Abstract
Background: A systematic review of the literature was performed to
estimate the impact of hemiarthroplasty compared with total shoulder
arthroplasty on function and range of motion in patients suffering from
osteoarthritis of the shoulder.
Methods: We conducted an electronic search for relevant studies
published in any language from 1966 to 2004, a manual search of the
proceedings from five major orthopaedic meetings from 1995 to 2003, and a
review of the reference lists from potentially relevant studies. Four
randomized clinical trials, with similar eligibility criteria and surgical
techniques, that compared hemiarthroplasty and total shoulder arthroplasty for
the treatment of primary osteoarthritis of the shoulder were found to be
eligible. Authors from three of the four studies provided original patient
data. Analysis of covariance focused on the two-year outcome and included a
comparison of the aggregate University of California at Los Angeles shoulder
score, four University of California at Los Angeles domain scores, and range
of motion.
Results: A total of 112 patients (fifty managed with
hemiarthroplasty and sixty-two managed with total shoulder arthroplasty), who
had a mean age of sixty-eight years, were included in this analysis. A
significant moderate effect was detected in the function domain of the
University of California at Los Angeles shoulder score (p < 0.001) in favor
of total shoulder arthroplasty (mean [and standard deviation], 8.1 ±
0.3) compared with hemiarthroplasty (mean, 6.6 ± 0.3). A significant
difference in the pain score was found in favor of the total shoulder
arthroplasty group (p < 0.0001). However, the large degree of heterogeneity
(p = 0.006, I2 = 80.2%) among the studies decreased our confidence
that total shoulder arthroplasty provides a true, consistent benefit with
regard to pain. There was a significant difference in the overall change in
forward elevation of 13° (95% confidence interval, 0.5° to 26°) in
favor of the total shoulder arthroplasty group (p = 0.008).
Conclusions: At a minimum of two years of follow-up, total shoulder
arthroplasty provided better functional outcome than hemiarthroplasty for
patients with osteoarthritis of the shoulder. Since continuous degeneration of
the glenoid after hemiarthroplasty or glenoid loosening after total shoulder
arthroplasty may affect the eventual outcome, longer-term (five to ten-year)
results are necessary to determine whether these findings remain consistent
over time.
Level of Evidence: Therapeutic Level I. See Instructions
to Authors for a complete description of levels of evidence.
Neer popularized shoulder hemiarthroplasty to treat humeral head
fractures, osteonecrosis of the humeral head, and arthritis of the shoulder
joint1. Problems
arose, however, if the surrounding musculotendinous rotator cuff was
deficient2 or if the
articular surface of the glenoid was
abnormal3.
Additionally, patients who underwent hemiarthroplasty ran the risk of
continued erosion of the glenoid surface, leading to increased pain and
decreased function over
time4. Thus,
hemiarthroplasty began to give way to total shoulder arthroplasty, which
involves the replacement of both the humeral head and the
glenoid5. Total
shoulder arthroplasty, however, is not without problems. These include the
increased complexity of the procedure, increased blood loss, increased
operating-room time, and increased
cost6. In addition,
some patients who are followed for longer time-periods show signs of glenoid
component loosening, which may lead to decreased
function1,2.
Several cohort studies have compared the outcomes after hemiarthroplasty
with those after total shoulder
arthroplasty1-5,7-9
and had inconsistent conclusions as to which procedure is best. Since
considerable controversy remains as to whether hemiarthroplasty or total
shoulder arthroplasty is the better treatment option for patients with
osteoarthritis, the purpose of this study was to conduct a systematic review
and meta-analysis of randomized clinical trials that primarily compared the
effectiveness of hemiarthroplasty and total shoulder arthroplasty at two years
postoperatively in patients with primary osteoarthritis of the shoulder.
Literature Search
We undertook a computer-assisted search of the online bibliographic
databases MEDLINE (1966 through week 2 of June 2004), CINAHL (1982 through
week 2 of June 2004), and EMBASE (1980 through week 25 of 2004) and the
Cochrane Central Register of Controlled Trials (second quarter of 2004) to
identify relevant studies published in any language. We used the Cochrane
strategy for randomized controlled
trials10 and
database-appropriate search terms, including arthroplasty and excluding
articles on hip and knee arthroplasty, and we further limited the search by
using the text word "shoulder." In addition, we conducted a manual
search of the proceedings from five major orthopaedic meetings from 1995 to
December 2003. A review of the reference lists from potentially relevant
studies complemented other searches. The specific search strategies are
available from the authors.
Selection of Studies
Eligible studies included randomized trials that compared hemiarthroplasty
and total shoulder arthroplasty in patients with a diagnosis of primary
osteoarthritis of the shoulder who were followed for a minimum of two years
and that used a measure of functional outcome and/or range of motion (forward
elevation and/or external rotation). The electronic search produced 311
abstracts. Both reviewers identified only one eligible study and, on the basis
of a review of the full text, this paper was included in the study. The
agreement between reviewers was 100% for both the review of the abstract and
the full text.
Both reviewers identified four abstracts from conference proceedings. One
of these abstracts was from the published study that was included and three
were from studies that had not yet been published. One of the abstracts was
presented more than once at different conferences over the five years
reviewed. Thus, only the abstract containing data for the two-year assessment
was used.
Validity Assessment
The authors of all included studies were contacted before assessing the
quality of each study since three of the four studies were present in abstract
form only. This was done to request data and to obtain further details on the
study design. Quality was assessed according to six criteria, including
concealment of randomization, blinding of patients and data collectors,
proportion of subjects randomized who dropped out, use of validated outcomes,
and use of the intention-to-treat method of analysis. Quality assessment was
not used to determine inclusion or exclusion of trials into this
meta-analysis, but it served to generate hypotheses to explain potential
heterogeneity between trials and helped to decide on the appropriate strength
of inference from the data.
Potential Heterogeneity
Following quality assessment, we defined three a priori hypotheses to
address potential differences in treatment effect between studies (variability
in the magnitude of effect, also referred to as heterogeneity of results) that
cannot be explained by chance alone. These hypotheses included a lack of
concealment of randomization, whether data collectors were aware of patient
group allocation (blinding), and use of uncemented or cemented fixation of the
humeral prosthesis. These hypotheses were tested with use of sensitivity
analyses.
Data Abstraction
Three of the four primary investigators of the studies that were included
contributed their original data set to create a common data set for the
meta-analysis. The University of California at Los Angeles (UCLA) functional
shoulder assessment
tool11 was common
among all studies and was thus selected as the primary outcome for this
meta-analysis. This instrument assigns a score to patients on the basis of
five separate domains: pain, function, active forward flexion, strength of
forward flexion, and overall satisfaction. There is one item for each of these
areas. The weighting is such that pain accounts for 10 points; function, 10
points; forward flexion, 5 points; strength, 5 points; and overall
satisfaction, 5 points, giving a total of 35 points (see Appendix). The
overall satisfaction item was omitted since it can be collected only after an
intervention and not before and after an intervention, as is ideal in most
clinical trials. The fourth study did not collect UCLA data but did collect
functional data with use of the scoring system of Constant and
Murley12. Other
commonly used outcome measurements were range-of-motion measurements,
including active forward elevation and external rotation.
Statistical Analysis
The intention-to-treat principle, whereby all patients are analyzed in the
group to which they were randomized, guided all analyses. Use of the
intention-to-treat principle has the potential to provide a conservative
estimate of treatment effect. However, by conducting an efficacy analysis,
which violates the intention-to-treat principle by analyzing patients
according to the treatment they received (either by removing the data of
patients who were randomized to hemiarthroplasty but crossed over to total
shoulder arthroplasty, or by including these data in the total shoulder
arthroplasty group), we almost certainly introduce a biased estimate of the
treatment effect in favor of the hemiarthroplasty group. Specifically, since
not only would the balance of the prognostic factors between the groups that
was established through randomization be compromised, but by removing the data
from patients who had failure of the hemiarthroplasty and crossed over to
total shoulder arthroplasty (especially if we include these data in the total
shoulder arthroplasty group), we would bias the estimate of effect in favor of
hemiarthroplasty.
The analysis was conducted with use of two statistical programs. The first
program, Review Manager (version 4.1, 2003; The Cochrane Collaboration,
Oxford, United Kingdom), uses the inverse of the variances for each study to
weight its treatment effect in the pooled analysis, thereby assigning greater
weight to larger studies with a more precise estimate of the treatment effect.
Because it provides a more conservative estimate of the precision of treatment
effect, we chose to conduct the pooled analyses with the random-effects model,
which considers both the between-study and within-study variance in treatment
effects, over the fixed effects model, which considers only the within-study
variance. The random-effects model assumes that studies included in the
meta-analysis are only a sample of all possible studies that could be
conducted, while the fixed-effects model assumes that the studies that are
included represent the entire population of studies that could be conducted on
the topic.
When the estimates of effect across studies are pooled, the underlying
assumption is that the effect is similar across the range of patients,
interventions, and outcomes among the studies. A formal assessment of the
variability of results across studies (heterogeneity) allows reviewers to test
the validity of this assumption. For each pooled analysis, we included two
statistical tests that provide insight into the degree of heterogeneity: the
Cochran chi-square
test13 and the
I2
value14. The
Cochran chi-square test provides an opportunity to reject the null hypothesis
that the underlying effect is the same across studies but may be underpowered
when only a small number of studies are available. The I2 value
estimates the percentage of total variation in results across studies that is
due to heterogeneity among studies rather than that due to chance. Low,
moderate, and high levels of heterogeneity are roughly categorized by
I2 values of 25%, 50%, and 75%, respectively.
The second analysis was conducted with use of SPSS software (release 11.0;
SPSS, Chicago, Illinois) and the individual patient data from three of the
four investigators. Analysis of covariance, which is analogous to a t test but
allows for adjustment of the analysis for baseline scores, gives a more
powerful estimate of the treatment effect than that provided by Review
Manager.
Since we were uncertain of whether to include the data from the trial by
Jonsson et al.15
(i.e., no concealment of randomization followed by unbalanced exclusion of
randomized patients), we conducted a sensitivity analysis to determine the
robustness of the results when data from that trial were added. In that study,
five (9%) of the fifty-six patients randomized, or 17% of the patients managed
with total shoulder arthroplasty, in whom the glenoid was found
intraoperatively to be insufficient to support a glenoid prosthesis, were
withdrawn from the trial. Similar patients were not withdrawn from the
hemiarthroplasty group. This almost certainly introduces bias in favor of
total shoulder arthroplasty and underscores the importance of including all
patients who are randomized in the analysis and in their original groups.
Specifically, the hemiarthroplasty group is now more likely to include
patients with severe glenoid bone loss or defects, which will most likely bias
this group toward poorer outcomes. To conduct the sensitivity analysis, we
used the standardized mean difference of the change score since different
functional instruments (the UCLA
system11 and the
Constant and Murley
system12) had been
used. A similar sensitivity analysis was conducted with use of the weighted
mean difference of the change score for the range-of-motion data since all
measurements were conducted with use of a standard universal goniometer that
measured in degrees.
Characteristics of the Studies That Were Included
Four trials were eligible for inclusion into the meta-analysis. The
trial conducted by Gartsman et
al.6 was the only
one that had published results. Their study included fifty-one patients
(fifty-five shoulders) who were randomly assigned to hemiarthroplasty or total
shoulder arthroplasty. Four patients were lost to follow-up and were not
counted in the analysis. Forty-seven patients (fifty-one shoulders) remained;
twenty-four shoulders had a hemiarthroplasty, and twenty-seven shoulders had
total shoulder arthroplasty. Hemiarthroplasty and total shoulder arthroplasty
were performed with use of the Global Shoulder Arthroplasty System (DePuy
Orthopaedics, Warsaw, Indiana). The criteria for inclusion into the trial
included a diagnosis of osteoarthritis, an intact rotator cuff, and a
concentric glenoid. Diagnoses other than osteoarthritis were criteria for
exclusion. An unblinded data collector assessed shoulder function
preoperatively and postoperatively at two weeks, six weeks, three months, six
months, and one year after the operation and yearly thereafter. Shoulder
function was assessed with use of the UCLA shoulder
score11, the
American Shoulder and Elbow Surgeons (ASES) standardized rating
system16, and
range-of-motion assessment. The investigators reported that the total shoulder
arthroplasty group had significantly less pain (p = 0.002) and significantly
greater internal rotation (p = 0.003) than the hemiarthroplasty group.
Unsatisfactory results were reported by five patients who had a
hemiarthroplasty and by one who had total shoulder arthroplasty. Three of the
five shoulders with an unsatisfactory result after hemiarthroplasty were
revised to total shoulder arthroplasty at nineteen, thirty-nine, and
forty-eight months postoperatively.
Lo et al.17
conducted a trial (published in abstract form only) that included thirty-nine
patients (forty-one shoulders) randomly assigned to hemiarthroplasty
(twenty-one shoulders) or total shoulder arthroplasty (twenty shoulders)
performed with use of the Neer-II prosthesis (3M, St. Paul, Minnesota).
Patients were randomized intraoperatively if they had a diagnosis of
osteoarthritis of the shoulder, had no previous shoulder surgery, and had no
cuff tear arthropathy, no major trauma to the shoulder, and no major medical
illness, infection, paralysis of the study limb, or other concurrent
diagnoses, such as osteonecrosis or rheumatoid arthritis. A blinded data
collector assessed shoulder function preoperatively and at two weeks, six
weeks, and at three, six, twelve, eighteen, and twenty-four months
postoperatively and yearly thereafter using the Western Ontario Osteoarthritis
of the Shoulder (WOOS)
index18, ASES
rating system16,
Constant and Murley
system12, UCLA
shoulder score11,
McGill pain
score19, Short
Form-12 (SF-12)20,
and range-of-motion assessment. Patients were also unaware of their group
assignment. No significant differences were reported for any outcome measure
at one or two years postoperatively. Complications included two intraoperative
fractures (one humeral fracture in the hemiarthroplasty group and one glenoid
fracture in the total shoulder arthroplasty group), two late rotator cuff
tears (one in each group) requiring no further surgical intervention, and one
deep infection in the total shoulder arthroplasty group that resolved
following arthroscopic lavage and a course of antibiotics. One patient in the
total shoulder group died from a thromboembolism two days following surgery.
Three patients underwent revision to a total shoulder arthroplasty at twelve,
eighteen, and forty-eight months postoperatively.
Sandow et al.21
conducted a trial (published in abstract form only) that included twenty-nine
patients (thirty-two shoulders) randomly assigned to hemiarthroplasty
(fourteen shoulders) or total shoulder arthroplasty (eighteen shoulders)
performed with use of the Global Shoulder Arthroplasty System (DePuy
Orthopaedics). Patient randomization occurred intraoperatively following
demonstration of an intact rotator cuff, glenoid wear that did not
substantially alter version, and the absence of other factors that would
constitute a specific indication for either hemiarthroplasty or total shoulder
arthroplasty. A blinded data collector assessed shoulder function
preoperatively and at six and twelve months postoperatively and yearly
thereafter with use of the
UCLA11 and
Constant12
shoulder-rating systems and with range-of-motion measurements. Patients in the
total shoulder arthroplasty group reported significantly less pain, according
to a visual analogue pain scale, compared with those in the hemiarthroplasty
group (p < 0.03). Four patients in the hemiarthroplasty group underwent
revision to a total shoulder arthroplasty at twenty-four months (two
shoulders), thirty-six months (one shoulder), and forty-eight months (one
shoulder). Two patients in the hemiarthroplasty group died at six and
forty-eight months postoperatively, and one patient in the total shoulder
arthroplasty group died at twelve months postoperatively. This study was
terminated prematurely by the institutional review board for efficacy prior to
reaching the estimated sample size.
Jonsson et al.15
conducted a trial (published in abstract form only) that included fifty-six
patients with both rheumatoid arthritis and osteoarthritis randomly assigned
to hemiarthroplasty (thirteen with rheumatoid arthritis and eleven with
osteoarthritis) or total shoulder arthroplasty (twelve with rheumatoid
arthritis and thirteen with osteoarthritis) before surgery. Randomization was
stratified according to the type of arthritis. Five patients were excluded
during surgery subsequent to randomization because the bone stock appeared
insufficient for glenoid replacement. Two patients were excluded following
surgery for complications, including one deep infection and one nerve injury.
A significant improvement in the
Constant12 score
was reported for the total shoulder arthroplasty group compared with the
hemiarthroplasty group (p = 0.01). No difference was detected between the
groups with respect to active forward elevation (p = 0.065) and active
external rotation (p > 0.05). Subgroup analysis revealed no significant
differences in outcomes when patients with rheumatoid arthritis were compared
with patients with osteoarthritis. Nonetheless, we included only data
collected from patients with osteoarthritis.
Table I presents a summary
of the results of the quality assessment.
Patients
In three of the four studies, if both shoulders underwent arthroplasty,
both shoulders were randomized into the trial, which violates the assumptions
of the statistical tests of independent observations. Thus, we excluded data
collected from the second shoulder of patients who had been randomized twice,
which resulted in the removal of data for six shoulder arthroplasties. One
hundred and nineteen patients remained. Of those, four were patients who died
in the early postoperative period (two in the hemiarthroplasty group and two
in the total shoulder arthroplasty group) and three were patients with missing
data, leaving 112 patients (fifty in the hemiarthroplasty group and sixty-two
in the total shoulder arthroplasty group) with complete data for analysis of
function with use of the UCLA shoulder score. No data on forward elevation and
external rotation data were available for ninety-nine patients and fifty-nine
patients, respectively. All patients with range-of-motion data contributed
scores to the UCLA data. These values do not include patients from the trial
conducted by Jonsson et
al.15.
Of the 112 patients, sixty-eight were female (thirty had a hemiarthroplasty
and thirty-eight had a total shoulder arthroplasty). The mean age was 67.7
years for both treatment groups. The groups were similar with respect to the
mean baseline value for the UCLA total score (10.5 for the hemiarthroplasty
group and 10.4 for the total shoulder arthroplasty group), forward elevation
(87.9° and 82.2°, respectively), and external rotation (20.4° and
22.0°, respectively). Data on the patient characteristics for each study
are presented in Table II.
The patients in the study by Gartsman et
al.6 were, on the
average, three years younger than those in the study by Sandow et
al.21 and five
years younger than those in the study by Lo et
al.17 (p <
0.0001). Furthermore, the preoperative functional scores reported by Gartsman
et al.6 were worse
than those in the study by Lo et
al.17 and Sandow et
al.21, which is
reflected by an average difference of approximately 4 points in the baseline
UCLA score (p < 0.0001). In addition, although the patients in the trials
were similar with respect to preoperative forward elevation, those in the
trial described by Gartsman et
al.6 had
significantly worse average external rotation at baseline than did the
patients in the study by Sandow et
al.21 (p =
0.023).
Quantitative Data Synthesis
Of the fifty patients randomized to hemiarthroplasty, ten patients (20%)
crossed over to the total shoulder arthroplasty group because of excessive
pain or stiffness; however, only three patients (6%) crossed over before the
two-year assessment (at twelve, eighteen, and nineteen months). The remaining
patients who had crossed over (as of the time of writing) did so at
twenty-four months (two patients) and at thirty-six months (one patient),
thirty-nine months (one patient), and forty-eight months (three patients).
Functional Outcome
When the mean change in the function domain of the UCLA scoring system was
considered (Fig. 1), a
significant moderate effect was detected in favor of total shoulder
arthroplasty, with a difference of 1.4 points (95% confidence interval, 0.5 to
2.4) (p = 0.003). For this domain, the results were very homogeneous (p =
0.84, I2 = 0%).
When the analysis was repeated with use of data on individual patients
(analysis of covariance), the results were similar. A significant difference
with respect to function at two years (p < 0.001) was detected in favor of
the total shoulder arthroplasty group (8.1 ± 0.3; 95% confidence
interval, 7.6 to 8.7) compared with the hemiarthroplasty group (6.6 ±
0.3; 95% confidence interval, 5.9 to 7.2). Thus, on the average, patients who
underwent a total shoulder arthroplasty had only a slight restriction in
activities and were able to do work above shoulder level at two years, whereas
patients who underwent hemiarthroplasty were able to do most activities of
daily living but were not able to do work above shoulder level. There was no
evidence of heterogeneity between studies for this domain.
There was a significant difference (p = 0.04) in the mean change in the
pain score of 2.0 points (95% confidence interval, 0.1 to 3.9) in favor of the
total shoulder arthroplasty group, which represents a moderate effect. Both
the Cochran chi-square test of heterogeneity (p = 0.006) and the I2
value (80.2%) indicate a high degree of heterogeneity in the results among the
studies (Fig. 1) and suggest
that an interpretation of the results of this particular domain is difficult
and could lead to spurious conclusions.
When this analysis was repeated with use of individual patient data, the
results were similar. There was a significant difference (p < 0.0001) in
the pain score in favor of the total shoulder arthroplasty group (8.6 ±
0.3; 95% confidence interval, 8.0 to 9.1) compared with the hemiarthroplasty
group (6.5 ± 0.3; 95% confidence interval, 5.9 to 7.1), but there was
also a significant interaction between which study the data came from and the
mean change in the preoperative and postoperative scores (p = 0.004). A
significant interaction of this sort reflects the heterogeneity among the
study results and indicates that, for each study, the magnitude of the mean
change between the preoperative and postoperative scores is inconsistent
across studies, making interpretation of an overall pooled estimate for the
effect on pain difficult. Specifically, the mean changes in the pain score
between the groups in the studies by Lo et al., (0.1; 95% confidence interval,
-1.5 to 1.7), Gartsman et al. (2.1; 95% confidence interval, 0.9 to 3.4), and
Sandow et al. (3.8; 95% confidence interval, 2.2 to 5.5) were quite different.
Lo et al. found essentially no difference between the groups with respect to
the mean change in the preoperative and postoperative pain scores, and the
other two studies found a large or very large benefit in favor of total
shoulder arthroplasty.
The other domains of mobility and strength did not demonstrate a
significant difference between the groups with respect to the mean change in
the preoperative and postoperative scores
(Fig. 1) nor were significant
differences detected when individual patient data were analyzed. Patients were
able to gain, on the average, 30° in forward elevation and to progress
from fair to good strength. There was no evidence of heterogeneity among the
studies for these domains.
Although the overall aggregate of the domains is usually considered to
represent an overall UCLA shoulder score, we believe that this is potentially
misleading because of the heterogeneity in the pain domain among the studies.
Nonetheless, we provided this analysis since overall scores are reported
throughout the literature. Thus, there was a significant difference (p =
0.008) in the mean change in the overall UCLA shoulder score of 3.9 points
(95% confidence interval, 1.0 to 6.8), which represents a moderate effect
size, in favor of the total shoulder arthroplasty group. The test of
heterogeneity was borderline in terms of significance (p = 0.12), and the
I2 value (52.9%) indicates moderate heterogeneity among studies.
The heterogeneity in pain domains explains this moderate level of
heterogeneity in the magnitude of effect.
When the analysis was repeated with use of individual patient data
(analysis of covariance), the results were similar. A significant difference
(4.2; 95% confidence interval, 2.4 to 5.9) was detected in the overall UCLA
shoulder score at two years postoperatively in favor of the total shoulder
arthroplasty group (p < 0.0001), and there was a significant effect with
regard to which study the data came from (p = 0.034), which represented the
heterogeneity among the studies.
The sensitivity analysis indicated that the addition of data on the mean
change in the overall Constant score from the study by Jonsson et
al.15 did not
change the estimate of the treatment effect except to make it more precise
(Fig. 2). The estimate of
heterogeneity among the trials decreased (46% [p = 0.16] to 19% [p = 0.30])
when data from the study by Jonsson et
al.15 were
added.
Range of Motion
No significant difference between the groups at two years postoperatively
was detected with respect to the change in forward elevation (p = 0.316) or
the change in external rotation (p = 0.270) when individual patient data were
used. On the average, forward elevation increased by 43° in the patients
who underwent total shoulder arthroplasty compared with 31° in the
patients who underwent hemiarthroplasty. The average increase in external
rotation was 28° for the patients who had a total shoulder arthroplasty
compared with 24° for those who had a hemiarthroplasty. Considerable
variability in these measurements as well as a reduced number of patients for
whom data were available contributed to the possibility of making a Type-II
error (declaring no significant difference when one truly exists) and may
explain why a significant difference (p = 0.008) in the change in forward
elevation (13°; 95% confidence interval, 0.5° to 26°) is found
(Fig. 3) when data from the
study by Jonsson et
al.15 are included.
These data were included in the analysis since the estimated effect from this
trial was not different from the other trials as evidenced by the unchanged
I2 value of 0% and the fact that the test for heterogeneity in both
this analysis and the analysis for external rotation was not significant.
We conducted a meta-analysis of four small randomized clinical
trials to provide a more precise overall estimate of the effect of total
shoulder arthroplasty compared with hemiarthroplasty of the shoulder on pain
and function at two years postoperatively. Our results demonstrate better
function at two years in patients managed with total shoulder arthroplasty.
Uncertainty remains with respect to the estimates of the relative effect of
the two procedures, since no study included in this analysis is without
methodological weaknesses.
Since we were uncertain of whether to include the data from the study by
Jonsson et al.15
because of the high potential for biased results in favor of the total
shoulder arthroplasty, we conducted a sensitivity analysis to determine the
robustness of the results when data from this trial were added. At this early
follow-up, we found no evidence of heterogeneous results among the studies and
thus included this study in the pooled analysis. However, since glenoid wear
has been shown to progress despite hemiarthroplasty, pooled analyses for
long-term comparisons should again test for evidence of heterogeneity since
the systematic effects of this efficacy analysis may become apparent over
time.
An additional methodological limitation is the use of outcome measures that
have not been sufficiently validated. Both the
UCLA11 and
Constant12
shoulder-rating tools were published before the advent of modern measurement
methodology. Despite their popularity and widespread use, there is little
published information documenting the reliability, validity, and
responsiveness of either instrument. However, the results of these trials
suggest that the instruments are able to demonstrate moderate differences in
the change in function between two treatments with relatively small sample
sizes. These results, therefore, provide compelling evidence of the
responsiveness of the instruments. Longer-term follow-up studies of the
current trial participants and future studies should use measures that have
been shown to be both valid and reliable, such as the WOOS
index18, the ASES
standardized
tool16, and the
Disabilities of the Arm, Shoulder and Hand (DASH)
questionnaire22-25.
Our results reveal a large degree of heterogeneity among the studies with
regard to the relative impact of the interventions on pain. The
hemiarthroplasty group did far better with respect to pain in the trial
described by Lo et
al.17 than in the
other studies, and this resulted in negligible differences between treatments
with respect to pain. This degree of heterogeneity makes pooling to generate a
single estimate of effect questionable. One possible reason for the difference
is that patients participating in the trial conducted by Lo et
al.17 had greater
function before surgery than did the patients participating in the other two
trials. When the average age and baseline functional scores in the study by Lo
et al.17 are
compared with the averages in the other two trials, there is no evidence to
support this hypothesis.
Clinicians should view the trials conducted to date as preliminary
observations. Wise decisions with regard to the choice for hemiarthroplasty or
total shoulder arthroplasty will require trials with longer-term follow-up
with documentation of outcomes that include glenoid erosion following
hemiarthroplasty and its effect on important outcomes for patients. In the
four randomized trials included in this meta-analysis, ten patients (20%)
crossed over from hemiarthroplasty to total shoulder arthroplasty. The
predictors of failure of hemiarthroplasty have not yet been adequately
investigated. Longer-term review of the patients included in these trials is
important to provide this potential prognostic data.
Conversely, in several studies on total shoulder
arthroplasty7,8,26,27,
progressive radiolucent lines have been observed on plain radiographs, which
is evidence of loosening of the glenoid component. At this time, the
relationship between glenoid loosening and pain, function, range of motion, or
quality of life has not been clearly established. If glenoid loosening occurs
frequently following total shoulder arthroplasty and if the functional
consequences of loosening are sufficiently serious, hemiarthroplasty may
ultimately prove to be the superior procedure because it preserves bone stock,
allowing conversion to a total shoulder arthroplasty in the case of failure.
On the other hand, a failed total shoulder replacement is thought to have a
much poorer prognosis as there are no good revision prostheses. In the study
by Sandow et al.21,
however, shoulders with a failed hemiarthroplasty were associated with glenoid
erosion that compromised the ability to convert to total shoulder
arthroplasty, and this finding may contradict the argument for predictable
revision of a failed hemiarthroplasty to total shoulder arthroplasty.
Similarly, Carroll et
al.28, in a series
of sixteen consecutive patients who underwent revision total shoulder
arthroplasty for a failed hemiarthroplasty, reported that less than half (47%)
of the patients had a satisfactory outcome at a mean of 5.5 years following
revision. Furthermore, Antuna et
al.29, in a series
of forty-eight shoulders that required revision surgery following total
shoulder arthroplasty, reported that 86% of the patients who underwent
implantation of a new glenoid component had satisfactory pain relief at a mean
of 4.9 years following revision.
It is important to assess the underlying costs associated with these
complications in the long term. We know that total shoulder arthroplasty is
more expensive at the time of implantation because the prosthesis is more
expensive and a longer operating time is
required6,17.
Total costs at five years, however, may favor total shoulder arthroplasty when
the costs of revision surgery and rehabilitation are considered.
In conclusion, the results of this study indicate that, at a short-term
follow-up of two years, total shoulder arthroplasty provides more consistent
improvement in function than hemiarthroplasty for patients with primary
osteoarthritis of the shoulder. Because of the potential for continued
degeneration of the glenoid in patients managed with a hemiarthroplasty and
for glenoid loosening in patients managed with total shoulder arthroplasty,
longer-term (five to ten-year) results are necessary to determine whether
these findings remain consistent over time.
A table depicting the UCLA functional shoulder assessment tool is available
with the electronic versions of this article, on our web site at
(go to
the article citation and click on "Supplementary Material") and on
our quarterly CD-ROM (call our subscription department, at 781-449-9780, to
order the CD-ROM). ?
Note: The authors thank Margaret McGee for her valuable review
of the manuscript and Ulf Lillkrona for providing further details for one of
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