Andreas Kannenberg, MD PhD, Director Medical Affairs Evidence-based and biomechanical considerations for selection of mechanical prosthetic knees Andreas Kannenberg, MD PhD, Director Medical Affairs

Importance of prosthetic knee selection Background Importance of prosthetic knee selection For 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 ambulation support as many as possible activities of daily living

Body of evidence on prosthetic knee selection Mechanical prosthetic knees – 2 systematic reviews van der Linde et al. 2004 only 5 studies on mechanical prosthetic knees had good enough quality to be included in the review one 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 unit advanced swing phase control mechanisms (pneumatic or hydraulic) may improve gait symmetry and velocity of active prosthesis users van 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

Body of evidence on prosthetic knee selection Mechanical prosthetic knees – 2 systematic reviews Samuelsson et al. 2012 Systematic review of all studies in lower limb prosthetics 818 studies found 737 excluded as not pertinent or duplicates 73 studies excluded for poor quality 8 studies had sufficient methodological quality to be reviewed Not 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): 145-158

Prosthetic knee selection Do prosthetic knee classifications help? Various knee classifications exist all are based on technologies used for stance and swing control extensive background knowledge of features and functions of knee technologies is needed features and functions of prosthetic knees using the same technology may differ remarkably prosthetic knee classifications do not facilitate clinical decision making

Prosthetic knee selection Biomechanical considerations – Stance control Knee flexion under weight bearing no knee flexion limited knee flexion unlimited knee flexion locked knee friction brake knee 4-bar polycentric knee multiaxial knee (≥5 axes) bouncing adapter hydraulic knee modified after: Blumentritt S: Biomechanical aspects of the indications of prosthetic knee joints. Orthopädie-Technik 2004,55(6):508-524 (Article in German)

Mechanical knee stability and function A reciprocal relationship Stability* Function locked knee friction brake knee 4-bar polycentric knee multiaxial knee (≥5 axes) hydraulic knee free 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 recovery modified after: Blumentritt S: Biomechanical aspects of the indications of prosthetic knee joints. Orthopädie-Technik 2004,55(6):508-524 (Article in German)

Locked knee Benefit total stability (prevention of knee collapse) at all times and circumstances Disadvantages walking with a stiff prosthetic leg at all times compensatory movements to produce foot clearance no stance flexion for shock absorption does not support reciprocal gait (step-over-step) on uneven ground or slope and stair descent 3R40 3R41 Suitable for mobility grade 1 (household) ambulators or amputees who are not able to safely control a more functional knee only.

Friction brake knee Benefit able to flex during swing phase – more natural swing pattern and foot clearance Disadvantages requires full extension at heel strike no stance flexion for shock absorption does not allow for knee flexion at late stance (pre-swing) does not support reciprocal gait on uneven ground or slope and stair descent 3R90 / 3R92 3R49/15, 3R42 Suitable for high mobility grade 1 (household) and low to medium mobility grade 2 (limited community) ambulators.

4-bar polycentric knee 3R36/20 Benefit(s) usually very safe at heel strike shortening of calf during swing – improved foot clearance allows for knee flexion at late stance – more natural and dynamic gait pattern shortening of thigh during sitting – more natural appearance Disadvantages requires full extension at heel strike no stance flexion for shock absorption does not support walking on uneven ground, slopes, and stairs information on centrode required to match knee and patient 3R78 4-bar knees with a safe centrode are suitable for medium to high mobility grade 2 (limited community) and mobility grade 3 (unlimited community) ambulators.

Multiaxial knee with ≥5 axes 3R60 EBS / 3R60 EBSpro Additional benefits to 4-bar knee may support limited stance flexion for shock absorption may support walking on shallow slopes and sligthly uneven ground Disadvantages requires full extension at heel strike stance flexion of ≥5° requires stance extension dampening to prevent buckling does not support reciprocal gait on heavily uneven ground or steeper slope and stair descent Multiaxial knees are suitable for medium to high mobility grade 2 (limited community) and mobility grade 3 (unlimited community) ambulators who tolerate stance flexion.

Hydraulic knee Benefits may support stance flexion for shock absorption may support loading for sitting down may support reciprocal gait on uneven ground as well as slope and stair descent Disadvantages requires full extension at heel strike stance flexion of ≥5° requires stance extension dampening to prevent buckling switch 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 manner 3R80

Hydraulic knee Hydraulic knees are suitable for mobility grade 3 (unlimited community) and 4 (very active [“athlete“]) ambulators only.

Free single axis knee and very dynamic 4-bar knee Benefits full voluntary control of the prosthesis may allow for (free swing) reciprocal gait on uneven ground as well as slope and stair descent if properly motor controlled by the residual limb Disadvantages absolutely no safety features other than posterior offset of the knee or instant center of rotation, respectively requires full extension at heel strike requires 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“ manner 3R95 3R55

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.

Prosthetic knee selection Biomechanic al considerations – Swing control Swing phase control one (fixed) gait speed low to medium range of gait speeds full spectrum of gait speeds Friction Pneumatic Hydraulic Swing extension assist if full extension prior to heel strike.cannot be reached reliably

C-Leg research summary 14 clinical trials with 236 patients 12 biomechanical studies with 129 patients 5 patient surveys with 368 patients 3 health-economic studies with 146 patients in 3 countries 1 systematic review The C-Leg combines excellent safety (not only stability) and support of function such as safe reciprocal gait on uneven terrain and slope and stair descent.

Prosthetic knee selection Summary Prosthetic knee selection Current 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.

Thank you for your attention. andreas.kannenberg@ottobock.de