Page 81 - HA Convention 2015

Masterclasses

MC4.1 Advances in Joint Replacement 13:15 Convention Hall C

Path to Articular Surface Mount (ASM) Navigation Total Knee Replacement of Public Hospital in Hong Kong — Monday, 18 May
Local Hospital Experience
Wong KY
Department of Orthopaedics and Traumatology, Princess Margaret Hospital, Hong Kong

Total knee replacement (TKR) is an effective operative procedure to restore the functions of knee joint by restoring its
overlying mechanical alignment, rotational alignment and soft tissue balance. The overall survival rate is higher than 90%
after 15 years with revision as end-point.

Traditional operative procedure of TKR by using intra-medullary or extramedullary alignment guides could only restore 70%
to 80% of mechanical alignment. Navigated TKR could reduce the relative risk of three degree outliner by 25%. Articular
Surface Mount Navigation (ASM) is an anchoring concept with the tracker pin placed over the articular and metaphysis region
of proximal tibia and distal femur. It takes the advantage of traditional navigation TKR for distal femoral cut and proximal
tibial cut to improve the overall mechanical alignment. It reduces the risk of stress raiser and peri-prosthetic fracture over the
cortical bone tracker pin. It decreases the operative procedure in rotational alignment and soft tissue balance in traditional
navigation TKR as study shows that those navigated procedure are not more accurate than traditional techniques which
remain surgeon-dependent procedure despite improvement in instrumentation.

A stemmed prosthesis of revision TKR system may be employed for severe varus or valgus deformity of knee in primary
TKR. Traditional procedure of stemmed prosthesis involves the use of intramedullary cutting guide. Study shows that there
is a mismatch of surface centre of knee to the shaft centre. An offset block may be employed to compensate the mismatch
during implantation of prosthesis which may increase loss of host bone and operative time. Combination of ASM navigation
procedure first and follow by reverse method to identify the tibial or femoral shaft centre by using the best placed tibial or
femoral tray. It can reduce the use of offset block.

MC4.2 Advances in Joint Replacement 13:15 Convention Hall C

Blood Management and Venous Thromboembolic Complications in Total Knee Replacement HOSPITAL AUTHORITY CONVENTION 2015
Wong YC
Total Joint Replacement Centre; Department of Orthopaedics and Traumatology, Yan Chai Hospital, Hong Kong

The transfusion rate in total knee replacement (TKR) varies from 10% to 90%. Currently a low haemoglobin trigger point for
transfusion and tranexamic acid are used widely to decrease blood transfusion. We have introduced a protocol to reduce
unnecessary cross-match and transfusion to our patients. Type-and-screen (T&S) was performed only when pre-operative
haemoglobin level was less than 11g/dl. Intra-operative measures to decrease blood loss included tourniquet use to achieve
a bloodless field, meticulous haemostasis and soft tissue dissection, continuous arthrotomy closure, and low suction
pressure drainage. Post-operatively, drains were removed after 24 hours. No blood was transfused unless the post-operative
haemoglobin level was less than 8g/dl or the patient was symptomatic. From October 2011 to February 2014, 9% and 5% of
the 1,084 TKRs performed had T&S and transfusion respectively.

Venous thromboembolism (VTE) is a common complication following total knee replacement and can be lethal. The
reported incidence of deep vein thrombosis (DVT) ranged from 17% to 51% with prophylaxis in constrast with 58% to 84%
without prophylaxis. Pharmacological prophylaxis includes low molecular weight heparins, fondaparinux or the new oral
anticoagulants. Mechanical prophylaxis includes pneumatic foot pumps and calf compression device. Yan Chai Hospital
adopted a protocol that includes compression pumps, graduated pressure stockings, early ambulation on day-one, and
highly selective use of chemical prophylaxis to patients with history of venous thromboembolism. Since 2004, routine
ultrasonograhic screening was performed after the operation. The rate of proximal and distal DVT was 25% out of the
1,300 TKRs performed in 2011. However, the proximal DVT was only 1% and the remaining majorities were DVT distal to
popliteal vein with low risk of proximal migration. In our utrasonograhic follow-up study of distal DVT, there was 1% proximal
progression of thrombosis. The non-fatal pulmonary embolism rate was 0.2%. No mortality cases were reported.

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