Comparison of deformity with respect to the talus in patients with posterior tibial tendon dysfunction and controls using multiplanar weight-bearing imaging or conventional radiography

Weight-Bearing Computed Tomography of the Foot and Ankle-What to Measure?

Weight-bearing computed tomography (WBCT) was introduced in 2012 for foot and ankle applications as a breakthrough technology that enables full weight-bearing, three-dimensional imaging unaffected by x-ray beam projections or foot orientation. The literature describing the use of WBCT in the treatment of foot and ankle disorders is growing, and this article provides an overview of what can be measured with WBCT.

Joint coverage analysis in progressive collapsing foot deformity

Progressive collapsing foot deformity (PCFD) is characterized by a progressive subluxation of the peritalar bones and respective joints. Two-dimensional conventional radiographs are limited in their ability to visualize the peritalar bones and joints with adequate detail to describe the complex three-dimensional deformity. An improved understanding of the relationship between joint coverage and deformity would allow clinicians to use coverage analysis to distinguish among the stages of PCFD. The aim of this study was to analyze the joint coverage of the six articular relationships within the talocrural, subtalar, and Chopart joints using weightbearing computed tomography (WBCT) scans. Ten individuals with a flexible hindfoot and ten individuals with a rigid hindfoot presentation of PCFD were compared to twenty-seven asymptomatic control individuals. The three most relevant findings are: (I) the anterior-medial facet of the subtalar joint contains the greatest reduction in coverage for patients with a rigid deformity, (II) an increase in talonavicular overlap (TNO) moderately correlated with a decreased coverage in the: tibiotalar, anterior-medial subtalar, talonavicular joints, and (III) the calcaneocuboid joint lacks radiographic values to adequately quantify alignment and coverage. To conclude, there were significant differences in coverage area of various articulating regions throughout the hind- and midfoot when comparing PCFD patients to asymptomatic control individuals. Relevant radiographic measures correlating to articular coverage areas of clinical interest were identified, possibly helping to better quantify PCFD in clinical practice.

Modified hindfoot alignment radiological evaluation and application in the assessment of flatfoot

BACKGROUND

Alignment is indispensable for the foot and ankle function, especially in the hindfoot alignment. In the preoperative planning of patients with varus or valgus deformity, the precise measurement of the hindfoot alignment is important. A new method of photographing and measuring hindfoot alignment based on X-ray was proposed in this study, and it was applied in the assessment of flatfoot.

METHODS

This study included 28 patients (40 feet) with flatfeet and 20 volunteers (40 feet) from January to December 2018. The hindfoot alignment shooting stand independently designed by our department was used to take hindfoot alignment X-rays at 10 degree, 15 degree, 20 degree, 25 degree, and 30 degree. We measured the modified tibio-hindfoot angle (THA) at the standard hindfoot aligment position (shooting at 20 degree) and evaluated consistency with the van Dijk method and the modified van Dijk method. In addition, we observed the visibility of the tibiotalar joint space from all imaging data at five projection angles and evaluated the consistency of the modified THA method at different projection angles. The angle of hindfoot valgus of flatfoot patients was measured using the modified THA method.

RESULTS

The mean THA in the standard hindfoot aligment view in normal people was significantly different among the three evaluation methods (P < .001). The results from the modified THA method were significantly larger than those from the Van Dijk method (P < .001) and modified Van Dijk method (P < .001). There was no significant difference between the results of the modified THA method and the weightbearing CT (P = .605), and the intra- and intergroup consistency were the highest in the modified THA group. The tibiotalar space in the normal group was visible in all cases at 10 degree, 15 degree, and 20 degree; visible in some cases at 25 degree; and not visible in all cases at 30 degree. In the flatfoot group, the tibiotalar space was visible in all cases at 10 degree, visible in some cases at 15 degree and 20 degree, and not visible in all cases at 25 degree and 30 degree. In the normal group, the modified THA was 4.84 ± 1.81 degree at 10 degree, 4.96 ± 1.77 degree at 15 degree, and 4.94 ± 2.04 degree at 20 degree. No significant differences were found among the three groups (P = .616). In the flatfoot group, the modified THA of 18 feet, which was visible at 10 degree, 15 degree and 20 degree, was 13.58 ± 3.57 degree at 10 degree, 13.62 ± 3.83 degree at 15 degree and 13.38 ± 4.06 degree at 20 degree. There were no significant differences among the three groups (P = .425).

CONCLUSIONS

The modified THA evaluation method is simple to use and has high inter- and intragroup consistency. It can be used to evaluate hindfoot alignment. For patients with flatfeet, the 10 degree position view and modified THA measurement can be used to evaluate hindfoot valgus.

A comparison between the Bluman et al. and the progressive collapsing foot deformity classifications for flatfeet assessment

INTRODUCTION

Bluman et al., flatfoot classification is based on posterior tibial tendon (PTT) dysfunction leading to a chronological appearance of several foot deformities. An expert consensus recently proposed a new classification named Progressive Collapsing Foot Deformity (PCFD) in which the focus was shifted to five different independent foot and ankle deformities and their flexibility or rigidity. The aim of this study was to compare Bluman and PCFD classifications. We hypothesize that both classifications will be reliable and that the PCFD classification will allow a larger distribution of the different types of foot deformity.

MATERIALS AND METHODS

We performed a retrospective IRB-approved study including 92 flatfeet. Three foot and ankle surgeons reviewed patient files and radiographs to classify each foot using both classifications. Bluman classification was performed one time as initially described and a second time after removing the Angle of Gissane sclerosis sign. Interobserver reliabilities were determined with Fleiss' kappa values.

RESULTS

Interobserver reliabilities of Bluman and PCFD classifications were, respectively, substantial 0.67 and moderate 0.55. PCFD Class C and D reliabilities were, respectively, slight 0.07 and fair 0.28. The 276 readings were spread into 10 substages in Bluman and 65 subclasses in PCFD. The progressivity of the Bluman classification prevented the combination of flexible hindfoot valgus (II Bluman, 1A PCFD), midfoot abduction (IIB, 1B) and medial column instability (IIC, 1C) which was frequent in our study (112/276 readings, 40.6%). By removing the Angle of Gissane sclerosis sign from the Bluman classification, the prevalence of stage III decreased from 44.2 to 10.1%.

CONCLUSIONS

Bluman and PCFD classifications were reliable. The PCFD classification showed a larger distribution of different types of flatfeet but Classes C and D need better definition. The progressivity of Bluman classification causes inconsistencies and Gissane angle sclerosis sign is inappropriately used and might lead to incorrect surgical indications.

Prevalence and pattern of lateral impingements in the progressive collapsing foot deformity

INTRODUCTION

The prevalence of lateral bony impingements [i.e., Sinus Tarsi (STI), Talo-Fibular (TFI) and Calcaneo-Fibular (CFI)] and their association with Peritalar Subluxation (PTS) have not been clearly established for progressive collapsing foot deformity (PCFD).This study aims to assess the prevalence of STI, TFI and CFI in PCFD, in addition to their association with PTS. We hypothesized that STI and TFI would be more prevalent than CFI.

MATERIALS AND METHODS

Seventy-two continuous symptomatic PCFD cases were retrospectively reviewed. Weightbearing computed tomography (WBCT) was used to assess lateral impingements and classified as STI, TFI and CFI. PTS was assessed by the percent of uncovered and the incongruence angle of the middle facet, and the overall foot deformity was determined by the foot and ankle offset (FAO). Data were collected by two fellowship-trained independent observers.

RESULTS

Intra-observer and inter-observer reliabilities for impingement assessment ranged from substantial to almost perfect. STI was present in 84.7%, TFI in 65.2% and CFI in 19.4%. PCFD with STI showed increased middle facet uncoverage (p = 0.0001) and FAO (p = 0.0008) compared to PCFD without STI. There were no differences in FAO and middle facet uncoverage in PCFD with TFI and without TFI. PCFD with CFI was associated with STI in 100% of cases. PCFD with CFI showed decreased middle facet incongruence (p = 0.04) and higher FAO (p = 0.006) compared to PCFD without CFI.

CONCLUSIONS

STI and TFI were more prevalent than CFI in PCFD. However, only STI was associated with PTS. Conversely, CFI was associated with less PTS, suggesting a different pathological mechanism which could be a compensatory subtalar behavior caused by deep layer failure of the deltoid ligament and talar tilt.

The Foot and Ankle Kinematics of a Simulated Progressive Collapsing Foot Deformity During Stance Phase: A Cadaveric Study

BACKGROUND

Progressive collapsing foot deformity (PCFD) is a complex pathology associated with tendon insufficiency, ligamentous failure, joint malalignment, and aberrant plantar force distribution. Existing knowledge of PCFD consists of static measurements, which provide information about structure but little about foot and ankle kinematics during gait. A model of PCFD was simulated in cadavers (sPCFD) to quantify the difference in joint kinematics and plantar pressure between the intact and sPCFD conditions during simulated stance phase of gait.

METHODS

In 12 cadaveric foot and ankle specimens, the sPCFD condition was created via sectioning of the spring ligament and the medial talonavicular joint capsule followed by cyclic axial compression. Specimens were then analyzed in intact and sPCFD conditions via a robotic gait simulator, using actuators to control the extrinsic tendons and a rotating force plate underneath the specimen to mimic the stance phase of walking. Force plate position and muscle forces were optimized using a fuzzy logic iterative process to converge and simulate in vivo ground reaction forces. An 8-camera motion capture system recorded the positions of markers fixed to bones, which were then used to calculate joint kinematics, and a plantar pressure mat collected pressure distribution data. Joint kinematics and plantar pressures were compared between intact and sPCFD conditions.

RESULTS

The sPCFD condition increased subtalar eversion in early, mid-, and late stance (P < .05), increased talonavicular abduction in mid- and late stance (P < .05), and increased ankle plantarflexion (P < .05), adduction (P < .05), and inversion (P < .05). The center of plantar pressure was significantly (P < .01) medialized in this model of sPCFD and simulated stance phase of gait.

DISCUSSION

Subtalar and talonavicular joint kinematics and plantar pressure distribution significantly changed with the sPCFD and in the directions expected from a PCFD foot. We also found that ankle joint kinematics changed with medial and plantar drift of the talar head, indicating abnormal talar rotation. Although comparison to an in vivo PCFD foot was not performed, this sPCFD model produced changes in foot kinematics and indicates that concomitant abnormal changes may occur at the ankle joint with PCFD.

CLINICAL RELEVANCE

This study describes the dynamic kinematic and plantar pressure changes in a cadaveric model of simulated progressive collapsing foot deformity during simulated stance phase.

Medial Column Fusions in Flatfoot Deformities: Naviculocuneiform and Talonavicular

Progressive collapsing foot deformity (PCFD; commonly referred to as flatfoot deformity) is a complex condition classically characterized by hindfoot valgus, midfoot abduction, and forefoot varus. Medial column arthrodesis can be used to reliably correct severe, arthritic, and unstable PCFD involving the medial column. Although both naviculocuneiform arthrodesis and talonavicular arthrodesis have their own indications, patient selection and careful radiographic and clinical assessment are crucial for any medial column arthrodesis. Herein, the authors discuss the indications for medial column arthrodesis procedures, outcomes as reported in the literature, and several case examples using medial column arthrodesis in deformity correction.

Diagnostic accuracy of measurements in progressive collapsing foot deformity using weight bearing computed tomography: A matched case-control study

BACKGROUND

We aimed to investigate the diagnostic accuracy of known two-dimensional (2D) and three-dimensional (3D) measurements for Progressive Collapsing Foot Deformity (PCFD) in weight-bearing computed tomography (WBCT). We hypothesized that 3D biometrics would have better specificity and sensitivity for PCFD diagnosis than 2D measurements.

METHODS

This was a retrospective case-control study, including 28 PCFD feet and 28 controls matched for age, sex and Body Mass Index. Two-dimensional measurements included: axial and sagittal talus-first metatarsal angles (TM1A and TM1S), talonavicular coverage angle (TNCA), forefoot arch angle (FFAA), middle facet incongruence angle (MF°) and uncoverage percentage (MF%). The 3D Foot Ankle Offset (FAO) was obtained using dedicated semi-automatic software. Intra and interobserver reliabilities were assessed. Receiver Operating Characteristic (ROC) curves were calculated to determine diagnostic accuracy (Area Under the Curve (AUC)), sensitivity and specificity.

RESULTS

In PCFD, mean MF% and MF° were respectively 47.2% ± 15.4 and 13.3° ± 5.3 compared with 13.5% ± 8.7 and 5.6° ± 2.9 in controls (p < 0.001). The FAO was 8.1% ± 3.8 in PCFD and 1.4% ± 1.7 in controls (p < 0.001). AUCs were 0.99 (95%CI, 0.98-1) for MF%, 0.96 (95%CI, 0.9-1) for FAO, 0.90 (95%CI, 0.81-0.98) for MF°. For MF%, a threshold value equal or greater than 28.7% had a sensitivity of 100% and specificity of 92.8%. Conversely, a FAO value equal or greater than 4.6% had a specificity of 100% and a sensitivity of 89.2%. All other 2D measurements were significantly different in PCFD and controls (p < 0.001).

CONCLUSIONS

MF% and FAO were both accurate measurements for PCFD. MF% demonstrated slightly better specificity. FAO better sensitivity. A combination of threshold values of 28.7% for MF% and 4.6% for FAO yielded 100% sensitivity and specificity.

Assessment of Flatfoot Deformity Using Digitally Reconstructed Radiographs: Reliability and Comparison to Conventional Radiographs

BACKGROUND

Digitally reconstructed radiographs (DRRs) generated from weightbearing computed tomography (WBCT) may potentially substitute for weightbearing plain radiographs (XRs) but have not been clinically validated. This study aims to test the reliability of 6 radiographic parameters of progressive collapsing foot deformity (PCFD) as measured on DRR, to investigate whether DRR represents comparably to XR through the same measurements, and to compare agreement of DRR and XR measurements of a standardized arch height parameter with reference measurements made on WBCT.

METHODS

DRR generated from preoperative WBCT of 71 patients (72 feet) treated surgically for PCFD were retrospectively compared with preoperative weight-bearing XR after exclusion criteria were applied. Six radiographic measurements were performed, including Meary angle, calcaneal pitch (CPA), medial cuneiform height (MCH), AP talar-first metatarsal angle (T-1MT), talonavicular coverage (TNCA), and talar incongruency (TIA). Arch height was measured on XR, DRR, and WBCT using a validated, standardized, navicular-based index. Intraclass correlation coefficients assessed DRR intraobserver and interobserver reliability. Paired samples t tests tested differences between XR and DRR. Bland-Altman limits of agreement analysis compared DRR and XR agreement with WBCT measurements.

RESULTS

Measurements were within standard PCFD ranges on XR and DRR. All measurements demonstrated excellent intrarater reliability and good to excellent interrater agreement, consistent with previous literature on XR. No differences were found for Meary, CPA, or TNCA. Minor differences were observed for MCH, T-1MT, and TIA. DRR measurements demonstrated greater agreement with WBCT than XR measurements.

CONCLUSION

DRR from WBCT may be a promising substitute for XR in the clinical evaluation of PCFD. Radiographic measurements made on DRR demonstrated good to excellent reliability. Although small differences were found between XR and DRR for certain measurements, DRR more accurately represented medial arch anatomy compared to gold standard WBCT data than XR. If validated as a clinical substitute, DRR could eventually obviate XR where WBCT is available.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Assessment of Progressive Collapsing Foot Deformity Using Semiautomated 3D Measurements Derived From Weightbearing CT Scans

BACKGROUND

In progressive collapsing foot deformity (PCFD), hind- and midfoot deformities can be hard to characterize based on weightbearing plain radiography. Semiautomated 3-dimensional (3D) measurements derived from weightbearing computed tomography (WBCT) scans may provide a more accurate deformity assessment. In the present study, automated 3D measurements based on WBCT were used to compare hindfoot alignment of healthy individuals to patients with PCFD.

METHODS

The WBCT scans of 20 patients treated at our institution with either a flexible (N = 10) or rigid (N = 10) PCFD were compared with the WBCT scans of a control group of 30 healthy individuals. Using semiautomated image analysis software, from each set of 3D voxel images, we measured the talar tilt (TT), hindfoot moment arm (HMA), talocalcaneal angle (TCA; axial/lateral), talonavicular coverage (TNC), and talocalcaneal overlap (TCO). The presence of medial facet subluxation as well as sinus tarsi/subfibular impingement was additionally assessed.

RESULTS

With the exception of the TCA (axial/lateral), the analyzed measurements differed between healthy individuals and patients with PCFD. The TCA axial correlated with the TNC in patients with PCFD. An increased TCO combined with sinus tarsi impingement raised the probability of predicting a deformity as rigid.

CONCLUSION

Using 3D measurements, in this relatively small cohort of patients, we identified relevant variables associated with a clinical presentation of flexible or rigid PCFD. An increased TCO combined with sinus tarsi impingement raised the probability of predicting a deformity as rigid. Such WBCT-based markers possibly can help the surgeon in decision-making regarding the appropriate surgical strategy (eg, osteotomies vs realignment arthrodesis). However, prospective studies are necessary to confirm the utility of the proposed parameters in the treatment of PCFD.

LEVEL OF EVIDENCE

Level III, case-control study.

Combined weightbearing CT and MRI assessment of flexible progressive collapsing foot deformity

BACKGROUND

The objective of this study was to evaluate the correlation between Weightbearing CT (WBCT) markers of pronounced peritalar subluxation (PTS) and MRI findings of soft tissue insufficiency in patients with flexible Progressive Collapsing Foot Deformity (PCFD). We hypothesized that significant correlation would be found.

METHODS

Retrospective comparative study with 54 flexible PCFD patients. WBCT and MRI variables deformity severity were evaluated, including markers of pronounced PTS, as well as soft tissue degeneration. A multiple regression analysis and partition prediction models were used to evaluate the relationship between bone alignment and soft tissue injury. P-values of less than .05 were considered significant.

RESULTS

Degeneration of the posterior tibial tendon was significantly associated with sinus tarsi impingement (p = .04). Spring ligament degeneration correlated to subtalar joint subluxation (p = .04). Talocalcaneal interosseous ligament involvement was the only one to significantly correlate to the presence of subfibular impingement (p = .02).

CONCLUSION

Our results demonstrated that WBCT markers of pronounced deformity and PTS were significantly correlated to MRI involvement of the PTT and other important restraints such as the spring and talocalcaneal interosseus ligaments.

LEVEL OF EVIDENCE

Level III, Retrospective comparative study.

Spare the Talonavicular Joint! The Role of Isolated Subtalar Joint Fusion in the Treatment of Progressive Collapsing Foot Deformity

Surgical management of progressive collapsing foot deformity continues to evolve. Previous studies have demonstrated that fusion of the talonavicular joint results in limited hindfoot motion and, therefore, may accelerate adjacent-joint arthrosis. Recent literature has supported using alternative arthrodesis constructs that spare the talonavicular joint, such as naviculocuneiform or isolated subtalar fusions, which may maintain some hindfoot motion through the talonavicular joint yet adequately address a patient's deformity. Concomitant reconstructive procedures may be used in addition to subtalar fusion to address severe deformities. Isolated subtalar fusions may be considered in cases of sinus tarsi or subfibular impingement deformities.

Three-Dimensional Distance and Coverage Maps in the Assessment of Peritalar Subluxation in Progressive Collapsing Foot Deformity

BACKGROUND

Progressive collapsing foot deformity (PCFD), formerly termed adult-acquired flatfoot deformity, is a complex 3-dimensional (3D) deformity of the foot characterized by peritalar subluxation (PTS). PTS is typically measured at the posterior facet, but recent studies have called this into question. The objective of this study was to use 3D distance mapping (DM) from weightbearing computed tomography (WBCT) to assess PTS in patients with PCFD and controls. We hypothesized that DMs would identify the middle facet as a superior marker for PTS.

METHODS

We analyzed WBCT data of 20 consecutive stage I patients with PCFD and 10 control patients with a novel DM technique to objectively characterize joint coverage across the entire peritalar surface, including both articular and nonarticular regions. Joint coverage was defined as the percentage of articular area with DMs <4 mm and impingement when distances were <0.5 mm. Comparisons were performed with independent t tests or Wilcoxon tests. P values <.05 were considered significant.

RESULTS

Overall, coverage was decreased in articular regions and impingement was increased in nonarticular regions of patients with PCFD with a significant increase in uncoverage in the middle (46.6%, P < .001) but not anterior or posterior facets. Significant increases in sinus tarsi coverage were identified (98.0%, P < .007) with impingement in 6 of 20 patients with PCFD. Impingement of the subfibular region was noted in only 1 of 20 cases but narrowing greater than 2 standard deviations was noted in 17 of 20 patients.

CONCLUSION

Objective DMs identified significant markers of PTS in the middle but not posterior or anterior facets. We confirmed prior 2-dimensional data that suggested uncoverage of the middle facet provided a more robust and consistent measure of PTS than measures in the posterior facet.

LEVEL OF EVIDENCE

Level III, case-control study.

Imaging of Peritalar Instability

Undiagnosed medial ankle instability can be a prerequisite for pathogenic progression in the foot, particularly for adult acquired flatfoot deformity. With the complex anatomy in this region, and the limitations of each individual investigational method, accurately identifying peritalar instability remains a serious challenge to clinicians. Performing a thorough clinical examination aided by evaluation with advanced imaging can improve the threshold of detection for this condition and allow early proper treatment to prevent further manifestations of the instability.

Weight-bearing radiographs and cone-beam computed tomography examinations in adult acquired flatfoot deformity

BACKGROUND

Optimal characterization of Adult acquired flatfoot deformity (AAFD) on two-dimensional radiograph can be challenging. Weightbearing Cone Beam CT (CBCT) may improve characterization of the three-dimensional (3D) structural details of such dynamic deformity. We compared and validated AAFD measurements between weightbearing radiograph and weightbearing CBCT images.

METHODS

20 patients (20 feet, right/left: 15/5, male/female: 12/8, mean age: 52.2) with clinical diagnosis of flexible AAFD were prospectively recruited and underwent weightbearing dorsoplantar (DP) and lateral radiograph as well as weightbearing CBCT. Two foot and ankle surgeons performed AAFD measurements at parasagittal and axial planes (lateral and DP radiographs, respectively). Intra- and Inter-observer reliabilities were calculated by Intraclass correlation (ICC) and Cohen's kappa. Mean values of weightbearing radiograph and weightbearing CBCT measurements were also compared.

RESULTS

Except for medial-cuneiform-first-metatarsal-angle, adequate intra-observer reliability (range:0.61-0.96) was observed for weightbearing radiographic measurements. Moderate to very good interobserver reliability between weightbearing radiograph and weightbearing CBCT measurements were observed for the following measurements: Naviculocuneiform-angle (ICC:0.47), Medial-cuneiform-first-metatarsal-gapping (ICC:0.58), cuboid-to-floor-distance (ICC:0.68), calcaneal-inclination-angle(ICC:0.7), axial Talonavicular-coverage-angle(ICC:0.56), axial Talus-first-metatarsal-angle(ICC:0.62). Comparing weightbearing radiograph and weightbearing CBCT images, statistically significant differences in the mean values of parasagittal talus-first-metatarsal-angle, medial-cuneiform-first-metatarsal-angle, medial-cuneiform-to-floor-distance and navicular-to-floor-distance was observed (P < 0.05).

CONCLUSION

Moderate to very good correlation was observed between certain weightbearing radiograph and weightbearing CBCT measurements, however, significant difference was observed between a number of AAFD measurements, which suggest that 2D radiographic evaluation could potentially underestimate the severity of AAFD, when compared to 3D weightbearing CT assessment.

Morphologic analysis of the subtalar joint using statistical shape modeling

Weightbearing computed tomography (WBCT) enables visualization of the foot and ankle as patients stand under load. Clinical measurements of WBCT images are generally limited to two-dimensions, which reduces the ability to quantify complex morphology of individual osseous structures as well as the alignment between two or more bones. The shape and orientation of the healthy/normal subtalar joint, in particular, is not well-understood, which makes it very difficult to diagnose subtalar pathoanatomy. Herein, we employed statistical shape modeling to evaluate three-dimensional (3D) shape variation, coverage, space, and congruency of the subtalar joint using WBCT data of 27 asymptomatic healthy individuals. The four most relevant findings were: (A) talar and calcaneal anatomical differences were found regarding the presence of (a) the talar posterior process, (b) calcaneal pitch, and (c) curvature of the calcaneal posterior facet; (B) the talar posterior facet articular surface area was significantly greater than the calcaneal posterior facet articular surface area; (C) the posterior facet varied in joint space distance, whereas the anteromedial facet was even; and (D) the posterior and anteromedial facet of the subtalar joint was consistently congruent. Despite considerable shape variation across the population, the posterior and anteromedial articular facets of the subtalar joint were consistently congruent. Results provide a detailed 3D analysis of the subtalar joint under a weightbearing condition in a healthy population which can be used for comparisons to pathological patient populations. The described SSM approach also shows promise for clinical evaluation of the subtalar joint from 3D surface reconstructions of WBCT images.

Consensus for the Use of Weightbearing CT in the Assessment of Progressive Collapsing Foot Deformity

RECOMMENDATION

There is evidence that the use of WEIGHTBEARING imaging aids in the assessment of progressive collapsing foot deformity (PCFD). The following WEIGHTBEARING conventional radiographs (CRs) are necessary in the assessment of PCFD patients: anteroposterior (AP) foot, AP or mortise ankle, and lateral foot. If available, a hindfoot alignment view is strongly recommended. If available, WEIGHTBEARING computed tomography (CT) is strongly recommended for surgical planning. When WEIGHTBEARING CT is obtained, important findings to be assessed are sinus tarsi impingement, subfibular impingement, increased valgus inclination of the posterior facet of the subtalar joint, and subluxation of the subtalar joint at the posterior and/or middle facet.

LEVEL OF EVIDENCE

Level V, consensus, expert opinion.

Assessment of Posterior and Middle Facet Subluxation of the Subtalar Joint in Progressive Flatfoot Deformity

BACKGROUND

Adult acquired flatfoot deformity (AAFD) is a complex 3-dimensional pathology characterized by peritalar subluxation (PTS) of the hindfoot. For many years, PTS was measured at the posterior facet of the subtalar joint. More recently, subluxation of the middle facet has been proposed as a more accurate and reliable marker of symptomatic AAFD, enabling earlier detection. The objective of this study was to compare the amount of subluxation between the medial and posterior facets in patients with AAFD.

METHODS

In this institutional review board-approved retrospective comparative study, a total of 76 patients with AAFD (87 feet) who underwent standing weightbearing computed tomography (WBCT) as a standard baseline assessment of their foot deformity were analyzed. Two blinded fellowship-trained orthopedic foot and ankle surgeons with >10 years of experience measured subtalar joint subluxation (as a percentage of joint uncoverage) at the both posterior and middle facets. One of the readers also measured the foot and ankle offset (FAO). PTS measurements were performed at the sagittal midpoint of the articular facets using coronal plane WBCT images. Intra- and interobserver agreement was measured for PTS measurements using the intraclass correlation coefficient (ICC). The intermethod agreement between the posterior and middle facet subluxation was assessed using Spearman's correlation and bivariate analysis. Paired comparison of the measurements was performed using the Wilcoxon test. A multivariate analysis and a partition prediction model were used to assess influence of PTS measurements on FAO values. P values of <.05 were considered significant.

RESULTS

ICCs for intra- and interobserver reliabilities were 0.97 and 0.93, respectively, for posterior and 0.99 and 0.97, respectively, for middle facet subluxation. The intermethod Spearman's correlation between subluxation of the posterior and middle facets was measured at 0.61. In a bivariate analysis, both measurements were found to be significantly and linearly correlated (P < .0001; R² = 0.42). Measurements of middle facet subluxation were found to be significantly higher than those for posterior facet subluxation, with a median difference (using the Hodges-Lehman factor) of 17.7% (P < .001; 95% CI, 10.9%-23.6%). We also found that for every 1% increase in posterior facet subluxation there was a corresponding 1.6-fold increase in middle facet subluxation. Only middle facet subluxation measurements were found to significantly influence FAO calculations (P = .003). The partition prediction model demonstrated that a middle facet subluxation value of 43.8% represented an important threshold for increased FAO.

CONCLUSION

This study is the first to compare WBCT measurements of subtalar joint subluxation at the posterior and middle facets as markers of PTS in patients with AAFD. We found a positive linear correlation between the measurements, with subluxation of the middle facet being significantly more pronounced than that of the posterior facet by an average of almost 18%. This suggests that middle facet subluxation may provide an earlier and more pronounced marker of progressive PTS in patients with AAFD.

LEVEL OF EVIDENCE

Level III, retrospective comparative cohort study.

Weight-bearing CT Scans in Foot and Ankle Surgery

Weight-bearing CT (WBCT) scans of the foot and ankle have improved the understanding of deformities that are not easily identified on radiographs and are increasingly being used by orthopaedic surgeons for diagnostic and preoperative planning purposes. In contrast to standard CT scans, WBCT scans better demonstrate the true orientation of the bones and joints during loading. They have been especially useful in investigating the alignment of complex pathologies such as adult-acquired flatfoot deformity in which patients have been found to have a more valgus subtalar joint alignment than in a normal cohort and high rates of subfibular impingement. Studies using WBCT scans have also provided new insight into more common lower extremity conditions such as hallux valgus, ankle fractures, and lateral ankle instability. WBCT scans have allowed researchers to investigate pronation of the first metatarsal in patients with hallux valgus compared with normal feet, and patients with lateral ankle instability have been found to have more heel varus than healthy control subjects. Understanding the application of WBCT scans to clinical practice is becoming more important as surgeons strive for improved outcomes in the treatment of complicated foot and ankle disorders.

Multiplanar Semiautomatic Assessment of Foot and Ankle Offset in Adult Acquired Flatfoot Deformity

BACKGROUND

Semiautomatic 3-dimensional (3D) biometric weightbearing computed tomography (WBCT) tools have been shown to adequately demonstrate the relationship between the center of the ankle joint and the tripod of the foot. The measurement of the foot and ankle offset (FAO) represents an optimized biomechanical assessment of foot alignment. The objective of this study was to evaluate the correlation between FAO and traditional adult acquired flatfoot deformity (AAFD) markers, measured in different planes. We hypothesized that the FAO would significantly correlate with other radiographic markers of pronounced AAFD.

METHODS

In this retrospective comparative study, we included 113 patients with stage II AAFD, 43 men and 70 women, mean age of 53.5 (range, 20-86) years. 3D coordinates (x, y, and z planes) of the foot tripod (most plantar voxel of the first and fifth metatarsal heads, and calcaneal tuberosity) and the center of the ankle joint (most proximal and central voxel of the talar dome) were assessed by 2 blinded and independent fellowship-trained orthopedic foot and ankle surgeons. The FAO was automatically calculated using the 3D coordinates by dedicated software. Multiple WBCT parameters related to the severity of the deformity in the coronal, sagittal, and transverse planes were manually measured.

RESULTS

We found overall good to excellent intra- (range, 0.75-0.99) and interobserver (range, 0.73-0.99) reliability for manual AAFD measurements. FAO semiautomatic measurements demonstrated excellent intra- (0.99) and interobserver (0.99) reliabilities. Hindfoot moment arm (HMA) (P < .00001), subtalar horizontal angle (P < .00001), talonavicular coverage angle (P = .00004), and forefoot arch angle (P = .0001) were the only variables found to significantly influence and correlate with FAO measurements, with an R² value of 0.79. An HMA value of 19.8 mm was found to be a strong threshold predictor of increased values of FAO, with mean values of FAO of 6.5 when the HMA was lower than 19.8 mm and 14.6 when the HMA was equal to or higher than 19.8 mm.

CONCLUSION

We found that 3D WBCT semiautomatic measurements of FAO significantly correlated with some traditional markers of pronounced AAFD. Measurements of FAO were also found to be slightly more reliable than the manual measurements. The FAO offers a simple and more complete biomechanical and multiplanar assessment of the AAFD, representing in a single measurement the 3D components of the deformity.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Hindfoot alignment of adult acquired flatfoot deformity: A comparison of clinical assessment and weightbearing cone beam CT examinations

BACKGROUND

Clinical assessment of hindfoot alignment (HA) in adult acquired flatfoot deformity (AAFD) can be challenging and weightbearing (WB) cone beam CT (CBCT) may potentially better demonstrate this three-dimensional (3D) deformity. Therefore, we compared clinical and WB CBCT assessment of HA in patients with AAFD.

METHODS

In this prospective study, we included 12 men and 8 women (mean age: 52.2, range: 20-88) with flexible AAFD. All subjects also underwent WB CBCT and clinical assessment of hindfoot alignment. Three fellowship-trained foot and ankle surgeons performed six hindfoot alignment measurements on the CT images. Intra- and Inter-observer reliabilities were calculated using intra-class correlation (ICC). Measurements were compared by paired T-tests, and p-values of less than 0.05 were considered significant.

RESULTS

The mean of clinically measured hindfoot valgus was 15.2 (95% confidence interval [CI]: 11.5-18.8) degrees. It was significantly different from the mean values of all WB CBCT measurements: Clinical Hindfoot Alignment Angle, 9.9 (CI: 8.9-11.1) degrees; Achilles tendon/Calcaneal Tuberosity Angle, 3.2 (CI: 1.3-5.0) degrees; Tibial axis/Calcaneal Tuberosity Angle, 6.1 (CI: 4.3-7.8) degrees; Tibial axis/Subtalar Joint Angle 7.0 (CI: 5.3-8.8) degrees, and Hindfoot Alignment Angle 22.8 (CI: 20.4-25.3) degrees. We found overall substantial to almost perfect intra- (ICC range: 0.87-0.97) and inter-observer agreements (ICC range: 0.51-0.88) for all WB CBCT measurements.

CONCLUSIONS

Using 3D WB CBCT can help characterize the valgus hindfoot alignment in patients with AAFD. We found the different CT measurements to be reliable and repeatable, and to significantly differ from the clinical evaluation of hindfoot valgus alignment.

LEVEL OF EVIDENCE

Level II-prospective comparative study.

Analysis of three-dimensional computed tomography talar morphology in relation to pediatric pes planovalgus deformity

Intraosseous alignment of the tarsal bone has not been investigated in relation to various foot deformities. This study aimed to investigate three-dimensional computed tomography (3D CT) talar morphology in children with idiopathic and neuromuscular pes planovalgus. Eleven children [nine boys, two girls; mean (SD) age: 10.5 (2.8) years] with idiopathic pes planovalgus and 15 children [three boys, 12 girls; mean (SD) age: 10.8 (3.4) years] with neuromuscular pes planovalgus were included. All patients underwent 3D CT and weight-bearing anteroposterior, lateral, and axial radiography. Demographic data and talar 3D CT and radiographic measurements were compared between both groups. The correlation between the measurements was also analyzed. The neuromuscular group showed significantly more severe deformity than the idiopathic group in the radiographic and 3D sagittal talus measurements. The 3D coronal talus measurement showed a significant negative correlation with the axial hindfoot alignment in the idiopathic group while the 3D transverse talus measurement was significantly correlated with the lateral talocalcaneal angle in the neuromuscular group. 3D intraosseous alignment of the talus is correlated with pes planus deformity. Longitudinal and biomechanical studies including a control group are necessary to elucidate the role of 3D talar morphology on a dynamic imbalance in pes planovalgus.

Subtalar joint alignment in ankle osteoarthritis

BACKGROUND

Although it has been proposed that in mid-stage ankle osteoarthritis, the subtalar joint can compensate for deformities above the ankle joint, the evidence is weak. We thus investigated subtalar joint alignment in different stages of ankle osteoarthritis using weightbearing computed tomography (CT) scans.

METHODS

The subtalar joint of 88 patients with osteoarthritis of the ankle joint and a control group of 27 healthy volunteers were assessed. Subgroups were performed according to the ankle deformity (varus and valgus) and stage of ankle joint osteoarthritis. Subtalar joint alignment was assessed on weightbearing CT scans.

RESULTS

A more valgus subtalar joint alignment was found in patients with varus ankle osteoarthritis. No significant difference of the subtalar joint alignment was evident when comparing different stages of ankle osteoarthritis.

CONCLUSIONS

Varus ankles compensate in the subtalar joint for deformities above the ankle joint. Compensation does not correlate with the stage of ankle osteoarthritis.

The value of axial loading three dimensional (3D) CT as a substitute for full weightbearing (standing) 3D CT: Comparison of reproducibility according to degree of load

BACKGROUND

Full weightbearing (WB) three dimensional computed tomography (3D CT) is an excellent imaging tool. However, due to its high cost, it is only used in a few hospitals. We evaluated the usefulness and cost-effectiveness of axial loading (AL) 3D CT by comparing bony alignments with standing radiographs, and assessed reproducibility according to the degree of AL.

METHODS

Eighty patients (156 feet), who underwent standing radiographs and 3D CT with an AL device from January 2016 to May 2017, were investigated. According to the degree of AL (AL force×100/body weight), the patients were randomly assigned to three groups: Group A (30-50%; n=21, 40 feet), Group B (50-70%; n=32, 63 feet), and Group C (70-100%; n=27, 53 feet). The following angles were measured three times by two orthopedists: hallux valgus (HVA), 1st-2nd intermetatarsal (IMA1-2), and talo-navicular coverage (TNCA), calcaneal pitch (CPA), talo-1st metatarsal (T1MA), and talo-calcaneal angle (TCA). Agreements between the two imaging methods were analyzed and compared according to the degree of axial loading in each group.

RESULTS

Intra- and interobserver reliability was excellent (>0.75). In Group A (30-50% AL), all of the angles except HVA and IMA1-2 differed (p<.05). In Group B (50-70%), TNCA (p=.023), T1MA (p=.017), and TCA (p=.035) differed. In Group C (70-100%), none of the angles differed between the two imaging methods (p>.05). Higher agreement between the two imaging methods was realized when 70% or more(>70%) AL was applied.

CONCLUSIONS

AL 3D CT with >70% axial load has full WB effects and can be substituted for expensive full WB 3D CT.

Adult-Acquired Flatfoot Deformity

Adult-acquired flatfoot deformity (AAFD) comprises a wide spectrum of ligament and tendon failure that may result in significant deformity and disability. It is often associated with posterior tibial tendon deficiency (PTTD), which has been linked to multiple demographic factors, medical comorbidities, and genetic processes. AAFD is classified using stages I through IV. Nonoperative treatment modalities should always be attempted first and often provide resolution in stages I and II. Stage II, consisting of a wide range of flexible deformities, is typically treated operatively with a combination of soft tissue procedures and osteotomies. Stage III, which is characterized by a rigid flatfoot, typically warrants triple arthrodesis. Stage IV, where the flatfoot deformity involves the ankle joint, is treated with ankle arthrodesis or ankle arthroplasty with or without deltoid ligament reconstruction along with procedures to restore alignment of the foot. There is limited evidence as to the optimal procedure; thus, the surgical indications and techniques continue to be researched.

Evaluation of peritalar subluxation in adult acquired flatfoot deformity using computed tomography and weightbearing multiplanar imaging

BACKGROUND

The aim of this study was to assess the inferior talus-superior talus (inf-tal-sup-tal) angle (previously proven reliable in multiplanar-weight bearing imaging (MP-WB)) on both computed tomography (CT) and MP-WB scans. We sought to compare the angle between the two modalities in both AAFD and control groups, as well as to compare the groups to each other.

METHODS

Inf-tal-sup-tal angles were compared between a stage II AAFD group (n=38) with routine MP-WB and CT scans and a control group (n=20) with preoperative CT scans for lisfranc injuries and normal hindfoot alignment after healing.

RESULTS

The CT inf-tal-sup-tal angle was significantly greater in AAFD compared to control (AAFD, 12±6; control, 5±4; p<0.001), but was even greater with MP-WB. There was no significant correlation between inf-tal-sup-tal angles on MP-WB and CT (Pearson's=0.29, p=0.08).

CONCLUSIONS

MP-WB imaging proved to be correlated more strongly with AAFD than CT by revealing greater hindfoot valgus. This confirmed that CT scans are useful in predicting AAFD, but cannot be used as a surrogate for MP-WB scans.

Correlation of Clinical Evaluation and Radiographic Hindfoot Alignment in Stage II Adult-Acquired Flatfoot Deformity

BACKGROUND

Previous work has demonstrated that the amount of radiographic hindfoot correction required at the time of adult-acquired flatfoot deformity (AAFD) operative treatment can be predicted by the amount of radiographic deformity present before surgery. Successful outcomes after reconstruction are closely correlated with hindfoot valgus correction. However, it is not clear if differences exist between clinical and radiographic assessment of hindfoot valgus. The purpose of this study was to evaluate the correlation between radiographic and clinical evaluation of hindfoot alignment in patients with stage II AAFD.

METHODS

Twenty-nine patients (30 feet) with stage II AAFD, 17 men and 12 women, mean age of 51 (range, 20-71) years, were prospectively recruited. In a controlled and standardized fashion, bilateral weightbearing radiographic hindfoot alignment views were taken. Radiographic parameters were measured by 2 blinded and independent readers: hindfoot alignment angle (HAA) and hindfoot moment arm (HMA). Clinical photographs of hindfoot alignment were taken in 3 different vertical camera angulations (0, 20, and 40 degrees). Pictures were assessed by the same readers for standing tibiocalcaneal angle (STCA) and resting calcaneal stance position (RCSP). Intra- and interobserver reliability were assessed by Pearson/Spearman's and intraclass correlation coefficient (ICC), respectively. Relationship between clinical and radiographic hindfoot alignment was evaluated by a linear regression model. Comparison between the different angles (RCSP, STCA, and HAA) was performed using the Wilcoxon rank-sum test. P values of less than .05 were considered significant.

RESULTS

We found overall almost perfect intraobserver (range, 0.91-0.99) and interobserver reliability (range, 0.74-0.98) for all measures. Mean value and confidence interval (CI) for RCSP and STCA were 10.8 degrees (CI, 10.1-11.5) and 12.6 degrees (CI, 11.7-13.4), respectively. The position of the camera did not influence readings of clinical alignment ( P > .05). The mean HMA was 18.7 mm (CI, 16.3-21.1 mm), and the mean HAA was 23.5 degrees (CI, 21.1-26.0). Clinical and radiographic hindfoot alignment were found to significantly correlate ( P < .05). However, the radiographic HAA demonstrated increased valgus compared to both clinical alignment measurements, with a mean difference of 12.8 degrees from the RCSP (CI, 11.0-14.5, P < .0001) and 11.0 degrees from the STCA (CI, 9.2-12.8, P < .0001).

CONCLUSION

We found significant correlation between radiographic and clinical hindfoot alignment in patients with stage II AAFD. However, radiographic measurements of HAA demonstrated significantly more pronounced valgus alignment than the clinical evaluation. The results of our study suggest that clinical evaluation of hindfoot alignment in patients with AAFD potentially underestimates the bony valgus deformity. One should consider these findings when using clinical evaluation in the treatment algorithm of flatfoot patients.

LEVEL OF EVIDENCE

Level II, prospective comparative study.

Foot pressure pattern, hindfoot deformities, and their associations with foot pain in individuals with advanced medial knee osteoarthritis

This survey clarified foot pressure patterns and hindfoot deformities in individuals with advanced knee osteoarthritis (OA) and analyzed their associations with foot pain. Sixty-four individuals with unilateral knee OA who underwent total knee arthroplasty (TKA) were divided into the following groups: no foot pain (n=26; men:women, 4:22; mean age, 73.7 years), foot pain resolved after TKA (12; 2:10; 75.8), and foot pain remaining after TKA (26; 4:22; 74.7). Elderly individuals without pain or deformity in either knee (54; 10:44; 74.3) were controls. Navicular height ratio of the medial longitudinal arch, leg-heel angle, and partial foot pressure as the percentage of body weight (%PFP) were calculated.%PFPs of the medial and lateral heel regions before TKA were significantly lower for the no foot pain group than for controls. One year after TKA, %PFP improved significantly. In the foot pain resolved group, before TKA, the leg-heel angle was significantly higher, and%PFPs of the medial and lateral heel regions and navicular height ratio before TKA were significantly lower than those of controls. One year after TKA, all parameters improved significantly. In the foot pain remaining group, similar abnormalities were observed before TKA; however, significant improvement was only observed for%PFP of the medial heel region 1year after TKA. More than half of the patients with advanced knee OA had foot pain. This improved in approximately one-third, 1year after TKA. Hindfoot deformities are probably associated with foot pain in individuals with advanced knee OA.

Finite element simulation on posterior tibial tendinopathy: Load transfer alteration and implications to the onset of pes planus

BACKGROUND

Posterior tibial tendinopathy is a challenging foot condition resulting in pes planus, which is difficult to diagnose in the early stage. Prior to the deformity, abnormal internal load transfer and soft tissue attenuation are anticipated. The objective of this study was to investigate the internal load transfer and strain of the ligaments with posterior tibial tendinopathy, and the implications to pes planus and other deformities.

METHODS

A three-dimensional finite element model of the foot and ankle was reconstructed from magnetic resonance images of a 28-year-old normal female. Thirty bones, plantar fascia, ligaments and tendons were reconstructed. With the gait analysis data of the model subject, walking stance was simulated. The onset of posterior tibial tendinopathy was resembled by unloading the tibialis posterior and compared to the normal condition.

FINDINGS

The load transfer of the joints at the proximal medial column was weaken by posterior tibial tendinopathy, which was compromised by the increase along the lateral column and the intercuneiforms during late stance. Besides, the plantar tarsometatarsal and cuboideonavicular ligaments were consistently over-stretched during stance. Particularly, the maximum tensile strain of the plantar tarsometatarsal ligament was about 3-fold higher than normal at initial push-off.

INTERPRETATION

Posterior tibial tendinopathy altered load transfer of the medial column and unbalanced the load between the proximal and distal side of the medial longitudinal arch. Posterior tibial tendinopathy also stretched the midfoot plantar ligaments that jeopardized midfoot stability, and attenuated the transverse arch. All these factors potentially contributed to the progress of pes planus and other foot deformities.

Weightbearing CT Scan Assessment of Foot Alignment in Patients With Hallux Rigidus

BACKGROUND

An association between hallux rigidus and metatarsus primus elevatus (MPE) has been suggested, although there remains no general consensus about the nature of this relationship. Past studies were limited due to inaccuracies of assessing MPE on 2-dimensional radiographs. The aims of this study were to (1) assess and compare foot alignment in patients with and without hallux rigidus using 3-dimensional (3D) reconstructions from weightbearing computed tomography (CT) and (2) assess intraobserver and interobserver reliability of these measurements.

METHODS

A prospective study was performed in 50 consecutive patients with symptomatic hallux rigidus and 50 control patients who underwent a weightbearing CT. Two investigators measured first and second metatarsal declination angles, first and second metatarsal lengths, first to second intermetatarsal angle (IMA), hallux valgus angle (HVA), and foot width on 3D CT reconstructions. Measurements were repeated after 1 month. Student t tests were performed to compare hallux rigidus and control groups. Intraclass and interclass correlation coefficients were calculated to evaluate reliability.

RESULTS

The first to second metatarsal declination ratio was less in patients with hallux rigidus (mean, 0.81) than controls (mean, 0.92; P < .001). Patients with Coughlin and Shurnas grade 3 and 4 hallux rigidus had greater first metatarsal declination than patients with grade 1 and 2 hallux rigidus. Last, IMA was higher (mean, 13 degrees) but HVA was lower (mean, 11 degrees) in patients with hallux rigidus than controls (IMA mean, 12 degrees; HVA mean, 15 degrees; P = .04). Intraobserver (ICC1,1 ≥ 0.93) and interobserver (ICC3,1 ≥ 0.85) reliability were good to excellent for all measured parameters.

CONCLUSIONS

Patients with hallux rigidus had MPE. Patients with grade 3 and 4 hallux rigidus had more MPE than patients with grade 1 and 2 hallux rigidus. There was no clear correlation between hallux rigidus and bunions. Finally, weightbearing CT proved to be a reliable method of assessing all measured parameters.

LEVEL OF EVIDENCE

II, prospective comparative series.

Influence of tibialis posterior muscle activation on foot anatomy under axial loading: A biomechanical CT human cadaveric study

BACKGROUND

Collapse of the medial longitudinal arch and subluxation of the subtalar joint are common occurrences in adult flatfoot deformity. Controversy exists about the role of the tibialis posterior (TP) tendon as first and/or essential lesion. Subtle changes in the foot configuration can occur under weight bearing.

PURPOSE

This human cadaveric study is designed to investigate the effect that isolated actuation of the TP tendon has on the medial longitudinal arch and the hindfoot configuration under simulated weight bearing.

METHODS

A radiolucent frame was developed to apply axial loading on cadaveric lower legs during computer tomography (CT) examinations. Eight pairs of fresh-frozen specimens were imaged in neutral position under foot-flat loading (75N) and under single-leg stance weight bearing (700N) without and with addition of 150N pulling force on the TP tendon. Measurements of subtalar joint subluxation, forefoot arch angle and talo-first metatarsal angle were conducted on each set of CT scans.

RESULTS

Subtalar subluxation, talo-first metatarsal angle and talo-navicular coverage angle significantly increased under single-leg stance weight bearing, whereas forefoot arch angle significantly decreased. Actuation of the TP tendon under weight bearing did not restore the forefoot arch angle or correct subtalar subluxation and talo-metatarsal angle.

CONCLUSION

Significant effect that weight bearing has on the medial longitudinal arch and the subtalar joint configuration is demonstrated in an ex-vivo model. In absence of other medial column derangement, actuation of the TP tendon alone does not seem to reconstitute the integrity of the medial longitudinal arch or correct the hindfoot subluxation under weight bearing.

CLINICAL RELEVANCE

The findings of this study together with the developed model for ex-vivo investigation provide a further insight in foot anatomy.

Flexible Adult Acquired Flatfoot Deformity: Comparison Between Weight-Bearing and Non-Weight-Bearing Measurements Using Cone-Beam Computed Tomography

BACKGROUND

The 3-dimensional nature of adult acquired flatfoot deformity can be challenging to characterize using radiographs. We tested the hypothesis that measurements on weight-bearing (WB) cone-beam computed tomography (CT) images were more useful for demonstrating the severity of the deformity than non-weight-bearing (NWB) measurements.

METHODS

We prospectively enrolled 12 men and 8 women (mean age, 52 years; range, 20 to 88 years) with flexible adult acquired flatfoot deformity. The subjects underwent cone-beam CT while standing (WB) and seated (NWB), and images were assessed in the sagittal, coronal, and axial planes by 3 independent observers who performed multiple measurements. Intraobserver and interobserver reliabilities were assessed with the Pearson or Spearman correlation and the intraclass correlation coefficient (ICC), respectively. Measurements were compared using paired Student t tests or Wilcoxon rank-sum tests. P < 0.05 was considered significant.

RESULTS

We found that overall the measurements had substantial intraobserver and interobserver reliability on both the NWB images (mean ICC, 0.80; range, 0.49 to 0.99) and the WB images (mean ICC, 0.81; range, 0.39 to 0.99). Eighteen of 19 measurements differed between WB and NWB cone-beam CT images, with more pronounced deformities on the WB images. The most reliable measurements, based on intraobserver and interobserver reliabilities and the difference between WB and NWB images, were the medial cuneiform-to-floor distance, which averaged 29 mm (95% confidence interval [CI] = 28 to 31 mm) on the NWB images and 18 mm (95% CI = 17 to 19 mm) on the WB images, and the forefoot arch angle (mean, 13° [95% CI = 12° to 15°] and 3.0° [95% CI = 1.4° to 4.6°], respectively) in the coronal view and the cuboid-to-floor distance (mean, 22 mm [95% CI = 21 to 23 mm] and 17 mm [95% CI = 16 to 18 mm], respectively) and the navicular-to-floor distance (mean, 38 mm [95% CI = 36 to 40 mm] and 23 mm [95% CI = 22 to 25 mm], respectively) in the sagittal view.

CONCLUSIONS

Measurements analogous to traditional radiographic parameters of adult acquired flatfoot deformity are obtainable using high-resolution cone-beam CT. Compared with NWB images, WB images better demonstrated the severity of osseous derangement in patients with flexible adult acquired flatfoot deformity.

LEVEL OF EVIDENCE

Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Diagnostics in tarsal fusion: The theory and practise in The Netherlands

BACKGROUND

This study compares the preferences of Dutch orthopaedic surgeons for different diagnostic modalities in performing tarsal fusions versus consensus, evidence or expert opinion reported in the literature.

METHODS

A literature search of Medline was performed to obtain evidence-based information on various diagnostic tools. In addition, 89 registered Dutch foot and ankle surgeons were sent a questionnaire concerning the diagnostic modalities use in tarsal fusion.

RESULTS

Fifty-eight (65%) questionnaires were returned. The experienced surgeons measured outcomes significantly more often than other surgeons. Diagnostic injections were often used, although scant evidence exists in the literature. Postoperative diagnostics mainly consist of X-ray examination, although there is consensus in the literature that computed tomography is more accurate.

CONCLUSIONS

The study revealed some surprising discrepancies concerning the use of diagnostic imaging in tarsal fusion. More clinical research is needed to identify the most effective diagnostic imaging modalities so as to encourage their wider adoption.

The subtalar joint: A complex mechanism

Subtalar joint anatomy is complex and can vary significantly between individuals.

Movement is affected by several adjacent joints, ligaments and periarticular tendons.

The subtalar joint has gained interest from foot and ankle surgeons in recent years, but its importance in hindfoot disorders is still under debate.

The purpose of this article is to give a general overview of the anatomy, biomechanics and radiographic assessment of the subtalar joint.

The influence of the subtalar joint on the evolution of ankle joint osteoarthritis is additionally discussed.

Cite this article: EFORT Open Rev 2017;2:309-316. DOI: 10.1302/2058-5241.2.160050

In Vivo Plantar Pressures in Adult-Acquired Flatfoot Compared to Control Using an Intraoperative Pedobarographic Device

BACKGROUND

Intraoperative pedobarography has the potential to aid surgical decisions, but no parameters exist to guide its use.

QUESTIONS/PURPOSES

This study compared supine plantar pressures between flatfoot patients and controls using a previously validated intraoperative pedobarographic device and examined associations between supine, walking, and standing plantar pressures.

METHODS

Ten preoperative patients with stage II adult-acquired flatfoot deformity (AAFD) were compared to ten healthy controls. Supine plantar pressures were assessed using the pedobarographic device. Standing and walking plantar pressures were assessed with an EMED-XT sensor array (Novel). Maximum force (MF) and peak pressure (PP) were calculated for nine anatomical foot regions adjusting for age and BMI.

RESULTS

No differences in plantar pressures were found between flatfoot patients and controls in the supine or standing positions. During walking, flatfoot patients had greater MF of the first, second, and third metatarsals (p ≤ 0.018) and greater PP of the first and second metatarsals than controls (p ≤ 0.010). Supine MF and PP were both strongly positively correlated with their respective pressure measurements for both standing and walking in multiple foot regions (p ≤ 0.05, all analyses). Correlations in the first metatarsal region were generally weak and not statistically significant.

CONCLUSION

This device did not show differences in supine plantar pressures of flatfoot patients and healthy subjects, highlighting the limitations of intraoperative devices in guiding flatfoot correction. The differences between flatfoot and controls during walking and the correlations between supine and walking conditions suggest that dynamic plantar pressures are a more useful parameter in guiding flatfoot reconstruction.

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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

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. 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 OF EVIDENCE

Level III, case-control study.

Mid-flexion instability after total knee arthroplasty: woolly thinking or a real concern?

The term mid-flexion instability has entered the orthopaedic literature as a concept, but has not been confirmed as a distinct clinical entity. The term is used freely, sometimes as a synonym for flexion instability. However, the terms need to be clearly separated. A cadaver study published in 1990 associated joint line elevation with decreased stability at many angles of flexion, but that model was not typical of clinical scenarios. The literature is considered and it is proposed that the more common entity of an uncorrected flexion contracture after a measured resection arthroplasty technique is more likely to produce clinical findings that suggest instability mid-flexion. It is proposed that the clinical scenario encountered is generalised instability, with the appearance of stability in full extension from tight posterior structures. This paper seeks to clarify whether mid-flexion instability exists as an entity distinct from other commonly recognised forms of instability.

The influence of the Peroneus Longus muscle on the foot under axial loading: A CT evaluated dynamic cadaveric model study

BACKGROUND

Subtle hypermobility of the first tarsometatarsal joint can occur concomitantly with other pathologies and may be difficult to diagnose. Peroneus Longus muscle might influence stability of this joint. Collapse of the medial longitudinal arch is common in flatfoot deformity and the muscle might also play a role in correcting Meary's angle.

METHODS

A radiolucent frame was used to simulate weightbearing during CT examination. Eight pairs fresh-frozen lower legs were imaged in neutral position under non-weightbearing (75N), weightbearing (700N) and with 15kg weights hung from Peroneus Longus tendon. Measurements included first metatarsal rotation, intermetatarsal angle, first tarsometatarsal joint subluxation and Meary's angle.

FINDINGS

Weightbearing significantly increased Meary's angle and significantly decreased first tarsometatarsal joint subluxation (both P<0.01). Pulling Peroneus Longus tendon significantly increased first metatarsal rotation (P<0.01), significantly decreased the intermetatarsal angle (P<0.01) and increased non-significantly Meary's angle (P=0.52).

INTERPRETATION

A considerable effect weightbearing has on the medial longitudinal arch and first tarsometatarsal joint was observed. Pulling Peroneus Longus tendon improved first metatarsal subluxation but increased its rotation. The study calls into question the importance of this tendon in maintaining the medial longitudinal arch and raises concerns about rotational deformity of the first metatarsal following hallux valgus correction without first tarsometatarsal arthrodesis.

CLINICAL RELEVANCE

Study outcomes will provide more insight in foot pathology.

WHAT IS KNOWN ABOUT THE SUBJECT

Weightbearing affects anatomy of the foot. No reliable information is available concerning the influence of the Peroneus muscle.

WHAT THIS STUDY ADDS TO EXISTING KNOWLEDGE

This study investigates the influence of weightbearing and the impact the Peroneus muscle on the anatomy of the foot.

Descriptive Quantitative Analysis of Rearfoot Alignment Radiographic Parameters

Although the radiographic parameters of the transverse talocalcaneal angle (tTCA), calcaneocuboid angle (CCA), talar head uncovering (THU), calcaneal inclination angle (CIA), talar declination angle (TDA), lateral talar-first metatarsal angle (lTFA), and lateral talocalcaneal angle (lTCA) form the basis of the preoperative evaluation and procedure selection for pes planovalgus deformity, the so-called normal values of these measurements are not well-established. The objectives of the present study were to retrospectively evaluate the descriptive statistics of these radiographic parameters (tTCA, CCA, THU, CIA, TDA, lTFA, and lTCA) in a large population, and, second, to determine an objective basis for defining "normal" versus "abnormal" measurements. As a secondary outcome, the relationship of these variables to the body mass index was assessed. Anteroposterior and lateral foot radiographs from 250 consecutive patients without a history of previous foot and ankle surgery and/or trauma were evaluated. The results revealed a mean measurement of 24.12°, 13.20°, 74.32%, 16.41°, 26.64°, 8.37°, and 43.41° for the tTCA, CCA, THU, CIA, TDA, lTFA, and lTCA, respectively. These were generally in line with the reported historical normal values. Descriptive statistical analysis demonstrated that the tTCA, THU, and TDA met the standards to be considered normally distributed but that the CCA, CIA, lTFA, and lTCA demonstrated data characteristics of both parametric and nonparametric distributions. Furthermore, only the CIA (R = -0.2428) and lTCA (R = -0.2449) demonstrated substantial correlation with the body mass index. No differentiations in deformity progression were observed when the radiographic parameters were plotted against each other to lead to a quantitative basis for defining "normal" versus "abnormal" measurements.

Assessment of coronal plane subtalar joint alignment in peritalar subluxation via weight-bearing multiplanar imaging

BACKGROUND

Patients with adult-acquired flatfoot deformity (AAFD) develop peritalar subluxation, which may stem from valgus inclination of the inferior surface of the talus. We hypothesized that patients with AAFD would have an increased valgus tilt of the subtalar joint in the coronal plane compared to controls when assessed with a novel multiplanar weight-bearing imaging (MP-WB).

METHODS

Eighteen normal and 36 stage II AAFD patients scheduled to undergo operative reconstruction were evaluated by MP-WB through measuring 3 novel angles of the subtalar joint in the coronal view: (1) angle between inferior facet of the talus and the horizontal/floor (inftal-hor), (2) angle between inferior and superior facets of the talus (inftal-suptal), and (3) angle between inferior facet of the talus and superior facet of the calcaneus (inftal-supcal). Intra- and interobserver reliability were evaluated via intraclass correlation coefficients (ICCs). Differences in angles between AAFD patients and controls were evaluated using Wilcoxon rank-sum test.

RESULTS

Intra- and interobserver reliability were excellent for inftal-hor (ICC .942 and .991, respectively) and inftal-suptal (ICC .948 and .989, respectively), and moderate-good for inftal-supcal (ICC .604 and .742, respectively). Inftal-hor and inftal-suptal angles were found to be significantly greater in AAFD patients (P < 0.001) at all 3 locations along the posterior subtalar joint, while inftal-supcal did not demonstrate a significant difference (P = .741). While controls exhibited varus orientation at the anterior aspect of the joint, AAFD patients maintained a valgus orientation throughout.

CONCLUSION

Inftal-hor and inftal-suptal angles provided a reliable means of evaluating the orientation of the subtalar joint axis in AAFD via MP-WB, and showed that the subtalar joint had increased valgus orientation in AAFD compared to controls. This may allow for identification of patients at risk for developing AAFD, and could potentially be used in guiding operative reconstruction.