TREATMENT OF POSTTRAUMATIC LABRAL INTERPOSITION WITH SURGICAL HIP DISLOCATION AND LABRAL REPAIR

Abstract

We report a case of a 12-year-old male with delayed presentation of a spontaneous incongruous reduction of a hip dislocation due to labral-chondral acetabular rim fragment entrapment The patient was treated with a staged hip arthroscopy and subsequent surgical dislocation and open repair. At two-year follow-up, the patient had an excellent clinical and radiographic outcome.

INTRODUCTION

Traumatic hip dislocation in children is a relatively un-common injury. Failure to achieve concentric reduction of the hip is a complication of the injury,^1-9 and can be overlooked,^2-3,9-12 especially in patients with spontaneous reduction.^10-12 Labral interposition has been reported as a potential mechanical block to concentric reduction in both children^{1-3,5-9,11-15} and adults.^4,16-20 Labral interposition has historically been treated with excision^{4,6,11,16-18,20} to en-able anatomic reduction. However, as our understanding of the importance of labral function has changed, surgical techniques of labral repair have been popularized.

To minimize the risk of femoral head osteonecrosis, open reduction of the dislocated hip with labral interposition has generally been performed through a surgical approach from the direction of dislocation.²¹ As our understanding of the vascularity of the femoral head has improved, open surgical hip dislocation has been applied to the treatment of a variety of intra-articular hip disorders.^22-23 We report the case of a 12-year-old male child with a history of a spontaneously reduced traumatic hip dislocation and delayed presentation with a painful, incongruous hip reduction. Diagnostic arthroscopy revealed an incarcerated labral-chondral acetabular rim fragment that was repaired definitively via a surgical hip dislocation approach.

CASE REPORT

A 12-year-old male presented to our clinic with persistent left hip pain two months after a left hip injury. The patient was involved in an accident during competitive waterskiing, and he reported a flexion/adduction injury with immediate onset of severe left hip pain. He was un-able to bear weight on the extremity and was evaluated in a local emergency room. Radiographs were reportedly normal at that time and the patient was managed with symptomatic measures, crutches and protected weight bearing. After four weeks, he continued to have pain that prevented him from progressing his weightbearing status. MRI obtained four weeks after injury showed sequelae of a hip dislocation including osteochondral fragments within the joint, fracture of the lip of the posterior acetabular wall, and ligamentum teres rupture. The patient was evaluated by an orthopaedic surgeon who recommended continued conservative treatment given that the osteochondral fragments appeared to involve the non-weightbearing portion of the femoral head. The patient was maintained non-weightbearing for an additional four weeks.

Eight weeks after injury, the patient continued to show minimal improvement in his symptoms and progression of weight bearing was not tolerated. A repeat MRI was performed which demonstrated unchanged osteochondral fragments within the joint and a widened medial joint space. The patient was referred to our institution for evaluation and treatment.

Physical examination demonstrated a healthy appearing 12-year-old male. With attempted ambulation the patient experienced severe hip pain and demonstrated a severe limp. The left hip was very irritable with range of motion testing and he had positive impingement and Patrick's tests. Range of motion was 95 degrees of flexion, 20 degrees internal rotation in flexion, and 30 degrees external rotation in flexion. Plain radiographs demonstrated persistent medial joint-space widening with a possible loose body entrapped in the medial joint (Figure 1A-B). ACT scan demonstrated a small avulsion fracture of the posterior rim and a small intra-articular loose body (Figure 1C-D). Therefore, the patient was diagnosed with an incongruous reduction due to labral and/or osteochondral fragment incarceration.

Figure 1.

(A,B) Preoperative AP pelvis and frog-leg lateral radiographs demonstrate subtle widening of the medial joint space. (C,D) Preoperative CT axial and coronal images demonstrate a loose body (arrow) within the joint.

Due to persistent pain, an incongruous reduction and mechanical obstruction to anatomic head reduction, hip arthroscopy was recommended for definitive diagnosis and potential definitive treatment. The patient was taken to the operating room for arthroscopic assessment with loose body removal, reduction of labral interposition, and possible labral debridement or repair. At arthroscopy, we observed a large posterosuperior, labral/acetabular rim chondral avulsion fragment entrapped within the acetabular fossa (Figure 2A). This tissue was relatively immobile due to surrounding fibrous scar tissue. The anterior labrum appeared intact and stable, but was con-tused and had adjacent synovitis (Figure 2B). No major chondral injury to the acetabular surface was noted. Abrasions were observed on the femoral head over a 2 × 2 cm area in the superior and anterosuperior regions. Due to the large size, posterior location and established scarring, the decision was made to offer definitive treat-ment of the posterior rim avulsion with an open surgical dislocation procedure.

Figure 2.

Arthroscopic images demonstrate (A) entrapped, irreducible posterior labral-chondral complex avulsion (*) and (B) extensive synovitis throughout the joint. Intraoperative images from surgical hip dislocation demonstrate (C) entrapped labral-chondral complex avulsion, (D) reduction of fragment to acetabular rim, (E) labral repair, and (E) final repair.

One week after arthroscopy, an open surgical hip dislocation with trochanteric flip osteotomy was performed.²² The entrapped posterior labrum was attached to a 2 × 1 cm avulsed epiphyseal fragment from the acetabular rim that was adherent to the acetabular fossa (Figure 2C). The fragment and labrum were dissected free from surrounding scar tissue and the epiphyseal fragment was excised. A small portion of the posterior-inferior labrum was severely macerated and was excised. The remainder of the labrum was repaired to the posterior rim (Figure 2D-F).

The patient was managed postoperatively with continuous passive motion (CPM), isometric exercises and progressive weight bearing and strengthening. Specifically, he was toe-touch weight bearing for four weeks and then progressed to full weight bearing. Active exercises were initiated at four weeks and resistance strengthening started eight weeks after surgery. The patient was released to full activities four months after the surgical dislocation procedure. At two-year follow-up, the patient had no residual pain or limitations. His Harris Hip Score was 100 points. He demonstrated full symmetric range of motion and no radiographic changes of avascular necrosis or joint-space loss (Figure 3). He was able to return to unrestricted activities including competitive water-skiing.

Figure 3.

AP pelvis radiograph two years postoperatively demonstrate restored joint congruency and trochanteric osteotomy union.

DISCUSSION

We present a case of a 12-year-boy with a presumed hip dislocation and spontaneous incongruous reduction following a waterskiing accident This patient presented to us eight weeks after the injury with persistent pain and inability to bear weight Arthroscopy revealed an entrapped posterior labrum and rim epiphysis fragment An open surgical dislocation with excavation of the entrapped posterior labrum from the acetabular fossa and labral repair was then performed. At two-year follow-up, the patient had an excellent clinical result and radiographic outcome.

In children with hip dislocations, soft tissue interposition preventing congruous hip reduction has historically been reported to be rare,¹³ but more recent series have noted it to be present in 7.5-25% of cases.^1,6-7,9,15 Incongruous reductions have been most commonly reported secondary to labral interposition, osteochondral fragments, and capsular interposition.^1-15 In one large series, approximately 25% of patients required surgical intervention for labral interposition or osteochondral fragments¹. One study noted difficulty in obtaining a concentric reduction as more common in children six to ten years old.¹⁵

Several authors have reported acute labral entrap-ments with associated epiphyseal avulsion fragments in children.^2-3,5 Chun et a.1⁵ reported a case of entrapment of a posterior labral avulsion with an attached epiphyseal fragment in a child following posterior dislocation. This was treated with fragment excision and labral repair from a posterolateral approach.

In cases of spontaneous reduction, the lack of radio-graphic confirmation of dislocation may lead to delayed diagnosis and failure to recognize incongruous reduction²¹, as occurred in this case. Only a few cases of soft tissue interposition after spontaneous reductions of hip dislocations in children have been reported.^10-12 Cases of unrecognized incongruous reductions have been associated with poorer outcomes,^1-2,12 but rarely avascular necrosis. Incongruous reductions are most commonly noted by widening of the medial joint space on plain radiographs.^1,6-10,19,21 Additionally, a break in Shenton's line has also been reported as a significant finding.⁹ In this case, even at presentation to our institution two months after injury, medial joint space widening was evident on plain radiographs. Some authors have reported that up to 3 mm of joint space widening may be due to hematoma or joint laxity,^1,8,24 while other have questioned this assertion.^3,11,21,25 Nevertheless, this finding should raise suspicion regarding an entrapped labrum or osteochondral fragment, especially when this radiographic finding is associated with persistent hip symptoms.

Evidence of joint-space widening should be investigated with further imaging, including computed tomography (CT) or magnetic resonance imaging (MRI).^3,7,21 Radiographs may not demonstrate subtle widening or noncalcified loose bodies that can be seen with CT. However, advanced imaging techniques may fail to accurately identify the cause of incongruous reduction, as occurred in this case.

In children with hip dislocations, avascular necrosis is of particular concern. Rates of avascular necrosis after isolated hip dislocation in children have been reported to be 3-15%.^1,8,21 As with adults, posterior hip dislocations in children are much more common than anterior dislocations.²¹ Open reductions of irreducible or incongruous hip dislocations have generally relied on posterior approaches, with authors generally recommending a surgical approach which protects femoral head vascularity.¹¹ In adults, Epstein recommended avoiding anterior approaches after posterior dislocations due to concern for the ascending branch of the lateral femoral circumflex artery and several cases of avascular necrosis.^26-27 In a recent review of dislocations in children, Herrera-Sota et al.²¹ recommended an approach from the direction of dislocation. However, anatomic studies have not supported this, with evidence that the primary blood supply is from the medial femoral circumflex artery.^22-23 Siebenrock and Ganz have demonstrated that based on this knowledge, open surgical hip dislocation can be performed without compromising the femoral head vascularity in patients with acetabular fractures or femo-roacetabular impingement^22,28 Open surgical dislocation has been reported to be successfully utilized in patients with fractures associated with hip dislocations, including acetabular fractures and femoral head fractures. The use of surgical dislocation has also been reported in children for slipped capital femoral epiphysis and other hip deformities.

This approach allows for superior visualization com-pared to traditional posterior approaches.^22,28-29 Several authors have reported missed intra-articular pathology at open reduction if the femoral head is not redislocated.^9,18 Good visualization of intra-articular pathology, especially labral interposition, is important for not only detection but treatment at time of open reduction in cases where labral interposition is present. Leunig et al.³⁰ reported the use of surgical dislocation in a series of adults with acetabular fractures and concomitant labral avulsions.

The importance of the labrum to normal hip function has been only recently recognized.^31-33 In patients with femoroacetabular impingement, preliminary evidence has shown superior outcomes of patients with labral repair compared to labral debridement.^34-35 Labral preservation is likely equally important in hips after traumatic dislocation. The use of a surgical approach, which allows for adequate visualization and access for labral repair, is important when open reduction is performed. Preoperative imaging studies can aide in identifying the cause of incongruous reduction.

CONCLUSION

We report a case of a 12-year-old male with delayed presentation of spontaneous incongruous reduction of a hip dislocation due to a labral-epiphyseal fragment entrapment. The patient was treated with a staged hip arthroscopy and subsequent open repair. At two-year follow-up, the patient had an excellent clinical and radiographic outcome.

In this case we utilized hip arthroscopy for diagnostic purposes and for potential treatment as loose body removal or labral excision could have been performed arthroscopically. Due to the size, location, scarring and possibility for labral repair, definitive treatment was performed with a surgical dislocation approach.