Management of periprosthetic femoral fractures following total knee arthroplasties using locking plates or intramedullary nailing. Comparative study of 567 cases

INTRODUCTION

Proximal femur fractures in elderly patients pose a common problem that requires surgical management. The main objective of this study was to compare the results of treatment by locked plate (LP) and by anterograde (AIN) or retrograde (RIN) intramedullary nailing. The secondary objective was to analyze the complications related to each group. The hypothesis of this study was that the radiological and clinical results of each group were comparable.

MATERIALS AND METHODS

The data of 438 patients from 8 centers were studied retrospectively with 365 LP and 69 cases of intramedullary nailing (49 AIN and 20 RIN). The groups were comparable in terms of mean age (75±2years), mean preoperative Parker score (5.3±0.5) and mean KOOS score (74±2). Most patients lived at home before their fracture [n=375 (86%)]. At follow-up, the joint range of motion, the KOOS and Parker scores, living premises, the time required to regain full weight-bearing, the time required for consolidation as well as the reduction alignment: frontal, sagittal, horizontal.

RESULTS

The average follow-up was: 79±2weeks (65 to 82). The functional and radiological results were comparable, although nailing allowed a faster return to weight-bearing (1±2weeks for nailing versus 7±2weeks for LP, p=0.048) and a better postoperative Parker score (5.5±0.5 for nailing versus 4.7±0.2 for LP, p=0.045). Rotational malalignment in femoral nailing was often in the direction of internal rotation, compared to the LP (p=0.045). Complications were comparable with the exception of mortality, which was more frequent for LP [22.5% in the LP group versus 13% in the nailing group (p=0.045)]. Complications were categorized as: mechanical complications 6.8% of LP, 5.7% of nailing (p>0.05), infections [11% of LP, 5.8% of nailing (p>0.05)], surgical revisions [2% of LP, 10% of nailing (p>0.05)].

DISCUSSION AND CONCLUSION

The hypothesis was refuted. These results show that nailing conferred a faster recovery of weight-bearing, a better Parker score, and is associated with a lower mortality rate. The morbidity rate is comparable between the two techniques. Indeed, when the indication for osteosynthesis by LP or by nailing is made, and both choices are technically justifiable, it would be prudent to favor the technique, which carries the least risk, which in this case is nailing. This conclusion must, however, be taken in to consideration with regard to the reduced number of nailing. A larger series of nailing, particularly retrograde, would be necessary to be able to confirm this last difference between the 2 groups.

LEVEL OF EVIDENCE

IV; comparative retrospective study.

Use of semi-constrained total knee arthroplasty in gonarthrosis with collateral ligament insufficiency: Clinical and functional outcomes

INTRODUCTION

Achieving stability in total knee arthroplasty (TKA) is crucial for long-term implant survival. In cases of severe deformity or ligament laxity, constrained implants may be required. Traditionally, increasing constraint involved intramedullary stems. However, there are intermediary alternatives, including employing a constrained polyethylene insert without stems, thereby avoiding complications related to them. The study aims to evaluate our experience with a non-modular constrained (NMC) implant in primary TKA.

MATERIAL AND METHODS

We conducted a retrospective review of the clinical and radiographic outcomes of 108 non-stemmed primary TKAs performed at our institution between 2013 and 2021 in patients with at least 10° deformity or 10mm ligament laxity. Data included demographics, preoperative and postoperative deformities, clinical outcomes and revision rates.

RESULTS

A total of 103 patients (108 knees) with a mean age of 74 were followed up for a minimum of 2 years. The mean postoperative range of motion was 105°/0°. The median Oxford Knee Score, Knee Society Score and Knee Society Function Score were 43.5, 92 and 90, respectively. 17 knees had varus deformity (mean tibiofemoral angle of 2.7°), and 87 knees had excessive valgus deformity (mean tibiofemoral angle of 15.1°). The remaining 4 knees had a neutral alignment. The mean postoperative tibiofemoral angle was 6.8°. The overall revision rate was 6.5% (7 patients): 3 deep periprosthetic infections, 2 patellar dislocations, 1 stiffness and 1 aseptic loosening.

CONCLUSION

Our experience demonstrates favorable mid-term outcomes with the NMC implant, providing a safe alternative to stemmed implants in primary TKA, particularly in cases of severe deformity or ligament laxity.

The effect of mobile application-based rehabilitation in patients with total knee arthroplasty: A systematic review and meta-analysis

OBJECTIVE

Mobile applications have been used frequently in post-operative orthopedic rehabilitation in recent years. However, no systematic review has emphasized the importance of mobile applications in the rehabilitation process after total knee arthroplasty (TKA). This systematic review and meta-analysis aimed to evaluate the effectiveness of mobile application-based rehabilitation practices in patients with TKA.

MATERIAL AND METHODS

PubMed, Web-of-Science, Scopus, ScienceDirect and Cochrane databases were searched. The Physiotherapy Evidence Database (PEDro) and the Revised Cochrane risk-of-bias tool randomized trials 2 (RoB2) tools were used to demonstrate the methodological quality and risk of bias.

RESULTS

A total of 584 articles were screened. Finally, six papers were included in the systematic review. PEDro scores ranged from 4 to 7 (median: 5.5), indicating fair to good methodological quality. All studies were classified as "some concerns" in RoB2. Mobile application-based rehabilitation demonstrated better scores on pain, range of motion (ROM), objective and subjective function, satisfaction and compliance in general. Meta-analysis proved that mobile application-based telerehabilitation demonstrated better results on subjective function (ES:0.57, 95% CI: 0.11-1.02).

CONCLUSION

Compared to conventional rehabilitation, application-based telerehabilitation provides more effective results in function, pain and ROM. Furthermore, mobile application-based rehabilitation should also be considered regarding patient satisfaction and compliance.

Design, fabrication and experiments of a hydraulic active-passive hybrid prosthesis knee

BACKGROUND

Due to low friction, passive mechanical prostheses move compliantly followed by the stump and are used widely. Advanced semi-active prostheses can both move passively like passive prostheses and provide active torque under specific conditions. However, the current mechanical-hydraulic coupling driven semi-active prostheses, in order to meet the low passive friction requirements with a low active transmission ratio, lead to a significant problem of insufficient active torque.

OBJECTIVE

A hybrid active and passive prosthesis was developed to solve the incompatibility problem of low passive friction and high active driving torque of semi-active prostheses.

METHODS

The mechanical structure and control strategy of the prosthesis were demonstrated. The performance of the prosthesis was tested by bench and human tests.

RESULTS

Passive subsystem damping adjustment ranges from 0.4 N⋅(mm/s)-1 to 300 N⋅(mm/s)-1. The switching time between the damping and the active subsystem is 32 ± 2 ms. The continuous active torque output is more than 24 Nm. In level walking, the peak torque is about 28 Nm.

CONCLUSION

The proposed active-passive hybrid hydraulic prosthesis could satisfy both low passive friction and high active actuation.

Total Knee Arthroplasty with Non-Stemmed Tibial Components among Obese Patients: Clinical and Radiologic Evaluation and Review of Literature

Objective

This study aimed to evaluate the radiologic and clinical outcomes of TKA with non-stemmed tibial components in relation to their body mass index (BMI).

Methods

In this retrospective cohort study, the outcome of TKA with non-stemmed tibial components based on their BMI was evaluated (BMI<30 vs. BMI≥30). The patients' function was assessed using the International Knee Documentation Committee (IKDC) and Lysholm knee questionnaires. Radiologic evaluation for probable signs of loosening was performed using two quantitative scoring systems by Ewald and Bach et al. Moreover, we reviewed the current literature on the application of non-stemmed tibial components in obese patients.

Results

Twenty-one patients (two men and 19 women) with BMI≥30 and a mean age of 65.1±9.5 years, and 22 patients (three men and 19 women) with BMI<30 and a mean age of 63.6±8.5 years were studied. The mean follow-up periods with BMI≥30 (47.0±19.8 months) and BMI<30 (49.2±18.7 months) were comparable (p=0.618). No patients in either group experienced clinical loosening. Besides, none of the patients had any kind of revision surgery. The patients in both BMI groups had comparable IKDC scores (both the total score and its sub-scores; p>0.05). Furthermore, the total Lysholm knee scores were similar in both groups (p=0.122). Using both scoring systems, the peri-prosthetic bone radiolucency near the tibial components was similar in both groups (p>0.999).

Conclusion

The present study found no significant difference in the radiologic or clinical outcome of non-stemmed TKA in patients with BMIs under and over 30.

Similar outcomes of constrained condylar knee and rotating hinge prosthesis in revision surgery for extension instability after primary total knee arthroplasty

BACKGROUND

Instability is one of the most common reasons for total knee arthroplasty (TKA) failure. Constrained prosthesis can be used for significant ligamentous laxity, but there is not much evidence on the appropriate level of restriction for unstable varus-valgus TKA. The objective of this study was to compare the outcome and survival at a minimum follow-up of five years between rotating hinge knee prosthesis (RHK) and constrained condylar knee prosthesis (CCK) for extension instability following primary TKA.

HYPOTHESIS

For symptomatic extension instability after primary TKA, good functional outcomes and survival can be achieved with both designs.

MATERIAL AND METHODS

Consecutive patients with unstable primary TKA who underwent revision with either RHK (n=34) or CCK (n=30) were retrospectively compared. Assessments were performed by the Knee Society Scores (KSS), and visual analogue scales (VAS) for pain and patient satisfaction. Radiological evaluation was made. Complications and re-operations were analyzed.

RESULTS

Mean post-operative follow-up was 10.3 (range 5-16) years for both groups. At the final follow-up, there was no significant difference between groups in the KSS-knee (p=0.228) or KSS-function (p=0.324) score, VAS-pain (p=0.563), VAS-satisfaction (p=0.780), major complication rate (p=0.194), or TKA survival at 10 years (p=0.091).

CONCLUSION

The present study showed comparable good functional outcomes and survival at long-term between RHK and CCK arthroplasties. Both designs can be recommended for revision of total knee arthroplasty with symptomatic extension instability.

LEVEL OF EVIDENCE

Level III.

Insufficient evidence to confirm benefits of custom partial knee arthroplasty: a systematic review

PURPOSE

The purpose of this systematic review was to synthesise the available literature and critically appraise current evidence on the functional and radiographic outcomes as well as reoperation and revision rates of custom partial knee arthroplasty, i.e., unicompartmental knee arthroplasty (UKA), bicompartmental knee arthroplasty (BKA), and patellofemoral arthroplasty (PFA).

MATERIAL AND METHODS

This systematic review was performed in accordance with the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), and a protocol was registered with Prospero. On 25 May 2021, two authors independently searched and screened Level I-IV studies that reported on outcomes of custom partial knee arthroplasty using the databases of MEDLINE^®, EMBASE^®, and the Cochrane Library without restriction on date of publication. Findings from eligible articles were synthesised and tabulated, and quality assessments were done according to the guidelines of the Joanna Briggs Institute (JBI) Checklists.

RESULTS

Fifteen articles were eligible for data extraction, of which two comparative and four case series were on custom UKA (follow-up, 0-9 months), one comparative and five case series on custom BKA (follow-up, 0.25-72 months), and three case series on custom PFA (follow-up, 2-119 months). Three studies on custom UKA reported mean Knee Society Score (KSS) Knee of 86-94 and mean KSS Function of 94-95, and two studies on custom BKA reported mean KSS Knee of 90-94 and KSS function of 81, whereas one study on custom PFA reported KSS Knee of 91 and KSS Function of 89. Custom implants tended to have less bone-implant mismatch compared to off the shelf (OTS) implants. Revision rates were 3-25% for custom UKA (at 0-109 months), 3-5% for custom BKA (at 12-72 months), and 0-14% for custom PFA (at 2-119 months).

CONCLUSION

Due to the small number of comparative studies and lack of consistency in reported outcomes, it remains difficult to ascertain the benefits of custom partial knee arthroplasty. Anecdotal evidence suggests that, compared to OTS implants, custom implants result in less bone-implant mismatch and that 78-91% of patients are either satisfied or very satisfied after custom partial knee arthroplasty.

LEVEL OF EVIDENCE

IV.

Accelerometer-Based Navigation versus Conventional Total Knee Arthroplasty for Posttraumatic Knee Osteoarthritis

BACKGROUND

Posttraumatic osteoarthritis (PTOA) frequently comprises femoral or tibial deformity, which makes it difficult to perform total knee arthroplasty (TKA). Accelerometer-based navigation (ABN) could be effective in restoring a neutral mechanical axis (MA) in TKA, but a limited number of studies have been reported in association with PTOA. Therefore, we aimed to compare the lower limb MA between ABN-assisted TKA (ABN-TKA) and conventional TKA in patients with PTOA.

METHODS

We conducted a retrospective analysis of 28 PTOA patients who underwent TKA using a conventional system (cTKA group, n = 16) and the ABN system (iTKA group, n = 12). Standing long-leg radiographs were assessed for MA and prosthesis alignment as primary outcomes. A postoperative MA deviating beyond ± 3° was defined as an outlier. Perioperative outcomes, Oxford Knee Score (OKS) at 2-year follow-up, and complications were also assessed.

RESULTS

The cTKA group and the iTKA group had a mean age of 63.07 years and 65.25 years, respectively. The iTKA group had significantly better MA accuracy when compared to the cTKA group (1.60° ± 2.09° vs. 3.59° ± 1.34°, p = 0.01). The iTKA group showed significantly less MA outlier than the cTKA group (78.6% vs. 25.0%, p = 0.02). The prosthesis alignment and OKS were comparable between the groups. There were 2 periprosthetic joint infections in the cTKA group and 1 periprosthetic fracture of the distal femur in the iTKA group.

CONCLUSIONS

For PTOA of the knee, both conventional TKA and ABN-TKA significantly improved the postoperative mechanical alignment and functional outcomes. The ABN-TKA seemed to offer higher accuracy and less MA outlier when compared to conventional TKA, and thus ABN could be a good alternative option.

The mid-term survival of cemented, uncemented, and hybrid fixation of the ACS mobile bearing total knee arthroplasty

Background

Till today, Cemented Fixation in Total Knee Arthroplasty (TKA) is significantly more used than Hybrid or Uncemented Fixation. The purpose of this study was to compare Cemented, Uncemented and Hybrid Fixation of the ACS Mobile Bearing TKA at Mid-term follow-up.

Methods

This study was an extended data report of our prospective single-center, single-blinded randomized controlled clinical trial comprising 105 patients. The primary outcome was survival at five years of follow-up calculated by Kaplan-Meier and Log-rank test. The secondary outcome was function based on patient-reported outcome measures (PROMs).

Results

Eighty-three patients were included, of which 25 belonged into group A (Cemented), 28 in group B (Uncemented), and 30 in group C (Hybrid). Mean follow-up was 5.8 ± 0.7 (range 5-7) years. The 5-year survival rates were 96.8% (95%CI: 90.5; 100) in the Cemented group, 94.2% (95%CI: 86.4; 100) in the Uncemented group, and 93.8% (95%CI: 85.4; 100) in the Hybrid group for revision for any reason (p = 0.80). Functional outcome was similar among the groups.

Conclusion

In our cohort of ACS Mobile Bearing TKA, there was no difference between Cemented, Uncemented, and Hybrid Fixation with regard to survival and function at Mid-term follow-up.

Trial registration

Dutch Trial Register (NTR3893), 2013-03-12.

Level of evidence

II.

Mechanically aligned total knee arthroplasty with the extension-first technique does not equally restore neutral knee alignment in all preoperative knee phenotypes

PURPOSE

The aim of this study was to determine the change in the long leg axis according to the preoperative knee phenotype using the mechanically aligned extension-first technique in total knee arthroplasty. The hypothesis of this study was that the knee phenotype would have an impact on the postoperative leg axis.

METHODS

This was a retrospective comparative study comprising 224 whole-leg radiographs of 112 patients. The leg axes of the pre- and postoperative radiographs were measured and categorized into three preoperative limb phenotypes (based on the hip-knee-ankle angle [HKA]) according to Hirschmann et al. (varus-HKA < 178.5°, neutral-HKA 178.5°-181.5°, and valgus-HKA > 181.5°). Additionally, femoral phenotypes (based on the femoral mechanical angle [FMA], i.e., the mechanical medial distal femoral angle [mMDFA], as well as the tibial phenotypes [based on the tibial mechanical angle, i.e., the medial proximal tibial angle (MPTA)] was calculated. The change in the long leg axis was analyzed and compared with the preoperative limb phenotype.

RESULTS

Significantly more patients with preoperative varus alignment shifted to neutral alignment (46.3%, n = 31) than did patients with preoperative valgus alignment (38.9%; n = 14). Moreover, 43.3% of patients (n = 29) with the varus phenotype remained in a varus alignment, compared with the 58.3% of patients with preoperative valgus phenotype (n = 21) remaining in valgus alignment. These findings were similar for both females (p < 0.001) and males (p = 0.015).

CONCLUSION

Using an extension-first mechanically aligned surgical technique, varus phenotypes predominantly result in neutral leg axes or remain varus, neutral phenotypes remain neutral, and valgus phenotypes remain valgus or change to neutral phenotypes. This study showed that preoperative knee phenotypes in valgus knees influence this technique more strongly than estimated in previous investigations, which is in line with modern alignment philosophies for TKA.

LEVEL OF EVIDENCE

Level IV, retrospective comparative study.

A review of current practices in periprosthetic joint infection debridement and revision arthroplasty

BACKGROUND

Periprosthetic joint infection remains a significant challenge for arthroplasty surgeons globally. Over the last few decades, there has been much advancement in terms of treatment and diagnosis, however, the fight rages on. As management of periprosthetic joint infections continues to evolve, it is critical to reflect back on current debridement practices to establish common ground as well as identify areas for future research and improvement. BODY: In order to understand the debridement techniques of periprosthetic joint infections, one must also understand how to diagnose a periprosthetic joint infection. Multiple definitions have been elucidated over the years with no single consensus established but rather sets of criteria. Once a diagnosis has been established the decision of debridement method becomes whether to proceed with single vs two-stage revision based on the probability of infection as well as individual patient factors. After much study, two-stage revision has emerged as the gold standard in the management of periprosthetic infections but single-stage remains prominent with further and further research.

CONCLUSION

Despite decades of data, there is no single treatment algorithm for periprosthetic joint infections and subsequent debridement technique. Our review touches on the goals of debridement while providing a perspective as to diagnosis and the particulars of how intraoperative factors such as intraarticular irrigation can play pivotal roles in infection eradication. By providing a perspective on current debridement practices, we hope to encourage future study and debate on how to address periprosthetic joint infections best.

Computer-Assisted Surgery Enables Beginner Surgeons, Under Expert Guidance, to Achieve Long-Term Clinical Results not Inferior to Those of a Skilled Surgeon in Knee Arthroplasty

PURPOSE

The purpose of this study is to determine whether the use of a surgical navigation system in total knee replacement (TKR) enables beginner and intermediate surgeons to achieve clinical PROM outcomes as good as those conducted by expert surgeons in the long term.

METHODS

We enrolled 100 consecutive patients whose total navigated knee arthroplasty (TKA) was performed in our institution from 2008 to 2010. According to the principal surgeon's surgical experience, the patients were divided into three groups: (1) beginner surgeons, with no more than 30 previous knee replacement performances, (2) intermediate surgeons, with more than 30 but not more than 300, and (3) expert surgeons, with more than 300 knee replacements. Demographic data collected on the cohort included gender, laterality, age, and body mass index (BMI). The outcome measures assessed were Forgotten Joint Score (FJS), implant positioning, limb alignment, and prosthesis survival rate. A margin of equivalence of ± 18.5 points in the FJS scale was prespecified in terms of the minimal clinically important difference (MCID) to compare the FJS results obtained in the long period between the groups of interest.

RESULTS

The mean follow-up was 11.10 ± 0.78, 10.86 ± 0.66, and 11.30 ± 0.74 years, respectively, for each of the groups. The long-term FJS mean score was 80.86 ± 21.88, 81.36 ± 23.87, and 90.48 ± 14.65 for each group. The statistical analysis proved noninferiority and equivalence in terms of the FJS results reported in the long term by patients in Groups 1 or 2 compared to those in Group 3. More specifically, it has been proved that the mean difference between groups is within the interval of equivalence defined in terms of the MCID. The overall prostheses survival rate was 93.7%.

CONCLUSION

Navigated assisted TKA, under expert guidance, can be as effective when performed by beginner or intermediate surgeons as performed by senior surgeons regarding the accuracy of implant positioning, limb alignment, and long-term clinical outcome.

THE RESULTS OF A COMPARISON OF A BRAZILIAN AND AN IMPORTED KNEE PROSTHESIS - 5 YEARS OF FOLLOW-UP

Introduction

To compare the functional results, satisfaction rates, and revisions of total knee arthroplasties performed by the same surgical team using either Brazilian or imported implants, with a minimum follow-up of 5 years after surgery.

Materials and Methods

A retrospective cohort study analyzing the medical records and interviews of patients who underwent total knee arthroplasty with Brazilian or imported implants with a minimum of 5 years after surgery.

Results

One hundred and fifty patients were evaluated (164 knees). In the functional questionnaire, 71% of patients had favorable answers in the group of patients who underwent surgery using the Brazilian prosthesis and 74.8% in the group with imported implants (p=0.634). There was no statistical difference in satisfaction between the groups, with 78.4% of patients satisfied or very satisfied in the Brazilian implant group and 90.7% in the imported implant group (p=0.053). Loosening of the implants was reported in 5.3% versus 4.7% (p>0.999).

Conclusion

The total knee arthroplasties performed by the same surgical team with a minimum follow-up period of 5 years showed similar levels of satisfaction, function, and complications with both the Brazilian and imported implants. Level of Evidence III, cohort study.

Mid-term implant survival, functional and radiological results and mechanical complications of mega-prosthetic reconstruction around the knee with the PENTA® system

AIM

Mega-prosthetic reconstruction is the most common treatment method for massive osteoarticular defects caused by tumor resection around the knee. The new implant is a highly modular rotational-hinged megaprosthesis system with a distinct pentagonal stem geometry and variable implantation options. The aim of this study is to present the mid-term implant survival characteristics, functional and radiological results and mechanical complication profile of the new megaprosthesis.

METHODS

One hundred and one mega-prosthetic knee reconstruction procedures in 90 patients (M/F: 51/39) utilizing the new implant system were retrospectively analyzed. In 68 patients, the megaprosthesis was used for primary reconstruction following tumor resection while it was used for revision of other implants in 22. The mean age was 28.5 (7-66) years and the mean follow-up was 59.2 (24-124) months. The most common primary pathology was osteosarcoma with 63-70% patients, the most common anatomical site of involvement was the distal femur with 56-62% patients.

RESULTS

Henderson Type 2 failure (aseptic loosening) was seen in only 2-2.2% patients while Type 3 (structural failure) was seen in 29-32.2% Although the 5-year anchorage survival rate was 94.3%, overall mechanical implant survival was 76.1% at 5 years due to a relatively high failure rate in the first-generation hinge mechanism of the implant. The 5-year hinge survival rate demonstrated a significant improvement rate from 61.7% to 87.2% between the first and second generations of the implant (p = 0.027). The mean MSTS score was 24 out of 30 (14-29). The mean cumulative ISOLS radiographic score for index megaprosthesis operations was 19.7 (12-24), which corresponded to excellent outcome.

CONCLUSION

The new megaprosthesis system is a reliable choice for the reconstruction of tumor-related massive osteoarticular defects around the knee. Although long-term follow-up is necessary for a definitive evaluation of the implant's survival characteristics, midterm follow-up yields exceptional anchorage properties related to pentagonal stem geometry with very good functional outcomes.

Knee osteoarthritis with patellar dislocation treated by total knee arthroplasty using a lateral parapatellar approach-ingenuity of exposure and closure

Knee osteoarthritis with patellar dislocation is a rare and difficult-to-treat condition. Several reports of total knee arthroplasty (TKA) combined with various realignment procedures have been published. A 77-year-old man with knee pain was referred to our hospital. Plain radiography revealed a laterally dislocated patella, with osteoarthritic changes in the femorotibial joint. He simply underwent TKA via a lateral parapatellar approach without realignment. We devised methods of exposure and closure to maximize the effect of lateral release by the lateral parapatellar approach. TKA using the lateral parapatellar approach might be effective in treating knee osteoarthritis with patellar dislocation.

Effect of the soft tissue artifact on marker measurements and on the calculation of the helical axis of the knee during a gait cycle: A study on the CAMS-Knee data set

The soft tissue artifact (STA) is a phenomenon occurring when the motion of bones or anatomical segments is measured by means of skin markers: the biological tissues between the markers and the bone produce a relative motion bone-markers that leads to inaccuracies in the estimation of rigid body poses or kinematics. The aim of this study was to quantify the STA by exploiting a recently published gait analysis dataset. The dataset was composed of six adult subjects with a total knee arthroplasty who underwent gait analysis trials. The motion of the knee was concurrently recorded by means of (i) fluoroscopy imaging and (ii) an optoelectronic system and redundant markers attached to the thigh and shank. The STA was studied by comparing the results calculated on the marker sets with the results obtained from the fluoroscopy data. The stance and swing phases were considered separately. Rigid STA motion and local STA deformation were studied separately. In addition to previous studies, the instantaneous helical axis (IHA) of the knee was calculated and the effect of the STA on its calculation was assessed.

The largest rigid-motion STA effect was observed on the thigh cluster (~10 deg. and ~ 18 mm). The shank cluster was mainly affected during the swing phase (~7 deg. and ~ 17 mm). The local STA deformation affected differently the markers. The largest effect was ~16 mm and the lowest was ~4 mm. The estimation of the IHA was not reliable when based only on markers, having an estimation error of ~17 deg. and ~ 25 mm. A high variability of results across subjects was observed.

Increasing the height of the anterior lip on a tibial insert in a posterior stabilized knee prosthesis has little effect on the wear rate

A high anterior lip on a total knee prosthesis is an effective way of reducing anterior translation, but the effect on joint wear is unclear. Using finite element analysis (FEA), this study quantitatively compared wear rates and anterior contact stresses in three posterior stabilized knee prostheses with different heights for the anterior lip during six daily activities (walking, stair ascent, stair descent, sit-to-stand, pivot turn and crossover turn). The wear rate and location of maximum wear depth were similar for the three lip heights tested, but the knee with the highest anterior lip also showed slight anterior wear scaring due to articular contact stress during swing phase, which was highly dependent on the shape of the contact interface. This study illustrates that tibial inserts with a high anterior lip maintain a wear rate similar to moderate and low lip posterior stabilized designs.

Value of the synovial C-reactive protein test in the diagnosis of total hip and knee periprosthetic joint infections: A case-control study

INTRODUCTION

The diagnosis of periprosthetic joint infection (PJI) can be challenging and rests on several principles. The use of diagnostic biomarkers, such as the synovial C-Reactive Protein (CRP), seems promising. The purpose of this study was to determine whether synovial CRP was a more discriminating test than serum CRP for the diagnosis of hip and knee PJI.

MATERIALS AND METHODS

In total, 194 patients were included in this single center prospective study: 42 primary arthroplasties (control group [CG]), 111 revisions for aseptic prosthesis (aseptic revision group [ARG]), and 41 revisions for septic prosthesis (septic revision group [SRG]) based on the Musculoskeletal Infection Society (MSIS) criteria.

RESULTS

The serum and synovial CRP levels were significantly higher in the SRG than the other two groups (SRG serum CRP=75.6mg/L vs. ARG serum CRP=6mg/L and CG serum CRP=2.7mg/L, p<0.001; SRG synovial CRP=31.5mg/L vs. CG synovial CRP=2.6mg/L and ARG synovial CRP=1.7mg/L, p<0.001). The positive likelihood ratios (LR+) were very similar for both the synovial CRP cut-off value of 4.4mg/L (LR+=7.04; sensitivity [Se] 82.5%, specificity [Sp] 88.3%) and the serum CRP cut-off value of 9mg/L (LR+=6.3; Se 87.5%, Sp 86.1%).

CONCLUSION

This study showed that synovial CRP testing was not more discriminating than serum CRP in the diagnosis of hip and knee PJI. A serum CRP level greater than 9mg/L was a sign of PJI.

LEVEL OF EVIDENCE

III; case-control study.

Prosthesis size distribution in Oxford phase III unicompartmental knee arthroplasty - Based on more than 1900 Chinese patients

Introduction

It is difficult to determine the optimal size of unicompartmental knee arthroplasty (UKA) prosthesis both pre-operatively and intra-operatively. Inappropriate femoral and tibial components are still the leading cause of failure. Several guidelines based on the Western population may not apply to the Chinese patients. We consequently try to investigate distributions of Oxford-UKA prosthesis in Chinese patients in order to provide a good reference for surgeons preoperatively.

Methods

From January 2010 to December 2019, 1909 patients (2307 knees) with primary anteromedial osteoarthritis accepted Oxford phase III UKA. Statistical analyses were performed on the distributions of the femoral, tibial, and matching of the femoral-tibial prosthesis. The possible factors affecting the sizes of femoral components, including gender, height based on gender were investigated.

Results

1. The distributions of femoral size components include extra-large (XL) 0, large (L) 1.08%, medium (M) 26.09%, small (S) 59.64%, extra-small (XS) 13.18%; the tibial sizes components were F 0, E 0.69%, D 7.80%, C 19.59%, B 24.79%, A 34.16%, AA 12.96%. 2. The matching of femur-tibia components were L-E 0.52%,L-D 0.52%,M-E 0.17%, M-D 7.28%,M - C 16.60%,M - B 1.95%,M-A 0.13%, M-AA 0.04%, S-C 2.99%, S-B 22.67%, S-A 31.12%, S-AA 2.82%, XS-B 0.17%, XS-A 2.90% and XS-AA 10.10%. The optimal matches between femoral and tibial components were: XL with F; L with E; M with C and D; S with A and B. 3. The patient's gender and height based on gender are necessary considerations for selection of femoral components (P＜0.01).

Conclusion

In Chinese patients, the size of femoral components is mainly small (S) for women, medium (M) for men. The tibial components of female patients are mainly A and B, whereas C is predominant for male patients. The more commonly used matching forms are S-A and S-B.

Lower early revision rates after uncemented Oxford Unicompartmental Knee Arthroplasty (UKA) than cemented Oxford UKA: A meta-analysis

BACKGROUND

UKA has been proved to offer good results in treating patients with unicompartmental knee osteoarthritis (OA). However, there is still a controversy about the better fixation mode in UKA procedure between cemented and uncemented prosthesis. Therefore, this meta-analysis was conducted to compare clinical and radiological outcomes of cemented versus uncemented Oxford UKA.

HYPOTHESIS

The study surmised that uncemented Oxford UKA was associated with shorter operation time, higher function scores, lower revision rate and less radiolucency than cemented Oxford UKA.

METHODS

A meta-analysis to compare postoperative outcomes between cemented and uncemented Oxford UKA wsa conducted. The primary outcomes included Oxford knee score (OKS), revision rate, and incidence of radiolucency. The secondary outcomes included operation time, knee society score (KSS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), range of motion (ROM). PubMed, Embase, Web of Science, the Cochrane Library and China national knowledge infrastructure were searched until April, 2020 to identify studies for including. Relevant data were analyzed using RevMan v5.3.

RESULTS

We identified nine studies involving 901 patients meeting our inclusion criteria. No significant difference of OKS was found in both groups. Compared with cemented group, uncemented Oxford UKA group was associated with lower revision rate (95% CI: 0.90 to 3.73; OR=1.83) and less radiolucent lines (95% CI: 0.79 to 9.52; OR=2.75) after following up for at least 2years. The operation time was significantly shorter by 10.12minutes (95% CI: p<0.00001) in the uncemented group when compared against the cemented group. The KSS, WOMAC, ROM were not significantly different between two groups.

CONCLUSIONS

Uncemented Oxford UKA had lower revision rate, shorter operation time and less radiolucent lines than cemented Oxford UKA did. There is still need for more long follow-up clinical trials with high evidence level to determine which method of fixation is of preferable for Oxford UKA in the future.

LEVEL OF EVIDENCE

I.

Implant design affects walking and stair navigation after total knee arthroplasty: a double-blinded randomised controlled trial

BACKGROUND

Dissimilar total knee arthroplasty implant designs offer different functional characteristics. This is the first work in the literature to fully assess the Columbus ultra-congruent mobile (UCR) system with a rotating platform.

METHODS

This is a double-blinded randomised controlled trial, comparing the functional performance of the low congruent fixed (CR DD), ultra-congruent fixed (UC) and UCR Columbus Total Knee Systems. The pre-operative and post-operative functional performance of twenty-four osteoarthritic patients was evaluated against nine control participants when carrying out everyday tasks. Spatiotemporal, kinematic and kinetic gait parameters in walking and stair navigation were extracted by means of motion capture.

RESULTS

The UC implant provided better post-operative function, closely followed by the UCR design. However, both the UC and UCR groups exhibited restricted post-operative sagittal RoM (walking, 52.1 ± 4.4° and 53.2 ± 6.6°, respectively), whilst patients receiving a UCR implant did not show an improvement in their tibiofemoral axial rotation despite the bearing's mobile design (walking, CR DD 13.2 ± 4.6°, UC 15.3 ± 6.7°, UCR 13.5 ± 5.4°). Patients with a CR DD fixed bearing showed a statistically significant post-operative improvement in their sagittal RoM when walking (56.8 ± 4.6°).

CONCLUSION

It was concluded that both ultra-congruent designs in this study, the UC and UCR bearings, showed comparable functional performance and improvement after TKA surgery. The CR DD group showed the most prominent improvement in the sagittal RoM during walking.

TRIAL REGISTRATION

The study is registered under the clinical trial registration number: NCT02422251 . Registered on April 21, 2015.

[End-of-stem pain in hip and knee arthroplasty]

End-of-stem pain after knee and hip arthroplasty with diaphyseal supportive stems is a frequently overlooked and potentially underestimated complication. A commonly recurring clinical phenome is the symptom-free interval after surgery of weeks to months, with new onset of symptoms under stress only later. The patient is often again reliant on walking sticks. End-of-stem pain is a diagnosis of exclusion. Pain is projected into the tip of the stem, and if differential diagnoses such as loosening are excluded, then the patient might be treated with a "bending-plate". Since bone cement has a similar elastic modulus to human cortical bone, a change of method to a cemented implant can also be expedient. In the primary situation, in addition to cemented stems, the use of "split-stems" could be useful. After revision surgery of any kind, a timely cessation of pain confirms the diagnosis.

[Functional assessment in total knee arthroplasty comparing the posterior cruciate ligament preservation versus postero-stabilization]

INTRODUCTION

The two most commonly used types of prostheses are the total knee prosthesis with posterior cruciate ligament preservation and posterior cruciate ligament replacement.

OBJECTIVE

To assess whether there is a difference in functionality between the two procedures.

MATERIAL AND METHODS

Observational, retrospective and cross-sectional study with 134 patients divided into group A (N = 67) with ligament preservation and group B (N = 67) with posterior substituting. Using the American Association Scale for Knee Prosthetics with Insall modification to assess functionality. Statistical analysis: use of 2 with Yates correction.

RESULTS

In group A the results: excellent (31%); good (24%); regular (22%) bad (22%). In group B the results: excellent (34%); good (31%); regular (16%) and bad (19%); without statistical difference between the two groups.

CONCLUSIONS

No statistically significant difference was observed between age, gender, laterality of injury, or between number of patients with excellent results, good regular and bad according to the scale used. The high percentage of poor results in both groups of this series for the knee prosthesis is striking.

A longterm prospective follow-up study of resurfacing miniprosthesis suitable for patients above sixtyfive years with localized cartilage lesions or early osteoarthritis in the knee

Purpose

The aim of the study was to investigate the long-term outcomes of the Focal Femoral Condyle Resurfacing Prosthesis for treatment of localized cartilage lesion in patients > 65 years.

Methods

This was a prospective case series study. Non-reopererated patients initially treated with resurfacing condylar miniprothesis (HemiCAP/UniCAP) were evaluated clinically and radiographically at 7–10 years follow-up (mean 9 years). The clinical examination included the Knee Society Score (KSS) and Visual Analogue Scale (VAS) pain score and EQ5D. The radiographic examination included the Kellgren-Lawrence (KL) grade for investigate of OA progression. A comparison analysis of the preoperative and follow-up subjective outcome data and a Kaplan-Meier implant survival analysis were performed.

Results

Twenty-three patients were included in the study (9 HemiCAP and 14 UniCAP). There were seven revisions (one HemiCap and six UniCap respectively) (30%) and three patients had died. Follow-up examinations were performed on 10 patients. When comparing follow-up with the preoperative state, there were significant increases in the KSS objective (50.0 ± 8.3) vs. 90.0 ± 6.3)) and KSS function (45.0 ± 11.7) vs. 85.0 ± 4.7)) scores, a decrease in the pain VAS score (7.0 ± 0.9) vs. (4.0 ± 1.9)). Radiographic evaluation demonstrated increase in osteoarthritis development with a KL medial score (2.0 ± 0.6) and KL lateral score (1.4 ± 0.6) vs. (2.0 ± 0.9)).The EQ5D-score was 86 ± 8.4 and patients Health-score was 85 ± 18).

Conclusions

Resurfacing implant treatment for early OA in patients above 65 years can require revision to knee arthroplasty in 30% of patients. But in patients that are not revised long-term improvements in subjective clinical outcome was demonstrated. This suggests that even elderly patients with isolated cartilage lesions or early OA might benefit from the limited invasive resurfacing implant treatment.

Level of evidence

IV

[Locking plate fixation of distal periprosthetic femoral fractures : Clinical outcome and mortality]

Hintergrund

Die Versorgung distaler periprothetischer Femurfrakturen (PFF) stellt aufgrund des geriatrischen Patientenkollektivs eine große interdisziplinäre Herausforderung dar und erfolgt (abhängig vom Frakturtyp) häufig mittels winkelstabiler Plattenosteosynthese (WPO), wobei bisher nur wenige Daten zum klinischen Outcome existieren. Ziel der Untersuchung ist die Identifikation von Risikofaktoren für ein schlechtes Outcome und erhöhte Mortalität.

Methoden

In dieser retrospektiven Studie wurden 36 Fälle mit distaler PFF untersucht. Eingeschlossen wurden nur Versorgungen mit WPO. Neben relevanten Vorerkrankungen (ASA-Score, Charlson Index), der Frakturmorphologie und relevante Komplikationen, wurden u.a. die 1- und 3-Jahres-Mortalität, sowie das klinische Outcome mit Hilfe des Lysholm-Scores erfasst.

Ergebnisse

Die 1- und 3- Jahres Mortalität betrug 9% bzw. 26%, wobei dies ausschließlich ASA 3 und 4 Patienten betraf. Der Lysholm Score zeigte eine hohe Variabilität (65 ± 27 Punkte) mit höheren Werten in der ASA 1-2 Subgruppe (82 vs. 63 Punkte) aber unabhängig vom Frakturtyp. Als Risikofaktoren für die 3-Jahres Mortalität konnten der präoperative ASA-Score, der Charlson Komorbiditätsindex und das Patientenalter identifiziert werden.

Diskussion

Die dargestellte Fallserie weist eine hohe absolute Mortalitätsrate auf, auch wenn diese im Vergleich zu bisher publizierten Daten, etwas geringer war. Die Rate an Sekundärdislokationen, fehlender Frakturheilung oder Folgeoperationen war ebenfalls gering. Die WPO erscheint daher als geeignete Versorgung für Frakturen mit stabiler Prothese. Jedoch besteht eine hohe Variabilität im klinischen Outcome unabhängig vom Frakturtyp, sowie signifikant erhöhte Mortalitätsraten bei vorerkrankten Patienten.

Metallosis after knee replacement: a review

INTRODUCTION

Although metallosis is a well-known complication after total hip arthroplasty, little is known about this phenomenon after total (TKA) or unicompartmental knee arthroplasty (UKA). The aim of the present work was to review the current knowledge about the reasons and the diagnostic as well as therapeutic management of metallosis after knee arthroplasty.

MATERIALS AND METHODS

A literature search was performed through PubMed until April 2019. Search terms were "metallosis" in combination with "knee", "knee prosthesis", "knee arthroplasty" and "knee replacement", respectively. All publications were analyzed regarding publication year, level of evidence, number of knees/patients treated, type of prosthesis, metallosis cause, time period between primary implantation and metallosis emergence, laboratory examination, treatment, complications and follow up.

RESULTS

A total of 38 studies reporting on a total of 97 knees were identified. 29 studies reported on metallosis after TKA, 8 after UKA, and one study after both procedures. The time period between the primary implantation and metallosis emergence ranged between 6 weeks and 26 years. The most common reason was the failure of a metal-backed patellar component in 40%, followed by implant/structural- and PE failure (wear/dislocation) in 27% and 18% of the cases, respectively. Complete blood cell count, serum chemistry, erythrocyte sedimentation rate or C-reactive protein serum values were not indicative to diagnose metallosis. The diagnosis was confirmed by histopathological analyses and macroscopic evaluation during surgery. Depending on the particular cause various surgical procedures have been performed. Complete prosthesis exchange was the most common one showing no complications in 89.4% of the cases.

CONCLUSIONS

Metallosis after knee arthroplasty is a rare and perhaps underestimated or under published complication. A systematic diagnostic approach is necessary for the timely and correct diagnosis. A thorough debridement as well as a (sub)total synovectomy should be always performed. In cases with a damaged component, a partial/complete prosthesis exchange leads to the best results. Should a malalignment be the cause of the metallosis, then it should be corrected within the revision surgery.

[Distal femur replacement in extensive defects of the distal femur in revision arthroplasty]

OBJECTIVE

Use of distal femur replacement implants in advanced bone defects after multiple bone-damaging revision surgery on the knee joint.

INDICATIONS

Advanced femoral bone defects (AORI IIb and III defects) in revision arthroplasty of the knee joint.

CONTRAINDICATIONS

Persistent or current joint infection, general infection, defect and/or nonreconstructable insufficient extensor apparatus.

SURGICAL TECHNIQUE

Standard access including existing skin scars, arthrotomy, removal of cement spacer if necessary and removal of multiple tissue samples; preparation of tibia first to define the joint line, then preparation of the femur. Determining the resection height of the remaining femur corresponding to the preoperative planning. Gradual drilling using flexible medullary drills and then preparation by femoral rasps. Two stem systems are available for coupling to the distal femur (MUTARS). First there is the standard MUTARS stem (available lengths of 90, 120 and 160 mm); if longer shafts are required, so-called revision shaft (RS) stems are necessary (stems available in 150, 200 and 250 mm). In case of extensive femoral defects extension sleeves in different lengths can be used to reconstruct the femur. After preparation the implant position and the joint line height is checked.

POSTOPERATIVE MANAGEMENT

Full weight bearing, in case of existing bony defects possibly partial load of a maximum of 10 kg für 6 weeks; regular wound control; limitation of the degree of flexion only with weakened or reconstructed extensor apparatus.

RESULTS

Between February 2015 and August 2018, a total of 34 distal femurs were implanted. In 19 patients, the implantation was performed after septic and aseptic loosening of a knee prosthesis. All patients had an intraoperative AORI III defect of the femur. Of the 19 patients who underwent a distal femur implantation, 7 had to be revised due to a persistent infection; 4 of these 7 patients had to be revised several times and, finally, had a conversion to a knee arthrodesis. One patient had to undergo a revision with a stem change due to a secondary aseptic loosening of the cemented stem. The mean follow-up period was 11.2 months (range 4-29 months). The follow-up included clinical examination, KSS (Knee Society Score) and X‑ray analysis. A significant improvement in range of motion from 65 ± 16° to 83 ± 14° (p < 0.01) was noted. The KSS improved significantly from 69 ± 9 points preoperatively to 115 ± 15 points postoperatively. Four patients complained of persistent symptoms during exercise after 9 months; femoral shaft pain was denied by all patients. After about 11 months, an implant survival rate of 73.7% was observed in the patient collective.

[Daptomycin-induced eosinophilic pneumonia associated with an early endoprosthesis infection]

Acute eosinophilic pneumonia (AEP) is a rare disease characteristically involving eosinophilic infiltration of lung parenchyma as well as fever, dyspnea, and coughing. A differentiation is made between primary and secondary AEP depending on the underlying etiology. Substances that most frequently cause secondary AEP are antibiotics, such as the lipopeptide daptomycin. This is a case report about a 69-year-old female patient who underwent antibiotic treatment with daptomycin for an infection of a knee prosthesis. During the treatment, signs of pneumonia developed and included the increased dependence on mechanical ventilation of the previously intubated patient, infiltrates on a chest X‑ray, fever, and an increase in serum inflammation markers. Proof of bacteria as an underlying pathogen was not possible. A thoracic computed tomography (CT) scan showed opacities that are commonly seen in interstitial lung disease. Termination of daptomycin treatment due to renal failure led to an improvement of pulmonary symptoms. Re-exposure to daptomycin resulted in a recurrence of the symptoms. The diagnostic criteria for AEP according to Uppal et al. include 1) current exposure to daptomycin, 2) dyspnea with increased oxygen requirements or necessity for mechanical ventilation, 3) new infiltrates on chest X‑ray or CT scan, 4) bronchoalveolar lavage with eosinophilia >25%, 5) improvement of clinical symptoms following daptomycin withdrawal, and 6) fever. With 5 out of the 6 criteria by Uppal et al. positive-an eosinophilia >25% being the only unmet criteria-an AEP induced by daptomycin was diagnosed. Withdrawal of daptomycin as well as high-dose cortisol bolus treatment led to a rapid recovery.

Combined use of virtual monochromatic images and projection-based metal artifact reduction methods in evaluation of total knee arthroplasty

OBJECTIVES

To evaluate the effect of the combined use of virtual monochromatic imaging (VMI) and projection-based metal artifact reduction (PB-MAR) methods on further artifact reduction and image quality in total knee arthroplasty (TKA) patients.

METHODS

Fifty-seven knee joints from 36 patients who had a previous history of TKA for bilateral or unilateral knee joints were included in this study. Four sets of images were compared between non-MAR, PB-MAR, VMI, and VMI + PB-MAR. For quantitative analysis, the area, mean attenuation, artifact index (AI), and contrast-to-noise ratio (CNR) were calculated for each protocol. Regarding qualitative analysis, overall artifact and depiction of soft tissue and bony structure were compared using relative visual grading analysis.

RESULTS

In the femoral region, the VMI + PB-MAR protocol showed the best MAR performance in quantitative measures including area, mean attenuation, and AI (p < .001). However, MAR protocols with VMI showed significantly lower CNRs than did the protocols without VMI in the tibial region (p < .001). On qualitative analysis, VMI + PB-MAR also showed fewer overall artifacts than did the other two MAR protocols. Soft tissue was best depicted in VMI + PB-MAR protocol, and PB-MAR showed the best performance for the depiction of bony structure (p < .001).

CONCLUSIONS

The combined use of VMI and PB-MAR showed better MAR performance than did PB-MAR or VMI alone. In areas with severe metal artifacts, the VMI + PB-MAR and PB-MAR protocols were useful for the evaluation of soft tissue and bone structure, respectively.

KEY POINTS

• The combination of artifact reduction methods is effective in reducing metal artifacts in CT. • Soft tissue was best depicted in the combined protocol of projection- and dual-energy-based methods, and projection-based protocol showed the best performance for the depiction of bone structure in case of severe metal artifacts.

Cost-effectiveness and budget impact of the microprocessor-controlled knee C-Leg in transfemoral amputees with and without diabetes mellitus

BACKGROUND

The safe use of a prosthesis in activities of daily living is key for transfemoral amputees. However, the number of falls varies significantly between different prosthetic device types. This study aims to compare medical and economic consequences of falls in transfemoral amputees who use the microprocessor-controlled knee joint C-Leg with patients who use non-microprocessor-controlled (mechanical) knee joints (NMPK). The main objectives of the analysis are to investigate the cost-effectiveness and budget impact of C-Legs in transfemoral amputees with diabetes mellitus (DM) and without DM in Germany.

METHODS

A decision-analytic model was developed that took into account the effects of prosthesis type on the risk of falling and fall-related medical events. Cost-effectiveness and budget impact analyses were performed separately for transfemoral amputees with and without DM. The study took the perspective of the statutory health insurance (SHI). Input parameters were derived from the published literature. Univariate and probabilistic sensitivity analyses (PSA) were performed to investigate the impact of changes in individual input parameter values on model outcomes and to explore parameter uncertainty.

RESULTS

C-Legs reduced the rate of fall-related hospitalizations from 134 to 20 per 1000 person years (PY) in amputees without DM and from 146 to 23 per 1000 PY in amputees with DM. In addition, the C-Leg prevented 15 or 14 fall-related death per 1000 PY. Over a time horizon of 25 years, the incremental cost-effectiveness ratio (ICER) was 16,123 Euro per quality-adjusted life years gained (QALY) for amputees without DM and 20,332 Euro per QALY gained for amputees with DM. For the period of 2020-2024, the model predicted an increase in SHI expenditures of 98 Mio Euro (53 Mio Euro in prosthesis users without DM and 45 Mio Euro in prosthesis users with DM) when all new prosthesis users received C-Legs instead of NMPKs and 50% of NMPK user whose prosthesis wore out switched to C-Legs. Results of the PSA showed moderate uncertainty and a probability of 97-99% that C-Legs are cost-effective at an ICER threshold of 40,000 Euro (≈ German GDP per capita in 2018) per QALY gained.

CONCLUSION

Results of the study suggest that the C-Leg provides substantial additional health benefits compared with NMPKs and is likely to be cost-effective in transfemoral amputees with DM as well as in amputees without DM at an ICER threshold of 40,000 Euro per QALY gained.

Predictors of extended length of stay after unicompartmental knee arthroplasty

PURPOSE

To identify factors that independently predict extended length of stay after unicompartmental knee arthroplasty (UKA) surgery (defined as length of stay longer than 3 days), and to identify factors predicting early post-operative complications.

METHODS

A retrospective analysis of all patients undergoing UKA from January 2016-January 2019 at our institution was performed. Clinical notes were reviewed to determine the following information: Patient age (years), gender, American Society of Anesthesiologists (ASA) grade, weight (kg), height (meters), body mass index (BMI), co-morbidities, indication for surgery, surgeon, surgical volume, surgical technique (navigated or patient-specific instrumentation), implant manufacturer, estimated blood loss (ml), application of tourniquet during the surgery, application of drain, hospital length of stay (days) and surgical complications.

RESULTS

Multivariate regression analysis showed that ASA 3-4 vs. ASA 1-2 [OR 4.4 (CI; 1.8-10.8, p = 0.001)] and a history of cardiovascular disease [OR 2.8 (CI; 1.4-5.5), p = 0.004)] were significant independent predictors of prolonged length of stay. Hosmer-Lemeshow goodness of fit of the model showed a p-value of 0.214. Nagelkerke R-Square was 0.2. For complications, multivariate regression analysis showed that ASA 3-4 vs. ASA 1-2 [OR 5.8 (CI; 1.7-20.7)] and high BMI (BMI >30) [OR 4.3 (CI; 1.1-17.1)] were significant independent predictors of complications. Hosmer-Lemeshow goodness of fit was 0.89 and Nagelkerke R-Square was 0.2. Patients treated with robotics (Navio) techniques had shorter length of stay median 51 h (IQR; 29-96) when compared to other techniques 72 h (IQR; 52-96), p = 0.008.

CONCLUSION

Based on the results of our study, high ASA grade (≥3) appears to be the most important factor excluding eligibility for fast-track UKA. Any number of co-morbidities may increase ASA, but in and of themselves, apart from a history of cardiovascular disease, they should not be seen as contraindications. Appropriate patient selection, technical tools and details during the surgery could facilitate fast track surgery.

Automated detection & classification of knee arthroplasty using deep learning

BACKGROUND

Preoperative identification of knee arthroplasty is important for planning revision surgery. However, up to 10% of implants are not identified prior to surgery. The purposes of this study were to develop and test the performance of a deep learning system (DLS) for the automated radiographic 1) identification of the presence or absence of a total knee arthroplasty (TKA); 2) classification of TKA vs. unicompartmental knee arthroplasty (UKA); and 3) differentiation between two different primary TKA models.

METHOD

We collected 237 anteroposterior (AP) knee radiographs with equal proportions of native knees, TKA, and UKA and 274 AP knee radiographs with equal proportions of two TKA models. Data augmentation was used to increase the number of images for deep convolutional neural network (DCNN) training. A DLS based on DCNNs was trained on these images. Receiver operating characteristic (ROC) curves with area under the curve (AUC) were generated. Heatmaps were created using class activation mapping (CAM) to identify image features most important for DCNN decision-making.

RESULTS

DCNNs trained to detect TKA and distinguish between TKA and UKA both achieved AUC of 1. Heatmaps demonstrated appropriate emphasis of arthroplasty components in decision-making. The DCNN trained to distinguish between the two TKA models achieved AUC of 1. Heatmaps showed emphasis of specific unique features of the TKA model designs, such as the femoral component anterior flange shape.

CONCLUSIONS

DCNNs can accurately identify presence of TKA and distinguish between specific arthroplasty designs. This proof-of-concept could be applied towards identifying other prosthesis models and prosthesis-related complications.

CAPAbility: comparison of the JOURNEY II Bi-Cruciate Stabilised and GENESIS II total knee arthroplasty in performance and functional ability: protocol of a randomised controlled trial

Background

Osteoarthritis of the knee is a common condition that is expected to rise in the next two decades leading to an associated increase in total knee replacement (TKR) surgery. Although there is little debate regarding the safety and efficacy of modern TKR, up to 20% of patients report poor functional outcomes following surgery. This study will investigate the functional outcome of two TKRs; the JOURNEY II Bi-Cruciate Stabilised knee arthroplasty, a newer knee prosthesis designed to provide guided motion and improve knee kinematics by more closely approximating a normal knee, and the GENESIS II, a proven existing design.

Aim

To compare the change in Patient-reported Outcome Measures (PROMs) scores of the JOURNEY II BCS and the GENESIS II from pre-operation to 6 months post operation.

Methods

CAPAbility is a pragmatic, blinded, two-arm parallel, randomised controlled trial recruiting patients with primary osteoarthritis due to have unilateral TKR surgery across two UK hospitals. Eligible participants (n = 80) will be randomly allocated to receive either the JOURNEY II or the GENESIS II BCS knee prosthesis. Baseline measures will be taken prior to surgery. Patients will be followed at 1 week, 6 to 8 weeks and 6 months post-operatively. The primary outcome is the Oxford Knee Score (OKS) at 6 months post-operatively. Secondary outcomes include: other PROMs, biomechanical, radiological (computerised tomography, (CT)), clinical efficacy and safety outcomes. An embedded qualitative study will also investigate patients’ perspectives via interview pre and post surgery on variables known to affect the outcome of TKR surgery. A sub-sample (n = 30) will have additional in-depth interviews to explore the themes identified. The surgeons’ perspectives on the operation will be investigated by a group interview after all participants have undergone surgery.

Discussion

This trial will evaluate two generations of TKR using PROMS, kinematic and radiological analyses and qualitative outcomes from the patient perspective.

Trial registration

International Standard Randomised Controlled Trials Number Registration, ID: ISRCTN32315753. Registered on 12 December 2017.

Factors associated with infection of primary total knee prosthesis in older adults in a referral hospital in Peru. 2012-2015

OBJECTIVE

To determine the risk factors associated with prosthetic knee infection in elderly patients in a referral hospital in Peru.

PATIENTS AND METHODS

A case and control study was performed. The calculated sample was 44 cases and 132 controls. The data were collected retrospectively from clinical records. U-Mann Whitney and Chi-square tests were performed in the comparison of cases and controls. Odds ratios (OR) were calculated in a binary logistic regression analysis to identify the risk factors, a P<.05 and a 95% confidence interval (CI) were considered significant.

RESULTS

Significant (P<.05) risk factors evidenced in the bivariate analysis were obesity (OR=9.72; 95%CI: 4.47-21.14), smoking (OR=4.06; 95%CI: 1.59-10.39), rheumatoid arthritis (OR=4.66; 95%CI: 1.52-14.32), diabetes mellitus type2 (OR=5.63; 95%CI: 2.69-11.78), persistent drainage (OR=9.27; 95%CI: 3.85-22.31), superficial infection (OR=6.87; 95%CI: 3.25-14.49) and prolonged hospital stay (OR=4.67; 95%CI: 2.26-9.64). In the multivariate analysis where it was adjusted for confounding variables, it was determined that risk factors were obesity (ORa=9.14; 95%CI: 3.28-25.48), diabetes mellitus (ORa=3.77; 95%CI: 1.38-10.32), persistent drainage (ORa=4.64; 95%CI: 1.03-20.80) and superficial wound infection (ORa=27.35; 95%CI: 2.57-290.64).

CONCLUSIONS

Risk factors for prosthetic knee infection identified in this study are preventable. The main risk factors were obesity, diabetes mellitus type2, superficial wound infection and persistent drainage, which were considered together or separately to be risk factors in the population studied.

Multimodal strategy in surgical site infections control and prevention in orthopaedic patients - a 10-year retrospective observational study at a Polish hospital

Introduction

Surgical site infections (SSIs) are among the most common healthcare-associated infections. They are associated with longer post-operative hospital stays, additional surgical procedures, risk of treatment in intensive care units and higher mortality.

Material and methods

SSIs were detected in patients hospitalized in a 40-bed orthopaedics ward in 2009–2018. The total number of study patients was 15,678. The results were divided into two 5-year periods before and after the introduction of the SSI prevention plan. The study was conducted as part of a national Healthcare-Associated Infections Surveillance Programme, following the methodology recommended by the HAI-Net, European Centre for Disease Prevention and Control Program (ECDC).

Results

One hundred sixty eight SSIs were detected in total, including 163 deep SSIs (SSI-D). The total SSI incidence rate was 1.1%, but in hip prosthesis: 1.2%, in knee prosthesis: 1.3%, for open reduction of fracture (FX): 1.3%, for close reduction of fracture (CR): 1.5, and 0.8% for other procedures. 64% of SSI-D cases required rehospitalisation. A significantly reduction in incidence was found only after fracture reductions: FX and CR, respectively 2.1% vs. 0.7% (OR 3.1 95%CI 1.4–6.6, p < 0.01) and 2.1 vs. 0.8% (OR 2.4 95%CI 1.0–5.9, p < 0.05). SSI-Ds were usually caused by Gram-positive cocci, specially Staphylococcus aureus, 74 (45.7%); Enterobacteriaceae bacillis accounted for 14.1% and Gram-negative non-fermenting rods for 8.5%.

Conclusions

The implemented SSI prevention plan demonstrated a significant decrease from 2.1 to 0.7% in SSI-D incidence only in fracture reductions, without changes in epidemiology SSI incidence rates in other procedures. Depending on the epidemiological situation in the ward, it is worthwhile to surveillance of SSIs associated to different types of orthopaedic surgery to assess the risks of SSI and take preventive measures.

Total knee replacement on more than 20° valgus: A case control study

INTRODUCTION

Lower-limb valgus deformity exceeding 20° is a particular case, with few publications assessing the impact of the severity of the valgus. The present retrospective case control study compared a series of>20° valgus versus a series of 10-20° valgus, assessing (1) operative data [approach, type of total knee replacement (TKR)], (2) complications and implant survival, and (3) clinical and radiological results.

HYPOTHESIS

Severe valgus deformity requires TKR with greater constraint, incurring a higher rate of complications and poorer implant survival.

MATERIAL AND METHOD

A multicenter retrospective study for the period January 2006 to December 2010 included 53 patients, with a mean age of 72±10 years, presenting>20° valgus. The study series was matched for age and gender with a series of 53 cases of 10-20° valgus. Convexity laxity was greater in the>20° group (p=0.004).

RESULTS

There was no significant inter-group difference in approach (p=0.13). Greater constraint was more frequent in the>20° group (7/53 versus 1/53; p=0.03), independently of convexity laxity or Krackow grade (p=0.14). There were 7 complications (13.2%) in the>20° group and 7 in the 10-20° group (NS). Eight-year survivorship was 95.12% in the>20° group and 94.9% in the 10-20° group (p=0.63). There were no significant differences in Oxford score (p=0.30) or HKA angle (p=0.78) at last follow-up.

CONCLUSION

The study hypothesis was partially confirmed: greater constraint was more frequent in>20° valgus. The number of complications was low, and survival was identical to that of a control group with less severe deformity.

LEVEL OF EVIDENCE

III, retrospectivecase controlstudy.

UniCAP offers a long term treatment for middle-aged patients, who are not revised within the first 9 years

PURPOSE

The aim of this study was to investigate the long-term outcome of the unicompartmental knee resurfacing prosthesis (UniCAP) using clinical and radiographic assessments, and to evaluate the revision and survival rates.

METHODS

This was a prospective cohort study of patients with UniCAP prostheses with 6-9 years of follow-up. The clinical examination included the Knee Society Score (KSS) and Visual Analogue Scale (VAS) score. The radiographic examination included the Kellgren-Lawrence (KL) grading scale. A comparison analysis of the clinical preoperative and follow-up data and a Kaplan-Meier survival analysis were performed.

RESULTS

Of the 64 UniCAP patients, 36 (56%) were revised and one died. Examinations were performed on 23 (85%) of them. When compared with the preoperative data, the examinations showed a significant increase in the KSS objective [mean = 47.4, standard deviation (SD) = 5.8 vs. mean = 90.0, SD = 6.9] and function (mean = 46.7, SD = 6.8 vs. mean = 91.1, SD = 6.9) scores, a decrease in the VAS-score (mean = 7.3, SD = 0.5 vs. mean = 3.4, SD = 1.4) and a significant increase in the KL medial score (mean = 1.7, SD = 0.6 vs. mean = 2.1, SD = 0.5). The Kaplan-Meier survival rate after 5 years indicated good long-term outcomes.

CONCLUSIONS

There was a survival rate of approximately 40% after 9 years of follow-up, but in the group of patients (35-65 years old) not eligible for a final total arthroplasty. These patients were often left with pain and disability. This implant can be a temporary or even long-term treatment because it improved the disability and function over the long-term without a major progression in the osteoarthritis, function or pain. Long term results of this mini-prosthesis have not been previously reported.

LEVEL OF EVIDENCE

IV.

[Clinical outcomes with cruciate-substituting ultra-congruent and posterior stabilized in total knee arthroplasty]

Objective: To investigate clinical outcomes of total knee arthroplasty with ultra-congruent insert(UC) or posterior stability insert (PS). Methods: A retrospective study was performed on 97 patients (17 males, 80 females, 119 knees) with knee osteoarthritis who received total knee arthroplasty. Of the patients, 42 cases (50 knees) received UC protheses and 55 cases (69 knees) received PS protheses in total knee arthroplasty by the same surgeon in Peking University Third Hospital from March 2015 to November 2015. The data including age, gender, body mass index (BMI), range of motion (ROM), Western Ontario and McMaster Universities (WOMAC) osteoarthritis index and Hospital for Special Surgery Knee Score (HSS) before and after the surgery were collected and compared in the two groups. The data were compared between the two groups by single-sample t test. Results: There was no significant differences in age, gender, BMI, ROM, HHS and WOMAC scores between the two groups before operation(all P>0.05). At 3 months and 2 years of follow-up, ROM, HSS and WOMAC scores were significantly improved in the two groups(all P<0.05), but there was no statistical difference between the two groups(t=-0.303, -1.593, Z=-0.500, all P>0.05). One patient with PS prosthesis recieved revision surgery due to prothesis loosening; and no complication found in the UC group(χ(2)=0.731, P>0.05). Conclusion: There is no obvious difference between PS and UC in TKA, UC insert seems to be a practical alternative to the PS.

[Dexmedetomidine combined with ropivacaine for continuous femoral nerve block improved postoperative sleep quality in elderly patients after total knee arthroplasty]

Objective: To investigate the effect of dexmedetomidine adding to ropivacaine for continuous femoral nerve block on the improvement of postoperative sleep quality in elderly patients after total knee arthroplasty. Methods: One hundred and sixty patients aged 60 years or older in Jishuitan Hospital scheduled for single total knee arthroplasty between Nov. 2016 and Jun. 2017 were recruited. All patients received spinal anesthesia and were randomized to receive either combined ropivacaine and dexmedetomidine (0.2% ropivacaine 250 ml and 5 μg/kg dexmedetomidine, at a rate of 5 ml/h or 0.1 μg·kg^-1·h^-1 dexmedetomidine, dexmedetomidine group) or only ropivacaine (0.2% ropivacaine, at a rate of 5 ml/h, controlled group) for continuous femoral nerve block as postoperative analgesia after surgery. The severity of postoperative pain was assessed with numeric rating scale at 4, 24, and 48 hours after surgery both at rest and with movement. Subjective sleep quality and delirium were evaluated daily during the first 3 days postoperatively. Results: The subjective sleep quality scores were 2(1-4), 2(1-4) and 4(2-8), 4(2-7) in dexmedetomidine group and controlled group respectively on the 1st and 2nd days after surgery. The scores of dexmedetomidine group were much better than those of controlled group (Z=-4.597, -4.183, both P<0.05). The difference was statistically significant. The NRS pain scores at rest were 2(1-2), 2(1-4), and 3(2-5), 3(2-6) in dexmedetomidine group and controlled group respectively at 24 and 48 hours after surgery. The scores of dexmedetomidine group were lower than those of controlled group (Z=-6.671, -4.010, both P<0.05). The difference was statistically significant. The NRS pain scores with movement were 1(1-2), 3(2-4), 3(2-3) and 3(2-4), 5(3-6), 5(4-7)in dexmedetomidine group and controlled group respectively at 4, 24 and 48 hours after surgery. The scores of dexmedetomidine group were lower than those of controlled group (Z=-7.167, -6.824, -7.473, all P<0.05). The difference was statistically significant. The incidence of 3-day delirium was lower in dexmedetomidine group (5%) than that in controlled group (15%) (χ²=4.444, P<0.05). The difference was statistically significant. There were no significant differences between groups regarding the incidences of adverse events. Conclusion: Dexmedetomidine combined with ropivacaine for continuous femoral nerve block may improve subjective sleep quality, postoperative analgesia, and reduce delirium in the elderly after total knee arthroplasty.

Functional assessment and satisfaction of transfemoral amputees with low mobility (FASTK2): A clinical trial of microprocessor-controlled vs. non-microprocessor-controlled knees

BACKGROUND

The benefits of a microprocessor-controlled knee are well documented in transfemoral amputees who are unlimited community ambulators. There have been suggestions that transfemoral amputees with limited community ambulation will also benefit from a microprocessor-controlled knee. Current medical policy restricts microprocessor-controlled knees to unlimited community ambulators and, thereby, potentially limits function. This clinical trial was performed to determine if limited community ambulators would benefit from a microprocessor-controlled knee.

METHODS

50 unilateral transfemoral amputees, mean age 69, were tested using their current non-microprocessor-controlled knee, fit with a microprocessor-controlled knee and allowed 10 weeks of acclimation before being tested, and then retested with their original mechanical knee after 4 weeks of re-acclimation. Patient function was assessed in the free-living environment using tri-axial accelerometers. Patient satisfaction and safety were also measured.

FINDINGS

The subjects demonstrated improved outcomes when using the microprocessor-controlled knee. Subjects had a significant reduction in falls, spent less time sitting, and increased their activity level. Subjects also reported significantly better ambulation, improved appearance, and greater utility.

INTERPRETATION

This clinical trial demonstrated that transfemoral amputees with limited mobility clearly benefit from a microprocessor-controlled knee. Notably, a reduction in falls occurred while the subjects engaged in more physical activity, which resulted in increased subject satisfaction. The increased activity resulted in a greater exposure to fall risk, but that risk was moderated by the advanced technology. ClinicalTrials.gov No: NCT02240186.

Interimplant femoral fractures: risk factors, treatment and evolution

OBJECTIVE

The aim of this study is to determine the risk factors involved in the development of these fractures and analyze the treatments used as well as their influence on the clinical and functional prognosis of patients.

MATERIALS AND METHODS

We made an observational, retrospective case-control study, with a sample of 38 patients (40 femoral bones) operated in our hospital, who had two femoral ipsilateral implants, proximal and distal. We found 10 cases of interimplant fracture and 28 patients who had not suffered a fracture (2 of them had bilateral implants). We analyzed the influence of different variables, such as age, gender, comorbidities, radiological variables, type of treatments employed, clinical evolution, etc. RESULTS: the female sex was predominant in both groups, 80.7 was the average age. Osteoporosis was statistically significant (P=.007) for the development of these fractures. We did not find statistical significance in the radiological variables. Surgical treatment was the most frequent, and the plate of osteosynthesis the most employed option. We found a death rate of 40% at 4 years. Although all fractures healed, the survivors' ambulation ability was reduced.

CONCLUSIONS

interimplant fractures are predominant in elderly women. Osteoporosis is a statistically significant risk factor. Despite optimal treatment and fracture healing, functional outcomes were decreased. Specific classification systems and therapeutic algorithms are necessary to improve the management and prognosis of these patients.

Two sequential free flaps for coverage of a total knee implant

Knee revision arthroplasty following peri-prosthetic joint infections is a formidable challenge. Patients are at a high risk of recurrent infection, and the soft tissue over the revised implant is often of questionable quality. Flap reconstruction has improved the salvage rates of infected arthroplasties, and should be considered in all cases of revision arthroplasty. We present a challenging case requiring staged reconstruction with two free latissimus dorsi flaps after the initial use of a medial gastrocnemius flap.

Intraarticular synovial sarcoma of the knee rising from a lateral meniscus - a case report

Synovial sarcoma (SS) is a rare mesenchymal tumor, accounting less than 10% of soft tissue sarcomas. We report a case of intraarticular SS mimicking nodular synovitis and lateral meniscus rupture. Due to clinical and radiological presentation, arthroscopic synovectomy was performed, and histology confirmed nodular synovitis. After four years the lesion recurred and new arthroscopic biopsy was performed, revealing a monophasic SS with SYT/SSX1 translocation. Repeated histology of the first specimen confirmed appearance of a nodular synovitis microscopically, with no morphological criteria for a sarcoma, but molecular analysis showed positive SYT/SSX1 translocation. Wide extraarticular knee resection and reconstruction with a tumor megaendoprosthesis-allograft composite was performed with a negative tumor margins. This case report showed that in a case of benign histological appearance, underlying sarcoma is possible and could be identified in early stages only with an advanced pathology methods.

LEVEL OF EVIDENCE

Level IV historical case.

Knee arthroplasty with rotating-hinge implant: an option for complex primary cases and revisions

Objective

To present the indications, technical aspects, and initial results of the first cases using Endo-Model™ implants in Brazil.

Methods

A prospective study was conducted. It included nine patients submitted to a total knee arthroplasty, of which six were primary and three were revisions, using exclusively the Endo-Model™ implant. These patients were followed for an average of 12 months and evaluated with functional scores, such as the Knee injury and Osteoarthritis Outcome Score (KOOS), Knee Society Score (KSS), and visual analog pain scale (VAS).

Results

There were statistically significant improvements in all scores evaluated in every patient. Only one complication occurred postoperatively (apraxia of the peroneal nerve) and did not require surgery revision.

Conclusion

The use of a rotating-hinge implant for knee arthroplasty is a new option for complex cases with severe instability in Brazil; the initial results are satisfactory.

Morphometric evaluation of the knee in Chinese population reveals sexual dimorphism and age-related differences

PURPOSE

Morphologic data of the knee is very important in the design of total knee prostheses. Generally, the designs of the total knee prostheses are based on the knee anatomy of Caucasian population. Moreover, in forensic medicine, a person's age and sex might be estimated by the shape of their knees. The aim of this study is to utilize three-dimensional morphometric analysis of the knee in Chinese population to reveal sexual dimorphism and age-related differences.

MATERIALS AND METHODS

Sexually dimorphic differences and age-related differences of the distal femur were studied by using geometric morphometric analysis of ten osteometric landmarks on three-dimensional reconstructions of 259 knees in Chinese population. General Procrustes analysis, PCA, and other discriminant analysis such as Mahalanobis and Goodall's F test were conducted for the knee to identify sexually dimorphism and age-related differences of the knee.

RESULTS

The shape of distal femur between the male and female is significantly different. A difference between males and females in distal femur shape was identified by PCA; PC1 and PC2 accounted for 61.63% of the variance measured. The correct sex was assigned in 84.9% of cases by CVA, and the cross-validation revealed a 81.1% rate of correct sex estimation. The osteometric analysis also showed significant differences between the three age-related subgroups (< 40, 40-60, > 60 years, p < 0.005).

CONCLUSION

This study showed both sex-related difference and age-related difference in the distal femur in Chinese population by 3D geometric morphometric analysis. Our bone measurements and geometric morphometric analysis suggest that population characteristics should be taken into account and may provide references for design of total knee prostheses in a Chinese population. Moreover, this reliable, accurate method could be used to perform diachronic and interethnic comparisons.

Ten-year patient-reported outcomes following total and minimally invasive unicompartmental knee arthroplasty: a propensity score-matched cohort analysis

PURPOSE

For patients with medial compartment arthritis who have failed non-operative treatment, either a total knee arthroplasty (TKA) or a unicompartmental knee arthroplasty (UKA) can be undertaken. This analysis considers how the choice between UKA and TKA affects long-term patient-reported outcome measures (PROMs).

METHODS

The Knee Arthroplasty Trial (KAT) and a cohort of patients who received a minimally invasive UKA provided data. Propensity score matching was used to identify comparable patients. Oxford Knee Score (OKS), its pain and function components, and the EuroQol 5 Domain (EQ-5D) index, estimated on the basis of OKS responses, were then compared over 10 years following surgery. Mixed-effects regressions for repeated measures were used to estimate the effect of patient characteristics and type of surgery on PROMs.

RESULTS

Five-hundred and ninety UKAs were matched to the same number of TKAs. Receiving UKA rather than TKA was found to be associated with better scores for OKS, including both its pain and function components, and EQ-5D, with the differences expected to grow over time. UKA was also associated with an increased likelihood of patients achieving a successful outcome, with an increased chance of attaining minimally clinically important improvements in both OKS and EQ-5D, and an 'excellent' OKS. In addition, for both procedures, patients aged between 60 and 70 and better pre-operative scores were associated with better post-operative outcomes.

CONCLUSION

Minimally invasive UKAs performed on patients with the appropriate indications led to better patient-reported pain and function scores than TKAs performed on comparable patients. UKA can lead to better long-term quality of life than TKA and this should be considered alongside risk of revision when choosing between the procedures.

LEVEL OF EVIDENCE

II.

Knee Implant Loosening Detection: A Vibration Analysis Investigation

Knee implant loosening is mainly caused by the weakness of the prosthesis-bone interface and is the main reason for surgical revisions. However, pre-operative diagnosis is difficult due to lack of accurate tests. In this study, we developed a vibration-based system to detect the loosening of the tibial implant of an instrumented knee prosthesis. The proposed system includes an instrumented vibrator for transcutaneous stimulation of the bone in a repeatable manner, and accelerometer sensors integrated into the implants to measure the propagated vibration. A coherence-based detection technique was proposed to distinguish the loosened implants from the secure ones. Fourteen ex vivo lower limbs were used, on which the knee prosthesis was implanted, and harmonic-forced vibration was applied on the tibia. The input–output coherence measure provided 92.26% accuracy, a high sensitivity (91.67%) and specificity (92.86%). This technique was benchmarked against power spectrum based analysis of the propagated vibration to the implant. In particular, loosening detection based on new peak appearance, peak shift, and peak flattening in power spectra showed inferior performance to the proposed coherence-based technique. As such, application of vibration on our instrumented knee prosthesis together with input–output coherence analysis enabled us to distinguish the secure from loose implants.

Validation of a new classification system for interprosthetic femoral fractures

Interprosthetic femoral fracture (IFF) incidence is gradually increasing as the population is progressively ageing. However, treatment remains challenging due to several contributing factors, such as poor bone quality, patient comorbidities, small interprosthetic fragment, and prostheses instability. An effective and specific classification system is essential to optimize treatment management, therefore diminishing complication rates. This study aims to validate a previously described classification system for interprosthetic femoral fractures.

[Clinical efficiency and activity range of stiff knee by total knee arthroplasty]

OBJECTIVE

To observe clinical effect and influencing factor of total knee arthroplasty (TKA) for the treatment of stiff knee.

METHODS

From January 2010 to October 2014, 20 patients(25 knees) with stiff knee were treated with TKA. Among them, including 2 males(3 knees) and 18 females(22 knees), aged from 55 to 78 years old with an average of(64.5± 4.9) years old, the courses of disease ranged from 5 to 21 years with an average 8.3 years. Preoperative and postoperative HSS (hospital for special surgery knee score) score, activity range and complications were observed and compared.

RESULTS

All patients were followed up from 12 to 69 months with an average of 35.3 months. Ten patients occurred complications after operation. HSS score was improved from 32.36±12.31 preoperatively to 80.70±18.52 postoperatively, and had statistical difference between two groups;7 knees obtained excellent results, 15 knees good and 3 knees moderate. Activity range was improved from(39.4±5.3)°preoperatively to (92.5±11.2)° at the latest follow up.

CONCLUSIONS

Total knee arthroplasty for stiffness knees is feasible and could obtain satisfied activity range and function.