Posterior dislocation of the hip associated with ipsilateral trochanteric fracture - a very rare case

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Posterior dislocation of the hip associated with ipsilateral trochanteric fracture - a very rare case

O. Alexa, B. Puha, B. Veliceasa, D. Pãduraru
Clinical case, no. 6, 2009
* Department of Orthopedics and Trauma, University of Medicine and Pharmacy Iasi, Romania
* Department of Orthopedics and Trauma
* Department of Anatomy


Introduction
Dislocation of the hip is usually caused by high-energy trauma. The indirect mechanism of injury occurs in car accidents, where the knee hits against the car board; the impact is transmitted through the patella and the femur, reaching hip level and pushing the femoral head towards the posterior. These dislocations are frequently associated with fractures of the femoral head or of the acetabulum, depending on the force of impact.
Apart from this association, fractures of the proximal femur can exceptionally occur with hip dislocation; due to their rarity, most of them are presented in literature as case reports. However, there are extremely few reported cases that describe a posterior hip dislocation associated with an intertrochanteric fracture in a previously healthy adult. Literature search revealed only few other such cases, all from distinct geographical areas.

Case presentation
A 41 years old male was admitted to emergency department after being involved in a car accident. He was in the right front seat and his car was hit by another driver that fell asleep behind the wheel; the impact was frontal. Among his chief complaints were: severe pain in his right hip and functional impotency in the right inferior limb. General examination showed a shortened right inferior limb, together with significant swelling of the upper thigh and an external rotation of the lower limb. No open wounds were noted in that region. Examination of the skeletal system also revealed important swelling in the right elbow and both the knees.
Standard radiographs in anterior-posterior (AP) incidence were performed after admittance; the x-rays revealed a posterior dislocation of the femoral head associated with an intertrochanteric fracture in the right hip (fig. 1.). The fracture was not associated with peripheral nerve damage nor with vascular lesions and no other fractures were noted. In order to better assess the extent of the damage and to better plan the treatment, a computer tomography (CT) was performed, together with a 3-D reconstruction of the right hip (fig. 2). CT examination confirmed the diagnosis and indicated the exact position of the femoral head (posterior and superior from the acetabulum) and the important displacement of the femoral fracture.
Next days after admittance, the patient underwent surgery in order to obtain both a reduction of the dislocation and a fixation of the intertrochanteric fracture. A closed reduction followed by external fixation was excluded due to the impossibility of maneuvering the femoral head back into the cotyloid cavity; open reduction remained the only possible option. The patient was placed in a supine position and under spinal anesthesia the hip was exposed by a lateral incision. For reducing the hip dislocation, maneuvering the femoral head back in place was necessary; in order to obtain it, the helicoidal instrument used in hip artroplasties for removing the femoral head was introduced through the fracture site in the superior femoral extremity and the dislocation was reduced. Afterwards, the trochanteric fracture was reduced and fixated with a Dynamic Hip Screw (DHS). After surgery, radiographs were performed in order to assess the results (fig. 3). On this image, a small fractured fragment displaced from the posterior wall of the acetabulum was noted; however, this fracture did not affect the stability of the hip reduction. The patient's subsequent progress was satisfactory. Eight days after the surgery he was discharged and after 45 days partial weight bearing walking was allowed. Follow-up one year after the surgery showed no signs of avascular necrosis of the femoral head.
Figure 1
Figure 2
Figure 3

Discussion
Hip dislocations are usually the result of high-energy trauma (car accidents). Typically, the driver or the passenger suffer a knee injury with the hip in flexion. The force of the impact is transmitted in the femoral axis, leading to a posterior dislocation of the femoral head; this is sometimes associated with fracture of posterior acetabular columns and/or femoral head fractures. Such injuries only occur if the femur is intact – otherwise the force of the impact cannot be transmitted to the hip joint. Although sometimes the energy of the trauma can lead to a diaphysar or subtrochanteric fracture, in such cases the dislocation of the hip is highly improbable.
Associations between hip dislocations and ipsilateral trochanteric or diaphysar fractures are extremely rare and they usually appear in literature as case presentations. More frequent by comparison, but still rare, hip dislocations can be associated with diaphysar femoral fractures. Wiltberger (1) estimated that the incidence of the association of hip dislocation and ipsilateral diaphysar fracture is 1/100,000 fractures.
In his research, Dehne (2) underlines the fact that to that moment only 19 such cases had been reported and 7 others only mentioned by literature. His paper described seven patients with hip dislocation and ipsilateral diaphysar fracture that he had treated and 9 others treated by different surgeons. Other authors have mentioned this type of lesion: Saxena (3), and Schoenecker (4) and three such cases have been reported in children – Barquet (5), Malkawi (6) and Yamamoto (7). Among these associations of lesions, the most frequently encountered type of dislocation is the posterior one. Anterior hip dislocations are rare in such circumstances, Sambandan (8) reporting there are only six such cases in literature, his being the seventh.
When discussing a diaphysar fracture associated with an ipsilateral hip dislocation, authors emphasize the importance of correct diagnosis for both lesions; most of the times, the hip dislocation is overlooked due to the fact that these situations occur in accidents following high-energy trauma and the surgical evaluation is mainly directed towards the femoral fracture. According to Dehne (2), out of 42 cases of diaphysar fracture associated with an ipsilateral hip dislocation, only 15 were correctly diagnosed; in 17 of these cases, the dislocation was overlooked and in the other 10 cases the time of diagnosis for the dislocation is not mentioned.
The association between trochanteric fractures and ipsilateral hip dislocations are even less mentioned in literature. Korovessis (9) and Maruoka (10) each present such a case involving anterior dislocation and fracture of the greater trochanter. The treatment consisted in orthopedic reduction of the hip dislocation followed by open reduction of the greater trochanter; they reported excellent short and long-term results. This association can be explained because the mechanical axis of the femur remains intact after the greater trochanter fracture, thus creating the premises for the hip dislocation.
Associations between hip dislocations and inter-trochanteric fractures are extremely rare; literature search reveals only 3 similar cases. Barquet (11) presented an association between a fracture-dislocation of the femoral head and an ipsilateral fracture of the trochanter and femoral diaphysis. According to Singh (12), his 2006 case presentation of an association between inferior hip dislocation and inter-trochanteric ipsilateral fracture was the first one mentioned in literature. The treatment consisted in an open reduction of the hip dislocation, followed by fixation with DHS of the trochanteric fracture.
To a certain extent similar to the case we report, Agarwal (13) describes for the first time a case in which the posterior hip dislocation was associated with a comminutive ipsilateral trochanteric fracture. Author’s first approach consisted in an attempt of orthopedic reduction with the aid of a Schanz screw. Because this method proved to be unsuccessful, the dislocation was treated by open reduction through a lateral approach, and it was followed by the reduction of the trochanteric fracture and fixation with a Dynamic Hip Screw. Singh (14) presents a case similar by mechanism, only the fracture interested the subtrochanteric region.
Regarding treatment, Sir Astley Cooper (1824) was the first to suggest a successful approach. Today, most authors recommend an open reduction of the femoral fracture and an orthopedic reduction of the dislocation. If the latter is diagnosed 2-3 months after its occurrence, an open reduction is necessary and in some cases a shortening of the femoral diaphysis is required in order to compensate the tensions that have appeared due to muscle retraction. The most frequent complication of such cases is represented by the aseptic necrosis of the femoral head, depending on how much time has passed between the occurrence of the injury and the reduction of the dislocation. According to most authors, performing an open reduction for the hip dislocation could also increase the chances of developing this complication.

Conclusions
This case presentation is important due to the rarity of the injury. Usually such traumas lead to either hip dislocation or femur fracture. The association of the two is atypical and hard to explain through common mechanisms. Taking into account the increase of trauma due to car accidents, these unusual injuries will become more and more frequent, modifying present concepts for hip dislocation mechanisms.

References
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