Sixty primary hip arthroplasties were performed in Crowe grade 2 to 4 hip dysplasia since 1973 using a modified transtrochanteric osteotomy which is reliable short cut to reach down the lateral aspect of the greater trochanter. Our hypothesis consists of the adaptability of Thomas test to show the reducibility of the disloction in the coronal plane. In practice, if the dynamic potential while abduction and flexion exceeds from the 90° to coronal plane, the femoral head slips down to the acetabulum through poor sciatic notch. Thereby led to Protrusio acetabulii which implicative compromised capsular insufficiency but assessment of outcome study has been improved.

The results have been reasonably acceptable, with the longest follow-up greater than 35 years. We confirmed that the frog leg lateral radiography is effective for determining the operative indication of high riding dislocation of the DDH. However irreducible frog leg lateral position is absolutely contraindicated in these situation. We also aware of not only the complexity in abductor length but abundant amount of vastus lateralis when reattaching the trochanter, which may arises against stability of the abductors and vastus lateralis in continuity.

Spinal fusion has been used as the gold standard to treat some spinal disorders such as degenerative disc or disc herniation of the cervical spine. However, some clinical complications have been reported caused by high stiffness of spinal fusion. Recently, total disc arthroplasty using motion preservation devices such as artificial discs (ADs) have been proposed as an alternative treatment technique. In current study, we analysed biomechanical influences including inter-segmental motion, facet joint forces, and ligament stresses of two different clinical available ADs and compared with those of intact cervical spine in various loading conditions using finite element analysis.

A three dimensional finite element model was developed for C2-C7 spinal motion segment based on CT images and previous anatomical literatures. The finite element models for two different types of ADs, semi-constraint (Prodisc-C^®, Synthes, U.S.A) and un-constraint (Mobi-C^®, LDR Spine, U.S.A), were developed. Each AD was inserted at C6–C7 segments. Superior and inferior plates of ADs were fixed on inferior plane of C6 and superior plane of C7 vertebrae, respectively. Based on the conventional surgical techniques, anterior longitudinal ligaments and some parts of intervertebral disc in C6–C7 motion segment were removed to insert ADs. Inferior plane of C7 vertebra was constrained in all directions and 1Nm of flexion, extension, lateral bending and torsion were applied on superior plane of C2 vertebra with 50N of compressive load along follower load direction.

Rotation angle in flexion of C5–C6 segment in cases of semi-constraint and un-constraint AD was 3.3° and 3.7°, respectively. Both values were greater than that in case of the intact cervical spine by 18% and 32%, respectively. Rotation angle in extension, lateral bending and torsion were greater than intact model by 45%, 26% and 43% for the case of semi-constraint AD and 55%, 35%, 100% for the case of un-constraint one, respectively. In extension, facet joint forces were about two times higher than intact model in cases of semi-constraint and un-constraint AD. Also in flexion, on average, ligament stresses in cases of semi-constraint and un-constraint AD were higher than intact model by 66% and 116%, respectively.

The results of this study showed that ADs were useful to generate inter-segmental motion at surgical level. And the un-constraint type of AD had higher mobility than semi-constraint one. However, high mobility of ADs would lead not only higher facet joint forces but also ligament stresses than intact cervical spine. Therefore, more careful care must be taken to choose surgical method of total disc arthroplasty.

The high-flex total knee arthroplasty system was introduced to enhance knee flexion and to facilitate tibiofemoral articulation at high-flexion by the design modification of an increased thickness of the posterior wall of the femoral component by 2 mm compared with the standard total knee prosthesis. However, several clinical studies on the effectiveness of designs intended to provided high flexion following total knee arthroplasty have produced conflicting results. We performed a prospective, randomized study to compare the ranges of motion of the high-flex and standard total knee replacements in patients who were managed with simultaneous bilateral total knee arthroplasty.

This study comprised of three independent groups of patients.

The first group: Fifty patients (mean age, 68 years old) received a standard NexGen LPS prosthesis in one knee and a NexGen LPS-Flex prosthesis in the contralateral knee. Two patients were men, and 48 were women. At a mean of 2.1 years postoperatively, the patients were assessed clinically and radiographically with use of the knee-rating systems of the KS and HSS.

After a minimum follow-up of two years, we found no significant differences among the first, second and the third groups with regard to range of knee motion, or clinical and radiographic results.

In the knee joint surgery such as total knee arthroplasty (TKA), the implant should be inserted in proper position with correct bone alignment because the abnormal kinematics of implanted knees by implant mal-positioning or mal-alignment could cause failure of surgery. Therefore, quantitative information of a 3D kinematics of the knee joint is very helpful to evaluate the surgical treatment such as planning of size and alignment of the implant. In this study, a 2D/3D image matching method was developed to estimate the kinematics of the knee joint based on an automated pixel by pixel comparison of images.

Two projection images were obtained from the 3D object in two perpendicular directions where the given dual X-ray images were taken. The 3D object was translated and rotated automatically and continuously until its projection images were matched with the X-ray images in a given tolerance range. The optimization algorithm was used to minimise the root mean square error between the gray scale values of each pixel in the projection image and the given X-ray image. For estimating the position and orientation of the knee joint, the 3D knee joint models were reconstructed from CT data. The 3D model was matched with the given dual X-ray images by using the developed 2D/3D image matching method. The tibial and femoral components were then combined into the whole knee joint model. By adding fiducial markers based on clinically conventional method, the posterior and mediolateral translation of femur with respect to tibia as well as the flexion angle were measured.

In the experiment with the cubic phantom, the position errors were below 0.10 mm and the orientation errors were below 0.05 o when using dual X-ray images. For the given dual X-ray images, the relative in vivo kinematics of the femur was measured as the posterior translation was 3.0 mm and the mediolateral translation was 0.9 mm. In addition, the flexion angle of the knee joint from the sagittal view was 51o while the angle measured from the given X-ray image was 50 o.

The previous 2D/3D image matching methods operated manually took long time and was dependent on the operator. Recently, automated image matching method has developed by applying optimization algorithms. In this study, the optimal position and orientation were obtained by the direct pixel by pixel comparison, which are easy to implement and modify the algorithm. The present automated method could accelerate the matching process and stabilise the repeatability. In addition, the image matching method with dual images was used to improve the out-of-plane accuracy since the image matching method with a single X-ray image has a limitation of methodology in detecting out-of-plane translation and rotation though the in-plane accuracy was acceptable. The present 2D/3D image matching method is a powerful tool for the accurate determinations of 3D position and orientation of the knee joint and could provide informative characterization of implant designs and surgical options of the knee surgery.

Background: A common clinical scenario encountered by an orthopaedic surgeon is a patient with a secure cementless acetabular shell and a failed polyethylene liner. One treatment option is to cement a new liner into the fixed shell. The purpose of this study was to evaluate the radiographic outcome of this technique.

Materials and Methods: From November 2001 to April 2006, 11 liner were cemented into well-fixed cementless acetabular shell of 10 patients. There were 6 males and 5 women of average age 54.3 (range 41~73) years at the time of the revision surgery. The indication for the revision procedure were aseptic loosening and wear in 9 cases, and periprosthetic fracture in 2 cases. The pre-existing screws in the shell were removed, and screw holes were filled with allogenic bone graft or cementaion. The patients were evaluated the radiographic evidence of progressive loosening and osteolysis. The average follow up period was 35.2 (range 24~76) months.

Results: There were no changes in cup and liner position or progression of osteolytic lesion around the femoral or acetabular components in the last follow-up radiographs. No compications such as a deep or superficial infection or deep vein thrombosis occurred. There were no hip dislocations.

Conclusion: A liner cemented into a secure, well-positioned cementless acetabular shell provide stability and durability at short and long term follow up. This technique also has advantages of preventing bone loss associated with removal of a well fixed component, and lower surgical morbidity and more liner options. Careful attention to the preparation of the liner, the sizing of the component, and the cementing technique are likely to reduce the failure of this construct.

Background: Ceramic-on-ceramic couplings are an attractive alternative bearing surfaces to eliminate or reduce problems related to polyethylene wear debris. Past disappointing experiences with alumina ceramic bearings have led to many improvements in the manufacture and the design of ceramic implants. The purpose of this study was to report the results of contemporary alumina-on-alumina total hip arthroplasties (THAs) with regard to wear, osteolysis, and fracture of the ceramic after a 10-year minimum follow-up.

Methods: We evaluated the results of a series of 66 primary alumina-on-alumina THAs with a metal-backed socket and a cementless stem in 59 patients. All of the patients were 64 years old or younger (mean, 42 years), and a single surgeon performed all of the procedures. They were evaluated clinically and radiographically at the 120 to 126 months follow-up (average, 123 months). During the follow-up, special regards were addressed to wear, periprosthetic osteolysis and ceramic failure.

Results: During the follow-up period, two patients (two hips) had died with the prosthesis in situ as the result of an unrelated medical condition. The mean Harris hip score was 94 points at the latest follow-up evaluation. All of the prostheses had radiographic evidence of a bone ingrowth. No implant was loosened radiographically and no implant was revised. Ceramic wear was not detectable in the 28 hips where differentiation of the femoral head from the cup was possible on radiographs. Periprosthetic osteolysis was observed in no hip. A fracture of the alumina femoral head and a peripheral chip fracture of the alumina insert occurred in one hip following a major motor vehicle accident. A periprosthetic femoral fracture, which required open reduction and internal fixation with metal cables, had occurred in one hip. This fracture healed without problem.

Conclusion: The results of contemporary alumina-on-alumina THAs with a metal-backed socket and a cementless stem were encouraging after a minimum follow up of 10 years. We believe that these improved alumina-on-alumina bearing implants offer a promising option for younger active patients.

Biocompatibility of Co-Cr alloy was significantly improved by forming rough TiO2 layer on the surface. The TiO2 layer was formed by coating the Co-Cr alloy with Ti through electron beam deposition followed by micro-arc oxidation (MAO) of the Ti. Biocompatibility of Co-Cr alloy was enhanced by coating with titanium, and it was improved further by micro-arc oxidation treatment. MAO process was dependent on the thickness of coated titanium layer and applied voltage. There were close relationships between the phase, morphology and thickness of TiO2 layer and the applied voltage. Biocompatibility of the specimens coated with Ti and MAO treated after Ti coating were evaluated by in vitro ALP activity tests.

The purpose of this study was to examine surface characteristics of 30 alumina and 24 zirconia ceramic femoral heads and to identify phase transformation in zirconia heads. We also studied penetration rate of alumina and zirconia heads into UHMWPE liner. The alumina heads had been implanted for a mean of 11.3 years (8.1 to 16.2) and zirconia heads for a mean of 9.8 years (7.5 to 15).

The mean surface roughness values of explanted alumina heads (Ra 40.12 nm and Rpm 578.34 nm) were similar to those for the explanted zirconia heads (Ra 36.12 nm and Rpm 607.34 nm). The mean value of monoclinic phase of two control non-implanted zirconia heads was 1% (0.8–1.5) and 1.2% (0.9–1.3), respectively. The mean value of monoclinic phase of 24 explanted zirconia heads was 7.3% (1% to 26%).

In the alumina head group, mean linear penetration rate of UHMWPE liner was 0.10 mm/yr (0.09 to 0.12) in hips with low Ra and Rpm values (13.22 nm and 85.91 nm, respectively). The mean linear penetration rate of UHMWPE liner was 0.13 mm/yr (0.17 to 0.23) in the hips with high Ra and Rpm values (198.72 nm and 1329 nm, respectively). This differences was significant (P=0.041)

In the zirconia head group, the mean linear penetration rate of UHMWPE liner was 0.09 mm/yr (0.07 to 0.14) in hips with low Ra and Rpm values (12.78 nm and 92.99 nm, respectively). The mean linear penetration rate of UHMWPE liner was 0.12 mm/yr (0.08 to 0.22) in hips with high Ra and Rpm values (199.21 nm and 1381 nm, respectively). This difference was significant (P=0.039).

The explanted zirconia heads which had a minimal phase transformation had similar surface roughness and a similar penetration rate of UHMWPE liner as the explanted alumina head.

Architectural changes in occurring in the proximal femur (resorption) after total hip arthroplasty (due to stress shielding) continues to be a problem. In an attempt to reduce these bony changes the concept of short and femoral neck sparing stem designs have been advocated. The purpose of this study was to evaluate the early clinical and radiological results, especially stem fixation and bone remodeling of proximal femur after total hip arthroplasty.

A total of forty-five patients (fifty-four hips) were included in the study. There were twenty men and twenty-five women. The mean age at the time of operation was 53.9 years (range, twenty-six to seventy-five years). Clinical and radiological evaluation were performed at each follow-up. Bone densitometry was carried out on all patients one week after operation and at the final follow-up examination. The mean follow-up was 1.3 years (range, one to two years).

The mean preoperative Harris hip score was 45 points (range, 15 to 48 points), which improved to a mean of 96 points (range, 85 to 100 points) at the final follow-up. No patient complained of thigh pain at any stage. No acetabular or femoral osteolysis was observed and no hip required revision for aseptic loosening of either component. One hip (2%) required open reduction and fixation with a cable for calcar femorale fracture. Bone mineral densitometry revealed a minimal bone remodeling in the acetbulum and proximal femur.

The geometry of this ultra-short anatomic neck sparing cementless femoral stem has proved to provide effective initial stability even without the diaphyseal portion of the stem. We believe that femoral neck preservation and lateral flare of the stem provide an axial and torsional stability and more natural loading of the proximal femur.

Modified posterior approach preserving short external rotators would be able to contribute greatly to prevent dislocation after total hip arthroplasty. We modified the posterior approach to the hip by preserving the external rotator muscles in order to enhance joint stability after total hip arthroplasty in patients with osteonecrosis of the femoral head. The aim of the this study was to determine the influence of external rotator preserving posterior approach in primary total hip replacement on early dislocation and clinical outcome.

Three hundred sixty-four primary total hip replacements were divided into two groups based on how the external rotators were treated at surgery. External rotator preservation (Group 1, 165 hips) group was compared with reattachment (Group 2, 199 hips) group by evaluating the clinical and radiographic outcome at one year postoperative. Anteversion was significantly less in Group 1 as compared to Group 2 (P < 0.001). There was no significant difference in inclination between the groups (P > 0.05 in all comparisons). No dislocations were found in 165 hips with external rotator preservation whereas dislocations was noted in 11 (3.9%) in Groups 2, respectively. Group 1 had the higher mean Harris hip score (97.2±2.9 points) as compared with Group 2(94.9±3.4).

The results of this study showed that external rotators could play an important role in preserving joint stability after total hip arthroplasty in patients with osteonecrosis of the femoral head. It can be implied that this modified posterior approach would be able to contribute greatly to prevention of dislocation, and improve clinical outcome after total hip arthroplasty.

There was used cement in first generation total ankle arthroplasty, but first generation of ankle arthroplasty was abandoned because of aseptic loosening of component. For the treatment of aseptic loosening of ankle arthroplasty, there had been many methods. One of methods of revisional ankle arthroplasty is the ankle arthodesis. The authors report a case of revisional ankle arthroplasty using allograft with hybrid external fixation.

45 year old male had surgery of cemented total ankle arthroplasty on his right ankle 20 years ago. He went to our clinics because of motionless and pain of his right ankle. He got the mild pain on his right ankle after 5 years surgery. His pain was managed by oral NSAIDS for 15 years. The pain was aggravated recently. There were osteophytes on posterior aspect of ankle joint and radiolucency around the implant, subtalar arthrosis at the radiograph. There was also sclerosis around the ankle joint.

The authors decided revisional surgery. At the operative findings, we can see the loosening of talar and tibial component and large posterior osteophyte bridging between remained talus and tibial bone. There were no infection signs. After remove the implant, there was big space remained. For the regaining the limb length, we used femoral head allograft. The graft was fixed with 6.5 mm cannulated screws and addition fixed with ilizarov external fixation. Also additional auto bone graft from the osteophytes was applied. Compression over the ilizarov external fixation was done at the end of the operation. Weight bearing was allowed immediate after surgery. Ilizarov ring was removed 6 weeks after surgery. At the 3 months after surgery, bony union was obtained on radiographs.

AOFAS score was improved from 30 to 70 6 mo after surgery. There was no pain on his right ankle. Patient satisfied with arthrodesis with allograft at final follow-up.

The purpose of this study is to compare the two prosthesis which were used for total ankle arthroplasty. From Sept. 2003 to Jun 2007, 13 patients and 14 ankles that could be follow up more than 2 years. Semiconstrained type (Group I, 7cases) and Unconstrained type (Group II, 7cases) were used for total ankle arthroplasty. Mean age was 63.2 year-old, 12 ankles are men and 2 ankles were women. Mean follow up periods were 31.1 months. The criteria to compare the clinical result were postoperative range of motion (ROM), AOFAS foot score and residual bone stock of medial malleolus.

Postoperative ROM of group I was 37.5±7.1 degree and of group II was 51.4±8.9. Postoperative AOFAS score of group I was 76.1±13.8 and of group II was 86.0±5.7. Residual bone stock in medial malleolus of group I was 6.1mm±0.7 and of group II was 11.5mm±0.9. Total number of complication in our study was 9 cases. 3 cases were a malleolar fracture, two occurred at intra-operation, the other at follow-up period. Re-operation was done in 6 cases, 3 cases were calcaneal corrective osteotomy, 2 cases were resection of a heterotopic bone and one case was pedicular flap operation for skin problem.

In our hospital, mobile bearing type prosthesis showed good result than a semiconstrained type in respect of ROM improvement and of residual bone stock in medial malleolus. AOFAS score between two groups showed no definite difference. But small number of patients and short term follow up period is a defect in our study, afterward more population and long term follow up period are needed.

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.

We developed a modified posterior approach that preserved the short external rotator muscles to prevent dislocation after THA or BHA. The present study aimed to evaluate the effectiveness of short external rotator preserving posterior(ERP) approach for bipolar hemiarthroplasty in treatment of femoral neck fractures in patients with neurologic disorders. Between March 2004 and February 2006, we performed 187 cementless bipolar hemiarthroplasties for displaced femoral neck fractures on 36 patients with neurologic disorders, who were operated on by ERP approach (Group 1) and 151 patients without neurologic deficits, who were operated on by conventional posterolateral approach (Group 2). We compared operation time, the amount of postoperative blood loss, the early postoperative complication rates, the dislocation rate within 1 year, and duration of hospital stay between two groups.

The amount of postoperative blood loss was significantly decreased in group 1(p < 0.01). There were no significant differences in mean operation time and early postoperative complication rate including wound problem, deep vein thrombosis or infection and duration of hospital stay. There was no dislocation after operation in group 1, but seven patient (4.6%) had dislocation in group 2. Nine patients (25.0%) died within postoperative 1 year in group 1 and twenty six patients (17.2%) died in group 2.

Cementless bipolar hemiarthroplasty through ERP approach provides a favorable outcome for treatment of displaced femoral neck fracture in patients with neurologic disorders who is considered as high risk of dislocation. Also, it decreases the postoperative blood loss and the needs of postoperative abduction brace.

The use of stem provides consistent component alignment with immediate stable fixation and protects grafted bone by reducing stress on metaphyseal area in revision total knee arthroplasty. One of major concern with use of stems involves stem tip pain in cementless diaphyseal engaging stem. The purpose of this study is to evaluate the effect of stem design and method of fixation on stem tip pain in revision total knee arthroplasty by finite element analysis.

3D finite element model of normal tibia was reconstructed from CT scan images of 26 year old male and the CAD model of revision total knee arthroplasty was developed using commercial software(CATIA^®, Dassault system, USA, version 8.20). The tibia component models were assembled based on conventional surgical procedure. The design changes of stem such as the length, diameter and slot were performed and methods of fixation including press fit and coefficient of friction was considered. The contact pressure and von-Mises stress around the stem and the micromotion at the interface were evaluated for a 2000 N of external load by finite element analysis to investigate the effect of stem design and methods of fixation on stem tip pain. The longer length and larger diameter press fit stem significantly increase the contact pressure & stress at the end of stem. The distal slot reduces the contact pressure & stress at the end of stem. Less displacement between tibial component and bone was noted in the increased coefficient of friction.

It would be better to avoid using press fit stem with extended length and larger diameter in revision total knee arthroplasty. More flexibility of stem tip would be favorable because of less concentration of stress. Stem fixation with higher coefficient of friction would be recommended for less displacement of tibial component. Stem with shorter length enough to engage proximal diaphysis, closer diameter of proximal canal and minimal press fit could be accepted to reduce stem tip pain if patient’s surgical anatomy such as bone loss and quality is tolerable in revision total knee arthroplasty.

We investigated whether simultaneous bilateral sequential total hip replacement (THR) would increase the rate of mortality and complications compared with unilateral THR in both low- and high-risk groups of patients.

We enrolled 978 patients with bilateral and 1666 with unilateral THR in the study. There were no significant pre-operative differences between the groups in regard to age, gender, body mass index, diagnosis, comorbidity as assessed by the grading of the American Society of Anesthesiologists (ASA), the type of prosthesis and the duration of follow-up. The mean follow-up was for 10.5 years (5 to 13) in the bilateral THR group and 9.8 years (5 to 14) in the unilateral group.

The peri-operative mortality rate of patients who had simultaneous bilateral THR (0.31%, three of 978 patients) was similar to that of patients with unilateral THR (0.18%, three of 1666 patients). The peri-operative mortality rate of patients in the bilateral group was similar in high risk and low risk patients (0.70%, two of 285 patients vs 0.14%, one of 693 patients) and this was also true in the unilateral THR group (0.40%, two of 500 patients vs 0.09%, one of 1166 patients). Patients with bilateral THR required more blood transfusions and a longer hospital stay than those in the unilateral THR group. There was no significant difference (p = 0.32) in the overall number of complications between the groups. This was also true for the low-risk (p = 0.81) vs high-risk (p = 0.631) patients.

Our findings confirm that simultaneous sequential bilateral THR is a safe option for patients who are considered to be either high or low risk according to the ASA classification.

We wished to determine whether simultaneous bilateral sequential total knee replacement (TKR) carried increased rates of mortality and complications compared with unilateral TKR in low- and high-risk patients.

Our study included 2385 patients who had undergone bilateral sequential TKR under one anaesthetic and 719 who had unilateral TKR. There were no significant pre-operative differences between the groups in terms of age, gender, height, weight, body mass index, diagnosis, comorbidity and duration of follow-up, which was a mean of 10.2 years (5 to 14) in the bilateral and 10.4 years (5 to 14) in the unilateral group.

The peri-operative mortality rate (eight patients, 0.3%) of patients who had bilateral sequential TKR was similar to that (five patients, 0.7%) of those undergoing unilateral TKR. In bilateral cases the peri-operative mortality rate (three patients, 0.4%) of patients at high risk was similar to that (five patients, 0.3%) of patients at low risk as it was also in unilateral cases (two patients, 1.0% vs three patients, 0.6%). There was no significant difference (p = 0.735) in either the overall number of major complications between bilateral and unilateral cases or between low- (p = 0.57) and high-risk (p = 0.61) patients. Also, the overall number of minor complications was not significantly different between the bilateral and unilateral group (p = 0.143).

Simultaneous bilateral sequential TKR can be offered to patients at low and high risk and has an expected rate of complications similar to that of unilateral TKR.

The purpose of this study was to determine objectively the outcome of total knee replacement in patients with ankylosed knees.

There were 82 patients (99 knees) with ankylosed knees who underwent total knee replacement with a condylar constrained or a posterior stabilised prosthesis. Their mean age was 41.9 years (23 to 60) and the mean follow-up was for 8.9 years (6.6 to 14). Pre- and post-operative data included the Hospital for Special Surgery (HSS), the Knee Society (KS) and the Western Ontario and McMaster University Osteoarthritis index (WOMAC) scores.

The mean HSS, KS and WOMAC scores improved from 60, 53, and 79 pre-operatively to 81, 85, and 37 at follow-up. These improvements were statistically significant (p = 0.018, 0.001 and 0.014 respectively). The mean physical, social and emotional WOMAC scores also improved significantly (p = 0.032, p = 0.023 and p < 0.001 respectively). The mean satisfaction score was 8.5 (sd 1.5).

Total knee replacement gives good mid-term results in patients with ankylosed knees.

It has been suggested that the wear of ultra-high molecular weight polyethylene (UHMWPE) in total hip replacement is substantially reduced when the femoral head is ceramic rather than metal. However, studies of alumina and zirconia ceramic femoral heads on the penetration of an UHMWPE liner in vivo have given conflicting results.

The purpose of this study was to examine the surface characteristics of 30 alumina and 24 zirconia ceramic femoral heads and to identify any phase transformation in the zirconia heads. We also studied the penetration rate of alumina and zirconia heads into contemporary UHMWPE liners. The alumina heads had been implanted for a mean of 11.3 years (8.1 to 16.2) and zirconia heads for a mean of 9.8 years (7.5 to 15).

The mean surface roughness values of the explanted alumina heads (Ra 40.12 nm and Rpm 578.34 nm) were similar to those for the explanted zirconia heads (Ra 36.21 nm and Rpm 607.34 nm). The mean value of the monoclinic phase of two control zirconia heads was 1% (0.8% to 1.5%) and 1.2% (0.9% to 1.3%), respectively. The mean value of the monoclinic phase of 24 explanted zirconia heads was 7.3% (1% to 26%).

In the alumina group, the mean linear penetration rate of the UMWPE liner was 0.10 mm/yr (0.09 to 0.12) in hips with low Ra and Rpm values (13.22 nm and 85.91 nm, respectively). The mean linear penetration rate of the UHMWPE liner was 0.13 mm/yr (0.07 to 0.23) in hips with high Ra and Rpm values (198.72 nm and 1329 nm, respectively). This difference was significant (p = 0.041).

In the zirconia head group, the mean linear penetration rate of the UHMWPE liner was 0.09 mm/yr (0.07 to 0.14) in hips with low Ra and Rpm values (12.78 nm and 92.99 nm, respectively). The mean linear penetration rate of the UHMWPE liner was 0.12 mm/yr (0.08 to 0.22) in hips with high Ra and Rpm values (199.21 nm and 1381 nm, respectively). This difference was significant (p = 0.039).

The explanted zirconia heads which had a minimal phase transformation had similar surface roughness and a similar penetration rate of UHMWPE liner as the explanted alumina head.