Introduction

Partial knee arthroplasty (PKA) has demonstrated the potential to improve patient satisfaction over total knee arthroplasty. It is however perceived as a more challenging procedure that requires precise adaptation to the complex mechanics of the knee. A recently developed PKA system aims to address these challenges by anatomical, compartment specific shapes and fine-tuned mechanical instrumentation. We investigated how closely this PKA system replicates the balance and kinematics of the intact knee.

Background

A principle of Total Knee Arthroplasty (TKA) is to achieve a neutral standing coronal alignment of the limb (Hip Knee Ankle (HKA) angle) to reduce risks of implant loosening, reduce polyethylene wear, and optimise patella tracking. Several long-term studies have questioned this because the relationship between alignment and implant survivorship is weaker than previously reported. We hypothesize standing HKA poorly predicts implant failure because it does not predict dynamic HKA, dynamic adduction moment, and loading of the knee during gait. Therefore, the aim of our study is to assess the relationship between the standing (or static) and the dynamic (gait activity) HKAs.

The mechanical alignment (MA) for Total Knee Arthroplasty (TKA) with neutral alignment goal has had good overall long-term outcomes. In spite of improvements in implant designs and surgical tools aiming for better accuracy and reproducibility of surgical technique, functional outcomes of MA TKA have remained insufficient. Therefore, alternative, more anatomicaloptions restoring part (adjusted MA (aMA) and adjusted kinematic alignment (aKA) techniques) or the entire constitutional frontal deformity (unicompartment knee arthroplasty (UKA) and kinematic alignment (KA) techniques) have been developed, with promising results. The kinematic alignment for TKA is a new and attractive surgical technique enabling a patient specific treatment. The growing evidence of the kinematic alignment mid-term effectiveness, safety and potential short falls are discussed in this paper. The current review describes the rationale and the evidence behind different surgical options for knee replacement, including current concepts in alignment in TKA. We also introduce two new classification systems for “implant alignments options” (Figure 1) and “osteoarthritic knees” (Figure 2) that would help surgeons to select the best surgical option for each patient. This would also be valuable for comparison between techniques in future research.

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Treatment of osteoarthritis of the knee remains a challenging problem since the evolution of the disease may be different in each compartment of the knee, as well as the state of the ligaments. Total knee arthroplasty may provide a reliable long-lasting option but do not preserve the bone stock. In another hand, compartmental arthroplasty is a bone and ligament sparing solution to manage limited osteoarthritis of the knee affecting the medial, lateral or the patello-femoral compartment.1, 2, 3

Patient's selection and surgical indication are based on the physical examination and on the radiological analysis including full-length x-rays and stress x-rays. Clinical experience has shown the need for high flexion in patients who have both high flexibility and a desire to perform deep flexion.

Additionally the shape differences related to anatomy or the patient expectations after the surgery may also affect the surgeon decision. 4

The limited incision into the extensor mechanism allows a quicker recovery which represents a functional improvement for the patient additionally to the cosmetic result. A dedicated physiotherapy starting on the following day allowing weight bearing exercises protected by crutches and focusing on early mobilization and range of motion combined to a multimodal pain management approach is critical despite the type of individualized solution chosen for the patient knee. 5

Since bony landmarks may be different form a patient to another one as well as anatomical shapes, several tools have been developed in order to provide the surgeons an assisted tool during the surgery adapted to each knee, this include navigation, patient specific instrumentation and robotic surgery.

Whether to resurface the patella during a primary Total Knee Replacement (TKR) performed as a treatment of degenerative osteoarthritis remain a controversial issue. Patellar resurfacing was introduced because early implants were not designed to accommodate the native patella in an anatomic fashion during the range of motion. Complications related to patella resurfacing became a primary concern and have been associated with the variable revision rates often report post TKR. Subsequent modifications in implant design have been made to offer the surgeon option of leaving the patella un-resurfaced.

Numerous clinical trials have been done to determine the superiority of each option. Unfortunately, there is little consensus and surgeon preference remains the primary variable. One of the major reasons given to support patella resurfacing is to eliminate Anterior Knee Pain post operatively. However, studies have shown that this problem was not exclusively found in non-resurfaced patients so the author conclude that anterior knee pain is probably related to component design or to the details of the surgical technique, such as component rotation rather that whether or not the patella is resurfaced.

An increasing rate of complications with the extensor mechanism after patellar resurfacing led to the concept of selective resurfacing of the patella in TKR. Decision making algorithms with basis of clinical, radiographic and intraoperative parameters have been developed to determine which patients are suitable for patella resurfacing and which are suitable for patella non-resurfacing.

Finally, the continued study of this topic with longer follow up term in randomized, controlled, clinical trials remains essential in our understanding of patella in TKR. The development of joint registry will allow surgeons to draw conclusions on the basis of larger numbers of patients and will improve the reporting of the results of patellar non resurfacing in clinical trials. In general, surgeons in United States always resurface while their counterparts in Europe tend to never resurface.

Improving the adaptation between the implant and the patient bone during total hip arthroplasty (THA) may improve the survival of the implant. This requires a perfect understanding of the tridimensional characteristics of the patient hip. The perfect evaluation of the tridimensional anatomy of the patient hip can be done pre-operatively using X-rays and CT-scan. All patients underwent a standard x-rays evaluation in the same center according to the same protocol. Pre-operatively, the frontal analysis of the hip geometry was performed and the optimal center of rotation, CCD angle, neck length and lever arm was analyzed to choose the optimal solution for proper balance of the hip in order to obtain adequate range of motion, appropriate leg length, and correct tension of the abductors muscles. Standard or lateralized monoblock stems can be valid or modular neck shape can be choosen among 9 available shape. These 9 frontal shapes are available in standard, anteverted or retroverted shapes, leading to 27 potential neck combinations. In case of important hip deformation, a custom implant can be used in order to balance the extra-medullar geometry without compromising the intra-medullary adaptation of the stem.

We prospectively included 209 hips treated in our institution with total hip arthroplasty performed using a supine Watson-Jones approach and the same anatomic stem. The mean patient age was 68 years and the mean BMI 26 Kg/m². Intra-operatively the sagittal anatomy of the hip was analyzed and standard, ante or retro modular necks were tested for the frontal shape defined pre-operatively.

According to the pre-operative frontal planning, non-standard necks were required in 24 % of the cases to restore the anatomy of the hip. Intra-operatively, a sagittal correction using anteverted neck was required in 5% of the cases and retroverted necks in 18% of the cases. Harris hip score improved from 56 to 95 points at min. 5 year follow-up. No leg length discrepancy greater than 1 cm was observed. Restoration of the lever arm (mean 39.3 mm, range 30 to 49 mm) and of the neck length (55.2, range 43 to 68 mm) was adapted for 95% compared to the non operate opposite side. Disturbed anatomy like in DDH or post-traumatic cases may require additional solutions to balance the hip such combined osteotomy or customized stem and neck.

Introduction:

Recent studies have concluded that gender influences hip morphology at the time of surgery as well as dysplastic development of the hip. This may lead to a particular choice of implant including stem design and/or neck modularity. In this study we hypothesized that not only gender but also morphotype and etiology (primary osteoarthritis versus aseptic osteonecrosis) may be a significant factor to predict the anatomy of the hip at the time of total hip arthroplasty (THA).

Introduction

Previous fluoroscopic studies compared total knee arthroplasty (TKA) kinematics to normal knees. It was our hypothesis that comparing TKA directly to its non-replaced controlateral knee may provide more realistic kinematics information. Using fluoroscopic analysis, we aimed to compare knee flexion angles, femoral roll-back, patellar tracking and internal and external rotation of the tibia.