Received: 6 May 2002Revised: 12 July 2002Accepted: 30 July 2002Published online: 2 October 2002© Springer-Verlag 2002

Abstract A case of unilateral ball-and-socket ankle joint associatedwith short limb and hypoplastic sus-tentaculum tali is reported. We thinkthat hypoplastic sustentaculum taliwas the cardinal feature in the ana-tomical and kinematic alterations ofthe foot in this patient. We reviewthe embryonic development of hind-foot to ascertain the possible originof this unusual finding.

Keywords Ball-and-socket anklejoint · Sustentaculum tali · Ankle ·Calcaneus abnormalities

Eur Radiol (2002) 12:S48–S50DOI 10.1007/s00330-002-1666-x M U S C U L O S K E L E TA L

Fernando Ruiz SantiagoCelestino Picazo MorenoLuis Cañadillas BareaErnesto García Bautista

Ball-and-socket ankle joint with hypoplasticsustentaculum tali

Introduction

The ball-an-socket ankle joint (BSAJ) is a well-knownentity in orthopedic and radiology literature character-ized by a spherical articulation between the tibia and thetalus [1, 2]. It is supposed to be an adaptive response toeither congenital or acquired foot abnormalities. Themore frequent congenital type results from an overallmisdevelopment of the ankle and foot including local ab-normalities such as tarsal coalition or ray alterations. Ac-quired forms have been described after surgical proce-dures of the hindfoot [2]. To our knowledge, no previousreport has described the hypoplastic sustentaculum taliand its morphological and functional significance in thedevelopment of this entity.

Case report

A 15-year-old boy came to the orthopedic surgeon complaining ofmild and intermittent right ankle pain. Symptoms presented spo-

radically during years, developing after prolonged normal dailyactivities such as walking or running.

Physical examination revealed a right varus heel and metatar-sus with slight supination of foot during walking. X-ray film dem-

F.R. Santiago (✉) · C.P. MorenoL.C. Barea · E.G. BautistaDepartment of Radiology, Hospital of Traumatology (Ciudad Sanitaria Virgen de las Nieves),Carretera de Jaen SN, 18013 Granada,Spaine-mail: ferruizsan@terra.es

Present address:F. Ruiz Santiago, C-Julio Verne 8, 7B,18003 Granada, Spain

Fig. 1 Anteroposterior X-ray film of both ankles shows on theright side a shortening of the leg and the typical features of a ball-and-socket ankle joint

agent. We think that this feature was of great importancein the morphological anatomy and functional impairmentof the foot in this patient.

We think that the rounded talar shape was secondaryto the disturbed or increased ankle mobility. This mecha-nism has also been involved in patients with ankle insta-bility in Larsen syndrome, poliomyelitis, and congenitalinsensitivity to pain [2, 3]. Even when tarsal coalitiondoes exist, the loss of subtalar joint motion will lead toan increased stress at the tibiotalar joint level. In everycase it is important that the promoting agent act beforethe 5 years of age when talocrural joint is still immature,with a high remodeling capacity [4]. Pathological pro-cesses that disturb ankle mobility after this age do notlead to significant morphological changes of the talardome [5].

In our case, the lack of sustentacular facet constraintto talar head may be compared to the denominated“stripped bold” described by Bruckner for individualswith continuous medial and anterior facets of the calca-neus [6]. In both cases, medial rotation of the talar headincreases leading to ligamentous laxity and unstable foot,promoting the development of the “ball-and-socket” de-formity.

Embryology explains the early fetal origin of this fea-ture. The talus and calcaneus begin to chondrify at theseventh week of embryonic development. The sustentac-ulum tali is formed from a cellular condensation betweenthese two cartilaginous anlages at the eighth week andsoon after becomes part of the cartilaginous body of theos calci [7]. It functions as a bracket that supports the ta-lar head and its variations are reflected in the morpholo-gy of the talus [8].

Ossification of the sustentaculum tali begins at ap-proximately 5 years of age but is not complete for atleast another 1–2 years [9]. When fully developed, it canrange from an elliptical to triangular form measuring ap-proximately 22 mm in length and 14 mm in width. It canbe classified as long or short. In the first case it is contin-uous with the anterior process, leading to fusion of themiddle and anterior calcaneal facets. In the second caseit has an abrupt anterior border separated from the anteri-or process by a notch [10].

Bones, like other biological organs, should show anallometric growth or harmonic relationship between theshape of its different parts and related elements [11]. Wethink that in our case the calcaneus merits attention be-cause it is the only affected bone that does no keep thenormal proportion between its parts, the body, and thesustentaculum tali. Two possible explanations are pro-posed: firstly, a lesion on the cellular anlage of susten-taculum tali that results in small or reduced growth ofthis apophysis leading to secondary deformity of sur-roundings structures. The second possibility may be anabnormal fitness of bones of hindfoot with overload onthe sustentaculum tali when the child begins to walk. But

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onstrated a shortening of the tibia of 1.5 cm and the characteristicfeatures of a BSAJ (Figs. 1, 2). The trochlear surface of the taluswas hemispherical and convex. The tibial articular surface showeda reciprocal congruent concavity. The sulcus tali was flattened andthe subtalar joint was in horizontal position and straightened. Inorder to depict all bone abnormalities, a CT scan was performed.Bone coalition was excluded and a small calcaneus with hypoplas-tic sustentaculum tali was demonstrated (Fig. 3). Physical examand bone survey of whole upper and lower extremities excludedother bone abnormalities.

Discussion

Congenital BSAJ has been associated with short limb,tarsal coalition, absence of rays, and hypoplasia of thefibula [1]. To our knowledge, no previous report has de-scribed the hypoplastic sustentaculum tali as a related

Fig. 2 Lateral X-ray film of the right ankle demonstrates a round-ed dorsal aspect of the talus, a flattened sulcus tali, and a straight-ened subtalar articulation

Fig. 3 Axial computed tomography of both feet from superior toinferior depicting the hypoplastic sustentaculum tali on the rightside

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in the latter case, bone hypertrophy and degenerativechanges should be expected. Then, the lack of reactivebone changes fit better with the congenital origin of thisfeature. The damaging agent probably acted when thedevelopment of sustentaculum tali was beginning and itwas the most vulnerable part of the foot.

In conclusion, we present a unique case of BSAJ re-lated to a hypoplastic sustentaculum tali that supports thetheory of ankle hypermobility as a causal agent of thisdeformity. The detection of this abnormality in X-rayfilms is an indication for CT in order to investigate asso-ciated disorders of ankle and foot.

References

1. Channon GM, Brotherton BJ (1979)The ball and socket ankle joint. J BoneJoint Surg Br 61:85

2. Pistoia F, Ozonoff MB, Wintz P (1987)Ball and socket ankle joint. SkeletalRadiol 16:447–451

3. Bettin D, Karbowski A, Schwering L(1996) Congenital ball and socketanomaly of the ankle. J Pediatr Orthop16:492–496

4. Takakura Y, Tamai S, Masuhara K(1986) Genesis of the ball and socket an-kle joint. J Bone Joint Surg Br 5:834–837

5. Korvin H (1934) Coalitio talocalcane-are. Z Orthop Chir 60:105

6. Bruckner J (1987) Variations in the hu-man subtalar joint. J Orthop SportsPhys Ther 8:489–494

7. Kawashima T, Uhthoff HK (1990) Pre-natal development around the susten-taculum tali and its relation to talocal-caneal coalitions. J Pediatr Orthop10:238–243

8. Drayer-Verhagen F (1993) Arthritis ofthe subtalar joint associated with sus-tentaculum tali facet configuration.J Anat 183:631–634

9. Gould N, Alvarez R, Trevino S et al.(1989) Development of the child’sarch. Foot Ankle 9:241–245

10. Olexa TA, Ebraheim NA, Haman SP(2000) The sustentaculum tali: anatom-ic, radiographic, and surgical consider-ations. Foot Ankle 21:400–403

11. Futuyma DJ (1986) Evolutionary biol-ogy. Sinauer, Sunderland, Massa-chussetts, pp 412–419