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. 2024 Jun 6;52:101067. doi: 10.1016/j.tcr.2024.101067

‘PRUT’ – A cadaveric study to understand the mechanism of this rare paediatric elbow injury with a comprehensive review of literature

Swapnil Keny a, Nihar Modi b,, Murtaza Haidermota b, Nikhil Gokhale b, Seema Khambatta c, Aryan Keny d
PMCID: PMC11252064  PMID: 39021888

Abstract

Introduction

Proximal radio-ulnar translocation (PRUT) with elbow dislocation, without a fracture, is an extremely unusual injury.

Case

A 6-year-old female child presented to us with posterior elbow dislocation, PRUT and incomplete ulnar nerve palsy. A hematoma aspiration and reduction of the elbow joint were done with a hyper-supination manoeuvre to reverse the translocation. She was managed with an above-elbow cast for 4 weeks and showed good radiological and functional outcomes on subsequent follow-ups until 1 year.

Conclusion

Early recognition of PRUT and a thorough clinico-radiological assessment are mandatory when dealing with paediatric elbow injuries. Our cadaveric study with illustrations defines the mechanism of this rare injury for better understanding.

Keywords: Children, Proximal radioulnar translocation, PRUT, Ulnar nerve, Isolated elbow dislocation, Paediatric elbow injury, Convergent elbow dislocation, Cadaveric, Mechanism

Introduction

Elbow dislocations in the paediatric age group are rare and comprise 3–6 % of elbow injuries in childhood [1]. They are more common in the age group of 11–15 years [2]. Posterior elbow dislocations form the most common type and commonly involves the non-dominant limb [[2], [3], [4], [5]]. Translocation type of dislocation is the rarest form of elbow dislocation in children where the radial head and olecranon swap places resulting in radial head articulating with the trochlea and olecranon tending to go towards the capitellum [6]. Paediatric elbow dislocations are usually complex, and involve fractures around the elbow, epiphyseal separation or avulsion injuries [5]. Isolated elbow dislocations without presence of any fractures are infrequent, and as such very few studies have been reported in literature [1,7]. Nerve involvement, with isolated posterior elbow dislocation is extremely rare, and reports of such injuries are limited.

We present a rare case of a PRUT (proximal radio-ulnar translocation) with a posterior elbow dislocation and ulnar nerve paresis, in a 6 year old female child.

The patient's father provided informed consent regarding data submission for research and publication.

Case report

A 6-year-old right hand dominant female child was brought by her father to the emergency department with the history of a fall 2 h back, with the point of the extended and pronated left elbow making forceful contact with the edge of the step. She presented with a painful and deformed left elbow, and with inability to move her left forearm. It was tender, swollen, deformed and held in 40 degrees of flexion, with the support of the contralateral limb. The forearm seemed to be in a fixed and pronated state. Active range of movements were not possible, and trivial passive movements elicited pain. Radial artery pulsations were palpable. The hand was pink, warm and the fingers showed a capillary refill time of less than 2 s. On careful neurological examination, light touch sensation in the ulnar nerve territory of the left hand was decreased as compared to the other hand, with marked sensory diminution over the little finger. The pain, temperature, deep touch sensations and the motor examination of the left upper limb were unremarkable. Close examination of the radiographs revealed the presence of a posterior dislocation and convergent translocation of the left elbow, without any fracture (Fig. 1).

Fig. 1.

Fig. 1

AP and lateral radiographs showing a left sided elbow joint with posterior dislocation without any bony injury.

An urgent MRI scan of the left elbow was performed to rule out cartilaginous and ligamentous injuries. MRI of the left elbow revealed dislocation of the ulno-trochlear and radio-capitellar joint, with the presence of hemarthrosis. It also showed articulation of the radial head with the humeral trochlea and of the ulnar olecranon with the humeral capitellum. The lateral collateral ligament and the lateral ulnar collateral ligament revealed full thickness tears at the proximal attachments, while the medial collateral ligament showed the same at the distal attachment. Bulkiness of the ulnar nerve was noticeable at the level of the distal end of the humerus along with an annular ligament tear (Fig. 2).

Fig. 2.

Fig. 2

MRI showing ulnar nerve at the distal humerus (left), ulno-trochlear dislocation with hemarthrosis(centre) and proximal radioulnar translocation (right).

Under short general anaesthesia and image intensifier control, the haematoma was aspirated percutaneously from the elbow joint, via a posterior portal. A closed reduction with a hyper-supination manoeuvre was then performed. Closed, stable reduction was achieved and a bivalved cast in 100 degrees of flexion and full supination was applied to hold the reduction and to immobilize the left elbow (Fig. 3).

Fig. 3.

Fig. 3

Radiographs showing a stable and relocated left elbow joint.

The patient was reviewed after 1 week, at which the radiographs showed a congruent left elbow joint with maintained reduction (Fig. 4). Sensations of the left hand in the ulnar nerve territory, which were diminished at the initial presentation, were now restored and equal in both limbs. The bivalved cast was replaced by an above elbow full cast in full supination. The cast was removed at 4 weeks and a check radiograph showed the presence of a congruent elbow joint (Fig. 5). Gradual rehabilitation including flexion-extension and pronation-supination were initiated. By the end of 2 months, the child had regained complete arc of range of motion (Fig. 6). At the 6-month followup, there was no varus-valgus laxity which was confirmed clinically as well as with stress radiographs. Additionally, the QuickDASH score was found to be 2.3, Mayo Elbow Performance Score (MEPS) was found to be 95, and the child was seen to be carrying out all activities of daily life without any difficulties [8]. A similar radiological and functional outcome was found at the 1 year follow-up. We replicated the mechanism of this injury in the cadaveric lab on a preserved specimen of the elbow with intact osteoligamentous anatomy. This was done to depict the patho-mechanics of PRUT, on an illustrated cadaveric model to understand the cascade of events in this rare injury.

Fig. 4.

Fig. 4

AP and lateral radiographs of the left elbow joint at 1 week follow-up showing maintained reduction.

Fig. 5.

Fig. 5

AP and lateral radiographs of the left elbow joint at 4 week follow-up, showing maintained reduction after cast removal.

Fig. 6.

Fig. 6

Complete range of motion. Complete flexion(top left), extension(top right), supination(bottom left) and pronation (bottom right).

Discussion

The elbow joint is the second most frequently dislocated major joint due to trauma after the shoulder [1]. However, paediatric elbow dislocation is a rare injury and occurrence of an isolated dislocation without any bony injury is even more scarce. This is attributed to the biomechanical factors related to growth of the immature elbow and constantly changing activity patterns in this age group [9]. Additionally, the relative weakness of the bones compared to the joints, in this age group, tends to cause bony lesions instead of isolated dislocations [6,10].

Axial force on the proximal radius due to a fall on an outstretched hand, with the forearm in pronation and extension, seems to be the mechanism for dislocation-translocation injuries [9]. Incorrect manipulation of an elbow dislocation in pronation is an iatrogenic cause of the same injury. [11]. According to the accepted classification, proximal radioulnar joint (PRUJ) injury may or may not occur with elbow dislocations [9]. If a PRUJ injury is present with the dislocation, it can be divergent (anteroposterior or mediolateral) or convergent/translocation (swapping places of the radial and ulnar head) type. The translocation type of PRUJ injury, which was described 40 years ago, is the rarest form of elbow dislocation in the paediatric age group [12]. Our patient had a translocation type of elbow dislocation with an exactly similar mechanism of fall as described above. We conducted a cadaveric dissection to demonstrate the likely mechanism of the translocation type of PRUJ injury, as proposed by Combourieu et al. Our MRI findings align with the injury mechanism that we have outlined. To the best of our knowledge, ours is the only study that has shown the mechanism of translocation type of PRUJ injury on a cadaveric elbow (Fig. 7, Video 1).

Fig. 7.

Fig. 7

Cadaveric dissection of the left elbow showing ligaments and structures clinically relevant to the mechanism of convergent proximal radio-ulnar translocations.

PRUT injuries require a hypersupination manoeuvre to correct the translocation [6]. An MRI scan was done to rule out incarcerated osteocartilagenous fragments in the joint and a “TRASH” (The radiographic appearance seemed harmless) lesion, which could have changed the management [13]. After establishing that there were no fractures, and impediments to the reduction, and the hematoma being a possible hindrance to the reduction, we proceeded to perform a closed reduction. Aspiration of the hematoma, along with traction and flexion, helped in reducing the posterior dislocation. Following this, we performed a hypersupination manoeuvre with pressure on the medial side of the radial head and lateral side of the olecranon to reduce the translocation by pushing the radial head over the ulna.

Combourieu et al. have stated that almost half the cases are overlooked and diagnosed late [14]. The elbow dislocation reduces with a “clunk” which improves the flexion and extension and gives the feeling of a “pseudoreduction” as described by Carey et al., but the presence of a translocation continues to keep the elbow in fixed pronation, and is often missed [15,16]. Additionally, the rarity of this injury makes it difficult for physicians to think about the possibility of a translocation [15].

Most PRUTs do not reduce with closed reduction [17]. Late diagnosis, soft tissue interposition and associated fractures often necessitate an open reduction. Some authors, have adopted a dual incision approach with ligament avulsion repairs in their study [17]. Hong-Kee Yoon et al., have described a mini open technique in their study to manage the same [15]. We managed our case with a successful closed reduction. Having aspirated the hematoma, the block to the reduction was removed, and with the hypersupination and manipulation technique as mentioned above reduction was achieved.

We found an excellent functional outcome in our patient with respect to the QuickDASH and MEPS score. It echoed the findings of the study by Nussberger et al. on functional outcomes in traumatic elbow dislocations managed with non-operative treatment [8].

A thorough clinical and radiological assessment is the keystone to the diagnosis of such injuries. After a closed reduction, always look for limited forearm rotation (especially supination) and check for relief of pain. Radiologically, always rule out abnormal articulation of the proximal radio-ulnar joint and humerus on true AP radiographs [15].

Conclusion

PRUT with elbow dislocations are very rare injuries and can be easily misdiagnosed if radiographs are not carefully evaluated. Associated injuries should always be looked for, and a late diagnosis leads to poor functional outcomes with the need of a surgical intervention. A thorough clinico-radiological assessment helps to treat this injuries well and at the earliest. Furthermore, our cadaveric study defines the mechanism of this rare injury to understand it better.

The following is the supplementary data related to this article.

Video 1

Video illustration showing the mechanism of convergent proximal radio-ulnar translocation.

Download video file (5.9MB, mp4)

Source of funding

None.

CRediT authorship contribution statement

Swapnil Keny: Conceptualization, Data curation. Nihar Modi: Conceptualization, Data curation, Investigation, Methodology, Software, Writing – original draft, Writing – review & editing. Murtaza Haidermota: Investigation, Resources. Nikhil Gokhale: Validation, Visualization. Seema Khambatta: Methodology, Resources. Aryan Keny: Investigation.

Declaration of competing interest

The authors do not have any conflict of interests.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Video 1

Video illustration showing the mechanism of convergent proximal radio-ulnar translocation.

Download video file (5.9MB, mp4)

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