Prosthetic alignment and biomechanics Dr Winson Lee htwinsonpolyu

Prosthetic alignment and biomechanics 假肢对线和生物力学 Dr. Winson Lee htwinson@polyu. edu. hk

• Bench alignment 作台对线 – Initial relationship between socket, knee and foot, before fitting on the amputee – 安装上截肢者之前，初步接受腔，膝和脚之间的 关系。 • Static alignment静态对线 • Dynamic alignment动态对线 – Begin after all suitable adjustments made during static alignments – 适当的静态对线调整后开始 • Mal-alignment will affect comfort and stability • 不良对线会影响舒适性和稳定性

Bench alignment 作台对线 • AP前后: – Socket preflexed at 5 degrees 接受腔预弯在 5度 • Make hip extensors more effective • 使髋关节伸肌更有效 • Aids in maintaning the ischial tuberosity on the posterior shelf • 措施以维持坐骨结节在后架 • If flexion contracture is present, this angle is added to the preflexion • 如果屈曲挛缩存在，这个角度是添加到预弯角 – A plumb line dropped from the greater trochanter 铅垂线从大转 子下垂 • 5 mm in front of the knee center 膝盖前方 5毫米 – Provide stability 提供稳定性 • 10 -15 mm behind the center of the foot • 脚的中心后10 -15毫米

Bench alignment 作台对线 – Knee bolt is horizontal, and is perpendicular to the line of progression – 膝关节螺栓水平，并垂直于进展线 • ML 内外: – The center of the heel is directly under, or slightly lateral to the point at which the ischial tuerosity contacts the posterior shelf of the socket – 脚跟中心是直属向下，或稍微外侧於坐骨结节接触接受腔 后架的点

• Positions of anatomical landmarks 解剖标志的位置 – Ischial tuberosity 坐骨结节 • 25 mm lateral to the inside posterior medial corner of the socket • 接受腔后内侧角的外侧 25 mm – Greater trochanter 大转子 • Mark a point 25 mm anterior to the posterior medial corner of the socket • 在接受腔后内侧角前25毫米标志一点 • Draw a vertical line crossing the point, the greater trochanter will be along the line • 画一条垂直线交叉這点，大转子将沿著這线

Static alignment 静态对线 • When the amputee stand between parallel bars with equal weight borne on both legs, check: • 当截肢者站立在双杠之间，双腿承担同等重量時，检查： – Bench alignment 作台对线 – Socket comfort 接受腔舒适 • No pressure on the pubic ramus • 没有耻骨支压力 • No adductor rolls • 没有内收肌组织肉滚 • Anterior brim not contacting ASIS when amputee bend forward • 截肢者前倾時，接受腔前方没有接触前后路髂棘 – If suction socket is used, check if there is vacuum losing

Static alignment 静态对线 – Prosthesis length 假体长度 – 膝关节稳定性 Knee stability (TKA line) • Shift weights to the prosthesis and back to the sound side • 权重移到假肢再返回健侧 • Stand with even weight put on each foot, and attempt to flex the prosthetic knee, then return to extended position • 以每只脚承担相等重量的站立，并试图弯曲膝关节，然后返回到扩展 的位置 – The foot should be under the ischial tuberosity – 脚应在坐骨结节之下 – The socket does not rotate against the ischial tuberosity – 接受腔不该在坐骨粗隆旋转 – Location of suspensory attachment – 悬吊附着位置

Dynamic alignment 动态对线 • Doing the following during dynamic alignment: • 在做动态调整如下： – Ask the amputee to take one step back and forth to evaluate knee stability – 要求截肢者来回踏一步评估膝关节的稳定性 – Ask the amputee to take a few steps, starting with the sound limb, then switch to the prosthetic side – 要求截肢者踏前几步，首先从健全肢体，然后切换到假 肢方

Dynamic alignment 动态对线 – Check if the base of support is appropriate (510 cm) – 检查支援基地是否适当的（5 - 10厘米） – Check if the trunk bends to the prosthetic side – 检查躯干是否弯曲假肢方

– Check if there is excessive heel rise during swing, or any impact of the knee at the end of swing phase – 检查摆动过程中鞋跟是否过高，或摆动结束時有否任何膝关节冲 击 • Adjust the knee friction and extension aid • 调整膝盖摩擦和助伸裝置 – Check if the heel is compressed about 10 mm during loading response – 检查脚跟在著地時否是压缩约 10 mm • If not, inappropriate heel durometer is used • 如果没有，不当鞋跟硬度

Alignment and biomechanics 对线和生物力学

• AP alignment 前后对线 – Prosthetic knee joint placement 人 膝关节安置 • Forward placement of the socket 接受腔向前安置 – More stable prosthetic knee – 更稳定的人 膝关节 • Backward placement of the socket 接受腔向后安置 – Less stable prosthetic knee – 欠稳定的人 膝关节

• AP alignment前后对线 – Early stance phase 早期的站立阶段： • Non-amputees非截肢者 – After heel strike, there will be knee flexion controlled by quadriceps – 脚跟著地后，膝关节屈曲将由股四头控制 • Trans-femoral amputees大腿截肢者 – Must prevent prosthetic knee from uncontrolled flexion immediately after heel strike – 必须防止脚跟著地后膝关节不受控屈曲 – Ground reaction force in front of the knee axis, maintaining it in extension – 地面反作用力在膝关节轴前方，维护它的伸展 – Hip extension keeps the prosthetic knee in extension

• AP alignment 前后对线 – Mid to late stance phase: 中至后站立期: • Trans-femoral amputees大 腿截肢者 – Tend to flex the prosthetic knee, by doing hip flexion – 倾向由髋关节屈曲，至弯曲人 膝关节。 – At that time, the ground reaction force acts on the anterior region of the prosthetic foot – 在此刻，地面反作用力作用于 假肢脚前区

– Longer toe lever arm would delay knee flexion – 长趾杠杆臂会延误膝关节屈 曲 – Shorter toe lever arm would make knee flexion earlier – 脚趾较短的杠杆臂会令膝关 节屈曲較早

• AP alignment 前后对线 – Swing phase 摆动期: • Non-amputees非截肢者 – The hamstrings produce knee flexion, which clears the foot off the ground – 腿筋肌肉产生膝屈曲，令脚離開地面 – Towards late swing phase, the hamstrings restricts knee extension – 晚摆动阶段，腿筋肌肉限制伸膝 • Trans-femoral amputees大腿截肢者 – Hip flexion produces prosthetic knee flexion – 膝关节屈曲产生人 髋关节屈曲

– The anterior force at the proximal end of the shank and the posterior inertial effect at the distal end continue to flex the knee joint – 在小腿近端的前方力和在远端的后方惯性力， 继续作用弯曲膝关节 – Very active amputees may tend to cause excessive knee flexion – 非常活跃的截肢者可能倾向于造成过度的膝 关节屈曲 – Appropriate use of an extension aid can resist too much knee flexion – 适当使用助伸裝置能抵御太多的膝关节屈曲

• ML alignment 内外对线 – Center of the heel directly under the point at which the ischial tuerosity – 脚跟中心点在坐骨粗隆直下方 • No tendency for the prosthesis to change its angular relationship • 假肢没有改变其角的关系的趋势

– In reality, the resultant ground reaction force and the body weight of the wearer are not collinear – 在现实中，由此产生的地面反应力和穿着者 的体重不共线 • Tendency of the socket to rotate接受腔有 旋转趋势 • The soft tissues are compressed and generate counter forces to stop the rotation软组织被压缩并产生反作用力停止转动

• ML alignment内外对线 – If the foot is inset 如果脚掌內置 • Rotation of the prosthesis causes high pressure at the lateral distal and medial proximal areas of the residual limb • 假体旋转令残肢远端外侧及近端内侧承受高压 Foot inset – If the foot is inset 如果脚掌外置 • Rotation of the prosthesis causes high pressure at the proximal lateral and distal medial areas of the residual limb • 假体旋转令残肢远端内侧及近端外侧承受高压 – The greater the inset/outset, the higher the pressure – 內置/外置越大，压力越大 Foot outset

• ML alignment 内外对线 – If there is too much foot outs 如果脚掌過于外置 • Lateral movement of the femur during stance phase happen • 站立期時，股骨向外侧运动期 • The pelvis drops on the opposite side • 对面的骨盆下降 • Amputees may laterally bend the trunk to compensate

Gait deviations and malalignment 步态偏差和不当对线

Lateral trunk bending 躯干倾向假肢侧 • The trunk bends to the prosthetic side from loading response to mid-stance. • 由著地至中站立中期，躯干趋向假肢弯曲 • Causes原因: – The prosthesis too short假肢太短 – Weak hip abductors弱髋外展肌 • Shift over the prosthesis to compensate for the tendency of pelvic drop on the sound side • 假肢移位，以补偿对健侧盆骨下降趋势

Lateral trunk bending 躯干倾向假肢侧 – Inadequate adduction of the socket 接受腔 内收不足 • Reduce the effectiveness of the hip abductor in stabilizing the pelvis • 减少髋关节外展肌在稳定骨盆的成效 – Insufficient support by lateral socket wall 接受腔外侧墙壁没有足够的支持 • Inability to block lateral movement of the femur, causing the pelvis to drop on the sound side when the prosthesis is in stance. The amputee shift towards the prosthetic side to compensate • 无法阻挡股骨向外侧运动，导致假肢在站立期時， 健侧盆骨下降边时。截肢者移向假肢以补偿。 – Short residual limb – 短残肢

Abducted gait 外展步态 • The width of the walking base is more than the normal range of 5 -10 cm • 步行基础的宽度大于正常(5 -10 cm)的范围 • Causes原因： – The prosthesis is too long – 假体过长 – Pain in the perinium due to 会阴疼痛因: • Adductor roll 内收卷 • Excessive pressure at medial brim 内侧边 缘过度压力

Abducted gait 外展步态 – Contracted hip abductors – 收缩的髋外展肌 – Shank aligned in valgus position – 小腿置于外翻位置 – Amputees feel insecure: – 截肢者感到不安全

Circumduction划弧外展步态 • Causes原因： – The prosthesis is too long假体过长 – Prosthetic socket is too small (ischial tuberosity is above the posterior shelf) – 假肢接受腔太小（坐骨结节在后架以上） – Foot set in plantarflexion – 足跖屈太多

Circumduction划弧外展步态 – Inadequate suspension causing prosthesis to fall off – 悬挂不足造成假肢脱落 – Excessive knee friction/ extension aid too tight – 膝关节摩擦装置太強/助伸装置太紧

Vaulting 提髋 • The amputee raises the body by early and excessive plantarflexion of the sound foot during swing of the prosthetic side • 截肢者在假肢摆动期利用健则过早和过度的足跖屈来提高 身体 – The prosthesis is too long假体过长 – Prosthetic socket is too small (ischial tuberosity is above the posterior shelf) – 假肢接受腔太小（坐骨结节在后架以上） – Foot set in plantarflexion – 足跖屈太多 – Inadequate suspension causing prosthesis to fall off悬挂不足造成假肢脱落

Vaulting 提髋 – Excessive knee friction/ extension aid too tight – 膝关节摩擦装置太強/助伸装置太紧 – Insufficient knee friction膝盖摩擦不足 • Too much heel rise • 脚跟上升太多 • The body is no longer at maximum elevation when the prosthetic foot is at its lowest point • 当假肢脚在的最低点时，身体不再在提到最高 • The foot would not clear the ground • 脚没有离地 • Vaulting to compensate • 提髋以补偿

Whip 击地 • Occur at toe-off 发生在脚趾离地时 • Causes原因： Medial whip – Improper ligament of knee bolt in the transverse plane – 膝关节螺栓在水平面对线不当 – The socket is too tight – 接受腔太紧 – Improperly contoured to accommodate muscle contractions – 不当轮廓，以适应肌肉收缩 Lateral whip

Foot slap 假腳拍地 • The prosthetic foot plantarflexes excessively and hits the floor at foot flat • 假肢足跖屈太多，在脚平放时 拍打地面 – Cause: Plantar-flexion bumper durometer is too low – 原因：假脚后跟缓冲器太软

Uneven heel rise 不均匀的足跟著地 • The heel of the prosthetic side rises more or less than that of the sound limb, from toeoff to mid-swing • 由脚趾离地时到中摇摆期，假肢方脚跟比健全肢体 上升较多或较少 • Cause of excessive heel rise原因： – Not enough knee friction – 膝盖摩擦不足 – No enough extension aid – 助伸装置不足 – Excessive hip flexion – 髋关节过度屈曲

Terminal impact 假肢摆动末期膝关节撞击 • The prosthetic shank comes to a sudden stop, with visible and audible impacts at full extension at terminal swing • 假肢小腿部分在摆动末期全展时突然停止，并 出现耳闻目睹的撞击。 • Causes原因： – – – – Not enough knee friction 膝盖摩擦不足 Too much extension aid 助伸装置太多 Fear of inadvertent knee flexion 恐惧无意的膝关节屈曲 Extension stop of the knee is too

Excessive lordosis 腰椎前凸 • Excessive lumbar lordosis when the prosthesis is in stance, and the trunk may bend posteriorly • 当假肢站立时，过多的腰椎前凸，而且躯干可能向后 弯曲 • Causes原因： – – – Hip flexion contracture 髋关节屈曲挛缩 Not enough socket flexion 接受腔屈曲不足 Not enough anterior brim support 前部边缘没有足够的的支持

Foot rotation at heel strike 假肢在足跟著地時旋转 • When the heel contacts the ground, it rotates laterally, sometimes medially • 当脚跟接触地面，有时向外旋转，有时向内旋转 • Cause原因： – The SACH heel cushion is too hard – SACH足跟垫太硬 – Plantar flexion bumper of the single-axis foot is too hard – 假脚的后缓冲器太硬