- Discussion:
- coronoid helps to resist varus stress and posterior elbow subluxation (radial head also resists posterior subluxation);
- at least 50% of the coronoid must be present for the ulno-humeral joint to have normal function (ie for joint to be stable);
- associated w/
elbow dislocation in upto 40%;
- references:
-
The anteromedial facet of the coronoid process of the ulna
- classification and treatment:
- type I: frx of the tip of the coronoid process;
- very common with
elbow dislocation w/ radial head fracture = (terrible triad)
- type II: frx or comminution constitutes about half of coronoid;
- treated w/ early motion if no instability is present;
- type III: frx or comminution constitues more than half of coronoid;
- almost always involves
dislocation (see below);
- fractures near coronoid base are associated w/ increased instability due to loss of stabilizing function of coronoid itself as well as loss
of the insertion of the
anterior band of the MCL and anterior joint capsule;
- Radiographs:
- coronoid fracture fragment may appear
small and may be confused with a radial head fracture;
-
opening angle:
- angle formed by lines drawn from the tip of the olecranon to coronoid and a line drawn down the axis of the ulna;
- ref:
Coronoid fracture patterns.
- Dislocation + Coronoid Process Frx: Classification;
- frx is due to avulsion by brachialis when elbow is hyperextened;
-
type I: avulsion of the tip of the coronoid process;
-
type II: involving less than 50% of the process
- for above types closed reduction and early motion is recommended;
- fixation of frx fragments may not guarantee stability;
- consider external fixation distraction device;
-
type III: frag involving > 50% of process
- almost always associatted w/ posterior dislocation;
- assoc w/ high redislocation rate & requires ORIF
- there will be assoc valgus instability since
MCL inserts onto the fracture fragment;
- if frx pattern is not amenable to rigid fixation, is an indication for an external fixation distraction device;
- left untreated, the worst of all scenarios may develop: ie, an unstable eblow joint which is also stiff and painful;
- in the report by Closkey et al, elbows of cadavera were tested before and after fracture of the coronoid process to assess the stabilizing contribution
of the coronoid process under axial loading;
- there was no significant difference, at any flexion position, in posterior axial displacement between the intact elbows and the elbows
in which 50 percent or less of the coronoid process was fractured (type I and type II) (p = 0.43);
- there were significant differences, across all flexion positions, in posterior axial displacement between the intact elbows and
the elbows in which more than 50 percent of coronoid process was fractured (type III) (p = 0.006);
- in response to axial load, elbows with a fracture involving more than 50 percent of the coronoid process displace more readily
than elbows with a fracture involving 50 percent or less of the coronoid process, especially when the elbow is flexed 60 degrees and beyond;
- surgical approach:
- w/ associated radial head fracture: consider lateral
approach to the coronoid fracture;
- w/ isolated
coronal fracture: consider medial or
anterior approach;
-
fixation technque:
-
anterior approach:
- medial approach:
- ulnar nerve is transposed anteriorly;
- FCU heads are split and the anterior head is retracted anteriorly;
- cannulated screw fixation:
- ACL tibial guide is used to guide a K wire thru the posterior olecranon and up into the coronoid region;
- Huston suture passer is passed thru small drill holes thru the coronoid process and ulna which allow passage of heavy non absorable suture for fixation;
- references:
- The Role of Coronoid Process in Elbow Stability. A Biomechanical Analysis of Axial Loading. Closkey JBJS [Am] 82-A: 1749-53, 2000
-
Optimal screw orientation for fixation of coronoid fractures.
Reconstruction of the coronoid process with a radial head fragment. Esser RD. Orthopedics. 20(2):169-71, 1997 Feb.
Soft tissue attachments of the ulnar coronoid process. An anatomic study with radiographic correlation. DJN Cage et al. CORR. Vol 320. 1995. p 154-158.
Posterior Dislocation of the Elbow with Fractures of the Radial Head and Coronoid. David Ring, MD Journal of Bone and Joint Surgery (American) 84:547-551 (2002)
Medial oblique compression fracture of the coronoid process of the ulna.
Fracture of the Anteromedial Facet of the Coronoid Process. Surgical Technique
The anteromedial facet of the coronoid process of the ulna
Optimal screw orientation for fixation of coronoid fractures
The Effect of Anteromedial Facet Fractures of the Coronoid and Lateral Collateral Ligament Injury on Elbow Stability and Kinematics
