THE EFFECT OF CALCANEAL OSTEOTOMY AND LATERAL COLUMN LENGTHENING ON THE PLANTAR FASCIA. A BIOMECHANICAL INVESTIGATION
November 18th, 1997
Greg A. Horton, MD; Mark S. Myerson, MD; Brent G. Parks; and Yong-Wook Park, MD
Abstract
Medial calcaneal displacement osteotomy or lateral column lengthening fusion has been advocated to augment tendon transfer in planovalgus foot deformity associated with chronic posterior tibial tendon insufficiency. It is hypothesized that plantar fascia tightening occurs with these procedures, helping to restore a more normal longitudinal arch.
To investigate this further, nine fresh frozen cadaveric below-knee specimens were utilized. A flat foot model was created by sectioning of the posterior tibial tendon, spring ligament, talonavicular capsule, and deltoid ligament. A liquid metal strain gauge, calibrated to measure fractional changes in length, was sutured proximally to the origin and distally into the thickest portion of the medial band of the plantar fascia. Specimens were axially loaded to 400 N and plantar fascia strain was measured. Fractional length changes in the plantar fascia were then measured after a medial displacement calcaneal osteotomy and after a lateral column lengthening through the calcaneocuboid joint. Tightening of the plantar fascia did not occur with either medial calcaneal displacement or lateral column lengthening. The plantar fascia became significantly less taut with both medial displacement and lateral column lengthening. We found lateral column lengthening to produce significantly looser plantar fascia than medial displacement of the calcaneal tuberosity.
Introduction
Posterior tibial tendon insufficiency is probably the most common source of acquired adult flat foot deformity and can be a considerable source of pain and disability. Surgical reconstruction of posterior tibial tendon insufficiency has been recommended in an attempt to decrease pain and increase inversion strength. Reconstruction of the posterior tibial tendon utilizing a flexor digitorum tendon transfer has been shown to be successful in achieving these goals.13 Although inversion strength is improved and pain is relieved, the underlying planovalgus foot deformity does not substantially improve with a flexor tendon transfer alone.14 Deformity can alternatively be corrected by arthrodesis procedures that stiffen the foot, but doing so can lead to increased stresses at adjacent joints.1,4 In an attempt to preserve motion and possibly improve the long-term results, the addition of calcaneal osteotomy to the flexor digitorum longus tendon transfer has been suggested.7,16-18
Preliminary reports on medial displacement calcaneal osteotomy18 and lateral column lengthening through the calcaneocuboid21 joint have documented clinical and radiographic improvement in the foot structures with restoration of a more normal longitudinal arch. Despite the fact that clinical and radiographic improvement of the flat foot position are improved by this procedure, the exact mechanism by which this occurs in incompletely understood. One hypothesis is that plantar fascia tightening occurs, helping to restore a more normal longitudinal arch by the windlass mechanism.15 The current investigation was designed to document the effect of medial displacement calcaneal osteotomy and lateral column lengthening through the calcaneocuboid joint on plantar fascia tension. This was done in an effort to define the potential role of the plantar fascia in restoration of the longitudinal arch produced by these procedures.
Materials and Methods
Nine fresh-frozen cadaver below-knee specimens were utilized. The plantar fascia was exposed by removing the plantar skin in the non-weight-bearing portion of the foot. The plantar heel and metatarsal pads were left intact. The skin was also removed along the medial boarder of the foot to expose the posterior tibial tendon and the medial supporting capsuloligamentous structures. A flat foot model was created by sectioning the posterior tibial tendon, spring ligament, talonavicular capsule, the medial aspect of the subtalar joint, and the deltoid ligament.3 The soft tissue sectioning performed produced a moderately severe flat foot deformity. The plantar fascia was left intact. A liquid metal strain gauge (2.5 cm in length) calibrated to measure fractional changes in length was then sutured to the plantar fascia. A 3.0-mm (internal diameter) stainless steel tube shrouded the gage to prevent crushing. The gauge was sutured proximally to the central origin (strained 10% of its original length) and distally into the thickest portion of the medial band of the plantar fascia (Fig. 1). The resting length was approximately 3.0 cm. The specimens were axially loaded to 400 N on an MTS MiniBionix System (MTS Systems, Eden Prairie, MN). A baseline tension (length) of the section of plantar fascia was recorded. Readings were electronically recorded by a personal computer integrated into the system.
A calcaneal osteotomy was then performed using a thin oscillating saw blade. This osteotomy was made transversely to the lateral border of the os calcis and inclined approximately 45o to the plantar surface of the hindfoot. No wedge was removed and no attempt was made to tilt the tuberosity into varus. The posterior calcaneal tuberosity was translated 10 mm medially and held using two threaded Steinmann pins. The specimen was again loaded to 400 N and readings were recorded (Fig. 2). The position of the osteotomy remained stable with no proximal migration of the calcaneal tuberosity noted in any of the specimens during loading.
The osteotomy was then replaced to the original native position and pinned. Repeat loading was performed to assure that the osteotomy was stable and that no substantial changes in baseline resting tension had occurred. A lateral column lengthening was then performed through the calcaneocuboid joint. The joint was distracted with a lamina spreader and a 10-mm block was inserted into the joint. The specimen was again loaded and plantar fascia tension measurements were recorded. Data were analyzed using paired Student t-tests.
Results
Analysis of the results revealed that all manipulations described resulted in a relative lengthening of the plantar fascia, ie the plantar fascia became less taut. Measurements for both the medial calcaneal osteotomy and the calcaneal lengthening revealed a decrease in the resistance of the liquid metal strain gauge, which translates into a relative shortening of the gauge and less tension in the plantar fascia. The changes in plantar fascia length are shown in Table 1. All nine specimens were included for analysis of the calcaneal osteotomy data. During distraction of the calcaneocuboid joint in one specimen, the osteoporotic bone was crushed by the lamina spreader, making the exact amount of distraction difficult to measure. This specimen was not utilized for analysis of the lateral column lengthening data.
Medial translation resulted in an average of 1.2 + 0.5 mm of loosening of the plantar fascia (range, 0.580 to 2.184 mm). Lateral column lengthening resulted in even greater loosening of the plantar fascia with an average of 2.7 + 1.9 mm (range, 1.092 to 6.55 mm). The differences between the index plantar fascia length and the length after the manipulations were statistically significant for both groups (p < 0.002). Lateral column lengthening produced statistically significantly looser plantar fascia than did medial calcaneal osteotomy (p < 0.004).
Discussion
Medial displacement calcaneal osteotomy and lengthening through lateral column have both been advocated to augment tendon transfer in planovalgus foot deformity associated with chronic posterior tibial tendon insufficiency.17,18,21 Although preliminary clinical data are encouraging, the mechanism(s) by which these osteotomies correct the valgus hindfoot deformity is incompletely understood.
The posterior tibial tendon normally functions as a primary invertor of the foot in addition to an adductor of the forefoot. Anatomically, the posterior tibial tendon is located well medial to the axis of the subtalar joint. This, in addition to its relative size, makes it the most powerful invertor of the foot. Primary opposition of the posterior tibial tendon is by the peroneus brevis, which functions to evert the heel and abduct the foot. With weightbearing, the loss of function or chronic insufficiency of the posterior tibial tendon leads to a gradual stretching of the medial static structures and is exacerbated by the muscle imbalance created by the unopposed pull of the peroneus brevis. In time, this deformity results in secondary attenuation of the medial capsuloligamentous supporting structures, which elongate and become functionally ineffective. Deformity develops with loss of the medial longitudinal arch, abduction of the forefoot, and excessive heel valgus.
Numerous surgical procedures, ranging from direct repair to triple arthrodesis, have been described as treatment for posterior tibial insufficiency.1,2,5,8-11,13,14 Evans6 described correction of pes planus deformity by lengthening the lateral column through the neck of the calcaneus. Because of the potential for calcaneocuboid arthritis,19 lateral column lengthening through the calcaneocuboid joint, with arthrodesis, has been advocated for progressive flat foot deformity in adults.21 Recently, this has been combined with flexor digitorum longus transfer and calcaneal osteotomy to restore inversion strength while improving hindfoot valgus and restoring the medial longitudinal arch.20
The exact mechanism by which calcaneal lengthening corrects valgus deformity is not entirely known. It has been shown that a 1-cm lengthening of the calcaneus by the Evans technique results in an increase in the anteroposterior and lateral talometatarsal angle, calcaneal pitch, and talonavicular coverage.22 Mosca15 has suggested that the effects of lengthening of the lateral column results in elevation of the longitudinal arch and correction of the valgus deformity due to the windlass effect of the plantar fascia. It is assumed that the mechanism(s) by which calcaneal neck osteotomy and distraction calcaneocuboid arthrodesis function is(are) similar.
Koutsogiannis12 described a transverse medial displacement osteotomy of the calcaneus as treatment for flexible flat foot. This osteotomy, in combination with a flexor tendon transfer, has recently been described as treatment for posterior tibial tendon insufficiency.18 Valgus heel deformity results in a lateralization of the pull of the tendo Achilles. Normally, the gastrocnemius-soleus complex inserts just medial to the axis of the subtalar joint, and the posterior tibial tendon works with the gastrocnemius-soleus complex to stabilize the hindfoot and invert the heel. Once inversion of the heel is initiated, the gastrocnemius-soleus pull is even more medial and the muscle serves as a secondary invertor. If heel inversion cannot be initiated, the heel stays in a valgus position.
Medial translation of the calcaneus, combined with flexor digitorum longus transfer, has been shown to result in radiographic improvement in the talometatarsal angle, talonavicular coverage, and medial cuneiform height. It has been suggested that the mechanism by which the medial translation osteotomy effects these changes is the result of a functional medial transfer of the Achilles tendon insertion. This shift helps the gastrocnemius-soleus to function as a secondary invertor and probably has a protective effect on the flexor digitorum longus transfer.
The purpose of this investigation was to examine the effect of medial displacement osteotomy and lateral column lengthening through the calcaneocuboid joint on plantar fascia tension. The original hypothesis was that these manipulations would result in increased tension on the plantar fascia with elevation of the medial longitudinal arch secondary to an increase in the windlass mechanism. The results obtained reveal that tightening of the plantar fascia does not occur with either medial calcaneal displacement or lateral column lengthening. Medial translation resulted in an average of 1.1 mm of loosening of the plantar fascia. Lateral column lengthening through the calcaneocuboid joint resulted in even more loosening of the plantar fascia (average, 1.9 mm). Lateral column lengthening was shown to produce statistically significantly looser plantar fascia than medial displacement.
In this investigation, the liquid metal strain gauge was attached only to a single band of the plantar fascia. If sampling had been performed medially, laterally, and centrally, portions of the fascia may have been lengthened while other portions shortened. However, if the windlass mechanism was responsible for elevation of the medial longitudinal arch, it is assumed that the central medial portion (the portion that was measured) would be tighter. Strains on the long plantar ligament were not examined in this investigation. The long plantar ligament anatomically is located deep to the plantar fascia, spanning from the os calcis to the cuboid tuberosity. More superficial insertion is also present at the lateral three or four metatarsal bases. It has been suggested that the long plantar ligament is important in the success of calcaneal neck osteotomy.22
In conclusion, tightening of the plantar fascia does not occur with either medial calcaneal displacement or lateral column lengthening. The plantar fascia becomes significantly less taut with both medial displacement and lateral column lengthening. We found lateral column lengthening to produce significantly looser plantar fascia than medial displacement. Although both procedures have been shown to restore a more normal medial longitudinal arch, tightening of the plantar fascia does not appear to be the mechanism by which these changes occur.
References
1. Angus, P.D., and Cowell, H.R. Triple arthrodesis. A critical long-term review. J. Bone Joint Surg. 68B:260-265, 1986.
2. Bennett, G.L., Graham, C.E., and Mauldin, D.M. Triple arthrodesis in adults. Foot Ankle, 12:138-143, 1991.
3. Deland, J.T., Arnoczky, S.P., and Thompson, F.M. Adult acquired flatfoot deformity at the talonavicular joint: reconstruction of the spring ligament in an in vitro model. Foot Ankle, 13:327-332, 1992.
4. Deland, J.T., Lee, K.-T., Hogle, S., Nations, S., Peterson, M.G., and Otis, J.C. Range of motion before and after calcaneocuboid fusion with lateral column lengthening. Presented at the Summer Meeting of the American Orthopaedic Foot and Ankle Society, Coeur d'Alene (ID), July 3, 1994.
5. Deland, J.T., Otis, J.C., Lee, K., and Kenneally, S.M. Lateral column lengthening with calcaneocuboid fusion: range of motion in the triple joint complex. Foot Ankle Int. 16:729-733, 1995.
6. Evans, D. Calcaneo-valgus deformity. J. Bone Joint Surg. 57B:270-278, 1975.
7. Fairbank, A., Myerson, M.S., Fortin, P., and Yu-Yahiro, J. The effect of calcaneal osteotomy on contact characteristics of the tibiotalar joint. Foot, 5:137-142, 1995.
8. Funk, D.A., Cass, J.R., and Johnson, K.A. Acquired adult flat foot secondary to posterior tibial-tendon pathology. J. Bone Joint Surg. 68:95-102, 1986.
9. Graves, S.C., Mann, R.A., and Graves, K.O. Triple arthrodesis in older adults. Results after long-term follow-up. J. Bone Joint Surg. 75A:355-362, 1993.
10. Jahss, M.H. Spontaneous rupture of the tibialis posterior tendon: clinical findings, tenographic studies, and a new technique of repair. Foot Ankle, 3:158-166, 1982.
11. Kettelkamp, D.B., and Alexander, H.H. Spontaneous rupture of the posterior tibial tendon. J. Bone Joint Surg. 51A:759-764, 1969.
12. Koutsogiannis, E. Treatment of mobile flat foot by displacement osteotomy of the calcaneus. J. Bone Joint Surg. 53B:96-100, 1971.
13. Mann, R.A. Rupture of the tibialis posterior tendon. Instr. Course Lect. 33:302-309, 1984.
14. Mann, R.A., and Thompson, F.M. Rupture of the posterior tibial tendon causing flat foot. Surgical treatment. J. Bone Joint Surg. 67A:556-561, 1985.
15. Mosca, V.S. Calcaneal lengthening for valgus deformity of the hindfoot. Results in children who had severe, symptomatic flatfoot and skewfoot. J. Bone Joint Surg. 77A:500-512, 1995.
16. Myerson, M.S. Adult acquired flatfoot deformity. Treatment of dysfunction of the posterior tibial tendon. J. Bone Joint Surg. 78A:780-792, 1996.
17. Myerson, M.S., and Corrigan, J. Treatment of posterior tibial tendon dysfunction with flexor digitorum longus tendon transfer and calcaneal osteotomy. Orthopedics, 19:383-388, 1996.
18. Myerson, M.S., Corrigan, J., Thompson, F., and Schon, L.C. Tendon transfer combined with calcaneal osteotomy for the treatment of posterior tibial tendon insufficiency: a radiological investigation. Foot Ankle Int. 16:712-718, 1995.
19. Phillips, G.E. A review of elongation of os calcis for flat feet. J. Bone Joint Surg. 65B:15-18, 1983.
20. Pomeroy, G.C., and Manoli, A., II: A new operative approach for flat foot secondary to tibialis posterior tendon insufficiency: a preliminary report. Presented at the 9th Annual Specialty Day Meeting of the American Orthopaedic Foot and Ankle Society, Atlanta (GA), February 25, 1996.
21. Sands, A., Grujic, L., Sangeorzan, B., and Hansen, S.T., Jr. Lateral column lengthening through the calcaneo-cuboid joint: an alternative to triple arthrodesis for correction of flatfoot. Presented at the 25th Annual Meeting of the American Orthopaedic Foot and Ankle Society, Orlando (FL), February 19, 1995.
22. Sangeorzan, B.J., Mosca, V., and Hansen, S.T. Effect of calcaneal lengthening on relationships among the hindfoot, midfoot, and forefoot. Foot Ankle, 14:136-141, 1993.
Figure Legends
Fig. 1. Gauge positioning. The gauge was sutured proximally to the central origin (strained 10% of its original length) and distally into the thickest portion of the medial band of the plantar fascia.
Fig. 2. The posterior calcaneal tuberosity was translated 10 mm medially and held using two threaded Steinmann pins. The specimen was again loaded to 400 N and readings were recorded.
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