Screw Placement and Types Matter

Transcription

1 Screw Placement and Types Matter The Blasted Distal Femur Facture: How to Improve Outcomes Abstract ID#: 1506 Friday October 13, 2017 Kyle Jeray University of South Carolina, Greenville Pinpoint open 59 y/o Male Moped Rider Contralateral tibial shaft fracture Disabled but works as painter Smokes 1 ppd Drinks 3-6 beers/day NIDDM, HTN CT Treatment Choice? 59 y/o Male Evaluation of Distal Femur Fractures CT scan gives details about articular surface involvement May be beneficial to wait until after external fixation (if being used)? 5. How Often Do We See (Hoffa) Coronal Plane Fractures with Intra-articular Fractures of the Distal Femur? A 10% B - 35% C 50% D 75% Evaluation of Distal Femur Fractures Don t forget the Hoffa fragment! 38% of intercondylar distal femur fractures have a coronal plane fracture (Nork et al, J Orthop Trauma, 87:564, 2005) Most precisely diagnosed via CT scanning 76% single condyle 85% lateral condyle Open fx 2.8 x coronal fx than closed fx Coronal fx diagnosed in 47% with CT and only 21% with xray only 1

2 Treatment Choice? 59 y/o Male 3. Which Implant When Used Alone is Contraindicated for a Comminuted Distal Femur Fracture? A - Condylar buttress plate B - Blade plate C - Dynamic Condylar Screw ( DCS ) D - Locked plate E - Retrograde medullary nail These are Fixed Angle Devices Condylar Buttress Plate Is Not Its ALL about the SCREWS! Instability with metaphyseal comminution (medially) Implant does not resist varus collapse Need locking screws to create fixed angle construct Screws Outside the Plate Important! Screws Outside the Plate Important! Don t forget about reduction Lag screws of appropriate length Standard or headless? 2

3 How Many Screws? Plate Length and Screw Numbers Enough to create stability Rule of thumb is 8 cortices Shorter plates less working length Signs of fixation frustration Cables Short plates stiffer Shorter plates higher risk of failure I= bh3/12 Unicortical versus Bicortical? 59 y/o - Post-op Day 19 Not as much fixation as bicortical screws Does not minimize stress at end of plate versus standard screws Failure Why? Not the Plate Screw length often as important as number! Only the lag screw survived Failure Why? Location! Place screws in good bone! Missed posterior condyles 3

4 Similar Case Start Over Nonlocking screws outside the plate Reduction completed before plate applied Note screws location and length You control the stiffness Locking screws in plate to provide support to resist varus Better? Reduction and Mechanics Longer plate Longer screws Better position of screws Improved joint reduction Reduction and Mechanics Mechanics Nonlocking Screws with Large Washer to support Are screws alone enough? Bone quality plays a role Osteoporotic bone may require plate support or locking screws in plates 4

5 Healed Far Cortical Locking FCL reduces construct stiffness: Standard bicortical drill hole Narrow, flexible screw shaft Controlled motion envelope d Cantilever bending of screw shaft Increased screw working length How can the stiffness of locked internal fixators be controlled? Stoffel, Injury, 2003 Approach Gain Cons A plate cross-section stiffness strength B plate elevation stiffness: 35% (2 6 mm) 1 strength, clinical use C plate span stiffness: ns 2, 5% 1, 60% 3 strength: 33% 3, longer plates D Far Cortical Locking stiffness: > 80% comparable strength 4 Far Cortical Locking Screws Parallel gap motion Bi-phasic stiffness LP FCL A B axial load [N] high small load load d C D One or two holes should be omitted on each side of the fracture to initiate spontaneous fracture healing, including the generation of callus formations. 1. in-house testing; 2. Field, Injury, 99; 3. Stoffel, Injury, 2003; 4. Bottlang, JBJS, 2009 displacement [mm] 51 y/o MCA open distal femur fracture 3 Months F/U 5

6 Screws matter! Summary Locking screws have a role create fixed angle to support varus forces in distal femur Nonlocking screws work consider medial fixation as well if using nonlocking screws Summary Far cortical locking screws can decrease the stiffness of the construct and encourage callus formation By varying location of screws the surgeon can effect the stiffness as well (working length) How many screws? Just enough but not too many! 6