Biomedical subjects

Yoshio Koga

Publications and source records attributed to Yoshio Koga.

8 recordsLinked to original sources

PubMed2006

Three-dimensional knee motion before and after high tibial osteotomy for medial knee osteoarthritis.

BACKGROUND: High tibial osteotomy (HTO) is an established surgical option for treating medial knee osteoarthritis. HTO moves the mechanical load on the knee joint from the medial compartment to the lateral compartment by changing the leg alignment, but the effects of the operation remain unclear. The purpose of this study was to evaluate the change in three-dimensional knee motion before and after HTO, focusing on lateral thrust and screw home movement, and to investigate the relationship between the change in knee motion and the clinical results. METHODS: A series of 19 patients with medial knee osteoarthritis who had undergone HTO were evaluated. We performed a clinical assessment, radiological evaluation, and motion analysis at 2.4 years postoperatively. The clinical assessment was performed using the Japanese Orthopaedic Association knee score. RESULTS: The score was significantly improved in all patients after operation. Motion analysis revealed that lateral thrust, which was observed in 18 of the 20 knees before operation, was reduced to 7 knees after operation. Regarding active terminal extension of the knee, three patterns of rotational movement were observed before operation: screw home movement (external rotation), reverse screw home movement (internal rotation), and no rotation. By contrast, after operation, only reverse screw home movement and no rotation were observed; the screw home movement disappeared in all patients. In the knees with reverse screw home movement after operation, the preoperative score was significantly lower than those in the knees with no rotation after operation. CONCLUSIONS: Kinetically, HTO was useful for suppressing lateral thrust in medial knee osteoarthritis, although the rotational movement of the knee joint was unchanged.

Adult↗

PubMed2005

Contact pressure in anterior cruciate ligament bone tunnels: comparison of endoscopic and two-incision technique.

PURPOSE: To investigate differences in contact pressure in the bone tunnel between the inside-out and outside-in techniques used for anterior cruciate ligament reconstruction. TYPE OF STUDY: In vitro cadaveric analysis. METHODS: Four fresh-frozen cadaver knees were tested. A femoral tunnel was generated through the tibial tunnel (inside-out technique). Another femoral tunnel was created using a rear-entry guide at the same intra-articular exit (outside-in technique). Aluminum cylinders containing 4-way (anterior, posterior, medial, and lateral) conductive rubber pressure sensors at the entrance of the joint were inserted into the tibial and femoral tunnels. Dynamic changes in the contact pressure of grafts in the femoral and tibial tunnels during 0 degrees to 130 degrees of knee flexion were measured. RESULTS: Contact pressure of the graft migrated from the anterior to the posterior portion of the femoral tunnel upon alignment of the femoral and tibial tunnels. At 0 degrees, 30 degrees, and 60 degrees of knee flexion, significantly greater contact pressure was observed at the anterior portion of the femoral tunnel made by the inside-out technique compared with that in the tunnel made by the outside-in technique. At 0 degrees, 30 degrees, and 60 degrees of knee flexion, significantly greater contact pressure was observed at the lateral portion of the femoral tunnel made by the outside-in technique. Constant contact pressure was observed in the medial portion of the tunnel made by the inside-out technique. Pressure changes in the tibial tunnel were slight; moreover, changes were not influenced by the femoral tunnel direction under any conditions. CONCLUSIONS: This study shows that contact pressure in the femoral tunnel is influenced by the direction of the femoral tunnel. CLINICAL RELEVANCE: The femoral tunnel direction in anterior cruciate ligament reconstruction is an important factor for femoral tunnel enlargement. A horizontal direction of the femoral tunnel might be needed for mature bone graft incorporation.

Anterior Cruciate Ligament↗

PubMed2004

The effect of an ankle brace on the 3-dimensional kinematics and tibio-talar contact condition for lateral ankle sprains.

Ten fresh-frozen cadaveric ankles were studied to investigate the effect of an ankle brace (Air-Stirrup) on the three-dimensional (3-D) motion and contact-pressure distribution of the talo-tibial joint with lateral ligamentous injury. Three-dimensional motion and contact-pressure distribution were simultaneously measured under dynamic conditions employing a direct linear-transformation technique and a dynamic-pressure sensor, respectively. Inversion increased significantly upon severing of the anterior talo-fibular (ATF) ligament and calcaneo-fibular (CF) ligaments; however, restoration to the intact level was observed following application of the ankle brace. Internal rotation also increased upon severing of the lateral ligaments in the plantar flexion; however, this difference was not altered by using the ankle brace. The contact area on the articular surface of the talus shifted from posterior to anterior between plantar flexion and dorsal flexion; additionally, a high pressure area was evident in the medial aspect of the talus following severing of the lateral ligaments. Upon application of the ankle brace, however, no significant changes were apparent in the contact condition. The results of this study suggest that stabilization against inversion is the major function of braces in terms of protection of ankle sprains. Ankle sprains, however, often occur in combinations of inversion, plantar flexion and internal rotation; therefore, restriction of plantar flexion and internal rotation may also be an important function of the ankle brace.

Ankle Injuries↗

PubMed2004

Three-dimensional lower extremity alignment assessment system: application to evaluation of component position after total knee arthroplasty.

A 3-dimensional (3D) lower extremity alignment assessment system based on biplanar computed radiography, a camera calibration procedure, and 3D image fitting techniques was developed. The goal of this study was to examine the errors associated with applying this 3D technique to determine component alignment after total knee arthroplasty (TKA). Tibial and femoral component alignment after TKA (varus--valgus, flexion-extension, and internal--external angulations) in 4 patients was determined directly with reconstructions from computed tomography (CT) scans and indirectly with the proposed bone and component image fitting techniques. Mean differences between alignment values from the CT and image fitting techniques ranged from 0.18 degrees to 0.78 degrees, and maximum differences ranged from 0.30 degrees to 0.90 degrees. The proposed 3D method can be reliably used to assess component alignment after TKA.

Arthroplasty, Replacement, Knee↗

PubMed2004

Properties of the tibial component regarding impact load.

Load transmission through knee prostheses was examined to clarify how the tibial component behaves under dynamic loading conditions. We did Genesis II total knee arthroplasty using sawbones and measured impact load transmission ratios using the split-Hopkinson pressure bar technique. We also measured the polyethylene strain when an impact load was applied using a strain gauge bonded to the anterior surface of the polyethylene. The impact load transmission ratios of metal-backed and all-polyethylene tibial components were less than 4%. Greater load transmission was observed with metal-backed components, which suggests that some of the applied dynamic load is transferred directly to the tibial cortical bone. Increasing polyethylene thickness decreased impact load transmission ratios in both components, which might lower the cancellous bone stresses beneath tibial implants. Greater strain in the tibial component was observed in all-polyethylene components. Increased polyethylene thickness did not significantly decrease the polyethylene strain, probably because of the nonlinear elastic behavior of the polyethylene material. The distant positioning of the strain gauge may, however, have prevented the detection of local contact strains. Recent clinical studies did not confirm our theoretical predictions, suggesting that other factors contribute more significantly to the clinical outcome in current total knee arthroplasty.

Arthroplasty, Replacement, Knee↗

PubMed2003

Intraoperative measurements of knee motion in total knee arthroplasty.

A photostereometric technology-based knee motion analysis system was developed and intraoperative kinematics during total knee arthroplasty (TKA) was investigated. Ten knees were evaluated and two different types of posterior-cruciate-retaining TKA (Genesis-I and Genesis-II) were used. Both TKA showed posterior translation of the medial and lateral femoral condyle with knee flexion. The motion pattern of the estimated contact point of Genesis-II was small initial rollback followed by sliding motion, then rollback again more than 60 degrees. In Genesis-II, the amount of translation of the medial condyle was significantly larger than that of the lateral, suggesting that the lateral condyle acted as a rotational pivot. Our developed knee motion analysis system was non-contact, high resolution and can evaluate both kinematics and estimated contact pattern. The results of this study suggest that intraoperative measurement using this analysis system has advantages for the investigation of in-vivo kinematics and contact condition in TKA.

Arthroplasty, Replacement, Knee↗

PubMed2002

Rotational muscle strength of the limb after anterior cruciate ligament reconstruction using semitendinosus and gracilis tendon.

PURPOSE: To investigate the influence of harvesting semitendinosus and gracilis tendons on the rotational muscle strength of the limb after anterior cruciate ligament (ACL) reconstruction. TYPE OF STUDY: Prospective study. METHODS: We performed a prospective study of 62 consecutive (34 male, 28 female) patients with ACL reconstructions using the semitendinosus and gracilis tendons. The mean age at surgery was 20.8 years. The semitendinosus tendon was harvested in 32 patients (ST group), and semitendinosus and gracilis tendons in 30 patients (STG group). The peak isokinetic torques for extension, flexion, internal rotation, and external rotation were measured before and 12 months after ACL reconstruction using the Cybex 6000B system (Cybex Division of Lumex, Ronkonkoma, NY). The rotational torque was measured at 30 degrees/sec and 120 degrees/sec. RESULTS: Before reconstruction, the mean isokinetic peak torque of the involved limb was decreased in extension and internal rotation. The mean isokinetic peak torque of the involved limb in extension recovered 12 months after ACL reconstruction; however, the weakness in internal rotation persisted. The preoperative weakness of the involved limb in extension and internal rotation recovered in the male patients, but not in the female patients after postoperative rehabilitation. The peak torque of the involved limb in internal rotation was decreased in the STG group, but not in the ST group. CONCLUSIONS: The internal rotational torque was influenced by harvesting the semitendinosus and gracilis tendons after ACL reconstruction, especially in female patients and patients from whom the gracilis tendon was harvested. Semitendinosus and gracilis tendons are important for the internal rotation of the limb and it was difficult to compensate for this function. Thus, we recommend harvesting the semitendinosus tendon only if tendon quality is sufficient to further minimize harvesting morbidity.

Adult↗

PubMedDate not supplied

Influence of the femoral tunnel location and angle on the contact pressure in the femoral tunnel in anterior cruciate ligament reconstruction.

BACKGROUND: The causes of bone tunnel enlargement after anterior cruciate ligament reconstruction have not been thoroughly investigated. HYPOTHESIS: A malpositioned femoral tunnel and an acute femoral tunnel angle may increase the mechanical stress in the femoral tunnel. STUDY DESIGN: Controlled laboratory study. METHODS: Three femoral tunnels (normal, anterior, and acute) and the tibial tunnel were made in four fresh-frozen cadaveric knees. Aluminum cylinders containing pressure-sensitive conductive rubber sensors at the joint entrance were inserted into the femoral tunnels. Dynamic changes in the contact pressure of the graft in the femoral tunnel were measured. RESULTS: Peak contact pressures and dynamic changes in contact pressure for the normal and anterior femoral tunnels demonstrated no differences. Maximum contact pressure of the graft was observed at the anterior portion with the knee in full extension and at the posterior portion with deep knee flexion. Consistent contact pressure occurred at the anterior aspect of the acute femoral tunnel throughout the range of motion. Mean contact pressure at the anterior region of the acute femoral tunnel was significantly higher than that of the normal femoral tunnel at 60 degrees, 90 degrees, and 120 degrees of knee flexion. CONCLUSIONS: The consistent contact pressure in the anterior aspect of the acute femoral tunnel may erode the anterior portion of the femoral tunnel, resulting in bone tunnel enlargement. CLINICAL RELEVANCE: The femoral tunnel direction in anterior cruciate ligament reconstruction is an important factor in reducing femoral tunnel enlargement.

Anterior Cruciate Ligament↗