The Anatomic Study And Clinical Value Of The Anteromedial Facet Of The Ulna Coronoid Process

Objective: coronoid fractures of the ulna are relatively uncommon, yet they play an important role in the stability of the elbow. in the past, the ulnar coronoid process fractures are classified according to the anterior-to-posterior size of the fracture fragment. In recent years, the O'Driscoll classification system for coronoid fractures based on the location and morphology of the coronoid fractures,which associcates with the elbow injury pattern,and help guide clinical treatment. especially the O'Driscoll classification system present the concept of the anteromedial fracture of the coronoid process of the ulna, which is being gradually recognized as a special type of fracture,and is considered by the a varus posteromedial rotational force.As a coronoid process fracture pattern put forward in n recent years,the basis experimental study is little. in this experiment,we measure anatomic data of the anteromedial facet of the ulna coronoid process and provide basis for the diagnosis and treatment of the anteromedial fracture of the ulna coronoid process.Methods: the present study was done on 16 upper extremities from 8 embalmed human,adult cadavers.5 males ,the average ages of the cadavers were 40 years,3 females,the average ages of the cadavers were 35 years.There was no evidence of previous trauma or arthrosisin any of the specimens.upper extremities specimens was divided between forearm and elbow,hand and wrist,and then get rid of the forearm skin, subcutaneous tissue and the extensor group, flexor group, pronator supinator, veins, nerves and joint capsule, radius will be separated from ulna,remove all residual soft tissue of the ulna surface, pay attention to the amputation of forearm and elbow, not to cause fracture of coronoid process of ulna. The"trochlear notch"plane was defined by 3 anatomic landmarks: the tip of the coronoid process, the tip of the olecranon and the base of the trochlear notch.the tie line from the tip of the olecranon to the mid-point of distal ulna form the central axis of ulna, The"axis ulna"plane was defined by the sagittal plane through the central axis of ulna. The"trochlear notch"plane and the"axis ulna"plane are two different plane, they form an angle.A is defined by the location where the anteromedial facet protrudes as a distinct process separate from the proximal ulnar metaphysis.B is defined by the location where the parallel of the anterior central axis of ulna cross through the eage of he coronoid process.C is defined by the location where the parallel of the posterior central axis of ulna cross through the eage of he coronoid process. The inboard part of the line composed by BC is the anteromedial facet that was unsupported by the proximal ulnar metaphysis and diaphysis. Measure the angle formed by the"trochlear notch"plane and the"axis ulna" plane.Measurements by vernier caliper:1,the width of the anteromedial facet which defined the distance from the coronoid process medial to the"trochlear notch"plane2,the width of the medial facet which defined the distance from the coronoid process medial to the"axis ulna"plane3,the anteromedial facet width unsupported by the proximal ulnar metaphysis and diaphysis ,which defined the distance from the coronoid process medial to the line"BC"4,the anteromedial facet height which defined the distance from the"A"to the horizontal plane the tip of coronoid process medial formed. Calculate the percentage that the width of the anteromedial facet that was unsupported by the proximal ulnar metaphysis and diaphysis occupies in the width of the anteromedial facet and medial facet. Attache the rubber adhesive tape to the articular surface of the coronoid process of ulna,then mark along the edge of articular surface and B,C carefully, to distinguish the anteromedial facet that was unsupported by the proximal ulnar metaphysis and diaphysis from the anteromedial facet.take down the rubber adhesive tape and attache it to the grid paper,then cut along the mark.Measure the area of the anteromedial facet unsupported by the proximal ulnar metaphysis and diaphysis and the anteromedial facet by the method of lattice. The area of each small grid is the 1 square millimeter, Calculate the total of all the small grids, greater than or equal to half of the small grid area is calculated by a small grid, less than half of the small grid is not calculated. Calculate the percentage that the area of the anteromedial facet that was unsupported by the proximal ulnar metaphysis and diaphysis occupies in the area of the anteromedial facet.Results: 1,the angle formed by the"trochlear notch"plane and the"axis ulna"is 11°2,the width of the anteromedial facet which defined the distance from the coronoid process medial to the"trochlear notch"plane is 16.14±1.57mm3,the width of the medial facet which defined the distance from the coronoid process medial to the"axis ulna"plane is 18.27±1.67mm4,the anteromedial facet width unsupported by the proximal ulnar metaphysis and diaphysis is 8.57±1.11mm5,the anteromedial facet height is 23.57±3.44mm6,the percentage that the width of the anteromedial facet that was unsupported by the proximal ulnar metaphysis and diaphysis occupies in the width of the anteromedial facet is 53.16±4.46% 7,the percentage that the width of the anteromedial facet that was unsupported by the proximal ulnar metaphysis and diaphysis occupies in the width of the medial facet is 46.85±3.21% 8,the percentage that the area of the anteromedial facet that was unsupported by the proximal ulnar metaphysis and diaphysis occupies in the area of the anteromedial facet is 48.30±4.21%.Conclusions : the anteromedial facet of the coronoid process extends from the proximal ulnar metaphysis and diaphysis,about half of which is relatively unsupported as a distinct process. the anteromedial facet width unsupported by the proximal ulnar metaphysis and diaphysis is 8.5mm,the percentage that the width of the anteromedial facet that was unsupported by the proximal ulnar metaphysis and diaphysis occupies in the width of the anteromedial facet is approximately 53% .the percentage that the area of the anteromedial facet that was unsupported by the proximal ulnar metaphysis and diaphysis occupies in the area of the anteromedial facet is approximately 48%,this makes the anteromedial facet vulnerable to injury, particularly with a varus injury force. this provides anatomic basis for varus posteromedial rotational force,the fracture fragment of the anteromedial facet is too small to find,clinical doctor should attach great importance to avoid misdiagnosis.