Orthopedics

Feature Article 

Columbus Navigated TKA System: Clinical and Radiological Results at a Minimum of 5 Years With Survivorship Analysis

Sam Hakki, MD; Khaled J. Saleh, MD; Anish G. Potty, MD; Victor Bilotta, MD; Daniel Oliveira, MD

Abstract

The major factors that determine a favorable long-term clinical and functional outcome after conventional total knee arthroplasty (TKA) include correct implant positioning and restoration of the mechanical axis with soft tissue balancing to reduce aseptic failure; hence, the need for further developmental strategies that improve the accuracy and reproducibility of the surgical technique remains paramount for contemporary navigation research. Not all navigation systems are the same. The literature published thus far on mid-term results of navigated TKA relies on software that has no step-by-step soft tissue balancing with the tibia-first technique. The results are equivalent to those of conventional TKA.

Therefore, the current authors conducted a minimum 5-year follow-up of a soft tissue–based navigated TKA system with the goal of soft tissue balancing. They analyzed intraoperative alignment and range of motion measurements, functional outcomes, radiographic assessment, and survival rates of high-flexion, high-conformity unresurfaced patella TKAs. The results at 5 years revealed a component revision rate of 0% compared with other nonnavigated TKAs (2.8% revision rate). The authors achieved a well-balanced TKA with a 0°±2° mechanical axis and an improved range of motion from 95° preoperatively to 110° postoperatively.

The authors are from the Department of Orthopedic Surgery (SH, VB) and the Department of Radiology (DO), Department of Veterans Affairs, Bay Pines VA Healthcare System, Bay Pines, Florida; and the Department of Surgery (KJS, AGP), Southern Illinois University School of Medicine, Springfield, Illinois.

The authors have no relevant financial relationships to disclose.

This study is based upon work supported by the Department of Veterans Affairs, Veterans Health Administration, and Office of Research and Development. The contents of this article do not represent the views of the Department of Veterans Affairs of the US government.

Correspondence should be addressed to: Sam Hakki, MD, Department of Orthopedic Surgery, Department of Veterans Affairs, Bay Pines VA Healthcare System, 10000 Bay Pines Blvd, Bldg 100 3A-158, Bay Pines, FL 33744 (samhakki@gmail.com).

Abstract

The major factors that determine a favorable long-term clinical and functional outcome after conventional total knee arthroplasty (TKA) include correct implant positioning and restoration of the mechanical axis with soft tissue balancing to reduce aseptic failure; hence, the need for further developmental strategies that improve the accuracy and reproducibility of the surgical technique remains paramount for contemporary navigation research. Not all navigation systems are the same. The literature published thus far on mid-term results of navigated TKA relies on software that has no step-by-step soft tissue balancing with the tibia-first technique. The results are equivalent to those of conventional TKA.

Therefore, the current authors conducted a minimum 5-year follow-up of a soft tissue–based navigated TKA system with the goal of soft tissue balancing. They analyzed intraoperative alignment and range of motion measurements, functional outcomes, radiographic assessment, and survival rates of high-flexion, high-conformity unresurfaced patella TKAs. The results at 5 years revealed a component revision rate of 0% compared with other nonnavigated TKAs (2.8% revision rate). The authors achieved a well-balanced TKA with a 0°±2° mechanical axis and an improved range of motion from 95° preoperatively to 110° postoperatively.

The authors are from the Department of Orthopedic Surgery (SH, VB) and the Department of Radiology (DO), Department of Veterans Affairs, Bay Pines VA Healthcare System, Bay Pines, Florida; and the Department of Surgery (KJS, AGP), Southern Illinois University School of Medicine, Springfield, Illinois.

The authors have no relevant financial relationships to disclose.

This study is based upon work supported by the Department of Veterans Affairs, Veterans Health Administration, and Office of Research and Development. The contents of this article do not represent the views of the Department of Veterans Affairs of the US government.

Correspondence should be addressed to: Sam Hakki, MD, Department of Orthopedic Surgery, Department of Veterans Affairs, Bay Pines VA Healthcare System, 10000 Bay Pines Blvd, Bldg 100 3A-158, Bay Pines, FL 33744 (samhakki@gmail.com).

Since their first use by Leitner et al1 in 1997, image-free navigation systems have become the simplest and most widely used computer-assisted tools for total knee arthroplasty (TKA). Although significant geographical variations exist regionally and internationally in the use of this technology, the use of computer navigation allows more accurate and reproducible positioning and alignment of TKA components compared with conventional techniques.2–5 Despite this, contradictory evidence exists, with recent meta-analyses arriving at markedly different conclusions.6,7

Soft tissue balancing in the knee may be enhanced, resulting in improved functional outcome, and polyethylene wear rates may be reduced, resulting in increased prosthesis longevity. However plausible this seems, no convincing literature exists for the cause, implying that TKA component alignment may not be critical to a good short-term functional result.8–11 The major factors that determine a favorable long-term clinical and functional outcome after conventional TKA include correct implant positioning and restoration of the mechanical axis and soft tissue balancing to reduce aseptic failure12,13; hence, the need for further developmental strategies that improve the accuracy and reproducibility of the surgical technique remains paramount for contemporary navigation research. Aseptic implant failure remains a major reason for low survivorship after TKA. The 3 most common causes of aseptic loosening modalities14 are patella component or extensor mechanism failure15–17 compared with the femoral and tibial components,18–21 alignment failure18,22,23 in which the components are more than 4° off the mechanical axis, and soft tissue balancing failure in which alignment could be restored but the knee is unstable.22

The results of TKA prostheses that retain or excise the posterior cruciate ligament are available,24–26 as are polyethylene conformity studies that demonstrate how to improve TKA kinematics and minimize wear.27 However, little information has been published on the mid-term outcomes of high-flexion, higher-conformity28,29 polyethylene with patella-sparing designs.

The current authors undertook a minimum 5-year follow-up of such a TKA system (Columbus Navigated TKA; Aesculap AG, Tuttlingen, Germany) with the goal of analyzing the following data: (1) the intra-operative alignment and stability measurements of the TKA with navigation soft tissue balancing; (2) the functional outcomes, radiographic assessment, and survival rates of high-flexion, high-conformity unresurfaced patella TKA; and (3) the range of motion (ROM) of the high-flexion TKA system during the study period.

Materials and Methods

Between February 2004 and April 2005, the authors prospectively collected and retrospectively analyzed data on 100 consecutive patients who signed institutional review board consent for primary patella-sparing TKA. Four patients were lost to follow-up, leaving 96 patients for initial analysis (Table 1). During the 5-year study period, 17 patients died; the data from their final visit was recorded. Data for the remaining 79 patients were recorded at 4 and 6 months and 5 years postoperatively by independent observers. At 5 years postoperatively, mid-term TKA survival rate, clinical and radiological outcomes, and visual analog scale (VAS) pain and satisfaction scores were analyzed.

Demographic Data

Table 1: Demographic Data

Perioperative Data

Preoperative Data. Each patient underwent a medical history review, a physical examination with an emphasis on ROM, routine radiographs, and the validated functional outcome measures of the Knee Society score (KSS), Oxford Knee Index (OKI), and VAS pain score. Patients with unfavorable functional scores and no major medical history were included, as were those who were cleared by medical service as being mild to intermediate risk for surgery. Patients with a high anesthetic risk were excluded.

Intraoperative Data. Intraoperatively, data were collected by computer navigation, including ROM, alignment, stability, and knee gap balance.30 A detailed description of surgery was documented, including soft tissue release, the use of cement, implant size, and complications.

Inpatient Postoperative Care. Standard postoperative TKA protocol was implemented. Rehabilitation began the day after surgery and continued for 6 weeks. Data regarding serious complications were documented.

Clinical Outcome Measures

Knee Society Score. The KSS questionnaire comprises 2 components: clinical and functional component scores of the knee joint and patient function scores. A higher score represents a better outcome (maximum score=100).

Oxford Knee Score. The OKI 12-item questionnaire is subjective, and a lower score indicates a better outcome (highest score=48).31

OrthoPilot Computer Navigation System. The OrthoPilot computer navigation system (Aesculap AG) was used to implant the Columbus prosthesis. It relies on optical trackers attached to the femur, tibia, and ankle and measures the mechanical axis, ROM, gap measurement, and mediolateral deflection angles intraoperatively.

Visual Analog Scale Pain Score. The patient draws a line on a score sheet from 0, indicating no pain, to 10, indicating maximum pain. Patient satisfaction VAS score ranges from 0 to 100, where 85 to 100 represents an excellent result, 70 to 84 represents a good result, 60 to 69 represents a fair result, and less than 60 represents a poor result.32

Radiological Outcome. Anteroposterior, lateral, and Merchant view radiographs with standing views were obtained in accordance to the Knee Society total knee arthroplasty roentgenographic evaluation and scoring system (TKA-RESS).33 The radiologist (D.O.) who read the radiographs was blinded to clinical outcome. The research coordinators, who were not employees of the investigators, entered all data into a secure Veterans Affairs computer.

Implant Features and Design

The Columbus TKA implant was a fixed platform with a high congruence and a posterior 3° polyethylene slope (Figures 1A, B), and the highest load was posterior (Figure 1C). The implant was either standard conforming polyethylene for posterior cruciate ligament sparing or it had a greater curvature for posterior cruciate ligament sacrificing. The shape of the trochlear flange allowed for nonresurfacing of the patella. The tibiofemoral sizes were interchangeable in all sizes (Figure 2). The smallest tibia insert was size 10, which, as it sloped 3° posteriorly, thinned out to 7 mm minimum. Similarly, as size 12 sloped 3° posteriorly, it thinned out to a minimum of 9 mm, and so on for every size (Table 2).

Illustrations of the Columbus Navigated TKA (Aesculap AG, Tuttlingen, Germany). The length of the posterior femoral condyles is reduced with a small radius (45°). When combined with the 3° polyethylene posterior slope, the total intrinsic flexion ability of the implant is theoretically improved up to 90°+45°+3°=138°. Abbreviations: 8, thickness in mm of the posterior prosthesis (posterior-femoral cut), 9, thickness in mm of the distal prosthesis (distal-femoral cut); A, height of the posterior condyle; AP, anteroposterior; B, height of the anterior condyle; BOX, anteroposterior distance of the distal femoral bone; C, distance between the peg hole and the posterior condyle; ML, mediolateral; Z, length of the peg (A). Illustration of the Columbus Navigated TKA with a built-in posterior slope of 3° in a standard deep dish or ultracongruent version (B). Illustration showing that maximum load force (2.5× body weight) while heel strike is at 0° is at the posterior half of the polyethylene on an area of approximately 236 mm2 (red and blue). This is expected in a 3° posterior slope tibial polyethylene design. Abbreviations: L, lateral; M, medial (C). [Images reprinted with permission from Aesculap Implant Systems, LLC.]

Figure 1: Illustrations of the Columbus Navigated TKA (Aesculap AG, Tuttlingen, Germany). The length of the posterior femoral condyles is reduced with a small radius (45°). When combined with the 3° polyethylene posterior slope, the total intrinsic flexion ability of the implant is theoretically improved up to 90°+45°+3°=138°. Abbreviations: 8, thickness in mm of the posterior prosthesis (posterior-femoral cut), 9, thickness in mm of the distal prosthesis (distal-femoral cut); A, height of the posterior condyle; AP, anteroposterior; B, height of the anterior condyle; BOX, anteroposterior distance of the distal femoral bone; C, distance between the peg hole and the posterior condyle; ML, mediolateral; Z, length of the peg (A). Illustration of the Columbus Navigated TKA with a built-in posterior slope of 3° in a standard deep dish or ultracongruent version (B). Illustration showing that maximum load force (2.5× body weight) while heel strike is at 0° is at the posterior half of the polyethylene on an area of approximately 236 mm2 (red and blue). This is expected in a 3° posterior slope tibial polyethylene design. Abbreviations: L, lateral; M, medial (C). [Images reprinted with permission from Aesculap Implant Systems, LLC.]

Chart showing that femoral and tibial sizes were interchangeable. A size 5 femoral and size 3 tibial combination was most commonly used.

Figure 2: Chart showing that femoral and tibial sizes were interchangeable. A size 5 femoral and size 3 tibial combination was most commonly used.

Frequency of Size and Type of Polyethylene Used

Table 2: Frequency of Size and Type of Polyethylene Used

Surgical Technique

All patients underwent a subvastus approach with a tibia-first technique at a 0° slope. Computer navigation screw trackers were inserted in the medial side of the femur and tibia approximately 4 inches away from the joint. After gap balancing, the distal femoral level of resection and rotation could be determined by the navigation data. Trial components were then inserted, and the knee was put through ROM to finalize the tibia tray rotation and assess the mediolateral deflection angles in extension and flexion. The tibia was cemented first, followed by the femur. The osteophytes around the patella were trimmed, and the edges were bovied (Figure 3).

Merchant view radiograph of the right knee showing an unresurfaced patella (A). Intraoperative photograph showing the patella being bovied circumferentially (B). Intraoperative photograph showing the subvastus approach to the left knee with excellent tibiofemoral exposure. Note that the patella is displaced in the lateral gutter (C). Anteroposterior (D), lateral (E), and Merchant view (F) radiographs at 5-year follow-up.

Figure 3: Merchant view radiograph of the right knee showing an unresurfaced patella (A). Intraoperative photograph showing the patella being bovied circumferentially (B). Intraoperative photograph showing the subvastus approach to the left knee with excellent tibiofemoral exposure. Note that the patella is displaced in the lateral gutter (C). Anteroposterior (D), lateral (E), and Merchant view (F) radiographs at 5-year follow-up.

Results

Clinical

At index surgery, patients comprised 7 women and 93 men with an average age of 69.15 years. The higher proportion of men was due to the normal higher proportion of men among the veterans treated at the authors’ institution. Preoperative diagnosis was osteoarthritis in the majority of patients. Average body mass index (BMI) was 31.2 kg/m2 (Table 1). Average tourniquet time was 50.7 minutes (range, 28–62 minutes). Mean hospital stay was 3.7 days (range, 2–5 days). Preoperative deformity was defined as varus in 66% of patients and valgus in 27%, with an overall range of 22° varus to 18° valgus, with fixed flexion deformity of more than 10° in 45% of cases. The posterior cruciate ligament was retained in all cases, except for 11 knees, in which they were either partially or fully released.

Following the soft tissue–balanced TKA protocol,30 twelve percent of patients underwent collateral ligament release and 18% underwent posterior capsule release (medial side, lateral side, or both). Lateral retinacular release was performed in 2 patients with severe valgus deformity (Table 3). Intraoperative assessment of knee stability with the leg in extension revealed a mean varus and valgus deflection of 1.43° of the 180° mechanical axis (range, 2° varus to 2° valgus). Mean extension angle was −2.5°. Flexion improved from a mean of 94.68° to 125° intraoperatively. However, a mean loss of approximately 15° occurred at 5 years (Figure 4). The femoral component was cemented in 87 patients, all tibial trays were cemented, and all patellae were unresurfaced. Implanted polyethylene thickness was a minimum of 7 mm in 43% of patients, 9 mm in 30%, 11 mm in 18%, and 13 mm in 5%. Femoral and polyethylene insert sizes are shown in Figure 2 and Table 2.

Soft Tissue Release

Table 3: Soft Tissue Release

Graph showing range of motion (ROM). Note the decrease in mean range of motion from 125.44° intraoperatively (Intra-OP) to 110.35° at 5 years postoperatively (Post Op), and the noticeable improvement from the preoperative (Pre-OP) range of motion of 94.68°.

Figure 4: Graph showing range of motion (ROM). Note the decrease in mean range of motion from 125.44° intraoperatively (Intra-OP) to 110.35° at 5 years postoperatively (Post Op), and the noticeable improvement from the preoperative (Pre-OP) range of motion of 94.68°.

Mean KSS knee score improved from 45.46 points preoperatively to 89.85 points postoperatively. Mean KSS functional score improved from 44.38 points preoperatively to 81.79 points postoperatively (Figures 5, 6). OKI improved from 41.11 points preoperatively to 22.07 points postoperatively (Figure 7). Compared with the KSS, significant improvement in the OKI score was noted as early as 4 months, with little change after 6 months. Most patients were capable of doing household chores and were subjectively satisfied with the function of their artificial knee in the first 6 months postoperatively.

Graph showing mean Knee Society (KSS) knee score during 5 years of follow-up (FU). Note the significant improvement in the score between 6 months and 5 years (10 points), which emphasizes the importance of educating the patients to continue physical therapy beyond 6 months. Abbreviation: Preop, preoperative.

Figure 5: Graph showing mean Knee Society (KSS) knee score during 5 years of follow-up (FU). Note the significant improvement in the score between 6 months and 5 years (10 points), which emphasizes the importance of educating the patients to continue physical therapy beyond 6 months. Abbreviation: Preop, preoperative.

Graph showing mean Knee Society (KSS) functional score during 5 years of follow-up (FU). Note the significant improvement in the score between 6 months and 5 years (13 points), which emphasizes the importance of educating the patients to continue physical therapy beyond 6 months. Abbreviation: Preop, preoperative.

Figure 6: Graph showing mean Knee Society (KSS) functional score during 5 years of follow-up (FU). Note the significant improvement in the score between 6 months and 5 years (13 points), which emphasizes the importance of educating the patients to continue physical therapy beyond 6 months. Abbreviation: Preop, preoperative.

Graph showing that mean Oxford score improved significantly to 22.07 at 5-year follow-up (FU). Abbreviation: Preop, preoperative.

Figure 7: Graph showing that mean Oxford score improved significantly to 22.07 at 5-year follow-up (FU). Abbreviation: Preop, preoperative.

Mean VAS pain score improved from 7.1 preoperatively to 3.6 six months postoperatively and 1.6 five years postoperatively (range, 0–10 years). Final mean VAS satisfaction score was 86.8 (range, 23–100). Sixty-six percent of patients scored 85 to 100 satisfaction (excellent), 25% of patients scored 70 to 84 (good), 6% scored 60 to 69 (fair), and 3% scored less than 60 (poor). The poor results occurred in the 3 cases of reoperation.

Radiological

Seventy percent of patients had preoperative varus/valgus deformities of less than 10°. The other 30% had deformities of 10° or more. Mean 5-year radiological mechanical axis was 1.16°±4°. Results of the Knee Society TKA-RESS radiolucency of femoral and tibia components were as follows (Tables 46):

Number of Patients With Radiolucent Lines on Lateral Radiographs of Femoral Components During 5-year Study Period

Table 4: Number of Patients With Radiolucent Lines on Lateral Radiographs of Femoral Components During 5-year Study Period

Number of Patients With Radiolucent Lines on AP Radiographs of Cemented Tibial Components During 5-year Study Period

Table 5: Number of Patients With Radiolucent Lines on AP Radiographs of Cemented Tibial Components During 5-year Study Period

Number of Patients With Radiolucent Lines on Lateral Radiographs of Cemented Tibial Components During 5-year Study Period

Table 6: Number of Patients With Radiolucent Lines on Lateral Radiographs of Cemented Tibial Components During 5-year Study Period

Femoral Component. Radiolucency was found about the femoral component in 5 (6%) patients, of which 4 were cemented and 1 uncemented.

Tibia Component. Radiolucency was found about the tibial tray on the anteroposterior view in 9% (n=7) of knees and on the lateral view in 6% (n=5) of knees. None of these lines were deemed to be progressive. None of the components were found to be radiologically loose or tilting. No revision on the tibia component was necessary.

Native Patella. A total of 3.5% of patients reported patellar pain when climbing stairs or rising from a chair. No correlation existed between the tilting and the symptoms. Sixty-three (80%) patients had 0° to 5° or less patellar tilting, and 16 (20%) patients had 5° to 17° patellar tilting. Nine (12%) patients had lateral patellar displacement of 3 mm or more. None had patellar displacement of 5 mm or more, and no subluxation or dislocation occurred. One patella was resurfaced 14 months postoperatively due to persistent, severe patellar pain and a low satisfaction score. Resurfacing improved his pain score and satisfaction at 5 years.

No patients had vascular injuries, skin necrosis, deep infection, or fractures. Three stitch abscesses were noted in the first 2 weeks postoperatively and were successfully treated with oral antibiotics for 2 weeks with complete resolution. The 17 deceased patients showed KSS, OKI, and ROM improvement at their last visit, with no radiological evidence of component loosening or malpositioning.

Reoperation. In the first year postoperatively, 2 arthroscopic procedures for arthrofibrosis were performed in 2 different patients. A third reoperation was patellar resurfacing for intractable anterior knee pain, although no tilting or subluxation of the patella existed. A fourth and final reoperation was removal of a noncemented femoral component after the second year. Inspection of polyethylene and other components was unremarkable in all reoperations. No polyethylene exchange was necessary in any case (Figure 8).

Graph showing incidence and timing of reoperation with an overall 96% survivorship.

Figure 8: Graph showing incidence and timing of reoperation with an overall 96% survivorship.

Survivorship. The 5-year survivorship based on the need for reoperation for any reason was 97% (Figure 8). Excluding the cases of arthrofibrosis, resurfacing, and exchange of cementless to cemented femoral components, survivorship was 100% for the femoral and tibial components. Based on component-related revisions, the survivorship curve (derived from life-table analysis) revealed a 5-year survivorship of 100%.

Discussion

This study found 100% survivorship of implants with low revision rates and comparable 5-year functional outcomes and quality of life scores using the Columbus Navigated TKA system in a subset of patients with high medical comorbidities. The outcome and survival of TKA relies on 3 major factors: implant design, surgical technique, and patient factors related to comorbidity and compliance. The current authors addressed all of these issues and tried to improve on all modes of failure to improve survivorship.

Implant design may have the potential to cause a higher degree of polyethylene wear.19,34–36 One mechanism leading to wear is the use of a thin layer of polyethylene with a nonconforming articulating surface because it tends to aggregate loading stress, leading to subsurface delamination and increased wear compared with thicker, more conforming designs.20,21,23,37 Another cause of wear is the mismatch of femoral tibial sizes in which small contact area will create stresses that exceed the yield strength of polyethylene. Flat-on-flat articulations, although conforming when in perfect alignment, are susceptible to high edge loading during walking.37

The implant in the current study has a coronal and sagittal plane–conforming design, and any size femoral component will fit any size tibial component. The smallest polyethylene size is 10, which is 7 mm at its thinnest part posteriorly as the tibial insert slopes posteriorly 3°, creating an anterior upsweep. The slope serves 2 purposes: to increase flexion and to avoid anterior gliding, which increases shear forces at the interface that may enhance polyethylene wear.38 Therefore, the authors were able to avoid the nominal danger zone39 and avoid polyethylene wear requiring exchange. However, in cruciate-sparing designs, a tight posterior cruciate ligament may force the femur back during flexion and create high contact stresses.40,41 This usually happens on a flat polyethylene surface where the femur may glide anteriorly and posteriorly. Also, a tight posterior cruciate ligament may jam the TKA in flexion or reduce the flexion gap in comparison with the extension gap.40,42 The current authors resolved this with partial or full release of the contracted posterior cruciate ligament. The decision to change from cruciate retaining to cruciate sacrificing entailed a polyethylene change from deep dish to ultracongruent, without extra resection of the femur or residual instability.

To address the surgical technique aspects of TKA survivorship, namely soft tissue balancing and preventing malalignment,43 the current authors used navigation tools to keep the components aligned in the mechanical axis of 0°±1.14° in all cases with stable balanced soft tissue (maximum total mediolateral deflection of 4°), reducing the incidence of aseptic component loosening. With a 3° posterior polyethylene slope design and high posterior angle femoral component, the implant used was developed to achieve higher knee flexion, but a 15° loss existed at 5 years postoperatively from a mean intra-operative flexion of 125°; however, these results match those of other high-flexion knee designs at 2-year follow-up.44,45 Preoperative ROM and patient lifestyle may play a greater role than femoral design44 in determining final knee ROM at 5 years.

The third factor of survival and outcome, which relied on patients’ responses to instructions on how to live with their artificial knee, is reflected by the satisfaction rate, which was similar to that reported in other studies.7,46–48 However, a high 5-year mortality rate was noted among the veterans in this study. This is likely due to the high incidence of multiple medical comorbidities among these patients and was associated with the TKA (Table 7). Fourteen of the 17 patients who died were older than 70 years. Therefore, further studies will be required to address whether young veterans warrant TKA.

Mortality Rate: Time and Cause of Death

Table 7: Mortality Rate: Time and Cause of Death

Frequent radiolucent lines of the tibia (9%) and femur (6%) were found; however, they were considered poor predictors of future TKAs as long as they were not progressive and no component tilting or sinking existed.49–51 One explanation for frequent radiolucency is that conformity will transfer the increased shear forces from the femur and polyethylene to the cement–bone or prosthesis–bone interface.22,25,52 A careful cementing technique involves using the thumb to press cement into the medial tibia and on the undersurface of the tibia, and this may help minimize the incidence of these changes.53

The current study had a low patellar resurfacing rate of 1.3%. This is likely due to the design of the anterior groove of the femoral component. The anterior femoral groove was thinned out and angled 7° laterally to stabilize the patella, allowing it to track more naturally. Other factors54,55 are the subvastus approach, preserving the vastus medialis obliquis mechanism, and attempting to keep the patella medial. The combination of these factors may explain the lack of subluxation or dislocation of the native patella. However, painful symptomatic anterior knee pain related to climbing stairs and rising from a chair occurred in 3.5% of patients in this study, and resurfacing may not completely relieve this pain. Other factors may be more pertinent, such as avoiding overstuffing of the patellofemoral joint, avoiding an internally rotated tibial component, making an appropriate distal femoral cut, and limiting extreme femoral rotation (more than 5°).

Although the authors did not perform formal lateral retinacular release except in a few severe valgus cases, they routinely released the lateral patellofemoral ligament as part of cleaning the patellar rim of osteophytes. Therefore, they recommend no patellar resurfacing for economic reasons, bone preserving, and a resulting better rate of reoperation as compared with a resurfaced patella, which has been cited in metal-backed patellae15–17 and all-polyethylene implants.56,57 Using a subvastus approach may allow for reoperation to resurface the patella without further damaging the quadriceps muscles, but for a classic medial parapatellar TKA approach, primary resurfacing may be a better choice.

In most TKA series, survivorship of between 90% to 99% has been reported at 10 years.25,26,34 Survivorship analysis should be compared in relation to follow-up26,58 and whether all patients were clinically assessed.59 The current study’s follow-up was unique due to the veterans’ national database, which allows accurate monitoring of cases, even those lost to follow-up who may have undergone reoperation elsewhere in the United States. Therefore, the reoperation rate reported in this study is fairly accurate for this series.

The limitations of this study were that it was a small, prospective case series and that the majority of veterans were men. Therefore, interpreting these results for a global population should be done with caution. However, the modes of failure are universal and the principles to overcome these at every stage should always be kept in mind for the best outcome.

Conclusion

The correlation of survivorship with individual components enables the identification of mechanisms of failure and selective improvement of components in a modular system. Component revision rate for all TKA types at 5 years averages approximately 2.8%,60 compared with the current study’s 5-year component survivorship of 100%. The overall survival was 96% for a patella-sparing, high-flexion TKA system.

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Demographic Data

DemographicData
No. of patients100
  No. lost to follow-up4
  No. died during study17
  No. at final 5-y follow-up79
Diagnosis, %
  Idiopathic gonarthrosis76
  Posttraumatic gonarthrosis23
  Rheumatoid arthritis1
Side, No.
  Right55
  Left45
Sex, No.
  Male89
  Female7
Mean age (range), y
  Men67.6 (45 to 85)
  Women70.7 (44 to 84)
Mean follow-up (range), y5.3 (5 to 6)
Mean weight (range), kg96.7 (42.5 to 140.5)
Mean BMI (range), kg/m231.2 (18 to 44)
Mean tourniquet time (range), min50.7 (28 to 62)
Mean hospital stay (range), d3.8 (2 to 5)
Deformity
  Varus, %66
  Valgus, %27
  Varus to valgus range, deg22 to 18
  Neutral, %7
  Fixed flexion >5°, %45
Preoperative ROM, deg
  Extension−12 to 13
  Flexion70 to 125

Frequency of Size and Type of Polyethylene Used

Polyethylene Size and TypeFrequency%Cumulative FrequencyCumulative %
T1 14 deep dish11.0511.05
T2 10 deep dish11.0522.11
T2 10 deep dish +77.3799.47
T2 12 deep dish66.321515.79
T2 14 ultracongruent11.051616.84
T2 14 deep dish33.161920.00
T2 16 deep dish11.052021.05
T3 10 deep dish +22.112223.16
T3 10 deep dish2627.374850.53
T3 12 ultracongruent11.054951.58
T3 12 deep dish1515.796467.37
T3 14 ultracongruent11.056568.42
T3 14 deep dish88.427376.84
T3 16 deep dish11.057477.89
T4 10 deep dish66.328084.21
T4 12 ultracongruent11.058185.26
T4 12 deep dish66.328791.58
T4 14 deep dish +22.118993.68
T4 14 deep dish22.119195.79
T4 16 deep dish11.059296.84
T5 10 deep dish11.059397.89
T5 12 deep dish11.059498.95
T5 16 deep dish22.096100.00

Soft Tissue Release

Soft TissueRelease PerformedRelease Not PerformedNo. (%)
Medial collateral ligament108696 (10)
Lateral collateral ligament29496 (2)
Lateral retinaculum29496 (2)
Posterior capsule187896 (18)
Posterior cruciate ligament49296 (4)

Number of Patients With Radiolucent Lines on Lateral Radiographs of Femoral Components During 5-year Study Period

ZoneFollow-up (mm)
4 mo (<2)4 mo (⩾2)6 mo (<2)6 mo (⩾2)5 y (<2)5 y (⩾2)
1000050
2001040
3000000
4000030
5000000
6000000
7000000

Number of Patients With Radiolucent Lines on AP Radiographs of Cemented Tibial Components During 5-year Study Period

ZoneFollow-up (mm)
4 mo (<2)4 mo (⩾2)6 mo (<2)6 mo (⩾2)5 y (<2)5 y (⩾2)
1000071
2000041
3000051
4000041
5000051
6000020
7000071

Number of Patients With Radiolucent Lines on Lateral Radiographs of Cemented Tibial Components During 5-year Study Period

ZoneFollow-up (mm)
4 mo (<2)4 mo (⩾2)6 mo (<2)6 mo (⩾2)5 y (<2)5 y (⩾2)
1000030
2000060
3101011
4000051
5001040

Mortality Rate: Time and Cause of Death

Patient Age, yDate of SurgeryDate of DeathCause of DeathComorbidities
8506/21/0409/29/08Acute renal insufficiency with rapid ventricular rate, congestive heart failure, intravascular volume depletionType II diabetes mellitus, congestive heart failure, hypertension
5106/24/0412/28/06Acute renal failureHypertension, obesity, peripheral vascular disease, hyperlidpidemia
7407/02/0412/09/06UnknownVenous insufficiency, chronic renal failure, hyperkalemia, chronic obstructive pulmonary disease, hypertension, obesity, spinal stenosis
8408/03/0411/08/07Natural causesHypothyroidism, leukocytosis, skin cancer, hypercholesterolemia, type II diabetes mellitus, coronary artery disease, gout, hypertension, atrial fibrillation, prostate cancer
7108/25/0407/09/08UnknownDementia, stroke, hyperlipidemia, hypertension
8201/10/0504/13/08Congestive heart failureSkin cancer, renal calculi
7309/20/0406/22/05Acute myelogenous leukemia/pleural effusionObesity, peptic ulcer disease, rheumatoid arthritis, hypertension
6910/07/0405/13/07Prostate cancer with metastasis to boneTransient ischemic attack, hypertension
7801/20/0510/26/08StrokeHypertension, hyperlipidemia, chronic renal failure
5301/31/0507/06/06UnknownHypertension, hepatitis C
7602/02/0506/30/09Chronic kidney disease, natural causesOrthostatic hypotension, chronic kidney disease, asthma, stroke, hyperlipidemia, peripheral vascular disease, arteriosclerotic cardiovascular disease
7502/10/0507/26/08Right side heart failure secondary to pulmonary hypertension and valvular heartPleural effusion, hyperlipidemia, atrial fibrillation, hyptertension, type II diabetes mellitus, obesity
8002/24/0505/23/09Lung cancer with metastisis to boneOrthostatic hypotension, dementia, hyperlipidemia, pleural effusion, congestive heart failure, bladder cancer, anemia, tachycardia, chronic liver disease, hypothyroidism, type II diabetes mellitus, obesity
7903/04/0509/01/06Acute/chronic renal failure, bladder cancerHydronephrosis
8203/09/0510/28/07Non-Hodgkin’s lymphomaDeep vein thrombosis, hypertension
4903/10/0509/03/08UnknownHepatitis C
8604/08/0508/29/08Congestive heart failureHypoxemia, skin cancer, deep vein thrombosis, pulmonary fibrosis, hyperlipidemia, chronic ischemic heart disease, angina pectoris

10.3928/01477447-20130222-19

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