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.

Frontal and lateral plain radiographs are the first choice for follow-up observations of the osteotomy boundary that faces the femoral and tibial components of a TKA. However, as plain radiographs provide no information in the image depth direction, it is difficult to determine the exact position of early-stage bone radiolucent lines. A new tomosynthesis technique, which uses both iterative reconstruction and metal extraction methods, has recently attracted attention. We report that this technique provides multi-slice images of the boundary between the metallic implant and the osteotomy surface, which is difficult to observe using conventional multi-slice imaging methods such as CT and MRI, and permits semi-three-dimensional evaluations of polyethylene wear.

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 range of motion (ROM) after total knee arthroplasty (TKA) is one of the most important factors for patient satisfaction, especially in Asian countries. To enhance the knee flexion angle, “high-flexion” designs have been introduced in total knee prostheses. One of such design was a new design of femoral prosthesis, which increased the posterior cut on the bone by 2 mm and thickened the posterior condyle, allowing the posterior condylar radius to continue further. There were several reports on postoperative ROM of such “high-flexion” posterior-stabilized (PS) total knee prosthesis. However, there was no report on the postoperative ROM of “high-flexion” cruciate ligament retaining (CR) total knee prosthesis. The purpose of this study was to compare the ROM associated with standard and high-flexion posterior CR total knee prostheses.

One hundred and fifty-one consecutive patients (176 knees) had CR total knee prosthesis. 89 knees had standard CR TKA (NexGen CR, Zimmer, Warsaw, IL), and 87 knees had high-flexion CR knee prostheses (NexGen CR-Flex, Zimmer, Warsaw, IL). Differences in the age, diagnosis, preoperative Knee Society Score (KSS), and preoperative ROM of the knee between two groups were not significant. At one year postoperatively, the patients were assessed clinically and radiographically.

The mean postoperative KSS knee score was 96.2 points for the standard CR prosthesis group and 96.7 points for the high-flexion CR prosthesis group (p=0.464). The mean postoperative KSS function score was 83.4 points for the standard CR prosthesis group and 84.8 points for the high-flexion CR prosthesis group (p=0.446). The mean postoperative ROM was 110.8 degrees in the standard CR prosthesis group, and 114.0 degrees in high-flexion prosthesis group (p=0.236). No knee had aseptic loosening, revision, or osteolysis.

Previous report showed that “high-flexion” PS design did not increase postoperative ROM compared to standard design. However, there was no report on the postoperative ROM of “high-flexion” CR total knee prosthesis. We found no significant differences between the standard CR group and “high-flexion” CR group with regard to ROM or clinical and radiographic parameters. However, in the cases which achieved high flexion, “high-flexion” design, which chamfered posterior femoral edge, can reduce the possibility of deformation from posterior contacts under lord. Therefore, the results of the current study suggested that “high-flexion” CR design is not the design that increase ROM significantly, but might be the safe design even when the knee achieved deep flexion.

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.

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.