EXTENSOR ANATOMY AND REPAIR

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EXTENSOR ANATOMY
AND REPAIR
DR. MARK D. LABANDTER
EXTENSOR TENDON ANATOMY

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EXTRINSIC EXTENSORS I
THE EXTRINSIC EXTENSORS ENTER THE
HAND THROUGH SIX COMPARTMENTS
FORMED BY THE EXTENSOR RETINACULUM
THE TENDONS ARE COVERED BY A
SYNOVIAL SHEATH ONLY AT THE WRIST
LEVEL
IN 50% OF THE POPULATION THE V FINGER
HAS NO EXTENSOR DIGITORUM COMMUNIS
ONLY THE EXTENSOR DIGIT MINIMI
EXTRINSIC EXTENSOR II
IN ADDITION TO THE EDC THE INDEX HAS
THE EXTENSOR INDICIS PROPRIUS (A
COMMON DONOR TENDON)
THE JUNCTURE TENDINUM JOIN THE EDC
PROXIMAL TO THE MCPJ, THEREFORE
LACERATIONS PROXIMAL TO THE
JUNCTURE ALLOW EXTENSION BY PULL
FROM AN ADJACENT FINGER

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ANATOMY OF EXTENSOR
APPARATUS OF THE DIGIT
INTRINSIC EXTENSORS
FOUR DORSAL INTEROSSEI > ABDUCTORS
THREE PALMAR INTEROSSEI >
ADDUCTORS
FOUR LUMBRICAL MUSCLES
THE INTRINSIC MUSCLES FLEX THE MCPJ
AND EXTEND THE PIPJ AND DIPJ
THE TENDONS OF THE INTRINSIC MUSCLES
FORM THE LATERAL BANDS WHICH JOIN
THE EXTRINSIC EXTENSOR AT THE
PROXIMAL PHALANX AND EVENTUALLY
FORM THE CENTRAL SLIP

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THUMB EXTENSOR MECHANISM
DIFFERS FROM THAT OF THE
FINGERS IN THAT EACH JOINT HAS AN
INDEPENDENT TENDON
THE EPL EXTENDS THE IPJ
THE EPB EXTENDS THE MCPJ
THE ABDUCTOR POLLICIS LONGUS
EXTENDS THE CARPOMETACARPAL
JOINT
VERDAN’S 8 ZONE SYSTEM
VERDAN’S ZONE SYSTEM ALLOWS
FOR A LOGICAL DISCUSSION OF
TREATMENT PLANS AND OUTCOMES
ASSOCIATED WITH EACH AREA

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ZONE I INJURY
(DIPJ; MALLET FINGER)
DISRUPTION OF EXTENSOR TENDON
CONTINUITY OVER THE DIPJ PRODUCES
THE FLEXION DEFORMITY OF THE DIPJ
KNOWN AS MALLET FINGER
UNTREATED FOR A PROLONGED TIME,
HYPEREXTENSION OF THE PIPJ
DEVELOPES BECAUSE OF HYPERLAXITY OF
THE PIPJ
THE RESULTING DEFORMITY IS KNOWN AS
A SWAN-NECK DEFORMITY
SWAN-NECK DEFORMITY

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MALLET FINGER TYPE I
CLOSED OR BLUNT TRAUMA WITH
LOSS OF TENDON CONTINUITY WITH
OR WITHOUT AN AVULSION
FRACTURE
TREATMENT IS CONTINOUS
SPLINTING OF THE DIPJ IN
EXTENSION FOR 6 WEEKS,
FOLLOWED BY 2 WEEKS OF NIGHT
SPLINTING
ORTHOPEDIC CLOSED
TREATMENT

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MALLET FINGER TYPE II
LACERATION AT OR PROXIMAL TO DIPJ
WITH LOSS OF TENDON CONTINUITY
TREATMENT IS SUTURING OF THE TENDON
ALONE OR DERMATOTENODESIS -
INCORPORATING THE TENDON AND THE
SKIN IN THE SAME SUTURE WITH
SPLINTING IN EXTENSION FOR 6 WEEKS,
FOLLOWED BY 2 WEEKS OF NIGHT
SPLINTING
MALLET FINGER TYPE III
DEEP ABRASION WITH LOSS OF SKIN,
SUBCUTANEOUS COVER, AND
TENDON SUBSTANCE
TREATMENT REQUIRES IMMEDIATE
SOFT-TISSUE COVERAGE AND
PRIMARY GRAFTING OR LATE
RECONSTRUCTION USING A FREE
TENDON GRAFT

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MALLET FINGER TYPE IV
IV A – TRANSEPIPHYSEAL PLATE FRACTURE IN CHILDREN
TREATMENT IS CLOSED REDUCTION FOLLOWED BY
SPLINTING FOR 3-4 WEEKS
IV B – HYPERFLEXION INJURY WITH FRACTURE OF THE
ARTICULAR SURFACE OF 20-50%
TREATMENT IS SPLINTING FOR 6 WEEKS, FOLLOWED BY
2 WEEKS OF NIGHT SPLINTING
IV C – HYPEREXTENSION INJURY WITH FRACTURE OF THE
ARTICULAR SURFACE OF MORE THAN 50% WITH EARLY OR
LATE PALMER SUBLUXATION OF THE DISTAL PHALANX
TREATMENT IS OPEN REDUCTION AND INTERNAL
FIXATION USING A KIRSCHNER WIRE WITH THE ADDITIONAL
PROTECTION OF A SPLINT FOR 6 WEEKS
ZONE II INJURY
(MIDDLE PHALANX)
THE INJURIES ARE DUE TO LACERATION OR
CRUSH INJURIES
TREATMENT WHEN LESS THAN 50% OF THE
TENDON WIDTH IS CUT INVOLVES WOUND
CARE AND SPLINTING FOR 7-10 DAYS,
FOLLOWED BY ACTIVE MOTION
TREATMENT WHEN MORE THAN 50% OF
THE TENDON WIDTH IS CUT INVOLVES
PRIMARY REPAIR FOLLOWED BY 6 WEEKS
OF SPLINTING

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ZONE III INJURY
(PIPJ; BOUTONNIERE DEFORMITY)
THE BOUTONNIERE DEFORMITY IS
CAUSED BY DISRUPTION OF THE
CENTRAL SLIP AT THE PIPJ AND
PROLAPSE OF THE LATERAL BANDS
CAUSING FLEXION OF THE PIPJ AND
HYPEREXTENSION OF THE DIPJ
BOUTONNIERE DEFORMITY

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MECHANISM OF INJURY
BOUTONNIERE DEFORMITY
THE INJURY CAN BE CLOSED OR OPEN,
AND THE CENTRAL SLIP MAY AVULSE WITH
OR WITHOUT A BONY FRAGMENT
IN CLOSED TRAUMA THE BOUTONNIERE
DEFORMITY MAY DEVELOP GRADUALLY
APPEARING10-14 DAYS AFTER THE INITIAL
INJURY
TREATMENT FOR CLOSED INJURIES
INVOLVES SPLINTING OF THE PIPJ IN
EXTENSION FOR 4-6 WEEKS
SURGICAL INDICATIONS
CLOSED BOUTONNIERE
FAILED NONOPERATIVE TREATMENT
DISPLACED AVULSION FRACTURE AT
THE BASE OF THE MIDDLE PHALANX
AXIAL AND LATERAL INSTABILITY OF
THE PIPJ WITH LOSS OF ACTIVE OR
PASSIVE EXTENSION

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PRIMARY REPAIR
PRIMARY REPAIR BY SUTURING THE
CENTRAL SLIP TO THE MIDDLE
PHALANX WITH OR WITHOUT THE
BONY FRAGMENT. KIRSCHNER WIRE
FIXATION OF THE PIPJ FOR 10-14
DAYS, FOLLOWED BY AN EXTENSION
SPLINT UNTIL THERE IS
RADIOGRAPHIC EVIDENCE OF BONY
UNION
SNOW RECONSTRUCTION OF
CENTRAL SLIP
CENTRAL SLIP RECONSTRUCTION
WITH A DISTAL PEDICLE TENDON
FLAP TAKEN FROM THE EXTENSOR
TENDON AT THE PROXIMAL PHALANX
AND TURNED OVER 180 DEGREES TO
BE FIXED ON THE BASE OF THE
MIDDLE PHALANX

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SNOW I
SNOW II

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BURKHALTER AND AIACHE
TENDINOPLASTY
CENTRAL SLIP RECONSTRUCTION BY
HEMISECTION OF EACH OF THE
LATERAL BANDS WHICH ARE THEN
SUTURED SIDE TO SIDE
BURKHALTER AND AIACHE
TENDINOPLASTY

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OPEN BOUTONNIERE
DEFORMITY
FOR OPEN INJURIES SURGICAL
REPAIR MIGHT BE AVOIDED BY
SPLINTING, BECAUSE THE TENDON
ENDS DO NOT RETRACT IN THIS AREA
ZONE IV INJURY
(PROXIMAL PHALANX)
COMPLETE LACERATIONS ARE TREATED
BY PRIMARY REPAIR FOLLOWED BY 6
WEEKS OF SPLINTING IN EXTENSION
PARTIAL LACERATIONS WITH NO LOSS OF
PIPJ EXTENSION ARE TREATED BY
SPLINTING THE PIPJ IN EXTENSION FOR 3-4
WEEKS WITHOUT TENDON SUTURING
WHICH IS EQUIVALENT TO PRIMARY
REPAIR

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ZONE V
(METACARPOPHALANGEAL JOINT)
INJURIES OVER THE MCPJ ARE USUALLY OPEN
AND OCCUR WITH THE JOINT IN FLEXION, SO THE
TENDON INJURY WILL BE PROXIMAL TO THE
DERMAL INJURY
THE INJURY IS OFTEN CAUSED BY STRIKING
SOMEONE IN THE MOUTH WITH A CLENCHED FIST.
THIS IS A CONTAMINATED WOUND AND SHOULD
BE IRRIGATED AND LOOSELY SUTURED, TREATED
WITH BROAD SPECTRUM ANTIBIOTIC THERAPY
TREATMENT INVOLVES SPLINTING WITH THE
WRIST IN 40-45 DEGREES EXTENSION AND THE
MCPJ IN 15-20 DEGREES FLEXION. THE TENDON
LACERATION IS REPAIRED 7-10 DAYS LATER, IF
NEEDED
ZONE VI INJURY
( DORSAL HAND)
SINGLE OR PARTIAL TENDON
LACERATIONS MAY NOT RESULT IN LOSS
OF EXTENSION BECAUSE EXTENSOR
FORCES ARE STILL TRANSMITTED
THROUGH THE JUNCTURE TENDINUM
DIAGNOSIS, THEREFORE, IS BEST MADE BY
DIRECT INSPECTION
TREATMENT IS PRIMARY REPAIR AND
SPLINTING IN EXTENSION FOR 4-6 WEEKS
IF THE EXTENSOR DIGITORUM COMMUNIS
IS INVOLVED, ALL FINGERS SHOULD BE
SPLINTED

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ZONE VII INJURY
(WRIST)
PARTIAL RELEASE OF THE
RETINACULUM IS REQUIRED FOR
EXPOSURE OF THE LACERATED
TENDONS
SOME PORTION OF THE
RETINACULUM SHOULD BE
PRESERVED TO PREVENT EXTENSOR
BOWSTRINGING
ZONE VIII INJURY
(DORSAL FOREARM)
LACERATED EXTRINSIC MUSCLES
ARE TREATED BY PRIMARY REPAIR
AND STATIC IMMOBILIZATION OF THE
WRIST IN 45 DEGREES OF EXTENSION
AND MCPJ IN 15-20 DEGREES OF
FLEXION FOR 4-5 WEEKS
DYNAMIC MOTION OF THE MCPJ
SHOULD BE STARTED AT 2 WEEKS

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THUMB INJURIES
MALLET THUMBS ARE RARE BECAUSE THE TERMINAL
EXTENSOR TENDON IS MUCH THICKER ON THE THUMB
OPEN MALLET THUMB IS TREATED BY PRIMARY REPAIR,
FOLLOWED BY SPLINTING FOR 6 WEEKS
CLOSED MALLET THUMB CAN BE TREATED BY SPLINTING
ALONE
ISOLATED LACERATION OF THE EPB IS RARE AND REPAIR IS
RECOMMENDED EVEN THOUGH EXTENSION OF MCPJ IS
POSSIBLE WITH EPL ALONE
ISOLATED EPL LACERATION IS TREATED BY PRIMARY
REPAIR AND SPLINTING FOR 3-4 WEEKS WITH THE WRIST IN
40 DEGREES OF EXTENSION AND SLIGHT RADIAL DEVIATION
AND THE MCPJ IN EXTENSION
DYNAMIC SPLINTING FOR
EXTENSOR INJURIES
EARLY CONTROLLED MOTION WITH A
DYNAMIC EXTENSOR SPLINT DECREASES
ADHESIONS AND SUBSEQUENT
CONTRACTURES
USUALLY USED FOR ZONE V – VIII INJURIES
THE SPLINT ALLOWS INCOMPLETE ACTIVE
FLEXION AND PASSIVE EXTENSION
AFTER 4 WEEKS FULL ACTIVE EXTENSION
IS INITIATED

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