Does Surgical Technique Influence Patient Satisfaction after the Triathlontm Knee Replacement?

Research article

Does Surgical Technique Influence Patient Satisfaction after the Triathlontm Knee Replacement?

Corresponding author:Gordon Bannister, Department of Orthopaedics, North Bristol NHS Trust, 19, Cranbrook Road, Redland, Bristol, BS67BL, UK. Tel: 0044 117 9248440; Email: gordon-bannister@tiscali.co.uk

Abstract

Patient satisfaction varies after primary total knee arthroplasty (TKA), is established within three to six months of surgery and may be better with the TriathlonTM TKA. Early recovery is improved by the subvastus approach and intra-operative, local anaesthetic field block and patient satisfaction by patellar resurfacing. Our hypothesis is that the combination of these techniques improves patient satisfaction with the TriathlonTM further.

A questionnaire including patient satisfaction and the Oxford Knee Score (OKS) was sent to 267 consecutive patients who had received a TriathlonTM TKA by the above standardised technique under the care of one surgeon comparing the results with a contemporanous series of the same TKA from the same centre.

The response rate to the questionnaires was 68.9%. 11.6% of patients were not satisfied. They were significantly more likely to have a lower OKS, higher OKS pain score, less improvement in the OKS pain score, less improvement in walking distance, greater reliance on walking aids, more post-operative complications and less fulfillment of their expectations than those who were satisfied.

The TriathlonTM gives high levels of patient satisfaction but the surgical technique used here does not improve upon results reported elsewhere.


Keywords
: Knee; Arthritis; Arthroplasty; TriathlonTM; Subvastus approach; Patient Satisfaction.

Introduction

Increasing numbers of total knee arthroplasties (TKAs) are being performed [1] but some 17% of patients in the National Joint Registry of England and Wales [2] and Swedish Knee Arthroplasty Registry [3] are not satisfied with the outcome. A recent systematic review reported the median  percentage of satisfied patients was 88.9% [4] . Patient satisfaction after TKA in the literature ranges from varies from 75% [5] to 98% [6] (Table 1).

The TriathlonTM (Stryker, Kalamazoo, MI, USA) is a third generation high-flexion TKA with a single radius, shorter posterior condyles and consistent posterior condyles between sizes. It was introduced to increase the range of motion and has been increasingly implanted in England and Wales [1]. The TriathlonTM has better instrumentation than its predecessor, the Kinemax Plus (Stryker, Kalamazoo, MI, USA), and gives higher levels of patient satisfaction than the Kinemax Plus and most other prostheses (Table 1). The quadriceps sparing, subvastus approach improves early recovery after TKA compared with a medial parapatellar approach [7]. Patellar resurfacing reduces the rate of revision and improves patient satisfaction [3] and intra-operative local anaesthetic field blocks reduce post-operative pain [8]. As patient satisfaction with TKR is established within three to six months of the procedure [9,10] we hypothesized that the better earlier recovery promoted by the subvastus approach, patellar resurfacing and local anaesthetic field block would combine to improve patient satisfaction with the TriathlonTM in the medium term.

Material and Methods

We explored this hypothesis by recording the patient reported results of the primary TriathlonTM TKAs performed on 261 patients (282 TKAs) at one elective orthopedic center over a four year period. A questionnaire was sent to each patient at a mean 2.5 years (0.6 – 4.5) after TKA. The 20 patients with bilateral TKAs were sent a separate questionnaire for each knee. At follow up 14 patients had died (one with bilateral TKAs) leaving 247 consecutive patients (267 TKAs) for inclusion in the study. The outcome measures were the patient-reported satisfaction [10], the Oxford knee score (OKS) [11], pain, walking distance, use of walking aids, rate of recovery, return to work and fulfilment of pre-operative expectations [10,12]. Patient reported satisfaction comprised four categories. The very satisfied and satisfied were combined into one category denoted as ‘Satisfied’ and the unsure and dissatisfied into ‘Not satisfied’ [2].

Surgery was performed either by or under the direct supervision of the senior author. In all cases, a posterior cruciate-retaining TriathlonTM TKA system (Stryker, Kalamazoo, MI, USA) was implanted under tourniquet with a subvastus approach, patellar resurfacing and intraoperative field block of 40ml 0.25% Bupivacaine with Adrenaline (1 in 200,000). 20ml was infiltrated into the posterior capsule before cementation and a further 20ml to the incised capsule and skin edges while the cement was polymerizing.  The tourniquet was released immediately after cementation of the prostheses and field block before wound closure and hemostasis secured. A standardized post-operative rehabilitation regime was used for all patients aimed at mobilization the day after surgery. Thromboprophylaxis with 150mg aspirin was used for 35 days.

Results were compared with a contemporaneous study from the same unit [13] in which the TriathlonTM TKA was implanted by a variety of techniques by a number of surgeons and the published literature (Table 1)

The study was approved as a service evaluation audit by the institutional clinical audit department and informed, written consent was obtained from all participants included in this study. The nature of this approval for the study required that a single questionnaire be sent once to each patient. No further questionnaires or telephone contact were permitted and non-responders could not be pursued further.

Data were analysed using SPSS version 20.0 (SPSS Inc, Chicago, Illinois). The assumption of normal distribution was tested using a Kolmogorov-Smirnov test. Continuous variables were compared between groups with a two-tailed t-test for normally distributed and a Mann-Whitney U test for non-parametric data. The chi-squared test was used to compare categorical data between groups, however if the expected number was less than five a Fisher’s Exact test was used. Correlation was assessed using Spearman’s rank test. All tests were two-tailed and a p-value of <0.05 was considered statistically significant.

Results

184 questionnaires were returned from 168 patients giving an overall response rate of 68.9%. Not all questionnaires were fully completed therefore response rates for different parts of the questionnaire varied. There was no significant difference in patient demographics between responders and non-responders.

38.6% (n=68) patients reported no knee pain, 56.8% (n=100) minimal or no pain (0-1 out of 10) and 19.9% (n=35) moderate to severe pain (5-10 out of 10). In 8.5% (n=15), pain was unchanged or worse post-operatively. The mean postoperative OKS was 34.9 (n=182, SD 10.6, range 4-48) and median 39 (n=182, IQR 29-43).  The mean walking distance increased in 65.9% (n=108) patients and deteriorated in 6.7% (n=11). Overall 42.6% (n=72) could walk more than 1km post-operatively compared with 12.7% (n=21) pre-operatively. 76.2% (n=32) of patients who could walk more than 100m pre-operatively could walk more than 1km post-operatively but 23.1% (n=9) of patients walking less than 10m pre-operatively were still confined to this distance. 56.8% patients reported additional co-morbidities including back pain, hip pain and respiratory or cardiovascular disease that restricted their walking distance. A walking aid was used by 58.0% (n=105) of patients pre-operatively and 48.6% (n=88) post-operatively. Post-operatively, a walking aid was used by 90.0% (n=9) of pre-operative frame users, compared to 58.9% (n=56) of pre-operative stick users and 30.3% (n=23) of patients who had previously used no aids. 70% (n=7) of pre-operative frame users still used a frame post-operatively, compared to 2.1% (n=2) pre-operative stick users and 2.6% (n=2) of patients who had used no aids. Patients using no walking aids pre-operatively were more likely to deteriorate than those using them (30.3% vs. 1.9%, p<0.0001).  The median time taken to return to current function was between three and six months. 48.5% (n=83) reached their current level of function within 6 months and 75.4% (n=129) in less than 1 year. 24.6% (n=42) took more than 1 year to return to their current level of function. At the time of questionnaire 50.6% (n=84) were still noticing improvements in their knee. 6.0% (n=47) patients worked pre-operatively of whom 76.6% (n=36) returned post-operatively. 46.4% (n=83) reported that their knee had limited their ability to work pre-operatively. Only 40.5% (n=15) of those who returned to work resumed full time or normal duties and 13.5% (n=5) part time, light duties. No patient not working pre-operatively worked post-operatively. In patients aged under 65 there were 64.6% (n=31) who worked pre-operatively, 83.9% (n=26) of whom returned post-operatively.68.6% (n=120) of all patients reported being unable to do activities or hobbies that they wanted to pre-operatively compared to 45.2% (n=76) post-operatively.

Overall 21.5% (n=38) thought that the operation had not met their expectations almost 45% of whom (n= 17) were not satisfied with their TKA. 79.5% (n=132) expected pain relief and 44.6% (n=74) improvement in mobility or activity. Patients who reported that the operation had met their expectations had a better OKS (38.2 vs. 22.3, p<0.0001) and greater improvement in pain score (6.9 vs. 2.6, p<0.0001) than those whose expectations had not been met. We considered that 10.2% (n=17) aspired to unrealistic expectations given the limitations of TKA. They expected ‘to be normal’, ‘a normal knee’, ‘a normal life’, ‘to walk perfectly normally’, ‘to regain full mobility’, ‘to be as agile as pre-degenerative changes’, ’to be fully functional’, ‘it would be perfect’, ‘to be complete pain free’ and ‘to do anything with it’. Despite this 58.8% (n=10) of these thought that the operation had met their expectations.

47.9% (n=70) patients were very satisfied, 40.4% (n=59) were satisfied, 4.1% (n=6) were unsure and 7.5% (n=11) were dissatisfied. Overall 88.4% (n=129) were satisfied and 11.6% (n=17) were not satisfied. Patients who were satisfied had a higher OKS (p<0.001), lower post-operative pain score (p<0.001), greater improvement in walking distance (p<0.001), used walking aids less frequently (p=0.003), reported fewer post-operative complication (p=0.02), fewer further procedures on their TKA (p=0.004) and continuing improvement in their TKA (p<0.001), felt that their knee was better than before the operation (p<0.001), with hindsight would have the operation again ( p=0.007), would recommend the operation to a friend ( p=0.002) and had more of their expectations  met by the operation (p=0.002) (Table 2). There was no significant difference between the pre-operative pain scores, age, gender or operated side between those who would be satisfied and those who would not (Table 2).

Discussion

Retrieval in the literature varies from 29% [13] to 94% [6] with a mean of 77% and was relatively low in this study because of the restriction of the institutional approval to a single postal contact. As in previous work, lack of patient satisfaction was associated with pain and function [2,10,12-14] , complications [2,13,14] and unfulfilled expectation [9,12,14,5,15]. 

The OKS [2, 6, 17], walking [15], rate of recovery [9, 10] and return to work [17] and recreational activity [18] were comparable to other reports. Scott et al [18] (2012) from Edinburgh, Scotland, UK and Kim et al [19] (2015) from Seoul, Korea both stratified respectively 17 and 11 aspirations of patients and the degree to which they were met. Ability to perform acts of daily living and pain relief were common to the first four aspirations of both. The Scottish patients prioritized walking without aids and negotiation of stairs whilst the Koreans favored high flexion activities. Negotiation of stairs and high flexion activity were realised least frequently in both studies. The TriathlonTM TKR does not achieve the higher flexion it was designed to deliver [20].

Patient satisfaction is one of the main aims of TKR but varies over time [21] and in different studies of close temporal relationship from the same center. In Edinburgh, Scotland (Table 1), a rate of satisfaction of 83% with the Kinemax Plus and Triathlon in a retrospective review [10] increased to 93% and 98% [6] respectively in a controlled trial suggesting that the Hawthorne effect of following up patients carefully to assess outcome improves satisfaction

All patients in this study who were not satisfied failed to have their expectations satisfied even though they were met more frequently in this series than in other studies [15,16].  Many authors suggest that expectations can be managed by appropriate informed consent before surgery but retention of the information from this can be as low as 21% [22].

The strength of this study is the standardization of prosthesis and surgical technique, the identification of persistent inability to walk distances if surgery is delayed until the preoperative distance is less than 10m and the association of continuing improvement with patient satisfaction. It is the only study to standardize both the prosthesis and surgical technique. The weakness is the retrieval rate and that it is a retrospective Level 4 review.

The standardization of technique and the availability of a contemporary study [13] from the same institution using the same prosthesis but different operative techniques disprove the hypothesis that a combination of a subvastus approach and perioperative local anesthetic field block with patellar resurfacing improves patient satisfaction after the TriathlonTM TKA.

The implications of this study are that in current practice, 90% of patients should be satisfied after TKA. There is potential to improve this by individually targeted informed consent to clarify patient expectation provided patients retain the information and improving the technical performance of TKA to minimize post-operative complications and further surgery.

References 

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