Posterior interosseous artery flap

PIA flap,,,everything to know about it.

1. POSTERIOR INTEROSSEOUS ARTERY FLAP. B.PUNITHAVASANTHAN, HAND AND MICRO SURGERY FELLOW, SKIMS-SOURA.

2. COURSE OF THE POSTERIOR INTEROSSEOUS ARTERY - It originates from the Common Interosseous Artery or the Ulnar Artery (18 %) -Passes between the oblique cord and interosseous membrane - Emerges in the deep extensor compartment of the forearm underneath the supinator at an average distance of 7.9cm (range: 7.4-9.8 cm) from the lateral epicondyle and 14.5 cm (range: 12.1-17 cm) from the ulnar styloid .

3. At this point the interossoeous recurrent artery emerges and runs proximally deep to the Anconeous giving off fasciocutaneous and Musculocutaneous perforators At deep posterior forearm PIA diameter ranges from 1.5-2.5 mm accompanied by at least two venae comitans running in the septum between Extensor Carpi Ulnaris and Extensor Digiti Minimi giving off fasciocutaneous perforators throughout its length. It also gives a nutrient artery to the ulna around 12-15 cm proximal to ulnar styloid . In the lower third of the posterior forearm, direct septo-periosteal branches to the ulna are present .

4. Proximal pedicle dissection shows the septum between the EDQ and ECU and containing the PIA; the arrow shows the Proximal perforator.

5. Along its course ,the PIA gives 7-10 cutaneous branch on average. Largest is the proximal cutaneous branch,and the medial cutaneous branch (1-2 cm distal to midforearm ) are the most consistent branches.

6. At distal forearm,PIA anastamose with AIA (2-3 cm proximal to DRUJ),the dorsal carpel arch,And a vascular plexus surrounding the ulnar head.

7. The Posterior Interosseous Nerve runs along with the posterior interosseous artery. This relation to the important cutaneous perforator and the PIA itself is important in the dissection of the flap to avoid denervation of the ECU ( Buchler and Frey Phenomena). ECU branch passes through the septum proximal or distal to the most proximal perforator from the PIA .

8. RELATION OF BRANCH OF PIN TO ECU AND MOST PREDOMINANT CUTANEOUS PERFORATOR OF PIA

9. In proximal forearm..PIA artery B/w APL and EDM or ECU. In MID forearm.. PIA is below the forearm fascia In a Intermuscular septum b/w EDM( Radially ) And ECU ( ulnarly ).

10. Posterior Interosseous Artery Flap A septocutaneous flap based on the PIA was originally described by Zancolli and Angrigiani in 1985 Penteado had described it in 1986. Costa et al added the ulna segment and described the osteocutaneous PIA flap in 1988.

11. Indications. defects of first web space proximal dorsum of hand proximal palm of hand. defects of dorsum forearm, volar aspect of forearm dorsum of proximal phalanges. Contraindication. Prior trauma to the dorsum of the wrist or forearm, which may have injured the PIA. absence of vascular connection between the AIA and PIA, although this is rare

12. Marking of the flap Elbow is flexed at 90° with wrist fully pronated . A straight line is drawn from the lateral epicondyle to distal radioulnar joint. This acts as the vascular axis of the flap. The distance from the pivot point to the near edge of the defect is measured a marking of the same length is made over the proximal vascular axis on the flap. About 2.5 cm proximal to distal radioulnar joint on this axis, a perforator is heard with audio Doppler and marked. This represents the anastomosis between AIA and PIA and is also the pivot point of the flap

13. Mark the ulnar border of the flap over subcutaneous part of ulna,,this facilitates easy identification of ECU

14. Anatomic variations of PIA. (beware??) In mid forearm.In 8% a noticable reduction of calibre upto vanishing of PIA is noted,in these patients PIA anastamose with AIA through A perforating branch. In 5 % ,PIA simply ends in one small final branch without any distal anastamosis . There may be absence of Interosseous Recurrent Artery or hypoplasia or there may be no cutaneous perforators arising from it. The relation of the branch of the PIN to the ECU to the most proximal and clinically most important perforator of the PIA is variable and this is important for reliability of the flap as well as to avoid extensor paresis in the post-operative period. septocutaneous perforators lie between EDC and EDM: in 10%

15. Maximum flap length :two third of line connecting Lat epicondyle and DRUJ. Maximum flap width :lateral edges of radius and ulna. Primary closure possible if defect is 3-4 cm. For sensate flap include posterior cutaneous nerve of forearm in the flap.

16. Reverse (retrograde) PIA flap (Hand) The incision is started distally, with inclusion of the widest possible fascial base to maximize skin perfusion, Dissect underneath the deep fascia towards the axis until the fasciocutaneous septum between the ECU and the EDQ was identified The septum is harvested as a unit, the artery was not dissected out from it.

17. The septum was exposed from the radial and ulnar sides, alternating as needed. proximal to proximal perforator PIA is ligated and cut to elevate the distally based flap. During pedicle dissection, careful attention to preserve cutaneous perforating arteries; The pedicle was dissected distally to the level of the DRUJ, where the PIA anastomose with the AIA

18. Direct ( anterograde ) PIA flap (Elbow) The point of rotation is proximal at the origin of the PIA from the interosseous trunk. The skin paddle was positioned distally in the forearm so that it can be rotated to cover the elbow. In contrast to the retrograde technique, the flap was designed around the more distal cutaneous perforators including at least 3-4 cutaneous perforators in the pedicle.

19. Because of reliable anatomy of the distal perforators of the PIA the antegrade PIA flap is a viable option that allows to cover small-medium size elbow defects without requiring a microsurgical anastomosis or sacrifice a major forearm artery and may increase the armamentarium for soft-tissue coverage of the elbow

20. Extended Posterior Interosseous Artery Flap a distal variant (type 2) of the PIA flap, which changes the pivot point of the classic variant (type 1) and which can provide full coverage of single or multiple digits in the entire dorsum and palmar surface of the fingers. Zaidenberg et al J Hand Surg Am. Vol. 42, March 2017 after analysing 26 cadaveric specimens and clinical study in 19 patients with soft tissue defects distal to the proximal interphalangeal joint of the fingers they found PIA was identified reaching the dorsal carpal arch in all With the use of this new flap, there was a mean length gain of 8.5 cm . The mean arterial diameter in the segment studied was 0.8mm (range 0.6-1.2 mm).

21. -Gains a mean length of 8 cm extra , -Can cover upto DIP

22. Osteocutaneous PIA flap. Both EPL and EIP have sufficient attachment to sustain a length of ULNA via periosteal supply, The EPL is attached more proximally and more suitable for use in a distally based flap, Harvest only one third of width of ulna with a maximum length of 10 cm in adult

23. Keep the wrist hyperextended for first 2 weeks. Attempted usually for thumb reconstruction For giving a thumb post (so EPL use will not create any disability). Avoid tunneling and kinking of pedicle.

24. Complications Early postoperative complications Flap venous congestion Partial flap necrosis Complete flap necrosis Hematoma Wound infection Delayed graft take Graft rejection ECU weakness Late complication Hypertrophic scar Hyperkeratosis AVOID harvesting of tissue distal to the territory irrigated by the proximal perforator. AVOID excessive tension placed transversely across the flap during closure, kinking or twisting of the pedicle, or by iatrogenic injury to the pedicle AVOID the use of subcutaneous tunnels

25. Which flap is best for hand defects?? The distally based radial artery forearm flap is considered the workhorse for covering large hand defects. But this flap should not be used in badly mutilated hands where the additional loss of the radial artery could compromise hand viability , The ulnar artery based flap is based on the major arterial supply to the hand and sacrificing the ulnar artery is the major disadvantage of this flap The dorso ulnar flap , based on the ascending branch of the dorso ulnar artery is a distally based flap but has a short pedicle with limited rotation. Only defects on the ulnar -dorsal side of the hand and proximal palm can be reached The anterior interosseous flap with its skin paddle on the dorso radial side can provide skin, tendon, muscle and bone of distal radius but dissection is demanding involving fragile and anatomically variable vessels

26. Why PIA flap is a better option?? sacrifice of this vessel is not detrimental to hand vascularity . even with damage of radial or ulnar arteries or palmar arches this flap can still be used due to retrograde flow of this flap by the anastomosis between the posterior and anterior interosseous arteries can also be raised as an osteofasciocutaneous unit, including a vascularised bone segment from the ulna for thumb reconstruction. The flap can be based proximally to repair defects in the elbow region with direct flow through the posterior interosseous artery it does not interfere with the lymphatic drainage of the hand as seen in other forearm flaps (Radial or ulnar ) which are based volarly the requirement for intact distal ulnar –radial arterial communication to raise a distally based radial forearm flap no longer applies

27. How to improve the reliability of PIA flap?? INCLUDE The intermuscular septum and the deep fascia in the flap to augment circulation with the blood supply provided by septocutaneous perforators and suprafascial plexus. Without passing the pedicle under a subcutaneous tunnel, a skin extension over the fasciovascular pedicle canbe used as a roof of the tunnel to prevent edema and congestion. larger tissue can be recruited by proximally including the Anconeus muscle, proximal perforators from the Interosseous Recurrent Artery Look for Buchler and Frey phenomena ,if seen, the branch of PIN was divided and re- anastomosed .

28. About 2.5 cm proximal to distal radioulnar joint on this axis, a perforator is heard with audio Doppler and marked. This represents the anastomosis between AIA and PIA and is also the pivot point of the flap. At least two cutaneous perforators should be identified and included in the flap. More fascia should always be included near the pivot point and if the flap is to be of a significant size

29. Look for ECU PIN branch crossing most proximal perforator from the PIA the PIA gives 7-10 cutaneous branch on average Confrom PIA anastamosis with AIA prior to surgery. Include At least two cutaneous perforators in the flap. Avoid tunneling of pedicle. Osteocutaneous PIA flap For thumb reconstruction Beware of anatomic variations of PIA