Abstract. Background. Conventional TKR aims for neutral mechanical alignment which may result in a smaller lateral distal femoral condyle resection than the implant thickness. We aim to explore the mismatch between implant thickness and bone resection using 3D planning software used for Patient Specific Instrumentation (PSI) TKR. Methods. This is a retrospective anatomical study from pre-operative MRI 3D models for PSI TKR. Cartilage mapping allowed us to recreate the native anatomy, enabling us to quantify the mismatch between the distal lateral femoral condyle resection and the implant thickness. Results. We modelled 292 knees from PSI TKR performed between 2012 and 2015. There were 225 varus knees and 67 valgus knees, with mean supine hip-knee-angle of 5.6±3.1 degrees and 3.6±4.6 degrees, respectively. In varus knees, the mean cartilage loss from medial and lateral femoral condyle was 2.3±0.7mm and 1.1±0.8mm respectively; the mean overstuffing of the lateral condyle 1.9±2.2mm. In valgus knees, the mean cartilage loss from medial and lateral condyle was 1.4±0.8mm and 1.5±0.9mm respectively; the mean overstuffing of the lateral condyle was 4.1±1.9mm. Conclusions. Neutral alignment TKR often results in overstuffing of the lateral condyle. This may increase the patello-femoral pressure at the lateral facet in flexion. Anterior knee pain may be persistent even after patellar resurfacing due to tight lateral retinacular structures. An alternative method of alignment such as anatomic alignment may minimise this problem

Aims. The transepicondylar axis is a well-established reference for the determination of femoral component rotation in total knee arthroplasty (TKA). However, when severe bone loss is present in the femoral condyles, rotational alignment can be more complicated. There is a lack of validated landmarks in the supracondylar region of the distal femur. Therefore, the aim of this study was to analyze the correlation between the surgical transepicondylar axis (sTEA) and the suggested dorsal cortex line (DCL) in the coronal plane and the inter- and intraobserver reliability of its CT scan measurement. Methods. A total of 75 randomly selected CT scans were measured by three experienced surgeons independently. The DCL was defined in the coronal plane as a tangent to the dorsal femoral cortex located 75 mm above the joint line in the frontal plane. The difference between sTEA and DCL was calculated. Descriptive statistics and angulation correlations were generated for the sTEA and DCL, as well as for the distribution of measurement error for intra- and inter-rater reliability. Results. The external rotation of the DCL to the sTEA was a mean of 9.47° (SD 3.06°), and a median of 9.2° (IQR 7.45° to 11.60°), with a minimum value of 1.7° and maximum of 16.3°. The measurements of the DCL demonstrated very good to excellent test-retest and inter-rater reliability coefficients (intraclass correlation coefficient 0.80 to 0.99). Conclusion. This study reveals a correlation between the sTEA and the DCL. Overall, 10° of external rotation of the dorsal femoral cortical bone to the sTEA may serve as a reliable landmark for initial position of the femoral component. Surgeons should be aware that there are outliers in this study in up to 17% of the measurements, which potentially could result in deviations of femoral component rotation. Cite this article: Bone Jt Open 2024;5(12):1067–1071

Introduction. Oriental people habitually adopt formal sitting and squatting postures, the extreme flexion of the knees allowing of this. The influence exercised by pressure and posture are, therefore, found at the posterior side of knee joint. However, we don't have many report about articular cartilage of posterior femoral condyle. Objectives. The purpose of this study was to reveal the accurate prevalence and related factors to the presence of degenerative changing of the articular cartilage of posterior femoral condyle in cadaveric knee joints. Methods. One hundred and thirty two knees from 66 cadavers (42 male knees and 24 female knees, formalin fixed, Japanese anatomical specimens) were included in this study. The average age of the cadavers was 81.4 (56–101) years. Knees were macroscopically evaluated the depth of cartilage degeneration of the patellofemoral joint, medial and lateral femoral condyle, medial and lateral posterior femoral condyle following the Outerbridge's classification. Grading was as follows: Grade 1: normal cartilage or softening and swelling of the cartilage. Grade 2: partial-thickness defect which did not reach the subchondral bone and was less than 1.3 cm in diameter. Grade 3: partial-thickness defect which did not reach the subchondral bone and was more than 1.3 cm in diameter. Grade 4: exposed subchondral bone and visible reactive tissue formation. When there were multiple lesions of different Outerbridge's classification grades, the sizes of the lesions were added up. Lesions with degenerative changes more severe than Outerbridge's classification grade 3 were regarded as OA lesions. Statistical analysis was performed to reveal the correlation between the occurrences of cartilage degeneration of medial and lateral posterior femoral condyle and medial and lateral femoral condyle and gender. Results. The prevalence of OA-positive was 48.5% (64 knees). Analyzing in the prevalence in gender, male was 31% (26 knees) OA-positive, female was 79.2% (38knees) OA-positive. The frequency of OA-positive was significantly higher in females than in males (P < 0.001). The prevalence of OA-positive in posterior condyle was 53.1% (34 knees) in 64 knees of OA-positive. Analyzing in the prevalence in gender, male was 15.4% (4 knees) in 26 knees of OA-positive, female was 78.4% (30knees) in 38 knees of OA-positive. The frequency of OA-positive in posterior condyle was significantly higher in females than in males (P < 0.001). Conclusions. In this study, the prevalence of OA-positive in posterior condyle was evaluated in cadaveric knees. The prevalence of OA-positive in posterior condyle was 53.1% in OA-positive knees, and was significantly correlated with the gender

With medial unicompartmental osteoarthritis (OA) there is occasionally a full-thickness ulcer of the cartilage on the medial side of the lateral femoral condyle. It is not clear whether this should be considered a contraindication to unicompartmental knee replacement (UKR). The aim of this study was to determine why these ulcers occur, and whether they compromise the outcome of UKR. Case studies of knees with medial OA suggest that cartilage lesions on the medial side of the lateral condyle are caused by impingement on the lateral tibial spine as a result of the varus deformity and tibial subluxation. Following UKR the varus and the subluxation are corrected, so that impingement is prevented and the damaged part of the lateral femoral condyle is not transmitting load. An illustrative case report is presented. Out of 769 knees with OA of the medial compartment treated with the Oxford UKR, 59 (7.7%) had partial-thickness cartilage loss and 20 (2.6%) had a full-thickness cartilage deficit on the medial side of the lateral condyle. The mean Oxford Knee Score (OKS) at the last follow-up at a mean of four years was 41.9 (13 to 48) in those with partial-thickness cartilage loss and 41.0 (20 to 48) in those with full-thickness loss. In those with normal or superficially damaged cartilage the mean was 39.5 (5 to 48) and 39.7 (8 to 48), respectively. There were no statistically significant differences between the pre-operative OKS, the final review OKS or of change in the score in the various groups. We conclude that in medial compartment OA, damage to the medial side of the lateral femoral condyle is caused by impingement on the tibial spine and should not be considered a contraindication to an Oxford UKR, even if there is extensive full-thickness ulceration of the cartilage

Coronal plane fractures of the posterior femoral condyle, also known as Hoffa fractures, are rare. Lateral fractures are three times more common than medial fractures, although the reason for this is not clear. The exact mechanism of injury is likely to be a vertical shear force on the posterior femoral condyle with varying degrees of knee flexion. These fractures are commonly associated with high-energy trauma and are a diagnostic and surgical challenge. Hoffa fractures are often associated with inter- or supracondylar distal femoral fractures and CT scans are useful in delineating the coronal shear component, which can easily be missed. There are few recommendations in the literature regarding the surgical approach and methods of fixation that may be used for this injury. Non-operative treatment has been associated with poor outcomes. The goals of treatment are anatomical reduction of the articular surface with rigid, stable fixation to allow early mobilisation in order to restore function. A surgical approach that allows access to the posterior aspect of the femoral condyle is described and the use of postero-anterior lag screws with or without an additional buttress plate for fixation of these difficult fractures. Cite this article: Bone Joint J 2013;95-B:1165–71

The purpose of this study was to evaluate the long-term functional and radiological outcomes of arthroscopic removal of unstable osteochondral lesions with subchondral drilling in the lateral femoral condyle. We reviewed the outcome of 23 patients (28 knees) with stage III or IV osteochondritis dissecans lesions of the lateral femoral condyle at a mean follow-up of 14 years (10 to 19). The functional clinical outcomes were assessed using the Lysholm score, which improved from a mean of 38.1 (. sd. 3.5) pre-operatively to a mean of 87.3 (. sd. 5.4) at the most recent review (p = 0.034), and the Tegner activity score, which improved from a pre-operative median of 2 (0 to 3) to a median of 5 (3 to 7) at final follow-up (p = 0.021). The radiological degenerative changes were evaluated according to Tapper and Hoover’s classification and when compared with the pre-operative findings, one knee had grade 1, 22 knees had grade 2 and five knees had grade 3 degenerative changes. The overall outcomes were assessed using Hughston’s rating scale, where 19 knees were rated as good, four as fair and five as poor. We found radiological evidence of degenerative changes in the third or fourth decade of life at a mean of 14 years after arthroscopic excision of the loose body and subchondral drilling for an unstable osteochondral lesion of the lateral femoral condyle. Clinical and functional results were more satisfactory

We describe the mid-term results of a prospective study of total knee replacement in severe valgus knees using an osteotomy of the lateral femoral condyle and computer navigation. There were 15 knees with a mean valgus deformity of 21° (17° to 27°) and a mean follow-up of 28 months (24 to 60). A cemented, non-constrained fixed bearing, posterior-cruciate-retaining knee prosthesis of the same design was used in all cases (Columbus-B. Braun; Aesculap, Tuttlingen, Germany). All the knees were corrected to a mean of 0.5° of valgus (0° to 2°). Flexion of the knee had been limited to a mean of 85° (75° to 110°) pre-operatively and improved to a mean of 105° (90° to 130°) after operation. The mean Knee Society score improved from 37 (30 to 44) to 90 points (86 to 94). Osteotomy of the lateral femoral condyle combined with computer-assisted surgery gave an excellent mid-term outcome in patients undergoing total knee replacement in the presence of severe valgus deformity

We reviewed lesions of the femoral condyles seen in 5,000 knee arthroscopies, recording the findings and the age and sex of the patients. We were able to distinguish the characteristics of developing and late osteochondritis dissecans, acute and old osteochondral fractures, chondral separations, chondral flaps and idiopathic osteonecrosis, and suggest that these are separate distinct conditions. Haemarthrosis was associated only with acute osteochondral fractures. The characteristic feature of osteochondritis dissecans was an expanding concentric lesion at the 'classical' site on the medial femoral condyle which appeared during the second decade of life and progressed to a concave steep-sided defect in the mature skeleton. Caffey's (1958) classification of epiphyseal dysplasias could not be applied to osteochondritis dissecans, which appeared to have a gradual onset without acute trauma. Much of the controversy about the cause of osteochondritis dissecans is the result of imprecise nomenclature

Large osteochondral defects of the femoral condyle still pose a difficult problem to treat. A variety of options is available but most of result in replacement with inferior fibrous or hyaline-like cartilage in the load-bearing zone of the knee joint. We present the five year results of Mega-OATS. This technique utilizes the posterior femoral condyle for coverage of osteochondral defects and is called Mega-OATS. From July 1999, 33 patients of mean age 34.3 years (15–59) were treated with MEGA-OATS. Fifteen patients additionally underwent high tibial osteotomy and two bone grafting using bone harvested from the proximal tibia. The average defect size was 6.2±1.8 cm2. The mean follow up was 66.4±13.2 months. The technique calls for excision of the posterior femoral condyle which is placed in a specially designed work station. The Lysholm score increased post-operatively from 49.0±19.4 to 88.5±14.9 12 months post surgery to 85.5±16.0 five years post surgery. Three months post-operatively, patients attained a full range of motion and became fully weight-bearing. There was no difference in patients undergoing combined surgery with high tibial osteotomy and patients undergoing Mega OATS as a single procedure after five years. No post-operative meniscal lesions of the posterior horn have been observed. Mega-OATS achieves a congruent reconstruction of the articular surface in the load bearing zone of the femoral condyle. We consider it a good alternative and salvage procedure in the treatment of large osteochondral defects of the femoral condyle

Large osteochondral defects are difficult to treat, but several treatment options are available. The posterior condyle transfer salvage technique described by Wagner in 1964 and Imhoff in 1990 has been developed further and is now used for coverage of large osteochondral defects in the load-bearing zone. The new technique is called MEGA-OATS. From July 1999, 25 patients of mean age 33.3 years (17 to 60) were treated with MEGA-OATS. Thirteen patients additionally underwent high tibial osteotomy and two bone grafting, using bone harvested from the proximal tibia. The mean follow up was 17.8 months. The technique calls for excision of the posterior femoral condyle which is placed in a specially designed work station. A MEGA-OATS cylinder of diameter 20 mm to 35 mm is prepared and, using the press-fit technique, grafted into the prepared defect zone. The Lysholm score increased postoperatively from 66.33 (49 to 71) to 87.8 (72 to 97). Three months postoperatively control MRI showed incorporation of all cylinders. Between six and 12 weeks postoperatively patients attained a full range of motion and became fully weight-bearing. To date one superficial infection resolving on oral antibiotics and two cases of arthrofibrosis four months postoperatively that required arthroscopic release were seen. No postoperative meniscal lesions of the posterior horn have been observed. MEGA-OATS achieves a congruent reconstruction of the articular surface in the load-bearing zone of the femoral condyle. We consider it a good alternative in the treatment of large osteochondral defects of the femoral condyle in young patients

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

Large osteochondral defects are difficult to treat, but several treatment options are available. The posterior condyle transfer salvage technique described by Wagner in 1964 and Imhoff in 1990 has been developed further, and is now used for coverage of large osteochondral defects in the load-bearing zone. The new technique is called MEGA-OATS. From July 1999, 17 patients of mean age 39 years (16 to 6) were treated by MEGA-OATS. Two patients additionally underwent high tibial osteotomy and two bone grafting, using bone harvested from the proximal tibia. The mean follow-up was 12 months. The technique calls for excision of the posterior femoral condyle, which is placed in a specially designed work station. A MEGA-OATS cylinder of diameter 20 mm to 35 mm is prepared and, using the press-fit technique, grafted into the prepared defect zone. The Lysholm score increased postoperatively from 63 (49 to 71) to 81 (72 to 85). Three months postoperatively control MRI showed incorporation of all cylinders. Between six and 12 weeks postoperatively, patients attained a full range of motion and became fully weight-bearing. To date no postoperative complications or meniscal lesions of the posterior horn have been observed. MEGA-OATS achieves a congruent reconstruction of the articular surface in the load-bearing zone of the femoral condyle. We consider it a good alternative in the treatment of large osteochondral defects of the femoral condyle in young patients

Juvenile Osteochondritis dissecans (JOCD) in humans and subchondral cystic lesions (SCL) in horses (also termed radiolucencies) share similarities: they develop in skeletally immature individuals at the same location in the medial femoral condyle (MFC) and their etiology is only partially understood but trauma is suspected to be involved. JOCD is relatively uncommon in people whereas SCLs arise in 6% of young horses leading to lameness. Ischemic chondronecrosis is speculated to have a role in both osteochondrosis and SCL pathogenesis. We hypothesize that MFC radiolucencies develop very early in life following a focal internal trauma to the osteochondral junction. Our aims were to characterize early MFC radioluciencies in foals from 0 to 2 years old. Distal femurs (n=182) from Thoroughbred horses (n=91, 0–2 years old), presented for post-mortem examination for reasons unrelated to this study, were collected. Radiographs and clinical tomodensitometry were performed to identify lesions defined as a focal delay of ossification. Micro-tomodensitometry (m-CT) and histology was then performed on the MFCs (CT lesions and age-matched subset of controls). Images were constructed in 3D. The thawed condyles, following fixation, were sectioned within the region of interest, determined by CT lesion sites. Hematoxylin eosin phloxin and safran (HEPS) and Martius-Scarlet-Blue (MSB) stains were performed. Histological parameters assessed included presence of chondronecrosis, fibrin, fibroplasia and osteochondral fracture. An additional subset of CT control (lesion-free) MFCs (less 6 months old) were studied to identify early chondronecrosis lesions distant from the osteochondral junction. One MFC in clinical CT triages controls had a small lesion on m-CT and was placed in the lesion group. All m-CT and histologic lesions (n=23) had a focal delay of ossification located in the same site, a weight bearing area on craniomedial condyle. The youngest specimen with lesions was less than 2 months old. On m-CT 3D image analysis, the lesions seemed to progressively move in a craniolateral to caudomedial direction with advancing age and development. Seventy-four percent (n=17/23) of the lesions had bone-cartilage separation (considered to be osteochondral fractures) confirmed by the identification of fibrin/clot on MSB stains, representing an acute focal bleed. Fibroplasia, indicating chronicity, was also identified (74%, n=17/23). In four cases, the chondrocytes in the adjacent cartilage were healthy and no chondronecrosis was identified in any sections in the lesions. Nineteen cases had chondronecrosis and always on the surface adjacent to the bone, at the osteochondral junction. None of the subset of control specimens, less than 6 months old (n=44), had chondronecrosis within the growth cartilage. Early subchondral cystic lesions of the medial femoral condyle may arise secondary to focal internal trauma at the osteochondral junction. The presence of fibrin/clot is compatible with a recent focal bleed in the lesion. Medial femorotibial joint internal forces related to geometry could be the cause of repetitive trauma and lesion progression. In the juvenile horse, and potentially humans, the early diagnosis of MFC lesions and rest during the susceptible period may reduce progression and promote healing by prevention of repetitive trauma, but requires further study

In a prospective randomised trial 76 knees with isolated degenerative changes in the medial femoral condyle of grades 3 or 4 were treated by either arthroscopic debridement (40) or washout (36). All knees were followed up for at least one year and 58 for five years. The mean follow-up time was 4.5 years in the debridement group and 4.3 years in the washout group. At one year 32 of the debridement group and five of the washout group were painfree and at five years 19 of a total of 32 survivors in the debridement group and three of the 26 in the washout group were also free from pain. The mean improvement in a modified Lysholm score was 28 for the debridement group at one year and 21 at five years. In the washout group it was only 5 at one year and 4 at five years. For knees with lesions of the medial femoral condyle of grades 3 or 4, arthroscopic debridement appears to be the treatment of choice with over half the patients free from pain after five years

Four children are described, each with spontaneous osteonecrosis affecting nearly one-third of the lateral femoral condyle. All the children had a motor and a sensory deficit in the affected limb: two had been previously treated for neuroblastoma of the spine, one for an infected lumbar dermoid cyst and one had spina bifida. We consider that these disorders, singly or in combination, may lead to repeated excessive loading of the lateral femoral condyle, which cannot be appreciated in a knee that is not protected by normal sensation

We reviewed seven patients with coronal fractures of the lateral femoral condyle and studied the mechanism of injury and the radiological features. The influence of soft tissue attachments on the displacement and the blood supply were investigated by clinical and cadaveric studies. All three fractures which were initially undisplaced lost position early during conservative management. Internal fixation gave good results at review, and is recommended to avoid the risk of malunion and possible secondary osteoarthritis

Introduction:In the last years spontaneous osteonecro-sis of the knee is described to be an important, but underestimated cause of osteoarthritis of the knee. The most frequent one is located in the medial femoral condyle. Materials and methods:Between 1993 and 2000, 24 cases with osteonecrosis of the medial femoral condyle in stage II, III and IV were surgically treated. Mean age at surgery was 59 (range 33–66), 17 female, 7 male. The mean follow Ð up period was 27(range 12–44) month. The etiology was found in 27% of the cases (trauma, intraarticular steroid therapy, dislipidemy). In 73% of patients the cause was not identiþed. At 3 patients the location was bicompartimental. This surgical technique well þxed modiþes the center of the mechanical unload protecting the osteonecrosis area allowing its revascularization. Results:From 24 patients surgically treated with this technique the results were very good in 69,2%, good in 25,2%and failure in 5,6%. The very good and good results were obtained at patients with osteonecrosis of medial femoral condyle stages II and III. Conclusions:In conditions of redistribution of mechanical requirement at knee level, of good þxing HTO without bone grafting represent a technique of treatment in osteonecrosis of the medial femoral condyle allowing the revascularization of the area, improvement or even the disappearance of the symptoms well as the prevention or the delaying of osteoarthrites of the knee

Full thickness cartilage defects of the femoral condyles are frequent, can be highly symptomatic, and pose treatment challenges when encountered in middle-aged patients. A history of biological repair procedures is frequent and patient management is complex in order to delay joint replacement procedures in active patients. Focal metallic resurfacing provides a joint preserving bridging procedure with a clinical exit into primary arthroplasty. Methods. This study presents a review of several multicenter investigations exploring the clinical benefits and validity of focal resurfacing in 78 patients, ages 35–67, with a follow-up ranging from 2 to 6 years. All patients were treated with a 15 or 20 mm contoured resurfacing implant on the medial or lateral femoral condyle. Results. At 2 years follow up, average scores for WOMAC domains improved by over 100% (40 preop to 86 postop where 100 = best). At 3 year follow-up KOOS scores were within 88 to 102% of a normal aged matched population (domain range 72–91 where 100 = best). At a minimum of 5 years, the KOOS domains were close to normative reference levels on pain relief, symptoms, and activities of daily living (range 83–89% of normal). Radiographic results demonstrated solid fixation, preservation of joint space, and no change in the osteoarthritic stage. Conclusion. The procedure adds a new layer to reconstructive treatment options in the long-term management of knee arthrosis and arthritis and allows for a clinical alternative to lifestyle changes required by many patients who failed cartilage procedures and continue to have an isolated symptomatic defect precluding them from joint arthroplasty

Spontaneous osteonecrosis of the knee (SPONK) usually involves a single condyle or plateau. The medial femoral condyle is most often involved and spontaneous osteonecrosis of medial tibial plateau is a rare condition, representing only 2 % of all necrosis reported in the knee. Therefore, SPONK with both involvement of medial femoral condyle(MFC) and medial tibial plateau(MTP) might be extremely rare. SPONK in each MFC or MTP respectively might be extended into corresponding side of the knee at their advanced final stage, howevere, in that situations, significant degenerative change would accompany and it might be difficult to differentiate final staged SPONK form severe osteoarthritis. To the best of our knowledge, SPONK affecting both medial femoral condyle and medial tibial plateau without significant secondary osteoarthritis changes is not reported, even though it was difficult to know which occurred first. We experienced 3 patients with histologically proven osteonecrosis of the medial tibial condyle and medial tibial plateau, and report their radiologic features. All 3 patients showed similar ridiograhic patterns. Medial portion of medial tibial plateau and lateral portion of medial femoral condyle showed longitudinal fracture like-subchondral collapse. Standing anteroposterior radiograph at 30 degree knee flexion showed well fitted features such as “locked” medial condyle. Varus angulation was present. Significant degenerative changes was not shown except for subchondral sclerosis. T1-weighted coronal and Fat suppressed T2-weighted MR images showed subchondral collapse with ill-defined diffuse bone marrow edema changes on both tibial and femoral condyles. At surgical findings, longitudinal track-like groove was shown in both medial femoral condyle and medial tibial plateau. Articular cartilage was denuded and showed glistening surface with bone defect of lateral side of medial femoral condyle and medial side of tibial articular surface. Histological analysis shows necrotic bone, surrounded by an area of fibrovascular granulation tissue on both femoral and tibial sides. Total knee arthoplasty was performed in all 3 patients. As a result of very low prevalence of both involvement of MFC and MTP and limited number of our cases, we could not conclude that radiologic features in our cases are typical radiologic pattern of both involvement. However, based on our cases, we believe that this characteristic radiologic features may considered as one of the possible various radiologic findings of simultaneous involvement in MFC and MTP and allow diagnosis for SPONK with both involvement in MFC and MTP to be facilitated

Introduction:. Unicompartmental knee arthroplasty has been shown to have lower morbidity, quicker rehabilitation and more normal kinematics compared to conventional TKA, but subchondral defects, or severe osteoarthritic changes, of the medial compartment may complicate component positioning. Successful UKA in these patients requires proper planning and exact placement of the components to ensure adequate and stable fixation and proper postoperative kinematics. This study presents a series of three patients with spontaneous osteonecrosis of the knee receiving a UKA with CT-based haptic robotic guidance. Methods:. This series includes two females and one male with spontaneous osteonecrosis of the medial femoral condyle who underwent outpatient mini-incision medial UKA using the MAKO Surgical Rio Robotic Arm System. Pre-operatively all patients were found to have pain with weight bearing that would not improve despite non-arthroplasty treatment. Results:. The first patient was a 69 year old female (BMI of 22.85) with a left medial femur size 3, tibia size 4, bearing size 4×8 mm. The patient improved her ROM from 3–112° pre-operatively to 0–130° at 18 months post-operatively. The second patient was a 69 year old female (BMI of 25.68) with a right medial size 2 femur and 3 tibia and a 3×9 mm bearing. ROM increased from 0–120° pre-operatively to 0–145° at 2 year follow-up. The third patient was a 74 year old male (BMI of 26.5) who underwent previous knee arthroscopy with subsequent SPONK. Conclusion:. The difficulty in treatment of SPONK with UKA solutions includes planning for the full coverage of the ON lesions while also addressing alignment, tracking and balancing needs simultaneously. Using the advanced planning tools of the MAKO Rio software, full coverage of ON lesions can be safely planned and verified preoperatively. The intraoperative flexibility of the system allows surgeon to map out the lesions intraoperatively, where visible, and aid in the proper implant positioning and size adjustment as necessary