The occurrence of bipartite patellar disruption simultaneously with quadriceps tendon avulsion is an extremely rare injury which is often misdiagnosed as a patellar avulsion fracture. We present our case of bipartite patellar disruption and quadriceps avulsion which we treated in our institution with open reduction and internal fixation of the bipartite component and anchor repair of the tendon component.

A 45-year-old male, fence erector (weight: 108 kg, height: 178 cm) presented to Accident and Emergency Department after slipping on a mat and impacting his left knee on a concrete step. He had no significant medical history. His main complaints were anterior knee pain, swelling and inability to weight bear. He scored 5/10 for both subjective and objective pain scores. It was an isolated injury and on examination, his knee injury was closed. The knee was significantly swollen and tender, more so over the pre-patellar and supra-patellar regions. The patient was able to actively flex his knee but could not demonstrate straight leg raise. However, any movement was very painful, (scored 3 on the baseline score admission on moving). Left hip and ankle examination were normal and no neurological abnormalities were detected. The patient received 60 mg codeine phosphate, 1 g paracetamol and 400 mg ibuprofen orally as pain relief.

Anterior posterior and lateral radiographs of his left knee were obtained and these showed a superolateral patellar bipartite fracture. (Figure 1A-B) The patient denied having any injury to his patella prior to the incident. The patient was diagnosed with quadriceps tendon avulsion and bipartite patella through clinical examination and radiographic evidence.

Operative treatment was discussed with the patient and informed consent was obtained. The patient was treated surgically under general anaesthetic in the supine position. Tourniquet was used for 90 minutes during the operation. A longitudinal midline incision approach was used. Operative findings included a complete tear of quadriceps tendon at its insertion to the patella with disruption of the bipartite patella which had displaced a result of the injury. (Figure 2) The displaced fragment of the bipartite patella was judged to be significant in size therefore reduced to its anatomical position and internally fixed to the main patellar fragment using two 4.0 mm ASNIS screws under direct intraoperative X-ray control. (Figure 3) The distal quadriceps tendon then was repaired into the superior pole of patella using two 5.0 mm Miteck anchors. Repair of the retinaculum on the sides was completed using 2.0 Vicryl. The wound was closed in layers with Vicryl and Monocryl with the knee in slight flexion. The knee was then placed into a cylinder splint and he was scheduled to a follow-up clinic. Meanwhile he was encouraged to do range of motion ankle exercises.

Follow-up at nine month revealed that the patient was back at work which involves heavy lifting. The patient described painless walking on flat surfaces but described slight pain on walking quickly. On examination patient appeared to walk normally. There were no palpable gaps around the suprapatellar region or along the extensor mechanism and no bony tenderness over the patella or over the tendon. He could fully straighten his knee and do active straight leg raise comparable to the contra lateral side. Fully flexion of his knee was possible without discomfort and there was no joint effusion or joint line tenderness. Anterior drawer test and Lachman test were negative and the posterior cruciate ligament and collaterals were clinically stable. McMurray test was negative for both menisci. Check X-rays were also normal. (Figure 4A-B) There was also no evidence of distal neurovascular deficit. However, the patient did have an area the size of a penny over the lateral aspect of the scar that was hypersensitive. This is likely to be due to the midline knee approach.

The occurrence of bipartite patella simultaneously with quadriceps avulsion is an uncommon injury which is often misdiagnosed as a patellar avulsion fracture. [1]

Bipartite patella occurs when the secondary ossification centre of the patella fails to fuse with the primary center. [1] It has an incidence of 2-6%, with males having a higher predisposition rate (8:1). [2] It occurs bilaterally in 43% of patients with bipartite patella. [2] However, usually it is asymptomatic (98% of cases). [3] [4] Bipartite patella is often diagnosed incidentally by plain radiographs. [3] [5]

Direct trauma may disrupt the synchondroses, causing irritation and inflammation which manifests with fracture like symptoms. Onset either occurs gradually or immediately after the injury. [6]

Common symptoms of inflamed/irritated bipartite due to trauma include; anterior knee pain, swelling of the synchondrosis and painful range of motion of the knee. [5]

In 1943, Saupe developed a classification system describing the three types of bipartite patella. (Table 1) [7] [8]

For fractured bipartite patella, if there is an extra articular fragment it can be excised, however if there is an intra articular fragment open reduction and internal fixation is advised. [2] [9] [10] [11] Different methods of internal fixation are described in literature including tension band wiring, using parallel interfragmentary lag screws and the combination of tension band wiring with cannulated lag screws. Biomechanical evaluation of different approaches has reported that patellar fractures stabilized with screws were significantly less likely to displace than the tension band technique. [12] The preferred method for this patient by the operating surgeon was fixation with interfragmentary screws.

A diagnosis of quadriceps avulsion is obtained through a full history and examination. It characteristically presents with a triad of pain, supra patellar gap and a loss of extensor mechanism of the affected leg. [13]

There are several diagnostic imaging mediums such as plain radiographs, magnetic resonance imaging (MRI) and ultrasound. Plain radiographs should be the initial tool used as they demonstrate a good overall view, show loss of quadriceps and supra patellar mass etc. MRI scan is the most effective in establishing injury pattern. [14]

The treatment for incomplete quadriceps avulsion is non operative, immobilization in extension followed by a physiotherapy program. [14] [15]

Complete rupture/avulsion indicates prompt surgical management within 72 hours, which yields best results according to literature. [15] [16] [17] Most patients obtain a good range of motion but some may have persistent weakness preventing them from carrying out strenuous exercise. [17]

Delay in surgery of more than 72hrs gives suboptimal results due to quadriceps tendon retraction and patella bafa. [18]

Although bipartite patella and quadriceps avulsion is rare, repairing the avulsed tendon with fixation of the bipartite fragment in our case resulted in a good outcome. Therefore we can recommend this method of treatment in such an injury.

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