Aim. Nail patella syndrome (NPS) is a skeletal dysplasia with patellofemoral dysfunction as a key symptom. We present the first in-depth radiological evaluation of the knee in a large series of NPS patients and describe the typical malformations. Patients and Methods. Conventional radiological examination of 95 skeletally mature patients with NPS was performed. Patellar morphology was classified according to the Wiberg classification as modified by Baumgartl and Ficat criteria, and trochlear shape was classified according to the Dejour classification. Results. Patellar aplasia was present in 4/90 (4%), and patellar hypoplasia in 77/90 (86%) of patients. The prevailing patellar shapes were type III, type IV and Hunter’s cap. No patellar shape genotype-phenotype association could be found. The malformations of the distal femur comprised shortening of the lateral femoral condyle in 46 out of 84 patients (55%), with a prominent anterior surface of the lateral femoral condyle in 47 out of 84 patients (56%) and a flat anterior surface of the medial femoral condyle in 78 out of 85 patients (92%). The trochlea was type A1 according to the Dejour classification in 79 out of 85 patients (93%). . Conclusion. An easily recognisable characteristic quartet of malformations consisting of patellar aplasiaor hypoplasia and the malformations of the distal femur was found in 22 out of 81 patients (27%), with the majority displaying at least three malformations. Take home message: The distinct malformations of the knee in nail patella syndrome are easily recognisable on conventional radiographs and lead to the correct interpretation of the aberrant morphology which is essential in the treatment of these patellofemoral disorders. Cite this article: Bone Joint J 2016;98-B:483–9

Introduction. The degree of cartilage degeneration assessed intraoperatively may not be sufficient as a criterion for patellar resurfacing in total knee arthroplasty (TKA). However, single-photon emission tomography/computed tomography (SPECT/CT) is useful for detecting osteoarthritic involvement deeper in the subchondral bone. The purpose of the study was to determine whether SPECT/CT reflected the cartilage lesion underneath the patella in patients with end-stage osteoarthritis (OA) and whether clinical outcomes after TKA without patellar resurfacing differed according to the severity of patellofemoral (PF) OA determined by visual assessment and SPECT/CT findings. Methods. This study included 206 knees which underwent TKA. The degree of cartilage degeneration was graded intraoperatively according to the International Cartilage Repair Society grading system. Subjects were classified into four groups according to the degree of bone tracer uptake (BTU) on SPECT/CT in the PF joint. The Feller's patella score and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) were assessed preoperatively and postoperative 1 and 2 years. Results. The increased BTU in the PF joint was associated with more severe degenerative cartilage changes underneath the patella (P < 0.001). The risk for the presence of denudated cartilage was greater in the high uptake group (odds ratio = 5.89). There was no association between clinical outcomes and visual grading of patellar cartilage degeneration or the degree of BTU on SPECT/CT. Discussion and Conclusions. The visual assessment of the degree of cartilage degeneration underneath the patella and preoperative SPECT/CT evaluation of the PF joint were not predictive of clinical outcome after TKA with unresurfaced patella

Introduction & aims. Resurfacing of the patella is an important part of most TKA operations, usually using an onlay technique. One common practice is to medialise the patellar button and aim to recreate the patellar offset, but most systems do not well control alignment of the patella button. This study aimed to investigate for relationships between placement and outcomes and report on the accuracy of patella placement achieved with the aid of a patella Patient Specific Guide (PSG). Method. A databse of TKR patients operated on by five surgeons from 1-Jan-2014 who had a pre-operative and post-operative CT scan and 6-month postoperative Knee Osteoarthritis and Outcome (KOOS) scores were assessed. Knees were excluded if the patella was unresurfaced or an inlay technique was used. All knee operations were performed with the Omni Apex implant range and used dome patella buttons. A sample of 40 TKRs had a patella PSG produced consisting of a replication of an inlay barrel shaped to fit flush to the patient's patella bone. The centre of the quadriceps tendon on the superior pole of the patella bone and the patella tendon on the inferior were landmarked. 3D implant and bone models from the preoperative CT scans were registered to the post-operative CT scan. The flat plane of the implanted patella button was determined and the position of the button relative to the tendon attachments calculated. Coverage of the bone by the button and patellar offset reconstruction were also calculated. The sample of 40 TKRs for whom a patella PSG was produced had their variation in placement assessed relative to the wider population sample. All surgeries were conducted with Omni Apex implants using a domed patella. Results. A total of 322 patients were identified in the database, and 82 were subsequently excluded as inlay rather than onlay patella. 59% (142) were female and the average age was 68.9 years (+/− 7.2). Coverage percentage of the cut patella surface by the button was 67% (± 7%), with 83% (200) knees having greater than 60%, and 40% (96) greater than 70%. Component position was on average centralised in terms of mediolateral position (0.09mm ± 1.93 lateral). When comparing the alignment of the patients whose knees used PSG guides with those who did not, it was found there was a statistically significant reduction in the variation that both external rotation error and flexional error had (p-values 0.048 and 0.022 respectively.). Excess medialisation of the patella button was found to weakly correlate with reduced postoperative KOOS symptoms scores (coefficient=0.14, p-value = 0.035). When subdivided into patients who reported knee clicking sometimes or more often and those who did not, patients with highly medialised buttons had a 1.5× likelihood of reporting clicking of their knee joint (p-value = 0.036). Conclusions. The patella-femoral joint remains a crucial component in the TKA knee, but the process of resurfacing the bone is not well controlled and can negatively influence patient outcomes. PSG's are one potential mechanism of controlling patella component alignment

Patello-femoral arthritis can result in a considerable thinning of the patella. The restoration of an adequate patella thickness is key to the successful outcome of knee arthroplasty. The objectives were (1) to establish a reproducible patella width:thickness index including chondral surface and (2) to investigate whether there is a difference between bone alone and bone/chondral construct thickness as shown by MRI. Forty three MRI scans of young adults, mean age 27 (range 17–38), 34 male and 9 female, were studied. Exclusion criteria included degenerative joint disease, patello-femoral pathology or age under 16/over 40 (102 patients). The bony and chondral thickness of the patella and its width were measured. Inter/intra observer variability was calculated and correlation analysis performed. We found a strong correlation between patella plus cartilage thickness and width (Pearson 0.75, P < 0.001). The mean width:thickness ratio was 1.8 (SD 0.10, 95% CI 1.77–1.83). Without cartilage the ratio was 2.16 (SD 0.15, 95% CI 2.11–2.21), correlation was moderate (Pearson 0.68, P < 0.001). The average patella cartilage thickness was 4.1mm (SD 1.1, 95% CI 3.8–4.5). The narrow confidence intervals for the ratio of patella width:thickness suggest that patella width can be used as a guide to accurate restoration of patella thickness during total knee or patella-femoral replacement. We would recommend a ratio of 1.8:1

Introduction. The trochlea of a typical patellofemoral replacement or anterior flange of a total knee replacement usually extends past the natural trochlea and continues onto the femoral anterior cortex. One reason for this is that it allows a simple patella button to be permanently engaged in the trochlea groove in an attempt to ensure stability. On the natural patella, the apex helps to guide it into the trochlea groove as the knee moves from full extension into flexion. The aim is to study whether a generalised patella can be created that is close in form to a healthy patella. Method. MRI scans were taken of 30 patellae. Characteristics of these patellae (height, width, thickness, apex angle) were measured. The apex angle was found to be similar between patellae (mean=126 degrees, sd = 8.8), as were the ratios between height and width (mean width/height = 1.05, sd = 0.07) and between thickness and width (mean width/thickness = 1.8, sd = 0.19). These patellae were then segmented to create a surface including cartilage, resulting in 30 STL (stereolithography) files in which the surfaces are represented by triangle meshes. To design the average patella the individual patellae were aligned to a standard frame of reference by placing a set of landmarks on the proximal/distal, medial/lateral and anterior/posterior extents of each (fig.1). The vertical axis was defined as passing parallel to the proximal/distal points and the horizontal as passing parallel to the medial/lateral points when looking along the computed vertical axis. The origin centre of the frame of reference was chosen to be mid-way between these points. The mean width was then computed and each patella scaled linearly around the origin to give them all equal width. All the aligned patellae were then averaged together to provide a composite cartilaginous patella. The averaging process was achieved by taking one patella as a seed. The patella chosen for seed was that whose parameters were closest to the average width, height and thickness. An approximately normal vector was passed a point ‘P’ on the seeds, and the points at which these intersected the other models were then determined. The closest intersection point to ‘P’ on each model was chosen and these averaged together. ‘P’ is then replaced in the model with this average point. The averaging process then continues with all the remaining points on the seed model in the same manner to build the average models. Results and Discussion. The mean patella was compared with individual patellae. This comparison was performed by taking each point on the mean patella and finding the closest point on individual patellae - a colour coded map of differences was obtained (fig.2) along with a mean of the absolute difference for each patella. The absolute mean difference ranged from 0.56mm to 1.33mm, averaging at 0.85mm. This shows a reasonable fit between the average patella and each individual example, raising the possibility of using the average shape in future research to develop anatomical patellofemoral replacements and for planning patella resurfacing

Introduction. Patella femoral joint bearings in total knee replacements have shown low wear (3.1 mm. 3. /MC) under standard gait simulator conditions. 1. However, the wear in retrieval studies have shown large variations between 1.3 to 45.2 mm. 3. /year. 2. Previous in vitro studies on the tibial femoral joint have shown wear is dependent on design, materials and kinematics. 3. . The aim of this study was to investigate the influence of the design (geometry) and shape on the wear rate of patella femoral joints in total knee replacements. Materials and Methods. The Leeds/Prosim knee simulator was used to investigate the wear of two types of commercially available patellae. The PFC Sigma cobalt chrome femoral component was coupled with 2 types of patellae buttons: round and oval dome. The UHMWPE was the same for the both types – GUR1020 GVF (gamma irradiated in vacuum and foiled packed). 25% bovine serum was used as the lubricant. The test were carried out at three conditions – high medial lateral (ML) rotations (<4°) and uncontrolled ML displacement (<4 mm), low ML rotation (<1°) and uncontrolled ML displacement (<4 mm); the physiological gait cycle; and low ML rotation and controlled ML displacement (<1.5 mm). In this abstract the two designs were tested in physiological gait condition (Figure 1). Patella ML displacement and tilt were passively controlled and measured after every 300,000 cycles. A ligament resisting force equivalent to 10 N4 was applied on the lateral side of the patella to avoid patella slip. Five samples of each design were tested for 3 million cycles at a cycle rate of 1 Hz. The wear volume was obtained gravimetrically every million cycles and presented with 95% confidence limits. Statistical significance was taken at p<0.05. Results and Discussions. The wear rate of PFC sigma round dome patella was higher (8.63 ± 3.44 mm. 3. /million cycles) compared to the PFC sigma oval dome patella (6.28 ± 3.89 mm. 3. /million cycles) (Figure 2). However, no significant difference in the wear rates was found between the two shapes (P=0.2). The low area of contact of oval dome patella (31.2% of total surface area) as compared to round dome patella (39.9%) led to low wear. 5. . The wear volume and the patellar tilt were positively correlated for oval dome and round dome patella, R. 2. > 0.9 (Figure 3). Increase in the patellar tilt resulted increase in sliding distance in perpendicular direction of polymer orientation. This led to higher wear volume. Conclusions. Wear rate decreased with change of patella shape from round dome to oval dome although not significantly. Increase in the patellar tilt resulted in increase in the wear volume. Acknowledgement. This research was supported in part by the DePuy and EPSRC. In addition, it was partially funded through WELMEC, a Centre of Excellence in Medical Engineering funded by the Wellcome Trust, under grant number WT 088908/Z/09/Z and additionally supported by the NIHR (National Institute for Health Research) as part of collaboration with the LMBRU (Leeds Musculoskeletal Biomedical Research Unit)

Patella instability is a common problem with many surgical options. We prospectively evaluated the results of medial patella femoral ligament (MPFL) reconstruction with an autogenous gracilis or semitendinous graft. With a minimum follow up of one year patients were reviewed using the Kujala scoring system. Twenty MPFL reconstructions were performed on seventeen patients over a two year period, from January 2004 to December 2005. There were 13 females and 4 males. Three patients had bilateral involvement. Thirteen patients had a lateral release with their MPFL reconstruction and three had a distal realignment procedure as well to correct their patella instability. The mean follow up was 17 months (range 12 to 26 months). The average age was 25 years old at operation (range 13 to 47) and the average age of their first dislocation was 16 (range 0-35). Nine patients had previous surgical treatment for patella instability. The average hypermobility score in the patients was 5/9 and six patients scored 9/9. At follow up 18 out of 20 patients (90%) had stable tracking with no further subluxations/dislocations. Of the two with unstable tracking, one had a stable patella before falling several times onto her knee. An MRI confirmed the ligament was intact but a type 2 trochlear dysplasia was present and a Bereiter trochleoplasty was subsequently performed. The other patient described no frank dislocation but instead subluxations. Eighteen of the twenty reconstructions (90%) achieved a stable patella. Overall Kujala scores increased by a third

Aim. To assess if there is a reproducible relationship between the width and thickness of the normal patella. Method. 43 MRI scans of young adults, average age 27 (range 17–38) were studied. Exclusion criteria included a diagnosis of degenerative joint disease, patella-femoral pathology or age under 16/over 40 (102 patients). The bony thickness of the patella, the chondral thickness and patella width were measured, as was the location of maximal patella thickness. Inter/intra observer variability was calculated and correlation analysis performed. Results. There was a strong correlation between overall patella thickness (bone plus cartilage) and width (Pearson 0.75, P < 0.001). The width: thickness ratio is 1.8:1 (standard deviation 0.102, 95% confidence interval 1.6–2.0). The average patella cartilage thickness is 4.1mm (SD 1.3). The thickest region of the patella lies 54% (SD 2.32) from the lateral border and 54% (SD 7.9) from the superior pole. Conclusion. We propose that the normal “Index of Patella Width: Thickness” = 1.8:1. It can be used as a guide for restoring patella thickness during TKR or patella-femoral replacement to that of a knee free from age related wear and osteoarthritis. This maximal thickness should be slightly medial and distal in the patella. MULTIPLE DISCLOSURES

Aims: The purpose of this study was to determine whether patella replacement or RAP of the patella is advantageous in TKA. Methods: 100 patients were recruited to enter a randomised, prospective, double blind clinical trial to determine the efþcacy of patellar resurfacing during total knee arthroplasty. All patients receive the same posterior cruciatesparing prosthesis, and all operations were performed by, or under the direct supervision of the þrst author. Evaluation consisted of the determination of the HSS-Score, the knee society scores, speciþc questions relating to patellafemoral symptoms, radiographs, measurement of torques and stability of one leg standing. All knees were followed at 3 month and 18 month postoperatively. Results: There was no signiþcant difference between the two groups with regard to the HSS-Score, and the KS-scores. Excentric and concentric torques were higher in the group with RAP of the patella. One leg standing was more stable in the group with RAP of the patella. In both groups one patient complained of severe anterior knee pain. The patient with RAP of the patellar was treated successfully with secondary patella resurfacing. Conclusions: The clinical outcome and the prevalence of anterior knee pain after TKA with the PFC-∑ knee was not inßuenced by whether or not the patella had been resurfaced. Force and balance are slightly better after TKA with RAP of the patella

Aims. The mid-term results of kinematic alignment (KA) for total knee arthroplasty (TKA) using image derived instrumentation (IDI) have not been reported in detail, and questions remain regarding ligamentous stability and revisions. This paper aims to address the following: 1) what is the distribution of alignment of KA TKAs using IDI; 2) is a TKA alignment category associated with increased risk of failure or poor patient outcomes; 3) does extending limb alignment lead to changes in soft-tissue laxity; and 4) what is the five-year survivorship and outcomes of KA TKA using IDI?. Methods. A prospective, multicentre, trial enrolled 100 patients undergoing KA TKA using IDI, with follow-up to five years. Alignment measures were conducted pre- and postoperatively to assess constitutional alignment and final implant position. Patient-reported outcome measures (PROMs) of pain and function were also included. The Australian Orthopaedic Association National Joint Arthroplasty Registry was used to assess survivorship. Results. The postoperative HKA distribution varied from 9° varus to 11° valgus. All PROMs showed statistical improvements at one year (p < 0.001), with further improvements at five years for Knee Osteoarthritis Outcome Score symptoms (p = 0.041) and Forgotten Joint Score (p = 0.011). Correlation analysis showed no difference (p = 0.610) between the hip-knee-ankle and joint line congruence angle at one and five years. Sub-group analysis showed no difference in PROMs for patients placed within 3° of neutral compared to those placed > 3°. There were no revisions for tibial loosening; however, there were reports of a higher incidence of poor patella tracking and patellofemoral stiffness. Conclusion. PROMs were not impacted by postoperative alignment category. Ligamentous stability was maintained at five years with joint line obliquity. There were no revisions for tibial loosening despite a significant portion of tibiae placed in varus; however, KA executed with IDI resulted in a higher than anticipated rate of patella complications. Cite this article: Bone Jt Open 2022;3(8):656–665

Abstract. Objectives. The outcomes from patella fracture have remained dissatisfactory despite advances in treatment, especially from operative fixation1. Frequently, reoperation is required following open reduction and internal fixation (ORIF) of the patella due to prominent hardware since the standard technique for patella ORIF is tension band wiring (TBW) which inevitably leaves a bulky knot and irritates soft tissue given the patella's superficial position2. We performed a systematic review to determine the optimal treatment of patella fractures in the poor host. Methods. Three databases (EMBASE/Medline, ProQuest and PubMed) and one register (Cochrane CENTRAL) were searched. 476 records were identified and duplicates removed. 88 records progressed to abstract screening and 73 were excluded. Following review of complete references, 8 studies were deemed eligible. Results. Complication rates were shown to be high in our systematic review. Over one-fifth of patients require re-operation, predominantly for removal of symptomatic for failed hardware. Average infection rate was 11.95% which is higher than rates reported in the literature for better hosts. Nevertheless, reported mortality was low at 0.8% and thromboembolic events only occurred in 2% of patients. Average range of movement achieved following operative fixation was approximately 124 degrees. Upon further literature review, novel non-operative treatment options have shown acceptable results in low-demand patients, including abandoning weight-bearing restrictions altogether and non-operatively treating patients with fracture gaps greater than 1cm. Regarding operative management, suture/cable TBW has been investigated as a viable option with good results in recent years since the materials used show comparable biomechanics to stainless steel. Additionally, ORIF with locking plates have shown favourable results and have enabled aggressive post-operative rehabilitation protocols. TBW with metallic implants has shown higher complication rates, especially for anterior knee pain, reoperation and poor functional outcomes. Conclusion. There is sparse literature regarding patella fracture in the poor host. Nevertheless, it is clear that ORIF produces better outcomes than conservative treatment but the optimal technique for patella ORIF remains unclear. TBW with metallic implants should not remain the standard technique for ORIF; low-profile plates of suture TBW are more attractive solutions. Non-operative treatment may be considered for low-demand individuals however any form of patellectomy should be avoided if possible. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Aims. This study aimed to investigate the relationship between changes in patellar height and clinical outcomes at a mean follow-up of 7.7 years (5 to 10) after fixed-bearing posterior-stabilized total knee arthroplasty (PS-TKA). Methods. We retrospectively evaluated knee radiographs of 165 knees, which underwent fixed-bearing PS-TKA with patella resurfacing. The incidence of patella baja and changes in patellar height over a minimum of five years of follow-up were determined using Insall-Salvati ratio (ISR) measurement. We examined whether patella baja (ISR < 0.8) at final follow-up affected clinical outcomes, knee joint range of motion (ROM), and Knee Society Score (KSS). We also assessed inter- and intrarater reliability of ISR measurements and focused on the relationship between patellar height reduction beyond measurement error and clinical outcomes. Results. The ISR gradually decreased over five years after TKA, and finally 33 patients (20.0%) had patella baja. Patella baja at the final follow-up was not related to passive knee ROM or KSS. Interestingly, when we divided into two groups - patella baja and patella normal-alta (ISR ≥ 0.8) - the patella baja group already had a lower patellar height before surgery, compared with the patella normal-alta group. The ISR measurement error in this study was 0.17. Both passive knee flexion and KSS were significantly decreased in the group with a decrease in ISR of ≥ 0.17 at final follow-up. Conclusion. Patellar height gradually decreased over five years of follow-up after TKA. The reduction in patellar height beyond measurement error following TKA was associated with lower clinical outcomes. Cite this article: Bone Jt Open 2021;2(12):1075–1081

Recognized anatomic variations that lead to patella instability include patella alta and trochlea dysplasia. Lateralization of the extensor mechanism relative to the trochlea is often considered to be a contributing factor; however, controversy remains as to the degree this contributes to instability and how this should be measured. As the tibial tuberosity-trochlear groove (TT-TG) is one of most common imaging measurements to assess lateralization of the extensor mechanism, it is important to understand its strengths and weaknesses. Care needs to be taken while interpreting the TT-TG value as it is affected by many factors. Medializing tibial tubercle osteotomy is sometimes used to correct the TT-TG, but may not truly address the underlying anatomical problem. This review set out to determine whether the TT-TG distance sufficiently summarizes the pathoanatomy, and if this assists with planning of surgery in patellar instability. Cite this article: Bone Jt Open 2022;3(3):268–274

Abstract. Objectives. The aim of this study was to develop an in vitro GAG-depleted patella model and assess the biomechanical effects following treatment with a SAP:CS self-assembling hydrogel. Methods. Porcine patellae (4–6 month old) were harvested and subject to 0.1% (w/v) sodium dodecyl sulfate (SDS) washes to remove GAGs from the cartilage. Patellae were GAG depleted and then treated by injection with SAP (∼ 6 mM) and CS (10 mg) in Ringer's solution through a 30G needle. Native, GAG depleted and SAP:CS treated patellae were tested through static indentation testing, using 15g load, 5mm indenter over 1hr period. The degree of deformation of each group was assessed and compared (Mann-Whitney, p<0.05). Native, GAG depleted, sham (saline only) and SAP:CS treated paired patellae and femurs were additionally characterized tribologically through sequential wear testing when undergoing a walking gait profile (n=6 per group). The cartilage surfaces were assessed and compared (Mann-Whitney, p<0.05) using the ICRS scoring system, surface damage was illustrated through the application of Indian ink. Results. Static indentation tests indicated significant increase in indentation deformation of GAG depleted group compared to native group (n=6, p<0.01) and significant reduction in deformation of SAP:CS treated group compared to GAG depleted group (n=6, p<0.05). Sequential wear tests indicated a significant increase in the cartilage damage on the both surfaces of the patellofemoral joint in the GAG depleted group, compared to the native group (n=6, p<0.001), Following SAP:CS treatment, significant protection from damage was observed on femoral surface (n=6, p<0.005), with some non-significant reduction in damage on the patella surface. Sham injections showed no significant increase in damage compared to the native and treated samples. Conclusions. The ∼50% reduction of GAGs represented a moderate osteoarthritic patella cartilage model. This same loss transferred to the dynamic wear tests with significant changes in the damage on the femoral counter face associated with the GAG loss. SAP:CS treatment showed promise in restoring cartilage stiffness to treat Chondromalacia patella in static indentation tests. Sequential wear tests showed that the SAP:CS treatment protects the cartilage layer of both surfaces in the patellofemoral joint from damage in an extreme degeneration model. The sham injections showed that injecting cartilage with a 30G and saline does not cause any significant damage to the cartilage layer. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Introduction: In this study the optimal angle of fixation or splintage for partially weight bearing fractures of the patella was determined by a gait analysis measurement system. Subjects and Methods: A knee brace was applied to eight subjects and locked at 0, 10, 20 and 30 degrees. Measurements were also taken for an unlocked brace and in the absence of a brace. The subjects were instructed on partial weight bearing mobilisation. Three dimensional motion analyses were performed using an infrared 8-camera system. The ground reaction force was recorded by two 3-dimensional force plates embedded in the walkway. Kinematic and kinetic data was collected and the data was transferred to a computer programme for further analysis and the forces acting on the patella were calculated. Results: The results showed that the forces acting on the patella were directly proportional to the knee flexion angle. The results also showed that the knee flexion angle does not always correspond with the angle set at the knee brace; however they did exhibit a direct relationship. Conclusion: Our findings show that, for partially weight bearing patella fractures, the optimum form of splintage corresponds with a low knee flexion angle

Background: Patella tendonitis is a condition often found in athletes but is also found in less active patients. It usually responds to conservative management (rest, physiotherapy and anti-inflammatory drugs) but some progress to surgery. A retrospective study was done to look at the results of this surgery in our hospital. Patients and Methods: From 2001 to 2007, nineteen knees in sixteen patients had open patella tendon decompression. Eleven patients were still involved in sporting activity. All surgery was performed by the same surgeon. The patients were brought back to a clinic for review, examination and VISA score. Results: All but one patient had an improvement in their pain score. Of the 11 patients that played sport, eight were able to return to sport. Five of these returned to competition. Five patients would not have the surgery again. Only two of these had still played sport. Three of these had other knee pathology found at arthroscopy. Conclusions: The results of the surgery were satisfactory, although they were more favourable in the patients that were still involved in sporting activities. The rehabilitation time was much longer than had been expected by most patients

Abstract. Introduction. There is growing interest in the use of robotic Total Knee Arthroplasty (TKA) to improve accuracy of component positioning. This is the first study to investigate the radiological accuracy of implant component position using the ROSA® knee system with specific reference to Joint Line Height, Tibial Slope, Patella Height and Posterior Condylar Offset. As secondary aims we compared accuracy between image-based and imageless navigation, and between implant designs (Persona versus Vanguard TKA). Methodology. This was a retrospective review of a prospectively-maintained database of the initial 100 consecutive TKAs performed by a high volume surgeon using the ROSA® knee system. To determine the accuracy of component positioning, the immediate post-operative radiograph was reviewed and compared with the immediate pre-operative radiograph with regards to Joint Line Height, Tibial Slope, Patella Height (using the Insall-Salvati ratio) and Posterior Condylar Offset. Results. Mean age of patients undergoing ROSA TKA was 70 years (range, 55 to 95 years). Mean difference in joint line height between pre and post-operative radiographs was 0.2mm (range −1.5 to +1.8mm, p<0.05), posterior condylar offset mean change 0.16mm (range −1.4 to +1.3mm, p<0.05), tibial slope mean change 0.1 degrees (p<0.05) and patella height mean change 0.02 (range −0.1 to +0.1 p<0.05). No significant differences were found between imageless and image-based groups, or between implant designs (Persona versus Vanguard). Conclusion. This study validates the use of the ROSA® knee system in accurately restoring Joint Line Height, Patella Height and Posterior Condylar Offset

Aims. The rate of day-case total knee arthroplasty (TKA) in the UK is currently approximately 0.5%. Reducing length of stay allows orthopaedic providers to improve efficiency, increase operative throughput, and tackle the rising demand for joint arthroplasty surgery and the COVID-19-related backlog. Here, we report safe delivery of day-case TKA in an NHS trust via inpatient wards with no additional resources. Methods. Day-case TKAs, defined as patients discharged on the same calendar day as surgery, were retrospectively reviewed with a minimum follow-up of six months. Analysis of hospital and primary care records was performed to determine readmission and reattendance rates. Telephone interviews were conducted to determine patient satisfaction. Results. Since 2016, 301/7350 TKAs (4.1%) in 290 patients at our institution were discharged on the day of surgery. Mean follow-up was 31.4 months (6.2 to 70.0). In all, 28 patients (9.3%) attended the emergency department or other acute care settings within 90 days of surgery, most often with wound concerns or leg swelling; six patients (2.0%) were readmitted. No patients underwent a subsequent revision procedure, and there were no periprosthetic infections. Two patients (0.7%) underwent secondary patella resurfacing, and one patient underwent arthroscopic arthrolysis after previous manipulation under anaesthetic (MUA). Three patients (1.0%) underwent MUA alone. Primary care consultation records, available for 206 patients, showed 16 patients (7.8%) contacted their general practitioner within two weeks postoperatively; two (1.0%) were referred to secondary care. Overall, 115/121 patients (95%) telephoned stated they would have day-case TKA again. Conclusion. Day-case TKA can be safely delivered in the NHS with no additional resources. We found low incidence of contact with primary and secondary care in the postoperative period, and high patient satisfaction. Cite this article: Bone Jt Open 2023;4(8):621–627

“The shortest distance between two points is a straight line.” This explains many cases of patellar maltracking, when the patellar track is visualised in three dimensions. The three-dimensional view means that rotation of the tibia and femur during flexion and extension, as well as rotational positioning of the tibial and femoral components are extremely important. As the extensor is loaded, the patella tends to “center” itself between the patellar tendon and the quadriceps muscle. The patella is most likely to track in the trochlear groove IF THE GROOVE is situated where the patella is driven by the extensor mechanism: along the shortest track from origin to insertion. Attempts to constrain the patella in the trochlear groove, if it lies outside that track, are usually unsuccessful. Physiologic mechanisms for tibial-femoral rotation that benefit patellar tracking (“screw home” and “asymmetric femoral roll-back”) are not generally reproduced. Practical Point. A patellofemoral radiograph that shows the tibial tubercle, illustrates how the tubercle, and with it the patellar tendon and patella itself, are all in line with the femoral trochlea. To accomplish this with a TKA, the femoral component is best rotated to the transepicondylar axis (TEA) and the tibial component to the tubercle. In this way, when the femoral component sits in its designated location on the tibial polyethylene, the trochlear groove will be ideally situated to “receive” the patella. Knee Mechanics. Six “degrees of freedom” refers to translation and rotation on three axes (x,y,z). This also describes how arthroplasty components can be positioned at surgery. The significant positions of tibial, femoral and patellar components are: 1. Internal-external rotation (around y-axis) and 2. Varus-valgus rotation (around z axis). 3. Medial-lateral translation (on x-axis). The other positional variables are less important for patella tracking. Biomechanical analyses of knee function are often broken down into: i. Extensor power analysis (y-z or sagittal plane) and ii. Tracking (x-y or frontal plane). These must be integrated to include the effects of rotation and to better understand patellar tracking. Effect of Valgus. Frontal plane alignment is important but less likely to reach pathological significance for patellar tracking than rotational malposition clinically. For example if a typical tibia is cut in 5 degrees of unintended mechanical valgus, this will displace the foot about 5 cm laterally but the tibial tubercle only 8 mm laterally. An excessively valgus tibial cut will not displace the tubercle and the patella as far as mal-rotation of the tibial component. Effect of Internal Rotation of Tibial Component. By contrast, internal rotation of the tibial component by 22 degrees, which is only 4 degrees in excess of what has been described as tolerable by Berger and Rubash, displaces the tubercle 14 mm, a distance that would place the center of most patella over the center of the lateral femoral condyle, risking dislocation. Dynamically, as the knee flexes, if the tibia is able to rotate externally this forces the tubercle into an even more lateral position, guaranteeing that the patella will align lateral to the tip of the lateral femoral condyle, and dislocate. The design of femoral components, in particular the varus-valgus angle of the trochlear groove, has an effect on patellar tracking. This effect will be accentuated by the surgical alignment technique of the femoral and tibial components. Component positions that mimic the orientation of the normal anatomy usually include more valgus alignment of the femoral component. This rotates the proximal “entrance” of the femoral trochlear groove more medially, making it more difficult for the patella to descend in the trochlear groove

Abstract. Introduction. Isolated patellofemoral joint(PFJ) osteoarthritis affects approximately 10% of patients aged over 40 years and treatment remains controversial. Our aim was to evaluate long term functional and radiological outcomes following PFJ arthorplasty with the Femoro Patella Vialli (FPV) prosthesis as this evidence is lacking in literature. Methodology. A retrospective review of prospectively collected PROMS in patients undergoing Patellofemoral arthroplasty. Single centre trial. Between 2004 and 2008, 101 FPV patellofemoral arthroplasties were performed in 80 patients with isolated patellofemoral joint osteoarthritis. Data was collected as a part of routine follow-up for up to 6 years and additional long term data was collected at 16 years. Results. At 6 year follow up the mean OKS was 29 and by 16 year follow up it was 26 which was not a statistically significant drop. 22 patients (29 knees) had died, 32 (32%) had been revised, 25 to total knee replacement using primary arthroplasty components. Mean OKS in the revised group was 27 which was not a statistically significant difference when compared to the unrevised group. Mean time to revision was 4 years. The cumulative survival analysis of the FPV implant was 76% at 5 years, 64% at 10 years. Conclusion. Our findings suggest the FPV patellofemoral prosthesis provides good pain relief and clinical outcomes however, the survivorship for this particular implant maybe lower as compared to the available literature. Patient reported outcomes are maintained over the implant life and are no worse once revised implying a staged approach to arthroplasty is reasonable

It is a not so uncommon clinical scenario: well-fixed, well-aligned, balanced total knee arthroplasty with continued pain. However, radiographs also demonstrate an unresurfaced patella. The debate continues and the controversy remains as whether or not to routinely resurface the patella in total knee arthroplasty. In perhaps the most widely referenced article on the topic, the overall revision rates were no different between the resurfaced (9%) and the unresurfaced (12%) groups and thus their conclusion was that similar results can be obtained with and without resurfacing. However, a deeper look in to the data in this study shows that 4 times more knees in the unresurfaced group were revised for patellofemoral problems. A more recent study concluded that selectively not resurfacing the patella provided similar results when compared to routinely resurfacing. The study does emphasise however, that this conclusion depends greatly on femoral component design and operative diagnoses. This suggests that selective resurfacing with a so-called “patella friendly” femoral component in cases of tibio-femoral osteoarthritis, is a safe and effective strategy. Finally, registry data would support routine resurfacing with a 2.3 times higher relative risk of revision seen in the unresurfaced TKA. Regardless of which side of the debate one lies, the not so uncommon clinical scenario remains; what do we do with the painful TKA with an unresurfaced patella. Precise and accurate diagnosis of the etiology of a painful TKA can be very difficult, and there is likely a strong bias towards early revision with secondary patellar resurfacing in the painful TKA with an unresurfaced TKA. At first glance, secondary resurfacing is associated with relatively poor outcomes. Correia, et al. reported that only half the patients underwent revision TKA with secondary resurfacing had resolution of their complaints. Similarly, only 53% of patients in another series were satisfied with the procedure and pain relief. The conclusions that can be drawn from these studies and others are that either routine patellar resurfacing should be performed in all TKA or, perhaps more importantly, we need to better understand the etiology of pain in an otherwise well-aligned, well-balanced, well-fixed TKA. It is this author's contingency that the presence of an unresurfaced patella leads surgeons to reoperate earlier, without truly identifying the etiology of pain or dissatisfaction. This strong bias; basically there is something more that can be done, therefore we should do it, is the same bias that leads to early revision of partial knee arthroplasty. While very difficult, we as knee surgeons should not revise a partial knee or secondarily resurface a patella due to pain or dissatisfaction. Doing so, unfortunately, only works about half the time. The diagnostic algorithm for evaluating the painful, uresurfaced TKA includes routinely ruling out infection with serum markers and an aspiration. Pre-arthroplasty radiographs should be obtained to confirm suitability and severity of disease for an arthroplasty. An intra-articular diagnostic injection with Marcaine +/− corticosteroid should provide significant pain relief. MARS MRI may be beneficial to evaluate edema within the patella. Lastly, operative implant stickers to confirm implant manufacturer and type are critical as some implants perform less favorably with unresurfaced patellae. To date, no studies of secondary resurfacing describe the results of this, or similar, algorithms for defining patellofemoral problems in the unresurfaced TKA and therefore it is still difficult to conclude that poor results are not simply due to our inherent bias towards early revision and secondary resurfacing of the unresurfaced patella

Treatment of simple and complex patella fractures represents a challenging clinical problem. Controversy exists regarding the most appropriate fixation method. Tension band wiring, aiming to convert the pulling forces on the anterior aspect of the patella into compression forces across the fracture site, is the standard of care, however, it is associated with high complication rates. Recently, anterior variable-angle locking plates have been developed for treatment of simple and comminuted patella fractures. The aim of this study was to investigate the biomechanical performance of the novel anterior variable-angle locking plates versus tension band wiring used for fixation of simple and complex patella fractures. Sixteen pairs of human cadaveric knees were used to simulate either two-part transverse simple AO/OTA 34-C1 or five-part complex AO/OTA 34-C3 patella fractures by means of osteotomies, with each fracture model created in eight pairs. The complex fracture pattern was characterized with a medial and a lateral proximal fragment, together with an inferomedial, an inferolateral and an inferior fragment mimicking comminution around the distal patellar pole. The specimens with simple fractures were pairwise assigned for fixation with either tension band wiring through two parallel cannulated screws, or an anterior variable-angle locking core plate. The knees with complex fractures were pairwise treated with either tension band wiring through two parallel cannulated screws plus circumferential cerclage wiring, or an anterior variable-angle locking three-hole plate. Each specimen was tested over 5000 cycles by pulling on the quadriceps tendon, simulating active knee extension and passive knee flexion within the range from 90° flexion to full knee extension. Interfragmentary movements were captured by motion tracking. For both fracture types, the articular displacements, measured between the proximal and distal fragments at the central aspect of the patella between 1000 and 5000 cycles, together with the relative rotations of these fragments around the mediolateral axis were all significantly smaller following the anterior variable-angle locked plating compared with the tension band wiring, p < 0.01. From a biomechanical perspective, anterior locked plating of both simple and complex patella fractures provides superior construct stability versus tension band wiring

Resurfacing the patella is performed the majority of the time in the United States and in many regions it is considered standard practice. In many countries, however, the patella is left un-resurfaced an equal amount of the time or even rarely ever resurfaced. Patella resurfacing is not a simple or benign procedure. There are numerous negative sequelae of resurfacing including loosening, fragmentation, avascular necrosis, lateral facet pain, stress fracture, acute fracture, late fracture, and restricted motion. In a study by Berend, Ritter, et al, failures of the patella component were reported 4.2% of the time at an average of only 2.6 years. A study was undertaken at Washington University in recent years to determine rather more clinical problems were observed following total knee replacement with or without patella resurfacing. Records were maintained on all problem total knees cases with well localised anterior knee pain. The referral area for this clinic is St. Louis which is among the largest American cities, with the highest percentage of total knees that are performed without patella resurfacing. During 4 years of referrals of total knee patients with anterior knee pain, 47 cases were identified of which 36 had a resurfaced patella and 11 had a non-resurfaced patella. Eight of 36 resurfaced patellae underwent surgery while only 2 of 11 non-resurfaced patellae underwent subsequent surgery. More than 3 times as many painful total knees that were referred for evaluation had already had their patella resurfaced. In spite of the fact that approximately equal number of total knees were performed in this area without patella resurfacing, far more patients presented to clinic with painful total knee in which the patella had been resurfaced. The numerous pathologies requiring a treatment following patella resurfacing included patella loosening, fragmentation of the patella, avascular necrosis patella, late stress fracture, lateral facet pain, oblique resurfacing, and too thick of a patellar composite. In a large multi-center randomised clinical trial at 5 years from the United Kingdom in over 1700 knees from 34 centers and 116 surgeons, there was no difference in the Oxford Score, SF-12, EQ-5D, or need for further surgery or complications. The authors concluded, “We see no difference in any score, if there is a difference, it is too small to be of any clinical significance”. In a prospective of randomised clinical trial performed at Tulane University over 20 years ago, no differences were observed in knee score, a functional patella questionnaire, or the incidence of anterior knee pain between resurfaced and un-resurfaced patellae at time intervals of 2–4 years, 5–7 years, or greater than 10 years. Beyond 10 years the knee scores of total knee patients with a resurfaced patella had declined significantly greater than those with a non-resurfaced patella. There are numerous advantages of not resurfacing the patella including less surgical time, less expense, a lower risk of “major” complications (especially late complications), and if symptoms develop in an un-resurfaced patella, it is an easier salvage situation with more options available. A small percentage of total knee patients will be symptomatic whether or not their patella is resurfaced. Not resurfacing the patella retains more options and has fewer complications. The major determinant of clinical result and the presence of anterior knee pain after knee replacement is surgical technique and component design not whether or not the patella is resurfaced. Patella resurfacing is occasionally necessary for patients with inflammatory arthritis, a deformed or maltracking patella, or symptoms and pathology that are virtually restricted to the patellofemoral joint. For the vast majority of patients, however, patella resurfacing is not necessary

Abstract. A study was done to test the strength of various configurations of tension band wiring (TBW) and we report clinical results of ‘Horizontal Figure of Eight TBW’ (H – 8 TBW). In an experimental lab, a model of the fractured patella was mounted on a Nene tensile testing machine and various configurations of TBWs were tested in different positions of Kirschner wires. The strength of TBW and various knots securing the ends of wires were analysed on load/displacement graphs. The experimental results were compared with the theoretical results using trigonometry and mathematical equations. Since 1986, H – 8 TBW (Sonanis and Bhende modification) was used clinically in 42 patients (40 fractured patella, and 2 greater trochanteric osteotomies) in 26 males and 16 females and all patients were followed up to average 18 months. Experimentally H – 8 TBW (0.8mm wire) could resist maximum distraction force of 700 N and achieved maximum compression. Placement of the two Kirschner wires at the mid way between centre and edge of patella at the level of fracture site achieved optimum rotational stability and compression. Crimping method of gripping the ends of wires was the most secured method (120 N). Clinically bony union using H-8 TBW was achieved in all 41 patients. Complications seen were wire discomfort in 3 patients and one death. We conclude that H – 8 TBW achieved maximum compression, optimum K wire placement was at the 1/4th distance from the edge of the patella, and crimping the ends of wire secured best fixation

We retrospectively analysed the MR scans of 25 patients with patellofemoral dysplasia and ten control subjects, to assess whether there was any change in the morphology of the patella along its vertical length. Ratios were calculated comparing the size of the cartilaginous and subchondral osseous surfaces of the lateral and medial facets. We also classified the morphology using the scoring systems of Baumgartl and Wiberg. There were 18 females and seven males with a mean age of 20.2 years (10 to 29) with dysplasia and two females and eight males with a mean age of 20.4 years (10 to 29) in the control group. In the patient group there was a significant difference in morphology from proximal to distal for the cartilaginous (Analysis of variance (ANOVA) p = 0.004) and subchondral osseous surfaces (ANOVA, p = 0.002). In the control group there was no significant difference for either the cartilaginous (ANOVA, p = 0.391) or the subchondral osseous surface (ANOVA, p = 0.526). Our study has shown that in the dysplastic patellofemoral articulation the medial facet of the patella becomes smaller in relation to the lateral facet from proximal to distal. MRI is needed to define clearly the cartilaginous and osseous morphology of the patella before surgery is considered for patients with patellofemoral dysplasia

The decision to resurface the patella has been well studied. While regional differences exist, the overwhelming choice by most Surgeons in the United States is to resurface the patella. Data supports that this is the correct choice. Articular cartilage on metal has not been shown to be a good long term bearing surface. Cushner et al. has also shown that cartilage in the arthritic knee has significant pathologic abnormalities. Patella surfacing has excellent long-term results with a low complication rate. Anterior knee pain is a common complaint after knee replacement and is even more common in TKA with un-resurfaced patella. Pakos et al. had more reoperations and greater anterior knee pain when the patella was NOT resurfaced. Parvizi et al. also found less patient satisfaction with un-resurfaced patellas. Meta-analysis results indicate higher revision rates with un-resurfaced patellas. Bilateral knee studies also favor resurfaced patella. Higher revision rates were also confirmed in the Swedish Registry with a 140% higher revision rate in TKA with un-resurfaced patellas In addition, second operations to resurface the patella often are unsuccessful at alleviating pain. Surgeons who choose not to resurface the patella must accept that their patients will have the same or greater degree of anterior knee pain and a significantly greater risk for reoperation

Patella resurfacing is becoming more routine in total knee replacements with recent reports indicating improved long term outcomes. Despite this, patella osteotomy relies heavily on how the cutting jig is applied rather than on fixed anatomical landmarks. Recognised complications of asymmetric patella resection are patella fractures, patella maltracking, bony impingement and pain. Accurate instruments have been developed for other aspects of total knee replacements. However cutting guides for the patella tend to be cumbersome with poor reproducibility. Patella tilt is defined as the angle subtended by a line joining the medial and lateral edges of the patella and the horizontal. Keeping this angle to a minimum results in congruent alignment of the patella button within the trochlear groove. Current patella cutting jigs do not take this angle into consideration as they require full eversion of the patella laterally, not only making accurate placement of the jig difficult but also putting excessive strain on the surrounding soft tissue. This study describes a new cutting technique for the patella osteotomy which is referenced off the distal femoral condyles ensuring a more accurate and reproducible cut without having to evert the patella. With the femoral component trial in situ and the patella in its normal anatomical lie, the knee is flexed to 30°. The patella cutting jig is then applied in the usual manner making sure that adequate thickness of patella remains but it is placed parallel to a line joining the two condyles of the femoral component. By cutting the patella in this position parallel to the distal femoral condyles, patella tilt is minimised and the patella button will be aligned evenly within the trochlear groove. Currently all patients requiring patella resurfacing at our institution are undergoing this technique and the short term results have been very promising. This study presents a novel patella cutting technique that utilises a fixed landmark to ensure a more accurate and reproducible osteotomy. We are planning a large scale trial comparing pre- and post-operative knee scores and radiological assessment of patients having this new technique compared to standard cutting techniques. This will allow us to report on the longer term effects and pave the way for better patella resurfacing instrumentation

Maltracking of the patella associated with TKA is usually the result of several factors coming together in the same patient. Causes of maltracking include residual valgus limb alignment, valgus placement of the femoral component, patella alta, poor prosthetic geometry, internal rotation of the femoral or tibial component, excessive patellar thickness, asymmetric patellar preparation, failure to perform a lateral release when indicated, capsular dehiscence, and dynamic instability. Prior to wound closure after implantation of total knee arthroplasty, patellar tracking should be evaluated to assess the potential need for lateral release. The incidence of lateral release in the past was quite high in some series. Most experienced surgeons will report a lateral release rate less than 5% for varus knees. It is usually higher for valgus knees because they are often associated with patella alta and preoperative subluxation. The classic intraoperative test for patellar tracking has been referred to as the “rule of no thumb” In this test, first suggested by Fred Ewald, the patella is returned to the trochlear groove in extension with the capsule unclosed. The knee is then passively flexed and one assesses whether or not the patella tracks congruently without capsular closure. If it does and the medial facet of the patellar component contacts the medial aspect of the trochlea no lateral release need be considered. If the patella dislocates or tilts, lateral release may be necessary. The test should be repeated with 1 suture closing the capsule at the level of the superior pole. If tracking then becomes congruent without excessive tension on the suture, no release is necessary. If tilting still persists, some surgeons like to assess tracking with the tourniquet deflated so that any binding effect on the quadriceps can be eliminated from the test. A tight PCL can also impart apparent patellar tilt as the femoral component is drawn posteriorly while the tibia (with its tubercle) moves anteriorly

Whether to resurface the patella during a primary Total Knee Replacement (TKR) performed as a treatment of degenerative osteoarthritis remain a controversial issue. Patellar resurfacing was introduced because early implants were not designed to accommodate the native patella in an anatomic fashion during the range of motion. Complications related to patella resurfacing became a primary concern and have been associated with the variable revision rates often report post TKR. Subsequent modifications in implant design have been made to offer the surgeon option of leaving the patella un-resurfaced. Numerous clinical trials have been done to determine the superiority of each option. Unfortunately, there is little consensus and surgeon preference remains the primary variable. One of the major reasons given to support patella resurfacing is to eliminate Anterior Knee Pain post operatively. However, studies have shown that this problem was not exclusively found in non-resurfaced patients so the author conclude that anterior knee pain is probably related to component design or to the details of the surgical technique, such as component rotation rather that whether or not the patella is resurfaced. An increasing rate of complications with the extensor mechanism after patellar resurfacing led to the concept of selective resurfacing of the patella in TKR. Decision making algorithms with basis of clinical, radiographic and intraoperative parameters have been developed to determine which patients are suitable for patella resurfacing and which are suitable for patella non-resurfacing. Finally, the continued study of this topic with longer follow up term in randomized, controlled, clinical trials remains essential in our understanding of patella in TKR. The development of joint registry will allow surgeons to draw conclusions on the basis of larger numbers of patients and will improve the reporting of the results of patellar non resurfacing in clinical trials. In general, surgeons in United States always resurface while their counterparts in Europe tend to never resurface

Functional restoration of patella kinematics is an essential component of TKA, whether the patella is replaced or not. This goal is accomplished by a multifactorial approach: establish proper component position and alignment, especially rotation; avoid IR of the femoral and ER of the tibial components; maintain correct joint line position; achieve symmetrical soft tissue balance. Most modern TKA designs have an anatomic trochlear groove shape to enable midline tracking. Patella implants are better designed as well with three equilateral lugs for fixation and either dome or anatomic shape. The apex of the patella component should be aligned with the apex of the patella raphe which is more medial than lateral. This method leaves an island of exposed lateral patella facet which is managed with the “lateral slat technique” to be described. It is essentially an intraosseous lateral release. The early mobilization of modern TKA patients demands watertight closure to prevent soft tissue attenuation and late tracking issues. When confronted with a patient with a laterally dislocated patella, implementation of the “lateral slat technique” should be done at the approach to obtain midline tracking. Such patients require a median parapatellar (MPP) approach and may need distal-lateral vastus medialis advancement (Insall procedure). Adherence to the principles iterated herein will produce a happy patient with good patello-femoral kinematics and function

Purpose. In vivo comparative gap measurements were performed in 3 different patella positions (reduced, subluxated and everted) using offset-type-force-controlled-spreader-system. Methods. Prospectively, 50 knees were operated by TKA using a navigation-assisted gap balancing technique. The offset-type-force-controlled-spreader-system was used for gap measurements. This commercially-available instrument allows controllable tension in patella reduced position. The mediolateral gaps of knee extension (0°) and flexion (90°) angle were recorded in 3 different patella positions; reduced, subluxated and everted. Any gap differences of more than 3 mm were considered as a meaningful difference. Correlation between the difference with the demographic data, preoperative radiologic alignment and intraoperative data was analyzed. For statistical analysis, ANOVA and Pearson correlation test were used. Results. The gaps in patella eversion demonstrated smaller gaps both in knee extension and flexion position compared to the gaps of patella reduction position. The amount of decreased gaps was more definite in knee flexion position. Statistically significant difference were observed for the lateral gap of patella eversion compared to gap of patella reduction in knee flexion position (p<0.05). There were notable cases of variability in knee flexion position. Significant portion 12 (24%) knees of patella subluxation and 33 (66%) knees of patella evertion demonstrated either increased or decreased gaps in knee flexion position compared from the gaps of patella reduction position. Conclusion. The gaps in patella eversion demonstrated smaller gaps both in knee extension and flexion position compared to the gaps of patella reduction position. The amount of decreased gaps was more definite in knee flexion position. Therefore, the intraoperative patellar positioning has influence on the measurement of the joint gap. Keeping the patella in reduced position is important during gap balancing

Objective. The aim of this study was to evaluate the shape of patella relative to the femoral epicondylar axis and to find sex differences. Materials and methods. Computed tomography (CT) images of 100 knees with tibiofemoral osteoarthritis in 100 patients were prospectively collected. All patients were diagnosed as varus-type osteoarthritis with no destructive patellar deformity. Fifty patients were male and 50 female. The average male age was 70.8±14.6 (mean ± SD) years and the average female age was 73.3±6.7 years. Forty nine knees were right and 51 knees were left. The average height of males was 162.6±7.4 cm and that of females 149.6±5.7 cm. Males were significantly taller than females. The CT scan was performed with 2mm-interval slices in the vertical plane to the long axis of femoral shaft. Every CT image was examined to determine the maximum distance between the medial and lateral femoral epicondyle (inter-epicondylar distance, IED) along the epicondylar axis. The maximum patellar width and thickness were also measured at the image which had these maximum distances, while patellar cartilage thickness in anteroposterior diameter was not measured in this study. For evaluating the patellar size, each measured value was divided by IED and calculated each ratio. The ratio of patellar width to patellar thickness was also calculated. All parameters were compared between males and females. Statistical software Statview ver.5.0 (SAS Institute Inc.) was used for all analyses with significance being set at the 5% level. Results. Measured values are presented on Table 1. The average IED, patellar width and patellar thickness of males were all significantly larger than those of females. As shown in Table 2, by contrast, each ratio to IED was almost the same between the sexes and there were no significant differences. The ratio of patellar width to patellar thickness was 46.7±2.6% in males and 46.6±2.9% in females. Discussion. Although some studies have assessed the actual measurement values of patella, no prior study, to our knowledge, has morphologically evaluated the patella relative to the femur. This is the first study to investigate the configuration and location of patella relative to femoral epicondylar axis. Our results showed the configuration of patella relative to the femoral epicondylar axis was the same between sexes. The patellar width is approximately 56% and TGD is approximately 39% of IED. The most common complications after the surgery are related to patellofemoral problems. The ideal thickness of the resurfaced patella has not been clearly investigated. Patellar disabilities are associated with both decreased and increased patellar thickness— a thin patella could lead to anteroposterior patellar instability and a thick patella could increase the risk of stiffness of the knee and patellar subluxation. Therefore, it is desirable to restore the original patellar thickness during surgery. The results of current study showed that the ratio of patellar width to the patellar thickness was about 47%, which is useful to determine the thickness of patella during surgeries for severely damaged knees or revision surgeries

Patella resurfacing in revision total knee arthroplasty is a controversial issue. While performing revision TKA we must consider some different situations: previously resurfaced patella or not, in case of resurfaced patella, if it is fix or loosened, in case of loosened patella is there a bone loss or not. If patella wasn’t previously resurfaced, we can preserve natural patella performing at least a regularization of its osteophytes, or we can realize a primary resurfacing. If patella was previously resurfaced and still well fixed, we preserve domed component if not grossly damaged. Its revision is performed if it is damaged or not congruent. If patella was previously resurfaced and loosened the two possibilities are the revision or the retention of the bony patella. In case of previously resurfaced and loosened patella, with severe bone loss, we can preserve the bony shell, or we can realize revision with the use of cortical grafting or we can performa patelloplasty, or complete patellectomy. Finally, in these cases it’s possible the revision with tantalum patella. Outcomes of patella resurfacing in revision total knee arthroplasty are usually fair: low functional and pain scores, quadricipite leverage loss, worse patellar tracking, anterior pain, patellar fractures, knee stiffness

OBJECTIVES. The use of a mobile bearing has been suggested to decrease the rate of patellar complications after total knee arthroplasty (TKA). However, to resurface or retain the native patella remains debated. Few long-term results have been documented. The present retrospective study was designed to evaluate the long-term (more than 10 years) results of mobile bearing TKAs on a national scale, and to compare pain results and survivorship according to the status of the patella. The primary hypothesis of this study was that the 10 year survival rate of mobile bearing TKAs with patella resurfacing will be different from that of mobile bearing TKAs with native patella retaining. METHODS. All patients operated on between 2001 and 2004 in all participating centers for implantation of a TKA (whatever design used) were eligible for this study. Usual demographic and peri-operative items have been recorded. All patients were contacted after the 10 year follow-up for repeat clinical examination (Knee Society score (KSS), Oxford knee questionnaire). Patients who did not return were interviewed by phone call. For patients lost of follow-up, family or general practitioner was contacted to obtain relevant information about prosthesis survival. TKAs with resurfaced patella and TKAs with retained native patella were paired according to age, gender, body mass index and severity of the coronal deformation (with steps of 5°). Pain score, KSS and Oxford knee score were compared between two groups with a Student t-test at a 0.05 level of significance. Survival curve was plotted according to the actuarial technique, using the revision for mechanical reason as end-point. The influence of the patella status was assessed with a logrank test at a 0.05 level of significance. RESULTS. 1,604 TKAs were implanted during the study time-frame. 849 cases could be paired according to age, gender, BMI and severity of the pre-operative coronal deformation (2/1 ratio) into two groups: resurfaced patella (496 cases) and retained patella (243 cases). There was no difference in any baseline criteria between both groups. 150 patients deceased before the 10 year follow up (18%). Final follow-up was obtained for 489 cases (58%). 31 reoperations (prosthesis exchange or patellofemoral revision) were performed during the study time frame (4%), with 17 reoperations for mechanical reasons (3%). KSS and Oxford knee score were significantly higher for TKAs without patella resurfacing, there was a significant difference between the 13 year survival rates of TKAs with resurfaced patella (97%) and TKAs with retained native patella (93%). CONCLUSIONS. The primary hypothesis was confirmed: 10 year survival rate of mobile bearing TKAs with patella resurfacing was better than mobile bearing TKAs with native patella retaining. Patella resurfacing may lead to a better survival after mobile bearing TKA. However, the clinical results were better after patella resurfacing when the index TKA was not revised

1346 Primary TKR’s were evaluated. In keeping with the principle of Insall all patellas were resurfaced with the only exclusion being a previous patellectomy or excessive patella erosion. Most TKR were of posterior cruciate substituting devices (IB11 (56.9%) or Nexgen LPS (42.3%)). The reason for operation was OA (94.5%), RA (2.9%), and others 2.6%. Most knees were in varus (68.5%), 17% were in valgus, and 14.5% were in neutral alignment. The method of preparing the patella and extensor mechanism was as follows: A total fat pad excision was performed, debulking the patella thickness of 1mm. The patella component was placed medially and superiorly, a peri-patella synovectomy was performed, and a release of the lateral patella femoral ligaments was done. A lateral release was performed in 17.5% of patients. Follow up ranges from 9 months to 15 years. Reoperation for patella problems was necessary in only 5 patients (0.37%). There was 1 case of patella subluxation, 1 case of persistent anterior knee pain, and 3 patients with a patella clunk (in IB 11 knees only). In our hands this approach has led to excellent long term results without some of the potential complications described in the literature and warrants continued use of routine patella resurfacing when doing TKR

To resurface or not to resurface the patella… that is the question. It all comes down to where you practice. It is controversial in that there is a risk of possible complications from resurfacing versus the potential for simply having complaints of pain which may supposedly arise from the anterior knee stemming from the unresurfaced patella. The evolution of more favorable anatomic femoral component designs which are very friendly to the patellofemoral articulation have resulted in lower patella resurfacing complications. The insertion of appropriately externally rotated tibial and femoral components, if not reducing anterior knee pain, have certainly minimised the risk of resurfaced patella complications. Also, with current surgical techniques of component insertion, the lateral release rate is extremely low, thus avoiding the possibility of avascularity developing in the resurfaced patella. This complication will almost completely be eliminated if the patella thickness is kept greater than 13 mm after patella resection. In my experience, patella complications from the resurfaced patella are extremely rare. Many unicompartmental knees require re-operation because of the development of progressive patellofemoral arthritis. Re-operation from anterior knee pain from progressive arthritis from the unresurfaced patella has given inferior results. Overall, meta-analysis data demonstrates decreased satisfaction, increased anterior knee pain and higher early revision rates in the unresurfaced group. National joint registries, especially the Australian registry support routine resurfacing; complications are low and outcomes are improved. Even though there exists controversy as to whether the patella should be resurfaced or not, there is an overwhelming consensus in the U.S. that there is little downfall nowadays with respect to resurfacing the patella

Patellofemoral symptoms are a prominent cause of dissatisfaction following knee arthroplasty. This may relate to difficulty in knowing where to resect the bone and in placing prosthetic components to reproduce the anatomy accurately. This study developed geometrical data to facilitate these procedures during TKR. Thirty CT scans of patients above the age of 55 without patellofemoral disease were performed. Three dimensional images were reconstructed using computer software that enabled manipulation of these images and measurements to be taken. These models allowed the shape of the patella to be modelled, its size and the track it takes in the normal trochlea. The anterior and proximal patellar planes could be described as flat surfaces with an rms of 0.4 and 0.3mm. The angle between these planes was 112° (stdev 5°). The median ridge of the articular surface was a straight line with an rms of 0.2mm and the average angle between the anterior plane and this line was 12° (stdev4°). The angle between the anterior plane and a line fitted to the posterior aspect of the apex of the patella was 56° (stdev 2°). Having oriented the patella with the proximal plane vertical, the distal pole of the patella was within 2mm of the same sagittal plane as the median ridge of the articular surface in all cases. The functional centre of the patella was defined as a point in the centre of 2 planes orthogonal to the sagittal plane at the midpoint between the most proximal and most distal points on the median ridge. In the transverse section this centre was always on the line separating the superficial and deep surfaces of the patella. Also the length, width and thickness of the patellae were measured at 22mm +/−4mm, 47mm +/− 3mm and 24 mm+/− 2 mm. The average ratio of the lateral facet to medial facet width was 1.3 (range 0.8–1.6). The average ratio of the patellar width to thickness was 2.0 (S.D. 0.106, 95%CI 1.96 to 2.03) with a strong correlation(r= 0.89). From this work we have concluded that the anterior and proximal planes of the patella, which will not be affected by the disease, can be defined and used as a frame of reference for the patella, which will be helpful for navigating the patella and restoring its anatomical form in the presence of erosive changes. The patella has a constant shape, so that its articular surface can be defined in relatively simple terms, and can be referenced off its non articular surface

In the knee, involvement is mainly synovial, with local extension eroding the bone. Pure tuberculous osteitis is rare, with a few occasional reports. Patella tuberculosis is extremely rare. We report the case of patella tuberculosis with 7-years decline. A 10-years old boy suffered from knee siftness and pain. The patient had correct BCG vaccination. Clinical examination was relatively unrevealing, with tenderness on palpation of the medial joint surface of the patella, patellar crepitation, and slight effusion. On standard X-ray, the lateral view showed a circumferential rosette form with a light peripheral halo. The patient underwent open surgery with a medial parapatellar approach and arthrotomy. Joint fluid was sampled. Direct exploration of the medial side of the patella found soft but continuous cartilage on palpation. The histoligical examination confirmed the diagnosis of tuberculosis. The patient had 12 month anti-tuberculosis chemotherapy. After 7 years of the treatement, the patient had no recurrence and good clinical result. Bone tuberculosis remains difficult to diagnose. Certain locations should always be borne in mind, however rare, in case of pandemic or immunodeficiency. In case of osteolysis, associated with abscess or not, infectious etiology is to be considered and appropriate samples should be taken. Diagnosis is confirmed by histology and bacteriology. The slow evolution of bone tuberculosis requires local treatment of lesions and abscesses. Antibiotherapy regularly ensures recovery

Introduction. The metal-backed patella was originally designed to address shortcomings found with cemented, all-polyethylene patellae. However, complications relating to an all-polyethylene patella were reported to account for up to half of all knee revisions. At the same time, good fixation with bone ingrowth was observed in both titanium and cobalt chromium porous-coated patellae. The advantages provided by using a metal-backed patella, such as uniform load sharing, decreased polyethylene deformation, and potential for biological fixation, may be unjustly outweighed by the fear of patellar component failure; high rates of failure have not been inherent to all metal-backed patella designs. Over the past decade, we have used a metal-backed patella design with excellent results that may be due largely to the design features of the component. Also, we believe there are certain selection criteria that should be strictly adhered to when implanting metal-backed patellae. Correct selection criteria and improved component design strongly indicate the use of press-fit metal-backed patellae. Methods. This single-center study was designed to conduct clinical and independent radiographic review of primary metal-backed, press-fit patella patients with a minimum five-year follow-up. Potential patients were recruited from a group of existing metal-backed patella patients within the principal investigator's medical practice. All patients recruited for this study were required to have undergone primary knee replacement surgery at least five years prior to clinical and radiographic evaluation. Patients were included if they had a diagnosis of noninflammatory degenerative joint disease. Patients with a BMI >40 were excluded from this study. Radiographic analysis was conducted by an independent reviewer according to the current Knee Society Total Knee Arthroplasty Roentgenographic Evaluation and Scoring System. Any radiographs that the reviewer deemed questionable were shown to a second independent orthopaedic surgeon for review, comment, and validation of observations. Kaplan-Meier survivorship was determined for all metal-backed patellae. For survival analysis, only knees with radiographic data were included (74 knees). KSS, WOMAC, and SF-36 scores were calculated also. Results. Seventy-four patients (88 knees) were enrolled in the study, 31 women (41.2%) and 43 men (58.1%). At the time of surgery, the average age was 59.7 years (range, 40–86 years), and the average BMI was 30.6 (range, 19.1–39.6). The breakdown of patients who completed the study and those who were lost to follow-up is shown in Table 1. One metal-backed patella was revised at 49 months for loosening at the bone/implant interface. Survivorship of the metal-backed patellae at minimum five-year follow-up was estimated to be 93.95% with bounds of 73.61% and 98.74%. No radiolucencies greater than 1 mm were observed in any radiographs (Fig. 1), with the exception of the one revision case. Conclusion. Our experience with this metal-backed patella design has been excellent. Failure does not occur due to dissociation of the plastic. As the porous coating is almost under constant compression, biological fixation is assured in most instances, as confirmed by our minimum five-year radiological results. Improved component design and adherence to the correct patient selection criteria absolutely indicate the use of press-fit metal-backed patellae

The purpose of this study was to test the hypothesis that patella alta leads to a less favourable situation in terms of patellofemoral contact force, contact area and contact pressure than the normal patellar position, and thereby gives rise to anterior knee pain. A dynamic knee simulator system based on the Oxford rig and allowing six degrees of freedom was adapted in order to simulate and record the dynamic loads during a knee squat from 30° to 120° flexion under physiological conditions. Five different configurations were studied, with variable predetermined patellar heights. The patellofemoral contact force increased with increasing knee flexion until contact occurred between the quadriceps tendon and the femoral trochlea, inducing load sharing. Patella alta caused a delay of this contact until deeper flexion. As a consequence, the maximal patellofemoral contact force and contact pressure increased significantly with increasing patellar height (p < 0.01). Patella alta was associated with the highest maximal patellofemoral contact force and contact pressure. When averaged across all flexion angles, a normal patellar position was associated with the lowest contact pressures. Our results indicate that there is a biomechanical reason for anterior knee pain in patients with patella alta

BACKGROUND. Patella resurfacing in TKA remains controversial. The purpose of this study was to compare the long-term clinical outcome in TKA in patients undergoing bilateral TKAs with one patella resurfaced and the other patella nonresurfaced. METHODS. Twenty-nine patients (58 knees) underwent primary bilateral TKA for osteoarthritis. These patients were enrolled in a prospective randomised double blinded study and represent a subset of a larger study of patella resurfacing. All patients received the same posterior cruciate sparing TKA. Patients each had one knee randomised to treatment with or without patella resurfacing. The contralateral knee then received the alternative patellar treatment, such that all patients had one knee with a resurfaced patella and the other nonresurfaced. Clinical evaluations consisted of routine radiographic and clinical follow-up and included with a Knee Society Score patellofemoral specific patient questionnaire. Twenty-eight patients (56 knees) participated and were followed for a mean of 118 months (range, 69–146 months). RESULTS. There were no significant differences between the knees treated with and without patellar resurfacing with regard to range of motion, KSCRS, or the pain and function scores. Forty-six percent (13/28 patients) of patients preferred the resurfaced knee, 36% (10/28) the nonresurfaced knee, and 18% (5/28) had no preference. Two patients (7%) in the nonresurfaced group required revision for a patellofemoral related complication, compared to one patient (3.5%) in the group with a resurfaced patella. CONCLUSIONS. Ten year follow-up reveals equivalent results for resurfaced and nonresurfaced patellae in TKA with regards to ROM, KSCRS, pain and function, or patellofemoral symptoms. In this large series of bilateral TKAs, 64% of patients either preferred the unresurfaced knee or had no preference

Patella management in total knee arthroplasty remains controversial. Minimizing patella related problems is the main goal in any type of knee arthroplasty. This can be achieved with and without resurfacing. However, patella resurfacing resulted in, at times, catastrophic failures, which increased the popularity of patella non resurfacing, particularly with anatomical femoral groove designs. If patella non resurfacing is to be recommended, clinical outcomes must be equal or better than those of routine patella resurfacing in the specific prosthesis utilized. From a large cohort of over 6000 TKA five studies were conducted to analyze isokinetic strength, subjective, clinical, and radiographic outcomes as well as histopathological data. Isokinetic strength, subjective, clinical, and radiographic outcomes favor nonresurfacing in TKA with proper femoral component rotation and conforming patellar groove. Our data indicate that patella subluxation and femoral component malrotation is significantly associated with development of arthrofibrosis. On the base of our studies we propose specific surgical techniques for optimal patella treatment (patelloplasty) in TKA

We describe our experience with the ‘four-in-one’ procedure for habitual dislocation of the patella in five children (six knees). All the patients presented with severe generalised ligamentous laxity and aplasia of the trochlear groove. All had a lateral release, proximal ‘tube’ realignment of the patella, semitendinosus tenodesis and transfer of the patellar tendon. The mean age at the time of the operation was 6.1 years (4.9 to 6.9), and the patients were followed up for a mean of 54.5 months (31 to 66). The clinical results were evaluated using the Kujala score. There has been no recurrence of dislocation. All the patients have returned to full activities and the parents and children were satisfied with the clinical results. The mean Kujala score was 95.3 (88 to 98). Two patients had marginal skin necrosis which healed after debridement and secondary closure. These early results in this small group have shown that the ‘four-in-one’ procedure is effective in the treatment of obligatory dislocation of the patella in children with severe ligamentous laxity and trochlear aplasia

Treatment of both simple and complex patella fractures is a challenging clinical problem. The aim of this study was to investigate the biomechanical performance of recently developed lateral rim variable angle locking plates versus tension band wiring used for fixation of simple and complex patella fractures. Twelve pairs of human anatomical knees were used to simulate either two-part transverse simple AO/OTA 34C1 or five-part complex AO/OTA 34C3 patella fractures by means of osteotomies, with each fracture model created in six pairs. The complex fracture pattern was characterized by a medial and a lateral proximal fragment, together with an inferomedial, an inferolateral, and an inferior fragment mimicking comminution around the distal patellar pole. The specimens with simple fractures were pairwise assigned for fixation with either tension band wiring through two parallel cannulated screws, or a lateral rim variable angle locking plate. The knees with complex fractures were pairwise treated with either tension band wiring through two parallel cannulated screws plus circumferential cerclage wiring, or a lateral rim variable angle locking plate. Each specimen was tested over 5000 cycles by pulling on the quadriceps tendon, simulating active knee extension and passive knee flexion within the range of 90° flexion to full knee extension. Interfragmentary movements were captured via motion tracking. For both fracture types, the longitudinal and shear articular displacements measured between the proximal and distal fragments at the central patella aspect between 1000 and 5000 cycles, together with the relative rotations of these fragments around the mediolateral axis were all significantly smaller following the lateral rim variable angle locked plating compared with tension band wiring, p<0.01. Lateral rim locked plating of both simple and complex patella fractures provides superior construct stability versus tension band wiring under dynamic loading

In 1995 in the Journal of Skeletal Radiology the article “CT determination of tibial tubercle lateralization in patients presenting with anterior knee pain” was published. My astute Perth colleagues recognised the significance of this article and drew it to my attention on one of my regular visits to my training home town. For me, this serendipity was very significant. The principles that I have used have not changed in the last twelve years and hopefully sharing this experience may be helpful to you. Principles of CT extensor mechanism assessment. 20° of flexion is the critical point for assessment of patella malalignment. Once the patella is engaged in the trochlear groove only gross malalignment can be recognised. The study of 50 subjects with asymptomatic knees without patella problems establish that patella tubercule lateralisation averages 7mms. in an asymptomatic human population. Patella tubercule lateralization of 9mms. or more identifies accurately patients with patellofemoral malalignment with the specificity of 95% and sensitivity of 85% Combined with a 90° lateral x-ray this examination can be used to plan surgery and provide predictable outcomes. It can also be used for post op assessment if required. Index surgical technique. This is a combined arthroscopic and open patella realignment. The arthroscopic side involves a patellofemoral chondroplasty, removal of significant plica and a lateral retinacular release. The open component is via a lateral parapatellar incision, an anteromedial medialisation patella tubercule transfer fixed with interfragmentory screws. Variations. Medial hamstring patellofemoral ligament reconstruction. For adolescence, multi directional instability and under corrected surgical failures. Distalisation. For patella alta Lateral patellofemoral tenodesis For over corrected medial subluxation. Patellectomy. For patellofemoral arthritis in a patient with well aligned extensor mechanism. Combined with other procedures. For example ACL, PCL reconstructions, closing wedge osteotomy of the patella and opening wedge osteotomy of the lateral femoral condyle and patella arthroplasty. Acute patella dislocations. 50% have operable lesions and many are predisposed to their dislocation due to malalignment, so my routine there is an x-ray, CT assessment and MRI. Personal Series. Retrospective review of the consecutive series from 2000 to present using this series to present results but also to highlight complications and failures. Conclusion. Personal experience of this investigative technique and the surgical principles emanating from that have been used reliably for the last twelve years to produce predictable outcomes in patellofemoral malalignment

We used three-dimensional movement analysis by computer modelling of knee flexion from 0° to 50° in 14 knees in 12 patients with recurrent patellar dislocation and in 15 knees in ten normal control subjects to compare the in vivo three-dimensional movement of the patella. Flexion, tilt and spin of the patella were described in terms of rotation angles from 0°. The location of the patella and the tibial tubercle were evaluated using parameters expressed as percentage patellar shift and percentage tubercle shift. Patellar inclination to the femur was also measured and patellofemoral contact was qualitatively and quantitatively analysed. The patients had greater values of spin from 20° to 50°, while there were no statistically significant differences in flexion and tilt. The patients also had greater percentage patellar shift from 0° to 50°, percentage tubercle shift at 0° and 10° and patellar inclination from 0° to 50° with a smaller oval-shaped contact area from 20° to 50° moving downwards on the lateral facet. Patellar movement analysis using a three-dimensional computer model is useful to clearly demonstrate differences between patients with recurrent dislocation of the patella and normal control subjects

1. Two cases of haemangioma of the patella are reported. 2. In one case pain alone brought the patient for treatment; in the other, a pathological fracture was the first symptom. 3. In neither case was a firm diagnosis made before excision and histological examination of the patella. 4. In each case a good result followed removal of the patella: this is probably the best method of treatment. 5. The literature relating to haemangioma of bone and to tumours of the patella is briefly reviewed

Patella infera can cause knee pain and lead to patellofemoral osteoarthritis. Treatment is usually unsatisfactory. We describe a case of severe patella infera after operative treatment for fracture of the patella. We used Ilizarov external fixation and gradual lengthening of the patellar tendon. The patellar height was restored and the patient’s symptoms were much improved

Purpose of Study: To develop a non-invasive technique to assess and analyse patella kinematics during the gait cycle. Methodology and Results: Ten subjects with no history of patellofemoral syndrome or patella maltracking on clinical examination were individually assessed on eight dynamic walking trials each. Retroreflective markers were attached to the proximal, distal, medial and lateral poles of the patella and the position of the patella relative to the centre of the knee joint was tracked and recorded during their gait cycle using a nine camera (120Hz) ViconTM infra-red motion analysis system. It was found that there was more medial-lateral motion (shift) of the patella than proximal-distal (tilt) motion during the gait cycle. It was noted that the patella shift motion occurred in the swing phase or the early stance phase of the gait cycle of all subjects with the maximum patella shift occurring when the knee was flexed between 30–56 degrees in the majority of subjects. Similarly the patellar tilt motion occurred in the swing phase or the early stance phase of the gait cycle with the maximum patella tilt occurring between 20–36 degrees of knee flexion in the majority of subjects. Conclusion: The results of this study show that patella motion can be identified non-invasively using the ViconTM motion analysis system. These results indicate that normally the maximum amount of patella shift and tilt occurs in the swing and early stance phases of the gait cycle and that abnormal patella motion can be detected if excessive shift or tilt occurs outside of these phases

INTRODUCTION. Patellar tendon (PT) autograft is an excellent choice repairing anterior cruciate ligament (ACL) ruptures. Published studies testing the biomechanical characteristics after plasty usually refer to grafts with 10mm wide. The thickness of PT and geometry of the patella have been overlooked. The purpose of this study was to understand the geometry of PT and patella in our population, regarding their use in Bone - Patellar Tendon - Bone (BTB) technique, in order to evaluate their biomechanical efficiency and study their relationship with anthropometric parameters. MATERIAL. 100 individuals (50/50) who underwent knee MRI (3-Tesla). Ages between 18–65years. METHODS. Retrospective study. Standardized protocol for measuring the PT and patella based in MRI images. Interview to obtain personal data. Statistical analysis using SPSS®. RESULTS. Sample (mean ±SD): age 41 ±14years, weight 73 ±12kg, height 167 ±10cm, BMI 26,04 ±4,13; length PT/patella −41,3 ±6,1mm/29,6 ±4,2 mm, width PT/patella −25,3 ±3,2mm/43,4 ±4,14mm; thickness PT −3,79 ±1,01mm/22,8 ±2,2mm; Men have thicker and wider patella and PT than women (p<0.001). The patella is also longer in males (p<0.001). There is statistical significant relationship between weight and height to width, thickness and length of PT and patella (p<0.01). Body Mass Index (BMI) doesn't have statistical correlation with geometry of the PT and patella. DISCUSSION. The PT remains as an excellent option in ACL repair. The anatomy and quality of the graft are essential to achieving good functional results. The choice of middle third tendon to the BTB plasty does not always correspond to the 10mm width, as used in most biomechanical tests. Also patellar integrity can be at risk (when collecting the bone block) if patella geometry is not considered. To our knowledge, there is only one similar study in literature, preformed in Asian individuals. CONCLUSION. Preoperatively accessing the geometry of Patella and PT can be crucial in obtaining efficient grafts and decreasing morbidity over the extensor mechanism