The effect of infrapatellar fat pad excision on complications after minimally invasive TKA: a randomized controlled trial

A Novel Infrapatellar Fat Pad Preservation Technique in Total Knee Arthroplasty Reduced Postoperative Pain and Wound Complications

OBJECTIVE

The management of the infrapatellar fat pad (IPFP) during total knee arthroplasty (TKA) remains controversial. This study aimed to evaluate a novel IPFP preservation technique-"the medially pedicled IPFP flap"-for reducing postoperative pain, wound complications, and improving functional recovery after TKA.

METHODS

A retrospective analysis was conducted on TKA cases at our institution from 2018 to 2021, including those with IPFP preservation (medially pedicled flap) versus IPFP complete resection. Patient demographics, perioperative parameters (blood loss, operative time, length of hospital stay, visual analogue scale [VAS] score, white cell count [WBC], C-reactive protein [CRP], erythrocyte sedimentation rate [ESR], and wound oozing), and postoperative follow-up data (VAS, Knee Society [KSS], or Knee Society functional assessment [KSFA] scores) were compared between groups. Independent sample t-tests were used to compare continuous data and chi-squared tests were used to compare categorical data between groups.

RESULTS

Six hundred thirty patients were included, with 278 in the medial pedicled IPFP flap group (preservation group) and 352 in the IPFP resection group (resection group). The operative time was significantly shorter in the preservation versus resection group (125.5 ± 23.2 vs 130.3 ± 28.7 mins, p = 0.03), as was the length of hospital stay (8.4 ± 2.7 vs 9.2 ± 2.3 days, p < 0.01). Regarding pain, the preservation group had significantly lower VAS scores on postoperative day 2 (2.0 ± 0.8 vs 2.4 ± 1.2, p < 0.001) and day 3 (1.5 ± 0.5 vs 1.8 ± 1.0, p < 0.001). CRP and ESR levels on postoperative day 5 were also significantly lower in the preservation group. Wound oozing rates were significantly lower in the preservation versus resection group (0.7% vs 2.8%, p = 0.04). No significant differences existed in VAS, KSS, or KSFA scores at the last follow-up.

CONCLUSION

The novel IPFP preservation technique significantly improved surgical exposure, shortened operative time and length of hospital stay. It also reduced wound pain and oozing compared to IPFP resection.

Are short term outcomes superior following total knee arthroplasty when infra-patellar fat pad is resected? A systematic review and meta-analysis

BACKGROUND

Data suggests the infra-patellar fat pad (IPFP) is resected in the majority of total knee arthroplasty cases. Current literature suggests there may be scope for increasing preservations rates. A systematic review and meta-analysis of available literature was performed to assess if resection of IPFP resulted in superior patient outcomes.

METHODS

Scopus, PubMed, Cochrane, Embase and CINAHL were systematically searched in February 2024 for articles of relevance and meta-analysis conducted. A standardized mean difference and confidence interval of 95% was calculated. An odds ratio was calculated for all included datasets. Heterogeneity was assessed for using the I2 statistic.

RESULTS

Thirteen studies were included within this review. IPFP resection shortened the patella tendon at 6 months post-operatively (OR, 0.07; 95% CI, 0.02-0.12, P = 0.006). Results favoured preservation at 12 months post-operatively (OR, 0.02; 95% CI, -0.02 to 0.06, P = 0.32). Oxford Knee Society (OKS) results statistically favoured preservation at 6 months (OR, 1.57; 95% CI, 0.74-2.39, P = 0.0002). Findings at 12 months favoured resection (OR, -0.49; 95% CI, -5.39, 4.41, P = 0.84). Resection increased anterior knee pain at 6-12 months post-operatively (OR, 1.45; 95% CI, 1.12-1.89, P = 0.005). Combined subgroup analysis of flexion favoured resection (OR, -2.15; 95% CI, -6.52 to 2.22, P = 0.34).

CONCLUSION

OKS and patella tendon length results favoured preservation at 6 months however did not reach minimal clinically important difference. Combined subgroup analysis of flexion did not yield a statistically significant result. Rates of anterior knee pain at 6-12 months favoured preservation.

Effect of preservation of Hoffa's fat pad on patellar height in primary total knee arthroplasty procedures

BACKGROUND

We have previously reported our experience of the effect of complete excision of Hoffa's fat pad on patella height post TKR. In this study, we compared the change of patellar height post TKR before and after the senior author changed his practice to preserving Hoffa's fat pad.

METHODS

This was a retrospective analysis of a prospective series of TKRs performed or directly supervised by the senior author. In Group 1 were 72 patients performed before April 2011 who had complete excision of Hoffa's fat pad to maximise exposure during the procedure. In Group 2 were 138 patients performed after April 2011 who had the minimum excision of Hoffa's fat pad to allow adequate surgical exposure. The surgical technique and rehabilitation protocol were identical in all other respects. Patellar height was assessed using the Caton-Deschamps Index both immediately postoperative and at a minimum follow up of 1 year.

RESULTS

Group 1 included 28 males, 44 females with mean age 68.36 years. The mean CDI in this group changed from 0.54 immediately post-operatively to 0.46 at minimum one year follow-up (P = 0.001) indicating progressive patella baja. Group 2 included 56 males, 82 females with mean age 65 years. The mean CDI changed from 0.67 immediately post-operative to 0.68 at minimum one year post follow-up (P = 0.32) indicating no statistically or clinically relevant post-operative change in patellar height.

CONCLUSION

Total excision of Hoffa's fat pad is associated with progressive post-operative patella baja. This can be avoided by resecting the minimum amount of fat pad to allow adequate exposure during the procedure.

Effect of Infrapatellar Fat Pad Preservation vs Resection on Clinical Outcomes After Total Knee Arthroplasty in Patient with End-Stage Osteoarthritis

Purpose

The management of infrapatellar fat pad (IPFP) during total knee arthroplasty (TKA) is the subject of ongoing debate. There is conflicting evidence whether IPFP should be preserved or resected during TKA to improve clinical outcomes. This study sought to establish if there is a benefit of one over another in terms of clinical function & patient satisfaction.

Material & Methods

Total of 67 patients (96 knees), 11 males & 56 females with a mean age of 66.29 years, who underwent TKA between 2016 and 2020 were included in the study. The planning for IPFP preservation (IPFP-P) on right side (50 knees) & IPFP resection (IPFP-R) on left side (46 knees) was done prospectively. We prospectively evaluated clinical outcomes post-TKA, comparing the right knee to the left knee in terms of IPFP-P vs IPFP-R using the oxford knee scoring (OKS) system. The SF-12 was used to evaluate and compare patient satisfaction between the two groups.

Results

The mean OKS in the IPFP-P group was 42.86 ± 2.63 & in the IPFP-R group was 44.22 ± 2.40. The OKS differed significantly between the two groups (p < 0.05). Patient with IPFP-R group had significantly better OKS. The mean Sf-12 (physical & mental component) in the IPFP-P was 51.05 ± 4.15 & 59.29 ± 2.53 & in IPFP-R was 51.23 ± 4.74 & 59.24 ± 2.78, showing no significant differences.

Conclusion

Our study shows that IPFP-R gave marginally better patient-reported functional outcome scores (OKS), but there was no difference in patient satisfaction (SF-12 scores) between the two groups.

Decreased Trochlear Length Associated with Increased Anterior Knee Pain Following Total Knee Arthroplasty: A New Anatomical Perspective

BACKGROUND

Anterior Knee Pain (AKP) and patello-femoral crepitus (PFCr) continue to plague total knee arthroplasty (TKA) patients despite advances and modifications to implant design and surgical techniques. We present our study of the femoral trochlear length measurement pre- and post-implantation and its association with AKP/PFCr and clinical scores.

METHODS

Using computer navigation, we obtained several measurements in 263 TKA (posterior-stabilized) patients, which included femoral native trochlear measurement (NTM) and difference in trochlear length (DTL) between implant and native trochlea. We report their association with Knee Society Score (KSS), Western Ontario McMaster University Arthritic Index(WOMAC), and AKP/PFCr at 1 year postoperatively.

RESULTS

Mean KSS and WOMAC Scores were significantly worse in patients who had AKP (P=0.005 and P=0.002 respectively). Receiver Operating Characteristic (ROC curve) showed a statistically significant association between native trochlear measurement and AKP (Area under the curve[AUC] =0.609, P=0.014). Lower the native trochlear measurement, greater was the incidence of AKP. Analysis of the ROC curve identified the cut-off value of NTM to be ≤ 25.5 with sensitivity of 76.7(95% Confidence Interval (CI)- 57.7 - 90.1) and specificity of 46.9(95%CI- 41.9 - 55.1). Patients who had NTM of ≤25.5 had an odds ratio of 3.09 to have AKP. The DTL ranged from 7.4 to 32.1 millimeters, indicating that post-implantation there was lengthwise overstuffing along the trochlea in every patient.

CONCLUSION

We found that the shorter the native femoral trochlea and greater the difference between implanted and native trochlea, the higher was the occurrence of AKP. A mismatch in trochlear measurement pre- and post-implantation resulted in lengthwise overstuffing in the anterior knee causing AKP and PFCr.

Correlation between the Signal Intensity Alteration of Infrapatellar Fat Pad and Knee Osteoarthritis: A Retrospective, Cross-Sectional Study

Infrapatellar fat pad (IPFP) inflammation is a common pathological manifestation in knee osteoarthritis (OA). However, the significance of IPFP signal intensity alteration for clinical diagnosis and treatment of knee OA needs further research. We assessed IPFP signal intensity alteration (0-3), IPFP maximum cross-sectional area (CSA) and IPFP depth, meniscus injury, bone marrow edema, and cartilage injury from magnetic-resonance imaging (MRI) in 41 non-KOA patients (K-L grade 0 and grade I) and 68 KOA patients (K-L grade 2,3 and 4). We found that IPFP signaling was altered in all patients with KOA whose alteration was closely related to the K-L grading. We found that the IPFP signal intensity was increased in most OA patients, especially the ones in the late stage. There were significant differences in IPFP maximum CSA and IPFP depth between groups in KOA and non-KOA patients. Moreover, Spearman correlation analysis showed that IPFP signal intensity was moderately positively correlated with age, meniscal injury, cartilage injury, and bone marrow edema, and negatively correlated with height, while not correlated with visual analogue scale (VAS) scoring and body mass index (BMI). In addition, women have higher IPFP inflammation scores on MRI than men. In conclusion, IPFP signal intensity alteration is associated with joint damage in knee OA, which may have clinical significance for diagnosing and treating KOA.

Resection of Infrapatellar Fat Pad during Total Knee Arthroplasty Has No Impact on Postoperative Function, Pain and Sonographic Appearance of Patellar Tendon

Routine resection of the infrapatellar fat pad (IFP) during total knee arthroplasty (TKA) is controversial, as it may result in shortening of the patellar tendon (PT) and anterior knee pain. This prospective study examined whether IFP excision during TKA affects joint function, anterior knee pain, PT dimensions and sonographic structure. A total of 65 consecutive patients undergoing TKA for osteoarthritis were randomized into two groups: IFP was resected in one and retained in the other. Patients were examined preoperatively, at 6 weeks and 6 months postoperatively: pain (Numerical Rating Scale-NRS), range of motion (ROM) and knee function (Knee Injury and Osteoarthritis Outcome Score-KOOS score) were evaluated; sonographic examination determined the length, structure and vascularity of the PTs. In both groups there were postoperative improvements in NRS and KOOS scores, although IFP resection did not influence clinical outcomes or sonographic parameters. At 6 weeks and 6 months postoperatively for both groups there were no differences between NRS scores (Mann-Whitney test, p = 0.511 and p = 0.579), ROM scores (Mann-Whitney test, p = 0.331, p = 0.180) or all KOOS subscores. IFP excision had no effect on sonographic parameters. This study suggests that IFP resection during TKA does not influence postoperative functional outcomes, pain scores, patellar tendon length and thickness, or sonographic structure.

Total Infrapatellar Fat Pad Excision Leads to Worse Isokinetic Performance in Total Knee Arthroplasty: A Randomized Controlled Trial

There are concerns that total infrapatellar fat pad (IPFP) excision in total knee arthroplasty (TKA) results in patellar tendon shortening due to ischemic contracture, but individual preference of the surgeon is still the main determinant between total or partial excision. The aim of this randomized controlled study was to compare isokinetic performance and clinical outcome of TKAs with total and partial excision of the IPFP. Seventy-two patients scheduled to undergo TKA for primary knee osteoarthritis by a single surgeon were randomly assigned to either total or partial excision group. Patients were evaluated preoperatively and at postoperative 1 year, with Knee Society Score (KSS) and isokinetic measurements. The physiatrist performing isokinetic tests and patients were blinded to the study. There were no significant differences between the groups in respect of age, body mass index, gender, and preoperative KSS and isokinetic performance. Postoperatively, both groups had improved KSS knee and KSS function scores, with no difference determined. Knee extension peak torque was significantly higher postoperatively in the partial excision group at postoperative 1 year (p = 0.036). However, there were no significant differences in knee flexion peak torque following TKA (p = 0.649). The results of this study demonstrated that total excision of the IPFP during TKA is associated with worse isokinetic performance, which is most likely due to changes in the knee biomechanics with the development of patella baja. Partial excision of the IPFP appears to be a valid alternative to overcome this potential detrimental effect without impeding exposure to the lateral compartment. This is a Level I, therapeutic study.

The Corpus Adiposum Infrapatellare (Hoffa’s Fat Pad)—The Role of the Infrapatellar Fat Pad in Osteoarthritis Pathogenesis

In recent years, the infrapatellar fat pad (IFP) has gained increasing research interest. The contribution of the IFP to the development and progression of knee osteoarthritis (OA) through extensive interactions with the synovium, articular cartilage, and subchondral bone is being considered. As part of the initiation process of OA, IFP secretes abundant pro-inflammatory mediators among many other factors. Today, the IFP is (partially) resected in most total knee arthroplasties (TKA) allowing better visualization during surgical procedures. Currently, there is no clear guideline providing evidence in favor of or against IFP resection. With increasing numbers of TKAs, there is a focus on preventing adverse postoperative outcomes. Therefore, anatomic features, role in the development of knee OA, and consequences of resecting versus preserving the IFP during TKA are reviewed in the following article.

The impact of infrapatellar fat pad excision versus preservation after total knee replacement on anterior knee pain, functional outcome and patellar height: Randomized controlled trial

Introduction

Although better surgical exposure is encountered with the excision of infrapatellar pad of fat (IPPF) during total knee replacement (TKR), some studies showed an increase in anterior knee pain and other specific complications associated with such a step. The purpose of this study was to add in literature a new comparison between IPPF excision and preservation during TKR, focusing on the anterior knee pain, functional range, oxford knee score and patellar height through a randomized clinical trial

Methods

This prospective randomized study was conducted from 2016 to 2019 on 90 patients with knee osteoarthritis treated with elective primary TKA by same surgeons at one hospital with the same implant design with a mean follow up of 18 month. Patients were randomized into two groups: one group including patients with IPPF complete excision and the other group include patients with IPPF preservation. No patella resurfacing was done. Pre and postoperative anterior knee pain was recorded and compared using VAS score in addition to Oxford knee score.

Results

At 6 months follow-up, 10 knees and 14 knees (27%) had anterior aching discomfort with a mean postoperative extension were −5.3 and −5.2 in IPPF preservation and excision group patients, respectively. There was no statistically significant differences between both groups regarding anterior knee pain, range of motion, oxford knee score or patellar height measurement through the follow up period. No patellar complications were recorded in all cases.

Conclusion

Although Infrapatellar fat pad excision in TKA resulted in a minor increase in number of patients with postoperative anterior knee pain, it was of no statistically significant difference. Hence, whenever a better surgical exposure is needed, IPPF excision should be considered. Additional large scale randomized studies should be added to the calling literature for more result validation and guidelines formulation.

Early removal of the infrapatellar fat pad/synovium complex beneficially alters the pathogenesis of moderate stage idiopathic knee osteoarthritis in male Dunkin Hartley guinea pigs

BACKGROUND

The infrapatellar fat pad (IFP) is the largest adipose deposit in the knee; however, its contributions to the homeostasis of this organ remain undefined. To determine the influence of the IFP and its associated synovium (IFP/synovium complex or IFP/SC) on joint health, this study evaluated the progression of osteoarthritis (OA) following excision of this unit in a rodent model of naturally-occurring disease.

METHODS

Male Dunkin-Hartley guinea pigs (n=18) received surgical removal of the IFP in one knee at 3 months of age; contralateral knees received sham surgery as matched internal controls. Mobility and gait assessments were performed prior to IFP/SC removal and monthly thereafter. Animals were harvested at 7 months of age. Ten set of these knees were processed for microcomputed tomography (microCT), histopathology, transcript expression analyses, and immunohistochemistry (IHC); 8 sets of knees were dedicated to microCT and biomechanical testing (material properties of knee joints tissues and anterior drawer laxity).

RESULTS

Fibrous connective tissue (FCT) developed in place of the native adipose depot. Gait demonstrated no significant differences between IFP/SC removal and contralateral hindlimbs. MicroCT OA scores were improved in knees containing the FCT. Quantitatively, IFP/SC-containing knees had more osteophyte development and increased trabecular volume bone mineral density (vBMD) in femora and tibiae. Histopathology confirmed maintenance of articular cartilage structure, proteoglycan content, and chondrocyte cellularity in FCT-containing knees. Transcript analyses revealed decreased expression of adipose-related molecules and select inflammatory mediators in FCTs compared to IFP/SCs. This was verified via IHC for two key inflammatory agents. The medial articular cartilage in knees with native IFP/SCs showed an increase in equilibrium modulus, which correlated with increased amounts of magnesium and phosphorus.

DISCUSSION/CONCLUSION

Formation of the FCT resulted in reduced OA-associated changes in both bone and cartilage. This benefit may be associated with: a decrease in inflammatory mediators at transcript and protein levels; and/or improved biomechanical properties. Thus, the IFP/SC may play a role in the pathogenesis of knee OA in this strain, with removal prior to disease onset appearing to have short-term benefits.

Fragility Index as a Measure of Randomized Clinical Trial Quality in Adult Reconstruction: A Systematic Review

Background

The Fragility Index (FI) and Reverse Fragility Index are powerful tools to supplement the P value in evaluation of randomized clinical trial (RCT) outcomes. These metrics are defined as the number of patients needed to change the significance level of an outcome. The purpose of this study was to calculate these metrics for published RCTs in total joint arthroplasty (TJA).

Methods

We performed a systematic review of RCTs in TJA over the last decade. For each study, we calculated the FI (for statistically significant outcomes) or Reverse Fragility Index (for nonstatistically significant outcomes) for all dichotomous, categorical outcomes. We also used the Pearson correlation coefficient to evaluate publication-level variables.

Results

We included 104 studies with 473 outcomes; 92 were significant, and 381 were nonstatistically significant. The median FI was 6 overall and 4 and 7 for significant and nonsignificant outcomes, respectively. There was a positive correlation between FI and sample size (R = 0.14, P = .002) and between FI and P values (R = 0.197, P = .000012).

Conclusions

This study is the largest evaluation of FI in orthopedics literature to date. We found a median FI that was comparable to or higher than FIs calculated in other orthopedic subspecialties. Although the mean and median FIs were greater than the 2 recommended by the American Academy of Orthopaedic Surgeons Clinical Practice Guidelines to demonstrate strong evidence, a large percentage of studies have an FI < 2. This suggests that the TJA literature is on par or slightly better than other subspecialties, but improvements must be made.

Level of Evidence

Level I; Systematic Review.

Infrapatellar Fat Pad Resection or Preservation during Total Knee Arthroplasty: A Systematic Review

Considerations of how to improve postoperative outcomes for total knee arthroplasty (TKA) have included preservation of the infrapatellar fat pad (IPFP). Although the IPFP is commonly resected during TKA procedures, there is controversy regarding whether resection or preservation should be implemented, and how this influences outcomes. Therefore, the purpose of this systematic review was to evaluate how IPFP resection and preservation impacts postoperative flexion, pain, Insall-Salvati Ratio (ISR), Knee Society Score (KSS), patellar tendon length (PTL), and satisfaction in primary TKA. PubMed, EBSCO host, and SCOPUS were queried to retrieve all reports evaluating IPFP resection or preservation during TKA, which resulted into 488 studies. Two reviewers independently reviewed these articles for eligibility based on pre-established inclusion and exclusion criteria. Eleven studies were identified for final analysis, which reported on 11,996 cases. Patient demographics, type of surgical intervention, follow-up duration, and clinical outcome measures were collected and analyzed. Complete resection was implemented in 3,723 cases (31%), partial resection in 5,458 cases (45.5%), and preservation of the IPFP in 2,815 cases (23.5%). Clinical outcome measures included PTL (5 studies), knee flexion (4 studies), pain (6 studies), KSS (3 studies), ISR (3 studies), and patient satisfaction (1 study). No differences were found following IPFP resection for patient satisfaction (p = 0.98), ISR (p > 0.05), and KSS (p > 0.05). There was mixed evidence for PTL, pain, and knee flexion following IPFP resection versus preservation. Studies of shorter follow-up intervals suggested improved pain following resection, while reports of longer follow-up times indicated that resection resulted in increased pain. Given the mixed data available from the current literature, we were unable to conclude that one surgical technique can definitively be considered superior over the other. More extensive research, including randomized controlled trials, is required to better elucidate potential differences between the surgical handling choices. Future studies should focus on patient conditions in which one technique would be best indicated to establish guidelines for best surgical outcomes in those patients.

Effects of infrapatellar fat pad preservation versus resection on clinical outcomes after total knee arthroplasty in patients with knee osteoarthritis (IPAKA): study protocol for a multicentre, randomised, controlled clinical trial

INTRODUCTION

The infrapatellar fat pad (IPFP) is commonly resected during total knee arthroplasty (TKA) for better exposure. However, our previous studies have suggested that IPFP size was protective against, while IPFP signal intensity alteration was detrimental on knee symptoms and structural abnormalities. We hypothesise that an IPFP with normal qualities, rather than abnormal qualities, should be preserved during TKA. The aim of this study is to compare, over a 1-year period, the postoperative clinical outcomes of IPFP preservation versus resection after TKA in patients with normal or abnormal IPFP signal intensity alteration on MRI.

METHODS AND ANALYSIS

Three hundred and sixty people with end-stage knee osteoarthritis and on the waiting list for TKA will be recruited and identified as normal IPFP quality (signal intensity alteration score ≤1) or abnormal IPFP quality (signal intensity alteration score ≥2). Patients in each hospital will then be randomly allocated to IPFP resection group or preservation group. The primary outcomes are the summed score of self-reported Knee Injury and Osteoarthritis Outcome Score (KOOS), KOOS subscales assessing function in daily activities and function in sport and recreation. Secondary endpoints will be included: KOOS subscales (pain, symptoms and quality of life), Knee Society Score, 100 mm Visual Analogue Scale (VAS) Pain, timed up-and-go test, patellar tendon shortening, 100 mm VAS self-reported efficacy of reduced pain and increased quality of life, and Insall-Salvati index assessed on plain X-ray. Adverse events will be recorded. Intention-to-treat analyses will be used.

ETHICS AND DISSEMINATION

The study is approved by the local Medical Ethics Committee (Zhujiang Hospital Ethics Committee, reference number 2017-GJGBK-001) and will be conducted according to the principle of the Declaration of Helsinki (64th, 2013) and the Good Clinical Practice standard, and in compliance with the Medical Research Involving Human Subjects Act . Data will be published in peer-reviewed journals and presented at conferences, both nationally and internationally.

TRIAL REGISTRATION NUMBER

This trial was registered at Clinicaltrial.gov website on 19 October 2018 with identify number NCT03763448.

Infrapatellar Fat Pad and Knee Osteoarthritis

Osteoarthritis is the most prevalent arthritis typically characterized by degradation of cartilage. However, its pathogenesis is not fully understood. Currently, osteoarthritis is best considered a disease of the whole "joint organ". Infrapatellar fat pad (IFP), an adipose tissue near synovium, is now attaching importance to researchers for its inflammatory phenotype. In this narrative review, a large body of evidence has been gathered for the involvement of IFP in the development of knee osteoarthritis. Additionally, the underlying mechanisms of how IFP can be involved in this process have been proposed. However, further investigations are needed to better understand its precise role in this process and its underlying mechanism, and beyond that, to develop new strategies to slow down the degenerative process and explore an effective and timely diagnosis of the disease.

Multimodal approach to intraarticular drug delivery in knee osteoarthritis

The expectations from any future disease-modifying treatment for knee osteoarthritis (KOA) are extremely high as it has to impact the joint as a whole leading to favorable alterations of diverse tissues and functions. In this light, targeting the knee only from the inside may not be biologically justified for the management of a whole joint disease such as KOA. Our hypothesis to test is whether any injectable therapeutic intervention alone can lead to disease modification of KOA which is viewed in the complexity of the modern concept of osteoarthritis (OA) as a whole joint disease. Therefore, we aimed at analyzing the intraarticular route to the KOA patient in an attempt to unveil its "biological" constraints. A comprehensive search through databases was carried out using specific keywords to add objectivity to the main messages. The literature analysis has shown that "cutting-edge" intraarticular therapies may offer a key to non-invasive symptomatic relief. Changing the course of KOA, however, may necessitate a multimodal approach towards the knee joint including a combination of intraarticular injections with interventions on multiple levels. Importantly, our understanding of OA has evolved redefining the concept of the disease, being in interaction with the human body as a whole. Any future conservative disease-modifying treatment of KOA should aim at a multimodal, holistic approach towards the knee joint including but not limited only to intraarticular injections. A combination with other interventions should be further researched.

Infrapatellar fat pad resection or preservation during total knee arthroplasty: a meta-analysis of randomized controlled trials

BACKGROUND

The infrapatellar fat pad (IPFP) or Hoffa's fat pad is often resected during total knee arthroplasty in order to improve visibility. However, the management of the IPFP during total knee arthroplasty (TKA) is the subject of an ongoing debate that has no clear consensus. The purpose of this review was to appraise if resection of the IPFP affects clinical outcomes.

METHODS

We conducted a meta-analysis to identify relevant randomized controlled trials involving infrapatellar fat pad resection and infrapatellar fat pad preservation during total knee arthroplasty in electronic databases, including Web of Science, Embase, PubMed, Cochrane Controlled Trials Register, Cochrane Library, Highwire, CBM, CNKI, VIP, and Wanfang database, up to March 2020.

RESULTS

Nine randomized controlled trials, involving 783 TKAs (722 patients), were included in the systematic review. Outcome measures included patellar tendon length (PTL), Insall-Salvati ratio (ISR), rate of anterior knee pain, Knee Society Scores (KSS), and knee range of motion. The meta-analysis identified a trend toward the shortening of the patellar tendon with IPFP resection at 6 months (P = 0.0001) and 1 year (P = 0.001). We found no statistical difference in ISR (P = 0.87), rate of anterior knee pain within 6 months (p = 0.45) and 1 year (p = 0.38), KSS at 1 year (p = 0.77), and knee range of motion within 6 months (p = 0.61) and 1 year (0.46).

CONCLUSION

Based on the available level I evidence, we were unable to conclude that one surgical technique of IPFP can definitively be considered superior over the other. More adequately powered and better-designed randomized controlled trial (RCT) studies with long-term follow-up are required to produce evidence-based guidelines regarding IPFP resection.

An investigation of the anatomy of the infrapatellar fat pad and its possible involvement in anterior pain syndrome: a cadaveric study

The infrapatellar fat pad (IFP) is an extrasynovial, intracapsular, adipose body occupying the space in the knee joint between the inferior border of the patella, the femoral condyles, tibial plateau and patellar tendon. Little is known about the anatomy and normal function of the IFP, but it has been suggested to play a role in the aetiology of Anterior knee pain syndrome, including that associated with osteoarthritis. Forty-three knees from 11 male and 15 female embalmed cadavers (mean age 84 years; range 55-97 years) were investigated. The cadavers were donated and the study performed in compliance with the provisions of the UK Human Tissue Act (2004). The quadriceps tendon and the medial and lateral patellar retinacula were dissected from the patella, which was then reflected antero-distally. The IFP was carefully excised and details of its morphology and attachments to components of the knee joint were recorded, together with the presence of articular surface pathology on the patella and femoral condyles. The principal novel findings of the current study were that 81% of IFPs were attached to the superior border of the patella by supero-medial extensions and 65% were attached by supero-lateral extensions; the supero-medial extensions were larger than the supero-lateral extensions. The superior extensions of the IFP were always attached anteriorly to the patellar retinacula and in four individuals the extensions formed a full loop around the superior border of the patella. The volume of IFPs with attachments to the superior border of the patella was significantly greater (p = .007) than those without, and the IFP was attached to the medial meniscus in significantly (p = .009) more knees with IFP attachment to the superior border of the patella than those without. All IFPs were attached to the medial anterior horn of the meniscus and the medial Kaplan's ligament. Ninety-seven per cent were attached to the lateral anterior horn of the meniscus and 97% to the lateral Kaplan's ligament. The length of IFP attachment to the lateral meniscus was significantly longer (p = .004) than that to the medial meniscus. Ninety-seven per cent of IFPs were attached to the superior portion of the patellar tendon with the mean tendon attachment being 60%. Ninety-one per cent of IFPs were attached to the inferior border of the patella. Significantly fewer knees with patellar (p = .001) and femoral (p = .002) articular surface osteophytes exhibited superior IFP extensions and these extensions were significantly shorter in knees with patellar (p = .000) and femoral (p = .006) osteophytes, compared with those without. The IFP was attached to the medial meniscus in significantly fewer knees with femoral (p = .050) and patellar (p = .023) osteophytes than those without. All IFPs not attached to the anterior horn of the lateral menisci, medial Kaplan's ligament, superior patella or inferior border of the patella, were in knees with articular surface osteophytes. This relationship between IFP morphology and knee joint pathology suggests a functional role for the IFP that requires further investigation.

Daily and short-term application of joint movement for the prevention of infrapatellar fat pad atrophy due to immobilization

[Purpose] To mobilize the knee joint during cast fixation and to determine whether infrapatellar fat pad changes can be prevented. [Materials and Methods] We randomly allocated Wistar rats into 3 groups as follows: normal group, raised in normal conditions (n=5); contracture group, immobilized with cast fixation (n=5); and prevention group, treated with joint movement during immobilization (n=5). We immobilized the right hindlimb using cast fixation. Joint movement in the prevention group was accomplished by repeatedly pulling the right hindlimb caudally and then returning the leg to the bent position for 10 minutes every day for 2 weeks. We used a metronome to maintain a constant speed, with one set lasting 2 seconds (1-second traction and 1-second return). [Results] The contracture group had adipose cells of various sizes and fibrosis in the infrapatellar fat pad. These changes were also found in milder forms in the prevention group. We found significant differences in the cross section of adipose cells and in knee extension restriction between the groups. [Conclusion] Promoting joint movement may not only have a therapeutic effect on adipose cells but also a preventative effect.

Insall-Salvati ratio stabilizes one year after mobile-bearing total knee arthroplasty and does not correlate with mid-to-long-term clinical outcomes

PURPOSE

It has not been established whether changes in the length of the patellar tendon (LPT) after total knee arthroplasty (TKA) affect clinical outcomes. Therefore, this prospective cohort study aimed to evaluate changes in the LPT over time postoperatively and clarify their impact on clinical outcomes after bilateral TKA, performed with differently designed mobile-bearing (meniscal-bearing and rotating-platform) implants on contralateral knees.

METHODS

51 patients who required staged bilateral mobile-bearing TKA were recruited. LPT was evaluated by measuring the Insall-Salvati ratio (ISR) preoperatively and at 1 week, 6 months, and 1, 2, and ≥ 5 years postoperatively. Hospital for Special Surgery score and range of motion were assessed at the final follow-up.

RESULTS

Based on the ISR, there were no differences in the patterns of change between the two types of implant (n.s.). At the 6-month follow-up, the ISRs of both implants had significantly decreased (p = 0.002). Throughout the follow-up, the ISR was significantly lower (p < 0.001) for the meniscal-bearing knees than for the rotating-platform knees. After the 1-year follow-up, there were no further substantial changes in the ISR in either group. There was also no significant correlation between the ISR and clinical outcomes.

CONCLUSIONS

LPT decreased after both mobile-bearing TKAs for up to 1 year postoperatively, although the decrease was more significant for the meniscal-bearing knees than the rotating-platform knees. After 1 year postoperatively, however, these conditions had stabilized, with no further changes. Thus, LPT plays a minimal role in mid-to-long-term clinical outcomes after TKA.

LEVEL OF EVIDENCE

Therapeutic prospective study, Level II.

Preservation vs. resection of the infrapatellar fat pad during total knee arthroplasty part II: A systematic review of published evidence

BACKGROUND

The management of the infrapatellar fat pad (IPFP) during total knee arthroplasty (TKA) is the subject of ongoing debate. In part 2 of this two part series the authors aimed to investigate if resection of the IPFP affects clinical outcomes.

METHODS

A systematic search of CENTRAL Cochrane library, Medline, Embase and Web-of-science databases for the past 10 years was performed. Studies of patients undergoing primary TKA comparing outcomes between IPFP resection and preservation were included. The meta-analysis was performed with Review Manager 5.3.

RESULTS

Seven studies, involving 2815 patients (3312 knees) were included in the systematic review, of which two were RCTs. Outcome measures included patellar tendon length (PTL), post-operative pain, Knee Society Scores (KSS) and Functional Scores. Meta-analysis identified a trend toward shortening of the patellar tendon with IPFP resection. Resection correlated with a lower incidence of post-operative pain at one to two months, however at three to six months pain scores were higher in this group. No statistical difference was found in KSS and Functional Scores.

CONCLUSION

There is wide variation in practice with regard to the IPFP in TKA. The available literature with regard to resection or preservation of the IPFP is not conclusive.

IMPLICATIONS

There is no clear consensus in the literature on the resection or preservation of the IPFP indicating a clear need for high quality studies in the future to provide meaningful answers.

Preservation vs. resection of the infrapatellar fat pad during total knee arthroplasty Part I: A survey of current practice in the UK

BACKGROUND

The management of the infrapatellar fat pad (IPFP) during total knee arthroplasty (TKA) is the subject of ongoing debate. In part 1 of this two-part series, we present an overview of current practice regarding the management of the IPFP in elective TKA among surgeons in the UK.

METHODS

A web-based survey was offered to 269 delegates of the BASK 2017 annual conference.

RESULTS

The survey showed a large variation in practice. Of the 173 responders, 86.7% were consultants; 62.4% partially resected the IPFP; 23.1% totally resected the IPFP, and 9.8% preserved it. Forty percent felt that resection made a difference. Only 23% stated that they were aware of guidelines/evidence.

CONCLUSION

There is wide variation in practice with regard to the IPFP in TKA. The available literature with regard to resection or preservation of the IPFP is not conclusive.

IMPLICATIONS

There are no definitive guidelines available for the management of the IPFP in TKA resulting in a wide variation in practice amongst surgeons.

Systemic and local adipose tissue in knee osteoarthritis

Knee osteoarthritis (OA) is the most common joint disease. Body adipose tissue has been shown to be related to the development and progression of knee OA. Among systemic adipose tissues, subcutaneous adipose tissue is significantly and negatively associated with muscle mass and forces, and could be related to the presence and progression of knee OA. Visceral adipose tissue is associated with increased cartilage loss and production of pro-inflammatory cytokines. Intra-muscular adipose tissue is associated with knee osteoarthritic changes, but it remains controversial if inter-muscular adipose tissue has a role to play in the pathogenesis for knee OA. Knee local adipose tissue such as infrapatellar fat pad (IPFP) can interact with neighbouring tissues, and may have a biphasic effect in knee OA. The underlying mechanisms for the roles of the systemic and local fat in knee OA could be related to biomechanical, metabolic, inflammatory factors and fat fibrosis, which may have a separated or combined effect on OA. Tissue engineering from systemic or local adipose tissue is a new research direction, and adipose tissue-derived stem cells from systemic or local adipose tissue may be beneficial for OA cartilage repair. Research on systemic and local adipose tissue would provide novel approaches for prevention and treatment of knee OA, but further studies are required to explore the roles of different adipose tissues in knee OA and the effects of stem cells derived from different adipose tissues on knee OA.

Different Factors Conduct Anterior Knee Pain Following Primary Total Knee Arthroplasty: A Systematic Review and Meta-Analysis

BACKGROUND

A systematic review and meta-analysis was performed to investigate the risks associated with anterior knee pain (AKP) following primary total knee arthroplasty (TKA).

METHODS

A computerized search was performed of the following databases: MEDLINE, Embase, and Cochrane Central (published prior to July 2017). A total of 37 studies, which included 1641 cases of AKP and 168,090 TKAs, were included in the meta-analysis.

RESULTS

A subgroup analysis revealed that compared with those without the following medical conditions, patients who had an infrapatellar fat pad excision and more than 12 months of follow-up (odds ratio [OR] 12.58, 95% confidence interval [CI] 3.245-48.781) were more likely to have AKP after TKA. Circumpatellar electrocautery (>12 months: OR 0.50, 95% CI 0.326-0.760; ≤12 months: OR 0.59, 95% CI 0.408-0.867) and patellar resurfacing (OR 0.25, 95% CI 0.131-0.485) may decrease the risk of AKP. Other factors, including the prosthesis bearing type (mobile bearing or fixed bearing) and the approach (midvastus compared with the medial parapatellar approach), were not significant risk factors for AKP.

CONCLUSION

The use of strategies such as patellar denervation and patellar resurfacing in primary TKA is recommended because they are safe and result in good clinical outcomes in preventing AKP. Caution should be taken when using an infrapatellar fat pad excision, because there is an increased risk of AKP at long-term follow-up (>12 months). Future studies should investigate these different strategies to confirm the underlying mechanisms and help prevent the occurrence of AKP after TKA. The timing of AKP onset remains unclear and requires further research.

Application of different patella height indices in patients undergoing total knee arthroplasty

BACKGROUND

One complication of total knee arthroplasty (TKA) is patella baja (PB). Patellar tendon shortening and joint line elevation are two main causes of PB. The purpose of this study was to determine the incidence of PB before and after TKA by measuring the patellar height and provide evidence for choosing a suitable index.

METHODS

In total, 256 consecutive patients who underwent primary TKA were included in this study. Radiographic measurements were performed; the Insall-Salvati (IS) index, modified IS (MIS) index, Blackburne-Peel (BP) index, and Caton-Deschamps (CD) index were computed; and the incidence of PB was calculated before and after the operation. The consistency between the IS and MIS indices and between the BP and CD indices was analyzed.

RESULTS

The preoperative incidence of true PB (TPB) and pseudo-PB (PPB) was 9.4 and 0.8%, respectively. The postoperative incidence of TPB and PPB was 10.2 and 9.0%, respectively. The consistency between the IS and MIS indices was moderate preoperatively (pre-kappa = 0.602) and postoperatively (post-kappa = 0.742). The consistency between the BP and CD indices was moderate preoperatively (pre-kappa = 0.742) and good postoperatively (post-kappa = 0.797).

CONCLUSION

The incidence of PB, especially PPB, increased after TKA. The CD and BP indices are of greater importance for the diagnosis of PB after TKA. The MIS index is a better choice than the IS index to measure the length of the patellar tendon. To measure the height of the joint line, the BP index is better postoperatively and the CD index is better preoperatively.

Patellar tendon length during knee flexion of meniscal-bearing and rotating total knee arthroplasty implants

PURPOSE

The length of the patellar tendon after total knee arthroplasty (TKA) has most commonly been compared with preoperative measurements. However, there are no reports that discuss changes in the length of the patellar tendon during knee flexion after TKA. The purpose of this study was to evaluate changes in the length of the patellar tendon during knee flexion and to clarify the impact of changes in patellar tendon strain on the length of the patellar tendon and post-operative range of motion (ROM) after TKA.

METHODS

Thirty-six patients undergoing sequential bilateral TKA for osteoarthritis were evaluated. Patients received a meniscal-bearing (MB) implant on one side and a rotating platform (RP) implant on the other and were followed for a median of 115 months (range 60-211 months). The lengths of the patellar tendon at maximum extension, 30°, 60°, 90° and maximum flexion were measured, and the post-operative ROM of both knees were assessed. The effects of implant design and the knee flexion angle on the length of the patellar tendon were analysed using a linear mixed-effects model. The relationship between patellar tendon strain and post-operative knee ROM was assessed using Pearson's correlation coefficients.

RESULTS

Post-operative clinical scores were similar for MB and RP implants. Neither the implant design nor the knee flexion angle significantly affected the length of the patellar tendon. The ROMs in the two designs at final follow-up were equivocal (114° in MB, 113° in RP). There was no correlation between patellar tendon strain and ROM in knees with either implant type.

CONCLUSIONS

Patellar tendon lengths after mobile-bearing TKA with implants that permitted different anteroposterior constraints were relatively constant at varying degrees of knee flexion. Differences in patellar tendon strain may not impact ROM. These results provide conclusive evidence that the quality of the patellar tendon may play a less important role in ROM after TKA.

LEVEL OF EVIDENCE

Therapeutic study, Level II.

[Anterior knee pain after total knee arthroplasty : Causes, diagnosis and treatment]

BACKGROUND

Anterior knee pain is one of the most common complications after total knee arthroplasty. An incidence of up to 30 % has been reported in peer-reviewed studies.

TARGET

The purpose of this study was to systematically review the literature and to identify determinants that have been analyzed with regard to anterior knee pain.

CAUSES

Patient- and knee-specific characteristics, prosthetic designs and operative techniques are addressed as well as functional and neurologic determinants. Instability, increased contact pressure in the patellofemoral joint and patella maltracking due to malrotation of components, offset errors, ligament insufficiencies or patella baja are mechanical reasons for anterior knee pain. Functional causes include pathologic gait patterns, quadriceps imbalance and dynamic valgus. They have to be differentiated from infectious and inflammatory causes as well as soft tissue impingement, arthrofibrosis and neurologic diseases.

TREATMENT

A differentiated treatment algorithm is recommended. Often conservative treatment options exist, however, particularly with most mechanical causes revision surgery is necessary.

How is patella height modified after total knee arthroplasty?

INTRODUCTION

Since the first measurement method of patella height in 1929 (Janssen), more than 16 methods have been described. Most of these measures are not suitable to measure patella height after total knee arthroplasty (TKA). One of us (JC) modified the original Caton Deschamps (oCD), index with a new relative index called modified Caton Deschamps (mCD) index, by using new landmarks. The purpose of this study was to determine how patella height is modified after TKA.

MATERIAL AND METHOD

Sixty primary TKAs were consecutively prospectively enrolled. One type of implant was used (cementless postero-stabilized TKA, rotating plateau, cemented patella resurfacing). Patient's characteristics, functional and radiological outcomes were recorded pre-operatively and at one year follow-up. Pre-operative and post-operative outcomes were compared by paired t-test. Post-operative outcomes were compared between groups by one-way analysis of variance.

RESULTS

Average difference between pre and post-operative mCD was 0.19 in this series. In 81.7% of cases, patella was lowered. Patients were classified in three groups according to patella height lowering. Between these three groups, no significant statistical differences (IKS score knee and function, range of motion) could be identified.

DISCUSSION

In TKA, patella assessment in sagittal plane is as important as frontal or horizontal planes. True patella infera (TPI) is mostly due to patella tendon shortening measured by oCD. Pseudo patella infera (PPI) measured by mCD is mostly due to joint line elevation (over femoral cut with an over thickness of the tibial component). In this study a moderate patella lowering (minor than 15%) does not have a significant impact on the functional results (IKS, ROM) nevertheless in 80% patella is lowered. The next step will be to analyze precisely what factors are influencing this lowering and what prevention could be suggested in primary and revision TKA.

Outcome Assessment in Total Knee Arthroplasty: A Systematic Review and Critical Appraisal

BACKGROUND

The Outcome Measures in Rheumatology (OMERACT) initiative developed a core outcome set (COS) of domains to assess effectiveness of interventions for knee osteoarthritis. These domains (pain, physical function, patient global assessment, imaging at 1 year) should be assessed in every trial to make research evidence meaningful and comparable. We systematically evaluated and critically appraised the use of measurement instruments and outcome domains in prospective studies evaluating patients with knee osteoarthritis undergoing total knee arthroplasty (TKA) and assessed their accordance with the OMERACT COS.

METHODS

Literature search was performed until August 26, 2014, in Medline and Embase. Clinical trials and prospective observational studies with ≥50 participants and a follow-up of ≥1 year were included. We collected general study characteristics, comprehensive information on measurement instruments, and corresponding domains used.

RESULTS

This systematic review identified low accordance of used outcome domains with the OMERACT COS of domains published in 1997. Only 4 of 100 included studies included all recommended core domains. Pain (85% of studies) and physical function (86%) were assessed frequently, whereas patient global assessment (21%) and joint imaging (≥1 year; 27%) were rarely assessed. There was substantial heterogeneity in the use of measurement instruments (n = 111) investigating TKA.

CONCLUSION

More efforts are required to implement the existing COS. In addition, a more consistent use of adequate measurement instruments is important to make research evidence on TKA more relevant, better comparable, and thus more useful for guideline developers and clinical decision makers.

Infrapatellar fat pad aggravates degeneration of acute traumatized cartilage: a possible role for interleukin-6

OBJECTIVES

The infrapatellar fat pad (IPFP), which is located underneath the patella, close to cartilage surfaces, functions in distributing mechanical load and has been shown to produce cytokines. This study aims to assess the involvement of the IPFP in the progression of post-traumatic osteoarthritis (OA) through investigating the crosstalk between the IPFP and injured cartilage in vitro.

METHODS

A single blunt impact (36 MPa) on healthy bovine articular cartilage explants was used to generate traumatized cartilage. Conditioned media from IPFP and traumatized cartilage (FP-CM and TC-CM) were prepared separately. After culturing in FP-CM, the posttraumatic cartilage explants were analyzed for expression of cartilage degeneration associated genes and secretion of the interleukin (IL)-6, into the culture medium. The effect of traumatized cartilage on IPFP was studied by treating IPFP-derived adipocytes and IPFP adipose-derived stromal cells (ADSC) with TC-CM followed by analysis of cytokine expression.

RESULTS

FP-CM aggravated glycosaminoglycan (GAG) release in traumatized cartilage, but did not significantly affect healthy cartilage. FP-CM raised gene expression of cyclooxygenase-2, inducible nitric oxide synthase, and IL-6 in traumatized cartilage explants, and lowered expression of tissue inhibitor of metalloproteinases-1, 2, 3, compared to non-conditioned medium. Of particular significance is that medium IL-6 levels increased substantially in both FP-CM and FP-CM treated traumatized cartilage cultures. Extrinsic IL-6 treatment of traumatized cartilage simulated part of the effects of FP-CM. TC-CM elevated levels of IL-6 expression in IPFP derived adipocytes and ADSCs.

CONCLUSIONS

IPFP aggravates post-traumatized cartilage degeneration, and IL-6 is a candidate tissue degeneration mediator.

Influence of the Infrapatellar Fat Pad Resection during Total Knee Arthroplasty: A Systematic Review and Meta-Analysis

Background

To enhance surgical exposure, resection of the infrapatellar fat pad (IPFP) is usually a routine procedure in total knee arthroplasty (TKA). However, there is conflicting evidence regarding whether IPFP resection during TKA impairs clinical outcome. We performed a systematic review and meta-analysis to clarify the influence of IPFP resection on primary TKA.

Methods

Embase, PubMed, and the Cochrane Library were systematically searched up to August 2016 to identify relevant studies. All clinical studies comparing IPFP resection (IPFP-R) and IPFP preservation (IPFP-P) in patients undergoing primary TKA were obtained. The meta-analysis was performed with Revman 5.3 and STATA 12.0 software. The weighted mean was estimated by using random effects (RE) models with 95% CIs, heterogeneity was assessed using the H statistic and the inconsistency index (I²).

Results

Seven studies involving 2,734 patients (3,258 knees) were included. IPFP resection trended to increase the incidence of postoperative anterior knee pain within 2 months postoperatively, compared with patients in whom the IPFP was preserved (odds ratio [OR]s 2.12[0.95, 4.73], p = 0.07). An increased incidence of anterior knee pain was observed in the IPFP resection group > 12 months postoperatively, but the difference was not significant (OR, 3.69 [0.81, 16.82], p = 0.07). In addition, a trend towards more shortening of the patellar tendon was also observed in the IPFP-R group. No significant results were found regarding postoperative knee function.

Conclusion

These results suggest that preserving the IPFP may be superior to IPFP resection in patients undergoing primary TKA, due to the relatively lower rate of anterior knee pain after short-term follow-up.

The effect of infrapatellar fat pad resection on outcomes post-total knee arthroplasty: a systematic review

INTRODUCTION

The infrapatellar fat pad (IPFP) is resected in approximately 88 % of total knee arthroplasty (TKA) surgeries. The aim of this review is to investigate the impact of the IPFP resection on clinical outcomes post-TKA.

MATERIALS AND METHODS

A systematic search of five major databases for all relevant articles published until May, 2015 was conducted. Studies comparing the effect of IPFP resection and preservation on outcomes post-TKA were included. Each study was then assessed individually for level of evidence and risk of bias. Studies were then grouped into post-operative outcomes and given a level of evidence ranking based on the collective strength of evidence.

RESULTS

The systematic review identified ten studies suitable for inclusion, with a total of 10,163 patients. Within these ten studies, six post-operative outcomes were identified; knee pain, vascularisation of the patella, range of motion (ROM), patella tendon length/patella infera, wound complications and patient satisfaction. Moderate evidence increased knee pain with IPFP resection post-TKA was found. Conflicting evidence was found for patella vascularisation and patellar tendon length post-TKA. Moderate evidence for no difference in ROM was found. One low quality study was found for wound complications and patient satisfaction.

CONCLUSIONS

This systematic review is limited by the lack of level one randomised controlled trials (RCTs). There is however moderate level evidence that IPFP resection increases post-operative knee pain. Further level one RCTs are required to produce evidence-based guidelines regarding IPFP resection. Systematic Review Level of Evidence: 3.

Inflammation of the infrapatellar fat pad

The infrapatellar fat pad (IFP) of Hoffa's fat pad is the main adipose structure within the knee joint. It is located between the joint capsule and the synovial membrane, which lines its posterior aspect. The IFP is composed chiefly of adipocytes and receives an abundant supply of blood vessels and nerves. Immune cells can infiltrate the IFP, which can become a major source of numerous proinflammatory mediators (cytokines and adipokines). The physiological role for the IFP remains unclear but may involve shock absorption and the protection of adjacent tissues. Hoffa's disease is characterized by inflammation, hypertrophy, and fibrosis of the pad in response to repetitive trauma. Anterior knee pain is the most common symptom. In advanced forms, metaplasia of the IFP may result in the development of a sometimes sizable osteochondroma. The IFP may also contribute to the pathophysiology of knee osteoarthritis, in particular via procatabolic and proinflammatory effects on its synovial lining. Finally, in patients with knee osteoarthritis, inflammation of the IFP may be a source of pain.

The Infrapatellar Adipose Body: A Histotopographic Study

The infrapatellar fat pad (IFP) can be regarded as a peculiar form of fibro-adipose tissue localized close to the synovial membrane and articular cartilage. The aims of the present study were to analyze the microscopic anatomy of the IFP through histological and ultrastructural methods, comparing it with that of the subcutaneous tissue of the abdomen and of the knee. Ten specimens of IFP were sampled from bodies of the Donation Program of the University of Padua without a history of osteoarthritis. The IFP consisted of white adipose tissue, of lobular type, with lobules delimited by thin connective septa. The IFP lobule areas were smaller (p < 0.05) and the interlobular septa were thicker (p > 0.05) than those of subcutaneous tissues of the abdomen, whereas the IFP lobule areas were larger (p < 0.05) and the interlobular septa were thinner than those of the subcutaneous tissue of the knee (p < 0.05). The IFP adipocytes present a mean area of 3,708 ± 976 µm2 with a large intercellular space, whereas the mean area of the abdominal tissues was greater (6,082 ± 628 µm2; p < 0.05). At scanning electron microscopy the IFP adipocytes were covered by thick fibrillary sheaths, creating a basket around the adipocytes. The structural characteristics of the IFP (lobular aspect of the adipose tissue, thickness of the septa with scarce elastic fibers) could act as a plastic portion aimed at the absorption of pressure variation during knee articular activity. The extensive distribution of nerves suggests a possible role of the IFP as a mechanoreceptor, corresponding to a tridimensional connective mesh working in the proprioceptive regulation of the activity of the knee joint.

Pathophysiology of obesity on knee joint homeostasis: contributions of the infrapatellar fat pad

Osteoarthritis (OA) is a debilitating condition characterized by inflammation, breakdown, and consequent loss of cartilage of the joints. Epidemiological studies indicate obesity is an important risk factor involved in OA initiation and progression. Traditional views propose OA to be a biomechanical consequence of excess weight on weight-bearing joints; however, emerging data demonstrates that systemic and local factors released from white adipose depots play a role. Hence, current views characterize OA as a condition exacerbated by a metabolic link related to adipose tissue, and not solely related to redistributed/altered weight load. Factors demonstrated to influence cartilage and bone homeostasis include adipocyte-derived hormones (“adipokines”) and adipose depot released cytokines. Epidemiological studies demonstrate a positive relation between systemic circulating cytokines, leptin, and resistin with OA types, while the association with adiponectin is controversial. Local factors in joints have also been shown to play a role in OA. In particular, this includes the knee, a weight-bearing joint that encloses a relatively large adipose depot, the infrapatellar fat pad (IFP), which serves as a source of local inflammatory factors. This review summarizes the relation of obesity and OA as it specifically relates to the IFP and other integral supporting structures. Overall, studies support the concept that metabolic effects associated with systemic obesity also extend to the IFP, which promotes inflammation, pain, and cartilage destruction within the local knee joint environment, thus contributing to development and progression of OA.

The Impact of an Intact Infrapatellar Fat Pad on Outcomes after Total Knee Arthroplasty

Background. The infrapatellar fat pad (IPFP) is currently resected in approximately 88% of Total Knee Arthroplasties (TKAs). We hypothesised that an intact IPFP would improve outcomes after TKA. Methods. Patients with an intact IPFP participated in this cross-sectional study by completing two surveys, at 6 and 12 months after TKA. Both surveys included questions regarding kneeling, with the Oxford Knee Score also included at 12 months. Results. Sixty patients participated in this study. At 6 and 12 months, a similar number of patients were able to kneel, 40 (66.7%) and 43 (71.7%), respectively. Fifteen (25.0%) patients were unable to kneel due to knee pain at 6 months; of these, nine (15%) were unable to kneel at 12 months. Moreover, at 12 months, 90.0% of the patients reported minimal or no knee pain. There was no correlation between the inability to kneel and knee pain (p=0.13). There was a significant correlation between the inability to kneel and reduced overall standardised knee function scores (p=0.02). Conclusions. This was the first study to demonstrate improved kneeling and descending of stairs after TKA with IPFP preservation. These results in the context of current literature show that IPFP preservation reduces the incidence of knee pain 12 months after TKA.

Infrapatellar fat pad preservation reduces wound complications after minimally invasive total knee arthroplasty

INTRODUCTION

The aim of this study was to determine whether pain intensity and wound complication rates differ between patients with and without preservation of the infrapatellar fat pad (IPFP) after minimally invasive total knee arthroplasty (TKA). The authors also sought to determine whether IPFP preservation affects operation time.

MATERIALS AND METHODS

This retrospective study included 448 knees with primary TKA. The IPFP was totally resected in 201 knees (IPFP-R group), and was preserved in 247 knees (IPFP-P group). Pain score was determined using the visual analog scale during the first 72 h after surgery. Wound complication rates and operation times were also evaluated. A wound complication was defined as persistent wound drainage for three or more days after surgery.

RESULTS

There was no difference in pain levels between the two groups. However, there were fewer wound complications in the IPFP-P group (3 %) than in the IPFP-R group (13 %). The operation time was longer in the IPFP-P group than in the IPFP-R group (70 vs. 64 min, respectively).

CONCLUSIONS

Although IPFP preservation delayed operation time, it decreased wound complications after MIS TKA. These findings are important to consider when deciding whether or not to resect the IPFP. Whenever possible, IPFP preservation is probably the preferred technique to reduce wound complications.

Management of extreme patella baja using in-situ hamstring tendon autograft

Successful total knee arthroplasty requires a functioning extensor mechanism. Patella baja following total knee arthroplasty can cause extensor mechanism dysfunction and produce poor outcomes. We present a case of severe patella tendon shortening following revision total knee arthroplasty with almost complete ankylosis of the distal pole of the patella to the proximal tibia. This resulted in effective extensor mechanism dysfunction with pain and severely limited knee flexion. We report a novel method of reconstruction of the patella tendon at the time of revision arthroplasty together with the one-year clinical outcome and review of the literature.