Yiu-Chung Wong

Knee flexion after total knee arthroplasty

Purpose. To identify factors related to knee flexion after total knee arthroplasty in a Chinese population. Methods. Records of 242 total knee arthroplasties were retrospectively reviewed. The parameters evaluated were age, gender, diagnosis, preoperative knee flexion and extension, preoperative flexion arc, tibiofemoral angle, Knee Society knee score and functional score, and implant design. Results. Advanced age, female gender, and good preoperative flexion and flexion arc were related to better postoperative flexion. Postoperative flexion tended to migrate to the middle range despite different ranges of preoperative flexion. Preoperative tibiofemoral malalignment had no significant effect on postoperative flexion. Conclusion. Contemporary designs of posterior stabilised prostheses with right and left femoral components were superior to older designs.

Risk factors for periprosthetic joint infection in total knee arthroplasty

Purpose. To evaluate the incidence and risk factors of periprosthetic joint infection (PJI) in patients undergoing total knee arthroplasty (TKA) in a high-volume hospital. Methods. Records of 1133 primary TKAs were reviewed. Correlation between surgery volume and infection rate was determined. Risk factors for PJI were identified using case-control analysis of variables. TKAs performed between October 2012 and March 2013 without infection were used as controls. Results. Of 1133 TKAs, 8 (0.71%) PJI occurred. The organisms involved were Staphylococcus aureus (n=4), coagulase-negative staphylococci (n=2), Pseudomonas aeruginosa (n=1), and methicillin-resistant S aureus (n=1). In the 6-month period chosen as the control period, one (0.52%) out of 192 TKAs developed PJI. Hospital annual volume did not correlate with infection rate (p=0.766). Significant risk factors included young age, comorbidities such as diabetes, anaemia, thyroid disease, heart disease, lung disease, and long operating time. Six of the 8 patients with PJIs had at least one risk factor. However, the number of patients with infection was too small to have sufficient power. Conclusion. Comorbidities are a risk factor for PJI. Perioperative optimisation of comorbidities and the use of antibiotic-loaded cement in patients with severe comorbidities should be considered.

Blood management protocol for total knee arthroplasty to reduce blood wastage and unnecessary transfusion

Purpose. To compare outcomes of 2 cohorts of patients who underwent total knee arthroplasty (TKA) before and after the introduction of a blood management protocol. Methods. Records of 97 and 96 consecutive patients who underwent unilateral TKA before and after introduction of the blood management protocol, respectively, were reviewed. Before introduction of the protocol, patients were cross-matched for blood before surgery. Transfusion after surgery was at the discretion of the surgeons or the on-call doctors. After introduction of the protocol, only patients with a preoperative haemoglobin level of <110 g/l underwent ‘type and screening’ of blood group. 2 units of blood were cross-matched preoperatively when multiple red-cell antibodies were identified or postoperatively when blood transfusion was required. Only patients with a postoperative haemoglobin level of <80 g/l or being symptomatic received blood transfusion until the haemoglobin level reached >100 g/l. Those with a postoperative haemoglobin level of 80 to 100 g/l were given iron sulphate 300 mg twice daily for a month. Results. The 2 groups did not differ significantly in age, sex ratio, pre- and post-operative haemoglobin levels, and drain output. Comparing outcome before and after introduction of the protocol, the transfusion rate (10.3% vs. 3.1%, p=0.046), cross-match rate (100% vs. 3.1%, p<0.001), and cross-match to transfusion ratio (9.7:1 vs. 1:1, p<0.001) decreased. Among transfused patients, the decreased postoperative haemoglobin level indicated a lower transfusion trigger point (100 g/l vs. 75 g/l, p<0.006) No patient developed infection, cardiovascular or cerebrovascular complications within 30 days. Conclusion. The blood management protocol for TKA is effective in reducing unnecessary allogeneic blood transfusions and wastage of unused blood, without an increase in postoperative complications.

Short duration and low suction pressure drain versus no drain following total knee replacement

Purpose. To compare the short-term outcome in patients with or without a drain (short duration and low suction pressure) following total knee replacement (TKR). Methods. A consecutive series of 106 women and 48 men (mean age, 69 years) underwent unilateral TKR. The first 77 patients used a low suction pressure (200 mm Hg) drain following TKR for 24 hours, and the next 77 patients used no drain. Results. The 2 groups were comparable in terms of preoperative characteristics, the proportion of patients with pharmacological prophylaxis for deep vein thrombosis, the tourniquet time, and mode of anaesthesia. The mean drain output in the drain group was 221 ml. The time to achieve straight-leg-raising was earlier in the drain group (3.1 vs. 4.2 days, p<0.001). Conclusion. The use of a short duration, low suction pressure drain following TKR enabled an earlier return of quadriceps power, without increasing haemoglobin drop and transfusion rate.

A Prospective Study of Venous Thromboembolic Prophylaxis Using Foot Pumps Following Total Knee Replacement in a Chinese Population

Purpose The purpose of this study was to evaluate foot pumps as mechanical prophylaxis for deep vein thrombosis (DVT) following total knee replacement (TKR) in a Chinese population. Methods All consecutive patients following TKR during 2002–2006 received routine duplex ultrasound surveillance for DVT 9 days postoperatively. The demographic data and risk factors were recorded. No medication was given for DVT prophylaxis in all patients. Results We evaluated 91 consecutive TKRs in 85 patients. Although 44 knee replacements (Group 1) done before December 2004 were not given foot pumps, 47 knee replacements (Group 2) done afterwards were given foot pumps. All patients were followed up for more than 6 months. DVT was detected in three cases (6.8%) in Group 1 compared with four knees (8.5%) in Group 2. Proximal thrombosis was observed in two knees (4.5%) in Group 1 compared with two knees (4.3%) in Group 2. No patient had pulmonary embolism. Six out of 59 (10.2%) patients who underwent the operations under general anaesthesia suffered from DVT, whereas one in 28 (3.6%) patients operated under spinal anaesthesia had DVT. All had no statistical significance. Conclusion The rate of proximal DVT after TKR was low (4.5%) without pharmacological prophylaxis. We advise against the use of pharmacological prophylaxis in Chinese population for TKRs because of the low risk of proximal DVT and its possible bleeding complications. Foot pump did not lower the rate of DVTfurther, and its use for DVT prophylaxis in TKR is not necessary.

Unicompartmental knee replacement – An underrated alternative of total knee replacement: A matched comparative study analysing their benefits and risks in local population

Introduction: The demand of knee arthroplasty is increasing worldwide with aging population. Even though unicompartmental knee replacement is associated with fewer complications namely stroke, myocardial infarction, thrombo-embolism, blood transfusion and mortality, it merely comprises 3e8% of knee arthroplasties. The aim of the study is to establish the role of unicompartmental knee replacement by evaluating the benefits and risks of unicompartmental knee replacement versus total knee replacement in Hong Kong population. Methods: All unicompartmental knee replacement performed in our institute from 2011 to 2014 were reviewed. Comparative analyses were performed on pre-operative, operative and post-operative parameters. Primary total knee replacement performed in the same period was chosen as control group with 1:1 matching for age, sex, BMI and pre-operative range of motion. Results: There were 46 unicompartmental knee replacement. It comprises 3.3% of all knee arthroplasties in our institute. The mean follow-up time was 12.8 months (4e38 months). There was no significant difference in all pre-operative parameters except WOMAC score. All operative parameters favored unicompartmental knee replacement significantly (operation time 76 vs 91 minutes; wound size 7.5 vs 12.4 cm; haemoglobin drop 0.75 vs 2.46g/dl, p < 0.05). Early post-operative parameters also favored unicompartmental knee replacement (Deep vein thrombosis rate 4.3 vs 23.9%; length of stay 5.4 vs 7.0 days, p < 0.05). There was no infection or mortality in both groups. Conclusion: Because of less operative risk and faster rehabilitation, this study suggested that unicompartmental knee replacement is more cost effective and might be a better choice for patients with unicompartmental arthritis in local population.

Incidence of Deep Vein Thrombosis and Its Natural History Following Unilateral Primary Total Knee Replacement in Local Chinese Patients—A Prospective Study: 本地中國籍患病者接受單側全膝關節置換後出現深部靜脈栓塞的發病率和自然史 – 一個前瞻性研究

Purpose: This prospective study was to investigate the incidence and the fate of deep vein thrombosis (DVT) among Chinese patients following unilateral primary total knee replacement (TKR). The influence of tourniquet time and the mode of anaesthesia on DVT were evaluated. Method: 390 patients who underwent unilateral cemented primary TKR were investigated. Patients whose body-massindex (BMI) exceeded 30kg/m2 were given chemoprophylaxis with low molecular heparin postoperatively. DVT was diagnosed using duplex ultrasonography on 4th to 7th days after operation. DVT was classified into two groups, distal and proximal. Patients who had DVT on the first scan were assigned two follow-up scans. Result: The incidence of DVT was 25.7%. 97 patients (24.9%) had distal DVT, whereas 3 had proximal DVT (0.8%). Among patients with DVT, 18 (18%) of them resolved at first follow up scan, 82 persisted, and there were no proximal progression. At the 6th week scanning, 57 patients (57%) were free from DVT, while 42 patients (42%) had persistent DVT. There was one (1%) case which the distal DVT had proximal migration, but there was no pulmonary embolism. Tourniquet time and mode of anaesthesia did not reveal any statistical significance on the incidence of DVT. Conclusion: This prospective study showed that the incidence of DVT after unilateral primary TKR in Hong Kong Chinese patient was high. However, most of them are distal to popliteal vein with low risk of proximal migration. More than half of them resolved at about two months after the operation.