The unicompartmental knee is the preferred side in individuals with both a unicompartmental and total knee arthroplasty.

PURPOSE: To determine the preferred knee in patients with both one total and one unicompartmental knee arthroplasty. METHOD: Patients simply with a unicompartmental (UKA) and total knee arthroplasty (TKA) on contralateral sides were retrospectively screened from three senior knee surgeon's logs over a 15 year period. Patients safe and free from other diseases to affect gait were approached. A total of 16 patients (mean age 70 ± 8) agreed to ground reaction force testing on an instrumented treadmill at a fair pace and incline. A gender-ratio identical group of 16 healthy control subjects (mean age 67 ± 10) and 16 patients with ipsilateral medial knee OA (mean age 66 ± 7) were analysed to compare. RESULTS: Radiographically the mode preoperative Kellgren-Lawrence knee grade for each side was 3. Postoperatively, the TKA side had a mean coronal femoral component alignment of 7° and a mean tibial coronal alignment of 89° with a mean posterior slope of 5° in the sagittal plane. The UKA side had a mean coronal femoral component alignment of 7° and a mean tibial coronal alignment of 86° with a mean posterior slope of 4° in the sagittal plane. In 7 patients, the TKA was the first procedure, while 6 for the UKA and 3 done simultaneously. Gait analysis demonstrated in both walking conditions the UKA limb was the preferred side through all phases of loading (p < 0.05) and nearer to normal than the TKA limb when compared to healthy controls and patients with knee OA. The greatest difference was observed between the transition of weight acceptance and midstance (p = 0.008), when 22% more load was taken by the UKA side. CONCLUSION: By using a dynamic metric of an everyday activity, a distinct gait difference between differing arthroplasty types were established. A more natural loading pattern can be achieved with unicompartmentals as compared to total knees. LEVEL OF EVIDENCE: Retrospective comparative study, Level III.

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.

Unicompartmental knee arthroplasty enables near normal gait at higher speeds, unlike total knee arthroplasty.

Top walking speed (TWS) was used to compare UKA with TKA. Two groups of 23 patients, well matched for age, gender, height and weight and radiological severity were recruited based on high functional scores, more than twelve months post UKA or TKA. These were compared with 14 preop patients and 14 normal controls. Their gait was measured at increasing speeds on a treadmill instrumented with force plates. Both arthroplasty groups were significantly faster than the preop OA group. TKA patients walked substantially faster than any previously reported series of knee arthroplasties. UKA patients walked 10% faster than TKA, although not as fast as the normal controls. Stride length was 5% greater and stance time 7% shorter following UKA - both much closer to normal than TKA. Unlike TKA, UKA enables a near normal gait one year after surgery.

T1-weighted sodium MRI of the articulator cartilage in osteoarthritis: a cross sectional and longitudinal study.

Structural magnetic resonance imaging (MRI) has shown great utility in diagnosing soft tissue burden in osteoarthritis (OA), though MRI measures of cartilage integrity have proven more elusive. Sodium MRI can reflect the proteoglycan content of cartilage; however, it requires specialized hardware, acquisition sequences, and long imaging times. This study was designed to assess the potential of a clinically feasible sodium MRI acquisition to detect differences in the knee cartilage of subjects with OA versus healthy controls (HC), and to determine whether longitudinal changes in sodium content are observed at 3 and 6 months. 28 subjects with primary knee OA and 19 HC subjects age and gender matched were enrolled in this ethically-approved study. At baseline, 3 and 6 months subjects underwent structural MRI and a 0.4ms echo time 3D T1-weighted sodium scan as well as the knee injury and osteoarthritis outcome score (KOOS) and knee pain by visual analogue score (VAS). A standing radiograph of the knee was taken for Kellgren-Lawrence (K-L) scoring. A blinded reader outlined the cartilage on the structural images which was used to determine median T1-weighted sodium concentrations in each region of interest on the co-registered sodium scans. VAS, K-L, and KOOS all significantly separated the OA and HC groups. OA subjects had higher T1-weighted sodium concentrations, most strongly observed in the lateral tibial, lateral femoral and medial patella ROIs. There were no significant changes in cartilage volume or sodium concentration over 6 months. This study has shown that a clinically-feasible sodium MRI at a moderate 3T field strength and imaging time with fluid attenuation by T1 weighting significantly separated HCs from OA subjects.

T2* measurement of the knee articular cartilage in osteoarthritis at 3T.

PURPOSE: To measure reproducibility, longitudinal and cross-sectional differences in T2* maps at 3 Tesla (T) in the articular cartilage of the knee in subjects with osteoarthritis (OA) and healthy matched controls. MATERIALS AND METHODS: MRI data and standing radiographs were acquired from 33 subjects with OA and 21 healthy controls matched for age and gender. Reproducibility was determined by two sessions in the same day, while longitudinal and cross-sectional group differences used visits at baseline, 3 and 6 months. Each visit contained symptomological assessments and an MRI session consisting of high resolution three-dimensional double-echo-steady-state (DESS) and co-registered T2* maps of the most diseased knee. A blinded reader delineated the articular cartilage on the DESS images and median T2* values were reported. RESULTS: T2* values showed an intra-visit reproducibility of 2.0% over the whole cartilage. No longitudinal effects were measured in either group over 6 months. T2* maps revealed a 5.8% longer T2* in the medial tibial cartilage and 7.6% and 6.5% shorter T2* in the patellar and lateral tibial cartilage, respectively, in OA subjects versus controls (P < 0.02). CONCLUSION: T2* mapping is a repeatable process that showed differences between the OA subject and control groups.

Radiographic features predictive of patellar maltracking during total knee arthroplasty.

Despite improvements in component design and surgical technique, some patients still require lateral retinacular release during TKA to improve patella tracking. We studied 148 fixed-bearing TKAs to identify parameters in pre-operative knee radiographs that would predict intraoperative patellar maltracking. Digital radiographs and software were used to measure coronal alignment, distal femoral valgus angle, proximal tibia varus angle, patellar tilt, patellar shift, Insall-Salvati ratio, and patellar component placement and alignment. Patellar tracking was assessed after all components had been cemented, using both no-touch and modified "towel clip" techniques. The only radiographic parameter independently associated with maltracking was patellar shift. The median pre-operative patellar lateral shift in patients who had maltracking was 4.1 mm compared to 0.0 mm in those who did not. Patients who had a patellar shift of more than 3.0 mm had a high likelihood of maltracking, with estimated positive and negative predictive values of 78 and 95%, respectively. Pre-operative patellar shift may thus be clinically relevant for identifying osteoarthritic patients who have a higher likelihood for patellar maltracking during TKA. Variations in the intrinsic risk for maltracking within patient study populations may account for the widely differing reported rates of patellar maltracking, and our data suggest that information on pre-operative patellar shift may be helpful in stratifying these sample populations.

A technique of staged lateral release to correct patellar tracking in total knee arthroplasty.

Optimal patellar tracking and component alignment are important in achieving a well-functioning total knee arthroplasty (TKA). The patella is constrained partly by design of the prosthetic trochlear groove, and patellar tracking is governed by a combination of static and dynamic factors. Maltracking may result from excessive or unbalanced tension in the surrounding soft tissues. This article describes a staged progressive lateral release of the patellar retinaculum in TKA, which is classified into 6 stages. Stage 1 transects the deep lateral patellofemoral ligament; stages 2 to 6 extend the lateral patellar incision distally from vastus lateralis to the tibial tubercle. This technique was used in a series of 96 primary TKAs. We report the rates of the various stages of lateral release and the variables that might affect the decision to perform such a release.

Arthroscopic appearances of the meniscofemoral ligaments: introducing the "meniscal tug test".

To evaluate the feasibility of identifying the anterior and posterior meniscofemoral ligaments (aMFL and pMFL, respectively) at arthroscopy, both visually and using the "meniscal tug test", which exploits the anatomical attachments of the posterior cruciate ligament (PCL) and MFLs. This is an observational type of study. Arthroscopy using anteromedial and anterolateral portals was performed in 68 knees in 68 patients (36 right, 32 left). The MFLs were identified using several anatomical cues, including their femoral and meniscal attachments, their obliquity relative to the PCL, and the meniscal tug test. Identification was classed as easy or hard by the operating surgeon. From 68 knees, the aMFL was seen and confirmed to be an MFL using the tug test in 60 (88%). Identification of the aMFL was classed as easy in 64 (94%), whilst the pMFL was easy to identify in only 6 (9%) of knees, of which 3 had a ruptured PCL. Thus, with the exception of PCL-deficient knees, it was felt that the meniscal "tug test" as applied in this study was not suitable for the pMFL. The study shows that identification of the aMFL is possible in most knees at arthroscopy, using the "tug test" and other anatomical cues. However, identification of the pMFL may require a posterior portal. A subgroup of PCL injuries in which the MFLs were intact was also observed. The "meniscal tug test" can be used in arthroscopic examinations of the PCL to distinguish between fibres of the true PCL from the MFLs, thus avoiding the misdiagnosis of partial versus complete PCL rupture. This will also aid studies examining the role of the MFLs in stabilising the PCL-deficient knee.

Synovial shelves of the knee: association with chondral lesions.

The objectives of the present study were to evaluate whether synovial shelves of the knee are associated with increased incidence of chondral lesions and to determine which types of plica are associated with significant articular damage. Data were collected prospectively from 1,000 consecutive knee arthroscopies. Of these patients, 321 (32.1%) were found to have synovial shelves of the knee. Patients details (age, sex, duration of symptoms, injuries, and possible mechanism of injury), operative details (types and number of portals, equipment used), intra-articular findings (articular, meniscal and synovial lesions, and stability characteristics) and procedures performed were recorded on a special database. Synovial shelves of the knee were recorded using a modification of the Sakakibara classification. Articular lesions were noted on anatomic articular maps of the different functional zones using a functional zoning system that presaged the current ICRS system. An increased incidence of articular lesions was found in patients with synovial shelves, in comparison with patients without shelves (94.7 vs. 81% respectively; P < 0.001). Patients with larger and more fibrotic shelves were found to have increased incidence of cartilage lesions, in comparison with patients with type smaller and less fibrotic shelves (96.5 vs. 86.4%, respectively; P = 0.002), as well as cartilage lesions with bigger size (84 vs. 71.4%, respectively; P = 0.02). Patella (P < 0.001), and specific areas (P < 0.001) of the medial femoral condyle, were areas with increased incidence of cartilage lesions, in patients with synovial shelves. In conclusion, synovial shelves of the knee are associated with an increased incidence of cartilage lesions. Larger shelves, particularly with chronic inflammation are associated with more frequently occurring and larger articular lesions. Areas with increased incidence of chondral lesions, in patients with plicae, include particularly the lower patella and the non-weight-bearing medial femoral condyle.

Is there an association between articular cartilage changes and degenerative meniscus tears?

PURPOSE: The objective of the present study was to evaluate whether horizontal cleavage and complex meniscus tears, which are degenerative tears, are associated with an increased incidence of cartilage damage, in comparison with patients having other patterns of meniscal injury. TYPE OF STUDY: Case series study. METHODS: Data were collected prospectively from 497 consecutive knee arthroscopies carried out from 1997 to 2001. Patient data (age, sex, duration of symptoms, injuries, and possible mechanism of injury), operative details (types and number of portals, equipment used), intra-articular findings (articular, meniscal and synovial lesions, and stability characteristics), and procedures performed were recorded. Articular lesions were noted on anatomic articular maps of the different functional zones using a system that presaged the current Internal Cartilage Repair Society system. RESULTS: A comparison of patients with horizontal cleavage and complex meniscal tears to patients with other types of meniscal tear showed for the former (1) increased incidence of chondral lesions (88.4% v 69.6%, respectively, P < .001), (2) increased severity--type III and IV Outerbridge classification--of chondral lesions (52.8% v 29.4%, respectively, P < .001), and (3) increased incidence of patients having more than 1 chondral lesion (65.3% v 33%, respectively, P < .001). CONCLUSIONS: Complex and horizontal cleavage meniscal tears are highly associated with an increased incidence and severity of cartilage degeneration compared with other types of meniscal tears. Degenerative meniscus tears are not as benign as was previously thought. New age-related categories of chondral damage are emerging. LEVEL OF EVIDENCE: Level IV, case series prognostic study.

Internal derangements of the knee associated with patellofemoral joint degeneration.

The objective of the present study was to evaluate whether internal derangements of the knee joint are associated with patellofemoral joint (PFJ) degeneration. Data were collected prospectively from 1,000 consecutive knee arthroscopies. Chondral lesions were observed in 854 patients, and these patients were included in this study. Patients' details (age, sex, duration of symptoms, injuries, and possible mechanism of injury), operative details (types and number of portals, equipment used), intra-articular findings (articular, meniscal and synovial lesions, and stability characteristics) and procedures performed were recorded. Articular lesions were noted on anatomic articular maps of the different functional zones, using a system which presaged the current ICRS system. Using this zoning system, it was easy for the authors to separate the patients with isolated patellofemoral degeneration and arthritis and to do the statistical analysis. Increased incidence of isolated patellofemoral degeneration was noted in patients with synovial shelves, in comparison with patients without shelves (24.7% vs. 15.5%, respectively; P=0.001). Patients with severe patellofemoral maltracking were found to have increased incidence of isolated patellofemoral degeneration in comparison with patients without patella maltracking (64.7% vs. 18% respectively; P<0.001). In conclusion, patellofemoral maltracking and synovial shelves of the knee are highly associated with PFJ degeneration. On the contrary, meniscal tears and ligamentous injuries are associated mainly with degeneration of other compartments of the knee joint and not the PFJ.