Femoral component rotation and arthrofibrosis following mobile-bearing total knee arthroplasty

The purpose of this study was to evaluate the femoral component rotation in a small subset of patients who had developed arthrofibrosis after mobile-bearing total knee arthroplasty (TKA). Arthrofibrosis was defined as flexion less than 90 degrees or a flexion contracture greater than 10 degrees following TKA. From a consecutive cohort of 3,058 mobile-bearing TKAs, 49 (1.6%) patients were diagnosed as having arthrofibrosis, of which 38 (86%) could be recruited for clinical assessment. Femoral rotation of a control group of 38 asymptomatic TKA patients matched for age, gender, and body mass index was also evaluated. The surgical epicondylar axis was compared with the posterior condylar axis for the femoral prosthesis. Femoral components in the arthrofibrosis group were significantly internally rotated by a mean of 4.7 degrees (SD 2.2 degrees , range 10 degrees internal to 1 degrees external). In the control group, the femoral component had a mean 0.3 degrees internal rotation (SD 2.3 degrees , range 4 degrees internal to 6 degrees external). Following mobile-bearing TKA, there is a significant correlation between internal femoral component rotation and chronic arthrofibrosis.     

Tibial component coverage and rotational alignment accuracy after mobile-bearing total knee arthroplasty

Background

Tibial component coverage (TCC) and tibial rotational angle (TRA) have been studied simultaneously in simulations, but not in clinical studies after total knee arthroplasty (TKA). The purposes of this study were (1) to evaluate TCC and rotational setting postoperatively in mobile-bearing TKA patients and (2) to compare the results with previously published simulation data.

Methods

We prospectively examined 100 patients who underwent primary TKA using the LCS^® Total Knee System (LCS) posterior cruciate ligament-substituting prosthesis. Clinical outcomes, TCC (coverage area of the tibial component over the tibia), and TRA (relative to the femoral transepicondylar axis (TEA)) were assessed. Quantitative three-dimensional computed tomography was used to assess TCC and TRA. All values are expressed as median (25th percentile, 75th percentile) using minus (?) for internal and plus (+) for external rotation.

Results

Hospital for Special Surgery scores improved from 46 (36, 50) preoperatively to 92 (90, 92) postoperatively. TRA showed a median divergence of ? 2.0° (? 4.75°, + 2.74°). All knees were located within 10° of the TEA (range ? 10.0° to + 9.7°). The median TCC of the knees was 82.7% (80.6, 84.7%), and there were no knees that hung over the tibial component in any direction.

Conclusions

The LCS prosthesis had good clinical outcomes, comparable TCC, and improved TRA as compared to previous reports, as all knees were located within 10° of the TEA. Simultaneous optimization of both TCC and TRA may contribute to the excellent long-term outcomes that have been observed with this system.

Level of evidence

Level II, Prognostic study.

     

Femoral component loosening in total knee arthroplasty

From experience with over 1600 condylar-type total knee arthroplasties performed between 1974 and 1981, the authors identified 15 knees in which the femoral component had loosened and shifted into flexion on the end of the femur. This mode of failure was related to inadequate support of the prosthetic posterior condyle, which resulted from inaccurate surgical cuts, poor cementing technique, or deficient bone stock either primary or secondary to persistent rheumatoid synovitis. Newer prosthetic designs that allow for greater range of motion and maximal function will further test the critical posterior condylar bone interface, as a result of which a higher incidence of femoral component loosening with flexion shift may be seen. Femoral component design changes and surgical techniques that sustain the posterior femoral condyle metal-bone interface may thus be necessary. Femoral components with intramedullary stems may be appropriate for high-risk patients.     

Frontal plane kinematics after mobile-bearing total knee arthroplasty.

Frontal plane kinematics including condylar lift-off and medial to lateral translation were investigated in 10 patients who had total knee arthroplasty with a mobile-bearing rotating platform or a similar implant that had been modified with a posterior stabilizer. The rotating platform had condylar lift-off (average, 2 mm) and medial tibial translation (average, 4.3 mm) in all implants tested. The posterior-stabilized prosthesis had significantly less condylar lift-off (average, 1.2 mm) and medial translation (average, 1.7 mm). The difference is attributed to constraint of the posterior stabilizer mechanism in the frontal plane. The important kinematic functions of frontal plane condylar lift-off and medial to lateral translation must be accounted for by contemporary total knee prosthetic designs because abnormalities may lead to abnormal wear and loss of prosthetic fixation.     

Femoral shaft fractures after cemented total hip arthroplasty

Summary Thirty-seven femoral shaft fractures occurred in 2360 cemented hip arthroplasties carried out between 1971 and 1989 at varying intervals after operation (average 3.7 years). Three types of fracture were recognised and treatment depended on the type, as did the prognosis. Good results were obtained in 70% of the cases.

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Résumé Sur une série consécutive de 2360 prothèses totales de hanche cimentées, réalisées dans notre hôpital de 1971 à 1989, on a observé 37 fractures de la diaphyse fémorale. Ces fractures sont survenues après un délai variable (3,7 ans en moyenne). Le pronostic de la consolidation de la fracture et de l'avenir de la prothèse dépend du type de la fracture, évalué selon la classification de Johansson. Le type II a été le plus fréquent (51%), suivi par le type III (30%) et le type I (19%). Le traitement a été différent selon le type de la fracture, avec 70% de bons résultats.

     

Tibial baseplate fracture associated with polyethylene wear and osteolysis after total knee arthroplasty

INTRODUCTION

Fracture of the tibial baseplate following total knee arthroplasty is very rare given the developments in modern prosthesis design. Tibial baseplate fracture secondary to polyethylene wear, osteolysis and component malalignment in an elderly obese patient is reported in the present article.

PRESENTATION OF CASE

A 69-year-old woman had undergone total knee arthroplasty eleven years prior to presentation and reported nine months of chronic pain, which was caused by a neglected fracture of the baseplate.

DISCUSSION

We discuss the prevention of implant fracture after total knee arthroplasty and address the risk factors associated with this complication.

CONCLUSION

The present case emphasizes the importance of properly informing patients and encouraging them to report such complaints immediately to allow for early revision and prevention of component fracture, especially in patients with risk factors such as obesity and component, malalignment.     

Femoral fracture through a previous pin site after computer-assisted total knee arthroplasty

Computer-assisted total knee arthroplasty has been gaining popularity given the proposed benefits of increased accuracy of the femoral and tibial cuts, quantitative feedback on soft tissue balancing, and the potential for performing the procedure through smaller incisions with decreased soft tissue trauma. Most navigation systems require femoral and tibial threaded pin insertion for placement of guidance trackers, which when removed leave behind defects in the bone that may act as stress risers. We present 2 cases of a femoral fracture through a previous pin site where a guidance tracker had been placed for computer-assisted total knee arthroplasty. Both patients were informed that data concerning the cases would be submitted for publication. To our knowledge, this complication has not previously been reported for this procedure.     

Sagittal laxity after posterior cruciate ligament-retaining mobile-bearing total knee arthroplasty

Posterior cruciate ligament stretching after posterior cruciate ligament-retaining (CR) total knee arthroplasty (TKA) can lead to an increase in sagittal laxity, knee dysfunction, or accelerated damage to the tibial bearing surface. We conducted a prospective study on 74 consecutive mobile-bearing CR TKA to determine if knee laxity changed with time or if knees with large initial laxity experienced greater increases in laxity. Patients were studied with radiographic posterior and anterior drawer examinations at 3 and 23 months. Model-based shape-matching techniques were used to measure TKA kinematics. We found a 1-mm increase in posterior drawer. Knees with large postoperative drawers did not exhibit increased laxity at last follow-up. The use of a mobile-bearing CR TKA did not significantly modify the midterm knee sagittal laxity.     

Patellar fracture after total knee arthroplasty

BACKGROUND: Patellar fracture can occur as a complication following total knee arthroplasty. The purpose of this study was to evaluate a large series of patellar fractures to determine the results of different forms of treatment of specific fracture types. METHODS: A retrospective review identified eighty-five fractures (in seventy-seven patients) following 12,464 consecutive total knee arthroplasties performed between 1985 and 1998. Seventy-eight fractures occurred after primary total knee arthroplasty and seven, after revision total knee arthroplasty. Five fractures were treated elsewhere, and two others were lost to follow-up. The results of treatment of the remaining seventy-eight fractures were reviewed. Fractures were classified according to three main criteria: integrity of the extensor mechanism, fixation status of the patellar implant, and quality of the remaining bone stock. The mean duration of follow-up was 3.6 years. RESULTS: The prevalence of patellar fracture after total knee arthroplasty was 0.68%; fractures were significantly more prevalent among men (1.01%) than among women (0.40%) (p = 0.0004). Thirty-eight fractured patellae had a stable implant and an intact extensor mechanism (Type I). All but one were treated nonoperatively, and there was only one late failure of nonoperative treatment, which required operative intervention. Twelve fractures were associated with disruption of the extensor mechanism (Type II). Eleven were treated operatively; six knees had complications and five had a reoperation. Twenty-eight fractures occurred in association with a loose patellar component (Type III). Twenty were treated operatively; nine knees had complications, and four had a reoperation. CONCLUSIONS: Patellar fractures after total knee arthroplasty are infrequent. Treatment can be guided by three main criteria: integrity of the extensor mechanism, fixation status of the patellar implant, and quality of the remaining bone. Fractures associated with a stable implant and an intact extensor mechanism were usually treated successfully with nonoperative means, with minimal complications. When operative treatment was required, it was associated with a high rate of complications and reoperations.     

Early aseptic loosening of a total knee arthroplasty due to Gore-Tex particle-induced osteolysis

Anterior cruciate ligament reconstruction with the use of synthetic graft material has been used as an alternative to biologic grafts. The use of these grafts has largely been abandoned in reconstruction of the anterior cruciate ligament because of mechanical failure of the graft and production of wear debris leading to synovitis and recurrent effusions. This article presents a case of early, extensive periprosthetic osteolysis around a total knee arthroplasty associated with wear debris from retained fragments of a Gore-Tex (WL Gore and associates, Inc, Flagstaff, Ariz) (polytetrafluoroethylene) anterior cruciate ligament graft.     

Sex-related outcome differences after implantation of low-contact-stress mobile-bearing total knee arthroplasty

Purpose

The aim of the study was to investigate outcome differences between female and male patients after implantation of low-contact-stress (LCS) mobile-bearing total knee prostheses at a minimum follow-up of five years with respect to clinical and radiological parameters.

Methods

We retrospectively analysed 128 prostheses in 126 patients (90 women and 34 men) using our hospital database. Data was extracted with respect to range of motion (ROM), the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, the Knee Society Score (KSS) and radiolucent lines on conventional X-rays.

Results

At follow-up, we observed no significant differences between female and male patients after LCS total knee prostheses. Benefit after implantation of LCS total knee prostheses after five years of minimum follow-up was not significantly different between female and male patients in terms of clinical outcome or radiolucent lines.

Conclusions

We found no factors in favour of gender-specific total knee prostheses.     

Fracture of the femoral component associated with polyethylene wear and osteolysis after total knee arthroplasty

Fracture of the femoral component associated with polyethylene wear and osteolysis after total knee arthroplasty (TKA) has not been well reported before. A 63-year-old man with osteoarthritis of the right knee underwent TKA with a New Jersey LCS Knee, with cementing on the tibia and patella but not on the femoral component. After 42 months, in addition to wearing of polyethylene of the tibia and patella, severe osteonecrosis of the medial femoral condyle was noted. Osteonecrosis caused loss of osseous support of the medial flange of the femoral component, and the bone ingrowth of the central and lateral flange to the distal femur was so good that it overcame the yield stress of the metal of the femoral component and caused fracture of the femoral component. The osteolytic area was filled with autogenous iliac bone, and a new femoral component was inserted and cemented. The patient's condition became satisfactory with relief of pain. Although uncommon, fracture of the femoral component does occur associated with polyethylene wear and osteolysis.     

Femoral component loosening after total hip arthroplasty.

To determine the long-term durability of total hip arthroplasty and to identify factors responsible for femoral component loosening, 106 total hip arthroplasties were reviewed in patients with a minimum postoperative period of 3 years. Seventy-four had Charnley-Müller prostheses and 32 had Charnley prostheses. Femoral component loosening occurred in 16 of 106 hips. Not all loose components were symptomatic. The femoral component at risk was the femoral Charnley-Müller type that had been inserted in varus position in a functioning active heavy patient who previously had had a femoral head prosthesis.     

Changes in the three-dimensional load-bearing axis after mobile-bearing total knee arthroplasty

Background

The purpose of this study was to assess changes in the three-dimensional (3D) load-bearing mechanical axis (LBMA) preoperatively and at 3 weeks and more than 1-year follow-up after total knee arthroplasty (TKA), and effects of the degree of constraint in the anteroposterior (AP) direction because of the retention of the posterior cruciate ligament (PCL) and the implant design on the changes in LBMA.

Methods

We evaluated 157 knees from 131 patients, including 79 knees that received meniscal-bearing-type (PCL-retaining) and 78 knees that received rotating-platform-type (PCL-substituting) prostheses. Quantitative 3D computed tomography was used to assess changes in the location of the pre- and postoperative LBMA at the tibial plateau level.

Results

Changes in the 3D axis were mainly found from medial to lateral and posterior to anterior in both implant designs with no significant differences. Change in the mediolateral (ML) direction was improved soon after TKA, but change in the AP direction improved more gradually over time. The different constraints in the AP direction because of the retention of the PCL and different implant designs did not affect the changes in the LBMA.

Conclusions

The LBMA in the AP direction more than 1 year postoperatively, as well as the LBMA in the ML direction at 3 weeks, appears to shift toward the location found in normal knees after TKA, regardless of the type of prosthetic constraint. These changes may be an important factor that influences the periarticular knee bone mineral density which load bearing may be related to.

Level of evidence

Level II, Prognostic study.

     

Modular, mobile-bearing hinge total knee arthroplasty.

Early reports of hinge total knee arthroplasty showed high rates of complications and implant failure. Third-generation modular, mobile-bearing, hinge knee arthroplasty systems have evolved to decrease the deleterious stresses that contributed to the failures of earlier designs. The combined series of Barrack et al and Jones et al documents midterm results using the S-ROM Hinge Knee System for patients with significant soft and hard tissue deficiencies not suitable for standard, less constrained, revision knee systems. The combined series included 30 knees with a mean followup of 49 months. Knee Society clinical scores improved from 52 to 134 points. There were no mechanical failures of the implants. The knee system used provides press-fit diaphyseal stems and metaphyseal filling and loading sleeves, all of which showed apposition and positive remodeling of bone at followup radiographic analysis. The excellent midterm results of this modular, mobile-bearing, linked knee system suggest the orthopaedic surgeon can display increasing confidence in the selection of such a knee system when confronted with catastrophic, salvage knee arthroplasty.     

Alignment changes due to incomplete component seating in total knee arthroplasty

Mechanical axis restoration remains a primary goal of total knee arthroplasty. Incomplete asymmetrical component seating, through intended or unintended alterations in surgical technique, changes the component alignment and, thus, the overall mechanical axis. Using a trigonometric analysis, it was determined that incomplete seating of 1 to 5 mm can alter the coronal alignment by 0.7° to 4.9°, depending on the amount of asymmetry as well as the size of the femoral or tibial component. This analysis quantifies the degree of changes surgeons should expect when incomplete component seating is encountered intraoperatively.     

Successful biologic fixation with mobile-bearing total knee arthroplasty

A popular rotating-platform total knee implanted with a cementless technique was studied to determine long-term durability of fixation. A total of 70 knees in 59 patients (34 men, 25 women) was included. The primary indication for surgery was osteoarthritis (80%). A total of 23 of the 70 knees was available at final follow-up (average, 16 years). Clinical and radiographic data suggested durable fixation. In addition, the entire cohort of patients was studied with Kaplan-Meier statistics. Survivorship with respect to aseptic loosening was 97% at 17 years. Only 1 of the 70 knees was revised for aseptic loosening. However, overall survivorship was 76%, which was primarily because of failures of the metal-backed rotating patella.