Chapter 71=Malformations of the Appendicular Skeleton (the Limbs)

1/ 19/2015 Chapt er 7 1. Malf orm at ions o f The Appendicula r Sk eleton (the Limbs) - Re v iew of Med ica l Em bry olo gy Book - L ifeMap Disco v ery ht tp: //disco very .lif emapsc.com/ lib rary /re v ie w -o f-m edical-e mbry olo gy /ch apter-7 1-malf ormatio ns- of-t he-a ppendicula r-sk ele ton-t he-li mbs 1/ 2 Free for academic non-profit institutions. All other users need a commercial license from LifeMap S ciences , Inc. Sign In | Join Now EMBRYONIC DEVEL OPMENT & STEM CELL COMPENDIUM Analyze your genes GEN ECARDS SUITE GeneCar ds MalaCar ds LifeMap Discovery PathCar ds GeneA naly tics GeneA LaCart Va rElect + + + I. Introduc tion: abnormali ties of the ext remities var y greatly, a nd minor defe cts in development are relatively common. Major limb malformations are rare. Most are of a hereditary nature, such as chromosomal abnormalities. Environmental factors, such as drugs, have often caused an "epidemic" of limb deformities, e.g., thalidomide, which had been used as a sedative and antina useant. Oft en, c ombina tions of bo th envir onmental and hereditary factors have been involved. In addition, mechanical factors such as reduced amniotic fluid have been associated with limb deformities. In the extreme form, one or bot h ext remi ties are abs ent (amelia) or are represented only by hands an d fee t w hich ar e att ached to the trunk by smal l i rregul ar bones (meromeli a). Sometimes all s egments of the extremities ar e present but are very short (micromelia) II. Types of defici encies A. CLEFT HAND O R FOOT (lobste r-cla w d eformities) are rare; 1 or more central digital rays or digits are absent, resulting in a hand or foot divi ded into 2 parts and opposing each other like a lobster cla w. T he remaini ng d igits are usually fused (syndact yly) B. CLUB HAND OR CONGENITAL ABSENCE OF RADIUS: the radius is partly or t ota lly absent. The hand deviates to the radial side and t he ulna is bowed C. CLUB FOOT OR TALIPES EQUINOV ARUS: is common; see n in males more frequently 1. The sole of the foot is turned i nwards, a nd the foot is adducted and plantar flexed at the midtarsal joint D. BRACHYDACTY LY: not common; there is an a bnormal shortness of the finger s or toes d ue t o siz e reduct ion of the phal anges. This i s an inherited domina nt t ra it ofte n associ ated with short stature E. POLYDACTY LY OR SUPERNUMERAR Y DIGITS: extra fingers or toes are seen; is a common occurr ence and due t o an inheri ted domina nt trait 1. The e xtra digit ma y be i ncomplet ely formed, lack muscle fixation, and be useless 2. In the hand , it is usua ll y found on t he radial or ulnar side (not central); in the foot, it is usually on the fibular side F. SYNDACTY LY (FUSED OR WEBBED DIGI TS): one of the most common malformations. It is the result of failure of differentiation between 2 or more digits. It is inherited as a simple dominant or recessive trait 1. The we bbing betwee n the toes or fi ngers fa il s to brea k down duri ng d evelopment 2. In some cases, there is als o fusion of bones 3. It is most frequently s een bet wee n fingers 3 and 4 and toes 2 and 3 G. CONGENITA L HI P DISLOCATION: the capsule of the hip j oint is abnorma ll y relax ed at birth w ith underdevelopment of t he acet abul um of the hip and head of the femur 1. Dis location usuall y takes pla ce afte r bi rth 2. It is a r elatively common phenome non and i s more frequen tly seen in females 71. Malformations of The Appendicular Skeleton (the Limbs) Review of MEDIC AL EMBRYOLOGY Book b y BEN PANSKY, Ph.D, M.D. PREV NEXT TABLE OF CONTENT 70. Dermatome And Cutaneous Innervati on Of The Li mbs 72. Development Of The Integumentary System: Ectoderma…