Hemiarthroplasty -Monopolar versus Bipolar

Hemiarthroplasty

1. Arthroplasty Issues: Hemiarthroplasty versus THA Hemi More revisions 6-18% Smaller operation Less blood loss More stable 2-3% dislocation Total Hip Fewer revisions 4% Better functional outcome More dislocations 11% early 2.5% recurrent [Cabanela, Orthop 1999] [Lu –Yao JBJS 1994] [Iorio CORR 2001]

2. Hemiarthroplasty Issues: Unipolar vs. Bipolar Unipolar Lower cost Simpler Bipolar Theoretical less wear More modular More expensive Can dissociate NO PROVEN ADVANTAGE

3. TYPES OF HEMIARTHROPLASTY Hemiarthroplasties may be either unipolar ( eg Thompson and Austin Moore) or bipolar ( eg Hastings , Exeter bipolar). Either type may be uncemented or cemented into the femur. Four good quality systematic reviews found no evidence of superiority of bipolar implants ; increasing support for THR ; B etter function of cemented implants over uncemented . The use of bone cement has been associated with intraoperative morbidity. This can be reduced by intramedullary lavage and modern cementing techniques . Uncemented stems are associated with more thigh pain and poorer overall function.115-117

4. Cement should be used when undertaking hemiarthroplasty , unless there are cardiorespiratory complications, particularly in frail older patients. Radiological studies have suggested that, in many patients, bipolar prostheses move almost entirely at the outer articulation,and therefore simply act as expensive unipolar prostheses. The main theoretical benefit of a bipolar prosthesis is a reduction in the amount of acetabular wear, minimising pain, joint destruction and mobility problems. Such problems appear to be directly related to the patient’s activity levels (degree of mobility and independence of living) and the time since operation. Bipolar hemiarthroplasty should not be performed in preference to unipolarhemiarthroplasty , as there is limited evidence of any clinical benefit.

5. Hierarchy of Evidence Randomized Trials Prospective Cohort Studies Retrospective Case Series Case Control Studies Opinion Meta-analysis Level 1 Level 2 Level 3 Level 4 Level 5

6. Cochrane Meta-analysis . Parker (2005) N=7 RCTs, 857 participants No differences in complications, mortality or function Level II

7. Hemiarthroplasty versus internal fixation for displaced intracapsular fracture NICE CG124 recommends that replacement arthroplasty ( hemiarthroplasty or total hip replacement) should be performed in patients with a displaced intracapsular fracture.

8. Key reference Waaler Bjørnelv GM, Frihagen F, Madsen JE et al. (2012) Hemiarthroplasty compared to internal fixation with percutaneous cannulated screws as treatment of displaced femoral neck fractures in the elderly: cost-utility analysis performed alongside a randomized, controlled trial. Osteoporosis International 23: 1711–9 Supporting reference Frihagen F, Nordsletten L, Madsen JE (2007) Hemiarthroplasty or internal fixation for intracapsular displaced femoral neck fractures: randomised controlled trial. BMJ 335: 1251–4

9. The data suggest improved clinical and quality of life outcomes with total hip replacement versus hemiarthroplasty following displaced intracapsular fracture, consistent with the recommendation in NICE CG124 to offer total hip replacements to appropriate patients.

10. Key reference Hedbeck CJ, Enocson A, Lapidus G et al. (2011) Comparison of bipolar hemiarthroplasty with total hip arthroplasty for displaced femoral neck fractures: a concise four-year follow-up of a randomized trial. The Journal of Bone and Joint Surgery (American volume) 93: 445–50 Supporting reference Blomfeldt R, Törnkvist H, Eriksson K (2007) A randomised controlled trial comparing bipolar hemiarthroplasty with total hip replacement for displaced intracapsular fractures of the femoral neck in elderly patients. The Journal of Bone and Joint Surgery (British volume) 89: 160–5

11. ORIF vs Bipolar vs THR Prospective randomized multicenter Displaced FN fxs , pts > 60 years 298 pts- ORIF (118); cemented bipolar (111); cemented THR (69) ORIF fixation failure (AVN,NU) - 37% ORIF – 8x more likely to require revision surgery than bipolar and 5x than THR Functional outcome highest for THR Keating et al, JBJS 2006

12. Boot Camp 2013 Phoenix, AZ Femoral Neck Fractures in the Elderly Unipolar vs. Bioplar No consensus

13. Theoretical advantage of bipolar over unipolar : Prosthesis-prosthesis articulation theoretically decreases acetabular wear by shifting some hip movement away from the acetabulum to the internal prosthesis-prosthesis articulation . Does the articulation move? - Maybe Drinker and Murray, JBJS, 1979 – only minor motion at inner bearing Phillips, JBJSBr , 1987 – Bateman Bipolar Prosthesis, 76 pts with preexisting OA, 80% had inner bearing motion primarily Any better outcomes? – Not convincingly .

14. Cochrane review 2004 – 7 RCTs with 857 pts. Each study suffering from small numbers and only short term f/u. • No difference for: dislocation, acetabular cartilage erosion, deep wound,sepsis , reoperations, deep vein thrombosis, or mortality. Australian National Joint Replacement Registry, 2011 – higherrevision rates in unipolar than bipolar in age <75. • Selection bias inherent.

15. Disadvantages of bipolar: Cost Potential consequences of polyethylene wear debris Increased chance of a dislocation requiring open reduction • Factors leading to acetabular cartilage erosion are age, activity level, and length of follow-up

16. Summary: Given the above disadvantages, unipolar hemiarthroplasty may be recommended in older, less active pts with shorter life expectancy. Given this, we are left with question - who to use bipolar on? The other group may be appropriate for THA.