Patellar resurfacing versus nonresurfacing in total knee arthroplasty: A meta-analysis of randomised controlled trials

Purpose

Patella resurfacing or nonresurfacing in total knee arthroplasty remains controversial. The aim of this study was to evaluate the efficacy of patellar resurfacing through an evaluation of the current literature.

Methods

We carried out a meta-analysis of randomised controlled trials comparing total knee arthroplasties performed with and without patellar resurfacing. Outcomes of reoperation, anterior knee pain and knee scores were analysed.

Results

Fourteen trials assessing 1,725 knees were eligible. The absolute risk of reoperation was reduced by 4 % (95 % confidence interval, 2–6 %) in the patellar resurfacing arm (between-study heterogeneity, P = 0.05, I² = 42 %), implying that one would have to resurface 25 patellae (95 % confidence interval, 17–50 patellae) in order to prevent one reoperation. There was no difference between the two groups in terms of anterior knee pain, knee pain score, Knee Society score and knee function score. But in the studies followed up for a mean time of not less than five years, a difference was found between the two arms in Knee Society scores (RR = 2.14, 95 % confidence interval, 0.76–3.52; P = 0.002).

Conclusions

The available evidence indicates that patellar resurfacing reduces the risk of reoperation after total knee arthroplasty. Patellar resurfacing patients may make a difference in long-term follow-up (five or more 5 years) of Knee Society scores. In other aspects, the benefit of patellar resurfacing is limited. Additionally, more carefully and scientifically designed randomised controlled trials are required to further prove the claim.     

Selective Patella Resurfacing in Contemporary Cruciate Retaining and Substituting Total Knee Arthroplasty: A Matched Cohort Analysis

BackgroundLeaving the patella unresurfaced in total knee arthroplasty (TKA) is increasing due to modern patella-friendly implants, awareness that complications are not uncommon with resurfacing, and knowledge that historical studies were scientifically confounded. This study examined the effect of selective patellar resurfacing on patient-reported outcome measures (PROMs) using modern implants and techniques in cohorts rigorously matched for demographics and osteoarthritis severity.MethodsA total of 166 TKAs performed without patellar resurfacing were case-control matched to 166 TKAs with patella resurfacing. Case-control matching was based on demographics, American Society of Anesthesiology Physical Status, comorbidities, and osteoarthritis severity. No significant differences were observed between cohorts for demographics (P ≥ .347), comorbidities (P ≥ .443), or radiographic osteoarthritis severity (P ≥ .078). Radiographic alignment and prospectively collected PROMs were evaluated preoperatively and at latest clinical follow-up.ResultsPreoperatively, patellar tilt was less for the unresurfaced patella group (3 versus 4°, P = .003); however, postoperative patellar tilt was not different (3 versus 3°, P = .225). At a mean of 2.1 years follow-up (range, 1 to 7), University of California Los Angeles Activity Level was significantly higher for the unresurfaced patella group (6.3 versus 5.5, P = .002), but the mean group difference did not reach a minimal clinically important difference. There were no other significant differences in PROMs or reoperation rates between cohorts (P ≥ .135).ConclusionIn contemporary cruciate retaining and substituting TKA designs, not resurfacing the patella in select patients may achieve comparable PROMs and re-operation rates; and potentially greater activity level compared to patella resurfacing at early follow-up.Level of EvidenceIII.     

Patellar resurfacing complications in total knee arthroplasty

Purpose

The ideal management of the patella during total knee arthroplasty (TKA) is still controversial. Patellar retention is generally associated with an increased rate of anterior knee pain; however, patient satisfaction is similar in cases of replacement or retention. When the patella is replaced, potential severe complications can occur. Aim of this study was to retrospectively review results of a continuous series of patients having been treated with TKA and patella resurfacing.

Methods

The charts of 1,600 consecutive total knee prostheses were analysed to evaluate the rate of patellar resurfacing. All implants were posterior stabilized; 310 patients having received a patellar replacement were reviewed at follow-up (FU) examination. Complete physical examination as well as administration of the Hospital for Special Surgery (HSS) score was performed. X-rays analysis included weightbearing anteroposterior (AP) and lateral views of the injured knee and bilateral skyline views at 30° flexion.

Results

Two hundred and eighty patients were available for clinical and imaging investigation at an average FU of 96 (58–144) months. Mean age at the time of surgery was 70 (62–80) years. Mean HSS score was 85.9 ± 7.6. The overall rate of patellofemoral complications was 7 % (19 cases); 13 patients claimed anterior knee pain, five had symptomatic patellar maltracking and one had patellar component loosening.

Conclusion

Our data are in accordance with those available in the literature. Recent meta-analyses demonstrated lower risk of re-operation after patellar resurfacing. However, when complications of the resurfaced patella occur, they can be potentially catastrophic events.     

Patellar resurfacing as a second stage procedure for persistent anterior knee pain after primary total knee arthroplasty

Purpose

Knee pain after total knee arthroplasty may be caused by an unresurfaced patella. Secondary isolated resurfacing of the previously unresurfaced patella in total knee arthroplasty remains controversial. The aim of this retrospective study was to evaluate the outcome after patellar resurfacing as a second stage procedure.

Methods

The study included 22 patients (13 female/nine male) who underwent resurfacing of the patella with a mean follow-up of 61.8 ± 39.2 months. The mean age of the patients was 60 ± 9.7 years at the time of operation. The average period between total knee arthroplasty and patellar resurfacing was 26.3 ± 15.2 months. The patient’s subjective satisfaction was assessed by a custom-made questionnaire.

Results

The mean Knee Society Score improved significantly from 60.1 ± 8.3 to 77.0 ± 6.3 (p = 0.0063). The mean functional score also improved significantly from 42.7 ± 2.3 to 60.2 ± 3.9 (p = 0.001). Three patients (13.6%) needed further operative revision.

Conclusions

Although clinical scores showed significant improvement some patients continued to have pain and remained dissatisfied without detecting a specific reason. Further studies are needed to better elucidate the benefit of patellar resurfacing as second stage procedure.     

Intramedullary nailing versus proximal plating in the management of closed extra-articular proximal tibial fracture: a randomized controlled trial

BackgroundExtra-articular proximal tibial fractures account for 5–11 % of all tibial shaft fractures. In recent years, closed reduction and minimally invasive plating and multidirectional locked intramedullary nailing have both become widely used treatment modalities for proximal and distal tibial metaphyseal fractures. This study was performed to compare plating and nailing options in proximal tibia extra-articular fractures.ResultsPostoperative hospital stay (p = 0.035), time to full weight-bearing, and union time (p = 0.004) were significantly less in the IMN group than in the PTP group, but there was no clear advantage of either technique in terms of operative time (p = 0.082), infection rate (p = 0.738), range of motion of the knee (p = 0.462), or degrees of malunion and nonunion.ConclusionBoth implants have shown promising results in extra-articular proximal tibial fractures, and provide rigid fixation that prevents secondary fracture collapse.

Level of evidence

Level 2, randomized controlled trial.     

All-inside meniscal repair surgery: factors affecting the outcome

BackgroundMeniscal injury is currently a well-recognized source of knee dysfunction. While it would be ideal to repair all meniscus tears, the failure rate is significantly high, although it may be reduced by careful selection of the patients. Our objective was to assess the outcome of meniscal repair surgery and the role of simultaneous reconstruction of the anterior cruciate ligament (ACL).Results136 Meniscal repairs were performed in 122 patients with a mean age of 26.8 years. Mean follow-up duration was 9 months. 63 % of the patients underwent medial and 37 % underwent lateral meniscal repair, with failure rates of 19 % for medial and 12 % for lateral menisci. Ligament injuries were found in 61 % of the patients (n = 83). Failure of meniscal repair occurred in 14.5 % (n = 12) of the patients who had early ACL reconstruction and in 27 % (n = 22) of the patients who had delayed ACL reconstruction (p = 0.0006). The failure rate was found to be 13 % in patients who were younger than 25 years (61 %) and 15 % in patients who were older than 25 years (39 %).ConclusionThe success rate of meniscal repair was found to be significantly better when ACL reconstruction was performed simultaneously with meniscal repair.

Level of evidence

Level IV.     

Does Implant Design Influence Failure Rate of Lateral Unicompartmental Knee Arthroplasty? A Meta-Analysis

BackgroundLateral unicompartmental knee arthroplasty (UKA) is a viable solution for isolated lateral compartment arthritis. Several prosthetic designs are available such as fixed-bearing metal-backed (FB M-B), fixed-bearing all-polyethylene (FB A-P), and mobile-bearing metal-backed (MB M-B) implants. The purpose of this meta-analysis is to compare failure rates of different prosthetic designs.MethodsPreferred Reporting Items for Systematic Reviews and Meta-Analyses systematic review was conducted using 4 databases (MEDLINE, EMBASE, Cochrane, and PubMed) to identify all studies that investigate outcomes of lateral UKA. Twenty-one studies met the inclusion criteria, and failure rates were compared by implant type and follow-up time separately in order to assess potential confounding factors. Two separate analyses have been performed among different implant designs (FB M-B vs FB A-P vs MB M-B) and different follow-ups (<5 years, between 5 and 10 years, >10 years).ResultsThe failure rate of FB M-B lateral UKA was significantly lower compared to other lateral UKA designs present in the market (0.8% vs 8.6% and 7.1% for FB M-B, FB A-P, and MB M-B, respectively). No significative difference among groups has been detected when comparing all implants with regard to follow-up time.ConclusionConsidering actual evidence, for a surgeon approaching lateral UKA, the FB M-B design is preferable, given the lower failure rates and subsequently a longer implant survivorship.     

A comparative study of two percutaneous pinning techniques (lateral vs medial–lateral) for Gartland type III pediatric supracondylar fracture of the humerus

BackgroundThe management of displaced supracondylar fracture of the humerus with closed reduction and percutaneous pin fixation is the most widely accepted method of treatment, but controversy continues regarding the pin fixation techniques. A prospective randomized controlled study was undertaken to compare the stability, functional outcome and iatrogenic ulnar nerve injury between lateral pin fixation and medial–lateral pin fixation.ResultsThere were two (6.5 %) iatrogenic ulnar nerve injury cases in the medial–lateral entry group and two (6.5 %) cases with mild loss of reduction in the lateral entry group. No major loss of reduction was observed in either of the groups. There was no statistically significant difference in change of Baumann angle, metaphyseal–diaphyseal angle, Flynn grade, carrying angle, and the total elbow range of motion (P < 0.05) between the two groups.ConclusionsLateral pin fixation offers similar functional and radiological outcome and almost equal mechanical stability compared with medial–lateral pinning without the risk of iatrogenic ulnar nerve injury.

Level of evidence [OCEBM 2011]

Level 2.     

Mobile-Bearing has no Benefit Over Fixed-Bearing Total Knee Arthroplasty in Joint Awareness and Crepitus: A Randomized Controlled Trial

BackgroundGiven higher component conformity, rotational availability of polyethylene insert, and more physiologic patellofemoral tracking, mobile-bearing (MB) total knee arthroplasty (TKA) is supposed to offer advantages in joint perception and crepitus. The purpose of this study was to investigate whether MB TKA offers superior outcomes over fixed-bearing (FB) TKA in terms of joint awareness and crepitus.MethodsThis prospective, randomized, controlled trial included 49 FB and 49 MB TKAs that shared the same posterior-stabilized femoral component. Primary outcomes included joint awareness assessed with the Forgotten Joint Score and crepitus graded according to severity and sound at 3 years postoperatively. Secondary outcomes were the range of motion, the Knee Society Score, Western Ontario and McMaster Universities Osteoarthritis Index, component position, and joint line level on radiographs.ResultsThe Forgotten Joint Score showed no significant difference between the FB (67 points; range, 0-100) and MB groups (63 points; range, 13-100) (P = .440). For crepitus, no significant differences were found in the overall incidence rate (FB group, 18%; MB group, 12%; P = .386) and grade (grade 1, 6 versus 5; grade 2, 2 versus 1; grade 3, 1 versus 0, respectively). There were no significant differences in range of motion, Knee Society Score, and Western Ontario and McMaster Universities Osteoarthritis Index, as well as radiographic outcomes between the two groups (all, P > .05).ConclusionMB TKA offers no benefits in terms of joint awareness and crepitus compared with FB TKA at mean 3 years postoperatively. The theoretical advantages of MB TKA have yet to be demonstrated in practice, leaving the selection of bearing type to the surgeon’s judgment.Level of EvidenceLevel II.     

Anatomic vs Dome Patella: Is There a Difference Between Fixed- vs Mobile-Bearing Posterior-Stabilized Total Knee Arthroplasties?

BackgroundIt has been hypothesized that the patella, working in conjunction with both medial and lateral femoral condyles, can influence kinematic parameters such as posterior femoral rollback and axial rotation. The objective of this study is to determine the in vivo kinematics of subjects implanted with a fixed-bearing (FB) or mobile-bearing (MB) posterior-stabilized (PS) total knee arthroplasty (TKA), with a specific focus on evaluating the impact that Anatomic and Medialized Dome patellar components have on tibiofemoral kinematic patterns.MethodsTibiofemoral kinematics were assessed for 40 subjects; 20 with an anatomic patella and 20 with a dome patella. Within these groups, 10 subjects received an FB PS TKA and 10 subjects received an MB PS TKA. All subjects were analyzed using fluoroscopy while performing a deep knee bend activity. Kinematics were collected during specific intervals to determine similarities and differences in regard to patella and bearing type.ResultsThe greatest variation in kinematics was detected between the 2 Anatomic patellar groups. Specifically, the MB-Anatomic subjects experienced greater translation of the lateral condyle, the highest magnitude of axial rotation, and the highest range of motion compared to the FB-Anatomic subjects. Subjects with a Dome Patella displayed much variability among the average kinematics, with all parameters between FB and MB cohorts being similar.ConclusionThe findings in this study suggest that subjects with an Anatomic patellar component could have more normal kinematic patterns with an MB PS TKA as opposed to an FB PS TKA, while subjects with a Dome patella could achieve similar kinematics regardless of TKA type.     

Analysis on anatomical references to assess the coronal alignment of tibial and femoral cuts in mega prosthetic knee replacement

BackgroundIn megaprosthetic knee replacement, surgeons use cutting guides that depend on anatomLevel of evidenceical references to determine the ideal cutting plane alignment. In this work, we investigated the accuracy of using femoral cortical surfaces and tibial canal portions as the references. The study aims to improve the design and use of the cutting guides.ResultsAt the central femoral region, on average, both lateral and medial cortical surfaces give accurate alignment of the ideal cutting plane (0.6° and 0.8°, respectively), with no significant difference (p > 0.01). At the distal region, the lateral cortical surface gives significantly better alignment compared to the medial cortical surface (p < 0.01), but not as accurate (1.4°) as in the central region. For tibia, the central tibial canal gives significantly accurate alignment of the ideal cutting plane (−0.3°) on average, compared to the proximal tibial canal (p < 0.01).ConclusionsFor a femoral cut, both lateral and medial cortical surfaces are the best anatomical references, but only at the central region. For a tibial cut, the central anatomical axis is the best reference.

Level of evidence

IV.     

The Fate and Relevance of the Patella in Two-Stage Revision Total Knee Arthroplasty for Periprosthetic Joint Infection

BackgroundIt remains unclear whether reimplantation of a patellar component during a two-stage revision for periprosthetic total knee arthroplasty infection (PJI) affects patient reported outcome measures (PROMs) or implant survivorship. The purpose of this study was to evaluate whether patellar resurfacing during reimplantation confers a functional benefit or increases implant survivorship after two-stage treatment for PJI.MethodsTwo-stage revisions for knee PJI performed by three surgeons at a single tertiary care center were reviewed retrospectively. All original patellar components and cement were removed during resection and the patella was resurfaced whenever feasible during reimplantation. PROMs, implant survivorship, and radiographic measurements (patellar tilt and displacement) were compared between knees reimplanted with a patellar component versus those without a patellar component.ResultsA total of 103 patients met the inclusion criteria. Forty-three patients (41.7%) underwent reimplantation with, and 60 patients (58.3%) without a patellar component. At a mean follow-up of 33.5 months, there were no significant differences in patient demographics or PROMs between groups (P ≥ .156). No significant differences were found in the estimated Kaplan-Meier all-cause, aseptic, or septic survivorship between groups (P ≥ .342) at a maximum of 75 months follow-up. There was no significant difference in the change (pre-resection to post-reimplant) of patellar tilt (P = .504) or displacement (P = .097) between the groups.ConclusionPatellar resurfacing during knee reimplantation does not appear to meaningfully impact postoperative PROMs or survivorship. Given the risk of potential extensor mechanism complications with patellar resurfacing, surgeons may choose to leave the patella without an implant during total knee reimplantation and expect similar clinical outcomes.Level of EvidenceLevel III.     

The effects of medial synovial plica excision with and without lateral retinacular release on adolescents with anterior knee pain

ObjectivesTo describe the functional outcomes in patients aged ≤18 years with anterior knee pain treated with medial plica excision with or without lateral release.MethodsWe identified 135 patients including 30 bilateral cases (165 knees) with a mean ± SD age of 15.1 ± 2.0 years. Patient and surgical information was recorded and a follow-up athletic questionnaire and an International Knee Documentation Committee (IKDC) Subjective Knee Evaluation form were sent out. Statistical analysis evaluated predictors of residual pain, reoperation, return to sports, IKDC score and satisfaction with surgery.ResultsAt a final mean follow-up of 4.4 years (range 2–7.5), 36 % of patients were pain free, 46 % had mild residual pain and 18 % had pain not improved from surgery. Reoperation was more likely following isolated plica excision (7/41; 17 %) versus plica excision with lateral release (8/124; 6 %), although not statistically significant, P = 0.06. Mean IKDC score (107 knees) was 76.9 ± 17.8 (range 31–100). Most patients (86/99; 87 %) were satisfied with surgery and were able to return to sports (104/120; 87 %).ConclusionsWhile most patients were satisfied and able to return to sports following plica excision with or without lateral release, residual symptoms were common.     

Medial patellofemoral ligament anatomy: is it a predisposing factor for lateral patellar dislocation?

Purpose

Because the medial patellofemoral ligament (MPFL) is the primary restraint to lateral dislocation of the patella, we aimed, in this controlled study, to verify whether the MPFL with different measurements could be considered another predisposing factor for patellar dislocation.

Methods

A group of 100 consecutive individuals without the criteria for patellar dislocation (trochlear dysplasia, patella alta and lateral patellar tilt) was recruited as a control group and underwent magnetic resonance imaging (MRI) study and another group of 50 patients with patellar instability. Femoral condyles, interepicondylar distance, length and thickness of the MPFL were measured.

Results

In the control group, the MPFL was 38–60 mm long. Individuals with patellar instability who had no episode of patellar dislocation had a 4.11-mm longer ligament than controls (p = 0.032), while patients with instability with a previous history of dislocation had a 13.54-mm longer MPFL than controls (p < 0.001). Thickness of the MPFL at the patellar insertion was lower in individuals with patellar instability with a history of dislocation (p < 0.001). An instability coefficient (IC) less than 1.3 indicates that the MPFL is insufficient.

Conclusions

Individuals with patellar instability and previous patellar dislocation present with longer MPFL when compared to controls, and an associated IC less than 1.3 can be considered a predisposing factor for patellar dislocation. Treatment of patellar instability is a challenge, and it is difficult to identify what is the predisposing factor. This study has verified the measurements of the MPFL for the first time and presents values of thickness and length that can be considered as indications for surgical reconstruction.Level of evidence: III.     

A prospective randomized radiographic and dual-energy X-ray absorptiometric study of migration and bone remodeling after implantation of two modern short-stemmed femoral prostheses

BackgroundThe aim of this prospective randomized study was to analyze migration and strain transmission of the Metha™ and Nanos™ femoral prostheses.ResultsThere was no significant change of varus−valgus alignment or clinically relevant migration of the Metha™ or Nanos™ prostheses during postoperative follow-up. After 12.3 months, the DEXA scans showed small but significant differences of bone mineral density in Gruen zones 1 (minus ~8 %) and 6 (plus ~9 %) for the Metha™ and in Gruen zone 1 (minus ~14 %) for the Nanos™ (paired t test). Visual analog scale (VAS) and Harris Hip Score (HHS) improved significantly for both implants (Nanos™/Metha™ 12.3 months postoperatively HSS 96.5/96.2; VAS 0.7/0.8, respectively). COR or offset did not change significantly after surgery.ConclusionsNeither implant showed signs of impaired osseointegration. DEXA demonstrated proximally located load transfer with only moderate proximal stress shielding.

Level of evidence

II.     

Risk factors for acute compartment syndrome of the leg associated with tibial diaphyseal fractures in adults

BackgroundWe sought to examine the occurrence of acute compartment syndrome (ACS) in the cohort of patients with tibial diaphyseal fractures and to detect associated risk factors that could predict this occurrence.ResultsOf the cohort of patients 772 (69 %) were male (mean age 39.60 ± 15.97 years) and the rest were women (mean age 45.08 ± 19.04 years). ACS of the leg occurred in 87 (7.73 %) of all tibial diaphyseal fractures. The mean age of those patients that developed ACS (33.08 ± 12.8) was significantly lower than those who did not develop it (42.01 ± 17.3, P < 0.001). No significant difference in incidence of ACS was found in open versus closed fractures, between anatomic sites and following IM nailing (P = 0.67). Increasing pain was the most common symptom in 71 % of cases with ACS.ConclusionsWe found that younger patients are definitely at a significantly higher risk of ACS following acute tibial diaphyseal fractures. Male gender, open fracture and IM nailing were not risk factors for ACS of the leg associated with tibial diaphyseal fractures in adults.

Level of evidence

Level IV.     

Predisposing factors for early infection in patients with open fractures and proposal for a risk score

BackgroundThe primary goals of orthopedic treatment of open fractures are to prevent infection, stabilize bone injury and restore limb function. The objective of the current study was to identify risk factors associated with infection in patients suffering from open fractures, using the strength of association of these factors to propose a score that enables risk stratification in initial care.ResultsThirty-one patients out of 122 were infected (25.4 %). Infection was significantly associated with exposure time up to 24 h (mean 30.3 h; p = 0.007). Fractures classified as Gustilo III had a greater chance of infection (74.2 %; p = 0.042), especially type IIIB (41.9 %). Fractures classified as Tscherne II and III had a greater chance of infection (48.4 and 25.8 %, respectively; p = 0.001).ConclusionsIt was possible to show that the exposure time and the types of fracture classified as Gustilo III and Tscherne II and III are associated with the outcome of infection. It was also possible to create a risk score (IRS) for predicting infection in these types of fractures, which can be used in the initial care of the patient, with a sensitivity of 0.840, specificity of 0.544, cut-off of 6.5 and area under the curve of 0.709 (p = 0.002).

Level of evidence

Level III.     

Patella in total knee arthroplasty: to resurface or not to��a cohort study of staged bilateral total knee arthroplasty

The aim of this study was to assess medium term results of patellar resurfacing in total knee arthroplasty, specifically looking at anterior knee pain, patellofemoral function and need for reoperation. A prospective cohort study was conducted with patients undergoing staged bilateral knee arthroplasty with the patella being resurfaced only on one side. This was due to change in the clinical practice of the senior author. Sixty patients were reviewed clinically and radiologically on a regular basis. The surgery was either performed or supervised by the senior author in all cases. All patients received the cemented press-fit condylar© prosthesis. The Knee Society clinical rating system was used. Scores were recorded pre-operatively and post-operatively at three months, one year, two years and three yearly thereafter. The mean age of patients in the study group was 75 years (range: 62–89 years). There were 42 women and 18 men in the study. The mean duration of follow-up was 4.5 years (range: 2–12 years). There was no significant difference in the pre-operative scores in both groups. There were significantly better scores (p < 0.05) on the resurfaced side as compared to the non-resurfaced side at final follow-up. No revision was carried out for patellofemoral complications on the resurfaced side. Four patients required revision in the form of patellar resurfacing on the non-resurfaced side for persistent anterior knee pain. Patellar resurfacing is recommended in total knee arthroplasty for better functional outcome with regards to anterior knee pain and patellofemoral function.     

Contemporary femoral designs in total knee arthroplasty: effects on the patello-femoral congruence

Purpose

The objective of this study was to evaluate the radiological and clinical correlations between implant design and patellar positioning in patients who underwent TKA utilizing femoral implants with modern designs.

Methods

Thirty consecutive PFC PS Sigma TKAs, characterized by a new prolonged anterior flange and a “smoother” trochlea, were prospectively reviewed. All patellae were replaced. All patients were evaluated pre-operatively and prospectively at two years follow-up both clinically according to the Knee Society score as well as radiographically. This included computed tomography (CT); patellar tilt, patellar conformity angle, patellar lateralization, and femoral component external-rotation in relation to the clinical trans-epicondylar axis.

Results

Average patellar tilt at follow-up was 3° (±7.5°) with respect to a pre-operative 18.5° (±8.5°). Average patellar congruence angle at follow-up was −3° (range, −11° to +9°) with respect to a pre-operative 10.3° (range, + 1.5° to 25.5°). Average lateralization index at follow-up was 2.7 mm (range, −3.4 mm to +7.1 mm) with respect to a pre-operative 12.2 mm (± 4.8 mm). Femoral component positioning related to the trans-epicondylar axis showed an external rotation of 2.80° (± 2.10°) at follow-up with respect to 5.7° (± 1.80°). Clinically, two (6.6%) patients reported patello-femoral complications related to imperfections in the surgical technique more than the implant''s design.

Conclusions

This study highlighted that modern femoral designs in TKA allow for a correct reproducibility of a normal patello-femoral conformity. Strict surgical principles are paramount to avoid patello-femoral complications even when modern implants are used.