Purpose: Most displaced olecranon fractures can be treated with ORIF. However with severe comminution or bone loss, excision of the fragments and repair of the triceps to the ulna is recommended. The triceps can be reattached to either the anterior or posterior aspect of the ulna. The purpose of this in-vitro study was to determine the effect of triceps repair technique on elbow laxity and extension strength in the setting of olecranon deficiency.

Method: Eight unpreserved cadaveric arms were used (age 75 ± 11 years). Surface models were generated from CT images and sequential olecranon resections in 25% increments were performed using real-time navigation. Muscle tendons (biceps, brachialis, brachioradialis and triceps) were sutured to actuators of an elbow motion simulator, which produced active extension. A tracking system recorded kinematics in the varus and valgus positions. A triceps advancement was performed using either an anterior or posterior repair to the remaining olecranon in random order. Triceps extension strength was measured in the dependent position with the elbow flexed 90° using a force transducer located at the distal ulnar styloid, while triceps tension was increased from 25–200 N. Outcome variables included maximum varus-valgus elbow laxity and triceps extension strength. Two-way repeated measures ANOVAs were performed for laxity comparing resection level and repair method. Three-way repeated measures ANOVAs were performed for triceps extension strength comparing triceps tension, resection level and repair method. Significance was set at p < 0.05.

Results: Progressive olecranon resection increased elbow laxity (p < 0.001). Although the posterior repair produced slightly greater laxity for all but the 50% resection, this difference was not significant (p = 0.2). The posterior repair provided greater extension strength than the anterior repair at all applied triceps tensions and for all olecranon resections (p = 0.01). The initial 0% resection reduced extension strength for both repairs (p < 0.01), however, there was no effect of progressive olecranon resections (p = 0.09).

Conclusion: There was no significant difference in laxity between the anterior and posterior repairs. Thus even for large olecranon resections, the technique of triceps repair does not have significant influence on joint stability. Extension strength was not reduced by progressive olecranon resections, perhaps due to wrapping of the triceps tendon around the trochlea putting it in-line with the ulna and giving it a constant moment arm. Triceps extension strength was higher for the posterior repair. This is likely due to the greater distance and hence moment arm of the posterior repair to the joint rotation center. Conversely, the anterior repair brings the triceps insertion closer to the joint center, reducing the moment arm. Since there was no significant difference in laxity between the repairs, the authors favour the posterior repair due to its significantly higher triceps extension strength.

Purpose: The purpose of this study was to determine the effect of serial olecranon resections on elbow stability.

Method: Eight fresh, previously frozen cadaveric arms underwent CT scanning. The specimens were mounted in an in-vitro motion simulator, and kinematic data was obtained using an electromagnetic tracking system. Simulated active and passive flexion was produced with servo-motors and pneumatic pistons attached to specific muscles. Flexion was studied in the dependent, horizontal, varus, and valgus positions. Custom computer navigation software was utilized to guide serial resection of the olecranon in 12.5% increments. A triceps advancement repair was performed following each resection.

Results: Serial olecranon resections resulted in a significant increase in valgus-varus (V-V) laxity for both passive (p< 0.001) and active (p=0.04) flexion. For passive motion this increase reached statistical significance following the 12.5% resection. This corresponded to an increase in V-V laxity of 1.4 ± 0.1o and a total laxity of 7.5 ± 1.0o. For active flexion this increase reached significance following the 62.5% resection. This corresponded to an increase in V-V laxity of 5.6 ± 1.1o and a total laxity of 11.2 ± 1.5. There was no significant effect of sequential olecranon excision on elbow kinematics or stability with the elbow in the vertical or horizontal positions. The elbows became grossly unstable after resection of greater than 75% of the olecranon.

Conclusion: A progressive increase in the varus-valgus laxity of the elbow was seen with sequential excision of the olecranon. Laxity of the elbow was increased with excision of 75% of the olecranon, likely due to the loss of the bony congruity and attachment site of the posterior band of the medial collateral ligament. Gross instability resulted when 87.5% or greater was removed, likely due to damage to the anterior band of the medial collateral ligament as it inserts on the sublime tubercle of the ulna. Rehabilitation of the elbow with the arm in the dependant position should be considered following excision of the olecranon; varus and valgus orientations should be avoided. The contribution of the olecranon to elbow stability may be even more important in patients with associated ligament injuries or fractures of the elbow.