Despite the well-documented improvement in coronal alignment achieved by computer assisted navigation, varying results have been reported for sagittal alignment. Current navigation systems rely on a sagittal femoral mechanical axis identified by the navigation system, but little information is available on the relationship between the sagittal mechanical axis and anatomical axes for intra-operative or postoperative radiographic assessments. We asked whether deviations exist between sagittal femoral mechanical axis and anatomical axes and attempted to identify predictors of the deviations found.

In 100 consecutive patients (200 knees) undergoing TKA, angles between two anatomical axes (the anterior cortical line and mid-medullary line) and two sagittal mechanical axes identified by current navigation systems were measured as proxies of the deviations between them on true lateral radiographs of the whole femur. Correlation analyses and multivariate regression were carried out to identify predictors of deviations.

Significant deviations existed with wide ranges between the anatomical axes and the sagittal mechanical axes. Degree of femoral bowing and femoral length were found to be predictors of deviations between sagittal femoral mechanical axes and anatomical axes.

This study suggests that surgeons applying navigation technology to TKA need to consider deviations between the sagittal femoral mechanical axes and anatomical axes when they intend to place a femoral component at a target sagittal orientation with respect to an anatomical reference.

Recently, it has been reported that the posterior stabilised implant clinically used for the total knee replacement (TKR) may have a risk of failures caused by pressure and stress concentrated on the tibial post. Malalignment of the implant or variable loading applied to the implant are one of the major causes of the failure in posteriori stabilised TKR. The purpose of this study is to biomechanically analyse the effect of implant malalignment on the failure risk of the implant in posteriori stabilised TKR by estimating von-Mises stress on the implant.

Finite element models of a knee joint and a posteriori stabilised implant were developed from 1mm slices of CT images and 3D CAD software, respectively. The posterior stabilised implant consists of a femoral component, a tibial post, and a tibial tray. The finite element models of TKR for the neutral alignment case as well as the different malalignment cases (3° and 5° of valgus and varus angulations, 2° and 4° of anterior and posterior tilts, and 3° of external rotation) were developed. Then, the von-Mises stress, which is which was chosen as the fracture risk parameter, acting on the implant were analysed by using CAE software. Loading condition at the 40% of one whole gait cycle such as 2000N of compressive load, 25N of anterior-posterior load, and 6.5Nm of torque was applied to the TKR models.

The maximum von-Mises stresses were concentrated on the anterior region of the tibial post regardless of the oblique loadings. In the rotationally additional loading (3° of external rotation), excessive stresses occurred in the anterior medial and posterior lateral areas. The maximum stress was 18.3MPa in neutral position. The maximum stress increased by 10% in anterior tilt 2°, 15% in anterior tilt 4°, 25% in posterior tilt 2°, 54% in posterior tilt 4°, 116% in varus 3°, 262% in varus 5°, 318% in valgus 3°, 389% in valgus 5°, 6% in external rotation 3° compared with that in the neutral position case. In addition, 32.0MPa of maximum stress occurred on the posterior lateral area of the base component in rotationally additional loading.

The results showed that the implant malalignment could accelerate the stress concentration on the anterior region of the tibial post as in the result of clinical study. In the case of additional rotation, high stress concentration on the anterior medial and posterior lateral areas as well as on the tibial base surface could generate wear or fracture of tibial post. From the additional rotation case, we can expect that higher conformity implant will generate higher stress concentrations than lower conformity implant even though we did not compare the effect of conformity ratio on the stress concentration in the tibial polyethylene component. This study showed that careful consideration of the implant malalignment would be necessary to improve the clinical outcome in the posteriori stabilised TKR.

Aims: To evaluate the outcomes of the primary total hip arthroplasties using nonmodular cementless acetabular component with titanium mesh coating þxed by press-þt technique. Methods: Eighty-two primary total hip arthroplasties in 75 patients were performed consecutively. Sixty-two hips were eligible for follow up of average 62 months (range, 48–84). The mean age was 59 years. The clinical evaluation was done by modiþed Harris hip score (HHS) and radiologic evaluation including stability of component, polyethylene wear rate (Dorr method) and remodeling pattern was done. Results: Mean HHS improved from 50.2 points preoperatively to 90.5 points at the last follow up. Excellent or good results were found in 52 hips (84%). All components were stable radiologically. The average thickness of polyethylene was 13.06mm. The linear polyethylene wear rate was 0.073mm/years (range, 0.01–0.23). Wear rate was correlated with the thickness of polyethylene signiþcantly (p=0.049). Any pelvic osteolysis was not found. The polar gap was found in 25 hips (40%) at initial radiographs and has disappeared during follow up in 22 hips (88%). One hip was revised due to chronic unreduced dislocation. There were 9 heterotrophic ossiþcations, 6 nonrecurrent dislocations, and 2 transient sciatic nerve palsies. Conclusion: Total hip arthroplasty using nonmodular cementless acetabular component seemed to enhance satisfactory early mid-term result in terms of stability and acetabular remodeling with minimal wear and pelvic osteolysis.

Aims: To evaluate the early midterm outcomes of primary total hip arthroplasty (THA) using Hydroxyapatite (HA)-coated on smooth surface acetabular component with 28 mm metal head on polyethylene liner articulation. Methods: Seventy primary THA in 63 patients with HA-coated acetabular component were performed consecutively between June 1993 and August 1996. Fifty-four cases were eligible for follow-up of average 71 months (48–104) and the mean age of index operation was 49 years (23–71). The clinical results were analyzed by modiþed Harris hip score, and the radiologic evaluation in terms of stability, polyethylene wear rate (Dorr method), osteolysis around acetabular component was done. Results: Mean Harris hip score improved from 50.9 to 82.2 at the last follow-up. Excellent or good results were found in 38 cases (70%). Eight cases (15%) were unstable radiologically. Pelvic osteolysis was found at 18 cases (33%). The mean polyethylene wear rate was 0.146 mm/year (0.01–0.45). Wear rate of hip dyaplasia was greater than osteonecrosis signiþcantly (p< 0.05). Seven cases (13%) were revised (5 mechanical failures, 2 deep infections). Any bone ongrowth was not found during revision surgery for loose components. Complications included 5 heterotrophic ossiþcations, 2 deep infections, and 1 nonrecurrent dislocation. Conclusion: Primary THA using HA-coated on smooth surface acetabular component showed unsatisfactory clinical results, accelerated polyethylene wear rate accompanying high incidence of osteolysis, and high loosening rate due to lack of bony ongrowth at early midterm.

Introduction: The purpose of this study was to compare the results of the efficacy of two decompressive methods (multiple drilling vs standard core decompression) for the treatment of precollapse osteonecrosis of the femoral head.

Methods: The results in a consecutive series of 54 patients (65 hips) who had undergone multiple drilling (31 patients, 35 hips) or core decompression (23 patients, 30 hips) for the treatment of precollapse osteonecrosis of the femoral head between September 1991 and July 2001 were reviewed. The average duration of follow up was 60.3 months (range, 24–103 months) in the multiple drilling group and 44.8 months (range, 24 to 84 months) in the core decompression group. The presence of collapse and radiographic progression in each group was evaluated prospectively with collapse of the femoral head defined as a failure. Harris hip scores (HHS) were used to evaluate clinical status preoperatively and at the most recent follow up.

Results: Radiographically and clinically, high failure was significantly related to the larger size and laterally located lesion (LHI of less than 12%, Urbaniak IIC, Ohzono IC and Kerboul index of more than 240 degrees) in both groups. The average preoperative and the last HHS was 86.7 to 73.7 in the core decompression group and 87.0 to 74.6 in the multiple drilling group. Compared to the core decompression group, the multiple drilling group had significantly longer times before collapse (mean 42.3 months vs 22.6 months, p=0.011) and a lower rate of collapse within 3 years after operation (55.0% vs 85.7%, p=0.03).

Discussion: Decompressive methods have worse outcomes in case of lesions of larger size and lateral location, even in precollapse stage. Multiple drilling has significantly longer time before collapse and a lower rate of collapse within 3 years after operation than standard core decompression.

According to the knee simulator test results in 1970s, the total decrease in thickness of UHMWPE tibial tray in combination with ceramic femoral component [F-Comp] was less than one tenth as that of the combination with metal [1]. These advantages led to development of total knee prosthesis [TKP] with alumina ceramics. In this study, we report the wear surface observation, the clinical wear and the oxidation of the retrieved TKP used clinically for 23 years, comparing with a metal TKP.

The retrieved TKP was implanted in 1979, and retrieved on January 9th in 2002. This TKP consisted of an alumina ceramic F-Comp and a UHMWPE tray combined with a alumina ceramic tibial component. Observations of the surface of alumina F-Comp and UHMWPE tray were carried out using SEM. Shape of UHMWPE tray was determined three-dimensionally. Comparing the result with original shape based on the product’s plan, liner wear and volumetric wear were calculated. Oxidation index was determined by Fourier transform infrared spectrophotometry.

Alumina F-Comp did not have any scratch on the surface by seeing with naked eye. UHMWPE tray had deformation and scratches obviously. The liner wear rate was 37 micrometer/year and volumetric wear rate was 18.8 mm3/year. The oxidation indexes were 0.6 in the unworn area, 1.2 in the worn area and 0.2 in the inner area.

SEM observations of the F-Comp demonstrated no scratch or pit. In contrast, many scratches were clearly observed on the UHMWPE tray. However, higher magnification observations did not demonstrate severe wear, which was shown on the wear analysis of a metallic F-Comp. Oxidation degradation is a problem to solve. However, the low wear rate and mild wear pattern demonstrate that ceramic F-Comp reduced UHMWPE wear.

Improved cement technique by interposing less than two layers of hydroxyapatite (HA) granules between bone and bone cement at the cementing (Interface Bio-active Bone Cement : IBBC) have been performed in total knee arthroplasty (TKA) since 1987.

We performed IBBC technique in 153 knees (130 patients) in TKA from 1987 to 1993. One hundred and forty knees (120 patients) could be followed up clinically and radiologically. Follow up rate was 91.5%. A mean follow-up period was 9.5 years (6 to 13 years) after surgery. As a control, clinical results of TKA with conventional cementing (Non-IBBC) which were operated in 44 knees (44 patients) in 1986 were used.

In IBBC cases, radiolucent lines on the tibial components were seen 7.1%, 2.9%, 1.4%, 3.6%, 0%, 0% and 0% at Zone ‡T to ‡Z of the anteroposterior view, while in Non-IBBC cases, 40.9%, 13.6%, 9.1%, 27.3%, 11.4%, 4.5% and 13.6% at Zone ‡T to ‡Z, respectively. In IBBC cases peri-prosthetic osteolysis of the tibial components were seen in three knees (2.1%), while 29.5% in Non-IBBC cases. Aseptic loosening of the tibial component was only one case (0.7%) in IBBC cases, while 9.1% in Non-IBBC cases.

In IBBC, bone cement bound to HA mechanically immediately after surgery and HA granules bound to the bone physicochemically after bone ingrowth into the spaces around the HA granules. In Non-IBBC, spaces will appear between bone and bone cement due to osteoporosis and/or atrophy after long years. However, in IBBC, bone and bone cement will contact by interposing HA forever due to osteoconductive effect of HA.

In conclusion, the IBBC has significantly reduced the incidence of radiolucent lines and periprosthetic osteolysis in TKAs. IBBC is a method combining the advantage of cementless HA coating and bone cement.

We have used Interface Bioactive Bone Cement (IBBC) in all cases of total joint arthroplasties since 1987. The method is improved cement technique by interposing less than two layers of hydroxyapatite (HA) granules between bone and the polymethylmethacrylate (PMMA) bone cement. We report one patient who underwent revision surgery after total knee arthroplasty (TKA) using IBBC.

The patient is a woman aged 70 years at the time of revision surgery. Right TKA was performed with the diagnosis of rheumatoid arthritis. An alumina ceramic total knee prosthesis was inserted using IBBC. Pain and walking ability were once improved after the primary TKA. However, the gait disturbance recurred after the patient fell on the ground. Radiographic findings showed severe genu varum, but neither radiolucent lines around the components nor migration of the components were seen. This was revised with semiconstrained prosthesis for the purpose of improving lateral instability at 31 months after the primary TKA.

Avulsion of fibular attachment of collateral ligament was seen at the time of the revision surgery. As PMMA cement was strongly adhered to the bone, it was removed together with cancellous bone. Histologically, HA granules bound to the bone directly after bone ingrowth into the spaces around the HA granules. This is the reason we have described IBBC as a method having the both advantages of cementless HA coating and PMMA bone cement.

After the revision surgery, the walking ability was improved.

In conclusion, this case showed excellent characteristics of IBBC.

Objectives: To assess the early diagnostic procedures and results of treatment for pyogenic discitis and to propose the ideal method of treatment for it.

Materal and Methods: 35 patients underwent open discectomies : 24 males and 11 females. 34 had single level and one had two-level discectomies. Blood were analysed on pre- and postop 3rd, 7th, 14th days, and 6 weeks. MRI exam in 6 patients and bone scintigraphy in 3 were done. Clinical symptoms of infection was observed on the postop 7 day on average. The characteristic features were back pain with muscle spasm, muscle cramping in legs, malaise, mild fever. 32 had conservative treatment and two had anterior radical surgery. Tobramycin, cloxacillin, and clindamycin were used for 4–6 weeks.

Results: WBC, ESR, CRP and body temperatures (BT) at postop 3rd, 7th and 14 days, and 6 weeks were checked; WBC were 11,500, 13,000, 9,300, 6,300 respectively: ESRs at one hour were 39, 50, 46, and 26mm : CRPs were 16.8, 23.5, 8.1 and 2.5. BT on average at postop 3rd, 7th and 14th days were 37.6, 37.4 and 37.2. Muscle spasm subsided together with cramping in legs 7–12 days after chemotherapy, but back pain persisted even after control of infection in most of the cases. MRI disclosed the infection in 5 of 6 cases, while in all 3 bone scans were positive. Infection was controlled in all. In 2 cases bony destruction advanced during chemotherapy, and in 2 other cases after anterior surgery infection exacerbated and spreaded to the neighbouring bone and joints.

Conclusion: Antibiotic therapy is found sufficient in controlling discitis, and surgery should be reserved for the patients without response to antibiotics.

We report the long-term radiographic results of the total hip arthroplasty with use of the cementless porous coated Harris-Galante (H-G) stem. Seventy-five consecutive patients, eighty-eight hips formed the basis of this study. Fifty patients were male, twenty-five patients were female, and thirteen patients were bilateral. The mean age of patients at operation was 42 years. They were followed up for an average of thirteen years four months (ten years two months to fourteen years four months). The diagnosis was avascular necrosis of the femoral head in 49 cases, degenerative osteoarthritis in 32 cases. Clinical results were estimated by modified Harris hip score and thigh pain, and radiographic results by periodically checked plain X-ray film. The average Harris hip score increased from 60 points preoperatively to 83 points at the most recent follow-up examination. The hip pain score increased from 31 points to 41 points. Clinically severe thigh pain was observed in 3 cases (4%). In radiographic evaluation, subsidence more than 5mm was seen in 2 cases (2%). Periprosthetic osteolytic lesion was observed in 15 cases (17%), but the lesions do not influence stability of the stem. Femoral stem stability by Engh was stable in 72 cases, fibrous stable in 12 cases, unstable in 4 cases. Pedestal formation, cortical hypertrophy of the distal femur, and stress shielding was observed more than 40%. Subcollar resorption was identified in 29% and ectopic ossification in 15%. Revision of the femoral stem was needed in 4 cases for aseptic loosening. At 10 years probability of survival of the stem using Kaplan-Meyer method was 95.5%. Use of the cementless H-G stem yielded the excellent long-term outcome, but osteolysis and stress shielding would be the main problems to solve.