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.