Important Differences Exist in Posterior Condylar Offsets in an Osteological Collection of 1,058 Femurs

Sexual dimorphism of the posterior condylar offset of the femur and the medial posterior slope of the tibia in non-arthritic knees of Egyptian adults: an MRI study

BACKGROUND

The aim of this magnetic resonance imaging (MRI) study was to investigate controversial sexual dimorphism of the posterior condylar offset of the femur (the offset) and the posterior slope of the tibia (the slope) in non-arthritic knees of Egyptian adults.

METHODS

On 100 male and 100 female MRIs of non-arthritic knees, linear measurements of the distal part of the femur (the offset) and the angular measurements of the proximal part of the tibia (the slope) were performed and compared regarding sex and ethnicity. The intraclass correlation coefficient (ICC) was used to test the interrater agreement.

RESULTS

Both offsets and the lateral offset ratio were larger in males (p < 0.001), the medial offset ratio, and the medial slope in females (p from < 0.001 to 0.007), whereas the lateral slope was sex-free (p = 0.41). Irrespective of sex, however, the medial offset with its ratio, and the medial slope were larger than their counterparts (p < 0.001). Our means of the offsets, their ratios, and the slopes mostly differed from those of other ethnicities (p from ≤ 0.001 to 0.004). ICCs > 0.8 proved MRI's precision was high.

CONCLUSION

There was a sexual dimorphism of both the offset and the medial slope in non-arthritic knees of Egyptian adults. We believe future designs of knee implants should consider these differences in order to improve postoperative range of motion and patients' satisfaction after total knee arthroplasty. Level of evidence Level III Retrospective Cohort Study. Trial registration ClinicalTrials.gov identifier: NCT03622034, registered on July 28, 2018.

Reliability of the posterior condylar offset

The posterior condylar offset (PCO) has been proposed as a determinant of a postoperative range of motion after total knee arthroplasty, although there is no consensus. This study aimed to demonstrate the error introduced by forcing the femoral rotation to overlap both condyles for the "true" lateral X-ray projection for the PCO measurement. We hypothesize that the angular discrepancy between the posterior femoral cortical reference plane and the posterior condylar axis plane due to rotation invalidates the acquisition of reliable measurements on X-rays. We have measured the PCO in 50 "true" lateral X-rays and compared it with the medial and lateral condyles PCO's assessed on a computed tomography-scan-based three-dimensional (3D) model of each knee. PCO based on the 3D imaging differed significantly between the medial (25.8 ± 3.67 mm) and lateral (16.59 ± 2.92 mm) condyle. Three-dimensional PCO values differ significantly from those determined in the radiographic studies. Also, the mean values of the medial and lateral condyle PCO measurements differed significantly (p < 0.001) with all PCO measurements on radiographs. We have identified a difference between the posterior cortical plane and the posterior condylar axis projections, both on the axial plane with a mean value of 11.23° ± 3.64°. Our data show an interplane discrepancy angle between the posterior femoral diaphyseal cortical and the posterior condylar axis plane (due to the femur's necessary rotation to overlap both condyles) may invalidate the 2D X-ray PCO assessment as a reliable measurement.

The distal femur trochlear groove appears to compensate for tibial deformity but not femoral deformity in an investigation of five-hundred and seventy-nine cadaveric skeletons

BACKGROUND

The etiology of patellofemoral disorders is multifactorial. Preoperative patellofemoral anatomy evaluation is of great importance in patients undergoing surgery for patellofemoral disorders. Although anatomical risk factors of patellofemoral disorders have been thoroughly investigated in clinical and radiological studies, there are sparse data regarding the association between trochlear dysplasia with other anatomical parameters. This study sought to explore those associations using a large osteological collection.

METHODS

Five-hundred and seventy-nine cadaveric skeletons were obtained from the Hamann-Todd osteological collection. Mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), femoral version, tibial torsion, lateral position of the tibial tubercle, and femoral length were modeled as predictors of medial and lateral flange height of the distal femur trochlea at various degrees of knee flexion.

RESULTS

The average age and standard deviation for the 1158 lower extremities analyzed was 55.9 ± 10.2 years. There were 500 males (86%) and 79 females. Increasing MPTA or tibial valgus predicted increasing lateral femoral flange height at 0, 30, and 50 degrees of knee flexion [(standardized beta 0.111, p = 0.01), (standardized beta 0.129, p < 0.001), and (standardized beta 0.186, p < 0.001), respectively]. Increasing internal tibial torsion predicted increased medial flange height at 30 and 50° [(standardized beta - 0.114, p = 0.006), (standardized beta - 0.108, p = 0.006), respectively]. Increased femoral retroversion predicted increasing lateral flange height at 0 and 30 degrees [(standardized beta - 0.105, p = 0.005), (standardized beta - 0.098, p = 0.004), respectively].

CONCLUSIONS

To maintain the equilibrium necessary for effective patellar tracking, the depth of trochlear groove appears to effectively compensate for some of the anatomical parameters of the proximal tibia associated with patellofemoral disorders, and appears to be less influenced by femoral alignment. The clinical relevance of these findings warrants further investigation, and emphasizes the importance of carefully assessing the lower limb alignment in the management of patellofemoral disorders.

Patient Satisfaction, Functional Outcomes, and Implant Survivorship in Patients Undergoing Customized Unicompartmental Knee Arthroplasty

Customized unicompartmental knee arthroplasty (C-UKA) utilizes implants manufactured on an individual patient basis, derived from pre-operative computed tomography images in an effort to more closely approximate the natural anatomy of the knee. The outcomes from 349 medial and lateral fixed-bearing C-UKA were reviewed. Implant survivorship analysis was conducted via retrospective chart review, and follow-up analysis was conducted via a single postoperative phone call or email. The rate of follow-up was 69% (242 knees). The average age at surgery was 71.1 years and the average body mass index was 28.8 kg/m2. Seven revision arthroplasties (2.1%) had knowingly been performed at an average of 1.9 years postoperatively (range: 0.1-3.9 years), resulting in an implant survivorship of 97.9% at an average follow-up of 4.2 years (range: 0.1-8.7) and 97.9% at an average of 4.8 years (range: 2.0-8.7) when knees with less than two years of follow-up were excluded. The reasons for revision were implant loosening (one knee), infection (two knees), progression of osteoarthritis (two knees), and unknown reasons (two knees). The average KOOS, JR. interval score was 84 (SD: 14.4). Of those able to be contacted for follow-up analysis, 67% were "very satisfied," 26% were "satisfied," 4% were "neutral," 2% were "dissatisfied," and 1% were "very dissatisfied." When asked if the knee felt "natural," 60% responded with "always," 35% responded with "sometimes," and 5% responded with "never." After analyzing a large cohort of C-UKA, we found favorable rates of survivorship, satisfaction, and patient-reported functional outcomes.

Gender-related morphological differences in sulcus angle and condylar height for the femoral trochlea using magnetic resonance imaging

PURPOSE

This study aimed to elucidate the primary differences in trochlear morphology between men and women utilizing three-dimensional magnetic resonance image reconstruction of the femoral trochlea.

METHODS

Differences in anthropometric femoral trochlea data of 975 patients (825 women, 150 men) were evaluated. The following morphological parameters were measured at three flexion angles (15°, 30°, and 45°) of the femoral trochlea: the sulcus angle, condylar height, and the trochlear groove orientation and mediolateral groove position.

RESULTS

The sulcus angle was significantly greater in women than in men at 15° and 45° flexions (P < 0.05). However, there was no gender difference found in the sulcus angle at 30° flexion. Medial and lateral condylar height values were greater in men than in women for the three flexion angles (P < 0.01). The trochlear groove orientation and mediolateral groove position showed no gender-related differences.

CONCLUSIONS

Magnetic resonance image reconstruction demonstrated that measurement of trochlear morphology varied significantly between men and women. This study provides guidelines for the design of a suitable femoral component for total knee arthroplasty, considering gender-specific differences in the Korean population. Biomechanical guidelines for total knee arthroplasty in Korean individuals can be optimized using our finding, so as the risk of patellar dislocation to be decreased. Surgeons should be aware of gender differences in femoral trochlear to optimize choice of implant.

LEVEL OF EVIDENCE

III.

Gender differences in morphology exist in posterior condylar offsets of the knee in Korean population

PURPOSE

This study aimed to analyze the morphometric data from magnetic resonance images of arthritic knees in Korean adults, and to identify the existence of morphological differences of femoral posterior condylar offset (PCO) between genders.

METHODS

The differences in anthropometric PCO data in 975 patients (825 female and 150 male) were evaluated. The distances from the anterior and posterior femoral shaft cortex line to the most posterior femoral condyle tangent line were defined as the anterior-posterior dimension (AP) and the PCO. The PCO ratio (PCOR) was calculated as PCO/AP.

RESULTS

The medial PCO was greater than the lateral PCO (26.3 ± 2.2 vs. 24.3 ± 2.3 mm, p < 0.01). This difference was observed in both female patients (medial: 26.2 ± 2.2 mm vs. lateral: 24.2 ± 2.2 mm, p < 0.01) and male patients (medial: 26.8 ± 2.3 mm vs. lateral: 24.8 ± 2.4 mm, p < 0.01). The medial and lateral PCO values were also greater in male patients than in female ones (p < 0.01). In contrast, PCOR was greater in female patients than in male ones, both in the medial and lateral femoral condyles (p < 0.01).

CONCLUSIONS

It was shown that medial and lateral PCO and PCOR were asymmetric, and that there was gender difference in Korean population in our study. In addition, our data showed that the PCOR of contemporary TKAs may be small for Asian patients that may not be sufficient to meet the needs of the Korean patient population. These results confirm that a gender-specific femoral component design is necessary to recreate the PCO for male and female Asian populations.

LEVEL OF EVIDENCE

Non-consecutive patients, Level III.

What Is the Possible Impact of High Variability of Distal Femoral Geometry on TKA? A CT Data Analysis of 24,042 Knees

BACKGROUND

Previous studies analyzing femoral components of TKAs have demonstrated the limited ability of these components to accommodate size variations seen in the patient population, particularly width and femoral offset.

QUESTIONS/PURPOSES

The purpose of this study was to use a large data set of knee CT scans (1) to determine the variations in the distal and posterior femoral geometries and to determine whether there is a correlation between distal condylar offset and posterior femoral offset as a potential parameter for symmetry/asymmetry; and (2) to evaluate what proportion of knees would have a substantial mismatch between the implant's size or shape and the patient's anatomy if a femoral component of a modern standard TKA of symmetric (sTKA) or asymmetric (asTKA) designs were to be used.

METHODS

A retrospective study was performed on 24,042 data sets that were generated during the design phase for a customized TKA implant. This data set was drawn from European and US-American patients. Measurements recorded for the femur included the overall AP and mediolateral (ML) widths, widths of the lateral condyle and the medial condyle, the distal condylar offset (DCO) between the lateral and medial condyles in the superoinferior direction, and the posterior femoral offset (PFO) as the difference between the medial and lateral posterior condylar offset (PCO) measured in the AP direction. A consecutively collected subset of 2367 data sets was further evaluated to determine the difference between the individual AP and ML dimensions of the femur with that of modern TKA designs using two commercially available implants from different vendors.

RESULTS

We observed a high degree of variability in AP and ML widths as well as in DCO and PFO. Also, we found no correlation between DCO and PCO of the knees studied. Instances of a patient having a small DCO and higher PCO were commonly seen. Analysis of the DFOs revealed that overall, 62% (14,906 of 24,042) of knees exhibited DCO > 1 mm and 83% (19,955 of 24,042) of femurs exhibited a > 2-mm difference between the lateral and medial PCO. Concerning AP and ML measurements, 23% (544 of 2367) and 25% (592 of 2367) would have a mismatch between the patient's bony anatomy and the dimensions of the femoral component of ± 3 mm if they would have undergone a modern standard sTKA or asTKA design, respectively.

CONCLUSIONS

Analysis of a large number of CT scans of the knee showed that a high degree of variability exists in AP and ML widths as well as in DCO and PFO.

CLINICAL RELEVANCE

These findings suggest that it is possible that a greater degree of customization could result in surgeons performing fewer soft tissue releases and medial resections than now are being done to fit a fixed-geometry implant into a highly variable patient population. However, as an imaging study, it cannot support one approach to TKA over another; comparative studies that assess patient-reported outcomes and survivorship will be needed to help surgeons decide among sTKA, asTKA, and customized TKA.

Sagittal magnetic resonance imaging-scan orientation significantly influences accuracy of femoral posterior condylar offset measurement

BACKGROUND

In total knee arthroplasty the femoral posterior condylar offset (PCO) may serve as a potential branch for correct femoral component positioning. The technique of adjusting the sagittal magnetic resonance imaging (MRI)-scan on which it is measured has not been investigated in previous literature, but may be subject to variances due to knee joint positioning or axial localizer scan angulation. The purpose of this study was to investigate the effect of simulated femur rotation on the accuracy of PCO measurement.

MATERIALS AND METHODS

Ten asymptomatic knee joints underwent MRI investigations. A sagittal plane perpendicular to the transepicondylar axis was defined as the true-sagittal plane (tsP). Sagittal images were reformatted in the tsP and angulated by 5° and - 5° in medial and lateral direction. In total each knee received three scans in 0°, 5° and - 5° axial localizer scan angulation. Medial and lateral PCO measurement was performed in each MRI-scan angulation.

RESULTS

Simulated external rotation decreased medial PCO size by 1.7 mm (95% CI 0.5994-3.127) (p = 0.012), and simulated internal rotation increased medial PCO size by 2.1 mm (95% CI 1.142-2.994) (p = 0.001). Lateral PCO size increased by 1.9 mm (95% CI 0.5660-3.412) and decreased by 2.1 mm (95% CI 1.142-2.994) with simulated external and internal rotation, respectively (p = 0.011; p = 0.0007).

CONCLUSION

This study shows the high sensitivity of medial and lateral PCO measurements to small changes of MRI axial localizer scan angulations simulating minor degrees of internal or external femur rotation. Thus, absolute PCO values should be interpreted with caution if the sagittal image acquisition is not standardized.

Radiographic measurement of the posterior femoral offset is not precise

PURPOSE

The posterior femoral offset may significantly impact the final flexion range after total knee arthroplasty (TKA). The purpose of the present study was to compare a conventional, radiologic-based technique with an intra-operative, surgical navigation-based technique for the measurement of posterior femoral offset. The tested hypothesis was that the two measurement techniques produce different results both before and after TKA.

METHODS

One-hundred consecutive cases referred for end-stage knee osteoarthritis have been studied. Posterior femoral offsets, measured pre- and post-TKA from radiographs, as well as those measured from a navigation system intra-operatively, were analysed. The pre-TKA measured offsets, post-TKA measured offsets and the changes (pre- vs. post-TKA) in the offsets were statistically compared between the radiologic and the navigated measurement techniques at a 0.05 level of significance.

RESULTS

The mean paired difference between pre-TKA radiologic and navigated measurement was 4 ± 4 mm (p < 0.001). There was a significant and moderate positive correlation with a good coherence between the two measurements. The mean paired difference between post-TKA radiologic and navigated measurement was 6 ± 5 mm (p < 0.001). There was a significant and moderate positive correlation but a poor coherence between the two measurements.

CONCLUSIONS

The conventional radiologic technique for the measurement of the posterior femoral offset cannot be reliably used either for pre-TKA planning of the posterior femoral resection and antero-posterior sizing of the femoral component, or for post-TKA quality control of the reconstruction of the posterior femoral offset.

LEVEL OF EVIDENCE

Level IV.

An Anatomic Investigation Into the Relationship Between Posterior Condylar Offset and Posterior Tibial Slope of One Thousand One Hundred Thirty-Eight Cadaveric Knees

BACKGROUND

Posterior condylar offset (PCO) and posterior tibial slope (PTS) have critical consequences in total knee arthroplasty, especially with regards to sagittal plane balancing. However, there has only been limited investigation into the functional consequences of each, and there have only been anecdotal observations regarding any associations between PCO and PTS.

METHODS

In a large osteological study of 1138 knees, standardized measurements of PCO and PTS were taken using previously described techniques on specimens of different age, race, and gender. Multiple linear regression was performed to determine the independent predictors of medial and lateral PTS.

RESULTS

Mean standardized medial PCO was greater than lateral PCO (1.22 ± 0.16 vs 1.15 ± 0.19 mm, P < .001) and medial PTS was greater than lateral PTS (7.3 ± 3.8° vs 5.7 ± 3.7°, P < .001). Decreasing PCO, female gender, and African-American race were associated with both increased medial and lateral PTS. Neither age nor femoral length correlated with medial or lateral PTS.

CONCLUSION

These data are the first to quantify that an inverse correlation between PCO and PTS exists. This relationship represents an important area for future biomechanical and clinical studies.

Association Between Tibial Malunion Deformity Parameters and Degenerative Hip and Knee Disease

OBJECTIVES

Tibia fractures are the most common long bone fracture. Criteria for closed and open reduction are based on the amount of fracture shortening, angulation, and rotation, with high success rates achieved if acceptable alignment is maintained. However, there exists limited data available regarding the long-term consequences of specific deformation patterns.

METHODS

The tibiae of 2898 cadaveric skeletons were manually inspected for evidence of fracture. Specimens with midshaft fractures were identified as candidates for study; intraarticular fractures were excluded. Fracture shortening, location, angulation, rotation (torsion), and translation were measured using previously described techniques. Degenerative joint disease of the knee and hip was graded from 0 to 3 in fracture specimens using a previously published system. Correlations between fracture characteristic and osteoarthritis were evaluated.

RESULTS

Thirty-seven tibia fractures were present in 36 skeletons. In patients with tibia fractures, ipsilateral knee arthritis was greater than that of the contralateral side (P < 0.001). Knee arthritis was greater in fractures with coronal plane deformity greater than 5 degrees (P = 0.006) and with rotational deformity greater than 10 degrees (P = 0.004). There were no differences in knee arthritis based on laterality, shortening, sagittal deformity, fracture type, or translation in any plane (P > 0.05 for all). There were no differences in hip arthritis on the ipsilateral side compared with the contralateral side (P = 0.149). However, tibiae that were shortened by more than 10 mm had higher grades of ipsilateral hip arthritis (P = 0.009).

CONCLUSIONS

The results of this study suggest that coronal and axial plane malalignment and shortening are of the greatest consequence following tibia fracture. These conclusions strengthen the recommendations of authors who have emphasized restoring tibial length following fracture, and providing anatomic restoration in the coronal and axial planes.

Anatomic Investigation of Commonly Used Landmarks for Evaluating Rotation During Forearm Fracture Reduction

BACKGROUND

Evaluating rotation during open reduction and internal fixation of a forearm fracture is of paramount importance. In challenging cases, surgeons may utilize radiographic relationships between proximal and distal radial and ulnar landmarks to assess rotational position. However, to our knowledge, limited anatomic data are available to confirm these relationships.

METHODS

Six hundred cadaveric radii and ulnae were obtained. Digital representations of the bicipital tuberosity, the radial styloid, the coronoid process, and the ulnar styloid were acquired, and the rotational profiles between respective landmarks were calculated. In order to validate the results and investigate the ability to differentiate rotated osseous positions, each bone was imaged in increments of 10° of rotation and the profile of each landmark was measured.

RESULTS

The radial styloid was at a mean of 158° ± 14° of supination relative to the bicipital tuberosity. The ulnar styloid was at a mean of 185° ± 14° of supination relative to the coronoid process. Imaging of the bones in increments of 10° of rotation supported the relationships above. It was also found that a 1-mm difference in profile size corresponded to up to 60° of rotation for the average ulna, compared with 10° for the average radius.

CONCLUSIONS

Our findings suggest that using the bicipital tuberosity and the radial styloid to assess intraoperative rotation of the radius on anteroposterior radiographs may be of limited value; the landmarks were not generally 180° apart. Although the rotational positions of the coronoid process and the ulnar styloid were, on average, closer to 180°, surgeons should be aware of the wide range of normal anatomy as well as the inability to judge rotation by as much as 60°, even for an "ideal" ulna.

CLINICAL RELEVANCE

This study, to our knowledge, represents the first anatomic investigation of the rotational profiles between the osseous landmarks used to assess forearm rotation after fracture. We recommend that surgeons first image the bicipital tuberosity at its largest profile, supinate the arm 20°, and confirm that the radial styloid is at its largest profile. The ulna can then be assessed to support the lack of rotational deformity in the forearm.

A cadaveric investigation into the demographic and bony alignment properties associated with osteoarthritis of the patellofemoral joint

BACKGROUND

Patellofemoral joint osteoarthritis is common, although circumstances dictating its evolution and pathogenesis remain unclear. Advances in surgical technique have improved the ability to modify long-bone alignment in the coronal, sagittal, and axial planes. However, to our knowledge, there is no significant long-term data available in regard to the relationship between anatomic alignment parameters most amenable to surgical modification and patellofemoral joint osteoarthritis.

METHODS

Five-hundred and seventy-one cadaveric skeletons were obtained from the Hamann-Todd osteological collection. Mechanical lateral distal femoral angle, medial proximal tibial angle, tibial slope, femoral version, tibial torsion, the position of the tibial tubercle relative to the width of the tibial plateau, trochlear depth, and patellar size were measured using validated techniques. A previously published grading system for patellofemoral joint arthritis was used to quantify macroscopic signs of degenerative joint disease.

RESULTS

Increasing age (standardized beta 0.532, p<0.001), female gender (standardized beta 0.201, p=0.002), and decreasing mechanical lateral distal femoral angle (standardized beta -0.128, p=0.025) were independent correlates of increased patellofemoral joint osteoarthritis. A relatively more laterally positioned tibial tubercle trended towards predicting patellofemoral joint osteoarthritis (standardized beta 0.080, p=0.089).

CONCLUSIONS

These findings confirm that patellofemoral joint osteoarthritis is strongly associated with increasing age and female gender. Valgus alignment of the distal femur, a relatively more lateral location of the tibial tubercle, and a shallower trochlear grove appear to have modest effects on the development of patellofemoral joint osteoarthritis.