Pre-milling technique improves the accuracy of posterior femoral condyle cut and reduces the tibial recut in Oxford unicompartmental knee arthroplasty.

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.

Preoperative Arithmetic Hip-Knee-Ankle Angle as a Predictor of Postoperative Leg Alignment in Medial Oxford Unicompartmental Knee Arthroplasty.

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.

Caliper-Based Restricted Kinematic Alignment Total Knee Arthroplasty.

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.

A Muscle-Preserving Short Transverse Incision for Unicompartmental Knee Arthroplasty: A Technical Note.

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.

Relationship between inferior alveolar nerve canal position at mandibular second molar in patients with prognathism and possible occurrence of neurosensory disturbance after sagittal split ramus osteotomy.

PURPOSE: To elucidate the relationship between the anatomic position of the inferior alveolar nerve (IAN) at the mandibular second molar and the occurrence of neurosensory disturbances of the IAN after sagittal split ramus osteotomy (SSRO) in patients with mandibular prognathism. Also, the present study evaluated the difference in anatomic position of the IAN between patients with and without mandibular prognathism. PATIENTS AND METHODS: Computed tomography images were taken of 28 patients with mandibular prognathism and 30 without prognathism. On these scans, the IANs from the mandibular second molar region to the mandibular foramen in the mandibular ramus were identified. The present study was designed as a cross-sectional study. The distance from the buccal aspect of the IAN canal to the outer buccal cortical margin of the mandible in the mandibular second molar regions was measured on the computed tomography images. Also, the linear distance between the superior aspect of the IAN canal and the alveolar crest in these regions was calculated. In addition, we investigated the presence or absence of contact between the IAN canal and the inner buccal cortical margin of the mandible from the mandibular second molar to the mandibular foramen in the mandibular ramus. Next, we examined whether neurosensory disturbances occurring after SSRO were related to the position of the IAN at the mandibular second molar. RESULTS: A significant difference was found in the occurrence of neurosensory disturbances of the IAN after SSRO between men and women (χ(2) test, P < .05). For the distance from the buccal aspect of the IAN canal to the outer buccal cortical margin of the mandible in the mandibular second molar region, a significant difference was found between groups with and without neurosensory disturbances (Student's t test, P < .01). The shorter the distance from the buccal aspect of the IAN canal to the outer buccal cortical margin, the more frequent the occurrence of neurosensory disturbances of the IAN. CONCLUSIONS: The present results have demonstrated that gender and the anatomic position of the IAN canal at the mandibular second molar are significantly related to the occurrence of neurosensory disturbances of the IAN after SSRO. Therefore, surgeons should clearly inform patients of the increased possibility of neurosensory disturbances after SSRO when the patients are female and are found to have a shorter distance from the buccal aspect of the IAN canal to the outer buccal cortical margin.