Background

While total shoulder arthroplasty (TSA) is a generally successful procedure, glenoid loosening remains a common complication. Though the occurrence of loosening was related to patient-specific factors, biomechanical factors related to implant features may also affect the fixation of the glenoid component, in particular increased glenohumeral mismatch that could result in eccentric loads and translations. In this study, a novel test setup was used to quantify glenohumeral pressures for different motion patterns after TSA.

Since the development of biomimetic and ceramic bone reconstructive in the early 1970, these specialised bioreactors intended for bone or cartilage regeneration have come a long way in trying to design an alternative procedure other than autogenous bone grafting. However, all known biomaterials still fall short of inducing substantial bone formation in vitro or in vivo, especially when treating large bony defects. As such there is a necessity to develop novel bone-reconstructive biomaterials that can more appropriately be utilised and can induce substantial more bone formation than current scaffolds. Using the rapid prototyping technique (Friedrich-Baur BioMed Center, Bayreuth, Germany) to develop new and improved hydroxyapatite/β-tricalcium phosphate devices, which can be predesigned to any outer shape with controlled pore structure and exhibit a unique intrinsic porosity <150µm due to the 3D-printing process to fit any skeletal bone loss site, the aim of our laboratories was to test the osteoinductive capacity of these new bioreactors in an in vitro culture system utilising adipose-derived stem cells (ADSCs). Immunofluorescent staining revealed that beside the standard surface protein expression patterns typical for ADSCs, the cells also produced osteoblast specific proteins, specifically osteocalcin, osteopontin and dentin matrix acidic phosphoprotein 1. ADSCs seeded on the surface of the biomimetic scaffolds showed constant proliferation, maintained viability and differentiation throughout the scaffold, including the small intrinsic pores. Subsequent, qRT-PCR also revealed that alkaline phosphatase and osteocalcin expression was significantly increased upon addition of osteogenic medium but even more so when human recombinant morphogenetic protein 2 (hBMP-2) was included. Immunofluorescent data of protein expression was consistent with qRT-PCR data. Taken into account with previous results by our laboratories in respect to adipose tissue as a viable inductive medium that can form substantial new bone formation in vivo the present results demonstrated that the investigated bioceramic devices possess the necessary capacity that could, together with adipose tissue, provide the next leap necessary to finally and decisively induce substantial or total new bone formation in clinical bone defects of humans.

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.

Introduction

Glenoid loosening, still a main complication for shoulder arthroplasty, was suggested to be related implant design, surgical aspects, and also bone quality. However, typical studies of fixation do not account for heterogeneity in bone morphology and density which were suggested to affect fixation failure. In this study, a combination of cyclic rocking horse tests on cadaver specimens and microCT-based finite element (microFE) analysis of specimens of a wide range of bone density were used to evaluate the effects of periprosthetic bone quality on the risks of loosening of anatomical keeled or pegged glenoid implants.

Introduction

Insufficient arthroscopic cuff tear reconstruction leading to massive osteoarthritis and irreparable rotator cuff tears might be salvaged by implantation of an inverted total shoulder prosthesis Delta in the elderly. However, despite the generally high success rate and satisfying clinical results of inverted total shoulder arthroplasty, this treatment option has potential complications. Therefore, the objective of this study was a prospective evaluation of the clinical and radiological outcome after a minimum of 2 years follow-up of patients undergoing inverted shoulder replacement with or without prior rotator cuff repair.

Introduction

Unicompartmental knee arthroplasty (UKA) in patients with isolated medial osteoarthritis of the knee is nowadays a standard procedure with good results, especially with the minimally-invasive approach. However, the survival rate of the unicompartmental knee prostheses is inferior to that of total knee prostheses. Therefore, further studying of UKA is still necessary. In most mobile bearing designs the femoral component has a spherical surface and therefore its positioning is not crucial. The role of the tibial slope in UKA has not been investigated so far. The manufacturers recommend tibial slopes with values between 10° positive slope and 5° negative slope. Most surgeons try to reconstruct the anatomical slope with a high failure by measuring the slope on x-rays. The aim of this study was to investigate the influence of the tibial slope on the wear rate of a medial UKA.

Objectives: The aim of this study was a clinical and radiological evaluation of 68 shoulders operated with the Delta reverse-ball-and-socket total shoulder prosthesis by the senior author with a mean follow-up of 42 months.

Methods: This is a retrospective study in one consecutive series of 68 shoulders, operated by the senior author, which were clinically assessed using the Constant score for pain, Constant Shoulder Score, Oxford Shoulder Score, UCLA Shoulder rating scale, DASH Score, Rowe Score for Instability and Oxford Instability Score. Radiological evaluation was graded by the classification according to Nerot et al. and complications were analysed according to Goslings and Gouma. Patients were evaluated before surgery and at a mean clinical follow-up of 42 months.

Results: There was a significant improvement in all clinical and stability scores. On the average, the Constant score for pain increased from 4.62 to 11.08 points (p< 0.05); the Constant Shoulder Score from 32.65 to 60.31 (p> 0.05); the Oxford Shoulder Score increased from 32.65 to 60.31 (p< 0.05) and the UCLA Shoulder rating scale increased from 15.08 to 27.42 (p< 0.05). The evaluation of stability showed an increase from 49.42 to 80.19 points in the Rowe Score for Instability and from 22.04 to 37.62 in the Oxford Instability score (p< 0.05). According to the Nerot classification, 65 percent of patients were graded as “0”, 20 percent as “1”, 3 percent as “2”, 6 percent as “3” and 6 percent as “4”. Eight complications occurred in terms of a nerve lesion which was graded according to Goslings and Gouma as “1” once, loosening of the humeral stem which was graded as “2” three times and loosening or fracture of the glenoid component which was graded as “2” in five times. At mean follow-up of 42 months, one patient of this series had died of decrepitude which was graded as “4” and one patient was lost of follow-up.

Conclusions: We summarize, that there were significant advantages identified in terms of the Constant score for pain, all clinical scores and the instability scores. Radiological analyses showed 85 percent of patients without or with a small notch only. On the other hand, the rate of complications should be taken into account. We conclude that shoulder arthroplasty with the Delta prosthesis shows significant benefits in terms of less shoulder pain, a higher stability and a gain of range of motion but on the other hand, we emphasize that this treatment remains a salvage procedure in the elderly only.

In recent years UHMWP sutures have gained more and more popularity in shoulder surgery. They have an increased tensile strength but were shown to have a higher rate of knot slippage due to their smooth surface. There exist different testing protocols on suture testing in dry or in wet conditions.

The purpose of this study was to gain some inside as to whether or not the knot security of sliding and non-sliding knots with different suture materials is influenced by dry or wet testing conditions.

We tested five common suture materials, all of them USP #2. The PDSII, the Ethibond and three ultra high molecular weight polyethylene (UHMWPE) sutures: Fiber Wire, Orthocord and Herculine. As non-sliding knots we used Square knot and Revo knot and for sliding knots we used Fisherman and Roeder knot. 10 samples of each knot type were tested. In the first group knot tying and biomechanical testing were performed under dry conditions. In the second group the sutures were soaked in saline solution for 3 min. before knot tying and afterwards tested in saline bath. Cyclic loading was performed to simulate the physiological conditions. We started with a tensile load of 25 N. After 100 cycles, the load was increased to 50 N for another 100 cycles. Until suture rupture or knot slippage of 3 mm the tensile load was gradually increased by 25 N per 100 cycles. Under dry conditions 170 suture ruptures and 30 knot slippages were recorded. Under wet testing conditions 186 suture ruptures and 14 knot slippages were seen, which tested statistically significant. Failure by knot slippage (n=44) was seen under dry and saline testing conditions mainly with UHMWPE sutures particularly with Herculine suture. Knot slippage occured only with sliding knots. With the Ethibond suture no knot slippage was found regardless of the testing conditions and applied knot type. Across all knot types the UHMPE-sutures were significantly stronger in ultimate load to failure than Ethibond and PDSII under dry and wet testing conditions.

Is the information we get from testing dry suture material reliable and helpful for our daily practice? Our study clearly showed: No! The mode of failure and the number of knot-failure differs significantly in wet testing conditions compared to dry testing. We found that the number of knot-failures is higher when tested with dry sutures than in wet testing conditions. The soaking of the suture material with fluid improves its “skid-resistance”. As we expected showed the UHMWP sutures with their smooth surface a high number of knot-failures compared to polyethylen suture Ethibond, which did not show a single knot-failure in dry or wet tesing conditions. The maximum failure load showed clearly the superiority of the new UHMWP suture material, with around 300 N being double as high as for polyethylen and polydioxone sutures.

The incidence of rotator cuff tears increases with age, thus the rotator cuff tear is often associated with osteoporotic or osteopenic bone in the proximal humerus, especially with female patients. For testing of fixation devices such as suture anchors used in rotator cuff repair often animal bones are used. They are easily to obtain, inexpensive and some have been found to be similar to human bone. But can we rely on the results drawn from these studies in our daily surgical practice?

The purpose of this study was to compare the trabecular bone mineral density, the trabecular bone volume fraction and the cortical layer thicknes in the greater tubercle in different species to evaluate their infiuence on primary stability of suture anchors under a cyclic loading protocol representing the physiologic forces placed on rotator cuff repairs in vivo. We hypothezised that maximum pullout forces as well as the modes of failure are different for a suture anchors in different humeri. The available three different types of anchor fixation design (screw: Spiralok 5mm, Super Revo 5mm, press-fit: Bioknotless RC, wedging: Ultrasorb) were tested. The bone mineral density (BMD) of the humeri was measured by a 64-slice-computed tomography system. Each anchor was tested individually until failure. The sutures were pulled at 135° to the axis of the humeral shaft, simulating the physiological pull of the supraspinatus tendon. Starting with 75 N the tensile load was gradually increased by 25 N after everey 50 cycles until failure of the anchor fixation system occurred. The ultimate failure load, the system displacement after the first pull with 75 N and the mode of failure were recorded.

The ultimate failure loads of each anchor were different in the human osteopenic, human healthy, ovine and bovine humeri. The statistical significancies for pull out forces between the anchors varied from species to species. The biomechanical testing of suture anchors for arthroscopic rotator cuff repair in ovine and bovine humeri does not give reliable data that can be transferred to the human situation. The significances between the suture anchors found in ovine and bovine humeri are different from the results in human humeri. When taking the impaired bone quality of older patients into account the results from ovine and bovine humeri are even less predictable. We found a positive correlation between maximum failure load and cortical layer thickness for the Super Revo and the Ultrasorb anchor. The ultimate failure load seems to depend mainly on the cortical thickness and on the subcortical trabecular bone quality.

Introduction: Knotless Suture Anchors provide numerous advantages in arthroscopic rotator-cuff (RC) repair such as, reducing the difficulties of knot tying, reducing surgical exposure, thus decreasing morbidity. The purpose of this in-vitro study was to compare the pull-out strength of three new knotless suture anchors in correlation with bone quality using the following anchors: Opus Magnum 2 -ArthroCare Co., USA; Push Lock and Swivel Lock -Arthrex Inc., USA.

Material & Methods: Ten healthy and ten osteopenic macroscopically intact humeri with an average age of 51.7 and 79.5 years, respectively, were loaded with the three knotless suture anchors according to the manufacturers’ description. The healthy humeri had a mean trabecular BMD of 152.77 mgCa-HA/ml. The osteopenic humeri had a mean trabecular bone mineral density of 54.02 mgCa-HA/ml. The humeri were positioned in a custom - engineered adjustable fixation device, stabilising the direction of the pull of the sutures at an angle of 135° to the axis of the humeral shaft (Universal testing device Z010/TN2A – Zwick GmbH, Ulm, Germany). The anchors were cyclically loaded to simulate postoperative conditions.

The ultimate pull-out strenngth, the initial displacement in millimeters after the first pull with 75 N and the modes of failure were recorded.

Results: The mean ultimate failure loads of the Opus Magnum 2, PushLock and SwiveLock anchors in osteopenic humeri were 135.0, 102.5 and 130.0 N (p> 0.05), respectively, and in healthy humeri 142.5 N, 182.5 N and 202.5 N (p> 0.05), respectively. The initial system displacement in osteopenic humeri of the Opus Magnum 2, PushLock and SwiveLock anchors were 3.53 mm, 16.11 mm and 3.23 mm (p< 0.01), respectively, and in healthy humeri 3.71 mm, 1.98 mm, and 1.96 mm (p> 0.05), respectively.

Discussion: The results of this study show that in osteopenic humeri, the Opus Magnum 2 and SwiveLock anchors display significant superiority in system displacement with an initial pull of 75N compared to the PushLock anchor in osteopenic bone, but all three anchors fail to provide significance in the ultimate failure load. PushLock anchor might cause a greater gap formation between the RC-tendon and greater tubercle interface in osteopenic humeri due to inferior gripping and therefore should not be used solely for RC repair. Due to a manufacturing flaw the suture holding fixture of the Opus Magnum 2 anchor “breaks” when a mean force of 138.75 N is applied to the system, regardless of the bone quality, thus disabling the anchor to unfold it’s properties in healthy bone. Whereas the results in osteopenic bone are comparable to the other two anchors. SwiveLock provides the best support of all three anchors in healthy humeri.

Background: In regenerative medicine the autologous cartilage implantation (ACI) has been used for the repair of cartilage defects. As modification of ACI, the matrix assisted ACI is used nowadays with varying results. There is a general discussion about whether supporting scaffolds should be used or whether a scaffold-free cartilage repair is the method of choice. The major problem of scaffold-free regenerates is how to keep the cells in place after transplantation. Aim of this study was to examine a new scaffold-free diffusion-culture model, which uses a mega-congregate of chondrocytes cultured at an air-medium interface. This scaffold-free high-density diffusion culture could be used to repair cartilage defects.

Material and methods: Human chondrocytes from passage 1–7 were expanded in monolayer and transferred to pellet-culture or diffusion-culture. After one week cultures were stained with toluidine blue and safranin-O and evaluated by immunohistochemical staining for type II collagen. Quantitative real time reverse transcriptase polymerase chain reaction (qRT-PCR) was performed for the mRNAs of cartilage markers.

Results: Positive alcian blue staining was detectable in diffusion-culture for human chondrocytes up to passage 7. Within passages the amount of proteoglycan production in relationship to the number of cells increased. There was a positive signal for Collagen type II in diffusion-cultures up to passage 7.

In qRT-PCR a redifferentiation of human chondrocytes was shown by the transfer into diffusion-culture. Within passage 1 to 3 human chondrocytes which were cultured in monolayer lost the ability to express Collagen Type II but could regain it if they were transferred to diffusion-culture. At diffusion-culture chondrocytes showed the highest expression of Collagen type II at passage 1 when compared to monolayer or to pellet-culture.

Conclusion: It could be shown that the cultivation in a scaffold-free diffusion-culture can lead to redifferentiation of human chondrocytes Chondrocytes in diffusion-cultures tend to form their own matrix and produce Collagen type II at higher amounts than in monolayer or in normal pellet-cultures. Therefore diffusion-culture congregates might be an appropriate tool to be used for a new scaffold-free cartilage regeneration approach.

Introduction: Arthroplasty plays a growing role in our society today. Due to scientific and medical progress there are an increasing number of viable candidates and the improvement of quality of life thereafter speaks for itself.

Even though the operations are largely successful, complications after joint replacement surgery occur frequently. Approximately 10% of lower limb arthroplasties need surgical revision, of which 70% are due to loosening. The purpose of this study was to assess the feasibility of 18-fluorodeoxyglucose positron emission tomography (18F-FDG-PET) in detecting septic and aseptic endoprosthetic loosening of hip and knee endoprostheses.

Materials and Methods: Thirty-three patients (age range: 45 – 90y) with lower limb arthroplasty complaints (74 prostheses) were studied preoperatively with 18F-FDG-PET. All patients underwent surgery at a later stage with microbiological culturing to differentiate aseptic and septic loosening and to confirm the final diagnosis. Prostheses were tested intraoperatively for stability and microbiology.

Results: The sensitivity/specificity of 18F-FDG-PET towards implant loosening in the hip was 80%/87%, in the knee 56%/82%.

The sensitivity/specificity for infectious loosening in hip replacement arthroplasties was 67%/83%, in the knee 14%/89%.

Discussion: 18F-FDG-PET seems an excellent method for detecting hip endoprosthetic loosening and a moderate tool to diagnose hip implant infection. It should not be seen as the method of choice to diagnose knee endoprosthetic loosening and infection.

Aim: The aim of the study was to investigate the influence of bone density of the greater tuberosity on mechanical strength of different bone anchors for rotator cuff surgery. Especially in osteopenic bone the metal bone anchors and transosseus sutures are still the “gold-standard” in rotator cuff surgery.

Material and Methods: Four bone anchors, each standing for a specific group of bone anchor, and two suture materials were tested. One of them was the metallic Super Revo screw 5.0 (Linvatec), the absorbable screw Spiralok 5.0 (Mitek), the absorbable press-fit anchor Bioknotless RC (Mitek) and the absorbable Ultrasorb RC (Linvatec). The suture materials tested was the well known V-37 (Ethicon) and the new Orthocord (Mitek) both USP 2. All fixations systems were tested on a) 6 pairs of fresh-frozen human shoulders from young adults (range 20–50 yrs.) and b) 6 pairs of fresh frozen human shoulders from elderly (range 60–93 yrs.). Cyclic loading was performed, as it was considered the best way to simulate the postoperative conditions in a manner similar to those used in prior studies until the system failed. The maximum tensile strength, the failure mode, and the displacement of the fixation device (system displacement) under load at the first cycle at 75 N and at the maximum tensile strength were recorded.

Results: The absorbable Spiralok 5 mm screw anchor showed the highest failure load with a mean of 171 N in osteopenic bone. The suture material Orthocord and V-37 had the lowest mechanical strength in osteopenic bone with a mean of 125 N resp. 114 N. The remaining anchors had an almost identical failure load with means of 150 N (Super Revo 5 mm and Bioknotless RC) and 151 N (Ultrasorb RC). No statistical significance was found though. Comparing the mechanical strength of each fixation system in healthy and osteopenic bone no statistical significant difference was found except for the V-37 suture. In healthy bone the failure load of V-37 suture had a mean of 204 N and in osteopenic bone of 114 N.

Discussion: The absorbable Spiralok 5 mm screw showed a good performance in healthy and osteopenic bone when compared with standard bone anchor like the titan Super Revo 5 mm screw or transosseous sutures. Absorbable anchors have certain advantages, besides that usually they are more expensive. They can easily be overdrilled in case of rupture of the suture material, and they do not interfere during later revision surgery or for imaging studies such as magnetic resonance imaging.

Introduction: Due to a lack of techniques there is only some data of testing mechanical influence on chondroctyes grown in 3-D tissue-culture over several months. In a new perfusion-chamber these mechanical factors could be studied in in-vitro tissue culture. Experimental Method: Chondrocytes which had been isolated by enzymatic digestion of mature pigs were seeted in Aga-rose on resorpable PDA/PGA (Ethisorb®) implants. These implants were cultured for 2, 6 and 12 weeks with alternating pressures of 0.5 MPa. Beneath a unpressurized control group, pressure was applied for 1 sec with a rest of 1 sec, for 2 sec with a rest of 8 sec and for 20 sec with a rest of 80 sec. Dulbecos medium was used for perfusion. Results and discussion: After 6 weeks the resorbable carrier has dissolved, in the following weeks the different groups showed different cartilage development (Fig. 1). After 12 weeks the 20/80 sec group showed collagen II and also major collagen I production in immunohistology, the 1/1 sec group showed only small traces of collagen I and masses of collagen II production. Further immunochemistry and scaning electron microscopy was able to show typical aspects of differentiated cartilage. Conclusion: The in-vitro differentiation of chondrocytes to mature cartilage is linked to certain mechanical factors. A frequency of 1/1 sec pressure is more favourable than lesser frequencies.

Introduction: Due to a lack of techniques there is only some data of testing mechanical influence on chondroc-tyes grown in 3-D tissue-culture over several months. The authors developed therfore a new perfusion-chamber to study these mechanical factors in in-vitro tissue culture. Methods: A pneumatic computer-controlled bioreactor which allows the application of pressure between 0,1 – 2 MPa in frequencies less than 1 Hz over a period of several months was developed. The reactor is made of stainless steel and closed to the surrounding atmosphere with a steril, flexible and pressure resistant layer of film. 8 scaffolds with a maximal diameter of 10 mm and a maximal height of 15 mm can be studied independently in respect to pressure parameters. A continous flow of medium allows an excellent nutrition, temperature is controlled by a closed heat unit. In a first system three bioreactors are used simultaneousely. Results: In first cultures of tissues over a period of three months sterility was well contained without any mechanical problems. With a high degree of automation a nearly uncontrolled running was possible.

The disadvantages of sawing for precise bone cuts are well known: untrue cuts, heat and metal wear. The main limiting factors of available milling devices are the difficult handling and high costs, especially if the devices are based on a robot. Supported by clinical users and mechanical engineers a milling concept adopted from machining has been realised in order to overcome this limitations. The „All-in-One Milling-Tool“ achieves the same precision of a robot by a mechanically guided milling resection far below the necessary investment for a robot. Three methods are provided for the alignment of the resection planes and will be discussed: intramedullary adjustment, 3D CT-based planning and intramedullar performance as well as the performance under control by navigation. All versions are based on a handheld resection and guarantee a visual and haptical feedback for the surgeon. The use of navigation has the advantage of the accurate transfer of the 3D plan into the OR, the interactive facilitated alignment und resection steps and the documentation of planned and actual implant position.

The disadvantages of sawing for precise bone cuts are well known: untrue cuts, heat and metal wear. The main limiting factors of available milling devices are the difficult handling and high costs, especially if the devices are based on a robot. Supported by clinical users and mechanical engineers a milling concept adopted from industrial machining has been realised in order to overcome this limitations. The “All-in-One Milling-Tool” achieves the same precision of a robot by a mechanically guided milling resection far below the necessary investment for a robot. Once fixed at the femur, the device allows all femural and tibial resections. Three methods are provided for the alignment of the resection planes and will be discussed: intramedullary adjustment, 3D CT-based planning and intramedullar performance as well as the performance under navigation control. All versions are based on a handheld resection and guarantee a visual and haptical feedback for the surgeon. The use of navigation has the advantage of the accurate transfer of the 3D plan into the OR, the interactive guided and facilitated alignment und resection steps and the documentation of planned and actual implant position.