Adult Acquired Flatfoot Deformity Patients Research Articles

Isolated Gastrocnemius Recession for Flexible Adult Acquired Flatfoot Deformity

Category:Hindfoot; Midfoot/ForefootIntroduction/Purpose:Adult acquired flatfoot deformity (AAFD) frequently has an associated gastrocnemius contracture, which is a primary focus of most non-operative treatment protocols. When conservative measures fail, AAFD reconstruction often includes a gastrocnemius recession. Most reconstruction procedures involve a period of post-operative non-weight-bearing, which can be difficult for elderly patients. Beginning in 2011, patients with flexible AAFD patients and at risk of non-compliance with weight-bearing restrictions, were offered a staged approach with initial isolated gastrocnemius recession followed by reconstruction, if required. Gastrocnemius recession may allow passive correction of the deformity, improve orthotic fit and obviate the need reconstruction (Figure). The goal of this study was to retrospectively evaluate patient reported outcomes following an isolated gastrocnemius recession for flexible AAFD.Methods:A total of 49 patients met the inclusion criteria: isolated gastrocnemius recession for flexible AAFD, no previous ipsilateral surgery and >6 months follow-up. Of 49 eligible patients, 29 (31 feet) participated. Pre-operative and post-operative outcomes were compared for Foot and Ankle Ability Measure activities of daily living subscale (FAAM-ADL), visual analog scale (VAS), and the PROMIS Physical Function Short Form 10a (PROMIS PF SF 10a). Additionally, patients were asked about satisfaction, willingness to undergo the procedure again and whether orthotic provided better relief. Mean and standard deviation were compared using a two-tailed paired t-test with significance.Results:FAAM-ADL and PROMIS PF SF 10a significantly improved from 55.9 and 37.3 pre-operatively to 71.6 and 42.0 (p=0.01, p=0.046) respectively. 70% of patients were either satisfied or very satisfied, 67% would undergo the procedure again, and 64.5% of patients had improved relief with use of orthotics post-operatively.Conclusion:A staged approach with initial isolated gastrocnemius recession for the management of flexible AAFD in elderly patients can be effective. These results for patient recorded outcomes, patient satisfaction, willingness to undergo the procedure again and improvement in orthotic relief may guide the shared decision-making process with elderly patients when offered a reconstruction versus staged approach.

Is Lateral Impingement a Good Predictor of Peritalar Subluxation in Patients with Adult Acquired Flatfoot Deformity?

Category:Ankle Arthritis; Ankle; Hindfoot; OtherIntroduction/Purpose: Sinus tarsi and Subfibular impingement are considered the main causes of lateral foot pain in patients with Adult Acquired Flatfoot Deformity (AAFD). They are considered important markers in the spectrum of progressive peritalar subluxation (PTS) in patients with AAFD. Recent literature has also highlighted the use of the Middle Facet of the subtalar joint as a more accurate indicator of PTS. The objective of this study was to assess the relationship between lateral impingement and middle facet PTS. Our hypotheses were that patients with sinus tarsi and subfibular impingement would demonstrate more severe PTS than patients with no impingement, and that subfibular impingement would represent a better indicator of pronounced deformity when compared to sinus tarsi impingement.Methods: In this retrospective comparative Cohort Study, we included 110 AAFD patients that underwent standing weightbearing CT (WBCT) as a standard baseline assessment of their foot deformity. The presence or absence of sinus tarsi and subfibular impingements, as well as the incongruence angle and percentage of subluxation of the middle facet of the subtalar joint, were manually measured on multiplanar reconstruction (MPR) WBCT images by a blinded fellowship-trained foot and ankle surgeon. Descriptive statistics were used to describe the rate of sinus tarsi and subfibular impingement as well as mean values for middle facet incongruence angle and subluxation. Wilcoxon test was used to compare the values of PTS at the middle facet in patients with or without sins tarsi and subfibular impingement. A partition prediction model was used to assess the values of middle facet PTS that would foresee a higher risk for lateral impingement. P-values <0.05 were considered significant.Results: Seventy-five percent (n=82) of the AAFD patients had sinus tarsi impingement and 64% (n=70) of the AAFD patients had subfibular impingement. The mean value and 95% CI for middle facet incongruence angle and subluxation percentage were respectively 10.5o (CI, 8.7 to 12.2o) and 28.7% (CI, 23.5 to 33.9%). Middle facet subluxation was significantly higher in patients with sinus tarsi and subfibular impingement by respectively 22.6% and 23.9%, both p-values <0.0001. No similar significant differences were observed on incongruence angle measurements. The partition model demonstrated that the middle facet subluxation percentage was the best predictor of both sinus tarsi (R2=0.15) and subfibular impingements (R2=0.17), with 24.9% subluxation representing an important threshold for higher risk of sinus tarsi (90% incidence) and subfibular impingements (84% incidence).Conclusion: Our results showed significantly increased middle facet subluxation in AAFD patients with sinus tarsi and subfibular impingement. Subfibular impingement was less frequent and associated with more pronounced deformity than sinus tarsi impingement. Measurements of the percentage of subluxation of the middle facet were also found to be the best predictor of impingement, with 29.4% representing an important threshold value above which the risks for both sinus tarsi and subfibular impingement were significantly higher. With that in mind, we would recommend close assessment and follow-up of the amount of middle facet subluxation in the decision-making for the treatment of AAFD patients.

TL 18088 - Subluxation of the middle facet of the subtalar joint as a marker of adult acquired flatfoot deformity peritalar subluxation

Introduction: Progressive peritalar subluxation (PTS) occurs in patients with adult acquired flatfoot deformity (AAFD) and is usually assessed in coronal plane images of the subtalar joint (SJ) posterior facet (PF). In this case control study, we investigated the use of the middle facet (MF) as an indicator of PTS using weightbearing computed tomography (WBCT). We hypothesized that significantly increased joint uncoverage and incongruence would be noted in patients with AAFD. Objective: To assess the amount of subluxation of the middle facet of the subtalar joint as a marker of PTS in patients with symptomatic AAFD when compared to controls using coronal plane WBCT images. Methods: We included 30 patients with stage II AAFD (20 females/10 males), aged 57.4 (range, 24 to 78) years, and 30 matched-pair controls (20 females/10 males), with a mean age of 51.8 (range, 19 to 81) years, who underwent WBCT. Two independent and blinded fellowship-trained foot and ankle surgeons measured the amount of subluxation (percentage of uncoverage) and the incongruence angle of the MF at the midpoint of its longitudinal length, using coronal WB CBCT images. Intra- and interobserver reliability were assessed by the intraclass correlation coefficient (ICC). A comparison was performed using the paired Student’s T-test or for each pair the Wilcoxon test. P-values lower than 0.05 were considered significant. Results: Substantial to almost perfect intra- and interobserver reliability was observed for both measurements. The MF demonstrated significantly increased PTS in patients with AAFD, with a mean value for joint uncoverage of 45.3% (95% CI, 40.5% to 50.1%), as compared to 4.8% (95% CI, 0% to 9.6%) in controls (p&lt;0.0001). Significant differences were also found for the incongruence angle, with a mean value of 17.3 degrees (95% CI, 15.5 to 19.1) in AAFD patients and 0.3 degrees (95% CI, -1.5 to 2.1) in controls (p&lt;0.0001). A joint incongruence angle of more than 8.4 degrees was found to be diagnostic for symptomatic stage II AAFD. Conclusion: We described the use of the subtalar joint middle facet as a marker for PTS in patients with AAFD. Significant differences in the percentage of joint uncoverage and incongruence were found compared with the controls.

Weightbearing CT and MRI findings of Stage II Flatfoot Deformity: Can We Predict Patients at High- Risk for Foot Collapse?

Category:HindfootIntroduction/Purpose:Adult acquired flatfoot deformity (AAFD) is characterized by concurrent bony deformities, tendinous and ligamentous insufficiencies. Weightbearing CT (WBCT) allows excellent dynamic evaluation of the relative three-dimensional positioning of the tarsal bones. MRI provides accurate evaluation of soft tissue integrity in the unloaded foot. Study’s objective was to evaluate the correlation between bone deformity and soft tissue insufficiency in patients with stage II AAFD, using WBCT and MR images. We hypothesized that significant correlation would be found between WBCT measurements of increased longitudinal arch collapse, hindfoot valgus, peritalar subluxation and forefoot abduction, with MRI findings demonstrating degree of soft tissue involvement.Methods:This retrospective comparative study included 55 patients (56 feet) with stage II AAFD, 20 men and 35 women, mean age of 52.5 (range, 20 to 78) years. Multiple WBCT and MRI variables related to the severity of the deformity were evaluated by four blinded and independent readers (two radiologists and two foot and ankle surgeons), including: arch collapse (navicular-floor distance and forefoot arch angle), hindfoot alignment angle (HAA), forefoot abduction (talonavicular uncoverage angle), subtalar joint subluxation, sinus tarsi and subfibular impingement, and soft tissue insufficiency (posterior tibial tendon, spring and talocalcaneal ligaments). Tendinous and ligamentous involvement on MRI were graded from zero (normal) to four (complete tear). Intra- and interobserver reliabilities were assessed by Pearson/Spearman’s and intraclass correlation coefficient, respectively. A multiple regression analysis was used to evaluate the relationship between bone alignment (WBCT variables) and soft tissue injury (MRI variables). P-values of less than 0.05 were considered significant.Results:We found overall good to excellent intra (range, 0.83-0.99) and interobserver reliability (range, 0.71-0.97) for WBCT measurements and MRI readings. Spring ligament superomedial component involvement was the only finding to correlate with medial column collapse and decreased navicular-floor distance (p=0.03). Superomedial spring ligament and PTT degeneration were also significantly correlated with increased HAA (p<0.01). Involvement of the talocalcaneal interosseous ligament significantly correlated with increased forefoot abduction as measured by the talonavicular uncoverage angle. Spring ligament degeneration, of both superomedial and inferior components, and talocalcaneal interosseous ligaments significantly correlated to subtalar joint subluxation (p<0.001). Involvement of the talocalcaneal interosseous ligament was the only one to significantly correlate to the presence of subfibular impingement (p=0.02). Degeneration of the PTT was significantly associated with sinus tarsi impingement (p=0.04).Conclusion:This study is the first to evaluate correlation between bone, tendinous and ligamentous involvement in AAFD patients, using WBCT and MR images. Our results demonstrated that progressive bone deformity in WBCT is significantly correlated to MRI involvement of the PTT and other important restraints such as the spring and talocalcaneal ligaments. The implications are that WBCT can predict ligamentous injuries and that MRI can predict dynamic bone deformity in AAFD patients. Furthermore, the correlation of bone and soft tissue involvement could impact surgical planning of flatfoot patients, decreasing thresholds for additional soft tissue procedures such as a spring ligament reconstruction.

Middle Subtalar Joint Facet Subluxation as a Marker of Collapsing Flatfoot Deformity: A Case-Control Study

Category:HindfootIntroduction/Purpose:Peritalar subluxation comprises part of the three-dimensional and complex distortion that occurs in patients with adult-acquired flatfoot deformity (AAFD) and is characterized by subluxation of the hindfoot through the triple joint complex. It is traditionally graded on weightbearing computed tomography (WBCT) coronal plane images, depending upon the degree of angulation and subluxation of the posterior facet of the subtalar joint. In this case-control study, we describe a new marker of peritalar subluxation represented by the amount of subluxation and joint incongruence of the middle facet of the subtalar joint. We hypothesized that the amount of joint subluxation and incongruence at the middle facet would be significantly increased in patients with AAFD when compared to controls.Methods:Case-control study, we included 30 patients with stage II AAFD (19 females/11 males), mean age 52.2 (range, 29 to 81) years, and 30 controls (18 females/12 males), mean age 49.3 (range, 28 to 83) years, that underwent WBCT as part of the evaluation of their foot condition. Age and gender were statistically similar in both groups. The amount of subluxation of the subtalar joint at the middle facet (% of uncoverage) and angle of joint incongruence, both measured at the midpoint of its longitudinal length, was measured in coronal WB CBCT images by two independent and blinded fellowship-trained foot and ankle surgeons. A second set of measurements was performed after one month (wash-out period). Intra- and interobserver reliability were assessed by Pearson/Spearman’s and Intraclass Correlation Coefficient (ICC), respectively. Comparison was performed using Paired Student T-Test or each pair Wilcoxon rank sum test. P-values lower than 0.05 were considered significant.Results:We found overall good to excellent intra- (range, 0.90-0.95) and interobserver reliability (range, 0.75-0.93) for the measurements. We found significantly increased subluxation of the subtalar joint at the middle facet in patients with AAFD, with a mean value for middle facet uncoverage of 45.3% (95% CI, 40.5% to 50.1%), when compared to 4.8% (95% CI, 0% to 9.6%) in controls (p<0.0001). Significant differences were also found for middle facet subtalar joint incongruence angle, with a mean value of 17.3 degrees (95% CI, 15.5 to 19.1) in AAFD patients and 0.3 degrees (95% CI, -1.5 to 2.1) in controls (p<0.0001).Conclusion:We described the use of the subtalar joint middle facet as a marker for peritalar subluxation in patients with AAFD. We found significant and marked differences in the percentage of joint uncoverage and incongruence when compared to controls. Hopefully, the use of the middle facet as an indicator for peritalar subluxation can potentially help in the early detection of high- risk AAFD patients for progressive collapse and development of sinus tarsi and subfibular impingement, as well as arthritic degeneration of the subtalar joint. Future longitudinal and prospective studies are needed.

Weightbearing CT and MRI findings of Stage II Flatfoot Deformity

Category: Hindfoot Introduction/Purpose: Adult acquired flatfoot deformity (AAFD) is characterized by concurrent bony deformities, tendinous and ligamentous insufficiencies. Weightbearing CT (WBCT) is a new imaging technique that allows excellent evaluation of the relative three-dimensional positioning of the tarsal bones in dynamic deformities such as AAFD. MRI, on the other hand, provides an accurate evaluation of soft tissue integrity in the unloaded foot. The objective of this study was to evaluate the correlation between bone deformity and soft tissue insufficiency in patients with stage II AAFD, using WBCT and MR images. We hypothesized that a significant correlation would be found between WBCT measurements of increased longitudinal arch collapse, hindfoot valgus, peritalar subluxation and forefoot abduction, with MRI findings demonstrating degree of involvement of ligaments and posterior tibial tendon (PTT). Methods: This retrospective comparative study included 55 patients (56 feet) with stage II AAFD, 20 men and 35 women, mean age of 52.5 (range, 20 to 78) years. Multiple WBCT and MRI variables related to the severity of the deformity were evaluated by four blinded and independent readers (two radiologists and two foot and ankle surgeons), including: arch collapse (navicular-floor distance and forefoot arch angle), hindfoot alignment angle (HAA), forefoot abduction (talonavicular uncoverage angle), subtalar joint subluxation, sinus tarsi and subfibular impingement, and soft tissue insufficiency (posterior tibial tendon, spring and talocalcaneal ligaments). Tendinous and ligamentous involvement on MRI were graded from zero (normal) to four (complete tear). Intra- and interobserver reliabilities were assessed by Pearson/Spearman’s and intraclass correlation coefficient, respectively. A multiple regression analysis was used to evaluate the relationship between bone alignment (WBCT variables) and soft tissue injury (MRI variables). P-values of less than 0.05 were considered significant. Results: We found overall good to excellent intra (range, 0.83-0.99) and interobserver reliability (range, 0.71-0.97) for WBCT measurements and MRI readings. Spring ligament superomedial component involvement was the only finding to correlate with medial column collapse and decreased navicular-floor distance (p=0.03). Superomedial spring ligament and PTT degeneration were also significantly correlated with increased HAA (p&lt;0.01). Involvement of the talocalcaneal interosseous ligament significantly correlated with increased forefoot abduction as measured by the talonavicular uncoverage angle. Spring ligament degeneration, of both superomedial and inferior components, and talocalcaneal interosseous ligaments significantly correlated to subtalar joint subluxation (p&lt;0.001). Involvement of the talocalcaneal interosseous ligament was the only one to significantly correlate to the presence of subfibular impingement (p=0.02). Degeneration of the PTT was significantly associated with sinus tarsi impingement (p=0.04). Conclusion: This study is the first to evaluate correlation between bone, tendinous and ligamentous involvement in AAFD patients, using WBCT and MR images. Our results demonstrated that progressive bone deformity in WBCT is significantly correlated to MRI involvement of the PTT and other important restraints such as the spring and talocalcaneal ligaments. The implications are that WBCT can predict ligamentous injuries and that MRI can predict dynamic bone deformity in AAFD patients. Furthermore, the correlation of bone and soft tissue involvement could impact surgical planning of flatfoot patients, decreasing thresholds for additional soft tissue procedures such as a spring ligament reconstruction.

Influence of investigator experience on reliability of adult acquired flatfoot deformity measurements using weightbearing computed tomography

BackgroundOur purpose was to assess the reliability of measurements of adult-acquired flatfoot deformity (AAFD) taken by investigators of different levels of clinical experience using weightbearing computed tomography (WBCT). MethodsNineteen AAFD patients underwent WBCT. Three investigators with different levels of clinical experience made AAFD measurements in axial, coronal, and sagittal planes. Intra- and interobserver reliability were assessed. Mean values for each measurement were compared between investigators. ResultsAfter a training protocol, substantial to perfect intra- and interobserver reliability was observed for most measures, regardless of the investigator’s experience level. Significant differences between investigators were observed in 2 of 21 measured parameters: medial cuneiform–first metatarsal angle (P=0.003) and navicular–medial cuneiform angle (P=0.001). ConclusionsAAFD radiographic measurements can be performed reliably by investigators with different levels of clinical experience using WBCT. Level of evidenceLevel II, prospective comparative study.

Hindfoot Alignment of Adult Acquired Flatfoot Deformity

Category: Hindfoot Introduction/Purpose: Assessment of hindfoot alignment in adult acquired flatfoot deformity (AAFD) can be challenging. Clinical judgment and radiograph studies while important may not represent the accurate valgus alignment of the affected patients. Weightbearing (WB) ConeBeam CT (CBCT) is an emerging imaging modality that may potentially better demonstrate the three-dimensional (3D) deformity, facilitating visualization of important soft-tissue and bony landmarks and helping in surgical planning. Based on the relative position of bone and soft-tissue axes, different measurements of hindfoot alignment can be obtained with CT images. Therefore, we compared clinical assessment of hindfoot valgus alignment in AAFD patients with different possible measurements performed on WB CBCT images. Methods: In this prospective, IRB-approved study, 20 patients (20 feet, 15 right and 5 left) with clinical diagnosis of flexible AAFD were included. There were 12 males and 8 females, with a mean age of 52.2 years (range, 20 – 88 years of age), and average BMI of 30.35 kg/m2 (range, 19.00 – 46.09 kg/m2). Patients underwent clinical assessment of hindfoot alignment as well as WB CBCT. Two independent and blinded foot and ankle board-certified surgeons performed different hindfoot alignment measurements on the WB CBCT images that included: 3D “clinical” alignment; Achilles tendon axis/calcaneal tuberosity angle; angles formed between the tibial axis and the calcaneal tuberosity, calcaneal axis and line connecting midpoint of subtalar joint and most inferior part of calcaneal tuberosity. Positive values were considered valgus alignment. Mean differences between the measurements modalities were compared by paired T-test. Intra- and Inter-observer reliability for the WB CBCT measurements were calculated using Pearson correlation. Results: The mean clinical hindfoot valgus measured was 15.15o (SD 7.7o). It was found to be significantly different from the mean values of all WB CBCT angles modalities: 3D “clinical” alignment (10.42o, p &lt; 0.015); Achilles tendon/calcaneal tuberosity angle (2.96o, p &lt; 0.0001); tibial axis/calcaneal tuberosity angle (5.42o, p &lt; 0.0001); tibial axis/subtalar joint angle (7.52o, p &lt; 0.0001) and tibial axis/calcaneal axis angle (20.39o, p &lt; 0.017). We found an excellent intra-observer agreement for all WB CBCT 3D measurements (range, 0.8863 – 0.9713, p &lt; 0.0001). There was also good to excellent inter-observer reliability, with the exception of the 3D “clinical” alignment (r=0.450, p &lt; 0.04), that showed moderate correlation. Conclusion: The use of 3D WB CBCT imaging can help characterize the valgus hindfoot alignment in patients with adult acquired flatfoot deformity. We found the different CBCT measurements modalities to be reliable and repeatable, and to significantly differ from the clinical evaluation of hindfoot valgus alignment.

Talar Anatomy and Subtalar Joint Alignment on Weight-Bearing Computed Tomography

Category: Hindfoot Introduction/Purpose: Underlying bony deformities may contribute to the development of adult acquired flatfoot deformity (AAFD), although the exact pathogenesis remains unknown. Subtalar valgus tilt and underlying talar deformity can both be accurately assessed using multiplanar weightbearing computed tomography (MP-WB). On coronal MP-WB images, two angles have been used to reliably evaluate the subtalar joint axis in AAFD: (1) the angle between the inferior facet of the talus and the horizontal (inftal-hor), and (2) the angle between the inferior and superior facets of the talus (inftal-suptal). While previous work showed that these angles differ significantly between AAFD patients and controls, it is not known how they correlate with radiographic measures of flatfoot. We hypothesized that they would correlate strongly with commonly used radiographic measures of AAFD. Methods: 45 patients with stage II AAFD and 17 control patients underwent MP-WB imaging as well as standard weightbearing radiographs. Inftal-hor and inftal-suptal were measured on the coronal MP-WB images of all patients. These measurements were then correlated with standard radiographic measurements used to assess AAFD: talar-first metatarsal angle on antero-posterior (AP) and lateral views, talocalcaneal angle on AP and lateral views, talonavicular coverage angle, calcaneal pitch, medial column height, and hindfoot alignment. Basic demographic data including age, sex, and body mass index (BMI) were also collected. Differences between AAFD and control patients were assessed using independent samples t-tests and Mann-Whitney U tests. To examine the correlation between each MP-WB measurement and each radiographic measurement, a factorial generalized linear model (GLM) was constructed with presence of flatfoot, the radiographic measurement, and their interaction as covariates. Results: The flatfoot group was older than the control group (p=0.049); the two groups did not differ in terms of sex or BMI. The patients with AAFD differed significantly from the controls in all measured angles (p≤0.001 for each). Inftal-hor and inftal- suptal correlated with radiographic measures of flatfoot to the same degree in patients with and without AAFD. After accounting for differences between flatfoot and control patients, inftal-hor did not significantly correlate with any of the radiographic angles. Inftal-suptal, however, did significantly correlate with AP coverage angle, AP talar-first metatarsal angle, calcaneal pitch, Meary’s angle, medial column height, and hindfoot alignment (Figure). Conclusion: As measured on coronal MP-WB images, patients with stage II AAFD had more innate valgus in their talar anatomy as well as more valgus alignment of their subtalar joints than did control patients. The inftal-suptal angle correlated significantly with other measures of flatfoot deformity including arch collapse and forefoot abduction. Though causation cannot be established directly from this study, the data does suggest that AAFD may develop in patients with a valgus inclined subtalar joint axis. This information can be used to identify those patients likely to develop progressive flatfoot deformity and may ultimately guide the approach to surgical reconstruction.

Comparison of Coronal Subtalar Alignment between Adult Acquired Flatfoot Deformity Patients and Controls Using Standard CT and Weight-Bearing Multiplanar Imaging

Category: Hindfoot Introduction/Purpose: In a previous study using novel multiplanar weight-bearing imaging (MP-WB), the inferior talus-superior talus (inftal-suptal) angle reliably evaluated the coronal orientation of the subtalar joint axis and was significantly greater in stage II adult-acquired flatfoot deformity (AAFD) patients compared to controls. Since the inftal-suptal angle relies solely on the morphology of the talus, which is theoretically unchanged at the time of flatfoot reconstruction, we hypothesized that it should be similar in pre-operative MP-WB scans compared to post-operative non-weight-bearing standard CT scans of a stage II AAFD group. We secondly hypothesized that the post-operative CT angle of AAFD patients is significantly greater than the pre-operative CT scan angle of controls. Such information could allow for the assessment of AAFD with a less expensive and more readily available tool. Methods: Patients enrolled in the authors’ institution’s Foot and Ankle Registry with a diagnosis of stage II (flexible) AAFD and undergoing flatfoot reconstruction surgery were identified. Both MP-WB scans and post-operative CT scans were obtained in the flatfoot group to assess deformity and healing of the lateral column lengthening or tarsometatarsal fusion, respectively. A control group with pre-operative CT scans for lisfranc injuries (unrelated forefoot pathology) and normal hindfoot alignment on exam after final healing was identified. Standard weight-bearing radiographic imaging was obtained pre-operatively in the AAFD group and after final healing in the control, and 5 previously-established radiographic parameters were measured. The inftal-suptal angle was measured in CT scans of the control and AAFD groups, and in MP-WB scans of the AAFD group. Differences in CT inftal- suptal and radiographic parameters between AAFD and controls were assessed with independent samples t-tests. The correlation between inftal-suptal angles measured by MP-WB and CT in the AAFD group was assessed with Pearson’s correlation coefficients. Results: 38 stage II AAFD patients (38 feet; 53% female; age 56.7±11.7 years) undergoing flatfoot reconstruction surgery from November, 2008 to December, 2014 and with MP-WB scans 61.9±77.5 days pre-operatively and CT scans 51.3±8.6 days post- operatively were identified. 20 patient controls (20 feet; 45% female; age 35.7±13.4 years) with CT scans 13.8±20.5 days pre- operatively from June, 2006 to October, 2013, were evaluated. All plain radiographic parameters differed significantly between AAFD and control groups (Table 1), verifying placement of patients into their respective groups based on previously-established norms. The inftal-suptal CT angle additionally differed between the AAFD and control groups (p &lt; 0.001). The correlation between inftal-suptal angles measured by MP-WB and CT scans was relatively weak (Pearson’s=0.29) and did not reach statistical significance (p = 0.08). Conclusion: In summary, inftal-suptal angles of AAFD patients were significantly greater than those of controls on CT scans, and MP-WB imaging proved more predictive of AAFD than CT imaging. This study confirmed that while CT scans are useful in predicting stage II AAFD, they cannot be used as a surrogate for MP-WB scans, as they do not fully capture the amount of valgus. The most probable explanation of this is the re-formatting of CT scans into sagittal and coronal planes or a difference in the position of the foot during the scan, both leading to a potential difference in the planes of CT imaging and MP-WB imaging.

Correlation of Talar Anatomy and Subtalar Joint Alignment on Weightbearing Computed Tomography With Radiographic Flatfoot Parameters

Underlying bony deformity may be related to development of adult-acquired flatfoot deformity (AAFD). Multiplanar weightbearing (MP-WB) computed tomography can be used to identify subtalar deformity which may contribute to valgus hindfoot alignment. On coronal MP-WB images, 2 angles reliably evaluate the subtalar joint axis: the angle between the inferior facet of the talus and the horizontal (inftal-hor) and the angle between the inferior and superior facets of the talus (inftal-suptal). Although these angles have been shown to differ significantly between flatfoot patients and controls, no study has investigated their relationships with other components of AAFD. We hypothesized that these angles would correlate strongly with commonly used radiographic measures of AAFD. Forty-five patients with stage II AAFD and 17 control patients underwent MP-WB imaging and standard weightbearing radiographs. MP-WB measurements were correlated with standard radiographic measurements of AAFD. Differences between AAFD and control patients were assessed using independent samples t tests and Mann-Whitney U tests. To assess correlations between each MP-WB measurement and radiographic measurement, factorial generalized linear models (GLMs) were constructed. Patients with AAFD differed from the controls in all measured angles (P ≤ .001 for each). After accounting for differences between flatfoot and control patients, inftal-hor was not significantly correlated with any of the radiographic angles. Inftal-suptal, however, correlated with the AP coverage angle, AP talar-first metatarsal angle, calcaneal pitch, Meary's angle, medial column height, and hindfoot alignment after accounting for differences between flatfoot patients and controls. Meary's angle alone explained 48% of the variation in inftal-suptal angles. As measured on coronal MP-WB images, patients with stage II AAFD had more innate valgus in their talar anatomy as well as more valgus alignment of their subtalar joints than did control patients. It is possible that this information could be used to identify patients likely to have progression of deformity and may ultimately guide the approach to operative reconstruction. Level III, case-control study.

A population of patient-specific adult acquired flatfoot deformity models before and after surgery.

Following IRB approval, a cohort of 3-D rigid-body computational models was created from submillimeter MRIs of clinically diagnosed Adult Acquired Flatfoot Deformity patients and employed to investigate postoperative foot/ankle function and surgical effect during single-leg stance. Models were constrained through physiologic joint contact, passive soft-tissue tension, active muscle force, full body weight, and without idealized joints. Models were validated against patient-matched controls using clinically utilized radiographic angle and distance measures and plantar force distributions in the medial forefoot, lateral forefoot, and hindfoot. Each model further predicted changes in strain for the spring ligament, deltoid ligament, and plantar fascia, as well as joint contact loads for three midfoot joints, the talonavicular, navicular-1st cuneiform, and calcaneocuboid. Radiographic agreement ranged across measures, with average absolute deviations of <5° and <4mm indicating generally good agreement. Postoperative plantar force loading in patients and models was reduced for the medial forefoot and hindfoot concomitant with increases in the lateral forefoot. Model predicted reductions in medial soft-tissue strain and increases in lateral joint contact load were consistent with in vitro observations and elucidate the biomechanical mechanisms of repair. Thus, validated rigid-body models offer promise for the investigation of foot/ankle kinematics and biomechanical behaviors that are difficult to measure in vivo.