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ORIGINAL ARTICLE Table of Contents   
Year : 2003  |  Volume : 37  |  Issue : 3  |  Page : 2
Clinical and radiological results of the PCL substituting prosthesis


Department of Orthopaedics, Lok Nayak & G. B. Pant Hospitals, Maulana Azad Medical College, New Delhi, India

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   Abstract 

Fifty one consecutive total knee replacements were performed in 34 patients with osteoarthritis and rheumatoid arthritis using the IB-II PCL substituting prosthesis between May1997 to April 2000. All these patients had deformities around their knees in the coronal plane i.e., they either had genu varum or genu valgum. Twelve of these suffered from rheumatoid arthritis and 22 suffered from primary osteoarthritis. Pre- and post-operative evaluation was done according to the Hospital for Special Surgery (HSS) scoring system. Radiographic assessment was done for tibio­femoral alignment and translucencies in the various zones. The results in the varus and the valgus knees were compared.
Seventy percent (36/51) of the knees had a varus deformity while 30% (15/51) had a valgus deformity. The mean tibio-femoral angle was 10.4 degrees in the varus group and 15.6 degrees in valgus group. The average pre-operative HSS score in the varus group was 22.5 and that for the valgus group was 25.5. After surgery, the score improved to an average of 85 in the varus group and 82.5 in the valgus group. All the patients in both the groups were of clinically poor functional range prior to the surgery. After the surgery, one case in genu valgum group and two cases in genu varum group showed clinically poor results. From this study, we conclude that total knee arthroplasty by using a posterior stabilized PCL substituting prosthesis, is an effective procedure for improving the functional capacity of the degenerated and deformed knees. It is also confirmed that varus deformed knees provide better functional results as compared to the valgus knees.

Keywords: Knee deformity - Deformity correction - IB II PCL substituting prosthesis

How to cite this article:
Dhaon B K, Upadhyay A, Jain V, Nigam V, Jaiswal A. Clinical and radiological results of the PCL substituting prosthesis. Indian J Orthop 2003;37:2

How to cite this URL:
Dhaon B K, Upadhyay A, Jain V, Nigam V, Jaiswal A. Clinical and radiological results of the PCL substituting prosthesis. Indian J Orthop [serial online] 2003 [cited 2019 Dec 11];37:2. Available from: http://www.ijoonline.com/text.asp?2003/37/3/2/48535

   Introduction Top


Deformities in coronal plane are relatively common in patients of osteoarthritis (OA) and rheumatoid arthritis (RA). Such patients suffer from debilitating pain and stiffness and are the candidates for total knee arthroplasty. The importance of proper axial alignment after total knee replacement has been widely accepted for successful results. [1],[2],[3] It is widely held that the varus knees definitely do better than the valgus knees, the alignment of which is more difficult to correct. [3] This study was aimed to assess the clinical results of total knee arthroplasty using the PCL substituting prosthesis [4] in Indian population. The radiological correction following total knee arthroplasty was also assessed. Separate assessment of the outcomes in the varus knees from the valgus knees was made. We also compared our results with the previously available studies in the literature which have mostly been done in the western world.


   Material and Methods Top


From May 1997 to April 2000, 51 total knee arthroplasties were performed in 34 patients (12 male and 22 females; average age 64.2 years) suffering from degenerative and inflammatory diseases of knee, using an IB-II PCL substituting prosthesis. Twelve patients had RA and 22 patients had OA. Bilateral replacement was performed in 17 patients. The average pre-operative HSS score for varus knees was 22.5 (range 16-40) and that for valgus knees was 25.5 (range 13-33) [Table 1].

Radiological assessment: Pre-operative radiological assessment of affected knees was carried out using antero­posterior (taken in standing position), lateral and skyline views. Pre-operative tibio-femoral angle (TFA), i.e., the angle formed by the anatomical axes of femur and tibia, was defined. The template supplied by the implant manufacturer was used to decide the angle of the distal femoral cut aiming for a post-operative TFA 5 to 9 degrees valgus.

Operative technique: All the patients were operated under prophylactic antibiotic cover in the routine operation theatre using tourniquet. No prophylactic anticoagulant was given to any of the patients. The exposure was done using the anterior approach to the knee. The articular surfaces were implanted after putting the trial prosthesis following the bone cuts. The soft tissue balancing was done after putting the trial prosthesis. Posterior capsulotomy was done in patients who had residual flexion deformities after implanting the prosthesis. The incision was closed in 3 layers over a suction drain and a cylindrical slab was applied with the knee in 30 degrees of flexion.

Mobilization: The drain was removed after 24 hrs. and the wound was inspected on the 5 th post -operative day. At the same time, the posterior splint was also discarded and passive exercises through the range of motion were started. Full weight bearing mobilization was allowed on the 5 th post-operative day with the help of a walker.

Follow-up: The patients were followed up in the OPD every 3 months for 1 year and then every year. At each visit clinical evaluation was done using the HSS scoring system. Post-operative radiographs were taken in a way similar to the one described for the pre-operative evaluation. The TFA was measured to obtain the final alignment of the knee.


   Results Top


Thirty six knees had varus deformity while 15 had a valgus deformity. All the patients with OA had genu varum while majority of the patients with RA (75%) had genu valgum. The mean TFA was 14.4 degrees (range 1-25 degrees) in the varus group and 15.6 degrees (range 11-30 degrees) in the valgus group [Table 1]. The mean post-operative TFA in the varus group was 5.3 degrees of valgus (range 2-8 degrees) and in the valgus group 5.8 degrees of valgus (range 3-9 degrees) [Table 2]. The average flexion deformity was 9 degrees (range 0-30 degrees) in the varus group and 14.5 degrees (range 7-30 degrees) in the valgus group. There was no residual post-operative flexion deformity. The average pre-operative range of motion in the varus group was 58.3 degrees (range 10-90 degrees)). This improved to an average post-operative range of motion of 96 degrees (range 40-130 degrees). In the valgus group, the average pre-operative range of motion was 43.2 degrees (range 25-65 degrees). In the post-operative follow-up the average range of motion was 97.4 degrees (range 80-115 degrees). The average pre-operative HSS score in the varus group was 22.5 (range 16-40) and that for valgus group was 25.5 (range 13-33). After surgery, the score improved to an average of 85 (range 55-100) in the varus group and 82.5 (range 61-100) in the valgus group [Table 2]. All the patients in both the groups were of clinically poor functional range prior to the surgery. After the surgery, only one case in genu valgum group and two cases in genu varum showed clinically poor results. The poor result in varus group was in a patient of bilateral OA with severe varus deformity and stiffness of both the knees. In this patient bilateral partial avulsion of the patellar tendon had occurred during surgery inspite of quadriceps snip procedure. In the valgus group one knee got infected resulting into a poor outcome Delayed wound healing was seen in 2 patients suffering from RA One patient with a severe valgus deformity had a transient common peroneal nerve palsy which recovered after 4 weeks.


   Discussion Top


Most of the patients who undergo total knee replacements have coronal plane deformities around their knees. This could be genu varum as seen mostly in OA or genu valgum as seen usually in RA. The correction of the deformities while doing a total knee arthroplasty is very important for the function and life of the replaced knee [1] .

A straight appearing knee usually has a valgus of 5 to 9 degrees in mature women and 4 to 7 degrees in men. Thus, 5 to 9 degrees of valgus in the TFA is aimed for the normal biomechanics of the knee joint. Tew and Waugh 1 observed that the knees most likely to remain stable were those aligned to a TFA of 7 degrees. As opposed to the varus deformity the valgus knees present a trickier situation. This is a complex multiplanar deformity with varying degrees of flexion and external rotation deformity at the knee joint and secondary remodelling at the tibial diaphysis [3] . Thus good functional results are more difficult to obtain in valgus knees. In our series the valgus knees had a worse average post-operative HSS score (82.5) as compared to the varus knees (85) but the post­operative range of motion was marginally better. This is explained on the basis of the residual instability in the valgus knees which causes more pain and a subsequently reduced walking distance for these patients.

Karachalios et al [2] reported a valgus angle of 6 degrees in the post-operative period in patients who had an average pre-operative varus angulation of 24 degrees. In the group under our study, the average post-operative alignment was 5.3 degrees of valgus for a mean of 14.4 degrees varus in the pre-operative period. Ewald et al [5] and Teeny et al [6] had suggested that the pre-operative varus deformity had a tendency to stay in varus even after surgery. But none of our patients stayed in varus in the postoperative period and the minimum valgus angle after surgery was 2 degrees.

For the valgus knees, Krackow et al [7] reported a TFA of 18.1 degrees pre-operatively and 5.2 degrees post­operatively. Karachalios et al [2] reported the pre-operative angle to be 27 degrees and post-operative angle to be 9.2 degrees. In our study group, the patients with a valgus deformity had a pre-operative TFA of 15.6 degrees. This improved to a post-operative TFA of 5.8 degrees.

Teeny et al [6] reported an average flexion deformity of 3 degrees in patients with varus deformity. Our patients had an average flexion deformity of 9 degrees in the varus group prior to surgery. Following the surgery, none of our patients from the varus group showed a residual flexion contracture. But in two cases with pre-operative severe flexion contracture, there was an extension lag of 8 and 10 degrees. This extension lag subsequently improved with vigorous quadriceps exercises because after the correction of the flexion deformity, it is the weakened quadriceps musculature which leads to a residual extension lag. The valgus group had a mean pre-operative flexion deformity of 14.5 degrees prior to surgery.

Following surgery only one patient had a residual extension lag. We suggest that a rigorous pre-operative schedule of quadriceps drill can dramatically improve the post-operative outcome, especially in patients who have a pre-operative flexion deformity.

The average range of motion in the varus group was 58.3 degrees before TKR. This improved to an average of 96 degrees post-operatively. In the valgus group, the average pre- and post-operative range of motion was 43.2 degrees and 97.4 degrees respectively. Teeny et al have shown the average range of motion in the knee with pre-operative varus deformity to be 98 degrees. [6] Krackow et al reported a 99 degrees arc-of-motion in patients with pre-operative valgus deformities. [7]

Teeny et al [6] gave an average functional improvement of 61 points in the varus group. In our study, the average functional score in the varus group was 22.5 pre­operatively and 85 post-operatively. Thus we achieved an average improvement of 62.5 points. For the valgus group, Krackow et al [7] have reported an average improvement of 53.2 points from the pre-operative score. In our study, we achieved a functional improvement of 57 points, with the average pre- and post-operative scores being 25.5 and 82.5 respectively.

Karachalios et al [2] reported less than 1mm wide radiolucent lines around the tibia in 36% of cases with varus or valgus deformities. Twenty eight percent of their cases had less than 1 mm radiolucent lines around the femoral component. None of these finding are clinically significant enough as a precursor of implant loosening. In our study, we have not noticed significant radiolucent line around the tibial or femoral component. This is because our study is relatively short term and significant radiolucency at the bone-cement interface as a sign of component loosening appears only on long term use of the replaced knee. Laskin et al [8] reported the "Wedge Sign" representing a tension phenomenon in the cement on the convex side of an incompletely corrected deformity. This indicates an abnormal alignment of the prosthetic knee and is visible on x-rays soon after the surgery. We could not find this sign in any of our cases. This relates well with the corrective alignment that we achieved in the deformed knees of our patients.

Deep vein thrombosis (DVT) has been reported quite commonly in the western literature. Lotke et al [9] concluded that although 40-60% of the patients show evidence of thrombi in their calf veins most of them are not serious INDIAN JOURNAL OF ORTHOPAEDICS enough to warrant the use of prophylactic anticoagulant therapy. None of our patients had clinical symptoms suggestive of DVT although no prophylactic anticoagulant therapy was given. One patient suffered from post-operative infection. The patient was subjected to a thorough surgical toilet. The infection did not subside even after 6 weeks of intravenous antibiotics. Implants were removed as part of a two-stage procedure to eliminate the infection. One patient with severe OA with stiffness of both the knees suffered from avulsion of patellar tendon in spite of a quadriceps snip procedure. This resulted in pronged immobilization of the knee with a restricted range of motion. The patient showed poor results because of the decreased range of motion and medial tibial pain. Two patients had delayed wound healing over the lower end of incision, possibly due to their poor nutritional status and collection of haematoma which was not properly drained by the vacuum suction drain. Both these patients had rheumatoid arthritis. Stern et al [10] and Krackow et al [11] have reported an incidence of common peroneal nerve palsy in more than 3% of cases. All these cases had valgus deformities in the pre -operative period. In our study this incidence was less than 2%. After the study we conclude that total knee replacement by using a posterior stabilized PCL-substituting prosthesis is an effective procedure for improving the functional capacity of the degenerated and deformed knees. The surgeon can provide better functional results in varus knees as against the results in valgus knees and the complications are also less. The proportion of patients with valgus knees in our study was smaller than the varus knees so the representative character of the valgus results may be less than their counterparts in the varus group. Also, a longer term study may provide more information about the complications like aseptic loosening in these implants.[Figure 1],[Figure 2]

 
   References Top

1.Tew M, Waugh W. Tibio-femoral alignment and the re­sults of total knee replacement J Bone Joint Surg [Br] 1987; 67-B: 551.  Back to cited text no. 1    
2.Karachalios T, Sarangi PP, Newmann JH. Severe varus and valgus deformity treated by total knee arthroplasty. J Bone Joint Surg [Br] 1994; 76-B: 738-742.   Back to cited text no. 2    
3.Miyasaka KC, Ranawat CS, Mullaji A. 10 to 20 years folowup of total knee arthroplasty for valgus deformities. Clin Orthop 1997; 345:29-37.  Back to cited text no. 3  [PUBMED]  [FULLTEXT]
4.Insall JN, Lachiewicz PF, Burstein AH. The posterior stabilized condylar prosthesis: a modification of total condy-lar design. Two to four years clinical experience. J Bone Joint Surg [Am] 1982; 69-A: 1318.   Back to cited text no. 4    
5. Ewald FC, Jacobs MA, Miegel RE. Kinematic total knee replacement. J Bone Joint Surg [Am] 1984; 66-A: 1032.  Back to cited text no. 5    
6. Teeny SM, Krackow KA, Hungerford DS, Jones MM. Primary total knee arthroplasty in patients with severe varus deformity. Clin Orthop 1991; 273: 19-31.  Back to cited text no. 6    
7. Krackow KA, Jones MM, Teeny SM. Primary total knee arthroplasty in patients with fixed valgus deformity. Clin Orthop 1991; 273: 9-18.  Back to cited text no. 7    
8. Laskin RS, Schob CJ: Medial capsular recession for severe varus deformities. J Arthroplasty 1987; 2 (4): 313-316.  Back to cited text no. 8    
9. Lotke PA, Steinberg ME, Ecker ML: Significance of deep vein thrombosis in the lower extremity after total joint ar-throplasty. Clin Orthop 1994; 299: 25.  Back to cited text no. 9    
10. Stern SH, Moekel BH, Insall JN: Total knee arthroplasty in valgus knee. Clin Orthop 1991; 273: 5-8.   Back to cited text no. 10    
11. Krackow KA, Maar DC, Mont MA, Carrol C. Surgical decompression of peroneal nerve palsy after total knee ar-throplasty. Clin Orthop 1993; 292: 223.  Back to cited text no. 11    

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Correspondence Address:
B K Dhaon
TypeVI/11, Maulana Azad Medical College Campus, Kotla Road, New Delhi-110002
India
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Source of Support: None, Conflict of Interest: None


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    Abstract
    Introduction
    Material and Methods
    Results
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