Aims

Obtaining solid implant fixation is crucial in revision total knee arthroplasty (rTKA) to avoid aseptic loosening, a major reason for re-revision. This study aims to validate a novel grading system that quantifies implant fixation across three anatomical zones (epiphysis, metaphysis, diaphysis).

Aims

The diagnosis of periprosthetic joint infection (PJI) continues to present a significant clinical challenge. New biomarkers have been proposed to support clinical decision-making; among them, synovial fluid alpha-defensin has gained interest. Current research methodology suggests reference methods are needed to establish solid evidence for use of the test. This prospective study aims to evaluate the diagnostic accuracy of high-performance liquid chromatography coupled with the mass spectrometry (LC-MS) method to detect alpha-defensin in synovial fluid.

Primary total knee arthroplasty (TKA) is a reliable procedure with reproducible long-term results. Nevertheless, there are conditions related to the type of patient or local conditions of the knee that can make it a difficult procedure. The most common scenarios that make it difficult are discussed in this review. These include patients with many previous operations and incisions, and those with severe coronal deformities, genu recurvatum, a stiff knee, extra-articular deformities and those who have previously undergone osteotomy around the knee and those with chronic dislocation of the patella.

Each condition is analysed according to the characteristics of the patient, the pre-operative planning and the reported outcomes.

When approaching the difficult primary TKA surgeons should use a systematic approach, which begins with the review of the existing literature for each specific clinical situation.

Cite this article: Bone Joint J 2015;97-B(10 Suppl A):30–9.

Extensor mechanism disruption in total knee arthroplasty (TKA) occurs infrequently but often requires surgical intervention. We compared two cohorts undergoing extensor mechanism allograft reconstruction, one group had an extensor mechanism rupture, and the other had a recurrent ankylosed knee. Thirteen consecutive patients with extensor mechanism disruption or ankylosis after TKA were treated. Two different types of extensor mechanism allografts were used: quadriceps tendon-patella-patella tendon-tibial tubercle, and Achilles tendon allograft(Fig1). Demographic factors, diagnosis at extensor failure, Knee Society clinical rating scores, radiographs, and patient satisfaction were recorded. The average time from extensor mechanism disruption to surgery was 6.6 months (range, 1-24 months). At a mean followup of 24 months (range, 6-46 months), all patients were community ambulators. None of the patients showed a postoperative extensor lag. Average postoperative maximum flexion was 97° (90-115°) for the ruptured group and 80° (75-90) for the ankylosed grup. All patients thought their functional status had improved, and 87% were satisfied with the results of the allograft reconstruction (Fig 2, 3, 4, 5). One patient had allograft failure due to recurrent infection after re-revision for sepsis. The total extensor mechanism allograft and Achilles tendon allograft both were successful in the treatment of the failed extensor mechanism and showed promising results for the treatment of the ankylosed knee.

The aim of tissue sparing surgery in total knee arthroplasty is to reduce surgical invasivity to the entire knee joint. Surgical invasion should not be limited only toward soft tissues but also toward bone. The classic technique for total knee arthroplasty implies intramedullary canal invasion for proper femoral component positioning. This phase is associated to fat embolism, activation of coagulation, and occult bleeding from the reamed canal. The purpose of our study was to validate a new extramedullary device which relies on templated data.

Two-hundred patients in four different orthopaedics centres were randomized to undergo primary total knee arthroplasty either using standard intramedullary femoral instruments (IM group) or using a new extramedullary device (EM group). A new set of instruments was developed to control the sagittal and coranl plane of the distal femoral resection. The extramedullary instrument was calibrated referencing to templated data obtained from the preoperative long-limb radiograph (Fig 1, 2). Varus-valgus orientation of the resection were established by moving the two paddles according to templated data. An L-shaped sliding tool (5 centimetres long) over the anterior cortex controls the flexion-extension parameter of the resection and is intended to allow a cut flush with the anterior cortex at 0° of angulation with the distal aspect of the femoral diaphysis on the sagittal plane

Femoral component coronal alignment was within 0±3° of the mechanical axis in 86% of the IM group and 88% of the EM group. Sagittal alignment of the femoral component was 0±3° in 80% of the IM group and 94% of the EM group. There was no difference in the average operative time between the two groups. The EM group showed a trend toward less postoperative blood loss

Extramedullary reference with careful preoperative templating can be safely utilized during total knee arthroplasty.

The anterior curve of the tibial plateau cortex represents a realiable and reproducible landmark which may help aligning the tibial component with the femoral component and the extensor mechanism

Few studies analyzed the tibial component rotational alignment during total knee arthroplasty. Malrotation can affect both patello-femoral and tibio-femoral postoperative function. We evaluated the rotational relationship between femur and tibia, and we investigated which tibial landmark consistently matches the rotation of the femoral epicondylar axis in full extension (Fig 1).

Axial magnetic resonance images of 124 normal knees (statistical power 1-beta=0.8) were analyzed separately by three authors. Scanograms were obtained with the knee in full extension and with the long axis of the foot (second metatarsal bone) aligned on the neutral sagittal plane. The surgical epicondylar axis was drawn and projected over the proximal tibia and tibial tuberosity slices. Multiple anatomical tibial rotational landmarks were drawn and symmetric tibial component digital templates of different sizes were aligned according to each landmark. Alignment of the virtual tibial components was then compared to that of the projected femoral epicondylar axis (Fig 2). The best antero-posterior line to achieve rotational matching between the components was drawn on the proximal tibia slice of each patient.

Results of rotation (positive = external rotation, negative = internal) relative to the epicondylar axis were (Fig 3): (a) Medial third-to the middle third of the tibial tubercle 1.2°+/−5.7, (b) Akagi's line (centre of the posterior cruciate ligament tibial insertion to the most medial part of the tibial tubercle) -11.5+/−6.5, (c) The anterior curved tibial plateau cortex (curve-on-curve matching between the tibial template and the anterior cortex) 1.0+/−2.9. Intraclass correlation coefficient resulted 0.923, 0,881, and 0.949 for the Akagi's line, Middle third of tibial tubercle, and the curve-on-curve reference respectively.

The anterior curve of the tibial plateau cortex represents a realiable and reproducible landmark which may help aligning the tibial component with the femoral component and the extensor mechanism (Fig 4, 5).

Different femoral designs in TKA have shown multiple effects on the conformity of the patella-femoral joint. Historically, this anatomical relationship may interfere with clinical results. The objective of this study was to compare the reproducibility of a correct patello-femoral conformity in patients underwent TKA utilizing modern femoral implants.

Femoral intramedullary canal referencing is utilized by most of the total knee arthroplasty (TKA) systems. Violation of the canal is performed in order to engage rod instruments in the femoral diaphysis and to refer of the anatomical axis of the femur. Fat embolism, activation of the coagulation cascade, and bleeding may occur from the reamed femoral canal. The purpose of our study was to validate a new set of _minimally-invasive friendly_ instruments which allow to prepare the femur without violating the intramedullary canal. Twenty-five consecutive patients undergoing primary TKA through a mini-subvastus approach were enrolled in the study after informed consent had been obtained. Results of this cohort (group 1) were compared to another contemporary group (group 2) of 25 TKAs operated by the same surgeon using intramedullary instruments. The two groups were matched for gender, deformity, degree of arthritis, and surgical approach. Reliability of the new extramedullary set of instruments was first tested in ten cadaveric limbs. Preoperative long weight-bearing AP and lateral view of the knee were obtained taking care of neutral limb positioning. Template of the mechanical and anatomical axis were performed. Distal femoral resection was planned according to the template, and considering a bone cut perpendicular to the mechanical axis of the femur. Measurement from the template were reproduced on the distal femoral cutting jig. Flexion-extension control of the distal femoral resection was obtained using the anterior meta-diaphyseal cortex reference. Depth of resection, and varus-valgus angulation were selected according to the previous measurements and referring over the most prominent distal femoral condyle. A double check was performed using an extra-medullary rod referring two and a half finger-breaths medially to the antero-superior iliac spine. Postoperative blood loss, pain, swelling, functional recovery, and complications were recorded. Radiographic alignment was measured with long film. Mechanical axis was within 0±2° in 88% of group 1 and 84% of group 2 (p> 0.05). There were no difference between the two groups regarding the operative time. In group 1, postoperative blood loss (740 vs 820 mL) was reduced but this difference did not reach the statistical significance (p=0.07). No difference was found in terms of postoperative pain, knee swelling, and functional recovery. Extramedullary reference with careful preoperative templating can be safely utilized during total knee arthroplasty. Avoiding the violation of the femoral canal may enhance the benefits of a less invasive approach.

Opening wedge high tibial osteotomy (HTO) for varus knee osteoarthritis has shown several advantages over the classic closing wedge technique. The aim of the current prospective study was to evaluate mid-term clinical and radiographic results, as well as complications, of medial opening wedge osteotomy using the hemicallotasis technique. Forty-nine high tibial oste-otomies were performed for unilateral varus primary osteoarthritis from 1999 to 2002. A medial incomplete osteotomy was performed after elevating the superficial collateral ligament. Four pins were inserted, two hydroxyapatite-coated in the metaphyseal bone, and two standard conical pins in the diaphyseal bone. The correction started 4–5 days postoperatively. The patient managed the correction by adjusting half of a turn twice each day. When the desired correction was achieved, the device was locked. Eight-to-nine weeks after surgery, the radiographic healing was evaluated, and if adequate, the device was removed on a outpatient basis. The mean age of the patients was 57 years (range, 32–70 years). The mean follow-up was 5 years (range, 4–7 years). The mean hip-knee-ankle angle (HKA) was 167 (range 164–171) deg preoperatively and 182 (range, 176–186) deg at follow up. We did not observe any early or late collapse of the new bone wedge. Union was achieved in all patients, and the mean time to fixation was 69 (range 60–85) days. Knee Society score improved from 52 points preoperatively to 93 at follow up. Eighty-five percent of the patients showed excellent-to-good clinical outcome. None of the knees had required revision surgery at follow-up. No meta-diaphyseal mismatch was noted on both the sagittal and coronal plain at radiographic analysis. Patellar height (IS ratio) reduced, on average, from 1.1 (±0.4) to 0.9 (±0.4), but no patella was found to be baja. Complications included a number of superficial infection uneventfully healed such as two cellulitis with erysipelas-like rushes, and five minor (grade I-II) pin tract infections. There were two technical problems. One obese patient developed an undisplaced inter-condylar fracture of the proximal tibial osteotomized fragment, which subsequently healed and the patient achieved a good clinical outcome. In another patient the anterior pin on the metaphyseal fragment was positioned too anteriorly, and was thereafter repositioned. There were no neurologic or vascular complications. Using the hemicallotasis technique for HTO the authors obtained a precise correction with a relatively low complication rate. The use of an external fixator allowed quick surgery, early weight-bearing, immediate knee motion, avoiding permanent hardware on bone. Conversion to a total knee arthroplasty seems to be easy when this technique has been employed, but the influence of pin tract infection on possible septic failures remains to be determined.

Introduction: Patello-femoral complications are a major problem after total knee arthroplasty (TKA). Purpose of the present study was to analyze patello-femoral complications and function after two different posterior-stabilized TKA designs (Optetrak 913 vs IB-II).

Materials and Methods: This study was performed in two consecutive phases. In the first phase 1410 TKA’s performed by the senior author between 1994 and 1998 were considered for chart review. Within this period, the last 300 IB-II and the first 300 913 performed were analyzed for patello-femoral complication rate. In the second phase, of the 600 charts analyzed, two matched groups (50 patients each of IB-II and 913), were selected for a clinical (Knee Society score), functional (HSS Patellar score) and radiological assessment (AP, Lateral, Merchant, modified-wb Merchant views).

Results: A lateral retinacular release was performed in 30% for the IB-II and 16% for the 913 (p=0.02). The following patello-femoral complications were encountered (phase-1):

IB-II 913

Patellar clunk 3.5% 0.3%

Dislocation 0% 0.3%

Fracture 0% 0.3%

Loosening 0% 0%

Clinical results at follow-up (phase-2) did not show any significant difference between the two matched groups in terms of Knee and Function scores (p=0.7). Patellar score showed a higher rate of excellent and good results in the 913 group (88% vs 81%: p=.043). Anterior knee pain was only mild and activity related in 26% of the IB-II and 14% of the 913 (p=.025). In a multivariate regression analysis, radiographic patellar tilt, subluxation, and height, did not correlate with clinical outcomes, whilst bone-implant contact showed a trend towards a higher incidence of pain, particularly when associated with asymmetric patellar resection.

Discussion: At an intermediate follow-up, the Optetrak 913 prostheses showed fewer complications and an improved patello-femoral function compared to the IB-II prosthesis.

Introduction: Patello-femoral evaluation after total knee arthroplasty (TKA) is not addressed by most knee scoring systems. Patellar radiographic assessment after TKA is obtained with static, unloaded views that may not reproduce the in-vivo patello-femoral kinematics. The purpose of this study was to develop and validate new reliable and reproducible clinical and radiographic assessment tools for analysis of the patello-femoral joint in TKA.

Materials and Methods: The existing axial Merchant view was modified by positioning the standing patient in the semi-squatted position with the knees at 45°. Relationship between X-ray source, the angle of incidence on the joint, and the cassette position, were kept unchanged from the original view. The standing position and consequent muscle involvement were the only differences. The quality of the view was confirmed on a cadaveric knee model with multiple markers. Safety, reproducibility and clinical reliability were obtained in 100 posterior-stabilized TKA’s. These patients were assessed by a new Patella Scoring System (0–100 points). This system considers anterior knee pain, crepitus, stair performance and quadriceps strength. Radiographic abnormalities are calculated as deductions. Intra- and inter-observer variability were obtained comparing the results of two different investigators.

Results: The modified Merchant view showed significant patello-femoral tracking changes in 68% of patients. Twenty-one cases of bone-implant contact were observed when load was applied. Correlation between excellent-good clinical outcome and excellent patello-femoral performance was significantly higher for the Patellar Score compared to Knee Society Clinic or Function scores (p=.022, p=.014). Multivariate regression analysis of radiographic tilt, subluxation, and height, did not correlate with clinical outcomes, whilst bone-implant contact showed higher incidence of pain, particularly when associated with asymmetric patellar resection.

Conclusion: These new patello-femoral clinical and radiological assessment methods employed in the study represent additional valuable tools for the comprehensive evaluation of results in TKA.

The influence of Posterior Cruciate Ligament (PCL) removal and re-establishment of the posterior condylar recess on flexion and extension gaps width during posterior-stabilized Total Knee Arthroplasty (TKA) is still controversial. It has been reported that PCL resection lead to a selective increase of the flexion space of 3–4 mm, creating a potential for instability in flexion. Our hypothesis was that these surgical steps will equally increase both gaps. Measurements of the flexion and extension gaps heights were obtained during different surgical phases in 50 consecutive primary posterior-stabilised TKAs using a tensor device and a calibrated torque wrench. There was a slight symmetrical increase in both gaps after PCL release. In extension the width of the gap increased on average 1.3 mm and 1.0 mm in the medial and lateral compartment respectively. The same pattern was observed in flexion, averaging 1.3 mm medially and 1.3 mm laterally. Another increase of the two gaps was observed after the posterior condylar osteophytes were removed and the posterior recess was re-established. The gaps in extension increased, with respect to the baseline value, on average 1.8 mm medially and 1.8 mm laterally, while in flexion the increase averaged 2.0 mm and 2.2 respectively on the medial and lateral side. Again there were no statistical differences between flexion and extension gaps. No independent differences between the flexion and extension gaps were found in any considered surgical phase. PCL removal and re-establishment of posterior condylar recess does not seem to require any additional consideration in gap balancing during posterior-stabilized TKA.

Introduction: Static finite-element (FE) analysis has been extensively used to examine polyethylene stresses in Total Knee Arthroplasty (TKA). The aim of this study was to use an explicit-dynamic FE approach with force driven models to simulate both kinematics and internal stresses within a single analysis of the Meniscal Bearing Knee (MBK, Zimmer, Warsaw, IN).

Material and methods: The MBK is a mobile-bearing prosthesis (rotating and AP-gliding) with complete femoro-tibial conformity throughout motion owing to spherical femoral condyles. The FE meshes of the MBK were created from data obtained from the manufacturer as Initial Graphics Exchange Specification (IGES) files. Three-dimensional FE models of the original MBK design and of two modified versions (MBK-Flex and MBK-PS) were generated in Hypermesh 5.1 software. The tibial insert was modeled as a flexible body with 82212 noded solid tetrahedral elements (Poisson ratio: 0.46). The femoral and tibial components were modeled as rigid bodies. Linear soft tissue constraints (30 N/mm AP and 0.6 N-m/degree rotational displacements) were included. Axial load was 4.9mm medially displaced to achieve a medially-biased (60–40) condylar load allocation. Waveforms to simulate gait, stair-climbing and deep-knee-bending with the FE models were obtained from the proposed International Standards Organization 14243–1 and from literature data.

Results: Peak contact stresses for each activity evaluated were below 14 MPa for both the original and modified MBK versions. Kinematics analysis showed similar amount of displacements (average rotations: 3.7°: average AP-glide: 2.5mm) for the various design during gait. In simulated stair-climbing and deep-knee-bending the PS version showed a more reproducible pattern of posterior roll-back in flexion without increasing contact stresses.

Conclusion: Explicit FE analysis is an efficient screening tool before in-vivo or in-vitro testing. It allows to test the effects of variables such as change in prosthetic design, surgical techniques and loads on knee forces and kinematics.

Introduction: Inadequate control of postoperative pain after total knee arthroplasty (TKA) has been associated with a poor functional recovery. This study investigated whether the addition of a single injection femoral nerve block (FNB) to continuous epidural analgesia (EA) provides improved pain control, lowered side effects, and a further acceleration in achievement of rehabilitation goals.

Material and methods: Eighty patients undergoing TKA and receiving EA with 18 ml of 0.5% marcaine were randomized whether to receive or not a single dose of FNB. A nerve stimulator and 30 ml of 0.375% marcaine with 5 μg/ml of epinephrine were used to perform FNB prior to surgery. Post-operative continuous EA was self-administered by the patient adding bolus (up to 4bolus/hour) to the basal infusion rate of 2 ml/hour of 0.175% marcaine. Standardized post-operative rehabilitation protocol were followed for both groups. Therapists and clinicians were blinded to treatment group. Overall narcotic consumption, bolus dosing, and side effects were recorded. Outcomes measurements included postoperative strength and sensation, range of motion and progression, pain score (VAS), achievements of functional milestones and length of stay.

Results: Femoral nerve block group had significantly lower pain scores and lower epidural consumption in comparison to the group without block (p< 0.01). Range-of-motion was significantly greater through post-operative day three in the FNB group (p< 0.04). There was a consistent trend toward improved achievements in rehabilitation milestones after FNB. Decreased quadriceps strength was noted in 33% of the FNB patients on post-operative day one compared to 10% of the patients with isolated EA.

Discussion: We found significant improvements both in terms of analgesia and in functional parameters adding a FNB to continuous EA following TKA. Combination of the two techniques has a sound basis for preventing severe post-operative pain after TKA.

The use of stems with constrained condylar knee (CCK) prosthesis components has been advocated both for primary and revision total knee arthroplasty (TKA). CCK “nonmodular” implants without diaphyseal stems reduce the invasion of the medullary canal, thereby reducing operative time and costs; render a subsequent revision procedure easier, and avoid possible stem pain. The present study is the first report on mid-term results of stemless CCK for primary TKA.

This cross-sectional study reviewed the outcome for 248 knees (180 patients) in which primary TKA was performed using the Exactech nonmodular CCK between 1997 and 2001. The patients had an average age of 68 years and the preoperative diagnosis was osteoarthritis in 94%. Preoperative deformity was severe (82% Ahlback grade 4–5). Valgus deformity was present in 59% and averaged 15° (7–33°). Varus deformity, present in 41% of the patients, averaged 13° (5–22°). Fifty-seven percent of the patients had multiple joint involvement (category C).

Clinical and radiological follow-up at an average of 47 months (range, 24–72 months) was obtained for 192 TKAs (148 patients). Of the total group, there were 15 deaths and 17 patients were lost to follow-up. The Knee Society score improved from 36 to 89 and the functional score from 42 to 76 postoperatively. Varus-valgus laxity improved from 11° (range: 0–30°) to 2° (range:0–6°). Nonprogressive radiolucent lines were present in 16%. Failure rate, defined as revision, was 3% (two infections, two aseptic loosenings, one broken post, and one supra-condylar femoral fracture). In six knees (3%) patello-femoral complications developed: five patellar clunks and one dislocation.

Use of a stemless “nonmodular” CCK for primary severely damaged knees demonstrated reliable mid-term results with a low complication rate.