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Yuki Tochigi

Publications and source records attributed to Yuki Tochigi.

16 recordsLinked to original sources
PubMed2006

In vivo measurement of translational stiffness of rabbit knees.

This paper describes the design, evaluation, and preliminary results of a specialized testing device and surgical protocol to determine translational stiffness of a rabbit knee, replicating the clinical anterior drawer test. Coronal-plane transverse pins are inserted through the rabbit leg, two in the tibia and one in the distal femur, to hold and reproducibly position the leg in the device for tests at multiple time points. A linear stepper motor draws the tibia upward then returns to the home position, and a load cell measures the resisting force; force-displacement knee stiffness is then calculated. Initial evaluation of this testing device determined the effects of preconditioning, intra-operator repeatability, rabbit-to-rabbit variability, knee flexion angle (90 degrees vs. 135 degrees ), and anterior cruciate ligament (ACL) sectioning (0%, 25%, 50%, 75%, 100%). Knee stiffness generally decreased as ACL sectioning increased. This testing device and surgical protocol provide an objective and efficient method of determining translational rabbit knee stiffness in vivo, and are being used in an ongoing study to evaluate the effect of knee instability (via partial to complete ACL sectioning) on the development of post-traumatic osteoarthritis.

Animals↗
PubMed2006

Talar dome access for osteochondral lesions.

BACKGROUND: Recently, osteochondral grafting has become a popular procedure for treating challenging talar dome lesions. However, no guidelines exist for selection of the surgical approach to obtain perpendicular access to the talar dome. HYPOTHESIS: The majority of the talar dome can be accessed for perpendicular resurfacing procedures without need for osteotomy. STUDY DESIGN: Descriptive laboratory study. METHODS: Nine human cadaveric ankles were dissected in a standard fashion to expose the talar dome. Seven approaches were used, including 4 arthrotomies (anteromedial, anterolateral, posteromedial, and posterolateral) and 3 osteotomies (anterolateral [Chaput], distal fibula, and medial malleolar). The area available for perpendicular access to the dome was determined for each approach. RESULTS: On average, 17% (range, 10%-24%) of the medial talar dome and 20% (range, 16%-25%) of the lateral talar dome could not be accessed without osteotomy. On the lateral aspect of the superior talar dome surface, an anterolateral osteotomy adds a mean of 22% to sagittal plane exposure. Malleolar osteotomies, when performed using the method described, provide access to the entire medial and lateral sides; however, there remains a mean residual 15% (range, 11%-38%) of the central talar dome that cannot be accessed in a perpendicular manner with any approach. CONCLUSION: Most of the talar dome can be accessed perpendicularly for resurfacing without malleolar osteotomy. Osteotomies substantially increase the access and are needed for extensive lesions. Part of the central portion of the talar dome is inaccessible to perpendicular resurfacing techniques with any standard approach. CLINICAL RELEVANCE: This study generated clear clinical guidelines to help decision making regarding the surgical approach to resurface the talar dome with osteochondral techniques. The majority of the talar dome can be accessed without osteotomy.

Cartilage, Articular↗
PubMed2006

Intra-articular contact stress distributions at the ankle throughout stance phase-patient-specific finite element analysis as a metric of degeneration propensity.

A contact finite element (FE) formulation is introduced, amenable to patient-specific analysis of cumulative cartilage mechano-stimulus attributable to habitual functional activity. CT scans of individual human ankles are segmented to delineate bony margins. Each bone surface is projected outward to create a second surface, and the intervening volume is then meshed with continuum hexahedral elements. The tibia is positioned relative to the talus into a weight-bearing apposition. The articular members are first engaged under light preload, then plantar-/dorsi-flexion kinematics and resultant loadings are input for serial FE solutions at 13 instants of the stance phase of level walking gait. Cartilage stress histories are post-processed to recover distributions of cumulative stress-time mechano-stimulus, a metric of degeneration propensity. Consistency in computed contact stress exposures presented for seven intact ankles stood in contrast to the higher magnitude and more focal exposures in an incongruously reduced tibial plafond fracture. This analytical procedure provides patient-specific estimates of degeneration propensity due to various mechanical abnormalities, and it provides a platform from which the mechanical efficacy of alternative surgical interventions can be estimated.

Ankle Injuries↗
PubMed2006

Arthroscopic visualization of the posterior subtalar joint in the prone position: a cadaver study.

PURPOSE: Subtalar arthroscopy in the prone position is thought to allow broader access to the posterior aspect of the joint than in the standard supine or lateral position. This study is aimed to assess if using the posteromedial (PM) portal in the prone position can increase the working area available through the dorsal and ventral posterolateral (PL) portals commonly used in the standard techniques. TYPE OF STUDY: In vitro cadaver study. METHODS: Six below-knee cadaver specimens were subjected to experimental arthroscopy on the posterior subtalar joint in a simulated prone position. On both the talar and calcaneal surfaces, the working areas (the maximal extent available to a working instrument while preserving surrounding cartilage) for the PL portals and the PM portal were identified. The combined area was compared with the area available from the PL portals alone, to assess the area extended with the PM portal. RESULTS: The talar working areas provided by the PL portals and PM portal were 31% +/- 13% and 26% +/- 8% of the total articular surface, respectively. The combined working area (43% +/- 13%) was greater than the PL working area alone; use of the PM portal increased the working area by a factor of 1.45. The calcaneal working areas from the PL and PM portals were 25% +/- 11% and 20 +/- 7%, respectively. The combined working area (35% +/- 14%) was similarly increased by a factor of 1.46 using the PM portal compared with PL portals alone (P < .05). CONCLUSIONS: In prone subtalar arthroscopy, significant extension of the working area was found by adding the PM portal to the standard PL portals, on both the talar and calcaneal surfaces. CLINICAL RELEVANCE: The PM portal that can be used in the prone position has a potential to increase the arthroscopic working area in the posterior subtalar joint.

Aged↗
PubMed2006

Ankle alignment on lateral radiographs. Part 1: sensitivity of measures to perturbations of ankle positioning.

BACKGROUND: In ankles with end-stage osteoarthritis or with total ankle replacement (TAR), radiographic landmarks based on joint surface morphology usually are obscured and inadequate for radiographic measurement. Furthermore, because of difficulty in reproducibly positioning the ankle for a standing radiograph, any radiographic measure to accurately describe ankle alignment must tolerate perturbations of ankle positioning on clinical radiographs. To identify a radiographic measure of anteroposterior tibial-talar alignment that meets those requirements, three methods were compared to determine their sensitivity to perturbations in ankle positioning. METHODS: Ten cadaver ankles had lateral radiographs taken in varying ankle positions in nine prespecified positions in the transverse plane and in seven positions in the sagittal plane. The anteroposterior tibial-talar alignment was quantified by three methods. Sensitivities to changes of ankle position in each plane were then compared. RESULTS: With the tibial-axis-to-talus ratio (T-T ratio: the ratio into which the midlongitudinal axis of the tibial shaft divides the longitudinal talar length), sensitivity to ankle positional changes in either plane was lowest, with errors associated with 10 degrees of ankle malpositioning being 2.2%. The posterior-tibial-line-to-talus ratio (P-T ratio: a similar ratio, but using the posterior longitudinal line of the tibial shaft) showed higher sensitivity in the transverse plane than the T-T ratio, though the associated errors in either plane were nearly comparable. The tibial-axis-to-lateral-process distance (T-L distance: the perpendicular distance from the tibial axis to the tip of the lateral talar process) showed highest sensitivity in both planes. CONCLUSIONS: The T-T ratio tolerated perturbations of ankle positioning best among the tested measures. This measure is potentially applicable to clinical radiographic measurement when determining the anteroposterior tibial-talar alignment in ankles with articular degeneration or TAR. The P-T ratio also appears to have reasonable tolerance.

Aged↗
PubMed2006

Ankle alignment on lateral radiographs. Part 2: reliability and validity of measures.

BACKGROUND: In ankles with end-stage osteoarthritis or after total ankle replacement (TAR), radiographic landmarks based on joint surface morphology usually are obscured and inadequate for measurement. Two methods for quantifying anteroposterior tibial-talar alignment without relying on those landmarks were identified in a corollary cadaver-based study. This study aimed to verify reliability and validity of those candidate measures. METHODS: On clinical radiographs of 33 nonarthritic and 35 arthritic ankles, the anteroposterior tibial-talar alignment was quantified by the two methods; the tibial-axis-to-talus ratio (T-T ratio: the ratio into which the midlongitudinal axis of the tibial shaft divides the longitudinal talar length) and the posterior-tibial-line-to-talus ratio (P-T ratio: a similar ratio, but using the posterior longitudinal line along the tibial shaft). Two observers performed every measurement twice to evaluate intraobserver and interobserver reliability of the candidate measures. For nonarthritic ankles, the anteroposterior tibial-talar alignment was further determined by a control measure that directly quantified orientation of the talar dome relative to the tibial shaft. Correlation of the T-T and P-T ratios with the control measure was then evaluated for validity. RESULTS: Measurement of the T-T ratio with arthritic ankles was highly reproducible with the coefficients of determination (R(2)) greater than 0.95, for either interobserver or intraobserver. Correlation between this measure and the control measure was supported (R(2) = 0.60, p < 0.0001). Reliability of the P-T ratio also was strong (R(2) > 0.91), although both reliability and validity of this measure were relatively inferior to the T-T ratio. CONCLUSIONS: The T-T ratio reliably and validly described the anteroposterior tibial-talar alignment on clinical radiographs, regardless of the condition of ankle joint surface. This measure appears to be a reliable radiographic measure for determining the magnitude of anteroposterior talar subluxation in ankles with articular degeneration or after TAR and can facilitate clinical investigations.

Adolescent↗
PubMed2006

Contribution of articular surface geometry to ankle stabilization.

BACKGROUND: Passive ankle stability under weight-bearing conditions has been found to depend substantially on the role of the articular surface geometry. In the present study, it was hypothesized that, in the ankle under axial loading, contact-stress changes in response to alterations of external load involve reproducible and specific patterns to maintain ankle stability. METHODS: Six cadaver ankles with the peri-ankle ligaments intact were tested. Each specimen, held at several predetermined ankle positions under a primary one-body-weight axial force, was subjected to an additional secondary load. The secondary load-specifically, anterior/posterior shear force, inversion/eversion torque, or internal/external rotation torque-was applied independently, while motion associated with the two other secondary loading directions was unconstrained. Contact stress in the tibiotalar articulation was monitored by a real-time contact-stress sensor. Site-specific stress changes solely due to secondary loading at each load/position were identified by subtraction of the corresponding axial-force-only baseline distribution. The role of these stress changes in ankle stabilization was studied for each specimen by analyzing the data with a computer model of ankle geometry. RESULTS: In the cadaver experiment, anterior and posterior shear forces caused reproducible positive changes in articular contact stresses on the anterior and posterior regions, respectively. Similar changes with version torques occurred on the medial and lateral regions. Positive changes with internal/external rotation torques occurred at two diagonal locations: anterolateral and posteromedial, or anteromedial and posterolateral. In the model analysis, these stress-change patterns were found to be effective in ankle stabilization, and the levels of contribution by the articular surface were calculated as accounting for approximately 70% of anterior/posterior stability, 50% of version stability, and 30% of internal/external rotation stability. CONCLUSIONS: The documented changes in contact stress illustrate the major role of articular geometry in passive ankle stabilization. The levels of contribution by the articular surface that we calculated are consistent with those reported in the literature. These findings support the conceptual mechanism of ankle stabilization by redistribution of articular contact stress.

Aged↗
PubMed2006

Ankle morphometry on 3D-CT images.

Understanding three-dimensional (3D) morphology of the ankle is essential for a better total ankle replacement. Current designs neither mimic the articular geometry at the bearing surface interfaces nor match the native bony bed with the implant's external dimensions. This is likely due to insufficient anthropometric data on sizing and geometry. We performed this study to determine the range of possible sizes of ankle joints based on high-resolution 3D-CT images. Clinical 3D-CT images from twenty-one normal ankles (11 males, 10 females) were subjected to morphometric evaluation. A local coordinate system for measurement was established based on talar anatomic landmarks. Measurements included the width of the superior talar dome surface (measured at the anterior, middle, and posterior portions) and the arc radius of the talar dome. The results yielded an average anterior width of 29.9 +/- 2.6 mm, a middle width of 27.9 +/- 3.0 mm, and a posterior width of 25.2 +/- 3.7 mm. The talar dome radius was 20.7 +/- 2.6 mm. The width linearly decreased from anterior to posterior (p < 0.001). A significant gender difference was found in both the width and the radius (p-values < 0.05), except at the middle width (p = 0.07). The data describe talar topography in a Caucasian U.S. adult cohort, suggesting the capability of the 3D-CT approach for ankle morphometric evaluation and sizing for the fabrication of total ankle replacements.

Adult↗
PubMed2005

Isoform-specific expression and induction of udp-glucuronosyltransferase in immunoactivated peritoneal macrophages of the rat.

Phase I drug-metabolizing enzymes such as cytochrome P450 in immunocytes are known to play a role in metabolic activation of toxic and immunosuppressive compounds such as polycyclic aromatic hydrocarbon (PAH). UDP-glucuronosyltransferase (UGT), a drug-metabolizing phase II enzyme, accelerates elimination of these compounds; however, there is little information on the expression and function of UGT in immunocytes. In this study, we investigated the expressions of UGT isoforms in rat peritoneal macrophages and the role of UGT in macrophage functions. Expressions of UGT1A1, 1A6, and 1A7 were observed in macrophages by immunohistochemical staining and reverse transcriptase-polymerase chain reaction. When macrophage cells cultured in plates were exposed to 1-naphthol and 3-hydroxybenzo-[a]pyrene (3-OH-B[a]P), these glucuronides increased in the medium, indicating that macrophages glucuronidated the chemicals. The production of the glucuronides of 1-naphthol and 3-OH-B[a]P was induced by lipopolysaccharide (LPS) treatment of the cultured macrophage cells. Northern blot analysis revealed that UGT1A7 mRNA was induced by LPS treatment. This result is the first evidence that a drug-metabolizing enzyme is induced by immunoactivation. The results indicated that macrophages can detoxify various toxic and immunosuppressive compounds with UGT, and that ability is enhanced by immunoactivation. We propose that macrophages contribute to protection against not only macromolecules as immunocytes but also small molecules such as the immunosuppressive agents PAHs in peripheral blood and interstitial tissues.

Animals↗
PubMed2005

Contact stress transients during functional loading of ankle stepoff incongruities.

Cartilage deformation demonstrates viscoelastic behavior due to its unique structure. However, nearly all contact studies investigating incongruity-associated changes in cartilage surface stresses have been static tests. These tests have consistently measured only modest increases in contact stresses, even with large incongruities. In this study, an experimental approach measuring real-time contact stresses in human cadaveric ankles during quasi-physiologic motion and loading was used to determine how stepoff incongruities of the distal tibia affected contact stresses and contact stress gradients. Peak instantaneous contact stresses, in ankles with stepoffs between 1.0 and 4.0mm of the anterolateral articular surface, increased by between 2.3 x and 3.0 x compared to the corresponding intact ankle values. Peak instantaneous contact stress gradients in stepoff configurations increased by between 1.9 x and 2.6 x the corresponding intact configuration values. Anatomic reduction of the displaced fragment restored intact contact stresses and contact stress gradients. Intact and anatomic configurations demonstrated a heterogeneous population of low-magnitude, randomly oriented contact stress gradient vectors in contrast to high-magnitude, preferentially oriented gradients in stepoff configurations. Peak instantaneous contact stresses may be important pathomechanical determinants of post-traumatic arthritis. Abnormal contact stress gradients could cause regional pathological disturbances in cartilage stress and interstitial fluid distribution. Measuring contact stresses and contact stress gradients during motion allowed potential incongruity-associated pathologic changes in loading that occur over the complete motion cycle to be investigated.

Ankle Joint↗
PubMed2005

Tensile engagement of the peri-ankle ligaments in stance phase.

BACKGROUND: Development of reconstructive operative procedures to restore normal ankle kinematics after injury requires an understanding of the biomechanics of the ankle during gait. The contribution of the peri-ankle ligaments to ankle motion control is not yet well understood. Knowledge of the tensile engagement of the peri-ankle ligaments during stance phase is necessary to achieve physiologic motion patterns. METHODS: Eleven fresh-frozen cadaver ankles were subjected to a dynamic loading sequence simulating the stance phase of normal level gait. Simultaneously, ligament strain was continuously monitored in the anterior talofibular, calcaneofibular, and posterior talofibular ligaments, as well as in the anterior, middle, and posterior superficial deltoid ligaments. Eight of these specimens underwent further quasi-static range-of-motion testing, where ligament tension recruitment was assessed at 30 degrees plantarflexion and 30 degrees dorsiflexion. RESULTS: In the dynamic loading tests, none of the ligaments monitored showed a reproducible strain pattern indicating a role in ankle stabilization. However, in the extended range-of-motion tests, most ligaments were taut in plantarflexion or dorsiflexion. CONCLUSIONS: A consistent combination of individual ligament strain patterns that principally control ankle motion was not identified; none of the ligaments studied were reproducibly recruited to be a primary stabilizing structure. The peri-ankle ligaments are likely to be secondary restraining structures that serve to resist motion to avoid extreme positions. Stance phase ankle motion appears to be primarily controlled by articular congruity, not by peri-ankle ligament tension.

Aged↗
PubMed2004

Pathomechanic determinants of posttraumatic arthritis.

The etiology of posttraumatic arthritis is poorly understood. One possible mechanism involves a mechanical insult to the cartilage matrix that affects chondrocyte function. To better understand the etiology of posttraumatic arthritis, pathomechanic changes in articular contact mechanics resulting from injury during physiologic motion and loading need to be determined. Previous studies of injury-associated changes in articular contact mechanics, using static testing methods, have measured relatively modest increases in contact stresses. Static testing cannot measure transient loads associated with motion or loading rates. This testing method poorly simulates normal viscoelastic cartilage properties, and accounts for contact stress changes in a single or limited number of joint positions. In this study, time-variant contact stresses in two ankles with an anterolateral stepoff were measured during quasiphysiologic motion and loading. Contact stresses were integrated over the entire range of motion to estimate pathomechanic loads that accumulate over the entire motion cycle. Numerical techniques were applied to time-variant contact stress data to calculate contact stress directional gradients and contact stress rates of change. Contact stress directional gradients and rates of change were integrated over the complete motion cycle to estimate whole-cycle accumulation of these potential pathomechanic parameters.

Ankle Injuries↗
PubMed2004

The role of the interosseous talocalcaneal ligament in subtalar joint stability.

BACKGROUND: Injury of the interosseous talocalcaneal ligament (ITCL) has been recognized as a cause of subtalar instability, though lack of an accepted clinical test has limited the ability of clinicians to reliably make the diagnosis. Clinical effects of ITCL failure remain unclear because of insufficient understanding of the role of the ligament. METHODS: Load-displacement characteristics of the subtalar joint were studied in six cadaver specimens using an axial distraction test and a transverse multi-direction drawer test. In all tests, cyclic loading (+/-60 N) was applied, and load-displacement responses were collected before and after sectioning of the ITCL. Two parameters were used to analyze the data: neutral-zone laxity as a measure of joint play, and flexibility as a measure of resistance to applied force. RESULTS: In the axial distraction test, sectioning increased both neutral-zone laxity and flexibility (p =.01 and.02, respectively). In the transverse test, sectioning caused increase of both neutral-zone laxity and flexibility (p <.001, for each). Neutral-zone laxity increased most greatly along an axis defined roughly by the posterior aspect of the fibula and the central region of the medial malleolus. Flexibility increased most in the medial direction (p <.05, for each). CONCLUSIONS: Results confirmed the role of the ITCL in maintaining apposition of the subtalar joint, as well as suggested its role in stabilizing the subtalar joint against drawer forces applied to the calcaneus from lateral to medial. The dominant direction of increased neutral-zone laxity described above suggests the optimal direction for detecting subtalar instability involved with ITCL injury. CLINICAL RELEVANCE: ITCL failure may result in subtalar instability and should be examined with a drawer force along the preferential axis roughly from the posterior aspect of the fibula to the central region of the medial malleolus. Further clinical evaluation is required to determine whether ITCL failure is reliably detectable.

Adult↗
PubMed2003

Effect of arch supports on ankle-subtalar complex instability: a biomechanical experimental study.

BACKGROUND: Subtalar instability, which may cause persistent symptoms after severe inversion ankle sprains, often involves failure of the interosseous talocalcaneal ligament (ITCL). While several clinicians have reported surgical treatment for this pathology, nonsurgical management policy has not been well considered. Previously, it was proposed that ITCL failure possibly causes looseness of the tarsal arch construction resulting in abnormal ankle-subtalar kinematics occurring with axial forces. In the current study the author hypothesized that arch-support insole functions to improve abnormal joint kinematics in ankle-subtalar complex instability. METHODS: Five fresh-frozen cadaver lower extremities with simulated ankle-subtalar complex instability, which was created by combined sectioning of the anterior talofibular ligament (ATFL) and the ITCL, were subjected to a biomechanical experiment. Cyclic axial loading from 9.8 to 668 N was applied with a material testing machine, while three-dimensional angular displacements in both the ankle and subtalar joints were determined with electric goniometers. The specimens were tested before and after inserting an arch-support insole that supports the medial-longitudinal and transverse arches of the foot. RESULTS: Inserting the insole decreased the maximum ankle internal rotation, from 3.3 degrees +/- 0.9 degrees to 2.3 degrees +/- 0.4 degrees (p = .028), while subtalar rotation was not significantly changed. CONCLUSIONS: The medial longitudinal arch-support insole reduced abnormal ankle internal rotation created by combined sectioning of the ATFL and ITCL, likely due to improved arch configuration stability.

Adult↗
PubMedDate not supplied

Incongruity-dependent changes of contact stress rates in human cadaveric ankles.

Cartilage biosynthetic transduction and injury characteristics have been shown to be particularly sensitive to changes in contact stress rates. This study investigated incongruity-associated changes in contact stress rates that resulted from an articular surface stepoff of the distal tibia in human cadaveric ankles. Ten human cadaveric ankles were subjected to quasi-physiologic stance-phase motion and loading and instantaneous contact stresses were captured at 132 Hz over the entire articular surface using a custom-fabricated stress transducer. An osteoarticular fragment consisting of the anterolateral 25% of the distal tibia was osteotomized. Testing was repeated after displacing the fragment proximally between 0.0 mm to 4.0 mm in 1.0 mm increments. Transient contact stress measurements were used to calculate contact stress rates. Compared to intact ankles, the anatomic configuration had modest increases in global and peak postitive and negative contact stress rates throughout the motion cycle. In contrast, stepoff specimens had significant increases in global and complete motion cycle peak positive and negative contact stress rates, as high as 3.1X intact values in specimens with a 4.0 mm stepoff. Contour plots of contact stress rates also demonstrated an instability event during motion. An anterolateral stepoff of the distal tibia caused significant changes in positive and negative contact stress rates in cadaveric ankles. Incongruity-associated changes in contact stress rates and incongruity-associated instability events may be important pathomechanical determinants of post-traumatic arthritis.

Ankle Injuries↗