B George, R S Gaheer, A Ratnam

Address for Correspondence

B George
Orthopaedic Department,
Dumfries and Galloway Royal Infirmary,
Dumfries, UK.

Subcapital and intertrochanteric fractures of the femur are amongst the most common injuries encountered in orthopaedic practice. However a combination of these injuries has rarely been reported. Simultaneous presentation of both these fractures on the same side has been reported only once[i]. There have been few reports where a subcapital fracture occurred after internal fixation of an intertrochanteric fracture. We report a case of a subcapital fracture occurring after removal of dynamic hip screw in a healed pertrochanteric fracture. This was subsequently treated with a cemented hemiarthroplasty.

J.Orthopaedics 2007;4(1)e14

Case report

A 73-year-old patient presented to us with a pertrochanteric fracture. This was treated promptly by closed reduction and DHS fixation(fig 1a,b). She made an uneventful recovery following the operation and was discharged home after adequate mobilisation. However 5 years after the DHS fixation she attended orthopaedic clinic with lateral thigh pain. Check Xrays at this stage showed the fracture to be healed (Fig 2a,b)and the pain was thought to be implant related. Blood tests done at this stage did not suggest an infective cause to symptoms. As this pain was unrelieved in the following months it was decided to remove the implant. This was done as an elective procedure following which she started mobilising without any pain. Few weeks later she re-presented to orthopaedics with sudden onset of hip pain. X-rays taken showed that she had a fracture of the subcapital region of the femur (fig 3). No history of trauma was forthcoming. It was decided to go ahead with a cemented hemiarthroplasty (fig 4) of the hip, following which she was again discharged home.

Discussion

The aetiology of subcapital fracture following fixation of pertrochanteric fracture is not well known5. There seems to be two main categories of these fractures- with the implant insitu and after implant removal. Attempts have also been made to understand the role of different types of implant.  (Fixed Vs dynamic) Various possible explanations have been put forward by different authors. Tronzo postulated that stress fractures at the tip of fixed implant could occur. He reported two cases where Jewitt nails were used to treat intertrochanteric fractures[vi]. Suggestions that a dynamic hip implant would prevent these complications[vii] have been proven wrong as subsequent reports of similar fractures after DHS has come out 2,[viii],[ix]. Poor positioning of the screw in a DHS has been suggested as a cause of subsequent fracture of the neck of femur[x].

Reports of subcapital fractures occurring after the removal of a pertrochanteric fracture fixation device is even rarer and more difficult to explain with the above postulations. Buciuto et al reported seven patients with such fractures5. (3 following DHS and 4 following blade plate). They however did not give any possible explanation to the occurrence of such fractures. Taylor et al reporting a similar case postulated that significant local osteoporosis can occur in a hip protected by the implant, and subsequent minor trauma after implant removal may cause a fracture to the hip2.  Removal of implant itself may cause the inferior portion of the neck to be compromised if the screw was placed too inferiorly in the first place. Retrospectively analysing our case we believe this may be a possible explanation in our case.

        Fig 1a.                 Fig 1b.                 Fig 2a.                   Fig 2b.

                                      Fig 3.                       Fig 4.

Conclusion

Although very rare, these complications discussed above are very significant once they occur and necessitate another major operation in most cases. With an ageing population we are likely to see more and more of such complications. Whatever be the possible cause of these unusual fractures,  the surgeon needs to be aware of these complications and a period of protected weight bearing may be indicated in selected patients following implant removal from the  hip.

Reference :

This is a peer reviewed paper 

Please cite as : B George:Spontaneous femoral neck fracture after removal of Dynamic Hip Screw

J.Orthopaedics 2007;4(1)e14

URL: http://www.jortho.org/2007/4/1/e14

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