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Aims: The aims of this study were: 1) to describe extended restricted kinematic alignment (E-rKA), a novel alignment strategy during robotic-assisted total knee arthroplasty (RA-TKA); 2) to compare residual medial compartment tightness following virtual surgical planning during RA-TKA using mechanical alignment (MA) and E-rKA, in the same set of osteoarthritic varus knees; 3) to assess the requirement of soft-tissue releases during RA-TKA using E-rKA; and 4) to compare the accuracy of surgical plan execution between knees managed with adjustments in component positioning alone, and those which require additional soft-tissue releases. Methods: Patients who underwent RA-TKA between January and December 2022 for primary varus osteoarthritis were included. Safe boundaries for E-rKA were defined. Residual medial compartment tightness was compared following virtual surgical planning using E-rKA and MA, in the same set of knees. Soft-tissue releases were documented. Errors in postoperative alignment in relation to planned alignment were compared between patients who did (group A) and did not (group B) require soft-tissue releases. Results: The use of E-rKA helped restore all knees within the predefined boundaries, with appropriate soft-tissue balancing. E-rKA compared with MA resulted in reduced residual medial tightness following surgical planning, in full extension (2.71 mm (SD 1.66) vs 5.16 mm (SD 3.10), respectively; p < 0.001), and 90° of flexion (2.52 mm (SD 1.63) vs 6.27 mm (SD 3.11), respectively; p < 0.001). Among the study population, 156 patients (78%) were managed with minor adjustments in component positioning alone, while 44 (22%) required additional soft-tissue releases. The mean errors in postoperative alignment were 0.53 mm and 0.26 mm among patients in group A and group B, respectively (p = 0.328). Conclusion: E-rKA is an effective and reproducible alignment strategy during RA-TKA, permitting a large proportion of patients to be managed without soft-tissue releases. The execution of minor alterations in component positioning within predefined multiplanar boundaries is a better starting point for gap management than soft-tissue releases.
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Introduction: The use of image-free robotic systems for total knee arthroplasty (TKA) is gaining popularity. Although the surgical transepicondylar axis (sTEA) is considered the optimal femoral rotational reference during TKA, it is difficult to define intra-operatively. Conventional and image-free robot-assisted TKA (RA-TKA) therefore rely on the use of Whiteside's axis (WSA) or the posterior condylar axis (PCA) as surrogate references. The PCA is considered to be associated with less variability than the WSA. The authors present a simple technique to permit calibration of femoral component rotation (FCR) using the PCA as a reference for image-free robotic systems that do not permit this option. Technique: The image-free robotic systems used by the authors (Navio and CORI, Smith and Nephew, Memphis, TN, USA) permit calibration of FCR only when the perpendicular to WSA is used as a reference. When the PCA is selected as a reference, a fixed 3° of external rotation is set by the robot. The technique proposed by the authors involves the use of the former setting, followed by internal rotation of the perpendicular to the WSA to co-align it with the PCA. The planning menu subsequently permits virtual surgical planning using the PCA as the femoral rotational reference and permits adjustments in rotational positioning of the femoral component while displaying the effect of rotation on bony resection and vice versa in real time. In addition, coaligning the perpendicular to the anatomic trans-epicondylar axis (aTEA) displays the internal rotation of the PCA with respect to the aTEA. This information can be used for setting rotational boundaries with respect to the PCA while using various alternate alignment strategies, like functional alignment, since the relation between the aTEA and sTEA is less likely to be affected by dyplasia and wear when compared with the PCA or WSA. Conclusion: This simple technique permits optimally calibrated rotational positioning of the femoral component during image-free RA-TKA, using the PCA as a reference. It can be applied for optimizing surgery in knees with altered or outlier anatomy, as well as routinely, especially when alternate alignment strategies are used.
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Pilar cysts are derived from the outer layer of the root sheath of hair follicles. They were conventionally thought to arise from hair-bearing skin like the scalp. However, this notion has been refuted recently. Pilar cysts of the hand are extremely rare, with only a few case reports in the literature. We report the case of a 40-year-old male patient, with no known medical co-morbidities, who presented with a swelling over his left thumb. It was occasionally painful, and caused difficulty in grasping objects. Physical examination revealed a 2.5 x 1.5 cm swelling over the volar aspect of the thumb, at the level of the proximal phalanx. MRI revealed the presence of a well-defined cystic lesion superficial to the flexor tendons. The possibility of an epidermal cyst was considered, and the patient was advised surgery in view of his symptoms and progression in the size of the swelling. He underwent excision of the lesion along with a segment of adherent skin. Histopathological examination of the lesion revealed the presence of a pilar cyst. The patient did not have recurrence of symptoms following surgery, and was found to be doing well at the three-year follow-up. This case report urges a re-thinking of the possible origins of pilar cysts from atypical locations.
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AIMS: Total hip arthroplasty (THA) in patients with post-polio residual paralysis (PPRP) is challenging. Despite relief in pain after THA, pre-existing muscle imbalance and altered gait may cause persistence of difficulty in walking. The associated soft tissue contractures not only imbalances the pelvis, but also poses the risk of dislocation, accelerated polyethylene liner wear, and early loosening. METHODS: In all, ten hips in ten patients with PPRP with fixed pelvic obliquity who underwent THA as per an algorithmic approach in two centres from January 2014 to March 2018 were followed-up for a minimum of two years (2 to 6). All patients required one or more additional soft tissue procedures in a pre-determined sequence to correct the pelvic obliquity. All were invited for the latest clinical and radiological assessment. RESULTS: The mean Harris Hip Score at the latest follow-up was 79.2 (68 to 90). There was significant improvement in the coronal pelvic obliquity from 16.6o (SD 7.9o) to 1.8o (SD 2.4o; p < 0.001). Radiographs of all ten hips showed stable prostheses with no signs of loosening or migration, regardless of whether paralytic or non-paralytic hip was replaced. No complications, including dislocation or infection related to the surgery, were observed in any patient. The subtrochanteric shortening osteotomy done in two patients had united by nine months. CONCLUSION: Simultaneous correction of soft tissue contractures is necessary for obtaining a stable hip with balanced pelvis while treating hip arthritis by THA in patients with PPRP and fixed pelvic obliquity. Cite this article: Bone Jt Open 2021;2(9):696-704.