Permissible limits of flexor digitorum profundus tendon advancement—An anatomic study

Permissible limits of flexor digitorum profundus tendon advancement—An anatomic study

Permissible limits of flexor digitorum profundus tendon advancement-An anatomic study Lacerations of the profundus tendon distal to the superficialis ...

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Permissible limits of flexor digitorum profundus tendon advancement-An anatomic study Lacerations of the profundus tendon distal to the superficialis insertion can be treated by advancement of the proximal cut end of the tendon to its insertion. In the English-language literature, limits cited for the distance a profundus tendon can be safely advanced vary from 0.75 to 2.5 cm and appear to be based on clinical impressions. Our cadaver model suggested the degree of tendon advancement tolerable was 1 cm. A delicate balance exists in the profundus tendon system, and this should be considered when surgical advancement is contemplated. (J HAND SURG 1987;12A:30-3.)

Matthew M. Malerich, M.D., Robert A. Baird, M.D., William McMaster, M.D., and Jon M. Erickson, M.D., Irvine and Bakersfield, Calif.

Lacerations of the flexor digitorium profundus tendon distal to the insertion of the superficial is can be managed in a variety of ways . Tenodesis,1. 2 capsulodesis, and arthrodesis 3 are salvage procedures and sacrifice active distal interphalangeal motion for stability. Primary or secondary repair, grafting/os or profundus advancement" 3 are the procedures of choice since they attempt to reestablish normal function in the injured finger. Wagner9 reviewed 27 patients after profundus tendon advancement and cited several common complications . Shortening of the lacerated profundus caused a flexion deformity of the repaired digit and hyperextension in the adjacent digits. Although described as clinically insignificant, these imbalances progressed as shortening became more extensive. Our clinical experience showed a loss of grip strength and impaired flexion in adjacent fingers in addition to the above with excessive advancement.

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Anatomy The deformities caused by excessive advancement are the result of the unique communications between

From the Division of Orthopedic Surgery, University of California, Ivine, Irvine, Calif., and Bakersfield , Calif.

Fig. 2. Flexion lag to adjacent digits with profundus tendon advancement of 1.5 cm to long finger.

Received for publication Oct. 15, 1985; accepted in revised form April 9, 1986. This article was accepted for publication before July I, 1986. No conflict-of-interest statement was requested from the authors. Reprint requests: Matthew M. Malerich, M.D. , 2634 " G" St., Bakersfield, CA 93301 .

adjacent profundus tendons. Proximally, the profundi originate from a common muscle, with the ulnar three forming essentially a common tendon . In the palm and forearm inconstant tendinous slips interconnect the profundi. Further distally, the produndus tendons of the

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THE JOURNAL OF HAND SURGERY

Vol. 12A, No. I January 1987

Lacerations of flexor digitorium profundus tendon

EXTENSION LOSS AFTER TENDON ADVANCEMENT

31

FLEXION LAGS ADJACENT DIGITS (IN MILLIMETERS) FROM THE DISTAL PALMAR CREASE

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Fig. 3. The extension loss, in degrees, with each 0.5 cm increment of advancement; note similar slopes after slack in system was eliminated.

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long, ring, and small fingers are joined by the bipennate origins of the lumbricals. Verdan iO noted in his monograph "Syndrome of the Quadriga" that restricting the gliding amplitude of one of the profundus tendons by suturing it to the extensor in finger amputations would restrict the gliding amplitude of the remaining three because of these communications. Current limits cited for the distance a profundus tendon can safely be advanced without impairment of functions vary from 0.75 cm to 2.5 cm'-6. 10. \I and appear to be based on clinical impressions. We attempted to define, in a laboratory setting, the limits for advancement of a severed flexor digitorum profundus tendon and the nature of the resultant deformities.

Material and methods Nine fresh, unembalmed cadaver hands were used (Fig. 1). The insertion of the profundus tendon was defined by identifying the most proximal attachment of its fibers to the terminal phalanx. The tendon was then marked with a nylon suture at 0.5 cm intervals for a distance of 2 cm from the insertion. A pull-out wire was attached for later reinsertion, so that the remaining digits could be tested. A drill hole was made at the site of profundus insertion, and the profundus tendons were

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Fig. 4. The flexion lag, in degrees, that an advance tendon creates in its counterparts.

then drawn through the hole to each of the marked intervals. Before flexion contractures were measured, the force acting on the fingertip was measured in ten adults at the midportion of the distal phalanx with an Instron test loading machine. The results were as follows: Index finger, ll20 g; long finger, lOOO g; ring finger, 700 g; and small finger, 760 g. Measurements were made with the wrist and finger joints in the fully extended neutral position. Flexion contractures were then determined by applying the appropriate extensor force to each finger after each increment of profundus shortening. In the test model, this would give the maximum active extension possible after shortening of the profundus tendon. The flexion lag of the adjacent digits was measured by cross-clamping the profundus muscle mass at the most proximal tendinous attachments and applying traction to the muscle-tendon unit (Fig. 2). The flexion lag of the adjacent digits was recorded both in degrees and in the distance by which the rounded surface of the fingertip pad failed to reach the depth of the distal

32

The Journal of HAND SURGERY

Malerich et al.

FLEXION LAGS OF ADJACENT DIGITS (DEGREES)

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Fig. 6. The flexion lag in adjacent digits, expressed in distance by which the finger pad misses the distal palmar crease when a tendon is advanced.

Fig. 5. Flexor profundus tendon to index finger (A). flexor profundus tendons to long, ring, and small fingers (B). oblique tendinous slip from index finger to ulnar three profundi (C).

palmar crease. Traction was applied to the individual tendinous slips to see if further flexion of the adjacent digits could be achieved.

Results Fig. 3 shows the amount of extension lost in each finger after four increments of profundus advancement. In every case, the appropriate extensor force was first applied to the tip of the finger. The amount of extension lost for all the fingers when the profundus tendon is advanced I cm would appear to be insignificant. The index finger, however, was not significantly contracted until advancement reached 2 cm. Advancement of the ulnar three profundi 1.5 cm causes at least a 40° loss of full extension. These data, presented in graphic fonn, make the relationship clearer. The index finger is not as susceptible to deformity, because of its lesser communication with the other three profundi . After slack in the system is lost, however, all advanced tendons seem to retard full

extension to the same degree for a given amount of advancement, as shown by the similar slopes. Fig. 4 illustrates the flexion lag that the advanced tendon creates in the remaining three fingers represented by the bars in the graph. The first graph shows the flexion lag in degrees for each increment of advancement (shown by the different shading) that the advanced tendon has on the other three. Note that the index finger has a minimal restriction effect on the ulnar three fingers even at 2 cm of advancement, whereas the ulnar three fingers produce considerable flexion lags in their counterparts, with the index finger relatively spared, except when the long finger is advanced 2 cm. The nonreciprocal effect that the long finger has on the index finger appears to be caused by oblique tendinous connections, which we noted in our cadaver specimens (Fig. 5). Similar relationships are shown in Fig. 6; measurements of the distance the adjacent fingers miss the distal palmar crease. The index again shows relative independence.

Discussion The cadaver hand is an imperfect model used to predict clinical results. Partial dehiscence of repair sites and elongation of tendon collagen fibers do not occur. The stretching out of flexion deformities, which occurs

Vol. 12A, No. 1 January 1987

with increased use of the injured hand is not possible. By contrast, many factors that impair a clinical result are also erased, particularly the formation of adhesions. In this sense, the cadaver hand represents the ideal end result. Advancement is one of the techniques favored for the repair of a laceration of the profundus tendon distal to the superficialis insertion. A secure tendon-to-bone juncture is created, allowing the possibility of early active motion. Advancement eliminates the problem of encroachment of a tendon anastomosis at the A4 pulley, commonly seen with primary or secondary repair, although this can be partially remedied by resecting a portion of the distal annulus. However, before undertaking advancement to the 1 cm limit suggested, one should consider that distal interphalangeal joint flexion accounts for only 15% of the area under the flexion curve, as shown by Littler. 5 When done in excess, profundus advancement can create more problems than it solves because of the anatomic interconnections between individual profundus tendons. Disruption of the del;cate balance with the extensor mechanism results in a loss of full extension of the repaired finger, tethering to the other profundi restricts their flexion amplitude and causes a loss of grip strength. If superficialis function is congenitally absent, a common occurrence in the small finger, then a flexion lag might also occur if an adjacent tendon is advanced excessively.

Summary and conclusions The upper limits for advancement of the long, ring, and small finger profundi suggested by this study was found to be 1 cm. In nine hands the profundus to the index finger could be advanced up to 1.5 cm without significant deformity because of its limited communication with the ulnar three profundi. Similar oblique communications, which we found between the long and index pro fundi (Fig. 5) have been shown by Lindburg and Comstock l2 to exist between the flexor pollicis longus and index profundus in 25% of cadaver hands dissected. Conceivably, these tendinous connections could impair flexor pollicis longus

Lacerations of flexor digitorium profundus tendon

33

excursion if the index profundus was advanced 1.5 cm as data in this study suggest. The incidence of communications between the index finger and the ulnar profundi is unknown. This study was done on adult hands and the data should not be applied to the hands of children or infants. An end-to-end repair, the alternative to advancement, which adheres to or impinges on the A4 pulley, will still produce an acceptable result, a functional tenodesis will be created, proximal interphalangeal and metacarpophalangeal joint motion should be unaffected, and a balanced tendon system will remain. REFERENCES 1. Kleinert HE, Forshew FC, Cohen MJ: AAOS symposium

2.

3.

4. 5. 6.

7. 8. 9.

10. 11. 12.

on tendon surgery in the hand. St Louis, 1975, The CV Mosby Co, P 115 Spak I: Tenodesis of the distal finger joint-a method of repair by loss of the flexor profundus function. Acta Chir Scand 110:338, 1955-56 Kahn S: A dynamic tenodesis of the distal interphalangeal joint, for use after severance of the profundus alone. J Plast Reconstr Surg 51 :536, 1973 Verdan CE: AAOS symposium on tendon surgery in the hand. St Louis, 1975, The CV Mosby Co, P 6 Littler JW: In Converse JM, editor: Reconstructive plastic surgery. Philadelphia, 1977, WB Saunders, pp 31-89 Watson AB: Some remarks on the repair of flexor tendons in the hand, with particular reference to the technique of free grafting. Br J Surg 43:35, 1956 Littler JW: The severed flexor tendon. Surg Clin North Am 39:435, 1959 Littler JW: Free tendon grafts in secondary flexor tendon repair. Am J Surg 74:315, 1947 Wagner CJ: Delayed advancement in the repair of lacerated flexor profundus tendons. J Bone Joint Surg 40:1241, 1958 Verdan CE: Syndrome of the Quadriga. Surg Clin North Am 40:425, 1960 Kleinert HE, White W: Primary repair of flexor tendons. Orthop Clin North Am 4:865, 1973 Lindburg RM, Comstock BE: Anomalous tendon slips from the flexor pollicis longus to the flexor digitorum profundi. J HAND SURG 4:79-83, 1979