The Olympia femoral stem is a stainless steel, anatomically shaped, polished and three-dimensionally tapered implant designed for use in cemented total hip arthroplasty (THA). The primary aim of this study was to determine the long-term survivorship, radiographic outcome, and patient reported outcome measures (PROMs) of the Olympia stem.

Between May 2003 and December 2005, 239 patients (264 THAs) underwent a THA with an Olympia stem in our institution. PROMs were assessed using the Oxford Hip Score (OHS), EuroQol-5 dimensions (EQ-5D) score and patient satisfaction at mean 10-years following THA. Patient records and radiographs were then reviewed at a mean of 16.5 years (SD 0.7, 15.3 to 17.8) following THA to identify occurrence of complications or revision surgery for any cause.

Mean patient age at surgery was 68.0 years (SD 10.9, 31–93 years). There were 156 women (65%, 176 THAs). Osteoarthritis was the indication for THA in 204 patients (85%). Stem survivorship at 10 years was 99.2% (95 % confidence interval [CI], 97.9%-100%) and at 15 years was 97.5% (94.6%–100%). The 15-year stem survival for aseptic loosening was 100%. Only one occurrence of peri-prosthetic fracture was identified, with no episodes of dislocation found. At a mean of 10 (SD 0.8, 8.7 –11.3) years follow-up, mean OHS was 39 (SD 10.3, range 7 – 48) and 94% of patients reported being very satisfied or satisfied.

The Olympia stem demonstrated excellent 10-year PROMs, very high rates of stem survivorship and negligible peri-prosthetic fracture and dislocation rate at final follow-up beyond 15 years.

Successful return to work (RTW) is a crucial outcome after primary total knee arthroplasty (TKA) in patients under 65 years old. We aimed to determine whether TKA facilitated RTW in patients <65 years, whose intention was to return preoperatively.

We prospectively assessed 106 TKA patients under 65 years over a 1 year period both preoperatively and at 1 year following surgery. Patient demographics were collected including Oxford knee score, Oxford-APQ, VAS pain/health scores and EQ-5D. A novel questionnaire was distributed to delineate pre-operative employment status and post-operative intentions. This included questions on nature of pre and post-operative occupation, whether joint disease affected their ability to work and details of retirement plans and how this was affected by their knee.

69 patients intended to return to work following their TKA. Following arthroplasty, 57/69 patients (82.6%) returned to work at a mean of 16.4 weeks (SD 16.6). Univariate analysis showed significant factors facilitating RTW included, pre-operative oxford knee score, pre-operative Oxford-APQ score and pre-operative EQ-5D score. These were not predictive on multivariate analysis.

This study finds that TKA facilitates return to work in 83% of those who intend to return to work following their surgery. This could have significant positive and health and financial cost implications for the individual, health system and society.

Patient reported outcomes and satisfaction scores following excision of interdigital Morton's neuroma have been recently established. However, little is known regarding what patient factors affect these outcomes. This is the first and largest prospective study to determine which patient factors influence surgical outcome following Morton's neuroma excision.

Over a seven-year period, 99 consecutive patients (112 feet) undergoing surgical excision of Morton's neuroma were prospectively studied. 78 patients were female with a mean age at operation of 56 years. Patient recorded outcomes and satisfaction were measured using the Manchester-Oxford Foot Questionnaire (MOXFQ), Short Form-12 (SF12) and a supplementary patient satisfaction survey three months pre and six months post-operatively. Patient demographics were recorded in addition to co-morbidities, deprivation, associated neuroma excision and other forefoot surgery.

Obesity, deprivation and revision surgery proved to statistically worsen MOXFQ outcomes post-operatively (p=0.005, p=0.002 and p=0.004 respectively). Deprivation significantly worsened the mental component of the SF12 (p=0.043) and depression the physical component (p=0.026). No difference in outcome was identified for age, sex, time from diagnosis to surgery, multiple neuroma excision and other forefoot surgeries. 23.5percnt; of deprived patients were dissatisfied with their surgery compared to 7percnt; of the remaining cohort.

Patient reported outcomes following resection of symptomatic Morton's neuroma are shown to be less favourable in those patients who display characteristics of obesity, depression, deprivation and in those who undertake revision neuroma resection. Surgery can be safely delayed, as time to surgery from diagnosis bears no impact on clinical outcome.

Risk of revision following total knee replacement is relatively high in patients under 55 years of age, but little is reported regarding non-revision outcomes. This study aims to identify predictors of dissatisfaction following TKR in patients younger than 55 years of age.

We assessed 177 TKRs (157 consecutive patients) from 2008 to 2013. Data was collected on age, sex, implant, indication, BMI, social deprivation, range of motion, and prior knee surgery in addition to Oxford Knee Score (OKS) and SF-12 score. Postoperative data included knee range of motion, complications, and OKS, SF-12 score and satisfaction measures at one year.

Overall, 24.9% of patients (44/177) were unsure or dissatisfied with their TKR. Significant predictors of dissatisfaction on univariable analysis (p<0.05) included: Kellgren-Lawrence grade 1/2 osteoarthritis; indication; poor preoperative OKS; postoperative complications; and poor improvements in OKS and pain component score (PCS) of the SF-12. Odds ratios for dissatisfaction by indication compared to primary OA: OA with previous meniscectomy 2.86; OA in multiply operated knee 2.94; OA with other knee surgery 1.7; OA with BMI>40kgm-2 2; OA post-fracture 3.3; and inflammatory arthropathy 0.23. Multivariable analysis showed poor preoperative OKS, poor improvement in OKS and postoperative stiffness, particularly flexion of <90°, independently predicted dissatisfaction (p<0.005).

Patients coming to TKR when under 55 years of age differ from the ‘average’ arthroplasty population, often having complex knee histories and indications for surgery, and an elevated risk of dissatisfaction.

British national guidelines recommend agents which antagonise factor Xa or warfarin as prophylaxis of venous thromboembolism (VTE) in lower limb arthroplasty. However, they discourage the use of aspirin prophylaxis.

We conducted a prospective, multi-centre audit between two national centres, Ninewells Hospital in Dundee and the Royal Infirmary in Edinburgh to compare bleeding and VTE risk. Only Edinburgh routinely uses aspirin as VTE prophylaxis. The study comprises a number of cycles from 2013 to 2015. Consecutive groups of patients were identified prospectively using elective theatre data and information extracted from their case-notes on type of VTE prophylaxis, VTE occurrence, wound complications and length of hospital stay for a period of nine weeks post-operatively.

262 Edinburgh patients and 92 Dundee patients were included. Most Edinburgh patients were prescribed aspirin in hospital and on discharge (188/262, 71.8%), in line with local protocol. In Dundee, dalteparin was most commonly prescribed in hospital (68/92, 73.9%) and rivaroxaban on discharge (57/92, 62.0%).

The Edinburgh group had a 1.5% incidence of pulmonary embolus (PE) and a 1% rate of deep venous thrombosis (DVT), 2% had problems with wound haematoma and one patient (0.4%) required a transfusion; no wound washouts were required. In Dundee there was 0% PE, 2% DVT, 5% had problems with haematoma, 3% required transfusion and 2% required washout. There was no difference in length of hospital stay, with a mode of 4 days for both centres.

Non-fatal PE was prevented in Dundee patients but possibly at the cost of greater incidence of wound complications.

Current knowledge regarding outcomes following surgical treatment of Morton's neuroma remains incomplete. This is the first prospective study to report the pre- and post-operative patient reported outcomes and satisfaction scores following excision of interdigital Morton's neuroma.

Over a seven year period, 99 consecutive patients (112 feet) undergoing surgical excision of Morton's neuroma were prospectively studied. 78 patients were female with a mean age at operation of 56 years. Patient recorded outcomes and satisfaction were measured using the Manchester-Oxford Foot Questionnaire (MOXFQ), Short Form-12 (SF12) and a supplementary patient satisfaction survey three months pre and six months post-operatively.

Statistically significant differences were found between the mean pre- and post-operative MOXFQ and physical component of the SF-12 (p< 0.05). No difference in outcome was identified in patients in whom multiple neuromas were operated compared to single site surgery. However, revision surgery proved to statistically worsen MOXFQ outcomes post-operatively p< 0.004. Overall satisfaction was reported as excellent (49%) or good (29%) by the majority of patients but 10% were dissatisfied with poor (8%) or very poor (2%) results expressed. Only 64% were pain free at the time of follow-up and 8% of patients MOXFQ scores worsened.

These findings illustrate that overall, patient reported outcomes following resection of symptomatic Morton's neuroma are acceptable but may not be as favourable as earlier studies suggest. Caution should be taken when considering revision surgery which has shown to be a poor prognostic indicator. Contrary to current knowledge, multiple site surgery can be safely undertaken.

Current knowledge regarding outcomes following surgical treatment of Morton's neuroma remains incomplete. This is the first prospective study to report the pre- and post-operative patient reported outcomes and satisfaction scores following excision of interdigital Morton's neuroma.

Over a seven year period, 99 consecutive patients (112 feet) undergoing surgical excision of Morton's neuroma were prospectively studied. 78 patients were female with a mean age at operation of 56 years. Patient recorded outcomes and satisfaction were measured using the Manchester-Oxford Foot Questionnaire (MOXFQ), Short Form-12 (SF12) and a supplementary patient satisfaction survey three months pre and six months post-operatively.

Statistically significant differences were found between the mean pre- and post-operative MOXFQ and physical component of the SF-12 (p<0.05). No difference in outcome was identified in patients in whom multiple neuromas were operated compared to single site surgery. However, revision surgery proved to statistically worsen MOXFQ outcomes post-operatively p<0.004. Overall satisfaction was reported as excellent (49%) or good (29%) by the majority of patients but 10% were dissatisfied with poor (8%) or very poor (2%) results expressed. Only 64% were pain free at the time of follow-up and 8% of patients MOXFQ scores worsened.

These findings illustrate that overall, patient reported outcomes following resection of symptomatic Morton's neuroma are acceptable but may not be as favourable as earlier studies suggest. Caution should be taken when considering revision surgery which has shown to be a poor prognostic indicator. Contrary to current knowledge, multiple site surgery can be safely undertaken.

Clostridium difficile is associated with a range of gastrointestinal disorders ranging from diarrhoea to toxic megacolon. Alteration of the normal gut flora by antibiotics is a key predisposing factor. Although antibiotic prophylaxis is routinely administered during joint replacement surgery, there has been controversy about both type and duration of prophylaxis. The primary aim of this study was to determine the incidence of C. diff associated disease (CDAD) following hip and knee replacement and to investigate potential risk factors.

A laboratory database was interrogated to identify patients developing CDAD after hip or knee replacement from January 2006 to December 2008. A database of arthroplasty patients was used to identify a control group of patients without CDAD to compare the effects of prescription of antibiotics for reasons other prophylaxis of deep infection, comorbidity and the use of gastroprotective agents.

Eight patients developed CDAD. There were 1.7 cases of CDAD per 1000 joint replacements. Patients developing CDAD were more likely to have been prescribed additional antibiotics (p=0.047). There were no differences in the use of gastroprotective agents (p=0.703). A trial of a new prophylaxis regime would require 43,198 patients in each arm to show a reduction to 1 case per 1000 procedures.

Cefuroxime based antibiotic prophylaxis is safe in patients undergoing elective joint replacement. Extremely large studies would be required to show marginal clinical benefits of new regimes. One prophylaxis policy will not suit all orthopaedic patient groups or procedures.

Introduction: Foot and ankle involvement in rheumatoid arthritis is common. Pain and disability secondary to planovalgus deformity and the arthritic process are difficult to control with conservative measures. Arthroplasty of the ankle is associated with high failure rates and does not completely correct the deformity. Arthrodesis of the hindfoot is a good option to alleviate pain, correct the deformity and improve functional ability, however has not been well reported in the literature.

Aims: To determine change in quantitative measures of patient health, pain and functional ability following hindfoot arthrodesis in patients with rheumatoid arthritis, and to assess patient satisfaction postoperatively.

Methods: 24 consecutive additive hindfoot arthrodeses were performed by a single surgeon on 22 patients with rheumatoid arthritis. Patients were assessed preoperatively using the Short Form-12 Health Survey (SF-12), Manchester-Oxford Foot Questionnaire (MOXFQ) and pain scores. These assessments were repeated at 6 and 12 months postoperatively, with an additional satisfaction questionnaire.

Results: There was a marked and sustained improvement in the post-operative SF-12, MOXFQ and pain scores, with 71% of patients reporting no pain at 12 months. 19 out of 22 patients reported being satisfied or very satisfied with the operation. Bony union was achieved in all patients, both on clinical and radiological criteria. Most patients returned to normal footwear, some with slight modification to facilitate a more normal gait cycle.

Conclusions: This study shows that additive hindfoot arthrodesis can be a very effective procedure in the management of moderate to severe ankle and hind-foot disease in rheumatoid arthritis. Patients should be counselled regarding the considerable recovery period; however significant improvement in the patient’s general health, foot function and pain can be expected.

Antibiotic prophylaxis is routinely administered during joint replacement surgery and may predispose patients to Clostridium difficile-associated disease (CDAD). The primary aim of this study was to determine the incidence of this following joint replacement, using a cefuroxime-based regimen. Patients developing CDAD were compared with a control group of patients without CDAD. The incidence of the former was 1.7 per 1000 primary joint replacements. Those patients prescribed additional antibiotics had a higher incidence of CDAD (p = 0.047), but there was no difference between the two groups in relation to the use of gastroprotective agents (p = 0.703). A trial of a new prophylaxis regimen would require 43 198 patients in each arm to show a reduction of one case per 1000 procedures. Cefuroxime-based antibiotic prophylaxis is safe in patients undergoing primary elective joint replacement.

Good perioperative analgesia following Total Knee Replacement facilitates rehabilitation and may reduce hospital stay. A multimodal drug injection has been shown to provide excellent pain control and functional recovery, and was introduced into the operating practice of one Arthroplasty surgeon during his Total Knee Replacements.

We compared the rehabilitation of 27 consecutive patients (group 1) following their Total Knee Replacement under spinal anaesthesia receiving the periarticular infiltration mixture, consisting of levobupivacaine, ketorolac and adrenaline at the end of surgery. Their rehabilitation was compared to group 2, a historical group operated on by the same surgeon before the introduction of the multimodal drug injection. These patients were age and sex matched and had received a Femoral and Sciatic block at the time of their operation.

Patients in group 1 had lower analgesic and anti-emetic requirements than group 2. Group 1 also had a shorter time to Strait Leg raise.

Periarticular multimodal drug injection can improve perioperative analgesia and mobilisation following Total Knee Replacement as well as reducing opioid side effects.

Background: Several factors can alter a cements viscosity and hence it’s handling characteristics. An in vitro study was performed to ascertain whether anecdotal observations of differences in handling between batches of the same cement brand existed.

Methods: 3 batches of Simplex P Tobramycin (SPT), Refobacin Bone Cement (RBC), SmartSet GHV (SSG) and Palacos R+G (PRG) were tested. 6 replicates of each batch were vacuum mixed and their viscosity in relation to time was measured in laboratory conditions (50 ±5% humidity and 23 ±1°C) using a rheometer. 6 replicates of each batch had their handling characteristics examined after they were hand mixed in theatre conditions.

Results: Inter and intra-batch variability was seen in the viscosity of all brands of cements tested. Inter-batch calculations were influenced by high intra-batch viscosity variability. The viscosity of RBC cement was very similar to SSG, but significantly different to PRG (p = 0.01 at 5N and p = 0.009 at 40 N).

Interpretation: Our results suggest that in clinical practice extrinsic factors such as preparation conditions and methods probably play a more important role than the cements intrinsic variability. However, variability in handling and viscosity will exist in all brands of cement prepared in theatre conditions and the surgeon needs to be aware why they may act differently.

Introduction: Cement pressurisation is key to achieving good cement-bone interdigitation in THR. To obtain adequate pressurisation the medullary canal must be sealed distally using a cement restrictor. The cement restrictor must remain stable in the femoral canal.

Methods: Five different cement restrictors were evaluated, namely the Exeter Cement Plug, Biostop G, Hardinge, Rex CementStop and a preinjected cement plug. The restrictor was deployed in a sawbone that had been reamed to produce a distal flare, based on radiographic measurements. Low viscosity bone cement pressurised using a cement ram connected to a 10bar air supply. An electronic pressure valve increased the pressure in the cement. Cement pressure and cement restrictor displacement were continuously measured. The pressure valve and recording of measurements was controlled by a customised computer package.

Results: The Rex CementStop withstood the greatest pressures (mean 565.8kPa). This was a significantly greater pressure than any of the other cement restrictors (p< 0.001). Pre-injected cement plugs were able to resist the next highest pressures (mean 350.4kPa). They did not displace but leaked cement and were technically difficult to deliver in the distal femur. Cement restrictors that function well above the isthmus were ineffective (Biostop mean 118.7kPa) or could not be deployed below the isthmus (Exeter). The Hardinge recorded a mean 162.3kPa.

Discussion: During pre-operative templating it is important to consider where the cement restrictor will sit in the femur. When the cement restrictor is going to be deployed beyond the femoral isthmus, an alternate method of cement restriction may need to be used. Universal sized plugs (e.g. Hardinge) function poorly in this situation. Press-fit plugs such as Biostop and Exeter are severely compromised when inserted past the femoral isthmus. Pre-injected cement plugs are variable in efficacy. The expandable Rex CementStop reliably occluded the femur, allowing the highest pressures to be generated.

Introduction: An intra-medullary cement restrictor is an integral part of modern cementing technique in total hip arthroplasty. Failure of the restrictor to contain cement, flawed surgical technique or dislocation of the restrictor during pressurisation can all result in a deficient cement mantle. A radiographic analysis of hip replacements using a biodegradable restrictor was undertaken to determine the incidence of restrictor failure, the influence of femoral canal morphology on restrictor failure and to describe the cement mantle quality in successful and failed distal cement restriction.

Methods: x-rays from 299 consecutive hip replacements using the amberflex restrictor were analysed. The cortical index, canal-calcar ratio and femoral type, according to Dorr, were recorded. 3 modes of restrictor failure were identified:

Cement leakage –cement was seen to have escaped past the cement restrictor

Results: 84 cases of restrictor failure were observed – 44 dislocations, 24 leakages and 16 penetrations. The mode of failure was not correlated with femoral type, cortical index or canal-calcar ratio. A strong association was found between restrictor failure and grades c and d cement mantles using the chi squared test. A correlation between cortical index, canal-calcar ratio and femoral type was not observed.

Discussion: The ability of a cement restrictor to occlude the femoral canal and resist pressurisation is very important if a good quality cement mantle is to be achieved. Technical error was likely to be an important factor in many of the observed cases of restrictor failure, especially penetrative failure. Surgical technique is more important than femoral morphology in determining the successful use of this restrictor.

Objectives : To determine the change in passive knee kinematics after Oxford Unicompartment Arthoplasty (UKA) (Biomet, Uk); and to compare the change in kinematics post-operatively between image guided and the normal surgical procedure.

Background: In anteromedial osteoarthritis, only the medial compartment of the knee is affected and the collateral ligaments as well as the cruciate mechanism are intact. These preconditions make the knee suitable for UKA. The operative technique of the Oxford UKA theoretically allows the surge on to replicate the natural kinematics of the knee, due to accurate ligament balancing and fully congruent meniscal bearing design of the prosthesis. Our hypothesis was that no difference in tibiofemoral kinematics is observed after UKA. In addition we also hypothesised that the results of the image guided surgery would be the same as the normal surgical procedure.

Design/Methods: To test this hypothesis, we conducted a study using 13 normal human cadaveric knees. For kinematic analysis, the Surgetics TM surgical navigation system (Praxim, France), equipped with custom written tracking software, was used. Reference markers were mounted to the proximal tibia and the distal femur. In a standardized set-up, the knee was positioned in a leg holder and preoperative kinematics of the normal knee was recorded after a para-patellar mini-incision (70–90 mm). Joint kinematics were recorded during passive knee flexion and plotted against flexion angle. Oxford UKA was performed; the standard Phase III instrumentation was used for six knees and the image guided procedure was used for seven knees. The main difference between the standard and image guided procedures was that the inter-medullary rod was not used for the image guided surgery. After the operation postoperative kinematics were recorded using the same measurement protocol. All data were processed using Matlab 6.1 analysis software (The Math Works Inc., MA, USA). Preoperative and postoperative tibiofemoral kinematics were determined and compared. The mechanical axes of the tibia and femur were determined and kinematics represented as functions of knee flexion range. Over both the flexing and extending cycles of the knee the changes in tibiofemoral rotation (& #916;ROT), tibiofemoral ab/adduction (& #916;ABD), and distances between the origins of the mechanical axes (& #916;X, & #916;Y, & #916;Z) were calculated between pre and post-operative states.

Design/Methods: To test this hypothesis, we conducted a study using 13 normal human cadaveric knees. For kinematic analysis, the Surgetics TM surgical navigation system (Praxim, France), equipped with custom written tracking software, was used. Reference markers were mounted to the proximal tibia and the distal femur. In a standardized set-up, the knee was positioned in a leg holder and preoperative kinematics of the normal knee was recorded after a para-patellar mini-incision (70–90 mm). Joint kinematics were recorded during passive knee flexion and plotted against flexion angle. Oxford UKA was performed; the standard Phase III instrumentation was used for six knees and the image guided procedure was used for seven knees. The main difference between the standard and image guided procedures was that the inter-medullary rod was not used for the image guided surgery. After the operation postoperative kinematics were recorded using the same measurement protocol. All data were processed using Matlab 6.1 analysis software (The Math Works Inc., MA, USA). Preoperative and postoperative tibiofemoral kinematics were determined and compared. The mechanical axes of the tibia and femur were determined and kinematics represented as functions of knee flexion range. Over both the flexing and extending cycles of the knee the changes in tibiofemoral rotation (& #916;ROT), tibiofemoral ab/adduction (& #916;ABD), and distances between the origins of the mechanical axes (& #916;X, & #916;Y, & #916;Z) were calculated between pre and post-operative states.

Conclusions: The image guidance system used in our study is a valuable tool for assessing pre- and postoperative knee kinematics. Oxford Unicompartmental Knee Arthroplasty with the Phase III instrumentation in the presence of the cruciate mechanism reproduces the normal kinematics of the knee very accurately. The image guided procedure, performed without the inter-medullary rod, produced similar results to the standard surgery. Image guidance has a great potential for the assessment of pre- and post-replacement kinematics of the knee joint during surgery.

Aims: To evaluate the function of cement restrictors beyond the femoral isthmus.

Introduction: Pressurisation of cement is key to achieving good cement-bone interdigitation in Total Hip Replacement. During insertion of the femoral stem, pressures of up to 1000kPa may be generated. To maintain pressurisation the medullary canal must be sealed distally using a cement restrictor. As a secondary effect, cement restrictors also prevent excess injection of cement into the medullary canal. To fulfil these functions the cement restrictor must remain stable in the femoral canal.

Methods: Five different cement restrictors were evaluated, namely the Exeter Cement Plug (Stryker, UK), Biostop (De Puy, UK), Hardinge (De Puy, UK), Rex CementStop (A-One-Medical, Netherlands) and a preinjected cement plug (Surgical Simplex, Stryker, UK). The restrictor was deployed in a sawbone that had been rasped to produce a distal flare. Low viscosity bone cement (Surgical Simplex, Stryker, UK) was injected and pressurised using a custom made cement ram connected to a 10bar pressurised air supply. An electronically controlled pressure valve increased the pressure in the cement. Pressure in the cement was measured using a pressure transducer. A linear variable displacement transducer was used to measure movement of the cement restrictor. Leakage of cement around the restrictor was also recorded. Activation of the pressure valve and recording of measurements was controlled by a customised computer package.

Results: The Rex CementStop withstood the greatest pressures (mean 565.8kPa). This was a significantly greater pressure than any of the other cement restrictors (p= 0.027). Pre-injected cement plugs were able to resist the next highest pressures (mean 350.4kPa). They did not displace but leaked cement and were technically difficult to deliver in the distal femur. Cement restrictors that function well above the isthmus were ineffective (Biostop mean 118.7kPa) or could not be deployed below the isthmus (Exeter). The Hardinge cement restrictor recorded a mean 162.3kPa.

Discussion: It is important for a surgeon to consider where the cement restrictor will sit in the femur during pre-operative templating in Total Hip Replacement. When the cement restrictor is going to be deployed beyond the femoral isthmus, an alternate method of cement restriction may need to be used. Universal sized plugs (e.g. Hardinge) function poorly in this situation. Press-fit plugs such as Biostop and Exeter have been previously shown to allow the generation of high pressures in bone cement when sited above the femoral isthmus or in stove pipe femurs. However their function is severely compromised when inserted past the femoral isthmus. Pre-injected cement plugs are variable in efficacy. The expandable Rex CementStop was simple to use and reliably occluded the femur, allowing the highest pressures to be generated.

Introduction: Minimally invasive surgery (MIS) presents challenges in achieving alignment for unicompartmental knee arthroplasty (UKA). Aim: Development and assessment of an image guidance system for MIS implanted Oxford UKA.

Methods: The Surgetics platform which uses intra-operative data acquisition was chosen as the base system. Software was developed to determine height of tibial cut, image guidance of saws, alignment of components and assessment of ligament tension. The accuracy of component placement was assessed in vitro using matched pairs of knees randomised into navigated (NAV n=10) and standard manual (MAN n=10) procedures; standardised postoperative A-P and lateral radiographs were used. Pre and post-operative kinematics were assessed (NAV n=6, MAN n=7). The changes postoperatively over knee flexion and extension were calculated for tibiofemoral rotation (ΔROT) and ab/adduction (ΔABD).

Results: Accurate component placement was achieved with both methods without significant differences. Tibial cut height was more accurately in the NAV group (re-cut rate: NAV 33%, MAN 50%). NAV femoral component placement was as accurate as MAN with intramedullary rod. For the flexing cycle mean ΔROT was −0.06° (range 6.08° to −3.93°) and mean ΔABD was −0.04° (range 3.39° to −5.72°). There were no observable differences between the NAV and MAN kinematics. Overall, no observable differences were found between pre and post-operative kinematics.

Conclusions: Image guidance produces accurate placement through MIS approach and reduces the amount of tibial bone resection.

Background: In anteromedial osteoarthritis, only the medial compartment of the knee is affected and the collateral ligaments as well as the cruciate mechanism are intact. These preconditions make the knee suitable for UKA. Our hypothesis was that no difference in tibiofemoral kinematics is observed after UKA. In addition we also hypothesised that the results of the image guided surgery would be the same as the normal surgical procedure.

Design/Methods: To test this hypothesis, we conducted a study using 13 normal human cadaveric knees. For kinematic analysis, the SurgeticsTM surgical navigation system (Praxim, France), equipped with custom written tracking software, was used. Reference markers were mounted to the proximal tibia and the distal femur. In a standardised set-up, the knee was positioned in a leg holder and preoperative kinematics of the normal knee was recorded after a para-patellar mini-incision . Joint kinematics were recorded during passive knee flexion and plotted against flexion angle. Oxford UKA was performed; the standard Phase III instrumentation was used for six knees and the image guided procedure was used for seven knees. After the operation postoperative kinematics were recorded using the same measurement protocol. All data were processed using Matlab 6.1 analysis software (The MathWorks Inc., MA, USA). Preoperative and postoperative tibiofemoral kinematics were determined and compared. The mechanical axes of the tibia and femur were determined and kinematics represented as functions of knee flexion range. Over both the flexing and extending cycles of the knee the changes in tibiofemoral rotation (ΔROT), tibiofemoral ab/adduction (ΔABD), and distances between the origins of the mechanical axes (ΔX, ΔY, ΔZ) were calculated between pre and post-operative states.

Results: The mean differences between pre- and postoperative kinematics for all cases are given as the mean and range in parentheses. For the flexing cycle was ΔROT −0.06 (6.08 to −3.93) degrees, ΔABD was −0.04 (3.39 to −5.72) degrees, ΔX was 0.69 (2.69 to −1.84) mm, ΔY was −0.22 (4.13 to −3.41) mm and was ΔZ 0.27 (4.09 to −1.47) mm. For the extending cycle was ΔROT 0.1 (5.87 to −3.61) degrees, ΔABD was −0.06 (5.72 to −5.95) degrees, ΔX was 0.35 (2.73 to −2.39) mm, ΔY was −0.39 (5.58 to −3.08) mm and was ΔZ 0.21 (3.77 to −1.12) mm. There were no observable differences between the standard and image guided changes in kinematics. Overall, no observable differences were found between pre and post-operative kinematics.

Conclusions: The image guidance system used in our study is a valuable tool for assessing pre- and postoperative knee kinematics. Oxford Unicompartmental Knee Arthroplasty with the Phase III instrumentation in the presence of the cruciate mechanism reproduces the normal kinematics of the knee very accurately.

The increasing number of primary hip arthroplasties leads to a corresponding increase in revision hip arthroplasty. In Germany approximately 15.000 cemented total hip arthroplasties are revised annually. In these cases cement removal remains a critical point in this procedure. Ultrasonic instruments have shown to facilitate the removal of bone cement considerably. But during the use of these divices large ammounts of fumes are emitted. For occupational safety reasons, we analized the fumes emitted from the ultrasonic instrument while removing PMMA bone under standardized in vitro conditions using GC-FID-analysis and GC-masspectrometry. The analysis revealed PMMA concentrations of 5 ml/m3 (ppm9 corresponding to 10% of the MAK-value (maximum working concentration). For occupational safety matters the PMMA fumes emitted are considered safe.

We performed an experimental study to determine the effectiveness of computer assisted robotic bone preparation with regard to primary rotational stability in comparison to hand broaching. Forty-five synthetic femora were prepared by one of two robotic systems (Robodoc n = 12 and CASPAR n = 12) or by one experienced surgeon (n = 21). Seven different types of cementless femoral components were implanted using a standard protocol and measured in a specially designed testing machine with displacement in six degrees of freedom. For each implant at lease 3 measurements were taken for the handbroached and the robotic milled group, respectively. In addition the contact areas between the stems and the bone were visualised.

S-ROM, Antega and ABG stems were lightly more stable in hand broached femora. Osteolock (prepared by both robotic systems) and Vision 2000 stems were more stable in the robot group without changing the movement pattern. G2 and Versys ET performed higher stability with a change to more proximal fixation in the robotic group. Finally four of seven stems had an increase in rotational stability with the robotically milled cavities. The findings highlight the current difficulties in creating a perfect match of robotically milled cavity and stem geometry to achieve enhanced stability. The contact areas differed in some prosthesis in the way of preparation. In some stem geometries area of fixation and the movement pattern of the stem differ with the mode of preparation.