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W P Yau

Publications and source records attributed to W P Yau.

14 recordsLinked to original sources
PubMed2006

Assessment of the proximal femoral morphology using plain radiograph-can it predict the bone quality?

We evaluated the relationship between the radiological indices that assessed the proximal femoral morphology and the degree of osteoporosis in 45 Chinese cadaveric femora. Canal-calcar ratio, canal flare index, morphological cortical index, and canal bone ratio were determined in the plain anteroposterior radiographs. Canal bone ratio is the ratio between the endosteal and outer diameters of the proximal femur at 10 cm below the lesser trochanter. Bone mineral density of the proximal femora was measured with dual-energy x-ray absorptiometry, and T score that depicted the degree of osteoporosis was determined. Canal bone ratio showed a strong correlation with the T score (r = -0.71, P < .001) and the best overall performance in diagnosing osteoporosis with receiver operating characteristic curve analysis. The proximal femur was likely to be osteoporotic if the canal bone ratio was 0.49 or higher.

Absorptiometry, Photon↗
PubMed2005

Residual posterior femoral condyle osteophyte affects the flexion range after total knee replacement.

We followed up 92 patients with total knee replacement and a pre-operative knee flexion of at least 90 degrees . The patients were followed up regularly at 3 months, 6 months and 1 year. The outcome measured was the amount of maximum passive knee flexion at the end of 1 year after replacement. The potential factors affecting the final flexion range were investigated. After regression analysis, apart from pre-operative knee flexion (p<0.001), the most significant independent surgical factors that predict the amount of post-operative flexion were presence of residual posterior femoral condyle osteophyte (p=0.046) and overstuffing the patella by more than 2 mm during resurfacing of the patella (p<0.001).

Aged↗
PubMed2005

Intraobserver errors in obtaining visually selected anatomic landmarks during registration process in nonimage-based navigation-assisted total knee arthroplasty: a cadaveric experiment.

This study investigated the intraobserver errors in obtaining visually selected anatomic landmarks that were used in registration process in a nonimage-based computer-assisted total knee replacement (TKR) system. The landmarks studied were center of distal femur, medial and lateral femoral epicondyle, center of proximal tibia, medial malleolus, and lateral malleolus. Repeated registration in the above sequence was done for 100 times by a single surgeon. The maximum combined errors in the mechanical axis of the lower limb were only 1.32 degrees (varus/valgus) in the coronal plane and 4.17 degrees (flexion/extension) in the sagittal plane. The maximum error in transepicondylar axis was 8.2 degrees. The errors using the visual selection of anatomic landmarks for the registration technique of bony landmarks in nonimage-based navigated TKR did not introduce significant error in the mechanical axis of the lower limb in the coronal plane. However, the error in the transepicondylar axis was significant in the "worst-case scenario."

Arthroplasty, Replacement, Knee↗
PubMed2005

Sagittal bowing of the distal femur in Chinese patients who require total knee arthroplasty.

PURPOSES: The importance of the femoral sagittal bowing on total knee arthroplasty is under-recognized. The bowing could lead to potential errors in positioning of the femoral component if it is ignored. We aimed to document the femoral sagittal bowing at different segments of the Chinese femur and to discuss the implications of this sagittal bowing on total knee arthroplasty. METHODS: One hundred lateral radiographs of the entire lower limbs of 85 Chinese patients admitted for total knee arthroplasty were digitized. The radii of curvature of the intramedullary canal of the proximal, middle and distal one-third of the femora were measured. RESULTS: The average age of the patients was 67.3 years. The radii of curvature of the proximal, middle and distal one-third of the femora were 1081.6, 926.2 and 715.1 mm, respectively. The distal one-third of the femora was significantly more bowed than the other parts of the femora (p<0.001). The distal femoral bowing was more profound in rheumatoid patients and in those with a short femur. CONCLUSIONS: The lateral contour of the Chinese femur is like a hockey stick. This exaggerated sagittal bowing in the Chinese femur can affect the final sagittal position of the femoral component and has implications for the choice of implant design. In revision setting, a long and straight press-fit stem might either endanger the anterior cortex or deflect the femoral component to an abnormally extended position.

Adult↗
PubMed2004

Posterior cruciate ligament-substituting total knee arthroplasty in young rheumatoid patients with advanced knee involvement.

The integrity and strength of the posterior cruciate ligament (PCL) in the rheumatoid knee are known to be suboptimal. However, the results of PCL-substituting total knee arthroplasty in rheumatoid patients are not well documented. We reviewed 86 PCL-substituting total knee arthroplasties in 52 rheumatoid patients with grade IV or V radiographic disease. The mean age at surgery was 41.9 years. All patients underwent follow-up evaluation for an average of 7.8 years. Revision was performed for 1 knee because of aseptic loosening of the tibial component, and for 3 knees because of deep infection. An isolated insert exchange was performed on one knee. Using revision of any component for aseptic loosening or radiographic loosening as the end point, the mean 10-year survival rate was 94.0%.

Actuarial Analysis↗
PubMed2004

Critical radiological analysis after Austin Moore hemiarthroplasty.

The aim of this study is to investigate the causes of prosthesis loosening in patients treated with Austin Moore hemiarthroplasty (AMA). The clinical and radiological outcomes were documented in a quantitative manner after 7 years follow-up of 144 patients. At the time of final follow-up, 52 patients had died and 48 patients were lost to follow-up, leaving a total of 44 patients for analysis. Immediate post-operative X-rays were studied for the initial alignment of prosthesis, the fit of the prosthesis and the degree of osteoporosis. X-rays on latest follow-up were studied for evidence of loosening. All patients were assessed clinically with the hip score of hospital for special surgery. It was found that hip pain was significantly related to subsidence and pivoting of the prosthesis (P = 0.014 and 0.035, respectively). Significant increase in subsidence was noted if the stem of prosthesis was not fitting well within the shaft of femur (P = 0.006). When the patient was younger than 73 years old at the time of operation, there was more subsidence of the prosthesis at the final follow-up (P = 0.001). It was concluded that the fill of AMA within the shaft of femur should be greater than 70% to avoid early loosening. Relatively younger patients with acute fracture of the neck of femur should be treated by methods other than cementless AMA.

Age Factors↗
PubMed2004

Factors leading to blood transfusion among Chinese patients undergoing total knee replacements: a retrospective study.

PURPOSE: To investigate the risk factors leading to blood transfusion among Chinese patients undergoing total knee replacement. METHODS: From July 2001 to June 2002, a total of 128 primary total knee replacements were performed in 83 Chinese patients (38 unilateral and 45 one-stage sequential bilateral). No pharmaceutical prophylaxis against deep vein thrombosis was used. The risk factors leading to allogenic blood transfusion were analysed. RESULTS: The important predictive factors for postoperative blood transfusion were preoperative haemoglobin level (p=0.005), intra-operative blood loss (p<0.001), and bilateral total knee replacements (p<0.001). CONCLUSION: To reduce the need of allogenic blood transfusion, we suggest administering erythropoietin or iron supplements to increase the haemoglobin level for patients undergoing total knee replacement. Routine use of intra-operative blood salvage can be considered for patients undergoing one-stage bilateral total knee replacement. Use of a postoperative blood salvage system is recommended for surgeries that may result in major intra-operative blood loss.

Aged↗
PubMed2004

Extensively coated femoral components in revision hip arthroplasty: follow-up study of 23 patients.

PURPOSE: To review the outcome of revision hip arthroplasty using extensively coated femoral components. METHODS: We reviewed the results of revision involving 24 extensively porous-coated cementless femoral components in 23 patients, whose mean age was 52.4 years (range, 28.0-79.0 years). Most revisions were performed for aseptic loosening of the previously cemented femoral component. All patients were followed up for a minimum period of 24.0 months (mean, 61.1 months). RESULTS: Of the 24 femoral stems, 20 showed bone ingrowth, 3 showed stable fibrous ingrowth, and one was unstable because of deep infection. Intra-operative anterior femoral diaphyseal perforation occurred in 2 hips during the insertion of straight femoral components of 200 mm. Postoperative radiographs displayed marked cortical erosion in 3 other hips and cortical perforation in one. CONCLUSION: The results from the use of extensively coated femoral components were promising. Nevertheless, anterior cortical perforations were also common, which may be related to more bowing of the femora among the Chinese patients. Caution must be exercised when inserting a long, straight, extensively coated femoral component.

Adult↗
PubMed2003

Efficacy of a single dose of cefazolin as a prophylactic antibiotic in primary arthroplasty.

We analyzed the wound infection rate of 1,367 primary total hip and knee arthroplasties performed between 1991 and 1999. Two hundred and fifteen arthroplasties were performed with 3 doses (3 x 750 mg) of cefuroxime, and 1,152 arthroplasties were performed with a single preoperative dose (1 x 1 g) of cefazolin as antimicrobial prophylaxis. All wound infections that occurred within 2 years of the index surgery were analyzed. The deep wound infection rate of total hip arthroplasty was 1.1% (95% confidence interval [CI], 0%-3.3%) in the cefuroxime group and 1.1% (95% CI, 0%-2.2%) in the cefazolin group (Fisher's exact test, P = 1.0). The deep wound infection rate of total knee arthroplasty in the cefuroxime group (1.6%; 95% CI, 0%-3.8%) was not significantly different from the cefazolin group (1.0%; 95% CI, 0.3%-1.7%) (Fisher's exact test, P =.63). We concluded that a single dose (1 g) of cefazolin given at anesthetic induction offered similar protection to 3 doses (3 x 750 mg) of cefuroxime in preventing infection in primary total joint arthroplasty.

Aged↗
PubMed2003

Practicing cementing technique with a toy: Play-Doh.

Cementing technique has direct impact on the longevity of a total hip arthroplasty, and the proper technique can only be acquired by practice. Using acrylic bone cement to practice cementing technique in a bioskill workshop is expensive and can cause occupational hazards. In this article, we describe a toy that can replace acrylic bone cement in a bioskill workshop. Play-Doh (Hasbro Inc, Pawtucket, RI) is an inexpensive, reusable and non-toxic modeling toy that mimics the doughy phase of acrylic bone cement.

Arthroplasty, Replacement, Hip↗
PubMed2002

Review article: knee flexion after total knee arthroplasty.

Many factors affect or predict the flexion range achieved after total knee arthroplasty. While the knees that have good preoperative flexion have better final flexion, knees with good preoperative flexion do lose some flexion whereas those with poor preoperative flexion can gain flexion. Although studies of different prosthetic designs have produced conflicting results, recent studies appear to favour posterior cruciate ligament (PCL)--substituting over PCL-retaining prostheses. Several factors related to surgical techniques have been found to be important. These include the tightness of the retained posterior cruciate ligament, the elevation of the joint line, increased patellar thickness, and a trapezoidal flexion gap. Vigorous rehabilitation after surgery appears useful, while continuous passive motion has not been found to be effective. Obesity and previous surgery are poor prognostic factors; certain cultural factors, such as the Japanese style of sitting, offer 'unintentional' passive flexion and result in patients with better range. If the flexion after surgery is unsatisfactory, manipulation under anaesthesia within 3 months of the total knee arthroplasty can be beneficial.

Arthroplasty, Replacement, Knee↗
PubMed2001

The performance of three vacuum-mixing cement guns--a comparison of the fatigue properties of simplex P cement.

We tested three commercially available cement-mixing systems (Howmedica, Summit and Stryker). After mixing the cement was allowed to cure in metal moulds under standard conditions. Sixty-nine cement blocks were produced. The fatigue behavior of the blocks was tested until failure. A wide scattering of results was observed in all the three systems. Uneven mixing of the polymer and monomer was observed in the Howmedica system. A significantly stronger cement (P=0.018) was produced with the Stryker system.

Bone Cements↗
PubMed2001

Unusual complication associated with femoral intramedullary alignment guide in total knee arthroplasty.

The few reported complications related to the use of a femoral intramedullary alignment guide in total knee arthroplasty include increase in perioperative bleeding and fat embolism. We report 3 patients suffering from an unusual complication, concerning trapping of the tibial locking pin inside the intramedullary canal of the femur secondary to the use of an intramedullary alignment guide. Methods of retrieving the locking pin from the medullary canal are discussed.

Aged↗