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Flexor and extensor tendon injuries of the hand
UPPER LIMB TRAUMA
points in the hand has implications for the expected outcome after injury. The hand is therefore split into zones (Figure 1) that describe different segments of anatomy. Until the 1950s, zone II injuries were considered too difficult to repair, and still have the highest postoperative rupture rate.
Flexor and extensor tendon injuries of the hand Jill Arrowsmith
Diagnosis The diagnosis can be obvious if the: • injury overlies the path of the tendons • normal resting cadence of the fingers is lost (Figure 2) • patient is unable to actively flex the involved proximal interphalangeal or distal interphalangeal joints when the unaffected digits are held in extension (quadregia action). Diagnosis is often more difficult in children or adults who are unable to cooperate, or if there is a partial division of the tendon which can cause limited, painful flexion. A divided tendon may not be visible in the wound if the injury occurred with the hand in flexion.
Robert E Page
Although the exact incidence is unknown, hand injuries involving either the flexor or extensor tendons are very common. Careful assessment and management is required to ensure a rapid return to normal function. This contribution should be read in conjunction with ‘Fractures of the hand’, page 256.
Flexor tendons
Principles of repair Tetanus immunity must be checked. A booster of tetanus toxoid is given if it has been more than 10 years since the last dose. General or regional anaesthesia (axiliary block) – a long tourniquet time may be needed. Proximal incisions to retrieve the retracted end of the tendon may be needed. Cleansing and debridement of the wounds must be performed meticulously, with only minimal debridement of the tendon to preserve length. Prophylactic antibiotics are required. A single perioperative dose of an anti-Staphylococcal and Streptococcal antibiotic (e.g. flucloxacillin) is sufficient for most clean, incised wounds. Contaminated injuries require broad-spectrum antibiotic cover (e.g. augmentin), usually for a minimum of 24 hours. Extensile incisions need good exposure. Straight-line scars across joints, which can cause subsequent contractures, should be avoided. Atraumatic surgical technique reduces the likelihood of adhesion formation. You are allowed to pick up the cut end of the tendon with your forceps only once! Do not try to retrieve the proximal end of the tendon by blindly passing forceps down the sheath. If ‘milking’ (by massaging the tendon forward with the finger and wrist inflexion) does not allow the tendon to be visualized, identify it proximally. Pass a fine feeding tube alongside the tendon within the sheath to the wound site. Stitch this to the tendon proximally and then pull the tube distally until you can retrieve the cut end of the tendon. Preservation of the pulleys is important. Use small incisions or ‘vents’ to identify the tendon and allow the repair site to glide. Retain as much of the biomechanically important A2 and A4 pulleys (Figure 1) as possible. Core stitch is a grasping suture within the main body of the tendon (Figure 3). It provides most of the strength of the repair, and requires a 1 cm bite of each side of tendon. Most surgeons use a nonabsorbable suture, either a 3-0 or 4-0 monofilament (e.g. Prolene) or a braided polyester (e.g. Ethibond). The two-strand modified Kessler stitch is most commonly used (Figure 3). Tendon repair strength is directly proportional to the number of suture strands crossing the repair. Four-strand stitches are about 70% stronger than two-strand repairs. As most units use an early
Anatomy The wrist and digit flexors arise mainly from the common flexor origin of the medial epicondyle of the humerus. There are two wrist flexors. • Flexor carpi radialis passes through a groove in the trapezium to insert into the bases of the 2nd and 3rd metacarpals. • Flexor carpi ulnaris with the pisiform as a sesamoid inserts into the base of the 5th metacarpal. At the wrist, the independent flexor digitorum superficialis tendons lie volar, or palmar, to the conjoined flexor digitorum profundus tendons. They pass distally deep to the transverse carpal ligament through the carpal tunnel and into the palm. The lumbrical muscles arise from the flexor digitorum profundus tendons at this point. The paired flexor digitorum superficialis and flexor digitorum profundus tendons to each finger enter the flexor synovial sheath for the finger at the level of the metacarpal neck. The flexor sheath has synovial layers that provide nutrition for the tendons, and a retinacular layer that has a series of condensations (pulleys) which are important biomechanically during finger movement. The flexor digitorum superficialis tendon splits in two, passes around the flexor digitorum profundus tendon and inserts into the base of the middle phalanx. It flexes the proximal interphalangeal joint. The flexor digitorum profundus tendon passes between the flexor digitorum superficialis slips and carries on distally to insert into the distal phalanx. It flexes both the proximal and distal interphalangeal joints. The flexor pollicis longus passes through the carpal tunnel already within a flexor sheath to insert into the distal phalanx of the thumb. The thumb flexor sheath has three pulleys. The varying arrangement of the flexor tendons at different
Jill Arrowsmith is a Specialist Registrar at Northern General Hospital, Sheffield, UK. Robert E Page is a Consultant Plastic Surgeon at Northern General Hospital and Sheffield Children’s Hospital, Sheffield, UK.
SURGERY
252
© 2003 The Medicine Publishing Company Ltd
UPPER LIMB TRAUMA
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a
The diagnosis of flexor tendon injuries. The ‘pointing finger sign’ (arrow) following division of the tendons a and restoration of normal resting cadence following tendon repair b.
b
2
active mobilization regimen postoperatively, the repair has to be sufficiently strong to tolerate unresisted active flexion. Some surgeons now routinely use four-strand repairs. Peripheral stitch is a continuous stitch that runs circumferentially around the tendon repair site. Most surgeons use a 6-0 monofilament (e.g. Prolene) with a variety of stitches in use (Figure 3). Peripheral stitching tidies the repair to allow better ‘gliding’ (smooth running of the tendon within the sheath) and contributes a significant amount of strength to the repair. It also helps prevent gapping of the tendon ends at the repair site, thus reducing adhesion formation.
SURGERY
Zone I injuries – the flexor digitorum profundus tendon may be divided within 1 cm of its insertion so that it is not possible to place a core suture in the distal tendon. A core suture is placed in the proximal tendon end instead. The suture ends are passed through, or around, the distal phalanx to emerge at the midnail level. The tendon is moved up to the bone and the suture tied on the nail over a button. The main core suture is removed after 6 weeks. Closed avulsion injuries commonly affect the flexor digitorum profundus of the ring finger and are classified by the amount of proximal retraction of the tendon. 253
© 2003 The Medicine Publishing Company Ltd
UPPER LIMB TRAUMA
Tendon repairs �����������
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Modified Kessler
Continuous running ��������
Halsted continuous horizontal mattress
Modified Kessler + horizontal mattress ��������
Tsuge
Silverskiold cross stitch ��������������� ������������������
3
Splintage is by a dorsal splint. This restricts the amount of tension across the repair, and reduces the potential for joint contracture. The position of splintage for an early active mobilization regimen (see below) is: • wrist in neutral or slight (up to 20o) flexion • metacarpophalangeal joints in 50–70o flexion • interphalangeal joints extended.
usually responds to exercise modification if diagnosed early. Tendon adherence is less common with an early active mobilization regimen. It impairs full movement of the finger. After the initial scars have matured and softened, the scarred tendon is re-explored and released (tenolysis). Intensive therapy postoperatively is needed to prevent recurrent adhesion formation.
Postoperative management Most postoperative management regimens in the UK are based on early active mobilization, because the strength of a tendon repair increases if stress is applied to it. Also, movement of the repair site reduces the number and strength of adhesions. Early active regimen involves repetitions of unresisted active flexion, passive flexion and active extension within the confines of the splint at intervals throughout the day. If possible, the regimen should begin on day one, post-operation. After about 6 weeks, movement and grip strength are gradually increased by using small, spring-loaded weights. The total rehabilitation period is about three months. Wrist flexor tendon repairs are protected by a splint, holding the wrist slightly flexed for 3 weeks.
Extensor tendons Anatomy The extrinsic extensor tendons arise in the forearm and pass through six compartments beneath the extensor retinaculum (Figure 1). Their course is also divided into zones. First compartment – the extensor pollicus brevis runs with the abductor pollicus longus, inserting into the proximal phalanx of the thumb to extend the metacarpophalangeal joint. Second compartment – the extensor carpi radialis longus and brevis insert into the bases of the 2nd and 3rd metacarpals. Third compartment – the extensor pollicus longus passes around Lister’s tubercle of the radius and inserts into the distal phalanx of the thumb to extend the interphalangeal joint. Fourth and fifth compartments – the extensor digitorum communis tendons with the additional independent long extensor of the index finger run under the fourth compartment, and the independent little finger extensor runs under the fifth compartment. Extensor digitorum communis has multiple interconnections, juncturae tendinum, in the dorsum of the hand. These interconnections may allow extension of a digit even when its main extensor digitorum communis tendon has been divided. The main action of the long extensors of the fingers is to extend the metacarpophalangeal joints. On the dorsum of the fingers, the extensor tendons spread out to become part of a complex apparatus that includes the insertions
Complications Rupture of the tendon repair occurs in around 3.5% of flexor tendon repairs in early active mobilization regimens, with a much higher (around 10%) rate for zone II repairs. It may be detected either by the patient (who feels a sudden ‘snap’ and is then unable to flex the affected joint) or by the therapist. If detected within a few days, immediate secondary repair may be possible. If diagnosis is delayed, muscle sarcomere shortening will probably make direct repair impossible and a tendon graft will be required. Joint contracture affects the interphalangeal joints if the patient has persistent difficulty extending the fingers to the splint. It SURGERY
254
© 2003 The Medicine Publishing Company Ltd
UPPER LIMB TRAUMA
of the intrinsic muscles of the hand. The intrinsic muscles extend the interphalangeal joints, via the central slip for the proximal interphalangeal joint and the two lateral bands for the distal interphalangeal joint. This arrangement of the extensor apparatus over the dorsum of the digits is maintained by the relative lengths of inflexible tendon which constitute it. As it is difficult to repair a tendon maintaining its original length, once part of the system is injured, it may create a secondary deformity of the finger. Sixth compartment – the extensor carpi ulnaris tendon inserts into the fifth metacarpal.
the metacarpophalangeal and distal interphalangeal joints free, for several weeks. Open injuries require debridement and repair under local anaesthetic. The tendon is 0.5 mm thick at this point, so it is often necessary to incorporate part of the thicker lateral bands into the repair to hold the suture. A 4-0 monofilament suture, either as a ‘figure of eight’ or a modified Kessler stitch, is used. The proximal interphalangeal joint is splinted in extension for 4–6 weeks with a K-wire, while allowing active flexion of the distal interphalangeal joint. Protected flexion of the proximal interphalangeal joint is required for a further 4 weeks.
Management Mallet finger (zone I, Figure 4) is involuntary flexion of the distal phalanx caused by the disruption or tearing of the extensor tendon. It can be either an open or closed injury. Closed injuries are due to forced flexion of the extended finger and may be associated with an avulsion fracture of the distal phalanx. Most are successfully managed by splinting the distal interphalangeal joint only in extension using either a ready-made splint (e.g. Stack) or a customized version. Splinting is continued for at least six weeks. If extension loss redevelops, the splint is re-applied for 2 weeks. If the fracture fragment is large and the remaining distal phalanx subluxed due to the unopposed action of flexor digitorum profundus, a longitudinal K-wire may be required to reduce and hold the distal interphalangeal joint. The fracture fragment may also require reduction and fixation, although this is needed less often. The K-wire is kept for six weeks. Open injuries need careful cleaning under local anaesthetic. The tendon alone, or the tendon and skin together, are repaired with a 4-0 or 5-0 suture. K-wire the distal interphalangeal joint as with the closed injury for 6 weeks.
MCP joint area injuries (zone V) are open injuries and are often caused by human teeth following a punch injury. The metacarpophalangeal joint may also be involved, so the radiograph should be carefully checked for joint damage and tooth fragments. A high index of suspicion of joint involvement is required as patients may not admit to the cause of the injury: explore and irrigate the joint if concerned. The associated tendon injury is often partial and at a different level, and can be repaired as a secondary procedure when the infection is under control. Clean tendon lacerations can be repaired primarily with a core stitch if the tendon bulk permits. Dorsum of the hand injuries (zone VI) can be difficult to diagnose, as the affected finger may still extend via the junctura tendinae, but there is usually some impairment of extension. A local anaesthetic is used; the juncturae prevent the proximal tendon end from retracting, making identification of the tendon ends and subsequent repair technically easy. The tendon is repaired with a 4-0 monofilament core stitch if bulky enough, or a mattress or ‘figure of eight’ stitch is used.
Central slip injuries (zone III) can be open or closed. The acute injury does not usually present as a boutonnière deformity (finger deformity with proximal interphalangeal joint flexion and distal interphalangeal joint extension). Development of this requires time for the intact lateral bands to migrate volarwards, pulling the proximal interphalangeal joint into flexion as the distal interphalangeal joint is extended. Closed injuries may be associated with an avulsion fracture of the middle phalanx. Most are successfully treated by external splintage of the proximal interphalangeal joint in extension, leaving
Wrist injuries (zone VII) need general or regional anaesthetic for repair, because the proximal cut tendon ends often retract into the forearm, necessitating extension of the laceration. The extensor retinaculum may be injured or need to be incised to enable the tendon repair. It is important to retain or repair part of the retinaculum to prevent ‘bowstringing’ of the tendons with wrist extension. Postoperative splintage: tendon repairs from zone V proximally are managed with a volar splint, keeping the wrist in around 40o of extension and the metacarpophalangeal joints flexed around 20o. The area is usually immobilized for three weeks, but some units use a dynamic splinting protocol similar to that for flexor tendon injuries. u
FURTHER READING Green D P, Hotchkiss R N, Pederson W C, Lampert R, Eds. In: Green‘s Operative Hand Surgery. 4th edition. New York: Churchill Livingstone, 1999.
4 Mallet finger.
SURGERY
255
© 2003 The Medicine Publishing Company Ltd
points in the hand has implications for the expected outcome after injury. The hand is therefore split into zones (Figure 1) that describe different segments of anatomy. Until the 1950s, zone II injuries were considered too difficult to repair, and still have the highest postoperative rupture rate.
Flexor and extensor tendon injuries of the hand Jill Arrowsmith
Diagnosis The diagnosis can be obvious if the: • injury overlies the path of the tendons • normal resting cadence of the fingers is lost (Figure 2) • patient is unable to actively flex the involved proximal interphalangeal or distal interphalangeal joints when the unaffected digits are held in extension (quadregia action). Diagnosis is often more difficult in children or adults who are unable to cooperate, or if there is a partial division of the tendon which can cause limited, painful flexion. A divided tendon may not be visible in the wound if the injury occurred with the hand in flexion.
Robert E Page
Although the exact incidence is unknown, hand injuries involving either the flexor or extensor tendons are very common. Careful assessment and management is required to ensure a rapid return to normal function. This contribution should be read in conjunction with ‘Fractures of the hand’, page 256.
Flexor tendons
Principles of repair Tetanus immunity must be checked. A booster of tetanus toxoid is given if it has been more than 10 years since the last dose. General or regional anaesthesia (axiliary block) – a long tourniquet time may be needed. Proximal incisions to retrieve the retracted end of the tendon may be needed. Cleansing and debridement of the wounds must be performed meticulously, with only minimal debridement of the tendon to preserve length. Prophylactic antibiotics are required. A single perioperative dose of an anti-Staphylococcal and Streptococcal antibiotic (e.g. flucloxacillin) is sufficient for most clean, incised wounds. Contaminated injuries require broad-spectrum antibiotic cover (e.g. augmentin), usually for a minimum of 24 hours. Extensile incisions need good exposure. Straight-line scars across joints, which can cause subsequent contractures, should be avoided. Atraumatic surgical technique reduces the likelihood of adhesion formation. You are allowed to pick up the cut end of the tendon with your forceps only once! Do not try to retrieve the proximal end of the tendon by blindly passing forceps down the sheath. If ‘milking’ (by massaging the tendon forward with the finger and wrist inflexion) does not allow the tendon to be visualized, identify it proximally. Pass a fine feeding tube alongside the tendon within the sheath to the wound site. Stitch this to the tendon proximally and then pull the tube distally until you can retrieve the cut end of the tendon. Preservation of the pulleys is important. Use small incisions or ‘vents’ to identify the tendon and allow the repair site to glide. Retain as much of the biomechanically important A2 and A4 pulleys (Figure 1) as possible. Core stitch is a grasping suture within the main body of the tendon (Figure 3). It provides most of the strength of the repair, and requires a 1 cm bite of each side of tendon. Most surgeons use a nonabsorbable suture, either a 3-0 or 4-0 monofilament (e.g. Prolene) or a braided polyester (e.g. Ethibond). The two-strand modified Kessler stitch is most commonly used (Figure 3). Tendon repair strength is directly proportional to the number of suture strands crossing the repair. Four-strand stitches are about 70% stronger than two-strand repairs. As most units use an early
Anatomy The wrist and digit flexors arise mainly from the common flexor origin of the medial epicondyle of the humerus. There are two wrist flexors. • Flexor carpi radialis passes through a groove in the trapezium to insert into the bases of the 2nd and 3rd metacarpals. • Flexor carpi ulnaris with the pisiform as a sesamoid inserts into the base of the 5th metacarpal. At the wrist, the independent flexor digitorum superficialis tendons lie volar, or palmar, to the conjoined flexor digitorum profundus tendons. They pass distally deep to the transverse carpal ligament through the carpal tunnel and into the palm. The lumbrical muscles arise from the flexor digitorum profundus tendons at this point. The paired flexor digitorum superficialis and flexor digitorum profundus tendons to each finger enter the flexor synovial sheath for the finger at the level of the metacarpal neck. The flexor sheath has synovial layers that provide nutrition for the tendons, and a retinacular layer that has a series of condensations (pulleys) which are important biomechanically during finger movement. The flexor digitorum superficialis tendon splits in two, passes around the flexor digitorum profundus tendon and inserts into the base of the middle phalanx. It flexes the proximal interphalangeal joint. The flexor digitorum profundus tendon passes between the flexor digitorum superficialis slips and carries on distally to insert into the distal phalanx. It flexes both the proximal and distal interphalangeal joints. The flexor pollicis longus passes through the carpal tunnel already within a flexor sheath to insert into the distal phalanx of the thumb. The thumb flexor sheath has three pulleys. The varying arrangement of the flexor tendons at different
Jill Arrowsmith is a Specialist Registrar at Northern General Hospital, Sheffield, UK. Robert E Page is a Consultant Plastic Surgeon at Northern General Hospital and Sheffield Children’s Hospital, Sheffield, UK.
SURGERY
252
© 2003 The Medicine Publishing Company Ltd
UPPER LIMB TRAUMA
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a
The diagnosis of flexor tendon injuries. The ‘pointing finger sign’ (arrow) following division of the tendons a and restoration of normal resting cadence following tendon repair b.
b
2
active mobilization regimen postoperatively, the repair has to be sufficiently strong to tolerate unresisted active flexion. Some surgeons now routinely use four-strand repairs. Peripheral stitch is a continuous stitch that runs circumferentially around the tendon repair site. Most surgeons use a 6-0 monofilament (e.g. Prolene) with a variety of stitches in use (Figure 3). Peripheral stitching tidies the repair to allow better ‘gliding’ (smooth running of the tendon within the sheath) and contributes a significant amount of strength to the repair. It also helps prevent gapping of the tendon ends at the repair site, thus reducing adhesion formation.
SURGERY
Zone I injuries – the flexor digitorum profundus tendon may be divided within 1 cm of its insertion so that it is not possible to place a core suture in the distal tendon. A core suture is placed in the proximal tendon end instead. The suture ends are passed through, or around, the distal phalanx to emerge at the midnail level. The tendon is moved up to the bone and the suture tied on the nail over a button. The main core suture is removed after 6 weeks. Closed avulsion injuries commonly affect the flexor digitorum profundus of the ring finger and are classified by the amount of proximal retraction of the tendon. 253
© 2003 The Medicine Publishing Company Ltd
UPPER LIMB TRAUMA
Tendon repairs �����������
�������������������
Modified Kessler
Continuous running ��������
Halsted continuous horizontal mattress
Modified Kessler + horizontal mattress ��������
Tsuge
Silverskiold cross stitch ��������������� ������������������
3
Splintage is by a dorsal splint. This restricts the amount of tension across the repair, and reduces the potential for joint contracture. The position of splintage for an early active mobilization regimen (see below) is: • wrist in neutral or slight (up to 20o) flexion • metacarpophalangeal joints in 50–70o flexion • interphalangeal joints extended.
usually responds to exercise modification if diagnosed early. Tendon adherence is less common with an early active mobilization regimen. It impairs full movement of the finger. After the initial scars have matured and softened, the scarred tendon is re-explored and released (tenolysis). Intensive therapy postoperatively is needed to prevent recurrent adhesion formation.
Postoperative management Most postoperative management regimens in the UK are based on early active mobilization, because the strength of a tendon repair increases if stress is applied to it. Also, movement of the repair site reduces the number and strength of adhesions. Early active regimen involves repetitions of unresisted active flexion, passive flexion and active extension within the confines of the splint at intervals throughout the day. If possible, the regimen should begin on day one, post-operation. After about 6 weeks, movement and grip strength are gradually increased by using small, spring-loaded weights. The total rehabilitation period is about three months. Wrist flexor tendon repairs are protected by a splint, holding the wrist slightly flexed for 3 weeks.
Extensor tendons Anatomy The extrinsic extensor tendons arise in the forearm and pass through six compartments beneath the extensor retinaculum (Figure 1). Their course is also divided into zones. First compartment – the extensor pollicus brevis runs with the abductor pollicus longus, inserting into the proximal phalanx of the thumb to extend the metacarpophalangeal joint. Second compartment – the extensor carpi radialis longus and brevis insert into the bases of the 2nd and 3rd metacarpals. Third compartment – the extensor pollicus longus passes around Lister’s tubercle of the radius and inserts into the distal phalanx of the thumb to extend the interphalangeal joint. Fourth and fifth compartments – the extensor digitorum communis tendons with the additional independent long extensor of the index finger run under the fourth compartment, and the independent little finger extensor runs under the fifth compartment. Extensor digitorum communis has multiple interconnections, juncturae tendinum, in the dorsum of the hand. These interconnections may allow extension of a digit even when its main extensor digitorum communis tendon has been divided. The main action of the long extensors of the fingers is to extend the metacarpophalangeal joints. On the dorsum of the fingers, the extensor tendons spread out to become part of a complex apparatus that includes the insertions
Complications Rupture of the tendon repair occurs in around 3.5% of flexor tendon repairs in early active mobilization regimens, with a much higher (around 10%) rate for zone II repairs. It may be detected either by the patient (who feels a sudden ‘snap’ and is then unable to flex the affected joint) or by the therapist. If detected within a few days, immediate secondary repair may be possible. If diagnosis is delayed, muscle sarcomere shortening will probably make direct repair impossible and a tendon graft will be required. Joint contracture affects the interphalangeal joints if the patient has persistent difficulty extending the fingers to the splint. It SURGERY
254
© 2003 The Medicine Publishing Company Ltd
UPPER LIMB TRAUMA
of the intrinsic muscles of the hand. The intrinsic muscles extend the interphalangeal joints, via the central slip for the proximal interphalangeal joint and the two lateral bands for the distal interphalangeal joint. This arrangement of the extensor apparatus over the dorsum of the digits is maintained by the relative lengths of inflexible tendon which constitute it. As it is difficult to repair a tendon maintaining its original length, once part of the system is injured, it may create a secondary deformity of the finger. Sixth compartment – the extensor carpi ulnaris tendon inserts into the fifth metacarpal.
the metacarpophalangeal and distal interphalangeal joints free, for several weeks. Open injuries require debridement and repair under local anaesthetic. The tendon is 0.5 mm thick at this point, so it is often necessary to incorporate part of the thicker lateral bands into the repair to hold the suture. A 4-0 monofilament suture, either as a ‘figure of eight’ or a modified Kessler stitch, is used. The proximal interphalangeal joint is splinted in extension for 4–6 weeks with a K-wire, while allowing active flexion of the distal interphalangeal joint. Protected flexion of the proximal interphalangeal joint is required for a further 4 weeks.
Management Mallet finger (zone I, Figure 4) is involuntary flexion of the distal phalanx caused by the disruption or tearing of the extensor tendon. It can be either an open or closed injury. Closed injuries are due to forced flexion of the extended finger and may be associated with an avulsion fracture of the distal phalanx. Most are successfully managed by splinting the distal interphalangeal joint only in extension using either a ready-made splint (e.g. Stack) or a customized version. Splinting is continued for at least six weeks. If extension loss redevelops, the splint is re-applied for 2 weeks. If the fracture fragment is large and the remaining distal phalanx subluxed due to the unopposed action of flexor digitorum profundus, a longitudinal K-wire may be required to reduce and hold the distal interphalangeal joint. The fracture fragment may also require reduction and fixation, although this is needed less often. The K-wire is kept for six weeks. Open injuries need careful cleaning under local anaesthetic. The tendon alone, or the tendon and skin together, are repaired with a 4-0 or 5-0 suture. K-wire the distal interphalangeal joint as with the closed injury for 6 weeks.
MCP joint area injuries (zone V) are open injuries and are often caused by human teeth following a punch injury. The metacarpophalangeal joint may also be involved, so the radiograph should be carefully checked for joint damage and tooth fragments. A high index of suspicion of joint involvement is required as patients may not admit to the cause of the injury: explore and irrigate the joint if concerned. The associated tendon injury is often partial and at a different level, and can be repaired as a secondary procedure when the infection is under control. Clean tendon lacerations can be repaired primarily with a core stitch if the tendon bulk permits. Dorsum of the hand injuries (zone VI) can be difficult to diagnose, as the affected finger may still extend via the junctura tendinae, but there is usually some impairment of extension. A local anaesthetic is used; the juncturae prevent the proximal tendon end from retracting, making identification of the tendon ends and subsequent repair technically easy. The tendon is repaired with a 4-0 monofilament core stitch if bulky enough, or a mattress or ‘figure of eight’ stitch is used.
Central slip injuries (zone III) can be open or closed. The acute injury does not usually present as a boutonnière deformity (finger deformity with proximal interphalangeal joint flexion and distal interphalangeal joint extension). Development of this requires time for the intact lateral bands to migrate volarwards, pulling the proximal interphalangeal joint into flexion as the distal interphalangeal joint is extended. Closed injuries may be associated with an avulsion fracture of the middle phalanx. Most are successfully treated by external splintage of the proximal interphalangeal joint in extension, leaving
Wrist injuries (zone VII) need general or regional anaesthetic for repair, because the proximal cut tendon ends often retract into the forearm, necessitating extension of the laceration. The extensor retinaculum may be injured or need to be incised to enable the tendon repair. It is important to retain or repair part of the retinaculum to prevent ‘bowstringing’ of the tendons with wrist extension. Postoperative splintage: tendon repairs from zone V proximally are managed with a volar splint, keeping the wrist in around 40o of extension and the metacarpophalangeal joints flexed around 20o. The area is usually immobilized for three weeks, but some units use a dynamic splinting protocol similar to that for flexor tendon injuries. u
FURTHER READING Green D P, Hotchkiss R N, Pederson W C, Lampert R, Eds. In: Green‘s Operative Hand Surgery. 4th edition. New York: Churchill Livingstone, 1999.
4 Mallet finger.
SURGERY
255
© 2003 The Medicine Publishing Company Ltd