The TL Hex (Orthofix) is a relatively new hexapod frame system that we have been using at our institution since August 2013 to treat acute fractures and correct tibial and femoral deformity. We report our initial experience of 48 completed treatments with this novel system in 46 patients and discuss illustrative cases. For acute fracture, 30 patients (24 male, 7 female) required framing with a mean age of 43 years (range 19–80). One patient underwent bilateral framing. The tibia was involved in all cases. In two cases, the femur also required framing. Open fractures occurred in 13 cases (43.3%). For elective limb reconstruction, 16 patients (14 male, two female) required framing with a mean age of 35 years (range 16–67). One patient underwent bilateral framing. The tibia was involved in all but one case, which affected the femur. Surgical indications included congenital deformity in four cases, malunion in eight cases, non-union in three cases and chronic infection in two cases. For acute fractures, the mean frame time was 164 days (range 63–560) and all but one fracture achieved union. Complications included pin, wire or strut failure requiring adjustment (three patients) and pin site infection (six patients). Three patients are being considered for residual deformity correction or treatment of non-union. In the elective limb reconstruction group, mean frame time was 220 days (range 140–462). All treatments successfully achieved deformity correction and bone union. Complications included two pin site infections. There was no evidence of recurrence of infection in the two osteomyelitis cases. In conclusion, the TL Hex frame system appears to be a safe and reliable tool for limb reconstruction. We have observed acceptable frame times, low complication rates and almost 100% bony union

Summary Statement. Repetitive loading of degenerated human intervertebral discs in combined axial compression, flexion and axial rotation, typical of manual handling lifing activities, causes: an increase in intradiscal maximum shear strains, circumferential annular tears and nuclear seperation from the endplate. Introduction. Chronic low back pain (LBP) is a crippling condition that affects quality of life and is a significant burden to the health care system and the workforce. The mechanisms of LBP are poorly understood, however it is well known that loss of intervertebral disc (disc) height due to degeneration is a common cause of chronic low back and referred pain. Gross disc injury such as herniation can be caused by sudden overload or by damage accumulation via repetitive loading, which is a cause of acute LBP and an accelerant of disc degeneration. The aim of this study was to determine for the first time the relationship between combined repetitive compression, flexion and axial rotation motion of degenerated cadaver lumbar spine segments, and the progression of three-dimensional (3D) internal disc strains that may lead to disc herniation and macroscopic tissue damage. Patients & Methods. Seven degenerated human lumbar functional spinal units (FSUs) underwent pre-test MRI, had a grid of tantalum wires inserted into the mid-transverse plane of the disc and were subjected to 20,000 cycles of repetitive loading in combined compression (1.7 MPa), flexion (11–13°) and right axial rotation (2–3°) in a six degree of freedom hexapod robot. Stereoradiographs were taken at cyclic intervals (1, 500, 1000, 5000, 10000, 15000 and 20000 cycles) from which 3D intradiscal principal strains and maximum shear strains (MSS) were calculated and partitioned into nine disc anatomical regions. After testing the discs underwent post-test MRI followed by macroscopic assessment to identify tissue damage. A repeated measures ANOVA having a within-subjects factor of cycle number, and a between-subjects factor of disc region was used to examine the effects of cycle number and disc region on MSS. Results. No visible evidence of disc herniation occurred after 20,000 cycles, however circumferential annular tears and nucleus separation from the endplate were observed in all specimens in agreement with observed signal changes in post-test MRI images. There was a significant effect of both cycle number, disc region and the interaction of cycle number x disc region on MSS (p<0.001). MSS was significantly larger after 20,000 cycles compared with the first loading cycle in the anterior, left anterolateral, left lateral, and left posterolateral disc regions (p<0.037). Minor changes in MSS were seen in the posterior and nucleus regions. The largest increases were observed in the left anterolateral and left posterolateral regions after 20,000 cycles. Discussion/Conclusion. A significant increase in MSS was observed across most regions in the disc after 20,000 repetitive loading cycles, especially in the left anterolateral and left posterolateral regions. No herniation was observed, although macroscopic and MRI evidence of circumferential annular tears and nuclear separation from the endplate occurred, suggesting internal disc tissue disorganisation that may indicate a progression towards eventual herniation