CHAPTER OUTLINE
- ♦ History and Clinical Examination
- ♦ Investigations
- ♦ Radiographic Classification of Osteoarthritis of Knee
- ♦ Physiotherapy, Education and Training
- ♦ Medicines to be Started
- ♦ Medicines to be Stopped Prior to Surgery
- ♦ Informed Consent for Surgery
- ♦ Patient and Relatives' Signature for Risk/Benefit Ratio
- ♦ Preoperative Planning for TKR
- ♦ Applied Anatomy
- ♦ Types of Total Knee Replacement
- ♦ Preparation of the Patient for Surgery and Arranging Blood
INTRODUCTION
Patient is preferably admitted 2–3 days prior to surgery for the purpose of:
- History and clinical examination.
- Investigations.
- Physiotherapy, education and training.
- Medical fitness and PAC (Preanesthetic checkup).
- Informed consent for surgery and high-risk consent if associated with medical illness.
- Patient and relative's signature for risk/benefit ratio.
- Preoperative planning and templating.
- Preparation of the patient for surgery and arranging blood.
However, all these purposes can be fulfilled on OPD basis and can be admitted one day prior to surgery.
History and Clinical Examination
Painful severe disabling arthritic joint with or without deformity, not responding to nonsurgical treatment, adversely affecting activities of daily living, ADL (such as ability to walk, climbing of stairs, performing job, care for self, knee bending activities, sleep pattern, sexual function) and quality of life.
Types of Patients according to Pain and Function (Krackow)
- No useful activities: Marked difficulty even in routine essential activities.
- Minimal useful activities: Moderate difficulty in indoor activities, just able to get outside house.
- Major limitations of activities: Mild difficulty in indoor activities, major difficulty in outdoor activities.
- Moderate limitations of activities: Can perform indoor activities but limited long distance walking.
Review of previous medical records: History of local injection, arthroscopy, HTO or any surgery.
Past history of trauma, medical/surgical illness.
Treatment history: Note the name of the medicines. Socioeconomic condition.
General Examination
Normal higher functions, record—Pulse, BP, pallor, jaundice, edema, lymphadenopathy, chest, CVS, abdomen, assess the chest expansion and cardiopulmonary status in cases of spondyloarthropathies.
Local Examination
Knee Joints
Right Knee | Left Knee | |
|---|---|---|
Skin condition | ||
Swelling | ||
Quadriceps wasting | ||
Local temperature | ||
Tenderness | ||
Crepitus | ||
Fixed flexion deformity (FFD) | ||
Hyperextension | ||
Varus/Valgus deformity | ||
Ligament laxity | ||
Range of motion (ROM) |
- Intercondylar distance.
- Intermalleolar distance.
- Distal pulsation (Posterior tibial and dorsalis pedisartery), neurological deficit, look for varicose veins and calf tenderness.
Examination of adjacent joints
Hips, ankles and spine.
Hip Joints
Right hip | Left hip | |
|---|---|---|
Skin condition | ||
Swelling | ||
Wasting | ||
Level of anterior superior iliac spine (ASIS) | ||
Lumbar lordosis | ||
Local temperature | ||
Tenderness | ||
Femoral pulsation | ||
Deformity (FFD, fixed adduction, abduction or rotation) | ||
Movements:
| ||
Adductor tightness |
Limb length discrepancy, gait, Trendelenburg's test, squatting, cross-legged sitting.
Note: If the ipsilateral hip and knee joints are involved then hip should be operated first to decide the mechanical axis and to get adequate movement of hip required during total knee replacement.
Investigations
- X-rays
- Both knee joints—anteroposterior (AP) (standing or stress) and Lateral views (in 20° of flexion)
- Patella skyline view
- Both hip joints with upper 2/3rd thigh and 15° internal rotation—AP view
- Involved hip with upper 2/3rd thigh—lateral view
- Both ankle joints—AP view
- Preferably take full length lower limbs standing X-ray (from both hips to both ankles)—AP view
- LS spine—AP and lateral view
- X-ray chest—posteroanterior (PA) view
- X-ray cervical spine—AP and lateral view [for ankylosing spondylitis (AS)].
- Routine:
- Blood—Hb, PCV, TLC, DLC, ESR, blood group, PT, PTT, INR, platelet count, blood sugar (fasting and PP), LFT (S. bilirubin, SGOT, SGPT, S. protein), S. alk. phosphatase, RFT (BUN, S. creatinine), S. uric acid, S. electrolytes (Na+, K+), RAF and CRP [for rheumatoid arthritis, (RA)]
- Routine examination of urine
- ECG.
- Special—HIV, HbsAg, AntiHCV, VDRL.
- Others—PFT and HLA B27 (for ankylosing spondylitis, AS), 2D ECHO, thallium scan, USG, CT, MRI, DEXA scan, color Doppler, bone scanning, arthroscopy, thyroid function tests, lipid profile, etc., if indicated.
Radiographic Classification of Osteoarthritis of Knee
Ahlback's classification: This reflects the anatomic and pathologic progression of medial compartment osteoarthritis and useful to decide the method of treatment.
Grade | AP view (stress X-ray) | Lateral view in 20° of flexion |
|---|---|---|
1 | Reduction of joint space | |
2 | Obliteration of joint space | |
3 | Tibial plateau attrition <5 mm | Posterior part of plateau intact |
4 | Attrition 5–10 mm | Attrition extending to posterior margin of the plateau |
Severe subluxation of the tibia | Anterior subluxation of tibia >10 mm |
In grade 1, there is reduction in height of the medial articular cartilage (Fig. 1.1). In grade 2, there is loss of articular cartilage down to bone (Fig. 1.2). In grade 3, there is anteromedial bone attrition of the tibial plateau (Fig. 1.3). In grade 4, the lesion includes the posterior margin of the plateau; the progression from grade 3 to grade 4 is associated with rupture of the anterior cruciate ligament (Figs 1.4A and B). In grade 5, there is anterior subluxation of the tibia more than 1 cm (Fig. 1.5). The amount of tibial subluxation is measured as the distance between vertical lines drawn from the posterior edge of the medial femoral condyle and the posterior margin of the medial tibial plateau. Osteophytes should be ignored in the measurement.3
Grade 1, 2 and 3 are suitable for high tibial osteotomy (HTO) or unicondylar knee replacement and grade 4, 5 for total knee replacement (TKR).
Physiotherapy, Education and Training
- Quadriceps exercise and knee bending exercise, active ankle and toes movement, straight leg raising exercise.
- Education about surgery and postoperative protocols:
- Avoid squatting or sitting on floor, jogging or running, local massage or heat therapy, crosslegged sitting.
- Use of western type of toilet.
- Sit on high chair approximately 20 inches height.
- Training to come out from the bed without flexing at hip in case of hip replacement surgery and abduction exercise of hip.
Medicines to be Started
In cases of osteoporosis where DEXA scan shows T score < −2.5, following medicines are started:
- Injection Deca-durabolin 25 mg IM weekly or 3 weekly for 3 injections.
- Tablet Shelcal 500 mg BD.
- Tablet Alpha—D3 OD.
- Osteofos 70 mg once weekly at least 30 minutes before breakfast in the morning with a full glass of water (not less than 200 mL). Alternatively, in postmenopausal woman, injection Ibandronate sodium 3 mg/3mL intravenously every 3 months or injection Zolendronic acid 5 mg/100 mL infusion bottle once per year.
- In cases with severe osteopososis, injection teriparatide 20 μg daily self-injection is taken subcutaneously in thigh or abdominal wall at the same time each day and to be continued for 1½ year.
Medicines to be Stopped Prior to Surgery
- If the patient is taking Aspirin and/or Thienopyridine platelet inhibitors Clopidogrel (Clopid) and Ticlopidine, they should be stopped at least one week prior to surgery and can be restarted after one week after surgery.
- If the patient is taking Methotrexate [disease modifying antirheumatic drugs, (DMARD)] or Abatacept in rheumatoid arthritic cases, it should be stopped at least one month prior to surgery. It can be restarted one month after surgery.
- If the patient is taking Infliximab for the treatment of spondyloarthropathies, it should be stopped at least two months prior to surgery and can be restarted after three months of surgery.
Informed Consent for Surgery
Patient and Relatives' Signature for Risk/Benefit Ratio
Preoperative Planning for TKR
It is essential to prepare for the case and to anticipate situations that may arise during surgery for a successful outcome.
The goal of total knee replacement is to restore the joint line by inserting a prosthesis that is of the same thickness as the bone and cartilage that was removed and thus to relieve pain and normalize range of motion while providing stability through the gait cycle.
- Full length lower limbs standing X-ray (from both hips to both ankles)—AP view.
- Identify angle between mechanical and anatomical axis for distal femoral cut.
- Lateral X-ray is required for sizing of femoral component with the help of templates.
Usually templating is not required for primary TKR but it is recommended if there is severe deformity with large defect, post-high tibial osteotomy (HTO) and revision TKR.
Vertical axis of body: This extends from the centre of gravity to the ground. Draw a vertical line from the center of symphysis pubis. In normally aligned lower limb, this will intersect perpendicular to the transverse knee and ankle axes (Fig.1.6).
Mechanical axis of the lower limb: Draw a line from the center of head of femur to the center of the ankle. Normally, this line should pass through the base of lateral tibial spine (Fujisawa point) (Fig.1.6). Because the hips are more widely separated than the knees and ankles, this mechanical axis is in 3° of valgus from the vertical axis of the body, i.e. 3° mechanical axis valgus (Fig. 1.6). If this line passess through the center of the knee joint, then it is called neutral mechanical axis. Thus this line passes near or through the center of knee in the normally aligned lower limb which allows even load sharing between the medial and lateral condyles. Mechanical axis of lower limb also called Mikulicz line or load bearing axis or load line. The Mikulicz line (mechanical axis or load bearing axis or load line) intersects the total width of the tibia plateau lateral from the eminentia at a point at 62% to 66% of the distance from the medial border, called the Fujisawa point.
Jakob and Murphy have elaborated the method of passage of the mechanical axis based on the amount of cartilage space remaining on the medial side as determined from varus stress radiographs. When the mechanical axis passes through the center of the knee, the medial compartment bears 70% of the load. When the mechanical axis is moved into 4 degrees of valgus, the load is 50% medial and 50% lateral. When the mechanical axis is moved into 6 degrees of valgus, the load is 40% medial and 60% lateral.
Mechanical axis of the femur: Draw a line from center of head of femur to the highest point of the femoral notch. Draw another line perpendicular to this mechanical axis at the highest point of femoral notch.
Normally, mechanical axis of lower limb passes slightly lateral to the centre of knee and mechanical axis of femur in 3 degree mechanical axis valgus (Figs 1.6 to 1.8) or coincident in neutral mechanical axis.
Anatomic axis of femur: Draw a line from pyriform fossa to the highest point of the femoral notch. It is in 6° of valgus from mechanical axis of femur and 9° of valgus from vertical axis of body (Fig. 1.6).6
Mechanical/anatomic axis of the tibia: Draw a line from the midpoint between the tibial spines (i.e. center of proximal tibia) to the center of ankle. Draw another line perpendicular to the tibial axis at the level of upper tibial surface. The mechanical axis of the tibia is in 3 degrees of varus from the vertical axis of the body (Fig. 1.6).
Anatomic axis of tibia is a line that bisects medullary canal while mechanical axis of the tibia is the line from center of proximal tibia to center of ankle. Usually mechanical axis and anatomic axis of tibia are coincident. If there is tibial deformity then mechanical and anatomic axis are not the same.
Determine the angle between mechanical and anatomical axis of the femur. Determine the angle between the lines perpendicular to the mechanical axis of femur and mechanical axis of tibia. The aim is to make these two lines parallel (i.e. converting the trapezoidal space into rectangular space) and hence to achieve 3 degree mechanical axis valgus or at least neutral mechanical axis of lower limb.
Normally, the anatomic axes of the femur and the tibia (fimorotibial angle, FTA) form a valgus angle of 6° ± 2°.
Hip-Knee-Ankle (HKA) angle: It is the angle between mechanical axes of femur and tibia. An HKA angle of less than 180 degree is defined as varus. Normal HKA angle is 183 to 185 degree which is measured on the medial side of the knee. As a convention, the HKA angle may be expressed as its angular deviation from 180°. Varus deviations are negative and valgus deviations are positive. The normal alignment of the lower limb is 3 to 5 degree positive (+ 3 to + 5).
In a normal knee, the tibial articular surface is in approximately 3° of varus with respect to the mechanical axis and the femoral articular surface is in a corresponding 9° of valgus. Since the tibia is cut perpendicular to the mechanical axis, hence the femoral cut is done at 9°−3° = 6° i.e. 5° to 7° valgus of the anatomic axis of femur to get the distal cut perpendicular to the mechanical axis of femur. Thus the tibial tray is implanted perpendicular to the mechanical axis of the tibia and the femoral component is implanted in 5° to 7° valgus of the anatomic axis and thus perpendicular to the mechanical axis of femur.
Long-term success of joint replacement depends on restoration of the normal alignment of the lower limb, thereby bringing the transverse axis of the knee parallel to the ground in anatomic two-legged stance and restoring normal weight distribution across the joint (Fig 1.8).
In osteoarthritis of knee, following changes occur in the axes (Fig. 1.7)—
- Mechanical axis of lower limb passes through the medial compartment or medial to the knee joint (Normally passes through lateral joint at Fujisawa point).
- Hip-knee-ankle (HKA) angle <180 degree when measured on the medial side (Normal HKA angle is 183 to 185 drgree).
- Anatomic axis and mechanical axis varus angles (Normal 3 to 5 degree mechanical axis valgus and 8 degree anatomic axis valgus).
Varus malalignment of lower limb is due to mechanical axis deviation (MAD) which is usually attributed to femoral or tibial osseous defomitties or both and also due to ligament laxity. The initiation of osteoarthritis occurs when healthy cartilage experiences some condition (traumatic or chronic) that causes kinematic changes during amulation at the knee to shift the load-bearing contact location of the joint to a region not conditioned to the new loading. The rate of progression of osteoarthritis is associated with increased load during ambulation. Noyes has classified the varus deformities as “primary varus” that is caused by a bony varus deformity arising from the tibia and femur. A “double varus” deformity develops when there is secondary loss of articular cartilage of the knee along with degeneration of menisci (intra-articular varus). In later stage, the “triple varus” is being contributed by laxity of the posterolateral ligament complex causing a hyperextension varus deformity.
As the varus deformity progress, there is maltracking of patella which leads to arthritis of patellofemoral joint and gradually progresses to arthritis of lateral compartment (i.e. triple compartment osteoarthritis).
Fig. 1.7: Osteoarthritis right knee with varus angle and left knee after total knee replacement with restoration of 3 degree mechanical axis valgus and mechanical axis passes through Fujisawa point
Ultimately, there is failure of ACL and PCL with stretching of lateral collateral ligament which leads to subluxation of knee joint (Fig. 1.1 to 1.5).
During knee replacement surgery, the damaged joint is resurfaced by using tibial and femoral cutting jigs in such a way that the mechanical axis reverts back to normal level, i.e passes through Fujisawa point and 3 to 5 degree mechanical axis valgus (Fig. 1.7 and 1.8).
Applied Anatomy
Knee Joint
It is made of three joints:
- Medial condyloid joint between medial condyle of femur and corresponding medial meniscus and condyle of tibia (Medial compartment).
- Lateral condyloid joint between lateral condyle of femur and corresponding lateral meniscus and condyle of tibial (Lateral compartment).
- Patellofemoral joint between patella and femur.
Fig. 1.8: Restoration of normal alignment of lower limbs after bilateral TKR and THR (3 degree mechanical axis valgus, 8 degree anatomic axis valgus and mechanical axis of lower limb passes through Fujisawa point)
The femur and tibia are connected together by the following ligaments:
- Articular capsule (capsular ligament).
- Ligamentum patellae.
- Oblique popliteal ligament.
- Tibial collateral ligament.
- Fibular collateral ligament.
- Anterior cruciate ligament.
- Posterior cruciate ligament.
- Medial and lateral menisci.
- Transverse ligament—connects the anterior convex margin of the lateral meniscus to the anterior end of the medial meniscus.
- Coronary ligament—portions of the capsule which connect the periphery of each meniscus with the margin of the head of the tibia.
Other structures are synovial membrane, lateral patellofemoral plicae, infrapatellar fat pad and bursae around the knee joint.
Arrangement of Neurovascular Structures around the Knee
The arrangement of neurovascular structures can be linked to the points on the face of a clock as shown in Figure 1.9:8
Popliteal vein: It lies directly in the midline posteriorly at 12 O' clock position.
Tibial Nerve: It lies just medial to popliteal vein at the 11 O' clock position in left knee and 1 O'clock position in right knee.
Popliteal artery: It lies just lateral to popliteal vein at 1 O' clock position in left knee and 11 O' clock position in right knee.
Bifurcation of popliteal artery: The popliteal artery bifurcates below the joint line into anterior and posterior tibial arteries at the 2 O' clock position in left knee and 10 O' clock position in right knee.
Common peroneal nerve: It lies further laterally against the neck of fibula, distal to the joint line at the 3 O' clock position in left knee and 9 O' clock position in the right knee.
Damage to neurovascular structures may occur between 11 O' clock and 3 O' clock positions in left knee and between 9 O' clock and 1 O' clock position in right knee. Careful surgical technique and knowledge of the neurovascular anatomy at the knee will help in avoiding neurovascular injury during TKR.
Blood Supply to the Knee (Fig. 1.10)
The blood supply to the knee arises predominantly from the peripatellar anastomotic ring which is formed by the contributions of:
- The superior and inferior genicular arteries (medial and lateral) which are branches of popliteal artery.
- The supreme genicular artery which is the branch of superficial femoral artery.
- The anterior recurrent tibial artery.
Anterior knee circulation is dependent on the dermal plexus which originates from arterioles travelling with the midline subcutaneous fascia. Hence, during midline skin incision, do not undermine the skin and raise the skin flaps deep to the fascial layer to avoid skin necrosis. The blood supply from the medial side is generally more significant than that arising from the lateral side. Consequently, when faced with more than one parallel longitudinal incision, the lateral incision should be selected.
Lateral inferior genicular artery is usually cut during surgery and requires coagulation by electrocautery.
Movements of Knee Joint
- Flexion and extension.
- Internal and external rotation in certain position of the joint.
The movements of flexion and extension at knee joint differs from those in a typical hinge joint. The axis around which motion takes place is not a fixed one but shifts forward during extension and backward during flexion and the commencement of flexion and the end of extension are accompanied by rotatory movements associated with the fixation of the limb in a position of great stability.
Types of Total Knee Replacement
In a normal knee, anterior cruciate ligament (ACL) is an important stabilizer but in a prosthetic joint ACL is not necessary for adequate functioning and PCL is more important to prevent posterior shift or sag of tibia in order to maintain relative position of femur and tibia, and thereby also to maintain adequate quadriceps function. When PCL is not working or has to be sacrificed to correct severe deformities, it must be substituted in the prosthesis by a Spine-Cam mechanism. TKR is of 3 types depending on the degree of mechanical stability provided by the design of the artificial knee—
- Nonconstrained (Cruciate-retaining or CR design).
- Semiconstrained (Cruciate-substituting or posterior stabilized or PS design).
- Constrained (hinged design).
Nonconstrained (Cruciate-retaining or CR design): In this implant, the artificial components are not linked to each other and have no stability built into the system. Stability relies on intact PCL. Here ACL is sacrificed but PCL is retained. In CR design, lateral distal femoral condyle of femoral component is longer in anteroposterior direction than the corresponding medial condyle. This disparity creates unequal rolling distances (i.e. differential rolling) and facilitates external rotation of femur when flexion begins and vice versa internal rotation of femur to bring about screw-home movement in final degree of knee extension. As the flexion increases, center of femur moves posteriorly relative to tibia and this shift can be as much as 8 mm on 0–120 degree flexion. This is known as femoral rollback in flexion and is an important part of normal knee biomechanics which is guided mainly by PCL and lateral collateral ligaments. This rollback is duplicated when CR design prosthesis is used. Femoral rollback is facilitated by less dished surface geometry of posterior part of tibial polyethylene. Hence tibial articular surface of CR prosthesis is flat looking as compared to the sagittal profile of corresponding femoral component.
Semiconstrained (Cruciate-substituting or posterior stabilized or PS design): This type of artificial knee has some stability built into it in the form of Spine-Cam mechanism. Here both ACL and PCL are sacrificed. In PS femoral component medial and lateral femoral condyle have same length anteroposteriorly and hence differential rotaion does not occur. The tibial articular surface is more dished and deeper to allow controlled motion between femur and tibia. Spine-Cam mechanism is a mechanical substitution for PCL and consists of a post in the middle of tibial polyethylene and a metal stabilizing bar (cam) in intercondylar area of femoral prosthesis. Both are so positioned that the stabilizing bar (cam) is posterior to tibial post. Polyethylene tibial post has an extension to prevent medial or lateral displacement of post around either of femoral condyle when knee is flexed beyond 90 degree. In order to accommodate polyethylene tibial post and femoral cam, the middle of posterior stabilized femoral component has a dropped box built in, which requires removal of some bone from intercondylar area of femur to accommodate this box. We are using PFC sigma cruciate-substituting fixed bearing and cruciate-substituting mobile bearing (rotating platform high flexed TKR, i.e. RPF) knee implants.
Constraint or hinged variety implants are rarely used as a first choice of surgical options. In this case, the two components of the knee joint are linked together with a hinged mechanism. This type of knee replacement is used when the knee is highly unstable and the person's ligaments will not be able to support the other type of knee replacements. It is useful in the treatment of severely damaged knees particularly in very elderly people undergoing a revision replacement procedure. The disadvantage of this type of knee joint is that it is not expected to last as long as the other types.
A unicondylar knee replacement replaces only half of the knee joint. It is performed if the damage is limited to one side of the joint only with the remaining part of the knee joint being relatively spared. Here only that area 10of the knee joint is replaced which is severely damaged. However, even with only half of the joint destroyed, many surgeons prefer doing a total knee replacement believing this is a better procedure than the half-knee (unicondylar) replacement. But equally, there are surgeons who believe it is more appropriate to perform a unicondylar knee in the right circumstance.
In place of unicondylar knee replacement for medial compartment osteoarthritis (MCOA), we are performing high tibial osteotomy (HTO) by hemicallotasis HCO) using a dynamic axial fixator (DAF) in younger patients and total knee replacement in elderly.
Preparation of the Patient for Surgery and Arranging Blood
Arrange 2 units of blood for replacement of each knee or hip joint.
2 days prior to surgery: Thorough bath with antiseptic soap (e.g. dettol soap).
1 day prior to surgery:
- Thorough bath with antiseptic soap (e.g. dettol soap) in the morning.
- Injection Enoxaparin sodium (Clexane), a low molecular weight heparin (LMWH), 40 mg/0.4 mL SC (subcutaneously) at 8.00 AM (1st dose, 24 hours prior to surgery).
- Injection TT (Tetanus toxoid) 1 amp. IM stat if not immunized previously or immune status is not known.
- Injection Xylocaine sensitivity test.
- Scrubbing of the part by betadine scrub in the evening.
- Soap water enema at 5.00 PM.
- Injection Dexona (Dexamethasone) 4 mg IV at 8.00 PM (1st dose, 12 hours prior to surgery).
- Tablet Reglan 1 tab at bed time.
- Tablet Rantac 1 tab at bed time.
- Tablet Alprax (0.25 mg) 1 tab at bed time.
- NBM (Nil by mouth) after 10.00 PM.
On the day of surgery:
- Injection Cefotaxime 1 g IV just before sending the patient to OT.
- Injection Amikacin 500 mg IV just before sending the patient to OT. In cases where BUN and serum creatinine are on higher side, use Augmentin 1.2 g IV in place of injection Amikacin.
- Injection Dexona (Dexamethasone) 4 mg IV 2nd dose, just before sending the patient to OT.
- Part preparation—Shaving and antiseptic dressing from umbilicus to toes including private parts on the operative side of limb and up to lower thigh on the other side. Shaving should be done on the day of surgery just before sending the patient to OT to avoid colonization of bacteria. Operative side limb is wrapped in a sterile towel or sterile polyethylene drape.
- Side room in OT: Premedication (Injection Reglan and injection Glycopyrrolate/Atropine) and change of clothes.
- Patient is taken on OT table.
- Anesthesia: Preferably spinal + epidural
- Bladder is catheterized.
Note:
- If the patient is diabetic and on hypoglycemic agents, switch over to insulin prior to surgery. Withhold morning dose of insulin and send fasting blood sugar.
- If the patient is hypertensive and on antihypertensive medicines, give antihypertensive medicines with sips of water in the early morning.
- Alternative low molecular weight heparins (LMWH) are Dalteparin (Fragmin), Nadroparin (Fraxiparine), Tinzaparin (Innohep), Reviparin (Clivarin), Parnaparin (Fluxum), Fondaparinux sodium (Arixtra).
Recently one of the following oral anticoagulant can be used:
- Rivaroxaban (Xarelto).
- Apixaban (Eliquis).
- Dabigatran (Pradaxa).
The dose of Rivaroxaban (Xarelto) is 10 mg once daily. The initial dose should be taken within 6 to 10 hours of completing surgery, provided that hemostasis has been established. Treatment duration is two weeks for TKR and five weeks for THR. It can be taken with or without meal. Coagulation monitoring is not required. There should be 18 hours gap between last dose of Xarelto and removal of epidural catheter and the next dose has to be given 6 hours after the removal of catheter followed by every 24 hourly.
The dose of Apixaban (Eliquis) is 2.5 mg twice daily. The initial dose should be taken 12 to 24 hours after surgery. The treatment duration is 10 to 14 days for TKR and 32 to 38 days for THR. It can be taken with or without food.
Dabigatran (Pradaxa) is started 110 mg stat 1–4 hours postsurgery on day 1. From day 2, it is given 220 mg (110 mg capsule × 2) up to 10 days for TKR and 35 days in THR. In patients more than 75 years, moderate renal impairment and patients taking Amiodarone and Verapamil, effective lower dose is 75 mg OD on day 1 started within 1–4 hours and 150 mg (75 mg capsule × 2) once daily.