Purpose The purpose of this systematic review and meta-analysis was to investigate the variability in femoral geometric ratios among knees of diferent sexes and races, and to appreciate whether the observed variability is accommodated by commonly implanted total knee arthroplasty (TKA) components. The hypothesis was that the anthropometric studies report considerable variability of femoral geometric ratios among sexes and races. Methods This systematic review and meta-analysis was performed according to the Preferred Reporting Items for Systematic reviews and Meta-analyses (PRISMA) criteria. Two authors independently conducted an electronic search using MEDLINE ® and Embase ® on 6 July 2020 for clinical studies reporting on femoral geometric ratios among sexes and races. Femoral geometric ratios were graphically represented as means and 2 standard deviations, and compared to those of 13 commonly implanted femoral components. Results A total of 15 studies were identiied that reported on a combined total of 2627 knees; all reported the aspect ratio, and 2 also reported the asymmetry ratio and trapezoidicity ratio. Men had wider knees than women, and compared to Caucasian knees, Arabian and Indian knees were wider, while East Asian were narrower. There were no diferences in asymmetry ratio between men and women, nor among Caucasian and East Asian knees. Men had more trapezoidal knees than women, and East Asian knees were more trapezoidal than Caucasian knees. The commonly implanted femoral components accommodated less than a quarter of the geometric variability observed among sexes and races. Conclusion Anthropometric studies reported considerable sexual dimorphism and racial diversity of femoral geometric ratios. Since a surgeon generally only uses one or a few TKA brands, bone-implant mismatch remains unavoidable in a large proportion of knees. These indings support the drive towards personalized medicine, and accurate bone-implant it may only be achievable through customisation of implants, though the clinical beneits of custom TKA remain to be conirmed. Level of evidence IV.

PurposeThe purpose of this systematic review and meta‐analysis was to investigate the variability in tibial geometric ratios among knees of different sexes and races to determine whether commercially‐available tibial baseplates accommodate the morphologic diversity. The hypothesis was that anthropometric studies report considerable variability of tibial geometric ratios among sexes and races. MethodsThis systematic review and meta‐analysis was performed according to the preferred reporting items for systematic reviews and meta‐analyses (PRISMA) criteria. Two authors independently conducted an electronic search using MEDLINE® and Embase® on 28 January 2021 for clinical studies reporting on tibial geometric ratios. Tibial geometric ratios, as reported by the clinical studies, were represented by plotting their means and two standard deviations for comparison to two symmetric and two asymmetric commercially‐available tibial baseplates. ResultsA total of 27 articles that reported on a combined total of 20,944 knees were eligible for data extraction. Variation in tibial aspect ratios was equal among sexes. The greatest variation in aspect ratio was observed among East Asians, followed by Caucasians, African‐Americans, Indian and Middle Easterns. The variation in tibial asymmetry ratio was larger among men compared to women. The greatest variation in asymmetry ratio was observed among African‐Americans, followed by Caucasians, East Asians, Indian and Middle Easterns. Bone‐implant mismatch of > 3 mm overhang or > 4 mm under‐coverage with four commercially‐available tibial baseplates occurred in large proportions of knees due to variations in aspect ratio (in 17–100% of knees) and asymmetry ratio (in 7–100% of knees). ConclusionAnthropometric studies reported considerable inter‐individual variability of tibial geometric ratios, which exceeded effects of sexual dimorphism and racial diversity. Bone–implant mismatch may be unavoidable in a large proportion of knees, when considering that a surgeon generally only uses one or a few TKA brands. These findings support the drive towards patient‐specific implants to potentially achieve accurate bone–implant fit by implant customisation. Level of evidenceIV.

Purpose To report the early clinical and radiographic outcomes of custom total knee arthroplasty (TKA) in knees that had prior osteotomies and/or extra-articular fracture sequelae. Methods The authors retrospectively analysed a consecutive series of 444 knees that received custom TKA between 2016 and 2019 and identiied 41 knees that had prior extra-articular events (osteotomies or fracture sequelae). Patients responded to pre-and post-operative (> 12 months) questionnaires, including Knee Society Score (KSS), Oxford Knee Score (OKS), Forgotten Joint Score (FJS) and Knee injury and Osteoarthritis Outcome Score (KOOS). Net improvements were calculated by subtracting pre-from post-operative scores. In addition to a preoperative CT scan, pre-and post-operative long-leg weightbearing radiographs were obtained, on which the hip-knee-ankle (HKA) angle, femoral mechanical angle (FMA, between femoral mechanical axis and joint line) and tibial mechanical angle (TMA, between tibial mechanical axis and joint line) angles were measured, and alignment was planned within a 'target zone' of FMA and TMA within 85°-95° and HKA angle within 175°-183°. Agreements between preoperative, planned and post-operative angles were calculated using intra-class correlation coeicients (ICC). Results From the initial 41 knees, 3 had incomplete post-operative data and 1 was revised for painful stifness due to uncorrected rotational malunion, leaving 37 knees for analysis. Twenty had prior osteotomies (tibia, n = 18, femur, n = 2), 8 had isolated fractures (tibial, n = 3; femoral, n = 5), and 9 had both osteotomies and fractures. Postoperative coronal alignments were 90.4° ± 2.4° for FMA, 89.3° ± 2.6° for TMA and 179.9° ± 3.0° for HKA angle. Agreements between planned and achieved alignments were fair to excellent, and 29 (78%) knees were within the 'target zone'. At a mean follow-up of 15 ± 5 months, all clinical scores had improved signiicantly (p < 0.001). Conclusions Custom TKA granted satisfactory clinical outcomes and a low complication rate in knees that had prior osteotomies and/or extra-articular fracture sequelae. Using custom implants and strategies for coronal alignment, 29 (78%) of the 37 knees were successfully aligned within the 'target zone', and 35 (95%) of the 41 knees did not require ligament release. Level of evidence IV.