Outcomes of Dual Mobility Bearings in Revision Total Hip Replacements

Background Dual mobility bearings have gained attention in the prevention of instability in revision total hip replacement. This study aimed to evaluate the use of dual mobility bearings in revision total hip replacement. The primary outcome was the rate of dislocation. Secondary outcomes included the rate of re-operation for any reason, surgical complications, serious medical adverse events, and 90-day mortality rate. Methods A single-centre case series of 55 consecutive operations in 49 patients who underwent revision total hip replacement using dual mobility bearings with a minimum follow-up of three months was studied.  Results Early dislocation occurred in one case (2%), and there were no intra-prosthetic dislocations at a mean follow-up of 16 months. The rate of re-operation for any reason was 6/55 (11%) cases, and the post-operative infection rate was 2/55 (4%) cases. Serious medical adverse events occurred in 2/55 (4%) cases. The 90-day mortality rate was 1/55 (2%) cases. Two cases (2%) had cup abduction or anteversion angles outside of the safe zones although there were no dislocations in these patients. Conclusion This case series demonstrates a low dislocation rate in the early post-operative period for dual mobility bearings in revision total hip replacement. Dual mobility bearings show promise as an early low dislocation implant in revision total hip replacement. It remains to be determined whether dual mobility bearings are low-wear implants in the long term.

Subsidence in Centraliser Sign: A Novel Tool to Help Predict Early Subsidence in Periprosthetic Femoral Fractures Around Polished Tapered Stems Treated With Internal Fixation

Background When treating periprosthetic femoral fractures (PPF) around polished taper slip stems (PTS), determining which patients can be successfully treated with internal fixation can be challenging. We have described the subsidence-in-centraliser (SINC) sign as a radiographic feature of PPF around PTS stems. We hypothesise that a positive SINC sign can help predict a poorer outcome for the fixation of these fractures. Patients and methods Retrospective identification of PPFs around cemented PTS with an appreciable centraliser on radiographs was conducted at a single centre. A positive SINC sign was defined as a post-injury radiograph demonstrating >50% reduction in the radiographic lucency representing the stem centraliser when compared to pre-injury films or complete obliteration of distal lucency when no pre-injury film was available. The primary outcome was the rate of subsequent stem subsidence on follow-up radiographs comparing SINC-positive and SINC-negative fractures, which were managed with open reduction and internal fixation (ORIF). Results Fifty-four patients were included in the analysis. The mean age was 76.8 years, and the mean follow-up for all patients was 12.7 months. Thirty-five fractures were deemed SINC-positive, and 19 were SINC-negative. 17/17 (100%) SINC-positive fractures managed with fixation underwent further subsidence (mean 5.4 mm, SD 2.8). A positive SINC sign demonstrated a sensitivity of 90.5% and specificity of 100% for subsequent stem subsidence in fractures treated without revision. SINC positive fractures underwent significantly more subsidence compared with SINC negative fractures when fixed (5.4 mm vs. 0.28 mm, U = 6.50, p<0.001) at a mean follow-up of 12.7 months. The SINC sign demonstrated strong inter- (k=0.96) and intra-rater (k=0.86) reliability. Conclusion The SINC sign can serve as a useful adjunct in the decision to fix or revise PPF around PTS. A positive SINC sign may represent a cement mantle that cannot be reconstituted anatomically, leading to subsidence after treatment with ORIF.

Accuracy of Total Hip Arthroplasty Templating Using Set Calibration Magnifications

Background Templating for total hip arthroplasty has been adopted over recent decades as a reliable and accurate method for pre-operative planning. The use of calibration markers for this process provides a recognised benefit at the expense of cost, availability and error. Many surgeons use a set magnification of 118% to account for calibration errors when templating total hip arthroplasty. This study aims to assess the accuracy of templating with standardised magnifications and assess the effect of BMI on templating accuracy. Materials and methods A retrospective analysis was performed using a single-surgeon series of 119 consecutive total hip arthroplasties. Anteroposterior radiographs were taken pre- or post-operatively without calibration hardware. Pre-operatively, the total hip arthroplasty was templated on TraumaCad (BrainLab Inc, Westchester, IL) using either 118% or 119% calibration magnification. Post-operative magnification was calibrated using the known femoral head diameter. Templated and implanted prostheses were compared for size. Results At 118%, 61.1% of cups matched those templated with 96.3% of cups within two sizes. At 119%, 52.5% of cups used matched their templates with 100% within two sizes. There was no significant difference between 118% and 119% cup size prediction (p=0.49). A trend was noticed in increasing magnification error with increasing BMI. However, BMI had no significant effect on the accuracy of templating cup size within two cup sizes (p=0.58). Conclusion. Templating acetabular cups using a set magnification of 118% or 119% yields accurate results and provides a reliable method to template without calibration equipment. Whilst BMI can affect magnification error, this has no significant effect on the accuracy of implanted cups and stems within two sizes.

Fixation and Implant Retention of Extracapsular Femoral Neck Periprosthetic Fractures Around Hip Resurfacing Arthroplasty - A Case Series

BACKGROUND

Extracapsular femoral neck fractures in the presence of a resurfacing hip arthroplasty (RHA) appear to be independent of suboptimal technique during the initial implantation of the RHA and present with a similar etiology as native hip fractures - that is, a fragility fracture related to pathological or age-related osteoporosis, as a consequence of trauma. In the presence of a well-fixed and previously well-functioning RHA, the options for management include revision arthroplasty or open reduction and internal fixation (ORIF). In the absence of loosening through mechanisms of wear, infection, metallosis, or suboptimal prosthesis positioning, many authors have advocated ORIF with implant retention. However, there is often debate regarding the use of total hip arthroplasty in these cases.

CASE SERIES

The authors conducted a thorough assessment of the literature followed by a retrospective review of outcomes for three patients treated by ORIF with implant retention for extracapsular femoral neck fractures around a RHA, using a standardized technique. All patients were independently mobile and active with well-fixed and well-functioning RHAs before the date of injury. All patients suffered low-energy trauma resulting in the fracture. There were no intraoperative or perioperative complications. All patients achieved full weight-bearing status and independent mobility. Two patients achieved radiographic union and returned to full range of movement and independent mobilization comparable to their preoperative state. One patient was lost to follow-up.

CONCLUSION

The authors believe that fixation of extracapsular proximal femoral fractures distal to a well-fixed, well-functioning RHA is a good management option in an independent and active patient. A higher level of evidence is needed to investigate the surgical management options of these injuries comparing osteosynthesis with revision arthroplasty.

COVID-19: lessons learnt and priorities in trauma and orthopaedic surgery

The COVID-19 pandemic is the most serious health crisis of our time. Global public measures have been enacted to try to prevent healthcare systems from being overwhelmed. The trauma and orthopaedic (T&O) community has overcome challenges in order to continue to deliver acute trauma care to patients and plan for challenges ahead. This review explores the lessons learnt, the priorities and the controversies that the T&O community has faced during the crisis. Historically, the experience of major incidents in T&O has focused on mass casualty events. The current pandemic requires a different approach to resource management in order to create a long-term, system-sustaining model of care alongside a move towards resource balancing and facilitation. Significant limitations in theatre access, anaesthetists and bed capacity have necessitated adaptation. Strategic changes to trauma networks and risk mitigation allowed for ongoing surgical treatment of trauma. Outpatient care was reformed with the uptake of technology. The return to elective surgery requires careful planning, restructuring of elective pathways and risk management. Despite the hope that mass vaccination will lift the pressure on bed capacity and on bleak economic forecasts, the orthopaedic community must readjust its focus to meet the challenge of huge backlogs in elective caseloads before looking to the future with a robust strategy of integrated resilient pathways. The pandemic will provide the impetus for research that defines essential interventions and facilitates the implementation of strategies to overcome current barriers and to prepare for future crises.

Bilateral osteochondral defects of the patellae in an 11-year-old girl

Osteochondral defect or osteochondritis dissecans (OCD) of the knee usually affects young, active populations. It is a challenging diagnosis as patients typically present with poorly localised activity-related pain, which is non-specific and covers many differentials. We present an active 11-year-old girl with bilateral osteochondral defects of the patellae: a rare clinical disorder which was affecting her sporting activities. She had a 12-month history of bilateral anterior knee pain before the diagnosis was achieved with appropriate imaging. Her pain significantly improved with activity modification and physiotherapy. Follow-up will require outpatient clinic assessment and imaging to determine if non-operative management continues to be successful or surgery may be required. This case report emphasises the importance of appropriate high index of suspicion when managing patients with non-specific knee pain. It also demonstrates the importance of judicious use of imaging to avoid a missed or delayed diagnosis.

Resuming elective hip and knee arthroplasty in the COVID-19 era: a unique insight into patient risk aversion and sentiment

INTRODUCTION

There has been guidance from the government and orthopaedic community on how best to ensure the safety of our patients and colleagues as we recommence elective surgery in the UK. The primary aim was to determine what proportion of patients feel they should proceed with their elective hip and knee arthroplasty surgery during the COVID-19 climate. The secondary aim was to investigate what variables affected this decision.

METHODS

Patient information from a single surgeon's waiting list in a district general hospital were recorded. A standardised telephone discussion was had with all the patients noting the severity of pain and the potential reasons for not wanting to proceed with surgery.

RESULTS

A total of 70.6% (96/136) of patients wished to proceed with surgery; 29.4% (40/136) did not wish to proceed. The decision to proceed with surgery was not correlated with sex, American Society of Anesthesiologists grade or COVID-19 risk. Those who wished to proceed with surgery had a mean age of 68.5 years while those who did not had a mean age of 72.4 years (P = 0.03). Within the matched subgroups, patients under the age of 70 years were more willing to proceed with primary hip arthroplasty surgery (87.9%) compared with primary knee arthroplasty surgery (57.1%; P = 0.007); 75% of the patients who did not wish to proceed with surgery expressed concerns about perioperative COVID-19 infection.

CONCLUSION

There is a significant proportion of arthroplasty patients on waiting lists who would be willing to accept the increased risks associated with COVID-19 to undergo surgery on an urgent basis. The subgroup of younger patients awaiting hip arthroplasty is more willing than those awaiting knee arthroplasty to proceed with surgery.

Telemedicine in orthopaedics and its potential applications during COVID-19 and beyond: A systematic review

Introduction

Telemedicine is the delivery of healthcare across a distance using some form of communication technology. The COVID-19 pandemic has led to increased adoption of telemedicine with national orthopaedic governing bodies advocating its use, as evidence suggests that social distancing maybe necessary until 2022. This systematic review aims to explore evidence for telemedicine in orthopaedics to determine its advantages, validity, effectiveness and utilisation.

Methods

Databases of PubMed, Web of Science, Scopus and CINAHL were systematically searched and articles were included if they involved any form of telephone or video consultation in an orthopaedic population. Findings were synthesised into four themes: patient/clinician satisfaction, accuracy and validity of examination, safety and patient outcomes and cost effectiveness. Quality assessment was undertaken using Cochrane and Joanna Briggs Institute appraisal tools.

Results

Twenty-one studies were included consisting of nine randomised controlled trials (RCTs). Studies revealed high patient satisfaction with telemedicine for convenience, less waiting and travelling time. Telemedicine was cost effective particularly if patients had to travel long distances, required hospital transport or time off work. No clinically significant differences were found in patient examination nor measurement of patient-reported outcome measures. Telemedicine was reported to be a safe method of consultation.

Discussion

Evidence suggests that telemedicine in orthopaedics can be safe, cost effective, valid in clinical assessment and with high patient/clinician satisfaction. However, more high-quality RCTs are required to elucidate long-term outcomes. This systematic review presents up-to-date evidence on the use of telemedicine and provides data for organisations considering its use during the COVID-19 pandemic and beyond.

Cement Pedestal Spacer Technique for Infected Two-stage Revision Knee Arthroplasty: Description and Comparison of Complications

BACKGROUND

Infection following total knee arthroplasty (TKA) is a significant complication, with an incidence of up to 2% in primary TKA and 4%-8% in revision cases. Two-stage revision is the gold standard treatment for long-lasting infections of TKA. The purpose of this study was to describe the cement pedestal spacer technique used in infected two-stage revision knee arthroplasty and compare complications against conventional fixed and mobile cement spacers.

PATIENTS AND METHODS

A retrospective review was conducted in all cases who underwent two-stage TKA revision for infection between 2009 and 2015. These cases were separated into groups depending on the cement spacer utilized (fixed, mobile nonpedestal, and mobile spacers with cement pedestal). The cement pedestal technique involves press fitting a cement cylinder into the femur before definitive spacer insertion.

RESULTS

Forty four patients underwent two-stage revision TKA. Fewest complications were observed in the pedestal group, with no spacers having subluxed/tilted. The longest followup was also observed in the pedestal group (mean 52.5 months). Mobile spacers with no cement pedestal displayed the highest reinfection rate (16.7%) and the greatest number of cases with complications (malalignment, subluxation, tilting, and spacer fracture). All patients in the pedestal group were ambulatory after the first-stage revision.

CONCLUSIONS

The cement pedestal technique minimizes complications by optimizing component positioning and balancing. It also safely extends the indication for an articulated spacer into a set of cases with more extensive bone loss and allows for extended monitoring of inflammatory markers.

Differences in trochlear parameters between native and prosthetic kinematically or mechanically aligned knees

INTRODUCTION

Kinematic (KA) and mechanical (MA) alignment techniques are two different philosophies of implant positioning that use the same TKA implants. This might generate differences in the resulting prosthetic trochleae parameters between the two techniques of alignment. Our study aim was to test the following hypotheses : (1) mechanically or kinematically aligned femoral implant understuffs the native trochlear articular surface and poorly restores the native groove orientation, and (2) the orientation of the prosthetic trochlear groove and trochlear fill are different between MA and KA.

METHODS

Three-dimensional models of the femur were made from segmentation of preoperative Magnetic Resonance Imaging scans (MRIs) of ten subjects with isolated medial tibiofemoral osteoarthritis. In-house planning and analysis software kinematically and mechanically aligned a modern cruciate retaining femoral component and determined differences in parameters of the trochlear fit between native and prosthetic trochleae, and between KA and MA prosthetic trochleae.

RESULTS

The MA prosthetic trochleae did not fill (understuffed) the entire length of the native medial facet and the proximal 70% of the native groove and lateral facet, and oriented the trochleae groove 8° more valgus than native. The KA prosthetic trochleae understuffed the proximal 70% of the native trochleae, and had a groove 6° more valgus than native. The KA trochleae understuffed the medial facet distally and oriented the groove 2° less valgus and 3° more internally rotated than the MA trochleae.

CONCLUSION

MA and KA prosthetic trochleae substantially understuff and create a prosthetic groove more valgus compared to native trochlear anatomy, and they also differed between each other regarding trochleae stuffing and groove alignment. Although randomized trials have not shown differences in patellofemoral complications between KA and MA, a femoral component designed specifically for KA that more closely restores the native trochlear anatomy might improve patient reported satisfaction and function.

LEVEL OF EVIDENCE

Level 2 controlled laboratory study.

Alignment options for total knee arthroplasty: A systematic review

In spite of improvements in implant designs and surgical precision, functional outcomes of mechanically aligned total knee arthroplasty (MA TKA) have plateaued. This suggests probable technical intrinsic limitations that few alternate more anatomical recently promoted surgical techniques are trying to solve. This review aims at (1) classifying the different options to frontally align TKA implants, (2) at comparing their safety and efficacy with the one from MA TKAs, therefore answering the following questions: does alternative techniques to position TKA improve functional outcomes of TKA (question 1)? Is there any pathoanatomy not suitable for kinematic implantation of a TKA (question 2)? A systematic review of the existing literature utilizing PubMed and Google Scholar search engines was performed in February 2017. Only studies published in peer-reviewed journals over the last ten years in either English or French were reviewed. We identified 569 reports, of which 13 met our eligibility criteria. Four alternative techniques to position a TKA are challenging the traditional MA technique: anatomic (AA), adjusted mechanical (aMA), kinematic (KA), and restricted kinematic (rKA) alignment techniques. Regarding osteoarthritic patients with slight to mid constitutional knee frontal deformity, the KA technique enables a faster recovery and generally generates higher functional TKA outcomes than the MA technique. Kinematic alignment for TKA is a new attractive technique for TKA at early to mid-term, but need longer follow-up in order to assess its true value. It is probable that some forms of pathoanatomy might affect longer-term clinical outcomes of KA TKA and make the rKA technique or additional surgical corrections (realignment osteotomy, retinacular ligament reconstruction etc.) relevant for this sub-group of patients. Longer follow-up is needed to define the best indication of each alternative surgical technique for TKA. Level I for question 1 (systematic review of Level I studies), level 4 for question 2.

The kinematic alignment technique for TKA reliably aligns the femoral component with the cylindrical axis

INTRODUCTION

Kinematic alignment (KA) technique is an alternative technique for positioning a TKA, which aims a patient-specific implant positioning in order to reproduce the pre-arthritic knee anatomy. Because reliability in implant positioning is of interest to obtain reproducible good functional results, our study tests the hypothesis that the medial and lateral distal and posterior positions of the planned and surgically implanted kinematically aligned femoral component are similar.

METHODS

Preoperative knee magnetic resonance imaging (MRI) and postoperative knee computed tomography (CT) of 13 patients implanted with a KA Persona^® TKA (Zimmer, Warsaw, USA) using manual instrumentation (kinematically-aligned TKA procedure pack^®, Zimmer Biomet, Warsaw, USA) were segmented to create 3D femoral models. The kinematic alignment position of the femoral component was planned on the 3D model created from the preoperative MRI. Differences in the positions of the planned and surgically implanted kinematically-aligned femoral component were determined with in-house analysis software.

RESULTS

The average differences between the medial and lateral distal and posterior positions of the planned and surgically implanted kinematically-aligned femoral component were inferior to 1mm and no statistically significant. In terms of variability, 62% (8/13) of performed implants matched all four positions within 1.5mm, and the maximum difference was 3mm.

CONCLUSION

In this small series, intraoperative kinematic positioning of the femoral component with the specific manual instrumentation closely matched the planned position, which suggests that this technique reliably aligned the flexion-extension axis of the femoral component to the cylindrical axis.

LEVEL OF EVIDENCE

Level 3.

Mechanical alignment technique for TKA: Are there intrinsic technical limitations?

BACKGROUND

Mechanically aligned (MA) total knee arthroplasty (TKA) is affected by disappointing functional outcomes in spite of the recent improvements in surgical precision and implant designs. This might suggest the existence of intrinsic technical limitations. Our study aims to compare the prosthetic and native trochlear articular surfaces and to estimate the extent of collateral ligament imbalance, which is technically uncorrectable by collateral ligament release when TKA implants are mechanically aligned.

STUDY HYPOTHESIS

Conventional MA technique generates a high rate of prosthetic overstuffing of the distal groove, distal lateral trochlear facet and distal lateral femoral condyle (Hypothesis 1), and technically uncorrectable collateral ligament imbalance (hypothesis 2)? Disregarding the distal femoral joint line obliquity (DFJLO) when performing femoral cuts explains distal lateral femoral prosthetic stuffing and uncorrectable imbalance (hypothesis 3)?

METHODS

Twenty patients underwent a conventional MA TKA. Pre-operative MRI-based 3D knee models were generated and MA TKA was simulated. Native and prosthetic trochlear articular surfaces were compared using in-house analysis software. Following the automatic determination by the planning software of the size of the extension and flexion gaps, an algorithm was applied to balance the gaps and the frequency and amplitude of technically uncorrectable knee imbalance were estimated.

RESULTS

The conventional MA technique generates a significant slight distal lateral femoral prosthetic overstuffing (mean 0.6mm, 0.8mm, 1.25mm for the most distal lateral facet point, groove, and at the most distal point of lateral femoral condyle, respectively) and a high rate of type 1 and 2 uncorrectable knee imbalance (30% and 40%, respectively). The incidence of distal lateral prosthetic overstuffing (trochlea and condyle) and uncorrectable knee imbalance were strongly to very strongly correlated with the DFJLO (r=0.53 to 0.89).

CONCLUSION

Conventional MA technique for TKA generates frequent lateral distal femoral prosthetic overstuffing and technically uncorrectable knee imbalance secondary to disregarding the DFJLO when adjusting the femoral component frontal and axial rotations, respectively.

LEVEL OF EVIDENCE

level 4.

Femoral articular geometry and patellofemoral stability

BACKGROUND

Patellofemoral instability is a major cause of anterior knee pain. The aim of this study was to examine how the medial and lateral stability of the patellofemoral joint in the normal knee changes with knee flexion and measure its relationship to differences in femoral trochlear geometry.

METHODS

Twelve fresh-frozen cadaveric knees were used. Five components of the quadriceps and the iliotibial band were loaded physiologically with 175N and 30N, respectively. The force required to displace the patella 10mm laterally and medially at 0°, 20°, 30°, 60° and 90° knee flexion was measured. Patellofemoral contact points at these knee flexion angles were marked. The trochlea cartilage geometry at these flexion angles was visualized by Computed Tomography imaging of the femora in air with no overlying tissue. The sulcus, medial and lateral facet angles were measured. The facet angles were measured relative to the posterior condylar datum.

RESULTS

The lateral facet slope decreased progressively with flexion from 23°±3° (mean±S.D.) at 0° to 17±5° at 90°. While the medial facet angle increased progressively from 8°±8° to 36°±9° between 0° and 90°. Patellar lateral stability varied from 96±22N at 0°, to 77±23N at 20°, then to 101±27N at 90° knee flexion. Medial stability varied from 74±20N at 0° to 170±21N at 90°. There were significant correlations between the sulcus angle and the medial facet angle with medial stability (r=0.78, p<0.0001).

CONCLUSIONS

These results provide objective evidence relating the changes of femoral profile geometry with knee flexion to patellofemoral stability.

Quantifying the contribution of pincer deformity to femoro-acetabular impingement using 3D computerised tomography

OBJECTIVE

To provide a simple, reliable method for the three-dimensional quantification of pincer-type hip deformity.

MATERIALS AND METHODS

Computerised tomography scans of 16 normal female hips and 15 female hips with clinical femoro-acetabular impingement (FAI) and radiographic signs of pincer secondary to acetabular protrusio were analysed. After orientating the pelvis in the anterior pelvic plane, the acetabular centre was determined, and the ratios of its coordinates to the corresponding pelvic dimensions were calculated. Acetabular coverage of the femoral head and centre-edge angles were also measured for the two groups.

RESULTS

In hips with a pincer, the hip was medialised by 37 % (p = 0.03), more proximal by 5 % (p = 0.05) and more posterior by 9 % (p = 0.03) compared with the normal hips. Coverage of the femoral head in protrusio hips was significantly greater than normal (average 71 % vs 82 %, p = 0.0001). Both the lateral centre-edge angle and the combined anterior-posterior centre-edge angle were greater in protrusio hips than in the normal ones (48° vs 37 °, p < 0.001; and 216° vs 176°, p < 0.0001 respectively).

CONCLUSION

Displacement in acetabular protrusio occurs in all planes. This CT-based method allows for the accurate and standardised quantification of the extent of displacement, as well as 3D measurement of femoral head coverage. In the adult female population, a combined centre-edge angle of over 190° suggests an acetabulum that is too deep and a potential cause of symptoms of femoro-acetabular impingement. Conversely, an acetabulum that has a combined centre-edge angle of less than 190° may be considered to be of normal depth, and therefore not contributing a pincer to FAI should it occur.

Length-change patterns of the collateral ligaments after total knee arthroplasty

PURPOSE

Total knee arthroplasty (TKA) is a procedure with function dependent upon correct tensioning of the soft-tissue constraints. The purpose of this study was to examine the length-change behaviour of the collateral ligaments during knee flexion-extension before and after TKA. The influence of differing degrees of internal-external rotation of the femoral component on slackening/tightening of the collateral ligaments during knee flexion was to be studied.

METHODS

The length-change patterns of the collateral ligaments were measured in eight intact knees in vitro: sutures were passed along the ligaments and attached to displacement transducers. Measurements were repeated after TKA with the femoral component in neutral rotation, then with 5° internal and 5° external rotation.

RESULTS

Both the MCL and LCL slackened during knee flexion from 0° to 110° flexion, at all stages of the experiment. In the native knee, the MCL slackened 2 mm, whilst the LCL slackened 7 mm. The MCL slackened a further 3 mm and the LCL a further 4 mm during flexion post-TKA. A 5° external rotation of the femoral component slackened the MCL 2 mm more and tightened the LCL by 2 mm. The opposite effects resulted from 5° internal rotation.

CONCLUSIONS

The collateral ligaments slackened more than normal following TKA, and these length changes were increased by femoral component rotation. External rotation of the femoral component to address patellar tracking may slacken the MCL and thus lead to valgus instability in the flexed knee.

The effect of femoral component rotation on the kinematics of the tibiofemoral and patellofemoral joints after total knee arthroplasty

PURPOSE

Complications after total knee arthroplasty (TKA) often involve the patellofemoral joint, and problems with patellar maltracking or lateral instability have sometimes been addressed by external rotation of the femoral component. This work sought to measure the changes of knee kinematics caused by TKA and then to optimise the restoration of both the patellofemoral and tibiofemoral joint kinematics, by variation of femoral component internal-external rotation.

METHODS

The kinematics of the patella and tibia were measured in eight cadaveric knees during active extension motion. This was repeated with the knee intact, with a Genesis II TKA in the standard position (3° of external rotation) and with the femoral component at ±5° rotation from there.

RESULTS

Both patellar and tibial motions were significantly different from normal with the standard TKA rotation, with 3° tibial abduction at 90° flexion and reversal of the screw-home from 5° external rotation to 6° internal rotation. The patella was shifted medially 6 mm in flexion and tilted 7° more laterally near extension. Femoral rotation to address one abnormality caused increased abnormality in other degrees of freedom. Internal and then external rotation of 5° caused tibial abduction and then adduction of 5° at 90° flexion. These femoral rotations also caused increased patellar lateral tilt of 4° with femoral external rotation and decreased tilt by 4° with internal rotation. Thus, correction of tibial abduction in flexion, by external rotation of the femoral component, worsened the patellar lateral tilt near extension.

CONCLUSIONS

It was concluded that femoral rotation alone could not restore all aspects of both patellar and tibial kinematics to normal with this specific implant. The clinical relevance of this is that it appears to be inadvisable to reposition the femoral component, in an attempt to improve patellar tracking, if that repositioning may then cause abnormal tibiofemoral kinematics. Further, the pattern of patellar tracking, with the type of TKA used in this study, could not be adjusted to normal by femoral component rotation.

The position and orientation of total knee replacement components: a comparison of conventional radiographs, transverse 2D-CT slices and 3D-CT reconstruction

We studied the intra- and interobserver reliability of measurements of the position of the components after total knee replacement (TKR) using a combination of radiographs and axial two-dimensional (2D) and three-dimensional (3D) reconstructed CT images to identify which method is best for this purpose. A total of 30 knees after primary TKR were assessed by two independent observers (an orthopaedic surgeon and a radiologist) using radiographs and CT scans. Plain radiographs were highly reliable at measuring the tibial slope, but showed wide variability for all other measurements; 2D-CT also showed wide variability. 3D-CT was highly reliable, even when measuring rotation of the femoral components, and significantly better than 2D-CT. Interobserver variability in the measurements on radiographs were good (intraclass correlation coefficient (ICC) 0.65 to 0.82), but rotational measurements on 2D-CT were poor (ICC 0.29). On 3D-CT they were near perfect (ICC 0.89 to 0.99), and significantly more reliable than 2D-CT (p < 0.001). 3D-reconstructed images are sufficiently reliable to enable reporting of the position and orientation of the components. Rotational measurements in particular should be performed on 3D-reconstructed CT images. When faced with a poorly functioning TKR with concerns over component positioning, we recommend 3D-CT as the investigation of choice.

Combined single photon emission computerised tomography and conventional computerised tomography (SPECT/CT) in patellofemoral disorders: a clinical review

Patellofemoral disorders are common conditions seen in a knee clinic but can present a great diagnostic challenge to the orthopaedic surgeon. Combined single photon emission computerised tomography with conventional computer tomography (SPECT/CT) provides the clinician with precise anatomical and physiological information of the patellofemoral joint. We present a clinical review that highlights the value of SPECT/CT in patients with patellofemoral disorders, where other modalities such as radiographs, MRI, and conventional CT did not provide sufficient information. SPECT/CT has proven to be helpful for establishing the diagnosis and guidance for further treatment. SPECT/CT should be recognised as a valuable diagnostic tool in orthopaedic patients.

An unusual case of persistent groin pain after total hip arthroplasty: a case report

INTRODUCTION

Arthroplasty is a well-established routine elective surgical procedure in orthopaedics. To a great extent, diagnosis, treatment and post-operative rehabilitation in these patients is standardised. In a busy clinic, surgeons from time to time tend to focus their attention on common causes of joint pain, but it may lead them to overlook sinister but less common pathologies. Here we report a case of a patient with groin pain due to pre-operatively undetected pelvic metastases from a pyeloureteral carcinoma who underwent total hip arthroplasty. There are several case reports which deal with primary or secondary tumours which were either discovered at the time of replacement surgery or developed at the site of prosthesis years after total hip or knee replacement. To the best of our knowledge, this is the first case report in which a metastatic cancer was missed pre-operatively and intra-operatively both by the radiologist and by the orthopaedic surgeon and should be reported so that surgeons are reminded to be careful when dealing with seemingly routine cases.

CASE PRESENTATION

A 79-year-old Caucasian woman presented to the arthroplasty clinic with groin pain. Initial radiographs showed subtle bilateral abnormalities in the pelvis. Neither the radiologist nor the orthopaedic surgeon recognized it. A diagnosis of osteoarthritis of the hip was established, and she underwent total hip arthroplasty. Despite initial improvement, the patient came back with worsening hip pain three months later. Further radiological examination revealed multiple metastatic lesions throughout the pelvis due to a pyeloureteral carcinoma.

CONCLUSIONS

This case report emphasizes the importance of meticulous, unbiased pre-operative assessment of patients and their radiographs, even in so-called routine clinical cases. Often subtle radiological changes are classed as normal, especially if they are bilateral. Further radiological imaging should be recommended in all cases where unexplained clinical features or radiological findings are present.

Clinical value of SPECT/CT for evaluation of patients with painful knees after total knee arthroplasty--a new dimension of diagnostics?

BACKGROUND

The purpose of our study was to evaluate the clinical value of hybrid SPECT/CT for the assessment of patients with painful total knee arthroplasty (TKA).

METHODS

Twenty-three painful knees in patients following primary TKA were assessed using Tc-99m-HDP-SPECT/CT. Rotational, sagittal and coronal position of the TKA was assessed on 3D-CT reconstructions. The level of the SPECT-tracer uptake (0-10) and its anatomical distribution was mapped using a validated localization scheme. Univariate analysis (Wilcoxon-Mann-Whitney, Spearmean's-rho test, p < 0.05) was performed to identify any correlations between component position, tracer uptake and diagnosis.

RESULTS

SPECT/CT imaging changed the suspected diagnosis and the proposed treatment in 19/23 (83%) knees. Progression of patellofemoral OA (n = 11), loosening of the tibial (n = 3) and loosening of the femoral component (n = 2) were identified as the leading causes of pain after TKA.Patients with externally rotated tibial trays showed higher tracer uptake in the medial patellar facet (p = 0.049) and in the femur (p = 0.051). Patients with knee pain due to patellofemoral OA showed significantly higher tracer uptake in the patella than others (p < 0.001).

CONCLUSIONS

SPECT/CT was very helpful in establishing the diagnosis and guiding subsequent management in patients with painful knees after TKA, particularly in patients with patellofemoral problems and malpositioned or loose TKA.

The effect of femoral component rotation on the extensor retinaculum of the knee

Malrotation of the femoral component may cause patellofemoral complications after total knee replacement (TKR). We hypothesized that femoral component malrotation would cause excessive lengthening of the retinacula. Retinacular length changes were measured by threading fine sutures along them and attaching these to the patella and to displacement transducers. The knee post-TKR was flexed-extended while the quadriceps were tensed, then the measurements repeated after rotating the femoral component 5 degrees internally and then 5 degrees externally. Internal rotation shortened the medial patellofemoral ligament (MPFL) significantly from 100 degrees to 0 degrees extension. External rotation lengthened the MPFL significantly from 90 degrees to 0 degrees extension. The transverse fibers of the lateral retinaculum showed no significant differences. The MPFL attaches directly from bone to bone, so it was lengthened directly by movement of the trochlea and patella, whereas the deep transverse fibers of the lateral retinaculum attach to the mobile iliotibial tract, so they were not lengthened directly.

Cams and pincer impingement are distinct, not mixed: the acetabular pathomorphology of femoroacetabular impingement

BACKGROUND

Many impinging hips are said to have a mix of features of femoral cam and an overcovered acetabulum causing pincer impingement. Correction of such a mixed picture by reduction of the cam lesion and the acetabular rim is the suggested treatment.

QUESTIONS/PURPOSES

We therefore asked two questions: (1) Is the acetabulum in cam impingement easily distinguishable from the pincer acetabulum, or is there a group with features of both types of impingement? (2) Is version or depth of socket better able to distinguish cam from pincer impingement?

METHODS

We analyzed the morphologic features of the acetabulum and rim profile of 20 normal, healthy hips, 20 with cams and 20 with pincers on CT. Pelvises were digitized, orientated to the best-fit acetabular plane, and a rim profile was plotted.

RESULTS

Cam hips were shallower than normal hips, which in turn were shallower than pincer hips (84 degrees +/- 5 degrees versus 87 degrees +/- 4 degrees versus 96 degrees +/- 5 degrees, respectively). The rim planes of cam, normal, and pincer hips had similar version (23 degrees, 24 degrees, 25 degrees), but females were 4 degrees more anteverted than males.

CONCLUSIONS

We concluded cam and pincer hips are distinct pathoanatomic entities. Cam hips are slightly shallower than normal, whereas pincers are deeper.

CLINICAL RELEVANCE

Before performing surgery for cam-type femoroacetabular impingement, surgeons should consider measuring the acetabular depth. The cam acetabulum is shallower than normal and may be rendered pathologically shallow by acetabular rim resection leading to early joint failure.

Surgical treatment of complex bicruciate knee ligament injuries in elite athletes: what long-term outcome can we expect?

BACKGROUND

A traumatic knee dislocation represents a serious injury, particularly for athletes who have the highest demands on their knee function.

PURPOSE

Our aim was to analyze the long-term outcome and return to sports after traumatic knee dislocation in elite athletes treated surgically according to a standardized treatment protocol and to identify predictive factors for a successful outcome.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A review of hospital medical records yielded 26 elite athletes with a knee dislocation (torn bicruciate ligaments and at least one torn collateral ligament), who had undergone an open complete single-stage reconstruction/primary repair of the cruciates and collateral ligaments including the posterolateral corner from January 1983 to August 2006. Return to sport (start of sport-specific training) was recorded. Return to the former level of sports activity was assessed. At a median follow-up of 8 years (range, 1-23 years), 24 patients (92%) were evaluated for instrumented anterior-posterior laxity (KT-1000 arthrometer) and scored on the visual analog scale (VAS pain, satisfaction), International Knee Documentation Committee form (IKDC), American Knee Society score, and Lysholm and Tegner score. Standard weightbearing and stress radiographs were taken.

RESULTS

Seventy-nine percent of patients (n = 19) returned to their previous sport after a median time of 5.5 months (range, 1.5-36 months), with 8 of them returning to preinjury levels. Eight percent had a VAS pain score >3. Thirteen percent of patients showed a flexion deficit >15 degrees , and 8% showed an extension deficit >10 degrees . The mean side-to-side differences for anterior and posterior laxity were 2.3 mm (range, 1-5 mm) and 2.0 mm (range, 2-7 mm), respectively. The total IKDC score was normal in 4, nearly normal in 12, abnormal in 6, and severely abnormal in 2 patients. The median Lysholm score was 91.8 (range, 37-100). The median Tegner score decreased from 9 (range, 7-10) to 7 (range, 2-10). The median American Knee Society score was 190 (range, 162-200). The median radiological anterior-posterior side-to-side differences in 30 degrees and 90 degrees flexion were 1 mm (range, 1-6 mm)/1 mm (range, 0-11 mm) and 1 mm (range, 0-7 mm)/3 mm (range, 0-11 mm), respectively. Patients treated more than 40 days after injury had a poorer outcome on the satisfaction and relative Tegner scores. This group was also less successful in returning to sport compared with patients treated earlier.

CONCLUSION

Athletes treated by early, open, complete single-stage reconstruction within 40 days of injury had better outcomes. Although 19 of 24 patients returned to sports with good functional outcomes and ligamentous stability, only 8 of 24 athletes reached their preinjury sports activity level.

Patellofemoral joint kinematics: the circular path of the patella around the trochlear axis

Differing descriptions of patellar motion relative to the femur have resulted from previous studies. We hypothesized that patellar kinematics would correlate to the trochlear geometry and that differing descriptions could be reconciled by accounting for differing alignments of measurement axes. Seven normal fresh-frozen knees were CT scanned, and their kinematics with quadriceps loading was measured by an optical tracker system. Kinematics was calculated in relation to the femoral epicondylar, anatomic, and mechanical axes. A novel trochlear axis was defined, between the centers of spheres best fitted to the medial and lateral trochlear articular surfaces. The path of the center of the patella was circular and uniplanar (root-mean-square error 0.3 mm) above 16+/-3 degrees (mean+/-SD) knee flexion. In the coronal plane, this circle was aligned 6+/-2 degrees from the femoral anatomical axis, close to the mechanical axis alignment. It was 91+/-3 degrees from the epicondylar axis, and 88+/-3 degrees from the trochlear axis. In the transverse plane it was 91+/-3 degrees and 88+/-3 degrees from the epicondylar and trochlear axes, respectively. Manipulation of the data to different axis alignments showed that differing previously published data could be reconciled. The circular path of patellar motion around the trochlea, aligned with the mechanical axis of the leg, is easily visualized and understood.

Combined single-photon emission computerized tomography and conventional computerized tomography (SPECT/CT): clinical value for the knee surgeons?

Single-photon emission computerized tomography in combination with conventional computer tomography (SPECT/CT) is an emerging technology that may hold great clinical value to the orthopaedic knee surgeon. Post-operative knee pain is a familiar condition seen in most orthopaedic clinics. Here, we present the value of SPECT/CT in three such cases of pain after surgical treatment of knee osteoarthritis (high tibial osteotomy, medial unicompartmental arthroplasty, total knee arthroplasty). In these patients with post-operative knee pain, SPECT/CT has proved to be beneficial in establishing the diagnosis and providing guidance for further treatment.

The structural properties of the lateral retinaculum and capsular complex of the knee

Although lateral retinacular releases are not uncommon, there is very little scientific knowledge about the properties of these tissues, on which to base a rationale for the surgery. We hypothesised that we could identify specific tissue bands and measure their structural properties. Eight fresh-frozen knees were dissected, and the lateral soft tissues prepared into three distinct structures: a broad tissue band linking the iliotibial band (ITB) to the patella, and two capsular ligaments: patellofemoral and patellomeniscal. These were individually tensile tested to failure by gripping the patella in a vice jaw and the soft tissues in a freezing clamp. Results: the ITB–patellar band was strongest, at a mean of 582 N, and stiffest, at 97 N/mm. The patellofemoral ligament failed at 172 N with 16 N/mm stiffness; the patellomeniscal ligament failed at 85 N, with 13 N/mm stiffness. These structural properties suggest that most of the load in-vivo is transmitted to the patella by the transverse fibres that originate from the ITB.

Iliotibial band tension reduces patellar lateral stability

This study investigated the effect of loading the iliotibial band (ITB) on the stability of the patellofemoral joint. We measured the restraining force required to displace the patella 10 mm medially and laterally (defined as medial and lateral stability, respectively) in 14 fresh-frozen knees from 0 to 90 degrees knee flexion. The testing rig allowed the patella to rotate and translate freely during this displacement. The quadriceps was separated into five components and loaded with 175 N total tension. Testing was performed at 0 to 90 N ITB tension. With no ITB tension, the lateral restraining force ranged from 82 to 101 N across 0 to 90 degrees flexion. Increasing ITB tension caused progressive reduction of the lateral restraining force. The maximum reduction was 25% at 60 degrees flexion and 90 N ITB tension. Medial restraining force increased progressively with increasing knee flexion and increasing ITB loads; it ranged from 74 N at 0 degrees knee flexion and 0 N ITB tension to 211 N at 90 degrees knee flexion and 90 N ITB tension. The maximum effect was an increase of medial restraining force of 50% at 90 degrees flexion and 90 N ITB tension.

The anatomical tibial axis: reliable rotational orientation in knee replacement

The rotational alignment of the tibia is an unresolved issue in knee replacement. A poor functional outcome may be due to malrotation of the tibial component. Our aim was to find a reliable method for positioning the tibial component in knee replacement. CT scans of 19 knees were reconstructed in three dimensions and orientated vertically. An axial plane was identified 20 mm below the tibial spines. The centre of each tibial condyle was calculated from ten points taken round the condylar cortex. The tibial tubercle centre was also generated as the centre of the circle which best fitted eight points on the outside of the tubercle in an axial plane at the level of its most prominent point. The derived points were identified by three observers with errors of 0.6 mm to 1 mm. The medial and lateral tibial centres were constant features (radius 24 mm (SD 3), and 22 mm (SD 3), respectively). An anatomical axis was created perpendicular to the line joining these two points. The tubercle centre was found to be 20 mm (SD 7) lateral to the centre of the medial tibial condyle. Compared with this axis, an axis perpendicular to the posterior condylar axis was internally rotated by 6 degrees (SD 3). An axis based on the tibial tubercle and the tibial spines was also internally rotated by 5 degrees (sd 10). Alignment of the knee when based on this anatomical axis was more reliable than either the posterior surfaces or any axis involving the tubercle which was the least reliable landmark in the region.

Learning how to resurface cam-type femoral heads with acceptable accuracy and precision: the role of computed tomography-based navigation

BACKGROUND

Resurfacing arthroplasty for cam-type deformities, which are a common cause of early osteoarthritis, is a technically demanding operation. Like any other arthroplasty, it requires both accuracy and precision. On the basis of the results of series reported by expert surgeons, we considered it desirable that this operation should be performed within +/-10 degrees of the desired angular orientation and +/-6 mm of entry-point translation in 95% of hips. Technological aids are now available to help surgeons achieve that level of accuracy. Three models of cam-type hips of increasing severity were used to assess the efficacy of three systems of instrumentation at delivering the required level of accuracy and precision.

METHODS

Thirty-two students of surgical technology were instructed in hip resurfacing and shown detailed plans of the desired operative outcome for the three hips with cam-type deformity. They then used conventional instruments, imageless navigation, and computed tomography-based navigation to perform the operation as accurately as possible.

RESULTS

Conventional instrumentation produced an unacceptably wide range of entry-point errors. Imageless navigation was able to deliver adequate accuracy and precision in varus-valgus angulation and superoinferior translation, but was less satisfactory in version and anteroposterior translation. Computed tomography-based navigation enabled novice surgeons to navigate hips that had difficult cam-type deformity with acceptable precision in all four degrees of freedom measured.

CONCLUSIONS

Only computed tomography-based navigation appears to be appropriate for delivering both the accuracy and the precision needed by surgeons on the steep part of their learning curve. Neither conventional neck-based instrumentation nor imageless navigation provided enough help for novice surgeons learning to perform this technically challenging operation.