Clinical and radiographic outcomes following hinge fracture during open-door cervical laminoplasty

To investigate the clinical and radiographic fate of fractured hinges in open-door cervical laminoplasty, 135 segments of 36 patients who had undergone follow-up for more than two years after open-door cervical laminoplasty due to compressive cervical myelopathy were reviewed clinically and radiographically. Hinge fractures were identified by the intraoperative finding of obvious instability or click sounds (an obvious fracture), or by immediate postoperative computed tomography (CT) images showing a discontinuity of both the inner and outer cortex or a displacement of more than 1 mm at the lamina hinge site (an occult fracture). At two years post-surgery, union and displacement of the fractured hinges were evaluated with CT and the clinical outcome was assessed by the Japanese Orthopedic Association (JOA) and Neck Disability Index (NDI) scores. Immediate postoperative CT scans revealed 28 hinge fractures in 16 patients. Only three fractures were identified during surgery, with most being identified on postoperative CT. Nineteen laminae showed non-displaced cortical discontinuity, five were anteriorly displaced by more than 1 mm, and four were displaced posteriorly. Twenty-five laminae (89.3%) had achieved union according to the two-year postoperative CT scan. No de novo neurologic symptoms were found to be associated with hinge fracture. The two-year postoperative JOA and NDI scores did not differ significantly between patients with or without a hinge fracture. Most fractures at the hinge site occurred without intraoperative recognition, and usually re-unified without significant displacement or adverse clinical effects. When hinge fractures occur, careful observation without additional intervention is recommended.     

单开门椎管扩大成形微型钢板固定术后椎板铰链侧不同程度骨折的断端骨愈合对比

目的对比颈椎单开门椎管扩大成形微型钢板固定术后椎板铰链侧不同程度骨折的断端骨愈合情况。方法回顾性分析2010年1月至2012年12月采用颈椎单开门椎管扩大成形微型钢板固定术治疗的79例患者的临床资料。根据术后CT扫描结果,将椎板铰链侧骨折分为不完全骨折和完全骨折。完全骨折分为四型：Ⅰ型,骨折断端无移位或分离;Ⅱ型,骨折断端部分移位或分离;Ⅲ型,骨折断端完全移位或分离;Ⅳ型,骨折断端向椎管内移位或塌陷。观察椎板铰链侧骨折愈合情况并比较不同类型骨折愈合率的差异。结果随访12～45（21．2±5．6）个月。术后1周CT扫描395个节段,椎板铰链侧完全骨折占58．2％（230/95）;其中Ⅰ型占66．1％（152／230）,Ⅱ型占25．7％（59／230）,Ⅲ型占6．5％（15／230）,Ⅳ型占1．7％（4／230）。术后6个月不完全骨折的骨性愈合率为97．6％（161／165）,高于完全骨折的80．9％（186／230）,差异有统计学意义（P〈0．05）。术后3,6个月不同类型完全骨折骨性愈合率比较差异均有统计学意义（P〈0．05）,Ⅲ型完全骨折术后骨性愈合率最低。结论椎板铰链侧完全骨折以Ⅰ型为主,完全骨折的骨性愈合率低,Ⅲ型完全骨折术后骨性愈合率最差。     

Curved versus straight-cut hinges for open-door laminoplasty: A finite element and biomechanical study

In this study, the stabilities of the hinge sides of plate-augmented open-door laminoplasties based on cutting in a curved or straight line were compared using a finite element (FE) model and an experimental assessment. Using FE models generated from CT scans of a human subject, straight and curved techniques for cutting the hinge side were evaluated. Compressive forces were applied to both simulated models, and the stress distributions on the respective hinge sites were evaluated by comparing the maximum von Mises stresses. Biomechanical testing procedures were then carried out on porcine cervical vertebrae, with straight- and curved-cut groups loaded to failure, and the corresponding reaction forces on the hinge sites were recorded using a loading cell. The FE analysis results revealed no significant differences between the straight- and curved-cut groups in terms of maximum stress forces on the superior, middle, or inferior portions of the hinge sites. In the experimental study, the curved-cut group withstood higher loads to failure at the hinge site than the straight-cut group. The ability of the curved-cut laminoplasty hinges to withstand higher compressive loading to failure than straight-cut hinges suggests the potential of the proposed technique to reduce the risk of hinge fracture and displacement.     

Decompressive laminoplasty in multisegmental cervical spondylotic myelopathy: bilateral cutting versus open-door technique

Purpose  The aim of the study was to evaluate patients with multisegmental cervical spondylotic myelopathy (MCM) surgically treated via a dorsal approach. Two different laminoplasty techniques were compared by assessment of enlargement of the spinal canal and the neurological outcome. Methods  Thirteen patients (mean age 49 years, 11 males) underwent decompressive laminoplasty over a 7-year period. The average duration of symptoms was 21 months. The pre- and postoperative degree of myelopathy was assessed by both the Nurick grading and the Japanese Orthopaedic Association myelopathy score (JOA score). Preoperatively, the mean Nurick grade was 3.1 and the mean JOA score was 11. Two different techniques of expansive laminoplasty were used. Six patients underwent a bilateral cutting (BL) technique with retropositioning of the laminae and bilateral mini-plating (BL group). Seven patients were operated on by simple open-door (OD) laminoplasty with unilateral mini-plating (OD group). Postoperatively, CT scans were obtained for all patients to measure the sagittal diameter of the spinal canal. The mean clinical and radiological follow-up was 33 months. Results  Four to five laminae were involved in all patients.The mean operation time was 180 min. Complications occurred in two patients of BL group, with immediate postoperative neurological deterioration due to ventral displacement of the laminae. Overall, the average sagittal diameter (SD) of the spinal canal increased from 9.2 ± 1.3 mm to 12.4 ± 1.3 mm after surgery. The average enlargement of SD was significantly higher for the OD group (p < 0.0075 ). In total, the improvement rate was 38% according to the Nurick grading and 69% according to the JOA score. For the OD group, improvement rates were 57% (Nurick) and 71% (JOA). Conclusions  Decompressive laminoplasty is comparable with anterior surgery in neurological outcome. The OD technique seems to be superior to our BL technique regarding both the enlargement of SD and complication rate.     

微型钢板与锚定法在单开门颈椎管扩大成形术中应用的对比研究

目的与锚定法比较,评价微型钢板法单开门颈椎管扩大成形术的临床效果。方法 2005年1月-2008年10月,收治35例多节段脊髓型颈椎病患者,根据完成单开门椎管扩大成形术的方法不同分为微型钢板组(15例)及锚定法组(20例)。其中微型钢板组男10例,女5例;年龄(51.2±11.5)岁。病程6～60个月,平均14个月。术前日本骨科协会(JOA)评分为(7.7±2.5)分。锚定法组男13例,女7例;年龄(50.7±10.8)岁。病程3～58个月,平均17个月。术前JOA评分为(7.8±2.9)分。两组患者性别、年龄、术前JOA评分等比较差异均无统计学意义(P>0.05),具有可比性。结果患者切口均Ⅰ期愈合。35例均获随访,随访时间24～68个月,平均32个月。锚定法组和微型钢板组手术时间分别为(113±24)min和(111±27)min,差异无统计学意义(t=0.231 3,P=0.818 5)。术后3个月锚定法组和微型钢板组椎管扩大率分别为40%±18%和60%±24%,比较差异有统计学意义(t=2.820,P=0.008)。术后3、24个月两组JOA评分均显著高于术前(P<0.01),但术后3个月两组间JOA评分差异无统计学意义(t=1.620 5,P=0.114 6),术后24个月微型钢板组JOA评分明显高于锚定法组(t=3.454 3,P=0.001 5)。术后3～6个月,X线片、MRI及CT示两组门轴侧沟槽达骨性融合,术后24个月均未发生再关门现象。微型钢板组并发症发生率为13.3%(2/15),显著低于锚定法组25.0%(5/20),差异有统计学意义(χ2=7.160 0,P=0.008 6)。结论微型钢板法单开门颈椎管扩大成形术可获得术后即刻稳定性,有助于患者早期行功能锻炼,并发症少,临床效果满意。     

后路颈椎管扩大成形钛板固定术与传统单开门椎管扩大成形术治疗发育性颈椎管狭窄症的对比研究

目的比较观察后路颈椎管扩大成形钛板固定术与传统单开门椎管扩大成形术治疗发育性颈椎管狭窄症的临床疗效。方法回顾分析49例发育性颈椎管狭窄症患者的临床资料,随机分为两组,其中观察组25例采用钛板固定,对照组24例采用丝线悬挂,对比分析两组患者手术情况,术后症状改善情况JOA评分,末次随访术后椎板开门角度,脊髓后移距离,术后测量颈椎曲度的改变,轴性症状发生率,以及观察手术时间、术中出血量对比情况。结果经术后6个月~3年的随访,观察组术后6个月JOA评分改善率为(62.5±16.0)%,对照组为(59.2±9.8)%,两组比较差异无统计学意义(P0.05)。观察组椎板开门角度为(43.6±3.5)°,对照组为(40.5±4.1)°,两组比较差异有统计学意义(P0.05)。观察组末次随访时脊髓平均后移距离(2.97±1.8)mm,对照组为(2.96±1.7)mm,两组比较差异无统计学意义(P0.05)。观察组术后6个月颈椎曲度为(18.6±4.8)°,与术前(18.3±4.8)°比较差异无统计学意义(P0.05);对照组术后6个月颈椎曲度为(17.0±5.6)°,与术前(19.9±6.2)°比较差异无统计学意义(P0.05);观察组术后6个月轴性症状发生率为12.0%,明显低于对照组的41.7%,两组比较差异有统计学意义(P0.05)。两组患者无一例出现C5神经根麻痹。结论后路颈椎管扩大成形钛板固定术与传统单开门椎管扩大成形术皆为治疗发育性颈椎管狭窄症的有效术式,但后路颈椎管扩大成形钛板固定术更能降低术后再关门及术后轴性症状的发生率,是治疗发育性颈椎管狭窄症的一种有效治疗术式。     

单开门椎管扩大成形术后保留颈后韧带复合体加微型钛板固定的生物力学

目的:探讨保留颈后韧带复合体单开门椎管扩大成形术联合微型钛板固定的生物力学特性。方法:制备新鲜羊颈椎标本10具,分成两组,每组5具。A组,保留颈后方韧带复合体单开门椎管扩大成形术组;B组,保留颈后韧带复合体联合微型钛板固定单开门椎管扩大成形术组。两组先分别测完整标本状况下弯曲、左右侧屈及轴性旋转的生物力学数据。A组、B组制成手术模型标本后再分别测上述生物力学数据,与完整标本对比。结果:A组术后在抵抗前屈载荷时与完整标本时无明显差异(P>0.05),但在抵抗左右侧屈(P<0.05)及对抗轴向旋转载荷时稳定性较完整标本下降(P<0.05)。B组术后在抵抗前屈载荷及左右侧屈载荷时与完整标本比较无明显差异(P>0.05),在对抗轴向旋转载荷时稳定性较完整标本下降(P<0.05),但较A组差异小(P<0.05)。结论:保留颈后方韧带复合体结合微型钛板固定的单开门椎管成形术,其颈椎标本在对抗侧屈及轴性旋转载荷方面的生物力学稳定性优于单纯保留颈后方韧带复合体的单开门椎管成形术。     

保留颈后方韧带复合体对单开门颈椎板成形术生物力学特性的影响

目的:观察保留颈后方韧带复合体对单开门颈椎板成形术的生物力学特性的影响。方法:新鲜羊颈椎标本24具,分成三组,每组8具。A组,完整标本组,保留伸肌,切除前方结构;B组,在A组方法处理基础上行保留颈后方韧带复合体单开门颈椎板成形术;C组,在A组基础上行传统单开门颈椎板成形术。在电子万能试验机上行生物力学试验,测试项目包括三点折弯试验、轴向拉伸试验和压缩试验。分析比较三组间的差异性。结果:三点折弯试验标本变直时A、B两组位移无差异,C组与A、B两组比较均明显减小(P<0.05);在变直时A、B两组加载力无差异,C组则较A、B两组明显变小(P<0.05)。拉伸试验在变直时B组与A组比较加载力明显变小(P<0.05),C组与A组相比显著变小(P<0.01),同时C组与B组比较也明显变小(P<0.05);10N位移B、C两组与A组相比均明显增大(P<0.05)。压缩试验中在前方加压10N时B组与A组比较位移明显变大(P<0.05),C组显著大于A组(P<0.01),同时C组亦明显大于B组(P<0.05)。结论:在对抗导致颈椎变直和前屈的应力方面,保留颈后方韧带复合体完整性的单开门手术标本明显优于破坏了其完整性的传统单开门手术标本。     

Modified Open-Door Laminoplasty Using a Ceramic Spacer and Suture Fixation for Cervical Myelopathy

Purpose

To introduce a new simple technique using suture anchors and ceramic spacers to stabilize the elevated laminae in open-door cervical laminoplasty. Although ceramic spacers were placed in the opened laminae and fixed with nylon threads in this series, it was occasionally difficult to fix the nylon threads to the lateral mass.

Materials and Methods

Study 1: A preliminary study was conducted using a suture anchor system. Sixteen consecutive patients who underwent surgery for cervical myelopathy were prospectively examined. Study 2: The second study was performed prospectively to evaluate the feasibility of this new technique based on the result of the preliminary study. Clinical outcomes were examined in 45 consecutive patients [cervical spondylotic myelopathy (CSM)] and 43 consecutive patients (OPLL). The Japanese Orthopedic Association scoring system (JOA score), axial neck pain, and radiological findings were analyzed.

Results

1) In one case, re-operation was necessary due to dislodgement of the ceramic spacer following rupture of the thread. 2) In all patients, postoperative CT scans showed that the anchors were securely inserted into the bone. In the CSM group, the average JOA score improved from 9.5 points preoperatively to 13.3 at follow-up (recovery 51%). In the OPLL group, the average JOA score improved from 10.1 (5-14) points preoperatively to 14.4 (11-16) at follow-up (recovery 62%). There were no serious complications.

Conclusion

The use of the suture anchor system made it unnecessary to create a hole in the lateral mass and enabled reliable and faster fixation of the HA spacers in open-door laminoplasty.     

Risk factors associated with upper extremity palsy after expansive open-door laminoplasty for cervical myelopathy

Background contextPostoperative paresis, so-called C5 palsy, of the upper extremities is a common complication of cervical surgery. There have been several reports about upper extremity palsy after cervical laminoplasty for patients with cervical myelopathy. However, the possible risk factors remain unclear.PurposeTo investigate the factors associated with the development of upper extremity palsy after expansive open-door laminoplasty for cervical myelopathy.Study designA retrospective review of medical records.Patient sampleA total of 102 patients (76 men and 26 women) were eligible for analysis in this study. The mean age of the patients was 58.7 years (range 35–81 years). Sixteen patients (13 men and 3 women, average age 62.8 years) with palsy were categorized as Group P, and eighty-six patients (63 men and 23 women, average age 57.8 years) without palsy as Group C.Outcome measuresThe demographic data collected from both groups were age, sex, duration of symptoms, disease, and type of surgical procedure. Cervical curvature index, width of the intervertebral foramen (WIF) at C5, anterior protrusion of the superior articular process (APSAP), number of compressed segments, high–signal intensity zone at the level corresponding to C3–C5 (HIZ:C3–C5), and posterior shift of the spinal cord (PSSC) were also evaluated.MethodsUpper extremity palsy was defined as weakness of Grade 4 or less of the key muscles in the upper extremity by manual muscle test without any deterioration of myelopathic symptoms after surgery. Comparisons were made with screen for the parameters with significant differences, and then we further analyzed these parameters by logistic regression analysis (the forward method) to verify the risk factors of the upper extremity palsy.ResultsSignificant differences in diagnosis, the type of procedure, WIF, APSAP, and HIZ:C3–C5 were observed between the two groups. No statistical difference in PSSC between the groups was noted (2.06 vs. 2.53 mm, p=.247). In logistic regression analysis, ossification of the posterior longitudinal ligament (OPLL), cervical open-door laminoplasty together with posterior instrumented fusion (CLP+PIF), and WIF were found to be significant risk factors for postoperative upper extremity palsy.ConclusionsPatients with preoperative foraminal stenosis, OPLL, and additional iatrogenic foraminal stenosis because of CLP+PIF were more likely to develop postoperative upper extremity palsy. Attention should be given to the WIF determined on preoperative computed tomography of the C5 root. To prevent iatrogenic foraminal stenosis, appropriate distraction between spine segments should be provided during placement of the rod.