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.

Back foot influence on dorsiflexion using three different positions of the weight bearing lunge test.

OBJECTIVES: To determine whether back foot (BF) position influences dorsiflexion range of motion (DFROM) during three different positions of the weight bearing lunge test (WBLT). DESIGN: Randomised, repeated measures design. SETTING: Sports clubs. PARTICIPANTS: 52 athletes participating in cutting and pivoting sports. MAIN OUTCOME MEASURES: DFROM was obtained using a WBLT in three different BF positions: BF heel in full contact with the floor, BF heel raised off the floor and BF was non weight bearing (NWB). All measurements were obtained using three methods: inclinometer at the tibial tuberosity, toe to wall distance and goniometer angle from the lateral malleolus to the fibula head. Differences between testing positions were determined using a repeated measures one-way ANOVA and reliability analysis was performed using the Intraclass Correlation Coefficient (ICC). RESULTS: DFROM was statistically significantly different for all three positions of the WBLT for each measurement technique (P < .001). These results were associated with large effect sizes for all BF positions and measurement techniques. Reliability ICC values were excellent for all measurements (ICC 0.94-0.99). CONCLUSIONS: Results show that DFROM differs depending upon the position of the BF during the WBLT. Further research is needed to establish the reproducibility of these three BF positions due to the variability observed.

Fibular and metatarsal osteosynthesis in a southern brown howler monkey (Alouatta guariba clamitans).

Here we describe a successful surgical management of a distal fibular fracture combined with a tarsocrural luxation and multiple metatarsal fractures in the left foot of a southern brown howler monkey (Alouatta guariba clamitans). We achieved satisfactory outcome by applying intramedullary pinning for each of the bone fractures and closed reduction of joint luxation-kept in place only by bone alignment, without further ligament reconstruction. Bone healing occurred uneventfully within eight weeks and the monkey's foot regained its normal function. Therefore, we could properly release the patient back into the wild.

El peroné: mal alumno, pero buen profesor. (¿Qué tiene prioridad biológica: la integridad, o la supervivencia?) / Fibula: a bad pupil but a good profesor. (What comes first, integrity or survival?)

La concepción original del mecanostato como un regulador de la rigidez estructural ósea orientado a mantener un determinado 'factor de seguridad' en todos los esqueletos parece no corresponder por igual a cualquier hueso y para cualquier tipo de estímulo. Hemos descubierto que la estructura cortical diafisaria del peroné humano manifiesta un comportamiento ambiguo del sistema, referido al uso del pie. La diáfisis peronea, además de ser insensible al desuso, se rigidiza, como sería de esperar, por entrenamientos en disciplinas deportivas que rotan o revierten el pie (hockey, fútbol, rugby); pero, llamativamente, se flexibiliza en su mitad proximal por entrenamiento en carrera larga, que optimiza el rendimiento del salto que acompaña a cada paso. La referida rigidización robustecería la región peronea de inserción de los músculos que rotan o revierten el pie, favoreciendo la locomoción sobre terrenos irregulares o 'gambeteando', propia de especies predadoras como los leopardos. La 'inesperada' flexibilización proximal, pese a reducir la resistencia a la fractura por flexión lateral (poco frecuente en el hombre), favorecería la absorción elástica de la energía contráctil de la musculatura inserta, optimizando el rendimiento del salto al correr, condición vital para especies presas como las gacelas. La falta de analogía de estas respuestas de la estructura peronea a distintos entrenamientos, incompatible con el mantenimiento de un factor de seguridad, sugiere su vinculación preferencial con la optimización de aptitudes esqueléticas con valor selectivo. Esto ampliaría el espectro regulatorio del mecanostato a propiedades esqueléticas 'vitales', más allá del control de la integridad ósea. Su manifestación en el hombre, ajena a connotaciones selectivas (quizá resultante del mantenimiento de genes ancestrales), permitiría proponer la indicación de ejercicios orientados en direcciones preferenciales a este respecto, especialmente cuando estas coincidieran con las de las fuerzas que podrían fracturar al hueso. (AU)

The original notion of the mechanostat as a regulator of bone structural rigidity oriented to maintain a certain 'safety factor' in all skeletons does not seem to correspond equally to every bone and for any type of stimulus. We have discovered that the diaphyseal cortical structure of the human fibula shows an ambiguous behavior of the system, with reference to the use of the foot. The peroneal shaft, in addition to being insensitive to disuse, becomes stiffened, as might be expected, by training in sport disciplines that involve rotating or reversing the foot (hockey, soccer, rugby); but, remarkably, it becomes more flexible in its proximal half by long-distance running training, which optimizes the performance of the jump that accompanies each step. The stiffening would strengthen the peroneal region of insertion of the muscles that rotate or reverse the foot, favoring locomotion on uneven terrain or 'dribbling', typical of predatory species such as leopards. The 'unexpected' proximal flexibilization, despite reducing the resistance to lateral flexion fracture (rare in human), would favor the elastic absorption of contractile energy from the inserted muscles, optimizing jumping performance when running, a vital condition for prey species such as gazelles. The lack of analogy of these responses of the peroneal structure to different training, incompatible with the maintenance of a safety factor, suggests its preferential link with the optimization of skeletal aptitudes with selective value. This would expand the regulatory spectrum of the mechanostat to 'vital' skeletal properties, beyond the control of bone integrity. Its manifestation in humans, oblivious to selective connotations (perhaps resulting from the maintenance of ancestral genes), would make it possible to propose the indication of exercises oriented in preferential directions, especially when they coincide with the direction of the forces that could fracture the bone. (AU)

Is Proximal Fibula Epiphysiodesis Necessary When Performing a Proximal Tibial Epiphysiodesis?

BACKGROUND: Controversy exists regarding the need for proximal fibular epiphysiodesis in conjunction with proximal tibial epiphysiodesis to prevent relative overgrowth of the fibula. The purpose of this study was to determine the incidence of relative fibular overgrowth in patients who had undergone proximal tibial epiphysiodesis with or without proximal fibular epiphysiodesis to manage leg-length discrepancy. METHODS: We identified patients who had undergone proximal tibial epiphysiodesis, with or without concomitant fibular epiphysiodesis, followed to skeletal maturity, and with adequate scanograms to measure tibial and fibular lengths. We assessed tibial and fibular lengths, ratios, and distances between the tibia and fibula proximally and distally preoperatively and at skeletal maturity, and obvious radiographic proximal migration of the fibular head. RESULTS: A total of 234 patients met inclusion criteria, including 112 girls and 122 boys. In total, 179 patients had undergone concomitant fibular epiphysiodesis, and 55 had not. The fibular epiphysiodesis group was significantly younger preoperatively than the nonfibular epiphysiodesis group (average: 12.3 vs. 13.6 y), which accounted for most of the preoperative differences noted between the groups. Within the subset of younger patients (≥2 y of growth remaining at the time of epiphysiodesis), there were statistically significant differences between those with or without fibular epiphysiodesis at skeletal maturity in the proximal tibial-fibular distance (P<0.01) and the tibia:fibula ratio (0.96±0.02 vs. 0.98±0.02; P<0.02), but not in the distal tibial-fibular distance (P=0.46). Obvious fibular head proximal migration was noted in 10 patients, including 5/179 with concomitant proximal fibular epiphysiodesis, and 5/55 without (P<0.01). No patient was recorded as symptomatic with radiographic overgrowth, and no peroneal nerve injury occurred in any patient in this cohort. CONCLUSIONS: On the basis of this study, concomitant proximal fibular epiphysiodesis does not appear to be necessary in patients with 2 years or less of growth remaining, nor does it unequivocally prevent fibular head overgrowth. While the tibia:fibula ratio was quite consistent in general, there were individuals with relative fibular head prominence for whom fibular epiphysiodesis may be appropriate, particularly in relatively immature patients. LEVEL OF EVIDENCE: Level III-retrospective comparative study.

Association of Bolster Duration With Uptake Rates of Fibula Donor Site Skin Grafts.

Importance: The fibula free flap donor site is associated with both short-term and long-term morbidity. Split-thickness skin graft (STSG) loss can lead to long delays in donor site healing and is associated with significant adverse sequelae. Patients may experience initial good STSG uptake after bolster removal but may have subsequent partial or total loss related to contact pressure or shearing. Objective: To determine if increased duration of bolster use is associated with increased STSG uptake rates following fibula free flap reconstruction. Design, Setting, and Participants: This retrospective cohort study included patients 18 years and older undergoing fibula free flap reconstruction following head and neck extirpative surgery at a tertiary care academic medical center from May 2013 to March 2019. The donor sites were photographed 4 weeks postoperatively, and areas of graft uptake were measured using image processing software. The baseline demographic, comorbidity, and operative characteristics were also collected. Interventions: A fine mesh gauze with 3% bismuth tribromophenate and petrolatum blend bolster was sutured over leg STSGs placed on fibula free flap donor sites intraoperatively, and the ankle and lower leg were immobilized for 5 days in a plaster splint. Bolsters were either removed on postoperative day 5 or 14. Thereafter, the STSGs were covered with a petroleum and bismuth gauze and a cotton dressing. Main Outcomes and Measures: Rates of donor site infection and STSG percentage uptake at 4 weeks. Results: Of the 42 included patients, 31 (74%) were male, and the mean (SD) age was 62.1 (13.1) years. A total of 20 patients were included in the 5-day group, and 22 were included in the 14-day group. The 14-day bolster group had a higher mean percentage skin graft uptake rate compared with the 5-day bolster duration group (77.5% vs 59.9%), with an effect size of -0.632 (95% CI, -1.260 to -0.004). Patients with Adult Comorbidity Evalution-27 scores of 3 had poorer rates of STSG uptake compared with patients with Adult Comorbidity Evalution-27 scores of 0 to 2 (65.9% vs 82.9%), with an effect size of 0.599 (95% CI, -0.191 to 1.389). No donor site infections were noted in either group. Conclusions and Relevance: Fourteen-day bolster application to the fibula free flap donor site was associated with better STSG uptake rates than 5-day bolster application.

Biomechanical properties of anuran long bones: correlations with locomotor modes and habitat use.

Long bones are subjected to mechanical loads during locomotion that will influence their biomechanical properties through a feedback mechanism (the bone mechanostat). This mechanism adapts the spatial distribution of the mineralized tissue to resist compression, bending and torsion. Among vertebrates, anurans represent an excellent group to study long bone properties because they vary widely in locomotor modes and habitat use, which enforce different skeletal loadings. In this study, we hypothesized that (a) the cortical bone mass, density and design of anuran femur and tibiofibula would reflect the mechanical influences of the different locomotor modes and habitat use, and (b) the relationships between the architectural efficiency of cortical design (cross-sectional moments of inertia) and the intrinsic stiffness of cortical tissue [cortical mineral density; the 'distribution/quality' (d/q) relationship] would describe some inter-specific differences in the efficiency of the bone mechanostat to improve bone design under different mechanical loads. To test this hypothesis, we determined tomographic (peripheral quantitative computed tomography) indicators of bone mass, mineralization, and design along the femur and tibiofibula of four anuran species with different modes of locomotion and use of habitat. We found inter-specific differences in all measures between the distal and proximal ends and mid-diaphysis of the bones. In general, terrestrial-hopper species had the highest values. Arboreal-walker species had the lowest values for all variables except for cortical bone mineral density, which was lowest in aquatic-swimmer species. The d/q relationships showed similar responses of bone modeling as a function of cortical stiffness for aquatic and arboreal species, whereas terrestrial-hoppers had higher values for moments of inertia regardless of the tissue compliance to be deformed. These results provide new evidence regarding the significant role of movement and habitat use in addition to the biomechanical properties of long bones within a morpho-functional and comparative context in anuran species.

Posterior malleolus fractures in Bosworth fracture-dislocations. A combination not to be missed.

OBJECTIVES: Posterior malleolar fractures (PM) have been linked to inferior outcome in malleolar fractures. This study aims to analyze the prevalence and pathoanatomy of PM fractures in Bosworth fracture-dislocations (BF). MATERIALS & METHODS: Radiographs and computed tomography (CT) scans of 13 patients treated at our institution and 97 cases published between 1947 and 2018, identified in a systematic literature search, were evaluated with respect to the pathoanatomy of BF. In all 13 cases from the present study and in 10 cases from the literature, axial CT scans were performed. RESULTS: All 13 patients (100%) with BF from the present series and 61 of 97 documented cases (63%) of BF from the literature were associated with a PM fracture. In patients with a complete CT analysis, dislocation of the fibula behind the posterior tibial rim was associated with extraincisural (Bartonícek / Rammelt type 1) PM fractures. Displacement of the fibula between the displaced PM fragment and the tibia was associated with Bartonícek / Rammelt types 2 and 3 PM fractures. CONCLUSIONS: Seventy prevent of all reported BF are associated with a PM fracture. The true prevalence may be even higher because of the historically infrequent use of CT imaging. The pathoanatomy of the PM fragment is highly variable as is the kind of fibular displacement in BF. Therefore, CT scanning should be performed routinely in BF. Displaced PM fractures in BF involving the incisura should be treated operatively via a direct posterolateral approach.

Age-related site-specific modifications in diaphyseal structural properties of the human fibula: Furrows and cross-sectional geometry.

OBJECTIVES: Fibular structure is related to locomotor behavior, which allows an exploration of mobility in past human populations with diaphyseal cross-sectional geometry (CSG). However, bone structure depends on age-related changes. Nonmechanical alterations can affect biomechanical investigations. In this study, we examined how the cortical area and the variables used as functional markers in the fibular diaphysis (i.e., CSG and furrows) change with aging. We predict classic and specific modifications, and we discuss functional interpretations based on bone structure. MATERIALS AND METHODS: The sample consisted of 124 individuals of known age in whom the fibular furrow depths were measured with calipers. Microcomputed tomography (micro-CT) scanning of 38 individuals provided CSG (e.g., cortical area, shape index, and robusticity) and fibular furrow indices. CSG was studied at five cross sections taken along the diaphysis. Linear regression analyses and age group comparisons were conducted. RESULTS: The cross-sectional shape summary by fibular furrows and shape index and the total area did not change with aging; in contrast, the cortical area and the robusticity (Zp-std) decreased with age. DISCUSSION: The decrease in robusticity (Zp-std) with aging is due to the maintenance of total area, which is related to the specific mechanical environment of the fibula, and to the loss of cortical bone and not to the decrease in mechanical stress. This finding is consistent with the lower bone modeling capacity in aged individuals, which also explains the lack of significant changes in the diaphyseal shape. Thus, fibular structure in older individuals is due to a combination of early bone adaptations to stress and aging effects.

Relative fibular strength and locomotor behavior in KNM-WT 15000 and OH 35.

Relative fibular/tibial strength has been demonstrated to vary with locomotor behavior among anthropoid primates. In this study fibular/tibial strength was determined in KNM-WT 15000, a juvenile Homo erectus individual (1.5 Ma), and in OH 35, a Homo habilis (or possibly Paranthropus boisei) individual (1.8 Ma), and compared to that of adult modern humans (n = 79), chimpanzees (n = 16), gorillas (n = 16) and orangutans (n = 11). Ontogenetic changes in fibular/tibial strength were also analyzed due to KNM-WT 15000's juvenile status. Cross-sectional properties at midshaft were derived from multi-plane radiography and external contours, or CT scanning. Comparisons of log-transformed fibular/tibial polar second moment of area and anteroposterior (A-P) and mediolateral (M-L) second moments of area were carried out between extant species. Fossil deviations from each extant taxon's mean proportion were calculated in standard deviation (SD) units for that taxon. Great apes differ significantly from modern humans, with relatively stronger fibulae, particularly in the M-L plane. KNM-WT 15000 is more than 2 SD from all great apes (≥3 SD in the M-L plane) and within 1 SD of modern humans for almost all variables. This is not a result of its age, as fibular/tibial strength slightly decreases with age (i.e., becomes less like that of great apes) in humans. OH 35 falls within 1 SD of chimpanzees and orangutans for the majority of cross-sectional proportions, but more than 1 SD from humans. KNM-WT 15000 is demonstrated to be fully modern, complimenting other indications of complete terrestrial bipedality and possibly showing adaptations for endurance running. OH 35 has some human-like features; however, the relative strength of the two bones aligns the specimen with great apes, consistent with a significant degree of arboreality, in particular, vertical climbing.

Motion of the distal tibiofibular syndesmosis under different loading patterns: A biomechanical study.

PURPOSE: The distal tibiofibular syndesmosis is an important structure for ankle stability. The objective of this study was to evaluate the motion of the syndesmosis under different loading patterns and determine the characteristics of the syndesmotic motion. METHODS: Six fresh cadaveric lower extremity specimens with the knee reserved were tested in this study. The skin and muscles were removed with all ligaments around the syndesmosis and knee and ankle joint intact. An axial load of 600 N was applied to the specimens with the ankle joint in 10° dorsiflexion, neutral position, and 15° plantar flexion using a universal material testing machine. Then, with the ankle joint positioned neutrally, a combination of 600-N axial and 5-Nm torsional external rotation loading was applied to the specimens. The medial-lateral and anterior-posterior displacement and rotation of the distal fibula relative to the distal tibia were measured. RESULTS: Under the axial loading, the distal fibula tended to move medially and anteriorly and rotate internally with the ankle positioned from the neutral position to 15° plantar flexion. Meanwhile, when the ankle was positioned from the neutral position to 10° dorsiflexion, the distal fibula tended to move laterally and posteriorly and rotate externally. Under the combined loading, with respect to the isolated axial loading, the distal fibula tended to move medially and posteriorly, and rotate externally relative to the distal tibia. CONCLUSION: Micro motion existed in the syndesmosis. The relative motion of the syndesmosis was correlated to the ankle position and loading patterns.

Fibula: The Forgotten Bone-May It Provide Some Insight On a Wider Scope for Bone Mechanostat Control?

The human fibula responds to its mechanical environment differently from the tibia accordingly with foot usage. Fibula structure is unaffected by disuse, and is stronger concerning lateral bending in soccer players (who evert and rotate the foot) and weaker in long-distance runners (who jump while running) with respect to untrained controls, along the insertion region of peroneus muscles. These features, strikingly associated to the abilities of the fibulae of predator and prey quadrupeds to manage uneven surfaces and to store elastic energy to jump, respectively, suggest that bone mechanostat would control bone properties with high selective connotations beyond structural strength.

Mechanical Loading Differentially Affects Osteocytes in Fibulae from Lactating Mice Compared to Osteocytes in Virgin Mice: Possible Role for Lacuna Size.

Hormonal changes during lactation are associated with profound changes in bone cell biology, such as osteocytic osteolysis, resulting in larger lacunae. Larger lacuna shape theoretically enhances the transmission of mechanical signals to osteocytes. We aimed to provide experimental evidence supporting this theory by comparing the mechanoresponse of osteocytes in the bone of lactating mice, which have enlarged lacunae due to osteocytic osteolysis, with the response of osteocytes in bone from age-matched virgin mice. The osteocyte mechanoresponse was measured in excised fibulae that were cultured in hormone-free medium for 24 h and cyclically loaded for 10 min (sinusoidal compressive load, 3000 µÎµ, 5 Hz) by quantifying loading-related changes in Sost mRNA expression (qPCR) and sclerostin and ß-catenin protein expression (immunohistochemistry). Loading decreased Sost expression by ~ threefold in fibulae of lactating mice. The loading-induced decrease in sclerostin protein expression by osteocytes was larger in lactating mice (55% decrease ± 14 (± SD), n = 8) than virgin mice (33% decrease ± 15, n = 7). Mechanical loading upregulated ß-catenin expression in osteocytes in lactating mice by 3.5-fold (± 0.2, n = 6) which is significantly (p < 0.01) higher than the 1.6-fold increase in ß-catenin expression by osteocytes in fibulae from virgin mice (± 0.12, n = 4). These results suggest that osteocytes in fibulae from lactating mice with large lacunae may respond stronger to mechanical loading than those from virgin mice. This could indicate that osteocytes residing in larger lacuna show a stronger response to mechanical loading.

Strain Distribution in the Anterior Inferior Tibiofibular Ligament, Posterior Inferior Tibiofibular Ligament, and Interosseous Membrane Using Digital Image Correlation.

BACKGROUND: Ligament repair and augmentation techniques can stabilize syndesmosis injuries. However, little is known about the mechanical behavior of syndesmotic ligaments. The aim of this study was to analyze full-field strain, strain trend under foot rotation, and subregional strain differences of the anterior inferior tibiofibular ligament (AITFL), posterior inferior tibiofibular ligament (PITFL), and interosseous membrane (IOM). METHODS: Eleven fresh-frozen lower limbs were dissected to expose the AITFL, PITFL, and IOM. The foot underwent rotation from 0° to 25° internal and 35° external, with 3 ankle positions (neutral, 15° dorsiflexion, and 25° plantarflexion) and a vertical load of 430 N. Ligament strain was recorded using digital image correlation. RESULTS: The mean strain on the AITFL with 35° external rotation was greater in the proximal portion compared with distal portion in the neutral position ( P = .009) and dorsiflexion ( P = .003). The mean strain in the tibial insertion and midsubstance near tibial insertion were greater when compared with other regions ( P = .018 and P = .009). The subregions of mean strain in the PITFL and IOM groups were not significantly different. The strain trend of AITFL, PITFL, and IOM showed common transformation, just when the foot was externally rotated. CONCLUSION: The findings of this study show that a significantly high strain was observed on the proximal part and the midsubstance near the Chaput tubercle of the AITFL when the ankle was externally rotated. All 3 ligaments resisted the torque in the syndesmosis by external rotation of the foot. CLINICAL RELEVANCE: This study allows for better understanding of the mechanical behavior of the syndesmosis ligaments, which could influence the repair technique and AITFL augmentation techniques.

Cross-sectional properties of the lower limb long bones in the Middle Pleistocene Sima de los Huesos sample (Sierra de Atapuerca, Spain).

The recovery to date of three complete and five partial femora, seven complete tibiae, and four complete fibulae from the Atapuerca Sima de los Huesos site provides an opportunity to analyze the biomechanical cross-sectional properties in this Middle Pleistocene population and to compare them with those of other fossil hominins and recent modern humans. We have performed direct comparisons of the cross-sectional geometric parameters and reduced major axis (RMA) regression lines among different samples. We have determined that Atapuerca Sima de los Huesos (SH) fossils have significantly thicker cortices than those of recent modern humans for the three leg bones at all diaphyseal levels, except that of the femur at 35% of biomechanical length. The SH bones are similar to those of Neandertals and Middle Pleistocene humans and different from Homo sapiens in their diaphyseal cross-sectional shape and strength parameters. When standardized by estimated body size, both the SH and Neandertal leg bones have in general greater strength than those of H. sapiens from the early modern (EMH), Upper Paleolithic (UP), and recent populations (RH). The Sima de los Huesos human leg bones have, in general terms, an ancestral pattern similar to that of Pleistocene humans and differing from H. sapiens.

Role of the Deltoid Ligament in Syndesmotic Instability.

BACKGROUND: The deltoid ligament (DL) is the principal ligamentous stabilizer of the medial ankle joint. Little is known, however, about the contribution of the DL toward stabilizing the syndesmosis. The aim of this study was to arthroscopically evaluate whether the DL contributes to syndesmotic stability in the coronal plane. METHODS: Eight above-knee cadaveric specimens were used in this study. A lateral hook test was performed by applying 100 N of lateral force to the fibula in the intact state and after sequential transection of the DL, anterior-inferior tibiofibular ligament (AITFL), interosseous ligament (IOL), and posterior-inferior tibiofibular ligament (PITFL). At each stage, distal tibiofibular diastasis was measured arthroscopically at both the anterior and posterior third of the incisura and compared to stress measurements of the intact syndesmosis. Measurements were performed using probes ranging from 0.1 to 6.0 mm, with 0.1-mm increments. RESULTS: There was no significant increase in diastasis at either the anterior or posterior third of the tibiofibular articulation after isolated DL disruption, nor when combined with AITFL transection. In contrast, a significant increase in diastasis was observed following additional disruption of the IOL (anterior and posterior third diastasis, P= .012 and .026, respectively), and after transection of all 3 syndesmotic ligaments (anterior and posterior third diastasis, P=.001 and .001, respectively). CONCLUSION: When evaluating the syndesmosis arthroscopically in a cadaveric model under lateral stress, neither isolated disruption of the DL nor combined DL and AITFL injuries destabilized the syndesmosis in the coronal plane. In contrast, the syndesmosis became unstable if the DL was injured in conjunction with partial syndesmotic disruption that included the AITFL and IOL. CLINICAL RELEVANCE: Disruption of the DL appeared to destabilize the syndesmosis in the coronal plane when associated with partial disruption of the syndesmosis (AITFL and IOL).

Outcome of distal tibia physeal fractures: a review of cases as related to risk factors.

INTRODUCTION: The physeal fractures represent the 20-30% of all fractures of the child. The distal tibial physis is the third most frequently injured. The most important complication is the premature physeal closure (PPC). Aim of this study is to evaluate risk factors that can influence the outcome like fracture pattern, fracture displacement, mechanism of injury and treatment method. MATERIAL AND METHODS: The records of 46 patients treated for distal tibia physeal fractures between 2003 and 2013 were reviewed. Initial injury radiographs were categorized according to Salter-Harris and Dias-Tachdjian classifications and the initial and post-treatment fracture displacementwas measured. Any complex fractures had preoperative CT for additional assessment. Three different types of treatment were compared: closed reduction and casting versus closed reduction and percutaneous pinning versus ORIF. RESULTS: Therewas significantly less residual displacement in patients who had ORIF versus those who had closed reduction and percutaneous Kirschner wires or plaster only. In fractures with an intact fibula, we found significantly less initial and residual displacement. The Dias-Tachdjian classification is significantly correlated with the displacement. Patients studied with CT show a less degree of post reduction displacement. At the final follow-up we found only one PPC as complication. CONCLUSION: The physeal fractures are very common in children and the main goal is to avoid any complications. It is clear that the development of complications after distal tibial fractures is due to multiple contributing factors like skeletal maturity, severity of injury, fracture type, degree of comminution and displacement aswell as adequacy of reduction. A premature physeal closure is the most common complication. The fibula fracture can play an important role in initial displacement. The presence of an intact fibula and a good anatomical reduction have a significant positive influence on fracture outcome.

The fibular meniscus of the kangaroo as an adaptation against external tibial rotation during saltatorial locomotion.

The kangaroo knee is, as in other species, a complex diarthrodial joint dependent on interacting osseous, cartilaginous and ligamentous components for its stability. While principal load bearing occurs through the femorotibial articulation, additional lateral articulations involving the fibula and lateral fabella also contribute to the functional arrangement. Several fibrocartilage and ligamentous structures in this joint remain unexplained or have been misunderstood in previous studies. In this study, we review the existing literature on the structure of the kangaroo 'knee' before providing a new description of the gross anatomical and histological structures. In particular, we present strong evidence that the previously described 'femorofibular disc' is best described as a fibular meniscus on the basis of its gross and histological anatomy. Further, we found it to be joined by a distinct tendinous tract connecting one belly of the m. gastrocnemius with the lateral meniscus, via a hyaline cartilage cornu of the enlarged lateral fabella. The complex of ligaments connecting the fibular meniscus to the surrounding connective tissues and muscles appears to provide a strong resistance to external rotation of the tibia, via the restriction of independent movement of the proximal fibula. We suggest this may be an adaptation to resist the rotational torque applied across the joint during bipedal saltatory locomotion in kangaroos.

Biomechanics of the classic metaphyseal lesion: finite element analysis.

BACKGROUND: The classic metaphyseal lesion (CML) is strongly associated with infant abuse, but the biomechanics responsible for this injury have not been rigorously studied. Radiologic and CT-pathological correlates show that the distal tibial CML always involves the cortex near the subperiosteal bone collar, with variable extension of the fracture into the medullary cavity. Therefore, it is reasonable to assume that the primary site of bone failure is cortical, rather than intramedullary. OBJECTIVE: This study focuses on the strain patterns generated from finite element modeling to identify loading scenarios and regions of the cortex that are susceptible to bone failure. MATERIALS AND METHODS: A geometric model was constructed from a normal 3-month-old infant's distal tibia and fibula. The model's boundary conditions were set to mimic forceful manipulation of the ankle with eight load modalities (tension, compression, internal rotation, external rotation, dorsiflexion, plantar flexion, valgus bending and varus bending). RESULTS: For all modalities except internal and external rotation, simulations showed increased cortical strains near the subperiosteal bone collar. Tension generated the largest magnitude of cortical strain (24%) that was uniformly distributed near the subperiosteal bone collar. Compression generated the same distribution of strain but to a lesser magnitude overall (15%). Dorsiflexion and plantar flexion generated high (22%) and moderate (14%) localized cortical strains, respectively, near the subperiosteal bone collar. Lower cortical strains resulted from valgus bending, varus bending, internal rotation and external rotation (8-10%). The highest valgus and varus bending cortical strains occurred medially. CONCLUSION: These simulations suggest that the likelihood of the initial cortical bone failure of the CML is higher along the margin of the subperiosteal bone collar when the ankle is under tension, compression, valgus bending, varus bending, dorsiflexion and plantar flexion, but not under internal and external rotation. Focal cortical strains along the medial margins of the subperiosteal bone collar with varus and valgus bending may explain the known tendency for focal distal tibial CMLs to occur medially. Further research is needed to determine the threshold of applied forces required to produce this strong indicator of infant abuse.