Comparison of patellar retention versus resurfacing in LCS mobile-bearing total knee arthroplasty

Purpose  

The aim of this retrospective study was to compare clinical outcomes of total knee arthroplasty (TKA) with and without patellar resurfacing using the Low Contact Stress (LCS) mobile-bearing prosthesis in 275 osteoarthritic knees (199 patients) after a minimum of 7 years of follow-up.     

Patellar tendon length during knee flexion of meniscal-bearing and rotating total knee arthroplasty implants

Purpose

The length of the patellar tendon after total knee arthroplasty (TKA) has most commonly been compared with preoperative measurements. However, there are no reports that discuss changes in the length of the patellar tendon during knee flexion after TKA. The purpose of this study was to evaluate changes in the length of the patellar tendon during knee flexion and to clarify the impact of changes in patellar tendon strain on the length of the patellar tendon and post-operative range of motion (ROM) after TKA.

Methods

Thirty-six patients undergoing sequential bilateral TKA for osteoarthritis were evaluated. Patients received a meniscal-bearing (MB) implant on one side and a rotating platform (RP) implant on the other and were followed for a median of 115 months (range 60–211 months). The lengths of the patellar tendon at maximum extension, 30°, 60°, 90° and maximum flexion were measured, and the post-operative ROM of both knees were assessed. The effects of implant design and the knee flexion angle on the length of the patellar tendon were analysed using a linear mixed-effects model. The relationship between patellar tendon strain and post-operative knee ROM was assessed using Pearson’s correlation coefficients.

Results

Post-operative clinical scores were similar for MB and RP implants. Neither the implant design nor the knee flexion angle significantly affected the length of the patellar tendon. The ROMs in the two designs at final follow-up were equivocal (114° in MB, 113° in RP). There was no correlation between patellar tendon strain and ROM in knees with either implant type.

Conclusions

Patellar tendon lengths after mobile-bearing TKA with implants that permitted different anteroposterior constraints were relatively constant at varying degrees of knee flexion. Differences in patellar tendon strain may not impact ROM. These results provide conclusive evidence that the quality of the patellar tendon may play a less important role in ROM after TKA.

Level of evidence

Therapeutic study, Level II.

     

In vivo kinematics comparison of fixed- and mobile-bearing total knee arthroplasty during deep knee bending motion

Purpose

The in vivo kinematics of fixed-bearing and mobile-bearing total knee prostheses remains unclear, particularly for knee flexion over 120°. The purpose of this study was to compare the in vivo kinematics of fixed-bearing and mobile-bearing posterior-stabilized prosthesis during deep knee bending with knee flexion exceeding 120° under weight-bearing conditions.

Methods

In vivo kinematics was analysed for 20 patients implanted with either a fixed-bearing posterior-stabilized or mobile-bearing posterior-stabilized prosthesis. Under fluoroscopic surveillance, each patient performed weight-bearing deep knee bending. Motion between each component was analysed using a two- to three-dimensional registration technique, which uses computer-assisted design models to reproduce the spatial positions of the femoral and tibial components from single-view fluoroscopic images.

Results

Patients who had fixed-bearing prostheses experienced posterior femoral rollback at a mean of 1.4 mm (SD 1.6) of the medial condyle, whereas patients who had mobile-bearing prostheses experienced 0.8 mm (SD 1.2). The posterior femoral rollback of the femoral lateral condyle in patients with a fixed-bearing prosthesis was a mean of 6.4 mm (SD 1.7) motion in the posterior direction, whereas patients who had a mobile-bearing prosthesis had 6.5 mm (SD 2.4) motion. The mean tibial internal rotation was 7.5° (SD 2.1) for fixed-bearing prosthesis and 9.2° (SD 3.2) for mobile-bearing prosthesis.

Conclusions

The present results demonstrated that the fixed-bearing and mobile-bearing posterior-stabilized designs had similar posterior condylar translation and tibial axial rotation during weight-bearing deep knee flexion exceeding 120°.

Level of evidence

Retrospective comparative study, Level III.     

In vivo kinematics of mobile-bearing total knee arthroplasty during deep knee bending under weight-bearing conditions

Purpose  

Little is known about the in vivo kinematics of mobile-bearing total knee arthroplasty, especially at deep knee flexion under weight-bearing conditions.     

Anterior knee pain after total knee arthroplasty: does it correlate with patellar blood flow?

Purpose  

Total knee arthroplasty (TKA) disturbs patellar blood flow, an unintended accompaniment to TKA that may be a cause of postoperative anterior knee pain. We examine whether disrupted patellar blood flow correlates with anterior knee pain following TKA.     

Gait analysis and electromyography in fixed- and mobile-bearing total knee replacement: a prospective, comparative study

Purpose  

The theoretical superiority of mobile-bearing total knee arthroplasties (TKAs) has not yet been proven in clinical studies. The aim of the current study was to compare and to analyse in a patient population that had received either a fixed or a mobile TKA differences in gait analysis electromyography and clinical scores.     

The role of the medial ligamentous structures on patellar tracking during knee flexion

Purpose  

The influence of the medial patellar ligamentous structures on patellar tracking has rarely been studied. Thus the main purpose of this cadaveric biomechanical study was to determine the influence of the medial patellofemoral (MPFL), medial patellomeniscal (MPML) and medial patellotibial (MPTL) ligaments on the three-dimensional patellar tracking during knee flexion. This study was conducted using a validated cadaveric optoelectronic protocol for analysis of patellar kinematics.     

Fixed- versus mobile-bearing unicondylar knee arthroplasty: are failure modes different?

Purpose

An ongoing controversy exists on whether mobile-bearing design is superior over fixed-bearing design in unicondylar knee arthroplasties (UKAs). The present study conducted a systematic review to ascertain differences in performance between fixed- and mobile-bearing designs in UKAs.

Methods

A literature search was performed in PubMed, Embase, Scopus and the Cochrane Library. A total of 9 comparative studies involving 915 knees comparing outcomes of mobile-bearing UKAs with fixed-bearing UKAs were included in the current analysis. Outcomes of interest included knee function, quality of life, radiographic outcomes, reasons and incidence of reoperation, timing of failures, and survivorship.

Results

The results presented no significant differences between the two designs in terms of knee scores, range of motion, limb alignment, implant positioning, incidence of radiolucent lines and overall reoperation rates. However, their differences have been noted in their modes and timing of failures. Early failures are related to the risk of bearing dislocation in the mobile-bearing design. In contrast, later failures are related to the risk of polyethylene wear in the fixed-bearing design.

Conclusions

The available evidence has not confirmed the advantage of mobile-bearing UKAs over fixed-bearing UKAs but pointed out specific modes of failure.

Level of evidence

Therapeutic study (systematic review and meta-analysis), Level III.     

Patellar resurfacing in total knee arthroplasty for osteoarthritis: a meta-analysis

Purpose  

Whether to resurface the patella during a primary total knee arthroplasty remains a controversial issue. The aim of this study was to determine the advantages and disadvantages of patellar resurfacing during total knee arthroplasty for osteoarthritis through an evaluation of the current literature.     

Secondary patellar resurfacing in the treatment of patellofemoral pain after total knee arthroplasty

Purpose  

This paper reports a prospective review of patients who, between 2004 and 2007, underwent secondary patellar resurfacing (SPR) due to anterior knee pain after a primary total knee arthroplasty (TKA). The aim was to evaluate the clinical outcomes obtained with the SPR and to compare them with radiological findings.     

Increased patellofemoral pressure after TKA: an in vitro study

Purpose

Considering the discrepant results of the recent biomechanical studies, the purpose of this study was to simulate dynamic muscle-loaded knee flexion with a large number of specimens and to analyse the influence of total knee arthroplasty (TKA) without and with patellar resurfacing on the patellofemoral pressure distribution.

Methods

In 22 cadaver knee specimens, dynamic muscle-loaded knee flexion (15°–90°) was simulated with a specially developed knee simulator applying variable muscle forces on the quadriceps muscles to maintain a constant ankle force. Patellofemoral pressures were measured with flexible, pressure-sensitive sensor foils (TEKSCAN) and patellofemoral offset with an ultrasound motion-tracking system (ZEBRIS). Measurements were taken on the native knee, after total knee arthroplasty and after patellar resurfacing. Correct positioning of the patellar implant was examined radiologically.

Results

The maximal patellofemoral peak pressure partly increased from the native knee to the knee with TKA with intact patella (35°–90°, p < 0.012) and highly increased (twofold to threefold) after patellar resurfacing (20°–90°, p < 0.001). Concurrently, the patellofemoral contact area decreased and changed from a wide area distribution in the native knee, to a punctate area after TKA with intact patella and a line-shaped area after patellar resurfacing. Patellar resurfacing led to no increase in patellar thickness and patellofemoral offset.

Conclusions

Despite correct implantation of the patellar implants and largely unchanged patellofemoral offset, a highly significant increase in pressure after patellar resurfacing was measured. Therefore, from a biomechanical point of view, the preservation of the native patella seems reasonable if there is no higher grade patellar cartilage damage.     

The “sliver sign”: a specific radiographic sign of acute lateral patellar dislocation

Objective  

The objective of this work is to assess the prevalence of the sliver sign, defined as an intraarticular linear or curvilinear ossific density, in association with knee effusion in patients with acute knee trauma, as a predictor of recent lateral patellar dislocation (LPD).     

Valid MR imaging predictors of prior knee arthroscopy

Purpose  

To determine whether fibrosis of the medial patellar reticulum (MPR), lateral patellar reticulum (LPR), deep medial aspect of Hoffa’s fat pad (MDH), or deep lateral aspect of Hoffa’s fat pad (LDH) is a valid predictor of prior knee arthroscopy.     

The knee adduction moment in hamstring and patellar tendon anterior cruciate ligament reconstructed knees

Purpose

The external knee adduction moment during gait has previously been associated with knee osteoarthritis, and although it has been shown to be greater following anterior cruciate ligament (ACL) reconstruction surgery compared to a control group, it has not been compared between different graft types. Given that the incidence of radiographic knee osteoarthritis appears to be greater following patellar tendon compared to hamstring tendon ACL reconstruction, this study tested the hypothesis that the knee adduction moment would also be increased following patellar tendon ACL reconstruction.

Methods

In 48 male participants (16 patellar tendon graft, 16 hamstring graft and 16 controls), the external knee adduction moment was measured during level walking in a gait laboratory at mean of 10?months after surgery.

Results

There was no difference in the knee adduction moment between the hamstring and patellar tendon groups, and both patient groups had a significantly reduced knee adduction moment compared to the control group. In the hamstring group, the smaller adduction moment was associated with the patients walking with less knee varus whereas in the patellar tendon group, the smaller moment was associated with the patients walking with a decreased vertical ground reaction force.

Conclusions

These results indicate that in male patients during the early stages of recovery from ACL reconstruction, the knee adduction moment is not greater than controls for either hamstring or patellar tendon graft types. Although the knee adduction moment was similar between the two graft types, the overall magnitude of the moment was influenced by different biomechanical factors.

Level of evidence

III.     

Patellar tracking should be taken into account when measuring radiographic parameters for recurrent patellar instability

Purpose

To date, many radiographic parameters on patellar instability have their measurements taken statically, and have not been studied in various degrees of flexion according to the patellar tracking. There are also limited data regarding the use of these parameters in predicting recurrent patellar dislocation. The current study aims to review the radiographic parameters of the patellofemoral joint in different degrees of knee flexion and to correlate them with the presence of recurrent instability.

Methods

A 10-year retrospective study was conducted on all patients who had computed tomography patellar-tracking scan done for patellar instability when aged 18 years or younger. The computed tomography patellar-tracking scans were performed with the knee in extension, 10° flexion, and 20° flexion. The axial radiographic parameters were evaluated at the patellar equator, roman arch, and distal patellar pole. Sagittal and coronal parameters were noted. Radiographic parameters were then correlated with recurrent patellar instability.

Results

The femoral sulcus angle and trochlear groove depth at the distal patellar pole in 10° knee flexion (p value 0.04 and 0.03, respectively) and patellar equator in 20° knee flexion (p value 0.02 and 0.03, respectively) had the most significant clinical correlations with recurrent instability on multivariate analysis. Other radiographic parameters found to have significant clinical correlation on univariate analysis include the patellar tilt angle, congruence angle, femoral sulcus angle, trochlear groove depth, and Wiberg’s classification.

Conclusions

As per the knee dynamics, axial radiographic parameters had the most significant correlation with recurrent patellar instability when measured at the distal patellar pole in 10° knee flexion and at the patellar equator in 20° knee flexion. Future axial radiographic evaluation of patellofemoral instability should then be performed at these degrees of knee flexion and axial cuts. Trochlear dysplasia, as measured by the femoral sulcus angle and trochlear groove depth, was the most significant predictor of recurrent patellar instability in the skeletally immature. Wiberg’s classification was also a novel factor found to have clinical correlation with patellofemoral instability.

Level of evidence

III.

     

The influence of patellar dislocation on the femoro-tibial loading during total knee arthroplasty

Purpose  

Balancing the gap is essential in total knee arthroplasty (TKA). The purpose of this study was to quantify the influence of patellar position on femoro-tibial joint load in TKA. We hypothesized that resetting of the patella increased medial joint load and decreased lateral joint load.     

Autologous matrix-induced chondrogenesis combined with platelet-rich plasma gel: technical description and a five pilot patients report

Purpose  

This pilot study was designed to describe the technical details and to present the preliminary outcome of autologous matrix-induced chondrogenesis (AMIC) combined with platelet-rich plasma gel, the so called AMIC plus technique, for the treatment of patellar cartilage defects in the knee.     

No difference in patellar tracking between symmetrical and asymmetrical femoral component designs in TKA

Purpose

Poor knee extension function after total knee arthroplasty (TKA) is associated with factors including articular geometry and alignment. Femoral trochlear geometry has evolved from symmetrical to become more prominent proximal–laterally, with the groove aligned proximal–lateral to distal–medial. This study in vitro tested the hypothesis that a modern asymmetrical prosthesis would restore patellar tracking and stability to more natural behaviour than an older symmetrical prosthesis.

Methods

Six knees had their patellar tracking measured optically during active knee extension. Medial–lateral force versus displacement stability was measured at fixed angles of knee flexion. The measurements were repeated after inserting each of the symmetrical and asymmetrical TKAs.

Results

Significant differences of patellar lateral displacement stability, compared to normal, were not found at any angle of knee flexion. The patella tracked medial–laterally within 2.5 mm of the natural path with both TKAs. However, for both TKAs near knee extension, the patella was tilted laterally by approximately 6° and was also flexed approximately 8° more than in the natural knee.

Conclusion

The hypothesis was not supported: The more anatomical component design did not provide more anatomical patellar kinematics and stability.     

Less anterior knee pain with a routine lateral release in total knee arthroplasty without patellar resurfacing: a prospective,randomized study

Purpose

Anterior knee pain is a major cause of complaint in total knee arthroplasty (TKA) without patellar resurfacing. The concept of improved patellar tracking and decreased retropatellar contact pressure for lateral retinacular release theoretically suggests that patients with lateral retinacular release in TKA would achieve a lower incidence of anterior knee pain when compared without lateral retinacular release. We sought to determine (1) whether those patients who received a routine lateral retinacular release in TKA would attain lower incidence of anterior knee pain as compared to patients who received TKA without lateral retinacular release and (2) whether lateral retinacular release would increase the lateral retinacular release-related complications.

Methods

A total of 148 patients who underwent TKA with the use of the Gemini MK II mobile bearing were randomized to receive either routine lateral retinacular release (intervention group) or not (control group). Patients were assessed by the visual analogue scale for anterior knee pain, the Knee Society clinical scoring system of knee score and function score, and patellar score for clinical function. Patients’ satisfaction and lateral retinacular release-related complications were also evaluated.

Results

The overall incidence of anterior knee pain in the intervention group at 18 months follow-up was 5.6 %, while that of the control group was 20.6 % (p = 0.009). No statistical difference was detected between the two groups in terms of lateral retinacular release-related complications (n.s.), patients’ satisfaction (n.s.), knee score (n.s.), function score (n.s.), and patellar score (n.s.) at 18 months follow-up.

Conclusion

The present study suggests that routine lateral retinacular release can reduce anterior knee pain and does not increase lateral retinacular release-related complications, in TKA with the use of the Gemini MK II mobile bearing without patellar resurfacing.

Level of evidence

Therapeutic, Level I.     

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.