Yoshikazu Tsuneizumi

Lateral Laxity in Flexion Increases the Postoperative Flexion Angle in Cruciate-Retaining Total Knee Arthroplasty

Thirty-eight patients diagnosed with osteoarthritis underwent 41 cruciate-retaining total knee arthroplasties. In varus and valgus tests at flexion, subjects were seated on a table at 80° of knee flexion; 50 N was applied perpendicular to the lower leg. The factors affecting the postoperative flexion angle were investigated in a multiregression analysis. The mean joint angles of the flexion-valgus and flexion-varus tests were 3.4° ± 1.4° and 6.2° ± 2.5°, respectively. The flexion-varus angle was correlated with the postoperative flexion angle (P < .01). The mean postoperative flexion angles were 110.8° ± 9.6° and 118.1° ± 8.0° in the groups with the flexion-varus angle of 6° or less and more than 6°, respectively (P = .02). Slack lateral laxity in flexion had a significant effect during knee flexion in cruciate-retaining total knee arthroplasty.

The tibial crest as a practical useful landmark in total knee arthroplasty.

BACKGROUND The middle one-third of the tibial crest in the coronal plane and the fibula in the sagittal plane are known as landmarks for extramedullary guides in total knee arthroplasty (TKA). However, there are few foundational anatomic studies about them. We conducted this study to confirm whether these landmarks are reliable. METHODS We evaluated 100 Japanese knees using 3D imaging software. We examined our data for correlations between the angle of deviation from the mechanical axis and patient-specific factors (i.e. hip-knee-ankle angle, tibial length, tibial bowing, and tibial torsion) to determine whether there are any individual factors affecting their reliability. RESULTS The mean angles between each of the axes defined by the fibula and the tibial crest with the mechanical axis were 2.9°±0.6° of valgus and 0.7°±0.9° of varus in the coronal plane and 2.2°±0.8° of posterior and 3.6°±1.0° of anterior inclination in the sagittal plane. The middle one-third of the tibial crest (TCL) was revealed as a useful landmark, especially in female patients, who possess TCLs that were within 3° of the tibial mechanical axis in the coronal plane. There were no patient-specific factors strongly affecting reliability of these landmarks. CONCLUSIONS We can use these landmarks even if the patient has tibial bowing or severe varus deformity. Although not considering soft tissue thickness, our study demonstrated that the tibial crest in the coronal and sagittal planes could be useful guidelines in performing TKAs. LEVEL OF EVIDENCE II.

Evaluation of joint laxity against distal traction force upon flexion in cruciate-retaining and posterior-stabilized total knee arthroplasty.

BackgroundSeveral studies have reported varus-valgus stability in the extension position after total knee arthroplasty (TKA). However, few studies have evaluated joint laxity in the flexion position postoperatively. The purpose of the study was to evaluate joint laxity against distal traction force on flexion after cruciate-retaining and posterior-stabilized total knee arthroplasties.MethodsA total of 44 knees (22 knees cruciate-retaining, 22 knees posterior-stabilized) in 40 patients with osteoarthritis were tested in this study. The subjects were seated at a table and their knee joints were fixed at 80° of flexion to avoid overlapping images of condyles and the femoral shaft. Tibial shafts were adjusted to be parallel to the radiographic films, and posteroanterior radiographs were obtained. Flexion stress tests were performed with a distal traction of 100 N at a neutral foot position. Radiographs were obtained at neutral and traction positions. The distance from the perpendicular line of the top of the polyethylene insert to the midpoint on the tangential line of the femoral condyle was measured (joint space distance) at each side.ResultsIn the flexion-neutral position, average joint space distances were 0.1 ± 0.2 mm in cruciate-retaining (CR) TKA knees and 0.2 ± 0.3 mm in posterior-stabilized (PS) TKA knees. With flexion-traction stress tests, the average joint space distances were 0.5 ± 0. 5 mm in CR TKA knees 2.4 ± 1.2 mm in PS TKA knees. Average changes of joint space distances between the two positions were 0.3 ± 0.4 mm (CR TKA) and 2.2 ± 1.5 mm (PS TKA). The changes in joint space distances between neutral and traction positions of PS TKA knees were significantly larger than those of CR TKA knees in flexion stress tests (P < 0.01).ConclusionThe posterior cruciate ligament acted as a stabilizer against distal traction force in the CR-TKA knees. However, the laxity of PS-TKA knees against distal force differed among individual cases.

The Effect of a Sagittal Cutting Error of the Distal Femur on the Flexion-Extension Gap Difference in Total Knee Arthroplasty

The aim of this study was to determine how much a distal femoral cutting error would affect the flexion-extension gap difference (flexion gap minus extension gap) in total knee arthroplasty (TKA). We evaluated 15 knees using a computer-simulation technique. Bone cutting errors of -2°, 2° and 4° of extension were simulated in three TKA systems. A distal femoral cutting error of 2° of extension or flexion caused a change in the difference between the flexion and extension gaps of approximately two mm in all three TKA systems. Surgeons should recognize that distal femoral cutting errors have a significant effect on the flexion-extension gap difference in TKA and pay particular attention to the alignment of the distal cutting surface.

The Effect of Rotational Fixation Error of the Tibial Cutting Guide and the Distance Between the Guide and the Bone on the Tibial Osteotomy in Total Knee Arthroplasty

Computed tomography based computer simulation studies were made on fifty consecutive patients with osteoarthritis scheduled for TKA. Proximal tibial cutting was simulated with the cutting guide placed at different rotational errors (-10°, 0°, 10° and 20° of internal rotation) and different distances (4 cm and 8 cm) between the alignment rod and the bone. Only ten degrees of rotation error with 8 cm of distance resulted in over 3° of varus or valgus tibial cut. Our study demonstrated that rotational mismatch between the proximal and distal part of the tibia should be avoided and the distance between the alignment rod and the bone should be as short as possible to achieve proper tibial alignment.

The distance from the extramedullary cutting guide rod to the skin surface as a reference guide for the tibial slope in total knee arthroplasty

BACKGROUND Although sagittal tibial alignment in total knee arthroplasty (TKA) is important, no landmarks exist to achieve a reproducible slope. The purpose of this study was to evaluate the clinical usefulness of the distance from the guide rod to the skin surface for the tibial slope in TKA. METHODS Computer simulation studies were performed on 100 consecutive knees scheduled for TKA. The angle between the line connecting the most anterior point of the predicted tibial cut surface and the skin surface 20 cm distal to the predicted cut surface (Line S) and the mechanical axis (MA) of the tibia in the sagittal plane was measured. RESULTS The mean (±SD) absolute angle difference between the Line S and the MA was 0.9°±0.7°. The Line S was almost parallel to the MA in the sagittal plane (95% and 99% within two degrees and three degrees of deviation from MA, respectively). CONCLUSION The guide rod orientation is a surrogate for the tibial cut slope because the targeted posterior slope is usually built into the cutting block and ensuring the rod is parallel to the MA in the sagittal plane is recommended. Therefore the distance between the skin surface and the rod can be a useful guide for the tibial slope. LEVEL OF EVIDENCE II.

A Useful Anatomical Reference Guide for Stem Anteversion during Total Hip Arthroplasty in the Dysplastic Hip

Computed tomography scans of 50 dysplastic hips were obtained and reconstructed using preoperative planning software for total hip arthroplasty. The anteversion of the stem implanted parallel to the line connecting the trochanteric fossa and the middle of the medial cortex of the femoral neck (T line) was measured. The cutting heights of 5mm and 10mm above the lesser trochanter were simulated. The mean difference of the anteversion of the stem using the T line and the native femoral anteversion was 2.7° (95% CI: 1.0°-4.5°) and 3.5° (95% CI: 1.5°-5.5°) at cutting heights of 5mm and 10mm respectively. An anteversion using a T line is compatible with native femoral anteversion even in developmental dysplasia of the hip.

The rectangular flexion gap is associated with an increased knee flexion angle in a cruciate-sacrificing rotating platform mobile-bearing total knee arthroplasty

BACKGROUND The knee flexion angle after a total knee arthroplasty is an important indicator of clinical outcome. However, there is little appropriate information about the correlation between the ligament balancing and knee flexion angle after total knee arthroplasty. The purpose of this study was to investigate the effect of the ligamentous balance in extension and flexion on knee flexion angle one year after posterior cruciate ligament sacrificing rotating platform total knee arthroplasty. METHODS Eighty-five total knee arthroplasties in 71 patients were investigated in this study. The postoperative knee flexion angle and the percentage of improvement in the balanced group in which the difference between varus and valgus was less than 2° and the unbalanced group in extension and the rectangular group in which the asymmetry of the flexion gap was within 2° and the trapezoidal group in flexion were compared. The factors affecting postoperative knee flexion angle were also investigated in a forced entry multiple regression analysis. RESULTS The mean flexion angle improved significantly from 116.2° to 122.5° in the rectangular group. By contrast, in the trapezoidal group, no significant improvement was seen (from 115.5° to 117.4°). The statistically significant difference was found between the rectangular and trapezoidal group in flexion in terms of the improvement of the knee flexion angle while there was no difference between the balanced and unbalanced group in extension. The multiple regression analysis showed that the asymmetry of the flexion gap was a predictor of the postoperative knee flexion angle. CONCLUSIONS Asymmetric flexion gap affected negatively the postoperative knee flexion angle after posterior cruciate ligament sacrificing rotating platform total knee arthroplasty. A gap balancing technique is recommended for this type of implant.

A new technique for single-segment bone graft, decompression, and fusion in patients with C1/2 canal stenosis: technical note

Posterior fusion is a standard procedure for C1/2 instability [1–5], and is indicated for a wide variety of conditions that cause atlantoaxial instability, such as inflammatory disease, trauma, degenerative disease, and anatomic anomalies. These pathological conditions often necessitate not only stabilization but also spinal cord decompression, but there are few reports that focus on the surgical technique for simultaneous decompression and fusion [6, 7]. Although conventional C1 laminectomy is the gold standard for decompression at the atlas, it provides little space for bone grafting to fuse, which is a serious deficiency when fusion is indicated. Innovations in surgical instruments have brought about remarkable progress in providing rigid initial fixation [2, 3, 5], but instrument failure, such as loosening and breakage leading to nonunion, is always a possibility [8, 9]. Bone grafting is indispensable in avoiding this complication, as permanent stability can be achieved once fusion has occurred. In this report, we introduce a new technique for achieving single-segment bone grafting, decompression, and fusion in patients with C1/2 canal stenosis. We also present two representative patients who underwent surgery with this technique, the first with an irreducible axis odontoid fracture secondary to trauma, and the second with a retro-odontoid pseudotumor.