Excision of Intra-articular Knee Heterotopic Ossification Using a 70° Arthroscope

Abstract

Heterotopic ossification is ectopic lamellar bone formation within soft tissue and can result in significant functional limitations. There are multiple underlying etiologies of HO including musculoskeletal trauma and traumatic brain injury. Intra-articular HO of the knee is rare and is typically located within the cruciate ligaments. We report a case of a 24-year-old female who presented with worsening right knee pain and limited knee extension two and a half years after a motor vehicle crash with multiple lower extremity fractures. Physical examination of the knee revealed anterior pain, limited extension, and a palpable infrapatellar prominence. Imaging showed a retropatellar tendon, intra-articular excrescence of bone proximal to the anterior tibial plateau. Diagnostic arthroscopy with a 70° arthroscope identified HO at the proximal anterior tibial plateau, which was excised with a high-speed burr under direct visualization. At the three-month follow-up, the patient remained asymptomatic and returned to sport. Retropatellar tendon, intra-articular anterior knee HO is a rare but debilitating clinical entity that can be successfully and safely managed with excision under direct visualization using a 70° arthroscope.

Figure 1

Preoperative right knee radiographs demonstrate retrograde femoral rod fixation and antegrade tibial rod fixation: (a) anterior-posterior view; (b) posterior-anterior flexion view; (c) lateral view, which best demonstrates the anterior intra-articular heterotopic.

Figure 2

Preoperative right knee magnetic resonance imaging study. The red arrows indicate the anterior intra-articular heterotopic ossification: (a) select coronal T2 image; (b) select sagittal T2 image. A red arrow indicates the anterior intra-articular heterotopic ossification in both images.

Figure 3

Intra-operative views using a 70° arthroscope of the anterior intra-articular heterotopic ossification: (a) before debridement of fat pad and dissection away from patellar tendon; (b) after partial fat pad debridement; (c) after complete fat pad debridement and dissection away from patellar tendon.

Figure 4

Intraoperative views using a 70° arthroscope of the anterior intra-articular heterotopic ossification: (a) after fat pad debridement and dissection away from the patellar tendon before excision with burr; (b) after removal of surrounding periosteum and synovium with shaver; (c) after complete HO resection with a burr; (d) global view after complete HO resection.

Figure 5

Intraoperative fluoroscopic lateral image of the right knee to confirm adequate resection of the anterior intra-articular heterotopic ossification.

Figure 6

Diagnostic arthroscopy after heterotopic ossification resection to confirm the absence of loose bodies: (a) patellofemoral joint; (b) notch, anterior cruciate ligament right of the probe; (c) medial compartment with medial femoral condyle, medial meniscus, and medial tibial plateau visualized; (d) lateral compartment with lateral femoral condyle, lateral meniscus, with the probe under the meniscal root, and lateral tibial plateau visualized.

Figure 7

Three-month postoperative radiographs confirming complete resection of the anterior intra-articular heterotopic ossification: (a) anterior-posterior image; (b) lateral image.