Thumb Hypoplasia, Ulnar Longitudinal Deficiency (ULD) & Ulnar Dimelia

Thumb Hypoplasia

Essential Information:
This congenital condition is characterized by structural anomalies in the thumb which can range from minor differences in size to complete absence of the digit.  The affected extremity can show varying degrees of functional loss depending upon the severity of structural changes.
  • Etiology
    • Embryologic insult during upper limb development and antero-posterior limb patterning
    • Theory: insult to the zone of polarizing activity (ZPA)
  • Genetics
    • Unknown, but if associated with radial deficiency there can be a deletion of chromosome 22q11
  • Incidence
    • about 5% of all congenital hand anomalies
    • right side is slightly more common, equal sex ratios
  • Risk Factors
    • In animals, exposure to some mutagens (busulfan) can cause radial dysplasia and thumb anomalies
    • Associated Conditions
      • Radial dysplasia
      • VACTERL
      • Holt-Oram syndrome
      • Thrombocytopenia absent radius
      • Fanconi anemia
Clinical Evaluation:
  • History / Exam Findings
    • thumb structures are hypoplastic (or thumb absence)
    • are the thumb findings bilateral
    • check for other associated physical anomalies
      • spine, cardiac, renal, esophageal, other limbs
  • Imaging / Lab Studies
    • imaging
      • radiographs of entire upper extremity
      • spine radiographs if anomalies suspected
      • renal ultrasound
    • hematologic tests
      • thrombocytopenia
      • chromosome fragility test (Fanconi anemia)
  • Classification Schemes
    • based on the work of:
    • Five types of Thumb Hypoplasia
      • Type I:  small thumb, mild hypoplastic structures
      • Type II:  tight first webspace, some thenar muscle loss, unstable MCP joint
      • Type III:  all features of Type II with some loss of intrinsic and extrinsic musculature
        • subtype III A:has a stable MCP loint
        • subtype III B:has an unstable MCP joint
      • Type IV:  tiny thumb attached to hand by rudimentary skin bridge, may have some bone elements (‘pouce flottant’)
      • Type V:  aplasia, loss of all thumb structures, can affect radial carpal bone structure
  • Conservative
    • generally reserved for Type I thumbs, these patients function well
  • Surgical
address specific deformities
  • tight webspace
    • z-plasty lengthening, flap tranposition
  • MCP laxity
    • usually UCL laxity, reconstruct with free graft or FDS(IV) transfer if opposition needed as well
    • gross instability – consider MCP joint chondrodesis
  • thumb opposition
    • as above
  • aberrant extrinsic muscles
    • re-route tendons, supplemental transfers - usually from FDS(IV)
  • Type IIIA thumb – stable MCP joint, therefore reconstruct
    • distraction lengthening of thumb metacarpal
    • widen first webspace, stabilize MCP joint, opposition transfer
  • pollicization or microvascular toe transfer
    • used as reconstruction for Types IIIB, IV and V thumbs 
  • Prognosis
    • Type I:good, minor functional difficulty
    • Type II: potential limitations due to stability of MCP joint
    • Type IIIA: strength and motion issues
    • Type IIIB, IV, V: depends on success of pollicization
  • Potential Complications
    • recurrent webspace contracture (uncommon)
    • MCP laxity
    • diminished function of digit after pollicization
Recommended Readings
  • Riley SA, Burgess RC.Thumb Hypoplasia.J Hand Surg 2009; 34A: 1564-1573 
  • James MA, Green HD, McCarroll HR Jr, Manske PR. The association of radial deficiency with thumb hypoplasia. J Bone Joint Surg 2004;86A:2196 –2205 

  • James MA, McCarroll HR Jr, Manske PR. Characteristics of patients with hypoplastic thumbs. J Hand Surg 1996;21A:104–113 

  • Tay SC, Moran SL, Shin AY, Cooney WC III. The hypoplastic thumb. J Am Acad Orthop Surg 2006;14:354–366

Ulnar Longitudinal Deficiency (ULD)

Essential Information:
Ulnar longitudinal deficiency (ULD) is a general term that encompasses a wide range of conditions varying from absence of ulnar rays and ulnar carpal bones to complete absence of the ulna; radial head dislocation or radiohumeral synostosis, and shoulder abnormalities.
  • Etiology
    • thought to be due to a dysfunction between sonic hedgehog (Shh) and the zone of polarizing activity (ZPA)
  • Genetics
    • sporadic; some reports of syndromes with x-linked inheritance
  • Incidence
    • postulated to be between 1 in 5,000 to 100,000 live births
    • 4-10 times less common than radial longitudinal deficiency
    • rarely bilateral
  • Risk Factors
    • associated with:
      • proximal focal femoral deficiency
      • fibular deficiency
      • scoliosis
Clinical Evaluation:
  • History / Exam Findings
    • ulnar posturing of hand / wrist
    • absent ulnar digits (possible syndactyly of remaining digits)
    • first webspace anomalies
    • deficient ulnar carpal bones, carpal coalitions possible
    • forearm often bowed, limited forearm rotation
    • elbow instability (radial head dislocation) or stiffness (synostosis)
  • Imaging / Lab Studies
    • plain radiographs of entire upper extremity
    • may need MRI to evaluate joints (synostosis)
  • Classification Schemes
Several schemes - all descriptive of the anatomic anomalies
  • traditional (Ogden)
    • 4 types; based on presence/absence of ulna
  • updated (originally Bayne with modifications)
    • 6 subtypes; based on morphology of ulna, radius, carpus, elbow and first webspace
  • Conservative
    • most patients highly functional
    • specific modalities
      • splinting and stretching the wrist deformity
      • therapy for joint mobilization
  • Surgical
    • syndactyly releases
    • first webspace anomalies
      • deepen webspace
      • osteotomy of thumb metacarpal
    • wrist deformity
      • removal cartilage anlage (fibrous remnant of ulna), with
      • wrist centralization
    • forearm position
      • corrective osteotomy to improve position
      • lengthening of radius
      • conversion to one-bone forearm
    • elbow motion
      • ? radial head excision
      • ? synostosis osteotomy 
  • Prognosis
    • generally good, patients highly functional
  • Potential Complications
    • uncommon, but related to surgical procedures
      • e.g. distraction lengthening of forearm
        • delayed union of regenerate
        • tightening of flexor tendons

Recommended Readings
  • Ogden JA, Watsen HK, Bohne W. Ulnar dysmelia. J Bone Joint Surg 1976;58: 467-475.
  • Havenhill TG, Manske PR, Patel A, Goldfarb CA. Type 0 ulnar longitudinal deficiency. J Hand Surg 2005;30A: 1288-1293.
  • Cole RJ, Manske PR. Classification of ulnar deficiency according to the thumb and first web. J Hand Surg 1997;22A: 479-488.

Ulnar Dimelia

Essential Information:
This is a congenital upper extremity anomaly characterized by an absent thumb and a ‘mirror-like’ duplication of the ulnar bony structures in the hand, wrist and forearm.
  • Etiology
    • ectopic expression of the zone of polarizing activity (ZPA) or
    • anterior expression of sonic hedgehog
  • Genetics
    • not identified
  • Incidence
    • sporadic
  • Risk Factors
    • none known
Clinical Evaluation:
  • History / Exam Findings
    • usually see 7 or 8 fingers, and an absent thumb
    • 2 ulnae in the forearm
  • Imaging / Lab Studies
    • plain radiographs
  • Classification Schemes
    • Al-Qattan (1998): 2 basic types
      • classic: 2 ulnae in forearm
      • non-classic: hypoplastic radius and ulna
  • Conservative
    • can be considered if radial digits ‘oppose’ the ulnar digits
  • Surgical
    • pollicization of 1 of the radial digits (with ablation of the other radial digits) for opposition function
  • Prognosis
    • hand function can be improved surgically (as above)
    • limited forearm rotation
  • Potential Complications
    • related to surgical care
Recommended Readings
  • Al-Qattan MM, Al-Thunayan A, DeCordier M, Nandagopal N, Pit- kanen J. Classification of the mirror hand-multiple hand spectrum. 
  • Groper PT.Ulnar Dimelia.J Hand Surg Am. 1983; 8: 487-491.
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