MonopolarBipolar hip prosthesis in femoral neck fractures

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Monopolar/Bipolar hip prosthesis in femoral neck
fractures

• Mr A D Patel
• Consultant trauma and Orthopaedic surgeon
• Norwich UK
• ARTOF
• 10th EFFORT Congress Vienna

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Objectives

• Problems with monopolar prosthesis
• Bipolar prosthesis
• Acetabular wear
• Protrusio
• Dislocation
• Loosening
• Randomised studies
• Cochrane review
• Costs
• Conclusions

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Monopolar prosthesis for fractured neck of femur

• Austin Moore and Thompson in 1950s
• Widespread use

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Problems

• Acetabular wear
• 7 at 2 yrs
• 10 at 2yrs 8mths
• 13 at 3yrs
• 24 at 5 yrs
• Protrusio
• Dislocation 0.3 to 10
• Loosening-all uncemented loose

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Bipolar prosthesis-advantages

• Decreased acetabular cartilage wear
• Decreased protrusio
• Decreased dislocation rate
• Decreased component loosening
• Ease of conversion to THR

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Bipolar prosthesis-decreased acetabular cartilage
wear

• None Hastings hip at 4 years
• None Giliberty hip 2.4yrs
• None Christianssen hip 2.5yrs
• Merlo 42 cartilage wear, 25 protusions overall
  better clinically
• Decreased protrusio
• Decreased dislocation rate
• Decreased component loosening
• Ease of conversion to THR

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Bipolar prosthesis-advantages

• Decreased acetabular cartilage wear
• Decreased protrusio
• Decreased dislocation rate
• Decreased component loosening
• Ease of conversion to THR

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Movement at the ball and head interface
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Inner bearing motion

• Tsukamoto 1992 Acta Orthop Scand
• Cadaveric motion studies Bipolar implants
• Stems loaded with lt 10kg motion at both bearings
• Stems loaded gt 20 kg motion mainly outer bearing
• Inference with walking motion at outer bearing

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H Drinker and WR Murray JBJS 1979

• 101 Bateman bipolar prosthesis
• 13 Bateman arthroplasties followed 2 and 3.4 yrs
  and with motion studies
• Far less motion at all stages
• By 3.4yrs motion at inner bearing half of that at
  2 yrs
• All patients at any stage reduction in inner
  bearing motion with weightbearing compared to
  supine unloaded position

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Verberne 1983 JBJS

• 20 patients Variokopf prosthesis
• Movements measured post-op, 1 and 3 months
• By 3 months almost no movement at inner bearing

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Brueton 1993 Injury

• Size of inner head important
• Small heads 22mm allowed bipolar motion
• Large heads 32mm hindered inner bearing motion
• Verberne 32mm head

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Degreif 2000 Orthopaedics

• Ceramic bipolar heads
• 277 patients
• 77 available review 3-8 yrs
• 3 hip pain
• 4 protrusio
• 4 revision of cup

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Reduced acetabular wear and protrusio

• Dependant on maximal movement at the ball head
  interface
• Most studies show bipolar becomes monopolar after
  a period of time
• Worn acetabulum better movement
• No long term studies to monitor these

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Bipolar prosthesis-advantages

• Decreased acetabular cartilage wear
• Decreased protrusio
• Decreased dislocation rate
• Decreased component loosening
• Ease of conversion to THR

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Dislocation

• James Varley and Martyn Parker 2004
• Last 40 years of publications133 articles
• 23,107 cases
• Increased risk with a posterior approach
• Increased risk with use of cement
• After adjustments no difference monopolar and
  bipolar
• Increased risk open reduction for bipolar

Stability of hip hemiarthroplasties International
Orthopaedics 2004
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Dislocation 3.4
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Problems with dislocations

• Bipolar
• Difficult
• Open reduction common
• Inter-prosthetic dislocations always needs open
  reduction

• Monopolar
• Relatively easy reduction

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Bipolar prosthesis-advantages

• Decreased acetabular cartilage wear
• Decreased protrusio
• Decreased dislocation rate
• Decreased component loosening
• Ease of conversion to THR

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Decreased component looseningEase of conversion
to THR

• Technical advances inevitably better stem design
  in bipolar
• Modular allowing appropriate neck lengths
• Better cementing techniques
• Similar advances in more modern monopolar

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Calder, Anderson, Jagger, Harper, Gregg JBJS 1994

• Randomised prospective trial
• 432 patients aged 65 to 79 yrs
• ORIF v.cemented Thompsons v. cemented bipolar
  Monk
• Better scores in Nottingham Health Profile for
  bipolar
• Better Harris hip scores
• Better mobility, pain and social function

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Calder, Anderson, Jagger, Harper, Gregg JBJS 1996

• Randomised prospective trial 250 cases
• One surgeon, Hardinge approach
• Cemented Thompson v. cemented bipolar Monk
• gt 80 yr old
• Mental test score over half
• 2 years no difference complications, pain, limp,
  Harris score, satisfaction

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Raia 2003 Clin Orthop Relat Res

• 115 gt65 yrs old
• Non institutionalized, cognitively or physically
  impaired
• Randomized to monopolar/bipolar
• 1 year follow up
• No difference quality of life and functional
  outcomes

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Cochrane review 2004

• 7 prospective randomised trials
• 857 cases
• No difference between monopolar and bipolar
• Dislocation, acetabular cartilage wear, deep
  wound sepsis, reoperations, deep vein thrombosis,
  or mortality
• Limitations small sample size, short follow up 2
  years
• Difficult to show theoretical advantage of less
  wear
• 50 mortality within 5 yrs gt70 yrs age

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Health Economics

• Reduced costs with monopolar
• Mean hospitalization cost bipolar 12,290 v.
  8896 monopolar
• Current climate
• Fear talk about cost but this is because of
  ignorance little in the current literature

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Conclusion

• Decreased acetabular cartilage wear- possibly
  with better clinical function
• Decreased dislocation
• Under 80yrs better pain relief, mobility
• Over 80yrs no difference overall
• Dislocation similar but with bipolar need open
  reduction
• Health economics - cost implications

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Thank you
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