JBJS | Cemented Rotating-Platform Total Knee Replacement : A Nine to Twelve-Year Follow-up Study*

The Journal of Bone & Joint Surgery, Volume 82, Issue 5

Articles | May 01, 2000

Cemented Rotating-Platform Total Knee Replacement : A Nine to Twelve-Year Follow-up Study*

John J. Callaghan, M.D.†; Matt W. Squire, M.D.†; Devon D. Goetz, M.D.‡; Patrick M. Sullivan, M.D.‡; Richard C. Johnston, M.D.†

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Investigation performed at Iowa Methodist Hospital, Des Moines, and University of Iowa College of Medicine, Iowa City, Iowa
*One or more of the authors has received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this article. In addition, benefits have been or will be directed to a research fund, foundation, educational institution, or other nonprofit organization with which one or more of the authors is associated. No funds were received in support of this study.
†Department of Orthopaedic Surgery, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, Iowa 52242-1088. Please address requests for reprints to J. J. Callaghan. E-mail address for J. J. Callaghan: john-callaghan@uiowa.edu.
‡Des Moines Orthopaedics, 6001 Westown Parkway, West Des Moines, Iowa 50266-7702.

The Journal of Bone & Joint Surgery. 2000; 82:705-705

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Abstract

Background: Although the LCS (low contact stress) rotating-platform mobile-bearing knee replacement has been used extensively, there have been few intermediate or long-term clinical and radiographic follow-up studies evaluating the device. The purpose of this study was to report the nine to twelve-year results of a consecutive series of patients who had a primary total knee replacement performed with this device.

Methods: Between November 1985 and November 1988, the senior author (R. C. J.) performed 119 consecutive total knee arthroplasties in eighty-six patients with LCS rotating-platform femoral and tibial components and a Townley all-polyethylene dome patellar component. All components were fixed with cement. The average age of the patients at the time of the operation was seventy years (range, thirty-seven to eighty-eight years). Fifty-two patients (seventy-six knees) were female, and thirty-four patients (forty-three knees) were male. The patients were evaluated with clinical knee ratings and radiographic analysis nine to twelve years following the knee replacement.

Results: At the time of the nine to twelve-year follow-up, sixty-four patients (eighty-six knees) were alive, eighteen patients (twenty-eight knees) had died, and four patients (five knees) had been lost to follow-up. Of the 114 knees in the eighty-two patients for whom the final outcome was known, none required a reoperation and none had a dislocation of the mobile-bearing prosthesis. For the forty-five patients (sixty-six knees) who returned for final clinical and radiographic follow-up examinations at nine to twelve years, the average clinical and functional Knee Society ratings were 30 points (range, 2 to 70 points) and 44 points (range, 0 to 80 points) preoperatively and 90 points (range, 63 to 102 points) and 75 points (range, 30 to 100 points) at the final follow-up evaluation. The average Hospital for Special Surgery knee rating was 57 points (range, 28 to 80 points) preoperatively and 84 points (range, 59 to 97 points) at the final follow-up evaluation. The average active range of knee flexion was from 0 degrees (range, 0 to 10 degrees) to 102 degrees (range, 15 to 120 degrees) at the final follow-up evaluation. Seven of the sixty-six knees were painful anteriorly. There was no periprosthetic osteolysis and no evidence of loosening on follow-up radiographs.

Conclusions: After nine to twelve years of follow-up, the cemented LCS rotating-platform knee replacement was found to be performing well, with durable clinical and radiographic results.

Figures in this Article

Introduction

Introduction | Materials and Methods | Results | Discussion | References

Mobile-bearing total knee prostheses were designed to reduce polyethylene contact stresses, thus potentially decreasing the fatigue wear associated with polyethylene failure in knee arthroplasty^1,9,18-20,23. However, we know of few reports on the intermediate or long-term results associated with these devices^6,8,19,39. The poor results obtained when the senior author (R. C. J.) employed a constrained rotating hinged device for primary total knee arthroplasty prompted him to start using an LCS (low contact stress) cemented rotating-platform design (LCS rotating platform; DePuy, Warsaw, Indiana) in November 1985. The purpose of the present study was to evaluate the nine to twelve-year results of a single surgeon's experience with the use of this design.

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Fig. 1:: Photograph of the LCS rotating-platform femoral and tibial components and the Townley dome single-post patellar component (DePuy).

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Fig. 2-A::
Figs. 2-A through 2-G: Radiographs of the left knee of a woman with severely symptomatic osteoarthritis who was operated on at the age of sixty-three years. The clinical and functional Knee Society ratings¹⁶ were 40 and 60 points preoperatively and 95 and 100 points at the final follow-up evaluation. The Hospital for Special Surgery knee ratings²¹ were 60 points preoperatively and 95 points at the final follow-up evaluation. The patient could walk without support, had no pain, and could flex the knee from 0 to 120 degrees at the final follow-up evaluation.
Fig. 2-A: Preoperative anteroposterior radiograph.

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Fig. 2-B:: Preoperative lateral radiograph.

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Fig. 2-C:: Anteroposterior and lateral radiographs made immediately postoperatively.

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Fig. 2-D::

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Fig. 2-E:: Figs. 2-E, 2-F, and 2-G: Anteroposterior, lateral, and Merchant-view radiographs made at the final follow-up evaluation, nine years postoperatively, showing maintenance of the bone-cement interface.

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Fig. 2-F::

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Fig. 2-G::

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TABLE I: Radiolucency at Bone-Cement Interfaces in the Sixty-six Knees Followed for Nine to Twelve Years

*The results are given as the number of knees.

Zone	Location	Radiolucency*
Femoral component (lateral radiograph)
I	Anterior flange	12
II	Anterior chamfer	8
III	Posterior chamfer	6
IV	Posterior flange	8
V	Anterior to peg	3
VI	Around peg	0
VII	Posterior to peg	0
Tibial component (anterior radiograph)
I	Medial	7
II	Medial to peg	0
III	Lateral to peg	0
IV	Lateral	3
V	Medial to post	0
VI	Distal to post	0
VII	Lateral to post	0
Patellar component (Merchant-view radiograph²⁶)
I	Medial	4
II	Lateral	7
III	Peg	0

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TABLE I: Radiolucency at Bone-Cement Interfaces in the Sixty-six Knees Followed for Nine to Twelve Years

*The results are given as the number of knees.

Zone	Location	Radiolucency*
Femoral component (lateral radiograph)
I	Anterior flange	12
II	Anterior chamfer	8
III	Posterior chamfer	6
IV	Posterior flange	8
V	Anterior to peg	3
VI	Around peg	0
VII	Posterior to peg	0
Tibial component (anterior radiograph)
I	Medial	7
II	Medial to peg	0
III	Lateral to peg	0
IV	Lateral	3
V	Medial to post	0
VI	Distal to post	0
VII	Lateral to post	0
Patellar component (Merchant-view radiograph²⁶)
I	Medial	4
II	Lateral	7
III	Peg	0

Materials and Methods

Introduction | Materials and Methods | Results | Discussion | References

Between November 1985 and November 1988, the senior author performed 119 consecutive primary total knee arthroplasties with the LCS rotating platform in eighty-six patients. Fifty-two patients (seventy-six knees) were female, and thirty-four patients (forty-three knees) were male. The average age of the patients at the time of the operation was seventy years (range, thirty-seven to eighty-eight years). The diagnosis was osteoarthritis in 105 knees, rheumatoid arthritis in twelve knees, and post-traumatic arthritis in two knees. A previous operation had been performed in nine knees. These operations included three valgus tibial osteotomies, two meniscectomies, one arthrotomy, one arthroscopic procedure, one distal femoral osteotomy, and one sequestrectomy. During this time, the senior author used no other designs for primary total knee arthroplasty; however, if a patient had good range of motion and arthritis that was limited to only one of the compartments of the knee (medial or lateral), with or without mild-to-moderate arthritis of the patellofemoral compartment, a unicondylar replacement was performed (seventy-five knees). Hence, this series was consecutive but selective, with the selectivity weighted toward the knees with the worst disease that were seen by the senior author during the interval studied.

The procedure included a midline skin incision with a medial parapatellar quadriceps-splitting incision into the joint. The posterior and anterior cruciate ligaments were excised in all patients. Ligamentous balancing was performed, and an attempt was made to resect enough tibial bone to achieve a surface that was perpendicular to the shaft of the tibia in the coronal plane with minimal anterior or posterior slope in the sagittal plane. The distal part of the femur was resected with an attempt to achieve femoral-tibial alignment of 5 to 7 degrees in the coronal plane. The patellar resection was performed with an attempt to remove a volume of bone that was equal to or slightly more than that of the component to be implanted. In performing the femoral and tibial resection, care was taken to balance the so-called flexion and extension gaps and to alleviate any flexion contracture. The LCS rotating-platform femoral and tibial components were used with a Townley all-polyethylene dome center-post patellar component (DePuy) (Fig. 1). All components were fixed with cement. Although others have used this device without cement, the senior author used cement because of success with cement in the hip and because of the durable results reported with cemented total condylar knee replacement at the time of the index procedure.

Postoperatively, all patients began walking with crutches or a walker and began working on active and passive range-of-motion exercises on the day after the operation. Continuous-passive-motion machines were not used during the time interval that was studied. The patients used the crutches or a walker, with full weight-bearing, for six to eight weeks and used a cane for six weeks.

Preoperative and follow-up ratings according to the systems of the Knee Society¹⁶ and The Hospital for Special Surgery²¹ and a questionnaire designed to assess anterior knee pain² were obtained for the living patients who were examined clinically and radiographically (sixty-six knees). All of these patients and the living patients who were telephoned but did not return for examination (twenty knees) were asked the clinical questions on the rating sheets and the questionnaire by a junior author (M. W. S.).

Early postoperative and final follow-up standing anteroposterior, lateral, and Merchant-view radiographs²⁶ were evaluated, according to the method of The Knee Society¹⁶, for radiolucency at the bone-cement interfaces around the three components, any change in the position of the components, femoral-tibial alignment in the coronal plane, and osteolysis. The range of flexion recorded at the final follow-up evaluation was the active flexion of the knee.

Results

Introduction | Materials and Methods | Results | Discussion | References

At nine to twelve years following the procedure, sixty-four patients (eighty-six knees) were alive, eighteen patients (twenty-eight knees) had died, and four patients (five knees) had been lost to follow-up. Nineteen of the living patients (twenty knees) would not return for the follow-up evaluation performed for this study because they were infirm or because they were doing well and did not believe that they needed an evaluation. None of these patients and none of the patients who had died required a revision of the prosthesis. The average duration of radiographic follow-up for this group was 5.2 years (range, 0.1 to 8.1 years), and none of these knees had radiographic evidence of loosening or osteolysis. Eight patients (ten knees) did not have a radiograph made within two years because they died before that time or because they failed to return for a scheduled two-year radiographic examination. Forty-five (70 percent) of the living patients (sixty-six [77 percent] of the knees in living patients) were followed clinically and radiographically for at least nine years (average, 9.7 years; range, nine to twelve years) after the operation, and the remainder of this report will focus on these patients. The average age at the time of the operation was sixty-seven years (range, thirty-nine to eighty years), and the average age at the time of follow-up was seventy-seven years (range, fifty to eighty-nine years).

The preoperative femoral-tibial angle in the coronal plane averaged 4 degrees of valgus (range, 17 degrees of valgus to 20 degrees of varus), and that at the final follow-up evaluation averaged 5 degrees of valgus (range, 10 degrees of valgus to 2 degrees of varus). The average clinical and functional Knee Society ratings were 30 points (range, 2 to 70 points) and 44 points (range, 0 to 80 points), respectively, preoperatively and 90 points (range, 63 to 102 points) and 75 points (range, 30 to 100 points), respectively, at the final follow-up evaluation. The Hospital for Special Surgery knee ratings preoperatively and at the time of final follow-up averaged 57 points (range, 28 to 80 points) and 84 points (range, 59 to 97 points), respectively. The average active range of flexion was from 10 degrees (range, -15 to 40 degrees) to 110 degrees (range, 45 to 140 degrees) preoperatively and from 0 degrees (range, 0 to 10 degrees) to 102 degrees (range, 15 to 120 degrees) at the final follow-up evaluation. At the final follow-up evaluation, forty-five knees were not painful, fifteen were mildly painful, five were moderately painful, and one was severely painful. One patient could perform strenuous labor, seven patients could perform moderately strenuous labor, twenty patients could perform light labor, twelve patients were semi-sedentary, and five patients were sedentary. Twenty-six patients could walk an unlimited distance, eight patients could walk for thirty to sixty minutes, five patients could walk for ten to thirty minutes, and six patients could walk for less than ten minutes. Twenty-six patients required no support to walk, ten patients required part-time support, and nine patients required full-time support. During the nine to twelve-year follow-up period, no knee was revised and there were no dislocations of the mobile bearing polyethylene. When the patients were specifically questioned about anterior knee pain, the responses indicated that fifty-nine knees were not painful, four were occasionally painful, and three were moderately painful with activity. The anterior pain was associated with getting up from a chair in all seven knees; with getting out of an automobile in six knees; and with negotiating steps, walking, and rest in two knees each. Forty-four patients (sixty-five knees) were satisfied with the result of the operation. The remaining patient was dissatisfied because of poor range of flexion (0 to 15 degrees).

Radiographs of the sixty-six knees showed little radiolucency at the bone-cement interfaces around the components (Table I). No knee had any circumferential radiolucency around any of the three components. In fact, no knee had radiolucency in more than three zones around the tibial or femoral component or in more than one zone around the patellar component. No knee had any obvious asymmetrical wear of the tibial or patellar polyethylene (Fig. 2-A,Fig. 2-B,Fig. 2-C,Fig. 2-D,Fig. 2-E,Fig. 2-F, and Fig. 2-G).

Discussion

Introduction | Materials and Methods | Results | Discussion | References

Total knee arthroplasties with well designed fixed-bearing prostheses have provided durable long-term fixation, with prosthetic survival rates of 95 to 97 percent reported at ten to fifteen years^{10,11,13,17,24,29,30,32,33,35-40,42}. However, some fixed-bearing designs have had problems with polyethylene wear and fixation failure^{11,14,25,35,43-46}. In the middle to late 1970s, mobile-bearing knee prostheses were designed to reduce contact stresses in the polyethylene and to potentially decrease wear^{1,3,5,7,9,12,19,20,27}. In addition, it was postulated that the mobile bearing would minimize bone-prosthesis stresses at the tibial surface^5,19. However, few results and no long-term results that we are aware of have been reported with the LCS rotating-platform design, even though it has been used for fifteen years^6,8,34,39. In the designing surgeon's report of his first twelve years of experience with this rotating-platform prosthesis, survivorship analyses with component revision as the end point revealed that 97 pecent of forty-three cemented components and 98 percent of sixty-five cementless components had survived at ten years; no confidence intervals were reported⁸. In the only other report of which we are aware that included a large number of patients managed with this prosthesis, Sorrells demonstrated a ten-year survival rate (and 95 percent confidence interval) of 94 ± 4 percent in a series of 665 knees followed for one to thirteen years³⁹. Neither study included radiographic follow-up or the number of knees with a ten-year follow-up. The present study, in which detailed clinical and radiographic evaluation was performed at nine to twelve years, demonstrated the safety and efficacy of this rotating-platform mobile-bearing device, which has been used extensively in clinical practice.

The senior author's poor initial experience with total knee arthroplasty with a constrained design led him to start using, in 1985, a rotating-platform mobile-bearing design for all primary procedures. However, unlike many proponents of this mobile-bearing design, he fixed all components with cement and used an all-polyethylene patellar component instead of the mobile-bearing metal-backed component designed for the prosthesis⁶. The authors performed the present study to evaluate the long-term durability of the LCS rotating-platform design with cement fixation and to determine whether any detrimental effects (such as dislocation of bearings, backside wear of the mobile bearing contributing to particulate debris, and periprosthetic osteolysis) occurred over time.

The results from the present study confirm that a well designed rotating-platform type of mobile-bearing total knee replacement can perform well over the long term. No components were revised because of failure of fixation or polyethylene wear, and there were no patellar problems, such as patellar fracture, subluxation, or dislocation, that required a reoperation. The rotating-platform mobile-bearing tibial component may help the patellar component to center itself in knees with 5 to 10 degrees of rotational mismatch between the tibial and femoral components⁴¹. This may partially account for the absence of patellar fractures as well as loosening, wear, subluxation, or dislocation of the patellar component. Another unique feature of this prosthesis is the anterior-proximal to posterior-distal (15-degree) resection of the distal part of the femur, which allowed the designers to make the patellofemoral groove deeper and longer than that in many of the femoral component designs of the late 1970s and early 1980s. This feature may also account for the low prevalence of patellar problems and anterior knee pain in the present study, in which only seven of sixty-six knees were painful anteriorly and only three of the seven had more than occasional anterior pain. The present study cannot be used to document the safety and efficacy of this device when used without cement or with a rotating patella, as the senior author always used cement and a cemented dome patellar component because of his concerns about the thin polyethylene of metal-backed patellar components.

Potential problems associated with this design that may not be encountered with fixed-bearing designs include dislocation of the polyethylene platform and debris from backside polyethylene wear^4,8. However, no dislocations were noted in this study; care was taken to balance the flexion and extension gap precisely. There was little radiolucency at the bone-cement interfaces around the components and no radiographic evidence of periprosthetic osteolysis or asymmetrical accelerated polyethylene wear, although early detection of either osteolysis or wear in the total knee arthroplasty construct can be difficult on plain radiographs. Authors of studies of fixed-bearing posterior-cruciate-substituting designs have reported occasional revisions because the substituting post of the tibial component has dislocated from the femoral component box^22,31. Also, some authors have reported concern about backside wear of modular fixed-bearing tibial components because of motion between the metal modular tibial tray and the polyethylene insert^15,28,43. Inherent in a rotating platform or any other mobile-bearing design is an attempt to minimize backside wear with use of a hard, polished, chromium-cobalt tibial tray, which better accommodates motion.

In conclusion, the present study shows the durability of the LCS rotating-platform mobile-bearing total knee replacement after nine to twelve years of follow-up. Although platform dislocation and periprosthetic osteolysis from backside wear of the bearing surface are potential problems, they were not noted in this series. Avoidance of a loose flexion gap may account for the absence of platform dislocation but also for the average active range of flexion of only 102 degrees. Rotating patellar components have been used with this design; however, only cemented all-polyethylene components were used in the present study without complications and with minimal occurrence of patellofemoral pain. This rotating-platform design appears to be safe as well as efficacious in an older population.

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Fig. 1:: Photograph of the LCS rotating-platform femoral and tibial components and the Townley dome single-post patellar component (DePuy).

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Fig. 2-B:: Preoperative lateral radiograph.

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Fig. 2-C:: Anteroposterior and lateral radiographs made immediately postoperatively.

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Fig. 2-D::

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Fig. 2-F::

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Fig. 2-G::

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TABLE I: Radiolucency at Bone-Cement Interfaces in the Sixty-six Knees Followed for Nine to Twelve Years

*The results are given as the number of knees.

Zone	Location	Radiolucency*
Femoral component (lateral radiograph)
I	Anterior flange	12
II	Anterior chamfer	8
III	Posterior chamfer	6
IV	Posterior flange	8
V	Anterior to peg	3
VI	Around peg	0
VII	Posterior to peg	0
Tibial component (anterior radiograph)
I	Medial	7
II	Medial to peg	0
III	Lateral to peg	0
IV	Lateral	3
V	Medial to post	0
VI	Distal to post	0
VII	Lateral to post	0
Patellar component (Merchant-view radiograph²⁶)
I	Medial	4
II	Lateral	7
III	Peg	0

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TABLE I: Radiolucency at Bone-Cement Interfaces in the Sixty-six Knees Followed for Nine to Twelve Years

*The results are given as the number of knees.

Zone	Location	Radiolucency*
Femoral component (lateral radiograph)
I	Anterior flange	12
II	Anterior chamfer	8
III	Posterior chamfer	6
IV	Posterior flange	8
V	Anterior to peg	3
VI	Around peg	0
VII	Posterior to peg	0
Tibial component (anterior radiograph)
I	Medial	7
II	Medial to peg	0
III	Lateral to peg	0
IV	Lateral	3
V	Medial to post	0
VI	Distal to post	0
VII	Lateral to post	0
Patellar component (Merchant-view radiograph²⁶)
I	Medial	4
II	Lateral	7
III	Peg	0