Extensor Tendons and Flexor Tendons

Zone 1 & 2 Protocols

• No passive flexion for 3 months

• If Swan Neck develops place PIP joint in 35-45 degrees of flexion while maintaining DIP in extension

• Weeks 1-6 (could be up to 8 weeks)

  • DIP in full extension (0 to +10 degrees hyper)

  • Monitor for signs of swan neck deformity

• Week 6

  • DIP ROM 25-35 degrees flex - monitor for extension lag

  • If extension lag persists, continue splinting for two more weeks

    • >15 degrees

• Week 7

  • Progress DIP flex ROM to 35-45 degrees flexion - monitor ext lag

• Week 8

  • Progress DIP flex ROM to 45-55 degrees

• Week 9

  • Progress to full flexion

  • initiate tendon glides

**5-10 degree lag normal in hypermobile joints**

Zones 3 & 4 Protocol (No Lateral Band Involvement)

• Weeks 1-4 (could be up to 6 weeks)

  • Orthotic or plaster of paris to immobilize PIP in ext; DIP not included

  • Initiate DIP flexion ROM within confines of orthotic

    • done to centralize lateral bands and prevent ORL ligament shortening

• Week 6

  • Wean out of PIP ext orthotic/cast

  • Begin gentle PIP flex ROM to 30 degrees flexion

• Week 7

  • Advance PIP flex ROM to 40-50 degrees flex

• Week 8

  • Advance PIP flex ROM to 60-85 degrees flex

  • PIP joint blocking can begin here

• Week 9

  • Advance to full PIP flex ROM

  • Tendon gliding exercises

  • continue joint blocking

• Week 10

  • Begin progressive strengthening

Zones 3 & 4 Protocol (Lateral Band Involvement)

• Weeks 1-4 (could be up to 6 weeks)

  • Orthotic or plaster of paris to immobilize PIP in ext with DIP included

  • Initiate DIP flexion ROM at week 4

• Week 6

  • Wean out of PIP ext orthotic/cast

  • Begin gentle PIP flex ROM to 30 degrees flexion; continue isolated DIP ROM

• Week 7

  • Advance PIP flex ROM to 40-50 degrees flex

• Week 8

  • Advance PIP flex ROM to 60-85 degrees flex

  • PIP joint blocking can begin here

• Week 9

  • Advance to full PIP flex ROM

  • Tendon gliding exercises

  • continue joint blocking

• Week 10

  • Begin progressive strengthening

Zones 3 & 4 SAM Protocol (with and without lateral band involvement)

• Zone 3: Boutonnière Deformity

• Week 1

  • Fabricate volar immobilization orthotic with PIP/DIP at 0 degrees

  • Fabricate ½ two volar static exercise orthoses

    • Orthotic #1 Lateral Band Involvement: PIP 30 degrees flexion, DIP 20 degrees flexion - done to centralize lateral bands and prevent ORL ligament shortening

    • Orthotic No Lateral Band Involvement #2 : PIP 0 degrees, DIP free

  • Remove immobilization splint hourly for 10-20 reps of AROM PIP and DIP motion using both orthoses as template

    • Wrist held in 20-30 deg flexion, MP at 0 deg

    • if lateral bands repaired, limit DIP flex to 30-35 in orthosis #1; if not injured, fully flex and extend DIP

• Week 2

  • If no extensor lag: progress orthosis #1 Lateral Band Involvement to PIP 40-50, DIP 30-40

  • Remove immobilization splint hourly for 10-20 reps of AROM PIP and DIP motion using both orthoses as template

    • Wrist held in 30 deg flexion, MP at 0 deg

    • if lateral bands repaired, limit DIP flex to 30-40 in orthosis #1; if not injured, fully flex and extend DIP

• Week 3

  • If no extensor lag: progress orthosis #1 Lateral Band Involvement to PIP 50-60, DIP 40-50

  • Remove immobilization splint hourly for 10-20 reps of AROM PIP and DIP motion using both orthoses as template

    • Wrist held in 30 deg flexion, MP at 0 deg

    • if lateral bands repaired, limit DIP flex to 40-50 in orthosis #1; if not injured, fully flex and extend DIP

• Week 4

  • If no extensor lag: progress orthosis #1 Lateral Band Involvement to PIP 70-80, DIP 50-60

  • Remove immobilization splint hourly for 10-20 reps of AROM PIP and DIP motion using both orthoses as template

    • Wrist held in 30 deg flexion, MP at 0 deg

    • if lateral bands repaired, limit DIP flex to 50-60 in orthosis #1; if not injured, fully flex and extend DIP

• Week 5

  • Wean from orthoses

  • Continue flexion without restriction

• Week 6

  • D/C orthosis

  • Begin strengthening

Conservative management involves 6 weeks of immobilization

Sagittal Bands

• Zone 5 injury can include this

• Typically on radial side of digit

  • RA patients and cause of ulnar drift

• Conservative Tx: Yoke orthosis; but if from RA, it may need primary repair

• Affected in Zone 5; watch out for subluxation

  • If ulnar one is lost, EDC drops off radially

  • If radial one is lost, EDC drops off ulnarly

Juncturae Tendinae

• Zone 6 injury

  • If the EDC is repaired proximal to the juncturae tendinum, all metacarpals are splinted in extension.

  • If the EDC is repaired distal to juncturae tendinum, only the metacarpal of the repaired tendon is splinted in extension, and the adjacent MP’s can either be splinted in slight flexion or left free

• links all branches of EDC from IF - SF

  • When there is excursion distally, with MCP flexion of digits, it brings the one with the injury, forward and backwards with it; must keep adjacent digits to injured digit in extension to promote stability while healing

Saddle Syndrome

• Differential diagnosis in Zones 4, 5, & 6

• Results in stiffness to MCPs and can look like they are unable to extend

  • Common causes of this injury include crush injuries, a contusion from a direct blow, a fall on an outstretched hand, and torquing stresses

• Two different types: both cases it involves a deep transverse metacarpal ligament on volar surface of MCP joints

  • Lumbricals and volar interossei split like scissors and deep transverse MCP ligament rides between the split

    • If lumbricals and volar interossie adhere to each other and not the dTML, when attempting intrinsic plus position, with proximal excursion of lumbricals and Volar interossei, the dTML ‘splits’ the adhesion, resulting in pain

    • If lumbricals adhere to volar interossei AND the dTML with distal excursion, there is pain with intrinsic minus position as the adhesion pulls away from dTML

Extensor Tendon Protocol Zones 4 (proximal aspect of P1), Zone 5, Zone 6

• Week 1-3

  • Orthotic: place wrist in 30-45 degrees of extension and MCPs at 0 degrees of ext; PIP/DIP free

  • Depending on affected tendons:

    • If only EDC, EIP, or EDM affected, able to begin very gentle tenodesis of wrist to 40 deg ext to 10 degrees wrist extension

    • If wrist extensors (ECRL, ECRB) affected, begin very gentle wrist tenodesis to 40 deg ext to 20 deg wrist ext

  • Begin hook fisting within confines of orthotic

  • Wound care/edema management

• Week 3

  • Progress MCP flexion to allow 40-50 degrees flexion (progress by 10-20 degrees each week)

  • Modify orthosis to place wrist in neutral

• Weeks 4-6

  • Progress MCP flexion to 50-60 degrees flexion (progress by 10-20 degrees each week)

  • Begin wrist AROM within pain free arc: wrist extension, wrist flexion, wrist radial/ulnar deviation

  • Start weaning from splint at ~ week 5

• Week 6

  • Begin tendon glides

  • progress full wrist AROM

  • d/c splint (if no extension lag noted)

  • After achieving full fist, begin progressive strengthening

Extensor Tendons Dynamic Outrigger Protocol Zones 4 (proximal aspect of P1), Zone 5, Zone 6

• Cumbersome and expensive protocol due to dynamic orthotic

• Orthotic outrigger holds MCPs in extension

• Weeks 1-3

  • Forearm based dynamic digital extension splint Wrist 25-30 degrees ext, MP at 0, PIPs free

  • Fabricate static forearm based Splint at night, wrist at 30-40 ext, MPs at 0, PIPs free.

  • AROM flexion: isolated joint and tendon gliding (hook and straight fist).

  • Passive extension via elastic recoil of the dynamic splint. 10-20 reps hourly.

  • Begin active MP flexion to 30-40 degrees (via flexion block on dynamic splint).

    • Progress MP flexion as tolerated.

  • Perform wrist and digit PROM in extension and tenodesis out of splint 10 repetitions hourly

• Weeks 4-6

  • Come out of splint for exercise

  • Progress MP flexion to 40-60 (week 4), 70-80 (week 5).

  • Initiate full fisting if not already done.

  • Composite wrist and finger flexion.

  • Active digital extension exercises out of splint.

• Week 6

  • D/C splint. Dynamic flexion splinting PRN.

  • AAROM, PREs, heat and stretch, reverse putty scraping

Sagittal Band Conservative Protocol

• Most commonly injured: radial side

• Weeks 1-6

  • 24/7 wear of relative motion orthosis

  • Injured digit +30-40 degrees MCP extension

  • Edema management

  • Pain management

    • US; heat & cold modalities

• Week 7-8

  • RMO part time

  • MCP AAROM and AROM activities without orthotic

    • EDC glides

    • Towel walking

    • Tendon glides

Extensor Tendon ICAM Protocol (Zones 4-7)

• ICAM = Immediate Controlled Active Motion - digit inclusion; indicated for simple EDC lacerations only

  • IF only - Splint IF and SP in ext

  • LF only - Splint LF and RF in ext

  • RF only - splint RF/LF only in ext

  • SF only - splint SF/IF only

  • Not allowed:

    • RF and SF in ext

    • IF and LF in ext

    • 3-4 digits in ext

• Orthotic: per evidence, only yolk splint is needed with no static wrist support; initially evidence supported use of static wrist support, but no longer supports it - test has been updated to reflect this

• Weeks 1-3

  • Fab RMO placing involved digit in 15-20 deg extension relative to unaffected digits

  • Scar management

  • Edema management

• Weeks 3-5

  • Complete AROM within limits of RMO

  • Continue scar and edema management

• Week 6

  • D/C RMO; buddy strapping can be used during activity and wean as tolerated

  • begin composite fisting

  • begin progressive resistive exercises

Extensor Tendon Protocol Zones 7 & 8 (When just wrist extensors involved)

• Weeks 1-3

  • Immobilize wrist in 40 degrees extension

  • Begin gentle wrist tenodesis - 40 degrees ext to 20 degrees ext

  • Wound care/edema management

  • Scar management with wound closure

  • ROM of uninvolved joints

• Week 3

  • Progress gentle wrist ROM within pain free range

    • Wrist extension/flexion with open hand

    • Wrist extension/flexion with closed hand

    • Radial and ulnar deviation

• Week 4

  • Allow full wrist ROM; monitor for ext lag

    • Wrist extension/flexion with open hand

    • Wrist extension/flexion with closed hand

    • Radial and ulnar deviation

  • Begin aggressive scar massage

• Week 5

  • PROM of wrist if no ext lag

• Week 6

  • wean out of orthosis

  • progress resistive strengthening

Thumb Zone T1 (Mallet Th) Non-Operative - No Early Active

• Weeks 1-8

  • Orthotic - IP in ext or hyperextension - 24/7 wear

  • AROM of unaffected joints

• Week 9

  • Wear splint at night and between exercise sessions

  • Progress IP flex AROM between 0-20 degrees - if ext lag develops, return to orthosis for an additional week

• Week 10

  • Wear splint at night and between exercise sessions

  • Progress IP flex AROM between 0-40 degrees - if ext lag develops, return to orthosis for an additional week

• Week 11

  • Wear splint at night and between exercise sessions

  • Progress IP flex AROM between 0-60 degrees - if ext lag develops, return to orthosis for an additional week

• Week 12

  • D/C orthosis

  • Begin progressive strengthening if there is weakness - functional tasks cans support strengthening

Thumb Zone T1 (Mallet Th) Operative - No Early Active

• Weeks 1-6

  • Orthotic - IP in ext or hyperextension - 24/7 wear

  • AROM of unaffected joints

  • wound care ; edema management

  • scar management

• Week 7

  • Wear splint at night and between exercise sessions

  • Progress IP flex AROM between 0-20 degrees - if ext lag develops, return to orthosis for an additional week

• Week 8

  • Wear splint at night and between exercise sessions

  • Progress IP flex AROM between 0-40 degrees - if ext lag develops, return to orthosis for an additional week

• Week 9

  • D/C orthosis if no ext lag develops

  • Progress IP flex AROM between 0-60 degrees - if ext lag develops, return to orthosis for an additional week

• Week 10

  • Begin progressive strengthening if there is weakness - functional tasks cans support strengthening

Thumb Extensor Tendon Zones T2, T3, T4

• Week 1-3

  • Orthotic - hand based TH spica with CMC in slight palmer abduction, radial extension, IP and MP at 0 degrees

  • Edema management

  • Wound care/ scar management

• Week 3

  • Begin 25-30 degrees combined AROM of IP/MP jt flexion

  • AROM opposition to IF

  • Orthotic use between exercise sessions

  • Scar management

• Week 4

  • Advance patient to 45-50 degrees of combined AROM of IP/MP jt flexion - advance pt by 20 degrees

  • AROM opposition to LF

  • Orthotic use between exercise sessions

  • Scar management

• Week 5

  • Advance patient to 65-70 degrees of combined AROM of IP/MP jt flexion - advance pt by 20 degrees

  • AROM opposition to RF

  • Orthotic use between exercise sessions

  • Scar management

• Week 6

  • D/C orthosis

  • Advance patient to full flexion of IP/MP jts.

  • AROM opposition to SF and base of SF

  • Begin strengthening

Thumb Extensor Tendon Zone TV

• Extensor retinaculum complicates this

• Weeks 1-3

  • Fab volar resting pan for TH and wrist - MCP in neutral, no hyperexptension, with wrist in slight extension

  • Begin ROM

    • With the wrist, CMC, and MCP joints in extension, actively flex IP to 60 degrees and passively extend IP

    • With wrist in 20 degrees of flexion, CMC and MCP in neutral, perform place and holds IP extension

• Week 3

  • Begin 25-30 degrees AROM of combined IP/MP joint flexion; monitor for ext lag

  • AROM opposition to IF

  • Orthotic use between exercise sessions

  • Scar management

• Week 4

  • Advance patient to 45-50 degrees of combined AROM of IP/MP jt flexion - advance pt by 20 degrees

  • AROM opposition to LF

  • Orthotic use between exercise sessions

  • Scar management

• Week 5

  • Advance patient to 65-70 degrees of combined AROM of IP/MP jt flexion - advance pt by 20 degrees

  • AROM opposition to RF

  • Orthotic use between exercise sessions

  • Scar management

• Week 6

  • D/C orthosis

  • Advance patient to full flexion of IP/MP jts.

  • AROM opposition to SF and base of SF

  • Begin strengthening

4 types of Mallet Injuries

1. Sift Tissue Mallet - Type 1

   1. Resulting for jam injury. Ex. Playing basketball and accidentally hitting DIP within flexed position resulting in stretching or tearing of the tendon

2. Tendon Laceration - Type 2

   1. Sharp simple wound for closure; oftentimes conservative management

3. Abrasive Mallet - Type 3

   1. Mountain bike abrasion injury; gravel or dirt can complicate things; wound care; watch for infection

4. Bony Mallet-Avulsive - Type 4

Test for Boutonniere Deformity

• Elson’s Test: assesses for central slip and lateral band fx

  • If torn, DIP is rigid in extension (+)

  • If intact, DIP is floppy (-)

• Pseudo boutonnière: flexion of the PIP but the DIP typically not involved; more likely resulting from volar plate injury.

What digit is the most common digit to have an extensor tendon injury?

Third digit; its centralized and most prominent

What percentage of the tendon needs to be lacerated for the surgeon to do a repair?

greater than 50%; if less than 50%, tendon will be able to heal as vascularity of extensor tendons is rich

Extensor tendon weakness compared to flexor tendons

3-4x/weaker

Zone 5

occurs from fight bite injury; A "fight bite" injury, also known as a clenched fist injury, occurs when a person's clenched fist strikes another person's mouth, causing a wound on the hand from the teeth.

The lumbricals originate off of the flexor digitorum profundus and attach where? And at what zone?

Extensor mechanism; zone 5 starting point into zone 3

Between what days are extensor tendons more likely to re-rupture?

7-10 days

Flexor Tendon Repair Types, Strand numbers, and suture materials

• Repairs

  • locking - better outcomes

  • Grasping

• # of Strands

  • 2-8

  • 2 = weak and does not withstand early active motion

  • 4 = Gold standard; early active

  • 6 = bulky-ish; early active

  • 8 = strong, but bulky; scarring and trigger finger

• Suture materials

  • Nylon

  • Epitendinous sutures - prevemts tendon from getting caught on pulley

  • Fiberwire = highest tensile strength

Flexor Tendon Repair Complications

• PIP flexion contracture

• Trigger finger: tendons cannot glide through pulley

• Swan Neck: muscle imbalance

• Quadriga effect: over advancement of FDP during surgical procedure, resulting in flexion lag of adjacent digits due to shortened common muscle belly

• Lumbrical plus finger: rupture of FDP distal to FDS insertion

Kleinert Flexor Tendon Protocol

• Orthotic:

  • Dorsa blocking orthotic with wrist at 45 degrees and MCPs at 40 deg flex; rubberband on affected digits for passive flexion assist

  • Modifications:

    • Palmer pulley on strap for DIP flex

    • Palmer pan at night for retraining D2-D5

    • All fingers banded for protection

• Weeks 0-3 Controlled PROM

  • Hourly active extension against rubberband 10x

  • Palmer pan worn nocturnally; holding fingers against dorsal block

  • One handed ADLs and dressing techniques

• Weeks 3-4

  • Adjust wrist to neutral orthosis

  • Hourly PROM tendon gliding

• Weeks 4-6

  • Gentle active flexion without rubberband, every other hour; gentle active tendon glides

• Week 6

  • D/c dorsal blocking orthosis

  • Static progressive as needed

  • Differential tendon glide

• Weeks 6-8

  • Add light resistance

• Modifications

  • Active extension exercises hourly without the rubberband 10-15X at 3 weeks +

  • Rubberband applied to all digits, not just affected one

  • Use of nightime volar pan to hold D2-D5 to DBS for protection

Indiana Flexor Tendon Protocol

• Orthoses

  • DBS - FA length, wrist neutral and MCPS at 50 degrees flexion; new protocol calls for slight wrist ext

  • Synergistic Exercise Orthosis: Hinged wrist at 30 degrees extension block at wrist, MCPs at 60 degrees, IPs free with dorsal block in full extension

• Weeks 0-4 Full time DBS use

  • Hourly HEP and tenodesis orthosis

    • 15 reps of passive flex/ext to PIP jt

    • 15 reps of passive flex/ext to DIP jt.

    • 15 reps of passive composite flex/ext

  • Synergistic exercise orthosis 25x with place and hold in wrist extension with composite finger flexion

• Week 4

  • D/c synergistic orthosis

  • Continue DBS

  • Synergistic or tenodesis to wrist every two hours

  • Light active finger flexion and extension

• Week 5

  • Add FDP glide (hook fist) and FDS glide (straight fist)

• Week 6

  • D/c DBS

  • Joint blocking ***do not use on SF FDP***

• Week 8

  • Add in passive ext

  • Add in light resistance

• Week 14

  • return to normal tasks and activity level as tolerated

Modified Duran Protocol

• Orthotic: DBS with wrist at 20 degrees flexion and MCPs at 40-50 deg flexion; palmar pan for nocturnal use; fingers strapped into DBS at night and between exercises

• Weeks 0-3 Controlled PROM

  • Palmer pan for nocturnal use

  • Differential passive tendon gliding

    • PIP PROM with DIP in flexion

    • DIP PROM with PIP in flexion

• Week 4:

  • Synergistic wrist tenodesis begun in clinic only

• Week 5:

  • Gentle active joint blocking AROM

  • FDS glides

  • Full fist

  • One handed training techniques in dressing

• Week 6:

  • D/C DBS

  • Dynamic or static progressive splinting as needed

• Weeks 7-8

  • light resistance training

  • return to work training and work hardening

Original duran use rubberband 4x/day weeks 0-4; tenodesis motion 4+ weeks with rubberband traction for passive flex, active ext; week 5 differential tendon gliding; 6+ weeks light active strengthening

St. John’s Flexor Tendon Protocol

• Orthoses

  • Casting days 1-5

  • Day 2 - Week 2: FA based DBS

  • Weeks 2-6: Hand Based DBS

  • Week 6: D/C

• Day 4 - 2 Weeks Controlled AROM (move it, don’t use it)

  • PROM flexion full fist

  • AROM composite flexion to 1/3rd fist

  • Active extension of IPs and MCPs within confines of orthotic

• Weeks 2-4

  • Modify FA DBS to hand based Manchester Orthotic

  • Begin tenodesis within hand based orthotic

  • Progress active flexion to ½ to 2/3rd fist

  • 45 degrees active wrist extension

  • work toward full fist by week 6

• Weeks 4-8

  • D/C hand based orthosis and start light strengthening at week 6

  • Static progressive or yoke as needed

  • work hardening and prepare for return to work

  • Return to full duty work at week 8

Gail Groth Pyramid of Progressive Forces

• Specifically for Zone 2, but applies to a lot of other zones

• Order of pyramid progression:

  • Protected passive ext

  • place and holds

  • active composite fist

  • hook fist and straight fist

  • isolated joint motion

  • D/C splint

  • resistive composite fist

  • resisted hook and straight fist

  • resisted isolated joint motion

• Formula:

  • Current weeks active DIP flexion - Previous weeks active DIP flexion divided by previous week active DIP flexion X 100 = % of change

  • If less than 5 degree discrepancy between active and passive

    • If a discrepancy is noted, you want to start measuring with Groth formula

  • If less than 10% of change, patient needs to be advanced up pyramid

  • If change is 10% or greater, level of care being provided is appropriate

Strickland Total Active Motion (TAM)

• PIP Flexion AROM + DIP Flexion AROM= ___________ - any ext lags at IPs divided by 175 X 100 = percentage of progress

  • Excellent = 85-100%

  • Good = 70-84%

  • Fair = 50-69%

  • Poor = <50%

Flexor tendon work of flexion

Keep intervention under 30 neutons of force within the 6 week mark

Ideal time to start therapy after flexor tendon repair:

p/o days 3-5

When is a 4 strand repair the weakest?

Week 1

Ideal time to start strengthening with no increase in risk of rupture

8 week ideally then d/c if not scarred down

Complete Passive Protocol

• Weeks 0-3 or 4

  • DBS

  • Therapy (if allowed):

    • PROM flex of digits

    • wound care

  Weeks 3-6

  • Orthotic modified to wrist in neutral position

  • Take orthotic off hourly:

    • PROM digit flex/ext

    • tendon glides

    • wrist tenodesis

• Weeks 5-6

  • D/c orthosis

  • static progressive if needed

  • digit blocking

  • gentle resistance

Manchester Splint Pros

• Significantly less flexion contractures

• Improvement in DIP joint flexion as it prevents adherence of FDP

Gapping Complication

• Can happen with place and holds when tendon gets stuck on A4 pulley and then gaps without fully rupturing

  • results in rupture or weak finger

• Gapping above 3mm incompatible with good results

• Lalonde recommends place and holds in short arc

Quadriga Effect

tightening or scarring of FDP resulting in flexion lag of adjacent digits due to tight FDP ***Jesus****

Lumbrical Plus Finger

Occurs from a lax FDP which results in tension to the lumbrical as lumbrical insert and attach to FDP - finger would extend instead of straighten

middle finger most often affected

Cannot be addressed in therapy- must be addressed in surgery; often a result of a long tendon graft

Which flexor tendon is likely to rupture?

FDP; stuck in scar in A1 pulley

Which tendon shares a common muscle belly for LF, RF and SF?

FDP - requires splinting of all fingers as opposed to just one

How much can the A2 pulley be vented for effective tendon gliding?

30%

A patient cut his FDS/FDP over 2 years ago and is unable to flex his PIP and DIP. What surgery would he typically undergo to regain motion of the PIP and DIP jt?

Hunter rod and then grafting

Vincula

promote blood supply in flexor tendons

Made of folds of mesotendon - connective tissue sheath attaching tendon to its fibrous sheath

Vincular system exits on the dorsal surface of the tendon

Flexor Tendon Repair Tensile Strength

• Day 1 p/o

  • greater tensile strength days 3-5

• Days 3-5 p/o

  • least tensile strength following repair secondary to softening tendon ends

• Days 5-21 p/o

  • tensile strength increases slowly as collagen matures and cross linking continues

transverse retinacular ligament and lateral band migration

• prevents dorsal migration of the lateral bands

• originates from the volar capsule of the PIP joint and inserts on the volar border of the conjoined lateral bands at the middle phalanx

Triangular ligament and lateral band migration

• prevents volar migration of lateral bands.