Effect of TLIF Cage Placement on In Vivo Kinematics

BACKGROUND

The influence of interbody cage positioning on clinical outcomes following lumbar interbody fusion is not well understood, though it has been hypothesized to play a significant role in stability of the treated level. The purpose of this study was to evaluate any correlations between cage placement in TLIF procedures and post-operative kinematics.

METHODS

Thirteen patients who had previously undergone a TLIF procedure were evaluated using the Vertebral Motion Analysis (VMA) system, an automated fluoroscopic method of tracking kinematics in vivo. Upright and recumbent bending platforms were used to guide patients through a set range of motion (ROM) standing up and lying down, respectively, in both flexion-extension (FE) and lateral bending (LB). Intervertebral ROM was measured via fluoroscopic images captured sequentially throughout the movement. DICOM images acquired by the VMA system were used to calculate cage positioning. Intra-rater and inter-rater reliability of TLIF cage position were also assessed.

RESULTS

Statistically significant correlations were noted between sagittal cage position and lying LB (r = -0.583, p = 0.047), and coronal cage positioning with both standing (r = 0.672, p = 0.012) and lying LB (r = 0.632, p = 0.027). Additionally, the correlation between sagittal cage position and standing FE was trending towards significance (r = -0.542, p = 0.055).

CONCLUSIONS

The intuitive correlation between coronal cage position and both standing and lying lateral bending ROM is supported by the data from this study, suggesting placement closer to midline is optimal for stability. Additionally, the VMA system appears to be a sensitive and repeatable means to obtain information on postoperative kinematic outcomes. Further work to establish the relationship between cage placement, these kinematic outcomes and, potentially, functional pain outcomes seems to be warranted based on the results obtained here.

Early surgeon impressions and technical difficulty associated with laparoendoscopic single-site surgery: a Society of American Gastrointestinal and Endoscopic Surgeons Learning Center study

BACKGROUND

Interest in laparoendoscopic single-site surgery (LESS) is growing rapidly among surgeons. This study aimed to characterize current surgeon impressions about LESS and to determine the relative difficulty of performing a simulated LESS task using a multiport access device.

METHODS

This study was conducted at the 2009 Society of Gastrointestinal Endoscopic Surgeons (SAGES) Learning Center. The 56 study participants were asked to complete pre- and post-test questionnaires regarding their level of training, prior clinical experience, and opinions about LESS. Technical skill performance was evaluated using the standardized fundamentals of laparoscopic surgery Peg Transfer task scored according to time and error metrics. The participants completed three repetitions: conventional laparoscopy (LAP), LESS with nonarticulated instruments (LESS Straight), and LESS with articulated instruments (LESS Articulating).

RESULTS

Complete data were collected for 45 (80%) of the 56 participants, which included 27 practicing surgeons, nine minimally invasive surgery (MIS) fellows, seven residents, and two allied health professionals. Five surgeons (LESS experienced) had managed at least one LESS case in the preceding 6 months. Participants rated their comfort with LESS as 2.0 ± 1.2 (5-point scale, 1 = very uncomfortable). Compared with conventional laparoscopy, the participants indicated that LESS had 97% better cosmesis, 25% decreased postoperative pain, 18% faster recovery, 97% more demanding, 73% increased rate of complications, and 82% anticipated wide adoption. They all indicated a readiness to offer LESS to their patients if appropriately trained. Peg Transfer performance was significantly worse for LESS than for LAP (40-65% performance decline), and for LESS Articulating than for LESS Straight (44% performance decline). Construct validity for the LESS simulated tasks was supported because the LESS-experienced scores were significantly better than the LESS-nonexpert scores.

CONCLUSION

Despite the increased technical difficulty associated with the LESS approach, surgeons are enthusiastic about offering these techniques and seeking additional training. Robust simulation-based methods that foster skill acquisition through repetitive practice and verification of proficiency are needed such that safe adoption may be fostered.