Histomorphometric, CT arthrographic, and biomechanical mapping of the human ankle

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.

Outcomes of Autologous Osteochondral Transplantation With and Without Extracellular Matrix Cartilage Allograft Augmentation for Osteochondral Lesions of the Talus

BACKGROUND

Autologous osteochondral transplantation (AOT) using a cylindrical graft in the treatment of osteochondral lesions of the talus (OLTs) is typically indicated for patients with larger lesions. However, with lesions that are irregular in shape, the AOT graft may not completely replace the lesion. For these lesions, we utilize extracellular matrix cartilage allograft (EMCA) augmentation in AOT to act as a physiologic grout at the host-graft interface.

PURPOSE

To determine if the combination of EMCA with concentrated bone marrow aspirate (CBMA) would improve integration of the host-graft interface and subsequently reduce postoperative cyst formation after AOT. It was also hypothesized that EMCA in conjunction with CBMA would demonstrate improved MOCART (magnetic resonance observation of cartilage repair tissue) scores and functional outcome scores at a minimum 2 years after surgery.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A retrospective analysis was performed comparing patients treated with AOT/CBMA alone and AOT with CBMA/EMCA. Clinical outcomes were evaluated with the Foot and Ankle Outcome Score. Magnetic resonance imaging appearance was evaluated with the use of the MOCART (magnetic resonance observation of cartilage repair tissue) score. Cyst formation was also evaluated on postoperative magnetic resonance imaging.

RESULTS

A total of 26 patients were included in the AOT + CBMA/EMCA group (10 male, 16 female), and 34 patients were included in the AOT/CBMA group (17 male, 17 female). The mean Foot and Ankle Outcome Score significantly improved in both groups (P < .001) across all subscales (symptoms, pain, activities of daily living, sports activities, and quality of life), but there was no significant difference between groups at final follow-up. There was no significant difference in mean MOCART scores between the groups (P = .118). In the AOT/CBMA group, 3 patients (8.8%) complained of knee pain, and 1 (2.9%) required additional surgery (hardware removal). In the AOT + CBMA/EMCA group, 2 patients (7.7%) complained of knee pain, and 6 patients (23%) required additional surgery (3 hardware removals and 3 arthroscopic debridements of scar tissue in the ankle).

CONCLUSION

We found that while EMCA with CBMA has benefit in regeneration and repair of OLT treated with bone marrow stimulation, there appears to be little benefit of EMCA over CBMA alone as a physiologic grout at the graft-host interface in OLT treated with AOT.

Accessibility and Thickness of Medial and Lateral Talar Body Cartilage for Treatment of Ankle and Foot Osteochondral Lesions

BACKGROUND

The purposes of this study were to determine (1) if cartilage thicknesses on the talar dome and medial/lateral surfaces of the talus were similar, (2) whether there was sufficient donor cartilage surface area on the medial and lateral talar surfaces to repair talar dome cartilage injuries of the talus, and (3) whether the cartilage surface could be increased following anterior talofibular ligament (ATFL) and sectioning of the tibionavicular and tibiospring portion of the anterior deltoid.

METHODS

Medial and lateral approaches were utilized in 8 cadaveric ankles to identify the accessible medial, lateral, and talar dome cartilage surfaces in 3 conditions: (1) intact, (2) ATFL release, and (3) superficial anterior deltoid ligament release. The talus was explanted, and the cartilage areas were digitized with a coordinate measuring machine. Cartilage thickness was quantified using a laser scanner.

RESULTS

The mean cartilage thickness was 1.0 ± 0.1 mm in all areas tested. In intact ankles, the medial side of the talus showed a larger total area of available cartilage than the lateral side (152 mm² vs 133 mm²). ATFL release increased the available cartilage area on the medial and lateral sides to 167 mm² and 194 mm², respectively. However, only the lateral talar surface had sufficient circular graft donor cartilage available for autologous osteochondral transplantation (AOT) procedures of the talus. After ATFL and deltoid sectioning, there was an increase in available graft donor cartilage available for AOT procedures.

CONCLUSION

The thickness of the medial and lateral talar cartilage surfaces is very similar to that of the talar dome cartilage surface, which provides evidence that the medial and lateral surfaces may serve as acceptable AOT donor cartilage. The surface area available for AOT donor site grafting was sufficient in the intact state; however, sectioning the ATFL and superficial anterior deltoid ligament increased the overall lateral talar surface area available for circular grafting for an AOT procedure that requires a larger graft. These results support the idea that lateral surfaces of the talus may be used as donor cartilage for an AOT procedure since donor and recipient sites are similar in cartilage thickness, and there is sufficient cartilage surface area available for common lesion sizes in the foot and ankle.

CLINICAL RELEVANCE

This anatomical study investigates the feasibility of talar osteochondral autografts from the medial or lateral talar surfaces exposed with standard approaches. It confirms the similar cartilage thickness of the talar dome and the ability to access up to an 8- to 10-mm donor graft from the lateral side of the talus after ligament release. This knowledge may allow better operative planning for use of these surfaces for osteochondral lesions within the foot and ankle, particularly in certain circumstances of a revision microfracture.

Effect of cartilage thickness mismatch in osteochondral grafting from knee to talus on articular contact pressures: A finite element analysis

Objectives

The aim of this study was to investigate the effect of cartilage thickness mismatch on tibiotalar articular contact pressure in osteochondral grafting from femoral condyles to medial talar dome using a finite element analysis (FEA).

Materials and methods

Flush-implanted osteochondral grafting was performed on the talar centromedial aspect of the dome using osteochondral plugs with two different cartilage thicknesses. One of the plugs had an equal cartilage thickness with the recipient talar cartilage and the second plug had a thicker cartilage representing a plug harvested from the knee. The ankle joint was loaded during a single-leg stance phase of gait. Tibiotalar contact pressure, frictional stress, equivalent stress (von Mises values), and deformation were analyzed.

Results

In both osteochondral grafting simulations, tibiotalar contact pressure, frictional stress, equivalent stress (von Mises values) on both tibial and talar cartilage surfaces were restored to near-normal values.

Conclusion

Cartilage thickness mismatch does not significantly change the tibiotalar contact biomechanics, when the graft is inserted flush with the talar cartilage surface.

Implications of Classification of Os Trigonum: A Study Based on Computed Tomography Three-Dimensional Imaging

BACKGROUND The os trigonum is an accessory bone that is not fully fused with the talus during secondary ossification, and is one of the risk factors of posterior malleolus impact syndrome. The purpose of this study was to classify the os trigonum and to guide the diagnosis and treatment of related clinical diseases. MATERIAL AND METHODS Ankle computed tomography (CT) scans of 586 Chinese patients between October 2014 and October 2018 were reviewed. CT images of 1011 ankle joints were reconstructed to evaluate the classification of the os trigonum and the measurement of anatomical parameters. RESULTS The incidences of os trigonum in 3 groups were determined as type I (1.9%), type II (10.5%), and type III (14.7%). The macro-axis of type II (0.89±0.31) cm was significantly larger than with type I (0.65±0.24 cm) and type III (0.74±0.23 cm) (p<0.05).The minor axis of similar of type I (0.41±0.23 cm) was significantly shorter than that of type II (0.58±0.32 cm) and type III (0.55±0.16 cm) (p<0.05).The distance from os trigonum to calcaneal tubercle was significantly different than that of type I (1.33±0.52 cm), type II (1.67±0.55 cm), and type III (1.84±0.45 cm) (p<0.05). CONCLUSIONS This study showed that os trigonum has a high incidence. Type I was the least common, the volume of type II was larger, and type III was more common. The anatomical parameters of each type may improve treatment of related diseases and the further development of ankle arthroscopic surgery.

3D grating-based X-ray phase-contrast computed tomography for high-resolution quantitative assessment of cartilage: An experimental feasibility study with 3T MRI, 7T MRI and biomechanical correlation

Objective

Aim of this study was, to demonstrate the feasibility of high-resolution grating-based X-ray phase-contrast computed tomography (PCCT) for quantitative assessment of cartilage.

Materials and methods

In an experimental setup, 12 osteochondral samples were harvested from n = 6 bovine knees (n = 2 each). From each knee, one cartilage sample was degraded using 2.5% Trypsin. In addition to PCCT and biomechanical cartilage stiffness measurements, 3T and 7T MRI was performed including MSME SE T2 and ME GE T2* mapping sequences for relaxationtime measurements. Paired t-tests and receiver operating characteristics (ROC) curves were used for statistical analyses.

Results

PCCT provided high-resolution images for improved morphological cartilage evaluation as compared to 3T and 7T MRI. Quantitative analyses revealed significant differences between the superficial and the deep cartilage layer for T2 mapping as well as for PCCT (P<0.05). No significant difference was detected for PCCT between healthy and degraded samples (P>0.05). MRI and stiffness measurements showed significant differences between healthy and degraded osteochondral samples. Accuracy in the prediction of cartilage degradation was excellent for MRI and biomechanical analyses.

Conclusion

In conclusion, high-resolution grating-based X-ray PCCT cartilage imaging is feasible. In addition to MRI and biomechanical analyses it provides complementary, water content independent, information for improved morphological and quantitative characterization of articular cartilage ultrastructure.

Prospective Computed Tomographic Analysis of Osteochondral Lesions of the Ankle Joint Associated With Ankle Fractures

BACKGROUND

Osteochondral lesions (OCLs) associated with ankle fracture correlate with unfavorable outcome. The goals of this study were to detect OCLs following ankle fracture, to associate fracture type to OCLs and to investigate whether OCLs affect clinical outcome.

METHODS

100 ankle fractures requiring operative treatment were prospectively included (46 men, 54 women; mean age 44 ± 14 years, range 20-77). All ankle fractures (conventional radiography; 71 Weber B, 22 Weber C, 1 Weber A, 4 isolated medial malleolus and 2 isolated posterior malleolus fractures) were treated by open reduction and internal fixation. Multidetector computed tomography (CT) was performed postoperatively. For each OCL, the location, size, and Loomer OCL classification (CT modified Berndt and Harty classification) were determined. The subjective Foot and Ankle Outcome Scoring (FAOS) was used for clinical outcome at 1 year.

RESULTS

OCLs were found in 10/100 ankle fractures (10.0%). All OCLs were solitary talar lesions. Four OCLs were located posteromedial, 4 posterolateral, 1 anterolateral, and 1 anteromedial. There were 2 type I OCLs (subchondral compression), 6 type II OCLs (partial, nondisplaced fracture) and 2 type IV OCLs (displaced fracture). Mean OCL size (largest diameter) was 4.4 ± 1.7 mm (range, 1.7 mm to 6.2 mm). Chi-square analysis showed no significant association between ankle fracture type and occurrence of OCLs. OCLs did occur only in Lauge-Hansen stage III/IV ankle fractures. There were no significant differences in FAOS outcome between patients with or without OCLs.

CONCLUSIONS

Ten percent of investigated ankle fractures had associated OCLs on CT. Although no significant association between fracture type and OCL was found, OCLs only occurred in Lauge-Hansen stage III/IV ankle fractures. With the numbers available, OCLs did not significantly affect clinical outcome at 1 year according to FAOS.

LEVEL OF EVIDENCE

Level IV, observational study.

The Notch of Harty (Pseudodefect of the Tibial Plafond): Frequency and Characteristic Findings at MRI of the Ankle

OBJECTIVE

The purpose of this study is to report the frequency and characteristic findings of the notch of Harty as seen on MRI.

MATERIALS AND METHODS

One hundred six consecutive ankle MRI studies performed at 1.5 or 3 T were reviewed retrospectively by two radiologists. Findings relating to the notch of Harty and ankle joint were recorded and analyzed, including qualitative assessment of the presence of the notch, focal chondral thinning or focal subcortical osteosclerosis at the notch, notch width and depth, osteochondral lesions elsewhere in the ankle, subchondral edema signal or cystic change at the tibial plafond, and the presence of an ankle joint effusion.

RESULTS

The study group of 106 patients consisted of 48 male and 58 female patients, with a mean age of 44.5 years (SD, 17.5 years). The notch was identified in 48 of 106 patients (45%) (24 male and 24 female patients; mean age, 43.1 years; range, 7-79 years). When present, the notch averaged 6.2 mm (SD, 1.6 mm) in width and 1.2 mm (SD, 0.5 mm) in depth. The notch was graded as prominent in six of the 106 ankle MRI examinations (6%). Subchondral edemalike signal or cystic change was not localized to the notch in any case. Between patients with versus those without a notch, there was no statistically significant difference in age, sex, subjacent subcortical osteosclerosis, ankle joint effusion, osteochondral lesions elsewhere in the ankle, or subchondral bone marrow edema at the tibial plafond.

CONCLUSION

The notch of Harty can be observed as an anatomic variant on MRI and should be differentiated from a traumatic osteochondral lesion.

Correlation between subchondral bone plate thickness and cartilage degeneration in osteoarthritis of the ankle

BACKGROUND

Osteoarthritis (OA) is characterized not only by cartilage degeneration, but also subchondral bone changes. The subchondral bone plate (SBP) plays an important role in cartilage metabolism, and elucidation of the relationship between the SBP and cartilage degeneration would be helpful to determine the most appropriate treatment strategy for ankle OA. The purpose of this study was to evaluate the SBP and to compare it with cartilage degeneration with arthroscopic findings.

METHODS

Computed tomography (CT) was used to compare the thickness of the SBP of 11 ankle OA patients with that of 11 non-ankle OA patients in 9 areas of the talar dome. The French Society of Arthroscopy (SFA) grading system was used to analyze the relationship between findings on the thickness of SBP and on articular cartilage degeneration in ankle OA.

RESULTS

The SBP in ankle OA was significantly thicker than that of the non-OA ankle. The more severe the articular cartilage degeneration, the thicker the SBP became. The SBP on the sclerotic trabecular bone was significantly thicker than that on decreased trabecular bone. The SFA grade for sclerotic subchondral bone was significantly higher than that for decreased trabecular bone.

CONCLUSION

This study shows that the thickness of SBP and the findings of subchondral bone such as decreased trabecular bone and sclerosis in CT are related to the cartilage degeneration of ankle OA, although a small number of patients were analyzed.

LEVEL OF EVIDENCE

Level III, comparative series.

Biochemical cartilage alteration and unexpected signal recovery in T2* mapping observed in ankle joints with mobile MRI during a transcontinental multistage footrace over 4486 km

OBJECTIVE

The effect of ultra-long distance running on the ankle cartilage with regard to biochemical changes, thickness and lesions is examined in the progress of a transcontinental ultramarathon over 4486 km.

METHOD

In an observational field study, repeated follow-up scanning of 22 participants of the TransEurope FootRace (TEFR) with a 1.5 T MRI mounted on a mobile unit was performed. For quantitative biochemical and structural evaluation of cartilage a fast low angle shot (FLASH) T2* weighted gradient-echo (GRE)-, a turbo-inversion-recovery-magnitude (TIRM)- and a fat-saturated proton density (PD)-weighted sequence were utilized. Statistical analysis of cartilage T2* and thickness changes was obtained on the 13 finishers (12 male, mean age 45.4 years, BMI 23.5 kg/m²). None of the nine non-finisher (eight male, mean age 53.8 years, BMI 23.4 kg/m²) stopped the race due to ankle problems.

RESULTS

From a mean of 17.0 ms for tibial plafond and 18.0 ms for talar dome articular cartilage at baseline, nearly all observed regions of interest (ROIs) of the ankle joint cartilage showed a significant T2*-signal increase (25.6% in mean), with standard error ranging from 19% to 33% within the first 2500 km of the ultra-marathon. This initial signal behavior was followed by a signal decrease. This signal recovery (30.6% of initial increase) showed a large effect size. No significant morphological or cartilage thickness changes (at baseline 2.9 mm) were observed.

CONCLUSION

After initial T2*-increase during the first 2000-2500 km, a subsequent T2*-decrease indicates the ability of the normal cartilage matrix to partially regenerate under ongoing multistage ultramarathon burden in the ankle joints.