Busch-Hoffa fracture: A systematic review

Abstract

Background:

Accomplish a thorough review on the existing biomechanical and clinical studies about coronal plane fractures of the distal femur.

Methods:

We performed an electronic search of PubMed/MEDLINE database from April to June, 2023. The terms for the database search included “Hoffa fractures,” OR “Busch-Hoffa fractures” OR “coronal plane fractures of the distal femur.”

Results:

The search identified 277 potentially eligible studies. After application of inclusion and exclusion criteria, 113 articles were analyzed in terms of the most important topics related to coronal plane fractures of the distal femur.

Conclusion:

Lateral coronal plane fractures of the distal femur are more frequent than medial, present a more vertical fracture line, and usually concentrate on the weight bearing zone of the condyle. The Letenneur system is the most used classification method for this fracture pattern. Posterior-to-anterior fixation using isolated lag screws (for osteochondral fragments—Letenneur type 2) or associated with a posterior buttressing plate (when the fracture pattern is amenable for plate fixation—Letenneur types 1 and 3) is biomechanically more efficient than anterior-to-posterior fixation. Anterior-to-posterior fixation using lag screws complemented or not by a plate remains a widely used treatment option due to the surgeons’ familiarity with the anterior approaches and lower risk of iatrogenic neurovascular injuries. There is no consensus in the literature regarding diameter and number of screws for fixation of coronal plane fractures of the distal femur.

1. Introduction

The first description of the coronal plane fracture of the distal femur was credited to Friedrich Busch in 1869.^[1,2] Albert Hoffa,^[3] in 1888, defined this fracture pattern as an intra-articular unicondylar fracture in the coronal plane of the distal femur, using the illustration made by Busch in his book. For this reason, Bartonicek and Rammelt advocate that the most appropriate nomenclature for this pattern is Busch-Hoffa fracture.^[1] The Busch-Hoffa fracture is rare and sometimes goes unnoticed in the initial evaluation, especially when it is part of a multifragmentary fracture of the distal femur. It occurs more frequently on the lateral condyle than on the medial condyle,^[4,5] and may also be bicondylar.^[6] As it is an intra-articular, vertical and unstable fracture, the Busch-Hoffa fracture requires anatomical reduction and stable fixation to allow early range of motion and reduce the incidence of complications such as fixation failure, nonunion, and joint stiffness.^[7–9] Due to the inherent fracture instability, a nonunion of Busch-Hoffa fracture may occur, requiring a demanding surgical procedure. Bone loss, infection, and soft tissue contractures are factors that contribute to making this procedure challenging.^[10]

The treatment of Busch-Hoffa fracture consists of anatomical reduction, with perfect restauration of the articular surface and fixation with the principle of absolute stability.^[4] Fixation depends on the size of the fractured fragment, its location, the orientation of the fracture line, and the presence of comminution. Fixation using a posterior buttressing plate associated with posterior-to-anteriorly (P-A) introduced lag screws provides more adequate stability than fixation with screws introduced from the anterior to posterior direction.^[11] However, in special situations in which P-A fixation is impossible, anterior-to-posterior (A-P) fixation can be performed, supplemented whenever possible by the adjuvant use of a horizontal plate with screws.^[11] Small fragments benefit from P-A fixation using only lag screws, due to the absence of a metaphyseal fragment for plate placement. In these cases, A-P fixation using only screws is contraindicated, since interfragmentary compression will be insufficient to promote a stable construct which may lead to fixation failure.^[11]

The large variety of studies related to the surgical techniques used in the treatment of Busch-Hoffa fractures makes it worthy of a review that synthesizes treatment outcomes, challenges, and solutions from biomechanics to clinical aspects. It is also necessary to carry out experimental tests and numerical simulations that help optimization of surgical techniques through a mechanical analysis of the stress and deformations that operate in the composite assemblies (bones, screws, and plates). Therefore, the primary objective of this literature review is an analysis from biomechanical and clinical perspectives, with the objective of bringing to light knowledge that enables the optimization of clinical outcomes and minimization of complications in the treatment of Busch-Hoffa fractures.

2. Methods

We performed a Systematic Review of the literature using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.^[12] An electronic search of PubMed/MEDLINE database was carried out from April to June, 2023. The terms for the database search included “Hoffa fractures,” OR “Busch-Hoffa fractures,” OR “coronal plane fractures of the distal femur.” The PICOS strategy was used to address Participants (patients with coronal plane fractures of the distal femur), Intervention (treatment with or without fracture fixation), Comparison (different fixation strategies), Outcomes (functional outcomes and complications), and Study Design (all study designs were included due to the rarity of Busch-Hoffa fractures). The search identified 277 potentially eligible studies. The inclusion criteria were scientific articles written in English that addressed coronal plane fractures of the distal femur. Studies not specifically addressing coronal plane fractures of the distal femur (74 studies), in duplicity, or in a language other than English (51 studies) were not included. A critical analysis of titles, abstracts, and inclusion and exclusion criteria of all potentially eligible articles, followed by independent review of the full text of the selected articles, was performed by one of the authors. After this qualitative analysis, 39 articles were excluded due to important missing information, such as treatment method (approach, description of fixation method, and treatment strategy). Considering that Hoffa fractures are relatively rare, studies with all levels of evidence were included. Figure 1 depicts the included studies (113 articles), according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020.^[12] Ethical approval was not necessary because this paper is a systematic review.

Figure 1.

Literature review flowchart.

3. Results

The literature highlights important information regarding management of coronal plane fractures of the distal femur. The 113 remaining articles addressed the fracture pattern (morphology and classification), trauma mechanism and epidemiology, diagnosis, and treatment strategies based on biomechanical and clinical aspects. For didactic reasons in results presentation, each of the following topics will thoroughly cover the most relevant information regarding Busch-Hoffa fractures.

3.1. Classification

In order to standardize and facilitate the understanding of the location, size, and configuration of the femoral condyle fracture, Letenneur et al^[13] proposed a classification system for Busch-Hoffa fractures, considering the fragment size and orientation of the fracture line. Type I is a pattern whose fracture line extends towards the posterior cortex of the distal metaphysis of the femur; type II is an entirely intra-articular (osteochondral) fracture, which can be subdivided into A, B, or C according to the fragment size (A-75% of the condyle size, B-50% and C-25%); type III is characterized by an oblique fracture line, being therefore a more stable pattern.^[13–15] Analyzing types I, II, and III, the type II presents smaller size, less blood supply and, theoretically, a greater probability of osteonecrosis and nonunion, although this fact has not been proven in the literature.^[16]

Figure 2 illustrates the types of fracture according to the Letenneur classification. Pires et al^[17] proposed a modification to the original Letenneur classification, adding a variant pattern characterized by the presence of a type I fracture associated with a comminution zone or an intercalary fragment, which produces joint depression in the weight bearing zone of the femoral condyle. This modification of the original classification is supported by the mapping study of 74 distal fractures of the femur in the coronal plane carried out by Xie et al.^[5] The authors reported that central comminution (intercalary fragment) was present in 44.9% of coronal fractures of the lateral condyle. The authors also demonstrated that lateral fractures, in addition to being more frequent, have a more vertical fracture line and are more concentrated in the weight bearing zone of the femoral condyle than medial fractures.^[5] Richards et al,^[18] in a retrospective analysis of 55 CT scans of patients with intercondylar fractures of the distal femur, observed that 26 patients (47%) presented no coronal plane fracture line, 6 (11%) presented a medial coronal plane fracture, 15 (27%) presented a lateral coronal plane fracture, and 8 (15%) presented bicondylar coronal plane fractures. The authors identified several major fracture fragments, as described: anteromedial, posteromedial, anterolateral, and posterolateral fracture fragments.^[18] Intercondylar comminution as well as medial and lateral central condylar comminution at load bearing zone of the condyles were frequently observed. Orapiriyakul et al,^[4] in their case series, reported that the lateral fractures were more common and more complex than the medial ones.

Figure 2.

Classification of lateral femoral condyle fractures according to Letenneur with the addition of type I variant as recommended by Pires et al.^[11]

As above mentioned, lateral Busch-Hoffa fractures present different morphology and characteristics from medial fractures. Therefore, Pires et al^[17] proposed a new classification system especially developed for coronal plane fractures of the medial condyle, based on the size of the fractured fragment and the presence of comminution (Fig. 3). This new classification system guides the approach choice and fixation strategy. Busch-Hoffa fractures are still categorized as 33-B3.2 (Unicondylar) or 33-B3.3 (Bicondylar) according to the AO/OTA Classification system.^[19–21]

Figure 3.

Classification of medial femoral condyle fractures in the coronal plane, according to Pires et al,^[17] adapted—c = comminution.

Chandrabose et al^[22] proposed a classification system based on the analysis of computed tomography of 103 patients, stratifying the fracture patterns and the most indicated methods of fixation. Bagaria et al^[23] proposed a radiological classification system for Hoffa fractures based on fracture configuration and consequent optimal treatment strategy along with a review of the literature. However, the authors highlighted that this classification system may be considered as arbitrary as it is not based on any biomechanical or long-term follow-up prognosis analysis.

3.2. Epidemiological aspects and injury mechanisms

Busch-Hoffa fractures usually occur as a result of high-energy trauma,^{[11,14,19,24,25]} mostly caused by traffic accidents with the knee in a flexed position. According to Wagih et al,^[26] in the flexed position, the posterior portion of the lateral condyle is the one that receives the first impact. They are almost 10 times less frequent than fractures that affect the proximal part of the femur.^[21] Onay et al^[19] studied the long-term outcomes of treating Hoffa fractures. In a total of 524 distal femur fractures, 14 patients presented a Hoffa fracture, representing 2.67% of total, 12 of which were due to accidents involving bicycles, motorcycles, and other vehicles. Gao et al^[27] observed that, out of a total of 13,702 patients with fractures that occurred within an 8-year interval, 728 (5.3%) presented distal femur fractures, 82 of which were Hoffa patterns. Bel et al^[25] analyzed 163 unicondylar fractures, 18% with a coronal plane pattern. Arastu et al^[28] reported that fractures occur 3 times more frequently on the lateral condyle than on the medial one. The usual injury mechanism was a combination of vertical shear and torsion forces with the knee in a flexed position.^[29,30]

Typical riding posture involves sitting with the knee flexed in a slightly abducted position and this predisposes the posterior aspect of the lateral femoral condyle to receive a traumatic axial load.^[29] In those situations, the lateral femoral condyle is also more subject to direct oblique or lateral impact of the patella, thus causing the Busch-Hoffa fracture.^[16,31] Arastu et al also reported that a possible reason for the fracture could be the application of a force in the vertical plane on the posterior femoral condyle, corresponding to various degrees of knee flexion.^[6,28] Manfredini et al^[29] reported that the trochlear-condylar groove could be a potential structurally unstable point where the fracture could originate and spread to other planes.^[6] Harna et al^[32] reported that the suggested mechanism involves an axial load to the lateral femoral condyle, with the knee in 90° or more of flexion, which produces posterior tangential fracture patterns. Holmes et al^[33] postulated that shear forces act along the fracture line at the femoral condyle, which makes its treatment even more challenging.^[29,34]

3.3. Diagnosis and treatment

Neglected or chronically untreated Busch-Hoffa fractures can evolve to nonunion or malunion, causing pain, disability, and knee arthritis.^[35] The fracture diagnosis can be challenging and often requires adequate clinical analysis, complemented with imaging work-up. White et al^[31] advocate that Hoffa fractures are not easy to visualize on radiographs in anteroposterior views, especially in non-displaced or minimally displaced patterns. Computed tomography is indicated to investigate coronal fracture lines, as well as to better understand the fracture orientation, fragment size, and presence or absence of comminution or joint depression.^{[6,24,25,27,36–38]}

The variation between different aspects of this fracture makes it difficult to delineate a specific treatment protocol.^[6] Nonoperative treatment usually leads to nonunion, malunion and/or joint stiffness due to prolonged immobilization. Therefore, surgical intervention is usually indicated for Busch-Hoffa fractures.^[39,40] Open reduction with internal fixation is the current standard of care.^{[6,15,16,25,37,41]} This rational approach that combines anatomic reduction, joint surface restoration, stable fixation, and early joint mobilization is critical for achieving a satisfactory outcome.^[8,9,42]

Traditionally, coronal plane fractures of the distal femur are treated with screws alone (depending on the fragment size) or associated with posterior buttressing plates.^[7,15,32] Usually, screw directions are perpendicular to the fracture line in the coronal plane and along the longest axis of the femoral condyle. The screws used to fix Busch-Hoffa fractures vary from mini-fragment implants (2.0, 2.4, or 2.7 mm), cortical screws (3.5 or 4.5 mm) or cancellous cannulated screws (3.5, 4.0, 4.5, or 6.5 mm), depending on the size of the fractured fragment and surgeon’s preference. Maheshwari et al^[43] conducted a study with 30 patients to compare the use of conventional and headless screws. The authors reported more complications and failures when using headless screws.

The use of plates positioned with a buttressing role promotes more stability and stiffness, preventing vertical displacement^[4,32] However, depending on the fractured fragment size, placement of buttressing plates may be impossible due to the absence of a posterior metaphyseal zone for plate accommodation. Min et al performed open reduction and internal fixation in 8 patients, using plate and 6.5 mm headless compression screws in P-A direction, considering this treatment strategy an effective alternative for Busch-Hoffa fractures.^[44] However, what is observed in the literature and in clinical practice is that fixations are more commonly performed from the A-P direction, due to the surgeons’ familiarity with the anterior approaches and lower risk of iatrogenic neurovascular injuries. Nevertheless, screws applied in the P-A direction are biomechanically more stable and provide greater fixation stiffness^[31,45–47] Gavaskar et al^[9] reported the outcomes of 18 patients with Busch-Hoffa fractures who were fixed using both, screws in the anterior-to-posterior and posterior-to-anterior directions, not observing differences in reduction and fixation failure. Despite the aforementioned techniques, as reported by Arastu et al,^[28] the ideal stiffness required for fixation of this fracture pattern is still unknown. Harna et al^[32] advocate that internal fixation with low compression force can result in high shear stress at the fracture site, interrupting osteogenesis and promoting nonunion. Singh et al,^[40] observing the treatment of 6 patients where 3 had fixation failures, highlighted the difficulty of reconstructive surgery for this type of fracture. The study of Trikha et al^[8] compiles a review of 32 patients, all treated with open reduction and internal fixation, using lateral approach to address lateral and a medial approach to address medial Busch-Hoffa fractures.

Using P-A fixation, Jarit et al^[48] observed that there is a greater risk of injury to neurovascular structures, especially the peroneal nerve, which is at risk along the medial border of the biceps femoris. In addition, the lateral superior geniculate artery is also at risk. Yao et al^[49] highlighted the difficulty to insert a P-A screw using direct lateral approach, which is more familiar for surgeons and with a lower risk of iatrogenic neurovascular injury. Bel et al^[25] observed that surgical treatment through an adequate anterior approach allows anatomical reduction and stable fixation. However, for screw placement, care must be taken to countersink the screw head to prevent friction between the metal and the cartilage during knee mobilization.^[48,50]

Lu et al,^[39] in a case series of 45 patients with Busch-Hoffa fractures (15 type I, 12 type II and 18 type III), observed that the mean duration of surgery and mean blood loss were significantly higher in the group of patients treated with screws associated with the posterior plate compared to patients treated with screws alone. The likely explanation for this is the need of a more extensive approach, which potentially increases bleeding. Patients treated with screws associated with the plate presented greater range of motion. At the final follow-up, all patients presented fracture healing and progressed without loss of reduction, nonunion, or malunion. Orapiriyakul et al,^[4] observing the size of the fragment, reported the lack of consensus on the approach for fixation of type II Hoffa fractures, since smaller fragments present greater difficulty to be fixed and compromised blood supply can lead to nonunion or osteonecrosis.^[4,15] Gao et al^[27] described important points that should be highlighted, among them the protection of the nutrient artery and the insertion of the collateral ligament, especially in type II Hoffa fractures.

Orapiriyakul et al^[4] analyzed 20 cadaveric specimens and observed that for fragments smaller than 18.3% of the anteroposterior diameter of the medial condyle and 10.1% of the lateral one, the fracture may be inaccessible by the anterior parapatellar approach, being recommended for fractures larger than 28.7% from the medial condyle and 19.9% from the lateral condyle. In fractures smaller than 28.7% for the medial condyle and 19.9% for the lateral condyle, the direct medial extensile approach or the posterolateral approach can be adopted, respectively. The authors also reported that combined approaches can be performed in complex fracture patterns.

The screw diameter, its length, trajectory, as well as the number of threads are directly related to the stability of the assembly.^[4,19] Therefore, there is a need to carry out experimental and numerical studies comparing different implants, in different screw trajectories, with the objective of optimizing the mechanical response, but without losing focus on preserving soft tissues.

3.4. Experimental biomechanical studies

The standard fixation method for Busch-Hoffa fractures is the use of screws, with the principle of interfragmentary compression to achieve absolute stability.^[24] In larger fragments, in which there is a posterior metaphyseal fragment, a buttressing plate associated with lag screws improves stability. Although several types of construct have been described, depending on the size of the fragment and presence of comminution, the literature remains controversial with respect to the ideal fixation.

Although closer to a real situation, human cadaveric bones have mechanical properties influenced by age and bone density that vary from sample to sample, which presents itself as a potential bias in a comparative analysis. Variations in anatomy, in the size of anatomical structures and in bone density can contribute to high standard deviations, in addition to the greater difficulty in obtaining cadaveric bones that have the same age profile as individuals susceptible to fractures.^[51,52] Therefore, to carry out experimental tests, some authors choose for the use of synthetic models, since they maintain a standard of mechanical properties and anatomical homogeneity, which allows a more accurate observation of the fixation techniques and thus guarantees methodological consistency.^[29,45] Attention should be paid to the use of synthetic models with mechanical characteristics similar to the bone density of the study population for a given fracture pattern. In the case of Busch-Hoffa fractures, most patients are young adults, which requires synthetic models that simulate the mechanical properties of this population profile.^[53] However, the use of composite femurs can limit the direct comparison of experimental results to a clinical situation, since the absence of soft tissues is still a potential bias.^[54]

Sun et al^[45] experimentally tested 16 adult synthetic femurs to fix Letenneur type I fractures. The mechanical tests were performed evaluating the fixation with 6.5 mm partially threaded screws, 3.5 mm screws and locking compression plate, obtaining greater axial stiffness and load until failure in the group of plate fixation. The authors also reported that, for the treatment of Letenneur type I fractures, fixation with the plate, either in the posterior or lateral position, provides significantly higher stability than isolated screws, regardless the screws trajectory. The authors also emphasized that the lateral plate presented a better behavior than the posterior one, reinforcing that the plate in a posterior position is more difficult to place and shape. However, lateral plate fixation involved 2 fragment fixation elements, while posterior fixation involved only one, which can be understood as a potential bias.^[45]

Yao et al^[49] mechanically studied Letenneur type I fractures, dividing 16 synthetic bones into 2 groups, to observe the effects of varying the trajectories of the 6.5 mm cannulated screws. The authors reported better mechanical performance in crossed screws than in those with a traditional parallel trajectory. Hak et al^[55] experimentally evaluated 20 composite femurs with different fixations among 1 and 2 3.5 mm screws and 1 and 2 partially threaded (cannulated) 6.5 mm screws, finding greater stability in the latter type of fixation for Letenneur type II fractures. Jarit et al^[48] rehearsed 8 pairs of embalmed femurs, creating Busch-Hoffa fractures for simulation, and evaluated 2 types of fixation with 6.5 mm cancellous screws. The authors concluded that the P-A direction provides greater fixation stability than fixation in the A-P trajectory.^[48]

The use of several screws for fixation in biomechanical experiments, as well as the use of screws with a larger diameter, despite providing greater mechanical efficiency, produce greater damage to the joint surface.^[51,55] Yao et al^[49] observed, based on the load-displacement curve, that all the studied specimens exhibited changes in the slope of the curve before catastrophic failure, which indicated loss of fixation, followed by plastic deformation until failure. For biomechanical testing, the specimens were placed on specific bases that vary according to the model of the machine used and the load was applied at a speed that varies from 1 mm/min^[45] to 2 0 mm/min^[55] and a load up to 2000 N.^[45] Figure 4 illustrates an experimental test model for a better understanding of a biomechanical scenario for evaluation of Busch-Hoffa fixation constructs.

Figure 4.

Typical scheme of application of shear load for performing mechanical tests of Hoffa fractures.

3.5. Numerical simulation studies

Simulation studies are useful for predicting and demonstrating the influence of specific factors on a given system. Since clinical studies can be influenced by several controlled and uncontrolled variables, finite element (FE) models can effectively focus on a single variable, disregarding the effect of other variables and thus, determine the best response for the variable under analysis.^[49] In addition, experimental tests can validate and compare the response of these numerical models, thus performing a smaller quantity of experimental tests and looking at more data using numerical analysis.^[56,57]

Freitas et al^[47] numerically analyzed, from a biomechanical point of view, 4 fixation constructs (4.5 mm cortical screws and 7 mm cannulated screws in the anteroposterior and posterior-anterior directions) for the treatment of Busch-Hoffa Letenneur type II fractures. The authors concluded that fixation with a 7 mm cannulated screw in the P-A direction presented the best mechanical results, causing a decrease in vertical displacement and greater stability. However, evaluating the Von Misses tension, the anteroposterior direction with a 7 mm screw (7 A-P) provided the greatest reduction in tension peak when compared to the different models, thus considering the best effect. The study by Freitas et al,^[47] to the best of our knowledge, is the only one to analyze Hoffa fractures using the FE method, numerically simulating this type of fracture and its surgical solutions.

A summary of clinical studies about the method of fixation, trajectory of fixation and approach is presented in Table 1 for lateral condyle fractures, Table 2 for medial condyle fractures, and Table 3 for bicondylar fractures.

Table 1.

Summary of studies of Bush-Hoffa fractures in the lateral condyles.

Author/s	Fracture location	Fixation method	Screws direction	Surgical approach	Study design
Yao et al[49]	Lateral (type I)*	Two parallel 6.5 mm partially threaded cannulated screws	AP, PA, and PL	Not report	Experimental
Noufal et al[58]	Lateral	Single 30 mm Herbert headless cannulated screw	AP	Arthroscopy	Case report
Freitas et al[47]	Lateral (type II)*	4.5 mm cortical screws and 7 mm cannulated screw	AP and PA	Not report	Computer simulation
Goos et al[59]	Lateral	Two headless compression screws	AP	Lateral parapatellar	Case report
Huang et al[60]	Lateral	Two 4.5 mm headless compression screws and a locking plate	PA	Posterolateral	Case report
Soni et al[61]	Lateral	Two partially threaded screws	AL and PL	Lateral approach (not specified)	Case report
Agarwal et al[62]	Lateral	Two 6.5 mm partially threaded cannulated cancellous screws and a lateral buttress plate (Recon plate)	AP	Swashbuckler	Case report
Tripathy et al[35]	Lateral	Two partially threaded cancellous lag screws	PA	Posterolateral	Case report
Supe et al[63]	Lateral type II*	Two 4.5 mm cannulated cancellous screws	AP	Lateral para patellar	Case report
Chouhan et al[64]	Lateral type II C*	Three headless compression screws	PA	Direct lateral	Case report
Sun et al[45]	Lateral type I *	4 types, 1 6.5 mm partially threaded cannulated screw in PA direction with a 3.5 mm 6-hole LCP metaphyseal plate, 2 6.5 mm partially threaded cannulated screws in PA orientation, 1 6.5 mm partially threaded cannulated screw in PA orientation plus a 3.5 mm 7-hole LCP metaphyseal plate, 2 6.5 mm partially threaded cannulated screws in AP direction	AP and PA	Fixation in anterior-to-posterior and posterior-to-anterior.	Experimental study
Tetsunaga et al[65]	lateral	3.5 mm 1/3 tubular plate combined with an LCP	AP and PL	A lateral incision was made and the distal femur was approached between the iliotibial tract and the biceps femoris muscle	Case series
Liu et al[66]	Lateral type II	L-shaped contralateral proximal and 3 anterior to posterior 5.0 mm headless cannulated	AP and PL	Lateral (not specified)	Case report
Xu et al[7]	Lateral type I e III*	A 3.5 mm or 4.5 mm screw and 2 screws were 6.5 mm screws	PL and PA	Posterior (not specified)	Case series
Ercin et al[67]	Lateral	Two to 4 6.5 mm cancellous cannulated screws	AP	Symmetrical	Case series
Jain et al[68]	Lateral	Two anteroposterior 6.5 mm partially threaded cancellous cannulated screws.	AP	Lateral parapatellar mini arthrotomy	Case report
Gammon et al[69]	Lateral	Two synthes 3.0 headless compression screws.	PA	Lateral parapatellar arthrotomy	Case report
Shi et al[70]	Lateral type I, II and III*	Cannulated screws, contoured locking plate (Synthes, LCP Reconstruction Plate 3.5, straight with combined hole, 5-hole, 70mm, 6-hole, 84mm, 7-hole, 99 mm)	AP e PA	Lateral approach	Case series
Cheng et al[71]	Lateral	two 6.5 mm cancellous screws with 16 mm thread	AP	Lateral parapatellar	Case report
Kumar and Malhotra[72]	Lateral	Two lag screws;	AP	Lateral (not specified)	Case series
Iguchi et al[73]	Lateral type III*	Three 4.5 mm headless screws and distal femoral locking plates	AP	Lateral parapatellar	Case report
Oztürk et al[74]	Lateral type II*	Two partially threaded cannulated 4.5-mm-diameter titanium cancellous lag screws	AP	Medial parapatellar arthrotomy	Case report
Wagih et al[26]	Lateral	Two 6.5 mm partially threaded cancellous lag screws	AP	Arthroscopic-assisted reduction	Case report
Pei et al[75]	Lateral type III*	Calcaneal reticular plate with 2 cannulated screws	AP	Anterolateral	Case report
Singh et al[76]	Lateral	At least 2 6.5 cannulated screws	AP	Swashbuckler approach	Case series
Jordan et al[77]	Lateral	Two lag-screws and a locking-plate	PL	Lateral (not specified)	Case report
Iwai et al[78]	Lateral	Two 5 mm cannulated screws	AP	Lateral subvastus	Case report
Soraganvi et al[79]	Lateral	Two cancellous screws	PL	Lateral arthrotomy	Case report
Compagnoni et al[80]	Lateral	Two parallel cannulated screws (50 mm long, diameter 4 mm—Synthes	PL	Lateral (not specified)	Case report
Vaishya et al[81]	Lateral	Two 6.5 mm cannulated screws	AP	Lateral (not specified)	Case report
Werner and Miller[82]	Lateral	Two additional 5.5 mm cannulated partially threaded screws	PA	Posterolateral	Case report
Xiao et al[83]	Lateral type II – C*	Double-thread headless compression screws with the diameter of 3.5 mm	PA and PL	Antero medial and lateral-posterior	Case report
Somford et al[84]	Lateral	Three Acutrak Plus headless compression screws and 3.5 mm bicortical lag screw	AP and PA	Lateral parapatellar	Case series
Potini et al[85]	Lateral	Two Bio-Compression Screws and 1 Synthes cannulated screw	PA	Lateral (not specified) parapatellar arthrotomy	Case report

AP = anteroposterior, LCP = locking compression plate, PA = posteroanterior, PL = posterolateral, PM = posteromedial.

Table 2.

Summary of studies of Bush-Hoffa fractures in the medial condyles.

Author/s	Fracture location	Fixation method	Screws direction	Surgical approach	Study design
Mushtaq et al[41]	Medial	Two headless screws	PA	Parapatellar	Case report and literature review
Harna et al[32]	Medial	Locking plate and 1 6.5mm cannulated cancellous screw and 1 4.5mm Herbert screw	PL	Medial subvastus	Case report
Sun et al[86]	Medial type III *	two 4.5-mm cannulated cancellous lag screws	AP	Arthroscopic	Case report
Ranjan et al[87]	Medial	two 4.5 mm partially threaded cannulated cancellous screws	PA	Medial (not specified)	Clinical case and literature review
Jiang et al[88]	Medial type III*	Three 3.5-mm cannulated cancellous screws	PA	Posteromedial	Case report
AlKhalife et al[89]	Medial	Two 4.0 mm partially threaded cancellous screws	AP	Medial parapatellar	Case report
Zhang et al[90]	Medial type II*	Two percutaneous 6.5 mm partially threaded cannulated cancellous screws; 2 compression screws and 2 3.5 mm reconstruction plates	PA and AL	Parapatellar arthrotomy and medial	Case series
Jiang et al[91]	Medial	One dynamic compression plate was locked with 2 cortical screws proximally and 4 cortical screws distally	PL	Lateral approach	Case report
Goel et al[92]	Medial	6.5 mm cannulated cancellus screws with washers	PA	Arthroscopic	Case report
Salunke et al[93]	Medial type I	Two cannulated cancellous screws	PA	Subvastus	Case report
Xu et al[7]	Medial type I,II e III*	A 3.5 mm or 4.5 mm screw and 2 screws were 6.5 mm screws	PL	Posterior (not specified)	Case series
Ercin et al[67]	Medial	Two to 4 6.5 mm cancellous cannulated screws	AP	Symmetrical	Case series
Sasidharan et al[94]	Medial	Two 4 mm partially threaded cannulated cancellous screws	AP	Medial parapatellar arthrotomy	CASE report – reconstructive osteotomy
Calderazzi et al[95]	Medial	Four headless de 3,5 mm	PA	Medial (not specified)	Case report
Marzouki et al[96]	Medial	Two 6.5 cannulated screws	AP	Medial	Case report
Singh et al[76]	Medial	At least 2 6.5 cannulated screws	AP	Para-patellar approach	Case series
Mootha et al[97]	Medial	3.0 mm × 4.0 mm cannulated partially threaded cancellous screws	AP	Medial parapatellar	Case report
Nandy et al[98]	Medial	Two 6.5 mm partially threaded cannulated cancellous screws and a 6 hole 3.5 mm recon plate	AP and PL	Medial subvastus	Case report
Biau et al[99]	Lateral	Three Herbert Screws	AP	Not reported	Case report
Kapoor et al[100]	Medial type II – C*	Two nonparallel headless Herbert screws	PA	Posterior	Case report
Say et al[101]	Medial	Two cannulated screws	AP	Arthroscopy-assisted reduction	Case report
Somford et al[84]	Lateral and medial	One Acutrak 4/5 and 3 Acutrak plus headless compression screws and 4 screws (two were placed anteroposterior and 2 posteroanterior)	AP and PA	Lateral medial	Case series
Ozan et al[102]	Medial type III	Two 4.5-mm headless compression screws and one inserted from the medial to the lateral direction	PA and PL	Medial parapatellar arthrotomy	Case report

AP = anteroposterior, LCP = locking compression plate, PA = posteroanterior, PL = posterolateral, PM = posteromedial.

Table 3.

Summary of studies of bicondylar Busch-Hoffa fractures.

Author/s	Fracture location	Fixation method	Screws direction	Surgical approach	Study design
Lee et al[103]	Bicondylar	Acutrak 4/5 headless compression screws, 3.5 mm 1/3 tubular plate and 2 4.5 mm cortical screws	PA	Parapatellar arthrotomy	Case report
Kondreddi et al[104]	Bicondylar	Four 4-mm cancellous screws (2 for each condyle)	AP	Parapatellar arthrotomy	Case report
Chaudhary and Raghuwanshi[105]	Bicondylar	Two 4 mm cancellous screws in the lateral condyle, 1 4 mm cancellous screw and 1 Herbert screw in the medial condyle. The lateral condylar sagittal fragment was then fixed using 2 4 mm cancellous lag screws placed in a lateral to medial direction	AP e PL	Swashbuckler	Case report
Harna et al[106]	Bicondylar	2.9 mm Herbert screws	–	Swashbuckler	Case report
Julfiqar et al[107]	Bicondylar	4.5 mm cannulated cancellous screw	AP	Not reported	Case report
Haq et al[108]	Bicondylar	Five 6.5 mm cannulated cancellous screw	AP	Swashbuckler	Case report
Harna et al[109]	Bicondylar	Two 7 mm partially threaded cannulated screw for condyle	AP	Not reported	Case report
Joseph et al[110]	Bicondylar	Four synthes 6.5 mm partially threaded cancellous screws (one in lateral condyle and 3 in medial condyle)	PA	Not report	Case report
Kini et al[111]	Bicondylar	One lag screws for medial and 2 lag screws for lateral	AP	Not report	Case report
Dua et al[112]	Bicondylar	Three 6.5 mm, partially threaded cancellous screws (lateral) and 2 6.5-mm, partially threaded cancellous screws (medial)	AP	Swashbuckler	Case report
Lal et al[113]	Bicondylar	4.5 mm cannulated cancellous screws	AP	Lateral (not specified)	Case report
Papadopoulos et al[30]	Bicondylar	Three 6.5 mm cancellous screw	AP and AP	Lateral (not specified)	Case report

AP = anteroposterior, LCP = locking compression plate, PA = posteroanterior, PL = posterolateral, PM = posteromedial.

4. Discussion with critical analysis of the literature

Busch-Hoffa fracture management remains challenging and a standard and universally accepted treatment protocol is still lacking, given the great variability of approaches and fixation techniques. The Letenneur^[13] classification system, which is the most used, serves as a parameter to outline the type of intervention and thus allow guidance for definition of the fixation strategy. Anatomical reduction, stable fixation, and early rehabilitation should, therefore, be the goals of treatment.^[60] According to Tables 1, 2, and 3, more than 50% of the surgeons used the fixation in the A-P direction, which is consistent with the familiarity of this approach to most surgeons.

Despite the lower risk of iatrogenic neurovascular injuries, mechanical studies have shown that P-A fixation is mechanically more efficient. However, posterior approaches require a greater learning curve for the surgeon, since they are more complex and present a higher risk of iatrogenic neurovascular injury

The vast majority of studies on Busch-Hoffa fractures are case series, many of them with scarce information on fracture morphology, classification and treatment strategies. Although several approaches have been described for Busch-Hoffa fractures, a biomechanical analysis of the best strategy to provide adequate stability for different fracture patterns is still necessary. Therefore, carrying out a systematic review of the literature, with a critical and translational analysis of the clinical and benchtop aspects, is essential to optimize outcomes and minimize complications.

Experimental tests are excellent tools to evaluate the mechanical behavior of different fixation constructs. The use of synthetic models is helpful for reducing the variability of properties and behavior between different samples, which is a key factor to properly assess the mechanical intervention variables.

The experimental evaluation of the mechanical performance of a proposed fixation construct increases safety and effectiveness of a surgical procedure. The use of numerical methods of stress and strain analysis, such as those presented using FEs, has the great advantage of reducing costs and expanding the horizons of conventional mechanical tests. Knowledge of the field of tensions and deformations allows creating an interface between engineering and orthopedic surgery through the transfer of important information about the situation the body is exposed to, such as areas of increased tension that can be areas that generate pain/discomfort or points of greatest displacement that can cause nonunion or malunion.

Numerical models also allow measurement of interfragmentary movements with the aim of evaluating and isolating the most important parameters, such as the distribution of stress or strain within the bone and implant, which are very difficult to measure experimentally. However, it is known that there are important limitations in numerical models that deserve to be highlighted, such as predicting the contact between the bone fragments and the forces originating from the muscle and ligament structures that contribute to the stabilization of the set.^[114,115]

The literature lacks studies specifically addressing Letenneur type III fractures, which is justified by the lower potential of complication of this larger and more stable fracture pattern and with less potential for complications.

5. Final considerations

The literature is still relatively scarce regarding Busch-Hoffa fractures, which justifies the development of a translational approach between lab (biomechanical studies) and clinical aspects, represented here in the form of a critical review of the literature. Although the literature is still controversial regarding a well-established treatment protocol, there are studies that outline surgical solutions considered more effective in the light of current knowledge. It should be noted that there are few biomechanical studies on Busch-Hoffa fractures, especially those related to numerical modeling, being an open field of research.

Acknowledgments

Authors would like to acknowledge the support of CEFET-MG, CAPES, UFMG, CNPq, and FAPEMIG.

Author contributions

Conceptualization: João Marcos Guimarães Rabelo, Robinson Esteves Pires.

Funding acquisition: João Marcos Guimarães Rabelo, Carlos Alberto Cimini, Estevam Barbosa de Las Casas.

Investigation: João Marcos Guimarães Rabelo.

Methodology: João Marcos Guimarães Rabelo.

Resources: João Marcos Guimarães Rabelo, Robinson Esteves Pires.

Supervision: Robinson Esteves Pires, Estevam Barbosa de Las Casas, Carlos Alberto Cimini.

Visualization: Estevam Barbosa de Las Casas, Carlos Alberto Cimini.

Writing – original draft: João Marcos Guimarães Rabelo, Robinson Esteves Pires.

Writing – review & editing: João Marcos Guimarães Rabelo, Robinson Esteves Pires, Estevam Barbosa de Las Casas, Carlos Alberto Cimini.