Relationship between facet joint opening on CT and facet joint effusion on MRI in patients with lumbar spinal stenosis: analysis of a less invasive decompression procedure

OBJECTIVE Both facet joint opening (FJO) on CT and facet joint effusion (FJE) on MRI are reportedly indicators of segmental instability in the lumbar facet joints of patients with lumbar spinal stenosis (LSS). However, no study has investigated both parameters simultaneously. Therefore, the association between these findings and which parameter is better for predicting clinical outcomes after surgical treatment remains unclear. The purpose of this study was to investigate the relationship between FJO and FJE in patients who underwent less invasive decompression procedures for LSS and to investigate the impact of these findings on clinical outcomes. METHODS This study included 1465 lumbar levels (L1–2 to L5–S1) in 293 patients who underwent less invasive surgery for LSS and had ≥ 5 years of follow-up. FJO was defined as joint space widening ≥ 2 mm on preoperative axial CT images. FJE was defined as fluid effusion in the facet joint on preoperative axial T2-weighted MR images. The characteristics and distributions of FJO and FJE were investigated with other preoperative radiological findings. The association between need for further surgery and FJO/FJE was analyzed according to intervertebral level. RESULTS FJO was observed at 402 levels (27%), and FJE was found at 306 levels (21%). The correspondence rate between FJO and FJE was 70% (kappa 0.195, p < 0.01). One hundred thirty-seven levels (9%) had both FJO and FJE. Levels with both FJO and FJE more commonly had lateral olisthesis, lateral wedging, and axial intervertebral rotation than other levels (p < 0.001). Levels with both FJO and FJE were more likely than other levels to need further surgery (OR 2.42, p = 0.027). CONCLUSIONS The correspondence rate between FJO and FJE was not high. However, multivariate analysis showed that levels with both FJO and FJE had a higher risk of requiring further surgery than those with other radiological findings, such as lateral olisthesis, lateral wedging, and axial intervertebral rotation. Patients with levels with both FJO and FJE need careful long-term follow-up after undergoing a less invasive decompression procedure.

CommentsLon L. Fuller: Private Ordering and Mediation

One of the first major law review articles on mediation, published in 1971, Lon L. Fuller’s Mediation—Its Forms and Functions, is an important piece of dispute resolution scholarship for several reasons. While this commentary focuses upon the article’s discussion of private social ordering, Fuller’s discussion foreshadows three major dispute resolution developments. In his discussion of the negotiation process, Fuller reveals a remarkable understanding of negotiation as he explains the difficulty of timing the disclosure of information and the gains of reciprocity. Today we view this in terms of the Negotiator’s Dilemma—which Lax and Sebenius famously wrote about fifteen years later. Similarly, his discussion of mediation as a means of assisting with the dissolution of marriage presages the first use of mediation in child-custody disputes by approximately ten years. Finally, he even hints at the demise of the joint opening session in mediation when he describes the opening sessions of collective bargaining, with or without a mediator’s assistance, as serving “only a ceremonial and ritualistic purpose” (p. 322). If that’s all it’s for, why not get rid of it? As interesting as it is to find the hints of these developments, a much more integral factor in the article’s importance is Fuller’s stature as one of the preeminent legal theorists of the twentieth century. According to his biographer, Fuller was “one of the four most important American legal theorists of the last hundred years” (Summers, p. 1) and “the greatest proceduralist in the in the history of legal history” (Summers, p. 151). His jurisprudence, which formed the basis of mid-twentieth-century secular natural law, argued that the purposes of law, the internal reasoning within law, and law’s internal morality must be considered when one is engaged in legal analysis. Not only did these notions become central to “thinking like a lawyer” (Powers, p. 221), they also were to be applied to legal processes, including mediation, not solely to abstract notions of law....

Preliminary Design for Segmental Joint of Precast Tunnel Liner

Responses of the segmental tunnel liner to external forces are primarily dependent on complicated interactions among construction process, soil structural interactions, segmental (longitudinal) joint characteristic etc. However, most proposed liner’s design procedures and recommendations are basically empirical and experience based, especially when the roles of tunnel joint are concerned. In the present study, a preliminary design calculation for the segmental joint with consideration of three practical conditions was proposed. The method adopts two main assumptions; the stiffness reduction factor and simplified pre-stressed concrete blocks, so that the flexural capacity of the segmental joint and its interactions to the main reinforced concrete segment body can be designated. Calculation examples are given for three most probable cases, namely, 1) the unbolted joint without joint opening, 2) the bolted joint without joint opening and 3) the unbolted segmental joint with allowing joint opening. Based on these calculations, the required compressive strength of concrete, thickness of liner, steel reinforcement, bolts and number of segments of the liner could be specified. The proposed method could well provide an engineer a tool to determine the initial joint configuration and its interaction to the overall tunnel lining.

The Influence of Longitudinal Force on the Internal Force Distribution and Deformation Coordination Mechanism for Segment Lining

A series of local prototype tests are conducted on the Sutong GIL (Gas-Insulated Line) and Shiziyang Tunnel. These tests investigate the redistribution law of segment deformation and the bending moment during construction. The results reveal that the transfer ability of deformation and the bending moment improve with an increase in the longitudinal force. Stage characteristics are observed for the effect of the longitudinal force on the opening of the circumferential joints. Segments are fully contacted for the circumferential joints when the joint opening is not observed. The frictions between the segments are the key factors for the bending moment and segment deformation control. The opening of the circumferential joint with an increase in the joint opening then becomes the primary control factor. The transfer ability becomes stable when the load continues increasing after mortise and tenon contact. Better transfer ability occurs with a general segment with four pairs of mortises and tenons. This was presented as a smaller value of an increasing rate and the stable magnitude of the joint opening. From the perspective of practical engineering, mortises and tenons can be added to the vault to increase the load and deformation transfer ability of the general segment after the loss of the longitudinal force.