Posterior Cruciate-substituting Total Knee Arthroplasty Research Articles

Is Highly Cross-Linked Polyethylene Safe for Use in High-Flexion Posterior Stabilized Total Knee Arthroplasty?

BackgroundApplication of highly cross-linked polyethylene (HXLPE) to a posterior cruciate-substituting total knee arthroplasty (TKA) might add the risk of fracture and failure of the tibial polyethylene insert. The purpose of this study is to evaluate the long-term (up to 19 years) clinical and radiographic results of posterior cruciate-substituting TKAs with HXLPE or conventional polyethylene. MethodsThis study analyzed the results of 1,217 patients (444 men and 773 women; mean age of 65 ± 7 years, range, 31-85) (2,434 knees) who had received a NexGen LPS-Flex prosthesis with a conventional tibial insert in one knee and the same prosthesis with an HXLPE tibial insert in the contralateral knee. The mean duration of follow-up was 17 years (range, 15-19). ResultsThe 2 groups did not differ significantly (P > .05) with regard to the clinical and radiographic results. No knee in either group had a fracture of the tibial polyethylene post or failure of the locking mechanism of the tibial polyethylene insert or osteolysis. Twenty-eight knees (2.3%) in the HXLPE group and 26 knees (2.1%) in the conventional polyethylene group were revised. The estimated survival rate at 17 years was 97.7% in the HXLPE group and 97.9% in the conventional polyethylene group. ConclusionThe data suggest that clinical and radiographic findings at a mean of 17 years after posterior cruciate-substituting TKA are the same for patients treated with HXLPE and those treated with conventional polyethylene.

Effect of Posterior Tibial Slope Change on Postoperative Range of Motion and Clinical Outcomes after Posterior Cruciate-Substituting Total Knee Arthroplasty.

The posterior tibial slope (PTS) is usually adjusted by less than 5 degrees, without considering its individual difference, during posterior cruciate-substituting (PS) total knee arthroplasty (TKA). The effect of these individual changes of PTS would be important because clinical results depending on postoperative PTS were reported conflictingly. We investigated the effect of the change in PTS on the postoperative range of motion (ROM) and clinical scores after PS TKA. We retrospectively reviewed 164 knees from 107 patients who underwent PS TKA with a 2-year follow-up. We analyzed the preoperative and postoperative PTS, ROM, visual analog scale pain scale, Western Ontario and McMaster University Index (WOMAC), Hospital for Special Surgery Knee Score, Knee Society Score, and Forgotten Joint Score (FJS). The association of the absolute change in PTS with ROM and clinical scores was analyzed using correlation analysis and multiple regression analysis. As a result, the mean PTS and mean ROM changed from 9.6 ± 3.4 and 120.1 ± 15.4 degrees preoperatively to 2.0 ± 1.3 and 128.4 ± 9.3 degrees postoperatively, and the mean PTS change was 7.6 ± 3.5 degrees. The PTS change had no statistically significant association with the postoperative ROM and clinical scoring systems, although it did have a weak positive correlation with WOMAC function, No 10 (difficulty in rising from sitting) (correlation coefficient = 0.342, p = 0.041), and moderate positive correlation with the FJS, No. 6 (awareness when climbing stairs) (correlation coefficient = 0.470, p = 0.001). The authors concluded that the amount of change in PTS did not affect the postoperative ROM and clinical scores, although proximal tibial resection with a constant target of PTS resulted in individually different changes in the PTS after PS TKA.

Ultracongruent insert design is a safe alternative to posterior cruciate-substituting total knee arthroplasty: 5-year results of a randomized controlled trial

PurposeIf substitution of the posterior cruciate ligament in total knee arthroplasty is necessary, there are two options available: posterior stabilized (PS) design with a post-cam mechanism or anterior-lipped ultracongruent (UC) inserts. UC inserts have the advantage that no femoral box is necessary and a standard femoral component can be used. The aim of this study was to compare the range of motion (ROM) and patient-reported outcome (PRO) after UC and PS fixed-bearing TKA. Better ROM in PS TKA and no difference in PRO between both designs was hypothesized.MethodsA randomized controlled trial with 127 patients receiving a fixed-bearing UC or PS design of the same knee system was performed. Nine patients died and there were four revision surgeries. 107 patients completed the 5-year follow-up. Patient-reported outcome was assessed. Patellofemoral problems were evaluated using selected applicable questions of the Oxford Knee Score (getting up from a table, kneeling, climbing stairs).ResultsSurgical time was 10 min shorter in the UC group (p < 0.001). After 5 years, both groups demonstrated good knee function and health-related quality of life without significant differences between the groups. Both groups demonstrated a high satisfaction score and the majority of patients would undergo this surgery again. Patellofemoral problems were recognized more frequently in the PS group (p = 0.025).ConclusionBoth designs demonstrated similar good results after 5 years. Stabilization with an anterior-lipped UC insert can be considered a safe alternative to the well-established PS design if cruciate substitution is necessary.Level of evidence1.

Unacceptable failure rate of a ceramic-coated posterior cruciate-substituting total knee arthroplasty.

BackgroundAseptic loosening is one of the most elusive problems in total knee arthroplasty. We compared the failure rates of posterior cruciate-substituting total knee arthroplasty utilizing implants with hardened surface coating to a previous cohort of patients who underwent the procedure with traditional cruciate-retaining noncoated cobalt-chrome implants.MethodsA retrospective study was conducted of 1099 total knee arthroplasties performed from 2009 to 2017. Two hundred forty-nine total knee arthroplasties performed from January 2015 to March 2017 under a single design were reviewed retrospectively and compared to the author’s previous 850 total knee arthroplasties performed from January 2009 to December 2014 under a different design.ResultsThis series demonstrated an alarming debonding of cement in the tibial implant. The resultant failure rate of 6% (P < .001) is higher than observed in 850 total knee arthroplasties in the previous 5 years and higher than those reported in the literature giving cause for concern regarding this implant.ConclusionsDue to the observed excessive failure rate, the authors recommend exercising high levels of caution using this implant with hardened surface treatment until further testing can be ascertained as to the root cause of failure.

In vivo Kinematics of the Knee after a Posterior Cruciate-Substituting Total Knee Arthroplasty: A Comparison between Caucasian and South Korean Patients.

PurposeThis study compared in vivo kinematic differences between Caucasian and South Korean patients after a posterior-substituting total knee arthroplasty (PS-TKA).Materials and MethodsIn vivo motions of 9 Caucasian and 13 South Korean knees with a PS-TKA during weight bearing single leg lunge were determined using a dual fluoroscopic imaging technique. Normalized tibiofemoral condylar motions and articular contact locations were analyzed.ResultsFemoral condylar motions of the two groups showed a similar trend in anteroposterior translation, but the South Korean patients were more anteriorly positioned than the Caucasian patients at low flexion and maximal flexion angles in both medial and lateral compartments (p<0.05). Mediolateral femoral condyle translations were similar between the two groups. For tibiofemoral articular contact kinematics, the South Korean patients had significantly more anterior contact locations at the medial compartment at low flexion angles, and more lateral contact locations at the lateral compartment at 0° and 90° flexion compared to the Caucasian patients (p<0.05). The South Korean patients had significantly larger distances between the medial and lateral contact locations at 60° and 90° flexion compared to the Caucasian patients (p<0.05).ConclusionsThe study revealed that while the Caucasian and South Korean knees had similar femoral condylar motions, after PS-TKA the South Korean patients showed different articular contact point kinematics compared to the Caucasian patients.

Midterm comparison of posterior cruciate-retaining versus -substituting total knee arthroplasty using the Genesis II prosthesis: A multicenter prospective randomized clinical trial

The purpose of the current study was to compare midterm outcomes of posterior cruciate-retaining (CR) versus posterior cruciate-substituting (PS) procedures using the Genesis II total knee arthroplasty (TKA) system (Smith and Nephew, Memphis, TN). Ninety-nine (99) CR and 93 PS TKA's were analyzed in this prospective, randomized clinical trial. Surgeries were performed at seven medical centers by participating surgeons. Clinical outcomes (Knee Society Score, Range of Motion, WOMAC, SF-12, and Radiographic Findings), in addition to postoperative complications, were evaluated with a minimum follow-up of 5 years. Following data analysis, there were no significant differences in patient demographics or preoperative clinical measures between the two groups. At the latest follow-up interval, no significant differences were found between the CR and PS groups with regards to functional assessment, patient satisfaction, or postoperative complication. However, the PS group did display statistically significant improvements in range of motion when compared with the CR group. The results of this investigation would suggest that, while comparable in regards to supporting good clinical outcomes, the PS Genesis II design does appear to support significantly improved postoperative range of motion when compared with the CR design.

The rationale for a total knee implant that confers anteroposterior stability throughout range of motion

The topic at hand in this series of presentations concerns the design of total knee prostheses. This presentation concerns the rationale for an implant to confer anteroposterior stability without the need for a central “cam and post” mechanism, as is common in posterior cruciate-substituting total knee arthroplasty prostheses.

Fracture of the polyethylene tibial post in a posterior cruciate-substituting total knee arthroplasty mimicking patellar clunk syndrome: A report of 5 cases

Fracture of the tibial post in posterior cruciate-substituting total knee arthroplasty has been described in several reports. Additionally, wear of the cam and post mechanism, including polyethylene debris generation and osteolysis of the peri-implant bone stock as been described. Users of a cam and post type posterior stabilized total knee arthroplasty are also familiar with the rare occurrence of the “patellar clunk syndrome,” in which suprapatellar fibrous nodular scar tissue becomes entrapped in the intercondylar box of the femoral component as the knee extends from the flexed position and produces a palpable and sometimes audible “clunk.” This condition is easily managed with arthroscopic excision of the scar tissue. A small series of 5 patients who presented with symptoms of a patellar clunk syndrome but who in fact had a fracture of the tibial post causing subluxation of the femur on the tibia is presented. The diagnostic characteristics that will help differentiate between the 2 problems is highlighted.

Femoral rollback after cruciate-retaining and stabilizing total knee arthroplasty.

Limited data comparing the kinematics of posterior cruciate ligament-retaining or substituting total knee arthroplasty with its own intact knee under identical loadings is available. In the current study, posterior femoral translation of the lateral and medial femoral condyles under unloaded conditions was examined for intact, cruciate-retaining, cruciate ligament-deficient cruciate-retaining and posterior-substituting knee arthroplasties. Cruciate-retaining and substituting total knee arthroplasties behaved similarly to the cruciate-deficient cruciate-retaining total knee arthroplasty between 0 degrees and 30 degrees flexion. Beyond 30 degrees, the posterior cruciate-retaining arthroplasty showed a significant increase in posterior translation of both femoral condyles. The posterior cruciate-substituting arthroplasty only showed a significant increase in posterior femoral translation after 90 degrees. At 120 degrees, both arthroplasties restored approximately 80% of that of the native knee. Posterior translation of the lateral femoral condyle was greater than that observed in the medial condyle for all knees, indicating the presence of internal tibial rotation during knee flexion. The data showed that the posterior cruciate ligament is an important structure in posterior cruciate-retaining total knee arthroplasty and proper balancing is imperative to the success of the implant. The cam-spine engagement is valuable in restoring posterior femoral translation in posterior cruciate-substituting total knee arthroplasty.

Femoral condylar lift-off in vivo in total knee arthroplasty.

We carried out weight-bearing video radiological studies on 40 patients with a total knee arthroplasty (TKA), to determine the presence and magnitude of femoral condylar lift-off. Half (20) had posterior-cruciate-retaining (PCR) and half (20) posterior-cruciate-substituting (PS) prostheses. The selected patients had successful arthroplasties with no pain or instability. Each carried out successive weight-bearing knee bends to maximum flexion, and the radiological video tapes were analysed using an interactive model-fitting technique. Femoral lift-off was seen at some increment of knee flexion in 75% of patients (PCR TKA 70%; PS TKA 80%). The mean values for lift-off were 1.2 mm with a PCR TKA and 1.4 mm with a PS TKA. Lift-off occurred mostly laterally with the PCR TKA, and both medially and laterally with the PS TKA. Separation between the femoral condyles and the articular surface of the tibia was recorded at 0 degrees, 30 degrees, 60 degrees and 90 degrees of flexion. Femoral condylar lift-off may contribute to eccentric polyethylene wear, particularly in designs of TKA which have flatter condyles. Coronal conformity is an important consideration in the design of a TKA.

Femoral condylar lift-off in vivo in total knee arthroplasty

We carried out weight-bearing video radiological studies on 40 patients with a total knee arthroplasty (TKA), to determine the presence and magnitude of femoral condylar lift-off. Half (20) had posterior-cruciate-retaining (PCR) and half (20) posterior-cruciate-substituting (PS) prostheses. The selected patients had successful arthroplasties with no pain or instability. Each carried out successive weight-bearing knee bends to maximum flexion, and the radiological video tapes were analysed using an interactive model-fitting technique. Femoral lift-off was seen at some increment of knee flexion in 75% of patients (PCR TKA 70%; PS TKA 80%). The mean values for lift-off were 1.2 mm with a PCR TKA and 1.4 mm with a PS TKA. Lift-off occurred mostly laterally with the PCR TKA, and both medially and laterally with the PS TKA. Separation between the femoral condyles and the articular surface of the tibia was recorded at 0°, 30°, 60° and 90° of flexion. Femoral condylar lift-off may contribute to eccentric polyethylene wear, particularly in designs of TKA which have flatter condyles. Coronal conformity is an important consideration in the design of a TKA.

Range of motion after total knee arthroplasty The effect of implant design and weight-bearing conditions

Knee range of motion was determined in 60 patients to assess the effect of weight bearing on maximal knee flexion. Three patient subgroups were investigated: patients with normal knees, patients implanted with posterior cruciate-retaining (PCR) total knee arthroplasty (TKA), and patients implanted with posterior cruciate-substituting (PS) TKA. Maximal knee flexion was determined using videofluoroscopy both in a passive, non-weight-bearing mode and during active weight bearing. Flexion was diminished with weight bearing in all three subgroups ( P < .045). Patients with normal knees exhibited significantly greater knee flexion than either TKA subgroup when measured either with or without weight bearing ( P < .001). Knee flexion of both TKA subgroups was similar when measured passively without weight bearing. Patients with PS TKA demonstrated greater flexion than patients with PCR TKA when measured in weight bearing ( P < .025), despite having less range of motion and lower clinical performance ratings preoperatively. Measurement of knee range of motion in a weight-bearing fashion may be a superior method of assessment of functional capabilities.

Supracondylar femoral fracture above a PFC posterior cruciate-substituting total knee arthroplasty treated with supracondylar nailing: A unique technical problem

Supracondylar fracture above a total knee arthroplasty with a posterior cruciate-substituting design presents a challenging problem to the orthopaedic surgeon. The standard treatment using a intramedullary rod is made difficult by the design of the PFC cruciate-substituting total knee arthroplasty (Johnson & Johnson Orthopaedics, Raynham, MA), which prevents entry of a standard supracondylar nail to the medullary canal of the femur. A technique for using an interlocking intramedullary rod to treat a supracondylar fracture above a posterior cruciate-substituting total knee arthroplasty is described. A case is presented illustrating this technique.