CASE STUDY 14 Acute patellar dislocation in adults What are the reasons for the first acute dislocation? How can we document the pathoanatomy? What is our treatment concept? Table CS14 Patellofemoral joint examination Diagnostic clues Findings Diagnostic clues Findings Pain Diffuse patellofemoral Patellar apprehension Severely positive to lateral joint Tenderness Diffuse, medial more Q angle Normal value than lateral Effusion Haemarthrosis Catching Sometimes Swelling Diffuse Locking Sometimes with osteochondral fragment Patellar position, Lateralization after Range of motion Flexion decreased relaxed, 0 reposition Patellar position, contracted, 0 Lateralization Radiographs Normal or dysplastic trochlea, bone fragment Patellar position, 30 Often not enough flexion Other Weakness of the quadriceps muscle Patellar mobility Increased to lateral Patellar gliding mechanism Unstable, painful Patellofemoral Disorders: Diagnosis and Treatment. Edited by Roland M. Biedert 2004 John Wiley & Sons, Ltd ISBN: 0-470-85011-6
228 CASE STUDY 14 ACUTE PATELLAR DISLOCATION IN ADULTS History This 26 year-old male sustained a direct trauma to his left patella from the medial side, thus producing a first complete patellar dislocation to lateral. Reposition of the patella was necessary under anaesthesia in the emergency room. Comments Even moderate violence may be sufficient to cause an inherently weak patellofemoral joint to dislocate. Often it is difficult to state whether pathological conditions, such as patella alta, dysplastic trochlea, torsional abnormalities of the lower extremity or ligament laxity, are responsible for the resultant instability of the joint. 1 3 Physical examination and additional investigations help to determine the underlying pathoanatomy. Course of action Figure CS14.1 Excessive haematoma after complete lateral patellar dislocation (anteroposterior view, left knee) Physical examination Before repositioning, the dislocated patella lay laterally beside the femoral condyle and the trochlear groove was empty. After repositioning, the patella was slightly lateralized. Excessive haemarthrosis is frequent (Figure CS14.1). This, together with the pain, weakens the quadriceps activity and severely decreases knee flexion. Palpation is especially painful over the injured medial soft tissue structures. Radiographs Before repositioning, anteroposterior and axial views showed a completely dislocated patella. After repositioning, the anteroposterior view may show slight lateralization of the patella (ruptured medial structures). The lateral view may reveal a dysplastic trochlea (Figure CS14.2).The axial view may show an osteochondral fragment (Figure CS14.3). Figure CS14.2 (lateral view) Axial CT evaluation Dysplastic trochlea with crossing sign Axial CT scans are helpful to analyse the congruence of the patellofemoral joint and the form of
PLAN 229 the lateral side. These were the indications for the surgical intervention. After a lateral parapatellar incision, the patellofemoral joint was already open on the medial side, caused by the complete ruptures of the retinaculum and the medial patellofemoral ligament (Figure CS14.4). This facilitated access to the joint through the medial posttraumatic gap. Inspection of the joint revealed a dysplastic trochlea with a completely flat lateral femoral condyle (Figure CS14.5). These findings determined the following surgical steps: Figure CS14.3 Osteochondral fragment lateral to the femoral condyle after complete patellar dislocation (radiograph, axial view, left knee) the trochlea. 3 5 In cases with severe soft tissue injuries on the medial side documented by MRI, CT scans are not mandatory for surgery, because the indication for open revision and reconstruction is already given. Raising the lateral femoral condyle (Figure CS14.6). Removing the osteochondral fragment. Suturing and reconstructing the medial stabilizing structures (see Case Studies 6 and 13). Lengthening the lateral retinaculum (see Case Studies 6, 8, 13 and 18). Special considerations Acute and first complete patellar dislocations may be treated conservatively or operatively. Indications for a surgical intervention are excessive soft tissue injury on the medial side, such as rupture of the medial patellofemoral ligament, retinaculum and aponeurosis of the vastus medialis obliquus muscle, osteochondral fractures, massive haemarthrosis and dysplastic trochlea. Nonsurgical treatment often leads to unsuccessful healing and habitual patellar dislocations. 3,6,7 However, the results of the nonoperative treatment depend on the quality of conservative management and the underlying pathoanatomy. 8,9 Plan The aim of the treatment is to stabilize the patella and to eliminate the risk of further dislocations. The radiographs of this patient showed a dysplastic trochlea and an osteochondral fragment on Figure CS14.4 Intraoperative anteroposterior view showing the ruptured soft tissue structures on the medial side (left knee)
230 CASE STUDY 14 ACUTE PATELLAR DISLOCATION IN ADULTS Figure CS14.5 Intraoperative anterolateral view showing the flat dysplastic trochlea (patella retracted with hooks to lateral; left knee) Timeline Hospital 5 7 days Mobilization 2nd day Weightbearing Partial 10 kg for 4 weeks Complete After 6 weeks, depending on healing of osteotomy and muscular control Brace Sometimes With excessive soft tissue injuries Sports Bicycle After 4 weeks Everything Depends on final result but not before 4 months Figure CS14.6 Intraoperative anterolateral view of the reconstructed trochlea after raising the lateral femoral condyle. Note the normal trochlear groove, improving the osseous stability of the patella Postoperative care and rehabilitation Goals Stabilization of the patella. Protection of the healing of the medial and lateral soft tissue structures and the osteotomy. Dynamic muscular balancing of the patella in the trochlea. Summary The presented case describes a clear diagnostic situation. The keypoints are the predisposing factors. Precise evaluation of the real pathoanatomy is mandatory for the selection of treatment and the prevention of redislocations. Surgical treatment is recommended when an obvious pathology is documented and the risk for the development of habitual patellar dislocations is high. 3,8,9 References 1. Macnicol MF (1986) The Problem Knee. London, William Heinemann Medical Books 2. Hutchinson MR, Ireland ML (1995) Patella dislocation. Physician Sportsmed 23: 53 60 3. Biedert RM (2002) Patellaluxation beim Kind und Jugendlichen. Sportorthopädie-Sporttraumatologie 18: 164 168 4. Biedert RM, Gruhl C (1997) Axial computed tomography of the patellofemoral joint with and without quadriceps contraction. Arch Orthop Trauma Surg 116: 77 82
SUGGESTED READING 231 5. Martinez S, Korobkin M, Fondren FB et al (1983) Diagnosis of patellofemoral malalignment by computed tomography. J Comput Assist Tomogr 7: 1050 1053 6. Vainionpää S, Laasonen E, Silvennoinen T et al (1990) Acute dislocation of the patella. A prospective review of operative treatment. J Bone Joint Surg Br 72: 366 369 7. Mäenpää H, Matti U, Lehto UK (1997) Patellar dislocation. The long-term results of nonoperative management in 100 patients. Am J Sports Med 25: 213 217 8. Arnbjornsson A, Egund N, Rydling O et al (1992) The natural history of recurrent dislocation of the patella. Long-term results of conservative and operative treatment. J Bone Joint Surg Br 74: 140 142 9. Atkin DM, Fithian DC, Marangi KS et al (2000) Characteristics of patients with primary acute lateral patellar dislocation and their recovery within the first 6 months of injury. Am J Sports Med 28: 472 479 Suggested reading Mäenpää H, Matti U, Lehto UK (1997) Patellar dislocation. The long-term results of nonoperative management in 100 patients. Am J Sports Med 25: 213 217 Vainionpää S, Laasonen E, Silvennoinen T et al (1990) Acute dislocation of the patella. A prospective review of operative treatment. J Bone Joint Surg Br 72: 366 369