Flexor Tendon Injuries

Brian Miller, MD

Leif Sigurdson, MD, FRCSC

Flexor Tendon Injuries

• Restoration of satisfactory digital function after flexor tendon lacerations remains one of the most challenging problems in hand surgery

• Prior to the 1960’s tendons lacerated in “no man’s land” were not repaired in favor of delayed grafting

Flexor Tendon Injuries

• Kleinert and Verdan (1960’s) showed superior results with primary repair leading to general acceptance of this approach

• Years of anecdotal experience and surgical dogma followed pertaining to repair techniques and postoperative management

Flexor Tendon Injuries

• In the past 25 years more scientifically sound research has advanced our understanding of flexor tendon structure, nutrition, healing, biomechanics, response to stress, repair techniques

• Many studies have examined passive and active motion protocols

• Greatest limiting factor: absence of a universal system for assessing outcome

Flexor Tendon Injuries

• Questions– Primary repair vs delayed grafting?– Repair of FDS and FDP vs FDP alone?– Flexor sheath excision? repair? neither?– Type of suture material?– Repair technique?– Benefit of postoperative motion? Active or

passive? How much?

Tendon Morphology

• 70% collagen (Type I)• Extracellular components

– Elastin– Mucopolysaccharides (enhance water-binding

capability)

• Endotenon – around collagen bundles• Epitenon – covers surface of tendon• Paratenon – visceral/parietal adventitia

surrounding tendons in hand• Synovial like fluid environment

Anatomy

• Extrinsic flexors– Superficial group

• PT, FCR, FCU, PL

• Arise from medial

epicondyle, MCL,

coronoid process

Anatomy

• Extrinsic Flexors– Intermediate group

• FDS• Arises from medial

epicondyle, UCL, coronoid process

• Usually have independentmusculotendinous originsand act independantly

Anatomy• Extrinsic flexors

– Deep group• FPL – originates from

entire medial third of volar radius

• FDP – originates on proximal two thirds of the ulna, often has common musculotendinous origins

Anatomy

• Carpal tunnel– 9 tendons– Median

nerve

Anatomy• Flexor sheaths

• approx distal palmar crease

– Predictable annular pulley arrangement

• Protective housing• Gliding surface• Biomechanical

advantage• Synovial layers

merge at MP level

• Flexor tendons weakly attached to sheath by vinculae

Anatomy

• Camper’s Chiasma

Tendon Nutrition

• Vascular– Longitudinal vessels

• Enter in palm• Enter at proximal synovial fold

– Segmental branches from digital arteries• Long and short vinculae

– Vessels at osseous insertions

• Synovial fluid diffusion– Imbibition (pumping mechanism)

Tendon Nutrition

• Dorsal vascularity• Avascular zones

– FDS (over proximal phalanx

– FDP (over middle phalanx)

• Nutrition vital for rapid healing, minimization of adhesion and restoration of gliding

Biomechanics

• Effeciency of flexor system = the degree to which tendon excursion and muscle contraction translates into joint motion

• Governed by integrity of the pulley system and resistance to glide– A2 and A4 most significant

• Pulleys decrease the moment arm length at each joint leading to increased joint motion

Biomechanics

Tendon Healing

• Inflammatory phase (0-5 d); fibroblastic phase (5d – 6wks); remodelling (6wks-9mos)

• Intrinsic vs extrinsic healing

• Balance between the two determines amount of extrinsic adhesion vs intrinsic tendon healing

Tendon Healing

• Factors affecting tendon healing, and adhesion formation– Surgical technique

• decreased vascularity• gapping

– Postoperative motion (passive, active)

Tendon Adhesion

• Increased adhesion formation with:– Traumatic/surgical injury

• Crush injuries

– Ischemia• Disruption of vinculae

– Immobilization– Gapping at repair site– Excision/injury to flexor sheath components

• Debate over benefit of sheath repair

Tendon Adhesion

• Experimental attempts to minimize adhesion formation– Oral: steroids, antihistamines, NSAIDS– Topical: beta-aminoproprionitrile,

hydrocyprolins, hyaluronic acid, collagen solutions, fibrin

– Physical: silicone/cellophane wrapping, polyethylene tubes, interposed sheath flaps

• Varying lab success but none proven definitively or adopted into clinical practice

Tendon Healing

• “It now seems irrefutable that the most effective method of returning strength and excursion to repaired tendons involves the use of strong, gap resistant suture techniques followed by the frquent application of controlled motion stress”

-Strickland

Diagnosis

• History

Diagnosis

• History

Diagnosis

• Physical exam

• Abnormal resting posture

• Absent FDP / FDS function

• Associated digital nerve and digital vessel injury

• Discuss nature of injury and postoperative course with patient

Zones of Injury

FDS Insertion

Flexor Sheath(proximal)

TCL(distal edge) Carpal Tunnel

Flexor Tendon RepairTiming

• Delayed equal or better than emergent repair– Acute or subacute acceptable– Tendon deterioration/shortening after several

wks– Delay several days if wound infected

Incisions

• Factors– Avoid crossing joints

at 90 deg.– Preference– Existing lacerations– Need to expose other

structures

Tendon Retrieval

• Avoid trauma to synovial sheath lining

• Forcep/hemostat/skin hook if proximal stump visible

• Proximal to distal milking, reverse esmarch

• Suction catheter

• Suture catheter to proximal tendons in palm and deliver distally

Tendon Retrieval

- Retraction often limited to A1/A2 pulley region by vinculae

- If lacerated proximal to vinculae or if vinculae disrupted, tendon ends may retract into plam

- If proximal stumps have retracted into the palm the correct orientation of FDS and FDP must be re-established (such that FDP lies volar to Camper’s Chiasm)

Repair Techniques

• Ideal– Gap resistant– Strong enough to tolerate forces generated by

early controlled active motion protocols• 10-50% decrease in repair strength from day 5-21

post repair in immobilized tendons• This is effect is minimized (possibly eliminated)

through application of early motion stress

– Uncomplicated– Minimal bulk– Minimal interference with tendon vascularity

Core Sutures

• Current literature supports several conclusions regarding core sutures– Strength proportional to number of strands– Locking loops increase strength but may collapse and

lead to gapping– Knots should be outside repair site– Increased suture callibre = increases strength– Braided 3-0 or 4-0 probably best suture material– Dorsally placed suture stronger and biomechanically

advantageous– Equal tension across all strands

Dorsal vs Volar

– Historically dorsal placement avoided due to tendon vascular anatomy

– Diffusion now felt to be primary source of nutrition during healing

– Biomechanical advantage and increased tensile strength found during finger flexion with dorsal sutures (Komanduri, Soejima, Stein)

– Increase work of flexion with volar sutures (Aoki)

Locking vs Grasping Loops

– Locking stronger, and greater gap resistance in two stranded repairs (Manske et al.)

– Dorsal vs volar placement did not affect strength with locking repairs, but did affect strength of grasping repairs (Stein)

Cross-Sectional Area

– Increasing the cross-sectional area of the locking loop from 10 to 50% proportionately increased the ultimate tensile strength of the repair (Hatanaka, Manske)

• Has been demonstrated with core and circumferential suture tecniques

Circumferential Sutures

– Initially were designed to improve tendon glide

– Have been shown to add tensile strength (by 10–50%) and gap resistance to repairs (Diao, (Diao, Pruitt, Silverskiold, Wade)Pruitt, Silverskiold, Wade)• Also confirmed in cyclic loading studiesAlso confirmed in cyclic loading studies

– Running locked, horizontal mattress, epitenon/intrafibre, and cross-stitch have been shown to be the strongest

Gap Formation

• Gapping at tendon repair site associated with increased adhesion formation in laboratory/histological analysis (Lindsay)

• Gapping > 3mm correlated with decreased tensile strength in canine model (Gelberman)

• Gapping > 2mm correlated with poorer clinical results (Seradge)

Ultimate Strength and Repair Technique

• Proportional to number of strands– 6 and 8 strand repairs strongest

• Steep learning curve• Increased bulk and resistance to glide• Increased tendon handling and adhesion formation • May not be necessary for forces of early active

motion

– Several four strand repairs appear to have adequate strength without complexity of 6 and 8 strand repairs

Kessler

Modified Kessler(1 suture)

Kessler-Tajima(2 sutures)

Cruciate 4 Strand Repair

- McLarney

The ideal repair? - Strickland

Strength vs Force(Core suture with running epitendinous suture)

• Some 2-strand repairs vulnerable during 1-3 wks post repair with light active motion

Suture Knot Location

• In – interference with healing at repair site• Out – interference with tendon gliding• Knots outside superior in one in vitro study

(Aoki)• Statistically significant increase in tensile

strength at 6 wks with knots-inside technique in canine model (Pruitt)

• Few studies• No consensus

Suture Material/Size

– Historically stainless steel (strongest and least reactive) but difficult to work with

– Braided synthetics now most common (ethibond, ticron, mersilene)

– Increased caliber felt to increase tensile strength

– 2-0 or 3-0 recommended with early active motion protocols as many 4-0 suture strength are less than the fatigue strength of many 2 and 4 strand repairs

Repair Augmentation

– Augmenting repairs with tendon splints or mesh has been associated with concerns related to decreased tendon glide and increased adhesion formation due to foreign body reaction

– Has not been accepted in clinical practice

Sheath Repair

• Advantages– Barrier to extrinsic adhesion formation– More rapid return of synovial nutrition

• Disadvantages– Technically difficult– Increased foreign material at repair site– May narrow sheathand restrict glide

• Presently, no clear cut advantage to sheath repair has been established

Partial Lacerations

• Controversy in past as partial lacerations were felt to predispose to entrapment, triggering and rupture

• Repair if > 50%

• Some advocate repair of partial lacerations > 60%

Tendon Advancement

– Previously advocated for zone 1 repairs, as moving the repair site out of the sheath was felt to decrease adhesion formation

– Disadvantages• Shortening of flexor system• Contracture• Quadregia effect• Little excursion distally, therefore adhesions near

insertion less of an issue

Tendon Excursion

Summary

• Strong gap resistant repair• 4 strand, locking epitendinous (or

equivalent), 3-0 suture needed for early active motion– 4-0 suture, modified Kessler, running

epitendinous suture adequate for more conservative protocols

• No sheath repair• Large grasping/locking loops

Rehabilitation

Rehabilitation

• Early post-repair motion stress– Shown to increase recovery of tensile

strength, decrease adhesions in multiple animal models

– Load at failure for mobilized tendons twice that for immobilized tendons at 3 wks (Gelberman)

Rehabilitation

– Application of early motion in small amounts is felt by most surgeons to biologically alter the process of scar formation and maturation at the repair site such that collagen is laid down parallel to the axial forces (increase strength), and tendon adhesions are stretched (increased tendon glide)

Rehabilitation

• Mayer (1916)– The operation should never be undertaken

unless the surgeon himself can perform effective postoperative care

– Early motion should be instituted at the right time

– graded exercises should be used with corrective splints

Rehabilitation

• Bunnel (1918)– Postoperative immobilization– Active motion beginning at 3 wks postop.– Suboptimal results by today’s standards

• Improved suture material/technique as well as postoperative rehabilitation protocols

Rehabilitation

• Kleinert (1950s)– Posterior splint, wrist in flexion– Rubber bands from fingernails to volar wrist

area hold fingers in flexion– Patient able to actively extend against rubber

bands (within confines of splint)– Fingers pulled passively back into flexion– Used widely since with some modifications– Showed superior results with primary repair vs

delayed grafting

Rehabilitation

• Tendon excursion– MP motion = no flexor tendon excursion– 1.5 mm of excursion per 10 degrees of joint

motion for DIP (FDP) and PIP (FDS, FDP)– These values decrease after repair by approx.

65% (DIP motion) and 10% (PIP motion)

Rehabilitation

• Splints– Improved excursion with “palmar bar”

modification of Kleinert splint– Improved differential FDS/FDP excursion with

Mayo clinic “synergistic” dynamic tenodesis splint

– Improved excursion with wrist extension (45 degrees)

– MP’s at 90 degrees, IP’s in extension when at rest

– Decreased tension at repair with wrist extension (45o)and MP flexion (90o)

Rehabilitation

Rehabilitation

– Distal palmar bar modification of Kleinert type splint

Mobilization Protocols

• Active extension with rubber band flexion– Eg. Kleinert splint, usually modified with wrist

extension, MP flexion (90 degrees) and palmar bar to improve digital flexion

• Controlled passive motion– Posterior splint applied post-op– Controlled passive motion at regular intervals

Mobilization Protocols

• Controlled active motion– Proponents believe that excursion with

passive protocols is generally poor compared to that achieved with light active motion

• Therefore fewer adhesions and improved outcome

– Risk: tendon rupture• Published rupture rates similar to those with

passive protocols

– 4 and 6 strand repairs with strong epitendinous suture

– Wrist extension and MP flexion

Mobilization Protocols

• Many studies have described various protocols for early protected passive and active motion

• Results are almost always superior to previous more conservative protocols

FDP Avulsions

• Commonly male athletes

• Forced extension at DIP during maximal flexion (jersey finger)

• Often missed due to normal xray and intact flexion at MP and PIP– Opportunity for FDP reinsertion lost if

treatment delayed

FDP Avulsions

Leddy and Packer

FDP Avulsions

- Type 1: zig-zag exposure- Tendon delivered through

pulley system with catheter passed retrograde

- Fixed to base of phalanx with monofilament suture through distal phalanx and nail plate and tied over button

- Fix within 7-10 days before tendon degeneration and myostatic shortening occurs

FDP Avulsions

- Type 2: small bony fragment retracts to A3 level- Can fix up to 6 wks

post injury (less shortening)

- May convert to type 1 if tendon slips through A3 pulley and into palm

- Use same technique as for type 1

FDP Avulsions

- Type 3: large bony fragment retracts to A4 level- Bony reduction and

fixation of fragment

Children

• Usually not able to reliably participate in rehabilitation programs

• No benefit to early mobilization in patients under 16 years

• Immobilization > 4 wks may lead to poorer outcomes

Reconstruction

Single Stage Tendon GraftingZone 2

• Indications– Delayed treatment making end to end repair

impossible• Patient factors prevent repair• Late referral, missed tendon laceration or avulsion

– Supple joints with adequate passive ROM

Single Stage Tendon Grafting Zone 2

• Technique– 1 cm distal FDP stump left intact– 1 cm of FDS insertion left intact (decreased

adhesion formation vs granulating insertion site)

– Tenodesis of FDS tail to flexor sheath (10-20 deg of flexion) optional

• Hyperextension at PIP in absence of FDS tendon occurs occasionally

Single Stage Tendon Grafting Zone 2

• Technique– Graft donors

• Palmaris longus• Plantaris• Long toe extensors• (FDS)• (EIP)• (EDM)

Single Stage Tendon Grafting Zone 2

• Technique– Graft passed through pulley system

• Atraumatic technique

– Distal fixation with tension set proximally or proximal fixation first

– Multiple methods for fixation of graft ends

Single Stage Tendon Grafting Zone 2

• Technique– Distal

juncture

Single Stage Tendon Grafting Zone 2

• Technique– proximal

juncture

Pulvertaft weave creates a stronger repair vs end to endtechniques, and allows for greater ease when setting tension

Single Stage Tendon Grafting Zone 2

• Setting tension– GA

• With wrist neutral• Fingers fall into semi flexed position (slightly less

than ulnar neighbour), allowing estimation of tension

– Local anesthesia, active flexion– Electrical stimulation

• Bunnel – “tendons shrink”• Pulvertaft – “tendons stretch”

Secondary Reconstruction Zone 1

• Zone 1 (functioning FDS)– Eg. Late presentation of FDP avulsion– DIP fusion– Tendon graft

• Risks damaging FDS function through injury/adhesions in a very functional finger

• ? Young patients, supple joints, need for active DIP flexion

Secondary Reconstruction Zones 3, 4 and 5

• Usually associated with 3 – 5 cm gap– Interposition graft– FDS to FDP transfer– End to side profundus juncture

Two Stage Reconstruction

• Primary grafting likely to give poor result, but salvage of functioning finger still desirable

• Sub-optimal conditions– Extensive soft tissue scarring

• Crush injuries• Associated fractures, nerve injuries

– Loss of significant portion of pulley system

Two Stage Reconstruction

• Patient selection– Motivated– Absence of neurovascular injury– Good passive joint motion

• Balance benefits of two additional procedures in an already traumatized digit with amputation/arthrodesis

Two Stage Reconstruction

• Stage 1– Excision of tendon remnants

• Distal 1 cm of FDP left intact, remainder excised to lumbrical level

• FDS tail preserved for potential pulley reconstruction

– Incision proximal to wrist• FDS removed/excised• Hunter rod then placed through pulley system and

fixed distally (suture or plate and screw – depending on implant)

Two Stage Reconstruction

• Stage 1– Rod extends proximally to distal forearm in

plane between FDS and FDP– Test glide– Reconstruct pulleys as needed if implant

bowstrings

Two Stage Reconstruction

• Stage 1– Postop

• Start passive motion at 7 days• Continue x 3mos to allow pseodosheath to form

around implant• Before stage 2 joints should be supple, and

wounds soft

Two Stage Reconstruction

• Stage 2 – implant removal and tendon graft insertion– Distal and proximal incisions opened– Implant located proximally and motor selected

(FDP middle/ring/small, FDP index)– Graft harvested, sutured to proximal implant

and delivered distally• Fixed to distal phalanx with pull out wire over

button

Two Stage Reconstruction

• Stage 2 – implant removal and tendon graft insertion– Proximally sutured to motor with pulvertaft

weave

• FDS transfer from adjacent digit described• Obviates need for graft• Difficulty with length/tension

• Postop• Early controlled motion x 3 wks, then slow

progression to active motion

Pulley Reconstruction

• Pulley loss– Bowstringing = tendon taking shortest

distance between remaining pulleys– Biomechanical disadvantage

• Excursion translates into less joint motion

– Adhesions/rupture at remaining pulleys due to increased stress

– A2 and A4 needed (minimum) • Most biomechanically important• Some authors advocate reconstructing a 3 or 4

pulley system for optimal results

Pulley Reconstruction

• Most done in conjunction with a two stage tendon reconstruction

• Can be done with single stage tendon graft

• generally if extensive pulley reconstruction is required it is better to do a two stage procedure

Pulley Reconstruction

• Methods– Superficialis tendon

• Insertion left intact• Remnant sutured to original pulley rim, to

periosteum, or to bone through drill holes

– Tendon graft• Sutured as above• Passed through hole drilled in phalanx (risk of

fracture)• Wrapped around phalanx (requires 6-8 cm of graft)

Pulley Reconstruction

Pulley Reconstruction

• Methods– Extensor retinaculum

• Excellent gliding surface• Difficult to harvest the 8-6 cm required for fixation

around phalanx

– Artificial materials• Dacron, PTFE, nylon silicone• Due to abundant atogenous material and

disadvantages of artificial materials, this has not become common clinical practice

• May be stronger in long term vs autogenous

Tenolysis

– Release of nongliding adhesions for salvage in poorly functioning digits with previous tendon injury

– Avoid in marginal digits• May not tolerate additional vascular/neurologic

injury

– May need concomitant collateral ligament release, capsulotomy

– Prepare patient for possible staged reconstruction

Tenolysis

• Timing– 3-6 mos. Post repair (minimum)– Plateau with physiotherapy

• Anesthesia– Local with sedation

• Allows patient participation• Tests adequacy of release• Motivates patient

Tenolysis

• Technique– Zig zag incisions– Adhesions divided maintaining non-limiting

adhesions– Pulleys reconstructed as needed

• If extensive or not possible convert to staged reconstruction

– Immediate motion postop.