No associations between self-reported knee joint instability and radiographic features in knee osteoarthritis patients prior to Total Knee Arthroplasty: A cross-sectional analysis of the Longitudinal Leiden Orthopaedics Outcomes of Osteo-Arthritis study (LOAS) data

Association of a Wider Medial Gap (Medial Laxity) in Flexion with Self-Reported Knee Instability After Medial-Pivot Total Knee Arthroplasty

BACKGROUND

Medial-pivot total knee arthroplasty (TKA) is designed with high articular conformity in the medial compartment in order to achieve stability. The subjective outcome of patients has been reported to be good postoperatively; however, the association between the objective and subjective knee stability and the influence of subjective stability on the overall outcomes of TKA remained unknown. Our hypothesis was that postoperative flexion joint-gap imbalance could affect subjective knee instability following TKA in medial-pivot prostheses. The purpose of this study was to analyze the association between the joint gap in flexion and subjective knee instability and between subjective knee instability and outcomes following medial-pivot TKA.

METHODS

A total of 769 patients who underwent primary TKA with use of medial-pivot prostheses were enrolled. Clinical outcomes included knee range of motion, Knee Society Score-2011 (KSS-2011), Forgotten Joint Score-12 (FJS-12), patient-reported subjective knee instability, and axial knee radiography to assess flexion joint-gap balance measured at the final follow-up. Clinical outcomes were compared between patients with and without subjective knee instability. Moreover, associated factors were analyzed for postoperative subjective knee instability.

RESULTS

Overall, 177 patients (23%) reported experiencing postoperative subjective knee instability. Knee flexion (p = 0.04); KSS-2011 symptom (p<0.001), satisfaction (p<0.001), expectation (p=0.008), and activity (p<0.001) subscales; and FJS-12 (p < 0.001) were significantly worse in patients with subjective knee instability. The KSS-2011 subjective score differences were greater than the minimal clinically important difference. Older age at the time of surgery (odds ratio, 1.04; p = 0.04) and a wider postoperative joint gap in flexion on the medial side (odds ratio, 1.21; p = 0.001) were significant risk factors for subjective knee instability. A gap angle of -2.9° (i.e., medial laxity) was the threshold to predict postoperative knee instability (sensitivity, 0.29; specificity, 0.91).

CONCLUSIONS

Postoperative flexion joint-gap laxity on the medial side following medial-pivot TKA affected the patient-reported subjective knee instability scores. Postoperative KSS-2011 subjective scores following medial-pivot TKA were poorer in patients with subjective knee instability.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Comparison of KOOS Scores of Middle-Aged Patients Undergoing Total Knee Arthroplasty to the General Dutch Population Using KOOS Percentile Curves: The LOAS Study

BACKGROUND

We aimed to investigate the application of the Knee Injury and Osteoarthritis Outcome Score (KOOS) percentile curves, using preoperative and postoperative data of patients with knee osteoarthritis undergoing total knee arthroplasty (TKA).

METHODS

We used Longitudinal Leiden Orthopedics Outcomes of Osteo-Arthritis study data of patients between 45 and 65 years and undergoing primary TKA. KOOS scores (0-100) were obtained preoperatively and 6, 12, and 24 months after TKA. Preoperative knee radiographs were assessed according to Kellgren-Lawrence (KL) in a subset (37%) of patients. Comorbidities were self-reported using a standardized questionnaire. The median (interquartile range) population-level KOOS scores were plotted on previously developed population-based KOOS percentile curves. In addition, we assessed the application of the curves on patient level and investigated differences in scores between patients with preoperative KL scores ≤2 and ≥3 and presence (vs absence) of comorbidities.

RESULTS

The study population consisted of 853 patients (62% women, mean age 59 years, body mass index 30 kg/m²) with knee osteoarthritis undergoing primary TKA. Preoperatively, median KOOS scores of all subscales were at or below the 2.5^th percentile. Scores increased to approximately the 25^th percentile 12 months postoperatively. Greater improvements were observed in pain and less improvements in sport and recreational function and quality of life. Patients with higher preoperative KL scores and without comorbidities showed greater improvements.

CONCLUSION

The KOOS percentile curves provided visual insights in knee complaints of patients relative to the general population. Furthermore, the KOOS percentile curves give insight in how preoperative patient characteristics are correlated with postoperative results.

Association Between Clinical Symptoms and Radiographic Features in Late-Stage Knee Osteoarthritis Using a New Radiographic Parameter

OBJECTIVE

In this study, we proposed a new radiographic parameter, the plateau attrition index (PAI), and the PAI grades (PAIs) to explore the relationship between subchondral attrition of the tibial plateau and symptoms of knee osteoarthritis (OA) in patients with late-stage knee osteoarthritis.

METHOD

One hundred nineteen patients with late-stage knee osteoarthritis were enrolled. The Kellgren and Lawrence (K/L) grades and hip-knee-ankle (HKA) angle were used to characterize the radiographic features of knee OA. The bone attrition of the tibial plateau was determined by the PAI and PAIs. The symptoms of knee OA were assessed by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), which is composed of the WOMAC pain (WOMP), WOMAC stiffness (WOMS), and WOMAC function (WOMF) subscores. WOMAC pain scores were divided into non-weight-bearing pain (NWBP) and weight-bearing pain (WBP) subcategories. The Pearson correlation coefficient was used to determine the relationship between the PAI, HKA angle, and WOMAC scores. The Spearman rank correlation coefficient was used to evaluate the correlation between the WOMAC score and the PAIs and K/L grades.

RESULTS

The distribution of the WOMAC scores according to the PAIs was significant (P < .01). A positive correlation was identified between the PAI and the WOMAC, WOMP, WOMF and WBP scores (r = 0.29, 0.34, 0.26 and 0.34, P < .01, respectively). In addition, the PAIs was also significantly correlated with the WOMAC, WOMP, WOMF, and WBP scores (r = 0.37, 0.38, 0.35 and 0.44, P < .01, respectively).

CONCLUSIONS

The attrition of tibial subchondral bone determined by the new parameter, the plateau attrition index, was correlated with symptoms, especially weight-bearing pain in late-stage knee OA.

Two-year RSA migration results of symmetrical and asymmetrical tibial components in total knee arthroplasty: a randomized controlled trial

AIMS

The objective of this study was to compare the two-year migration pattern and clinical outcomes of a total knee arthroplasty (TKA) with an asymmetrical tibial design (Persona PS) and a well-proven TKA with a symmetrical tibial design (NexGen LPS).

METHODS

A randomized controlled radiostereometric analysis (RSA) trial was conducted including 75 cemented posterior-stabilized TKAs. Implant migration was measured with RSA. Maximum total point motion (MTPM), translations, rotations, clinical outcomes, and patient-reported outcome measures (PROMs) were assessed at one week postoperatively and at three, six, 12, and 24 months postoperatively.

RESULTS

A linear mixed-effect model using RSA data of 31 asymmetrical and 38 symmetrical TKAs did not show a difference in mean MTPM migration pattern of the tibial or femoral components. Mean tibial component MTPM at two years postoperative of the asymmetrical TKA design was 0.93 mm and 1.00 mm for the symmetrical design. For the femoral component these values were 1.04 mm and 1.14 mm, respectively. No significant differences were observed in other migration parameters or in clinical and PROM measurements.

CONCLUSION

The TKA design with an asymmetrical tibial component has comparable component migration with the proven TKA with a symmetrical tibial component. This suggests the risk of long-term aseptic loosening of the two designs is comparable. Cite this article: Bone Joint J 2021;103-B(5):855-863.

Neuromechanical assessment of knee joint instability during perturbed gait in patients with knee osteoarthritis

Knee joint instability is frequently reported by patients with knee osteoarthritis (KOA). Objective metrics to assess knee joint instability are lacking, making it difficult to target therapies aiming to improve stability. Therefore, the aim of this study was to compare responses in neuromechanics to perturbations during gait in patients with self-reported knee joint instability (KOA-I) versus patients reporting stable knees (KOA-S) and healthy control subjects. Forty patients (20 KOA-I and 20 KOA-S) and 20 healthy controls were measured during perturbed treadmill walking. Knee joint angles and muscle activation patterns were compared using statistical parametric mapping and discrete gait parameters. Furthermore, subgroups (moderate versus severe KOA) based on Kellgren and Lawrence classification were evaluated. Patients with KOA-I generally had greater knee flexion angles compared to controls during terminal stance and during swing of perturbed gait. In response to deceleration perturbations the patients with moderate KOA-I increased their knee flexion angles during terminal stance and pre-swing. Knee muscle activation patterns were overall similar between the groups. In response to sway medial perturbations the patients with severe KOA-I increased the co-contraction of the quadriceps versus hamstrings muscles during terminal stance. Patients with KOA-I respond to different gait perturbations by increasing knee flexion angles, co-contraction of muscles or both during terminal stance. These alterations in neuromechanics could assist in the assessment of knee joint instability in patients, to provide treatment options accordingly. Furthermore, longitudinal studies are needed to investigate the consequences of altered neuromechanics due to knee joint instability on the development of KOA.

A High Proportion of Patients Have Unfulfilled Sexual Expectations After TKA: A Prospective Study

BACKGROUND

Most patients have high expectations about restoration of the knee function after TKA, expecting a more active life after retirement. However, 20% to 30% of patients report that their expectations are not met postoperatively. Among those unmet expectations may be the anticipation to engage in sexual activity after surgery, but few studies have evaluated sexual activity after arthroplasty.

QUESTIONS/PURPOSES

In this study, our purposes were (1) to evaluate the anticipation and the fulfillment of sexual activity after TKA in men and women, and (2) to identify prognostic factors for the fulfillment of anticipated postoperative sexual activity.

METHODS

This was a prospective, multicenter study of all 1371 patients scheduled for TKA between June 2012 and July 2015. The study was part of the Longitudinal Leiden Orthopaedics Outcomes of Osteoarthritis Study (LOAS). After screening according to LOAS inclusion criteria, 1213 respondents remained. Our primary study endpoint was whether sexual expectations were met 1 year after TKA; we used the sexual-activity-expectation question from the Hospital for Special Surgery (HSS) Knee Replacement Expectations Survey, which allows the patient to score the result on a 5-point scale. To assess postoperative fulfillment of sexual activity 1 year after TKA, we asked the patient to score the current status of sexual activity on the same 5-point scale: 1 (back to normal), 2 (large improvement), 3 (moderate improvement), 4 (slight improvement), and 5 (does not apply). Patients with incomplete data on the preoperative expectation- and postoperative fulfillment-question of sexual activity were excluded, leaving 71% (866 of 1213) patients for analysis. The difference between the pre- and postoperative scores determined whether expectations of sexual activity were unfulfilled (lower than expected) or fulfilled/exceeded (neutral or higher than expected). Pre- and postoperatively, the Knee Injury and Osteoarthritis Outcome Score (KOOS), the Short Form-12 Mental and Physical Component Summary scores (SF-12 MCS and SF-12 PCS), the EuroQoL-5 Dimensions (EQ-5D), and the EQ-5D VAS scale were used. Multivariate regression models were used for analysis.

RESULTS

Preoperatively, 54% patients (467 of 866) anticipated postoperative sexual activity after recovery from surgery. Both genders showed that the proportion who anticipated "back to normal" sexual activity decreased with higher age. Likewise, postoperative fulfillment of anticipated sexual activity was found in 58% (111 of 191 for men; 159 of 276 for women). Younger women (younger than 65 years of age) experienced fulfillment more often compared with younger men. A positive postoperative change in functional and health status was associated with fulfilled/exceeded scores of patients anticipating postoperative sexual activity. A better preoperative health status, the EQ-5D VAS score (odds ratio [OR] 1.02 [95% CI 1.01 to 1.03]; p = 0.006), was associated with a higher likelihood of fulfillment of anticipated postoperative sexual activity.

CONCLUSION

In both men and women, two of five patients who anticipated postoperative sexual activity indicated that their expectation of sexual activity was not met 1 year after TKA. These patients had worse functional recovery scores compared with patients who achieved the anticipated level of sexual activity. The latter is associated with functional recovery. Surgeons should be aware that many patients anticipate restoration of normal sexual activity, and that this may be the expectation for patients of all ages and for women and men alike. The results underscore the need for more qualitative research to understand this topic in greater depth.

LEVEL OF EVIDENCE

Level II, therapeutic study.

Preoperative Radiographic Osteoarthritis Severity Modifies the Effect of Preoperative Pain on Pain/Function After Total Knee Arthroplasty: Results at 1 and 2 Years Postoperatively

BACKGROUND

Osteoarthritis (OA) severity as demonstrated by preoperative radiographs and preoperative pain play an important role in the indication for total knee arthroplasty (TKA). We investigated whether preoperative radiographic evidence of OA severity modified the effect of preoperative self-reported pain on postoperative pain and function 1 and 2 years after TKA for OA.

METHODS

Data from the Longitudinal Leiden Orthopaedics Outcomes of Osteoarthritis Study (LOAS), a multicenter cohort study on outcomes after TKA, were used. OA severity was assessed radiographically with the Kellgren and Lawrence (KL) score (range, 0 to 4). Pain and function were evaluated with the Knee injury and Osteoarthritis Outcome Score (KOOS). After adjustment for body mass index (BMI), age, sex, and the Mental Component Summary scores from the Short Form-12, multivariate linear regression analyses with an interaction term between the preoperative KL score and preoperative pain were performed.

RESULTS

The study included 559 patients. The preoperative KL score was independently associated with 1-year postoperative pain and function (β = 5.4, 95% confidence interval [CI] = 1.4 to 9.4, and β = 7.7, 95% CI = 3.2 to 12.2), while preoperative pain was associated only with postoperative pain (β = 0.3, 95% CI = 0.1 to 0.6) and not with postoperative function (β = 0.2, 95% CI = -0.2 to 0.5). Comparable associations were found between 2-year postoperative pain and KL score (β = 8.0, 95% CI = 3.2 to 12.7) and preoperative pain (β = 0.5, 95% CI = 0.1 to 0.8) and between 2-year postoperative function and KL score (β = 7.7, 95% CI = 3.2 to 12.2). The study showed a trend toward the KL score modifying the effect of preoperative pain on 1-year postoperative pain (β = -0.1, 95% CI = -0.1 to 0.0) and 2-year postoperative pain (β = -0.1, 95% CI = -0.2 to 0.0) and on 1 and 2-year function (β = -0.1, 95% CI = -0.2 to 0.0 for both), with the effect of preoperative pain on postoperative pain and function seeming to become less important when there was radiographic evidence of greater preoperative OA severity.

CONCLUSIONS

Patients with less pain and higher KL grades preoperatively had better function and pain outcomes 1 and 2 years after TKA. However, the effect of preoperative pain on the postoperative outcomes seems to become less important when the patient has radiographic evidence of more severe OA. We believe that analysis of the severity of preoperative pain is an important proxy for optimal postoperative patient outcome.

LEVEL OF EVIDENCE

Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

The assessment of instability in the osteoarthritic knee

Patient-reported instability is a common complaint amongst those with knee arthritis.

Much research has examined the assessment of self-reported instability in the knee; however, no definitive quantitative measure of instability has been developed.

This review focuses on the current literature investigating the nature of self-reported instability in the arthritic knee and discusses the possibilities of further investigation.

Cite this article: EFORT Open Rev 2019;4:70-76. DOI: 10.1302/2058-5241.4.170079

Patient Expectations of Sexual Activity After Total Hip Arthroplasty: A Prospective Multicenter Cohort Study

Background

This study aimed to evaluate patients' expectations of postoperative sexual activity (SA) after total hip arthroplasty.

Methods

A prospective multicenter cohort study of 1,271 patients managed with total hip arthroplasty was performed using patient-reported outcome measures of the Longitudinal Leiden Orthopaedics Outcomes of Osteo-Arthritis Study (LOAS). Preoperative SA expectations and their fulfillment after 1 year were assessed with the Hospital for Special Surgery expectations survey. The Hip disability and Osteoarthritis Outcome Score (HOOS) was used to measure functional status, and the Short Form-12 Mental and Physical Component Summary scores (SF-12 MCS and SF-12 PCS) and EuroQol-5 Dimensions (EQ-5D) questionnaire were used to measure health status. Two subgroups were defined preoperatively: the SA-Expecting Group and the No-SA-Expecting Group. The postoperative outcomes with regard to SA (i.e., the difference between postoperative and preoperative SA scores) were classified as "unfulfilled" (score, ≤-1), "fulfilled" (score, 0), or "exceeded" (score, ≥1). Multivariate regression analyses were used, with t tests to compare means between groups.

Results

In total, 952 (74.9%) patients returned both preoperative and postoperative HSS questionnaires. Preoperatively, 605 patients (63.6%) expected to have postoperative SA. At 1 year, 43.5% of participants reported that this expectation was unfulfilled. In the No-SA-Expecting Group, 18.2% (63 of 347) regained SA, predominantly men. Postoperative SA fulfillment was related to preoperative musculoskeletal (p = 0.001) and non-musculoskeletal comorbidities (p = 0.004) and the postoperative HOOS, SF-12 PCS, SF-12 MCS, EQ-5D, and EQ-5D visual analog scale (VAS) scores (p < 0.001). Postoperative HOOS-symptoms (odds ratio [OR] 1.04; 95% confidence interval [CI], 1.02 to 1.06; p < 0.001), and HOOS-sport (OR, 1.01; 95% CI, 1.00 to 1.03; p = 0.032) were associated with postoperative SA fulfillment, as was older age (inversely; e.g., ≥76 years compared with ≤60 years: OR, 0.28; 95% CI, 0.13 to 0.62; p = 0.002). Correspondingly, for the No-SA-Expecting Group, higher age was also inversely associated with regaining postoperative SA (e.g., ≥76 years: OR, 0.07; 95% CI, 0.02 to 0.21; p < 0.001).

Conclusions

Of the patients who expected to be sexually active after surgery, 43.5% perceived this expectation to be unfulfilled; 24.3% were still sexually inactive despite most having expected a return to normal SA. Approximately one-fifth of patients who did not expect postoperative SA in fact regained SA. During preoperative consultations, surgeons should pay attention to expectation management surrounding SA.

Level of Evidence

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Self-reported knee instability associated with pain, activity limitations, and poorer quality of life before and 1 year after total knee arthroplasty in patients with knee osteoarthritis

Information on the association of self-reported knee instability with clinical outcomes after Total Knee Arthroplasty (TKA) and 1 year follow-up is scarce. The aims were to determine (i) the course and prevalence of self-reported knee instability before and 1 year after TKA and (ii) the associations of preoperative, postoperative, and retained self-reported knee instability with pain, activity limitations, and quality of life (QoL) in patients with knee osteoarthritis. Patients undergoing primary TKA, selected from the Longitudinal Leiden Orthopaedics and Outcomes of OsteoArthritis Study, had their knee instability measured using a questionnaire. The Knee injury and Osteoarthritis Outcome Score pain, activity limitations, and QoL subscales were administered before and 1 year after surgery. Multivariable regression analyses were performed to examine associations between knee instability, pain, activity limitations, and QoL, adjusted for covariates (age, gender, comorbidities, and radiographic severity). Of the 908 included patients, 649 (71%) and 187 (21%) reported knee instability before and following TKA, respectively. Of the patients with preoperative knee instability, this perception was retained in 165 (25%) cases. Knee instability was preoperatively associated with pain (B -9.6; 95%CI: -12.4 to -6.7), activity limitations (B -7.5; 95%CI: -10.2 to -4.8), and QoL (B -4.7; 95%CI: -7.0 to -2.4) and postoperatively with pain (B -15.0; 95%CI: -18.5 to -11.6), activity limitations (B -15.1; 95%CI: -18.4 to -11.8), and QoL (B -18.7; 95%CI: -22.3 to -15.3). Retained knee instability was associated with postoperative pain (B -15.1; 95%CI: -18.9 to -11.2), activity limitations (B -14.1; 95%CI: -17.8 to -10.4), and QoL (B -18.0; 95%CI: -21.7 to -14.3). In conclusion, in clinical care, self-reported knee instability is retained postoperatively in 25% of the patients. Retained knee instability is associated with more pain, activity limitations, and poorer QoL postoperatively. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2671-2678, 2018.

Self-reported Instability in Knee Osteoarthritis: A Scoping Review of Literature

BACKGROUND

Knee Osteoarthritis (OA) is a disabling musculoskeletal condition among the elderly. Self-reported instability is one of the impairments associated with osteoarthritis. A complete understanding of the self-reported instability in knee OA is essential, to identify the best strategies for overcoming this impairment. The focus of this scoping review is to provide an overview of evidence supported information about the prevalence and other associated features of selfreported instability in Knee OA. A broad search of the database PubMed with keywords such as knee osteoarthritis and instability resulted in 1075 articles. After title abstract and full-text screening, 19 relevant articles are described in the review. Overall, there is less amount of published literature on this topic. Studies reported prevalence rates of more than 60% for self-reported instability in knee osteoarthritis, which causes functional deterioration and high fear of falls. The most probable causative factors for self-reported instability in knee OA were altered sensory mechanisms and decreased muscle strength.

CONCLUSION

To conclude, self-reported knee instability in knee OA requires thorough evaluation and directed treatment with further studies providing rationalistic evidence-based management strategies. The current literature regarding self-reported knee instability is summarized, highlighting the research gaps.

Not Physical Activity, but Patient Beliefs and Expectations are Associated With Return to Work After Total Knee Arthroplasty

BACKGROUND

After total knee arthroplasty (TKA), 17%-60% of the patients do not or only partially return to work (RTW). Reasons for no or partial RTW remain unclear, warranting further research. Physical activity (PA) has proven beneficial effects on work participation. Therefore, we hypothesized that preoperative PA is associated with RTW after TKA.

METHODS

Working TKA patients participating in an ongoing prospective cohort study were included. Preoperatively and 1 year postoperatively, patients were asked to define their work status and PA level according to the Dutch Recommendation for Health-Enhancing PA and the Fitnorm. Multivariate logistic regression analysis was performed to assess the effect of PA on RTW, taking into account established prognostic factors for RTW among TKA patients.

RESULTS

Of 283 eligible patients, 266 (93%) completed the questionnaires sufficiently. Preoperatively, 141 patients (54%) performed moderate PA for ≥5 d/wk and 42 (16%) performed intense PA for ≥3 d/wk. Concerning RTW, 178 patients (67%) reported full RTW, 59 patients (22%) partial RTW, and 29 patients (11%) no RTW. Preoperative PA was not associated with RTW. Patients who reported that their knee symptoms were not or only partially work-related had lower odds of no RTW (odds ratio 0.37, 95% confidence interval 0.17-0.81). Also, for each additional week patients expected to be absent from work, the likelihood of no RTW increased (odds ratio 1.11, 95% confidence interval 1.03-1.18).

CONCLUSION

No association between preoperative PA and RTW after TKA was found. Patient beliefs and preoperative expectations did influence RTW and should be addressed to further improve RTW after TKA.

Frailty in end-stage hip or knee osteoarthritis: validation of the Groningen Frailty Indicator (GFI) questionnaire

Frailty is highly prevalent in the elderly, increasing the risk of poor health outcomes. The Groningen Frailty Indicator (GFI) is a 15-item validated questionnaire for the elderly. Its value in patients with end-stage hip or knee osteoarthritis (OA) has not yet been determined. This study assesses the validity of the GFI in this patient group. End-stage hip or knee OA patients completed the GFI (range 0-15, ≥ 4 = frail) before arthroplasty surgery. Convergent validity was determined by Spearman-rank correlation between the SF-12 physical (PCS) and mental (MCS) component scores and the physical and mental GFI-domains, respectively. Discriminant validity was assessed by means of overall GFI-score and the pain-domain of the Hip/Knee Osteoarthritis Outcome Score (HOOS/KOOS). Altogether 3275 patients were included of whom 2957 (90.3%) completed the GFI. Mean GFI-scores were 2.78 (2.41) and 2.28 (1.99) in hip and knee OA-patients, respectively, with 570 (35.9%) of hip and 344 (24.1%) of knee patients considered frail. The convergent validity was moderate to strong (physical domain R = - 0.4, mental domain R = - 0.6) and discriminant validity low (R HOOS/KOOS-pain domain = - 0.2), confirming the validity of the GFI-questionnaire in this population. With 90% of participants completing the GFI, it is a feasible and valid questionnaire to assess frailty in end-stage hip and knee OA-patients. One-third (33.3%) of the patients undergoing hip arthroplasty and a quarter (24.1%) of those undergoing knee arthroplasty are frail. Whether this is associated with worse outcomes and can thus be used as a pre-operative predictor needs to be explored.