Aims

The aim of this study was to evaluate medium- to long-term outcomes and complications of the Stanmore Modular Individualised Lower Extremity System (SMILES) rotating hinge implant in revision total knee arthroplasty (rTKA) at a tertiary unit. It is hypothesized that this fully cemented construct leads to satisfactory clinical outcomes.

Introduction

In total knee arthroplasty, the aim is to relieve pain and provide a stable, functional knee. Sagittal stability is crucial in enabling a patient to return to functional activities. Knee implants with a medial pivot (MP) design are thought to more accurately reproduce the mechanics of the native joint, and potentially confer greater antero-posterior stability through the range of flexion than some other implant designs.

Tranexamic Acid (TA) has been shown to reduce transfusion rates in Total Knee Replacement (TKR) without complication. In our unit it was added to our routine enhanced recovery protocol. No other changes were made to the protocol at this time and as such we sought to examine the effects of TA on wound complication and transfusion rate.

All patients undergoing primary TKR over a 12 month period were identified. Notes and online records were reviewed to collate demographics, length of stay, use of TA, thromboprophylaxis, blood transfusion, wound complications and haemoglobin levels. All patients received a Columbus navigated TKR with a tourniquet. Only patients who received 14 days of Dalteparin for thromboprophylaxis were included.

124 patients were included, 72 receiving TA and 52 not. Mean age was 70. Four patients required a blood transfusion all of whom did not receive TA (p = 0.029). Mean change in Hb was 22 without TA and 21 with (p = 0.859). Mean length of stay was 6.83 days without Tranexamic Acid and 5.15 with (p < 0.001). 15% of patients (n=11) of the TA group had a wound complication, with 40% of patients (n=21) in the non TA group (p = 0.003). There was one ultrasound confirmed DVT (non TA group). No patients were diagnosed with pulmonary embolus.

In our unit we have demonstrated a significantly lower transfusion rate, wound complication rate and length of stay, without any significant increase in thromboembolic disease with the use of TA in TKR.

Purpose. Traditional total knee arthoplasty techniques have involved implantation of diaphyseal stems to aid in fixation expecially when using constrained polyethylene inserts. While the debate over cemented vs uncemented stems continues, the actual use of stems is considered routine. The authors' experience with cemented stemmed knee revisions in older patients with osteoporotic bone has been favorable. Our younger patients with press-fit stems from varying manufacturers have been plagued with a relatively high incidence of component loosening and stem tip pain in the tibia and occasionally thigh. We report the early results of the first 20 total knee revisions using press-fit metaphyseal filling sleeved stemless implants with constrained bearings. Methods. Twenty three patients with failed primary or revision total knees were assigned to receive stemless sleeved revision knee designs using the DePuy MBT/TC3 system. Reasons for revision included loosening, implant fracture, stiffness, instability, and stem pain. Twenty patients (ages ranging from 42–73) were successfully reconstructed without stems. Six knees with significant uncontained cavitary defects were included. Three patients with unexpectedly osteoporotic metaphyseal bone were revised with cemented stemmed implants and excluded. All cases used cement for initial fixation on the cut bone surface and fully constrained mobile bearing inserts. Results. Follow up ranged from six months to three years. All patients had radiographic evidence of well fixed stable implants on most recent examination. All four cases of revision for “end of stem pain” had complete resolution of symptoms within two weeks of revision surgery. Long leg anterior posterior mechanical alignment x-rays measured within two degrees of neutral in all cases. Knee Society Scores improved an average of 34 points. Clinical results for revision for stiffness had the lowest final scores post operatively. Conclusion. Stemmed total knee arthroplasty revision implants with or without cement are considered the standard for most revision reconstructions. Recently, primary total hip replacements using newer short metaphyseal stems have shown promising early clinical results. This case series of twenty total knee revisions using stemless press-fit metaphyseal sleeves shows similarly favorable outcomes. The complications of stemmed implants such as stem tip pain and difficulty of cemented stem removal can be avoided successfully in non-osteporotic bone reconstructions. With stable bony ingrowth visible on early post-operatyive radiographs, long term stable fixation even with constrained bearings is expected. Longer follow up will be needed to validate this technique for routine use

Total knee arthoplasty (TKA) remains a standard treatment for advanced knee arthritis. The aim of the procedure is to restore function and relieve pain ideally for the rest of patient's life. Patient matched templating (PMT) or patient specific instrumentation (PSI) is a recent development for alignment of TKA components that uses disposable guides. The users of PSI claim it to be the optimum balance of new technology and conventional technique by reducing the complexity of conventional alignment and sizing tools. To assess the clinical and radiological outcome of Primary TKA done with PSI. More than 200 cases of TKA have been done in our unit using PSI and we analysed the radiographic outcome of these cases postoperatively. We also reviewed the clinical outcome of 103 patients with 1 year and 43 patients with 2 year follow-up. Data was collected prospectively: pre-operatively and at 1 year and 2 years post-operatively including Oxford knee score (OKS), WOMAC and American knee society score (AKS). Standard AP and lateral films were done pre-operatively and post-operatively. Mean age was 66 years. There were 56 female and 47 male patients. Mean post-operative angles on standard films were: Alpha = 95.6, Beta = 88.4, Saggittal femur = 3.4 and Saggittal tibia = 90.8. Of the 103 cases with 1 year follow-up, there was significant improvement in all clinical outcome scores. Mean OKS improved from 18 to 39 at 1 year and remained the same at 2 years, WOMAC improved from 40 to 18 in both 1 and 2 years post-op. AKS Total improved from 79 to 173 at 1 year and 170 at 2 years. Performing TKA using PSI is safe and provides good radiological alignment in the coronal and sagittal plane. Significant improvement in outcome scores were seen at one and two year follow up and reached levels that compared favourably with other reported series of TKA outcome from our unit

Orthopaedic surgeons and their patients continue to seek better functional outcomes after total knee replacement, but TKA designs claim characteristic kinematic performance that is rarely assessed in patients.

The objectives of this investigation is to determine the in vivo kinematics in knees with Cruciate Retaining TKA using Patient Specific Technology during activities of daily living and to compare the findings with previous studies of kinematics of other CR TKA designs.

Four knees were operated by Triathlon CR TKA using Patient Specific Technology and a fluoroscopic measurement technique has been used to provide detailed three-dimensional kinematic assessment of knee arthroplasty function during three motor tasks. 3D fluoroscopic analysis was performed at 4-month follow-up.

The range of flexion was 90°(range 5°–95°) during chair-rising, 80°(range 0°–80°) during step up and 100° (range 0°–100°) during leg extension. The corresponding average external rotation of the femur on the tibial base-plate was 7.6° (range +4.3°; +11.9°), 9.5° (+4.0°; 13.5°) and 11.6° (+4.5°; +16.1°). The mean antero-posterior translations between femoral and tibial components during the three motor tasks were +4.7 (−3.7; +1.0), +6.4 (−3.8; +2.6) and +8,4 (−4.9; +3.5) mm on the medial compartment, and −2.5 (−7.1; −9.6), −3.6 (−6.1; −9.7), −2.6 (−7.7; −10.3) mm on the lateral compartment, respectively, with the medial condyle moving progressively anterior with flexion, and the medial condyle moving progressively posterior with flexion.

We compared Triathlon CR PSI TKA results from this study with Genesis II CR TKA, with Duracon CR TKA, with Triathlon CR TKA and with the healthy knee kinematics. The results of this study showed no screw home mechanism. The internal rotation of the tibia with knee flexion is close to normal, better than Genesis II, Duracon and Triathlon CR TKA operated with standard surgery.

The medial condyle is characterized by the same pattern of the other implants, with a paradoxical anterior translation of 5 mm.

The lateral condyle shows a posterior rollback better than Triathlon CR operated with standard surgery.

For the first time is demonstrated that the surgical technique can modify the tibio-femoral kinematics.

Introduction. A few follow-up studies of high flexion total knee arthoplasties report disturbingly high incidences of femoral loosening. Finite element analysis showed a high risk for early loosening at the cement-implant interface at the anterior flange. However, femoral implant fixation is depending on two interfaces: cement-implant interface and the cement-bone interface. Due to the geometry of the distal femur, a part of the cement-bone interface consists of cement-cortical bone interface. The strength of the cement-bone interface is lower than the strength of the cement-implant interface. The research questions addressed in this study were: 1) which interface is more prone to loosening and 2) what is the effect of different surgical preparation techniques on the risk for early loosening. Materials & methods. To achieve data for the cement-(cortical)bone interface strength and the effects of different preparation techniques on interfacial strength, human cadaver interface stress tests were performed for different preparation techniques of the bony surface and the results were implemented in a finite element (FE) model as described before. The FE model consisted of a proximal tibia and fibula, TKA components, a quadriceps and patella tendon and a non-resurfaced patella. For use in this study, the distal femur was integrated in the FE model including cohesive interface elements and a 1 mm bone cement layer. In the model, the cement-bone interface was divided into two areas, representing cortical and cancellous bone. The posterior-stabilised PFC Sigma RP-F (DePuy, J&J, USA) was incorporated in the FE knee model following the surgical procedure provided by the manufacturer. A full weight-bearing squatting cycle was simulated (ROM = 50°-155°). The interface failure index was calculated. Results. Overall, the highest stresses were found at the proximo-medial part beneath the anterior flange of the femoral component. Highest shear stresses were found at the cement-implant interface (peak shear stress of 3.33 MPa at 150° of flexion). Highest tensile stresses were found at the cement-cortical bone interface (peak tensile stress of 1.30 MPa at 150° of flexion). The failure index was highest at the cement-bone interface. When the total anterior flange was covering cancellous bone, 0.4% of the cement-bone interface would fail and 0% of the cement-implant interface at 145° of flexion. In the more realistic simulation of cortical bone with periost, almost 31.3% of the complete cement-bone interface would fail even within normal range of motion (<120°). This can be reduced by drilling holes through the cortex to 2.6%. Discussion. Obviously, the FE knee model utilized in this study contains limitations which may have affected the interface stresses calculated. However, the results presented here clearly demonstrate high risk of early loosening at the cement-bone interface. This risk can be reduced by some simple preparation techniques of the cortex behind the anterior flange. Proper anterior fixation of the femoral component, and thus adequate surgical technique, is essential to reduce the risk of femoral loosening for high-flexion TKA

To date, there are no clear guidelines from the National Institute of Clinical Excellence or the British Orthopaedic Association regarding the use of Autologous Blood Transfusion (ABT) drains after elective primary Total Knee Replacement (TKR). There is little evidence to comparing specifically the use of ABT drains versus no drain. The majority of local practice is based on current evidence and personal surgical experience.

We aim to assess whether the use of ABT drains effects the haemoglobin level at day 1 post-operation and thus alter the requirement for allogenic blood transfusion. In addition we aim to establish whether ABT drains reduce post-operative infection risk and length of hospital stay.

Forty-two patients undergoing elective primary TKR in West London between September 2011 and December 2011 were evaluated pre- and post-operatively. Patient records were scrutinised. The patient population was divided into those who received no drain post-operatively and those with an ABT drain where fluid was suctioned out of the knee in a closed system, filtered in a separate compartment and re-transfused into the patient.

Twenty-six patients had ABT drains and 4 (15.4%) required an allogenic blood transfusion post-operatively. Sixteen patients received no drain and 5 (31.3%) required allogenic blood. There was no statistical difference between these two groups (p=0.22). There was no statistical difference (p=0.75) in the average day 1 haemoglobin drop between the ABT drain and no drain groups with haemoglobin drops of 2.80 and 2.91 respectively. There was no statistical difference in the length of hospital stay between the 2 groups (p=0.35). There was no statistical difference (p=0.26) in infection rates between the 2 groups (2 in ABT drains Vs. 0 in no drains). Of the 2 patients who experienced complications one had cellulitis and the other had an infected haematoma, which was subsequently washed out.

The results identify little benefit in using ABT drains to reduce the requirement for allogenic blood transfusion in the post-operative period following TKR. However, due to small patient numbers transfusion rates of 31.3% in the ABT drain group Vs. 15.4% in the no drain group cannot be ignored. Therefore further studies including larger patient numbers with power calculations are required before a true observation can be identified.

Introduction. Patellofemoral complications remain a very common post-operative problem in association with total knee arthoplasty (TKA). As malrotation of the femoral component is often considered crucial for the outcome, we analyzed absolute rotational femoral alignment in relation to patellar tracking pre- and postoperatively and matched the results with the two year functional outcome. Methods. Femoral rotation and component rotation was assessed by axial radiography using condylar twist angle (CTA). The lateral patellar displacement, patellar tilt and Insall-Salvati index were measured on conventional radiographs. All assessments were done pre-operatively and at 2-year follow up. The series included 48 consecutive TKA (21 men, 27 women) performed at a single high-volume joint-replacement-center in 2008. All operations were performed using a tibia first-ligament balancing technique without patella resurfacing. The implant used was a condylar unconstrained ultracongruent rotating platform design. Outcome was assessed using the international knee society score (KSS) and the Kujala Score for anterior knee pain. Results. Preoperative CTA showed 6.4±2. 5° (X±SD) of internal femoral rotation (IR) (range, 1° of external rotation (ER) to 12° of IR) compared to postoperative CTA of 3.9°±2.98° (X±SD) of IR (range, 9.5° IR to 3.8°of ER) Preoperative patella lateral displacement showed a mean of 1.1mm (−2mm, 6mm), compared to postoperative patella lateral displacement with a mean of 1.7mm (−3mm, 6mm). Postoperative mean patella tilt was 6.65° (1.8°, 11.7°) postoperatively compared to 8.55° (4.3°,11.5°) preoperatively. No correlation was found between CTA post surgery and patella positioning (r=0.034, 95% CI). IR of the femoral component >3°did not show increased patella lateral displacement/tilt compared to 0° or ER. No correlation was found between the Kujala score and internal rotation of the component (r=0.082, p=0.05). At 2 year post OP KSS reached > 185 of max. 200 points in over 82% of patients. Conclusion. The influence of IR of the femoral component on patellofemoral kinematics remains controversial. As demonstrated, IR does not imperatively lead to patella maltracking and/or patellofemoral symptoms. Functional outcome in this series shows that relative rotation of the femoral component in accordance with natural variations as seen in the pre-operative assessment allows for good and excellent results

Orthopedic surgery is one of the most blood-consuming surgeries. Currently there has been a radical change in transfusion policies, developing a series of therapeutic measures essentially created to minimize the use of allogeneic blood. On the one hand, the safety of our patients must be even more our main objective. On the other hand, our economic resources are more restricted and therefore we must evaluate our surgical techniques and proceedings in order to be safer and more cost-effective. The aim of this study is to report our results of the blood lost, the percentage of blood loss, the necessity of transfussions and how many blood pakages are needed. From a sample of 2400 total knee arthroplasties proceedings, we analyze some surgical proceedings such as lligament balance, patelar traking, artrotomy, ischemia, femoro-tibial axis and type of arthroplasty. We also examine the total blood lost and the percentage of total blood loss after 4 hours, after 24hours and after 48 hour of the total knee arthoplasty surgery. We made a statistical analysis with t-test or anova test when it was necesassary. The outcome of our investigation show that the blood loss when the ischemia is less than 50 minutes is 1470 cc and 1603 cc when is more than 50 minuntes (p<0.05). If we use the medial arthrotomy, the total bleeding is 1563cc, but with subvastus arthrotomy is 1294cc (p<0.05). If we use a primary rotational total knee arthroplasty the bleeding is 953cc, but if we use a PS or PCR the bleeding is 874cc (p<0.05). As a conclusion we should know that our patients have more blood loss when the ischemia is more than fifty minutes, the bleeding is higher when we make a medial arthrotomy and when we use a rotational knee primary arthroplasty

Purpose

To compare Radiostereometric Analysis (RSA) and subjective outcomes of Total Knee Arthroplasty (TKA) and Total Ankle Arthroplasty (TAA).

Purpose. Prospective randomized intervention trial to determine whether patients undergoing rotating platform total knee arthroplasty have better clinical outcomes at two years when compared to patients receiving fixed bearing total knee arthroplasty as measured by the WOMAC, SF-36 and Knee Society (KSS) scores. Method. 67 consecutive patients (33 males and 34 females; average age 66 years) were randomized into either receiving a DePuy Sigma rotating platform (RP) total knee arthroplasty (29 patients) or a DePuy Sigma fixed bearing (FB) total knee arthroplasty (38 patients). Inclusion criteria included patients between the ages of 45–75 undergoing single-sided total knee arthoplasty for clinically significant osteoarthritic degeneration. Pain, disability and well-being were assessed using the WOMAC, KSS, and SF-36 preoperatively and at 6 months, 1 year and 2 years post-operatively. In addition, intraoperative measures were collected. Pre-operative radiographs were analyzed using the Kellgren and Lawrence Score, modified Scotts Scoring and mechanical axis. Post-operative radiographs were collected at 1 and 2 years and analyzed to identify evidence of prosthetic loosening, implant positioning and limb alignment. Results. The two groups were well-matched following randomization (age, BMI, side) and had no significant differences in intraoperative measures (operative time, estimated blood loss). There were no differences in the groups with respect to their preoperative radiographs. The average female patient was younger compared to their male cohorts (mean female = 63; mean male 68 p=0.005). The post-operative radiographs did not reveal any differences between RP and FB groups when comparing sagittal alignment of femoral and tibial components, patellar tilt and patellar location. With respect to clinical outcomes, both groups reported statistically significant improvements in KSS, WOMAC and SF-36 scores. There were no differences in their pre- and post-operative SF-36 mental component scores. The 1 year WOMAC function score was significantly higher (worse outcome) in the FB group (mean = 18) compared to the RP group (mean 7.8) (p < 0.01). Two year KSS scores were significantly higher (better outcome) in the FB group (mean = 95.7) compared to the RP group (mean = 85.9) (p < 0.05). Conclusion. Both rotating platform and fixed bearing total knee arthroplasty result in clinical improvement over pre-operative function, but has no effect on the mental component of the SF-36. The current study suggests that there is not a clear benefit in selecting either a rotating platform or a fixed bearing total knee system; rather both implants result in improved function. Interestingly, when comparing the results of the WOMAC and KSS, although both measure functional outcomes, when applied to the same population demonstrate differing sensitivity

Purpose. The patella provides a mechanical advantage to the knee extensor mechanism. Patellectomy, performed for trauma or patellofemoral arthrosis, does not preclude the development of tibiofemoral arthrosis. Total knee arthroplasty is the mainstay of treatment for tibiofemoral arthrosis. The purpose of this study was to evaluate the outcomes of total knee arthoplasty in patients who previously underwent patellectomy. Method. A retrospective analysis was completed on a prospectively collected database to identify all patients who underwent total knee arthroplasty following a previous patellectomy. Sixty-one total knee arthroplasties in 57 patients were identified. Patient demographics as well as functional outcome scores, including WOMAC and Knee Society Scores, were evaluated. Results. Thirty-six females (63.2%) and 21 males (36.8%) underwent a Total knee arthroplasty between July 1984 and April 2010. Mean follow up was 6.0 years (3 months–20 years). Mean Age and BMI was 59.8 8.6 and 30.5 5.8 respectively. Patellectomy was performed for trauma (56) and patellofemoral arthosis (five). All polyethylene inserts were cruciate substituting. There were five deaths and 10 knees (16.4%) required revision surgery. Causes for failure included aseptic loosening (2), polyethylene wear (3), component fracture (2), infection (2) and stiffness (1). WOMAC scores improved from 38.0 14.1 pre-operatively to 58.5 22.1 at latest review. Knee Society scores improved from 81.5 31.2 to 136.0 41.0. Range of motion and extensor lag changed preoperatively from 105.7 15.9 and 4.3 15.5 degrees to 110.7 12.1 and 6.3 7.1 degrees postoperatively. Conclusion. Despite the mechanical disadvantage to the knee extensor mechanism rendered by patellectomy, total knee arthroplasty is an effective treatment option for tibiofemoral arthrosis in these patients

Aim. We aim to compare revision rates and functional outcome scores in between two contemporary total knee arthoplasty systems. Methods. A search was carried out of a prospectively maintained outcomes database to identify all patients receiving total knee replacement (TKR) in the department between 2005 and 2006, when evaluation of different knee arthroplasty systems was being undertaken. Data on the first 93 consecutive patients receiving a Scorpio (Stryker, Allendale, NJ) implant and the first 93 consecutively receiving a PFC (DePuy, Warsaw, IN) implant were reviewed. Four year revision rates and functional scores were recorded. Results. Patient demographics were similar in both groups. Six of ninety three Scorpio implants were listed for revision over the four year period (6%). Five of these were for aseptic loosening. Three further patients are currently being investigated for pain and have radiological evidence of loosening with no clinical evidence of infection. No PFC implants required revision in the four year period (p = 0.013). There was no difference in Oxford Scores pre-operatively, or at 3 months, 1 year and 2 years post-operatively. Discussion. There is a significant difference in revision rates between the two prostheses, and the revision rate of the Scorpio prosthesis is far higher than would be expected. The majority of these have been revised for aseptic loosening. Those prostheses surviving to four years had similar clinical outcomes. The reasons for this higher than expected revision rate in the Scorpio group require further exploration

Purpose. Introduce an Integrated Approach for Orthopedic-Sports Medicine Practice and Patient Care Management that. Is built around effective and efficient surgical techniques, and patient care management processes. Integrates Operations and Service Excellence best practices with patient care management processes. Integrates orthopedic care delivery between outpatient clinic, pre-surgery, surgery, inpatient, (acute care) and post acute care settings. Delivers exceptional clinical, patient satisfaction and financial outcomes as validated by independent national healthcare benchmarking organization. Helps position Ortho-Sports medicine services for strategic growth. Is replicable to develop Ortho-Sports Medicine Centers of Excellence. Presentation illustrates the ‘Ten Elements’ approach to implement the Ortho-Sports Medicine Centers of Excellence and demonstrate the effectiveness of the approach with an outcomes study from over 1000 total knee arthroplasty (TKA) procedures. During the presentation, the speakers would share the key clinical, patient satisfaction, and financial outcomes achieved by the implementation of the best practices defined in our ‘Ten Elements’ approach. All performance data elements are collected, validated and analyzed by an independent third party, national healthcare benchmarking company. During the presentation Dr. Bramlett would elaborate on the surgical protocol, and the key differentiating steps in procedure technique from traditional approach that significantly enhances procedure effectiveness, efficiency and lowers the patient complication rate as demonstrated by benchmarking data. Speakers would further present the key elements of Total Knee Arthoplasty procedure that focus on patient education, patient participation in pre-surgical weight loss and pre-habilitation program, anesthesia approach, avoiding tourniquet use and deep veen thrombosis (DVT) risk reduction, early post operative patient ambulation and weight bearing, and post operative patient management approach. On average the ortho-sports medicine clinical of Alabama TKA patients are disharged from the hospital in 2.6 days, and experience 65 percent less complications than expected for a similar patient population and assume early control of their independent functionality

Background

Post operative analgesia is an important part of Total Knee Arthroplasty (TKA) to facilitate early mobilisation and patient satisfaction. We investigated the effect of periarticular infiltration of the joint with chirocaine local anaesthetic (LA) on the requirement of analgesic in the first 24 hrs period post op.

Ligament balancing can be difficult to perfect in total knee arthoplasty (TKA), where current surgical practice is subjective and highly dependent on the individual surgeon. Proper ligament balancing contributes to postoperative stability, prosthetic alignment, and proprioception. Conversely, imbalance is linked to increased wear rates of the polyethylene component within the implant and, in turn, early surgical revision. With the end goal of quantification of joint compartmental pressures, pressure sensor arrays have been designed to quantify contact stresses within the knee during TKA. Flexible, capacitive pressure sensors are designed as simple parallel plates, enabling a robust solid state design. Modification of cleanroom microfabrication processes enable realization of these arrays on polyimide (common in microdevices), and polyethylene (common in joint replacements). Readout circuitry implements an Analog Devices capacitance to digital chip and output is compared to direct LCR meter data. Testing verifies the highly linear response of the sensors with applied normal loads corresponding to pressure magnitudes present in passive (intraoperative) knee flexion. Spatial resolution of the arrays is 0.5 mm, with a critical dimension of 25 micrometers, allowing the magnitude and location of forces to be accurately recorded. The MEMS pressure sensors are mounted on a tibial trial, with the body of the trial housing all circuitry. The sensors are read sequentially, and the data undergoes analog to digital conversion prior to wireless data transmission at 2.4 GHz. An Instron machine is used for compressive loading for laboratory calibration and testing. This paper outlines device fabrication, readout circuit implementation, and preliminary results

Background and purpose: Development of minimal invasive operation techniques has given unicompartemental knee arthroplasty (UKA) renewed interest. Indications for use of UKA are however debated, and short-term advantages of UKA over total knee arthroplasty (TKA) should be weighed against the higher risk of reoperation. More knowledge on long term results of pain and function after knee arthroplasties is therefore needed and was the purpose of this study.

Methods: Patient-reported pain and function were collected at least two years after the operations in postal questionnaires from 1643 osteoarthritis patients reported to the Norwegian Arthroplasty Register with intact primary TKA (n=1271) or UKA (n=372). The questionnaire contained instruments for calculation of the knee specific Knee Osteoarthritis Outcome Score (KOOS), and for quality of life (EQ-5D, post- and pre-operative). 5 subscales from KOOS were used as outcome. To incorporate an outcome for anterior knee pain an additional subscale based on 7 questions from KOOS, clinically accepted to be related to such discomfort, was calculated. Pain and satisfaction from a visual analogue scale (VAS) were also used as outcomes together with improvement in EQ-5D index score. The outcomes were measured on a scale from 0 (worst) to 100 (best) units with an argued minimal perceptible clinical difference of 8–10 units. Group differences were analysed with multiple linear regression, adjusted for confounding by age, gender, Charnley category, time since operation and preoperative EQ-5D index score.

Results: UKA performed better than TKA for the KOOS subscales Activity in Daily Living (difference in mean outcome score =−3.4,p=0.02) and Sport and Recreation (difference =−4.4,p=0.02) and for Anterior Pain (difference=−4.5,p< 0.01). The difference was also significant for the outcome Pain(VAS) but now in favour of TKA (difference=3.3,p=0.02). Motivated by the discrepancy in the results of the pain related outcomes, Anterior Pain (UKA best), Pain(VAS) (TKA best) and Pain(KOOS) (no difference) further investigation of the questions (0=best to 4=worst) used for calculation of Pain(KOOS) and Anterior Pain were performed. Patients that had undergone UKA had more often pain from the knee (difference=0.26,p< 0.01), while they had less pain when they were bending the knee fully (difference=−0.37,p< 0.01) and less problems when squatting (difference=−0.25,p< 0.01).

Interpretation: Estimated differences did not reach the level of minimal perceptible clinical difference. There are however indication of differences in the way the two treatment groups experience knee related discomfort. Even though UKA offers a lower level of pain and less problems in activities involving bending of the knee, these patients seem to experience pain from the knee more often.