Painful OA is linked to CNS changes in pain processing. Temporal summation of pain (TSP) is a measure of one such CNS change, central sensitization. TSP is defined using a series (≥0.33Hz) of painful stimuli and is a predictor of postoperative pain, experienced by 20% of patients after total knee replacement (TKR) surgery. This study has developed a protocol to use functional MRI to assess CNS changes in OA pain processing.

This pilot includes 3 participants with chronic knee OA pain awaiting TKR (62 ± 4.4) and 5 healthy volunteers (50 ± 13.6). 3-Tesla BOLD fMRI brain scans were recorded during short series of one second painful stimuli, applied using an automated inflatable cuff to the calf muscle of the leg with the affected knee or left side in healthy volunteers. The pain intensity at onset and during the 10 painful stimuli were recorded using a numerical rating scale. The pattern of brain activation was averaged across noxious stimuli, and the differential activation compared the 1st vs. 10th (last) stimulus. Bone marrow lesions (BMLs), synovitis and effusion size were scored from 3-Tesla knee MRI's using MOAKS scoring.

TSP was raised in OA patients compared to control group (p=0.023). TSP brain activity in the chronic OA patients displayed higher signal within the subgenual anterior cingulate (sgACC) compared to healthy volunteers. Knee MRI identified OA patient's exhibited higher BML scores (p=0.038) and more knee effusion (p=0.018), but the lack of synovitis did not differ from control group (p=0.107).

Enhanced TSP in chronic knee OA pain may be linked with augmented responses in emotional circuitry. BMLs and effusion size appear to contribute more with pain than synovitis. These results may help understand sensitization to improve outcomes for patients with knee OA undergoing TKR surgery.

Spinal surgery deals with the treatment of different pathological conditions of the spine such as tumors, deformities, degenerative disease, infections and traumas. Research in the field of vertebral surgery can be divided into two main areas: 1) research lines transversal to the different branches; 2) specific research lines for the different branches. The transversal lines of research are represented by strategies for the reduction of complications, by the development of minimally invasive surgical techniques, by the development of surgical navigation systems and by the development of increasingly reliable systems for the control of intra-operative monitoring. Instead, specific lines of research are developed within the different branches. In the field of oncological pathology, the current research concerns the development of in vitro models for the study of metastases and research for the study of targeted treatment methods such as electrochemotherapy and mesenchymal stem cells for the treatment of aneurysmal bone cysts. Research in the field of spinal deformities is focused on the development of increasingly minimally invasive methods and systems which, combined with appropriate pharmacological treatments, help reduce trauma, stress and post-operative pain. Scaffolds based on blood clots are also being developed to promote vertebral fusion, a fundamental requirement for improving the outcome of vertebral arthrodesis performed for the treatment of degenerative disc disease. To improve the management and the medical and surgical treatment of vertebral infections, research has focused on the definition of multidisciplinary strategies aimed at identifying the best possible treatment path. Thus, flow-charts have been created which allow to manage the patient suffering from vertebral infection. In addition, dedicated silver-coated surgical instrumentation and bone substitutes have been developed that simultaneously guarantee mechanical stability and reduce the risk of further local infection. In the field of vertebral traumatology, the most recent research studies have focused on the development of methods for the biostimulation of the bone growth in order to obtain, when possible, healing without surgery. Methods have also been developed that allow the minimally invasive percutaneous treatment of fractures by means of vertebral augmentation with PMMA, or more recently with the use of silicone which from a biomechanical point of view has an elastic modulus more similar to that of bone. It is clear that scientific research has changed clinical practice both in terms of medical and surgical management of patients with spinal pathologies. The results obtained stimulate the basic research to achieve even more. For this reason, new lines of research have been undertaken which, in the oncology field, aim at developing increasingly specific therapies against target receptors. Research efforts are also being multiplied to achieve regeneration of the degenerated intervertebral disc and to develop implants with characteristics increasingly similar to those of bone in order to improve mechanical stability and durability over time. Photodynamic therapies are being developed for the treatment of infections in order to reduce the use of antibiotic therapies. Finally, innovative lines of research are being launched to treat and regenerate damaged nerve structures with the goal, still far from today, of making patients with spinal cord injuries to walk

Tourniquets have been used for many years during total knee arthroplasty (TKA). With a growing demand for TKA in recent years, tourniquet use has been surrounded by ongoing controversy due to many conflicting advantages and disadvantages of tourniquet use. Quantifying the case for or against tourniquet use in TKA, in terms of patient focused outcomes, is a priority. This meta-analysis analysed, the never before assessed, impact of tourniquet use during TKA on post-operative pain. We completed a systematic review and meta-analysis using PRISMA reporting guidelines to assess the impact of tourniquet use on patients post-TKA. Post-operative pain was the primary outcome. Secondary outcomes were post-operative range of motion (ROM) and length of stay (LOS). The initial search yielded 230 studies, of which 14 met the inclusion criteria. A post-operative increase in pain and reduction in ROM when using a tourniquet appeared significantly more likely when compared to no tourniquet use during TKA, yet with no overall difference in post-operative LOS. Subgroup meta-analysis demonstrated a trend that favoured the half-course tourniquet for reduced post-operative pain in patients when compared to full tourniquet use during TKA. This systematic review and meta-analysis concluded that the after-effects of tourniquet use in TKA patients and its impact on post-operative pain and ROM are indeed significant. We recommend further randomized controlled trials (RCTs) focusing on TKA patient outcomes of post-operative pain and ROM. Conflict of interest: The authors certify that they have NO affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers' bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript

Introduction and Objective. Continuous peripheral nerve blocks (cPNBs) have shown good results in pain management after orthopedic surgeries. However, the variation of performance between different subspecialities is unknown. The aim of this study is to describe our experience with cPNBs after lower limb orthopedic surgeries in different subspecialties. Materials and Methods. This prospective cohort study was performed on collected data from cPNBs after orthopedic surgeries in lower limbs. Catheters were placed by experienced anesthesiologists using sterile technique. After catheterization, the patients were examined daily, by specially educated acute pain service nurses. The characteristics of the patients, duration of catheterization, severity of the post-operative pain, need for additional opioids, and possible complications were registered. Results. We included 246 patients (=547 catheters). 115 (21%) femoral, 162 (30%) saphenous, 66 (12%) sciatic, and 204 (37%) popliteal sciatic nerve catheter were used. The median duration of a catheter was 3 days [IQR = 2 – 5]. The proportion of femoral, sciatic, saphenous, and popliteal nerve catheters with duration of more than two days was 81%, 79%, 73%, and 71% for, respectively. This proportion varied also between different subspecialties. 91% of the catheters remained in place for more than two days in amputations (n=56), 89% in pediatric surgery (n=79), 76% in trauma (n=217), 64% in foot and ankle surgery (n=129), and 59% in limb reconstructive surgery (n=66). The proportion of pain-free patients were 77 – 95% at rest, 63 – 88% at mobilization. 79 – 92% did not need increased opioid doses, and 50 – 67% did not require PRN opioid. 443 catheters (81%) were removed as planned. The cause of unplanned catheter removal was loss of efficacy in 69 (13%), dislodgement in 23 (4.2%), leakage in 8 (1.5%), and erythema in 4 catheters (0.73%). No major complication occurred. Conclusions. 81% of catheters remained in place until planned removal and opioid usage after surgery was lower than expected. Catheters were efficient in both adult and pediatric surgery; however, a variation was seen between orthopaedic subspecialities regarding duration of nerve catheter usage

Objectives. To explore the therapeutic potential of combining bone marrow-derived mesenchymal stem cells (BM-MSCs) and hydroxyapatite (HA) granules to treat nonunion of the long bone. Methods. Ten patients with an atrophic nonunion of a long bone fracture were selectively divided into two groups. Five subjects in the treatment group were treated with the combination of 15 million autologous BM-MSCs, 5g/cm. 3. (HA) granules and internal fixation. Control subjects were treated with iliac crest autograft, 5g/cm. 3. HA granules and internal fixation. The outcomes measured were post-operative pain (visual analogue scale), level of functionality (LEFS and DASH), and radiograph assessment. Results. Post-operative pain evaluation showed no significant differences between the two groups. The treatment group demonstrated faster initial radiographic and functional improvements. Statistically significant differences in functional scores were present during the first (p = 0.002), second (p = 0.005) and third (p = 0.01) month. Both groups achieved similar outcomes by the end of one-year follow-up. No immunologic or neoplastic side effects were reported. Conclusions. All cases of nonunion of a long bone presented in this study were successfully treated using autologous BM-MSCs. The combination of autologous BM-MSCs and HA granules is a safe method for treating nonunion. Patients treated with BM-MSCs had faster initial radiographic and functional improvements. By the end of 12 months, both groups had similar outcomes. Cite this article: H.D. Ismail, P. Phedy, E. Kholinne, Y. P. Djaja, Y. Kusnadi, M. Merlina, N. D. Yulisa. Mesenchymal stem cell implantation in atrophic nonunion of the long bones: A translational study. Bone Joint Res 2016;5:287–293. DOI: 10.1302/2046-3758.57.2000587

Post-operative pain is well recognised in patients undergoing shoulder surgery. With the recent advances in arthroscopic shoulder surgery over the last decade, a larger number of cases are being performed in day surgery units. These procedures are generally performed under general anaesthetic with either an interscalene or suprascapular nerve block or local anaesthetic infiltration. The aim of our prospective audit was to investigate the adequacy of analgesia provided for patients, undergoing day case arthroscopic shoulder procedures in a rural district general hospital, to ensure best medical care and to tailor certain procedures to appropriate analgesic pathways in the future. Fifty consecutive patients, who underwent day case arthroscopic shoulder surgery, were contacted by telephone one week post surgery, to assess their post-operative pain scores and analgesic requirements. Patients who received a nerve block were found to have a significantly longer duration of pain relief (p < 0.001). These patients also had significantly less pain performing their usual activities of daily living in the immediate post-operative period (p = 0.05), compared to patients who only had local anaesthetic infiltration. There was no trend found between the type of procedure and post-operative pain scores. Our audit has confirmed that nerve blocks provide longer pain relief, but has also highlighted the need to take into consideration pre-operative pain and pain perception to enable analgesia to be tailored

Objective. There is limited information about the extent to which the association between pre-operative and chronic post-operative pain is mediated via pain-on-movement or pain-at-rest. We explored these associations in patients undergoing total hip (THR) and total knee (TKR) replacement. Methods. 322 and 316 patients receiving THR and TKR respectively were recruited into in a single centre UK cohort (APEX) study. Pre-operative, acute post-operative and 12-month pain severity was measured using self-reported pain instruments. The association between pre-operative / acute pain and chronic post-operative pain was investigated using structural equation modelling (SEM). Results. Patients with high levels of pre-operative pain were more likely to report chronic pain after THR (β=0.195; p=0.02) and TKR (β=0.759; p<0.0001). Acute post-operative pain-on-movement was not associated with chronic pain after TKR or THR after adjusting for pre-operative pain, however acute pain-at-rest was associated with chronic pain after THR (β=0.20; p<0.0002) but not TKR after adjusting for pre-operative pain. Analysis of pain-at-rest and pain-on-movement highlighted differences between THR and TKR patients. Chronic pain after THR was weakly associated with pain-at-rest during the pre-operative (β=0.11; p=0.068) and acute post-operative period (β=0.21; p<0.0001). In contrast, chronic-pain after TKR was strongly associated with the severity of pain-on-movement during the pre-operative period (β=0.51; p=0.001). Conclusions. SEM illustrated the different patterns of association between measures of pain over time in patients undergoing THR and TKR for osteoarthritis. These findings highlight the importance of future work which explore the mechanisms underlying pain-on-movement and pain-at-rest. Level of Evidence. 2. Approvals. The APEX trials were registered as an International Standardised Randomised Controlled Trial (96095682), approved by Southampton and South West Hampshire Research Ethics Committee(09/H0504/94) and all participants provided informed written consent

We aimed to determine the impact of anaesthetic techniques on post-operative analgesic utilisation in people undergoing total knee arthroplasty. We conducted a prospective study at a district general hospital to assess post-operative analgesia use via patient controlled analgesia (PCA) in patients undergoing a elective total knee arthroplasty. Subjects were divided into three groups; group 1 (general anaesthetic and local nerve block, n = 39), group 2 (spinal only, n= 39) and group 3 (general anaesthetic only, n = 38). The primary outcome measure was post-operative morphine consumption through a PCA within the first 24 hours. All subjects were followed up post-operatively by a dedicated pain control nurse. Data was analysed using SPSS version 17 for Windows (SPSS Inc, Chicago, IL, USA). Results are reported as mean (SD) unless stated otherwise. No significant difference in the age or sex distribution between groups was demonstrable. There was no statistical difference in the average usage of morphine when comparing Group 1 compared to group 2, (77.57 (49.56) vs 65.80 (44.71), p=0.27), group 1 compared to group 3, (77.57 (49.56) vs 77.80 (45.52) p=0.98) and finally group 2 compared to group 3, (65.80 (44.71) vs 77.80 (45.52), p=0.25). In this cohort of patients undergoing total knee arthroplasty the anaesthetic technique used does not appear to have an influence on the post-operative pain management

Patients undergoing total knee arthroplasty (TKA) experience significant post-operative pain. We report the results of a new comprehensive patient care plan to manage peri-operative pain, enable early mobilisation and reduce length of hospital stay in TKA. A prospective audit of 1081 patients undergoing primary TKA during 2008 and 2009 was completed. All patients followed a planned programme including pre-operative patient education, pre-emptive analgesia, spinal/epidural anaesthesia with propofol sedation, intra-articular soft tissue wound infiltration, post-operative high volume intermittent ropivacaine boluses with an intra-articular catheter and early mobilisation. The primary outcome measure was the day of discharge from hospital. Secondary outcomes were verbal rating pain scores on movement, time to first mobilisation, nausea and vomiting scores, urinary catheterisation for retention, need for rescue analgesia, maximum flexion at discharge and six weeks post-operatively, and Oxford score improvement. The median day of discharge to home was post-operative day four. Median pain score on mobilisation was three for first post-operative night, day one and day two. 35% of patients ambulated on the day of surgery and 95% of patients within 24 hours. 79% patients experienced no nausea or vomiting. Catheterisation rate was 6.9%. Rescue analgesia was required in 5% of cases. Median maximum flexion was 85° on discharge and 93° at six weeks post-operatively. Only 6.6% of patients had a reduction in maximum flexion (loss of more than 5°) at six weeks. Median Oxford score had improved from 42 pre-operatively to 27 at six weeks post-operatively. The infection rate was 0.7% and the DVT and PTE rates were 0.6% and 0.5% respectively. This multidisciplinary approach provides satisfactory post-operative analgesia allowing early safe ambulation and discharge from hospital. Anticipated problems did not arise, with early discharge not being detrimental to flexion achieved at six weeks and infection rates not increasing with the use of intra-articular catheters

Objectives

This study reports on a secondary exploratory analysis of the early clinical outcomes of a randomised clinical trial comparing robotic arm-assisted unicompartmental knee arthroplasty (UKA) for medial compartment osteoarthritis of the knee with manual UKA performed using traditional surgical jigs. This follows reporting of the primary outcomes of implant accuracy and gait analysis that showed significant advantages in the robotic arm-assisted group.

Objectives

We investigated the effects on fracture healing of two up-regulators of inducible nitric oxide synthase (iNOS) in a rat model of an open femoral osteotomy: tadalafil, a phosphodiesterase inhibitor, and the recently reported nutraceutical, COMB-4 (consisting of L-citrulline, Paullinia cupana, ginger and muira puama), given orally for either 14 or 42 days.

Ketamine has been used in combination with a variety of other agents for intra-articular analgesia, with promising results. However, although it has been shown to be toxic to various types of cell, there is no available information on the effects of ketamine on chondrocytes.

We conducted a prospective randomised controlled study to evaluate the effects of ketamine on cultured chondrocytes isolated from rat articular cartilage. The cultured cells were treated with 0.125 mM, 0.250 mM, 0.5 mM, 1 mM and 2 mM of ketamine respectively for 6 h, 24 hours and 48 hours, and compared with controls. Changes of apoptosis were evaluated using fluorescence microscopy with a 490 nm excitation wavelength. Apoptosis and eventual necrosis were seen at each concentration. The percentage viability of the cells was inversely proportional to both the duration and dose of treatment (p = 0.002 and p = 0.009). Doses of 0.5 mM, 1 mM and 2mM were absolutely toxic.

We concluded that in the absence of solid data to support the efficacy of intra-articular ketamine for the control of pain, and the toxic effects of ketamine on cultured chondrocytes shown by this study, intra-articular ketamine, either alone or in combination with other agents, should not be used to control pain.

Cite this article: Bone Joint J 2014; 96-B:989–94.

We dissected 20 cadaver hips in order to investigate the anatomy and excursion of the trochanteric muscles in relation to the posterior approach for total hip replacement. String models of each muscle were created and their excursion measured while the femur was moved between its anatomical position and the dislocated position. The position of the hip was determined by computer navigation.

In contrast to previous studies which showed a separate insertion of piriformis and obturator internus, our findings indicated that piriformis inserted onto the superior and anterior margins of the greater trochanter through a conjoint tendon with obturator internus, and had connections to gluteus medius posteriorly. Division of these connections allowed lateral mobilisation of gluteus medius with minimal retraction. Analysis of the excursion of these muscles revealed that positioning the thigh for preparation of the femur through this approach elongated piriformis to a maximum of 182%, obturator internus to 185% and obturator externus to 220% of their resting lengths, which are above the thresholds for rupture of these muscles.

Our findings suggested that gluteus medius may be protected from overstretching by release of its connection with the conjoint tendon. In addition, failure to detach piriformis or the obturators during a posterior approach for total hip replacement could potentially produce damage to these muscles because of over-stretching, obturator externus being the most vulnerable.

Impaction allograft is an established method of securing initial stability of an implant in arthroplasty. Subsequent bone integration can be prolonged, and the volume of allograft may not be maintained. Intermittent administration of parathyroid hormone has an anabolic effect on bone and may therefore improve integration of an implant.

Using a canine implant model we tested the hypothesis that administration of parathyroid hormone may improve osseointegration of implants surrounded by bone graft. In 20 dogs a cylindrical porous-coated titanium alloy implant was inserted into normal cancellous bone in the proximal humerus and surrounded by a circumferential gap of 2.5 mm. Morsellised allograft was impacted around the implant. Half of the animals were given daily injections of human parathyroid hormone (1–34) 5 μg/kg for four weeks and half received control injections. The two groups were compared by mechanical testing and histomorphometry. We observed a significant increase in new bone formation within the bone graft in the parathyroid hormone group. There were no significant differences in the volume of allograft, bone-implant contact or in the mechanical parameters.

These findings suggest that parathyroid hormone improves new bone formation in impacted morsellised allograft around an implant and retains the graft volume without significant resorption. Fixation of the implant was neither improved nor compromised at the final follow-up of four weeks.

We compared time-dependent changes in the biomechanical properties of single-and double-row repair of a simulated acute tear of the rotator cuff in rabbits to determine the effect of the fixation techniques on the healing process.

A tear of the supraspinatus tendon was created in 80 rabbits which were separated into two equal groups. A single-row repair with two suture anchors was conducted in group 1 and a double-row repair with four suture anchors in group 2. A total of ten intact contralateral shoulder joints was used as a control group. Biomechanical testing was performed immediately post-operatively and at four and eight weeks, and histological analysis at four and eight weeks.

The mean load to failure in group 2 animals was greater than in group 1, but both groups remained lower than the control group at all intervals. Histological analysis showed similar healing properties at four and eight weeks in both groups, but a significantly larger number of healed tendon-bone interfaces were identified in group 2 than in group 1 at eight weeks (p < 0.012).

The ultimate load to failure increased with the number of suture anchors used immediately post-operatively, and at four and eight weeks. The increased load to failure at eight weeks seemed to be related to the increase in the surface area of healed tendon-to-bone in the double-row repair group.

We studied the effect of vitamin C on fracture healing in the elderly. A total of 80 elderly Osteogenic Disorder Shionogi rats were divided into four groups with different rates of vitamin C intake. A closed bilateral fracture was made in the middle third of the femur of each rat. Five weeks after fracture the femora were analysed by mechanical and histological testing. The groups with the lower vitamin C intake demonstrated a lower mechanical resistance of the healing callus and a lower histological grade. The vitamin C levels in blood during healing correlated with the torque resistance of the callus formed (r = 0.525). Therefore, the supplementary vitamin C improved the mechanical resistance of the fracture callus in elderly rats. If these results are similar in humans, vitamin C supplementation should be recommended during fracture healing in the elderly.

Ovine articular chondrocytes were isolated from cartilage biopsy and culture expanded in vitro. Approximately 30 million cells per ml of cultured chondrocytes were incorporated with autologous plasma-derived fibrin to form a three-dimensional construct. Full-thickness punch hole defects were created in the lateral and medial femoral condyles. The defects were implanted with either an autologous ‘chondrocyte-fibrin’ construct (ACFC), autologous chondrocytes (ACI) or fibrin blanks (AF) as controls. Animals were killed after 12 weeks. The gross appearance of the treated defects was inspected and photographed. The repaired tissues were studied histologically and by scanning electron microscopy analysis.

All defects were assessed using the International Cartilage Repair Society (ICRS) classification. Those treated with ACFC, ACI and AF exhibited median scores which correspond to a nearly-normal appearance. On the basis of the modified O’Driscoll histological scoring scale, ACFC implantation significantly enhanced cartilage repair compared to ACI and AF. Using scanning electron microscopy, ACFC and ACI showed characteristic organisation of chondrocytes and matrices, which were relatively similar to the surrounding adjacent cartilage.

Implantation of ACFC resulted in superior hyaline-like cartilage regeneration when compared with ACI. If this result is applicable to humans, a better outcome would be obtained than by using conventional ACI.

The re-establishment of vascularity is an early event in fracture healing; upregulation of angiogenesis may therefore promote the formation of bone. We have investigated the capacity of vascular endothelial growth factor (VEGF) to stimulate the formation of bone in an experimental atrophic nonunion model.

Three groups of eight rabbits underwent a standard nonunion operation. This was followed by interfragmentary deposition of 100 μg VEGF, carrier alone or autograft.

After seven weeks, torsional failure tests and callus size confirmed that VEGF-treated osteotomies had united whereas the carrier-treated osteotomies failed to unite. The biomechanical properties of the groups treated with VEGF and autograft were identical. There was no difference in bone blood flow.

We considered that VEGF stimulated the formation of competent bone in an environment deprived of its normal vascularisation and osteoprogenitor cell supply. It could be used to enhance the healing of fractures predisposed to nonunion.

We used a canine intercalary bone defect model to determine the effects of recombinant human osteogenic protein 1 (rhOP-1) on allograft incorporation. The allograft was treated with an implant made up of rhOP-1 and type I collagen or with type I collagen alone.

Radiographic analysis showed an increased volume of periosteal callus in both test groups compared with the control group at weeks 4, 6, 8 and 10. Mechanical testing after 12 weeks revealed increased maximal torque and stiffness in the rhOP-1 treated groups compared with the control group.

These results indicate a benefit from the use of an rhOP-1 implant in the healing of bone allografts. The effect was independent of the position of the implant. There may be a beneficial clinical application for this treatment.

One of the most controversial issues in total knee replacement is whether or not to resurface the patella. In order to determine the effects of different designs of femoral component on the conformity of the patellofemoral joint, five different knee prostheses were investigated. These were Low Contact Stress, the Miller-Galante II, the NexGen, the Porous-Coated Anatomic, and the Total Condylar prostheses. Three-dimensional models of the prostheses and a native patella were developed and assessed by computer. The conformity of the curvature of the five different prosthetic femoral components to their corresponding patellar implants and to the native patella at different angles of flexion was assessed by measuring the angles of intersection of tangential lines.

The Total Condylar prosthesis had the lowest conformity with the native patella (mean 8.58°; 0.14° to 29.9°) and with its own patellar component (mean 11.36°; 0.55° to 39.19°). In the other four prostheses, the conformity was better (mean 2.25°; 0.02° to 10.52°) when articulated with the corresponding patellar component. The Porous-Coated Anatomic femoral component showed better conformity (mean 6.51°; 0.07° to 9.89°) than the Miller-Galante II prosthesis (mean 11.20°; 5.80° to 16.72°) when tested with the native patella. Although the Nexgen prosthesis had less conformity with the native patella at a low angle of flexion, this improved at mid (mean 3.57°; 1.40° to 4.56°) or high angles of flexion (mean 4.54°; 0.91° to 9.39°), respectively. The Low Contact Stress femoral component had the best conformity with the native patella (mean 2.39°; 0.04° to 4.56°). There was no significant difference (p > 0.208) between the conformity when tested with the native patella or its own patellar component at any angle of flexion.

The geometry of the anterior flange of a femoral component affects the conformity of the patellofemoral joint when articulating with the native patella. A more anatomical design of femoral component is preferable if the surgeon decides not to resurface the patella at the time of operation.