INTRODUCTION

Cup orientation of total hip arthroplasty (THA) is critical for dislocation, range of motion, polyethylene wear, pelvic osteolysis, and component migration. But, substantial error under manual technique has been reported specially in revision THA due to a bone loss and poor anatomical landmark. We have used three kinds of navigation systems for cup positioning in primary and revision THA.

INTRODUCTION

Recently, as the number of total knee arthroplasty (TKA) is increasing, the number of revision TKA due to loosening or osteolysis is rapidly increasing. Large bone defect is one of the most critical issues during revision TKA. Therefore, early detection of bone loss around the TKA prosthesis before bone loss has been enlarged is very important. However, it is difficult to detect the loosening or ostolysis at the early stage around the femoral component even using fluoroscopically guided plain radiograph. A novel technique of tomography (Tomosynthesis; Shimazu Corporation, Kyoto, Japan) was introduced to detect the small bone loss. The purpose of this study was to examine, in a pig model of radiolucent line and osteolysis around TKA, the sensitivity and specificity of detection of radiolucent line and osteolysis using fluoroscopically guided plain radiographs and a novel technique of tomography.

Over the past decade, there has been an increase in the number of total knee arthropalsty (TKA). Demand of TKA for the young patients who often have high physical demands is also increasing. However, the revision rate in such young patients is much higher due to polyethylene (PE) wear and instability (Julin J, Acta Orthop 2010). Therefore, next generation total knee prostheses are expected to decrease PE wear and to provide stability.

Although in vitro study such as wear simulator test provides important information about PE wear, we have often encountered the discrepancy between the in vitro results and in vivo results. Thus we have performed in vivo PE wear particle analysis, and showed that in vivo PE wear was affected by the design of articulating surface and the materials of femoral component and PE insert (Minoda Y, JBJS Am 2009). Medial pivot design, ceramic femoral component, and highly cross-linked PE decreased in vivo PE wear particle generation.

Patients who underwent bilateral staged TKAs were more likely to prefer medial pivot prosthesis or ACL-PCL retaining prosthesis than the other types of prostheses, because they feels “more stable overall” (Pritchett JW, J Arthroplasty 2011). In vivo fluoroscopic 3D analysis showed that medical pivot and bi-cruciate substituting designs restored physiological knee motion and provided higher reproducibility (Mueller J. Komistek RD, Trans ORS 2009, Iwakiri K, Trans ORS 2007).

The excellent mid-term clinical results of those newly introduced total knee prosthesis, such as alumina medial pivot TKA (Iida T, ORS 2008), medial pivot TKA (Mannan K, JBJS Br 2009, Kakachalions T, Knee 2009), ACL-PCL retaining TKA (Clouter JM, JBJS Am 1999), and highly cross-linked PE (Hodrick JT, CORR 2008), have been reported.

From the point of view of in vivo PE wear, in vivo stability, and the mid-term clinical results, we suspect that medial pivot prosthesis is one of the prostheses which meet the demand in future especially for young active patients.

Introduction

There is many reports about complications with a resurfacing total hip arthroplasty (RHA). One of the most common complications is the femoral neck fracture. A notch and malalignment were risk factors for this. For an accurate implanting the femoral component in RHA, we performed 3D template and made a patient specific template (PST) using 3D printer and applied this technique for a clinical usage. We report a preliminary early result using this novel technique.

Introduction

Osteonecrosis of the femoral head (ONFH) is one of the most serious complications associated with corticosteroid therapy. In patients with ONFH, collapse of the femoral head often occurs and causes severe hip pain and impaired hip joint function. Despite the widely spread use of corticosteroids for treating various diseases and a known association between prevalence of ONFH and daily dose of corticosteroids, the pathomechanism for the development of ONFH has not been identified. Since hepatic cytochrome P4503A (CYP3A) is a predominant enzyme responsible for metabolizing corticosteroids and its activities varies more than 10-fold, low hepatic CYP3A activity leads to a remarkable increase of corticosteroid levels and its effect. We have previously reported that hepatic CYP3A levels are significantly lower in patients with corticosteroid-induced ONFH than that in control patients and patients with alcohol-related ONFH and that hepatic CYP3A activity inversely correlated with the incidence of osteonecrosis and extent of the necrotic area caused by the same dose of corticosteroids in a rabbit model, suggesting possible prevention of the corticosteroid-induced osteonecrosis by adjusting corticosteroid dose based on the level of individual hepatic CYP3A activity prior to corticosteroid therapy. To examine hepatic CYP3A activity, measuring clearance of administrated midazolam (MDZ) is a reliable method, as shown by the significant correlations between the clearance of midazolam and hepatic CYP3A levels measured by biopsy and the clearance of other CYP3A-specific substrates. However, the method is invasive and time consuming for measuring clearance of administrated MDZ, needing multiple blood samplings over half a day for each subject. The aim of this study was to develop the simple, safe and noninvasive methods for measuring the level of hepatic CYP3A activity, which is applicable to prevent the occurrence of corticosteroid-induced osteonecrosis prior to corticosteroid therapy.

The introduction of porous tantalum metal (Trabecular Metal; Zimmer, Warsaw, IN) for acetabular component fixation in total hip arthroplasty has shown optimum fixation qualities and “gap filling” effect. Recently, trabecular metal was introduced in tibial component for total knee prosthesis, however its effect on the bone mineral density (BMD) was not reported. The purpose of this study was to compare the BMD of proximal part of the tibia between trabecular metal and another cemented tibial component.

31 knees receiving trabecular metal tibial component and 33 knees receiving cemented tibial component (PFC Sigma RP, Depuy, Warsaw, IN) had dual energy x-ray absorptiometry (DEXA) scans at preoperatively and 3 weeks, 3, 6, 12, 18, 24 months post-operatively. To assess peri-prosthetic BMD, three regions of interest (ROI) were measured for each case. They were medial aspect (ROI 1), center aspect (ROI 2) and lateral aspect (ROI 3) of tibia. Average follow up period was 1.8 (range: 1.5 to 2) years. In both groups, BMD in tibia decrease postoperatively. Comparing postoperative decrease of BMD in lateral aspect of tibia (ROI 3) between both groups, it was significantly less in trabecular metal component (−0.09 g/cm2 +/−0.27) than cemented tibial component (−0.31 g/cm2 +/− 0.21) (p=0.0007).

We conclude that trabecular metal tibial component showed a favorable effect on BMD of proximal part of the tibia after total knee arthroplsaty.

Cup orientation of total hip arthroplasty (THA) is critical for dislocation, range of motion, polyethylene wear, pelvic osteolysis, and component migration. But, substantial error under manual technique has been reported. Therefore, various navigation systems were introduced to reduce outliers. CT based navigation (CTN) was reported to reduce outliers in cup orientation. Recently, a noble technique, fluoroscopy-CT-based navigation (FCTN), has recently been developed using 2D-3D matching technique. Because of much less registration points, FCTN might be friendly to MIS THA and cases with sever bone deformity. Between October 2006 and April 2008, 33 THAs were performed through MIS approach with navigations.

We prospectively randomized those into two groups, CTN and FCTN groups. We implanted cementless hemispherical cups in 18 hips using CTN (VectorVision CT Hip 3.1) and in 15 hips using FCTN (VectorVision CT Hip 3.5). For all the patients, volumetric post-operative CT scan was performed to measure 3D cup orientation. using 3D image-processing software (JMM, Japan). The difference from target angles of anteversion was 2.7 ± 2.4 degrees in FCTN group, and 12.1 ± 5.7 degrees in CTN group (p < 0.001). The absolute value of difference from target angles of inclination was 2.7 ± 2.4 degrees in FCTN group, and 6.5 ± 4.5 degrees in CTN group (p = 0.006). FCTN does not need surface registration around acetabulum, which is great advantage to MIS THA. Our study clearly showed that FCTN significantly improved a cup orientation to CTN.

Highly closslinked polyethylene has been developed to reduce polyethylene wear and to expect the longevity of THA. In daily activity of patients, total hip prostheses repeatedly suffer impact loading. However, the mechanical properties, especially impact load transmission, are not well investigated and the viscoelasticity might influence the loosening of cemented all-polyethylene cup. In this study, the impact load transmission through the complex of polyethylene cup, ceramic ball and metallic femoral stem was investigated.

Impact compressive tests on the complex were performed using Hopkinson pressure bar apparatus. Conventional and highly crosslinked polyethylene cups of three different sizes (40mm, 50mm, 56mm)were compared. The impact load was applied either from the cup or from the stem. The impact load transmission ratio (ILTR) i.e. the ratio of the magnitude of transmitted load to that of incident one was investigated. The loading pulse profiles were theoretically calculated based on the one dimensional elastic wave propagation theory and were compared with experimental results.

The ILTR was independent of the cup size in all experimental conditions. When the impact load was applied from the cup, the ILTR was not different between two types of polyethylene. On the other hand, when the impact load was applied from the stem, the ratio was greater than the previous loading condition, while the ratio of crosslinked polyethylene was significantly lower than that of conventional one (p < 0.05). The theoretically predicted stress pulse profiles were well correlated to the experimental ones.

The lower ILTR in highly crosslinked polyethylene is considered to be due to lower stiffness. These mechanical properties increase the deformity of the cup and may cause the loosening of the cup. These results indicated that the ILTR was not different among cup sizes, while the ratio was significantly affected by the loading conditions and the type of polyethylene.

Highly crosslinked polyethylene has been developed to reduce polyethylene wear and to expect the longevity of THA. In daily activity of patients, total hip prostheses repeatedly suffer impact loading. However, the mechanical properties, especially impact load transmission, are not well investigated and the viscoelasticity might influence the loosening of cemented all-polyethylene cup. In this study, the impact load transmission through the complex of polyethylene cup, ceramic ball and metallic femoral stem was investigated.

Impact compressive tests on the complex were performed using Hopkinson pressure bar apparatus. Conventional and highly crosslinked polyethylene cups of three different sizes (40mm, 50mm, 56mm) were compared. The impact load was applied either from the cup or from the stem. The impact load transmission ratio (ILTR) i.e. the ratio of the magnitude of transmitted load to that of incident one was investigated. The loading pulse profiles were theoretically calculated based on the one dimensional elastic wave propagation theory and were compared with experimental results.

The ILTR was independent of the cup size in all experimental conditions. When the impact load was applied from the cup, the ILTR was not different between two types of polyethylene. On the other hand, when the impact load was applied from the stem, the ratio was greater than the previous loading condition, while the ratio of crosslinked polyethylene was significantly lower than that of conventional one (p < 0.05). The theoretically predicted stress pulse profiles were well correlated to the experimental ones.

The lower ILTR in highly cross linked polyethylene is considered to be due to lower stiffness. These mechanical properties increase the deformity of the cup and may cause the loosening of the cup. These results indicated that the ILTR was not different among cup sizes, while the ratio was significantly affected by the loading conditions and the type of polyethylene.

Acetabular revision in patients with bone deficiency is often difficult because of the poor quality and quantity of the acetabular bone stock. The purpose of this study was to evaluate the midterm clinical and radiographic outcomes of acetabular revision with use of an impaction bone-grafting technique and a cemented polyethylene cup.

Results: thirty consecutive acetabular revisions were performed with impaction bone-grafting and use of a cemented cup in twenty-eight patients with bone deficiency. The average age at the revision was sixty-eight years. The minimum duration of follow-up of all reconstructions that were still functioning or that were followed until the time of death was three years (mean, 8.1 years; range, three to fifteen years). The acetabular bone defects were classified as cavitary in fifteen hips and as combined segmental-cavitary in fifteen hips according to AAOS classification.

One hip had a repeat revision. Radiographic analysis that had not been revised showed loosening in four hips. All these four hips were treated by bulk bone graft covering more than 50% of cups. Kaplan-Meier analysis demonstrated a prosthetic survival rate, with aseptic loosening as the end point, of 72% at fourteen years and, with revision as the endpoint, of 100% at ten years and 83% at fourteen years.

Impaction bone-grafting was an excellent option to manage acetabular revision surgery. However, excessive bulk bonegraft should not be used.

Introduction: Osteonecrosis of the femoral head (ONFH) has a close association with corticosteroid therapy. As corticosteroids are accepted to be metabolized mainly by CYP3A4 in the liver, low constitutive levels of the enzyme might lead to an excessive response to corticosteroids and lead to adverse events including bone necrosis. This clinical study was designed to elucidate this hypothesis and to present potential modalities to avoid corticosteroid-associated ONFH by tailoring the steroid dose according to individual metabolic capacities of corticosteroid.

Materials and Methods: Twenty-two steroid-associated ONFH patients, 27 alcohol-related ONFH patients, and 65 general population controls were enrolled in this study. To estimate functional level of hepatic CYP3A4 level, a midazolam (MDZ) clearance test was carried out in respective subjects. The results from the tests were compared between those groups.

Results: The distribution profile of the MDZ clearance in steroid-associated ONFH patients were shifted to the left, indicating lower hepatic CYP3A4 activity in those patients when compared with the general population. By using an unconditional logistic regression model, patients with low (< 9.7) MDZ clearance due to low hepatic CYP3A4 activity were at 9.5 times greater risk for corticosteroid-induced ONFH compared with those with high (9.7+) MDZ clearance (OR 9.5 [95% CI 2.79–32.2], p< 0.001). The hepatic CYP3A4 activity was not associated with prevalence of alcohol-associated ONFH.

Discussion: A significantly low constitutive hepatic CYP3A4 function in corticosteroid-associated ONFH patients was found. The corticosteroid-associated ONFH might result from excessive responsiveness to corticosteroids in those patients due to prolonged exposure of bone to high levels of corticosteroids because of low functional level of the steroid metabolizing enzymes. The steroid-associated ONFH might be avoided by tailoring the corticosteroid dose in accordance with the functional level of hepatic CYP3A4.

Introduction: Recently, highly cross-linked polyethylene has been highlighted in THAs, which is thought to reduce wear. However, little is known about an accurate nature of cross-linked polyethylene particles and long term wear in vivo. One of the authors implanted all polyethylene cups irradiated by 100 Mrad in 1970’s. Recently, we performed two revisions with this cup. In the present study, we extracted polyethylene particles and analyzed them.

Methods: Case1 was revised for a stem fracture and ace-tabular loosening at 25 years postoperatively and case2 for acetabular loosening at 27 years postoperatively. There was no osteolysis on X rays. We extracted polyethylene particles using a tiussue digestion and iamge analysis using computed iamge analyzer developed by Cambell.

Results: Equivalent circle diameter (ECD) was 0.73mm, roundness was 0.69, aspect ratio (AR) was 1.4 and number of particles was 6.0x108/g wet tissue in case1. ECD was 0.57mm, roundness was 0.62, AR was 1.54 and number of particles was 5.8x108/g in case2. SEM showed that granule or globular shapes were abundant and fibril shapes were rare.

Discussion and conclusion: Cross-linked polyethylene particles were less, a little smaller and much rounder in compared with our previous result of conventional polyethylene particles in peri-implant tissue after more than 25 years postoperatively in vivo.

Introduction: In 1970’s, Oonishi et al found out that the polyethylene cross-linked by gamma-ray irradiation (dose=100Mrad) had high wear performance, and then clinically used it as the material for acetabular sockets. He has reported excellent outcomes. In this study, we measured the wear three-dimensionally, and the oxidation by microscopic Fourier transform infrared spectrophotometry in retrieved high-dose cross-linked polyethylene [100Mrad PE] sockets implanted over 25 years.

Materials and methods: We revised two 100Mrad PE sockets (SOM type manufactured by Mizuho medical (JAPAN)), due to aseptic loosening, which had been implanted for 27 years approximately. The liner and volumetric wear were measured as previously reported [1]. Measuring points for oxidation index were (1) near surface point in unworn area, (2) near surface point in worn area, and (3) inner area which left any surface by > =2.5mm.

Results and discussion: The liner wears were 0.06mm and 0.29mm respectively. The volumetric wears were 25.8mm3 and 91.8mm3. The liner-wear rate of them were 0.002mm/year and 0.010 mm/year. The oxide index of each socket was 0.75, 0.62, 0.25 and 1.73, 0.67, 0.28, in order of the unworn area, the worn area and the inner area. Many researchers have reported that the annual liner-wear rate of UHMWPE sockets is from 0.1 to 0.2mm/year. We showed extremely less wear rate of the 100 Mrad PE sockets in comparison with UHMWPE sockets. Oxidation index in the worn area was approximately the same as that of UHMWPE sockets, which were determined in our previous study [2]. These results showed that 100Mrad PE sockets had maintained the high performance to the wear for long-term clinical use.

Recently, highly cross-linked polyethylene has been highlighted in THAs which is thought to reduce wear. However, little is known about an accurate nature of cross-linked polyethylene particles and long term wear in vivo. One of the authors implanted all polyethylene cups irradiated by 100 Mrad in 1970s. Recently, we performed two revisions with this cup. In the present study, we extracted polyethylene particles and made direct wear measurements on retrieved cups.

Case one was revised for a stem fracture and acetabular loosening at 25 years postoperatively and case two for acetabular loosening at 27 years postoperatively. There was no osteolysis on X rays. We extracted polyethylene particles using a tiussue digestion and image analysis developed by Cambell and measured wear of retrieved cups using casting and 3D scanner developed by us.

Equivalent circle diameter (ECD) was 0.73 um, roundness was 0.69, aspect ratio (AR) was 1.4 and number of particles was 6.0 hundreds million/g wet tissue in case one. ECD was 0.57 um, roundness was 0.62, AR was 1.54 and number of particles was 5.8 hundreds million/g in case two. SEM showed that granule or globular shapes were abundant and fibril shapes were rare. Direct wear measurement showed concentric wear patterns were observed with very low linear wear (less than 0.03 mm).

Cross-linked polyethylene particles were less, a little smaller and much rounder in compared with our previous result of conventional polyethylene in peri-implant tissue. No unidirectional and significant amount of wear was observed in retrieved cups even after over 25 years.