Aims. Nearly 99,000 total knee arthroplasties (TKAs) are performed in UK annually. Despite plenty of research, the satisfaction rate of this surgery is around 80%. One of the important intraoperative factors affecting the outcome is alignment. The relationship between joint obliquity and functional outcomes is not well understood. Therefore, a study is required to investigate and compare the effects of two types of alignment (mechanical and kinematic) on functional outcomes and range of motion. Methods. The aim of the study is to compare navigated kinematically aligned TKAs (KA TKAs) with navigated mechanically aligned TKA (MA TKA) in terms of function and ROM. We aim to recruit a total of 96 patients in the trial. The patients will be recruited from clinics of various consultants working in the trust after screening them for eligibility criteria and obtaining their informed consent to participate in this study. Randomization will be done prior to surgery by a software. The primary outcome measure will be the Knee injury and Osteoarthritis Outcome Score The secondary outcome measures include Oxford Knee Score, ROM, EuroQol five-dimension questionnaire, EuroQol visual analogue scale, 12-Item Short-Form Health Survey (SF-12), and Forgotten Joint Score. The scores will be calculated preoperatively and then at six weeks, six months, and one year after surgery. The scores will undergo a statistical analysis. Discussion. There is no clear evidence on the best alignment for a knee arthroplasty. This randomized controlled trial will test the null hypothesis that navigated KA TKAs do not perform better than navigated MA TKAs. Cite this article: Bone Jt Open 2021;2(11):945–950

Aims. Medial pivot (MP) total knee arthroplasties (TKAs) were designed to mimic native knee kinematics with their deep medial congruent fitting of the tibia to the femur almost like a ball-on-socket, and a flat lateral part. GMK Sphere is a novel MP implant. Our primary aim was to study the migration pattern of the tibial tray of this TKA. Methods. A total of 31 patients were recruited to this single-group radiostereometric analysis (RSA) study and received a medial pivot GMK Sphere TKA. The distributions of male patients versus female patients and right versus left knees were 21:10 and 17:14, respectively. Mean BMI was 29 kg/m. 2. (95% confidence interval (CI) 27 to 30) and mean age at surgery was 63 years (95% CI 61 to 66). Maximum total point motions (MTPMs), medial, proximal, and anterior translations and transversal, internal, and varus rotations were calculated at three, 12, and 24 months. Patient-reported outcome measure data were also retrieved. Results. MTPMs at three, 12, and 24 months were 1.0 mm (95% CI 0.8 to 1.2), 1.3 mm (95% CI 0.9 to 1.7), and 1.4 mm (0.8 to 2.0), respectively. The Forgotten Joint Score was 79 (95% CI 39 to 95) and Knee Injury and Osteoarthritis Outcome Score obtained at two years was 94 (95% CI 81 to 100), 86 (95% CI 75 to 93), 94 (95% CI 88 to 100), 69 (95% CI 48 to 88), and 81 (95% CI59 to 100) for Pain, Symptoms, Activities of Daily Living, Sport & Recreation, and Quality of Life, respectively. Conclusion. In conclusion, we found that the mean increase in MTPM was lower than 0.2 mm between 12 and 24 months and thus apparently stable. Yet the GMK Sphere had higher migration at one and two years than anticipated. Based on current RSA data, we therefore cannot conclude on the long-term performance of the implant, pending further assessment. Cite this article: Bone Jt Open 2021;2(9):737–744

Aims

The aim of this study was to report patient and clinical outcomes following robotic-assisted total knee arthroplasty (RA-TKA) at multiple institutions with a minimum two-year follow-up.

Aims

In the UK, the NHS generates an estimated 25 megatonnes of carbon dioxide equivalents (4% to 5% of the nation’s total carbon emissions) and produces over 500,000 tonnes of waste annually. There is limited evidence demonstrating the principles of sustainability and its benefits within orthopaedic surgery. The primary aim of this study was to analyze the environmental impact of orthopaedic surgery and the environmentally sustainable initiatives undertaken to address this. The secondary aim of this study was to describe the barriers to making sustainable changes within orthopaedic surgery.

Abstract. Background. Infections are rare and poorly studied complications of unicompartmental knee athroplasty (UKA) surgery. They are significantly less common compared to infections after total knee arthroplasties (TKAs). Optimal management of periprosthetic joint infections (PJIs) after a UKA is not clearly defined in the literature. We present the results of a multicentre retrospective series of UKA PJIs treated with Debridement, Antibiotics and Implant Retention (DAIR). Methodology. Patients presenting between January 2016 and December 2019 with early UKA infection were identified at three specialist centres using the Musculoskeletal Infection Society (MSIS) criteria. All patients underwent a standardized treatment protocol consisting of the DAIR procedure and antibiotic therapy comprising two weeks of intravenous (IV) antibiotics followed by six weeks of oral therapy. The main outcome measure was overall survivorship free from reoperation for infection. Results. A total of 3225 UKAs (2793 (86.2%) medial and 432 (13.8%) lateral UKAs) were performed between January 2016 and December 2019. Nineteen patients had early infections necessitating DAIR. The mean follow-up period was 32.5 months. DAIR showed an overall survivorship free from septic reoperation of 84.2%, with an overall survivorship free from all-cause reoperation of 78.95%. The most common bacteria were Coagulase-negative Staphylococci, Staphylococcus aureus and Group B Streptococci. Three patients required a second DAIR procedure but remained free from re-infection at follow-up obviating the need for more demanding, staged revision surgery. Conclusions. In infected UKAs, the DAIR procedure produces a high rate of success, with a high survivorship of the implant

Introduction. Mechanical or corrosive failure of total knee arthroplasties (TKAs) is difficult to diagnose with current laboratory and radiographic analyses. As such, the goal of this study was to determine the mean blood concentration of cobalt, chromium, and titanium in a series of revision TKAs with mechanical implant failure and evaluate whether they facilitated identification of the underlying TKA failure mechanism. Methods. Serum cobalt, chromium, and titanium levels and synovial fluid characteristics were evaluated in 12 patients (13 aseptic revision TKAs) who underwent revision TKA between 2000 and 2020 at a single academic institution for mechanical implant failure or corrosion. Seventy-five percent were re-revisions of previously revised TKAs. Mean time to revision was 6 years. Modular metallic junctions were present in 100%. Twenty-five percent did not have another in situ total joint arthroplasty, and the remaining patients did not have a metal-on-metal articulation that could lead to elevation in serum metal ion levels. Mean follow-up after the revision TKA was 8 months. Results. Mean serum cobalt, chromium, and titanium concentrations were 11 ng/mL, 6 ng/mL, and 3 ng/mL, respectively. Serum metal ion levels facilitated failure mechanism identification in 75%, which included modular junction failure (6 cases), constraint locking mechanism failure (3 cases), corrosion of modular metallic interfaces (2 cases), and implant fracture (1 case). Arthrocentesis was performed in 75%. Mean synovial fluid cell count was 950 cells/mcL. Monocytes were the predominant mean cell type (41%), followed by neutrophils (35%), and lymphocytes (22%). Conclusion. Serum metal ion assessment should be considered when the etiology of painful primary or revision TKAs, particularly those with modular metallic junctions, remains elusive after routine evaluation

Introduction. With the rising utilization of total joint arthroplasty, the role of simultaneous-bilateral surgery has expanding impact. The purpose of this study is to examine the risk of perioperative complications for this approach in total knee arthroplasty to inform shared decision making. Methods. We used nation-wide linked discharge data from the Hospital Cost and Utilization Project from 2005–2014 comparing outcomes of simultaneous-bilateral and staged-bilateral total knee arthroplasties (TKAs). Hierarchical logistic regression analysis was used to compare mortality within 30 days, 90 days and 1 year, perioperative risks within 30–60 days, and infection and mechanical complications within 1 year. Results. 63,579 patients were analyzed including 27,301 simultaneous-bilateral and 36,278 staged-bilateral TKAs. Patients who underwent simultaneous surgery had a significantly higher adjusted odds ratio of death within 30 days (OR=3.31, 95% CI=2.15–5.08, p<0.001), myocardial infarction (OR=2.54, 95% CI=1.96–3.28, p<0.001), ischemic stroke (OR=2, 95% CI=1.39–2.87, p=0.002), cardiac complications (OR=1.3, 95% CI=1.12–1.5, p=0.007), digestive complications (OR=1.85, 95% CI=1.59–2.15, p<0.001), deep vein thrombosis (OR=1.31, 95% CI=1.18–1.45, p<0.001), and pulmonary embolism (OR=1.76, 95% CI=1.49–2.08, p<0.001) with a lower adjusted odds ratio of hematoma (OR=0.55, 95% CI=0.45–0.68, p<0.001), knee infection (OR=0.83, 95% CI=0.71–0.98, p=0.023), and major mechanical malfunction (OR=0.78, 95% CI=0.65–0.94, p=0.009). There was no difference in the adjusted OR for minor mechanical malfunction. The absolute risk difference for any complication between groups was 1% or less. Conclusion. Despite higher odds of experiencing many complications for patients undergoing simultaneous-bilateral versus staged total knee arthroplasty, the absolute difference in perioperative risks between these groups is small. This study of a large population informs surgeons and patients regarding the safety of simultaneous surgery. Level of Evidence: Therapeutic Level III. Keywords: knee arthroplasty; simultaneous; bilateral; staged; joint replacement

Background. Periprosthetic joint infection (PJI) after knee arthroplasty surgery remains a serious complication. Yet, there is no international consensus on the surgical treatment of PJI. The purpose was to assess the prosthesis survival rates, risk of re-revision, and mortality rate following the different surgical strategies (1-stage or 2-stage implant revision, and irrigation and debridement (IAD) with implant retention) used to treat PJI. Methods. The study was based on 653 total knee arthroplasties (TKAs) revised due to PJI in the period 1994 to 2016. Kaplan-Meier (KM) and multiple Cox regression analyses were performed to assess the survival rate of these revisions and the risk of re-revisions. We also studied the mortality rates at 90 days and 1 year after revision for PJI. Results. Of the 653 revision TKAs; 329, 81, and 243 revisions were performed with IAD, 1-stage, and 2-stage revision procedures, respectively. During the follow-up period, 19%, 12.3% and 11.5% of the IAD, 1-stage, and 2-stage revision cases were re-revised due to PJI, respectively. With any reasons of re-revision as end-point the 5 year KM survival of the index revision procedure was 76%, 82%, and 84% after IAD, 1-stage, and 2-stage revision, respectively. Similarly, the 5-year KM survival with a re-revision for infection as end-point was 79%, 88%, and 87% after IAD, 1-stage, and 2-stage revision, respectively. There were no statistically significant differences between 1-stage and 2-stage revision for re-revision of any reasons (RR=1.6; 95% CI: 0.8–3.1) nor did we find a difference for re-revision due to deep infection (RR=1.4; 95% CI: 0.6–3.1) as end-point. In an age-stratified analysis, however, the risk of re-revision for any causes was 4 times increased after 1-stage revision compared to 2-stage revision in patients over 70 years of age (RR=4.2, 95% CI: 1.3–13.7) but the risk was similar for deep infection as end-point. Age had no statistically significant effect on the risk of re-revision for knees revised with the IAD procedure. The 90-days and 1-year mortality rate after revision for PJI were 2.1% and 3.6% after IAD, 1.2% and 1.2% after 1-stage revision, and 0.4% and 1.6% after 2-stage revision and there were no statistically significant differences in mortality rate according to revision procedure. Conclusion. IAD had good results compared to earlier published studies. Despite that 1-stage revisions had a 4 times higher risk for re-revision compared to 2-stage revisions in older patients, the overall outcomes after 1-stage and 2-stage revision were similar

Genesis 2 (Smith &Nephew) PS type total knee arthroplasties (TKAs) originally required measured resection technique. Between 2009 and 2013, cemented 102 TKAs were performed with modified gap technique in 29 men and 73 women with a mean age of 75 years at the time of surgery. At the time of final follow up, complications included four DVTs, one knee flexion contracture, two superficial infections. Femoro-tibial angle (FTA) was improved from 110 to 123 degrees, and mean extension of knee was improved from −8.5 to −2.1 degrees. Three TKAs with painful patello-femoral component after un-replaced patellar cases required patellar replacements. There was no radiographic evidence of loosening, osteolysis, or polyethylene wear. When patellar replacement was performed, cemented Genesis 2 PS type offered good gap balancing and excellent early outcomes with modified gap technique

Background. The modern modular implants allow surgeons to combine different combinations of components within the same brand of which some may have completely different design. During 1999–2012 the same cemented femur component was used together with a cemented stemmed tibia baseplate and also against a cemented pegged tibia baseplate. We decided to compare the revision rate of total knee arthroplasties (TKAs) using these two tibia baseplates. Methods. This is a register study. During 1999–2012, 32,429 cemented, CR TKA's of a specific brand were reported to the Swedish Knee Arthroplasty Register (SKAR). The part numbers for the femur, tibia and insert (in modular implants) were available in 99.2% of cases. The most common combination used the cemented CR femur against a cemented stemmed baseplate in 50.3% of cases while the same CR femur was used against a cemented pegged baseplate in 8.3% of cases, mainly at two hospitals. In order to make the material more comparable, only patients having osteoarthritis (OA) were included and only TKAs using two types of regular constraint inserts and in which the patella had been left un-resurfaced. Chi-Square test was used to investigate gender distribution in the groups and t-test for the mean age at surgery. Kaplan Meier analysis and the log-rank test were used to evaluate the risk of revision until the end of 2016. A p-value <0.05 was considered statistically significant. Results. After exclusions, there were 15,287 knees with the stemmed and 2,479 with the pegged tibia baseplate. The mean follow-up time was 8.1 years (range 0–18). The proportion of women in the stemmed group was 59% and 60% in the pegged group (p=0.32) and the mean age at surgery for the groups was 69.9 years and 70.0 years, respectively (p=0.41). The cumulative revision rate (CRR) at 15 years for TKAs using the stemmed baseplate was 3.0% (95% CI: 2.6–3.5) as compared to 5.8% (95% CI: 4.0–8.3) for the pegged baseplate (p=0.003). When only revisions for loosening were considered, the CRR was respectively 0.6% (95% CI: 0.4–0. 9) and 3. 8% (95% CI: 2.3–6.3) (p<0.001). Conclusion. We found that TKAs using the pegged base plate had significantly higher risk for revision, both for all reasons as well as for only loosening. As the pegged baseplate surgeries were performed mostly at only two hospitals it is possible that local factors are to blame. However, considering that after stopping using the pegged baseplate, the two hospitals performed least as well as other hospitals using the same brand we think it is likely that the pegged plate has a higher risk of loosening and that our observation warrants that the performance of pegged plates is investigated in other registers

The merit of staging bilateral total knee arthroplasties (separate procedures) versus replacing both joints at the same anaesthetic (sequential) is a topic debated in literature. The aim of this study was to evaluate & compare the clinical outcome in patients who had undergone either bilateral staged or sequential total knee arthroplasties (TKAs). METHODS: Computerized database and medical records of patients who had had bilateral TKAs in the Tayside region between 1984 and 2003 were retrospectively evaluated. Outcome was assessed using Knee Society Score, Pain Score, Function Score and Range of Movement. RESULTS: 438 sequential and 526 staged procedures were evaluated. The sequential group had better function score at 1 and 3 years (P< 0.001). There was no other statistically significant difference in the outcome measures. The mean ages of the sequential and staged study groups were 70.67 and 69.19 years, respectively (P=0.011). CONCLUSION: Sequential TKA appears to confer a functional advantage over staged procedures in the short and medium term

The current incidence of periprosthetic supracondylar femoral fractures around total knee arthroplasties (TKAs) is 0.3% to 2.5%, but may well be increasing. An acceptable treatment is to insert a supracondylar nail, but not all TKAs will permit the passage of a supracondylar nail. Method: We ascertained the ten most common TKA prostheses currently used in the United Kingdom from the National Joint Registry (NJR) Report published in September 2005. We used samples of each prosthesis with a saw bone model and checked their compatibility for accepting a supracondylar nail. Results: We present the dimensions of the intercondylar notches of the top ten TKA prostheses, which account for over 90% of TKAs performed over the last year nationally. Our reference chart demonstrates which of these are suitable for use with supracondylar nails. Discussion: Most of the TKAs commonly used in the UK will allow supracondylar nailing for fixation of peri-prosthetic fractures. There are, however, notable exceptions and our chart provides a quick and easy reference for knee surgeons involved in these cases

Backgrounds. In order to permit soft tissue balancing under more physiological conditions during total knee arthroplasties (TKAs), we developed an offset type tensor to obtain soft tissue balancing throughout the range of motion with reduced patella-femoral (PF) and aligned tibiofemoral joints and reported the intra-operative soft tissue balance assessment in cruciate-retaining (CR) and posterior-stabilized (PS) TKA [1, 2]. However, the soft tissue balance in unicompartmental knee arthroplasty (UKA) is unclear. Therefore, we recently developed a new tensor for UKAs that is designed to assist with soft tissue balancing throughout the full range of motion. The first purpose of the present study is to assess joint gap kinematics in UKA. Secondly, we attempted to compare the pattern in UKA with those in CR and PS TKA with the reduced PF joint and femoral component placement, which more closely reproduces post-operative joint alignment. Methods. Using this tensor, we assessed the intra-operative joint gap measurements of UKAs performed at 0, 10, 30, 45, 60, 90, 120 and 135° of flexion in 20 osteoarthritic patients. In addition, the kinematic pattern of UKA was compared with those of CR and PS TKA that were calculated as medial compartment gap from the previous series of this study. Results. While the joint gap measurements of UKAs increased from full extension to extension (10 degrees of flexion), these values remained constant throughout the full range of motion. Of note, the gap values of CR TKA were significantly smaller from midrange to deep flexion compared with PS TKA, and furthermore UKA showed a significantly smaller gap from extension to midrange flexion compared with CR TKA. Conclusions. Accordingly, we conclude that the intra-operative joint gap kinematic pattern in UKA differs from the pattern in TKA

Introduction: We reviewed clinical results of the performance of FNK-type total knee arthroplasties (TKAs) for treatment of rheumatoid arthritis (RA) knees. Materials and Methods: Materials we had studied were 372 knee joints in 202 cases (21.1%) with RA (36 joints in 22 male patients, and 336 joints in 180 female) out of 1762 knee joints in 1032 cases who had undergone TKA using FNK type prostheses between May 1995 and December 2003. A mean age of patients at index procedures was 62.4 years (24 – 74 years), with a mean follow-up period of 6.7 years (1 – 9.4 years). With these cases, we discussed clinical evaluation on the basis of JOC rating scores, postoperative range of motion, complications, and others. Results: 288 knee joints (77.4%) in 144 patients were involved in bilateral simultaneous TKA. The range of motion (ROM) had shown a significant improvement from a preoperative average of 15.2 – 110.2° to 2.3 – 125.0° at the last follow-up. There have been no cases of revision surgery at all, with excellent postoperative results

Purpose: A common difficulty with manually-performed total knee arthroplasties (TKAs) is obtaining accurate intra-operative soft tissue balancing, an aspect of this procedure that surgeons traditionally address through their “subjective feel” and experience with an unphysiological joint condition. We have therefore developed a new tensor for TKAs that enables us to assess for soft tissue balancing throughout the range of motion about the knee with a reduced patello-femoral (PF) joint and femoral component in place. This tensor permits us to intra-operatively reproduce the post-operative alignment of the PF and tibio-femoral joints. The main purpose of this study is to compare ligament balance in cruciate-retaining (CR) and posterior-stabilized (PS) TKAs. Methods: Using the tensor, we intra-operatively compared the ligament balance measurements of CR and PS TKAs performed at 0, 10, 45, 90 and 135° of flexion, with the patella both everted and reduced. From a group of 40 consecutive females (40 varus osteoarthritic knees) blinded to the type of implant received, we prospectively randomized 20 patients to receive a CR TKA (NexGen CR Flex) and the other 20 patients a PS TKA (NexGen LPS Flex). The CR TKA group had a mean age of 73.7 ± 1.3 years while the PS TKA group had a mean age of 73.8 ± 1.7 years. Results: The mean values of varus angle in CR TKA with the knee at 0, 10, 45, 90 and 135 degrees of flexion were 3.0, 3.2, 2.7, 4.2 and 5.1 ° with the patella everted, and 3.9, 4.2, 2.5, 2.0 and 2.0 ° with the patella reduced. The mean values of varus angle in PS TKA at these same degrees of flexion, respectively, were 3.0, 4.1, 6.0, 6.2 and 6.1 ° with the patella everted, and 3.8, 4.1, 6.3, 6.3 and 4.9 ° with the patella reduced. While the ligament balance measurements with a reduced patella of PS TKAs slightly increased in varus from extension to mid-range of flexion (p< 0.05), these values slightly decreased for CR TKA (p< 0.05). Additionally, the ligament balance at deep knee flexion was significantly smaller in varus for both types of prosthetic knees when the PF joint was reduced (p< 0.05). Conclusion: Accordingly, we conclude that the ligament balance kinematic patterns differ between everted and reduced patellae, as well as between PS and CR TKA

Purpose: We report the results at more than five years of a consecutive series of total knee arthroplasties (TKAs) implanted without cement and with preservation of the posterior cruciate ligament (PCL). Material and methods: This series included 98 patients who underwent 109 primary TKAs between 1994 and 1998. Mean patient age was 67.7 years. The press-fit Interax prosthesis has a macroporous hydroxyapatite coating since 1996. The patella was resurfaced in 92% of the cases with a cemented polyethylene button. Ligament balance and joint space were controlled by progressive release of the ligaments with a tensor derby. Clinical assessment was based on the KSS. Radiological assessment included the femorotibial axis, the position of the implants, and the bone-implant interfaces. Results: Seven (6.4%) of the patients were lost to follow-up. Fifteen (13.4%) died or were demented and two (1.8%) developed late infection and were not included in the primary analysis. Thus, 85 patients (77.9%) were retained for analysis at a mean 5.2 years follow-up. The KSS improved from 33.4 preoperatively to 79.4 at last follow-up. The KSS function score improved from 55.1 to 82.4. Knee flexion was 124.5° preoperatively and 113.1° at last follow-up. Anteroposterior laxity greater than 5 mm was observed in 4.8% at last follow-up. Radiologically, the mechanical femorotibial axis changed from 184.4° to 180.6°. Alpha 95.6°, geta 89.1°, omega 4.77°, gamma 3.8°, sigma 89.4°. Patellar height was 0.84 preoperatively and 0.65 at last follow-up. Lucent lines were observed 3.5 times less frequently with hydroxyapatite coated implants. Patellar loosening and femorotibial loosening were observed in one patient each. Revision procedures were necessary for three prostheses for bipolar loosening, painful stiff knee, and anteroposterior instability. Non-infectious survival rate was 94.1% at 5.2 years. Discussion: These mid-term clinical results are comparable with those reported in the literature for cemented or non-cemented implants with or without preservation of the posterior cruciate ligament. Longer follow-up is however necessary to assess the anteroposterior stability. The radiographic measurements provide a good demonstration of the operative precision and proper ligament balance. Hydroxyapatite coating improves bony fixation of the implants and provides a fixation comparable with cemented implants. Conclusion: This series confirms the mid-term reliability of the non-cemented Interax THA with preservation of the posterior cruciate ligament

Aims

Body exhaust suits or surgical helmet systems (colloquially, ‘space suits’) are frequently used in many forms of arthroplasty, with the aim of providing personal protection to surgeons and, perhaps, reducing periprosthetic joint infections, although this has not consistently been borne out in systematic reviews and registry studies. To date, no large-scale study has investigated whether this is applicable to shoulder arthroplasty. We used the New Zealand Joint Registry to assess whether the use of surgical helmet systems was associated with lower all-cause revision or revision for deep infection in primary shoulder arthroplasties.

Aims

Metal particles detached from metal-on-metal hip prostheses (MoM-THA) have been shown to cause inflammation and destruction of tissues. To further explore this, we investigated the histopathology (aseptic lymphocyte-dominated vasculitis-associated lesions (ALVAL) score) and metal concentrations of the periprosthetic tissues obtained from patients who underwent revision knee arthroplasty. We also aimed to investigate whether accumulated metal debris was associated with ALVAL-type reactions in the synovium.

Aims

A substantial fraction of patients undergoing knee arthroplasty (KA) or hip arthroplasty (HA) do not achieve an improvement as high as the minimal clinically important difference (MCID), i.e. do not achieve a meaningful improvement. Using three patient-reported outcome measures (PROMs), our aim was: 1) to assess machine learning (ML), the simple pre-surgery PROM score, and logistic-regression (LR)-derived performance in their prediction of whether patients undergoing HA or KA achieve an improvement as high or higher than a calculated MCID; and 2) to test whether ML is able to outperform LR or pre-surgery PROM scores in predictive performance.

Aims

The purpose of this study was to compare reoperation and revision rates of double plating (DP), single plating using a lateral locking plate (SP), or distal femoral arthroplasty (DFA) for the treatment of periprosthetic distal femur fractures (PDFFs).