Reconstruction of Anatomic Humeral Head Retroversion
Following 4-Part Fractures of the Proximal Humerus:
A Comparison of Two Techniques
**Flurin, PH; ***Wright, T; ****Zuckerman, J; *Angibaud, L; *Roche, C
*Exactech, Gainesville, FL; ** Bordeaux-Merignac Sports Clinic, FR;
***Shands Hosp., Gainesville, FL; ****Hosp. for Joint Diseases, NY, NY
ORS 2005
Based on Poster #646 (in Poster Session 1)
presented at Orthopaedic Research Society 2005
INTRODUCTION
Accurate reconstruction of anatomic Humeral Head Retroversion (HHR) is a significant concern in
treatment of 3 and 4 part fractures of the proximal humerus. Inadequate reconstruction (i.e. attaching the
greater and lesser tuberosities to the prosthesis in too much or too little version) alters muscle lever-arms,
rotator cuff tension, stability, and joint kinematics. Combined, these factors can impede or hinder
tuberosity healing ultimately leading to tuberosity complications: an important predictor of poor
outcomes1. The specific aim of this study is to evaluate the null hypothesis that there is no difference in
the ability of two different techniques to accurately reconstruct anatomic HHR.
Technique 1: Conventional method of restoring the HHR according to a fixed angle (HHREP) relative to
the epicondylar axis (EP) (Figure 1A)2.
Technique 2: Proposed method of restoring the HHR according to a fixed angle (HHRBG) relative to a
plane passing through both the intramedullary (IM) axis and the center of the bicipital groove (BG)
(Figure 1A).
DEFINITIONS
Humeral Head Equatorial Plane (HHEP): Defined as the plane perpendicular to the anatomic neck
passing through the superior and inferior points on the articular surface.
Bicipital Groove Anterior Offset (BGAO): Defined as the distance between the BG and the IM axis in
the anterior/posterior plane.
Bicipital Groove Lateral Offset (BGLO): Defined as the distance between the BG and the IM axis in
the medial/lateral plane.
MATERIALS and METHODS
A Coordinate Measuring Machine (MC 850, Zeiss, Esslingen, Germany) (CMM) was used to quantify the
anatomy of 49 dried cadaveric humeri (31 left, 18 right, courtesy of Prof. Vital at the Bordeaux Medical
University in France). The CMM digitized the center line of the bicipital groove along its course on the
proximal humerus relative to the IM axis (1st axis), the humeral head equatorial plane (2nd axis), and the
axis orthogonal to the previous two (3rd Axis). This technique was associated with an angular accuracy of
±1° and a linear accuracy of ±0.75 mm. This data was used to quantify the BGAO and BGLO of the
bicipital groove at four different heights: H1 to H4 (Figure 1B).
HHPO
B
A
BGAO
HHEP
H1
Hα
H4
HHREP anatomic
HHRBG anatomic
BGLO
Figure 1: The location of the BG in the coronal plane was analyzed relative to the IM axis using BGAO and
BGLO.(A) A fifth level (Hα) was introduced at the level of the most inferior aspect of the articular surface, this
level is assumed to be the location of the surgical neck.(B) Hα was found to be between H3 and H4.
HHREP anatomic was measured as the angle between the EP axis and the HHEP.
HHRBG anatomic was calculated as the angle between the plane passing through the IM axis and the
center of the BG at the level Hα and the HHEP using Equation 1.
Equation 1:
HHRBG anatomic = ARCTAN (BGAOα/BGLOα)
In order to evaluate the reliability associated with each technique to predict HHR, a computational
analysis was performed. This analysis calculated the angular error between the anatomic HHR and the
mean HHR. The error associated with HHREP (∆HHREP) is calculated using Equation 2. Similarly, the
error associated with HHRBG (∆HHRBG) is calculated using Equation 3.
Equation 2: ∆HHREP = ABS(HHREP anatomic – HHREP mean)
Equation 3: ∆HHRBG = ABS(HHRBG anatomic – HHRBG mean)
RESULTS
The bicipital groove was found to be in an anterior and lateral position with respect to the IM axis. The
pooled BGAO and BGLO values are presented in Table I. The mean value of HHREP anatomic (i.e.
HHREP mean) was determined to be 20.1° ± 11.0° (1.1 to 41.5°). The mean value of HHRBG anatomic
(i.e. HHRBG mean) was determined to be 43.7° ± 9.9° (21.9 to 69.6°). The mean angular error associated
with HHREP and HHRBG to predict the anatomic HHR is presented in Table II.
Table I
H1
H2
H3
Hα
H4
BGAO (AVG ± STD, mm)
7.3 ± 2.8
7.6 ± 2.2
7.4 ± 1.8
7.4 ± 1.6
7.2 ± 1.5
BGLO (AVG ± STD, mm)
8.2 ± 2.1
10.8 ± 1.9
8.2 ± 1.7
7.7 ± 1.7
5.9 ± 1.6
Table II
HHREP
HHRBG
Difference (∆/HHRBG)
HHR error (AVG ± STD)
8.8 ± 6.5º
7.9 ± 5.8º
+11.4%
DISCUSSION and CONCLUSION
The results of this study demonstrate that using the bicipital groove as an anatomic landmark to
reconstruct HHR is at least as reliable as using the EP axis. It was observed that this reliability is closely
related to the value of the BGLO (i.e., the larger the BGLO, the more accurate the technique that uses the
BG) (Table III). However, no statistical difference was observed in the reliability of either technique at
restoring HHR. Therefore, we accept the null hypothesis.
Table III
HHR error
(AVG ±
STD)
HHREP
HHRBG
Difference (∆/HHRBG)
BGLO < 8 mm
8.2 ± 5.9º
8.8 ± 5.6º
-6.8%
BGLO > 8 mm
9.6 ± 7.5º
6.8 ± 5.9º
+41.2%
It is interesting to note that the location of the bicipital groove was observed to be more predictable
distally than proximally. The course of the BG along the proximal humerus occurs in a plane parallel to
the HHEP (BGAO is consistent from H1 to H4). To take advantage of this finding, the authors designed
an asymmetric fracture stem that utilizes a lateral fin anteriorly offset by 7.5 mm (Figure 2A). As a result,
this feature mimics the location of the BG and can facilitate the reconstruction of the tuberosity fragments
around the metaphyseal portion (Figure 2B). In addition, aligning the anterior-lateral fin with the center
of the BG at the level of the humerus shaft offers a simple method to reproduce the HHR. This statement
is particularly true when the fractured humerus shows a large BGLO and the bicipital groove is well
defined.
A
HHEP
IM axis
B
7.5 mm
Figure 2: Proposed humeral fracture stem
REFERENCES
1.Boileau P, et al. Tuberosity malposition and migration: reasons for poor outcomes after
hemiarthroplasty for displaced fractures of the proximal humerus. JSES. #11: 401-412. 2002.
2.Kontakis GM, et al. The technique of hemiarthroplasty in four-part fractures of the upper end of the
humerus. www.acta-ortho.gr/v52t1_9.html
Product of this poster sponsored by:
Exactech, Inc., General Research Fund
002S 0205