DIFFERENCES IN HIP MUSCLE STRENGTH AND STATIC BALANCE IN PATIENTS WITH TRANSFEMORAL AMPUTATIONS CLASSIFIED AT DIFFERENT K-LEVELS: A PRELIMINARY CROSS-SECTIONAL STUDY
Authors: John Stefanie , Orlowski Katja , Mrkor Kai-Uwe , Edelmann-Nusser Jürgen , Witte Kerstin 
Published: January 2022

BACKGROUND: Following amputation, patients with lower limb amputations (LLA) are classified into different functional mobility levels (K-levels) ranging from K0 (lowest) to K4 (highest). However, K-level classification is often based on subjective criteria. Objective measures that are able to differentiate between K-levels can help to enhance the objectivity of K-level classification.
OBJECTIVE(S): The goal of this preliminary cross-sectional study was to investigate whether differences in hip muscle strength and balance parameters exist among patients with transfemoral amputations (TFA) assigned to different K-levels.
METHODOLOGY: Twenty-two participants with unilateral TFA were recruited for this study, with four participants assigned to K1 or K2, six assigned to K3 and twelve assigned to K4. Maximum isometric hip strength of the residual limb was assessed in hip flexion, abduction, extension, and adduction using a custom-made diagnostic device. Static balance was investigated in the bipedal stance on a force plate in eyes open (EO) and eyes closed (EC) conditions. Kruskal-Wallis tests were used to evaluate differences between K-level groups.
FINDINGS: Statistical analyses revealed no significant differences in the parameters between the three K-level groups (p>0.05). Descriptive analysis showed that all hip strength parameters differed among K-level groups showing an increase in maximum hip torque from K1/2-classified participants to those classified as K4. Group differences were also present in all balance parameters. Increased sway was observed in the K1/2 group compared to the K4 group, especially for the EC condition.
CONCLUSION: Although not statistically significant, the magnitude of the differences indicates a distinction between K-level groups. These results suggest that residual limb strength and balance parameters may have the potential to be used as objective measures to assist K-level assignment for patients with TFA. This potential needs to be confirmed in future studies with a larger number of participants.
Layman's Abstract
Patients with lower limb amputation (LLA) are classified into different mobility levels, so-called K-levels, which are ranging from K0 (lowest) to K4 (highest). K-level classification is relevant for the patients as it determines the type of prosthetic components available. However, K-level can vary greatly based on the clinician or orthopedic technician individual assessment. Objective data from physical performance tests can help to improve K-level classification. Therefore, muscle strength tests of the amputation stump as well as balance tests were performed in this study to determine whether these parameters have the potential to support K-level classification. Twenty-two participants with a thigh amputation participated in the study (four K1/2-, six K3- and twelve K4-participants). Hip muscle strength on the amputation side was assessed as well as static balance in the double leg stance with eyes open and eyes closed. Analysis of the data showed that all hip strength parameters differed between the K-level groups, with maximum strength increasing from the K1/2 group to the K4 group. Group differences were also seen in the balance parameters with greater body sway for the K1/2 group when compared to the K4 group, especially when participants had their eyes closed. These results show that muscle strength tests of the residual limb and static balance tests may serve as additional measures to improve K-level assignment for patients with LLA. This was only an initial study and further studies with a larger number of participants are required to confirm these results.
Article PDF Link: https://jps.library.utoronto.ca/index.php/cpoj/article/view/37456/28905
How To Cite: John S, Orlowski K, Mrkor K.U, Edelmann-Nusser J, Witte K. Differences in hip muscle strength and static balance in patients with transfemoral amputations classified at different K-levels: A preliminary cross-sectional study. Canadian Prosthetics & Orthotics Journal. 2022; Volume 5, Issue 1, No.5. https://doi.org/10.33137/cpoj.v5i1.37456
Corresponding Author: Stefanie John,Department of Sports Science, Faculty of Humanities, Otto von Guericke University, Magdeburg, Germany.E-Mail: Stefanie.John@ovgu.deORCID ID: https://orcid.org/0000-0001-6722-7195