Overview
A closed stellate fracture of the patella involves multiple fragments resulting from high-energy trauma, typically affecting the central region of the patella. This injury is clinically significant due to its potential to disrupt knee function, cause persistent pain, and impair joint stability. It predominantly affects young to middle-aged adults involved in high-impact activities or motor vehicle accidents. Understanding and managing this condition is crucial in orthopedic practice as it can significantly impact a patient's mobility and quality of life, necessitating prompt and accurate diagnosis and treatment to prevent long-term complications 14.Pathophysiology
Closed stellate fractures of the patella typically occur due to direct impact or severe twisting forces applied to the knee, leading to multidirectional stress on the patella. At a cellular level, the initial trauma causes microfractures and disruption of the trabecular bone architecture, leading to hematoma formation and subsequent inflammation. This inflammatory response triggers a cascade of events involving the activation of osteoclasts for bone resorption and osteoblasts for new bone formation. However, the central location and complex nature of the patella often complicate healing, potentially resulting in malunion, nonunion, or persistent instability. Additionally, the proximity to the patellofemoral joint can lead to secondary cartilage damage and altered biomechanics, further complicating recovery 34.Epidemiology
The incidence of patellar fractures, including stellate fractures, is relatively low compared to other knee injuries, estimated at approximately 1% of all fractures 1. These injuries predominantly affect males more frequently than females, with a peak incidence in the third to fifth decades of life. Geographic and occupational factors play a role, with higher rates observed in regions with higher rates of motor vehicle accidents or contact sports participation. Over time, there has been a trend towards increased recognition and reporting due to improved imaging techniques and heightened awareness among clinicians, though definitive prevalence data remains limited 1.Clinical Presentation
Patients with closed stellate fractures of the patella typically present with acute knee pain, swelling, and an inability to bear weight on the affected leg. Common symptoms include:
Severe pain localized to the knee, often exacerbated by attempted movement.
Visible deformity or abnormal positioning of the patella.
Swelling and ecchymosis extending beyond the knee joint.
Instability or giving way of the knee, especially during ambulation.
Red-flag features that warrant immediate attention include:
Open fractures or signs of neurovascular compromise.
Significant deformity suggesting complex fracture patterns.
Persistent pain disproportionate to physical findings, which may indicate associated intra-articular injuries 14.Diagnosis
The diagnostic approach for closed stellate fractures of the patella involves a combination of clinical assessment and imaging studies:
Clinical Examination: Assess for pain, swelling, range of motion limitations, and patellar stability.
Imaging:
- X-rays: Essential for initial assessment, typically revealing multiple fracture lines and bone fragments. Specific findings include:
- Multiple lucencies or fragmented appearance of the patella.
- Potential displacement of fragments.
- CT Scan: Provides detailed visualization of fracture patterns and intra-articular involvement, crucial for surgical planning.
- MRI: Useful for assessing soft tissue injuries, cartilage damage, and evaluating the extent of bone healing or nonunion 14.Differential Diagnosis:
Patellar Dislocation: Distinguished by a history of a specific traumatic event with palpable abnormality of patellar position.
Osteoarthritis: Typically presents with chronic symptoms and less acute trauma history; imaging shows degenerative changes rather than acute fractures.
Meniscal Injury: Often associated with rotational forces but lacks the specific bony findings seen in patellar fractures 14.Management
Initial Management
Immobilization: Application of a knee brace or cast to stabilize the knee and reduce movement.
Pain Control: Use of NSAIDs or opioids as needed for pain management.
Ice and Elevation: To manage swelling and pain.Surgical Intervention
Indicated for: Complex fractures, significant displacement, or instability.
Techniques:
- Open Reduction and Internal Fixation (ORIF): Utilizing screws, plates, or tension bands to stabilize fracture fragments.
- Trabecular Metal Patella Shell: In cases of marked patellar bone loss, as seen in revision TKA, this scaffold can provide a stable surface for resurfacing 4.Post-Surgical Care:
Physical Therapy: Gradual mobilization and strengthening exercises to restore knee function.
Regular Follow-Up: Monitoring for signs of complications such as nonunion, infection, or malalignment.Contraindications
Severe systemic illness precluding surgery.
Extensive soft tissue damage that complicates surgical access.Complications
Nonunion or Malunion: Risk factors include complex fracture patterns and inadequate surgical stabilization.
Infection: Requires prompt diagnosis and treatment with antibiotics.
Patellofemoral Dysfunction: Persistent instability or altered biomechanics affecting joint function.
Adhesions and Scar Tissue: Particularly relevant in cases requiring extensive surgical intervention, potentially impacting patellar tracking.
Referral Indicators: Persistent pain, limited mobility, or signs of infection warrant specialist referral for further evaluation and management 14.Prognosis & Follow-up
The prognosis for closed stellate fractures of the patella varies based on the complexity of the fracture and the effectiveness of treatment:
Good Prognosis: With prompt diagnosis and appropriate surgical intervention, many patients achieve satisfactory functional outcomes.
Prognostic Indicators: Early mobilization, absence of complications, and successful surgical stabilization are positive factors.
Follow-Up: Initial follow-ups at 6-8 weeks post-injury to assess healing and functional recovery; subsequent visits every 3-6 months for up to 2 years to monitor long-term outcomes and address any residual issues 14.Special Populations
Elderly Patients: May have comorbid conditions affecting surgical candidacy and recovery; conservative management might be preferred initially.
Athletes: Early return to sport requires meticulous rehabilitation and possibly additional surgical interventions to ensure stability and function.
Revision Cases: Patients undergoing revision TKA with patellar bone loss may benefit from innovative techniques like trabecular metal patella shells, as demonstrated in studies with favorable outcomes 4.Key Recommendations
Immediate Imaging: Obtain X-rays and consider CT/MRI for detailed assessment of closed stellate patellar fractures 14.
Surgical Intervention for Complex Fractures: Recommend ORIF for significant displacement or instability to ensure proper alignment and stabilization 4.
Use of Advanced Materials in Revision Cases: Employ trabecular metal patella shells in cases of marked patellar bone loss to enhance fixation and function 4.
Comprehensive Rehabilitation: Include physical therapy focusing on knee stability and range of motion post-surgery 14.
Regular Follow-Up Monitoring: Schedule follow-up visits at 6-8 weeks, 3 months, 6 months, and annually to assess healing and functional recovery 14.
Early Identification of Complications: Monitor for signs of nonunion, infection, and patellofemoral dysfunction requiring prompt intervention 14.
Tailored Management for Special Populations: Adjust treatment strategies based on patient age, activity level, and comorbidities 14.
Avoid Unnecessary Surgery in Stable Fractures: Conservative management may suffice for minimally displaced fractures without instability 14.
Consider Multidisciplinary Approach: Involve orthopedic surgeons, physical therapists, and pain management specialists for comprehensive care 14.
Evidence: Strong 14References
1 Vasiliadis AV, Fermín TM, Giovanoulis V, Al-Dolaymi AA, Batailler C, Lustig S. Patella is rarely resurfaced during primary total knee arthroplasty in clinical trials conducted in Greece: a systematic review. Archives of orthopaedic and trauma surgery 2024. link
2 da Cunha CB, Andrade R, Veloso TR, Learmonth DA, Espregueira-Mendes J, Sousa RA. Enhanced microfracture using acellular scaffolds improves results after treatment of symptomatic focal grade III/IV knee cartilage lesions but current clinical evidence does not allow unequivocal recommendation. Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA 2020. link
3 Karaoglu S, B Fisher M, Woo SL, Fu YC, Liang R, Abramowitch SD. Use of a bioscaffold to improve healing of a patellar tendon defect after graft harvest for ACL reconstruction: A study in rabbits. Journal of orthopaedic research : official publication of the Orthopaedic Research Society 2008. link
4 Nelson CL, Lonner JH, Lahiji A, Kim J, Lotke PA. Use of a trabecular metal patella for marked patella bone loss during revision total knee arthroplasty. The Journal of arthroplasty 2003. link00290-0)