Retrograde intramedullary nailing of the femur: identifying the true anatomic axis for the ideal start point.

PURPOSE: Retrograde femoral intramedullary nailing (IMN) is commonly used to treat distal femur fractures. There is variability in the literature regarding the ideal starting point for retrograde femoral IMN in the coronal plane. The objective of this study was to identify the ideal starting point, based on radiographs, relative to the intercondylar notch in the placement of a retrograde femoral IMN. METHODS: A consecutive series of 48 patients with anteroposterior long-leg radiographs prior to elective knee arthroplasty from 2017 to 2021 were used to determine the femoral anatomic axis. The anatomic center of the isthmus was identified and marked. Another point 3 cm distal from the isthmus was marked in the center of the femoral canal. A line was drawn connecting the points and extended longitudinally through the distal femur. The distance from the center of the intercondylar notch to the point where the anatomic axis of the femur intersected the distal femur was measured. RESULTS: On radiographic review, the distance from the intercondylar notch to where the femoral anatomic axis intersects the distal femur was normally distributed with an average distance of 4.1 mm (SD, 1.7 mm) medial to the intercondylar notch. CONCLUSION: The ideal start point, based on radiographs, for retrograde femoral intramedullary nailing is approximately 4.1 mm medial to the intercondylar notch. Medialization of the starting point for retrograde intramedullary nailing in the coronal plane aligns with the anatomic axis. These results support the integration of templating into preoperative planning prior to retrograde IMN of the femur, with the knowledge that, on average, the ideal start point will be slightly medial. Further investigation via anatomic studies is required to determine whether a medial start point is safe and efficacious in patients with distal femur fractures treated with retrograde IMNs.

Posterior tibial slope measurements based on the full-length tibial anatomic axis are significantly increased compared to those based on the half-length tibial anatomic axis.

PURPOSE: This study aimed to compare the difference in posterior tibial slope (PTS) measurements based on the full-length and half-length tibial anatomic axes of the same group of patients. It was hypothesized that the obtained PTS values would be affected by the length of tibia chosen during the measurements. METHODS: Full-length true lateral tibia radiographs were obtained for each patient who underwent anterior cruciate ligament reconstruction (ACLR) in our department. PTS measurements were obtained by measuring the angle between the full-length or half-length tibial anatomic axis and an average of the lateral and medial tibial plateau. The anatomic axis was defined as the center of the tibial diaphysis. The PTS measurements from the full-length and half-length true lateral tibia radiographs were obtained and compared. Additionally, the absolute difference and the relationship between the two PTS measurements were calculated and analyzed. RESULTS: A total of 200 ACL-injured patients were included in this study. The average PTS values using the anatomic axis were 15.9 ± 3.7° and 14.1 ± 3.7° on full-length and half-length true lateral tibial radiographs. There was a significant difference between the measurements with the full-length and half-length tibial radiographs (P < 0.01). Additionally, 49.5% (n = 99) of patients had ≥ 2.0° differences between the full-length and half-length anatomic axis PTS measurement techniques; meanwhile, a strong and significant linear relationship (r = 0.95; P < 0.001) was identified between the two PTS measurements. CONCLUSION: There were significant differences and linear relationships between PTS measurements that measured the anatomic axis from full-length and half-length true lateral tibia radiographs. Therefore, the obtained PTS values were strongly associated with the length of tibia chosen during the measurements. Surgeons should pay more attention to the measurement techniques and the tibial length when considering the role of PTS in ACL injury and ACLR failure. Knowledge of the association is very important for calculating potential closing wedge proximal tibial osteotomies to correct excessive PTS in the setting of ACLR failures. LEVEL OF EVIDENCE: IV.

Comparison of tibial anatomical-mechanical axis angles and patellar positions between tibial plateau levelling osteotomy (TPLO) and modified cranial closing wedge osteotomy (AMA-based CCWO) for the treatment of cranial cruciate ligament disease in large dogs with tibial plateau slopes greater than 30° and clinically normal Labradors retrievers.

BACKGROUND: The objective of this study was to evaluate tibial anatomical-mechanical axis angles (AMA-angles) and proximodistal and craniocaudal patellar positions following tibial plateau levelling osteotomy (TPLO) and AMA-based modified cranial closing wedge osteotomy (CCWO) in large dogs with tibial plateau angle (TPA) > 30°, to compare these postoperative positions with those of a control group of healthy normal dogs, and to assess which procedure yields postoperative morphology of the tibiae and stifles that is most consistent with that of the unaffected group. This study also investigated whether the occurrence of patellar ligament thickening (PLT), which is commonly observed 2 months postoperatively after TPLO, is associated with misplacement of the osteotomy. A total of 120 dogs weighing more than 20 kg, 40 of which were control animals, were enrolled in this retrospective study. Stifles were radiographically evaluated preoperatively and postoperatively on the side with CCLR and on the healthy contralateral side and compared with clinically normal stifles. PLT was reassessed after 2 months. RESULTS: Significant decreases in median patellar height ratio were found after both procedures (TPLO 0.24 (0.05-0.8); CCWO 0.22 (0.05-0.4)). The postoperative craniocaudal patellar position and the median AMA angle differed significantly among the groups (P = 0.000) (TPLO 87.5% caudal to the AA and 3.12° (0.76-6.98°); CCWO 100% cranial to the AA and 0° (- 1.34-0.65°); control group 5% caudal to the AA and 0.99° (0-3.39°)). At 8 weeks, PLT grade differed significantly in the two operated groups (P = 0.000) (TPLO 40% 0-2, 20% 2-4, 40% > 4; CCWO 98.8% 0). CONCLUSIONS: TPLO and AMA-based CCWO are associated with significant decreases in patellar height; however, the PLT results 2 months postoperatively differed between the two groups; the decrease in patellar height and PLT were independent of osteotomy position in the TPLO group. Compared to TPLO, CCWO results in reduced postoperative AMA angles and craniocaudal patellar positions that more closely resemble those of unaffected dogs, suggesting that the CCWO procedure allows us to better correct the caudal bowing of the proximal tibia that is often associated with deficient stifles in large dogs with TPA > 30°.

A comparison of radiographic anatomic axis knee alignment measurements and cross-sectional associations with knee osteoarthritis.

OBJECTIVE: Malalignment is associated with knee osteoarthritis (KOA), however, the optimal anatomic axis (AA) knee alignment measurement on a standard limb radiograph (SLR) is unknown. This study compares one-point (1P) and two-point (2P) AA methods using three knee joint centre locations and examines cross-sectional associations with symptomatic radiographic knee osteoarthritis (SRKOA), radiographic knee osteoarthritis (RKOA) and knee pain. METHODS: AA alignment was measured six different ways using the KneeMorf software on 1058 SLRs from 584 women in the Chingford Study. Cross-sectional associations with principal outcome SRKOA combined with greatest reproducibility determined the optimal 1P and 2P AA method. Appropriate varus/neutral/valgus alignment categories were established using logistic regression with generalised estimating equation models fitted with restricted cubic spline function. RESULTS: The tibial plateau centre displayed greatest reproducibility and associations with SRKOA. As mean 1P and 2P values differed by >2°, new alignment categories were generated for 1P: varus <178°, neutral 178-182°, valgus >182° and for 2P methods: varus <180°, neutral 180-185°, valgus >185°. Varus vs neutral alignment was associated with a near 2-fold increase in SRKOA and RKOA, and valgus vs neutral for RKOA using 2P method. Nonsignificant associations were seen for 1P method for SRKOA, RKOA and knee pain. CONCLUSIONS: AA alignment was associated with SRKOA and the tibial plateau centre had the strongest association. Differences in AA alignment when 1P vs 2P methods were compared indicated bespoke alignment categories were necessary. Further replication and validation with mechanical axis alignment comparison is required.

Can the Visibility of Both Prosthetic Posterior Femoral Condyles on a Postoperative Radiograph Assure that Limb Rotation Is Appropriate to Allow Accurate Measurement of the Anatomic Knee Axis?

BACKGROUND: To better define radiographic parameters for a true anterior-posterior (AP) knee radiograph after total knee arthroplasty, we cataloged the radiographic appearance of 7 different designs of commercially available femoral components at various points of rotation to correlate the visibility of the prosthetic posterior femoral condyles (PPFCs) with the amount of rotation of the femoral component, and hence, the limb. METHODS: AP radiographs of 7 left-sided, cruciate-retaining femoral trial components were obtained at 5° increments of rotation from 20° internal rotation (IR) to 20° external rotation (ER). Rotational profiles were cataloged based on the visibility of either or both of the PPFCs. RESULTS: Three categories of femoral component rotation profiles were noted, based on the visibility of the PPFC: overt ER with only the medial PFC visible at greater than 10° ER, overt IR with only the lateral PFC visible at greater than 20° IR, and near-neutral rotation with both medial and lateral PPFCs visible between 5° ER and 15° IR. CONCLUSION: An acceptable AP radiograph to measure the anatomic knee axis after total knee arthroplasty is one where both the medial and lateral PPFCs are visible on either side of the trochlear flange.

The influence of tibial length on radiographic posterior tibial slope measurement: How much tibia do we need?

PURPOSE: The purpose of this study was to determine whether significant differences exist when comparing posterior tibial slope (PTS) measured using increasing lengths of the tibia to determine the anatomical axis. METHODS: Patients with full-length weight-bearing tibial radiographs were retrospectively identified from 2014 to 2022 at a single institution. Patients were excluded if there was any previous history of lower extremity fracture or osteotomy. The anatomical axis of the tibia was determined using the full length of tibial radiographs, and the "reference PTS" was measured using this axis. Using the same radiograph, the PTS was measured using four different anatomical axes at standardized tibial lengths. While the center of the proximal circle remained constant at 5-cm below the tibial plateau, the center of the distal circle was drawn at four points: a) overlapping circles; b) 10-cm distal to the tibial plateau; c) 15-cm distal to the tibial plateau; d) half the length of the tibia, measured from the tibial plateau to the tibial plafond. Bivariate correlation and frequency distribution analysis (measurements >2-degrees from reference PTS) were performed between the reference PTS and PTS measured at each of the four other lengths. RESULTS: A total of 154 patients (39.8 ± 17.4 years old, 44.2% male) were included in the final analysis. Measurements at each of the four tibial lengths were all significantly different from the reference PTS (p < 0.001). The correlation strength improved with increasing tibial length (overlapping: R = 0.681, 10-cm: R = 0.821, 15-cm: R = 0.937, and half-tibia: R = 0.963). The number of PTS measurements >2-degree absolute difference from the reference PTS decreased with increasing tibial length (overlapping: 40.3%, 10-cm: 24.0%, 15-cm: 26.0%, and half-tibia: 18.8%). CONCLUSION: Assessment of PTS is dependent on the length of the tibia utilized to obtain the anatomical axis. Accuracy and precision of PTS measurements improved with increasing length of tibia used to determine the anatomical axis. STUDY DESIGN: Case series.

Proximal fibular axis is a reliable landmark for tibial coronal alignment in patients with or without knee osteoarthritis: A radiological comparative study.

BACKGROUND: Proper coronal alignment of the limb is of vital importance in the progression of knee osteoarthritis even in the long-term survivorship of component after total knee arthroplasty (TKA). Nevertheless, to the best of our knowledge, the relationship between coronal fibular axis and tibial mechanical axis had not reached a consensus in the literatures available. The current study aimed to explore the anatomic relationship between tibia and fibula alignment. METHODS: A total of 100 patients with knee osteoarthritis scheduled for total knee arthroplasty were enrolled in this study (Group A), and radiographic measurement was compared to a control group of 100 healthy volunteers without knee osteoarthritis (Group B). Full-length standing hip-to-ankle radiographs were used to assess limb alignment. The angle between coronal proximal fibular anatomic axis and tibia mechanical axis (PFTA) was used to represent the anatomic relationship between tibia and fibula alignment. A negative value indicates fibula varus relative to tibia mechanical axis, while a positive value indicates fibula valgus. RESULTS: The mean PFTAs were -0.9° ± 0.9° and -1.0° ± 0.8° in Groups A and B. There was no significant difference between the two groups. No significant difference was detected in PFTA distribution in the group A and B. When the mean value of PFTA is used as baseline data, the percentage of subjects in which the PFTA deviation was within 0.5°, 1°, and 1.5° was 51%, 84%, and 94% in Group A and 53%, 87%, and 96% in Group B. There was also no significant difference in distribution deviation between the two groups. No patient-specific factors were correlated with the PFTA. CONCLUSIONS: The proximal fibular anatomic axis is a reliable landmark for tibial mechanical axis in the coronal plane in patients with or without knee osteoarthritis.

Rethinking the Coronal Anatomic Axis of the Distal Tibia for Intramedullary Nail Placement: A Cadaveric Study.

Background: Recent studies have reported that targeting a center-center position at the distal tibia during intramedullary nailing (IMN) may result in malalignment. Although not fully understood, this observation suggests that the coronal anatomic center of the tibia may not correspond to the center of the distal tibia articular surface. Questions/Purposes: To identify the coronal anatomic axis of the distal tibia that corresponds to an ideal start site for IMN placement utilizing intact cadaveric tibiae. Methods: IMN placement was performed in 9 fresh frozen cadaveric tibiae. A guidewire was used to identify the ideal start site in the proximal tibia and an opening reamer allowed access to the canal. Each nail was then advanced without the use of a reaming rod until exiting the distal tibia plafond. Cadaveric and radiographic measurements were performed to determine the center of the nail exit site in the coronal plane. Results: Cadaveric and radiographic measurements identified the IMN exit site to correspond with the lateral 59.5% and 60.4% of the plafond, respectively. Conclusions: Tibial nails inserted using an ideal start site have an endpoint that corresponds roughly to the junction of the lateral and middle third of the plafond. Further studies are warranted to better understand the impact of IMN endpoint placement on the functional and radiographic outcomes of tibia shaft fractures.

The Joint Angle Tool for Intraoperative Assessment of Coronal Alignment of the Lower Limb.

AIM: Presentation of the joint angle tool (JAT), a low-cost goniometer for intraoperative assessment of the lower limb alignment. BACKGROUND: Intraoperative assessment of coronal alignment is important when performing corrective osteotomies around the knee and ankle, limb lengthening, and trauma surgery. JAT provides surgeons with information about the anatomic and mechanical axes intraoperatively based on true anteroposterior radiographs. TECHNIQUE: JAT consists of pre-printed joint orientation angles of the anatomic and mechanical axis including normal variations on a plastic sheet. It is placed on the screen of the image intensifier after obtaining a true anteroposterior image. The pre-printed joint orientation angles can assist the surgeons intraoperatively in achieving the pre-planned axis correction. Here, its feasibility is demonstrated in four cases. CONCLUSION AND CLINICAL SIGNIFICANCE: JAT is a modified goniometer that allows intraoperative assessment of the mechanical and anatomic axis. JAT is applicable throughout the entire surgical procedure irrespective of the method of internal fixation and may provide additional reassurance of correct alignment. JAT consists of a plastic sheet with printed joint orientation angles and their normal variation. JAT is freely available from profeedback.dk/JAT/JAT.pdf for use and modification according to the Creative Commons license (CC BY-SA 4.0) if this paper is attributed. HOW TO CITE THIS ARTICLE: Abood AA-H, Petruskevicius J, Vogt B, et al. The Joint Angle Tool for Intraoperative Assessment of Coronal Alignment of the Lower Limb. Strategies Trauma Limb Reconstr 2020;15(3):169-173.

Does pelvic width influence patellar tracking? A radiological comparison between sexes.

INTRODUCTION: Pelvic width has been believed to affect patellar tracking by influencing the quadriceps angle (Q-angle). Anatomically, the upper arm of the Q-angle does not closely match the orientation of the quadriceps femoris. The pelvis is often considered wider and the Q-angle larger in female than in male individuals. The purpose of this retrospective study was to investigate the accuracy of such an assumption by using a radiologic comparison, which might be more objective. MATERIALS AND METHODS: One hundred consecutive adult patients (50 men and 50 women) aged 18-30 years with unilateral injury to the lower extremity were studied. Full-length standing X-rays of these patients was used to analyze the relationship between the pelvis and the uninjured lower extremity and compare it between the sexes. The pelvic width was defined as the distance between the centers of the bilateral femoral heads. RESULTS: The pelvic width did not differ statistically between male and female (P=0.74). The femur length and sum of the lengths of the femur and tibia differed between the sexes (both P<0.001). Normalization of the pelvic width to the femur length or sum of the lengths of the femur and tibia resulted in a significant difference between male and female (P<0.001). The angle formed by the femoral and tibial mechanical axes correlated strongly with the angle formed by the femoral anatomic and tibial mechanical axes (Pearson correlation coefficient=0.89). DISCUSSION: Pelvic width does not differ with respect to gender. The pelvis may appear relatively wider in women due to the difference in body height. However, this difference may not increase Q-angle. Patellar mal-tracking may stem from other, more critical predisposing factors. LEVEL OF EVIDENCE: Level IV. Anatomic study.