This case highlights the close association between osteo-fibrous dysplasia (OFD) and adamantinoma, drawing attention to the role for more radical treatment options when treating OFD. We discuss the advancements in joint-sparing endoprostheses using bicortical fixation. Finally we describe a unique biomedical design allowing for manufacture of an end cap to allow amputation through a custom made joint-sparing proximal tibial replacement as opposed to an above knee amputation. A 37 year old presented 7 years ago having sustained a pathological fracture of her tibia. Subsequent biopsy revealed OFD, curettage with bone graft was performed. She later developed recurrence, two percutaneous biopsies confirmed OFD. 6 years following her initial diagnosis she was referred to RNOH with further recurrence, a biopsy at this stage revealed a de-differentiated adamantinoma. A joint-sparing proximal tibial replacement was performed and adjuvant chemotherapy administered, she remained well for one year. Recurrence was noted at the distal bone-prosthesis interface, histology revealed a high grade dedifferentiated osteosarcoma, limb preservation was not deemed possible and an amputation was performed through the prosthesis. The proximal tibial device was uncoupled leaving a residual 7 cms insitu, a small custom made end cap was attached to the remaining prosthesis and a myocutaneous flap fashioned over it, this ultimately enabled the patient to mobilise well with a below–knee orthotic device. This case highlights the need for more radical surgery when treating cases of OFD and the relationship between OFD and adamantinoma. It also introduces a joint-sparing proximal tibial device for use in proximal tibial tumours that do not invade the proximal tibial metaphysis. The biomechanical design solution has given us the unique option of preserving the knee joint allowing the patient a below knee amputation whereas previously an above knee amputation would have been performed thereby significantly reducing her functional outcome

Trabecular bone is a multiscale hierarchical composite material that is known to display time-dependant properties. However, most biomechanical models treat this material as time independent. Time-dependant properties, such as creep and relaxation, are thought to play an important role in many clinically relevant orthopaedic issues: implant loosening, vertebral collapse, and non-traumatic fractures. In this study compressive multiple-load-creep-unload-recovery (MLCUR) tests were applied to human trabecular bone specimens. 15 female femoral heads were harvested, with full ethical approval and patient consent, at the time of total hip replacement. Central cores were extracted and cut parallel under constant irrigation. Specimens were embedded in end caps using surgical cement, an epoxy tube was secured around the end caps and filled with phosphate buffered saline (PBS) to ensure the specimens remained hydrated throughout. Embedded samples were scanned by microCT (SkyScan 1172, Bruker) at a resolution of 17µm to determine microarchitecture. Bone volume fraction (BVF) was used to represent microarchitecture. Specimens had an effective length of 16.37mm (±1.90SD) with diameter of 8.08mm (±0.05SD), and BVF of 19.22% (±5.61SD). The compressive MLCUR tests were conducted at 5 strain levels, 2000µε, 4000µε, 6000µε, 8000µε and 10000µε. At each strain level, the load required to maintain each strain was held for 200s (creep) then unloaded to 1N for 600s (recovery). The instantaneous, creep, unloading and recovered strains can be easily obtained from the strain-time curves. Stress-strain plots revealed the Young's modulus. Data was modelled using line of best fit with appropriate curve fitting. R2 values were used to indicate association. Mechanical testing demonstrated the expected time independent relationship between BVF and stiffness: higher stiffness was found for specimen with higher BVF and this was consistent for all strain levels. Creep strain was found to depend on instantaneous strain and BVF. At low levels of instantaneous strain, there was a greater amount of creep strain in low BVF samples (R2 = 0.524). This relationship was no longer apparent at higher strain levels (R2 = 0.058). Residual strain also depended on the applied instantaneous strain and BVF: at low levels of strain, residual strain was similar with all BVF (R2 = 0.108) and at high levels of strain, residual strain was greater in low BVF samples (R2 = 0.319). The amount of instantaneous strain applied to each sample is constant, variations in stiffness result in different applied loads. In low BVF bone, the stiffness is also low, therefore the stress required to reach designed strain is also lower: yet, there is more creep and less recovery. We have demonstrated that even at loads below recognised yield levels, time-dependence affects the mechanical response and residual strain is present. In cases of low BVF, deflection due to creep, and increased irrecoverable strain could have clinically relevant consequences, such as implant loosening and vertebral collapse. The role of time-dependant properties of bone is seldom considered. This data could be developed into a constitutive model allowing these time-dependant behaviours to be incorporated in finite element modelling, leading to better predictions of implant loosening, especially for lower quality bone

Intramedullary nailing is acknowledged as a safe and effective mode of treatment for many tibial fractures. Implant removal is frequently indicated either as an elective procedure following union or because of problems such as infection or delayed fracture union. It is therefore essential that intramedullary rod removal should be reasonably straightforward and atraumatic. We describe three cases in which bony growth into the implant has made rod removal either difficult or impossible. We include photographs of two removed implants with clearly visible areas of osseo-integration with bony growth into the cannulation through the interlocking holes as well as radiographs demonstrating the same phenomenon. The average time between insertion and removal was 16 months. In all cases an end cap had been used such that insertion of the extraction device was straightforward but for two patients nail removal was extremely difficult due to bone ingrowth and in the third patient the nail had to be left in-situ. All three implants were made of titanium and the patients were all active young males. The authors have never encountered this problem with steel rods and speculate that the osteointegrative property of titanium is the major causative factor. We suggest that unremoved intramedullary rods represent a major risk in fracture management and that close monitoring of these implants should be undertaken

Introduction and Aims: A retrospective review of the medical records and radiographs of patients treated with operative fixation of two-part proximal humerus fractures was undertaken to compare the results of different modes of fixation. Comparison was made between ORIF with a blade plate, percutaneous Kirschner wire fixation, and intramedullary nail fixation utilising a Polarus nail. Method: Thirty-six patients were treated with intramedullary fixation, 11 with blade plate fixation and 10 with percutaneous fixation, utilising Kirschner wires. Union rates were 34/36 (94%) for the Polarus nail, 9/10 (90%) for K-wire fixation and 9/11 (82%) for blade plate fixation. Time to union averaged 12.4 weeks for the Polarus nail, 11 weeks for K-wire fixation and 21 weeks for blade plate fixation. Average active shoulder range of motion in forward flexion/abduction were 125/118 degrees for intramedullary nail, 132/132 degrees for the blade plate and 112/111 degrees for patients treated with K-wire fixation. Results: The major discrepancy in comparison of the different modes of fixation was in the complication rate. Ten complications occurred in the group treated with intramedullary fixation. These included one non-union, one painless fibrous non-union and back out of the proximal interlocking screw in eight patients, five of which required screw removal. Seven of 11 patients treated with blade plate fixation experienced complications, including two non-unions, two malunions, two with functionally limiting heterotopic ossification, one arthrofibrosis and one with persistent pain. The complications associated with percutaneous Kirschner wire fixation included one non-union, two malunions, four developed functionally limiting heterotopic ossification, five incidences of early pin removal secondary to pin migration, one arthrofibrosis requiring surgical intervention and one infection requiring surgical irrigation and debridement. Conclusion: Results comparable in all groups. Fewer complications seen with intramedullary fixation. Majority of complications with Polarus nail related to backing out of proximal interlocking screw. Modification of implant to include end cap, which locks the proximal screw seems to eliminate complication. Results indicate that intramedullary nail fixation is superior to blade plate fixation or pecutaneous Kirschner wire fixation for two-part proximal humerus fractures