Background: Cactus thorn injuries are an uncommon cause of inflammatory joint pathologies that are often difficult to identify and treat. Patients present with diverse symptoms and findings, requiring a high degree of clinical suspicion for diagnosis. Curative treatment is primarily surgical, including synovectomy, irrigation and debridement, and foreign body removal. In this case, we describe a patient presenting to a Southwest pediatric hospital with a cactus thorn physeal injury resulting in limb deformity.

Case Presentation: An otherwise healthy 12-year-old active boy presented with knee pain, stiffness, and uneven gait secondary to 2 cm leg length discrepancy (LLD) and genu valgum three years after sustaining a cactus thorn injury to the lateral aspect of his right knee. He had a history of three prior irrigation and debridements at the time of injury and received several months of antibiotics, but no foreign bodies were found and cultures were negative. Advanced imaging showed early degenerative changes that will likely ultimately require a total knee arthroplasty. At our institution, he underwent right knee manipulation under anesthesia, arthroscopic loose body removal, and synovectomy to improve range of motion, right distal medial femoral hemiepiphysiodesis to prevent worsening of genu valgum, and left femur epiphysiodesis to prevent worsening of LLD. Right distal femur lateral opening wedge osteotomy was later performed to fully correct the valgus deformity. His knee extension improved, but persistent flexion limited to 70 degrees caused physical limitations. CT scan and dynamic ultrasound demonstrated a known posterior osteophyte as a mechanical block and a thorn embedded in the posterior knee soft tissues. Five years after initial injury, he underwent an open procedure with osteophyte excision and thorn removal with ultrasound assistance. Knee range of motion improved to 0-95 degrees which was maintained at his most recent follow-up. He now has normal coronal alignment of his bilateral lower extremities with return to all activities despite his persistent LLD.

Discussion: This case is the first to describe a partial physeal closure and resulting limb deformity due to an intra-articular cactus thorn injury. This is significant given most documented thorn injuries describe temporary disability that resolves after definitive surgical treatment, whereas this patient suffered permanent joint damage. To date, he has undergone six operative procedures and will likely require future total knee arthroplasty. While this is an uncommon result of a thorn injury, this case emphasizes the importance of identifying and removing intra-articular bodies to minimize subsequent joint damage.