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Functionalanatomyofthemedialligamentouscomplexoftheelbow.Itsroleinanteriorposteriorinstability

ARTICLEinSURGICALANDRADIOLOGICANATOMY·OCTOBER2001

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PierreMansat

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Original articles Functional anatomy of the medial ligamentous complex of the elbow. Its role in anterior posterior instability M. Rongières1, 2, H. Akhavan2, P. Mansat2, M. Mansat2, P. Vaysse1 and J. B écue1 1 Laboratoire d'anatomie appliquée, Faculté de Médecine Toulouse-Rangueil, Université Paul Sabatier, 133 route de Narbonne, F-31062 Toulouse cedex, France 2 Service de Chirurgie Orthopédique et Traumatologique, Hôpital Purpan, Place du Docteur Baylac, F-31059 Toulouse cedex, France Received July 27, 1999 / Accepted in final form July 06, 2001 Key words: Instability - Collateral ligaments - Elbow joint - Functional anatomy - Pathomechanics Correspondence to: M. Rongières E-mail: rongieres.m@chu-toulouse.fr

Abstract Abstract The question remains unanswered regarding the role of repair of medial ligament injuries associated with subluxation of the elbow and non-reconstructable radial head fracture and whether or not this will decrease the risk of chronic instability and cubitus valgus. The goal of this study was to define the role of the medial ligamentous complex of the elbow in elbow instability and to describe the anatomy of the complex in 35 fresh-frozen cadaver elbows. We documented medial ligamentous complex anatomy and compared our results to those in the literature. 25 elbows were dissected in order to describe the different bundles of the medial ligament complex and to precise the positions of the elbow that placed each in tension section of the different ligamentous bundles was done to study the role of each in elbow stability. 10 other elbows were dissected and used for the ligamentous section studies which were performed subcutaneously. We found two bundles at the level of the anterior portion and termed them superficial and deep. Section of the anterior bundle lead to posterior subluxation of the elbow at 30-100° flexion in both supination and pronation. Posterior subluxation was obtained after an anterior capsulotomy medial epicondylectomy did not compromise the stability of the elbow after a complete section of the insertion of the deep fibers of the anterior bundle. Elements thus required for stability of the elbow are integrity of the articular surface of the humerus and the ulna, and the anterior bundle of the medial ligamentous complex.

The descriptive anatomy of the collateral ligg. of the elbow has been well known since the 19th century [22], but controversies still exist, above all in the English literature, concerning the description of the ligaments in the lateral plane [1, 2, 8, 10-13 , 24] and the specific roles of the medial and lateral ligamentous complexes in elbow stability in the postero-anterior plane [3-13 , 15 , 16 , 18]. The main question that exists in ligamentous injuries, either associated with fractures or not, is whether or not repair of the medial ligamentous complex should be done. Our goal was to precisely describe each ligamentous complex, especially the medial plane, because recent studies only describe an anterior bundle and a posterior bundle, the transverse bundle being ulno-ulnar. All classic descriptions include three bundles anterior, intermediate and posterior by a cadaver study, which disagrees with current literature. We describe an intermediate bundle in two layers, superficial and deep, which are fundamental for postero -anterior stability of the elbow. Material and methods We studied 35 fresh frozen cadaver elbows from 15 men and 10 women aged 40 to 86 years (average age 71 years). 15 other elbows were excluded because they showed scarring or stiffness. The cadavers were studied within four days after death. All elbows in the study had mobility which was near to normal without operative scarring and without instability on initial tests. Description of different ligamentous bundles of the collateral ulnar ligament This study was done with 25 elbows, removing skin and subcutaneous tissue. The medial epicondylar mm. were dissected and resected, passing between the muscles and the capsulo-ligamentous plane. The cutaneous incision was

centered on the medial epicondyle, one centimeter proximal to it and eight centimeters below it. The fibers of the different muscles were cut transversely, distal to the joint line and elevated from distal to proximal, and from the flexor carpi ulnaris to the flexor carpi radialis mm., disinserting their fibers from the capsule plane with dissection scissors in order to not injure the fibrous ligamentous structures. The distribution of the different bundles of the medial ligamentous complex was studied and compared to the data of the literature. An analysis of tensioning of different bundles in different degrees of flexion and extension of the elbow from 0 to 140 degrees was performed in order to appreciate the role of each bundle and stability of the elbow. Analysis of ligamentous factors in postero-anterior stability of the elbow On 25 dissected elbows After section of different ligamentous complexes, the postero-anterior stability of the elbow was analyzed visually with photographs after flexion and extension. On 10 elbows which were not dissected After section of the capsulo-ligamentous structures through a cutaneous approach, two centimeters long, centered on the medial ligamentous plane, we performed an X-ray analysis of the postero-anterior stability of the elbow. Results The medial ligamentous complex (ulnar collateral ligament) It was composed of three primary bundles, anterior, intermediate and posterior, and an accessory bundle also called the arciforme bundle, or as was in the past, the lig. of Cooper, actually called the transverse bundle. The anterior bundle (Figs. 1-3)

Fig. 1 Drawing. Medial ligamentous complex of the elbow (in elbow flexion). a, anterior bundle b, intermediate bundle (in French) a+b, anterior bundle for O'Driscoll c, posterior bundle

Fig. 3 Medial ligamentous complex of the elbow (in elbow flexion). Resection of the medial epicondyle. a, deep ground of the intermediate bundle b, medial epicondyle resected to see the deep ground of the intermediate bundle It was weak and very thin. It took origin from the anterior aspect of the medial epicondyle and ended on the medial border of the coronoid process. It was tight in extension and appeared relaxed after 90° of flexion. The intermediate bundle (Figs. 1-3) This was a thick fibrous layer flattened from front to back, located immediately deep to and behind the anterior bundle. It was composed of two layers, superficial and deep. The superficial layer inserted on the anterior aspect and on the inferior border of the medial epicondyle, and ended on the medial border of the coronoid process, just behind the anterior bundle. Several superficial fibers were prolonged to the medial border of the ulna, deep to the tendon of the brachialis. The deep layer (Fig. 3) was demonstrated well after medial epicondylectomy. It inserted in a fan shape from the junction of the medial epicondyle and trochlea up to the cartilaginous edge of the trochlea of the humerus, and terminated on the medial border of the coronoid process, fused with the superficial layer. The intermediate bundle was tight in extension but its maximal tension was between 30° and 90° of flexion and it appeared lightly slackened beyond 120° of flexion. The posterior bundle (Figs. 1, 2)

Fig. 2 Medial ligamentous complex of the elbow (in elbow flexion). a, anterior bundle b, intermediate bundle (in French) a+b, anterior bundle for O'Driscoll c, posterior bundle ME, medial epicondyle It was fan shaped. It inserted proximally on the posterior inferior portion of the medial epicondyle (beneath and behind the intermediate bundle) and ended distally, semi -circularly on the medial border of the olecranon. It was completely relaxed in extension and tightened after 60° of flexion. Study of postero-anterior stability of the elbow Dissected elbows The stability of the elbow was not compromised after section of the anterior bundle and/or posterior bundle of the medial ligamentous complex. Section of the intermediate bundle was followed by a posterior subluxation from 30° to 100° of elbow flexion, in supination and in pronation. Posterior subluxation was obtained after anterior capsulotomy. A medial epicondylectomy only compromised the stability of the elbow after complete section of the insertion of the deep fibers (dissection technique of O'Driscoll.) [15]. Non dissected elbows The isolated section of the medial capsulo-ligamentous complex did not disturb the postero-anterior instability of the elbow. Discussion The majority of anatomic treatises in the English literature ignore the anterior bundle within the medial ligamentous complex [1, 2, 8, 10-13 , 24]. This might be because the medial epicondylar origin of the ligament is more of a ventral capsular reinforcement than an actual part of the ulnar collateral lig. Its very oblique orientation in front and outside and the predominance of its fibers in the frontal plane would be the proof. Our study agrees with the descriptive anatomy of elbow ligaments published by classical French authors [22], and we add here the description in two planes (superficial and deep) of the middle or intermediate bundle (older literature) or the anterior bundle (English literature) of the ulnar collateral lig. This was recently described in literature with an anatomic study, including histology14], but the concept was clearly established in the anatomic work of O'Driscoll who, in order to show this bundle, had to resect the medial epicondyle [16]. We can reclassify our anterior bundle and intermediate bundle into one single actual anterior bundle to correspond to the English description, but the work of Callaway [4] made the opposite point in separating the anterior bundle into an anterior band (the most important for stability), that which we confirm, and a posterior band.

The different tensions of the ligamentous bundles with flexion and extension are known [12, 13, 17]. Variations in tension are explained by the approximation or separation of the points insertions of the different bundles with flexion and extension. The stabilization factors of the elbow are multiple [1, 5, 7, 12, 13, 16, 19]. They are osteo -cartilaginous, capsulo-ligamentous and muscular. The intricacy of the static and dynamic elements makes the analysis of their specific roles very complex. The mechanism of posterior subluxation of the elbow was a subject of controversy in the literature [1, 4, 7, 8, 13, 14, 19]. Two theories disagree regarding the role of hyperextension, based on the importance of injury to the medial structures and the role of flexion, based on the importance of lesions of the lateral structures. According to Schwab [20], hyperextension leads to injury to the intermediate bundle of the medial (ulnar) collateral lig., followed by a slight flexion that ruptures the posterior bundle, with passage of the coronoid behind the trochlea, then continuing further into a new hyperextension completing the posterior subluxation. Josefsson [9] found a medial lesion in all cases of his series of 31 subluxations explored surgically, and a lateral lesion was present in only 18 cases. For him the isolated section of the lateral (radial) collateral lig. only gave a minimal instability or none at all. The theory based on the importance of medial lesions does not explain postero-lateral subluxations [15, 16]. Osborne [18] underlined the role of repair laterally in the treatment of recurrent subluxations of the elbow, although authors have often since confirmed his theory [5, 7, 8, 12, 16, 19]. More recently O'Driscoll and Morrey [15 , 16] defined postero-lateral subluxation of the elbow, a clinical entity above all encountered after surgical treatment of epicondylar pain (with disinsertion of the lateral ligamentous complex) or after posterior subluxation of the elbow. The clinical signs were lateral pain with a feeling of instability without true subluxation. The clinical examination and a radiological exam under general anesthesia confirm the diagnosis It is question of axial compression of the elbow in slight flexion in valgus and supination (lateral pivot shift test). After studying cadavers compared to the clinical lesion, the authors propose a classification of postero-anterior instabilities of the elbow in three stages Stage 1 Postero-lateral subluxation Stage 2 Perched position (or posterior subluxation of the elbow) Stage 3 Posterior subluxation 3a Without rupture of the medial intermediate bundle 3b With rupture of the intermediate bundle. These different stages occur according to the same mechanism, thought to be an axial compression in supination, valgus and slight flexion [16]. The beginning of the injury being rupture of the intermediate bundle of the lateral ligamentous complex (Stage 1), extending in a circumferential fashion to the postero-anterior capsule (Stage 2), then completed by the injury to the medial complex without rupture to the intermediate bundle (Stage 3a) or with rupture of the intermediate bundle (3b). Our study is in agreement with the last theory with several exceptions. The mechanism of valgus does not appear to be necessary but it was present in the clinical situation. Also we were not able to obtain a distinction between stages 3a and 3b, but our methodology being different, the comparison is not easy. Additionally the disagreement existing in the literature about the importance of surgical repair of the intermediate bundle [9, 12 , 16] and the disagreement existing in our series regarding the mechanism of subluxation in the dissected elbows and in the non -dissected elbows, underlines the importance of the stabilizing role of muscular elements, but this still must be defined. A biomechanical study evaluated the stabilizing role of the lateral epicondylar mm. and qualified them as secondary stabilizers (especially the wrist extensors). The humero-ulnar articulation appears to be the chief element of postero -anterior stability of the elbow. Pre-requisites for this stability are the integrity of the articular surfaces and the intermediate bundle of the medial and lateral ligamentous complexes. The muscular tension of the elbow has a fundamental role but this has not been defined. Injury to the lateral ligamentous complex extending circumferentially to the medial side after axial compression of the elbow in valgus, supination and slight flexion explains best the different stages of postero -anterior instability of the elbow. Acknowledgements: Thanks to M.-P. Roux, R. Joly, H. Desroques for their tecnical help and support for iconography and Joseph Failla M.D. (Detroit, MI, USA) for his help in the translation.

References

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