The primary aim of this study was to compare the knee specific functional outcome of partial compared with total knee replacement (TKR) for the management of patellofemoral osteoarthritis. Fifty-four consecutive Avon patellofemoral replacements were identified and propensity score matched to a group of 54 patients undergoing a TKR with patella resurfacing for patellofemoral osteoarthritis. The Oxford knee score (OKS), the Short Form (SF-) 12 and patient satisfaction were collected (mean follow up 9.2 years). Survival was defined by revision or intention to revise. There was no significant difference in the OKS (p>0.60) or SF-12 (p>0.28) between the groups. The TKR group was significantly less likely to be satisfied with their knee (95.1% versus 78.3%, OR 0.18, p=0.03). Length of stay was significantly (p=0.008) shorter for the Avon group (difference 1.8 days, 95% CI 0.4 to 3.2). The 10 year survival for the Avon group was 92.3% (95% CI 87.1 to 97.5) and for the TKR group was 100% (95% CI 93.8 to 100). There was no statistical difference in the survival rate (Log Rank p=0.10). The Avon patellofemoral replacement have a shorter length of stay with a functional outcome and satisfaction rate that is equal to that of TKR. The benefits of the Avon need to be balanced against the increased rate of revision when compared with TKR

Introduction. There is a challenge to detect partial tear of the ACL, the number of bundle injured and the proportion of fibers torn. The MRI was shown efficient to individualize the two anteromedial (AM) and posterolateral (PL) bundles of the ACL. The purpose of this study was to assess the ability of the MRI to detect partial tears of the ACL on axial views to display the AM and PL bundles. Materials and methods. This retrospective study included 48 patients (19 partial tears of the ACL, 16 complete rupture of the ACL and 13 normal knee) who underwent both arthroscopy and MRI examinations of the knee. The conventional MRI protocol included one sagittal T1- weighted sequence and 3 proton-density fat sat. The images from MRI were analysis by a radiologist specialized in musculoskeletal imaging who was blinding to the arthroscopic findings. The criteria for the analysis of MRI were divided into primary (those involving the ACL himself) and secondary signs (associated abnormalities). The primary signs included the horizontalisation of the ACL (ACL axis), the global ACL signal intensity and the signal intensity of each AM and PL bundle. The secondary signs included bone bruise, osteochondral impaction, popliteus muscle injury, medial collateral ligament injury and joint effusion. The ACL was classified as normal, partially or totally torn. The rupture of the AM and PL bundle was specified. Results. In our study, MRI was found to have a 75% sensitivity and a 73% specificity for the diagnosis of partial tears of the ACL. The sensitivity to detect AM bundle lesion was 88% but the specificity was 50%. The lack of horizontalisation of the ACL was a very good sign, for partial tears of the ACL, with a sensitivity of 84% and a specificity of 81% (p<0.05). Regarding the secondary signs, there was no significant difference to distinguish partial and complete tear. However, we found that there was a greater probability to find a partial tear of the ACL with the lack of joint effusion, bone bruise and medial collateral ligament injury. Quantifying the proportion of injured fibers was unsuccessful and was found as a failure of the MRI. Conclusions. MRI exhibited lower sensitivity and specificity for partial tear than for complete rupture of the ACL. However 3 important arguments can guide us: the lack of horizontalisation of the ACL, a continuous ACL signal, the display of one of two bundles on the axial view

ACL (anterior cruciate ligament) partial tears include various types of lesions, and an high rate of these lesions evolve into complete tears. Most of the techniques described in literature for the surgical treatment of chronic partial ACL tears, don't spare the intact portion of the ligament. Aim of this study was to perform a prospective analysis of the results obtained by augmentation surgery using gracilis and semitendinosus tendons to treat partial sub-acute lesions of the ACL. This technique requires an “over the top” femoral passage, which enables salvage and strengthening of the intact bundle of ACL. The study included 97 patients treated consecutively at our Institute from 1993 to 2004 with a mean injury-surgery interval of 23 weeks (12–39). Patients were followed up by clinical and instrumental assessment criteria at 3 months, 1 year and 5 years after surgery. Clinical assessment was performed with the IKDC form. Subjective and functional parameters were assessed by the Tegner activity scale. Instrumental evaluation was done using the KT-2000 instrument: the 30 pound passive test and the manual maximum displacement test were performed. We obtained good to excellent results in 95.9% of cases. We didn't observed recurrences in ligamentous laxity. We believe that the described technique has the advantage of being little invasive, compatible with the ACL anatomy, and enables very rapid functional recovery and return to sport

Background/Aims. The development of extendable prostheses has permitted limb salvage surgery in paediatric patients with bone tumours in proximity to the physis. Prostheses are extended to offset limb length discrepancy as the child grows. Aseptic loosening (AL) is a recognised complication. The implant stem must fit the narrow paediatric medullary canal and remain fixed while withstanding growth and increasing physical demands. Novel designs incorporate a hydroxyapatite (HA) coated collar that manufacturers claim improves bony ongrowth and stability, providing even stress distribution in stem and shoulder regions and providing a bone-implant seal, resulting in decreased AL and prolonged survival. This study aims to assess whether there is a relationship between bony ongrowth onto a HA collar and AL. Hypothesis: Bone ongrowth onto the HA collar of extendable prostheses is associated with more stable fixation and less AL despite patient growth. Methods. Retrospective review of 51 primary partial femoral extendable prostheses implanted over 12 years from 1994–2006 (followed up to death at a mean of 2.5±2.2 years or last clinical encounter at a mean of 8.6 years) and 24 subsequent revisions, to ascertain failure rate and mode, together with a cohort study reviewing bony ongrowth onto the HA coated collar in 10 loose and 13 well fixed partial femoral, humeral and tibial implants. Patient growth was measured as a change in bone:implant-width ratio. Results. 21 (41.2%) primary femoral implants failed at a mean 42.8 months, 5 through AL. 1 secondary implant was revised for AL. 2 implants displayed evidence of progressive AL but had not failed at last follow-up. 5 of 11 tibial component revisions in distal femoral replacement were due to AL. 1 major complication occurred after revision surgery for AL in a primary implant: deep infection requiring 2 stage revision. Bony collar ongrowth was significantly higher in all 4 quadrants (anterior, posterior, medial and lateral) in the well-fixed as opposed to loose group, demonstrating a strong negative relationship in each quadrant between bony ongrowth and AL (p0.001) in the presence of patient growth as shown by increased bone:implant width ratio. In both groups, collar ongrowth was greatest in the posterior quadrant. Summary and Conclusions: AL has been confirmed as a common cause of failure in massive extendable endoprostheses. Revision surgery is difficult and may cause serious complications. For the first time, a significant relationship between a well fixed implant stem and bony ongrowth onto a HA coated collar in the context of massive implants used in tumour surgery has been demonstrated. This newly-proven relationship may result in longer-term implant survival and thus a reduced need for revision surgery. It is hoped that this study will provide the basis for further study of this relationship

Purpouse. We hypothesized that patients receiving a medial collagen meniscus implant (MCMI) would show better clinical, radiograpich and Magnetic Resonanace Imaging (MRI) outcomes than patients treated with partial medial meniscectomy (PMM) at minimum 10 year FU. Material and Methods. Thirty-three non-randomized patients (males, mean age 40 years) were enrolled in the study to receive a MCMI (17 patients) or as control treated with a PMM (16 patients). All of them were clinically evaluated at time zero, 5 and minimum 10 years after surgery (mean FU 133 months, range 120–145) by Lysholm, VAS for pain, objective IKDC knee form and Tegner activity level. SF-36 score was performed pre-operatively and at final FU. Bilateral weight-bearing XRays were executed at time zero and at final FU. Minimum 10 years FU MRI images were compared with collected pre-operative MRI images by means of Yulish score. Genovese score was also used to evalute MCMI MRI survivorship. Results. MCMI group showed significantly lower VAS for pain (p = 0.0091), higher objective IKDC (p = 0.0026), Teger index (p = 0.0259) and SF-36 (p = 0.0259 for PHI and p = 0.0036 for MHI) scores compared with PMM group at minimum 10 year FU. Radiographic evaluation showed a significantly lower medial joint line height (p = 0.0002) and side-to-side difference (p = 0.0003) narrowing in MCMI group respect to PMM group at final FU. Discussion. Improvements in pain relief, activity level, objective IKDC score and joint-line preservation are detectable with the use of MCMI at a minimum 10 year FU. On the authors knowledge this is the first long-term controlled trial regarding this device, and our findings confirmed the mid-term good results achieved by Rodkey et al (1). Conclusions. This data support the use of meniscal scaffolds to treat irreparable partial meniscal lesions. Long-term prospective randomized controlled trials on a larger population are necessary to determine the extent and duration of the benefits observed

Background. Extendable partial femoral replacements (EPFR) permit limb salvage in children with bone tumours in proximity to the physis. Older designs were extended through large incisions or minimally invasive surgery. Modern EPFR are lengthened non-invasively. Lengthening improves functional score (Futani, 2006) but has been associated with complications including infection (Jeys, 2005). This study is the first to look specifically at the relationship between EPFR lengthening and complications. Method. Retrospective review of 51 paediatric (<16 years) oncology patients undergoing primary (1 °) EPFR (minimally/noninvasive) between 06/1994 and 01/2006. Exclusions: 1 patient with 5cm extension without medical intervention and 5 patients with incomplete data. Results. There was a negative relationship between age at 1 ° operation and EPFR lengthening (p = 0.03). Mean lengthening for all (including revision) EPFR was 3cm (range 0–13.05). 28 (64%) patients were lengthened a mean 4.8cm at a mean 7 procedures each. 18 were not lengthened, of which 12 were deceased at last followup and 1 had undergone amputation. Lengthening of secondary prostheses contributed a mean 3.7cm to limb length. 2 tertiary implants were lengthened noninvasively by 1.2cm (3 lengthenings) and 1.275cm (5 lengthenings). 16 of 21 failed 1 ° femoral components had been lengthened. The 21 implants underwent a mean 4.2 lengthenings in comparison to mean 1.3 lengthenings in the 28 that did not fail. Number of 1 ° prosthetic lengthenings was positively related to risk of component failure (p = 0.035) and total number of complications (p = 0.049). Complication rate was also related to total lengthening of 1 ° prosthesis (in cm) (p = 0.004). There was a statistically insignificant (p = 0.059) trend towards increased infection rate with higher number of minimally invasive lengthening procedures. Complications were commoner in those undergoing lengthening (mean 3 vs 1.75 in non-lengthened prostheses). Number of lengthenings correlated with number of complications (p = 0.001). Total lengthening of distal EPFR correlated with incidence of knee fixed flexion deformity (FFD)(p = 0.034). Median lengthening was 3cm in those with FFD and 0cm in those without (p = 0.019). Open lengthening procedures caused 6 complications: 2 deep & 3 superficial infections and recurrent subluxation requiring acetabuloplasty in a proximal replacement. Summary/Conclusions. The inverse relationship between age at 1 ° operation and lengthening is expected if the aim of offsetting limb length discrepancy during growth is being achieved. Lengthening is associated with increased complications (particularly infection and FFD) and femoral component failure, suggesting that lengthening procedures are implicated in the cause of some complications. 5 infective complications after lengthening were theoretically avoidable if noninvasive growers were used

Coronal plane fractures of the posterior femoral condyle, also known as Hoffa fractures, are rare. Lateral fractures are three times more common than medial fractures, although the reason for this is not clear. The exact mechanism of injury is likely to be a vertical shear force on the posterior femoral condyle with varying degrees of knee flexion. These fractures are commonly associated with high-energy trauma and are a diagnostic and surgical challenge. Hoffa fractures are often associated with inter- or supracondylar distal femoral fractures and CT scans are useful in delineating the coronal shear component, which can easily be missed. There are few recommendations in the literature regarding the surgical approach and methods of fixation that may be used for this injury. Non-operative treatment has been associated with poor outcomes. The goals of treatment are anatomical reduction of the articular surface with rigid, stable fixation to allow early mobilisation in order to restore function. A surgical approach that allows access to the posterior aspect of the femoral condyle is described and the use of postero-anterior lag screws with or without an additional buttress plate for fixation of these difficult fractures.

Cite this article: Bone Joint J 2013;95-B:1165–71.

Aims. The aim of this study was to assess the safety and clinical outcome of patients with a femoral shaft fracture and a previous complex post-traumatic femoral malunion who were treated with a clamshell osteotomy and fixation with an intramedullary nail (IMN). Methods. The study involved a retrospective analysis of 23 patients. All had a previous, operatively managed, femoral shaft fracture with malunion due to hardware failure. They were treated with a clamshell osteotomy between May 2015 and March 2020. The mean age was 42.6 years (26 to 62) and 15 (65.2%) were male. The mean follow-up was 2.3 years (1 to 5). Details from their medical records were analyzed. Clinical outcomes were assessed using the quality of correction of the deformity, functional recovery, the healing time of the fracture, and complications. Results. The mean length of time between the initial injury and surgery was 4.5 years (3 to 10). The mean operating time was 2.8 hours (2.05 to 4.4)), and the mean blood loss was 850 ml (650 to 1,020). Complications occurred in five patients (21.7%): two with wound necrosis, and three with deep vein thrombosis. The mean coronal deformity was significantly corrected from 17.78° (SD 4.62°) preoperatively to 1.35° (SD 1.72°) postoperatively (p < 0.001), and the mean sagittal deformity was significantly corrected from 20.65° (SD 5.88°) preoperatively to 1.61° (SD 1.95°; p < 0.001) postoperatively. The mean leg length discrepancy was significantly corrected from 3.57 cm (SD 1.27) preoperatively to 1.13 cm (SD 0.76) postoperatively (p < 0.001). All fractures healed at a mean of seven months (4 to 12) postoperatively. The mean Lower Extremity Functional Scale score improved significantly from 45.4 (SD 9.1) preoperatively to 66.2 (SD 5.5) postoperatively (p < 0.001). Partial cortical nonunion in the deformed segment occurred in eight patients (34.8%) and healed at a mean of 2.4 years (2 to 3) postoperatively. Conclusion. A clamshell osteotomy combined with IMN fixation in the treatment of patients with a femoral shaft fracture and a previous post-traumatic femoral malunion achieved excellent outcomes. Partial cortical nonunions in the deformed segment also healed satisfactorily. Cite this article: Bone Joint J 2023;105-B(4):449–454

Introduction. Patellofemoral instability is one of the most common presentations to a children's orthopaedic clinic. Recurrent patellar dislocations and instability episodes are painful, disabling and increase the risk of irreversible chondral damage. The medial patellofemoral ligament is the primary static stabiliser to prevent lateral dislocation of the patella and is almost always torn or attenuated in these cases. Reconstruction of this ligament is commonly performed using autologous hamstring tendon however there has been some interest recently in use of quadriceps tendon as a graft. Children with patellar instability also present unique challenges due to the small size of the patella and the presence of open growth plates which may require adaptations to the common techniques. Methods. Patients undergoing medial patellofemoral ligament reconstruction using quadriceps tendon autograft were identified using electronic theatre records. Prospectively collected clinical records and imaging findings were reviewed and underlying pathology, additional procedures at time of MPFL reconstruction, current function and need for further revision surgery determined. Results. Between January 2019 and August 2023, 50 MPFL reconstructions were performed in 37 children using partial thickness quadriceps autograft. Patient age at time of surgery ranged from 5 to 17 years (median age 13 years). The technique was utilised for a variety of indications including recurrent traumatic and habitual patellofemoral instability, fixed dislocations, and revision MPFL reconstruction. Conclusion. Partial thickness quadriceps tendon autograft can be used safely to primarily reconstruct the medial patellofemoral ligament in paediatric population, including those children with open growth plates. It also has utility in revision cases following previous failed hamstring MPFL reconstruction. We have noted that the younger the child, the more distal to the physis lies the femoral point of isometricity, rendering this a safe and reproducible treatment in this age group. Use of this technique has increased in our unit as we have observed that patients seem to be satisfied with their clinical and functional outcomes with a low incidence of short- and medium-term complications

Accurate evaluation of lower limb coronal alignment is essential for effective pre-operative planning of knee arthroplasty. Weightbearing hip-knee-ankle (HKA) radiographs are considered the gold standard. Mako SmartRobotics uses CT-based navigation to provide intra-operative data on lower limb coronal alignment during robotic assisted knee arthroplasty. This study aimed to compare the correlation between the two methods in assessing coronal plane alignment. Patients undergoing Mako partial (PKA) or total knee arthroplasty (TKA) were identified from our hospital database. The hospital PACS system was used to measure pre-operative coronal plane alignment on HKA radiographs. This data was correlated to the intraoperative deformity assessment during Mako PKA and TKA surgery. 443 consecutive Mako knee arthroplasties were performed between November 2019 and December 2021. Weightbearing HKA radiographs were done in 56% of cases. Data for intraoperative coronal plane alignment was available for 414 patients. 378 knees were aligned in varus, and 36 in valgus. Mean varus deformity was 7.46° (SD 3.89) on HKA vs 7.13° (SD 3.56) on Mako intraoperative assessment, with a moderate correlation (R= 0.50, p<0.0001). Intraoperative varus deformity of 0-4° correlated to HKA measured varus (within 3°) in 60% of cases, compared to 28% for 5-9°, 17% for 10-14°, and in no cases with >15° deformity. Mean valgus deformity was 6.44° (SD 4.68) on HKA vs 4.75° (SD 3.79) for Mako, with poor correlation (R=0.18, p=0.38). In this series, the correlation between weightbearing HKA radiographs and intraoperative alignment assessment using Mako SmartRobotics appears to be poor, with greater deformities having poorer correlation

Aims. The purpose of this study was to identify factors associated with limitations in function, measured by patient-reported outcome measures (PROMs), six to nine months after a proximal humeral fracture, from a range of demographic, injury, psychological, and social variables measured within a week and two to four weeks after injury. Patients and Methods. We enrolled 177 adult patients who sustained an isolated proximal humeral fracture into the study and invited them to complete PROMs at their initial outpatient visit within one week of injury, between two and four weeks, and between six to nine months after injury. There were 128 women and 49 men; the mean age was 66 years (. sd. 16; 18 to 95). In all, 173 patients completed the final assessment. Bivariate analysis was performed followed by multivariable regression analysis accounting for multicollinearity using partial R. 2. , correlation matrices, and variable inflation factor. Results. Many variables within a week of injury and between two and four weeks after injury correlated with six- to nine-month PROMs in bivariate analysis. Kinesiophobia measured within a week of injury (Tampa Scale for Kinesiophobia-11: partial R. 2. = 0.14; p = 0.000) and self-efficacy measured between two and four weeks (Pain Self-efficacy Questionnaire-2: partial R. 2. = 0.266; p < 0.001) were the strongest predictors of limitations (measured by Patient Reported Outcome Measurement Information System Upper Extremity Physical Function Computer Adaptive Test (PROMIS UE)) at six to nine months in multivariable analysis. Similar findings were observed with other types of PROM. Regression models accounted for a substantial amount of variance in all PROMs at both timepoints (e.g. 66% of the overall variance within one week, and 70% within two to four weeks for PROMIS UE at six to nine months). . Conclusion. Recovery from a proximal humeral fracture appears to be enhanced by overcoming fears of movement or reinjury within a week after injury and greater self-efficacy (developing resilience and more effective coping strategies) within a month. Such factors are modifiable using enhanced communication skills and cognitive behavioural treatments. These findings could be a catalyst for the routine assessment and treatment of psychological and social factors in the management of patients with fractures. Cite this article: Bone Joint J 2019;101-B:715–723

Aims. Patients who sustain neck of femur fractures are at high risk of malnutrition. Our intention was to assess to what extent malnutrition was associated with worse patient outcomes. Methods. A total of 1,199 patients with femoral neck fractures presented to a large UK teaching hospital over a three-year period. All patients had nutritional assessments performed using the Malnutrition Universal Screening Tool (MUST). Malnutrition risk was compared to mortality, length of hospital stay, and discharge destination using logistic regression. Adjustments were made for covariates to identify whether malnutrition risk independently affected these outcomes. Results. Inpatient mortality was 5.2% (35/678) in the group at low risk of malnutrition, 11.3% (46/408) in the medium-risk group, and 17.7% (20/113) in the high-risk group. Multivariate analysis showed each categorical increase in malnutrition risk independently predicted inpatient mortality with an odds ratio (OR) of 1.59 (95% confidence interval (CI) 1.14 to 2.21; p = 0.006). An increased mortality rate persisted at 120 days post-injury (OR 1.64, 95% CI 1.20 to 2.22; p = 0.002). There was a stepwise increase in the proportion of patients discharged to a residence offering a greater level of supported living. Multivariate analysis produced an OR of 1.34 (95% CI 1.03 to 1.75; p = 0.030) for each category of MUST score. Median length of hospital stay increased with a worse MUST score: 13.9 days (interquartile range (IQR) 8.2 to 23.8) in the low-risk group; 16.6 days (IQR 9.0 to 31.5) in the medium-risk group; and 22.8 days (IQR 10.1 to 41.1) in the high-risk group. Adjustment for covariates revealed a partial correlation coefficient of 0.072 (p = 0.008). Conclusion. A higher risk of malnutrition independently predicted increased mortality, length of hospital stay, and discharge to a residence offering greater supported living after femoral neck fracture. Cite this article: Bone Joint J 2021;103-B(1):164–169

Introduction. Throughout the years treatment of patellar fractures have been held in much controversy and various treatment procedures have been described. In the literature, there are only a few studies that compare the results of the different treatment modalities. Materials & Methods. This study reviews our experience with patellar fractures and correlates results of different treatment modalities to grade of patellar comminution and to the length of follow-up. It consists of 114 patients (71 M, 43 F, 17–76 year old: mean- 43 years), followed for 2–9 years (mean- 3.5 years). Patients were treated by P.O.P. cast for undisplaced fractures (12 Pts), and by various surgical modalities for displaced or comminuted fractures such as O.R.I.F (53 Pts), partial patellectomy (37 Pts) and total patellectomy (12 Pts). Patients were evaluated by Lisholm functional score, by objective knee tests, and radiographically. Results. Correlation to treatment modalities showed that functional results were excellent and good in 86% of the patients following conservative treatment by P.O.P. cast, 77% treated by O.R.I.F., 75% treated by partial patellectomy and 78% treated by total patellectomy (objective results −79%, 72%, 72%, 66.66% respectively). No statistical differences were found between these groups. However, the correlation between these treatment modalities to grade of patellar comminution revealed that in two fragment fractures similar results were observed following partial patellectomy and O.R.I.F., whereas in patients with three or more fragment fractures, a significantly better outcome was observed after partial patellectomy (79% and 62% respectively). The patients with comminuted patellar fractures treated by partial patellectomy had also a better short and long-term outcome than with all other techniques. Conclusions. Based on this study it seems that O.R.I.F. remains as the first optimal treatment in simple two parts patellar fractures, where partial patellectomy should be considered as the treatment of choice in patients with patellar fractures of three or more fragments. Total patellectomy is the optional treatment in patients with comminuted fractures

Aims. The treatment of late presenting fractures of the lateral humeral condyle in children remains controversial. . Methods. We report on the outcome for 16 children who presented with a fracture of the lateral humeral epicondyle at a mean of 7.4 weeks (3 to 15.6) after injury and were treated surgically. Results. The mean follow-up was four years (1.1 to 8.9), at which time the mean age of the patients was 8.7 years (3.2 to 17.8). . The mean Dhillon functional score improved from 3.3 to 5.6 and the mean overall scores improved from 5.6 to 8.5. . A total of seven patients had a fishtail deformity and eight had partial lateral epiphyseal closure. None had avascular necrosis. MRI showed an abnormal cartilage signal, incongruence of the joint surface and partial premature closure of the lateral physis in four patients. . Discussion. Neither age at the time of injury, the time interval between injury and operation, nor the pre-operative function were correlated with the incidence of complications. . These results support the use of internal fixation for children with a lateral humeral epicondylar fracture with a delayed presentation. Take home message: Open reduction and internal fixation yielded a satisfactory outcome within 16 weeks in children with a lateral humeral epicondylar fracture with a delayed presentation. Cite this article: Bone Joint J 2016;98-B:244–8

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The aim of this study was to describe services available to patients with periprosthetic femoral fracture (PPFF) in England and Wales, with focus on variation between centres and areas for care improvement.

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Posterior column plating through the single anterior approach reduces the morbidity in acetabular fractures that require stabilization of both the columns. The aim of this study is to assess the effectiveness of posterior column plating through the anterior intrapelvic approach (AIP) in the management of acetabular fractures.

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To assess the feasibility of a randomized controlled trial (RCT) that compares three treatments for acetabular fractures in older patients: surgical fixation, surgical fixation and hip arthroplasty (fix-and-replace), and non-surgical treatment.

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The aim of this study was to compare the functional and radiological outcomes and the complication rate after nail and plate fixation of unstable fractures of the ankle in elderly patients.

We investigated the stability of seven Schatzker type II fractures of the lateral tibial plateau treated by subchondral screws and a buttress plate followed by immediate partial weight-bearing. In order to assess the stability of the fracture, weight-bearing inducible displacements of the fracture fragments and their migration over a one-year period were measured by differentially loaded radiostereometric analysis and standard radiostereometric analysis, respectively. The mean inducible craniocaudal fracture fragment displacements measured −0.30 mm (−0.73 to 0.02) at two weeks and 0.00 mm (−0.12 to 0.15) at 52 weeks. All inducible displacements were elastic in nature under all loads at each examination during follow-up. At one year, the mean craniocaudal migration of the fracture fragments was −0.34 mm (−1.64 to 1.51). Using radiostereometric methods, this case series has shown that in the Schatzker type II fractures investigated, internal fixation with subchondral screws and a buttress plate provided adequate stability to allow immediate post-operative partial weight-bearing, without harmful consequences

Introduction. Radiolucencies beneath the tibial component are well recognized in knee arthroplasty; the aetiology and significance are poorly understood. Non-progressive narrow radiolucencies with a sclerotic margin are thought not to be indicative of loosening. Factors which decrease the incidence of radiolucencies include cementless fixation and the use of pulse lavage. Leg/component alignment or BMI do not influence radiolucency. We are not aware of any studies that have looked at the effect of load type on radiolucency. The Oxford domed lateral tibial component was introduced to decrease the bearing dislocation rate that was unacceptably high with the flat tibial tray. However, the introduction of the domed tibial component alters the forces transmitted through the implant-cement-bone interface. As the Oxford UKR uses a fully congruent mobile bearing, the forces transmitted through the interface with a flat tray are compressive, except for the effect of friction. However, with the domed tibial component shear forces are introduced. The aim of this study was to assess the prevalence of radiolucency beneath the previous flat design and the new domed tibial tray. Patients and methods. A consecutive series of 248 cemented lateral UKRs (1999–2009) at a single institution were assessed. The first 55 were with a flat tibia and the subsequent 193 with a domed component. One year post-op radiographs were assessed, by two observers, for the presence (full or partial) and distribution of radiolucency. The distribution and thickness of each radiolucency. Cases were excluded for missing or poorly aligned radiographs. Results. In the flat group there were 42 patients (17 male, 25 female) with 42 joints. In the domed group there were 139 patients (44 male, 95 female) with 146 joints. There was a statistical significant difference between groups for the presence and extent of radiolucency (p<0.001). In the flat group, 6 (14%) had a full radiolucency and 18 (43%) had a partial radiolucency. 14 of the 18 partial radiolucencies involved the far lateral zones (1&2) and 3 partial radiolucencies involved the keel. In the domed group 6, (4.1%) had a full radiolucency and 13 (8.9%) had a partial radiolucency. All radiolucencies observed were less than 1 mm thick. Intra-class correlation for inter-observer agreement for assessment of radiolucency was 0.679. Discussion. The introduction the domed lateral tibial component results in a reduction in prevalence of radiolucency compared to a flat component. This suggests, as the mode of fixation is identical, that the forces across the tibial-cement-bone interface have a significant effect on the development of the tissue at that interface. In particular it suggests that compressive forces alone tend to cause soft tissue to be formed at the interface, whereas shear force causes bone