Magnetic resonance imaging has emerged as an important modality in the non-invasive evaluation of osseous and soft-tissue structures in the post-traumatic knee. However, it is sometimes radiologically impossible to determine with confidence if a focus of high signal intensity in the meniscus is confined to the substance of the meniscus or if it extends to involve the joint surface. This is a critical differentiation because the latter represents menisci tears that can be found and treated arthroscopically, whereas the former represents degradation, intrasubstance tears or perhaps normal variants that are not amenable to arthroscopic intervention.

The aim of this study was to investigate the occurrence of altered signal intensity in the posterior horn of the medial meniscus in correlation with arthroscopic findings.

Sixty-four patients with suspected post-traumatic internal derangement of the knee who underwent magnetic resonance imaging prior to arthroscopy were evaluated retrospectively. There were 48 males and 16 females. Mean age was 28.2 years. Tears of the posterior horn of the medial meniscus were diagnosed unequivocally (Grade 3 signal) in 18 patients and equivocally (Grade 2/3 signal) in 10 patients. Arthroscopic correlation revealed 16 tears (89%) in the unequivocal group and only one tear (10%) in the equivocal group).

A meniscal tear is unlikely when magnetic resonance imaging shows a focus of high signal intensity in the posterior horn of the medial meniscus that does not unequivocally extend to involve the inferior or superior joint surface. An appropriate trial of non-operative treatment is recommended in such questionable cases. Magnetic resonance imaging is a useful diagnostic tool, however, it should be used selectively, and in conjunction with history and clinical examination in evaluating internal derangement of the knee.

Introduction: Surgical treatment of unstable fractures of the pelvic ring is a well established technique both to stabilise the ring and reduce bleeding and to facilitate healing in an anatomic position and thereby facilitate rehabilitation. While the pathoanatomic differences between vertically and rotationally unstable fractures are well known, the purpose of this paper is to highlight the difference in expected outcome for these two injuries.

Objective: To review the clinical and radiological outcome following operative treatment of unstable fractures of the pelvic ring and compare the outcome for type B and type C injuries.

Design: Retrospective study of patients treated consecutively with review of initial admission notes and clinical and radiological follow-up.

Patients: From January 1988 to July 1997, one hundred and sixteen patients were treated with traumatic disruption of the pelvic ring. Of these, ninety-five with type B or C fractures required definitive surgical stabilisation of their injuries, forty-five with Tile type B fractures and fifty with Tile type C fractures. There were sixty-three males and thirty-two females with an average age of thirty-three years.

Intervention: All patients had operative treatment for definitive management of pelvic ring disruptions.

Outcome measures: All patients were reviewed clinically and radiologically at a mean of fifty one months. Clinical review consisted of assessment of persistent pain, ability to ambulate, ability to return to work, clinical evidence of persistent instability of mal union. Radiological review was for evidence for mal union or non union.

Results: At final review (mean fifty-one months) ninety-one patients were independently mobile. Of the four patients who required a stick or crutch, two had type B2.1 fractures and two had type C1.3 fractures. Three of these patients had associated acetabular fractures and this may have been contributory.

Sixty patients were completely pain free at follow up. Seventeen patients complained of occasional mild pain after exercise but did not require analgesia. Eleven patients had moderate pain that occasionally required analgesia. Seven patients had severe causalgic type pain, all of who had had evidence of nerve injury at presentation. Only type C fractures with neurologic deficit at presentation had severe pain at follow up. Overall the incidence of pelvic pain, both anterior and posterior, was significantly higher in type C fractures.

There were three non unions, all in type C fractures and one of these required surgery. There were fourteen mal unions, nine leg length discrepancies in type C fractures and five patients with a significant internal rotation deformity of greater than 15° in type B fractures.

Conclusions: The outcome of surgical treatment of unstable pelvic fractures is worse following vertically and rotationally unstable fractures (type C) than after fractures that are only rotationally unstable (type B). This is valuable information when considering the prognosis for these injuries.