Management of proximal tibiofibular joint instability

OVERVIEW

Chapter synopsis

Proximal tibiofibular joint instability is an uncommon injury that can often be difficult to diagnose. Anterior instability is the most common pattern of instability involving disruption or attenuation of the posterior ligaments. If conservative treatment fails, anatomic reconstruction of the posterior ligaments can restore stability and reduce symptoms.

Important points

The presentation is often atraumatic or confusing in nature
Conservative treatment methods should be exhausted before considering operative intervention.
A thorough exam to rule out other pathologies and assess for generalized ligamentous laxity is an important part of the workup.
Liberal use of diagnostic injections and taping/bracing can be helpful to confirm the diagnosis

Clinical/surgical pearls

Great care must be taken while dissecting out the peroneal nerve in the setting of gross instability that can distort the normal anatomy and location of the nerve.
The fibular tunnel is drilled anterior to posterior to recreate the posterior proximal tibiofibular ligaments and to avoid injury to the fibular collateral ligament attachment laterally
Confirm anatomic reduction of the fibular head while tensioning the reconstruction graft at 60 degrees of knee flexion and neutral rotation.

Clinical/surgical pitfalls

Confirm the location of the fibular guide pin before reaming to decrease the chance of a fibular head blowout.
Avoid blowout into the proximal tibiofibular joint when reaming the tibial tunnel by confirming pin placement with fluoroscopy prior to reaming.

Introduction

Proximal tibiofemoral joint instability is an exceedingly rare injury. Ogden, who first described the anatomy of the proximal tibiofibular joint (PTFJ) in 1974, predicted that there were as few as 108 cases of PTFJ instability in the preceding century. ^, The rationale for the uncommon nature of this condition is due to its highly protected anatomic location with extensive attachments that provide it with stability. Since Ogden’s initial paper, recent data has suggested that PTFJ instability may be more common than Ogden had described. In one investigation, 9 out of the 22 volunteers from the San Diego marathon in 1994 exhibited PTFJ hypermobility. While hypermobility does not equal symptomatic instability, this study suggests that there might be more laxity and mobility about the joint than was initially thought, and it may not be quite as protected from instability as initially believed.

Pre-operative considerations

Anatomy

The PTFJ is a synovial joint that exhibits variable shape and orientation. The fibula has a triangular cartilage surface, and the corresponding tibial articular cartilage has an ovoid or circular surface. The most common shape is a saddle shape or a trochoid shape. The PTFJ is known to communicate with the knee joint in approximately 12% of cases. Functionally, however, the orientation of the joint is more important than its shape. The oblique orientation is the most common variant, present in up to 85% of individuals. Looking from the lateral radiographic projection, if the joint is deviated more than 20 degrees off the horizontal axis, then it is considered an oblique joint. If the PTFJ is less than 20 degrees off of the horizontal axis, it is considered a horizontal joint. Ogden reported that up to 70% of the cases of instability were seen in this more common oblique orientation. ^,

The PTFJ has abundant soft tissue attachments. Structures that act to reinforce the PTFJ include the PTFJ ligaments, fibular collateral ligament (FCL), biceps femoris, popliteofibular ligament (PFL), and other nearby muscular attachments. In general, these structures tend to relax in flexion, so there is some normal laxity to anterior translation at 90 degrees of knee flexion. More recently, LaPrade et al. further elucidated the anatomy of the PTFJ by re-examining the locations and biomechanical properties of the PTFJ ligaments. ^, The anterior ligaments are thicker and more numerous, with between 1 to 4 bands found anteriorly. In contrast, the posterior ligaments are thinner and typically are the ones more frequently injured with instability.

Patient history and presentation

The patient may either present with traumatic injury with dislocation of the proximal tibiofibular joint or with atraumatic subluxation of the PTFJ. Atraumatic subluxation is often more common in patients with generalized ligamentous laxity or with formal collagen disorders such as Ehlers-Danlos syndrome. Atraumatic subluxations are thought to represent up to 23% of all cases of PTFJ instability. Patients with a history of traumatic injury most commonly have anterolateral dislocations with disruption of the posterior ligaments.

Part of the difficulty in the diagnosis of PTFJ instability lies in the fact that many cases are atraumatic, and many of the traumatic cases may spontaneously reduce, masking the clinical suspicion for this injury. Patients with PTFJ instability often present with very vague symptoms and frequently cannot recall any history of trauma. Therefore, the clinical picture of PTFJ instability can easily be confused with other pathologies. In some instances, patients may have even had previous surgery for some of the other confounding pathologies without relief. Such confounding pathologies include lateral meniscus tears, fibular collateral ligament (FCL) injuries, biceps femoris pathology, and even iliotibial (IT) band syndrome.

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