Midfoot pain |
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Adult acquired flatfoot deformity IN the midfoot, the most common condition causing pain is adult acquired flatfoot deformity( see figure 10). While this condition is mainly attributed to degenerative changes of the tibialis posterior tendon, it is actually a spectrum of deformity with progressive soft tissue attenuation followed by degeneration in the hindfoot. Also, it is always important to remember that the number one differential with adult acquired flatfoot deformity is midfoot arthritis with collapse.
This condition can mimic adult acquired flatfoot deformity with progressive flat foot and pain. This is why it is of the utmost importance to first get anteroposterior and lateral weight-bearing radiographs of the foot to look at the overall alignment of the mid and hindfoot and to exclude significant midfoot osteoarthritis as the cause of the deformity. Once this has been excluded, one can focus on the adult acquired flatfoot deformity and its management.
Aetiology Tibialis posterior tendinopathy is most common in middle-aged females, with the condition affecting around 4 % of women over the age of 40. 17 The disease is also more common in those with physiological flat feet. The natural history of the disease is initial pain at the arch of the foot worsened on activity and relieved with rest.
This may be followed by a semitraumatic event where the patient feels something pop. After the event, the pain may actually settle but the deformity will worsen and management depends on the stage of the disease and the patient’ s symptoms. 18
History The history depends on when the patient presents. A patient with early disease and tendinopathy will present with pain in the posteromedial ankle and an ache in the arch that is worsened on activity and may be relieved with overthe-counter insoles. This arch pain must be distinguished from plantar fasciitis. Patients usually describe
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Figure 10. Adult flat foot. Source: Drvgaikwad http:// bit. ly / 2j08utP |
Figure 11. Radiograph of bunion correction: forefoot abduction with heel correction.
plantar fasciitis as pain in the heel and this condition will be discussed fully in the next section. As the disease progresses in adult acquired flatfoot deformity and the tibialis posterior tendon attenuates or ruptures, pain is no longer felt on the medial side. As this is a chronic condition, patients do not usually present complaining of increasing deformity. The main complaint in disease that has progressed to deformity is lateral ankle pain due to impingement of the subtalar joint on the sinus tarsi. In very late stage disease, the patient may complain of significant hind foot pain and difficulty walking due to hindfoot arthritis.
Examination Start by looking at the patient from the front and side assessing the weight-bearing arch. Examine the patient from behind, assessing whether the heel is in neutral or more likely, valgus. Ask the patient to stand on tiptoes and then on single leg tiptoes. Allow them to support themselves but watch for compensatory pushing off the good leg. Weakness in push off suggests tibialis posterior weakness. Watch whether the heels go into normal varus on tiptoes or if they are fixed in valgus. If they are fixed in valgus, this suggests significant chronicity of disease and arthritis in the hindfoot.
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Also look at the toes from the back. If you can see more than two toes laterally this is called the‘ too many toes sign’ and suggests forefoot abduction. 19 Be careful of the resting position of the foot as any rotation of the leg can demonstrate false results. For this reason the author examines forefoot abduction on the couch by correcting the heel valgus and assessing the forefoot position( see figure 11). This is a compensatory mechanism that patients develop that suggests more chronic disease, and has implications for surgical management. Finally, assess the tibialis posterior along its length for pain.
Investigations The first-line investigation in adult acquired flatfoot deformity is always a weight-bearing anteroposterior and lateral radiograph of the foot. This will exclude midfoot arthritis as a differential, allowing assessment of flattening of the arch, hindfoot valgus and forefoot abduction.
If there are positive findings on the plain radiograph and the patient has clinical findings in keeping with the aforementioned history and examination, no further investigations are required. If however, the patient has posteromedial pain and arch ache but a normal radiograph, it may be prudent to get further imaging to confirm the diagnosis.
Options are an ultrasound scan or an MRI. Ultrasound is dynamic and in the correct hands can give very detailed information about the tibialis posterior tendon, partial tears, inflammation and other medial structures such as the spring ligament. However, it is operatordependent, and is probably best utilised by specialist referral to a musculoskeletal radiologist with an interest in this technique. In the community, a safer and more reliable option may be an MRI, which will show inflammation in the tendon sheath if there is injury.
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Management Management of adult acquired flatfoot deformity is controversial. Most authors agree that the first |
line of treatment for almost all patients should be conservative. 20
For early disease with flexible deformity, a corrective orthosis, with a deep heel cup and a medial arch support can help to correct foot biomechanics. In a proportion of patients, this may be enough to halt disease.
Even in patients with significant fixed deformity, accommodative orthoses can relieve symptoms and allow avoidance of surgery. There is evidence that physiotherapy with Achilles stretching and eccentric leg exercises improves outcomes and as such, physiotherapy should also be part of the initial management. 21
It is the author’ s opinion that if conservative measures do not alleviate symptoms over a period of three months it is wise to consider surgical intervention.
At the first meeting the patient will be counselled on the stage of their disease and what operative intervention would involve if it were to be required.
In early stage disease, we almost always reconstruct( rather than repair) the tendon using the long flexors to the small toes. This tendon has connections with other foot tendons and there is no noticeable deficit in toe function. When this procedure was initially used, there was a significant failure rate. It has since been understood that due to the heel valgus, the reconstruction is always under significant tension and as such, we now routinely also perform a heel shift. 22 It is also our practice in early and moderate disease to use a sinus tarsi spacer, which corrects the arch of the foot.
As disease progresses, more complex procedures are required up to fusion of all of the joints of the hindfoot.
Recovery after any adult acquired flatfoot deformity procedure is prolonged, with six weeks’ immobilisation after osteotomy and twelve weeks after hindfoot fusion. That is why it is our preference to treat patients conservatively if possible and to operate early if symptoms do not settle or if deformity continues to progress. cont’ d next page
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