Transtibial Prosthetics PDF

TRANSTIBIAL NOTES TT landmarks: tibial crest, fib head, patella Socket Theory: Always total contact, goal is to manage/minimize unwanted pressures Pressure tolerant (blue): Patellar Tendon Bar, Medial Tibial Flare, Popliteal Fossa, Pretibials (lateral flat aspect of fibula) Pressure intolerant (p...

TRANSTIBIAL NOTES TT landmarks: tibial crest, fib head, patella Socket Theory: Always total contact, goal is to manage/minimize unwanted pressures Pressure tolerant (blue): Patellar Tendon Bar, Medial Tibial Flare, Popliteal Fossa, Pretibials (lateral flat aspect of fibula) Pressure intolerant (pink): tibial tubercle, crest, and distal end, fibular head, distal fibula, tibial condyles, hamstring tendons -​ Appropriate loading of the ptB and posterior popliteal area stabilizes the limb and helpss suspend the limb in the prosthesis, minimizing excessive pressure on the distal end during  weight bearing. The PTB pressure also helps with rotational control and aids the patient in assessing fit and sock ply. -​ Pressure along the lateral fibular shaft aids in countering the varus thrust that normally occurs at the knee in MSt. -​ The medial tibial flare is on of the largest pressure tolerant areas. Prosthetic prescription: Consider: -​ Are they a prosthetic candidate? -​ Strength to control prosthesis safely? WB capability? Acceptance? Cognitive ability? -​ Functional needs, and client goals -​ Functional category -​ Consider physical/cognitive fitness, fiddle threshold, activity level ORDER: 1.​ Socket Design & Trimlines 2.​ Interface a.​ Liner? (Gel, pelite, etc) 3.​ Suspension 4.​ Socket materials and Style a.​ Laminated, thermoplastic, carbon fiber? b.​ Endoskeletal vs. Exoskeletal 5.​ Componentry 6.​ Cosmesis Socket Design -​ Pressure = Force/Area -​ Goal is to distribute pressures into areas that can tolerate it and reduce unwanted pressures over intolerant areas -​ Need to consider tissue tolerance and tissue density/firmness -​ Inclination of Surfaces -​ Created by modifications and flexion of the socket, improves weight bearing capabilities of the residuum instead of having vertical weight bearing surfaces -​ Hydraulic Theory: TSB sockets with enough circumferential pressure can “float” the bones within the soft tissue through hydrostatic loading -​ Flaring: Gentle transitions throughout the shape PTB Socket Much more emphasis is put on weight bearing through pressure tolerant areas. Much more drastic modifications.  Indications: primary amputees, sensitive residual limbs (more relief potential), bulbous distal end (pelite “stove pipe” liner for donning), poor hand dexterity, eyesight, or hemiparesis (much easier to don/doff) Contraindications: highly active users can find too restrictive, some find PTB prosthesis piston, some cannot tolerate the pressure on their patellar tendon required for PTB socket style to work TSB Socket Weight bearing occurs all over the residuum. Total surface bearing does not mean equal surface bearing. Softer and smoother all around. Greater SA to distribute pressures, prevents edema and aids in venous return, better sensory/proprioceptive feedback Indications: active amputees benefit from potentially lower trimlines, increased proprioception, better venous return, more comfortable for most Contraindications: new amputees (volume fluctuations for first 18 months), dialysis patients (volume fluctuations), residuum shorter than 10cm, increased perspiration (increased skin breakdowns) Supracondylar: Socket extends above patella and medial/lateral femoral condyles. Posterior wall is the same as PTB. Quadriceps bar provides additional suspension over patella and helps prevent genu recurvatum. Approx 2 cm higher than adductor tubercle. 1cm difference between supracondylar circumference and knee centre circumference required. Purpose: controls genu recurvatum, additional frontal plane control (varus/valgus control), increased SA Indications: Genu recurvatum (provides sensory feedback for knee extension when standing), Mild M/L knee instability, short residuum (greater SA for WB, longer lever arm) Contraindications: obese or very muscular patients (cannot achieve purchase over femoral condyles), patients with moderate to severe ligamentous laxity (metal joint or thigh corset required) Advantages: suspension is an inherent part of the socket, less restrictive to circulation than thigh corset, aids in knee stability, rotational control, and pressure distribution, reduces pistoning Disadvantages: modifications over the patella and femoral condyles must be precisely located, enclosed patella can inhibit comfortable kneeling, may be less cosmetic and more destructive to clothing Supracondylar cuff suspension: a strap proximal to the femoral condyles -​ Convenient for amp, can provide some extension control, easily adjustable -​ Does not provide M/L support, can hav a tourniquet effect, trimlines must be quite distal, pinches when seated Can be made with a pelite liner, a removable wedge, or a removable socket brim Suprapatellar: additional suspension from quadriceps barr above patella, resists genu recurvatum Indications: genu recurvatum, mild M/L support, short residual limb Contraindications: obesity, very muscular patients, or extreme ligament laxity Pros: suspension is an inherent part of the socket, less restrictive than a cuff or thigh corset, aids in knee stability, rotational control, and pressure distribution, reduces pistoning Cons: modificationss over the patella and femoral condyles must be precisely located, enclosed patella can inhibit comfortable walking, may be less cosmetic due to higher trimlines Thigh corset Indications: long time user, short residuum, unstable knee in any plane, pressure intolerant residuum, external need for more support (sports) Pros: increased knee stability/support, suspension, reduced residuum forces, increased proprioception Cons: weight, heat, restrictive, muscle wasting/edema, pistoning, cosmesis, fabrication, damage to clothing Joint position: must be co-lineear and co-planar. Approx 4.5 cm above PTB, generally perpendicular to LoP, Interface Selection Def: a surface forming a common boundary between two bodie, spaces, or phases Should reduce shear and improve comfort No interface/hard socket -​ Just socks or sheaths, sometimes includes a distal end pad Pros: -​ Very intimate fit (little shearing and friction) -​ Overall cosmesis due to less bulk -​ Easy to keep clean -​ Durability (no compressible materials that need to be replaced over time) Cons: -​ Noo wiggle room, need a stable volume and almost perfect fit -​ Not appropriate for those with fragile skin or very boney prominences -​ Not for those with volume fluctuations (new amps, diabetics, etc) Prosthetic socks Accomplish 3 goals: 1.​ Help cushion the forces on the limb during ambulation 2.​ Help accommodate changes in volume  3.​ Wick moisture away from the skin However 10+ ply compromises the fit of the prosthesis and a new socket is required. Pelite/Soft Liners Pros: -​ Anatomical suspension possible -​ Additional protection and comfort compared to skin or sock Cons: -​ Difficult to keep hygienic -​ Material compresses and both socket and linear need to be refabricated -​ Not great for active patients Gel Liners Clinical indications: -​ Reduced soft tissue, intolerant skin, redundant tissue, suspension needs, limb shape (really smooths over bumps and ridges), cosmesis Contraindications: -​ Hygiene, inability to don, client care of device, heat, allergy, invaginations (can still use, but educate patients on risk of skin breakdown and macerations), build height, cost (can they afford now and replacements later?) Pros: absorbs some shear force and disperse forces during gait, can provide suspension mechanism Cons: skin reaction possible, require dexterity and upper strength to donn and doff, increased attention and time to donn, increased demand for cleaning, contact dermatitis/bacterial infections/folliculitis possible Material Selection: All decrease friction, increase weight bearing area, and increase padding and may reduce shear forces. The ideal material has high stiffness, protection from impact and minimal change in thickness during use. May be desirable to have characteristics similar to biotissues being replaced. -​ Silicone -​ Custom options, Ossur, ottobock orr can be made in house -​ Standard -​ Gel socks (3mm) an option -​ can vary on durometer or shore, stiffer but does not deform as much as TPE -​ Urethane -​ Excellent for very delicate skin i.e. skin grafts -​ does return to original shape and acts the most like natural muscle. Its an advantage because it keeps consistency as far as thickness in the liner (especially important for elevated vac) also has flow properties, so it moves into areas of lesser pressure when loaded -​ Can be used with elevated vacuum  -​ Utilizes TSWB socket modifications (total reduction regardless of boney prominences because urethane creates its own equilibrium) -​ Mineral Oil Based (TPE- Thermoplastic Elastomer) -​ Body heat will change it’s shape over time -​ Wear out quicker -​ changes shape more and more quickly than muscle but when the stress is released it does not return to its original shape, therefore can be heated and shaped Other things to consider with liners are things like their profile (cross sectional densities), orientation, wave features etc Flexible sockets with rigid frame -​ Frame over pressure tolerant areas, cutouts over intolerant ones Pros: improved comfort and decreased heat Cons: not very well researched Suspension Selection Sleeve Suspension -​ Create a seal between the limb, liner, and the prosthesis = suction suspension -​ A one way expulsion valve can help enhance suction, but is not needed -​ Must have contact of sleeve to skin to create seal -​ Uses friction and negative pressure to create an airtight seal and suspend the socket Advantages: -​ Excellent suspension due to near suction like effect -​ No circulatory restriction -​ Prevention of tissue bulge at posterior opening -​ Cosmesis -​ Simplicity -​ Air tight therefore water doesn’t get into the socket Disadvantages: -​ Heat/Sweating (closed environment = contained heat = sweat accumulates) -​ Sometimes difficult to don, requires dexterity and upper strength -​ Fragile, limited durability -​ Liner + Sleeve = excess material in popliteal region, especially when sitting or with knee flexed -​ Skin irritation possible Suction -​ One way valve -​ Need a proximal seal (sleeve, ring)  Locking Pin -​ Serrated pin engages locking mechanisms in a locking mechanism within the socket -​ Provides auditory feedback (clicking when locked in) -​ Actively pulls the residuum down into the socket, very good for really tissuey limbs -​ Issues with milking and elongating the end of the residuum -​ Not indicated for very active individuals -​ There is pressure during swing phase (milking/elongation) from weight of prosthesis -​ Locking mechanism option: -​ clutch, once engaged, turn the crank and pull limb into the socket -​ ratchet, clicks with noise, grooves on pin, button release lock -​ Friction, smooth pin, infinite number of locking positions ​ Advantages: -​ Secure and simple -​ Less cumbersome, don’t require a suspension sleeve -​ Donning and doffing is simple and easy for some -​ Audible feedback, confidence/security the prosthesis is suspended -​ Lots of pin lock options ​ Disadvantages: -​ Distal tissue stretching or milking, and pistoning of the prosthesis are both associated with pin use -​ Distal umbrella tends to wear out the distal end of the liner -​ Some have trouble aligning pin with the hole -​ Fabrication time and difficulty can increase with a pin -​ Pin locks can emit noise (clicking, squeaking) -​ Clearance: can add length to socket -​ Cosmesis: push buttons can look undesirable, pylon might have to lean if alignment adjustments are required Beil & Street found much lower overall occlusive pressure on proximal tissue with suction suspension over pin, and lower peak suction at the distal end The theory is that the pin linear squeezes proximally and creates a large suction distally. Hypothesis is that it creates daily and chronic skin changes. Lanyard Suspension -​ Hold liner in socket with cord attached to the end of the liner -​ Useful for water prosthesis or when build height is limited -​ More delicate than pin lock -​ Maintenance is crucial, lanyard is delicate Anatomical Suspension Supracondylar: contours over medial and lateral femoral condyles, purchase over top provides suspension through internal pelite liner (PTB-SC or PTS suspension) -​ Pros: no straps, sleeves, or belts; simple to don; assists with knee stability (both M/L and extension control), comfortable in sitting, increases SA so good for short residuums, -​ Cons: bulky, shows through most pants, can cause atrophy proximal to the condyles over time, friction over condyles is tough to avoid from rotation, not suitable for very muscular or obese patients Supracondylar - Suprapatellar (PTB-SC-SP) -​ Added high anterior wall, addition suspension from quadriceps bar above patella, can be indicated to limit knee extension, poor cosmesis especially in sitting Elevated Vacuum -​ Component that uses vacuum pump built into shank -​ Expensive, slightly heavier, can be useful though -​ More positive suspension (makes prosthesis feel lighter), improved limb health has been proposed (improved socket fit from less volume changes and improved blood flow) -​ Socket fit is extra important here, limb needs to be quite stable, no voids between limb and socket, always needs a gel liner -​ System seals the liner to the socket walls, drawing fluid into the residual limb ​ Inclusion and pros: -​ Must use urethane or silicone liner -​ Fairly stable limb volume, less than 5 ply -​ Reduced pistoning needed -​ Increased proprioception -​ Can be useful for shorter residual limbs Exclusion and cons: -​ Knee flexion contracture > 15 degrees -​ Long term limb volume fluctuations, however it can be used to stabilize volume -​ Cognitive limitations to understanding proper donning and use of the vacuum -​ Inconsistent donning -​ Immature limb -​ Cosmesis, requires an external valve Cuff Suspension -​ Attached slightly posteriorly to the midline, critical for sitting comfort Pros: -​ Easy to donn/doff -​ Easy to adjust  -​ Can limit knee hyperextension Cons: -​ Can limit knee flexion -​ Socket rotation -​ No M/L support Waist Belt and Anterior Strap -​ Elastic anterior strap allows extra length during knee flexion and provides some assistance to knee extension -​ Can be used as auxiliary or primary suspension -​ Pros: easy to donn/doff -​ Cons: elastic becomes stretched out quickly, many straps and buckles require dexterity, sensation and sight Fork strap attachment: 1 cm distal to PTB, 2.5 cm anterior to joint centre Thigh lacer with side joints Pros: -​ Increased surface area, M/L stability, A/P stability depending on joints used or if theres a check strap included Cons: -​ Bulky, hard to keep clean, lots of technical work Foot Selection SACH foot (Solid ankle cushioned heel) -​ Poor energy return -​ Stable -​ Low cost -​ Easy to replace/build -​ Reliable -​ Useful for slower, low activity users -​ Useful for training -​ Mostly for people who are only standing, not ambulating really K1 Foot. Most basic foot on the market. Recommended only for those with limited functional ability and potential to ambulate. Primarily for transfers and limited ambulators. Soft heel allows for impact absorption at heel strike but provides minimal energy return and anterior support. Articulated - Single Axis -​ Smoother heel strike to midstance, high stability after midstance -​ Adjustable plantar flexion bumper -​ Added weight -​ Not common in TT prescription  -​ Exception: weak quads - decreases flexor moment at the knee more quickly -​ Moderate cost, easy to service Also suitable for K1 ambulators. For patients ambulating at a single speed who require greater stability during weight acceptance due to weak knee extensors or poor balance. Articulated - Multi-axis -​ Accommodates uneven terrain in all planes -​ Lower energy efficiency -​ Patient must have strength and coordination to control added movement -​ Common in TT rx -​ Added weight K2 feet. Often can be adjusted with different bumpers within the feet. Dynamic/Energy Storing -​ Useful for moderate to high activity patients but not limited to them -​ Energy is stored and returned via spring which is integral to the foot/shank -​ Relatively light weight -​ Relatively high cost -​ NO ACTIVE MOMENT Appropriate for K3 patients (beyond normal locomotion and walk at variable cadences). Compared to SACH feet, they reduce energy consumption, offer increased ankle motion, reduce sound side loading, and store and return more energy. Should bee considered forr those at rissk of overuse injures. Hydraulic Controlled -​ Adjusts to various terrain and heel heights -​ Accommodates sitting/squatting -​ Reports of improved gait symmetry, stability, and reduced load on the residuum Microprocessor feet -​ Foot ankle complexes that are capable of adapting and responding to real time situational needs -​ Variable walking speeds, terrains -​ Heavier than most other feet, require nightly charging, -​ Indicated for K3 who encounter inclines in their activities of daily living -​ Contraindicated for very high activity, heavy body weight, and frequent exposure to water, dirt, and extreme temperatures. -​ Advantages: better adaptation to slsopes and stairs, increased stability of uneven terrain, and decreased fall risk -​ Disadvantages: cost, weight, greater maintenance requirements, need for greater clearance under prosthetic foot Powered feet -​ Go beyond dampening by generating an active moment (DF or PF) -​ Research demonstrratees a significant reduction in metabolic cost, which allows people with amputations to walk with less energy and better gait symmetry -​ Heavy and expensive Heel height adjustable feet -​ User changes ankle position to accommodate for different heel heights to maintain a consistent alignment 0-2’ -​ Moderate activity Fibular Hemimelia 1.​ Shorter femur on affected side 2.​ Valgus presentation at the knee 3.​ Anterior tibial bowing 4.​ Skin dimple at apex of bowing Alignment: refers to the spatial orientation of the prosthesis socket relative to the foot. It affects the magnitude and direction of the ground reaction force throughout the gait cycle. 4 goals: 1. Facilitating heel strike at initial contact 2. Providing adequate single limb stability during the stance phase 3. Creating smooth forward progression (rollover) 4. Ensuring adequate swing phase toe clearance Bench alignment: -​ 5 degrees of flexion -​ The reason for the 5 degrees of socket flexion is to elongate quadriceps muscles slightly so that they are better prepared to accept the full weight of the body and to aid in shock absorption during loading response. -​ 5 degrees of adduction -​ The 5 degrees of adduction ensures that the foot is sufficiently inset to create the appropriate varus moment during stance. This properly loads the proximomedial and distolateral aspects of the limb that are best able to carry those forces. -​ Top of the foot is level in all planes -​ Medial border of the foot is in the line of progression -​ Sagittal = knee centre through the ⅓ foot length from heel Goals of optimal alignment arre stance stability, swing clearance, equal step length, and energy efficiency. Endoskeletal -​ Advantages: adjustability (modular components) and realistic appearance (from various cover options) Exoskeletal -​ More durable and easily cleanable -​ Often heavier and always less adjustable Transtibial Amputations -​ 2.5cm of residual limb for every 20cm of pt height is ideal. Typically resulting in between 12.5-17.5cm. -​ Staples usually stay in for 3 weeks, longer if needed Burgess -​ Most common. Post flap. -​ Modified: soleus is removed to debulk -​ Myodesis is performed by attaching the posterior compartment muscles to the tibia Bruckner -​ Removes tib ant and the bulk of the soleus -​ Modified bruckner also removes the fibula -​ No clear benefit in literature -​ For individuals with severe PAD to decrease risk of postoperative necrosis Ertl -​ Osteomyoplastic amputation with a tibiofibular synostosis -​ Bone bridge between the distal tib and fib Osseointegration -​ osseointegrated implants allow for physiologic weight bearing, improved range of motion at the proximal joint, and osseoperceptive (a.k.a. osseoproprioception) sensory feedback ​ Indications: offered to patients who have demonstrated considerable difficulty with their conventional socket-based prosthesis. Especially for transfemorals. ​ Contraindications: dysvascular patients with PVD and/or diabetes due to higher risk of infection and likely shorter anticipated survival -​ Most commonly reported complication is infection. Superficial infection reported as high as 55% of pts, although most can be treated with antibiotics. Long term risk of osteomyelitis in TF osseointegration is 20% at 10 years, with a 9% risk of implant removal due to infection. -​ Other complications include aseptic loosening (2-6%0 and periprosthetic fracture (0-4%) also occur Random stuff: -​ Neuroma pain affects 13% of TT and 32% of TF patients. TMR has been used to reorganize the nerves and reduce their bundling. Targeted nerve implantation, and RPNI are also used