A prospective study to review the functional outcome between patellofemoral resurfacing versus non resurfacing in total knee replacement

INTRODUCTION

The role of universal patellar resurfacing in total knee arthroplasty remains controversial. Patellar resurfacing was not a feature of many early total knee arthroplasty designs.¹ Using such historic designs, anterior knee pain was problem in about 40% to 58% of patients.² Many Orthopedicians used to perform patellar resurfacing routinely only to decrease incidence of anterior knee pain and rate of revision caused by patellofemoral problems.³ Patellofemoral problems seen in 5% to 30% of contemporary tricompartmental designs, have become a major cause of morbidity and reoperation in TKA with patellar resurfacing.⁴ Patellar resurfacing can result in complications (including fracture, patellar, component failure, osteonecrosis, instability, tendon rupture and patellar clunk syndrome).⁵ Because of such complications now attention is being shifted to patellar non-resurfacing. Modern prostheses are designed to incorporate the patella in a way that it reduces contact stress between patella and prosthesis, so that they behave like normal patellofemoral joints, consequently reducing postoperative AKP.⁶ The cause of anterior knee pain after replacement was may be due to soft tissue afflictions (such as tendinitis, bursitis, plica syndrome and neuroma), reflex sympathetic dystrophy and maltracking. Routinely performed patellar resurfacing has reduced patellofemoral-related pain but prospective randomised trials have not provided consistent results in the short- to medium-term.⁷ Numerous controlled clinical trials have compared TKA clinical outcomes between patellar non-resurfacing and resurfacing procedures, but results have been inconclusive.⁸ In this present study the nonresurfacing group patella was treated by removal of osteophytes. Patella was reshaped to match the trochlea of the femoral prosthesis and circumpatellar denervation was done. Whereas in resurfacing group the patella was resurfaced with a cemented component and the incidence of AKP and knee function between the patellar resurfacing and nonresurfacing groups was compared. The main aim of this study was to produce evidence-based indications for patellar resurfacing in knee replacement. Our hypothesis was that patellofemoral resurfacing would influence the disease- specific outcome of osteoarthritic patients undergoing knee replacement.

METHODS

A randomized prospective double-blinded control study was conducted using predetermined outcome measures of knee replacement with and without patellar resurfacing. A total of 63 patients suffering from tricompartmental osteoarthritis were treated with TKA between April 2013 to September 2013 at Preethi hospital, Madurai. Inclusion criteria were patients with primary unilateral/bilateral TKA and those with degenerative osteoarthritis of the knee that did not respond to nonsurgical treatment. Exclusion criteria were patients with patellar resection, a history of patellar fracture, patellar instability treated with extensor reconstruction, high tibialosteotomy, a history of septic arthritis and osteomyelitis, serious medical illness limiting walking ability, and other lower limb joint disease. Ethical approval was given by the Medical Ethics Committee of our hospital. Written informed consent was obtained from all study participants. Data obtained will be recorded in MS Excel sheets and statistical data analysed using Windows SPSS version 22 software program.

Surgical procedures

All patients received the same type of cemented posterior stabilized prosthesis (PFC; Depuy Orthopaedics, Warsaw, USA). A standard anterior midline skin incision taken and medial parapatellar approach was adopted to open the knee joint. Bone cuts and soft-tissue balancing were performed in the sequential manner. In the patellar resurfacing group, patellar resurfacing was performed with a cemented inset oval dome component. The height of the patella was measured before and after operation with help of callipers, and in no case differed by more than 2 mm (Figure 1 group A). In the patellar non-resurfacing group, patellar osteophytes were removed, the patella was reshaped to match the trochlea of the femoral prosthesis, and the soft tissue around the patella was cauterized using an electro cautery to destroy the patellar innervation (circumpatellar denervation) (Figure 2). Optimal patellar tracking was ensured by appropriate soft-tissue balancing. If the patella subluxated during passive testing of the range of movement, a lateral release was performed ≥2.5 cm from the lateral patellar border.A standardized perioperative regimen was used for all patients. In detail, second generation 3 g/day cephalosporin was injected intravenously for 5 days from 1 day prior to the operation. After surgery, active static quadriceps strengthening exercise, active straight-leg raising and knee range of movements (flexion-extension) was encouraged in the immediate postoperative period. Walking with partial weight bearing was permitted 24 h postoperatively under the supervision of a physiotherapist and full weight bearing was started from postoperative day 3.

Study evaluation

A total of 63 patients were included in this study and were randomized in a two groups (group A patellar resurfacing group n=30. group B patellar non-resurfacing n=33). Preoperative evaluation was performed using the Anterior knee pain scale, knee society score, knee society function score and patient satisfaction score. Postoperative follow-up assessments were performed at 3 months, 6 months and 1 year respectively. Data was collected at the end of 1 year, and was analysed in this present study.

RESULTS

Total of 63 patients participated in this study and data from these patients were reviewed. During follow-up for the period of 1 year. In non resurfacing group there were 33 patients and 30 in the patellar resurfacing group were considered. In the resurfacing group, the difference between pre- and postoperative heights of the patellae was <2 mm for each patient. There were no statistically significant between-group differences regarding age, gender, body mass index, complaints of anterior knee pain, preoperative knee society scores (Table 3 and Table 4 respectively). The mean±SD duration of surgery was 80.3±20.4 min in the nonresurfacing group and 83.7±27.8 min in the resurfacing group; this difference was not statistically significant. Lateral retinacular release was performed in three patients in the nonresurfacing group and in one patients in the resurfacing group, with no significant between-group differences.

The findings of postoperative clinical evaluations are summarized in Table 4.

At 1 year postoperatively, there were no significance - group differences in terms of Knee Society Pain Score, Knee Society Function Score and Total Knee Society Score, but incidence of anterior knee pain was significantly reduced in patellar resurfacing group. All patients in this study underwent suture removal in post operative day 12^th however in 2 patients in non resurfacing group suture removal was delayed upto post operative day 15^th due to delayed healing problems as the patient were highly diabetic.

DISCUSSION

Whether to resurface the patella during a primary total knee arthroplasty performed for the treatment of degenerative osteoarthritis remains a controversial issue. Parameters that have been suggested as being useful in guiding this decision include patient height and weight (body mass index), the presence of anterior knee pain preoperatively. This present study compares the clinical outcomes of two modalities: patellofemoral resurfacing and patellar non-resurfacing. In our study there was no differences found in relation to knee society score and knee society function score between the two methods at the end of 1 year.

Anterior knee pain is a key search term when looking for literature describing optimal patellar treatment in Total knee arthroplasty. Patient having patello femoral arthritis and sever patellar degeneration have complaints of anterior knee pain. Various study show incidences of anterior knee pain with the patellar resurfacing regimen as 3.1% and in patellar non resurfacing group as 42%. The postoperative AKP rate in our present study was 12.1% in the non-resurfacing group and 6.5% in the resurfacing group. Study stated that there is significant difference in terms of anterior knee pain relief in patellar resurfacing group. In this present study, patella was replaced with the cemented polythene oval dome implant after proper assessment of patellar thickness with caliper measurement. Implant is more medialised to prevent lateral tracking of patella and to prevent alteration in biomechanics of patellar tracking, this also prevents incidence of anterior knee pain post TKA. In patellofemoral osteoarthritis, the patella get shifted laterally due to the loss as well as damage to the cartilage on the lateral facet, this increases the pressure in the lateral patellofemoral joint.⁹ In the study conducted by Liu reports that patellar thickness in the Asians is less than that of Western populations, with the thinnest part being only 13–14 mm.¹⁰ Hence patient selection for patellar resurfacing is very important. It is recommended to resurface patella only if patellar size is about 20-22 mm. It has been suggested that patients be stratified to receive patellar resurfacing by the condition of their patellar articular cartilage and the presence of preoperative anterior knee pain.

CONCLUSION

The result of study showed that there was significant improvement in anterior knee pain scale and incidence of anterior knee pain is comparative less in resurfacing group. However there is no significant difference for both group in functional outcome after period of 1 year follow up, except the patient’s satisfaction scale. Patellofemoral resurfacing should always be performed in patients who have symptoms of patellofemoral pain and severe degeneration in patellofemoral side. The use of an appropriate prosthetic design and careful surgical technique can provide good results of TKA even with or without performing patellar resurfacing. Resurfacing should only be done if patella size is about 20-22mm otherwise patellar resurfacing doesn’t have any added advantage nor an added benefit.

ACKNOWLEDGEMENTS

We thank Depuy Company who had provided PFC prosthesis for all 63 patients. We also thank concern Anaesthesist and OT staff who have contributed equally in this study by defining their own role of responsibility.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: The study was approved by the institutional ethics committee

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