Thumb Hypoplasia

Ashraf Abdelaziz MD

Lecturer of orthopedic surgery

Hand and reconstructive surgery

Alzhraa University Hospital

Al-Azhar university

2014

Review

Introduction

Classification

Clinical Examination

Management

Introduction

Congenital thumb hypoplasia

frequently associated with partial or

complete absence of the radius

Epidemiology

◦ 4.6% of congenital deformities consist of

thumb hypoplasia

◦ 1/100,000 live births

Male = female

Bilateral involvement in 60% of patients

The right thumb is more affected

Associated anomalies

◦ > 80% of patients have

associated anomalies including;

VACTERL syndrome

Holt-Oram syndrome

Thrombocytopenia absent radius (TAR)

Fanconi anemia

Classification (modified)Blauth classification 1967

I Minimal shortening and narrowing

II

Web space narrowing

Hypoplastic intrinsic thenar muscles

MCP joint instability

A: uniaxial B: Multiaxial

III

A

Type II +extrinsic tendon abnormalities,

Hypoplastic metacarpal , and stable

carpometacarpal

B

Type II + extrinsic tendon abnormalities, Partial

metacarpal aplasia , and unstable

carpometacarpal

IV Floating thumb

V Absent thumb

Buck-Gramcko incorporated soft-tissue

abnormalities in his classification of thumb

hypoplasia.

Lister subdivided Blauth grade II into IIA

and IIB, based on the stability of the MCP

joint; uniaxial or multiaxial.

The importance of Lister’s modification is

that with grade IIA, the MCP joint can be

reconstructed,

The most common type of thumb hypoplasia is type V

Buck-Gramcko modification of the Blauth classification

Hand Clin 1990

Type III B

Type III B

Type IV

Clinical examination

Careful upper limb examination

Passive motion of all joints.

Assessment of laxity of the collateral ligaments

of the interphalangeal (IP) joint and MCP .

Inspection

Extrinsic tendon abnormalities

Hypoplasia of thenar musculature

Absence of skin creases indicate 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.

Radiographs

◦ recommended views

bilateral films of hand, wrist and forearm

Studies

Labs

◦ Peripheral blood smear and CBC

important to rule out Fanconi anemia

Additional studies

◦ Chromosomal challenge test

detects Fanconi anemia before bone marrow failure

Treatment

Nonoperative

◦ Observation

Type I thumb hypoplasia.

Operative Management of the hypoplastic

thumb is determined by the grade of thumb

hypoplasia.

Opposition tendon transfer (Opponensplasty)

Type I hypoplasia with insufficient thumb abduction

Release of first web space, Opponensplasty,

and Stabilization of MCP joint

Type II and IIIA hypoplasia

Opponensplasty

An opponensplasty is the preferred to augment the deficient thenar muscles

The choice of donor tendon and pulley reconstruction is debatable

performed using

Flexor digitorum superficialis(FDS)or

Abductor digiti minimi(ADM).

It is recommended about 1-2 years of age

The ring finger flexor digitorum superficialis (FDS) has

adequate length for both tendon transfer and UCL

reconstruction.

The abductor digiti minimi(ADM)

First web space deepening

usually performed with Z-plasty or V-Y flap

partial release of the insertions of the intrinsic

muscles (ie, first dorsal interosseous, )

Stabilization of MCP joint

Three options

Fusion

Reconstruction of UCL with FDS

Reconstruction of UCL with free tendon graft

A type IIIA also requires transfers to

overcome the extrinsic musculotendinous

abnormalities

Extensor indicis proprius(EIP) is good for

Extension of the thumb.

And reconstruction of the flexor pollicis

longus(FPL).

Pollicization

◦ Type IIIB, IV, V hypoplasia

◦ Tips

Plan skin incision to avoid skin grafts

Isolate index finger on its

neurovascular bundles

Detach first dorsal and palmar

interosseous muscles

Removing most index metacarpal and

epiphyseal plate

Stabilize index MCP joint (40°

ABD, 15°EX, and 120° pronation).

Reattach and balance

musculotendinous units

Reconstruct long extensor

tendons

Rebalance flexor tendons

Type V with polydactyl

Summary

Thumb hypoplasia frequently associated with

other anomalies.

Blauth classification with other modifications are

very important for management of thumb

Hypoplasia.

Good clinical examination with lab investigations

are very important before reconstruction.

Thank you