- Discussion:
- function of the PTFJ
- accept 1/6 the axial load of the leg
- resist torsional stresses originating from the ankle
- resist tensile forces created with weight bearing
- resists lateral bending forces
- subluxation is common in preadolescent females and resolves with skeletal maturity
- may be confused with a Lateral meniscus tear
-
anatomy:
- synovial joint
- in 10% of the population, the proximal tibiofibular joint is contiguous with the knee joint
- product of embryogenesis
- anterior joint capsule significantly thicker than posterior
- anterior joint capsule composed of three ligamentous bands
- bands pass obliquely upward and attach to the lateral tibial condyle
- posterior tibiofibular ligament is composed of two broad, thick ligamentous bands
- bands pass obliquely from the fibular head to the posterior aspect of the tibial condyle
- reinforced by the popliteus tendon
- additional Stabilizers
- LCL
- arcuate Ligament
- fabellofibular lig.
- popliteofibular lig.
- popliteus
- biceps femoris tendon (inserts on the styloid process and fibular head and helps prevent anterior movement of fibular head)
- anatomic variation
- two general anatomic variants
- oblique
- several studies have identified a higher propensity for instability/dislocation with the oblique variant
- oblique variant defined as >20 degrees of inclination from horizontal plane
- variable surface area averaging 17mm2, which
predisposes to instability
- more constrained articulation which increases torsional loads and predisposes to instability
- horizontal
- horizontal variant
- less than 20 degrees of inclination
- fibular head is seated in a groove behind a prominent lateral tibial ridge which enhances stability
- planar, circular surface with on average 26mm2 of surface area
-
kinematics:
- knee flexion
- anterior shift of the proximal fibula in flexion
- biceps relaxes in flexion
- LCL relatively loose > 30 degrees of flexion
-
knee extension:
- LCL and biceps femoris tighten and proximal fibula shifts posteriorly
-
mechanism of injury:
- inherently stable joint
- ligamentous support
- protected position
- added protection of the LCL in extension
- injury occurs with knee in flexion, the ankle is internally rotated and plantar-flexed
- isolated dislocations are typically seen in activities requiring aggressive twisting motions of the knee
- soccer
- parachuting
- horseback riding
- may also be seen in trauma cases with assoc:
- posterior hip dislocation;
- open tibiofibular fx
- ankle Fx
- twisting injury or direct blow (car bumper)
-
instability/dislocation patterns
- subluxation
- dislocation
- anterolateral
- posteromedial
- superior
- typically preadolescent females
- may have generalized ligamentous laxity or CTD
-
exam findings
- lateral knee pain
- frequently bilateral
- may have locking/popping
- often present without Hx of trauma
- aggravated by direct pressure over the fibular head
-
dislocations:
- patients c/o pain, swelling, and sometimes prominence of the fibular head
- many are unable to bear weight secondary to pain
- ankle motion exacerbates knee pain
- transient peroneal nerve palsy especially with posteromedial and superior dislocations
- anterolateral dislocation
- fall on a flexed knee with the foot inverted and plantarflexed
- flexion leads to LCL laxity, predisposing to lateral dislocation
- peroneal muscles, EHL and EDL pull the proximal fibula anteriorly
- most common pattern of proximal tibiofibular dislocation (>85%)
- lateral knee pain, swelling, and prominence of the fibular head
- ankle motion exacerbates knee pain
- may be unable to bear weight secondary to pain
- posteromedial dislocation
- likely mechanism is direct trauma from car bumper of a horseback rider striking knee on gatepost
- often associated with a Peroneal nerve injury
- about 10 percent of proximal TF dislocations
- posteromedial dislocation
- superior dislocation
- classically associated with a concomitant high-energy ankle injury and superior migration of the entire fibula
- interosseous membrane disrupted
- 2% of proximal tibiofibular dislocations
- physical examination
- important to evaluate and document Neuro exam
- knee and ankle exam
- including LCL
- prominent lateral mass
- extremely TTP, worsens with ankle dorsiflexion & eversion as well as knee extension
- biceps femoris tendon may appear as a tense cord
-
chronic subluxation:
- best to examine c knee flexed at 90 degrees
- translation assessed in ant/post and med/lat planes
- radulescucent sign
- elicited in prone position
- one hand stabilizes the thigh and the leg is internally rotated in an attempt to produce anterior fibular subluxation
- physical examination
- Helfet Sign
- patient bears full weight through the affected limb
- if the patient has PTF instability they will hook the contralateral limb about the affected calf in an attempt to stabilize the PTF joint
- imaging
- plain radiographs in true AP and Lateral planes (72% sensitive)
- comparison radiographs of the contralateral extremity (increases sensitivity to 82%)
- resnick’s line – follows the lateral tibial spine and should be found over the midpoint of the fibular head
- CT if dx is equivocal (86% sens compared c 82% on plain films)
-
treatment: atraumatic subluxation
- non-surgical mgmt is usually successful
- casting for 2-3 weeks
- strap applied 1cm below fibular head
- avoid activities that place knee in hyperflexion
- usually in preadolescent females and Symptoms are self-limiting
-
treatment of acute dislocation:
- closed reduction
- may be performed under local or general anesthesia
- knee in
80-110 degrees of flexion
- ankle dorsiflexed and externally rotated
- reverse the injury
- audible pop as head relocates
- reassess knee stability/LCL once relocated
- immobilization?
- controversial
- some authors advocate casting for 3 weeks vs. soft dressing with protected WB advanced to full WB over 6 weeks
- open reduction
- for failed closed reduction
- for posteromedial and superior dislocations
- closed reduction may fail if the fibula is perched on the lateral tibial ridge with an intact LCL
- following Open reduction the joint should be stabilized with
- temporary screw
- K wire
- associated ligamentous injuries should be repaired
-
treatment of acute dislocation:
- after ORIF the knee and ankle should be immobilized for 6 weeks
- K-wires or screws can be removed after 6-12 weeks
- recurrent symptoms
- ogden reported that 57% (N=33) of pts c acute dislocations required surgery for recurrent symptoms
- surgical options
- arthrodesis
- isolate/protect the peroneal nerve
- denude articular surfaces of cartilage
- joint reduction and fixation with a cancellous lag screw
- immobilization for 6 weeks
- full weight bearing in 8 weeks
- prevents fibular rotation
- concern regarding increased rotational stress at ankle joint
- ? may lead to pain and arthritic changes of the ankle joint
- insufficient data to support/refute this theory
- resection of fibular head
- particularly appealing in the face of Peroneal nerve palsy in pts with chronic subluxation/dislocation
- LCL and Biceps secured to the tibia
- similar concerns as PTF arthrodesis as well as concern of knee instability with compromise of PLC
- N = 6 (tumor or autograft), avg 61 months F/U
- ? Effect of unilateral marginal resection of the proximal fibula on knee stability and gait.
- reconstruction of the PTFJ
- using one half of the biceps femoris tendon and a strip of deep fascia the PTFJ is reconstructed
- knee immobilized for 6 weeks and then PWB
- Giachino, JBJS 1986
reported return to previous activity level s recurrent symptoms in 2 patients
- 20 x 2cm strip of ITB still attached to Gerdy’s tubercle can
be passed from anterior to posterior through a drill hole in the tibia and underneath the LCL
Proximal Tibiofibular Joint Ganglion Cysts.
