Using a dynamic biomechanical model of malunion of the shoulder, we have determined the change in deltoid force required for abduction with various combinations of superior and posterior displacement of fractures of the greater tuberosity of the humerus. We tested eight fresh human cadaver shoulders in a dynamic shoulder-testing apparatus during cycles of glenohumeral abduction from 0° to 90°. The greater tuberosities were osteotomised and stabilised to represent malunion with combinations of superior and posterior displacements of 1 cm and less. The peak force was measured for each displacement in each specimen and statistically compared with values of no displacement using a repeated-measures analysis of variance. The abduction force was significantly increased by 16% (p = 0.006) and 27% (p = 0.0001) by superior displacements of 0.5 cm and 1 cm, respectively, while combined superior and posterior displacement of 1 cm gave an increase in force of 29% (p = 0.001). While treatment criteria for acceptable residual displacement of the greater tuberosity are widely used, there is little information on the direct biomechanical effects of displacement on shoulder mechanics. Although the results of conservative treatment are influenced by a number of factors, including associated injuries, rehabilitation and the pre-existing function of the shoulder, our data suggest that small amounts of residual displacement may alter the balance of forces required to elevate the arm at the glenohumeral joint

In normal, physiological circumstances there is ample room in the spinal canal to accommodate the spinal cord. Our study aimed to identify the degree of compromise of the spinal canal which could be anticipated in various atlantoaxial pathological states. We examined paired atlas and axis vertebrae using high-definition radiography and simultaneous photography in both normal and simulated pathological orientations in order to measure the resultant dimension of the spinal canal and its percentage occlusion.

At the extreme of physiological axial rotation (47°) the spinal canal is reduced to 61% of its cross-sectional area in neutral rotation. The spinal cord is thus safe from compromise.

Atlantoaxial subluxation of up to 9 mm reduces the area of the spinal canal, in neutral rotation, to 60% with no cord compromise. Any rotation is, however, likely to cause cord compression.

The mechanism of fixation in atlantoaxial rotatory subluxation could be explained by bony interlocking of the facet joint, reproducible in dry bones.

Objectives. All-suture anchors are increasingly used in rotator cuff repair procedures. Potential benefits include decreased bone damage. However, there is limited published evidence for the relative strength of fixation for all-suture anchors compared with traditional anchors. Materials and Methods. A total of four commercially available all-suture anchors, the ‘Y-Knot’ (ConMed), Q-FIX (Smith & Nephew), ICONIX (Stryker) and JuggerKnot (Zimmer Biomet) and a traditional anchor control TWINFIX Ultra PK Suture Anchor (Smith & Nephew) were tested in cadaveric human humeral head rotator cuff repair models (n = 24). This construct underwent cyclic loading applied by a mechanical testing rig (Zwick/Roell). Ultimate load to failure, gap formation at 50, 100, 150 and 200 cycles, and failure mechanism were recorded. Significance was set at p < 0.05. Results. Overall, mean maximum tensile strength values were significantly higher for the traditional anchor (181.0 N, standard error (. se). 17.6) compared with the all-suture anchors (mean 133.1 N . se. 16.7) (p = 0.04). The JuggerKnot anchor had greatest displacement at 50, 100 and 150 cycles, and at failure, reaching statistical significance over the control at 100 and 150 cycles (22.6 mm . se. 2.5 versus 12.5 mm . se. 0.3; and 29.6 mm . se. 4.8 versus 17.0 mm . se. 0.7). Every all-suture anchor tested showed substantial (> 5 mm) displacement between 50 and 100 cycles (6.2 to 14.3). All-suture anchors predominantly failed due to anchor pull-out (95% versus 25% of traditional anchors), whereas a higher proportion of traditional anchors failed secondary to suture breakage. Conclusion. We demonstrate decreased failure load, increased total displacement, and variable failure mechanisms in all-suture anchors, compared with traditional anchors designed for rotator cuff repair. These findings will aid the surgeon’s choice of implant, in the context of the clinical scenario. Cite this article: N. S. Nagra, N. Zargar, R. D. J. Smith, A. J. Carr. Mechanical properties of all-suture anchors for rotator cuff repair. Bone Joint Res 2017;6:82–89. DOI: 10.1302/2046-3758.62.BJR-2016-0225.R1

The medial periosteal hinge plays a key role in fractures of the head of the humerus, offering mechanical support during and after reduction and maintaining perfusion of the head by the vessels in the posteromedial periosteum. We have investigated the biomechanical properties of the medial periosteum in fractures of the proximal humerus using a standard model in 20 fresh-frozen cadaver specimens comparable in age, gender and bone mineral density. After creating the fracture, we displaced the humeral head medial or lateral to the shaft with controlled force until complete disruption of the posteromedial periosteum was recorded. As the quality of periosteum might be affected by age and bone quality, the results were correlated with the age and the local bone mineral density of the specimens measured with quantitative CT. Periosteal rupture started at a mean displacement of 2.96 mm (. sd. 2.92) with a mean load of 100.9 N (. sd. 47.1). The mean maximum load of 111.4 N (. sd. 42.5) was reached at a mean displacement of 4.9 mm (. sd. 4.2). The periosteum was completely ruptured at a mean displacement of 34.4 mm (. sd. 11.1). There was no significant difference in the mean distance to complete rupture for medial (mean 35.8 mm (. sd. 13.8)) or lateral (mean 33.0 mm (. sd. 8.2)) displacement (p = 0.589). The mean bone mineral density was 0.111 g/cm. 3. (. sd. 0.035). A statistically significant but low correlation between bone mineral density and the maximum load uptake (r = 0.475, p = 0.034) was observed. This study showed that the posteromedial hinge is a mechanical structure capable of providing support for percutaneous reduction and stabilisation of a fracture by ligamentotaxis. Periosteal rupture started at a mean of about 3 mm and was completed by a mean displacement of just under 35 mm. The microvascular situation of the rupturing periosteum cannot be investigated with the current model

When performing the Scandinavian Total Ankle Replacement (STAR), the positioning of the talar component and the selection of mobile-bearing thickness are critical. A biomechanical experiment was undertaken to establish the effects of these variables on the range of movement (ROM) of the ankle. Six cadaver ankles containing a specially-modified STAR prosthesis were subjected to ROM determination, under weight-bearing conditions, while monitoring the strain in the peri-ankle ligaments. Each specimen was tested with the talar component positions in neutral, as well as 3 and 6 mm of anterior and posterior displacement. The sequence was repeated with an anatomical bearing thickness, as well as at 2 mm reduced and increased thicknesses. The movement limits were defined as 10% strain in any ligament, bearing lift-off from the talar component or limitations of the hardware. Both anterior talar component displacement and bearing thickness reduction caused a decrease in plantar flexion, which was associated with bearing lift-off. With increased bearing thickness, posterior displacement of the talar component decreased plantar flexion, whereas anterior displacement decreased dorsiflexion

Aims

This study intended to investigate the effect of vericiguat (VIT) on titanium rod osseointegration in aged rats with iron overload, and also explore the role of VIT in osteoblast and osteoclast differentiation.

Objectives. Taper junctions between modular hip arthroplasty femoral heads and stems fail by wear or corrosion which can be caused by relative motion at their interface. Increasing the assembly force can reduce relative motion and corrosion but may also damage surrounding tissues. The purpose of this study was to determine the effects of increasing the impaction energy and the stiffness of the impactor tool on the stability of the taper junction and on the forces transmitted through the patient’s surrounding tissues. Methods. A commercially available impaction tool was modified to assemble components in the laboratory using impactor tips with varying stiffness at different applied energy levels. Springs were mounted below the modular components to represent the patient. The pull-off force of the head from the stem was measured to assess stability, and the displacement of the springs was measured to assess the force transmitted to the patient’s tissues. Results. The pull-off force of the head increased as the stiffness of the impactor tip increased but without increasing the force transmitted through the springs (patient). Increasing the impaction energy increased the pull-off force but also increased the force transmitted through the springs. Conclusions. To limit wear and corrosion, manufacturers should maximize the stiffness of the impactor tool but without damaging the surface of the head. This strategy will maximize the stability of the head on the stem for a given applied energy, without influencing the force transmitted through the patient’s tissues. Current impactor designs already appear to approach this limit. Increasing the applied energy (which is dependent on the mass of the hammer and square of the contact speed) increases the stability of the modular connection but proportionally increases the force transmitted through the patient’s tissues, as well as to the surface of the head, and should be restricted to safe levels. Cite this article: A. Krull, M. M. Morlock, N. E. Bishop. Maximizing the fixation strength of modular components by impaction without tissue damage. Bone Joint Res 2018;7:196–204. DOI: 10.1302/2046-3758.72.BJR-2017-0078.R2

Different calcaneal plates with locked screws were compared in an experimental model of a calcaneal fracture. Four plate models were tested, three with uniaxially-locked screws (Synthes, Newdeal, Darco), and one with polyaxially-locked screws (90° ± 15°) (Rimbus). Synthetic calcanei were osteotomised to create a fracture model and then fixed with the plates and screws. Seven specimens for each plate model were subjected to cyclic loading (preload 20 N, 1000 cycles at 800 N, 0.75 mm/s), and load to failure (0.75 mm/s). During cyclic loading, the plate with polyaxially-locked screws (Rimbus) showed significantly lower displacement in the primary loading direction than the plates with uniaxially-locked screws (mean values of maximum displacement during cyclic loading: Rimbus, 3.13 mm (. sd. 0.68); Synthes, 3.46 mm (. sd. 1.25); Darco, 4.48 mm (. sd. 3.17); Newdeal, 5.02 mm (. sd. 3.79); one-way analysis of variance, p < 0.001). The increased stability of a plate with polyaxially-locked screws demonstrated during cyclic loading compared with plates with uniaxially-locked screws may be beneficial for clinical use

Objectives. Rotator cuff tears are among the most frequent upper extremity injuries. Current treatment strategies do not address the poor quality of the muscle and tendon following chronic rotator cuff tears. Hypoxia-inducible factor-1 alpha (HIF-1α) is a transcription factor that activates many genes that are important in skeletal muscle regeneration. HIF-1α is inhibited under normal physiological conditions by the HIF prolyl 4-hydroxylases (PHDs). In this study, we used a pharmacological PHD inhibitor, GSK1120360A, to enhance the activity of HIF-1α following the repair of a chronic cuff tear, and measured muscle fibre contractility, fibrosis, gene expression, and enthesis mechanics. Methods. Chronic supraspinatus tears were induced in adult rats, and repaired 28 days later. Rats received 0 mg/kg, 3 mg/kg, or 10 mg/kg GSK1120360A daily. Collagen content, contractility, fibre type distribution and size, the expression of genes involved in fibrosis, lipid accumulation, atrophy and inflammation, and the mechanical properties of the enthesis were then assessed two weeks following surgical repair. Results. At two weeks following repair, treatment groups showed increased muscle mass but there was a 15% decrease in force production in the 10 mg/kg group from controls, and no difference between the 0 mg/kg and the 3 mg/kg groups. There was a decrease in the expression of several gene transcripts related to matrix accumulation and fibrosis, and a 50% decrease in collagen content in both treated groups compared with controls. Additionally, the expression of inflammatory genes was reduced in the treated groups compared with controls. Finally, PHD inhibition improved the maximum stress and displacement to failure in repaired tendons. Conclusions. GSK1120360A resulted in improved enthesis mechanics with variable effects on muscle function. PHD inhibition may be beneficial for connective tissue injuries in which muscle atrophy has not occurred. Cite this article: J. P. Gumucio, M. D. Flood, A. Bedi, H. F. Kramer, A. J. Russell, C. L. Mendias. Inhibition of prolyl 4-hydroxylase decreases muscle fibrosis following chronic rotator cuff tear. Bone Joint Res 2017;6:57–65. DOI: 10.1302/2046-3758.61.BJR-2016-0232.R1

We have evaluated four different fixation techniques for the reconstruction of a standard Mason type-III fracture of the radial head in a sawbone model. The outcome measurements were the quality of the reduction, and stability. A total of 96 fractures was created. Six surgeons were involved in the study and each reconstructed 16 fractures with 1.6 mm fine-threaded wires (Fragment Fixation System (FFS)), T-miniplates, 2 mm miniscrews and 2 mm Kirschner (K-) wires; four fractures being allocated to each method using a standard reconstruction procedure. The quality of the reduction was measured after definitive fixation. Biomechanical testing was performed using a transverse plane shear load in two directions to the implants (parallel and perpendicular) with respect to ultimate failure load and displacement at 50 N. A significantly better quality of reduction was achieved using the FFS wires (Tukey’s post hoc tests, p < 0.001) than with the other devices with a mean step in the articular surface and the radial neck of 1.04 mm (. sd. 0.96) for the FFS, 4.25 mm (. sd. 1.29) for the miniplates, 2.21 mm (. sd. 1.06) for the miniscrews and 2.54 mm (. sd. 0.98) for the K-wires. The quality of reduction was similar for K-wires and miniscrews, but poor for miniplates. The ultimate failure load was similar for the FFS wires (parallel, 196.8 N (. sd. 46.8), perpendicular, 212.5 N (. sd. 25.6)), miniscrews (parallel, 211.8 N (. sd. 47.9), perpendicular, 208.0 N (. sd. 65.9)) and K-wires (parallel, 200.4 N (. sd. 54.5), perpendicular, 165.2 N (. sd. 37.9)), but significantly worse (Tukey’s post hoc tests, p < 0.001) for the miniplates (parallel, 101.6 N (. sd. 43.1), perpendicular, 122.7 N (. sd. 40.7)). There was a significant difference in the displacement at 50 N for the miniplate (parallel, 4.8 mm (. sd. 2.8), perpendicular, 4.8 mm (. sd. 1.7)) vs FFS (parallel, 2.1 mm (. sd. 0.8), perpendicular, 1.9 mm (. sd. 0.7)), miniscrews (parallel, 1.8 mm (. sd. 0.5), perpendicular, 2.3 mm (. sd. 0.8)) and K-wires (parallel, 2.2 mm (. sd. 1.8), perpendicular, 2.4 mm (. sd. 0.7; Tukey’s post hoc tests, p < 0.001)). The fixation of a standard Mason type-III fracture in a sawbone model using the FFS system provides a better quality of reduction than that when using conventional techniques. There was a significantly better stability using FFS implants, miniscrews and K-wires than when using miniplates

Objectives. The present study describes a novel technique for revitalising allogenic intrasynovial tendons by combining cell-based therapy and mechanical stimulation in an ex vivo canine model. Methods. Specifically, canine flexor digitorum profundus tendons were used for this study and were divided into the following groups: (1) untreated, unprocessed normal tendon; (2) decellularised tendon; (3) bone marrow stromal cell (BMSC)-seeded tendon; and (4) BMSC-seeded and cyclically stretched tendon. Lateral slits were introduced on the tendon to facilitate cell seeding. Tendons from all four study groups were distracted by a servohydraulic testing machine. Tensile force and displacement data were continuously recorded at a sample rate of 20 Hz until 200 Newton of force was reached. Before testing, the cross-sectional dimensions of each tendon were measured with a digital caliper. Young’s modulus was calculated from the slope of the linear region of the stress-strain curve. The BMSCs were labeled for histological and cell viability evaluation on the decellularized tendon scaffold under a confocal microscope. Gene expression levels of selected extracellular matrix tendon growth factor genes were measured. Results were reported as mean ± SD and data was analyzed with one-way ANOVAs followed by Tukey’s post hoc multiple-comparison test. Results. We observed no significant difference in cross-sectional area or in Young’s modulus among the four study groups. In addition, histological sections showed that the BMSCs were aligned well and viable on the tendon slices after two-week culture in groups three and four. Expression levels of several extracellular matrix tendon growth factors, including collagen type I, collagen type III, and matrix metalloproteinase were significantly higher in group four than in group three (p < 0.05). Conclusion. Lateral slits introduced into de-cellularised tendon is a promising method of delivery of BMSCs without compromising cell viability and tendon mechanical properties. In addition, mechanical stimulation of a cell-seeded tendon can promote cell proliferation and enhance expression of collagen types I and III in vitro. Cite this article: J. H. Wu, A. R. Thoreson, A. Gingery, K. N. An, S. L. Moran, P. C. Amadio, C. Zhao. The revitalisation of flexor tendon allografts with bone marrow stromal cells and mechanical stimulation: An ex vivo model revitalising flexor tendon allografts. Bone Joint Res 2017;6:179–185. DOI: 10.1302/2046-3758.63.BJR-2016-0207.R1

This study evaluated the effect on movement under load of three different techniques for re-attachment of the tuberosities of the humerus using test sawbones. In the first, the tuberosities were attached both to the shaft and to each other, with one cerclage suture through the anterior hole in the prosthesis. The second technique was identical except for omission of the cerclage suture and in the third the tuberosities were attached to the prosthesis and to the shaft. An orthogonal photogrammetric system allowed all segments to be tracked in a 3D axis system. The humeri were incrementally-loaded in abduction, and the 3D linear and angular movements of all segments were calculated. Displacement between the tuberosities and the shaft was measured. The first and second techniques were the most stable constructs, with the third allowing greater separation of fragments and angular movement. Separation at the midpoint of the tuberosities was significantly greater using the latter technique (p < 0.05). The cerclage suture added no further stability to the fixation

The treatment of bony defects of the tibia at the time of revision total knee replacement is controversial. The place of compacted morsellised bone graft is becoming established, particularly in contained defects. It has previously been shown that the initial stability of impaction-grafted trays in the contained defects is equivalent to that of an uncemented primary knee replacement. However, there is little biomechanical evidence on which to base a decision in the treatment of uncontained defects. We undertook a laboratory-based biomechanical study comparing three methods of graft containment in segmental medial tibial defects and compared them with the use of a modular metal augment to bypass the defect. Using resin models of the proximal tibia with medial defects representing either 46% or 65% of the medial cortical rim, repair of the defect was accomplished using mesh, cement or a novel bag technique, after which impaction bone grafting was used to fill the contained defects and a tibial component was cemented in place. As a control, a cemented tibial component with modular metal augments was used in identical defects. All specimens were submitted to cyclical mechanical loading, during which cyclical and permanent tray displacement were determined. The results showed satisfactory stability with all the techniques except the bone bag method. Using metal augments gave the highest initial stability, but obviously lacked any potential for bone restoration

Biomechanical studies involving all-wire and hybrid types of circular frame have shown that oblique tibial fractures remain unstable when they are loaded. We have assessed a range of techniques for enhancing the fixation of these fractures. Eight models were constructed using Sawbones tibiae and standard Sheffield ring fixators, to which six additional fixation techniques were applied sequentially. The major component of displacement was shear along the obliquity of the fracture. This was the most sensitive to any change in the method of fixation. All additional fixation systems were found to reduce shear movement significantly, the most effective being push-pull wires and arched wires with a three-hole bend. Less effective systems included an additional half pin and arched wires with a shallower arc. Angled pins were more effective at reducing shear than transverse pins. The choice of additional fixation should be made after consideration of both the amount of stability required and the practicalities of applying the method to a particular fracture

We obtained simultaneous measurements of sagittal knee laxity in 12 consecutive patients after reconstruction of the anterior cruciate ligament (ACL), using the Stryker laxity tester and radiostereometric analysis (RSA). The mean anteroposterior (AP) displacement when a 90 N load was applied in both directions was 5.3 ± 2.7 mm with RSA and 9.8 ± 1.6 mm with the external device (p < 0.001). The corresponding measurements at a load of 180 N were 5.7 ± 2.4 mm and 13.8 ± 3.7 mm, respectively (p < 0.001). More than 50% of the sagittal knee movement, as measured by the external device at a load of 180 N, was not true femorotibial displacement of the joint but was due to soft-tissue deformation

We revised 24 consecutive hips with loosening of the femoral stem using impaction allograft and a cemented stem with an unpolished proximal surface. Repeated radiostereometric examinations for up to two years showed a slow rate of subsidence with a mean of 0.32 mm (−2.0 to +0.31). Fifteen cases followed for a further year showed the same mean subsidence after three years, indicating stabilisation. A tendency to retroversion of the stems was noted between the operation and the last follow-up. Retroversion was also recorded when displacement of the stem was studied in ten of the patients after two years. Repeated determination of bone mineral density showed an initial loss after six months, followed by recovery to the postoperative level at two years. Defects in the cement mantle and malalignment of the stem were often noted on postoperative radiographs, but did not correlate with the degrees of migration or displacement. After one year, increasing frequency of trabecular remodelling or resorption of the graft was observed in the greater trochanter and distal to the tip of the stem. Cortical repair was noted distally and medially (Gruen regions 3, 5 and 6). Migration of the stems was the lowest reported to date, which we attribute to the improved grafting technique and to the hardness of the graft

The treatment of fractures of the proximal tibia is complex and makes great demands on the implants used. Our study aimed to identify what levels of primary stability could be achieved with various forms of osteosynthesis in the treatment of diaphyseal fractures of the proximal tibia. Pairs of human tibiae were investigated. An unstable fracture was simulated by creating a defect at the metaphyseal-diaphyseal junction. Six implants were tested in a uniaxial testing device (Instron) using the quasi-static and displacement-controlled modes and the force-displacement curve was recorded. The movements of each fragment and of the implant were recorded video-optically (MacReflex, Qualysis). Axial deviations were evaluated at 300 N. The results show that the nailing systems tolerated the highest forces. The lowest axial deviations in varus and valgus were also found for the nailing systems; the highest axial deviations were recorded for the buttress plate and the less invasive stabilising system (LISS). In terms of rotational displacement the LISS was better than the buttress plate. In summary, it was found that higher loads were better tolerated by centrally placed load carriers than by eccentrically placed ones. In the case of the latter, it appears advantageous to use additive procedures for medial buttressing in the early phase

Aims

Metaphyseal tritanium cones can be used to manage the tibial bone loss commonly encountered at revision total knee arthroplasty (rTKA). Tibial stems provide additional fixation and are generally used in combination with cones. The aim of this study was to examine the role of the stems in the overall stability of tibial implants when metaphyseal cones are used for rTKA.

The outcome of a cemented hip arthroplasty is partly dependent on the type of cement which is used. The production of an interface gap between the stem and the cement mantle as a result of shrinkage of the cement, may be a factor involved. Palacos R, Palacos LV (both with gentamicin), CMW 1, CMW 2, CMW Endurance (CMWE) and Simplex were prepared under vacuum and allowed to cure overnight in similar cylinders. The next day this volume was determined by the displacement of water. Shrinkage varied between 3.82% and 7.08% with CMWE having the lowest and Palacos LV the highest. This could be a factor to consider when choosing a cement for a shape-closed stem

We have determined whether somatosensory evoked potentials (SEPs) were detectable after direct mechanical stimulation of normal, injured and reconstructed anterior cruciate ligaments (ACLs) during arthroscopy. We investigated the position sense of the knee before and after reconstruction, and correlated the SEP with instability. Reproducible SEPs were detected in all 19 normal ACLs and in 36 of 38 ACLs reconstructed during a period of 13 months. Of the 45 injured ACLs, reproducible SEPs were detected in 26. The mean difference in anterior displacement in the SEP-positive group of the injured ACL group was significantly lower than that in the SEP-negative group. In the reconstructed group, the postoperative position sense was significantly better than the preoperative position sense. Our results indicate not only that sensory reinnervation occurs in the reconstructed ACL, but also that the response to mechanical loads can be restored, and is strongly related to improvement in position sense

In a study combining tissue mechanics and fracture morphology for the first time, we examined the ruptured surfaces of anterior cruciate ligaments of rabbits and related their appearance to the initial loading conditions. Sixteen specimens were stretched to failure at rates of displacement of 10 and 500 mm/min. We used video images to study the changes which occurred during the fracture process and SEM to examine the appearance of the ruptured surfaces. The surfaces of ligaments tested at 10 mm/min had more pulled-out collagen fibres and the fibres had more pronounced waviness compared with those tested at 500 mm/min. We have shown that the macroscopic appearance of ruptured ligaments can be related to their microscopic appearance and that it is possible to deduce whether failure was by gradual tearing of the fibres or catastrophic failure

Objectives

Microindentation has the potential to measure the stiffness of an individual patient’s bone. Bone stiffness plays a crucial role in the press-fit stability of orthopaedic implants. Arming surgeons with accurate bone stiffness information may reduce surgical complications including periprosthetic fractures. The question addressed with this systematic review is whether microindentation can accurately measure cortical bone stiffness.

Objectives

Degenerative disc disease (DDD) and osteoarthritis (OA) are relatively frequent causes of disability amongst the elderly; they constitute serious socioeconomic costs and significantly impair quality of life. Previous studies to date have found that aggrecan variable number of tandem repeats (VNTR) contributes both to DDD and OA. However, current data are not consistent across studies. The purpose of this study was to evaluate systematically the relationship between aggrecan VNTR, and DDD and/or OA.

Objectives

Preservation of both anterior and posterior cruciate ligaments in total knee arthroplasty (TKA) can lead to near-normal post-operative joint mechanics and improved knee function. We hypothesised that a patient-specific bicruciate-retaining prosthesis preserves near-normal kinematics better than standard off-the-shelf posterior cruciate-retaining and bicruciate-retaining prostheses in TKA.

Objectives

Unicompartmental knee arthroplasty (UKA) is a demanding procedure, with tibial component subsidence or pain from high tibial strain being potential causes of revision. The optimal position in terms of load transfer has not been documented for lateral UKA. Our aim was to determine the effect of tibial component position on proximal tibial strain.

Objectives

Intramedullary fixation is considered the most stable treatment for pertrochanteric fractures of the proximal femur and cut-out is one of the most frequent mechanical complications. In order to determine the role of clinical variables and radiological parameters in predicting the risk of this complication, we analysed the data pertaining to a group of patients recruited over the course of six years.

Objectives

The objective of this study was to investigate the therapeutic effect of peripheral blood mononuclear cells (PBMNCs) treated with quality and quantity control culture (QQ-culture) to expand and fortify angiogenic cells on the acceleration of fracture healing.

Objectives

Vancomycin and fosfomycin are antibiotics commonly used to treat methicillin-resistant Staphylococcus aureus (MRSA) infection. This study compares the in vitro inhibitory effects against MRSA of articulating cement spacers impregnated with either vancomycin or fosfomycin.

Objectives

We investigated the effects on fracture healing of two up-regulators of inducible nitric oxide synthase (iNOS) in a rat model of an open femoral osteotomy: tadalafil, a phosphodiesterase inhibitor, and the recently reported nutraceutical, COMB-4 (consisting of L-citrulline, Paullinia cupana, ginger and muira puama), given orally for either 14 or 42 days.

Objectives

This study tests the biomechanical properties of adjacent locked plate constructs in a femur model using Sawbones. Previous studies have described biomechanical behaviour related to inter-device distances. We hypothesise that a smaller lateral inter-plate distance will result in a biomechanically stronger construct, and that addition of an anterior plate will increase the overall strength of the construct.

Malpositioning of the trochanteric entry point during the introduction of an intramedullary nail may cause iatrogenic fracture or malreduction. Although the optimal point of insertion in the coronal plane has been well described, positioning in the sagittal plane is poorly defined.

The paired femora from 374 cadavers were placed both in the anatomical position and in internal rotation to neutralise femoral anteversion. A marker was placed at the apparent apex of the greater trochanter, and the lateral and anterior offsets from the axis of the femoral shaft were measured on anteroposterior and lateral photographs. Greater trochanteric morphology and trochanteric overhang were graded.

The mean anterior offset of the apex of the trochanter relative to the axis of the femoral shaft was 5.1 mm (sd 4.0) and 4.6 mm (sd 4.2) for the anatomical and neutralised positions, respectively. The mean lateral offset of the apex was 7.1 mm (sd 4.6) and 6.4 mm (sd 4.6), respectively.

Placement of the entry position at the apex of the greater trochanter in the anteroposterior view does not reliably centre an intramedullary nail in the sagittal plane. Based on our findings, the site of insertion should be about 5 mm posterior to the apex of the trochanter to allow for its anterior offset.

Cite this article: Bone Joint J 2014;96-B:1274–81.

Objectives

The purpose of this study was to compare the results and complications of tibial lengthening over an intramedullary nail with treatment using the traditional Ilizarov method.

Objectives

The major problem with repair of an articular cartilage injury is the extensive difference in the structure and function of regenerated, compared with normal cartilage. Our work investigates the feasibility of repairing articular osteochondral defects in the canine knee joint using a composite lamellar scaffold of nano-ß-tricalcium phosphate (ß-TCP)/collagen (col) I and II with bone marrow stromal stem cells (BMSCs) and assesses its biological compatibility.

Objectives

Ligaments which heal spontaneously have a healing process that is similar to skin wound healing. Menopause impairs skin wound healing and may likewise impair ligament healing. Our purpose in this study was to investigate the effect of surgical menopause on ligament healing in a rabbit medial collateral ligament model.

Using an osteotomy of the olecranon as a model of a transverse fracture in 22 cadaver elbows we determined the ability of three different types of suture and stainless steel wire to maintain reduction when using a tension-band technique to stabilise the bone. Physiological cyclical loading simulating passive elbow movement (15 N) and using the arms to push up from a chair (450 N) were applied using an Instron materials testing machine whilst monitoring the osteotomy site with a video extensometer. Each osteotomy was repaired by one of four materials, namely, Stainless Steel Wire (7), No 2 Ethibond (3), No 5 Ethibond (5), or No 2 FiberWire (7).

There were no failures (movement of > 2 mm) with stainless steel wire or FiberWire and no significant difference in the movements measured across the site of the osteotomy (p = 0.99). The No. 2 Ethibond failed at 450 N and two of the five of No. 5 Ethibond sutures had a separation of > 2 mm at 450 N.

FiberWire as the tension band in this model held the reduction as effectively as stainless steel wire and may reduce the incidence of discomfort from the hardware. On the basis of our findings we suggest that a clinical trial should be undertaken

Objectives

The objective of this study was to compare the elution characteristics, antimicrobial activity and mechanical properties of antibiotic-loaded bone cement (ALBC) loaded with powdered antibiotic, powdered antibiotic with inert filler (xylitol), or liquid antibiotic, particularly focusing on vancomycin and amphotericin B.

Objectives

The need for bone tissue supplementation exists in a wide range of clinical conditions involving surgical reconstruction in limbs, the spine and skull. The bone supplementation materials currently used include autografts, allografts and inorganic matrix components; but these pose potentially serious side-effects. In particular the availability of the autografts is usually limited and their harvesting causes surgical morbidity. Therefore for the purpose of supplementation of autologous bone graft, we have developed a method for autologous extracorporeal bone generation.

The biomechanics of the patellofemoral joint can become disturbed during total knee replacement by alterations induced by the position and shape of the different prosthetic components. The role of the patella and femoral trochlea has been well studied. We have examined the effect of anterior or posterior positioning of the tibial component on the mechanisms of patellofemoral contact in total knee replacement. The hypothesis was that placing the tibial component more posteriorly would reduce patellofemoral contact stress while providing a more efficient lever arm during extension of the knee.

We studied five different positions of the tibial component using a six degrees of freedom dynamic knee simulator system based on the Oxford rig, while simulating an active knee squat under physiological loading conditions. The patellofemoral contact force decreased at a mean of 2.2% for every millimetre of posterior translation of the tibial component. Anterior positions of the tibial component were associated with elevation of the patellofemoral joint pressure, which was particularly marked in flexion > 90°.

From our results we believe that more posterior positioning of the tibial component in total knee replacement would be beneficial to the patellofemoral joint.

Although much has been published on the causes of slipped upper femoral epiphysis and the results of treatment, little attention has been given to the mechanism of the slip. This study presents the results of the analysis of 13 adolescent femora, and the attempts to reproduce the radiological appearances of a typical slip. The mean age of the skeletons was 13 years (11 to 15). It was found that the internal bony architecture in the zone of the growth plate was such that a slip of the epiphysis on the metaphysis (in the normal meaning of the word slip) could not take place, largely relating to the presence of a tubercle of bone projecting down from the epiphysis. The only way that the appearance of a typical slipped upper femoral epiphysis could be reproduced was by rotating the epiphysis posteromedially on the metaphysis. The presence and size of this peg-like tubercle was shown radiologically by CT scanning in one pair of intact adolescent femurs.

Normal function of the patellofemoral joint is maintained by a complex interaction between soft tissues and articular surfaces. No quantitative data have been found on the relative contributions of these structures to patellar stability. Eight knees were studied using a materials testing machine to displace the patella 10 mm laterally and medially and measure the force required. Patellar stability was tested from 0° to 90° knee flexion with the quadriceps tensed to 175 N. Four conditions were examined: intact, vastus medialis obliquus relaxed, flat lateral condyle, and ruptured medial retinaculae. Abnormal trochlear geometry reduced the lateral stability by 70% at 30° flexion, while relaxation of vastus medialis obliquus caused a 30% reduction. Ruptured medial retinaculae had the largest effect at 0° flexion with 49% reduction. There was no effect on medial stability. There is a complex interaction between these structures, with their contributions to loss of lateral patellar stability varying with knee flexion.

We compared time-dependent changes in the biomechanical properties of single-and double-row repair of a simulated acute tear of the rotator cuff in rabbits to determine the effect of the fixation techniques on the healing process.

A tear of the supraspinatus tendon was created in 80 rabbits which were separated into two equal groups. A single-row repair with two suture anchors was conducted in group 1 and a double-row repair with four suture anchors in group 2. A total of ten intact contralateral shoulder joints was used as a control group. Biomechanical testing was performed immediately post-operatively and at four and eight weeks, and histological analysis at four and eight weeks.

The mean load to failure in group 2 animals was greater than in group 1, but both groups remained lower than the control group at all intervals. Histological analysis showed similar healing properties at four and eight weeks in both groups, but a significantly larger number of healed tendon-bone interfaces were identified in group 2 than in group 1 at eight weeks (p < 0.012).

The ultimate load to failure increased with the number of suture anchors used immediately post-operatively, and at four and eight weeks. The increased load to failure at eight weeks seemed to be related to the increase in the surface area of healed tendon-to-bone in the double-row repair group.

Objectives

The objective of this study is to determine an optimal antibiotic-loaded bone cement (ALBC) for infection prophylaxis in total joint arthroplasty (TJA).

Impaction allograft is an established method of securing initial stability of an implant in arthroplasty. Subsequent bone integration can be prolonged, and the volume of allograft may not be maintained. Intermittent administration of parathyroid hormone has an anabolic effect on bone and may therefore improve integration of an implant.

Using a canine implant model we tested the hypothesis that administration of parathyroid hormone may improve osseointegration of implants surrounded by bone graft. In 20 dogs a cylindrical porous-coated titanium alloy implant was inserted into normal cancellous bone in the proximal humerus and surrounded by a circumferential gap of 2.5 mm. Morsellised allograft was impacted around the implant. Half of the animals were given daily injections of human parathyroid hormone (1–34) 5 μg/kg for four weeks and half received control injections. The two groups were compared by mechanical testing and histomorphometry. We observed a significant increase in new bone formation within the bone graft in the parathyroid hormone group. There were no significant differences in the volume of allograft, bone-implant contact or in the mechanical parameters.

These findings suggest that parathyroid hormone improves new bone formation in impacted morsellised allograft around an implant and retains the graft volume without significant resorption. Fixation of the implant was neither improved nor compromised at the final follow-up of four weeks.

We report the effects of local administration of osteogenic protein-1 on the biomechanical properties of the overstretched anterior cruciate ligament in an animal model. An injury in the anterior cruciate ligament was created in 45 rabbits. They were divided into three equal groups. In group 1, no treatment was applied, in group II, phosphate-buffered saline was applied around the injured ligament, and in group III, 12.5 μg of osteogenic protein-1 mixed with phosphate-buffered saline was applied around the injured ligament. A control group of 15 rabbits was assembled from randomly-selected injured knees from among the first three groups. Each rabbit was killed at 12 weeks.

The maximum load and stiffness of the anterior cruciate ligament was found to be significantly greater in group III than either group 1 (p = 0.002, p = 0.014) or group II (p = 0.032, p = 0.025). The tensile strength and the tangent modulus of fascicles from the ligament were also significantly greater in group III than either group I (p = 0.002, p = 0.0174) or II (p = 0.005, p = 0.022).

The application of osteogenic protein-1 enhanced the healing in the injured anterior cruciate ligament, but compared with the control group the treated ligament remained lengthened. The administration of osteogenic protein-1 may have a therapeutic role in treating the overstretched anterior cruciate ligament.

External fixation of distal tibial fractures is often associated with delayed union. We have investigated whether union can be enhanced by using recombinant bone morphogenetic protein-7 (rhBMP-7).

Osteoinduction with rhBMP-7 and bovine collagen was used in 20 patients with distal tibial fractures which had been treated by external fixation (BMP group). Healing of the fracture was compared with that of 20 matched patients in whom treatment was similar except that rhBMP-7 was not used.

Significantly more fractures had healed by 16 (p = 0.039) and 20 weeks (p = 0.022) in the BMP group compared with the matched group. The mean time to union (p = 0.002), the duration of absence from work (p = 0.018) and the time for which external fixation was required (p = 0.037) were significantly shorter in the BMP group than in the matched group. Secondary intervention due to delayed healing was required in two patients in the BMP group and seven in the matched group.

RhBMP-7 can enhance the union of distal tibial fractures treated by external fixation.

A cavovarus foot deformity was simulated in cadaver specimens by inserting metallic wedges of 15° and 30° dorsally into the first tarsometatarsal joint. Sensors in the ankle joint recorded static tibiotalar pressure distribution at physiological load.

The peak pressure increased significantly from neutral alignment to the 30° cavus deformity, and the centre of force migrated medially. The anterior migration of the centre of force was significant for both the 15° (repeated measures analysis of variance (ANOVA), p = 0.021) and the 30° (repeated measures ANOVA, p = 0.007) cavus deformity. Differences in ligament laxity did not influence the peak pressure.

These findings support the hypothesis that the cavovarus foot deformity causes an increase in anteromedial ankle joint pressure leading to anteromedial arthrosis in the long term, even in the absence of lateral hindfoot instability.

Critical size defects in ovine tibiae, stabilised with intramedullary interlocking nails, were used to assess whether the addition of carboxymethylcellulose to the standard osteogenic protein-1 (OP-1/BMP-7) implant would affect the implant’s efficacy for bone regeneration. The biomaterial carriers were a ‘putty’ carrier of carboxymethylcellulose and bovine-derived type-I collagen (OPP) or the standard with collagen alone (OPC). These two treatments were also compared to “ungrafted” negative controls. Efficacy of regeneration was determined using radiological, biomechanical and histological evaluations after four months of healing. The defects, filled with OPP and OPC, demonstrated radiodense material spanning the defect after one month of healing, with radiographic evidence of recorticalisation and remodelling by two months. The OPP and OPC treatment groups had equivalent structural and material properties that were significantly greater than those in the ungrafted controls. The structural properties of the OPP- and OPC-treated limbs were equivalent to those of the contralateral untreated limb (p > 0.05), yet material properties were inferior (p < 0.05). Histopathology revealed no residual inflammatory response to the biomaterial carriers or OP-1. The OPP- and OPC-treated animals had 60% to 85% lamellar bone within the defect, and less than 25% of the regenerate was composed of fibrous tissue. The defects in the untreated control animals contained less than 40% lamellar bone and more than 60% was fibrous tissue, creating full cortical thickness defects. In our studies carboxymethylcellulose did not adversely affect the capacity of the standard OP-1 implant for regenerating bone.

We performed a biomechanical study to compare the augmentation of isolated fractured vertebral bodies using two different bone tamps. Compression fractures were created in 21 vertebral bodies harvested from red deer after determining their initial strength and stiffness, which was then assessed after standardised bipedicular vertebral augmentation using a balloon or an expandable polymer bone tamp.

The median strength and stiffness of the balloon bone tamp group was 6.71 kN (sd 2.71) and 1.885 kN/mm (sd 0.340), respectively, versus 7.36 kN (sd 3.43) and 1.882 kN/mm (sd 0.868) in the polymer bone tamp group. The strength and stiffness tended to be greater in the polymer bone tamp group than in the balloon bone tamp group, but this difference was not statistically significant (strength p > 0.8, and stiffness p = 0.4).

We split 100 porcine flexor tendons into five groups of 20 tendons for repair. Three groups were repaired using the Pennington modified Kessler technique, the cruciate or the Savage technique, one using one new device per tendon and the other with two new devices per tendon. Half of the tendons received supplemental circumferential Silfverskiöld type B cross-stitch. The repairs were loaded to failure and a record made of their bulk, the force required to produce a 3 mm gap, the maximum force applied before failure and the stiffness. When only one device was used repairs were equivalent to the Pennington modified Kessler for all parameters except the force to produce a 3 mm gap when supplemented with a circumferential repair, which was equivalent to the cruciate.

When two devices were used the repair strength was equivalent to the cruciate repair, and when the two-device repair was supplemented with a circumferential suture the force to produce a 3 mm gap was equivalent to that of the Savage six-strand technique.