The arcade of Frohse and its relationship to posterior interosseous nerve paralysis.

A cause for spontaneous paralysis of the posterior interosseous nerve has been sought for many years. In recent times an increasing number of reports on this subject has appeared. Sharrard’s (1966) cases were of particular interest because the approach to the problem was direct. If the paralysis did not subside within six weeks, exploration was carried out promptly. He described a fibrous band across the nerve, release of which restored function. Capener (1964) reported similar experiences and likened the compression to that seen in carpal tunnel syndrome. Later (1966) he described a sharp aponeurotic edge of the supinator in relation to “ tennis elbow.” This paper reports an anatomical study of the upper limbs in twenty-five adults and ten full-term foetuses and describes a probable anatomical factor, the arcade ofFrohse, in traumatic and non-traumatic progressive paralysis of the posterior interosseous nerve. Through this arcade, described by Frohse (Frohse and Fr#{228}nkel 1908), the posterior interosseous nerve passes to enter the plane between the two heads of the supinator muscle. The most proximal part of the superficial head of the supinator muscle may be tendinous and form a fibrous arch. Arising in a semi-circular manner from the tip ofthe lateral epicondyle, its fibres arch downwards 1 centimetre and then gain attachment to the medial aspect of the lateral epicondyle just lateral to the articular surface of the capitulum. The posterior