Mueller Weiss syndrome (MWS) of the navicular is a rare cause of midfoot pain in adults that develops due to disruption of the navicular blood supply and its subsequent collapse. This deformity presents as a progressive painful clinical course, often aggravated by weight bearing activity.
This is an unusual condition that is best diagnosed with a weight-bearing radiograph of the frontal and lateral views.
Causes
Acute trauma or repetitive microtraumas may result in vascular disruption and decreased blood flow to the navicular bone. This is believed to lead to bone necrosis and the eventual collapse of the midfoot, causing foot pain and altered weight-bearing. Over time, the navicular bone may become misshaped and develop extra bone fragments (known as accessory navicular bone) on the outside of the arch. The extra bone is not needed for normal foot function, but can cause pressure imbalance, changes in the shape of the arch, and painful symptoms.
The condition is most often seen in females aged 40-60, and tends to develop slowly. Symptoms include chronic midfoot pain, swelling and tenderness over the dorsomedial midfoot and hindfoot. Radiographic findings include lateral navicular collapse with comma-shaped appearance, increased radiodensity and fragmentation, and medial or dorsomedial protrusion of the navicular bone.
It is unclear what causes the condition, but it can be aggravated by long-term flatfoot deformities and certain activities. In most cases, the patient will experience gradual onset of pain and stiffness in the middle of the arch, usually after walking for prolonged periods. Other contributing factors may include abnormal foot structure, previous injuries and unequal pressure on the foot over time.
Treatment for Mueller Weiss syndrome usually starts with conservative approaches, including physiotherapy and immobilization in a brace or removable walking boot. The goal is to restore normal alignment of the arch and decrease pain and inflammation. If nonsurgical treatments do not provide relief, surgery may be recommended, which involves removing the accessory bone, reshaping the area and repairing the posterior tibial tendon to improve function.
Although Rafael Nadal has recovered from his injury and is back on the tennis courts, he will likely experience flare-ups of Mueller Weiss syndrome in the future. It is important for patients to know about this condition so they can recognize the early signs and symptoms, get diagnosed quickly, and start treatment early. Digital physiotherapy platforms like TrakPhysio can play a vital role in early diagnosis and treatment of conditions like this. This will help ensure optimal outcomes for patients, and allow them to return to their favorite activities as soon as possible.
Symptoms
Muller Weiss syndrome (MWS) is a disorder of the foot characterized by a collapse and deformity of the tarsal navicular bone. It typically occurs in adults between the ages of 40 and 60. It is thought to be due to disruption of the vascular supply to the navicular bone, causing osteonecrosis. The navicular bone has a unique vascular supply, with the medial plantar artery providing its blood supply to the plantar aspect and the dorsal pedal artery providing its blood supply to the dorsal and lateral aspects. When the navicular bone is compressed, it is disrupted at its mid-line, causing a loss of blood supply and eventual bone necrosis [1, 2]. The compressive loading that causes MWS also results in lateral displacement of the navicular bone over the calcaneus, creating the classic “comma shaped” appearance on weightbearing radiographs. This lateral shift also drives the hindfoot into varus, creating a paradoxical pes planus varus deformity of the midfoot and hindfoot [3, 4].
The diagnosis of MWS is made with a combination of patient history and examination and weightbearing plain radiographs of the foot and ankle. Patients with MWS typically present with longstanding, subtle pain in the midfoot that worsens with weight-bearing activity. The pain may also be exacerbated by certain activities, such as jumping and running. Unlike Kohler disease, which is a childhood osteochondrosis of the navicular bone, most MWS patients are already symptomatic at the time of radiographic diagnosis.
Lateral weightbearing radiographs of the foot show a comma shape in the navicular bone, with varying degrees of naviculocuneiform and talonavicular arthritis. This condition can also lead to a biplanar or triplanar deformity of the hindfoot, depending on the degree of navicular displacement.
Treatment of MWS is typically conservative, with the use of a rigid insole with a medial arch support and a lateral heel wedge. If this does not relieve symptoms, the Dwyer calcaneal osteotomy and perinavicular joint fusion can be used. However, because of the high rates of failure with these treatments, multicenter, randomized controlled trials are needed to determine the best approach.
Diagnosis
The navicular bone of the foot is a complex articulating structure that articulates with the head of the talus proximally, the cuboid inferolaterally, and three cuneiforms distally. It contributes to the medial longitudinal and transverse arch of the foot, and is supported by the spring ligament, lateral cuneonavicular ligament, and plantar cuneonavicular ligament. When the navicular bone experiences a disruption of its vascular supply, it can begin to collapse, leading to pain and deformity of the midfoot and hindfoot. In children, this is known as Koehler’s disease, but it can also occur in adults, and is referred to as Mueller Weiss syndrome (MWS).
Diagnosing MWS is difficult because the clinical course is often non-specific and the onset of symptoms occurs slowly over time. However, radiographic findings are characteristic of the condition and help to differentiate it from other conditions that impact the navicular bone such as stress fractures or coalitions.
X-rays can reveal a fractured or fragmented navicular bone, and if the condition is advanced, an atrophic change of the forefoot metatarsal may be seen on the AP view. The first metatarsal can appear longer than the second metatarsal on the AP view due to force bypass from the shortened navicular bone through the first cuneiform metatarsal joint [19].
A CT scan is the gold standard for diagnosing MWS because it allows precise visualization of the navicular and surrounding structures. It enables the clinician to identify a disruption of the navicular vasculature and the presence of bone graft necrosis.
The MRI can demonstrate fluid collection within the navicular cavity, edema of the adjacent tissues, and evidence of associated navicular stress fractures or coalitions. Magnetic resonance imaging can also help to determine the degree of navicular fragmentation and associated talonavicular joint arthritis.
In MWS, the patient will typically elect conservative management with a CAM boot and weight-bearing as tolerated. If the condition progresses, surgical intervention is warranted and may consist of a talonavicular cuneiform fusion with autograft or percutaneous navicular decompression. The goal of surgery is to stiffen the arthritic navicular, talar, and cuneiform joint(s) to avoid a collapsed arch, and prevent progressive hindfoot and forefoot deformity.
Treatment
Mueller Weiss syndrome (MWS) is an idiopathic foot condition in which the navicular bone of the midfoot collapses and deforms due to disruption of its blood supply. It is primarily seen in adults, mostly women in their forties to sixties and can cause chronic mid-foot pain, stiffness and deformity. Its etiology is unknown but may be associated with abnormal foot structure, past injuries, or excessive pressure on the midfoot over time.
While it is common to see osteonecrosis of the navicular bone in childhood, which is known as Kohler’s disease, it is much rarer for it to occur spontaneously in adulthood, which is what this case report describes. It is important to recognize MWS in order to prevent extensive deformity and decrease foot pain.
There are several treatment options available for MWS. Some patients respond to conservative management such as a CAM boot and limiting weight bearing activities. Other patients may require surgery. Treatment can involve the insertion of a tibial autograft or a talonavicular cuneiform joint arthrodesis.
This patient elected to undergo surgical intervention. During the procedure, the navicular bone was removed along with its adjacent ligaments, and the remaining fragments of the navicular bone were packed with iliac cancellous bone graft. The calcaneal and cuboid bones were fixed with full thread Hallow screws and locking plates. The patient was placed in a splint and allowed to gradually return to pain-tolerated non-weight-bearing for 12 weeks after the surgery.
MWS of the navicular is an under-recognized cause of foot pain in adults. Insufficient attention to MWS can lead to misdiagnosis and inadequate treatment, resulting in more severe deformity. Incorporating MWS into the diagnosis of flatfoot and pes planus is essential, especially in patients who are prone to paradoxic flatfoot varus, where the shifting of the navicular over the calcaneus drives the subtalar joint into varus. This can be easily identified on radiographic images, and can help guide treatment of MWS. Dwyer calcaneal osteotomy with lateral displacement is an effective treatment for MWS and should be considered in patients who do not respond to conservative therapy.