The Journal of Bone & Joint Surgery

The Journal of Bone & Joint Surgery, Volume 87, Issue 9

Scientific Articles | September 01, 2005

Effects of Elbow Flexion and Forearm Rotation on Valgus Laxity of the Elbow

Marc R. Safran, MD¹; Michelle H. McGarry, MS²; Steve Shin, MD²; Steve Han, BS²; Thay Q. Lee, PhD²

¹ Department of Orthopaedic Surgery, University of California, San Francisco, 500 Parnassus Avenue, MU 320W, San Francisco, CA 94143. E-mail address: safranm@orthosurg.ucsf.edu
² Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System (09/151), and University of California, Irvine, 5901 East 7th Street, Long Beach, CA 90822. E-mail addresses for T.Q. Lee: tqlee@med.va.gov; tqlee@uci.edu

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The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

Investigation performed at Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System (09/151) and University of California, Irvine, Long Beach, California

The Journal of Bone and Joint Surgery, Incorporated

J Bone Joint Surg Am, 2005 Sep 01;87(9):2065-2074. doi: 10.2106/JBJS.D.02045

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Abstract

Background: Clinical evaluation of valgus elbow laxity is difficult. The optimum position of elbow flexion and forearm rotation with which to identify valgus laxity in a patient with an injury of the ulnar collateral ligament of the elbow has not been determined. The purpose of the present study was to determine the effect of forearm rotation and elbow flexion on valgus elbow laxity.

Methods: Twelve intact cadaveric upper extremities were studied with a custom elbow-testing device. Laxity was measured with the forearm in pronation, supination, and neutral rotation at 30°, 50°, and 70° of elbow flexion with use of 2 Nm of valgus torque. Testing was conducted with the ulnar collateral ligament intact, with the joint vented, after cutting of the anterior half (six specimens) or posterior half (six specimens) of the anterior oblique ligament of the ulnar collateral ligament, and after complete sectioning of the anterior oblique ligament. Laxity was measured in degrees of valgus angulation in different positions of elbow flexion and forearm rotation.

Results: There were no significant differences in valgus laxity with respect to elbow flexion within each condition. Overall, for both groups of specimens (i.e., specimens in which the anterior or posterior half of the anterior oblique ligament was cut), neutral forearm rotation resulted in greater valgus laxity than pronation or supination did (p < 0.05). Transection of the anterior half of the anterior oblique ligament did not significantly increase valgus laxity; however, transection of the posterior half resulted in increased valgus laxity in some positions. Full transection of the anterior oblique ligament significantly increased valgus laxity in all positions (p < 0.05).

Conclusions: The results of this in vitro cadaveric study demonstrated that forearm rotation had a significant effect on varus-valgus laxity. Laxity was always greatest in neutral forearm rotation throughout the ranges of elbow flexion and the various surgical conditions.

Clinical Relevance: The information obtained from the present study suggests that forearm rotation affects varus-valgus elbow laxity. Additional investigation is warranted to determine if forearm rotation should be considered in the evaluation and treatment of ulnar collateral ligament injuries of the elbow joint.

Figures in this Article

Elbow instability is a challenging clinical problem. The diagnosis of injury to the ulnar collateral ligament, especially the degree of laxity, is difficult, even for experienced clinicians^1,2. Other than stress radiographs, which can be misleading^1,3, there are no objective tests or measures of valgus laxity. The elbow is the second most commonly dislocated major joint in the body, and the ulnar collateral ligament is usually injured in association with elbow dislocation^4-6. The mechanism of injury occurs with a fall on an outstretched hand, which applies both a valgus stress and an external rotatory moment on the elbow joint^7,8. This is important because long-term follow-up has shown that elbows with persistent valgus laxity following dislocation have inferior overall clinical and radiographic results compared with elbows without increased valgus laxity following dislocation⁹. Furthermore, persistent elbow instability, although uncommon, is being recognized more frequently following elbow dislocation. The ulnar collateral ligament also may be injured as a result of excessive or repetitive valgus loading associated with a throwing-type motion of the upper extremity^3,10-12. This type of injury has been seen in athletes who participate in baseball^3,13, volleyball, tennis¹⁴, javelin^15,16, water polo, and football¹⁷. Disruption of the ulnar collateral ligament can result in loss of velocity during baseball pitching, instability of the elbow, and excessive stress and injury to other structures in and about the elbow, such as the ulnar nerve, the flexor-pronator tendon group, or the posteromedial or lateral elbow joint surfaces^10,18,19.

Studies have been performed to assess the contributions of the osseous architecture, ligaments, and capsule about the elbow to varus-valgus and anterior-posterior stability in varying degrees of flexion-extension^20-31. Research has shown that stability of the elbow is provided by osseous, ligamentous, and capsular structures as well as by muscles^20-31. Some controversy exists with regard to the contribution of forearm musculature to valgus stability to the elbow; however, joint compression due to the anterior and posterior muscle contractions about the elbow do appear to contribute to elbow stability^32-35.

The main structure that resists valgus loading, especially in the middle part of the range of elbow motion, is the ulnar collateral ligament complex (also known as the medial collateral ligament or medial ulnar collateral ligament)^20-26,36-42. The ulnar collateral ligament is comprised of three ligaments: the anterior oblique ligament (the most important ligament in throwing athletes, also known as the anterior band or anterior bundle), the posterior oblique ligament (also known as the posterior band or posterior bundle), and the transverse ligament (also known as Cooper's ligament)^{20-26,37,40,41,43}. The transverse ligament is considered to be unimportant with regard to valgus loading. The anterior oblique ligament may be further subdivided into two functional components: the anterior and posterior bands (although in some studies, these structures are referred to as the anterior and posterior bundles). These bands become selectively tensioned throughout the range of elbow motion^21,26,37,40.

Between 20° and 120° of elbow flexion, the soft tissues, particularly the ulnar collateral ligament complex, are the main elbow stabilizers that resist valgus loading^{20-22,24-27,37,40-42}. The anterior band of the anterior oblique ligament has been shown to be the most important ligamentous structure to resist valgus loading²². Biomechanical studies of elbow stability have revealed that valgus laxity is most evident at 70° of elbow flexion when the ulnar collateral ligament is cut^21,41. Thus, valgus laxity of the elbow has been shown to be affected by the degree of elbow flexion.

However, the elbow predominantly participates in two planes of motion: flexion-extension and pronation-supination. The effect of forearm rotation on valgus laxity and stability of the elbow is not well understood. In our review of the literature, it was notable that many investigators neglected to mention the position of the forearm when testing valgus stability of the elbow. The few researchers who did mention forearm rotation noted that the contribution of forearm rotation was negligible; however, no data were provided to support this statement^20,40. In fact, while studies have revealed that the forces across the radiocapitellar joint depend on forearm rotation²⁷, the effect of forearm pronation on the degree of valgus elbow laxity has received only limited attention^28,44-47.

The hypothesis of the present study was that forearm rotation affects valgus laxity at different degrees of elbow flexion when the origins and insertions of the muscles that cross the elbow joint are left intact. It was also hypothesized that this effect persists with valgus loading when the ulnar collateral ligament is intact, partially cut, and completely sectioned. Therefore, the objective of the present study was to quantify the effects of forearm rotation and elbow flexion on valgus laxity of the elbow in a human cadaveric model that involved use of the entire upper extremity with intact musculature.

Materials and Methods

Materials and Methods | Results | Discussion | References

The number of specimens needed for the present study was determined with use of an analysis-of-variance-based power analysis (JMP 3.2 statistics software package; SAS Institute, Cary, North Carolina) and the mean and standard deviation ranges from preliminary tests performed on three specimens. A minimum of six specimens was needed to show a significant difference between different ligament-sectioning conditions and between different degrees of elbow flexion, and a minimum of two specimens was needed to show a significant difference between different forearm rotation positions. Therefore, six specimens were chosen for each ligament-sectioning group (one group in which the anterior half of the anterior oblique ligament was transected first and one group in which the posterior half was transected first), for a total of twelve specimens. Seven right and five left specimens were obtained from nine female and three male donors. The mean age of the donors at the time of death had been 73 ± 9 years (range, forty-nine to eighty-three years). All specimens were examined radiographically and macroscopically prior to dissection. Specimens with pathological changes (such as arthritis), a previous fracture, and/or previous operative treatment were not included in the study. The cadaveric upper extremities were stored at -20°C and were thawed overnight prior to study.

Prior to testing, the specimens were disarticulated from the cadaver at the scapulothoracic joint. All structures, including muscles and tendons from the scapula to the hand, were left intact. The skin and the subcutaneous tissue were removed for the study, and all of the other tissues were maintained. The specimens were kept moist with intermittent irrigation with physiologic saline solution throughout the entire period of study.

The entire upper extremity was tested with a custom elbow valgus laxity-testing system (Fig. 1). After removal of the skin and the subcutaneous fat, both the humerus and the forearm were centered and fixed in two cylinders that were used to secure the specimen to the testing system. A muscle-splitting approach was used to attach the humerus to the humeral cylinder with use of screws. The length of the radius was measured from the radial head to the distal styloid process with the arm in pronation. Two 1.6-mm fixation screws were then placed in the radius, one at the middle part of the forearm and the other 3 in (7.6 cm) distal to the screw in the middle part of the radius, to fix the radius to the metal cylinder. The specimen was then mounted onto the testing system, which allowed six degrees of freedom of both the humerus and the forearm.

Once the specimen was mounted onto the testing system, the elbow was flexed and extended for several cycles to allow the humerus to reach an anatomic neutral position, with the epicondyles aligned parallel to the baseplate of the testing system in the medial-lateral plane. The humeral rotation was then locked at this position throughout each phase of testing. The forearm cylinder was placed in 30° of flexion (as measured with a goniometer) and was secured at this position for all tests. The elbow flexion angle could then be adjusted by changing the humeral height. Once the humerus was adjusted for each flexion angle, each degree of freedom of the humerus was locked at this position. The forearm was aligned in neutral rotation by aligning the distal radioulnar plane perpendicular to the base of the testing device or epicondylar axis while observing hand position. Pronation was then defined as 90° of internal rotation from this position, and supination was defined as 90° of external rotation from this position. All forearm rotation positions were marked on the forearm cylinder and mounting device so that the forearm could be returned to the exact rotation position throughout each testing phase. The distance from the medial epicondyle to the varus-valgus torque application point (center of rotation) was measured to determine the amount of load needed for torque application. The torque was applied with use of a pulley-and-weight system that was attached to the medial-lateral forearm translator. Once the forearm was placed in the appropriate rotation, the cylinder could be locked in this position. During varus-valgus load application, three degrees of freedom of the elbow (medial-lateral translation, superior-inferior translation, and varus-valgus rotation) were free. Prior to each measurement of valgus laxity, the specimen was preconditioned for five cycles with 2 Nm of valgus torque. Valgus laxity was measured with use of a Microscribe 3DLX digitizing system (Immersion, San Jose, California) by digitizing two points along an extension plate that was attached to measure varus-valgus rotation. The two points along the plate were digitized at the position of the forearm with the application of 1 Nm of varus torque (the starting position). These two points lie on the proximal-distal axis of the forearm (Fig. 1). The same two points were digitized again after the application of 1 Nm of counterbalance and an additional 2 Nm of valgus torque (Fig. 1). Valgus laxity was then calculated with use of the four digitized points and the formula: Valgus Laxity=cos^-1varus₁varus₂•valgus₁valgus₂|varus₁varus₂||valgus₁valgus₂|

Valgus laxity was directly measured with 2 Nm of valgus torque with use of the custom testing system with the forearm in pronation, supination, and neutral rotation and with the elbow in 30°, 50°, and 70° of flexion. This resulted in nine elbow positions (30° of flexion with pronation, 30° of flexion with neutral rotation, 30° of flexion with supination, 50° of flexion with pronation, 50° of flexion with neutral rotation, 50° of flexion with supination, 70° of flexion with pronation, 70° of flexion with neutral rotation, and 70° of flexion with supination). Testing was performed for five ligament conditions: (1) with the specimen intact, (2) after venting of the joint with a 19-gauge needle, (3) after demarcation of the anterior oblique ligament, (4) after transection of the anterior half (six specimens) or posterior half (six specimens) of the anterior oblique ligament, and (5) after complete transection of the anterior oblique ligament (Fig. 2). The degrees of elbow flexion that were tested were based on currently used clinical tests, in which the elbow is placed in approximately 30° of flexion^{3,11,12,17,48-54} and 45° of flexion⁵⁵, and on biomechanical data suggesting that the greatest medial joint laxity is near 70° of flexion^{21,22,36,41,42}. The applied loads were based on previous load-displacement studies²⁵ and on studies that have shown that valgus torques of >2.5 Nm may result in ulnar collateral ligament avulsion fractures²¹.

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Fig. 1: Illustration depicting the upper extremity mounted on custom testing device, showing the six degrees of freedom. Valgus laxity was measured by digitizing two points on a plate that was attached to the forearm-mounting device.

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Fig. 2: Flowchart showing the experimental design and the independent and dependent variables.

Demarcation of the anterior oblique ligament was performed with use of a muscle-splitting approach⁵⁶ to limit injury to other structures and to maintain soft-tissue integrity. The anterior border of the ligament was palpated with the elbow in 30° of flexion, and a 10-mm longitudinal cut was made along the ligament fibers with use of a scalpel. The posterior border of the ligament was then palpated with the elbow in 70° of flexion, and a 10-mm longitudinal cut was made along the posterior border (Fig. 3, A). The width of the anterior oblique ligament was measured with use of digital calipers. The width of the ligament was then divided in half to demarcate the anterior half and the posterior half because it is difficult to determine the exact functional division between the anterior and posterior bands. After demarcation, the ligament could be divided reliably into two equal halves (the anterior band and the posterior band) for testing. For six specimens the anterior half was transected first, followed by complete sectioning of the ligament, and for the remaining six specimens the posterior half was transected first, followed by complete sectioning of the ligament (Fig. 3, B, C, and D).

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Fig. 3: Photographs illustrating the experimental conditions of the anterior oblique ligament, showing the humerus (H), the forearm (FA) with the ligament demarcated (A), with the anterior half cut (B), with the posterior half cut (C), and with the ligament fully cut (D).

The sequence for forearm rotation, elbow flexion, and varus-valgus loading was randomized throughout the testing protocol to minimize bias related to the viscoelastic effects of the soft tissues. Three trials were recorded for each position, and the average of the three trials was used for analysis. A multifactorial repeated-measures analysis of variance was performed for statistical analysis, followed by a univariate repeated-measures analysis of variance with a Tukey post hoc test for individual comparisons, with the level of significance set at p < 0.05. All data are reported as the mean and the standard deviation, in degrees of valgus laxity.

Results

Materials and Methods | Results | Discussion | References

Effect of Order of Ligament Sectioning

The valgus laxity associated with sectioning either the anterior half or the posterior half of the anterior oblique ligament was compared with that associated with the other ligamentous conditions (intact, vented, demarcated, and fully transected) (Tables I and II). The average width of the anterior oblique ligament was 7.2 mm (standard deviation, 1.7; standard error, 0.5). Among the specimens in which the anterior half of the anterior oblique ligament was transected prior to full transection, the valgus laxity after full transection was significantly greater than the valgus laxity associated with the intact, vented, and demarcated conditions at each of the nine positions (Table I) (p = 0.0001 to 0.006). Valgus laxity following full sectioning of the anterior oblique ligament was significantly greater than that associated with sectioning of only the anterior half of the ligament at four positions: 30° of flexion with neutral rotation (p = 0.04), 50° of flexion with pronation (p = 0.04), 70° of flexion with pronation (p = 0.006), and 70° of flexion with neutral rotation (p = 0.04). There were no significant differences in valgus laxity when sectioning of the anterior band was compared with the intact, vented, and demarcated conditions.

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TABLE I Valgus Laxity with the Application of 2 Nm of Valgus Torque in the Group of Six Elbows in Which the Anterior Band Was Transected Prior to Full Transection of the Anterior Oblique Ligament

Elbow Flexion Angle (deg)	Forearm Rotation	Valgus Laxity (deg)
		Intact	Vented	Demarcated	Anterior Band Cut	Full Cut
30	Pronation	5.5 ± 2.8	6.5 ± 3.0	6.5 ± 2.9	8.2 ± 5.0	11.2 ± 7.0
30	Neutral	10.7 ± 3.9	11.5 ± 3.9	11.0 ± 4.4	12.9 ± 5.3	16.1 ± 7.1
30	Supination	9.6 ± 3.6	9.6 ± 3.9	9.8 ± 3.9	10.8 ± 5.3	12.6 ± 4.8
50	Pronation	6.0 ± 3.0	6.4 ± 3.4	6.9 ± 2.9	8.3 ± 5.0	12.3 ± 6.7
50	Neutral	10.6 ± 3.5	11.3 ± 4.1	11.2 ± 4.0	13.6 ± 6.4	16.6 ± 6.8
50	Supination	9.0 ± 3.9	9.3 ± 4.4	9.4 ± 4.4	10.7 ± 6.0	12.6 ± 4.9
70	Pronation	6.1 ± 4.0	7.2 ± 3.2	7.8 ± 3.7	8.5 ± 4.0	11.8 ± 4.4
70	Neutral	11.1 ± 4.5	11.0 ± 3.8	11.0 ± 3.4	12.0 ± 5.2	14.9 ± 4.5
70	Supination	7.9 ± 3.9	7.8 ± 3.4	8.0 ± 3.8	8.9 ± 4.9	10.9 ± 4.0

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TABLE I Valgus Laxity with the Application of 2 Nm of Valgus Torque in the Group of Six Elbows in Which the Anterior Band Was Transected Prior to Full Transection of the Anterior Oblique Ligament

Elbow Flexion Angle (deg)	Forearm Rotation	Valgus Laxity (deg)
		Intact	Vented	Demarcated	Anterior Band Cut	Full Cut
30	Pronation	5.5 ± 2.8	6.5 ± 3.0	6.5 ± 2.9	8.2 ± 5.0	11.2 ± 7.0
30	Neutral	10.7 ± 3.9	11.5 ± 3.9	11.0 ± 4.4	12.9 ± 5.3	16.1 ± 7.1
30	Supination	9.6 ± 3.6	9.6 ± 3.9	9.8 ± 3.9	10.8 ± 5.3	12.6 ± 4.8
50	Pronation	6.0 ± 3.0	6.4 ± 3.4	6.9 ± 2.9	8.3 ± 5.0	12.3 ± 6.7
50	Neutral	10.6 ± 3.5	11.3 ± 4.1	11.2 ± 4.0	13.6 ± 6.4	16.6 ± 6.8
50	Supination	9.0 ± 3.9	9.3 ± 4.4	9.4 ± 4.4	10.7 ± 6.0	12.6 ± 4.9
70	Pronation	6.1 ± 4.0	7.2 ± 3.2	7.8 ± 3.7	8.5 ± 4.0	11.8 ± 4.4
70	Neutral	11.1 ± 4.5	11.0 ± 3.8	11.0 ± 3.4	12.0 ± 5.2	14.9 ± 4.5
70	Supination	7.9 ± 3.9	7.8 ± 3.4	8.0 ± 3.8	8.9 ± 4.9	10.9 ± 4.0

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TABLE II Valgus Laxity with the Application of 2 Nm of Valgus Torque in the Group of Six Elbows in Which the Posterior Band Was Transected Prior to Full Transection of the Anterior Oblique Ligament

Elbow Flexion Angle (deg)	Forearm Rotation	Valgus Laxity (deg)
		Intact	Vented	Demarcated	Posterior Band Cut	Full Cut
30	Pronation	8.8 ± 2.9	9.4 ± 2.8	9.9 ± 2.9	10.8 ± 2.5	13.3 ± 2.9
30	Neutral	12.0 ± 2.7	12.5 ± 2.8	12.6 ± 2.6	13.7 ± 2.5	15.7 ± 2.5
30	Supination	9.3 ± 2.9	9.9 ± 2.7	10.1 ± 2.2	10.8 ± 2.2	12.8 ± 1.8
50	Pronation	8.3 ± 2.0	9.1 ± 2.5	9.6 ± 2.9	11.0 ± 2.5	12.8 ± 2.4
50	Neutral	10.0 ± 1.9	10.7 ± 1.8	10.5 ± 2.2	12.1 ± 1.3	14.9 ± 1.9
50	Supination	9.3 ± 2.3	9.5 ± 2.1	10.2 ± 1.7	11.1 ± 2.0	13.1 ± 2.3
70	Pronation	9.6 ± 4.1	9.6 ± 2.7	10.0 ± 2.5	11.9 ± 2.0	14.0 ± 3.5
70	Neutral	10.8 ± 2.7	11.7 ± 2.6	11.7 ± 2.0	13.1 ± 1.6	15.7 ± 2.3
70	Supination	9.9 ± 2.8	10.0 ± 2.6	10.8 ± 2.2	11.8 ± 2.4	13.9 ± 3.0

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TABLE II Valgus Laxity with the Application of 2 Nm of Valgus Torque in the Group of Six Elbows in Which the Posterior Band Was Transected Prior to Full Transection of the Anterior Oblique Ligament

Elbow Flexion Angle (deg)	Forearm Rotation	Valgus Laxity (deg)
		Intact	Vented	Demarcated	Posterior Band Cut	Full Cut
30	Pronation	8.8 ± 2.9	9.4 ± 2.8	9.9 ± 2.9	10.8 ± 2.5	13.3 ± 2.9
30	Neutral	12.0 ± 2.7	12.5 ± 2.8	12.6 ± 2.6	13.7 ± 2.5	15.7 ± 2.5
30	Supination	9.3 ± 2.9	9.9 ± 2.7	10.1 ± 2.2	10.8 ± 2.2	12.8 ± 1.8
50	Pronation	8.3 ± 2.0	9.1 ± 2.5	9.6 ± 2.9	11.0 ± 2.5	12.8 ± 2.4
50	Neutral	10.0 ± 1.9	10.7 ± 1.8	10.5 ± 2.2	12.1 ± 1.3	14.9 ± 1.9
50	Supination	9.3 ± 2.3	9.5 ± 2.1	10.2 ± 1.7	11.1 ± 2.0	13.1 ± 2.3
70	Pronation	9.6 ± 4.1	9.6 ± 2.7	10.0 ± 2.5	11.9 ± 2.0	14.0 ± 3.5
70	Neutral	10.8 ± 2.7	11.7 ± 2.6	11.7 ± 2.0	13.1 ± 1.6	15.7 ± 2.3
70	Supination	9.9 ± 2.8	10.0 ± 2.6	10.8 ± 2.2	11.8 ± 2.4	13.9 ± 3.0

Among the specimens in which the posterior band was transected prior to full transection of the anterior oblique ligament, valgus laxity following full transection was significantly greater than that associated with the intact, vented, and demarcated conditions at all nine positions (Table II) (p = 0.0001 to 0.03). Valgus laxity after full transection was significantly greater than that after sectioning of only the posterior band at six positions: 30° of flexion with pronation (p = 0.002), 30° of flexion with neutral rotation (p = 0.01), 30° of flexion with supination (p = 0.008), 50° of flexion with neutral rotation (p = 0.02), 50° of flexion with supination (p = 0.03), and 70° of flexion with supination (p = 0.02). Valgus laxity following transection of the posterior band of the anterior oblique ligament was significantly greater than that associated with the intact condition at four positions: 30° of flexion with pronation (p = 0.007), 30° of flexion with neutral rotation (p = 0.03), 50° of flexion with pronation (p = 0.004), and 50° of flexion with supination (p = 0.04).

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Fig. 4: Bar graph illustrating the effect of the flexion angle on valgus laxity, with the forearm in neutral rotation and with the application of 2 Nm of valgus torque, for the specimens in which the anterior half of the anterior oblique ligament was transected prior to full transection (p > 0.05 for all comparisons).

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Fig. 5: Bar graph illustrating the effect of the flexion angle on valgus laxity, with the forearm in neutral forearm rotation and with the application of 2 Nm of valgus torque, for the specimens in which the posterior half of the anterior oblique ligament was transected prior to full transection. ^*p < 0.05.

Effect of Elbow Flexion

Among the six specimens in which the anterior band was cut prior to full transection, no significant differences in valgus laxity were noted in association with the flexion angle when the values for each ligamentous condition and forearm rotation were compared (p = 0.07 to 0.99). There was a trend toward decreasing laxity at 70° compared with 30° and 50° for the anterior-cut and full-cut conditions, but the differences were not significant (Fig. 4).

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Fig. 6: Bar graph illustrating the effect of forearm rotation on valgus laxity, with the elbow in 30° of flexion and with the application of 2 Nm valgus torque, for the specimens in which the anterior half of the anterior oblique ligament was transected prior to full transection. ^*p < 0.05.

With only the posterior band cut, no significant differences in valgus laxity were noted in association with the flexion angle (p = 0.99 to 0.11) under any of the conditions except for one. With the posterior band demarcated and the forearm in neutral rotation, the valgus laxity at 30° was significantly greater than that at 50° (12.6° ± 2.6° compared with 10.5° ± 2.2°; p = 0.04) (Fig. 5).

Effect of Forearm Rotation

Among the specimens in which the anterior band was transected prior to full transection of the anterior oblique ligament, the valgus laxity with the forearm in neutral rotation was significantly greater than that with the forearm in pronation for all flexion angles and conditions (p = 0.0003 to 0.01) (Fig. 6). Similar trends were seen at each flexion angle. At 30° and 50° of elbow flexion, valgus laxity with the forearm in pronation was significantly greater than that with the forearm in supination under the intact condition (p = 0.0009 for 30° of elbow flexion and p = 0.03 for 50° of elbow flexion), the vented condition (p = 0.01 for 30° of elbow flexion and p = 0.03 for 50° of elbow flexion), and the demarcated condition (p = 0.01 for 30° of elbow flexion and p = 0.03 for 50° of elbow flexion). Valgus laxity with the forearm in neutral rotation was greater than that with the forearm in supination at 30° of flexion with the ligament fully cut (p = 0.02), at 50° of flexion with the anterior band transected (p = 0.03) and with the ligament fully cut (p = 0.02), and at 70° of flexion for all conditions (p = 0.0005 to 0.03).

Among the specimens in which the posterior band was transected prior to full sectioning of the anterior oblique ligament, a similar trend of increased valgus laxity was noted with the forearm in neutral rotation as compared with pronation and supination. Specifically, at 30° of elbow flexion, valgus laxity with the forearm in neutral rotation was greater than with the forearm in pronation (p = 0.0002 to 0.009) and supination (p = 0.0003 to 0.003) for all conditions (Fig. 7). At 50° of elbow flexion, valgus laxity with the forearm in neutral rotation was significantly greater than that with the forearm in pronation only with the anterior oblique ligament fully cut (p = 0.03). At 70° of elbow flexion, valgus laxity with the forearm in neutral rotation was significantly greater than that with the forearm in pronation for the vented (p = 0.02) and demarcated (p = 0.04) conditions and was greater than that with the forearm in supination with the posterior band transected (p = 0.04).

For both groups (the group in which the anterior half of the ligament was transected prior to full transection and the group in which the posterior half of the ligment was transected prior to full transection), the valgus laxity with the forearm in neutral rotation with the ligament intact was generally larger than that with the forearm in pronation and supination with the anterior or posterior half of the ligament cut (Tables I and II). However, the only significant difference was observed in the group in which the posterior half of the ligament was transected first; specifically, at 30° of elbow flexion, the valgus laxity with the ligament intact and the forearm in neutral rotation was significantly greater than that with the posterior half of the ligament cut and the forearm in supination (12.0° ± 2.7° compared with 10.8° ± 2.2°; p = 0.02).

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Fig. 7: Bar graph illustrating the effect of forearm rotation on valgus laxity, with the elbow in 30° of flexion and with the application of 2 Nm valgus torque, for the specimens in which the posterior half of the anterior oblique ligament was transected prior to full transection. ^*p < 0.05.

Discussion

Materials and Methods | Results | Discussion | References

Several studies have been performed to evaluate the contribution of different structures about the elbow to the stability of the joint. We identified only one study that specifically investigated the effects of forearm rotation on elbow stability⁴⁶, although a few reports in the literature have discounted the effect of rotation on stability of the elbow^20,44,57. Unfortunately, those studies evaluated stability with an incomplete upper extremity specimen and most of the studies involved specimens that were devoid of muscles and noncapsuloligamentous soft tissues crossing the joints^{20-22,24-27,37,40-42}. To our knowledge, the present report describes the first study in which valgus stability of the elbow has been evaluated in completely intact upper extremity specimens that included all muscles that cross the joint.

Our findings confirm the importance of forearm rotation on elbow stability and laxity. Our review of the literature showed that the reports on several major studies of elbow stability did not mention the position of forearm rotation in the description of testing methods^23,24,26,37. Thus, it is not possible to directly assess the effect of forearm rotation on elbow stability on the basis of those studies. Other authors have specifically mentioned that forearm rotation does not influence the stability and laxity of the elbow joint^20,40.

Most investigators who have investigated elbow valgus stability and laxity have fixed the forearm in one position of rotation, although this position has varied among studies. Callaway et al.²¹ studied valgus laxity with the muscles crossing the elbow joint detached and the forearm fixed in neutral rotation. Those authors identified the anterior band of the anterior oblique ligament as the primary restraint to valgus loading and stated that valgus laxity was not affected by elbow flexion when the ulnar collateral ligament was intact. Hotchkiss and Weiland²² tested valgus laxity with the forearm maintained in full pronation and with all soft tissues, except the capsule and ligaments, being excised prior to testing. Those authors also noted that the anterior oblique ligament was the primary stabilizer to valgus stability and that the radial head was a secondary stabilizer. Morrey and An²⁵ studied elbow stability with all muscles detached while the forearm was held in neutral rotation. Later, Morrey et al.²⁰ studied valgus laxity with the forearm in supination. In a pilot study assessing the contributions of the ulnar collateral ligament and radial head to valgus stability during dynamic flexion of the elbow, those investigators identified no change in motion patterns in association with differing degrees of forearm rotation. Sojbjerg et al.^41,58 maintained the forearm in neutral rotation in their studies of elbow stability. Tanaka et al.⁵⁹ studied the three-dimensional kinematics of the ulnohumeral joint with the forearm in neutral rotation.

Only a couple of reports have mentioned testing in different degrees of forearm rotation. King et al.⁴⁴ used a dynamic model that simulated active elbow motion to study the stabilizing effects of radial head arthroplasty in ulnar collateral ligament-deficient cadaveric elbows. The varus-valgus laxities were similar with the forearm in pronation and supination in all positions of elbow flexion under each condition. Pribyl et al.⁵⁷, in a study of five cadaveric elbows that were tested for resistance to valgus stress under various conditions (with the radial head intact, with the radial head resected, and with insertion of a radial head implant), reported that forearm rotation had no effect on valgus stability when the ligments were intact.

Previous studies have investigated the effect of forearm rotation on varus stability of the elbow. Jensen et al.²⁸, in a study of two elbow specimens, reported that pronation and supination had no effect on varus or external rotation stability. In another study of varus instability, Olsen et al.⁴⁵ found that varying rotations of the forearm did not affect the stability of elbows with all ligaments intact or with transection of the lateral collateral ligament, lateral ulnar collateral ligament, and annular ligament.

In what we believe to be the only study that has formally assessed the effect of forearm rotation on elbow stability and laxity, Pomianowski et al.⁴⁶ concluded that forearm rotation does affect valgus elbow stability. Those authors used upper extremity specimens with the wrist disarticulated. They made no mention about tension on the forearm muscles that cross the elbow joint, despite the use of weights to stimulate muscle forces to the tendons of the biceps, brachialis, and triceps. The authors concluded that valgus laxity is more evident with the forearm in pronation, regardless of the status of the ulnar collateral ligament and elbow flexion. Using a similar testing scenario, the same authors tested different radial head prostheses for valgus stability⁴⁷. Again, they found that forearm pronation resulted in the greatest amount of valgus laxity as compared with supination or neutral rotation.

One of the main differences between the present study and the study by Pomianowski et al.⁴⁶ was that in our model all of the muscles that cross the elbow had intact origins and insertions, whereas in the study by Pomianowski et al.⁴⁶ the insertions of several muscles that cross the elbow were not intact. Another difference was the number of positions of elbow flexion and forearm rotation. Leaving the muscles that cross the elbow joint completely intact allows passive tension to accumulate within the musculotendinous unit, which may result in an increase in joint compression force and thereby provide some stability to the elbow and some resistance to varus-valgus loading. We believe that experiments in which the musculature is completely intact more closely replicate the clinical scenario with regard to evaluation of the elbow.

In the present study, neutral rotation resulted in the greatest degree of valgus laxity, regardless of the ligamentous condition. With pronation, this finding may be due to the fact that radiocapitellar joint-compression forces increase as a result of proximal migration of the radius, possibly because of increased passive tension within the supinator and/or distal biceps musculotendinous units and/or the interosseous membrane, thereby increasing the contribution of the osseous articulation in valgus elbow stability²⁵. With supination, this finding may be due to the intact flexor-pronator muscles. In supination, there is an increase in passive tension in the pronator muscles, which may provide added passive stability to the medial part of the elbow.

The findings of the present in vitro cadaveric study support the concept that valgus laxity of the elbow is affected by forearm rotation. Clinically, these findings may help with the clinical examination of the elbow in patients with an injury of the the ulnar collateral ligament. Our results suggest that ulnar collateral ligament laxity should be tested clinically, and possibly evaluated with stress radiographs or ultrasound, with the forearm in neutral rotation. Furthermore, positioning of the forearm may need to be considered during tensioning of a graft at the time of ulnar collateral ligament reconstruction, although this issue still needs to be studied. ?

References

Materials and Methods | Results | Discussion | References

Azar FM, Andrews JR, Wilk KE, Groh D. Operative treatment of ulnar collateral ligament injuries of the elbow in athletes. Am J Sports Med.2000;28: 16-23.2816 2000 [PubMed]

Thompson WH, Jobe FW, Yocum LA, Pink MM. Ulnar collateral ligament reconstruction in athletes: muscle-splitting approach without transposition of the ulnar nerve. J Shoulder Elbow Surg.2001;10: 152-7.10152 2001 [CrossRef]

Conway JE, Jobe FW, Glousman RE, Pink M. Medial instability of the elbow in throwing athletes. Treatment by repair or reconstruction of the ulnar collateral ligament. J Bone Joint Surg Am.1992;74: 67-83.7467 1992

Safran MR, Salyers S, Fu FH. Elbow dislocations. In: Reider B, editor. Sports medicine: the school-age athlete. Philadelphia: WB Saunders; 1996. p 235-46.235 1996

Letts M. Dislocations of the child's elbow. In: Morrey BF, editor. The elbow and its disorders. 2nd ed. Philadelphia: WB Saunders; 1993. p 288-315.288 1993

Josefsson PO, Gentz CF, Johnell O, Wendeberg B. Surgical versus non-surgical treatment of ligamentous injuries following dislocation of the elbow joint. A prospective randomized study. J Bone Joint Surg Am.1987;69: 605-8.69605 1987 [PubMed]

O'Driscoll SW, Morrey BF, Korinek S, An KN. Elbow subluxation and dislocation. A spectrum of instability. Clin Orthop Relat Res.1992;280: 186-97.280186 1992

O'Driscoll SW. Classification and spectrum of elbow instability: recurrent instability. In: Morrey BF, editor. The elbow and its disorders. 2nd ed. Philadelphia: WB Saunders; 1993. p 453-63.453 1993

Eygendaal D, Verdegaal SH, Obermann WR, van Vugt AB, Poll RG, Rozing PM. Posterolateral dislocation of the elbow joint. Relationship to medial instability. J Bone Joint Surg Am.2000;82: 555-60.82555 2000 [CrossRef]

Werner SL, Fleisig GS, Dillman CJ, Andrews JR. Biomechanics of the elbow during baseball pitching. J Orthop Sports Phys Ther.1993;17: 274-8.17274 1993

Jobe FW, Stark H, Lombardo SJ. Reconstruction of the ulnar collateral ligament in athletes. J Bone Joint Surg Am.1986;68: 1158-63.681158 1986

Andrews JR, Timmerman LA. Outcome of elbow surgery in professional baseball players. Am J Sports Med.1995;23: 407-13.23407 1995 [CrossRef]

Barnes DA, Tullos HS. An analysis of 100 symptomatic baseball players. Am J Sports Med.1978;6: 62-7.662 1978 [PubMed][CrossRef]

Priest JD, Jones HH, Nagel DA. Ebow injuries in highly skilled tennis players. J Sports Med.1974;2: 139-49.2139 1974 [PubMed]

Miller JE. Javelin thrower's elbow. J Bone Joint Surg Br.1960;42: 788-92.42788 1960

Waris W. Elbow injuries in javelin throwers. Acta Chir Scand.1946;93: 563.93563 1946 [PubMed]

Norwood LA, Shook JA, Andrews JR. Acute medial elbow ruptures. Am J Sports Med.1981;9: 16-9.916 1981 [PubMed][CrossRef]

Fleisig GS, Andrews JR, Dillman CJ, Escamilla RF. Kinetics of baseball pitching with implications about injury mechanisms. Am J Sports Med.1995;23: 233-9.23233 1995 [PubMed][CrossRef]

Safran MR. Ulnar collateral ligament injury in the overhead athlete: diagnosis and treatment. Clin Sports Med.2004;23: 643-63, x.23643 2004 [CrossRef]

Morrey BF, Tanaka S, An KN. Valgus stability of the elbow. A definition of primary and secondary constraints. Clin Orthop Relat Res.1991;265: 187-95.265187 1991 [PubMed]

Callaway GH, Field LD, Deng XH, Torzilli PA, O'Brien SJ, Altchek DW, Warren RF. Biomechanical evaluation of the medial collateral ligament of the elbow. J Bone Joint Surg Am.1997;79: 1223-31.791223 1997 [PubMed]

Hotchkiss RN, Weiland AJ. Valgus stability of the elbow. J Orthop Res.1987;5: 372-7.5372 1987 [PubMed][CrossRef]

King GJW, Morrey BF, An KN. Stabilizers of the elbow. J Shoulder Elbow Surg.1993;2: 165-74.2165 1993 [CrossRef]

Morrey BF, An KN. Functional anatomy of the ligaments of the elbow. Clin Orthop Relat Res.1985;201: 84-90.20184 1985 [PubMed]

Morrey BF, An KN. Articular and ligamentous contributions to the stability of the elbow joint. Am J Sports Med.1983;11: 315-9.11315 1983 [CrossRef]

Regan WD, Korinek SL, Morrey BF, An KN. Biomechanical study of ligaments around the elbow joint. Clin Orthop Relat Res.1991;271: 170-9.271170 1991

Morrey BF, An KN, Stormont TJ. Force transmission through the radial head. J Bone Joint Surg Am.1988;70: 250-6.70250 1988 [PubMed]

Jensen SL, Olsen BS, Sojbjerg JO. Elbow joint kinematics after excision of the radial head. J Shoulder Elbow Surg.1999;8: 238-41.8238 1999 [CrossRef]

Morrey BF, An KN. Stability of the elbow: osseous constraints. J Shoulder Elbow Surg.2005;14(1 Suppl S): 174S-8S.14174S 2005 [PubMed][CrossRef]

Safran MR, Baillargeon D. Soft-tissue stabilizers of the elbow. J Shoulder Elbow Surg.2005;14(1 Suppl S): 179S-85S.14179S 2005 [PubMed][CrossRef]

An KN, Hui FC, Morrey BF, Linscheid RL, Chao EY. Muscles across the elbow joint: a biomechanical analysis. J Biomech.1981;14: 659-69.14659 1981 [CrossRef]

Blasier RB, Soslowsky LJ, Malicky DM, Palmer ML. Posterior glenohumeral subluxation: active and passive stabilization in a biomechanical model. J Bone Joint Surg Am.1997;79: 433-40.79433 1997 [PubMed][CrossRef]

Payne LZ, Deng XH, Craig EV, Torzilli PA, Warren RF. The combined dynamic and static contributions to subacromial impingement. A biomechanical analysis. Am J Sports Med.1997;25: 801-8.25801 1997 [PubMed][CrossRef]

Wuelker N, Korell M, Thren K. Dynamic glenohumeral joint stability. J Shoulder Elbow Surg.1998;7: 43-52.743 1998 [PubMed][CrossRef]

Park MC, Ahmad CS. Dynamic contributions of the flexor-pronator mass to elbow valgus stability. J Bone Joint Surg Am.2004;86: 2268-74.862268 2004

Field LD, Altchek DW. Evaluation of the arthroscopic valgus instability test of the elbow. Am J Sports Med.1996;24: 177-81.24177 1996 [CrossRef]

Fuss FK. The ulnar collateral ligament of the human elbow joint. Anatomy, function and biomechanics. J Anat.1991;175: 203-12.175203 1991

Guttierez LF. A contribution to the study of the limiting factors of elbow flexion. Acta Anat.1964;56: 146-64.56146 1964 [PubMed][CrossRef]

Rijke AM, Goitz HT, McCue FC, Andrews JR, Berr SS. Stress radiography of the medial elbow ligaments. Radiology.1994;191: 213-6.191213 1994 [PubMed]

Schwab GH, Bennett JB, Woods GW, Tullos HS. Biomechanics of elbow instability: the role of the medial collateral ligament. Clin Orthop Relat Res.1980;146: 42-52.14642 1980 [PubMed]

Sojbjerg JO, Ovesen J, Nielsen S. Experimental elbow instability after transection of the medial collateral ligament. Clin Orthop Relat Res.1987;218: 186-90.218186 1987 [PubMed]

Timmerman LA, Andrews JR. Histology and arthroscopic anatomy of the ulnar collateral ligament of the elbow. Am J Sports Med.1994;22: 667-73.22667 1994 [CrossRef]

Kapanji IA. The physiology of joints. In: Upper limb. New York: Churchill Livingstone; 1970. p 84.84 1970

King GJ, Zarzour ZD, Rath DA, Dunning CE, Patterson SD, Johnson JA. Metallic radial head arthroplasty improves valgus stability of the elbow. Clin Orthop Relat Res.1999;368: 114-25.368114 1999 [PubMed]

Olsen BS, Sojbjerg JO, Dalstra M, Sneppen O. Kinematics of the lateral ligamentous constraints of the elbow joint. J Shoulder Elbow Surg.1996;5: 333-41.5333 1996 [PubMed][CrossRef]

Pomianowski S, O'Driscoll SW, Neale PG, Park MJ, Morrey BF, An KN. The effect of forearm rotation on laxity and stability of the elbow. Clin Biomech (Bristol, Avon).2001;16: 401-7.16401 2001 [PubMed][CrossRef]

Pomianowski S, Morrey BF, Neale PG, Park MJ, O'Driscoll SW, An KN. Contribution of monoblock and bipolar radial head prostheses to valgus stability of the elbow. J Bone Joint Surg Am.2001;83: 1829-34.831829 2001

Andrews JR, Wilk KE, Satterwhite YE, Tedder JL. Physical examination of the thrower's elbow. J Orthop Sports Phys Ther.1993;17: 296-304.17296 1993

Jobe FW, ElAttrache N. Diagnosis and treatment of ulnar collateral ligament injuries in athletes. In: Morrey BF, editor. The elbow and its disorders. 2nd ed. Philadelphia: WB Saunders Co; 1993. p 566-72.566 1993

Jobe FW, Kvitne RS. Elbow instability in the ahlete. Instr Course Lect.1991;40: 17-23.4017 1991

Kvitne RS, Jobe FW. Ligamentous and posterior compartment injuries. In: Jobe FW, editor. Operative techniques in upper extremity sports injuries. St. Louis: Mosby; 1996. p 411-30.411 1996

O'Driscoll SW. Elbow instability. Hand Clin.1994;10: 405-15.10405 1994 [PubMed]

Timmerman LA, Schwartz ML, Andrews JR. Preoperative evaluation of the ulnar collateral ligament by magnetic resonance imaging and computed tomography arthrography. Evaluation in 25 baseball players with surgical confirmation. Am J Sports Med.1994;22: 26-32.2226 1994 [PubMed][CrossRef]

Yocum LA. The diagnosis and nonoperative treatment of elbow problems in the athlete. Clin Sports Med.1989;8: 439-51.8439 1989 [PubMed]

Bennett JB, Green MS, Tullos HS. Surgical management of chronic medial elbow instability. Clin Orthop Relat Res.1992;278: 62-8.27862 1992

Smith GR, Altchek DW, Pagnani MJ, Keeley JR. A muscle-splitting approach to the ulnar collateral ligament of the elbow. Neuroanatomy and operative technique. Am J Sports Med.1996;24: 575-80.24575 1996 [PubMed][CrossRef]

Pribyl CR, Kester MA, Cook SD, Edmunds JO, Brunet ME. The effect of the radial head and prosthetic radial head replacement on resisting valgus stress at the elbow. Orthopedics.1986;9: 723-6.9723 1986 [PubMed]

Sojbjerg JO, Ovesen J, Gundorf CE. The stability of the elbow following excision of the radial head and transection of the annular ligament. An experimental study. Arch Orthop Trauma Surg.1987;106: 248-50.106248 1987 [CrossRef]

Tanaka S, An KN, Morrey BF. Kinematics and laxity of the ulnohumeral joint under valgus-varus stress. J Musculoskeletal Res.1998;2: 45-54.245 1998 [CrossRef]

Topics

elbow region ; ligaments ; pronation ; supination ; forearm ; elbow flexion

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Marc R. Safran, Michelle H. McGarry, Steve Shin, Steve Han, Thay Q. Lee; Effects of Elbow Flexion and Forearm Rotation on Valgus Laxity of the Elbow. The Journal of Bone & Joint Surgery. 2005 Sep;87(9):2065-2074.

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