Charnley-Kerboull Total Hip Replacement Long Term Results In Patients Younger Than 50 Results of a 30 years experience L Kerboull, M Hamadouche, M Kerboull.

Long term results in patients under 50 Reliability of THR outcome in young people is still being debatedReliability of THR outcome in young people is still being debated The cemented metal/PE Kerboull system is now old and someone could think that it is no more indicated for young patients in the third millenium ?The cemented metal/PE Kerboull system is now old and someone could think that it is no more indicated for young patients in the third millenium ? Results published in CORR Jan 2004Results published in CORR Jan 2004

The series 287 THR performed from 1975 to THR performed from 1975 to 1990 Randomly sorted from a cohort of 2804 patientsRandomly sorted from a cohort of 2804 patients Senior and junior surgeonsSenior and junior surgeons 222 patients, 144 females and 78 males222 patients, 144 females and 78 males Mean age : 40,1 y ( ± 8 y ; 15, y).Mean age : 40,1 y ( ± 8 y ; 15, y). Mean weight : 63 kg (± 18,2 kg ; 37 – 116 kg)Mean weight : 63 kg (± 18,2 kg ; 37 – 116 kg)

The series : preoperative diagnosis Previous surgery : 123 hips

Operative Technique Transtrochanteric approachTranstrochanteric approach Charnley-Kerboull standard implantsCharnley-Kerboull standard implants Cup all polyCup all poly CMW type 1, mixed in airCMW type 1, mixed in air Distal plugDistal plug Acetabular reconstruction in 92 hipsAcetabular reconstruction in 92 hips

Operative Technique : femoral implant Implants design SurfaceSection Neck diamete r (mm) Hips MK I PolishedQuadrangular13139 CMK 2 MattOval1351 MK III PolishedQuadrangular1027 CMK 3 MattOval1070 Polished 166 Matt 121

Methods Merle d’Aubigné and Postel clinical scoring systemMerle d’Aubigné and Postel clinical scoring system Cup : Charnley and Delee classificationCup : Charnley and Delee classification Stem : Gruen and Amstutz classificationStem : Gruen and Amstutz classification Linear Wear : Chevrot and Kerboull MLinear Wear : Chevrot and Kerboull M Cystic osteolysisCystic osteolysis Heterotopic ossificationsHeterotopic ossifications Statistical analysisStatistical analysis

Type of Loosening Socket Femoral Stem Definite loosening Migration ≥ 3 mm and/or 3° Complete radiolucent line ≥ 2 mm Subsidence ≥ 3 mm Cement mantle fracture Complete radiolucent line ≥ 2 mm Radiolucent line in Zone I ≥ 2 mm Probable loosening Complete radiolucent line < 2 mm Potential loosening Radiolucent line in 2 zones Methods : Modified Harris classification for radiological loosening

Status Mean follow-up (years) Number of hips Reviewed 16,1 ± 4,6 210 ( 73,2%) Died of unrelated causes 5,4 ± 3,1 10 (3,5%) Lost to follow-up 10,8 ± 5,1 42 (14,6%) Revised 12,6 ± 6,1 25 (8,7%) Mean follow-up : 14,5 years ( ± 5.1, 6m to 25 y) 52 hips had a follow-up greater than 20 years

Complications 3 non unions of the trochanter 1%, 1 reoperated 2 Deep infections, 1 acute treated by articular debridment and 1 chronic revised. 3 dislocations, 1 revised 1% 1 hematoma reoperated 3 heterotopic ossification grade 4, 1 reoperated 3 palsies of the peroneal nerve

Clinical results : PMA score preop postop Mean : 9,6 Mean : 17,4 83% of the hips rated excellent to very good

Radiological results : Cup loosening No loosening Definite or probable loosening Potential loosening Number of hips 23882,9%155,2%248,4% Wear > 0,1 mm/y

Radiological results : cup wear Mean femoral head penetration : 1,3 mm ± 1,5 mm (0 – 8 mm) 0,1mm/y 91 hips 196 hips 0.02 mm/y versus 0.28 mm/y P < ans

Wear related factors

Normal versus abnormal wear Factor P value Age0,7 Sexe ratio 0,2 Activity0,34 Weight0,9 Year of surgery 0,0001Factor P value Follow-up0,5 Diagnosis0,1 Cup position 0,8 Osteolysis0,0001 Surgeon0, : 0,095 mm/an 1980 : 0,158 mm/an Intrinsic properties of PE was the main related factor These changes were due to manufacturing process variations

PE Quality is the main factor Bilateral cases 17 y 18 y

Radiological results : Stem loosening No loosening Definite or probable loosening Potential loosening Number of hips 27195,1%124,2%40,7% 10 aseptic, 1 septic, 1 after a periprosthetic fracture osteolysis

Radiological loosening : stem Implants design SurfaceSectionAsepticlooseningHips MK I PolishedQuadrangular1139 CMK 2 MatteOval251 MK III PolishedQuadrangular027 CMK 3 MatteOval770 Matt vs Polished : p = 0,0001

Matt or polished surface ? Square or rounded cross section ?

Mechanical basis Fact: - Bone, cement and stem form a composite - All mentioned materials have different E-Moduli Cortex: Gpa PMMA:1.8 Gpa WHN Stainless Steel250 Gpa - All material deform differently under load this leads to micro motions

Why the polished stem became matt ? Initiation of stem loosening:Initiation of stem loosening: debonding of the cement to prosthesis interface Improvement of the bond through a matt surface

But ……… With a Matt surface –No relative movement between stem and cement possible –Micromotions result in localy debonded areas at the bone cement interface which create an abrasive medium that induce osteolisys Bone PMMA Stem

While a polished surface Allowes micro movements in the stem to cement viscoelastic interface that protect the bone cement interface Bone PMMA Stem

Does a polished cimented stem always subside ? Subsidence: Unlike other stems the CMK is not designed to subside and does not subside. « The French paradox »: Langlais, Ling, Kerboull, Sedel. JBJS Br, « The French paradox »: Langlais, Ling, Kerboull, Sedel. JBJS Br, Why ?? - We choose the stem which best fills the medullary canal - We choose the stem which best fills the medullary canal there is no space for the stem to subside. there is no space for the stem to subside. - The collar decreases the distal force applied to ciment plug - The stem does not get loose due to the cohesion forces acting on the two polished (cement/stem) surfaces.

Round or Rectangular cross section ? Rounder cross section –Prevents hook stresses at the angle –But Increased shear stresses at the interface Rectangular cross section –Might induce hook stresses –Applies compressive stresses on the cement Stems are prone to relative rotation when torque forces are applied

Round vs Rectangular M2 M1 shear stress compressive stress M1 F1 a F1 b a b

The cross section is very delicate: Too round results in problems Too edgy might result in problems (increased hoop stresses) Look for a compromise Almost rectangular with smooth angles cross section design ?

Ra 0.9  m (35  inch) MK 2 : 4 % at 15 Y. Ra 1.7  m (67  inch) CMK 3 : 21 % at 10 Y. Matt surface What was the most deleterious change Matt surface or rounded cross section

Revisions : 25 Loosening or wear : 22 7 loosened stems 7 loosened stems 10 loosened cups 5 worn cups 5 worn cups Other : 3 1 septic 1 recurrent dislocation 1 femoral fracture

Survival rate : revision 0,2,4,6, years 85,4% 95% sup : 92,4 % 95% inf : 78,4 % Suvival rate % Follow-up years

Survival rate : cup loosening age NS

Survival rate : stem loosening age NS

P= 0,0001 Survival rate : stem loosening, surface finish Suvival rate % Follow-up years 0,2,4,6, polished matt 88,5% 96,4%

Survival rate : wear dependant Wear <= 0,1 94,8 % Wear > 0,1 70,6 % P = 0,002 Suvival rate % Follow-up years

What we learnt at the end of this study The Kerboull cemented prosthesis could provide satisfactory and durable results for 20 years in 85 % of patients younger than 50 years.The Kerboull cemented prosthesis could provide satisfactory and durable results for 20 years in 85 % of patients younger than 50 years. So in our mind it remains a good solution, specially for young patient when anatomic and bony conditions are disturbed.So in our mind it remains a good solution, specially for young patient when anatomic and bony conditions are disturbed. PE wear, when higher than 0.1 mm/y, is the only unsolved problem.PE wear, when higher than 0.1 mm/y, is the only unsolved problem. PE wear is mainly influenced by PE intrinsic qualitiesPE wear is mainly influenced by PE intrinsic qualities Surface of a cemented stem must be definitely polished to protect cement and bone from excessive stresses.Surface of a cemented stem must be definitely polished to protect cement and bone from excessive stresses.

Do we need different implants for young people? When we change implant, we also experiment new problems and our rate of failure increases compared with our routine techniqueWhen we change implant, we also experiment new problems and our rate of failure increases compared with our routine technique So we must change for a good reasonSo we must change for a good reason –Bearing surfaces : may be –Type of fixation : definitely no, except if imposed by the mechanical properties of the bearing surfaces when using a new implant, If our operative technique is reliable don’t change it, if possible when using a new implant, If our operative technique is reliable don’t change it, if possible

Conclusions Proven designs are not numerous because a long time is necessary to evaluate a hip prosthesisProven designs are not numerous because a long time is necessary to evaluate a hip prosthesis Before changing try to correct the identified problemsBefore changing try to correct the identified problems Fashion, experimental studies and marketing features are not always our best friends !Fashion, experimental studies and marketing features are not always our best friends !

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