Hoffa fracture is a relatively rare fracture of the coronal surface of the femoral condyle. Because the fracture is located posterior to the condyle, mostly involves the articular surface, and often occurs in combination with other types of fractures of the distal femur, it makes this type of fracture difficult to diagnose or treat. From 2000 to 2006, 132 patients were admitted to our hospital with supracondylar-intercondylar fractures of the distal femur, of which 18 were combined with Hoffa fractures, 5 were treated non-operatively, and the rest were treated surgically, with different surgical methods. The specific treatment is reported as follows: Data and Methods I. General Data The group consisted of 18 cases, 13 males and 5 females, aged 21-54 years, with an average age of 34 years. There were 5 cases of left femur and 13 cases of right femur, 6 cases of medial condyle coronal fracture and 12 cases of epicondyle. The causes of injury were: traffic injury in 8 cases, fall from height in 6 cases, crush injury in 3 cases, and smash injury in 1 case. 8 cases of hoffa fracture were diagnosed only from radiographs, 6 cases were diagnosed from radiographs combined with CT films, and the remaining 4 cases were found intraoperatively. According to the principle of AO fracture classification, the fractures were all type 33-C3. In 13 cases, epidural anesthesia was used in the supine position, and the knee was routinely disinfected and toweled, so that the knee was flexed about 30°. Firstly, the Hoffa fracture end was repositioned, and if there was a bone compression defect, autogenous bone or artificial bone was taken for bone grafting to make the joint surface flat. Then two 6-mm cancellous bone screws were fixed perpendicular to the fracture line from anterior to posterior. In one case, a posterior lateral incision was made, and the Hoffa fracture block was fixed with screws from posterior to anterior after exploration of the posterior knee nerve and blood vessels. Non-operative treatment: Five cases were treated non-operatively, all of them were combined with severe cranio-cerebral injury or other reasons not suitable for surgery. In three cases, after 8 weeks of bone traction on the affected limb, external fixation with a plaster cast was applied, and in one case, tibial tuberosity traction with external fixation with a splint was applied. In all patients with traction, the patients were encouraged to move the knee joint in bed as early as possible after the pain and swelling had decreased, and external fixation in a plaster cast was applied after 8 weeks, and the patients were started to move in bed with an abductor after about 10-14 weeks. In another case, the patient was admitted to the hospital for direct external fixation in a cast after fracture manipulation. For non-operative patients, the bed rest time should be as long as possible, usually 2,5-3 months. III. Postoperative treatment Surgical patients with firmly fixed fracture ends can have joint activities on CPM to reduce the occurrence of postoperative complications and be given symptomatic, anti-inflammatory and hemostatic medications. For non-operatively treated patients, knee activities should be performed as early as possible while traction or external fixation is being performed. Before starting to get out of bed, the knee joint can be moved in bed, and when getting out of bed, the patient should first hold the crutches to make the affected limb perform functional exercise under non-weight-bearing. Results All 18 patients were followed up for 8-16 months, with a mean of 13 months. All patients had bone healing after 12 weeks of radiographs, except for one case of delayed healing. Three of the surgical patients presented with joint pain without signs of traumatic arthritis, while four of the non-surgically treated patients presented with complications such as pain, deformity healing, and traumatic arthritis, respectively, and one of them had a combination of internal derangement of the knee. Applying Letenneur et al.’s (1978) Hoffa fracture postoperative functional recovery assessment system for evaluation, excellent: 12 cases, acceptable 3 cases, and poor 3 cases, the excellent rates after surgical and non-surgical treatment were 84, 6%, and 20%, respectively, and there was a significant difference between the excellent rates of surgical and non-surgical treatment. This indicates that the treatment of this type of fracture is better with surgical than non-surgical treatment. Discussion In 1904, Hoffa first described an isolated coronal fracture of the posterior femoral condyle, later called the Hoffa fracture. Simple coronal fractures of the femoral condyle are not common, but are often combined with supracondylar and intercondylar fractures of the femur and fractures of the tibial plateau. According to the classification principle of AO fracture, the supracondylar-intercondylar fracture of the femoral condyle with a combined coronal surface fracture is type 33-C3, which is a more serious fracture. Due to the complexity and concealment of this type of fracture, it makes it difficult to diagnose and treat. Therefore, correct diagnosis and reasonable treatment are both very important. 1. Mechanism of injury Studies have shown that coronal fractures of the femur often occur in combination with high-energy distal femoral supracondylar-intercondylar fractures, and more epicondylar than medial condylar. Thus, the mechanism of injury is similar to that of simple supracondylar-intercondylar fractures of the femur. The violence that causes the fracture is both direct and indirect. Those caused by traffic accidents are mostly direct violence. Before the car accident, the patient was mostly in a sitting position with knee flexion greater than 90 degrees and often with joint valgus. At this time, the femoral epicondyle was located in the most anterior position, and when impacted from the front, the supracondylar-intercondylar fracture of the femur appeared first due to the external force and the presence of the patella, and at the same time, the posterior coronal fracture of the femoral condyle was caused by the impact of the tibial plateau on the posterior part of the femoral condyle. In contrast, injuries caused by fall from height injuries are often caused by indirect violence. When the communicated violence between the tibiofemoral caused by the fall is accompanied by knee extension, the stress on the femoral epicondyle is more concentrated than the medial condyle due to the physiological valgus of the knee, and the structure of the epicondyle is anatomically weaker than the medial condyle. After the fall, the knee joint is changed from the extension position to the maximum flexion position to absorb some of the kinetic energy, and at this time, the posterior femoral condyle is under the greatest stress, so it is easy to cause the fracture of the coronal surface of the epicondyle. The diagnosis of simple supracondylar-intercondylar femoral fracture is relatively simple, and most of them can be diagnosed from X-rays alone, but for distal femoral fractures combined with Hoffa fracture, sometimes it is difficult to detect even intraoperatively because the coronal fracture is hidden. At present, there are few reports on hoffa fractures in China and the number of reported cases is small. Shi Weidong reported 13 cases in 10 years, and Yang Tao et al. reported 8 cases in 3 years. Despite the few related reports, the actual situation is somewhat higher than reported. A study of 202 cases of supracondylar-intercondylar fractures of the femur was conducted abroad and found that 38% of the supracondylar-intercondylar fractures of the femur were combined with coronal surface fractures. Possible reasons for the low number of reports are that some occult fractures and complex fractures are not detected by plain radiographs and that preoperative physicians rarely use other ancillary tests. Among the 18 patients in our group, 6 cases were diagnosed after radiographs combined with CT examinations. In another 4 cases, Hoffa fractures were not detected on preoperative radiographs and were only detected during intraoperative fixation of the intercondylar fracture of the femur. CT can diagnose these fractures with more certainty and reduce the rate of missed fractures. nork et al. applied CT scans to 102 patients with supracondylar-intercondylar femoral fractures, and 47% were diagnosed as coronal fractures, compared to 29% of the other 100 cases without CT scans. To reduce the underdiagnosis of Hoffa fractures, the routine use of CT in patients with femoral condylar fractures has been proposed. However, it is sometimes difficult to perform CT examinations on all emergency patients because most patients are admitted to the hospital with compound injuries and are in a hurry to manage life-threatening conditions after taking radiographs. For this reason, in patients with severe distal femoral supracondylar-intercondylar fractures, firstly, they should be on high alert, and CT examination should still be performed after the general condition is stabilized if the injury is too severe for CT examination at the time of admission. Secondly, patients who cannot be diagnosed by ordinary plain films but are highly suspected should also undergo CT examination to make up for the lack of radiographs. The treatment of fracture is different from the treatment of simple supracondylar-intercondylar fracture of the distal femur. In cases with combined Hoffa fracture, the fracture often involves the articular surface and is mostly intra-articular comminuted fracture, which requires high treatment of the fracture and currently advocates surgery. In our group of 18 patients, 13 cases were treated surgically and 5 cases were treated non-surgically. The former had an excellent postoperative rate of 84.6%, which was significantly higher than the latter (20%). The common surgical incisions are the anterolateral and medial knee incisions, and the posterior knee incision can be used if there is a suspected combination of posterior knee vascular or nerve injury that needs to be explored. It is important to fix the Hoffa fracture first during the surgical internal fixation of these fractures. If other fracture blocks are fixed first, the repositioning and fixation of the coronal fracture will be difficult. Temporary fixation of the coronal fracture block with two kerf pins prior to screw fixation will prevent rotation or displacement of the fracture fragment when the screws are screwed in. The fracture block is then fixed to the medial and lateral condyles with two screws, which should be oriented either anteriorly to posteriorly or laterally to medially. In our group of operated patients, two cases were fixed with absorbable screws for coronal fractures, while supracondylar-intercondylar fractures were fixed with locked intramedullary nails with good postoperative follow-up, which had the advantage that the screws fixing the Hoffa fracture did not have to be removed, avoiding secondary open surgery. There was also one patient in our group who had difficulty in the placement of L-plate after fixation of Hoffa fracture due to obstruction of sagittal screws, which was later changed to condylar plate. Therefore, when performing coronal fracture block fixation, the difficulty of the next step of intercondylar fracture fixation with L-plates should be thought of intraoperatively. Since condylar plates can be screwed into cancellous screws in different directions, it has been proposed that condylar plates should be preferred for the fixation of these fractures. Poor alignment of the fracture ends and poor recovery of joint function with nonoperative treatment can lead to re-displacement even in nondisplaced Hoffa fractures during the course of nonoperative treatment. Four of the five cases in our group developed complications such as pain, malunion, inversion of the knee and traumatic arthritis after nonoperative treatment, respectively. One of the patients with external fixation was eager to get out of bed within half a month, which resulted in complete failure of external fixation. 4. Complications The knee is the largest and most complex joint in the human body. Fractures of the coronal surface of the femoral condyle are often intra-articular fractures, often combined with injuries to the meniscus, cruciate ligament, tibial plateau, etc., and the fracture block has other tissues, and there are important vascular nerves around the fracture, so the requirements for repositioning and fixation are high, and if not handled properly, it will not only affect the healing of the fracture, but also cause many complications. The main complications are deformed healing, joint stiffness, traumatic arthritis and pain. In our group of patients, seven cases presented with different complications, mainly traumatic arthritis and pain, Moore et al. concluded that inappropriate internal fixation and technical errors are the main causes of postoperative complications in this type of fracture. A good functional recovery of the knee depends on intraoperative anatomical repositioning as much as possible, strong internal fixation and early and timely functional exercises, and for most patients, traumatic arthritis and postoperative pain become inevitable. For this reason, the occurrence of complications caused by improper treatment should be minimized. For example, the soft tissue attached to the fracture block is the source of its blood and should be protected intraoperatively to prevent necrosis of the fracture block; small fracture blocks, which are often attached to part of the joint, should not be easily removed to avoid future joint pain; fractures with articular surface compression should be performed with one-stage bone grafting to reduce excessive complications due to uneven articular surface; premature weight holding of the affected limb is likely to cause re-displacement of the fracture, therefore, before getting out of bed, the Therefore, before getting out of bed, the patient should first perform functional exercises of the knee joint in bed, and when getting out of bed, the affected limb should be protected. In conclusion, although these fractures occur frequently, there are not many reports on the diagnosis and treatment of these fractures, and there are still many problems in the treatment process.