Abstract
Background: Surgical excision of the radial head is frequently
required after a comminuted fracture of the radial head. The outcome of this
procedure is often unpredictable, with some patients experiencing ulna-sided
pain in the wrist secondary to proximal migration of the radius. Insertion of
a radial head prosthesis could prevent proximal radial migration and restore
normal load-sharing at the wrist. The thickness of the radial head implant is
an important variable in restoring anatomical radial length; however, the
effects of varying the length of implants that were used to reconstruct the
radius on load-sharing at the wrist have not been studied biomechanically, to
our knowledge.
Methods: A miniature load cell was attached to fifteen fresh-frozen
cadaveric forearms to record force in the distal part of the ulna as the wrist
was axially loaded to 134 N of compression force. Proximal displacement of the
radius relative to the capitellum was also recorded. Loading tests on intact
forearms were performed with the elbow in valgus and varus alignment and with
three positions of wrist rotation (neutral, 45° of pronation, and 45°
of supination). Loading tests were then repeated, with the same positions of
varus and valgus elbow alignment and wrist rotation as had been used in the
tests of the intact forearm, after radial head excision and subsequent
insertion of metal radial head implants that restored anatomical length,
implants that produced a radial length that was longer than the anatomical
length, and implants that produced a radial length that was shorter than the
anatomical length. Testing of these different implant thicknesses was repeated
after sectioning of the interosseous membrane.
Results: The mean distal ulnar forces and mean proximal radial
displacements following insertion of an implant that restored anatomical
length were not significantly different from the corresponding values for the
intact forearm. At neutral wrist rotation, replacing that implant with an
implant that increased the radial length by 4 mm (after sectioning of the
interosseous membrane) decreased the mean distal ulnar force from 13.4% to
3.3% of the applied wrist force with the elbow in valgus alignment and from
29.1% to 8.6% with the elbow in varus alignment. Replacing the implant that
restored anatomical length with one that decreased the length by 4 mm (after
sectioning of the interosseous membrane) significantly increased the mean
distal ulnar force from 13.4% of the applied wrist load to 33.3% with the
elbow in valgus alignment and from 29.1% to 51.6% with it in varus alignment.
The mean distal ulnar forces were not significantly affected by the position
of wrist rotation when the elbow was in valgus alignment. However, when the
elbow was in varus alignment, the mean distal ulnar forces associated with all
reconstructed radial lengths were significantly higher when the wrist was
placed in 45° of supination.
Conclusions: In this cadaveric model, insertion of a metal implant
maintained distal ulnar forces at normal levels, at all three positions of
wrist rotation, when the radius had been restored to its original anatomical
length. Distal ulnar forces and proximal radial displacements were
significantly affected by the reconstructed length of the radius.
Clinical Relevance: Radial head implants are utilized to prevent
proximal migration of the radius as the wrist is loaded; this is especially
important when the interosseous membrane has been ruptured and thus cannot
help to limit radial displacement. At the time of surgery, comminution and
displacement of a radial head fracture may make estimation of the original
radial length difficult. Our results demonstrate that, in terms of distal
ulnar loading, it is preferable to insert an implant that is too thick rather
than too thin.
Surgical excision of the radial head is frequently required after a
comminuted radial head fracture, especially when the comminution and
displacement are so severe that open reduction and internal fixation of the
fracture is not technically
feasible1-3.
There are two important clinical scenarios in which this injury occurs. In one
scenario, the distal radioulnar ligament complex and the interosseous membrane
are uninjured and remain intact. In that instance, it is thought that
increased tightening of the interosseous membrane can lead to loss of forearm
supination or that subsequent subluxation of the distal radioulnar joint can
lead to wrist pain and decreased grip
strength3. In the
second clinical scenario, the interosseous membrane (and possibly the distal
radioulnar ligament complex) is damaged during large proximal displacements of
the radius as the radial head collapses. In either case, there is a subset of
patients in whom pain in the wrist and forearm will develop after radial head
excision4.
The outcome of radial head excision is often unpredictable and sometimes
poor. The clinical results of replacements with silicone elastomer radial head
implants have been disappointing, and their use is no longer
recommended5-7.
The clinical failure of these implants was primarily due to a poor choice of
material, which fragmented under high forces at the elbow, and to the
secondary synovitis that developed from the implant debris that was generated.
Although this disappointing experience with silicone elastomers is a reason
for caution, the fundamental concept of radial head replacement is sound.
Recently, renewed interest in this procedure has been expressed by some
surgeons who have used metal radial head
implants8,9.
Currently, there are several options for replacing a resected radial head,
including a radial head allograft, a one-piece metal prosthesis, a two-piece
metal prosthesis, and a modular radial head implant with multiple stem lengths
and head sizes. Each of these choices has advantages and disadvantages that
hinge on certain parameters, such as ease or difficulty of use, associated
complications, and ability to adjust the size or length of the prosthesis. The
effect on load-sharing at the wrist of varying the reconstructed length of the
radius with modular implants has not been studied biomechanically, to our
knowledge.
The overall hypotheses of this study were that the thickness of a radial
head implant (and hence the reconstructed length of the radius) significantly
affects the force transmitted through the distal part of the ulna and that,
for a given reconstructed length, distal ulnar forces are significantly
altered by resection of the interosseous membrane. The experimental objectives
were (1) to perform baseline measurements of distal ulnar force and proximal
displacement of the radius relative to the capitellum in an intact forearm
during axial loading of the wrist, (2) to repeat the measurements after
insertion of a metal radial head implant that restored the radius to its
anatomical length and after insertion of implants that produced radial lengths
that were less than and greater than anatomical lengths, (3) to measure
varus-valgus laxity of the elbow before and after insertion of the implants,
and (4) to repeat the forearm loading tests with each reconstructed length
after resection of the interosseous membrane.
Fifteen fresh-frozen cadaver forearms were used for this study. The donors
ranged from sixty-five to ninety-one years of age (mean, 77.8 years) at the
time of death; eight were men and seven were women. Radiographs of all of the
forearms revealed normal anatomy without substantial pathological findings in
the wrist, forearm, or elbow. Ulnar variance, as measured radiographically,
was +1 mm in one forearm, 0 mm in four, —1 mm in five, —2 mm in
two, —3 mm in two, and —5 mm in one. The mean ulnar variance (and
standard deviation) was —1.27 ± 1.53 mm. All forearms were potted
proximally at the distal humeral level and distally at the central three
metacarpals. The first and fifth metacarpals were removed.
A custom-designed miniature load cell was used for measurement of distal
ulnar force. The load cell consisted of a strain-gauged beam element that was
connected to prongs cemented into the distal part of the ulna. The load cell
was installed and then was calibrated in situ for each
specimen10. A
linear variable differential transducer (Schaevitz Engineering, Pennsauken,
New Jersey) was used to measure displacement of the radial head relative to
the capitellum. The cylindrical coil of the transducer was placed into the
casing of an insert threaded into a hole drilled into the lateral epicondyle;
an extension of the magnetic core rod passed into a hole drilled through the
capitellum and came into contact with the radial head. A schematic diagram of
the displacement transducer and a description of its installation can be found
in a previous
publication11.
The potted humerus was mounted to a fixture attached to the crosshead of a
materials testing system machine (model 812; MTS, Minneapolis, Minnesota); the
elbow was flexed to 90°. Load was applied to the potted central three
metacarpals of the hand at a rate of approximately 1 mm/sec, with a maximum
applied load of 134 N. Testing was performed at neutral wrist rotation (the
plane of the three metacarpals aligned with the flexion-extension plane of the
elbow), 45° of wrist pronation, and 45° of wrist supination. For these
tests, the wrists were in neutral flexion-extension and neutral
dorsiflexionvolar flexion. The wrists were maintained in these positions
manually as the forearms were loaded.
Previous studies from this
laboratory10-13
have shown that load-sharing at the wrist depends on the varus-valgus position
of the elbow. The varus and valgus testing positions were defined, as
previously10, by
applying a 2.5-N-m valgus moment to the elbow (which forced the radial head
into contact with the capitellum) and a 2.5-N-m varus moment to the elbow
(which created an initial gap between the radial head and the capitellum).
Varus-valgus laxity of the elbow was measured with an inclinometer
(resolution, 0.5°) to record the relative angulation between pins drilled
transversely into the humeral condyles and the proximal part of the ulna as
2.5-N-m varus and valgus moments were applied to the elbow joint. The
associated displacement of the radial head relative to the capitellum was also
recorded by the linear variable differential transducer between varus and
valgus alignments.
The implant used for this study was the EVOLVE Modular Radial Head System
(Wright Medical Technology, Arlington, Tennessee), which is a two-part modular
prosthesis with up to five separate stem and fifteen separate head components.
We utilized aluminum trial implants for this study, which are identical in
geometry and size to an actual implant. The head and stem components could be
assembled and disassembled as needed during the course of testing.
Varus-valgus laxity of each intact forearm specimen was measured. Forearm
loading tests were performed at the three positions of wrist rotation and with
varus and valgus elbow alignment. Distal ulnar force (recorded at 134 N of
applied wrist load) and proximal radial displacement (calculated as the
difference between displacement values at 13 N and 134 N of applied wrist
force) were determined in each test. These initial measurements of distal
ulnar force, proximal radial displacement, and varus-valgus laxity served as
baseline levels.
Using a dial caliper, a measurement was made of the distance between the
articular surface of the radial head and a reference mark on the proximal part
of the radius at a fixed distance from the radial head; this was used to
establish the anatomical radial length. The radial head was then resected near
the base of the neck, perpendicular to the radial shaft. Next, an appropriate
stem size and head diameter, matched to the size of the radial head that had
been removed, were selected. Ring-shaped disk spacers were inserted as needed
beneath the head of the implant to restore the reconstructed radial length to
within 0.5 mm of that of the intact specimen. This was referred to as the 0-mm
implant thickness (i.e., the anatomical thickness). Reconstructed lengths that
were 2 and 4 mm longer than the anatomical length were achieved by inserting
thicker radial head components (+2 and +4-mm implants). Similarly, implants
that were 2 and 4 mm thinner than the 0-mm implant were used to produce
reconstructed radial lengths that were shorter than the anatomical length
(—2 and —4-mm implants).
Varus-valgus laxity was measured with each implant thickness, with the
interosseous membrane intact. Forearm loading tests were then repeated with
each implant thickness at each position of wrist rotation. The implant loading
tests were performed with the elbows in the varus and valgus alignment that
had been determined for the intact specimens. Finally, the entire interosseous
membrane, including the central band, was sectioned, and the measurements of
distal ulnar force and proximal radial displacement were repeated.
Statistical Methods
A one-way repeated-measures analysis-of-variance model was used to
determine significant differences in mean varus-valgus laxity between the
different conditions: the intact specimens, those with a —4-mm implant,
those with a —2-mm implant, those with a 0-mm implant, those with a
+2-mm implant, and those with a +4-mm implant. For each combination of
specimen-status conditions (varus and valgus elbow alignment as well as intact
and sectioned interosseous membrane), a one-way repeated-measures
analysis-of-variance model was used to determine significant differences in
mean distal ulnar forces and mean proximal radial displacements between the
specimens with a 0-mm implant and the intact specimens, those with a
—4-mm implant, those with a —2-mm implant, those with a +2-mm
implant, and those with a +4-mm implant. With each implant thickness, a paired
Student t test was used to determine significant differences in mean distal
ulnar force and mean proximal radial displacement between the specimens with
an intact interosseous membrane and those with a sectioned interosseous
membrane. For each combination of specimenstatus conditions (varus and valgus
elbow alignments as well as intact and sectioned interosseous membrane), a
one-way repeated-measures analysis-of-variance model was used to determine
significant differences in mean distal force among the three positions of
wrist rotation for the intact specimens, those with a 0-mm implant, those with
a —4-mm implant, and those with a +4-mm implant. Multiple pairwise
comparisons between means were made with use of the Student-Newman-Keuls
procedure. The level of significance was p < 0.05.
The mean varus-valgus laxity of the intact forearm (measured as the
angulation of the proximal part of the ulna relative to the distal part of the
humerus) was 10.0° (range, 5° to 17°). The mean laxity increased
2.0° after insertion of a 0-mm implant (p < 0.05), and the
corresponding increase in the mean joint-separation distance in the lateral
joint compartment was 1.41 mm (p < 0.05). The mean laxities (in degrees)
with the +2, —2, +4, and —4-mm implants were not significantly
different from the mean laxity with the 0-mm implant
(Table I). The mean radial head
displacements (in millimeters) with the +2 and +4-mm implants were
significantly smaller (p < 0.05) than the displacement with the 0-mm
implant; the mean change in displacement was —1.03 mm with the +2-mm
implant and —1.95 mm with the +4-mm implant.
The mean distal ulnar force (as a percentage of the applied wrist force) in
the intact forearm was 22.3% with the elbow in varus alignment and 12.1% with
it in valgus alignment. With the interosseous membrane present, the mean
distal ulnar forces with the 0-mm implant were not significantly different
from the corresponding values for the intact forearm
(Fig. 1), but the mean distal
ulnar forces with the +2 and +4-mm implants were significantly smaller than
the corresponding values with the 0-mm implant. With the elbow in varus
alignment, replacement of the 0-mm implant with the +4-mm implant decreased
the mean distal ulnar force from 18.2% of the applied wrist force to 7.6% with
the interosseous membrane present and from 29.1% to 8.6% with the interosseous
membrane sectioned. With the elbow in valgus alignment, replacement of the
0-mm implant with the +4-mm implant decreased the mean distal ulnar force from
12.5% of the applied wrist force to 3.3% with the interosseous membrane
present and from 13.4% to 3.3% with the interosseous membrane sectioned
(Fig. 1).
With the interosseous membrane intact, the mean distal ulnar force with the
—4-mm implant (20.5%) was significantly greater than that with the 0-mm
implant (12.5%) only when the elbow was in valgus alignment
(Fig. 1). It should be noted
that the mean distal ulnar forces with the —4-mm implant and the
interosseous membrane intact were equivalent to those with a resected radial
head and the interosseous membrane intact. This was true because the tensed
interosseous membrane prevented contact of the —4-mm implant with the
capitellum (as confirmed visually) under 134 N of applied wrist load, even
with valgus alignment of the elbow. With the elbow in varus alignment and the
interosseous membrane present, the mean distal ulnar forces with the +2 and
+4-mm implants were significantly smaller than the value with the —4-mm
implant. With the elbow in valgus alignment and the interosseous membrane
present, the mean distal ulnar forces with the 0, +2, and +4-mm implants were
significantly smaller than the value with the —4-mm implant.
With the interosseous membrane sectioned, the mean distal ulnar forces with
the —2 and —4-mm implants were significantly greater than the
corresponding values with the 0-mm implant with the elbow in varus alignment
(Fig. 1). Replacement of the
0-mm implant with the —4-mm implant increased the mean distal ulnar
force from 29.1% of the applied wrist force to 51.6% with the elbow in varus
alignment and from 13.4% to 33.3% with it in valgus alignment. The mean distal
ulnar forces with the interosseous membrane sectioned were significantly
greater than the corresponding levels with the interosseous membrane present
when the 0, —2, and —4-mm implants were tested with the elbow in
varus alignment and when the —4-mm implant was tested with the elbow in
valgus alignment.
The mean proximal radial displacements with the 0-mm implant and the
interosseous membrane present were not significantly different from the
corresponding values for the intact forearm
(Fig. 2). With the elbow in
varus alignment and the interosseous membrane present, the mean proximal
radial displacements with the +2 and +4-mm implants were significantly smaller
than the corresponding values with the 0-mm implant and the mean displacements
with the —2 and —4-mm implants were significantly greater than the
corresponding values with the 0-mm implant. With the elbow in varus alignment
and the interosseous membrane present, the mean proximal radial displacements
with the 0, +2, and +4-mm implants were significantly smaller than the
displacement with the —4-mm implant. With the elbow in valgus alignment
and the interosseous membrane present, the mean proximal radial displacement
with the +4-mm implant was significantly smaller than the corresponding value
with the 0-mm implant, the mean displacements with the —2 and
—4-mm implants were significantly greater than the corresponding value
with the 0-mm implant, and the mean displacements with the —2, 0, +2,
and +4-mm implants were significantly smaller than the corresponding value
with the —4-mm implant (Fig.
2). With the elbow in varus alignment, the mean proximal radial
displacements with the interosseous membrane sectioned were significantly
greater than the corresponding levels with the interosseous membrane intact in
the tests with the —2 and —4-mm implants.
With the elbow in valgus alignment, the mean distal ulnar forces with the
wrist in 45° of pronation and supination were not significantly different
from the corresponding values with the wrist in neutral rotation
(Fig. 3). The mean distal ulnar
forces with the —4 and +4-mm implants were significantly different from
the corresponding values with the 0-mm implant at all three positions of wrist
rotation. With the elbow in varus alignment, the mean distal ulnar forces with
the wrist in 45° of pronation were not significantly different from the
corresponding values with the wrist in neutral rotation
(Fig. 4), whereas the mean
distal ulnar forces with the wrist in 45° of supination were significantly
higher than corresponding values with the wrist in neutral rotation. With an
intact interosseous membrane and the elbow in varus alignment, changing the
wrist rotation from neutral to 45° of supination increased the mean distal
ulnar force from 7.6% of the applied wrist force to 15.5% when the +4-mm
implant was tested, from 18.2% to 30.5% when the 0-mm implant was tested, and
from 21.5% to 30.3% when the —4-mm implant was tested
(Fig. 4). With a sectioned
interosseous membrane and the elbow in varus alignment, changing the wrist
rotation from neutral to 45° of supination increased the mean distal ulnar
force from 8.6% to 18.2% with the +4-mm implant, from 29.1% to 42.2% with the
0-mm implant, and from 51.6% to 63.5% with the —4-mm implant
(Fig. 4).
We have found only three previous biomechanical studies related to loading
of radial head implants in cadavera. Knight et
al.9 performed load
versus displacement tests on fresh-frozen and embalmed radiohumeral joints
before and after insertion of cobalt-chromium and silicone radial head
implants. They reported that the mean load versus displacement curve was not
altered after prosthetic replacement of the radial head, but they gave no
statistical support for this statement.
Sellman et al.14
performed load versus displacement tests on ten fresh-frozen cadaveric
forearms before and after insertion of radial head implants made of titanium
or silicone. The calculated stiffness values after titanium radial head
replacement averaged 89% of the stiffness of the intact forearm, whereas the
values after silicone replacement averaged 66% of the stiffness of the intact
forearm.
Gupta et al.15
inserted a single load cell into the radius of four fresh-frozen forearm
specimens and loaded the wrists before and after implantation of an ultra-high
molecular weight polyethylene or a silicone radial head implant.
Qualitatively, they observed that more proximal radial force was transmitted
by the polyethylene than by the silicone, but no statistical analysis was
presented.
In the present study, we used a previously published
methodology10,11
to investigate the effects of radial head implantation on distal ulnar
loading. We believe that we are the first to investigate the biomechanical
effects of varying the length of the reconstructed radius with use of a radial
head implant.
We found that the mean varus-valgus laxity of the elbow increased 2.0°,
with an associated increase in displacement of 1.41 mm, after insertion of the
0-mm implant. While these increases were significant (p < 0.05), the
clinical implication is unclear. The increase in laxity could be due in part
to increased mobility of the reconstructed radial head following section of
the annular ligament, which acts to stabilize a natural radial head.
The relationship between varus-valgus laxity of the elbow and implant
thickness was particularly interesting. One would expect that use of a
—4-mm implant would leave a larger-than-normal gap between the
reconstructed head and the capitellum. Theoretically, this would increase
elbow laxity since the prosthetic radial head would have farther to travel
before coming into contact with the capitellum as a valgus moment is applied.
Table I shows that there were
no significant differences in the mean laxities or displacements among the 0,
—2, and —4-mm implants. We concluded that the medial collateral
ligament, not radial head contact, was the primary structure limiting the
valgus position of the ulna. Conversely, a +4-mm implant would be expected to
decrease varus-valgus laxity because the thicker implant would lengthen the
radius, which in turn would reduce valgus laxity. This was confirmed by the
measurements of varus-valgus displacement but not by the angular measurements
recorded by the inclinometer.
A comparison of the changes in distal ulnar force and proximal radial
displacement with changes in the implant thickness revealed similar trends. An
increase in proximal radial displacement was accompanied by a corresponding
increase in distal ulnar force. Greater proximal radial displacement created
an increased ulnar positive variance at the wrist, which in turn increased
distal ulnar loading.
Overall, distal ulnar forces and proximal radial displacements were greater
with varus elbow alignment than they were with valgus alignment. With varus
alignment, there was a greater initial gap between the radius and capitellum;
this allowed more radial displacement proximally, which produced higher ulnar
forces. It is noteworthy that, with the —4-mm implant, the mean distal
ulnar force with the sectioned interosseous membrane was significantly greater
than that with the intact interosseous membrane. No contact of the radial head
with the capitellum was detected visually at 134 N of applied wrist force
(varus or valgus) when the interosseous membrane was intact. Therefore, in
this study, when the interosseous membrane was intact, the distal ulnar forces
and proximal radial displacements with the —4-mm implants were
equivalent to those with the resected radial head. With the interosseous
membrane sectioned, the radius was free to displace proximally until it came
into contact with the capitellum.
The changes in the distal ulnar force that occurred with forearm rotation
were particularly interesting. With the elbow in valgus alignment, the radial
head was seated against the capitellum, providing a stable axis for forearm
rotation. Thus, ulnar load was not affected by forearm rotation in valgus
alignment. With varus alignment, the radial head was pulled away from the
capitellum; this did not provide a stable proximal pivot point for forearm
rotation. Thus, with the elbow in varus alignment, distal ulnar forces with
the wrist in 45° of supination were consistently higher than those with
the wrist in neutral rotation.
With the exception of the —5-mm ulnar variance in one forearm, the
ulnar variances in the specimens in this study were representative of those in
a normal patient
population16.
Although the present study and previous studies in our
laboratory10,11
have shown that ulnar variance can significantly affect distal ulnar loading,
all of the load-sharing results after implant insertion were compared with the
values for the intact condition for each specimen. Since relative changes
between implant thicknesses were analyzed, we do not believe that the ulnar
variances in the intact specimens affected the overall conclusions of the
study.
Our study of cadavera demonstrated that the reconstructed length of the
radius following replacement of the radial head significantly affected loading
of the distal part of the ulna. Insertion of an implant that restored the
anatomical radial length restored physiological levels of distal ulnar
loading. Theoretically, this would be the most desirable surgical goal.
Selection of a radial head implant that is too thin creates a reconstructed
radius that is too short, which should be avoided to prevent increased distal
ulnar loading, even though a thinner implant may be technically easier to
insert. This is especially important when the interosseous membrane is
unavailable to help limit proximal displacement of the radius into the space
created between the implant head and the capitellum.
In contrast, selection of an implant that is too thick creates a
reconstructed radius that is longer than normal, which effectively makes the
wrist ulnar negative. This scenario may be more desirable in terms of reduced
distal ulnar loading; however, less ulnar load means greater radial load,
which in turn means greater loading between the implant and the capitellum.
Poor congruency between the implant and capitellum could have clinical
consequences such as increased cartilage wear at the interface, implant
loosening, elbow arthritis, pain, and loss of motion. Of course, the surgeon
must still consider the degree of distal radial loading that may affect other
conditions that are present, such as Kienböck disease or radioscaphoid
pain syndrome.
We found that when the 0-mm implant was assembled, with the stem and head
locked together in one piece, it could be inserted with modest effort.
Insertion of the —2 and —4-mm one-piece implants was easy.
Insertion of an assembled, one-piece +4-mm implant was impossible in some
specimens because of soft-tissue constraints and space limitations. We did not
experience this difficulty to the same extent when the interosseous membrane
was sectioned. Clinically, if radial head replacement is being performed with
the interosseous membrane intact, or tight, the surgeon may have difficulty
inserting a relatively thick one-piece implant. We found it much easier to
insert all of the implant thicknesses when the stem was first inserted into
the canal and the head was then assembled to the stem in situ.
Radial head fractures present a difficult problem for surgeons. If the head
is comminuted, crushed, or displaced, it can be difficult to estimate the
original radial length. Our results suggest that, if a reasonable estimation
of the original radial length is not possible, it is advisable to insert the
thickest radial head implant possible to avoid abnormally high distal ulnar
loading, in the absence of other known pathological changes along the radial
side of the wrist.
Although the magnitudes of changes in wrist loading that are required to
relieve or produce symptoms of ulna-sided wrist pain are unknown, this study
quantified the changes in distal ulnar loading that can be expected under the
controlled conditions of these experiments.
Note: The authors thank Steven R. Jackson for his assistance
with analysis of the data. They also thank Wright Medical Technology for
providing the trial implants used in this study.
Radin EL, Riseborough EJ.
Fractures of the radial head. A review of eighty-eight cases and analysis of
the indications for excision of the radial head and non-operative treatment.
J Bone Joint Surg Am.1966;48:
1055-64.481055
1966
[PubMed]
Swanson AB, Jaeger SH, La Rochelle
D. Comminuted fractures of the radial head. The role of silicone-implant
replacement arthroplasty. J Bone Joint Surg Am.1981;63:
1039-49.631039
1981
[PubMed]
Coleman DA, Blair WF, Shurr D.
Resection of the radial head for fracture of the radial head. Long-term
follow-up of seventeen cases. J Bone Joint Surg Am.1987;69:
385-92.69385
1987
[PubMed]
Sowa DT, Hotchkiss RN, Weiland
AJ. Symptomatic proximal translation of the radius following radial head
resection. Clin Orthop.1995;317:
106-13.317106
1995
[PubMed]
Morrey BF, Askew L, Chao EY.
Silastic prosthetic replacement for the radial head. J Bone Joint
Surg Am.1981;63:
454-8.63454
1981
Martinelli B. Silicone-implant
replacement arthroplasty in fractures of the radial head. A follow-up report.
Bull Hosp Jt Dis Orthop Inst.1985;45:
158-61.45158
1985
[PubMed]
Carn RM, Medige J, Curtain D, Koenig
A. Silicone rubber replacement of the severely fractured radial head.
Clin Orthop.1986;209:
259-69.209259
1986
[PubMed]
Harrington IJ, Tountas AA.
Replacement of the radial head in the treatment of unstable elbow fractures.
Injury.1981;12:
405-12.12405
1981
[PubMed][CrossRef]
Knight DJ, Rymaszewski LA, Amis AA,
Miller JH. Primary replacement of the fractured radial head with a metal
prosthesis. J Bone Joint Surg Br.1993;75:
572-6.75572
1993
[PubMed]
Markolf KL, Lamey D, Yang S, Meals R,
Hotchkiss R. Radioulnar load-sharing in the forearm. A study in cadavera.
J Bone Joint Surg Am.1998;
80: 879-88.80879
1998
[PubMed]
Shepard MF, Markolf KL, Dunbar
AM. Effects of radial head excision and distal radial shortening on
load-sharing in cadaver forearms. J Bone Joint Surg
Am.2001;83:
92-100.8392
2001
Markolf KL, Dunbar AM, Hannani K.
Mechanisms of load transfer in the cadaver forearm: role of the interosseous
membrane. J Hand Surg [Am].2000;25:
674-82.25674
2000
[PubMed][CrossRef]
Shepard MF, Markolf KL, Dunbar
AM. The effects of partial and total interosseous membrane transection on
load sharing in the cadaver forearm. JOrthop Res.2001;19:
587-92.19587
2001
[CrossRef]
Sellman DC, Seitz WH Jr, Postak PD,
Greenwald AS. Reconstructive strategies for radioulnar dissociation: a
biomechanical study. J Orthop Trauma.1995;9:
516-22.9516
1995
[PubMed][CrossRef]
Gupta GG, Lucas G, Hahn DL.
Biomechanical and computer analysis of radial head prostheses. J
Shoulder Elbow Surg.1997;6:
37-48.637
1997
[CrossRef]
Freedman DM, Edwards GS Jr, Willems
MJ, Meals RA. Right versus left symmetry of ulnar variance. A radiographic
assessment. Clin Orthop.1998;
354: 153-8.354153
1998
[PubMed][CrossRef]