|Year : 2014 | Volume
| Issue : 1 | Page : 78-83
Does pre-operative flexion factor influence the post operative range of motion in total knee arthroplasty
Ganesh Babu Natarajan, Veera Ram Narayan, Vijayaraghavan
Department of Orthopaedics, Sri Ramachandra Medical College (SRMC), Porur, Chennai, Tamilnadu, India
|Date of Web Publication||6-Jun-2014|
Ganesh Babu Natarajan
B2 Private Clinic, Department of Orthopaedics, Sri Ramachandra University, Porur, Chennai - 600 116, Tamilnadu
Source of Support: None, Conflict of Interest: None
Background: Range of motion and flexion are important outcome measures following total knee arthroplasty. Many of the activities of daily living require knee flexion in the range of 45 to 105°. Several factors affect postoperative range of motion (ROM), including pre-operative and post operative factors, among which pre-operative ROM is the most important factor. Aim: To analyze the patient's pre-operative flexion factor responsible for the outcome of range of motion in post operative Total Knee Replacement (TKR). Materials and Methods: We studied 80 patients having Total Knee Replacement (TKR) by a single surgeon in SRMC, Chennai, between 2005 and 2010 with a minimum follow up of upto 1 year. Results: The mean pre-operative flexion was 85° and post operative mean flexion was 115°. Obesity is associated with poor flexion after TKR. Knees with Rheumatoid arthritis started with a lesser flexion (80°) than those with Osteoarthritis (90°) and the change in flexion score has shown a significant difference of 40 and 20°, respectively. Average post operative range of motion for patient with pre-operative ROM <90° was 110° flexion, whereas in patients with pre-operative ROM >90° flexion, the average post operative ROM was 120° flexion. This shows, the gain in flexion is more in patients with <90° than those with >90° pre-operative flexion. Conclusion: Yes, the pre-operative flexion significantly influenced the post operative flexion and it is a good parameter for predicting the post operative outcome.
Keywords: Post operative flexion, pre operative flexion, range of motion, total knee replacement pre-operativepre-operative
|How to cite this article:|
Natarajan GB, Narayan VR, Vijayaraghavan. Does pre-operative flexion factor influence the post operative range of motion in total knee arthroplasty. J Orthop Traumatol Rehabil 2014;7:78-83
|How to cite this URL:|
Natarajan GB, Narayan VR, Vijayaraghavan. Does pre-operative flexion factor influence the post operative range of motion in total knee arthroplasty. J Orthop Traumatol Rehabil [serial online] 2014 [cited 2020 Jul 8];7:78-83. Available from: http://www.jotr.in/text.asp?2014/7/1/78/134025
| Introduction|| |
Total knee replacement has an objective to provide relief in pain, correct deformity and allow a functional range of movement for daily activities. Even with the evolution of new surgical techniques, newer implants and good operative tissue handling, stiffness is still a common problem. Range of motion and flexion are important outcome measures following total knee arthroplasty. Many of the activities of daily living require knee flexion in the range of 45 to 105°.  It has been recommended that goals of total knee replacement (TKR) should include obtaining knee range of motion (ROM) from 0 to 105°.  Several factors affect postoperative ROM, including pre-operative and post operative factor, with pre-operative ROM being the most important factor  .
The objective of this study is to evaluate that patient's pre-operative flexion ROM influence the post operative flexion range in TKR.
| Materials and methods|| |
We studied 86 patients having Total Knee Replacement (TKR) by a single surgeon in Sutter Roseville Medical Center SRMC, Chennai, between 2005 and 2010. Patients were evaluated for ROM pre-operatively and post operatively from 6 weeks to 1 year. In this study, we analyzed the post-operative change in ROM at the end of 1 year post operative period. We also divided the patient into 2 groups, the range of motion for patients with pre-operative ROM <90° as group 1 and pre-opervative ROM >90° group 2.
Were primary osteoarthritis, rheumatoid arthritis, correction of varus, valgus and post traumatic deformity. Absolute exclusion criteria were infection, osteomyelitis, pathological bone lesions, revision total knee replacement or previous surgery like high tibial osteotomy, and synovectomy. During the follow up, 6 patients were lost and were excluded, so totally 80 arthroplasties were evaluated.
The prosthesis used were Depuy PFC (50 knees), Optetrack (25 knees), Smith and Nephew Genesis II (5 knees). Both Curciate retaining (CR) and Curciate substitute (CS) designs were used in this study.
All patients underwent medial para-patellar approach, with cement used to fix both femoral and tibial components. Patellar replacement was based on etiology, patella articular surface and thickness of patella. The indications for patella retention were a small patella, nearly normal articular cartilage, minimal pre-operative patellofemoral pain, poor patellar bone quality and young age. When patellar retention was performed, osteophytes of the patella were removed and marginal electrocauterization was carried out. All wound closures were performed on the knees with flexion from 90° to 110°.
Following surgery, Knee active and passive flexion exercises were started from second post operative day after drain removal. For poorly motivated patients, knee was mobilized with continuous passive motion (CPM) support. Patients were walked with knee brace and walker support for 6 weeks post operative. Later based on Quadriceps strength (if satisfactory without extensor lag) patient was made to walk independently and allow to do stairs with supervision. All patients were given LMWH post operatively till the time of discharge (till patient regained satisfactory mobilization).
Clinical follow up
In addition to the pre-operative assessment, passive ROM was measured at 6 weeks, 3 months and 12 months interval. Active knee flexion, extension, and flexion arc were measured using a goniometer with patients lying supine. Change in flexion was calculated on a patient by subtracting the pre-operative flexion from the post operative flexion. Post operative outcome were analyzed with Knee Society Scoring system (KSS) and Patello-femoral scoring (PFS) system [Table 1]. These differences were compared with various variables like age, sex, diagnosis, Body mass index (BMI), pre-operative flexion, different prosthesis design and patellar replacement [Table 2].
Statistical analysis used
Statistical analysis and comparisons were performed using Chi square test with significance taken for P < 0.05.
| Results|| |
We performed a total of 86 TKR between 2005 and 2010, out of which 6 patients were lost during the follow up. On 61 patients, 80 TKR were done with bilateral TKR in 19 patients, out of which 36 were males and 44 were females. The mean age at operation was significantly less for patient with rheumatoid arthritis (51 years) than for those with osteoarthritis (63.6 years).
There is no evidence of association between age and postoperative flexion. Thus, age had no demonstrable effect on the post operative ROM.
[Table 3] shows various parameters before and after surgery. The mean pre-operative flexion was 85° and post operative mean flexion was 115°, which shows significance with P value as 0.033. There were no Fixed Flexion Deformity (FFD) post operatively and results show a very significant increase in Knee Society Score. Average FFD and ROM were 10° and 90° respectively during pre-operative period. There were, however, no correlation between pre-operative flexion deformity, extensor lag and the change in flexion after arthroplasty.
Out of 80 knees, 11 TKR were done for Rheumatoid arthritis and rest for Osteoarthritis knees. Knees with Rheumatoid arthritis started with a lesser flexion (80°) than those with Osteoarthritis (90°) and the change in flexion score has shown a significant difference of 40° and 20°, respectively [Table 4]. In both Osteoarthritis and Rheumatoid arthritis knees, a mean gain in flexion range was 30°.
Obesity is associated with poor flexion range after TKR. Majority of patients with higher BMI (>30) had postoperative ROM of less than 100° [Table 5]. Likewise, if BMI was less than 25, patients had good postoperative ROM above 100°. Out of 27 patients who were obese (BMI >30), 21 patients had post operative ROM below 100°. Patients with BMI between 25 and 30 had almost equal result in these two groups. So patients with BMI >30 or <25 can be a predictor for postoperative ROM.
Patellar replacements were done in 13 out of 80 knees, which fulfilled the inclusion criteria for patella replacement. In both diagnostic groups (Osteoarthritis and Rheumatoid arthritis), patients having patella replacement had a significantly higher Patello-Femoral score (PFS) than those who did not have a patella replacement [Table 6]. Even though knees with patella replacements showed a significant improvement in PFS, there was no significant improvement in terms of post operative ROM [Table 7].
Average post operative range of motion for patients with pre-operative ROM <90° was 110° flexion, whereas patient with pre-operative ROM >90°, flexion the average post operative ROM was 120°. This shows the gain in flexion is more in groups with <90° than patient with >90° of pre-operative flexion, which is statistically significant (P value is 0.003) [Table 8].
|Table 8: Change in postoperative flexion according to pre-operative flexion|
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From immediate post operative to 6 weeks post operative period, the average ROM where 80° flexion with the mean KSS as 126. At the end of 3 months, the average ROM increased to 100° and improved to 120° by the end of 6 months. At the end 1 year postoperatively, the average KSS and ROM were 180 points and 115°, respectively [Figure 1] and [Figure 2].
It also shows that, there was no correlation between the delay before mobilization and the outcomes of ROM post operatively.
When we correlate the 3 different companies of knee prosthesis to post operative ROM, we could not find any significant difference in the post operative gain in flexion. We only had 2 cases out of 80 knees with high flexion prosthesis, but we can't make out any difference in change in flexion post operatively.
[Table 9] shows the extent of pre-operative and post-operative flexion attained using different prostheses. Depuy PFC, the most common design we used. Although there was no significant difference in pre-operative flexion, the Optetrack group and the Genesis group yielded better postoperative flexion. There was no significant gain in postoperative flexion between the groups, but to do any fair comparison we need equal number of different prosthesis.
Curciate retaining knees (64) and Curciate substitute knees (16) were used in this study. Between these two kinds of prosthesis, there was no influence with the post operative range of motion [Table 10].
|Table 9: Pre-operative and postoperative flexion according to different prosthesis design|
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| Discussion|| |
Patients and surgeons expect an excellent outcome following TKR. The level of postoperative range of motion strongly influences the ability of the patient to perform the activities of daily living. Laubenthal et al.  showed that the patients require 67° of flexion during the gait balance phase, 83° for stepping up stairs, 100° stepping down, 93° for standing up from a chair and between 71° and 117° for reaching an object on the floor. The average range of motion that can be obtained after total knee arthroplasty varies from 85 to 115° with various designs of prostheses with some exceptions.  Even in our study the average post operative ROM is 115 0.
A study about the factors influencing better outcome can be useful to the surgeon to get the best possible clinical outcome. Our study confirms that several factors interact to affect the ROM of TKR.
The study confirms that pre-operative flexion is a valuable parameter for the prognosis of postoperative flexion after TKR; agreeing with the findings by Ritter et al.,  Harrey et al.,  and Schurman and Rojer.  Parsley et al,  stated that patients with little flexion before surgery tend to gain motion and those having a bigger flexion tend to loose it. In this study, patients with a flexion less than 90° have gained more motion than those with a flexion more than 90°.
Pre-operative flexion is considered the most critical determinant of postoperative flexion. ,,,,,,,, Poor and long-standing pre-operative flexion may result in bone and soft tissue changes, that may not be reversed by TKR.  There was a positive correlation between pre-operative and postoperative flexion; the better the pre-operative flexion, the better the post-operative flexion. However, good flexors tend to lose flexion while the poor flexors tend to gain some.  TKR can produce a predictable result, not totally dictated by poor pre-operative flexion. However, restoration or even improvement in ROM for those with good pre-operative flexion may be limited by implant design and soft tissue tension.
Shoji et al.,  studied 192 patients who underwent primary TKR; Patients were divided into 3 groups according to their postoperative knee flexion. In patients with a flexion of more than 120°, only 7% were obese. In contrast, patients who had flexion between 100° and 120°, 28% were obese. In patients with flexion of 100° or less as many as 78% were obese. Patient who were very obese had large thigh and acted as mechanical block to restrict flexion, in spite of good surgical technique.
Other factors such as age, sex, etiology, type and kind of prosthesis did not show much evidence in influencing the outcome on postoperative ROM at the end of one year follow up interval.
Wound closures were performed on the knee with flexion from 90° to 110°. Loss of flexion occurs due to the relative shortening of the extensor mechanism, together with the skin tightness, if the wound was closed with the knee extended. In a study done by Emerson et al.,  it was found that the flexion range of the flexion-closure group surpassed the pre-operative flexion range by 2° six months post-operatively, whereas the extension-closure group had 4° less flexion compared with their pre-operative flexion.
Patellar replacement was a controversial topic in TKR and still its influence on post operative range of motion is not clear. Even in our result, replacing the patella did not improve the ROM, but it increases PFS post operatively.
By saving the Posterior Cruciate Ligament (PCL), femoral rollback is preserved. This step, together with modification of the prosthetic geometry, provides greater posterior clearance and permits more flexion motion. Femoral rollback can also be achieved by substituting the PCL with a posterior stabilized design with a femoral cam mechanism.
A meta-analysis of 130 studies reporting patient outcomes after TKR  found that the mean range of motion was 99° (range, 84°-113°) after a PCL sacrificing TKR, 107° (range, 65°-123°) after PCL retaining knee surgery and 103° (range, 85°-115°) after PCL-substituting knee surgery.
Our study has failed to show better flexion with PCL retain knees. But the number of cases with Cruciate Substitute and Cruciate Retain knees was not equal to have a fair comparison to drive into any conclusion in our study.
| Conclusion|| |
Yes, the pre-operative flexion significantly influenced the post operative flexion and it is a good parameter for predicting the post operative outcome, were the conclusion derived out on the basis of results shown from our study. However, good flexors tend to have less gain in flexion while the poor flexors tend to gain more. Patients with BMI >30 or <25 can be a predictor for poor and good postoperative ROM respectively.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9], [Table 10]