Mid-term results of an anatomic total knee replacement design.

INTRODUCTION: A significant proportion of patients remain dissatisfied following total knee arthroplasty (TKA) surgery. Reasons for this are unclear. Contemporary implants seek to mirror innate anatomy. Such innovations are necessarily subject to scrutiny to validate their use. The Zimmer-Biomet Persona® Personalized Knee system is such an anatomic TKA. This work seeks to establish medium term survival data and patient reported outcomes for this implant. METHODS: This was a cohort study of prospectively collected data on all patients undergoing Persona TKA at our institution. Patients were managed using a standardised protocol for intra- and post-operative care. Survivorship data were collected using our National Joint Registry and corroborated with local data. Range of motion, Oxford Knee Score (OKS) and patient satisfaction were recorded at six weeks and one year post-operatively. Hip-knee-ankle radiographs were used to record pre- and post-operative alignment. RESULTS: Data were collected for 749 knees in 679 patients. Overall survivorship was 99.0% at a mean 5.35 years, with seven patients undergoing revision surgery during the study period. Significant improvements in the OKS (mean 20.7 points) and range of motion were observed (mean 104.6° at one year). 94.9% of patients were satisfied at one year. Mean correction was to a mechanical femoro-tibial angle of 0.8° varus. CONCLUSIONS: We demonstrate excellent medium term survival of the Persona TKA in this large cohort, coupled with improvements in patient reported outcomes, range of motion and patient satisfaction at one year which compare favourably to other implants.

No changes in bone mineral density following total knee arthroplasty using an all-polyethylene tibial component.

PURPOSE: Polyethylene particles produced from metal-backed tibial (MBT) implants are understood to contribute to bone loss and component loosening. This, along with advanced surgical techniques, improved materials and increasing costs, has renewed interest in all-polyethylene tibias (APTs). We investigated peri-APT bone mineral density (BMD) in patients, expecting to find no differences between two post-operative values. METHODS: Patients over 65 years, with BMI ≤ 37.5 kg/m2 and no previous joint replacements were recruited to have computer-navigated total knee arthroplasty using an APT. The study cohort (n = 27) had mean age of 71.9 (SD 4.35) and BMI of 31.2 (SD 3.8). The BMD examinations were performed 6 weeks and 18 months post-operatively. Six regions of interest (ROI) were identified on anterior/posterior and lateral dual-energy X-ray absorptiometry scans. For each ROI, BMD relative differences (RDs) were determined between limbs and RDs at the two time points were compared. RESULTS: No differences were found between the RDs for any ROI. No revisions or complications were reported. At 18 months post-operatively, 79.2% of the cohort were very satisfied or satisfied with the outcome of their surgery and Oxford Knee Scores improved significantly compared to pre-operatively (p < 0.001). Mean knee range of motion was 102° (SD 10.7°), and mean leg alignment was 2.0° valgus (1-6°valgus). CONCLUSION: Results from BMD analysis suggest that implants were well fixated without compromising function. We believe that using APTs with computer navigation is a viable cheaper option to MBTs for patients who are less active, have lower BMI and good bone quality.

Patient compliance with hip precautions 12 weeks following primary elective total hip arthroplasty.

INTRODUCTION: Patients are routinely advised to follow hip precautions following their total hip arthroplasty (THA) surgery. There is lack of evidence regarding compliance with these precautions and when patients return to activities of daily living following their surgery. MATERIALS AND METHODS: We designed a new questionnaire to discover when patients return to their activities of daily living. Two hundred and ninety seven consecutive patients who attended 12 week follow up arthroplasty clinic following their primary elective THA were asked to complete the questionnaire. RESULTS: All patients who attended the follow up clinic at 12 weeks responded to the questionnaire. Only 6.3% (n = 19) of the patients reported that they restricted their daily activities, as prescribed for the full 12 week period, while 50% (n = 148) of patients stopped using prescribed adaptive equipment by 6 weeks after their operation. There were no dislocations recorded among the study group. CONCLUSION: We found that the majority of patients do not adhere to hip precautions advice. They return to their activities of daily living prior to the end of prescription period based on their pain and activity level. Lack of adherence to hip precautions do not predispose to hip dislocation in the immediate post-operative period.

Implant design affects walking and stair navigation after total knee arthroplasty: a double-blinded randomised controlled trial.

BACKGROUND: Dissimilar total knee arthroplasty implant designs offer different functional characteristics. This is the first work in the literature to fully assess the Columbus ultra-congruent mobile (UCR) system with a rotating platform. METHODS: This is a double-blinded randomised controlled trial, comparing the functional performance of the low congruent fixed (CR DD), ultra-congruent fixed (UC) and UCR Columbus Total Knee Systems. The pre-operative and post-operative functional performance of twenty-four osteoarthritic patients was evaluated against nine control participants when carrying out everyday tasks. Spatiotemporal, kinematic and kinetic gait parameters in walking and stair navigation were extracted by means of motion capture. RESULTS: The UC implant provided better post-operative function, closely followed by the UCR design. However, both the UC and UCR groups exhibited restricted post-operative sagittal RoM (walking, 52.1 ± 4.4° and 53.2 ± 6.6°, respectively), whilst patients receiving a UCR implant did not show an improvement in their tibiofemoral axial rotation despite the bearing's mobile design (walking, CR DD 13.2 ± 4.6°, UC 15.3 ± 6.7°, UCR 13.5 ± 5.4°). Patients with a CR DD fixed bearing showed a statistically significant post-operative improvement in their sagittal RoM when walking (56.8 ± 4.6°). CONCLUSION: It was concluded that both ultra-congruent designs in this study, the UC and UCR bearings, showed comparable functional performance and improvement after TKA surgery. The CR DD group showed the most prominent improvement in the sagittal RoM during walking. TRIAL REGISTRATION: The study is registered under the clinical trial registration number: NCT02422251 . Registered on April 21, 2015.

Identifying car ingress movement strategies before and after total knee replacement.

Background: Post-operative performance of knee bearings is typically assessed in activities of daily living by means of motion capture. Biomechanical studies predominantly explore common tasks such as walking, standing and stair climbing, while overlooking equally demanding activities such as embarking a vehicle. Aims: The aim of this work is to evaluate changes in the movement habits of patients after total knee arthroplasty surgery in comparison to healthy age-matched control participants. Methods: A mock-up car was fabricated based on the architecture of a common vehicle. Ten control participants and 10 patients with severe osteoarthritis of the knee attended a single- and three-motion capture session(s), respectively. Participants were asked to enter the car and sit comfortably adopting a driving position. Three trials per session were used for the identification of movement strategies by means of hierarchical clustering. Task completion time was also measured. Results: Patients' movement behaviour didn't change significantly following total knee arthroplasty surgery. Control participants favoured different movement strategies compared to patients post-operatively. Group membership, height and sidedness of the affected joint were found to be non-significant in task completion time. Conclusion: This study describes an alternative movement identification technique for the analysis of the ingress movement that may be used to clinically assess knee bearings and aid in movement simulations and vehicle design.

Variations in pelvic dimensions: An anatomical and computed tomography study.

The anterior pelvic plane (APP) is a useful anatomical reference with both clinical and research applications in orthopedic surgery and rehabilitation medicine. It is used as a marker for computer-assisted total hip replacement and image-guided assessment of the hip center in clinical gait analysis. Despite its common use, no published data exist on the variations in height and width in an adult population. The aim of this study was to determine the range of dimensions for the anterior pelvic plane found in the Scottish adult population. Thirty-five human cadavers and 100 pelvic computed tomography (CT) scans were examined. Pelvic height and width were measured, and the ratios were determined. The mean width and height for combined cadaver and CT pelves were found to be 238.0 mm (SD 20.1, range 188.3-273.8) and 92.7 mm (SD 10.5, range 71.2-114.7), respectively. The mean width-to-height ratio for all pelves was 2.59 (SD 0.31, range 1.73-3.50). There were no statistically significant differences in means between males and females. The variations of APP dimensions within an adult population are presented. These will be of value in the validation of algorithms for computer navigation and hip joint center calculation in total hip arthroplasty and gait analysis. Furthermore, differences in dimensions between cadaveric and CT measurements have been shown which may have implications for further research and the validity of reference data dependent on data-point acquisition. Clin. Anat. 31:981-987, 2018. © 2018 Wiley Periodicals, Inc.

Risk Factors for Surgical Site Infection Following Lower Limb Arthroplasty: A Retrospective Cohort Analysis of 3932 Lower Limb Arthroplasty Procedures in a High Volume Arthroplasty Unit.

BACKGROUND: Surgical site infection (SSI) is a debilitating complication of lower limb arthroplasty with significant morbidity and increased costs. Numerous risk factors are associated with SSI. METHODS: In an effort to identify novel risk factors for SSI, we undertook a retrospective cohort study of 1832 primary total hip arthroplasties and 2100 primary total knee arthroplasties performed in our high volume arthroplasty unit over a 2-year period. RESULTS: Two risk factors were identified for SSI following total hip arthroplasty: body mass index ≥30 and peri-operative blood transfusion. Eight risk factors were identified for SSI following total knee arthroplasty: hypertension, peri-operative blood transfusion, skin closure using 2-octyl cyanoacrylate, use of oral steroids, reduced serum mean cell volume, reduced mean cell hemoglobin, elevated serum neutrophil count, and use of warfarin or rivaroxaban for venous thromboembolism prophylaxis. CONCLUSIONS: Our work proposes a number of previously undocumented risk factors in relation to SSI. Further investigation is required to ascertain the magnitude of their effect.

Textured insoles reduce vertical loading rate and increase subjective plantar sensation in overground running.

The effect of textured insoles on kinetics and kinematics of overground running was assessed. 16 male injury-free-recreational runners attended a single visit (age 23 ± 5 yrs; stature 1.78 ± 0.06 m; mass 72.6 ± 9.2 kg). Overground 15-m runs were completed in flat, canvas plimsolls both with and without textured insoles at self-selected velocity on an indoor track in an order that was balanced among participants. Average vertical loading rate and peak vertical force (Fpeak) were captured by force platforms. Video footage was digitised for sagittal plane hip, knee and ankle angles at foot strike and mid stance. Velocity, stride rate and length and contact and flight time were determined. Subjectively rated plantar sensation was recorded by visual scale. 95% confidence intervals estimated mean differences. Smallest worthwhile change in loading rate was defined as standardised reduction of 0.54 from a previous comparison of injured versus non-injured runners. Loading rate decreased (-25 to -9.3 BW s-1; 60% likely beneficial reduction) and plantar sensation was increased (46-58 mm) with the insole. Fpeak (-0.1 to 0.14 BW) and velocity (-0.02 to 0.06 m s-1) were similar. Stride length, flight and contact time were lower (-0.13 to -0.01 m; -0.02 to-0.01 s; -0.016 to -0.006 s) and stride rate was higher (0.01-0.07 steps s-1) with insoles. Textured insoles elicited an acute, meaningful decrease in vertical loading rate in short distance, overground running and were associated with subjectively increased plantar sensation. Reduced vertical loading rate could be explained by altered stride characteristics.

Identification of Movement Strategies During the Sit-to-Walk Movement in Patients With Knee Osteoarthritis.

Patients with osteoarthritis of the knee commonly alter their movement to compensate for lower limb weakness and alleviate joint pain. Movement alterations may lead to weight-bearing asymmetries, and potentially to the progression of the disease. This study presents a novel numerical procedure for the identification of sit-to-walk strategies and differences in movement habits between control adults and persons with knee osteoarthritis. Ten control and 12 participants with osteoarthritis performed the sit-to-walk task in a motion capture laboratory. Participants sat on a stool with the height adjusted to 100% of their knee height, then stood and walked to pick up an object from a table in front of them. Different movement strategies were identified by means of hierarchical clustering. Trials were also classified as to whether the left and right extremities used a bilateral or an asymmetrical strategy. Participants with osteoarthritis used significantly more asymmetrical arm strategies (P = .03) while adopting the pushing through the chair strategy more often than the control subjects (P = .02). The results demonstrated that the 2 groups favor different sit-to-walk strategies. Asymmetrical arm behavior possibly indicates a compensation for the weakness of the affected leg. The proposed procedure may be useful to rapidly assess postoperative outcomes and developing rehabilitation strategies.

Effects of 1 week of unilateral ankle immobilization on plantar-flexor strength, balance, and walking speed: a pilot study in asymptomatic volunteers.

CONTEXT: Ankle immobilization is often used after ankle injury. OBJECTIVE: To determine the influence of 1 week's unilateral ankle immobilization on plantar-flexor strength, balance, and walking gait in asymptomatic volunteers. DESIGN: Repeated-measures laboratory study. SETTING: University laboratory. PARTICIPANTS: 6 physically active male participants with no recent history of lower-limb injury. INTERVENTIONS: Participants completed a 1-wk period of ankle immobilization achieved through wearing a below-knee ankle cast. Before the cast was applied, as well as immediately, 24 h, and 48 h after cast removal, their plantar-flexor strength was assessed isokinetically, and they completed a single-leg balance task as a measure of proprioceptive function. An analysis of their walking gait was also completed Main Outcome Measures: Peak plantar-flexor torque and balance were used to determine any effect on muscle strength and proprioception after cast removal. Ranges of motion (3D) of the ankle, knee, and hip, as well as walking speed, were used to assess any influence on walking gait. RESULTS: After cast removal, plantar-flexor strength was reduced for the majority of participants (P = .063, CI = -33.98 to 1.31) and balance performance was reduced in the immobilized limb (P < .05, CI = 0.84-5.16). Both strength and balance were not significantly different from baseline levels by 48 h. Walking speed was not significantly different immediately after cast removal but increased progressively above baseline walking speed over the following 48 h. Joint ranges of motion were not significantly different at any time point. CONCLUSIONS: The reduction in strength and balance after such a short period of immobilization suggested compromised central and peripheral neural mechanisms. This suggestion appeared consistent with the delayed increase in walking speed that could occur as a result of the excitability of the neural pathways increasing toward baseline levels.

Post-operative gait analysis in total hip replacement patients-a review of current literature and meta-analysis.

Gait analysis has been used to measure gait adaptations following total hip replacement (THR) for many years. In this time, advances have been made in implant technology and surgical procedure. However, gait adaptations persist after surgery. This review of seven published studies, where gait characteristics were compared between post-operative THR patients and healthy controls, had the objective of investigating current practice in gait analysis of this patient population and to determine if there is a consensus on post-operative gait changes associated with THR. Levels of methodological quality and study design were found to be variable. Meta-analyses were performed on all gait variables reported by at least three studies to determine overall Cohen's d effect sizes and 95% confidence intervals. Reductions in walking velocity (d=-0.79; CI=-1.54, -0.04), stride length (d=-1.06; CI=-1.62, -0.49) and sagittal hip range of motion (d=-1.58; CI=-2.12, -1.04) were observed. Increases in peak hip flexion (d=0.52; CI=-0.01, 1.09) and extension (d=0.54; CI=-0.10, 1.09) moments were found, although these were likely to be of less clinical significance. Reduced peak hip abduction was also observed (d=-0.58; CI=-1.09, -0.06). Future developments in THR technology and surgical methods should therefore aim to reduce the differences between patients and controls in terms of walking velocity, stride length, hip range of motion and hip abduction moments.