Introduction

In order to prepare hamstring autograft, suture fixation to the tendon is required to secure and handle the tendon during harvest and preparation. We use a simple, grasping suture which doesn't require suture of the tendon, thus saving time and avoiding violation of the graft itself. We present this technique, with results of mechanical testing compared to a standard whip suture, traditionally used to handle hamstring autograft.

Introduction

The role of porosity in the longevity of polymethylmethacrylate (PMMA) bone cement mantles remains unclear, although porosity reduction is probably desirable. It is not known whether pore patterns, pore distribution or pore morphology contribute to failure, since it is difficult to assess these features with traditional techniques. We used a novel microtomographic technique to quantitatively and qualitatively assess porosity in PMMA cements of differing viscosities to establish whether pore distribution can be effectively assessed and to document any differences in porosity (in both quantity, distribution and morphology). Each cement was also examined with and without the addition of vacuum, since this is thought to reduce porosity.

The diagnosis and treatment of disorders of the long head of the biceps tendon remains controversial. There is uncertainty as to the role of the long head of biceps and it can be difficult to determine whether the patient's pathology is coming from the biceps or other adjacent structures. In addition, the appropriate type of treatment remains controversial.

We retrospectively reviewed the files of the senior author's experience in over 4000 arthroscopic shoulder procedures. We examined cases involving isolated biceps pathology, excluding those patients with rotator cuff tears and labral pathology, involving 92 biceps tenotomies and 103 biceps tenodeses.

Our analysis supports the benefit of clinical examination over all types of radiological investigations. The benefits and technique of biceps tenodesis is described including surgical technique. Irritation by PLA interference screw is examined. A paradigm is put forward to help in diagnosis and management of these lesions.

Long head of biceps pathology is a significant cause of shoulder pain in association with other shoulder problems and in isolation. Biceps tenodesis and tenotomy is an efficacious way of dealing with this pathology.

Thermal damage to bone related to the exothermic polymerisation of bone cement (PMMA) remains a concern. A series of studies were conducted to examine PMMA bone interface during cemented arthroplasty.

In vitro and in vivo temperature distributions were performed in the laboratory and human and animal surgery. In vivo (10 patients) measurements of cement temperature during cementing of BHR femoral prosthesis using thermocouples. Intra-operative measurement of cement temperature in BHR in the presence of femoral head cysts was examined in patients. The BHR femoral heads were sectioned to assess cement mantle as well as position of thermocouples. An additional study was performed in sheep with PMMA implanted into cancellous defects. Thermocouples were used to monitor temperature in the cement as well as adjacent bone. Histology and CT was used to assess any thermal damage.

The exothermic reaction of PMMA during polymerization does indeed result in an increase in temperature at the interface with bone. The in vivo study recorded a maximum temperature of 49.12C for approximately three minutes in the cancellous bone underneath the BHR prosthesis. This exposure is probably not sufficient to cause significant injury to the femoral head. The maximum temperature of the cement on the surface of the bone was 54.12C, whereas the maximum recorded in the cement in the mixing bowl was 110.2C.

In the presence of artificial cysts within the bone, however, temperatures generated within the larger cysts, and even at the bone-cement interface of these cysts, reached levels greater than those previously shown to be harmful to bone. This occurred in one case even in the 1 cc cyst.

Routine histology revealed a fibrous layer at the cement bone interface in the sheep study. Fluorescent microscopy demonstrated bone label uptake adjacent to the defect site. Histology did not reveal thermal necrosis in the defects in terms of bony necrosis. CT data was used to measure the amount of PMMA placed into each defect. This analysis revealed a range of volumes that did not seem to influence the histology.

The heat of cement polymerisation in resurfacing as performed in our study is not sufficient to cause necrosis. This may reflect the ability of the body to rapidly conduct heat away by acting as a heat sink. The temperature-conducting properties of the metal prosthesis are also likely to be important.

Posterolateral spinal fusion using autograft in adult rabbits has been reported by many groups using the Boden model. Age in general has an adverse effect on skeletal healing; although, its role in posterolateral fusion is not well understood. This study examined the influence of animal age on spinal fusion using a standard model and experimental endpoints. We hypothesised that fusion quality and quantity would be less with increasing age.

A single level posterolateral fusion between the fifth and sixth lumbar segments were performed in six-month and two-year-old New Zealand white rabbits (n=6 per group) using morcelized iliac crest autograft. All animals were sacrificed at 12 weeks following surgery. Posteroanterior Faxitron radiographs and CT scans were taken and DICOM data was analysed (MIMICS Version 12, Materialise, Belgium). Axial, sagittal, coronal and three-dimensional models were created to visualise the fusion masses. Bone mineral density (BMD) of the fusion mass was measured using a Lunar DPXL Dexa machine. An MTS Bionix testing machine was then used to assess peak load and stiffness. Sagittal and coronal plane histology was evaluated in a blinded fashion using H&E, Tetrachrome and Pentachrome stains. Assessment included overall bony response on and between the transverse processes. Radiographs and CT confirmed a more robust healing response in younger animals. Radiographic union rates decreased from 83% to 50% in the aged animals. A neo- cortex surrounding the fusion mass was observed in the younger group but absent in the aged animals. Fusion mass BMD and that of the vertebral body was decreased in the older animals (P<0.05). Tensile mechanical data revealed a 30% reduction in peak load (P=0.024) and 34% reduction in stiffness (P=0.073) in the two-year-old animals compared with the six-month-old animals. Histological evaluation demonstrated a reduction in overall biological activity in the two-year-old animals. This reduction in activity was observed in the more challenging intertransverse space as well as adjacent to the transverse processes and vertebral bodies at the decortication sites. Numerous sites of new bone formation was present in the middle of the fusion mass in the six-month-old animals while the bone graft in the two-year- old animals were less viable.

Skeletal healing is complex and mediated by both local and systemic factors. This study demonstrated that ageing leads to an impaired and delayed skeletal repair.

Where autograft is utilised, diminished graft osteoinductivity and reduced levels of growth factors and nutritional supply in the surrounding milieu explains our observations. The aged rabbit posterolateral spinal fusion model has not been previously described but would be a useful to evaluate new treatment modalities in a more challenging host environment.

Cortical bone is a complex composite material composed of an inorganic mineral phase and organic matrix of type I collagen and various non-collagenous proteins. The hierarchical organisation of bone results in a transversely isotropic material with the mechanical properties in the long-axis (z) being superior to the radial and circumferential axes which are equivalent. This directional dependence of bone has been well reported, whilst the mechanisms/anisotropy are more difficult to study. This study examined the anistropic nature of cortical bone and the influence of different sterilisation procedures.

Ninety cortical bone cubes were prepared using established techniques (Walsh and Guzelsu) and randomly allocated to three treatments; control, 15 KGy, Super Critical Fluid (SCF) (n=30 per group). The ultrasonic moduli was examined using longitudinal sound waves at 5 MHz using a pulse receive technique. Unconfined compression was performed non-destructively in longitudinal (z), circumferential (ï±) and radial orientations (r). Samples were tested to failure in the z axis. A two-way analysis of variance (treatment and time) followed by a Games Howell post hoc test and covariate analysis was performed using SPSS for Windows.

Data from this study revealed some interesting and intriguing results with respect to the effects of gamma irradiation and dense gas technology on the properties of cortical bone and load transmission. A statistical decrease in the compressive stiffness and strength was noted with 15 KGy of whilst SCF treatment did not alter the properties in the r or ï orientations. Similar results were found with respect to the ultrasonic moduli (data not shown). The pilot data confirmed the adverse effects of bone in compression following gamma irradiation as we found in our recently presented ORS work. However, the study in compression demonstrated that the directional dependence that makes cortical bone a transversely isotropic material is removed following gamma irradiation with SCF did not appear to have this effect.

The effects of gamma irradiation on the mechanical performance of allografts in the long bone axis may play a role in their in vivo performance. The removal of the anisotropy following gamma irradiation provides insight into the relationship(s) between the mineral and organic constituents, which requires further study.

The aim of this study was to compare the outcome of cemented TKR using either oxidized zirconium (oxinium) or cobalt chrome (CoCr) femoral components in patients undergoing simultaneous bilateral TKR. Patients involved in the study received one of each prosthesis, thereby acting as their own control. The hypothesis was that there would be no difference in the clinical and radiographic outcome between the two prosthetic materials.

Forty consecutive patients who were undergoing bilateral Genesis ll TKR consented to participate in the study. Patients were assessed preoperatively, at five days, six weeks and one, two and five years, postoperatively. The outcome measures included the KOOS, Knee Society Score, BOA Patient Satisfaction Scale, and radiographs at six weeks and one, two and five years. In two patients polyethlylene exchange was performed at 56 months from surgery during patellofemoral resurfacing. The four retrieved polyethylene liners were studied for wear with the aid of a stereo zoom microscope and an environmental scanning electron microscope (ESEM). Both the patients and the all examiners were blinded as to the prosthesis type throughout the study.

Forty patients (80 knees) were included in the study. At five years, three patients were deceased and two had developed senile dementia. No patients were lost to follow up. At five years from surgery the CoCr knee was preferred by 41% of patients compared to 13% who preferred the Oxinium knee (p=0.009). There was no significant difference in range of motion between the two prosthesis at five days, six weeks or one, two and five years. There were also no significant differences between the two prostheses in any of the other variables assessed. The four retrieved polyethylene inserts showed similar patterns of wear in terms of both wear types and patterns under examination with both the stereo zoom and scanning electron microscope with no clear differences between CoCr and Oxinium bearing against the polyethlylene. There was no difference in the grade or incidence of radiographic lucencies between the two prosthesis at five years.

At five years after surgery the only significant difference between the Genesis II Oxinium prosthesis and the CoCr prosthesis was a subjective preference for the CoCr prosthesis by a higher proportion of patients. There were no unexpected complications associated with the use the Oxinium femoral implants. In the four retrieved polyethylene liners, no significant differences were identified between the two prosthesis materials in terms of detectable wear type and patterns. Continued follow up of this cohort is planned to establish whether Oxinium femoral implants have an improved survivorship compared to CoCr femoral component in total knee replacement to warrant the additional cost.

‘High flexion’ polyethylene tibial tray inserts are available from total knee replacement (TKR) manufacturers. There is currently no published data available that examines how much extra knee flexion these new implants give or if there are any wear consequences for the change in design. The high flexion inserts are narrower posteriorly than standard inserts and have chamfers anteriorly and on the post in cruciate sacrificing designs.

This prospective randomised controlled trial of 100 patients undergoing posterior stabilised TKR compared knee flexion, measured intra-operatively by a computer navigation system, of the standard and high flexion trial inserts in the same knee. Patients were then randomised to receive either a standard or ‘high flexion’ definitive component and the stability assessed. The post-operative knee flexion of all patients was measured at six months.

High flexion inserts did not give significantly more knee flexion than standard inserts either per-operatively at the trial insert stage, or at six months post-op and resulted in marginally more anterior draw. The average per-operative difference in flexion between standard and high flex inserts measured in the same knee was 3.2° (range -4-18°) The average knee flexion at 6 months post op was 106° for both groups. The average change in knee flexion comparing pre and post op was 2.3° for the high flex group and 0.6° for the standard insert group.

Laboratory Tek scan contact pressure analysis at the surface of the standard and high flexion designs was not significantly different, but the thinner polyethylene of the high flexion design raises questions about wear characteristics. High flexion polyethylene inserts are probably not justified in terms of improved knee flexion, but may be a useful option in certain technical circumstances during TKR such as patella baja or if the patella impinges on the post in deep flexion.

We present a biomechanical cadaveric study investigating the effect of type II Superior Labrum Anterior Posterior (SLAP) lesions on the load-deformation properties of the Long Head of Biceps (LHB) and labral complex. We also report our assessment of whether repair of the type II SLAP lesion restored normal biomechanical properties to the superior labral complex.

Using a servo-controlled hydraulic material testing system (Bionix MTS 858, Minneapolis, MA), we compared the load-deformation properties of the LHB tendon with:

the LHB anchor intact;

Seven fresh-frozen, cadaveric, human scapulae were tested. We found that the introduction of a type II SLAP lesion significantly increased the toe region of the load deformation curve compared to the labral complex with an intact LHB anchor. The repair techniques restored the stiffness of the intact LHB but failed to reproduce the normal load versus displacement profile of the labral complex with an intact LHB anchor.

Of the two suture techniques, the mattress suture best restored the normal biomechanics of the labral complex.

We conclude that a type II SLAP lesion significantly alters the biomechanical properties of the LHB tendon. Repair of the SLAP lesion only partially restores the biomechanical properties. We hypothesise that repairs of type II SLAP lesions may fail at loads as low as 150N, hence the LHB should be protected following surgery.

Introduction: Monobutyrin (MB) has been shown to be a potent angiogenic factor for adipose tissue. It is one of the many compounds secreted from adipocytes adding to the knowledge that adipose tissue is not merely a storage unit but has an endocrine function. Adipocytes and osteoblasts share a common precursor. In osteoporosis the proportion of fat in bone increases. As both are present at a fracture site the addition of MB may enhance fracture healing by stimulating angiogenesis.

Method: 138 Sprague Dawley rodents were ovarect-omised at 12 weeks of age. After a further 24 weeks each animal underwent a right closed femoral fracture stabilized with a retrograde k-wire using a standard model (Walsh et al. 1997). Animals were randomised into control (empty or substrate only) or MB of varying concentrations (2.5μg, 7.5μg, 25μg, 75μg). A percutaneous injection of 0.2mls of each of the above was then injected into the fracture site. Animals were culled at 1, 3 and 6 week time points post surgery. The right and left femurs were dissected out and analyzed using radiographic, mechanical testing, micro computed tomography and histology endpoints. Statistical analysis was perfomed with SPSS for windows.

Results: All animals recovered well from the procedure and no adverse reactions were noted following the addition of MB. A progression to union was seen with time in all groups. Mechanical testing did not result in a statistical difference between groups, however the trend showed improved healing in the 7.5μg Monobutyrin group. Radiographic grading again showed no statistical difference however, interestingly micro CT data showed an increasing trend in both trabecular number and bone surface area to volume with increasing concentrations of MB.

The histology results implied a potential acceleration in the early stage of fracture healing in the high dose (75 μg) MB group. However progression to union following this initial early phase acceleration was delayed as callus volume increased rather than union according to micro CT and histological data.

Discussion: The ability to augment fracture healing has significant clinical implications considering the “greying of society”. This study investigated the possibility of improving fracture healing by incorporating the angiogenic factor, Monobutyrin in an estrogen deficient animal model. Although the results do not conclusively demonstrate an improvement in fracture healing, they do imply that MB does affect the early phase of fracture healing in the estrogen deficient model. This study is limited in that the effects of MB on fracture healing in a non-estrogen deficient model was not considered. The ideal release kinetics for Monobutyrin as well as other factors remains unknown.

Repair of chronic Achilles tendon rupture is technically complex. Flexor jallucis longus (FHL) and peroneus brevis (PB) tendon transfers have been described, but the mechanical properties of these tissues have not been well reported.

The FHL, PB and tendo achilles (TA) tendons were harvested from 17 fresh frozen human cadavers free of gross pathology (mean age 69 years). Samples were tested in uniaxial tension at 100% per minute. Samples were secured using special jigs for the bony aspect or by freezing the tendons in cryogrips using liquid carbon dioxide. The peak load (N), linear stiffness (N/mm) and energy to peak load (N*mm) were determined. Mechanical data was analysed using one way analysis of variance (ANOVA) followed by a Games Howell multiple comparison post-hoc test.

Fifty one tendons were harvested and mechanical testing was successfully completed in all samples apart from one PB that slipped from the grips during testing (sample was omitted from the analysis). The mean ultimate loads differed for each group, with the TA tendons being the strongest (1724.5 N ± 514.3) followed by FHL (511.0 N ± 164.3) and PB (333.1 N ± 137.2) (P< 0.05). Similar results were found with respect to energy, with TA tendons absorbing the most energy followed by FHL and PB (P< 0.05). Stiffness for the TA tendons (175.5 N/mm ± 94.8) was greater than FHL (43.3 N/mm ± 14.1) and PB (43.6 N/mm ± 18.9), which did not differ from each other.

FHL is stronger than PB, but have similar stiffness. The mechanical properties of PB and FHL were both inferior to TA. Graft stiffness appears to be an important variable rather than ultimate load based on the clinical success of both techniques.

Metal-on-metal articulations are increasingly used in THR. Hypersensitivity reactions to the metal ions can occur. The symptoms and signs are similar to a patient presenting with an infected prosthesis. Correct diagnosis before revision surgery is crucial to implant selection and operation planning. We present a practical approach to this diagnostic problem.

The history, clinical findings, hip scores, radiology, serum metal ions, ESR, C-RP, hip arthroscopy and aspirate results, synovial fluid metal ion levels, labelled white cell/colloid scan, 99m-technetium scan, revision hip findings and histology of a typical patient who had an allergic response to a metal-on-metal hip articulation are presented, and how the findings differ from a patient with an infected implant. Clinical examination, hip scores and serum metal ion levels were repeated one year after revision of the metal-on-metal hip articulation to a ceramic-on-ceramic.

In hypersensitivity, the periarticular tissues undergo lymphocyte-dominated infiltration, the histology differs from that found in infection. The white cell labelled/colloid scan also uses this difference for diagnosis. Hip aspiration is the single best investigation for infection.

Conclusion: There is no single investigation available in most hospitals that will reliably differentiate infection from allergy in the painful THR. Hip aspiration, labelled white cell/colloid scan and histology obtained from hip arthroscopy biopsy are the most useful investigations.

Intro: Anatomical abnormality associated with severe developmental dysplasia of the hip presents technical difficulties at THR. Patients often present at a younger age and may have had previous surgery.

We report the difficulties encountered during surgery, and the long term results of patients who had Crowe 3 or 4 DDH and a technically difficult primary hip arthroplasty using the modular S-ROM stem.

Method: 28 patients were entered into the prospective trial. The average age of the patient at surgery was 45 (range 23–74 years). All patients underwent surgery by the senior author using the S-ROM femoral stem. They were followed up for an average of 10 years (range 5–16 years), clinical scores recorded by a clinician other than the surgeon and radiographs were examined by an independent radiologist.

Results: 21 patients required a significant autologous bone graft, one patient had a large allograft and six patients required femoral shortening at the time of their THR.

4 patients had a technical complication during surgery. The average pre-op Harris Hip Score was 37, at 5 years it was 83, and at 10 years 81. The SF12 measure of physical and mental wellbeing was 43.90 physical/54.48 mental at 5 years, and 41.64 physical/54.03 mental at 10 years. The WOMAC average score (the lower the score the better the outcome) was 27 at 5 years and 23 at 10 years.

None of the S-ROM stems had been revised, 2 hips had undergone acetabular revision and one hip had a liner exchange. None of the S-ROM stems were loose at latest follow-up. Four hips had osteolysis in Gruen zone 1, one hip had osteolysis in zone 7, and one hip had osteolysis in zone 1 and 7. There was no evidence of osteolysis around or distal to the sleeve.

Conclusion: The S-ROM stem used in primary THR shows excellent results at 10 years in patients with anatomical abnormality related to severe DDH.

S-ROM stem/sleeve modularity allows femoral component anteversion independent of the position of best fit in the proximal femur, and helps overcome the technical difficulty in these patients.

Bone allograft use in trauma and orthopaedic surgery is limited by the potential for cross infection due to inadequate acceptable decontamination methods. Current methods for allograft decontamination either put the recipient at risk of potentially pathogenic organisms or markedly reduce the mechanical strength and biological properties of bone. This study developed a technique of sterilization of donor bone which also maintains its mechanical properties.

Whole mature rat femurs were studied, as analogous to strut allograft. Bones were inoculated by vortexing in a solution of pathogens likely to cause cross infection in the human bone graft situation. Inoculated bones were subjected to supercritical carbon dioxide at 250 bar pressure at 35 degrees celsius for different experimental time periods until a set of conditions for sterilization was achieved. Decontamination was assessed by vortexing the treated bone in culture broth and plating this on suitable culture medium for 24 hours. The broth was also subcultured. Controls were untreated-, gamma irradiated- and dehydrated bone. Mechanical testing of the bones by precision three-point bending to failure was performed and the dimensions and cross-section digitally assessed so values could be expressed in terms of stress.

Mechanical testing revealed bone treated with supercritical carbon dioxide was consistently significantly stronger than that subjected to gamma irradiation and bones having no treatment (due to the minor dehydrating effect of the carbon dioxide). Terminal sterilization of bone is achieved using supercritical carbon dioxide and this method maintains the mechanical properties.

The new technique greatly enhances potential for bone allograft in orthopaedic surgery.

Introduction: Lesser toe problems and metatarsalgia are common complaints in patients presenting with foot problems. Associated toe deformities include mallet toes, hammer toes, claw toes. The patient may complain of pain over the proximal interphalangeal joint from shoe ware, diffuse or localized pain under the metatarsal heads, or swelling and irritation of the metatarsophalangeal joint. Most patients can be treated with shoe ware modification, NSAID medication, tapping of toes, orthotics, or steroid injections. Surgical treatment includes flexor to extensor transfers, PIP excision arthroplasty, plantar condylectomy and metatarsal osteotomy.

Indications and Complications: The osteotomy is performed when there instability of the MTP joint, reduction of MTP joint subluxation or dislocation, relatively long ray with transfer metatarsalgia. Complications include avascular necrosis, joint stiffness, transfer metatarsalgia to subsequent toes, and plantar flexion of the metatarsal.

Surgical Technique: The Weil osteotomy is performed through a dorsal incision, performing a dorsal capsulotomy of the MTP joint and plantar flexing the proximal phalanx to expose the metatarsal head. The osteotomy is started in dorsal aspect of the metatarsal head and is made along the shaft keeping parallel to the floor. Key points are to make a long osteotomy cut to allow broad surface area for healing, avoid lowering the head by performing the cut parallel to the floor. The head will naturally displace proximally, most authors recommending 5–10mm of shortening.

Fixation: The osteotomy is fixed using a twist off screw. Factors that influence fixation include angle of screw insertion, size of the screw and the number of screws. Fixation in relatively porotic bone is improved when using two screws.

Distraction osteogenesis (DO) is useful for bone lengthening and deformity correction. Unfortunately, this often requires prolonged use of an external fixator with concomitant morbidities. This study investigates whether low-magnitude, high-intensity vibrations (Dynamic Motion Therapy, DMT) can accelerate maturation of regenerate bone in DO, thus reducing the duration of external fixation. 28 NZ White Rabbits underwent a right mid-tibial osteotomy with application of an Orthofix M-103 fixator (Orthofix, Busselengo, Italy). Distraction commenced on day 3 at 0.5 mm every 12 hours for 12 days. All animals were sacrificed on day 45. Animals were randomly assigned into 4 groups:

control group;

DMT was applied with the Juvent platform (Juvent, Somerset, NJ) for 10 minutes/day. X-ray and CT scans were taken prior to mechanical testing. All specimens were processed for histology. X-rays and CT scans showed evidence of cortical remodelling and re-establishment of the medullary canal in animals treated with DMT (groups 2, 3 and 4). This was most pronounced in animals treated during the distraction and consolidation phases (group 4). Regenerate bone in the control group (group 1) was more disorganised, with a delayed union evident in 1 animal. Group 1 achieved peak torque and stiffness values of 70% and 50% of the contralateral (unoperated) tibia respectively. No significant difference was seen in peak torque and stiffness between groups 2, 3, and 4, however each was significantly higher than group 1 (P< 0.05). H& E staining revealed less porosity in the newly formed cortical bone and a more defined medullary canal in animals treated with DMT than in the control group. Low-magnitude, high-intensity vibrations appear to accelerate cortical remodelling and reestablishment of a medullary canal. Regenerate bone in animals treated with DMT was also mechanically superior. The timing of DMT therapy did not appear to be important. Further studies are required to determine the optimal timing and duration of DMT therapy.

Although effects of mechanical stimulation with high frequency, low magnitude vibrations on bone mass and bone mineral density in animal and clinical studies have been proven effective, its effects on fracture healing is less well described.

20 Sham and 20 ovarectomised (Ovx) Sprague Dawley rats at 22 weeks of age, had intra-medullary k-wire fixation followed by controlled mid-shaft fractures.

The animals were divided into subgroups of 3 week Sham and Ovx treated and non-treated and 6 week Sham and Ovx treated and non-treated groups.

The treated animals were vibrated for 20mins daily on a DMT (dynamic motion therapy) platform which had a frequency of 30hz, 8-micron vertical displacement and 3g force, the non treated animals allowed to move freely. Xrays, DEXA studies, micro computed tomography, Histological analysis and Mechanical studies performed at the end point.

DMT treated animals had more bridging callus on radiographic and micro computed tomographic analysis compared to non-treated groups especially the OVX groups at 3 weeks compared to controls or Shams (using Image J software). DEXA studies showed increased bone mineral density and bone mineral content in the treated animals compared to the controls. Histological analysis showed increased callus and woven bone being laid down in the treated OVX groups.

In the 6-week groups, the treated OVX groups had healed, remodelled fractures compared to the non-treated groups or Sham controls where the fracture gaps were still visible. Although significance was not achieved on mechanical analysis due to small sample size, in the OVX non-operated femora group that were treated with DMT there were indications that they were stronger than the control counterparts.

High frequency low magnitude vibrations with the Juvent DMT device enhances fracture healing in oestrogen deficient models and this model could be used as a platform for clinical studies in future.

In vitro testing of spinal motion segments provides valuable information about the effects of surgical procedures on the biomechanics of the spine. Few studies, however have investigated the effect of varying laboratory testing environments on the outcome of these tests. This study aims to identify differences in mechanical properties induced by testing in one of three testing environments, and trends due to repeated testing over time.

27 sheep lumbar motion segments were tested in either,

air at 18°C while wrapped with gauze soaked in Phosphate Buffered Saline (PBS),

Specimens were cycled through +/−8Nm in axial rotation, lateral bending, and flexion/extension. Tests were repeated every hour for 6 hours. Torque and angle were recorded and each bending mode was repeated for 4 cycles, the last 3 of which were used in calculations. Stiffness (5–7Nm), neutral zone (NZ), NZ stiffness, Range of Motion (ROM) energy under the loading curve and hysteresis area were calculated and evaluated with ANOVA.

Post hoc comparisons found differences in stiffness, hysteresis area and energy of bending between room temperature and both heated conditions during flexion/extension. Differences were also noted between the room temperature and PBS bath conditions for stiffness and hysteresis area during lateral bending. One explanation of the results could be the thermo-sensitive properties of spinal ligaments and intervertebral fibrocartilages.

Repeated testing was a factor that affected the outcome of NZ, NZ stiffness, ROM and energy under the loading curve in all modes of torsion. If not accounted for during repeated tests this could lead to confounding results. Many of the traditionally reported variables (NZ, ROM) showed changes with repeated testing while hysteresis area remained relatively steady during repeated tests while identifying differences between testing groups. This variable may be useful in evaluating the condition of a motion segment with less time related effects.

Treatment of chronic Achilles tendon ruptures can be technically demanding due to tendon retraction, atrophy and short distal stumps. Although rare, re-rupture following surgical treatment is a major late complication.

Biomechanical studies on the strength of reconstructed Achilles tendon using autologous tendon grafts have not been well documented.

This study examined the time zero in vitro mechanical properties of a reconstructed Achilles tendon (TA) using the peroneus brevis (PB) or the flexor hallucis longus (FHL) tendons in a human cadaver model (n=17).

The TA was reconstructed using the same technique for all specimens. Biomechanical testing was performed using an MTS 858 Bionix testing machine and structural properties (failure load, stiffness and mode of failure) were determined.

Average failure load was significantly higher in the PB-group (p=0.0116) (PB: 343.82 N (+/− 124.90 N, FHL: 241.54 N (+/− 82.17 N)). There was no significant difference in stiffness (p=0.212), (PB: 16.53 N/mm (+/− 6.25 N/mm), FHL: 14.00 N/mm (+/− 3.84 N/mm)) or energy (p=0.075).

Mode of failure was the same for all specimens, with the tendon graft cutting through either the distal or proximal TA-stump. Reinforcement of these stumps could lead to increased failure loads. Based on the biomechanical data, the present study supports the use of either FHL or PB to reconstruction chronic TA tendon ruptures. The greater failures loads for PB may not be clinically relevant considering the peak loads. The addition of the suturing pattern, whilst is does reconstruct the tendon, does not provide a similar ability to resist the load.

Introduction: The use of bioabsorbable devices in sports medicine surgery in the shoulder and knee continues to evolve as new designs, devices and materials become available. Concerns over potential problems associated with metal artifacts and permanent metal devices continue to motivate the development and use of polymeric based devices. Calaxo interference screws (Smith & Nephew Endoscopy, Andover, MA) are composed of a novel bioabsorbable material blend of poly DL- lactide – co – glycolide 85:15 (65%) and calcium carbonate (35%). These screws have been shown to be osteoconductive when placed in the centre of a 4 stranded tendon graft in an ovine ACL reconstruction [1]. The screws are fully resorbed at 26 weeks with new bone formation in the tunnel. In general, osteoconductive materials are often more effective when placed adjacent to a bony bed. This study investigated whether positioning the Calaxo screw adjacent to the bone tunnel was superior to screw placement within the tendon as in our previous study [1].

Materials and Methods: An intra-articular anterior cruciate ligament (ACL) reconstruction model using 2 doubled over tendon autografts whip stitched and inserted into the right hind limb of 8 sheep were used. Animals were culled at 26 or 52 weeks following surgery (n=4 per time point) and data was compared using the same surgical model but with screws placed in the center of the 4 stranded graft (Walsh et al., 2006). The tibias were CT scanned and processed for paraffin histology along the axis of the bone tunnel. Three dimensional models using the DICOM data obtained from the CT where made using MIMICS (Materialise, Belgium).

Result & Discussion: Results showed excellent biocompatibility of the screws with no adverse reactions at 26 and 52 weeks as in our previous study [1]. The screws were fully resorbed by 26 weeks with new bone replacing the PLC material. Similarly, the screws were not detectable at 52 weeks with new bone formation where the screw had previously resided. The intra-articular portion of the graft, articular cartilage and synovium was normal at 26 and 52 weeks as previously reported [1]. Tendon – bone healing proximal to the screw progressed in a normal fashion. No calcification of the intraarticular portion of the graft was noted. Computed tomography, 3D models and histology revealed an osteoconductive response to the PLC material with new bone formation as the material degraded in vivo.

Placement of the screw adjacent to the tendon graft and thus against the bone tunnel appears to provide superior results compared to screw placement in the middle of the graft sleeve device. This effect may be due to direct contact of the osteoconductive material to the adjacent bone bed.

[1] Walsh et al., Arthroscopy 2006, in press.