excursion meaning of tendon

Flexor Tendon

• Zone I is just beyond the insertion of the FDS to the insertion of the FDP. This zone is occupied only by the FDP.
• Zone II is from the distal palmar crease to the distal insertion of the FDS, and injuries in this zone more likely than not involve both flexor tendons.
• Zone III begins just distal to the distal edge of the transverse carpal ligament (at the origin of the lumbrical muscles) and ends at the distal palmar crease.
• Zone IV is the region of the carpal tunnel.
• Zone V is at the wrist and distal forearm.
• The normal posture of the fingers reveals a progressive flexion posture, or cascade, with the little finger being the most flexed, and the index being the least flexed.
• Findings at surgery confirmed complete laceration of the FDS and FDP in this zone II injury.
• There is a comparative lack of flexion in the ring finger (loss of cascade) compared with the adjacent fingers, and a lack of flexion at the DIP joint when making a fist.
• This is an avulsion of the insertion of the FDP of the ring finger.
• Trapping the adjacent fingers in extension permits only the FDS to flex the PIP joint.
• This maneuver works because the FDS is functionally characterized as four independent muscle bellies with four separate tendons.
• The FDP is easily isolated by blocking motion at the PIP joint.
• Laceration of the flexor tendons represents a significant and serious injury.
• Surgical repair is best performed by experienced surgeons who have suitable facilities and instruments available for repair.

surgeries are performed in a timely fashion but on an elective basis.

• If both tendons are lacerated, both tendons are repaired.
• Zone II injuries are the most likely to result in adhesions and loss of function.
• The post-operative management of these injuries is very important, and should be considered a part of the surgical protocol.
• Most flexor tendon injuries are due to lacerations of the palmar surface of the digits or palm.
• These lacerations are more often than not transverse in orientation.
• Figure 12.1-8 demonstrates how these traumatic incisions may be appropriately extended to achieve surgical exposure and at the same time avoid a pernicious scar that might produce a contracture.
• The wounds may also be extended by using oblique limbs of extension that also meet the same needs.
• Tendon sutures have been fabricated from various materials, including stainless steel, nylon, polypropylene, and polyester.
• Because of its ease of use, strength, and minimal elasticity, 3-0 and 4-0 braided polyester sutures are commonly used for flexor tendon repairs.
• Many techniques have been developed for reapproximation of the lacerated flexor tendons since Bunnell developed his well-known tendon-grasping suture more than 50 years ago.
• Although there may not be an ideal suture technique, there are some underlying principles in all suture techniques: ease of suture placement, secure knots that will not slip or stretch out, a smooth suture junction without gapping or bunching, and sufficient strength to allow early supervised motion programs (see the section on rehabilitation that follows).
• A suture technique developed by Strickland is depicted in Figure 12.1-9 . It begins as a two-strand, core-grasping technique supplemented by a second-core suture and a running and locking epitendinous suture.
• The strength of a given suture repair is nearly directly proportional to the number of strands of suture material that cross the repair site, and to the size of the suture material.
• A four-strand repair is stronger that a two-strand repair.
• The addition of a peripheral epitendinous suture to the core sutures has been found to increase the strength of the repair site in a significant fashion. This helps prevent gap formation that may lead to adhesions and failure to recover useful motion in the digit.
• The epitendinous suture may also “tidy up,” reconform, and “debulk” the repair site to permit easy passage of the repair site through the critical pulleys.
• Atraumatic technique is a useful descriptive term to note that careful meticulous dissection and gentle handling of all tissues is very important in the management of flexor tendon injuries.
• After extending the wound and opening the sheath at the anticipated repair site, it is necessary to retrieve the two tendon ends. The distal end is usually retrieved by flexing the digit.

intact vincula, may be grasped with fine tooth forceps and brought distally.

• Blind repeated probing up the proximal sheath with a grasping instrument is to be avoided . If the proximal end cannot be easily grasped or “milked down” by digital massage, then a small and moistened feeding tube catheter is passed proximally (usually into the palm), and the retracted tendon is sutured to the catheter at this level. The catheter is then brought distally into the repair site, carrying with it the proximal tendon stump. When the two stumps are adjacent, a 22-gauge hypodermic needle is passed transversely through the sheath to impale and fix the proximal tendon.
• A repair of the surgeon’s choice and experience is performed.
• Indiscriminant excision of the membranous or retinacular portions of the sheath is to be avoided, but portions of the sheath may be incised or excised to promote placement of the sutures.
• Repair of the incised sheath has been advocated by some surgeons, but such repair should not compromise the gliding movement of the repaired tendons in the sheath.
• Early passive motion by applying small but frequent forces in opposite directions modifies and elongates restrictive tendon adhesions.
• Load at failure of mobilized tendons tested at 3 weeks was twice that of immobilized tendons, and the favorable differences continued at all intervals through 12 weeks.
• Each 10 degrees of PIP flexion results in FDP and the FDS excursion of about 1.5 mm.
• These and other studies and experience have led to the progressive evolution and development of tendon mobilization protocols and techniques that focus on promoting motion at the PIP joint.
• The first technique is the most widely used at this time. An orthotic device maintains the wrist and MCP joints in slight flexion.
• An elastic band is attached to the fingernail of the involved digit, this elastic band is passed beneath a midpalmar bar and is anchored proximally on a portion of the orthotic device.
• Figure 12.1-10 demonstrates an example of a currently used method.

by serial passive movement of the DIP, PIP, and MCP joints.

• Those that use this method state that it is less likely to result in flexion contracture when compared to the elastic band traction method.
• The introduction and use of 4-6 strand tendon repair methods has made it possible to use this method with a certain level of safety in terms of its major complication of tendon rupture.
• In any splinting program, it is best to maintain the interdigital joints in extension to minimize the likelihood of flexion contractures.
• The specific details of these three methods are beyond the scope of this text and will no doubt evolve and change. Also, completely new methods may be developed in response to the need for better final results.
• Utilization of any of these methods requires a team approach with a surgeon and therapist.
• A cooperative patient is mandatory for success when using any of these methods.
• The methods of early excursion of the tendon repair site just reviewed are a form of extrinsic mechanical means to limit adhesions.
• The material is semipermeable, allowing passage of synovial fluid nutrients to the tendon repair site—but unfortunately, the method was associated with an increased rupture rate and a diminished strength of site repair.
• Studies have suggested that hyaluronic acid (HA) may limit the formation of adhesions following zone II flexor tendon repair, and a recent study found that an HA membrane applied circumferentially around the tendon repair site inhibited the formation of restrictive adhesions.
• Histologic examination of the tendon repair sites did not demonstrate any interference with intrinsic tendon repair.
• The application of 5-fluorouracil to the repair site has been reported to result in diminished adhesions, without an increased risk of rupture.
• Not all tendon repairs result in useful recovery of function; lysis of adhesions may be required in selected cases.
• The indications for this procedure are when the patient has reached a plateau in their progress from splinting and therapy.
• The needs of the patients, as well as their age, occupation, and the digit involved, may aid in the decision-making process.
• The wise surgeon will recognize that a tenolysis operation may sometimes reveal a disrupted tendon and a severely compromised bed that only a staged tendon reconstruction can solve. Both the surgeon and patient must be prepared for this eventuality.
• Surgeons vary in their opinion regarding the timing of tenolysis. Most would wait several months after primary repair or tendon grafting before considering this option.
• Active participation of the patient is critical to the success of the operation and local anesthesia with intravenous sedation as needed is used.
• All adhesions are excised, and the critical portions of the pulley system are preserved.
• During the procedure, the active pull-through of the tendon is noted by having the patient actively flex the digit.
• The procedure ends when an adequate level of flexion is achieved.
• Aftercare includes a splint that permits immediate and continued flexion of the digit.
• In selected patients, an indwelling catheter may be left in place for 4 to 5 days for the instillation of small amounts of local anesthetic during exercise periods.
• Any concomitant surgical procedures, such as capsulotomy, increase the risk for a poor result.
• Primary tendon repairs that have failed after repair and tenolysis are associated with joint contracture, have a known loss of critical pulleys, and, in patients in whom conventional tendon grafting is likely to fail, are candidates for two-stage tendon reconstruction.
• The insertion of a silastic Hunter-tendon prosthesis permits the formation of a scar-free bed and sheath for subsequent insertion of a free tendon graft.
• Contraindications include those digits with marginal circulation and sensibility, and patients unwilling or unable to engage in a prolonged, often tedious, and difficult rehabilitation process.
• The first stage consists of wide exposure of the flexor sheath and pulley system through a zigzag incision.
• The excised tendon material is kept moist for possible use as material to reconstruct pulleys.
• If available, one or two slips of the superficialis are left attached to use in pulley reconstruction.
• If any joint contractures are present and not corrected by excision of the flexor tendons, then joint release is performed by a palmar plate release and a collateral ligament incision.
• Dissection in the palm is carried to the level of the lumbrical origin.
• A second incision is made at the flexor aspect of the wrist to accept the proximal end of the silastic Hunter-tendon prosthesis.
• A suitably sized prosthesis (3 to 6 mm in width) is inserted from the fingertip to the wrist.
• The end of the Hunter tendon is sutured beneath the distal stump of the profundus.
• Some methods of pulley reconstruction are illustrated in Figure 12.1-11 .
• The tendon should also glide freely when the digit is extended. It should not buckle or bulge.
• Aftercare includes a bulky dressing, followed by a supervised passive exercise program.
• This stage is performed when satisfactory passive motion has been obtained. It usually takes 3 or more months.
• A suitable tendon graft (usually the plantaris, or, if not available, one of the long toe extensors) is attached to the proximal end of the Hunter tendon. The distal end of the Hunter tendon is detached and pulled distally to atraumatically insert the tendon graft into the new flexor sheath.
• The distal anastomosis (first) is made into the stump of the profundus at the DIP joint, and the proximal anastomosis (at the wrist) made by joining the graft to a suitable donor—such as the profundus—to one of the central digits. An interweave technique is used to place the graft in the substance of the donor motor.
• Appropriate tension may be verified by noting extension of the operated digit when the wrist is flexed and flexion of the digit when the wrist is extended.
• Rehabilitation following the second stage reconstruction is via an active extension-elastic band flexion method, as previously described.
• Figure 12.1-12 demonstrates a two-stage Hunter tendon reconstruction sequence.
• Although adequate tendon strength and function may be maintained after partial tendon lacerations, some partial lacerations may result in entrapment and triggering of the tendon against an adjacent pulley.
• Current recommendations are for repair of lacerations greater than 50% of the tendon, and debridement of the tendon edges in those less than 50%.
• Under no circumstances should the tendon ends be excised or “squared-up” to make the repair technically easier or more “tidy.” Any shortening of a flexor tendon may result in the loss of extension of the digit.
• This injury is likely to occur in certain sports such as flag or regular football, in which forceful grasping is used to grab a flag or jersey of an opponent.
• The FDP of the ring finger is most often injured, and may be misdiagnosed by coaches and others as a “sprained finger.” Radiographs are often negative.
• Figure 12.1-6 shows a classic clinical case that was diagnosed and treated a few days after injury. Function was restored.
• The avulsion may occur with a small or substantial bone fragment. The prognosis is based on the level to which the FDP retracts, the remaining blood supply of the tendon, the length of time between the injury and treatment, and the presence and size of the bone fragment.
• If seen early, it may be threaded back down the flexor sheath and reattached, followed by routine mobilization.
• If not, the treatment choices include leaving it alone (or trimming the tendon stump in the palm if it is symptomatic and interferes with function), performing an arthrodesis of the DIP joint, or performing a tendon graft.
• The latter choice carries with it the risk of compromise to the intact FDS, and may not always be a suitable alternative.
• These injuries may be reattached as late as 6 weeks after the injury, with satisfactory results.
• Type III injuries present with a large bone fragment that becomes trapped at the distal edge of the A4 pulley, and are comparatively easy to reattach due to the lack of significant retraction, as well as a sizeable bone fragment.
• The key to a successful outcome in this injury is early diagnosis and treatment.

Carpal Instabilities and Fracture-Dislocations of the Carpus

Extensor Tendon

Hand Fractures Fracture-Dislocations

Injection Injuries

Compartment Syndrome

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Excursion of the flexor digitorum profundus tendon: a kinematic study of the human and canine digits

Affiliation.

• 1 Orthopaedic Bioengineering Laboratory, University of California, San Diego 92093.
• PMID: 2303949
• PMCID: PMC9730741
• DOI: 10.1002/jor.1100080203

The most common problem following primary flexor tendon repair is the failure of the tendon apparatus to glide, secondary to the formation of adhesions. Early motion following tendon repair has been shown to be effective in reducing adhesions between the tendon and the surrounding sheath. Therefore, it is important to determine the amount of flexor tendon excursion along the digit during joint motion. In this study, the excursion between the flexor digitorum profundus (FDP) tendon and the sheath was examined in both human and canine digits. Based on roentgenographic measurements and joint kinematic analysis, the motion of the bones, the FDP tendon, and the sheath were measured with respect to joint rotations. It was found that the canine flexor tendon apparatus behaved similarly to that of the human for the motions studied. The amount of tendon excursion was very small in regions distal to the joint in motion (approximately 0.1 mm/10 degrees of joint rotation). There was little displacement of the sheath (0.2-0.3 mm), except at the metacarpal joint region during metacarpophalangeal (MCP) joint motion and at the proximal interphalangeal (PIP) joint region during PIP joint motion. Tendon excursion relative to the tendon sheath was the largest in zone II during PIP joint rotation (1.7 mm/10 degrees of joint rotation). These results suggest that PIP joint motion may be most effective in reducing adhesions following tendon repair in zone II.

Publication types

• Research Support, Non-U.S. Gov't
• Research Support, U.S. Gov't, P.H.S.
• Fingers / anatomy & histology
• Fingers / physiology*
• Joints / anatomy & histology
• Joints / physiology
• Metacarpophalangeal Joint / anatomy & histology
• Metacarpophalangeal Joint / physiology
• Metacarpus / anatomy & histology
• Metacarpus / physiology
• Movement / physiology
• Tendons / anatomy & histology
• Tendons / physiology*

Grants and funding

• R01 AR033097/AR/NIAMS NIH HHS/United States
• AR 33097/AR/NIAMS NIH HHS/United States

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• MB 1 Preclinical Medical Students
• MB 2/3 Clinical Medical Students
• ORTHO Orthopaedic Surgery

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Flexor Tendon Injuries

• Flexor Tendon Injuries are traumatic injuries to the flexor digitorum superficialis and flexor digitorum profundus tendons that can be caused by laceration or trauma.
• Diagnosis is made clinically by  observing the resting posture   of the hand to assess the digital cascade and  the absence of the tenodesis effect. 
• Treatment is usually direct end-to-end tendon repair. 
• occurs in 4.83 per 100,000 
• commonly results from volar lacerations and may have concomitant neurovascular injury 
• produced by tenocytes within the tendon
• stimulated by surrounding synovial fluid and inflammatory cells
• implicated in the formation of scarring and adhesions
• occurs in 3 phases
• functions as a flexor of the DIP joint
• assists with PIP and MCP flexion
• shares a common muscle belly in the forearm
• index and long fingers are innervated by the AIN of the median nerve
• ring and small fingers are innervated by the ulnar nerve
• functions as a flexor of the PIP joint 
• assists with MCP flexion
• FDS to the small finger is absent in 25% of people
• innervated by the median nerve
• located within the carpal tunnel as the most radial structure
• innervated by the AIN of the median nerve
• primary wrist flexor
• inserts on the base of the second metacarpal
• closest flexor tendon to the median nerve
• inserts on the pisiform, hook of hamate, and the base of the 5th metacarpal
• innervated by the ulnar nerve
• located at the level of the proximal phalanx where FDP splits FDS
• thicker and stiffer than cruciate pulleys
• most important pulleys to prevent flexor tendon bowstringing
• A1, A3, and A5 arise from the volar plate
• allows the annular pulleys to approximate each other during digital flexion
• A2 contributes least to arc of motion of thumb
• most important pulley to prevent flexor tendon bowstringing (along with A1 pulley)
• occurs when flexor tendons are located within a sheath
• it is the more important source distal to the MCP joint
• nourishes flexor tendons located outside of synovial sheaths
• vincular systemosseous bony insertions, reflected vessels from the tendon sheath, and longitudinal vessels from the palm
• osseous bony insertionsreflected vessels from the tendon sheath, and longitudinal vessels from the palm
• reflected vessels from the tendon sheath
• longitudinal vessels from the palm
• loss of active flexion strength or motion of the involved digit(s)
• evidence of malalignment or malrotation may indicate an underlying fracture
• assess skin integrity to help localize potential sites of tendon injury
• look for evidence of traumatic arthrotomy
• normally wrist extension causes passive flexion of the digits at the MCP, PIP, and DIP joints
• maintenance of extension at the PIP or DIP joints with wrist extension indicates flexor tendon discontinuity
• active PIP and DIP flexion is tested in isolation for each digit
• important given the close proximity of flexor tendons to the digital neurovascular bundles
• may have associated fracture
• used to assess suspected lacerations
• partial lacerations
• may be associated with gap formation or triggering
• lacerations > 60% of tendon width
• failed primary repair
• chronic untreated injuries
• single stage procedure
• chronic FPL rupture
• > 75% laceration
• epitendinous suture at the laceration site is sufficient
• no benefit of adding core suture
• easy placement of sutures in the tendon
• secure suture knots
• smooth juncture of the tendon ends
• minimal gapping at the repair site
• minimal interference with tendon vascularity
• sufficient strength throughout healing to permit application of early motion stress to the tendon
• delayed treatment leads to difficulty due to tendon retraction
• incisions should always cross flexion creases transversely or obliquely to avoid contractures (never longitudinal)
• meticulous atraumatic tendon handling minimizes adhesions
• linear relationship between strength of repair and # of sutures crossing repair
• 4-6 strands provide adequate strength for early active motion
• high-caliber suture material increases strength and stiffness and decreases gap formation
• locking-loops decrease gap formation
• ideal suture purchase is 10mm from cut edge
• core sutures placed dorsally are stronger
• improves tendon gliding by reducing the cross-sectional area
• improves strength of repair (adds 20% to tensile strength)
• allows for less gap formation (first step in repair failure)
• produces less gliding resistance than other techniques
• theoretically improves tendon nutrition through synovial pathway
• clinical studies show no difference with or without sheath repair
• most surgeons will repair if it is easy to do
• A2  pulleys in digits 
• A4 pulleys in digits
• oblique pulley in thumb
• 25% of A2  can be incised with little resulting functional deficit
• 100% of A4 can be incised with little resulting functional deficit
• in zone 2 injuries, repair of one slip alone improves gliding
• compared to repair of both slips
• tendon repairs are weakest between postoperative day 6 and 12
• repair usually fails at suture knots
• repair site gaps > 3mm are associated with an increased risk of repair failure
• increased risk with zone 2 injuries
• usually epinephrine 1:100,000 and 7mg/kg lidocaine
• from 1:400,000 to 1:1000 is safe
• 1% lidocaine with 1:100,000 epi for a 70kg person
• dilute with saline (50:50) to get 0.5% lidocaine, 1:200,000 epi
• dilute with 150cc saline to get 0.25% lidocaine and 1:400,000 epi
• add 10cc of 0.5% bupivacaine with 1:200,000 epi
• proximal and middle phalanges, use 2ml
• distal phalanx, use 1ml
• palm, use 10-15ml
• no tourniquet, no sedation
• allows intraoperative assessment for repair gaps by getting awake patient to actively flex digit
• allows on-the-spot debulking of bunched repairs
• allows division of A4 pulley and venting (partial division) of A2 pulleys
• allows repair of tendons inside tendon sheaths as patients can demonstrate that the inside of the sheath has not been inadvertently caught
• immobilize for 3 days
• begin active midrange motion after day 3 (form a partial fist with 45 degree flexion at MP, PIP and DIP joints, or "half a fist 45/45/45 regime")
• supple skin
• sensate digit
• adequate vascularity
• full passive range of motion of adjacent joints
• only perform if the flexor sheath is pristine and the digit has full ROM
• Stage I - SR is placed to create a favorable tendon bed
• pulvertaft weave proximally and end-to-end tenorrhaphy distally
• SR is placed in the flexor sheath, pulleys are reconstructed (as needed), and a loop between the proximal stumps of FDS and FDP is created in the palm
• SR is retrieved, FDS is cut proximally and reflected distally through the pseudosheath and either attached directly to FDP stump or secured with a button
• less graft diameter-rod diameter mismatch
• fewer adhesions than extrasynovial grafts
• relies on only 1 tenorrhaphy site (distal or proximal) to heal at any one time (vs. Hunter technique where 2 tennoprhaphy sites are healing simultaneously)
• the proximal end has already healed after stage I
• most common
• indicated if longer graft is needed
• extensor digitorum longus to 2nd-4th toes
• extensor indicis proprius
• flexor digitorum longus to 2nd toe
• one pulley should be reconstructed proximal and distal to each joint
• pulley reconstruction should occur first if a tendon graft is being used
• belt loop method
• FDS tail method
• subsequent tenolysis is required more than 50% of the time
• localized tendon adhesions with minimal to no joint contracture and full passive digital motion
• may be required if a discrepancy between active and passive motion exists after therapy
• wait for soft tissue stabilization (> 3 months) and full passive motion of all joints
• careful technique to preserve A2 and A4 pulleys
• follow with extensive therapy
• especially in zone II
• leads to improved tendon healing biology
• limits restrictive adhesions and leads to increased tendon excursion
• indicated for children and non-compliant patients
• casts/splints are applied with the wrist and MCP joints positioned in flexion and the IP joints in extension
• low force and low excursion
• active finger extension with patient-assisted passive finger flexion and static splint
• active finger extension with dynamic splint-assisted passive finger flexion
• low force and high tendon excursion
• adds active wrist motion which increases flexor tendon excursion the most
• moderate force and potentially high excursion
• dorsal blocking splint limiting wrist extension
• perform “place and hold” exercises with digits
• most common complication following flexor tendon repair
• higher risk with zone 2 injuries
• physical therapy
• perform if 4-6 months after tendon repair and significant loss of excursion
• 15-25% rerupture rate
• if the sheath is intact and allows passage of a pediatric urethral catheter or vascular dilator, perform primary tendon grafting
• if the sheath is collapsed, place Hunter rod and perform staged grafting
• rates as high as 17%
• Swan-neck deformity
• Trigger finger
• Lumbrical plus finger

Technique guides are not considered high yield topics for orthopaedic standardized exams including ABOS, EBOT and RC.

• - Flexor Tendon Injuries

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28 The Flexor Tendons and the Flexor Sheath

Sandeep Jacob Sebastin and Beng Hai Lim 28 The Flexor Tendons and the Flexor Sheath The forearm flexor muscles (flexor–pronator group) are present in the anterior (volar) compartment of the forearm. Most of them originate from the medial epicondyle of the humerus (common flexor origin). They include eight muscles that may be divided into three distinct functional groups: (1) muscles that rotate the radius on the ulna (pronator teres [PT] and pronator quadratus [PQ]); (2) muscles that flex the wrist (flexor carpi radialis [FCR], palmaris longus [PL], and flexor carpi ulnaris [FCU]); and (3) muscles that flex the digits (flexor digitorum superficialis [FDS], flexor digitorum profundus [FDP], and flexor pollicis longus [FPL]). 1 Anatomically, these eight muscles are arranged in three distinct layers or compartments. The superficial compartment includes (radial to ulnar) PT, FCR, PL, and FCU. The intermediate compartment includes the FDS, and the deep compartment includes the FPL, FDP, and the PQ. 2 In general, the term flexor tendon refers to the tendinous portions of the wrist (FCR, PL, and FCU) and digital flexors (FDS, FPL, and FDP). They extend from the musculotendinous junction in the midforearm to their respective bony insertions. The flexor sheath refers to the specialized tissue that covers the digital flexor tendons (FDS, FPL, and FDP). This sheath allows the tendons to glide and turn around a corner to produce smooth and efficient flexion of the digits. 2 The arrangement of the flexor tendons and the flexor sheaths changes as they proceed from the distal forearm to the digits. This chapter will discuss the gross and functional anatomy of the flexor tendons and the flexor sheath with specific reference to clinical correlations. 28.1 Flexor Tendons There are 12 flexor tendons. They include the tendons of the three wrist flexors (FCR, PL, and FCU) (▶ Fig 28.1 ), the thumb flexor (FPL), and four tendons each for the finger flexors (FDS and FDP). Fig. 28.1 Dissection of the volar distal forearm showing the Flexor Carpi Radialis (FCR) tendon and Palmaris longus (PL) tendons along with the median nerve, the ulnar nerve and the radial artery. The Flexor Carpi Ulnaris (FCU) tendon is also seen. 28.1.1 Flexor Carpi Radialis Etymology: Flexor is derived from the Latin word flexus, meaning “bent” (thus flexor indicates “that which bends,” or “bending”). Carpi is derived from Latin word carpalis and the Greek word karpos , both of which indicate “wrist” (the carpus). Radialis again is derived from the Latin word radii, which means “spoke” (used to describe the radius of the forearm). 3 , 4 Origin: The tendinous portion of the FCR begins approximately 15 cm proximal to the radial styloid, and the muscular portion ends approximately 8 cm from the radial styloid. 5 , 6 Course: The tendon is located on the radial superficial aspect of the forearm. It is ulnar to the radial artery, radial to the median nerve and the tendon of the PL, and superficial to the tendon of the FPL. It enters a fibro-osseous tunnel at the proximal border of the trapezium. In this tunnel, it is bounded radially by the body of the trapezium, palmarly by the trapezial crest and transverse carpal ligament, and ulnarly by a retinacular septum. This septum is continuous with the transverse carpal ligament and separates the tendon from the contents of the carpal tunnel. The tendon is in direct contact with the trapezium and lies in close relation to the distal aspect of the radius, the scaphoid tubercle, the scaphotrapeziotrapezoid (STT) joint, and the carpometacarpal (CMC) joint of the thumb. 5 Nigro has divided the fibro-osseous tunnel for the FCR into four sections. These sections, from proximal to distal, are (1) the forearm aponeurosis that encircles the FCR tendon (palmar carpal ligament), (2) the tunnel formed between the radial insertions of the flexor retinaculum and the scaphoid tubercle, (3) the tunnel formed at the trapezial groove, and (4) the insertion of the FCR tendon at the second metacarpal base. 7 Insertion: The FCR tendon is inserted at three locations. A small slip inserts into the trapezial crest or tuberosity, 80% of the remaining tendon is inserted on the base of the second metacarpal, and 20% inserts on the base of the third metacarpal. The deep palmar arch is located 2 to 3 mm distal to the insertion of the tendon. 5 Characteristics: The FCR tendon is covered with a synovial sheath that extends from the musculotendinous origin till the metacarpal insertion. This sheath is thin proximally and consists only of paratenon. Four to five cm proximal to the radial styloid, the tendon is circumferentially invested by the transverse fibers of the antebrachial fascia and thickens to about 3 mm at the level of the trapezial crest. The FCR tendon gradually changes from a relatively flat and wide configuration in the forearm to an elliptical shape at the wrist. The fibers of the FCR tendon undergo a torsion of approximately 180° as it progresses from proximal to distal. Half of this torsion occurs in the forearm and half in the sheath of the FCR at wrist level. The rotation of its fibers is constant and is usually 180° in the clockwise direction in the right forearm and anticlockwise in the left forearm. 8 Simovitch et al have suggested the presence of a putative wrist annular pulley for the FCR tendon in 80% of the cadavers in their study. This pulley was present 1.5 cm proximal to the wrist flexion crease and measured approximately 2.1 × 1.5 cm in size. 9 The maximum excursion of the FCR tendon in adults is 4 cm. 10 Variations: An absence of the FCR has been reported. 11 Other variations of the FCR tendon include slips of attachment to the base of the fourth metacarpal and the tubercle of the scaphoid. The FCR brevis is a small muscle that arises from the palmar surface of the radius between origins of the FPL and the PQ. The tendon of the FCR brevis inserts into base of the second and third metacarpal. 12 Clinical correlations: Volar wrist ganglions are the second most commonly seen ganglion in the hand and wrist (18–20%). They arise from the radiocarpal joint or the STT joint and are intimately related to the FCR tendon sheath and the radial artery. A relatively uncommon pathology involving the FCR tendon sheath is FCR tendinitis. This may be primary as a result of tendon irritation within the narrow confines of the trapezial tunnel or secondary in association with scaphoid cysts, STT osteoarthritis (OA), thumb CMC joint OA, or scaphoid fractures. 5 Attritional rupture of FCR has been reported in association with STT osteoarthritis. 13 A split tendon graft can be harvested from the FCR tendon. This is useful in patients who need a short graft but lack the PL. This tendon graft can be harvested by using two to three small transverse incisions. 14 The split FCR tendon graft with the distal insertion preserved is frequently used in ligamentous reconstruction following excision of the trapezium (LRTI procedure) 15 and in scapholunate ligament reconstruction (Brunelli or the three ligament tenodesis procedure). 16 , 17 The tendon of the FCR is commonly transferred to the extensor digitorum communis (EDC) in patients with radial nerve palsy. Although the FCU is stronger, the FCR is a better choice for this transfer, having a greater excursion. In addition, in patients who have a low radial nerve palsy (posterior interosseous nerve palsy) and intact radial wrist extensors, preserving the FCU maintains balance between the radial and ulnar deviators of the wrist. A split transfer of the FCR tendinomuscular unit has also been described to provide independent thumb and finger extension. 18 28.1.2 Palmaris Longus Etymology: Palmaris is derived from the Latin word palma , which means “pertaining to the palm.” Longus is the Latin for “long.” 3 , 4 Origin: The tendon of the PL begins in the midforearm and has a relatively small musculotendinous portion. A study in a Japanese population estimated that the intramuscular length of the tendon was approximately 0.6 to 1.2 cm. 19 Course: The PL tendon is initially deep to the antebrachial fascia. In the distal third of the forearm, approximately 5 cm proximal to the distal wrist crease, it passes through an oval opening in the antebrachial fascia to become subcutaneous. 20 The PL tendon is ulnar to the FCR and superficial to the median nerve (▶ Fig. 28.1 ). At the level of the wrist, the PL tendon is superficial to the flexor retinaculum, which is in continuity with the antebrachial fascia (▶ Fig. 28.2 ). Fig. 28.2 Dissection of the palm and distal forearm shows the palmaris longus tendon and the palmar fascia. Insertion: Distal to the flexor retinaculum, the PL tendon broadens in a fanlike fashion to merge into the palmar aponeurosis (PA; ▶ Fig. 28.2 ). The PA can be divided into two layers: the superficial one formed by longitudinal fibers (that is in 3 layers), and a deep one, adherent to the skin formed by transverse fibers continuous laterally with the deep fascia of the hand. The PL tendon is in continuity only with the longitudinal fibers of the PA. In addition to the insertion into the PA, fibrous expansions arise from each side of the distal part of the PL tendon that insert into the deep fascia overlying the thenar and hypothenar eminences. The expansions to the thenar eminence were generally thicker. 20 Characteristics: A study in a Japanese population determined that the mean length and width of the PL tendon were 16.6 ± 1.8 cm and 0.4 ± 0.08 cm, respectively. They also determined that the length of the tendon correlated with the length of the forearm and was approximately 50.7 ± 6.5% of forearm length. 19 This corresponds to earlier reports in Caucasian populations also. 20 , 22 The mean cross-sectional area of the PL tendon is 3.1 mm 2 , mean volume is 529 mm 3 , and stiffness is 42.0 ± 4.1 N/mm. 22 Variations: The PL muscle is one of the most variable muscles in the human body, not only in terms of its absence but also in terms of muscle variations and anomalies. Its absence was first reported in 1559 by Colombo in De Re Anatomica Libri and has been the subject of several cadaveric as well as in vivo studies. 23 The highest reported prevalence of absence of the PL tendon (64%) was reported in the Turkish population. The overall prevalence of the absence of the PL tendon in different Caucasian populations is approximately 22%. In contrast, it is quite low in Black (3%), Asian (4.5%), and Native American (7.1%) populations. There is disagreement in the literature regarding the symmetry of absence and whether absence is more common in women. Given the wide variations between the different ethnic groups, we feel that a general figure for the absence of the PL tendon cannot be quoted. It is, therefore, important for surgeons to observe these variations and be familiar with the values of the ethnic groups they treat or study. 23 Many variations in morphology of the PL tendon have been reported, including tendon multiplicity and anomalous insertions into antebrachial fascia, thenar fascia, carpal bones, or the FCU tendon. 24 Clinical correlations: The tendon of the PL is the most frequently used source of a tendon graft. A single PL tendon graft can be used to reconstruct a single FDP tendon from its insertion till the palm. If a longer graft is required (till the forearm) or multiple fingers need to be reconstructed, one must consider other grafts such as the plantaris or fascia lata. The PL tendon has also been used for reconstruction of collateral ligaments of the metacarpophalangeal (MCP) and interphalangeal (IP) joints and for correction of the swan neck deformity. The PL has been used as a motor to provide palmar abduction in patients with low median nerve palsy. The tendon of PL is harvested along with a strip of the PA and transferred to the insertion of the abductor pollicis brevis. This tendon transfer, also known as the Camitz transfer, is especially valuable in low demand patients with severe long-standing carpal tunnel syndrome. 25 The PL has also been used as a motor to restore thumb extension by a transfer to the extensor pollicis longus in patients with radial nerve palsy. 26 A number of clinical maneuvers have been described in literature to determine the presence of the PL tendon preoperatively. We prefer the use of the resisted wrist flexion test described by Mishra in determining the presence of the PL. In this test, the examiner passively hyperextends the MCP joints of the fingers to make the PA taut. The patient is then asked to attempt active flexion of the wrist. The tendon of the PL can then be clearly visualized. 27 28.1.3 Flexor Carpi Ulnaris Etymology: Flexor is derived from the Latin word flexus, meaning “bent” (thus flexor indicates “that which bends,” or “bending”). Carpi is derived from Latin word carpalis and Greek word karpos , both of which indicate “wrist” (the carpus). Ulnaris is derived from the Latin word ulna, which means “elbow.” 3 , 4 Origin: The tendon of the FCU is formed in the distal third of the muscle along the anterolateral border. It is quite thick and unlike the FCR has muscle fibers inserting into it almost till the level of its insertion. Course: The tendon of the FCU is quite short, and in the distal half of the forearm, the ulnar artery and nerve pass deep and radial to the FCU tendon (▶ Fig. 28.1 ). Insertion: The FCU tendon inserts mainly onto the pisiform, with extensions onto the hook of hamate and the base of the fifth metacarpal via the pisohamate and pisometacarpal ligaments. In addition, some fibers insert into the flexor retinaculum and the bases of the third and fourth metacarpals. The pisiform is believed to be a sesamoid bone that lies within the FCU tendon. Characteristics: The FCU tendon is approximately 47 ± 4.7 mm in length and has a cross-sectional area of 27.4 ± 3.6 mm 2 . 28 Unlike the tendons of the FCR and the digital flexors, the FCU does not have a tendon sheath. 29 In addition to its function as a flexor and ulnar deviator of the wrist, the tendon of the FCU plays a role in stabilizing the wrist; in the strong power grip, such as when holding a hammer; and in stabilizing the pisiform. When a subject is asked to abduct the small finger against resistance, the FCU synergistically contracts to stabilize the pisiform, and this in turn stabilizes the origin of the abductor digiti minimi. This can be used to test the function of the FCU by palpating the FCU tendon while asking the subject to abduct the small finger against resistance. The maximum excursion of the FCU tendon in adults is 3.3 cm. 10 Variations: Many variations of the insertion of the FCU tendon have been described. In addition to the multiple insertions described earlier, it may have extensions to the metacarpals of the small, ring, or long fingers or to the capsule of the CMC joints. A split FCU tendon with the ulnar nerve passing between the split has also been described. 30 Clinical correlations: There have been reports of patients with FCU tendinopathy. These patients present with pain about 3 to 4 cm proximal to the pisiform and histology shows features of tendinosis (degeneration) and not tendinitis (inflammation). 31 The FCU has been used as a motor in tendon transfers for radial and median nerve palsies. A split FCU transfer with independent innervation based on both heads of the FCU has also been described. 32 The FCU is designed optimally for force generation and less for excursion. Therefore, the FCR may represent a better option for tendon transfer. The ulnar nerve and artery lie deep and radial to the FCU tendon. The ulnar nerve can be blocked by infiltrating local anesthetic agent deep to the palpable FCU tendon. In order to obtain a complete block of the ulnar nerve, the dorsal branch of the ulnar nerve needs to be blocked by injecting a wheal of anesthetic around the ulnar styloid. 28.1.4 Flexor Digitorum Superficialis/Sublimis Etymology: Flexor is derived from the Latin word flexus meaning “bent” (thus flexor indicates “that which bends,” or bending). Digitorum is derived from the Latin word digitus or digitorum , indicating the digits. Superficialis denotes its superficial location in the forearm. Sublimis is again derived from Latin, meaning “superficial.” Origin: The FDS has two heads of origin—a proximal humeroulnar head and a distal radial head. The median nerve and ulnar artery pass below the muscular arch formed by the two heads of the FDS. The humeroulnar head lies in a deeper plane. It has a complex digastric anatomy with a large flat common tendon that connects a single proximal muscle belly to two or three separate distal muscles that give rise to the tendons to the index, ring, and small fingers. The tendon to the index and small fingers arises completely from the distal muscle bellies, whereas the tendon to the ring finger arises partly from distal muscle belly and partly from the humeroulnar head. 33 The radial head lies in a superficial plane and gives rise to the tendon to the long finger. Although the FDS is often thought of as four independent muscles, only the long finger FDS has truly independent function. The superficialis tendons to the index, ring, and small fingers have a common proximal muscle belly, act as a conjoined unit, and do not have completely independent actions. Course: The FDS tendons to the ring and long fingers are superficial and central, whereas the tendons to the index and small fingers are deep and located radially and ulnarly, respectively (▶ Fig. 28.3 ). This arrangement of tendons is maintained in the forearm and in the carpal tunnel. Once the tendons exit from the carpal tunnel, they diverge toward the respective fingers. In the forearm, these tendons are deep to the PL, FCR, PT, and radial artery and are superficial to the FDP, FPL, ulnar artery, and median nerve. In the palm, the tendons of the FDS are deep to the superficial palmar arch and the digital branches of the median and ulnar nerves (▶ Fig. 28.4 ) and are superficial to the tendons of the FDP, along with the lumbricals and the deep palmar arch. 34 Fig. 28.3 Volar distal forearm dissection showing the Flexor Digitorum Superficialis (FDS) tendons as well as the median nerve. The FDS tendons to the ring and middle fingers are superficial and central, whereas the tendons to the index and small fingers are deep and located radially and ulnarly respectively. Flexor carpi radialis: FCR, flexor digitorum superficialis: FDS, flexor pollicis longus: FPL. Fig. 28.4 In the palm, the tendons of the FDS are deep to the superficial palmar arch and the digital branches of the median and ulnar nerves, and superficial to the tendons of the FDP along with lumbricals and the deep palmar arch. At the level of the MCP joint, the FDS tendon changes from a relatively oval configuration to a flattened tendon. This divides into two slips over the proximal third of the proximal phalanx to form an interval for the passage of the tendon of the FDP—the “bifurca” (▶ Fig. 28.5 ). The two slips of the FDS rotate 180° with the radial slip moving in a clockwise direction and the ulnar slip in an anticlockwise direction (▶ Fig. 28.6 ). The slips of the FDS encircle the FDP tendon as they pass from proximal to distal. They are initially palmar to the FDP tendon, then become lateral, and finally end up dorsal to the FDP tendon (▶ Fig. 28.7 ). As the two slips approach each other dorsal to the FDP tendon at the level of the neck of the proximal phalanx, they divide again into a radial and an ulnar band. The radial band of the radial slip and the ulnar band of the ulnar slip continue straight ahead (linear bands), whereas the ulnar band of the radial slip and the radial band of the ulnar slip decussate in an X pattern behind the FDP tendon (▶ Fig. 28.8 ) forming the chiasm of Camper. 35 The chiasma can be variable in terms of anatomy and morphology. 36 Fig. 28.5 This diagram shows the orientation of the FDS tendon in the digit and its relationship to the FDP tendon. The anatomy and fiber orientation of the “bifurca” and the Camper Chiasma are clearly seen. (Copyright Kleinert Institute, Louisville, KY). Fig. 28.6 Dissection showing the anatomy of the FDS tendon in the digit. The anatomy and the fiber orientation of the “bifurca” and the Camper’s Chiasma are well visualized. Fig. 28.7 Relationship of the FDS and the FDP. The FDP tendon is passing thru the “bifurca” of the FDS. Fig. 28.8 View of the FDS at the level of the proximal phalanx and the PIP joint showing the “bifurca” and the Camper’s Chiasma and the insertion of the FDS onto the base of the middle phalanx. Insertion: These crossing bands join with the linear bands to form the triangular insertion of the FDS tendon into the lateral crests on the palmar aspect of the shaft of mid-middle phalanx (▶ Fig. 28.8 ), lying on either side of the FDP tendon (▶ Fig. 28.7 ). Characteristics: The FDS is the prime flexor of the proximal interphalangeal (PIP) joint of the fingers. It also contributes to flexion at the wrist and the MCP joint. When making a fist, it has a slight adduction component and brings the fingers together. The small finger FDS is also believed to have a minor opposing action at the CMC joint. 30 There are also differences in strength and available excursion between the FDS tendons to the four fingers. The long finger FDS is 75% stronger than the ring or the index fingers, while the small finger FDS is 50% weaker than the index or ring finger FDS. 33 The maximum excursion of the FDS tendon in adults is 6.4 cm. 10 Variations: Most variations of the FDS involve the muscle belly. They include accessory muscle slips that connect the muscle to other forearm flexors, absence of the radial head, and the presence of anomalous muscles in the palm that can result in carpal tunnel syndrome. 30 The muscle belly and/or the tendon to the small finger may be absent. The prevalence of absence of FDS to the small finger can vary from 6.5% in Asian populations up to 21% in Caucasian populations. 37 Clinical correlations: When evaluating an injured hand for the presence of a flexor tendon injury, one must differentiate between an injury to the FDS and the FDP. The FDP can be easily evaluated by checking flexion of the distal interphalangeal joint (DIP), as it is the only flexor of that joint. Testing for injury to the FDS is more complex, because the PIP joint is flexed both by the FDS and the FDP. Therefore, one needs to check the function of the FDS while blocking the action of the FDP. The standard test for the FDS takes advantage of the fact that the FDP tendons to the long, ring, and small fingers share a common muscle belly and lack independent function. The finger being tested is allowed to flex while the examiner blocks the action of the FDP tendon by preventing flexion of the DIP joint of the other two fingers. The standard test is not reliable for the index finger, because the index finger FDP has an independent muscle belly. In addition, the action of the FDS to the small finger may be dependent on the FDS to the ring finger, and they may need to be tested together. 38 We prefer to use the test described by Mishra to evaluate the FDS. 39 In this test, the subject is asked to press the fingertip pulp of all the fingers together against the proximal part of the palm, such that the DIP joint is kept extended. If the FDS is acting, the DIP joint remains in a position of extension to hypertension while the MCP and PIP joints are fully flexed. If the FDS of any of the fingers is injured or absent, the DIP joint flexes. This test works on the principle that the FDP can flex the PIP joint only after it has flexed the DIP joint. If the DIP joint is maintained in extension, PIP joint flexion is purely a function of the FDS. The FDS tendon is often used is a motor for tendon transfers, because it is believed to have an independent function, making it easy to retrain, and its function at the donor finger can be taken over by the FDP. However as previously mentioned, only the FDS tendon to the middle finger is truly independent. The index and small finger FDS tendons are closely linked as they arise from a common proximal muscle. They have independence only of their distal fibers. If one of these tendons is transferred to the dorsal side of the forearm (nonsynergistic transfers), only the distal fibers would transfer, as the proximal muscle belly would need to simultaneously be a flexor and an extensor. In addition, the index finger FDS is necessary for pulp pinch with the thumb and the small finger FDS is quite slender and often absent. For these reasons, the FDS tendons to the long or ring finger are preferred for tendon transfers. The FDS to the long finger is most suited for nonsynergistic transfers. One must also be aware of the morbidity associated with these transfers. The loss of FDS can result in a swan neck deformity in mobile hands from loss of the volar restraint and a PIP joint flexion contracture from tenodesis of the stump of the divided FDS. The loss of FDS of the middle finger will result in inability to perform a chuck grip (pulp-to-pulp pinch between the index finger, middle finger, and thumb), and the loss of the ring finger FDS may result in a decrease in grip strength. The use of the ring finger FDS for a transfer to the dorsum of the forearm or hand may require division of the band of muscle fibers that often connects it to the digastric tendon in the midforearm. 33 , 40

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