Transtibial Prosthetics Overview

Transtibial Notes

• Landmarks: Tibial crest, fibular head, patella
• Socket Theory: Total contact to minimize unwanted pressure.
• Pressure Tolerant Areas (Blue): Patellar tendon bar, medial tibial flare, popliteal fossa, lateral flat aspect of fibula.
• Pressure Intolerant Areas (Pink): Tibial tubercle, crest, distal end, fibular head, distal fibula, tibial condyles, hamstring tendons.
• Appropriate Loading: Loading the PTB and posterior popliteal area stabilizes the limb, minimizing distal end pressure during weight bearing.

Prosthetic Prescription

• Candidate Assessment: Evaluate strength, cognitive ability, functional needs and client goals.
• Functional Category: Consider physical and cognitive capacities, fiddle threshold, and activity level.
• Socket Design & Trimlines: Consider socket design, including liner materials (gel, pelite, etc), suspension systems, and socket materials (laminated, thermoplastic, carbon fiber).
• Socket Style: Options include endoskeletal and exoskeletal socket styles.
• Componentry: Consider prosthetic components.
• Cosmesis: Assess cosmetic needs.

Socket Design

• Pressure = Force/Area: Goal is to distribute pressure to tolerant areas to reduce pressure on intolerant areas.
• Tissue Tolerance: Consider tissue tolerance and density/firmness.
• Surface Inclination: Modifications and flexion in the socket improve weight bearing capabilities.
• Hydraulic Theory: TSB sockets can "float" the bones to distribute pressure within soft tissue through hydrostatic loading.
• Flaring: Gentle transitions within socket shape.

Indications and Contraindications

• Indications (Primary Amputees): Sensitive residual limbs, poor dexterity, difficulty with eyesight, or hemiparesis.
• Indications for TSB: Active amputees that benefit from lower trimlines, greater proprioception, improved venous return and proprioception feedback.
• Contraindications (TSB): New amputees (within first 18 months), dialysis patients (with volume fluctuations), residuum less than 10cm, excessive perspiration.
• Contraindications for High-Activity Users/PTB: Highly active users, or those who find PTB prosthesis piston to be too restrictive. May cause pressure on the patellar tendon making it difficult to work.
• Contraindications for Supracondylar Socket: Obese or muscular patients, and those with moderate to severe ligament laxity. Those with a short residuum (need greater surface area for weight bearing.)
• Contraindications for Thigh Corset: Obesity, very muscular patients, or extreme ligament laxity.

Socket Types

• Supracondylar: Socket extends above the patella and femoral condyles.
• Suprapatellar: Suspension from the quadriceps bar above the patella, resisting genu recurvatum.
• Thigh Corset: External support for pressure-intolerant residuum, improving support and stability for sports, etc.

Interface Selection

• Interface Definition: Surface that forms a common boundary between two bodies, spacing or phases.
• Goals : Smooth, reduces shear, and improves comfort..
• Interface Types: No interface/hard socket with a distal end pad, just socks or sheaths,

Suspension Selection

• Sleeve Suspension: Generates suction between the limb, liner, and prosthesis. Requires close contact between sleeve and skin to create seal and suspend the socket.
• Supracondylar: Contours over femoral condyles with purchase for a superior suspension system.
• Elevated Vacuum: Component with a vacuum pump to improve limb health, and stabilizes volume changes. Good for shorto residuum, and higher mobility.
• Cuff Suspension (Supracondylar): Attachment at the femoral condyles, provides additional extension control and is easily adaptable.

Foot Selection

• Solid Ankle Cushioned Heel (SACH) foot: Low cost, stable, and relatively easy to use for slower activities.
• K1 Foot: Suitable for those restricted to limited mobility, and training. Provides low impact
• Articulated Single Axis: Highly stable after midstance. Suitable for greater flexibility, and midstance stability.
• Additional Considerations: Heel differences should be adjusted according to user needs.

Other Considerations

• Locking Pin: Engages locking mechanisms within the socket for support, with audible feedback. Easy to don and doff.
• Clinical Indications: Reduced soft tissue, intolerance to skin, redundant tissue, and requires suspension.
• Additional Types of Liner: Pelite/soft liners, gel liners, which wick moisture, material compress, require frequent refabrication, not ideal for active users.

Random Stuff

• Neuroma: Pain in nerves, common complication (especially in TT and TF)