Posteromedial Approach to the Coronoid Process of the Ulna
Posteromedial Approach to the Coronoid
Process of the Ulna
This approach provides excellent exposure of the coronoid process and the medial aspect of the proximal ulna.10,11
Because the approach is through the bed of the ulnar nerve this structure is at risk in this exposure. The approach does not utilize an internervous plane exposure and therefore cannot be extended but it does provide excellent exposure of the anteromedial aspect of the coronoid process of the ulna, medial collateral ligament of the elbow, and the sublime tubercle. The uses of the posteromedial approach include the following:
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Open reduction and internal fixation of fractures of the coronoid process of the ulna. A lateral approach may be preferred if the fracture is associated with a fracture of the radial head and/or rupture of the lateral collateral ligament of the elbow.
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Repair of the medial collateral ligament of the elbow—usually in conjunction with fixation of the coronoid process.
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Exposure of the sublime tubercle of the ulna for stabilization of fractures.
Position of the Patient
Place the patient lateral on the operating table with the arm supported by a padded arm board or table. Exsanguinate the limb by elevating it and then apply a tourniquet as high up on the arm as possible. Allow the elbow to flex and the forearm to hang over this padded table (see Fig. 3-6). This position is ideal for open reduction and internal fixation of a coronoid fracture because flexion relaxes the pull of the brachialis muscle. In addition this position allows the limb to be pulled by gravity which assists in the reduction of fractures of the proximal ulna.
Landmarks and Incision
Landmarks
Palpate the large, bony olecranon process at the upper end of the ulna and identify the medial epicondyle and the lateral epicondyle of the distal humerus.
Incision
Make a curved incision 8 cm long on the medial aspect of the elbow. Begin the incision proximally just posterior to the medial epicondyle and extend it distally to run along the medial aspect of the forearm (Fig. 3-19).
Internervous Plane
Superficially this exposure does not utilize a true internervous plane. The approach is made between the humeral head of the flexor carpi ulnaris and the ulnar head of the flexor carpi ulnaris which are both innervated by the ulnar nerve (see Fig. 3-45). The deep dissection lies between the ulnar innervated flexors of the wrist and the deep head of the pronator teres (innervated by the median nerve) (see Fig. 3-45).
Superficial Surgical Dissection
Palpate the ulnar nerve as it runs in the groove behind the medial condyle of the humerus. Incise the fascia over the nerve, starting proximally at the level of the medial epicondyle. Isolate the nerve lifting it out of its groove on the back of the medial epicondyle (Fig. 3-20). Define the interval between the two heads of the flexor carpi ulnaris, and develop this plane. Try to preserve branches of the ulnar nerve going to the flexor carpi ulnaris. Identify the sublime tubercle of the ulna. This is a prominent smooth elevation on the medial aspect of the lip of the coronoid process. The ulna nerve is actually in contact with this tubercle and when the nerve is mobilized from its canal the bone is exposed (see Fig. 3-21).
Deep Surgical Dissection
Identify the medial collateral ligament of the elbow just below the sublime tubercle. If needed strip off the soft tissue from the medial aspect of the coronoid process (Fig. 3-22). In cases of fracture this dissection had often been done for you. Complete exposure of the medial aspect of the proximal ulna involves detachment of the origins of the ulna heads of the pronator teres and the flexor carpi ulnaris. These heads are very small.
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Figure 3-19 Make a 8-cm curvilinear incision on the medial aspect of the elbow beginning at the posterior aspect of the medial epicondyle and ending on the medial aspect of the forearm.
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Figure 3-20 Isolate the ulnar nerve from the posterior aspect of the medial epicondyle to the interval between the two heads of flexor carpi ulnaris.
Dang
Nerves
The ulnar nerve must be dissected out and isolated so as to protect it (see Fig. 3-20). Small branches of the ulnar nerve enter the ulnar and humeral head of the flexor carpi ulnaris and should be preserved if possible. Often many small vessels run with the ulnar nerve in its cubital tunnel and require ligation.
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Figure 3-21 Develop a plane between the two heads of flexor carpi ulnaris. Lift the ulna nerve away from the ulna to reveal the sublime tubercle.
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Figure 3-22 Detach the ulna heads of flexor carpi ulnaris and pronator teres from the ulna to reveal the proximal ulna and coronoid process.
How to Enlarge the Approach
Extensile Measures
Enlarge the exposure proximally by developing the plane between the triceps and the brachialis muscles. An osteotomy of the medial epicondyle can be performed for viewing the medial side of the elbow joint (see Fig. 3-18). Distally this approach is not extensile because it does not utilize an internervous plane and the many small nerves going to the humeral and ulnar heads of the flexor carpi ulnaris would be at risk if the dissection was carried out more distally. This is a very specific exposure designed to expose the medial side of the coronoid.