Gait changes offset stability, pain relief of triple arthrodesis

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From Biomechanics Magazine May 2005

Gait changes offset stability, pain relief of triple arthrodesis

The effect on foot biomechanics may include alterations to force

distribution, gait pattern, and range of motion.

By: Chul Kim, Alvin Ngan, and , DPM

In 1923, Ryerson is reported to have developed the triple arthrodesis

procedure for patients with infantile paralysis and similar

disabilities for the purpose of improving foot function by providing

stability, correcting the deformity, and eliminating pain.1 Triple

arthrodesis refers to a fusion of the talocalcaneal, talonavicular,

and calcaneocuboid joints. In modern practice, triple arthrodesis

provides a stable, pain-free platform for ambulation for patients

with various indications.

Due to the complexity of the gait pattern, fusion of these joints has

a significant impact on other joints, muscles, ligaments, nerves, and

integument, as well as the vascular system, proximal and distal to

the surgical site. However, the most important effect of the triple

arthrodesis is its effect on gait dynamics. This has become a focus

of debate regarding the purpose and the effectiveness of triple

arthrodesis.

Indications

Triple arthrodesis is indicated for multiple lower extremity

pathologies related to neurological, vascular, musculoskeletal, and

biomechanical etiologies. McGlamry noted three main functions of the

triple arthrodesis procedure: to provide stability for the foot, to

correct the deformity, and to eliminate pain, resulting in overall

improved foot function.1 Biomechanically, triple arthrodesis is

indicated for valgus deformities, including posterior tibial tendon

dysfunction and tarsal coalition. The procedure also has applications

for varus foot deformities, such as cavovarus and talipes

equinovarus. Additional indications include joint instability and

resistance to conservative therapy for arthritic conditions

(rheumatoid arthritis, degenerative joint disease, post-traumatic

arthritis), neurological disorders (cerebral palsy, Charcot Marie

Tooth, muscular dystrophy), and infections (poliomyelitis,

tuberculosis).1

Biomechanical implications

Although triple arthrodesis may alleviate pain and improve foot

function, these benefits are not achieved without cost. A multitude

of biomechanical sequelae have been documented, most notably

alterations of range of motion, force distribution, and gait pattern.

Range of motion. Triple arthrodesis is intended to reduce or

eliminate the motion of the talonavicular, calcaneocuboid, and

subtalar joints. In a study involving simulated arthrodesis of

cadaveric feet, Gellman et al measured a 60.5% reduction of rearfoot

inversion and eversion, and approximately a 50% reduction of

supination and pronation of the whole foot postoperatively.2 This

demonstrates a significant loss of motion at the arthrodesed joints.

It follows that there should be a profound effect on joints proximal

and distal to the surgical site.

One of the most obvious sites to be affected is the ankle joint. Some

authors have found that ankle joint ROM is reduced following triple

arthrodesis.1-3 According to Beischer et al, the ankle joint loses 8

degrees in total ROM during the third rocker (propulsion) phase of

gait.3 Similarly, Gellman et al measured a 12.5% loss of dorsiflexion

and a 15.5% loss of plantar flexion resulting from triple

arthrodesis.2 This loss of ankle joint ROM forces compensation at the

knee joint, which was found to increase flexion by 13% during the

third rocker phase. Furthermore, Jahss suggests that the loss of

ankle joint motion also contributes to compensation resulting in an

increased forefoot ROM.4

In light of these findings, there is little doubt that triple

arthrodesis can force compensations at the ankle joint.5 If changes

at the ankle joint can be avoided, knee and forefoot compensations

may also be eliminated. Indeed, surgical techniques developed in the

past decade have allowed the ankle joint ROM to be retained.6

Force distribution. In a normal foot, the weight of the human body is

distributed to minimize any form of pathology. However, with triple

arthrodesis, the dynamics of pedal mechanics change dramatically.

According to Stein et al, normal subjects bear the most weight on the

forefoot and the heel.7 In contrast, patients who underwent triple

arthrodesis shifted the main weight-bearing load from the forefoot to

the midfoot, which received 15.2% body weight, rather than the normal

9%.7 These findings are also supported by Southwell et al, who found

the presence of symptomatic force concentration in the midfoot after

triple arthrodesis.8 In addition to the midfoot, weight on the heel

in arthrodesis patients is greater than normal, 59.4% of body weight

compared to 48.2%.7 Changes have also been detected within the

forefoot, where the main load shifts from the medial rays to the

lateral rays; the medial forefoot bears 57% of the total forefoot

load in normal subjects, but only 38.6% in arthrodesis patients.7

The shift in weight distribution can most likely be attributed to a

loss of pronation following the surgical procedure. One might expect

that the elevated pressure points at the heel, midfoot, and lateral

rays may result in foot deformities such as tailor's bunions or fat

pad atrophy of the calcaneus. These findings indicate the importance

of using orthoses postoperatively to off-load high-pressure areas.

Shock absorption is another subject of concern following triple

arthrodesis. During the gait cycle, ground reaction forces are

absorbed by the subtalar joint as the lower extremity strikes the

ground. The subtalar joint achieves this primarily by shifting from a

supinated position (during heel contact) to a pronated position

(during forefoot loading).5 It can therefore be inferred that triple

arthrodesis patients will have a diminished ability to absorb shock

secondary to the loss of subtalar joint pronation.9

Gait pattern. Gait is a complex process, one that depends greatly on

joints within the foot and ankle having adequate ranges of motion.

Eliminating motion in the foot will therefore result in deviations

from the normal gait pattern. Beischer et al described this

extensively in a study of gait analysis following triple

arthrodesis.3 The authors suggested that postoperative gait changes

stem from the abnormal, rigid position of the rearfoot. The

arthrodesed rearfoot may produce a less effective lever arm for the

triceps surae, resulting in less plantar-flexory power generation at

toe-off compared to normal. Indeed, Beischer et al discovered a 45%

decrease in ankle joint plantar-flexory power during propulsion. The

authors also cited a 33% loss of ankle joint ROM during the third

rocker phase. Compensation for loss of ankle joint ROM occurs at

adjacent joints, especially the knee, as evidenced by the 13%

increase in knee flexion during third rocker (propulsion) phase.3

Other compensations include a shortened stride length and shorter

support time, which effectively reduce the amount of ankle

dorsiflexion required during gait. Beischer et al recorded a 5.1%

decrease in stride length on the affected foot and a 3.1% decrease in

foot support time compared to normal patients.3

The modification of gait pattern following triple arthrodesis may

have ramifications proximally in the kinetic chain. For example,

excessive knee flexion may result in proximal muscular pathology,

such as tight hamstrings and low back pain.5

Alternative procedures

Because of the biomechanical complications resulting from triple

arthrodesis, the necessity of the procedure is questionable. This

prompts a much needed investigation of alternative procedures, or

modifications to the current procedure, in order to reduce the

problems inherent in triple arthrodesis. For example, isolated

fusions, such as subtalar arthrodesis, have been shown to result in

less loss of ROM than triple arthrodesis. Dubois et al10 found only a

5 degrees loss of ankle joint ROM with subtalar arthrodesis, and a

less significant loss of plantar-flexor power than with the triple

arthrodesis performed by Beischer et al. In contrast to triple

arthrodesis, ROM loss in subtalar joint arthrodesis was not

sufficient to induce compensation at any proximal joints such as the

knee or hip. Most important, subtalar joint arthrodesis resulted in a

globally symmetrical gait pattern after unilateral surgery. No

statistical difference from normal values were reported in peak

ground reaction force, length of gait cycle, length of stride,

duration of double/single foot weight-bearing, or duration of the

oscillation phase were noted by Dubois in any of the three cardinal

planes during the gait cycle in patients with subtalar arthrodesis.10

However, the subtalar arthrodesis did result in a slight delay in

peak activation of the rectus femoris muscle and a slight early

activation of the tibialis anterior muscle at toe-off, when compared

to normal subjects. Dubois also found that the medial rotation of the

tibia was not transmitted to the foot upon heel contact.10

The joints involved in triple arthrodesis do not function

individually; rather, their functions are interdependent. One must

consider which joint or joints in the triple-joint complex

(talonavicular, subtalar, calcaneocuboid) should be fused and which

should be left alone to maintain optimal foot function. Astion et al

performed isolated fusions of each of the three joints to determine

the effect of each fusion on ROM of the adjacent joints and on

posterior tibial tendon excursion.11 Isolated talonavicular

arthrodesis almost completely eliminated subtalar and calcaneocuboid

joint ROM (only 2 degrees of motion remained for both), and reduced

posterior tibial tendon (PTT) excursion by 75% of the preoperative

range. In contrast, calcaneocuboid joint arthrodesis reduced only 8%

of subtalar and 33% of talonavicular joint ROM, without a

statistically significant effect on PTT excursion. Lastly, subtalar

joint arthrodesis reduced talonavicular ROM by 74%, calcaneocuboid

ROM by 44%, and PTT excursion by 64%. Astion et al's study suggests

the talonavicular joint is the key determinant of foot function

following triple arthrodesis; its fusion essentially eliminates

motion of surrounding joints, and has the most pronounced effect on

PTT function.11

Various arthrodesis procedures serve specific purposes for different

types of patients. For example, patients who are more active

throughout the day generally do better with double arthrodesis

(calcaneocuboid and talonavicular joints) than triple arthrodesis.

Triple arthrodesis may debilitate these patients in the long run more

than the double arthrodesis, according to Donatto et al.6

Complications

The majority of patients are generally satisfied with the ability of

the triple arthrodesis procedure to alleviate pain and improve foot

function. Anywhere from 77% to 94% of patients are satisfied

postoperatively.1 However, because of the invasiveness of triple

arthrodesis and the loss of foot mobility following surgery,

complications should be expected. The most common of these include

degenerative joint disease, pseudoarthrosis, recurrence of deformity,

avascular necrosis, ankle instability, chronic edema, and

postincisional entrapment neuropathy. Degenerative joint disease has

been documented in a number of studies. Southwell et al documented

that 88% of patients studied postoperatively developed DJD,

especially at the ankle and the tarsometatarsal joint.8

Several factors have been postulated to affect the development of DJD

of the ankle. One is the loss of motion at the subtalar, midtarsal,

and talonavicular joints, which induces excessive compression at the

end range of ankle dorsiflexion.12 Another contributing factor is

preoperative equinus. Patients with this deformity will suffer from

more profound ankle DJD due to the subtalar joint's inability to

compensate for equinus after arthrodesis.12 Although Southwell8

discovered DJD in nearly all his patients, it is important to note

that occurrence rates of postoperative arthritis have been highly

varied throughout studies; while some cases resulted in substantial

pain, other studies9 reported asymptomatic patients. Nevertheless,

surgeons must practice proper techniques in order to lower the risk

of DJD. To reduce additional stress on adjacent joints, proper

positioning of the foot prior to fusion should be considered for

every triple arthrodesis procedure. Banks1 suggests the heel should

be neutral to slightly everted and the midtarsal joint slightly

valgus, to increase medial column stability (first ray to touch the

ground) and permit enhanced first metatarsophalangeal joint motion.

Finally, the entire foot should be abducted 10 degrees to 15 degrees

lateral to the leg for normal function.

Reports of pseudoarthrosis vary from 0% to 36% among various

studies.1 Historically, the talonavicular joint was the most

problematic, but with the use of a two-incision approach, rather than

the traditional lateral incision, fusions have met with greater

success.1 More recently, Banks suggests that the calcaneocuboid joint

appears to be the primary site for delayed healing because it is most

susceptible to disruption on weight-bearing.1 This is expected since

plantar forces have been reported to shift toward the midfoot

postoperatively.10 Immobilization and nonweight-bearing should be

stressed to reduce the risk of symptomatic pseudoarthrosis.

According to Banks, a 12% to 62% recurrence of the preoperative

deformity has been documented.1 The most common causes of these

residual deformities include undercorrection, an inadequate period of

immobilization, failure to align the foot with the ankle joint, loss

of position during cast changes, failure of fusion, muscle imbalance,

and surgery at too young an age. Southwell documented multiple

pathologies related to the residual deformities.8 A calcaneovalgus

residual deformity, for example, increases symptomatic posterior heel

force concentration following triple arthrodesis. Any residual

biomechanical compensations will contribute to postoperative

complications as well. Residual forefoot supination, for example,

increases symptomatic force concentration under the fifth metatarsal

joint and toe, while forefoot pronation increases midfoot and medial

metatarsal load bearing (although this is generally asymptomatic).

Angus et al suggested that the most common manifestation of residual

deformity following triple arthrodesis is the pes cavus or pes valgus

foot type.12 Any pre-existing foot deformities may therefore need to

be addressed during surgery. For example, patients with equinus

should consider tendo-achilles lengthening as an adjunct to the

arthrodesis.12

Avascular necrosis, especially of the talus, navicular, and the

cuneiforms, is also a critical complication of triple arthrodesis.

Angus et al12 suggested that about 7% of patients suffer from AVN

after surgery. However, proper technique, such as a bilateral

incision, will allow better visual inspection of the joint and

prevent accidental damage to arteries, and therefore limit AVN.1

Ankle instability is rare, but may occur following triple

arthrodesis.1 When it does occur, lateral instability is more common

than medial. This problem stems from incorrectly positioning the

calcaneus in varus, or sectioning of the lateral ankle ligaments.1

This potential complication can be avoided by placing the heel in

neutral to slightly valgus, and repairing any damaged ligaments.

Entrapment of the sural nerve postoperatively may provoke

dysesthesias on the lateral side of the foot, creating an irritation

that is uncomfortable for the patient. Sural nerve entrapment usually

results from scar tissue surrounding the dissected area.1 In the

event this occurs, Coughlin et al suggested that postoperative

correction through neurolysis or resection of the nerve may be

necessary.13

Conclusion

Triple arthrodesis is a dynamic procedure indicated for relief of

pain, improved foot function, correction of deformity, and increased

stability. However, as with any surgical procedure, complications can

develop after triple arthrodesis, including degenerative joint

disease, pseudoarthrosis, and residual deformities. Most important,

the effect of triple arthrodesis on the biomechanics of the foot is

profound. Alterations in the gait pattern, force distribution, and

range of motion may enhance or aggravate the patient's ability to

ambulate. Effective planning, proper technical execution, and

sensible postoperative management are required for the benefit of the

patient. Furthermore, other procedures, such as isolated joint

arthrodesis, may also be considered for similar indications. Although

triple arthrodesis is a time-proven procedure, its effectiveness is

not fully understood. Much additional research is needed to determine

the most appropriate use of this procedure in the future.

Chul Kim and Alvin Ngan are students at the Scholl College of

Podiatric Medicine at lind lin University of Medicine and

Science in North Chicago, IL. They will graduate in 2006.

, DPM, practices with Affiliated Podiatrists, in Chicago.

The original draft of this article received the 2004 Drs. Harold,

& Marc Feder Orthopedics Award given to students of the

M. Scholl College of Podiatric Medicine.

References

1. Banks AS, Downey MS, DE, SJ. McGlamry's

comprehensive textbook of foot and ankle surgery, 3rd ed.

Philadelphia: Lippincott & Wilkins 2001; vol. 2:1167-1191.

2. Gellman H, Lenihan M, Halikis et al. Selective tarsal arthrodesis:

An in vitro analysis of the effect on foot motion. Foot Ankle 1987;8

(3):127-133.

3. Beischer AD, Brodsky JW, Pollo FE, Peereboom J. Functional outcome

and gait analysis after triple or double arthrodesis. Foot Ankle Int

1999;20(9):545-553.

4. Jahss MH. Disorders of the foot and ankle: medical and surgical

management. Philadelphia: W.B. Saunders, 1991;3:2627-2630.

5. Valmassy RL. Clinical biomechanics of the lower extremities. St.

Louis: Mosby, 1996:32-55.

6. Donatto KC. Arthritis and arthrodesis of the hindfoot. Clin Orthop

1998;(349):81-92.

7. Stein H, Simkin A, ph K. The foot-ground pressure distribution

following triple arthrodesis. Arch Orthop Trauma Surg 1981;98(4):263-

269.

8. Southwell RB, Sherman FC. Triple arthrodesis: a long-term study

with force plate analysis. Foot Ankle 1981;2(1):15-24.

9. de Heus JA, Marti RK, Besselaar PP, Albers GH. The influence of

subtalar and triple arthrodesis on the tibiotalar joint. J Bone Joint

Surg 1997;79-B(4):644-647.

10. Dubois D, Revuelta N, Blatt JL, et al. Tridimensional gait

analysis after unilateral subtalar arthrodesis. Rev Chir Orthop

Reparatrice Appar Mot 2001:87(7):685-695.

11. Astion DJ, Deland JT, Otis JC, Kenneally S. Motion of the

hindfoot after simulated arthrodesis. J Bone Joint Surg 1997; 79-A

(2):241-246.

12. Angus PD, Cowell HR. Triple arthrodesis: a critical long-term

review. J Bone Joint Surg 1986;68-B(2):260-265.

13. Coughlin MJ, Mann RA. Surgery of the foot and ankle. St. Louis:

C.V. Mosby,1999:687-688.

CHANGES IN RANGE OF MOTION AND KINETIC DATA POSTARTHRODESIS

Ipsilateral knee flexion +13%

Ankle ROM -33%

Plantar flexion at toe-off -53%

Peak external ankle dorsiflexion moment -13%

Mean max. power generation at ankle (compared to other side) -45%

Source: Reference #3