- The patellar is a sesamoid bone.
- The proximal part of the patellar allow attachment of the quadriceps tendon while the distal pole allows the infrapatellar tendon to attach it to the infrapatellar tuberosity,
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Patellar Fractures
Patellar Fractures
Anatomy
Coronal view of left knee
Sagittal view of left knee
Muscles around the knee joint
Soft Tissue Extensor mechanism
Fascia from vastus lateralis/medialis and tensor fascia lata form the patellar retinaculum
An intact extensor mechanism allows knee range of motion (ROM) i.e. knee extension
Knee ROM
Patellar fractures
Injury mechanism
- Direct trauma with compression can produce complete, simple, stellate or comminuted fracture
- Indirect injury mechanism due to forcible pull of the quadriceps tendon with the knee in flexion
If the retinaculum is intact then there is usually minimal fracture fragment displacement.
Associated injuries:
- Assess for ipsilateral lower limb hip, tibia and ankle injuries
Presentation
- Pain to the knee area
- Swelling
- Palpable patellar defect
- Unable to extend the knee when extensor mechanism is lost
- High riding patellar
Descriptive Patellar Fracture Classification
(Cramer et al)
- Transverse
- Vertical
- Marginal
- Comminuted
- Osteochondral
- Sleeve
OTA/AO Patellar fracture Classification
Management
- Nondisplaced stable fractures or fractures with <2mm articular incongruency and <3 mm fragment displacement with an intact extensor mechanism can be managed non-operatively with brace/cast.
- Good/excellent results have been reported in 99% of fractures managed in plaster immobilization with the criteria of intact extensor mechanism with < 3mm articular step and <4 mm of fracture widening (Boström et al).
- Displaced fractures with >2mm articular congruity or >3mm fragment displacement with loss of extensor mechanism require open reduction and internal fixation (ORIF).
- Fixation modalities include:
- Kirshner wires/screw fixation with tension band wiring.
- Circumferential cerclage wiring depending on the fracture configuration.
- Retinaculum is repaired.
Patellectomy:
- Partial patellectomy is indicated in irreparable, severely comminuted inferior pole patellar fractures. A soft tissue repair is done.
- Complete patellectomy is indicated in irreparable, severely comminuted patellar fractures. Every attempt should be made to repair the patellar where possible as a total patellectomy result in a >49% reduction in quadriceps strength.
Patellar fixation with Kirshner wire tension band wiring
K-wire patellar fixation with figure of 8 tension band wiring
Screw fixation with figure of 8 tension band wiring
An alternative material to consider to the traditional stainless steel tension band wiring include braided polyester suture (No 5 Ti-cron, No 5 Ethibond) thread with good results (McGreal et al, Patel et al, Lee et al) or Fibrewire (Lee BJ et al) as there are fewer complications relating to stainless steel wire.
Patellectomy
Surgery
- Partial patellectomy for irreparable comminuted fragments
- Soft tissue repair procedure
Acute repair using modified Krackow technique
after partial inferior pole fracture patellectomy
Authors preferred reconstruction method for chronic Infrapatellar extensor mechanism disruption
Rehabilitation
- Patellar fractures with an intact extensor mechanism with minimal displacement is managed in a brace or Plater of Paris for 4 weeks
- Stable surgery fixated patellar fractures are managed in a knee brace with knee range of motion (ROM) limited to 30° for 4 weeks then increasing ROM. Noncompliant individuals require Plaster of Paris for 6 weeks (Melvin et al)
Knee range of motion (ROM) brace allows the degree of knee ROM to be set. Brace or apply plaster of Paris for 4 weeks for patellar fractures with intact extensor mechanism or for stable post ORIF fracture set brace 0° -30°.
Foot ROM, pre and/or post surgery allowing lower limb circulation
Download ASSIC Performance Fingerprint or Strength & Conditioning apps to create or download guideline (pre and post surgery) rehab routines
References
- Patellar fractures: Contemporary approach to treatment. Cramer KE, Moed BR. J Am Acad Orthop Surg 1997;5:323-331.
- AAOS Comprehensive Orthopaedic Review. Volume 1; page 629. Jay R Lieberman.
- Fracture of the patella: A study of 422 patellar fractures. Acad Orthop Surg 2008;16(8): 455-461. A Boström.
- FibreWire tension band for patellar fractures. Camarda L, La Gattuta A, Butera M, Siragusa F, D’Arienzo M. J Orthop Traumatol 2016 Mar;17(1): 75-80.
- The effect of patellectomy on knee function. Sutton FS Jr, Lipke J, Kettelkamp DB. Joint Surg Am 1976;58(4): 537-540.
- The biomechanical evaluation of plyester as a tension band for the internal fixation of patellar fractures. McGreal G, Joy A, Mahalingam K, Cashman WF. J Med Eng Technol 1999;23(2): 53-56.
- Fixation of patella fractures with braided polyester suture. Patel VR, Parks BG, Wang Y, Ebert FR, Jinnah RH. Injury 2000;31(1): 1-6.
- Modified Tension Band Wiring Using FiberWire for Patellar Fractures. Lee BJ, Chon J, Yoon JY, Jung D. Clinics in Orthopaedic Surgery 2019;11:244-248.
- Patellar fractures in adults. J S Melvin, S Mehta. J Am Acad Orthop Surg 2011;19: 198-207.
