Discussion
Our goal in this study was to determine the maximum articular surface loss that can be tolerated before a BP construct becomes unstable. This finding applies to situations in which the degree of comminution makes reconstruction of the articular surface impossible. Contrary to our hypothesis, the ulnohumeral joint remained stable despite extensive loss of congruity within the sigmoid notch. In 1 specimen, the joint remained stable at 88% loss of olecranon. However, the 2 constructs had different ROM results: ROM was significantly lower at more resections with AS but remained unchanged from baseline with BP.
Dorsal plating has become standard treatment for comminuted olecranon fractures, and many studies, both clinical and biomechanical, have reported favorable results, good functional outcomes, and acceptable ROM.3,7,10,13,18-20,25 However, the multiple studies on the use of various plates in comminuted olecranon fractures did not address whether articular congruity was maintained during reductions or how much articular surface was reconstructed. Although we may reasonably assume larger studies included cases with some unmeasured loss of articular congruity, it is difficult to directly compare our findings with those of other studies. In addition, it is possible those studies did not include fractures that were deemed unfit for BP (because of very severe comminution) and underwent AS instead. Only 1 case series has focused on BP without complete articular reconstruction.8 The cases in that series had good outcomes with good stability—consistent with our finding of extreme comminution in a worst-case scenario.
Complete elbow stability after AS is consistent with findings in the literature.4,6,12,14,16 As AS is reserved for severely comminuted fractures and bone resections,21,23,26 our findings can be compared with the earlier findings. In AS, either the proximal pieces or the intermediate pieces are removed to create a smaller but congruent articular surface, with less concern for nonunion.21 When the proximal piece is removed, the triceps muscle is advanced to the ulnar shaft, creating a slinglike structure for the trochlea.4,11,16,23 When the intermediate piece is removed, the proximal piece is advanced to the shaft along with the triceps.12,14,27 In either technique, the triceps muscle is advanced distally, potentially affecting its extensibility and moment arm.23
Although small in numbers, case series and retrospective reviews have found that AS has good outcomes,4,14,16 whereas our study found significantly decreased ROM. A few patients in these studies lost ROM or triceps strength,12,14,16 but the cause, AS or fracture severity, is unclear. It is possible only 0% to 20% of the olecranon was resected in those cases, whereas our study found no significant change in ROM. It is also possible that cadaveric muscles do not stretch as well as muscles in vivo. Biomechanical studies have demonstrated changes in triceps stretch and strength,23,26 but perhaps these changes are subclinical or overcome with therapy and time.12,14 There are no data regarding whether patients who undergo AS (vs another fixation method) need more physical therapy. In extreme resection, some reduction in ROM is expected.13
The ulnohumeral joint is a primary static stabilizer of the elbow joint.28-30 Recent studies on the role of the ulnohumeral joint in elbow stability have focused mainly on the coronoid process in the setting of dislocation.28,29,31,32 According to these studies, 50% of the coronoid must remain intact for the elbow to be stable when all other stabilizers are intact.32 In our study, resections preserved the coronoid and the ligamentous stabilizers of the elbow. It is therefore possible that the elbow joint remained stable despite the considerable articular surface loss. Although the term ulnohumeral joint refers to both the coronoid and the remaining articular surface, our findings support the coronoid as a primary stabilizer and the remaining articular surface as a secondary static stabilizer.