Introduction

Highly crosslinked, ultra-high molecular weight polyethylene (HXLPE) acetabular liners inherently have a risk of fatigue failure associated with femoral neck impingement. One of the potential reasons for liner failure was reported as crosslinking formulations of polyethylene, increasing the brittleness and structural rigidity. In addition, the acetabular component designs greatly affect the mechanical loading scenario, such as the offset (lateralized) liners with protruded rim above the metal shells, which commonly induce a weak resistance to rim impingement. The purpose of the present study was to compare the influence of the liner offset length on the impingement resistance in the annealed (first generation) and vitamin E-blended (second-generation) HXLPE liners with a commercial design.

Aims

The purpose of this study was to compare two different types of metal-on-metal (MoM) bearing for total hip arthroplasty (THA): one with a large femoral head (38 mm to 52 mm) and the other with a conventional femoral head (28 mm or 32 mm). We compared clinical outcome, blood metal ion levels, and the incidence of pseudotumour in the two groups.

INTRODUCTION

To obtain appropriate joint gap and soft tissue balance, and to correct the lower limb alignment are important factor to achieve success of total knee arthroplasty (TKA). A variety of computer-assisted navigation systems have been developed to implant the component accurately during TKA. Although, the effects of the navigation system on the joint gap and soft tissue balance are unclear. The purpose of the present study was to investigate the influence of accelerometer-based portable navigation system on the intraoperative joint gap and soft tissue balance.

Introduction

In total hip arthroplasty (THA), polyethylene (PE) liner oxidation leads to material degradation and increased wear, with many strategies targeting its delay or prevention. However, the effect of femoral head material composition on PE degradation for ceramic-PE articulation is yet unknown. Therefore, using two different ceramic materials, we compared PE surface alterations occurring during a series of standard ceramic-PE articulation tests.

Introduction

Total knee arthroplasty (TKA) has achieved excellent clinical outcomes and functional performances. However, there is a need for greater implant longevity and higher flexion by younger and Asian patients. We determined the relationship between mobility and stability of TKA product because they are essential for much further functional upgrading. This research evaluated the geometry characteristics of femorotibial surfaces quantitatively by measuring their force of constraint by computer simulation and mechanical test.

INTRODUCTION

The concept of anatomical stam is fit-and-fill in the proximity of the femur and to expect wall fixation, following to reduce thigh pain and stress shielding. Although the femoral medullary form and size are different in each races. CentPillar TMZF stem (stryker ^®) is anatomical stem designed based on computer-tomography of Japanese femurs. The purpose of this study was to evaluate clinical and radiographic outcomes of CentPillar TMZF stem at a mean of 3.6 years postoperatively.

Introduction

Recently, computer-aided orthopaedic surgery has enabled three dimensional (3D) preoperative planning, navigation systems and patient matched instrument, and they provide good clinical results in total knee arthroplasty. However, the preoperative planning methods and the criteria in total elbow arthroplasty (TEA) still have not sufficiently established due to the uncertainty of 3D anatomical geometry of the elbow joints. In order to clarify the 3D anatomical geometry, this study measured 3D bone models of the normal elbow joints. Additionally this study attempted to apply the 3D preoperative planning to ordinary surgery. Then the postoperative position of implant has evaluated as compared with the position in 3D preoperative planning.

[Background]

Factors determining improvement of the long-term outcome of total knee arthroplasty include accurate reproduction of lower limb alignment. To acquire appropriate lower limb alignment, tibial component rotation is an important element for outcomes. We usually determine the tibial component rotation using the anatomical rotaional landmark of the proximal tibia and range of motion technique. In addition we followed by confirmation of overall lower limb alignment referring to the distal tibial index. When the tibia have a rotational mismatch between its proximal and distal AP axis, a larger error of the distal tibial index than those of other rotational landmark is of concern. The purpose of this study is to evaluate the reliability of the distal tibial AP axis as a reference axis of tibial compornent rotation in the intraoperative setting.

Introduction

In most cases of revision acetabular total hip arthoplasty (THA), some degree of bone loss will be accompanied. If the bone loss is massive, the management of bone defect is more challenging problem. We consider that using cementless accetabular cup for revision acetabular reconstruction is good indication when stable interface fit between the acetabular cup and bone is achieved. The purpose of this study is to review the result of revision hip arthroplasty using cementless acetabular cup with and without bone graft.

The Taperloc Microplasty stem design was based on that of the Taperloc stem with flat tapered wedge and the distal portion of the Taperloc stem was shortened by 35mm.

We report the minimum two-year follow up (mean, 26 months) of 68 primary total hip arthroplasty using the Taperloc Microplasty stem. 39 Magnum acetabular cups and 29 M2a Taper acetabular cups were inserted with metal on metal articulation. The series comprised 67 patients (20 men, 47 women) with a mean age at operation of 65 years (31 to 85). The principal diagnosis was osteosrthritis.

Their mean JOA Hip Score improved significantly from 36 points preoperatively to 96 points at two-year follow up. Radiological asseement showed good bony stability in all implants. There was one case of post operative anterior dislocation. We did not see intra-operative fracture previously reported for this implant. There were no clinical and radiological complications related to MOM articulation.

This short-term follow up study demonstrates that the clinical outcome of the Tapeloc Microplasty stem is comparable with that of standard Taperloc stem and other flat taper wedge stems.

[Background]

Bipolar hemiarthroplasty (following BHA) have historically had poor results in patients with idiopathic osteonecrosis of femoral head (OFNH). However, most recent report have shown excellent results with new generation BHA designs that incorporate advances in bearing technology. These optimal outcomes with bipolar hemiarthroplasty will be more attractive procedure for young patients who need bone stock for future total arthroplasty. The purpose of the current study was to evaluate the clinical and radiographic finding of this procedure for the treatment of OFNH at our institution after 7-to 21years follow-up.

Modulus femoral prosthesis is a modular cementless femoral system which consists of 5 degree tapered conical stem made of a titanium alloy with 8 fins of 1mm and modular neck. Modular neck enables to control any ideal stem anteversion as a surgeon prefers. This system is considered to be useful in severe hip deformity, for example developmental dysplasia of the hip (DDH). In this study, clinical and radiographic outcomes of the Modulus femoral prosthesis were evaluated at a mean of 3.6 (2–6) years postoperatively.

We assessed the results of 193 primary total hip arthroplasty using a Modulus femoral prosthesis in 169 patients (15 males, 154 females) undergoing surgery between September 2007 and December 2011. The mean age at the time of surgery was 65.6 (31–86) years old. The diagnoses were osteoarthritis (OA) in 178 hips (including 167 hips of DDH), rapidly destructive coxopathy (RDC) in 6 hips, rheumatoid arthritis (RA) in 6 hips, osteonecrosis in 2 hips, and subchondral insufficiency fracture in one hip. Clinical outcomes were assessed using Japan Orthopedic Association (JOA) hip scores and complications. Radiographic assessments were including stem alignment, bone on-growth, cortical hypertrophy, stress shielding and stem subsidence.

43.8 points of the preoperative mean JOA score was significantly improved to 93.1 points postoperatively. In one case intraoperative femoral fracture was occurred. One dislocation had occurred and thigh pain was observed in one hip. No revision surgery was required. In 192 hips of 193 hips (99.5%), stem was implanted in neutral position (within ±2 degrees). Bone on-growth was observed in all cases (94.3% in zone 3; 73.1% in zone 5; 30.6% in zone 2; 22.3% in zone 6). Cortical hypertrophy was observed in 66 hips (34.2%) at zone 3 and 5. Reduction of bone density due to stress shielding was observed (1^st degree was 58.5%; 2^nd degree was 29.5%; 3^rd degree was 11.9%; 4^th degree was 0%). In 22 cases (11.4%), more than 2mm of stem subsidence was observed, however the subsidence was stopped within 6 months in all cases.

Modulus femoral prosthesis showed good clinical results and radiographic findings up to 6 years postoperatively.

Introduction

Vitamin-E (VE, dl-α-tocopherol) is a powerful antioxidant for highly cross-linked polyethylene (XLPE). It was previously reported that VE-stabilized XLPE succeeded in retaining no measurable oxidation even after accelerated aging tests combined with cyclic loading or lipid absorption. Thus, VE-stabilized XLPE is nowadays recognized worldwide as one of the new standard materials in total hip arthroplasty (THA). However, the effects of such VE addition on physical behavior of polyethylene remain to be fully elucidated by contrast to the clear statement of its chemical role (i.e., the enhanced oxidation resistance) in the published literature. In this presentation, we shall attempt to provide those missing notations and to explore the microstructural and biomechanical role of VE in XLPE acetabular liner on the molecular scale.

Metal on metal total hip arthroplasty (MoM THA) provides the potential improvement in articular wear. However, several adverse events including pseudotumor had been reported. Magnetic resonance imaging (MRI) was considered to be the proposal tool for detection of pseudotumor after MoM THA. In this study, we performed the screening of pseudotumor after MoM THA using the MRI.

We studied 43 patients with M2a Magnum® (Biomet) and 34 patients with M2a Taper® (Biomet) of MoM THA from December 2009 to December 2011 with follow-up of 2.5 years (2.0–4.0 years) after surgery. MRI assessments were performed at a mean of 2.1 years postoperatively. Pseudotumor findings were graded using Anderson classification (Skeletal Radiol, 2011: 40; 303). Age, sex, height, weight, Harris Hip Score, EQ5D satisfaction score, UCLA activity score, and blood metal ion levels were evaluated.

The prevalence of pseudotumor was 27.2%; 56 normal (Type A), 13 mild (C1), 8 moderate (C2) and none were graded severe (C3). Weight and BMI in the mild group was significantly higher than those in normal. There was no significant difference in age, sex and height among these groups. With regard to Harris Hip score, pain and ROM score in moderate group was significantly lower than that in normal and mild group. EQ5D satisfaction score and UCLA activity score showed not significant differences among groups. 3.01±3.32 μg/L of blood cobalt ion levels in the moderate groups was significantly higher than 0.97±0.64 μg/L in normal group. Blood cobalt ion levels of 1 mild and 2 moderate were over the threshold of 7 μg/L. These patients were implanted with M2a Taper, not M2a Magnum. 14% of the prevalence in the patients with M2a Magnum was significantly lower than 41% in the patients with M2a Taper. No revision surgeries were required.

The patients with no pseudotumor did not show the increase of blood metal ion. Contrarily, several patients showed the increase of blood metal ion in case of detecting pseudotumor. MRI assessments were useful for screening of pseudotumor after MoM THA and blood metal ion should be investigated for patients with mild and moderate pseudotumor in MoM THA.

Background:

Total knee arthroplasty (TKA) has achieved excellent clinical outcomes and functional performances. However, younger and Asian patients require even greater implant longevity and higher flexion. It is necessary for much further functional upgrading to design TKA with mobility and stability. Therefore, we determined the relationship between mobility and stability of TKA.

Metal on metal total hip arthroplasty provides the potential improvement in articular wear and the use of large-diameter femoral heads following the prospect for reduction in the risk of dislocation. The purpose of this study was to compare the clinical and radiographic outcomes as well as serum metal ion level between the two different component designs with small and large femoral heads in metal on metal total hip arthroplasty.

We studied 39 patients with large head (Magnum®, Biomet; cup size minus 6 mm) and 37 patients with small head (M2a taper®, Biomet; 28 or 32 mm head) of metal on metal total hip arthroplasty between December 2009 to October 2011 with follow-up of 2.1 years (1.0–3.3 years) after surgery. Harris Hip Score, UCLA activity score, EQ-5D, radiographic assessment, and serum cobalt and chromium ion levels were evaluated.

Harris Hip Score, UCLA activity score, and EQ-5D were improved after surgery in small and large head groups, however, no significant differences were observed between both groups. Cup inclination was below 50 degree in all prosthesis. No loosening and no osteolysis were observed. Cobalt and chromium ion was not detected before surgery; however, metal ion levels of both groups were increased after surgery in time dependent manner. There was no significant difference between two groups at one year after surgery. One patient in each group showed the increase of cobalt ion level over 7 ppb (15.4 ppb, 12.9 ppb) without any clinical symptom including pain. Cup inclination was 29 degree in both patients and cup anteversion was 38 and 41 degree, respectively.

There was no significant difference of ion levels between both groups. No dislocation was observed in large head group while one dislocation occurred in small head group. No patients required the revision surgery.

This metal on metal component, especially with large femoral heads, showed the good clinical results at the maximum follow up of 3.3 year after surgery. However, the ion level of two patients increased over 7 ppb and longer follow-up will be needed.

Introduction

Bi-Metric® cementless primary stem is tapered, rounded conical shaped and coated with plasma spray porous to one-third from the proximal. Fixation is achieved by a press-fit insertion in the Metaphyseal-diaphyseal junction. From 1986 until now, nearly 700 Bi-Metric® stems have been implanted at our hospital. The purpose of this study was to present the clinical and radiological findings including a survival analysis of a consecutive Bi-Metric® stems series followed for over 10 years.

Introduction

Regarding TKA, patient specific cutting guides (PSCG), which have the same fitting surface with patient's bones or cartilages and uniquely specify the resection plane by fitting guides with bones, have been developed to assist easy, low cost and accurate surgery. They have already been used clinically in Europe and the USA. However little has been reported on clinical positioning accuracy of PSCG. Generally, the methods of making PSCG can be divided into 3 methods; construct 3D bone models with Magnetic Resonance (MR) images, construct 3D bone models with Computed Tomography (CT) images, and the last is to construct 3D bone models with both MR and CT images. In the present study, PSCG were made based on 3D bone models with CT images, examined the positioning accuracy with fresh-frozen cadavers.

INTRODUCTION

Several reports suggest that low-intensity pulsed ultrasound stimulation (LIPUS) facilitates chondrogenesis¹⁾. Recently it has been suggested that LIPUS may be transmitted via Integrin: a protein which mediates cellular attachment between cells and extracellular matrix²⁾. In this study, the Arg-Gly-Asp (RGD) amino acid sequence, which is a ligand of Integrin, was induced to the fibroin substrates by either gene transfer or physical mixing, and the variation of chndrocyte response to LIPUS was evaluated.

Aims

Recently, total knee arthroplasty (TKA) has been generalized as an operation that achieves excellent clinical results. However, younger and Asian patients require even greater implant longevity and functional performance. We hypothesized a novel posterior cruciate-retaining TKA design that restores the anatomical jointline in both sagittal and coronal planes, maintains the femoral posterior condylar offset, and provides low contact stress would provide enhanced patient function with the potential for greater implant longevity.

INTRODUCTION

Osteoarthritis (OA) can be artificially simulated ex vivo on healthy articular cartilage (AC) samples by use of proteolytic enzymes. In this article we will present preliminary analyses of the physical degradation of AC when subjected to alternating mechanical stresses. Since AC damage due to OA is believed to be mechanically induced, the first step towards the realisation of an improved understanding of degenerative behaviour of AC under physiological loading conditions is to perform ex vivo tests which mimic such conditions at best.

It have been reported that the wear volume of vitamin E-containing UHMWPE tested with a knee joint simulator was approximately 30% lower than that of virgin UHMWPE at 5 million cycles. However, the wear resistance mechanism of vitamin E-containing UHMWPE has not yet been clarified. The present study examines the effects of the addition of vitamin E on the frictional properties of ultra-high molecular weight polyethylene (UHMWPE) under several different load and serum conditions.

Friction tests were carried out using a computer-controlled pin-on-disk friction test apparatus. The UHMWPE pin was mounted vertically at the tip of the leaf spring and linear reciprocating sliding motion for 2,000 cycles with an amplitude of 1 mm and a frequency of 1 Hz, was applied under 3 MPa or 30 MPa loading against Co-28Cr-6Mo alloy disk. The lubricant bath was filled with 5 ml of ultrapure water, fresh serum, post-friction (PF) serum or diluted-PF (DPF) which were kept at a temperature of 37°C. The friction force between the UHMWPE pin and the Co-28Cr-6Mo alloy disk was calculated from the displacement of the leaf spring during the sliding motion.

Vitamin E-containing UHMWPE showed a significantly higher friction force than that of virgin UHMWPE in fresh serum lubricant at 30 MPa loading, while there were little differences in either ultrapure water or PF serum or DPF serum. And vitamin E-containing UHMWPE tends to exhibit a lower dynamic friction force within the first few hundred cycles in the case of all serum lubricants at 30 MPa loading. These results suggest that some interaction between the UHMWPE surface and the native conformation proteins was specifically affected by the addition of vitamin E and that some weeping of vitamin E might occur at early stage of sliding. Our results also suggest the importance of the conformational changes of serum proteins for the wear testing.

We retrospectively reviewed 40 hips in 36 patients who had undergone acetabular reconstruction using a titanium Kerboull-type acetabular reinforcement device with bone allografts between May 2001 and April 2006. Impacted bone allografts were used for the management of American Academy of Orthopaedic Surgeons Type II defects in 17 hips, and bulk bone allografts together with impacted allografts were used for the management of Type III defects in 23 hips. A total of five hips showed radiological failure at a mean follow-up of 6.7 years (4.5 to 9.3), two of which were infected. The mean pre-operative Merle d’Aubigné score was 10 (5 to 15) vs 13.6 (9 to 18) at the latest follow-up. The Kaplan-Meier survival rate at ten years, calculated using radiological failure or revision of the acetabular component for any reason as the endpoint, was 87% (95% confidence interval 76.3 to 97.7). A separate experimental analysis of the mechanical properties of the device and the load-displacement properties of bone grafts showed that a structurally hard allograft resected from femoral heads of patients with osteoarthritis should be preferentially used in any type of defect. If impacted bone allografts were used, a bone graft thickness of < 25 mm was acceptable in Type II defects.

This clinical study indicates that revision total hip replacement using the Kerboull-type acetabular reinforcement device with bone allografts yielded satisfactory mid-term results.

While there are many variation laboratory and clinical studies using metal-on-metal (MOM) bearings after introduction of the 28mm MOM THR in 1988, the mapping of wear phenomena in such retrieval cases has been mimimal. In laboratory study, 28mm MOM bearing’s wear-rate was low with “run-in” and “steady-state” than large diameter MOM without theory of fluid-filum lubrication. In clinical results were not superior to the same way of laboratory study. We present a detailed analysis of 33 retrieved MOM hip bearings with 1–11 years follow-up,

We compiled 33 retrieval cases (MetasulTM: Zimmer/CenterPulse Inc., Austin, TX) including clinical information, ion concentrations from ball diameters, cup designs and stripe wear damage. The bearing surfaces were mapped using reflected light microscope (RLM), white light interferometer (Zygo Newview 600, Zygo.) and SEM(XL-30 FEG). Wear maps were constructed according to types of surface wear identified.

Patients ranged from 36 to 76 years of age (Means: 56.9 years); 54% were males. Main causes for revision were progressive radiographic lines around the cups, osteolysis and pain. The 28mm ball diameter was used in 86% of cases (largest = 52mm ball). The CoCr liner incorporated a polyethylene adaptor in 75% of cases. Cup diameter > 50mm was present in 75% of cases. Eight femoral stems were recovered and all showed major impingement marks around the neck and five also had a metallosis (Mode-4A). Stripe wear was evident on 71% of CoCr balls with medial stripes twice as common as lateral. Stripe wear was identified in 25% of CoCr liners and extended 25–160° circumference around the liners. Clear liner rim damage was present in 10 (30%) and 3 demostrated severe damage of polyethelene adaptors.

There are many limitations to such retrieval studies. These data are biased to cases that failed due to hip pain, radiographic signs of progressive osteolysis and some with high levels of metal ions. There was also the bias of having predominantly a CoCr sandwich design (polyethylene adaptor in 75% of cases). In early 1980s, the thin walled UHMWPE cup was introduced and used larger diameter balls for decreased risk of dislocation. However, unfortunally these big-ball cups produced significant PE wear debris, and diameter trends were returned to the Chanley’s small-ball paradigm again. In the same time (late of 1980’s), these second-generation MOM (28,32mm) was introduced for low wear characteristics alternate THR bearings, with sacrificing of joint stability and motion range. However, use of the small ball added well-known risks of impingement, subluxation and dislocation with rigid cups. In this study, using the ‘damage modes’ from McKellop, normal mode-1 wear occurred in only 14% of cases whereas modes 2–4 had an incidence approaching 30% each and signs of cup impingement were evident in 64% of cases. Thus summarizing MOM wear phenomena in “small” 28mm sandwich cup designs, there was retrieval evidence showing that damage modes 2–4 likely placed these patients at risk for adverse wear effects.

Wear in polyethylene liners appears to be exacerbated by 3rd-body abrasion effects with the CoCr ball combinations used for total hip replacements. This has implications for various wear modes encountered in patients. Yet clinical and laboratory studies have offered weak and sometimes contradictory wear relationships with respect to crosslinking, ball diameter and roughness, and 3rd-body wear effects. Our hip simulator model investigated the effect of severe wear challenges by 3rd-body cement particles, using large diameter CoCr and alumina balls, with highly-crosslinked polyethylene liners (HXPE) irradiated to 75kGy compared to contemporary controls (CXPE 35kGy).

The polyethylene liners were gamma-irradiated to 35/75kGy under N2 (CXPE/HXPE). We used 32 and 44mm CoCr balls (ENCORE, Austin, TX) and 44mm alumina-ceramic (Biolox-forte, CeramTecAG) as ‘scratch-resistant’ standard of comparison. We compared 5 bearings pairs with different roughness characteristics using both new and pre-worn polyethylene liners. A 12-station orbital hip simulator with a physiological load profile (0.2kN–3kN load, frequency 1Hz) with cups mounted in “Inverted- position”. Diluted bovine serum (Hyclone Inc., Logan, UT) was used as lubricant (20mg/ml protein, 400ml volume). In phase I, all cups were run in standard (‘clean’) lubricant for 1.5 million cycles (1.5Mc). In phase II, the liners were run in a PMMA slurry of serum (5mg/ml) for 2Mc. In phase III, implants were run ‘clean’ for 1.5Mc. Wear-rate was measured each 0.25Mc event, and surface roughness measured by SEM (XL-30FEG) and white light interferometry (Newview600, Zygo) every 0.5Mc.

In phase I, Wear withnew CXPE and HXPE liners averaged 182mm3/Mc and 30mm3/Mc. Thus the HXPE liners averaged a 6.0-fold wear reduction compared to controls. Compared to new liners, the pre-worn CXPE and HXPE liners showed 10% and 25%, greater wear respectively. Here it was noted that CoCr balls maintained similar roughness (Sa:8–12nm). And alumina balls showed small, gradual increase (Sa: 2 to 2.5nm). The HXPE maintained a superior finish to CXPE controls. Roughness revealed a gradual decrease with time, pre-worn CXPE from 0.28 to 0.15um and pre-worn HXPE from 0.18 to 0.04um (Sa). In contrast, new HXPE showed a dramatic smoothing (0.8 to 0.1um) 92.8% decreased in first 0.5Mc. These effects have not been previously quantified. In phase II with abrasive mode, the liner wear-rates increased dramatically by 6 and 80-fold for CXPE and HXPE, respectively. These data confirmed that HXPE was sensitive to ‘severe’ wear against CoCr and alumina balls. In phase III, the polyethylene roughness dropped by > 90% and wear decreased to phase-I values. The wear-ratio was now 2:1 for CXPE:HXPE as predicted by the ‘diameter’ and ‘crosslinking’ algorithms.

It was clear that surface roughness was not a confounding factorfor either the CoCr or alumina balls. It was the polyethylene surface roughness that appeared to influence wear rates. Our analysis showed that there was a transient due to patches of abrasive cement transferring onto CoCr ball surfaces. Overall the actual roughness of the CoCr balls did not change and was therefore not a factor in increased polyethylene wear.

The objective of this study was to compare the wear mode of 100 Mrad PE cups run in a hip simulator to retrieved 100 Mrad PE cups, and to evaluate the efficacy of the PE wear model.

15 In-vitro PE cups: 3 each 0,2.5.50,100 and 150 Mrad (9 channel hip simulator, 6.2 million cycle duration, physiological load profile by Paul, 2000N maximum load at 1Hz using 30% bovine serum). 5 Retrieved PE cups: three SOM cups (Mizuho Medical Instrument Co., COP alloy 28 mm head)-0 Mrad after 8 years of clinical use, two 100 Mrad cups after 15 years of clinical use, two T28 PE 2.5 Mrad cups (Zimmer): 18 years and 13 years of clinical use. The cups were examined using a SEM (Philip XL30 FEG) for wear scar locations and PE wear-topography.

Original machine marks were observed in the weight-bearing areas of the highly cross-linked in-vitro PE. No machine marks were observed for the 0 and 2.5 Mrad in-vitro cups and none were seen in any of the retrieved cups. The formation of more nodules and fibrils in the 0Mrad cups compared to the extensivley cross-linked cups (in-vitro and retrieved) was striking. The frequency of occurrence and length of the fibrils and nodules was dependent on the dose of gamma irradiation. More ripples were formed in the 2.5 Mrad and higher cups compared to the non-irradiated cups (in-vitro and retrieved). The in-vitro cups formed more ripples than the retrieved cups. In general, the SEM features for in-vitro Mrad cups appeared similar to those of the retrieved Mrad cups.

The in-vitro Mrad cups accurately reflected the conditions of the artificial joint in living body. Therefore, comparisons of retrieved PE cups with simulator PE cups appeared to be a very powerful research tool.

(2) SEM observation demonstrated far less wear damage in the extensively cross-linked cups than in the non-extensively cross-linked PE. Thus the extensive cross-linked PE cups appeared to be a significant improvement over conventional PE cups in terms of wear resistance.

Wear of UHMWPE and Clinical results of bioceramic total knee replacement have not been well reported yet. The ultra high molecular weight polyethylene surfaces of the tibial components were examined in 3 retrieved knees with non-infectious loosening, and were almost normal in appearance with only minor scratch lines 33 to 59 months after the initial arthroplasty. Bioceramic total knee arthroplasty was concluded to show satisfactory results except for the initial several cases done with rather poor surgical techniques. The wear of UHMWPE surface in ceramic knee was observed to be much less and milder than that of metal prosthesis.

Total knee arthroplasty (cementless) using Yokohama Medical Ceramic Knee was performed in 64 knees and, excluding 4 knees with the prostheses retrieved, was evaluated in 60 knees of 47 patients.

There ware 1 man (1 knee) and 31 women (44 knees) who had rheumatoid arthritis with a mean age of 56.8±11.9 years, and 2 men (2 knees) and 11 women (13 knees) with osteoarthritis with a mean age of 70.6±6.9 years. The mean follow-up duration was 48.1±9.2 months ranging from 33 to 60 months.

The maximum knee flexion was 115±24 degrees before and 104±20 degrees after arthroplasty in the rheumatoid group, and 107±40 degrees before and 101±26 degrees after arthroplasty in the osteoarthritis group.

Clinical evaluation using The Hospital for Special Surgery Knee Criteria showed 7 knees as Excellent, 34 as Good, 7 as Fair and 12 as Poor after surgery. Complications consisted of infection (1 case), tibial plateau fracture (1), avulsion fracture of the tibial tuberosity (1) and patellar dislocation (1)

We studied the most superficial layer of macroscopically normal articular cartilage obtained from human femoral heads, using polarising microscopy and SEM. The most superficial layer, 4 to 8 microns thick, was acellular consisting of collagen fibrils. This layer could be peeled away as a thin film, with no broken collagen fibrils on its inferior surface or on the surface of subjacent cartilage layers. The orientation and diameter of collagen fibrils were different on these two surfaces. Our findings suggest that the most superficial layer is an independent one which is only loosely connected to the fibrous structure in the layer deep to it.

Delayed union or non-union of the scaphoid was treated by a bone graft on a pronator quadratus pedicle in eight cases. This produced earlier union than the Russe procedure. The procedure is simple and is recommended for old un-united scaphoid fractures.

Excision of the lunate was performed for 18 patients with Kienbock's disease; 14 were followed up for an average of almost 12 years. Carpal collapse progressed with time, but rearrangement of the remaining carpal bones preserved a satisfactory range of movement and grip strength. Degenerative changes were not severe. All the patients had relief of pain, were able to carry out their normal activities, and all but two could perform strenuous activities.