探討頸椎深層肌力量對於椎板整形術後頸椎穩定度之影響-體外頸椎肌肉模型

Abstract

簡介: 頸椎脊髓神經病變(Cervical radiculomyelopathy)可進一步細分為脊髓型頸椎病變(Myelopathy)及脊髓脊神經根病變(Radiculomyelopathy)。脊髓型頸椎病變的原因主要為椎管狹窄(Spinal stenosis)，脊髓脊神經根病病變的原因主要為椎間孔狹窄(Foraminal stenosis)。發生椎管狹窄的原因有骨刺增生、後縱韌帶鈣化(Ossification of Posterior Longitudinal Ligament, OPLL)等等，而發生椎間孔狹窄的原因有脊椎退化、椎間盤突出等。此類病變通常開始為保守治療，例如牽引(Traction)、熱/冷敷、電療等等，如果保守治療無效時，就會採取手術方法。手術方式分為前路減壓及後路減壓兩種，前路減壓手術常見的有前側椎體切除術(Anterior Cervical Discectomy and Fusion, ACDF)與前側椎間盤切除與融合術(Anterior Cervical Corpectomy with Fusion, ACCF)；後路減壓手術常見的有椎板切除術(Laminectomy)與椎板整形術(Laminoplasty)。後路減壓的椎板整形術為常用於治療椎管狹窄的手術，其術後臨床效果良好，但由於手術時會將後側的肌肉剝離，臨床觀察指出深層肌於術後有逐漸萎縮的現象，併發症為頸椎自然曲度(Alignment)喪失、活動度(Range of motion, ROM)下降及軸向痛(Axial pain)等。 目的: 椎板整形術後，後側深層肌會有萎縮現象，造成肌肉功能缺損(Muscle dysfunction)。有關於深層肌功能缺損對於頸椎穩定度與曲度變化的研究較少，因此本研究的目的為探討頸椎深層肌功能缺損對於椎板整形術後，頸椎穩定度及曲度變化之影響。本研究結果可評估術後病人是否要接受進一步的物理治療以減緩後側深層肌功能缺損。 材料與方法: 本實驗使用離體動物(In vitro animal model)測試，使用八副豬頸椎C2~C7節進行體外肌肉模擬生物力學測試。使用細繩、滑輪及砝碼模擬肌肉走向及力量。實驗方法總共分為兩大部分，第一部先驗證完整的頸椎在有或無肌肉模擬時的活動度與穩定度，並與過去文獻比較，以及各別肌肉功能缺損時對曲度及穩定度的影響。第二部分為建置後縱韌帶鈣化術前以及椎板整形術後生物力學模型，後縱韌帶鈣化模型主要是利用優力膠塞入椎孔模擬臨床時活動度下降及曲度朝後凸(Kyphosis)的變化。椎板整形術則是將後側椎板扳開後，以骨板及撐開器固定，並模擬後側深層肌力量減小，探討術後深層肌在不同功能缺損程度時對曲度變化、活動度及穩定度的影響。 結果: 第一部分結果顯示加上肌肉後，活動度與中性區(Neutral zone, NZ)與先前未加肌肉時的研究相比，在活動度與中性區都有下降的趨勢，且中性區較活動度下降幅度多，證明此體外肌肉模擬機台的確能模擬頸部肌肉功能。肌肉功能缺損後，斜方肌及深層肌對頸椎整體曲度與穩定度影響最大(包含了活動度上升、曲度後凸增加及中性區上升)。在第二部分的實驗，發現在後縱韌帶鈣化後，活動度比健康時下降約40%，曲度後凸增加，與臨床觀察一致。在椎板整形術後之深層肌功能缺損探討方面，手術節數為三節(C4/6)或四節(C3/6)時，其相互間的結果差異不大。就曲度而言，隨著深層肌功能變差，曲度有後凸增加的趨勢，頸椎變得更直。當深層肌功能維持在50%時，在曲度變化上與後縱韌帶鈣化組並無顯著差異，當深層肌功能維持70%時，在曲度變化上與後縱韌帶鈣化組有顯著差異，代表更能夠維持頸椎自然曲度。就活動度而言，隨著深層肌功能變差，活動度逐漸上升，當深層肌功能維持30%時與後縱韌帶鈣化組顯著上升，當深層肌功能維持50%及70%時，在活動度方面與後縱韌帶鈣化組無顯著差異。就中性區而言，深層肌功能缺損變差，中性區逐漸上升，代表穩定度下降。當深層肌功能維持50%與70%時，中性區方面與健康組(加上肌肉)及後縱韌帶鈣化組無顯著差異。 結論: 本研究目的在探討椎板整形術後深層肌功能缺損對頸椎生物力學影響。在曲度方面，我們發現當深層肌肌肉功能維持至少50%時，可使頸椎曲度維持在術前的狀態，當維持70%時可以改善頸椎的曲度，雖然無法回到正常時頸椎的自然曲度，但是相較於術前已有改善。穩定度方面，當深層肌功能維持至少50%時，可使穩定度回復至健康時狀態。因此建議病患在椎板整形術後須接受進一步的物理治療，以減緩後側深層肌功能缺損對頸椎穩定度及曲度產生影響。

Background. Cervical radiculomyelopathy can be subdivided into myelopathy and radiculopathy. The main cause of myelopathy is spinal stenosis due to the formation of bone spurs, ossification of posterior longitudinal ligament (OPLL) and other degenerative changes of the spinal column. Radiculopathy on the other hand is mainly due to foraminal stenosis related to spondylosis and disc herniations. Although conservative treatments such as traction, hot/cold compress, electrotherapies are firstly prescribed, surgical intervention is often indicated. Surgery is categorically divided into either as anterior or posterior approach. Anterior approach includes anterior cervical discectomy and fusion (ACDF) and anterior cervical corpectomy with fusion (ACCF). Laminectomy and laminoplasty are the most common posterior decompression surgeries. However, owing to the intraoperative procedure of the laminoplasty, the dissection of the extensor muscles will results in the muscle atrophy. The clinical complications associated with muscle atrophy include the loss of cervical lordosis, decreasing the range of motion (ROM), and increased axial spinal pain. Purpose. Patients usually suffer atrophy of extensor deep muscles causing muscle dysfunction after laminoplasty. However, limited research focused on the impact of deep muscle dysfunctions on cervical alignment change and the cervical stability, respectively. A better understanding of the relationship will allow further inferences made on the importance of physical therapy treatments on post-operative muscle dysfunction. Material and Methods. The in-vitro model system was constructed from eight porcine cadaveric cervical spines (C2-C7) to simulate the biomechanical testing of human cervical muscles. Cables, pulleys, and weights were used to simulate the direction and force of the muscles. This study is divided into two sections: first, the ROM and stability of the constructed cervical model were measured in the presence and absence of muscles in order to compare the results with other published work. Once the applicability of the constructed model has been established, individual muscle dysfunction will be simulated to better understand the corresponding effect on the overall stability of the cervical spine. The second part of the study involved the simulation of an OPLL model and subsequently followed with simulated laminoplasty. To achieve the simulation of OPLL, a polyurethane tube was inserted into the spinal cord space to replicate the increase in the stiffness and kyphosis of the spinal column observed in OPLL patients. Once the biomechanical properties of the simulated OPLL model has been documented, a simulated laminoplasty involving cutting, splitting and fixing of lamina by plate and spacer was carried out. The aim of this part of the study is to better understand the impact of surgical intervention on the superficial and deep muscles of the neck, as well as the associated cervical alignment, ROM and stability change. Results. For the first part of the study, it was found that the ROM and neutral zone (NZ) decreased significantly for all of the muscles were intact in comparison to the one without muscles attachment. Furthermore, the normalised ratio of NZ was found to reach greater decrease than the ROM. Such finding is consistent with published data and validated the applicability of the simulated spine model. In terms of the impact of the individual muscles, it was found that the trapezius and the deep muscles showed the greatest effect on the ROM and stability, i.e. removal of these muscles were associated with the greatest increase in ROM and NZ. For the simulation of the OPLL model, it was found that the ROM decreased by 40% with a change of alignment into kyphosis. After the laminoplasty simulation procedure, a trend of gradual decrease of the cervical lordosis with the decrease of muscle function was observed. When the muscle was at 30% of original muscle function, the cervical lordosis significantly decreased when compared to both the intact and the OPLL group. In contrast, at 70% of original muscle function, the lordotic angle significantly increased when compared with the OPLL group, however, it was found to be still significantly less than the intact group. For the neutral zone results, no significant difference was found between the different muscle function levels and the intact group, however, a significant difference was found between the 30% muscle function group and the OPLL group where the NZ increased significantly in the 30% muscle function group. Conclusion. This study focused mainly on the biomechanical impacts of cervical muscle dysfunctions after laminoplasty. In terms of the alignment change, at least 50% deep muscle function was required to achieve the same alignment status as pre-laminoplasty in the OPLL state, and 70% of original deep muscle function was required to improve the cervical alignment to be better than the pre-operative state. It was noted that even with the 70% muscle function, the cervical alignment failed to return to its healthy state levels. In summary, identified decrease of cervical lordosis and the high levels of muscle function required to re-gain cervical alignment after laminoplasty highlights the importance of early and specific deep muscle retraining post-operatively.