Aims. The aim of this study was to determine the risk of tibial eminence avulsion intraoperatively for bi-unicondylar knee arthroplasty (Bi-UKA), with consideration of the effect of implant positioning, overstuffing, and sex, compared to the risk for isolated medial unicondylar knee arthroplasty (UKA-M) and bicruciate-retaining total knee arthroplasty (BCR-TKA). Methods. Two experimentally validated finite element models of tibia were implanted with UKA-M, Bi-UKA, and BCR-TKA. Intraoperative loads were applied through the condyles, anterior cruciate ligament (ACL), medial collateral ligament (MCL), and lateral collateral ligament (LCL), and the risk of fracture (ROF) was evaluated in the spine as the ratio of the 95. th. percentile maximum principal elastic strains over the tensile yield strain of proximal tibial bone. Results. Peak tensile strains occurred on the anterior portion of the medial sagittal cut in all simulations. Lateral translation of the medial implant in Bi-UKA had the largest increase in ROF of any of the implant positions (43%). Overstuffing the joint by 2 mm had a much larger effect, resulting in a six-fold increase in ROF. Bi-UKA had ~10% increased ROF compared to UKA-M for both the male and female models, although the smaller, less dense female model had a 1.4 times greater ROF compared to the male model. Removal of anterior bone akin to BCR-TKA doubled ROF compared to Bi-UKA. Conclusion. Tibial eminence avulsion fracture has a similar risk associated with Bi-UKA to UKA-M. The risk is higher for smaller and less dense tibiae. To minimize risk, it is most important to avoid overstuffing the joint, followed by correctly positioning the medial implant, taking care not to narrow the bone island anteriorly. Cite this article: Bone Joint Res 2022;11(8):575–584

Purpose: To determine the outcome following anterior tibial spine avulsion in skeletally mature patients. Summary: The study group comprised 83 knees with anterior tibial spine avulsion. The mean age of patients at injury was 35. Twenty knees with displaced tibial spine fractures were treated with fixation of the tibial spine and 63 patients with undisplaced or minimally displaced fractures were treated non-operatively. Twenty two percent of the non operatively managed knees developed symptomatic instability and 10% of knees treated with tibial spine fixation developed instability (p=0.22). Stiffness was more common in knees treated with tibial spine fixation than in knees managed nonoperatively (60% vs 19%, p < 0.0005). There was a tendency for increased stiffness in older patients treated with surgical fixation of the tibial spine. Conclusion: Tibial spine fracture in skeletally mature patients is associated with significant risk of knee stiffness and instability

Aim: To review the outcomes for avulsion fractures of the tibial spine in children managed by arthroscopic internal fixation using a canulated screw. Materials & Methods: A retrospective review was performed of 8 tibial spine avulsion fractures in children managed operatively by arthroscopic canulated screw fixation over a 4 year period. All fractures were graded grade III or IV (Meyer and McKeevers) in severity. Notes and radiographs were reviewed and Lysholm scores were obtained. The average age of our patients was 10.6 years and the average duration of follow up was 23.6 months (Range: 3–52 months). The average Lysholm score achieved was 88.9 (median 94.5, range 61–100) with the score demonstrably improving after the first year from injury. Bony healing was seen in all cases. One patient needed manipulation under anaesthesia to realize full movement. Conclusions: On the basis of these results, we recommend arthroscopic canulated screw fixation as the treatment of choice for tibial spine avulsions. It takes over a year, however, to achieve optimal results. This series represents the largest collection of these uncommon injuries hitherto reported from the UK

Introduction: Avulsion fractures of the anterior tibial spine are not so common. The best form of treatment for displaced fractures is still debatable. Aims: We aimed to analyze the results of different forms of internal fixation for avulsion fractures of the anterior tibial spine. Material and Methods: Twenty-five patients with avulsion fractures of the anterior tibial spine had open reduction and internal fixation with different implants (AO screw, Herbert screw, stainless steel wire loop and absorbable stitch) and techniques. The mean follow up period was 3.66 years. They were evaluated clinically and radiologically, using KT 1000 arthrometer for ACL laxity and goniometer for range of movements. The outcome was measured using Lysholm Knee Score. Results: Significant residual anterior laxity despite adequate fracture union was a common finding. Maximum ACL laxity was seen in adults in whom absorbable stitches had been used and they had a corresponding lower Lysholm score. Significant migration of the Herbert screws was noted in two of five patients in which it was used. Five of the eight patients with higher Lysholm score had AO screw fixation. Three patients with steel wire loop for stabilization of the fracture also had better results comparatively. Three individuals who had their knee immobilised in 25°–50° of flexion developed fixed flexion deformities, which took 12–18 months to recover. Conclusions: The use of absorbable stitches as the primary method of fixation for avulsion fractures of the tibial spine should be avoided in adults. Herbert screw in this situation has a tendency to migrate. AO screws and non-absorbable loop yields better functional outcome. Immobilization of the knee in excessive flexion leads to prolonged fixed flexion deformity. Early range of movements can be achieved by replacing cast with a brace allowing flexion up to 90 degrees

Abstract. Background. Anterior cruciate ligament (ACL) injuries with coinciding posterolateral tibial plateau (PLTP) depression fractures are rare. According to the most up to date literature, addressing the PLTP is crucial in preventing failure of the ACL. However, the surgical management of these injuries pose a great challenge to orthopaedic surgeons, given the anatomical location of the depressed PTP fragment. We report a case of a 17-year-old patient presenting to our department with this injury and describe a novel fixation method, that has not been described in the literature. Surgical Technique. A standard 2-portal arthroscopy is used to visualise the fractures. The PLTP is addressed first. With the combined use of arthroscopy and fluoroscopy, a guide pin is triangulated from the anteromedial aspect of the tibia, towards the depressed plateau fragment. Once the guide pin is approximately 1cm from the centre of the fragment, it is over-drilled with a cannulated drill, and simultaneously bluntly punched up to its original anatomical location. Bone graft is then used to fill the void, supported by two subchondral screws. Both fluoroscopy and arthroscopy are used to confirm adequacy of fixation. Finally, the tibial spine avulsion fracture is repaired arthroscopically using the standard suture bridging technique. Conclusion. We describe a novel, one-stage, minimally invasive approach that addresses both the ACL injury and PLTP fracture. We highlight the advantages of utilising this approach and functional outcomes

Purpose of the study: We describe a new modified arthroscopic technique of surgically treating avulsion fractures of the tibial eminence using the Scorpion device (Arthrex, Naples, FL). Methods and results: A 57 year-old female who sustained a type II fracture of the tibial spine was treated with arthroscopic fracture fixation using the Scorpion device to place a whip stitch into the substance of the anterior cruciate ligament (ACL). Tibial tunnels were made on the anteromedial aspect of the tibia using the Acufex ACL guide (Smith and Nephew, Mansfield, MA) and the sutures were passed through these tunnels and tied over a bony bridge. At 6 months after surgery, the patient was asymptomatic and had returned to her daily activities. She had regained full range of movement and had a clinically stable knee, confirmed on KT 2000 arthrometer. Radiographs showed anatomic reduction and fracture union. Conclusion: The Scorpion device which is commonly used in arthroscopic shoulder surgery provides significant advantages as it can be used arthroscopically to place a whip stitch in the substance of the ACL. The hook at its end can be used to retrieve suture loop from the joint, thus reducing instrumentation and operating time. It is a user friendly arthroscopic technique that restores the necessary tension in the ACL, provides stable fracture fixation, and also results in a cosmetic end result

Purpose Of The Study: Avulsion fractures of the anterior tibial spine are uncommon injury and we have evaluated the results in-patients who have undergone arthrotomy and fixation of the fracture. Material & Method: Twenty five patients were followed up between 21–108 months (mean 44 months) after the operation. They were evaluated clinically, radiologically and the residual ACL laxity was measured with KT 1000. Lysholm scoring scale has been used to assess the outcome. Eight fractures were fixed with a single AO screw; 5 with Herbert screws; 4 with a steel wire loop and 8 with absorbable stitch. Results: Significant residual anterior laxity despite adequate fracture union was a common finding. The ACL laxity was maximum in adults in whom absorbable stitch had been used to fix the fracture and they had a corresponding lower Lysholm score. In 2 out of the 5 patients where Herbert screws had been used there was significant migration of the screws. Additional articular damage was observed in 3 patients who were pedestrians hit by a car. All 3 ended up with restricted knee movements and poor results. Three individuals who had their knee immobilised in 250–500 of flexion developed flexion deformities, which took 12–18 months to recover. Conclusions: We recommend that use of absorbable stitches as a method of fixation be avoided in adults. Herbert screws in this situation have a tendency to migrate. AO screws or a non-absorbable loop should be used were possible. Immobilisation of the knee in excessive flexion leads to prolonged flexion deformity and we recommend immobilising the knee in no more than 100 of flexion

Aim: The purpose of study was to analyse osseous changes of tibial spine in radiographs of knees with aplasia of cruciate ligament. Methods: 13 patients with aplasia of cruciate ligament and respective x-rays were examined and analysed. Diagnosis were proofen by MRI or Arthroscopy. Moreover we checked patients with anterior and complete aplasia of cruciate ligament (s) separately. Results: We found typical signs of hypolasia and aplasia of intercondylar eminence in radiagraphs which correlate with anterior or complete aplasia of cruciate ligaments. These changes we classiþed in 3 types. Conclusion: Using this classiþcation it is possible to get a strong indication for aplasia of cruciate ligament only on the basis of x-rays

Abstract. Background. Little scientific evidence is available regarding the effect of knee joint line obliquity (JLO). Methods. 10 fresh-frozen human cadaveric knees were axially loaded to 1500 N in a materials testing machine with the joint line tilted 0, 4, 8, and 12 degrees varus and valgus, at 0, and 20 degrees of knee flexion. The mechanical compression axis was aligned to the centre of the tibial plateau. Contact pressures / areas were recorded by sensors inserted between the tibia and femur below the menisci. Changes in relative femoral and tibial position in the coronal plane were obtained by an optical tracking system. Results. medial and lateral JLO caused significant tibiofemoral subluxation and pressure distribution changes. Medial (varus) JLO caused the femur to sublux medially down the coronal slope of the tibial plateau, and vice versa for lateral (valgus) downslopes (P=0.01). Areas of peak pressure moved 12 mm and 8 mm across the medial and lateral condyles, onto the ‘downhill’ meniscus and the ‘uphill’ tibial spine. Changes in JLO had only small effects on maximum contact pressures. Conclusion. A change of JLO during load bearing caused significant mediolateral tibiofemoral subluxation. The femur slid down the slope of the tibial plateau to abut the tibial eminence and also to rest on the downhill meniscus. Clinical Relevance. These results provide important information for understanding the consequences of creating coronal JLO and for clinical practice in terms of osteotomy planning regarding the effect on JLO

Abstract. Objectives. There is renewed interest in bi-unicondylar arthroplasty (Bi-UKA) for patients with medial and lateral tibiofemoral osteoarthritis, but a spared patellofemoral compartment and functional cruciate ligaments. The bone island between the two tibial components may be at risk of tibial eminence avulsion fracture, compromising function. This finite element analysis compared intraoperative tibial strains for Bi-UKA to isolated medial unicompartmental arthroplasty (UKA-M) to assess the risk of avulsion. Methods. A validated model of a large, high bone-quality tibia was prepared for both UKA-M and Bi-UKA. Load totalling 450N was distributed between the two ACL bundles, implant components and collateral ligaments based on experimental and intraoperative measurements with the knee extended and appropriately sized bearings used. 95th percentile maximum principal elastic strain was predicted in the proximal tibia. The effect of overcuts/positioning for the medial implant were studied; the magnitude of these variations was double the standard deviation associated with conventional technique. Results. For all simulations, strains were an order of magnitude lower than that associated with bone fracture. Highest strain occurred in the spine, under the anteromedial ACL attachment, adjacent to transverse overcut of the medial component. Consequently, Bi-UKA had little effect on strain: <10% increases were predicted when compared to UKA-M with equivalent medial cuts/positioning. However, surgical overcutting/positional variation that resulted in loss of anteromedial bone in the spine increased strain. The biggest increase was for lateral translation of the medial component: 44% and 42% for UKA-M and Bi-UKA, respectively. Conclusions. For a large tibia with high bone quality, Bi-UKA with a well-positioned lateral implant had no tangible effect on the risk of tibial eminence avulsion fracture compared to UKA-M. Malpositioning of the medial component that removes bone from the anterior spine could prove problematic for smaller tibiae. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

The December 2015 Children’s orthopaedics Roundup. 360 . looks at: Paediatric femoral fractures: a single incision nailing?; Lateral condylar fractures: open or percutaneous?; . Forearm refracture: the risks; Tibial spine fractures; The child’s knee in MRI; The mechanics of SUFE; Idiopathic clubfoot

Purpose: The purpose of this study was to examine how the “ideal” tibial nail insertion point varies with tibial rotation and to determine what radiographic landmarks can be used to identify the most suitable rotational view for insertion of a tibial intramedullary nail. Methods: Twelve cadaveric lower limb specimens with intact soft tissues around the knee and ankle joints were used. A 2.0mm Kirschner wire was placed in the center of the anatomic safe zone and centered on the tibial shaft. The leg was rotated and imaged using a fluoroscopic C-arm until the K-wire was positioned just medial to the lateral tibial spine (defined as the neutral anteroposterior radiograph). The leg was then fixed and radiographs were taken in 5 degree increments by rotating the fluoroscope internally and externally (in total, a 50 degree arc). Following this a second K-wire was placed in 5 mm increments both medially and laterally and the fluoroscope rotated until this second K-wire was positioned just medial to the lateral tibial spine. Radiographs were digitized for measurements. Results: Given the presence of a 30 degree rotational arc through which the radiograph appeared anteroposterior, it was possible to improperly translate the start point up to 15 mm. Relative external rotation of the image used for nail placement led to a medial insertion site when using the lateral tibial spine as the landmark. A line drawn at the lateral edge of the tibial plateau to bisect the fibula head correlated with an entry point that was central or up to 5 mm lateral to the ideal entry point. The use of a fibula head bisector line avoided a medial insertion point. Conclusions: Rotation of the tibia may result in up to 15 mm of translation of the start point that may be unrecognized. Relative external rotation of the film used for nail placement leads to medial insertion sites when using the lateral tibial spine as a landmark. The fibula head bisector line can be used to avoid choosing external rotation views and thus avoid medial insertion points

Tibial eminence fractures were historically thought of as a condition of skeletal immaturity. Increasingly this injury has been recognized in adults. The aim was to report on the demographics, mechanism, treatment and outcomes of this injury in adult and paediatric patients. A retrospective review of all patients presenting to Dunedin Hospital, for management of a displaced tibial eminence fracture, between 1989 and 2009. 19 cases were identified, 10 skeletally mature and 9 skeletally immature. Alpine skiing with a forced flexion and rotation injury accounted for 7 cases, primarily adult females (5 cases). A hyper-extension and rotation injury accounted for 7 cases, primarily in skeletally immature males (4 cases), while direct trauma accounted for 5 cases, primarily males (4 cases). Associated injuries were more commonly seen in adults and those with high energy trauma. Stiffness was the most common complication (10 cases). Tibial spine fractures are more common in adults than previously thought. Female skiers appear to be a group at particular risk. Our most common complication was stiffness. Early range of motion is essential to reduce the problem of stiffness and extension impingement. Laxity is an infrequent problem in adults and children

This study was designed to identify the radiological changes of the knee that correlated with an unfavorable outcome when treated with an intra-articular knee viscoelastic supplementation. A prospective cohort of 60 patients receiving a standard course of intra-articular knee viscoelastic supplementation with a commercial uncrosslinked hyaluronic acid derivative of an intermediate molecular weight were studied. Follow-up was for 12 weeks post treatment with clinical improvement measured using the Western Ontario and McMasters Universities Osteoarthritis Index. Radiographs of the relevant knee were viewed and graded for the severity of joint space, osteophyte, tibial spine, sclerosis, cyst formation, alignment and general severity by an observer blinded to the outcome of the treatment. There were no appreciable differences noted in the age, sex, length of follow up, prior treatment, the severity of symptoms before treatment and number of intra-articular injections given per course in each radiographic category identified. There was a significant amount of improvement in patients with a minor loss of medial and lateral joint space in all outcome measures. Minimal changes in tibial spine and global appearance also indicated a positive outcome in stiffness, pain and overall improvement. Thus, patients with moderate to severe osteoarthritic changes in joint space on radiographic examination would not significantly benefit from intra-articular knee viscoelastic supplementation. In addition, we feel that changes in the tibial spine and global appearance are not reviewed consistently enough to be included as part of our recommendation. As such, we conclude that only patients with a minimal to mild loss in joint space on radiological examination should form part of the target group who are likely to benefit from intra-articular knee viscoelastic supplementation

Introduction and Aims: A number of x-ray appearances have been identified as indicative of discoid menisci. None are reliable or statistically significant. The purpose of this paper is to identify a reliable radiographic sign, diagnostic of the discoid lateral meniscus. Method: The anteroposterior view radiographs of 14 knees in 13 patients with arthroscopically proven discoid meniscus were studied. Ages ranged from 11 to 26, with a mean age of 18.4 ± 4.84 years, right to left ratio 9/5, male to female ratio 8/5. Fifteen normal knees in 14 people were used as a control group, age from 11 to 30, mean age 16.20 ± 6.41, right to left ratio 8/7, male to female ratio 6/8. The parameters measured were: Lateral Joint Space (LJS); Height of the Lateral Tibial Spine (LTS); change of the Medial Tibial Spine (MTS); Height of Fibular Head (HFH); changes of the Edge of the Lateral Tibial Plateau (ELTP), cupping of the lateral tibial plateau, and squaring of the lateral femoral condyle. Results: There was no significant difference between the two groups in LJS, height of LTS, cupping of the lateral tibial plateau, and squaring off of the lateral femoral condyle. There was a difference between the two groups in HFH which was statistically significant at an absolute value of p = 0.033, but not significant in normalised value p = 0.056. The medial tibial spine was sharpened in three patients. There were 12 positive changes on ELTP out of 14 patients (85.71%) in the discoid group, while only one positive of 15 (6.67%) in the normal group, and the difference between the two groups was statistically significant at p< 0.01. The diagnosis parameters were Sensitivity (Se) = 85.71%, Specificity (Sp) = 93.33%, Positive predictive value (PV+) = 92.31%, Negative predictive value (PV−) = 87.50%, Correct rate (ñ) = 89.66%. The typical change on the edge of lateral tibial plateau is sharpening and/or formation of a spur. Conclusion: Sharpening with spur formation on the edge of lateral tibial plateau is a diagnostic radiological sign of a discoid lateral meniscus

In the vast majority of patients, the anatomical and mechanical axes of the tibia in the coronal plane are widely accepted to be equivalent. This philosophy guides the design and placement of orthopaedic implants within the tibia and in both the knee and ankle joints. However, the presence of coronal tibial bowing may result in a difference between these two axes and hence cause suboptimal placement of implanted prostheses. Although the prevalence of tibial bowing in adults has been reported in Asian populations, to date no exploration of this phenomenon in a Western population has been conducted. The aim of this study was to quantify the prevalence of coronal tibial bowing in a Western population. This was an observational retrospective cohort study using anteroposterior long leg radiographs collected prior to total knee arthroplasty in our high volume arthroplasty unit. Radiographs were reviewed using a Picture Archiving and Communication System. Using a technique previously described in the literature for assessment of tibial bowing, two lines were drawn, each one third of the length of the tibia. The first line was drawn between the tibial spines and the centre of the proximal third of the tibial medullary canal. The second was drawn from the midpoint of the talar dome to the centre of the distal third of the tibial medullary canal. The angle subtended by these two lines was used to determine the presence of bowing. Bowing was deemed significant if more than two degrees. The position of the apex of the bow determined whether it was medial or lateral. Measurements were conducted by a single observer and 10% of measurements were repeated by the same observer and also by two separate observers to allow calculation of intraclass correlation coefficients (ICCs). A total of 975 radiographs consecutively performed in the calendar years 2015–16 were reviewed, 485 of the left leg and 490 of the right. In total 399 (40.9%) tibiae were deemed to have bowing more than two degrees. 232 (23.8%) tibiae were bowed medially and 167 (17.1%) were bowed laterally. The mean bowing angle was 3.51° (s.d. 1.24°) medially and 3.52° (s.d. 1.33°) laterally. Twenty-three patients in each group (9.9% medial/13.7% lateral) were bowed more than five degrees. The distribution of bowing angles followed a normal distribution, with the maximal angle observed 10.45° medially and 9.74° laterally. An intraobserver ICC of 0.97 and a mean interobserver ICC of 0.77 were calculated, indicating excellent reliability. This is the first study reporting the prevalence of tibial bowing in a Western population. In a significant proportion of our sample, there was divergence between the anatomical and mechanical axes of the tibia. This finding has implications for both the design and implantation of orthopaedic prostheses, particularly in total knee arthroplasty. Further research is necessary to investigate whether prosthetic implantation based on the mechanical axis in bowed tibias results in suboptimal implant placement and adverse clinical outcomes

Introduction:. Proper rotational alignment of the tibial component is a critical factor in the outcome of total knee arthroplasty (TKA), and misalignment has been implicated as a major contributing factor to several mechanisms of TKA failure. In this study we examine the relationship between bony and soft tissue tibial landmarks against the knee motion axis (plane that best approximates tibiofemoral motion through range of motion). Methods:. The kinematic motions of 16 fresh-frozen lower limb specimens were analyzed in simulated lunging and squatting. All the tendons of the quadriceps and hamstrings were independently loaded to simulate a lunging or squatting maneuver. All specimens underwent CT scan and the 3D position of the knee was virtually reconstructed. Ten anatomic axes were identified using both the intact tibia and the resected tibial surface. Two axes were normal vectors to either the medial-lateral plateau center or the posterior tibial surface. Seven axes were defined between the tibial tubercle (the most prominent point, center of the tubercle, or medial third of the tubercle) and soft tissue landmarks of the tibia (the medial insertion of the patellar tendon, the center of the PCL and ACL, and the tibial spines). The last axis was the Knee Motion Axis (KMA), which was defined as the longitudinal axis of the femur from 30 to 90 degrees of flexion. Results:. The closest approximation of the KMA was provided by the axis from the PCL to Medial Tibial Spine Axis, which was internally rotated 1.9 ± 7.6 degrees (Table – 1). The closest axis to the KMA in external rotation was the axis from the tibial plateau center to the medial third of the tibial tubercle, which was externally rotated 2.8 ± 4.3 degrees. The most precisely located constant axis was from the center of the tibia to the center of the tibial tubercle, which was externally rotated by 14.9 ± 3.7 degrees. Conclusions:. The line connecting the center of the PCL and the mid-point between the medial and lateral tibial spines was the closest to the functional tibial rotation. Though no individual landmark exactly correlated with the KMA in all knees, we found that the average anteroposterior motion of the femur with the tibia from 30 to 90 degrees of the femur could be consistently described by these landmarks, and that the addition of soft-tissue landmarks to prior bony topography can provide reliable indications to the location of the KMA

The rotational alignment of the tibia is an as yet unresolved issue for arthroplasty surgeons. Functional variation may be due to minor malrotation of the tibial component. The aim was to find a reliable method for positioning the tibial component in arthroplasty. CT scans of 21 knees were reconstructed in three dimensions and oriented vertically. A plane was taken 20 mm below the tibial spines. The centre of each tibial condyle was calculated from points taken round that condylar cortex. A tibial tubercle centre was also generated as the centre of the circle that best fit points on the surface of the tubercle in the plane of its most prominent point. The derived points were identified by three observers with errors of 0.6 – 1mm. The medial and lateral tibial centres were constant features (radius 24mm ± 3mm, and 22mm ± 3mm respectively). An ‘anatomic’ axis was created perpendicular to a line joining these two points. The tubercle centre was found 20mm ± 7mm lateral to the medial tibial centre. Compared to this axis, an axis perpendicular to the posterior condylar axis was internally rotated by 6° ± 3°. An axis based on the tibial tubercle and the tibial spines was also internally rotated by 6° ± 10°. We conclude that alignment of the knee when based on this ‘anatomic’ axis is more reliable than either of the posterior surfaces. It is also more reliable than any axis involving the tubercle, which is the least reliable feature in the region. The ‘anatomic’ axis can be used in navigated knee arthroplasty for referencing the rotational alignment of the tibial component

Introduction. An accurate and reproducible tibial tunnel placement without danger for the posterior neurovascular structures is a crucial condition for successful arthroscopic reconstruction of the posterior cruciate ligament (PCL). This step is commonly performed under fluoroscopic control. Hypothesis: Performing the tibial tunnel under exclusive arthroscopic control leads to accurate tunnel placement according to recommendations in the literature. Materials and Methods. Between February 2007 and December 2009, 108 arthroscopic single bundle PCL reconstructions in tibial tunnel technique were performed. The routine postoperative radiographs were screened according to defined quality criterions: 1. Overlap of the medial third of the fibular head by the tibial metaphysis on a-p views 2. Overlap of the dorsal femoral condyles within a range of 4 mm on lateral views 3. X-ray beam parallel to tibial plateau in both views. The radiographs of 48 patients (48 knees) were enrolled in the study. 10 patients had simultaneous ACL reconstruction and 7 had PCL revision surgery. The tibial tunnel was placed under direct arthroscopic control through a posteromedial portal using a standard tibial aming device. Key anatomical landmarks were the exposed tibial insertion of the PCL and the posterior horn of the medial meniscus. During digital analysis of the postoperative radiographes, the centre of the posterior tibial outlet was determined. On the a-p view, the horizontal distance of this point to the medial tibial spine was measured. The distance to the medial border of the tibial plateau was related to its total width. On the lateral view the vertical tunnel position was measured perpendicularly to a tangent of the medial tibial plateau. Results. The mean mediolateral tunnel position was 49,3 ± 4,6%, 6,7 ± 3,6 mm lateral to the medial tibial spine. On the lateral view the tunnel centre was 10,1 ± 4,5 mm distal to the bony surface of the medial tibial plateau. Neurovascular damage was observed in none of our patients. Conclusion. The results of this radiological study confirm that exclusive arthroscopic control for tibial tunnel placement in PCL reconstruction yields reproducible and accurate results according to the literature. Our technique avoids radiation, facilitates the operation room setting and enables the surgeon to visualize the key landmarks for tibial tunnel placement

Introduction & aims. Patient specific instrumentation (PSI) is a useful tool to execute pre-operatively planned surgical cuts and reduce the number of trays in surgery. Debate currently exists around improved accuracy, efficacy and patient outcomes when using PSI cutting guides compared to conventional instruments. Unicompartmental Knee Arthroplasty (UKA) revision to Total Knee Arthroplasty (TKA) represents a complex scenario in which traditional bone landmarks, and patient specific axes that are routinely utilised for component placement may no longer be easily identifiable with either conventional instruments or navigation. PSI guides are uniquely placed to solve this issue by allowing detailed analysis of the patient morphology outside the operating theatre. Here we present a tibia and femur PSI guide for TKA on patients with UKA. Method. Patients undergoing pre-operative planning received a full leg pass CT scan. Images are then segmented and landmarked to generate a patient specific model of the knee. The surgical cuts are planned according to surgeon preference. PSI guide models are planned to give the desired cut, then 3D printed and provided along with a bone model in surgery. PSI-bone and PSI-UKA contact areas are modified to fit the patient anatomy and allow safe placement and removal. The PSI-UKA contact area on the tibia is defined across the UKA tibial tray after the insert has been removed. Further contact is planned on the tibial eminence if it can be accurately segmented in the CT and the anterior superior tibia on the contralateral compartment, see example guide in Figure 1. Contact area on the femur is defined on the superior trochlear groove, native condyle, femur centre and femoral UKA component if it can be accurately segmented in the CT. Surgery was performed with a target of mechanical alignment using OMNI APEX PS implants (Raynham, MA). The guide was planned such that the OMNI cut block could be placed on the securing pins to translate the cut. Component alignment and resections values were calculated by registering the pre-operative bones and component geometries to post-operative CT images. Results. Four UKA to TKA surgeries have been performed using revision PSI guides. The maximum difference from planned to achieved component alignments are: Femoral valgus = 2.4â□°, Tibial varus = 2.5â□°, Femoral internal rotation = 3.6â□°, Femoral flexion = 5.1â□° and tibial slope = 2.9â□°, see boxplot of results in Figure 2. All median values are within 2.5â□° of the planned alignment. A further five cases are to be analysed. Conclusions. A PSI guide designed for UKR to TKR revision surgery has been successfully used in surgery with acceptable errors. A larger study must be performed to determine the reliability and reproducibility of the design and method over a wide range of patient anatomy and UKA imaging flare