Introduction: Interspinous implants have recently been proposed as an alternative in the treatment of lumbar spinal stenosis and foraminal stenosis. Interspinous implants are thought to unload the facet joints, restore foraminal height and provide improved spinal stability especially in extension with a minimally invasive approach. It has been proposed that, combined with a tension band, stabilisation could also be obtained in flexion, thus avoiding the need for pedicle screw fixation. Little biomechanical data exists to support these notions. The aim of this in vivo study was to investigate the effect of a novel, minimally invasive, unilaterally inserted interspinous implant on flexion-extension range of motion of the lumbar spine.

Methods: Following the induction of general anesthesia, ten adolescent Merino lambs (24–30 kg) underwent a destabilisation procedure at the level of L1–L2, thus simulating a stenotic degenerative spondylolisthesis, as described previously. All animals were placed in a sidelying posture and lateral radiographs were taken in the neutral posture and in end stage flexion and extension trunk positions with the central ray at the level of L1–L2. The flexion manouvre was reproduced in each subject by securing a rope above the carpus (forelimb) and the tarsus (hindlimb). This same radiographic protocol was repeated following the insertion of an 8 mm InSwing interspinous device at L1–L2, and again with the implant secured by means of a tension band tightened to 1 N/m around the L1 and L2 spinous processes. Care was given to respect the integrity of the supra-spinous ligament. The insertion technique requires a minimally invasive unilateral approach, therefore leaving the attachment of the erector spinae muscle on the contralateral side intact. Using Cobb’s method, intersegmental range of motion (ROM) was assessed in each of the conditions and compared. A paired t-test compared ROM for each of the experimental conditions (P< .05).

Results: The addition of the InSwing interspinous implant reduced mean total flexion-extension ROM from 6.3 degrees to 5.3 degrees which was further reduced to 3.6 degrees with the device secured by means of a tension band. These differences were not statistically significant, but the addition of the tension band to the interspinous device resulted in a significant reduction of lumbar flexion (p< .05).

Discussion: The interspinous device tended to reduce the total flexion-extension ROM at the level of the implant, however the results were not significant. The addition of a tension band was found to significantly stabilize the spine in flexion. To our knowledge, this is the first in vivo study radiographically showing the advantage of using an interspinous device, specifically InSwing, to stabilize the spine in flexion. These results are important findings particularly for patients with clinical symptoms of instable degenerative spondylolisthesis.

Aims: Fixation failure due to osteoporosis is a major complication of osteosynthesis using compression hip screws (CHS). Biocompatible materials have been developed to improve CHS purchase and to limit fixation failure. Cortoss™ is a novel, injectable composite that interdigitates with bone, mimicking native cortical bone. This pilot study tested the immediate anchoring strength and safety of Cortoss in patients with peritrochanteric fracture. Methods: Ethical Committee approval and patient informed consent were obtained. Screws were advanced under fluoroscopy to their final position, and torque was measured electronically. Screws were backed out approximately 1 cm, 2.5 mL Cortoss was injected under fluoroscopy, and the screw was reinserted. An increase in rotational torque of at least 30% was achieved after allowing time for the bone filler to set. Results: The study population consisted of 20 patients (18 females, 2 males), 70 years or older (range 70 to 96 years) with osteoporosis. The mean preaugmentation torque was 1.23 Nm (range 0 to 4.8 Nm) and the mean postaugmentation torque was 1.81 Nm (range 0.7 to 4.8 Nm). All 20 screws were judged clinically tight after fixation. X-ray images showed that Cortoss contacted the screw threads and interdigitated with surrounding bone. No adverse events were reported. Conclusions: Cortoss provided safe and effective anchorage of CHS. By preventing screw cutout, Cortoss may provide long-term benefit to osteoporotic hip fracture patients by limiting fixation failure.

Purpose: Healing may be problematic after lag screw osteosynthesis of pertrochanteric fractures in osteoporotic bone due to the greater risk of defective fixation. Acrylic cement has been proposed to reinforce the fixation of the lag screw in these patients, principally to avoid the risk of cutout, but the acrylic cement’s thermal toxicity, its poor biocompatibility, and the difficult manipulation are important drawbacks. Cortoss® is a new composite biomaterial composed of bisphenol-aglycidly (bis-GMA) which could be an attractive alternative to classical cements. Cortoss is an injectable material with mechanical properties similar to human cortical bone. The purpose of this clinical study was to describe the new method for injection the material and to assess the anchoring force and safety of Cortoss in osteoporotic patients undergoing surgical fixation of pertrochanteric fractures.

Material and methods: This prospective study was approved by the local ethics committee. Twenty consecutive patients aged 70 years or more with pertro-chanteric fracture were included. The lag screw was inserted under fluoroscopic guidance, and the maximum insertion torque was measured. The screw was then unscrewed seven turns (length of the threaded head), and 2.5 cm Cortoss was injected via a polyimide catheter measuring 2.5 mm in diameter. The screw was then rescrewed in place to a troque 30% above that measured without Cortoss

Results: Eighteen women and two men, age 70 – 96 years, gave their informed consent to participate in the study. Mean maximal insertion torque without Cortoss was 1.23 Nm (min 0, max 4.8 Nm), which was increased 30% with Cortoss. Posto-operative x-rays showed that the screw head was embedded in an envelope of Cortoss and that the Cortoss had diffused into the adjacent bone. There were no adverse effects.

Discussion and conclusion: Cortoss provided effective reinforcement of the fixation as demonstrated by the higher insertion torque. Cortoss can also increase the mechanical resistance of the screw-cancellous bone interface, limit fixation default, and reduce secondary displacement of the lag screw in patients with osteoporotic bone. Improved stability can also reduce immobilisation time and facilitate bone healing without increasing the risk of secondary displacement and subsequent morbidity. Due to its safety, easy use, and efficacy, Cortoss provides a better alternative than acrylic cement for reinforcement of lag screw fixation of porotic bone.