Introduction

We developed original KKS non-cement THA system and used clinically over 10 years. KKS means Keio Kyocera Series. This system was developed co-ordinating with Keio-University and Kyocera Company in Japan. Our concept was to make original THA system suitable for Japanese people. Osteoarthritis of the hip in Japanese people caused mainly from developmental dysplasia of the hip. So the shape of femoral medullary canal is characteristic compared with foreign patients. We analyzed the femoral medullary canal shape in typical Japanese osteoarthritis 50 cases of the hip by the use of CT scan. From the results of these analyses, we determined the optimal shape of KKS non-cement stem for Japanese patients. It has double tapered shape in distal stem shaft. Proximal taper angle of the stem is 4 degree, and distal one is 3 degree. The proximal part of stem has characteristic notch in anterior and posterior and lateral surface to tolerate rotational stability.

Introduction

We have used CT-based navigation system for THA from 2004 (Fig, 1). The purpose is to set acetabular socket in optimal position. We have used two different matching methods in these navigation THA surgeries. The old one is Land-mark matching method (L-method), using conventional paired point matching procedure during surgery. The new one is CT-based fluoroscopy-matching system (F-method), that is new technology of image matching procedure before starting surgery (Fig. 2). We compared the accuracy of socket setting angle with these two systems and discuss the usefulness of navigation system.

We have used CT-based total hip navigation system from 2003, to set the acetabular socket in optimal position. At first, we had used CT-based land-mark matching system. It needs matching procedure during surgery, touching paired points in surgical exposure. From 2006, we started to use new navigation system, called CT-based fluoroscopy-matching system, which was developed by BrainLAB Company (Vector-vision 2.7.1., 3.5.1.). For this new system, pre-surgical image matching procedure is need. Fluoroscopic images with 2 different directions must be taken in operation room. Then fluoroscopic images and CT reconstructive images were matched in computer with special program. Matching procedure was done before surgical incision. We compared the advantage of these two systems about technical problem, radiation exposure, time need for procedure, and accuracy. And then we discussed how to use these two different systems for THA patients.

Accuracy was compared for 241 THA patients using these navigation systems. 152 cases were with CT-based land-mark matching system and 89 patients with CT-based fluoroscopy matching system. Final verification angle of acetabular socket setting in navigation during surgery was recorded for each case. The operative angle, which is referred from Murray, is used to show the socket setting angle (inclination and anteversion) in these navigation systems. Post-operative CT scan was taken to evaluate the actual socket setting angle. The values between verification angle during surgery and post-operative CT measured angle were calculated and compared statistically.

Results were followed. New CT-based fluoroscopy matching method (F method): Average setting angle (operative angle) of socket in these 89 cases were 42.9 +/− 5.1 degree in inclination angle, and 28.5 +/− 7.9 degree in anteversion angle. The absolute difference in 89 cases between final verification angle and post-operative CT measurement angle was 2.9 degree (on average) +/− 2.5 degree in inclination angle, and 2.8 degree (on average) +/− 2.6 degree in anteversion angle. Conventional CT-based land-mark matching method (L method): The absolute difference in 152 cases between final verification angle and post-operative CT measurement angle was 4.2 degree (on average) +/− 3.2 degree in inclination angle, and 4.4 degree (on average), +/− 3.7 degree in anteversion angle. Absolute differences of setting angle in fluoroscopy matching groups showed statistically low compared with land-mark matching groups (P<0.01).

Technical problems: L method is difficult to learn actual procedure. F method is easy to learn procedure. Image matching was done automatically by computer program. Radiation exposure during surgery: L method needs no additional radiation. F method needs radiation to get 2 fluoroscopic images. Total amount time need for navigation: L method needs extra 10 minutes during surgery in case of skilled-doctor. F method needs extra 20 minutes before starting surgery in case of all kind doctors. The accuracy of acetabular socket setting: Absolute errors in socket setting with theses two systems were within 5 degree together on average. These results showed the usefulness of both systems. Compared the accuracy between these 2 systems, F methods showed high accuracy. The accuracy of F methods is always high. It has no influence with deformity around hip joint, because fluoroscopic image matching was done with lower part of pubic bone, especially around symphysis pubis.

For ordinary THA cases with skilled-doctor, CT-based land-mark matching system is useful, because this system is very convenient and needs only extra 10 minutes during surgery. For severe deformed cases with all kind doctors, CT-based fluoroscopy matching system is useful, because this system showed high accuracy even for severe deformed cases. Before surgical incision, fluoroscopic matching procedure has finished. This system needs no extra time after surgery starts.

In the light of the increasing popularity of femoral resurfacing implants, there has been growing concern regarding femoral neck fracture. This paper presents a detailed investigation of femoral neck anatomy, the knowledge of which is essential to optimise the surgical outcome of hip resurfacing as well as short hip stem implantation.

Three-dimensional lower limb models were reconstructed from the CT-scan data by using the Mimics (Materialise NV, Leuven, Belgium). We included the CT data for 22 females and nine males with average age of 60.7 years [standard deviation: 16.4]. A local coordinate system based on anatomical landmarks was defined and the measurements were made on the unaffected side of the models.

First, the centre of the femoral head was identified by fitting an optimal sphere to the femoral head surface. Then, two reference points, one each on the superior and the inferior surface of the base of femoral neck were marked to define the neck resection line, to which an initial temporary neck axis was set perpendicular. Cross-sectional contours of the cancellous/cortical border were defined along the initial neck axis. For each cross-sectional contour, a least-square fitted ellipse was determined. The line that connects the centre of the ellipse at the base of the femoral neck and the centre of the femoral head was defined as the new neck axis. The above process was repeated to reduce variances in the estimation of the initial neck axis. The neck isthmus was identified according to the axial distributions of the cross-sectional ellipse parameters.

The short axis of the ellipse decreased monotonically since it was calculated from the center of the femoral head to the neck resection level (base of neck), whereas the long axis changed with the local minima. The cross section at which the long axis of the fitted ellipse had the local minima was determined as the neck isthmus.

The following measurements were made on the proximal part of the femur. The neck axis length measured from the center of the femoral head to the lateral endosteal border of the proximal femur was 67.3 mm [6.4]. The length between the center of the femoral head and the neck isthmus was 22.5 mm [2.7]. The diameter of the ellipse long axis at the neck isthmus was 27.6 mm [3.5] and was 23.6 mm [3.3] for the short axis.

The center of the neck isthmus did not align with the neck axis. The deviation of the isthmus from the neck axis which we defined as the isthmus offset was 0.7 mm [0.4].

If an alternative neck axis was defined between the center of the femoral head and the center of the neck isthmus, there would be a certain degree of angular shift with respect to the original neck axis. An angular shift of 1.8 degrees between the two axes can be expected for a 0.7-mm isthmus offset. In the worst case, an angular shift of 4.59 degrees was estimated for a subject with the largest isthmus offset of 1.93 mm.

Further investigations would be necessary to determine the axis configuration that represents the clinically relevant centre of the femoral neck. In order to reduce the deviations in the three-dimensional determination of the femoral neck axis, the reference anatomical landmarks and methods of evaluation should be carefully selected.

Dislocation after total hip arthroplasty (THA) remains a significant clinical problem. The acetabular cup position is one of the main factors in the incidence of dislocation after THA. We reviewed dislocation cases in 247 primary THA

Between 1997 and 2001, 247 patients underwent a primary THA procedure. The original diagnoses in these patients were as follows: osteoarthritis (OA, n = 190), osteonecrosis (ION, n=28), rheumatiod arthritis (RA, n=16), and rapidly destructive coxarthropathy (RDC, n=13). A posterolateral approach was used in all cases. We examined mainly the acetabular cup position (ante-version and inclination angle) using anteroposterior radiographs

Six dislocations (2.4%) occurred : three anterior dislocations and three posterior dislocations. Dislocation rate according to the original diagnoses were as follows, 2 dislocations in OA (1.1%), 2 dislocations in RA(12.5%), 2 dislocations in RDC(15.4%) and no dislocation in ION. All cases were treated with close reduction and no component revision was needed. On X-P measurement of setting the acetabular cup in all cases, the mean ante-version angle was 16.3617;6.8 degrees and inclination angle was 43.3& #61617;7.3 degrees. In comparison with these measurement values, there was no statistical difference between the dislocation groups and no-dislocation groups. The number of the cases within Lewinnek’s safe zone in acetabular cup was 178 (72%). The dislocation rate in these 178 cases was low (1.1%).

Setting the acetabular cup in adequate position is one of the major factors avoiding dislocation after THA. We have been performimg computer - assisted THA since 2003. Computer - assisted surgery enables the acetabular cup position to be precisely planned before surgery and allows superior positioning during surgery.

We investigated the incidence of PE (Pulmonary Embolism)and DVT (Deep Vein Thrombosis) after THA by the use of MDCT (multi-detect or row CT scan). The purpose of this study was to evaluate the meaning of blood coagulation molecular markers (FDP D-dimer, Soluble Fibrin Monomer Complex) for the prospect of PE and DVT after THA.

We studied 30 THA patients. There were 2 men and28 women. The value of D-dimer and SFMC before and after THA was examined. MDCT was carried out for DVT and PE investigation, in all cases 7 days after-THA. The relation between the values of blood coagulation molecular markers and existence of PE and DVT was evaluated.

PE occurred in 2 cases and DVT in 4 cases out of 30 cases. D-dimer values of these 2 PE cases in 7 days after THA were higher (18,39), compared with average values (12). Among DVT 4 cases, in 1 case DVT existed on thigh and in other 3 cases existed on calf. The SF values in 7 days showed extremely higher in only thigh DVT case (99), compared with average values (16.6). The value of SFMC fell down rapidly in a few days, representing the biphasic property.

MDCT is very effective for the diagnosis of PE and DVT. But it is difficult to make examination many times. It is very convenient to be able to evaluate PE and DVT by blood examination. From the results of this study, D-dimer may be sensitive for the diagnosis of PE and SFMC also may be useful for DVT. SFMC reacts more rapidly to abnormalities of thrombus and hemostasis. So it has possibilities to clarify the temporal responses of the DVT and PE more precisely.

Since the autumn of 2003, a computer-assisted system (VectorVision® Hip, version 2.1, Brain LAB, Germany) has been used to perform total hip arthroplasty (THA) operations in our hospital. In the present study, the postoperative acetabular cup position was evaluated using the records of the system and the data measured from postoperative radiographs.

To date, 18 patients have been treated using this-system. We studied the cup inclination and anteversion records in this system recorded in the THA procedures. We also measured the cup inclination and anteversion using postoperative radiographs, according to the method described by Pradhan. The inclination and ante-version were the ‘operative’angles for this system and were the ‘radio graphical’ ones for measuring from the radiographs according to the definition described by Murray.

The initial planning of the acetabular cup position was 45° ‘operative’ inclination and 20° ‘operative’ ante-version. From the system records, the average ‘operative’ inclination was 46.5°± 3.9° and the average ‘operative’ anteversion was 25.5°± 6.0°. The average ‘radio graphical’ inclination measured from the postoperative radiographs was 49.0°± 6.0°, and the average ‘radio graphical’ anteversion was 10.6°± 5.8°.

Between the ‘operative’ angles from this system and the ‘radio graphical’ angles from the postoperative radiographs, the inclination was approximately the same, while the anteversion was different. When the ‘radio graphical’ anteversion was corrected for X-ray beam spreading and then converted to the ‘operative’ anteversion, the resulting ‘operative’ anteversion was 21.1°± 7.8°. And when the ‘operative’ anteversion recorded by this system was corrected for the pelvic tilt, the corrected ‘operative’ anteversion was 22.1°± 6.5°. The average difference between these corrected ‘operative’ anteversion in each case was 5.8°± 3.8°. Especially in 10 of the 18 cases, each difference was within 5°. The accuracy of the cup position using this computer-assisted system was shown by this study.

We have developed lameller etched titanium (L.E.T.) structure, as a new bone-prosthesis interface. L.E.T. has a laminating structure consisting of a thin board made of porous etched titanium layer. We call this structure, a space controlled interface, because its pore shape, pore size and porosity within the interface can be controlled easily.

Purpose: We compared the binding capacity of L.E.T. system with the conventional beads surface, by experimental study.

Materials and Methods: We implanted two types of interface in 30 canine femora, one with LET and, the other with a conventional beads surface structure as a control. Hydroxyapatite (HA) is coated on L.E.T. stem. The dogs were killed three, six, ten weeks later. The harvested femora were cut off seven sections follow by a push out strength test and calculate the rate of bone ingrowth by measuring images of backscattered electron imaging-scanning electron microscopy (BEI-SEM) of each cross section using the NIH Image. Thin-sectioned tissues were then stained with toluidine blue.

Results: The push-out strength of the L.E.T. stems were 146 to 384% greater and its rate of bone ingrowth were 193 to 226% greater than that of the conventional beads stems. HA coated L.E.T. implants had the new bone formation down to the bottom of the porous portion even after three weeks, the findings which was not seen in the conventional beads stems in microscopic and BEI-SEM finding.

Discussion and Conclusion: Space controlled interface (L.E.T.) was proven to keep an adequate pore within the interface and induce true bone ingrowth in the space. Using L.E.T. structure, faster bone ingrowth and stronger fixation of the stem to the bone can be obtained.

We developed LET (Lamellar Etched Titanium) porous structure as a new bone-prosthesis interface, which is made by piling up and fusing the etched titanium thin layers. This method can control pore size and porosity easily and obtain definite interconnective open pore structure (average porosity 65%, average pore size 500 micrometer)

Materials and method: The characteristics of bone ingrowth of LET coated with hydroxyapatite (HA) have been studied in a transcortical rabbit model.

We implanted two types of interface, one with LET and the other with a conventional rough surface structure, which is made with inert gas-shielded arc spraying (ISAS) technique (Ra 40 micrometer) Both materials have coated with HA using the flame spray method. Mechanical and histological studies were performed at 2, 4, 9 and 12 weeks.

Results: Previous scanning electron microscopy study of HA coated LET revealed an even HA layer consecutively distributed from its surface to the bottom without pore obstruction. Mechanical detaching tests showed that the interfacial tensile strength of LET increased with time and were significantly higher than that of ISAS at 4, 9 and 12 weeks (P< 0.05). Histological studies demonstrated that LET had induced deep and wide bone ingrowth into the pore structure. Even at 2 weeks, the immature bone trabeculae were observed stretching to the bottom of LET and, at 9 and 12 weeks, the new bones infiltrated into porous structure changed into maturing osseous tissue. Further, residual new bones of the detached side were observed in and on the pores of LET. It suggested that detaching occurred inside of new bones. In contrast, no residual bone was found onto ISAS implant at 4, 9 and 12 weeks.

Conclusion: The LET structure was proved to have desirable properties for bone ingrowth and, furthermore, the osteoinductivity of HA could enhance its character.

In revision hip Arthroplasty, there often exists the intact femoral cortex under the level of loosened stem. In such cases we used a mid-length full-porous Cementless stem, because femoral bone remodeling and reinforcement could be obtained. We evaluated the readiographical change in femur after the inplantation of full-porous Cementless stem.

Materials and methods: Thirteen revision hip Arthroplasties with the use of mid-length full-porous Cementless stem (Ostenics Specilty Stem) were evaluated. Before revision operation, aseptic loosening and sinking of femoral stem were seen in all hips. In three hips, varus shift of femoral component was seen, and in one hip, anterior shift was seen. Bone graft was done only around the proximal femoral defect. No bone graft was done at the level of middle and distal bone defect of the femur. The average age at revision operation was 59 (43-75) years old. Average follow up was 32 (15-59) months. All hip were evaluated clinically and radiographically, especially about the femoral cortical bone remodellig after operation.

Results: Ten patients were pain free, and three had thigh pain. Subsidence of the stem occurred in one patient who complained of thigh pain. In this patient, cortical enlargement and thinning of femur was extreme before operation. Other 12 cases have no subsidence of the stem. Ten patients had a satisfactory result in clinically and radiographically. In six patients, who had bone defect of middle and distal femur before operation, the new bone formation between stem and the cortex of the femur was seen at the latest follow up. Femoral bone remodeling was optained in the middle and distal femur without bone graft.

Conclusion: Revision hip Arthroplasty with the use of full porous Cementless stem is a useful option because femoral bone remodeling and reinforcement can be obtained.

We developed K.K.S. (Keio-Kyocera Series) THA sytem. The aim is to develop original THA system suitable for Japanese patients. We produced MCF (means Medullary Canal Filling) stem, based on the anatomical anlysis of Japanese typical osteoarthritic patients (53 cases) by the measurements with CT scan. By the use of this stem, excellent canal fitting and initial rigid fixation can be obtained. We used this stem together with non-cement porous socket from 1992. At first the surface of this stem was smooth (S groupe), from 1994 the surface was altered to porous surface (P groupe), and then from 1995 HA coating to porous surface (H groupe) was added. The purpose of this study is to compare the biological fixation ability among stems with same shape and different surface.

Material and methods: Materials were patients for which Non-cement K.K.S. THA was done, 33 cases, 35 joints. Average age at operation was 55 (43-64) years old. Follow-up terms were 5-8 years. According to stem surface, all cases were divided to 3 groupes (S: 14 joints, P: 10 joints, H: 11 joints) and evaluated clinically and radiographically. The evaluation was done at the point of 5 years after operation for all cases. Clinically existence of thigh pain was evaluated. Radiographically sinking of the stem and osteolysis around femur were evaluated.

Results: Thigh pain was existed on S group: 6/14; 43%, P groupe: 0/10; 0%, H groupe: 2/11; 18%. Stem sinking was seen only on S groupe: 12/14; 84%. Osteolysis was seen only on 1 joint in S groupe. The result of S groupe was apparently poor clinically and radiographically.

Conclusion: To keep the early biological fixation of stem, not only anatomical shape for getting excellent canal fitting but also porous surface structure is needed.

Objective: We had performed bipolar hemi-arthroplasty for osteoarthritis of the hip, with the technique of ace-tabular reaming until 1991. We studied the long-term results of this procedure radiographically.

Materials and methods: 62 patients (70 hips) were followed up for at least eight years after bipolar hemi-arthroplasty without cement. The diagnosis of all patients was osteoarthritis of the hip, which mainly came from dysplasia of the hip. The patients consisted of 13 men and 49 women. The average age at the operation was 43 years old (36–74 years old). The average duration of follow-up was 11 years (8–14 years). Smooth-surface press-fit type stem (Omnifit, Osteonics) was implanted for all cases. Focal osteolysis around component, the migration of the outer head and the subsidence of stem, were evaluated radiographically. By reviewing serial A-P radiographs, the first recognition of osteolysis and the extension of the lesion were researched.

Results: The mean migration of the outer head was 3.0mm medially and 9.1mm superiorly. The mean subsidence of stem was 7.2mm at final follow-up. The ace-tabular focal osteolysis was identified in 31 hips (44 %) and was first recognized at average 3.1years(1–9years) postoperatively. The femoral focal osteolysis was identified in 33 hips (47%) and was first recognized at average 2.3 years (1–9years) postoperatively. After the first recognition of osteolysis, the lesion was progressively spreading, especially on femoral side.

Conclusion: From these results, bipolar hemi-arthroplasty with the technique of acetabular reaming should not be indicated for osteoarthritis of the hip. This procedure causes osteolysis, which is progressive, and the migration of the outer head so often that it is difficult to preserve acetabular bone stock.