Remodeling of the cancellous bone is more active than that of the cortical bone. It is known that the remodeling is governed by the intracancellous fluid pressure. Particularly, the lacunocanalicular pore (PLC) fluid pressure (FP) is essential for survival of the osteocyte and communication of remodeling signals between the PLC and intertrabecular pore (PIT). As a result, knowledge about the PLCFP generation of trabeculae is required to understand human cancellous bone biology. At this moment, the PLCFP measurement of human trabeculae is not reported. The purpose of this study was a direct measurement of PLCFP generation of human proximal femoral trabeculae in the direction of superior-to-fovea. Twenty one microscopic cylindrical trabecular specimens from trabeculae of five fresh human proximal femur (75 to 77 years) were fabricated using a micro-milling machine composed of the laser (Teemphotonics: 532nm), 3-dimensional PZT stage (PI Gmbh, resolution: 0.5nm), and microscope (lens: Navitar, and CCD: Hitachi) with the image processor. The fabrication resolution of the micro-milling machine was 0.4 um. Based on the trabecular trajectory of femoral head, the specimens were obtained in the direction of superior-to-fovea. The cylindrical specimen size had 120 um in diameter and 240 um in length. The test methods described in the previous study were utilized. The used undrained uniaxial strain condition could induce the maximum PLCFP within the trabecular elastic limit.

The measured trabecular PLCFP (±SD) at the strain of 0.4% was 693.7±79.1 kPa. Since this experiment is equivalent to the instantaneous response of PLCFP with free flow boundaries after application of an extremely fast loading speed such an ideal step loading, a PLCFP generation in the physiological condition will be much less than the results obtained in this study. Base on the linear isotropic poroelasticity, the obtained Skempton's coefficient is almost 0. Thus, the load bearing capability by trabecular PLC fluid is negligible. The Biot coefficient is 0.35 which is higher than that of the cortical tissue (0.14). As a result, the intraosseous fluid communication through trabecular surfaces is active compared to that through Haversian canal surfaces. This imply that mass transports from the trabecular PLC into the PIT and from the PIT into the trabecular PLC could be significantly affected by the PITFP (the physiological blood systolic and diastolic pressure: 16 and 11 kPa, respectively) that acts as the FP boundary condition for the PLC flow. It is known that the PLC flow generates the electrical charges on the trabecular surface (‘+’ for being spouted into the PIT and ‘−’ for being flown into the PLC), which control differentiation and proliferation of the osteoblast and mesenchymal stem cell. Thus, significant changes in the PITFT could cause changes in the intra-trabecular PLC flow characteristics, mass transports between the PLC and PIT, and electrical charges on the trabeculae. Eventually, these could result in pathologies related to the trabecular remodeling.

Posterolateral rotatory instability (PLRI) is the most common type of elbow instability. It is caused by an insufficiency of the lateral ligamentous complex, which consists mainly of the radial collateral ligament (RCL) and the lateral ulnar collateral ligament (LUCL).

Investigate the influence of serial sectioning of the lateral ligamentous complex on elbow stability in a cadaveric model of PLRI.

Kinematics of six fresh frozen cadaveric elbow specimens were measured by digitizing anatomical marks with a Microscribe 3DLX digitizing system (Revware Inc, Raleigh, NC). Each specimen was tested under four conditions: Intact, LUCL tear, LUCL and RCL tear, and complete Tear (LUCL, RCL and capsule tear). Each specimen was tested in 30°, 60° and 90° elbow flexion angles. Varus- laxity was measured in supination, pronation, and neutral forearm rotation positions and total forearm rotation was measured with 0.3 Nm of torque. Statistical significant differences between the conditions were detected using a two-way ANOVA with Tukey's post-hoc test.

The radial head dislocated in all specimens in LUCL and RCL tear and Comp but not in LUCL tear. Total forearm ROM did not increase form intact to LUCL tear (p>0.05) but significantly increased in LUCL and RCL tear (p=0.0002) and complete tear (p<0.0001) in all flexion angles. Additionally, ROM in LUCL tear significantly differed from LUCL and RCL tear and complete tear (p=0.0027 and p=0.0002). A similar trend was seen with the varus angle. While there was a significant difference when the intact condition was compared to both the LUCLand RCL tear and complete tear conditions (p<0.0001 and p<0.0001), there was no difference between the intact and LUCL tear conditions.

LUCL tear alone is not sufficient to cause instability and increase ROM and varus angle, meanwhile the increase of ROM and varus angle with additional capsular tear was not significant compared to LUCL and RCL tear. The increase of ROM after LUCL and RCL tear is an unknown symptom of PLRI.

Insufficiency of the lateral collateral ligamentous complex causes posterolateral rotatory instability (PLRI). During reconstruction surgery the joint capsule is repaired, but its biomechanical influence on elbow stability has not been described. We hypothesized that capsular repair reduces ROM and varus angle after reconstruction of the lateral collateral complex.

Six fresh frozen cadaveric elbow specimens were used. Varus laxity in supination, pronation and neutral forearm rotation with 1 Nm load and forearm rotaitonal range of motion (ROM) with 0.3 Nm torque were measured using a Microscribe 3DLX digitizing system (Revware Inc, Raleigh, NC). Each specimen was tested under four different conditions: Intact, Complete Tear with LUCL, RCL and capsule tear, LUCL/RCL reconstruction + capsule repair and LUCL/RCL reconstruction only. Reconstruction was performed according to the docking technique (Jones, JSES, 2013) and the capsule was repaired with mattress sutures. Each condition was tested in 30°, 60° and 90° elbow flexion. A two-way ANOVA with Tukey's post-hoc test was used to detect statistical differences between the conditions.

Total ROM of the forearm significantly increased in all flexion angles from intact to Complete tear (p<0.001). ROM was restored to normal in 30° and 60° elbow flexion in both reconstruction conditions (p>0.05). LUCL/RCL Reconstruction + capsule repair in 90° elbow flexion was associated with a significantly lower ROM compared to intact (p=0.0003) and reconstruction without capsule repair (p=0.015). Varus angle increased significantly from intact to complete tear (p<0.0001) and restored to normal in both reconstruction conditions (p>0.05) in 30° and 60° elbow flexion. In contrast varus angle was significantly lower in 90° elbow flexion in both reconstruction conditions compared to intact (both p<0.0001).

Reconstruction of the lateral collateral complex restores elbow stability, ROM and varus laxity independent of capsular repair. Over tightening of the elbow joint occurred in 90° elbow flexion, which was aggravated by capsular repair. Over all capsular repair can be performed without negatively affecting elbow joint mobility.