Conservative Hip Replacement for avascular necrosisE. Munting, P. PoilvacheCliniques Universitaires Saint-Luc, BruxellesClinique Saint-Pierre, OttigniesHpital de Waterloo-Braine

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

Femoral component : optionsPreservation of the femoral head and resurfacingReplacement of the femoral head and : fixation in the diaphysis (stem) fixation in the metaphysis

Femoral head replacement with metaphyseal fixation an old idea !1938Wiles1954Postel and Merle d'Aubign1941McKee1949Judet and Judet1952Thomson1953Haboush1957 Picchio1980 Huggler and Jacobs1982Munting and Vincent

Specification chart Preserve bone stockNormal stress pattern in the boneFemoral head replacementEasy revision

Conception and Experimental workDesign and biomechanical assessment of prototypes on a hip simulator Finite Element analysis of experimental and clinical casesHydroxyapatite coating development and animal experiments

Implant design study

Femoral componentNo medullary stemScrews for initial fixationHydroxyapatite coatingModular head

Angular resection of the femoral neckLamellae in the proximal metaphysisCortical and cancellous supportFixation :Geometrical interference

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

Pilot study04/1989 01/199243 patients, 48 hips33 males, 15 femalesMean age: 36.4 years (19 49)

Etiology (pilot study n = 48)Primary arthritis 6rheumatod arthritis 4Ankylosing spondylitis 5Septic arthritis 2Post-traumatic arthritis 7Congenital dysplasia / dislocation 6Aseptic necrosis12Miscellaneous 6

Results (pilot study n: 48) Follow-up : 14 to 16 years1 patient (2 hips) deceased3 lost to follow-up (living abroad)18 revised : 8 early revisions (malposition)10 late revisions (polyethylene wear)26 hips known to be functional.

Revisions secondary to implant malposition (n=8) Varus position : CDA < 120 (n=6)lack of contact withthe bone resection (n=2)

Second series01/1995 05/2000154 hipsMean age: 40.8 years (17 56 years)

Second series (01/1995 05/2000)154 hips14 early revisions4 late revisions for poly. wear (alumina/poly.)

Survival probability: femoral component( Kaplan - Meier )n = 48 pilot studyyn = 154 second series

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

Aseptic necrosis (69 hips)

Aseptic necrosisFrom 04/1989 to 02/200356 patients (50 males/6 females)64 hipsMean age: 49 years (22 64)Mean follow-up: 7 years5 revisions59 implants still in place

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

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?)

7 years14 years

Need for improved instrumentsThe cutting and drilling guides should be monoblock, in order to avoid rotational mismatch

ConclusionsThis experience supports that a purely metaphyseal anchorage of a stemless implant can provide a long lasting fixationThis type of implant is suitable even when the femoral head is destructedIt permits the use of a ceramic on ceramic bearingIt is conservative, as a primary implant can easily be used if revision is needed