Douglas D. R. Naudie

Aims: The search for enhanced fixation and longevity in total knee arthroplasty (TKA) continues. Radiostereometric analysis (RSA) allows early detection of implant migration predictive of future aseptic loosening and is the recommended method for evaluating new implants. This multicentre RSA study evaluated early fixation and migration stability of a novel cementless tibial baseplate used in primary TKA. Methods: A total of 30 patients undergoing primary TKA were enrolled at two academic centres. All patients received a porous cementless tibial baseplate combined with either a cementless or cemented femoral component. The patella was selectively resurfaced based on surgeon preference and was resurfaced using either a cementless onlay or a cemented inset biconvex design. During surgery, RSA beads were inserted into the tibia, femur, and patella. RSA examinations were performed at six weeks (baseline), six months, 12 months, and 24 months postoperatively. The primary outcome was change in maximum total point motion (MTPM) of the tibial baseplate over 24 months. Secondary outcomes included component migration patterns and patient-reported outcome measures (PROMs). Results: In total, 29 patients completed minimum 24-month follow-up. Mean tibial baseplate MTPM was 1.018 mm (SD 0.742) at six months and 1.210 mm (SD 0.571) at 24 months. The change in MTPM between six and 12 months was −0.096 mm (SD 0.551) and between 12 and 24 months was 0.095 mm (SD 0.603), remaining below accepted RSA thresholds associated with increased risk of aseptic loosening. Translational and rotational migration stabilized by six months. Patients reported substantial improvement in functional (Oxford Knee Score, Forgotten Joint Score) and health-related (EuroQol five-dimension questionnaire) PROMs and high satisfaction at 12 and 24 months. Conclusion: This novel cementless tibial baseplate demonstrated early stabilization with no evidence of continuous migration over two years. These RSA findings suggest a low risk of future aseptic loosening, and support the early fixation performance of this implant design. Cite this article: Bone Jt Open 2026;7(9):1239–1247.

NO DIFFERENCE IN SUBSIDENCE BETWEEN MODERN MONOBLOCK AND MODULAR TITANIUM FLUTED TAPERED FEMORAL STEMS

Purpose: The necessity of stemmed components when performing a varus-valgus constrained (VVC) primary total knee arthroplasty (TKA) is unclear. The purpose of this study is to compare the outcomes of primary VVC TKA with and without stems at a minimum of two years. Methods: Patients in our prospectively collected database with primary VVC TKAs were identified. Patient demographics, prosthesis data, time in vivo, characteristics of revision, and radiographs and PROMs were compared between the stemmed and un-stemmed cohorts. Results: Sixty-five patients with 69 primary VVC TKAs were identified; 17 were implanted with stems and 52 without stems. Five of the stemmed TKAs (5/17) required revision at 15.1 years, while only one of the un-stemmed TKA (1/52) required a revision at 21.6 years (p=0.003) for aseptic loosening. Of the 5 stemmed TKAs requiring revision, 3 were for aseptic loosening and 2 were for PPJI. The un-stemmed cohort had a significantly higher final total KSS (p=0.048). Conclusion: There was no increase in aseptic loosening or revision surgery in patients with non-stemmed primary VVC TKA compared to those with stemmed VVC TKA at mid-term follow-up. Utilizing non-stemmed TKA with VVC in appropriate cases is safe and may reduce cost, shorten operative time, and preserve bone-stock.

Introduction: Corrosion at the head–neck interface of modular components in total hip arthroplasty (THA) has been reported as a cause of failure of modern total hip replacement implants. While this method of failure has been well described, it remains poorly understood. The purpose of this study is to review the three most commonly used uncemented femoral stems at our institution over the last fifteen years and to correlate any established risk factors with rates of revision, particularly corrosion. Methods: We reviewed 2095 patients from March 2000 to September 2015 who underwent total hip arthroplasty with one of three uncemented femoral stem designs. All stems were made of a Ti6Al4V alloy with a 12/14 taper design. We included only those stems coupled with a CoCr head and a highly crosslinked polyethylene liner. We evaluated age, gender, body mass index (BMI), femoral head size, head length, neck angle and offset and correlated these to the incidence of all cause revision, as well as revision excluding infection. Results: There were no recognized corrosion-related revisions identified. There was no association between age, BMI, gender, head length, neck angle and offset to all cause revision or revision with infection excluded (p> 0.05). Femoral head size less than 32mm was associated with higher all cause revision rates (OR 4.60 (95% CI 1.8, 11.8)) and when excluding infection as a reason for revision (OR 4.94 (95% CI 1.7, 14.41)). Conclusion: Over the last fifteen years, we have not identified any cases of corrosion with the three most commonly used femoral stems used at out institution. While we acknowledge that no femoral stem is immune to corrosion, certain femoral stem designs may be uniquely resistant to this mode of failure. Level of Evidence: III.

The aim of this study was to obtain micro‐computed tomography derived measurements of the rat proximal femur, to create parameterized rat hip implants that could be surgically installed in a clinically representative small animal model of joint replacement. The proximal femoral anatomy of N = 25 rats (male, Sprague‐Dawley, 390‐605 g) was quantified. Key measurements were used to parameterize computer‐aided design models of monoblock rat femoral implants. Linear regression analysis was used to determine if rat hip dimensions could be predicted from animal weight. A correlation analysis was used to determine how implants could be scaled to create a range of sizes. Additive manufacturing (3D printing) was used to create implants in medical‐grade metal alloys. Linear regressions comparing rat weight to femoral head diameter and neck‐head axis length revealed a significant nonzero slope (P < .05). Pearson's correlation analysis revealed five significant correlations between key measurements in the rat femur (P < .05). Implants were installed into both cadaveric and live animals; iterative design modifications were made to prototypes based on these surgical findings. Animals were able to tolerate the installation of implants and were observed ambulating on their affected limbs postoperatively. Clinical significance: We have developed a preclinical rat hip hemiarthroplasty model using image‐based and iterative design techniques to create 3D‐metal printed implants in medical‐grade metal alloys. Our findings support further development of this model for use as a low‐cost translational test platform for preclinical orthopaedic research into areas such as osseointegration, metal‐on‐cartilage wear, and periprosthetic joint infection.

Purpose To examine implant migration and articular behavior of primary total knee arthroplasty (TKA) at 10 years after index surgery and correlate to implant alignment. Methods Thirty-five patients underwent a cemented posterior stabilized total knee arthroplasty with a surgical objective of neutral alignment and were enrolled in a long-term radiostereometric analysis (RSA) study. At 10 years after surgery, patients were analyzed for implant migration using RSA as well as radiographic assessment of articular behavior at four positions of knee flexion. Implant position and alignment was measured on full-length radiographs. Patient demographics and reported outcomes were also collected. Results No difference between patient demographics or patient-reported outcomes were found. When categorized into neutral and varus groupings, no difference in migration was present. If alignment was considered as a continuous variable, there was no correlation between overall leg alignment and migration, however, migration increased with an increasing varus tibial alignment. Although contact location did not differ between neutral and varus groups through a range of motion, condylar liftoff was much more common in the varus group, of which all were lateral liftoff. Conclusions Increased tibial varus results in increased implant migration. Overall varus limb alignment is correlated with isolated lateral compartment liftoff, and liftoff occurs more commonly than in neutral aligned knees. The increased migration and liftoff raise concerns about the longevity of malaligned total knee replacements. If a goal of overall varus limb alignment is desired for TKA, the tibia should remain neutral. Level of evidence Level III.

➢ Trunnionosis, characterized by corrosion and fretting of the taper, is a well-known entity commonly demonstrated in retrieval specimens. While there have been a number of recent reports regarding the potential for adverse local tissue reactions related to trunnionosis, it remains a relatively infrequent cause for failure of total hip replacement implants. ➢ A number of factors, including both biomechanical and bioelectrochemical factors, have a known impact on the development and severity of trunnionosis. Furthermore, specific implant design and material-related factors have been shown to influence the risk of trunnionosis leading to adverse local tissue reactions. ➢ Retention of a well-fixed femoral stem, in spite of corrosion of the male taper junction, is acceptable in the majority of cases. ➢ A ceramic head, often in combination with a titanium adaptor sleeve, is the most common replacement reported in the current literature to treat trunnionosis. ➢ In patients with modular-neck total hip replacements, revision of the femoral stem is likely required if corrosion at the modular neck-stem junction is encountered.

Purpose Knee arthroplasty is an effective and reproducible way of treating advanced knee arthritis; however, results are not always favorable. Knee arthroscopy has been described in symptomatic knee arthroplasty, but opinion is divided over its utility. The purpose of this systematic review is to examine existing evidence supporting knee arthroscopy in the setting of knee arthroplasty. Methods Predetermined inclusion criteria were used to search the databases EMBASE, MEDLINE, and PubMed for articles addressing knee arthroplasty patients who subsequently underwent arthroscopy. Inclusion criteria limited our search to human and English language studies with clearly described surgical indications. Article screening was conducted in duplicate. Results Before duplicate screening, 2,179 studies were retrieved and 52 ultimately satisfied the inclusion criteria. A total of 609 patients underwent knee arthroscopy of a symptomatic knee arthroplasty and 120 patients went on to require further surgery post-arthroscopy. Peripatellar fibrosis and pain with no clear diagnosis were the most commonly described indications for surgery. Conclusion Knee arthroscopy is a safe diagnostic and therapeutic tool in symptomatic knee arthroplasty with variable efficacy depending on indication. It has diagnostic utility in painful knee arthroplasty patients and is a reliable therapeutic option for those with post-arthroplasty diagnoses; although 20% of the patients go on to require further surgery. Level of Evidence IV This is a systematic review of level IV studies.