Subtalar joint alignment in ankle osteoarthritis

Does the Sagittal Radiographic Morphology of Subtalar Joint Affect the Alignment of Foot?

OBJECTIVES

The etiology of flatfoot and cavus foot is multicausal and controversial. So far, no literature reports the relationship between the sagittal morphology of subtalar joint and the alignment of foot. The purpose of this study was to explore whether the subtalar alignment would influence the configuration of foot.

METHODS

From January 2017 to January 2020, we included 109 feet in the flatfoot group, 95 feet in the cavus group, and 104 feet in the control group in this retrospective comparative study. The Gissane angle and calcaneal posterior articular surface inclination angle represented the sagittal morphology of the subtalar joint. Meary's angle, calcaneal pitch angle, and talar pitch angle reflected the alignment of foot. They were measured in the weightbearing foot X-rays. The angles in different groups were compared via Mann-Whitney U test. We calculated the correlation between the sagittal alignment of subtalar joint and the alignment of foot using Spearman's correlation analysis. Interobserver and intraobserver reliability were calculated.

RESULTS

The Gissane angle, calcaneal posterior articular surface inclination angle, Meary's angle, talar pitch angle, and calcaneal pitch angle were significantly different in the three groups. The Gissane angle had an excellent correlation with the Meary's angle (r = 0.850, p < 0.0001), and the talar pitch angle (r = -0.825, p < 0.0001), and a good correlation with the calcaneal pitch angle (r = 0.638, p < 0.0001). The calcaneal posterior articular surface inclination angle had an excellent correlation with the Meary's angle (r = -0.902, p < 0.001), and the talar pitch angle (r = 0.887, p < 0.0001), and a good correlation with the calcaneal pitch angle (r = -0.702, p < 0.0001). The interobserver and intraobserver reliability for all radiographic measurements was good to excellent.

CONCLUSION

A subtalar joint with a larger Gissane angle and a more horizontal calcaneal posterior articular surface angle tended to have a higher foot arch and vice versa. The inspiration from this study was that the deformities of flatfoot and cavus foot may relate to the subtalar deformity.

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.

CT in osteoarthritis: its clinical role and recent advances

Computed tomography (CT) is a widely available imaging method and considered as one of the most reliable techniques in bone assessment. Although CT has limited tissue contrast and needs radiation exposure, it has several advantages like fast scanning time and high spatial resolution. In this regard, CT has unique roles in osteoarthritis (OA) and its variable utilities have been reported. Hence, this review highlights the clinical role of CT in OA of representative joints. In addition, CT showed the several technical advancements recently, for example, acquiring the CT image with standing, obtaining the dual-energy data, and novel photon-counting detector development. Therefore, the recent studies and potential utility of these new CT systems in OA are also discussed.

Decreased Peritalar Subluxation in Progressive Collapsing Foot Deformity with Ankle Valgus Tilting

Background

Middle facet subluxation (MFS) has been established as an early indicator of peritalar subluxation. However, when progressive collapsing foot deformity (PCFD) affects the ankle leading to a valgus talar tilt (Class E), structures and anatomic relationships distal to the ankle joint may be affected. Therefore, this study aimed to assess radiographic parameters of peritalar subluxation in patients with PCFD who either did or did not have a valgus ankle. Our hypothesis was that these parameters would differ in Class E patients, upsetting their capability to quantify deformity.

Methods

We performed a prospective comparative study utilizing weight-bearing computed tomography (WBCT) images of 21 feet with PCFD and with valgus of the ankle and 64 with flexible PCFD without ankle involvement. Parameters including MFS, the medial cuneiform-to-floor distance, the forefoot arch angle, the talonavicular coverage angle, the hindfoot moment arm (HMA), the foot-ankle offset (FAO), and the talar tilt angle (TTA) were measured and compared. Variables that influence the presence of ankle valgus and overall alignment were assessed by multivariable regression models.

Results

Patients with PCFD and ankle valgus demonstrated a higher mean HMA (20.79 mm [95% confidence interval (CI), 17.56 to 24.02 mm] versus 8.94 mm [95% CI, 7.09 to 10.79 mm]), FAO (14.89% [95% CI, 12.51% to 17.26%] versus 6.32% [95% CI, 4.96% to 7.68%]) and TTA (95% CI, 17.10° [14.75° to 19.46°] versus 2.30° [95% CI, 0.94° to 3.65°]) and lower mean MFS (21.84% [95% CI, 15.04% to 28.63%] versus 38.45% [95% CI, 34.55% to 42.34%]) compared with the group without ankle valgus (p < 0.0001 for all). The FAO was influenced by MFS in the group without ankle valgus (p <0.0001) but not in the group with ankle valgus (p = 0.9161). FAO values of ≥12.14% were a strong predictor (79.2%) of ankle valgus deformity.

Conclusions

Subluxation of the middle facet was not as severe and did not influence the overall alignment in patients with PCFD who had valgus of the ankle (Class E). These findings suggest a distal peritalar reduction in the presence of a proximal deformity, making MFS an imprecise disease parameter in this scenario. An FAO value of ≥12.14% was a strong indicator of ankle deformity in patients with PCFD.

Level of Evidence

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

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.

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.

Changes in the subtalar joint alignment after supramalleolar osteotomy for varus ankle arthritis

BACKGROUND

The subtalar joint may compensate for tibio-talar deformity, but what would happen to the joint after the deformity was corrected is not well known. Supramalleolar osteotomy (SMOT) is an effective procedure for the treatment of varus deformity of ankle arthritis. The objective of this study was to investigate the subtalar joint alignment pre and postoperatively following SMOT, and the factors which influenced the alignment of the subtalar joint.

METHODS

Thirty-one patients with varus ankle arthritis (Takakura stage 2, 3a and 3b) who were treated using SMOT were retrospectively reviewed. The subtalar and ankle joint alignment was measured on weightbearing radiograph and weightbearing computerized tomography (WBCT).

RESULTS

The foot and ankle offset (FAO), tibial articular surface angle (TAS), tibio-talar surface angle (TTS), and subtalar vertical angle (SVA) were significantly corrected (P＜0.05). The subtalar inclination angle (SIA) decreased in 19 patients and increased in the other 12 cases after the SMOT (P＜0.001). The shift of subtalar joint (ΔSIA) showed an inverse correlation with the preoperative FAO (P＜0.001, r = -0.621).

CONCLUSIONS

The shift of subtalar joint after SMOT could maintain the neutral position of the hindfoot and showed a negative correlation with the preoperative FAO. The ΔSIA was greater in the severer preoperative hindfoot deformity.

LEVEL OF EVIDENCE

Level IV, case series.

Effect of total ankle replacement on the 3-dimensional subtalar joint alignment in varus ankle osteoarthritis

BACKGROUND

Varus ankle osteoarthritis (OA) is typically associated with peritalar instability, which may result in altered subtalar joint position. This study aimed to determine the extent to which total ankle replacement (TAR) in varus ankle OA can restore the subtalar alignment.

METHODS

Fourteen patients (15 ankles, mean age 61 ± 6 years) who underwent TAR for varus ankle OA were analyzed using semi-automated measurements based on weight-bearing computed tomography. Twenty healthy individuals served as a control group.

RESULTS

All angles improved between preoperative and a minimum of 1 year (mean 2.1 years) postoperative and were statistically significant in 6 out of 8 angles (P < 0.05).

CONCLUSIONS

Our findings indicate that talus repositioning after TAR restores the subtalar joint alignment which may improve hindfoot biomechanics. Future studies are required to implement these findings for TAR in presence of hindfoot deformity.

LEVEL OF EVIDENCE

IV.

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.

Three-dimensional ankle, subtalar, and hindfoot alignment of the normal, weightbearing hindfoot, in bilateral posture

The first goal of this study was to develop reliable three-dimensional definitions of alignment for the ankle, subtalar, and hindfoot joints. These alignments are based on three-dimensional morphological features derived from renderings of the bones obtained from weightbearing computer tomography. The second goal was to establish a database quantifying the alignment of the ankle, subtalar, and hindfoot joints in a healthy population during weightbearing bilateral standing. This level 1 study was performed on 95 normal subjects in which random subjects were recruited into a control group. Weightbearing computed tomography scans of the leg were collected in neutral, bilateral, standing posture. In 30 of the subjects, both the left and right leg was scanned. Six alignment parameters for each joint were calculated from morphological measurements conducted on three-dimensional renderings of the bones. Intra- and intertester reliability was assessed from repeated measurements by several testers. Analysis of variance statistics of the alignment parameters showed no statistical differences due to age, gender, or foot side. Intraclass correlation coefficient analysis showed excellent inter- and intratester reliability. It was concluded that the alignment process is comprehensive and reliable. Therefore, without classification by gender or age, it may be used as a foundation for quantifying abnormal alignment associated with various ankle deformities. Clinical significance: The alignment methodology and control database may be used to diagnose ankle, subtalar, and hindfoot misalignment. It can also serve as basis for surgical planning designed to restore normal alignment in various hindfoot pathologies, such as ankle realignment in total ankle replacement.

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.

Coronal plane Calcaneal-Talar Orientation in Varus Ankle Osteoarthritis

BACKGROUND

We do not yet fully understand how the subtalar joint position is related to the varus osteoarthritic ankle joint. The purposes of this study were (1) to investigate the coronal orientation of the calcaneus relative to the talus according to the ankle osteoarthritis stage, talar tilt (TT), and (2) to determine if there is TT threshold at which apparent subtalar compensation begins to fade.

METHODS

We retrospectively reviewed 132 ankles that underwent weightbearing computed tomography (WBCT) for varus ankle osteoarthritis. The TT, subtalar inclination angle (SIA), and calcaneal inclination angle (CIA) were measured using WBCT. Ankles were divided into 5 groups according to Takakura stage and 2 groups according to the apparent compensation status of the subtalar joint and compared the index of the inclination of the subtalar joint relative to the ankle (SIA) or the index of the inclination of the calcaneus relative to the ankle (CIA). Additionally, we explored the relationship between SIA or CIA and the TT.

RESULTS

Apparent subtalar compensation (SIA and CIA) was significantly lower in Takakura stages 3b and 4. The SIA and CIA significantly differed according to the apparent compensation status (P < .001 and P = .030, respectively). The CIA of the noncompensated group varied widely, whereas the SIA was relatively constant. Furthermore, TT was greater than 9.5, which indicated a high probability of a noncompensated heel (sensitivity, 92.6%; specificity, 89.7%).

CONCLUSION

The position of the calcaneus appears compensatory with coronal plane orientation in varus ankle osteoarthritis when the TT is ≤9.5 degrees.

LEVEL OF EVIDENCE

Level IV, case series.

Characteristic Bone Morphology Change of the Subtalar Joint in Severe Varus Ankle Osteoarthritis

The subtalar joint has a possible compensatory mechanism for supramalleolar deformities; the failure of this mechanism causes the progression of ankle osteoarthritis. However, the reason for this failure has not been fully elucidated. This study aimed to evaluate the characteristics of the morphologic changes in the subtalar joint in varus ankle osteoarthritis using computed tomography. The study included 30 patients with severe osteoarthritis (modified Kellgren-Lawrence classification grade ≥ 3; mean age: 68.5 years) and 30 patients without- or with early osteoarthritis (grade 0-1; mean age: 43.0 years) as the control group. The location of cysts, osteophyte formation in the subtalar joint, and thickness of the subchondral bone plate were evaluated. In the osteoarthritis group, cyst formation was observed on the posterolateral side of the posterior facet of the calcaneus in 6 cases (20%) and of the talus in 7 cases (23.3%). Osteophyte formation was observed in the talus in 21 cases (70.0%) and in the calcaneus in 29 cases (96.6%). Osteophyte formation was observed on the posterior or lateral side of the posterior facet, and osteophyte contact between the talus and calcaneus was observed. The subchondral bone plate of the posterior medial side of the posterior facet of the talus was significantly thicker in the osteoarthritis group. The subtalar joint is less affected in severe varus ankle osteoarthritis containing a thickened subchondral bone plate in the posteromedial aspect of the posterior talar facet.

Superiority of upper ankle arthrodesis over total ankle replacement in the treatment of end-stage posttraumatic ankle arthrosis

PURPOSE

Surgical treatment of end-stage posttraumatic upper ankle arthrosis is challenging. Highly variable revision rates have been reported with total ankle arthroplasty (TAA) of the upper ankle joint. The aim of this retrospective study was to compare revision rates with tibiotalar arthrodesis (TTA) and TAA with a prosthesis to determine the superior treatment approach.

METHODS

Data for 148 patients (96 males and 52 females) with end-stage posttraumatic upper ankle arthrosis-including 88 treated with TTA and 60 with TAA between 2008 and 2013, with a mean follow-up of 59 months-were analysed. Bone fusion was confirmed by x-ray radiography and computed tomography.

RESULTS

The overall revision rate was 28%; the rate was higher with TAA (42%) than with TTA (18%). The TAA group showed an increase in revisions from 12- to 24-month postsurgery. The most common cause of revision in the TAA group was cysts (20%), and the most frequent reason for revision was nonunion (8%). Mean American Orthopaedic Foot and Ankle Society (AOFAS) and Foot and Ankle Outcome (FAO) scores in all patients were 55.5 and 53.1, respectively, with no significant difference between the TTA and TAA groups (p > 0.05). In nine cases (15%) the prosthesis was explanted or converted to TTA. TAA patients who underwent conversion to TTA had worse outcomes (AOFAS score = 39; FAO score = 35.29).

CONCLUSION

TAA is associated with a high rate of revisions, especially from the 2nd year postsurgery. Therefore, TTA is the treatment of choice for end-stage posttraumatic upper ankle arthrosis. Level of evidence Level III, comparative series.

Joint Preservation for Posttraumatic Ankle Arthritis After Tibial Plafond Fracture

Management of posttraumatic ankle arthritis due to tibial plafond fracture is technically demanding. The distal tibial plafond-plasty could be an alternative to preserve the ankle joint for young patients with limited ankle arthritis. The surgical principles are to realign the mechanical axis, reconstruct the articular surface of the distal tibial plafond, and achieve a congruent and stable ankle joint. In addition to the anteroposterior view of the ankle joint, the lateral view was also paramount for surgeons to fully evaluate the reduction quality. The revision procedures are as follows: osteotomy for exposure, articular surface reconstruction, bone grafting, and osteotomy fixation.

The Assessment of Ankle Osteoarthritis with Weight-Bearing Computed Tomography

The standard for diagnostic radiographic imaging in foot and ankle surgery was until 2012 radiographs with full weight-bearing without any useful alternative. Weight-bearing cone-beam computed tomography (WBCT) was introduced 2012 for foot and ankle use as a new technology that allows 3D imaging with full weight-bearing which should be not influenced by projection and/or foot orientation. The assessment of ankle osteoarthritis with WBCT including the description of healthy status, effect of alignment and7or (in)stability is extensively illustrated in this review article.

Joint Preservation Surgery for Varus and Posterior Ankle Arthritis Associated with Flatfoot Deformity

This article introduces novel types of ankle arthritis related to a flatfoot deformity. There has been a long-held belief that severe unmanaged flatfoot deformity leads to valgus ankle arthritis, due to deltoid ligament insufficiency. However, flatfoot deformity can also give rise to varus ankle arthritis as the talus and calcaneus subluxate into opposite directions. Plantarflexion and posterior translation of the talus in the sagittal plane contributes to the eccentric narrowing of the posterior aspect of the tibiotalar joint, which the authors termed posterior ankle arthritis. Subtalar arthrodesis was performed to address the opposing dynamics of the talus and calcaneus, and was combined with a medial longitudinal arch reconstruction in most cases of posterior ankle arthritis and in selected cases of varus ankle arthritis, and satisfactory clinical and radiological results were achieved.

Comparison of Radiological and Clinical Outcomes in Patients Treated with Standard Plating versus Intramedullary Nailing in Distal Tibial Fracture

Objective

To evaluate clinical and radiological outcomes including hindfoot alignment after plate vs intramedullary nailing (IMN) for distal tibia fracture and to define radiologic parameters that influence changes in hindfoot alignment.

Methods

Among 92 patients with distal tibia metaphyseal fractures treated from 2002 to 2015, 39 cases of intramedullary nailing and 53 cases of standard plate osteosynthesis were performed. Union rate and complication rate were compared in both groups. Radiographic measurements including hindfoot angulation, moment arm, calcaneal pitch angle, and Meary angle were evaluated at a minimum of 1‐year follow‐up. Hindfoot alignment changes after surgery were compared between both groups using student t‐test. Correlation and regression were analyzed between fracture alignment parameters and hindfoot alignment.

Results

All patients ultimately healed, with an average union period of 26 weeks in both groups. The AOFAS and VAS scores were not significantly different between the two groups. Complications were similar between the two groups. Hindfoot alignment angle, calcaneal pitch, and Meary angle showed no significant differences between the groups. The hindfoot moment arm increased with valgus in the IMN group. A low correlation was detected between angulation at the fracture site in the coronal view and hindfoot alignment (angulation and moment arm) changes (R = 0.38). A significantly high correlation was noted only between transverse rotation and hindfoot alignment changes (R = 0.79).

Conclusions

Rotation in the transverse plane notably influenced changes in hindfoot alignment. And this suggests that patients with distal tibia fracture should be closely monitored for hindfoot alignment changes caused by intraoperative transverse rotation regardless of the fixation method.

Outcomes of Joint Preservation Surgery in Valgus Ankle Arthritis Without Deltoid Ligament Insufficiency

BACKGROUND

To date, information about the role of proximal alignment correction in treating nontraumatic valgus ankle arthritis is limited. This study aimed to report outcomes of realignment surgery, including supramalleolar correction in valgus arthritic ankles without evidence of deltoid ligament insufficiency.

METHODS

Thirteen patients (13 ankles) who underwent joint preservation surgery for valgus ankle arthritis without evidence of deltoid ligament insufficiency were reviewed. Medial opening wedge supramalleolar osteotomy (n = 11) and varization supramalleolar dome osteotomy (n = 2) were performed to realign the hip-knee-ankle-hindfoot axis. Concomitant hindfoot correction was accompanied with either medial displacement calcaneal osteotomy (n = 8) or subtalar arthrodesis (n = 5). Pain, functional outcome (Foot Function Index [FFI]), radiographic arthritis grade (grades 0-4), 9 plain radiographic parameters, and 2 weightbearing computed tomography parameters were evaluated pre- and postoperatively. All patients completed a minimum 2-year follow-up.

RESULTS

Preoperatively, 10 ankles (77%) demonstrated a varus tibial plafond, and 3 ankles (23%) demonstrated a valgus or neutral tibial plafond. Postoperatively, radiographic arthritis grade improved in all except 1 patient, and the mean talar tilt angle improved from 5.5 to 1.7 degrees. The mean pain score (visual analog scale) decreased significantly from 7.3 to 2.5 (P < .05), and the mean FFI improved significantly from 57.7 to 18.6 (P < .001). None of the patients underwent conversion to joint-sacrificing procedures at the latest follow-up.

CONCLUSION

This study demonstrated a possible relationship between lower limb malalignment and valgus ankle arthritis. Realignment surgery, including supramalleolar osteotomies, which straightens the mechanical axis and decreases the slope of the tibial plafond, may be a reasonable approach in joint preservation of valgus ankle arthritis without deltoid ligament insufficiency.

LEVEL OF EVIDENCE

Level IV, case series.

Poor Correction Capacity of Preexisting Ankle Valgus Deformity after Total Knee Arthroplasty

This study investigated the differences in ankle alignment changes after TKA in patients with varying preexisting ankle deformities. We retrospectively examined 90 knees with osteoarthritis and varus deformity in 78 patients who underwent TKA. Preoperative and postoperative radiographic parameters were analyzed. According to their preexisting ankle deformity, patients were assigned to the valgus or varus group. Overall, 14 (15.6%) cases were of preoperative valgus ankle deformity; the remainder were of preoperative varus ankle deformity. Hip-knee-ankle angle (HKA), tibial plafond-ground angle (PGA), and talus-ground angle (TGA) all exhibited significant correction in both groups; however, tibial plafond-talus angle (PTA) and superior space of ankle joint (SS) only changed in the varus group. The median PTA and SS significantly decreased from 1.2° to 0.3° (p < 0.001) and increased from 2.5 to 2.6 mm (p = 0.013), respectively. Notably, ∆PTA positively correlated with ∆HKA in the varus group (r = 0.247, p = 0.032) but not in the valgus group. Between-group differences in postoperative PTA (p < 0.001) and ∆PTA (p < 0.001) were significant. The degree of ankle alignment correction after TKA differed between patients with preexisting varus and valgus ankle deformities. TKA could not effectively correct the preexisting ankle valgus malalignment.

Imaging of the Pes Cavus Deformity

Direct-type cavus foot deformities are most commonly encountered and are primarily sagittal plane deformities. Direct deformities should be delineated from rarer triplane pes cavovarus deformities. The lateral weight-bearing radiograph is the cornerstone of imaging evaluation of direct pes cavus foot deformity. The apex of Meary talo-first metatarsal angle on the lateral radiograph represents the pinnacle of the cavus deformity and assists in subclassification of the deformity. With routine application, ancillary radiographic imaging techniques, such as the modified Saltzman view or the modified Coleman block test, can give valuable insight into deformity assessment and surgical planning.

Use of Calcaneal Osteotomies in the Correction of Inframalleolar Cavovarus Deformity

Cavovarus deformity is a complicated condition most commonly resulting from neurologic, posttraumatic, or iatrogenic pathologic conditions. Careful evaluation of the cavovarus patient is necessary in determining appropriate treatment course. Weight-bearing radiographs are necessary, and advances in computed tomographic technology can be beneficial in identifying level of involvement. In the case of operative treatment of inframalleolar deformity, assessment of the subtalar joint position and relation of calcaneocuboid joint can be of assistance. Multiple osteotomies have been described providing uniplanar, biplanar, and triplanar correction and in the appropriate setting can prove beneficial to the surgeon in treating hind-foot cavovarus deformity.

WEIGHT-BEARING CONE BEAM CT SCANS AND ITS USES IN ANKLE, FOOT, AND KNEE: AN UPDATE ARTICLE

Imaging plays a key role in the preoperative diagnosis, surgical planning, and postsurgical assessment of the foot, ankle, and knee pathologies. Interpreting diagnostic imaging accurately is crucial for the clinical practice of orthopedic surgeons. Although among the most used imaging modalities, radiographic assessments are amenable to errors for various technical reasons and superposition of bones. Computed tomography (CT) is a conventional imaging procedure that provides high-resolution images, but fails in considering a truly weight-bearing (WB) condition. In an attempt to overcome this limitation, WB cone beam CT technology has being successfully employed in the clinical practice for the past decade. Besides economically viable and safe, the WB cone beam CT considers WB conditions and provides high-quality scans, thus allowing an equitable and correct interpretation. This review aims to address extensive description and discussion on WBCT, including imaging quality; costs; time consumption; and its applicability in common foot, ankle, and knee, conditions. With this technology increasing popularity, and considering the extensive literature on medical research, radiologists and orthopedic surgeons need to understand its potential applications and use it optimally. Level of Evidence III, Systematic review of level III studies.

3D Assessment in Posttraumatic Ankle Osteoarthritis

BACKGROUND

Auto-generated 3-dimensional (3D) measurements based on weightbearing cone-beam computed tomography (CT) scan technology may allow for a more accurate hind- and midfoot assessment. The current study evaluated the reliability and clinical relevance of such measurements in patients with posttraumatic end-stage ankle osteoarthritis.

METHODS

Seventy-two patients treated at our institution for posttraumatic end-stage ankle osteoarthritis, with available weightbearing conventional radiographs and a cone-beam CT scan, were analyzed. Twenty healthy individuals aged between 40 and 70 years served as controls. Seven variables were measured on weightbearing conventional radiographs (2D) and compared to 3D measurements that were based on reconstructions from weightbearing cone-beam CT scans. The reliability of each measurement was calculated and subgroups formed according to commonly observed deformities.

RESULTS

Inter- and intraobserver reliability was superior for 3D compared to 2D measurements. The accuracy of 3D measurements performed on osteoarthritic ankles was similar to 3D measurements performed on healthy individuals. Thirty-three of the 72 included patients (46%) evidenced an inframalleolar compensation of a supramalleolar/intra-articular ankle deformity (78% = varus compensation; 22% = valgus compensation), whereas 24 of those 72 patients (33%) showed no compensation or a further increase of a supramalleolar/intra-articular ankle deformity (67% = varus deformity; 33% = valgus deformity).

CONCLUSION

Auto-generated 3D measurements of the hind- and midfoot were found to be reliable in both healthy individuals and patients with posttraumatic end-stage ankle osteoarthritis. Such measurements may be crucial for a detailed understanding of the location and extent of hindfoot deformities, possibly impacting decision making in the treatment of end-stage ankle osteoarthritis.

LEVEL OF EVIDENCE

Level III, comparative study.

Supramalleolar osteotomy in post-traumatic valgus ankle osteoarthritis

PURPOSE

To assess how the level of the deformity, the stage of the osteoarthritic process, and the role of additional surgeries impact radiographic and clinical outcomes following an extra-articular medial closing supramalleolar osteotomy for treatment of post-traumatic valgus ankle osteoarthritis.

METHODS

About 56 consecutive patients who underwent an extra-articular medial closing wedge osteotomy for post-traumatic valgus ankle osteoarthritis were retrospectively analyzed. Subgroups were formed according to the pre-operative level of deformity and preoperative stage of ankle osteoarthritis. Additional surgical steps required to achieve a properly balanced hindfoot were also noted. Radiographic and clinical outcomes of each subgroup were compared with each other, and the role of additional surgical steps required to achieve a balanced hindfoot was investigated.

RESULTS

Radiographic and clinical outcomes improved significantly between pre-operative assessment and the last follow-up. Patients with a pre-operative supramalleolar deformity showed superior radiographic outcomes compared to patients with an intra-articular deformity. Clinical outcomes did not differ significantly between these two subgroups. The pre-operative stage of ankle osteoarthritis significantly impacted radiographic outcomes but did not influence clinical outcome measures. An additional fibula or calcaneus osteotomy was necessary for 55% and 23% of all patients, respectively.

CONCLUSION

Extra-articular medial closing supramalleolar osteotomies show satisfactory mid- to long-term radiographic and clinical outcomes in patients with post-traumatic valgus ankle osteoarthritis.

Is Lower-limb Alignment Associated with Hindfoot Deformity in the Coronal Plane? A Weightbearing CT Analysis

BACKGROUND

The goals of lower limb reconstruction are to restore alignment, to improve function, and to reduce pain. However, it remains unclear whether alignment of the lower limb and hindfoot are associated because an accurate assessment of hindfoot deformities has been limited by superposition on plain radiography. Consequently, surgeons often overlook hindfoot deformity when planning orthopaedic procedures of the lower limb. Therefore, we used weight-bearing CT to quantify hindfoot deformity related to lower limb alignment in the coronal plane.

QUESTIONS/PURPOSES

(1) Is lower-limb alignment different in varus than in valgus hindfoot deformities for patients with and without tibiotalar joint osteoarthritis? (2) Does a hindfoot deformity correlate with lower-limb alignment in patients with and without tibiotalar joint osteoarthritis? (3) Is joint line orientation different in varus than in valgus hindfoot deformities for patients with tibiotalar joint osteoarthritis? (4) Does a hindfoot deformity correlate with joint line orientation in patients with tibiotalar joint osteoarthritis?

METHODS

Between January 2015 and December 2017, one foot and ankle surgeon obtained weightbearing CT scans as second-line imaging for 184 patients with ankle and hindfoot disorders. In 69% (127 of 184 patients) of this cohort, a combined weightbearing CT and full-leg radiograph was performed when symptomatic hindfoot deformities were present. Of those, 85% (109 of 127 patients) with a median (range) age of 53 years (23 to 75) were confirmed eligible based on the inclusion and exclusion criteria of this retrospective comparative study. The Takakura classification was used to divide the cohort into patients with (n = 74) and without (n = 35) osteoarthritis of the tibiotalar joint. Lower-limb measurements, obtained from the full-leg radiographs, consisted of the mechanical tibiofemoral angle, mechanical tibia angle, and proximal tibial joint line angle. Weightbearing CT images were used to determine the hindfoot's alignment (mechanical hindfoot angle), the tibiotalar joint alignment (distal tibial joint line angle and talar tilt angle) and the subtalar joint alignment (subtalar vertical angle). These values were statistically assessed with an ANOVA and a pairwise comparison was subsequently performed with Tukey's adjustment. A linear regression analysis was performed using the Pearson correlation coefficient (r). A reliability analysis was performed using the intraclass correlation coefficient.

RESULTS

Lower limb alignment differed among patients with hindfoot deformity and among patients with or without tibiotalar joint osteoarthritis. In patients with tibiotalar joint osteoarthritis, we found knee valgus in presence of hindfoot varus deformity and knee varus in presence of hindfoot valgus deformity (mechanical tibiofemoral angle 0.3 ± 2.6° versus -1.8 ± 2.1°; p < 0.001; mechanical tibia angle -1.4 ± 2.2° versus -4.3 ± 1.9°; p < 0.001). Patients without tibiotalar joint osteoarthritis demonstrated knee varus in the presence of hindfoot varus deformity compared with knee valgus in presence of hindfoot valgus deformity (mechanical tibiofemoral angle -2.2 ± 2.2° versus 0.9 ± 2.4°; p < 0.001; mechanical tibia angle -1.8 ± 2.1° versus -4.3 ± 1.9°; p < 0.001). Patients with more valgus deformity in the hindfoot tended to have more tibiofemoral varus (r = -0.38) and tibial varus (r = -0.53), when tibiotalar joint osteoarthritis was present (p < 0.001). Conversely, patients with more valgus deformity in the hindfoot tended to have more tibiofemoral valgus (r = 0.4) and tibial valgus (r = 0.46), when tibiotalar joint osteoarthritis was absent (p < 0.001). The proximal joint line of the tibia had greater varus orientation in patients with a hindfoot valgus deformity compared with greater valgus orientation in patients with a hindfoot varus deformity (proximal tibial joint line angle 88.5 ± 2.0° versus 90.6 ± 2.2°; p < 0.05). Patients with more valgus deformity in the hindfoot tended to have more varus angulation of the proximal tibial joint line angle (r = 0.31; p < 0.05).

CONCLUSIONS

In patients with osteoarthritis of the tibiotalar joint, varus angulation of the knee was associated with hindfoot valgus deformity and valgus angulation of the knee was associated with hindfoot varus deformity. Patients without tibiotalar joint osteoarthritis exhibited the same deviation at the level of the knee and hindfoot. These distinct radiographic findings were most pronounced in the alignment of the tibia relative to the hindfoot deformity. This suggests a detailed examination of hindfoot alignment before knee deformity correction at the level of the proximal tibia, to avoid postoperative increase of pre-existing hindfoot deformity. Other differences detected between the radiographic parameters were less pronounced and varied within the subgroups. Future research could identify prospectively which of these parameters contain clinical relevance by progressing osteoarthritis or deformity and how they can be altered by corrective treatment.

LEVEL OF EVIDENCE

Level III, prognostic study.

Visualization and quantification of the degenerative pattern of the talus in unilateral varus ankle osteoarthritis

The aim of this study was to quantify and visualize the degenerative patterns of the talus in ankle osteoarthritis (OA). The differences in talar morphology between sides of patients with unilateral varus ankle OA (medial talar tilt > 4°) were compared. Computed tomography images of both feet of 35 patients (OA: 22 patients, control: 13 patients) were analyzed. Each surface model of the right and left tali was registered to the opposite talus via a mirror-image technique and an iterative closest point algorithm. The surface deviation between the two models was quantified and visualized by deviation color maps. The results quantitatively demonstrated that osteophytes are generated in the area under the antero-medial margin of the trochlea in OA tali. In severe OA tali, bone resorption of more than 2 mm in the medial portion of the trochlea, as well as a similar degree of osteophyte formation on the lateral surface, was also seen. Stereotypical patterns of degeneration occurring in OA tali were successfully visualized and quantified by left-right comparison of patients with unilateral ankle OA. Such information would contribute to better understanding of the development of ankle OA and preoperative planning of total ankle arthroplasty and arthrodesis.

Can Weightbearing Computed Tomography Scans Be Used to Diagnose Subtalar Joint Instability? A Cadaver Study

Chronic hindfoot instability is a frequent problem that includes the ankle and/or the subtalar joint. While ankle joint instability can be diagnosed clinically, accurate assessment of the subtalar joint remains elusive. This study's purpose was to assess the ability of weightbearing computed tomography (CT) scans to detect subtalar joint instability. Seven pairs of fresh frozen male cadavers (tibial plateau to toe-tip) were tested. A radiolucent frame held specimens in a plantigrade position while non-weightbearing and weightbearing CT scans (with and without torque application) were taken. First, intact ankles (Native) were scanned. Second, one specimen from each pair underwent interosseous talo-calcaneal ligament (ITCL) transection, while the contralateral underwent calcaneo-fibular ligament (CFL) transection. Third, the remaining intact ITCL or CFL was transected. Finally, the deltoid ligament was transected in all ankles. Eight radiographic measurements were performed to assess the congruency of the subtalar joint on digitally reconstructed radiographs and single CT images. Axial loading did not impact most measurements, whereas torque did impact most measurements. Radiographic measurements performed at the subtalar joint level were more reliable and better predictors for subtalar joint instability compared with measurements performed at the ankle joint level. While torque application is crucial to identify subtalar joint instability, axial load application should be avoided. Measurements to assess the subtalar joint stability should primarily be performed at the subtalar joint level rather than at the ankle joint level when using weightbearing CT scans. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2457-2465, 2019.

Influence of the ankle position and X-ray beam angulation on the projection of the posterior facet of the subtalar joint

OBJECTIVE

Using digitally reconstructed radiographs (DRRs), we determined how changes in the projection angle influenced the assessment of the subtalar joint.

MATERIALS AND METHODS

Weightbearing computed tomography (CT) scans were acquired in 27 healthy individuals. CT scans were segmented and processed to create DRRs of the hindfoot. DRRs were obtained to represent 25 different perspectives to simulate internal rotation of the ankle with and without caudal angulation of the X-ray beam. Subtalar joint morphology was quantified by determining the joint space curvature, subtalar inclination angle (SIA), calcaneal slope (CS), and projection of the subtalar joint line on three-dimensional (3-D) reconstructions of the calcaneus.

RESULTS

The curvature of the projected joint space was altered substantially over the different DRR projections. Simulated caudal angulation of the X-ray beam with respect to the ankle decreased the SIA and CS significantly. Internal rotation also had a significant impact on the SIA and CS if the X-ray beam was in neutral or in 10° of caudal angulation. An antero-posterior (AP) view of the ankle showed the posterior area of the posterior facet, whereas a more anterior area was visible with internal rotation of the foot and caudal angulation of the X-ray beam.

CONCLUSION

Internal rotation of the foot of 20° is recommended to assess the posterior aspect of the posterior facet, whereas a combined 20° internal rotation of the foot and 40° caudal angulation of the X-ray beam is best to assess the anterior aspect of the posterior facet of the subtalar joint.

Secondary Subtalar Joint Osteoarthritis Following Total Ankle Replacement

BACKGROUND

An advantage of total ankle replacement (TAR) compared to ankle fusion is that by maintaining motion, the occurrence of hypermobility of adjacent joints may be prevented. This could affect the development of symptomatic subtalar joint osteoarthritis (OA). The aim of the study was to determine the incidence of subtalar joint fusion and the progression of subtalar joint OA following TAR.

METHODS

Secondary subtalar joint fusion rate was determined from a cohort of 941 patients receiving primary TAR between 2000 and 2016. The indication for fusion, the time interval from primary TAR to fusion, and the union rate were evaluated. To assess the progression of subtalar joint OA, degenerative changes of the subtalar joint were classified in 671 patients using the Kellgren-Lawrence score (KLS) prior to TAR and at latest follow-up.

RESULTS

In 4% (37) of the patients, a secondary subtalar joint fusion was necessary. The indication for fusion was symptomatic OA in 51% (19), hindfoot instability in 27% (10), osteonecrosis of the talus in 19% (7), and cystic changes of the talus in 3% (1) of the patients. Time from primary TAR to subtalar joint fusion due to progressive OA was 5.0 (range, 0.3-10) years and for other reasons 1.6 (range, 0.2-11.6) years (P = .3). In 68% (456) of the patients, no progression of subtalar joint OA was observed.

CONCLUSION

The incidence of secondary subtalar joint fusion was low. The most common reason for subtalar joint fusion following TAR was symptomatic OA.

LEVEL OF EVIDENCE

Level IV, case series.

Torque application helps to diagnose incomplete syndesmotic injuries using weight-bearing computed tomography images

OBJECTIVE

Accurate identification of distal tibio-fibular syndesmotic injuries is essential to limit potential deleterious post-traumatic effects. To date, conventional radiographs, computed tomography (CT), and magnetic resonance imaging (MRI) have shown limited utilization. This cadaver study evaluates the utility of weight-bearing CT scans on the assessment of incomplete and more complete syndesmotic injuries.

MATERIALS AND METHODS

Ten male cadavers (tibial plateau to toe-tip) were included. Weight-bearing CTs were taken under four test conditions, with and without torque on the tibia (corresponding to external rotation of the foot and ankle). First, intact ankles (native) underwent imaging. Second, the anterior-inferior tibio-fibular ligament (AITFL) was transected (condition 1). Then, the deltoid ligament (condition 2) was transected, followed by the interosseous membrane (IOM, condition 3). Finally, the posterior-inferior tibio-fibular ligament (PITFL) was transected (condition 4). The medial clear space (MCS), the tibio-fibular clear space (TFCS), and the tibio-fibular overlap (TFO) were assessed on digitally reconstructed radiographs (DRRs), and on axial CT images.

RESULTS

The TFO differentiated isolated AITFL transection from native ankles when torque was applied. Also under torque conditions, the MCS was a useful predictor of an additional deltoid ligament transection, whereas the TFCS identified cadavers in which the PITFL was also transected.

CONCLUSION

Torque application helps to diagnose incomplete syndesmotic injuries when using weight-bearing CT. The TFO may be useful for identifying incomplete syndesmotic injuries, whereas the MCS and TFCS predict more complete injuries.

Extraarticular Supramalleolar Osteotomy in Asymmetric Varus Ankle Osteoarthritis

BACKGROUND

In recent years, supramalleolar osteotomy has become a valuable alternative for treatment of ankle osteoarthritis. The aim of this study was to investigate whether the preoperative stage of ankle osteoarthritis or tilt of the talus in the ankle mortise impacts radiologic and clinical outcomes following a supramalleolar osteotomy.

METHODS

Forty-four patients who underwent a supramalleolar osteotomy for posttraumatic asymmetric varus ankle osteoarthritis were included. Subgroups were formed according to the preoperative stage of ankle osteoarthritis and the tilt of the talus in the ankle mortise. The radiographic and clinical outcomes of each subgroup were compared, and survival rates calculated.

RESULTS

Ankles with a preoperative Takakura stage of 2 and 3a showed a significant higher survival rate at 5 years (88% [95% CI, 67-100] and 93% [95% CI, 80-100]) compared with ankles with a preoperative Takakura stage of 3b (47% [95% CI, 26-86]; P = .044). The 5-year survival rate for patients with a preoperative tilt of the talus in the ankle mortise of 4-10 degrees was 85% (95% CI, 68-100), while patients with a preoperative tilt of >10 degrees showed a 5-year survival rate of 65% (95% CI, 46-93; P = .117).

CONCLUSION

Supramalleolar osteotomy was a valuable treatment option for early to mid-stage posttraumatic asymmetric varus ankle osteoarthritis.

LEVEL OF EVIDENCE

Level IV, retrospective cohort study.

Imaging of the subtalar joint: A novel approach to an old problem

Evaluation of the subtalar joint using conventional radiographs is difficult. The purpose of this study was to assess how the posterior facet of the subtalar joint is projected on eight standard radiographic views of the foot and ankle. Weightbearing computed tomography (CT) scans of 27 volunteers without ankle pathology were performed. Eight standard views of the foot and ankle (antero-posterior [AP] view, mortise view, subtalar view, four different Broden views) were reconstructed using digitally reconstructed radiographs (DRRs). The appearance of the posterior facet of the subtalar joint was assessed for each view. In addition, the position of the joint line was projected onto three-dimensional (3-D) models of the calcaneus. We found (i) on the AP view of the ankle joint, the posterior part of the posterior facet is visualized and appears convex (calcaneal side); (ii) on the mortise view of the ankle joint, a slightly more anterior part (compared to the AP view) is visualized and appears either convex or flat; (iii) on the subtalar view, the anterior part of the posterior facet is visualized and appears either convex, flat or concave; and (iv) using the Broden views, the posterior and anterior part of the posterior facet can be visualized. This study clarifies which parts of the posterior facet of the subtalar joint are visualized on eight standard views of the foot and ankle. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Compensatory Function of the Subtalar Joint for Lower Extremity Malalignment

It is important to evaluate the subtalar joint and hip-knee-ankle alignment to understand lower extremity alignment. In this review, we focused on the compensatory changes in the subtalar joint alignment for the deformity of the knee and ankle joint, reviewing previous research. The subtalar joint alignment was compensatory valgus in patients with varus knee and ankle deformity, whereas it was uncertain whether the subtalar joint alignment was compensatory varus in patients with valgus knee and ankle deformity. The subtalar joint valgus alignment improved after total knee arthroplasty or high tibial osteotomy for varus knee deformity, even if the deformity was severe. In contrast, whether the subtalar joint alignment changed after the surgery for ankle or valgus knee deformity has not been considered. Further research on the compensatory function of the subtalar joint is needed.