Hip resurfacing may be a useful surgical procedure when patient selection is correct and only implants with superior performance are used. In order to establish a body of evidence in relation to hip resurfacing, pseudotumour formation and its genetic predisposition, we performed a case-control study investigating the role of HLA genotype in the development of pseudotumour around MoM hip resurfacings.

All metal-on-metal (MoM) hip resurfacings performed in the history of the institution were assessed. A total of 392 hip resurfacings were performed by 12 surgeons between February 1st 2005 and October 31st 2007. In all cases, pseudotumour was confirmed in the preoperative setting on Metal Artefact Reduction Sequencing (MARS) MRI. Controls were matched by implant (ASR or BHR) and absence of pseudotumour was confirmed on MRI. Blood samples from all cases and controls underwent genetic analysis using Next Generation Sequencing (NGS) assessing for the following alleles of 11 HLA loci (A, B, C, DRB1, DRB3/4/5, DQA1, DQB1, DPB1, DPA1). Statistical significance was determined using a Fisher's exact test or Chi-Squared test given the small sample size to quantify the clinical association between HLA genotype and the need for revision surgery due to pseudotumour.

Both groups were matched for implant type (55% ASR, 45% BHR in both the case and control groups). According to the ALVAL histological classification described by Kurmis et al., the majority of cases (63%, n=10) were found to have group 2 histological findings. Four cases (25%) had group 3 histological findings and 2 (12%) patients had group 4 findings. Of the 11 HLA loci analysed, 2 were significantly associated with a higher risk of pseudotumour formation (DQB1*05:03:01 and DRB1*14:54:01) and 4 were noted to be protective against pseudotumour formation (DQA1*03:01:01, DRB1*04:04:01, C*01:02:01, B*27:05:02).

These findings further develop the knowledge base around specific HLA genotypes and their role in the development of pseudotumour formation in MoM hip resurfacing. Specifically, the two alleles at higher risk of pseudotumour formation (DQB1*05:03:01 and DRB1*14:54:01) in MoM hip resurfacing should be noted, particularly as patient-specific genotype-dependent surgical treatments continue to develop in the future.

Revision hip arthroplasty requires a comprehensive appreciation of abnormal bony anatomy. Advances in radiology and manufacturing technology have made three-dimensional representation of actual osseous anatomy obtainable. These models provide a visual and tactile reproduction of the bony abnormality in question.

Life size three dimensional models were manufactured from CT scans of two patients. The first had multiple previous hip arthroplasties and bilateral hip infections. There was a pelvic discontinuity on the right and a severe postero-superior deficiency on the left. The second patient had a first stage revision for infection and recurrent dislocations. Specific metal reduction protocols were used to reduce artefact. The dicom images were imported into Mimics, medical imaging processing software. The models were manufactured using the rapid prototyping process, Selective Laser Sintering (SLS).

The models allowed accurate templating using the actual prosthesis templates prior to surgery. Acetabular cup size, augment and buttress sizes, as well as cage dimensions were selected, adjusted and re-sterilised in advance. This reduced operative time, blood loss and improved surgical decision making. Screw trajectory simulation was also carried out on the models, thus reducing the chance of neurovascular injury.

With 3D printing technology, complex pelvic deformities can be better evaluated and can be treated with improved precision. The life size models allow accurate surgical simulation, thus improving anatomical appreciation and pre-operative planning. The accuracy and cost-effectiveness of the technique were impressive and its use should prove invaluable as a tool to aid clinical practice.

Introduction

Osteoporosis is a common skeletal disorder characterised by a reduced bone mass and a progressive micro-architectural deterioration in bone tissue leading to bone fragility and susceptibility to fracture. With a progressively aging population, osteoporosis is becoming an increasingly important public health issue. The Wnt/β-catenin pathway is a major signalling cascade in bone biology, playing a key role in regulating bone development and remodelling, with aberrations in signalling resulting in disturbances in bone mass.

Osteoporosis is a common skeletal disorder characterised by a reduced bone mass and a progressive microarchitectural deterioration in bone tissue leading to bone fragility and susceptibility to fracture. The Wnt/β-catenin pathway is a major signaling cascade in bone biology, playing a key role in regulating bone development and remodeling, with aberrations in signalling resulting in disturbances in bone mass.

Our objectives were to assess the gene expression profile of primary human osteoblasts (HOBs) exposed to dexamethasone with a view to identifying key genes driving bone mass regulation and to assess the effects of the Wnt antagonist Dickkopf-1 (Dkk1) on the bone profile of primary human osteoblasts exposed in vitro to dexamethasone.

HOBs were cultured in vitro and exposed to 10–8M dexamethasone over a time course of 4hr, 12hr and 24hr. RNA isolation, cDNA synthesis, in vitro transcription and microarray analysis were performed. Microarray data was validated by quantitative real time RT-PCR. Dkk1 expression was silenced using small interfering RNA (siRNA). Quantitative RT-PCR was performed to confirm gene knockdown. Control and Dex-treated HOBs were compared with respect to bone turnover. Markers of bone turnover analyzed included alkaline phosphatase activity, calcium deposition, osteocalcin expression, along with cell proliferation and cellular apoptosis.

Global changes in HOB gene expression were elicited by dexamethasone.

Development associated gene pathways were co-ordinately dysregulated with the expression profile of key genes of the Wnt Pathway significantly altered. Dkk1 expression in HOBs was increased in response to dexamethasone exposure with an associated reduction in alkaline phosphatase activity, calcium deposition and osteocalcin expression. Silencing of Dkk1 expression, as confirmed by quantitative RT-PCR, was associated with an increase in alkaline phosphatase activity and calcium deposition, along with increased cell proliferation and reduced cellular apoptosis.

Dkk1 is an antagonist of Wnt/β-catenin signalling and plays a key role in regulating bone development and remodeling. Silencing the expression of Dkk1 in primary human osteoblasts has been shown to rescue the effects of dexamethasone-induced bone loss in vitro. The pharmacological targeting of the Wnt/β-catenin signaling pathway offers an exciting opportunity for the development of novel anabolic bone agents to treat osteoporosis and disorders of bone mass.

Introduction: The Sheehan total knee endoprosthesis has been widely used since 1971. It incorporates a semi-constrained hinge with intramedullary stems cemented into the femur and tibia for fixation. This gives a stable polycentric knee mechanism that allows axial rotation as well as simulating other knee movements. This design has certain disadvantages including the large amount of bone resected for implantation and its constrained nature which predisposes to loosening. Revision rate of up to 30% have been reported. We discuss the difficulties encountered during revision and the techniques that need to be used to overcome these.

Patients and methods: We reviewed the records of 21 patients who required revision of Sheehan TKRs between 1987 and 2001. Reason for revision was recorded and all patients were scored using the Knee Society Index of Severity Instrument (Saleh et al CORR 2001). The operative details were examined and technical difficulties at the time of surgery recorded. Per-operative and early post-operative complications related to the revision procedure were also noted.

Results: The average age of patients requiring revision was 65 years old (range 39–79). The average time from primary surgery to revision was 16.2 years (range 8–20 years). The reasons for primary surgery were rheumatoid arthritis in 9 and osteoarthritis in 12. Revision surgery was required for pain associated with tibial subsidence and painful bone on bone contact in 14.Two patients had dislocation of their tibial on femoral component. One patient had a one-stage revision for infection and one had revision for a fractures tibial intramedullary stem. Three patients had revision to anterior flanged femoral components to facilitate patellar resurfacing for patello-femoral pain. The overall complication rate approached 80%!

Discussion: While the Sheehan TKR was of great benefit to a large number of patients it is not without its problems. These results show that prostheses coming to revision did not necessarily fail early and so with time we can expect more to present for revision. The high complication rate and the need for complex reconstructive techniques attest to the difficulty of revising these prostheses. Some of these problems are the legacy of the prosthetic design and should be borne in mind when taking on these cases.

Introduction and Aims: The aim of this study was to evaluate the role of Whole Body MR (WBMR) in the staging of Musculo Skeletal (MSK) tumors, on a premise that a single study might present an alternative to the traditional imaging.

Method: Forty-two patients were referred for MR evaluation for primary bone or soft tissue sarcomas. These studies were done between October 2001 and April 2003. Each patient had a WBMR, Localised MR, CXR and CT Thorax, and bone scan.

Results: In 42 patients screened, 32 had a primary malignant musculo skeletal tumor. There were 14 primary bone tumors and 18 soft tissue sarcomas. Of the 32 patients concordance between WBMR imaging and the other staging modalities was identified in 27 patients. Discordance was identified in five patients. Two lesions were identified on WBMR and not seen on other imaging modalities. Two lesions not identified by WBMR, subsequently seen on CT thorax. One lesion was not seen on WBMR but seen on localised MR. Eight of the 32 patients had pulmonary metastases. In these patients concordance between the WBMR and CT Thorax was identified in five of eight patients and discordance was identified in three of eight patients where nodules were identified on CT Thorax and not on WBMR. Four patients were noted to have osseous metastases, all seen on WBMR. One bone scan failed to pick up metastasis seen on WBMR. One patient was identified as having a soft tissue metastasis on Whole Body MR, which was not identified on the conventional CT Thorax.

Case studies:

Case 1: Metastatic Leiomyosarcoma

Case 2: Metastatic Ewings sarcoma

Case 3: Metastatic Epithelioid sarcoma

Conclusion: Whole body MR Scanning techniques allow whole body imaging in as little as eight minutes. It is a useful technique in staging and assessing total tumor burden, but still should be performed in conjunction with a CT Thorax.

Surgical treatment of complex deformities necessitates a detailed appreciation of the complex three dimensional abnormal anatomies involved. Preoperative planning for these complex cases traditionally involves x-ray and computerised tomography (CT). These modalities offer only two-dimensional images to represent three-dimensional anatomy. Advances in digital imaging have allowed three-dimensional reconstructions to be derived from CT images. These greatly improve understanding of complex deformities, but will never be able to replace the intuitive understanding that is gained by handling a physical model.

The Rapid Prototyping technique Selective Laser Sintering (SLS) is used in the industrial setting to manufacture prototype models from Computer Aided Designs (CAD). This technology can be utilised to convert CT images into accurate three-dimensional physical models of the human bony anatomy.

We present the use of SLS modelling to aid in the preoperative planning of complex reconstructive surgery in children. Cases include bladder exstrophy, developmental dysplasia of the hip and reconstruction of a complex elbow malunion.

The models provide invaluable visual and tactile information to the operating surgeon, accurately demonstrating the abnormal anatomy in an easily comprehensible manner. They allow estimation of the magnitude and degree of corrections necessary and evaluation of bony deficiencies.

Introduction: Articular fractures, especially in weight-bearing joints of the lower extremity, require anatomical reduction for good long-term function. If anatomic reduction is achieved 90% of patients have good results. Accurate anatomical reduction of acetabular fractures is made difficult y the complicated anatomy of the acetabulum and pelvis. Plain films and computerised tomography are very useful in the assessment, classification and planning for surgery of these fractures, but conventional imaging only provides two dimensional images of these fractures. While interpretation of traditional imaging techniques becomes better with experience novel techniques may assist in the understanding of these complex injuries. This project presents the use of three dimensional life size models which can be rapidly manufactured from CT scans to facilitate fracture classification and operative planning.

Patients and Methods: Standard 4 mm CT cuts were reformatted to 2 mm and saved as DICOM files for a series of 15 consecutive patients with complex acetabular fractures (not including isolated posterior wall injuries). These were imported into Mimic (Materialise) data conditioning software, which allowed manipulation and thresholding of images so that a three-dimensional computer model could be built. The data was exported to the Selective Laser Sintering (SLS) system and a life size three-dimensional model constructed. Three consultant orthopaedic surgeons and three senior trainees were asked to classify, using the system of Letournel, each fracture using 1) conventional radiographs (AP pelvis, Judet views and CT scans). 2) Using a model. As no absolute of fracture type was available the Kappa statistic was used to evaluate inter and intraobserver agreement. This compared an observed level of agreement with the level of agreement that would be expected by chance alone.

Results: Interobserver agreement was not absolute using either conventional radiographs or the sintered model. For the consultants the kappa statistic using conventional radiographs was 0.61 while the kappa value using the model was 0.76 (p=< 0.05). For the trainees the kappa was 0.42, using conventional radiographs and 0.71 using the model (p=< 0.01)>

Discussion: The complex three-dimensional anatomy of the pelvis and acetabulum make assessment and classification of fractures of these structures notoriously difficult. The value of accurate fracture classification is well recognised particularly in the treatment of intra-articular injuries. The use of this real life model of a fractured pelvis has been shown in this study to significantly reduce the degree of interobserver variability in the classification of these injuries. This effect is particularly evident for less experienced surgeons.

Conclusion: The technique is available and relatively inexpensive. These models may be of great benefit for preoperative planning, classification and assessment of prognosis in acetabular fractures. Its use should prove invaluable as a tool to aid clinical practice.

Introduction: The Ganz periacetabular osteotomy aims to improve femoral head coverage in dysplastic hips. It is joint preserving procedure and therefore is ideally preformed before significant articular cartilage degeneration. One proposed advantage of this procedure is that it partially preserves the posterior column and does not disrupt the vascular supply of the main fragment. This study aims to 1) assess the role of MR imaging in the perioperative evaluation of articular cartilage and labrial tissues prior to Ganz osteotomies and 2) to document any alteration in the vascularity of the acetabular fragment post operatively.

Patient and Methods: Twenty patients (all female, average age 18.2 years) under consideration for peracetabular osteotomy for hip dysplasia and MR Studies of the pelvis as part of the perioperative assessment. Sixteen patients had follow-up imaging at 4, 12 and 26 weeks post surgery, at which time evidence of healing, oedema, vascularity and femoral head coverage were assessed.

Discussion: MR imaging has proven to be a reliable method of assessing articular cartilage health before considering pelvic osteotomy. Hopefully this will allow more appropriate selection of patients likely to benefit from this procedure. In addition MRI scanning allows clearer assessment of other articular elements, such as labium and ligamentum teres, that are difficult to visualize with plain radiographs and CT scans. A further benefit of MR scanning is that, as this study has shown the vast majority of patients who are potential candidates are female of childbearing age and it voids the use of ionizing radiation in this sensitive group of patients. This study has shown that despite some early alterations in osteotomy fragment vascularity the ultimate outcome is that vascularity is substantively unharmed by periacetabular osteotomy.

Conclusion: MR imaging is extremely useful in the perioperative workup and postoperative follow-up in patients undergoing Ganz periacetabular osteotomies.

Introduction: The Sheehan total knee endoprosthesis has been widely used since 1971. It incorporates a semi-constrained hinge with intramedullary stems cemented into the femur and tibia for fixation. This gives a stable polycentric knee mechanism that allows axial rotation as well as stimulating other knee movements. This design has certain disadvantages including the large amount of bone resected for implantation and its constrained nature, which predisposes to loosening. While clinically excellent results have been reported in 95% of patient by some authors, other papers have reported much lower rates of successful outcome and revision rates of up to 30%. Few papers however report the difficulties encountered during revision or the techniques that need to be used to overcome these.

Patients and Methods: We reviewed the records of 21 patients who required revision of Sheehan TKR’s between 1987 and 2001. Reason for revision was recorded and all patients were scored using the Knee Society Index and Severity Instrument (Saleh et al CORR 2001). The operative details were examined and technical difficulties at the time of surgery recorded. Per-operative and early post-operative complications related to the revision procedure were also noted.

Results: The average age of patients requiring revision was 65 years old (range 39–79). The average time from primary surgery to revision was 16.2 years (range 8–20 years). The reasons for primary surgery were rheumatoid arthritis in 9 and osteoarthritis in 12. Revision surgery was required for pain associated with tibial subsidence and painful bone contact in 14. Five of these also had varus/valgus instability in excess on 30°. Two patients had dislocation of their tibial on femoral component. One patient had a one-stage revision for infection and one had revision for a fractures tibial intramedullary stem. Three patients had revision to anterior flanged femoral components to facilitate patellar resurfacing for patello-femoral pain. In 14 patients the knee was revised to a second Sheehan prosthesis as the degree of bone loss was insufficient to allow cement removal and bone stock reconstruction. Three patients were revised to stemmed Co-ordinate (DepuyTM) revision prostheses, one to a standard AMK surface replacing prosthesis and one to a hinged Finn prosthesis due to global instability. Seven patients required impaction bone grafting and required structural grafting for severe bone loss. The overall complication rate approached 80%! Two patients had wound breakdown, one required grafting. Five patients had persistent wound ooze successfully treated with antibiotics alone. To patients had cortical perforation, which was bypassed by the prosthetic stem, two suffered post-operative fractures, one requiring ORIF, one bracing. Four patient required re-revision, two to kinemax prostheses and two to further Sheehan prostheses.

Discussion: While the Sheehan TKR was of great benefit to a large number of patients it is not without its problems. These results show that prostheses coming to revision did not necessarily fail early and so with time we can expect more to present for revision. The high complication rate and the need for complex reconstructive techniques attest to the difficulty of revising these prostheses. Some of these problems are the legacy of the prosthetic design and should be borne in mind when taking on these cases.