Dislocation/subluxation of meniscal bearing elements after New Jersey low-contact stress total knee arthroplasty

From October 1985 to April 1986, 43 consecutive New Jersey low-contact stress total knee arthroplasties (TKAs) were performed for degenerative arthritis of the knee. At the one-year follow-up examination, 91% of the patients had good to excellent results based on the Hospital for Special Surgery scoring system. Four patients, however, sustained dislocation/subluxation of the meniscal bearing elements. Three of these occurred within 13 days postoperatively, and one patient sustained a dislocation at six months postoperatively. These four patients were treated with revision TKA. Despite following the precise technique in performance of this procedure, a 9.3% incidence of dislocation/subluxation of the meniscal bearing elements occurred.     

Patellar instability after total knee arthroplasty

Twenty-five knees with symptomatic lateral patellar instability after total knee arthroplasty (TKA) were treated by operative realignment. Causes of instability include errors in surgical technique, quadriceps imbalance, and trauma. Fourteen knees had proximal realignment, nine had combined proximal and distal realignment, and two had component revision. At an average follow-up period of 50 months, 20 knees had normal patellar tracking and five had recurrent instability. Two patellar tendon ruptures occurred after combined realignment. Proximal realignment alone, in the absence of component malposition, is recommended for the management of patellar instability. Component malposition should be corrected by component revision. Combined proximal and distal realignment procedures are recommended only with great caution because of the predisposition to serious complications such as patellar tendon rupture.     

Patellar complications after total knee arthroplasty

Summary. One hundred total knee arthroplasties implanted between 1989 and 1993 in 70 women and 30 men (average age 67.4 years) have been retrospectively reviewed. Six late patellar complications occurred: two fractures, two subluxations, one dislocation and one loosening. Four had a further operation. The patient’s age, type of implant, lateral patellar release, thickness of the implant and the final range of movement were studied. Complications have been more common in men (8.7%) than women (5.2%) with a statistically significant difference (p <0.05). This may be because men make a greater functional demand on their arthroplasties. No other factors were relevant.

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Résumé. Nous avons analysé 100 arthroplasties totales de genou implantées entre 1989 et 1993 à des patients avec un age moyen de 67,4 ans, dont soixante-sept femmes et trente-trois hommes. Nous avons trouvé six complications patellaires tardives dont la classification est la suivante: deux fractures de rotule, une mobilisation par déterioration des pivots d’ancrage, deux subluxations et une luxation. Quatre de ces malades ont été réopérés et les deux autres ont suivi un traitement par réeducation. Nous avons étudié les possibles facteurs qui favorisent ces complications. Ni l’age, ni le genre d’implant, ni la libération du rétinaculum patellaire, ni la grosseur de la rotule, ni l’arc de mobilité finale n’ont exercé une influence sur l’apparition de complications patellaires. Par contre celles-ci ont été plus fréquentes parmi les hommes (8.7%) que parmi les femmes (5,2%) avec une différence statistiquement significative (p <0.05). Il se peut que cela soit d? aux plus grandes demandes que les hommes exigent de l’arthroplastie.

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Accepted: 18 May 1995     

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.     

Tibiofemoral contact stress after total knee arthroplasty: Comparison of fixed and mobile-bearing inlay designs

We measured tibiofemoral contact stresses and the load-bearing contact area of fixed and mobile-bearing inlay knee prostheses under dynamic loading conditions. An electronic resistive pressuremeasuring sensor was used to detect contact stresses and contact area in five cadaver knees. Stresses were measured with the tibial component aligned normally, as well as in internally- and externally-rotated positions. The average peak contact stresses measured on the fixed inlay were greater (medial 21 MPa and lateral 21 MPa) than those on the mobile inlay (medial/lateral 7.7/5.3 MPa, p = 0.04). Although the average peak contact stresses of the fixed standard inlay greatly exceeded the contact stresses of the other two inlay designs in each malrotated position tested, no statistically significant differences were seen. The data suggest that the ability of the inlay to translate on the tibial baseplate permits the inlay to align itself on the femoral component so that the contact surface area is maximized and contact stresses are reduced.     

Patellar height and patellofemoral congruence

Summary The patellar tendon/patella ratio and the patellofemoral congruence was estimated in 118 knees. There was a statistically significant positive correlation between the two measurements, high-riding patella occurring with patellofemoral incongruence.

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Zusammenfassung Das Patellarsehnen/Patella-Verhältnis und die Konkruenz des Femoropatellargelenkes wurden in 118 Knien bestimmt. Es zeigte sich eine statistisch zu sichernde Korrelation zwischen Patellahochstand und Inkonkruenz im Femoropatellargelenk.

     

Tibiofemoral contact stress after total knee arthroplasty: comparison of fixed and mobile-bearing inlay designs

We measured tibiofemoral contact stresses and the load-bearing contact area of fixed and mobile-bearing inlay knee prostheses under dynamic loading conditions. An electronic resistive pressure-measuring sensor was used to detect contact stresses and contact area in five cadaver knees. Stresses were measured with the tibial component aligned normally, as well as in internally- and externally-rotated positions. The average peak contact stresses measured on the fixed inlay were greater (medial 21 MPa and lateral 21 MPa) than those on the mobile inlay (medial/lateral 7.7/5.3 MPa, p = 0.04). Although the average peak contact stresses of the fixed standard inlay greatly exceeded the contact stresses of the other two inlay designs in each malrotated position tested, no statistically significant differences were seen. The data suggest that the ability of the inlay to translate on the tibial baseplate permits the inlay to align itself on the femoral component so that the contact surface area is maximized and contact stresses are reduced.     

Patellar tendon rupture after total knee arthroplasty

Between 1973 and 1985, 18 knees in 17 patients were treated for rupture of the patellar tendon after total knee arthroplasty (TKA), accounting for 0.17% of the TKAs performed at the authors' institution during the same interval. Follow-up study was from two and one-half years to four years. Four ruptures occurred in patients who had had a distal patellar realignment procedure, and one occurred after knee manipulation. Only two xenograft reconstructions and two of four staple fixation procedures were successful. After treatment of the patellar tendon rupture, four knees developed deep infection. Avoidance of this complication seems paramount because the results of treatment are discouraging. Patients at high risk at the time of the initial TKA seem to be those with limited preoperative motion in whom surgical exposure is difficult.     

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.     

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.     

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.     

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.     

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.

     

Patellar clunk syndrome after posterior stabilized total knee arthroplasty

Two hundred thirty-six posterior stabilized total knee arthroplasties (TKAs) were performed consecutively. Twenty-seven patellar clunk syndromes were identified in 25 patients. Insall-Salvati ratio, position of joint line, postoperative patellar height, and anterior-posterior position of tibial tray were measured. It was found that postoperative low-lying patella (P<.001) and anterior placement of tibial tray (P=.011) was associated with patellar clunk syndrome. Thirteen patients had bilateral TKAs of the same prosthesis (5 bilateral AMK knees and 8 bilateral Insall Burstein knees) but unilateral patellar clunk syndrome. The nonclunk sides were used as control for comparison with the clunk sides. The congruency and tilting of the patellar button in the skyline view were documented. It was observed that the congruency of the patellar button was less satisfactory in the clunk side (P=.019).     

Osteolysis after unidirectional and multidirectional mobile-bearing total knee arthroplasty in young patients

We questioned whether a difference exists between multidirectional and unidirectional mobile-bearing total knee arthroplasties in terms of clinical results and the prevalence of polyethylene wear and periprosthetic osteolysis. We studied 62 patients who underwent simultaneous bilateral total knee arthroplasties, with a unidirectional prosthesis implanted in 1 knee and a multidirectional one in the other. Of the patients, 9 were men and 53 were women, with a mean age of 57.6 years (35-60 years). The minimum follow-up was 11 years (mean, 11.8 years; range, 11-13 years). Preoperative and postoperative knee and functional scores were not different between the 2 groups. No knee in either group had detectable tibial polyethylene liner wear or osteolysis on radiographs or on computed tomography scans. Two (3%) knees in each group were revised.     

Alternatives to patellofemoral arthroplasty

When surgical intervention becomes necessary in the treatment of a patient with isolated patellofemoral arthritis, the primary alternatives to arthroplasty are tubercle anteriorization or anteromedialization, patellectomy, and cartilage transplantation. The relative merits of these options should be discussed with each patient. There must be healthy central and proximal patella cartilage in order to expect a good result from a tibial tubercle anteriorization. Patellectomy leaves a well-defined functional deficit and therefore is better to avoid whenever possible, although relief of pain after patellectomy can be substantial. Cartilage resurfacing of the trochlea is an attractive alternative. Combining a resurfacing procedure with decompression of the joint by anteromedial or anterior tibial tubercle transfer should help protect the resurfaced area. Replacement of the patellofemoral joint, properly done on a well aligned extensor mechanism, is most attractive when both patella and trochlea are deficient or when an alternative procedure is unacceptable.     

Femoral component fracture due to osteolysis after cemented mobile-bearing total knee arthroplasty

A 58-year-old man with osteoarthritis in the left knee underwent a total knee arthroplasty with a New Jersey anterior-posterior gliding low contact stress mobile-bearing implant. All femoral, tibial, and patellar components were implanted with bone cement. Pain developed at 43 months postsurgery, and plain radiography revealed a vertical crack in the femoral component and osteolysis at the medial femoral condyle. The femoral and tibial components were revised, and the bone defect at the medial femoral condyle was reconstructed using an allogeneic strut bone graft. Microscope examination identified polyethylene particles with foreign body granulomatous reaction, and scanning electron microscopy revealed fatigue failure of the femoral component. Osteolysis due to polyethylene particles can lead to fracture of the femoral component after cemented anterior-posterior gliding low contact stress mobile-bearing total knee arthroplasty.