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BACKGROUND: This study aimed to investigate the difference in lateral distal femoral angle (LDFA) between knees with medial osteoarthritis (mOA) and knees without osteoarthritis, and to explore the validity of the assumption that there is no bone wear on the femoral articular surface in kinematic alignment total knee arthroplasty (KA-TKA). METHODS: The study included 69 patients with mOA on one side of the knee and but no OA on the other side. LDFA, medial proximal tibial angle (MPTA), mechanical hip-knee-ankle angle (mHKA), and arithmetic hip-knee-ankle angle (aHKA) were measured and compared between the knees. Pearson's correlation coefficient and paired t-tests were used for statistical analysis. RESULTS: The LDFA and MPTA were significantly more varus in mOA knees than in knees non-OA knees, with differences of 1.0° ± 2.3° and 0.9° ± 2.0°, respectively. The difference between mHKA of the non-OA side and aHKA of the mOA side was not significant, indicating that it is appropriate to use aHKA as an estimation of postoperative alignment after kinematically-aligned total knee arthroplasty without anatomical correction. However, there was a significant difference in MPTA and aHKA between male and female patients in both mOA and non-OA knees. CONCLUSIONS: The assumption that there is no bone wear on the femoral articular surface is rejectable, and the constant compensation thickness of 2 mm for cartilage wear may not be sufficient. Further research is needed to estimate the amount of bone wear in both femur and tibia side to develop more individualized surgical planning strategies in KA-TKA.
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Artroplastia de Reemplazo de Rodilla , Fémur , Osteoartritis de la Rodilla , Humanos , Artroplastia de Reemplazo de Rodilla/métodos , Femenino , Osteoartritis de la Rodilla/cirugía , Osteoartritis de la Rodilla/fisiopatología , Masculino , Anciano , Fémur/cirugía , Persona de Mediana Edad , Fenómenos Biomecánicos , Articulación de la Rodilla/fisiopatología , Articulación de la Rodilla/cirugía , Articulación de la Rodilla/diagnóstico por imagenRESUMEN
BACKGROUND: Recuts are sometimes needed in UKA because of inadequate posterior tibial cut thickness. We investigated the efficacy of a pre-milling technique (the first milling is done prior to the posterior condylar cut) in Oxford unicompartmental knee arthroplasty to enhance bone cut thickness and to minimize tibial recuts. PATIENTS AND METHODS: Between January 2021 and January 2023, a posterior condyle cut was made before milling in 213 knees in 152 patients (conventional group), while the pre-milling technique was used in 198 knees in 140 patients (pre-milling group). The thickness of the posterior condyle and the rate of tibial recuts were compared between the groups. RESULTS: The bone cut thickness was thinner in the conventional group than in the pre-milling group in small-size (4.7 mm ± 0.6 mm and 5.0 mm ± 0.6 mm, P = 0.0001) and in medium-size (5.1 mm ± 0.5 mm and 5.4 mm ± 0.5 mm, 0.0001) femoral components, whereas there was no difference in large-size femoral components. However, the thickness was still less than the component thickness (5.17 mm for small, 5.57 mm for medium and 6.17 mm for large) in both groups. Tibial recuts were more prevalent in the conventional group than in the pre-milling group (14 knees, 7%, 3 knees 2%, P = 0.002). CONCLUSIONS: The pre-milling technique was found to increase the bone cut thickness in small and medium femoral components, reducing the need for tibial recuts. Further research is warranted to optimize the pre-milling technique and to investigate its long-term impact on patient outcomes.
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Artroplastia de Reemplazo de Rodilla , Fémur , Prótesis de la Rodilla , Tibia , Humanos , Artroplastia de Reemplazo de Rodilla/métodos , Femenino , Tibia/cirugía , Masculino , Anciano , Fémur/cirugía , Persona de Mediana Edad , Anciano de 80 o más Años , Estudios Retrospectivos , Diseño de PrótesisRESUMEN
Introduction This study aimed to evaluate whether the arithmetic hip-knee-ankle angle (aHKA) can be used to predict the postoperative HKA. Methods This study included 248 knees in 166 patients who underwent Oxford unicompartmental knee arthroplasty (UKA) between February 2021 and November 2022. Through preoperative and postoperative long-leg radiography, the medial proximal tibial angle (MPTA) and the lateral distal femoral angle (LDFA) were expressed as the deviation from the perpendicular line to the mechanical axes, and the mechanical HKA (mHKA) was defined as the angle between the femoral and tibial mechanical axes. Using the MPTA and LDFA, the arithmetic HKA (aHKA; MPTA + LDFA) and the joint line obliquity (JLO; MPTA - LDFA) were calculated, and the preoperative and postoperative values were compared. Results The preoperative aHKA and the postoperative mHKA values were similar (-0.38° ± 2.96°) and significantly smaller than the difference between the preoperative and postoperative mHKAs (4.58° ± 3.60°, P < 0.05). Meanwhile, the MPTA tended to be varus, and the LDFA tended to be valgus. Eventually, the JLO inclined more medially from -6.33° ± 3.42° preoperatively to -8.97° ± 3.92° postoperatively, representing a significant difference (P < 0.05). Conclusion The preoperative aHKA was similar to the postoperative mHKA. Therefore, it can be regarded as a predictor of postoperative leg alignment after Oxford UKA. Meanwhile, there was a medial incline of the joint line. Further investigation is required to evaluate the effect of such a joint line alteration.
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Restricted kinematic alignment total knee arthroplasty (rKA-TKA) is a reasonable selection for avoiding an extreme alignment that has been conceded to induce implant failure. However, computer-aided devices (CAS), such as navigation, robotics, and patient-specific instrumentation, are necessary to perform rKA-TKA. This paper reports on the surgical technique of kinematic alignment total knee arthroplasty (KA-TKA) using mechanical instruments. The lateral distal femoral angle (LDFA) and the medial proximal tibial angle (MPTA) are measured from preoperative long radiographs or CT of the lower limb, and the arithmetic hip-knee-ankle angle (aHKA) is calculated from the MPTA - LDFA. The predefined restriction boundaries are used to determine the osteotomy angle. In our practice, the LDFA is 85° to 93°, the MPTA is 85° to 90°, and the aHKA is 5° varus to 3° valgus. If correction of the femoral osteotomy is required, this can be achieved by changing the thickness of the paddle set on the distal articular surface or by adjusting the angle of the variable angle femoral cutting guide. For the tibia, the distal end of the extramedullary rod, with the proximal part placed in the center of the knee joint, should be adjusted so that it does not exceed the lateral malleolus. This limits the medial tilt of the osteotomy plane to within 5.5°. These techniques allow restricted KA to be performed with existing mechanical instruments without using CAS.
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We describe the use of a short transverse incision technique with muscle retention for unicompartmental knee arthroplasty (UKA). The incision is made transversely just above the joint line, followed by a detachment of subcutaneous soft tissue from the underlying capsule and fascia to create a mobile window. The fascia is incised along the medial border of the vastus medialis and the capsule of the suprapatellar pouch is incised laterally, preserving vastus medialis muscle. All procedures are performed within the mobile window while controlling the knee flexion angle. Following implantation, the capsule and fascia are anatomically repaired. This approach was used in 30 consecutive patients who underwent Oxford UKA, including one bi-unicompartmental knee arthroplasty without complications. Importantly, no patients had any disturbances of the infrapatellar branch of the saphenous nerve disturbances such as numbness, hyperesthesia, hypoesthesia, or neuroma pain. The transverse approach is thought to be a safe and feasible method for UKA.