Midlateral Approach to the Flexor Sheaths, Proximal and Middle Phalanges

The midlateral approach is a popular way of reaching the flexor tendons and digital nerves in the fingers. It affords access to the neurovascular bundle on the incised side of the finger; at the same time, it is difficult to extend into the palm. Its uses include the following:

Open reduction and stabilization of phalangeal fractures
Exposure of the fibrous flexor sheath and its contents
Exposure of the neurovascular bundle

Position of the Patient

Place the patient supine on the operating table, with the arm stretched out on an arm board. Good lighting and a good exsanguinating bandage and tourniquet are essential (see Fig. 5-15).

Landmarks and Incision

Landmarks

The proximal and distal interphalangeal creases are the key to this skin incision. They extend around the medial and lateral surfaces of the fingers and end slightly nearer the dorsal than the volar surface of the finger.

The creases may disappear if the finger is very swollen or if it is struck in full extension. If so, the surgical landmark for the skin incision is the junction between the wrinkled dorsal and the smooth volar skin on the side of the finger (see Fig. 5-50).

Incision

Make a longitudinal incision on the lateral aspect of the finger, starting at the most dorsal point of the proximal finger crease. Continue cutting distally to the distal interphalangeal joint, passing just dorsal to the dorsal end of the flexor skin crease. Extend the incision farther distally toward the lateral end of the fingernail. The incision actually is dorsolateral rather than truly lateral (see Fig. 5-50). Alternatively, flex the finger and make an incision connecting dorsal end points of the interphalangeal crease.

Internervous Plane

There is no true internervous plane, because no intermuscular interval is developed. The nerve supply to the finger comes mainly from two sources, the dorsal digital nerves and the volar, or palmar, digital nerves. Because the skin incision marks the division between these two supplies, it causes no significant areas of hypoesthesia.

Figure 5-52 Develop the skin flap down to the flexor sheath, maintaining the neurovascular bundle in the volar flap.

Superficial Surgical Dissection

Develop a volar skin flap by incising the subcutaneous flap in line with the skin incision. The fat over the proximal interphalangeal joint is quite thin; take care not to incise the joint itself. Continue the dissection toward the midline of the finger, angling slightly in a volar direction. The main neuromuscular bundles lie in the volar flap (Fig. 5-52).

Deep Surgical Dissection

If the approach is being used for tendon exploration and repair incise the fibrous flexor sheath longitudinally to expose the underlying tendon (Fig. 5-53). Tendon damage is often associated with damage to the digital nerve and in such cases the neuromuscular bundles also can be dissected out from within the volar flap (Fig. 5-54).

If the approach is being used for bony surgery expose the periosteum of the phalanx just dorsal to the insertion of the flexor sheath. Develop an epiperiosteal plane dorsally lifting the extensor tendon off the bone. Try to preserve as much periosteum as possible. Avoid incision into the flexor sheath as bleeding around the flexor tendons may result in adhesions (Fig. 5-55).

Dang

Nerves

The palmar digital nerve is in danger if the skin incision and approach drift too far in a volar direction. This approach always should begin just dorsal to the end of the interphalangeal creases. If the approach does begin at this site, the danger to the palmar digital nerve will be diminished (see Fig. 5-50A).

Vessels

The volar digital artery runs with the digital nerve on its dorsal side. It also may be damaged if the approach moves too far in a volar direction (see Fig. 5-50).

How to Enlarge the Exposure

Continue the dissection around the fibrous sheath to expose the neurovascular bundle on the opposite side. Note that the exposure gained is not as good as that offered by a zigzag volar approach.