Changes in patellar alignment after total knee arthroplasty

Influence of Patellar Tilt Angle in Merchant View on Postoperative Range of Motion in Posterior Cruciate Ligament-Substituting Fixed-Bearing Total Knee Arthroplasty

Background

We investigated whether the patellar tilt angle influences the maximum knee flexion after total knee arthroplasty (TKA) performed by using a posterior cruciate ligament-substituting (PS) fixed-bearing prosthesis in patients with relatively loose or tight flexion gap.

Methods

In this prospective cohort study, we followed up 169 patients for at least 2 years after TKA using PS fixed-bearing prosthesis. The patients were divided into two groups according to the flexion gap value-calculated by subtracting the thickness of the final bearing from the flexion gap measured intraoperatively under 200-cN·m force after patellar reduction and insertion of the final femoral and tibial components-into a relatively tight group (group T; 3-6.5 mm) and a relatively loose group (group L; 7-11 mm). Patellar tilt angles and maximum non-weight-bearing active knee flexion angles were assessed postoperatively. Group T was further divided into subgroup Tn if the patellar tilt angle was < 5° and subgroup Tw if the angle was ≥ 5°. Pearson correlation test was used for the correlation analysis of the flexion gap, patellar tilt angle, and postoperative flexion range.

Results

The mean postoperative flexion was 137.3° in group T and 137.5° in group L. The mean patellar tilt angle was 6.5° in group T and 6.9° in group L. In group T, a strong negative correlation (r = -0.78, p < 0.05) was observed between the patellar tilt and postoperative flexion range. However, further analysis revealed that only the subgroup Tw showed a strong negative correlation (r = -0.76, p < 0.05). Significant correlations were not found in the subgroup Tn and group L.

Conclusions

In TKA where a relatively tight flexion gap (≤ 6.5 mm) is created because of concerns about postoperative flexion instability due to a loose flexion gap, the patellar tilt angle should be < 5° for maximal postoperative knee flexion.

The Influence of Preoperative Radiographic Patellofemoral Degenerative Changes and Malalignment on Patellofemoral-Specific Outcome Scores Following Fixed-Bearing Medial Unicompartmental Knee Arthroplasty

BACKGROUND

There is controversy as to whether the presence of degenerative changes and malalignment of the patellofemoral joint is a contraindication to medial unicompartmental knee arthroplasty. Therefore, the aim of the present study was to examine the influence of preoperative radiographic patellofemoral joint osteoarthritis and alignment on intermediate-term knee and patellofemoral joint-specific patient-reported outcomes following fixed-bearing medial unicompartmental knee arthroplasty.

METHODS

We performed a retrospective review of the records on a consecutive series of patients who had undergone robotic arm-assisted fixed-bearing onlay medial unicompartmental knee arthroplasty and had a minimum duration of follow-up of 2 years. All records were collected from a single surgeon's arthroplasty registry. Patients with severe bone loss or grooving of the lateral patellar facet were excluded. Radiographic assessment was performed with use of the Kellgren-Lawrence and Altman classification systems as well as with patellofemoral joint alignment measurements. The latest follow-up consisted of a patient-reported questionnaire, including the Kujala (Anterior Knee Pain Scale) score, the Knee Injury and Osteoarthritis Outcome Score (KOOS), Junior (JR), and satisfaction levels.

RESULTS

A total of 536 patients (639 knees) were included. After a mean duration of follow-up (and standard deviation) of 4.3 ± 1.6 years (range, 2.0 to 9.2 years), good-to-excellent Kujala scores were reported independent of the presence of patellofemoral joint osteoarthritis preoperatively (Kellgren-Lawrence grade 0 compared with ≥1, p = 0.82; grade ≤1 compared with ≥2, p = 0.84). Similar findings were found when osteoarthritis was present in either the medial or lateral side of the patellofemoral joint as defined by an Altman score of ≥2 (medial, p = 0.81; lateral, p = 0.90). KOOS scores and satisfaction also were not affected by degenerative patellofemoral joint changes. Furthermore, neither the patellar tilt angle nor the congruence angle influenced patient-reported outcomes.

CONCLUSIONS

Preoperative radiographic mild to moderate patellofemoral joint degeneration (Kellgren-Lawrence grades 1 through 3) and/or malalignment did not compromise intermediate-term knee and patellofemoral joint-specific patient-reported outcomes in patients managed with fixed-bearing medial unicompartmental knee arthroplasty. On the basis of the results of the present study, we believe that neither mild to moderate patellofemoral degeneration nor abnormal patellar tilt or congruence should be considered a contraindication to fixed-bearing medial unicompartmental knee arthroplasty.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Role of Anatomical Patella Replacement on Anterior Knee Pain

BACKGROUND

Anterior knee pain (AKP) remains a complex issue affecting patient satisfaction after total knee arthroplasty. Several radiographic parameters have been shown to be causative factors with various designs. The aim of this study is to evaluate the known radiographic parameters of AKP and clinical outcomes (ie, AKP) in the setting of a modern prosthesis with an anatomic patella button.

METHODS

Between July 2012 and December 2013, 90 total knee arthroplasties received 3 skyline views taken at 30°, 45°, and 60°. A patient-administered questionnaire was administered at 2-year follow-up to assess the incidence of AKP, painless noise, and satisfaction. Radiographs were analyzed for patellofemoral overstuffing, patellar tilt, and patellar displacement, and evaluated the patella resection angle.

RESULTS

On the patient-administered questionnaire, 10 (11.1%) patients reported AKP of a mild-to-moderate nature. Thirty-one had the best view at 30 Merchant views, 24 had best views at 45, and 35 had best views at 60. We found that patellar resection angle correlated with AKP (odds ratio 1.21, P = .044) and painless noise (odds ratio 1.22, P = .034). Patellar displacement and patellofemoral stuffing did not correlate with AKP or painless noise. No radiographic measurements correlated with changes in Knee Society Score pain or function scores or range of motion.

CONCLUSION

We found that a patellar resection angle correlated with the incidence of AKP and painless noise at 2-year follow-up. We failed to find any correlation with patellofemoral overstuffing, patellar displacement, or patellar tilt with clinical outcomes. We recommend the use of 3 Merchant views to fully evaluate the patellofemoral joint.

Chronological Changes in Axial Alignment of the Ipsilateral Hip and Knee After Total Hip Arthroplasty

BACKGROUND

Internal rotation of the hip and lateral patellar tilt increases after total hip arthroplasty (THA). However, it remains unknown whether these parameters change with time after the index THA.

METHODS

A total of 91 patients undergoing 2-stage bilateral primary THAs between January 2008 and May 2014 were included to assess the association of chronological changes in internal rotation of the hip or lateral patellar tilt with anthropometric and perioperative parameter and changes in alignment after the index THA. Chronological changes were assessed as changes between postoperative computed tomography on the index surgery and the preoperative computed tomography on the contralateral THA. Internal rotation of the hip was defined as the angle between the posterior intercondylar line and a line passing through the posterior inferior iliac spines. Lateral patellar tilt was defined as the angle between the posterior intercondylar line and a line joining the medial and lateral edges of the patella.

RESULTS

Internal rotation of the hip and lateral patellar tilt changed until 2 years after the index surgery by a mean of -2° (range -17.3° to 17.7°) and -2° (range -18.2° to 5.3°), respectively. Adductor tenotomy was associated with increasing internal rotation of the hip with time (adjusted R² 0.076); leg lengthening and larger preoperative femorotibial angle were associated with decreasing lateral patellar tilt with time (adjusted R² 0.159).

CONCLUSION

Both internal rotation of the hip at rest and lateral patellar tilt decreased by approximately 2° until 2 years after surgery and there was a large variation in chronological change.

Magnitude of Deformity Correction May Influence Recovery of Quadriceps Strength After Total Knee Arthroplasty

BACKGROUND

Malalignment of the lower extremity is commonly seen in patients with severe osteoarthritis undergoing total knee arthroplasty (TKA) and is believed to play a role in quadriceps strength loss. Deformity correction is typically achieved through surgical techniques to provide appropriate ligamentous balancing. Therefore, this study examined the influence of change in lower extremity alignment on quadriceps strength outcomes after TKA.

METHODS

Seventy-three participants (36 male; mean age, 62 years; and mean body mass index, 29.7 kg/m2) undergoing primary unilateral TKA were used in this investigation. Before surgery and at 1 and 6 months after surgery, measures of isometric knee extensor strength, quadriceps activation, and long-standing plain films were collected. Using the films, measures of mechanical axis, distal femoral angle (DFA), proximal tibial angle, and patellofemoral angle were performed. Hierarchical linear regression was used to evaluate how change in alignment from baseline to 1 and 6 months influenced the change in quadriceps strength.

RESULTS

DFA was found to significantly contribute to changes in quadriceps strength at 1 and 6 months after TKA above those contributed by associated covariates. None of the other measures of lower extremity alignment were found to contribute to quadriceps strength in this sample.

CONCLUSION

Reductions in quadriceps strength experienced after TKA are likely to be influenced by changes in lower extremity alignment. Specifically, measures of DFA were found to significantly contribute to these changes. Future work is needed to prospectively examine measures of lower extremity alignment change and recovery after TKA.

Superior-inferior position of patellar component affects patellofemoral kinematics and contact forces in computer simulation

BACKGROUND

Anterior knee pain has been reported as a major postoperative complication after total knee arthroplasty, which may lead to patient dissatisfaction. Rotational alignment and the medial-lateral position correlate with patellar maltracking, which can cause knee pain postoperatively. However, the superior-inferior position of the patellar component has not been investigated. The purpose of the current study was to investigate the effects of the patellar superior-inferior position on patellofemoral kinematics and kinetics.

METHODS

Superior, central, and inferior models with a dome patellar component were constructed. In the superior and inferior models, the position of the patellar component translated superiorly and inferiorly, respectively, by 3mm, relative to the center model. Kinematics of the patellar component, quadriceps force, and patellofemoral contact force were calculated using a computer simulation during a squatting activity in a weight-bearing deep knee bend.

FINDINGS

In the inferior model, the flexion angle, relative to the tibial component, was the greatest among all models. The inferior model showed an 18.0%, 36.5%, and 22.7% increase in the maximum quadriceps force, the maximum medial patellofemoral force, and the maximum lateral patellofemoral force, respectively, compared with the superior model.

INTERPRETATION

Superior-inferior positions affected patellofemoral kinematic and kinetics. Surgeons should avoid the inferior position of the patellar component, because the inferior positioned model showed greater quadriceps and patellofemoral force, resulting in a potential risk for anterior knee pain and component loosening.

Medial Unicondylar Knee Arthroplasty Improves Patellofemoral Congruence: a Possible Mechanistic Explanation for Poor Association Between Patellofemoral Degeneration and Clinical Outcome

The purpose was to determine the effect of medial fixed bearing unicondylar knee arthroplasty (UKA) on postoperative patellofemoral joint (PFJ) congruence and analyze the relationship of preoperative PFJ degeneration on clinical outcome. We retrospectively reviewed 110 patients (113 knees) who underwent medial UKA. Radiographs were evaluated to ascertain PFJ degenerative changes and congruence. Clinical outcomes were assessed preoperatively and postoperatively. The postoperative absolute patellar congruence angle (10.05 ± 10.28) was significantly improved compared with the preoperative value (14.23 ± 11.22) (P = 0.0038). No correlation was found between preoperative PFJ congruence or degeneration severity, and WOMAC scores at two-year follow up. Pre-operative PFJ congruence and degenerative changes do not affect UKA clinical outcomes. This finding may be explained by the post-op PFJ congruence improvement.

Optimal patellar alignment with minimally invasive approaches in total knee arthroplasty after a minimum five year follow-up

PURPOSE

Patellofemoral syndrome is still a common complication after total knee arthroplasty (TKA). However, the effects of specific surgical approaches on patellar tracking and alignment remain incompletely understood. In this study, we compared patellar alignment in patients who underwent TKA via three different techniques.

METHODS

A total of 96 patients who completed a minimum follow-up of five years were involved in three groups: 30 patients were treated with the traditional medial parapatellar approach (MPP group), 35 patients were treated with the mini-medial parapatellar approach (MMP group) and 31 were treated with a quadriceps-sparing approach (QS group). Radiographic data for patellar alignment and clinical results were compared.

RESULTS

Patellar tilt and patellar displacement at the final follow-up evaluation differed significantly among the three groups [P < 0.01, analysis of variance (ANOVA)]. The MMP and QS groups exhibited more proper patellar alignment than the MPP group. The clinical results did not differ significantly among the groups (P > 0.05, ANOVA). In addition, there were no correlations between postoperative patellar alignment and clinical scores.

CONCLUSIONS

The results of this study indicate that TKA performed using minimally invasive approaches yields superior patellar alignment compared to the traditional MPP approach.

Distal femoral condyle is more internally rotated to the patellar tendon at 90° of flexion in normal knees

Background

The configuration of the distal surface of the femur would be more important in terms of the patellofemoral (PF) joint contact because the patella generally contacts with the distal surface of the femur in knee flexion. Some total knee arthroplasty (TKA) designs configurate medially prominent asymmetric femoral condyles. This difference in the design of distal femoral condyle may affect the PF joint congruity in knee flexion. Furthermore, some surgeons advocate a concept aligning the symmetric components parallel to the native joint inclination, not perpendicular to the mechanical axis. This concept would also make a difference on the PF joint congruity at the distal femur in knee flexion. However, no fundamental study has been reported on the PF congruity at the distal femur to discuss the theoretical priority of these concepts.

The current study investigated the angular relationship between the tibial attachment of the patellar tendon and the distal surface of the femur at 90° of flexion in normal knees.

Methods

The open magnetic resonance images of 45 normal knees at 90° of flexion were used to measure the angles between the tibial attachment of the patellar tendon, the equatorial line of the patella, and the distal surface of femoral condyles.

Results

The distal surface of femoral condyles was internally rotated relative to the tibial attachment of the patellar tendon and the equatorial line of the patella in all the knees (8.2° ± 3.5° and 5.8° ± 2.5°, respectively), not parallel.

Conclusions

Distal femoral condyle is internally rotated to the patellar tendon at 90° of flexion in normal knees. When the symmetric femoral component is aligned perpendicular to the femoral mechanical axis, the patellar tendon would be possibly more twisted than the condition in normal knees, and the deviation of the PF contact force on the patellar component might be caused. The configuration and alignment of the distal condyle of the femoral component can affect the PF joint congruity in knee flexion. In this respect, our results provide important information in considering designs and alignment in the distal femur of TKA and the PF joint congruity in knee flexion.

Internal rotation of femoral component affects functional activities after TKA--survey with the 2011 Knee Society Score

The 2011 Knee Society Knee Scoring System (KSS) was developed as a new patient-derived outcome measure to better characterize satisfaction, expectations, and physical activities after total knee arthroplasty. The rotational alignment of the femoral and tibial components was assessed with computed tomography in 75 patients (92 knees), and its effect on the scores of the KSS was evaluated. Internal rotation of the femoral component relative to the surgical epicondylar axis significantly decreased the score of functional activities and slightly decreased the score of satisfaction. Femoral component malrotation did not affect the scores of symptoms and expectations. Tibial component malrotation did not affect any of the scores of the 2011 KSS. Surgeons should avoid internal rotation of the femoral component to preserve functional activities.

Lateral patellar facetectomy and medial reefing in patients with lateral facet syndrome after patellar-retaining total knee arthroplasty

We analyzed clinical outcomes of partial lateral patellar facetectomy and medial reefing in patients with lateral patellar facet syndrome with painful patellar-retaining total knee arthroplasty. 34 patients were followed for a mean of 40 months. All 34 patients were matched with those having secondary patellar resurfacing without facetectomy. Both groups experienced significant pain relief and range of motion improvement. The facetectomy group had higher Kujala scores than those in patellar resurfacing group. Patients with facetectomy had significantly less pain postoperatively. There were significant differences in postoperative lateral patellar tilt and congruency angle in both groups. The mid-term results for LPF with medial reefing are promising to resolve pain in patients with lateral patellar facet syndrome in patellar-retaining TKA. Therapeutic level III (retrospective comparative study).

Patellar tilt and thickness do not influence postoperative flexion in a high-flex design total knee arthroplasty

PURPOSE

The purpose of this short-term study was to determine whether patellar thickness and tilt influence the postoperative flexion in a high-flex design total knee arthroplasty (TKA).

METHODS

Between 2007 and 2009, 106 patients underwent surgery for TKA using rotating platform flex prosthesis (DePuy, Warsaw, Ind). All of them were suffering from end-stage osteoarthritis. All patients were evaluated preoperatively and at 12 months of follow-up. Maximum active, non-weight-bearing flexion was the primary outcome parameter. Standard standing antero-posterior and lateral weight-bearing radiographs were made. The patellofemoral joints were evaluated in skyline views taken with the knees at approximately 60° of flexion. Patellar thickness, patellar tilt, Caton-Deschamps indices and lower limb alignment were measured.

RESULTS

The mean flexion observed before surgery was 125° ± 15° and after 1 year was 128° ± 13°. The mean patellar thickness preoperatively was 24.5 ± 2.9 and 25.8 ± 3.2 mm at 12 months after surgery. The mean patellar tilt before the procedure was 2.9° ± 4.1° and after 12 months of follow-up was -0.8° ± 5.0°. The mean preoperative hip-knee-ankle was 2.6° ± 6.2°. No significant correlation was found between postoperative patellar tilt and thickness and postoperative flexion (n.s.).

CONCLUSIONS

Patellar tilt and thickness after TKA are factors that depend on the surgery. The resection of the patella can influence both patellar thickness and patellar tilt. By developing adequate surgical instruments, it would be possible to avoid the occurrence of an exaggerated patellar tilt or a major difference in patellar thickness. However, these two factors did not seem to influence the postoperative flexion in a high-flex design TKA, which can be seen as one of the most important outcome factors after TKA.

Patellar tracking after total knee arthroplasty performed without lateral release

There is limited clinical data on patellar maltracking in patients who have undergone total knee arthroplasty (TKA) without lateral release. We performed a retrospective review of 191 consecutive TKAs performed by one surgeon through the subvastus approach without lateral release from 2007 to 2008. Radiographic measurements were made using the preoperative and postoperative 2 years radiographs. Multivariate logistic regression analysis was performed to determine the risk factors for patellar maltracking after TKA performed without lateral release. TKA resulted in increases in the patellar tilt and displacement (P<0.05). The presence of preoperative patellar tilt and displacement were predictive of postoperative patellar tilt and displacement in patients who underwent TKA through the subvastus approach without lateral release (P<0.05).