Spontaneous Patella Dislocation - Case Study Example

Case Study- Spontaneous Patella Dislocation Introduction Patella or knee cap is a sesamoid bone developed in the tendon of quadriceps muscle in the front of the knee. In fact, it is the largest sesamoid bone in the body. It rides in the groove of the lower femur called trochlea. Its main function is to coordinate the forces of the tendons of the knee joint by acting as a lever and pulley (1). During extension of the knee, the patella magnifies the force exerted by the quadriceps (1) by increasing the angulation of the line of pull on the leg. It is held in place by the fibrous capsule and various ligaments (lateral or fibular collateral ligament, medial or tibial collateral ligament, patella-fibular ligament, patella-tibial ligament and oblique popliteal ligament) attached to it along with the quadriceps tendon and the patellar tendon. Because of these, the patella slides only in the groove upwards and downwards. However, in full extension, the patella does not fit into the trochlear groove and lies over the smooth synovial tissue that overlies the supratrochlear tubercle (1). When the patella comes out of the groove abnormally, it is known as dislocation. Case history 20 year old Catherine Joseph was brought to the casualty on a Saturday morning after she developed severe pain in the right knee following twisting of the leg as she was rushing down the stairs while going to college. On admission to casualty, she reported severe pain over the right knee. She held her knee in flexed position and was unable to extend her right leg. On examination, Catherine’s right knee was swollen and there was some ecchymosis on the medial aspect of the knee joint. Palpation revealed tenderness over the adductor tubercle and prominent medial femoral condyle. Enquiry revealed no history of patella dislocation in the past. Apprehension test was negative. There was no family history of such a condition either. A diagnosis of acute spontaneous patellar dislocation was made in her. Tests ruled out neurological defects and vascular complications of that limb. Considering the fact that this is the first episode of dislocation of patella and there is no history suggestive of predisposition to dislocation, Catherine was managed conservatively. Prior to reduction, radiographs of the affected knee were taken and the possibility of any fracture ruled out. After that reduction was performed. Catherine was asked to lie down on her back and elevate her right leg. She was then asked to flex at the hip level as much as possible up to 90 degrees. Then, with one assistant applying pressure over the lateral aspect of the patella inwards, the surgeon straightened the leg by lifting gradually but firmly at the ankle. The patella could be brought back to place easily. No sedation was given for the procedure. Post reduction radiographs also ruled out any fractures. A splint was then applied (knee immobilizer) to the right knee joint in extended position and the patient discharged home with some analgesics. She was advised immobilization of that knee for 3 weeks followed by physical therapy for quadrilateral muscle strengthening. She was also advised not exceed optimal knee joint-loading capacities to prevent recurrence. It is almost 6 months since the trauma and Catherine has resumed back to normal activities. Discussion Dislocation of the patella occurs most commonly in the young. It is more common in females (2). However, among athletes, it is more common in males (1). The dislocation can occur either due to direct injury to the patella or due to twisting of the leg. In the former case, dislocation is usually associated with fractures. When dislocation occurs due to simple twisting of the leg, it is known as spontaneous dislocation which can be recurrent. During twisting, there is flexion and external rotation of the leg with simultaneous contraction of the quadriceps tendon which pulls the patella laterally (3). Spontaneous patella dislocation commonly occurs to the lateral side. Medial patellar dislocation is usually associated with direct trauma (3) or occurs as a surgical complication. In 28- 50% of dislocations, fractures are common (3) and hence the need fro pre-reduction radiographs. This is important because the intra-articular fragments, if not removed may cause degenerative arthritis (3). Also, patellar dislocation may be associated with fractures of proximal tibia or distal femur, or any neurological or vascular complications, in which case, reduction must not be attempted (4). One important aspect of treatment is the need to decide whether the patient should be managed conservatively or should be advised surgical intervention. This is because of the high incidence of recurrence in spontaneous dislocations. One in six patients with acute spontaneous dislocation will develop recurrent dislocation, the incidence of which decreases with age (5). In the age group 11 to 14 years, the incidence of dislocation is 60% (5). In 24% of spontaneous dislocations, there will be a positive family history of patellar dislocation (6). Spontaneous dislocation usually occurs due to inherent instability of the patella. This could be due to laxity of the ligaments keeping the bone in place as in Ehlers Danlos Syndrome, excessive femoral anteversion, external rotation deformity of tibia, patella alta where in the bone is high riding, patellar dysplasia, defective lateral trochlear margin and shallow femoral groove (1). The dislocation is almost always lateral. This is because of the outward angulation between the long axes of the thigh and leg. The dislocation is prevented by the lateral edge of the patellar articular surface of the femur which is actually deeper than the medial edge, and the insertion of the vastus medialis on the medial border of the patella which extends to a lower level than that of the vastus lateralis on the lateral border. While attempting patellar reduction, the first thing to do is to look for any obvious defect which has predisposed to the dislocation. After that, reduction must be attempted only after ruling out fractures by radiograph and palpation. In case of presence of fracture, reduction is not attempted and the knee is splinted as found and ice applied to the knee to reduce swelling. The patient should then be referred to the orthopedic surgeon for operative management. While transporting, the patient should be made to lie down in supine position with the injured leg elevated and flexed so as to relax the quadriceps muscle (3). In this position, lifting the straightened leg under the ankle while simultaneously applying firm pressure to the lateral aspect of the patella spontaneously reduces the dislocation (3). Post reduction, the patient will have relief of pain except for some tenderness along medial patellar and lateral femoral lines (3). Post reduction radiographs are necessary to rule out any osteochondral fractures (4). These fractures are often missed in pre-reduction radiographs. Reduction itself is a safe procedure and no complications usually occur due to it. Also, this reduction does not require any sedation. Post reduction, immobilization of the knee must be done for about 2- 3 weeks. Beyond this, immobilization is not advisable due to the risk of muscle atrophy, knee joint contractures and retropatellar crepitations (7). After the period of immobilization, the patient should undergo physiotherapy for quadriceps muscle contraction. Surgery must be considered in those with high risk for recurrent dislocation. Surgery involves medial patello femoral ligament and vastus medialis obliquus muscle repair (8). Various studies have shown the rupture of the medial retinaculum of the patella and injury to vastus medialis muscle in most of the cases (8-10). The risk factors for recurrent dislocation include osteochondral fracture of lateral femoral condyle, age less than 14, highly active athlete, palpable medial vastus defect, contralateral evidence of dysplasia, family history and patella alta (6). Magnetic resonance imaging and arthroscopy may be helpful in deciding who may need to go in for surgery. In a study by Sally and others (10), magnetic resonance imaging revealed effusion in 100% cases, tears of the femoral insertion of the medial patellofemoral ligament in 87%, increased signal in the vastus medialis muscle in 78%, lateral fem oral condyle   in 87% and medial patellar bone bruises in 30%. In the arthroscopic examination that they performed revealed osteo chondral lesions involving the patella and the lateral femoral condyle in 68% of cases. Surgical exploration revealed tears of the medial patello femoral ligament off the femur in 94% of the patients. Sally and colleagues (10) reported that 58% of the patients who underwent surgery involving medial patello femoral ligament returned to their previous sport with no or minor limitations. In those with no predisposition to recurrent dislocation, there is no benefit due to surgery (11). References 1. Malanga,GA. Patella injury and dislocation. [online] 2006 [Cited 2007 Sep10]; Available from URL: http://www.emedicine.com/sports/topic95.htm 2. Cash JD. Hughston JC. American Journal of Sports Medicine 1988;16(3):244-9. 3. Patellar reduction procedure. [Online] 2006. [Cited 2007 Sep10]; Available from URL: http://72.14.235.104/search?q=cache:a3PeBd0eVvwJ:www.adaweb.net/departments/paramedics/swo/1v.pdf+Patella+dislocation-+reduction&hl=en&ct=clnk&cd=4&gl=in  4. Rosh AJ. Joint Reduction, patella. [Online} 2007 [Cited 2007 Sep10]; Available from URL: eMedicine from WebMD. http://www.emedicine.com/proc/topic109263.htm 5. Fleming P, Connoly P, Rice J Mc Cormack D. Recurrent patellar dislocation- a review. [Cited 2007 Sep10]; Available from URL: http://www.iol.ie/~rcsiorth/journal/volume3/issue2/pat.htm   6. Abraham DJ, Miller F. Patellar dislocations. [online] 1996. [Cited 2007 Sep10]; Available from URL: http://gait.aidi.udel.edu/res695/homepage/pd_ortho/educate/clincase/patdis.htm 7. Maenpaa H, Lehto MU. Patellar dislocation. The long-term results of nonoperative management in 100 patients. Am J Sports Med. Mar-Apr 1997; 25(2):213-7 8. Ahmad, CS, Stein BES, Matuz, D, Henry JH. Immediate Surgical Repair of the Medial Patellar Stabilizers for Acute Patellar Dislocation. The American Journal of Sports Medicine 2000; 28:804-810. 9. Vainionpaa,S., Laasonen E, Silvennionen T Vasenius J and Rokkanen P.  Journal of Bone and Joint Surgery - British Volume 1990; 72-B(3): 366-369. 10. Sally PI, Poggi J, Speer KP, Garret WE. Acute Dislocation of the  Patella. A Correlative Pathoanatomic Study. The American Journal of Sports  Medicine 1996; 24:52-60.  11. Buchner M, Baudendistel B, Sabo D, Schmitt H. Acute traumatic primary patellar dislocation: long-term results comparing conservativeand surgical treatment. Clin J Sport Med. Mar 2005;15(2):62-6. Bibliography Abraham DJ, Miller F. Patellar dislocations. [online] 1996. [Cited 2007 Sep10]; Available from URL: http://gait.aidi.udel.edu/res695/homepage/pd_ortho/educate/clincase/patdis.htm Ahmad, CS, Stein BES, Matuz, D, Henry JH. Immediate Surgical Repair of the Medial Patellar Stabilizers for Acute Patellar Dislocation. The American Journal of Sports Medicine 2000; 28:804-810. Buchner M, Baudendistel B, Sabo D, Schmitt H. Acute traumatic primary patellar dislocation: long-term results comparing conservativeand surgical treatment. Clin J Sport Med. Mar 2005;15(2):62-6. Cash JD. Hughston JC. American Journal of Sports Medicine 1988;16(3):244-9   Fleming P, Connoly P, Rice J Mc Cormack D. Recurrent patellar dislocation- a review. [Cited 2007 Sep10]; Available from URL: http://www.iol.ie/~rcsiorth/journal/volume3/issue2/pat.htm Maenpaa H, Lehto MU. Patellar dislocation. The long-term results of nonoperative management in 100 patients. Am J Sports Med. Mar-Apr 1997; 25(2):213-7   Malanga,GA. Patella injury and dislocation. [online] 2006 [Cited 2007 Sep10]; Available from URL: http://www.emedicine.com/sports/topic95.htm Patellar reduction procedure. [Online] 2006. [Cited 2007 Sep10]; Available from URL: http://72.14.235.104/search?q=cache:a3PeBd0eVvwJ:www.adaweb.net/departments/paramedics/swo/1v.pdf+Patella+dislocation-+reduction&hl=en&ct=clnk&cd=4&gl=in Rosh AJ. Joint Reduction, patella. [Online} 2007 [Cited 2007 Sep10]; Available from URL: eMedicine from WebMD. http://www.emedicine.com/proc/topic109263.htm Sally PI, Poggi J, Speer KP, Garret WE. Acute Dislocation of the Patella. A Correlative Pathoanatomic Study. The American Journal of Sports Medicine 1996; 24:52-60. Vainionpaa,S., Laasonen E, Silvennionen T Vasenius J and Rokkanen P. Journal of Bone and Joint Surgery - British Volume 1990; 72-B(3): 366-369     Read More