Aims

Anchorage of pedicle screw rod instrumentation in the elderly spine with poor bone quality remains challenging. Our study aims to evaluate how the screw bone anchorage is affected by screw design, bone quality, loading conditions, and cementing techniques.

Segmental bone transport (SBT) using an external fixator is currently a standard treatment for large-diameter bone defects at the donor site with low morbidity. However, long-term application of the device is needed for bone healing. In addition, patients who received SBT treatment sometimes fail to show bone repair and union at the docking site, and require secondary surgery. The objective of this study was to investigate whether a single injection of recombinant human bone morphogenetic protein 2 (rhBMP-2)-loaded artificial collagen-like peptide gel (rhBMP-2/ACG) accelerates consolidation and bone union at the docking site in a mouse SBT model.

Six-month-old C57BL/6J mice were reconstructed by SBT with external fixator that has transport unit, and a 2.0-mm bone defect was created in the right femur. Mice were divided randomly into four treatment groups with eight mice in each group, Group CONT (immobile control), Group 0.2mm/d, Group 1.0mm/d, and Group BMP-2. Mice in Group 0.2mm/d and 1.0mm/d, bone segment was moved 0.2 mm per day for 10 days and 1.0 mm per day for 2 days, respectively. Mice in Group BMP-2 received an injection of 2.0 μg of rhBMP-2 dissolved in ACG into the bone defect site immediately after the defect-creating surgery and the bone segment was moved 1.0 mm/day for 2 days.

All animals were sacrificed at eight weeks after surgery. Consolidation at bone defect site and bone union at docking site were evaluated radiologically and histologically.

At the bone defect site, seven of eight mice in Group 0.2mm/d and two of eight mice in Group 1.0mm/d showed bone union. In contrast, all mice in Group CONT showed non-union at the bone defect site. At the docking site, four of eight mice in Group 0.2 mm/d and three of eight mice in Group 1.0 mm/d showed non-union. Meanwhile, all mice in Group BMP-2 showed bone union at the bone defect and docking sites. Bone volume and bone mineral content were significantly higher in Group 0.2mm/d and Group BMP-2 than in Group CONT. HE staining of tissue from Group 0.2mm/d and Group BMP-2 showed large amounts of longitudinal trabecular bone and regenerative new bone at eight weeks after surgery at the bone defect site. Meanwhile, in Group CONT and Group 1.0mm/d, maturation of regenerative bone at the bone defect site was poor. Differences between groups were analyzed using one-way ANOVA and a subsequent Bonferroni's post-hoc comparisons test. P < 0.05 was considered significant.

rhBMP-2/ACG combined with SBT may be effective for enhancing bone healing in large bone defects without the need for secondary procedures.

Segmental bone transport (SBT) with an external fixator has become a standard method for treatment of large bone defect. However, a long time-application of devices can be very troublesome and complications such as nonunion is sometimes seen at docking site. Although there have been several studies on SBT with large animal models, they were unsuitable for conducting drug application to improve SBT. The purpose of this study was to establish a bone transport model in mice. Six-month-old C57BL/6J mice were divided randomly into bone transport group (group BT) and an immobile control group (group EF). In each group, a 2-mm bone defect was created in the right femur. Group BT was reconstructed by SBT with external fixator (MouseExFix segment transport, RISystem, Switzerland) and group EF was fixed simply with unilateral external fixator (MouseExFix simple). In group BT, a bone segment was transported by 0.2 mm per day. Radiological and histological studies were conducted at 3 and 8 weeks after the surgery. In group BT, radiological data showed regenerative new bone consolidation at 8 weeks after the surgery, whereas high rate of nonunion was observed at the docking site. Histological data showed intramembranous and endochondral ossification. Group EF showed no bone union. In this study, experimental group showed good regenerative new bone formation and was similar ossification pattern to previous large animal models. Thus, the utilization of this bone defect mice model allows to design future studies with standardized mechanical conditions for analyzing mechanisms of bone regeneration induced by SBT.

The reduction for unstable femoral intertrochanteric fracture should be extramedullary, which means that the proximal fragment protrudes for the distal fragment. However, only few articles have compared extramedullary and intramedullary reductions in a biomechanical study. Thus, we created unstable femoral intertrochanteric fracture models using imitational bone (extramedullary and intramedullary groups, each with 12 cases) and evaluated their biomechanical stabilities. The fracture type was 31-A2 according to the AO-OTA Classification of Fractures and Dislocations and greatly lacked bone on the posterior side. We performed compression examination and evaluated stiffness. The implant used for fixation was TFNA (DePuy Synthes). We applied axial compression with 20 adduction in the standing position. Statistical analysis was performed using the Mann-Whitney U test. No significant difference in initial loading force was found between the two groups. However, the axial stiffness of the extramedullary bone showed a significant increase (p < 0.05) in high loading force (800–1000 N). This means that the stability of the extramedullary reduction was superior to that of the intramedullary reduction in terms of high loading force in the standing position. We suggest that antero-medial bony buttress is important for unstable femoral intertrochanteric fractures. These data indicate that extramedullary reduction and fixation for unstable femoral intertrochanteric fractures increase stability.

Smith's fractures generally occur when falling on a flexed wrist; however, orthopedic trauma surgeons often encounter distal radius fractures with volar displacement in patients who have allegedly fallen on the palm of their hands. This study aimed to reveal both the basic and clinical pathogenesis of Smith's fracture through a step-by-step investigation. We enrolled 17 patients with Smith's fractures, of which 71% fell on the palm and only 6% on the dorsum of the hand. First, we interviewed the outpatients to determine the mechanics of the injury and the position of their arm during injury. Second, we created a three-dimensional (3D) finite element model to predict the arm's position when the Smith's fracture occurred, which finite element analysis revealed as a 30° angle between the long axis of the forearm and the ground in the sagittal plane. Third, using this predicted position, we conducted experiments on 10 fresh frozen cadavers to prove the possibility of causing a Smith's fracture by falling on the palm of the hand. The results showed Smith-type fractures in seven of 10 wrists, whereas Colles-type fractures did not occur. Finally, we analyzed stress distribution in the distal radius when a Smith's fracture occurs using the 3D finite element model. In conclusion, this study demonstrates that Smith's fractures can also occur by falling on the palm of the hand.

Objectives

To compare the effect of femoral bone tunnel configuration on tendon-bone healing in an anterior cruciate ligament (ACL) reconstruction animal model.

Introduction

Stemless shoulder implants have recently gained increasing popularity. Advantages include an anatomic reconstruction of the humerus with preservation of bone stock for upcoming revisions. Several implant designs have been introduced over the last years. However, only few studies evaluated the impact of the varying designs on the load transfer and bone remodeling. The aim of this study was to compare the differences between two stemless shoulder implant designs using the micro finite element (µFE) method.

Impact relief ability of Metal-on-Metal artificial hip joint with multi-garter spring using drop impact tester for practical use

Toshiaki Kaneeda, Xinming Zhao and Hiroshi Matsuura

Metal-on-metal (MoM) joints can provide better wear properties than hard-on-polymer joints, leading to reducing osteolysis. However during gait, MoM hip joints have no material to relieve impact. These impacts can cause severe pain in postoperative patients. Kaneeda proposed double-shell MoM artificial hip joints in which multi garter springs were inserted between the inner and outer acetabular shell as an impact relief device. The proposed double-shell metal-on-metal artificial hip joint is composed of two layers, as shown in Fig. 11).

A garter spring is usually used when by loading and a compression stress from the outside to the center axis. In the model testing for garter spring, it is demonstrated that garter spring had impact relief ability, then using dual garter springs could lead to better impact relief ability than single one2).

In this work, the impact relief ability of model hip joint were investigated by using the Instron CEAST 9340 machine as shown in Fig. 2. The machine is a floor standing impact system designed to deliver 0.30–405J of energy and equipped with precise locating system for height. A holding device of double-shell cup was made to fix the right position. A shape of drop impact weight was modified for this experiment. The model hip joint was applied vertical load over 6000N, which is estimated to be equal to maximum vertical load during jumping. The ability in the case of single garter spring and dual garter springs was evaluated in the model hip joint, comparing with UHMWPE liner in the same size of femur head. Each testing was conducted 10 times.

Fig. 3 shows load-time curve detected. From the results, it can be seen that in both case Load L gradually rise with Time T, then reach maximum values, finally L gently drop: maximum impact load as well as maximum impact load arriving time also presented nearly the same values. Much differences in shape of the curve between model hip joint with dual garter springs and UHMWPE liner could not be recognized. The model hip joint with dual garter springs may has enough impact relief ability.

Introduction

Over the past decade, the use of negative pressure wound therapy (NPWT) devices has increased and expanded to include a wide variety of patients. However, the safety and efficacy of NPWT over skin in open fractures is still unknown. The purpose of this study was to evaluate the complication rate and outcome of open fractures treated by NPWT over closed wounds or flaps.

Direct anterior approach (DAA) is an inter-muscular approach that needs no muscle detached. In THA through DAA approach, exposure of the acetabulum is facilitated, while the key points of this approach are femoral lift-up and hip extension to get sufficient access to the femoral canal. To investigate the strategy for femoral lift-up, we released the capsule step by step and measured the distance of femoral lift-up at each step in cadavers and clinical cases. The effects of hip extension on femoral lift-up were also evaluated.

Three fresh frozen cadavers were used. In supine position, the hip joint was exposed through DAA by two experienced surgeons. After anterior capsulotomy and femoral head resection, posterior capsule release was performed followed by superior capsule release in one side, and superior release was followed by posterior release in the other side. Finally, internal obturator muscle was released in both side. At each step, the distance of femoral lift-up was measured under the traction force of 70N. The effects of hip extension were investigated in 0, 15 and 25 degrees hyper-extension. Thirty-six THA were performed through DAA. Posterior capsule release was performed followed by superior capsule release in 13 hips, and superior release was followed by posterior release in 23 hips. At each step, the distance of femoral lift-up was measured under the traction force of 70N at each step same as the cadaver study.

In cadaver study, anterior capsulotomy and posterior capsule release affected little the femoral lift-up. The distance increased after superior capsular release. The distance decreased as hip hyperextension unless the superior capsule was released. The effect of internal obturator muscle release was not observed. In clinical studies, the same tendency was observed in clinical cases. Superior capsule release was the most effective for the femoral lift-up.

The results of this study indicate that superior capsule release is the first step for the femoral liftup. The second step is hip extension to get access to the femoral canal. By performing these procedures step by step, rasping and stem insertion can be achieved with minimal soft tissue release.

Introduction: In total hip arthroplasty, the angle of acetabular component is a critical factor for the postoperative dislocation and the longevity of prostheses. The angle is principally determined in relation to anterior pelvic plane. It is reported that the pelvis tends to tilt posteriorly along with aging. Furthermore, the pelvic tilt might change after THA. The changes might be infiuenced by the hip condition and lumbar lordosis. We measured the pelvic tilt and the lumbar lordosis, and evaluated the effects of contralateral hip and lumbar lordosis on pelvic tilt after THA.

Materials and Methods: Fifty-one unilateral patients and 30 bilateral patients were enrolled in this study. The diagnosis was dysplastic osteoarthritis in all patients. In unilateral patients, the hip was affected in one side and the other hip was normal or acetabular dysplasia without symptoms. In bilateral patients, THAs in both hips were done within two months.

Pelvic inclination angle (PIA) and lumbar lordotic angle (LLA) were measured on the standing lateral X-rays before operation and 1-month, 6-month and 1-year post-operation. The effects of patient age, BMI, ROM of the hip, preoperative PIA and LLA on the changes of PIA were statistically investigated using multiple linear regression analysis. We divided the patients into three groups with regard to pre-operative PIA (anterior group: PIA < 0, intermediate group: 0 < PIA < 10, posterior group: PIA > 10) and with regard to pre-operative LLA (insufficient group: LLA < 20, moderate group: 20 < LLA < 40, severe group: LLA > 40).

Results: Overall, significant factor was only preoperative PIA. In bilateral cases, preoperative PIA and patient age affected the changes of PIA after THA. In patients with severe lordosis, preoperative PIA and LLA were significant factors. PIA increased in anterior tilt group and PIA did not change in intermediate group, while PIA gradually decreased in posterior group. In insufficient lordosis group, PIA remarkably increased after THA compared with that in severe group.

Discussion: Pelvic tilt after THA has been reported without considering the conditions of contralateral hip and lumbar spine. By categorizing patients with regard to the conditions of hips and lumbar spine, we can prospect the tendency of the direction of PIA changes. These results indicated that pre-operative PIA was related the changes of PIA in bilateral group. PIA slightly increased in all bilateral patients, PIA tended to close each other in unilateral patients. Further investigation is necessary to prospect the estimated PIA value after THA.