High Reliability for Semiautomated 3D Measurements Based on Weightbearing CT Scans

Morphological changes in flatfoot: a 3D analysis using weight-bearing CT scans

BACKGROUND

Flatfoot is a condition resulting from complex three-dimensional (3D) morphological changes. Most Previous studies have been constrained by using two-dimensional radiographs and non-weight-bearing conditions. The deformity in flatfoot is associated with the 3D morphology of the bone. These morphological changes affect the force line conduction of the hindfoot/midfoot/forefoot, leading to further morphological alterations. Given that a two-dimensional plane axis overlooks the 3D structural information, it is essential to measure the 3D model of the entire foot in conjunction with the definition under the standing position. This study aims to analyze the morphological changes in flatfoot using 3D measurements from weight-bearing CT (WBCT).

METHOD

In this retrospective comparative our CT database was searched between 4-2021 and 3-2022. Following inclusion criteria were used: Patients were required to exhibit clinical symptoms suggestive of flatfoot, including painful swelling of the medial plantar area or abnormal gait, corroborated by clinical examination and confirmatory radiological findings on CT or MRI. Healthy participants were required to be free of any foot diseases or conditions affecting lower limb movement. After applying the exclusion criteria (Flatfoot with other foot diseases), CT scans (mean age = 20.9375, SD = 16.1) confirmed eligible for further analysis. The distance, angle in sagittal/transverse/coronal planes, and volume of the two groups were compared on reconstructed 3D models using the t-test. Logistic regression was used to identify flatfoot risk factors, which were then analyzed using receiver operating characteristic curves and nomogram.

RESULT

The flatfoot group exhibited significantly lower values for calcaneofibular distance (p = 0.001), sagittal and transverse calcaneal inclination angle (p < 0.001), medial column height (p < 0.001), sagittal talonavicular coverage angle (p < 0.001), and sagittal (p < 0.001) and transverse (p = 0.015) Hibb angle. In contrast, the sagittal lateral talocalcaneal angle (p = 0.013), sagittal (p < 0.001) and transverse (p = 0.004) talocalcaneal angle, transverse talonavicular coverage angle (p < 0.001), coronal Hibb angle (p < 0.001), and sagittal (p < 0.001) and transverse (p = 0.001) Meary's angle were significantly higher in the flatfoot group. The sagittal Hibb angle (B =  - 0.379, OR = 0.684) and medial column height (B =  - 0.990, OR = 0.372) were identified as significant risk factors for acquiring a flatfoot.

CONCLUSION

The findings validate the 3D spatial position alterations in flatfoot. These include the abduction of the forefoot and prolapse of the first metatarsal proximal, the arch collapsed, subluxation of the talonavicular joint in the midfoot, adduction and valgus of the calcaneus, adduction and plantar ward movement of the talus in the hindfoot, along with the first metatarsal's abduction and dorsiflexion in the forefoot.

Méary's angle decoded: 3D analysis of first ray plantarflexion deformity in Charcot-marie-tooth disease

BACKGROUND

The typical cavovarus deformity seen in patients with Charcot-Marie-Tooth (CMT) involves plantarflexion of the first ray. The exact apex of the deformity has never been proven, although it is presumed to be within the medial cuneiform. The aim of this study was to utilize weight-bearing computed tomography (WBCT) to localize and quantify first ray plantarflexion deformity in CMT patients.

METHODS

WBCTs of 16 CMT patients with lateral Méary's angle > 20 degrees were compared to controls utilizing semi-automated analysis software. A local coordinate system based on the first metatarsal was used to avoid bias of proximal deformity. The tarsometatarsal angle was subdivided into components (cuneiform-cuneiform joint normal, tarsometatarsal joint and metatarsal-metatarsal joint normal) and compared between CMT and controls. CMT patient's first, second and third rays were also compared. Means were compared with a 2-sample t test (p < .05).

RESULTS

CMT patients had significantly more plantarflexion of the first ray than controls (16.4 versus 8.8 degrees respectively(p < 0.001)). The largest difference of was found at the medial cuneiform with 20.6 degrees of plantarflexion in CMT patients versus 14.8 degrees in controls (p < .0001). There was also approximately 2 degrees of plantarflexion at the TMT joint (p < .001).

CONCLUSIONS

Plantarflexion deformity in CMT patients is primarily an osseous deformity at the level of the medial cuneiform with a lesser contribution from the tarsometatarsal joint.

LEVEL OF EVIDENCE

III Retrospective comparative study.

Influence of the transverse tarsal arch on radiological components of progressive collapsing foot deformity

The importance of the transverse tarsal arch (TTA) has recently been extensively reevaluated and has even been considered to play a greater role in foot stability than the medial longitudinal arch (MLA). However, the relevance of this observation in the context of common clinical foot disorders, such as progressive collapsing foot deformity (PCFD), has not yet been fully clarified. In this biomechanical study, we examined ten pairs of human cadaveric feet by serial weight-bearing cone-beam computed tomography under controlled loading using a custom-designed testing machine. The MLA and TTA were transected separately, alternating the order in two study groups. A semiautomated three-dimensional evaluation of their influence on three components of PCFD, namely collapse of the longitudinal arch (sagittal Meary's angle), hindfoot alignment (sagittal talocalcaneal angle), and forefoot abduction (axial Meary's angle), was performed. Both arches had a relevant effect on collapse of the longitudinal arch, however the effect of transecting the MLA was stronger compared to the TTA (sagittal Meary's angle, 7.4° (95%CI 3.8° to 11.0°) vs. 3.2° (95%CI 0.5° to 5.9°); p = 0.021). Both arches had an equally pronounced effect on forefoot abduction (axial Meary's angle, 4.6° (95%CI 2.0° to 7.1°) vs. 3.0° (95%CI 0.6° to 5.3°); p = 0.239). Neither arch showed a consistent effect on hindfoot alignment. In conclusion, weakness of the TTA has a decisive influence on radiological components of PCFD, but not greater than that of the MLA. Our findings contribute to a deeper understanding and further development of treatment concepts for flatfoot disorders.

Forefoot Morphotypes in Cavovarus Feet: A Novel Assessment of Deformity

BACKGROUND

The cavovarus foot is a complex 3-dimensional deformity. Although a multitude of techniques are described for its surgical management, few of these are evidence based or guided by classification systems. Surgical management involves realignment of the hindfoot and soft tissue balancing, followed by forefoot balancing. Our aim was to analyze the pattern of residual forefoot deformities once the hindfoot is corrected, to guide forefoot correction.

METHODS

We included 20 cavovarus feet from 16 adult patients with Charcot-Marie-Tooth who underwent weightbearing CT (mean age 43.4 years, range: 22-78 years, 14 males). Patients included had flexible deformities, with no previous surgery. Using specialized software (Bonelogic 2.1, Disior) a 3-dimensional, virtual model was created. Using morphologic data captured from normal feet in patients without pathology as a guide, the talonavicular joint of the cavovarus foot was digitally reduced to a "normal" position to simulate the correction that would be achieved during surgical correction. Models of the corrected position were exported and geometrically analyzed using Blender 3.64 to identify anatomical trends.

RESULTS

We identified 4 types of cavovarus forefoot morphotypes. Type 0 was defined as a balanced forefoot (2 cases, 10%). Type 1 was defined as a forefoot where the first metatarsal was relatively plantarflexed to the rest of the foot, with no significant residual adduction after talonavicular joint correction (12 cases, 60%). Type 2 was defined as a forefoot where the second and first metatarsals were progressively plantarflexed, with no significant adduction (4 cases, 20%). Type 3 was defined as a forefoot where the metatarsals were adducted after talonavicular derotation (2 cases, 10%).

CONCLUSION

In this relatively small cohort, we identified 4 forefoot morphotypes in cavovarus feet that might help surgeons to recognize and anticipate the residual forefoot deformities after hindfoot correction. Different treatment strategies may be required for different morphotypes to achieve balanced correction.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

3D Analysis of Joint-Sparing Charcot-Marie-Tooth Surgery Effect on Initial Standing Foot Alignment

BACKGROUND

The complex deformities in cavovarus feet of Charcot-Marie-Tooth (CMT) disease are difficult to evaluate. The aim of this study was to quantify the initial standing alignment correction achieved after joint-sparing CMT cavovarus reconstruction using pre- and postoperative weightbearing computed tomography (WBCT).

METHODS

Twenty-nine CMT cavovarus reconstructions were retrospectively analyzed. Three-dimensional measurements were performed using semiautomated software (Bonelogic 2.1) to investigate changes in sagittal, axial, and coronal parameters. Pre- and postoperative data were compared, along with normative data. Correlation among the preoperative measurements and the amount of correction in sagittal, axial, and coronal parameters were analyzed.

RESULTS

The sagittal, axial, and coronal malalignment of the hindfoot, and the sagittal and axial malalignment of the forefoot, was significantly improved after corrective surgery (P < .05). Sagittal Meary angle (from 14.8 to 0.1 degrees), axial talonavicular angle (TNA, from 3.6 to 19.2 degrees), and coronal hindfoot alignment (from 11.0 to -11.1 degrees) showed significant changes postoperatively (P < .001). Hindfoot, forefoot sagittal, and forefoot axial parameters reached comparable outcomes compared with normative value (P > .05). Regarding amount of correction, Spearman correlation demonstrated that axial Meary angle and TNA were most strongly related to improvement in sagittal Meary angle and coronal hindfoot alignment.

CONCLUSION

Preoperative and postoperative WBCT measurements demonstrated that joint sparing CMT cavovarus reconstruction significantly improved sagittal, axial, and coronal deformities of CMT, and sagittal Meary angle was restored toward normative values. Apparent axial plane correction, the majority of which occurred at the talonavicular joint, had the strongest correlation with deformity correction in multiple planes. This suggests that soft tissue releases and correction of the talonavicular joint may be a key component of a cavovarus foot correction.

Association Between Weightbearing CT and MRI Findings in Progressive Collapsing Foot Deformity

BACKGROUND

Weightbearing computed tomography (WBCT) scans allow for a better understanding of foot alignment in patients suffering from progressive collapsing foot deformity (PCFD). However, soft tissue integrity (eg, spring ligament complex or tibialis posterior tendon) cannot be easily assessed via WBCT. As performing both WBCT and magnetic resonance imaging (MRI) might not be cost effective, we aimed to assess whether there is an association between osseous and soft tissue findings in WBCT and MRI.

METHODS

In this observational study, a consecutive cohort of 24 patients of various stages of PCFD (mean age 51 ± 18 years) underwent WBCT scans and MRI. Twenty-four healthy individuals of similar age, body mass index (BMI), and sex with WBCT scans were used as a control group. In addition to of osseous sinus tarsi impingement, 4 commonly used 3-dimensional (3D) measurements (talocalcaneal overlap [TCO], talonavicular coverage [TNC], Meary angle [MA], axial/lateral) were obtained using a dedicated postprocessing software (DISIOR 2.1, Finland) on the WBCT data sets. Sinus tarsi obliteration, spring ligament complex, tibiospring ligament integrity, as well as tibialis posterior tendon degeneration were evaluated with MRI. Statistical analysis was performed for significant (P < .05) correlation between findings.

RESULTS

None of the assessed 3D measurements correlated with either spring ligament complex or tibiospring ligament tears. BMI and TCO were found to be associated with tibialis posterior tendon tears. Seventy-five percent of patients with osseous sinus tarsi impingement on WBCT also showed signs of sinus tarsi obliteration on MRI.

CONCLUSION

Although WBCT reflects foot alignment and can reveal osseous sinus tarsi impingement in PCFD patients, the association between WBCT-based 3D measurements and ligament or tendon tears assessed via MRI is limited. WBCT appears complimentary to MRI regarding its diagnostic value. Both imaging options add important information and may impact decision making in the treatment of PCFD patients.

LEVEL OF EVIDENCE

Level IV, observational study.

Impact of the medial displacement calcaneal osteotomy on foot biomechanics: a systematic literature review

INTRODUCTION

Progressive collapsing foot deformity (PCFD), formally known as "adult-acquired flatfoot deformity" (AAFFD), is a complex foot deformity consisting of multiple components. If surgery is required, joint-preserving procedures, such as a medial displacement calcaneal osteotomy (MDCO), are frequently performed. The aim of this systematic review is to provide a summary of the evidence on the impact of MDCO on foot biomechanics.

MATERIALS AND METHODS

A systematic literature search across two major sources (PubMed and Scopus) without time limitation was performed according to the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) criteria. Only original research studies reporting on biomechanical changes following a MDCO were included. Exclusion criteria consisted of review articles, case studies, and studies not written in English. 27 studies were included and the methodologic quality graded according to the QUACS scale and the modified Coleman score.

RESULTS

The 27 included studies consisted of 18 cadaveric, 7 studies based on biomechanical models, and 2 clinical studies. The impact of MDCO on the following five major parameters were assessed: plantar fascia (n = 6), medial longitudinal arch (n = 9), hind- and midfoot joint pressures (n = 10), Achilles tendon (n = 5), and gait pattern parameters (n = 3). The quality of the studies was moderate to good with a pooled mean QUACS score of 65% (range 46-92%) for in-vitro and a pooled mean Coleman score of 58 (range 56-65) points for clinical studies.

CONCLUSION

A thorough knowledge of how MDCO impacts foot function is key in properly understanding the postoperative effects of this commonly performed procedure. According to the evidence, MDCO impacts the function of the plantar fascia and Achilles tendon, the integrity of the medial longitudinal arch, hind- and midfoot joint pressures, and consequently specific gait pattern parameters.

The position, orientation, and relative size of the fibularis longus tubercle in normal patients: A weightbearing CT assessment

The fibularis longus attaches to the base of the first metatarsal at the fibularis/peroneus longus tubercle (FLT/PLT). Theoretically, differences in FLT morphology may reflect changes in the function of the fibularis longus. This study defines the normal limits of the FLT position, orientation, and size in patients with morphologically normal foot anatomy. A retrospective analysis of 131 feet without deformity in 72 patients undergoing weightbearing CT (WBCT) at a single center was conducted. The position and morphology of the FLT was assessed with novel measurements including tubercle-floor distance, tubercle-metatarsal angle, and the angle between the floor and a line bisecting the FLT (bisecting angle). Roundness of the FLT was compared to a triangle limiting its shape (triangular ratio), with lower values indicating increasing roundness. We also report relative size of the FLT to the first metatarsal (X/Y ratio), and relative size of the first metatarsal and FLT to the second metatarsal (XY/Z ratio). There were no significant side to side differences for any measurement (p > 0.05). Mean values were: tubercle-floor distance 28.02 ± 2.63 mm, tubercle-metatarsal angle 32.7 ± 6.32 degrees, bisecting angle 65.58 ± 6.27 degrees, triangular ratio 0.69 ± 0.04, X/Y ratio 1.13 ± 0.20, and XY/Z ratio 3.44 ± -0.72. Bisecting angle strongly correlated with tubercle-metatarsal angle (Pearson correlation 0.840, p < 0.001) suggesting FLT rotation occurred independent of foot position. ICC was >0.943 for all measurements. This study reports the morphology of the FLT in individuals with normal feet. This normative data may be used in future studies examining differences between groups of patients with foot pathology, helping us better understand the role of fibularis longus in the development and treatment of foot disorders.

Comparison of the Usefulness of Computer-Assisted Three-Dimensional Analysis and Weight-Bearing Radiographs in Ankle Osteoarthritis

Background

To evaluate the degree of deformation in patients with ankle osteoarthritis (OA), it is essential to measure the three-dimensional (3D), in other words, stereoscopic alignment of the ankle, subtalar, and foot arches. Generally, measurement of radiological parameters use two-dimensional (2D) anteroposterior and lateral radiographs in a weight-bearing state; however, computer-aided 3D analysis (Disior) using weight-bearing cone-beam computed tomography (CBCT) has recently been introduced.

Methods

In this study, we compared the 2D human radiographic method with a stereoscopic image in patients with ankle arthritis. We enrolled 57 patients diagnosed with OA (28 left and 29 right) and obtained both standing radiographs and weight-bearing CBCT. Patients were divided by the Takakura stage. The interclass correlation coefficient (ICC) for each result was confirmed.

Results

On the ICC between 2D radiographs and 3D analysis, the tibiotalar surface angle and lateral talo-1st metatarsal angle showed a good ICC grade (> 0.6), while other parameters did not have significant ICC results. Three-dimension was superior to radiographs in terms of statistical significance.

Conclusions

We demonstrated that 2D and stereoscopic images are useful for the diagnosis of OA. Our study also confirmed that the radiographic features affected by ankle OA varied. However, according to the results, the typical radiography is not sufficient to diagnose and determine a treatment plan for ankle OA. Therefore, the method of using 3D images should be considered.

Normal Values for Distal Tibiofibular Syndesmotic Space With and Without Subject-Driven External Rotation Stress

BACKGROUND

The diagnosis and treatment of distal tibiofibular syndesmosis (DTFS) injury can be challenging, especially in cases of subtle instability that may be masked on 2-dimensional conventional radiographs. Weightbearing computed tomography (WBCT) has recently emerged as a useful diagnostic tool allowing direct assessment of distal tibiofibular area widening. The purpose of the current study was to examine and report normal threshold values for DTFS area measurements in a cohort of healthy volunteers, assessing the ankles in natural weightbearing position and under subject-driven external rotation stress.

METHODS

In this prospective study, we enrolled 25 healthy volunteers without a history of DTFS injury or high ankle sprain, previous foot and ankle surgery, or current ankle pain. Subjects with any prior ankle injuries were excluded. Study participants underwent bilateral standing nonstress and external rotation stress WBCT scans. The DTFS area (mm2) was semiautomatically quantified on axial-plane WBCT images 1 cm proximal to the apex of the talar dome using validated software. Syndesmosis area values were compared between "unstressed" and "stressed" ankles, as well as left and right ankles. Statistical analysis was performed using independent t tests/Wilcoxon analysis with statistical significance defined as P <.05.

RESULTS

The study cohort consisted of 50 ankles in 25 patients (12 males, 48%) with a mean age of 28.7 ± 9.3 years. In the unstressed ankle, the mean pooled DTFS area was determined to be 103.8 + 20.8 mm2. The mean syndesmosis area of unstressed left ankles (104.2 + 19.5 mm2) was similar to unstressed right ankles (109.2 + 17.2 mm2) in the cohort (P = .117). With external rotation stress, the DTFS area of left ankles (mean difference -0.304 mm2, CI -12.1 to 11.5; P = .082), right ankles (mean difference -5.5 mm2, CI 16.7-5.7; P = .132), and all ankles (mean difference -2.9 mm2, CI -10.8 to 5.1; P = .324) remained similar.

CONCLUSION

This study presents normal values and range for DTFS area calculation. In uninjured ankles with expected intact ligaments, subject-driven external rotation stress did not result in significant widening of the DTFS space as imaged on with WBCT.

LEVEL OF EVIDENCE

Level II, cross-sectional study.

Diagnostic applications and benefits of weightbearing CT in the foot and ankle: A systematic review of clinical studies

BACKGROUND

Foot and ankle weightbearing CT (WBCT) imaging has emerged over the past decade. However, a systematic review of diagnostic applications has not been conducted so far.

METHOD

A systematic literature search was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines after Prospective Register of Systematic Reviews (PROSPERO) registration. Studies analyzing diagnostic applications of WBCT were included. Main exclusion criteria were: cadaveric specimens and simulated WBCT. The Methodological Index for Non-Randomized Studies (MINORS) was used for quality assessment.

RESULTS

A total of 78 studies were eligible for review. Diagnostic applications were identified in following anatomical area's: ankle (n = 14); hindfoot (n = 41); midfoot (n = 4); forefoot (n = 19). Diagnostic applications that could not be used on weightbearing radiographs (WBRX) were reported in 56/78 studies. The mean MINORS was 9.8/24 (range: 8-12).

CONCLUSION

Diagnostic applications of WBCT were most frequent in the hindfoot, but other areas are on the rise. Post-processing of images was the main benefit compared to WBRX based on a moderate quality of the identified studies.

Medializing Calcaneal Osteotomy for progressive collapsing foot deformity alters the three-dimensional subtalar joint alignment

BACKGROUND

A medializing calcaneal osteotomy (MCO) is considered as one of the key inframalleolar osteotomies to correct progressive collapsing foot deformity (PCFD). While many studies were able to determine the post-operative hind- and midfoot alignment, alternations of the subtalar joint alignment remained obscured by superposition on plain radiography. Therefore, we aimed to assess the hind-, midfoot- and subtalar joint alignment pre- compared to post-operatively using 3D weightbearing CT (WBCT) imaging.

METHODS

Seventeen patients with a mean age of 42 ± 17 years were retrospectively analyzed. Inclusion criteria consisted of PCFD deformity corrected by a medializing calcaneal osteotomy (MCO) as main procedure and imaged by WBCT before and after surgery. Exclusion criteria were patients who had concomitant calcaneal lengthening osteotomies, mid-/hindfoot fusions, hindfoot coalitions, and supramalleolar procedures. Image data were used to generate 3D models and compute the hindfoot (HA), midfoot (MA) - and subtalar joint (STJ) alignment in the coronal, sagittal and axial plane, as well as distance maps.

RESULTS

Pre-operative measurements of the HA and MA improved significantly relative to their post-operative equivalents p < 0.05). The post-operative STJ alignment showed significant inversion (2.8° ± 1.7), abduction (1.5° ± 1.8), and dorsiflexion (2.3° ± 1.7) of the talus relative to the calcaneus (p < 0.05) compared to the pre-operative alignment. The displacement between the talus and calcaneus relative to the sinus tarsi increased significantly (0.6 mm±0.5; p < 0.05).

CONCLUSION

This study detected significant changes in the sagittal, coronal, and axial plane alignment of the subtalar joint, which corresponded to a decompression of the sinus tarsi. These findings contribute to our clinical practice by demonstrating the magnitude of alteration in the subtalar joint alignment that can be expected after PCFD correction with MCO as main procedure.

Supramalleolar Osteotomies in Cavovarus Foot Deformity: Why Patient-Specific Instruments Make a Difference

Supramalleolar osteotomy enables correction of the ankle varus deformity and is associated with improvement of pain and function in the short term and long term. Despite these beneficial results, the amount of surgical correction is challenging to titrate and the procedure remains technically demanding. Most supramalleolar osteotomies are currently planned preoperatively on 2-dimensional weight-bearing radiographs and executed peroperatively using free-hand techniques. This article encompasses 3-dimensional planning and printing techniques based on weight-bearing computed tomography images and patient-specific instruments to correct ankle varus deformities.

The Role Of Minimally Invasive Osteotomies In Cavovarus Foot Reconstruction: Detailed Technique And Evidence For Procedures

Percutaneous correction of cavus foot deformity can be achieved with satisfactory correction of foot anatomy and biomechanics. Surgical management of cavovarus foot reconstruction is an individualized combination of surgical procedures designed to correct deformity. Minimally invasive procedures using high-torque low-speed burr can facilitate large deformity correction without extensive soft tissue stripping. This article presents the operative technique for percutaneous cavus foot correction including a lateralizing calcaneal osteotomy and proximal first ray osteotomy. However, methodologically robust evidence to support this procedure is lacking at present, and further research, particularly, focusing on long-term clinical outcomes and follow-up is required.

Comparison of different fibula procedures in tibiotalocalcaneal arthrodesis with a retrograde intramedullary nail: a mid-term retrospective study

BACKGROUND

Tibiotalocalcaneal (TTC) arthrodesis with a retrograde intramedullary nail for severe tibiotalar and talocalcaneal arthritis has a high fusion rate; however, no studies have focused on how to handle the fibula intraoperatively to achieve better results. This study aimed to compare the efficacies of various fibular procedures.

METHODS

We retrospectively reviewed the cases of severe tibiotalar and talocalcaneal arthritis in adults treated with TTC arthrodesis using a retrograde intramedullary nail between January 2012 and July 2017. The patients were divided into three groups according to different fibular procedures: Fibular osteotomy (FO), fibular strut (FS), and fibular preservation (FP). Functional outcomes and pain were assessed using the American Orthopedic Foot and Ankle Society (AOFAS) ankle and hindfoot score and visual analog scales (VAS), respectively. The operation time, fusion time, radiographic evaluation, and complications were also recorded.

RESULTS

Fifty-eight patients with an average age of 53.2 (range, 32-69) years were enrolled in the final analysis. The numbers of patients enrolled in the three groups were 21, 19, and 18 in the FO, FS, and FP groups, respectively. The mean postoperative follow-up time was 66.0 (range, 60-78) months. All groups showed a high fusion rate (90.5% for FO, 94.7% for FS, and 94.4% for FP) and significant improvement in AOFAS ankle and hindfoot scores and VAS scores at the latest follow-up. There were no significant differences in these parameters among the three groups. The mean operation time of FS (131.3 ± 17.1 min) was longer than that of FO (119.3 ± 11.7 min) and FS (112.2 ± 12.6 min), but the fusion time was shorter (15.1 ± 2.8 weeks for FS, 17.2 ± 1.9 weeks for FO, and 16.8 ± 1.9 weeks for FP). Statistically significant differences were observed in these parameters.

CONCLUSIONS

TTC arthrodesis using a retrograde intramedullary nail is an effective procedure with a high rate of fusion to treat severe tibiotalar and talocalcaneal arthritis in adults; however, FSs can shorten fusion time when compared with FO and FP.

LEVEL OF CLINICAL EVIDENCE

Level 3.

Effect of Peritalar Subluxation Correction for Progressive Collapsing Foot Deformity on Patient-Reported Outcomes

BACKGROUND

Peritalar subluxation (PTS) is part of progressive collapsing foot deformity (PCFD). This study aimed to evaluate initial deformity correction and PTS optimization in PCFD patients with flexible hindfoot deformity undergoing hindfoot joint-sparing surgical procedures and its relationship with improvements in patient-reported outcome measures (PROMs) at latest follow-up. We hypothesized that significant deformity/PTS correction would be observed postoperatively, positively correlating with improved PROMs.

METHODS

A prospective comparative study was performed with 26 flexible PCFD patients undergoing hindfoot joint-sparing reconstructive procedures, mean age 47.1 years (range, 18-77). We assessed weightbearing computed tomography (WBCT) overall deformity (foot and ankle offset [FAO]) and PTS markers (distance and coverage maps) at 3 months, as well as PROMs at final follow-up. A multivariate regression model assessed the influence of initial deformity correction and PTS optimization in patient-reported outcomes.

RESULTS

Mean follow-up was 19.9 months (6-39), and the average number of procedures performed was 4.8 (2-8). FAO improved from 9.4% (8.4-10.9) to 1.9% (1.1-3.6) postoperatively (P < .0001). Mean coverage improved by 69.6% (P = .012), 12.1% (P = .0343) and 5.2% (P = .0074) in, respectively, the anterior, middle, and posterior facets, whereas the sinus tarsi coverage decreased by an average 57.1% (P < .0001) postoperatively. Improvements in patient-reported outcomes were noted for all scores assessed (P < .03). The multivariate regression analysis demonstrated that improvement in both FAO and PTS measurements significantly influenced the assessed PROMs.

CONCLUSION

This study demonstrated significant improvements in the overall 3D deformity, PTS markers, and PROMs following hindfoot joint-sparing surgical treatment in patients with flexible PCFD. More importantly, initial 3D deformity correction and improvement in subtalar joint coverage and extraarticular impingement have been shown to influence PROMs significantly and positively. Addressing these variables should be considered as goals when treating PCFD.

LEVEL OF EVIDENCE

Level II, prospective cohort study.

Application of external torque enhances the detection of subtle syndesmotic ankle instability in a weight-bearing CT

PURPOSE

Acute syndesmotic ankle injuries continue to impose a diagnostic dilemma and it remains unclear whether weightbearing and/or external rotation should be added during the imaging process. Therefore, the aim of this study was to assess if combined weightbearing and external rotation increases the diagnostic sensitivity of syndesmotic ankle instability using weightbearing CT (WBCT) imaging, compared to isolated weightbearing.

METHODS

In this retrospective study, patients with an acute syndesmotic ankle injury were analysed using a WBCT (N = 21; Age = 31.6 ± 14.1 years old). Inclusion criteria were an MRI confirmed syndesmotic ligament injury imaged by a WBCT of the ankle during weightbearing and combined weightbearing-external rotation. Exclusion criteria consisted of fracture associated syndesmotic injuries. Three-dimensional (3D) models were generated from the CT slices. Tibiofibular displacement and talar rotation were quantified using automated 3D measurements (anterior tibiofibular distance (ATFD), Alpha angle, posterior Tibiofibular distance (PTFD) and Talar rotation (TR) angle in comparison to the contralateral non-injured ankle.

RESULTS

The difference in neutral-stressed Alpha angle and ATFD showed a significant difference between patients with a syndesmotic ankle lesion and contralateral control (P = 0.046 and P = 0.039, respectively). The difference in neutral-stressed PTFD and TR angle did not show a significant difference between patients with a syndesmotic ankle lesion and healthy ankles (n.s.).

CONCLUSION

Application of combined weightbearing-external rotation reveals an increased ATFD in patients with syndesmotic ligament injuries. This study provides the first insights based on 3D measurements to support the potential relevance of applying external rotation during WBCT imaging. In clinical practice, this could enhance the current diagnostic accuracy of subtle syndesmotic instability in a non-invasive manner. However, to what extent certain displacement patterns require operative treatment strategies has yet to be determined in future studies.

LEVEL OF EVIDENCE

Level III.

Cone-Beam Weight-Bearing Computed Tomography of Ankle Arthritis and Total Ankle Arthroplasty

Weight-bearing computed tomography has multiple advantages in evaluating the hindfoot and ankle. It can assess hindfoot and ankle alignment, pathology in ankle arthritis, and complications related to total ankle replacements. It is an essential tool in ankle osteoarthritis diagnostic, preoperative planning, and total ankle replacement outcomes. It allows for better accuracy and reproducibility of alignment and implant size. In addition, it has the potential to more assertively detect complications related to weight bearing.

Association between the distal tibiofibular syndesmosis morphology classification and ankle osteoarthritis: a retrospective study

BACKGROUND

Syndesmosis injury is proposed to contribute to ankle stability and osteoarthritis (OA). However, whether distal tibiofibular syndesmosis structure is closely related to ankle OA is unclear. We hypothesized that different DTS morphology classifications would affect the biomechanics properties in ankle OA. The study aimed to determine the association between the distal tibiofibular syndesmosis (DTS) morphological classification and ankle OA.

METHODS

This is a retrospective study examining imaging data of 147 patients (87 males and 60 females) with ankle OA. Magnetic resonance imaging was used to access the DTS morphological classification, according to measuring various parameters. Joint space narrowing and osteophytes were measured using ankle weight-bearing radiography. The classification and parameters were analyzed to determine the relationship between the syndesmosis classification and the abnormality of ankle OA.

RESULTS

Five morphological classifications of the DTS, including Chevron (19.6%), Widow's peak (16.2%), Flat (22.3%), Trapezoid (32.0%), and Crescent (19.6%), were shown. There were statistical differences between DTS classification and tibial angle surface angle (TAS) (P = .009) and talar tilt angle (TTA) (P = .014). The TAS (degree) of the Crescent (86.47 ± 3.21) was less than Chevron (88.75 ± 2.72) (P = .006), Widow's peak (89.26 ± 3.15) (P = .001), Flat (88.83 ± 3.62) (P = .003) and Trapezoid (88.11 ± 2.62) (P = .041), respectively. The TTA (degree) of Crescent (86.83 ± 5.30) was less than Chevron (89.28 ± 2.46) and Widow's peak (89.82 ± 3.41). The men were greater than women for TAS (P = .008) and angle (P = .003), which are consistent with osteophyte (P = .019) and the modified Kellgren-Lawrence grades (P = .041) between gender.

CONCLUSIONS

DTS morphological classification might affect the biomechanics properties in TAS and TTA in ankle OA. In clinical practice, surgeons should pay attention to the effects of DTS on ankle OA.

LEVEL OF EVIDENCE

Level III, retrospective study.

Reliability of Cone Beam Weightbearing Computed Tomography Analysis of Total Ankle Arthroplasty Positioning and Comparison to Weightbearing X-Ray Measurements

BACKGROUND

The current reference standard for postoperative evaluation of total ankle arthroplasty (TAA) positioning, weightbearing radiography (WBXR), is subject to technical bias. Weightbearing cone beam computed tomography (WBCT) enables visualization of the foot's complex 3-dimensional (3D) structure under standing load. To date, no WBCT-based system for TAA positioning has been validated. The purpose of this study was to (1) assess TAA positioning using WBCT 3D models and (2) evaluate the agreement levels between 2 raters and thus evaluate the intermethod reliability with respect to WBXR.

METHODS

Fifty-five consecutive patients were retrospectively reviewed. Two raters independently created a 3D WBCT model using dedicated software and recorded the following measurements: α angle, tibiotalar surface angle (TSA), hindfoot angle (HFA), tibiotalar ratio (TTR), β angle, γ angle, and Φ angle. Measurements were repeated 2 months apart in similar, independent fashion and compared to WBXR. Interobserver, intraobserver, and intermethod agreements were calculated.

RESULTS

All 7 measurements showed good to excellent intraobserver and interobserver reliability (ICC 0.85-0.95). The intermethod (WBCT vs WBXR) agreement showed good agreement for the γ angle (ICC 0.79); moderate agreement levels for the α angle, TSA angle, β angle, and TTR (ICC 0.68, 0.69, 0.70, and 0.69, respectively); poor agreement for the HFA (ICC 0.25); and negative agreement for the φ angle (ICC -0.2).

CONCLUSION

Position analysis of TAA using WBCT demonstrated good to excellent interobserver and intraobserver agreement and can be reliably used. Additionally, a negative to moderate agreement between standard WBCT and standard WBXR was found.

LEVEL OF EVIDENCE

Level III, retrospective study.

Instabilität des oberen Sprunggelenks

Die symptomatische Bandinstabilität des oberen Sprunggelenks (OSG) ist eine häufige Pathologie und bedarf bei gescheiterter konservativer Therapie oft einer operativen Stabilisierung. Neben Anamnese und subjektiver Wahrnehmung des Patienten liefern klinische Untersuchung, funktionelle Diagnostik, Bildgebung und je nach Bedarf die Arthroskopie des Sprunggelenks wichtige Informationen. Meistens benötigt es eine Kombination mehrerer Untersuchungsmethoden, um die Diagnose einer behandlungsbedürftigen OSG-Instabilität zu stellen. Neben der Beurteilung der Stabilität ist ebenfalls die Feststellung von Zusatzpathologien wichtig. Dies beinhaltet auch das Erkennen einer pathologischen Rückfußachse, was essenziell für die weitere Behandlung sein kann. Die operative Therapie kann mittels Arthroskopie oder offener Operation mit weitgehend erfreulichen klinischen Resultaten durchgeführt werden.

Does the slope and length of the plantar calcaneal spur affect the clinic?

Since some of the patients with plantar calcaneal spur (PCS) do not have pain, we aimed to investigate the effect of the slope and length of the spur on this situation. The length and slope of PCS were measured by examining the radiological images of 50 patients in this prospective study. VAS, AOFAS and FFI scores of the patients were determined. Patients were divided into groups according to PCS length and slope. According to the slope of the spur, the mean AOFAS, FFI and VAS scores were, respectively; 94, 38, 1.3 in below 20 degrees; 80.1, 86.8, 4.8 in 20-30 degrees; and 70.1, 106, 6.7 in above 30 degrees. According to the length of the spur, the mean AOFAS, FFI and VAS scores were respectively; 84.9, 68.2, 3.7 in those with length 0-5 mm; 81.1, 81.7, 4.5 in those with a length of 5-10 mm; and 71.7, 102.5, 6.4 in those with a length of >10 mm. A significant correlation was found between the angle and length of the PCS with the values of VAS, AOFAS and FFI (p<0.05). We observed that PCSs with a slope of less than 30 degrees and shorter than 10 mm do not create a serious clinical picture. If there is severe pain and functional impairment in individuals with this characteristic spur, investigation of other possible causes of heel pain must be considered.

Effect of Medial Closing Wedge Distal Femoral Varization Osteotomy on Coronal Ankle and Hindfoot Alignment

BACKGROUND

To date, only a few studies have reported postoperative changes in coronal ankle alignment after valgus knee correction through medial closing wedge distal femoral varization osteotomy (MCWDFO). This study aimed to measure the changes of MCWDFO on coronal ankle and hindfoot alignment.

METHODS

We retrospectively reviewed the radiographic findings of 27 consecutive patients (34 cases) with knee valgus malalignment who underwent MCWDFO for either lateral knee joint osteoarthritis (OA) or recurrent patellar subluxation/dislocation (RPD). Several radiographic parameters were measured and compared based on the reason for operation, followed by the status of preoperative hindfoot alignment (hindfoot alignment angle [HAA] > 4 degrees, varus; -4 degrees ≤HAA ≤ 4 degrees, neutral; HAA < -4 degrees, valgus) in each group.

RESULTS

Overall, pre- and postoperative hindfoot alignments were within the neutral alignment range and were not significantly changed after the operation (P > .05). Nineteen cases were for lateral knee OA and 15 were for RPD, respectively. In both groups, preoperative neutral hindfoot alignments accounted for the largest portion (52.6% in the lateral OA group; 80.0% in the RPD group). Postoperatively, regardless of the reason for operation, hindfoot alignments changed toward the neutral range in all subgroups (ie, no changes in the preoperative neutral group; increased in the valgus group; decreased in the varus group).

CONCLUSION

We recommend that surgeons leave the hindfoot untouched when they plan the MCWDFO to correct knee joint valgus malalignment concomitant with hindfoot valgus or varus deviation as the hindfoot malalignment appears to change toward the neutral range postoperatively.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Correction of ankle varus deformity using patient-specific dome-shaped osteotomy guides designed on weight-bearing CT: a pilot study

BACKGROUND

Dome-shaped supramalleolar osteotomies are a well-established treatment option for correcting ankle deformity. However, the procedure remains technically demanding and is limited by a two-dimensional (2D) radiographic planning of a three-dimensional (3D) deformity. Therefore, we implemented a weight-bearing CT (WBCT) to plan a 3D deformity correction using patient-specific guides.

METHODS

A 3D-guided dome-shaped supramalleolar osteotomy was performed to correct ankle varus deformity in a case series of five patients with a mean age of 53.8 years (range 47-58). WBCT images were obtained to generate 3D models, which enabled a deformity correction using patient-specific guides. These technical steps are outlined and associated with a retrospective analysis of the clinical outcome using the EFAS score, Foot and Ankle Outcome Score (FAOS) and visual analog pain scale (VAS). Radiographic assessment was performed using the tibial anterior surface angle (TAS), tibiotalar angle (TTS), talar tilt angle (TTA), hindfoot angle (HA), tibial lateral surface angle (TLS) and tibial rotation angle (TRA).

RESULTS

The mean follow-up was 40.8 months (range 8-65) and all patients showed improvements in the EFAS score, FAOS and VAS (p < 0.05). A 3-month postoperative WBCT confirmed healing of the osteotomy site and radiographic improvement of the TAS, TTS and HA (p < 0.05), but the TTA and TRA did not change significantly (p > 0.05).

CONCLUSION

Dome-shaped supramalleolar osteotomies using 3D-printed guides designed on WBCT are a valuable option in correcting ankle varus deformity and have the potential to mitigate the technical drawbacks of free-hand osteotomies.

LEVEL OF EVIDENCE

Level 5 case series.

What is the best treatment for syndesmosis fixation? Suture-button or syndesmotic screw ? Bilateral CT-based early postoperative analysis

BACKGROUND

The aim of this study was to compare the effectiveness of syndesmotic screw (SS) and suture button (SB) on the reduction and fixation of syndesmosis via early postoperative bilateral computed tomography (CT).

METHODS

This single-center retrospective study included 76 patients aged ≥ 18 years with a unilateral syndesmosis injury. SS was applied to 40 patients and SB to 36 patients. The differences between the sides stabilized using SB or SS and the intact sides were analyzed using the parameters of tibio-fibular clear space (∆CS) and anterior or posterior sagittal translation (∆ST) depending on the orientation of the fibula. The cases in which the fibula was translocated to the posterior of the tibia after the change of ∆ST and ∆CS> 2 mm were evaluated as malreduction. Axial CT images taken from the level of syndesmosis fixation were divided into 4 zones according to the orientation angle of the implant sent from the fibula to the tibia.

RESULTS

No significant difference was found in the analyses performed between total patient group with malreduction and fixation groups in terms of ∆CS and ∆ST values (p = 0.708, p = 0.289). It was observed that the fixation material was in zone 3 in 54 patients and in zone 2 in 22 patients. No significant difference was found in the analyses performed between the SS and SB groups according to the implant zone (p = 0.191). In the SS group sent from Zone 2, the malreduction rate according to the ∆ST value of syndesmosis was found to be significantly higher than in the SB group (p = 0.008, p = 0.003).

CONCLUSION

When the implant is applied with the correct technique, there is no difference between SS and SB in terms of early postoperative reduction. When the SS is advanced at an inappropriate angle, it negatively affects the reduction of the fibula, while SB can better tolerate angle errors up to certain degrees due to its flexible structure. Therefore, it can be presumed that the suture button system is a more convenient method in the reduction and fixation of syndesmosis than the syndesmotic screw.

LEVEL OF EVIDENCE

Level IV.

Operative outcomes of a high-grade talar neck fracture - Lessons from 20 years' clinical experience in a single, tertiary hospital

BACKGROUND

The operative treatment of high-grade talar neck fractures remains challenging, despite numerous previous reports. Our goal was to determine long-term outcomes and to establish a plan for management of postoperative complications (especially, avascular necrosis [AVN] of talar body) after high-grade talar neck fractures. We hypothesized that not every case with AVN of talar body require secondary surgical interventions.

METHODS

We retrospectively reviewed the radiographic and clinical findings of 14 patients who underwent operative treatment for high-grade talar neck fractures (modified Hawkins type III and IV) between January 2000 and December 2017. The minimum follow-up duration for inclusion was 3 years. Using radiographs during follow-up, we assessed the development of AVN of the talar body, malunion, nonunion, and posttraumatic osteoarthritis. Information about the secondary operations and their outcomes were also investigated using visual analogue scale (VAS) and American orthopaedic foot and ankle society (AOFAS) ankle-hindfoot scale at the final follow-up.

RESULTS

In 10 of 14 patients (71.4 %), talar body AVN developed during follow-up. However, secondary operation was required in only 30.0 % (3 of 10 patients). In the remaining 7 patients who did not undergo secondary operation, the symptoms were tolerable with a maximum of 89 months follow-up; although the talar body presented sclerotic changes, but without talar dome collapse. The rates of malunion and post-traumatic subtalar osteoarthritis were 21.4 % and 14.3 %, respectively. No patients presented with fracture site nonunion. After a mean of 55.86 ± 14.45 months (range, 37-89) follow-up, the final mean VAS and AOFAS scores were 3.07 ± 0.73 (range, 2-4) and 80.43 ± 3.11 (range, 75-85), respectively.

CONCLUSION

We recommend leaving talar body AVN untouched, unless the patient's symptoms become intolerable. In our clinical practice, postoperative AVN could be stably maintained without talar dome collapse for more than 7 years, although the sclerotic change persisted. Despite the small number of patients, our clinical experience may benefit patients with high-grade talar neck fractures and surgeons who treat such rare, serious, and challenging foot injuries.

LEVEL OF EVIDENCE

Level IV, Case series.

Semi-automated 3-dimensional analysis of the normal foot and ankle using weight bearing CT - A report of normal values and bony relationships

BACKGROUND

Foot and ankle deformities have translational and rotational components in multiple planes, at multiple levels. Semi-automatic segmentation is a relatively new technology, which when used with weight-bearing CT (WBCT), can build an accurate model of the foot and calculate the orientation and relationships of bones under physiological load. However, few papers report reference values using these techniques. We report normative values for key bony relationships based on semi-automated analysis of WBCT.

METHODS

This was a single-centre, retrospective analysis of 100 feet without deformity from 55 adult patients undergoing WBCT as part of routine clinical activity (mean age 40.5 ± 17.3 years). Imaging was analysed using Bonelogic 2.1 (DISIOR, Finland). Semi-automatic segmentation was used to compute the various bony axes in 3-dimensional space. Selected coronal, axial and sagittal plane relationships were then calculated for bones of the hindfoot, midfoot and forefoot.

RESULTS

Data is presented on axial and sagittal plane relationships between the metatarsals in the forefoot, and the metatarsals and cuneiforms in the midfoot. In the hindfoot, the calcaneal pitch, talar-first-metatarsal angles, talonavicular coverage angles and Saltzman angles are reported. Coronal plane axes and their relationships are reported at multiple levels from hindfoot to forefoot. Results are presented as mean values with standard deviations and 95% confidence intervals.

CONCLUSIONS

We present an observational analysis of the normal values from non-deformed feet. We highlight the major relationships in the axial, sagittal and coronal planes as obtained by semi-automated analysis of WBCT. This data may serve as a reference for future research.

LEVEL OF EVIDENCE

Basic science study.

The Use of Advanced Semiautomated Bone Segmentation in Hallux Rigidus

Background:

Weightbearing computed tomography (WBCT) measurements allow evaluation of several anatomical points for a correct clinical-radiographic diagnosis of pathologies, such as hallux rigidus (HR). In addition, a new semiautomatic segmentation software obtains automated 3D measurements from WBCT scan data sets, minimizing errors in reading angular measurements. The study’s objective was (1) to evaluate the reliability of WBCT semiautomatic imaging measures in HR, (2) to evaluate correlation and agreement between manual and semiautomatic measures in the setting of HR, and (3) to compare semiautomatic measurements between pathologic (HR) and standard control groups.

Methods:

A retrospective study of HR patients was performed including 20 feet with HR. WBCT manual and semiautomatic 3D measurements were performed using the following parameters: (1) first metatarsal-proximal phalanx angle (1stMPP), (2) hallux valgus angle (HVA), (3) first to second intermetatarsal angle (IMA), (4) hallux interphalangeal angle (IPA), (5) first metatarsal length (1stML), (6) second metatarsal length (2ndML), (7) first metatarsal declination angle (1stMD), (8) second metatarsal declination angles (2ndMD), and (9) metatarsus primus elevatus (MPE). The differences between pathologic and control cases were assessed with a Wilcoxon test.

Results:

Interobserver and intraobserver agreement for manual vs semiautomatic WBCT measurements demonstrated excellent reliability. According to the Pearson coefficient, there was a strong positive linear correlation between both methods for the following parameters evaluated: HVA (ρ = 0.96), IMA (ρ = 0.86), IPA (ρ = 0.89), 1stML (ρ = 0.96), 2ndML (ρ = 0.91), 1stMD (ρ = 0.86), 2ndMD (ρ = 0.95), and MPE (ρ = 0.87). Comparison between the pathologic group with HR and the control (standard) group allowed for the differentiating of the pathologic (HR) from the non-pathologic conditions for MPE (p < 0.05).

Conclusion:

Semiautomatic measurements are reproducible and comparable to measurements performed manually, showing excellent interobserver and intraobserver agreement. The software used differentiated pathologic from nonpathologic conditions when submitted to semiautomatic MPE measurements.

Level of Evidence:

Level III, retrospective comparative study.

Weight-bearing cone-beam CT: the need for standardised acquisition protocols and measurements to fulfill high expectations-a review of the literature

Weight bearing CT (WBCT) of the lower extremity is gaining momentum in evaluation of the foot/ankle and knee. A growing number of international studies use WBCT, which is promising for improving our understanding of anatomy and biomechanics during natural loading of the lower extremity. However, we believe there is risk of excessive enthusiasm for WBCT leading to premature application of the technique, before sufficiently robust protocols are in place e.g. standardised limb positioning and imaging planes, choice of anatomical landmarks and image slices used for individual measurements. Lack of standardisation could limit benefits from introducing WBCT in research and clinical practice because useful imaging information could become obscured. Measurements of bones and joints on WBCT are influenced by joint positioning and magnitude of loading, factors that need to be considered within a 3-D coordinate system. A proportion of WBCT studies examine inter- and intraobserver reproducibility for different radiological measurements in the knee or foot with reproducibility generally reported to be high. However, investigations of test-retest reproducibility are still lacking. Thus, the current ability to evaluate, e.g. the effects of surgery or structural disease progression, is questionable. This paper presents an overview of the relevant literature on WBCT in the lower extremity with an emphasis on factors that may affect measurement reproducibility in the foot/ankle and knee. We discuss the caveats of performing WBCT without consensus on imaging procedures and measurements.

Operative strategy for tri-malleolar ankle fractures with posteromedial plafond involvement: a review of sixty six cases

PURPOSE

We aimed to summarize the radiographic and clinical outcomes in various conditions of tri-malleolar ankle fractures (TMFs) with posteromedial (PM) plafond involvement (TMF + PM) and determine the factors affecting their subjective clinical outcomes.

METHODS

Radiographic and clinical findings of 66 patients who underwent operative treatment for TMF + PM were retrospectively reviewed. The patients were classified into three groups according to the PM fracture line location. Type I fractures were defined when the PM fracture line extended medially beyond the PM corner of the distal tibia while type II fractures were those in which the PM fracture line was located laterally to the PM corner. Type III fractures were defined as medial malleolar avulsion fractures when the PM fracture integrated into the medial malleolus. Clinical outcomes were evaluated using a subjective rating scale (excellent, good, fair, poor, and bad). Satisfactory results were defined as excellent, good, and fair. Factors affecting satisfactory clinical outcomes were assessed using a binary logistic regression analysis. Independent variables included demographic, fracture-related, and operation-related factors and radiographic measurements at the final follow-up.

RESULTS

Satisfactory clinical outcomes were observed in 74.2% of the total patients; of these patients, 75.7% (28/37), 76.5% (13/17), and 66.7% (8/12) had type I, type II, and type III fractures, respectively. The binary logistic regression analysis revealed that age at the time of operation, number of incarcerated fragments (IFs), type of IFs, and postoperative articular step-offs (mm) were related to subjective clinical outcomes (all P < 0.05). A positive value for post-operative articular step-offs represented distal migration of the posterior malleolar fragments. The odds ratios for older age, increased numbers of IFs, rotated IFs, and positive articular step-offs were 0.936, 0.116, 0.020, and 0.295, respectively.

CONCLUSION

Because TMF + PM is highly unstable, a delicate approach is needed according to each patient's fracture condition. Although it is best to reduce the fractured articular surface, a negative step-off, rather than a positive step-off, would be more likely recommended if accurate reduction is impossible. This could be applied to manage IFs, especially when the IFs are rotated. Dimpling of the articular surface induced by the removal of a small IF was not related to unsatisfactory clinical outcomes.

Does tibialis posterior dysfunction correlate with a worse radiographic overall alignment in progressive collapsing foot deformity? A retrospective study

BACKGROUND

Posterior Tibial Tendon (PTT) dysfunction is considered to have an important role in Progressive Collapsing Foot Deformity (PCFD). The objective of our study was to assess the relationship between PTT status and three-dimensional foot deformity in PCFD.

METHODS

Records from 25 patients with PCFD were included for analysis. The PTT was considered deficient in patients with a positive single heel rise test or a deficit in inversion strength. Three-dimensional foot deformity was assessed using the Foot and Ankle Offset (FAO) from Weight-Bearing-CT imaging. Hindfoot valgus, midfoot abduction and medial longitudinal arch collapse were assessed on X-Rays using hindfoot moment arm, talonavicular coverage angle and Meary's angle respectively. Deland and Rosenberg MRI classifications were used to classify PTT degeneration.

RESULTS

PCFD with PTT deficit (13/25) had a mean FAO of 7.75 + /- 3.8% whereas PCFD without PTT deficit had a mean FAO of 6.68 + /- 3.9% (p = 0.49). No significant difference was found between these groups on the hindfoot moment arm and the talonavicular coverage angle (respectively p = 0.54 and 0.32), whereas the Meary's angle was significantly higher in case of PCFD with PTT deficit (p = 0.037). No significant association was found between PTT degeneration on MRI and FAO.

CONCLUSION

PCFD associated three-dimensional deformity, hindfoot valgus and midfoot abduction were not associated with PTT dysfunction. PTT dysfunction was only associated with a worse medial longitudinal arch collapse in our study. Considering our results, it does not appear that PTT is the main contributor to PCFD.

LEVEL OF EVIDENCE

Level III, Retrospective Comparative Study.

Supramalleolar Osteotomy for Ankle Varus Deformity Alters Subtalar Joint Alignment

BACKGROUND

Although correction of ankle and hindfoot deformity after supramalleolar osteotomy has been investigated extensively, the specific effect on the subtalar joint alignment remains elusive. This can be attributed to the limitations of 2-dimensional measurements, which impede an exact quantification of the 3-dimensional subtalar joint alignment. Therefore, we determined both the ankle, hindfoot, and subtalar joint alignment before and after supramalleolar osteotomy using autogenerated 3-dimensional measurements based on weightbearing CT imaging.

METHODS

Twenty-nine patients with a mean age of 50.4±10.6 years were retrospectively analyzed in a pre-post study design using weightbearing CT. Inclusion criteria were correction of ankle varus deformity by an opening wedge (n = 22) or dome osteotomy (n = 7). Exclusion criteria consisted of an additional inframalleolar arthrodesis or osteotomy. Corresponding 3-dimensional bone models were reconstructed to compute following autogenerated measurements of the ankle- and hindfoot alignment: tibial anterior surface (TAS), tibiotalar surface (TTS), talar tilt (TT) angle, hindfoot angle (HA). In addition, the talocalcaneal angle (TCA) in the axial (TCA_ax), sagittal (TCA_sag), and coronal (TCA_cor) plane were measured to assess the subtalar joint alignment.

RESULTS

The preoperative radiographic parameters of the ankle joint alignment (TAS=88±4 degrees, TTS=82±7 degrees, TT=5.8±4.9 degrees) improved significantly relative to their postoperative equivalents (TAS = 93±5 degrees, TTS = 88±7 degrees, TT=4.2±4.5 degrees; P < .05). The following radiographic parameters of the hindfoot and subtalar joint alignment improved significantly from preoperatively (8.7±8.9 degrees, TCA_ax = 41±10 degrees, TCA_sag = 48±10 degrees) to postoperatively (HA=4.5±8.6 degrees, TCA_ax = 38±9 degrees, TCA_sag = 44±11 degrees; P < .05). No significant differences could be detected in the coronal plane alignment of the subtalar joint (TCA_cor) pre- compared to postoperatively (P > .05).

CONCLUSION

This study quantified the 3-dimensional ankle, hindfoot, and subtalar joint alignment after a solitary supramalleolar osteotomy. We found alterations in the subtalar joint alignment, which occurred by 2 to 3 degrees in each anatomic plane. However, before recommendations can be given related to inframalleolar procedures in conjunction to supramalleolar osteotomies, further studies on the variation of subtalar joint alignment change are needed.

2D Manual vs 3D Automated Assessment of Alignment in Normal and Charcot-Marie-Tooth Cavovarus Feet Using Weightbearing CT

BACKGROUND

The complex deformities in cavovarus feet may be difficult to assess and understand. Weightbearing computed tomography (WBCT) is increasingly used in evaluating complex deformities. However, the bone axes may be difficult to calculate in the setting of severe deformity. Computer-assisted 3D axis calculation is a novel approach that may allow for more accurate assessment of foot alignment or deformity. This study aimed to assess differences in measurements done manually on 2D slices of WBCT vs 3D computer models in normal and cavus feet.

METHODS

We retrospectively analyzed WBCT scans from 16 normal and 16 cavus feet in patients with Charcot-Marie-Tooth disease. Six measurements were assessed: talar-first metatarsal angle (axial plane), forefoot arch angle (coronal plane), and Meary angle, calcaneal pitch, and cuneiform and navicular to floor distances (sagittal plane). 2D measurements were performed manually and 3D measurements were performed using specialized software (Bonelogic, DISIOR). Bland-Altman plots and linear regression were used to analyze differences.

RESULTS

There were no significant biases in measured variables in normal feet. In the cavovarus group, automated assessment calculated increased sagittal plane deformity (fixed bias 7.31 degrees for Meary angle, 2.39 degrees for calcaneal pitch) and less axial plane deformity (fixed bias 10.61 degrees for axial talar-first metatarsal angle). The latter also demonstrated proportional bias indicating greater discrepancy with increasing adduction.

CONCLUSION

Measurements were comparable in normal feet suggesting automated techniques can reliably assess the alignment of bony axes. However, automated calculations show greater sagittal and less axial deformity in cavovarus feet than measured by manual techniques. This discrepancy may relate to rotational deformity seen in cavovarus feet, which may not be easily assessed manually. 3D automated measurements may therefore play a role in better assessing and classifying the cavovarus foot, which may ultimately inform treatment algorithms.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Effect of weightbearing and foot positioning on 3D distal tibiofibular joint parameters

The aim of this study was to investigate the effect of different loading scenarios and foot positions on the configuration of the distal tibiofibular joint (DTFJ). Fourteen paired human cadaveric lower legs were mounted in a loading frame. Computed tomography scans were obtained in unloaded state (75 N) and single-leg loaded stand (700 N) of each specimen in five foot positions: neutral, 15° external rotation, 15° internal rotation, 20° dorsiflexion, and 20° plantarflexion. An automated three-dimensional measurement protocol was used to assess clear space (diastasis), translational angle (rotation), and vertical offset (fibular shortening) in each foot position and loading condition. Foot positioning had a significant effect on DTFJ configuration. Largest effects were related to clear space increase by 0.46 mm (SD 0.21 mm) in loaded dorsal flexion and translation angle of 2.36° (SD 1.03°) in loaded external rotation, both versus loaded neutral position. Loading had no effect on clear space and vertical offset in any position. Translation angle was significantly influenced under loading by - 0.81° (SD 0.69°) in internal rotation only. Foot positioning noticeably influences the measurements when evaluating DTFJ configuration. Loading seems to have no relevant effect on native ankles in neutral position.

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.