Intro/Purpose. Lateral partial knee replacement is indicated as an alternative to total knee replacement for isolated end stage lateral compartment degenerative joint disease. The purpose of this study is to report the surgical technique and clinical results of a large series of lateral partial knee replacements from two institutions. Methods. A retrospective review identified 205 lateral unicompartmental arthroplasty procedures performed in two practices over a six-year period (Aug 2011 – June 2017). Patients indicated for surgery met specific preoperative clinical and radiographic criteria confirming lateral compartment arthritic disease with a correctable deformity, intact full-thickness medial cartilage, competent anterior cruciate ligament, and minimal disease in the patellofemoral compartment. A single cemented fixed bearing tibial component design was used in all cases specifically designed for lateral compartment anatomy. Results. The average age was 65 years old and 76% were female. Average follow-up in the lateral partials was 1.7 years (range 0.5 years to 6 years). Knee Society Scores improved from 45 (pre-op) to 88 points (post-op). Range of motion improved from 6–115o (pre-op) to 0–122 o (post-op). No knees were revised to a TKA. One knee had an additional medial partial knee placed at 1.1 years post lateral partial knee replacement for medial disease progression. Two knees required an irrigation and debridement for traumatic wound dehiscence. Conclusion. This is the largest series of lateral partial knee replacements reported. Clinical improvements, range of motion, and survivorship were excellent at short-term follow-up. Long-term follow-up is needed for additional understanding of a novel implant designed specifically for the lateral compartment and the survivorship of the unreplaced compartments. We believe the lateral partial knee replacement to be a viable option for isolated lateral compartment disease in approximately 4% of patients

A prospective study of 276 TKA's performed in patients with valgus knee deformity ≥ 10° using a Modified Surgical Technique. MATERIALS AND METHODS. Bone cuts were used to balance the valgus knee and soft tissue release was confined to the postero-lateral capsule in severe deformity. The aim was to restore a “functional mechanical axis” as opposed to a “neutral” mechanical axis. All surgeries were performed between Jan2003 and Apr2007, under the care of a single surgeon using an LCS rotating platform. All patients had full length radiographs and outcome scores collected prospectively. RESULTS. The mean coronal alignment of the lower limb was corrected from 15.9°(10-45°) to 3.8°. 94% patients had their coronal alignment restored to = 7°. Sixteen knees with postoperative valgus ≥8° were analysed as a separate group. The mechanical axis deviation was corrected from 52.3mm to 8.8mm. The distal femoral cut was made at 5° valgus in 131 knees(47.5%), 6° in 111 knees(40.2%) and 7° in 24 knees(8.7%).78 knees(28%) were balanced only with bone cuts. 198 knees(72%) had release of posterolateral capsule. 16 knees(5.8%) also had release of IT band. Lateral patellar release was performed in 39 knees (14%) and 23 knees had patella contouring. 93%knees had central patello-femoral alignment postoperatively. One spinout was managed by closed reduction and a second patient had revision of tibial tray for collapse. Patellar subluxation occurred in two patients. The oxford knee score and the American Knee Society clinical score improved from 48.5 to 26 and 21.04 to 86.03 respectively. CONCLUSION. Adequate correction of valgus knee deformity was successfully achieved using our modified technique with satisfactory short term outcome. It is our opinion that the extensive release of soft tissues is not only unnecessary but also fraught with the potential for instability

Aims

Robotic arm-assisted surgery offers accurate and reproducible guidance in component positioning and assessment of soft-tissue tensioning during knee arthroplasty, but the feasibility and early outcomes when using this technology for revision surgery remain unknown. The objective of this study was to compare the outcomes of robotic arm-assisted revision of unicompartmental knee arthroplasty (UKA) to total knee arthroplasty (TKA) versus primary robotic arm-assisted TKA at short-term follow-up.

Abstract. Introduction. Mid-flexion instability may cause poor outcomes following TKA. Surgical technique, patient-specific factors, and implant design could all contribute to it, with modelling and fluoroscopy data suggesting the latter may be the root cause. However, current implants all pass the preclinical stability testing standards, making it difficult to understand the effects of implant design on instability. We hypothesized that a more physiological test, analysing functional stability across the range of knee flexion-extension, could delineate the effects of design, independent of surgical technique and patient-specific factors. Methods. Using a SIMvitro-controlled six-degree-of-freedom robot, a dynamic stability test was developed, including continuous flexion and reporting data in a trans-epicondylar axis system. 3 femoral geometries were tested: gradually reducing radius, multi-radius and single-radius, with their respective tibial inserts. 710N of compression force (body weight) was applied to the implants as they were flexed from 0–140° with three levels of anterior/posterior (AP) tibial force applied (−90N,0N,90N). Results. While in static tests, the implants performed similarly, functional stability testing revealed different paths of motion and AP laxities throughout the flexion cycle. Some designs exhibited mid-flexion instability, while others did not: the multi-radius design allowed increased AP laxity as it transitioned to each arc of reduced femoral component radius; the single-radius design had low tibial bearing conformity, allowing 16mm difference in the paths of mid-flexion versus extension motion. Conclusions. Preclinical lab testing reveals functional differences between different design philosophies. Implant design impacts kinematics and mid-flexion stability, even before factoring in surgical technique and patient-specific factors

Aims. The aim of this study was to evaluate whether achieving medial joint opening, as measured by the change in the joint line convergence angle (∆JLCA), is a better predictor of clinical outcomes after high tibial osteotomy (HTO) compared with the mechanical axis deviation, and to find individualized targets for the redistribution of load that reflect bony alignment, joint laxity, and surgical technique. Methods. This retrospective study analyzed 121 knees in 101 patients. Patient-reported outcome measures (PROMs) were collected preoperatively and one year postoperatively, and were analyzed according to the surgical technique (opening or closing wedge), postoperative mechanical axis deviation (deviations above and below 10% from the target), and achievement of medial joint opening (∆JLCA > 1°). Radiological parameters, including JLCA, mechanical axis deviation, and the difference in JLCA between preoperative standing and supine radiographs (JLCA. PD. ), an indicator of medial soft-tissue laxity, were measured. Cut-off points for parameters related to achieving medial joint opening were calculated from receiver operating characteristic (ROC) curves. Results. Patients in whom the medial joint opening was achieved had significantly better postoperative PROMs compared with those without medial opening (all p < 0.05). Patients who were outliers with deviation of > 10% from the target mechanical axis deviation had significantly similar PROMs compared with patients with an acceptable axis deviation (all p > 0.05). Medial joint opening was affected by postoperative mechanical axis deviation and JLCA. PD. The influence of JLCA. PD. on postoperative axis deviation was more pronounced in a closing wedge than in an opening wedge HTO. Conclusion. Medial joint opening rather than the mechanical axis deviation determined the clinical outcome in patients who underwent HTO. The JLCA. PD. identified the optimal postoperative axis deviation necessary to achieve medial joint opening. For patients with increased laxity, lowering the target axis deviation is recommended to achieve medial joint opening. The target axis deviation should also differ according to the technique of undergoing HTO. Cite this article: Bone Joint J 2024;106-B(3):240–248

Abstract. Introduction. Osteotomy is a recognised surgical option for the management of unicompartmental knee osteoarthritis. The effectiveness of the surgery is correlated with the accuracy of correction obtained. Overcorrection can potentially lead to excess load through the healthy cartilage resulting in accelerated wear and early failure of surgery. Despite this past studies report this accuracy to be as low as 20% in achieving planned corrections. Aim. Assess the effectiveness of adopting modern osteotomy techniques in improving surgical accuracy. Methodology. A prospective cohort study. Patients were identified who had undergone osteotomy surgery for unicompartmental knee OA using a standardised technique. The surgical techniques adopted to ensure accuracy included digital templating software (Orthoview), Precision saw(Stryker), bone wedge allograft and plate osteosynthesis (Tomofix). Pre and post operative analysis of standardised long leg X-rays was performed and the intended (I) and achieved(A) corrections were calculated. Results. A total of 94 (35F/59M) patients with a mean age of 52 years were identified who fulfilled the inclusion criteria for the study. 62 patients were treated with a tibial osteotomy, 21 with femoral and 11 with a double level osteotomy. Using a 10% acceptable range (AR) for error, in 89% of cases (84 of 94) the target Mikulicz point was achieved. Potential risk factors for overcorrection included female sex and osteotomy type, with a higher incidence of over correction observed with double level osteotomies (27%). Conclusion. This study demonstrates that meticulous digital software planning and surgical technique ensures accurate surgical correction in periarticular knee osteotomy surgery

Abstract. Introduction. In cementless UKR, early post-operative tibial fractures are 7x more common in very small tibias. A smaller keel has been shown to reduce this fracture risk, but its effect on fixation is unassessed. This mechanical study assesses the effect of keel interference and size on sagittal micromotion of the tibial component in physiological loading positions. Method. A high-resolution Digital Image Correlation setup was developed and validated to an accuracy of 50 micrometres. Variants of tibial components were 3D-printed: standard, no-interference, no-keel, and a new small keel. Components were implanted into bone-analogue foam which was machined to a CT-reconstructed small tibia, using surgical technique. Tibias were loaded to 200N in physiological loading positions: 8mm (step-up) and 15mm (lunge) posterior to midpoint, and micromotion was assessed. Results. In all tests, anterior lift-off was the largest micromotion observed. In ‘step-up’, a standard keel moved more than the no-interference and no-keel variants (340μm-vs-63μm-vs-30μm, p=0.002). In ‘lunge’ loading, the no-interference and no-keel variants moved more than the standard (826μm-vs-1003μm-vs-521μm, p=0.039). The small keel experienced less micromotion in ‘step-up’ (245μm-vs-340μm p=0.233, overall p=0.009) and ‘lunge’ (378μm-vs-521μm p=0.265, overall p=0.006) than the standard keel. Conclusion. The keel protects against large tibial micromotion during lunge movement. Counterintuitively, interference increases micromotion during step-up movement, likely due to implant pivoting around the bone-keel interface. Results suggest patients should be advised against lunge movements early post-operatively. The new smaller keel fixes similarly or better than the standard keel, making it viable for replacing the standard keel to potentially reduce fracture risk

Abstract. Background. Autologous chondrocyte implantation is a NICE approved intervention however it involves the morbidity of two operations, a prolonged rehabilitation and substantial healthcare costs. This study describes a novel, one-step, bone marrow (BM) derived mesenchymal stem cell (MSC) transplantation technique for treating knee osteochondral lesions and presents our prospective clinical study investigating the success of this technique in 206 lesions over a 5 year period. Methodology. The surgical technique involves harvesting BM from patients’ anterior superior iliac spines, centrifugation to isolate MSCs and seeding into a type 1 collagen scaffold (SyngenitTM Biomatrix). Autologous fibrin glue is used to secure the scaffold into the defect. Inclusion criteria included patients aged 15 – 55 years old with symptomatic osteochondral lesions >1cm2. Exclusion criteria included patients with ligament instability, uncorrected alignment, inflammatory arthropathy and a Body Mass Index >35 kg/m2. Outcome measures included the Modified Cincinnati Knee Rating System (MCKRS), complications and reoperations. Results. Mean MCKR scores showed statistically significant improvements compared to pre-operative scores at 6 months 58.79 ± 3.5 and 1 year postoperatively 63.82 ± 3.93 with further improvements at 2 years and 5 years which did not reach statistical significance. Survival rates were 97.9%, 94% and 93.2% at 1, 2 and 5 years. Multiple regression analysis identified previous cartilage surgery, microfracture and age as factors affecting MCKRS scores (p < 0.029, 0.001 and 0.030, respectively). Conclusions. One-step BM derived stem cell transplantation demonstrates satisfactory outcomes over a 5 year period

Aims. Ideal component sizing may be difficult to achieve in unicompartmental knee arthroplasty (UKA). Anatomical variants, incremental implant size, and a reduced surgical exposure may lead to over- or under-sizing of the components. The purpose of this study was to compare the accuracy of UKA sizing with robotic-assisted techniques versus a conventional surgical technique. Methods. Three groups of 93 medial UKAs were assessed. The first group was performed by a conventional technique, the second group with an image-free robotic-assisted system (Image-Free group), and the last group with an image-based robotic arm-assisted system, using a preoperative CT scan (Image-Based group). There were no demographic differences between groups. We compared six parameters on postoperative radiographs to assess UKA sizing. Incorrect sizing was defined by an over- or under-sizing greater than 3 mm. Results. There was a higher rate of tibial under-sizing posteriorly in the conventional group compared to robotic-assisted groups (47.3% (n = 44) in conventional group, 29% (n = 27) in Image-Free group, 6.5% (n = 6) in Image-Based group; p < 0.001), as well as a higher rate of femoral under-sizing posteriorly (30.1% (n = 28) in conventional group, 7.5% (n = 7) in Image-Free group, 12.9% (n = 12) in Image-Based group; p < 0.001). The posterior femoral offset was more often increased in the conventional group, especially in comparison to the Image-Based group (43% (n = 40) in conventional group, 30.1% (n = 28) in Image-Free group, 8.6% (n = 8) in Image-Based group; p < 0.001). There was no significant overhang of the femoral or tibial implant in any groups. Conclusion. Robotic-assisted surgical techniques for medial UKA decrease the risk of tibial and femoral under-sizing, particularly with an image-based system using a preoperative CT scan. Cite this article: Bone Joint J 2021;103-B(4):610–618

Abstract. Introduction. Patella Baja is a known complication of TKR. In this study, we report the effect of the senior author's change of practice from total excision to minimal resection of Hoffa's fat pad on patellar height. Methods. Retrospective analysis of a prospective series of TKRs performed or directly supervised by the senior author. Group 1 included 72 patients performed before April 2011 who had complete excision of Hoffa's fat pad to improve exposure during their TKR procedures. Group 2 included 138 patients performed after April 2011 who had the minimum excision of Hoffa's fat pad to allow exposure. There were no other changes in surgical technique, implant choice or rehabilitation protocol during this time. Patellar height was measured using the Caton–Deschamps Index (CDI) on standard lateral radiographs immediately postoperative and at a minimum follow up of 1 year. Results. Group 1 included 28 males, 44 females with mean age 68.36 years. The mean CDI in this group changed from 0.54 immediately post-operatively to 0.46 at minimum one year follow-up (P=0.001) indicating progressive Patella Baja. Group 2 included 56 males, 82 females with mean age 65 years. The mean CDI changed from 0.67 immediately post-operative to 0.68 at minimum one year post follow-up (P= 0.32) indicating no statistically or clinically relevant post-operative change in patellar height. Conclusions. Total excision of Hoffa's fat pad is associated with progressive post-operative patella baja which can be avoided by resecting the minimum amount of fat pad to allow adequate exposure

Abstract. Objectives. To determine the effectiveness of LIA compared to ACB in providing pain relief and reducing opiates usage in hamstring graft ACL reconstructions. Materials and Methods. In a consecutive series of hamstring graft ACL reconstructions, patients received three different regional and/or anaesthetic techniques for pain relief. Three groups were studied: group 1: general anaesthetic (GA)+ ACB (n=38); group 2: GA + ACB + LIA (n=31) and group 3: GA+LIA (n=36). ACB was given under ultrasound guidance. LIA involved infiltration at skin incision site, capsule, periosteum and in the hamstring harvest tunnel. Analgesic medications were similar between the three groups as per standard multimodal analgesia (MMA). Patients were similar in demographics distribution and surgical technique. The postoperative pain and total morphine requirements were evaluated and recorded. The postoperative pain was assessed using the visual analogue scores (VAS) at 0hrs, 2hrs, 4hrs, weight bearing (WB) and discharge (DC). Results. There was no statistically significant difference in opiates intake amongst the three groups. When comparing VAS scores; there were no statistical difference between the groups at any of the time intervals that VAS was measured. However, the GA+LIA group hospital's LOS (m=2.31hrs, SD=0.75) was almost half that of GA+ACB group (m=4.24hrs, SD=1.08); (conditions t(72)=8.88; p=0.000). There was no statistical significance in the incidence of adverse effects amongst the groups. Conclusion. The LIA technique provided equally good pain relief following hamstring graft ACL reconstructions when compared to ACB, while allowing for earlier rehabilitation, mobilisation and discharge

Background. In recent years, the use of modern cementless implants in total knee arthroplasty has been increasing in popularity. These implants take advantage of new technologies such as additive manufacturing and potentially provide a promising alternative to cemented implant designs. The purpose of this study was to compare implant migration and tibiofemoral contact kinematics of a cementless primary total knee arthroplasty (TKA) implanted using either a gap balancing (GB) or measured resection (MR) surgical technique. Methods. Thirty-nine patients undergoing unilateral TKA were recruited and assigned based on surgeon referral to an arthroplasty surgeon who utilizes either a GB (n = 19) or a MR (n = 20) surgical technique. All patients received an identical fixed-bearing, cruciate-retaining beaded peri-apatite coated cementless femoral component and a pegged highly porous cementless tibial baseplate with a condylar stabilizing tibial insert. Patients underwent a baseline radiostereometric analysis (RSA) exam at two weeks post-operation, with follow-up visits at six weeks, three months, six months, and one year post-operation. Migration including maximum total point motion (MTPM) of the femoral and tibial components was calculated over time. At the one year visit patients also underwent a kinematic exam using the RSA system. Results. Mean MTPM of the tibial component at one year post-operation was not different (mean difference = 0.09 mm, p = 0.980) between the GB group (0.85 ± 0.37 mm) and the MR group (0.94 ± 0.41 mm). Femoral component MTPM at one year post-operation was also not different (mean difference = 0.27 mm, p = 0.463) between the GB group (0.62 ± 0.34 mm) and the MR group (0.89 ± 0.44 mm). Both groups displayed a lateral pivot pattern with similar frequencies of condylar separation. Conclusion. There was no difference in implant migration and kinematics of a single-radius, cruciate retaining cementless TKA performed using a GB or MR surgical technique. The magnitude of migration suggests there is no risk of early loosening. The results provide support for the use of a cementless TKA as a viable alternative to cemented fixation

Limb alignment in total knee arthroplasty (TKA) influences periarticular soft-tissue tension, biomechanics through knee flexion, and implant survival. Despite this, there is no uniform consensus on the optimal alignment technique for TKA. Neutral mechanical alignment facilitates knee flexion and symmetrical component wear but forces the limb into an unnatural position that alters native knee kinematics through the arc of knee flexion. Kinematic alignment aims to restore native limb alignment, but the safe ranges with this technique remain uncertain and the effects of this alignment technique on component survivorship remain unknown. Anatomical alignment aims to restore predisease limb alignment and knee geometry, but existing studies using this technique are based on cadaveric specimens or clinical trials with limited follow-up times. Functional alignment aims to restore the native plane and obliquity of the joint by manipulating implant positioning while limiting soft tissue releases, but the results of high-quality studies with long-term outcomes are still awaited. The drawbacks of existing studies on alignment include the use of surgical techniques with limited accuracy and reproducibility of achieving the planned alignment, poor correlation of intraoperative data to long-term functional outcomes and implant survivorship, and a paucity of studies on the safe ranges of limb alignment. Further studies on alignment in TKA should use surgical adjuncts (e.g. robotic technology) to help execute the planned alignment with improved accuracy, include intraoperative assessments of knee biomechanics and periarticular soft-tissue tension, and correlate alignment to long-term functional outcomes and survivorship

Introduction. Surgeons performing a total knee replacement (TKR) have two techniques to assist them achieve proper bone resections and ligament tension – gap balancing (GB) and measured resection (MR). GB relies on balancing ligaments prior to bony resections, whereas bony resections are made based on anatomical landmarks in MR. Many studies have been done to compare the implant migration and kinematics between the two techniques, but the results have been varied. However, these studies have not been done on modern anatomically designed prostheses using radiostereometric analysis (RSA). Anatomical designs attempt to mimic the normal knee joint structure to return more natural kinematics to the joint, with emphasis on eliminating both paradoxical anterior motion and reduced posterior femoral rollback. Given the major design differences between anatomical and non-anatomical prostheses, it is important to investigate whether one surgical technique may have advantages another. We hypothesize that there would be no difference between GB and MR techniques in implant migration, but that GB might provide better knee kinematics. Methods. Patients were recruited to receive an anatomically designed prosthesis and randomized to groups where the GB or MR technique is used. For all patients in the study, RSA images were acquired at a 2 week baseline, as well as at 6 weeks, 3 months, and 6 months post-operatively. These images were used to collect the maximum total point motion (MTPM) of the tibial and femoral implant components relative to the bone using a model-based RSA software. A series of RSA images were also acquired at 3-months post-operatively at different knee flexion angles, ranging in 20° increments from 0° to 100°. Model-based RSA software was used to obtain the 3D positions and orientations of the femoral and tibial components, which were used to obtain the anterior-posterior (AP) contact locations for each condyle. Results. Results from 47 patients (27 GB, 20 MR) were analyzed. No significant differences were present between the two surgical techniques for tibial component MTPM at 6 weeks (mean difference=0.02 mm, p=0.61), 3 months (mean difference=0.01 mm, p=0.92), and 6 months (mean difference=0.01 mm, p=0.93) post-operatively. No significant differences were present between the two surgical techniques for femoral component MTPM at 6 weeks (mean difference=0.12 mm, p=0.08), 3 months (mean difference=0.05 mm, p=0.54), and 6 months (mean difference=0.13 mm, p=0.05) post-operatively. On the medial condyle, no significant differences in AP contact location were found at all angles between 0° and 80° of flexion (p-values from 0.28 to 0.95). There was a significant difference medially between the AP contact location of the two surgical techniques at 100° of flexion (p=0.01), indicating more posterior rollback on the medial condyle in the GB technique. On the lateral condyle, no significant differences in AP contact location were found at all angles of flexion (p-values from 0.13 to 0.62). On the medial condyle of the GB group, the AP contact location moved posteriorly 5.83 mm from 0° to 20°, anteriorly 2.60 mm from 20° to 60°, and posteriorly 7.40 mm from 60° to 100°. On the medial condyle of the MR group, the AP contact location moved posteriorly 5.36 mm from 0° to 20°, anteriorly 2.87 mm from 20° to 60°, and posteriorly 3.65 mm from 60° to 100°. On the lateral condyle of the GB group, the AP contact location moved posteriorly 6.87 mm from 0° to 20°, 0.30 mm from 20° to 60°, and 3.61 mm from 60° to 100°. On the lateral condyle of the MR group, the AP contact location moved posteriorly 6.86 mm from 0° to 20°, anteriorly 0.02 mm from 20° to 60°, and posteriorly 3.56 mm from 60° to 100°. Conclusions. The GB and MR techniques are very similar in terms of implant migration and overall kinematics when an anatomical prosthesis design is used for TKR. This study suggests that surgeon preference should be used when deciding which technique to use for implanting this anatomically designed knee replacement. For figures, tables, or references, please contact authors directly

Aims. Stemmed tibial components are frequently used in revision total knee arthroplasty (TKA). The purpose of this study was to evaluate patient satisfaction, overall pain, and diaphyseal tibial pain in patients who underwent revision TKA with cemented or uncemented stemmed tibial components. Methods. This is a retrospective cohort study involving 110 patients with revision TKA with cemented versus uncemented stemmed tibial components. Patients who underwent revision TKA with stemmed tibial components over a 15-year period at a single institution with at least two-year follow-up were assessed. Pain was evaluated through postal surveys. There were 63 patients with cemented tibial stems and 47 with uncemented stems. Radiographs and Knee Society Scores were used to evaluate for objective findings associated with pain or patient dissatisfaction. Postal surveys were analyzed using Fisher’s exact test and the independent-samples t-test. Logistic regression was used to adjust for age, sex, and preoperative bone loss. Results. No statistically significant differences in stem length, operative side, or indications for revision were found between the two cohorts. Tibial pain at the end of the stem was present in 25.3% (16/63) of cemented stems and 25.5% (12/47) of uncemented stems (p = 1.000); 74.6% (47/63) of cemented patients and 78.7% (37/47) of uncemented patients were satisfied following revision TKA (p = 0.657). Conclusion. There were no differences in patient satisfaction, overall pain, and diaphyseal tibial pain in cemented and uncemented stemmed tibial components in revision TKA. Patient factors, rather than implant selection and surgical technique, likely play a large role in the presence of postoperative pain. Stemmed tibial components have been shown to be a possible source of pain in revision TKA. There is no difference in patient satisfaction or postoperative pain with cemented or uncemented stemmed tibial components in revision TKA. Cite this article: Bone Joint J 2021;103-B(6 Supple A):165–170

Introduction. The revision rate of unicompartmental knee replacement (UKR) in national joint registries is much higher than that of total knee replacements and that of UKR in cohort studies from multiple high-volume centres. The reasons for this are unclear but may be due to incorrect patient selection, inadequate surgical technique, and inappropriate indications for revision. Meniscal bearing UKR has well defined evidence based indications based on preoperative radiographs, the surgical technique can be assessed from post-operative radiographs and the reason for revision from pre-revision radiographs. However, for an accurate assessment aligned radiographs are required. The aim of the study was to determine why the revision rate of UKR in registries is so high by undertaking a radiographic review of revised UKR identified by the United Kingdom's (UK) National Joint Registry (NJR). Methods. A novel cross-sectional study was designed. Revised medial meniscal bearing UKR with primary operation registered with the NJR between 2006 and 2010 were identified. Participating centres from all over the country provided blinded pre-operative, post-operative, and pre-revision radiographs. Two observers reviewed the radiographs. Results. Radiographs were provided for 107 revised UKR from multiple centres. The recommended indications were not satisfied in 30%. The most common reason was the absence of bone-on-bone arthritis, and in 16 (19%) the medial joint space was normal or nearly normal. Post-operative films were mal-aligned in 50%. Significant surgical errors were seen in 50%, with most errors attributable to tibial component placement and orientation. No definite reason for revision was identified in 67%. Reasons for revision included disease progression (10%), tibial component loosening (7%), dislocation of the bearing (7%), infection (6%) femoral component loosening (3%), and peri-prosthetic fracture (2% - one femur, one tibia). Discussion and Conclusion. This study found that improper patient selection, inadequate surgical technique, inappropriate revisions and poorly taken radiographs all contributed to the high revision rate. There is a misconception that UKR should be used for early OA. Bone-on-bone arthritis is a requirement and was definitely not present in about 20%. There were many surgical errors, particularly related to the tibial cut: The new instrumentation should reduce this. There was a high prevalence of mal-aligned radiographs. Revisions should be avoided unless there is a definite problem, as the outcome of revision is usually poor in this situation. 80% of UKR revisions could potentially be avoided if surgeons adhered to the recommended indications for primary and revision surgery, and used the recommended surgical techniques. This study therefore suggests that if UKR was used appropriately the revision rate would be substantially lower and probably similar to that of TKR

Abstract. Introduction. In cementless UKR, primary fixation of the tibial component is achieved by press-fitting a keel (i.e. with interference) into a vertical slot cut into the proximal tibia. This may adversely affect the structural integrity of surrounding bone. Early post-operative peri-prosthetic tibial fractures are 7x more common in very small knees, but the aetiology of these fractures is unknown - such sizes are rarely used in the UK but more common in Asian populations. This study explores the effect of keel-related features in fracture risk of these very small tibias. Method. This in vitro study compares the effect of keel and slot depth (standard vs 33% shallower vs nil) and loading position (anterior/posterior gait range limits: mid-tibia vs 8mm posterior) on fracture load and path. 3D-printed titanium components were implanted using surgical instrumentation/technique, in bone-analogue foam machined to a CT-reconstructed very small tibia which subsequently experienced a peri-prosthetic fracture. Results. Introducing a standard slot reduces load-to-fracture by 50% (1421N-vs-710N, p<0.0001). Press-fitting a standard keel further reduces load-to-fracture by 40% (710N-vs-423N, p=0.0001). A shallower slot/keel increases load-to-fracture substantially (slot: 27% increase, 904N-vs-710N p=0.0003, slot+keel: 60% increase, 683N-vs-423N p=0.0004). Deeper keels fractured more vertically (current 8.2° vs shallow 15.5° vs nil 21°, degrees-to-vertical, p<0.0001). There was no difference caused by loading position. Conclusion. In very small tibias, a standard cementless keel significantly weakens the bone and may contribute to fractures. Therefore, decreasing interference or using a shallower keel should decrease the risk of fracture, although it might compromise fixation

Introduction. t is accepted dogma in total knee arthroplasty (TKA) that resecting the posterior cruciate ligament (PCL) increases the flexion space by approximately 4mm, which significantly affects intra-operative decisions and surgical techniques. Unfortunately, this doctrine is based on historical cadaveric studies of limited size. This study purpose was to more accurately determine the effect of PCL resection on the tibiofemoral flexion gap dimension in vivo in a large sample. Methods. Tibiofemoral joint space measurements were made during 127 standardized TKAs by two arthroplasty surgeons. A medial parapatellar approach, computer navigation and provisional tibial and femoral bone cuts were performed in all cases with particular attention to preserving PCL integrity. Cases with an incompetent or damaged PCL were excluded. The tibiofemoral gap dimension was measured with a calibrated tension device at full extension, 45-degrees, and 90-degrees before and after complete PCL resection. Results. 52% of patients were female (66/127), with mean age and BMI of 69.4 years and 34.3 kg/m. 2. , respectively. After PCL resection, the mean joint space dimension increased 0.3mm (range, 0–3mm) at extension, 0.9mm (range, 0–4mm) at 45-degrees, and 1.7mm (range, 0–5mm) at 90-degrees (p<0.001). The 90-degree flexion space opened ≤1mm in 48% of patients and ≥3mm in only 10%. Dividing the flexion gap change by the femoral implant dimension to account and calibrate for patient size, the joint space at 90-degrees increased more in females (0.031 vs. 0.023, p=0.022). Conclusion. The tibiofemoral joint space increases progressively from extension, to mid-flexion through 90-degrees flexion after PCL resection, yet is substantially less than reported in historical studies. However, large variation in the degree of flexion space opening was observed with some patients failing to increase their flexion space whatsoever with PCL resection. This runs counter to conventional TKA understanding and should be considered in modern surgical techniques and education. For figures, tables, or references, please contact authors directly

Introduction. The effect of using thicker liners in primary total knee arthroplasty (TKA) on functional outcomes and aseptic failure rates remains largely unknown. As such, we devised a multicenter study to assess both the clinical outcomes and survivorship of thick vs thin liners after primary TKA. Methods. A search of our institutional databases was performed for patients having undergone bilateral (simultaneous or staged) primary TKA with similar preoperative and surgical characteristics between both sides. Two cohorts were created: thick liners and thin liners. Outcomes collected were as follows: change in Knee Society Score (DKSS), change in range of motion, and aseptic revision. Ad hoc power analysis was performed for DKSS (α ¼ 0.05; power ¼ 80%). Differences between cohorts were assessed. Results. 195 TKAs were identified for each cohort. DKSS and change in range of motion in the thin vs thick cohorts were similar: 51.4 vs 51.6 (P ¼ .86) and 11.1 vs 10.0 (P ¼ .66), respectively. No difference in aseptic revision rates were observed between thin and thick cohorts: all cause (4.1%, 3.1%; P ¼ .59), aseptic loosening (0.5%, 0.5%; P ¼ 1.0), instability (0.5%, 0.5%; P ¼ 1.0), all-cause revision for stiffness (3.1%, 2.1%; P ¼ .52), manipulation under anesthesia (2.1%, 2.1%; P ¼ 1.0), and liner exchange (0.5%, 0%; P ¼ .32). Conclusion. The results of this study suggest that both rates of revision surgery and clinical outcomes are similar for TKAs performed with thick and thin liners. Preoperative factors are likely to play an important role in liner thickness selection, and emphasis should be placed on ensuring sound surgical technique

Introduction. The ideal type of total knee arthroplasty (TKA) prosthesis remains a debatable topic with many different options available. Uncemented TKA has been a viable option due to its decreased operating room (OR) time but also because of its proposed improved long term fixation. Unfortunately, in the past uncemented TKA was associated with increased blood loss. Surgical technique and perioperative treatments have changed since these original studies and tranexamic acid (TXA) has become the gold standard for TKA blood loss management. The objective of this study was to evaluate if there was a difference in hemoglobin and hematocrit change, along with blood loss volume during surgery between cemented and cementless TKA when modern blood loss techniques are utilized. Methods. We retrospectively reviewed data from TKAs performed by three high volume surgeons between 2016 and 2019. We excluded bilateral TKA, revisions, hardware removal intraoperatively and other indications for TKA than primary OA. Power analysis determined 85 patients in both the cementless and cemented TKA groups. Patients were matched 1:1 for age, sex, BMI and surgeon. Use of TXA, intraoperative blood loss, differences in hemoglobin and hematocrit pre- and postoperatively days one, two, and three were recorded. Continuous variables were analyzed using T-tests and categorical variables were evaluated using Chi-squared tests. Results. No significant difference was observed between the cementless and cemented groups for hemoglobin (p=0.214), hematocrit (p=0.164), or intraoperative blood loss volume (p=0.343). A trend towards significantly shorter OR time was seen in the cementless group (p = 0.058). Conclusion. With modern TKA surgery, including the use of TXA, there is no difference in perioperative blood loss between cemented and cementless TKA. Unlike previous studies, the use of modern blood loss salvage techniques in conjunction with cementless TKA fixation, does not result in more blood loss during the perioperative period