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High-flexion, Motion-guided Total Knee Arthroplasty: Who Benefits the Most?

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Abstract

A multicenter study was performed to determine which patients have the most potential to benefit from total knee arthroplasty (TKA) with a high-flexion, guided-motion design. In 201 consecutive TKAs, the mean gain in range of motion (ROM) was 14º at 3 months and 24º at 6 months. The gain in flexion was significant at 3 and 6 months postoperatively. No differences were found based on preoperative diagnosis, age, or sex. There was a poor correlation between body mass index and ROM. Pre- and postoperative flexion also displayed a weak correlation. Patients with the least preoperative flexion (<90º) gained the most degrees of flexion (26º). We conclude that the use of a high-flexion, guided-motion TKA allows a significant functional improvement in patients with preoperative stiffness and the preservation of good flexion in patients with normal preoperative flexion.

Functional assessment of patients who underwent total knee arthroplasty (TKA) is gaining importance as the procedure is performed in younger patients. Also, patient expectations after TKA continue to increase. The prevailing reason for patient disappointment after TKA are pain and limited range of motion (ROM).

Several researchers use different cut-off levels and benchmarks when defining knee stiffness. Some physicians use flexion as a determinant and consider the knee stiff with a flexion limit at 85°¹ or at 90°.² Others define stiffness as a general limitation of the arc of motion to less than 70°.³ Some researchers take extension and flexion into account and define stiffness as a fixed flexion contracture of more than 20° or ROM of <45°,⁴ alternatively a fixed flexion contracture of >15° or flexion less than 75°.⁵ The literature shows more agreement regarding the ROM that is needed for functional activities.⁶ Sitting requires approximately 90°; stair climbing requires 80°; shoelace tying requires 105°; and lifting an object from the ground requires 70°. Individual ROM needs vary, however, depending on patient height and hip mobility. Generally, small patients require more flexion than large patients. Preoperative risk factors for postoperative stiffness include limited ROM before the operation, obesity, and prior surgery.^1-7 Intraoperative surgical errors and postoperative complications can also contribute to a patient’s dissatisfaction with ROM after TKA.

The strategic approach to treating a patient with preoperative stiffness consists of careful counseling and motivation of the patient, analysis of the causes of stiffness, specific surgical measures including tibial tuberosity shifts or quadriceps releases, the choice of the implant, and postoperative management.

The aim of this study was to determine which patients have the most potential to benefit from a TKA that is designed to achieve high flexion.

Materials and Methods

The patients underwent surgery at five different centers with an identical instrumentation set and similar surgical technique including a medial parapatellar approach and a measured resection technique for implant positioning and alignment. The prosthesis used was Journey (Smith & Nephew, Memphis, Tenn). The postoperative regimen consisted of regional pain blocks, early mobilization, and intensive rehabilitation. The patients were evaluated preoperatively and at 3, 6, and 9 months after the procedure. Age, sex, height, and weight were recorded. Outcomes were measured in terms of fixed flexion contracture, flexion, and knee function scores. Radiographs were taken to determine position and fixation of the implant and overall alignment.

Outcome in terms of flexion, fixed flexion contracture, and ROM was correlated to age, sex, height, weight, body mass index (BMI), preoperative flexion and ROM, and preoperative diagnosis.

Results

The study included 201 consecutive TKAs in 194 patients. Mean BMI was 30.32 kg/m² (range: 15.6-56.4 kg/m²); mean preoperative flexion was 112° (range: 70°-145°); and mean fixed flexion contracture was 5.2° (range: 0°-30°). At 3 months postoperatively, mean flexion was 120° (range: 80°-145°) and mean fixed flexion contracture 0.9° (range: 0°-10°). The mean gain in ROM was 14° at 3 months and 24° at 6 months. The gain in flexion was significant (Student’s t test, paired, two tailed: P<.005) both at 3 and 6 months. No differences were found based on preoperative diagnosis, age, or sex. The study showed a poor correlation between BMI and preoperative flexion and BMI and gain in ROM at 3 months and at 6 months.

Patients were stratified according to BMI: group 1, <25; group 2, 25 to 35; and group 3, >35. No significant differences were found among groups regarding gain in ROM at 3 and 6 months. Stratification based on preoperative flexion yielded 5 groups: group 1, <90°; group 2, 91° to 100°; group 3, 101° to 110°; group 4, 111° to 120°; and group 5, >120°. No significant difference in BMI (P=.38) or age (P=.07) was observed between the patients with the least preoperative flexion (group 1) and the patients with the most preoperative flexion (group 5). At 3 months, the mean gain in ROM was 26° in group 1, 19° in group 2 ,14° in group 3, 10° in group 4, and 0° in group 5 (Figure 1). The difference in gain was significant (P<.05) between all groups except between groups 3 and 4 (P=.247).

Discussion

Functional performance after TKA is important, especially to young and active patients. Recent research⁸ identified several areas of functional deficit in patients who underwent knee replacement. Functional deficits in ROM, strength, and stability are the most significant contributing factors to impaired function.

A motion-guided TKA may improve function in the three areas mentioned previously.^9-11 Stability is enhanced with a cam-post mechanism that also contributes to anterior (anterior cruciate ligament mimicking) stabilization and relatively conforming medial polyethylene geometry. Strength and ROM benefit from a more natural kinematic pattern including physiologic roll-back and axial rotation between tibia and femur. The researchers’ experience^9-11 shows that the specific femoral geometry covers the femoral condyles far backward, ensuring reliable and predictable posterior contact patterns in deep flexion (Figure 2).

In contrast to the previous studies,² the researchers’ data showed a poor correlation between BMI and preoperative flexion. The data correspond with the authors’ clinical experience that obesity does not necessarily lead to limited ROM. The data also show no significant correlation between BMI and postoperative flexion.

Generally, postoperative flexion relates well to preoperative flexion.^1,2,5-7 In this patient cohort, the authors also found a correlation between the pre- and postoperative flexion values, although the correlation coefficient is low (R=0.409).

The correlation is weak because patients with poor initial preoperative ROM gain significantly more ROM after the procedure than patients who had good preoperative flexion. In other words, the postoperative ROM equalizes among the stratified groups (Figure 3). As shown in Figure 3, the mean postoperative flexion at 3 months is lower for group 1 than for group 5 (111° versus 124°), but this difference is significantly lower than the preoperative difference between the groups. The net gain is, therefore, most important for groups 1 and 2, which represent the patients with the least preoperative flexion.

Conclusion

On the basis of these data, the researchers conclude that the use of a high-flexion TKA design can be indicated in patients with poor preoperative ROM. The patients have a significant chance of improving their function after the procedure. For patients with good preoperative flexion, the use of a high-flexion TKA allows them to maintain their ROM after the procedure.

References

1. Scranton PE Jr. Management of knee pain and stiffness after total knee arthroplasty. J Arthroplasty. 2001; 16:428-435.
2. Gandhi R, De Beer J, Leone J, et al. Predictive risk factors for stiff knees in total knee arthroplasty. J Arthroplasty. 2006; 21:46-52.
3. Christensen CP, Crawford JJ, Olin MD, Vail TP. Revision of the stiff total knee arthroplasty. J Arthroplasty. 2002; 17:409-415.
4. Nicholls DW, Dorr LD. Revision surgery for stiff total knee arthroplasty. Arthroplasty. 1990; 5(suppl):73.
5. Kim J, Nelson CL, Lotke PA. Stiffness after total knee arthroplasty: prevalence of the complication and outcomes of revision. J Bone Joint Surg Am. 2004; 86:1479.
6. Bong MR, Di Cesare PE. Stiffness after total knee arthroplasty. J Am Acad Orthop Surg. 2004; 12:164-171.
7. Daluga D, Lombardi AV, Mallory TH, Vaughn BK. Knee manipulation following total knee arthroplasty: analysis of prognostic variables. J Arthroplasty. 1991; 6:119-128.
8. Noble PC, Gordon MJ, Weiss JM, et al. Does total knee replacement restore normal knee function? Clin Orthop Relat Res. 2005; 431:157-165.
9. Ries M. The high-performance knee. In: Bellemans J, Ries M, Victor J, eds. Total Knee Arthroplasty: A Guide to Get Better Performance. Heidelberg, Germany: Springer Verlag; 2005:303-310.
10. Ries M, Victor J, Bellemans J, et al. Effect of guided knee motion and high flexion TKA on kinematics, implant stresses and wear. Paper presented at:73rd Annual American Academy of Orthopaedic Surgeons Meeting; March 22-26, 2006; Chicago, Ill: SE 33:593.
11. Victor J, Bellemans J. Physiologic kinematics as a concept for better flexion in TKA. Clin Orthop Relat Res. 2006; 452:53-58.

Authors

Dr Victor is from the Department of Orthopedics AZ St-Lucas, Brugge, Belgium; Dr Ries is from the Department of Orthopedic Surgery, University of California, San Francisco; Dr Bellemans is from University Hospitals, Leuven, Belgium; and Dr Van Hellemondt is from St Maartenskliniek, Nijmegen, The Netherlands.

Drs Victor, Ries, Bellemans, Robb, and Hellemondt are consultants for Smith & Nephew. Dr Ries has received financial contributions from Smith & Nephew in the past 12 months.