Leg length discrepancy following total hip replacement (THR) can contribute to poor hip function. Abnormal gait, pain, neurological disturbance and patient dissatisfaction have all been described as a result of leg length inequality after THR. The purpose of this study was to determine whether the use of computer navigation in THR can improve limb length restoration and early clinical outcomes. We performed a matched-pair study comparing 48 computer-assisted THR with 48 THRs performed using a traditional freehand alignment method. The same implant with a straight non-modular femoral stem was used in all cases. The navigation system used allowed the surgeon to monitor both acetabular cup placement and all the phases of femoral stem implantation including rasping. Patients were matched for age, sex, arthritis level, pre-operative diagnosis and pre-operative leg length discrepancy. At a minimum follow-up of six months, limb length discrepancy was measured using digital radiographs and a standardised protocol. The number of patients with a residual discrepancy of 10 mm or more and/or a postoperative over-lengthening were measured. The clinical outcome was evaluated using both the Harris Hip Score and the normalised Western Ontario and McMaster Universities (WOMAC) Arthritis Index. Restoration of limb length was significantly better in the computerassisted THR group. The number of patients with a residual limb length discrepancy greater than 10 mm and/or a post-operative over-lengthening was significantly lower. No significant difference in the Harris Hip Score or normalised WOMAC Arthritis Index was seen between the two groups. The surgical time was significantly longer in the computer-assisted THR group. No post-operative dislocations were seen.

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Patients older than 60 with unicompartmental knee arthritis can be treated with total or unicompartmental knee replacement. The aim of this study was to compare the results of matched paired groups of patients with isolated medial compartment knee arthritis replaced with either UKR (group A) or computer-assisted TKR (group B). The results included 68 knees at a minimum follow-up of 3 years. All patients had a varus deformity no greater than 8º and a BMI lower than 30. Patients were matched in terms of preoperative arthritis severity, age, gender and preoperative range of motion. In the computer-assisted TKR group, all the implants were positioned within 4º of the correct hip-knee-ankle angle and frontal tibial component angle. The surgical time and hospital stay were statistically longer in the CA TKR group. During the study no implant required revision. The results showed higher scores for a UKR in the treatment of isolated primary unicompartmental knee arthritis in patients older than 60 compared to a computer-assisted TKR. In this study a computer-assisted alignment system for TKR with optimal implant positioning did not produce equivalent clinical results compared to a UKR, but did increase the financial costs.Résumé Les patients âgés de plus de 60 ans, présentant une arthrose unicompartimentale du genou ont été traités soit par une prothèse totale, soit par une prothèse unicompartimentale. Le but de cette étude est de comparer les résultats de patients présentant une arthrose fémoro tibiale interne traités par une prothèse unicompartimentale (groupe A), ou par prothèse totale du genou mise en place par chirurgie assistée par ordinateur (groupe B). Les résultats incluent 68 genoux avec un suivi minimum de 3 ans. Tous les patients avaient une déformation en varus inferiure à 8 degrés et un BMI inférieur à 30. Les patients ont été comparés en fonction du degré d'arthrose, de l'âge, du sexe et de la mobilité pré opératoire. Dans la série prothèse totale, tous les implants ont été positionnés avec une marge de 4°par rapport à l'angle hanche cheville. Le temps opératoire et la durée d'hospitalisation ont été statistiquement plus importants dans le groupe prothèse totale. Aucun implant n'a nécessité de révision. Les résultats montrent que le score est bien meilleur dans les prothèses unicompartimentales pour le traitement des arthroses unicompartimentales, chez ces patients âgés de plus de 60 ans, comparé au traitement par prothèse totale avec chirurgie assistée par ordinateur. Cette étude montre que la mise en place par chirurgie assistée par ordinateur d'une prothèse totale du genou avec un positionnement optimal des implants peut donner un résultat équivalent à celui des prothèses unicompartimentales mais augmente le coût financier du traitement. IntroductionRecent trends in knee reconstructive surgery have included less invasive surgical approaches along with preserving

The results of this 48 months follow-up study suggest that Bi-UKR is a viable option for bicompartmental tibio-femoral arthritis at least as well as TKR but maintaining a higher level of function.

Bone morphology and morphometric measurements of the lower limb provide significant and useful information for computer-assisted orthopedic surgery planning and intervention, surgical follow-up evaluation, and personalized prosthesis design. Femoral head radius and center, neck axis and size, femoral offset and shaft axis are morphological and functional parameters of the proximal femur utilized both in diagnosis and therapy. Obtaining this information from image data without any operator supervision or manual editing remains a practical objective to avoid variability intrinsic in the manual analysis. In this article, we propose a heuristic method that automatically computes the proximal femur morphological parameters by processing the mesh surface of the femur. The surface data are sequentially processed using geometrical properties such as symmetries, asymmetries, and principal elongation directions. Numerical methods identify the axis of the shaft of femur (least squares cylinder fitting), the head surface and center (least squares sphere fitting), and the femur neck axis and radius (minimal area of the cross section by evolutionary optimization). The repeatability of the method was tested upon 20 femur (10 left + 10 right) surfaces reconstructed from CT scans taken on cadavers. The repeatability error of the automated computation of anatomical landmarks, angles, sizes, and axes was less than 1.5 mm, 2.5 degrees, 1.0 mm, and 3.5 mm, respectively. The computed parameters were in good agreement (landmark difference: <2.0 mm; angle difference: <2.0 degrees; axes difference: <2.5 degrees; size difference: <1.5 mm) with the corresponding reference parameters manually identified in the original CT images by medical experts. In conclusion, the proposed method can improve the degree of automation of model-based hip replacement surgical systems.

Purpose The aim of this study was to retrospectively compare the results of two matched-paired groups of patients who had undergone a medial unicompartmental knee arthroplasty (UKA) performed using either a conventional or a nonimage-guided navigation technique specifically designed for unicompartmental prosthesis implantation. Methods Thirty-one patients with isolated medialcompartment knee arthritis who underwent an isolated navigated UKA were included in the study (group A) and matched with patients who had undergone a conventional medial UKA (group B). The same inclusion criteria were used for both groups. At a minimum of six months, all patients were clinically assessed using the Knee Society Score (KSS) and the Western Ontario and McMaster Osteoarthritis Index (WOMAC) index. Radiographically, the frontal-femoral-component angle, the frontal-tibial-component angle, the hip-knee-ankle angle and the sagittal orientation of components (slopes) were evaluated. Complications related to the implantation technique, length of hospital stay and surgical time were compared. Results At the latest follow-up, no statistically significant differences were seen in the KSS, function scores and WOMAC index between groups. Patients in group B had a statistically significant shorter mean surgical time. Tibial coronal and sagittal alignments were statistically better in the navigated group, with five cases of outliers in the conventional alignment technique group. Postoperative mechanical axis was statistically better aligned in the navigated group, with two cases of overcorrection from varus to valgus in group B. No differences in length of hospital stay or complications related to implantation technique were seen between groups. Conclusion This study shows that a specifically designed UKA-dedicated navigation system results in better implant alignment in UKA surgery. Whether this improved alignment results in better clinical results in the long term has yet to be proven.

We showed that the X-ray based reconstruction of the distal femur is reasonable also in presence of pathologic bony conditions, featuring accuracy results similar to earlier reports in the literature that reconstructed normal femurs. This finding discloses the chance of applying the proposed methodology to the reconstruction of bony surfaces used in the PSI surgical approach.