Presentation on theme: "Andreas Kannenberg, MD PhD, Director Medical Affairs"— Presentation transcript:
1 Andreas Kannenberg, MD PhD, Director Medical Affairs Evidence-based and biomechanical considerations for selection of mechanical prosthetic kneesAndreas Kannenberg, MD PhD, Director Medical Affairs
2 Importance of prosthetic knee selection BackgroundImportance of prosthetic knee selectionFor transfemoral amputees selection of the most appropriate prosthetic knee is key to successful rehabilitation and reintegration into social and professional life.The prosthetic knee must meet two essential needs:provide the greatest safety possible during ambulationsupport as many as possible activities of daily living
3 Body of evidence on prosthetic knee selection Mechanical prosthetic knees – 2 systematic reviewsvan der Linde et al. 2004only 5 studies on mechanical prosthetic knees had good enough quality to be included in the reviewone study concluded that a Mauch SNS with a lock may enable vascular amputees to adopt a higher walking speed as compared to an unlocked knee unitadvanced swing phase control mechanisms (pneumatic or hydraulic) may improve gait symmetry and velocity of active prosthesis usersvan der Linde H, Hofstad CJ, Geurts ACH, Postema K, Geertzen JHB, van Limbeek J: A systematic review of the effect of different prosthetic components on human functioning with a a lower limb prosthesis. J Rehabil Res Dev 2004, 41 (4): 55-70
4 Body of evidence on prosthetic knee selection Mechanical prosthetic knees – 2 systematic reviewsSamuelsson et al. 2012Systematic review of all studies in lower limb prosthetics818 studies found737 excluded as not pertinent or duplicates73 studies excluded for poor quality8 studies had sufficient methodological quality to be reviewedNot a single study with mechanical prosthetic knees had enough methodological quality to be included in the review.Samuelsson KAM, Töytäri O, Salminen AL, Brandt Å: Effects of lower limb prosthesis on activity, participation, and quality of life: a systematic review. Prosthet Orthot Int 2012, 36(2):
5 Prosthetic knee selection Do prosthetic knee classifications help?Various knee classifications existall are based on technologies used for stance and swing controlextensive background knowledge of features and functions of knee technologies is neededfeatures and functions of prosthetic knees using the same technology may differ remarkablyprosthetic knee classifications do not facilitate clinical decision making
7 Mechanical knee stability and function A reciprocal relationshipStability*Functionlocked kneefriction brake knee4-bar polycentric kneemultiaxial knee (≥5 axes)hydraulic kneefree single axis knee*Stability = prevention of knee collapse during level walking( ≠ Safety !!! )Safety = stability during level walking stability during walking on uneven terrains, slopes, stairs toe clearance stumble recoverymodified after: Blumentritt S: Biomechanical aspects of the indications of prosthetic knee joints. Orthopädie-Technik 2004,55(6): (Article in German)
8 Locked kneeBenefittotal stability (prevention of knee collapse) at all times and circumstancesDisadvantageswalking with a stiff prosthetic leg at all timescompensatory movements to produce foot clearanceno stance flexion for shock absorptiondoes not support reciprocal gait (step-over-step) on uneven ground or slope and stair descent3R403R41Suitable for mobility grade 1 (household) ambulators or amputees who are not able to safely control a more functional knee only.
9 Friction brake kneeBenefitable to flex during swing phase – more natural swing pattern and foot clearanceDisadvantagesrequires full extension at heel strikeno stance flexion for shock absorptiondoes not allow for knee flexion at late stance (pre-swing)does not support reciprocal gait on uneven ground or slope and stair descent3R90 / 3R923R49/15, 3R42Suitable for high mobility grade 1 (household) and low to medium mobility grade 2 (limited community) ambulators.
10 4-bar polycentric knee3R36/20Benefit(s)usually very safe at heel strikeshortening of calf during swing – improved foot clearanceallows for knee flexion at late stance – more natural and dynamic gait patternshortening of thigh during sitting – more natural appearanceDisadvantagesrequires full extension at heel strikeno stance flexion for shock absorptiondoes not support walking on uneven ground, slopes, and stairsinformation on centrode required to match knee and patient3R784-bar knees with a safe centrode are suitable for medium to high mobility grade 2 (limited community) and mobility grade 3 (unlimited community) ambulators.
11 Multiaxial knee with ≥5 axes 3R60 EBS / 3R60 EBSproAdditional benefits to 4-bar kneemay support limited stance flexion for shock absorptionmay support walking on shallow slopes and sligthly uneven groundDisadvantagesrequires full extension at heel strikestance flexion of ≥5° requires stance extension dampening to prevent bucklingdoes not support reciprocal gait on heavily uneven ground or steeper slope and stair descentMultiaxial knees are suitable for medium to high mobility grade 2 (limited community) and mobility grade 3 (unlimited community) ambulators who tolerate stance flexion.
12 Hydraulic knee Benefits may support stance flexion for shock absorptionmay support loading for sitting downmay support reciprocal gait on uneven ground as well as slope and stair descentDisadvantagesrequires full extension at heel strikestance flexion of ≥5° requires stance extension dampening to prevent bucklingswitch mechanism between stance and swing is susceptible to unintentional switching – amputee must always be “alert“, prepared, and able to take over control with residual limb or fall in a controlled manner3R80
13 Hydraulic kneeHydraulic knees are suitable for mobility grade 3 (unlimited community) and 4 (very active [“athlete“]) ambulators only.
14 Free single axis knee and very dynamic 4-bar knee Benefitsfull voluntary control of the prosthesismay allow for (free swing) reciprocal gait on uneven ground as well as slope and stair descent if properly motor controlled by the residual limbDisadvantagesabsolutely no safety features other than posterior offset of the knee or instant center of rotation, respectivelyrequires full extension at heel strikerequires excellent residual limb strength and coordination to control and secure the prosthesis at any times and circumstances as well as the ability to fall in a controlled and “safe“ manner3R953R55
15 Free single axis knee and very dynamic 4-bar knee Free single axis and very dynamic 4-bar polycentric knees are suitable for mobility grade 4 (very active [“athlete“]) ambulators only.
16 Prosthetic knee selection Biomechanic al considerations – Swing controlSwing phase controlone (fixed) gait speedlow to medium range of gait speedsfull spectrum of gait speedsFrictionPneumaticHydraulicSwing extension assist if full extension prior to heel strike.cannot be reached reliably
17 C-Leg research summary 14 clinical trials with 236 patients12 biomechanical studies with 129 patients5 patient surveys with 368 patients3 health-economic studies with 146 patients in 3 countries1 systematic reviewThe C-Leg combines excellent safety (not only stability) and support of function such as safe reciprocal gaiton uneven terrain and slope and stair descent.
18 Prosthetic knee selection SummaryProsthetic knee selectionCurrent clinical evidence and technical classifications don´t facilitate individual prosthetic knee selection.Knee selection may be based on biomechanical considerations on certain stance and swing control features to be matched with the physical (and mental) capabilities as well as mobility needs of the amputee.Manufacturers have to provide more detailed information on their prosthetic knees than they currently do on their websites, marketing materials, and instructions for use.Manufacturers are summoned to initiate and support research with their prosthetic knees to produce clinical evidence to better guide individual clinical decision making.