Indications espoused for tuberosity surgery (often in combination with proximal soft tissue surgery) at one point included patellofemoral pain, instability, chondrosis, and arthrosis. Straight tibial tuberosity medialization (TTM) was initially associated with the names of specific surgeons, including Roux,² Elmslie, and Trillat³; anteriorization with Maquet⁴; and anteromedialization (AMZ) with Fulkerson.⁵ These tuberosity surgeries have, at times, been used to treat static patellar subluxation, recurrent lateral patellar instability, patellar pain, and patellofemoral chondrosis. Tuberosity surgery for treatment of recurrent or chronic patellofemoral dislocation or subluxation was based on the assumption that the primary pathologic process was in an increased Q (quadriceps) angle; for pain and chondrosis, elevation was promoted as the preferred procedure to dramatically decrease patellofemoral stress. Whereas it is obvious that repositioning of the distal point of the Q angle (tibial tuberosity) surgically does modify the Q angle, today the MPFL is accepted as the main restraint to lateral patellar instability. In fact, the Q angle, which formed the rational basis for planning of a TTM, is being questioned as a benchmark in light of the poor intraobserver reproducibility of the measurement as reviewed by Post.⁶ In addition, Fithian has questioned the role of TTM for lateral patellar instability. At the annual meeting of the American Orthopaedic Society for Sports Medicine in 2005, he presented a case series of recurrent lateral patellar instability treated by MPFL reconstruction with or without TTM. The results were the same in both groups. On the other hand, it must be acknowledged that Carney et al¹ has reported excellent long-term results in prevention of recurrent patellar instability with TTM, although critics note that his report is a clinical outcomes series without radiographs that might have demonstrated arthrosis (as predicted to occur with excessive medialization of the tuberosity in biomechanical studies by Kuroda et al⁷). Furthermore, because the extent of medialization with TTM has been variably defined, critics could imply that (1) some of the patients with instability successfully treated by TTM experienced spontaneous healing of the MPFL, (2) the MPFL lesion was marginally injured, or (3) the TTM “overmedialized” the tuberosity and constrained the patella into stability.

From a basic science approach, the initial tuberosity surgery focused on the action of the various force vectors on patellar position and motion and on the effect of tuberosity position on those vectors. However, the equation is more complicated; Teitge and colleagues,⁸ Powers and colleagues,⁹ Heino and colleagues,¹⁰ and others have emphasized the importance of the “other half” of the joint in motion—the trochlea and associated tibiofemoral torsion. Furthermore, Dejour and colleagues¹¹ have drawn attention to the importance of trochlear morphologic features (dysplasia) in patients with lateral patellar instability. In a comparative study, Paulos and colleagues¹² reviewed the efficacy of derotational high tibial osteotomy in the setting of significant tibial torsion, reporting that patients receiving derotational procedures had improved outcomes and had more symmetrical gait patterns than patients who underwent proximal-distal realignment. This finding was echoed by Fouilleron and colleagues,¹³ who reported very high satisfaction rates after derotational osteotomy for patients with femorotibial malrotation. Continued investigation is needed to better define the role of derotational osteotomies. In an attempt to objectify tuberosity surgery, we must define normal and abnormal positions of the tuberosity. We must in addition consider the extent of femoral internal torsion and tibial external torsion as per Teitge⁸ and Heino and colleagues.¹⁰

This objective approach to limb coronal and axial alignment from hip to ankle also measures (at the knee) an objective alternative to the Q angle, that is, the tibial tuberosity–trochlear groove (TT-TG) distance (Fig. 91-1). The TT-TG distance, as popularized by Dejour,¹⁴ quantitates the concept of tibial tuberosity malalignment locally at the knee. Studies suggest that a TT-TG distance of more than 15 to 20 mm is abnormal; most asymptomatic patients have distances that are less than 15 mm. Likewise, anteriorization was first shown mathematically to reduce patellofemoral stress, but direct measurement with pressure-sensitive film, real-time pressure transducer arrays, and finite element analysis modeling such as by Cohen and Ateshian show that although stresses are typically reduced with anteriorization, there is a unique response for each knee, and a global 50% force reduction cannot be assumed. More recently, measures of trochlear contact pressures by Rue and colleagues¹⁵ confirmed the utility of straight anteriorization in reducing patellofemoral contact pressure. Thus load transfer should play an important role in surgical planning, as opposed to the assumption that there will be an absolute decrease in stress. With use of these and other objective parameters, further studies may objectively quantify the preoperative pathologic process to aid in planning of tuberosity surgery.