The Adams-Berger reconstruction is an effective technique for treating distal radioulnar joint (DRUJ) instability. Graft preparation techniques vary amongst surgeons with insufficient evidence to support one technique over another. Our study evaluated the biomechanical properties of four graft preparation techniques. Extensor tendons were harvested from fresh frozen porcine trotters obtained from a local butcher shop and prepared in one of three configurations (n=5 per group): tendon only; tendon prepared with non-locking, running suture (2-0 FiberLoop, Arthrex, Naples, FL) spaced at 6 mm intervals; and tendon prepared with suture spaced at 12 mm intervals. A fourth configuration of suture alone was also tested. Tendons were allocated in a manner to ensure comparable average diameters amongst groups.
Restoration a joint's articular surface following degenerative or traumatic pathology to the osteochondral unit pose a significant challenge. Recent advances have shown the utility of collagen-based scaffolds in the regeneration of osteochondral tissue. To provide these collagen scaffolds with the appropriate superstructure novel techniques in 3D printing have been investigated. This study investigates the use of polyɛ-caprolactone (PCL) collagen scaffolds in a porcine cadaveric model to establish the stability of the biomaterial once implanted. This study was performed in a porcine cadaveric knee model. 8mm defects were created in the medial femoral trochlea and repaired with a PCL collagen scaffold. Scaffolds were secured by one of three designs; Press Fit (PF), Press Fit with Rings (PFR), Press Fit with Fibrin Glue (PFFG). Mobilisation was simulated by mounting the pig legs on a continuous passive motion (CPM) machine for either 50 or 500 cycles.
No animal model currently exists for hip abductor tendon tears. We aimed to 1. Develop a large animal model of delayed abductor tendon repair and 2. To compare the results of acute and delayed tendon repair using this model. Fourteen adult Romney ewes underwent detachment of gluteus medius tendon using diathermy. The detached tendons were protected using silicone tubing. Relook was performed at six and 16 weeks following detachment, histological analysis of the muscle and tendon were performed. We then attempted repair of the tendon in six animals in the six weeks group and compared the results to four acute repairs (tendon detachment and repair performed at the same time). At 12 weeks, all animals were culled and the tendon–bone block taken for histological and mechanical analysis. Histology grading using the modified Movin score confirmed similar tendon degenerative changes at both six and 16 weeks following detachment.
An established rabbit model was used to preliminarily investigate the effect of acellular triphase, namely bone-cartilage-tendon, scaffold (ATS) sandwiched with autologous bone mesenchymal stem cells (BMSCs) sheets on tendon-bone interface healing. Bone, fibrocartilage and tendon tissue were harvested from the rabbits and sectioned into a book-type scaffold. The scaffolds were decellularized and their characterization was presented. BMSCs were isolated and co-cultured with the scaffolds to verify their cytocompatibility. BMSCs sheets were fabricated and inserted into the book page of the scaffold to construct an autologous BMSCs-sheets/book-type ATS complex. The complex was implated in the right knee of rabbits which operated standard partial patellectomy for TBI regeneration using Imaging, histological and biomechanical examinations. The bone, fibrocartilage and tendon tissue were sectioned into a book-type scaffold before decellularization. Then we decellularized the above tissue and mostly preserved their microstructure and composition of the natural extracellular matrix, including collagen and proteoglycan. After the physicochemical and biological properties of the book-type ATS were evaluated, autologous BMSCs sheets were inserted into the book page of the scaffold to construct an autologous BMSCs-sheets/book-type ATS implants for TBI regeneration. In addition, the ATS has the advantages of non-toxicity, suitable for cell adhesion and growth as well as low immunogenicity while co-cultured with the BMSCs. At the same time, different scaffolds has the ability to induce the osteogenic, chondrogenic and tenogenic differentiation of BMSCs by immunofluorescence, reverse transcription-polymerase chain reaction and western blot analysis. To determine the efficacy of the tissue-engineered implants for TBI regeneration, we transplanted it into a rabbit patella-patellar tendon (PPT) injury model, and the rabbits were sacrificed at postoperative week 8 or 16 for the radiological, histological, and mechanical evaluation. Radiologically, Synchrotron radiation micro-computed tomography (SR-μCT) showed that BMSCs/ATS group significantly increased bone area, BV/TV, trabecular thickness and trabecular number at the healing interface as compared with other groups at postoperative week 8 or 16. Histologically, the BMSCs/ATS group showed more woven bone, and a more robust fibrocartilaginous junction with a characteristic matrix rich in proteoglycans was seen at the PPT healing interface in comparison with other groups after 8 weeks. At week 16, the healing interface in 3 groups displayed better remodeling with respect to postoperative week 8. Healing and remodeling at the PPT junction were almost complete, with a resemblance to a healthy BTI consisting of the characteristic 4 zones in all groups. At last, we used biomechanical test as functional parameters to evaluate the quality of tendon-bone healing.
Bone marrow concentrates are being used to augment soft tissue healing. However, only 0.01% of these cells meet the criteria of a mesenchymal stem cell (MSC), which likely accounts for the variability in reported results. Previous studies using an established rat rotator cuff repair model have demonstrated that bone marrow-derived MSCs had no effect on healing. In this study we evaluated the effect of purified human MSCs on rotator cuff healing in an athymic rat model. Hypothesis: Purified human MSCs added to the repair site will improve biomechanical strength and fibrocartilage formation of the healing tendon. Fifty-two athymic rats underwent unilateral detachment and repair of the supraspinatus tendon with either fibrin glue (control) or fibrin glue with 106 hMSCs (experimental) applied at the repair site. Flow cytometry verified the stem cell phenotype of the cells as CD73+, CD90+, CD105+, CD14-, CD34- and CD45-. Rats were sacrificed at 2 and 4 weeks, with 10 used for biomechanical testing and 3 for histologic analysis from each group.
Injury to the anterolateral ligament (ALL) has been reported to contribute to high-grade anterolateral laxity following anterior cruciate ligament (ACL) injury. Failure to address ALL injury has been suggested as a cause of persistent rotational laxity following ACL reconstruction. However, lateral meniscus posterior root (LMPR) tears have also has been shown to cause increased internal rotation and anterior translation of the knee. Due to the anatomic relationship of the ALL and the lateral meniscus, we hypothesise that the ALL and lateral meniscus work synergistically, and that a tear to the LMPR will have the same effect on anterolateral laxity as an ALL tear in the ACL deficient knee. Sixteen fresh frozen cadaveric knee specimens were potted into a hip simulator(femur) and a six degree-of-freedom load cell (tibia). Two rigid optical trackers were inserted into the proximal femur and distal tibia, allowing for the motion of the tibia with respect to the femur to be tracked during biomechanical tests. A series of points on the femur and tibia were digitised to create bone coordinate systems that were used to calculate the kinematic variables.
Introduction. Total ankle replacement (TAR) is surgically complex; malalignment can arise due to surgical technique or failure to correct natural varus/valgus malalignment. Across joint replacement, malalignment has been associated with pain, component edge loading, increased wear and higher failure rates. Good component alignment is considered instrumental for long term TAR success. The conforming surface geometry of mobile bearing TARs leaves no freedom for coronal plane malalignment. The aim of this study was to investigate the biomechanical effect of coronal alignment on a mobile bearing TAR. Methods. Three TARs (Zenith, Corin Group) were tested under five coronal malalignment angles from 0–10° in a single station electromechanical knee simulator applying a typical ankle gait profile. As swing phase load is critical to TAR contact mechanics but will vary depending on the joint laxity. Swing loads of 100N, 300N and 500N were investigated. A positive control test with a swing load of 1000N was also studied, and was expected to eliminate the majority of lift off effects. Under each condition, the version was allowed to move freely while tests were performed, and the version profile under each alignment angle was recorded. Each test was carried out for 600 cycles in 25% bovine serum. Under the same loading conditions, but without lubrication, a Tekscan sensor recorded data from two cycles to assess the change in contact pressure and area at the five coronal angles. Results. Across the three TARs the effect of the swing phase load varied the biomechanics with a similar pattern. The high swing load of 1000N eliminates the majority of version while with 100N swing loads the TAR abducts for the length of the swing phase only realigning when the force increases, the extent dependent on the malalignment angle. At both 300N and 500N swing loads there is an oscillation apparent which changes the contact mechanics. The Tekscan results (Figure 1b) show changes in the contact area at three points in the load cycle; swing, the lower peak and the peak load (Figure 1a). With any degree of malalignment, component lift off is highly prevalent under lower swing phase loads of 100–300N. As the swing load is increased, this effect is only noticeable at greater malalignment angles. Discussion. The observed component lift off results in edge loading and peak pressures occurring at the insert edges. When the insert is 10 degrees coronally malaligned and the insert is brought fully into contact, the peak pressure reaches 16–18MPa, a pressure similar to the yield stress of polyethylene. The high contact pressures will likely elevate the wear and may increase the potential for polyethylene failure. Conclusion.
Structural bone allografts are a viable option in reconstructing massive bone defects in patients following musculoskeletal (MSK) tumour resection and revision hip/knee replacements. To decrease infection risk, bone allografts are often sterilised with gamma-irradiation, which consequently degrades the bone collagen connectivity and makes the bone brittle. Clinically, irradiated bone allografts fracture at rates twice that of fresh non-irradiated allografts. Our lab has developed a method that protects the bone collagen connectivity through ribose pre-treatment while still undergoing gamma-irradiation.
Patients undergoing revision surgery of a primary total hip arthroplasty often exhibit bone loss and poor bone quality, which make achieving stable fixation and osseointegration challenging. Implant components coated in porous metals are used clinically to improve mechanical stability and encourage bone in-growth. We compared ultra-porous titanium coatings, known commercially as Gription and Porocoat, in an intra-articular model by press-fitting coated cylindrical implants into ovine femoral condyles and evaluating bone in-growth and fixation strength 4, 8 and 16 weeks post-operatively. Bilateral surgery using a mini-arthrotomy approach was performed on twenty-four Dorset-Rideau Arcott rams (3.4 ± 0.8 years old, 84.8 ± 9.3 kg) with Institutional Animal Care Committee approval in accordance with the Canadian Council on Animal Care. Cylindrical implants, 6.2 mm in diameter by 10 mm in length with surface radius of curvature of 35 mm, were composed of a titanium substrate coated in either Porocoat or Gription and press-fit into 6 mm diameter recipient holes in the weight-bearing regions of the medial (MFC) and lateral (LFC) femoral condyles. Each sheep received 4 implants; two Gription in one stifle (knee) and two Porocoat in the contralateral joint.
Ten percent of fractures end in delayed or non-union. NSAIDs have been linked to an inhibitory action on fracture repair for three decades yet the mechanism of action remains to be elucidated. Cancer research has identified that NSAIDs impede cell proliferation by inhibiting angiogenesis. It is proposed that a similar mechanism occurs in the induction of NSAID induced non-union. We have investigated this hypothesis in a randomised placebo control trial of the NSAID rofecoxib using a murine femoral fracture. All animals had an open femoral fracture treated using an external fixator. Outcomes measures included x-ray, histology and biomechanical testing, with laser Doppler used to assess blood flow across the fracture gap. Radiology showed similar healing patterns in both groups; however, at the later stages (day 32) the NSAID group had significantly poorer healing. Histological analysis showed that controls healed quicker (days 24 and 32), with more callus (day 8) and less fibrous tissue (Day 32).
