Ryo Sugama

External hip protectors are effective for the elderly with higher-than-average risk factors for hip fractures

SummaryIn our cluster randomised controlled trial for efficacy of hip protector with 672 ambulatory elderly women, a hip protector was more effective for prevention of hip fractures in residents with fall history (n = 202; hazard ratio (HR), 0.375; 95%CI, 0.14–0.98; p = 0.05) and body-mass index (BMI) ≤ 19.0 (n = 206; HR, 0.37; 95%CI, 0.14–0.95; p = 0.04) by a Cox proportional hazards regression model.IntroductionHip fractures result from both osteoporosis and falling. A potentially cost-effective method of preventing hip fractures involves the use of hip protectors but recent studies have revealed the uncertain effectiveness of hip protectors even in institutional settings.MethodsThis study was a cluster randomised controlled trial with nursing homes. We randomly assigned 76 homes with 672 ambulatory but frail elderly women. Several risk factors were assessed at baseline and incorporated into a Cox proportional hazards regression model. UMIN Clinical Trials Registry number is UMIN000000467. Research period was between January 2004 and March 2006.ResultsIn the intervention group, 19 hip fractures occurred (54.0/1,000 person-years), whereas 39 hip fractures occurred in the control group (78.8/1,000 person-years). Hazard ratio of hip fracture in the intervention group was 0.56 (95%CI, 0.31–1.03; p = 0.06) after adjusting for risk factors. In subgroup analysis, hip protectors were more effective for prevention of hip fractures in residents with fall history (n = 202; HR, 0.375; 95%CI, 0.14–0.98; p = 0.05) and BMI ≤ 19.0 (n = 206; HR, 0.37; 95%CI, 0.14–0.95; p = 0.04). Overall compliance with use of hip protectors was 79.7%.ConclusionRisk of hip fracture can be reduced by hip protectors among elderly women with fall history and low BMI.

In Vivo Analysis of Polyethylene Wear Particles After Total Knee Arthroplasty: The Influence of Improved Materials and Designs

Polyethylene wear particles induce macrophages to release cytokines, which can lead to osteolysis and aseptic loosening of total joint prostheses1. The generation of polyethylene wear particles is one of the most important factors that affects the midterm and long-term clinical results associated with total knee arthroplasty2,3. The generation of polyethylene wear particles is correlated with the activity level of the patient4, and greater demands are placed on a total knee prosthesis when it is implanted in a younger, more active patient5. Therefore, to achieve better long-term results for patients who have higher activity levels, modifications of materials (i.e., highly cross-linked polyethylene and alumina ceramic) and design (i.e., mobile bearing and medial pivot) have been developed to reduce polyethylene wear after total knee arthroplasty. It takes decades to evaluate the long-term results of newly introduced total knee prostheses. Thus, it is particularly important to examine in vivo polyethylene wear generation in new prostheses before they come into widespread use. It is difficult to determine the in vivo polyethylene wear of total joint prostheses (with the exception of total hips) with use of postoperative radiographs. To measure polyethylene wear in vivo, we developed and employed a method in which we isolated and analyzed polyethylene wear particles in the synovial fluid of knees that had a well-functioning total knee prosthesis6-9. The number, size, and shape of polyethylene wear particles have been reported to be critical factors in the development of osteolysis. Greater volume, submicrometer size, and an elongated shape of polyethylene wear particles all stimulate an increased macrophage response10-12. Our hypothesis was that modification of total knee arthroplasty materials and designs can influence the generation of polyethylene wear particles in vivo. In the present study, …

In vivo comparison of wear particles between highly crosslinked polyethylene and conventional polyethylene in the same design of total knee arthroplasties

Reduction of wear with highly crosslinked polyethylene (HXLPE) has been reported in in vitro and in vivo studies of total hip prostheses. However, use of HXLPE in total knee prostheses is still controversial. The aim of this study was to compare in vivo polyethylene wear particle generation of HXLPE with that of conventional polyethylene in total knee prostheses of the same design. Synovial fluid was obtained from four knees with HXLPE inserts and three knees with conventional polyethylene inserts at 1 year after operation. Polyethylene particles were isolated and examined using a scanning electron microscope and image analyzer. The total number of particles in each knee was 0.28 +/- 0.12 x 10(6) in HXPLE group (mean +/- standard error) and 6.87 +/- 2.85 x 10(6) in conventional polyethylene group (p = 0.040). Particle size (equivalent circle diameter) was 0.64 +/- 0.07 microm in HXPLE group and 1.21 +/- 0.21 microm in conventional polyethylene group (p = 0.030). Particle shape (aspect ratio) was 1.33 +/- 0.10 in HXLPE and 1.88 +/- 0.19 in conventional polyethylene (p = 0.035). Thepercentage of particles of submicron size was greater than 90% in HXLPE group and 55% in conventional polyethylene group. Except for the material of the polyethylene insert, the design and material of prostheses were completely the same in both groups. The HXLPE insert generated fewer, smaller, and rounder polyethylene wear particles than the conventional polyethylene insert in the early stage after surgery.

Intraoperative assessment of midflexion laxity in total knee prosthesis

BACKGROUND Soft-tissue balancing of the knee is fundamental to the success of a total knee arthroplasty (TKA). In posterior-stabilized TKA, there is no stabilizer of the anterior-posterior translation in the midflexion range in which the cam-post mechanism does not engage yet. Therefore, instability in the midflexion range is suspected to occur in posterior-stabilized TKA. The purpose of this study was to measure the joint gap throughout a full range of motion and to analyze the joint gap laxity in the midflexion range after implantation of a mobile-bearing posterior-stabilized total knee prosthesis. METHODS Joint gap kinematics in 259 knees with varus osteoarthritis were measured during TKAs using a tensor device with the same shape of a total knee prosthesis of the same design was used. After the implantation of a mobile-bearing posterior-stabilized prosthesis and the reduction of the patellofemoral joint, the joint gap was measured at 0°, 30°, 60°, 90°, 120°, and 145° of flexion. RESULTS The center size of the joint gap was tight in extension and deep flexion and loose at midflexion ranges, especially at 30° of flexion (p<0.001). The symmetry of the joint gap was varus at 0° and 145° of flexion (p<0.001). CONCLUSIONS Our results showed the joint gap laxity in the midflexion range after the implantation of a mobile-bearing posterior-stabilized prosthesis. Our new tensor device, which can attach the polyethylene insert trial, will provide the important information about the joint gap kinematics after implantation of total knee prostheses. LEVEL OF EVIDENCE IV.

Midflexion Laxity After Implantation Was Influenced by the Joint Gap Balance Before Implantation in TKA

The relationship between the joint gap before and after implantation in 259 knees during the total knee arthroplasty was investigated using a tensor device which can attach the polyethylene insert trial. Patients were divided into following 3 groups according to the joint gap balance before implantation (flexion joint gap--extension joint gap); group 1: >1mm; group 2: -1 to 1mm, and group 3: <-1mm. Joint gap after implantation was loose at 30°, 60°, 90°, and 120° of flexion in group 1 and 2, but loose only at 30° of flexion in group 3 (p<0.01). This study showed that loose flexion joint gap before implantation increased the risk of joint gap laxity after implantation especially at midflexion ranges.

Two-dimensional measurement misidentifies alignment outliers in total knee arthroplasty: a comparison of two- and three-dimensional measurements

PurposeTwo-dimensional (2D) and three-dimensional (3D) measurements of prosthetic alignment and “outliers” after total knee arthroplasty (TKA) might not necessarily be comparable. The aim of this study was to compare the use of 2D and 3D measurements in the identification of prosthetic alignment and outliers after TKA.MethodsThis cross-sectional study included 159 consecutive TKAs. All patients underwent plain radiography, fluoroscopy-guided radiography, and computed tomography after TKA. The same baseline was used for 2D and 3D measurements. The reliability of prosthetic alignment and outlier identification (> 3° from neutral alignment) was compared between the 2D and 3D measurements.ResultsThe mean prosthetic alignment and rate of outliers were not significantly different the between 2D and 3D measurements. The inter- and intra-observer reliabilities were higher for the 3D measurements than for the 2D measurements. The agreement between 2D and 3D measurements in outlier identification was poor, except for femoral coronal alignment. Cohen’s κ coefficients were 0.19 in femoral sagittal (poor), 0.02 in tibial coronal (poor), and 0.10 in tibial sagittal (poor) on plain radiography. The values were 0.23 in tibial coronal (poor) and 0.002 in tibial sagittal (poor) on fluoroscopy-guided radiography.ConclusionsThe agreement between 2D and 3D measurements in the identification of outliers was poor, even on fluoroscopy-guided radiography. Since 2D measurements have an inherent risk of misidentifying alignment outliers, this finding is clinically relevant. To properly analyze the correlation between outliers and clinical results, such as longevity, patient satisfaction, and patient-reported outcome, 3D measurements for prosthetic alignment are desirable.Level of evidenceIII.

An accelerometer-based portable navigation system improved prosthetic alignment after total knee arthroplasty in 3D measurements

PurposeThis study aimed to compare prosthetic alignment using three-dimensional (3D) measurements following total knee arthroplasty (TKA) performed using an accelerometer-based portable navigation system (KneeAlign2) versus the conventional technique.MethodsA total of 159 patients who had primary osteoarthritis of the knee with varus deformity underwent TKA. The KneeAlign2 system was used for distal femoral resection and tibial resection in 78 knees, and the conventional instrumentation (intramedullary for the femur and extramedullary for the tibia) was used in 81 knees. 3D computed tomography (CT) scans of the whole leg were taken after TKA. Femoral and tibial prosthetic alignments in the coronal, sagittal, and axial planes were measured using computer software. The operation time and estimated blood loss were calculated. Deep venous thrombosis (DVT) and pulmonary embolism (PE) were evaluated using the contrast-enhanced multi-detector row CT at 1 week after TKA.ResultsIn the femoral coronal plane, the mean and standard deviation of prosthetic alignment from neutral alignment were 1.2° [95% confidence interval (CI) 1.0°–1.4°) in the navigation group and 1.6° (95% CI 1.3°–2.0°) in the conventional group (p = 0.03). The femoral component outliers (> 3° away from the goal alignment) using the navigation system and the conventional technique were 3 and 15%, respectively, in the coronal plane (p < 0.01), and 15 and 43%, respectively, in the sagittal plane (p < 0.01). The outliers in tibial coronal and tibial sagittal planes were not statistically different between the two groups. There were no statistically significant differences between the two groups in operation time, blood loss, DVT, and PE.ConclusionUsing an accelerometer-based portable navigation system decreased the outliers of prosthetic alignment in femoral coronal and sagittal planes, and did not increase the complications such as operation time, blood loss, DVT, and PE. To our knowledge, this study is the first to investigate the usefulness of an accelerometer-based portable navigation system using the validated 3D measurement.Level of evidenceIII.

Impingement of the patellar component against the tibial post depends on the design of the post-cam mechanism: Comparison between 12 posterior stabilized total knee prostheses

BACKGROUND Patella-post impingement (PPI), contact of the patellar component with the tibial post, occurs during deep knee flexion after posterior stabilized total knee arthroplasty (TKA). In a previous pilot study, only two product lines were investigated. The aim of this study was to compare PPI between 12 contemporary posterior stabilized knee prostheses. METHODS Twelve posterior stabilized knee prostheses were implanted in full-length sawbone models of the femur and tibia using a navigation system. The distance between the lower edge of the patellar component and the cut surface of the tibia was defined as the tibial-patellar clearance (TPC), which represents the length of the patellar tendon. The TPC was set from 20 to 40 mm and the knee was moved from full extension to deep flexion while the knee angle at which PPI occurred (PPI angle) was recorded. RESULTS The PPI angle differed between prostheses (P < 0.05). Shorter TPCs resulted in smaller PPI angles and longer TPCs resulted in larger PPI angles (P < 0.05). To achieve more than 130° of flexion without PPI, the TPC should be prepared at a minimum of 20 mm for the NexGen LPS-Flex, Persona PS, Legion PS, and Evolution PS, 22 mm for the Attune RP and Journey II, 24 mm for the Triathlon PS, PFC Sigma PS, and Attune PS, and 26 mm for the NRG PS, Vanguard PS, and Vanguard RP. CONCLUSIONS The design of the tibial post significantly affects the PPI angle. To avoid PPI during deep flexion, appropriate TPC should be prepared during surgery.