A percutaneous, minimally invasive annulus fibrosus needle puncture model of intervertebral disc degeneration in rabbits

PURPOSE

Various animal models have been proposed to mimic the pathophysiologic process of intervertebral disc degeneration, a leading cause of back pain. The purpose of this study is to describe a minimally invasive technique via percutaneous needle puncture of the annulus fibrosus in New Zealand white rabbits.

METHODS

Under fluoroscopic guidance, an 18-gauge spinal needle was inserted 2 cm lateral to the midline spinous process. The needle was slowly advanced at approximately 45° angle until it was adjacent to the L5/L6 disc space. Lateral and anteroposterior views were used to verify correct needle position before advancing into the nucleus pulposus. The rabbits underwent weekly X-rays for 4 weeks to assess disc height index. MRI T2 relaxation was evaluated at week four to assess morphological changes. Discs were histologically graded on a 12-point scale to assess degeneration and compared to discs obtained from uninjured rabbits.

RESULTS

There were no complications associated with the percutaneous needle puncture procedure. All animals survived the duration of the experiment. Four weeks after injury, the disc height had progressively narrowed to approximately 50% of baseline. MRI assessment at the 4-week time point demonstrated a mean T2 relaxation time at the L5/L6 level that was 20.9% of the T2 relaxation time at the uninjured L4/L5 disc level ( p < 0.001). Histological analysis demonstrated lamellar disorganization of the annulus and decreased cellularity and proteoglycan content within the injured nucleus compared to uninjured control discs.

CONCLUSION

The present study demonstrated a reliable technique of inducing an annular tear via a percutaneous needle puncture. Compared to open surgical approaches, the percutaneous model produces similar progressive disc degeneration while minimizing harm to the animal subjects.

CLINICAL RELEVANCE

The present study establishes a technique for the introduction of novel therapeutic agents to treat disc degeneration that may translate to future clinical trials.

Epidural Abscess in the Lumbar Spine: A Single Institution's Experience With Nonsurgical and Surgical Management

The purpose of this study was to compare patient factors and outcomes in conservatively and surgically treated patients with spinal epidural abscess (SEA). This was a single-center retrospective review of adult patients treated for SEA of the lumbar spine. Primary treatment outcome was readmission for recurrent abscess. Sixty-one patients met inclusion criteria: 59% male, mean age 56.9 years, and body mass index 30.8 kg/m². Initially 47.5% of patients were treated with conservative measures and 52.5% were treated with surgery. In the conservative group, 31.0% failed treatment and underwent delayed surgery; 26.2% of the overall cohort was readmitted for SEA. Readmitted patients had a greater incidence of history of methicillin-resistant Staphylococcus aureus (p = .048), recurrent infections (p = .008), and recent sepsis and bacteremia (p = .005). Nearly one-third of patients failed initial conservative treatment and needed delayed surgery; however, no significant differences were found between the two treatment groups. Patients with a past history of infections may require more aggressive treatment and closer follow-up, because they are at higher risk for recurrence and readmission. (Journal of Surgical Orthopaedic Advances 28(3):224-231, 2019).

Transfer of the Dorsal Cutaneous Branch of the Ulnar Nerve for Restoration of Median Nerve Sensation: A Cadaveric Study

The use of dorsal cutaneous branch of the ulnar nerve (DCBUN) transfer for median nerve (MN) sensory restoration has not been evaluated anatomically and histologically in humans. The purpose of this study was to evaluate the feasibility of DCBUN to MN transfer for sensory restoration with respect to nerve branch pattern, length, and fascicle count match.Using seven fresh frozen cadaveric upper limb specimens, the DCBUN and its branch patterns, lengths, and sizes were recorded. The MN was exposed within the carpal tunnel and dissected distally to identify the common digital nerves (CDN). Simulated nerve transfer was performed with palmar coaptation of the DCBUN branches with the CDNs. Histological analysis of each nerve branch was performed. The seven specimens had a mean of 3.57 branches (range 2-4) off the DCBUN. The longest branch innervated the dorsal 4th web space, on average reaching 7.6 cm distal to the wrist crease. Transferring the DCBUN branches palmarly did not substantially change their maximum distance distal to the wrist crease. The MN CDNs and DCBUN branches had mean cross-sectional areas of 6.37 and 1.99 mm² , respectively, and mean fascicle counts of 10.4 and 4.05, respectively. The DCBUN provides 2-4 branches suitable for tension-free end-to-end transfer to the MN CDNs. The individual size of the DCBUN branch is smaller than CDN; however, combining two or more branches of the DCBUN would overcome the fascicle and size mismatch to reconstruct the 1st web space CDN for critical sensory restoration. Clin. Anat. 31:1006-1012, 2018. © 2018 Wiley Periodicals, Inc.