Does Interlimb Knee Symmetry Exist After Unicompartmental Knee Arthroplasty?

Background

Unicompartmental knee arthroplasty (UKA) has long been a treatment option for patients with disease limited primarily to one compartment with small, correctable deformities. However, some surgeons presume that normal kinematics of a lateral compartment UKA are difficult to achieve. Furthermore, it is unclear whether UKA restores normal knee kinematics and interlimb symmetry.

Questions/purposes

We determined knee kinematics exhibited during stair ascent by patients with medial- (MED-UKA) or lateral-UKA (LAT-UKA) and if the knee kinematics of the operated and nonoperated limbs were symmetrical.

Methods

Participants were 17 individuals with MED-UKA and nine with LAT-UKA, all with nondiseased contralateral limbs. For each limb, participants walked up four stairs for five trials while a motion-capture system obtained reflective marker locations. Temporal events were determined by force platform signals. Interlimb symmetry was classified for temporal gait and knee angular kinematics by comparing observed interlimb differences with clinically meaningful differences set at 5% of stride time for temporal variables and 5° for angular variables. The minimum postoperative followup was 6 months (median, 24 months; range, 6–53 months).

Results

Neither group demonstrated clinically meaningful mean interlimb differences. However, approximately half of participants of each UKA group displayed asymmetry favoring the operative or nonoperative limb with similar frequency.

Conclusions

Many patients undergoing UKA demonstrate kinematic interlimb symmetry during stair ascent. Interlimb asymmetry may be affected by a variety of factors unrelated to the UKA.

Clinical Relevance

A MED- or LAT-UKA can potentially restore normal knee function for a demanding task of daily life.     

Does Total Knee Arthroplasty Change Frontal Plane Knee Biomechanics During Gait?

Background  

Dynamic knee varus angle and adduction moments have been reported to be reduced after TKA. However, it is unclear whether this reduction is maintained long term.     

Knee manipulation for reduced flexion after Total Knee Arthroplasty. Is timing critical?

Background

Reduced flexion following knee arthroplasty (TKA) may compromise patient’s function and outcome. The timing of manipulation under anaesthesia (MUA) has been controversial. We present our experience in a high volume practice and analyse the impact of timing.

Does Greater Knee Flexion Increase Patient Function and Satisfaction After Total Knee Arthroplasty?

The purpose of this study was to determine whether high flexion leads to improved benefits in patient satisfaction, perception, and function after total knee arthroplasty (TKA). Data were collected on 122 primary TKAs. Patients completed a Total Knee Function Questionnaire. Knees were classified as low (≤110°), mid (111°-130°), or high flexion (>130°). Correlation between knee flexion and satisfaction was not statistically significant. Increased knee flexion had a significant positive association with achievement of expectations, restoration of a “normal” knee, and functional improvement. In conclusion, although the degree of postoperative knee flexion did not affect patient satisfaction, it did influence fulfillment of expectations, functional ability, and knee perception. This suggests that increased knee flexion, particularly more than 130°, may lead to improved outcomes after TKA.     

Can Original Knee Society Scores Be Used to Estimate New 2011 Knee Society Scores?

Background

The Knee Society Score (KSS) instrument is one of the most commonly reported primary outcome measures for total knee arthroplasty (TKA). Originally developed in 1989, the KSS was expanded and updated in 2011; however, the original KSS does not directly translate into the 2011 KSS. To date, no conversion algorithm has been developed, hindering the ability of researchers to adopt the 2011 KSS while maintaining their historical/longitudinal original KSS data.

Questions/purposes

The purpose of this study is to develop regression equations to map the original KSS to the 2011 KSS, allowing original and 2011 KSS data sets to be combined.

Methods

In this multicenter, nonrandomized study, a convenience sample of 815 patients undergoing primary TKA completed the original KSS questionnaire and the 2011 KSS questionnaire. Additionally, patient gender, patient age, and patient ethnicity were recorded. These data were then used to generate regression models to estimate the 2011 objective and function KSS from the original KSS. Of the 815 study patients, 476 (58%) were female and 339 (42%) were male at an average age of 67 years (SD 9.4). Roughly half of patients were assessed preoperatively (430 of 815 [53%]) with the remaining patients assessed postoperatively (386 of 815 [47%]). The average followup for postoperative patients was 4.4 years (SD 3.5 years).

Results

We have created a spreadsheet that can be used by individuals with no statistical training to crosswalk the objective and function subscores from the original KSS to the 2011 KSS [Supplemental materials are available with the online version of CORR®.]. The predictive model very accurately estimated the 2011 objective score, on average, within 0.22 points on the 100-point 2011 objective KSS at the cohort or aggregate level. The objective model accurately estimated the 2011 objective KSS within 8.83 points, on average, of the actual 2011 objective KSS at the individual patient level. However, as a result of large outliers, 37% of the estimated 2011 objective KSS were greater than 10 points from the actual 2011 objective KSS. To illustrate, if you use the model to estimate the 2011 objective KSS on a cohort of 100 patients, a patient with an original objective KSS of 88 will have an estimated objective KSS between 79 and 97 points. On the other hand, if you calculate an average original objective KSS of 88 for all 100 patients, the estimated average 2011 objective KSS will be 88 for the group. The predictive model accurately estimated the 2011 function KSS within 0.14 points on the 1000-point 2011 function KSS at the cohort level. At the patient level, the 2011 function KSS was also estimated within 8.8 points of the actual 2011 function KSS. However, 43% of the estimated function scores were greater than 10 points of the actual 2011 function KSS.

Conclusions

Clinicians and researchers can input their original KSS with demographic data into these equations to estimate the 2011 KSS objective and function scores. The small prediction error of 0.22 points that we calculated indicates that these models can be used to estimate the 2011 objective and function KSS at the aggregated cohort level. Although the average error score was within 10 points at the individual patient level, there was a high percentage of large errors resulting from outliers in the data set. These outliers seemed to be related to patients with excellent range of motion who had substantial pain and limited function or patients who have poor range of motion with excellent function and little pain. This may be inherent with the KSS or with the study sample. Nevertheless, one must use caution when estimating at the patient level. Additionally, the accuracy of the prediction scores decreases if any of the demographic variables included in this study are not available.

     

Does Arthroscopic Knee Surgery Work?

A recent randomized trial from the Finnish Degenerative Meniscal Lesion Study Group was published in the New England Journal of Medicine and attempted to determine the efficacy of partial meniscectomy without osteoarthritis. Patients were randomized to either arthroscopic partial meniscectomy or sham surgery. The authors concluded that the clinical outcomes after arthroscopic partial meniscectomy were no better than those after the sham surgical procedure. However, there are several important limitations of this trial that make it difficult to generalize to the 700,000 arthroscopic partial meniscectomies performed in the United States each year. In this small sample of 146 patients, patients with traumatic meniscal tears and locking symptoms—those most likely to benefit from a partial meniscectomy—were excluded. In addition, although patients with radiographic arthritis were excluded, most of the patients in the study had degenerative changes at the time of arthroscopy. Therefore it is difficult to determine whether the patients were symptomatic from their chondral degeneration or their degenerative meniscal tear. In our opinion this study does not change the role of surgery in current clinical practice. The primary indication for arthroscopic partial meniscectomy remains symptoms of well-localized joint line pain with acute onset and mechanical symptoms such as catching or locking that have failed comprehensive nonoperative management.     

Are Instrumented Knee Forces Representative of a Larger Population of Cruciate-Retaining Total Knee Arthroplasties?

Background

It is not known if the loads and motions reported for instrumented knees are generalizable to a larger population of total knee arthroplasty (TKA) patients. The purpose of this study is to (1) report axial implant force data for chair and stair activities for a population of cruciate-retaining TKA patients and (2) compare the population forces to those measured with instrumented TKAs.

Tramadol in Knee Osteoarthritis: Does Preoperative Use Affect Patient-Reported Outcomes After Total Knee Arthroplasty?

BackgroundThe 2013 American Academy of Orthopedic Surgeons evidence-based guidelines recommend against the use of preoperative narcotics in the management of symptomatic osteoarthritic knees; however, the guidelines strongly recommend tramadol in this patient population. To our knowledge, no study to date has evaluated outcomes in patients who use tramadol exclusively as compared with narcotics naive patients.MethodsThis is a retrospective study of prospectively collected data for patients who underwent unilateral primary total knee arthroplasty between January 2017 and March 2018. PRO scores were obtained using a novel electronic patient rehabilitation application, which pushed PRO surveys via email and mobile devices within 1 month prior to surgery and 3 months postoperatively.ResultsOne hundred and thirty-six patients were opiate naïve, while 63 had obtained narcotics before the index operation. Of those, 21 patients received tramadol. The average preoperative Knee Disability and Osteoarthritis Outcome Scores were 50.4, 49.95, and 48.01 for the naïve, tramadol, and narcotic populations, respectively, (P = .60). The tramadol cohort had the least gain in 3 months postoperative Knee Disability and Osteoarthritis Outcome Scores, improving on average 12.5 points in comparison to the 19.1 and 20.1 improvements seen in the narcotic and naïve cohorts, respectively (P = .09). This difference was statistically significant when comparing the naïve and tramadol populations alone in post hoc analysis (P = .016).ConclusionsWhen comparing patients who took tramadol preoperatively to patients who were opiate naïve, patients that used tramadol trended toward significantly less improvement in functional outcomes in the short-term postoperative period.     

Does the Oxford Knee Score Complement, Concur, or Contradict the American Knee Society Score?

The American Knee Society Score (AKSS) and the Oxford Knee Score (OKS) are commonly used outcome assessment tools following total knee arthroplasty. The literature is sparse with regard to direct correlation between the AKSS and the OKS. The present study aimed to elucidate any direct correlation between these two scoring systems. Preoperative and 1-year postoperative AKSS and OKS from 379 patients were analyzed statistically. Regression equations were developed based on curve fit models. The study found a good correlation between the two scoring systems. The OKS can be used as a screening tool to identify which patients need to be assessed clinically in the short term (<2 years) following total knee arthroplasty (TKA). This will have significant cost-benefit implications. It is also possible to predict the AKSS from OKS using mathematical equations developed for this study. This method of predicting the AKSS from the OKS has not previously been described.     

Robotic Arm–Assisted Total Knee Arthroplasty

Background

Robotic arm–assisted total knee arthroplasty (RATKA) has a number of potential advantages. Therefore, in order to more comprehensively assess this technology, we reviewed the (1) accuracy and precision; (2) soft-tissue protection; (3) patient satisfaction; (4) learning curve; and (5) its other potential benefits.

Success of Different Knee Arthrodesis Techniques After Failed Total Knee Arthroplasty: Is There a Preferred Technique?

Arthrodesis is a widely accepted treatment for failed total knee arthroplasty when further revision is contraindicated. In this study, we retrospectively review the pre-operative characteristics, operation techniques, treatment plans, and eventual outcomes in 42 consecutive patients (43 knees) who underwent knee arthrodesis at a single institution. Femorotibial fusion was achieved in 30 cases (75.0%). No cases of implant failure were recorded. Post-operative complications occurred in 20 cases (46.5%). Repeat arthrodesis was performed in 4 cases, and 2 patients eventually required above-the-knee amputation. Comparing the cases with successful vs. unsuccessful outcomes, there was a significant difference in days until hospital discharge following arthrodesis (P = .026), mean erythrocyte sedimentation rate prior to arthrodesis (P = .012), and the proportion of patients with post-operative wound complications (P = .021).     

Does a Standard Outpatient Physiotherapy Regime Improve the Range of Knee Motion After Primary Total Knee Arthroplasty?

The aim of this study was to investigate whether a standard course of outpatient physiotherapy improves the range of knee motion after primary total knee arthroplasty. One hundred and fifty patients were randomly assigned into one of 2 groups. One group received outpatient physiotherapy for 6 weeks (group A). Another received no outpatient physiotherapy (group B). Range of knee motion was measured preoperatively and at 1-year review. Validated knee scores and an SF-12 health questionnaire were also recorded. Although patients in group A achieved a greater range of knee motion than those in group B, this was not statistically significant. No difference either was noted in any of the outcome measures used. In conclusion, outpatient physiotherapy does not improve the range of knee motion after primary total knee arthroplasty.     

In Vivo Kinematic Comparison of a Bicruciate Stabilized Total Knee Arthroplasty and the Normal Knee Using Fluoroscopy

Background

The bicruciate stabilized (BCS) total knee arthroplasty (TKA) features asymmetrical bearing geometry and dual substitution for the anterior cruciate ligament and posterior cruciate ligament (PCL). Previous TKA designs have not fully replicated normal knee motion, and they are characterized by lower magnitudes of overall rollback and axial rotation than the normal knee.

Can a Convolutional Neural Network Classify Knee Osteoarthritis on Plain Radiographs as Accurately as Fellowship-Trained Knee Arthroplasty Surgeons?

BackgroundOsteoarthritis (OA) is the leading cause of disability among adults in the United States. As the diagnosis is based on the accurate interpretation of knee radiographs, use of a convolutional neural network (CNN) to grade OA severity has the potential to significantly reduce variability.MethodsKnee radiographs from consecutive patients presenting to a large academic arthroplasty practice were obtained retrospectively. These images were rated by 4 fellowship-trained knee arthroplasty surgeons using the International Knee Documentation Committee (IKDC) scoring system. The intraclass correlation coefficient (ICC) for surgeons alone and surgeons with a CNN that was trained using 4755 separate images were compared.ResultsTwo hundred eighty-eight posteroanterior flexion knee radiographs (576 knees) were reviewed; 131 knees were removed due to poor quality or prior TKA. Each remaining knee was rated by 4 blinded surgeons for a total of 1780 human knee ratings. The ICC among the 4 surgeons for all possible IKDC grades was 0.703 (95% confidence interval [CI] 0.667-0.737). The ICC for the 4 surgeons and the trained CNN was 0.685 (95% CI 0.65-0.719). For IKDC D vs any other rating, the ICC of the 4 surgeons was 0.713 (95% CI 0.678-0.746), and the ICC of 4 surgeons and CNN was 0.697 (95% CI 0.663-0.73).ConclusionsA CNN can identify and classify knee OA as accurately as a fellowship-trained arthroplasty surgeon. This technology has the potential to reduce variability in the diagnosis and treatment of knee OA.     

Oxford Unicompartmental Knee Arthroplasty Versus Age and Gender Matched Total Knee Arthroplasty – Functional Outcome and Survivorship Analysis

We compared the medium-term outcomes of age and gender matched patients with unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA). We retrospectively reviewed the pain, function and total knee society scores (KSS) for 602 UKAs and age and gender matched TKAs between 2001 and 2013. Function scores remained significantly better in UKAs from preoperative until 3 years follow up. The change of function scores was not significantly different. TKAs performed better than UKAs for pain scores. Total KSS for both groups were not significantly different in the study. Fewer medical complications were reported in UKA group. 6.30% of UKAs and 2.99% of TKAs were revised. The theoretical advantages of UKA were not borne out, other than in immediate postoperative complications.     

Predictive Factors of “Forgotten Knee” Acquisition After Total Knee Arthroplasty: Long-Term Follow-Up of a Large Prospective Cohort

Background

In a large prospective cohort, we recently showed that only 66.1% of total knee arthroplasty (TKA) with a perfect outcome according to Knee Society Knee Score was completely forgotten in all everyday activities. The main objective of this study was to identify clinical and orthopedic factors associated with the acquisition of “forgotten knee” (FK).

Does a Modified Gap-balancing Technique Result in Medial-pivot Knee Kinematics in Cruciate-retaining Total Knee Arthroplasty?: A Pilot Study

Background  

Normal knee kinematics is characterized by posterior femorotibial rollback with tibial internal rotation and medial-pivot rotation in flexion. Cruciate-retaining TKAs (CR-TKAs) do not reproduce normal knee kinematics.