TENDON TRANSFER COMBINED WITH CALCANEAL OSTEOTOMY FOR THE TREATMENT OF POSTERIOR TIBIAL TENDON INSUFFICIENCY: A RADIOLOGICAL INV
August 8th, 1995
Mark S. Myerson, MD; John Corrigan MCh, FRCSI (Orth), BSc; Francesca Thompson, MD; and Lew C. Schon, MD;
We present the radiographic results after flexor digitorum longus tendon transfer combined with a medial displacement calcaneal osteotomy for the treatment of posterior tibial tendon insufficiency. Eighteen patients with posterior tibial tendon insufficiency were reviewed at a range of 12 to 26 months after surgery. The 15 women and 3 men had a mean age of 54 years (range, 38 to 72 years). On the anteroposterior weight-bearing radiographs, the talar-first metatarsal and talonavicular coverage angles were measured pre- and postoperatively. The mean preoperative values for these angles were 21o (range, 3 to 45o) and 34o (range, 0 to 55o), respectively. The mean postoperative values for these angles were 8.5o (range, 0 to 35o) and 21o (range, -30 to 45o), respectively. The mean talar-first metatarsal angle decreased from 21 to 8.5o, a mean improvement of 12.5o, and the mean talonavicular coverage angle decreased from 34 to 21o, a mean improvement of 13o. On the lateral weight-bearing radiographs, the talar-first metatarsal angle and the distance from the medial cuneiform to the floor were measured pre- and postoperatively. The mean preoperative values were -22o (range, -10 to -40o) and 9 mm (range, 1 to 19 mm), respectively. The mean postoperative values were -9o (range, +5 to -25o) and 16 mm (range, 10 to 28 mm), respectively. The mean talar-first metatarsal angle decreased from -22 to -9o, a mean improvement of 13o, and the distance from the medial cuneiform to the floor increased from 9 to 16 mm, a mean improvement of 7 mm. We conclude that the use of a combined medial displacement osteotomy of the calcaneus with a tendon transfer for treatment of PTT insufficiency may offset the inherent weakness of the flexor digitorum longus transfer by reducing the antagonistic deforming force of heel valgus.
The posterior tibial tendon (PTT) acts to invert and plantarflex the foot and ankle. As a result of PTT insufficiency, the medial longitudinal arch collapses, the subtalar joint everts, the heel assumes a valgus position, and the foot abducts at the talonavicular joint.6 During the earlier phases of this attritional process, the foot is correctable but lacks dynamic support.12 Attempts to restore function to the PTT by direct repair have not been satisfactory.6 Therefore, motor substitution for the PTT by means of tendon transfer has been recommended.12 Tendon transfer generally improves patient symptoms but does not correct the deformity.18 Typically, the arch remains flat, the heel stays in valgus, and the forefoot remains abducted.8,12,18 This may reflect the inherent weakness of the flexor digitorum longus (FDL).19
Koutsogiannis11 recommended medial displacement calcaneal osteotomy to correct valgus hindfoot. We present the radiographic results of treatment of PTT insufficiency and its associated flatfoot deformities by FDL transfer, medial capsular plication of the talonavicular joint, and medial displacement osteotomy of the calcaneus.
Materials and Methods
Between 1991 and 1993, 25 patients with adult acquired flatfoot secondary to PTT insufficiency were treated with medial displacement osteotomy through the posterior third of the calcaneus combined with transfer of the FDL tendon and medial talonavicular capsular plication. Seven patients were excluded from the analysis because of inadequate preoperative radiographs. Therefore, 18 patients were included in our study group; 15 of those were treated at the Union Memorial Hospital in Baltimore and three were treated at Roosevelt Hospital in New York.
These 18 patients (15 females and 3 males) had a mean age of 54 years (range, 38 to 72 years). All patients were initially treated with various nonoperative modalities. Orthoses were used for a mean of 2.2 years (range, 6 months to 5.5 years); no medial T-strap or UCBL orthosis was used. Of the 18 patients, 8 were treated with a medial heel and sole wedge, 6 had accommodative orthoses, and 12 had rigid orthoses. A hinged polypropylene AFO was used in 8 patients for a mean of 5 months (range, 2 to 11 months) and a rigid AFO was used in 3 patients for a mean of 4 months (1 to 8 months). The indications for surgical treatment were: 1) a deformity which was correctable by passive manipulation, 2) a nonobese patient (obesity being defined as more than 2 standard deviations for age and height, eg a 200-lb 5'6" woman), and 3) the absence of continuous lateral foot pain. Seven patients had mild noncontinuous lateral foot pain.
The patient is placed in the lateral decubitus position on a bean bag. The incision begins superior to the calcaneus and posterior to the peroneal tendons and sural nerve. The incision curves gently in a distal and inferior direction, ending at the plantar lateral edge of the calcaneus. The lateral aspect of the calcaneus is exposed and a transverse calcaneal osteotomy is performed with an oscillating saw blade in line with the skin incision, taking care to remain approximately 1 cm posterior to the posterior process of the talus to avoid violating the articular surface of the posterior at its posterior extremity (Fig 1).
The osteotomy is at a right angle to the lateral border of the calcaneus and is inclined posteriorly approximately 45o to the plantar surface of the hindfoot. No wedge is removed from the calcaneus, and no attempt is made to tilt the tuberosity into varus. A toothless lamina spreader is placed in the osteotomy site and the medial soft-tissue attachments to the calcaneus are relaxed by spreading the lamina spreader. The lamina spreader is withdrawn, and the posterior calcaneal tuberosity is then translated medially by 10 mm and fixed with a 7-mm cancellous lag screw (Fig. 2). Care is taken to prevent the posterior tuberosity from sliding proximally. The screw is inserted from posterior, lateral and inferior to anterior, medial, and superior. The lateral incision is then closed, the bean bag is deflated and the patient is turned supine.
The tendon transfer is performed through a posteromedial incision in the line of the PTT (Fig. 3). The flexor retinaculum is opened and the ruptured PTT is inspected.
Of the 18 patients, 5 had complete disruption of the PTT, 7 had grossly visible longitudinal fissuring and attritional tears, and 6 had, in addition to edema and tenosynovitis, intratendinous degeneration on the deep aspect of the tendon.
The tendon is either advanced or used for a side-to-side tenodesis. If no functional excursion of the musculotendinous unit occurs when pulling on the proximal tendon remnant, the transected end is left free behind the medial malleolus. The tendon sheath of the FDL is then opened and exposed beneath the arch of the foot where it crosses superficial to the flexor hallucis longus tendon at the level of the naviculocuneiform joint; plantar retraction of the abductor hallucis brevis muscle belly improves exposure. Care is taken to avoid injury to the plantar vessels and nerve in close proximity. A tenodesis of the stump of the FDL to the flexor hallucis longus tendon is unnecessary if the FDL is transected proximal to the interconnection of these two tendons. A 4.5-mm drill hole is made in the navicular 1 cm lateral to its medial border and the tendon is passed through the drill hole from plantar to dorsal. Before suture of the tendon transfer, with the foot held inverted and slightly plantarflexed, the capsule of the talonavicular joint is plicated by excising a vertical ellipse approximately 6 to 8 mm in diameter (Fig. 4). The FDL tendon is then secured in this position to the adjacent periosteum. If the stump is long enough, additional strength of repair is achieved by suturing the tendon back on itself. The tension on the tendon is set halfway between its position at rest and maximum excursion, with the foot held in maximum inversion and slight plantarflexion (Fig. 5).
Postoperative Procedures and Evaluation
Patients were evaluated 2 weeks postoperatively when the cast was changed and the foot was immobilized in equinus and varus for a total of 4 weeks; a more plantigrade position was then assumed in a cast for an additional 2 weeks. A single cast change was usually sufficient to achieve a plantigrade position. At 6 weeks, weight-bearing was commenced. Seven patients used a range of motion walker and 11 patients used a hinged boot, each for 4 weeks. At 10 weeks, 13 patients used a stirrup ankle brace for 3 additional weeks, and 5 patients used the brace for 4 additional weeks.
The mean duration of follow-up was 20 months (range, 12 to 26 months). Radiographic assessment was performed using standardized weight-bearing views. Standing dorsoplantar radiographs were obtained with a focal distance of 47 inches and the beam 15o off the vertical, centered on the midfoot. Lateral radiographs were obtained with the plate medial to the foot. On the anteroposterior (AP) view, the parameters studied were talar-first metatarsal angle, talocalcaneal angle, and talonavicular coverage angle as described by Sangeorzan et al.14 (Fig. 6). On the lateral radiograph, the talar-first metatarsal angle, talocalcaneal angle, and the distance between the plantar cortex of the medial cuneiform and the floor were measured (Fig. 7).
The pooled radiological data for the 18 patients are shown in Table 1. On the AP projection, there was improvement in all the radiological parameters compared to preoperative values. The lateral talar-first metatarsal angle showed a mean improvement of 13o between the preoperative (-22o) and the postoperative (-9o) radiographs but did not return to the values seen on the unaffected side (-4o). The talonavicular coverage angle also improved overall by 13o and the distance from the medial cuneiform to the floor increased from a mean preoperative value of 9 mm to a mean postoperative value of 16 mm. On an individual basis, the value that showed the most consistent improvement postsurgically was the height of the medial arch as determined by the distance from the medical cuneiform to the floor. From the data in Table 1, a considerable spread in the radiological indices can be observed. This reflects variation in normal foot shape and the superimposed biplanar deformity (collapse of the arch and internal rotation of the forefoot) associated with rupture of the PTT. Patient #11 had corrected rotation but minimal correction of the arch and patient #8 had no change in forefoot rotation but had arch improvement.
The PTT acts to plantarflex the ankle, invert the subtalar joint, and adduct the forefoot with elevation of the medial longitudinal arch. However, when the PTT is insufficient, the weight-bearing portion of the foot is characterized by heel valgus, flattening of the arch, and external rotation of the foot relative to the tibia producing the "too many toes sign".8
Since the first description of the syndrome of PTT rupture by Key in 1953,10 the reported surgical treatment options have varied from simple suture to triple arthrodesis. The results of direct repair are generally poor,6,9 and a tendon transfer was recommended for the treatment of this clinical syndrome.12 The role of tendon transfer in the treatment of this condition is applicable when the joints of the hindfoot and midfoot are still mobile and before there is lateral impingement of the fibula against the calcaneus. Although tendon transfer for PTT insufficiency have been shown to improve symptoms of weakness,fatigue, and ankle pain, there is little, if any, anatomic correction.6-8,12,13
PTT insufficiency has also been treated by a variety of different arthrodeses. Arthrodeses are usually reserved for the more severe deformities that are not completely correctable passively or for those associated with degenerative arthritic changes at the subtalar or midtarsal joints. Arthrodesis options have included isolated talonavicular fusion,18 subtalar fusion,8 talonavicular and calcaneocuboid joint fusion,3 and triple arthrodesis.7,14 Although arthrodesis is indicated for treating a painful deformity that is fixed in valgus, there is an increased stress on adjacent joints.2,4
In addition to arthrodesis, lengthening of the lateral border of the foot by osteotomy through the anterior aspect of the calcaneus has been recommended.1,13,15 Evans5 first suggested this procedure for calcaneal valgus deformities in children and adolescents secondary to poliomyelitis, over-corrected clubfoot deformity, and traumatic injuries to the hindfoot, including remote injuries of the PTT. However, osteotomy of the calcaneus in a similar fashion, as Evans described it, with interposition bone graft has been reported a variety of authors1,13,15 as a treatment for idiopathic flatfeet. A transverse osteotomy through the posterior third of the calcaneus, which is the osteotomy described in the current report, was evidently first described by Gleich in 1893 as reported by Silver et al.17 This osteotomy has been used for the treatment of flatfoot.16 In 1971, Koutsogiannis11 reported on 19 patients with a mean age of 12 years who were treated with a medial displacement osteotomy of the posterior third of the calcaneus for pes planus. He recommended displacement of the osteotomy 1/3 to 1/2 the width of the calcaneus. In patients with mild to moderate flatfoot deformity, the correction of the hindfoot valgus was rewarding, but the medial longitudinal arch was rarely improved; there was no benefit for patients with severe pes planus.
The rationale behind combining a medial displacement osteotomy with a tendon transfer was to realign the valgus heel under the mechanical axis of the leg and reduce the deforming valgus moment of the gastrocnemius-soleus muscle group, thereby reducing the antagonistic forces on the flexor digitorum transfer to produce a more mechanically balanced foot. Conceptually, the combined procedures act as a "double tendon transfer": the Achilles tendon is transferred medially in addition to the FDL transfer to substitute for the degenerated PTT.
Although the majority of the patients in the current study seemed to benefit from this procedure, others did not. Forefoot adduction improved in Patient #11, for example, but sagittal radiographic indices deteriorated. Patient #18 achieved no improvement and is felt to have had a deformity that probably should have been managed with an arthrodesis. There were no predictive preoperative radiographs as to which patients would be expected to achieve a better correction and, therefore, the indications for this procedure are the same as those for a tendon transfer alone. Some patients were also noted to have secondary collapse at the naviculocuneiform joint, and therefore would persist with this deformity after either a simple tendon transfer or the combined procedure.
The relative contribution of the calcaneal osteotomy, tendon transfer, and plication of the talonavicular capsule to the correction of radiographic indices is impossible to determine. Radiographs taken during the first months of flexor tendon transfer alone may also demonstrate improvement in the various arch indices described above.18 Over time, however, the medial longitudinal arch invariably sags, and radiographic measurements return to preoperative values.18 We have yet to determine whether the radiographic improvement we have identified in our patients will remain stable over time, that is, for more than 26 months, currently the longest follow-up period for a patient in this study. No deterioration of the radiographic results was identified in this patient or in any of 5 patients who were evaluated more than 20 months postsurgery.
We conclude that the addition of a medial displacement osteotomy of the calcaneus is a relatively simple procedure that in the current series seems to offer mechanical advantages and has resulted in overall improvement int he radiographic parameters studied, which has not been the experience with tendon transfer alone.
1. Anderson, A.F. and Fowler, S.B. Anterior calcaneal osteotomy for symptomatic juvenile pes planus. Foot Ankle, 4(5):274-283, 1984.
2. Angus, P.D. and Cowell, H.R. Triple arthrodesis. A critical long-term review. J. Bone Joint Surg. 68B(2):260-265, 1986.
3. Baxter, D. and Clain, M. The results of transverse tarsal joint arthrodesis for acquired flatfoot deformity. Presented at the Meeting of the American Orthopaedic Foot and Ankle Society, Asheville (NC), July, 1993.
4. Bennett, G.L., Graham, C.E., and Mauldin, D.M. Triple arthrodesis in adults. Foot Ankle, 12(3):138-143, 1991.
5. Evans, D. Calcaneo-valgus deformity. J. Bone Joint Surg. 57B(3):270-278, 1975.
6. 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(1):95-102, 1986.
7. Jahss, M.H. Spontaneous rupture of the tibialis posterior tendon: clinical findings, tenographic studies, and a new technique of repair. Foot Ankle, 3(3):158-166, 1982.
8. Johnson, K.A. Tibialis posterior tendon rupture. Clin. Orthop. 177(Jul-Aug):140-147, 1983.
9. Kettelkamp, D.B. and Alexander, H.H. Spontaneous rupture of the posterior tibial tendon. J. Bone Joint Surg. 51A:759-764, 1969.
10. Key, J.A. Partial rupture of the tendon of the posterior tibial muscle. J. Bone Joint Surg. 35A:1006-1008, 1953.
11. Koutsogiannis, E. Treatment of mobile flat foot by displacement osteotomy of the calcaneus. J. Bone Joint Surg. 53B:96-100, 1971.
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Fig. 1. The gently curved skin incision is made on the lateral side posterior and in the line of the peroneal tendons, The sural nerve lies anterosuperiorly. The incision is deepened down to the bone and the periosteum is incised in the same plane as the skin incision and is reflected. The osteotomy is at an angle of 45o and is deep to the points of insertion of the Achilles tendon and plantar fascia.
Fig. 2. The osteotomy is displaced medially by 1 cm and fixed with a single lag screw.
Fig. 3. The medial incision for the FDL transfer is in the line of the PTT.
Fig. 4. The talonavicular capsule is plicated either in a vest-over-pants manner or by excising and suturing a vertical ellipse.
Fig. 5. The FDL tendon is passed from plantar to dorsal through the naviculum and is sutures under moderate tension.
Fig. 6. The talonavicular coverage angle was measured as follows. The x -- x line is the edge of the talar articular surface. The y -- y line is subtended from the edges of the naviculum. The subtended perpendicular from each line intersects to give the talonavicular coverage angle.
Fig. 7. The preoperative AP (A) and lateral (B) radiographs demonstrate the talometatarsal angle and the height of the medial cuneiform to the floor. The postoperative AP (C) and lateral (D) radiographs demonstrate improved alignment 29 months later.