Abstract
Background: Compaction bone-grafting has been suggested as a means
of improving the stability of the humeral component in shoulder arthroplasty,
but the clinical and radiographic results of the procedure have not been
reported in the literature, to our knowledge. To address this deficit, we
report on a series of shoulder arthroplasties performed with compaction
bone-grafting to secure humeral component fixation. These prostheses were
implanted in shoulders demonstrating a suboptimal interference fit of the
humeral component.
Methods: Fifty-eight shoulders in fifty-three patients were treated
with prosthetic shoulder arthroplasty that included compaction bone-grafting.
Clinical assessments were performed at regular intervals with use of visual
analog scales for pain, shoulder comfort and function, and overall quality of
life, and with use of patient self-assessments including the American Shoulder
and Elbow Surgeons Score and the validated Simple Shoulder Test. A detailed
radiographic analysis was performed by three raters to determine whether
radiolucent lines were present immediately postoperatively and at a later
follow-up interval. The humeral tilt angle was determined by measuring the
angle between the humeral axis and the component. Subsidence was also
evaluated. The mean of the raters' measurements was used in the analysis.
Results: The mean duration of follow-up was sixty-nine months
(range, twenty-six to 148 months). No loose stems were observed, and no
humeral component was revised. At the time of follow-up, there was significant
improvement in the Simple Shoulder Test scores and all visual analog scores (p
< 0.0001 in each instance). Thirty-four stems had no radiolucent line at
the time of follow-up, and the mean maximum thickness of the lucent lines was
0.21 mm in the entire group of fifty-eight shoulders. Most lucent lines
occurred near the distal stem tip. The mean tilt of the valgus and varus
humeral components was 2.2° and 2.6°, respectively, on the immediate
postoperative radiographs. No humeral component shifted from varus to valgus
or vice versa. The duration of follow-up was not correlated with the maximum
thickness of the humeral component lucency, and the presence or absence of a
prosthetic glenoid was also unrelated to the maximum thickness of the
lucency.
Conclusions: Compaction bone-grafting in shoulder arthroplasty can
yield stable and durable fixation of the humeral component, as seen clinically
and radiographically, without use of cement. Our findings provide evidence
that compaction bone-grafting in shoulder arthroplasty is an option to ensure
intermediate-term fixation (at a mean of five years) of humeral components
that have a suboptimal fit.
Level of Evidence: Therapeutic Level IV. See Instructions
to Authors for a complete description of levels of evidence.
Although aseptic loosening of the glenoid component is the most common mode
of failure of total shoulder
arthroplasties1-3,
radiographic assessments of humeral implants in several reports on shoulder
arthroplasty have shown that radiolucent lines also occur in association with
those components. In more extreme cases, the humeral component can shift in
position with respect to the
humerus4-7
(Figs. 1-A and 1-B). Techniques
to fix the humeral component in the medullary canal of the proximal part of
the humerus include the use of cement, insertion of the component into
un-prepared bone, insertion of the component into a humerus that has been
reamed and then broached, and utilization of porous-coated implants for tissue
ingrowth
fixation8-11.
Cement provides an effective means for fixing the humeral component
securely within the medullary canal of the proximal part of the humerus, but
if the prosthesis must be revised because of malposition, loosening, or
periprosthetic fracture, the presence of cement complicates implant removal
and may jeopardize the outcome of the revision.
In January 1992, we began using compaction bone-grafting to secure fixation
of the humeral component in shoulders in which the interference fit of that
component was suboptimal as a result of poor bone quality in the proximal part
of the humerus. The objective was to achieve implant stability by using
cancellous, morselized bone graft and hopefully to obviate the need for cement
fixation. As far as we know, the clinical and radiographic findings following
proximal humeral compaction bone-grafting in total shoulder arthroplasty and
hemiarthroplasty have not been reported previously. The intent of this report
was threefold: (1) to describe our technique and indications for using
proximal humeral compaction bone-grafting in shoulder arthroplasty; (2) to
examine the clinical implications of prospective radiographic outcome
findings; and (3) to test our hypothesis that compaction bone-grafting applied
to a press-fitted humeral prosthesis will be followed by low rates of
loosening as seen both clinically and radiographically.
Between January 1992 and July 1997, seventy-one consecutive shoulders in
sixty-six patients who were candidates for the study procedure were treated
with arthroplasty that included compaction bone-grafting. Thirteen patients
(thirteen shoulders) were lost to follow-up, leaving fifty-three patients
(fifty-eight shoulders; forty-two hemiarthroplasties and sixteen total
shoulder arthroplasties) who had complete clinical and radiographic follow-up
for more than twenty-four months after a shoulder arthroplasty that included
compaction bone-grafting. All seventy-one shoulders are included in our report
of the complications. No significant differences were found with respect to
age, weight, or height (as assessed with t tests) or with respect to gender
distribution (as assessed with the Fisher exact test) between the fifty-eight
shoulders that were included in the study and the thirteen shoulders with
incomplete follow-up. Thus, the fifty-eight shoulders that were included
appear to be an unbiased subset of the consecutive series.
Each of the fifty-eight shoulder arthroplasties was performed with a DePuy
Global shoulder modular prosthesis (DePuy [Johnson and Johnson], Warsaw,
Indiana). The body of the prosthesis has a cylindrical diaphyseal region
(ranging from 6 to 14 mm in diameter, in 2-mm increments) with proportionately
sized metaphyseal regions that incorporate a superior-to-inferior
taper2.
The diagnoses included osteoarthritis (twenty-nine shoulders), rheumatoid
arthritis (eight), posttraumatic arthrosis (eight), osteonecrosis (four),
cuff-tear arthropathy (six), failed total shoulder arthroplasty (one), failed
hemiarthroplasty (one), and nonspecific inflammatory arthritis (one). The
indication for each primary shoulder arthroplasty was glenohumeral arthrosis
that limited activities of daily living combined with pain in the shoulder
that was refractory to conservative measures.
The criterion for inclusion in the study was insufficient humeral component
stability after an attempt at press-fit insertion. For the purposes of the
study, we defined insufficient stability as (1) a prosthesis that did not
require tapping with a mallet to drive it into its final position and/or (2) a
prosthesis that could be moved manually after insertion. No shoulder that had
been treated with compaction bone-grafting without cement and had been
followed clinically and radiographically for at least twenty-four months was
excluded.
Of the fifty-eight shoulder prostheses, thirty-three (57%) were implanted
in men and twenty-five (43%), in women. The mean age at the time of the
operation was sixty years (range, twenty-seven to eighty-three years).
Thirty-eight shoulders were on the dominant side, one patient was
ambidextrous, and the remaining nineteen shoulders were on the nondominant
side. A clinical assessment was performed preoperatively and at one-year
intervals postoperatively. The mean duration of clinical follow-up was
sixty-nine months (range, twenty-six to 148 months). Two patients died, one at
forty-eight months and one at sixty months postoperatively, of causes
unrelated to the arthroplasty.
Active total elevation and active external rotation (with the arm adducted)
were measured in 5° increments with use of a 2-ft (0.6-m)-long handheld
goniometer. In addition, outcomes data were derived from patient
self-assessment questionnaires, including the validated Simple Shoulder Test
(SST) and the standardized assessment form proposed by the American Shoulder
and Elbow Surgeons
(ASES)12,13.
Visual analog scales were used preoperatively and postoperatively to measure
pain, shoulder comfort with the arm at rest, shoulder comfort during sleep,
the ability to use the arm full-time for work or recreation, overall shoulder
function, and overall quality of life. The data were analyzed with the
patient's identity masked. All patients in the study gave full verbal and
written consent for operative treatment and participation in this study. Our
institutional review board approved the study.
Radiographic Analysis
The initial postoperative and most recent radiographs were evaluated. The
mean duration of radiographic follow-up was fifty-eight months (range,
twenty-six to ninety-three months). An axillary radiograph and an
anteroposterior radiograph made perpendicular to the plane of the scapula,
with the humerus externally rotated 30°, were reviewed to determine the
presence of radiolucent lines about the humeral component by zone. Tilting and
subsidence of the humeral component were also measured.
The zonal analysis of humeral radiolucent lines was performed independently
by three raters using an adaptation of the system described by Gruen et
al.14. For the
evaluation, the area of humeral fixation was divided into seven zones: zones 1
and 7 were the lateral and medial aspects of the proximal third of the area
containing the stem, zones 2 and 6 were the lateral and medial aspects of the
middle third of the area containing the stem, zones 3 and 5 were the lateral
and medial aspects of the distal third of the area containing the stem, and
zone 4 was the area at the tip of the stem. Each zone was categorized
individually as having or not having a lucent line. If any of the raters
categorized a zone as having a lucent line, the zone was considered to have a
lucent line. In addition, a single variable captured the maximum thickness of
the widest radiolucent line, in millimeters, in any of these zones without
specifying the particular zone with the widest lucent line.
The humeral component tilt angle was measured independently by the three
raters as the angle, in degrees, between the humeral axis and the axis of the
component on the antero-posterior radiograph. When the angle was not 0°,
the rater indicated whether it was varus or valgus. The mean of the three
raters' measurements was used in the analyses. Postoperative and follow-up
radiographs were compared to determine whether the component had subsided or
shifted in position.
Statistical Analysis
Statistical analysis was performed with SAS software (version 8.2; SAS
Institute, Cary, North Carolina). Comparisons between preoperative and
postoperative findings were performed with matched-pairs two-tailed t tests
for interval level data. Comparisons between groups were done with two-tailed
t tests, and F tests were performed to determine whether homogeneity of
variance existed. In instances in which F tests were significant (p =
0.05), a Satterthwaite test was used. Pearson r correlation coefficients were
calculated to determine whether interval level variables were predictive of
one another, and Fisher exact tests were used to assess relationships between
categorical variables unless otherwise indicated.
Operative Technique
Subscapularis and Capsular Release
The operation was performed with the patient under general anesthesia and
in the beach-chair position. A deltopectoral approach, with emphasis on
preservation of the entire deltoid origin and insertion, was utilized. The
subscapularis was detached from its insertion on the lesser tuberosity and
separated from the underlying anterior aspect of the capsule. Adhesions were
released from the base of the coracoid process, and the entire anterior aspect
of the capsule was excised. These releases were performed in order to free the
subscapularis muscle-tendon unit for 360° about its long axis. The
subscapularis was reattached with 1-mm Cottony Dacron sutures (Deknatel, Fall
River, Massachusetts) passed through 2-cm-long bone tunnels from the neck of
the humerus to the osteotomy site. At the conclusion of the arthroplasty
procedure, the subscapularis tendon was reattached in a more medial location
at the proximal humeral osteotomy site, thereby functionally lengthening the
muscle-tendon unit by 1 to 2 cm.
Humeral Preparation
The articular surface of the humeral head was resected in a plane just
inside the rotator cuff insertion onto the greater tuberosity. The humeral
osteotomy ranged between 20° and 30° of retroversion. The location of
the varus-valgus angle of humeral head resection was determined by placing a
humeral osteotomy template along the anterior aspect of the arm parallel to
the shaft of the humerus. The superior-lateral portion of the mark was located
at the junction of the articular surface with the attachment of the rotator
cuff on the greater tuberosity.
A sharp-tipped reamer was introduced into the proximal part of the humerus
just posterior to the bicipital groove. Progressively larger reamers were used
until resistance was encountered in the diaphysis. The metaphysis was then
shaped with a broach that was scaled to the diaphyseal diameter. The
rotational orientation of the broach was kept constant during the broaching
process by virtue of four fins on the metaphyseal portion of the instrument.
This technique removed only the amount of bone necessary to accommodate the
prosthesis.
In every shoulder in the series, the prosthesis could be moved with
manually applied loads after final press-fitting. This was managed by
partially withdrawing the prosthesis from the humerus and introducing
morselized cancellous bone graft circumferentially into the humeral canal
(Figs. 2-A and 2-B). Cancellous
bone graft from the humeral head was used in all primary shoulder
arthroplasties, and cancellous allograft was utilized in the revision
procedures. The graft was morselized into 3 to 5-mm pieces with use of a 6-in
(15.2-cm) straight 5 × 12-mm rongeur. The prosthesis was then employed
as a tamp to compact the bone. The process was repeated with additional
morselized cancellous bone graft until a mallet was required to drive the
prosthesis into its final position and the prosthesis could not be rotated
within the canal or removed from the canal by manual traction.
Clinical
Active external rotation improved from a preoperative mean (and standard
deviation) of 9.0° ± 20.3° to a follow-up mean of 34.5°
± 17° (p < 0.0001). It improved (by 5° to 75°)
in forty-nine shoulders, did not change in three, and decreased (by 5° to
20°) in six. Active total elevation improved from a preoperative mean of
92.0° ± 32° to a follow-up mean of 123.2°
± 32° (p < 0.0001). It improved (by 5° to 120°)
in forty-five shoulders, did not change in five, and decreased (by 5° to
45°) in eight.
The mean SST score was 4.4 ± 3 points preoperatively, with an
improvement to 9.1 ± 3 points at the time of the last follow-up (p <
0.0001). The SST score improved (by 1 to 12 points) for fifty shoulders,
decreased (by 2 to 5 points) for seven, and did not change for one. The ASES
score increased from a preoperative mean of 40 ± 15 points to a
follow-up mean of 66 ± 28 points (p < 0.0001).
The visual analog score for pain improved from a preoperative mean of 62
± 24 points to a follow-up mean of 20 ± 23 points. The pain
score decreased (by 4 to 94 points) for fifty-two shoulders and increased (by
3 to 25 points) for six. The other preoperative and follow-up visual analog
scores are presented in Table
I. A significant mean improvement was observed in each (p <
0.0001).
Radiographic Findings
One of the fifty-eight stems was noted to have a 0.33-mm-thick lucent line
(as calculated by averaging the measurements of the three raters) in two zones
in the immediate postoperative period, and lucent lines were observed adjacent
to twenty-four of the fifty-eight stems at the time of final follow-up.
Multiple zones were seen to be involved on some follow-up radiographs (Tables
II and
III). Excluding the thirty-four
stems with no lu-cent line at the time of follow-up, the mean maximum
thickness of the lines was 0.47 mm (range, 0.17 to 1.17 mm, as calculated by
averaging the measurements of the three raters). When the stems without any
lucent line were included, the mean maximum thickness of the lucent lines at
the time of follow-up was 0.21 mm. The number of radiolucent lines in each
zone are shown in Table II.
The majority of the lucent lines observed at the time of follow-up appeared
to be near the distal tip of the stem (Fig.
3). To determine whether this distribution was significant, four
zones (1, 2, 6, and 7) were categorized as proximal zones and three zones (3,
4, and 5) were categorized as distal zones. Each shoulder was categorized
twice, in terms of whether a distal lu-cent line was present in at least one
zone or was not present and in terms of whether a proximal lucent line was
present in at least one zone or was not present. Lucent lines occurred more
frequently distally than proximally (p = 0.03, chi-square test).
In the evaluations of humeral component tilt, there was no instance in
which one of the raters indicated a valgus angle and another indicated a varus
angle. In some instances, there was disagreement about whether the angle was
0° (neutral) or either varus or valgus. Accordingly, the mean of the three
raters' measurements was calculated and, if the mean was not 0° (that is,
if one or more raters identified a tilt), then the angle was designated as
either varus or valgus in accordance with the judgment of the rater(s) who
identified a tilt. If all raters agreed that the tilt angle was 0°, then
the humeral component was considered to be in neutral.
The humeral component tilt angles are presented in
Table IV. Seventeen neutral,
seventeen valgus, and twenty-four varus humeral components were identified on
the immediate postoperative radiographs. The mean angles were 0°,
2.2°, and 2.6° for the neutral, valgus, and varus components,
respectively. At the time of follow-up, there were twenty neutral, fourteen
valgus, and twenty-four varus humeral components, and the mean angles were
0°, 2.7°, and 2.9°, respectively. The mean difference between the
immediate postoperative and follow-up angle measurements was —0.10°
± 0.68° (range, —3.3° to 0.83°). To conduct a test
aimed at determining whether stem tilt changed systematically over time, varus
values were arbitrarily assigned negative values and valgus values were
arbitrarily assigned positive values. A t test was conducted to determine
whether the mean (—0.10°) differed from 0°. The result was not
significant, indicating that, with the numbers studied, there was no tendency
for the mean tilt angle to shift (p = 0.25).
The largest absolute differences in tilt measurements between the immediate
postoperative and the follow-up time-period were 3.3°, 3.0°, and
1.3°, with the first two values associated with stems rated as being in
varus at baseline and in greater varus at the time of follow-up and the third
value associated with a stem rated as being in neutral at baseline and in
varus at the time of follow-up. All remaining differences in stem-tilt
measurements had absolute values of =1.0°.
With respect to tilt orientation, forty-nine of the fifty-eight shoulders
had the same ratings at the postoperative and follow-up intervals
(Table IV). Three humeral
components that had been rated as being in neutral at the immediate
postoperative interval were categorized as being in varus at the time of
follow-up, three that had been rated as being in varus at the immediate
postoperative interval were rated as being in neutral at the time of
follow-up, and three that had been rated as being in valgus at the immediate
postoperative interval were rated as being in neutral at the time of
follow-up. Thus, no humeral component was rated as shifting from varus to
valgus or vice versa. No component demonstrated subsidence.
Relationships Between Clinical and Radiographic Findings
No correlation was found between the duration of follow-up and the maximum
thickness, in millimeters, of the lucent lines adjacent to the humeral
component. This suggests that the increase in the thickness of the lucent
lines observed between the immediate postoperative radiographs and the
follow-up radiographs may not be progressive at least in the mid-term (Pearson
r = 0.15, p = 0.26).
No correlation was found between the maximum thickness, in millimeters, of
the lucent lines, and the follow-up ASES scores (Pearson r = 0.02, p = 0.91),
and the follow-up SST scores were not related to the presence or absence of
lu-cent lines at the time of follow-up. The mean SST score was 9.13 ± 3
points for the shoulders with no lucent line and 9.08 ± 3 points for
the shoulders with lucency (p = 0.95). The follow-up visual analog scores are
presented, according to whether or not there was lucency adjacent to the
humeral component, in Table V.
The mean score on each visual analog scale was superior in the group without a
lucent line. With the assumption that each scale is statistically independent,
a two-tailed sign test yields a p value of 0.03 for this series of visual
analog scale results.
Improvement in the visual analog score for pain was compared between the
shoulders with and those without lucency at the time of follow-up. The pain
score for the thirty-four shoulders without a lucent line changed from a
preoperative mean of 64 points to a follow-up mean of 18 points, which was an
improvement of 46 points. The pain score for the twenty-four shoulders with
lucency changed from a preoperative mean of 59 points to a follow-up mean of
24 points, an improvement of 35 points. The difference between the mean
improvements in these two groups was not found to be significant (p = 0.18),
but statistical power was modest. With the sample sizes available, the
difference that could be detected with 90% power with a two-tailed t test
(nQuery Advisor 5.0; Statistical Solutions, Cork, Ireland) was 25 points,
alpha = 0.05. There were no significant differences, between shoulders with
and those without a lucent line, with respect to preoperative to follow-up
improvement on any of the six visual analog scales; however, the group without
lucency had more improvement in the scores on each of the six scales (p =
0.03, two-tailed sign test).
There was also no significant difference in either of the range-of-motion
measurements between the group with and that without lucency adjacent to the
humeral component. The mean active total elevation at the time of follow-up
was 124° ± 34° in the group without lucency compared with
123° ± 30° in the group with lucency (p = 0.92). The mean
active external rotation was 35° ± 19° and 34° ±
14°, respectively (p = 0.97).
The shoulders treated with hemiarthroplasty were compared with those
treated with total shoulder arthroplasty to determine whether lucency adjacent
to the humeral component was related to the presence or absence of a
prosthetic glenoid. With the numbers studied, there was no evidence of a
difference in the mean maximum thickness of the lucent lines, measured in
millimeters, between those groups. The mean maximum thickness of the lucent
lines was 0.20 ± 0.26 mm in the sixteen shoulders treated with total
shoulder arthroplasty and 0.21 ± 0.31 mm in the forty-two treated with
hemiarthroplasty (p = 0.85).
The humeral components were categorized as neutral or non-neutral in
accordance with the measurement of their tilt at the time of follow-up, and
these two groups were compared to determine whether they differed with respect
to the mean maximum thickness of the lucent lines at the time of follow-up.
The mean maximum thickness of the lucent lines was 0.18 ± 0.28 mm for
the twenty neutral stems compared with 0.23 ± 0.30 mm for the
thirty-eight non-neutral stems. This difference was not significant (p =
0.52).
Complications
There were nine complications in the entire series, including the
fifty-eight shoulders that had been followed for twenty-four months or more
and the thirteen with incomplete follow-up. There were three intraoperative
complications. These included a case of transient motor dysfunction of the
axillary nerve, which resolved without sequelae within three months; a case of
radial nerve dysfunction, which resolved without sequelae within six weeks;
and a fracture of the proximal part of the humeral shaft, which was stabilized
with cerclage wires. No alteration of the postoperative rehabilitation was
required for the patient who had the fracture, which united uneventfully.
There were six postoperative complications. These included five cases of
symptomatic loosening of the glenoid component, all of which were managed with
removal of the component followed by grafting of the resulting glenoid defect
with cancellous bone. These revisions were performed at an average of
sixty-two months (range, thirty-six to eighty-four months) following the index
procedure. There was also one patient with painful glenoid arthrosis who
underwent conversion from a hemiarthroplasty to a total shoulder arthroplasty
at twenty-four months postoperatively.
Press-fitting of the humeral stem in total shoulder arthroplasty and
shoulder hemiarthroplasty has the advantage of preserving bone stock and
facilitating revision; however, numerous reports have described an increased
prevalence of complete radiolucent lines, subsidence, and tilting of the
humeral component when cement is not
employed4,5,9,15.
In a long-term follow-up study of the Neer-II prosthesis, radiographic changes
indicative of loosening were identified in forty (49%) of eighty-one shoulders
treated with an uncemented press-fit humeral component and in none of eight
treated with a cemented
component5.
In a more recent report, the results of seventy-two total shoulder
arthroplasties performed with a press-fit Neer-II humeral component were
assessed clinically and radiographically at an average of 4.1 years (range,
two to 7.8 years)7.
The humeral component was considered to be at risk for clinical loosening when
radiographs showed a lucent line of =2 mm in width that was present in
three or more zones, or when tilt or subsidence was identified on sequential
radiographs. Forty (56%) of the seventy-two components were judged to be at
risk for clinical loosening. This prevalence is greater than the rate of 31%
(twenty-five in the initial study group of eighty-one) for cemented glenoid
components in the same patient population. There were no identifiable
characteristics associated with the development of radiographic evidence of an
at-risk humeral component except a longer average duration of follow-up in the
at-risk group (4.7 years compared with 3.3 years, p = 0.001). Additionally,
humeral components at risk had a higher rate of endosteal erosion (p =
0.04).
A possible explanation for the high prevalence of adverse radiographic
findings associated with press-fit humeral components may be the marked
variability in proximal humeral morphology. The complex shape of the humeral
canal and the individual variability associated with this region may make it
difficult to achieve a highly conforming fit between a prosthesis and the
internal anatomy of the humerus. This hypothesis is supported by a cadaver
study by Robertson et
al.16, who examined
cross sections of the proximal part of the humeral canal using computerized
tomographic data and three-dimensional computer modeling. They determined that
proximal humeral cross sections are elliptical instead of circular. The study
also revealed that internal retroversion of the elliptical cross section
increases distally along the axis of the canal, with values depending on the
distance from the anatomic neck to the point of measurement; the proximal part
of the humeral canal is shaped like a slightly flattened tube or a narrow
funnel that has been twisted along its axis.
These findings have three important implications for humeral arthroplasty.
First, an uncemented stem with a proximal canal fit would align itself with
the internal contours of the proximal part of the humerus and be seated in
anatomic retroversion. However, if the humeral neck resection is not in
anatomic retroversion, the prosthetic collar may not sit evenly on the cut
bone surface. Second, as the degree of canal retro-version increases from
proximal to distal, there may be a mismatch in version alignment, especially
for longer-stemmed uncemented prostheses that are press-fit distally. Third,
no existing humeral component matches this shape. These findings portend
suboptimal contact between the bone and the prosthesis. Consequently, an
uncemented prosthesis that appears to be securely fixed intraoperatively may,
in fact, be tenuously fixed and loosen over time. In the past five years,
several
reports7,17,18
have suggested that cement fixation should be utilized for arthroplasty
systems that offer only a few sizes of straight humeral stems because these
components have a limited ability to achieve a robust press-fit in the highly
variable anatomy of the proximal part of the humerus. Conversely, modular
arthroplasty systems that offer a number of implant sizes, metaphyseal tapers,
tissue-ingrowth capability, and instrumentation for precise humeral
preparation would be more ideal for uncemented
fixation7,17,19.
To determine whether compaction bone-grafting can optimize the fit and fill
achieved between a humeral prosthesis and the humerus, Hacker et
al.18 conducted a
cadaver study using computerized tomography and void analysis. Their technique
employed conservative reaming and broaching of the humeral canal to fit the
prosthesis, followed by the liberal insertion of cancellous autograft. The aim
was to fill gaps between the endosteal surface and the prosthesis. Results
demonstrated a significant reduction in the voids between the humerus and the
prosthesis (p < 0.001). The effect was most marked in the proximal and
middle thirds of the implant. Clinically, these results suggest that
bone-grafting may offer a safe, simple, inexpensive, and effective means of
securing press-fit humeral components and avoiding the use of cement.
The present study indicates that compaction bone-grafting in association
with implantation of a modular humeral prosthesis with proportionately sized,
tapering metaphyseal segments and a cylindrical diaphysis results in
substantial functional improvement and pain relief at a mean of five years
postoperatively. According to conventional criteria, the majority of the
humeri in the study would be categorized as suboptimal or high-risk candidates
for implantation of a press-fit humeral component because of poor bone
quality. On the basis of previous reports in the
literature5,7,
twenty-nine to thirty-four of the fifty-eight humeral components in this
series would be expected to have radiographic signs of being at risk for
loosening. Instead, none had such signs. Additionally, there were no clinical
failures due to aseptic loosening of the humeral component. Lucencies were
very small or nonexistent and, when present, tended to be in distal zones.
There was some evidence that the presence of small lucent lines was associated
with slightly lower visual analog scores, although it is not clear whether
there is a causal relationship between these variables. It is possible that
small lucent lines and slightly lower visual analog scores are caused by a
third factor, such as the speed of graft integration into host bone. No
evidence of lucency progression over time and no differences in other clinical
outcomes according to lucency status were observed in this study.
The absence of findings related to failure of humeral component fixation in
this study contrasts with results in reported series in which compaction
bone-grafting was not
employed4,5,7,9,15.
The results with respect to pain relief and functional improvement are
comparable with those in reports on cemented and ingrowth humeral components
and are superior to those for press-fit cylindrical stem
implants5,7-10,15,20.
The inferences that may be drawn from the present study are subject to
limitations: (1) the patients were from a referral-based shoulder practice at
one institution and may not be representative of other patient populations;
(2) no postoperative computerized tomographic void analysis was performed to
assess the fit and fill achieved between the humeral component and the
humerus; (3) implant stability was determined by qualitative assessment, so a
quantitative measurement of press-fit stability was not established; (4) the
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of shoulders available for review precluded us from determining whether there
was a significant association between small lucent lines and an adverse effect
on patient outcome.
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