Talocalcaneal Tarsal Coalition
1. Definition—Developmental mal-deformation
a. Autosomal dominant failure of mesenchymal differentiation and segmentation that leads to a progressive, postnatal synchondrosis-to-synostosis of the middle facet (usually, but can be posterior facet) of the subtalar joint
i. with the gradual development of a rigid flatfoot (though neutral and varus hindfoot alignments have been reported) usually between the ages of 8 and 16 years
ii. and, in many cases, associated with secondary hypermobility of Chopart joints that can give the false impression of subtalar joint mobility when none exists (see Assessment Principle #10, Figures 3-10and 3-11, Chapter 3)
Figure 5-47. Painful skewfoot in a 13-year-old boy. A. AP view showing skew, or zig-zag, deformity. B. Laminar spreader in anterior calcaneus osteotomy showing good correction of talonavicular joint subluxation. Note apparent exaggeration of forefoot adductus. Medial cuneiform is trapezoid-shaped with proximal and distal joints converging medially. A transverse osteotomy has been made at the waist of the medial cuneiform. C. Hatched area highlights calcaneal graft. Medial cuneiform graft is well seen. Talus and first MT lines are now parallel. D. Lateral preoperative radiograph showing skew, or zig-zag, deformity in this plane as well. E. Postoperative correction of midfoot sag and low calcaneal pitch. Slight residual dorsal translation of MT line is due to mild midtarsal cavus. (From Mosca VS. Flexible Flatfoot and Skewfoot. In: Drennan JC, ed. The Child’s Foot and Ankle. New York: Raven; 1992:373, Figure 17.18.) (From the private collection of Vincent S. Mosca, MD.)
2. Elucidation of the segmental deformities
a. Forefoot—supinated
b. Midfoot—neutral or abducted
c. Hindfoot—valgus/everted or neutral (less common) or varus/inverted (rarely)
d. Ankle—plantar flexed (equinus) or neutral
3. Imaging
a. Standing AP, lateral, oblique, and Harris axial of foot (Figure 5-48)
b. CT scan in sagittal, coronal, and transverse planes, and with 3D reconstruction (see Assessment Principle #22, Figure 3-28, Chapter 3)
i. The coronal image is most important (Figure 5-49).
4. Natural history
a. Gradual development of a rigid flatfoot (though neutral and varus hindfoot alignments have been reported) usually between the ages of 8 and 16 years
b. Pain, in less than 25% of cases, that can be located at one or more of the following locations:
i. the site of the coalition
ii. under the head of the talus
iii. in the sinus tarsi area
iv. in or around the ankle joint
v. in Chopart joints
c. Recurrent ankle sprains, with or without any of the above, in some cases
Figure 5-48. Standing radiographs of a foot with a middle facet talocalcaneal tarsal coalition. A. AP radiograph shows a flatfoot, indicated by lateral positioning of the navicular on the head of the talus and with the foot-CORA in the head of the talus (see Assessment Principle #18, Figure 3-19, Chapter 3). B. Lateral radiograph shows a dorsal talar beak (white arrow), which is often found in a foot with a talocalcaneal tarsal coalition. It represents a traction spur, not degenerative arthritis of the talonavicular or subtalar joint. The C-sign of Lateur (white semicircular bone density just inside the yellow “C”) is a radiographic shadow that strongly indicates a middle facet talocalcaneal tarsal coalition. It is created by the continuity of the subchondral bone of the talar dome (talus) with the posterior aspect of the middle facet coalition (talus and calcaneus) and the bony roof of the sustentaculum tali (calcaneus). C. Harris axial radiograph shows a narrow, down-sloping, and irregular middle facet (white arrow), which are characteristics of a coalition.
5. Nonoperative treatment
a. For asymptomatic coalitions (at least 75% of cases)—None indicated
b. For activity-related pain
i. Activity modification, including temporary discontinuation of the pain-inducing activity
ii. Nonsteroidal anti-inflammatory drugs (NSAIDs)
iii. Immobilization in a CAM boot or cast for at least 6 weeks
6. Operative indications
a. Failure of nonoperative treatment to relieve pain that can be located at one or more of the following locations:
i. the site of the coalition
ii. under the head of the talus
iii. in the sinus tarsi area
iv. in or around the ankle joint
v. in Chopart joints
b. Failure of nonoperative treatment to prevent recurrent ankle sprains
Figure 5-49. Coronal slice CT scan image shows the three criteria for resectability of a talocalcaneal tarsal coalition according to Wilde, Torode, et al. (1994): (1) the ratio of the surface area of the coalition of the middle facet (yellow oval) to the surface area of the posterior facet should be less than 50%; (2) there should be no narrowing of the posterior facet (short green arrow) when compared to the cartilage height of the ankle joint (long green arrow); (3) there should be less than 16° of hindfoot valgus measured between the axis of the calcaneus and the line perpendicular to the ankle joint (indicated by the yellow arc). None of the three criteria for resectability are met on this image.
7. Operative treatment with reference to the surgical techniques section of the book for each individual procedure (according to Mosca and Bevan, JBJS 2012)
a. Middle facet talocalcaneal tarsal coalition resection with interposition fat grafting (see Chapter 8)
i. Perform this for a resectable coalition (defined as a middle facet coalition that is less than 50% the surface area of the posterior facet in a foot with a normal posterior facet) in a foot with less than 16° hindfoot valgus and with pain at the site of the coalition
b. Middle facet talocalcaneal tarsal coalition resection with interposition fat grafting (see Chapter 8) and concurrent (preferred) or staged calcaneal lengthening osteotomy (see Chapter 8) and gastrocnemius recession (see Chapter 7) or tendo-Achilles lengthening (see Chapter 7), as determined by the intraoperative Silfverskiold test (see Figure 3-13, Chapter 3)
i. Perform this for a resectable coalition (defined as a middle facet coalition that is less than 50% the surface area of the posterior facet in a foot with a normal posterior facet) in a foot with more than 16° hindfoot valgus and with pain at the site of the coalition and/or in the sinus tarsi (due to impingement) and/or under the talar head in the midfoot (due to the flatfoot deformity combined with a tight heel cord)
c. Calcaneal lengthening osteotomy (see Chapter 8) and gastrocnemius recession (see Chapter 7) or tendo-Achilles lengthening (see Chapter 7), as determined by the intraoperative Silfverskiold test (see Figure 3-13, Chapter 3)
i. Perform this for an irresectable coalition (defined as a middle facet coalition that is greater than 50% the surface area of the posterior facet and with a narrow posterior facet) in a foot with more than 16° hindfoot valgus and with pain under the talar head in the midfoot (due to the flatfoot deformity combined with a tight heel cord) and/or in the sinus tarsi (due to impingement) It does not make sense to resect a middle facet coalition if there is “significant” narrowing of the posterior facet. The histologic and radiographic manifestations of arthritis (degenerative joint disease) are thinning of the articular cartilage. Resection of a middle facet coalition will reestablish motion in a painless (because of immobility) posterior facet and, potentially, create pain.
Calcaneonavicular Tarsal Coalition
1. Definition—Developmental mal-deformation
a. Autosomal dominant failure of mesenchymal differentiation and segmentation that leads to a progressive, postnatal synchondrosis-to-synostosis between the navicular and the beak of the calcaneus
i. with the gradual development of a stiff/rigid flatfoot (though neutral and varus hindfoot alignments have been reported) usually between the ages of 8 and 16 years
2. Elucidation of the segmental deformities
a. Forefoot—supinated
b. Midfoot—neutral or abducted
c. Hindfoot—valgus/everted or neutral (less common) or varus/inverted (rarely)
d. Ankle—plantar flexed (equinus) or neutral
Figure 5-50. Radiographs of feet with CN tarsal coalitions. A. Fibrocartilaginous coalition (yellow arrow). B. Ossified coalition (yellow arrow). C. “Anteater nose” sign (bracketed by yellow arcs), representing radiographic appearance of the conjoined navicular and anterior calcaneus. D. AP view, often minimally helpful with diagnosis, because the coalition is out of the plane of the x-ray beam. E. Harris axial view shows normal middle facet of the talocalcaneal joint (dashed yellow arrow). Black dashed arrow identifies normal posterior facet. This is important information to ascertain, because both coalitions may exist in one foot. A CT scan is necessary for definitive confirmation of the preliminary x-ray evaluation of the subtalar joint.
3. Imaging
a. Standing AP, lateral, oblique, and Harris axial of foot (Figure 5-50)
b. CT scan in sagittal, coronal, and transverse planes, and with 3D reconstruction (Figure 5-51)
4. Natural history
a. Gradual development of a stiff/rigid flatfoot (though neutral and varus hindfoot alignments have been reported) usually between the ages of 8 and 16 years
b. Pain, in less than 25% of cases, that can be located at one or more of the following locations:
i. the site of the coalition
ii. under the head of the talus
iii. in the sinus tarsi area
iv. in or around the ankle joint
v. in Chopart joints
c. Recurrent ankle sprains with or without any of the above
Figure 5-51. CT scan images of a CN tarsal coalition. In a normal foot, there is no bone or cartilage connection between the calcaneus and navicular. In this foot with a CN tarsal coalition, there is a narrow, sclerotic, and irregular pseudo-articulation between those bones that is composed of fibro-cartilage (circled). A. Transverse view. B. Sagittal view. C. Coronal view. D. and E. 3D reconstructions. F. Coronal view of subtalar joint confirming that there is not a coincident talocalcaneal middle facet coalition.
5. Nonoperative treatment
a. For asymptomatic coalitions (at least 75% of cases)—none indicated
b. For activity-related pain
i. Activity modification, including temporary discontinuation of the pain-inducing activity
ii. NSAIDs
iii. Immobilization in CAM boot or cast for at least 6 weeks
6. Operative indications
a. Failure of nonoperative treatment to relieve pain that can be located at one or more of the following locations:
i. the site of the coalition
ii. under the head of the talus
iii. in the sinus tarsi area
iv. in or around the ankle joint
v. in Chopart joints
b. Failure of nonoperative treatment to prevent recurrent ankle sprains
7. Operative treatment with reference to the surgical techniques section of the book for each individual procedure
a. Calcaneonavicular (CN) tarsal coalition resection with interposition fat grafting (see Chapter 8)
i. Perform this for a resectable coalition (defined as a fibrocartilaginous coalition) in a foot with minimal (or no) hindfoot valgus and with pain at the site of the coalition
b. CN tarsal coalition resection with interposition fat grafting (see Chapter 8) and staged (or concurrent) calcaneal lengthening osteotomy (see Chapter 8) and gastrocnemius recession (see Chapter 7) or tendo-Achilles lengthening (see Chapter 7), as determined by the intraoperative Silfverskiold test (see Figure 3-13, Chapter 3)
i. Perform this for a resectable coalition (defined as a fibrocartilaginous coalition) in a foot with “significant” hindfoot valgus and with pain at the site of the coalition and/or in the sinus tarsi (due to impingement) and/or under the talar head in the midfoot (due to the flatfoot deformity combined with a tight heel cord)
c. Calcaneal lengthening osteotomy (see Chapter 8) and gastrocnemius recession (see Chapter 7) or tendo-Achilles lengthening (see Chapter 7), as determined by the intraoperative Silfverskiold test (see Figure 3-13, Chapter 3)
i. Perform this for an irresectable coalition (defined as an osseous coalition) in a foot with “significant” hindfoot valgus and with pain under the talar head in the midfoot (due to the flatfoot deformity combined with a tight heel cord) and/or in the sinus tarsi (due to impingement).