The Reliability of the Reversed Flow Posterior Interosseous Flap for the Coverage of Ulnar Hand Defects: A Series of 25 Cases

Introduction

The reverse posterior interosseous flap was first reported in 1986 by Lu et al [1] and Penteado et al [2].  Although, any upper extremity defect could be solved with either a distant pedicled flap or a free tissue transfer, the regional flaps from the forearm are considered the better options. The merits of a regional flap are single stage elevation, avoidance of hand dependency, early mobilization, and restriction of deformity to ipsilateral extremity [3].

The posterior interosseous artery (PIA) flap provides thin, soft and pliable skin with good colour and texture match. It has traditionally been used to cover defects up to the metacarpophalangeal joint and for reconstruction of the first web space. However, some authors have reported a high incidence of complications, particularly venous congestion with partial or total flap loss [4].

The current study reports our experience with the use of reversed PIA flap for coverage of ulnar aspect defects of the hand in a series of 25 patients. The technical difficulties, outcome, and complications rate are presented.

Materials and Methods

This prospective study was conducted on 25 patients presented to causality department at Ain Shams University Hospitals over a period of 4 years. These patients were complaining of defects over the ulnar aspect of the hand with exposure of bones or tendons necessitating flap coverage. Patients with associated wrist injuries that would preclude the use of this flap were excluded. In addition, patients with systemic diseases as diabetes, ischemic heart disease, atherosclerosis, and vascular diseases were excluded from the study to avoid the possibility of peripheral vascular diseases and their effect on the blood flow to the flap.

Complete history and physical examination were taken at the plastic surgery department. Allen’s test was done preoperatively to detect the dominant artery in case of failure of harvesting the posterior interosseous artery flap; Radial forearm flap was the next option. Preoperative plain X-ray hands (antero-posterior, oblique lateral views) were obtained. Preoperative colour duplex device was performed for assessment of the blood flow in the posterior interosseous artery was done for all patients.

Surgical Anatomy

The course of the posterior interosseous artery was marked following a line drawn between the lateral epicondyle of the humerus to the ulnar styloid process. It arises at a point 4-6 cm distal to the lateral epicondyle, usually as a branch of the common interosseous artery but on occasion directly from the ulnar artery 2. At the level of the proximal third of the forearm, the PIA runs with the posterior interosseous nerve (PIN), and gives off several well-defined septocutaneous perforators to the dorsal aspect of the forearm. The first proximal cutaneous branch is a large skin perforator with a variable origin that courses in the intermuscular septum to supply the subcutaneous tissue overlying the proximal third of the dorsal forearm [5].

In the distal third of the forearm, the PIA gives off several perforators (6- 8) which supply the skin together. Upon approaching the level of the wrist joint, 2 cm proximal to the distal radio-ulnar joint, the PIA anastomose with the dorsal recurrent branch of the anterior interosseous artery (AIA). Normal physiologic blood flow to the distal third of the forearm comes from this distal anastomosis, and not from the proximal PIA. This vascular arcade allows the PIA flap to be used as a reverse pedicled flap when the PIA is divided proximally. The reversed flow posterior interosseous artery flap is drained by the venae comitantes accompanying the feeding artery to the deep venous system with no superficial system drainage [6].

The PIA has a relatively narrow calibre in the middle third where also the anatomical variances are reported to be the most. Problems are encountered while trying to reach the most distant defects of the first web space, distal amputation defects, the radial, palmar areas and distal to PIP joints. More variations are met during dissection proximal to the distal third of the forearm [7].

Operative Technique

All surgical procedures were performed under general anaesthesia and tourniquet and by the same surgical team. Wound debridement including soft tissues and bones was undertaken till a healthy bed was reached for flap inset.

The reversed flow PIA flap was raised either from proximal, middle or distal one thirds of the forearm according to the size of the defect and the distal reach of the flap. Flap elevation started with dissection of the pedicle in the distal forearm (area of anastomosis between the posterior interosseous and the anterior interosseous artery arteries) to exclude any possibility of deficient anastomosis.

Two skin incisions were made on both sides of the marked course of the artery leaving about one cm skin bridge in-between. This skin bridge changed the shape of the island flap into a racquet shaped flap as described in a previous work [8]. The plane of dissection is between the skin and the ante-brachial fascia. Then, the fascia over the tendons of the tendons of the extensor digitorum communis (EDC) and extensor carpi ulnaris (ECU) was incised. The PIA could be observed coursing along the intermuscular septum between the extensor digiti quinti (EDQ) and the ECU. At the pivot point, the anastomosis arc was observed to ensure its existence.

Then, the radial edge of the flap was incised into the EDC. Dissection was continued on ulnar aspect towards the intermuscular septum between the EDQ and ECU. During the dissection, the fascia to the skin paddle is secured with interrupted sutures. Then, the ulnar edge was incised and dissected radially towards the septum, also along the plane between the fascia and the muscle.

The intermuscular septum between the EDQ and ECU is the landmark of dissection, along which the PIA and its venae comitantes course distally. After completing the dissection of the PIN, the intermuscular septum was detached from the ulna. The pedicle of the flap consisted of the PIA, venae comitantes and intermuscular septum between the EDQ and ECU. Finally the origin of the PIA was ligated and completes the harvest of the flap.

Results

This study included 25 patients (23 males and 2 females) with ages ranging from 12- 56 years with a mean of 25 years. The most affected age group was 20-30 years (74%).  Flap harvest time ranged 70- 90 minutes and total operative time ranged from 2-2.5 hours.

The size of the defects ranged from 3×4- 5×7 cm on the ulnar side of the hand with mean of 4.08 + 0.81 x 5.6 + 1 cm with exposed bones or tendons.  The posterior interosseous artery was found with efficient anastomosis and blood flow in all cases.

Regarding flap course and survival; 20 flaps (80%) passed uneventful, 4 flaps (16%) suffered from venous congestion, and one flap (4%) showed ischemia. Three flaps (the ischemic flap and 2 congested flaps) suffered total loss and required coverage using reversed flow radial forearm flap. The other 2 flaps survived without loss, so we had 22 survived flaps (88%) (Figures 1 & 2). All the donor sites needed coverage by split thickness skin grafts. Other recorded complications were wound infection occurred in 3 patients (12%) that resolved by conservative management and hematoma occurred in one case (4%) and required early evacuation; it is of note that the flap survived in all these cases.

Figure 1: (a) A Preoperative Photo of a 26 Male Patient with Post Traumatic Ulnar Side Defect of the rt Hand, (b) Debridement of All Scarred Tissues was Done, (c) the Flap is Harvested and Inset, (d) 2 Weeks Postoperative View Showing Distal Edge Necrosis, (e &f) 2 Moths Postoperative Views