“Spring-back” closure associated with open-door cervical laminoplasty

Background context

Spring-back complication after open-door laminoplasty as described by Hirabayashi is a well-known risk, but its definition, incidence, and associated neurologic outcome remain unclear.

Objective

To investigate the incidence and the neurologic consequence of spring-back closure after open-door laminoplasty.

Study design

A retrospective radiographic and clinical review.

Outcome measures

Lateral cervical spine X-rays were evaluated. Anteroposterior diameters (APD) of the vertebral canal of C3–C7 were measured. Spring-back was defined as loss of APD on follow-up in comparison to immediate postoperative canal expansion. The loss of the end-on lamina silhouette with consequent reappearance of the lateral profile of the spinous processes was also assessed to verify the presence of spring-back. Spring-back closure was classified based on whether the collapse was total or partial, and whether all the operated levels or only a subset had collapsed (ie, complete vs. partial closure, segmental closure vs. total-construct closure). Neurologic status was documented using the Japanese Orthopaedic Association (JOA) score.

Methods

Thirty consecutive patients who underwent open-door laminoplasty from 1995 to 2005 at a single institution with a minimum follow-up of 2 years were assessed. They were all operated on using the classic Hirabayashi technique. Radiographic outcomes were assessed independently by two individuals.

Results

Sixteen men and 14 women with an average follow-up of 5 years (range, 2–12 years) were included. Of these patients, 24 had cervical spondylotic myelopathy and six had ossification of the posterior longitudinal ligament. Spring-back closure was found in three patients (10%) and 7 of 117 laminae (6%) within 6 months of the operation, which was further confirmed by computed tomography and magnetic resonance imaging. All spring-back closures were partial segmental closures. Gender and age were not significant factors related to spring back (p>.05). The mean JOA score on follow-up was 12.5, with a recovery rate of 40%. All patients with spring back and available JOA data exhibited postoperative neurologic deterioration. Of the three patients with spring back, two patients underwent revision surgery, whereas one declined.

Conclusions

Spring-back closure occurred in 10% of our patients at or before 6 months after surgery. The incidence of spring-back by level (ie, 117 laminae) was 6%, mainly occurring at the lower cervical spine. All spring-back closures were partial segmental closures, most commonly involving C5 and C6. Postoperative neurologic deficit was associated with spring-back closure; therefore, surgeons should adopt preemptive surgical measures to prevent the occurrence of such a complication.     

Reducing radiation exposure in early-onset scoliosis surgery patients: novel use of ultrasonography to measure lengthening in magnetically-controlled growing rods

Background context

Magnetically-controlled growing rod (MCGR) technology has been reported for the treatment of early-onset scoliosis (EOS). Such technology allows for regular and frequent outpatient rod distractions without the need for additional surgery. However, pre- and postdistraction spine radiographs are required to verify the amount of lengthening. This increased exposure to ionizing radiation in developing children significantly increases their risk profile for radiation-induced cancer and noncancerous morbidity.

Purpose

This study addressed the first and novel application and reliability of the use of ultrasonography, that has no ionizing radiation exposure, as an alternative to plain radiographs in the visualizing and confirming of rod distractions.

Study design

A prospective study.

Patient sample

Six EOS patients who underwent surgical treatment with MCGRs were prospectively recruited.

Outcome measures

Imaging measurements based on ultrasound and plain radiographs.

Methods

All patients were imaged via ultrasound, ease of rod identification was established, and the reliability and reproducibility of optimal reference point selection assessed blindly by three individuals. The clinical algorithm, using ultrasound, was subsequently implemented. Plain radiographs served as controls.

Results

Assessment of the rod's neck distance on ultrasound demonstrated a high degree of interrater reliability (a=0.99; p<.001). Intrarater reliability remained high on repeat measurements at different time intervals (a=1.00; p<.001). Satisfactory interrater reliability was noted when measuring the rod's neck (a=0.73; p=.010) and high reliability was noted in assessing the housing of the rod (a=0.85; p=.01) on plain radiographs. Under blinded conditions, 2 mm rod distraction measured on radiographs corresponded to 1.7 mm distraction on the ultrasound (standard deviation: 0.24 mm; p<.001). Subsequently, the clinical algorithm using ultrasound, instead of radiographs, has been successfully implemented.

Conclusions

This is the first study to report the use of a novel technique using noninvasive, nonionizing ultrasound to reliably document rod distractions in EOS patients. A high level of inter- and intrarater reliabilities were noted. More importantly, the use of ultrasonography may result in fewer whole spine radiographs from being taken in patients who have had MCGRs implanted for EOS; thereby decreasing their exposure to ionizing radiation and the potential risk of future radiation-induced diseases.     

Distal Femur Rotation Relates to Joint Obliquity in ACL-deficient Chinese

Background

The lower limb osteometry of Chinese differs from that of whites. The joint line of the knee in the coronal plane in Chinese is more medially inclined and the posterior condylar angle of the distal femur in the axial plane is larger. However, it is unclear whether there is any direct association between the coronal plane and axial plane osteometry.

Questions/purposes

We asked whether the joint line obliquity of the knee is related to the posterior condylar angle of the distal femur in young Chinese subjects.

Methods

Ninety-nine young Chinese patients with anterior cruciate ligament injuries were recruited. The lower limb alignment and joint line obliquity were measured using standing long radiographs of the whole lower limb. The rotational alignment of the distal femur was assessed in the axial cuts of the MRI.

Results

The distal femur rotational alignment was associated with the obliquity of the knee in Chinese. The posterior condylar angle was 5° ± 2°. The knee was 5° ± 3° medially inclined.

Conclusions

The joint line of the knee in a group of young Chinese patients was more medially inclined than that of whites. The posterior condylar angle of the distal femur was larger. The presence of an association between distal femur rotational alignment and joint line obliquity in this group of young Chinese patients suggests a possible developmental cause explaining the difference in osteometry between races.