08 November 2023: Articles
Challenging differential diagnosis, Rare diseaseTheodoros Stavropoulos1ABDEF, Vasileios Giannatos 1ADEF*, Vasileios Papathanidis1AE, Anargyros Roumeliotis1EF, Konstantinos Koutas1BDF, Zinon T. Kokkalis1ABDEF
Am J Case Rep 2023; 24:e940411
BACKGROUND: Volar plate injuries are rare and difficult to diagnose and treat. Only a few cases have been described on the thumb, especially in children, that resulted in swan-neck type deformity. Conservative treatment has been suggested as first-line management, but surgical reconstruction utilizing flexor digitorum superficialis tenodesis has been described for refractive cases. Only a few attempted surgical repairs of the volar plate have been reported, since it is a technically demanding procedure.
CASE REPORT: We present the case of a neglected thumb volar plate injury in an 11-year-old girl after a thumb hyperextension injury. The patient presented 2 months after her injury with functional disability of her thumb. Magnetic resonance imaging had been performed, with no signs of volar plate injury, and she was consequently treated with an extension-blocking splint, with no effect. Clinical examination raised the suspicion of a thumb volar plate injury, which was confirmed during surgical exploration. Therefore, fixation with a bone anchor was performed, and the metacarpophalangeal joint was immobilized in 20° flexion with a percutaneously inserted Kirschner wire. After splinting for 3 weeks, the patient had 10 sessions of physical therapy. At 6-week follow-up, she presented with excellent active and passive range of motion and absence of pain.
CONCLUSIONS: Magnetic resonance imaging did not have high sensitivity. Six weeks after surgery, full range of motion was achieved, with no stiffness or tenderness at the first metacarpophalangeal joint, suggesting that a thumb volar plate injury had been managed surgically with a suture anchor with excellent results.
Keywords: Palmar Plate, Metacarpophalangeal Joint, Thumb Injury, Thumb Instability, Volar Plate
The thumb volar plate (also referred to as volar ligament, palmar plate, or palmar ligament) is a thick ligament on the underside of the metacarpophalangeal (MCP) joint of the thumb, which reinforces the joint capsule, enhances joint stability, and limits hyperextension [1,2]. The volar ligament is loose when the MCP joint is in flexion and tight when the MCP joint lies in extension. It is part of a 3-sided ligament-box configuration similar to that of the proximal interphalangeal joint. However, the thumb MCP joint volar plate differs from the proximal interphalangeal joint because there is no flexor sheath proximal to the plate. Thus, no strong check rein ligaments are present [3,4]. The palmar ligaments consist of a thick fibrocartilaginous part distally, but in its proximal end, the volar plate becomes membranous and blends with the volar capsule, which is attached to the head of the metacarpal bone. Therefore, ligament injury most often occurs in the proximal end of the ligament, in the metacarpal head [3–5]. Injury to the MCP joint volar plate of the thumb can result in serious functional impairment, producing pain and disability in the form of reduced pinch and grasp power, especially when it is not treated acutely and progresses into a chronic condition [3,4,6].
An 11-year-old girl presented to our hospital reporting thumb pain on slight movement and thenar bruising after a fall, during which the finger had been bent backwards, 3 months earlier. Magnetic resonance imaging (MRI; Figure 1) had been performed 2 months after the injury at a local pediatric hospital, with no signs of ligament injury but with a swan-neck type deformity, as noted clinically, and she had been treated with an extension-blocking splint for 2 weeks. A desirable result was not achieved, as the patient presented to our hospital later (3 months after the initial injury) with a persisting extension-flexion deformity of the thumb (Figure 2), with the MCP joint held in 50° hyperextension, a swan-neck type deformity, to be treated by a hand specialist in our department. On clinical examination, flexor pollicis longus spasm was noted.
After thorough history and clinical examination, we decided to treat the injury surgically, with the suspicion of volar plate rupture. Written informed consent was obtained from the patient’s parents in order to publically present this case. An X-ray was performed preoperatively to rule out an avulsion fracture. Under general anesthesia and tourniquet control, a longitudinal incision was made along the palmar surface of the MCP joint of the thumb (Figure 3A). The digital nerves and arteries were retracted and protected. After releasing the first annular pulley and retracting the flexor pollicis longus, the volar plate was revealed, and a complete tear was noted. The volar ligament was sutured to the metacarpal head with a Mitek Mini G2 suture anchor (Mitek Surgical Products, Westwood, MA, USA), bone anchor, plus 3.0 suture (Figure 3B–3D).
After the volar plate was sutured, we percutaneously trans-fixed the MCP joint with a Kirschner wire at 20° flexion for optimal tissue healing (Figure 3D). The wound was irrigated with saline, and the skin was closed. The thumb was immobilized with a splint for 3 weeks. After 3 weeks, active range of motion exercises began. A standard protocol of 10 physical therapy sessions consisting of passive and active flexion-extension thumb exercises was initiated. Paracetamol was used for analgesia only during the first postoperative day, as the patient did not have concerns of pain. On review 6 weeks after surgery, there was no pain, stiffness, or tenderness at the MCP joint of the thumb (Figure 4). The patient could perform usual daily activities without limitation.
The isolated thumb MCP joint volar plate injury in the pediatric group is a very rare occurrence. The unique anatomy of the pediatric population and the delayed presentation of this injury makes the present case even more unique. Bones are weaker than the ligaments and soft tissues, therefore children are more vulnerable to sustaining Salter Harris fractures through the epiphyseal growth plate rather than joint dislocations and soft tissue ruptures . However, in our case, no osseous damage was recognized on X-rays or MRI. Apart from thumb hyperextension, another possible mechanism for volar plate injury is usually a severe direct blow to the thumb [1,3]. On physical examination, tenderness is elicited over the volar aspect of the thumb MCP joint. Tenderness can also be localized dorsally due to impingement . Regarding clinical signs, a passive MCP joint extension deformity is characteristic of an MCP joint volar plate injury, along with flexor pollicis longus spasm, as encountered in our case . The abduction-collapse sign is another sign suggestive of volar plate instability. Maximum thumb and index abduction is requested from the patient, while the opposite hand is applying a resisting force. If the sign is positive, tenderness will be elicited and the MCP joint will give way and collapse . If damage to the volar plate is not properly treated, it can progress to chronic volar instability and MCP joint pain [1,3]. Most often, an avulsion fracture is present. However, a negative finding of fracture on X-ray does not eliminate the possibility of ligamentous or volar plate injury . Further imaging is not routinely recommended; however, in the case of clinical suspicion of a fracture, a computed tomography (CT) scan can be ordered. Ultrasonography is of high value to assess a tear of the volar plate. In the case of a tear, an ultrasound shows that the fibrocartilaginous structure is swollen and there is an intrasubstance hypoechoic cleft; these findings can be associated with fluid distension of the joint . MRI is also used to evaluate the injury and define its characteristics, including location and displacement . However, according to a recent study in which MRI was used for the diagnosis of ligament injuries around the thumb MCP joint, researchers concluded that MRI is moderately effective, but is more sensitive in diagnosing acute injuries . This was the finding in our case as well, as MRI was not sensitive enough to detect the volar plate rupture 2 months after the initial injury and a clinical diagnosis was made that led to surgery.
The treatment options available for volar plate injury include capsulodesis, sesamoid arthrodesis, tenodesis with palmaris longus, or extensor pollicis brevis tendons and thermal shrinkage of the volar plate via thumb MCP joint arthroscopy [6,9,10]. Non-operative treatment with an extension-blocking splint remains the first course of treatment, but the conversion to surgical treatment is highly likely, should the conservative modalities fail . Buddy strapping, however shows, favorable outcomes in children and remains the criterion standard for first-line management . Volar plate repair for chronic cases is rarely described in the literature owing to the demanding nature of the procedure, with the volar plate being sensitive to retraction or attenuation structure [12,13]. Kaneshiro et al presented a case series of 7 patients with chronic volar plate rupture of the little finger, 2 of which developed a swan-neck deformity, and all of which were successfully treated with late volar plate repair . Melone et al presented even greater outcomes at 8-year follow up with volar plate repair, with 23 out of 25 patients scoring excellent or good outcomes . Biomechanical studies have reported inferior outcomes of volar plate reconstruction or repair compared with those of the normal joint, but the surgical techniques do not vary significantly . Finally, Wollstein et al presented a series of 54 cases treated with volar plate repair on the chronic setting, with favorable outcomes . Caviglia et al performed a literature review in 2021 on the 2 prevailing techniques, flexor digitalis superficialis tenodesis and volar plate repair, concluding that flexor digitalis superficialis tenodesis is a safer, more reproducible procedure, showcasing, however, the excellent pain-free outcomes of the volar plate repair . In our case, an open procedure with suture anchors for volar plate reconstruction was used. When an open procedure is necessary, there are various surgical options, including volar and dorsal approaches; however, the optimal treatment option is still controversial. The volar approach offers a direct visualization and ease of repair, at the expense of a higher risk of neurovascular injury compared with the dorsal approach because of the location of the neurovascular bundles. However, when using a volar approach, the volar plate can be directly visualized and repaired easily . The arthroscopic approach is a minimally invasive method reducing the risks associated with the open volar approach, but it is a highly technical procedure and it has been reported mainly in adults [6,7]. In our case, we opted for the volar approach, as the chronic nature of the injury would make the repair more challenging, and we did not face any difficulties regarding the neurovascular bundles of the region, as we used careful tissue dissection.
The thumb MCP joint volar plate injury in the pediatric population is a less common event than in adults. Early diagnosis and treatment has a profound effect on the functional recovery and on preventing permanent deformity. However, diagnosis can be delayed, as in our case, because the diagnosis can be a challenge in itself, with MRI presenting only moderate sensitivity. Diagnosis can often be made from clinical examination when the MCP joint is in hyperextension and the interphalangeal joint lies in flexion. The mechanism of injury and the radiographs complete the diagnostic algorithm and help to confirm or exclude a possible avulsion fracture and joint subluxation or dislocation. The palmar approach is indicated in cases of neglected rupture, as it offers better access and visualization of the volar plate than does the dorsal approach. However, we must be careful to identify and protect the neurovascular bundle of the digital arteries and nerves.
FiguresFigure 1.. (A, B) Magnetic resonance imaging 2 months after injury showing a flexion-extension swan-neck type deformity of the thumb and no signs of volar plate rupture. Figure 2.. Preoperative passive extension-flexion deformity: (A) palmar aspect and (B) lateral aspect. Figure 3.. Intraoperative images showing (A) longitudinal incision along the palmar surface of the metacarpophalangeal joint of the thumb, (B) a bone anchor is inserted to the metacarpal head, (C) sutured volar plate and (D) immobilization of the metacarpophalangeal joint in 20° flexion using a Kirschner wire. Figure 4.. Photos showing (A) neutral position of the thumb, (B) flexion of the thumb, (C) extension and abduction of the thumb, (D) strong grasp power, and (E) extension of the thumb and flexion of other fingers.
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