Skeletal Radio1 (1992) 21:353 358
Skeletal Radiology
Computed tomography of talocalcaneal coalition: imaging techniques R.J. Wechsler, M.D., D. Karasick, M.D., and M.E. Schweitzer, M.D. Department of Radiology, Jefferson Medical College and Thomas Jefferson University Hospital, Philadelphia, Pennsylvania, USA
Abstract. The diagnosis of symptomatic talocalcaneal coalition requires an imaging study that demonstrates precise anatomic detail. C o m p u t e d t o m o g r a p h y affords the best method for the diagnosis. This essay reviews the computed tomographic a n a t o m y of taloealcaneal coalitions in several projections and stresses the routine use of the angled coronal and direct sagittal projections. Key words: Subtalar j o i n t - Tarsal c o a l i t i o n - C o m p u t e d t o m o g r a p h y - Calcaneus, foot
Tarsal coalitions are an i m p o r t a n t cause of foot pain and deformity, with talocalcaneal and calcaneonavicular coalition being the two m o s t c o m m o n types. Whereas calcaneonavicular coalitions are usually well visualized on conventional radiographs, the nature, location, and extent of talocalcaneal coalitions are best ascertained with computed t o m o g r a p h y (CT) [3-5]. We have found that the angled coronal and direct sagittal projections best demonstrate these coalitions.
Materials and methods CT scans were performed on 36 feet in 18 patients suspected of having a subtalar coalition. The patients ranged in age from 9 to 47 years. The studies were done at our institution between December 1988 and September 1991. At least two projections of the hindf~et were obtained at 5-ram intervals using 5-mm sections. Occasionally, overlapping 3-ram sections were obtained. Osseous coalition was diagnosed when there was complete cortical bridging. Nonosseous coalition was diagnosed when there was joint space narrowing with or without cortical irregularity and irregular cortical bone production [3-5]. Six feet were found to have osseous coalition and 5, nonosseous coalition. Surgical confirmation was available in 4 patients.
Correspondence to: R.J. Wechsler, Department of Radiology, Thomas Jefferson University Hospital, 111 South 1lth Street, Philadelphia, PA 19107, USA
Discussion The true incidence of tarsal coalition in the general population is not known but is probably far less than 1% [8]. Most patients with talocalcaneal coalition are symptomatic, often presenting during puberty. A few who are asymptomatic m a y develop symptoms following traumatic events. Symptoms include the painful peroneal spastic flatfoot. Certain patients have unexplained subtalar or hindfoot pain with diminished subtalar motion. Physical examination usually reveals a p e s planus with forefoot abduction and excessive calcaneal valgus on standing. Like calcaneonavicular bars, talocalcaneal coalitions are often bilateral, with a prevalance as high as 50% in some series [5]. Talocalcaneal coalition ossifies between 12 and 16 years of age, with an average age of 18 years at clinical presentation [8]. Men are more c o m m o n l y affected than women. Because of the relative complexity of the talocalcaneal articulations, understanding of the radiographic anatomy is essential to identify talocalcaneal coalitions. Although the talus and calcaneus articulate via three facets (anterior, middle, and posterior), the anatomic subtalar joint (" posterior subtalar j o i n t " ) consists of the articulation between the posterior calcaneal facet of the talus and the posterior talar facet of the calcaneus (Fig. 1). These posterior faccts are separated from the anterior and middle (medial) facets by the tarsal sinus. The anterior and middle (sustentaculum tall) facets of the calcaneus also articulate with the corresponding talar facets but in a separate synovial articulation. This " a n t e r o m e dial s u b t a l a r " joint is not an independent joint but is continuous with the talocalcaneonavicular joint. Thus, there are two talocalcaneal joints separated by the tarsal sinus : (1) the posterolateral (anatomic) subtalar joint and (2) the anteromedial talocalcaneonavicular joint (Fig. 1) [6]. In rare cases, the facets m a y be confluent [4]. The subtalar articulations are orientated approximately 45 ~ to the plantar surface of the standing foot (Fig. 1). The three forms of tarsal coalition are fibrous (syndesmosis), cartilaginous (synchondrosis), and osseous 9 1992 International Skeletal Society
354
R.J. Wechsler et al. : CT of talocalcaneal coalition
Fig. I A-C. Hindfoot bone specimen: A lateral view; B medial view; C superior view. AP, anterior process of calcaneus; PF, posterior facet of calcaneus; shaded area, bridging anterior and medial facet; solid area, posterior facet; ST, sustentaculum tali; TA, talus; TS, tarsal sinus; TU, calcaneal tuberosity
Fig. 2A-D. Computed tomography (CT) sections in axial plane. Sections A-D are scanned at 3-mm increments from caudad to cephalad. F, fibula; MF, middle facet; N, navicular Fig. 3. Osseous coalition of the anteromedial compartment. CT scan in axial plane reveals complete bony bridging across the middle facet (arrow)
(synostosis). The location o f the majority o f osseous talocalcaneal fusions is at the middle facet between the talus and the sustentaculum tali [5]. In children, a c o m m o n site o f nonosseous subtalar coalition is f o u n d just posterior to the sustentaculum tali [4].
C o n v e n t i o n a l radiographic changes suspicious for talocalcaneal coalition include " b r e a k i n g " o f the talar head. This region o f h y p e r t r o p h i c b o n e f o r m a t i o n reflects a b n o r m a l subtalar m o t i o n and stress. This stress is the result o f repetitive subtle discongruity at the talo-
R.J. Wechsler et al. : CT of talocalcaneal coalition
355
Fig. 4A-D. CT scans in coronal plane. Sections A-D are from anterior to posterior. A, anterior facet; C, calcaneus Fig. g. Coronal section anterior to the anterior facet through the cuboid navicular joint. Note the oblong configuration on the navicular as compared with the rounded shape of the talus in Fig. 4A. CU, cuboid
Fig. 6. Nonosseous coalition of middle facet in coronal plane. Joint space narrowing with sclerosis and cortical irregularity (arrows) is noted Fig. 7. Bilateral subtarsal coalitions. Coronal view reveals anteromedial bony coalition on the right with cortical bridging (arrows). There is nonosseous coalition of the left anteromedial compartment with joint space narrowing, sclerosis, and subchondral cyst formation (open arrows)
navicular articulation and subsequent periosteal elevation [5]. Additional routine radiographic signs of coalition include broadening of the lateral process of the talus and narrowing of the posterior talocalcaneal joint. The former is a result o f restricted subtalar motion. Conventional tomography and axial (Harris) views may both demonstrate talocalcaneal coalition but are less precise than CT in evaluating the extent of coalition and degree of associated degenerative arthritis. CT is an ideal modality for demonstrating subtalar coalition. The terminology used in this paper describes imaging planes of the foot with the foot dorsiflexed 90 ~ Therefore, the axial plane of the ankle will be imaged along the longitudinal axis of the foot plane. The coronal plane o f the ankle will demonstrate the toes in cross section, plantar to dorsal. The sagittal plane produces images along the long arch of the foot, perpendicular to the coronal plane.
CT sections in the axial (plantar) plane demonstrate the anteromedial articulation at the level of the sustentaculum tali just medial to the tarsal sinus. More cephalad, the posterior facet of the subtalar joint is lateral to the tarsal sinus. On more cranial images, the middle facet and posterior facet may converge, with only the posterior facet seen on the most cephalad images (Fig. 2) [2]. Osseous coalitions are manifest by continuity of adjacent marrow cavities or by complete cortical bridging (Fig. 3). Nonosseous coalitions appear as areas of joint space narrowing, sometimes with marginal cortical irregularity and/or irregular hypertrophic cortical reactive bone [4]. Direct nonreformatted coronal CT can be obtained with the patient lying supine and the hips and knees flexed to allow the legs to clear the gantry opening [1]. Scans are obtained perpendicular to the plantar surface. The most anterior sections reveal the talus articulating
356
R.J. Wechsleret al. : CT of talocalcaneal coalition
Fig. 8. Angled coronal projection. To obtain this view, the gantry is angled perpendicular to the plane of the subtalar joint. This is also along the long axis of the calcaneal tuberosity (TU) Fig. 9A-C. CT sections in angled coronal plane. Sections A-C ranging from more caudad to cephalad
Fig. 10A, B. Angled coronal view reveals osseous bridging of the medial facet (black arrows) with slight narrowing of the posterior facet (open arrows) (A) and nonosseous coalition of the medial facet (arrows (B)
with the anterior process of the calcaneus (Fig. 4). The anterior facet can be recognized when the talus appears rounded on these images. This appearance differentiates it from images of the cuboid navicular joint (Fig. 5) [3]. More posteriorly, the middle subtalar joint is visualized just above the sustentaculum tali. The posterior subtalar joint is lateral to the tarsal sinus (Fig. 4C). On more posterior sections, the posterior facet of the calcaneus is well seen (Fig. 4D). Both nonosseous (Fig. 6) and osseous coalitions can be appreciated with this projection. When the anteromedial joint is not horizontal in this projection but is slanted down and hypertrophied, a nonosseous coalition can be diagnosed (Fig. 7). An angled coronal projection (tuberosity plane) is more useful than the axial or coronal projections [2]. This scan is obtained by placing the feet in the gantry with knees bent and the feet slightly plantar flexed. The gantry is angled perpendicular to the plane of the subtalar joint by using the lateral digital view (Fig. 8). The plane of this scan is generally halfway between the axial and coronal planes and cuts the tuberosity along its long
axis. These sections demonstrate both the posterior and middle facets to best advantage because the greater part of these articulations is nearly perpendicular to the plane of the scan, whereas in the plantar and axial planes, the facets more closely parallel the corresponding imaging plane [2]. The most caudad sections reveal the anteromedial (talocalcaneonavicular joint) and posterolateral subtalar joint separated by the tarsal sinus. Cephalad sections above and posterior to the sustentaculum demonstrate the posterior facet (Fig. 9). Subtalar coalitions are easily seen in this plane (Fig. 10). Direct nonreformatted sagittal CT scans can be obtained on most patients. This is done by having the patient sit on the table parallel to the gantry with the involved foot closest to the gantry. The plantar surface of the foot is placed closest to the table with the long axis parallel to the gantry. The foot is inverted to keep the knee out of the gantry (Fig. 11). Through the midportion of the tarsal sinus, the anteromedial subtalar portion of the talocalcaneonaviscular joint is separated from the posterolateral subtalar joint (Fig. 12). This is
R.J. Wechsler et al. : CT of talocalcaneal coalition
Fig. llA-C. Technique for obtaining direct sagittal CT. A Patient seated on CT table parallel to gantry. Patient knee is flexed with the foot placed on the table. B The foot is inverted as it is placed within the gantry in order to keep the knee out of the gantry. C View from opposite side of gantry
357
Fig. 13. Direct sagittal CT reveals nonosseous anteromedial compartment coalition. Note narrowing, cortical irregularity, and sclerosis of anteromedial compartment (arrows) Fig. 14. Sagittal CT of calcaneus. Note subchondral cyst formation of the anterior process of the calcaneus (arrow)
Fig. 12A-C. CT sections in sagittal planes. Sections A-C are from medial to lateral
the only view in which the anterior facet as such can be clearly delineated. Talar coalitions are ideally seen in this projection (Fig. 13). This projection is helpful in evaluating other calcaneonavicular joint abnormalities (Fig. 14). The ability o f C T to display the complex a n a t o m y o f the talocalcaneal joint has i m p r o v e d the diagnostic evaluation o f patients with talocalcaneal coalitions. The
n o n r e f o r m a t t e d angled c o r o n a l and sagittal projections a p p e a r to be m o s t useful in d e m o n s t r a t i n g the nature and location o f these coalitions. W h e n these projections are obtained, the other available projections are n o t deemed necessary. T h e y allow a m o r e accurate assessm e n t o f joint width and extent o f coalition, thereby influencing treatment options [7].
358
References 1. Bower BL, Keyser CK, Gilula LA (1989) Rigid subtalar joint - a radiographic spectrum. Skeletal Radiol 17:583 2. Heger L, Wulff K (1985) Computed tomography of the calcaneus: normal anatomy. AJR 145:123 3. Herzenberg JE, Goldner JL, Martinez S, Silverman PS (1986) Computerized tomography of talocalcaneal tarsal coalition: a clinical and anatomic study. Foot Ankle 6:273
R.J. Wechsler et al. : CT of talocalcaneal coalition 4. Lee MS, Harcke HT, Kumar SJ, Bassett GS (1989) Subtalar joint coalition in children: new observations. Radiology 172: 635 5. Percy EL, Mann DL (1988) Tarsal coalition: a review of the literature and presentation of 13 cases. Foot Ankle 9 : 40 6. Resnick D (1974) Radiology of the talocalcaneal articulations: anatomic considerations and arthrography. Radiology 111 : 581 7. Scranton PE (1987) Treatment of symptomatic talocalcaneal coalition. J Bone Joint Surg [Am] 69:533 8. Stormont DM, Peterson HA (1983) The relative incidence of tarsal coalition. Clin Orthop 181:28
Skeletal Radiology
Computed tomography of talocalcaneal coalition: imaging techniques R.J. Wechsler, M.D., D. Karasick, M.D., and M.E. Schweitzer, M.D. Department of Radiology, Jefferson Medical College and Thomas Jefferson University Hospital, Philadelphia, Pennsylvania, USA
Abstract. The diagnosis of symptomatic talocalcaneal coalition requires an imaging study that demonstrates precise anatomic detail. C o m p u t e d t o m o g r a p h y affords the best method for the diagnosis. This essay reviews the computed tomographic a n a t o m y of taloealcaneal coalitions in several projections and stresses the routine use of the angled coronal and direct sagittal projections. Key words: Subtalar j o i n t - Tarsal c o a l i t i o n - C o m p u t e d t o m o g r a p h y - Calcaneus, foot
Tarsal coalitions are an i m p o r t a n t cause of foot pain and deformity, with talocalcaneal and calcaneonavicular coalition being the two m o s t c o m m o n types. Whereas calcaneonavicular coalitions are usually well visualized on conventional radiographs, the nature, location, and extent of talocalcaneal coalitions are best ascertained with computed t o m o g r a p h y (CT) [3-5]. We have found that the angled coronal and direct sagittal projections best demonstrate these coalitions.
Materials and methods CT scans were performed on 36 feet in 18 patients suspected of having a subtalar coalition. The patients ranged in age from 9 to 47 years. The studies were done at our institution between December 1988 and September 1991. At least two projections of the hindf~et were obtained at 5-ram intervals using 5-mm sections. Occasionally, overlapping 3-ram sections were obtained. Osseous coalition was diagnosed when there was complete cortical bridging. Nonosseous coalition was diagnosed when there was joint space narrowing with or without cortical irregularity and irregular cortical bone production [3-5]. Six feet were found to have osseous coalition and 5, nonosseous coalition. Surgical confirmation was available in 4 patients.
Correspondence to: R.J. Wechsler, Department of Radiology, Thomas Jefferson University Hospital, 111 South 1lth Street, Philadelphia, PA 19107, USA
Discussion The true incidence of tarsal coalition in the general population is not known but is probably far less than 1% [8]. Most patients with talocalcaneal coalition are symptomatic, often presenting during puberty. A few who are asymptomatic m a y develop symptoms following traumatic events. Symptoms include the painful peroneal spastic flatfoot. Certain patients have unexplained subtalar or hindfoot pain with diminished subtalar motion. Physical examination usually reveals a p e s planus with forefoot abduction and excessive calcaneal valgus on standing. Like calcaneonavicular bars, talocalcaneal coalitions are often bilateral, with a prevalance as high as 50% in some series [5]. Talocalcaneal coalition ossifies between 12 and 16 years of age, with an average age of 18 years at clinical presentation [8]. Men are more c o m m o n l y affected than women. Because of the relative complexity of the talocalcaneal articulations, understanding of the radiographic anatomy is essential to identify talocalcaneal coalitions. Although the talus and calcaneus articulate via three facets (anterior, middle, and posterior), the anatomic subtalar joint (" posterior subtalar j o i n t " ) consists of the articulation between the posterior calcaneal facet of the talus and the posterior talar facet of the calcaneus (Fig. 1). These posterior faccts are separated from the anterior and middle (medial) facets by the tarsal sinus. The anterior and middle (sustentaculum tall) facets of the calcaneus also articulate with the corresponding talar facets but in a separate synovial articulation. This " a n t e r o m e dial s u b t a l a r " joint is not an independent joint but is continuous with the talocalcaneonavicular joint. Thus, there are two talocalcaneal joints separated by the tarsal sinus : (1) the posterolateral (anatomic) subtalar joint and (2) the anteromedial talocalcaneonavicular joint (Fig. 1) [6]. In rare cases, the facets m a y be confluent [4]. The subtalar articulations are orientated approximately 45 ~ to the plantar surface of the standing foot (Fig. 1). The three forms of tarsal coalition are fibrous (syndesmosis), cartilaginous (synchondrosis), and osseous 9 1992 International Skeletal Society
354
R.J. Wechsler et al. : CT of talocalcaneal coalition
Fig. I A-C. Hindfoot bone specimen: A lateral view; B medial view; C superior view. AP, anterior process of calcaneus; PF, posterior facet of calcaneus; shaded area, bridging anterior and medial facet; solid area, posterior facet; ST, sustentaculum tali; TA, talus; TS, tarsal sinus; TU, calcaneal tuberosity
Fig. 2A-D. Computed tomography (CT) sections in axial plane. Sections A-D are scanned at 3-mm increments from caudad to cephalad. F, fibula; MF, middle facet; N, navicular Fig. 3. Osseous coalition of the anteromedial compartment. CT scan in axial plane reveals complete bony bridging across the middle facet (arrow)
(synostosis). The location o f the majority o f osseous talocalcaneal fusions is at the middle facet between the talus and the sustentaculum tali [5]. In children, a c o m m o n site o f nonosseous subtalar coalition is f o u n d just posterior to the sustentaculum tali [4].
C o n v e n t i o n a l radiographic changes suspicious for talocalcaneal coalition include " b r e a k i n g " o f the talar head. This region o f h y p e r t r o p h i c b o n e f o r m a t i o n reflects a b n o r m a l subtalar m o t i o n and stress. This stress is the result o f repetitive subtle discongruity at the talo-
R.J. Wechsler et al. : CT of talocalcaneal coalition
355
Fig. 4A-D. CT scans in coronal plane. Sections A-D are from anterior to posterior. A, anterior facet; C, calcaneus Fig. g. Coronal section anterior to the anterior facet through the cuboid navicular joint. Note the oblong configuration on the navicular as compared with the rounded shape of the talus in Fig. 4A. CU, cuboid
Fig. 6. Nonosseous coalition of middle facet in coronal plane. Joint space narrowing with sclerosis and cortical irregularity (arrows) is noted Fig. 7. Bilateral subtarsal coalitions. Coronal view reveals anteromedial bony coalition on the right with cortical bridging (arrows). There is nonosseous coalition of the left anteromedial compartment with joint space narrowing, sclerosis, and subchondral cyst formation (open arrows)
navicular articulation and subsequent periosteal elevation [5]. Additional routine radiographic signs of coalition include broadening of the lateral process of the talus and narrowing of the posterior talocalcaneal joint. The former is a result o f restricted subtalar motion. Conventional tomography and axial (Harris) views may both demonstrate talocalcaneal coalition but are less precise than CT in evaluating the extent of coalition and degree of associated degenerative arthritis. CT is an ideal modality for demonstrating subtalar coalition. The terminology used in this paper describes imaging planes of the foot with the foot dorsiflexed 90 ~ Therefore, the axial plane of the ankle will be imaged along the longitudinal axis of the foot plane. The coronal plane o f the ankle will demonstrate the toes in cross section, plantar to dorsal. The sagittal plane produces images along the long arch of the foot, perpendicular to the coronal plane.
CT sections in the axial (plantar) plane demonstrate the anteromedial articulation at the level of the sustentaculum tali just medial to the tarsal sinus. More cephalad, the posterior facet of the subtalar joint is lateral to the tarsal sinus. On more cranial images, the middle facet and posterior facet may converge, with only the posterior facet seen on the most cephalad images (Fig. 2) [2]. Osseous coalitions are manifest by continuity of adjacent marrow cavities or by complete cortical bridging (Fig. 3). Nonosseous coalitions appear as areas of joint space narrowing, sometimes with marginal cortical irregularity and/or irregular hypertrophic cortical reactive bone [4]. Direct nonreformatted coronal CT can be obtained with the patient lying supine and the hips and knees flexed to allow the legs to clear the gantry opening [1]. Scans are obtained perpendicular to the plantar surface. The most anterior sections reveal the talus articulating
356
R.J. Wechsleret al. : CT of talocalcaneal coalition
Fig. 8. Angled coronal projection. To obtain this view, the gantry is angled perpendicular to the plane of the subtalar joint. This is also along the long axis of the calcaneal tuberosity (TU) Fig. 9A-C. CT sections in angled coronal plane. Sections A-C ranging from more caudad to cephalad
Fig. 10A, B. Angled coronal view reveals osseous bridging of the medial facet (black arrows) with slight narrowing of the posterior facet (open arrows) (A) and nonosseous coalition of the medial facet (arrows (B)
with the anterior process of the calcaneus (Fig. 4). The anterior facet can be recognized when the talus appears rounded on these images. This appearance differentiates it from images of the cuboid navicular joint (Fig. 5) [3]. More posteriorly, the middle subtalar joint is visualized just above the sustentaculum tali. The posterior subtalar joint is lateral to the tarsal sinus (Fig. 4C). On more posterior sections, the posterior facet of the calcaneus is well seen (Fig. 4D). Both nonosseous (Fig. 6) and osseous coalitions can be appreciated with this projection. When the anteromedial joint is not horizontal in this projection but is slanted down and hypertrophied, a nonosseous coalition can be diagnosed (Fig. 7). An angled coronal projection (tuberosity plane) is more useful than the axial or coronal projections [2]. This scan is obtained by placing the feet in the gantry with knees bent and the feet slightly plantar flexed. The gantry is angled perpendicular to the plane of the subtalar joint by using the lateral digital view (Fig. 8). The plane of this scan is generally halfway between the axial and coronal planes and cuts the tuberosity along its long
axis. These sections demonstrate both the posterior and middle facets to best advantage because the greater part of these articulations is nearly perpendicular to the plane of the scan, whereas in the plantar and axial planes, the facets more closely parallel the corresponding imaging plane [2]. The most caudad sections reveal the anteromedial (talocalcaneonavicular joint) and posterolateral subtalar joint separated by the tarsal sinus. Cephalad sections above and posterior to the sustentaculum demonstrate the posterior facet (Fig. 9). Subtalar coalitions are easily seen in this plane (Fig. 10). Direct nonreformatted sagittal CT scans can be obtained on most patients. This is done by having the patient sit on the table parallel to the gantry with the involved foot closest to the gantry. The plantar surface of the foot is placed closest to the table with the long axis parallel to the gantry. The foot is inverted to keep the knee out of the gantry (Fig. 11). Through the midportion of the tarsal sinus, the anteromedial subtalar portion of the talocalcaneonaviscular joint is separated from the posterolateral subtalar joint (Fig. 12). This is
R.J. Wechsler et al. : CT of talocalcaneal coalition
Fig. llA-C. Technique for obtaining direct sagittal CT. A Patient seated on CT table parallel to gantry. Patient knee is flexed with the foot placed on the table. B The foot is inverted as it is placed within the gantry in order to keep the knee out of the gantry. C View from opposite side of gantry
357
Fig. 13. Direct sagittal CT reveals nonosseous anteromedial compartment coalition. Note narrowing, cortical irregularity, and sclerosis of anteromedial compartment (arrows) Fig. 14. Sagittal CT of calcaneus. Note subchondral cyst formation of the anterior process of the calcaneus (arrow)
Fig. 12A-C. CT sections in sagittal planes. Sections A-C are from medial to lateral
the only view in which the anterior facet as such can be clearly delineated. Talar coalitions are ideally seen in this projection (Fig. 13). This projection is helpful in evaluating other calcaneonavicular joint abnormalities (Fig. 14). The ability o f C T to display the complex a n a t o m y o f the talocalcaneal joint has i m p r o v e d the diagnostic evaluation o f patients with talocalcaneal coalitions. The
n o n r e f o r m a t t e d angled c o r o n a l and sagittal projections a p p e a r to be m o s t useful in d e m o n s t r a t i n g the nature and location o f these coalitions. W h e n these projections are obtained, the other available projections are n o t deemed necessary. T h e y allow a m o r e accurate assessm e n t o f joint width and extent o f coalition, thereby influencing treatment options [7].
358
References 1. Bower BL, Keyser CK, Gilula LA (1989) Rigid subtalar joint - a radiographic spectrum. Skeletal Radiol 17:583 2. Heger L, Wulff K (1985) Computed tomography of the calcaneus: normal anatomy. AJR 145:123 3. Herzenberg JE, Goldner JL, Martinez S, Silverman PS (1986) Computerized tomography of talocalcaneal tarsal coalition: a clinical and anatomic study. Foot Ankle 6:273
R.J. Wechsler et al. : CT of talocalcaneal coalition 4. Lee MS, Harcke HT, Kumar SJ, Bassett GS (1989) Subtalar joint coalition in children: new observations. Radiology 172: 635 5. Percy EL, Mann DL (1988) Tarsal coalition: a review of the literature and presentation of 13 cases. Foot Ankle 9 : 40 6. Resnick D (1974) Radiology of the talocalcaneal articulations: anatomic considerations and arthrography. Radiology 111 : 581 7. Scranton PE (1987) Treatment of symptomatic talocalcaneal coalition. J Bone Joint Surg [Am] 69:533 8. Stormont DM, Peterson HA (1983) The relative incidence of tarsal coalition. Clin Orthop 181:28
