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 from 20 % at 5 years to 12 % after 20 years follow-up 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 Preservation of the femoral head and resurfacing Replacement of the femoral head and : Replacement of the femoral head and : fixation in the diaphysis (stem) fixation in the diaphysis (stem) fixation in the metaphysis fixation in the metaphysis

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

6. Specification chart Preserve bone stock Preserve bone stock Normal stress pattern in the bone Normal stress pattern in the bone Femoral head replacement Femoral head replacement Easy revision 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 No medullary stem Screws for initial fixation Screws for initial fixation Hydroxyapatite coating Hydroxyapatite coating Modular head Modular head

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

12. DXA Study (prospective, 21 hips, 6-9 y. F-up) BMD is maintained in the proximal femur BMD is maintained in the proximal femur In patients with low initial values as 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 04/1989 – 01/1992 43 patients, 48 hips 43 patients, 48 hips 33 males, 15 females 33 males, 15 females Mean age: 36.4 years (19 – 49) Mean age: 36.4 years (19 – 49)

14. Etiology (pilot study n = 48) Primary arthritis 6 Primary arthritis 6 rheumatoïd arthritis 4 rheumatoïd arthritis 4 Ankylosing spondylitis 5 Ankylosing spondylitis 5 Septic arthritis 2 Septic arthritis 2 Post-traumatic arthritis 7 Post-traumatic arthritis 7 Congenital dysplasia / dislocation 6 Congenital dysplasia / dislocation 6 Aseptic necrosis12 Aseptic necrosis12 Miscellaneous 6 Miscellaneous 6

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

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

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

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

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

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

21. Aseptic necrosis (69 hips)

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

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

24. Aseptic necrosis (n: 64) 59 implants in place: 1 patient complaining of groin pain (psoas tendinitis?) 1 patient complaining of groin pain (psoas tendinitis?) 1 late instability (poly. wear) 1 late instability (poly. wear) 2 patients with mild trochanteric pain (screw?) 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 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 This type of implant is suitable even when the femoral head is destructed It permits the use of a ceramic on ceramic bearing 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 It is conservative, as a primary implant can easily be used if revision is needed