Congenital Elbow Disorders

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Chapter 15 Congenital Elbow Disorders

Introduction

Embryologically the elbow joint is visible at the 34th day of intrauterine life and any insult to the developing embryo around this period may produce elbow joint malformations. Although congenital anomalies such as radio-ulnar synostosis are present at birth, they may not be detected until early childhood. Primary genetic defects producing true congenital anomalies around the elbow may simulate developmental or acquired conditions resulting from infection, metabolic bone disease, tumours and haematological disorders.

Limb development coincides with development and maturation of the different organ systems during embryogenesis. Hence limb anomalies may be associated with concomitant systemic disorders including renal, cardiac and haematopoietic disorders. In addition, chromosomal syndromes like Carpenter syndrome, Apert syndrome, Antley–Bixler syndrome and Roberts syndrome present with elbow abnormalities.

Congenital elbow disorders can involve either the soft tissues, e.g. arthrogryposis, bone e.g. radio-ulnar synostosis, or the joint itself, producing instability. Ogino and Hikino1 classified congenital elbow deformities into three types based on the presence of associated anomalies:

Congenital anomalies of the elbow can be influenced by the proximal and distal limb anatomy. Treatment is also influenced by bilateral affection and the dominance of the limb. This chapter highlights the common anomalies of the elbow joint per se, and discusses and presents an up-to-date evaluation, treatment and literature review with special reference to surgical techniques.

Congenital elbow synostosis

Background and aetiology

The upper limb bud appears as a mass of mesoderm-derived mesenchyme covered by ectoderm on the ventrolateral wall of the 4-week-old embryo. Embryogenesis occurs over the next 4 weeks and most of the upper limb structures are present by 8 weeks after fertilization. Limb development is regulated by Hox genes (Hox A, B, C and D) . Hox genes encode various transcription factors that are responsible for the aggregation of the mesenchymal cells into condensations which form the pre-cartilaginous skeletal foundation of the limb. Limb orientation along the three anatomical axes is governed by three crucial signalling centres. The three signalling centres include the apical ectodermal ridge that is responsible for the proximal to distal differentiation of the limb, the zone of polarizing activity responsible for anteroposterior limb development and the Wingless-type (Wnt) signalling centre responsible for the dorsal to ventral axis configuration.

A single mesodermal condensation is seen along the long axis of the limb bud at week 4. Pre-chondrogenic cells in these condensations then differentiate into chondrocytes under the influence of bone morphogenetic proteins (BMPs). Sequential chondrification and ossification subsequently follow, resulting in the formation of bones and joints in the upper limb. The elbow becomes visible at 34 days. The humerus, radius and ulna are continuous with each other and are joined by a common perichondrium at 5 weeks of gestation. The forearm is in a neutral position and subsequently by the 6th week condensation of the tissue separates the cartilaginous anlage of the three bones. The forearm pronates at the 8th week due to growth discrepancy between the arterial tree and the radius.2

Any insult during this period of rapid limb development can result in congenital anomalies in the upper extremity, including congenital radio-ulnar synostosis, which results from failure of longitudinal segmentation and persistence of the cartilaginous anlage. Endochondral ossification then proceeds and the cartilaginous synostosis ossifies either partially or completely in the longitudinal or transverse plane. Elbow synostosis with limb hypoplasia occurs in thalidomide embryopathy.

Although most cases are sporadic, a positive family history in some cases of congenital radio-ulnar synostosis has suggested a genetic component. Inheritance may be autosomal dominant or recessive. Some of these cases, especially humeroradial synostosis may be syndromic as they are associated with other congenital syndromes like Carpenter syndrome, Apert syndrome, Antley–Bixler syndrome, Roberts syndrome,3,4 arthrogryposis and Cornelia de Lange syndrome. Chromosomal abnormalities such as Klinefelter syndrome5 may be associated with radio-ulnar synostosis.

Classification

Classically, synostosis has been divided anatomically into humeroradial, humero-ulnar, humeroradio-ulnar and radio-ulnar. Further subdivisions in the humeroradial group have been added based on the anatomical differences, namely classes 1 and 2:6

Table 15.1 Synostosis classification

Anatomical Humeroradial
  Humero-ulnar
  Radio-ulnar
Aetiological Class 1 – bone hypoplasia group with synostosis of elbow
  Class 2 – joint maldevelopment group with synostosis of elbow

Proximal radio-ulnar synostosis has also been classified on the basis of the radiological appearance. Mital7 presented a two-group classification system:

This was modified by Cleary and Omer8 to a four-group system:

The drawbacks of the above classification systems are that they are based purely on anatomy or radiological appearance and are not useful for evaluating the prognosis or treatment outcome. They do not indicate aetiological factors, inheritance pattern or a syndromic association.

An aetiological classification of elbow synostosis was proposed by McIntyre and Benson.9 They divided synostosis around the elbow into two classes:

All the three anatomical types can occur within each class, may be sporadic or familial and, if familial, may be inherited as an autosomal dominant or recessive trait. The class I group is associated with musculoskeletal abnormalities outside the affected limb in 25–55% of cases.10 Class II familial cases may be syndromic and associated with multiple synostosis syndrome, Pfeiffer syndrome, Apert syndrome and Antley–Bixler syndrome.

Presentation, investigations and treatment options

Congenital radio-ulnar synostosis

Congenital radio-ulnar synostosis is bilateral in 60–80% of cases, with some patients having a positive family history.

The child usually presents late, between the ages of 2 and 6 years, as the wrist and shoulder compensate for the lack of forearm rotation. The clinical features include absence of forearm rotation, resulting in difficulty performing certain tasks, including activities of daily living. The forearm is usually fixed in pronation and the elbow exhibits a mild flexion contracture. Hypermobility at the midcarpal and radiocarpal joints can disguise the lack of forearm rotation, particularly with neutral or mild pronation deformities. The child is able more readily to cope with a loss of pronation than loss of supination because of the compensation that is possible by the shoulder and wrist. As part of the abnormality there may be an associated radial head dislocation as in Cleary types III and IV cases.

Soft tissue abnormalities include thickening of the interosseous membrane with atrophy and fibrosis of the pronator quadratus, pronator teres and supinator. Synostosis may occur as a part of limb hypoplasia associated with ulnar or radial deficiency. In syndromic cases the diagnosis of synostosis may be delayed as the symptoms are superseded by numerous other problems typical of the syndrome. It is important to rule out non-musculoskeletal abnormalities that may coexist with radio-ulnar synostosis which include cardiac, haematopoietic and renal malformations.

Surgical techniques and rehabilitation

Mobilization procedure11

Kanaya described this procedure in the following four steps:

Rotational osteotomy

An alternative procedure to mobilize the synostosis is a rotational osteotomy.15,16

These have been described at two sites in the diaphysis of the radius and ulna17,18 or at one site in the distal diaphysis of the radius.19,20 An osteotomy at the synostosis is extremely complex, whereas an osteotomy at two sites in the diaphysis of the radius and ulna is easier, with fewer reported complications.

A single osteotomy of the radius can be performed subperiosteally distal to the synostosis. This has the advantage of a single surgical scar and avoids the need for internal fixation. This osteotomy is recommended in children between the ages of 3 and 6 years and is most commonly performed.

A single osteotomy of the distal radius is performed through a 4 cm skin incision made distally on the radiovolar aspect of the distal forearm. The diaphysis of the radius is exposed and the superficial radial nerve and the radial artery are identified and retracted ulnarward. A sharp longitudinal incision is made on the periosteum and reflected atraumatically from the radius to preserve the longitudinal continuity of the periosteum. Several drill holes are made in the transverse line to the radius using a K-wire and a transverse osteotomy is performed using a chisel (Fig. 15.2A). A meticulous periosteal repair is then performed and the distal forearm maximally supinated and immobilized in an above-elbow plaster cast (Fig. 15.2B).

Outcome including literature review

Operative procedures used in the treatment of congenital radio-ulnar synostosis fall into two major groups. Group 1 procedures are designed to restore rotation and remove the synostosis, while group 2 procedures restore the forearm to a fixed functional position. Several authors have reported poor results after separation of the synostosis and interposition of fat, muscle or silicone.11,2123

Kanaya et al performed the mobilization procedure in seven boys (average age 8 years 2 months) who had isolated proximal radio-ulnar synostosis. All seven children had a dislocation of the radial head preoperatively. A shortening-wedge osteotomy of the radius was performed in four patients at the time of the index procedure, while in three patients the radial head was manually reduced without an osteotomy. The radial head subsequently redislocated in the latter three patients and one of them had an osteotomy 2 years and 8 months after the index procedure to reduce and maintain the radial head alignment. At follow-up the total range of forearm rotation achieved averaged 71° with average supination of 26° and average pronation of 45°. There were no cases of reankylosis at an average follow-up of 4 years 4 months.12 The group who had a radial osteotomy in addition to the index procedure had an average arc of 83° of forearm rotation compared to the second group, who had an average arc of rotation of 40°.

Kamineni et al24 have described a new technique of restoring forearm rotation in post-traumatic proximal radio-ulnar synostosis. This involves resecting a 1 cm thick section of bone from the proximal radial shaft distal to the synostosis. They performed this surgery on seven patients and reported an improvement in forearm rotation from an average fixed pronation of 5° to an average arc of 98°.

Osteotomies to achieve a more functional forearm position are suitable for patients with marked pronation deformity. Green and Mital16 have reported the best results with derotational osteotomies through the fusion mass. This has the advantages of achieving a better correction and rapid healing of the osteotomy owing to the good coaptation of the divided ends. In their series results were excellent in 50%, good in 33%, fair in 6% and poor in 6%. Ogino and Hikino1 also favoured an osteotomy through the fusion mass, but recommended resection of 0.5 cm of bone at the osteotomy site in order to shorten the forearm. All the patients in their series had complete relief of symptoms.

Goldner and Lipton recommended derotation in the distal forearm to minimize circulatory problems.25 The osteotomy was done in the distal radius alone for younger patients and in both the radius and ulna in older patients.

A single osteotomy technique distal to the synostosis was reported by Kashiwa et al in 199919 and subsequently modified by Fujimoto et al.20 This osteotomy is performed at the distal radial diaphysis. Fujimoto presented the results of this osteotomy in three patients (four forearms) with congenital radio-ulnar synostosis. Bony union was achieved in all cases. The period of immobilization in plaster varied from 6 to 9 weeks. All patients achieved good correction, with functional improvement in activities of daily living.

Bolano26 has shown good results with an osteotomy and gradual correction of the rotation using a ring fixator. This technique is useful as there is less risk to the neurovascular structures and it has the added advantage of allowing the patients to choose the most functional position of their forearm.

The ideal position to place the forearm after the osteotomy depends on several factors. If the synostosis is bilateral and both hands are in pronation, Simmons and Waters27 recommended 20° of pronation in the dominant hand and a neutral position for the non-dominant. In unilateral cases, Green and Mital16 recommended 20–25° of supination as the supinated forearm can attain some amount of functional pronation by internal rotation, flexion and abduction at the shoulder. Ogino and Hikino1 from Japan recommend at least 70° of palmar supination, especially in the non-dominant hand, to enable the use of chopsticks by their patients. Hence the amount of angular correction is dependent on customs, dominant hand and bilaterality.

Complications

Following excision of a synostosis and mobilization of the forearm, reankylosis can occur, giving poor results21,22 and a risk of radial head dislocation and posterior interosseous nerve palsy.

Complications reported following derotational osteotomies include neurovascular compromise. Green and Mital reported one case of severe Volkmann’s contracture and one case of posterior interosseous nerve palsy from their series of 13 patients. Ogino and Hikino1 reported two posterior interosseous nerve palsies in 13 operations, both of which spontaneously recovered.

Simmons and Waters27 reported a 36% complication rate with loss of correction in three out of 21 children and an 18% incidence of vascular compromise. A decreased range of elbow movement has also been reported.

Conclusions and personal view

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