接受Pemberton氏切骨術治療單側發展性髖關節發育異常患者於步行時關節力學及平衡控制之研究

Abstract

及早矯正發展性髖關節發育異常(DDH)已被公認可以預防股骨頭缺血性壞死、髖臼發育不良以及退化性關節炎等嚴重併發症。Pemberton式切骨術因具有可調整髖臼容積與覆蓋方向之優點，使得髖關節得以獲得更適合的幾何關係而被廣泛用於及早的治療DDH。然而也有文獻指出患者在經Pemberton式切骨術復位後仍有較高的機會發生股骨頭缺血性壞死及退化性髖關節炎，而此二併發症的產生已被證實與走路時腳跟著地瞬間的異常受力有密切關聯。因此，量化走路時下肢的受力情形，將有利於了解青少年在及早接受Pemberton氏切骨術治療單側DDH後是否仍會有高風險產生股骨頭缺血性壞死及退化性髖關節炎。而進一步探討下肢關節力學、關節間協調性以及身體平衡控制如何影響其下肢受力情形的改變，則可助於設計可能降低下肢受力的復健訓練或其他生物力學策略。本研究徵召11位接受Pemberton氏切骨術治療單側DDH的女性(平均接受切骨術年齡為1.6±0.5歲；平均接受步態分析年齡為10.6±1.0歲)，以及12位年齡相符並作為控制組之健康女性接受步態分析檢查。與控制組相比，Pemberton組在兩腳的髖、膝以及踝皆有顯著較高的最大關節軸向力，兩腳的地面反作用力與髖關節軸向力的受力率亦明顯較高。較高的髖關節軸向受力率顯示Pemberton組的兩腳皆可能有較高風險會提早發生關節炎；而發生於患側髖關節的較大軸向力，亦可能在當手術後仍而覆蓋率不足或關節表面受破壞的情況下進而導致股骨頭缺血性壞死的發生。雖然Pemberton組的步行速度已接近正常者，顯示其步行效率已較未接受治療者或成年後才接受治療者有顯著改善，但她們仍表現出與控制組明顯不同的運動學與力動學模式，且其兩腳之間甚至是非對稱的改變。而這些在切骨術後仍出現的異常步態問題，包括可能因肌力降低所造成的力動學改變，則會導致上述兩腳有較大關節軸向力與髖關節受力率的表現。除了關節力學的改變外，Pemberton組的關節間協調模式亦與控制組顯著不同，且其兩腳間亦有不對稱的協調模式，而這些與控制組相異的關節間協調性皆可能是為了適應單側切骨術之後遺症所需改變關節力學的控制策略。但在長期調適的情況下，Pemberton組的關節間協調性變異已與控制組並無不同。此外，Pemberton組的動態平衡亦可能因手術後遺症之影響，使得其身體質量中心(COM)在三個方向上的運動範圍皆顯著增加且較不平順。其中，在單腳站立的開始(T2)，Pemberton組的COM有顯著較大的向上與向後加速度，此表現可呼應地面反作用力之踩煞力增加的結果、並可能與地面反作用力垂直分量受力率增加有關；而在腳尖離地(T4) 的向上加速度增加，則可能與地面反作用力垂直分量卸載率的增加有關。在冠狀平面上，COM在T2與在單腳站立的結束(T3)皆會增加朝向對側腳的加速度，這代表需要更多的肌力來抗衡因COM運動改變所伴隨增加的髖關節外展肌力矩。從上述的關節力學、關節間協調性以及動態平衡結果可發現，接受Pemberton氏切骨術治療單側DDH患者的異常步態表現可能會導致其下肢受力情況的改變、並提高退化性關節炎等併發症發生的風險。因此，建議Pemberton組應加強下肢肌力與訓練平衡控制，以改善異常步態並減少術後併發症的產生。

Early correction for developmental dysplasia of the hip (DDH) has been acknowledged to prevent the serious complications such as avascular necrosis (AVN), acetabular dysplasia and premature hip osteoarthritis (OA). Pemberton’s osteotomy, being able to adjust the volume of acetabulum and the direction of coverage for better congruency of the hip, has been suggested to be done before weight-bearing for better prognosis. However, patients after reduced DDH are still at higher risk of developing AVN and hip OA that are closely related to abnormal loadings at heel-strike of gait. Therefore, quantifying the loadings in the lower limbs during walking would help to understand whether adolescents with early treatment using Pemberton’s osteotomy for unilateral DDH were still at high risk of developing AVN and hip OA. Further study of the influence of changes in the joint mechanics, inter-joint coordination and body’s dynamic stability on the joint loadings might be useful for designing the rehabilitative training or other biomechanical strategies to decrease the abnormal joint loadings. Eleven females (age: 10.55±0.98 years) who had received Pemberton’s osteotomy for unilateral DDH at 1.63±0.47 years of age, and twelve age-matched healthy controls, were studied using gait analysis techniques. Compared to the controls, the Pemberton group displayed greater peak axial forces at the hip, knee and ankle in both limbs, with greater loading rates in the ground reaction force (GRF) and at the hips. The increased loading rates in both hips suggested the Pemberton group may be at higher risk of premature hip OA. The increased axial forces at the affected hip may be a contributing factor to the development of AVN, especially when incomplete coverage, insufficient congruency and/or damaged articular surfaces remain after the osteotomy. The Pemberton group walked with nearly normal walking speed, indicating their gait efficiency was better than that of the untreated patients or patients after treatment for adult hip dysplasia, but they displayed significantly different kinematic and kinetic patterns compared to the controls. Asymmetrical gait patterns were also found in the Pemberton group. These residual gait deviations, including kinetic changes that might be owing to muscle weakness, would contribute to the greater axial joint forces with a greater hip loading rate in both limbs. In addition to the altered joint mechanics, the inter-joint coordination patterns of the Pemberton was also significantly different from that of the control group and was asymmetrical between limbs, which might be a control strategy in accordance with the changed joint mechanics for accommodating to the residual deficits after an osteotomy for unilateral DDH. However, the variability of inter-joint coordination of the Pemberton group was similar to that of the controls, which might be due to the long-term adaptation for such altered mechanical condition. Dynamic stability of the Pemberton group was also affected by the residual deficits after an osteotomy, indicated by greater range and jerkier center of mass (COM) motion in all three directions. For the COM motion in the Pemberton group, significantly greater upward and posterior accelerations were noted at the beginning of the SLS (T2), and significantly greater upward accelerations were found at toe-off (T4). The former led to the increased braking force of the GRF and might be related to the greater loading rates of the vertical GRF, while the latter might be corresponded to the greater unloading rate of the vertical GRF. In the frontal plane, the Pemberton group showed increased acceleration of the body’s COM towards the contralateral limb at T2 and the end of the SLS (T3), which required for muscle effort, particularly for the hip abductors. In conclusion, the gait deviations in terms of joint mechanics, inter-joint coordination and dynamic stability of the patients received Pemberton’s osteotomy for unilateral DDH might lead to the changes in the loadings of the lower limb and increase risk of the complications such as premature hip OA. Strengthening of the bilateral lower limb muscles and training of the body’s balance control were suggested not only to achieve a better gait pattern but also to prevent the development of OA in the Pemberton group.