Introduction: The majority of midshaft humeral fractures will achieve a satisfactory outcome with non-operative management. However, internal fixation is occasionally required to assist with rehabilitation, particularly in multiply-injured patients. Although the clinical risks and benefits of the locking plate and humeral nail are well known, there is a paucity of data comparing their mechanical properties.

The aim of this study was to determine the torsional and 4-point bending properties of a midshaft humeral osteotomy reconstructed with either an intramedullary nail or locking plate.

Methods: 19 fresh cadaveric humeri were DEXA scanned to ensure similar BMD. Non-destructive 4-point bending was performed on the intact bone to determine stiffness in the sagittal and coronal planes. Load was applied using an MTS MiniBionix 858 (Mechanical Testing Systems, MN) at a rate of 1 mm/min to a maximum of 450 N.

A transverse midshaft osteotomy was created and a spacer ensured a constant 3-mm gap between the bone ends. Reconstruction was performed with either

Trigen humeral nail (Smith & Nephew, TN) – 10 specimens

Non-destructive 4-point bending was repeated, and then each humerus was embedded in a low-melting point alloy proximally and distally for torsional testing. Torque was applied at 5 deg/min until failure. Maximum torque, maximum angle and stiffness were calculated.

All data were analysed with SPSS for Windows (SPSS Inc., Il) using ANOVA.

Results: One specimen in the locking plate group fractured during plate application and was excluded from the study. Non-destructive bending tests showed no significant difference in stiffness of the intact bones between the two groups.

4-point bending: the bones reconstructed with the intramedullary nail were ~50% as stiff as the intact state in both planes. There was no statistically significant difference in stiffness between the intact bones and those reconstructed with the locking plate.

Torsional testing: the locking plate specimens were 3 times as stiff as the intramedullary nail specimens (P< 0.05) and failed at twice the torque (P< 0.05).

Discussion: Humeral intramedullary nails are reported to have an advantage over plates under axial loading (Chen et al, 2002). However, this study demonstrates that locking plates are superior to intramedullary nails in torsion and four-point bending. Although the clinical situation often dictates the most appropriate management, locking plates should be considered in patients when torsional or four-point bending loads are expected to predominate in the post-operative period.

Intro: Total knee replacement (TKR) manufacturers offer the option of high flexion tibial tray inserts. The polyethylene is narrower posteriorly than the standard insert and comes with the theoretical risk of reduced longevity due to thinner implant. This trial studied both the intra-operative and post-operative difference in knee flexion.

Method: 100 consecutive patients undergoing posterior stabilized Genesis II TKR with Brainlab navigation were studied. The flexion of each knee was assessed per-operatively using the Brainlab navigation system for both the high flex and standard tibial insert trials. Patients were then randomized to receive either a high flex or standard definitive implant and the knee flexion measured clinically with a goniometer six months post op.

Results: Intra-operatively the high flexion insert trial flexed more than the standard flex option by 3.2 degrees. Clinically at six months post op there was no difference in knee flexion between the two groups.

Conclusion: There is no clinical difference in knee flex-ion at six months post-op in patients with a high flex or standard tibial insert. However, we believe that in certain technical circumstances the high flex option is a valuable option for the surgeon to have available.

Negative ulnar variance, lunate shape and increased load transmission are associated with Kienbock’s disease. This may reflect trabecular alignment being more susceptible to shear forces along “fault planes” in Type 1 lunates, causing microfractures and avascular necrosis. The aim of this study was to assess the relationship between lunate bone structure, density and ulnar variance.

Standard 90/90 radiographs of 22 cadaveric wrists were taken for ulnar variance and lunate shape. The lunates were harvested and routine CT scans (1mm) were taken in 22/22 in the coronal, sagittal and transverse planes. DICOM files were analysed using Mimics (Materialise, Belgium) to measure Hounsfield units. MicroCT scans (SkyScan, Belgium) (40 μm) were taken in 10/22 in the coronal plane and measured for trabecular angle at the proximal and distal joint surfaces and the ‘tilting angle’ (between scaphoid and radius joint surfaces). Data was anlaysed using one-way ANOVA tests using SPSS for Windows.

Negative ulnar variance was noted in 7/22, neutral 10/22 and positive 5/22. Lunate shape according to Zapico was 0/22 Type 1, 18/22 Type 2 and 4/22 Type 3.

Lunate bone density was significantly lower in the ulnar positive specimens compared to ulnar negative and neutral (p< 0.001) (fig. 1).

The average trabecular angle measured 84.7° (+/− 4.5°) at the proximal and 90.3° (+/− 2.6°) at the distal joint surfaces and tilting angle was 115.7° (+/− 12.0°) (fig. 2). The 50% slice on the microCT correlated best with xray measurements of this angle.

This study quantifies the previous finding that load transmission through the lunate and hence lunate bone density is related to ulnar variance and that this is higher in ulnar negative wrists. MicroCT is a useful modality to assess trabecular structure and supports the ‘fault plane’ hypothesis of Kienbock’s Disease.

Introduction: A cosmetic deformity does not always occur after a biceps tenotomy. The anatomical restraints preventing distal excursion of the long head of biceps tendon following tenotomy have not previously been described. This study aims to evaluate the biceps sheath and its potential role as a restraint to distal excursion of the biceps following tenotomy.

Methods: Fifteen fresh cadaveric specimens were dissected free of overlying soft tissues to reveal the rotator cuff, biceps sheath and long head of biceps muscle belly and tendon. Eight specimens were used for gross anatomical analysis. Measurements of the length of the biceps sheath on the humeral (bone) side and tendon side were made using a digital caliper (Mitutoyo, Japan). The long head of biceps tendon was then released from the glenoid labrum and the excursion of the stump relative to the rim of the articular surface measured. The biceps sheaths of two specimens were used for histological analysis.

Seven specimens were used for mechanical analysis. A humeral osteotomy was performed distal to the insertion of pectoralis major, leaving intact the biceps sheath and the muscle belly of long head of biceps. The proximal humerus was attached to a custom-designed jig and the muscle belly of biceps grasped in cryogenic grips. Specimens were loaded on an MTS 858 Bionix mechanical testing machine (MTS Systems, MN) in uniaxial tension at a rate of 1 mm/sec until failure was observed.

Results: The biceps sheath surrounds the long head of biceps tendon and inserts into the bone of the proximal humerus. It is trapezoidal in cross-section, with a mean length of 75.1 mm on the bone side and 49.3 mm on the tendon side. The average excursion of the stump was to within 2.8 mm of the rim of the articular surface.

Histological examination of the biceps sheath revealed membranous tissue consisting of loose soft tissue with fat and blood vessels. Synovial tissue was also identified. The sheath was seen to loosely attach to the biceps tendon, with a more intimate attachment to the periosteum.

The mean force to pull the long head of biceps tendon out of the sheath 102.7 N (range 17.4 N–227.6 N)

Discussion: The biceps sheath is a consistent structure intimately associated with the biceps tendon. It appears to contain blood vessels which provide nutrition to the tendon, similar to the vincula of flexor digitorum pro-fundus. Mechanical testing reveals that a substantial force is sometimes required to pull the biceps tendon from the sheath. This may explain why biceps tenotomy does not routinely result in a “Popeye” biceps.

Introduction: Repair of chronic Achilles tendon rupture is technically complex. Flexor Hallucis Longus (FHL) and Peroneus Brevis (PB) Tendon transfers have been described, but the mechanical properties of these tissues have not been well reported.

Methods: 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.

Results: 51 tendons were harvested. 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.

Conclusions: 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.

Lacerations of the FDP tendon in zone one may be reattached to bone with a modified Bunnell pullout suture or with suture anchors. Eleven cadaveric fingers were submitted to cyclical testing of five hundred cycles with either a modified Bunnell pullout suture of 3-0 polypropylene or a micro-Mitek suture anchor with 3-0 Ethibond. Gap formation was 6.6mm in the modified Bunnell group and 2.0mm in the micro-Mitek group (p< 0.001). Load to failure was 37.6N in the pullout group and 28.5N in the anchor group (p< 0.005). Gap in the pullout group and low failure load in the anchor group are of concern.

Distal zone one FDP tendon lacerations are usually re-attached to bone by a modified Bunnell pullout suture of 3-0 polypropylene. This treatment may lead to moderate to severe losses of DIP joint motion in up to 50% of patients. Suture anchors have recently been introduced as a fixation alternative. Cyclical testing simulating five days of a passive mobilisation protocol was used to compare the Micro-Mitek anchor to the modified-Bunnell pullout suture in FDP tendon fixation.

Eleven cadaveric fingers FDP tendons were repaired to bone using a modified Bunnell pullout suture of 3-0 polypropylene or a micro-Mitek anchor with 3-0 Ethibond. Testing was done from 2N to 15N at 5N/sec, for a total of five hundred cycles. Gap formation at the tendon bone interface was measured. Load-to-failure was performed on all specimens.

No specimens failed during cyclic testing. Gap formation was 6.6mm (SD 1.2, range 4.9–8.2mm) and 2.0mm (SD = 0.4, range 1.7–2.7mm) for the pullout technique and the micro-Mitek anchor repair respectively (p< 0.001). Load to failure data was 37.6N (SD 4.7, range 31.8–45.1N) for the pullout group and 28.5N (SD 4.0, range 21.8–33.4N) for the micro-Mitek group (p< 0.005).

This data suggests that both fixation techniques may be adequate to sustain five days of simulated passive rehabilitation therapy. Significant gap formation in the modified Bunnell pullout group is of concern although this needs to be correlated in the clinical setting. The lower failure rate of the micro-Mitek group may leave a narrow margin of safety for passive rehabilitation.

Background: The Profix Total Knee Arthroplasty (Smith and Nephew, Memphis, USA) is designed to replace less bone than is resected from the posterior femoral condyles, and as a consequence the posterior condylar offset is reduced. The net effect of this is to increase the flexion gap with no effect on the extension gap. This is a deliberate design philosophy aimed at increasing postoperative flexion. This prospective cohort study has tested this theory.

Methods: 60 patients underwent primary posterior cruciate retaining (CR) TKA using this prosthesis. A matched group of patients, employing a different CR prosthesis which replaces excised bone in full, served as historical controls. Intra-operative measurements were made of the posterior condylar bone resected in each case. These measurements were then correlated with the flexion achieved both intra-operatively and at 6 months post-operatively.

Results: A positive correlation between pre-operative and post-operative flexion was found. However, there was no correlation between the relative increase in flexion gap secondary to the reduction in posterior offset and the resulting flexion range.

Conclusion: Post-operative flexion range is not increased by the resection of more bone from the posterior femoral condyles than is replaced by the prosthesis in TKA. The loss of bone stock will have implications for revision surgery and should be avoided.

Introduction and Aims: Adipose-derived stem cells (ADSCs) are capable of osteogenic differentiation under appropriate conditions in vitro (1). In this study we demonstrate the differences and similarities of the healing potential of ADSCs against the bone marrow-derived stem cell population (BMSCs) in the critical size ovine cancellous defect model, healed with culture expanded autologous stem cells from adipose tissue (ADSCs).

Method: Bone marrow aspirates and subcutaneous adipose tissue were harvested from 42 adult wethers. The population of stromal cells was derived from both tissues. Populations of bone marrow cells and adipose stromal cells were expanded in culture and stimulated with osteogenic medium for seven days. Cultured cell populations were harvested, mixed with a hydroxy-apatite carrier (Pro-Osteon 200R) and deposited into bilateral medial femoral condyle confined cancellous defect. Seven groups were examined: Bone graft+ ADSCs, Bone graft+ BMSCs, Carrier + ADSCs, Carrier+ BMSCs, Bone graft, Carrier, Empty defect. Two week, four week and eight week time-points were examined.

Results: All specimens were decalcified and five μm histological slides were stained using H& E and Masson’s Trichrome. Histomorphometry analysis on Masson’s Trichrome stained slides was performed using colour threshold-based software Bioquant Nova 6.50.10. Immunohistochemical staining for BMP4 and BMP7 and their downstream regulators: Smad4 and CBFA1 were evaluated in the defect area and graded in a blind fashion by two trained observers. There was a progressive and time-dependent increase in woven bone formation in the defects treated with ADSCs across all time points. The amount of bone formed in this group was comparable with the amount formed by the use of BMSCs.

Conclusion: The results of this study support the hypothesis that seeding porous hydroxyappatite with ADSCs does enhance bone formation and defect healing.

Introduction Zone 2 flexor tendon repairs can require ‘venting’ or partial resection of the A2 and/or A4 pulleys. We test a new technique where the pulley is divided and repaired with a V-Y plasty, increasing the pulley circumference. This allows access to perform the repair and/or permits free tendon gliding post-repair.

Methods Two groups of A2 and A4 pulleys from cadaveric fingers were divided and repaired in a V-Y fashion such that the circumference of the pulley tunnel was increased. The fingers were then mounted onto custom-made jigs and tested using a materials testing machine. One group had the A2 pulley assessed for changes in work of flexion by testing both before and after V-Y plasty. The second group had both the A2 and A4 pulleys tested for load to failure during functional loading. Biomechanical testing was performed.

Results There was a significant reduction in work of flexion after V-Y pulley expansion procedures were performed. Loads to failure for the A2 and A4 pulleys were in excess of 400% and 200% greater than one would expect in-vivo during a post-operative active mobilisation protocol. V-Y tendon pulley expansion increases the tunnel size while providing a mechanically sound pulley. It also maintains the pulley length and its coverage of the underlying tendon.

Conclusions This technique provides surgeons with an attractive alternative to simply ‘venting’ or resecting an otherwise troublesome pulley.

Introduction VEGF is a well known angiogenic peptide which has been shown to be central to endochondral ossification. Secondary fracture healing involves a combination of intramembranous and endochondral ossification. VEGF has been recently shown to be chemotactic for osteoblasts and chondroclasts. We therefore set out to examine the temporal and spatial expression of VEGF and its receptors in fracture healing. We report here the preliminary findings of our study.

Methods A closed mid-shaft fracture was produced in the right femora of nine 12 week old Sprague Dawley rats, stabilised by an intramedullary K-wire. The rats were sacrificed at one, two and four weeks. Through the use of immunohistochemistry, RT-PCR and in situ hybridisation.

Results We show that at each of the time points, VEGF is expressed in all of the cell types involved in fracture healing; the inflammatory cells, the osteo-progenitor cells,chondroblasts,chondrocytes,osteoblasts and osteoclasts as well as fibroblasts. We further show that there is persistent expression of VEGF in chondrocytes at four weeks.

Conclusions Our findings are consistent with the hypothesis that events in fracture healing reflect the processes that take place at the growth plate during embryonic development.

Introduction Recent publications have confirmed that as many as one in four retrieved femoral heads can be significantly contaminated with potential pathogens. Reports from the Centre for Disease Control in Atlanta, Georgia have described fatal outcomes from the unwanted transmission of bacterial disease with inadequately processed allograft materials. Surgeons requesting non terminally sterilised bone refer to theoretical biological and biomechanical deleterious effects of gamma irradiation. This study examines the accuracy of those claims.

Methods We have investigated the effects of varying levels of gamma irradiation (0kG, 15kG and 25kG) on the biological competence of morsellised allograft bone and its associated biomechanical impaction qualities. The biological study has used an in vivo model (nude rat) to quantify the effects of gamma irradiation on osteoinduction and osteoconduction. An in vitro impaction routine has been used to measure compaction, impaction and stiffness in the allograft product.

Results There were no statistical differences in the biomechanical or biological properties of the 0kG and 15kG specimens (P< 0.05). Gamma irradiation at the 25kG level resulted in an allograft product of higher biomechanical stiffness, unchanged osteoinductivity and slightly lower osteoconductivity (P< 0.05).

Conclusion Terminal gamma irradiation of 15kG reduces the risk of bacterial transmission with allograft products. It does not alter the efficacy of the allograft at biological and biomechanical levels. Gamma irradiation represents the mainstay of sterilisation of musculoskeletal allograft materials. Australian practices appear to be leading an international trend.

In relation to the conduct of this study, one or more the authors have received, or are likely to receive direct material benefits.

Introduction The four strand cruciate tendon repair has been described as the ideal technique, as it combines simplicity with the biomechanical advantages of four-strands. We wanted to determine if increasing the size of the locking loop increases the repair strength, and the gain in biomechanical integrity that various peripheral techniques provides.

Methods Forty-eight deep flexor tendons harvested from sheep hindlimbs were randomly divided into six groups of eight. All tendons were sharply transected. Initially, four groups were repaired using the cruciate core technique without a peripheral suture. The locking loops were set at 50%, 33%, 25%, or 10% of the volar CSA and then tested to failure. The final two groups of tendons were repaired using the established optimal locking loop size. These two groups were combined with either the simple running or the interlocking horizontal mattress (IHM) peripheral suture. These were then tested to failure and biomechanically assessed.

Results Repairs with locking loops of 25% had the greatest biomechanical properties; with load to two millimetre gap formation, load to failure and stiffness of 10N, 46.3 and 3.9N/mm respectively. Those with a 33%, 50% and 10% locking loops followed this. Those with 10% locking loops failed due to the suture material sliding out of the tendon. All other groups failed by suture breakage. Using the cruciate core technique with a 25% volar CSA locking loop, the load to two millimetre gap formation, load to failure and stiffness was 32.9N, 47.2N, and 7.6N/mm respectively when combined with the simple running peripheral suture and 46.4N, 79.4N and 9.9N/mm respectively when combined with the IHM repair. The IHM/cruciate combination was significantly better than the simple running/cruciate repair. Using the IHM technique in your tendon repair, this study demonstrates that the peripheral suture can provide approximately 75%, 40% and 60% of the total load to two millimetre gap formation, load to failure and stiffness respectively.

Conclusions Unlike the Kessler technique, increasing the size of the locking loop in the cruciate method decreases the repair strength. The ideal sized bite seems to be approximately 25% of the volar cross-sectional area. Additional, the peripheral suture is biomechanically vital to the integrity of the repair.

In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source.

Introduction Determining the extent of dynamic creep of a suture gives insight into the potential for formation of a flexor tendon repair site gap, with less creep having a positive benefit. We wanted to determine the dynamic creep of various suture materials using a cyclical testing protocol that simulates 30 days of active mobilisation.

Methods Four-strand loops, 20 mm in length, were created using Prolene, Ticron, Ethibond, and Mersilene (n=8 per group). Samples were loaded between 3.5N and 35N at 10 cycles per minute for 3000 cycles using a materials testing machine. All testing was conducted in phosphate buffered saline at 37° celsius. The dynamic creep was determined for each group. A separate group of suture loops were also created for load to failure testing. All data was analysed using ANOVA on SPSS software.

Results The loads to failure were 55.4, 65.5, 64.4 and 73.1N for Prolene, Ticron, Ethibond and Mersilene respectively. During cyclical testing, only one Prolene sample survived, with failure occurring after a mean of 1182 cycles (range 574 to 2660). Of those that failed, the mean creep was 3.80 mm (SD=0.51). In contrast, no specimens in the other groups failed, with a dynamic creep of 0.44 mm (SD=0.19), 0.32 mm (SD=0.17), and 0.28 mm (SD=0.07) for Ticron, Ethibond and Mersilene respectively.

Conclusions Regardless of your chosen suture technique for flexor tendon repairs, this study suggests that the suture material itself can play an important role in the eventual outcome. These results should be kept in mind when deciding on the suture material for your repairs.

Introduction The aim of this study was to determine the biomechanical properties of various combinations of four-strand core and peripheral suture techniques used in flexor tendon repairs.

Methods Seventy-two sheep flexor tendons were randomly divided into nine groups of eight. Tendons were sharply transected and repaired using three different four-strand core techniques: cruciate, modified-Kessler, and the modified Becker. These were combined with three different peripheral techniques: simple running, cross-stitch, and the recently described interlocking horizontal mattress (IHM). Tendons from these nine groups were loaded onto a materials testing machine and tested to failure using a crosshead speed of 20 mm/min. Load to two millimetre gap formation, load to failure, and stiffness was assessed. Data was analysed using ANOVA on SPSS for Windows.

Results For any given type of peripheral suture, no significant difference in biomechanical properties was found between the three core repair techniques. The only factor causing a significant difference in strength of the tendon repair was the type of peripheral suture technique used. Repairs with an IHM technique had significantly greater loads to 2 mm gap formation, load to failure, and stiffness, compared to the cross-stitch and simple running methods.

Conclusions This study demonstrates the superior biomechanical properties of the IHM technique. Increasing core suture complexity does not appear to have a significant impact on the overall mechanical integrity of the repair. These results should be considered when adopting a preferred repair technique.

Introduction: The realisation that the medical and lateral menisci of the knee have important load-bearing and stability functions has stimulated orthopaedic surgeons to aim for preservation rather than excision if at all possible. The absence of meniscal tissue has been shown to increase load through the articular cartilage and ultimately accelerate the process of osteoarthritic degeneration. A major limitation is the relative avascularity of a large portion of the normal meniscus. McAndrews and Arnoczky reported in 1996 that repair of the white-white and even red-white zone remains a challenge. Monobutyrin is an angiogenic factor that has been used in the stimulation of healing burns and we hypothesized that it may have a positive effect on the healing meniscus.

The aim of the study was to determine the effects of 0 Ticron suture soaked in polyhydroxybutyrate (PHB) on the histological and mechanical properties of healing meniscal tears in the red-white zone in an established animal model.

Methods: A bilateral medical meniscal incision model was used in 21 adult sheep.

Results: We confirmed that the PHB had no deleterious effects on the mechanical properties of the suture prior to commencing the surgery. Mechanical testing of the menisci at the set time-points demonstrated a significantly stronger repair in the PHB-soaked group. Macroscopic appearances were graded and found to be improved with PHB soaked sutures. On histological examination there were features suggestive of a more intense healing response including angiogenesis.

Conclusions: We have concluded that the use of butyric acid has no deleterious effects on the mechanical properties of the suture used and has positive effects on meniscal healing. We recommend further examination of this exciting development.

The use of plates and screws for the treatment of certain metacarpal fractures is well established. Securing plates with bicortical screws has been considered an accepted practice. However, no study has questioned this.

This study biomechanically assessed the use of bicortical versus unicortical screws in metacarpal plating. Eighteen fresh frozen cadaveric metacarpals were subject to midshaft transverse osteotomies and randomly divided into two groups. Using dorsally applied Leibinger 2.3mm 4 hole plates, one group was secured using 6mm unicortical screws, while the second group had bicortical screws. Metacarpals were tested to failure using a four point bending protocol in an apex dorsal direction on a servo-hydraulic testing machine with a 1kN load cell. Load to failure, rigidity, and mechanism of failure were all assessed.

Each group had three samples that did not fail after a 900 N load was applied. Of those that failed, the mean load to failure was 596N and 541 N for the unicortical and bicortical groups respectively. These loads are well in excess of those experienced by the in-vivo metacarpal. The rigidity was 446N/mm and 458N/mm of the uni-cortical and bicortical groups respectively. Fracture at the screw/bone interface was the cause of failure in all that failed, with screw pullout not occurring in any.

This study suggests that there may be no biomechanical advantage in using bicortical screws when plating metacarpal fractures. Adopting a unicortical plating method simplifies the operation, and avoids potential complications associated with overdrilling and oversized screws.

The behaviour of two different methods of reattachment of the flexor digitorum profundus tendon insertion was assessed. Cyclical testing simulating the first 5 days of a passive mobilisation protocol was used to compare the micro Mitek anchor to the modified-Bunnell pull-out suture. Twelve fresh-frozen cadaveric fingers were dissected to the insertion of the FDP tendon. The FDP insertion was then sharply dissected from the distal phalanx and repaired using one of two methods: group 1 -modified Bunnell pullout suture using 3/0 Prolene; group 2 micro Mitek anchor loaded with 3/0 Ethibond inserted into the distal phalanx. Each repaired finger was mounted on to a material testing machine using pneumatic clamps. We cyclically tested the repair between 2N and 15N using a load control of 5N/s for a total of 500 cycles. Gap formation at the tendon bone interface was measured every 100 cycles.

No specimens failed during cyclical testing. After 500 cycles, gap formation of the tendon-bone interface was 6.6mm (SD = 1.2mm), and 2.1 mm (SD = 0.3mm) for the pullout technique and the micro Mitek anchor repair respectively. Concerns related to suture anchors, such as anchor failure or protrusion, joint penetration, and anchor-suture junction failure, were not encountered in this study.

Cyclical loading results suggest that the repair achieved with both methods of fixation is sufficient to avoid failure. However, significant gap formation at the tendon-bone interface in the modified Bunnell group is of concern, suggesting it may not be the ideal fixation method.

Fracture healing involves many local and systemic regulatory factors. Progress in identifying signaling events downstream has been made with the discovery of a novel family of proteins, the Smad, as TGF-ß/activins/BMPs signal transducers. Smads are the vertebrate homologs of Mad (Mothers against decapentaplegic) gene from Drosophila and Sma genes from Caenorhabditis elegans. Smad-1, -2, -3, -5, -8 and -9 belong to the receptor-regulated class (R-Smad) which are activated by the TGF-ß type I and II receptors, forming heteromers with the common-mediator class (Co-Smad): Smad-4. Smad-6 and -7 (Anti-Smad) perform a negative regulatory or balancing role. Smad-2 and -3 regulate TGF-ß/activin effects, whilst Smad-1 and -5 work with BMPs. This study investigated the expression and localization of Smad proteins (Smad 1–6) and BMP-4 and -7 during fracture healing.

Eighteen 3-month old female CD-COB rats were used. A standard closed fracture was made in the mid-shaft of right femur using a 3-point bending device. The left limb served as the non-fracture control. The rats were divided into 3 groups (6 per group) and sacrificed at day 3, 10 and 28 after fracture. The femurs were harvested, fixed in buffered formalin for 48 hours and decalcified with 10% formic acid-formalin solution. The decalcified tissues were embedded in paraffin and 5μm sections were cut onto silane-coated slides. Representative slides from each block were stained with routine haematoxylin and eosin (H& E). Sections were cut for immunohistochemistry for protein marker expression by a standard procedure for Smads and BMP 4 and 7. Sections were viewed and analysed by colour video image analysis using a 40x objective, a 10x eyepiece, and a fixed frame of 128 × 128 pixels (49152.0 μm²). Ten fields per slide were examined.

Smad proteins (Smads 1, 4, and 6) were expressed during the early stages (day 3) of fracture healing by bone marrow stromal cells, osteoblasts, fibroblasts and chondrocytes located in the intramembranous and endochondral ossification regions around the fracture site. Differential expressions of individual Smads, particularly Smad 1 and Smad 6, at different time-points (Smad-1 was higher than Smad-6 at day 3, whilst Smad-6 was much higher than Smad-1 at day 10) suggest that Smad proteins are not simply BMP signal transducers. Smads may also be responsible for up- and/or down-regulation of transcriptional events during the intramembranous and endochondral ossification. Smad-4, a Co-SMAD, expression newly formed bone and cartilage suggests an additional function beyond the signal transduction in rat fracture healing. BMP-4 and BMP-7 were highly expressed at day 3 and 10. BMP-7 expression was greater than BMP-4 at day 3 but switched by day 10 (BMP-4 > BMP-7). Smads represent a new level where specific therapeutic strategies can be targeted considering the interactions with a number of BMPs.

Resorbable porous ceramics derived from chemically converted corals have been used successfully as bone graft substitutes for many years. Converted corals provide a 3D porous architecture that resembles cancellous bone with a pore diameter of 200–700 μm. The success of these corals as a bone graft substitute relies on vascular ingrowth, differentiation of osteoprogenitor cells, remodelling and graft resorption occurring together with host bone ingrowth into the porous microstructure or voids left behind during resorption. The resorption rate of the coral can be controlled by partial conversion to provide a hydroxyapatite (HA) layer via thermal modification. This study examined the resorption rates and bone formation of partially converted corals in a bilateral metaphyseal defect model.

Bilateral defects (5 mm x 15 mm) were created 3 mm below the joint line in the proximal tibia of 41 skeletally mature New Zealand white rabbits following ethical approval. Two variations of a calcium carbonate–HA coral (Pro Osteon 200 R, Interpore-Cross International, Irvine, CA) were examined with different HA thickness (200R; 14% or 200 RT; 28%). Empty defects (negative control) or defects filled with morcellised bone autograft from the defect sites (positive control) were performed. The tibiae were harvested at 6, 12, 24, 36 or 52 weeks, radiographed (standard x-rays and faxitron) in the anteroposterior and lateral planes. Tibias were processed for torsional testing and quantitative histomorphometry using back scattering scanning electron microscopy. Four additional rabbits were killed at time zero to determine the mechanical properties of the intact tibia (n=6 tibias) and 2 for tibias for time zero histomorphometry. Data were analysed using a 3-way analysis of variance.

No clinical complications were encountered in this study. Radiographic assessment revealed a progression in healing, implant resorption and bone infiltration. Cortical closure in the 200 R and 200RT treated defects was noted by 24 weeks. All specimens failed in torsional testing with a spiral fracture initiating at the distal defect site and extending into the distal diaphysis. Torsional properties reached intact control tibia levels by 24 weeks in both groups. No significant differences were noted between 200 R and 200 RT based on torsional data. SEM revealed progressive resorption of the calcium carbonate core of the 200 R and 200 RT with time, infiltration of bone and ingrowth to the HA layers. Time and measurement site (cortical versus cancellous) were significant for implant resorption, bone, and void. The thinner HA layer (200 R) resorbed more quickly compared to the thicker layer (200 RT) in the canal as well as cortical sites. Increased bone and decreased void were noted at the cortex measurement sites in the 200 R group at 24 weeks and in the 200 RT group at 12 and 24 weeks (p< 0.05). Implants were nearly completely resorbed by 52 weeks with only a few percent of implant remaining.

Clinical implantation represents the ultimate experiment of any component and often demonstrates areas of strengths and weaknesses not predicted from in vitro testing. Mobile bearing knees incorporate an additional articulating interface between the flat distal PE insert and a highly polished metal tibial tray. This can allow the proximal interface to retain high conformity whilst leading to reduced stresses at the bone – prosthesis interface by permitting complex distal interface compensatory motion to occur (rotation and/or translation). Retrieval reports on many of the new generation of mobile bearing implants remains scarce. This study presented a retrieval analysis of 9 mobile bearing inserts that had be in situ for less than 24 months.

Nine cemented mobile bearing implants (6 AP Glide, 1 LCS, 1 MBK and 1TRAK) were received into our Implant Retrieval Program. The femoral component, tibial tray and PE insert were macroscopically examined under a stereo-zoom microscope for evidence of damage. The PE inserts were graded for wear based on optical and SEM assessments. The proximal and distal surfaces of the PE inserts were subsequently assessed for surface roughness following ISO 97 (Ra and Rp) using a Surfanalyzer 5400 (Federal Products, Providence, RI). Virgin, unused PE inserts were analysed and served as a comparison to the retrieved implants.

Time in situ time for these implants ranged from 6 months to 24 months (mean 18.6). The implants were revised for instability and pain (AP glide) or dislocation (TRAK). Damage to the femoral components, in general, was minimal with some evidence of a transfer film of PE. The proximal surface of the tibial trays presented evidence of PE transfer as well as some scratches but in general were intact. The proximal PE and distal PE articulating surfaces demonstrated significant areas of damage due to third body wear which was identified on EDAX to be PMMA. Areas of burnishing were also present at the proximal and distal interface. The damage, in part, correlated with the complex kinematics of each design.