Osteochondral impression fracture of the patella after sports collision injury

Abstract

This article reports a case of a teenager who suffered a frontal collision sports injury. Computed Tomography (CT) revealed a fracture of the inferior pole of the patella without obvious displacement and retro patellar cortical impression with 5 mm step off. Surgical intervention was performed using β-tricalcium phosphate (β-TCP) and 3.0 cannulated screw fixation.

At 3-month follow-up, the wound showed good healing. No pain was observed. The patient was able to flex up to 100° with full extension. There were no signs of hydrops with full stability of the knee.

Good postoperative results can be obtained in osteochondral impression fractures of the patella using surgical intervention to elevate the osteochondral fragment, graft it with β-TCP and raft it with 3.0 cannulated screws.

Background

Patellar fractures are relatively rare, covering approximately 1% of all fractures.¹ Patients usually present with swelling of the knee, pain and an inability to raise the extended leg. Further diagnostics include X-ray. The Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association classification system differentiates 3 main categories, based on the involvement of articular cartilage and constellation of the fracture. Transverse fractures are often caused by a forced extension of the leg against maximum contraction of the quadriceps muscle. A direct anterior force on the patella results in a longitudinal fracture, which often involves comminution.² A recent review recommends fixating transverse fractures using non-absorbable braided suture tension bands in a ‘figure of 8’.³ Another review recommends screw fixation of vertically oriented fractures.⁴ Comminuted fractures should be treated using a minifragment locked neutralisation plate and screw fixation of fragments. Patellectomy should be avoided as it alters the function of the extensor mechanism.^{4 5} All methods aim to regain function of extension and anatomically reconstruction of the articular surface to prevent anterior knee pain and patellofemoral osteoarthritis. To our knowledge, little literature is available on the preferred surgical method of osteochondral impression fractures of the patella. Therefore, the aim of this report is to outline a specific case about a patellar cortical impression fracture, to describe the surgical technique used and to display the postoperative management and outcomes.

Case presentation

A female teenage patient presented on the emergency department. She suffered a frontal collision sports injury during soccer earlier the day. The injury was followed by immediate pain in her left knee and inability to bear weight on her left leg. History and family history were unremarkable. Physical examination showed a significant swelling of the left knee with a superficial abrasion anterior of approximately 4 cm. There was pressure pain on the patella. There was no pain in femur, tibia or fibula. Her stretch function was intact. Range of motion of the knee was painful and severely restricted. There were no abnormalities in the knee stability tests. There were no neurovascular abnormalities. Due to the mechanism of injury and the complaints she presented with, there was an indication for further examination using conventional radiography.

Investigations

Conventional radiographs (figures 1 and 2) showed significant effusion of the suprapatellar bursa with a patellar fracture of the caudal part. CT of the left knee revealed joint effusion/haemarthros with a fracture of the inferior pole of the patella without obvious displacement. In addition, a retro patellar cortical impression from mid to lower pole extending from the medial retro patellar facet with step off 5 mm was observed (figures 3 and 4). The distal femur, proximal tibia and fibula did not show any abnormalities. No loose intra-articular fragments were observed.

Figure 1.

Left knee Anterior Posterior (AP) X-ray.

Figure 2.

Left knee lateral X-ray showing effusion of the suprapatellar bursa with a patellar fracture of the caudal part.

Figure 3.

Left knee sagittal CT scan showing joint effusion/haemarthros with a fracture of the inferior pole of the patella with a retro patellar cortical impression from mid to lower pole extending from the medial retro patellar facet with step off 5 mm.

Figure 4.

Left knee CT reconstruction showing joint effusion/haemarthros with a fracture of the inferior pole of the patella with a retro patellar cortical impression from mid to lower pole extending from the medial retro patellar facet with step off 5 mm.

Differential diagnosis

Surgery was indicated based on the location of the impression on the patella and the risk of cartilage damage of the trochlea in a young patient. Operative treatment was chosen in shared decision making with the patient and her parents. An extension splint was fitted awaiting surgery. The operation was scheduled 15 days postinjury.

Treatment

Cefazolin based on weight was administered preoperatively. A longitudinal incision over the patella was made with diathermic detachment of the medial retinaculum (Peyer approach). The medial lower pole fracture was identified. A small medial arthrotomy of 2 cm was made. Step-off was clearly visible. Through the inferomedial side, the distal fragment could be brought back to normal height with the use of a chisel. β-TCP (ChronOs DePuy Synthes, Paoli, California, USA) was used to fill the gap and to hold the fragment in position. Peroperative fluoroscopy (figure 5) showed the defect filled with β-TCP crystals. Fixation (rafting technique) was carried out with a 3.0 cannulated screw under imaging guidance with good position (figure 6). Additionally, a crossed screw from caudal to proximal subchondral was introduced to adequately support the osteochondral fragment (figure 7). Fluoroscopy (figure 8) showed adequate screw and fracture position. The wound was rinsed and closed in layers, with tightly closing the synovium/Hoffa over the remaining small portion of the inferior defect to prevent dislocation of the β-TCP crystals.

Figure 5.

Intraoperative X-ray with β-TCP crystals in place. (β-tricalcium phosphate)

Figure 6.

Intraoperative X-ray after placing first 3.0 cannulated screw.

Figure 7.

Intraoperative X-ray after placing second 3.0 cannulated screw.

Figure 8.

Intraoperative control X-ray with adequate screw and fracture position.

Outcome and follow-up

Postoperative treatment consisted of full extension in an extension splint for 2 weeks. Load mobilisation was allowed. The patient was seen at the outpatient department 2 and 6 weeks postoperatively for wound control and clinical examination with radiographic evaluation. The extension splint was built up to flexion after 2 weeks with 30° every 2 weeks. Wound inspection showed no signs of infection. At functional control, the patient complained about stiffness of the knee joint. There was no pain. Physical examination showed no signs of infection or hydrops. The patient was able to flex the leg up to 50° and to lift the leg in straight position. All ligaments were stable. Control X-ray (figures 9–11) showed good position of the osteosynthesis material with no signs of complications. Physiotherapy was intensified, and the patient was allowed to mobilise without brace. After final examination at 3 months, the patient was able to flex up to 100° with full extension. There was no hydrops with full stability of the knee. No pain was observed.

Figure 9.

Postoperative control X-ray showing no signs of complications with good screw placement and fracture consolidation.

Figure 10.

Postoperative control X-ray showing no signs of complications with good screw placement and fracture consolidation.

Figure 11.

Postoperative control X-ray showing no signs of complications with good screw placement and fracture consolidation.

Discussion

Patellar fractures are a relatively rare but could lead to large implications when treated suboptimally. A recent study found poor outcomes (Lysholm scores) for 61% of the patients treated conservatively for minimally displaced patellar fractures.⁶ Gesslein et al ⁷ found improved clinical outcomes at midterm to long-term follow-up in patients with refixation of osteochondral fractures of the patella compared with debridement.

Surgical treatment should aim to re-establish function and anatomy of the intra-articular chondral surface, thereby preventing patellofemoral osteoarthritis. This can be achieved by either using cannulated screws, ‘figure of 8’ suture bands or a minifracture plate, depending on the comminution and orientation of the fracture. The advised surgical approach is by a midline incision in the case of non-comminuted patellar fractures.³ Currently, the interest in arthroscopic-assisted fixation of fractures around the knee is growing because of different advantages. These include patellar articular surface visualisation,⁸ easy removal of loose bodies or small intra-articular fragments,⁹ rinse and removal of haemarthros,¹⁰ which can also lead to pain relief and assessment that the screw does not interference with the articular surface.⁹ The thought is that these advantages lead to a better anatomical reduction of the fracture fragment with better outcomes with respect to development of patellofemoral osteoarthritis. Mei et al ¹¹ also recently concluded arthroscopic management of simple patellar fractures with percutaneous minimally invasive Kirschner wire tension band fixation as an effective method for management of patellar fractures. All these articles mentioned almost always concern transverse, longitudinal or oblique patellar fractures. In our case, it concerns an osteochondral impression fracture with step off resulting in an incongruent intra-articular chondral surface, which urged surgical repair. In this specific case, it was deliberately chosen to perform mini-open surgical treatment, because of the need for grafting of the defect. This mini-open approach ensured good visibility of the defect and articular surface reconstruction. Arthroscopy was not performed in this case as trauma mechanism, clinical findings and additional CT images did not raise suspicion of additional intra-articular injuries. In cases where no bone grafting would be indicated or when additional injuries are suspected, arthroscopic treatment of osteochondral impression fractures of the patella might be of interest. This needs further exploration in the future, as currently, there is no specific literature available on this type of treatment.

There is literature on impression fractures of the tibia plateau (Schatzker type 3¹²). In this type of fracture, the fragment is often repositioned using a chisel and held in place with bone graft and screw fixation.¹³ In addition, the use of allometric bone graft putty or bone allografts to resurface the articular cartilage show good results.^{14 15} In concordance with this type of fracture and operative technique, we performed surgery with the use of β-TCP and canulated screw fixation to restore function of this specific case with an osteochondral impression fracture of the patella.

Patient’s perspective.

I still remember that I fell on the ground in concerned match. I had a lot of pain in my knee. I was carried out off the field because I could not stand on my leg at that moment. I cooled my knee, and I was able to watch the game quietly while sitting on the bench. I called my parents to pick me up and when they arrived my knee was very thick and swollen. Because of that we decided to go to the hospital. When we arrived there, I got all kinds of tests and exams. I noticed that they staff on the emergency department did not quite get what was going on and what they needed to do for me. After I got the x-ray, I needed a CT scan. First, I was told that I would get a splint, but later on they told me that I might have to go to surgery. That was a bit scary to hear. A consultation with the orthopaedic surgeon followed. My mother and I were told that the orthopaedic surgeon advised an operation to restore the damage. Because this decision was decided with several orthopaedic surgeons and because that they discussed the pros and cons very extensive with us, the operation felt like a good choice.

The operation took place two weeks later, because of the swelling and because they wanted to have a certain orthopaedic surgeon with experience with this kind of surgery. On the one hand, we thought it was a complicated procedure, which made it exciting for me. On the other hand, it was also reassuring that an experienced person would operate on me. The surgery went well, and I was allowed to go home the same day. Afterwards we found that very quickly because I did not really know what to expect. I was in quite a lot of pain, I could not climb the stairs at home and did not had any walking aids. Fortunately, we received help from a befriended physiotherapist, which was very nice.

My knee was very stiff at first, but with intensive physical therapy I made small progress every week. Now, 6 months after the operation, I still go to the physiotherapist twice a week and mainly focus on muscle-strengthening exercised. I can walk, run, and cycle short distances normally again. My goal is to get back on the soccer field. I hope this will work again with the help of my therapist.

Learning points.

• This article reports a case of a teenager who suffered a frontal collision sports injury resulting in an osteochondral impression fracture of the patella.

• Restoration of osteochondral impression fractures of the patella could be excellently treated surgically with the use of β-tricalcium phosphate and 3.0 cannulated screw fixation.

• This surgical technique results in good outcomes clinically and radiographically after 6 weeks and 3 month follow-up.

Ethics statements

Patient consent for publication

Consent obtained from parent(s)/guardian(s)