Functional and radiological outcome of total knee replacement in osteoarthritis with varus deformity

R Sahaya Jose; Visnu Kannan

doi:10.4103/jodp.jodp_11_22

ORIGINAL ARTICLE

Year : 2022 | Volume : 5 | Issue : 2 | Page : 100-109

Functional and radiological outcome of total knee replacement in osteoarthritis with varus deformity

R Sahaya Jose¹, Visnu Kannan²
¹ Professor, Department of Orthopaedics, Sree Mookambika Institute of Medical Sciences, Kulasekaram, Tamil Nadu, India
² Postgraduate, Department of Orthopaedics, Sree Mookambika Institute of Medical Sciences, Kulasekaram, Tamil Nadu, India

Date of Submission	08-Feb-2022
Date of Decision	14-Feb-2022
Date of Acceptance	28-Feb-2022
Date of Web Publication	28-May-2022

Correspondence Address:
R Sahaya Jose
119, Jose Bhavan, Puthukudieruppu, Kanyakumari, Nagercoil - 629 001, Tamil Nadu
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jodp.jodp_11_22

Abstract

Aims: The aim of the study is to evaluate the functional and radiological outcome of total knee replacement for osteoarthritis knee with varus deformity, using medial parapatellar approach and posterior stabilized (PS) design. Settings and Design: This is a prospective observational study and nonprobability sampling technique. Materials and Methods: In this prospective study, 20 patients with osteoarthritis knee of Grades III and IV were selected according to Kellgren-Lawrence Grading system. In this study, we assess the functional outcome of total knee replacement using Knee Society Score and radiological outcome using radiographic alignment. The patients were regularly followed up for both functional and radiological outcome at 1^st, 3^rd, 6^th, 12^th, and 18 months and then yearly. Statistical Analysis Used: The collected data were analyzed by SPSS 20.00 using the Chi-square test. Results: Preoperatively, our overall mean Knee Clinical and Knee Functional Score was 30.9 and 36.45 which improved to 87.7 and 84 postoperatively with the significant P < 0.001. Our study shows that we have 80% of excellent and 15% good results following total knee replacement. Radiologically all patients have a near-normal radiographic alignment which in turn improves the functional outcome of the patients. Conclusion: Total knee replacement using nonconstrained, PS design and medial parapatellar approach gives functionally excellent pain relief, increased range of motion, restoration of normal function, low prevalence of patellofemoral complications, correction of varus and fixed flexion deformities, and restoration of normal mechanical alignment. Postoperatively, patients with near-normal radiographic alignment like femorotibial angle, posterior condylar offset, and posterior tibial slope have good functional outcome and faster rehabilitation. Correct positioning of the components axially and rotationally improve both the functional and radiological outcome. However, longer follow-up is needed to determine the long-term effect of Posterior Substitute Design.

Keywords: Kellgren-Lawrence grading, knee society score, osteoarthritis, total knee replacement, varus deformity

How to cite this article:
Jose R S, Kannan V. Functional and radiological outcome of total knee replacement in osteoarthritis with varus deformity. J Orthop Dis Traumatol 2022;5:100-9

How to cite this URL:
Jose R S, Kannan V. Functional and radiological outcome of total knee replacement in osteoarthritis with varus deformity. J Orthop Dis Traumatol [serial online] 2022 [cited 2023 Jun 5];5:100-9. Available from: https://jodt.org/text.asp?2022/5/2/100/346212

Introduction

Osteoarthritis is the most prevalent chronic joint disease due to degeneration of articular cartilage. The incidence of osteoarthritis is rising because of the aging population and the epidemic of obesity. Pain and loss of function are the main clinical features that lead to treatment, including nonpharmacological, pharmacological, and surgical approaches.^[1] Varus deformity of the knee is the most common angular deformity in osteoarthritis.^[2] The severity of the osteoarthritis can be graded according to the X-ray findings by the Kellgren-Lawrence (KL) system.^[3] Knee replacement surgery is a successful rewarding surgery done in tricompartmental osteoarthritis knee. A number of operations are now carried out every year worldwide with excellent results. Total knee replacement becomes necessary in patients with tricompartmental osteoarthritis in whom pain cannot be satisfactorily controlled by analgesics, physiotherapy involving static quadriceps strengthening exercises and intraarticular injections.^[4]

The advantage of primary total knee arthroplasty (TKA) is to re-establish the normal mechanical axis with a stable prosthesis that is well fixed.^[5] This is achieved by both the bone resection and the soft tissue balance. Surgical outcomes, patient satisfaction, and implant survival have improved steadily since its introduction and the operation has become widely accepted to afford relief of pain, restoration of range of motion (ROM), stability, and function.^[6] Medial parapatellar approach provides better visualization of the surgical field, reduced tissue trauma due to avoidance of excessive tissue compression by retractors, reduced surgical time and shorter learning curve for surgeons.^[7],[8] The posterior-stabilized condylar knee prosthesis which is one of the condylar prostheses developed and it was a modification of the total condylar knee prosthesis which is the “gold standard” for TKA longevity. It is a “posterior cruciate ligament-substituting” prosthesis, which has a tibial and femoral component articulation, that allows for femoral rollback during knee flexion. This mechanism make it both clinically and mechanically better.^[9] In our study, we use posterior substitute design for total knee replacement.

The Knee Society Score (KSS) system^[10] will assess the knee both clinically and functionally to provide a comprehensive scoring of the knee joint and will aid in assessing the functional outcome. The radiological outcome of TKA was assessed using radiographic alignment.

In our center, we do total knee replacement using medial parapatellar approach and posterior stabilized (PS) design for osteoarthritic patients with varus deformity and we have decided to evaluate the functional and radiological outcome of total knee replacement with the short-term follow-up of 18 months.

Materials and Methods

After getting Institutional Human Ethics Committee and Research Committee approval, this Prospective Observational Study was conducted among 20 patients who were diagnosed to have osteoarthritis knee with KL Grades III and IV with varus deformity up to 20° and Grade I and II flexion deformities.^[11] All the patients involved in the study were explained in detail and informed consent forms were obtained. We have included patients with age >60 years of either sex attending the orthopedic outpatients and inpatients department in our institution. Patients were grouped into one group based on nonprobability sampling technique. In our study, we have excluded the cases of rheumatoid arthritis with valgus knee, cases with Grades I and II KL grading, cases with any active infection, cases with previous high tibial osteotomy, neuropathic joint and skin disorders.

The most of the patients who underwent TKA were in the age group of 66–70 years which accounts 40% of our study. The minimum age of the patient was 61 years and the maximum age of the patient was 75 years. The mean age was 67 years. We have 11 female and 9 male patients in our study with a female preponderance. The male–female ratio is 1:1.2 in our study, accounting for about 55% female patients. The left knee joint was predominant in our study accounting for 55% of the patients. The severity of the arthritis was assessed with the KL grading system which revealed that 70% patients had Grade IV and 30% patients had Grade III system in our study. In our study, the mean follow-up period was 14.5 months. The maximum follow-up period was 18 months, whereas the minimum follow-up period was 12 months.

Preoperatively, the patients were assessed with the help of both knee society scoring system^[10] and knee radiographic evaluation system^[12] A detailed history was obtained from all patients in the study. The general condition of the patient was assessed and we also look for any fixed varus and flexion deformities and we also assess the extensor mechanism using MRC muscle grading.^[13] The patients involved in the study were explained in detail and informed consent was obtained. All patients underwent a weight-bearing anteroposterior (AP) view and a lateral view. These radiographs were done to assess the presence of osteophytes, joint space narrowing, subchondral sclerosis, loose bodies, subchondral cyst, bone defects over the femur/tibia, and bone stock evaluation. Full-length standing AP X-ray was taken to assess the mechanical axis and to determine the amount of varus deformity. In the AP and lateral view knee joint X-ray and computed tomography scan, we also assess the femorotibial angle, femoral-component axial and rotational alignment, tibial-component axial and rotational alignment, posterior condylar offset, and posterior tibial slope.

In our study, we use nonconstrained, PS, Maxx Freedom Knee System. Medial parapatellar approach^[14] was used for all the patients. Wound closure was done in flexion. All the patients were mobilized full weight bearing with walker support on the 2^nd postoperative day. Serial wound inspection is done on 2, 5, 8, 12, and 14^th postoperative day. Sutures were removed on the 14^th postoperative day. Regular postoperative follow-up is done on 1^st, 3^rd, 6^th, 12^th, and 18 months and then yearly follow-up was done. During the regular follow-ups, we assess the functional outcome using KSS^[10] and we assess the radiological outcome by assessing the femorotibial angle, femoral-component axial and rotational alignment, tibial-component axial and rotational alignment, posterior condylar slope, posterior tibial slope.^[12]

Results

A total of 20 cases were evaluated both clinically and radiologically. Clinical evaluation was done using the Knee Society Scoring System which reveals the following results.

According to the knee society scoring system, out of 20 patients, 16 patients (80%) had excellent results, three patients (15%) had good results and one patient (5%) had fair result [Figure 1].

Figure 1: Functional results in the study cases

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Before the surgery, four patients had a knee flexion of 70°, three patients had knee flexion of 75°, six patients had a knee flexion of 80°, three patients had knee flexion of 85°, and four patients had knee flexion of 90°. Postoperatively, in recent follow-up, four patients had a knee flexion of 120°, two patients had a knee flexion of 115°, seven patients had a knee flexion of 110°, two patients had a knee flexion of 105°, and three patients had a knee flexion of 100°. Two patients in this study had a knee flexion of 90°, respectively. The mean preoperative knee flexion was 80° and the mean recent postoperative knee flexion increased to 109 with a significant P < 0.001. There was an average increase in knee flexion of 29° postoperatively.

Preoperatively, 12 patients had severe pain with knee society clinical score of 0, six patients had moderate pain with score of 20, two patients had mild pain with score of 40. Postoperatively, in recent follow-up, 17 patients had no pain with score of 50 points. Two patients had mild pain with score of 40 and one patient had moderate pain with score of 20. No patient had severe pain with score of 0 points in this study. Postoperatively, all patients had good pain relief when compared to the preoperative status.

In this study, preoperatively, three patients cannot walk without support with knee functional score of 0, nine patients could walk <50 m with score of 15, five patients could walk <500 m with score of 25, and only three patients could walk more than 500 m with score of 35. Postoperatively, in recent follow-up, 10 patients could walk unlimited distance with knee functional score of 55, eight patients could walk more than 1 km with knee functional score of 50, and two patients could walk more than 500 m with score of 35. We did not have any patient with walking ability of <500 m.

Our overall mean preoperative Knee Clinical Score was 30.9 in our study, which improved to a mean postoperative score of 87.7 [Figure 2].

Figure 2: Comparison of knee clinical score in preoperative and recent postoperative follow-up periods

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Our overall mean Preoperative Knee Functional Score was 36.45, in our study which improved to a mean postoperative score of 84.7 [Figure 3].

Figure 3: Comparison of knee functional score in preoperative and recent postoperative follow-up periods

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Radiological evaluation was done by evaluating the femorotibial angle, posterior condylar offset, posterior tibial slope, femoral component axial and rotational alignment, and tibial component axial and rotational alignment.

The mean femorotibial angle preoperatively was 15.45° varus which was changed to 6.45° valgus postoperatively which is within the normal limit [Figure 4].

Figure 4: Comparison of femorotibial angle (°) in preoperative and postoperative cases

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The mean preoperative posterior condylar offset was 24.4 mm which increased to 27.6 mm postoperatively with a significant P < 0.001. There was a positive correlation between the postoperative increase in posterior condylar offset and an increase in postoperative knee flexion [Figure 5].

Figure 5: Comparison of posterior condylar offset in preoperative and postoperative cases

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In this study, preoperatively, one patient had a posterior tibial slope of 5°, four patients had a posterior tibial slope of 6°, eight patients had a posterior tibial slope of 7°, and seven patients had a posterior tibial slope of 8°. In our study, the mean posterior tibial slope was decreased from 7.05° to 5° postoperatively with a significant P < 0.001.

In this study, postoperatively, four patients had a femoral component valgus of 5°. Seven patients had femoral component valgus of 6°. Five patients had femoral component valgus of 7° and four patients had femoral component valgus of 8°, respectively.

In this study, postoperatively, four patients had a tibial component axial alignment of 87° and 88°, two patients had alignment of 89°. A maximum of 11 patients had neutral alignment of 90°and three patients had alignment of 91° and 92°.

Postoperatively, one patient had femoral component rotational alignment of 2.2°, two patients had alignment of 2.5°, three patients had alignment of 2.6°, three patients had a rotational alignment of 2.8°. A maximum of five patients had alignment of 3°. There were six patients with alignment of 3.2°and 4°, respectively.

In this study, postoperatively, five patients had tibial component rotational alignment of 16°, three patients had alignment of 17°. A maximum of 8 patients had alignment of 18°. There were four patients with alignment of 19°and 20°, respectively.

In our study, superficial skin infection was seen in 10% of patients, anterior knee pain was seen in 5% of patients, and 17 patients had no complications in this study [Figure 6].

Figure 6: Complications in the study cases

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Discussion

Total knee replacement in patients with osteoarthritis knee will significantly improve the functional outcome and quality of life like pain relief, deformity correction, and increased mobility. The posterior cruciate substituting design was found to be effective among the varied amount of implant designs available. A well-positioned and stable prosthetic construct and restoring the normal mechanical axis of the limb and joint line have been shown to have an important impact on the outcome of knee replacement. In this study, PS total knee replacement was done for 20 patients with severe tricompartmental osteoarthritis knee (KL Grades III and IV) with varus deformity.

Hoorntje et al.^[15] in their study on 327 TKA done patients, about 35% of patients were of Grade III KL grading and 8% of patients had KL Grade IV osteoarthritis. Oka et al.^[16] in their study on 193 patients with TKA about 10% patients were in Grade III and 90% of patients were in KL Grade IV osteoarthritis. In our study, we had 30% of osteoarthritis patients were in Grade III and 70% of patients were in Grade IV of KL grading system.

Tomek et al.^[17] carried out a study in 129 patients in which quadriceps sparing subvastus technique of TKA was compared with a medial parapatellar approach to determine which surgical technique led to better patient-reported function and less postoperative pain and opioid utilization and concluded that the quadriceps sparing subvastus technique yielded no significant early functional advantages or differences in opioid utilization compared with the medial parapatellar approach. In our study, all patients were operated on using the medial parapatellar approach.

Wood et al.^[18] in their study in 201 patients concluded that TKA with patellar resurfacing exhibited inferior clinical results as compared to TKA with patella retention. In Cho et al.^[19] study of 474 knees suggests that clinical and radiographic outcomes differ with patella retention in TKA. In our study, none of the patellas were resurfaced. All patellas were circumferentially denervated.

Faour et al.^[20] study of 516 knees concluded that better ROM recovery, short-term improvement in pain scores, better flexor muscle strength, and faster functional recovery when knees wounds were closed in flexion. In our study, wound closure was done in flexion for all the patients.

Richard^[21] reported a series of 100 patients with preoperative fixed varus or valgus deformities of 15 or more associated with flexion contractures. Such knees treated with PCL retention had less postoperative flexion, more severe residual flexion contractures, and less correction of the mechanical axis than knees with PCL substitution. In our study, preoperative varus deformity with flexion contractures was corrected in the patients using posterior substitute design TKA.

El-Ngehy et al.^[4] in their study the average preoperative knee flexion was 87.3°and the average postoperative knee flexion was 100.4°. In our study, the average knee flexion was 80° preoperatively which was increased to 109° postoperatively.

Haitham^[22] reported in their series of 45 knees, improvement of knee clinical score from 12.8 preoperatively to 91.5 postoperatively and the knee functional score improved from 36 preoperatively to 82 postoperatively. Lee et al.^[23] reported in their series of 168 knees, improvement of the mean knee clinical score from 21 preoperatively to 96 postoperatively and knee functional score from 39 to 77 in the mild varus group at 2-year follow-up and improvement of mean clinical score from 14 preoperatively to 97 postoperatively and the functional score from 33 to 79 in the severe varus group at 2-year follow-up. In our study, the mean clinical score improved from 30.9 preoperatively to 87.7 postoperatively and the mean knee functional score improved from 36.45 preoperatively to 84.7 postoperatively.

According to a study by Scott et al.,^[24] 83% of patients had excellent results, 15% patients had good results, none had fair results, and 2% had poor results. Steven M.Teeny et al.^[25] in their study reported that 59% of patients had excellent results, 41% of patients had good results, none had fair and poor results. Radhakrishna et al.^[9] in their study reported that 80% of patients had excellent results, 20% had good results, none had fair and poor results. Kadam et al.^[26] in his study reported that 80% of patients had excellent results, 12.5% of patients had good results, 5% of patients had fair results, and 2.5% of patients had poor results. Similarly, in our study, the outcome in 20 patients, excellent results [Figure 7], [Figure 8] and [Figure 9] were found in 80% of patients, good results [Figure 10] were found in 15% of patients, and 5% of patients had fair results [Figure 11], no patients had poor results [Table 1].

Figure 7: Case 1: Excellent result. (a) Preoperative X-ray. (b) preoperative standing, (c) preoperative knee extension, (d) Intraoperative, (e) postoperative X-ray: 18-month follow-up, (f) postoperative standing (18 months), (g) postoperative knee flexion (18 months): 0°-110°

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Figure 8: Case 2: Excellent result (a) preoperative X-ray, (b) preoperative standing, (c) preoperative knee extension, (d) intraoperative, (e) postoperative X-ray: 18-month follow-up, (f) postoperative standing (18 months), (g) postoperative knee flexion (18 months): 0°–100°

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Figure 9: Case 3: Excellent result. (a) Preoperative X-ray, (b) preoperative standing, (c) preoperative knee extension, (d) intraoperative, (e) postoperative X-ray: 18-month follow-up, (f) postoperative standing (18 months), (g) postoperative knee flexion (18 months): 0°–110°

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Figure 10: Case 4: Good result. (a) Preoperative X-ray, (b) preoperative standing, (c) preoperative knee extension, (d) intraoperative, (e) postoperative X-ray: 12-month follow-up, (f) postoperative standing (12 months), (g) postoperative knee flexion (12 months): 0°–90°

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Figure 11: Case 5: Fair result. (a) preoperative AP X-ray, (b) preoperative Lateral X-ray, (c) preoperative standing, (d) preoperative knee extension, (e) intraoperative, (f) postoperative X-ray: 12-month follow-up, (g) postoperative standing (12 months), (h) postoperative knee flexion (12 months): 0°–90°

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Table 1: Comparison of functional results with previous studies

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According to a study by Mullaji et al.^[27] (2005) in 173 knees, the mean tibiofemoral angle of 22.7 degrees of varus preoperatively (range, 15°–62°) was corrected to 53° valgus (range, 2°–9°) postoperatively. This is comparable to our study where the mean preoperative varus was significantly improved from 15.45° (range, 12° to 20°) to the postoperative valgus of 6.45° (range, 5°–8°).

In the study done by Tew and Waugh,^[28] 428 knee replacements followed up for 1 to 9 years were analyzed. It has shown that the lowest risk of failure occurs when the coronal tibiofemoral angle is in the “correct” range, varus 2°-valgus l2° and that this alignment is most likely to be maintained if an angle of around 5° of valgus has been achieved at operation and supports the hypothesis that a postoperative tibiofemoral angle near 7° valgus will contribute to, the highest continuing success rate. In our study, the mean preoperative varus was significantly improved from 15.45° (range, 12° to 20°) to the postoperative valgus of 6.45° (range, 5°–8°). There is less chance for the failure of components to occur in our study.

The study of Bellemans et al.^[29] found that the posterior condyle offset was related to the final flexion range in 150 consecutive knee arthroplasties. For every 1 mm increase in the posterior condyle offset, the maximum postoperative flexion will increase by 6.1°. In our study, postoperative posterior condylar offset increased by a mean of 3.20 mm and the knee flexion increased by a mean of 29° with a significant P < 0.001.

Okazaki et al.^[30] in their study in 40 knees indicated that when the posterior tibial slope decreased by 5°, the flexion gap decreased by 1.9 mm with cruciate-retaining-TKA and 1.2 mm with PS-TKA. In our study of PS total knee replacement, the mean posterior tibial slope decreased from 7.05° preoperatively to 5° postoperatively.

Longstaff et al.^[31] in 2009 conducted a study on 151 knee arthroplasties performed between 2003 and 2004 and reported that patients with neutral femoral alignment (±2°on neutral FMA) had better KSS scores at 1-year follow-up. In our study, all 20 patients had the femoral component alignment ranges from 5° to 8° valgus to the long axis of the femur with the maximum number of patients having 6° valgus and showing better KSS at recent postoperative follow-up.

According to a study by Berend et al.,^[32] 20 knees were revised for medial bone collapse which was associated with varus tibial component alignment more than 3.0°. In our study, the tibial component alignment ranges from 87° to 92° (<3.0°) to the long axis of the tibia with the maximum number of patients having 90°. There is less chance of tibial component failure among patients in our study.

According to Berger et al.^[33] in 75 knees, “rotational alignment of the femoral component can be accurately estimated using the posterior condylar angle. The posterior condylar angle, referenced from the surgical epicondylar axis, provides a visual rotational alignment check during primary arthroplasty and may improve the alignment of the femoral component at revision.” The rotational alignment of the femoral component in their study yielded a mean posterior condylar angle of 3.5° (±1.2°) of internal rotation. In our study, posterior condylar line was used as a reference and the mean rotational alignment of the femoral component for the femur was 3° internal rotation which is within the normal limit.

According to the study, Berger and Rubash,^[34] the ideal placement of the tibial component is 18 ± 2° of internal rotation. In patients who present with malfunctioning TKA and patellofemoral problems or rotational instability in an otherwise well aligned, well-fixed, and sterile TKA, rotational malalignment should be suspected. In our study using the external alignment jigs for tibia, the mean rotational alignment was 17.7° which is within the normal limit. There is less chance of patellofemoral problems or rotational instability in our study.

According to the study by Guirro et al.^[35] in 3000 prospective TKA, 2% of patients had superficial infections. Peersman et al.^[36] conducted a study on 113 knees, 14% of patients had superficial infections. In our study, 10% of patients had a superficial infection at 1-month follow-up. Patients were treated with antibiotic therapy for 6 weeks. The patients were recovered from acute superficial infection without any residual deformity and restricted ROM of the involved knee [Table 2].

Table 2: Comparison of superficial infection rate with previous studies

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According to the study by Sensi et al.^[37] in 50 patients, 8% of patients had anterior knee pain, in our study, 5% of patients had anterior knee pain. The pain was mild to moderate in these patients so patients were treated conservatively with analgesics and quadriceps strengthening exercises [Table 3].

Table 3: Comparison of anterior knee pain rate with previous studies

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Villanueva et al.^[38] in their study, 6 patients with dislocation of the knee following TKA are reported. The causes for the dislocations were an imbalance of the flexion gap, an inadequate selection of implants, malrotation of components leading to the incompetence of the extensor mechanism, or rupture of the medial collateral ligament. In our study, there were no knee dislocations reported after TKA.

In our study, two patients with diabetic mellitus had a complication of superficial skin infection postoperatively. Patients were treated with antibiotic therapy and good diabetic control. The patients were recovered from acute superficial infection without any residual deformity and restricted ROM of the involved knee.

In our study, one patient had a fair result. She was diagnosed to have severe osteoarthritic changes in the contralateral knee. The patient's functional outcome is reduced because of severe pain in the contralateral knee joint.

There is a limitation of our study due to short-term follow-up and low numbers of patients.

Conclusion

Total knee replacement using nonconstrained, PS design and medial parapatellar approach gives functionally excellent pain relief, increased ROM, restoration of normal function, low prevalence of patellofemoral complications, correction of varus and fixed flexion deformities and restoration of normal mechanical alignment. Postoperatively, patients with near-normal radiographic alignment like femorotibial angle, posterior condylar offset, and posterior tibial slope have good functional outcome and faster rehabilitation. Correct positioning of the components axially and rotationally improves both the functional and radiological outcome. However, longer follow-up is needed to determine the long-term effect of posterior substitute design.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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