The Quadriceps Vector is Most Parallel to the Spherical Axis With Minimal Difference for Gender or Ethnicity

Better forgotten joint scores when the angle of the prosthetic trochlea is lateral to the quadriceps vector in kinematically aligned total knee arthroplasty

PURPOSE

The primary aim was to analyze unrestricted kinematic alignment (unKA) total knee arthroplasty (TKA) and determine the frequency of medial deviation of the prosthetic trochlear angle (PTA) of the femoral component relative to the quadriceps vector (QV) that terminates at the anterior inferior iliac spine (AIIS), and whether patients with medial deviation had a worse Forgotten Joint Score (FJS) and Oxford Knee Score (OKS) relative to those with lateral deviation. The secondary aim was to determine the frequency of medial deviation for mechanical alignment (MA) TKA simulations.

METHODS

From a database of a single surgeon, the study extracted de-identified data on 147 patients with a CT scanogram showing the pelvis and AIIS, a limb with an unKA TKA, and a native (i.e., healthy) opposite limb. On the scanogram, an examiner, blinded to the PROMs, measured the PTA-QV angle on the unKA TKA and on the opposite limb simulated MA TKA by drawing the PTA at 6° valgus relative to the femoral mechanical axis and measuring the PTA-QV angle.

RESULTS

Medial deviation of the PTA occurred in 86% of patients with unKA TKA, and the 126 with medial deviation had a 17/1 point worse median FJS/OKS than the 21 with lateral deviation at a mean follow-up of 47 ± 8 months, respectively (p < 0.0001, p = 0.0053). In addition, 21%, 17%, and 8% of MA TKA had medial deviation after radiographic simulation using reported surgical errors for manual, patient-specific, and robotic instrumentation, respectively.

CONCLUSION

In most patients with unKA TKA and a smaller proportion with MA TKA, a PTA of 6° valgus was medial to the QV, which, by excluding the patient's Q-angle, might alter patellofemoral kinematics like an incorrectly oriented trochleoplasty. The 17-point worse FJS in the patients with an unKA TKA and medial deviation of the PTA suggests the surgical target should be to orient the PTA lateral to the QV.

LEVEL OF EVIDENCE

IV.

Medial-pivot design improved knee symptoms from anteroposterior instability in early-range flexion and resolved anterior knee pain in revision total knee arthroplasty

BACKGROUND

Instability can lead to poor functional results after tricompartmental total knee arthroplasty (TKA). We identified a group of patients who appeared to have antero-posterior (AP) instability in early-range flexion (i.e., 20 to 30° range) associated with anterior knee pain and feelings of instability. The purpose of this study was to assess the clinical results in terms of stability and anterior knee pain after revision TKA with a medial-pivot implant and to assess the effect of the implant positioning used in the revision technique.

METHODS

There were 45 patients (45 knees) evaluated retrospectively to assess standing lower extremity alignment and functional results by generating a knee stability score after revision TKA with medial pivot implant design.

RESULTS

Revision TKA using the medial-pivot TKA lowered the joint line by 3.6 millimeters (mm) (P<0.001) and positioned the tibia anteriorly by 3.5 mm (P<0.001) on radiographic measurements as compared with results after primary TKA. Moreover, medial pivot revision TKA improved AP stability by a 56-point change in score (P<0.001).

CONCLUSIONS

Revision TKA using a medial pivot design improved AP stability and anterior knee pain after failed primary procedures.

The three-dimensional quadriceps vector is most parallel to the spherical axis in Japanese varus osteoarthritic knees

BACKGROUND

The quadriceps femoris may be a reliable reference to proper alignment in total knee arthroplasty (TKA). We previously showed the quadriceps vector (QV) to be the most parallel to the spherical axis (SA-center hip to center medial condyle) for healthy knees. The purpose of this study was to determine whether the QV is the most parallel to the SA in knees with varus osteoarthritis (OA).

METHODS

CT imaging for 35 varus OA and 40 healthy Japanese knees was used to construct 3D models of the femur, patella and each quadriceps component for each subject. The QV was calculated using principal component analysis for direction and was compared with the relationship of the QV to the measurement axes of the lower extremity, including the anatomical, mechanical and spherical axes.

RESULTS

The direction of the QV for the OA knee group was different from that for the healthy knee group in 3D space (medio-lateral direction: women, p = 0.532, men, p = 0.540; antero-posterior direction: women, p = 0.141, men, p < 0.001). However, the angle of the QV in relation to measurement axes in the coronal plane was closest to the SA in both groups (around 1°), with no difference between the groups (women, p = 0.382, men, p = 0.943).

CONCLUSION

In the coronal plane, the SA most closely approximates the QV for both healthy and OA knees. The more posterior QV position in the 3D space may affect the patellofemoral joint.

Contribution of sex and body constitution to three-dimensional lower extremity alignment for healthy, elderly, non-obese humans in a Japanese population

BACKGROUND

Humans support their bodies exclusively by vertical balance in bipedal locomotion, and the body, especially the lower extremity, generally changes with age. Sex and body constitution are assumed to be associated with lower extremity alignment, but this association remains to be elucidated. This study sought to clarify this association in healthy, elderly, non-obese humans in a Japanese population.

METHODS

The present study investigated 55 healthy volunteers (mean age: 70 ± 6 years). A 3D extremity alignment system was applied under weight-bearing conditions on biplane long lower extremities X-rays using a 3D-to-2D image registration technique. The evaluation parameters included 3D hip-knee-ankle angle (3DHKA) alignment in the coronal (coronal alignment) and sagittal planes (sagittal alignment) and rotational alignment between the femur and tibia. The influences of sex and body constitution on all the alignment were analyzed.

RESULTS

Multiple linear regression analysis with the dependent variable of each alignment showed that sex was the dominant factor for coronal and rotational alignment (coronal: p <  0.01; rotational: p <  0.01), and body weight was the dominant factor for sagittal alignment (p <  0.01).

CONCLUSIONS

The association of sex with coronal and rotational alignment and of body constitution with sagittal alignment were proved in healthy, elderly, non-obese humans in a Japanese population. This finding can lead to further understanding of the etiology of many diseases and age-related changes.

Joint Line Modification in Kinematically Aligned Total Knee Arthroplasty Improves Functional Activity but Not Patient Satisfaction

BACKGROUND

Joint line modification in kinematically aligned total knee arthroplasty (KA-TKA) is attracting attention in expectation of optimizing patient satisfaction after TKA. This study aimed to examine the effects of joint line modification on Pain Catastrophizing Scale (PCS), painDETECT score, and new Knee Society Score (KSS) 2011, all of which are robustly related to patient satisfaction.

METHODS

The study enrolled 45 knees of 45 patients undergoing KA-TKA and a matched group of 45 knees of 45 patients undergoing mechanically aligned (MA) TKA as controls. At a mean of 31.6 months after TKA, new KSS 2011, PCS, and painDETECT score were assessed and compared between KA- and MA-TKA. Data from all 90 patients were pooled into one group for secondary multiple regression analysis to identify postoperative variables affecting patient satisfaction.

RESULTS

Assessment with new KSS 2011 showed no significant differences between the 2 TKAs preoperatively, but functional activity score was significantly higher with KA-TKA than with MA-TKA postoperatively (P = .047). Among the 4 categories of functional activity score, advanced activity score was significantly higher with KA-TKA than with MA-TKA (P = .003). Of the 5 advanced activities, the score for climbing ladder/step stool was significantly greater with KA-TKA (P = .004). KA-TKA failed to influence patient satisfaction score. Multiple regression analysis revealed that standard activity score and PCS affected patient satisfaction positively and negatively, respectively.

CONCLUSION

Joint line modification in KA-TKA improved functional activity but not patient satisfaction. PCS was a key element negatively affecting patient satisfaction.

Relationship between knee alignment in asymptomatic subjects and flexibility of the main muscles that are functionally related to the knee

Objective To assess the relationship between static frontal knee alignment in asymptomatic subjects and flexibility of the main muscles functionally related to the knee. Methods A descriptive cross-sectional study was performed in 33 healthy adults (19-31 years). The frontal knee angle (valgus/varus angle) was measured by photogrammetry and it was measured in the lateral side. Therefore, high values were assigned for genu varum and low values for genu valgum. Iliopsoas, gluteus maximus and medius, rectus femoris, biceps femoris, vastus of the quadriceps, and gastrocnemius muscles were stretched. Muscles were classified as normal, reflex hypomobile, or structural hypomobile. Results Women had significantly greater valgus than did men (right angle, women: 174.41°/men: 177.41°; left angle, women: 174.20°/men: 178.70°). The right frontal plane knee angle was higher in women with structural hypomobile vastus. The left frontal plane knee angle was higher in women with structural hypomobile iliopsoas. No relationships were found in men. Conclusions A tighter vastus of the quadriceps and tighter iliopsoas are related to greater genu varum in adult women. Stretching the vastus of the quadriceps and iliopsoas when there is a tendency for excess varus in the knee, to prevent overuse injury or early osteoarthritis, might be clinically relevant.

The location of the medial parapatellar arthrotomy influences intraoperative patella tracking

PURPOSE

The medial parapatellar arthrotomy (MPPA) is a commonly utilized surgical approach; however, the placement of the arthrotomy and its influence on intraoperative patellar tracking has not been evaluated.

METHODS

Six knees from three fresh frozen cadavers with transthoracic amputations were operated on. All underwent standard posterior stabilized total knee arthroplasty using a medial parapatellar approach placed at the border of the vastus medialis oblique (VMO)-quadriceps junction. Patellae were resurfaced in the standard fashion. All patellae tracked normally with the first arthrotomy placed at the junction of the VMO-quadriceps tendon using the "no touch" technique. Measurement of patellar lift-off from the implant surface of the medial aspect of the trochlea on the femoral component was made at 50°, 75°, and 90° of flexion and a merchant view radiograph taken to evaluate radiographic patellar tilt. To simulate a more lateral placement of the MPPA, a 5-6 mm slice of quadriceps tendon was then removed from the lateral aspect of the tendon from the patellar insertion to the most proximal portion of the arthrotomy. This simulated a 5-6 mm more lateral placement of the parapatellar arthrotomy. The same measurements and radiographs were taken as described previously. Two more times the same size slices was removed from the quadriceps tendon with subsequent measurements and radiographs obtained.

RESULTS

The mean patellar lift-off with the first arthrotomy was 0 ± 0 mm for 50°, 75°, and 90° of flexion. The mean lift with the second arthrotomy was 2 ± 2, 3 ± 3, and 4 ± 3 mm respectively. The third arthrotomy had a mean patellar lift-off of 3 ± 2, 4 ± 3, and 8 ± 2 mm respectively, while the fourth arthrotomy had a mean lift-off of 6 ± 2, 8 ± 2, and 9 ± 4 mm. There was a significant correlation between percentage of quadriceps cut at 1 cm above the superior pole of the patella and patellar lift-off at 50° (R ² = 0.70; p < 0.0001), 75° (R ² = 0.68; p < 0.0001), and 90° (R ² = 0.68; p < 0.0001) of flexion.

CONCLUSION

The location of the MPPA has a significant influence on intraoperative assessment of patellar tracking. An MPPA more lateral in the quadriceps tendon may independently influence the patellar tilt observed intraoperatively and should be taken into consideration when evaluating intraoperative patella tracking. An understanding of the independent influence the MPPA has on patellar tracking may decrease the need for lateral release if the surgeon notes the MPPA was made more than 5-10 mm from the junction of the VMO-quadriceps tendon junction.