19%, mobile talar=2.79%, p=.966). Overall implant survival rate at one, two, five, and ten years was 96.4%, 96.0%, 92.7%, and 79.4%, respectively, and did not differ by bearing type (Table 1). Conclusion: Implant survival was statistically significantly better for 3rd and 4th generation fixed bearing TAAs as compared to mobile bearing TAAs, controlling for length of follow-up. There was no statistically significant difference in total reoperation rate. This suggests that fixed bearing implants may offer improved implant survival compared to mobile bearing implants, though further research is needed to confirm these findings.

Category: Ankle Arthritis; Ankle Introduction/Purpose: The INBONE II is a fixed-bearing implant with a stemmed tibial component commonly used for total ankle arthroplasty (TAA). Despite its frequent use and previously reported outcomes within individual clinical studies, no study has systematically reviewed outcomes of TAA with this implant. The purpose of this study was to perform a systematic review of the literature and report on outcomes of TAA with the INBONE II. Methods: A systematic review of the literature was performed according to the Preferred Reporting Items for Systematic Review and Meta-analyses (PRISMA) guidelines. Databases searched included PubMed, Google Scholar, SCOPUS and CINAHL from database date of inception through February 28th, 2023. Clinical studies of INBONE II outcomes in peer reviewed journals were included. Outcomes included were survivorship, patient reported outcome measures (PROMs), and complications. Outcome results were compiled using weighted averages when possible. This review of 26 articles included 808 patients with 667 primary TAA and 141 revision TAA. Results: Survivorship, with failure defined as metal component revision, was 97.8% at an average follow-up of 49 months (range, 14-85.4 months) and 94.2% at an average follow-up of 25.7 months (range, 9.1-47.5) months for primary and revision TAA respectively. Complication rates for primary TAA included: 3.8% intra-operative fractures, 2.5% post-operative fractures, 1.8% deep infection, 8.0% wound complications, 1.6% rate of poly exchange, and 1.6% nerve injuries. Revision TAA complication rates included: 12.3% intra-operative fractures, 6.9% wound complications, 3.3% deep infections, and a 5.5% incidence of nerve injury. Average PROMs for primary TAA included: AOFAS American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot score improved 41 points, visual analog scale (VAS) scores decreased 5.9, and patient satisfaction of 92.6%. Revision TAA PROMs were not consistently reported. Conclusion: This study is the largest compilation of INBONE II outcomes and survivorship. Primary and revision TAA with the INBONE II results in satisfactory improvement in PROMs and low complication rates. The overall survivorship is 97.8% and 94.2% at an average follow-up of 49 months (range, 14-85.4 months) and 25.7 months (range, 9.1-47.5) for primary and revision total ankle arthroplasty respectively. These findings support continued use of this implant in primary and revision TAA.

Category: Ankle; Other Introduction/Purpose: Chronic ankle instability (CAI) is one of the most commonly encountered clinical problems by orthopaedic foot and ankle surgeons, however, little research exists on the impact of insurance status on the incidence and outcomes of CAI. This study aims to investigate the association between psychiatric diagnosis and insurance status in CAI patients to determine if insurance subgroups differ in rate of surgery and postoperative success, as well as identify if psychiatric diagnoses are more common within certain insurance types. Methods: A retrospective review was conducted of 276 patients (280 ankles) treated between 2005 and 2021 at an academic medical center by one of three fellowship-trained foot and ankle orthopaedic surgeons, of which 56 (20.0%) underwent surgery, seven (2.5%) underwent reoperation, and 130 (46.4%) had a concomitant psychiatric diagnosis (i.e., anxiety=111, depression=105, post-traumatic stress disorder [PTSD]=19, obsessive-compulsive disorder [OCD]=6, bipolar disorder [BPD]=5). Insurance type was categorized as privately- (n=147) or government-funded (n=121). For further analysis, the government-funded cohort was broken into the following groups: Medicare (n=77), Veterans Affairs (n=20), Worker’s Compensation (n=18), and Medicaid (n=6). Eleven patients (12 feet) were uninsured. Data collected included demographics, conservative and operative treatments, patient- reported outcome measures (PROMs) (e.g., Foot and Ankle Ability Measure [FAAM]), and reoperation rate. Results: When examining binomial insurance groups, rate of surgery (private=15.6%, government=24.8%; p=.061) approached, but did not reach, significance and reoperation rate (private=17.4%, government=10.0%; p=.451) did not differ. Postoperatively, PROMs did not differ between private and government insurance types, but FAAM Physical Function (p=.046) and Total (p=.035) scores were best with Medicare insurance when analyzing all insurance groups. Instance of mental illness (p=.111) or certain psychiatric diagnoses did not differ between privately- and government-insured patients, but depression (p=.013) and PTSD (p=.050) were significantly less common among patients with Veterans Affairs insurance. Conclusion: CAI patients were not found to have differing need for surgery between insurance types. This was similar for postoperative success, aside from Medicare patients having better reported FAAM scores. Furthermore, patients with a psychiatric diagnosis were not more common to an insurance group, but specific depression and PTSD diagnoses were least common for Veterans Affairs patients.

Category: Midfoot/Forefoot; Diabetes Introduction/Purpose: Charcot arthropathy is a neurotraumatic foot disorder seen in patients with peripheral neuropathy. Surgical reconstruction via medial column arthrodesis with beams can restore plantigrade foot anatomy with decreased soft tissue dissection and improved bony compression. Methods: We identified 12 patients with midfoot (n=7) or hindfoot (n=5) Charcot who underwent medial column beaming arthrodesis between 2015 and 2021 b y one of two fellowship-trained foot and ankle surgeons at an academic medical center. Data collected from patient charts included demographics, medical history, complications, and reoperation rate. Meary’s angle was measured on lateral weightbearing radiographs preoperatively and up to two years postoperatively. Mean follow-up time was 2.50 (range, 1.04-6.98) years. Statistical analysis included correlation, two-tailed Student t-test, and Chi-squared test. Results: Meary’s angle was recorded preoperatively for 12 patients (19.3° ± 6.7°) and postoperatively at three months for 12 patients (4.0° ± 6.7°), at six months for 12 patients (7.1° ± 9.7°), at one year for 11 patients (6.1° ± 9.4°), and at two years for five patients (10.2° ± 6.4°). However, two (16.7%) patients showed a loss of deformity correction, which was demonstrated by a Meary’s angle that was greater at final follow-up than preoperatively. Overall complication, infection, reoperation rates were 50.0%, 41.7%, and 58.3%, respectively. Finally, dependent on preoperative ulceration, those with and without an ulcer did not differ in Meary’s angle at any time point, overall complication, infection, nor reoperation rate. Conclusion: Although the results showed a relatively high complication rate, the use of beaming arthrodesis was generally able to maintain a plantigrade foot and overall alignment, while decreasing the recurrence of plantar ulceration.

Category: Ankle; Diabetes Introduction/Purpose: Charcot arthropathy of the foot and ankle is a challenging complication of peripheral neuropathy with a 0.1% and 5.0% incidence in the diabetic population. The purpose of this study is to assess rates of foot or ankle reconstructions (fusions) for Charcot arthropathy, describe the associated patient demographics and hospital settings, and project the volume of Charcot reconstructions anticipated to be performed in 2030. Methods: The National Inpatient Sample database was queried from 2016-2019 using International Classification of Diseases (ICD) codes for foot or ankle fusion (midfoot, hindfoot, or ankle) and a diagnosis of Charcot arthropathy, ultimately identifying 1,343 patients undergoing surgical procedures. Patient information collected included age, sex, race, primary payer status, year of surgery, length of hospital stays, and median household income quartile. Hospital information included bed size, census region, teaching status, and ownership. Results: Between 2016-2019, there were approximately 1,343 patients treated surgically with midfoot, hindfoot, or ankle arthrodesis for Charcot arthropathy, and the number of cases increased by 12.11% annually. Between 2019-2030, there is projected to be a 121.41% increase in the frequency of Charcot reconstruction procedures from 383 to 848 total annual cases. Patients undergoing these procedures are predominantly white, male, and in their 50s. The most common payers were Medicare and private insurance. The mean hospital length of stay was 5.80 days. The procedures performed were predominantly large, urban teaching hospitals in the south with a private, non-profit ownership structure. Conclusion: Surgical reconstruction of Charcot arthropathy of the foot and ankle is steadily increasing in prevalence. These patients are predominantly white, male, and in their 50s. It is important for orthopaedic foot and ankle surgeons to be trained in the surgical management and reconstruction of Charcot arthropathy to meet the expected growing surgical need, which is projected to be 848 procedures annually by 2030.

Category: Midfoot/Forefoot; Other Introduction/Purpose: Midfoot osteoarthritis affects over 16% of adults over the age of 50, interfering with activities of daily living and leisure. One form of non-operative management is cortico-steroid injections, which are often done under fluoroscopic guidance to improve accuracy. Operative intervention is sometimes performed, although non-union rates and continued pain after surgery can be challenging. This study aims to quantify how well midfoot and transverse tarsal joint arthritis can be treated non- operatively with fluoroscopic-guided injections. Methods: We reviewed the records of 132 patients (155 feet), who were newly diagnosed with midfoot arthritis between 2015 and 2019. Conservative management included periodic fluoroscopic-guided steroid injections at an academic medical center by a single fellowship-trained foot and ankle surgeon. These joints were identified by computed tomography prior. Mean age was 62.7 years and mean BMI was 30.9 kg/m 2 . Twenty-five feet (16.1%) eventually underwent surgical treatment, and one of those (4.0%) underwent reoperation. Results: On average, each foot received 3.1 (range, 1-21) injections, this did not differ between the surgical and conservative cohorts (operative=3.9, non-operative=3.0; p=.147). Of the 95 feet (61.3%) that received more than one injection, mean duration was 21.6 (range, 0.9-67.4) months. Injection duration did not differ between cohorts (operative=21.8 months, non-operative=21.6 months; p=.952). Cases treated surgically did not receive any injections postoperatively. Patients with higher pre-treatment Pain Catastrophizing Scale (PCS) scores in all subsection5-depression=2.9, p=.046) over a greater injection duration (depression=22.2 months, non-depression=11.4 months, p=.046). Conclusion: Overall, fluoroscopic-guided injections are sufficient for the non-operative treatment of midfoot and transverse tarsal joint arthritis, as only 16.1% of our cohort failed conservative treatment and required surgery. Therefore, although not always successful, non-operative treatment with fluoroscopic guidance injections is able to provide patients relief for an extended period.

Category: Ankle Arthritis Introduction/Purpose: Total ankle arthroplasty (TAA) and ankle arthrodesis (AA) are common surgical treatment options for end-stage ankle arthritis. Previous studies of trends in TAA utilization have shown a rapid increase in use from 2000-2010, likely due to improvements in implants and surgical techniques. The purpose of this study is to assess relative rates of TAA and AA utilization, investigate these trends in across populations and hospital settings, and project these trends in 2030. Methods: The National Inpatient Sample database was queried from 2016-2019 using International Classification of Diseases codes for TAA and AA to identify 8,787 patients (TAA=4,664, AA=4,123). Patient information collected included age, sex, race, primary payer status, year of surgery, length of hospital stay, and median household income quartile. The latter was determined by the NIS database using patient zip code, with the first quartile being the poorest and fourth quartile the richest. Hospital information included bed size, census region, teaching status, and ownership. Results: The ratio of TAA to AA increased from 0.90 in 2016 to 1.33 in 2019. Compared to AA patients, TAA patients were more significantly likely to be male (p=.004), white (p

Category: Hindfoot; Ankle Arthritis Introduction/ Purpose: Double arthrodesis of the subtalar (ST) and talonavicular (TN) joints, along with isolated TN arthrodesis, are commonly performed for hindfoot osteoarthritis and rigid hindfoot deformity. Few studies have examined the effects of the type of ST and TN fixation constructs on nonunion rate following double and isolated TN arthrodesis procedures. This study evaluates the effect of surgical construct on the union rate and time to fusion in patients undergoing double or isolated TN arthrodesis. Methods: Retrospective chart review identified 52 patients (52 feet) who underwent double or isolated TN arthrodesis between 2016 and 2021 by a fellowship-trained foot and ankle surgeon with at least six months of follow-up (mean=1.62 years, range=0.50- 4.39 years). Data collected included demographics, medical history, surgical indication, surgical constructs used, complications, reoperations, patient-reported outcome measures, and radiographic measures. ST constructs included one (n=4) or two (n=44; parallel=43, divergent=1) cannulated screws, while TN constructs included dorsal plate (n=2), dorsal plate and screw (n=10), isolated screws (n=3) screw and staple (n=29), or isolated staples (n=13). At the time of their surgery, the mean age was 60.39 (range, 17-80) years, mean body mass index (BMI) was 33.89 (range, 20.74-48.41) kg/m2, and most subjects were non-smokers (94.7%). Mean follow-up duration was 1.62 (range, 0.50-4.39) years. Results: Overall complication and reoperation rates were 26.3% and 12.3%, respectively. Among TN constructs, the time to ST (p=.026) and TN (p=.018) fusion was statistically significantly slower among patients receiving a plate and screw TN construct. Complication rate did not differ by construct, but reoperation rate was significantly higher for the plate and screw TN construct (p=.039). Postoperative Foot and Ankle Outcome Score (FAOS) Quality of Life (p=.028) and Total (p=.016) scores were significantly better among plate and screw TN constructs. Conclusion: The utilization of a screw and staple or isolated staple construct have a statistically significantly quicker time to fusion and lower reoperation rates than plate and screw constructs for the TN joint. These findings can be used to guide clinician decision-making while allowing physicians to take their personal construct preference into account, as well as serve as a useful starting point to other researchers interested in investigating the impact of surgical constructs on ST and TN fusions.

Category: Ankle; Ankle Arthritis Introduction/ Purpose: Total ankle arthroplasty (TAA) is an alternative to ankle arthrodesis for the treatment of end-stage arthritis while maintaining greater ankle motion and functionality. Early generation implants had unacceptably high complication rates. Increasing experience of foot and ankle surgeons with the procedure and newer third-generation designs have the potential to offer better outcomes; however, the literature has shown that articles written by design surgeons presents biased results. Therefore, the purpose of this study is to compare the reported outcomes between studies conducted by design and non-design surgeons. Methods: A comprehensive search of MEDLINE for all articles published between 1996 and 2021 was conducted with a minimum two-year follow-up. Two reviewers evaluated each study to determine whether it was eligible for inclusion and abstracted the data of interest. Meta-analytic pooling of group results across studies was performed, including patient-reported outcome measures (PROMs) (i.e., AOFAS, FFI, SF-36). Fifty-two implant groups met inclusion criteria, of which eight were authored by a design surgeon. In total, 4,693 subjects were included with a mean age of 59.89 years and mean BMI of 27.77 kg/m2. Statistical analysis between articles of design and non-design surgeons was performed using two-tailed Student t-test. Results: Overall, at mean follow-up of 68.91 months, the reoperation rate was 25.2% (design=23.5%, non-design=25.5%; p=.843), revision rate was 9.3% (design=9.0%, non-design=9.4%; p=.935), and conversion to arthrodesis rate was 5.0% (design=2.5%, non- design=5.5%; p=.243). According to the COFAS Reoperations Coding System (CROCS), the majority of reoperations were not around the ankle (Code 1: 76.65%). Mean postoperative plantarflexion (p=.007) and mean preoperative dorsiflexion (p=.006) were significantly greater among non-design surgeons’ reports. There was no difference in any pre- or postoperative PROM between groups. The implant survival rate at one, two, five, and ten years was 97.7% (design=98.5%, non-design=97.6%, p=.732), 96.5% (design=97.0%, non-design=96.4%, p=.865), 92.1% (design=96.4%, non-design=91.3%, p=.865), and 79.2% (design=87.9%, non- design=76.3%, p=.070), respectively. Conclusion: In the reporting of TAAs, design surgeons do not appear to be biased. Although reoperation, revision, and conversion to arthrodesis rates were worse among non-design surgeons, this was not significant. Similarly, implant survival was reportedly better for design surgeons, but this was not significant either. However, there was greater implant survival in the design surgeon group at ten years, as compared to non-design surgeons, with a p-value approaching statistical significance. Overall, there was no obvious evidence of bias in TAA implant studies when comparing design vs non-design surgeons.

Background: Scientific publication and original articles remain the primary method of sharing scientific findings and advancing the knowledge base of that subject. Despite the value of these publications, little research has surveyed what topics are being published. This study aims to identify and characterize the most common topics in current foot and ankle literature. Methods: We reviewed all 1514 published articles in a 5.5-year period (January 2014–June 2019) in 2 foot and ankle–specific journals: Foot & Ankle International ( FAI ) and Foot and Ankle Surgery ( FAS ). The articles were sorted into different topic domains to identify the 3 most common categories of publication. The top 3 domains were further characterized by level of evidence (LOE) as well as citations. Results: The 3 most published topics in foot and ankle literature were hallux valgus (8.3%), total ankle arthroplasty (TAA) (8.3%), and ankle fracture (6.6%). These 3 subjects accounted for 351 articles (23.2%). Other common topics were patient-reported outcomes (5.0%), osteochondritis dissecans (3.9%), syndesmotic injury (3.8%), ankle instability (3.7%), hallux rigidus (3.0%), and anatomy (2.8%). The average LOE for articles on hallux valgus, TAA, and ankle fracture was 3.27 from FAI , and the average number of annual citations for a given article in both journals was 3.05. Based on our study, there is no correlation between LOE and number of overall citations, but there is a significant, negative linear correlation in ankle fracture data. We also found that articles on TAA had the highest impact factor and that articles from FAI were cited more often than articles from FAS. Conclusion: The 3 most published topics in foot and ankle literature comprise only 23.2% of all articles. This finding is indicative of the wide variety of cases performed by orthopaedic foot and ankle surgeons. High-quality data are still needed in all topics. Level of Evidence: Level III, retrospective cohort study.

Category: Ankle, Ankle Arthritis, Hindfoot, Trauma Introduction/Purpose: Patients with talar avascular necrosis have limited treatment options to manage their symptoms. Historically, surgical options have been limited and can leave patients with little ankle motion and have high failure rates. The use of custom 3D printed total talar replacements (TTR) has arisen as a treatment option for these patients, possibly allowing for better preservation of hind-foot motion. Patients undergoing TTR will demonstrate a statistically significant improvement in FAOS scores at one year after surgery. Methods: We retrospectively reviewed 15 patients who underwent a TTR over 2 years. Patient outcomes were reviewed including age, sex, comorbidities, etiology of talar pathology, number and type of prior surgeries, pre-operative and post-operative weight bearing radiographs, as well as FAOS and VAS scores, and range of motion. Data analysis performed with student T-test and multivariate regression. Results: Results: FAOS scores showed statistically significant improvements post-operatively as compared to pre-operative scores. There was a statistically significant decrease in VAS pain scores from 7.0 pre-operatively to 3.4 post operatively. There was no significant difference in pre-operative and post-operative coronal and sagittal alignment on weight bearing radiographs. All FAOS sub-score shows statistically significant improvements, with the exception of the sports/recreation sub-scale, did show a trend towards improved outcomes (p =0.19). Average follow-up was 12.8 months. Conclusion: Our hypothesis was confirmed that these patients show statistically significant improvements in AOFS and VAS scores at 1 year. Sagittal and coronal alignment was well maintained at an average of 1 year following surgery. TTR represents an exciting treatment options for patients with talar avascular necrosis, though longer-term follow-up is needed.

Category: Trauma Introduction/Purpose: The current gold-standard for unstable distal fibula fractures is plate and screw fixation; however, intramedullary distal fibular fixation is becoming more commonplace. Although surgeons may consider this technique only for patients requiring extra soft tissue protection, recent studies are showing that it is a safe and effective technique for maintaining adequate reduction and promoting proper fracture healing in a wide-variety of ankle fractures. As newer techniques and equipment are developed, it is important to continue with analyzation of patient outcomes. Our study evaluates a intramedullary device that contains a unique proximal locking mechanism that deploys fins against the inner cortex to help maintain fracture length and control rotation. To our knowledge, no other study in the literature has evaluated this technique for distal fibula fractures. Methods: A retrospective case-series was conducted on all patients >18-years old with unstable ankle fractures treated with the same intramedullary distal fibular fixation, that contained the unique proximal locking system. Surgeries were performed at a single institution by a single surgeon between September 2015 and June 2018. Patient imaging was carefully assessed for quality of reduction using previously established guidelines classifying reductions as “good”, ”fair”, or “poor”. Patient charts were also assessed for comorbidities, initial fracture classification, postoperative complications, and need for additional surgery. Results: Forty-one patients were included in the study. Twenty-five patients were female and 16 patients were male. Average age was 52. Average follow-up was 10.0 months. Eleven fractures were bimalleolar (27%), eight were isolated distal fibula fractures (20%), eight were bimalleolar-equivalent fractures (20%), nine were trimalleolar fractures (22%), and five were pilon fractures (12%). Seventy-one percent were Weber B and 29% were Weber C. Based on the classification system, 37 fracture reductions (90%) were classified as ”good”, four were “fair” (10%), and no reductions were ”poor”. There were no instances of hardware failure, loss of reduction, or nonunion. One patient had a superficial wound infection, one patient had a deep wound infection, five patients require painful hardware removal, and one patient had a delayed union. Conclusion: This large case-series is the first study, to our knowledge, in the Foot and Ankle literature to evaluate this specific intramedullary distal fibular fixation system that contains a unique-proximal fixation mechanism within the canal itself. This technique was used for a variety of unstable ankle fractures and was shown to be both safe and effective, and will help guide future prospective studies comparing outcomes with the gold-standard plate and screw fixation.

Category: Hindfoot Introduction/Purpose: Many patients with talar avascular necrosis have limited treatment options to manage their symptoms. Historically, surgical options have included pan-talar fusions, tibio-talar-calcaneal fusions, and revascularization procedures. Unfortunately, these treatment options can leave patients with little ankle and hind-foot motion, can increase adjacent joint arthritis, and have significant failure rates. Recently, the use of custom 3D printed total talar replacements has arisen as a treatment option for these patients. Theoretically, this allows for better preservation of hind-foot motion as well as possibly less adjacent joint arthritis. Methods: We retrospectively reviewed 15 patients who underwent a 3D printed total talus replacement by a single surgeon over 2 years. Each patient had pre-operative CT scans of both the affected and non-affected talus. Custom 3D printed implants were made in two sizes based on templating performed on the contralateral talus. All total talus replacements were performed through a direct anterior approach. Patient outcomes were reviewed pre and post-operatively including age, sex, comorbidities, etiology of talar pathology, number and type of prior surgeries, as well as VAS scores, range of motion, and number of additional or subsequent procedures. Results: The average patient age was 45. 6/15 patients had previously undergone surgery on the ipsilateral hind-foot/ankle. There was a statistically significant decrease in VAS pain scores from 7.0 pre-operatively to 2.5 at final follow up. There was a statistically significant increase in both ankle and sub-talar motion at final follow up when compared to pre-op. Average follow-up was 8.4 months, with a minimum follow up of 3 months. Of the four patients with 1 year or longer follow up (average 13.3 months), VAS scores and ROM were similar to patients with shorter follow up duration. 3 patients had concomitant procedures, most commonly tendo-achillies lengthening. One patient required an additional procedure (incision and drainage) for treatment of wound dehiscence. Conclusion: 3D printed total talus replacements represent an exciting treatment options for patients with significant talar avascular necrosis. At early follow up, patients showed good improvement in VAS pain scores and actually improved their hindfoot and ankle motion. Certainly, longer term follow-up will be needed to evaluate the longevity of these implants. However, these implants represent an intriguing option for patients that lack an ideal surgical solution and show promise at very early follow up.

Category: Other Introduction/Purpose: The CDC estimates that at least 385,000 sharps injuries occur annually among US healthcare workers, which may even be as high as 800,000. Traditionally, wound closure demands the OR scrub tech to pre-load suture needles onto needle drivers that are presented to the surgeon and then passed back once the needle has been used. With frequent passing of contaminated needles, needle-stick injuries occur commonly in the OR. Operative Armour (Sharp Fluidics®, LLC) incorporates a novel needle trap that enables surgeons to independently self-secure and self-dispense suture needles during closure (Fig. 1). We hypothesized that the use of Operative Armour as compared to the standard technique of sequentially passed needles would reduce the number of sutures passes. Methods: Three cadaveric specimens were dissected in this study. A 12 cm long incision was made through an anterior and posterior approach to the ankle joint in each specimen. The incisions were cross-hatched at 1 cm intervals with a surgical marking pen to indicate closure points. Two layers, subcuticular and skin, were closed. All three participants were orthopedic foot and ankle fellows at our institution. All wound closures were done with interrupted suture technique using 2-0 vicryl pop-off suture (Covidien), containing 5 needles per pack. Group A used traditional suture passing from the scrub tech vs the Operative Armour in Group B. The participants completed three trials for each group first through the anterior and then through the posterior approach. Outcome measures included number of needle passes, dropped needles, and closure time. Results: Suture passes averaged 52±8.9 for Group A compared to 5.3±0.7 in Group B (p

Category: Ankle Arthritis Introduction/Purpose: Traditional intraoperative referencing for total ankle replacements (TAR) involves multiple steps and fluoroscopic guidance to determine mechanical alignment. Recent adoption of patient-specific instrumentation (PSI) allows for referencing to be determined preoperatively, resulting in less steps and potentially decreased operative time. We hypothesize that usage of PSI will result in decreased operating room time that offsets the additional cost of PSI as compared to standard referencing (SR). Additionally, we aim to demonstrate similar postoperative radiographic alignment between PSI and SR. Methods: Between 2014 and 2015, 87 patients undergoing TAR were enrolled in a prospectively collected TAR database. Patients were divided into cohorts based on PSI versus SR and operative times were reviewed. Radiographic alignment parameters were retrospectively measured at 6 weeks postoperatively. Time-driven activity-based costing (TDABC) was utilized to derive direct costs. Cost versus operative time-savings were examined via two-way sensitivity analysis to determine cost-saving thresholds for PSI applicable to a range of institution types. Cost-saving thresholds defined the price of PSI below which PSI is cost-saving. Results: A total of 35 PSI and 52 SR cases were evaluated with no significant differences identified in patient characteristics. Operative time from incision to completion of casting in cases without adjunct procedures was 127 minutes with PSI and 161 minutes with SR (p < 0.05). PSI demonstrated similar postoperative accuracy to SR in coronal tibial-plafond alignment (1.1° vs. 0.3° varus, p=0.06) and tibial component sagittal alignment (0.7° vs. 0.9° plantarflexion, p=0.14). TDABC methodology estimated a PSI cost-savings threshold range at our institution of $863 - $1,026 below which PSI pricing will provide net cost-savings. Two-way sensitivity analysis generated a globally applicable cost-savings threshold model based on institution-specific costs and surgeon-specific time-savings. Conclusion: This study demonstrates equivalent post-operative TAR alignment with PSI and SR referencing systems but with a significant decrease in operative time with PSI. Based on TDABC and associated sensitivity analysis, a cost-savings threshold of $863 - $1,026 is identified for PSI pricing at our institution below which PSI is less costly than SR. Similar internal cost accounting may benefit healthcare systems for identifying cost drivers and obtaining leverage during price negotiations.