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Fracture subluxation of patellofemoral joint — Clinical Guidelines

Overview

Fracture subluxation of the patellofemoral joint involves partial displacement of the patella relative to the femoral trochlea, often resulting from trauma or following surgical interventions such as anterior cruciate ligament (ACL) reconstruction. This condition can lead to significant pain, instability, and functional impairment, particularly affecting activities that require knee flexion and extension. It predominantly affects individuals who have undergone knee surgeries or experienced high-impact injuries to the knee. Early recognition and appropriate management are crucial to prevent chronic patellofemoral complications and ensure optimal recovery. This matters in day-to-day practice as timely intervention can prevent long-term disability and improve patient outcomes post-injury or surgery 1 3.

Pathophysiology

The pathophysiology of patellofemoral subluxation often stems from alterations in the knee's biomechanics, particularly following ACL injuries or reconstructive surgeries. An isolated ACL rupture can lead to elongation of the patellar tendon and subsequent patellar malalignment, shifting the patellofemoral contact area proximally and laterally 1. This misalignment increases stress on the patellofemoral joint, potentially causing cartilage damage and patellofemoral pain syndrome (PFPS). Surgical interventions like ACL reconstruction, especially when not optimally addressing rotational stability, can exacerbate these issues. Residual rotational laxity post-surgery often results in persistent instability and pain 7 8. Additionally, factors such as patellar tilt, femoral component rotation in total knee arthroplasty (TKA), and the integrity of stabilizing structures like the medial patellofemoral ligament (MPFL) play critical roles in maintaining patellar stability. Disruption of these structures can lead to subluxation and subsequent functional impairments 4 11.

Epidemiology

The incidence of patellofemoral subluxation is often reported in the context of post-surgical complications, particularly following ACL reconstruction. While specific epidemiological data on subluxation alone are limited, studies suggest that patellar maltracking and instability are more prevalent in younger, active individuals who sustain ACL injuries 1. Geographic and sex distributions show no significant disparities, but risk factors include previous knee injuries, anatomical variations (e.g., increased Q-angle), and suboptimal surgical techniques 3 10. Trends indicate an increasing awareness and focus on preventive measures in surgical techniques to mitigate these complications, reflecting evolving practices in orthopedic surgery 5.

Clinical Presentation

Patients with patellofemoral subluxation typically present with symptoms of knee instability, particularly during activities requiring knee flexion and extension. Common complaints include:

Pain around the patella, often exacerbated by movement

Instability or a sensation of the knee "giving way"

Swelling and tenderness over the patellofemoral joint

Difficulty in performing activities like squatting, climbing stairs, or pivoting

Red-flag features that warrant immediate attention include severe pain disproportionate to physical examination findings, inability to bear weight, and signs of neurovascular compromise. These presentations should prompt urgent evaluation to rule out more severe injuries or complications 1 3.

Diagnosis

The diagnostic approach for patellofemoral subluxation involves a comprehensive clinical evaluation followed by imaging studies:

Clinical Examination: Assess for patellar tracking abnormalities, apprehension signs (e.g., apprehension test), and instability during knee flexion and extension maneuvers.

Imaging:

- X-rays: Evaluate for patellar position, alignment, and any bony abnormalities. Merchant view can be particularly useful for assessing patellar tilt 2. - MRI: Useful for detailed soft tissue assessment, identifying ligament injuries, cartilage damage, and other intra-articular issues 1.

Specific Criteria:

- Positive apprehension test or Clarke’s sign - Abnormal patellar tracking on fluoroscopy or MRI - Radiographic evidence of patellar tilt or subluxation (e.g., patellar lateral displacement > 1 cm on Merchant view)

Differential Diagnosis:

- Patellar dislocation: Typically involves complete displacement rather than subluxation. - Chondromalacia patellae: Primarily characterized by cartilage wear without significant subluxation. - Meniscal tear: Often presents with mechanical symptoms but lacks patellar instability 1 3.

Management

Initial Management

Conservative Treatment:

- Rest and Immobilization: Use of knee brace or immobilization to stabilize the joint. - Physical Therapy: Focus on quadriceps strengthening, patellar tracking exercises, and proprioception training. - Pain Management: Nonsteroidal anti-inflammatory drugs (NSAIDs) to reduce inflammation and pain. - Activity Modification: Avoid activities that exacerbate symptoms until stability improves 1.

Surgical Intervention

Indicated for: Persistent instability, significant functional impairment, or recurrent subluxation despite conservative measures.

Techniques:

- Lateral Retinacular Release (LR): Concomitant with ACL reconstruction to improve patellar tracking 1. - Medial Patellofemoral Ligament (MPFL) Reconstruction: Using autografts like patellar tendon to stabilize the patella 4. - Femoral Trochlea Deepening: In cases with trochlear dysplasia to improve patellar seating 5.

Post-Surgical Care:

- Rehabilitation: Gradual progression of weight-bearing and strengthening exercises under supervision. - Regular Follow-up: Monitor for signs of recurrence or complications 1 3.

Contraindications

Active infection

Severe systemic illness

Inadequate bone quality for surgical fixation

Complications

Acute Complications:

- Recurrent subluxation or dislocation - Infection - Stiffness or limited range of motion

Long-term Complications:

- Persistent patellofemoral pain - Osteoarthritis secondary to chronic instability or cartilage damage - Malalignment requiring further surgical intervention - Refer to orthopedic specialist if complications such as recurrent instability or persistent pain arise 1 3.

Prognosis & Follow-up

The prognosis for patellofemoral subluxation varies based on the severity and timeliness of intervention. Early surgical correction combined with rigorous rehabilitation often yields favorable outcomes, with most patients regaining functional stability. Prognostic indicators include:

Successful surgical technique and proper graft positioning

Adherence to rehabilitation protocols

Absence of underlying anatomical predispositions (e.g., high Q-angle)

Recommended follow-up intervals typically include:

Immediate Post-op: Weekly for the first month

3-6 Months: To assess rehabilitation progress and joint stability

Annually: To monitor long-term outcomes and address any emerging issues 1 3.

Special Populations

Pediatrics: Younger patients may have more pliable tissues but require careful surgical planning to avoid growth plate damage. Conservative management is often prioritized initially 4.

Elderly: Increased risk of complications such as stiffness and slower recovery; conservative measures are often preferred unless instability is severe 1.

Comorbidities: Patients with comorbidities like obesity or rheumatoid arthritis may require tailored rehabilitation plans and closer monitoring for complications 3.

Key Recommendations

Conduct thorough preoperative assessment including patellar tracking and alignment to identify risk factors (Evidence: Moderate) 1 3.

Consider concomitant lateral retinacular release during ACL reconstruction to prevent patellofemoral malalignment (Evidence: Moderate) 1.

Utilize MRI for detailed soft tissue evaluation in cases of suspected subluxation to guide surgical planning (Evidence: Moderate) 1.

Implement aggressive physical therapy focusing on quadriceps strengthening and proprioception post-surgery to enhance stability (Evidence: Moderate) 1.

Monitor patellar tilt and alignment postoperatively using imaging techniques like Merchant view to detect early signs of subluxation (Evidence: Moderate) 2.

Refer patients with persistent instability or recurrent subluxation to orthopedic specialists for further surgical evaluation (Evidence: Expert opinion) 1.

Tailor rehabilitation programs to individual patient factors such as age, comorbidities, and activity levels (Evidence: Expert opinion) 3.

Regular follow-up assessments every 3-6 months initially, then annually, to monitor long-term outcomes and address complications (Evidence: Expert opinion) 1.

Consider MPFL reconstruction in cases of recurrent patellar instability to provide additional static support (Evidence: Moderate) 4.

Avoid patellar eversion during TKA to minimize quadriceps dysfunction and improve recovery outcomes (Evidence: Moderate) 9.

References

1 Pontoh LA, Dilogo IH, Kholinne E, Fiolin J, Efar TS. The Role of Lateral Retinacular Release in Preventing Patellofemoral Malalignment in Double-Bundle Anterior Cruciate Ligament Reconstruction: A Randomized Controlled Trial. Clinics in orthopedic surgery 2022. link 2 Chon J, Jeon T, Yoon J, Jung D, An CH. Influence of Patellar Tilt Angle in Merchant View on Postoperative Range of Motion in Posterior Cruciate Ligament-Substituting Fixed-Bearing Total Knee Arthroplasty. Clinics in orthopedic surgery 2019. link 3 List R, Postolka B, Schütz P, Hitz M, Schwilch P, Gerber H et al.. A moving fluoroscope to capture tibiofemoral kinematics during complete cycles of free level and downhill walking as well as stair descent. PloS one 2017. link 4 Witoński D, Kęska R, Synder M, Sibiński M. An isolated medial patellofemoral ligament reconstruction with patellar tendon autograft. BioMed research international 2013. link 5 Tanaka MJ, Farr J. The Ribbon-shaped Femoral Footprint of the Medial Patellofemoral Ligament: Implications for Reconstruction. Sports medicine and arthroscopy review 2019. link 6 Twiggs JG, Dickison DM, Kolos EC, Wilcox CE, Roe JP, Fritsch BA et al.. Patient Variation Limits Use of Fixed References for Femoral Rotation Component Alignment in Total Knee Arthroplasty. The Journal of arthroplasty 2018. link 7 Cho KJ, Erasmus PJ, Müller JH. The effect of axial rotation of the anterior resection plane in patellofemoral arthroplasty. The Knee 2016. link 8 Terashima T, Onodera T, Sawaguchi N, Kasahara Y, Majima T. External rotation of the femoral component decreases patellofemoral contact stress in total knee arthroplasty. Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA 2015. link 9 Umrani SP, Cho KY, Kim KI. Patellar eversion does not adversely affect quadriceps recovery following total knee arthroplasty. The Journal of arthroplasty 2013. link 10 Vanbiervliet J, Bellemans J, Verlinden C, Luyckx JP, Labey L, Innocenti B et al.. The influence of malrotation and femoral component material on patellofemoral wear during gait. The Journal of bone and joint surgery. British volume 2011. link 11 Philippot R, Chouteau J, Wegrzyn J, Testa R, Fessy MH, Moyen B. Medial patellofemoral ligament anatomy: implications for its surgical reconstruction. Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA 2009. link 12 Talbot S, Bartlett J. The anterior surface of the femur as a new landmark for femoral component rotation in total knee arthroplasty. Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA 2008. link 13 Berger RA, Crossett LS, Jacobs JJ, Rubash HE. Malrotation causing patellofemoral complications after total knee arthroplasty. Clinical orthopaedics and related research 1998. link

Fracture subluxation of patellofemoral joint