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Twenty year radiological and survival analysis of the titanium tibial keel Press-Fit Condylar TKA undertaken by a single surgeon

Abdul KHAN, Videsh RAUT

From the Lower Limb Arthroplasty Unit, Wrightington Hospital,

Hall Lane, Appley Bridge, 

Wigan WN6 9EP England (UK).


We reviewed 62 total knee arthroplasties by a single surgeon (VR) in 50 Patients. A cemented titanium PFC prosthesis with a tibial keel was used. There were 25 male and 25 female patients. The mean age was 65 years and 11 months (range 25 to 80 years). The mean radiological follow up was 14.1 years (range 10 to 20 years). Twelve patients had bilateral surgery undertaken separately. Forty six patients had osteoarthritis, 3 had rheumatoid arthritis and one JCA. Four knees underwent revision for aseptic loosening and 1 knee for deep infection. A total of 5 patients died during this follow up. Four of them died while being under review of unrelated causes and none showed any significant loosening at their last follow up. The fifth patient who had the deep infection died after an above knee amputation following a revision procedure. Two patients suffered a supra-condylar fracture of the femur after a fall treated successfully with supra condylar nails. At 20 years follow-up the survival rate, using revision for all causes as an end- point, was 92.1%. The survival rate at 20 years with revision for aseptic loosening as the end point was 93.6%. The survival rate for radiological loosening ( KSRES > 10 ) at 20 years was 92.1%. The cemented titanium keeled PFC knee prosthesis shows a good 20 year survivorship with our surgical technique and results are comparable to those reported of other contemporary knee prostheses.

J.Orthopaedics 2012;8(3)e1


PFC knee replacements, Titanium tibial keel, KSRES Scores, survival analysis.


Total knee replacement is becoming increasingly popular worldwide due to improvements in the technology and implants ( 1-9). Clinical decisions for selecting one implant over another must be supported by good long term results. There have been a number of papers published showing good medium term survival of cemented PFC knee replacements with modular tibial stem (1, 13, 16, 20, 23, 24, 25) but there is no publication in the English language literature on the long-term results of specifically the titanium keeled Tibial PFC prosthesis. We retrospectively looked at our long term results of the PFC knee replacement using a titanium tibial keel prosthesis. We used radiological and survival curve analysis, with strict definitions regarding end points to assess the outcome.


Between 1990 and 1997, 128 patients had total knee replacements performed by the senior author (VR). Of these, 50 patients underwent 62 total knee arthroplasties with a titanium tibial baseplate with keel, a PFC femoral component and a cruciate preserving posterior lipped polyethylene liner. The implants were cemented using CMW I Gentamicin loaded cement (DePuy, Leeds, UK). Excluded from the initial 128, were patients who had a modular tibial tray. There were 25 male and 25 female patients. The mean age was 65 years and 11 months (range 25 to 80 years). Twelve patients had bilateral surgery undertaken separately. Forty six patients had osteoarthritis, 3 had rheumatoid arthritis and one juvenile chronic arthritis. All procedures were undertaken in laminar flow theatres using body suits, routine prophylactic antibiotics, tourniquet and through a medial parapatellar arthrotomy.

The two components were always cemented separately using two separate mixes of cement. The cement was pressurized into the dried cut surface of the tibia and femur with direct finger pressure and some cement was applied on the under surface of the components and then the components were implanted. Continuous constant pressure was applied on the component till the cement had set. The jig to widen the keel slot in the tibia was never used. To help decrease any chances of “third body wear” from cement particles in the long term a special effort to remove extruded cement (cement debridement) was made easier by cementing the two components separately. Assessment Patients were examined at 3 months, 1, 2, 5, 7, 10 years and every 2 years thereafter with a standard weight bearing antero -posterior and lateral radiograph at each clinic attendance. Loosening of the arthroplasty was assessed using the Knee Society Roentgenographic Evaluation System (KSRES).

This system scores radiological loosening in a knee arthroplasty separately for the femoral, tibial and patella components which are summed to give a total score. All the assessments and scrutiny of the records was done entirely by an independent assessor (AK). A total score of four or less and non progressive is rated as “not significant”, a total score of five to nine should be “followed for progression”, and a total score of ten or above signifies “possible or impending failure” regardless of symptoms (10). The mean radiological follow up was 14.1 years (range: 10 – 20 years). None of the patients were lost to follow-up but we had 8 patients who had more than 10 years follow up who were discharged from the clinic to come back if there were any further problems and these 8 patients have not been reviewed in the past 5 years. Survival analysis Survival curves were analysed to assess revision for any cause, aseptic loosening and radiological loosening. 

Results :

Complete survival data were reviewed for all 62 knees at a minimum of 10 years post operatively. The mean radiological follow-up was 14.1 years. The average KSRES score for all three components, as well as the total score was less than four which is defined as non significant . Fifty six knees scored less than four ( Fig 1 ) and 6 scored over ten . Five of these 6 required revision while one did not undergo a revision due to medical reasons. 20 knees required a 8 mm poly insert, 26 knees required a 10 mm polyinsert, 11 knees required 12.5 mm poly insert and 5 knees required 15 mm poly insert.

Revision surgery

Four knees were revised for aseptic loosening and one for deep infection. Revision for aseptic loosening was done at 11, 12, 13 and 14 years after the primary procedure and both the components were revised. One patient with deep infection had a revision followed by an above-knee amputation and he eventually died. Four patients died while being under review of unrelated causes and none showed any significant loosening at their last follow-up. Two patients had traumatic supracondylar femoral fractures needing a supracondylar nail in the femur and they healed well without any problems.


One patient had lateral patellar subluxation on the radiograph with no functional disturbance and required no surgical intervention. One patient required revision for deep infection. Four patients had DVT and 2 patients needed MUA.

Survival analysis

Revision due to any cause Using revision, for any reason, as the end point, the survival at 14 years was 92.1% while the 20 year survival rate was still 92.1% (Fig. 2). Aseptic loosening Using revision for aseptic loosening as the end point, the survival at 14years was 93.6% while the 20 year survival rate was still 93.6% (Fig. 3).

Radiological loosening

Using radiological loosening as an end point ( KSRES score > 10 ), the survival at 14years was 92.1% while the 20 year survival rate was still 92.1% (Fig. 4). We had 8 patients who had more than 10 years follow up with no signs of loosening but were discharged from the clinic to come back if there were any further problems and were therefore not reviewed in the last 5 years. If we were to assume that these 8 patients failed immediately after their outpatient clinic review, then the survival rate at 14 years will be 79%, while the 20 year survival rate will still be 79%.

Discussion :

Total knee arthroplasty is an established procedure which greatly improves the quality of life of the patient (12). Certain criteria are required to ensure accurate reproducible results in survival analysis. These include strict definitions regarding end points, evaluations done systematically and having enough patients to allow statistical validity. The 10 year survival for total knee arthroplasty, using revision surgery as an end point, is over 91% for a number of well established prostheses (1, 2, 4, 5, 6, 7, 9, 13, 14, 15, 16, 21, 24, 25). With the PFC cemented modular system using modular tibial prosthesis, using revision surgery as an endpoint, Schai reports 90% 10 year survival, Khaw reports 95.5% 10-year survival. (13, 25) which is in line with the published data from other prostheses (1-9, 11, 14-19, 21, 22, 26-29 ) One criticism of survival analysis is the exclusion from the results of patients who are failing radiologically or clinically, but who do not undergo surgery.

These may be elderly or infirm patients who choose or are advised not to undergo revision surgery even in the presence of symptoms. This results in a falsely high survival rate. Hence, survival analysis based on radiological assessment is important to quantify impending failure. One patient in our study had radiological loosening as defined by a KSRES score greater than ten but did not have revision due to medical reasons. Recalculating data to account for patients with radiological failures (92.1% at 20 years in this series) gives more useful information to the surgeon regarding the actual survivorship of the implant. Although septic loosening can be iatrogenic in nature, it may slightly mask the surgical ability to implant a successful prosthesis. Aseptic loosening of an established prosthesis, however, is a good indicator of surgical technique and quality of the implant. Poly wear particles over time will contribute to the aseptic loosening of the prosthesis.

In our study, all the implants that showed KSRES scores of more than 10 showed evidence of significant poly wear. Hence, we feel it is important to record survival analysis for this separately. The 20 year survival rate of 93.6% in our series is as good as the published data (11, 14-19) which have shorter follow-up periods. There are few studies with long term results. Buechel FF et al (3) showed that survival of the Rotating Platform knee at 16 years was better for cemented prostheses compared to uncemented prostheses. Using revision as criterion, the survival rate of uncemented prosthesis was 83% compared to 97.7% for cemented prosthesis. The long term results of the anatomic graduated component PCL retaining total knee replacement published by Ritter et al (22) showed survival of 98.86% at 15 years using revision due to any cause as an end point. Van Loon et al (27) published their results using the Kinematic total knee replacement. The 14 year survival was 82% using revision as an end point. Our study is the only long term study using only PFC with a titanium tibial keel prosthesis as all the other long term PFC results were with modular tibial prosthesis.

The survival of PFC with modular tibial prosthesis in a study by Rodricks et al (23) at 15 years follow up for revision due to any cause was 91.5% and survival for aseptic loosening was 97.2%. Malin et al (16) in their study using PFC with a modular tibial prosthesis showed 15 year survival of 87.2% using aseptic loosening leading to revision as an end point. Santini et al (24) published the medium-term results of the PFC total knee replacement for the same senior author (VR) with a ten-year survival rate (using revision for aseptic loosening as an end point) of 97.04%. This series used both types of tibial prostheses viz. the keeled tibial prosthesis as well as the modular tibial prosthesis. There are weaknesses in our paper. First, it is a retrospective study. Secondly, we have only presented survival analysis with radiological review.

Thirdly, the total number of patients in the study is small. Although the same prosthesis was used by other surgeons in the same hospital, we only reviewed the results of one surgeon (VR) to maintain uniformity as the surgical technique will have considerable effect on the longevity of the prosthesis. We feel that our specific meticulous surgical technique as described before is important to achieve good cement injection and fixation and thereby achieve good long term survivorship as shown in our series. It is encouraging that the overall survival rates are in line with other published data even at this longer term follow-up, although the total numbers are smaller.


Our study shows good 20 year survivorship with the titanium keeled cemented PFC knee prosthesis. Our results are comparable to those of other contemporary knee prostheses which have been published.



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Figure 1 – AP / Lat Radiograph of the  knee with PFC prosthesis insitu.

Figure 2 – Kaplan Meier curve showing all cases of revision as an endpoint.

Figure 3 – Kaplan Meier curve showing revision for aseptic loosening as an endpoint.

Figure 4 – Kaplan Meier Survival curve showing radiological loosening (KSRES>10) as an endpoint.


This is a peer reviewed paper 

Please cite as :

J.Orthopaedics 2012;9(3)e1




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