Avulsion fractures of the tibial tubercle

INTRODUCTION

Avulsion fractures of the tibial tubercle are rare, accounting for <3% of all epiphyseal injuries and 1% of all physeal injuries.1,2 Several case series have been reported.2-6

We conducted a retrospective study to assess its epidemiology and treatment after 5 such cases occurred within one year in our hospital region, which serves a relatively small population.

MATERIALS AND METHODS

Records of 12 patients aged 11 to 17 (mean, 14) years with avulsion fractures of the tibial tubercle presenting to our hospital from April 1998 to September 2004 were retrospectively studied. Patient age, gender, involved side, injury mechanism, clinical and radiographic records, treatment, complications, and outcomes were reviewed. Fractures were categorised according to the modified Watson-Jones classification7 (Table 1) and clinically evaluated (Table 2).

RESULTS

Only one patient was female. Eight patients injured the right side, 3 the left side, and one both sides. They all engaged in sports or active play during the injury. Patient 1 had pre-existing Osgood Schlatter disease and was symptomatic prior to the injury. Two fractures were type IA, one type IB, 2 type IIB, 5 type IIIA, 2 type IIIB, and one type IV (Table 3). Patient 11 had associated patellar tendon avulsion.

Three patients with type-I fractures and one with a type-IIB fracture were treated with closed reduction and cast immobilisation (casting in extension) for 3 to 4 (mean, 3.8) weeks. The remaining 9 fractures were treated with open reduction and internal fixation; 4 were fixed with a single screw via a vertical incision just lateral to the tibial tubercle and periosteal suture, 3 with double screws (Fig.), and 2 with transfixing pins. Care was taken to avoid crossing the epiphyseal plate with the screws or pins. Rehabilitation emphasised restoration of knee movement and quadriceps strength.

The mean follow-up period was 39 (range, 23-59) months. No patient was lost to follow-up. No wound infections, hardware failures, or limb deformities (specifically genu recurvatum) were noted. At 6 months, the 12 affected legs had achieved a full range of knee movement. Ten patients had excellent results; 2 had fair results (patient 6 had persistent pain after vigorous activity and patient 9 had a loss of flexion of <10°). The hardware was removed from 7 patients.

DISCUSSION

Tibial tubercle avulsion is a rare injury, with incidence rates of 0.4 to 2.7% of all epiphyseal injuries.1,2,6 It may occur acutely or after a long history of apophysitis. Though an association with the Osgood-Shlatter disease has been suggested, no causal relationship has been found.2,5,8

The mean age at presentation is 14 (range, 13-16) years,1,2,6 but pre-adolescent (10-12 years of age) cases have also been reported.5,9 The youngest patient reported was a 9-year-old boy with a type-IA fracture.6 Tibial tubercle fractures almost always occur in males.1,3,6,8,10 This preponderance may be due to the greater proportion of males participating in jumping activities during adolescence, and increased exposure of physiologic epiphysiodesis of the proximal tibial tubercle at later ages.6,10

Injury mechanisms are either due to violent contraction of the quadriceps during extension (as in jumping) or by acute passive flexion of the knee against a contracting quadriceps (such as landing after a jump or fall).3,4 In a study of 2 adolescent gymnasts with tibial tubercle avulsions, extension strength of the contralateral and injured knee was found to be greater than that in non-athletic controls and their peers. The greater-than-usual strength of the quadriceps was able to overcome the strength of the tibial tubercle.11

The Watson-Jones classification originally categorised tibial tubercle fractures into 3 types,7 and was later modified with the addition of groups A and B to describe the level of comminution and displacement of the fragment.4 The type-IV avulsion fracture extends posteriorly through the physis and may displace the entire epiphysis with the tubercle.12 The group-C fracture includes possible avulsion of the patellar ligament.9

Acute tibial tubercle fractures may be associated with other knee injuries, particularly of the patellar and quadriceps tendons.2,3 Six cases of simultaneous patellar tendon avulsion and avulsion fracture of the tibial tubercle have been reported.2,6,9,13 Simultaneous quadriceps disruption and fracture of the tibial tubercle has also been reported.6

The goals of treatment are anatomic reduction of the fragment, restoration of extensor mechanism alignment, and maintenance of congruency of the tibial articular surface.3,6,10 Minimally displaced, small avulsion fragments have been treated successfully by closed reduction and cast immobilisation, with the knee extended.2,6,8 Two type-I and one type-II fractures were successfully treated with this method.8 Even in severely displaced fractures, before resorting to open reduction and internal fixation, an attempt at closed reduction is recommended.8 Persistence of even a small gap between the distal end of the tubercle and the adjacent metaphisis may indicate an interposed flap of periosteum.8

Most series recommend open reduction and internal fixation for all displaced fractures.2,3,6,8,10 A midline vertical incision is advocated to facilitate knee surgeries. A lateral parapatellar incision is a more direct approach and less likely to injure the infrapatellar branch of the saphenous nerve.14 Depending on the size of the avulsed fragment, fracture pattern, surgeon preference, and patient's age, fixation can be attained by pins or screws, and reinforced by repair of the torn periosteum.

Complications include loss of flexion, non- or mal-union, genu recurvatum, skin necrosis, patella infera, compartment syndrome, and deep venous thrombosis. Other than prominent screws, many series have reported no complications resulting from treating this fracture.2-6,15 As most of these injuries occur in adolescents near the end of growth, genu recurvatum is rarely of concern; only one such case has been reported.4

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