Romain Gaillard

Equivalent wear performance of dual mobility bearing compared with standard bearing in total hip arthroplasty: in vitro study

PurposeOsteolysis in total hip arthroplasty (THA) depends on polyethylene wear and dictates the survival of the prosthesis. Dual mobility in THAs, which is claimed to reduce dislocation risk, has very good long-term clinical results. However, little is known about how the liner wears in this design, compared to the standard single mobility model.MethodsA comparative study looking at wear of a conventional ultra-high-molecular-weight polyethylene liner, using gravimetric measurement, between dual mobility implants and standard implants, was performed on a simulator in accordance with a normed protocol based on the same dimensions, environmental conditions and stresses. A linear regression test was employed.ResultsUnder the same conditions (loading, cycles, sterilization, material and surface roughness), the gravimetric wear (for conventional polyethylene) is comparable between a standard and a dual mobility cup. This correlates to ten year follow-up results of dual mobility cup.Discussion - ConclusionThis in vitro equivalent wear serves to confirm the very good long-term clinical results observed with dual mobility bearing, whose use should not be restricted by concerns about increased polyethylene wear.

Total knee implant posterior stabilised by a third condyle: Design evolution and post-operative complications

BACKGROUND Despite excellent long-term outcomes, posterior stabilisation by a third condyle continues to receive unwarranted criticism regarding patellar complications and instability. HYPOTHESIS Complication rates with a tri-condylar posterior-stabilised implant are similar to those with other posterior-stabilised prostheses and have diminished over time due to improvements in prosthesis design. MATERIAL AND METHODS Post-operative complications and revision rates were assessed retrospectively in a prospective cohort of 4189 consecutive patients who had primary total knee arthroplasty (TKA) using a tri-condylar posterior-stabilised implant (Wright-Tornier) and were then followed-up for at least 24 months. The analysis included 2844 knees. The prosthesis generations were HLS1®, n=20; HLS2®, n=220; HLS Evolution®, n=636; HLS Noetos®, n=1373; and HLS KneeTec®, n=595. Complications were compared across generations by applying Fishers exact test, and survival was compared using the Kaplan-Meier method. RESULTS At last follow-up, there had been 341 (12%) post-operative complications in 306 (10.8%) knees, including 168 (5.9%) related to the implant, 41 (1.4%) infections, and 132 (4.6%) secondary complications unrelated to the implant. Re-operation was required for 200 complications (7%), including 87 (3.1%) consisting in revision of the prosthesis. Implant-related complications were stiffness (n=67, 2.4%), patellar fracture (n=34, 1.2%), patellar clunk syndrome (n=25, 0.9%), patellar loosening (n=3, 0.1%), tibial/femoral loosening (n=15, 0.5%), polyethylene wear (n=3, 0.1%), and implant rupture (n=1, 0.04%). Significant differences across generations were found for stiffness (P<0.0001), patellar fracture (P=0.03), clunk syndrome (P=0.03), and polyethylene wear (P=0.004), whose frequencies declined from one generation to the next. Overall 10-year survival was 92% with no significant difference across generations (P=0.1). DISCUSSION Outcomes of tri-condylar posterior-stabilised TKA are similar to those obtained using other posterior-stabilised implants. Neither patellar complications nor instability are more common, and improvements in implant design have contributed to correct early flaws. LEVEL OF EVIDENCE IV, historical cohort, retrospective assessment of prospectively collected data.

Fewer complications after UKA than TKA in patients over 85 years of age: A case-control study

INTRODUCTION Implanting a knee prosthesis in patients aged over 85 years is not without risk. Unicompartmental knee arthroplasty (UKA) is reputed to show lower morbidity and mortality than total knee arthroplasty (TKA). Elderly patients with isolated unicompartmental osteoarthritis without specific contraindications are thus good candidates for this procedure. The present retrospective case-control study compared complications rates in elderly patients receiving UKA versus TKA. The study hypothesis was that UKA incurs fewer complications, with equivalent functional results. MATERIAL AND METHODS Five hundred and forty-four UKAs were performed between 1987 and 2015; all patients aged 85 years or over (n=30) were included, and age-matched at a rate of 1 UKA for 3 TKAs in our database of 4,216 TKA procedures. Mean age was 87.5 years (range, 85-92 years). The main endpoint was complications rate; secondary endpoints comprised satisfaction, IKS function and knee scores, and implant survival. RESULTS Mean follow-up was 32 months (range, 12-118 months) for UKA and 34 months (range, 12-100 months) for TKA. The medical complications rate was significantly lower with UKA (6.7% versus 25.6%; P=0.02), with no early mortality. IKS scores were identical between UKA and TKA groups at last follow-up: knee, 93.8 (95% CI [89.7-98.0]) versus 89.5 (95% CI [85.6-93.4]), P=0.06; function, 63.8 (95% CI [53.1-74.5]) versus 67.0 (95% CI [61.3-72.7]), P=0.62. Satisfaction rates were likewise identical: 96% and 97%, respectively (P=0.77); and implant survivorship was identical (P=0.54). DISCUSSION Early medical complications were fewer after UKA than TKA in a population aged ≥85 years, with comparable clinical outcome. These results argue in favor of UKA in elderly patients with comorbidities. LEVEL OF EVIDENCE III, case-control study.

Anatomy, Physiology, and Biomechanics of the Native Knee

The knowledge of anatomy, physiology, and biomechanics of the knee is fundamental to fully understand the different surgical pathologies. In fact, the different approaches of the knee are based on precise anatomical criteria, in order not to harm the important structures. In addition, knee arthroplasty is based on the precise knowledge of the physiological movement of the joint and on its biomechanics to reproduce as accurately as possible the native knee. The knee is a complex joint, where each anatomical structure has a specific and important role, explaining the abundance pathology and its consequences for the patient. The physiological movement of the knee is not just a simple flexion-extension, but includes rotation, translation and angulation, allowing precise positioning and load transfer through the lower limb. The goal of this chapter is to help surgeon understand knee anatomy for his professional practice.