Summary Statement. Uptake of robotically-assisted orthopaedic surgery may be limited by a perceived steep learning curve. We quantified the technological learning curve and 5 surgeries were found to bring operating times to appropriate levels. Implant positioning was as planned from the outset. Introduction. Compared to total knee replacement, unicondylar knee replacement (UKR) has been found to reduce recovery time as well as increase patient satisfaction and improve range of motion. However, contradictory evidence together with revision rates concern may have limited the adoption of UKR surgery. Semi-active robotically-assisted orthopaedic tools have been developed to increase the accuracy of implant position and subsequent mechanical femorotibial angle to reduce revision rates. However, the perceived learning curve associated with such systems may cause apprehension among orthopaedic surgeons and reduce the uptake of such technology. To inform this debate, we aimed to quantify the learning curve associated with the technological aspects of the NavioPFS™ (Blue Belt Technologies Inc., Pittsburgh, USA) with regards to both operation time and implant accuracy. Methods. Five junior orthopaedic trainees volunteered for the study following ethical permission. All trainees attended the same initial training session and subsequently each trainee performed 5 UKR surgeries on left-sided synthetic femurs and tibiae (model 1146–2, Sawbones-Pacific Research Laboratories Inc, Vashon, WA, USA). A few days lapsed between surgeries, which were all completed in a two week window. Replica Tornier HLS Uni Evolution femoral and tibial implants (Tornier, France) were implanted without cementation. Each surgery was videoed and timings taken for key operation phases, as well as the overall operative time. A ball point probe with four reflective spherical markers attached was used to record the position of manufactured divots on the implant, which allowed the 3D position of the implant to be compared to the planned position. Absolute translational and rotational deviations from the planned position were analysed. Results. Total surgical time decreased significantly with surgery number (p < 0.001) from an initial average of 85 minutes to 48 minutes after 5 surgeries. All stages, except the cutting tool set up, demonstrated a significant difference in operative time with increasing number of surgeries performed (all p < 0.05) with the cutting phase decreasing from 41 to 23 minutes (p < 0.001). The translational and rotational accuracy of the implants did not significantly vary with surgery number. Discussion and Conclusion. The accuracy in implant position obtained by trainee surgeons on synthetic bones were similar to published data for experienced orthopaedic surgeons on other systems on cadavers. Whilst cadaver operations increase the complexity of operation, this should not theoretically affect the robotic system in preventing innaccurate implantation. Moreover, the fact that this accuracy was obtainable on the first surgery clearly demonstrates the system's ability in ensuring accurate implantation. Five surgeries dramatically reduced the total operative time, and moreover, the trend suggests that more surgeries would further decrease the total operation time. It was not the intention of the study to compare absolute trainee times on synthetic bones to surgeons with cadavers, but the learning curve of the protocol and technology suggests a halving of the operation time after 5 sessions would not be unrealistic

Intramedullary (IM) femoral alignment guide for unicondylar knee arthroplasty (UKA) is a classic and generally accepted technique to treat unicompartmental knee osteoarthritis. However, IM system has a risk of excessive blood loss, fat embolism and activation of coagulation.Moreover, the implant placement and limb alignment may be less accurate in IM for UKA than total knee arthroplasty. So we try to use extramedullary (EM) femoral alignment for UKA to avoid above disadvantages. To our knowledge, few current studies have been reported by now. We reported a series of cases treated through a newly developed EM technique and evaluated the accuracy of femoral component alignment and preliminary clinical results. Between January 2009 and January 2010, 11 consecutive patients(15 knees)consisting of 8 males and 3 females were enrolled. There were 7 cases in unilateral knee and 4 cases in bilateral knees. The mean age was 65.2 years (range 60∼72 years). Incision, surgical time, blood loss and complications were measured. The pre- and post operative function of the knees were evaluated by HSS score system. The pre- and postoperative femoral component alignment was measured and compared. All cases were followed up for average 15 months (10-22 months). The mean length of incision was 7.2cm (range 6 to 8cm), the mean surgical time was 115.0min(range 90 to 125min),the mean blood loss was 50.8ml (range 50 to 80ml). The mean preoperative HSS score increased from 75 (range 63 to 83) to 95 (range 88 to 97) postoperatively (p<0.05). All femoral components were within the recommended range for varus/valgus (±10 degree) and lexion/extension (±5 degree) angle. None had complications associated with reamed canal injury. By using our EM technique, we could achieve an accurate femoral component alignment and satisfactory clinical effect. However, strict comparison between EM and cconventional IM technique and large amount of cases are essential. Further mid- and long-term studies are required

A number of advantages of unicondylar arthroplasty (UKA) over total knee arthroplasty in patients presenting osteoarthritis in only a single compartment have been identified in the literature. However, accurate implant positioning and alignment targets, which have been shown to significantly affect outcomes, are routinely missed by conventional techniques. Computer Assisted Orthopaedic Surgery (CAOS) has demonstrated its ability to improve implant accuracy, reducing outliers. Despite this, existing commercial systems have seen extremely limited adoption. Survey indicates the bulk, cost, and complexity of existing systems as inhibitive characteristics. We present a concept system based upon small scale head mounted tracking and augmented reality guidance intended to mitigate these factors. A visible-spectrum stereoscopic system, able to track multiple fiducial markers to 6DoF via photogrammetry and perform semi-active speed constrained resection, was combined with a head mounted display, to provide a video-see-through augmented reality system. The accuracy of this system was investigated by probing 180 points upon a 110×110×50 mm known geometry and performing controlled resection upon a 60×60×15 mm bone phantom guided by an overlaid augmented resection guide that updated in real-time. The system produced an RMS probing accuracy and precision of 0.55±0.04 and 0.10±0.01 mm, respectively. Controlled resection resulted in an absolute resection error of 0.34±0.04 mm with a general trend of over-resection of 0.10±0.07 mm. The system was able to achieve the sub-millimetre accuracy considered necessary to successfully position unicondylar knee implants. Several refinements of the system, such as pose filtering, are expected to increase the functional volume over which this accuracy is obtained. The presented system improves upon several objections to existing commercial CAOS UKA systems, and shows great potential both within surgery itself and its training. Furthermore, it is suggested the system could be readily extended to additional orthopaedic procedures requiring accurate and intuitive guidance

Introduction. Hoffa fractures are rare, intra-articular fractures of the femoral condyle in the coronal plane and involving the weight-bearing surface of the distal femur. Surgical fixation is warranted to achieve stability, early mobilisation and satisfactory knee function. We describe a unique type of Hoffa fracture in the coronal plane with sagittal split and intra-articular comminution. There is scant evidence in current literature with regards to surgical approaches, techniques and implants. We report of our case with a review of the literature. Case report. A 40 year old male motorcyclist was involved in a high speed road traffic collision. X-rays confirmed displaced unicondylar fracture of the lateral femoral condyle. CT showed sagittal split of the Hoffa fragment and intra-articular comminution. MRI showed partial rupture of the anterior cruciate ligament. The patient underwent definitive surgical treatment via a midline skin incision and lateral parapatellar approach using cannulated screws, headless compression screws and anti-glide plate. Weightbearing was commenced at 8 weeks. Arthroscopy and adhesiolysis was performed at 12 weeks to improve range of motion. The patient was discharged at one year with a pain-free, functional knee. Discussion. Hoffa fractures are high-energy fractures, often seen in young male motorcyclists with flexed and slightly abducted knee. Most papers recommend surgical fixation, however there is no widely accepted surgical method or rehabilitation regime. Varying surgical approaches, screw direction, choice of implants, and post-operative care have been described. Surgical approach depends on the configuration of the fracture. The medial/lateral parapatellar approach is commonly used as it does not compromise future arthroplasty, but it does not allow access to fix posterior comminution. Arthroscopic-assistance may be used with good outcomes and less tissue dissection. AP screws are widely reported in the literature, most likely due to easier access to the fracture site. PA screws may provide better stability, but access is more difficult. Fixation often involves passing screws through the articular surface, therefore the area damaged should be kept to a minimum by using the smallest possible screw; headless compression screws leave a smaller footprint in the articular cartilage. Locking plate augmentation generally gives good outcomes. Conclusion. Hoffa fractures are rare and difficult to treat. Surgical treatment is the best choice for optimum post-operative knee function. There is no consensus on choice of surgical approaches, techniques and implants, as these are dependent on fracture configuration. In this particular case we emphasise the importance of using an anti-glide plate to address the sagittal component. Despite the need for a secondary procedure, the treatment has had positive outcomes and may be used as a guide for treatment of future Hoffa fractures of a similar sub-type

Background. Focal resurfacing can treat localised articular damage of the knee not appropriate for arthroplasty or biological repair. Independent results on these implants are limited. We previously published early results showing significantly improved Knee Injury & Osteoarthritis Outcome Score (KOOS4) without complication or re-operation, demonstrating this system gives good analgesia and functional improvement in selected patients. We present long-term follow-up of these patients. Methods. We prospectively evaluated medium- to long-term results in patients with localised, full-thickness articular cartilage defects of the knee undergoing HemiCAP resurfacing. All procedures were performed by one consultant surgeon. Post-operative rehabilitation was standardised. Outcome measures were KOOS4 score, visual analogue score (VAS), Kellgren and Lawrence arthritis grade, and re-operation rates. Results. Six patients were evaluated with mean follow-up time of 74 months (range 61–96). Mean age was 44.8 years (range 33–51). One lateral and five medial compartments were resurfaced. Mean pre-operative KOOS4 was 39.1, mean 22-month follow-up KOOS4 improved significantly to 79.6, and mean latest follow-up KOOS4 remained good at 71.3. Mean VAS was 8.8 at latest follow-up. There was no loosening, migration or increase in osteoarthritis grade. One patient underwent revision to unicondylar knee replacement for pain after three years with comparable results at another centre (medial compartment, two year follow-up pre-revision KOOS4 84.6, latest follow-up post-revision KOOS4 73.6, VAS 6). Cause of pain was unclear (heel pain causing prolonged altered weight-bearing or failure of HemiCAP). Conclusion. Our results demonstrate that the use of the joint-preserving HemiCAP system provides good pain relief and functional improvement in both the short and longer-term. Few studies assess functional outcomes of focal resurfacing for localised full thickness articular cartilage defects. Our study assesses both the contemporaneous and time-dependent behaviour of focal resurfacing. We believe this is one of the longest follow-up series to date

To assess the outcome of Offloading Knee brace (V-VAS) in the treatment of osteoarthritis of the knee. A total of 147 patients with knee arthritis were included in this study. Eighty six patients were followed up retrospectively and 61 patients were followed up prospectively. Average follow up was about 3.4 years in retrospective group and 1.2 years in prospective group. The Oxford knee score, Pain score, Walking distance and Patient satisfaction were evaluated. Average oxford scores before the brace was 19 and after the brace was 32. The pain scores before and after the brace was 8 and 3 respectively. The walking distance had improved to 900 yards. The patient satisfaction was 78%. Thirteen of eighty six patients in the retrospective group discontinued the brace, of these two had high tibial osteotomy, six patients had total knee replacement, one had unicondylar knee replacement, one patient had dislocation of patella and two elderly patients were house-bound because of medical problems. The Off loading knee brace is effective in the management of osteoarthritis of the knee. Patient satisfaction is high when using the brace. However compliance may be an issue in some of the patients. Education and early appointment for brace re-fitting increases patient compliance. Bracing is a beneficial treatment for severe medial OA of the knee

Summary Statement. This project proves that Patellofemoral (PF) joint degeneration is not a contraindication to medial unicompartmental knee replacement. Introduction. Unicompartmental knee arthroplasty (UKA) is a recognised procedure for treatment of medial compartment osteoarthritis. Patellofemoral (PF) joint degeneration is widely considered to be a contraindication to medial unicompartmental knee replacement. We examined the validity of this preconception using information gathered prospectively on consecutive patients who underwent UKA using the Repicci II® UKA prosthesis for medial compartment osteoarthritis. Methods. We prospectively collected data on 147 consecutive patients who underwent the Repicci II® UKA for medial compartment osteoarthritis. All operations were performed between July 1999 and September 2000 by the same surgeon. The status of the PF joint was assessed intra-operatively in all patients, and accordingly patients were divided into two groups, one group with a normal PF joint, and the second group with degenerative changes of the PF joint. Variables measured for outcome included the International Knee Society (IKS) score, limb alignment, and range of motion. Radiographs were assessed for progression of disease or failure of implant. The mean follow-up was 9.4 years (range: 5–10.7 years). Patients were reviewed initially at 2 weeks, and then at 6 months post-operatively. They were subsequently reviewed on an annual basis.. All patients completed an IKS score preoperatively and at last follow-up. Age, gender, BMI, length of hospital stay, perioperative complications, all subsequent surgery, including revision of the prosthesis, and survivorship at 10 years was recorded, and results of the 2 groups compared. Results. A total of 147 patients were included in the study. None were lost to follow-up. Sixty nine had associated PF osteoarthritis (group A) while 78 patients had a normal PF compartment when assessed intra-operatively (group B). Post-operative outcomes of the two groups were compared using the ANCOVA analysis with adjustment for pre-operation values firstly, and adjusting also for gender, age, BMI and follow-up secondly. There were no significant differences in terms of IKS, alignment, and flexion between the two groups. However, patients in group B had significantly better extension post-operatively than patients in group A (p<0.05). Conclusion. We concluded that damage to the articular cartilage of the patellofemoral joint to the extent of full-thickness cartilage loss is not a contraindication to the Repicci II® unicondylar knee arthroplasty for medial compartment osteoarthritis. However, extension is significantly improved post-operatively in those patients with minimal or no PF joint degenerative disease

The properties of impacted morsellised bone graft (MBG) in revision total knee arthroplasty (TKA) were studied in 12 horses. The left hind metatarsophalangeal joint was replaced by a human TKA. The horses were then randomly divided into graft and control groups. In the graft group, a unicondylar, lateral uncontained defect was created in the third metatarsal bone and reconstructed using autologous MBG before cementing the TKA. In the control group, a cemented TKA was implanted without the bone resection and grafting procedure. After four to eight months, the animals were killed and a biomechanical loading test was performed with a cyclic load equivalent to the horse’s body-weight to study mechanical stability. After removal of the prosthesis, the distal third metatarsal bone was studied radiologically, histologically and by quantitative and micro CT. Biomechanical testing showed that the differences in deformation between the graft and the control condyles were not significant for either elastic or time-dependent deformations. The differences in bone mineral density (BMD) between the graft and the control condyles were not significant. The BMD of the MBG was significantly lower than that in the other regions in the same limb. Micro CT showed a significant difference in the degree of anisotropy between the graft and host bone, even although the structure of the area of the MBG had trabecular orientation in the direction of the axial load. Histological analysis revealed that all the grafts were revascularised and completely incorporated into a new trabecular structure with few or no remnants of graft. Our study provides a basis for the clinical application of this technique with MBG in revision TKA

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.