Is double-strut fibula ankle arthrodesis a reliable reconstruction for bone defect after distal tibia tumor resection?-a finite element study based on promising clinical outcomes.

BACKGROUND: There are different surgical methods for primary malignant tumor located at distal tibia. Previous studies have reported that double-strut fibula ankle arthrodesis is an alternative option. The purpose of this study was to investigate the biomechanical effect of double-strut fibula ankle arthrodesis by finite element analysis (FEA). METHODS: Computer-aided design software was used to establish three-dimension models. Three different models were constructed: normal tibia-fibula-talus complex (model A), double-strut fibula ankle arthrodesis (model B), and reconstruction by ipsilateral fibula (model C). We used FEA to evaluate and compare the biomechanical characteristics of these constructs. Simulated load of 600 N was applied to the tibial plateau to simulate balanced single-foot standing. Output results representing the model von Mises stress and displacement of the components were analyzed. RESULTS: Construct stiffness was increased when the internal plate fixation was used. For axial load, model B (1460.5 N/mm) was stiffer than the construct of model A (524.8 N/mm), and model C (636.6 N/mm), indicating model B was more stable. Maximum stress on the fibular graft occurred on the proximal end. The von Mises stress and stress distribution of fibular graft in model B (71.4 MPa) and model C (67.8 MPa) were similar. In model B, the ipsilateral fibula in model B has a higher value of stress (16.1 MPa) than that in model A (0.5 MPa), indicating the ipsilateral fibula shared load after fusion with talus. CONCLUSIONS: Our computational findings suggest that double-strut fibula ankle arthrodesis is an acceptable construct for distal tibia defect and the ipsilateral fibula shares load after fusion with talus.

Magnetic Resonance Imaging and Outcomes of Osteochondral Lesions of the Talus Associated With Ankle Fractures.

BACKGROUND: Osteochondral lesions of the talus (OCLTs) secondary to ankle fractures have previously been reported in the literature. However, no study has evaluated OCLTs using magnetic resonance imaging (MRI) following ankle fracture treatment. The purpose of our study was to investigate accompanying OCLTs in patients with an ankle fracture and evaluate its relationship with the clinical outcomes. METHODS: Fifty-six patients with ankle fractures who were treated with either a nonoperative or operative method at our center between June 2016 and February 2017 were included in this prospective comparative study (37 men and 19 women; mean age, 44.6 ± 13 years; range, 20-65 years). The mean American Orthopaedic Foot & Ankle Society (AOFAS) scores were used to evaluate the clinical results in all patients in the second month and second year. The second-month ankle MR images were evaluated for OCLTs in all patients. Thirty patients were treated operatively and 26 nonoperatively. RESULTS: Accompanying OCLTs were detected in 19 of 56 patients (34%). Our results showed no statistically significant association between OCLT and fracture type, as well as the treatment type. In the second postoperative month, the mean AOFAS scores were 87.2 ± 10.8 and 77.6 ± 12.0 in patients with and without OCLTs, respectively (P = .005). In the second postoperative year, the mean AOFAS scores were 81.3 ± 6.8 and 86.2 ± 8.4 in patients with and without OCLTs, respectively (P = .031). The mean AOFAS score significantly decreased in the OCLT group in the second-year control, whereas a significant increase was observed in patients without OCLTs (P = .026 and P < .001, respectively). CONCLUSION: According to our results, the accompanying OCLTs were found in one-third of patients treated for ankle fractures. We observed a significant correlation between OCLT presence and the AOFAS score. According to the AOFAS score, OCLTs statistically significantly affected clinical results at 2 years. LEVEL OF EVIDENCE: Level II, prospective comparative study.

Simulated anterior translation and medial rotation of the talus affect ankle joint contact forces during vertical hopping.

The purpose of the present study was to identify the effects of anterior translation and medial rotation of the talus on ankle joint contact forces (AJF) during double-limb vertical hopping. A computational musculoskeletal model was used to calculate AJF under 225 different combinations of 0-10 mm (in 10/15 mm increments) anterior translation and 0-5° (in 5/15° increments) medial rotation for ten subjects. The results show anteroposterior AJF was moderately affected by anterior translation, while mediolateral AJF was strongly affected by medial rotation. Future research should investigate if interventions that manipulate misaligned talus position in-vivo can also reduce AJF.

A Randomized Controlled Trial Assessing the Evolution of the Weight-Bearing Ankle Dorsiflexion Range of Motion Over 6 Sessions of Talus Mobilizations in Older Adults.

BACKGROUND: Ankle range of motion declines with age, affecting mobility and postural control. OBJECTIVE: The objective of this study was to investigate the effects of a talus mobilization-based intervention among healthy community-dwelling older adults presenting with limited weight-bearing ankle dorsiflexion range of motion and determine how ankle mobility evolved over the treatment. DESIGN: This was a randomized clinical trial. SETTING: This study was conducted in an outpatient clinic. PARTICIPANTS: Community-dwelling, older adults over 60 years of age who had limited ankle mobility participated in this study. INTERVENTIONS: The experimental intervention consisted of 6 sessions of manual therapy applied in the ankle joint. The control group received the same volume of sham treatment. MEASUREMENTS: The primary outcome was the weight-bearing ankle dorsiflexion range of motion as measured using the lunge test. Data were collected at 9 time points: baseline, after each session, and follow-up. RESULTS: A total of 36 participants were analyzed. A single session of mobilization increased ankle range of motion by 8 degrees (95% confidence interval = 6 to 11). At the end of the sixth session, this effect had increased slightly to 11 degrees (95% confidence interval = 9 to 13). Significant between-group differences were found throughout the intervention. LIMITATIONS: Optimal dose and effects from follow-up evaluations for treatment volumes of fewer than 6 sessions remain unknown. CONCLUSIONS: Six sessions of a talus mobilization-based intervention in healthy community-dwelling older adults found that the greatest mobility gain in terms of the weight-bearing ankle dorsiflexion range of motion is produced after the first session. Additional sessions produce smaller improvements with a slight upward trend. Importantly, the restoration of joint mobility is enhanced over time after the end of the intervention.

Return to Sport After Arthroscopic Autologous Matrix-Induced Chondrogenesis for Patients With Osteochondral Lesion of the Talus.

OBJECTIVE: To determine the rate of return of patients to sport after arthroscopic autologous matrix-induced chondrogenesis (AT-AMIC) for outcomes 2 years after surgery. DESIGN: Retrospective observational cross-sectional study. SETTING: C.A.S.C.O.-Foot and Ankle Unit, Istituto Ortopedico Galeazzi, Milan, Italy. PATIENTS AND INTERVENTION: Twenty-six consecutive patients, 65.4% male (mean ± SD age: 33.7 ± 11.0 years), that underwent AT-AMIC procedure between 2012 and 2015 were selected retrospectively. From this population, only sporting patients at amateur's level were included. Arthroscopic autologous matrix-induced chondrogenesis was proposed in patients with pain and persistent disability. MAIN OUTCOME MEASURES: All patients were assessed with the American Orthopaedic Foot and Ankle Score (AOFAS), physical component score of the 12-Item Short Form Health Survey (SF-12), Halasi ankle activity score, and University of California, Los Angeles (UCLA) activity scale preoperatively and at 24 months postoperatively. RESULTS: Overall, 80.8% of the patient group returned to the same preinjury sport. The mean follow-up was 42.6 ± 10.9 months (range from 25 to 62 months). Significant differences were observed with reference to AOFAS, SF-12, Halasi, and UCLA scores at the last follow-up in patients who had undergone AT-AMIC (all, P < 0.001). CONCLUSIONS: A high percentage of patients return to their preinjury sport after AT-AMIC surgery.

Spatial Subchondral Bone Density Reflecting Joint Loading of the Talus in Different Canidae.

OBJECTIVE: Subchondral bone density distribution can be used to study joint biomechanics non-invasively. Differences in joint loading between related species can aid in the understanding of joint loading and the development of certain types of orthopaedic pathology. This study was conducted to evaluate density distribution in the subchondral bone of the talus of different Canidae species, as a parameter reflecting the long-term joint loading in the tarsocrural joint. MATERIALS AND METHODS: The tarsal joints of cadaveric dogs of different breeds were included, that is, German Shepherd (n = 5), Bouvier des Flandres (n = 3) and Labrador Retriever (n = 6).Additionally, golden jackals (n = 5) (Canis aureus) and wolves (n = 5) (Canis lupus) were included. Consecutive computed tomography slices were made and the subchondral bone density distribution was evaluated using computer tomographic osteoabsorptiometry. Different breeds and species were visually compared. RESULTS: Differences were found in the subchondral bone density distribution of the talus between breeds and between species (Canis familiaris, Canis lupus and Canis aureus). DISCUSSION AND CONCLUSION: Based on the density distribution, there are differences in loading conditions of the tarsocrural joint in different species of Canidae. The joint loading distribution is very similar between dogs of the same breed and within the same species. Although between-breed differences can be explained by conformational differences, the between-species differences remain subject to further research.

Radius of curvature at the talocrural joint surface: inference of subject-specific kinematics.

PURPOSE: The coupled behavior of talocrural joint motion is primarily determined by the morphological features of the talar trochlea and tibiofibular mortise. Features of the radius of curvature of the talocrural joint, however, remain unclear. The objectives of this study were to evaluate the radius of curvature at the mid, medial, and lateral regions of both the talar trochlea and the tibial plafond, and to estimate subject-specific kinematics of the talocrural joint. METHODS: Computed tomography images of 44 subjects with healthy talocrural joints were assessed by creating three-dimensional bone models. The radii of curvature of the anterior and posterior regions at the mid, medial, and lateral regions of both the talar trochlea and the tibial plafond were calculated. Hypothetical dorsiflexion and plantarflexion axes of the talocrural joint were estimated from the shape of the talar trochlea. Orientations and distances of these axes were calculated. RESULTS: At both the talar trochlea and the tibial plafond, the anteromedial and posteromedial radii exhibited the largest coefficients of variation. The anterior-to-posterior radius ratio (APRR) of the medial talar trochlea significantly correlated with the mid APRR, anterior medial-to-lateral radius ratio (MLRR), and posterior MLRR of the trochlea (r = 0.45, 0.52, - 0.60, respectively, and all P < 0.01). CONCLUSIONS: The asymmetric shape of the medial talar trochlea seems to determine a fixed or changing axis of rotation at the talocrural joint. This subject-specific rotational axis of the talocrural joint should be considered in the management of patients with ankle injuries.

Medial Longitudinal Arch: Accuracy, Reliability, and Correlation Between Navicular Drop Test and Footprint Parameters.

OBJECTIVE: The purpose of this study was to evaluate the correlation among the navicular drop test, the arch angle, the Staheli index and the Chippaux-Smirak index. The reliability and the correlation among the footprint parameters were also estimated. METHODS: A cross-sectional study (n = 86; 59.3% women; 27.8 years, standard deviation: 4.8 years) was carried out. The navicular drop test was evaluated and footprint parameters using a plantar pressure platform were recorded in the dominant foot. Pearson correlation coefficients, intraclass correlation coefficient, standard error of measurement, and minimum detectable change were calculated. RESULTS: Both intrarater and interrater reliability were excellent for all the parameters evaluated (intraclass correlation coefficients > 0.880). Statistically significant correlations existed between the navicular drop test and footprints parameters (arch angle = 0,643; Staheli index = 0.633; Chippaux-Smirak index = 0.614). The footprint parameters had excellent correlation with each other (0.838-0.881). The navicular drop test and the footprint parameters studied were reproducible and thus had excellent reliability. CONCLUSION: The correlations obtained between the navicular drop test and the footprint parameters evaluated were good. The navicular drop test appears to be a reproducible, valid, and simple test for evaluating medial longitudinal arch height, having fewer disadvantages than using footprint parameters.

Inferring locomotor behaviours in Miocene New World monkeys using finite element analysis, geometric morphometrics and machine-learning classification techniques applied to talar morphology.

The talus is one of the most commonly preserved post-cranial elements in the platyrrhine fossil record. Talar morphology can provide information about postural adaptations because it is the anatomical structure responsible for transmitting body mass forces from the leg to the foot. The aim of this study is to test whether the locomotor behaviour of fossil Miocene platyrrhines could be inferred from their talus morphology. The extant sample was classified into three different locomotor categories and then talar strength was compared using finite-element analysis. Geometric morphometrics were used to quantify talar shape and to assess its association with biomechanical strength. Finally, several machine-learning (ML) algorithms were trained using both the biomechanical and morphometric data from the extant taxa to infer the possible locomotor behaviour of the Miocene fossil sample. The obtained results show that the different locomotor categories are distinguishable using either biomechanical or morphometric data. The ML algorithms categorized most of the fossil sample as arboreal quadrupeds. This study has shown that a combined approach can contribute to the understanding of platyrrhine talar morphology and its relationship with locomotion. This approach is likely to be beneficial for determining the locomotor habits in other fossil taxa.

Calcaneal adduction and eversion are coupled to talus and tibial rotation.

The purpose of this study was to quantify isolated coupling mechanisms of calcaneal adduction/abduction and calcaneal eversion/inversion to proximal bones in vitro. The in vitro approach is necessary because in vivo both movements appear together, making it impossible to determine the extent of their individual contribution to overall ankle joint coupling. Eight fresh frozen foot-leg specimens were tested. Data describing bone orientation and coupling mechanisms between segments were obtained using bone pin marker triads. The bone movement was described in a global coordinate system to examine the coupling between the calcaneus, talus and tibia. The strength of coupling was determined by means of the slope of a linear least squares fit to an angle-angle plot. The coupling coefficients in the present study indicate that not only calcaneal eversion/inversion (coupling coefficient: 0.68 ± 0.15) but to an even greater extent calcaneal adduction/abduction (coupling coefficient: 0.99 ± 0.10) was transferred into talus and tibial rotation, highlighting the relevance of calcaneal adduction for the overall ankle joint coupling. The results of this study present the possibility that controlling calcaneal adduction/abduction can affect talus and tibial rotation and therefore the possible genesis of overuse knee injuries.

Finite Element Study of Implant Subsidence and Medial Tilt in Agility Ankle Replacement.

BACKGROUND Clinical studies indicate that in total ankle arthroplasty, postoperative implant subsidence and medial tilt become two significant concerns of the ankle replacement system, and which are associated with the contact between the bones and the talar component. Up to now, little attention has focused on the contact between the bones and the talar component. MATERIAL AND METHODS In order to address implant subsidence and medial tilt, one three-dimensional finite element model of contact between the bone and the talar components was built with the material properties of the cancellous bone interpolated from the experimental data, which represents variation of material properties through the cancellous bones. The finite element model was used to study the following: variation of the Young's modulus of the bones, stiffness of the talar component, loading direction, and loading magnitude with the implant subsidence. RESULTS The computational results reveal that a variety of Young's modulus of the cancellous bones causes the medial tilting of the talar component and that big plastic strains are associated with tilting. The implant subsidence increases from 0.169 mm to 0.269 mm when the loading changes from 272 kg to 408 kg. However, to the contrary, the implant subsidence decreases from 0.2676 mm to 0.1783 mm when Young's modulus of the bones increases 50%. However, the implant subsidence shows little change with a different Young's modulus of the talar component from 88 GPa to 132 GPa. CONCLUSIONS Our study indicates that a variety of different Young's modulus of the cancellous bones cause the medial tilting of the talar component. To solve subsidence and tilting, both the contact area and the variation of material properties should be taken into account.

Physical Therapy Rehabilitation of an Adolescent Preprofessional Dancer Following Os Trigonum Excision: A Case Report.

Study Design Case report. Background An os trigonum can be a source of pain for dancers due to impingement during repetitive ankle plantar flexion movements. Following excision of an os trigonum, it is important to have a gradual, progressive return-to-dance program for optimal recovery. The purpose of this case report is to describe the postoperative management and return-to-dance progression of an adolescent dancer post os trigonum excision. Case Description An adolescent preprofessional female dancer had an extensive history of left posterior heel pain, beginning at age 8, that led to surgical removal of an os trigonum at age 15. Post surgery, the patient was seen for a total of 22 visits over the course of 20 weeks. Treatment included therapeutic exercises, neuromuscular re-education, and manual therapy. Return-to-dance tests and guidelines were used to safely progress to full, unrestricted dance participation. Outcomes The dancer had a full return of ankle range of motion, strength, and balance, improved patient-reported outcome scores, and was able to fully return to dance participation. Discussion Treating a dancer following os trigonum excision should involve a screen for hypermobility, clear communication with the dance instructor, awareness of dance-specific biomechanics, and proper reintegration into dance participation. Level of Evidence Therapy, level 5. J Orthop Sports Phys Ther 2018;48(3):194-203. Epub 7 Nov 2017. doi:10.2519/jospt.2018.7508.

Distribution of Subchondral Bone Puncture Strength in the Talus and Tibial Plafond: A Biomechanical Study.

We investigated talus and tibial plafond subchondral bone puncture strength based on surface location. Puncture tests of the subchondral bone were performed in 9 equal zones on the articular surface of 12 cadaver specimens aged 49.1 years (range, 36-56 years). Compressive load was applied through a microfracture awl at 2 mm/min. Puncture strength was defined as the first load drop in load-deflection curves. In the talus, zone 1 (215 ± 91 N) and zone 2, the anterior medial and anterior middle zones, had significantly greater puncture strength than zones 7, 8, and 9, the posterior medial, middle, and lateral zones (104 ± 43 N, 115 ± 43 N, and 102 ± 35 N, respectively; P < .001). In the tibial plafond, zone 3, the anterior-lateral zone, and zone 7, the posterior medial zone, had significantly greater strength than zone 8, the posterior middle zone (202 ± 72 N, 206 ± 121 N, and 112 ± 65 N, respectively; P < .001) These results suggest that the subchondral bone is significantly weaker to penetrative force in the posterior region than in the anterior region of the talar dome and of the tibial plafond. These findings may have implications for microfracture awl design and for understanding the complex anatomy and physiology of the ankle joint. LEVELS OF EVIDENCE: Controlled laboratory study.

The effect of persistent toe walking on the skeletal development of the pediatric foot and ankle.

The aim of this study was to determine whether persistent idiopathic toe walking leads to compensatory skeletal changes in the pediatric foot and ankle. Foot radiographs of children diagnosed with idiopathic toe walking and sex-matched and age-matched controls were retrospectively reviewed. Five blinded providers assessed the foot radiographs for skeletal changes to the ankle. The relationship between each measure and toe-walking status was examined. Providers observed radiographic evidence of skeletal changes of the talus in idiopathic toe walkers compared with controls, suggesting that persistent toe walking impacts the skeletal development of the talus. LEVEL OF EVIDENCE: prognostic level III.

Carotenoid dietary intakes and plasma concentrations are associated with heel bone ultrasound attenuation and osteoporotic fracture risk in the European Prospective Investigation into Cancer and Nutrition (EPIC)-Norfolk cohort.

Carotenoids are found in abundance in fruit and vegetables, and may be involved in the positive association of these foods with bone health. This study aimed to explore the associations of dietary carotenoid intakes and plasma concentrations with bone density status and osteoporotic fracture risk in a European population. Cross-sectional analyses (n 14 803) of bone density status, using calcaneal broadband ultrasound attenuation (BUA) and longitudinal analyses (n 25 439) of fracture cases were conducted on data from the prospective European Prospective Investigation into Cancer and Nutrition-Norfolk cohort of middle-aged and older men and women. Health and lifestyle questionnaires were completed, and dietary nutrient intakes were derived from 7-d food diaries. Multiple regression demonstrated significant positive trends in BUA for women across quintiles of dietary α-carotene intake (P=0·029), ß-carotene intake (P=0·003), ß-cryptoxanthin intake (P=0·031), combined lutein and zeaxanthin intake (P=0·010) and lycopene intake (P=0·005). No significant trends across plasma carotenoid concentration quintiles were apparent (n 4570). The Prentice-weighted Cox regression showed no trends in fracture risk across dietary carotenoid intake quintiles (mean follow-up time 12·5 years), except for a lower risk for wrist fracture in women with higher lutein and zeaxanthin intake (P=0·022); nevertheless, inter-quintile differences in fracture risk were found for both sexes. Analysis of plasma carotenoid data (mean follow-up time 11·9 years) showed lower hip fracture risk in men across higher plasma α-carotene (P=0·026) and ß-carotene (P=0·027) quintiles. This study provides novel evidence that dietary carotenoid intake is relevant to bone health in men and women, demonstrating that associations with bone density status and fracture risk exist for dietary intake of specific carotenoids and their plasma concentrations.

Comparative analysis of trabecular bone structure and orientation in South African hominin tali.

Tali of several hominin taxa are preserved in the fossil record and studies of the external morphology of these often show a mosaic of human-like and ape-like features. This has contributed to a growing recognition of variability characterizing locomotor kinematics of Australopithecus. In contrast, locomotor kinematics of another Plio-Pleistocene hominin, Paranthropus, are substantially less well-documented, in part, because of the paucity of postcranial fossils securely attributed to the genus. Since the talus transmits locomotor-based loads through the ankle and its internal structure is hypothesized to reflect accommodation to such loads, it is a cornerstone structure for reconstructing locomotor kinematics. Here we quantify and characterize trabecular bone morphology within tali attributed to Australopithecus africanus (StW 102, StW 363, StW 486) and Paranthropus robustus (TM 1517), making quantitative comparisons to modern humans, extant non-human apes, baboons, and a hominin talus attributed to Paranthropus boisei (KNM-ER 1464). Using high-resolution images of fossil tali (25 µm voxels), nine trabecular bone subregions of interest beneath the articular surface of the talar trochlea were segmented to quantify localized patterns in distribution and primary strut orientation. It was found that trabecular strut orientation and shape, in some cases, can discriminate amongst species characterized by different locomotor foot kinematics. Discriminant function analyses using standard trabecular bone structural properties align TM 1517 with Pan and Gorilla, while other hominin tali structurally most resemble those of baboons. In primary strut orientation, Paranthropus tali (KNM-ER 1464 and TM 1517) resemble the human condition in the anterior-medial subregion, where strut orientation appears positioned to distribute compressive loads medially and distally toward the talar head. In A. africanus tali (particularly StW 486), primary strut orientation in this region resembles that of apes. These results suggest that Paranthropus may have had a human-like medial weight shift during the last half of stance phase but Australopithecus did not.

The Arterial Anatomy of the Deltoid Ligament: A Cadaveric Study.

BACKGROUND: There is an increasing interest in the operative treatment of deltoid ligament disruption in the setting of chronic ankle instability. Understanding the vascular anatomy of the deltoid complex is beneficial when considering operative procedures on the medial ankle and may provide insight into factors that lead to chronic deltoid insufficiency and ankle instability. METHODS: Thirty-two pairs of cadaveric specimens (64 total legs) were amputated below the knee, and the tibialis anterior, tibialis posterior, and peroneal arteries were injected with India ink and Ward's blue latex. Specimens then underwent chemical debridement to identify the vascular supply to the deltoid ligament. A subset of specimens also underwent intraosseous debridement using the modified Spalteholz technique. RESULTS: The vascular supply to the deltoid ligament was clearly visualized in 60 (93.8%) specimens. Fifty-eight specimens (96.7%) had arterial supply with an origin from the medial tarsal artery, 57 specimens (95%) had supply from the tibialis posterior artery, and 23 (38.3%) specimens had supply from the tibialis anterior artery. All specimens had at least 1 location of intraosseous vascular supply, either at the medial malleolus or medial talus. CONCLUSION: There were 3 separate extraosseous sources and 2 intraosseous sources of vascular supply to the deltoid ligament. CLINICAL RELEVANCE: Knowledge of the vascular supply may aid in identifying factors that predispose a subset of patients with medial ankle sprains to failure of conservative treatment, as well as provide useful anatomic information when considering operative treatment for chronic ankle instability.

A simple but reliable method for measuring 3D Achilles tendon moment arm geometry from a single, static magnetic resonance scan.

Current methods for measuring in vivo 3D muscle-tendon moment arms generally rely on the acquisition of magnetic resonance imaging (MRI) scans at multiple joint angles. However, for patients with musculoskeletal pathologies such as fixed contractures, moving a joint through its full range of motion is not always feasible. The purpose of this research was to develop a simple, but reliable in vivo 3D Achilles tendon moment arm (ATMA) technique from a single static MRI scan. To accomplish this, for nine healthy adults (5 males, 4 females), the geometry of a cylinder was fit to the 3D form of the talus dome, which was used to estimate the talocrural flexion/extension axis, and a fifth-order polynomial fit to the line of action of the Achilles tendon. The single static scan in vivo 3D ATMA estimates were compared to estimates obtained from the same subjects at the same ankle joint angles using a previously validated 3D dynamic MRI based in vivo ATMA measurement technique. The ATMA estimates from the single scan in vivo 3D method (52.5mm±5.6) were in excellent agreement (ICC=0.912) to the validated in vivo 3D method (51.5mm±5.1). These data show reliable in vivo 3D ATMA can be obtained from a single MRI scan for healthy adult populations. The single scan, in vivo 3D ATMA technique provides researchers with a simple, but reliable method for obtaining subject-specific ATMAs for musculoskeletal modelling purposes.

3D Optical Investigation of 2 Nail Systems Used in Tibiotalocalcaneal Arthrodesis: A Biomechanical Study.

BACKGROUND: Although retrograde intramedullary nails for tibiotalocalcaneal arthrodesis (TTCA) are an established fixation method, few studies have evaluated the stability of the available nail systems. The purpose of this study was to compare biomechanically the primary stability of 2 nail-systems, A3 (Small Bone Innovations) and HAN (Synthes), in human cadavers and analyze the exact point of instability in TTCA by means of optical measurement. METHODS: In 6 pairs of lower legs (n = 12) of fresh-frozen human cadavers with osteoporotic bone structure, bone mineral density (BMD) was determined. Pairwise randomized implantation of either an HAN or A3 nail was executed. Performance and stability were measured by quasi-static tests using 3D motion tracking (NDI Optotrak-Certus) followed by cyclic loading tests during dorsi- and plantarflexion. RESULTS: 3D optical analysis in quasi-static tests showed a significantly lower degree of movement for the HAN nail in rotational and dorsi-/plantarflexion, especially in the subtalar joint. Cyclic loading tests were consistent with quasi-static tests. CONCLUSION: The A3 nail offered lower stability during axial torsion in the ankle and subtalar joints and during plantar- and dorsiflexion in the subtalar joint in osteoporotic bones. This study was the first to examine the primary stability of different arthrodesis nails in TTCA and their bony parts with a 3D motion analysis. CLINICAL RELEVANCE: The better stability of the locking-only HAN nail in this osteoporotic test setup could lead to more favorable results in comparison to the A3 nail in clinical use.

A prospective follow up of age related changes in the subchondral bone density of the talus of healthy Labrador Retrievers.

BACKGROUND: During growth, the skeletal structures adapt to the increased loading conditions and mature to a fully-grown skeleton. Subchondral bone density reflects the effect of long-term joint loading and it is expected to change over time. The aim of this study was to describe the long-term changes in the density distribution of the subchondral bone of the talus of healthy Labrador Retrievers in a prospective study. RESULTS: The subchondral bone density distribution was evaluated using computed tomographic osteoabsorptiometry (CTOAM). Visually, all joints showed very similar density distribution patterns. No significant differences in the topography of the density maxima were found between t1 and t2. The mean density, maximum density, and maximum area ratio (MAR) were significantly increased with increasing age. CONCLUSIONS: The subchondral bone density of the talus of healthy Labrador Retrievers increases with increasing age. It is likely an adaptive response of the subchondral bone due to increased joint loading during growth.