Three-Dimensional Bowing Measurement of Distal Femur at Actual Size and Clinical Implications of Total Knee Arthroplasty.

Background and Objectives: To assess femoral shaft bowing (FSB) in coronal and sagittal planes and introduce the clinical implications of total knee arthroplasty (TKA) by analyzing a three-dimensional (3D) model with virtual implantation of the femoral component. Materials and Methods: Sixty-eight patients (average age: 69.1 years) underwent 3D model reconstruction of medullary canals using computed tomography (CT) data imported into Mimics® software (version 21.0). A mechanical axis (MA) line was drawn from the midportion of the femoral head to the center of the intercondylar notch. Proximal/distal straight centerlines (length, 60 mm; diameter, 1 mm) were placed in the medullary canal's center. Acute angles between these centerlines were measured to assess lateral and anterior bowing. The acute angle between the distal centerline and MA line was measured for distal coronal and sagittal alignment in both anteroposterior (AP) and lateral views. The diameter of curve (DOC) along the posterior border of the medulla was measured. Results: The mean lateral bowing in the AP view was 3.71°, and the mean anterior bowing in the lateral view was 11.82°. The average DOC of the medullary canal was 1501.68 mm. The average distal coronal alignment of all femurs was 6.40°, while the distal sagittal alignment was 2.66°. Overall, 22 femurs had coronal bowing, 42 had sagittal bowing, and 15 had both. Conclusions: In Asian populations, FSB can occur in coronal, sagittal, or both planes. Increased anterolateral FSB may lead to cortical abutment in the sagittal plane, despite limited space in the coronal plane. During TKA, distal coronal alignment guides the distal femoral valgus cut angle, whereas distal sagittal alignment aids in predicting femoral component positioning to avoid anterior notching. However, osteotomies along the anterior cortical bone intended to prevent notching may result in outliers due to differences between the distal sagittal alignment and the distal anterior cortical axis.

Differences in Pilon Fractures According to Ipsilateral Fibular Injury Patterns: A Clinical Computed Tomography-Based Mapping Study.

Background: Preoperative verification of fracture morphology is essential for determining the definitive fixation strategy in the management of a pilon fracture. This study aimed to determine the correlation between fibular injury patterns and fracture morphologies and introduce clinical implications. Methods: Computed tomography scans of 96 pilon fractures were retrospectively analyzed and divided into three types: intact fibula, simple fracture, and multifragment fracture. The principal fracture line and comminution zones were illustrated on a plafond template and diagrammatized on a 6 × 6 grid using PowerPoint software as fracture mapping. Correlations between fibular injury patterns and fracture morphologies, including comminution zones and principal fracture lines, were analyzed. Results: The thickest comminution zone was most often located in the anterolateral quadrant. According to fibular injury patterns, the comminution zone of the multifragment group was placed two grids more lateral than that of other groups. Lateral exits of the principal fracture line in the multifragment group were much more concentrated within the fibular incisura. Conclusions: In pilon fractures, a more complex fibular fracture pattern was related to the valgus position. Moreover, the articular fracture pattern of pilon fractures differed according to coronal angulation and fibular fracture pattern. These differences should influence the operative approach and placement of the plate.

The elbow is the load-bearing joint during arm swing.

BACKGROUND: Arm swing plays a role in gait by accommodating forward movement through trunk balance. This study evaluates the biomechanical characteristics of arm swing during gait. METHODS: The study performed computational musculoskeletal modeling based on motion tracking in 15 participants without musculoskeletal or gait disorder. A three-dimensional (3D) motion tracking system using three Azure Kinect (Microsoft) modules was used to obtain information in the 3D location of shoulder and elbow joints. Computational modeling using AnyBody Modeling System was performed to calculate the joint moment and range of motion (ROM) during arm swing. RESULTS: The mean ROM of the dominant elbow was 29.7°±10.2° and 14.2°±3.2° in flexion-extension and pronation-supination, respectively. The mean joint moment of the dominant elbow was 56.4±12.7 Nm, 25.6±5.2 Nm, and 19.8±4.6 Nm in flexion-extension, rotation, and abduction-adduction, respectively. CONCLUSIONS: The elbow bears the load created by gravity and muscle contracture in dynamic arm swing movement.

Biomechanical impact of elbow motion in elbow stiffness.

BACKGROUND: A mechanical block in the elbow due to osteophytes in the olecranon fossa is a common clinical symptom for elbow stiffness. PURPOSE/HYPOTHESIS: This study aims to understand the biomechanical characteristics or changes in the stiff elbow in the resting (or neutral) and swing position of the arm using a cadaveric model. The hypotheses included the following: (1) a difference exists in the articular contact pressure of the elbow by comparing the non-stiff and stiff models in in vivo studies; (2) the degree of stiffness would affect the increase of the joint loading of the elbow. STUDY DESIGN: Controlled laboratory study, cadaveric study. METHODS: Eight fresh-frozen specimens from individuals of both sexes were included in the biomechanical study. The specimen was mounted on a custom-designed jig system with gravity-assisted muscle contracture to mimic the elbow in a standing position. The elbow was tested in two conditions (the resting and passive swing). Contact pressure was recorded for three seconds in the resting position, which was the neutral position of the humerus. By dropping the forearm from 90° of the elbow flexion, the passive swing was performed. The specimens were tested sequentially in three stages of stiffness (stage 0, no stiffness; stage 1, 30° of extension limitation; and stage 2, 60° of extension limitation). After data collection was completed in stage 0, a stiff model was sequentially created for each stage. The stiff model of the elbow was created by blocking the olecranon by inserting a 2.0 K-wire into the olecranon fossa horizontally with the intercondylar axis. RESULTS: The mean contact pressures were 279 ± 23, 302 ± 6, and 349 ± 23 kPa in stages 0, 1, and 2, respectively. The increases in the mean contact pressure in stages 2 versus 0 were significant (P < 0.0001). The mean contact pressures were 297 ± 19, 310 ± 14, and 326 ± 13 kPa in stages 0, 1, and 2, respectively. The peak contact pressures were 420 ± 54, 448 ± 84, and 500 ± 67 kPa in stages 0, 1, and 2, respectively. The increases in mean contact pressure in stage 2 versus 0 were significant (P = 0.039). The increases in peak contact pressure in stages 0 versus 2 were significant (P = 0.007). CONCLUSIONS: The elbow bears the load created by gravity and muscle contracture in the resting and swing motion. Moreover, extension limitation of stiff elbow increases the load bearing in the resting position and swing motion. Careful surgical management should be considered for meticulous clearance of bony spur around olecranon fossa to resolve the extension limitation of the elbow.

Structure-mechanical analysis of various fixation constructs for basicervical fractures of the proximal femur and clinical implications; finite element analysis.

OBJECTIVE: This present study was conducted to determine the structural-mechanical stability of various fixation constructs through finite element (FE) analysis following simulation of a basicervical fracture and to introduce the clinical implications. MATERIALS AND METHODS: We simulated fracture models by using a right synthetic femur (SAWBONES®). We imported the implant models into ANSYS® for placement in an optimal position. Five assembly models were constructed: (1) multiple cancellous screws (MCS), (2) FNS (femoral neck system®), (3) dynamic hip screw (DHS), (4) DHS with anti-rotation 7.0 screw (DHS + screw), and PFNA-II (Proximal Femoral Nail Antirotation-II®). The femur model's distal end was completely fixed and 7° abducted. We set the force vector at a 3° angle laterally and 15° posteriorly from the vertical ground. Analysis was done using Ansys® software with von Mises stress (VMS) in megapascals (MPa) and displacement (mm) RESULTS: The displacements of the proximal femur were 10.25 mm for MCS, 9.66 mm for DHS, 9.44 mm for DHS + screw, 9.86 mm for FNS, and 9.31 mm for PFNA-II. The maximum implant VMS was 148.94 MPa for MCS, 414.66 MPa for DHS, 385.59 MPa for DSH + screw, 464.07 MPa for FNS, and 505.07 MPa for PFNA-II. The maximum VMS at the fracture site was 621.13 MPa for MCS, 464.14 MPa for DHS, 64.51 MPa for DHS + screw, 344.54 MPa for FNS, and 647.49 MPa for PFNA-II. The maximum VMS at the fracture site was in the superior area with the high point around the posterior screw in the MCS, anterosuperior corner in the DHS, the posteroinferior site of the FNS, and posterosuperior site around the entry point in the PFNA-II. In the DHS + screw, the stresses were distributed evenly and disappeared at the maximum VMS fracture site. CONCLUSION: Based on the fracture site and implant's stress distribution, the model receiving the optimal load was a DHS + screw construct, and the FNS implant could be applied to anatomically reduced fractures without comminution. Considering the high-stress concentration around the entry point, a PFNA-II fixation has a high probability of head-neck fragment rotational instability.

Biomechanical Effect of Disc Height on the Components of the Lumbar Column at the Same Axial Load: A Finite-Element Study.

Intervertebral discs are fibrocartilage structures, which play a role in buffering the compression applied to the vertebral bodies evenly while permitting limited movements. According to several previous studies, degenerative changes in the intervertebral disc could be accelerated by factors, such as aging, the female sex, obesity, and smoking. As degenerative change progresses, the disc height could be reduced due to the dehydration of the nucleus pulposus. This study aimed to quantitatively analyze the pressure that each structure of the spine receives according to the change in the disc height and predict the physiological effect of disc height on the spine. We analyzed the biomechanical effect on spinal structures when the disc height was decreased using a finite-element method investigation of the lumbar spine. Using a 3D FE model, the degree and distribution of von-Mises stress according to the disc height change were measured by applying the load of four different motions to the lumbar spine. The height was changed by dividing the anterior and posterior parts of the disc, and analysis was performed in the following four motions: flexion, extension, lateral bending, and axial rotation. Except for a few circumstances, the stress applied to the structure generally increased as the disc height decreased. Such a phenomenon was more pronounced when the direction in which the force was concentrated coincided with the portion where the disc height decreased. This study demonstrated that the degree of stress applied to the spinal structure generally increases as the disc height decreases. The increase in stress was more prominent when the part where the disc height was decreased and the part where the moment was additionally applied coincided. Disc height reduction could accelerate degenerative changes in the spine. Therefore, eliminating the controllable risk factors that cause disc height reduction may be beneficial for spinal health.

Three-dimensional morphologic features of Asian atypical femur and clinical implications of cephalomedullary nail fixation: Computational measurement at actual size.

PURPOSE: (1) To analyze three-dimensional (3D) morphologic features of atypical femur fracture at actual size without projection error; and (2) to provide clinical implications of cephalomedullary nail (CMN) fixation by separating the medullary canal and the cortex. MATERIALS AND METHODS: Fifty-nine atypical femurs (opposite non-fractured femurs) were reconstructed as 3D models with medullary canal by importing CT data into Mimics® software. A reference line was drawn from the tip of the greater trochanter to the center of the intercondylar notch and used for classifying bowing grade according to the centerline of medulla. Proximal and distal straight lines (length of 60 mm, diameter of 1 mm) were placed in the centerline of medulla. Acute angles between the two straight lines were measured as lateral and anterior bowing. The acute angle by straight line and reference line was measured as proximal and distal bowing in both AP and lateral view. The diameter of curve (DOC) of medulla along the posterior border was measured. RESULTS: The anterior bowing of all femur on lateral view was an average of 13.82° (range, 6.2°-31.1°, SD 3.91), and the values of proximal and distal anterior bowing were an average of 7.82° (range, 2.7°-14.3°, SD 2.23) and 6.0° (range, 2.2°-16.8°, SD 2.31), respectively. The lateral bowing of all femur on AP view was an average of 5.49° (range, 0.1°-17.3°, SD 4.48), and the values of proximal and distal anterior bowing were an average of 3.64° (range, 0.1°-11.3°, SD 2.70) and 2.48° (range, 0-7.4°, SD 1.98), respectively. The medullary canal was changed to be straightened and more bowed anteriorly. Concerning the lateral bowing grade of entire diaphysis, it was grade -I for 15 femurs, grade 0 for 21 femurs, grade I for nine femurs, grade II for five femurs, and grade III for nine femurs. Regarding anterior bowing grade, it was grade II for 14 femurs and grade III for 45 femurs. The average diameter of medullary canal was 1276.3 ± 232.25 mm. CONCLUSION: Asian atypical femur had three morphologic features: (1) straightened medullary canal, (2) positive values of lateral bowing, and (3) significantly increased ante-curvature of medullary canal. Considering that conventional CMN had about 4° of mediolateral angle, the disparity between implant and medullary canal might be clear. Thus, new nail design for Asian atypical femur that could increase the radius of curve (ROC) but decrease the mediolateral angle needs to be introduced.

Analysis of the physiological load on lumbar vertebrae in patients with osteoporosis: a finite-element study.

This study aims to investigate the difference in physiological loading on the spine in three different motions (flexion-extension, lateral bending, and axial rotation) between osteoporotic and normal spines, using finite element modelling. A three-dimensional finite element (FE) model centered on the lumbar spine was constructed. We applied two different material properties of osteoporotic and normal spines. For the FE analysis, three loading conditions (flexion-extension, lateral bending, and axial rotation) were applied. The von Mises stress was higher on the nucleus pulposus at all vertebral levels in all movements, in the osteoporosis group than in the normal group. On the annulus fibrosus, the von Mises stress increased at the level of L3-L4, L4-L5, and L5-S in the flexion-extension group and at L4-L5 and L5-S levels in the lateral bending group. The values of two motions, flexion-extension and lateral bending, increased in the L4 and L5 cortical bones. In axial rotation, the von Mises stress increased at the level of L5 of cortical bone. Additionally, the von Mises stress increased in the lower endplate of L5-S and L4-L5 in all movements, especially lateral bending. Even in the group with no increase, there was a part that received increased von Mises stress locally for each element in the three-dimensional reconstructed view of the pressure distribution in color. The von Mises stress on the lumbar region in the three loading conditions, was greater in most components of osteoporotic vertebrae than in normal vertebrae and the value was highest in the nucleus pulposus. Considering the increase in the measured von Mises stress and the local increase in the pressure distribution, we believe that these results can contribute to explaining discogenic pain and degeneration.

Effects of Location and Volume of Intraosseous Cement on Adjacent Level of Osteoporotic Spine Undergoing Kyphoplasty: Finite Element Analysis.

OBJECTIVE: Kyphoplasty (KP) is a surgery used to reduce pain and increase stability by injecting medical bone cement into broken vertebrae. The purpose of this study was to determine the ideal amount of cement and injection site by analyzing forces with the finite element method. METHODS: We modeled the anatomical structure of the vertebra and injected the cement at T12. By increasing the amount of cement from 1 cc to 22 cc, stress applied to T11 and L1 cortical was calculated. In addition, stress applied to the adjacent KP level was calculated with different injection sites (medial, anterosuperior, posterosuperior, anteroinferior, and posteroinferior). After 5 cc cement was inserted, adjacent end plate stress was analyzed. RESULTS: In this study, break point adjacent bone stress according to the capacity of cement was bimodal. Flexion/extension and lateral bending conditions showed similar break points (11.5-11.7 cc and 18.5-18.6 cc, respectively). When cement injection was changed, front under and back under had the highest stress values among various parts, whereas the center position showed the lowest stress value. CONCLUSIONS: With increasing amount of bone cement, stress on the upper and lower end plates of the cemented segment increased significantly. Thus, increasing cement amount to be more than 11.5 cc has a potential risk of adjacent fracture. Centrally injected bone cement can lower the risk of adjacent fracture after percutaneous KP.

Correction to: Implications of the Overlapping Degree Between Proximal Fibula and Tibia for Placing the Optimal Syndesmotic Screw: A Virtual Cadaveric Study.

[This corrects the article DOI: 10.1007/s43465-021-00437-y.].

Implications of the Overlapping Degree Between Proximal Fibula and Tibia for Placing the Optimal Syndesmotic Screw: A Virtual Cadaveric Study.

BACKGROUND: To determine the optimal direction of the syndesmotic screw and to introduce a consistent landmark for practical application by analyzing three-dimensional (3D) modeling and virtual implantation. METHODS: A total of 105 cadaveric lower legs (50 males and 55 females; average height, 160.6 ± 7.1 cm) were used to reconstruct a 3D model by using the Mimics® software and the joint morphology was evaluated. Syndesmotic cylinders (Ø3.5 mm/Length 100 mm) were transversely placed in the proximal end of the incisura fibularis for simulating screw fixation. The tibial proximal cylinder, which was tangent to the posterior tibial condyles, was traced and the angle between the two cylinders was measured as the tibial torsion angle (TTA). After rotating the syndesmotic cylinder parallel to the ground, the overlapping degree between the proximal fibula and tibia was assessed as a radiologic indicator. RESULTS: Concerning tibial torsion, the TTA was an average of 36.7° (range, 17.2°-54.4°; SD, 8.78) When the syndesmotic cylinder was rotated to be parallel to the ground, the proximal fibula had nonlinear or linear overlap with the lateral border of the tibia, regardless of the joint morphology. In this non-overlapping view, three Weber's indices for normal fibular length could be better visualized than the mortise view. CONCLUSION: The syndesmotic cylinder in the proximal end of the incisura fibularis could be consistently placed parallel to the ground by internally rotating the tibia until there was a nonlinear or linear overlap between the proximal fibula and the tibia, regardless of the joint morphology.

Computational simulation of cephalomedullary nailing in the osteoporotic Asian femur and clinical implications.

PURPOSE: To assess the conformity of PFNA-II® and introduce clinical implications of new cephalomedullary nail (CMN) by analyzing three-dimensional (3D) modeling with virtual implantation at the actual size. MATERIALS AND METHODS: Thirty-four patients (average age; 79 years, range 68-94 years) who sustained the intertrochanteric fracture of the femur were enrolled in the present study. After importing into Mimics® software, the intact femurs on the opposite side were selected as cropping areas to reconstruct the 3D femur model with the medullary canal. PFNA-II® and new CMNs (lateral angle 0° and 2°, CCD angle 130°; CMN0° and CMN2°) were processed at the actual size and ideally placed in the proximal femur using Mimics® software. The virtual entry point (EP), nail conformity, and anatomical relationships with the adjacent structures were assessed. RESULTS: The virtual EP of PFNA-II® was placed along the cervico-trochanteric (CT) junction in the posterior half around trochanteric fossa and always medial to the tip of greater trochanter (GT). There were six abutments in PFNA-II® models, one impingement in CMN 0°, and no impingement in CMN 2°. All the models with cortical abutment showed increased anterior and lateral bowing of the proximal shaft owing to age-dependent changes. Compared with PFNA-II®, with a decreasing tendency on the mediolateral angle of new CMNs, the virtual EP shifted to the medial and anterior side towards the CT junction. By simulating the intentional positioning in the media-to-lateral direction, the abutments in the PFNA-II® model could not be avoided. Furthermore, the lag screw of CMN 0° was placed ideally at the center or inferior side of the femoral head < 10 mm in any direction without a cortical abutment. CONCLUSION: To avoid cortical abutment of CMN in the Asian geriatric femur, the virtual EP would be technically placed in the medial to the GT tip, and the implant design should be changed to decrease the mediolateral angle.

Mood and Metabolic Health Status of Elderly Osteoporotic Patients in Korea: A Cross-Sectional Study of a Nationally Representative Sample.

This study aimed to investigate the association between osteoporosis and comorbidity, which are very common in Korea, and develop a treatment strategy to improve bone health based on the findings of the Korean National Health and Nutritional Examination Surveys (KNHANES). This study was based on data obtained from 4060 subjects (1755 males, 2305 females) aged above 60 years in the KNHANES (2016-2017). Well-trained medical staff performed the standard procedures and measured several variables including height, weight, and waist circumference. Interviews and laboratory tests were based on the diagnosis of hyperuricemia, dyslipidemia, type 2 diabetes mellitus (T2DM), osteoporosis, and depression. Comorbidities were defined as a self-reported physician diagnosis. The association of osteoporosis with depression and metabolic disease was assessed statistically using the complex sample analysis method of SPSS. The presence of osteoporosis, dyslipidemia, T2DM, hyperuricemia, obesity, abdominal obesity, and depression was 6.1 ± 0.5%, 15.2 ± 0.7%, 6.5 ± 0.4%, 13.4 ± 0.7%, 30.8 ± 0.8%, 19.4 ± 0.9%, 4.0 ± 0.2%, respectively. After adjusted by age, osteoporotic subjects were significance in the presence of abdominal obesity (p = 0.024, OR 0.80), hyperuricemia (p = 0.013, OR 0.68), dyslipidemia (p < 0.001, OR 1.84), and depression (p < 0.001, OR 2.56), respectively. Subgroup analyses showed dyslipidemia (female subjects, p < 0.001, OR 1.04; male subjects, p = 0.94, OR 1.09) and depression (female subjects, p < 0.001, OR 1.76; male subjects, p = 0.51, OR 0.62) were associated with osteoporotic female subjects but not in male subjects. The comorbidity of dyslipidemia and depression in female subjects was associated with osteoporosis and an odds ratio was 13.33 (95% CI: 8.58-20.71) (p < 0.001). The comorbidity of abdominal obesity (female subjects, p = 0.75, OR 0.97; male subjects, p = 0.94, OR 1.02) and hyperuricemia (female subjects, p = 0.27, OR 0.81; male subjects p = 0.07, OR 0.35) was not associated with osteoporosis in both Subgroup. The result of this study shows a strong dependency of comorbidity with dyslipidemia and depression in elderly women with osteoporosis. Therefore, efforts to improve dyslipidemia and depression might prevent compromised bone health.

Percutaneous bridge plating of extra-articular distal fibular fracture for the management of distal tibia type III open fracture.

PURPOSE: The aim of this study is to conduct clinical and radiographic evaluations of the use of percutaneous bridge plating for distal fibular fractures combined with distal tibia type III open fractures. METHODS: Thirty-four patients with acute distal third fibular shaft fractures (4F2A(c) and 4F2B(c) according to the AO/OTA classification) combined with distal tibia type III open fractures were enrolled. Concurrent fibular fractures were fixed with the percutaneous bridge plating simultaneously, while distal tibia open fractures were temporally stabilized with a spanning external fixator. Clinical and radiographic outcomes were evaluated using the Lower Extremity Functional Scale (LEFS), the proportional length difference of the fibula, the talocrural angle, the union rate of the fibula and tibia, the operation time, and complications at the final follow-up. RESULTS: All fibular fractures healed with an average bone healing time of 20.7 ± 6.3 weeks (range, 16-35). The mean proportional length difference was 0.492 ± 0.732% compared with that in the uninjured fibula. The functional assessment result according to the LEFS was 74.0 ± 3.70 points (range, 57-80). No cases of fibula fracture infection developed throughout the follow-up period in any of the patients. Iatrogenic postoperative superficial peroneal nerve injury was not found in any of the patients. CONCLUSION: With the perspective of minimizing soft tissue problems due to high-energy trauma, the application of percutaneous bridge plating for the treatment of distal fibular fractures can be an alternative to conventional treatment methods.

Posterior Displacement and Angulation of Displaced Lateral Clavicle Fractures: A 3-Dimensional Analysis.

BACKGROUND: The management of lateral clavicle fractures is often challenging because of difficulties in identifying displacement patterns that indicate an unstable fracture. HYPOTHESIS: The aim of this study was to evaluate displacement patterns through analysis using 3-dimensional (3D) rendering software for displaced lateral clavicle fractures. We hypothesized that most displaced lateral clavicle fractures would have posterior displacement and angulation as well as superior displacement of the medial fragment. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Radiographs of 37 displaced lateral clavicle fractures were imported into the 3D rendering software to reconstruct the fracture model. For the computational simulation of fracture reduction, the medial fragment was manipulated and returned into place using the software's moving tools. Two corresponding points were marked between the medial and lateral fragments to measure 3D spatial location in the x-axis (shortening), y-axis (horizontal displacement), and z-axis (vertical displacement). The displacement angle on the cranial view was also measured based on the medial end of the clavicle. RESULTS: There were 32 cases (86.5%) of superior displacement of the medial fragment (mean, 5.8 mm; range, -6.5 to 19.0 mm), 35 cases (94.6%) of posterior displacement of the medial fracture fragment (mean, 8.8 mm; range, -3.2 to 18.3 mm), and 23 cases (62.2%) of distraction of the fracture site (mean, 2.1 mm; range, -9.2 to 12.2 mm). All 37 patients revealed posterior angulation of the fracture site (mean, 8.9°; range, 2.2°-39.4°). CONCLUSION: Most displaced lateral clavicle fractures have posterior displacement and angulation as well as superior displacement of the medial fragment. Our results revealed that 3D evaluation of lateral clavicle fracture displacement patterns is useful for assessing fracture stability and making treatment decisions.

Three-dimensional analysis of lateral cortical hinge in medial open-wedge high tibial osteotomy: A computational simulation study of adult cadavers.

PURPOSE: The objective of this study was to improve the three-dimensional (3D) understanding of optimal lateral cortical hinge in medial open-wedge high tibial osteotomy (MOWHTO) via a computational cadaveric simulation of actual size. METHODS: The computed tomography data of 117 adult cadavers were imported into Mimics® software to design 3D models of tibia and fibula. To simulate the MOWTHO, a virtual cutting plane was developed inside the safe zone based on established landmarks. After splitting and distracting through the cutting plane, the 10-mm cylinder (Ø 30 mm; height 10 mm) was placed vertically to be occupied properly in the nonosteotomized lateral cortex. The cross points between the round cylinder and cutting plane represented the anterior and posterior hinge points, which were used to validate the 3D position and direction of cortical hinge. RESULTS: A 10-mm cylinder did not violate the proximal tibiofibular joint (PTFJ) and the protruding segment of the condylar area was less than 2 mm in 115 models. The connecting line between anterior and posterior hinge points was an average of 12.1° (range 0-24.1°, SD 4.64) to the lateral side. In the nonoverlapping anteroposterior projection between proximal fibula and tibia, the posterior hinge point was laid over the PTFJ as close as possible. Based on free 360° rotation and magnification without any tilt, no posterior cortical disruption of PTFJ was observed while securing a minimum width of 10 mm. CONCLUSION: If the posterior hinge point was placed immediately above the PTFJ without involvement, the nonosteotomized portion carried sufficient width greater than 10 mm, despite lateral rotation at an average hinge direction of 12.1°.

Assessment of osseous corridor for transiliac-transsacral screws and clinical applications: Computational simulation study.

BACKGROUND: Transiliac-transsacral (TITS) screw fixation might be necessary in some cases involving the vertical shearing injuries with transforaminal fracture and bilateral posterior ring injuries. However, the possibility of S1 TITS screw should be preoperatively assessed because the pelvic ring injuries with sacral dysmorphism had the insufficient osseous corridors. HYPOTHESIS: AxWS2 may predict the possibility of TITS screw fixation and be used as the new indicator to discriminate the sacral dysmorphism. MATERIALS & METHODS: The conventional CT images of eighty-two cadaveric pelvis imported into Mimics® software to reconstruct three-dimensional (3D) models. A 7.0 mm-sized screw was processed into a 3D model using a 3D-sensor at actual size and virtually implanted as S1 and S2 TITS screw using Mimics® software. The cortical violation around screw path was evaluated using 3D biplanar and conventional CT images. The osseous corridor widths around TITS screws were measured in the axial plane images and defined as AxWS1 and AxWS2, respectively. RESULTS: Despite no cortical violation in S2 of all models, cortical violation of S1 TITS screw was found in 20 models. Of them, 14 models (impossible models) were identified in the 3D biplanar images, and all 20 models (CT-violation models) were identified only in CT axial plane images. AxWS1 was<7mm in the impossible models and<9.0mm in the CT-violation models. AxWS2 negatively correlated with AxWS1 (R -0.450, p<0.01). By receiver operating characteristic curve analysis to identify the CT-violation model using AxWS2, the cut-off value of AxWS2 was 13.32mm (sensitivity 0.70, specificity 0.70). DISCUSSION: By using AxWS2, the possibility of S1 TITS screw fixation could be predicted and safely placed without cortical violation, if AxWS2 was less than 13mm. Considering the negative relationship with AxWS1, AxWS2 should be used as a new indicator to predict safe S1 TITS screw fixation. LEVEL OF EVIDENCE: III, controlled laboratory study.