The aim of this study was to compare the peak pull-out force
(PPF) of pedicle-lengthening screws (PLS) and traditional pedicle
screws (TPS) using instant and cyclic fatigue testing. A total of 60 lumbar vertebrae were divided into six groups:
PLS submitted to instant pull-out and fatigue-resistance testing
(groups A1 and A2, respectively), TPS submitted to instant pull-out
and fatigue-resistance testing (groups B1 and B2, respectively)
and PLS augmented with 2 ml polymethylmethacrylate, submitted to
instant pull-out and fatigue-resistance testing (groups C1 and C2,
respectively). The PPF and normalized PPF (PPFn) for bone mineral density
(BMD) were compared within and between all groups.Aims
Materials and Methods
Many studies have investigated the kinematics of the lumbar spine and the morphological features of the lumbar discs. However, the segment-dependent immediate changes of the lumbar intervertebral space height during flexion-extension motion are still unclear. This study examined the changes of intervertebral space height during flexion-extension motion of lumbar specimens. First, we validated the accuracy and repeatability of a custom-made mechanical loading equipment set-up. Eight lumbar specimens underwent CT scanning in flexion, neural, and extension positions by using the equipment set-up. The changes in the disc height and distance between adjacent two pedicle screw entry points (DASEP) of the posterior approach at different lumbar levels (L3/4, L4/5 and L5/S1) were examined on three-dimensional lumbar models, which were reconstructed from the CT images.Objectives
Methods
We conducted a prospective, randomized study comparing the outcomes of total knee arthroplasty (TKA) respectively through a quadriceps-sparing (QS) approach and a MIS medial parapatellar (MP) approach at 2-year follow-up. Sixty patients (80 knees) with primary osteoarthritis were enrolled in this study. Patients were blinded to be treated with and randomized to be grouped by either MP group (40 knees) or QS group (40 knees). Thirty-seven MIS MP TKAs and thirty-eight QS TKAs completed the 2-year follow-up. According to the isokinetic study, the recovery of muscle strength (peak muscle torque) and normalization of muscle balance (H/Q peak-torque ratio) were comparable in both groups at either 2-month or 2-year follow-up. Tourniquet and surgical time in the QS group was significantly longer (approximately 20 minutes) than that in the MP group. The hip-knee-ankle axis measured after surgery was significantly more varus in the QS group than that in the MP group. The axis in both groups did not significantly progress at 2-year follow-up. There were no infections and no revisions at 2-year follow-up in both groups. More outlier cases (4 knees) were noted in the QS group when compared with the MP group (no outlier). However, no differences regarding the clinic outcomes (including VAS, HSS knee score, ROM and satisfaction) were observed between these two groups after either two months or two years upon operation. In both groups, there was a significant improvement of these parameters at 2-year follow-up in contrast with 2-month follow-up and pre-operative status. In this study, we conclude that MIS medial parapatellar TKAs could achieve comparable recovery of muscle strength, normalization of hamstring-quadriceps muscle balance and clinical outcomes when compared with QS TKAs; moreover it provides more reliable alignment and fewer complications than quadriceps-sparing TKAs.
