Peritalar dislocations

1. Introduction 

Peritalar dislocation is an injury involving both the talo-calcaneal and talo-navicular joints.

It is a rare dislocation resulting from a high energy trauma such as a fall from a height and athletic injuries.

Grantham [1] coined the term “basket ball foot” because four of his five patients were injured while playing basket ball.

Medial dislocation is the most frequent (Fig. 1, Fig. 2); lateral dislocation presents more rarely, and with worse results being frequently associated with other fractures in the foot or open injuries (Fig. 3).

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Fig. 1. Medial peritalar dislocation. Note dislocation of talo-navicular joint.

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Fig. 2. Seven years after closed reduction, the radiogram shows the presence of mild degenerative arthritis.

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Fig. 3. (A) Lateral subtalar dislocation. (B) Three years after reduction, spontaneous fusion of the subtalar joint.

2. Methods 

From 1976 to 2000, 14 cases of subtalar dislocations were treated in our institution. Medial dislocation had occurred in 11 patients and lateral in three. The injury was closed in six cases, open in eight (five of 11 medial dislocations, three lateral dislocations).

The average age was 34 years (18–73); there were nine men and five women. The most frequently involved foot was the right. Dislocations resulted from motor vehicle accidents in eight cases, from sporting trauma in three cases, and from falls in the remaining three cases.

Eight patients (three with open lateral and five with open medial dislocations) had associated fractures (three multifragment fractures of the talus, one fracture of metatarsals, one malleolar fracture, one fracture of the cuboid and two fractures of the posterior process of the talus).

In one case of lateral dislocation there was rupture of the posterior tibial artery and the saphenus vein.

The eight open dislocations received emergency surgical treatment with meticulous wound and soft tissue toilet, and reduction of the dislocation and associated fractures. In four cases, we used temporary osteo-synthesis with Kirshner wires. A plaster cast was applied for 4–6 weeks, depending on wound and soft tissue healing and the presence of associated fractures.

The closed dislocations were reduced under general anaesthesia in the emergency department and immobilized in a plaster cast for 4 weeks. No patient required open reduction.

At a mean follow-up of 6 years (2–25 years) the final outcome was assessed clinically and radiographically.

Clinical results were graded on a 100-points AOFAS ankle-hindfoot scale [2] (Table 1).

Table 1. Ankle-hindfoot scale (100 points total)

	Pain (40 points)
	• None	40
	• Mild, occasional	30
	• Moderate, daily	20
	• Severe, almost always present	0
	Function (50 points)
	• Activity limitations, support requirement
	∘ No limitations, no support	10
	∘ No limitation of daily activities, limitation of recreational activities, no support	7
	∘ Limited daily and recreational activities, cane	4
	∘ Severe limitation of daily and recreational activities, walker, crutches, wheelchair, brace	0
	• Maximum walking distance, blocks
	∘ Greater than 6	5
	∘ 4–6	4
	∘ 1–3	2
	∘ Less than 1	0
	• Walking surfaces
	∘ No difficulty on any surface	5
	∘ Some difficulty on uneven terrain, stairs, inclines, ladders	3
	∘ Severe difficulty on uneven terrain, stairs, inclines, ladders	0
	• Gait abnormality
	∘ None, slight	8
	∘ Obvious	4
	∘ Marked	0
	• Sagittal motion (flexion plus extension)
	∘ Normal or mild restriction (30° or more)	8
	∘ Moderate restriction (15°–29°)	4
	∘ Severe restriction (less than 150)	0
	• Hindfoot motion (inversion plus eversion)
	∘ Normal or mild restriction (75–100% normal)	6
	∘ Moderate restriction (25–74% normal)	3
	∘ Marked restriction (less than 25% normal)	0
	• Ankle-hindfoot stability (anteroposterior, varus-valgus)
	∘ Stable	8
	∘ Definitely unstable	0
	Alignment (10 points)
	• Good, plantigrade foot, ankle-hindfoot well aligned	10
	• Fair, plantigrade foot, some degree of ankle-hindfoot malalignment observed, no symptoms	5
	• Poor, nonplantigrade foot, severe malalignment, symptoms	0

Fifty points were assigned to function, 40 points to pain, and 10 points to alignment. A score of ≥90 was considered an excellent result; 80–89 a good result; 70–79 a fair result and <70 a poor result.

The range of subtalar joint motion was evaluated by using the method described by Inman and Mann [3] and compared with the contralateral foot.

The presence of degenerative arthritis in the subtalar or talo-navicular joints was noted on plain radiographs.

3. Results 

The average score was 74 points (60–91).

According to 100-points scale, we considered “excellent” or “good” the cases with no pain, unrestricted daily and recreational activities, no limp, nearly complete subtalar motion and a well aligned ankle-hindfoot.

Eight patients (57%) were included in this group with a mean score of 88 points.

Two of these patients also exhibited a fracture of posterior process of the talus. None of the eight patients showed roentgenographical signs of degenerative arthritis.

We considered “fair” the cases with discontinuous pain or discomfort, especially when walking on an uneven surface, a partial restriction of daily and recreational activities, and up to a 50% restriction of subtalar motion with respect to the uninvolved side (mean score 74).

Two patients (14%) were included in this group. Both of them had open lesions with associated fractures: a cuboid fracture and a fracture of the calcaneus.

Radiographic signs of degenerative arthritis were present involving the subtalar and/or talo-navicular joints.

The remaining four cases (four open dislocations) showed “poor” results (mean score 62).

Patients in the “poor” group complained of continuous pain, showed limitation of daily and recreational activities, lost more then 50% of subtalar motion with respect to the healthy side, and exhibited hindfoot instability. Severe degenerative arthritis of the subtalar joint requiring the use of an ankle brace or special orthosis was found in all four cases.

Results with regard to injury type showed that medial dislocations had a good prognosis (eight excellent or good results out of eleven) while lateral subtalar dislocations tended to be worse (three poor results out of three).

Open lesions had a less favorable prognosis (two excellent or good results out of eight) unlike closed injuries that exhibited a better outcome (100%).

None of the 14 patients had talar necrosis, infection, or redislocation.

Symptoms of reflex sympathetic dystrophy were present in three cases which resolved after 6 months of therapy with calcitonin and vitamin D.

4. Discussion 

Peritalar dislocation is a rare injury and represents about 1–1.5% of all traumatic lesions of the foot [4]. Generally it occurs at between 20 and 40 years with a higher prevalence for males.

Gui [5] distinguished four types of peritalar dislocation:

The mechanism of injury has been reported as severe inversion (medial dislocation) or eversion (lateral dislocation) of the foot.

In medial dislocation, an inversion force applied to a plantarflexed foot twists the tarsus first out of the talo-navicular joint and than out of the subtalar joint. The calcaneus is displaced medially, while the head of the talus appears dorsally. The clinical aspect of the foot resembles a club foot, thus the descriptive term “acquired club foot” [6].

In lateral dislocation the calcaneus is displaced laterally while the head of the talus lies medially. The clinical position of the foot is that of an “acquired flat foot” [6].

In general, the majority of subtalar dislocations can be treated by closed reduction on condition that it is recognized early after the injury. Usually the reduction is stable.

Surgical treatment should be carried out in open injuries or soon after the failure of closed reduction [7]. Small fracture fragments should be debrided from the joints, while large fragments should be anatomically reduced and rigidly fixed.

The need for open reduction has been reported to range from 10–38% [7], [8], [9].

The most common causes of irreducible medial dislocation are buttonholing of the extensor retinaculum or of the extensor digitorum brevis, entrapment of the talus in the talo-navicular capsule or talocalcaneal impingement by fractures of their articular surfaces [10], [11], [12]. A rare cause of irreducible medial dislocation, recently described by Heck et al. [13], was impingement of the deep peroneal nerve and dorsalis pedis artery.

The most frequent cause of irreducible lateral dislocation is entrapment of the posterior tibialis tendon as subluxes over the medial malleolus [14].

Our series showed no cases of irreducibility after gentle closed attempts at reduction. However, it should be noted that multiple attempts are not recommended because this can cause further soft-tissue injury.

The results of surgical treatment may appear to be quite unsatisfactory because almost half of our patients did not have good outcome. These findings are similar to those reported by other authors [7], [8], [9], [14], [15].

We would generally consider those requiring open surgery to be more severe injuries with a higher incidence of associated fractures and articular cartilage damage that increase the chance of a poor prognosis. Intraarticular fractures increase the likelihood of persistent arthritis while fractures of adjacent bones require prolonged immobilization which may result in persistent stiffness of the subtalar joint.

Stiffness of the hindfoot is the most common problem after subtalar dislocation.

In our series six patients (43%) exhibited a reduction of subtalar motion. The majority of these cases were associated with high-energy trauma, concomitant fractures or open injuries.

Avascular necrosis is a quite rare complicance in spite of the poor vascularization of the talus [7], [8], [9], [14]. No case was reported in our series.

Degenerative arthritis of the subtalar joint is a worse complication [10], [14], [17]. Signs of subtalar and talo-navicular damage were found in six patients.

We believe that the talo-navicular joint is probably involved secondarily because of the functional interrelationship between subtalar and midtarsal joints. Degenerative arthritis seems to be related to the type of dislocation, the amount of soft tissue injury, and the presence of associated fractures [14], [15], [16]. The high forces required to cause peritalar dislocation can create cartilaginous lesions that are not detected on radiographs but affect the patient's clinical outcome. Computed tomography is recommended because plain radiographs failed to diagnose the osteocondral fracture. As such, CT scans should be performed nowadays as a routine after closed reduction to show or exclude additional occult lesions.

None of our patients underwent fusion. Surgery was proposed to two patients but they refused.

Four patients presented instability of the hindfoot with recurrent giving way, reduced mobility and difficulty in weight bearing. It is unclear whether this is related to the length of cast immobilization (6 weeks) or the type of lesion.

Zimmer and Johnson [18] attribute the high incidence of instability (five of their eight cases conservately treated) to an inadequate period of immobilization (4 weeks). For this reason, they recommend a plaster cast for more than 4 weeks.

As prolonged immobilization can cause articular stiffness with loss of function [16], we consider a period of between 4 and 6 weeks an acceptable compromise.

In conclusion, medial subtalar dislocations occur much more frequently than lateral ones. Most of them can be treated with closed reduction, and have a favorable prognosis [7], [19], [20].

Lateral subtalar dislocations have a higher incidence of soft tissue damage and cartilaginous lesions, are frequently irreducible by closed procedure and tend to have a poorer outcome.

The accurate diagnosis of occult osteocondral fragments, immediate reduction, an adequate period of immobilization and, in the case of irreducibility, open reduction without delay are the most important factors to prevent poor results.