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Radiograph Based Evaluation of Uncemented Humeral Hemi-Arthroplasty
John Ibrahim, MD
1, Sophie Darwiche, MD
2, Jefferson Li, MD
2, Michael J Niemann, MD
3, Mark E. Baratz, MD
4; Robert Kaufmann, MD
5(1)UPMC, Pittsburgh, PA, (2)University of Pittsburgh Medical Center, Pittsburgh, PA, (3)West Virginia University, Morgantown, WV, (4)Hand and Upper Extremity Surgery, University of Pittsburgh Medical Center, Washington, PA, (5)University of Pittsburgh, Pittsburgh, PA
Background:
Hemiarthroplasty may be considered for the treatment of elbow arthritis if the cartilage on the
proximal ulna is not damaged. The humeral component must reproduce native anatomy such as
the spool diameter, implant rotation, rotation axis. The goal of this study was to identify whether
a custom designed hemiarthroplasty implant that achieves fixation with intramedullary screws
can restore native anatomy based on radiographic parameters.
Methods:
We stripped six cadaveric specimens of soft tissue and obtained AP and lateral radiographs to
characterize distal humerus anatomy. We implanted hemiarthroplasty components using a
previously designed implant and obtained post implantation radiographs. Pre-implantation
measurements included: 1) the intramedullary canal diameter, 2) the valgus angle of the native
humerus on the AP view, 3) the angle between the intramedullary canal and the flexion-
extension axis, 4) the medial-lateral width of the flexion-extension axis on the AP view, and 5)
the trochlear width on the AP view. Each arm was its own pre-implantation comparative arm.
These measurements were compared with the post-implantation intramedullary screw size,
spool size, restoration of the centerline of rotation, and the location of the ulnohumeral
articulation.
Results:
Six cadavers (five male, one female) underwent implantation. The average age of the cadavers
was 62.7 years (range 53 - 74).
1) Mean difference in trochlear width on the AP radiograph was 3.39 mm (2.37 - 4.7mm)
2) Mean difference in position of the capitellum center on the AP radiograph was 5.28mm (3.92
- 7.29mm)
3) Mean difference in anterior offset of the capitellum on the lateral radiograph was 3.74 mm
(1.13 - 6.57 mm)
4) Mean difference between the humeral centerline to the center of the trochlea's narrowest
point on the AP radiograph was 0.5 mm (0.15 - 0.95 mm).
5) Mean difference in the offset between the centerline of rotation on the AP radiograph was
0.35mm (0.08 - 0.87mm)
6) Mean angle between the implant body and the intramedullary screw on the lateral radiograph
was 1.45 degrees (0.58 - 2.57 degrees)
Conclusions:
This study characterized distal humerus anatomy radiographically and compared these
parameters to an uncemented hemiarthroplasty. We were able to reproduce native anatomy
with an implant system utilizing intramedullary screw fixation. Recreation of native anatomy was
achieved with the trochlea center, capitellum center, and centerline of rotation.
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