Patellar complications after total knee arthroplasty

Dalí Sign: Characterization and Case Series of Patellar Bony Shell Morphological Changes after Two-Stage Revision for Periprosthetic Joint Infection

The fate of the patella in two-stage revision total knee arthroplasty (TKA) for periprosthetic joint infection (PJI) in which the patella is left as a bony shell is poorly described. The purpose of this case series is to describe a phenomenon we name the Dalí Sign, which is characterized by elongation and curvature of the patella around the lateral edge of the femoral component occasionally observed in patients undergoing two-stage revision without reimplantation of the patellar component.Our institutional surgical database was queried for patients who were treated with two-stage revision arthroplasty for PJI by the two senior authors. All available sequential skyline patellar radiographs were viewed from immediately prior to first-stage explantation to latest image at final outpatient follow-up at our institution and assessed for the abovementioned morphological changes.Included patients underwent a two-stage revision surgery for PJI at our institution, had a patellar component removed during the first stage of their treatment which included implant explantation and insertion of temporary antibiotic spacers, did not have the patellar component reimplanted during their second-stage revision surgery, and demonstrated radiographic patellar morphological changes at final follow-up. Patients' demographic, surgical, and outcome data were recorded.Our review identified six patients meeting these criteria. Mean follow-up after second-stage surgery was 12 months (range 2 to 21 months). At final follow-up, three patients were walking without pain, one patient was exercising to tolerance, one patient was walking with pain, and one was using a wheelchair or a walker for mobility.In this case series, we characterize the Dalí Sign, the elongation and curvature of the patellar bony shell over the femoral component after two-stage revision for PJI. Further comparative cohort studies are necessary to identify the incidence and risk factors for the development of this morphological change and to compare outcomes of patients with and without the Dalí Sign when left with a bony shell after staged revision TKA.

Revision for stiff knee after knee replacement

Stiffness following total knee replacement is defined as >15° flexion contracture and/or flexion <75° or, for other authors, arc of motion <70° or 45° or 50°. Alternatively, it could be defined as a range of motion less than the patient needs in order to be able to do what they wish. The first step in management is to determine the causes: preoperative (history of stiffness, patient-related risk factors, etc.), intraoperative (technical error: malpositioning, oversizing, overhanging, etc.), and postoperative (defective pain management and/or rehabilitation, etc.). Treatment depends on the interval since replacement and on the type of stiffness (flexion or extension), and should be multidisciplinary (surgery, rehabilitation, pain management). For intervals less than 3 months, manipulation under anesthesia gives good results for flexion. If this fails, surgery should be considered. If there was no significant technical error, arthrolysis may be indicated, and is usually arthroscopic. It is technically difficult, but has a low rate of complications. Open arthrolysis allows greater posterior release and replacement of the insert by a thinner model. In case of malpositioning or oversizing or of failure of other procedures, implant revision is the only option, although the risk of complications is high. After exposure, which is often difficult, the aim is to correct the technical errors and to restore joint-line height and two symmetrical, well-balanced spaces in extension and flexion. A semi-constrained or even hinged implant may be needed, although with uncertain lifetime for young patients in the latter case. In all cases, the patient needs to accept that treatment is going to be long, with more than the intervention itself (i.e., specific pain management and rehabilitation), and that expectations have to be reasonable as results are often imperfect. LEVEL OF EVIDENCE: expert opinion.

Patellar Instability after Total Knee Arthroplasty

Patellar instability following total knee arthroplasty (TKA) is a rare, yet serious complication, potentially requiring revision surgery or resulting in chronic dysfunction. When encountered, it is paramount to understand the etiologies, diagnostic approaches, treatment options, and outcomes of the selected treatment. The most common cause of patella instability is improper positioning of components, leading to lateral maltracking of the patella. Factors such as internal rotation and/or medialization of femoral or tibial components and lateralization of the patellar button have been identified as factors that contribute to instability. Additionally, a longstanding valgus deformity of the knee may exacerbate patella maltracking. Patients typically present with anterior knee pain, worsened by activities like stair climbing, and may report sensations of giving way. Radiographs and computed tomography scans aid in evaluating component positioning and rotation. Operative intervention is often necessary, with options ranging from soft tissue realignment to component revision. Lateral retinacular release is a common approach, although it is associated with complications such as osteonecrosis of the patella. Proximal or distal realignment procedures may be required if instability persists. Some recent case reports have also described medial patellofemoral ligament reconstruction as a treatment modality, but more investigation on the topic is still pending. It is important that the treatment strategy address the underlying cause, as failure to do so may result in recurrent instability. The best way to avoid patella instability is to pay attention to all the details of component position and soft tissue balance during the index procedure.

Can robotic arm-assisted total knee arthroplasty be applied to valgus deformity

INTRODUCTION

Total knee arthroplasty (TKA) in valgus knees is challenging. Optimal ligament balance, implant neutral or moderate valgus alignment are crucial but conventional instrumentations usually lead to outliers. Robotic arm assisted TKA (RATKA) advantages could answer this challenge. Objectives were to assess RATKA frontal alignment accuracy for valgus knees, rotational femoral component reliability, revision surgery rate and functional outcomes for this population.

METHODS

This study is based on a continuous series of 454 RATKA. Implants were positioned according to a patient-specific alignment and postero-stabilised inserts were used. Valgus values, range of motion, KOOS and revision surgery rates were assessed at one-year postoperative. Femoral component rotation was analysed intraoperatively.

RESULTS

MAKO navigation system confirmed valgus preoperative deformity for 34 patients. Mean postoperative valgus value was - 1.5°±1.53 (range, -5 to 1), 85% patients had a residual valgus between 0 and - 3°, 97% of patients had a difference < 3° between valgus planned and valgus measured at one year postoperatively. Mean femoral rotation was + 2.65°±1.87 (range, 0 to 6.8°) of external rotation related to posterior condylar angle. No revision surgery has been performed. Mean KOOS value at one year was 80.79. 76% of patients (n = 26) had a good (70-80) or excellent (> 80) KOOS score. Mean flexion value was 133°±12 (range, 100 to 140).

CONCLUSION

RATKA can be applicable in valgus knee, offering high precision in component positioning with very few outliers. It also facilitates component rotation positioning, providing excellent functional results and ROM.

Bilateral Patellar Avascular Necrosis Following Total Knee Arthroplasties

A 79-year-old female with a history of bilateral knee osteoarthritis presented with severe knee pain, eight years post-bilateral total knee arthroplasties (TKAs). Notably, a lateral retinacular release had been performed alongside each arthroplasty. On examination, she displayed new painful prominences along the lateral aspects of both knees. Radiographs and CT scans revealed near-complete resorption of the bilateral patellae, indicating advanced avascular necrosis (AVN). After discussing treatment options, the patient opted for revision surgery to remove the patellar hardware, leading to significant improvements in pain, function, and mobility. This case underscores the need for close, long-term follow-up in patients who undergo TKA with concurrent lateral retinacular release, to monitor for potential complications like AVN.

Intraoperative Patellofemoral Kinematic Acquisition: The Design, Testing, and Validation of a Setup for Clinical Studies

Background/Objectives: Abnormalities in patellar tracking, often overlooked in surgical planning, have been identified as a contributing factor to total knee arthroplasty (TKA) complications, including anterior knee pain, patellar subluxation, and dislocation. This study aims to evaluate the repeatability of a novel intraoperative setup for assessing patellofemoral kinematics and its interaction with prosthesis design and positioning during surgery. This setup may support personalized alignment techniques in TKA, potentially improving surgical outcomes. Methods: Kinematic data were collected under both native and post-TKA conditions, and the Repeatability Coefficient (RC), Intraclass Correlation Coefficient (ICC), and Limits of Agreement of the Mean were calculated to assess measurement reliability. Results: RC values indicated high repeatability, with patellar flexion averaging an RC of 1°. Rotation and tilt demonstrated an RC below 1° post-mid-flexion, while patellar shift maintained an RC of approximately 1.6 mm. ICC and the extended Bland and Altman analysis showed an excellent agreement (ICC > 0.9) and an expected mean difference of zero for all the measured parameters. Measurements were consistent across both flexion and extension, and between native and post-TKA conditions. Conclusions: The proposed setup for intraoperative patellofemoral kinematic assessment demonstrated high repeatability and practical utility. The approach was found to be non-intrusive to patellar motion tracking and can be robustly integrated into the intraoperative workflow. This method provides a reliable approach for real-time patellar tracking, which may contribute to more personalized and precise TKA procedures, potentially reducing post-surgical dissatisfaction and complications.

Frequent complications of deficient patellae after component removal in 1.5-stage exchange arthroplasty for periprosthetic joint infection

PURPOSE

To compare the complication rates between deficient patellae (remnant patellae after component removal) and non-resurfaced patellae after 1.5-stage exchange arthroplasty for periprosthetic joint infection and identify risk factors for complications of deficient patellae.

METHODS

Complications in 76 deficient patellae (group D) and 41 non-resurfaced patellae (group N), with a minimum follow-up of 2 years after 1.5-stage exchange arthroplasty were retrospectively analyzed. Demographic characteristics and mean follow-up period did not differ between the groups. The incidences of patellar maltracking, erosion, and fractures were investigated. Factors affecting each patellar complication in group D were investigated in terms of age, sex, body mass index, postoperative hip-knee-ankle angle (HKA), remnant patellar thickness, and change in joint line height.

RESULTS

The incidence of patellar maltracking and erosion was significantly higher in group D than in group N [maltracking: 16 (21.1%) vs. 0 cases (0%), p = 0.001; erosion: 30 (39.5%) vs. 2 cases (4.9%), p < 0.001]. The incidence of patellar fractures tended to be higher in group D [6 (7.8%) vs. 0 cases, p = 0.090]. In group D, postoperative valgus limb alignment and younger age were identified as significant factors that affected patellar maltracking (odds ratio of postoperative HKA = 1.628, p = 0.005) and erosion (odds ratio of age = 0.909, p = 0.009), respectively.

CONCLUSION

Close observation of the complications of deficient patellae is required after 1.5-stage exchange arthroplasty. Valgus limb alignment should be avoided to reduce the risk of complications. Early second-stage revision with patellar reconstruction can be considered in younger patients with deficient patellae.

LEVEL OF EVIDENCE

III.

Dorsal cortex line is more reliable than transepicondylar axis for rotation in revision total knee arthroplasty with severe bone loss

Aims

The transepicondylar axis is a well-established reference for the determination of femoral component rotation in total knee arthroplasty (TKA). However, when severe bone loss is present in the femoral condyles, rotational alignment can be more complicated. There is a lack of validated landmarks in the supracondylar region of the distal femur. Therefore, the aim of this study was to analyze the correlation between the surgical transepicondylar axis (sTEA) and the suggested dorsal cortex line (DCL) in the coronal plane and the inter- and intraobserver reliability of its CT scan measurement.

Methods

A total of 75 randomly selected CT scans were measured by three experienced surgeons independently. The DCL was defined in the coronal plane as a tangent to the dorsal femoral cortex located 75 mm above the joint line in the frontal plane. The difference between sTEA and DCL was calculated. Descriptive statistics and angulation correlations were generated for the sTEA and DCL, as well as for the distribution of measurement error for intra- and inter-rater reliability.

Results

The external rotation of the DCL to the sTEA was a mean of 9.47° (SD 3.06°), and a median of 9.2° (IQR 7.45° to 11.60°), with a minimum value of 1.7° and maximum of 16.3°. The measurements of the DCL demonstrated very good to excellent test-retest and inter-rater reliability coefficients (intraclass correlation coefficient 0.80 to 0.99).

Conclusion

This study reveals a correlation between the sTEA and the DCL. Overall, 10° of external rotation of the dorsal femoral cortical bone to the sTEA may serve as a reliable landmark for initial position of the femoral component. Surgeons should be aware that there are outliers in this study in up to 17% of the measurements, which potentially could result in deviations of femoral component rotation.

Medial Patellar Instability Following Total Knee Arthroplasty

Although lateral patellar instability has been discussed as a complication following total knee arthroplasty (TKA), there are no published reports of medial patellar instability. We present a case of a 72-year-old female patient with a remote history of medializing tibial tubercle osteotomy who underwent TKA complicated by a medial dislocation of the patella. Management consisted of lateral retinaculum imbrication, revision of the patellar component, and lateralizing tibial tubercle osteotomy in the setting of appropriate rotation of the tibial and femoral components. It is important to be aware of medial patellar instability as well as potential treatment options as this is a rare complication that can occur following TKA.

Total knee arthroplasty combined with simultaneous open reduction and internal fixation in the treatment of knee osteoarthritis with patellar fracture: a case report and review of the literature

BACKGROUND

Patients with severe knee osteoarthritis combined with patellar fracture are rare, and it is unclear whether single-stage surgery affects the enhanced recovery after surgery.

CASE PRESENTATION

This case report describes two patients of Han nationality. A 69-year-old male patient was previously diagnosed with severe knee osteoarthritis of the left knee joint and was treated conservatively with long-term oral nonsteroidal antiinflammatory drugs and intraarticular injection of sodium hyaluronate. He was hospitalized for acute left knee injury owing to a fall from a height. He was diagnosed with knee osteoarthritis of the left knee joint and patellar fracture. Another 74-year-old female patient was previously diagnosed with severe knee osteoarthritis, long-term oral nonsteroidal antiinflammatory drugs and topical Chinese medicine to relieve the pain. A month ago, she fell down the stairs and fractured the patella in her left knee, she was diagnosed with severe left knee osteoarthritis combined with an old left patella fracture. Both patients were successfully treated by single-stage primary total knee arthroplasty and fixation of the patellar fracture. They both carried out early functional exercise normally and successfully achieved enhanced recovery.

CONCLUSION

Successful single stage total knee replacement with patella management can not only reduce the number of operations, but also enable patients to achieve rapid postoperative recovery. However, single stage may increase the risk of local surgical complications. Therefore, for most patients, especially those with low risk of anesthesia related complications, standard of treatment remains first fixing the patellar fracture and when the fracture is healed proceed with the total knee arthroplasty.

Patellar resurfacing might not be mandatory in contralateral second total knee replacement even if performed during replacement of the first knee

INTRODUCTION

The appropriateness or necessity of patellar resurfacing in total knee arthroplasty (TKA) is not clearly established. The objective of the present study was to compare the clinical and functional results of patients with bilateral involvement, operated on in one knee by TKA with patellar resurfacing and in the other knee by TKA without resurfacing. The hypothesis was that there was no difference in results between the two sides.

METHOD

This was a retrospective cohort of patients operated on by TKA without patellar resurfacing in a second osteoarthritic knee after contralateral TKA with patellar resurfacing. Twenty consecutive patients who underwent second primary TKA constituted their own control group (40 knees). Iwano scores were comparable. Mean age was 75.9±6.2years. Mean time between the two procedures was 20.6±11.9months.

RESULTS

There were no differences in SF-36, KOOS or Lille patellofemoral scores between the right and left knees. Sixty-five percent of patients were unable to differentiate the performance of their knees in activities of daily living.

CONCLUSION

The present study did not differentiate results according to patellar resurfacing, showing the limitations of resurfacing for early functional gain after primary TKA. Resurfacing might thus not be essential, even if it was performed in replacement of the first knee.

LEVEL OF EVIDENCE

IV; retrospective cohort study.

Circumferential patellar denervation does not reduce anterior knee pain in total knee arthroplasty without patellar resurfacing; a prospective comparison

BACKGROUND

This study aimed to evaluate the effectiveness of circumferential patellar denervation in reducing anterior knee pain (AKP) and improving clinical outcomes after total knee arthroplasty (TKA) without patellar resurfacing.

MATERIALS AND METHODS

This prospective, non-randomized, observational study included patients who underwent primary TKA at our institution between August 2023 and January 2024. Patients were divided into two groups: those who received patellar denervation (PD group) and those who did not (NPD group). The primary outcome was the reduction in anterior knee pain (AKP), measured by the Visual Analog Scale (VAS). Secondary outcomes included the Kujala Knee Score, Western Ontario and McMaster Universities Arthritis Index (WOMAC), and range of motion (ROM). Assessments were conducted preoperatively and at 3 and 6 months postoperatively.

RESULTS

Four patients in the PD group and five in the NPD group were excluded from the study due to failure to complete follow-up. Thus, 74 female and 16 male patients with a mean age of 67.4 ± 4.2 years were included in the final analysis. There were no significant differences between the two groups with respect to age, sex, side of surgery, height, weight, BMI, grade of patellofemoral osteoarthritis, preoperative ROM, VAS score, Kujala score, and WOMAC score (p: n.s. for all variables). No significant differences were found between the groups for VAS, Kujala, and WOMAC scores at any time point (p: n.s.). Significant improvements in these scores over time were indicated by repeated measures ANOVA (p = 0.001 for both groups). Pairwise comparisons showed significant improvements from preoperative to postoperative months three and six and from postoperative months three to six (p = 0.001 for all comparisons). Both groups experienced decreased knee ROM at third month, which returned to preoperative values at sixth month with no significant differences. No complications were observed during the study.

CONCLUSIONS

Circumferential patellar denervation does not provide additional benefit in reducing anterior knee pain or improving functional outcomes compared to the non-denervation approach in TKA without patellar resurfacing.

LEVEL OF EVIDENCE

Level III, Prospective comparative study.

Primary Total Knee Arthroplasty for Treating Osteoarthritic Knees with Neglected Patellar Dislocation

Background and Objectives: Neglected patellar dislocation in the presence of end-stage osteoarthritis (OA) is a rare condition characterized by the patella remaining laterally dislocated without reduction. Due to the scarcity of reported cases, the optimal management approach is still uncertain. However, primary total knee arthroplasty (TKA) can serve as an effective treatment option. This study aimed to present the clinical and radiological outcomes achieved using our surgical technique. Materials and Methods: A retrospective review of 12 knees in 8 patients with neglected patellar dislocation and end-stage OA who underwent primary TKA was conducted. The surgical procedure involved conventional TKA techniques (e.g., medial parapatellar arthrotomy) and additional procedures specific to the individual pathologies of neglected patellar dislocation (e.g., lateral release, medial plication, and quadriceps lengthening). Clinical outcomes, including patient-reported outcome measures (PROMs) (Knee Society Scores and the Western Ontario and McMaster Universities Osteoarthritis Index) and knee range of motion (ROM), were assessed preoperatively and two years postoperatively. Radiological measures including mechanical femorotibial angle and patellar tilt angle were assessed preoperatively and until the last follow-up examinations. Any complications were also reviewed. Results: There were significant improvements in all PROMs, knee ROM, and radiological outcomes, including mechanical femorotibial angle and patellar tilt angle (all p < 0.05). At a mean follow-up of 68 months, no major complications requiring revision surgery, including patellar dislocation, were reported. Conclusions: Primary TKA is an effective procedure for correcting various pathologies associated with neglected patellar dislocation in end-stage OA without necessitating additional bony procedures. Satisfactory clinical and radiological outcomes can be expected using pathology-specific procedures.

Trochlea morphology demonstrates variability but no gender difference in osteoarthritic patients undergoing total knee arthroplasty

BACKGROUND

In recent years, coronal lower leg alignment has received significant attention. Two classifications recently described the variability in both femoral and tibial morphology, resulting in differing native lower limb alignment. The native trochlea and the variability in morphology has received less attention.

METHODS

This is a prospective cohort study of 200 patients undergoing robotically assisted TKA. Preoperative transverse CT scans were used to determine the posterior condylar axis (PCA), transepicondylar axis (TEA), lateral trochlear inclination (LTI), the sulcus angle (SA) and the anterior trochlear line (ATL). Outliers were defined as values > 1.5 IQR from median value. Trochlea dysplasia was defined as LTI < 12°. Gender differences were compared.

RESULTS

In total, 99 patients were female (49.4%). SA had a median of 137.0° (IQR 12°), ATL 4° (IQR 4), LTI 18° (IQR 7°). Median TEA-PCA was 5° external (IQR 3°). There were 5.0% outliers in SA, 3.0% of outliers in ATL, 3.5% outliers in LTI and 4.5% outliers in the TEA-PCA. Trochlear dysplasia was present in 11.5% of the measurements. There was no difference in any of the angles between the genders.

CONCLUSION

The present study demonstrates no difference in trochlea morphology between the genders, rather a significant number of overall outliers in trochlear morphology. Larger cohorts but also, more investigations, are needed to better understand the trochlear morphology of patients undergoing total knee arthroplasty. The personalized alignment strategies and implants need to account for this variability in the population.

Kinematic alignment recreates femoral trochlear geometry more closely than mechanical alignment in total knee arthroplasty : a CT analysis

Aims

This study aimed to evaluate if total knee arthroplasty (TKA) femoral components aligned in either mechanical alignment (MA) or kinematic alignment (KA) are more biomimetic concerning trochlear sulcus orientation and restoration of trochlear height.

Methods

Bone surfaces from 1,012 CT scans of non-arthritic femora were segmented using a modelling and analytics system. TKA femoral components (Triathlon; Stryker) were virtually implanted in both MA and KA. Trochlear sulcus orientation was assessed by measuring the distal trochlear sulcus angle (DTSA) in native femora and in KA and MA prosthetic femoral components. Trochlear anatomy restoration was evaluated by measuring the differences in medial, lateral, and sulcus trochlear height between native femora and KA and MA prosthetic femoral components.

Results

Femoral components in both MA and KA alignments exhibited a more valgus DTSA compared to native femora. However, DTSA deviation from native was significantly less in KA than in MA (4.8° (SD 2.2°) vs 8.8° (SD 1.8°); p < 0.001). DTSA deviation from native orientation correlated positively with the mechanical lateral distal femoral angle (mLDFA) in KA and negatively in MA (r = 0.53, p < 0.001; r = -0.18, p < 0.001). Medial trochlear height was not restored with either MA or KA, with MA resulting in lower medial trochlear height than KA in the proximal 20% of the trochlea. Lateral and sulcus trochlear height was not restored with either alignment in the proximal 80% of the trochlea. At the terminal arc point, KA replicated sulcus and lateral trochlear height, while MA led to over-restoration.

Conclusion

Femoral components aligned in KA demonstrated greater biomimetic qualities than those in MA regarding trochlear sulcus orientation and trochlear height restoration, particularly in valgus femora. Variability across knees was observed, warranting further research to evaluate the clinical implications of these findings.

Does Patellar Denervation with Electrocautery Benefits for Total Knee Arthroplasty without Patellar Resurfacing: A Meta-analysis of Randomized Controlled Trails

To investigate the effects of patellar denervation (PD) and non-patellar denervation (NPD) after primary total knee arthroplasty (TKA) without patellar resurfacing, this study conducted systematic electronic searches in November 2023 using PubMed, Embase, Web of Science, Cochrane, and Scopus, adhering to Cochrane Collaboration recommendations. Only randomized controlled trials (RCTs) were included. Additionally, a manual search was performed to identify potentially eligible studies from the reference lists of review articles. Two researchers independently conducted literature reviews, data extraction, and risk of bias assessments. The outcome analysis encompassed the incidence of anterior knee pain (AKP), visual analogue scale (VAS), range of motion (ROM), American Knee Society Score (KSS), Oxford Knee Score (OKS), patellar score (PS), complications, and reoperations. Meta-analysis was executed using RevMan 5.3 software. To enhance the credibility of the study, TSA v0.9 software was utilized to perform power analysis on the overall efficacy of primary and secondary outcomes. Twelve studies involving 1745 patients (1587 knees) were included, with 852 undergoing PD and 893 undergoing NPD. Results indicated a superior reduction in AKP incidence in the PD group compared to the NPD group. Statistically significant differences were observed between PD and NPD in KSS, OKS, and PS. However, the upper limit of the 95% confidence interval for each outcome fell below the minimal clinically important difference (MCID). No significant differences were found in VAS and ROM between PD and NPD. Additionally, PD was not associated with an increased incidence of complications or reoperations. Within 12 months and beyond, PD was proven to be a beneficial intervention in reducing AKP following TKA without patellar resurfacing, achieved without an increase in complications or reoperations. Regarding KSS, OKS, and PS, the minimal advantage achievable through PD may not be clinically significant.

Inferior patellar mobility before and after knee arthroplasty: A comparison with healthy knees

PURPOSE

The aim of this study was to evaluate patellar mobility in patients before and after knee arthroplasty (KA) and compare it with that of healthy subjects. It was hypothesised that patellar mobility is diminished in patients with osteoarthritis (OA) and remains unchanged after KA.

METHODS

A total of 101 patients (59 females and 42 males) with a mean age of 70.9 ± 9.9 years underwent KA and were compared with 25 healthy individuals (seven females and 18 males) with a mean age of 32.3 ± 9.3 years. Mediolateral patellar displacement was measured by applying a force of 10 N, and the medial and lateral patellar shifts were recorded separately using a validated novel patellostabilometer. Patients were examined preoperatively and at 3 months postoperatively, assessing the range of knee motion and the clinical and functional status based on the Oxford Knee Score (OKS), Kujala Score, subjective Knee Society Score (sKSS), Forgotten Joint Score (FJS) and Western Ontario and McMaster Universities Arthritis Index (WOMAC).

RESULTS

Total patellar displacement was 42.1 ± 6 mm for healthy subjects, 31 ± 6 mm before surgery and 32.8 ± 7.8 mm after surgery in osteoarthritic patients (p < 0.01). The mean lateral patellar shift differed significantly between healthy individuals (17.9 ± 4 mm) and osteoarthritic patients (15.1 ± 6 mm) (p < 0.01). The mean medial patellar mobility of healthy individuals (24.2 ± 7 mm) was significantly greater than that of osteoarthritic patients (15.8 ± 4.8 mm) (p < 0.01). All scores improved significantly postoperatively. No correlation was found between patellar mobility and OKS, Kujala Score, sKSS, FJS and WOMAC (r = -0.11). Improvement in patellar mobility also showed no correlation with clinical outcomes according to OKS, Kujala Score, sKSS, FJS and WOMAC (r = 0.08).

CONCLUSION

This study has demonstrated reduced patellar mobility in patients with OA. While patellar mobility significantly improved after KA, it may not hold clinical significance (p = 0.04). No impact on clinical outcome can be expected when the presurgical patella mobility is preserved in KA.

LEVEL OF EVIDENCE

Level IV.

Bilateral simultaneous total knee arthroplasty with and without patellar resurfacing. A prospective single surgeon series with a minimum follow-up of 7 years

BACKGROUND

Total knee arthroplasty (TKA) is the most effective treatment for end-stage adult knee osteoarthritis, but it has been reported that patient satisfaction may vary. A malfunction of the patellofemoral joint may produce anterior knee pain (AKP) for several reasons. While some surgeons systematically resurface the patella despite the risk of potential complications such as fracture, loosening, or wear of the patella, others prefer to preserve it to reduce AKP and revision rates. This study aimed to evaluate whether patellar resurfacing had better clinical and functional outcomes, complications, and revision rates in patients undergoing simultaneous bilateral total knee arthroplasty.

METHODS

We conducted a prospective cohort study, including patients who underwent bilateral simultaneous TKA in which the patella was replaced in one knee and preserved in the other, with a minimum follow-up of 7 years. We assessed clinical and functional outcomes with the Knee Society Score (KSS) and Visual Analogue Scale (VAS); complications and revision rates were also registered.

RESULTS

The final series consisted of 43 patients with 86 knee arthroplasties. After a mean of 7.6 years of follow-up, no significant differences were found regarding KSS (clinical: 82.8 ± 7.4 versus 83.2 ± 3.4, p = 0.92; functional 89.1 ± 8.2: versus 90.4 ± 6.8; p = 0.99), VAS (2.0 ± 0.9 versus 1.8 ± 1.0; p = 0.84), complications (10.5% versus 8.1%; p = 0.57), or revision rates (2.3% versus 2.3%; p = 0.99) when comparing patellar resurfacing versus retention.

CONCLUSION

In the context of total knee arthroplasty, patellar replacement did not demonstrate statistically significant differences concerning patellar retention in clinical nor functional outcomes, AKP, complications, or revision rates after a minimum of 7 years of follow-up.

A Sensorized 3D-Printed Knee Test Rig for Preliminary Experimental Validation of Patellar Tracking and Contact Simulation

Experimental validation of computational simulations is important because it provides empirical evidence to verify the accuracy and reliability of the simulated results. This validation ensures that the simulation accurately represents real-world phenomena, increasing confidence in the model's predictive capabilities and its applicability to practical scenarios. The use of musculoskeletal models in orthopedic surgery allows for objective prediction of postoperative function and optimization of results for each patient. To ensure that simulations are trustworthy and can be used for predictive purposes, comparing simulation results with experimental data is crucial. Although progress has been made in obtaining 3D bone geometry and estimating contact forces, validation of these predictions has been limited due to the lack of direct in vivo measurements and the economic and ethical constraints associated with available alternatives. In this study, an existing commercial surgical training station was transformed into a sensorized test bench to replicate a knee subject to a total knee replacement. The original knee inserts of the training station were replaced with personalized 3D-printed bones incorporating their corresponding implants, and multiple sensors with their respective supports were added. The recorded movement of the patella was used in combination with the forces recorded by the pressure sensor and the load cells, to validate the results obtained from the simulation, which was performed by means of a multibody dynamics formulation implemented in a custom-developed library. The utilization of 3D-printed models and sensors facilitated cost-effective and replicable experimental validation of computational simulations, thereby advancing orthopedic surgery while circumventing ethical concerns.

Isolated lateral-sided knee pain in total knee arthroplasty. A review

Isolated lateral-sided knee pain is a unique problem following total knee arthroplasty (TKA). Reported causes include soft tissue impingement against extruded cement, an overhanging tibial tray, remnant osteophytes rubbing against the iliotibial band (ITB), popliteal tendon impingement, fabella syndrome, and synovial tissue impingement in the lateral gutter. In addition, iliotibial band traction syndrome secondary to guided motion Bi-cruciate stabilizing knee arthroplasty has been recognized as a new clinical entity. Initial work up should include ruling out the most common causes of painful TKA including infection, aseptic loosening, and instability. Radiographs and CT scan are utilized to identify potential source of pain. Ultrasound evaluation (with elicited probe tenderness) can increase diagnostic accuracy. Ultrasound guided local anesthetic injections can confirm the source of pain. Anti-inflammatory medications, physical therapy with ITB stretches, and therapeutic local steroid injections are initial treatment modalities. Satisfactory resolution of symptoms may require surgical intervention directed at the specific cause and may avoid the morbidity associated with revision TKA.

Use of patellofemoral digital twins for patellar tracking and treatment prediction: comparison of 3D models and contact detection algorithms

Introduction: Poor patellar tracking can result in painful contact pressures, patella subluxation, or dislocation. The use of musculoskeletal models and simulations in orthopedic surgeries allows for objective predictions of post-treatment function, empowering clinicians to explore diverse treatment options for patients. Although a promising approach for managing knee surgeries, the high computational cost of the Finite Element Method hampers its clinical usability. In anticipation of minimal elastic deformations in the involved bodies, the exploration of the Multibody Dynamics approach emerged as a viable solution, providing a computationally efficient methodology to address clinical concerns related to the knee joint. Methods: This work, with a focus on high-performance computing, achieved the simulation of the patellofemoral joint through rigid-body multibody dynamics formulations. A comparison was made between two collision detection algorithms employed in the simulation of contact between the patellar and femoral implants: a generic mesh-to-mesh collision detection algorithm, which identifies potential collisions between bodies by checking for proximity or overlap between their discretized mesh surface elements, and an analytical contact algorithm, which uses a mathematical model to provide closed-form solutions for specific contact problems, but cannot handle arbitrary geometries. In addition, different digital twins (3D model geometries) of the femoral implant were compared. Results: Computational efficiency was considered, and histories of position, orientation, and contact force of the patella during the motion were compared with experimental measurements obtained from a sensorized 3D-printed test bench under pathological and treatment scenarios. The best results were achieved through a purely analytical contact detection algorithm, allowing for clinical usability and optimization of clinical outcomes.

Patella Fracture After Total Knee Arthroplasty: A Review

The management and underlying causes of patellar periprosthetic fractures (PPF) after total knee arthroplasty (TKA) constitute an issue of growing importance given the rising frequency of these procedures. Patella periprosthetic fractures, though relatively rare, pose significant challenges and are a frequent indication for revision surgeries. Despite a decrease in overall incidence, PPFs remain the second most common type of periprosthetic fractures after TKA. Several factors have been identified and associated with patient-specific factors, surgical technique errors, and implant-related causes. Currently extensor apparatus integrity, bone stock, and component loosening are the major concerns and indications for the selective treatment approach. In this study, a thorough review of the existing literature was performed summarizing the epidemiology, clinical manifestation, treatment approach, and functional outcome of PPF. This review aims to underline the significance of such predisposing factors, point out the severity of PPF, and offer insights into the optimal intra- and post-operative management of the patella.

Revision Medial Patellofemoral Ligament Reconstruction for Recurrent Instability After Patellofemoral Arthroplasty

Recurrent patellar instability is a rare complication after patellofemoral arthroplasty (PFA) and usually involves a traumatic injury. Medial patellofemoral ligament (MPFL) reconstruction after arthroplasty is a complicated and technically challenging surgical procedure because the lack of patellar bone stock due to resurfacing significantly increases the risk of patellar fracture. We present our surgical technique for revision MPFL reconstruction for recurrent instability after PFA. This technical note describes the use of 1.8-mm all-suture anchors for revision MPFL reconstruction in patients with decreased patellar bone stock after PFA. This technique reduces the risk of patellar fracture without compromising the integrity of the MPFL graft.

Conversion of Patellofemoral Arthroplasty to Robotic-Assisted Total Knee Arthroplasty

Conversion of patellofemoral arthroplasty to total knee arthroplasty (TKA) has been described as similar to primary TKA, although it may come with more challenges and worse outcomes. With the increased rate of revision following conversion TKA vs primary TKA, robotically assisted TKA provides an alternative technique to manual conversion. We present 3 cases of robot-assisted conversion of prior patellofemoral arthroplasty to TKA with good mechanical and clinical outcomes and no intraoperative complications.

Periprosthetic patella fractures in total knee replacement and revision surgeries: how to diagnose and treat this rare but potentially devastating complication-a review of the current literature

PURPOSE

Periprosthetic patella fractures (PPPFs) are infrequent but potentially devastating complications after total knee arthroplasty (TKA) and revision TKA (rTKA). These fractures may occur both in resurfaced and un-resurfaced patella. This review summarizes the current literature on PPPFs to help orthopedic surgeons diagnose and treat this uncommon but extremely challenging TKA complication.

METHODS

A comprehensive search was performed in three databases: PubMed, SCOPUS, and EMBASE. All relevant information was retrieved and summarized in this narrative review.

RESULTS

In the studies analyzed, there is a general trend in favor of nonsurgical treatment, except for implant loosening or extensor lag with extensor apparatus disruption, because surgery is often associated with poor clinical outcomes and high complication rates.

CONCLUSION

PPPF is a rare but catastrophic event in TKA and rTKA, occurring mainly in a reconstructed patella. Patient-, implant-, and surgical technique-related factors contribute to its multifactorial etiopathogenesis. Prevention plays a crucial role in reducing the PPPFs rate. Conservative management is the treatment of choice due to high surgery complication rates unless implant loosening, or extensor apparatus disruption occurs.

The Double-Patella Sign: A Patellar Implant Loosening Case Report

CASE

A 79-year-old man status post total knee arthroplasty (TKA) sustained atraumatic nondisplaced fracture of the inferior pole of the patella 1 year postoperatively. The patient had full radiographic healing and clinical resolution. Two years after injury, the patient reported new-onset knee pain and was found to have atraumatic inferior migration of the patellar component. The lateral radiograph appeared to demonstrate 2 patellae, coined "the double-patella sign."

CONCLUSION

Nondisplaced patellar fractures after TKA should be monitored even after full osseous healing for component loosening. Inferior migration of a loose patellar component can mimic 2 patellae on the lateral radiograph, mimicking a double patella.

Patellofemoral knee pain following total knee arthroplasty. Comparison between adjusted mechanical and inverse restricted kinematic alignment

Objective

The aim of this study was to assess the functional, radiological, and clinical outcomes of patellofemoral joint in patients who had total knee arthroplasty (TKA) without patellar resurfacing for end-stage osteoarthritis using inverse restricted kinematic alignment (irKA) compared to a control group using adjusted mechanical alignment (aMA), both executed with the same implant at the same Institution. The hypothesis was that patients undergoing TKA without patellar resurfacing for end-stage osteoarthritis using irKA would have superior outcomes related to the patellofemoral joint in comparison to a control group using aMA.

Methods

A retrospective examination of registries' prospectively obtained from patients who underwent primary TKA at our Institution between 2016 and 2020 was performed. 40 consecutive patients who underwent TKA implant using irKA were compared to a control group of 80 who had undergone adjusted mechanically-aligned TKA. Groups were matched for age and body mass index. Clinical assessment included Visual Analog Scale (VAS), Knee Osteoarthritis Outcome Score (KOOS), Knee Society Score (KSS), and Kujala Knee Score. Standard weight-bearing anteroposterior and lateral view x-rays were used for radiographic evaluation. Patellar height was assessed using Caton-Deschamps (C-D) and Insall index on lateral view films.

Results

In comparison to pre-operative status, both groups had postoperative improvements in VAS, KOOS, KSS, and Kujala ratings (p<0.001). Regarding Kujala score, there were no statistically significant differences between the groups (p = 0.68). Insall index and C-D index results were not statistically different across groups (p = 0.02 and 0.74 respectively).

Conclusion

Improvements in post-operative clinical and functional outcomes following TKA were associated with either irKA or aMA. There were no discernible changes between the two groups in terms of postoperative patellofemoral discomfort or variations in patellar height.

The trochlear sulcus of the native knee is consistently orientated close to the sagittal plane despite variation in distal condylar anatomy

PURPOSE

The aim of this study was to describe the native trochlear orientation of non-arthritic knees in three planes and to quantify the relationship between trochlear and distal condylar anatomy across race and sex.

METHODS

Computed tomography scans of 1578 femora were included in this study. The mediolateral position of the trochlear sulcus, the distal trochlear sulcus angle (DTSA) the medial sulcus angle (MSA) and the lateral sulcus angle (LSA) as well as the mechanical lateral distal femoral angle (mLDFA) were measured relative to a standard reference coordinate system. Multiple linear regression analyses were performed to account for potential confounding variables.

RESULTS

The mediolateral position of the trochlear sulcus had minimal mean deviation of the sagittal femoral plane. The mean DTSA was 86.1° (SD 2.2°). Multilinear regression analysis found mLDFA, sex, and age all influence DTSA (p < 0.05), with mLDFA having by far the greatest influence (r2 = 0.55). The medial facet of the trochlear sulcus was found to be flat proximally and more prominent distally. The lateral facet was relatively uniform throughout the arc.

CONCLUSION

In non-arthritic knees, due to a strong positive correlation between the DTSA and the mLDFA, the trochlear sulcus is consistently orientated in the sagittal femoral plane regardless of distal condylar anatomy. Minor deviations from the sagittal plane occur in a lateral direction in the middle part and in a medial direction at the proximal and distal part of the trochlea. These findings have relevance regarding the biomimetic design of total knee implants.

Anterior knee pain and sit-up tests predicts patients' satisfaction and improvement in quality of life after anterior stabilized total knee replacement without patellar resurfacing

PURPOSE

The purpose of this study was to assess patient satisfaction and identify risk factors for dissatisfaction after anterior stabilised conventional total knee arthroplasty (TKA) without patellar resurfacing, using the Goodman score.

METHODS

We conducted a cross-sectional study using data from our institutional database from 1 January 2018 to 1 March 2021. Patients who underwent TKA with the Vanguard® Cruciate Retaining Anterior Stabilized Knee System (Zimmer Biomet, Warsaw, Indiana, USA) without patellar replacement were included. Patients with other bearing surfaces (posterior stabilised or medial congruent) or diagnosed with infection or instability were excluded. Patients' reported outcomes, body mass index (BMI), passive range of motion, the timed up-and-go test, sit-up test, and algometry were assessed. Patients were also asked if they had anterior knee pain. Satisfaction was assessed using the Goodman scale, and logistic multivariate regression was used to identify variables associated with dissatisfaction and perceived improvement in quality of life.

RESULTS

A total of 131 TKA patients were included in the study. The median satisfaction score was 100 (interquartile range [IQR], 87.5 to 100), with the 75-point threshold at the 90th percentile according to Section A of Goodman. Section B of Goodman showed that 113 TKA patients (86.26%) reported "great improvement" or "more than I ever dreamed." Multivariate logistic regression revealed that anterior knee pain (OR 5.16, 95% CI 1.24 to 21.39), the sit-up test (OR 0.63, 95% CI 0.49 to 0.81), and BMI (OR 0.84, 95% CI 0.70 to 0.99) were significantly associated with patient dissatisfaction and a worse perceived improvement in quality of life. The receiver operating characteristics curve for the models had areas under the curve of 0.83 (95% CI 0.69 to 0.97) and 0.82 (95% CI 0.70 to 0.94), respectively.

CONCLUSION

Anterior stabilised TKA without patellar resurfacing can achieve 90% satisfaction and 86% improvement in quality of life. To improve these results, it is essential to prevent and treat anterior knee pain and enhance quadriceps strength.

LEVEL OF EVIDENCE

Level III (retrospective cohort study).

Mechanical complications after total knee arthroplasty

INTRODUCTION

With the increasing demand for total knee arthroplasty (TKA) and the burden of revision TKA on the healthcare system, as well as the quality of life implications for patients, it is extremely important for surgeons to be able to anticipate and prevent TKA mechanical complications. Surgeons must be familiar with the different causes and mechanisms of TKA complications so that they can properly treat patients with failed TKAs and better avoid these complications.

AREAS COVERED

This review addresses TKA mechanical complications and provides context for the topic. A detailed review of surgical factors, implant factors, and patient factors that contribute to mechanical complications after TKA is provided. All of the literature cited in this review was gathered from the PubMed online database using different keywords based on the section of the manuscript.

EXPERT OPINION

As surgeons and engineers solve certain issues in TKA, new challenges will inevitably arise. We must continue to push forward and innovate from both a surgical technique and implant design perspective.

Learning curve of robot-assisted total knee arthroplasty and its effects on implant position in asian patients: a prospective study

BACKGROUND

Robot-assisted total knee arthroplasty (r-TKA) can reportedly achieve more accurate implant positioning than conventional total knee arthroplasty (c-TKA), although its learning curve is controversial. Moreover, few studies have investigated r-TKA in Asians, who have different anatomical characteristics. This study aimed to determine the learning curve for r-TKA and compare implant positions between r-TKA and c-TKA according to the learning curve in Asian patients.

METHODS

This prospective study included 50 consecutive c-TKAs (group C), followed by 50 consecutive r-TKAs conducted using the MAKO robotic system (Stryker, USA). Cumulative summation analyses were performed to assess the learning curve for operative time in r-TKA. Accordingly, the r-TKA cases were divided into the initial (group I) and proficiency cases (group P). The femoral and tibial component positions in the coronal, sagittal, and axial planes and lower limb alignment were compared among the three groups.

RESULTS

r-TKA was associated with a learning curve for operative time in 18 cases. The operative time was significantly shorter in groups C and P than that in group I, with no significant difference between groups C and P. Groups I and P demonstrated fewer outliers with respect to lower limb alignment, femoral component coronal position, axial position, and tibial component sagittal position than those in group C, with no significant difference between groups I and P.

CONCLUSION

The operative time did not differ significantly between r-TKA and c-TKA after the learning curve. Surgeons could expect more accurate and reproducible lower limb alignment and implant positioning with r-TKA in Asian patients, irrespective of the learning curve.

Patellar Component Design Does Not Impact Clinical Outcomes in Primary Total Knee Arthroplasty

BACKGROUND

Round or oval implants are used in patellar resurfacing during total knee arthroplasty (TKA). However, whether component geometry affects clinical outcomes is unclear. This study aimed to determine if one implant shape conferred superior outcomes to the other.

METHODS

A retrospective review of primary TKA cases performed from 2016 to 2020 was conducted at an urban, tertiary academic center. Four hundred consecutive, primary TKAs were included in these analyses. Cases were included if a surgeon used the round design then oval design for fifty consecutive cases. Baseline demographic data and radiographic measurements were assessed. Surgical data, reasons for revision, and patient-reported outcome measures were analyzed. Independent samples t-test and chi-square tests were used to compare means and proportions. There were no demographic differences between the cohorts.

RESULTS

Postoperative patellar tilt was statistically different between the cohorts. Sixteen patients required revision surgery; however, revision rates did not differ between the cohorts. Of the 9 rounds, 1 button was revised for infection. Of the 7 ovals, 1 button was revised for infection and 1 for loosening. Veterans RAND 12 Physical Component Score at 3 months postoperatively was higher for the round cohort, but no differences were observed at 1 year.

CONCLUSION

While radiographic patellar tilt was significantly different between the cohorts, there was no clinical correlation in outcomes at 3 months or 1 year postoperatively. Longer-term follow-up studies are needed to evaluate the implications of patellar component design on outcomes and function. Nevertheless, the current study affirms that both designs are clinically equivalent which should be used to guide clinical decision-making.

LEVEL III EVIDENCE

Retrospective Cohort.

How to optimize patellar tracking in knee arthroplasty?

Good patellar tracking is needed for functionally successful total knee arthroplasty (TKA), and depends on several factors. The aim of the present Instructional Lecture is to identify the main factors and how to control them so as to optimize patellar tracking: more or less "patella-friendly" prosthetic trochlea design, requiring precise assessment and choice of model; patellar component design; type of tibial implant; surgical approach and management of peripatellar structures, and any lateral release; distal and posterior femoral bone cuts, determining femorotibial alignment, femoral component rotation and patellar height; tibial implant rotation with respect to the anterior tibial tubercle; patellar cut characteristics in resurfacing. In case of instability or patellar maltracking despite correct implant positioning, there are 2 main surgical techniques: medial patellofemoral ligament reconstruction, and anterior tibial tubercle medialization. To obtain optimal patellar tracking, correction of other factors should be associated: trochlear component design, distal and posterior femoral bone cuts, tibial implant positioning, patellar component shape and positioning, etc.

Patellar Resurfacing in Total Knee Arthroplasty, a Never-Ending Controversy; Case Report and Literature Review

Total knee arthroplasty (TKA) remains a lifesaving procedure for advanced gonarthrosis. However, patella resurfacing (PR) in TKA remains a controversial procedure, leading to extensive discussions amongst orthopedic surgeons, regarding its indications and results. Based on these premises, we present a clinical case of a 70-year-old Caucasian woman admitted for pain, swelling and limitation of left knee joint mobility. Her medical history records an Ahlback stage IV gonarthrosis with simultaneous bilateral TKA surgery performed in different hospital, when two NexGen cemented total prostheses were implanted with patellar resurfacing being performed only on the right side. Our clinical (American Knee Society Score, Lonner and Feller scales) and radiological evaluations (CT scan and Xray) revealed left patellar arthrosis and a slight lateral subluxation of the patella. The chosen treatment plan was revision surgery for PR and patellar prosthesis with a cemented patellar component, cross-linked polyethylene, no 32 NexGen model with 8.5 mm thickness. The immediate and distant postoperative evolution was favorable. Extensive literature review shows that, at present, PR remains at surgeon's discretion mainly based on his previous results. Therefore, we believe there is an imperative need to develop high quality studies based on accurate scientific evidence to universally establish valid guidelines for PR in TKA.

Short-Term Surface Damage Mechanisms of Retrieved Highly Cross-Linked Polyethylene Patellar Components

BACKGROUND

Previous retrieval studies of patellar components for total knee arthroplasty focused on historical designs and polyethylene materials that are no longer clinically relevant. Therefore, this study aimed to compare revision reasons and surface damage mechanisms of conventional, gamma inert sterilized polyethylene and highly cross-linked polyethylene (HXLPE) patellar components in contemporary designs from a single manufacturer.

METHODS

A total of 114 gamma inert and 76 HXLPE patellar components were gathered in a multicenter orthopaedic implant retrieval program. Patient age and body mass index were similar between cohorts (P = .27 and P = .42, respectively); however, the gamma inert cohort was implanted longer (μ_difference = 3.1 years; P = .005). A matched subset was created based on the total knee arthroplasty design, patellar shape, and implantation time. Revision reasons were gathered from revision operating notes, and surface damage was examined via the Hood scoring method. Differences between HXLPE and gamma inert cohorts were evaluated using Mann-Whitney U-tests.

RESULTS

The most common revision reasons were infection, loosening, and instability, with the most common patellar complication resulting in revision being patellar loosening for both cohorts with similar incidences for both (chi-square; P = .60, P = .59). The most common surface damage modes were burnishing, scratching, and pitting in both cohorts. Total surface damage was significantly higher in the gamma inert components (P = .02), but not in the matched subset (P = .46).

CONCLUSION

Overall, the clinical performance of HXLPE was similar to that of conventional polyethylene for patellar components with short implantation times. While this study provides much needed information on the performance of HXLPE patellae in short-term retrievals, long-term studies are still needed.

Peripheral patellar denervation has a better effect in reducing postoperative anterior knee pain than patellar resurfacing in TKA

Patellar resurfacing (PR) and peripheral patellar denervation (PD) are common surgical treatments for knee osteoarthritis (KOA) in total knee arthroplasty (TKA). The aim of study was to compare preventive effect on postoperative anterior knee pain (AKP) between PR and peripheral PD in TKA. A total of 202 patients who underwent unilateral TKA were randomized into 3 groups: T, TPD, and TPR. Patients in T group received simple TKA, patients in TPD group received TKA combined PD while patients in TPR group received TKA combined PR. Incidence, intensity, and presentation time of AKP and clinical outcomes were evaluated at 3, 6, 9, 12, 18, and 24 months postoperatively. The incidence of AKP was significantly lower and the intensity of AKP and patients' satisfaction score were significantly better at 3 months after surgery in group TPD and TPR compared with group T. Compared with group TPR, the intensity of AKP was significantly better at 3 months after surgery in group TPD. There were no significant difference in Oxford knee score, range of motion (ROM), patellar score, knee society score (KSS) and activities of daily living (ADL) score among 3 groups in the follow-up period. Both PD and PR can effectively reduce the intensity and incidence of AKP after TKA and improve patients' satisfaction at 3 months after TKA. Additionally, PD is more effective on alleviating AKP than PR.

Impact of patient and prosthesis characteristics on common reasons for total knee replacement revision: a registry study of 36,626 revision cases from Australia, Sweden, and USA

BACKGROUND AND PURPOSE

Total knee replacement (TKR) studies usually analyze all-cause revision when considering relationships with patient and prosthesis factors. We studied how these factors impact different revision diagnoses.

PATIENTS AND METHODS

We used data from 2003 to 2019 of TKR for osteoarthritis from the arthroplasty registries of Sweden, Australia, and Kaiser Permanente, USA to study patient and prosthesis characteristics for specific revision diagnoses. There were 1,072,924 primary TKR included and 36,626 were revised. Factors studied included age, sex, prosthesis constraint, fixation method, bearing mobility, polyethylene type, and patellar component use. Revision diagnoses were arthrofibrosis, fracture, infection, instability, loosening, pain, patellar reasons, and wear. Odds ratios (ORs) for revision were estimated and summary effects were calculated using a meta-analytic approach.

RESULTS

We found between-registry consistency in 15 factor/reason analyses. Risk factors for revision for arthrofibrosis were age < 65 years (OR 2.0; 95% CI 1.4-2.7) and mobile bearing designs (MB) (OR 1.7; CI 1.1-2.5), for fracture were female sex (OR 3.2; CI 2.2-4.8), age ≥ 65 years (OR 2.8; CI 1.9-4) and posterior stabilized prostheses (PS) (OR 2.1; CI 1.3-3.5), for infection were male sex (OR 1.9; CI 1.7-2.0) and PS (OR 1.5; CI 1.2-1.8), for instability were age < 65 years (OR 1.5; CI 1.3-1.8) and MB (OR 1.5; CI 1.1-2.2), for loosening were PS (OR 1.5; CI 1.4-1.6), MB (OR 2.2; CI 1.6-3.0) and use of ultra-high molecular weight polyethylene (OR 2.3; CI 1.8-2.9), for patellar reasons were not resurfacing the patella (OR 13.6; CI 2.1-87.2) and MB (OR 2.0; CI 1.2-3.3) and for wear was cementless fixation (OR 4.9; CI 4.3-5.5).

INTERPRETATION

Patients could be counselled regarding specific age and sex risks. Use of minimally stabilized, fixed bearing, cemented prostheses, and patellar components is encouraged to minimize revision risk.

Tibial tuberosity osteotomy and medial patellofemoral ligament reconstruction for patella dislocation following total knee arthroplasty: A double fixation technique

Introduction: Patella instability post total knee arthroplasty (TKA) is a rare complication. Tibial tubercle osteotomy (TTO) with medial patellofemoral ligament reconstruction (MPFLr) has not been well described for this indication. This paper describes a surgical technique to address the unique challenges faced when performing TTO and MPFLr in the prosthetic knee. Technique: This technique and video describe a TTO and MPFLr via an extensile incision and medial sub-vastus approach. A 6 cm long TTO is performed, if indicated, to medialise the extensor mechanism up to 1 cm and fixed with ×2 4.5 mm cortical screws. For the MPFLr, a quadriceps tendon autograft is utilized, with the natural insertion to the superior pole of the patella being left undisturbed. The graft is first attached with an interference screw and then reinforced with an endobutton to provide crucial cortical fixation to overcome the problem of low bone mineral density encountered in this area of the femur following TKA. Results: Five patients underwent MPFLr using the described technique. No failures or recurrence of instability occurred at the last follow-up. Pre-operative mean patella tilt and shift were 44° and 3.5 cm, respectively. Post-operatively, mean tilt and shift were 4.1° and 0.4 cm, respectively. There was one wound dehiscence requiring surgical debridement and closure. Conclusion: This paper describes a surgical technique to perform a TTO and MPFLr for patella instability post-TKA. The described method highlights key adaptations to address the unique challenges in this patient population.

Patellar dislocation following distal femoral replacement after extra-articular knee resection for bone sarcoma: A case report

BACKGROUND

For the treatment of bone sarcoma in the distal femur, wide-margin resection and knee reconstruction with tumor endoprosthesis are standard therapies. Extra-articular knee resection is required in cases of tumor invasion of the knee joint; however, the incidence of complications, such as aseptic loosening, prosthesis infection, and implant failure, is higher than that following intra-articular knee resection. To the best of our knowledge, there are three reports of patellar dislocations after replacement of a tumor endoprosthesis.

CASE SUMMARY

A 36-year-old man with no significant past medical history was admitted to our institution with continuous pain in his left knee for 4 mo. An open biopsy was performed, and the patient was diagnosed with a left distal femoral malignant bone tumor. Extra-articular knee resection and knee reconstruction with a tumor endoprosthesis were performed. Although the alignment of the tumor prosthesis was acceptable, knee instability was noticed postoperatively. The axial radiographic view of the patellar and computed tomography showed lateral patellar dislocation at 4 wk postoperatively. The patient had to undergo a lateral release and proximal realignment. He could perform his daily activities at 9 mo postoperatively. Radiography revealed no patellar re-dislocation.

CONCLUSION

Proximal realignment may be considered during primary surgery if there is an imbalance in the forces controlling the patellar tracking.

Comparison of clinical outcomes between patellar resurfacing and patellar non-resurfacing in cruciate retaining total knee arthroplasty

BACKGROUND

It is not established whether patellar resurfacing is better than patellar non-resurfacing during total knee arthroplasty (TKA). This study was to compare the clinical outcomes between groups with patellar resurfacing and non-resurfacing during cruciate retaining (CR) TKA.

METHODS

In this retrospective cohort study, subjects undergoing primary CR TKA for osteoarthritis between 2012 and 2019 were included. Of 500 subjects, 250 had patellar resurfacing (group 1) and 250 had patellar non-resurfacing (group 2) CR TKA. Knee society knee score (KSKS), knee society function score (KSFS), Western Ontario and McMaster Universities Osteoarthritis (WOMAC) scale, Kujala score, anterior knee pain, patellar compression test and range of motion (ROM) of the replaced knee were assessed and compared between the two groups.

RESULTS

There were no significant differences in KSKS, KSFS, WOMAC scale, Kujala score, prevalence of anterior knee pain and ROM of the replaced knee between the two groups at the last follow-up (p > .05). Group 2 had more subjects with positive patellar compression test than group 1 at the last follow-up (p = .010).

CONCLUSIONS

Clinical and functional outcomes of the replaced knee were not different between patellar resurfacing and non-resurfacing groups. Anterior knee pain was significantly reduced after total knee arthroplasty regardless of patellar resurfacing.

LEVEL OF EVIDENCE

Retrospective cohort study, Level III.

No difference between resurfaced and non-resurfaced patellae with a modern prosthesis design: a prospective randomized study of 250 total knee arthroplasties

PURPOSE

Despite numerous well-conducted studies and meta-analyses, the management of the patella during total knee arthroplasty (TKA) remains controversial. The aim of our study was to compare the clinical and radiological outcomes between patients with and without patellar resurfacing and to determine the influence of resurfacing on patellar tracking with a "patella-friendly" prosthesis.

METHODS

A single-centered prospective randomized controlled study was performed between April 2017 and November 2018. Two hundred and forty-five consecutive patients (250 knees) scheduled for TKA were randomized for patellar resurfacing or patella non-resurfacing. All patients received the same total knee prosthesis and were evaluated clinically and radiologically, including the International Knee Society Score (KSS knee and function), Forgotten Joint Score (FJS), anterior knee pain (AKP), pain when climbing stairs, patellar tilt, and patellar translation.

RESULTS

Two hundred and twenty-nine knees were available for clinical evaluation and 221 knees for radiographic analysis. The revision rate for patellofemoral cause was 3.1% (7 cases) with no difference between the groups (p = 0.217). There was no difference in survival rate between patellar resurfacing (88.3%) and non-resurfacing (85.3%) after 24 months (p = 0.599). There were no differences in KSS functional component (p = 0.599), KSS knee component (p = 0.396), FJS (p = 0.798), and AKP (p = 0.688) at a mean follow-up of 18 months. There was twice as much stair pain for the non-resurfacing group (17.1% versus 8.5%) (p = 0.043). There was patellar tilt in 43% of resurfaced knees (n = 50/116) versus 29% in non-resurfaced knees (n = 30/105) (p = 0.025); however, there was more patellar translation in the non-resurfaced group (21.0% versus 7.8%) (p < 0.001). There were no specific complications attributed to the patellar resurfacing procedure. There were four secondary patellar resurfacing procedures (3.6%) in the non-resurfaced group after a mean of 10 ± 7 months (1-17) postoperatively.

CONCLUSION

There is no superiority of patellar resurfacing or non-resurfacing in terms of clinical or radiological outcomes at mid-term. Secondary patellar resurfacing is rare. There is not enough evidence to recommend systematic patellar resurfacing with a "patella-friendly" prosthesis.

Fracture Risk With Patella Resurfacing During Total Knee Arthroplasty After Anterior Cruciate Ligament Reconstruction Using Bone-Patella-Bone Autograft: A Biomechanical Analysis

Background

Anterior cruciate ligament (ACL) tears are common injuries. Ipsilateral bone patellar tendon bone (BPTB) autograft has been frequently used for ACL reconstructions. A large percentage of patients who sustain ACL ruptures develop early osteoarthritis and require total knee arthroplasty (TKA). When patients with previous BPTB autograft for an ACL tear undergo TKA, there may be an increased risk of fracture after patellar resurfacing.

Methods

There were 20 artificial Sawbones and 10 cadaveric patellae resurfaced. To simulate the presence of a previous BPTB autograft, a bone plug was removed from the anterior surface of the patellae and was resurfaced with a cemented patellar button. Biomechanical testing was performed to determine the compressive load to fracture of patellae with and without previous BPTB autograft.

Results

The average maximum load to failure for the artificial Sawbones patellae without a previous BPTB autograft was 4551.40 N ± 753.12 compared with 2855.39 N ± 531.46 with a previous BPTB autograft (P < .001). The average maximum load to failure for the cadaveric patellae without a previous BPTB autograft was 7256.37 N ± 1473.97 compared with 5232.22 N ± 475.04 with a previous BPTB autograft (P = .021).

Conclusions

The results demonstrate a significantly lower maximum load to failure of a resurfaced patella in the presence of a previous BPTB autograft. This can be used to aid in the decision of whether to resurface the patellae in these patients and to educate patients that the presence of a previous BPTB autograft may be an increased risk factor for patella fracture after TKA.

A Study Investigating Whether BMI Is Associated With Acetabular Bone Size: Big Bones or a Big Myth?

Background

There is a common conception held by patients with a high body mass index (BMI) that they have “big bones”. Some people hold the assumption that their weight is attributed to larger bone stock rather than adipose tissue. It was the suspicion of the surgeons at our unit that this is often not the case. We therefore conducted a study investigating if there is any association between BMI and acetabular bone size.

Methods

We conducted a retrospective chart review of all patients undergoing total hip arthroplasty using the Trident acetabular system from Stryker at our tertiary level 1 trauma centre between September 2016 and August 2020. Patient demographic and surgical data were collected, and the association of BMI, height, and weight, with acetabular cup size was investigated using Pearson’s correlation coefficient and chi-square test for independence.

Results

A total of 418 patients were included in this study (52.4% female; age: 20-93 years; mean age: 62.51 years), with a mean BMI of 29.55 kg/m²(range: 14.95-52.32 kg/m²). A weak positive association between BMI and cup size, which was statistically significant (r = 0.107; n = 418; p = 0.02). The chi-square test for independence was used to study the association between obesity and cup size (large vs small), which demonstrated no significant difference (p = 0.08). There was a moderately strong positive association between height and cup size (r = 0.551; n = 418; p < 0.01). There was a weak positive association between weight and cup size, which was statistically significant (r = 0.355; n = 418; p < 0.01).

Conclusion

Our study suggests that there is indeed a weakly positive linear association between BMI and cup size among total hip arthroplasty patients. This effect was, however, more significant for height and weight, and there was no significant association between obese and non-obese groups with small versus large cup size implanted. We therefore conclude that clinically there is no significant relationship between obesity and acetabular bone size and that the “big bones” claim is indeed fallacious.

Patellar management during total knee arthroplasty: a review

The optimal management of the patella during total knee arthroplasty (TKA) remains controversial and surgeons tend to approach the patella with one of three general mindsets: always resurface the patella, never resurface the patella, or selectively resurface the patella based on specific patient or patellar criteria.

Studies comparing resurfacing and non-resurfacing of the patella during TKA have reported inconsistent and contradictory findings.

When resurfacing the patella is chosen, there are a number of available patellar component designs, materials, and techniques for cutting and fixation.

When patellar non-resurfacing is chosen, several alternatives are available, including patellar denervation, lateral retinacular release, and patelloplasty. Surgeons may choose to perform any of these alone, or together in some combination.

Prospective randomized studies are needed to better understand which patellar management techniques contribute to superior postoperative outcomes. Until then, this remains a controversial topic, and options for patellar management will need to be weighed on an individual basis per patient.

Cite this article: EFORT Open Rev 2021;6:861-871. DOI: 10.1302/2058-5241.6.200156

Influence of Patellar Morphology Classified by Wiberg Classification on Knee Joint Function and Patellofemoral Tracking After Total Knee Arthroplasty Without Patellar Resurfacing

BACKGROUND

To evaluate the influence of patellar morphology on knee joint function and patellofemoral tracking in patients with primary osteoarthritis after total knee arthroplasty (TKA) without patellar resurfacing.

METHODS

We performed a retrospective study of 156 patients with primary osteoarthritis who underwent TKA without patellar resurfacing from April 2018 to July 2019. As per Wiberg classification, patients were divided into Wiberg type I (group A, n = 38), II (group B, n = 88), and III (group C, n = 30) groups. The clinical data, postoperative follow-up data, and radiological data between three groups were compared.

RESULTS

There was no statistically significant difference in the HSS score and Feller score between the three groups before surgery and at each follow-up point after surgery (P > .05). At the last follow-up, there were no significant differences in the height and relative thickness of the patella between the three groups (P > .05). However, the incidence of anterior knee pain was significantly higher in group C than in the group B (P < .05). The patellar tilt angle was significantly larger in group C than in the groups A and B (both P < .05). The patellar facet angle was significantly larger in group A than in group B and C, which was also significantly larger in group B than in group C (both P < .05).

CONCLUSION

Patients with three different morphologic types of the patella both exhibited improved knee joint function after TKA, however, patients with Wiberg type Ⅲ patella were more prone to have poor patellofemoral tracking and anterior knee pain after surgery.

The Influence of Femoral Internal Rotation on Patellar Tracking in Total Knee Arthroplasty Using Gap Technique

Backgroud

Femoral internal rotation in total knee arthroplasty (TKA) is well known as one of the main causes of patellar maltracking. Although femoral internal rotation in TKA is considered unacceptable due to the risk of patellar maltracking, it is sometimes required for ligament balancing. We evaluated the influence of femoral internal rotation on patellar tracking in TKA performed using the gap technique.

Methods

From April 2008 to May 2018, 1,612 cases of TKA were done. Among them, 245 cases of TKA for osteoarthritis were followed up for at least 1 year and included in this study. We compared patellar tracking in two groups; group I consisted of 99 cases whose femoral rotation was less than 0° and group II consisted of 146 cases whose femoral rotation was 3°-5° external rotation. Preoperative femoral rotation was measured with the condylar twist angle (CTA) by using computed tomography. The patella was replaced in all cases. Patellar tracking was evaluated with patellar tilt angle (lateral tilt [+] and medial tilt [-]) in the merchant radiograph. Statistical analysis was done using Mann-Whitney U-test. Clinical assessment was performed using the Knee Society clinical rating system.

Results

The preoperative CTA was 5.3° ± 1.6° in group I and 5.4° ± 1.6° in group II, showing no statistically significant difference between groups (p = 0.455). Intraoperative femoral rotation was -0.5° ± 0.8° in group I and 3.9° ± 0.8° in group II when the gap technique was used (p < 0.001). The postoperative patellar tilt angle was -0.4° ± 3.6° in group I and 0.1° ± 4.1° in group II with no statistically significant difference (p = 0.251).

Conclusions

Compared with femoral external rotation, femoral internal rotation with ligament balance in TKA was not more associated with patellar maltracking. Therefore, patellar tracking might be related with ligament balance in flexion regardless of the anatomic femoral rotational alignment.

Use of Fulcrum Positioning as a Balancing Tool During Total Knee Arthroplasty on a Robotic Platform

Total knee arthroplasty is a common procedure performed to improve pain and dysfunction attributed to arthritis, yet postoperative patient dissatisfaction rates remain relatively high. Patient satisfaction and outcomes have been linked to successful joint gap balancing in the coronal and sagittal planes intraoperatively. In previously described balancing techniques, the fulcrum used for alignment changes is customarily centered on the intramedullary axis generating symmetric changes in medial and lateral gaps. We propose a novel technique in the literature that, with the use of robotic-arm assisted technology or similar systems, allows manipulation of the fulcrum center of rotation during pre-resection planning and intraoperative gap establishment before bony cuts to asymmetrically influence medial and lateral, flexion and extension gaps to aid in balancing during total knee arthroplasty.