Jaclyn Hill, MD
Lower limb amputations are the most common amputations. Indications for amputation include trauma, dysvascularity (issues with blood flow to the limb), infection, congenital deficiencies (deficiencies present at birth), tumor and other more rare potential conditions such as overgrowth syndromes. In the adult population, the most common of these indications is a dysvascular limb secondary to diabetes mellitus and peripheral vascular disease. For the general population, the lower extremity amputation rate is 2.4 per 10,000. The level of amputation is determined by several factors and include through ankle (Syme), transtibial (below knee), through knee, and transfemoral (above knee). Deformities of the residual limb include short residual limb length, flexion contractures (when a joint cannot fully straighten) and bony overgrowth in the pediatric population as well as post-amputation deformity of the limb such as a knock kneed (valgus) alignment or bow legged (varus) alignment. Additonal potential complications would be reviewed by your surgeon such as infection, wound issues, phantom limb pain and painful neuroma.
Causes of Post-Amputation Deformities
A. Short length of residual limb: The level and technique of amputation is determined by the surgeon based on the underlying pathology. Specific surgical goals include clear margins for tumor and being outside the zone of injury for trauma. Specific congenital anatomy and vascularity to the leg also influence the level of amputation. The surgical goal is to have a healed incision and well-padded end.
B. Flexion Contractures: Often occur after surgery in the knee and hip from the leg resting in a bent position for a long period of time.
C. Bony Overgrowth: Occurs in children who are still growing. It most frequently occurs in the tibia and fibula after transtibial amputations. It can also occur after transfemoral amputations.
D. Post-amputation malalignment of residual limb: In certain congenital limb deficiencies such as fibular hemimelia, there is a tendency of the limb to grow into a knock-kneed (valgus) alignment due to the limb defiency.
A. Short length of residual limb: Short residual limbs may have difficulty with prosthetic fitting. Ideal remaining length for transtibial amputation is 12.5-17.5 cm. Too long of a transtibial segment may limit options for prosthetic components.
B. Flexion Contractures: Knee and/or hip is unable to straighten. This may result in difficulty with prosthesis wear and walking ability.
C. Bony Overgrowth: A bony prominence is noted at the end of the limb. This is usually painful and prevents prosthetic wear.
D. Postamputation malalignment of the residual limb: You or your doctor may notice a progressive angulation of the residual limb as your child grows following amputation for a congenital limb deficiency. This type of potential limb deformity following amputation in growing children highlights the importance of routine orthopaedic followup.
Your doctor will perform a detailed physical examination of the residual limb looking at the skin, soft tissue, alignment and range of motion of remaining joints. Your doctor will also identify any areas of pain. Radiographs of the remaining leg may be obtained for further assessment. Discussion between the prosthetist and your orthopedics surgeon is very important to identify the obstacles for prothesis fitting.
A. Short length of residual limb: In certain cases it is possible to perform a bony lengthening procedure for the short portion of the limb. This is most often accomplished with the use of an external fixator or very short internal lengthening nail. Other surgical procedures may be discussed that change the contour of the leg to help with prosthetic fit. A repeat amputation at the next conventional level may also be discussed in certain situations.
B. Flexion Contractures: Splinting immediately after amputation may help to prevent this complication. However, if this does occur, physical therapy for stretching is the primary treatment option. Bracing can also be used to help straighten the joints. If unsuccessful, surgery may be discussed to lengthen tight tendons at the back of the knee or the front of the hip. In more difficult cases an external fixator might be considered.
C. Bony Overgrowth: Primary treatment includes removal of the overgrown bone and shortening of the remaining bone to provide good soft tissue coverage of the end of the limb. Your surgeon may also discuss using other surgical techniques to reduce the frequency of overgrowth.
D. Postamputation malalignment of the residual limb: In a growing child, malalignment of the residual limb following amputation may be managed with a guided growth strategy; other surgical options such as osteotomy and realignment may be discussed by your surgeon.
Patients with amputations can live very functional lives. It is very important to follow up with your surgeon regularly in a growing child and with any concerns in adults to assess for potential deformity or other issues. Most difficulties can be improved with treatment.