Introduction Congenital underdevelopment of the thumb frequently associated with partial or complete absence of the radius Epidemiology incidence 1/100,000 live births demographics male = female location bilateral involvement in ~60% of patients right hand more common than left Pathophysiology exact cause during embryologic development has yet to be elucidated Associated anomalies greater than 80% of patients will have associated anomalies including VACTERL Holt-Oram thrombocytopenia-absent radius (TAR) Fanconi anemia Classification & Treatment Treatment algorithm depends on presence of carpometacarpal joint stability Blauth Classification Type Description Treatment Type I Minor hypoplasia All musculoskeletal and neurovascular components of the digit are present, just small in size No surgical treatment required Type II All of the osseous structures are present (may be small) MCP joint ulnar collateral ligament instability Thenar hypoplasia Stabilization of MCP joint Release of first web space Opponensplasty Type IIIA Musculotendinous and osseous deficiencies CMC joint intact Absence of active motion at the MCP or IP joint Type IIIB Musculotendinous and osseous deficiencies. Basal metacarpal aplasia with deficient CMC joint Absence of active motion at the MCP or IP joint. Thumb amputation & pollicization Type IV Floating thumb Attachment to the hand by the skin and digital neurovascular structures Type V Complete absence of the thumb Presentation Physical exam inspection extrinsic tendon abnormalities pollex abductus flexor pollicus longus attaches to normal insertion and the extensor tendon hypoplasia of thenar musculature absence of skin creases indicates muscle or tendon abnormalities excessive abduction of MCP joint range of motion and instability ulnar collateral ligament laxity web-space tightness evaluation for associated anomalies is essential cardiac auscultation echocardiography kidneys ultrasound abdomen ultrasound Imaging Radiographs recommended views bilateral films of hand, wrist and forearm Studies Labs peripheral blood smear and complete blood count important to rule out Fanconi anemia Additional studies chromosomal challenge test detects Fanconi anemia before bone marrow failure Treatment Nonoperative observation indications Type I hypoplasia where augmentation of thenar musculature (thumb abduction) is not necessary Operative opposition tendon transfer (opponensplasty) indications Type I hypoplasia with insufficient thumb abduction release of first web space, opposition transfer, stabilization of MCP joint indications Type II and IIIA hypoplasia pollicization indications Type IIIB, IV, V hypoplasia Surgical Techniques Opponensplasty (opposition transfer) technique performed using flexor digitorum superficialis or abductor digiti minimi First web space deepening technique usually performed with Z-plasty Stabilization of MCP joint technique three options fusion reconstruction of UCL with FDS reconstruction of UCL with free tendon graft Pollicization technique plan skin incision to avoid skin grafts isolate index finger on its neurovascular bundles detach first dorsal and palmar interosseous muscles shorten digit by removing index finger metacarpal and epiphyseal plate stabilize index MCP joint reattach and balance musculotendinous units reconstruct long extensor tendons rebalance flexor tendons
QUESTIONS 1 of 3 1 2 3 Previous Next You have 100% on this question. Just skip this one for now. Take This Question Anyway (OBQ10.6) The parents of a newly adopted 3-year-old boy bring the child to the office for evaluation of his thumb. A clinical photograph is provided in figure A. Which of the following is the most important factor in determining thumb reconstruction versus ablation and pollicization? Review Topic | Tested Concept QID: 3094 FIGURES: A Type & Select Correct Answer 1 Stability of the carpometacarpal joint 86% (2866/3349) 2 Functional ROM of the wrist 1% (19/3349) 3 Functional ROM of the index, middle, ring, and small fingers 4% (126/3349) 4 Skin contracture of the first web space 2% (63/3349) 5 Absence of a thumb interphalangeal joint 8% (252/3349) L 1 Question Complexity B Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 1 You have 100% on this question. Just skip this one for now. Take This Question Anyway (OBQ05.256) What is the most important variable when deciding between reconstruction versus ablation of a hypoplastic thumb? Review Topic | Tested Concept QID: 1142 Type & Select Correct Answer 1 contralateral thumb function 4% (129/3270) 2 thenar muscle function 6% (212/3270) 3 presence of an extensor pollicis longus tendon 3% (96/3270) 4 carpometacarpal joint stability 78% (2546/3270) 5 metacarpophalangeal joint stability 8% (273/3270) L 1 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 You have 100% on this question. Just skip this one for now. Take This Question Anyway (OBQ04.120) Using the Blauth classification of thumb hypoplasia, grade IIIA can be treated with thumb reconstruction whereas grade IIIB is treated with thumb amputation & pollicization. What is the key difference between these two grades? Review Topic | Tested Concept QID: 1225 Type & Select Correct Answer 1 Presence of complete osseous structures 9% (266/3090) 2 Presence of intact musculotendinous structures 5% (150/3090) 3 Carpometacarpal joint stability 72% (2227/3090) 4 Metacarpophalangeal joint stability 11% (346/3090) 5 Presence of an extensor pollicis longus tendon 2% (77/3090) L 2 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3