Repair of pars interarticularis defect with a modified cable-screw construct

Operative treatment of symptomatic spondylolysis is not common. Multiple surgical techniques have been described for direct repairs of the pars defects. Reported success rates are high, although few reports describe successful return to sports in athletes. The purpose of the study was to assess the outcome after bone grafting and fixation of pars interarticularis defects utilizing a modification of the previously described techniques of Scott and of Songer. A retrospective single-arm cohort study was performed at a single center. This article reports on three athletes with symptomatic spondylolysis or grade I spondylolisthesis unresponsive to conservative management who were treated with bone grafting and a screw-cable repair. The outcome measure was the return to sports activities. A retrospective chart and radiographic analysis was conducted on three athletes. Patients were assessed for return to sports, clinical evidence of return to functional activities, and radiographic evidence of healing of the pars defects. All three patients proceeded to radiographic and clinical success. All patients reported resolution of their preoperative pain and return to sports. One patient did require occasional anti-inflammatory drugs for episodic low back pain. The use of this modified cable-screw technique for symptomatic spondylolysis provided excellent clinical, radiographic, and functional results in this small cohort.     

The location of the pedicle and pars interarticularis in the axis

STUDY DESIGN: This is an anatomic and radiologic study on the lateral mass of the C2 vertebra. OBJECTIVES: To define the location of the pedicle and pars interarticularis in the C2 vertebra. SUMMARY OF BACKGROUND DATA: Transpedicular screw fixation of the C2 has been addressed in the literature. However, the use of the anatomic terminology of the pedicle or pars interarticularis (isthmus) in C2 is confusing in most of orthopaedic and neurosurgical literature since C2 is considered a transitional vertebra. METHODS: Twenty dry C2 vertebrae were obtained for observation of the external anatomy of the C2 from superior, lateral, and inferior views. Six C2 vertebrae were harvested from cadavers and sectioned in the sagittal, horizontal, and coronal planes to observe the internal structures of the lateral mass using high resolution radiographs. RESULTS: Based on observation, the pedicle of the C2 vertebra is defined as the portion beneath the superior facet and anteromedial to the transverse foramen. The pars interarticularis or isthmus is defined as the narrower portion between the superior and inferior facets. No remarkable difference in bone density and trabecular bone orientation between the pedicle and pars interarticularis was noted. CONCLUSIONS: It is still more appropriate to call this procedure "transpedicular screw fixation" in the C2 to avoid confusion, although this technique requires placing a screw from the posterior aspect of the inferior articular process through the isthmus and pedicle into the vertebral body.     

Percutaneous pars interarticularis screw fixation: a technical note

Purpose

A conventional midline posterior approach is used for most of the described surgical techniques. We describe a technique of percutaneous fixation of the pars interarticularis, augmented where necessary by grafting the defect, which minimises muscle injury.

Method

A 4.5 mm partially threaded dynamic compression screw is placed over a wire inserted percutaneously across the pars interarticularis defect. Compression is achieved across the pars interarticularis defect on placement of the screw. The screw is locked in a compressed state.

Results

The patient is mobilised the same day with a corset for comfort and discharged the following day. Aerobic fitness is maintained for 3 months; then, focused rehabilitation performed until a CT scan confirms healing at 5–6 months, at which stage full (sports) activity is resumed.

Conclusions

The minimal tissue injury and small incision used allow for the minimising of complications and for a rapid recovery and discharge from hospital. With adolescents, we have the opportunity to treat symptomatic pars interarticularis defects with minimal disruption to their academic and physical development.

     

枢椎后路峡部螺钉固定的相关影像学测量

目的：通过CT测量探讨枢椎峡部螺钉固定技术的安全性和可行性。方法：收集2016年1月至2019年12月进行全颈椎CT检查的137例结构完整的上颈椎CT数据,其中男71例,女66例;年龄22~65（41.8±17.4）岁。通过Mimics19.0软件测量峡部螺钉技术相关的解剖学数据,包括峡部宽度、峡部垂直长度、峡部垂直高度、峡部螺钉通道长度、峡部螺钉通道头倾角度。并分析各项指标之间的相关性。结果：枢椎峡部宽度（9.05±1.63） mm,垂直长度（11.21±1.43） mm,垂直高度（17.53±2.93） mm。螺钉通道长度为（19.07±3.20） mm。峡部螺钉通道长度>14 mm的占94.53%,14~16 mm的占82.12%,16~18 mm的占63.14%,18~20 mm的占39.78%。螺钉通道的头倾角度为30°~68°,平均（46.06±8.06）°。螺钉通道长度和头倾角度呈高度正相关（r=0.965,P=0.000）。峡部垂直长度和螺钉通道长度,峡部垂直长度和螺钉的头倾角度之间都呈轻度正相关（r=0.240,P=0.000;r=0.163,P=0.007）。峡部宽度和螺钉通道长度,峡部宽度和螺钉通道的头倾角度之间都呈中度负相关（r=-0.333,P=0.000;r=-0.380,P=0.000）。结论：进行枢椎后路峡部螺钉固定安全、可靠,比枢椎后路椎弓根螺钉固定具有更大的适用范围,可以作为椎弓根螺钉的替代选择。     

Fracture of the pars interarticularis in adolescent athletes: a clinical-biomechanical analysis

Stress fracture of the pars interarticularis is an increasing cause of disability in highly competitive adolescent athletes. We have documented this lesion in 14 adolescent athletes engaged in repetitive training and competition exercises involving flexion/extension of the lumbar spine. An in vivo spinal muscle torque study in 11 normal adolescent girls also revealed mean torque values of 22.6 Nm for left lateral flexion and 27.4 Nm for hyperextension. The most common sports resulting in this lesion were gymnastics and hockey. In four patients the lesion was bilateral, and in 10 it was unilateral. Five of the unilateral lesions went on to heal with immobilization in a thoracolumbar spinal orthoses; however, none of the four bilateral lesions or the remaining five unilateral lesions healed in spite of 3 months of immobilization.     

A study of mechanoreceptors in fibrocartilage masses in the defect of pars interarticularis

We investigated the origin of low back pain associated with lumbar spondylolysis and spondylolytic spondylolisthesis by removing fibrocartilage masses from the lytic sites in symptomatic patients and staining the masses by the Gairns gold chloride method to examine mechanoreceptors. The fibrocartilage masses were found to contain four types of mechanoreceptors: Pacinian corpuscles, Ruffini receptors, Golgi tendon organ-like receptors, and free nerve endings. All of these mechanoreceptors were present at the periphery of the specimens, and Ruffini receptors and free nerve endings were abundant. Some mechanoreceptors had a slightly atypical structure, in addition to those with typical morphology. Comparison with mechanoreceptors in normal lumbar facet joint capsules showed that there were more mechanoreceptors in the fibrocartilage masses and a greater proportion of atypical structures at lytic sites. The presence of mechanoreceptors at lytic sites suggests that the fibrocartilage masses are not simply scar tissue filling the defect. Rather, these masses also appear to play a protective role by sensing instability via mechanoreceptors and transmitting this information as pain, while at the same time acting as ligament-like tissue that connects and stabilizes the separated vertebral arches. Received for publication on Dec. 2, 1998; accepted on May 12, 1999     

Quantitative assessment with SPECT imaging of stress injuries of the pars interarticularis and response to bracing

The evaluation and management of acute spondylolysis remains unclear in part because of outcome data that are primarily subjective. The aim of this study was to evaluate and monitor these patients objectively using quantitative single-photon emission computed tomography (SPECT). Thirty-four patients were so observed clinically between 1987 and 1996 and were studied with an initial and at least one follow-up SPECT scintigram. Initial radiographs and planar bone scans failed to demonstrate the pars lesion in 53 and 19% of the patients, respectively. The average SPECT ratio before brace treatment was 1.45. After treatment, this ratio significantly decreased to 1.27 (p = 0.03). A subset of patients remained symptomatic at follow-up. Their reduction in SPECT ratio averaged only 2.8% as compared with 13% for the remainder of the patients (p = 0.01). Patients diagnosed and braced in the early, more active stage of the condition (with greater intensity on SPECT) had more predictable symptom relief. An initial SPECT ratio of >1.5 was associated with complete symptom resolution after brace treatment. Patients treated with activity restriction only (>3 months) before bracing were more likely to have persistent symptoms and more modest improvement on SPECT (p = 0.01). These data, which use SPECT scintigraphy, support prompt treatment with brace immobilization for acute spondylolysis in children and adolescents.     

峡部断离对腰椎稳定性影响的实验研究

采用电－机械测量系统对８个正常结构和峡部断离后的新鲜尸体Ｌ５／Ｓ１脊椎功能单位，以６种不同载荷方式对其三维运动学变化做了研究。结果表明，峡部在腰椎各项运动中对腰椎稳定具有重要的力学作用，峡部断离将可能导致腰椎不稳。     

The value of SPECT in the detection of stress injury to the pars interarticularis in patients with low back pain

The medical cost associated with back pain in the United States is considerable and growing. Although the differential diagnosis of back pain is broad, epidemiological studies suggest a correlation between adult and adolescent complaints. Injury of the pars interarticularis is one of the most common identifiable causes of ongoing low back pain in adolescent athletes. It constitutes a spectrum of disease ranging from bone stress to spondylolysis and spondylolisthesis. Bone stress may be the earliest sign of disease. Repetitive bone stress causes bone remodeling and may result in spondylolysis, a non-displaced fracture of the pars interarticularis. A fracture of the pars interarticularis may ultimately become unstable leading to spondylolisthesis. Results in the literature support the use of bone scintigraphy to diagnose bone stress in patients with suspected spondylolysis. Single photon emission computed tomography (SPECT) provides more contrast than planar bone scintigraphy, increases the sensitivity and improves anatomic localization of skeletal lesions without exposing the patient to additional radiation. It also provides an opportunity for better correlation with other imaging modalities, when necessary. As such, the addition of SPECT to standard planar bone scintigraphy can result in a more accurate diagnosis and a better chance for efficient patient care. It is our expectation that by improving our ability to correctly diagnose bone stress in patients with suspected injury of the posterior elements, the long-term cost of managing this condition will be lowered.     

Experimental study on repair of the defect of the pars interarticularis in rat with bone morphogenetic protein and fibrin glue]

The possibility of repairing the defect of the pars interarticularis (pars defect) with Bone Morphogenetic Protein (BMP) and fibrin glue was studied. The pars defect established in the 5th lumbar vertebra of Wistar rat was treated with surgical implantation of a composite consisting of BMP, fibrin glue and autologous cancellous bone. At 3, 6, 9 and 12 weeks after implantation, the osteoinductive activity in the pars defect was observed histologically and compared with that of other composite implants such as BMP with fibrin glue, autologous cancellous bone alone and autologous cancellous bone with fibrin glue. Although perfect bone fusion was not obtained with any of the composites employed, a significant increase in bone formation was seen in a composite of BMP, fibrin glue and autologous cancellous bone (p less than 0.01) as compared with that seen in the others. Consequently, implantation of BMP and fibrin glue combined with some biomaterials which support osteo-induction of BMP and stabilize the pars defect might be successfully applied to repair the pars defect.     

Stress fractures of the lumbar pars interarticularis in athletes: a review based on long-term results of 18 professional cricketers

The physical demand of the modern game of cricket on the fast bowler is known to cause stress fractures of the lumbar spine. Between 1983 and 2001, we diagnosed pars interarticularis defects in 18 professional cricketers contracted to a single English County Cricket Club. Eight of these players were treated conservatively, with rest, supervised rehabilitation, bowling action analysis and re-education where necessary. The remaining 10 were treated operatively, 9 by Buck’s repair of the spondylolytic lesion. All 18 players returned to professional sport.

We recommend treatment of this select group of sportsmen in a unit consisting of a specialist physiotherapist, a bowling coach and a spinal surgeon. Should conservative measures fail, we recommend Buck’s repair as the operation of choice.     

Union of defects in the pars interarticularis of the lumbar spine in children and adolescents. The radiological outcome after conservative treatment

Lumbar spondylolysis can heal with conservative treatment, but few attempts have been made to identify factors which may affect union of the defects in the pars. We have evaluated, retrospectively, the effects of prognostic variables on bony union of pars defects in 134 young patients less than 18 years of age with 239 defects of the pars who had been treated conservatively. All patients were evaluated by CT scans when first seen and more than six months later at follow-up. The results showed that the spinal level and the stage of the defects were the predominant factors. The site of the defects in the pars, the presence or development of spondylolisthesis, the condition of the contralateral pars, the degree of lumbar lordosis and the degree of lumbar inclination all significantly affected union.