Orthopedic Surgery and Venous Thrombosis: Relationship to Antiphospholipid Antibodies? A Pilot Study

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Orthopedic Surgery and Venous Thrombosis
Relationship to Antiphospholipid Antibodies? A
Pilot Study

• Natalia Yazigi MD, Joseph Mazza MD, Hong Liang
  PhD, Mark Earll MD, William Hocking MD, James
  Burmester PhD, Steven Yale MD
• Marshfield Clinic and Marshfield Clinic Research
  Foundation, Marshfield, Wisconsin

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VenothromboembolismOrthopedic Surgery

• Compared to other surgical interventions,
  patients undergoing major orthopedic joint
  reconstructive procedures have one of the highest
  rates of thromboembolic disease.
• Without adequate mechanical or anticoagulation
  prophylaxis, 50 to 80 of total hip and knee
  arthoplasties will develop deep venous thrombosis
  (DVT).

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VenothromboembolismOrthopedic Surgery (contd)

• Total pulmonary embolism (PE) rates for hip
  arthroplasty ranges between 0.9 to 28 (fatal PE
  0.1-2.0) total PE rates for knee arthroplasty
  ranges between 1.5 to 10 (fatal PE 0.1-1.7).
• With pre-and post-operative anticoagulation
  regimens commonly used in these patients, the
  incidence of DVT has been reduced to 12-15.

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Incidence of VTE Within 91 Days of Surgery Among
Patients Without a Malignancy
Surgical procedure total 95 CI
Total hip arthroplasty 2.4 2.3-2.5
Total knee arthroplasty 1.7 1.7-1.8
ORIF femur 1.9 1.8-2.0
Shoulder arthroplasty 0.5 0.3-0.8
Thyroid surgery 0.2 0.1-0.4
Open cholecystectomy 0.5 0.4-0.6
Nephrectomy 0.4 0.2-0.6
Total abdominal hysterectomy 0.3 0.2-0.3
Replacement of the heart valve 0.5 0.5-0.6
White R et al, Thromb Heamost 2003, 90446
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Incidence DVT in Total Hip Arthroplasty
He Xing K. et al, Thrombosis Research, 2008,
1232434
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Thrombotic Stimuli During Total Hip and Knee
Arthoplasty

• Venous stasis Tourniquet placement, immobility
  during the postoperative period
• Endothelial injury Manipulation during
  preparation of the femoral prosthesis releases
  tissue thromboplastin and other thrombogenic
  molecules
• Hypercoaguability Thrombogenic stimuli -
  reduction in antithrombin III and inhibition of
  fibrinolysis due to blood loss

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Unexplained Factors for VTE in Orthopedic Surgery

• Hypothesis
• Bone contains a large concentration of
  phospholipids, which are found as structural
  components of fat and hematopoietic cells that
  comprise the bone marrow (hidden epitopes).
• Disruption or invasion of this site as a
  consequence of surgery causes inflammation and
  cellular apoptosis leading to turnover of
  phospholipid membranes.

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Unexplained Factors for VTE in Orthopedic Surgery

• Exposure of phospholipids, to normal immune
  surveillance, thereby eliciting an immunological
  response.
• Production of autoantibodies targeting
  phospholipid binding proteins, prothrombin
  complex, and membrane phospholipids (essential
  components of the coagulation cascade).

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Antiphospholipid Antibodies (APLa)

• Diverse group of autoantibodies that bind to a
  variety of antigens including
• (1) phospholipid binding proteins ?2GP1,
  prothrombin, protein c, protein s, annexin CV,
  HMW kininogen, complement factor H, and factor
  XI, which are components expressed or bound to
  the surface of vascular endothelial cells,
  platelets or other cells
• (2) negatively charged phospholipids
• (3) phospholipid-protein complexes

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Hypercoagulability in APLaProposed Mechanism

• Proposed mechanisms for the prothrombotic state
  induced by APLa include
• interference with prothrombin conversion to
  thrombin
• inhibition of activation of protein C and S
  pathways
• activation of platelets, monocytes and
  endothelial cells
• promotion of tissue factor synthesis and
  expression by suppression of the inhibitory
  activity of tissue factor pathway inhibitor
  (TFPI)
• interference with fibronolysis by inhibiting the
  conversion of plasminogen to plasmin

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Procoagulant and Anticoagulant Phospholipid-bound
Protein Targets for Antiphospholipid Antibodies
(APLa)
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What are APLas?

• Include among others, Lupus anticoagulants, B-2
  Glycoprotein 1 and anticardiolipin antibodies.
• Immunoglobulins that react with heterogeneous
  epitopes on ß2-GPI or prothrombin, and result in
  tests positive for lupus anticoagulant activity
  (coagulation assays) or anticardiolipin antibody.
• Due to the heterogeneity of these antibodies some
  antibodies may exhibit lupus anticoagulant
  effects while others are only active in
  anticardiolipin assays.
• Thus APLa are closely related, overlapping but
  not identical antibodies.

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APLa Frequency and Significance

• APLa can be found in the serum of individuals of
  all ages, in patients who are entirely
  asymptomatic and without a history of VTE.
• IgG ACLa have been found in
• 12 to 52 of clinically healthy elderly persons
• 2 of a younger population
• 1 to 9 of blood donors
• The presence of these antibodies in apparently
  healthy individuals has led to speculation that
  they have a physiologic function that remains to
  be elucidated.

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APLa Detection

• Screening
• direct activated partial thromboplastin time
  (dAPTT)
• prothrombin time (dPT)
• kaolin clotting time
• dilute Russel Viper Venom test (dRVVT)
• Because Russel Viper Venom (RVVT) directly
  activates coagulation factor X, it is considered
  the most sensitive laboratory assay for LA

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What are APLas?

• Neither screening test (ACLa or LA), is a 100
  sensitive
• In general, ACL test are more sensitive wheras ?2
  GP1 and LA have a higher degree of specificity
  for APS
• LA, medium to high titers of IgG ACL and IgG ?2
  GP1 antibodies are most strongly associated with
  thrombosis

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APLa Diagnosis

• The diagnosis of APS can be made only when a
  characteristic clinical presentation (vascular
  thrombosis, pregnancy morbidity) is combined with
  objective laboratory abnormalities (lupus
  anticoagulant, anticardiolipin Ab, Antiß2-GP1 Ab)
  are present on 2 or more occasions at least 12
  weeks apart.

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What is Lupus Anticoagulant?

• The LA phenomenon reflects the in vitro
  inhibition by antiphospholipid antibodies
  (anti-?2GP1 and anti-prothrombin antibodies) of
  phospholipid- dependent coagulation reactions.
• LA is a laboratory assay that tests for the
  presence of antibodies (APLa) that competes with
  coagulation proteins normally found on
  phospholipid templates thereby inhibiting the
  conversion of prothrombin to thrombin.
• By preventing the formation of the prothrombinase
  complex (Xa, Va and prothrombin) and subsequent
  fibrin clot, APLa interfere with phospholipid
  dependent coagulation pathways as reflected by
  the prolonged APTT and dilute Russel Venom Time
  (dRVVT).

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What are ?2 GP1 APLas?

• ?2 GP1 antibodies are useful to confirm the
  diagnosis in patients with low positive IgG ACL
  or only IgM or IgA ACLa positivity, in patients
  with unusual or equivocal features, or in those
  with negative ACLa and lupus anticoagulant in the
  presence of highly suggestive clinical features.
• ?2 GP1 antibodies have been identified in up to
  10 of patients testing negative for ACL and
  lupus anticoagulant and clinical features of APS.

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Anticardiolipin APLa

• ACL (IgG, IgM, or IgA) antibody
• APLa found in some patients with APS
• ACLa antibodies are measured using solid phase
  immunoassay using ?2 GP1 cofactor bound to
  negatively charged phospholipid, cardiolipin, or
  other anionic phospholipids
• Unlike LA, the detection of ACLa is not effected
  by anticoagulation therapy

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Pilot Study Overview

• Explore whether activation of the immune response
  as a consequence of de-novo auto-antigen exposure
  to phospholipids released during orthopedic (hip
  or knee replacement) surgery contributes to
  hypercoaguable states.

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Objectives

• Goal
• To determine whether elevated titers of
  Antiphospholipid antibodies (APLa) occurring as a
  result of tissue damage in the operative period
  correlates with the development and incidence of
  VTE.

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Specific Goals

• Primary goal
• Estimate the prevalence of elevated APLa titers
  that develop after postoperative hip and knee
  replacement surgery.
• Secondary goal
• Evaluate the association between the presence of
  elevated APLa titers and the occurrence of
  symptomatic venothromboembolic events.

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Study Design

• Prospective cohort study design
• 150 patients undergoing total knee or hip
  arthroplasty
• The trial will consist of up to a 30 day
  screening period
• Day 1 is designated as the day of surgery
• Laboratory testing for APLa will occur on the day
  prior to surgery, and Days 7 2, 14 2 , and 21
  2 postoperatively
• Subjects will be contacted by telephone on Day 56
  2 to determine whether a venothromboembolic (DVT
  or pulmonary embolism) event (VTE) had occurred.
  If a VTE was present, information will be
  obtained regarding the location and site of
  thrombosis and method of diagnosis.

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Study Methods

• Data will be obtained regarding previous history
  or VTE and whether patients have medical
  conditions, known to increase the risk of VTE,
  within 30 days prior to preoperative baseline
  blood draw.
• Primary outcomes will include determination of
  titers of ACLa and ß2GP1 antibodies and clotting
  time anomalies as detected by lupus anticoagulant
  and incidence of thromboembolism.
• The results of the doppler duplex ultrasound,
  ventilation/perfusion scan, and/or chest spiral
  computed tomography will be recorded and the
  occurrence of postoperative DVT or pulmonary
  embolism will be correlated with the results of
  preoperative and postoperative APLa levels.

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Inclusion Criteria

• Male or female 18 years of age who are
  scheduled for primary elective unilateral total
  knee or hip arthroplasty (i.e. first time the
  knee or hip is being replaced on the operative
  side).

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Exclusion Criteria

• Subjects with a history of objectively diagnosed
  deep venous thrombosis or pulmonary embolism
• Current anticoagulation therapy
• Positive APLa (ACLa or ß2GPI) antibodies or LA
  test previously or at the time of preoperative
  assessment
• Known autoimmune disorder such as scleroderma,
  systemic lupus erythematosus and rheumatoid
  arthritis
• Subjects with an active malignancy
• Subjects with an active infection
• Resident of a nursing home or long-term care
  facility
• Subjects who will be inaccessible due to
  geographic or social factors during treatment or
  follow-up

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Results Positive Distribution
Pre Day 7 Day 14 Day 21 Total
LA 0 (0/52) 71.15 (37/52) 71.15 (37/52) 75.00 (39/52) 78.82 (41/52)
ACLa 0 (0/52) 1.92 (1/52) 1.92 (1/52) 1.92 (1/52) 1.92 (1/52)
GP1 0 (0/52) 1.92 (1/52) 1.92 (1/52) 1.92 (1/52) 3.85 (2/52)
Total 0 (0/52) 71.15 (37/52) 71.15 (37/52) 75.00 (39/52)
The Table above showed that the rate of LA
positive is relatively high (71.15, 71.15, and
75.00 on day 7, day 14 and day 21,
respectively), while the rates of ACLa and GP1
positive are low (less than 2 on day 7, day 14
and day 21).