Extensor expansion

Abstract: Our observations support the view of Millesi that camptodactyly is due to an imbalance between the flexor and extensor forces acting upon the proximal interphalangeal joint. In 21 consecutive operations the insertion of the lumbrical muscle was abnormal. The muscle inserted into either the superficialis tendon (in three cases), the capsule of the metacarpophalangeal joint (in 15), or the extensor expansion of the adjacent finger (in four). The fourth palmar interosseous muscle was examined in the last 10 patients and was abnormal in five. It was absent in two patients, small in one, and inserted into the extensor expansion of the ring finger in two patients. Therefore, it is suggested that camptodactyly is an intrinsic minus deformity. It follows that treatment should consist of soft tissue release, as necessary, to correct the flexion deformity, followed by a tendon transfer to restore intrinsic action and maintain correction of the deformity.

Abstract: This study was performed to investigate the anatomy and variations of the human extensor tendons of the fingers and their intertendinous connections. Ninetyfive upper limbs of adult cadavers were dissected. The variations in the extensor tendons of the fingers, both proximal and distal to the extensor retinaculum, and their mode of insertion were observed. Also, the intertendinous connections were explored and the obtained data were analysed. The extensor pollicis longus and brevis tendons were found to be single, doubled or, rarely, absent. Their insertion could be traced to either the proximal phalanx, or through the extensor expansion to both phalanges, or rarely to the distal phalanx of thumb. The extensor indicis had a single tendon in all specimens. In the majority of specimens, extensor digitorum had no independent slip to the little finger; it gave off a single tendon to the index, double tendons to the middle finger and triple tendons to the ring finger. Extensor digiti minimi muscle often had double or triple tendons distal to the extensor retinaculum. Three types of juncturae tendinum (JT) were identified between the tendons of extensor digitorum in the 2nd, 3rd and 4th intermetacarpal spaces (IMS) of hands. Types 1 and 2 JT were seen in the three IMS. Type 3 JT was the most frequently identified of all juncturae and was always absent in the 2nd IMS. The percentages of the present data were compared with other researchers'data.

Abstract: The purpose of this investigation was to define the action of each of the thenar muscles and to correlate their individual actions with the action of the group as a whole. The attachments of the thenar muscles to the extensor expansion has been emphasized because extension at the distal joint of the thumb is an important part of their action. The explanation given for the dynamic flexion deformity of the distal thumb joint, or Froment's sign, that appears with ulnar-nerve paralysis, is based upon the failure of the muscles innervated by the ulnar nerve to extend the distal phalanx of the thumb during pinch. The actions of the abductor brevis, flexor brevis, and opponens muscles in producing similar movements of the thumb, but to different degrees, are described in order to simplify the analysis of the disability that arises following division of the median nerve.

Abstract: The cutaneous ligaments of the digits have been recognized by anatomists for several centuries, but the best known description is that of John Cleland. Subsequent varying descriptions of their morphology have resulted in the surgical community having an imprecise view of their structure and dynamic function. We micro-dissected 24 fresh frozen fingers to analyze the individual components of Cleland's ligamentous system. Arising from the proximal interphalangeal (PIP) joint, proximal, and sometimes middle phalanx, we found strong ligaments that ran proximally (PIP-P) and distally (PIP-D). On each side of each finger there was a PIP-P ligament present, which passed obliquely from the lateral side of the proximal and sometimes middle phalanx towards its insertion into the skin at the level of the proximal phalanx. The distal (PIP-D) ligaments were found to pass obliquely distally on the radial and ulnar aspects of the digit towards cutaneous insertions around the middle phalanx. A similar arrangement exists more distally with fibres originating from the DIP joint and middle phalanx (the DIP-P pass obliquely proximally, and the DIP-D, distally). Each individual PIP ligament consisted of three different layers originating from fibres overlying the flexor tendon sheath, periosteum or joint capsule, and extensor expansion. Ligaments arising at the DIP joint had two layers equivalent to the anterior two layers of the proximal ligaments. Cleland's ligaments act as skin anchors maintaining the skin in a fixed relationship to the underlying skeleton during motion and functional tasks. They also prevent the skin from 'bagging', protect the neurovascular bundle, and create a gliding path for the lateral slips of the extensor tendon.