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

The biphasic role of the infrapatellar fat pad in osteoarthritis

Osteoarthritis (OA) is a progressive degenerative disease resulting in joint deterioration. It is a whole organ disease characterized by cartilage degeneration and varying degrees of synovitis, involving pathological changes in all joint tissues, such as cartilage, subchondral bone, ligaments, meniscus, synovium, and infrapatellar fat pad (IPFP). IPFP is the largest adipose tissue structure in the knee joint and is composed of fat cells, immune cells and blood vessels. Moreover, IPFP is located close to the cartilage and bone surface so that it may reduce the impact of loading and absorb forces generated through the knee joint, and may have a protective role in joint health. IPFP has been shown to release various cytokines and adipokines that play pro-inflammatory and pro-catabolic roles in cartilage, promoting OA progression. Intra-articular injections of IPFP-derived mesenchymal stem cells and exosomes have been shown to reduce pain and prevent OA progression in patients with knee OA. Previous studies have shown that IPFP has a biphasic effect on OA progression. This article reviews the latest research progress of IPFP, discusses the role and mechanism of IPFP in OA, provide new intervention strategies for the treatment of OA. This article will also discuss the handling of IPFP during the procedure of total knee arthroplasty.

Hoffa's fat pad resection during total knee arthroplasty does not affect functioning and gait: a double-blind randomized clinical trial

INTRODUCTION

Hoffa's fat pad is considered a source of anterior knee pain and may limit prosthetic knee function. Resection of Hoffa's fat pad in total knee arthroplasty (TKA), however, is controversial, and little is known about the functional outcomes including gait quality. This double-blind randomized controlled trial (i) compared functional recovery between TKAs where Hoffa was resected or preserved, and (ii) compared recovery of self-reported function with objective (gait-related) outcomes.

MATERIALS AND METHODS

Eighty-five patients (age 66.4 ± 8.0 years, 47% women) scheduled to undergo TKA for primary osteoarthritis were randomly assigned to either fat pad resection or preservation. Subjective measures of functioning were assessed at baseline, 6 weeks, 3 months, and 12 months postoperatively and included the Knee Injury and Osteoarthritis Outcome Score (KOOS), Kujala, and visual analog scale (VAS) for pain. Objective measures of functioning were assessed at baseline, 3 months, and 12 months postoperatively and included instrumented range-of-motion and gait analysis. Longitudinal analyses (generalized estimating equations) were used to compare recovery between groups, and chi-square tests compared attainment of minimal clinical important difference (MCID) and patient acceptable symptom state (PASS). Finally, correlation analyses explored associations between subjective and objective recovery in function.

RESULTS

Resection patients showed poorer improvement in KOOS quality of life in the first 6 weeks (B=-10.02, 95% confidence interval (CI) [-18.91, -1.12], p = .027), but stronger improvement in knee extension after 3 months (B = 3.02, 95%CI [0.45, 5.60], p = .021) compared to preservation patients. Regarding MCID or PASS, no differences were noted between groups at 3 and 12 months (all p > .05). Subjective function substantially improved in the first 3 months, while objective outcomes improved only between 3 and 12 months. Moderate to strong correlations were identified between changes in knee flexion and gait with Kujala and KOOS in the resection but not in the preservation group.

CONCLUSIONS

Similar functional outcomes were achieved after TKA with or without resection of Hoffa's fat pad. Hence, removing the fat pad to promote surgical exposure will not affect functional outcomes including gait quality. Functional recovery of objective outcomes was not always consistent with subjective recovery, suggesting that both self-reported as well as objective, gait-related outcomes may provide meaningful information on functional recovery following TKA.

TRIAL REGISTRATION

This clinical trial was prospectively registered under the Netherlands Trial Registry (# NL3638). This registry has recently been replaced by the Dutch Trial Registry where this study can be accessed via https://onderzoekmetmensen.nl/en/trial/20994 .

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.

Change in patellar height in medial and lateral unicompartmental knee arthroplasty: a clinical trial

INTRODUCTION

Evidence on patellar height changes following unicompartmental knee arthroplasty (UKA) is lacking. Therefore, this study compared the patella height in patients who underwent medial versus lateral UKA. Moreover, a subgroup analysis was conducted to investigate whether sex, age, and BMI of the patients exert an influence on the postoperative patellar height.

METHODS

Radiographs and hospital records of patients undergoing UKA were prospectively collected. Surgeries were performed by one author with long experience in UKA in a highly standardised fashion. The implants were fixed-bearing medial PPK (Zimmer Biomet, Warsaw, Indiana, USA) and fixed-bearing lateral ZUK (Lima Corporate, Udine, Italy). The patellar height was measured using the Insall-Salvati and Caton-Deschamps indices.

RESULTS

A total of 203 patients were included: 119 patients were included in the medial and 84 in the lateral UKA. The mean age of the patients was 68.9 ± 6.7 years, and the mean BMI was 28.1 ± 4.1 kg/m2. 54% (110 of 203 patients) were women. On admission, between-group comparability was found in age, BMI, sex, and length of the follow-up. No between-group and within-group difference was detected pre- and post-operatively in the Insall-Salvati and Caton-Deschamps indices in patients who have undergone medial versus lateral UKA. Concerning the subgroup analyses, no between-group and within-group difference was detected pre- and post-operatively in all comparisons according to sex, age, and BMI.

CONCLUSION

No difference was found in patella height in patients who have undergone medial compared to lateral UKA. Furthermore, there was no evidence of an association between patient characteristics (sex, age, BMI) and patella height between medial and lateral UKA.

Evaluation of the therapeutic potential of infrapatellar fat pad adipose-derived stem cells and their secretome for regenerating knee articular cartilage in a rat model of osteoarthritis

Background

Mesenchymal stem cell (MSC) therapy has ameliorative effects for treating knee osteoarthritis (KOA) disease. Moreover, there is a growing interest in using MSCs-derived secretome (Sec) containing trophic factors secreted by MSCs for KOA treatment. Recently, some studies have suggested that the combination of MSCs and Sec has the potential to treat the diseases.

Aims

This study aimed to evaluate the ameliorative effects of combined administration of infrapatellar fat pad (IPFP)-derived MSCs, a type of adipose-derived stem cells (ASCs), for treating degenerated cartilage in a rat model of KOA.

Methods

IPFP-ASCs were isolated from the IPFP of male rats. Sec was obtained from IPFP-ASCs in the fourth passage. Eight weeks after the induction of KOA by collagenase II, the rats were divided into 5 groups (n=5), including a control group with no treatment, and four experimental groups that received sodium hyaluronate (Hyalgan®, Hya), ASCs, Sec, and IPFP-ASCs+Sec, respectively by an infrapatellar injection. To perform the pathological and radiological evaluations, the animals were sacrificed 8 weeks later.

Results

Our findings indicated that combined administration of the IPFP-ASCs and Sec statistically (P<0.05) improved scores of medial tibial and femoral condyles and medial fabella osteophytes. Also, it statistically (P<0.05) enhances the cartilage surface, matrix, cell distribution and population viability, and subchondral bone indices. No statistical difference was observed between IPFP-ASCs+Sec and IPFP-ASCs.

Conclusion

Administration of IPFP-ASCs+Sec has a therapeutic potential to treat KOA in rats. However, there is no difference in the combined administration of IPFP-ASCs and Sec with IPFP-ASCs alone.

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.

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.

Patellar height after unicompartmental knee arthroplasty: comparison between fixed and mobile bearing

PURPOSE

The purpose of this study was to determine the changes in patellar heights by comparing standardised pre- and post-operative radiographs in a consecutive series of patients undergoing unicompartmental knee arthroplasty (UKA) with two different approaches and implant designs [fixed bearing (FB) vs mobile bearing (MB)] and to correlate the patellar heights with clinical outcomes.

METHODS

One hundred and seventy-two UKA patients were prospectively enrolled in the study. 75 patients underwent a minimally invasive FB medial UKA (referred to hereinafter as the 'FB group'); 97 patients were treated with a minimally invasive MB medial UKA. The pre-operative and mid-term (1-year) post-operative patellar heights and clinical scores of these groups of patients were compared using the Insall-Salvati (IS) and Caton-Deschamps (CD) indices and the Oxford Knee Score (OKS).

RESULTS

No differences were found between the two groups either with regard to the pre-operative data (p > 0.05) or between pre- and post-operative radiographic scores at the time of each follow-up (p > 0.05). Both the groups reported a significant clinical improvement (p<0.05) as did all the sub-groups (p < 0.05). In the MB group, a higher CD index in females was found at the final follow-up stage (p = 0.043) and a higher pre-operative CD index was found in patients with BMI ≥ 28 (p = 0.040). A statistically negative correlation was found between the pre-operative OKS and pre-operative IS index (rho=- 0.165; p=0.031).

CONCLUSIONS

Both FB and MB arthroplastys with different surgical approaches did not change the patellar height regardless of the age, gender and BMI at short-medium-term follow-up. The post-operative patellar height seems not to be correlated with the clinical outcomes. A higher pre-operative IS index was correlated with knee pain and function.

LEVEL OF EVIDENCE

Level II-prospective comparative study.

STUDY REGISTRATION

Researchregistry6433- www.researchregistry.com .

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.

Effect of physical therapy on the flexibility of the infrapatellar fat pad: A single-blind randomised controlled trial

The infrapatellar fat pad plays a biomechanical role in the knee joint. After knee injury or surgery, its dynamics decrease because of an inflammatory response. Physical therapy might be one of the valuable treatments for the recovery of knee joint mobility. This study aimed to evaluate the immediate effect of physical therapy on the dynamics of the infrapatellar fat pad in healthy participants using ultrasonography. In this prospective, single-blind, randomised controlled trial, 64 healthy young participants were enrolled and randomly assigned to one of the following three interventions: manual therapy, hot pack treatment, and control. Ultrasound images of the infrapatellar fat pad were obtained before and after the intervention. The thickness change ratio of the infrapatellar fat pad was calculated to compare the changes between and within groups before and after the intervention. No significant inter-group differences were observed. The effect sizes were relatively small. Manual therapy or hot pack intervention might not have an immediate effect on infrapatellar fat pad flexibility in healthy participants. Thus, it is necessary to consider more intensive treatments to change the dynamics of the infrapatellar fat pad.

Mechanical behavior of infrapatellar fat pad of patients affected by osteoarthritis

The infrapatellar fat pad (IFP) is an adipose tissue present in the knee that lies between the patella, femur, meniscus and tibia, filling the space between these structures. IFP facilitates the distribution of the synovial fluid and may act to absorb impulsive actions generated through the joint. IFP in osteoarthritis (OA) pathology undergoes structural changes characterized by inflammation, hypertrophy and fibrosis. The aim of the present study is to analyze the mechanical behavior of the IFP in patients affected by end-stage OA. A specific test fixture was designed and indentation tests were performed on IFP specimens harvested from OA patients who underwent total knee arthroplasty. Experiments allowed to assess the typical features of mechanical response, such as non-linear stress-strain behavior and time-dependent effects. Results from mechanical experimentations were implemented within the framework of a visco-hyperelastic constitutive theory, with the aim to provide data for computational modelling of OA IFP role in knee mechanics. Initial and final indentation stiffness were calculated for all subjects and statistical results reveled that OA IFP mechanics was not significantly influenced by gender, BMI and sample preparation. OA IFP mechanical behavior was also compared to that of other adipose tissues. OA IFP appeared to be a stiffer adipose tissue compared to subcutaneous, visceral adipose tissues and heel fat pads. It is reasonable that fibrosis induces a modification of the tissue destabilizing the normal distribution of forces in the joint during movement, causing a worsening of the disease.

Recent Updates of Diagnosis, Pathophysiology, and Treatment on Osteoarthritis of the Knee

Osteoarthritis (OA) is a degenerative and chronic joint disease characterized by clinical symptoms and distortion of joint tissues. It primarily damages joint cartilage, causing pain, swelling, and stiffness around the joint. It is the major cause of disability and pain. The prevalence of OA is expected to increase gradually with the aging population and increasing prevalence of obesity. Many potential therapeutic advances have been made in recent years due to the improved understanding of the underlying mechanisms, diagnosis, and management of OA. Embryonic stem cells and induced pluripotent stem cells differentiate into chondrocytes or mesenchymal stem cells (MSCs) and can be used as a source of injectable treatments in the OA joint cavity. MSCs are known to be the most studied cell therapy products in cell-based OA therapy owing to their ability to differentiate into chondrocytes and their immunomodulatory properties. They have the potential to improve cartilage recovery and ultimately restore healthy joints. However, despite currently available therapies and advances in research, unfulfilled medical needs persist for OA treatment. In this review, we focused on the contents of non-cellular and cellular therapies for OA, and briefly summarized the results of clinical trials for cell-based OA therapy to lay a solid application basis for clinical research.

Role of adipose tissues in osteoarthritis

PURPOSE OF REVIEW

Epidemiologic studies reveal that the link between obesity and osteoarthritis cannot be uniquely explained by overweight-associated mechanical overload. For this reason, much attention focuses on the endocrine activity of adipose tissues. In addition to the systemic role of visceral and subcutaneous adipose tissues, many arguments highlight the involvement of local adipose tissues in osteoarthritis.

RECENT FINDINGS

Alteration in MRI signal intensity of the infrapatellar fat pad may predict both accelerated knee osteoarthritis and joint replacement. In this context, recent studies show that mesenchymal stromal cells could play a pivotal role in the pathological remodelling of intra-articular adipose tissues (IAATs) in osteoarthritis. In parallel, recent findings underline bone marrow adipose tissue as a major player in the control of the bone microenvironment, suggesting its possible role in osteoarthritis.

SUMMARY

The recent description of adipose tissues of various phenotypes within an osteoarthritic joint allows us to evoke their direct involvement in the initiation and progression of the osteoarthritic process. We can expect in the near future the discovery of novel molecules targeting these tissues.