退化性膝關節炎患者於跨越障礙物時平衡控制及關節間協調之研究

Abstract

中文摘要 退化性膝關節炎是中老年人最常見的關節炎。關節在長期承受重力及運動下，關節軟骨會退行性病變，連帶引起軟骨下硬骨增厚、關節變形、滑液膜和關節周圍結構相關變化的疾病，並失去彈性，進而發生關節疼痛、腫脹、僵硬、變形的情形，以致活動受限，罹患退化性關節炎之老人跨越障礙物之跌倒危險性增加，且可能造成嚴重後果。於跨越障礙物時平衡控制及關節間協調之研究有助於設計預測或預防跌倒之方法。本研究利用一配有七台紅外線攝影機之動作分析系統量測受測者跨越三種高度障礙物（10%、20% 及30％腳長）時全身之運動學資料，並利用兩塊測力板量測地面反作用力。本研究先建立年輕人及健康老年人跨越不同高度障礙物時之平衡控制資料，並以此為基礎進一步探討患退化性膝關節炎之老年人跨越不同高度障礙物時平衡控制及關節間協調，以瞭解退化性膝關節炎對行走跨越障礙物之影響。結果顯示面對不同高度的障礙物，健康年輕人利用調節垂直方向之身體質量重心位置，速度，及加速度來維持平衡控制。此外，身體質量重心之左右方向加速度隨著高度增加而增加，顯示左右方向之肌力在單腳支撐及雙腳支撐轉換時需用以調控已達成平順的重心位置轉移。如果因為左右方向之肌力及協調不足，則可能在跨越較高的障礙物時發生跌倒。前後方向之加速度也使前後方向身體質量重心及足底壓力中心之距離隨著障礙物高度增加而降低。關於老年人的平衡控制研究結果顯示，在跨障礙物的各關鍵時刻，老年人有較小的向內身體質量重心及足底壓力中心之角度，因此神經肌肉骨骼系統會有較多的餘力來控制擺盪腳之終端點控制。不論是年輕人或是老年人皆利用降低體質量重心及足底壓力中心之角度的策略來增加身體的穩定性。患退化性膝關節炎之老年人在行走時可以維持正常之身體質量重心之位置及速度，然後走路過程的加速度變化卻顯著較大。也許是因為患退化性膝關節炎之老年人控制身體重心的能力不足而產生這種比較不穩定的動作特徵。為了能夠維持單腳支撐後期較高的挑戰，前後加速度在整個步態過程當中都在作調控。前後方向身體質量重心及足底壓力中心之距離之降低，是患退化性膝關節炎之老年人為了降低膝關節負荷所採取的保守策略。在額狀面上，這個保守的策略也藉由增加身體質量中心向支撐腳的加速度來達成。當比較走路及跨障礙物這兩個任務身體質量中心之表現時，則發現身體質量中心與足底壓力中心之傾斜角度及角速度需要在面對跨障礙物時作必要的調節，尤其是在單腳支撐及雙腳支撐轉換時。其中患退化性膝關節炎之老年人不論是在走路或跨障礙物，其矢狀面上身體質量中心控制與拇指終端點與地面之距離皆能保持正常。患退化性膝關節炎之老年人在由單腳支撐至雙腳支撐轉換時，向前之能夠藉由降低身體質量中心與足底壓力中心之向前傾斜角度，並在由雙腳支撐至單腳支撐轉換時增加身體質量中心與足底壓力中心之向前傾斜角速度來維持轉換之間的穩定。即使先前之研究發現為了減少膝關節負荷及相關之疼痛，退化性膝關節炎老人作了一些下肢關節運動的改變，但是至於其關節間的協調卻沒有顯著的改變。有此顯示在跨越障礙物時，退化性膝關節炎老人在矢狀面上能穩定地應付雙腳退化所造成的負荷。保持正常且穩定之關節間協調可以用來當作治療介入的成效。而關節間協調之型態及變異性亦可用來評估治療效果。

Osteoarthritis (OA), defined by degradation of the articular cartilage and an increase in subchondral bone density, is a common joint disorder in the elderly. Knee OA has also been associated with falls in the elderly. Knee OA has been reported to affect the performance of ambulation, including level walking and obstacle-crossing. An increased risk of falling in patients with knee OA during obstacle-crossing, as opposed to unobstructed level walking, may be explained by the difference in the control of the body’s center of mass (COM) with respect to the center of pressure (COP) while trying to ensure sufficient foot clearance. Knowledge of the control of the body’s dynamic stability in patients with knee OA is helpful for the management of these patients and for the evaluation of treatment outcomes. In the present study, young, older and knee osteoarthritic subjects were recruited to investigate the influence of aging and aging-related disease on the balance control and inter-joint coordination of obstacle-crossing using motion analysis techniques. In young subject, it was found that vertical components of the COM motion, including position, velocity and acceleration, were all modulated to successfully cross obstacles of different height and that these modulations were different between the leading and trailing limbs. Since the acceleration of the COM is directly related to the forces applied to the COM, the increase in the magnitude of the M/L acceleration of the COM with increasing obstacle height suggests that increased forces from muscle contractions are required to ensure the control of the smooth transition of the COM position between single and double stance phase. If the M/L stability is compromised, due to muscle weakness or degradation of coordination, falls may occur. Whole body control through adjustments of the A/P acceleration of the COM to reduce A/P COM-COP distances was required for the necessary stability in the sagittal plane when crossing obstacles of increased height. For the elderly, at this critical time during obstacle-crossing the older group used smaller medial COM-COP inclination angles to cross the obstacle successfully without falling sideways, suggesting that the neuromusculoskeletal system may have more room to control the swing foot with sufficient foot clearance. Decreased inclination angles with increasing obstacle height suggest that the subjects tended to keep their COM position close to the COP position to increase the body’s stability. For the patients with knee OA, normal COM positions and velocities were found at key instances during the walking cycle but with significant changes in COM accelerations. This more jerky motion of the body’s COM may be a result of reduced ability associated with knee OA in the control of the motion of the COM. For better control of the COM in the A/P direction during the more challenging latter half of SLS, adjustments to the A/P acceleration of the COM throughout the complete gait cycle were needed. Diminished A/P COM–COP separation was a conservative strategy for patients with knee OA in order to maintain body stability with reduced joint loadings. In the frontal plane, this was achieved by increasing the acceleration of the body’s COM towards the stance leg. Strengthenging of the muscles of the lower extremities, as well as training of the control of the COM through a dynamic balance training program, are equally important for the dynamic stability of patients with knee OA. When comparing body’s center of mass motion during unobstructed with those during obstructed gait in patients with knee osteoarthritis, modulation of inclination angle and angular velocities were necessary when facing more challenging tasks such as obstacle-crossing, particularly so in patients with knee OA. While less stable COM control was found around the end stage of double stance phase during obstacle-crossing when compared to level walking, patients with knee OA successfully acquired strategies in the sagittal plane to maintain close-to-normal stable COM control with normal toe clearance during both level walking and obstacle-crossing. They achieved stable transitions from SLS to DLS through a reduced anterior inclination angle and from DLS to SLS through an increased anterior angular velocity. It is suggested that assessment of the ability to control dynamic stability in patients with knee OA should consider both the positions and velocities of the COM and the COP. For the inter-joint coordination, despite significant changes of the joint kinematics knee OA did not change significantly the way the motions of the lower limb joints are coordinated during obstacle-crossing. It appears that the OA group had adopted a particular biomechanical strategy among all possible strategies that can accommodate the OA-induced changes in the knee mechanics using unaltered inter-joint coordination control. This enabled the OA subjects to accommodate reliably the mechanical demands related to bilateral knee OA in the sagittal plane during obstacle-crossing. Maintaining normal and reliable inter-joint coordination could be considered as an outcome of therapeutic intervention, and the patterns and variability of inter-joint coordination can be used to evaluate treatment effects.