Study the Anatomical Variations of the Posterior Interosseous Artery and Its Clinical Applications

INTRODUCTION: Management of soft tissue defects of the hand is one of the most challenging issues in hand surgery. Defects may be sequelae of trauma, burns, congenital anamolies , tumour resection or infection. Their treatment may require not only surgical techniques such as simple skin grafting or local transposition flaps but also microsurgical procedures. The armamentarium for the treating hand surgeon consists of local techniques at the hand and forearm and free microsurgical techniques or distant flaps from other regions of the body1. In the past few years, new flaps have been explored with a more careful evaluation of donor sites; also, newly developed techniques such as the perforator flap and the propeller flap have come into the focus of interest. New flap techniques have to prove their advantages over established techniques with their well-known possibilities and risks before becoming routine procedures. The advantages and disadvantages of each technique regarding difficulty of harvest, reliability of anatomy, donorsite defect and other issues have to be carefully weighed one against the other when choosing the best technique suitable for each patient. AIMS AND OBJECTIVES: 1. To study the anatomical variations of the posterior interosseous artery and its clinical applications and to examine the posterior interosseous artery in the light of the ANGIOSOME concept while defining the cutaneous territory of this artery, muscle and bone blood supply. 2. To define the technical aspects of safe raising of the Posterior Interosseous Artery Flap and to define the safe technique of recruitment of larger tissue in the flap. 3. To obviate the necessity of test dissection prior to raising the flap. 4. To define the necessity and modified technique of Buchler and Frey procedure. MATERIALS AND METHODS: Patient Selection Criteria: 1. 20 in number. 2. Patients with defects of dorsum of hand, forearm, volar aspect of forearm and dorsum of proximal phalanges and first web space. 3. No exclusion criteria. 4. All these patients were primarily planned for a Posterior Interosseous Artery flap if Doppler examination confirmed the presence of perforators. 5. The pre-operative Doppler was done by 8MHz hand held Doppler. Number of Cadaveric Dissections: 10 in number of which 2 dissections were done in freshly amputated limbs. Method of Study: The study was conducted by performing dissection on dorsum of forearm and noting the course of Posterior Interosseous Artery, its perforators and the distal anastomosis. The same was done while raising the flap in the clinical cases. In all the dissections the flap was raised proximo-distally, based on the distal communication between posterior and anterior interosseous artery. OBSERVATIONS AND RESULTS: 1. The axis of the flap was planned on a line joining the lateral epicondyle and ulnar styloid process. 2. In the clinical study there were 13 male and 7 female patients. 3. The soft tissue defect in these patients were as a result of a) Post chemotherapy infusion necrosis: four in number (both Adriamycin based regimens), b) Post traumatic sequelae: ten in number, c) Post burns sequelae: three in number (electric burn injury), d) Post Infective sequelae: two in number, e) Post surgical defect: one in number. 4. The average age of these patients was 32.4 years. 5. Observations during Clinical Case Dissection: a) Average site of entry of PIA in the posterior compartment (no. of cm from ulna): 15.3 cm b) Percentage of site of origin of Interosseous Recurrent Artery at the level of oblique cord/interosseous membrane: 60% Percentage of site of origin of Interosseous Recurrent Artery at the level of Abductor Pollicis longus/ Supinator: 40% c) Percentage of dissections in which IRA is present deep to Anconeus: 75% Percentage of dissections in which IRA is deep to Anconeus & Supinator: 25% d) Percentage of dissections with one perforator from the IRA: 35% Percentage of dissections with two perforators from the IRA: 60% Percentage of dissections with three perforators from the IRA: 05% e) Average size of the PIA in the posterior compartment: 1.94 mm f) Percentage of dissections showing modified Buchler and Frey’s Phenomena: 30% g) Percentage of dissections in which septocutaneous perforators lie between EDC and EDM: 10% Percentage of dissections in which septocutaneous perforators lie between ECU and EDM: 90% h) Average number of perforators from the PIA: 3.6 i) Average distance of the first perforator from the ulnar styloid process: 9.5 cm j) Average size of PIA at termination : 0.9mm k) Average site of anastomosis between PIA and AIA from ulnar styloid process: 3.0 cm l) Pedicle management in the clinical cases: Tunneling: 7, Exteriorizing the pedicle and grafting: 8, Skin bridge opened to transfer the flap from pivot point to defect: 5, m) Largest flap dimensions : 13 by 8 cm, n) Smallest flap dimensions : 5 by 3.5 cm, o) Complications: Total flap necrosis: NIL, Rim necrosis: ONE (did not need secondary procedure), Donor site graft loss: ONE, Graft loss over pedicle: ONE, Venous congestion: NIL, Extensor paresis: NIL, Necessity of secondary surgery: ONE (grafting of donor and pedicle area), p) All patients had full range of motion following maximum of three weeks after surgery. CONCLUSIONS: 1) The fundamental basis of the Posterior Interosseous artery flap adheres to the ANGIOSOMAL concept 2) Test dissection is not required. Pre operative Doppler sufficient to establish anastomosis between AIA and PIA and the reverse flow. The anastomosis between the Anterior Interosseous and Posterior Interosseous Artery is consistently present in all our dissections and reverse flow was seen by pulsation of the artery after division. 3) The flap can be safely raised and larger tissue can be recruited by proximally including the Anconeus muscle, proximal perforators from the Interosseous Recurrent Artery and by ‘Y’ ligation of the artery beneath the origin and subsequently by sub-epimyseal dissection upto the distal end of the PIA where it anastomoses with the AIA. Raising the flap in a tear-drop configuration helps to relieve tension over the pedicle. 4) The axis of the flap is planned along a line joining the lateral epicondyle and the ulnar styloid process and not the distal radio-ulnar joint as described by previous authors. 5) The flap has good color, texture and thickness match with potential for neurotisation. There is sparing of the axial vessels, and morbidity of donor area is negligible. The weakness of ulnar extension due to ECU paresis was found to be negligible. 6) The Buchler and Frey phenomena was noted and in 35% of our cases the branch of PIN was divided and re-anastomosed