International Orthopaedics (SICOT) 4, 225-229 (1980) International Orthopaedics

© Springer-Verlag 1980

Anterior Transfer of the Toe Flexors for Equinovarus Deformity of the Foot

Kei ro Ono , K a z u o H i ro sh ima , Koich i Tada , and A k i o Inoue

Department of Orthopaedic Surgery, Osaka University Medical School, 1-1-50, Fukushima Osaka 553, Japan

S u m m a r y . Anterior transfer of the long toe flexors was carried out for the treatment of spastic equinovarus foot deformity in both adults and children. Adults in- cluded those with hemiplegia subsequent to a stroke, spastic hemiplegia due to cerebral palsy and spastic spinal paraplegia. Most of the children had cerebral palsy. The transfer was indicated for an equinovarus foot with persistent activity of the toe flexors, which produced curling of the toes in the swing phase of the gait or a fixed hammer toe deformity.

Fifty six patients were followed up for more than four years. In all cases correction of the equinovarus deformity was achieved and maintained. With satis- factory correction stability of the ankle improved, postural abnormalities during gait decreased and brac- ing was not required.

This study demonstrates the advantage of the long toe flexors for muscle transfer in these patients. The length of tendon available permitted easy transfer to the metatarsal. The defunctioning of the spastic mus- cles allowed gait improvement and function of the tibiaIis posterior and tibialis anterior was preserved.

R6sum6. Le transfert antgrieur des longs fldchisseurs des orteils a dtd utilis~ pour corriger la ddformation en varus dquin du pied spastique, rant chez l'adulte que chez l' enfant. Chez l' adulte, il s' agissait d'h6mipl6gies secondaires gl un accident vasculaire cgrgbral, d'hgmi- pldgies spastiques dues gl une paralysie cdr6brale, et de paraplggies m~dullaires spastiques. La plupart des en- rants dtaient atteints de paralysie c6rdbrale. Le transfert a paru indiqu~ en prdsence d'un pied varus gquin avec fl~chisseurs des orteils actifs, entrafnant soft une griffe des orteils au cours de la phase pendulaire de la mar- che, soft une attitude en marteau irrdductible.

Cinquante-six malades ont 6td suivis plus de quatre ans. Dans tous Ies cas la correction du varus gquin a dtd obtenue et s' est maintenue. Grfice fi une correction

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satisfaisante, la stabilit6 de la cheville a dtd amdlior6e, les anomalies posturales au cours de la marche ont diminud et l'appareillage est devenu inutile.

Ce travail d6montre la sup6riorit6 du transfert des longs fldchisseurs des orteils chez de tels malades. La longueur des tendons utilisables permet de les transpo- ser aisdment sur la face dorsale du mdtatarse. La sup- pression de l'activitd de muscles spastiques entrafne une amdlioration de la marche et prgserve la fonction des muscles jambiers antdrieur et postdrieur.

Key words: Spastic equinovarus, Tendon transfer

Since 1965 we have ca r r i ed out surgical t r e a t m e n t of equ inovarus de fo rmi ty of the foot in adul ts wi th hemip leg i a fo l lowing a s t roke by an te r io r t r ans fe r of the long f lexors of the toes [2], W e have also used this o p e r a t i o n for young pa t i en t s wi th s imilar de fo rm - ities due to ce r eb ra l pa lsy or o t h e r causes. This p a p e r descr ibes the t echn ique of the o p e r a t i o n and assesses the qual i ty of our results .

Material and Methods

Clinical Material We have followed ui 9 39 adult patients and 17 children for more than four years. The age at operation was between 4 and 76 years (Table 1).

Table i . Clinical details of treated patients

Adults Hemiplegia secondary to a cerebrovascular accident 32 Cerebral palsy 3 Spastic paraplegia 3 Traumatic brain injury 1

Total 39

Children Cerebral palsy Spastic paraplegia

16 1

Total 17

0 3 4 1 - 2 6 9 5 / 8 0 / 0 0 0 4 / 0 2 2 5 / $ 01.00

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Selection of Patients for Operation. Adults were given at least 12 months after the stroke to allow for full motor recovery. Early rehabilitation was instituted and the patients encouraged to stand and walk with short leg braces. Most patients recovered reasonable physical fitness but spastic deformities of the foot and toes devel- oped with improved motor activity. H a m m e r toe deformity caused a corn or callous on the dorsum or tip of the toes (Fig. 1), while the equinovarus foot made walking difficulty, particularly on the straw matt ing used at home where a corrective splint was not usually worn.

K. Ono et al.: Equinovarus Deformity of the Foot

but selective control of the flexor hallucis and flexor digitorum is not necessary.

This procedure is contraindicated in patients in whom there is no muscle tonus or where voluntary movement has not been re- gained in the calf muscles, the prolonged flaccid type. In children with cerebral palsy equinovarus or equinus foot deformity was also corrected using this operation. The transfer was used in spastic chil- dren who had been given extensive and continuous physiotherapy for at least one year, yet still needed a brace to correct equinovarus deformity. Severe involuntary movements or difficulties in standing and walking, even when using aids such as a crutch or cane, were considered to be contraindications for operation.

Adult patients with uncontrolled high blood pressure, severe myocardial damage, respiratory dysfunction, renal failure or anaemia which was not correctable by t rea tment were considered unsuitable for operation, as were patients with severe dementia, persistent incontinence, lack of motivation and marked involuntary movements .

Fig. 1. Fixed hammer toe deformity

In most patients the equinovarus and h a m m e r toe deformities occurred together and this combination benefited most from trans- fer of the long flexors of the toes. In the absence of fixed toe flexion, activity of the long flexors was confirmed by E M G studies during walking or by close observation of the swing phase (Fig. 2). Clinically activity of the long flexors can be demonst ra ted by active or resisted extension of the knee in the presence of equinovarus deformity, and toe flexion may also be observed when the ankle is dorsiflexed by a brace. Anter ior transfer of the toe flexors should not be under taken unless flexion of the toes can be demonstra ted,

Fig. 2. Toe curling in swing phase of gait

Operative Procedure (Figs. 3, 4 and 5)

The operation was carried out under general or continuous spinal anaesthesia.

An incision about 15 cm long was made in the posterior aspect of the lower leg and lengthening of the aponeurosis of the gastro- cnemius muscle, as described by Baker [1], was performed in each spastic patient. The triceps surae muscle and the Achilles tendon were retracted laterally and the underlying deep fascia incised lon- gitudinally, exposing the flexor digitorum longus muscle behind the lower part of the tibia. Similarly the thick muscle belly of the flexor hallucis longus was identified behind the fibula. Both muscles were dissected upward to the lower one third of the leg and downward to the ankle joint. The nerve and blood supply to these muscles was carefully preserved.

A second incision, slightly curved and 5 cm long, was made on the medial aspect of the foot centred over the tuberosity of the navicular. After the abductor hallucis had been freed and reflected plantarwards, both the flexor digitorum longus and the flexor hal- lucis longus tendons were identified where they crossed. The flexor digitorum longus tendon was then divided just proximal to the insertion of the quadratus plantae into this tendon and extracted from the posterior aspect of the leg through the first incision.

The flexor hallucis longus tendon was then divided through a third incision made over the plantar crease at the base of big toe. This tendon was also extracted from the posterior aspect of the leg through the first incision (Fig. 3 a - c ) , after dividing all fibrous slips which connect the flexor hallucis tendon to that of the flexor digi- to rum longus. These connecting slips, most often found joining the tendons of the second and third digits, are vestigial remnants of the primitive primate fibularis which sends slips to each of the five digits as shown in Figure 4.

The interosseous membrane was next exposed widely and a generous window cut into it to allow for easy rerouting of the tendons and muscles. Both tendons were then pulled through the window up to their muscle bellies, taking care to ensure that they were neither kinked nor constricted. In order to provide a wide window, resection of several centimetres of the fibula was occasion- ally required if the muscle belly of the flexors was especially thick. Prior to the rerouting, both muscles were usually freed from the fibula and tibia, respectively, sufficient to enable the placement of both muscles partially anterior to the interosseous membrane . Both tendons were then passed subcutaneously to the dorsum of the foot and inserted into the base of the fourth metatarsal (Fig. 5 a - b ) .

Fig. 3 a -e . a Three skin incisions for lengthening of aponeurosis of gastocne- mius and pulling out of toe flexors, b Flexor hallucis longus and flexor digito- rum longus divided in the sole of the foot. e. Flexor hallucis longus and flexor digitorum longus partially detached proximally and pulled out

a

i

b

Fig. 4. Connecting slips between flexor hallucis longus and flexor digitorium longus which are vestigial remnants of the primitive fibu- laris muscle. (Recopied from Grant's Method of Anatomy, The Williams and Wilkin's Company, 7th Edition, p. 423)

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Fig. 5 a and b. a Considerable moment of ankle dorsiflexion by anterior transfer of toe flexors to the metatarsal, b Attachment to the 4th metatarsal by a tendon loop

228

A fourth and last incision was made over the base of the fourth metatarsal, which was then exposed and stripped circumferentially of its periosteum. The flexor hallucis longus tendon was passed around the base of the metatarsal and sutured to the distal end of the tendon of flexor digitorum longus, making a loop. The ends of these tendons were interwoven under maximal tension in order to maintain full dorsiflexion of the foot.

Treatment After Operation

The leg was immobilized in a cast from the thigh to the toes with the knee flexed and the foot overcorrected for six weeks. Quadriceps femoris exercises were commenced soon after operation. After removal of the cast, active exercise of the leg and foot was begun. A short leg brace with a Klenzak apparatus was used for standing and walking for the next three months, and corrective night splints were also used during this period.

Results

The results are summar ized in Table 2, The length of the fol low-up was f rom four to eight years. We appraised the correc t ion of the equ inovarus and h a m m e r toe deformit ies and the deve lopmen t of fur- ther problems. The abil i ty to bear weight evenly on the sole of the foot, the stability of the ankle and the abili ty to walk wi thout a brace were assessed.

Satisfactory correc t ion of equ inovarus deformity was achieved and m a i n t a i n e d in all pa t ients and re- sul ted in even weight bear ing on the sole of the affect- ed foot (Figs, 6, 7). Recu r rence of the toe deformity was mi ld when compared with the appearance before

Table 2. Results following transfer of long flexors of the toes

Correction of equinovarus foot Correction of hammer toe Development of new deformity Improved stability of the ankle Easy toe clearance on walking Total number of patients

Adults Children 39 17 31 17

0 4 39 17 37 16 39 17

K. Ono et al.: Equinovarus Deformity of the Foot

opera t ion , and was usually due to activity of the short flexors of the toes, and in a few pat ients to fixed de- formity which requi red capsulotomy. There was no gradual recur rence of foot drop as is of ten seen with other types of t e n d o n t ransfer for spastic equ inovarus foot. No loosening of the t ransfer red t e n d o n was seen since the t e n d o n had been re inser ted on the me ta ta r - sal by a loop. Most pat ients were satisfied with their ability to clear their toes f rom the floor wi thout using a brace. Mild recur rence of the h a m m e r toe deformity did no t impai r their pe r fo rmance when walking. In- stabili ty of the ankle when s tanding and weakness of p lantar f lexion were not observed, since l eng then ing of the aponeurosis of gas t rocnemius by Baker ' s me- thod avoids the p rob lems caused by excessive length- ening of the tendo achilles.

Fig. 7 a and b. a Equinovarus deformity of the foot in a child with cerebral palsy before operation, b Correction of deformity and improved stability after operation

Planovalgus deformity occurred in one spastic child. Fore foo t depress ion appeared after opera t ion in three spastic chi ldren and was accompanied by mode ra t e restr ic t ion of p lan ta r f lexion due to exces- sive t ightness of the t ransfer red t e n d o n (Fig. 8). Despi te these problems the chi ldren benef i ted from

Fig. 6a-c. a Before operation: equinovarus foot deformity, with toe curling, b After operation: correction of both foot and toe deformity. c. Tightness of transferred tendons on attempts at toe flexion

K. Ono et al.: Equinovarus Deformity of the Foot 229

Fig. 8. Comparison of transferred and non-transferred feet eight years after operation to show development of forefoot depression and raised arch due to tightness of transferred tendons

the transfer, with lessening of the scissor gait a n d improved stability of the ankle. The transferred toe flexors were not able to dorsiflex the foot in any patient, regardless of age, the transfer acting merely as an active tenodesis which prevented equinovarus deformity.

Elongation of the tendo achilles has been commonly used but this operation replaces spasticity with muscle weakness, since if the Achilles tendon is lengthened sufficiently to prevent recurrence of the equinovarus deformity most patients cannot walk because of weakness of the triceps surae. Whenever tendon transfer is a t tempted it is always difficult to determine which muscle should be transferred and which muscle should be spared, since spastic deformity is not simply produced by a muscle imbalance. The transferred tendon is also required to cope with the unexpectedly strong spasticity of the triceps surae muscle. The plantar flexion force generated at the ankle at the t ime of heel strike, also stretches the transferred tendon.

We consider that transfer of the long toe flexors has advantages over other tendon transfers in these patients in that it allows simultaneous improvement of the equinovarus and claw toe deformities, does not interfere with the stability of the ankle and gives long tendons which may be positioned at any desired posi- tion on the dorsum of the foot. The transferred ten- dons should be repositioned as far in front of the axis of the ankle as possible in order to give maximum me- chanical advantage over the triceps surae, and meta- tarsal insertion by a tendon loop helps achieve this. The transferred muscle must be placed so that it runs as straight as possible through the interosseous mem- brane.

Anterior transfer of tibialis posterior may cause valgus deformity and depression of the medial arch with consequent pain. This muscle is a major stabiliser of the ankle and is best not transferred. The split anterior tibial tendon transfer has been advocated but results in inability to invert and evert the ankle [3].

Acknowledgement. We thank M. Ohara of Kyoto University for her assistance in the preparation of this manuscript.

Discussion

Equinovarus foot deformity is the most common dis- ability in patients with brain damage. A short leg brace with a T-strap is most commonly used to im- prove function, but the spasticity tends to increase in- side the brace and thus the hammer toe deformity will still occur. The numerous different operative proce- dures which have been advised for the correction of the spastic equinovarus foot indicate that there is no satisfactory surgical t reatment for the deformity.

References

1. Baker, L. D.: A rational approach to the surgical needs of the cerebral palsy patient. J. Bone Joint Surg. [Am.] 38, 313-323 (1956)

2. Ono, K., Doi, T., Inone, A., Kajiura, I.: Reconstructive surgery of the limb in the brain damaged adult. Med. J. Osaka Univ. 20, 245-271 (1970)

3. Waters, R. L., Perry, J., Garland, D.: Surgical correction of gait abnormalities following stroke. Clin. Orthop. 131, 54-63 (1978)