Muscle performance about the knee joint in patients who had distal femoralreplacement after resection of a bone tumor - An objective study with use of gait analysis

Background: The treatment of a malignant bone tumor in the distal aspect of the femur often requires great sacrifice of bone and muscle. The extent of quadriceps removal has been reported to influence the longterm functional efficiency of a patient's gait. The objective of the present study was to d etermine gait function as it relates to the residual quadriceps strength an d to the specific component or components of the quadriceps removed in pati ents treated with total knee replacement because of a malignant bone tumor in the distal aspect of the femur. Methods: Sixteen patients were evaluated after implantation of a modular hi nged cementless knee prosthesis, The patients were assigned to two groups o n the basis of the different components of the quadriceps muscle that were resected, Group 1 consisted of five patients who had removal of the vastus medialis and the vastus intermedius and two who had removal of the vastus m edialis only, Group 2 consisted of nine patients who had removal of the vas tus lateralis and the vastus intermedius. Residual muscular strength about the treated knee was measured by voluntary maximum contraction isometric te sting. Foot-ground reaction forces, kinematic and kinetic findings, and ele ctromyographic activity during free-speed walking were recorded. Results: The kinematic study showed that the patients in Group 1 tended to have a stiff-knee gait during stance, whereas those in Group 2 (in which th e vastus medialis was spared) had a more regular flexion-extension knee pat tern. Electromyographic findings showed that a higher percentage of patient s in Group 1 had reduced or absent rectus femoris activity during the loadi ng response. Compared with the contralateral side, knee-extension strength in the treated limb was decreased in both groups. However, there were no si gnificant differences between the groups with respect to the pattern of str ength loss. Conclusions: Good gait function can be achieved in patients with a distal f emoral tumor that is treated with distal femoral resection, partial excisio n of the quadriceps, and total knee arthroplasty with insertion of a hinged prosthesis. Patients in whom the vastus lateralis and vastus intermedius w ere removed had better gait performance and a more physiological knee-loadi ng pattern than did patients in whom the vastus medialis was removed.