Conservative Hip Replacement for avascular necrosis

1. Conservative Hip Replacement for avascular necrosis E. Munting, P. Poilvache Cliniques Universitaires Saint-Luc, Bruxelles Clinique Saint-Pierre, Ottignies Hôpital de Waterloo-Braine

2. THR in patients < 55 y. Revision rate : • from 20 % at 5 years • to 12 % after 20 years follow-up - Conflicting reports - Implant dependent - Patient dependent (activity…)

4. Femoral component : options • Preservation of the femoral head and resurfacing • Replacement of the femoral head and : • fixation in the diaphysis (stem) • fixation in the metaphysis

5. Femoral head replacement with metaphyseal fixation … an old idea ! 1938 Wiles 1954 Postel and Merle d'Aubigné 1941 McKee 1957 Picchio 1949 Judet and Judet 1980 Huggler and Jacobs 1952 Thomson 1982 Munting and Vincent 1953 Haboush

6. Specification chart • Preserve bone stock • Normal stress pattern in the bone • Femoral head replacement • Easy revision

7. Conception and Experimental work • Design and biomechanical assessment of prototypes on a hip simulator • Finite Element analysis of experimental and clinical cases • Hydroxyapatite coating development and animal experiments

8. Implant design study

9. Femoral component • No medullary stem • Screws for initial fixation • Hydroxyapatite coating • Modular head

10. Fixation : Geometrical interference • Angular resection of the femoral neck • Lamellae in the proximal metaphysis • Cortical and cancellous support

12. DXA Study(prospective, 21 hips, 6-9 y. F-up) • BMD is maintained in the proximal femur • In patients with low initial values as compared to the controlateral side, BMD increases after surgery J. Arthroplasty 12, 373-9, 1997

13. Pilot study • 04/1989 – 01/1992 • 43 patients, 48 hips • 33 males, 15 females • Mean age: 36.4 years (19 – 49)

14. Etiology (pilot study n = 48) • Primary arthritis 6 • rheumatoïd arthritis 4 • Ankylosing spondylitis 5 • Septic arthritis 2 • Post-traumatic arthritis 7 • Congenital dysplasia / dislocation 6 • Aseptic necrosis 12 • Miscellaneous 6

15. Results (pilot study n: 48) • Follow-up : 14 to 16 years • 1 patient (2 hips) deceased • 3 lost to follow-up (living abroad) • 18 revised : 8 early revisions (malposition) 10 late revisions (polyethylene wear) • 26 hips known to be functional.

16. Revisions secondary to implant malposition (n=8) • Varus position : CDA < 120° (n=6) • lack of contact with the bone resection (n=2)

17. Second series • 01/1995 – 05/2000 • 154 hips • Mean age: 40.8 years (17 – 56 years)

18. Second series (01/1995 – 05/2000) • 154 hips • 14 early revisions • 4 late revisions for poly. wear (alumina/poly.)

19. Survival probability: femoral component n = 154 second series n = 48 pilot study ( Kaplan - Meier ) y

20. Third series (06/2000 – 11/2005) • 130 hips • Mean age: 42 y. (14-56) • 9 early revisions: • 2 broken ceramic heads (alumina/alumina)

21. Aseptic necrosis (69 hips)

22. Aseptic necrosis • From 04/1989 to 02/2003 • 56 patients (50 males/6 females) • 64 hips • Mean age: 49 years (22 – 64) • Mean follow-up: 7 years • 5 revisions • 59 implants still in place

23. Aseptic necrosis (n: 64) • 5 revisions (7.8%) • Mean age at reoperation: 52 years • Mean time in situ: 3 years • Reasons for revision: • Varus positioning causing pain or loosening (4) • Recurrent dislocation (1)

24. Aseptic necrosis (n: 64) 59 implants in place: • 1 patient complaining of groin pain (psoas tendinitis?) • 1 late instability (poly. wear) • 2 patients with mild trochanteric pain (screw?)

25. 7 years 14 years

26. Need for improved instruments The cutting and drilling guides should be monoblock, in order to avoid rotational mismatch

27. Conclusions • This experience supports that a purely metaphyseal anchorage of a stemless implant can provide a long lasting fixation • This type of implant is suitable even when the femoral head is destructed • It permits the use of a ceramic on ceramic bearing • It is conservative, as a primary implant can easily be used if revision is needed