Bilateral recurrent discloation of the patella associated with below knee amputation: A case report
© Batra et al; licensee BioMed Central Ltd. 2005
Received: 22 July 2004
Accepted: 17 February 2005
Published: 17 February 2005
Recurrent dislocation of the patella in patients with below knee amputation is a known entity. Abnormally high-riding patella (patella alta) and medial patellofemoral ligament insufficiency in these patients predisposes them to patellar instability. The established treatment of this problem is surgical realignment.
A 25 year old male patient with bilateral below knee amputation presented with bilateral recurrent dislocation of the patella while walking on knees on uneven ground. Clinical and radiographic studies showed patella alta. A simple shoe modification was used to treat this patient.
A simple shoe modification can be used to treat such a condition which is otherwise treated surgically.
Recurrent dislocation of the patella can follow a violent initial dislocation, but occur more often in knees with one or more underlying anatomic abnormalities that predispose the patella to dislocation or subluxation. In these knees, less trauma is needed for dislocation to occur. The underlying pathologic condition causes an abnormal excursion of the extensor mechanism over the femoral condyles. High-riding patella (patella alta) and a damaged medial patellofemoral ligament at the time of first episode of dislocation leads to such an abnormality and leads to recurrent dislocation of the patella [1–4]. Patella alta has been reported in patients with below knee amputation using patellar tendon bearing prosthesis. The usual treatment in these cases is surgical reconstruction. We present a case of bilateral recurrent dislocation of the patella with below knee amputation which was managed conservatively.
High-riding patella (known as Patella alta) leads to patellar instability . In the presence of such instability, sudden laterally directed forces can lead to dislocation of the patella. The first episode of lateral dislocation of patella invariably damages the medial patellofemoral ligament (MPFL) which is the primary passive restraint to lateral patellar displacement[4, 5]. An injured MPFL leads to further instability and both the factors combined predispose to recurrent dislocation of the patella. In below knee amputees using patellar tendon bearing (PTB) prosthesis, the prolonged, upwardly directed force against the patellar tendon gradually elongate the tendon and produce patella alta [2, 3]. It takes a long time for such an instability to develop. The first incidence of patellar dislocation occurred after 5 years of amputation in our patient. Similar time lag was described by Mowery et.al. in his patients where the time lag was from 5–13 years .
The patient described here used to walk on knees for certain emergent and short mobility in-house activities e.g., going to toilet especially at night, going to kitchen etc. As most of rural houses in developing countries do not have cemented floors, walking on uneven ground cannot be prevented. Walking on knees in such conditions produces eccentric forces on the patella. Sudden laterally directed forces which might result when the knee strikes some elevated surface on medial side can lead to dislocation of patella in patients with patellar instability.
Walking on knees is usually discouraged in below knee amputees as it can lead to flexion contractures of the knee joint. In cases of bilateral amputees it is not always possible for the patients to wear prosthesis on both sides in emergency situations as discussed above. Considering these points, the occasional walking on knees could not be avoided in this patient. Surgical correction of instability would not have helped much as walking on knees on uneven ground could have nullified the results of surgery. A modified well moulded shoe was given to the patient for walking on knees that prevented any eccentric forces and protected the patella against dislocation.
6 months follow-up results were excellent in this patient with no episode of dislocation on either side. The patient was very comfortable in using the shoes as it takes him only 15 seconds to wear them. Hence a simple low cost shoe modification has been used to treat a condition which is mostly treated surgically.
Recurrent dislocation of the patella in cases of below knee amputees using patellar tendon bearing prosthesis is very rare and the usual treatment is surgical realignment. To our knowledge no case of bilateral recurrent dislocation of the patella in below knee amputees has been described in the literature. A simple shoe modification can be used in difficult situations to treat such a condition.
Written consent was obtained from the patient for publication of study.
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- The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1471-2474/6/9/prepub