Anatomic Lateral Distal Femoral Angle Research Articles

Comparing the Accuracy of Patient-Specific Guide and Universal Guide for Distal Femoral Osteotomy in Dogs.

To introduce a novel universal guide design for distal femoral osteotomy (DFO) to treat femoral deformities and other hindlimb orthopaedic diseases, and to compare its accuracy to the patient-specific guide in vitro and ex vivo on X-ray and computed tomography (CT). Thirteen anatomic specimens of canine femurs and 13 3D-printed femoral bone models were subjected to DFO using a patient-specific and a universal guide. The anatomical lateral distal femoral angle and anteversion angle were measured on radiographic and CT images before and after surgical procedure and used to compare the accuracy of the surgical guides in treating uniplanar or biplanar deformities. Bone models were used to compare the accuracy with ex vivo models. The mean correction errors were -1.18° to 0.72° on X-ray and -1.91° to 0.53° on CT scan. The analysis showed no statistically significant difference in the mean error between the groups based on type of guide used, nor in the mean error between groups based on whether anteversion correction was performed based on both the CT and X-ray imaging data. Both the patient-specific and universal guides can produce accurate results in DFO surgery, and the universal guide shows potential as a useful surgical tool.

Thick-Shell Sulcus Deepening Trochleoplasty for Recurrent Patellar Dislocation Leads to Clinically Meaningful Improvements and High Patient Satisfaction in Adolescents with Open Physes

ObjectivesTo evaluate clinical and radiological outcomes of thick-shell, sulcus deepening trochleoplasty in patients with open distal femoral physes and less than two years of growth remaining. We hypothesized that patients would have clinical and radiographic improvements in addition to high patient reported outcomes following thick-shell, sulcus deepening trochleoplasty. MethodsBone age was determined on preoperative Magnetic Resonance Imaging (MRI) using the Pennock Knee Bone Age Atlas. Pre- and postoperative radiographs were used to measure the anatomic lateral distal femoral angle (aLDFA) and Blumensaat angle. International Knee Documentation Committee (IKDC), Kujala, and numerical patient satisfaction scores were assessed. Pre- and postoperative aLDFA and Blumensaat angles as well as well as patient reported outcomes were analyzed via the Wilcoxon signed rank test. ResultsSeventeen adolescents (21 knees) with DeJour Types B and D trochlear dysplasia and open distal femoral physes underwent Dejour thick-shell, sulcus-deepening trochleoplasty at a single institution. In twelve females (16 knees, 76.2%) the median chronological and bone ages at time of operation was 14.9 and 14.3 years, respectively. In 5 males (5 knees, 27.7%), the median chronological and bone ages at time of operation were 15.7 and 15.2 years, respectively. Mean follow-up time was 64 months postoperatively. Physes were closed in all knees at the time of final clinical and radiographic follow-up. The mean change in aLDFA and Blumensaat Angle was 0.73 (p = 0.1074, 95% CI -0.09 – 1.57) and 0.88 degrees (p=0.0477, 95% CI 0.10 – 1.88), respectively. Median IKDC scores improved from 57.3 preoperatively to 90.9 postoperatively, for a mean difference of 26.1 (p = 0.00064, 95% CI 18.0 – 34.2). Median Kujala scores improved from 55.0 preoperatively to 95.0 postoperatively, for an mean change of 30.2 (p = 0.0008, 95% CI 19.6 – 40.8). Overall mean numerical patient satisfaction was high (mean 9.26/10). One of 21 knees (4.8%) underwent additional surgery to address recurrent patellar instability. ConclusionThick-shell sulcus deepening trochleoplasty for addressing recurrent lateral patellar instability in patients with open distal femoral physes and less than two years of growth remaining is safe and provides clinically meaningful improvements in addition to high patient satisfaction when combined with other patellar stabilization procedures. Level of EvidenceIV, Retrospective Case Series

Computed Tomographic Measurement Method for Morphoanatomical Comparison of Femur, Tibia, and Patella in Cats with and without Medial Patellar Luxation.

The aims of this study are to describe a computed tomographic (CT) measurement method of feline femoral, tibial, and patellar conformation, and to compare these measurements between a cat population diagnosed with medial patellar luxation (MPL) and cats without MPL. Eleven measurements were performed by two observers, including anatomical lateral distal femoral angle (aLDFA), femoral trochlear width (FTW) and femoral trochlear depth (FTD), anteversion angle of the femoral neck, patellar length, patellar width, patellar height, patellar volume, mechanical medial proximal tibial angle, tibial torsion angle, and tibial tuberosity displacement. Mean and standard deviation differences between the groups were statistically assessed. Intraobserver and interobserver interclass correlation coefficients (ICCs) were calculated. The aLDFA was significantly higher in the MPL II compared with the control and MPL III. The FTW was significantly larger in the MPL III than in the control or the MPL II group. The FTD in the control group was significantly larger than in the MPL II and III groups. The TTA of the control group was significantly smaller than the MPL II and III. The intraobserver ICC was high at 64%, and the interobserver ICC was high at 36% of the measurements. This study identified shallower FTD and increased TTA in cats diagnosed with MPL. The TTA difference was less than 5 degrees and FTD was less than 1 mm. The findings provide information on feline pelvic limb morphology. However, the differences between the two populations are small.

Retrograde intramedullary nail fixation with oblique fixed angle screws versus locking plates in periprosthetic supracondylar fractures after total knee arthroplasty.

Common surgical procedures in the treatment of periprosthetic distal femur fractures (PPFF) include osteosynthesis with fixed angle locking plates (LP) and retrograde intramedullary nails (RIN). This study aimed to compare LPs to RINs with oblique fixed angle screws in terms of complications, radiographic results and functional outcome. 63 PPFF in 59 patients who underwent treatment in between 2009 and 2020 were included and retrospectively reviewed. The anatomic lateral and posterior distal femoral angle (aLDFA and aPDFA) were measured on post-surgery radiographs. The Fracture Mobility Score (FMS) pre- and post-surgery, information about perceived instability in the operated leg and the level of pain were obtained via a questionnaire and previous follow-up (FU) examinations in 30 patients (32 fractures). The collective (median age: 78years) included 22 fractures treated with a RIN and 41 fractures fixed with a LP. There was no difference in the occurrence of complications (median FU: 21.5months) however the rate of implant failures requiring an implant replacement was higher in fractures treated with a LP (p = 0.043). The aPDFA was greater in fractures treated with a RIN (p = 0.04). The functional outcome was comparable between both groups (median FU: 24.5months) with a lower outcome in the post-surgery FMS (p = < 0.001). Fractures treated with RIN resulted in an increased recurvation of the femur however the rate of complications and the functional outcome were comparable between the groups. The need for implant replacements following complications was higher in the LP group.

Total knee arthroplasty following lateral closing-wedge high tibial osteotomy versus primary total knee arthroplasty: a propensity score matching study

BackgroundThe disparity in patient-reported outcomes between total knee arthroplasty (TKA) following high tibial osteotomy (HTO) and primary TKA has yet to be fully comprehended. This study aims to compare the patient-reported outcomes, radiological parameters and complication rates between TKA following HTO and primary TKA.MethodsSixty-five patients who underwent TKA following lateral closing-wedge HTO were compared to a matched group of primary TKA at postoperative 6-months and 1-year. Between-group confounders of age, gender, smoking status, Body Mass index, preoperative Numeric Rating Scale (NRS) pain in rest, Knee injury and Osteoarthritis Outcome Score-Physical function Shortform (KOOS-PS), EuroQol five-dimensional (EQ-5D) overall health score, and Oxford Knee Score (OKS) were balanced by propensity score matching. Patient-reported outcome measures were NRS pain in rest, KOOS-PS, EQ-5D overall health score, and OKS. Radiological parameters were femorotibial angle, medial proximal tibial angle, anatomical lateral distal femoral angle, posterior tibial slope, and patellar height assessed by Insall-Salvati ratio. The complication rates of TKA were compared between the two groups. The HTO survival time, the choice of staple removal before or during TKA in patients who underwent TKA following HTO patients, and the rate of patellar resurfacing were assessed. The p value < 0.0125 indicates statistical significance after Bonferroni correction.ResultsAfter propensity score matching, no significant between-group differences in the patient-reported outcome measures, radiographical parameters and complication rates were found (p > 0.0125). In the TKA following HTO group, with an average HTO survival time of 8.7 years, staples were removed before TKA in 46 patients (71%) and during TKA in 19 patients, and 11 cases (17%) had patella resurfacing. In the primary TKA group, 15 cases (23%) had patella resurfacing.ConclusionThe short-term assessment of TKA following HTO indicates outcomes similar to primary TKA. A previous HTO does not impact the early results of subsequent TKA, suggesting that the previous HTO has minimal influence on TKA outcomes.Level of evidenceIII, cohort study.

Technical Factors Contributing to Nonunion in Supracondylar Distal Femur Fractures Treated with Lateral Locked Plating: A Risk-Stratified Analysis.

To identify technical factors associated with nonunion after operative treatment with lateral locked plating. Retrospective cohort study. Ten Level 1 trauma centers. Six hundred fifteen adult patients with supracondylar distal femur fractures (OTA/AO Type 33A or C). Lateral locked plating. Surgery for nonunion. We observed nonunion rates of 2% in a low-risk of nonunion group (n = 129), 4% in a medium-risk group (n = 333), and 14% in a high-risk group (n = 153). Varus malreduction with an anatomic lateral distal femoral angle (aLDFA) greater than 84 degrees, was associated with double the odds of nonunion (OR, 2.1; 95% CI, 1.1 to 4.2; P = 0.03). Malreduction by medial translation of the articular block increased the odds of nonunion, with 30% increased odds per 4 mm of medial translation (95% CI, 1.0 to 1.6; P = 0.03). Working length increased the odds of nonunion primarily in the medium risk group, with an 18% increase in nonunion per 10 mm increase in working length (95% CI, 1.0 to 1.4; P = 0.01). Proximal screw density was protective against nonunion (OR, 0.71; 95% CI, 0.53 to 0.92; P = 0.02). Lateral plate length and type of plate material were not associated with nonunion. Malreduction is a surgeon-controlled variable associated with nonunion after lateral locked plating of supracondylar distal femur fractures. Longer working lengths were associated with nonunion, suggesting that simple bridge plating may be less likely to succeed for longer fractures. Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Comparison of the deformity reduction device (DRD) mini and the Slocum jig in the precision of torsional correction during distal femoral osteotomies in small to medium breed dogs.

Previous studies have compared the use of the Slocum- jig to the deformity reduction device (DRD) jig for the correction of distal femoral deformities of varying degrees in the frontal plane. The objective of the current study is to further investigate the use of the mini DRD jig in comparison to the Slocum jig for correction of varying degrees of torsional deformities of the distal femur. Femoral models (n = 60) were developed based on a CT scan of an approximately 16.5 kg normal canine femur. Models were created with a standard varus deformity of 15 degrees, and external torsional deformities of 15, 20, or 30 degrees. Using center of rotation of angulation (CORA) methodology, corrective osteotomies were planned and performed on each of the 3D printed models based on the group assigned. Modeling clay was applied the proximal femur to mimic visualization of a routine lateral surgical approach, while retaining the ability to palpate surgical landmarks. Post-correction anatomic lateral distal femoral angle (aLDFA) and femoral torsion angle (FTA) were measured and recorded. The mean post-correction FTA of groups using the DRD jig for correction were consistently closer to the ideal value compared to those using the Slocum jig, although these differences were not always statistically significant. Correction of external torsion between the DRD jig and the Slocum jig was significantly different in groups 1 and 2 (P = 0.026 and P = 0.046), but not in group 3. For the correction of varus deformity, no significant difference was found between the two jig types in any group. Results of this study suggest jig selection during distal femoral osteotomy for correction of torsional deformity may result in varying precision of post-correction alignment. Clinical significance of this variance remains unclear, and intra-operative visual assessment of alignment should be implemented to guide corrections.

Image-free handheld robotic-assisted technology improved the accuracy of implant positioning compared to conventional instrumentation in patients undergoing simultaneous bilateral total knee arthroplasty, without additional benefits in improvement of clinical outcomes

PurposeThe purpose of this study was to compare the clinical and radiological outcomes in patients who underwent simultaneous bilateral total knee arthroplasty (SB-TKA) using either robotic-assisted TKA (RA-TKA) or conventional TKA (C-TKA).MethodsIncluded were the patients who underwent SB-TKA between January 2018 and January 2020 and had a minimum follow-up of 2 years. Of 151 patients included, 117 patients were operated using an image-free handheld robotic sculpting system (RA-TKA group) and 34 patients operated using conventional instrumentation (C-TKA group). The key outcomes noted were multiple patient-reported outcomes (PROs), adverse events, and radiological outcomes. Two investigators independently measured the radiological outcomes on pre- and post-operative radiographs in coronal plane (medial proximal tibial angle [MPTA] and anatomic lateral distal femoral angle [aLDFA]) and sagittal plane (posterior tibial slope [PTS] and posterior condylar offset [PCO]). The chi-square test was used to examine categorical variables. Student’s t test was used to analyze the continuous variables.ResultsPatients in both groups were similar in baseline characteristics (gender, body mass index, incidence of comorbidities, and length of hospital stay) except that RA-TKA group patients younger (66.7 ± 8.9 vs 70.4 ± 10.5, P = 0.037) than C-TKA group. The operative time was longer in RA-TKA group as compared to C-TKA (189.3 ± 37.1 vs 175.0 ± 28.2, P = 0.040). The final PROs at each were similar between the two groups (P > 0.05). The values of PROs at final follow-up in RA-TKA compared to C-TKA were VAS pain (0.4 ± 0.9 vs 0.4 ± 0.5), KOOS-JR (89.3 ± 5.8 vs 87.1 ± 5.3), and physical (55.9 ± 2.8 vs 55.4 ± 3.2), mental (61.1 ± 4.4 vs 60.2 ± 4.7) component of VR-12 scores, and KSS satisfaction (37.5 ± 1.1 vs 37.1 ± 2.2) (all P > 0.50 or non-significant [n.s.]). While one patient in RA-TKA required revision of femoral component for peri-prosthetic fracture, none of the patient in conventional group were revised (0.85% vs 0%, P = n.s.). The proportion of patients with outliers in RA-TKA group was lower for aLDFA (2.6% vs 22.1%, P < 0.01) and PTS (0% vs 35%, P < 0.01).ConclusionThis comparative study in patients undergoing SB-TKA found reduction of outliers in femoral and tibial implant positioning with RA-TKA as compared to C-TKA. There were no differences in both groups for pain, function, and satisfaction at a minimum of 2 years of follow-up.Level of evidenceIII Therapeutic Study.

Accuracy and outcome of a handheld accelerometer-based navigation device compared to conventional alignment method in total knee arthroplasty in a Chinese population

Background Total knee arthroplasty (TKA) is a successful procedure in treatment of degenerative disease of the knee, and optimal component placement is essential for long-term implant survival. The purpose of this study was to compare the accuracy of the accelerometer-based KneeAlign 2 (KA2) navigation system against conventional methods for accurate positioning of the femoral and tibial components in TKA in a Chinese population. Methods A total of 123 (37 conventional and 86 KA2) cases of elective primary TKA were reviewed. Hip-knee-ankle (HKA) angle, mechanical lateral distal femoral angle (mLDFA), and anatomical lateral distal femoral angle (aLDFA) were measured from hip-to-ankle EOS radiographs. Accuracy of conventional alignment and KA2 navigation system was assessed by measuring the difference between intraoperative goal and postoperative radiographic measurements of the components for each respective case. Results There was no significant difference between conventional alignment methods and KA2 navigation in achieving a neutral mechanical alignment of the lower limb. KA2 navigation was significantly more accurate than conventional alignment methods for optimal positioning of the tibial component in both the coronal and sagittal plane, while no significant difference between the two groups was appreciated in the positioning of the femoral component in the coronal plane. Conclusions TKA using the accelerometer-based KA2 system was found to offer a high degree of accuracy in component alignment, and in particular, significantly improved tibial component alignment in comparison with conventional alignment methods in a Chinese population. However, no significant improvements were observed in neutral mechanical axis of the lower limb alignment and femoral component placement in the coronal plane.

Leg-Length and Alignment Changes in Children and Adolescents After Transphyseal Anterior Cruciate Ligament Reconstruction With Soft Tissue Graft: Results at 1-Year Follow-up.

Growth disturbance to leg length or coronal plane alignment are important considerations in pediatric anterior cruciate ligament (ACL) reconstruction (ACLR). The purpose of this study was to investigate the lower limb alignment and leg length of pediatric patients preoperatively and at approximately 1 year after transphyseal ACLR. Our hypothesis was that there would be no significant change in leg-length discrepancy (LLD) or operated-side alignment at follow-up. Case series; Level of evidence, 4. Data were extracted from the prospective Queensland Children's Hospital Pediatric ACL Injury Registry. Long-leg alignment radiographs were captured preoperatively and at an approximately 12-month postoperative follow-up. Radiographic measures included leg length, LLD (injured minus uninjured leg length), mechanical axis deviation (MAD), mechanical and anatomical lateral distal femoral angle (mLDFA and aLDFA, respectively), and medial proximal tibial angle. We evaluated the effect of time (annual vs baseline) on imaging measurements with analysis of covariance, using the covariates of age, sex, and body mass index. Data were available for 104 patients, of whom 34 (33%) had >12 months of skeletal growth remaining based on skeletal age. At an average follow-up time of 14.5 months after ACLR, there were no significant differences in mean lower limb alignment or longitudinal growth compared with baseline. However, seven patients demonstrated clinically significant changes to their mechanical axis or LLD (>10 mm change). A subgroup analysis of patients with >12 months of growth remaining (n = 34) demonstrated no statistically significant changes in mean alignment or LLD. Before surgery, LLD was -1.39 mm and the injured limb was in significantly more valgus compared with the uninjured lower limb (mean difference: MAD, 4.79 mm [95% CI, 2.64 to 6.94 mm]; mLDFA, -0.93° [95% CI, -1.29° to -0.57°], and aLDFA, -0.91° [95% CI, -1.31° to -0.50°]). After ACLR, there were no statistically significant changes in mean alignment or longitudinal growth; however, 7 out of 104 patients (6.7%) demonstrated clinically significant changes in alignment or LLD. Preoperatively, the injured limb was statistically significantly in more valgus compared with the uninjured limb with lateralized MAD.

Medial patellar luxation grade IV according to the Singleton system can be classified into skeletally immature and skeletally matured types.

To determine the signalment and musculoskeletal morphology of small-breed dogs affected by medial patellar luxation (MPL) grade IV based on the age of the CT scan. 40 small-breed dogs (54 limbs) with MPL grade IV. Dogs that had undergone corrective surgery for MPL grade IV and had performed CT of the hind limb before surgery were included. Signalment (age, body weight, sex, laterality, and breed) and concomitant cranial cruciate ligament rupture (CrCLR) were recorded. Femoral inclination angle, anatomical lateral distal femoral angle (aLDFA), femoral torsion angle, quadriceps muscle length to femoral length ratio (QML/FL), and patellar ligament length to patellar length were obtained by CT images. The dogs were categorized into 2 groups based on their age at the time of the CT scan, the skeletally immature group and the skeletally matured group. Signalment and group were included in the multiple regression analysis to determine the factors associated with each measurement parameter. A logistic regression analysis was conducted to determine the risk of CrCL concomitant with age. The multiple regression model demonstrated that the group was associated with the value of aLDFA and QML/FL. aLDFA was higher, and QML/FL was lower in group SI than in group SM. CrCLR was present in 5/54 limbs (9.2%), with a mean age of 70.8 months and it was associated with increasing age. In Singleton's classification, dogs classified as grade IV can be categorized into 2 groups based on musculoskeletal morphology and pathophysiology: the skeletally immature and skeletally matured types.

Evaluation of the quadriceps muscle length to femoral length ratio in small breed dogs with medial patellar luxation

To determine the quadriceps muscle length (QML) to femoral length (FL) ratio (QML/FL) and its associated factors in small breed dogs with medial patellar luxation (MPL) and to compare the differences in the QML/FL between MPL grades. Retrospective study. Small breed dogs (<10kg) with MPL: 78 dogs (134 limbs). Medical records and computed tomography (CT) images from 2008-2020 were reviewed. Furthermore, age, bodyweight, sex, laterality, MPL grade, femoral inclination angle (FIA), femoral torsion angle (FTA), anatomical lateral distal femoral angle (aLDFA), and patellar ligament length to patellar length ratio were included in the regression analysis to determine the factors associated with QML/FL. Each measurement parameter was compared among the four MPL grade groups. The final model demonstrated that the QML/FL increased with increasing age (p=.004) and decreased with increasing FTA and aLDFA (p=.015 and p < .001, respectively). The MPL grade IV group had a lower QML/FL than the grade I, II, and III groups (p=.002, p < .001, and p < .001, respectively). Among small breed dogs, those with MPL grade IV had a shortened QML associated with femoral deformities. Noninvasive evaluation of the QML/FL improves our understanding of the length mismatch between the quadriceps muscle and the femur.

Is lateral femoral condyle hypoplasia a feature of genu valgum? A morphological computed tomography study of 200 knees

BackgroundYoung surgeons are taught that genu valgum deformity is associated with hypoplasia of the lateral femoral condyle, despite the absence of supporting evidence. The objective of this study was to determine whether the lateral condyle was hypoplastic in genu valgum, by assessing the morphological features of the distal femur and their variations according to the severity of the coronal deformity. HypothesisThe lateral femoral condyle is not hypoplastic in genu valgum deformity. Material and methodsThe 200 included patients treated by unilateral total knee arthroplasty were divided into five groups based on their preoperative hip-knee-ankle (HKA) angle. The HKA angle, valgus cut angle (VCA), and anatomical lateral distal femoral angle (aLDFA) were measured on long-leg radiographs. Computed tomography images were then used to measure the medial and lateral anterior-posterior condylar lengths (mAPCL and lAPCL) and condylar thicknesses (mCT and lCT), distal femoral torsion (DFT), medial and lateral posterior condylar heights (mPCH and lPCH), and medial and lateral condylar volumes (mCV and lCV). ResultsNo significant differences were demonstrated across the five mechanical-axis groups for mAPCL, lAPCL, mCT, lCT, mPCH, or lPCH. The groups differed significantly regarding the VCA (p<0.0001), aLDFA (p<0.0001), DFT (p<0.0001), and mCV/lCV ratio (p<0.0001). VCA and aLDFA were smaller when the valgus exceeded 10°. DFT was similar in all varus knees (2.2°–2.6°) but significantly greater for knees with moderate (4.0°) or severe (6.2°) valgus. Finally, lCV was greater than mCV in valgus knees compared to varus knees. ConclusionThe presence of lateral condyle hypoplasia in knees with genu valgum seems open to question. Apparent hypoplasia noted during the standard physical examination may be chiefly ascribable to distal valgus of the femoral epiphysis in the coronal plane and, with the knee flexed, to distal epiphyseal torsion, whose severity increases with the degree of valgus deformity. These considerations should be taken into account when performing distal femoral cuts for TKA, to ensure the restoration of normal anatomy in patients with genu valgus. Level of evidenceIV.

Accuracy of Caudocranial Canine Femoral Radiographs Compared to Computed Tomography Multiplanar Reconstructions for Measurement of Anatomic Lateral Distal Femoral Angle.

This study aimed to compare the accuracy of sternal recumbency caudocranially obtained radiographs of canine femora to computed tomographic (CT) frontal plane reconstructions of the same femora for assessing anatomic distal lateral femoral angles (aLDFA). Multicentre, retrospective study utilizing 81 matched radiographic and CT studies of clinical patients undergoing assessment for various issues were reviewed. Anatomic lateral distal femoral angles were measured, and accuracy assessed with descriptive statistics and Bland-Altman plot analysis, with CT considered the reference standard. Sensitivity and specificity of a cut-off for measured aLDFA (102 degrees) were determined to assess radiography as a screening tool for significant deformity. Radiographs on average overestimated aLDFA by 1.8 degrees compared to CT. Bland-Altman analysis identified a 15.4 degrees 95% limit of agreement range and a tendency for greater overestimation at higher average measured value. Radiographic measurement of aLDFA of 102 degrees or less had a 90% sensitivity, 71.83% specificity, and 98.08% negative predictive value for the CT measurement being less than 102 degrees. Accuracy of aLDFA measurement by caudocranial radiographs does not demonstrate sufficient accuracy when compared to CT frontal plane reconstructions with unpredictable differences. Radiographic assessment is a useful screening tool to exclude animals with a true aLDFA of greater than 102 degrees with a high degree of certainty.

Outcomes of surgical management of closed periprosthetic distal femur fractures above total knee arthroplasties: A case series

Periprosthetic distal femur fractures present difficult treatment challenges and are expected to become more prevalent as the number of total knee arthroplasties (TKAs) continues to rise. The purpose of this study is to determine the functional outcomes and rate of re-operation following surgical treatment of closed distal femoral periprosthetic fractures above a TKA. We performed a retrospective review of 56 patients(45 females) who underwent surgical management of distal femur fractures (AO/OTA 33) above an ipsilateral TKA with a mean follow-up of 21 months (range, 12-78 months). Forty-three (77%) patients were treated with a lateral plate and screw construct, and 13 (23%) patients were treated with a retrograde intramedullary nail. There were 2 (4%) deep infections at a mean of 6 months (range, 5-7 months) post-operatively. At final follow-up, TKA components were retained in 53 (93%) patients, demonstrating a survivorship free of component revision following fracture treatment of 93% at 6.5 years. Survivorship free of any re-operation following fracture treatment was 86% at 6.5 years. Mean anatomic lateral distal femoral angle (aLDFA) was 84° (range, 72-89°) and mean anatomic posterior distal femoral angle (aPDFA) was 83° (range, 67-89°). There were 8 nonunions (14%) at 6 month follow-up, and no patients underwent a re-operation for malunion. This case series demonstrates increased revision rates and decreased survivorship of TKA components after surgical management of periprosthetic distal femur fractures. Surgeons must be aware of these potential complications when treating patients with periprosthetic distal femur fractures and counsel their patients appropriately. Therapeutic Level IV. See instructions for all others for a complete description of levels of evidence. • Closed distal femur fractures about a TKA demonstrate a high rate of non-union, 14% at 6-month follow-up. • Following this injury, patients experienced reduced mobility with only 82% being ambulatory after fixation, with 16% still wheelchair bound at 6 months after surgery. • As the number of annual TKA continues to rise, injuries involving those prosthetics will continue to rise.

Comparison of Hindlimb Conformation in Cats with and without Medial Patellar Luxation.

Medial patellar luxation (MPL) is the most common developmental cause of hindlimb lameness in cats. The association between femoral and tibial conformation and MPL measured on computed tomography (CT) has not been reported in cats. The aims were to report femoral and tibial conformation in cats with and without MPL and to report normal femoral and tibial angles. Angle of inclination of femoral neck (AI), anatomical lateral distal femoral angle (aLDFA), femoral trochanteric angle (FCT), angle of anteversion of femoral neck (AA), distal and proximal anteversion angle (DAA/PAA), overall tibial valgus (TV), tibial torsion (TT), tibial tuberosity displacement (TTD) and trochlear depth:patellar thickness ratio (T:P) were measured by three observers on CT of cats with and without MPL. Comparisons were made between groups. Inter-observer intraclass correlation coefficient (ICC) was calculated. Sixteen cats were recruited: eight control and eight with MPL. The aLDFA, PAA, TT, TTD and T:P were significantly less in cats with high-grade MPL. The AI, FCT, AA, DAA and TV were not significantly different. A high correlation was shown with inter-observer ICC in 33.33% and good correlation in 26.67% when comparing measurements between observers. This study suggests that cats with high-grade MPL have decreased TT, TTD and T:P and may require tibial tuberosity transposition and femoral trochleoplasty. The PAA, TT and aLDFA were decreased, although clinical significance may vary and these cats may not require correctional osteotomies. Results should be interpreted with caution as high/good levels of inter-observer ICC occurred in less than two-thirds of cases between observers.

An MRI-based Study to Investigate If the Patella is Truly Centred between the Femoral Condyles in the Coronal Plane

BackgroundAn AP knee radiograph is considered adequate if the patella is centred between the femoral condyles. Our previous studies demonstrated a tendency for lateral patellar deviation on an AP view orthogonal to the posterior femoral condyles. However, findings were based on cadaveric samples limited by the lack of soft tissue effects on patellar positioning.Materials and methodsAfter excluding those with deformity or damage to osseous or ligamentous structures, 106 knee MRI scans were randomly selected. Patellar centring was calculated as a percentage of total distal femoral intercondylar width and represented how lateral the centre of the patella is located with respect to the midpoint of the femoral condyles. Multiple regression analysis was performed to determine the relationship between patellar centring and age, gender, anatomic lateral distal femoral angle (aLDFA), medial proximal tibial angle (MPTA) and tibial tuberosity to trochlear groove (TT-TG) distance.ResultsThere were 35 males and 71 females included in the study with a mean age of 29 ± 14 years. Mean patellar centring was 8 ± 4%. There was a statistically significant correlation between TT-TG distance and positive (lateral) patellar centring (standardised β = 0.36, p <0.01). There were no associations between aLDFA and MPTA with patellar centring.ConclusionThis study demonstrates that the patella is rarely perfectly centred and is usually positioned slightly laterally within the femoral condyles in an AP view orthogonal to the posterior aspect of the femoral condyles. The use of supine MRI scans makes this data relevant to a patient on the operating room table.How to cite this articleShah NS, Kyriakedes JC, Liu RW. An MRI-based Study to Investigate If the Patella is Truly Centred between the Femoral Condyles in the Coronal Plane. Strategies Trauma Limb Reconstr 2022;17(2):63–67.

Using short knee radiographs to predict the coronal alignment after TKA: Is it an accurate proxy for HKA on full-length images?

BackgroundThe postoperative clinical outcomes has been extensively demonstrated to correlate with the coronal alignment after total knee arthroplasty (TKA). However, in different studies, either the hip-knee-ankle angle (HKA) on a full-length radiograph or the femorotibial angle (FTA) on a short knee film was used to categorize the postoperative coronal alignment. Meanwhile, several different FTA ranges were regarded as neutral alignment in different studies. As a result, it is still unknown that how FTA on short knee films and HKA related to each other. The FTA may be able to become an accurate proxy of HKA to predict the coronal alignment. The purpose of this study was to explore the correlation between the FTA and the HKA after TKA and to find the most accurate FTA range.MethodsAbout 223 patients were included in this study and standard weight-bearing short knee films as well as full-length radiographs were acquired. The pre- and postoperative FTA, as well as the postoperative anatomical lateral distal femoral angle (aLDFA) and anatomical medial proximal tibial angle (aMPTA) were measured on short knee films by two orthopedic surgeons independently. On full-length films, the pre- and postoperative FTA, the pre- and postoperative HKA, as well as the postoperative mechanical lateral distal femoral angle (mLDFA) and mechanical medial proximal tibial angle (mMPTA) were also recorded by two other surgeons independently. Pearson correlation analysis was performed to compare FTA and HKA, aMTPA and mMTPA, aLDFA and mLDFA, respectively.ResultsThe postoperative FTA and HKA had a good correlation (r = 0.86). The agreements were reached 82.7%, 71.0%, and 68.2% of all patients using three previously reported FTA ranges. When analyzing the independent alignment of the tibial tray and the femoral component, 84.1% and 57.9% of all patients was reached an agreement on the classification.ConclusionsOn most occasions, the consistence between the FTA and HKA in assessing the coronal limb alignment of the lower extremity and the tibial component is satisfactory. However, the postoperative full-length film is still needed to evaluate accurately the coronal alignment of the femoral component.

Predictors of a forgotten joint after medial fixed-bearing unicompartmental knee arthroplasty

BackgroundA forgotten joint is considered the ultimate goal of joint replacement. We aim to explore the predictive factors of a forgotten joint after fixed-bearing unicompartmental knee arthroplasty (UKA). MethodsThis retrospective cohort study used prospectively collected data from 302 cases of medial-compartment UKA with a minimum of 2-year follow-up. The primary outcome was the achievement of a forgotten joint after UKA, according to the Forgotten Joint Score (FJS-12) at the last follow-up. Patients with FJS-12 > 84 were considered to have forgotten UKA. Univariate and multivariate logistic regression analyses were conducted with preoperative patient characteristics and surgery-related factors as potential predictors. ResultsOf patients, 94 (31.1%) achieved a forgotten joint post-surgery. Multivariate logistic regression analysis revealed that preoperative hip-knee-ankle angle (HKAA), anatomic lateral distal femoral angle (aLDFA), and postoperative HKAA and HKAA changes were independent predictors of a forgotten joint. The probability of achieving a forgotten joint increased by 29% (OR = 1.29, 95% CI: 1.12–1.51) with a 1° increase in aLDFA. Preoperative HKAA, postoperative HKAA, HKAA changes (ΔHKAA), and outcomes exhibited a non-linear relationship. The probability of achieving a forgotten joint was the highest with preoperative HKAA > 172.0°, postoperative HKAA of 176.0–178.5°, and ΔHKAA < 5.5°. ConclusionTo achieve the forgotten joint state, the ideal HKAA range after medial fixed-bearing UKA is 176.0–178.5° and ΔHKAA should be <5.5°. Patients with smaller preoperative aLDFA and HKAA have a lower probability of achieving a forgotten joint after UKA.

Comminuted periprosthetic distal femoral fractures have greater postoperative extension malalignment

IntroductionComminution is a significant aspect of periprosthetic distal femoral fracture characterization and may influence post-surgical outcomes. Existing classification systems that guide treatment decisions do not take into account comminution and current literature is unclear on which surgical approach is optimal. We hypothesize that fractures with comminution will have poorer quality post-reduction alignment, especially with a lateral approach. Materials and methods37 study patients were identified with billing codes designating a distal femoral periprosthetic fracture. A retrospective chart review was performed to categorize fractures by absence or presence of comminution and medial parapatellar versus lateral surgical approach. These patients underwent an imaging evaluation for the primary outcome of reduction quality including the anatomic lateral distal femoral angle (LDFA) and the posterior distal femoral angle (PDFA). Differences in radiographic outcomes were analyzed with Wilcoxon/Kruskal-Wallis tests, and analysis by approach was through Fisher's exact test. ResultsPatients with comminuted fractures had significantly greater extension of the fragment (PDFA = 95.4° vs 90.0°, p = 0.018) and similar coronal alignment (LDFA = 85.3° vs 86.3°, p = 0.83) of the knee compared to non-comminuted fractures after surgical reduction. This difference was more prominent amongst those treated with a lateral approach (PDFA = 96.1° vs 89.4°, p = 0.032) than with a medial approach (PDFA = 93.7° vs 91.5°, p = 0.41) (Table 1). DiscussionCurrent classification systems and treatment guidelines for periprosthetic distal femoral fractures do not adequately address several issues that may influence treatment outcomes, especially comminution. Comminuted fractures had greater post-reduction extension malalignment, falling outside the recommended PDFA range of 87–90°, especially with a lateral approach. Consideration should be given to surgical approach and techniques to reduce excessive extension when treating comminuted periprosthetic distal femoral fractures.