Tendon graft length

T E N D O N GRAFT LENGTH By J. COLVILLE, F.R.C.S., and W. R. DICKm, F.R.C.S.

Plastic Surgery Unit, Royal Victoria Hospital, Belfast THE insertion of a tendon graft to restore flexor digitorum profundus action to a finger is a well-established procedure in hand surgery. Unfortunately the results following this are such that a full return of function cannot be guaranteed, and indeed, a much less perfect result is often accepted as the best that can be achieved by the combined efforts of surgeon and patient. This mediocrity is in accordance with the many variations in technique recommended by different surgeons and to this the authors propose to add yet another recommendation. This concerns the length of graft inserted. TABLE

Determination of Graft Length Author

Graft Length Assessment

Koch (I944)

Taut, not tight

Rank and Wakefield (I96o) Pulvertaft (I956)

Slightly more flexed than normal

Harrison (I96I)

To give a position similar to that of the uninjured contra-lateral digit

Bunnell (I944) Boyes (I964)

Graft slightly longer than normal (Graft shrinkage)

The Table illustrates the varying recommendations for tendon graft length by some well-known authors. As far as can be established from study of the literature and by communication with those regularly practising tendon grafting, the generally accepted method of assessing the length of graft inserted is as follows. After fixation of one end of the graft, sufficient length is inserted to permit the finger to assume a slightly exaggerated degree of flexion relative to the resting, and wrist-activated positions of the other fingers, and to impart a sensation of normal resistance on testing with gentle extension. This method of determining the length of graft demands both experience and skill which only follow repeated practice. These assets are not available to the trainee hand surgeon whose proficiency in this procedure is gained, to some extent, on a trial and error basis. If only for this reason alone, a more attainable method of determining graft length woukt be of value. The usual method of tendon grafting takes no account of muscle retraction. Obviously a tendon whose muscle belly has rested in a retracted state for many months or even years will offer more resistance to a return to a normal position than one which has been in a retracted state for a few weeks or months. The usual method does not allow for variations in muscle tone. The muscle belly of a divided tendon may be in a state of disuse atrophy if its tendon has retracted without gaining a firm attachment. On the other hand, if the tendon stump has become adherent after division, the muscle, acting on this new attachment, may possess quite normal tone. While the factors of muscle retraction and muscle tone remain variable to an un37

38

BRITISH JOURNAL OF PLASTIC SURGERY

known degree, any rule of thumb method of graft length assessment, based on finger position or graft tension, cannot be at all accurate. It has been shown by Williams (I965) that after 45 minutes of tourniquet application the stretch reflex arc is abolished, thus reducing muscle tone to that of a passive elastic body. On release of the tourniquet, muscle tone returns to normal, and this results in either an increase by upwards of IOO per cent. in anastomotic tension, or if this tension remains constant, then the "effective" length of the tendon must shorten. Since "anastomotic tension" is the same as resistance to attempted extension, and since effective length CROSS'SECTION OF FINGER. is really equivalent to finger position, the applip- . . . . . . . . . z . . . . . . . . . . -~, i cation of a tourniquet during graft length assessi i I,- ..... x .... -~ .... Y ..... ment again disqualifies graft tension, or finger i position, as reliable parameters in this procedure. If it were possible to relate a fixed point on ~ ~Ex.O EtR _ ~lG. . jUMBmCAL ~ l the divided tendon to a readily available fixed point in the hand then it would be possible to measure the length of graft required. This would ×=Y make the determination of graft length indepenZ : 2xY dent of muscle tone, muscle retraction and FIG. I tourniquet application and would put this part of the procedure on a more rational basis. An investigation was undertaken which attempted to relate the origin of the lumbrical muscle on the flexor digitorum "profundus tendon to a fixed point. After a few trial measurements it was found that, with the fingers fully extended and abducted, the metacarpophalangeal joint crease was equidistaflt from the lumbrical origin and the distal interphalangeal joint crease. In other words, the lumbrical origin-distal crease distance was twice the metacarpophalangeal joint crease-distal crease distance (Fig. I). Forty-five post-mortem hands were investigated. Hands affected by Dupuytren's contracture or rheumatoid arthritis were excluded, as were those of the very elderly, which were not considered suitable because their skin creases were too mobile for accurate assessment. The measurements for each finger are shown by plotting the distal interphalangeal-metacarpophalangeal joint crease distance against the distal interphalangeal joint crease-lumbrical origin distance. Figure 2 represents the measurements in millimetres on the index finger. The coordinates do not intersect at zero but only encompass the range of measurements plotted, otherwise the points would have been very congested. Most of these points fall close to the line which represents a z to I ratio between lumbrical origin-distal interphalangeal joint crease distance, and the metacarpophalangeal-distal interphalangeal joint crease distance. The ratios 2-1 to I and I "9 to I are also indicated and it is seen that almost all of the points plotted fall within these lines. ., Figure 3 for the long finger is very similar to that for the index finger and again the points fall more or less along the 2 to I ratio line. Figure 4 represents the ring finger. Here the plotted points are somewhat more scattered but still fall within the 2. I and I "9 limits. In Figure 5, where the little-finger measurements are plotted, a :~ to I ratio is not always found. This inconsistency in the little finger and to a lesser extent in the ring finger is due to the less condensed form of origin found in the double-headed lumbricals to these two fingers. Had some inconclusive types of lumbrical origin, recorded in the early numbers of the series, been excluded, a ratio of 2 to I would have been found more constantly. However, in this investigation eight little-finger and four ring-finger measurements were discarded because of this problem.

39

T E N D O N GRAFT L E N G T H

The points of reference on the finger creases and on the profundus tendon need precise definition if a 2 to I ratio is used to determine the normal position of the lumbrical origin on a divided profundus tendon. The lumbrical origin is taken as the angle between the muscle and tendon after separating all loose adhesions. The muscle INDEX FINGER /

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should be peeled back along the tendon until a little fleck of tendon is seen to strip with the muscle. This indication of firm attachment is the best method of determining this point consistently. Occasionally the little-finger lumbrical has no corresponding profundus attachment and arises entirely from the ring-finger tendon and in a few cases the little-finger lumbrical origin on the profundus tendon is so diffuse that an accurate point cannot be selected on the tendon. In these cases it would be necessary to revert to the standard method of graft length assessment.

4°

BRITISH JOURNAL OF PLASTIC SURGERY

The point on the metacarpophalangeal joint crease is defined as the intersection of the vertical mid-finger line with the transverse crease most representative of metacarpophalangeal joint flexion. In the long and ring fingers this crease is usually duplicated. If the duplicated creases arc close, and both contribute equally to metacarpophalangcal joint flexion, then a point midway between the creases is selected. If the creases are well separated, then the more proximal one is invariably representative of metacarpophalangcal joint flexion. The mid-finger position on the distal intcrphalangeal joint crease is usually easy to locate and a few minor creases occurring with the main crease cause no confusion. By hypcrcxtending the fingers these creases stand out sharply as red lines against the adjacent blanched skin. Before thc opcration starts, the intcr-crcasc distance is measured. The operation then proceeds according to the surgeon's usual plan. The graft, placed in its bed, is anchored distally and the finger is closed by skin suture. Closure of the finger in extension is more easily performed than in the semi-flexed position. The point on the tendon graft which by calculation should coincide with the lumbrical origin is marked with methylene blue and the lumbrical muscle-profundus tendon angle is similarly marked. The graft is inserted according to the surgeon's choice so that thc two marked points coincide. There nccd be no hesitation about using the lumbrical to cover the junctional zone as it is normally adhcrcnt here in any event, and there cannot exist the objection that the lumbrical-profundus balance is upset by doing so. The amplitude of the proximal tendon stump-graft junction is approximately 3"5 cm. in the long finger. It has bccn shown by Williams that the insertion of a i cm. length of excess graft to such a profundus tendon results in a failure to reach the distal palmar crease by 3 cm., and that a i cm. deficiency of graft length results in a combined extension deficiency of 7°0 at the intcrphalangeal joints. From these observations it is obvious that there is very little room for error in assessing tendon graft length, and small degrees of inaccuracy result in exaggerated degree of failure. This method of determining graft length is recommended on the basis of these measurements. The value of the procedure is as yet hypothetical as it is much too early to assess the results in terms of a higher success ratc. It certainly makcs tendon grafting a little easier to perform, and contributes a little to one particular field of hand surgery where there is ample scope for improvement. SUMMARY A method of determining the length of graft inserted is described. It has been found that the origin of the lumbrical muscle on a divided profundus tendon can be related to a fixed point in the hand. This point and the distal interphalangeal joint crease are equidistant from the metacarpophalangeal joint crease. By using this information the correct length of graft can be inserted without reference to the variable factors accepted at present as the parameters of graft length assessment. REFERENCES BOYES, J. H. (I964). In " Surgery of the Hand ", ed. Bunnell, S., 4th ed., p. 433. Philadelphia : Lippincott. BUNNPJ.L, S. (x944). " Surgery of the Hand ", pl 289. Philadelphia : Lippincott. HARRISON, S. H. (I96I). Br. ft. plast. Surg. x4, 2II. KOCH, J. (I944). Surgery Gynec. Obstet. 78, 9. PULVERTAFT,R. G. (I956). J. Bone fit Surg. 38B, r75. RANK, B. K. and WAKEFIELD, A. R. (I96O). " Surgery of Repair as applied to Hand Injuries ", p. I94. Edinburgh : Livingstone. WILLrAraS, S. B. (I965). Plastic reconstr. Surg. 36, 3x9.