Marc H. Balligand In the 1970s, Paul Maquet developed a technique dedicated to treat patello‐femoral chondromalacia in human patients (Figure 13.1) [1]. Patello‐femoral chondromalacia is suspected to be the consequence of excessive pressure in the patello‐femoral joint upon contraction of the quadriceps musculature during mobilization of the knee joint. Maquet logically deduced that the quadriceps muscle could take advantage of an increased lever arm to reduce its force exerting the same effect on the knee joint. This resultant increased lever arm in return reduced the patello‐femoral compressive force [2]. The technique designed by Maquet to increase the quadriceps lever arm consisted of performing an incomplete axial osteotomy of the tibial crest, allowing its distocranial rotation around a bony hinge. The displacement was maintained by interposing between the tibial crest and the proximal tibial metaphysis an autologous cortical graft harvested from the ilium (Figure 13.1). Altough esthetically questionable, the technique, referred to as the Maquet technique, appeared to be effective. When Maquet reported his original technique, it was noted that this procedure had another biomechanical effect: the directional change of the quadriceps musclature force reduced tibial thrust upon knee loading [3]. In 2002, Montavon and Tepic, inspired by the Maquet technique, described a new surgical procedure (referred to as the tibial tuberosity advancement technique or TTA) to stabilize the canine cranial cruciate ligament (CCL)‐deficient stifle joint [4]. More in‐depth information about the biomechanics and theory of the TTA can be found elsewhere [5, 6]. In a general sense, the TTA limits cranial tibial translation by increasing the lever arm of the quadriceps. Montavon and Tepic proposed to osteotomize the tibial crest (including the tibial tuberosity [TT]) and to displace it cranially so the resultant angle between the patella tendon and the tibia plateau would be 90°. In order to circumvent the need for an autologous cortical graft as Maquet used to do, they designed a spacer in the form of a titanium cage to place into the osteotomy gap. The required advancement of the tibial tuberosity, allowing the patella tendon to become perpendicular to the tibial plateau, was determined using a transparent layout (Kyon, Zurich, Switzerland) on a lateral radiograph of the stifle joint, positioned as it would be during stance phase (around 135°) and with the tibia in a physiological position (cranial subluxation reduced) (Figure 13.2a). In contrast to Maquet, Montavon and Tepic opted to completely free the tibial crest from the tibia, allowing the patella to remain in a physiological position but requiring the use of implants to secure the crest to the tibial shaft. Figure 13.1 Original design and rationale of the Maquet technique. Source: Redrawn from Maquet [1]. In 2010, Balligand and collaborators performed an incomplete longitudinal osteotomy of the tibial crest, preserving a distal bone hinge and therefore avoiding the need for implants other than the cage. In this procedure, named the modified Maquet technique or MMT, a cage was used as a spacer. Based on a growing series of clinical cases, the technique has been progressively refined. Initially, the osteotomy length was equal to the tibial crest length and a hole was drilled in the distal extent of the osteotomy (called the Maquet hole by certain authors) to act as a stress reducer. This hole was supposed to prevent the occurrence of fissures or even fractures upon advancement. The hole was rapidly abandoned, and the osteotomy length created was close to twice or even longer than the length of the tibial crest. This most recent version of the MMT was recognized as the new MMT or N‐MMT [7] (Figure 13.2b,c). It was also recognized that opening the osteotomy angle above 9–10° (the angle created at the distal osteotomy) would increase the incidence of perioperative fissure or fracture of the hinge. Therefore, a recommendation was made to stay below 10° and to calculate the length of the osteotomy according to the required advancement via a simple trigonometric method. In the equation: y = x/tg α x is the required advancement, α is set at 9° (or possibly lower), and y corresponds to the length of the osteotomy. Based on these calculations, the length (mm) of the osteotomy grossly equals 7.5 (7–8) times the width of the cage (mm), thus making the osteotomy lengths range from 25 to 105 mm corresponding to cage widths ranging from 3 to 15 mm (Table 13.1). To further refine the osteotomy, Brunel et al. developed an equation to reduce hinge fractures based as a function of the patient’s body weight (BW) [8]. The objective is to resist loads at the distal cortical hinge up to six times the dog’s body weight (in kilograms). Applying this assumption leads to a recommended thickness of the distal hinge between 1 and 7 mm for dogs weighing between 2 and 70 kg (Table 13.2). Finally, taking into account the viscoelasticity of the bone as a material, the author recommends to rotate the tibial crest around the distal bone hinge gradually and slowly, thus reducing even further the incidence of fissure/fracture. Although the cage used by the author is still the one initially designed by Tepic and Montavon (TTA, Kyon), various other types of cages/spacers made of various materials have been used with good to excellent clinical outcome (TTA‐2 [9]; TTA‐rapid [10]; titanium foam, modified Maquet procedure (MMP) [11]; β‐tricalcium phosphate [12]; bioabsorbable material [13]). A few surgeons proposed using K‐wires, as in the MMP [10], or absorbable sutures, as in the TTA‐2 [8], at the bone hinge in order to increase the ultimate tensile strength of the bone. In past years, the MMT has been reported also in cats with good clinical outcome, although the biomechanics of the cat’s stifle might differ from the dog [14, 15]. Further information on complications of CCL stabilization in the cat can be found in Chapter 16. Figure 13.2(a) Radiograph of the stifle joint in an appropriate position to measure the desired tibial tuberosity advancement (TTA). Note that the stifle is in close to maximal extension (>135°), the tibia is reduced in relation to the femur (a stick is seen to reduce the tibial translation). Neglecting to completely reduce the tibial subluxation leads inevitably to suboptimal advancement of the tibial tuberosity. (b) Method used by the author to determine the desired TTA: red line = tibial plateau slope (TPs), blue line PT1 = patellar tendon (PT) direction before advancement; blue line PT2 = desired PT direction after desired TTA (PT2 is now perpendicular to TPs); thin bright yellow arrow = TTA if TT is advanced perpendicularly to the osteotomy line; orange arrow = final desired TTA (gives the size of the cage) as TT is indeed rotated around the bone distal hinge (note that the difference between yellow and orange arrows is negligible). Dashed yellow line = tibial osteotomy, passing 1 cm (d) parallel and caudal to the cranial border of the tibial crest and joining a distal point along the cranial tibial cortex, several mm caudal to the cranial tibial border according to patient body weight (the hinge). (c) Immediate postoperative radiograph showing the cage in place (15 mm in this case) and a long rectilinear osteotomy. Table 13.1 Calculation of the osteotomy length in function of the desired TTA. The objective is to keep the opening angle of the osteotomy gap under 10°, a scenario that has been shown to limit the risk of hinge fracture upon advancement. A simple trigonometric function, y = x/tg α, is applied where x is the desired TTA, α (opening angle) is set at 9° (or possibly lower) and y corresponds to the osteotomy length. Calculations indicate that the osteotomy length grossly equals 7–8 times the width of the cage, meaning the osteotomy lengths range from 25 to 105 mm for cage widths ranging from 3 to 15 mm. Table 13.2 Calculation of bone hinge thickness in function of patient body weight (BW). The objective is to keep enough bone to resist a tension up to six times BW, a force that a dog could apply to the patella tendon upon jumping over a height. The following equation is applied: Thickness (mm) × 508.116 = (6× BW (N) + 417.561) − (15.68 × BW) (kg) [8]; calculations indicate thicknesses ranging from 1 to 7 mm for dogs with BW ranging from 2 to 70 kg. An adequate TTA measurement on the preoperative radiograph is a major prerequisite for successful surgery. Several strict conditions must be considered (Figure 13.2; Tables 13.1 and 13.2). Figure 13.3 Major effect of stifle extension angle on measurement of desired TTA. (a) The stifle is extended 145° and the desired TTA (green arrow) can be measured. (b) The same stifle is only extended 115° and the measurement indicates a desired caudal crest transposition which cannot be performed (red triangle). Neglecting to sufficiently extend the stifle (even beyond 135°) when the preoperative radiograph is taken to measure the desired TTA is a major cause of suboptimal TTA. The decision to evaluate the meniscus is surgeon dependent with multiple factors that need to be considered. Additional information on meniscal decision making can be found in Chapter 18. Figure 13.4 Illustration of the approximate 20° tilt of the oscillating saw blade when tibial osteotomy is performed. Neglecting to do so leads to widening of the hinge on the lateral side of the tibia (that has a triangular shape) which makes the hinge stiffer and more prone to fissure or even breakage upon advancement. Figure 13.5 Successive steps of the modified Maquet technique (MMT). (a) The osteotomy line is rectilinear with the medial side of the tibia parallel to the operating table and the oscillating saw blade slightly tilted by about 20° in a caudo‐medial to cranio‐lateral direction. The length of the osteotomy is determined preoperatively according to the desired TTA in order to stay equal to or under 10° of opening (Table 13.1). The width of the distal bone hinge is determined preoperatively according to the body weight of the patient (Table 13.2). (b,c) The opening of the osteotomy gap is slowly (over 3–5 minutes) increased by introducing successive spacers of 3, 6, 9, 12, and 15 mm (6 and 15 mm in the illustrated case). (d) The cage is secured to the tibia with two self‐tapping 1.8 mm screws at a divergent angle. The osteotomy gap is not grafted. Soft tissues are routinely closed. (e) The different spacers (Kyon) are fixed to a T‐handle; spacers are introduced in the gap on their narrow border and then slowly twisted 90° to spread the gap. Figure 13.6 Illustration of an isthmus (within red ellipse) along the cranial part of the tibia. This narrowing should be avoided as it creates a stress riser, possibly leading to fracture. Note also the inappropriate position of the cage, placed too high in the osteotomy gap, hence possibly not delivering the expected stabilizing effect due to lack of sufficient advancement.
13
Complications Associated with the Modified Maquet Technique
13.1 History
Width of cage (mm)
Length of osteotomy (mm)
3
25
6
45
9
65
12
85
15
105
BW (kg)
Hinge thickness (mm)
BW (kg)
Hinge thickness (mm)
1
0.91
15
2.10
5
1.25
20
2.52
6
1.33
30
3.37
7
1.42
40
4.22
8
1.50
50
5.07
9
1.59
60
5.92
10
1.67
70
6.77
13.2 Guidelines to Perform a Modified Maquet Technique
13.2.1 Preoperative
13.2.2 Intraoperative
13.2.3 Postoperative
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