Outcome of lateral retinacular nerve transection combined with release for recalcitrant iliotibial band friction syndrome.

In this retrospective study, a technique consisting in neurolysis of the lateral retinacular nerve combined with a partial release through elliptic excision of the iliotibial band (ITB) is evaluated for efficacy in recalcitrant ITB friction syndrome and compared with results from other techniques reported in literature. From April 2014 to December 2017, 21 patients suffering from recalcitrant ITB friction syndrome were surgically treated with the aforementioned technique. 15 patients (15 knees) were available for a written retrospective reassessment after completion of a follow-up period of at least 12 months. Residual pain was scored using the Visual Analogue Scale (VAS). The functional outcome was evaluated by two patient reported outcome measurement scales (PROMs), the Lysholm and the International Knee Documentation Committee (IKDC) score. Return to sport was analysed by duration of the inactivity period as well as by the Tegner score. Overall satisfaction was evaluated using a modified Boyden scale. At final follow-up of one year, the performed intervention resulted in a pain reduction (VAS 4.2 (1-8) to 1.4 (0-6)) and improved knee function (Lysholm 59.53 to 87.73, IKDC 75) with return to sport (Tegner 4.3 to 5.4) after a median of 23.8 weeks (6 to 52). Twelve patients reported good or excellent results (80%) at final follow-up, and 12 patients (80%) would undergo surgery again, if necessary. The treatment of recalcitrant ITB friction syndrome by combining neurectomy of the lateral retinacular nerve with elliptic excision of the ITB resulted in good to excellent results in 80% of treated cases with return to sport in 93%.

Microstructural adaptations of the subchondral bone are related to the mechanical axis deviation in end stage varus oa knees.

Recent studies highlighted the crucial contribution of subchondral bone to OA development. Yet, only limited data have been reported on the relation between alteration to cartilage morphology, structural properties of the subchondral bone plate (SBP) and underlying subchondral trabecular bone (STB). Furthermore, the relationship between the morphometry of the cartilage and bone in the tibial plateau and the OA-induced changes in the joint's mechanical axis remains unexplored. Therefore, a visualisation and quantification of cartilage and subchondral bone microstructure in the medial tibial plateau was performed. End stage knee-OA patients with varus alignment and scheduled for total knee arthroplasty (TKA) underwent preoperative fulllength radiography to measure the hip-knee-ankle angle (HKA) and the mechanical-axis deviation (MAD). 18 tibial plateaux were µ-CT scanned (20.1 µm/voxel). Cartilage thickness, SBP, and STB microarchitecture were quantified in 10 volumes of interest (VOIs) in each medial tibial plateau. Significant differences (p < 0.001) were found for cartilage thickness, SBP, and STB microarchitecture parameters among the VOIs. Closer to the mechanical axis, cartilage thickness was consistently smaller, while SBP thickness and STB bone volume fraction (BV/TV) were higher. Moreover, trabeculae were also more superior-inferiorly oriented, i.e. perpendicular to the transverse plane of the tibial plateau. As cartilage and subchondral bone changes reflect responses to local mechanical loading patterns in the joint, the results suggested that region-specific subchondral bone adaptations were related to the degree of varus deformity. More specifically, subchondral sclerosis appeared to be most pronounced closer to the mechanical axis of the knee.

Changes in coronal knee-alignment parameters during the osteoarthritis process in the varus knee.

OBJECTIVES: The idea to aim for an "individualized" alignment, whereby the constitutional alignment is restored, has gained much interest among knee surgeons. This requires insight into the prediseased, natural alignment of our patients' knees. The aim of this study is (1) to determine how the hip-knee-ankle (HKA) angle is influenced during the arthritic process and (2) to investigate the correlation between joint line changes and the progression of osteoarthritis (OA). It is our hypothesis that the most pronounced coronal parameter changes appear at the proximal tibia and at the joint line. METHODS: One hundred sequential full-length X-rays with a minimum follow-up of 1 year were retrospectively reviewed from a radiographic joint database. Patients had to be at least 50 years of age needed to have an HKA angle of more than 1.3° varus to be included. Patients with ipsilateral total hip arthroplasty, femoral or tibial fracture, osteotomy, or ligamentous repair were excluded. Fifteen alignment parameters were investigated on the sequential full-length X-rays. Moreover, the relationship between the alignment parameters and the Kellgren-Lawrence grade (KL grade) was determined by using linear mixed models. RESULTS: A progressive KL grade is associated with an increase of the HKA (p < 0.001). Mostly, HKA differs due to decrease of the medial tibial plateau (MPTA) angle (0.93°) and an increase of the joint line angle (JLCA) (0.86°). The mLDFA demonstrated the most pronounced changes in the beginning of OA (KL grade 1-2) (p = 0.049). In particular, the MPTA becomes considerably smaller (p = 0.004) in the later stage of OA (KL grade 3). Also, a progressive increase of the JLCA (p < 0.001) is observed upwards of KL grade 3. CONCLUSION: By comparing consecutive full-length X-rays in the same patients, it is possible to define the coronal alignment changes during the arthritic process. The HKA angle increases according the arthritic progression, whereby the most pronounced changes appear at the proximal tibia (MPTA) and at the joint line (JLCA).The alignment changes in varus OA knees can be divided in three stadia: (1) erosion of the distal medial femoral condyle, (2) erosion of the medial tibial plateau, and (3) a progressive increase of the joint line angle. LEVEL OF EVIDENCE: Therapeutic Study, Level III.

The pre-diseased coronal alignment can be predicted from conventional radiographs taken of the varus arthritic knee.

INTRODUCTION: The concept of restoring the constitutional, pre-diseased alignment has gained lots of interest among knee surgeons. Previous attempts to use the contralateral limb to bridge the gap between the arthritic and the constitutional alignment were unsuccessful. We investigated the usability of a mathematical formula to predict the constitutional (pre-diseased) coronal alignment once arthritis has occurred. It is our hypothesis that by using the KL grade, CPAK classification and four radiographic measurements of the arthritic knee, the pre-diseased coronal alignment could be predicted. MATERIAL AND METHODS: Hundred arthritic patients with consecutive X-rays were used to determine a mathematical formula. Five alignment parameters were determined on full-length X-rays: HKA angle, mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), joint line convergence angle (JLCA) and the tibial joint line angle (TJLA). A refinement of the algorithm was implemented based on a reference cohort, consisted of 250 young adults aged between 20 and 27 years. Moreover, all knees were subdivided based on their CPAK-phenotype and the Kellgren-Lawrence scale (KL scale). An independent arthritic cohort of 289 patients scheduled for primary total knee arthroplasty was included to verify the accuracy of the predicted HKAs (HKAPRED). RESULTS: In CPAK type 1, the HKAPRED was 3.86° varus (STD 1.39) and the HKAYHA was 4.0° varus. In CPAK type 2, the HKAPRED was 1.68° varus (STD 1.95) compared to a HKAYHA of 1.34° (STD 0.81). The average constitutional HKA is not different in both CPAK 1 (p = 0.61) and CPAK 2 (p = 0.25), and the difference in the mean is estimated to be equal to - 0.14 (95CI - 0.68 to 0.40) in CPAK 1 and 0.35 (95CI - 0.06 to 0.75) in CPAK 2. CONCLUSION: Using the KL grade, CPAK classification and four radiographic measurements of the arthritic knee, the pre-diseased coronal alignment can be predicted in 80% of the varus knees with an accuracy of ≤ 0.5°. The predicted HKA (HKAPRED) can be very useful in the current and future clinical practice.

Primary constrained-condylar-knee designs outperform posterior-stabilized and cruciate-retaining designs in high-grade varus osteoarthritic knees during short-term follow-up: a pilot study.

INTRODUCTION: High-grade varus osteoarthrosis (OA) is characterized by a pronounced intra-articular varus deformity and associated insufficiency of the lateral ligamentous complex. When performing a total knee arthroplasty (TKA) in such a knee, traditionally the alignment is restored to neutral, and the medial soft tissue structures are released to compensate for the lateral laxity and balance the joint. However, another option would be to leave the medial soft tissues untouched and accept the lateral laxity but to compensate for it using an ML-stabilized constrained-condylar knee (CCK) design. Our aim was to prove our hypothesis that such knees would demonstrate better clinical stability and better functionality as well as subjective outcome scores. MATERIALS AND METHODS: We searched our bicenter database of 912 primary TKAs (from 2016 to 2019) for primary TKA patients with a preoperative varus alignment of > 8°. After inclusion, 60 patients were divided into three groups by implant design: CCK (n = 21), posterior-stabilized (PS) (n = 20) and cruciate-retaining (CR) (n = 19). Oxford Knee Score (OKS), Forgotten Joint Score (FJS), Knee Society Score (KSS), UCLA-activity score, ML instability scores and both radiographic and clinical data were compared between groups. RESULTS: ML stability was significantly better in CCK designs (86% grade 0) compared to CR (37% grade 0) (p = 0.004) but not PS (70% grade 0) designs. No grade II instability was present in CCK and PS implants compared to 16% of CR implants. KSS and UCLA-activity score were higher in CCK designs compared to PS (p = 0.027, p = 0.041) and CR designs (p < 0.001, p = 0.007). OKS and FJS were higher in CCK designs compared to CR (p = 0.025, p = 0.008) but not to PS. CONCLUSION: The use of a CCK design to compensate for the lateral laxity in high-grade varus OA knees allowed to refrain from a medial release. CCK designs displayed improved clinical stability and better functionality as well as subjective outcome scores compared to less-constrained designs.

The lateral joint line opening: a radiographic indicative parameter for high grade varus knees.

PURPOSE: It is usually assumed that the severity of varus osteoarthritis (OA) of the knee is correlated with the axis deviation of the limb. Despite this, there is currently no clear radiographic definition to define a so-called 'high degree' varus knee, which is characterized by a pronounced lateral ligamentous laxity. The purpose of this study was to radiographically determine if the lateral joint line opening (LJLO) is an indicative parameter when defining so-called high grade varus knees. METHODS: Two hundred forty Full length radiographs of patients with end-stage varus osteoarthritis who were scheduled for Total knee arthroplasty (TKA) were evaluated. The Hip-knee-ankle-angle (HKA-angle), Joint-line-convergence-angle (JLCA) and the lateral joint line opening were measured. The lateral joint line opening is the shortest distance between the lateral tibial plateau and the deepest point of the lateral femoral condyle. Linear regression models were used to investigate the relationships between the radiographic measurements. RESULTS: Hip-knee-angle-angle, joint-line-conversion-angle, and lateral joint line opening were all positively correlated (p < 0.001). An increase of 1 mm lateral joint line opening causes an increase of 0.6° joint-line-conversion-angle (p = 0.029) below a cut-off point of 4.7 mm. For lateral opening values beyond 4.7 mm, the gradient increased to 1.2 (p < 0.001). A lateral joint line opening of 4.7 mm corresponds to a hip-knee-ankle-angle of 6.0° (95% CI [5.5; 6.5]). CONCLUSION: A lateral joint line opening of more than 5 mm in end-stage OA knees is indicative of increased lateral joint laxity. Those knees can be radiographically classified as so-called 'high-grade' varus knees. LEVEL OF EVIDENCE: Therapeutic study, Level III.

Operative management of isolated posterior cruciate ligament injuries improves stability and reduces the incidence of secondary osteoarthritis: a systematic review.

PURPOSE: To evaluate the evidence for operative and non-operative management of isolated posterior cruciate ligament (PCL) injuries. METHODS: Using Pubmed, EMBASE and Cochrane databases, a systematic review was conducted of studies investigating the treatment of isolated PCL injuries published until July 2020. Quality assessment was performed with the Cochrane risk of bias tool (level I), the Newcastle-Ottowa Scale (level II-III) and the National Institute of Health quality assessment tool (level IV). Clinical outcome measures included residual laxity, return to sports, patient-reported outcome measures, subsequent articular degeneration and complications. RESULTS: Twenty-seven studies [23 case series, 2 case-control, 1 cohort study and 1 randomized controlled trial (RCT)] including 5197 patients (5199 knees) with a mean age of 29.5 ± 3.6 years (range 15-68) fulfilled the study requirements. Significantly less residual laxity was found after posterior cruciate ligament reconstruction (PCLR) compared to non-operative management (3.43 vs. 5.47 mm, CI: 1.84-2.23, p < 0.001). Both treatment modalities yielded satisfying functional outcomes and a high return to sports (64-77%, mean: 70.3, CI: 67.8-72.2). Osteoarthritis (OA) occurred less frequently following PCLR (21.5 vs. 44.1%, p < 0.001). CONCLUSION: In the absence of level I RCTs, this systematic review suggests that surgical management for selected isolated PCL injuries is a reasonable option to consider, especially when the surgeon aims at minimizing residual laxity and presumably secondary osteoarthritis. LEVEL OF EVIDENCE: IV.

Discriminant validity of 3D joint kinematics and centre of mass displacement measured by inertial sensor technology during the unipodal stance task.

BACKGROUND: The unipodal stance task is a clinical task that quantifies postural stability and alignment of the lower limb joints, while weight bearing on one leg. As persons with knee osteoarthritis (KOA) have poor postural and knee joint stability, objective assessment of this task might be useful. OBJECTIVE: To investigate the discriminant validity of three-dimensional joint kinematics and centre of mass displacement (COM) between healthy controls and persons with knee KOA, during unipodal stance using inertial sensors. Additionally, the reliability, agreement and construct validity are assessed to determine the reproducibility and accuracy of the discriminating parameters. METHODS: Twenty healthy controls and 19 persons with unilateral severe KOA were included. Five repetitions of the unipodal stance task were simultaneously recorded by an inertial sensor system and a camera-based system (gold standard). Statistical significant differences in kinematic waveforms between healthy controls and persons with severe knee KOA were determined using one-dimensional statistical parametric mapping (SPM1D). RESULTS: Persons with severe knee KOA had more lateral trunk lean towards the contralateral leg, more hip flexion throughout the performance of the unipodal stance task, more pelvic obliquity and COM displacement towards the contralateral side. However, for the latter two parameters the minimum detectable change was greater than the difference between healthy controls and persons with severe knee KOA. The construct validity was good (coefficient of multiple correlation 0.75, 0.83 respectively) and the root mean squared error (RMSE) was low (RMSE <1.5°) for the discriminant parameters. CONCLUSION: Inertial sensor based movement analysis can discriminate between healthy controls and persons with severe knee KOA for lateral trunk lean and hip flexion, but unfortunately not for the knee angles. Further research is required to improve the reproducibility and accuracy of the inertial sensor measurements before they can be used to assess differences in tasks with a small range of motion.

A revisited technique for combined anterior cruciate ligament and anterolateral ligament reconstructions.

A new technique for combined anterior cruciate ligament and anterolateral ligament reconstructions is described. An iliotibial band strip is used as an ALL graft , leaving the distal insertion intact and fix it with a knotless anchor on the femoral origin, after tunneling it under the lateral collateral ligament.

Knee joint laxity is restored in a bi-cruciate retaining TKA-design.

PURPOSE: The goal is to evaluate the passive stability of a bicruciate retaining, cruciate retaining and bicruciate substituting TKA design in relation to the native knee stability in terms of the laxity envelope. A bicruciate retaining knee prosthesis was hypothesized to offer a closer to normal knee stability in vitro. METHODS: Fourteen cadaveric knee specimens have been tested under passive conditions with and without external loads, involving a varus/valgus and an external/internal rotational torque, distraction/compression force and an anteroposterior shear force. Subsequently, the native knee, bicruciate retaining, cruciate retaining and finally a bicruciate substituting total knee arthroplasty were tested. RESULTS: Through the range of motion, the width of the varus/valgus and internal/external laxity envelope for the native knee and the bicruciate retaining knee were almost equivalent, whereas the cruciate retaining and the bicruciate substituting knee displayed less laxity and more joint distraction. In all prosthetic knees, an equal anteroposterior laxity was seen for the lateral and medial side whereas in the native knee, a difference in laxity was seen between the stable medial side and the more mobile lateral side. CONCLUSION: Bicruciate retaining knee prostheses can restore normal laxity and thus have the potential to offer more normal knee function. Restoration of natural peri-articular soft-tissue tension is clinically important because of its obvious effects on joint stability and range of motion. Furthermore, the results of this study could help to establish the ideal ligament tension and laxity in more conventional implants by approaching the normal values for passive knee evaluation as presented here.

Risk analysis of tunnel collision in combined anterior cruciate ligament and anterolateral ligament reconstructions.

BACKGROUND: To assess the risk of tunnel collision in combined anterior cruciate ligament (ACL) and anterolateral ligament (ALL) reconstructions. METHODS: Three-dimensional (3D) CT reconstructions of 32 knees after transtibial (TT) (N = 16) or anteromedial portal (AMP) (N = 16) ACL reconstruction were used to simulate potential tunnel collision of the femoral ACL tunnel if combined with a virtual ALL reconstruction. The minimal distance between tunnels, the ALL tunnel length, and the lateral femoral condyle (LFC) width were measured. Moreover, the relationship between the ALL tunnel and the intercondylar notch, trochlear groove and posterior femoral cortex was determined. RESULTS: The highest rate of tunnel collision (81%) was observed when the ALL tunnel was aimed at 20° in the coronal plane and 0° in the axial plane. However, by aiming the ALL tunnel at 0° coronal and 40° axial angulation, collision was avoided in all patients and no violation of the trochlea was observed. Tunnel collision rate was significantly higher (P = 0.002) when the ACL tunnel was drilled by the AMP technique. CONCLUSIONS: Risk of tunnel collision was significantly increased when the tunnel was drilled at 0° in the axial plane. Tunnel collision was avoided by aiming the ALL tunnel 40° anteriorly and perpendicular to the anatomical axis of the femur. A more horizontal orientation of the ACL with the AMP technique is a risk factor for tunnel conflicts. CLINICAL RELEVANCE: ALL tunnel orientation needs to be adjusted to avoid tunnel conflicts in combined ACL-ALL reconstructions.

High risk of tunnel convergence during combined anterior cruciate ligament and anterolateral ligament reconstruction.

PURPOSE: To assess the risk of femoral tunnel convergence in combined anterior cruciate ligament (ACL) and anterolateral ligament (ALL) reconstructions. The hypothesis was that a more proximal and anterior orientation of the ALL femoral tunnel should reduce the risk of convergence with the ACL femoral tunnel. METHODS: 15 fresh-frozen cadaver knees were examined. An anatomic ACL femoral tunnel was drilled arthroscopically in each specimen and ALL tunnels were made in two directions: (1) 0° coronal angulation and 20° axial angulation, (2) 30° coronal angulation and 30° axial angulation. Computed tomography scans were performed to investigate tunnel convergence and to measure the minimal distance between tunnels, tunnel length and the LFC width. RESULTS: Tunnel convergence occurred in 20 of 30 cases (67%). Convergence was significantly reduced when tunnels were drilled at 30° coronal and 30° axial angulation (p < 0.05). The mean length of the ALL tunnel was 15.9 mm [95% CI (13.6; 18.1)] and was independent of ALL tunnel angulation. The mean minimal distance between the ALL and ACL tunnel was 3.1 mm [95% CI (2.1; 4.1)]. The odds ratio for tunnel convergence was 3.5 for small LFC, relative to large LFC (n.s.) CONCLUSION: A high risk of tunnel convergence was observed when performing combined ACL and ALL reconstructions. The clinical relevance of this work is that the occurrence of tunnel conflicts can be reduced by aiming the ALL tunnel in a more proximal and anterior direction. Surgeons should be aware of this, since tunnel convergence could jeopardize the ACL reconstruction and fixation.

Hinged versus CCK revision arthroplasty for the stiff total knee.

BACKGROUND: Total knee arthroplasty (TKA) remains the gold standard for end-stage knee osteoarthritis. The prevalence of stiffness after this procedure described in literature varies from 1.3% to 5.3%. The causes of arthrofibrosis after total knee arthroplasty are multifactorial. Revision TKA is a successful procedure when performed for loosening, instability, mechanical implant failure, or infection. The results of revision TKA for idiopathic arthrofibrosis and stiffening are however less favorable. PURPOSE: It has been the authors' impression that the poor results in arthrofibrosis could be in part related to the use of traditional PS or CCK-type revision implants. Our hypothesis is that better results can be achieved in case a rotating hinge design (RHK) is used. The reason could be that RHK designs allow for much more aggressive capsuloligament debridement and therefore more adequate fibrosis removal, while securing optimal implant stability, tibiofemoral rotational freedom, and flexion-extension space stability. The purpose of our study was to investigate in our database whether this hypothesis is correct. METHODS: Retrospectively, 40 patients with the defined range of knee motion were identified. Patients with underlying mechanical malalignment, component malposition, soft-tissue imbalance or infections were excluded. Twenty-two patients received a hinged-type prosthetic device (18 Zimmer RHK, four Stryker RHK) and 18 patients received a less constrained condylar type prosthetic device (17 Legion CCK, one Vanguard CCK). RESULTS: Preoperative data were similar for RHK as CCK-type implants except for knee pain score, which was significantly worse for the RHK group (36 vs 44, p = 0.049). At two years of follow-up, compared to CCK, the RHK group demonstrated significantly better postoperative results for knee function scores (68.9 vs 54.2, p = 0.0015), knee function improvement (22.8 vs 4.8, p = 0.0015), knee pain improvement (26.4 vs 9.4, p = 0.0050), greater maximal flexion (99.9° vs 81.4°, p = 0.0005), better maximal extension (-1.9° vs -6.2°, p = 0.0447), greater flexion gain (35.8° vs 14.2°, p = 0.0002), and greater extension gain (8.6° vs 2.0°, p = 0.0083). CONCLUSION: Our data show that revision arthroplasty of the stiff knee using a rotating hinged device can provide excellent results in selected cases. To date, this is the first study to describe the difference in outcome between revision total knee arthroplasty for idiopathic arthrofibrosis using a hinged or a constrained condylar knee device.

Principal component analysis as a tool for determining optimal tibial baseplate geometry in modern TKA design.

Optimal tibial component fixation in total knee arthroplasty (TKA) requires maximal tibial bone coverage, optimized mediolateral cortical fit as well as component rotation. Failure to achieve an optimal fit may result in component subsidence and loosening in case of undersizing, or overhang with subsequent soft tissue impingement in case of overhang. To date there is no consensus on optimal tibial component shape, and significant variability exists among different design manufacturers. In this study "principal component analysis" was used as a statistical tool in order to determine the ideal tibia baseplate shape, based upon anthropometric CT- scan data defining an average proximal tibial shape and variations. Gender specificity was evaluated and differences in geometry depending on anatomic constitution (varus, neutral, valgus) were analyzed. The results from our study indicate that in the arthritic knee differences in proximal tibial morphology at the resection level were mainly attributed to size and not shape. This is true for both Caucasian men and women, and is independent from the anatomical constitution.

The shape and orientation of the trochlea run more parallel to the posterior condylar line than generally believed.

PURPOSE: This study was set up to identify the native trochlear geometry and define its relationship with the rotational landmarks of the distal femur. METHODS: The rotational landmarks of the distal femur were analysed on CT-scans of 281 patients with end-stage knee osteoarthritis. RESULTS: The anterior trochlear line (ATL) was on average 4.3° (SD 3.3°) internally rotated relative to the surgical transepicondylar axis (sTEA). The ATL was on average 2.1° (SD 3.0°) internally rotated relative to the posterior condylar line (PCL). The relationship between the ATL and the sTEA was statistically different in the different coronal alignment groups (p = 0.004): 3.9° (SD 3.0°) in varus knees, 4.0° (SD 2.9°) in neutral knees and 5.4° (SD 3.8°) in valgus knees. The lateralisation of the trochlea, represented by the distance between the perpendicular to PCL and the perpendicular to the posterior parallel line to the sTEA, was on average 2.2 mm (SD 1.8 mm). CONCLUSION: The ATL was on average 4.3° (SD 3.3°) internally rotated relative to the sTEA and 2.1° (SD 3.0°) internally rotated relative to the PCL. The ATL is more externally orientated in varus knees and more internally rotated in valgus knees. The trochlear groove is lateralised by only 2.2 mm when the femoral component is externally rotated. LEVEL OF EVIDENCE: III.

Diagnosis of prosthetic joint infection with alpha-defensin using a lateral flow device: a multicentre study.

AIMS: The purpose of this current multicentre study is to analyse the presence of alpha-defensin proteins in synovial fluid using the Synovasure lateral flow device and to determine its diagnostic reliability and accuracy compared with the prosthetic joint infection (PJI) criteria produced by the Musculoskeletal Infection Society (MSIS). PATIENTS AND METHODS: A cohort of 121 patients comprising 85 total knee arthroplasties and 36 total hip arthroplasties was prospectively evaluated between May 2015 and June 2016 in three different orthopaedic centres. The tests were performed on patients with a chronically painful prosthesis undergoing a joint aspiration in a diagnostic pathway or during revision surgery. RESULTS: Based on the MSIS criteria, 34 patients (28%) would have had a PJI, and 87 patients had no PJI. Testing with the lateral flow device had a sensitivity of 97.1% (95% confidence intervals (CI) 84.5 to 99.9) and a specificity of 96.6% (95% CI 90.3 to 99.2). The positive predictive value was 91.7% (95% CI 77.7% to 98.3), and the negative predictive value was 98.8% (95% CI 93.6 to 99.9). Receiver operator characteristics analysis demonstrated an area under the curve for the Synovasure test of 0.97 (95% CI 0.93 to 1.00). CONCLUSION: Our findings suggest that the Synovasure test has an excellent diagnostic performance to confirm or reject the diagnosis of a PJI. The results are promising for the care of the painful or problematic knee and hip joint arthroplasty and the test should be considered as part of the diagnostic toolbox for PJIs. Cite this article: Bone Joint J 2017;99-B:1176-82.

Bone morphotypes of the varus and valgus knee.

BACKGROUND: Coronal deformity correction with total knee arthroplasty (TKA) is an important feature in the treatment of osteoarthritis (OA). The hypothesis of this study was that bone morphology would be different in varus and valgus deformity, both before osteoarthritis development as well as during and after the disease process of OA. MATERIALS AND METHODS: Retrospective study with measurements on preoperative and postoperative full leg standing radiographs of 96 patients who underwent TKA. The included patients were selected for this study because they had an OA knee on one side and a non-arthritic knee on the contralateral side presenting the same type of alignment as the to-be-operated knee (varus or valgus alignment on both sides). The control group of 46 subjects was a group of patients with neutral mechanical alignment who presented for ligamentous problems. A single observer measured mechanical alignment, anatomical alignment, anatomical-mechanical femoral angle and intra-articular bone morphology parameters with an accuracy of 1°. RESULTS: Varus OA group has less distal femoral valgus (mLDFA 89°) than control group (87°) and valgus OA group (mLDFA 85°). Varus OA group has same varus obliquity as control group (MPTA 87°) but more than valgus OA group (MPTA 90°). Joint Line Congruency Angle (JLCA) is 3°open on lateral side in varus and medially open in valgus OA group (2°). The non-arthritic valgus group presents a constitutional mechanical valgus of 184° Hip-Knee-Ankle (HKA) angle. DISCUSSION: Varus deformity in OA as measured with an HKA angle (HKA) <177° is a combination of distal femoral wear, tibial varus obliquity and lateral joint line opening. Valgus deformity in OA with an HKA > 183° is a combination of femoral distal joint line obliquity and wear combined with medial opening due to medial collateral ligament stretching. The clinical importance of bone morphotype analysis is that it shows the intra-articular potential of alignment correction when mechanical axis cuts are performed. CONCLUSION: Bone morphology in varus and valgus deformity is different before and after osteoarthritis. Perpendicular cuts to mechanical axes do not necessarily lead to neutral mechanical axis. Constitutional mechanical valgus was observed as 184° HKA angle before the development of OA. LEVEL OF EVIDENCE: Level IV study.

Predictors of outcome after manipulation under anaesthesia in patients with a stiff total knee arthroplasty.

PURPOSE: Flexion in a stiff total knee arthroplasty (TKA) can be improved by manipulation under anaesthesia (MUA). Although this intervention usually results in an improvement in range of motion, the expected result is not always achieved. The purpose of this study is to determine which factors affect range of motion after manipulation in patients with a stiff total knee. METHODS: After exclusion (n = 22), the data of 158 patients (138 knees) with a stiff knee after TKA who received a manipulation under anaesthesia between 2004 and 2014 were retrospectively analysed. Pre-, peri- and post-operative variables were identified and examined for their influence on flexion after the manipulation using Kruskal-Wallis and Mann-Whitney U tests and Spearman correlations. RESULTS: After MUA, a mean improvement in flexion of 30.3° was observed at the final follow-up. Preoperative TKA flexion, design of TKA and interval between TKA procedure and MUA were positive associated with an increase in flexion after MUA. MUA performed 12 weeks or more after TKA procedure deteriorated the outcome. CONCLUSIONS: Three factors, pre-TKA flexion type of prosthesis and interval between TKA procedure and manipulation under anaesthesia, were found to have impact on flexion after TKA and MUA were identified. Results are expected to be inferior in patients with low flexion before TKA procedure or with a long interval (>12 weeks) between the TKA procedure and the manipulation under anaesthesia. LEVEL OF EVIDENCE: IV.

International consensus on the definition and classification of fibrosis of the knee joint.

AIMS: The aim of this consensus was to develop a definition of post-operative fibrosis of the knee. PATIENTS AND METHODS: An international panel of experts took part in a formal consensus process composed of a discussion phase and three Delphi rounds. RESULTS: Post-operative fibrosis of the knee was defined as a limited range of movement (ROM) in flexion and/or extension, that is not attributable to an osseous or prosthetic block to movement from malaligned, malpositioned or incorrectly sized components, metal hardware, ligament reconstruction, infection (septic arthritis), pain, chronic regional pain syndrome (CRPS) or other specific causes, but due to soft-tissue fibrosis that was not present pre-operatively. Limitation of movement was graded as mild, moderate or severe according to the range of flexion (90° to 100°, 70° to 89°, < 70°) or extension deficit (5° to 10°, 11° to 20°, > 20°). Recommended investigations to support the diagnosis and a strategy for its management were also agreed. CONCLUSION: The development of standardised, accepted criteria for the diagnosis, classification and grading of the severity of post-operative fibrosis of the knee will facilitate the identification of patients for inclusion in clinical trials, the development of clinical guidelines, and eventually help to inform the management of this difficult condition. Cite this article: Bone Joint J 2016;98-B:1479-88.

Mean tensile strength of the PCL in TKA depends on the preservation of the tibial insertion site.

PURPOSE: The tibial insertion of the posterior cruciate ligament (PCL) frequently becomes damaged when performing a tibial cut in a PCL-retaining total knee replacement (TKA). The aim of this study was to quantify the functional effect of this structural damage on the tensile strength and failure load. METHODS: Six paired knees from fresh-frozen cadaver specimens were used. All soft tissues but the PCL were removed. In the left-sided specimens, a classic tibial cut at a depth of 9 mm with 3° of posterior slope was made, while in the right-sided specimens, a bone block was left in front of the tibial PCL insertion. After cementing a tibial tray, the specimens were mounted in a loading frame in 60° of flexion. The femur was translated anteriorly at a constant velocity rate of 0.5 mm/s. Tensions in the PCL were measured continuously until failure occurred. RESULTS: In one specimen, the tibial PCL insertion was completely removed by the tibial cut. In the other five paired specimens, the mean tensile strength of the PCL was 380.6 ± 154.7 N in the left-sided knees. In the right-sided knees, the mean tensile strength was 738.4 ± 166.7. The average right-to-left ratio was 2.2 ± 0.7 (p = 0.006). CONCLUSION: The results of this study indicate that the conventional technique for tibial preparation in cruciate-retaining total knee arthroplasty can result in a significant decrease in tensile strength of the PCL, rendering it susceptible to failure and subsequent midflexion instability. Therefore, we recommend leaving the posterior tibial cortex anterior to the PCL insertion intact when performing a cruciate-retaining TKA.