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The effect of a metal-back without a stem upon the fixation of a tibial prosthesis
The Effect of a Metal-back Without a Stem L 9 U p o n t h e F i x a t i o n o f a Tibial P r o s t h e s i s
G. T. R a i l t o n , F R C S , A. W a t e r f i e l d , F R C S , D. N u n n , F R C S , E d , a n d M . A. R. F r e e m a n ,
MD, FRCS
Abstract: Three methods of tibial component fixation without cement (as part of TKA) have been used at the London Hospital. All three methods have used the same polyethylene component fixed with two IIDP (Day) pegs. A metalback without a stem was added to the HDP in group 1. Group 2 consisted of an ttDP-only component. In group 3 a stem was added to the metal-back used in group 1. Radiological comparison showed the fixation of the polyethylene component with metal back but no stem to be inadequate; the component tilted into varus more frequently than the other configurations. It is suggested that failure was due to the increased rigidity of the metal-backed component (as compared with the HDP only) and that the rigidity (and the resultant tendency to rock) can be offset by a stem. It is concluded that.rigid (ie, metallic) tibial components should have a stem. Key words: tibial component, metal-backed component, stem.
In 1978 a m e t h o d of tibial fixation relying on two polyethylene pegs (6) was introduced for use with the Freeman/Samuelson prosthesis (Figs. IA,B). Clinical results both with and without cement were encouraging (4, 5) but concern was expressed that, without cement, the heavily loaded horizontal surface of the c o m p o n e n t might be abraded to produce HDP debris and hence osteolysis, were the prosthesis to m o v e relative to the bone (ie, were it to loosen). Since other two-pegged, metal-backed implants were reported as giving satisfactory clinical results, a metal-back was m a d e available for the Freeman/ Samuelson tibial prosthesis in 1985 to avoid this danger (Figs. 2A,B). In a parallel d e v e l o p m e n t a metal-back attached to a 120 m m stem was introduced for use as a revision prosthesis with the ICLH, and later the Free-
m a n / S a m u e l s o n prosthesis, in 1976. Satisfactory fixation results were reported using this device with PMMA u n d e r the horizontal surface (3). Accordingly, this configuration was used for s o m e primary procedures, with and without cement, from 1984 onwards (Figs. 3A,B). By 1987, a clinical impression had been gained at the London Hospital that the metal-backed prosthesis gave less satisfactory fixation results t h a n the oth'er two configurations w h e n used without cement. The metal-backed version was therefore withd r a w n and we n o w report this experience. A comparison between the other two c o m p o n e n t s based on RSA is reported elsewhere (1).
From the London Hospital Whitechapel El, London, England.
In 1981-,I 985 131 knees were primarily replaced under the care of the senior author using the s a m e operative technique, femoral and patellar prostheses
Reprint requests: M. A. R. Freeman, MD, FRCS, London Hospital Medical College, Arthritis and Rheumatism Council Building, 25-29 Ashfield Street, London E! IA, England.
Materials and Methods
$68
The Journal of Arthroplasty Vol. 5 Supplement October 1990
Fig. 1. (A) T h e a p p e a r a n c e , a n d (B) a n a n t e r o p o s t e r i o r r a d i o g r a p h of t h e p o l y e t h y l e n e c o m p o n e n t o n l y ( g r o u p 2).
T a b l e 1. T h e C o n d i t i o n o f t h e K n e e s I m m e d i a t e l y a f t e r O p e r a t i o n Tibial Component
Age Mean Range
Metal-back (Group 1)
HDP (Group 2)
64.8 years 57-77 years
65.6 years 58-73 years
2 10
1 11
Metal-back + 120 mm Stem (Group 3) 65.5 years 55-74 years
Sex
Male Female Diagnosis OA RA Mean tibiofemoral angle (Degrees Valgus) Mean % cover of proximal tibia
10 2 7.25 - 3.9 98
OA, osteoarthritis; RA, rheumatoid arthritis.
9 3 6.8 _ 2.2 99
3 9 8 4 7.6 _ 3.6 91
Metal-back in Tibial Prosthesis Fixation
9
Railton et al.
$69
ig. 2. (A) The appearance, and (B) an anteroposterior radiograph of tile polyethylene component with metal back (group
nd fixation without cement. Sixteen of these knees ad a metal-backed tibial component. One of these ;atients died within 2 years and one was revised for nfection. Of the 14 remaining knees (group 1), two ;vere revised for aseptic loosening of the tibial comPonent within 2 years of the operation. We compared the clinical and radiographic results n the remaining 12 knees in group 1 with 12 poly.thylene tibial components (group 2) and 12 comJonents having a metal back with a 120 ram-long, 9cm-diameter stem (group 3). The knees composing lroups 2 and 3 were selected from the 89 knees re)laced with one of these two tibiai configurations ind available for review so as to match those in iroup 1 with respect to the variables thought to affect ibial fixation, for example, age, sex, diagnosis, the t mmedlate postoperative alignment (5), and, as ~early as possible, proximal tibial cover (2) (Table
!).
Clinical and radiograph examinations using aneroposterior, lateral, and skyline views were carried )ut immediately after operation and at 2 years after iperation. The angle between the tibial component
and the axis of the tibia was measured. Changes in angle exceeding 3 ~ at 2 years were recorded. (The method of measurement did hot allow tilts of less than 3~ to be detected) (4).
Results The results at 2 years after operation are shown in Table 2.
Discussion The number of knees available in group 1 is small and cannot n o w be increased because the prosthesis has been withdrawn, Rather than compare these few knees with all those in the other two categories we chose to compare them with others that were selected in order to match those in group I with respect to the variables thought to affect the o u t c o m e of tibial
$70
The Journal of Arthroplasty Vol. 5 Supplement October 1990
Fig. 3. (A) Tile appearance, and (B) an anteroposterior radiograph of tile polyethylene component with metal back and stem (grpu p 3).
fixation. In this case the three groups are closely similar in this respect with, if anything, group 3 being the least satisfactory initially (Table 1). The results are based upon too few knees to be treated statistically, but there is a trend in favor of groups 2 and 3 with respect to the aseptic revision rate, tibial tilt, and pain. Since there is no evident countervailing advantage to the group 1 configuration as compared with that of group 3, we believe
that our decision to discontinue the metal-backed device without a stem was justified. Cadaver studies using other prostheses (7) have n o w confirmed our clinical impression that a stem improves the fixation of a rigid, (ie, metal-backed ) tibial prosthesis. This may be because, as Walker (8) has suggested, the increased rigidity of metal backing, as compared with an HDP prosthesis; increases the tendency for the prosthesis to rock (in an anter-
Table 2. Results at 2 Years Tibial Component
Revision rate at 2 years Number tilting more than 3 degrees in knees not revised Pain requiring analgesia in knees not revised
Metal-back + 120 m m Stem (Group 3)
Metal-back (Group 1)
ttDP (Group 2)
2/14 (14.2%) 4(33%)
0/48 (0%) 1(8%)
0/41 (0%) 0(0%)
1(8%)
0(0%)
0(0%)
Metal-back in Tibial Prosthesis Fixation
o p o s t e r i o r a n d v a r u s / v a l g u s sense) a n d t h a t t h e stem, acting like t h e keel o f a ship, c o m p e n s a t e s for this d i s a d v a n t a g e . I n c o n c l u s i o n , therefore, w e b e l i e v e that rigid tibial c o m p o n e n t s s h o u l d h a v e a stem.
References 1. Albrektsson BE J, Ryd L, Carlsson LV, Freeman MAR et al: The effect of a stem on the tibial component: a roentgen stereophotogrammetric analysis of stemmed and non-stemmed, uncemented tibial components in clinically successful Freeman-Samuelson knee arthroplasties. J Bone Joint Surg 72B:252, 1990 2. Bargren JH, Day WH, Freeman MAR, Swanson SAV: Mechanical tests on the tibial components of nonhinged knee prostheses. J Bone Joint Surg 60B:256, 1978
9
Railton et al.
$71
3. Benin KC, Freeman MAR, Ratcliffe SS et al: Stemmed revision arthroplasty for aseptic loosening in total knee replacement. J Bone Joint Surg 67B:242, 1985 4. Blaha JD, Insler HP, Freeman MAR et al: The fixation of a proximal tibial polyethylene prosthesis without cement. J Bone Joint Surg 64B:326, 1982 5. Brach Del Preyer EM, MacPherson IS, Freeman MAR, Samuelson KM: Esperienza clinica con la protesi di ginnocchio Freeman-Samuelson (1980-85). G Ital Ortopedia e Traumatologia Vol XIII:4:423, 1988 6. Day WH, Brown GC, Revell PA, Freeman MAR: Cementless fixation of tibial prostheses: A method for obtaining immediate fixation of polyethylene to cancellous bone. Trans Orthop Res Soc 4:223, 1979 7. Volz RG, Nizbet JK, Lee RW, McMustry MG: The mechanical stability of various non-cemented tibial components. Clin Orthop 226:38, 1988 8. Walker PS, Greene D, Bendow M et al: Fixation of the tibial components of knee prostheses. Trans Orthop Res Soc 4:95, 1975
G. T. R a i l t o n , F R C S , A. W a t e r f i e l d , F R C S , D. N u n n , F R C S , E d , a n d M . A. R. F r e e m a n ,
MD, FRCS
Abstract: Three methods of tibial component fixation without cement (as part of TKA) have been used at the London Hospital. All three methods have used the same polyethylene component fixed with two IIDP (Day) pegs. A metalback without a stem was added to the HDP in group 1. Group 2 consisted of an ttDP-only component. In group 3 a stem was added to the metal-back used in group 1. Radiological comparison showed the fixation of the polyethylene component with metal back but no stem to be inadequate; the component tilted into varus more frequently than the other configurations. It is suggested that failure was due to the increased rigidity of the metal-backed component (as compared with the HDP only) and that the rigidity (and the resultant tendency to rock) can be offset by a stem. It is concluded that.rigid (ie, metallic) tibial components should have a stem. Key words: tibial component, metal-backed component, stem.
In 1978 a m e t h o d of tibial fixation relying on two polyethylene pegs (6) was introduced for use with the Freeman/Samuelson prosthesis (Figs. IA,B). Clinical results both with and without cement were encouraging (4, 5) but concern was expressed that, without cement, the heavily loaded horizontal surface of the c o m p o n e n t might be abraded to produce HDP debris and hence osteolysis, were the prosthesis to m o v e relative to the bone (ie, were it to loosen). Since other two-pegged, metal-backed implants were reported as giving satisfactory clinical results, a metal-back was m a d e available for the Freeman/ Samuelson tibial prosthesis in 1985 to avoid this danger (Figs. 2A,B). In a parallel d e v e l o p m e n t a metal-back attached to a 120 m m stem was introduced for use as a revision prosthesis with the ICLH, and later the Free-
m a n / S a m u e l s o n prosthesis, in 1976. Satisfactory fixation results were reported using this device with PMMA u n d e r the horizontal surface (3). Accordingly, this configuration was used for s o m e primary procedures, with and without cement, from 1984 onwards (Figs. 3A,B). By 1987, a clinical impression had been gained at the London Hospital that the metal-backed prosthesis gave less satisfactory fixation results t h a n the oth'er two configurations w h e n used without cement. The metal-backed version was therefore withd r a w n and we n o w report this experience. A comparison between the other two c o m p o n e n t s based on RSA is reported elsewhere (1).
From the London Hospital Whitechapel El, London, England.
In 1981-,I 985 131 knees were primarily replaced under the care of the senior author using the s a m e operative technique, femoral and patellar prostheses
Reprint requests: M. A. R. Freeman, MD, FRCS, London Hospital Medical College, Arthritis and Rheumatism Council Building, 25-29 Ashfield Street, London E! IA, England.
Materials and Methods
$68
The Journal of Arthroplasty Vol. 5 Supplement October 1990
Fig. 1. (A) T h e a p p e a r a n c e , a n d (B) a n a n t e r o p o s t e r i o r r a d i o g r a p h of t h e p o l y e t h y l e n e c o m p o n e n t o n l y ( g r o u p 2).
T a b l e 1. T h e C o n d i t i o n o f t h e K n e e s I m m e d i a t e l y a f t e r O p e r a t i o n Tibial Component
Age Mean Range
Metal-back (Group 1)
HDP (Group 2)
64.8 years 57-77 years
65.6 years 58-73 years
2 10
1 11
Metal-back + 120 mm Stem (Group 3) 65.5 years 55-74 years
Sex
Male Female Diagnosis OA RA Mean tibiofemoral angle (Degrees Valgus) Mean % cover of proximal tibia
10 2 7.25 - 3.9 98
OA, osteoarthritis; RA, rheumatoid arthritis.
9 3 6.8 _ 2.2 99
3 9 8 4 7.6 _ 3.6 91
Metal-back in Tibial Prosthesis Fixation
9
Railton et al.
$69
ig. 2. (A) The appearance, and (B) an anteroposterior radiograph of tile polyethylene component with metal back (group
nd fixation without cement. Sixteen of these knees ad a metal-backed tibial component. One of these ;atients died within 2 years and one was revised for nfection. Of the 14 remaining knees (group 1), two ;vere revised for aseptic loosening of the tibial comPonent within 2 years of the operation. We compared the clinical and radiographic results n the remaining 12 knees in group 1 with 12 poly.thylene tibial components (group 2) and 12 comJonents having a metal back with a 120 ram-long, 9cm-diameter stem (group 3). The knees composing lroups 2 and 3 were selected from the 89 knees re)laced with one of these two tibiai configurations ind available for review so as to match those in iroup 1 with respect to the variables thought to affect ibial fixation, for example, age, sex, diagnosis, the t mmedlate postoperative alignment (5), and, as ~early as possible, proximal tibial cover (2) (Table
!).
Clinical and radiograph examinations using aneroposterior, lateral, and skyline views were carried )ut immediately after operation and at 2 years after iperation. The angle between the tibial component
and the axis of the tibia was measured. Changes in angle exceeding 3 ~ at 2 years were recorded. (The method of measurement did hot allow tilts of less than 3~ to be detected) (4).
Results The results at 2 years after operation are shown in Table 2.
Discussion The number of knees available in group 1 is small and cannot n o w be increased because the prosthesis has been withdrawn, Rather than compare these few knees with all those in the other two categories we chose to compare them with others that were selected in order to match those in group I with respect to the variables thought to affect the o u t c o m e of tibial
$70
The Journal of Arthroplasty Vol. 5 Supplement October 1990
Fig. 3. (A) Tile appearance, and (B) an anteroposterior radiograph of tile polyethylene component with metal back and stem (grpu p 3).
fixation. In this case the three groups are closely similar in this respect with, if anything, group 3 being the least satisfactory initially (Table 1). The results are based upon too few knees to be treated statistically, but there is a trend in favor of groups 2 and 3 with respect to the aseptic revision rate, tibial tilt, and pain. Since there is no evident countervailing advantage to the group 1 configuration as compared with that of group 3, we believe
that our decision to discontinue the metal-backed device without a stem was justified. Cadaver studies using other prostheses (7) have n o w confirmed our clinical impression that a stem improves the fixation of a rigid, (ie, metal-backed ) tibial prosthesis. This may be because, as Walker (8) has suggested, the increased rigidity of metal backing, as compared with an HDP prosthesis; increases the tendency for the prosthesis to rock (in an anter-
Table 2. Results at 2 Years Tibial Component
Revision rate at 2 years Number tilting more than 3 degrees in knees not revised Pain requiring analgesia in knees not revised
Metal-back + 120 m m Stem (Group 3)
Metal-back (Group 1)
ttDP (Group 2)
2/14 (14.2%) 4(33%)
0/48 (0%) 1(8%)
0/41 (0%) 0(0%)
1(8%)
0(0%)
0(0%)
Metal-back in Tibial Prosthesis Fixation
o p o s t e r i o r a n d v a r u s / v a l g u s sense) a n d t h a t t h e stem, acting like t h e keel o f a ship, c o m p e n s a t e s for this d i s a d v a n t a g e . I n c o n c l u s i o n , therefore, w e b e l i e v e that rigid tibial c o m p o n e n t s s h o u l d h a v e a stem.
References 1. Albrektsson BE J, Ryd L, Carlsson LV, Freeman MAR et al: The effect of a stem on the tibial component: a roentgen stereophotogrammetric analysis of stemmed and non-stemmed, uncemented tibial components in clinically successful Freeman-Samuelson knee arthroplasties. J Bone Joint Surg 72B:252, 1990 2. Bargren JH, Day WH, Freeman MAR, Swanson SAV: Mechanical tests on the tibial components of nonhinged knee prostheses. J Bone Joint Surg 60B:256, 1978
9
Railton et al.
$71
3. Benin KC, Freeman MAR, Ratcliffe SS et al: Stemmed revision arthroplasty for aseptic loosening in total knee replacement. J Bone Joint Surg 67B:242, 1985 4. Blaha JD, Insler HP, Freeman MAR et al: The fixation of a proximal tibial polyethylene prosthesis without cement. J Bone Joint Surg 64B:326, 1982 5. Brach Del Preyer EM, MacPherson IS, Freeman MAR, Samuelson KM: Esperienza clinica con la protesi di ginnocchio Freeman-Samuelson (1980-85). G Ital Ortopedia e Traumatologia Vol XIII:4:423, 1988 6. Day WH, Brown GC, Revell PA, Freeman MAR: Cementless fixation of tibial prostheses: A method for obtaining immediate fixation of polyethylene to cancellous bone. Trans Orthop Res Soc 4:223, 1979 7. Volz RG, Nizbet JK, Lee RW, McMustry MG: The mechanical stability of various non-cemented tibial components. Clin Orthop 226:38, 1988 8. Walker PS, Greene D, Bendow M et al: Fixation of the tibial components of knee prostheses. Trans Orthop Res Soc 4:95, 1975