The comparison between anterior and posterior approaches for removal of infected lumbar interbody cages and a proposal regarding the use of endoscope-assisted technique

Remove the infected interbody cage using endoscopy in lumbar spine revision surgery: A case series and technique report

BACKGROUND

Current revision surgery to remove the infected interbody cage following transforaminal lumbar interbody fusion (TLIF) surgery is challenging and traumatic. The purpose of this study is to introduce a novel surgical technique to remove the infected interbody cage for chronic infection.

METHODS

Three patients with chronic infection following TLIF surgery underwent revision surgery. Instrumentations were removed and a spinal endoscope was obliquely inserted to the disc space through the initial annular breach. Under endoscope, the cage was found, released, turned around, and dragged to the posterior edge of the disc space. The cage was then removed without distracting the dural sac and nerve roots. For two cases, appropriately sized structural iliac bone grafts were used for interbody fusion without extra instrumentations.

RESULTS

Using endoscope, the interbody cage was easy to identify and expose without disrupting the dural sac and nerve roots. With various endoscopic tools, the cage was easily released and removed. In this case series, the infected interbody cage was removed within thirty minutes without dural sac rupture and nerve root injury. The infection was controlled after the surgery, and the patients obtained good clinical outcomes. At 6-month follow-up, bony fusion was achieved in two patients who underwent interbody fusion.

CONCLUSIONS

This endoscopy assisted technique simplified the revision surgery for chronic infection followed TLIF surgery, with the advantages of no disruption of the neural tissues, bright surgical field and complete disc debridement.

Biomechanical evaluation of pedicle screw stability after 360-degree turnback from full insertion: effects of screw shape, pilot hole profile and bone density

Intraoperative pedicle screw depth adjustment after initial insertion, including both forward and backward adjustments, is sometimes necessary to facilitate rod application and ensure that the screw is in the correct position, which is determined by intraoperative fluoroscopy. Adjusting the screw with forward turns has no negative influence on the screw fixation stability; however, screw turnback may weaken the fixation stability. The aim of this study is to evaluate the biomechanical properties of screw turnback and demonstrate the reduction in the fixation stability after the screw is turned 360° from its full insertion position. Commercially available synthetic closed-cell polyurethane foams with three different densities simulating various degrees of bone density were utilized as substitutes for human bone. Two different screw shapes (cylindrical and conical) together with two different pilot hole profiles (cylindrical and conical) were tested. Following specimen preparation, screw pullout tests were conducted using a material test machine. The mean maximal pullout strength between full insertion and 360-degree turnback from full insertion in each setting was statistically analyzed. The mean maximal pullout strength after 360-degree turnback from full insertion was generally lower than that at full insertion. The reduced mean maximal pullout strength after turnback increased with decreasing bone density. Conical screws had significantly lower pullout strength after 360-degree turnback than cylindrical screws. The mean maximal pullout strength was reduced by up to approximately 27% after 360-degree turnback when using a conical screw in a low bone density specimen. Additionally, specimens treated with a conical pilot hole presented a less reduction in pullout strength after screw turnback as compared to those with a cylindrical pilot hole. The strength of our study was that we systematically investigated the effects of various bone densities and screw shapes on screw stability after turnback, which has rarely been reported in the literature. Our study suggests that pedicle screw turnback after full insertion should be reduced in spinal surgeries, particularly procedures that use conical screws in osteoporotic bone. Pedicle screw secured with a conical pilot hole might be beneficial for screw adjustment.

Application of Oblique Lateral Interbody Fusion Combined with Bridge-Locking Cage in Adjacent Segment Disease After Lumbar Fusion

OBJECTIVE

Adjacent segment disease (ASD) is considered any abnormal process that develops in the mobile segment next to spinal fusion, accompanied by related symptoms. To evaluate the efficacy and complications of oblique lateral interbody fusion (OLIF) combined with bridge-locking fusion on ASD after lumbar fusion.

METHODS

A total of 35 ASD patients who required re-operation after lumbar fusion in our hospital from March 2014 to March 2020 were retrospectively analyzed, among which 13 cases (seven males and six females; 62.3 ± 11.3 years old) received the treatment of OLIF + bridge-locking cage internal fixation (OLIF group), and 22 cases (14 males and eight females; 52.3 ± 17.8 years old) received the treatment of transforaminal lumbar interbody fusion (TLIF) + pedicle screw fixation (TLIF group). The comparison of the operation time, intraoperative blood loss, postoperative drainage volume, and length of hospital stay between the two groups of patients was performed using the t-test. The comparison of Visual Analogue Scale (VAS) and Oswestry Disability Index (ODI) at different time points before and after the operation was performed using analysis of variance for repeated measurement data. The fusion rate and postoperative complications of the two groups of patients were also evaluated.

RESULTS

The operation time of patients in the OLIF group (55.4 ± 12.4 min) was significantly shorter than that of patients in the TLIF group (94.3 ± 22.9 min) (P < 0.05), the length of stay of patients in the OLIF group (7.4 ± 2.3 day) was significantly shorter than that of patients in the TLIF group (12.4 ± 3.2 day) (P < 0.05); the intraoperative blood loss (62.2 ± 30.1 mL) and postoperative drainage (47.3 ± 22.4 mL) of patients in the OLIF group were significantly less than those of patients in the TLIF group with intraoperative blood loss (363.4 ± 120.2 mL) and postoperative drainage (285.5 ± 57.8 mL) (all Ps < 0.05). Besides, the VAS and ODI scores of the two groups of patients were improved 3 months after the operation and at the last follow-up (all Ps < 0.05). Three patients in the OLIF group developed complications such as hip flexion weakness and fusion cage sink, with an incidence of 23.1%. Three patients in the TLIF group developed complications including wound infection and intraoperative nerve injury, with an incidence of 22.7%.

CONCLUSION

The combination of OLIF and bridge-locking cage may be a safe and effective therapy for ASD patients after lumbar fusion operation.

Frailty as a Superior Predictor of Dysphagia and Surgically Placed Feeding Tube Requirement After Anterior Cervical Discectomy and Fusion Relative to Age

Frailty is a measure of physiological reserve that has been demonstrated to be a discriminative predictor of worse outcomes across multiple surgical subspecialties. Anterior cervical discectomy and fusion (ACDF) is one of the most common neurosurgical procedures in the United States and has a high incidence of postoperative dysphagia. To determine the association between frailty and dysphagia after ACDF and compare the predictive value of frailty and age. 155,300 patients with cervical stenosis (CS) who received ACDF were selected from the 2016-2019 National Inpatient Sample (NIS) utilizing International Classification of Disease, tenth edition (ICD-10) codes. The 11-point modified frailty index (mFI-11) was used to stratify patients based on frailty: mFI-11 = 0 was robust, mFI-11 = 1 was prefrail, mFI-11 = 2 was frail, and mFI-11 = 3 + was characterized as severely frail. Demographics, complications, and outcomes were compared between frailty groups. A total of 155,300 patients undergoing ACDF for CS were identified, 33,475 (21.6%) of whom were frail. Dysphagia occurred in 11,065 (7.1%) of all patients, and its incidence was significantly higher for frail patients (OR 1.569, p < 0.001). Frailty was a risk factor for postoperative complications (OR 1.681, p < 0.001). Increasing frailty and undergoing multilevel ACDF were significant independent predictors of negative postoperative outcomes, including dysphagia, surgically placed feeding tube (SPFT), prolonged LOS, non-home discharge, inpatient death, and increased total charges (p < 0.001 for all). Increasing mFI-11 score has better prognostic value than patient age in predicting postoperative dysphagia and SPFT after ACDF.

Biomechanical Comparison of Salvage Pedicle Screw Augmentations Using Different Biomaterials

Allograft bone particles, hydroxyapatite/β-hydroxyapatite-tricalcium phosphate (HA/β-TCP), calcium sulfate (CS), and polymethylmethacrylate (PMMA) bone cement are biomaterials clinically used to fill defective pedicles for pedicle screw augmentation. Few studies have systematically investigated the effects of various biomaterials utilized for salvage screw stabilization. The aim of this study was to evaluate the biomechanical properties of screws augmented with these four different materials and the effect of different pilot hole sizes and bone densities on screw fixation strength. Commercially available synthetic bones with three different densities (7.5 pcf, 15pcf, 30 pcf) simulating different degrees of bone density were utilized as substitutes for human bone. Two different pilot hole sizes (3.2 mm and 7.0 mm in diameter) were prepared on test blocks to simulate primary and revision pedicle screw fixation, respectively. Following separate specimen preparation with these four different filling biomaterials, a screw pullout test was conducted using a material test machine, and the average maximal screw pullout strength was compared among groups. The average maximal pullout strength of the materials, presented in descending order, was as follows: bone cement, calcium sulfate, HA/β-TCP, allograft bone chips and the control. In samples in both the 3.2 mm pilot-hole and 7.0 mm pilot-hole groups, the average maximal pullout strength of these four materials increased with increasing bone density. The average maximal pullout strength of the bone cement augmented salvage screw (7.0 mm) was apparently elevated in the 7.5 pcf test block. Salvage pedicle screw augmentation with allograft bone chips, HA/β-TCP, calcium sulfate, and bone cement are all feasible methods and can offer better pullout strength than materials in the non-augmentation group. Bone cement provides the most significantly augmented effect in each pilot hole size and bone density setting and could be considered preferentially to achieve larger initial stability during revision surgery, especially for bones with osteoporotic quality.