The osteocutaneous radial forearm free flap: A pictorial essay

The osteocutaneous radial forearm free flap (OCRFFF) is a versatile flap with the ability to reconstruct complex defects. We detail the techniques necessary to harvest an OCRFFF, including an outline on making 90‐degree osteotomies to maximize bone harvest. In this pictorial essay, we provide illustrations of the anatomy and surgical techniques necessary for OCRFFF harvest. Detailed discussion is provided on how to protect the perforators to the bone and the approach to making osteotomies in a 90‐degree fashion. The approach for prophylactic plating of the radius to prevent radius fractures is outlined. A case presentation on the real‐life utilization of this flap is included. The OCRFFF is an excellent head and neck reconstructive option. While there are limitations to its use for patients requiring dental rehabilitation or long/anterior mandibular defects, for the right patient and indication it has shown great success in reconstructive efforts.


| INTRODUCTION
The osteocutaneous radial forearm free flap (OCRFFF) has long been utilized as a workhorse flap for reconstruction of soft tissue and bony defects of the head and neck, allowing for harvest of up to 10-12 cm of bone.The concept of the radial forearm free flap was first introduced in the early 1980's and is now one of the most common flaps utilized for head and neck reconstruction. 1,2Beyond its utility for soft tissue reconstruction, the inclusion of bone as an OCRFFF permits for a wider application of this free flap, enabling head and neck surgeons to effectively reconstruct bony defects involving the midface, mandible, and other craniofacial regions.The OCRFFF has broad applications beyond the maxilla and mandible including the reconstruction of composite bone and soft tissue defects in the upper and lower extremities, 3,4 in urologic reconstruction, 5 cranial vault defects, 6 nasal defects, 7 and complex cricotracheal reconstruction. 8hile the surgical approach and critical anatomy is similar for the OCRFFF and fasciocutaneous radial forearm free flaps, there are critical steps that should be taken when for an OCRFFF to ensure a safe and viable flap harvest.This highly utilized free flap at our institution is a common choice given the long, reliable pedicle, relatively low donor site morbidity, and diverse utilization for osseous reconstruction in the head and neck.Our institution collaborates with our orthopedic surgeons to assist with prophylactic plating of the radius bone after the harvest is complete.While management of plating the radius bone varies among institutions, our team has appreciated reduced operative times, lower rates of complications, and high functional outcomes using a multi-specialty approach.In this pictorial essay, we describe the operative techniques associated with harvesting an OCRFFF, while illustrating vital anatomy and techniques for effectively harvesting the radius.While the technique has been previously described in the literature, there is some variation in strategies for performing osteotomies, with our technique detailing our methods for making 90-degree cuts in the bone to maximize the amount of useable bone harvested.Furthermore, our detailed illustrations provide a step-by-step approach enabling for a more in-depth understanding of harvesting an OCRFFF.

| Preoperative assessment
All patients undergoing any variation of a radial forearm flap should have an adequate history taken on their dominant hand and a discussion of any pertinent hobbies or work restrictions that could affect a surgeon's decision to proceed with an OCRFFF.Furthermore, obtaining a thorough history regarding prior surgeries of the forearm including fixation of fractures of the radius and examination for surgical scars.If there is any uncertainty, a plain radiograph of the donor forearm is recommended.
Performing an Allen's test is always necessary to ensure adequate collateral blood flow through the ulnar artery with the presence of a complete palmar arch.Pulse volume plethysmography studies have demonstrated that 57% of patients have radial artery dominance in three or more digits, while 21.5% have ulnar dominance and 21.5% have equal dominance. 9One study evaluating outcomes among patients with abnormal Allen's tests found that 15% of patients had an abnormal objective test, with 88% of those having normal duplex ultrasonography and proceeded with radial artery harvest. 10Among the 11% of patients with abnormal duplex ultrasonography, 60% had normal duplex ultrasonography on the contralateral forearm.Ultimately, the laterality of the donor site does not affect the reconstructive plan, but evaluation of vascular flow in both extremities should be performed with preference given to the non-dominant arm to limit donor site morbidity and quality of life after surgery.A majority of surgeons utilize a subjective Allen's test, assessing color change of the hand, which has comparable sensitivity and specificity to objective Allen's tests. 11Alternatively, utilizing a pulse-oximeter on the thumb while compressing the ulnar artery and waiting for a return of the pulse oximeter waveform after release of the artery is another tactic that can be used to assess for adequate collateral blood flow.A positive test indicates that there is sufficient dual blood supply to the hand and the surgeon is safe to proceed with free flap harvest.Lastly, when the choice for an OCRFF is made, the patient is instructed to defer any pre-operative lab draws and intravenous lines in this arm.

| Flap harvest
The patient is placed in the supine position with the operative upper extremity abducted on an arm board.Palpable landmarks that are critical for free flap planning include the styloid process of the radius and the radial artery (Figure 1).Compared to fasciocutaneous radial forearm free flaps where the incision is typically placed in a transverse skin crease at the wrist proximal to the radial styloid, for OCRFFFs the skin paddle incision should be placed proximal to the radial styloid, approximately 2.5 cm from the styloid process unless there is need for additional soft tissue flap distal to the harvested bone.The skin paddle is centered over the radial artery, and the planned incision should aim to include the cephalic vein.A lazy-S incision is then carried to the antecubital fossa.A tourniquet is placed at the biceps and inflated to 250 mm Hg prior to initiation of dissection.While we prefer the use of a tourniquet for identification of the perforators and efficiency, this is not required for this procedure.
An incision is made along the entire periphery of the skin paddle and carried proximally to the antecubital fossa.Identification and preservation of the cephalic vein is performed first.Skin flaps are raised just deep to the subcutaneous fat along the ulnar and radial aspect of the forearm until the flexor carpi radialis and brachioradialis muscle bellies are identified.The cephalic vein is identified as it courses over the fascia of the brachioradialis.Next, the vein is circumferentially freed from the surrounding subcutaneous tissue.It should be noted that there is some surgeon variation on the inclusion of the cephalic vein, however, our institution aims to include it into the flap harvest whenever possible.
Next, dissection continues along the ulnar aspect of the skin paddle.Using sharp dissection, the surgeon identifies the tendons of the palmaris longus and flexor carpi radialis (Figure 2).Dissection is carried directly onto the flexor carpi radialis tendon separating it from the surrounding forearm fascia, taking care to not violate the paratenon.The soft tissue flap and the pedicle are freed on the ulnar side, taking care to clip the perforators from the pedicle to the muscle.Next, dissection then proceeds along the radial aspect of the skin paddle.Again, using sharp dissection, the tendon of the brachioradialis muscle is identified and skeletonized in a subfascial plane circumferentially.It is essential to ensure that dissection is performed tight along the tendon to avoid any disruption to radial artery perforators to the radius located in the fibrofatty tissue adjacent to the tendon throughout this portion of the dissection.The course of the superficial radial nerve is then fully dissected until it is free of the overlying skin paddle and preserved.The distal cephalic After the flap design is mapped out on the forearm, a skin incision is made around the entire periphery of the outlined flap, ensuring to preserve the cephalic vein.Starting at the ulnar aspect the dissection is continued through the subcutaneous tissue until the tendons of the palmaris longus and flexor carpi radialis tendons are identified, ensuring this dissection is in the subfascial plane but maintaining the paratenon on the tendons.Then the dissection is continued at the radial aspect and both brachioradialis tendons are fully skeletonized sharply, taking great care to preserve the perforators to the bone and the superficial radial nerve.[Color figure can be viewed at wileyonlinelibrary.com] vein is ligated.The tendons of the brachioradialis are then sharply dissected off the radius bone with the tendons being fully skeletonized, leaving no soft tissue on the tendons and dropping the bone perforators onto the radius and keeping the septum intact.Next, the distal aspect of the dissection continues until the distal pedicle, including the radial vein and venae comitantes are located and ligated.The proximal pedicle is fully dissected along the brachioradialis as well, again preserving the radial nerve and keeping the septum between the bone and the soft tissue flap and pedicle completely intact.At the proximal pedicle, careful dissection is completed to identify the deep and superficial venous systems and whether a connection exists.If there is a connection, one can ligate a single superficial vein that can drain the flap, versus ligating separate deep and superficial veins that drain the flap independently.The course of the radial artery is also followed to reveal the take-off of the radial artery from the brachial artery, and more distally one can visualize the bifurcation of the artery from the radial recurrent artery.The radial artery should be ligated distally to the take-off the radial recurrent artery.
At this point, further exposure of the radius bone is performed in preparation for osteotomies (Figure 3).This can be performed on or off tourniquet, however, if tourniquet time is over 70 min, one should consider releasing the tourniquet for this portion of the flap harvest.First, the flexor pollicis longus and flexor digitorum superficialis tendons and muscle bellies are elevated off of the radius, maintaining a small cuff of muscle in order to preserve the periosteum but free the ulnar side of the radius.Depending on the length of bone required for reconstruction, the insertion of the pronator teres can also be released to facilitate more proximal exposure and length of the flap.It should be noted, however, that the bone does decrease is size more proximally and one should ensure there is adequate bone stock for harvest prior to detaching any pronator teres tendon.Next, the pronator quadratus is elevated and divided at 50% of the height of the radius bone, now exposing the bone fully for the ulnar cut.Lastly, the periosteum is incised using a 15 blade scalpel along the radial and ulnar aspect of the bone at 50% of the height of the bone on both sides.These incisions will be the location of the osteotomies.Of note, we find the small, wide orthopedic Hohmann retractors to be helpful in exposing the radius bone for both preparation and eventual osteotomies.Furthermore, pronation or supination of the hand can aid in exposure of the bone during the harvest.
After preparation of the bone, osteotomies can then be performed.Using a sagittal saw, radial and ulnar osteotomies are made perpendicular to the radius at a 90-degree angle, ensuring that osteotomies do not surpass a 50% height of the bone (Figure 4A).We recommend placing a retractor along the dorsal radius so the full diameter of the bone can be fully revealed given that a common error is to overestimate the diameter of the radius.This also protects the flexor muscles and tendons while osteotomies are made.Next, we perform osteotomies in the horizontal plane (Figure 4B).After reconfirming the appropriate depth and bone length, postage stamp monocortical cuts are made along the radial and The pronator quadratus is divided at 50% the height of the radius bone.Next, the flexor pollicis longus and flexor digitorum superficialis tendons are taken off the radius leaving a small cuff of muscle to preserve the underlying periosteum.Depending on the length of bone required for reconstruction, the surgeon can also take down part or all of the pronator teres proximally.Note that more of the pronator teres may need to be taken off the proximal radius for plating purposes after harvest.[Color figure can be viewed at wileyonlinelibrary.com] volar aspects of the bone.At this point, any remaining medullary attachments are freed using an osteotome, releasing the harvest skin paddle and partial radius bone.
After harvest of the radius is complete, any remaining pedicle dissection is completed.Once the surgeon is ready for free flap harvest, the artery and associated vena comitantes and cephalic artery are ligated, and the free flap is passed to the head and neck for flap inset and plating.

| Flap inset
Based on the size of the associated bone defect, the size of the radius can be trimmed to fit the defect as necessary, with osteotomies made to allow for contouring of the bone to fit the associated defect.Bone segments should not be less than 2 cm in length to ensure proper blood supply to the periosteum.Furthermore, perforators can typically be seen and one should be included in each bone segments if possible.If the flap is for the purposes of mandible reconstruction, a reconstruction plate is placed near the inferior border of the mandible and secured using bicortical screws prior to plating the free flap bone which is secured with monocortical screws.In the setting of midface reconstruction, mini-plates are typically used to secure the bone in place.Monocortical cuts are made in the radius, and a plate is secured using selftapping screws on the cut marrow surface of the bone.Once, the bone is plated the surgeon can then proceed with the remaining inset to the soft tissue component of the free flap.

| Prophylactic radius plating
Prior to completing prophylactic plating of the radius, a short 2-3 cm portion of the pronator teres muscle is frequently released to facilitate plate placement across the proximal osteotomy site.Similarly, additional pronator quadratus is released to fully expose the distal radius.The defect is then measured, and an appropriate plate is selected.The plate is positioned along the radial shaft allowing for at minimum two bicortical screws to be placed on both sides of the osteotomy site proximally and distally.Distally the plate is positioned proximal to the watershed line of the distal radius.Two plate options are utilized at our institution and are selected based on the amount of residual distal radius remaining.If limited bone remains distally or the plate seems prominent, a F I G U R E 4 Using a saw (we prefer the sagittal blade), osteotomies are then made to harvest 50% of the radius bone is harvested.(A) First superior and inferior cuts are made perpendicular to the radius bone, delineating the length of the radius bone the surgeon wishes to harvest.(B) Next, the depth of the bone to be harvested is then delineated using the saw.The depth is cut is made in a step wise fashion to ensure monocortical cuts on both the ulnar and radial side along the length of the bone.After these cuts have been made along both the ulnar and radial aspect of the hand, an osteotome can then be gently used to free the harvested bone.[Color figure can be viewed at wileyonlinelibrary.com] low-profile metaphyseal plate is utilized with a horizontal row of locking screws.Otherwise, a standard 3.5 mm small fragment locking plate is used.Ideally, a bicortical, non-locking screw is placed in the hole just distal to the distal osteotomy site.Additional bicortical or monocortical locking screws are placed in the more distal screw holes depending on position of the plate and risk for dorsal penetration.Locking screws are then spaced evenly throughout the distance of the defect with purchase in the dorsal and remaining volar cortex (Figure 5).Authors advocate for placement of bone cement with tobramycin to be placed in the defect to interdigitate with the screws and plate.This provides immediate construct rigidity and augmentation strength of the plate and screw construct.Finally, the distal quadratus pronator, flexor pollicis longus, and pronator teres are closed over the plate to ensure adequate soft tissue coverage over the hardware.The muscle is secured to the brachioradialis tendon ensuring preservation of the radial nerve.

| Closure and postoperative management
A drain is placed, and the proximal incision is closed with absorbable suture.The defect at the site of the skin paddle is closed using either a split thickness skin graft or a full thickness skin graft, the latter of which is harvested from the medial aspect of the medial arm skin.If skin laxity allows, authors advocate for use of full thickness skin graft given excellent cosmetic result and reduced wound complications related to tendon exposure.Either a bolster or wound vac are placed over the skin graft for approximately two weeks, and a splint with 30-degree volar extension is used for approximately 1 week postoperatively.

| DISCUSSION
The OCRFFF is a versatile and reliable flap that can be utilized to reconstruct a variety of bony defects in the head and neck.Here, we describe the operative technique with detailed illustrations that demonstrate the surgical techniques associated with an OCRFFF.Importantly, our method of performing 90-degree cuts perpendicular to the bone make it so the traditional "boat" cut osteotomy is no longer necessary, thus, one can maximize the amount of bone utilized for reconstruction, allowing for 10-12 cm of bone to be harvested for reconstruction (Figure 6).
When evaluating cases that are an excellent use of the OCRFFF, we would like to highlight one case that F I G U R E 5 After the dissection and bone cuts are complete, the OCRFFF is harvested and transferred to the defect.The radius bone is then prophylactically plated to reduce fracture risk, as the strength of the bone is significantly weakened after the partial thickness osteotomies are made.This is performed by the Orthopedic Surgery team at our institution with cementing of the bony defect after plating is complete.[Color figure can be viewed at wileyonlinelibrary.com] discusses the type of defect and patient that this flap is best suited for.Case presentation: Patient is an 88-yearold female that has a history of prior oral cavity cancer that underwent a partial glossectomy, neck dissection, and a left radial forearm free flap reconstruction with the patient declining recommendation for adjuvant radiation.She then presented for a surveillance visit with evidence of an ulcerative lesion of the retromolar trigone with concern on imaging for osseous invasion of the squamous cell carcinoma.Given her elderly age and concern for impaired mobility after a fibula free flap reconstruction, we opted to pursue an OCRFFF using her right arm.Additionally, the anticipated defect was going to result in a single straight segment of bone to reconstruct the mandible.The patient proceeded to the operating room for a composite oral cavity resection with mandibulectomy, neck exploration for access to free flap vessels, and a right OCRFFF, with a 5 cm segment of bone harvested with a 4 Â 6 cm skin paddle (Figure 7).The marrow side of the bone was then secured to the reconstructive plate using 6 mm screws (Figure 8), with the pedicle feeding into the right neck.The arm was closed in the standard fashion with placement of a full thickness skin graft from the medial arm skin with full take of the graft.The patient had an excellent recovery and proceeded with adjuvant radiation after surgery.
It should be noted that there are several cases when using an OCRFFF is not indicated.For patients presenting with large or long segment bone defects opting for immediate dental implantation, surgeons should consider utilizing a fibula or scapular free flap.While extended OCRFFF harvests that include the styloid process have been described in the literature to gain further length, it was noted that one-third of those patients suffered a radius facture postoperatively. 12Furthermore, when other options exist, we recommend avoiding use of this flap for anterior mandible defects due to inability to support the lip given the reduced height of the bone.In terms of postoperative complications, a multiinstitutional study noted 30.9% of patients undergoing OCRFFF had a late wound complication, with surgical site infections being most common. 13Importantly, radius fractures are exceedingly rare using this approach, with only 1.3% of patients experiencing fracture after undergoing an OCRFFF.Fortunately, we have not seen a postoperative radius fracture at our institution since using this described harvest and plating technique.
Ultimately, there are many variations to the standard fasciocutaneous radial forearm free flap that could also be employed for the OCRFFF, including harvesting the flap without the cephalic vein or harvesting the lateral antebrachial cutaneous nerves for an innervated flap.Thus, this flap as wide applicability in reconstructive surgery.

| CONCLUSION
At our institution for the appropriate patient and defect, we have experienced success with integrating the OCRFFF into our reconstructive toolbox.While there are limitations in the use of the OCRFFF for large multisegment mandible defects in patients wishing to have immediate dental implantation, there is widespread reported use of this flap for reconstruction of the mandible, midface, and defects of the orbital walls, which enables microvascular surgeons to obtain an optimal cosmetic outcome for patients suffering from head and neck cancer and trauma to the face.

F
I G U R E 1 Topographical anatomy of the OCRFFF.The OCRFFF is supplied by the radial artery.Along the radial side of the arm, the radial artery can be palpated and the free flap should be centered over the radial artery with inclusion of the cephalic vein.The styloid process of the bone is palpated and the distal aspect of the flap design shifted proximally based on anticipated bone cuts and flap design.[Color figure can be viewed at wileyonlinelibrary.com]

F
I G U R E 6 OCRFFF with a large segment of radius bone harvested measuring 10 cm, demonstrating the ability to harvest large segments of bone to reconstruct both the midface and mandible.[Color figure can be viewed at wileyonlinelibrary.com]F I G U R E 7 Imaging demonstrating the right OCRFFF free flap dissection with the 5 cm segment of bone harvested (black arrow).[Color figure can be viewed at wileyonlinelibrary.com]