- Email: [email protected]
“Coxa pedis” today
Accepted Manuscript Title: “COXA PEDIS” TODAY Author: G. Pisani PII: DOI: Reference:
S1268-7731(15)00079-X http://dx.doi.org/doi:10.1016/j.fas.2015.05.004 FAS 830
To appear in:
Foot and Ankle Surgery
Received date: Revised date: Accepted date:
11-7-2014 9-2-2015 2-5-2015
Please cite this article as: Pisani G, “COXA PEDIS” TODAY, Foot and Ankle Surgery (2015), http://dx.doi.org/10.1016/j.fas.2015.05.004 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Highlights
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We can discuss 1. subtalar joint 2. anomalous subtalar pronation syndrome 3. flexor digitorum longus transfer pro tibialis posterior tendon 4. coxa pedis actor or partecipant in the functional integration of the lower limb 5. anterior knee pain syndrome.
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“COXA PEDIS” TODAY
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Centro di Chirurgia del Piede “Prof. G. Pisani” Clinica Fornaca di Sessant, Corso Vittorio Emanuele II, 91 – 10128 Torino (Italy) [email protected]
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Abstract Coxa pedis is the talocalcaneonavicular joint and is the distal enarthrosis of the lower limb. It's defined Coxa because of: 1) the enarthrosic meaning from an anatomical point of view 2) the analogy to the hip. The stabilizing devices are structural, passive and active; the corresponding pathology is the "Coxa pedis destabilising syndrome". During walking, release and stiffening of the foot are related to the opening and closure of the kinetic chain of the coxa pedis: it's mutually reversible, while opening is a passive event, closure is an active one. Considering the importance of the flexor digitorum longus muscle in stabilizing the coxa pedis, is it logical transferring it in the tibialis posterior disfunction ? During walking, opening and closure of the kinetic chain of the coxa pedis intervene in the opening and closure of the kinetic chain of the entire lower limb. The kinetic chain closes starting from the bottom and moving upwards in the foot-knee-hip progression, and opens starting from the top and moving downwards. Even rotations along the orthogonal plane of the segmental axes of the limb contribute to the closure of the kinetic chain, Coxa pedis dysmorphism (cavovalgus foot: false flat foot) can cause, during growth, dysmorphism of the hip (residual anteversion) and of the knee (condyles or tibial tuberosity) instead of the reverse. Issues: subtalar joint; anomalous subtalar pronation syndrome; flexor digitorum longum transfer pro tibialis posterior tendon; coxa pedis actor or partecipant in the functional integration of the lower limb; anterior knee pain syndrome.
Keywords: Coxa pedis – Subtalar joint – Tibialis posterior disfunction – Flexor digitorum longus tendon transfer
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Why did I call my study Coxa Pedis today? Because even if I have written a lot and I have lectured a lot about the “coxa pedis” (1)(2)(3)(4) ,only recently I have understood its real meaning; anatomical, functional and clinical meaning. Coxa pedis (fig. 1) is the distal enarthrosis of the lower limb. It is important from a biomechanical point of view to understand the relations between foot, knee, hip and the reverse. In 1803 Antonio Scarpa from Pavia (Italy),in his book about the “Club foot” (5) ,described as acetabolo (fig.2)the anatomical formation comprising the posterior navicular and the anterior talar of the calcaneum articular surfaces and the glenoid, or fibrocartilago navicularis, which is interposed and connected between the two articular surfaces; these elements were all contained in a single articular capsule . Analyzing from an anatomical standpoint this acetabolo, we notice that the articular surfaces that form it are contained, as already mentioned, with the interconnected glenoid, in a single capsular structure. This means that they belong to a single joint, that is the talocalcaneonavicular joint (6). Consequently, the acetabolo cannot be divided, from a clinical standpoint, into two joints: the posterior one considered as anterior subtalar (7),or subtalar (8), joint and the distal one as talonavicular joint. For instance, to which of the two joints, anterior subtalar or talonavicular, does the glenoid belong? And, from a functional standpoint can the acetabolo be considered as belonging to the anterior subtalar joint functional unit with the posterior one? (9) A question is: can a subtalar joint, anterior and posterior, be defined from an anatomical standpoint? I would say: “No, it can’t” The contiguous articular relations between the talus and the calcaneous are mediated by two joints: the above mentioned talocalcaneonavicular joint in front and the talocalcaneal joint behind, as defined by Chiarugi (1946) (10) in the “proper sense of the word” to mean that all the other definitions, as posterior subtalar joint, are improper. Observing only the foot bones (fig.1) ,in which the two articular surfaces, navicular and calcaneal, are mutually distinguished and distant because the foot skeleton lacks the interposed glenoid and the peripheral capsule, defining anatomically the acetabolo can be a mistake. Subtalar, anterior and posterior, joint is a traditional, so to say, definition, but not an anatomical entity. The concept is recent to me. I previously overestimated the importance of the subtalar joint by defining its insufficiency syndrome (11) , and proposing the reconstruction of the talocalcaneal interosseous ligament (12) , talar arthroereysis
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with endorthesis (13) and arthrodesis with stable synthesis achieved through intraoperative compression (4) . The above statements question the so-called “Anomalous subtalar pronation syndrome, (14)(15) considered a set of pathological conditions to be related to the primitive anomalous pronation of the subtalar joint. The pronation of the calcaneum is always subsequent to medial and plantar destabilization of the coxa pedis (talar protrusion). What mentioned above has a functional and clinical meaning, and not only a semantic meaning. Later, in 1981 (SICP Congress in Bari) (1) and in 1987 (SICOT Congress in Munich) (2) ,I proposed an epiphysis, made of the talar head and neck, into the acetabolo defining the overall structure as “coxa pedis”, anatomically talocalcaneonavicular joint. Coxa doesn’t define only the anatomy but also the function. The first is that, though the definition talocalcaneonavicular joint is entirely correct from an anatomical standpoint, it does not convey the idea of the joint's function, while the term “coxa” has also a functional enarthrosic meaning, besides an anatomical one. The second point is that the term “coxa” refers to the analogies that exist between the “coxa” pedis and the “coxa” hip. These analogies are anatomical, developmental, malformative and clinical besides functional. From an anatomical standpoint (fig3), if we observe in a sagittal section a neonatal foot (3a), we will notice a well defined tibial diaphysis, medial malleolus, talar neck and head, and acetabolo profile. If then we imagine reversing the image by 180° (3b), the correspondence of the tibial diaphysis with the femoral diaphysis, of the medial malleolus with the lesser trochanter, of the talar neck and head with the femoral neck and head the analogy becomes evident; and the acetabolo profiles also correspond. There is also an important developmental postnatal correlation between the proximal femoral epiphysis and the talar “epiphysis” (16). Considering the detortion implemented to correct the physiological anteversion of the femoral neck on the one hand, and the physiological retroversion (adduction on the horizontal plane) of the talar neck on the other, it is interesting to notice that the two detortional moments, which start from more or less identical values around 45°, and finally settle, at the end of the developmental period, at values around 20°. But it must be observed that talar detortions close sooner, towards 6-7 years, than femoral detortions, which close later, around 14-15 years. We shall discuss this below.
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Malformative analogies concerning the hip include protrusion and dislocation. In the coxa pedis (fig.4),the analogy of dislocation is the club foot (a) in which the dorsal and lateral dislocation of the talar head, compared to the acetabolo, can be clinically observed. The analogy of protrusion is the congenital flat foot (vertical talar) (b) in which the talar head is, instead, embedded, and protrudes into the acetabolo. The clinical conditions are confirmed by the X-ray: the lateral view reveals the dorsal dislocation of the talar head in the club foot, and its protruding in the vertical talus. There are also analogies in terms of degenerative diseases. A study of radiographic images of arthrosis in the coxa pedis (fig.5) reveals some analogies with the primitive coxarthrosis (malum coxae senilis) (5a); others are, instead, typical of coxarthrosis in the dysplasic hip (5b) with the typical osteophytes. The stabilizing devices of the coxa pedis are structural: both passive and active; the corresponding pathology is the “Coxa pedis destabilising syndrome”. Structural stability is guaranteed by the anatomical epiphyso-acetabular congruence (fig.1). The passive stability is ensured by the peritalar calcaneo-navicular ligaments: the superomedial, the plantar (spring ligament) and the lateral one (medial branch of Chopart's or "Y" shaped ligament). The active stability is guaranteed by the tibialis posterior, the flexor digitorum longus and the flexor hallucis longus muscles. The functional mechanism of the coxa pedis during walking is interesting. At the start of the load bearing phase, the foot must be an elastic structure that is suitable to absorb the impact on the ground, and then it must become the rigid structure that is useful for the taking off. Release and stiffening are related to the opening and closure of the kinetic chain of the coxa pedis, and are mutually reversible; we have to take into account the fact that, while opening is a passive event, closure is an active one (4,24). Opening of the kinetic chain of the coxa pedis is a passive event for the medial misalignment of the tibial and talar axis, compared to the calcaneal axis (fig.6); hence, the talar plantar flexion and adduction are stimulated when the talus is loaded. This action is opposed by the tibialis posterior muscle and, particularly, by the flexor digitorum longus and by the flexor hallucis longus muscles, which modulate braking with their sustentacular reflection; this happens to maintain the talar sliding into the cotile pedis (modular mosaic-like structure)
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within a physiological range in order to avoid the destabilization of the coxa pedis. The talar sliding (above mentioned plantar flexion and adduction) when the kinetic chain opens, causes tension in the peritalar ligaments, which are rich in mechanoreceptors which, through a proprioceptive way (fig.7), activate the muscles that intervene at the closure of the kinetic chain (stabilization) of the coxa pedis; these muscles are the same that modulate braking when the kinetic chain opens. Now they intervene as actors of the closure: the tibialis posterior muscle by stabilizing the navicular to the talar head, the flexor digitorum longus and flexor hallucis longus by stabilizing the calcaneous to the talus by supinating it through their action, once again, on the sustentaculum tali with toes stabilized on the ground. Considering the importance of the flexor hallucis longus and of the flexor digitorum longus muscles in stabilizing the coxa pedis, we question whether the proposal to use the flexor digitorum longus as a transfer for tibialis posterior tendon disfunction (17)(18) is logical.. Personally I do not think it’s logical or, rather, if it seems to be logical with the open kinetic chain (foot not loaded) with the sustentaculum tali acting as fixed point of the flexors, and their action performed with inversion of the foot, it is not so in the closed kinetic chain (foot loaded) in which the fixed point of the flexors becomes the forefoot; it is stabilized in pronation by the peroneus longus and the intrinsic muscles, and long flexors perform their action on the sustentaculum with supination of the calcaneous stabilizing it to the talus. The transfer of a flexor digitorum longus can never compensate for the functional loss of the tibialis posterior muscle; instead, it entails an additional functional loss because a transferred tendon, anyhow, loses more or less 20% of its efficacy and, in this case, the transfer lacks the lesser toes physiological function. Authors who proposed that surgery (19), and others (20)(21)(22)(23), later proposed associating medial translation of the calcaneous posterior tuberosity in order to reduce the destabilizing effect of the coxa pedis caused by the physiological talocalcaneal misalignment. (fig. 6) Even this accessory osteotomic procedure does not seem to be very logical because, if there is no structured valgus of the calcaneous, it will at least lead to overload of the medial side of the tibiotalar joint in the course of time. In insuffiency of the tibialis posterior muscle, the osteodesis (fusion), of the navicular to the talus, with perfect congruency as in the closed kinetic chain, as it preserves complete flexor muscle function, I think it is better. Obviously, during walking, opening and closure of the kinetic (fig.8) chain of the coxa pedis intervene in the opening
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and closure of the kinetic chain of the entire lower limb. The kinetic chain closes starting from the bottom and moving upwards in the foot-knee-hip progression, and opens starting from the top and moving downwards (24) . The kinetic chain of the lower limb closes from the bottom in an upward direction (fig.9) as a result of gravity expressed by the upward force generated by the ground to oppose gravity itself (9a,b). Even rotations along the orthogonal plane of the segmental axes of the limb (9c) contribute to closure of the kinetic chain (stabilization), namely the internal rotation of the tibia and external rotation of the femur to stabilize the knee. By adopting this perspective of the coxa pedis integrated into the global function of the lower limb (24) we cannot help asking whether it is an actor or a participant in the intersegmental relations, specifically whether it is the distal (foot) that influences the proximal (knee, hip) one or thereverse (25). When I started my orthopedic practice in the early 1950s, I had learnt that the anti - version of the hip could cause the development of a flat foot, that is that a proximal dysmorphism could cause a distal disease. But a study of these so-called flat feet revealed that in many cases (fig.10a,b) what seemed to be a flat foot due to the contact of the medial side surface of the foot with the ground and to a valgus of the calcaneous, on the contrary presented, loading, to a podoscopic examination, the typical plantar images of the cavus foot (10c). These feet, which can be defined as cavovalgus, are false flat feet, since the bridge (10d) that turns sideways and touches the ground with one side, preserves its bridge-like structure (26) . Unlike the flat foot, the bridge collapses along the sagittal plane (fig. 10d) without, however, affecting the rotational moments which are, instead, present (standing up in close kinetic chain!) in the false flat feet (fig.11) , that is the cavovalgus feet. In the latter, the talar adduction (medial laxity of the cotile pedis: superomedial calcaneonavicular ligament) corresponds to the internal rotation on the horizontal plane, and since the talus is stabilized to the ankle in a closed kinetic chain, this rotation entails the rotation of the entire lower limb. This internal rotation can be observed as convergent rotulas. Can the cavovalgus foot and the subsequent suprasegmental rotational misalignment induce diseases during growth? (4) As far as the hip is concerned, the internal rotation of the limb compensates for physiological anteversion, which corrects itself at the age of 14-15 years also as a result of the action of the ileopsoas tendon that crosses the proximal end of the femur. When anteversion resulting from internal rotation of
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the limb has been compensated, and the action of the ileopsoas muscle has been reduced, there might be the residual anteversion of the hip at the end of the growth phase. If it is not correlated with the dysmorphism of the foot, such residual anteversion will be considered as primitive and essential. Even certain knee dysmorphisms can be interpreted as essential or primitive, if they are not correctly correlated with dysmorphism of the foot such as, for instance, the above mentioned cavovalgus foot. It is a known fact already from the laws of Roux and Delpech that the primitive mesenchymatic cell can evolve towards fibrogenesis or chondrogenesis or osteogenesis, producing fibrous or cartilaginous or osseous tissue, thus influencing morphogenesis, through the direction of the forces acting on it. As for the things above mentioned the forces that act eccentrically on the convergent knee subsequent to internal rotation of the limb, can determine condyles or tibial tuberosity dysmorphisms during the developmental phase. What has just been said above takes place with the subsequent femoropatellar syndromes (27) , whose pathogenetic expression is very often a dysmorphism of the coxa pedis (medial laxity: cavovalgus foot). The above discussion on the possibility of dysmorphisms of the foot affecting the limb proximal dysmorphisms during growth (morphogenesis), poses the question whether the influence of the foot on the hip can occur more easily than the influence of the hip on the foot. Considering that the load is expressed by the opposing force exerted by the ground against gravity, namely by a force that progresses in a distalproximal direction, and that detortions of the talar neck close before (6-7 years) those of the femoral neck (14-15 years), the likelihood of coxa pedis dysmorphism causing dysmorphism of the hip, rather than the reverse, is more probable (3) . As a conclusion these can be the issues: - subtalar joint - anomalous subtalar pronation syndrome - flexor digitorum longus transfer pro tibialis posterior tendon - coxa pedis actor or partecipant in the functional integration of the lower limb - anterior knee pain syndrome.
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Captions Fig. 1 - The talocalcaneonavicular joint or “coxa pedis,
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Fig. 2 - The acetabulum by Antonio Scarpa 1803; a) posterior articular surface of the navicular; b)anterior talar articukar surface of the calcaneum; c) glenoid or fibrocaartalago navicularis; d) capsular structure.
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Fig. 3 - a) neonatal foot bones; b) on the reverse similar hip bones.
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Fig. 4 – a) dislocation of the hip and the coxa pedis (club foot); b) protrusion of thr hip and thr coxa pedis (congenital flat foot or vertical talus).
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Fig. 5 – Degenerative pathology a) normal coxa pedis (malum coxae senilis); b) displaced coxa pedis (prortrusion),
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Fig. 6 – Medial tibiotalar axis misallignament.
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Fig. 7 - Propeioceptiver way coxa pedis active stabilisation . Fig. 8 – Closing and opening of the lower lib kinetic chain during walkimg
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Fig. 9 – a.b) gravity expressed by reacting forcs im upward direction from thr bottom to the top; c) rotator mechanisms in the orthogonal plan of the lower limb segmentary axes . Fig 10 – cavovalgus foot (false flat foot).like bridge which turn itself sidewards. Fig 11 – adduction of the talus (a) in closed kinetic chain (b.c ) corresponds to an internal rotation of lower limb,corrected after sugical correction of the cavo valgus foot on the left. (d)
Fig 12 – Ilpp: ileopsoas tendon . Fig 13- Tuberosity and condilar dysmorphism in internal rotation of the knee
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Bibliography 1 ) Pisani G - La chirurgia legamentosa nella protrusione della “coxa pedis. Relaz. congr. Soc. It. Med. e Chir. del Piede,Bari,giugno 1982
3 ) Pisani G. –The coxa pedis. Foot and Ankle 1994,1:67-75
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4 ) Pisani G. - Trattato di Chirurgia del Piede Ediz. Minerva Medica Torino; 1990,1993,2004.
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2 ) Pisani G - The concept of the “coxa pedis”. Relaz.XVI Congr. SICOT, Monaco di Baviera,17 agosto 1987.
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5 ) Antonio Scarpa - Memoria chirurgica sui piedi torti congeniti dei fanciulli e sulla maniera di correggere questa deformità”. In Pavia 1803. Appressi Giuseppe Comini. Ristampa Arti grafiche A. Gallati. A cura Zambelletti spa,1961.
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6 ) Chiarugi G. - Istituzioni di anatomia dell’uomo. Società editrice libraria, Milano1946.
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7 ) Pisani G. - La sindrome da insufficienza della sottoastragalica. In “Patologia del Piede”B. Martinelli, Trieste:Ed. Libreria Goliardica,1985.
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8 ) Pisani G. - Reconstruction du ligament interosseux dans les laxitès chroniques sous-astragaliennes. Podologie 1988;122-126,Parigi . Ed. Expansion Scientifiques Francaises,Parigi. 9) Pisani G. - Filosofia del “calcaneo stop”. Chir. del Piede,1997.21:47-53
10) Root M.I.,Orien W.P.,Weed J.H.- La funzione del piede normale e patologico. Ed. italiana I a cura di S. Giannini,Piccin. Piccin Editore, Padovav, 1999 11 )Dragonetti L. – Biomeccanica e anatomia funzionale dell’avampiede. In “Le metatarsalgie”: Aulo Gaggi Editore, Bologna,2002,9-15 12)PapparellaTreccia R. – Il piede dell’uomo. Ediz. Verducci Roma ,1977
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14) Mann R.A. - Posterior tibial tendon dysfunction. Treatment by flexor digitorum longus transfer. Foot Ankle Clinic 6(1): 77-87, vi, 2001.
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13)Myerson M.S. - Adult acquired flat foot deformity: Treatment of dysfunction of the posterior tibial tendon. J. Bone Joint Surg. Am. 78: 780-792, 1996.
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15) Myerson M.S., Corrigan J. - Treatment of posterior tibial tendon dysfunction with flexor digitorum longus tendon transfer and calcaneal osteotomy. Orthopaedics 19(5): 383-388, 1996.
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16) Guyton G.P., Jeng C., Krieger L.E., Mann R.A. - Flexor digitorum longus transfer and medial displacement calcaneal osteotomy for posterior tibial tendon dysfunction. A middleterm clinical follow-up. Foot Ankle Int. 22(8): 627-632, 2001.
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17)Fayazi A.H., Nguyen H.V., Juliano P.J. - Intermediate term follow-up of calcaneal osteotomy and flexor digitorum longus transfer for treatment of posterior tibial tendon dysfunction. Foot Ankle Int. 23(12): 1107-1111, 2002
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18)Wacker J.T., Hennessy M.S., Saxby T.S. - Calcaneal osteotomy and transfer of the tendon of flexor digitorum longus for stage-II dysfunction of tibialis posterior. Three- to five-year results. J. Bone Joint Surg. Br. 84(1): 54-58, 2002.
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19) Myerson M.S,, Badekas A., Schon L.C.- Treatment of stage II posterior tibial tendon deficiency with flexor digitorum longus tendon transfer and calcaneal osteotomy. Foot Ankle Int. 25(7), 445-450, 2004. 20) Pisani G. - Integrazione funzionale dell’arto inferiore. Chir. del Piede,2002;26:35-49
21 ) Pisani G. – Il piede attore o convenuto nelle interdipendenze torsionali con l’anca? Min. Ortop. 1983; 34,519 22 ) Pisani G. - l piede valgo evolutivo nell’infanzia. Chir. del Piede,1982;6:1-7
23) Pisani G. - )Dismorfismi della coxa pedis e disassetti sovra segmentari. Chir. del Piede 1994;18: 145-157
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S1268-7731(15)00079-X http://dx.doi.org/doi:10.1016/j.fas.2015.05.004 FAS 830
To appear in:
Foot and Ankle Surgery
Received date: Revised date: Accepted date:
11-7-2014 9-2-2015 2-5-2015
Please cite this article as: Pisani G, “COXA PEDIS” TODAY, Foot and Ankle Surgery (2015), http://dx.doi.org/10.1016/j.fas.2015.05.004 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
1
Highlights
Ac ce p
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M
an
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We can discuss 1. subtalar joint 2. anomalous subtalar pronation syndrome 3. flexor digitorum longus transfer pro tibialis posterior tendon 4. coxa pedis actor or partecipant in the functional integration of the lower limb 5. anterior knee pain syndrome.
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“COXA PEDIS” TODAY
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G. Pisani
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Centro di Chirurgia del Piede “Prof. G. Pisani” Clinica Fornaca di Sessant, Corso Vittorio Emanuele II, 91 – 10128 Torino (Italy) [email protected]
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Abstract Coxa pedis is the talocalcaneonavicular joint and is the distal enarthrosis of the lower limb. It's defined Coxa because of: 1) the enarthrosic meaning from an anatomical point of view 2) the analogy to the hip. The stabilizing devices are structural, passive and active; the corresponding pathology is the "Coxa pedis destabilising syndrome". During walking, release and stiffening of the foot are related to the opening and closure of the kinetic chain of the coxa pedis: it's mutually reversible, while opening is a passive event, closure is an active one. Considering the importance of the flexor digitorum longus muscle in stabilizing the coxa pedis, is it logical transferring it in the tibialis posterior disfunction ? During walking, opening and closure of the kinetic chain of the coxa pedis intervene in the opening and closure of the kinetic chain of the entire lower limb. The kinetic chain closes starting from the bottom and moving upwards in the foot-knee-hip progression, and opens starting from the top and moving downwards. Even rotations along the orthogonal plane of the segmental axes of the limb contribute to the closure of the kinetic chain, Coxa pedis dysmorphism (cavovalgus foot: false flat foot) can cause, during growth, dysmorphism of the hip (residual anteversion) and of the knee (condyles or tibial tuberosity) instead of the reverse. Issues: subtalar joint; anomalous subtalar pronation syndrome; flexor digitorum longum transfer pro tibialis posterior tendon; coxa pedis actor or partecipant in the functional integration of the lower limb; anterior knee pain syndrome.
Keywords: Coxa pedis – Subtalar joint – Tibialis posterior disfunction – Flexor digitorum longus tendon transfer
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Why did I call my study Coxa Pedis today? Because even if I have written a lot and I have lectured a lot about the “coxa pedis” (1)(2)(3)(4) ,only recently I have understood its real meaning; anatomical, functional and clinical meaning. Coxa pedis (fig. 1) is the distal enarthrosis of the lower limb. It is important from a biomechanical point of view to understand the relations between foot, knee, hip and the reverse. In 1803 Antonio Scarpa from Pavia (Italy),in his book about the “Club foot” (5) ,described as acetabolo (fig.2)the anatomical formation comprising the posterior navicular and the anterior talar of the calcaneum articular surfaces and the glenoid, or fibrocartilago navicularis, which is interposed and connected between the two articular surfaces; these elements were all contained in a single articular capsule . Analyzing from an anatomical standpoint this acetabolo, we notice that the articular surfaces that form it are contained, as already mentioned, with the interconnected glenoid, in a single capsular structure. This means that they belong to a single joint, that is the talocalcaneonavicular joint (6). Consequently, the acetabolo cannot be divided, from a clinical standpoint, into two joints: the posterior one considered as anterior subtalar (7),or subtalar (8), joint and the distal one as talonavicular joint. For instance, to which of the two joints, anterior subtalar or talonavicular, does the glenoid belong? And, from a functional standpoint can the acetabolo be considered as belonging to the anterior subtalar joint functional unit with the posterior one? (9) A question is: can a subtalar joint, anterior and posterior, be defined from an anatomical standpoint? I would say: “No, it can’t” The contiguous articular relations between the talus and the calcaneous are mediated by two joints: the above mentioned talocalcaneonavicular joint in front and the talocalcaneal joint behind, as defined by Chiarugi (1946) (10) in the “proper sense of the word” to mean that all the other definitions, as posterior subtalar joint, are improper. Observing only the foot bones (fig.1) ,in which the two articular surfaces, navicular and calcaneal, are mutually distinguished and distant because the foot skeleton lacks the interposed glenoid and the peripheral capsule, defining anatomically the acetabolo can be a mistake. Subtalar, anterior and posterior, joint is a traditional, so to say, definition, but not an anatomical entity. The concept is recent to me. I previously overestimated the importance of the subtalar joint by defining its insufficiency syndrome (11) , and proposing the reconstruction of the talocalcaneal interosseous ligament (12) , talar arthroereysis
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with endorthesis (13) and arthrodesis with stable synthesis achieved through intraoperative compression (4) . The above statements question the so-called “Anomalous subtalar pronation syndrome, (14)(15) considered a set of pathological conditions to be related to the primitive anomalous pronation of the subtalar joint. The pronation of the calcaneum is always subsequent to medial and plantar destabilization of the coxa pedis (talar protrusion). What mentioned above has a functional and clinical meaning, and not only a semantic meaning. Later, in 1981 (SICP Congress in Bari) (1) and in 1987 (SICOT Congress in Munich) (2) ,I proposed an epiphysis, made of the talar head and neck, into the acetabolo defining the overall structure as “coxa pedis”, anatomically talocalcaneonavicular joint. Coxa doesn’t define only the anatomy but also the function. The first is that, though the definition talocalcaneonavicular joint is entirely correct from an anatomical standpoint, it does not convey the idea of the joint's function, while the term “coxa” has also a functional enarthrosic meaning, besides an anatomical one. The second point is that the term “coxa” refers to the analogies that exist between the “coxa” pedis and the “coxa” hip. These analogies are anatomical, developmental, malformative and clinical besides functional. From an anatomical standpoint (fig3), if we observe in a sagittal section a neonatal foot (3a), we will notice a well defined tibial diaphysis, medial malleolus, talar neck and head, and acetabolo profile. If then we imagine reversing the image by 180° (3b), the correspondence of the tibial diaphysis with the femoral diaphysis, of the medial malleolus with the lesser trochanter, of the talar neck and head with the femoral neck and head the analogy becomes evident; and the acetabolo profiles also correspond. There is also an important developmental postnatal correlation between the proximal femoral epiphysis and the talar “epiphysis” (16). Considering the detortion implemented to correct the physiological anteversion of the femoral neck on the one hand, and the physiological retroversion (adduction on the horizontal plane) of the talar neck on the other, it is interesting to notice that the two detortional moments, which start from more or less identical values around 45°, and finally settle, at the end of the developmental period, at values around 20°. But it must be observed that talar detortions close sooner, towards 6-7 years, than femoral detortions, which close later, around 14-15 years. We shall discuss this below.
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Malformative analogies concerning the hip include protrusion and dislocation. In the coxa pedis (fig.4),the analogy of dislocation is the club foot (a) in which the dorsal and lateral dislocation of the talar head, compared to the acetabolo, can be clinically observed. The analogy of protrusion is the congenital flat foot (vertical talar) (b) in which the talar head is, instead, embedded, and protrudes into the acetabolo. The clinical conditions are confirmed by the X-ray: the lateral view reveals the dorsal dislocation of the talar head in the club foot, and its protruding in the vertical talus. There are also analogies in terms of degenerative diseases. A study of radiographic images of arthrosis in the coxa pedis (fig.5) reveals some analogies with the primitive coxarthrosis (malum coxae senilis) (5a); others are, instead, typical of coxarthrosis in the dysplasic hip (5b) with the typical osteophytes. The stabilizing devices of the coxa pedis are structural: both passive and active; the corresponding pathology is the “Coxa pedis destabilising syndrome”. Structural stability is guaranteed by the anatomical epiphyso-acetabular congruence (fig.1). The passive stability is ensured by the peritalar calcaneo-navicular ligaments: the superomedial, the plantar (spring ligament) and the lateral one (medial branch of Chopart's or "Y" shaped ligament). The active stability is guaranteed by the tibialis posterior, the flexor digitorum longus and the flexor hallucis longus muscles. The functional mechanism of the coxa pedis during walking is interesting. At the start of the load bearing phase, the foot must be an elastic structure that is suitable to absorb the impact on the ground, and then it must become the rigid structure that is useful for the taking off. Release and stiffening are related to the opening and closure of the kinetic chain of the coxa pedis, and are mutually reversible; we have to take into account the fact that, while opening is a passive event, closure is an active one (4,24). Opening of the kinetic chain of the coxa pedis is a passive event for the medial misalignment of the tibial and talar axis, compared to the calcaneal axis (fig.6); hence, the talar plantar flexion and adduction are stimulated when the talus is loaded. This action is opposed by the tibialis posterior muscle and, particularly, by the flexor digitorum longus and by the flexor hallucis longus muscles, which modulate braking with their sustentacular reflection; this happens to maintain the talar sliding into the cotile pedis (modular mosaic-like structure)
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within a physiological range in order to avoid the destabilization of the coxa pedis. The talar sliding (above mentioned plantar flexion and adduction) when the kinetic chain opens, causes tension in the peritalar ligaments, which are rich in mechanoreceptors which, through a proprioceptive way (fig.7), activate the muscles that intervene at the closure of the kinetic chain (stabilization) of the coxa pedis; these muscles are the same that modulate braking when the kinetic chain opens. Now they intervene as actors of the closure: the tibialis posterior muscle by stabilizing the navicular to the talar head, the flexor digitorum longus and flexor hallucis longus by stabilizing the calcaneous to the talus by supinating it through their action, once again, on the sustentaculum tali with toes stabilized on the ground. Considering the importance of the flexor hallucis longus and of the flexor digitorum longus muscles in stabilizing the coxa pedis, we question whether the proposal to use the flexor digitorum longus as a transfer for tibialis posterior tendon disfunction (17)(18) is logical.. Personally I do not think it’s logical or, rather, if it seems to be logical with the open kinetic chain (foot not loaded) with the sustentaculum tali acting as fixed point of the flexors, and their action performed with inversion of the foot, it is not so in the closed kinetic chain (foot loaded) in which the fixed point of the flexors becomes the forefoot; it is stabilized in pronation by the peroneus longus and the intrinsic muscles, and long flexors perform their action on the sustentaculum with supination of the calcaneous stabilizing it to the talus. The transfer of a flexor digitorum longus can never compensate for the functional loss of the tibialis posterior muscle; instead, it entails an additional functional loss because a transferred tendon, anyhow, loses more or less 20% of its efficacy and, in this case, the transfer lacks the lesser toes physiological function. Authors who proposed that surgery (19), and others (20)(21)(22)(23), later proposed associating medial translation of the calcaneous posterior tuberosity in order to reduce the destabilizing effect of the coxa pedis caused by the physiological talocalcaneal misalignment. (fig. 6) Even this accessory osteotomic procedure does not seem to be very logical because, if there is no structured valgus of the calcaneous, it will at least lead to overload of the medial side of the tibiotalar joint in the course of time. In insuffiency of the tibialis posterior muscle, the osteodesis (fusion), of the navicular to the talus, with perfect congruency as in the closed kinetic chain, as it preserves complete flexor muscle function, I think it is better. Obviously, during walking, opening and closure of the kinetic (fig.8) chain of the coxa pedis intervene in the opening
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and closure of the kinetic chain of the entire lower limb. The kinetic chain closes starting from the bottom and moving upwards in the foot-knee-hip progression, and opens starting from the top and moving downwards (24) . The kinetic chain of the lower limb closes from the bottom in an upward direction (fig.9) as a result of gravity expressed by the upward force generated by the ground to oppose gravity itself (9a,b). Even rotations along the orthogonal plane of the segmental axes of the limb (9c) contribute to closure of the kinetic chain (stabilization), namely the internal rotation of the tibia and external rotation of the femur to stabilize the knee. By adopting this perspective of the coxa pedis integrated into the global function of the lower limb (24) we cannot help asking whether it is an actor or a participant in the intersegmental relations, specifically whether it is the distal (foot) that influences the proximal (knee, hip) one or thereverse (25). When I started my orthopedic practice in the early 1950s, I had learnt that the anti - version of the hip could cause the development of a flat foot, that is that a proximal dysmorphism could cause a distal disease. But a study of these so-called flat feet revealed that in many cases (fig.10a,b) what seemed to be a flat foot due to the contact of the medial side surface of the foot with the ground and to a valgus of the calcaneous, on the contrary presented, loading, to a podoscopic examination, the typical plantar images of the cavus foot (10c). These feet, which can be defined as cavovalgus, are false flat feet, since the bridge (10d) that turns sideways and touches the ground with one side, preserves its bridge-like structure (26) . Unlike the flat foot, the bridge collapses along the sagittal plane (fig. 10d) without, however, affecting the rotational moments which are, instead, present (standing up in close kinetic chain!) in the false flat feet (fig.11) , that is the cavovalgus feet. In the latter, the talar adduction (medial laxity of the cotile pedis: superomedial calcaneonavicular ligament) corresponds to the internal rotation on the horizontal plane, and since the talus is stabilized to the ankle in a closed kinetic chain, this rotation entails the rotation of the entire lower limb. This internal rotation can be observed as convergent rotulas. Can the cavovalgus foot and the subsequent suprasegmental rotational misalignment induce diseases during growth? (4) As far as the hip is concerned, the internal rotation of the limb compensates for physiological anteversion, which corrects itself at the age of 14-15 years also as a result of the action of the ileopsoas tendon that crosses the proximal end of the femur. When anteversion resulting from internal rotation of
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the limb has been compensated, and the action of the ileopsoas muscle has been reduced, there might be the residual anteversion of the hip at the end of the growth phase. If it is not correlated with the dysmorphism of the foot, such residual anteversion will be considered as primitive and essential. Even certain knee dysmorphisms can be interpreted as essential or primitive, if they are not correctly correlated with dysmorphism of the foot such as, for instance, the above mentioned cavovalgus foot. It is a known fact already from the laws of Roux and Delpech that the primitive mesenchymatic cell can evolve towards fibrogenesis or chondrogenesis or osteogenesis, producing fibrous or cartilaginous or osseous tissue, thus influencing morphogenesis, through the direction of the forces acting on it. As for the things above mentioned the forces that act eccentrically on the convergent knee subsequent to internal rotation of the limb, can determine condyles or tibial tuberosity dysmorphisms during the developmental phase. What has just been said above takes place with the subsequent femoropatellar syndromes (27) , whose pathogenetic expression is very often a dysmorphism of the coxa pedis (medial laxity: cavovalgus foot). The above discussion on the possibility of dysmorphisms of the foot affecting the limb proximal dysmorphisms during growth (morphogenesis), poses the question whether the influence of the foot on the hip can occur more easily than the influence of the hip on the foot. Considering that the load is expressed by the opposing force exerted by the ground against gravity, namely by a force that progresses in a distalproximal direction, and that detortions of the talar neck close before (6-7 years) those of the femoral neck (14-15 years), the likelihood of coxa pedis dysmorphism causing dysmorphism of the hip, rather than the reverse, is more probable (3) . As a conclusion these can be the issues: - subtalar joint - anomalous subtalar pronation syndrome - flexor digitorum longus transfer pro tibialis posterior tendon - coxa pedis actor or partecipant in the functional integration of the lower limb - anterior knee pain syndrome.
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Captions Fig. 1 - The talocalcaneonavicular joint or “coxa pedis,
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Fig. 2 - The acetabulum by Antonio Scarpa 1803; a) posterior articular surface of the navicular; b)anterior talar articukar surface of the calcaneum; c) glenoid or fibrocaartalago navicularis; d) capsular structure.
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Fig. 3 - a) neonatal foot bones; b) on the reverse similar hip bones.
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Fig. 4 – a) dislocation of the hip and the coxa pedis (club foot); b) protrusion of thr hip and thr coxa pedis (congenital flat foot or vertical talus).
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Fig. 5 – Degenerative pathology a) normal coxa pedis (malum coxae senilis); b) displaced coxa pedis (prortrusion),
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Fig. 6 – Medial tibiotalar axis misallignament.
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Fig. 7 - Propeioceptiver way coxa pedis active stabilisation . Fig. 8 – Closing and opening of the lower lib kinetic chain during walkimg
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Fig. 9 – a.b) gravity expressed by reacting forcs im upward direction from thr bottom to the top; c) rotator mechanisms in the orthogonal plan of the lower limb segmentary axes . Fig 10 – cavovalgus foot (false flat foot).like bridge which turn itself sidewards. Fig 11 – adduction of the talus (a) in closed kinetic chain (b.c ) corresponds to an internal rotation of lower limb,corrected after sugical correction of the cavo valgus foot on the left. (d)
Fig 12 – Ilpp: ileopsoas tendon . Fig 13- Tuberosity and condilar dysmorphism in internal rotation of the knee
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Bibliography 1 ) Pisani G - La chirurgia legamentosa nella protrusione della “coxa pedis. Relaz. congr. Soc. It. Med. e Chir. del Piede,Bari,giugno 1982
3 ) Pisani G. –The coxa pedis. Foot and Ankle 1994,1:67-75
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4 ) Pisani G. - Trattato di Chirurgia del Piede Ediz. Minerva Medica Torino; 1990,1993,2004.
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2 ) Pisani G - The concept of the “coxa pedis”. Relaz.XVI Congr. SICOT, Monaco di Baviera,17 agosto 1987.
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5 ) Antonio Scarpa - Memoria chirurgica sui piedi torti congeniti dei fanciulli e sulla maniera di correggere questa deformità”. In Pavia 1803. Appressi Giuseppe Comini. Ristampa Arti grafiche A. Gallati. A cura Zambelletti spa,1961.
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6 ) Chiarugi G. - Istituzioni di anatomia dell’uomo. Società editrice libraria, Milano1946.
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7 ) Pisani G. - La sindrome da insufficienza della sottoastragalica. In “Patologia del Piede”B. Martinelli, Trieste:Ed. Libreria Goliardica,1985.
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8 ) Pisani G. - Reconstruction du ligament interosseux dans les laxitès chroniques sous-astragaliennes. Podologie 1988;122-126,Parigi . Ed. Expansion Scientifiques Francaises,Parigi. 9) Pisani G. - Filosofia del “calcaneo stop”. Chir. del Piede,1997.21:47-53
10) Root M.I.,Orien W.P.,Weed J.H.- La funzione del piede normale e patologico. Ed. italiana I a cura di S. Giannini,Piccin. Piccin Editore, Padovav, 1999 11 )Dragonetti L. – Biomeccanica e anatomia funzionale dell’avampiede. In “Le metatarsalgie”: Aulo Gaggi Editore, Bologna,2002,9-15 12)PapparellaTreccia R. – Il piede dell’uomo. Ediz. Verducci Roma ,1977
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14) Mann R.A. - Posterior tibial tendon dysfunction. Treatment by flexor digitorum longus transfer. Foot Ankle Clinic 6(1): 77-87, vi, 2001.
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13)Myerson M.S. - Adult acquired flat foot deformity: Treatment of dysfunction of the posterior tibial tendon. J. Bone Joint Surg. Am. 78: 780-792, 1996.
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15) Myerson M.S., Corrigan J. - Treatment of posterior tibial tendon dysfunction with flexor digitorum longus tendon transfer and calcaneal osteotomy. Orthopaedics 19(5): 383-388, 1996.
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16) Guyton G.P., Jeng C., Krieger L.E., Mann R.A. - Flexor digitorum longus transfer and medial displacement calcaneal osteotomy for posterior tibial tendon dysfunction. A middleterm clinical follow-up. Foot Ankle Int. 22(8): 627-632, 2001.
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17)Fayazi A.H., Nguyen H.V., Juliano P.J. - Intermediate term follow-up of calcaneal osteotomy and flexor digitorum longus transfer for treatment of posterior tibial tendon dysfunction. Foot Ankle Int. 23(12): 1107-1111, 2002
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18)Wacker J.T., Hennessy M.S., Saxby T.S. - Calcaneal osteotomy and transfer of the tendon of flexor digitorum longus for stage-II dysfunction of tibialis posterior. Three- to five-year results. J. Bone Joint Surg. Br. 84(1): 54-58, 2002.
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19) Myerson M.S,, Badekas A., Schon L.C.- Treatment of stage II posterior tibial tendon deficiency with flexor digitorum longus tendon transfer and calcaneal osteotomy. Foot Ankle Int. 25(7), 445-450, 2004. 20) Pisani G. - Integrazione funzionale dell’arto inferiore. Chir. del Piede,2002;26:35-49
21 ) Pisani G. – Il piede attore o convenuto nelle interdipendenze torsionali con l’anca? Min. Ortop. 1983; 34,519 22 ) Pisani G. - l piede valgo evolutivo nell’infanzia. Chir. del Piede,1982;6:1-7
23) Pisani G. - )Dismorfismi della coxa pedis e disassetti sovra segmentari. Chir. del Piede 1994;18: 145-157
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