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Introduction

Paralysis of the intrinsic muscles of the thumb will change the opposition function which is the result of a movement made up of three components: extension, adduction and pronation. ⁽³⁰⁾ The full movement of opposition is only possible if all the local anatomic structures are functional.

A thumb with paralysis of the intrinsic muscles will be dependent on the extrinsic muscles which will progressively lead to major functional imbalance with the final result being a thumb stiffened in adduction and retroposition with an interphalangeal joint fixed in flexion. Early medical care must be undertaken before these complications arise because their treatment is difficult, the results uncertain and often disappointing. Re-education, fitting of prosthesis and physiotherapy must all be an essential part of this protocol prior to any surgical reconstruction.⁽¹³⁾

Prerequisites to reconstruction surgery (2,7,16)

Patients need to be selected according to a certain number of criteria which will make the results of this surgical procedure all the better, while realizing that return to normal function is not possible. The ideal thumb for reconstruction surgery is one which is perfectly supple with a first web contracture free and the joints of the first column stable and mobile. In other cases, hard work needs to be carried out to soften up the thumb, its skin covering and to combat closing of the first web contracture. The classic methods of re-education and the orthotic devices regularly adapted need to be integrated into the surgical reconstruction programme. In addition, clear, simple information must be given to the patient in the preoperative period, underlying the functions it will be possible to restore and the results that can be expected.

Strategic rules for reconstruction programmes in paralysis of intrinsic muscles of the thumb ^(18,23)

The choice of procedures and the order in which they are to be implemented will be based on a systematic and thorough clinical examination which should determine:

1. the freedom and flexibility of the first web contracture;

2. trapezium-metacarpal stability;

3. the sectors of passive and active mobility of metacarpophalangeal and interphalangeal joints;

4. the quality of extension using Bourrel’s manoeuvre to seek pinch 1-3, and in measuring angle of extension [Fig. 6].

5. adduction strength using Froment’s sign while dissociating the effect on the interphalangeal joint (flexion deformity) but also on the metacarpophalangeal joint. Metacarpophalangeal hyperextension during the manœuvre for Froment’s sign (Jeanne’s sign) should lead to Bouvier’s manœuvre of the thumb ^(22,27) [Fig. 7].

6. Bouvier’s manœuvre of the thumb. ⁽⁶⁾ This consists in stabilising the metacarpophalangeal joint when correctly aligned or in slight flexion during strong pinch. There are two cases that can be met with. In the first, the interphalangeal flexion deformity disappears when the metacarpophalangeal joint is stabilized, a local anterior metacarpophalangeal procedure will need to be combined with an eventual transfer. In the second case, the flexion deformity is not corrected and a direct restorative procedure for interphalangeal extension will need to be carried out on the extensor during restoration of the opposition function [Fig. 9, 10].

7. Muscles available for transfer.

8. Trophic disorders which can be encountered in neglected, long-standing paralyses. Repair procedures are not recommended here.

 

Figure 1. Direction of transfers according to direction of pulley chosen A= Ascending transfer to re-establish extension-pronation B= Mixed transfer to re-establish adduction and extension C= Transversal transfer to re-establish adduction

Figure 2. Camitz’s transfer to re-establish extension

Figure 3. Thompson’s transversal transfer to re-establish adduction

 

Figure 4. Transfer of interphalangeal extensor to re-establish extension. This transfer can also be used in a mixed transfer.

Figure 5. Transfer of a half-strip of flexor pollicis longus to extensor pollicis longus to correct the defect of interphalangeal extension.

Figure 6. Bourrel’s sign in paralyses of extensors.

Figure 7. Clinical aspect of a long-standing median and ulnar nerve paralysis.

Figure 8. Froment’s and Jeanne’s sign.

Figure 9. Bouvier’s manœuvre with positive metacarpophalangeal joint.

Figure 10. Negative Bouvier’s manœuvre.

Figure 11. Result of the transfer of extensor indicis proprius of 2nd finger in complete paralysis of the intrinsic muscles. The transfer was inserted on the extensor pollicis longus to correct a Froment’s sign.

TREATMENT POSSIBILITIES (28,34,35)

The surgical possibilities are multiple and must be very precisely adapted to the patient’s disorder.

1. Adjuvant procedures required in motor restoration

- Stabilisation procedures for Trapezium-metacarpal, metacarpophalangeal and interphalangeal joints

If these joints are not correctly stabilized, the transfers for restoring opposition will lose their effectiveness.

- Anterior metacarpophalangeal capsuloplasties ^(3,4)

As with the metacarpophalangeal joints of the long fingers, the metacarpophalangeal joint of the thumb is often unstable in extension with Jeanne’s sign. There is an excellent indication for anterior capsuloplasties where the aim is to prevent metacarpophalangeal hyperextension during strong grip. The technical strategy involving the anteroposterior transosseous canal ensures that this procedure is both solid and considerably reliable over time. A variation described by Zancolli consists in practising a sesamoid-metacarpal arthrodesis. At present, the use of anchors considerably facilitates this type of surgical technique. Simple surgical procedures to shorten the metacarpophalangeal capsule have been abandoned because of their almost inevitable slackening over time.

- Metacarpophalangeal arthrodesis can also be necessary when in the presence of ankylosis which cannot be reduced by hyperextension. In this case, the extensor brevis can be usefully retrieved to re-establish function in the first dorsal interosseous muscle or paralysed extensors.

- Interphalangeal arthrodesis

When there is an ankylosis or stiffness of the interphalangeal joint in a position which is both extreme and functionally intolerable (>40°), an interphalangeal arthrodesis may be carried out. The choice for interphalangeal arthrodesis must be integrated into a more general plan for re-establishing thumb function. Indeed, this type of procedure enables the choice of either the extensor pollicis longus or the flexor pollicis longus which can be then used as a transfer for restoring opposition.

- Active tenodesis of the flexor pollicis longus ^(25,38) [Fig. 5].

When a flexion deformity can be reduced passively, it is perhaps preferable to carry out the technique using a radial strip from the flexor pollicis longus left pedunculated proximally which is inserted into the extensor apparatus opposite the interphalangeal joint. This procedure improves the possibility of pinch grasp. It is more appreciated by patients than interphalangeal arthrodesis.

-  Trapezium-metacarpal stabilisations

Trapezium-metacarpal instabilities are found generally in long-standing paralysis of the extensor muscles, notably in patients with hyperlaxity. It is sometimes necessary to have to stabilize the trapezometacarpal joint. In these cases, standard ligamentoplasty techniques are possible.

 

2. Transfers for restoring opposition. (1,47,48,49,51).

Depending on the type of paralysis and the motors available, a specific transfer technique needs to be chosen. The angle of reflection of this transfer will modify the moment it comes into action and therefore its effect on the thumb [Fig. 1]. 

- Extensor transfers or ascending transfers ^{(5,14,12,19,44)} [ Fig. 2,4].

They have in common their direction which is that of the muscle fibres of the abductor pollicis brevis. The transfer of the extensor pollicis brevis diverted around the palmaris longus and re-fixed on the terminal tendon of the paralysed abductor pollicis brevis is an excellent transfer, perhaps not very powerful but which will lift the thumb out of the palm of the hand. It can be easily retrieved during a metacarpophalangeal arthrodesis. Other routes have been described for this transfer, but they complicate the technique without providing any functional benefit. Other tendons can be used to re-establish this function of extension: the extensor pollicis longus, the extensor indicis proprius through the antibrachial interosseous membrane but they can also be diverted to periulnar which adds an adduction effect to their extensor effect. The Camitz transfer, although providing a grip which is neither very strong nor very far, can be used in isolated extensor paralysis, where it acts more by the effects of tenodesis than as a true active transfer [Fig. 2]. ^(8,15) The hypothenars have also been suggested to restore extension to the thumb, but they can only be used in strict paralysis of the median nerve. The distance is not very great so insertion tension must be great, which limits postoperative amplitude in backward displacement. Their indications should be exceptional in the case of paralysis of the intrinsic muscles. They should be reserved for restoration of the opposition function of the thumb in the case of hypoplasia, or agenesis of the intrinsic muscles in young children. ^{(33,41,43,52)}.

- Adduction transfers or transversal transfers. ^(45,46)

 

The indications for these are paralysis of the adductor muscles of the thumb which are the muscles providing key pinch strength. The most well known and probably the most powerful is the transfer of the flexor digitorum superficialis of the 3rd or 4th finger diverted around the aponeurosis palmaris as in Thompson’s technique [Fig. 3]. Although the results as far as recovery of pinch are remarkable, there are two pitfalls to be avoided. The first is the occurrence of a swan-neck deformity of the donor finger, a frequent complication in this type of tendon procedure. To avoid this complication, tenodesis using a strip of flexor digitorum superficialis fixed on the periostium of P1 in front of the proximal interphalangeal joint is carried out during the procedure using this tendon. This tenodesis stabilises solidly and durably the interphalangeal joint with a few degrees of flexion. The second complication which can occur in very active transfers is a progressive flexion deformity of the metacarpophalangeal joint which will limit the distance the thumb can move and thus decrease the possibility of grasping heavy objects (such as a bottle). This is because of transfers which are too strong, metacarpophalangeal joints which are lax in flexion, and probably lateralization of the extensor digitorum brevis on which it is generally inserted.

We believe it necessary to insert this transfer on the extensor pollicis longus with two strips, one radial, the other ulnar, which will ensure automatic axial rotation of the thumb column. Correction of the metacarpophalangeal flexion deformity can then be ensured afterwards by arthrodesis of the metacarpophalangeal joint or during the initial procedure by anchoring of the extensor pollicis brevis left inserted distally and fixed proximally on the neck of the first metacarpal bone providing an effective dorsal stabilisation.

 

- Mixed transfers. ^(11,34,35)

In a great number of cases, the patients are victims of severe paralysis involving all the sectors which constitute the overall function of opposition, so restorative transfers need to be chosen which will provide the fullest effects possible for extension, pronation and adduction. These are called mixed transfers. They have in common an angle of reflection around the pisiform bone or the flexor carpi ulnaris tendon (provided that it is not paralysed, or there will be an progressive slackening of the pulley). The flexor digitorum superficialis of the 3rd or 4th finger can be used with the same restrictions and precautions as for adduction transfers. Distal fixation dictates the use of two strips, one on the abductor brevis (extension effect) and on the fascia of the distal extension of the thumb (to prevent Froment’s sign), the other being somewhat dorsal and ulnar (automatic adduction and pronation effect). Transfer of the extensor indicis proprius in periulnar position presents the same mechanical properties but is not as strong and often a little short to carry out the double insertion. We use it particularly with a view to promoting the extensor component. However it is an excellent transfer, always available and easily useable as for le Bourrel’s sign [Fig. 4, 11].

Particular cases

- transfer of flexor longus or extensor longus of the thumb ^{(12,31,36,37,40,42)}.

Both these techniques are possible at no extra cost during interphalangeal arthrodesis or when the distal bone lysis of the thumb leaves only an unusable stump which is a regular occurrence in the complex paralyses of leprosy. The tendon transferred can be used as an ascending transfer for extension (anteroradial pulley), as a transversal transfer for adduction (aponeurotic pulley), or as a mixed transfer in complex paralyses (peripisiform pulley). The technique described by Oberlin and derived from that of Makin uses the flexor longus diverted through P1 or through a metacarpophalangeal arthrodesis. This method, by constructing a cylindrical thumb splint provides good quality extension but a rather weak adduction force. It should be considered as a salvage solution only. The indication should be reduced to paralysed thumbs with metacarpophalangeal joint stiffened in hyperextension and an interphalangeal joint ankylosed in flexion. This technique, the indications for which remain rare, enables a tip to tip pinch between thumb and long fingers providing that these fingers have retained their length and that the metacarpophalangeal joints are correctly stabilised.

- transfer of extensor carpi ulnaris tendon on to the extensor pollicis brévis tendon or to the extensor pollicis longus tendon. ⁽³²⁾ This rarely used method can be useful when arthrodesis of the metacarpophalangeal joint is carried out. The extensor pollicis brevis tendon is sectioned at the wrist, removed from its groove and restored by the extensor carpi ulnaris tendon withdrawn at its distal insertion and diverted to the anterior aspect of the wrist. The risk of this method is the progressive antero-ulnar lateralisation of the extensor pollicis brevis tendon insertion which results in loss of its extensor component. When arthrodesis is carried out on an interphalangeal joint, it would seem preferable to use the distal part of the extensor carpi ulnaris tendon which is sectioned at the forearm, transferred to the anterior aspect of the wrist and restored by the extensor carpi ulnaris tendon.

- rehabilitation of the first dorsal interosseous muscle. ^{(10,11,20,39)} To improve the strength of thumb-index pinch and in addition to restoration of the thumb itself, rehabilitation of the first dorsal interosseous muscle can be carried out using the extensor indicis proprius or the extensor pollicis brevis that is passed through the paralysed tendon to its insertion on the first phalanx of the index finger. This procedure improves stability of the metacarpophalangeal joint of the index in pulp to pulp and key pinch.

- filling the first web contracture. ^(21,29,50) Muscle atrophies are one of the most obvious signs of medioulnar paralysis. In areas where leprosy is endemic, this particular atrophy is a pointer to its origin and as such is a real desocializing stigma. Many patients therefore demand reconstruction of the posterior relief of the first web contracture. Transfers of de-epidermized cutaneous-fat grafts or of fatty lobules satisfy patients in most cases.

Excision of the first web contracture. ^(24,26)

In the absence of paralysed extensors and due to the effect of a flexor pollicis longus where the adduction component remains strong, the first web contracture can close up which then dictates an opening procedure before going on to the procedures for re-establishing opposition. The various repair procedures practised in indications other than paralysis of the intrinsic muscles can be used here (Z-flap, tridentate flap, etc.). When the l’étoffage cutané [cutaneous matter ?] is not sufficient, the dorsal fascia also need to be freed up, sometimes the transverse fasciculus of the adductor needs to be sectioned when it is retracted, the trapezium-metacarpal freed, and sometimes a trapeziectomy needs to be carried out when other procedures do not provide sufficient web contracture freedom. Often the extensor pollicis longus also needs to be freed up at the same time, removing it from its groove opposite Lister’s tubercle. This procedure will correct in part the position of fixed backward displacement of the thumb and thus free up a passive sector of extension which is a necessary prerequisite to any surgical procedure to restore the opposition function.

Technique for exceptions. ⁽¹⁷⁾

In the case of thumbs stiffened in retroposition-adduction, and when surgical manœuvres cannot correct the fixed position, an osteotomy for extension-pronation of M1 or a trapezium-metacarpal arthrodesis can be carried out. They will need to be completed by an adduction transfer. The aim of this salvage procedure is simply to reconstruct a tip-to side pinch and not a true opposition function.

 

Indications for surgery (tableau 1)

Choice of surgical procedures (3,6,16,22,27,34,49) :

The choice of surgical procedures is based on a thorough clinical examination. With flexible thumbs, the indications will be based on Bouvier’s manœuvre of the thumb.

- The manoeuvre is positive (Froment’s sign disappears when the metacarpophalangeal joint is stabilized in slight flexion).
• If the extensor muscles are strong, a simple anterior metacarpophalangeal capsuloplasty is carried out.
• If the extensor muscles are absent or weak, a metacarpophalangeal capsuloplasty combined with an extension transfer is carried out.

- The manoeuvre is negative (Froment’s sign does not disappear when the metacarpophalangeal joint is stabilised in slight flexion).
• The extensors are strong, an adduction transfer of the Thompson type is carried out.
• The extensors are absent, mixed transfers will be needed with a component associating extension and adduction. Transfers using an ulnar pulley, or transfer of the extensor indicis proprius to periulnar can then be chosen. Their insertion should be distal on the extensor longus apparatus to limit the residual flexion deformity component.
• In the case of persistent postoperative flexion deformity or better at the same time as restoration, the transfer of a radial half strip of flexor pollicis longus on the distal part of the extensor pollicis longus can be combined. Its effect seems to us to be more predictable than the insertion of the restorative transfer on the extensor pollicis longus.

Improvement in pinch stability can be reinforced by restoration of the first dorsal interosseous muscle. This intervention should ensure stability when in slight flexion and stability in the frontal plane of the metacarpophalangeal joint of the index finger.

Table 1. Tree diagram for decisions concerning paralysis of the thumb SEARCH FOR FROMENT’S SIGN Antépulseur = extensor Transfert antepulsion = extension transfer Pas de traitement = no treatment Stabilisation MP = MP joint stabilisation Stabilisation IP = IP joint stabilisation Transfert d’adduction = adduction transfer Transfert mixte = mixed transfer

Particular cases of stiff thumb. ^(9,26)

When Bouvier’s manœuvre of the thumb cannot be interpreted, the indications will need to be chosen case by case.

Stiff trapezium-metacarpal joint. ⁽²⁴⁾
The first la web contracture will need to be excised using the techniques mentioned above, not forgetting to free up the extensor pollicis longus from its posterior groove, sometimes undertaking an osteotomy to rotate and incline anteriorly the first metacarpal bone before implementing the transfer of restorative tendons. We are talking about salvage surgery here, where the hope for functional improvement, although limited, is often very useful for significantly handicapped patients.

Stiff metacarpophalangeal joint
Here the choice is limited to an arthrodesis fixed at a few degrees of flexion only. This will enable freeing up of the extensor pollicis brevis so that it reinforces the first dorsal interosseous muscle, or a transfer of extension. Metacarpophalangeal arthrodesis is always a procedure appreciated by patients.

Stiff interphalangeal joint
Although arthodesis is always possible, by shortening the thumb structure when flexion deformity is significant, indications should be limited because patients are often disappointed by the very small additional functional ability that it provides. If flexion deformity is moderate (<40°) the patient will need to accept the defect or an attempt could be made to combat it using the technique of tenodesis of the flexor pollicis longus which will enable preservation of a certain degree of active mobility. However, if flexion deformity is significant (>40°) arthrodesis will be appreciated by the patient whose pinch will be pulp to pulp and not nail to pulp.

Conclusion

The type of management for patients with paralysis of the intrinsic muscles of the thumb will be based on a detailed analysis of symptoms, specific preparation through physiotherapy, careful choice of orthotic device and a surgical procedure adapted to each patient. The aim when carrying out planned procedures is improvement in pinch ability. This is functional surgery and the benefits must be assessed by the patient himself. There are numerous procedures available but they sometimes need to be combined which makes the surgical indications difficult. Operating techniques require a lot of precision in the fine tuning which clearly implies fairly specific training for surgeons dealing with these problems.