Introduction: Shoulder arthroplasty in rheumatoid patients gives satisfactory pain relief and some recovery of motion. Long term complications are however frequent, such as loosening of the glenoid and rotatorcuff insufficiency. Proximal migration (PM) might be related to both these conditions, and is assumed to lead to deterioration in function and recurrence of pain.

Goal: Aim of this study was to evaluate the occurrence and identify risk factors for proximal migration after shoulder arthroplasty in a rheumatoid population.

Methods and patients: Data of 102 patients (FU 5.8 yrs) treated with a shoulder arthroplasty for rheumatoid gleno-humeral disease was analysed. Requirements were at least 3 years of follow–up and 3 follow-up moments. At each visit clinical scores and standardised radiographs were performed prospectively. Rotator-cuff status was scored per-operatively. For quantification of PM a validated measurement technique - The Spina Humeral centre method- was used. A significant decrease of the subacromial space was defined as more than two times the standard deviation of the measurement accuracy (3.65 mm).

Results: In 25 of 77 cases PM was present. PM commenced in two separate patterns, determined by the time-frame that passed before PM commenced. Early PM started directly during postoperative rehabilitation within the first two postoperative years, late PM after two years. This allowed group formation according to migration pattern; patients with no PM (PMnone), patients with late PM (PMlate) and those with early PM (PMearly). Age was higher in the PMearly group. Rotator cuff tears were more frequent and more severe in the PM groups. The ROM improved postoperatively in the PMnone and PMlate group, with deterioration of the latter in time. The HSS clinical outcome score improved in all groups.

Quality of rotator cuff repair did not alter PM outcome. PM did not occur more frequently in hemi-artho-plasty compared to total shoulder arthroplasty. A more upward oriented glenoid was observed in the PMearly and PMlate groups.

Neonatal brachial plexus palsy (NBPP) is frequently associated with internal rotation contractures of the shoulder as a result of muscle imbalance due to muscle fattening and/or fibrosis which favour the internal rotation of the shoulder. Botulinum toxin A (BTX-A) injection in the subscapularis (SC) muscle could weaken the SC and thereby restore muscle balance. The purpose of this study was to assess the effect of intra muscular injection of BTX-A in the SC on the passive external rotation and the need for external rotation surgery in NBPP patients after BTX-A injection.

A prospective comparative study was performed with 93 patients with progressive internal rotation contractures. Al patients underwent an MRI to determine the percentage of the humeral head anterior to the glenoid (PHHA) and glenoid version. Patients younger than 48 months old and with a minimum deformity (PHHA> =35%) or moderate deformity (PHHA< 35%) were included. Patients with a severe deformity or complete posterior dislocation were excluded. Fifteen consecutive patients were injected with BTX-A (2 U/kg body weight, botox^®) at two sites of the SC of the affected shoulder immediately after the MRI under general anesthesia. Seventy eight patients were included as a control group before the new BTX-A treatment was introduced. The passive external rotation was measured pre-MRI and at follow-up. The indication for external rotation surgery was determined after the MRI was performed.

No adverse events were observed. Pre-MRI, the mean passive external rotation in adduction in the BTX-A group was −5° (SE 8°) and in the control group 3° (SE 3°). In the BTX-A group, the mean passive external rotation in adduction increased with 53° (95% CI 31°–74°, p< 0.001) compared to the control group. After stratification the beneficial effect of BTX-A was observed in patients with a minimum deformity (54°, 95% CI 37°–71°, p< 0.001), but this was not significant in patients with a moderate deformity (47°, 95% CI −20°−115°, p=0.13) compared to the control group. The patients in the BTX-A group were less frequently indicated for external rotation surgery compared the control group (27% vs. 89%, p< 0.001). The maximum effect of BTX-A injection was observed at a mean follow-up of 3 months (SE 1). The control group was followed for a mean of 7 months (SE 0.4) to observe the natural history of internal rotation contractures. The groups were comparable regarding type of lesion, primary treatment, age, PHHA, glenoid version and passive external rotation pre-MRI (p 0.09–0.74).

BTX-A injections in the SC of NBPP patients reduce internal rotation contractures. This effect was mainly observed in patients with a minimum glenohumeral deformity. Restoration of muscle balance could prevent further glenohumeral deformation and could prevent external rotation surgery.

The need for a better understanding of factors that influence surgical outcome has grown as many complications are thought to be avoidable. One approach proven useful in studying surgical procedures is time-action analysis (TAA), a method which objectively determines the efficiency of individual steps. The aim of this study was to assess the surgical process of total knee arthroplasty using TAA, thus enhancing the insight into the procedure, influence of team members and adverse events, eventually leading to process improvement and reduction of error probability.

Methods: In two high output centres and one teaching hospital 37 TKA surgeries were recorded, using 3 different knee systems (NexGen, LCS and Triathlon). The process was analyzed using a fixed taxonomy and the duration, limitations and repetitions were determined using video analysis software. The efficiency of the surgeon was calculated by dividing the time the surgeon spends operating by the time operating plus the time spent talking, thinking or repeating.

Results: Although the two high output centres used different knee systems there was no difference in operating time (47min. (95%CI, 43.2 to 50.1) versus 47min. (42.1 to 51.9)). With an inexperienced nurse the waiting time increased in both hospitals during the femoral osteotomy phase (p= 0.01 and p=0.05). Comparing to a training hospital, the tibial alignment phase showed lower surgical efficiency for both the consultant and 6th year residents (80% vs. 95%, p=0.01). Also the nurse waiting time increased during all phases (18min. vs. 2min., p=0.00). In the teaching hospital more problems (communication, instrument and skill) occurred (mean 19 vs. 5 and 2, p=0.00) and twice as much communication problems existed with residents regardless of nurse experience. Surprisingly the number of problems handling instruments increased inversely with nurse experience (p=0.02) as did the waiting time (27min. vs. 15min.) again being highest in the femoral osteotomy phase (p=0.00).

Conclusion: The similar results in the high output centres show that TKA is a similar and structured process regardless of the knee system, its efficiency mainly dependent on surgical output. The decrease in resident efficiency is caused by less structured use of instruments and miscommunication with the nurse. For nurses the femoral osteotomy phase is most difficult, requiring high attention due to frequent changing of different pins and cutting blocks. Unfamiliarity with instruments (i.e. low volume) results in higher waiting times. Regardless of the knee system the steps of TKA are similar, therefore a consistent surgeon-nurse (OR tech) verbal interaction is advocated especially with a less experienced team. Training should focus knowledge of instruments using uniform names. Extra attention should be paid by those who do not often place knees to communication with the nurse and clear order of the procedure.

Background: Traumatic brachial plexus (BP) injuries may cause loss of elbow flexion. After nerve surgery active elbow flexion often remains insufficient. Muscle strength improvement via cell therapy would be a potential option and could avoid muscle transfer surgery. The primary objective of this pilot study was to assess the safety and feasibility of autologous bone marrow (BM)-derived mononuclear cell (MNC) injection in partly denervated m. biceps brachii of BP patients. Secondary, this study has focused on the myogenic potential of BM-derived MNC by assessing the morphological and functional improvement of the biceps.

Methods: Nine adult BP patients with insufficient force recovery of elbow flexion were included. Three escalating doses (0.9, 4 and 8 * 108) of MNCs were injected in the m. biceps brachii (group A, B and C). In group A, BM was aspirated under local anesthesia (60 ml). In group B and C, BM was aspirated in combination with a muscle tendon transfer (Steindler flexorplasty) under general anesthesia (350 and 650 ml respectively). A muscle biopsy was performed before and 3 months after transplantation. Furthermore, quantitative needle EMG, CT-scan and clinical function was obtained at pre-transplantation and at 3 and 6 months follow-up. The EMG and CT-scan data were blinded during analysis.

Results: No negative side effects were observed. Biopsies showed an increase of 80% in myofiber diameter (P = 0.007), 51% in satellite cells (P = 0.045), 83% in capillary to myofiber ratio (P < 0.001) and a decrease of 51% in fibrosis (P = 0.012). Histological changes were most apparent in group B with an increase of 126% in myofiber diameter (P = 0.019), 100% in capillary to myofiber ratio (P = 0.027), and a decrease of 70% in fibrosis (P = 0.023). EMG demonstrated an increase of 36% in amplitude (P = 0.045), 29% in duration (P = 0.005) and 29% in number of phases of the motor unit potentials (P = 0.002). CT-scan analysis showed a decrease of 48% in mean muscle density (P = 0.009).

Discussion: This study shows that BM-derived MNC transplantation in a partly denervated muscle of traumatic PB patients is safe and feasible. Muscle improvement was observed in muscle biopsies. Furthermore, changes in EMGs and CT-scans were also suggestive for muscle regeneration. The BM dose applied in group B could represent the optimal dose to enhance partly denervated muscles. The results of the present study require confirmation in a placebo-controlled study.

Background and purpose: The Souter-Strathclyde total elbow prosthesis is a well-studied replacement therapy for the destructed rheumatoid elbow joint. In the short-term results of a RSA-study we concluded that 8 out of 18 humeral components were at risk for loosening at two years of follow-up. Now we present the long-term results of this study to evaluate these predictions.

Patients and Methods: Twenty-one elbows (18 patients) were included in the RSA-study. At risk for loosening was defined as increase of translation of more than 0.4 mm or increase of rotation of more than one degree during the second postoperative year. The average follow-up was 98 months (range: 12–134 months). RSA-measurements were performed post-operatively, at 3 months, 6 months, 12 months and at yearly intervals thereafter. Prosthetic position and radiolucent lines (RLLs) were examined on conventional radiographs.

Results: Almost all humeral components, including the ones that were defined to be ‘at risk’ for loosening in our short-term study, showed increased and irregular migration in this long-term follow-up study. In contrast to this, the ulnar components were stable. Translations were most prominent in the posterior-anterior direction, the most prominent rotations took place about the transverse axis. No obvious influences of prosthetic alignment on micromotions were found. Four humeral components were clinically loose – three of them could be revised -, but only one of them was defined to be at risk for loosening in the short term study.

Radiological assessment based on conventional radiographs showed that a prediction of humeral loosening can be made within four years after surgery.

Interpretation: The RSA results clearly show that almost all humeral components migrate up to several millimeters and several degrees in an irregular manner, but often without clinical consequences.

Introduction: Using navigation the AP alignment of a total knee arthroplasty (TKA) improves. However, much less is known on the influence of navigation on the rotation of the femoral component.

The rotation of the femoral component is of high importance considering the balancing of the knee and the patellofemoral joint. The aim of our study was to evaluate the accuracy of the femoral component rotation when using navigation.

Materials and Methods: We evaluated twenty navigated TKA’s. The Vector Vision system of Brainlab was used during surgery. The preoperative data considering the rotation were stored. On postoperative CT scans the rotation of the femoral component was measured twice at different times by two observers. The posterior condylar angle (the angle between the posterior condylar line and the epicondylar line) was used to define the rotation. The definite position was compared to the per-operative data. The difference between the preoperative determined rotation and the postoperative rotational position was analyzed. The Cohen’s kappa coefficient was used to compare the agreement of results.

Results: The postoperative CT scan showed an average measured rotation of the femoral component (posterior condylar angle) of 3,8 degrees. The average rotation based on the navigation data was 5.8 degrees. The difference between the preoperative data and the definite position measured on the CT was 2,8 degrees with a large range. We found a moderate agreement between the two observers and a good agreement within the two observers.

Conclusion: The rotation of the femoral component is important in the knee kinematics and patellofemoral joint. Using navigation, it is (yet) not possible to accurately determine or improve the rotational position of the femoral component. Further development of the software and method of determining the epicondylar axis during surgery is needed to be able to improve the rotational position of the femoral component.

Aim: Suction fit is a common phenomenon of metal on metal (MOM) or ceramic on ceramic hip joints, in which the head and the cup can be hold to each other in the presence of lubricant. The aim of this study was to measure the suction force of MOM hip joints with different clearances and fluid viscosities.

Materials and Methods: CoCrMo hip prostheses of Ø50 mm with two diametral clearances of 100 and 200 microns were tested. A range of fluids were made using different ratios of deionized water and carboxy-methyl cellulose (CMC). The fluid viscosities ranged from 0.0011 to 0.3 Pa s determined by a cone-on-plate viscometer (Physica Rheolab MC100). Before the measurement, about 1 ml fluid was placed in the cup and the bearing surfaces of both the head and the cup were fully wetted by rotating the femoral ball in the cup. A pre-loaded 3kN was applied to push the head into the cup by a servohydraulic test machine, the femoral head was then lifted out of the cup at a rate of 2 mm/s and the maximum suction force value was recorded.

Results: Generally, the suction force increased with the increase of viscosity for both 100 and 200 microns clearances. In the lower range of the viscosity, the suction force increased rapidly, but when the viscosity reached a certain value it leveled off to about 190 N for the 100 microns clearance and 150 N for the 200 microns clearance. In the whole range of viscosity, the suction forces of 100 microns clearance were higher than those of 200 microns clearance and the differences were statistically significant (t-test, P< 0.01). In the lower range of viscosity (< 0.04 Pa s), the suction force of 100 microns clearance was more than two times higher than that of 200 microns clearance.

Discussion: For a MOM hip joint, suction force can be explained by the vacuum within the bearings. When the clearance is small and the lubricant viscosity is high, the edge of the bearing surfaces can be easily sealed off so that certain degree of vacuum can be produced between the head and the cup. In this test, the maximum suction force for the Ø50 mm MOM hip joint can be calculated as: F = (projected area) x (atmospheric pressure) = 196 (N). The results confirmed that the suction force of Ø50 mm components can not be higher than 196 N.

Although suction force may have a benefit in reducing the risk of dislocation, it may prevent lubricant recovery between the bearings and will influence the sliding resistance. If the suction force is too high, the head and cup can be held together such that the recovery of synovial fluid is restricted or impossible, even when the hip is not loaded during the swing phase. Both the clearance and the viscosity have a significant effect to determine the suction force and the lubrication of MOM hip joints. It is concluded that suction force is a factor to be considered during the selection of MOM hip joint clearance.

Aseptic loosening of the total TMC joint prosthesis occurs frequently and may depend on the design of the prosthesis. Numerous TMC prosthesis designs are available, and new designs are being developed and tested. One of the problems in the clinical studies of TMC prostheses is identifying and predicting prosthetic loosening at an early stage. Roentgen Stereophotogrammetric Analysis (RSA). allows assessment of three-dimensional micromotion of orthopaedic implants with high accuracy. Early micromotion (in the first two postoperative years) of most prostheses is strongly correlated with the development of aseptic loosening. We studied if RSA assessment was possible after total TMC joint arthroplasty.

In five cadaveric hands the TMC joint was replaced by the SR-TMC prosthesis. Tantalum beads of 0.8 mm were implanted in the trapezium and first metacarpal bone without extending the standard surgical exposure. The metacarpal prosthesis component was provided with 0.5 mm beads. A three-dimensional surface model of the trapezium component of the SR-TMC prosthesis was prepared to facilitate model-based RSA. After the surgical procedure, RSA radiographs were made of all hands in two commonly used positions for imaging of the TMC joint. The number of visually detected markers for each bone/implant was recorded. Of one cadaver hand, RSA radiographs were made in ten different positions to calculate the measurement error of the performed technique.

For the metacarpal bone, all beads were visible in all positions and both (L+R) RSA radiographs. For beads in the polyethylene metacarpal prosthesis component three beads seem sufficient, however in exceptional cases the most proximal placed bead might be invisible due to overprojection by the metal trapezium prosthesis component. Therefore the X-rays should be carefully checked at the radiology department before the patient leaves the ward. Alternatively, an extra bead can be placed in the prosthesis, although this is a lesser option due to possible weakening of the component caused by the placement of the beads. The use of different sizes of beads (0.5/0.8 mm) in the metacarpal bone and metacarpal prosthesis made the interpretation for the analyser easier

The accuracy analysis is currently carried out. First results of these measurements are promising and placement of tantalum beads for RSA analysis during TMC-joint replacement seems feasible.

Posttraumatic infection and osteomyelitis is a difficult to treat complication. Despite surgical interventions, there is great risk for recurrence of the infection and development of an invalidating osteomyelitis. For this reason, a retrospective, case control cohort study on patients with posttraumatic osteomyelitis was performed to evaluate the clinical outcome of a new therapy, i.e. VAC Instillation with Lavasept®, an instillation technique applied after the initial surgical debridement.

In the time period from 2/1999 to 2/2003, thirty three patients with posttraumatic osteomyelitis were included and were treated with the VAC technique and the white polyvinyl alcohol (PVA) foam in combination with lavasept® instillation. The PVA foam was instilled 3 times per day with a disinfectant fluid agent lavasept 0.2 % (polyhexanidum solution). The average time of treatment was 21 days (6–60). The average time that infected wounds became sterile or skin bacteria could be cultured (88.1 %) was 12 days (range 4 – 38; SD 8.9). The follow-up time was up to 72 months. For comparison a historical control group of 94 patients (male 58, mean age 47 (r 9–85) matched for site and severity of osteomyelitis, was identified in hospital records for a period of 20 years (1982–2002). These patients were treated with debridement, lavage and gentamycin beads.

Both groups were statistical comparable to sex, age, comorbidity and site of the osteomyelitis. In the V.A.C.® Instill® group the rate of recurrence of infection was 3/30 (10%), whereas 55/93 (58.5%) of the controls had a recurrence (p< 0.0001). Moreover, in those treated with VAC Instillation, the duration of hospital stay was shorter and the number of admissions and surgical procedures were smaller as compared with the controls (all p< 0.0001).

We conclude that in posttraumatic osteomyelitis VAC Instillation treatment may improve clinical outcome and reduce the need for repeated surgical interventions and hospital admissions in comparison to the present standard approach.

The most widely accepted method to measure kneekinematics is using external movement registration with the aid of skin-mounted markers. However, a large error component appears due to skin movement relative to the underlying bone. The goal of this study is to use fluoroscopy to quantify skin movement artefacts in patients with a total knee prosthesis during a step-up task.

The most widely accepted method to measure knee kinematics is using external movement registration with the aid of skin-mounted markers. However, a large error component appears due to skin movement relative to the underlying bone. The goal of this study is to use fluoroscopy to quantify skin movement artefacts in patients with a total knee prosthesis during a step-up task.

Translational and rotational errors attributed to soft tissue movement were three times larger for the femur than for the tibia about allaxes. The mean of the absolute rotational differences for the femur were2.6, 3.3 and 1.7 degrees about the X, Y and Z axes respectively. Absolute peak differences for individual subjects were 9.1, 12.9 and 10.5 mm along the X, Y and Z axes respectively.

This is the first study examining the 3D relative motion between surface-mounted and bone-anchored markers without the use of cortical pins anchored to the tibia and/or the femur. The results revealed no regular pattern of soft tissue error between subjects indicating the unlikely success of numerical methods for modeling and removing soft tissue motion artifacts when using standard motion capture methods.

Model-based Roentgen Stereophotogrammetric Analysis (RSA) measures micromotion of an orthopaedic implant with respect to its surrounding bone, without the use of markers on the implant. In previous studies with a total knee prosthesis, Model-based RSA showed to be very accurate. In this study, Model-based RSA is validated in a phantom experiment of a total hip prosthesis.

A metal backed, elliptical shaped EP-FIT PLUS ®cup was used in combination with a SL-PLUS ® hip-stem from PLUS Endoprothetik AG. In vivo conditions were simulated by using sawbones and perspex plates to mimic the bones and soft tissue. Virtual projections of the CAD models of the implant were fitted on the automatically detected contours in nine RSA radiographs and the error inmigration calculation was determined.

The standard deviations of the error in translation for the cup were: 0.03, 0.05, and 0.21 mm. (x, y, z-direction) The standard deviations of the error in orientation were respectively 0.56, 0.48, and 0.18 degrees (n = 10). For the stem, the standard deviations of the error in translation are: 0.09, 0.11, and 0.29 mm and for the orientation: 0.63, 2.03, and 0.24 degrees (n = 0).

The results for the cup are satisfactory, and make Model-based RSA a good alternative for conventional RSA. Especially for this type of metal backed, non hemispherical cup for which no markerless alternative is available. The error in orientation around the y-axis of the stem is of concern. Experiments with models from Reversed Engineering had similar low accuracy. We expect that the cause of these inaccuracies is the rectangular cross sectional shape of this specific hip stem, and we expect better results from experiments with differently shaped stems. The results of this study make very clear that Model-based RSA is avaluable and accurate technique, but phantom studies are always necessary to validate the accuracy for a specific implant shape.

Objective: Complex hand function problems in patients with rheumatic diseases may require the expertise of physicians and health professionals from multiple disciplines. The aim of the present study was to describe the characteristics, management strategies and outcomes of patients with rheumatic diseases who were referred to a multidisciplinary hand clinic.

Methods: All consecutive patients with complex hand function problems who were referred to a multidisciplinary hand clinic including a rheumatologist, an orthopaedic surgeon, a rehabilitation specialist, an occupational therapist and a physical therapist were included. Of all patients, sociodemographic characteristics, general disease characteristics, the most troubling impairments and limitations regarding hand function and deformities were recorded at baseline. The following measures of hand function were assessed at baseline and 3 months after treatment: the Sequential Occupational Dexterity Assessment (SODA), the Michigan Hand Outcomes Questionnaire (MHQ), the hand/finger function subscale of the Arthritis Impact Measurement Scales (AIMS), grip strength (Jamar dynamometer) and pain (visual analogue scale, VAS, 0–10 cm).

Results: Over a period of 28 months 69 patients were included. Basic characteristics, characteristics of hand function, impairments and limitations that were most frequently mentioned as well as the advised management strategies were recorded. In 38/54 patients (70%) the advised treatment was executed and 33 of them completed the follow-up assessment.

Conclusion: The most frequently mentioned impairments and limitations of patients with rheumatic diseases and hand function problems pertain to grip ability and grip strength, pain and shaking hands. Management advices, including conservative and surgical treatment, are followed by two-thirds of the patients. On average, patients who are treated improve significantly with respect to grip strength and overall hand function as measured by a questionnaire.

Various radiological classification systems exist for rheumatoid wrist progression but few have been evaluated for reliability and clinical application. In order to research these three sets of wrist radiographs of 35 rheumatoid patients, with an average duration of disease of 11 years, were classified according to four different classification systems (Larsen, Simmen, Wrightington and Modified Wrightington). The inter- and intraobserver reliability of each was calculated. The reliability of the Larsen and both Wrightington systems were good but the Simmen system had poor interobserver and intraobserver reproducibility. None of the classification systems satisfactorily assessed the distal radioulnar joint (DRUJ) and the Modified Wrightington system could not classify DRUJ disease in 6 of the 35 wrists.

Outcome measures must be valid, reliable and responsive to change criteria. The most common clinical outcome measures are Knee Society Scores, SF-36 quality of life scores, HAQ and DAS scores. However, performance based measures of functioning may not be dependent on patient report or observer judgment.

Examples of objective pre- and post-operative performance outcome measures are surface Electromyography (EMG) of muscles, kinematics and kinetics (gait analysis). For the evaluation of implant survival after joint arthroplasty, Roentgen Stereophotogrammetric Analysis (RSA) is the golden standard to assess micro-motion of the implants.

Surface EMG can be used to asses the stability of joints before and after intervention. Calibrating of raw EMG data is necessary to compare the data between subjects. It was shown that calibration of EMG data by means of isokinetic contractions on a dynamometer during flexion and extension was more reliable and repeatable than using a Maximum Voluntary Contraction in patients after total knee arthroplasty. After total knee arthroplasty RA patients have a lower net knee joint moment and a higher co-contraction than controls, indicating avoidance of net joint load and an active stabilization of the knee joint.

Fluoroscopy can be used to assess the kinematics of joints. In the pre-operative situation the use of CT models of the involved bones can be matched to the assessed fluoroscopic images. In the post-operative situation CAD models of the implants can be used for this purpose. In this way accurate 3D kinematics of joints can be assessed. During a step-up task of RA patients, the rotating platform of a mobile bearing knee showed no- or far less longitudinal rotation than the femur. Therefore, some of the theoretical advantages of this specific rotating platform knee prosthesis can be questioned. Fluoroscopy has also been used to assess soft tissue artifacts that occur in gait analysis i.e. displacements of skin-mounted markers relative to the underlying bone. The large soft tissue artefacts observed (displacements up to 17 mm and 12 degrees) question the usefulness of parameters found with external movement registration.

In order to assess the micromotion of implants after joint arthroplasty a measurement technique with a much higher accuracy than fluoroscopy is needed. RSA uses tantalum markers as landmarks bony structures and as landmarks on the implant. Recently a new RSA technique has been developed that does not rely on the attachment of artificial markers on the implant but uses CAD models of the implant instead. As an example of RSA as outcome measure, results showed that a calciumphosphate coating improves fixation of tibial components in RA patients, thus preventing mechanical loosening and subsequent long-term revision. In another clinical RSA study, it was found that mobile bearing knees are more predictable and forgiving with respect to micromotion compared to posterior stabilized tibial components in RA patients.

The results obtained by the above described performance outcome measures can be valued since the accuracy and precision of the used outcome measures are all published.

Elderly patients with a high mortality risk for revision surgery are severely handicapped by a loosened hip prosthesis. Loosening is mainly caused by particle-induced osteolysis leading to the formation of a synovium-like interface tissue. As an alternative to revision surgery we have investigated the possibility of removing the tissue using a gene therapy approach and thereafter stabilizing the prosthesis with percutaneous cement injection.

First we demonstrated that transduction of interface cells with a gene coding for E.coli nitroreductase (NTR) resulted in a 60-fold increase in sensitivity to the prodrug CB1954 that is converted to a toxic metabolite by NTR. Given these in-vitro data, we explored if intra-articular administration of this adenoviral vector encoding NTR followed by the prodrug was able to kill sufficient tissue in-vivo to allow refixation of the prosthesis by cement.

We report the first three patients from a phase 1 study of 12 patients with a loosened hip who are experiencing debilitating pain and have significant comorbidity. On day 1 the vector is injected into the hip joint and on day 3 the prodrug is injected. On day 10 three holes are drilled in the femur and one in the acetabulum. Biopsies are taken from the periprosthetic space and low viscosity cement (Osteopal, Biomet Merck, Sjöbo, Sweden) is injected under fluoroscopic guidance.

The first three patients have been included in the study and five more are planned for treatment before June 2005. The patients are females of 86, 72, and 79 years old. There were no adverse effects from vector injection (3x10 exp 9 particles). Six hours after prodrug injection the patients experienced nausea, (WHO grade 1) a commonly reported reaction to this prodrug. There was vomiting in two patients. Hip pain increased, but this was anticipated as this therapy will increase prosthesis loosening. 16 ml of cement was subsequently injected into the periprosthetic space in the first patient and 18 ml in the second. The patients were ambulated the day after surgery.

The first two patients have a follow-up of twelve and six weeks. There was no pain in the hip. The maximum walking distance had increased from 5 to 30 meters in the first patient.

The current study is the first to use in vivo intra-articular adenoviral mediated gene transfer in a clinical setting. Our preliminary results suggest that gene therapy and cement injection for hip prosthesis refixation is clinically feasible.

The advantages of high viscosity Simplex AF cement (PMMA) compared to low viscosity Simplex P are the low porosity, the high fatigue strength, the lower polymerization time, and the lower maximum polymerization temperature. A prospective, randomized, double-blind clinical study was conducted to assess the in vivo effects of viscosity of bone cement on the micromotion of a polished tapered stem and UHMWP-cup (Exeter, Stryker-Howmedica). Roentgen Stereophotogrammetric Analysis (RSA-CMS, Medis, The Netherlands) was used to measure micromotion.

Twenty patients were included in a Simplex AF group (70 ± 4.3 years), and twenty patients were included in a Simplex P group (71 ± 7.3 years). No significant differences in body mass index and clinical hip scores were observed between the two studied groups.

There was no significant difference of the subsidence of both high and low viscosity cemented Exeter stems. The subsidence was according to the literature and showed that the viscosity of the bone cement did not influence the cement-implant bond of this polished tapered stem design.

The total migration of the cups and the migration along the medial-lateral axis were significantly larger for the Simplex AF cemented cups compared to the Simplex P cemented cups (p=0.037). This can be explained by the higher cement mantle thickness in acetabular Gruen zone 2 (p=0.003) and 3 (p=0.004) of the Simplex AF cemented cups.

We conclude from this study that the viscosity of the bone cement has no effect on the subsidence of polished tapered stems and that a high cement mantle thickness around an UHMWP-cup has a negative effect on fixation.

The common factor in all (mechanical) prosthetic failure mechanisms is the induction of osteolysis around the endoprosthesis with subsequent prosthetic migration and finally loosening of the prosthesis. Both initial prosthesis-bone fixation and long-term prosthesis survival depend on the quality of the peri-prosthetic bone mass. The effects of treatment of RA patients with prednison are inhibition of osteoblastic activity and inhibition of calcium resorption from the intestines. The bone mass loss during the first six months of prednison treatment is substantial and will seldom be regained. Bisphosphonates are known to decrease osteoclastic activity and may therefore stop osteolysis at the bone-prosthesis interface.

The aim of the study was to evaluate a possible association of bisphosphonates with reduced migration of total knee prostheses (Interax, Howmedica Osteonics, Rutherfort, USA) in a high-risk group. Roentgen Stereophotogrammetric Analysis (RSA-CMS, Medis, The Netherlands) was used to measure the micromotion.

Retrospectively a group of nine RA patients treated with prednison (non-bisphosphonates group) and a group of fourteen RA patients (bisphosphonates group) treated with prednison in combination with bisphosphonates (Etidronate) were included from a prospective randomized study of 82 patients (Nelissen et al., 1998).

At the two-year follow-up evaluation, functional scores and knee scores did not differ significantly among the two groups. At the two-year follow-up evaluation, the non-bisphosphonates group subsided −0.47 ± 0.8 mm, and the bisphosphonates components subsided 0.07 ± 2.9 mm. In the analysis of variance with repeated measurements, with correction for follow-up time, sedimentation rate, and prosthesis fixation type, the bisphosphonates group migrated 1.20 mm less in the total migration (95% c.i.: 1.07–1.30 mm) compared to the non-bisphosphonates group.

In this study, bisphosphonates medication in addition to corticosteroid medication was associated with reduced migration of knee prostheses compared to corticosteroid medication alone.

The aim of this study was on the one hand to compare the fixation of a posterior stabilised prosthesis (PS) and a PCL retaining mobile bearing design (Interax, Howmedica Osteonics, Rutherfort, USA) and on the other hand to measure the mobility of the mobile bearing. All measurements were carried out by means of Roentgen Stereophotogrammetric Analysis (RSA-CMS, Medis, Netherlands).

A prospective,randomised,double-blind study (N=28) was conducted to assess the micromotion of the components. At the one-year follow-up evaluation, the micromotion of the PS-components and the mobile bearing components were not significantly different. The PS-tibial components subsided −0.063 ± 0.177 mm and the mobile bearing knee tibial components subsided 0.067 ± 0.084 mm. The PS tibial component showed a higher variability in the migration results indicating a number of PS with rather large micromotion.

For three patients, the in vivo motion of the mobile bearing with respect to the metal backing was assessed at 30, 60 and 90 degrees of passive flexion. Two of mobile bearings moved posteriorly (2.4 and 2.9 mm) at respectively 60 and 90 degrees of flexion and showed a medial-lateral translation of 0.03 and 3.5 mm. One mobile bearing moved only 0.4 mm posteriorly at 90 degrees of flexion but showed a lateral-medial translation of 3.1 mm.

The broad range of kinematic patterns of mobile bearings during flexion that is observed in fluoroscopic studies is also observed in this study. A possible positive effect of mobile bearing movement may be found in the smaller variability of the micromotion of the mobile-bearing knees compared to the PS knees. The assumption was that shear forces in tibial bones implanted with a mobile bearing prosthesis would be better dissipated from the prosthesis-bone interface resulting in less micromotion. The kinematics of an additional number of mobile bearing knees -already included in the micro-motion study- will have to be assessed in order to determine the relation between mobility and micromotion.