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Background: Although an association between intercuneiform (C1-C2) joint instability and the recurrence of hallux valgus (HV) deformity after the modified Lapidus procedure has been suggested, there is currently no radiographic evidence to support it. This study aims to investigate radiographic changes in the C1-C2 joint after the modified Lapidus procedure for HV correction, using weightbearing computed tomography (WBCT). Methods: This retrospective cohort study included 52 feet (50 patients) with HV who underwent modified Lapidus procedure and had preoperative and postoperative WBCT. Patients who had an additional transfixation screw between the first and second ray were excluded. The preoperative and average 6.5 months postoperative C1-C2 distance, C1-C2 angle, and C1-ground angle were measured on coronal multiplanar reconstructed WBCT images. Radiographic parameters between the recurrence group (n = 9) and nonrecurrence group (n = 43) were compared. Recurrence of HV deformity was characterized by a postoperative hallux valgus angle (HVA) greater than 20 degrees. Results: Nine of 52 patients (17.3%) had recurrence of their HV deformity. The recurrence group had greater changes in the C1-C2 distance; the median widening in the recurrence group was 0.7 mm (IQR, 0.6-0.8), whereas the nonrecurrence group was 0.3 mm (IQR, 0.1-0.4, P <.001). Regression analysis showed that increase in the C1-C2 distance were significantly associated with recurrence (odds ratio, 1.79; 95% CI, 1.18-3.77; P =.0015). Although no preoperative imaging parameters were associated with a change in the C1-C2 distance, increasing postoperative sesamoid position (r = 0.32, P =.022) and HVA (r = 0.28, P =.046) were correlated with a greater change in the C1-C2 joint gapping. Conclusion: Our study results suggest a possible association between early postoperative widening of the C1-C2 joint and the recurrence of the HV deformity following a modified Lapidus procedure. This raises, but does not answer, the question as to whether the routine stabilization of intercuneiform joint directly or indirectly may help reduce the rate of hallux valgus recurrence when performing the modified Lapidus procedure. [ABSTRACT FROM AUTHOR]

Background: There are limited data regarding risk factors associated with periprosthetic medial malleolar fractures in total ankle arthroplasty (TAA). This case-control study aimed to identify the risk factors and analyze the effect of prophylactic screw fixation in preventing a medial malleolar fracture after TAA. Methods: A case-control study was conducted on 149 patients who underwent primary TAA. Twenty patients with postoperative medial malleolar fractures >4 weeks postoperatively (cases) were identified. An additional 129 patients (controls) were randomly selected from the TAA database. Radiographic evaluation included tibial component coronal alignment and postoperative medial malleolar width. Demographics and radiographic variables were compared between cohorts. Logistic regression was used to investigate the association between medial malleolar fracture and postoperative coronal alignment, medial malleolar width, and prophylactic fixation of the medial malleolus. Results: Mean (SD) medial malleolar width was significantly smaller in the fracture cohort (8.52 mm [1.6]) than in the control group (11.78 mm [1.74]) (P <.001). Mean (SD) tibial component coronal alignment was 92.17 degrees (2.77) in the fracture cohort and 90.21 degrees (1.66) in the control group (P =.002). Regression analysis identified a significant negative association between postoperative medial malleolar width and the probability of fracture (OR = 0.06, 95% CI 0.01, 0.26, P <.001). Varus malalignment of the tibial component was positively associated with the probability of fracture (OR = 1.90, 95% CI 1.27, 2.86, P =.002). Prophylactic screw fixation resulted in more than 90% reduction in the odds of a fracture (OR = 0.04, 95% CI 0.01, 0.45, P =.01). ROC curve analysis determined a medial malleolar width of 10.3 mm as a potential threshold for predicting fracture. Conclusion: Decreased medial malleolar width and postoperative varus malalignment were associated with an increased risk of postoperative medial malleolar fracture. Therefore, surgeons should consider prophylactic screw fixation in patients with a medial malleolar width <10.3 mm or at risk of postoperative varus deformity. [ABSTRACT FROM AUTHOR]

Background: Isolated subtalar and talonavicular joint arthrodeses have been associated with adjacent joint arthritis and altered hindfoot kinematics during simplified loading scenarios. However, the effect on kinematics during dynamic activity is unknown. This study assessed changes in subtalar and talonavicular kinematics after isolated talonavicular (TNiso) and subtalar (STiso) arthrodesis, respectively, during stance simulations. Methods: Fourteen midtibia specimens received either a TNiso or STiso arthrodesis, with 7 randomized to each group. A 6-degree-of-freedom robot sequentially simulated the stance phase for the intact and arthrodesis conditions. Bootstrapped bias-corrected 95% CIs of the talonavicular and subtalar joint kinematics were calculated and compared between conditions. Results: The TNiso decreased subtalar inversion, adduction, and plantarflexion in late stance (P <.05). The subtalar range of motion in the sagittal and coronal planes decreased by 40% (P =.009) and 46% (P =.002), respectively. No significant changes in talonavicular joint kinematics were observed after isolated subtalar arthrodesis; however, the range of motion was reduced by 61% (P =.007) and 50% (P =.003) in the coronal and axial planes, respectively. Conclusion: In this model for arthrodesis, changes in subtalar kinematics and motion restriction were observed after isolated talonavicular arthrodesis, and motion restriction was observed after isolated subtalar arthrodesis. Surprisingly, talonavicular kinematics did not appear to change after isolated subtalar arthrodesis. Clinical Relevance: Both joint fusions substantially decrease the motion of the reciprocal adjacent joint. Surgeons should be aware that the collateral costs with talonavicular fusion appear higher, and it has a significant effect on subtalar kinematics during the toe-off phase of gait. [ABSTRACT FROM AUTHOR]

Background: Ankle arthritis leads to an elevated joint line compared to the nonarthritic ankle, as measured by the "joint line height ratio" (JLHR). Previous work has shown that the JLHR may remain elevated after total ankle arthroplasty (TAA). However, the clinical impact of this has yet to be determined. This study assessed the correlation between postoperative JLHR, post-TAA range of motion (ROM), and 1-year Patient-Reported Outcome Measurement Information System (PROMIS) scores. Methods: A retrospective review of 150 patients who underwent primary TAA was performed. Preoperative and postoperative JLHR, as well as postoperative dorsiflexion, plantarflexion, and total ROM, was calculated on weightbearing radiographs at a minimum of 1-year follow-up. Correlation between JLHR, post-TAA ROM, and 1-year PROMIS scores was investigated using Pearson correlation and multiple linear regression models. Interobserver reliability for the JLHR was also calculated. Results: Interobserver reliability for the JLHR was excellent (r = 0.98). Mean (SD) JLHR changed from 1.66 (0.45) to 1.55 (0.26) after TAA (P <.001), indicating that the joint line was lowered after TAA. An elevated joint line was correlated with decreased post-TAA dorsiflexion (r = −0.26, P <.001), total ROM (r = −0.18, P =.025), and worse 1-year PROMIS physical function (r = −0.22, P =.046), pain intensity (r = 0.22, P =.042), and pain interference (r = 0.29, P =.007). There was no correlation between the JLHR and post-TAA plantarflexion (r = −0.025, P =.76). Regression analysis identified a 0.5-degree reduction in post-TAA dorsiflexion with each 0.1-unit increase in JLHR (Coeff. = −5.13, P =.005). Conclusion: In this patient cohort, we found that an elevated joint line modestly correlated with decreased postoperative dorsiflexion, total ROM, and worse 1-year PROMIS scores. These data suggest that effort likely should be made toward restoring the native joint line at the time of TAA. In addition, future studies investigating the clinical outcomes after TAA may consider including a measure of joint line height, such as the JLHR, because we found it was associated with patient-reported outcomes. Level of Evidence: Level III, retrospective review of prospectively collected data. [ABSTRACT FROM AUTHOR]

Category: Ankle; Trauma Introduction/Purpose: Posterior malleolar fractures, are common in ankle injuries. Open reduction and internal fixation show better outcomes, particularly with direct reduction. While posterolateral fractures can be managed through a posterolateral approach, the optimal approach for large posterior and posteromedial fractures is uncertain. Different posteromedial approaches exist, but concerns persist about soft tissue dissection and posteromedial neurovascular bundle (NVB) safety. This study compares three posteromedial approaches — posteromedial (PM), Modified posteromedial (MoPM), and medial posteromedial (MePM) — measuring posterior malleolar visualization, distance to the neurovascular bundle, and tension. Results aim to compare them regarding bone exposure and safety to the posteromedial NVB. Methods: We used 12 cadaveric pieces and evaluated the following approaches: PM: longitudinal incision immediately parallel to the medial border of the Achilles tendon. The FHL fascia was opened and the FHL retracted laterally. MoPM longitudinal incision halfway between the posteromedial tibia's edge and the Achilles tendon's medial edge. The PTT was mobilized medially and the FDL laterally. MePM longitudinal incision along the posteromedial edge of the tibia. The i PTT tendon was retracted posteriorly and elevated Measurements included minimal tension on the posteromedial (NVB) flap, distance from the incision to the NVB, and percentage of malleolar exposure. Tension was gauged using a digital strain gauge on a Langenbeck retractor, while exposure was determined by marking bone edges and measuring medial-to-lateral length. Distribution of the data was assessed by the t-test. A one-way repeated measures ANOVA was conducted, when a significant difference was detected, the post hoc Tukey test was applied. Results: There were significant differences between the three approaches examined regarding the degree of posterior malleolar exposure and distance from the incision to the NBV, favoring the PM approach (71,00% ±1.83 and 25.50 mm ±4.20). The PM approach provided a significantly lower tension to the flap containing the posteromedial NVB (6.18 N ±1.28) compared to the other two approaches. Conclusion: The PM approach achieved the highest degree of posterior malleolar exposure, the lowest tension to the posteromedial NVB, and the greatest distance between the incision and the NBV. Thus, we believe it should be considered the approach of choice for large fractures of the posteromedial aspect of the PM. [ABSTRACT FROM AUTHOR]

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: Third-generation minimally invasive (MIS) bunionectomy requires a lateral shift of the metatarsal head, pushing the shaft into adduction and levering off the 1st-tarsometatarsal (TMT) joint. A previous study on plain radiographs reported postoperative 1st-TMT joint slippage in the transverse plane, with a medial subluxation of the 1st metatarsal base. However, risk factors and clinical implications have yet to be determined. This study sought to assess the prevalence of postoperative 1st-TMT joint slippage in the transverse plane and to identify associated risk factors using weight-bearing CT (WBCT) scans. In addition, the effect of 1st-TMT slippage on postoperative midshaft foot width was investigated. We hypothesized that postoperative 1st-TMT slippage in the transverse plane would be associated with preoperative 1st-TMT instability and increased postoperative midshaft foot width. Methods: Sixty-three consecutive patients who underwent MIS bunionectomy with available pre- and postoperative WBCT-scans were included. Radiographic measurements included hallux valgus angle(HVA), intermetatarsal angle(IMA), and midshaft foot width, measured from the 1st metatarsal shaft to the 5th metatarsal head on AP-foot radiographs. Tri-planar rotation angle(TAP), and 1st-TMT plantar-gap and medial-middle(MM) intercuneiform distances(mm) were obtained from WBCTs. Two raters measured pre- and postoperative 1st-TMT distances between the most lateral aspect of the medial cuneiform and 1st metatarsal base at the dorsal, central, and plantar thirds on axial cuts. The average corresponds to the overall 1st-TMT lateral distance, a measure of 1st-TMT slippage. Rater agreement was assessed. Paired t-tests were used to compare pre- and postoperative values. Logistic regression models were used to investigate the association of postoperative 1st-TMT lateral distance with potential risk factors (preoperative 1st-TMT lateral distance, 1st-TMT plantar-gap distance, IMA, TAP, and MM intercuneiform distance) and postoperative midshaft foot width. Results: The interobserver reliability of the 1st-TMT lateral distance was excellent (r=0.97). Mean (SD) 1st-TMT lateral distance increased from 0.26 mm(0.4) to 1.33 mm(0.9) after surgery(P< 0.05). Postoperative 1st-TMT lateral distance was > 2 mm in 15 patients(24%), and > 1 mm in 33(52%). Mean(SD) dorsal 1st-TMT lateral distance (2.7mm[1.3]) was significantly higher than central (0.85mm[1.1]) and plantar (0.55mm[0.99]) 1st-TMT lateral distances. Mean(SD) midshaft foot width increased from 80.04mm(6.7) to 84.25mm(6.1) postoperatively (P< 0.05). Regression analysis showed that pre- and postoperative 1st-TMT lateral distances were correlated (Coef=0.64,P=0.02), and identified a 1 mm increase in postoperative 1st-TMT lateral distance with each 0.63 mm increase in preoperative 1st-TMT plantar-gap distance (Coef=0.63,P=0.008). A significant positive correlation was also observed between postoperative 1st-TMT lateral distance and postoperative midshaft foot width (Coef=1.43,P< 0.05). Conclusion: Our study suggests a possible association between postoperative 1st-TMT joint slippage and preoperative 1st-TMT multiaxial instability following MIS bunionectomy. This raises an important question as to whether alternative techniques, such as modified Lapidus, should be preferred over MIS bunionectomy in patients with 1st-TMT instability. Notably, medial slippage was significantly higher at the dorsal aspect of the 1st-TMT joint, suggesting a component of rotational instability. It appears that 1st-TMT slippage is associated with a wider midshaft foot width postoperatively, and patients should be warned about it. Future studies assessing mid-to-long-term effects of 1st-TMT slippage, like recurrence or degenerative changes, are warranted. [ABSTRACT FROM AUTHOR]

Category: Sports; Other Introduction/Purpose: Minimally invasive approaches to Achilles tendon (AT) repair have garnered significant attention due to their reported effectiveness. Due to the limited visibility of the tendon, a crucial factor for the success of these approaches lies in the precise targeting and adequate capture of the tendon substance. Insufficient tendon capture can lead to re-rupture or tendon elongation, potentially leading to poor patient-outcomes. Since many of the current techniques or devices for minimally invasive AT repair rely on needle passage through a single axial plane, it is imperative to understand the axial plane orientation of the AT along its course. This study aims to elucidate the axial plane position and width of the AT from its distal insertion to a level well above its common tear site. Methods: In this retrospective study, magnetic resonance imaging (MRIs) from 82 individuals (mean age: 38.7 years) with no history of AT pathology were reviewed from the foot and ankle registry of a single institution. Any patients with evidence of foot and ankle malalignment or those with poor quality MRIs were excluded from the study. Multiplanar reconstruction of the MRI images was performed to enable synchronized viewing of both the sagittal and axial planes of each MRI scan. Measurements were made to determine the axial axis of the AT at distances of 3, 5, 7, 9, and 11 cm from its insertion. These measurements were taken in relation to both the transmalleolar (TM) axis and the axis at the AT insertion (Figure 1). The width of the AT was also measured at these corresponding levels. Results: The average rotation of the AT across all measurement levels showed an external rotation relative to the TM axis (Figure 2). The least rotation was observed at the 3cm level (2.1 degrees), while the maximum rotation was seen at both the 7cm and 9cm levels (11.2 degrees). There was a pattern where the AT showed an increasing external rotation as it extended proximally from 3cm to 9cm from its insertion. Between 5 cm and 7 cm from the insertion, there was a shift in the tendon's orientation (p<.0001), transitioning from internal to external rotation (Figure 2). Moreover, a noticeable reduction in the width of the AT was observed between the 5 cm and 7 cm measurement levels, distinct from the other levels. Conclusion: The rotational profile of the AT observed in this study indicates the need for caution regarding possible external rotation of the AT, especially when targeting its proximal portion using a minimally invasive approach, compared to its distal part. The considerable variations in AT orientations across different individuals underscore the potential benefits of using intraoperative assistive techniques such as ultrasonography to determine individual rotational profiles. Furthermore, the noted narrower width and rotational differences between the 5 cm and 7 cm levels could explain the frequent instances of AT ruptures within this specific range. [ABSTRACT FROM AUTHOR]

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: Hallux valgus(HV) is a triplanar deformity that includes the pronation of the first ray. Although there is little data regarding the effect of pronation on clinical outcomes, the rotational component of HV may play an important role. One study suggested that the modified Lapidus technique effectively decreased the pronation of the first ray. However, there is no evidence for alternative procedures such as minimally invasive(MIS) bunionectomy. This study sought to assess if MIS bunionectomy can effectively correct the first ray's pronation and determine the correlation with improved PROMIS scores. In addition, the association between postoperative first-ray pronation and the sesamoid station was investigated. We hypothesized a significant decrease in first-ray pronation after MIS bunionectomy, which would be associated with improved PROMIS scores. Methods: Sixty-three consecutive patients who underwent MIS bunionectomy with available pre- and at least 5-month postoperative WBCT-scans were included. Pre- and postoperative measurements of HV deformity, including the intermetatarsal angle(IMA) and hallux valgus angle (HVA) on plain radiographs, and triplanar pronation angle (TAP – a measure of first ray pronation) and sesamoid station from WBCTs, were performed as previously described. The TAP was referenced to the dorsal aspect of the second metatarsal base. Pre- and 1-year postoperative PROMIS scores were reviewed. Sample t-tests were used to compare pre- and postoperative values. The Kruskal-Wallis test assessed statistical differences between postoperative sesamoid station groups regarding postoperative TAP or IMA. Spearman rank (rho) was used to assess correlations between pre- to postoperative change in TAP with PROMIS scores in the physical function (PF), pain interference (PIF), and pain intensity (PI) domains. Scatterplots were simultaneously presented to visualize potential trends between TAP and PROMIS scores. Results: The mean TAP significantly decreased by 8.21º(95%CI -9.62,-6.8) after MIS bunionectomy (p< 0.05). Mean(SD) pre- and postoperative TAP values were 31.57º(8.3) and 23.36º(7.6), respectively. Similarly, mean HVA and IMA values decreased by 21.98º and 11.41º, respectively. Mean preoperative sesamoid station was 1.84, which decreased to 0.95 after surgery. Forty-four patients reduced their sesamoid position by one station. There was a statistically significant difference in TAP between postoperative sesamoid station groups (p=0.038). Mean(SD) postoperative TAP according to sesamoid station was 25.93º(6.2) for group 1, 23.83º(7.9) for group 2, and 18.75º(6.6) for group 3. No significant differences between groups were observed regarding IMA (p=0.25). There was a modest correlation between TAP change and PROMIS PF (rho = 0.046), PIF (rho = -0.30), and PI (rho = -0.03). Conclusion: Our study suggests that MIS bunionectomy is an effective tool for reducing first-ray pronation in patients with HV. Although there was a statistically significant correlation between first-ray pronation and sesamoid station, our results showed that patients with higher first-ray pronation had less reduced sesamoids. Therefore, these should be considered separate deformities, and the sesamoid station shouldn't be used as a guide for pronation correction. It appears that correction of the first-ray pronation is poorly associated with 1-year PROMIS scores. Consequently, future studies assessing mid-to-long-term effects of first-ray pronation on clinical outcomes, such as recurrence, are still warranted. [ABSTRACT FROM AUTHOR]

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: Hallux Valgus (HV) is a common foot condition often requiring surgical intervention. Minimally invasive bunionectomy (MISB) has gained popularity for HV correction. While previous research has focused on distal foot width changes following surgery, this study introduces a novel midshaft measurement to assess proximal transverse midfoot width. The study aims to provide a comprehensive evaluation of foot width changes post-MISB. Methods: A retrospective review of prospectively collected data was conducted for 44 patients who underwent MISB for HV via an institutional outcome registry. Demographic data, surgical details, radiographs, and foot width measurements were collected. Changes in hallux valgus angle (HVA) and intermetatarsal angle (IMA) were also measured. The novel midshaft bony and soft tissue foot width measurements were included. Two independent observers conducted all preoperative and postoperative measurements. Results: Intraclass correlation coefficients (ICCs) demonstrated high interobserver reliability (all ICCs >0.70) for all measurements. MISB resulted in a consistent reduction in distal foot width, both bony (8.17%) and soft tissue (5.24%)(p < 0.001). These reductions correlated with changes in HVA and IMA, suggesting the extent of deformity correction influenced distal foot width (all r > 0.375, p < 0.05). However, the study revealed that proximal foot width, as measured by midshaft bony width, increased (5.27%) in the majority of cases (p < 0.001). Changes in midshaft foot width showed no correlation with HVA or IMA alterations. Conclusion: MISB for HV leads to an increase in midshaft foot width due to the unique mechanics of the procedure. Simultaneously, there is a decrease in distal foot width, which correlates with the extent of deformity correction. This results in a more uniform foot width. These findings may influence patient satisfaction, comfort, and shoe wear capabilities post-surgery. Further research should assess patient perception and comfort regarding these foot width changes after MISB. [ABSTRACT FROM AUTHOR]

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: Following Minimally Invasive Bunionectomy (MISB), removal of hardware rates are about 5% and commonly due to midfoot pain near the distal metatarsal screw site. This distal screw head site corresponds to the proximal midshaft width measurement location, which has shown to increase postoperatively. One explanation for this increased width is medial subluxation of the first metatarsal at the tarsal-metatarsal (TMT) joint. This "TMT slippage" occurs as the metatarsal base is shifted medially to accommodate the metatarsal head lateralization at the metatarsal phalangeal joint. The force across the TMT joint overcomes the ligamentous stabilizers, allowing the metatarsal to "slip." The aim of this study was to investigate the relation between TMT slippage and removal of hardware (ROH) rates. Methods: A retrospective analysis of prospectively collected data identified 38 patients undergoing MISB for hallux valgus (HV) with subsequent distal chevron screw removal and a control group of 40 MISB cases without hardware removal. Demographic data and surgical details were obtained via chart review. Pre- and at least 6-month post-operative radiographs were measured to obtain transverse TMT slippage on anteroposterior (AP) radiographs (Figures 1). Additionally, distal foot width, midshaft foot width, hallux valgus angle (HVA) and intermetatarsal angle (IMA) were measured. Independent samples t-tests and chi-square analyses were used to compare continuous and categorical characteristics, respectively, between patients who underwent removal of hardware. Multivariable logistic regression modeling was used to identify risk factors for undergoing hardware removal. Results: Interobserver reliability, measured by intraclass correlation coefficients (ICCs), was high for all measurements (ICC > 0.70). The change in TMT slip was significantly higher in the hardware removal (ROH) group compared to the control group (+1.39 versus +0.80, p=0.004) (Table 1). A greater decrease in distal foot width (narrower distal width postoperatively) was associated with an increased likelihood of hardware removal (OR: 0.76), while smaller reductions in HVA and IMA were linked to a higher likelihood of requiring ROH (OR: 1.12 and 1.42, respectively). Notably, a larger increase in TMT slip correlated with the highest likelihood of being in the ROH cohort (OR: 2.87) (Table 2). TMT slippage did not correlate with any other measurements (all p > 0.05). Conclusion: Our study highlights the relationship between MISB outcomes and TMT slippage. Patients requiring distal chevron screw removal showed significantly higher transverse TMT slippage. Interestingly, a smaller distal foot width reduction was associated with decreased hardware removal likelihood, suggesting a potential protective mechanism. Conversely, smaller corrections of both HVA and IMA were associated with higher chances of hardware removal. Notably, for every 1-centimeter increase in TMT slippage postoperatively, there was a nearly 3-fold increase in the likelihood of distal chevron screw removal. Further research is needed to understand the mechanisms underlying TMT slippage and its impact on HV correction outcomes. [ABSTRACT FROM AUTHOR]

Category: Ankle Arthritis; Ankle Introduction/Purpose: Restoring the native joint line correlates with better clinical outcomes in total knee arthroplasty. Yet, the effect of joint line elevation on clinical outcomes after total ankle arthroplasty (TAA) remains unclear. A previous study reported that pre- and post-TAA joint line heights, as measured by the joint line height ratio (JLHR), were elevated compared to non- arthritic ankles. However, the clinical impact of this has yet to be determined. Therefore, this study assessed the relationship between the TAA joint line level with post-TAA range of motion (ROM) and PROMIS scores. We hypothesized that an elevated joint line would be associated with restricted post-TAA dorsiflexion and worse postoperative PROMIS scores. Methods: This is a single-center review of 150 patients who underwent primary TAA. Patients with (1)fibular or medial malleolar osteotomy, (2) component subsidence, and (3) incomplete radiographs or outcome scores were excluded. Demographic data, surgical protocol, pre- and postoperative radiographs, and 1-year postoperative PROMIS scores were reviewed. Radiographic measurements included JLHR, pre- and post-TAA tibiotalar dorsiflexion and plantarflexion, and tibial component sagittal alignment. Two graders measured post-TAA JLHRs, and the average of the two graders was used for the analysis. Rater agreement was assessed using intraclass correlation coefficients (two-way random effects model). Relationships between JLHR, post-TAA tibiotalar ROM, and PROMIS scores were investigated using Pearson correlation. Multiple linear regression models were used to investigate the association of JLHR with post-TAA tibiotalar total ROM, dorsiflexion, and plantarflexion, after adjusting for pre- TAA ROM, tibial component sagittal alignment, gastrocnemius release (GR), Tendo-Achilles lengthening (TAL), and polyethylene size. Results: The interobserver reliability of the JLHR was excellent (r=0.98). Mean JLHR decreased from 1.66 pre-TAA to 1.55 post- TAA (P < 0.001), indicating the joint line was significantly lowered postoperatively. Greater elevation of the post-TAA JLHR was associated with significantly decreased post-TAA dorsiflexion (r=-0.26, P< 0.001) and worse 1-year PROMIS physical function (r=- 0.22, P=0.046), pain intensity (r=0.22,P=0.042), and pain interference scores (r=0.29,P=0.007). There was no correlation between JLHR and post-TAA plantarflexion (P=0.76). Regression analysis identified a 5º reduction in post-TAA dorsiflexion with each 1.0 unit increase in JLHR (Coef=-5.13, P=0.005). Post-TAA total ROM (Coef=-3.6,P=0.21) and plantarflexion (Coef=0.91, P=0.67) were not associated with JLHR. Additionally, there was no association between post-TAA total ROM and tibial component sagittal alignment, GR, TAL, or polyethylene size. Conclusion: In this study, the joint line of the ankle was lowered after TAA, and the JLHR was a reliable and clinically applicable method for assessing it. An elevated joint line significantly correlated with restricted post-TAA dorsiflexion, but this may only be clinically relevant for patients with significant (>1.0 unit) changes in the joint line level. In addition, a higher joint line was correlated with worse 1-year PROMIS scores. These results suggest that surgeons should consider the joint line level during TAA preoperative planning to obtain improved clinical outcomes and ankle dorsiflexion. [ABSTRACT FROM AUTHOR]