Introduction

Modification in joint loading, and specifically shear stress, is found to be an important mechanical factor in the development of osteoarthritis (OA). Cartilage shear stresses can be investigated using finite element (FE) modelling, where typically in vivo joint loading as measured by an instrumented hip prosthesis is used as boundary condition. However, subject-specific gait characteristics substantially affect joint loading. The goal of this study is to investigate the effect of subject-specific joint loading as calculated using a subject-specific musculoskeletal model and integrated motion capture data on acetabular shear stress.

In the area of 3D printing, more and more maxillofacial surgery departments are equipped with 3D printers to build their own anatomical models or surgical guides. Prior to be printable, the patients' DICOM imaging data has to be converted to a 3D virtual model, a 3D mesh. The file format most commonly used is the STL (Standard Tesselation Language) file format. Many programs exist that are able to convert DICOM data to STL files. Commercial software, such as Surgicase CMF© are FDA- and CE-approved whereas free programs, available online do not have the approval. However, the latter are often used anyway because of financial reasons. In this article, we investigate whether 6 of these software solutions are equivalent or not.

Thin slice CT imaging data of a patient's mandible (in DICOM file format) was converted to STL meshes with 6 different software solutions. One commercial program, Surgicase CMF©, was used to build the reference model. Then 5 free programs were used to create 5 models of the same mandible, specifying the same thresholding parameters: InVesalius 3.0, 3DimViewer 2.2.4, 3D Slicer, itk-Snap and Seg3D. All of these models were loaded in Netfabb Basic 6.4 to retrieve dimensional data, geometric information and the number of holes in each mesh. Finally, the models were then compared to the reference model using CloudCompare 2.6.2.

All models created with free software differed from the reference model in the 3 dimensions. Mean length difference was −0.74 mm [−2.06; −0.32] (SD: 0.74), mean width difference −0.45 mm [−0.76; −0.25] (SD: 0.19) and mean height difference was 0.41 mm [0.14; 0.62] (SD: 0.18). Although the height was increased in all models, both the length and width were systematically decreased, resulting in an average decrease of volume of −7.1 cm³ [−7.45; −6.77] (SD: 0.32). The number of triangles used to create each mesh ranged from 20944 to 368244, resulting in a variation of the file size from 1023 Ko to 80462 Ko (0.16 to 12.70 times the file size of the reference model). Two of the free programs created meshes with errors, such as the presence of holes (non-watertight meshes) that could be repaired with Netfabb.

Free programs able to convert volume imaging data to a printable virtual mesh do not provide equivalent results. Variations were noted in the three plane of space with a systematic difference between free programs and the commercial FDA-approved one. While the length and width were less than a millimeter different to the reference, the dimension that most varied was the length with a difference reaching −2.06 mm with itk-Snap. Geometric data also varied significantly, the number of triangles composing the meshes being much different than the reference, resulting in variable file sizes. This traduces the fact that algorithms used by the programs are not the same. In the era of 3D printing made directly accessible in surgical departments, great attention should be paid to the accuracy of the models created with free software.

Several studies have shown that gait kinematics[1–3] and hip contact forces (HCFs)[4, 5] of patients following total hip arthroplasty (THA) do not return to normal, although improvements in kinematics are found compared to the pre-surgery. However, the evolution of HCFs after surgery has not been investigated. The goal of this study is to evaluate HCFs during gait in OA patients before and at 2 evaluation moments post-THA.

Fourteen unilateral hip OA patients before and 3- and 12-months post-THA surgery walked at self-selected speed, as well as 18 healthy control subjects. 3D marker trajectories were captured using Vicon (Oxford Metrics, UK) and force data was measured using two AMTI force platforms (Watertown, MA). A musculoskeletal model consisting of 14 segments, 19 degrees of freedom and 88 musculotendon actuators and including wrapping surfaces around the hip joint was used[6]. All analyses were performed in OpenSim 3.1[7]. The model was scaled to the dimensions of each subject using the marker positions of a static pose. A kalman smoother procedure was used to calculate joint angles[8]. Muscle forces were calculated using static optimization, minimizing the sum of squared muscle activations. HCFs were calculated and normalized to body weight (BW). First and second peak HCFs were determined and used for statistical analysis. To determine differences between HCFs of OA patients at the different evaluation moments, a Friedman test was used. In case of a significant difference, post-hoc rank-based multiple comparison tests with a Bonferonni adjustment was used. To compare controls and patients at each evaluation moment separate Man-Whitney U tests were used. Differences in HCFs between the affected and non-affected legs were expressed by a symmetry index (SI), i.e. the ratio between the HCFs of the affected leg over the non-affected leg, averaged over the stance phase of the gait cycle.

At the first and second HCF peaks, no significant differences were found between pre-, 3- and 12-months post-surgery (first peak average HCF: 2.68, 2.72 and 2.78BW respectively; second peak average HCF: 3.21, 3.83 and 3.77BW respectively). Compared to controls, significant differences are found for all evaluation moments at the first and second HCF peaks (average HCF controls: 3.43 and 5.15BW respectively). The SI was below 1 pre- and 3-months post-surgery (0.88 and 0.85 respectively), indicating decreased loading of the affected compared to the non-affected leg. At 12-months post-surgery SI was close to 1 (0.98).

As reported before[4, 5], first or second peak HCFs do not return to normal after THA. Although HCFs increase after THA compared to pre-surgery, significant differences with controls remain. Surprisingly, no significant differences are found between the different evaluation moments of the patients, indicating no clear improvements are found after THA. Further, average HCF peaks at 3- and 12-months post-surgery are similar, indicating no further improvements are found 3-months post-surgery. However, the SI was above or close to 1 at 12-months post-surgery, indicating hip loading evolved to a more symmetrical loading 12-months post-surgery.

Reconstructing mandibular and maxillary bone defects with free vascularized bone flaps requires to take into account the aesthetic and functional requirements to consider subsequent placement of dental implants. It implies a three-dimensional conformation of the bone fragment. This is usually done by making osteotomies on the bone harvested. The aim of our study was to evaluate the interest of virtual planning and 3D printing using free software and a consumer printer in this indication.

Invesalius® software (Technology of Information Renato Archer Center, Campinas, Brazil) was used to build virtual models from the patients' CT scan imaging data. The surgical procedure was planned using Meshmixer® (Autodesk, San Rafael, United States). Meshlab® software (Visual Computing Lab, Pisa, Italy) was used to design cutting guides for the flap harvest and modelling. 3D printing of these guides with a consumer printer (Ultimaker 2® Ultimaker B.V., Geldermalsen, the Netherlands) allowed the transfer of the planning to the operating room.

Three patients requiring mandibular reconstruction underwent an iliac crest free flap, a fibula free flap and a scapula free flap, and could benefit from this technique. In each case, the bone resection was performed virtually and the positioning of the bone available at the donor site was simulated on screen. This allowed to anticipate the position and orientation of the cutting planes on the bone flap. From the anatomy of the donor site and the cutting planes, harvest templates and cutting guides could be designed by computer. Planning the conformation of the bone flap to the recipient site has allowed an anatomical, aesthetic and functional reconstruction of the bone defect.

Surgeon-made virtual planning and “low cost” 3D printing helps harvest the bone flap and position and orient the osteotomies to adapt it to the defect. They provide, both the patient and the surgeon, reduced operative time and better anticipation of the result, particularly in the context of the maxillofacial reconstruction. Compared to commercially available custom-made devices, this technique allows the manufacture of the guides without delay and at a cheap price.

The management of maxillofacial injuries requires restoring the contours of the facial skeleton to achieve an aesthetic outcome. When fractures are simple, open reduction and rigid fixation with stock titanium osteosynthesis plates is usually sufficient. However, when the damage is more substantial (when the fracture is comminuted or in case of a bone defect) anatomical landmarks are lost and the reconstruction requires the use of titanium meshes. These meshes are usually modelled intraoperatively to restore the contours of the bone. This can be a tough and time consuming task in case of minimal invasive approach and intraoperative edema. When the injury is unilateral, printing a 3D anatomical model of the mirrored unaffected side is an easy way to accurately pre-bend the mesh preoperatively. With the emergence of “low cost” consumer 3D printers, the aim of our study was to evaluate the cost of this technique in a department of maxillofacial surgery.

The first part of the study was to evaluate free software solutions available online to determine which of these could be used to create 3D virtual models from the patients' volume imaging data, mirror the model and export an STL file suitable for 3D-printing with a consumer 3D-printer. The second part was to identify the desktop 3D-printers commercially available according to the different technology used, their prices and that of consumables required.

Five free software solutions were identified to create STL meshes of the patient's anatomy from thin slice CT scan DICOM data. Two more were available to repair, segment and mirror them to provide a clean STL file suitable for 3D printing with a desktop 3D printer. The prices of 2 different printers were then listed for each of the 3 additive manufacturing technologies available to date. Prices ranged from 2,299 € for the Ultimaker 2+© (Fuse Deposition Modeling, FDM), to 4,999 € for the Sintratec© printer (Selective Laser Sintering, SLS), the Formlabs 2© (stereolithography) being at an intermediate price of 3,299 €. Finally, the cost of the manufacture of a model was calculated for each of these printers. Considering a model of a supraorbital ridge printed to restore the anterior wall of the frontal sinus, the volume of the mesh is around 20 cm³. This represents a cost of less than 1 € with the FDM technology, 4.70 € with stereolithography and 1.50 € with the SLS printer.

Since patents of additive manufacturing have become part of the public domain, the cost of 3D printing technology has fallen drastically. Desktop printers are now an investment accessible to a surgery department and the cost of the material is low. This allows the surgeons, by the mean of free software, to directly create 3D models of their patients' anatomy, mirror them if needed and manufacture a template to pre-bend titanium meshes that will be subsequently sterilized for the surgery. Having the printer in the department reduces manufacturing lead times and makes this technique possible even for urgent cases.

The treatment of unstable distal radius fractures remains controversial. Volar locking plates provide stable fixation using the fixed angle device principle. More recently this technique has gained increasing popularity with several reports demonstrating good results. We present our experience from the first 259 patients performed at this institution.

Method: Local Ethics Committee approval was obtained prior to the onset of the study. Theatre records and implant forms were used to recruit all patients in whom a Distal Volar Radius (DVR) Plate, (DePuy, Leeds, United Kingdom) was used for an unstable distal radius fracture between August 2005 and February 2008. Surgery was performed either by a consultant, or a specialist registrar. Two hundred and fifty nine consecutive patients were identified. Six patients had bilateral distal radius fractures. Patient records were reviewed, and each patient contacted via a postal questionnaire and Patient-Rated Wrist Evaluation (PRWE). Other outcome measures included return to work and complication rate.

Results: Of the 259 patients 160 responses were received, response rate 62%. The mean follow up was 30.8 months, (Range 18–48). The mean age of the patients was 57.3 years (Range 16–93). The mean inpatient stay was 1.6 days, (mode 1 day). The median PRWE was 3; (range 0–83) and the mode was 0. Ninety four of the patients had a PRWE of ≤5. Seventy one out of 78 patients (91%) returned to the same job. The mean return to work was 40.6 days (SD37.5).

There were 13 minor complications in total (7.8%). Six patients had extensor tendon irritation, of which two patients required extensor tendon reconstruction. One further patient had a spontaneous EPL rupture which was not associated with prominent metal work. Four (2.4%) patients had median nerve symptoms postoperatively. Two patients subsequently required carpal tunnel decompression, the other two settled spontaneously. Two (1.2%), patients developed Complex Regional Pain Syndrome. One patient developed a minor superficial wound infection.

In all, 9 (5.4%) patients had removal of their metalwork, 6 for tendon irritation, 2 for wrist stiffness (one which was positioned too distally) and 1 for pin penetration into the joint.

Discussion: Our results show that the DVR plate can be used reliably with good results and an early return to high levels of function. This is the largest series to date of the use of this distal volar locking plate.

To assess the outcome of knee “arthrodesis” using cemented Endo-Model knee fusion nail in failed Total Knee Replacement (TKR) with significant bone loss due to infection. This is a retrospective case study of seven patients with infected TKR and multiple surgeries with significant bone loss.

All patients had antibiotic loaded cement with a temporary K-nail as a first stage procedure to eradicate infection. All seven patients had “arthrodesis” performed using cemented modular Endo-Model Knee Fusion nail (Waldemar Link, Hamburg) by the senior author. Cement was used to hold the stems in the diaphyses and not used around the coupling mechanism. The “arthrodesis” relied entirely on the coupling mechanism which has been shown to have good axial and torsional rigidity by mechanical testing. Outcome was assessed using pre and post Visual Analogue Score (VAS).

Mean age was 72.3 years(62–86). Mean follow up was 39.6 months (7–68). The VAS pain score improved from pre-operative mean score of 7.9 to a postoperative score of 1.5. One patient suffered fracture of femoral cement mantle at 50 months who underwent a technically easy exchange revision. One patient had recurrent infection with distal femoral fracture at 36 months and was revised to distal femoral replacement.

The Endo-Model knee arthrodesis nail restores limb lengths, has good early results in terms of pain relief and provides a stable knee “arthrodesis” in cases where there is significant bone loss and extensor mechanism insufficiency following an infected TKR.

Introduction: Knee arthroscopy is a common orthopaedic procedure. Growing demand on orthopaedic services has led to the introduction of new initiatives to reduce waiting lists and streamline services. Recently extended scope physiotherapists have placed patients directly on arthroscopy waiting lists without prior assessment by an orthopaedic surgeon.

Aim: To determine if extended scope physiotherapists perform to the same standards as their orthopaedic colleagues with regards to diagnosing knee pathology and making appropriate referrals for arthroscopy.

Method: Data was collected prospectively from Aug 2005. Patients were seen either in the physiotherapy led acute knee clinic or in orthopaedic outpatients by a consultant or registrar. Any patient placed onto a waiting list for knee arthroscopy was considered for the study. The clinical indications and diagnoses were recorded as well as demographic data. The arthroscopies were performed by one surgeon. The arthroscopic findings were compared with the clinical findings.

Results: 300 patients were included in the study – 100 in each of the groups. The physiotherapists saw fewer patients per clinic and had longer time-slots per patient. All three groups had similar presenting complaints, indications for surgery and demographics. The Consultant performed best with 87% agreement with his initial diagnosis. The physiotherapists had 77% agreement and the registrars 68% agreement. No unnecessary arthroscopies were performed in any group.

Conclusions: Extended scope physiotherapists perform a useful role in orthopaedic outpatients. They perform as well as their orthopaedic colleagues with regards to the selection of patients for arthroscopy and making appropriate diagnoses.

The management of displaced femoral neck fractures in independent, healthy patients remains controversial. Acetabular erosion is a time dependant phenomenon and our aim was to assess the long-term outcome of the Universal Head bipolar with an Exeter stem.

49 consecutive cemented bipolar hemiarthroplasties were performed in 49 patients between 1992 and 2000. Mean age was 71.6 (range 54–91). There were 13 male and 36 female. 23 patients were alive at final follow up. 17 patients were assessed in outpatients with clinical and radiographic assessment. 2 patients had a telephone questionnaire and 4 patients were lost to follow up or were unable to attend clinic. Kaplan-Meier Survivorship analysis was performed.

Median follow up was 7.1 years (range 5–13.3 years). 26 patients had died by the time of final follow up. 5/14 patients (36%) with an ASA score of 3 died within 30 days. There was one dislocation and one periprosthetic fracture. There were no deep infections. There were no revisions for aseptic loosening or acetabular erosion. 75.6% of surviving patients returned to their pre-injury mobility level at 1 year. 5 year cumulative survival was 60% (95% confidence interval 46–74%). There was a statistically significant reduction in cumulative survival for ASA grades 3 and 4 compared to 1 and 2 (p=0.004).

Cemented bipolar hemiarthroplasty for femoral neck fractures is a good alternative to Total Hip Arthroplasty for independent, healthy patients. There is no evidence of acetabular erosion. Careful patient selection is necessary as patients with high ASA scores have greater mortality rates regardless of surgical prosthesis.

Aim: To determine if extended scope physiotherapists perform to the same standards as their orthopaedic colleagues with regards to diagnosing knee pathology and making appropriate referrals for arthroscopy.

Method: Data was collected prospectively from Aug 2005. Patients were seen in a consultant led orthopaedic clinic by an Extended Scope Physiotherapist (ESP), a registrar or the consultant. All patients placed onto the waiting list for knee arthroscopy were considered for the study. The outpatient diagnosis and demographic data were recorded and compared against the arthroscopy findings. A single consultant surgeon performed the arthroscopies.

Results: 300 patients were included in the study (100 in each group). Each group was similar in terms of presenting complaint and demographics. There was no significant difference between the ESP’s and registrars in their ability to diagnose intraarticular pathology (CHI squared test: X 2.031, df 1, p=0.15). When only cruciate and meniscal pathology were considered there was also no significant difference between the ESP’s and the registrars (Fishers test p=0.12 and p=0.22 respectively, 2-tail test) The ESPs performed particularly well in their ability to diagnose cruciate injuries (sensitivity 100%, specificity 100% and PPV 100%). Both ESPs and registrars had high sensitivity but low specificity with regards to diagnosing meniscal pathology suggesting a low threshold for a positive diagnosis and a poor ability to correctly diagnose those patients who did not have a meniscal injury. Of the 300 patients only 9 unnecessary arthroscopies were requested. None were requested by the ESPs.

Conclusions: Extended scope physiotherapists perform a useful role in orthopaedic outpatients. They perform as well as orthopaedic registrars with regards to making the correct diagnosis and the selection of patients for arthroscopy.

Most hospitals have introduced digital radiography (PACS) systems. Accurate pre-operative templating prior to hip arthroplasty requires precise information on the magnification of the digital image. Without this information the benefits of expensive digital templating programs (Orthoview-£10000) cannot be realised.

To determine the magnification of a digital image involves the placement of a “calibration object” at the level of the hip joint. This is unpopular with patients and radiographers alike. We describe a method that requires a single measurement to be made from the greater trochanter to the digital film.

An AP pelvis x-ray was taken of 50 patients with hip replacements. The “predicted” magnification was calculated using the new method. As the size of the head of the prosthesis was known the “actual” magnification could be calculated also. There was no significant difference at 0.05, Wilcoxon T, 2-tail test.

Conventional radiography, which assumes a magnification of 20%, results in errors up to 11%. Templating may therefore predict an incorrectly sized prosthesis. Our method is as accurate as methods using a calibration object whilst being acceptable to patients and staff. Its use should lead to more accurate pre-operative templating prior to total hip arthroplasty

To determine if extended scope physiotherapists perform to the same standards as their orthopaedic colleagues with regards to diagnosing knee pathology and making appropriate referrals for arthroscopy.

Data was collected prospectively from Aug 2005. Patients were seen in a consultant led orthopaedic clinic by an Extended Scope Physiotherapist (ESP), a registrar or the consultant. All patients placed onto the waiting list for knee arthroscopy were considered for the study. The outpatient diagnosis and demographic data were recorded and compared against the arthroscopy findings. A single consultant surgeon performed the arthroscopies.

300 patients were included in the study (100 in each group). Each group was similar in terms of presenting complaint and demographics. There was no significant difference between the ESP’s and registrars in their ability to diagnose intraarticular pathology (CHI squared test: X 2.031, df 1, p=0.15). When only cruciate and meniscal pathology were considered there was also no significant difference between the ESP’s and the registrars (Fishers test p=0.12 and p=0.22 respectively, 2-tail test) The ESPs performed particularly well in their ability to diagnose cruciate injuries (sensitivity 100%, specificity 100% and PPV 100%). Both ESPs and registrars had high sensitivity but low specificity with regards to diagnosing meniscal pathology suggesting a low threshold for a positive diagnosis and a poor ability to correctly diagnose those patients who did not have a meniscal injury. Of the 300 patients only 9 unnecessary arthroscopies were requested. None were requested by the ESPs.

Extended scope physiotherapists perform a useful role in orthopaedic outpatients. They perform as well as orthopaedic registrars with regards to making the correct diagnosis and the selection of patients for arthroscopy.

The aim of our study was to investigate whether placing of the femoral component of a hip resurfacing in valgus protected against spontaneous fracture of the femoral neck.

We performed a hip resurfacing in 20 pairs of embalmed femora. The femoral component was implanted at the natural neck-shaft angle in the left femur and with a 10° valgus angle on the right. The bone mineral density of each femur was measured and CT was performed. Each femur was evaluated in a materials testing machine using increasing cyclical loads.

In specimens with good bone quality, the 10° valgus placement of the femoral component had a protective effect against fractures of the femoral neck. An adverse effect was detected in osteoporotic specimens.

When resurfacing the hip a valgus position of the femoral component should be achieved in order to prevent fracture of the femoral neck. Patient selection remains absolutely imperative. In borderline cases, measurement of bone mineral density may be indicated.

Introduction The effect of hip rotation on the measurement of femoral offset is determined firstly using artificial bones in an anatomical study and then in a patient population. Its effect on the choice of femoral component in total hip arthroplasty is discussed

Methods Radiographs were taken of a series of saw bone models rotated through a range of angles. The resultant offset was then measured Standardised and Control (unstandardised) radiographs of the pelvis were taken of patients presenting to orthopaedic outpatients. Femoral offset was measured from each radiograph

Results In the anatomical study angles of rotation differed significantly with respect to measurement of offset (p< 0.0001 Friedman 2-way analysis of variance by ranks). The greatest measurement of offset was at 15 degrees internal rotation. Offset decreased with external rotation. The clinical study had power of 80%. Femoral offset was increased in all the standardised x-rays compared with their controls (n=108, mean=7.64, SD=5.55, 95% CI (6.58,8.70)). A one-sample t-test was performed to see if the standardised and control films were greater than 5mm different (t=14.30 (107df), p< 0.01).

Conclusions The clinical study confirmed the findings of the anatomical study. A standardised AP radiograph of the pelvis improves the measurement of femoral offset. For surgeons using the Exeter hip system failure to account for offset could lead to the selection of a stem two sizes too small with regards to offset. Lesser degrees of rotation, not readily identified by looking at the radiograph, could still lead to the selection of an incorrectly sized stem. Offset has been shown to increase the range of movement, abductor strength and stability of the hip joint whilst decreasing the rate of wear. It therefore benefits patients to account for offset, ensuring a correctly sized hip replacement.

We evaluated histologically samples of synovial tissue from the knees of 50 patients with rheumatoid arthritis (RA). The samples were taken during revision for aseptic loosening. The findings were compared with those in 64 knees with osteoarthritis (OA) and aseptic loosening and in 18 knees with RA without loosening. The last group had been revised because of failure of the inlay or the coupling system of a constrained prosthesis. All the patients had had a total ventral synovectomy before implantation of the primary prosthesis.

In all three groups a foreign-body reaction and lymphocellular infiltration were seen in more than 80% of the tissue samples. Deposits of fibrin were observed in about one-third to one-half of the knees in all groups. Typical signs of the reactivation of RA such as rheumatoid necrosis and/or proliferation of synovial stromal cells were found in 26% of knees with RA and loosening, but not in those with OA and loosening and in those with RA without loosening.

Our findings show that reactivation of rheumatoid synovitis occurs after total knee replacement and may be a cofactor in aseptic loosening in patients with RA.