Quality-Adjusted Life Years Gained by Hip and Knee Replacement Surgery and Its Aftercare

Similar QALY gain in primary and revision knee arthroplasty: A cost analysis and Markov model

PURPOSE

The aim of this study is to investigate the cost-effectiveness of revision total knee arthroplasty compared to primary total knee arthroplasty in terms of cost-per-quality-adjusted life year (QALY).

METHODS

Data were retrieved for all primary and revision total knee replacement (TKA) procedures performed at a tertiary Swiss hospital between 2006 and 2019. A Markov model was created to evaluate revision risk and we calculated lifetime QALY gain and lifetime procedure costs through individual EuroQol 5 dimension (EQ-5D) scores, hospital costs, national life expectancy tables and standard discounting processes. Cost-per-QALY gain was calculated for primary and revision procedures.

RESULTS

EQ-5D data were available for 1343 primary and 103 revision procedures. Significant QALY gains were seen following surgery in all cases. Similar, but significantly more QALYs were gained following primary TKA (PTKA) (5.67 ± 3.98) than following revision TKA (RTKA) (4.67 ± 4.20). Cost-per-QALY was €4686 for PTKA and €10,364 for RTKA. The highest average cost-per-QALY was seen in two-stage RTKA (€12,292), followed by one-stage RTKA (€8982).

CONCLUSION

RTKA results in a similar QALY gain as PTKA. The costs of achieving health gain are two to three times higher in RTKA, but both procedures are highly cost-effective.

LEVEL OF EVIDENCE

Economic level II.

30-Days to 10-Years Mortality Rates following Total Knee Arthroplasty: A Systematic Review and Meta-Analysis of the Last Decade (2011-2021)

Mortality data following primary total knee arthroplasty (TKA) beyond 1-year postoperative time period is sparse. This systematic review and meta-analysis aimed to: (1) estimate contemporary mortality rates at 30 days, 90 days, 1 year, 5 years, and 10 years following primary TKA; and (2) identify risk factors and causes of mortality following TKA. PubMed, MEDLINE, Cochrane, EBSCO host, and Google Scholar databases were queried from January 1, 2011 to October 30, 2021 for all studies reporting mortality rates following primary TKA. A meta-analysis of proportions was conducted using a random-effects model to ascertain pooled mortality rates (95% confidence interval [CI]). Meta-regression was utilized to account for confounding effects on mortality rates due to the study's country of origin, median date of study data, average patient age, and patient gender ratios, with a level of significance maintained at p-value <0.05. A total of 44 articles were included in quantitative synthesis. The pooled 30-day mortality rate was 0.14% (95% CI:0.05-0.22%; n = 1,817,647). The pooled 90-day mortality rate was 0.35% (95% CI:0.0.28-0.43%; n = 1,641,974). The pooled 1-year mortality rate was 1.1% (95% CI:0.71-1.49%; n = 1,178,698). The pooled 5-year mortality rate was 5.38% (95% CI:4.35-6.42%; n = 597,041). The pooled 10-year mortality rate was 10.18% (95% CI:7.78-12.64%; n = 815,901). Our 30-day mortality rate was lower than previously reported. The most common causes of death at all time points were due to cardiac disease, cerebrovascular disease, and malignancy. Obesity demonstrated mixed effects on long-term mortality rates. Overall mortality rates of TKA remain low worldwide at all time points and immediate postoperative mortality rates continue to fall. Compared to symptomatic knee osteoarthritic patients reported in the literature, TKA patients qualitatively exhibited lower mortality rates, which may support the value of TKA in improving quality of life without associated excess mortality. Future long-term mortality studies should be conducted to account for geographical variability in mortality rates and further elucidate modifiable risk factors associated with mortality among TKA patients.

Microbiological Advantages of Open Incisional Biopsies for the Diagnosis of Suspected Periprosthetic Joint Infections

Background: Periprosthetic joint infection (PJI) represents a serious complication following total hip (THA) and knee arthroplasty (TKA). When preoperative synovial fluid cultures remain inconclusive, open incisional joint biopsy (OIB) can support causative microorganism identification. Objective: This study investigates the potential benefit of OIB in THA and TKA patients with suspected PJI and ambigious diagnostic results following synovial fluid aspiration. Methods: We retrospectively assessed all patients treated from 2016 to 2020 with suspected PJI. Comparing the microbiology of OIB and the following revision surgery, we calculated sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and the number needed to treat (NNT). Results: We examined the diagnostic validity of OIB in 38 patients (20 female) with a median age of 66.5 years. In THA patients (n = 10), sensitivity was 75%, specificity was 66.67%, PPV was 60%, NPV was 80%, and NNT was 2.5. In TKA patients (n = 28), sensitivity was 62.5%, specificity was 95.24%, PPV was 83.33%, NPV was 86.96%, and NNT was 1.42. Conclusions: Our results indicate that OIB represents an adequate diagnostic tool when previously assessed microbiological results remain inconclusive. Particularly in TKA patients, OIB showed an exceptionally high specificity, PPV, and NPV, whereas the predictive validity of the diagnosis of PJI in THA patients remained low.

Hydrotherapy Intervention for Patients Following Total Knee Arthroplasty: A Systematic Review

Background Hydrotherapy or aquatic exercise has long been known as a source of postoperative rehabilitation proposed in routine clinical practice. However, the effect on clinical outcome as well as the optimal timing of hydrotherapy in patients undergoing total knee arthroplasty (TKA) remain unclear. The purpose of this review was to assess the influence of aquatic physiotherapy on clinical outcomes and evaluate the role of the timing of aquatic-therapy for clinical outcomes after undergoing TKA.

Methods An extensive literature search was performed in Embase, PubMed, and the Cochrane Library for randomized controlled trials (RCTs) that evaluated the impact of hydrotherapy on patients after TKA. The methodological quality of the trials was evaluated based on the Cochrane Risk of Bias Tool.

Results All available studies on postoperative hydrotherapy after TKA were included. The primary endpoint was to evaluate the effect of hydrotherapy on clinical outcomes. The secondary outcome was to explore the role of the timing of aquatic therapy for clinical outcomes following TKA.

Conclusion Although definitive conclusions could not be reached due to insufficient data, most studies indicated that participants benefited from aquatic-therapy in muscle strength, rather than gait speed, after TKA. Currently available data demonstrated that early postoperative hydrotherapy possessed a greater potential to improve clinical outcomes in main clinical scores and quality-adjusted life years (QALYs).

Total Hip and Knee Arthroplasties Are Highly Cost-Effective Procedures: The Importance of Duration of Follow-Up

BACKGROUND

Total hip and knee arthroplasties (THA/TKA) are clinically effective but high cost procedures. The aim of this study is to perform a cost-effectiveness analysis of THA and TKA in the New Zealand (NZ) healthcare system.

METHODS

Data were collected from 713 patients undergoing THA and 520 patients undergoing TKA at our local public hospital. SF-6D utility values were obtained from participants preoperatively and 1-year postoperatively, and deaths and any revision surgeries from patient records and the New Zealand Joint Registry at minimum 8-year follow-up. A continuous-time state-transition simulation model was used to estimate costs and health gains to 15 years. Quality-adjusted life years (QALYs), treatment costs, and incremental cost-effectiveness ratios (ICERs) were calculated to determine cost effectiveness. ICERs below NZ gross domestic product (GDP; NZ$60 600) and 0.5 times GDP per capita were considered "cost effective" and "highly cost effective" respectively.

RESULTS

Cumulative health gains were 2.8 QALYs (THA) and 2.3 QALYs (TKA) over 15 years. Cost effectiveness improved from ICERs of NZ$74,400 (THA) and NZ$93,000 (TKA) at 1 year to NZ$6000 (THA) and NZ$7500 (TKA) at 15 years. THA and TKA were cost effective after 2 years and highly cost effective after 3 years. QALY gains and cost effectiveness were greater in patients with worse preoperative functional status and younger age.

CONCLUSION

THA and TKA are highly cost-effective procedures over longer term horizons. Although preoperative status and age were associated with cost effectiveness, both THA and TKA remained cost effective in patients with less severe preoperative scores and older ages.

Total knee arthroplasty improves the quality-adjusted life years in patients who exceeded their estimated life expectancy

Purpose

Total knee arthroplasty (TKA) is the treatment of choice for end-stage osteoarthritis though its risk-benefit ratio in elderly patients remains debated. This study aimed to evaluate the functional outcome, rates of complication and mortality, and quality-adjusted life years (QALY) in patients who exceeded their estimated life expectancy.

Methods

Ninety-seven TKA implanted in 86 patients who exceeded their estimated life expectancy at the time of TKA were prospectively included in our institutional joint registry and retrospectively analyzed. At latest follow-up, the functional outcome with the Knee Society Score (KSS), rates of complication and mortality, and QALY with utility value of EuroQol-5D score were evaluated.

Results

At a mean follow-up of three ± one years, the pre- to post-operative KSS improved significantly (p < 0.01). The rates of surgical and major medical complications related to TKA were 3% and 10%, respectively. The re-operation rate with readmission was 3% while no TKA was revised. The 30-day and one year mortality was 1% and 3%, respectively. The pre- to one year post-operative QALY improved significantly (p < 0.01). The cumulative QALY five years after TKA was four years. Assuming that these patients did not undergo TKA, their cumulative QALY at five years would have been only two years.

Conclusion

TKA is an effective procedure for the treatment of end-stage osteoarthritis in patients who exceeded their estimated life expectancy. TKA provided significant improvement in function and quality of life without adversely affecting overall morbidity and mortality. Therefore, TKA should not be contra-indicated in elderly patients based on their advanced age alone.

Evaluation of Health-related Quality of Life Improvement in Patients Undergoing Spine Versus Adult Reconstructive Surgery

STUDY DESIGN

Retrospective analysis of outcomes in single-level spine and primary hip and knee arthroplasty patients.

OBJECTIVE

The aim of this study was to compare baseline and postoperative outcomes in patients undergoing spine surgery procedures with total hip arthroplasty (THA) and total knee arthroplasty (TKA) to further define outcomes in orthopedic surgery.

SUMMARY OF BACKGROUND DATA

Computer-adaptive Patient Reported Outcome Information System (PROMIS) allows for standardized assessment of the health-related quality of life across different disease states.

METHODS

Patients who underwent spine surgery (anterior cervical discectomy and fusion, cervical disc replacement, lumbar laminectomy, microscopic lumbar discectomy, transforaminal lumbar interbody fusion or adult reconstruction surgery [THA, TKA]) were grouped. Mean Charlson Comorbidity Index (CCI), Baseline (BL), and 6-month PROMIS scores of physical function, pain interference, and pain intensity were determined. Paired t tests compared differences in CCI, BL, 6 months, and change in PROMIS scores for spine and adult reconstruction procedures.

RESULTS

A total of 304 spine surgery patients (age = 58.1 ± 15.6; 42.9% female) and 347 adult reconstruction patients (age = 62.9 ± 11.8; 54.1% Female) were compared. Spine surgery groups had more disability and pain at baseline than adult reconstruction patients according to physical function ([21.0, 22.2, 9.07, 12.6, 10.4] vs. [35.8, 35.0], respectively, P < 0.01), pain interference ([80.1, 74.1, 89.6, 92.5, 90.6] vs. [64.0, 63.9], respectively, P < 0.01), and pain intensity ([53.0, 53.1, 58.3, 58.5, 56.1] vs. [53.4, 53.8], respectively, P < 0.01). At 6 months, spine surgery patients remained more disabled and had more pain compared to adult reconstruction patients. Over the 6-month timespan, spine patients experienced greater improvements than adult reconstruction patients in terms of physical function ([+8.7, +22.2, +9.7, +12.9, +12.1] vs. [+5.3, +3.9], respectively, P < 0.01) and pain interference scores ([-15.4,-28.1, -14.7, -13.1, -12.3] vs. [-8.3, -6.0], respectively, P < 0.01).

CONCLUSION

Spinal surgery patients had lower BL and 6-month PROMIS scores, but greater relative improvement in PROMIS scores compared to adult reconstruction patients.

LEVEL OF EVIDENCE

3.

Changes in actual daily physical activity and patient-reported outcomes up to 2 years after total knee arthroplasty with arthritis

The current study aimed 1) to describe changes in patient-reported outcomes and physical activity measured with an accelerometer preoperatively, 6 months and 2 years postoperatively in older patients undergoing total knee arthroplasty (TKA) for arthritis, and 2) to examine the predictors of the changes in physical activity (PA). This study included 58 patients (mean age 72.6 years, 84.5% women) who completed the Oxford Knee Score (OKS) and the 8-item Short Form Health Survey. Physical activity measured mean steps per day, duration of light physical activity and moderate-to-vigorous physical activity (MVPA) per week. All PA indicators and patient-reported outcomes improved 6 months postoperatively. After 6 months, knee-related pain and function gradually improved, and MVPA increased. The OKS was a sole predictor of improvement in PA during the 2-year study period, suggesting the importance of disease-specific quality of life.

The Relationship Between Preoperative Oxford Hip and Knee Score and Change in Health-Related Quality of Life After Total Hip and Total Knee Arthroplasty: Can It Help Inform Rationing Decisions?

Background

In countries with publicly funded health care, there is an increasing need for explicit rationing for total joint arthroplasty (TJA). The Oxford Hip and Knee Scores (OHS/OKS) have been used to set access thresholds for TJA despite not being developed for that purpose. The aim of this study was to determine whether preoperative OHS/OKS can aid rationing decisions by investigating the changes in general health-related quality of life after TJA.

Methods

OHS/OKS, Short Form-12, and Short Form-6D (SF-6D) scores were collected preoperatively and at 1 year postoperatively in a cohort of patients undergoing total hip arthroplasty (THA; n = 713) and total knee arthroplasty (TKA; n = 520). The association between preoperative OHS/OKS and postoperative score and the change in OHS/OKS and SF-6D was investigated, adjusting for age and gender.

Results

The mean Oxford scores improved from 13.9 to 40.7 (OHS) and 15.6 to 37.4 (OKS). The mean SF-6D improved after THA (0.53 to 0.80) and TKA (0.56 to 0.78) (all P < .0001). Poorer preoperative Oxford scores were associated with poorer postoperative OHS/OKS and SF-6D but larger improvements. For every 5 points lower preoperative OHS/OKS, the postoperative SF-6D score was worse by a margin of 0.019 (THA) and 0.023 (TKA).

Conclusions

Preoperative OHS/OKS can help inform rationing decisions. A lower preoperative OHS/OKS will result in greater gains but a lower final outcome score in general health-related quality of life.

Which Nonsurgical Treatments Do Patients Believe Are Most Effective for Hip and Knee Arthritis?

BACKGROUND

The purpose of this study was to determine which nonsurgical treatments patients believe are most effective for managing pain secondary to hip and knee arthritis.

METHODS

Five hundred sixty-five consecutive patients were administered an anonymous questionnaire developed in consultation with a center with expertise in survey design. Statistical analyses included Student t-test, Fisher Exact, Wilcoxon Rank-Sum test, and generalized cost-effectiveness analysis.

RESULTS

Four hundred thirty-six patients completed the questionnaire (response rate 77.2%). Opioids (52 of 118; 44.1%), prescription nonsteroidal anti-inflammatory drugs (NSAIDs) (67 of 200; 33.5%), and corticosteroid injections (87 of 260; 33.5%) were reported as most effective. Stem cell and platelet-rich plasma injections were selected by three of 12 (25.0%) and three of 15 patients (19.5%), respectively, and physical therapy (PT) by 50 of 257 patients (19.5%). Twenty-five percent of respondents received opioids, commonly prescribed by primary care providers (48.2%) and orthopaedic surgeons (39.5%). Opioid use correlated with lower patient-reported effectiveness of PT, NSAIDs, and corticosteroid injections (P < 0.05). The highest cost-effectiveness ratios were NSAIDs, opioids, and acetaminophen (2.2, 3.7, 4.0, and 5.4, respectively). The lowest cost-effectiveness ratios were stem cell injections, platelet-rich plasma injections, and PT (1966.7, 520.8, and 138.6, respectively).

CONCLUSIONS

The nonsurgical treatments that are reported by patients to be most effective are oftentimes the least expensive.

Quantifying the Opportunity Cost of Resident Involvement in Academic Orthopaedic Sports Medicine: A Matched-Pair Analysis

PURPOSE

To quantify the cost of resident involvement in academic sports medicine by examining differences in operative time, relative value units (RVUs) per case, and RVUs per hour between attending-only cases and cases with resident involvement.

METHODS

A retrospective analysis of common sports medicine procedures identified by Current Procedural Terminology code was performed using data from the American College of Surgeons National Surgical Quality Improvement Program database from 2006 to 2015. Matched cohorts were generated based on demographic variables, comorbidities, preoperative laboratory values, and surgical procedures. Bivariate analysis examined mean differences in operative time, RVUs per case, and RVUs per hour between attending-only cases and cases with resident involvement. A cost analysis was performed to quantify differences in RVUs generated per hour in terms of dollars per case.

RESULTS

A total of 14,840 attending-only cases and 2,230 resident-involved cases were used to generate 2 matched cohorts (N = 4,460). Resident cases had greater mean operative times than attending-only cases, with operative time increasing as residents became more senior (P < .01). Residents participated in cases with larger mean RVUs per case (P < .01). Cases with lone attendings showed greater RVUs per hour (P < .01). The cost of resident involvement increased nearly 8-fold from postgraduate year 1 to postgraduate year 6 residents ($25.70 vs $200.07).

CONCLUSIONS

In academic sports medicine, the involvement of resident physicians increases operative time. The associated decrease in attending physician efficiency in RVUs per hour equates to an average cost per case of $159.18, with costs increasing as residents become more senior.

LEVEL OF EVIDENCE

Level III, retrospective comparative trial.

Treatment of a periprosthetic femur fracture around an antibiotic spacer with revision and an antibiotic plate

Infection following total hip arthroplasty can be a devastating complication, often necessitating a 2-stage surgery with the temporary placement of an antibiotic spacer. Fracture around this spacer is an uncommon complication that presents serious treatment challenges. Our manuscript details the successful surgical treatment of a previously unreported fracture around an antibiotic spacer, treated with revision to a hemiarthroplasty and placement of an antibiotic plate.

Periprosthetic Fracture of Greater Trochanter in Total Hip Replacement Stemming from Pin Site Placement in Navigation-Assisted Surgery

Surgeons are looking to use computer computer-assisted surgery (CAS) in total hip arthroplasty (THA) in order to quantify leg length measurement, angular cup placement, and enhance stability to provide enhanced accuracy in implant placement. As a result, CAS in THA is gaining popularity. This technology employs the use of pins and provides the surgeon with real-time feedback on positioning intraoperatively. Previous total knee arthroplasty (TKA) literature has reported pin-associated complications such as infections, neuropraxia, and suture abscess. To our knowledge, there have been reports of tibial stress fracture after CAS TKA, but this is the first report of a pin causing fracture of the greater trochanter leading to dislocation in THA. Further studies may be warranted to optimize pin placement for trackers to prevent fractures of the greater trochanter.

Predicting patient-reported outcomes following hip and knee replacement surgery using supervised machine learning

BACKGROUND

Machine-learning classifiers mostly offer good predictive performance and are increasingly used to support shared decision-making in clinical practice. Focusing on performance and practicability, this study evaluates prediction of patient-reported outcomes (PROs) by eight supervised classifiers including a linear model, following hip and knee replacement surgery.

METHODS

NHS PRO data (130,945 observations) from April 2015 to April 2017 were used to train and test eight classifiers to predict binary postoperative improvement based on minimal important differences. Area under the receiver operating characteristic, J-statistic and several other metrics were calculated. The dependent outcomes were generic and disease-specific improvement based on the EQ-5D-3L visual analogue scale (VAS) as well as the Oxford Hip and Knee Score (Q score).

RESULTS

The area under the receiver operating characteristic of the best training models was around 0.87 (VAS) and 0.78 (Q score) for hip replacement, while it was around 0.86 (VAS) and 0.70 (Q score) for knee replacement surgery. Extreme gradient boosting, random forests, multistep elastic net and linear model provided the highest overall J-statistics. Based on variable importance, the most important predictors for post-operative outcomes were preoperative VAS, Q score and single Q score dimensions. Sensitivity analysis for hip replacement VAS evaluated the influence of minimal important difference, patient selection criteria as well as additional data years. Together with a small benchmark of the NHS prediction model, robustness of our results was confirmed.

CONCLUSIONS

Supervised machine-learning implementations, like extreme gradient boosting, can provide better performance than linear models and should be considered, when high predictive performance is needed. Preoperative VAS, Q score and specific dimensions like limping are the most important predictors for postoperative hip and knee PROMs.

Effect of telerehabilitation on mobility in people after hip surgery: a pilot feasibility study

The goal of this study was to evaluate the effects of telerehabilitation on mobility in people following hip surgery. This feasibility pilot randomized controlled trial included a sample of 40 participants, with 22 male and 18 female patients and mean age (SD) of 67.5 (7.8) years following a surgical intervention. Participants were equally divided and randomly assigned to a telerehabilitation or control intervention group (6 weeks, 3 sessions/week). Telerehabilitation was based on video clips of common rehabilitation exercises focusing on the lower limbs. The control group received an exercise booklet. Both groups participated in physical therapy sessions, twice a week. Outcome measures included the Timed Up and Go test, 2-min walk test, 10-m walk test, sit to stand test, walking speed, and mean step length. Measurements were completed at baseline, at termination of the intervention, and at a 4-week follow-up examination. Improvements in both groups were demonstrated in all outcome measures in the postintervention evaluation. Improvements in the telerehabilitation group were greater in five of six tests compared with those achieved by the controls. The telerehabilitation group showed greater improvements in the 2-min walking test (86.1%) and walking speed (65.6%). During follow-up, the telerehabilitation group continued to improve in all outcome measures in contrast to the control group, who showed no changes in five of the six outcome measures. Telerehabilitation, a complementary treatment to standard physical therapy, generates a positive effect on mobility in people following hip surgery.

Quality-Adjusted Life Years After Hip and Knee Arthroplasty: Health-Related Quality of Life After 12,782 Joint Replacements

Background

The quality-adjusted life year (QALY) is the preferred outcome measurement for cost-effectiveness analysis in health care. QALYs measure patient health-related quality of life with use of a value between 0 and 1. Few studies have provided original data delineating QALYs after hip and knee arthroplasty. In the present study, we evaluated patient utility preoperatively and 2 years after total hip arthroplasty, hip resurfacing, revision hip arthroplasty, total knee arthroplasty, unicompartmental knee arthroplasty, and revision knee arthroplasty.

Methods

A single-hospital joint registry, which enrolled patients from 2007 to 2011, was retrospectively examined for all patients who underwent primary or revision hip or knee arthroplasty and who had preoperative and 2-year postoperative Short Form-36 (SF-36), Short Form-12 (SF-12), or EuroQol 5-Dimension (EQ-5D) scores available. Patient age, body mass index (BMI), sex, American Society of Anesthesiologists (ASA) score, and Charlson Comorbidity Index were recorded. QALYs were determined from the EQ-5D index and the Short Form-6 Dimension (SF-6D) index.

Results

Five thousand, four hundred and sixty-three patients underwent total hip arthroplasty, with a mean annual increase (and standard deviation) of 0.25 ± 0.2 QALY; 843 patients underwent hip resurfacing, with a mean annual increase of 0.24 ± 0.17 QALY; 5,398 patients underwent primary total knee arthroplasty, with a mean annual increase of 0.17 ± 0.19 QALY; and 240 patients underwent medial unicompartmental knee arthroplasty, with a mean annual increase of 0.16 ± 0.17 QALY. Aseptic revision arthroplasty (440 hips, 323 knees) was associated with a smaller QALY gain than primary arthroplasty. Patient age, BMI, female sex, ASA category, and higher preoperative health-related quality of life were negative predictors for QALY gain after primary arthroplasty. Forty additional hip procedures and 35 additional knee procedures were also analyzed.

Conclusions

Primary hip and knee arthroplasty, on average, result in substantially increased patient quality of life. Revision hip and knee replacement result in a lower, but still positive, gain in quality of life. However, there is a considerable variation in patient outcomes across all procedures. Our results may be used to improve the certainty of future cost-effectiveness analyses of hip and knee arthroplasty.

Level of Evidence

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

Periprosthetic Tibial Fractures

Periprosthetic fractures around total knee arthroplasty have become an increasingly common and challenging orthopaedic problem. Appropriate management of these fractures depends on careful scrutiny of radiographs and a thorough clinical history to exclude the diagnosis of a periprosthetic infection. In a periprosthetic tibial fracture with a stable, well-aligned tibial component and well-aligned mechanical tibial axis, the fracture can be successfully managed with closed reduction and cast immobilization; meticulous follow-up is essential to ensure that the alignment is maintained. Major fracture displacement, tibial component instability, and tibial component malalignment are all indications for surgical intervention. The ideal surgical intervention depends on the fracture characteristics and the stability and alignment of the tibial component.

Pin Site Complications Associated With Computer-Assisted Navigation in Hip and Knee Arthroplasty

BACKGROUND

There has been a great increase in the use of navigation technology in joint arthroplasty. In most types of navigation-assisted surgery, several temporary navigation pins are placed in the patient. Goals of this study are (1) to identify complications and (2) risk factors associated with placement of these pins.

METHODS

This is a retrospective cohort study of all navigation-assisted hip and knee arthroplasty performed a single institution over a 3-year period. Records were reviewed and outcome measures were tabulated in a database. Complications included in the database were pin site infection, deep prosthetic joint infection, neurologic injury, vascular injury, and fracture through a pin site.

RESULTS

A total of 3136 pin sites in 839 patients were included in the study. Five pin site complications were reported with a complication rate of 0.16% per pin site and 0.60% per patient. The complications-per-procedure were slightly higher for unicondylar knee arthroplasty (0.64%) compared with patellofemoral arthroplasty (0%) and total hip arthroplasty (0.46%), but not statistically significant. There were three infections, one neuropraxia, and one suture abscess. No periprosthetic fractures through a pin site were reported. All complications were resolved with nonoperative treatment. The infections required oral antibiotics, and were associated with transcortical drilling in two cases and juxtacortical drilling in the third.

CONCLUSION

Pins required for navigation-assisted arthroplasty have a low complication rate. Transcortical or juxtacortical drilling may be a risk factor for pin site infection; future studies should be directed at quantifying this effect.

Using Patient-Reported Outcomes for Economic Evaluation: Getting the Timing Right

BACKGROUND

Patient-reported outcome measures (PROMs) are becoming increasingly popular in orthopedic surgery. Preoperative and postoperative follow-up often elicit PROMs in the form of generic quality-of-life instruments (e.g., Short Form health survey SF-12 [SF-12]) that can be used in economic evaluation to estimate quality-adjusted life-years (QALYs). However, the timing of postoperative measurement is still under debate.

OBJECTIVES

To explore the timing of postoperative PROMs collection and the implications for bias in QALY estimation for economic evaluation.

METHODS

We compared the accuracy of QALY estimation on the basis of utilities derived from the SF-12 at one of 6 weeks, 3 months, 6 months, and 12 months after total knee arthroplasty, under different methods of interpolation between points. Five years of follow-up data were extracted from the St. Vincent's Melbourne Arthroplasty Outcomes (SMART) registry (n = 484). The SMART registry collects follow-up PROMs annually and obtained more frequent outcomes on subset of patients (n = 133).

RESULTS

Postoperative PROM collection at 6 weeks, 6 months, or 12 months biased the estimation of QALY gain from total knee arthroplasty by -41% (95% confidence interval [CI] -59% to -22%), 18% (95% CI 4%-32%), and -8% (95% CI -18% to -2%), respectively. This bias was minimized by collecting PROMs at 3 months postoperatively (6% error; 95% CI -9% to 21%).

CONCLUSIONS

The timing of PROM collection and the interpolation assumptions between measurements can bias economic evaluation. In the case of total knee arthroplasty, we recommend a postoperative measurement at 3 months with linear interpolation between preoperative and postoperative measures. The design of economic evaluations should consider timing and interpolation issues.