Focus on the tubercle transfer: Avoid complications, choose fixation
Surgical treatment of patellar instability has many components and successful outcomes have been reported with many different techniques. Colvin and West noted that more than 100 different surgical techniques or variations for treatment of patellofemoral instability existed in the orthopaedic literature. They also appropriately note that “instability of the patellofemoral joint is a multifactorial problem. Patellar stability relies on the limb alignment, the osseous architecture of the patella and the trochlea, the integrity of the soft tissue constraints, and the interplay of the surrounding muscles.”
What is fascinating today is that we have a multitude of surgical procedures that can deal with almost any anatomic factor noted in this review. Medial patellofemoral ligament reconstruction and lateral release (soft tissue constraints), trochleoplasty (osseous architecture) and tibial tubercle osteotomy (patellofemoral alignment and muscle balance) are all popular methods for treating recurrent patellar instability. Many of these common surgical methods can be combined in order to potentiate the overall effectiveness of surgical intervention. Each of the surgical methods named above can supplement the others by changing one aspect of the overall patellofemoral joint anatomy.
Jeffrey T. Sprang
Each of the surgical procedures relies on bony or soft tissue healing that must take place in order for the technique to be successful. One of the most commonly used surgical techniques is the tibial tubercle osteotomy. This blog will strive to focus less on indications for surgery and more on how proper osteotomy and fixation techniques can minimize complications while ensuring the maximum biomechanical benefits from a Fulkerson type tibial tubercle transfer.
Tibial tubercle osteotomy/Fulkerson principles
In his classic article in 1983, Fulkerson went into great detail about the oblique tibial tubercle osteotomy that would soon come to bear his name. In the article, Fulkerson made many technique points that bear review today as they help the surgeon to avoid some of the more common complications that have been reported in the medical literature since the popularization of the surgical technique. First, this osteotomy was acknowledged to be an evolution of previously described tibial tubercle osteotomy techniques that focused on medialization including the Elmslie-Trillat technique. Obliquely orienting the osteotomy allows manipulation of both the medialization of the tubercle and the anteriorization.
Other important principles outlined in the original technique include maintaining a fairly long bone fragment (perhaps 10 cm or more) from superior to inferior. Just as important is the admonition to try to slope the osteotomy so that the distal portion of the bone fragment maintains a small amount of continuity with the tibia, allowing the distal portion of the bone fragment to either remain intact or be of sufficiently small size that it may be green-sticked with movement of the bone fragment up the created slope. By avoiding a step-cut at the inferior pole of the patella, a stress riser in the anterior tibia can be avoided.
Of supreme importance is the cut on the lateral and proximal portion of the osteotomy that allow linkage of a transverse cut (behind the patellar tendon on the tibial tubercle) and the proximal end of the oblique saw cut. This oblique “back cut” allows the osteotomy to exit the proximal tibia without excessive cutting into the metadiaphysis of the tibia.
While all surgeons strive to minimize the length and breadth of incisions and surgical dissection visualization of the lateral and proximal tibia allows proper placement of this “back cut” in relation to the patellar tendon insertion and the proximal and lateral extent of the oblique cut.
In addition, extending the incision inferiorly allows good visualization of the distal end of the osteotomy allowing good control of the exit of the osteotomy on the anterior tibia.
Every surgery that gains in popularity is bound to have postsurgical complications. Fortunately, the reported clinical results of tibial tubercle transfer (either alone or in conjunction with other procedures) remains good. A careful review of some of the most commonly reported tubercle transfer complications provides good insight into some of the ways the postoperative course can be interrupted by problems.
In some cases patients were transitioned to full weight-bearing too soon and strenuous activities were attempted before the osteotomy had completely consolidated. Appropriate healing must be seen on postoperative radiographs and even then return to strenuous activities should be limited until at least 6 months post-surgery. Other authors have advocated a slow and gradual return to competitive sporting activities between 9 months and 12 months postoperatively.
In one retrospective series reported by Moyer, the distal end of the osteotomy was thought to be a contributing factor to a series of tibia fractures in the postoperative period. The authors ultimately recommended a gradual sloping exit to the distal osteotomy as it exits the tibia in order to eliminate a proven stress riser. Certainly osteotomy healing is individualized and return to activity should be closely monitored. A gradual resumption of loading and running could allow the tibia to slowly adjust to increasing loads and stresses after tibial tubercle osteotomy.
Many techniques have been described for fixation of Fulkerson and Elmslie-Trillat osteotomies. Authors have noted that 3.5-mm, 4.5-mm and 6.5-mm repair constructs have been used with some authors advocating single, double or triple screws. Recently our research group has investigated two of the more common repair constructs in an effort to evaluate the strengths and weaknesses of different fixation techniques.
We elected to compare Fulkerson osteotomies in our musculoskeletal laboratory that had been fixed with two 4.5-mm screws vs. osteotomies that had been fixed with three 3.5-mm screws. In our loading protocol both techniques performed equally well in matched-pair cadaveric specimens leading us to conclude that both fixation methods were entirely appropriate.
As we reviewed our clinical findings, it became apparent that patients who had undergone fixation using two 4.5-mm screws had painful or prominent hardware removed at a much higher rate than patients who had undergone fixation using three 3.5-mm screws (63 total patients: 7/31 with 4.5-mm screws removed and 0/32 with 3/5mm screws removed). This is despite our efforts to countersink and appropriately control for screw head size.
In all cases, the tibial osteotomies had gone on to uneventful union indicating that both repair constructs seemed to perform well in the clinical setting.
As one of the most common surgical treatments for patella dysfunction tibial tubercle osteotomy is a powerful procedure for changing patellofemoral biomechanics. By revisiting some of the most common reported complications surgeons can ensure that their techniques minimize the chance of tubercle failure, hardware prominence or tibial nonunion. Selecting appropriate osteotomy cuts while avoiding notching, extending recovery times to ensure tibial remodeling is complete and potentially using less prominent fixation can allow surgeons to proceed with confidence when using tibial tubercle osteotomies.
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Jeffrey T. Spang, MD, is an assistant professor with the Department of Orthopaedics at the University of North Carolina in Chapel Hill, N.C. He specializes in sports medicine.
Disclosure: Spang has no relevant disclosures.