Chapter 10 Venting of the Major Pulleys

Outline

Review of the history of the management of the flexor tendon sheath over the last half century is necessary to understanding why venting the pulleys has met with such resistance among hand surgeons. The author’s clinical research illustrating why venting of the A2 and A4 pulleys is necessary in clinical practice is then described. This is followed by review of other subsequent research supporting the practice of venting these pulleys as a necessary surgical activity to ensure safe rehabilitation of primary repairs of the digital flexor tendons.

To repair flexor tendon injuries in zones 1 and 2, it is inevitable that the tendon sheath be opened for access. Over the past 40 years, treatment of the sheath on completion of the tendon repair(s) appears to have been determined partly on theoretical grounds and partly by interpretation of the tendon healing research at the time.

History

After primary repair, the subsequent discrepancy between the external diameter of flexor tendons and the internal diameter of the tendon sheath was first discussed by Mason in 1940.¹ He pointed out the importance of excision of the sheath adjacent to the primary repair and over a sufficient length to allow free gliding of the repair. In 1958, Verdan² again highlighted this point, stating that “the sheath is excised over a distance of about two to three centimeters, the amount of the sheath to be resected was determined by estimating the physiological gliding amplitude at this level.” Ketchum,³ in 1977, also mentioned the need to excise a portion of the sheath. Although these authors were writing when it was assumed that adhesion formation between the tendons and the subcutaneous fat was necessary to achieve repair of the sutured tendon, a secondary need for adequate sheath excision to allow free movement of the repair is clear.

Following identification of a synovial means of nutrition and repair of injured flexor tendons, complete repair of the flexor tendon sheath was advocated both to reestablish the synovial environment of the tendon and to diminish formation of adhesions, no longer believed to be necessary for tendon healing and recognized to be a hindrance to movement.^1,⁴^–⁸ The methodology of complete closure of the sheath following primary tendon repair was elaborated by Lister.⁹ The zeal to completely close the flexor sheath waned in the 1980s and 1990s from a lack of supportive evidence that this is either necessary or beneficial.¹⁰^–¹⁶

Various authors at this time pointed out again that repaired, and thereby thickened, flexor tendons might not move freely in the closed tendon sheath, because of the increased diameter of the repaired tendon and/or narrowing of the sheath by the process of closing it.^1,¹⁶^–²² The problems identified after complete closure of the sheath were (1) complete immobility of the repair and (2) (more likely) snagging of the repair on the edges of adjacent pulleys during tendon movement. Such an impediment to full mobility might be expected to cause either a loss of range of motion of the digit or a rupture of the repair during early postoperative mobilization, depending on the vigor with which the hand was rehabilitated. It was suggested that it might be necessary to partially release or “vent” the sheath laterally to achieve a free-running repair.^1,^17,²¹ Strickland (1986) described and illustrated the technique of lateral “venting” pulleys but thought that this was only necessary when a particular bulky repair came to lie adjacent to a pulley, which restricted its full excursion.²¹ In most instances, he considered that complete sheath closure without this maneuver was possible. Schneider (1985) wrote that “excising a portion of the sheath in badly damaged cases may be required to allow free mobility of the tendon juncture” and also admitted having been forced to remove the A4 pulley on rare occasions with delayed repairs.²³ There has been no work done since Strickland (1986) to identify any useful difference between splitting the pulleys laterally and in the midline.

Throughout all of these reports, there was a palpable reluctance to condone such venting of pulleys as, in practice, this would usually entail partial division of the A2 or the A4 pulleys, the complete integrity of which was believed to be of great importance in maintaining the mechanical efficiency of the flexor system.^13,²⁴^–²⁷ Toward the end of this period, and coinciding with the waning of the enthusiasm for complete closure of the flexor sheath, Savage (1990) questioned the absolute need to preserve the A2 and A4 pulleys completely.²⁰ Tomaino and his colleagues subsequently lent support to Savage’s work.^28,²⁹

Author’s Clinical Research

There was also a degree of imprecision in these reports as to which pulleys should be vented and by how much and how often such releases were necessary. With this background, we designed a prospective study to examine those zone 2 injuries in which this problem arises most commonly, namely those occurring between the proximal end of zone 1 and the distal edge of the A2 pulley, designated zones 2A and 2B by Tang (1994)³⁰ in his proposed subdivision of the original zone 2 described by Verdan and Michon (1961)³¹ and modified to its present form by Kleinert and Weiland (1979).³² Over a period of 29 months, 126 consecutive fingers with zone 2A and 2B flexor tendon injuries were repaired as part of the routine emergency workload of our unit by senior trainee plastic and orthopedic surgeons, who had been briefed to vent the A2 or A4 pulley as necessary to achieve sound tendon repairs and to allow the repaired tendons to move passively through their full excursion before closing the finger.³³ Whenever possible, tendon repair was carried out through the wound of the tendon sheath with only sufficient further opening of the sheath as necessary to allow tendon suture. In zones 2A and 2B, this usually requires release of part of the A3 pulley, either distal, proximal, or both distal and proximal to the initial wound. As the A3 pulley and the adjacent C pulleys were not then considered essential to the preservation of full flexor mechanical function, particular efforts to preserve this part of the tendon sheath were not made and its fate was not recorded. When tendons were injured close to, or under the A4 pulley, extension of the tendon sheath wound to allow placement of the intratendinous core suture often required some degree of venting of the A4 pulley. A tendon injury adjacent to the distal edge of the A2 pulley does not usually require venting of the distal A2 pulley for repair as the tendons can be drawn out distal to the pulley to undertake the repair(s). In those fingers that were cut in partial flexion, the tendon injury was identified more distally when the finger was in the extended position necessary for surgical repair and was reached either by extending the primary opening or, more commonly, through a separate window of the sheath more distally. Fingers injured in flexion in zones 2A and 2B are those in which the repairs of the flexor digitorum profundus (FDP) tendon are likely to impinge on the proximal edge of the A4 pulley on finger extension. In fingers injured in extension, the tendon injury lies immediately beneath the laceration of the sheath. These repairs are liable to impinge on the distal edge of the A2 pulley on flexion of the finger. After completion of each repair, the finger was moved passively through a full range of motion and the repair observed for catching on the proximal edge of the A4 or distal edge of the A2 pulley. When catching occurred, the appropriate pulley was vented along one edge for as much of its length as was necessary to allow a full and unimpeded range of motion of the repair. The degree to which the A4 pulley had been vented was expressed as a percentage of the total length of the pulley. Venting of the distal edge of the A2 pulley was measured and expressed in millimeters as expressing this as a percentage of the whole of the A2 pulley would have involved unnecessary opening of the base of the finger and palm of the hand to measure the full length of the A2 pulley. After venting of the pulleys, and achieving free movement through the full range of motion of the finger, the sheath was laid over the flexor tendons, hemostasis was achieved, and the skin of the finger was closed. The fingers were then mobilized using the variant of the controlled (early) active motion regimen we routinely use and have described previously.³⁴

Only gold members can continue reading. Log In or Register to continue