Extensor Tendon Injuries James Ledgard Royal North Shore Hospital and Lismore Registrar Teaching 11th April 2017

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Outline Anatomy Zones of injury Recognition and Treatment Rehabilitation Complications

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Extensor Compartments

Innervation Q

Innervation

Innervation

Typical Arrangement Q The typical arrangement of finger extensor tendons is as follows: (1) single EIP inserting ulnar to the EDC tendon of the index finger; (2) single tendon from the EDC to the index and middle fingers; (3) double tendon from the EDC to the ring finger; (4) absent EDC to small finger, but usually a substantial junctura tendinum from the ring EDC to EDM; and (5) double EDM tendon to the little finger with a double insertion into the MP joint hood (see Figure 6.2).127

Extensor Apparatus

PLEASE WRITE IT IN YOUR OPERATION REPORTS Zones of Injury DIFFERENCES Anatomy Repair Excursion Rehab Complications PLEASE WRITE IT IN YOUR OPERATION REPORTS Boyes10 suggested that the amplitude of tendon excursion for the wrist extensors is 3.3 cm, and the amplitude of tendon excursion for the finger extensors and EPL is 5 cm; however, most of this excursion occurs over the forearm, wrist, and dorsal hand. The amplitude of tendon excursion over the dorsum of the finger is extremely small; this explains why small tendon gaps, overtightening of tendon repairs, or small amounts of bony shortening or angulation can lead to dra- matic extensor lags or restriction of flexion at the PIP and DIP joints. Vahey and associates125 found an experimental 12-degree PIP joint extensor lag was produced with every 1 mm of tendon lengthening over the proximal phalanx. Schweitzer and Rayan104 showed that 1 mm of terminal tendon lengthening resulted in a 25-degree DIP joint exten- sor lag, and that 1 mm of terminal tendon shortening severely restricted DIP joint flexion. Over the dorsum of the hand, it has been shown experimentally that relative lengthening of the extensor tendon by 2 mm produces an extensor lag of approximately 7 degrees at the MP joint. Because most MP joints had a “reserve” of hyperextension ability of about 35 degrees, however, 5 to 6 mm of relative extensor tendon lengthening in this zone may not produce a clinically relevant lack of extension.118

Zone 1 - Mallet Acute or Chronic Soft Tissue or Bony Closed or Open

Mallet Splint 8 weeks then wean Soft Tissue Mallet Unlikey to sustain a closed mallet injury if your PIPJ is flexed. Mallet Splint 8 weeks then wean

Bony Mallet X-Ray CONSIDER Fragment size Volar subluxation Only indication for surgery

Zone 3 – Central Slip Acute or Chronic Soft Tissue or Bony Closed or Open

Closed Central Slip SUSPECT IN Blunt PIPJ trauma Volar Dislocation

Diagnosis Suspicion Tenodesis Weak extension Elson test Q X-Ray Follow-up Splint in extension 6 weeks then wean/dynamic another 6 weeks

Elson Test

Zone 4 and 5 Partial Flat vs Round Avoid bunching Complex injury Rehab controversial Assess tension intra-operatively

Zone 6 Round Juncturae Tendinae Corset Technique Stiffer Quicker Less shortening In 1997, Howard and colleagues45 compared the MGH, modified Bunnell, and modified Krackow-Thomas repairs in cadaveric zone 6 extensor tendon lacerations, and found the MGH technique to be superior. In a 2005 study of zone 4 extensor tendon repairs with 4-0 nonabsorbable, braided polyester (Ticron) suture, Woo and coworkers133 found the modified Becker technique to be the strongest repair, with a significantly greater resistance to 1- and 2-mm gap and the greatest ultimate strength. Lee62 com- pared the augmented Becker, the modified Bunnell, and a new, running interlocking horizontal mattress technique and found the newer technique to be stiffer, to produce less shortening, and to be more rapid than the other techniques, without a significant difference in the ultimate load to failure. This newer technique, termed the corset suture, does not require the placement of core sutures (Figure 6.10). Lee SK, Dubey A, Kim BH, et al: A biomechanical study of extensor tendon repair methods: introduction to the running-interlocking horizontal mattress extensor tendon repair, J Hand Surg [Am] 35:19- 23, 2010.

Zone 7 Care with releasing compartments 4 and 6

Rehabilitation – Open Repairs Zone 1 – 2 Mallet splint 6 - 8 weeks Zone 3 Extension splint 6 weeks Zone 4 – 5 30/30/0/0 splint 4 weeks Zone 6 – 8 30/30 splint 4 weeks

Outcomes with Static Splinting 64% good or excellent Simple injury 45% Complex injury Flexion loss greater Extension loss Zones 1 - 4 worse Zones 5 - 8 Miller’s Outcome Classification System 1942 In 1990, Newport79 reported on the long-term results of extensor tendon repair treated with static splinting. Of patients without associated injury, 64% achieved good or excellent results, whereas only 45% of patients with associated injuries achieved good or excellent results. More fingers lost the ability to flex fully than lost the ability to extend. Injuries in zones 1 through 4 had a worse outcome than injuries in the more proximal zones. Newport ML, Blair WF, Steyers CM Jr: Long-term results of extensor tendon repair, J Hand Surg [Am] 15:961-966, 1990.

Rehabilitation – Open Repairs ALTERATIONS Partial injury Good repair Good therapist Motivated patient Complex injury CONSIDER Passive protocol Dynamic splint + Controlled flexion Active protocol Controlled flexion

Complications Extension Lag Poor Flexion Swan Neck Boutonniere

Swan Neck Deformity

Boutonniere Deformity Q What causes a Boutonniere deformity?

Boutonniere Deformity Q

Summary Anatomy is key Zone of injury is important so record it Repair Rehab Complications Prevention of complications through good management is better than cure

Foundation Skills for Surgical Educators https://respond.cc The session key is: 705558

Q 1. Why can this man with a nerve injury extend his wrist?

Q 1. Why can this man with a nerve injury extend his wrist? ECRB is innervated by the radial nerve. The radial nerve is spared. He has a partial radial nerve injury.

Q 1. Why can this man with a nerve injury extend his wrist? ECRB is innervated by the radial nerve. The radial nerve is spared. ✔ He has a partial radial nerve injury.

Q 2. Why are you able to extend your IF and LF independently? The typical arrangement of finger extensor tendons is as follows: (1) single EIP inserting ulnar to the EDC tendon of the index finger; (2) single tendon from the EDC to the index and middle fingers; (3) double tendon from the EDC to the ring finger; (4) absent EDC to small finger, but usually a substantial junctura tendinum from the ring EDC to EDM; and (5) double EDM tendon to the little finger with a double insertion into the MP joint hood (see Figure 6.2).127

Q 2. Why are you able to extend your IF and LF independently? They are innervated by a different nerve. Each has an independent musculotendinous unit. There is a separate tendon from EDC to both. The typical arrangement of finger extensor tendons is as follows: (1) single EIP inserting ulnar to the EDC tendon of the index finger; (2) single tendon from the EDC to the index and middle fingers; (3) double tendon from the EDC to the ring finger; (4) absent EDC to small finger, but usually a substantial junctura tendinum from the ring EDC to EDM; and (5) double EDM tendon to the little finger with a double insertion into the MP joint hood (see Figure 6.2).127

Q 2. Why are you able to extend your IF and LF independently? They are innervated by a different nerve. Each has an independent musculotendinous unit. ✔ There is a separate tendon from EDC to both. The typical arrangement of finger extensor tendons is as follows: (1) single EIP inserting ulnar to the EDC tendon of the index finger; (2) single tendon from the EDC to the index and middle fingers; (3) double tendon from the EDC to the ring finger; (4) absent EDC to small finger, but usually a substantial junctura tendinum from the ring EDC to EDM; and (5) double EDM tendon to the little finger with a double insertion into the MP joint hood (see Figure 6.2).127

Q 3. Why is the DIPJ not floppy when the Elson Test is positive?

Q 3. Why is the DIPJ not floppy when the Elson Test is positive? Because the injured central slip extends the DIPJ. Because the lateral bands tighten with flexion of the finger. Because the injured central slip puts proximal tension on the lateral bands.

Q 3. Why is the DIPJ not floppy when the Elson Test is positive? Because the injured central slip extends the DIPJ. Because the lateral bands tighten with flexion of the finger. Because the injured central slip puts proximal tension on the lateral bands. ✔

Q 4. What is the cause of a Boutonniere Deformity?

Q 4. What is the cause of a Boutonniere Deformity? Central slip failure. There are multiple causes for a Boutonniere Deformity. Lateral bands translate volar to the axis of rotation of the PIPJ.

Q 4. What is the cause of a Boutonniere Deformity? Central slip failure. ✔ There are multiple causes for a Boutonniere Deformity. Lateral bands translate volar to the axis of rotation of the PIPJ.

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