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2 Anteromedial Tibial 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 . 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 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 Proof cartilage 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. In regards to the medialization compo- cedure unless concomitant cartilage restoration has 185 151 nent, the goal of the osteotomy is to normalize the been planned. Certainly other contraindications may 186 152 TT–TG distance, which based on the literature, is be discovered at arthroscopy and would also halt pro- 187 153 within a range of 10–15 mm. By varying the slope and ceeding with AMZ. At this stage, based on clinical tilt 188 154 the extent of anteriorization, a variety of medialization or CT/MRI documented patellar tilt, an arthroscopic 189 155 distances can be achieved. The required angle can be lateral release may be performed if indicated. When 190 156 calculated by the inverse tangent of the desired ante- combined with PF cartilage restoration the lateral 191 157 rior movement divided by the desired medial move- release or lateral lengthening is performed in an open 192 158 ment Table 40.3. For example, a 60° osteotomy with manner to allow direct access for performing the carti- 193 159 15 mm of elevation will produce 8.7 mm of medializa- lage restoration procedure. Lateral release should 194 160 tion, which will normalize most tuberosity positions as allow neutralization of patella tilt and unrestricted cen- 195 161 it is rare for TT–TG distances of over 25 mm. When tral positioning of the patella relative to the trochlea; 196 162 more medialization is required, the slope may be however, care must be taken to ensure that medial 197 163 decreased; a slope of 45° would move the tubercle patella subluxation does not occur. It should be noted 198 164 15 mm medially with 15 mm of elevation. that lateral lengthening can maintain control not 199 offered by lateral release.4 200

165 40.4.2 Setup and Positioning 166 of the Patient 40.4.4 Incision and Exposure 201

167 The patient is positioned in the supine position with a 168 side post and a gel-pad under the ipsilateral hemipel- The longitudinal incision runs approximately 8–10 cm 202 169 vis. This facilitates an initial arthroscopic evaluation of distally beginning at the patellar tendon insertion to 203 170 the knee and limits externalUncorrected rotation of the limb during the tibial tubercle. TheProof incision can be extended prox- 204 171 the osteotomy. All extremities are well padded, a tour- imally to allow adequate exposure if concomitant car- 205 172 niquet is applied, and prophylactic antibiotics are tilage restoration is being performed. The patella 206 173 administered. General, spinal, epidural, or regional tendon is identified and released from capsule medi- 207 174 block anesthesia can be used depending upon patient ally and laterally to allow protection with a retractor 208 175 and surgeon preference. A thorough examination under and later tubercle elevation. The lateral incision is 209 extended distally along the lateral margin of the tibial 210 t3.1 Table 40.3 Reference guide for osteotomy slope tuberosity and tibial crest allowing subperiosteal ele- 211 t3.2 Osteotomy Elevation Medialization vation of the anterior compartment musculature and 212 t3.3 slope (°) (mm) (mm) thereby exposing the lateral wall of the . A cus- 213 t3.4 60 15 8.7 tom retractor is positioned at the posterior aspect of 214 the lateral tibia in order to protect the posterior neuro- 215 t3.5 50 15 12.5 vascular structures (deep peroneal nerve and anterior 216 t3.6 45 15 15 tibial artery) (Fig. 40.1). 217 4 J. Farr et al.

Fig. 40.2 The reference pin guide is orientated so it is perpen- Fig. 40.1 Anterior compartment musculature is elevated from dicular to the posterior cortex of the tibia the lateral wall of the tibial with retractor protecting neurovascu- lar structures posteriorly

218 40.4.5 Performing the Osteotomy

219 For the highly experienced surgeon the osteotomy may 220 be performed free-hand. Fulkerson originally used an 221 external fixator pin clamp to direct multiple pins in the 222 osteotomy plane and then complete it with osteot- 223 omes.11 Today, there are two commercially available 224 AMZ osteotomy systems (Tracker, DePuy Mitek, Inc, 225 Raynham, New Jersey and the T3 System, Arthrex, Inc, 226 Naples, Florida). The Tracker system was available 227 first and detailed illustrated surgical techniques using 228 the jig system have been published by both Fulkerson 229 and Farr. The T3 system will be used in this section to 230 illustrate the operative technique; however the approach 231 for each system and steps following fixation of the cut- 232 ting guide are similar. For the T3 system, an initial ref- 233 erence pin is orientatedUncorrected perpendicular to the posterior Proof 234 cortex of the proximal tibia (Fig. 40.2). The reference 235 pin is inserted through the pin guide into the tibial Fig. 40.3 Reference pin is inserted through the guide just distal 236 tuberosity, just distal to the patellar tendon attachment to Gird’s tubercle 237 to the tibial tuberosity (Fig. 40.3). Using preoperative 238 calculations for anteriorization and medialization, the 239 desired slope angle guide is assembled with the cutting the osteotomy distally. For emphasis, the desired 246 240 block and cutting block post. The cutting guide is then osteotomy forms a triangle shape that tapers distally 247 241 placed over the reference pin and the cutting block is allowing an exit through the anterior cortex to the lat- 248 242 positioned immediately medial to the tibial crest begin- eral wall of the tibia. The desired pedicle length for the 249 243 ning directly in line with the medial border of the osteotomy is approximately 7–10 cm. When correct 250 244 patella tendon, as it attaches to the tibial tuberosity positioning has been achieved and the entry and exit 251 245 (Fig. 40.4), and angled laterally to allow a lateral exit of sites have been confirmed, two break-away pins secure 252 40 Anteromedial Tibial Tubercle Osteotomy (Fulkerson Osteotomy) 5

Fig. 40.6 Oscillating saw cooled with saline creates the initial sloped osteotomy, exiting on the protective retractor

Fig. 40.4 The cutting guide is placed over the reference pin and the cutting block is positioned medial to the patella tendon

Fig. 40.7 Proximal cuts are completed with small osteotome

proximal osteotomy, approaching the tibial tuberosity 260 medially and laterally at the level of the patella tendon 261 insertion (Fig. 40.7). The tuberosity is now free. 262

Uncorrected40.4.6 Positioning Proof and Fixation 263

A ruler is used to measure the required amount of ante- 264 riorization and medialization based on preoperative cal- 265 Fig. 40.5 Break-away pins secure the cutting block after posi- culations and the pedicle position is adjusted along the 266 tioning is confirmed osteotomy slope. If required, the pedicles can be moved 267 proximally or distally to address any underlying patella 268 253 the cutting block in position (Fig. 40.5). With the retrac- alta or infra. A Kirschner wire is used to temporarily 269 254 tor still protecting neurovascular structures posteriorly, secure the pedicle when correct positioning has been 270 255 the cut is made with an oscillating saw which is simul- achieved. The tuberosity fragment is then drilled using 271 256 taneously cooled with saline (Fig. 40.6). The cutting interfragmentary lag technique and secured using two 272 257 block is removed and the oscillating saw is directed countersunk 4.5 mm cortical screws (Fig. 40.8). The 273 258 toward the distal exit of the osteotomy to finish the dis- screws are positioned perpendicular to the osteotomy 274 259 tal cut. A small osteotome is used to complete the (angled from the anteriolateral aspect of the pedicle to 275 6 J. Farr et al.

a • The goal is to “normalize” the tibial tubercle posi- 290 tion that is keeping within a range of 10–15 mm. 291 • The required amount of anteriorization and medial- 292 ization needed for normalization should be consid- 293 ered independently. The required osteotomy angle [AU4]294 is determined based upon these values. 295 • The osteotomy angle is equal to tan-1 of the desired 296 anterior movement (y) divided by the desired medial 297 movement (x), e.g., Angle = tan−1 (y/x) (For simplic- 298 ity, see Table 40.3) 299 • Assessment for patella alta using the Caton– 300 Deschamps ratio (normal range 0.8–1.2) is required 301 to determine if distalization is required. 302 • Strengthening of proximal core muscles must be a 303 focus of rehabilitation in conjunction with local 304 musculature. 305 • Anteromedialization can be performed in conjunc- 306 tion with other procedures including lateral release/ 307 b lateral lengthening, MPFL repair or reconstruction, 308 or cartilage restoration procedures. 309

40.5.2 Pitfalls 310

• Over medialization of the tibial tubercle can be det- 311 rimental secondary to increased medial patellofem- 312 Fig. 40.8 The distance of medialization and anteriorization is measured directly and the pedicle is secured with 2–4.5 mm oral and tibiofemoral stress. 313 [AU3] screws • Patients should be aware that pain over the screw 314 site is common and they may need removal at a 315 future date. 316 276 posteromedial tibia) so they are directed away from pos- • Weight bearing too early can lead to a fracture 317 277 terior neurovascular structures. The surgical site is of the proximal tibia if the patient is returned 318 278 closed in a standard fashion. to full weight bearing prior to radiographic 319 healing.2,12,29 320 • The MPFL is recognized as the key restraint to lat- 321 279 40.5 Pearls and Pitfalls Uncorrectederal patella dislocation. Proof Isolated tibial tuberosity 322 AMZ is not a substitute for MPFL repair or 323 280 40.5.1 Pearls reconstruction. 324 • Excessive anteriorization of the tuberosity can lead 325 281 • Preoperative rehabilitation and expectation coun- to skin healing problems and can cause clinically 326 282 seling is extremely important to prepare the patient significant sagittal plane rotation of the patella alter- 327 283 for surgery and recovery. ing contact areas. 328 284 • The TT–TG measurement is an objective alterna- • Isolated AMZ performed in the presence of chon- 329 285 tive to the Q-angle, quantifying the concept of tibial drosis will yield poor results when the wear patterns 330 286 tuberosity malalignment. are located in the: proximal patella, panpatella, or 331 287 • The mean TT–TG distance is 13 mm in asymptom- trochlea. However, AMZ in conjunction with carti- 332 288 atic patients and is considered excessive when lage restoration procedures in these regions can 333 289 above 20 mm. achieve good results. 334 40 Anteromedial Tibial Tubercle Osteotomy (Fulkerson Osteotomy) 7

335 40.6 Complications protected with a hinged knee brace in extension 360 which is unlocked at 2 weeks and discontinued when 361 there is adequate lower extremity control (usually by 362 336 Potential complications include those generally asso- 8 weeks). Early core proximal strengthening, quadri- 363 337 ciated with osteotomies of the lower limb. General ceps strengthening, and knee range of motion exer- 364 338 complications include malunion, nonunion, fracture cises are essential and a close relationship with an 365 339 at the osteotomy site,12,29 venous-thromboembolism, experienced physical therapist is key to optimizing 366 340 compartment syndrome, infection, and loss of fixa- the final results. The safe range of motion may need 367 341 tion. Complications specific to AMZ include persis- to be modified throughout the rehabilitation process 368 342 tent pain, arthrofibrosis and stiffness, progressive to accommodate for concomitant cartilage restorative 369 343 chondral deterioration, symptomatic hardware, com- procedures. 370 344 plex regional pain syndrome, and intraoperative 345 injury to the neurovascular structures including the 346 popliteal artery and its trifurcation16 and the deep per- 347 oneal nerve. 40.8 Conclusions 371

348 40.7 Postoperative Management Multiple case series have reported outcomes of the 372 AMZ procedures (Table 40.4). Despite the hetero- 373 349 To improve postoperative recovery and prepare for geneity in outcome measurements, results demon- 374 350 surgery, the patient should undergo a preoperative strate high percentages of excellent and good results 375 351 proximal core and kinetic chain strengthening pro- and improvements in objective, subjective, and 376 352 gram (lower back, pelvis, hip thigh, and leg). functional measures. Attention to details related to 377 353 Postoperatively the patient is treated with standard surgical planning and properly managing patient 378 354 compression dressings, protective bracing, and cryo- expectations is most likely to lead to good or excel- 379 355 therapy, and is monitored for immediate complica- lent results. Newer techniques (i.e., the T3 system) 380 356 tions. For the first 6 weeks the patient is limited to allow the surgeon to objectively determine the incli- 381 357 touch weight bearing with crutches and begins transi- nation of the osteotomy to properly restore patell- 382 358 tioning to full weight bearing after radiographs are ofemoral mechanics based upon the preoperative 383 359 noted to be acceptable at 6 weeks. The knee is planning. 384

t4.1 Table 40.4 Anteromedialization outcomes t4.2 Author, year Patient Mean follow-up Reported outcomes t4.3 number (range) t4.4 Fulkerson11 Uncorrected8 n/a Substantial relief of pain Proofand disability for all patients t4.5 Cameron et al.6 53 >12 months 66% Excellent, 16% good, 11% fair, 7% poor t4.6 Fulkerson et al.13 30 35 months (26–50) 35% Excellent, 54% good or very good, 4% fair, 7% poor t4.7 Sakai et al.26 21 5 years (2–13) Pain relief in ascending and descending stairs for 20/21

Pidoriano et al.22 37 47 months (12–96) 87% Good to excellent results with lateral or distal lesions, 55% t4.8 good to excellent results with medial lesions, 20% good to t4.9 excellent results with proximal or diffuse lesions t4.10

Bellemans et al.3 29 32 months (25–44) Significant improvements in mean Lysholm (62 preoperative, t4.11 92 postoperative, p < 0.001) and Kujala scores (43 preoperative, t4.12 89 postoperative, p < 0.001) t4.13

Buuck and Fulkerson5 42 8.2 years (4–12) 86% Good to excellent subjectively, 86% good to excellent on t4.14 clinical examination t4.15 8 J. Farr et al.

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Query Details Required Author’s Response AU1 Please check if the chapter title is correct. Chapter title in the table of contents is different. AU2 Please confirm the corresponding author and also confirm the affiliation details. AU3 Please provide part captions for part figures “a” and “b”. AU4 Please check if the edit to the sentence starting “The required.....” is OK. AU5 Please provide complete details for Ref. [15].