Femoral cartilage thickness measured on MRI varies among individuals: Time to deepen one of the principles of kinematic alignment in total knee arthroplasty. A systematic review.

PURPOSE: Kinematically aligned total knee arthroplasty (KA TKA), as a pure resurfacing procedure, is based on matching implant thickness with bone cut and kerf thickness, plus cartilage wear. However, the assumption of a consistent 2 mm femoral cartilage thickness remains unproven. This study aimed to systematically review the available literature concerning magnetic resonance imaging (MRI) assessment of femoral cartilage thickness in non-arthritic patients. Our hypothesis was that cartilage thickness values would vary significantly among individuals, thereby challenging the established KA paradigm of 'one-cartilage-fits-all'. METHODS: Systematic literature searches (Pubmed, Scopus and Cochrane Library) followed PRISMA guidelines. English-language studies assessing distal and posterior femoral cartilage thickness using MRI in non-arthritic adults were included. Studies lacking numerical cartilage thickness data, involving post-operative MRI, considering total femoro-tibial cartilage thickness, or failing to specify the compartment of the knee being studied were excluded. RESULTS: Overall, 27 studies comprising 8170 MRIs were analysed. Weighted mean femoral cartilage thicknesses were: 2.05 ± 0.62 mm (mean range 1.06-2.6) for the distal medial condyle, 1.95 ± 0.4 mm (mean range 1.15-2.5) for the distal lateral condyle, 2.44 ± 0.5 mm (mean range 1.37-2.6) for the posterior medial condyle and 2.27 ± 0.38 mm (mean range 1.48-2.5) for the posterior lateral condyle. DISCUSSION: Femoral cartilage thickness varies significantly across patients. In KA TKA, relying on a fixed thickness of 2 mm may jeopardize the accurate restoration of individual anatomy, leading to errors in implant coronal and rotational alignment. An intraoperative assessment of cartilage thickness may be advisable to express the KA philosophy at its full potential. LEVEL OF EVIDENCE: Level IV.

Accuracy of two-dimensional digital planning in uncemented primary hip arthroplasty: monocentric analysis of eight hundred implants.

PURPOSE: In the last decades, there has been a refinement in total hip arthroplasty, which allowed surgeons to achieve the highest performance and better patient outcomes. Preoperative planning in primary hip arthroplasty is an essential step that guides the surgeon in restoring the anatomy and biomechanics of the joint. This study aims to evaluate the accuracy of the 2D digital planning, considering cup sizing, stem sizing, and limb length discrepancy. Additionally, we conducted a multivariable analysis of demographic data and comorbidities to find factors influencing preoperative planning. METHODS: This retrospective study analyzed the planning accuracy in 800 consecutive uncemented primary total hip arthroplasty. We compared the preoperatively planned total hip arthroplasty with postoperative results regarding the planned component size, the implanted size, and the lower limb length restoration. Therefore, we investigated factors influencing planning accuracy: overweight and obesity, sex, age, past medical history, comorbidities, and implant design. All the surgeries were performed in the posterolateral approach by one expert surgeon who did the preoperative planning. The preoperative planning was determined to be (a) exact if the planned and the implanted components were the same size and (b) accurate if exact ± one size. The restoration of postoperative limb length discrepancy was classified into three groups: ± 3 mm, ± 5 mm, and ± 10 mm. This assessment was performed through a digital method 2D based on a standard hip X-ray. RESULTS: This court of 800 implants showed that planning was exact in 60% of the cups and 44% of the stems and was accurate in 94% of the cups and 80% of the stems. The postoperative limb length discrepancy was ± 3 mm in 91% and ± 5 mm in 97%. CONCLUSIONS: This study showed preoperative 2D digital planning great precision and reliability, and we demonstrated that it was accurate in 94% of the cups and 80% of the stems. Therefore, the preoperative limb length discrepancy analysis was essential to guarantee the recovery of the operated limb's correct length.

Modular versus monoblock stem in revision total hip arthroplasty: a systematic review and meta-analysis.

Background: Total hip arthroplasty (THA) is estimated to grow in the following decades with a consequent increase of THA revisions (rTHA). This systematic review and meta-analysis aims to compare modular and monoblock stem in rTHA surgery, focusing on clinical and radiological outcomes and complication rates. Methods: A literature search was performed using the following search strategy: ((Modular stem) OR (monolithic stem)) AND (hip review) on PubMed, Scopus, and Cochrane. Randomized controlled trials (RCTs) and observational studies (OS) compared clinical and radiological outcomes, and complication rates for monoblock and modular revision femoral stem were included. The risk of bias was assessed through the Methodological Index for Non-Randomized Studies (MINORS) score. The Review Manager (RevMan) software was used for the meta-analysis. The rate of complications was assessed using odds ratio (OR) with 95% confidence intervals (CIs). Results: The authors included 11 OS and one RCT with 3,671 participants (mean age: 68.4 years old). The mean follow-up was 46.9 months. There was no prevalence of subsidence for one type of stem. Mean subsidence was from 0.92 to 10 mm for modular stem and from 1 to 15 mm for monoblock stem. Postoperative Harris Hip Score (HHS) showed better results with modular stems without statistical significance [mean difference (MD) =1.32; 95% CI: -1.62 to 4.27; P=0.38]. No statistically significant difference was found for dislocations (OR =2.48; 95% CI: 0.67 to 9.14; P=0.17), infections (OR =1.07; 95% CI: 0.51 to 2.23; P=0.86), intraoperative fractures (OR =1.62; 95% CI: 0.42 to 6.21; P=0.48), and postoperative fractures (OR =1.60; 95% CI: 0.55 to 4.64; P=0.39). Conclusions: Modular and monoblock stems show comparable and satisfactory clinical and radiological outcomes for rTHA. Both stems are valid and effective options for managing femoral bone deficit in hip revision surgery. The main limitation of this study is the small number and low quality of enclosed studies that compared the two stems. Moreover, the modular stem is usually used for more complex cases with lower quality femoral bone stock.