2 Anteromedial Tibial Tubercle Osteotomy 1 3 (Fulkerson Osteotomy) 40 4 Jack Farr, Brian J. Cole, James Kercher, Lachlan Batty, [AU1] 5 and Sarvottam Bajaj 6 40.1 Introduction nature of the Fulkerson osteotomy allows for simul- 34 taneous anteriorization and medialization of the tib- 35 ial tubercle. By varying the angle of the osteotomy, the 36 7 The tibial tubercle (interchangeable with tuberosity) tubercle can be biased to a more anterior or more medial 37 8 is the most distal anchor of the extensor mechanism position. Since his initial description, the indications for 38 9 and can serve as a tool in altering patellofemoral (PF) this procedure have evolved significantly and continue 39 10 mechanics. Known collectively as distal realignment to be refined. This has been primarily driven by the evo- 40 11 procedures, osteotomies of the tibial tubercle are a use- lution and outcomes of patellofemoral resurfacing 41 12 ful method to treat a variety of PF conditions by allow- procedures as well as improved objective measures of 42 13 ing coronal, axial, and sagittal plane adjustments of the patellar alignment, contact area, and forces. 43 14 patellofemoral articulation which redistribute patellar The tibial tuberosity to trochlear groove (TT–TG) 44 15 contact pressures (force and contact area) and poten- distance, popularized by Dejour et al.8 as an objective 45 [AU2]16 tially improve tracking. Numerous tibial tubercle osteot- measure of tuberosity position, has helped quantify 46 17 omies have been described in the literature to treat PF abnormal tuberosity position and enhanced appropri- 47 18 pain, chondrosis, and instability. The most notable ate candidate identification for all tuberosity osteoto- 48 19 include medialization, initially described by Roux and mies including the AMZ. This becomes important 49 20 later popularized by Elmslie and Trillat, for the treat- because patellar contact pressures are very sensitive 50 21 ment of PF instability30 and anteriorization of the tibial to distal realignment.1,17,25 In addition, combining 51 22 tubercle described by Maquet18 performed to treat PF AMZ with PF cartilage restorative procedures such as 52 23 pain associated with arthritis. Each of these procedures autologous chondrocyte implantation and osteoartic- 53 24 takes advantage of important technical alterations in ular grafting procedures within the PF compartment 54 25 patellar kinematics. Anteriorization of the tubercle ele- have demonstrated superior results to either proce- 55 26 vates the distal extensor mechanism and serves to shift dure performed independently.10,14,19,21,28 56 27 patellar contact forces proximally, while medialization 28 results in a decrease of the lateral force vector. 29 In an effort to avoid complications associated 11 30 with the Maquet procedure, Fulkerson designed 40.2 Indications 57 31 a tubercle osteotomy known as the anteromedializa- 32 tion (AMZ) technique to address PF pain in con- When discussing the indications for AMZ it is impor- 58 33 junction with patellar maltracking. The oblique tant to note that as with most patellofemoral surger- 59 ies, it should only be performed after the patient has 60 tried and failed nonoperative measures that include a 61 Uncorrected Proof9 comprehensive “core to the floor” program of reha- 62 B.J. Cole () bilitation, bracing, and orthotics. Indications for 63 Departments of Orthopaedics & Anatomy and Cell Biology, AMZ are primarily based upon mechanical and chon- 64 Division of Sports Medicine, Cartilage Restoration Center at Rush, Rush University Medical Center, Chicago, IL, USA dral pathologies specific to each individual knee. 65 e-mail: [email protected] Malalignment is a term that has different meanings to 66 V. Sanchis-Alfonso (ed.), Anterior Knee Pain and Patellar Instability, 1 DOI: 10.1007/978-0-85729-507-1_40, © Springer-Verlag London Limited 2011 2 J. Farr et al. 67 different experts, but for the purposes of this chapter Table 40.1 Summary of indications for anteromedialization t1.1 68 it simply means alignment that is different from the Summary of AMZ indications: t1.2 69 average asymptomatic individual. A comprehensive • Lateral or distal patella chondrosis with an increased t1.3 70 review by Post et al.23 demonstrated that the “Q” TT–TG distance, excessive lateral tilt/subluxation, and the t1.4 absence of trochlea chondrosis. t1.5 71 angle was inadequate to use as a measure of mala- • As an adjunct procedure to patellofemoral cartilage t1.6 72 lignment of the tibial tuberosity. Using the objectively restoration in an effort to improve the contact area and t1.7 73 measured TT–TG, asymptomatic patients have dis- decrease PF forces to optimize the biomechanical t1.8 74 tances averaging 13 mm and those with instability environment of the new cartilage implant. t1.9 • Possibly, in conjunction with MPFL repair or reconstruc- t1.10 75 symptoms have average measurements of over tion in patients with markedly increased TT–TG distance. t1.11 76 15 mm.27 A panel of patellofemoral experts agreed 77 that TT–TG distances of over 20 mm were definitely 78 abnormal and would be potential candidates for mov- carefully assessed as medialization will significantly 114 15 79 ing the tibial tubercle. Patients with isolated chon- increase contact pressures between the medial patellar 115 80 drosis of the distal or lateral patella, who have excessive facet and trochlea.25 In addition, AMZ is contraindicated 116 81 lateral patellar tilt and/or subluxation associated with for proximal patella, panpatella, and bipolar chondrosis 117 82 an increased TT–TG distance and minimal trochlear based upon the outcomes from Pidoriano et al.22 118 83 chondrosis are optimal AMZ candidates based on a Advanced chondrosis of the central trochlea has 119 22 84 retrospective review of AMZ outcomes by Pidoriano. been associated with suboptimal results and is con- 120 85 It has been argued that rotational tuberosity abnormali- sidered a contraindication to AMZ as an isolated pro- 121 86 ties associated with subjective instability and pain may cedure.5,22 Standard contraindications to any osteotomy 122 87 be sufficiently treated with straight medialization or must also be considered, which includes smoking, 123 20 88 derotation of the tibial tubercle, although Pritsch infection, inflammatory arthropathy, marked osteopo- 124 24 89 et al. found 80% of 66 patients undergoing tubercle rosis inhibiting adequate fixation, complex regional 125 90 transfer for patellar instability and pain associated with pain syndrome, arthrofibrosis, inability to minimally 126 91 maltracking required anteriorization based on intraop- weight-bear, and noncompliant patients. A summary 127 92 erative examination. Second, patients who are under- of AMZ contraindications is presented in Table 40.2. 128 93 going PF cartilage restorative procedures have been 94 shown to benefit from a combined AMZ proce- 10,14,19,21,28 95 dure, where optimization of the biomechani- 40.4 Surgical Technique 129 96 cal environment and decreased stress across the 97 restored cartilage is required. Additionally, in patients Techniques for AMZ have classically been described 130 98 undergoing MPFL repair or reconstruction for recur- as an isolated procedure; however, AMZ typically 131 99 rent lateral patella instability, AMZ may be indicated includes lateral retinacular release or lengthening to 132 100 only in the setting of a significantly increased TT–TG untether the patella allowing the patellar medialization 133 101 distance. However, it should be noted that while this component, and is not uncommonly performed in 134 102 theoretically decreases the lateral vector forces on the conjunction with procedures such as MPFL repair/ 135 103 healing MPFL tissues, there is no randomized study of Uncorrectedreconstruction or Proofcartilage restorative procedures. 136 104 AMZ plus MPFL surgery versus MPFL surgery alone These procedures must be taken into consideration 137 105 published as of this writing. A summary of AMZ indi- when planning the surgical approach. 138 106 cations is presented in Table 40.1. Table 40.2 Summary of contraindications to anteromedialization t2.1 107 40.3 Contraindications Summary of contraindications to isolated AMZ: t2.2 • Normal TT–TG distance t2.3 108 Several contraindications to AMZ exist and potential • Medial patellofemoral chondrosis (only if not combined t2.4 with cartilage restoration procedure) t2.5 109 candidates must be assessed carefully prior to surgery. • As an isolated procedure, when not combined with t2.6 110 Anteromedialization is contraindicated in patients with a cartilage restoration, to treat proximal pole, panpatella, t2.7 111 normal TT–TG distance and in patients who have symp- trochlear, or bipolar chondrosis t2.8 112 toms not explained by an increased TT–TG distance. • General contraindications to osteotomy (i.e., smoking, t2.9 osteoporosis, inflammatory arthropathy) t2.10 113 The condition of the medial PF articulation should be 40 Anteromedial Tibial Tubercle Osteotomy (Fulkerson Osteotomy) 3 139 40.4.1 Preoperative Assessment anesthesia includes assessment of range of motion, 176 140 and Planning patella tracking, and patella displacement. The patient 177 is then prepped and draped in standard fashion. 178 141 The desired amount of anteriorization and medializa- 142 tion (based on the objective measurement of the 143 TT–TG distance) must be calculated preoperatively. 40.4.3 Arthroscopic Evaluation 179 144 These two components are considered separately and 145 then basic trigonometric ratios can be used to determine Initially, arthroscopic evaluation and documentation of 180 146 the desired angle for the osteotomy. Anteriorization of patellofemoral chondrosis is performed. The areas of 181 147 between 10 and 15 mm is most commonly recom- chondrosis are regionally mapped using the ICRS 182 148 mended as it decreases PF stress loads by approxi- region knee mapping system noting that significant 183 149 mately 20%7,8 and results in minimal sagittal rotation patellar chondrosis may lead to termination of the pro- 184 150 of the patella.