Medial Patellofemoral Ligament Isometry in the Setting of Patella Alta

Journal Pre-proof Medial Patellofemoral Ligament Isometry in the Setting of Patella Alta Nicole S. Belkin, MD, Kathleen N. Meyers, MS, Lauren H. Redler, MD, Suzanne Maher, PhD, Joseph T. Nguyen, MPH, Beth E. Shubin Stein, MD PII:

S0749-8063(20)30117-1

DOI:

https://doi.org/10.1016/j.arthro.2020.01.035

Reference:

YJARS 56772

To appear in:

Arthroscopy: The Journal of Arthroscopic and Related Surgery

Received Date: 30 July 2019 Revised Date:

8 January 2020

Accepted Date: 8 January 2020

Please cite this article as: Belkin NS, Meyers KN, Redler LH, Maher S, Nguyen JT, Shubin Stein BE, Medial Patellofemoral Ligament Isometry in the Setting of Patella Alta, Arthroscopy: The Journal of Arthroscopic and Related Surgery (2020), doi: https://doi.org/10.1016/j.arthro.2020.01.035. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier on behalf of the Arthroscopy Association of North America

Medial Patellofemoral Ligament Isometry in the Setting of Patella Alta

*Nicole S Belkin, MD1 Kathleen N Meyers, MS 2 Lauren H Redler, MD3 Suzanne Maher, PhD4 Joseph T Nguyen, MPH5 Beth E Shubin Stein, MD6

1

Assistant Attending, Sports Medicine and Shoulder Service, Columbia University Orthopedics

161 Fort Washington Ave, New York, NY 10032 [email protected]

2

Department of Biomechanics, Hospital for Special Surgery

535 E 70th St, New York, NY 10021 [email protected] 3

Assistant Attending, Sports Medicine and Shoulder Service, Columbia University Orthopedics

161 Fort Washington Ave, New York, NY 10032 [email protected]

4

Associate Scientist & Laboratory Director, Hospital for Special Surgery Research Institute

515 East 71st St, New York, NY 10021 [email protected] 5

Director, Biostatistics Core, Hospital for Special Surgery

535 E 70th St, New York, NY 10021 [email protected]

6

Associate Attending, Sports Medicine and Shoulder Service, Hospital for Special Surgery

Associate Professor of Orthopaedic Surgery, Weill Cornell Medical College 535 E 70th St, New York, NY 10021 [email protected]

* Corresponding author

1

Medial Patellofemoral Ligament Isometry in the Setting of Patella Alta

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

1

26

ABSTRACT

27

Purpose: To investigate alterations in technique for medial patellofemoral Ligament (MPFL)

28

reconstruction in the setting of patella alta and describe the effect of these alterations on MPFL

29

anatomometry.

30

Methods: Ten cadaveric knees were utilized. 4 candidate femoral attachment sites of MPFL were

31

tested. The attachment sites were Schottle’s point (SP), 5 mm distal to SP, 5 mm proximal to SP, and 10

32

mm proximal to SP. A suture anchor was placed at the upper 40% of the medial border of the patella

33

with the emanating suture used to simulate the reconstructed ligament. MPFL maximum length change

34

was calculated through a range of motion between 0° and 110°. Recordings at all four candidate femoral

35

attachments sites were repeated after a flat TT osteotomy and transfer to achieve alta as measured by

36

the Caton-Deschamps Index (CDI) of 1.3, 1.4 and 1.5.

37

Results: The 10 specimen had average CDI of 0.99, range 0.87 – 1.16. In the native tibial tubercle

38

condition, SP was more isometric through 20-70° range of motion, or anatomometric, than any other

39

candidate femoral attachment location. With patella alta with a CDI of 1.3 and 1.4, attachment site 5

40

mm proximal to SP exhibited more anatomometry than SP.

41

attachment site 10 mm proximal to SP exhibited more anatomometry than SP.

42

Conclusion: Increased patella alta significantly alters MPFL anatomometry. With increasing degrees of

43

patella alta, more proximal candidate femoral attachment sites demonstrate decreased change in length

44

compared to Schottle’s point. None of the varied femoral attachments produced anatomometry over

45

the entirety of the flexion range from 20-70 degrees, suggesting that in cases of significant patella alta,

46

proximalization the femoral attachment site of MPFL reconstruction may be necessary in order to

47

achieve an anatomometric MPFL reconstruction.

With patella alta with a CDI of 1.5,

2

48 49

Clinical Relevance: A standardized, isolated MPFL reconstruction may be prone to failure in the setting

50

of patella alta given the anisometry demonstrated. Alternative femoral attachment sites for MPFL

51

reconstruction should be considered in these patients.

52 53

INTRODUCTION

54

The medial patellofemoral ligament (MPFL) is the primary passive soft-tissue restraint to lateral patellar

55

displacement. Though patellar instability is multifactorial in etiology with trochlear dysplasia,1 lower

56

extremity malalignment,2 and other anatomic variants contributing to instability, deficiency of the MPFL

57

is believed to be the essential lesion leading to recurrent patellar dislocation.3,4 The effect of patella

58

alta on patellar instability has been demonstrated in numerous studies.5–8 Patella alta causes the patella

59

to travel unconstrained by the trochlear groove in extension, characterized by a lack of joint congruity

60

and increased instability.5,7,9–11

61

Patellar dislocation is common in the adolescent age group, with an incidence of 29 per 100,000,

62

and recurrence rates of 15-69% have been reported with nonoperative treatment.12–17 even higher rates

63

of recurrence have been found in patients with an acute patella dislocation and trochlear dysplasia to

64

have.

65

patellofemoral instability.3,18 The anatomic origin and insertion of the native MPFL have been described.

66

19,20

67

which, in its anatomic state, is isometric within the initial 20-70 degrees and then loosens with increased

68

flexion.21–23At present, there is a paucity of information regarding the isometricity of the reconstructed

69

MPFL in the setting of patella alta.

12

Thus, MPFL reconstruction has become the standard of care for treatment of recurrent

Additionally, the anatomometric nature of the MPFL has been shown; wherein the native MPFL

3

70

Schottle has described a point on the femur which re-creates an isometric MPFL and was found

71

to be the attachment point for the native MPFL19. The work done by Schottle was performed in 8

72

cadaveric specimens and did not include description of patellar height or trochlear morphology. A lack

73

of anatomic variants is a common limitation of cadaveric study of factors effecting patellar instability.

74

The point identified by Schottle has been shown to be anatomometric in patients with normal patella

75

height, we do not yet know what the anatomometric point is, or if there is one, in patients with patella

76

alta. A previous cadaveric study evaluating the effect of various tibial tubercle heights on MPFL

77

isometry demonstrated that increased Caton-Deschamps Index (CDI) resulted in increased MPFL

78

anisometry.24

79

We sought to investigate alterations in technique for Medial Patellofemoral Ligament (MPFL)

80

reconstruction in the setting of patella alta and to describe the effect of these alterations on MPFL

81

anatomometry.

82 83

We hypothesized that in the setting of patella alta a more proximal femoral attachment site, than that describe by Schottle, would be anatomometric.

84 85

MATERIALS AND METHODS

86

Specimen Preparation: Following approval from our institutional review board, ten fresh-frozen

87

cadaveric knees (4 female, 6 male; mean age 57 years, range 44-69 years; 6 right, 4 left), with no history

88

of disease or knee surgery, were obtained from Anatomic Gift Foundation, Inc., an independent, non-

89

profit, charitable, anatomic donation organization. No specimens were excluded from the investigation.

90

A power analysis was performed on data from previously published investigation which determined the

91

need for ten specimens.

4

92

Knees were stored at -20 deg C and thawed before experimentation. The specimens were

93

assessed and prepared by the first author, a Sports Medicine Surgery Fellow. None of the specimen

94

exhibited patella alta or trochlear dysplasia. Skin and subcutaneous fat were removed and the

95

quadriceps tendon isolated. The knees were placed on a custom testing fixture, where the femur was

96

fixed and the tibia was unconstrained through 120° of flexion. The quadriceps tendon was loaded with

97

10.8N in an anatomic direction using a weighted pulley system.

98

MPFL Reconstruction:

99

Schottle’s point19 was identified radiographically and a thin malleable pin was placed at this

100

location. Subsequently, locations 5 mm distal (d05), 5 mm proximal (p05) and 10 mm proximal (p10)

101

were identified utilizing a combination of radiographic guidance and direct measurement with a caliper

102

along a line parallel to the posterior femoral cortex (Figure 1). These locations were utilized based upon

103

a previous investigation that reported the effect of femoral attachment site on MPFL length change

104

patterns. 22 This study did not evaluate the effect of patella alta.

105

Thin malleable pins were also placed at these locations. The pins were then bent tangentially to

106

the cortical surface to act as pulleys. A suture anchor was placed at the upper 40%25 of the medial

107

border of the patella and the sutures emanating from the anchor were tied to prevent sliding. The

108

suture was passed around the pins on the medial femur and attached to a 1N weight. This suture passed

109

around each femoral attachment site to represent the simulated MPFL reconstruction.

110

Optical Tracking:

111

Four spherical retroreflective markers were attached to each bone (femur, tibia and patella) and

112

a single marker was attached to the suture acting as the MPFL. A 3D motion tracking camera system

113

(Motion Analysis Corporation, Santa Rosa, CA) was used to track the motion of the bone markers and

5

114

suture markers in real time. Length change of the suture was assessed similarly to a previously published

115

study, by using a 3D motion capture system.22,24 In brief, a pointer was used to identify anatomic

116

landmarks on the femur and tibia to build a knee coordinate system.26,27The 3D marker data was post

117

processed using custom software (MatLab, Mathworks, Natick, MA) to calculate suture motion and knee

118

flexion angle. Marker translation had a 3D resolution of 0.1mm.

119

Testing Procedure: The knee was ranged from full extension to 110° of flexion five times. The 3D

120

marker coordinates were recorded throughout. The native CDI was calculated by direct measurement of

121

the length from the anterior proximal corner of the tibial plateau to the most inferior point of the

122

patella articular surface divided by the length of the patella articular surface (Table 1).28

123

As previously described, a flat tibial tubercle osteotomy was performed, cutting the bone in the

124

coronal plane, parallel to the femoral condylar axis, 6cm in length. A section of bone was then removed

125

proximally to ensure room was available to translate the tubercle to simulate maximal patella alta. In a

126

randomized manner, CDI 1.3, 1.4 and 1.5 were created specific to each specimen’s native anatomy. A

127

digital caliper was used to confirm proximal translations of the tibial tubercle. During measurement and

128

cutting, the knee was held in full extension and the coronal plane was assumed to be parallel to the base

129

of the test rig. All candidate femoral attachment sites (d05, Schottle’s point, p05, p10) were evaluated

130

for each CDI variable (1.3, 1.4, 1.5) in a randomized order to avoid bias (Figure 2).

131

The mean length change (MLC) of the MPFL reconstruction was calculated throughout range of motion

132

20 - 70°.

133

Statistical Analysis: Analysis was performed on all 10 specimens. To analyze and control for the

134

clustered nature of the data, a generalized estimating equation (GEE) modeling technique was used to

135

measure the mean maximal length change of the ligament. Models were constructed to evaluate the

136

changes across the different femoral attachment sites as well as various conditions of patella alta. 6

137

Parameter estimates are reported as MLC and standard errors, with statistical significance defined as

138

P≤0.05. SAS version 9.3 (SAS Inc., Cary, NC) was used for all statistical analyses. Clinical significance for

139

isometry was deemed to be less than 2mm of MLC based on a prior study22.

140 141

RESULTS

142

Schottle’s Point (p00) Attachment Site in the in the setting of various degrees of Patella Alta:

143

When evaluating MPFL reconstruction utilizing Schottle’s point (p00), anatomometric behavior was

144

observed in the setting of native patellar height (native CDI) with MLC 1.2mm (P=0.192). This means

145

that over the knee flexion arc (20°-70°) the mean length did not exceed the clinical definition of isometry

146

(change less than 2mm) and also was not statistically different (the length of the ligament was not

147

different cross flexion angles) making the MPFL isometric in this configuration. A reconstruction

148

performed at Schottle’s point failed to produce an anatomometric MPFL in the setting of all degrees of

149

patella alta tested (CDI 1.3, 1.4, and 1.5). At CDIs 1.3, 1.4 and 1.5, MLCs were 2.2mm (P=0.501), 2.3

150

(P>0.999) and 2.5 (P>0.999) respectively, which is similar to that previously reported.2

151

The actual amount of translation of the tubercle to achieve a CDI of 1.3, 1.4, and 1.5 were within 1% of

152

the desired translation calculated based on each specimen’s native anatomy

153

Variable Femoral Attachment Sites (d05, Schottle’s point, p05, p10) in the setting of Native

154

Patellar Height: When evaluating the array of candidate femoral attachment sites in combination with

155

native patellar height (native CDI), Schottle’s point (p00) was more isometric through 20-70° range of

156

motion than any other candidate femoral attachment location with MLC 1.2mm (P=0.192). At the

157

femoral attachments sites p05, p10 and d05, MLCs were 3.3mm (P=0.002), 5.8mm (P<0.001) and 3.8mm

158

(P=0.011) respectively (Figure 3).

7

159

Variable Femoral Attachment Sites (Schottle’s point, p05, p10, d05) in the setting of Patella Alta

160

(CDI 1.3, 1.4, 1.5):In the setting of patella alta with a CDI of 1.3, p05 exhibited anatomometric behavior

161

with MLC 1.5mm (P=0.029). At the femoral attachments sites Schottle’s point, p10 and d05, MLCs were

162

2.2mm (P=0.501), 4.6mm (P=0.004) and 5.0mm (P<0.001) respectively (Figure 4).

163

In the setting of patella alta with a CDI of 1.4, p05 continued to exhibit the most anatomometric

164

behavior with MLC 1.0mm (P>0.999). At the femoral attachments sites Schottle’s point, p10 and d05,

165

MLCs were 2.3mm (P>0.999), 3.4mm(P=0.221) and 4.9mm (P<0.001) respectively (Figure 5).

166

With patella alta of CDI 1.5, p05 and p10 exhibited anatomometric behavior with MLC of -

167

0.7mm (P=0.099) and 0.8mm (P=0.099) respectively. MLC for reconstructions with femoral attachment

168

sites at Schottle’s point and d05 were 2.5mm (P>0.999) and 4.5mm (p<0.001). (Figure 6).

169 170

DISCUSSION

171

This study confirmed the hypothesis that increased patellar height leads to increasingly adverse

172

effects on the anatomometry of a simulated MPFL reconstruction anchored at Schottle’s point.

173

Additionally, our investigation found that, to a limit, these effects can be overcome by moving the MPFL

174

femoral insertion more proximal. We believe that in patients with native patella alta (CDI>1.3), the

175

native MPFL insertion site may well be found proximal to that described by Schottle. Given this

176

potential anatomic variability, we may want to focus on using anatomic landmarks (adductor tubercle

177

and medial femoral epicondyle) and ligament anatomometry rather than radiographic parameters in our

178

reconstructions.

179

The native MPFL has been shown to be isometric through 20 – 70° range of motion, or

180

anatomometric in nature.21,22,29 It has therefore been adopted as a surgical principle that the goal of an 8

181

anatomic reconstruction is to reconstruct a ligament that demonstrates this behavior.

Although

182

retrospective studies do show reduction in patella alta following MPFL reconstruction30, to our

183

knowledge, the ability to create an anatomometric reconstruction in the setting of patella alta has not

184

been thoroughly investigated.

185

Patella alta, as measured by the CDI, has been shown to be a risk factor predictive of recurrent

186

patellofemoral instability31. A cadaveric study by Singerman et al. demonstrated that patello-trochlear

187

contact during knee flexion was delayed until greater flexion angles in the setting of patella alta.32 These

188

finding elucidate the biomechanical etiology of instability associated with patella alta. Without early

189

bony congruence afforded by patello-trochlear contact, the patella is more vulnerable to a lateral

190

moment, and therefore subluxation and dislocation.

191

Our group has demonstrated that increased patellar height and elevated tibial tubercle-

192

trochlear groove distance (TT-TG), modeled by tibial tubercle osteotomy, both alter the isometry of a

193

reconstructed MPFL, with patellar height being the more powerful variable. In our study, anisometry

194

was observed with mild patella alta, CDI 1.2, and significantly worsened with increased alta of CDI 1.4,

195

with up to 3.94mm of mean maximal length change.24 The interaction of TT lateralization combined

196

with patella alta significantly increased the amount of anisometry seen in the reconstructed MPFL, with

197

up to 4.72mm of mean maximal length change demonstrated with the combination of TT-TG 25 mm and

198

CDI 1.4.

199

Elias et al. and Stephen et al. both showed that femoral tunnel malposition in MPFL

200

reconstruction can lead to increased medial contact pressures during knee flexion and altering the

201

patellar and femoral MPFL graft attachments leads to significant graft anisometry.22,23,33 Additionally,

202

graft length change patterns assessed intraoperatively have been shown to influence the early recovery

9

203

of knee range of motion post-operatively, but these previous investigations have been limited to

204

anatomic configurations representative of normal patellar height.34

205

Similar to our conclusions, the authors of a recently published computer modeling study

206

investigating MPFL strain found that the radiological MPFL insertion point can be used for

207

reconstruction in patients with patella alta, but recommended a slightly more proximal femoral

208

insertion to avoid early patellar instability during flexion. 35

209

Our results are useful to surgeons performing MPFL reconstructions in patients with patella alta

210

for several reasons. Firstly, techniques previously described in patients with normal patellar height do

211

not result in a truly anatomometric MPFL in patients with patella alta. Additionally, when performing an

212

isolated MPFL reconstruction in the setting of patella alta, it is critical to use anatomic landmarks to

213

identify the femoral insertion site AND to check anatomometry to ensure the reconstruction is behaving

214

like the native MPFL. We would caution against using fluoroscopy alone to identify the femoral insertion

215

as this may lead to an anisometric ligament, given our findings

216

LIMITATIONS

217

This investigation has limitations. Our conditions of patella alta were artificially created, thusly

218

may not precisely recapitulate the biomechanics of native alta. Trochlear dysplasia, known to be an

219

important factor contributing to patellofemoral instability, was not observed in our cadaveric specimens

220

and therefore could not be studied in this investigation. The native MPFL has a broad attachment to the

221

patella and there is some evidence that the fibers of the MPFL may be differentially isometric

222

throughout a range of motion and this could not be well represented by our single suture model.2922

223 224

CONCLUSION 10

225

Increased patella alta significantly alters MPFL anatomometry. With increasing degrees of

226

patella alta, more proximal candidate femoral attachment sites demonstrate decreased change in length

227

compared to Schottle’s point. None of the varied femoral attachments produced anatomometry over

228

the entirety of the flexion range from 20-70 degrees, suggesting that in cases of significant patella alta,

229

proximalization the femoral attachment site of MPFL reconstruction may be necessary in order to

230

achieve an anatomometric MPFL reconstruction.

231

REFERENCES

232

1.

Senavongse W1 AA. The effects of articular, retinacular, or muscular deficiencies on

233

patellofemoral joint stability: a biomechanical study in vitro. J Bone Jt Surg Br. 2005;87(4):577-

234

582.

235

2.

236 237

tibiofemoral and patellofemoral kinematics. J Orthop Res. 2001;19(5):834-840. 3.

238 239

Mizuno Y1, Kumagai M, Mattessich SM, Elias JJ, Ramrattan N, Cosgarea AJ CE. Q-angle influences

Yeung M, Leblanc M-C, Ayeni OR, et al. Indications for Medial Patellofemoral Ligament Reconstruction: A Systematic Review. J Knee Surg. 2015;1(C). doi:10.1055/s-0035-1564730

4.

Nomura E, Inoue M. Surgical technique and rationale for medial patellofemoral ligament

240

reconstruction for recurrent patellar dislocation. Arthrosc J Arthrosc Relat Surg. 2003;19(5):1-9.

241

doi:10.1053/jars.2003.50167

242

5.

243 244 245

Geenen E, Molenaers G, Martens M. Patella alta in patellofemoral instability. Acta Orthop Belg. 1989;55(3):387-393. http://www.ncbi.nlm.nih.gov/pubmed/2603680. Accessed July 18, 2016.

6.

Kannus PA. Long patellar tendon: radiographic sign of patellofemoral pain syndrome--a prospective study. Radiology. 1992;185(3):859-863. doi:10.1148/radiology.185.3.1438776

11

246

7.

247 248

Neyret P, Robinson a HN, Le Coultre B, Lapra C, Chambat P. Patellar tendon length--the factor in patellar instability? Knee. 2002;9(1):3-6. doi:S0968016001001363 [pii]

8.

Simmons E, Cameron JC. Patella alta and recurrent dislocation of the patella. Clin Orthop Relat

249

Res. 1992;(274):265-269. http://www.ncbi.nlm.nih.gov/pubmed/1729011. Accessed July 18,

250

2016.

251

9.

Huberti HH, Hayes WC. Patellofemoral contact pressures. The influence of q-angle and

252

tendofemoral contact. J Bone Joint Surg Am. 1984;66(5):715-724.

253

http://www.ncbi.nlm.nih.gov/pubmed/6725318. Accessed July 18, 2016.

254

10.

255 256

1979;10(1):117-127. http://www.ncbi.nlm.nih.gov/pubmed/582201. Accessed July 18, 2016. 11.

257 258

Insall J. “Chondromalacia patellae”: patellar malalignment syndrome. Orthop Clin North Am.

Insall J, Goldberg V, Salvati E. Recurrent dislocation and the high-riding patella. Clin Orthop Relat Res. 1972;88:67-69. http://www.ncbi.nlm.nih.gov/pubmed/5086583. Accessed July 18, 2016.

12.

Lewallen LW, McIntosh AL, Dahm DL. Predictors of Recurrent Instability After Acute

259

Patellofemoral Dislocation in Pediatric and Adolescent Patients. Am J Sports Med.

260

2013;41(3):575-581. doi:10.1177/0363546512472873

261

13.

Ahmad CS, Brown GD, Stein BS. The docking technique for medial patellofemoral ligament

262

reconstruction: surgical technique and clinical outcome. Am J Sports Med. 2009;37(10):2021-

263

2027. doi:10.1177/0363546509336261

264

14.

Cofield RH, Bryan RS. Acute dislocation of the patella: results of conservative treatment. J

265

Trauma. 1977;17(7):526-531. http://www.ncbi.nlm.nih.gov/pubmed/875088. Accessed July 18,

266

2016.

12

267

15.

268 269

2004;32(5):1114-1121. doi:10.1177/0363546503260788 16.

270 271

Fithian DC. Epidemiology and Natural History of Acute Patellar Dislocation. Am J Sports Med.

Hawkins RJ, Bell RH, Anisette G. Acute patellar dislocations. The natural history. Am J Sports Med. 14(2):117-120. http://www.ncbi.nlm.nih.gov/pubmed/3717480. Accessed July 18, 2016.

17.

Mäenpää H, Lehto MU. Patellar dislocation. The long-term results of nonoperative management

272

in 100 patients. Am J Sports Med. 25(2):213-217.

273

http://www.ncbi.nlm.nih.gov/pubmed/9079176. Accessed July 18, 2016.

274

18.

Lippacher S, Dreyhaupt J, Williams SRM, Reichel H, Nelitz M. Reconstruction of the Medial

275

Patellofemoral Ligament: Clinical Outcomes and Return to Sports. Am J Sport Med.

276

2014;42(7):1661-1668. doi:10.1177/0363546514529640

277

19.

Schöttle PB, Schmeling A, Rosenstiel N, Weiler A. Radiographic landmarks for femoral tunnel

278

placement in medial patellofemoral ligament reconstruction. Am J Sports Med. 2007;35(5):801-

279

804. doi:10.1177/0363546506296415

280

20.

281 282

Amis AA, Firer P, Mountney J, Senavongse W, Thomas NP. Anatomy and biomechanics of the medial patellofemoral ligament. Knee. 2003;10:215-220. doi:10.1016/S0968-0160(03)00006-1

21.

Perez-Prieto D, Capurro B, Gelber PE, et al. The anatomy and isometry of a quasi-anatomical

283

reconstruction of the medial patellofemoral ligament. Knee Surgery, Sport Traumatol Arthrosc.

284

2015:1-4. doi:10.1007/s00167-015-3865-4

285

22.

Stephen JM, Lumpaopong P, Deehan DJ, Kader D, Amis a. a. The Medial Patellofemoral

286

Ligament: Location of Femoral Attachment and Length Change Patterns Resulting From Anatomic

287

and Nonanatomic Attachments. Am J Sports Med. 2012;40:1871-1879.

288

doi:10.1177/0363546512449998 13

289

23.

Stephen JM, Kaider D, Lumpaopong P, Deehan DJ, Amis A a. The effect of femoral tunnel position

290

and graft tension on patellar contact mechanics and kinematics after medial patellofemoral

291

ligament reconstruction. Am J Sports Med. 2014;42(2):364-372. doi:10.1177/0363546513509230

292

24.

Redler L, Meyers K, Munch J, Dennis E, Nguyen J, Stein BS. Anisometry of Medial Patellofemoral

293

Ligament Reconstruction in the Setting of Patella Alta and Increased Tibial Tubercle-Trochlear

294

Groove (TT-TG) Distance. Arthrosc J Arthrosc Relat Surg. 2016;32(6):e10.

295

doi:10.1016/j.arthro.2016.03.054

296

25.

297 298

LaPrade RF, Engebretsen AH, Ly T V, et al. The anatomy of the medial part of the knee. J Bone Joint Surg Am. 2007;89(9):2000-2010. doi:10.2106/JBJS.F.01176

26.

Grood ES, Suntay WJ. A joint coordinate system for the clinical description of three-dimensional

299

motions: application to the knee. J Biomech Eng. 1983;105(2):136-144.

300

http://www.ncbi.nlm.nih.gov/pubmed/6865355. Accessed October 2, 2018.

301

27.

Gilbert S, Chen T, Hutchinson ID, et al. Dynamic contact mechanics on the tibial plateau of the

302

human knee during activities of daily living. J Biomech. 2014;47(9):2006-2012.

303

doi:10.1016/j.jbiomech.2013.11.003

304

28.

Pennock AT, Alam M, Bastrom T. Variation in tibial tubercle-trochlear groove measurement as a

305

function of age, sex, size, and patellar instability. Am J Sport Med. 2014;42(2):389-393.

306

doi:10.1177/0363546513509058

307

29.

Song SY, Pang C-H, Kim CH, Kim J, Choi ML, Seo Y-J. Length Change Behavior of Virtual Medial

308

Patellofemoral Ligament Fibers During In Vivo Knee Flexion. Am J Sports Med. 2015;43(5):1165-

309

1171. doi:10.1177/0363546514567061

310

30.

Fabricant PD, Ladenhauf HN, Salvati EA, Green DW. Medial patellofemoral ligament (MPFL) 14

311

reconstruction improves radiographic measures of patella alta in children. Knee.

312

2014;21(6):1180-1184. doi:10.1016/J.KNEE.2014.07.023

313

31.

314 315

Dejour H1, Walch G, Nove-Josserand L GC. Dejour_Factors of patellar instability an anatomic radiographic study. Knee Surg Sport Traumatol Arthrosc. 1994;2(1):19-26.

32.

Nho SJ, Magennis EM, Singh CK, Kelly BT. Outcomes after the arthroscopic treatment of

316

femoroacetabular impingement in a mixed group of high-level athletes. Am J Sports Med.

317

2011;39 Suppl:14S-9S. doi:10.1177/0363546511401900

318

33.

Elias JJ, Cosgarea AJ. Technical Errors During Medial Patellofemoral Ligament Reconstruction

319

Could Overload Medial Patellofemoral Cartilage: A Computational Analysis. Am J Sports Med.

320

2006;34(9):1478-1485. doi:10.1177/0363546506287486

321

34.

Tateishi T, Tsuchiya M, Motosugi N, et al. Graft length change and radiographic assessment of

322

femoral drill hole position for medial patellofemoral ligament reconstruction. Knee Surgery, Sport

323

Traumatol Arthrosc. 2011;19(3):400-407. doi:10.1007/s00167-010-1235-9

324

35.

Tischer T, Geier A, Lenz R, Woernle C, Bader R. Impact of the patella height on the strain pattern

325

of the medial patellofemoral ligament after reconstruction: a computer model-based study. Knee

326

Surgery, Sport Traumatol Arthrosc. 2016. doi:10.1007/s00167-016-4190-2

327

15

328 329 330 331

Figure 1. Candidate femoral attachment sites of MPFL tested (shown as a triangle, square, diamond and X) relative to the posterior femoral cortex and Blumensaat’s line.

332 333

Table 1: Demographic and Anatomic Data of Specimens Specimen 1 2 3 4 5 6 7 8 9 10

Age/Sex 57/M 63/M 69/M 62/M 52/M 60/F 57/F 57/M 44/F 52/F

Native CDI 1.06 0.95 0.87 1.02 0.90 1.08 0.96 0.91 1.16 0.94

334

16

335 336 337 338

Figure 2. Schematic of the test set-up showing load applied to the quadriceps tendon resulting in knee flexion/extension. The candidate femoral attachment points are again shown as a triangle, square, diamond and X.

339

340 341 342

Figure 3. Mean MPFL length change throughout range of motion in the setting of Native tibial tubercle location. The femoral attachment at Schottle’s point resulted in the most isometric reconstruction.

343 17

344 345 346

Figure 4. Mean MPFL length change throughout range of motion in the setting of alta 1.3. The reconstruction with the femoral attachment 5mm proximal to Schottle’s point was most isometric.

347

348 349 350 351

Figure 5. Mean MPFL length change throughout range of motion in the setting of alta 1.4. As with alta of 1.3, the reconstruction with the femoral attachment 5mm proximal to Schottel’s point was most isometric when alta was 1.4.

352

18

353 354 355 356

Figure 6. Mean MPFL length change throughout range of motion in the setting of alta 1.5 The reconstructions with the femoral attachments 5mm and 10mm proximal to Schottle’s point were both isometric.

19