Effect of Olecranon Resection on Joint Stability and Strain of the Medial Ulnar Collateral Ligament

Abstract

This study aimed to assess the effect of posteromedial olecranon resection on the stability of the elbow joint, forearm kinematics, and strain in the anterior bundle of the medial ulnar collateral ligament. Seven elbows were tested after resecting all soft tissues except the capsuloligamentous structures. Varus-valgus angulation, forearm rotation, and the length of the anterior bundle of the medial ulnar collateral ligament were measured at 3 posteromedial olecranon resection stages of 0, 4, and 8 mm, and at elbow flexion angles of 30°, 60°, and 90°. Posteromedial olecranon resection significantly increased varus and valgus laxities at 60° and 90° of elbow flexion but had a larger effect on varus motion than valgus movement. With more posteromedial olecranon resection, the valgus angulation and varus-valgus laxity proportionally increased. In most cases, parallel resections of the posteromedial olecranon significantly decreased the functional varus-valgus stiffness. There was no significant effect on strain in the anterior bundle of the medial ulnar collateral ligament due to olecranon resection. When treating an overhead athlete with posteromedial olecranon impingement, the resection should be limited to osteophytic overgrowth. Throwers may be susceptible to ulnar collateral ligament injury following posteromedial olecranon resection due to increased elbow laxity.

Arthroscopic removal of the olecranon osteophytes has been widely used as treatment for posterior elbow impingement due to olecranon osteophytes. However, there is controversy regarding how much resection is acceptable. Although many biomechanical and clinical studies about the elbow have been done, there are few studies about the biomechanical effects of olecranon resection.^1-5 An et al¹ reported that a 50% olecranon osteotomy (resection vertical to the proximal ulna shaft) significantly decreased varus-valgus elbow joint resistant force. Andrews et al² suggested that at moderate quasistatic valgus loads, ulnar collateral ligament strain is not significantly increased with increasing amounts of olecranon resection.^2,5 Recently, Kamineni et al^3,4 reported that valgus angulation of the elbow and strain in the medial collateral ligament increased in association with increased amount of olecranon resection. However, it is unclear which olecranon method is most effective, and there is little understanding about the anatomical changes in the elbow joint due to different resection methods.

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Figure 1: Five points along the anterior (a1-a5) and posterior borders (p1-p5) of the anterior bundle of the medial ulnar collateral ligament (AMUCL) were used as landmarks to measure the length with the Microscribe 3DLX (Immersion Corporation, San Jose, California) using points 1-5 and the Video Digitizing System (Motion Analysis Corporation, Santa Rosa, California) using points 2-4 for the midsubstance.

The aim of the current study was to quantify changes in elbow joint stability after resection of the posteromedial olecranon. Our cut direction of the posteromedial olecranon was parallel to the plane of the proximal ulnar shaft. This osteotomy method simulated the arthroscopic treatment for an overhead thrower with posteromedial olecranon osteophytes. The objectives of this study were to measure the elbow joint kinematics and the regional deformation and strain characteristics of the anterior bundle of the medial ulnar collateral ligament. We also proposed the functional varus-valgus stiffness as a joint stability criterion.

Methods

Seven fresh frozen cadaver elbows were prepared by dissecting all soft tissue except the capsule and ligaments. The average specimen age was 76.3 years (range, 64-84 years; 2 men, 5 women). Four right elbows and 3 left elbows were used. The humeral and forearm ends of the elbow specimen were fixed into PVC pipes using plaster of Paris. A guide rod was attached to the distal forearm to aid in positioning the elbow at flexion positions of 30°, 60°, and 90° and to apply the external valgus torque.

Varus-valgus angulation of the forearm, forearm rotation, and the length of the anterior bundle of the medial ulnar collateral ligament were measured at each olecranon resection stage and at elbow flexion angles of 30°, 60°, and 90°. The humerus was fixed on the testing device so that the longitudinal direction of the humeral PVC pipe, aligned along the humeral shaft direction, was parallel to the ground. The epicondylar axis was oriented perpendicular to the ground. Elbow flexion angles were set with the 3-dimensional coordinate measuring device (Microscribe 3DLX, Immersion Corporation, San Jose, California) and were confirmed visually with a goniometer. The accuracy of the Microscribe 3DLX was determined to be 0.30 mm.

Two anatomic coordinate systems were defined in the elbow joint, one for the distal humerus and another for the proximal forearm. The proximal forearm coordinate system was monitored relative to the humeral coordinate system to provide the kinematics of the forearm relative to the humerus because the humerus remained fixed.

Varus-valgus laxity of the elbow was measured by applying varus-valgus torque to determine the effect of olecranon resection. A steel rod was mounted to the distal end of each forearm to allow for the application of the varus or valgus torques by hanging an additional weight at 3 predetermined points along the rod. Because the elbow was mounted with the epicondylar axis perpendicular to the ground, an initial valgus torque was applied to the elbow due to the weight of the forearm and mounting device (internal torque) which averaged 1.40±0.12 Nm. The external torque was applied to have 1, 2, and 3 Nm in valgus and 3 Nm in varus if the forearm position was parallel to ground. Because the angle of the forearm changes after applying varus or valgus torque, the actual torque that was applied to the elbow decreased based on the final angle of the forearm. This torque was calculated based on the resulting valgus or varus angle.

The kinematic effects of parallel resection of the posteromedial olecranon were evaluated by measuring movements of the forearm relative to the humerus with a Microscribe 3DLX. Varus-valgus angulation was quantified as the tilting angle of the forearm from the base plane that was determined by a longitudinal vector of the humeral shaft and a vector connecting 2 distal humeral epicondyles. Internal-external forearm rotation was defined as the rotation of the forearm about the forearm longitudinal axis. The internal-external forearm rotation was quantified as the angular change from the rotational angle which was measured at the 30° of elbow flexion and at the starting of each olecranon resection stage. Valgus and varus angulation was calculated based on the neutral varus-valgus angle, defined as the midpoint between the total varus-valgus range of motion when 3 Nm of torque was applied. As a joint stability index, functional varus-valgus stiffness was proposed. Functional varus-valgus stiffness was defined as the ratio of the applied varus-valgus torque to the angular change from the neutral varus-valgus position.

The length of the anterior bundle of the medial ulnar collateral ligament from its origin on the humerus and its insertion on the ulna along both the anterior and posterior borders was measured using the Microscribe. The bony origin and insertions were marked with small screws along the anterior and posterior borders for reference points (Figure 1). Care was taken to avoid compromising the ligamentous insertions. The length of the anterior bundle of the medial ulnar collateral ligament midsubstance was measured using a Video Digitizing System (VDS; Motion Analysis Corporation, Santa Rosa, California).⁶ Three points along both borders of the anterior bundle of the medial ulnar collateral ligament were marked with dye for reference points of the midsubstance (Figure 1). At the starting point of the each sequential olecranon resection stage, the VDS camera was aligned with the plane of the anterior bundle of the medial ulnar collateral ligament. Strains along the anterior and posterior border were calculated as the length change from the baseline ligament length that was measured during each osteotomy stage at 30° of elbow flexion with no external torque applied.

All data were recorded for the intact elbow (0-mm olecranon resection). Sequential posteromedial olecranon osteotomies of 4 and 8 mm were then performed on each elbow using an osteotome and a burr, and data were recorded after each resection. The size of bony resection was measured from the visible articular edge of the posterior and posteromedial olecranon. Additional posteromedial articular surface was resected to the level of the lowest point of the greater sigmoid notch of the medial olecranon. These resections were performed in the plane parallel to the proximal ulnar plane formed by the ulnar shaft and the proximal ulnar medial-lateral direction. This cutting direction attempted to mimic extreme cases of what would be performed arthroscopically (Figure 2). Care was taken to preserve the posterior bundle of the anterior bundle of the medial ulnar collateral ligament.

All measurements were repeated twice and the average of the 2 trials was used for analysis. Statistical analysis was performed using a univariate repeated measures analysis of variance with a Tukey posthoc test for individual comparisions. The level of significance was set to 0.05.

Results

Varus and Valgus Angulation

The neutral varus-valgus position was measured at each amount of olecranon resection. The neutral varus-valgus position of the intact specimen was 15.0°, 13.8°, and 12.1° at 30°, 60°, and 90° of elbow flexion, respectively. As the elbow flexion increased, the central varus-valgus position moved varus in all resection stages.

Figure 2: Sequential 0-, 4-, and 8-mm posteromedial olecranon resections were performed in a direction parallel to the proximal ulna plane.

Varus and valgus angulation was measured as the difference from the neutral varus-valgus angular position of the intact specimen. Valgus angulation increased significantly with increased torque (P<0.05) at each oteotomy condition. At 60° and 90° of elbow flexion, valgus and varus angulation significantly increased following 8 mm of olecranon osteotomy (P<0.05; Table 1).

Total varus-valgus laxity was calculated as the total angular range of motion by 3 Nm of varus and valgus torques. Total varus-valgus laxity increased significantly following 8 mm of olecranon resection at 60° and 90° of elbow flexion (Figure 3). Varus-valgus laxity also significantly increased at 60° and 90° compared with 30° of elbow flexion following 8-mm olecranon osteotomy (P=0.04 and 0.02, respectively).

Functional Varus-Valgus Stiffness

The functional varus-valgus stiffness, a joint stability criterion, was calculated as the ratio of the applied varus-valgus torque to the angular change from the neutral varus-valgus position. In most cases, parallel resections of the posteromedial olecranon significantly decreased the functional varus-valgus stiffness (Figure 4).

Figure 4: The varus-valgus stability evaluated by the functional varus-valgus stiffness at 30° (A), 60° (B), and 90° (C) of elbow flexion. aP<0.05 vs 0-mm osteotomy, bP<0.05 vs 4-mm osteotomy. Figure 3: Varus-valgus laxity, with respect to the amount of olecranon resection. aP<0.05 vs 0-mm osteotomy, bP<0.05 vs 4-mm osteotomy. Abbreviation: flex, flexion; int, internal; T, torque.

AMUCL Strain

Origin-to-Insertion Strain From Microscribe Measurement. The strain of the origin-to-insertion of the anterior bundle of the medial ulnar collateral ligament along the anterior and posterior borders increased with valgus torque (P<0.05). This torque effect on strain was seen at each elbow flexion. As the elbow flexes, the apparent strain of the anterior border decreased by 7% while the apparent strain of the posterior border increased by 25%, relative to the baseline length after each resection stage at 30° of elbow flexion under no externally applied torque (Figures 5, 6). There was no significant change in the strain pattern of the anterior bundle of the medial ulnar collateral ligament following 4- and 8-mm posteromedial olecranon osteotomies at each flexion angle.

	Figure 5: The strain of the anterior border of the anterior bundle of the medial ulnar collateral ligament (AMUCL) origin-to-insertion according to olecranon resections at 30° (A), 60° (B), and 90° (C) of elbow flexion. Strains were calculated relative to the baseline length of the anterior band of the medial ulnar collateral ligament that was measured at 30° of elbow flexion with no external torque applied.
	Figure 6: The strain of the posterior border of the anterior bundle of the medial ulnar collateral ligament (AMUCL) origin-to-insertion according to olecranon resections at 30° (A), 60° (B), and 90° (C) of elbow flexion. Strains were calculated relative to the baseline length of the anterior border of the medial ulnar collateral ligament that was measured at 30° of elbow flexion with no external torque applied.

Midsubstance Strain from VDS Measurement. The higher valgus torque increases the strains of the anterior and posterior borders of the anterior bundle of the medial ulnar collateral ligament midsubstance at all elbow flexion angles (P<0.05). As elbow flexion increased from 30° to 90°, the apparent strain of the anterior border decreased ≤9% (resection=4 mm; torque=internal+external 2 Nm), and the apparent strain of posterior border increased ≤23% (resection=8 mm; torque=internal+external 3 Nm), relative to the baseline length after each resection stage at 30° of elbow flexion under no externally applied torque. Similar to the strain of the anterior bundle of the medial ulnar collateral ligament origin-to-insertion, the strain of its midsubstance was not significantly affected by olecranon resection.

Discussion

Different olecranon resection methods are thought to produce different elbow joint motions. The olecranon resection methods can be described relative to the proximal ulnar plane that is determined by the ulnar shaft direction and the proximal ulnar medial-lateral direction. A vertical olecranon resection resects the olecranon on the vertical plane to the proximal ulnar plane. A parallel olecranon resection resects the olecranon on the parallel plane to proximal ulnar plane. The oblique resection resects the olecranon on the distal-to-proximal oblique plane relative to the proximal ulnar plane.

An et al¹ evaluated a vertical resection the full-width of the proximal olecranon to study the effect of simulated olecranon fracture on the elbow joint reaction force. They wanted to see how increasing amounts of olecranon removal would affect elbow constraint. Andrews et al² and Levin et al⁵ have evaluated the strain in the ulnar collateral ligament with different resection methods to address either the medial or posterior olecranon. Recently, Kaminani et al^3,4 studied the kinematic changes due to the oblique resection of the proximal olecranon of 45°. Their oblique resection was developed so that similar amounts of articular surface would be taken with each measured resection.

The resection method used in this study was a parallel resection of the posterior and posterior-medial olecranon. This was chosen because the posterior and medial edges are the areas where osteophyte overgrowth is seen in the elbows of throwing athletes.

Elbow varus-valgus laxity with respect to the olecranon’s role has been studied. The importance of the proximal olecranon was demonstrated by An et al¹ who showed that resection of the proximal 25% of the olecranon would reduce elbow constraint by as much as 30% in full extension and 50% in 90° of flexion. Kamineni et al³ showed a significant change in valgus angulation with as little as 3 mm of posteromedial olecranon resection, but with a magnitude of approximately 1° or less. The current study also showed an increase in varus and valgus angulation with olecranon resection of 8 mm, with a greater increase in varus angulation. This may be accounted for by the difference in the type of osteotomy that was performed. Our osteotomy involved a resection parallel to the ulnar shaft that took away more of the lateral olecranon than that performed by Kamineni et al³.

The functional varus-valgus stiffness was proposed as a stability criterion of the elbow. The stiffness concept has been most widely accepted as a stability criterion in mechanical engineering and has been introduced in shoulder biomechanics.⁷ Previous studies showed laxity or joint reaction force, but these may be insufficient comparison tools for the effects of soft tissue and bony geometry on joint stability.^8-10 Clinically, a stiff joint is defined as a joint that has relatively narrow laxity in passive or active motion (ie, reduced motion). A quantitative evaluation for joint stiffness may be provided by the functional varus-valgus stiffness. The functional varus-valgus stiffness, uniquely defined in this study, is the integrated stiffness that was the varus-valgus laxity divided by varus-valgus torque, whereas the angular stiffness is originally the instantaneous stiffness that is the incremental angulation divided by incremental torque. Seeing the force versus elongation graph of soft tissue, soft tissue is easily elongated up to some considerable amount with little increased force. Within some range of force, the deformation increase will show a gentle slope with respect to force. Thereafter, up to some level of deformation, the instantaneous stiffness will not show any visible change. Instead of the rotational stiffness, the functional stiffness provides the integrated laxity divided by the integrated torque. The results showed that functional varus-valgus stiffness decreased with increasing olecranon resection.

In our experiment, we hoped to accurately assess the strain field in the anterior bundle of the medial ulnar collateral ligament with increasing amounts of torque and posteromedial olecranon resections of 4 and 8 mm. Prior studies have used differential variable reluctance transducers to determine strain change in the medial collateral ligament with olecranon resection.^2,4 Our study intentionally avoided using strain gauges, which are known for their difficulty in use and application in small ligament work. Strain gauge readings can vary depending on their placement and orientation within the ligament. Therefore, we used 2 systems—a 3-dimensional digitizer and a video digitizing system. Our experiment showed that excessive parallel resection of the posteromedial olecranon did not significantly affect the strain of the anterior bundle of the medial ulnar collateral ligament in a static situation. Andrews et al² had similar findings in a study using strain gauges.

Changes of olecranon bony structure will change constraint conditions in the elbow joint, resulting in a different bony articulation. The anatomical changes in elbow bony articulation due to posteromedial olecranon resection were expected using an intact cadaveric capsuloligamentous elbow. At 30° of elbow flexion, the posteromedial resected portion does not contact the trochlea, as shown in Figure 7. However, at 60° and 90° of elbow flexion, the proximal end of the olecranon contacts the trochlea so that the resected proximal olecranon directly affects the elbow articulation (Figure 7).

As the resected portion gets nearer to the moment axis, the effects of resection on varus and valgus angulation are greater. Near full extension, decreased bony constraint due to posteromedial olecranon resection will permit more articulation laxity between the sigmoid notch and trochlea. Therefore, posteromedial olecranon osteotomy may increase elbow extension. Through full flexion to extension, the resected posterior portion will give more valgus, varus, and varus-valgus laxities. The resected medial portion will move the pivot point of the moment arm of forearm medially under varus torque and provide less bony pivot constraint so that the elbow will have more varus laxity than valgus laxity.

There are several limitations to the current study. One is that we used a low number of elderly cadaver specimens. Another limitation was that we used cadaveric capsuloligamentous elbows that eliminated the stabilizing contribution of muscle loading. The muscular dynamics, especially the flexor pronator mass, certainly affect the strain across the anterior bundle of the medial ulnar collateral ligament. Therefore, in the current study, the results can be interpreted only with considering bony and capsuloligamentous constraints. The third was the use of nonarthritic, stable elbows. Obtaining a study sample of arthritic elbows with posteromedial osteophytes is unrealistic. We can only speculate that a 4-mm and 8-mm resection in a normal elbow would mimic removal of large posteromedial osteophytes in a thrower’s arthritic elbow. Removal of posteromedial osteophytes would increase laxity of the elbow and could make a pathologic anterior bundle of the medial ulnar collateral ligament or ulnar nerve more symptomatic in the postoperative patient. This is true especially when the elbow is placed under high levels of activity, such as a throwing athlete.

Figure 7: Skeletal humeroulnar articulation. Medial views of the humeroulnar articulation at 30° (A), 60° (B), and 90° (C) elbow flexion. Posterior views of the humeroulnar articulation at 30° (D), 60° (E), and 90° (F) elbow flexion. The triangle in A-C and the hatched area in D-F outlines the resected portion of the olecranon.

When treating the elbow of a long-term overhead athlete, it is important to remember the components of valgus extension overload. With repetitive stress, the medial ulnar collateral ligament and other medial soft tissues will stretch and allow increased valgus laxity with posteromedial impingement. Eventually the body attempts to “stabilize” the elbow with reactive bone formation on the posteromedial olecranon and humerus. Our experiment attempted to explore the potential relationship between surgically excising posteromedial osteophytes with some normal articular surface and the consequent development of medial ulnar collateral ligament laxity or rupture. This relationship has been observed in some athletes after such surgeries. There are 2 major reasons to explain this observation. One explanation is that the removal of osteophytes can alter the kinematics of the elbow, and place the anterior bundle of the medial ulnar collateral ligament under increased stress. Another explanation is that a destabilized elbow simply exposes an already insufficient anterior bundle of the medial ulnar collateral ligament to further stress. Although we have insufficient data to determine the true answer, our experiment does reveal altered elbow kinematics, specifically increased varus-valgus laxity with the parallel resection of the posteromedial olecranon.

Conclusion

Our study has shown that under static varus-valgus torque, there was no significant change in the strain pattern across the anterior bundle of the medial ulnar collateral ligament after posteromedial olecranon osteotomy. There is an alteration in elbow kinematics in that overall varus-valgus laxity is increased, with the largest increase in the varus direction at 90°. The elbow joint stability was evaluated by the functional varus-valgus stiffness. Parallel resection of posteromedial olecranon will decrease the elbow stability in higher degrees of elbow flexion (60° and 90° of flexion). We suggest that in the surgical treatment of posteromedial olecranon impingement, the amount of resection should be limited to the osteophytic overgrowth and elbow laxity should be evaluated at higher degrees of elbow flexion.

References

1. An KN, Morrey BF, Chao EY. The effect of partial removal of proximal ulna on elbow constraint. Clin Orthop Relat Res. 1986; (209):270-279.
2. Andrews JR, Heggland EJ, Fleisig GS, Zheng N. Relationship of ulnar collateral ligament strain to amount of medial olecranon osteotomy. Am J Sports Med. 2001; 29(6):716-721.
3. Kamineni S, Hirahara H, Pomianowski S, et al. Partial posteromedial olecranon resection: a kinematic study. J Bone Joint Surg Am. 2003; 85(6):1005-1011.
4. Kamineni S, ElAttrache NS, O’Driscoll SW, et al. Medial collateral ligament strain with partial posteromedial olecranon resection. A biomechanical study. J Bone Joint Surg Am. 2004; 86(11):2424-2430.
5. Levin JS, Zheng N, Dugas J, Cain EL, Andrews JR. Posterior olecranon resection and ulnar collateral ligament strain. J Shoulder Elbow Surg. 2004; 13(1):66-71.
6. Lee TQ, Dettling J, Sandusky MD, McMahon PJ. Age related biomechanical properties of the glenoid-anterior band of the inferior glenohumeral ligament-humerus complex. Clin Biomech (Bristol, Avon). 1999; 14(7):471-476.
7. Oosterom R, Herder JL, van der Helm FC, Swieszkowski W, Bersee HE. Translational stiffness of the replaced shoulder joint. J Biomech. 2003; 36(12):1897-1907.
8. Lee SB, An KN. Dynamic glenohumeral stability provided by three heads of the deltoid muscle. Clin Orthop Relat Res. 2002: (400):40-47.
9. Lee SB, Kim KJ, O’Driscoll SW, Morrey BF, An KN. Dynamic glenohumeral stability provided by the rotator cuff muscles in the mid-range and end-range of motion. A study in cadavera. J Bone Joint Surg Am. 2000; 82(6):849-857.
10. Beingessner DM, Dunning CE, Beingessner CJ, Johnson JA, King GJ. The effect of radial head fracture size on radiocapitellar joint stability. Clin Biomech (Bristol, Avon). 2003; 18(7):677-681.

Authors

Dr Lee (Yeon) is from the School of Mechatronics and Information Engineering, GwangJu Institute of Science and Technology, Republic of Korea; Dr Alcid is from the Ocean Medical Center, Toms River, New Jersey; Drs McGarry and Lee (Thay) are from the Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System and University of California, Irvine, and Dr ElAttrache is from the Kerlan-Jobe Orthopaedic Clinic, Los Angeles, California.

Drs Lee (Yeon), Alcid, McGarry, ElAttrache, and Lee (Thay) have no relevant financial relationships to disclose.

Investigations were performed at Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System and University of California, Irvine, California.

Correspondence should be addressed to: Thay Q. Lee, PhD, Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System (09/151), 5901 E 7th St, Long Beach, CA 90822.