Long-term results of Charnley arthroplasty

The Journal of Arthroplasty

Long-term

Results

of Charnley

A 12-16-Year

Follow-up

Vol. 9 No. 4 1994

Arthroplasty Study

G. Garellick, MD, P. Herberts, MD, C. Striimberg, MD, and H. Malchau, MD

Abstract: A retrospective, long-term study was initiated to analyze clinical function, failures, and radiographic status in 95 Charnley low-friction arthroplasties performed during 1973-1977. Only patients with primary osteoarthrosis were included, and no patients were lost during the follow-up period. At the follow-up evaluation, 39 patients (41 hips) were deceased. Ten hips were revised (including 3 of the deceased patients), leaving 47 hips available for follow-up evaluation. Four patients (5 hips) were interviewed by telephone, and the remaining 42 hips were examined by the authors. With a mean follow-up period of 14 years, many of the patients had excellent pain relief with a mean Harris hip score for pain of 42 points (maximum, 44 points). Ninetyfour percent of the patients were satisfied with their results. The survivorship for all 95 hips was 92% at 10 years and 83% at 16 years. Follow-up radiographs revealed that three (7%) of the femoral components were definitively loose, but only two (5%) of the acetabular components were probably loose. Forty-three percent of the hips had signs of polyethylene wear of the cup. The clinical and radiographic outcome is, in spite of an early cementing technique, very good in this long-term follow-up study. Key words: long-term results, Charnley low-friction arthroplasty, survivor analysis.

defined patient population operated on with standardized technique and followed for a long period of time.

Aseptic loosening is still the most common longterm failure of total hip arthroplasty. Revision rates, after 10 years, vary from 5 to 30% in certain subsets, notably young men.’ After the introduction of second-generation cementing techniques’ in the late 197Os, several centers have reported decreasing rates of implant loosening, especially for the femoral com-

Status of the 45 Living Patients Materials

ponent. 2-h Loosening of the acetabular component is an increasing problem, in spite of modern cementing techniques.4.7,8 Particulate

polyethylene,

From 1973 to 1977, a total of 95 Charnley lowfriction arthroplasties (LFAs) were performed in 90 patients. In order to obtain a homogeneous population, only patients with primary osteoarthrosis were included. All patients were operated on using Charnley’s original method, that is, the patient was in the supine position, the acetabulum was hand reamed, and a trochanteric osteotomy was performed. The average age of the patients at surgery was 67 years (range, 49-83 years). There were 58 women (61 hips) and 32 men (34 hips). Antibiotic prophylaxis was introduced in 1974. A conventional operating room was used.

polymethyl

methacrylate (PMMA), and metal debris is a potential risk for failure, even to a well-fixed implant. Particles of any kind around an implant stimulate macrophagic activity, leading to osteolysis and loosening.‘-‘a The aims of this retrospective study are to evaluate

the clinical results and radiographic

and Methods

status of a well-

From the University of Giiteborg, Department of Orthopardics, Sahlgren Hospital, GBteborg, Sweden. Reprint requests: Dr. GGran Garellick, Department of Orthopaedies, Sahlgren Hospital, S-413 45 GBteborg, Sweden.

333

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Vol. 9 No. 4 August

1. Number of Patients and Hips

Table No. at Start of Study Patients Hips

90 95

Deceased at Followup Evaluation (Nonrevised)

Deceased at Followup Evaluation (Revised)

36 3x

Table

Before surgery (n = 95) (n = 47) At follow-up evaluation

Revised at Follow-up Evaluation

3 3

At the follow-up evaluation, 39 patients were deceased (41 hips). Ten hips were revised (1 bilaterally). Three of the revised patients were among the 39 that were deceased. No patient was lost during the follow-up study. Forty-five patients (34 women and 11 men) with 47 nonrevised hips (36 hips in women and 11 in men) were available for evaluation (Table 1). Four (5 hips) of these patients were very old (>90 years) or suffering from senility, and they or their relatives were interviewed by telephone. These patients were included in part of the study. The remaining 41 patients (42 hips) were examined by us. Clinical function was evaluated according to the Harris hip scoring system.14 The average age of the patients at the follow-up evaluation was 78 years (range, 66-96 years). The average follow-up period was 14 years (range, 12-16 years). We classified the patients into clinical categories according to Charnley I5 (Table 2). As expected, there was a predomination of patients in category C. Standard anteroposterior (AP) and lateral radiographs of all hips were taken. Anteroposterior radiographs of the pelvis were not included because they were not part of our routine at that time. Variations in magnification were corrected by using the 22.2 mm caput as a reference. The following parameters were registered for the femoral component: AP orientation (varus, valgus, or neutral), lateral alignment (indicating prosthesis-inner cortex contact), and cement-mantle appearance, that is, thickness of the cement in the seven zones according to Gruen et al. ” We analyzed the follow-up radiographs for radiolucency or cement-prosthesis separation in the Gruen zones, cement fracture, migration, or calcar resorption. For the acetabular component, the following parameters were registered: inclination and cup height with reference to the teardrop line” and

Unilateral

1994

fl

$5

7

17

for

cement-mantle thickness in the three zone5 according to DeLee and Charnley.” Follow-up radiographs were analyzed for the presence of bone-cement demarcations or migration, and the rate ofpolyethylene wear was estimated according to Livermore et al. “I We had margins for what we classified as component migration. Only migration greater than 5 mm was classified as definitive migration. Continuous bone-cement demarcation greater than 1 mm was registered as radiolucency. We defined radiographic loosening according to Harris et al.;’ and classified bone destruction according to Gustilo and Pasternak.“’ Clinical Results At the follow-up evaluation, IO hips were revised or extracted. Three patients had a secondary, late deep infection. One patient was revised, and the prosthesis was extracted in another. The third patient was treated with life-long antibiotics. Surgery was contraindicated because of cardiac disease.Eight patients were revised for aseptic loosening after 5 (4 hips), 7, 11, 12, and 13 years. Two were total revisions, three stem revisions, two cup revisions, and one extraction. At the follow-up evaluation, the four (5 hips) patients interviewed by telephone were classified as category C. None of these patients presented with pain, and their pain score was 44 points. These four patients were excluded in other clinical evaluations, but were included in the survival analyses. The mean Harris hip score was 82 points (range, 35-99 points) at the follow-up evaluation (Fig. l), and the mean pain score was 42 points (range, 20-44 points) (Fig. 2). Two patients with the lowest Harris score had a radiographically definitely loose stem.

2. Clinical Categories

Hip Disease (A) W) 38 17

Remaining Evaluation

Bilateral

Hip Disease (B) W) 42 26

Multiple Joint Disease or Other Condition Impairing Walking ((3 (%) 20 57

Charnley LFA

l

Garellick et al.

335

number

Fig. 1. Harris hip score (range, 0- 100 points) for the 41 (42 hips) patients examined. The two lowest scores are the two patients with clinically and radiographically loose stems. 5

15

25

35

45

55

65

75

85

95

score meanvalue= ES

(35-99) n=42

Fig. 2. Painscore(range,O-44

points) for the 41 (42 hips) examined and 4 (5 hips) telephone-interviewed patients. The two lowest scoresare the patients with loose femoral components. 0

1 (0)

2 (10)

3 (20)

4 (30)

5 (40)

6 (44)

score meanvalue= zx

According to the Harris hip score, 69% of the patients were rated as good or excellent (range, 80- 100 points). If only pain was evaluated, 9 1% were rated as good or excellent (range, 40-44 points). Ninetyfour percent were satisfied, 4% were uncertain, and 2% were unsatisfied with the result. The mean Harris hip score varied, from 92 points in Charnley’s category A to 77 points in category C (Table 3). There

Table

3. Clinical Results: Scoring Related

to Clinical

Category Scoring

Category

System Harris Pain

hip score (n = 42) score (11 = 47)

A

Category B

Category C

92

85

77

33.5

41.7

41.9

(20-44) n=47

were no differences in the pain score between the clinical categories (Table 3). Radiographic

Results

When the postoperative radiographs were analyzed, it was found that 12% of the stems were positioned in varus and 14% in valgus. In 50% of the hips, the femoral component had contact with the inner cortex both proximally and distally. Cement thickness less than 2 mm was registered in the Gruen zones, and the results are given in Figure 3. As expected, the old cementing technique of digital packing without a restrictor often produced a thin cement mantle distally, and in some cases there was no cement at all in Gruen zones 3-5. Ten percent of the cups had an inclination exceeding 60”, and 14% were proximally positioned ( 1.5 cm above the teardrop). The cement mantle was less

336

The Journal of Arthroplasty

Vol. 9 No. 4 August 1994

i 29% /

Fig. 4. Cement thickness(<2mm) around the acetabular

26%

33%

Fig. 3. Cement thickness (<2mm) around the femoral

component after surgery. The digital packing technique often gave a thin cement mantle, and in somecases,no cement was observedat all in Gruen zones 3-5.

than 2 mm in 33% of the hips in zone 2 and in 29% in zone 3, that is, the cups were often pressed to the bottom of the acetabulum during the cementing procedure (Fig. 4). On the follow-up radiographs, we found that bone-cement lucency around the femoral component most commonly occurred in zones 1, 2, and 3, and only one hip had a 100% continuous radiolucency (this stem had a subsidence > 5 mm). Three hips had a cement-prosthesis separation in zone 1 and a subsidence greater than 5 mm. Two of these hips had a visible cement crack in the cement mantle. In 10 hips, we noted calcar resorption between 2 and 22 mm. Two hips had a 100% continuous radiolucency in all three zones around the acetabular component. None of the cups migrated more than 5 mm. Fortythree percent of the cups had signs of polyethylene wear (26% approximately I mm and 17% 2-3 mm).

componentafter surgery.The old cup had no distancepegs and was often pressedto the bottom of the acetabulum. One third of the componentshad thin cement in DeLeeCharnley zone 2.

Evaluation of the follow-up radiographs revealed three definitely loose femoral components and two probably loose acetabular components, according to the Harris’ criteria for component loosening. None of the loose hips had extensive bone destruction, and all were classified as Gustilo grade 1.“’ Two patients with definitely loose stems had clinical symptoms and were revised later in the follow-up year. The third patient had no symptoms and did not want a revision. The two patients with probably loose acetabular component had no symptoms.

Survival Materials

Analyses

of All Patients

and Methods

Survival analyses, according to Dobbs,” were performed on all 95 patients. Revision or extraction of one or both of the prosthetic components was used as the endpoint for failure. The two loose stems were included as revisions. The conservatively treated deep infection and the patient with a loose stern without symptoms were not considered failures since no prosthetic component was revised.

Results The 1O-year survivorship was 92% and at 16 years it was 83% (Table 4, Fig. 5). At the follow-up evaluation, 43% of the patients were deceased.

Charnley LFA Table

Interval Since Operation Wars)

O-I I-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 IO-11 11-12 12-13 13-14 14-15 15-16 16-17

4. Dobbs’21Analysis of All Patients No.at Start

of

Interval 95 92 88 87 84 83 79 77 68 68 65 65 59 55 52 51 46

Number Failed

Percentage Number of Deceased Survivors

-

100

3 4 1

-

1 1

2

4

97.7 97.7 93.0 93.0 91.7 91.7 91.7 91.7 90.1 88.5 86.9 86.9 83.4

-

-

2 8 0 3

I -

100 100 100

-

1 1 1 2 -

5

3 2 1 3 1

If only revisions due to aseptic loosenings were analyzed, the 1O-year survival rate was 94% and the 16-year rate was 85% (Fig. 5). The survival rates of the stem and cup were 96% each at 10 years and 87 and 93%, respectively, at 16 years.

Discussion There is wide variation in the methods used for the evaluation of the results after total hip arthroplasty. The need for a standardized assessment of the clinical and radiographic results after hip arthroplasty is obvious. ** Long-term results (> 10 years) of Charnley LFAs vary from 5 to 33% for failures, L5,23--27 depending on the definition of failure.

5. Survival analysis according to Dobbs,2’with revision or extraction as the endpoint for failure. Separate analysesof all revisions (including infections) and of aseptic loosening are shown. The dotted line showsthe mortality.

Garellick et al.

l

We compared our results to those reported in the literature for LFAs followed for more than 10 years. Failure is defined as removal or revision, and includes infections (Tables 5, 6). The failure rate in the literature varies from 6 to 16%. Some reports are difficult to evaluate because the number of patients lost during the follow-up evaluation is not reported. The pain relief of our 47 hips was excellent after an average follow-up period of 14 years, and 94% of the patients were satisfied with the result. According to the Harris hip score, only 69% of the patients had excellent or good results. This illustrates the difficulty in reporting the results after total hip arthroplasty. If a score system is used, it is necessary to correlate it to patient age, sex, diagnosis, level of activity, and clinical category. 2XAt the follow-up evaluation, the average age of the patients was 78 years and almost 60% were in Charnley category C. In such a population, it is obvious that the Harris hip score would be low in spite of the fact that the patients are pain-free and satisfied with the replaced hip. Activities of daily living is given great deal of weight in most hip scores. In the Harris hip scoring system, the activities of daily living function accounts for 47 of 100 points. A simplified score, including pain relief and satisfaction, would probably be a more appropriate way to measure and compare long-term results in an elderly patient population. The radiographic study gave a surprisingly good result. We arc aware that the conventional radiographic method is a rough method for measuring component loosening. The pre- and postoperative radiographs taken during 1973-1976 were of variable quality, and no standardized or AP radiographs of the pelvis were taken. Therefore, no component was considered as migrated unless we could measure 5 mm of movement. Using what is now recognized as an unsophisticated

Fig.

-~.l---~-.

SOL0

--

2

4

~~--~.-~78

6

all

revisions

-+

aseptic

10

postoperative +

337

~.

12

year

loosening

S

r. 14

mortality

~

J 16

338

The Journal of Arthroplasty

Vol. 9 No. 4 August 1994 1003

percent survivors I 9 z ” 3 -

kk\ 95

(

: 90 j

Fig. 6. Survival analysis of the femoral and acetabular components, respectively. Only aseptic loosening is shown.

85 !

-r

r-

4

6

8

10

postoperative

or old cementing technique and with several implants malpositioned, just 7% (3 hips) of the stems were definitively loose and 5% (2 hips) of the cups probably loose after 12- 16 years. One explanation could be that of the 37 radiographically stable hips, 31 were in women and only 6 were in men. The average weight in this group was 67 kg. Older women with low levels of activity and weight are known to be at a low risk for aseptic loosening. ’ Another explanation is that these patients were followed regularly for many years and were recommended to undergo revision when loosening was first evident on the radiograph.

Table 5. Long-term No. of Patients Studied

Author McCoy et al. ( 1988)L4 Wroblewski ( 1986)3’ Older (1986)" Dal1 et al. (1986)” Welch et al. ( 1988) ” Skeie ct al. (1991)“’

Table 6.

Author Jacobson et al. ( 1990)” Wejkner et al. (1988)35 Johnsson et al. ( 1988)” Cede11 ( 199 1) 37 This study

Follow-up

100

100 629

Long-term

Follow-up No. of Patients Studied 70

180 377

149 95

14

16

The etiology of aseptic loosening is multifactorial. According to one theory, wear particles of polyethylene, PMMA, and metal increase with time and stimulate macrophagic activity, osteolysis, and loosening.‘-’ 3 We found a high percentage of hips with an inadequate, thin cement mantle and direct contact between the prosthesis and inner cortex. Many hips had radiographic signs of polyethylene wear as well. Almost all of the hips had at least one of these ncgative factors for developing wear particles, but in spite of that, we found that 37 of 42 hips were radiographically stable and without granulomas after 12-l 6

Data of Charnley Low-friction Length of Follow-up Period Wears)

Arthroplasties

Percentage

Lost During Period

Failure Rate W-J

Follow-up Don’t Don’t Don’t Don’t

15 17 12 I2 16 II

426 153 98

12

year

know know know know

6 0 6 14 16 7

3 0

Data of Charnley Low-friction Length of Follow-up Period (years)

Arthroplasties:

Swedish

Percentage Lost During Follow-up Period

Reports Failure Rate (%)

12 10-13

3

9

3

16

4-14 15 14

0 7 0

13 I I I3

Charnley

years. None of the five hips with definitely or probably loose components had marked osteolysis. It appears that the fixation obtained was adequate for this specific implant, and Charnley’s idea about low friction giving a reduced torque on the components seems equally true today. Twenty-four percent of the hips had calcar resorption, and all except one of these hips had simultaneous polyethylene wear. Comparison between different studies would be easier if survival analyses were used routinely. Since they are not, the definition of failure or its endpoint is of critical importance. An implant that is still in place is not a complete definition of success, but is probably the best one for reporting long-term results, especially in multicenter studies.2’ In the survival analysis for aseptic loosening, we had a 94% survival rate after 10 years and 85% after 16 years. McCoy et a1.14 presented a 15-year followup study of 100 Charnley LFAs, and their Dobbs’ analysis gave similar results: 95% survival rate after 10 years and 93% after 16 years. Skeie et aL3” reported a lo-15-year follow-up study of 629 cases, with a 94% survival rate after 10 years and 88% after 16 years. Their analysis included some deep infections. It therefore seems reasonable to conclude that about 6% of total hip arthroplasties will be revised for aseptic loosening at 10 years. This finding, when early technique and a well-designed implant were used, was also reported from the National Register Study in Sweden.’ Prior to the introduction of newer techniques, such as cementless fixation, in patients over the age of 60-65 years, orthopedic surgeons have to consider these results. We have compared our observed failures to our estimated failures (Table 7). The difference between observed and estimated failures is due to mortality since we did not lose any patients during the followup period. After an average follow-up period of 14 years, we had 10 revisions because of aseptic loosening. Eight of these had an exchange of the femoral component and five of the acetabular component. Radiographic study revealed two cups with probable loosening without clinical symptoms, and consequently, we did not find any accelerated loosening of the acetabu-

7

IO

I‘,

16

Overall

failure%.

including

infections.

Estimated (According

Failures to Dobbsz’) (“h)

1.

2.

3.

4.

5.

6.

et al.

339

Ahnfelt L, Herberts P, Malchau H, Andersson GBJ: Prognosisof total hip replacement:a Swedishmulticenter study of 4,664 revisions. Acta Orthop Stand Suppl238, 1990 Harris WA, McCarthy JC, O’Neill DA: Femoralcomponent loosening using contemporary techniquesof femoral cementfixation. J Bone Joint Surg 64A: 1063. 1982 Harris WH, McGann WA: Looseningof the femoral componentafter useof the medullary-plug cementing technique. J Bone Joint Surg 68A:1064, 1986 Mulroy RD, Harris WH: The effect of improved cementing techniqueson component looseninKin total hip replacement: an 1l-year radiographic review. J Bone Joint Surg 72B:757, 19Y0 RobertsDW, PossR, Kelley I<: Radiographicc,omparisonof cementingtechniquesin total hip arthroplasty. J Arthroplasty 1:241, 1986 Russoti GM, Coventry MB, Stauffer RN: Cemented total hip arthroplasty with contemporary techniques: a five-year minimum follow-up study. Clin Orthop 735:141,

7.

9.

8 17

Garellick

References

8.

Observed Failures W)

l

Iar component during the late part of the follow-up period as predicted by many authors.“,L6.27 Recent reports by Mulroy and Harris4 and Ritter et al.‘,’ revealed increasing acetabular component loosening after 5 years, in spite of contemporary cementing techniques. They used femoral components with a head diameter of 28 mm or more and a high percentage of metal-backed cups. A head diameter greater than 28 mm is correlated to higher volumetric wear.” An increasing head diameter and metal backing also gave a much thinner layer of polyethylene compared to the LFA cup. These factors can possibly explain the high percentage of acetabular loosening in this study. We think that our earliest LFAs have performed remarkably well after 12-16 years. With contemporary cementing techniques, the long-term results will probably be even better.“-” Cemented hip arthroplasty continues to be the treatment of choice in older and relatively inactive patients.

Table 7. Observed versus Estimated Failures Length of Follow-up Period (years)

LFA

10.

1988

Rittcr MA, Keating EM, Faris PM, Brugo G: Mctalhacked acetabular cups in total hip arthroplasty. J Bone Joint Surg 72A:672, 1YYO Ritter MA, FarisPM, Keating EM, Brugo G: Influential factors in cemented acetabular cup loosening. J Arthroplasty 7:365, 1992 Anthony PP.Gie GA, Howie CR, Ling RSM: Localised endostalbone lysis in relation tv the femoral components of cemented total hip arthroplasties. J Bone Joint Surg 72B:971, 1900 Horowitz SM, Gautsch TL, Frondoza CG, Riley L: Macrophage exposure to polymethyl merhacrylate

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Vol. 9 No. 4 August

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