Charnley low-frictional torque arthroplasty
in patients under the age of 51 years
FOLLOW-UP TO 33 YEARS
B. M. Wroblewski, P. D. Siney, P. A. Fleming
From Wrightington Hospital, Wigan, England
etween November 1962 and December 1990 a
group of 1092 patients, 668 women and 424 men,
under the age of 51 years at the time of surgery,
underwent 1434 primary Charnley low-frictional
torque arthroplasties and are being followed up
indefinitely. Their mean age at operation was 41 years
(12 to 51). At the latest review in June 2001 the mean
follow-up had been for 15 years 1 month. Of the 1092
patients 54 (66 hips) could not be traced, 124 (169
hips) were known to have died and 220 (248 hips) had
had a revision procedure. At a mean follow-up of 17
years and 5 months, 759 patients (951 hips) are still
attending. In this group satisfaction with the outcome
is 96.2%.
The incidence of deep infection for the whole group
was 1.67%. It was more common in patients who had
had previous surgery (hemi- and total hip
arthroplasties excluded), 2.2% compared with 1.5% in
those who had not had previous surgery, but this
difference was not statistically significant (p = 0.4).
There were fewer cases of deep infection if
gentamicin-containing cement was used, 0.9%
compared with 1.9% in those with plain acrylic
cement, but this was not also statistically significant
(p = 0.4). There was a significantly higher rate of
revision in patients who had had previous hip surgery,
24.8% compared with 14.1% in those who had not
had previous surgery (p < 0.001).
At the latest review, 1.95% are known to have had
at least one dislocation and 0.4% have had a revision
for dislocation. The indication for revision was aseptic
loosening of the cup (11.7%), aseptic loosening of the
stem (4.9%), a fractured stem (1.7%), deep infection
(1.5%) and dislocation (0.4%).
B
B. M. Wroblewski, FRCS, Professor of Orthopaedic Biomechanics, Consultant Orthopaedic Surgeon
P. D. Siney, BA, Senior Research Fellow
P. A. Fleming, Research Assistant
The John Charnley Research Institute, Wrightington Hospital, Hall Lane,
Appley Bridge, Nr Wigan WN6 9EP, UK.
Correspondence should be sent to Professor B. M. Wroblewski.
©2002 British Editorial Society of Bone and Joint Surgery
0301-620X/02/410293 $2.00
540
With revision for any indication as the endpoint the
survivorship was 93.7% (92.3 to 95.0) at ten years,
84.7% (82.4 to 87.1) at 15 years, 74.3% (70.5 to 78.0)
at 20 years and 55.3% (45.5 to 65.0) at 27 years, when
55 hips remained ‘at risk’.
J Bone Joint Surg [Br] 2002;84-B:540-3.
Received 17 June 1999; Accepted after revision 12 October 2001
When Charnley introduced the low-frictional torque arthroplasty (LFA) into clinical practice he selected a group of
patients who were to be followed up indefinitely. He initiated this prospective study in November 1962, when highmolecular-weight polyethylene (HMWPE) was first
introduced as material for the socket. The series was closed
1
at the end of December 1965. Although popularly known
as the ‘first 500’ it included all operations carried out
during this period of 38 months. There were 905 primary
LFAs: 426 were primary LFAs, 336 had a cemented stem
with an uncemented metal-backed press-fit cup, 22 had a
polytetrafluoroethylene (PTFE) cup with a cemented stem
revised to an uncemented metal-backed cup and 121 had a
PTFE cup revised to a cemented cup. With time as the
numbers dwindled it became clear that a new group of
younger patients had to be introduced prospectively. This
2
decision, taken in 1974, proved to be correct because
when Charnley published his results at 12 to 15 years in
1979 only 77 LFAs (8.5%) of the original ‘first 500’ group
3
could be reviewed, and by 1983 only 42 (4.6%)
remained.
Patients and Methods
Patients undergoing a Charnley LFA between November
1962 and December 1990 were included in an indefinite
follow-up study in which the only criterion was age less
than 50 years at the time of LFA. All revisions from hemiand total hip arthroplasties were excluded, as were the
patients in whom either the design, material or surgical
technique did not conform to the standard protocol as
practised at that stage of the evolution of the operation.
Routine follow-up was at three months and then annually,
but with increasing follow-up and experience it was possible to ‘tailor’ the review for individual patients according
THE JOURNAL OF BONE AND JOINT SURGERY
CHARNLEY LOW-FRICTIONAL TORQUE ARTHROPLASTY IN PATIENTS UNDER THE AGE OF 51 YEARS
4,5
to the radiological appearances, the level of activity of
6
7
the patient or the rate of wear of the cup measured as
8
penetration. The clinical outcome was graded as described
9
by Merle d’Aubigné and Postel and modified by Charn10
ley. Over time a number of aspects became apparent. The
collection and processing of the information were becoming a daunting task, and a dedicted unit, the John Charnley
Research Institute, was established for the purpose. When
the information revealed specific issues such as fracture of
11
7
the stem or wear of the cup and loosening, each resulting
modification of materials, design or surgical technique
became the basis of a separate prospective study requiring
an increasing period of follow-up.
Two further aspects of this study must be appreciated.
First, the numbers in this group were dwindling and secondly the volume of information available could not be
presented in either a single communication or in a simple
form. We therefore present the clincal results and survivor12
ship analysis. Since we are continuing our policy of
13
advising early revision for failure we have used this as
the endpoint in the survivorship analysis, defining it as
exchange or removal of one or both components. The
results are reliable since there remain, as recommended by
14
Lettin, Ware and Morris, more than 40 hips still at risk at
the endpoint of the survivorship curve.
Results
There were 668 women and 424 men with a mean age of 41
years (12 to 51) and a mean weight of 65 kg (30 to 108).
They had 1434 LFAs. Of the 342 patients (31.3%) who had
bilateral LFAs, in 98 (9%) both hips had been replaced
under the same general anaesthetic while in 244 (22.3%)
both had been replaced by December 1990. The underlying
pathology of the hip and the type of previous operations are
shown in Table I. All LFAs had been carried out in a cleanair enclosure using total-body-exhaust suits, the development of which had been finalised in 1970. The
transtrochanteric approach was used routinely. The surgeons carrying out the operations were recorded as Professor Sir John Charnley 13%, the senior author (BMW)
40%, and senior residents 47%.
At the latest review in June 2001, the mean follow-up
was 15 years 1 month. A total of 54 patients (4.9%, 66
LFAs, 4.6%) could not be traced, 124 (11.4%; 169 LFAs,
11.8%) were known to have died, 220 (20.1%; 248 LFAs,
17.3%) had had a revision and 759 (69.5%; 951 LFAs,
66.3%) continued to attend. The mean follow-up of the
attending patients was 17 years 5 months.
Clinical. Assessment at the latest follow-up, at the last
follow-up before death or on readmission for a revision, has
shown that 90.3% were satisfied with the outcome, 80.5%
were free from pain and 9.8% had occasional discomfort. A
total of 68% had normal or nearly normal function and
68.5% had a full or nearly full range of movement of the
VOL. 84-B, NO. 4, MAY 2002
541
Table I. The underlying hip pathology (some patients had more than a
single disorder) and previous hip surgery (excluding hemi- and total hip
arthroplasty) in 1092 patients who had a Charnley LFA
Number
of hips
Diagnosis
Primary osteoarthritis
Congenital dislocation/subluxation
Perthes' disease
Slipped upper femoral epiphysis
Trauma
Septic arthritis
Chronic sepsis (tuberculosis)
Quadrantic head necrosis
Rheumatoid arthritis
Ankylosing spondylitis
Fractured neck of femur
Paget's disease
Fusion for unspecified pathology
Protrusio acetabuli
Unspecified
Previous hip surgery
None
Osteotomy: femoral/pelvic
Cup arthroplasty
Open reduction
Fusion/attempted fusion
Pin, plate or screw fixation
Other (soft-tissue procedures)
Percentage
298
395
77
55
85
5
37
68
292
91
38
1
18
47
10
20.79
27.55
5.37
3.84
5.93
0.35
2.58
4.74
20.36
6.35
2.65
0.07
1.26
3.28
0.70
1164
139
15
42
36
4
78
81.17
9.69
1.05
2.93
2.51
0.28
5.44
Table II. Complications after 1434 Charnley low LFAs observed within
one year of surgery, or during follow-up including revisions shown in
Table III
Number
Complications
of hips
Percentage
Within one year of surgery
Local
Haematoma
Delayed wound healing
Trochanteric nonunion
Dislocation
Infection
General
Deep-vein thrombosis (clinical)
Pulmonary embolism (non-fatal)
Cardiovascular
Abdominal
Urinary
Other
During follow-up
Dislocation
Deep infection
Loose cup
Loose stem
Fractured stem
Other (including trochanteric explorations)
Unexplained pain
14
3
34
5
9
1.0
0.2
2.4
0.4
0.6
26
45
3
5
28
10
1.8
3.1
0.2
0.4
2.0
0.7
24
24
261
93
25
69
3
1.7
1.7
18.2
6.3
1.7
4.8
0.2
Table III. Indication for revision of a Charnley LFA. Some patients had
more than a single indication for revision
Number
Indication
of hips
Percentage
Infection
22
1.53
Dislocation
6
0.42
Loose cup
152
10.6
Loose stem
70
4.9
Fractured stem
22
1.7
Unexplained pain
2
0.14
Socket wear
15
1.1
Other (includes removal of trochanteric wires)
20
1.4
542
B. M. WROBLEWSKI, P. D. SINEY, P. A. FLEMING
Table IV. Wear of the UHMWPE cup measured by penetration, migration and revision for aseptic loosening
Cup penetration (mm)
Number
Number migrating
% migrating
Number revised
% revised
0
73
0
0.0
0
0.0
0.1 to 1.0
754
108
14.3
42
5.5
1.1 to 2.0
261
76
29.1
33
12.6
2.1 to 3.0
195
71
36.4
36
18.5
Table V. Survivorship analysis of 1434 Charnley LFAs taking
Follow-up
Number
(yrs)
at start
Withdrawn
Failure
0
1434
0
0
1
1434
0
0
2
1434
27
3
3
1404
25
4
4
1375
13
5
5
1357
19
4
6
1334
23
10
7
1301
22
6
8
1273
26
16
9
1231
30
12
10
1189
37
20
11
1132
73
20
12
1039
64
16
13
959
58
24
14
877
66
8
15
803
82
15
16
706
59
22
17
625
64
7
18
554
56
9
19
489
67
8
20
414
55
10
21
349
44
4
22
301
53
4
23
244
54
6
24
184
57
5
25
122
26
0
26
96
28
4
27
64
18
3
28
43
13
3
29
27
9
0
30
18
7
0
31
11
7
0
32
4
2
0
33
2
0
0
34
2
2
0
hip. Of the 759 patients (951 LFAs) who have not had a
revision, 96.2% are satisfied with the outcome, 88% are
free from pain and 8.2% have occasional discomfort. A
total of 78.7% have normal or nearly normal function and
75.7% have a full or nearly full range of movement. The
complications within one year of surgery and those occurring during the period of follow-up including revisions are
shown in Table II.
Complications. Deep infection occurred in 24 LFAs
(1.67%) and was slightly more common in patients who
had had previous hip surgery (6/270; 2.2%) than in those
who had not (18/1164; 1.55%); this was not significantly
different (p = 0.4). Plain acrylic cement had been used in
1092 (76.2%) hips and deep infection occurred in 21
(1.9%); 20 (1.8%) have been revised. Gentamicin-containing cement had been used in 342 (23.8%) and deep infec-
3.1 to 4.0
91
43
47.3
21
23.1
4.1 to 5.0
40
24
60
13
32.5
5.1 to 6.0
10
5
50
3
30
revision for any reason as the endpoint
Number
Cumulative
at risk
success rate (%)
1434
100.00
1434
100.00
1420.5
99.79
1391.5
99.50
1368.5
99.14
1347.5
98.84
1322.5
98.08
1290
97.62
1260
96.35
1216
95.36
1170.5
93.65
1095.5
91.83
1007
90.24
930
87.66
844
86.71
762
84.74
676.5
81.49
593
80.31
526
78.60
455.5
76.84
386.5
74.25
327
73.03
274.5
71.57
217
68.81
155.5
65.59
109
65.59
82
60.71
55
55.26
36.5
47.04
22.5
47.04
14.5
47.04
7.5
47.04
3
47.04
2
47.04
1
47.04
6.1 to 7.0
10
7
70
4
40
95% confidence limits
100.00 to 100.00
100.00 to 100.00
99.55 to 100.00
99.13 to 99.87
98.65 to 99.62
98.27 to 99.41
97.35 to 98.81
96.80 to 98.44
95.33 to 97.36
94.21 to 96.52
92.30 to 95.00
90.27 to 93.38
88.50 to 91.98
85.68 to 89.64
84.58 to 88.84
82.39 to 87.09
78.85 to 84.13
77.44 to 83.18
75.49 to 81.70
73.45 to 80.24
70.50 to 78.01
68.92 to 77.14
67.06 to 76.09
63.70 to 73.92
59.55 to 71.64
58.37 to 72.82
52.48 to 68.95
45.49 to 65.03
35.94 to 58.15
32.90 to 61.19
29.42 to 64.66
22.54 to 71.54
8.30 to 85.78
0.00 to 94.49
0.00 to 100.00
tion occurred in three (0.9%), two of which have been
revised (p = 0.2).
Various methods of trochanteric re-attachment have been
used. Trochanteric nonunion occurred in 34 LFAs (2.4%).
There were no dislocations or revisions for dislocation in
this group of patients.
There were five dislocations (0.35%) within one year of
surgery and none required revision. By the latest review 28
(1.95%) are known to have had at least one dislocation and
six (0.42%) had been revised for dislocation. Other indications for revision are shown in Table III.
Wear of the UHMWPE cup. Wear was measured as
penetration using the method which has been previously
8
described. The mean rate of penetration for the whole
group was 0.1 mm/year (0.01 to 0.67) and the mean total
penetration was 1.4 mm (0.1 to 7). The correlation between
THE JOURNAL OF BONE AND JOINT SURGERY
CHARNLEY LOW-FRICTIONAL TORQUE ARTHROPLASTY IN PATIENTS UNDER THE AGE OF 51 YEARS
543
Fig. 1
Survivorship analysis of 1434 Charnley LFAs taking
revision for any reason as the endpoint.
the depth of penetration, the incidence of migration of the
cup and revision for aseptic loosening of the cup is shown
in Table IV.
Survivorship analysis. Taking revision for any reason as
the endpoint, the survivorship was 93.7% (92.3 to 95.0) at
ten years, 84.7% (82.4 to 87.1) at 15 years, 74.3% (70.5 to
78.0) at 20 years, and 55.3% (45.5 to 60.5) at 27 years
when 55 hips remained ‘at risk’ (Table V, Fig. 1).
Discussion
The long-term clinical results of the Charnley LFA remain
excellent even in young patients. Consistency of materials,
design and surgical technique, the availability of large
numbers of patients with long-term follow-up and regular
review have allowed a meaningful study of various parameters to be made and improvements to be introduced
while continuing the clinical practice. In order to contribute
to the understanding of the long-term results the selection
of young patients for an indefinite follow-up was essential.
Such a decision imposed demands on the skills of the
surgeon and the durability of the arthroplasty and is probably the most severe test of both, since it inevitably
involves patients whose level of activity and life expectation are high and includes a large percentage of patients
with developmental disorders of the hip and rheumatoid
arthritis.
The long-term problem of wear and loosening of the cup
7
is highlighted. It is in this area that further progress is to
be expected. A combination of ceramic and cross-linked
15
polyethylene gives excellent results at 12 years. If the rate
of wear is reduced the effects of wear particles, as a
possible cause of loosening of the component, may become
of academic interest only.
Two other aspects must be borne in mind when considering the clinical results. First, they may not reflect the
16
mechanical state of the arthroplasty, hence follow-up with
radiographs of good quality and continuity of the methods
used to record the data are essential. Secondly, the implant
cannot be considered to become an integral part of the
skeleton. The surgeon therefore has a continuing responsibility to monitor this as it changes with age. The surgeon
must also understand patients’ expectations, the patient
VOL. 84-B, NO. 4, MAY 2002
must accept the limitations of the operation and the system
using the procedure as a measure of ‘quality of outcome’
must be prepared to accept its share of responsibility.
This research was supported by the Peter Kershaw and John Charnley
Trusts.
No benefits in any form have been received or will be received from a
commercial party related directly or indirectly to the subject of this
article.
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