IATROGENIC METATARSUS ELEVATUS, FTOATING TOESGEN ERAI CONSI DERATIONS

Thomas F. Smith, D.P.M.
Mark Bernbach, D.P.M.
Introduction

problems of treatment and prevention will logicallyfollow. For simplicity of discussion the lesser ray will be
divided into the metatarsal, the metatarsophalangeal, andthe digit itself.

A floating toe is a potential complication of lesser
metatarsaland digital surgery. lt may be defined as a digitthat does not purchase the weight bearing surface instance and gait. The lack of plantarflexory purchasepower may be present for a multitude of reasons andMetatarsal

represents a functional imbalance of the forefoot.

Each metatarsal must assume a given degree of bodyweight to allow an even distribution of forces across theforefoot. The pressu re of weightbearing by the metatarsal or metatarsal loading is important to digital purchase.
Body weight must be transferred from the metatarsals
to the digits at the toe-off phase of gait to assist in digitalpurchase and to aid in preventing plantar callus formation. An even distribution of body weight is represented
by the absence of plantar callosity and the absence of

Floating toes may be no more than an objective clinicalsign that a subtle imbalance exists within the forefoot.
The problem is not always symptomatic. Floating toes
become symptomatic if the toe contacts the toe box ofthe shoe. Complaints of plantar lesions under adjacentmetatarsals usually develop. Unequal metatarsal loading
may occur following metatarsal surgery on trauma. The
floating toe can be a significant problem by itself but canalso lead to further forefoot problems.

floating toes.
As the metatarsal loads the subtalar and midtarsal
joints are pronating creating a relative elongation of thefoot. This elongation is evident clinically as a loweringof the longitudinal arch associated with internal leg rotation. The piantar fascia is placed under tension and will
not elongate. The traction created by the pull of the plantar fascia is transferred to its insertion in the bases ofthe proximal phalanges. A plantarflexory force is transferred to the base of the proximal phalanx thus stabilizing
the metatarsophalangeal joint. Dorsal migration of thedigit or f loating toes following proximal phalangeal baseresection attests to this function.

The loss of the buttressing effect of one digit for adjacent, digits may result in adjacent digit migration. Adjacent toes eventually migrate medially or laterally and occupy the void created by the floating toe. Such multiple

digital deformities can with time destroy an otherwise
satisfactory correction. This is especially true in progressive neuromuscular disease or in the presence of active arthritis. The stability of a single digit in plantarf lexion is vital to rnaintaining transverse plane alignmentsof all the digits.
A floating toe represents a complex problem of form
and function. The pathogenesis will be reviewed to arrive at a current logical approach to both conservativeand surgical management. Preoperative considerations
to prevent floating toes through appropriate procedural
selection is the first line of prevention.

It would seem a cavus foot with taunt plantar fascia
should not present with plantarflexory instability of themetatarsophalangeal joint and digital deformity. But thefact is that the cavus foot does not function with themetatarsal rays f ully pronated and elongated. ln {act, thereverse is true. Hammertoes not floating toes are a common finding associated with cavus foot. Hammertoes on
the cavus foot represent a weakening of the intrinsic
muscle stability at the metatarsophalangeal joint but thepathogenesis is not the same. Hammertoes result from

Pathogenesis
The function of the lesser rays represents a delicate
balance of flexor and extensor power. This primarily
sagittal plane balance must be maintained about threeaxes of motion or joint levels within each lesser ray. Abnormalities of virtually any level can result in floating
toes. An analysis of normal ray anatomy and function willmuscular imbalance of the toes and metatarsophalangeal

joints. A f loating toe represents a compromise of f lexor
power because of an unstable metatarsophalangeal joint.

help define the pathogenesis of floating toes. The

The goal of treatment for both floating toes and118

ty of the joint axis and joint motion. Without theirclawtoes is directed at reestablishing a flexor stabilizing
power at the metatarsophalangeal joint. The surgical approach will vary due to the variability in pathogenesis.

stabilizing inf luence, f lexor pu rchase power is extremeIy compromised. A stable joint axis must be present.
Muscle function can only then be expected to act effectively on the digit.

The windlass effect of the plantar fascia cannot beoverestimated. The function of the intrinsic muscles,
namely the interossei aided by the Iumbricales, is toassist in metatarsophalangeal joint and digital stability.
The extrinsic muscles can then act on the digit througha stable metatarsophalangeal joint. This dynamic muscle function implies maintenance of normal anatomicalignments. The cavus foot represents an example of abnormal structural alignments which contributes to grossmuscular imbalance.

lf a floating toe is present and a stable joint axis cannot be established, it is useless to reestablish flexor
power to the toe. Syndactylization may be the best solu-tion for flexor stabilization.
Anatom ically sou nd and f u nctional metatarsophalangeal joint or a metatarsophalangeal joint implant
may not necessarily be needed in order to restore astable axis. A good fibrous junction of metatarsal andHammertoes, clawtoes, and transverse plane deviations can disrupt the course of tendons and change theirrelationships to joint axes. Normal digital function also
implies free excursion of the tendons about the joints.
Adhesions or binding of the tendon along its course does
not permit motion even though active muscle power andphalanx will also provide stability to a metatarsophalangeal joint axis. This is often evident following
Hoff man type procedures. ln such circumstances functionally stable digits with good pu rchase can begood joint mobility may otherwise be present.

Another consideration is the structural alignment of
the articular cartilage about the joint. A severe hammertoe deformity or dislocated metatarsophalangeal joint
can result in angular adaptive changes of the phalangeal
base or metatarsal head. lf these structural changes arepresent and primary surgical relocation is attempted theproximal phalanx may continue to seek a congruous attitude of poor positional alignment. This is analogous toignoring the articular set angles in bunion deformity
assessment. Adequate metatarsal loading and good

maintained.

Metatarsal shortening, even in the presence of loadingof the ray may contribute to the floating toe problem.
A shortened metatarsal as a result of surgery or fracture
represents a shortened bony column and a relative
lengthening of soft tissues. The intrinsic muscles andplantar fascial slips become relaxed. The long flexor tendons derive from a common tendon. If the bony columnof only one particular ray is shortened, minimal compen-sation can occur. Not only is the loading capacity ofmetatarsals affected by parabola discrepancies but themuscle function may be likewise imbalanced. In fact, as
the load is decreased on one slip of the tendon it must
be correspondingly increased on the adjacent slips; thus
adding abnormal flexor loading to those tendons.

flexor power in the face of such structu ral joint

adaptation may not be sufficient to prevent recurrenceof a floating toe.

The Digit
The digit here will include the tendon structures traversing the phalanges and interphalange'aljoints. The muscle imbalance of floating toes is not so much an overpowering extension force as an absent or weakened flexor stabilization force. If a strong flexor force were present in the absence of metatarsophalangealjoint stability a hammertoe would develop rather than a floating toe.

Each metatarsal must load during stance and gait. Thisloading promotes plantarflexory stability o{ the metatarsophalangeal joint through plantar fascial and intrinsic
muscle mechanisms. Extrinsic muscles act more as adeforming force if purchase stability is lacking at themetatarsophalangeal joi nt.

The long extensor pulls the metatarsophalangeal joint
into extension in both deformities.

Metatarsophalangeal Joi nt

Flexion of the proximal interphalangeal joint in hammertoe deformity occurs from long flexor forces. Thelong extensor cannot counter the flexor pull at the proximal interphalangeal joint unless the metatarsophalangeal joint is held in a stable rectus position. A floating
toe bears out this biomechanical fact. ln a floating toe

The metatarsophalangeal joint represents an axis about
which motion of the proximal phalanx and metatarsal canoccur. lf the joint has been disrupted by metatarsal headresection or proximal phalangeal base resection afloating toe may develop by reasons previously discussed but also compounded by the absence of capsular andligamentous attachments. These soft tissue joint structures connect the osseous segments to promote stabili-

the principle difficulty stems from an absence of flexor
power.

119

sophalangeal joint stability. Skin plasty by excision of atransverse plantar elipse will place plantarflexory force
at the metatarsophalangeal joint. Likewise dorsal "2" or"V-Y" plasty can be utilized to relax dorsiflexory contracture of scar. The Iong flexor power can be transferredto the proximal phalanx in two ways. A flexor transfer
can be performed to the proximal phalanx or the prox-

The length of the bony segments within the digit is an
important consideration as weil. Discussion has alreadybeen directed to metatarsal length considerations. Concurrent digital and metatarsal surgery can result in extensive bony column shortening. Floating toes can result
from any excessive relaxation of soft tissue structures.
Care{ul maintenance of bony column length is important. lnappropriate performance of digital procedures
can compound a condition that is already predisposed
to a floating toe. Arthroplasty of the proximal interphalangeal joint can create an unstable toe by producing an unstable pseudoarthrosis.

imal interphalangeal joint can be arthrodesed. Arthrodesis of the proximal interphalangeal joint effectively
converts the long flexor into a plantar stabilizing forceof the metatarsophalangeal joint. The long flexor must
be carefully evaluated. Active flexor power and free excursion of the tendon must be present.

Treatment
The metatarsal segment may be found shortened or
Surgical management of floating toes centers aroundelevated and failing to load. Consideration may be given

two basic functional areas. The first is the necessity fora stable axis of metatarsophalangeal joint motion.
Without metatarsophalangeal stability reestablishing flexor power is useless. The second is the reestablishmentof flexor power. The potential for active flexor function
must be present if reestablishment of a functional digit
is to be successful.

to lengthening or lowering the affected metatarsal toreestablish its functional position and alignment. Flexor
power at the metatarsophalangeal joint can be aided byreestablishing tension of the soft tissues. An appropriate
metatarsal procedure can be an effective adjunct to assist
in promotion of digital purchase and in balancing coexistent iatrogenic plantar metatarsal imbalance.

Metatarsophalangeal Joint Axis

Flexor stability can be effectively aided by syndactyliza-tion. The f lexor power of an adjacent toe can be utilized
to aid purchase of a floating toe. This shouid not be considered a compromise of surgical reconstruction principles. Syndactylization may be all that is possible if joint
structuFes are compromised or flexor power cannot bereestablished. It can also be utilized as an adjunctive procedure with those techniques already described.

A stable metatarsophalangeal joint axis represents only
a functional point f rom which the phalanx can effectively
move with respect to the metatarsal. An anatomically nor-mal joint need not necessarily be present. An implant
can provide this stability. Fibrosis following metatarsal
head resection or phalangeal base resection can likewise
provide this stability.

Summarylf the metatarsophalangeal joint is present thenThe surgical approach to floating toes is a study inlogical understanding of the pathogenesis of a particular
deformity. Re-establishing plantarflexory force across asatisfactory excursion must be present. There should also
be an absence of adaptive structural changes. The

ligamentous tissues must be intact, allowing primarily
sagittal plane motion. Capsular and ligamentous dorsal
contracture if present must be released. lf adaptivechanges have occurred arthroplasty and/or implant procedures must be considered. Prior metatarsophalangeal
joint arthroplasty resulting in floating toes with metatarsophalangeal joint instability may require implant arthroplasty as well.

stable metatarsophalangeal joint is the goal ofreconstruction. lf this goal cannot be achieved the success of reconstructive attempts is in jeopardy. If subjec-

tive symptoms are not present, prevention of further
digital malalignments is indication enough for surgicaltreatment. The particulars of surgical management arewell illustrated in the course of the lecture.

Flexor Power

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