Partial olecranon excision: the relationship between triceps insertion site and extension strength of the elbow

PURPOSE

Partial excision with triceps reattachment is an accepted method for treating comminuted fractures of the olecranon. The currently recommended site for reattachment is along the articular margin of the remaining olecranon process. With computer models suggesting that this may lead to weakness of elbow extension, this study was performed to evaluate different sites for triceps reattachment with respect to extension strength of the elbow.

METHOD

Ten fresh frozen human cadavers were potted and the elbow placed in varying degrees of flexion (45 degrees, 90 degrees, and 135 degrees ). Incremental loads were applied to the triceps mechanism and the force generated was recorded using an Instron materials testing machine (Instron Corp., Canton, MA). A 50% olecranon excision was then performed, simulating a comminuted olecranon fracture. The triceps tendon was attached either anteriorly along the articular margin or posteriorly along the cortical margin. All specimens were tested at both insertion sites in random order.

RESULTS

A significant decrease in extension strength was observed between intact specimens and anterior attachment of the triceps tendon at all angles of elbow flexion. A decrease was only observed with posterior reattachment at 90 degrees. Posterior reattachment provided greater extensor strength than anterior attachment, with greatest differences seen at increasing positions of elbow extension.

CONCLUSIONS

Although anterior reattachment of the triceps tendon after partial excision of the olecranon is currently recommended by some, this results in diminished strength of the triceps mechanism. A greater mechanical advantage with increased strength is provided by a more posterior reattachment using the technique described. These differences are greatest at increasing positions of elbow extension where triceps strength is more functionally important.

Fractures of the olecranon: an in vitro study of elbow joint stresses after tension-band wire fixation versus proximal fracture fragment excision

BACKGROUND

Displaced fractures of the olecranon usually require operative treatment, by either open reduction with internal fixation (ORIF) or excision of the proximal fragment. However, the relative merits of these treatment options have not been fully delineated. One treatment outcome measure of joint function is residual intra-articular stress. The purpose of this study was to evaluate the effect of these two types of olecranon fracture treatment on humeroulnar joint stress.

METHODS

Eight matched pairs of fresh frozen cadaveric upper extremities were thawed; stripped of skin, muscular, and neurovascular tissue; and potted in polymethylmethacrylate. The intra-articular humeroulnar joint peak pressures were measured at 90 degrees of elbow flexion using pressure-sensitive film after application of a 0.15 kg-m torque through the remaining triceps muscle attachment. First, pretreatment (normal) pressures were obtained from the major contact regions of the humeroulnar joint. A 50% olecranon osteotomy was then performed simulating a fracture, and the elbows from each of the paired specimens were randomly assigned to one or the other of two treatment groups: ORIF (using a tension-band wiring technique) and proximal fragment excision. Joint pressures were remeasured. A two-tailed paired t test was used for statistical analysis.

RESULTS

After osteotomy, the peak pressures were higher, overall, in the excision group. Comparing each posttreatment experimental group to its pretreatment (normal) counterpart revealed that the peak pressures in the distal medial and distal lateral articular subzones were significantly higher for the fragment excision group (p = 0.005 and p= 0.0008, respectively), but were not significantly different in the ORIF group (p = 0.545 and p= 0.153, respectively).

CONCLUSION

The findings of this study indicate that ORIF restores the normal biomechanics of the elbow joint and proximal fragment excision results in abnormally elevated joint stresses. These elevated joint stresses may, over time, contribute to the development of elbow pain and osteoarthrosis. Therefore, ORIF should continue to be regarded as the treatment of choice for displaced fractures of the olecranon involving large proximal fracture fragments similar in size to those in this study.

Fractures of the proximal ulna olecranon and coronoid fractures

Fractures of the proximal ulna present unique challenges to the surgeon because of the complexity of the elbow joint. It is important not to underestimate the potential difficulty of these cases and to give each one thorough preoperative consideration before embarking on a surgical course. The primary principles of treatment are to restore joint congruity and stability while permitting early range of motion. A logical and consistent approach, based on the fracture characteristics and concomitant injuries, should produce predictable results.

The treatment of olecranon fractures by excision or fragments and repair of the extensor mechanism: historical review and report of 12 fractures

The operative treatment of olecranon fractures is controversial. Proponents of open reduction and internal fixation cite restoration of anatomy and rigid fixation, while proponents of excision of fracture fragments with repair of the extensor mechanism cite few complications and a rapid return of motion and function. An extensive review of the literature is presented, outlining the arguments in favor of each procedure. A series of cases is also presented. We report the results after excision of fragments and repair of the extensor mechanism for all 17 patients who underwent this procedure during the past 10 years at our hospitals. Evaluation included subjective, clinical, and radiographic assessment to provide a clinical score. Among the 12 patients with sufficient follow up to be rated, there were 7 excellent results, 4 good results, and 1 poor result. There were no complications. Our patients had a rapid return of motion and function with a rapid return to the preinjury level of activity. We believe the indications for this procedure may be even broader than suggested in the literature.

Analysis of mechanical factors affecting fixation of olecranon fractures

Fractures of the most distal part of the olecranon process differ from more proximal fractures because a plane of instability exists between the humerus and the radial head. Thus, the fixation of these fractures must resist the deforming forces of the forearm flexor muscles. The investigators fixed 10 paired cadaver ulnae with either the tension-band wire technique or a one-third tubular plate, and tested the specimens to simulate the effect of the biceps and brachialis muscles. The average maximum fixation stiffness for specimens fixed with the one-third tubular plate was found to be 163 N/mm compared with 53 N/mm for the tension-band wire group. This study indicates that for fractures of the distal part of the olecranon, fixation with screws and a one-third tubular plate affords better resistance to the forces applied by the brachialis and the biceps brachii than the tension-band wire technique.

Olecranon fractures treated with AO screw and tension bands

Twenty-eight patients averaging 36.4 years of age underwent open reduction and internal fixation of olecranon fractures. The AO cancellous screw was used alone in 16 and with tension banding in 12. Banding was used when the bone was soft or severely comminuted. The fractures were clinically healed at an average of nine weeks and roentgenographic healing with obliteration of the fracture line occurred at 13 weeks. Sixty-seven percent acquired full motion by the ninth postoperative week. All but two patients regained full supination and pronation. No patient lost greater than 30 degrees of extension and only two lost greater than 30 degrees of flexion. There were few operative difficulties or postoperative complications. We found the AO cancellous screw alone and in severely comminuted cases in combination with tension band wiring to be an excellent fixation device for olecranon fractures. It allows for early range of motion in young patients with excellent healing prospects by 16 weeks.