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There are many techniques for the treatment of chronic scapholunate dissociation. The three-ligament tenodesis (3LT) is used most widely, but reconstruction of the dorsal ligament alone may not provide sufficient stability. The Mark–Henry technique (MHT) compensates for the insufficient stability of 3LT by additional reconstruction of the volar ligament, but the procedure is complex. The SwiveLock technique (SWT), a recently introduced method, provides stability by using autologous tendons with synthetic tapes, but lacks long-term clinical results. To perform biomechanical comparisons of different reconstructive techniques for scapholunate dissociation using a controlled laboratory cadaveric model. Eleven fresh-frozen upper-extremity cadaveric specimens were prepared. The scapholunate distance, scaphoid rotation, and lunate rotation of the specimens were measured during continuous flexion–extension and ulnar–radial deviation movements. The data were collected using a wrist simulator with a linear guide rail system (tendon load/motion-controlled system) and a motion capture system. Results were compared in five conditions: (1) intact, (2) scapholunate dissociation, (3) SWT, (4) 3LT, and (5) MHT. Paired t-test was employed to compare the biomechanical characteristics of intact wrists to those of scapholunate dissociated wrists, and to those of wrists after each of the three reconstruction methods. SWT and MHT were effective solutions for reducing the widening in scapholunate distance. According to the radioscaphoid angle, all three reconstruction techniques were effective in addressing the flexion deformity of the scaphoid. According to the radiolunate angle, only SWT was effective in addressing the extension deformity of the lunate. In terms of scapholunate angle, only the results after SWT did not differ from those of the intact wrist. The SWT technique most effectively improved distraction intensity and rotational strength for the treatment of scapholunate dissociation. Taking into account the technical complexity of 3LT and MHT, SWT may be a more efficient technique to reduce operating time and minimize complications due to multiple incisions, transosseous tunnels, and complicated shuttling.

Background and Objectives: Guided-motion bicruciate-stabilized (BCS) total knee arthroplasty (TKA) includes a dual cam-post mechanism with an asymmetric bearing geometry that promotes normal knee kinematics and enhances anterior-posterior stability. However, it is unclear whether the improved biomechanics after guided-motion BCS TKA reproduce soft tissue strain similar to the strain generated by native knees. The purpose of this cadaveric study was to compare medial collateral ligament (MCL) strain between native and guided-motion BCS TKA knees using a video extensometer. Materials and Methods: Eight cadaver knees were mounted onto a customized knee squatting simulator to measure MCL strain during flexion in both native and guided-motion BCS TKA knees (Journey II-BCS; Smith & Nephew, Memphis, TN, USA). MCL strain was measured using a video extensometer (Mercury® RT RealTime tracking system, Sobriety s.r.o, Kuřim, Czech Republic). MCL strain level and strain distribution during knee flexion were compared between the native and guided-motion BCS TKA conditions. Results: The mean and peak MCL strain were similar between native and guided-motion BCS TKA knees at all flexion angles (p > 0.1). MCL strain distribution was similar between native and BCS TKA knees at 8 of 9 regions of interest (ROIs), while higher MCL strain was observed after BCS TKA than in the native knee at 1 ROI in the mid portion of the MCL at early flexion angles (p < 0.05 at ≤30° of flexion). Conclusions: Guided-motion BCS TKA restored the amount and distribution of MCL strain to the values observed on native knees.

Background: Recent evidence supports that restoration of the pre-arthritic condition via total knee arthroplasty (TKA) is associated with improved post-TKA performance and patient satisfaction. However, whether the restored pre-arthritic joint line simulates the native mid-flexion biomechanics remains unclear. Objective: We performed a matched-pair cadaveric study to explore whether restoration of the joint line via kinematically aligned (KA) TKA reproduced native knee biomechanics more accurately than the altered joint line associated with mechanically aligned (MA) TKA. Methods: Sixteen fresh-frozen cadaveric knees (eight pairs) were affixed onto a customized knee-squatting simulator for measurement of femoral rollback and medial collateral ligament (MCL) strain during mid-flexion. One knee from each cadaver was randomly designated to the KA TKA group (with the joint line restored to the pre-arthritic condition) and the other to the MA TKA group (with the joint line perpendicular to the mechanical axis). Optical markers were attached to all knees and rollback was analyzed using motion capture cameras. A video extensometer measured real-time variations in MCL strain. The kinematics and MCL strain prior to and following TKA were measured for all specimens. Results: KA TKA was better for restoring the knee kinematics to the native condition than MA TKA. The mid-flexion femoral rollback and axial rotation after KA TKA were consistently comparable to those of the native knee. Meanwhile, those of MA TKA were similar only at ≤40° of flexion. Furthermore, KA TKA better restored the mid-flexion MCL strain to that of the native knee than MA TKA. Over the entire mid-flexion range, the MCL strain of KA TKA and native knees were similar, while the strains of MA TKA knees were more than twice those of native knees at >20° of flexion. Conclusions: The restored joint line after KA TKA effectively reproduced the native mid-flexion rollback and MCL strain, whereas the altered joint line after MA TKA did not. Our findings may explain why patients who undergo KA TKA experience superior outcomes and more natural knee sensations during daily activities than those treated via MA TKA.

Abstract Background This study evaluated the technical adequacy of trans-articular sacroiliac joint (SIJ) fusion using three screws for non-traumatic SIJ pain, considering different grades of sacral dysplasia. Methods Cadaveric CT data of unilateral sacropelvic complexes for 72 individuals (53.4 ± 8.4 years) were selected. A 3D model was reformatted into the plain lateral radiograph to mark the articular surface of the SIJ. Subjects were classified into dysplastic (DYS) and non-dysplastic sacrum (NDS) groups. Proximal (PS), middle (MS), and distal screws (DS) with 10-mm diameter were virtually introduced to the iliac bone and the SIJ on the lateral image with a 5-mm safety margin. On a corresponding axial image, each screw was advanced vertically to the sagittal plane with the same safety margin. The entry points for each screw to the endplate of S1 (S2) and to the corresponding anterior sacral margin on the lateral image were measured, along with the maximal screw lengths on the axial image. Whether each screw passed through the SIJ was determined. Different types of sacral dysplasia and screws were compared statistically. Results Thirty-eight (26.4%) cases were DYS, and 106 (73.6%) were NDS. The entry points of all screws were significantly more distal in DYS than in NDS groups. The PS and MS screw lengths differed significantly between the 2 groups. Incidences of short sacral fixation (

The most important precondition for correction of the affected forearm using data from the contralateral side is that the left and right bone features must be similar, in order to develop patient-specific instruments (PSIs) and/or utilize computer-assisted orthopedic surgery (CAOS). The forearm has complex anatomical structure, and most people use their dominant hand more than their less dominant hand, sometimes resulting in asymmetry of the upper limbs. The aim of this study is to investigate differences of the bilateral forearm bones through a quantitative comparison of whole bone parameters including length, volume, bowing, and twisting parameters, and regional shape differences of the forearm bones. In total, 132 bilateral 3D radii and ulnae 3D models were obtained from CT images, whole bone parameters and regional shape were analyzed. Statistically significant differences in whole bone parameters were not shown. Regionally, the radius shows asymmetry in the upper section of the central part to the upper section of the distal part. The ulna shows asymmetry in the lower section of the proximal part to the lower section of the central part. Utilizing contralateral side forearm bones to correct the affected side may be feasible despite regional differences in the forearm bones of around 0.5 mm.

The purpose of this study was to investigate whether a watch-shaped external wrist band brace improves distal radioulnar joint (DRUJ) stability. Seven fresh cadaveric arms were used. Using a customized testing system, volar and dorsal translation forces were applied to the radius externally while the ulna was fixed. The test was performed with the forearm in neutral, 60° pronated, and 60° supinated positions, once without the brace and once with the brace applied. In each condition, the amount of translation was measured. Then, the triangular fibrocartilage complex (TFCC) was detached from the ulnar styloid process and the fovea ulnaris, and the same tests were performed again. Detachment of the TFCC significantly increased volar and dorsal translations in all forearm rotations compared to the intact condition (p < 0.05), except for the pronated dorsal translation of the radius (p = 0.091). Brace application significantly reduced volar and dorsal translations in all forearm rotations both in intact specimens and in TFCC-detached specimens (p < 0.05), except for pronated volar and dorsal translations in TFCC-detached specimens (p = 0.101 and p = 0.131, respectively). With the brace applied, the TFCC-detached specimens showed no significant difference in volar or dorsal translation in all forearm rotations compared to the intact specimens (p > 0.05). The external wrist band brace improved DRUJ stability in both normal and TFCC-torn wrists and reduced the DRUJ instability caused by TFCC tear to a near-normal level.

The fovea ulnaris is considered to be the center of rotation on the ulnar head during forearm rotation. The purpose of this study was to investigate whether the fovea ulnaris is truly isometric during forearm rotation in vivo. The three-dimensional reconstruction models of 21 wrist computed tomography images taken in supination and pronation were investigated. The models were superimposed so that the two ulnar heads were in the same position. Numerous points were set on the surface of the ulnar head with a mean distance of 0.2 mm between the nearest two points. Then, the models were superimposed with respect to the radius, and the distance between the same points on the ulnar head in pronation and supination (DFR) was measured. The rotation center was defined as the point with the shortest DFR. The isometric point was defined as a rotation center with a DFR of less than 0.2 mm. An isometric point was found in three cases and not in 18 cases. The distance the rotation center moved during forearm rotation (DFR of the rotation center) ranged from 0.1 mm to 2.4 mm. The position of the rotation center in the radioulnar direction was significantly correlated with the translation of the ulnar head and the amount of forearm rotation. The rotation center was located more ulnarly when the translation of the ulnar head or the amount of forearm rotation was greater. The isometricity of the foveal insertion of the TFCC during forearm rotation may not be consistent in vivo. The center of rotation on the ulnar head during forearm rotation appears to shift ulnarly with increasing translation of the ulnar head or forearm rotation.

Thus far, anatomical studies have reported data on the cervical pedicle, with the focus remaining on the pedicle itself. It was necessary to obtain more comprehensive data about the relationships between the lateral mass, pedicle, and transverse foramen for cervical pedicle screwing (CPS) and paravertebral foramen screwing (PVFS), a new technique. The purpose of this study was to describe the relationships between the lateral mass, pedicle, and transverse foramen. This study analyzed computed tomography images from 77 patients (42 female, 35 male; mean age: 63.95 years). The anatomical pedicle transverse angle (PTA) and linear parameters of the lateral mass were measured, and the relationship between the calculated angles and the anatomical PTA was investigated. θp was defined as the convergence angle from the posterolateral edge of the lateral mass to the pedicle, and θc was defined as the convergence angle from the posterolateral edge of the lateral mass to the anterolateral corner of the vertebral foramen. The thickness of the cortical bone of the medial wall of the lateral mass (cT) and the medial (mT) and lateral (lT) walls of the pedicle at C3-7 were also measured. The PTA was similar to θp and θc at C3-6, but different at C7. In all cases, the transverse foramen was located more anterior to the posterior wall of the cervical body at C3-6, but not at C7. mT and cT were significantly thicker than lT at all levels. Lateral fluoroscopic images show that when the probe is inserted along θc, it meets the counter corner of the lateral mass at C3-6 without invasion of the transverse foramen if it does not cross the posterior wall of the vertebral body. This can be significant when performing CPS and PVFS.

Computer-assisted orthopedic surgery and patient-specific instruments are widely used in orthopedic fields that utilize contralateral side bone data as a template to restore the affected side bone. The essential precondition for these techniques is that the left and right bone features are similar. Although proximal humerus fracture accounts for 4% to 8% of all fractures, the bilateral asymmetry of the proximal humerus is not fully understood. The aim of this study is to investigate anthropometric differences of the bilateral proximal humerus. One hundred one pairs of Korean humerus CT data from 51 females and 50 males were selected for this research. To investigate bilateral shape differences, we divided the proximal humerus into three regions and the proximal humerus further into five sections in each region. The distance from the centroid to the cortical outline at every 10 degrees was measured in each section. Differences were detected in all regions of the left and right proximal humerus; however, males had a larger number of significant differences than females. Large bilateral differences were measured in the greater tubercle. Nevertheless, using contralateral data as a template for repairing an affected proximal humerus might be possible.

Four pairs of fresh-frozen cadaver knees (eight knees, four male knees) with a mean age of 72 ± 7 years were used for tests involving a customized simulator capable of controlling quadriceps loading conditions. The muscle force distribution of the quadriceps for the normal loading condition was applied on the basis of muscle cross-sectional area data, as previously reported (VM: 31 N; RF/VI: 49 N; VL: 45 N). To simulate vastus medialis (VM) impairment, we set the muscle force for VM in the muscle force distribution of the quadriceps at zero (VM: 0 N; RF/VI: 49 N; VL: 45 N). The joint reaction forces and moments on knee joints that underwent total knee arthroplasty (TKA) did not differ significantly according to VM impairment status for all flexion angles (p > 0.05). Nevertheless, the vectors of internal–external moments mostly showed a tendency for alteration from external to internal due to VM impairment. This tendency was evident in 9 cases in 12 total test pairs (with and without VM impairment). Furthermore, the vectors of the anterior–posterior reaction forces mostly showed a tendency to increase anteriorly due to VM impairment. This tendency was also evident in 9 cases in 12 total test pairs (with and without VM impairment). These results indicate that posterior dislocation of the tibia may be induced if VM impairment occurs after TKA. In conclusion, VM impairment in knee joints undergoing TKA may contribute to posterior dislocation of the tibia by a paradoxical roll-back with enhancements of the anterior joint reaction force and external moment during knee-joint flexion. Our findings may be valuable for understanding the mechanism of potential instability and malfunction due to VM impairment in knee joints after TKA, and may help to optimize clinical/rehabilitation training plans to improve the prognosis (stability and function) of knee joints undergoing TKA.

Biomechanical studies assessing the major knee ligaments, such as the anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament (MCL), and lateral collateral ligament (LCL), have been conducted using various methodologies. However, despite the anterolateral ligament (ALL) being regarded as the important ligament for the stability of the knee, a lack of biomechanical research focusing on the ALL exists to date. Moreover, studies assessing the relative mechanical properties of each ligament of the knee are insufficient. Therefore, this study examined the mechanical properties of the ALL, MCL, and LCL and considered the relative differences between these ligaments. Twenty-one fresh cadaver knees were chosen to investigate the mechanical properties. The width, thickness, and length were measured. The stiffness, ultimate load, and elastic modulus were also tested. The MCL showed the greatest ultimate load (498.5 N) and the highest stiffness (71.97 N/mm), and the ALL presented the smallest ultimate load (146.64 N) and lowest stiffness (42.62 N/mm). Meanwhile, the LCL was second concerning the ultimate load (263.22 N) and stiffness (69.70 N/mm). The elastic modulus of the LCL (493.86 MPa) was greater than those of both the MCL and ALL (326.75 MPa and 345.27 MPa, respectively). There was no difference between the sides according to the different properties of all the ligaments. A sex difference was apparent only concerning the ultimate load for all the ligaments. Each ligament showed similar stiffness irrespective of its size; for this reason, stiffness should be considered initially and while conducting biomechanical simulations of these ligaments.

Background and Study Aim Cortical screws were proposed as an alternative to the traditional pedicle screws. Diverse experimental results support the biomechanical superiority of cortical screws compared to pedicle screws. Laminectomy is often part of multilevel lumbar surgeries. Laminectomy might weaken the medial bony edge at the entry of the divergently oriented screw and, thereby, the screw purchase. This study investigated the biomechanical strength of lumbar cortical screw after laminectomy. Objective To compare the fixation strength of cortical screws and traditional pedicle screws after lumbar laminectomy. Material and Methods A total of 120 pedicles from 60 lumbar vertebrae of 12 cadavers (8 men, 4 women) were assessed. The mean age of the cadavers was 73.4 ± 6.2 years (range: 62-82 years). Using a posterior midline approach, we inserted the traditional pedicle screws into one and the cortical screws into the other side of each vertebra. Laminectomy was performed after screw insertion. Vertical pullout strength and toggle strength testing were performed to compare the fixation strength between the two sides. Results After laminectomy, the pullout strength of the cortical screws was 718.92 ± 340.76 N, and that of the pedicle screws was 625.78 ± 287.10 N (p = 0.183). The toggle strength of the cortical screws was 544.83 ± 329.97 N; that of the pedicle screws was 613.17 ± 311.70 N (p = 0.145). No significant difference was found in biomechanical strength between the two types of screws. Conclusion Despite laminectomy, lumbar cortical screws offers comparable pullout and toggle biomechanical strength as traditional pedicle screws. [ABSTRACT FROM AUTHOR]

The article presents a descriptive study which measures the effect of leg position on the tension of lumbosacral vessels. It states that 10 unembalmed corpses were dissected using the Synframe system to reveal the abdominal artery and vein. Result indicates the reduction of tension in the abdominal aorta by 2.9% to 21.8% and assets that the result would be helpful not only in spinal surgery but also for other vascular surgeries especially patients with stenosis or atherosclerosis.

This paper reports a morphometric study of the C2 laminae to provide quantitative anatomical data for safe crossing laminar screw placement. A valid trajectory is essential for C2 crossing laminar screw placement. Although several clinical technique notes and modifications to define a safe screw trajectory have been introduced in the recent years, no morphometric analysis has been performed to confirm the accuracy of screw trajectory using this technique. In this study, morphometric analysis was performed on 100 Korean C2 three-dimensional reconstruction CT images. The reconstructive C2 vertebrae from the post-edge of the spinal canal to the spinal process were divided into several zones, 1 mm each. Each zone was chosen as the entry point to imitate a crossing laminar screw (3.5 mm diameter) placement. In each 1-mm zoned trajectory, the screw pass ratio (PR), safe screw angle range (SAR) and maximum screw length (MSL) were measured and compared with the data from the other zoned trajectories. The zone ‘5–6 mm posterior to the post-edge of the spinal canal’ was found to be a more feasible and safer entry point for guiding a crossing laminar screw placement than the other zones because this zone could provide a trajectory with maximal PR (85%), SAR (9.57 ± 4.36º) and a larger MSL (21.74 ± 2.44 mm) than the other areas. The recommended safe screw angle in the axial plane is 49.68 ± 4.94 to 59.19 ± 4.70º. However, the screw angle can vary considerably according to the individual variance. A preoperative evaluation of the screw trajectory is essential for safe screw placement using this technique. [ABSTRACT FROM AUTHOR]

This study used 110 CT images taken from donated Korean cadavers to create 3-D models of the following upper and lower limb bones: the clavicle, scapula, humerus, radius, ulna, hip bone (os coxa), femur, patella (knee cap), tibia, talus, and calcaneus. In addition, the bone volume and surface area were calculated to determine sex differences using discriminant analysis. Significant sex differences were found in all bones with respect to volume and surface area (p < 0.01). The order of volume was the same in females and males (femur > hip bone > tibia > humerus > scapula), although the order of surface area was different. The largest surface area in men was the femur and in women was the hip bone (p < 0.01). An interesting finding of this study was that the ulna is the bone with the highest accuracy for sex determination (94%). When using the surface area of multiple bones, the maximum accuracy (99.4%) was achieved. The equation was as follows: (discriminant equation of surface area; female < 0 < male) = 0.060 × clavicle + 0.020 × scapula + 0.045 × humerus + (-0.049) × radius + 0.093 × ulna + (-0.023) × hip bone + 0.091 × patella + (-0.052) × fibula + 0.043 × talus - 11.548. These results show that bone volume and surface area of extremity bones can be used for sex determination. [ABSTRACT FROM AUTHOR]