Deep surgical infections are a serious complication of total knee arthroplasty (TKA). Various protocols exist for treating these infections, each with its own advocates. In this series we report the one to five year follow-up of infected TKA that were treated with a two-stage revision knee replacement at the Glasgow Royal Infirmary between December 2003 and March 2009.

48 patients were identified from the hospital database. 6 of these were excluded as they did not meet the stipulated infection criteria. Another patient was excluded as no notes were available thereby the infection status could not be determined. Another 8 patients were excluded as these only had a first stage.

33 patients (16 male) average age 67y (49–88) met the inclusion criteria. Mean BMI was of 31.62 (19–47) and 8 patients suffered from rheumatoid arthritis. At presentation, the median for the ESR, CRP and WCC were 70.5, 133 and 8.5 respectively. The infective organism was identified in 22 patients. Following the first stage, the patients were treated with antibiotics (initially intravenous followed by oral) for an average of 11.8 weeks (4–52 weeks). This procedure failed to eliminate the infection in 6 patients (18.18%) who had further re-admissions for infection of the affected prosthesis. The resultant success rate is of over 80% which is comparable to literature data (success rates of 41% to 96% quoted). For these patients, the average time to review was 25.13 months (12–67months). At review these patients had a mean extension of 2.17° (0–10°) and a mean flexion of 98.26 (70–120°). These patients were all satisfied with their outcome.

Our results show a high successful rate of elimination of infection when a two-stage revision is used for infected knee prosthesis with over 80% of patients free of infection.

Unicompartmental knee arthroplasty (UKA) has been gaining popularity in recent years due to its perceived benefits over total knee replacements, such as greater bone preservation, reduced operating-room time, better postoperative range of motion and improved gait. However there have been failures associated with UKA caused by misalignment of the implants.

To improve the implant alignment a robotic guidance system called the RIO Robotic Arm has been developed by MAKO Surgical Corp (Ft. Lauderdale, FL). This robotic system provides real-time tactile feedback to the surgeon during bone cutting, designed to give improved accuracy compared to traditional UKA using cutting jigs and other manual instrumentation.

The University of Strathclyde in association with Glasgow Royal Infirmary has undertaken the first independent Randomised Control Trial (RCT) of the MAKO system against the Oxford UKA – a conventional UKA used in the UK. The trial involves 139 patients across the two groups.

At present the outcomes have been evaluated for 30 patients. 14 have received the MAKO unicompartmental knee arthroplasty and 16 the Oxford UKA. Both groups were seen 1 year post-operatively. Kinematic data was collected while subjects completed level walking using a Vicon Nexus motion analysis system. Three-dimensional hip, knee and ankle angles were compared between the two arthroplasty groups.

Our initial findings indicate that hip and ankle angles show no significant statistical difference, however there is a significant difference (p < 0.05) in the knee angles during the stance phase of gait. Data shows higher angles achieved by the MAKO group over the Oxford.

It would appear from our early findings that the MAKO RIO procedure with Restoris implants gives at least comparable functional outcome with the conventional Oxford system and may prove once our full sample is available for analysis to produce better stance phase kinematics with a more active gait pattern than the conventional Oxford procedure.

Further work includes analysing the data obtained from the patients in a number of other activities. These include a full biomechanical analysis of ascending and descending a flight of stairs, sit to stand and a deep knee lunge. The high demand/high flexion tasks in particular may reveal if there's an advantage to using the MAKO procedure over the Oxford. If there is a direct correlation between alignment and patient function then this effect could be more significant in the more demanding patient tasks.

The longitudinal midline and medial-parapatellar incision are commonly used in Total Knee Arthroplasty (TKA). Medial-parapatellar incision n offers a smaller wound, avoids creation of thin skin flaps and easier exposure in obese patients. This incision creates a lateral skin flap which may be subject to poor blood supply and delayed wound healing.

We undertook a Randomised Controlled Trial (n=20) comparing midline and medial-parapatellar incisions. Cutaneous blood-flow was measured using a Doppler Imager. Interstitial fluid measurements for lactate, pyruvate, lactate/pyruvate ratio and glucose were obtained from subcutaneous microdialysis catheters. Wound cosmesis was graded and skin sensation tested.

Immediately post-op there was no significant difference in subcutaneous blood flow, but by day 3 patients with medial-parapatellar incisions showed greater bloodflow than midline incisions, particularly on the medial side (387 vs 278units p=0.148). At both day 1 and 3 post-op the lateral flap of the medial parapatellar incision showed decreased blood flow compared to the medial side, though these failed to reach significance. In contrast the midline incision showed no discernable difference in blood flow between the medial and lateral flaps. Concentrations of subcutaneous glucose increased from 4 hours post-op in the midline group, returning to baseline by 24hours. In contrast, the parapatellar group remained at base line throughout. Lactate concentrations increased over time in both groups peaking at 12hours post-op. No difference was noted between incision types with regard to wound cosmesis.

We conclude that the use of a medial-parapatellar incision results in only minimal biochemical changes, which are unlikely to alter wound healing. Medial-parapatellar incision is therefore a safe alternative to a midline incision and can be utilised in appropriate complex cases to aid surgical exposure.

This RCT compared electromagnetic (EM) navigated and conventional total knee arthroplasty (TKA) in terms of clinical and functional outcomes. 200 patients (navigated=102, conventional=98) were recruited. Oxford Knee Scores (OKS) and the American Knee Society Score (AKSS) were recorded pre operation, 3 and 12 months after surgery. Post operative (coronal, sagittal and rotational) alignment was analysed from 3D CT scans taken 3 months after surgery. An objective functional assessment was completed using electrogoniometry on a sub group (navigated=60, conventional=57) at 12 months post surgery.

The EM group showed statistically significantly improved OKS (p=0.04) and AKSS (p=0.03) scores at 3 months post operation. However at 12 months post surgery there was no difference between the two groups. At the 1 year follow up it was reported that 9% of the navigated compared to 14% of the conventional group were dissatisfied with their surgical outcome.

The mechanical axis alignment of 90% of the navigated group was within 3 degrees of neutral compared to 84% of the conventional group. Although all alignment parameters except for tibial rotation was improved in the navigated group they did not reach significance apart from femoral slope alignment (p=0.01).

There was no statistically difference between the surgical groups in terms of the maximum, minimum and excursion knee joint angles during 12 functional activities. Only the knee kinematic function cycles for level walking resulted in statistically significant higher knee joint angles during 55–70% of the gait cycle in the navigated group.

Knee alignment was better restored following EM navigated TKA relative to conventional TKA, but the difference was not significant. The EM group showed greater clinical and functional improvements at early follow-up; however this difference was not sustained at 12 months. The EM group reported minimal gait improvements. Proving cost-effectiveness for navigation systems in TKA remains a challenge.

A retrospective analysis was carried out to determine the influence of pre-existing spinal pathology on the outcome of Total Knee Replacement surgery. Data was collected from 345 patients who had undergone Total Knee Replacement, at four centres in the UK, between 2000 and 2007. Oxford Knee Scores (OKS), American Knee Society Scores (AKSS) and SF-12 questionnaires were recorded prospectively. Data was collected pre-operatively and then post-operatively at 3 months, 1 year and 2 years. Patients were divided into those with (n=40) and without a history of low back pain (n=305). In addition to determining the influence of low back pain on outcome after Total Knee Replacement we also examined the influence of concomitant hip and ankle pathology in the same cohort of patients.

OKS scores were significantly worse for patients with symptomatic low back pain at 3 (p=0.05), 12 (p=0.009) and 24 months (p=0.039) following surgery. SF-12 physical scores followed a comparable pattern with significance demonstrated at 3 (p=0.038), 12 (p=0.0002) and 24 months (p=0.016). AKSS followed a similar pattern, but significance was only reached at 1 year (p=0.013). The mental component of the SF-12 measure demonstrated a significant improvement in patients' mental health post-operatively for patients with no history of low back pain. In contrast patients with low back pain showed no improvement in mental health scores post-operatively.

In contrast to low back pain, hip and ankle pathology had no statistically significant detrimental effect on the outcome of Total Knee Replacement surgery.

This study demonstrates that low back pain significantly affects the functional outcome after Total Knee Replacement surgery and that patients with low back pain show no improvement in mental health post-operatively.

The aim of this study was to determine the influence of electromagnetic (EM) navigation in total knee arthroplasty (TKA) on post operative function.

In this double blinded randomised control trial, patients with osteoarthritis either received TKA using conventional techniques (n = 49) or EM navigation (iNav Portable Navigation System, Zimmer Orthopaedics) (n = 52). All of the patients were reviewed in the Outcomes Clinic at 3 and 12 months. At 12 months post operation the patients completed an objective biomechanical functional assessment using flexible electrogoniometers, which recorded dynamic knee kinematics during daily activities. Knee joint flexion and extension moments were recorded at the 12 month post operation assessment. The functional assessment included validated questionnaires (Oxford Knee Score, American Knee Society Score, WOMAC Score and Short Form SF-36 Score). All patients underwent CT scanning of the implanted prosthesis to assess component alignment.

Improved alignment was recorded in the navigated group. However there was no significantly significant difference between the two surgical groups in terms of the subjective questionnaire scores. The biomechanical assessment showed no statistically significant differences in the maximum, minimum or excursion knee joint angles between the two surgical groups during the 12 daily functional tasks. However, significant differences were reported in level and slope walking activities during pre-swing phase (at around 60% of the gait cycle). The navigated group had significantly higher knee joint angles during pre swing suggesting a more vigorous push off into swing phase and a more ‘normal’ gait cycle. The two surgical groups were sub divided into males and females for the strength test. The female navigated group recorded a significantly greater hamstring (p = 0.03) and quadriceps (p = 0.003) moment. There was no significant difference in hamstring or quadriceps moments between the navigated and conventional male groups.

The knee kinematics and moment data suggests that the navigated group had an improved functional outcome. However the difference in the post-operation function of the two groups remains minimal despite the better alignment achieved using navigation.

Introduction

Total knee arthroplasty is an established and successful operation. In up to 10% of patients who undergo total knee arthroplasty continue to complain of pain [1]. Recently computerised tomography (CT) has been used to assess the rotational profile of both the tibial and femoral components in painful total knee arthroplasty.

Electromagnetic navigation versus conventional Total Knee Arthroplasty: Clinical improvements Optical and electromagnetic (EM) tracking systems are widely used commercially. However in orthopaedic applications optical systems dominate the market. Optical systems suffer from deficiencies due to line of sight. EM trackers are smaller but are affected by metal. The accuracy of the two tracker systems has been seen to be comparable1. Recent advancements in optical navigated TKA have shown improved overall limb alignment, implant placement and reduce outliers when compared to conventional TKA2-4.

This study is the first RCT to compare EM and conventional TKA. Two groups of 100 patients underwent TKA using either the EM navigation system or the conventional method. Frontal, sagittal and rotational alignment was analysed from a CT scan. Clinical scores including Oxford Knee Score (OKS) and Knee/Function American Knee Society Score (AKSS) were recorded pre-op, and at 3 and 12 months post-op. 3 month data presented includes 180 patients (n = 90). The 12 months data presented includes 140 (n = 70).

The two groups had similar mean mechanical axis alignments (EM 0.31o valgus, conventional 0.15o valgus). The mechanical axis alignment was improved in the EM group with 92% within +/-3o of neutral compared to 84% of the conventional group (p = 0.90). The alignment of the EM group was improved in terms of frontal femoral, frontal tibial, sagittal femoral, sagittal tibial and tibial rotation alignment. However, only the sagittal femoral alignment was significantly improved in the EM group (p = 0.04). Clinically, both TKA groups showed significant improvements in OKS and AKSS scores between both pre-op to 3 month post-op and 3 months to 12 months post-op (p<0.001). The OKS and the AKSS knee score for the EM group was significantly better at 3 months post-op (OXS p = 0.02, AKSS knee p = 0.04). However there was no difference between the groups at 12 months. The mean pre-op range of motion (ROM) for both groups was 105o. This decreased to 102o in the EM group and 99o in the conventional group at 3 months. There was a significant improvement at 12 months post-op, EM = 113o (p = 0.012) and conventional = 112o (p = 0.026). There was no significant difference in ROM between the two groups at 3 or 12 months post-op.

Therefore the alignment outcome of the EM TKA group was improved compared to the conventional group. The EM group also showed clinical improvements at 3 months post-op however these were not seen again at 12 months post-op. ROM was seen to decrease at 3 months post-op but then significantly improve by 12 month post-op.

Recent advancements in optical navigated TKA have shown improved overall limb alignment, implant placement and reduced outliers compared to conventional TKA. This study represents the first RCT comparing EM navigation and conventional TKA. 3D alignment was analysed from CT scans. Clinical scores (Oxford Knee Score (OKS) and American Knee Society Score (AKSS)) were recorded at pre-op, 3 and 12 months post-op. Data presented includes 180 patients (n=90 per group) at 3 months and 140 (n=70 per group) at 12 months.

The groups had similar mean mechanical axis alignments (EM 0.31° valgus; conventional 0.15° valgus). Mechanical axis alignment however was improved in the EM group with 92% within +/−3° of neutral compared to 84% of the conventional group (p=0.90). The EM group showed improved coronal and sagittal femoral alignment and improved coronal, sagittal and rotational tibial alignment, which was significant for sagittal femoral alignment (p=0.04). The OKS and AKSS scores were significantly better for the EM group at 3 months post-op (OKS p=0.02, AKSS p=0.04), but there was no difference between groups at 12 months. The mean pre-op range of motion (ROM) for both groups was 105°. This decreased at 3 months to 102° in the EM group and 99° in the conventional group, but there was a significant improvement by 12 months: EM=113° (p=0.012) and conventional=112° (p=0.026). ROM was statistically similar between groups at all assessment phases.

Knee alignment was better restored following EM navigated TKA relative to conventional TKA, but the difference was not significant. The EM group showed greater clinical improvements at early follow-up; however this difference was not sustained at 12 months. ROM was seen to decrease at 3 months but then significantly improve by 12 month post-op. Proving cost-effectiveness for navigation systems in TKA remains a challenge.

Total knee arthroplasty (TKA) is an established and successful operation. However patient satisfaction rates vary from 81 to 89% 1,2,3. Pain following TKA is a significant factor in patient dissatisfaction 1. Many causes for pain following total knee arthroplasty have been identified 4 but rates of unexplained pain vary from 4 to 13.1% 5,6. Recently computerised tomography (CT) has been used to assess the rotational profile of both the tibial and femoral components in painful TKA

We reviewed 57 patients with an unexplained painful following TKA and compared these to a matched control group of 60 patients with TKA. Datum gathered from case notes and radiographs using a prospective database to identify patients. The CT information recorded was limb alignment, tibial component rotation, and femoral component rotation and combined rotation.

The two matched cohorts of patients had similar demographics. A significant difference in tibial, femoral and combined component rotation was identified between the groups. The following mean rotations were identified for the painful and control groups respectively. Tibial rotation was 3.46 degrees internal rotation (IR) compared to 2.50 degrees external rotation (ER)(p=0.001). Femoral rotation was 2.30 IR compared to 0.36 ER(p=0.02). Combined rotation was 7.08 IR compared to 2.85 ER(p=0.001).

This is the largest study presently in the literature. We have identified significant internal rotation in a patient cohort with unexplained painful TKA when compared to a matched control group. Internal rotation of the tibial component, femoral component and combined rotation was identified as a factor in unexplained pain following TKA.

Fragility fractures are an increasing cause of morbidity and mortality in the elderly population. Their association with reduced bone mineral density (BMD) is well documented. It is a reasonable assumption that hip fracture severity is linked to the magnitude of bone loss, (the lower the BMD, the more severe the fracture), however it is not known whether this correlation exists. Our aim therefore was to investigate the relationship between BMD and hip fracture severity.

We reviewed 142 patients, 96 females and 46 males, mean age 74 years (49-92), who had sustained a hip fracture following a simple ground level fall. All had subsequently undergone DEXA bone scanning of the contralateral hip and lumbar spine. Fractures were classified as intra-capsular, extra-capsular or subtrochanteric, then sub-classified using the Garden, Jensen and Seinsheimer classifications respectively. They were grouped into simple (stable) or comminuted (unstable) fracture patterns. Risk factors for osteoporosis were recorded.

A low hip BMD (<2.5) was associated with an increased risk of extra-capsular fracture (p=0.025). However, no association with fracture type (extra vs. intra-capsular, p>0.05) was identified with the following variables; age, gender, BMI <25, smoking, and excess alcohol intake. We did not find any statistically significant associations between fracture severity and the nine principle variables tested for: age; gender; smoking; BMI < 25; alcohol excess and low hip or lumbar BMD T or Z score <-2.5.

Although the association between BMD and risk of fragility fractures is well documented, the results of this study would suggest that severity of hip fractures does not follow this correlation. Therefore, no assumption can be made about BMD of the proximal femur based on the severity of fracture observed on plain radiographs alone.

Total knee arthroplasty is an established and successful operation. In up to 13% of patients who undergo total knee arthroplasty continue to complain of pain. Recently computerised tomography (CT) has been used to assess the rotational profile of both the tibial and femoral components in painful total knee arthroplasty.

We reviewed 56 painful total knee replacements and compared these to 56 matched patients with pain free total knee replacements. Patients with infection, aseptic loosening, revision arthroplasties and gross coronal malalignment were excluded. Datum gathered from case notes and radiographs using a prospective orthopaedic database to identify patients. The age, sex, preoperative and postoperative Oxford scores, visual analogue scores and treatments recorded. The CT information recorded was limb alignment, tibial component rotation, femoral component rotation and combined rotation.

The two cohorts of patients had similar demographics. The mean limb alignments were 1.7 degrees varus and 0.01 degrees valgus in the painful and control groups respectively. A significant difference in tibial component rotation was identified between the groups with 3.2 degrees of internal rotation in the painful group compared to 0.5 degrees of external rotation in the control group (p=0.001). A significant difference in femoral component rotation was identified between the groups with 3.8 degrees of internal rotation in the painful group compared to 1.1 degrees of external rotation in the control group (p=0.001). A significant difference in the combined component rotation was identified between the groups with 6.8 degrees of internal rotation in the painful group compared to 1.7 degrees of external rotation in the control group (p=0.001).

We have identified significant internal rotation in a patient cohort with painful total knee arthroplasty when compared to a control group with internal rotation of the tibial component, femoral component and combined rotation. This is the largest comparison series currently in the literature.

Introduction

Unidirectional mobile bearing knees (RP) were developed to optimise the tibio-femoral articulation in an effort to enhance function and reduce polyethylene wear. The self aligning bearing should also benefit the patello-femoral joint further improving outcome. This study was designed to assess whether these potential benefits are realised in the clinical setting.

Summary

We report a large study of 331 patients at two years post operation who were prospectively randomised to receive either a rotating platform or a fixed bearing knee replacement of an otherwise identical design.

Introduction

Previous studies comparing cruciate retaining (CR) and cruciate sacrificing - posterior stabilised (PS) TKRs have failed to demonstrate a difference in outcomes based on numbers of patients recruited.

This large study compares clinical outcomes in groups having PS and CR TKR and reports the results at 1 and 2 years post-operatively.

Aim

The aim of the study was to assess the impact of a self aligning unidirectional mobile tibial bearing and the use of a patella button on lateral patella release rates within a knee system using a common femoral component for both the fixed and mobile variants.

Summary: This study compares the outcomes of a large series of 683 cruciate sacrificing (PS) and cruciate retaining (CR) TKRs at minimum 2 years follow-up. Patients with a PS component showed a greater improvement in the pain and knee components of the American Knee Society Score at both 1 and 2 years post-operatively and also demonstrated a greater improvement in knee flex-ion at both time points.

Introduction: Excellent clinical results have been reported with both PS and CR TKR designs. A number of randomised trials comparing the two techniques have failed to demonstrate a difference in outcomes based on the numbers of patients recruited.

It is hypothesised that cruciate retention in total knee arthroplasty may result in improved kinematics of the knee by maintaining the femoral rollback seen in the normal knee, resulting in improved function. This study compares clinical outcomes in groups having PS and CR total knee arthroplasty and report the results at 1 and 2 years post-operatively.

Methods: A total of 683 patients undergoing TKR surgery were consecutively enrolled in a prospective multi-centre study with 2 arms. In the first arm patients receiving a PS component were randomised to receive either a mobile bearing (176 patients) or fixed bearing (176 patients) implant. In the second arm, patients receiving a CR component were randomised to receive either a mobile bearing (161 patients) or fixed bearing (170 patients) implant. All patients were assessed pre-operatively and at one and two years postoperatively using standard tools (Oxford, AKSS, Patellar Score) by independent nurse specialists. The data from the 2 arms of the trial were then analysed to compare differences between PS and CR implants.

Results: Patients with a PS component showed a greater improvement in the pain component of the AKSS at 1 year (p=0.0003) and at 2 years (p=0.0085) post-op.

Patients with a PS also showed a greater improvement in the AKSS knee score at 1 (p=0.0001) and 2 (p=0.001) years.

Knee flexion improvement was also greater in the PS group at 1 (p=0< 0.0001) and 2 (p=0.0035) years.

PS knees also achieved better outcomes in these variables in the mobile and fixed subgroups.

There were no other significant differences in the scores between the two groups at any stage.

Conclusion: This study reports on a large prospective multi-centre series of PS and CR TKRs. Improvements in pain and knee components of the AKSS score and knee flexion at both 1 and 2 years follow-up were greater in PS knees. Although this difference was statistically significant, differences in real terms were relatively small.

Aim: The aim of the study was to assess the impact of a self aligning unidirectional mobile bearing TKR on lateral patella release rates within a knee system using a common femoral component for both the fixed and mobile variants.

Methods and Results: A total of 357 patients undergoing TKR were randomly allocated to receive either a Mobile Bearing (181 knees) or a Fixed Bearing (176 knees) PSTKR. Further sub-randomisation into patella resurfacing or retention was performed for both designs. The need for lateral patella release was assessed during surgery.

The lateral release rate was similar for fixed bearing (9%) and mobile bearing (9%) implants (p=0.95). Patella resurfacing resulted in lower lateral release rates when compared to patella retention (5.5% vs 13.5%; p=0.012). This difference was most marked in the mobile bearing group where the lateral release rate was 16% with patella retention compared to 3% with patella resurfacing (p=0.009).

Conclusion: The addition of a rotating platform tibial component has had no impact on the lateral release rate in this study. Optimising patella geometry by patella resurfacing appears more important than tibial bearing deisgn per se. The combination of a mobile bearing design and patella resurfacing appears the optimise patello-femoral tracking.

Aim: This study aims to establish whether or not mobile bearing TKR delivers the often stated benefits improved function and range of motion when compared to its fixed bearing equivalent.

Methods and Results: A total of 357 patients undergoing TKR were randomly allocated to receive either a Mobile Bearing (181 knees) or a Fixed Bearing (176 knees) PSTKR. Further subrandomisation into patella resurfacing or retention was performed for both designs. All knees were scored using standard tools (Oxford, AKSS and SF12) preoperatively and at intervals postoperatively by independent observers.

The range of motion increased from an average of 96 deg. (pre-op) to an average of 109 deg. at 1 year post-op for both the fixed and mobile bearing design. The management of the patella had no effect in either group.

The knee society and knee function scores increased equally for both the fixed bearing and mobile bearing knees with no differences noted.

Conclusion: There were no measurable differences in range of motion and clinical outcome scores at 1 year post-op for a mobile bearing design over its fixed bearing equivalent. It is likely that any potential advantages of a mobile bearing design will manifest in longevity rather than function.