Release of Extensive Post Traumatic Radio-Ulnar Synostosis with Vascularized Free Flap Interposition

Abstract

Radioulnar synostosis is a rare complication after a forearm or elbow injury. The severity of initial trauma, associated head injury along with timing and the type of surgical treatment have been implicated in the formation of extra bone leading to synostosis. Surgical intervention is the standard treatment and is recommended after the maturation of synostotic bone. Surgery involves resection of the extra bone with or without tissue interposition. Materials used for interposition may include synthetic materials, allografts, and vascularized and non-vascularized autologous tissue superiority of one material over the other has not been demonstrated. Reported is a case of extensive soft-tissue defect and severe type II synostosis, with a relevant review of the literature.

Level of Evidence Level IV.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43465-021-00395-5.

Introduction

Radioulnar synostosis is a rare but disabling complication following fractures and crush injuries of the forearm and elbow [1]. Bone overgrowth, subsequently leading to synostosis, can occur anywhere along the forearm and is not specific to the fracture site or the type of intervention. The reported incidence of post-traumatic radio-ulnar synostosis in the literature varies from 0 to 9.4% [2–4].

Radioulnar synostosis can manifest due to a variety of factors. These possible influencing factors have been listed in Table 1 [1–5]. Optimum treatment in the form of timely intervention, separate incisions to access radius and ulna, minimizing trauma to the interosseous membrane and careful tissue handling help to prevent or limit such a tendency [6–8].

Table 1.

Predisposing factors for post-traumatic radio-ulnar synostosis

Extensive soft tissue damage

Comminution at the fracture site

fractures involving both bones at the same level

Monteggia fractures

Delay in surgical intervention

Single access incision for fixing the both bone injury/injury to interosseous membrane

Traumatic brain injury

Prolonged immobilization with late rehabilitation

The presented case had extensive scarring and multi-segment synostosis of forearm bones. Relevant review of the literature is presented. Our literature search failed to retrieve a similar report.

Case Report

Thirty-five years old Mr. A presented to us with limited prono-supination of his right forearm, while wrist and elbow range of motion were well preserved. The original injury was sustained during a road traffic accident nearly 12 years before presentation. Back then, he had open fractures of the right radius and ulna and significant soft tissue loss. Fractures were managed with intramedullary nails, while the soft-tissue defect was covered with a skin graft at another hospital. The patient also had a significant head injury and was under neurosurgical intensive care for 14 days. His mentation was subsequently altered and had recovered gradually over the next few months. While the patient was recovering from his head injury, his forearm movements had gradually decreased. Patient though having some residual signs of head injury, was now relatively independent, striving for gainful employment and came seeking correction of his deformity.

At presentation, the patient had a grafted area involving almost 3/4th of the volar forearm and a significant limitation of prono-supination. The arm was locked in around 35° supination. Distal sensory and motor examination was within normal limits except for the loss of flexor pollicis longus (FPL) function (Fig. 1a, b).

Fig. 1.

a, b Patient with post-traumatic radio-ulnar synostosis. The graft can be appreciated to be adherent to the underlying soft tissues. Long flexors had full function while the FPL was not functional

The X-ray revealed three bony blocks extending from just distal to the radial tuberosity proximally to the distal 1/4th of the forearm and extensive heterotrophic calcification. Both proximal and distal radioulnar joints were spared (type II) (Fig. 2a, b). A Computer tomogram (CT) was obtained to assess further details about the extent of the bony block, and other tissues involvement (Fig. 3a–d). Both radial and ulnar vessels were well felt in the distal forearm. Allen’s test confirmed the communication between the radial and ulnar vessels. No angiogram was performed pre-operatively.

Fig. 2.

a, b X-ray images showing extensive heterotrophic ossification and extensive synostosis involving the shafts of radius and ulna, the proximal and distal joints were spared though

Fig. 3.

a–d CT images of the forearm, delineating the extent of the pathology. The 3D reconstructed images are on the left side, indicating cross sections at various levels that have been labeled and displayed on the right side. In addition, in the cross section, one can appreciate complete loss of volar soft tissue and skin graft directly applied to the muscles (white arrow), while on the dorsum, there is abundant subcutaneous tissue (yellow arrow)

In a two-team approach, while one team excised the skin graft, secured the vessels, and released synostosis, the other team harvested the anterolateral thigh flap, with a fascia lata extension from the contralateral thigh (Fig. 4a). The block involved central 3/5th of the interosseous space and had significant volar soft tissue involvement. After excision of the skin graft, the pronator insertion was released from the radius, and the muscle was reflected ulnarly. The flexors of the fingers and wrist also were released and retracted ulnarly, along with the median nerve. The anterior interosseous nerve and vessels could not be identified and isolated from the scar, as was the central part of the interosseous membrane. The critical central oblique band of the interosseous membrane and other accessory bands could not be identified separately from the bony block. The proximal oblique cord and distal oblique bundle were uninvolved while the dorsal accessory cord could be carefully dissected out and preserved.

Fig. 4.

a Schematic representation of the synostosis. The incision marked in green, shows de-epithelialization of the skin, further the interosseous space is approached from radial side and the forearm muscles along with the median nerve reflected radially to expose the bone block. b The ALT flap being inset, the fascia is fed between the two bones with help of a suture placed from the dorsum of the forearm. c Showing the fascia interposed between all the volar muscles and the radius and further between radius and ulna (median nerve was deep in the muscle mass, protected from the harms way). d The vessel running in the fascia can be appreciated in a film with contrast. Letters d and v indicate dorsal and volar side of the limb for orientation

The ALT flap was harvested based on septocutaneous perforators. A cuff of fascia was harvested along with the flap. The pedicle was dissected and kept ready but undivided to minimize the ischemia time. After confirming adequate excision of the bony block, the tourniquet was released, and hemostasis was achieved. No.1 nylon sutures were placed from the dorsum of the forearm and were brought to the volar forearm through the interosseous space (Fig. 4). Three such sutures were preplaced. The flap was then brought into the defect, aligned appropriately and secured with a few sutures. The sutures pre-placed earlier were now passed through the vascularized fascia and were passed back through the interosseous space over the dorsal forearm (Fig. 4). While the surgeon held the fascia interposed between the bones, the assistant tied the knots over the dorsum of the forearm drawing and retaining the interposed vascularized tissue in its new place (Fig. 4). Radial vessels served as donor distally in the forearm. End-to-end anastomosis was performed. Skin paddle was then used to cover the volar skin defect. Total surgical time was around 6 h.

Range of motion exercise was started from the fifth postoperative day and involved active and assisted pronation and supination. The flap survived completely and follow up x-rays revealed complete resolution of the synostosis (Fig. 5). The vascularised tissue interposed between the bones also could be appreciated (Fig. 4). After four years of follow-up, there has been no recurrence. His forearm pronation is 10° from − 35° pre-operatively, and supination is around 80° (35°, pre-operatively) (Fig. 5) (Video 1). His DASH score improved from 36.7 pre-operative to 16 postoperatively.

Fig. 5.

a–c Well settled flap and pronation and supination range of 10/80 degrees respectively while a complete resolution of the heterotrophic ossification can be observed

The patient subsequently underwent flap debulking and transfer of flexor superficialis of the ring finger to the FPL for the restoration of the thumb flexion. During surgery, the FPL tendon was found avulsed from the proximal attachment and tethered to scar tissue in the middle 1/3rd of the forearm. The patient is satisfied with the overall outcome (Fig. 6a–d).

Fig. 6.

a–d 2 years following the release, reasonable pronation and supination range were maintained. The Flap bulk was reduced, and the FPL was reconstructed with tendon transfer leading to a reasonable restoration of aesthesis and function

Discussion

Radio-ulnar synostosis is a rare but disabling complication following significant crush injury to the forearm. Vince and Miller [3] have proposed a classification system based on the anatomic location of the bone block. Jupiter and Ring [4] have further modified this classification by sub-classifying the proximal (type III) synostosis. These classifications are helpful guides for documentation, communication, and surgical approaches.

Surgical treatment is the gold standard in the management of post-traumatic radioulnar synostosis. The surgical goal is to release the bony block to improve the function while minimizing possible recurrence. Care should be observed to prevent any further soft tissue injury. Conservative management is rarely sufficient, when the arm is in a functional position, the patient is either very low demand or has significant co-morbidities, precluding any surgical intervention. Preoperative counselling is essential explaining possible complications, including neurovascular injury, recurrence and need for the postoperative therapy.

Optimal timing of surgery is still being debated [1, 3, 9]. Traditionally, a waiting period of twelve months to allow fracture healing and maturation of synostosis was advocated. While serial radiographs, bone scans, and serum alkaline phosphatase levels, are used to monitor the maturation process, none are completely reliable. Recently, authors have tried early release, with better functional outcome and similar recurrence rates [4].

Careful assessment of the radiographs and CT scan helps to determine the extent of the block. The anatomic classification proposed by Vince and Millar also describes the neurovascular structures to be expected around the bony blocks [3]. Any neurovascular injury can lead to further disablement and must be prevented with careful dissection under magnification.

Proposed materials for interposition include vascularized or non-vascularized autologous tissue, allografts, silicone, and polypropylene [1]. Free non-vascularized fascia has been proposed by a few authors but has higher recurrence rates and is no longer recommended [4].

Jupiter and Ring reported eight cases treated with free fat flap and ten cases with no interposition. Adjuvant therapy was not used in any of their patients. The results in both their groups were comparable [4]. Bell proposed the interposition of vascularized anconeus muscle with excellent results [10]. Free vascularized fat transfer also has been proposed in the past with good results. Recently, Pfanner et al. [11] presented two cases where a full range of motion was restored following the release and interposition of allogenic fascia lata graft. There has been no consensus regarding the benefit of interposition, neither regarding material to be used for interposition. Most of the studies, though suggested that some form of interposition gives a better outcome than isolated resection.

Among other treatment options, Kamineni et al. [12] have suggested a technique of removal of part of radius to create pseudoarthrosis, where excision of the bony block was not possible. Other authors have proposed a similar approach to proximal synostosis [13]. Adjuvant therapies following surgery include non-steroidal anti-inflammatory drugs (NSAIDs) and low-dose radiation; their efficacy is unproven with only a limited number of studies available [14]. Indomethacin also has been used to prevent heterotopic ossification following a total hip replacement. unfortunately, it also reduces bone healing, making it less desirable [14]. Few reports suggest that the radiation following surgery was successful in preventing recurrence [14]. Regular use of either radiation or Indomethacin is not recommended, though, it could be considered in patients with a greater possibility of recurrence.

After resection, the risk of recurrence has been proposed to be around 6–35%. The risk factors include extensive soft tissue injury or associated head injury [3, 4, 9].

While we review our case considering the available information, this patient presented very late. The synostosis had already matured, allowing immediate intervention. He had a loss of volar soft tissue cover and had residual symptoms of head injury, both increasing the risk of recurrence. After adequate release, the vascularized tissue helped to maintain a curtain of tissue between the separated bones and provided added vascularity for tissue healing. Soft tissue flap helped in achieving pliable and vascular cover to multiple vital structures, that were adherent to the skin graft earlier. A vascularized skin flap also paved the way for the future tendon transfer for FPL reconstruction, that would have been difficult to pass under the skin grafted area. Flap allowed both, easy access for the second surgery and the adipose tissue plane for the easy tendon glide and helped restore function without adhesions. The flap and the vessel running between bones could be appreciated in postoperative CT scan (Fig. 4). Smooth outline of both forearm bones without signs of recurrence, maintained range of forearm movements, and good excursion of tendon transfer under the flap suggested scar re-modulation and attested usefulness of the vascularized interposition and cover. The absence of a definite interosseous membrane and avulsed FPL muscle (loose tendon) at later exploration may indicate a severe original injury to these structures. This also suggests why AIN could not be found, that normally should be protected and retracted as shown in Fig. 4. Nearly four years of post-surgery, the patient enjoys a useful function and there is no radioulnar instability.

Critical factors in the management of this case were the complete release of the bone block, vascularized fascial interposition and cover, early mobilization and stretching. Careful planning and execution of these principles is key to a successful outcome even in cases with extensive multilevel synostosis.

Supplementary Information

Below is the link to the electronic supplementary material.

Funding

None.

Compliance with Ethical Standards

Conflict of Interest

The authors declare that they have no conflict of interest.

Ethics Approval

This is an observational study. The Khoula Hospital Research Ethics Committee has confirmed that no ethical approval is required.

Informed Consent

Informed consent was obtained from all individual participants included in the study.

Patient Consent

Patients signed informed consent regarding publishing their data and photographs. The participant has consented to the submission of the case report to the journal.