Arthroscopic Osteosynthesis of Femoral Head Malunion

Abstract

We present the case of a femoral head malunion with lateral cephalic femoroacetabular impingement managed by arthroscopic osteotomy/takedown, bone grafting, internal fixation, and cephaloplasty. The treatment rationale and surgical technique are presented. A successful outcome at 3 years was obtained with radiographic evidence of union without osteonecrosis. Even beyond acute femoral head osteosynthesis, arthroscopic surgery may enhance the ability to treat femoral head malunions. Moreover, arthroscopic osteosynthesis may address lateral cephalic FAI, a previously unreported condition.

Historically, the utility of arthroscopic hip surgery was limited to diagnostic and loose body and/or fracture fragment excision. Yamamoto et al.¹ published a series of such patients, mostly with hip dislocations, exemplifying the potential efficacy of this procedure. Moreover, they described one patient as having a Pipkin type 3 fracture-dislocation with an infra-foveal (non–weight-bearing) fragment reduced by closed means and arthroscopically fixated. The author² has since described the arthroscopic reduction and internal fixation of an acute isolated supra-foveal (weight-bearing) fracture fixated with Herbert screws. Moreover, the author has performed a similar procedure on a supra-foveal femoral head fracture associated with an anterior dislocation, again in the acute setting.³

Even less commonly reported, femoral head malunion has been treated only with open procedures. Yoon et al.⁴ reported a series of 3 patients with Pipkin type 1 infra-foveal malunions successfully treated with ostectomy through the Smith-Peterson approach. More recently, Ross and Clohisy⁵ described a case of femoral head malunion causing secondary cam impingement treated with open surgical hip dislocation and osteosynthesis. However, to our knowledge, the arthroscopic management of a femoral head malunion has not been previously described in the orthopaedic literature.

Case

An 18-year-old man presented to our clinic with a history of a fracture of the femoral head caused by a gunshot mechanism. He underwent emergency open reduction and internal fixation of his minimally displaced femoral head fracture with 3 screws and intravenous antibiotics during his 6-day hospitalization addressing his other injuries from a total of 5 bullets. He admits to weight bearing against medical advice 2 months postoperatively, and subsequent radiographs (Fig 1) and computed tomographic images at 5 months showed greater than 1 cm of inferior displacement and malunion without osteonecrosis. One of the screws was broken and another was bent, but no joint space violation or narrowing was seen.

Fig 1.

Preoperative anteroposterior pelvis radiograph detail of the left hip showing malunion of the femoral head (blue arrow) with secondary lateral cephalic FAI (red arrow) because of relative proximal protrusion of the femoral head lateral column, resulting from caudal displacement of the weight-bearing medial femoral head fragment. The bony damage to the lateral acetabular rim should be noted.

The patient was referred for specialty evaluation to determine whether an arthroscopic procedure could address this malunion or whether an open procedure would be necessary for clinical improvement and possible hip preservation. The patient's main complaints were perceived left lower extremity shortening and painful decreased hip motion. The referring surgeon's main concern was the osseous impingement of the intact lateral column of the femoral neck against the acetabular rim and increased risk of premature coxarthrosis.

Pertinent left hip examination findings included a relative 2-cm shortening of the affected lower extremity, positive log roll for pain and limited external rotation to 30°, positive Stinchfield examination, limited abduction to 25°, a positive anterior impingement test with ipsilateral groin pain and internal rotation limited to 15°, and a positive flexion–abduction–external rotation test for groin pain and relative decreased lateral knee–to–examination table distance difference of 5 cm.

The patient elected to proceed with the arthroscopic procedure with the understanding that if unsuccessful, a conversion to a formal open procedure would be performed and further surgery including future hip arthroplasty might be required.

Technical Note

Supine arthroscopic hip surgery with the patient under general anesthesia was performed with the operative hip placed in 10° of hip flexion, 20° of abduction, and 30° of internal rotation. The fluoroscopic templating technique was used to optimize positioning of the operative hip under distraction. We then released the traction (after marking our traction device for efficient reapplication) and percutaneously removed the long screw without incident under fluoroscopic guidance. Traction was reapplied, and the anterolateral viewing portal and the modified mid-anterior portal were established. Initial arthroscopic inspection showed grade 3 chondral changes adjacent to the malunion site, but the remainder of the femoral head cartilage was well preserved. We were unable to remove the smaller screws embedded in the femoral head. Attempts to arthroscopically mobilize the femoral head fragment were unsuccessful, consistent with a malunion. We introduced a 0.25-inch angled osteotome through an anterior portal and arthroscopically performed an osteotomy/takedown of the malunited femoral head fracture (Fig 2). The femoral head fragment was arthroscopically reduced by applying a cephalad-directed force from a straight osteotome positioned on the inferior aspect of a retained bent screw, enabling controlled reduction while distributing impact forces from the osteotome over a broader region (Fig 3). Once an anatomic reduction was verified on arthroscopic and fluoroscopic examination, bone grafting was performed under “dry” arthroscopic guidance. Demineralized bone graft putty (DBX; Synthes, West Chester, PA) was “muzzle loaded” into an arthroscopic cannula and then “injected” into the freshened takedown crevice by impaction with the blunt trocar. Fracture fixation with interfragmentary compression was provided by 3 percutaneous lag screws. Arthroscopic cephaloplasty was performed with a 5.5-mm round bur to remove a residual osteophyte from the lateral femoral head column. Arthroscopic dynamic examination showed improved range of motion without impingement to 120° of flexion, 35° of abduction, and 30° of flexed-hip internal rotation. The patient was admitted for overnight observation because of urinary retention before being discharged home. A supplemental video showing the key steps of this arthroscopic surgical technique is provided (Video 1).

Fig 2.

Supine arthroscopic view of the left hip from the anterolateral portal just before malunion takedown with the osteotome from an anterior portal.

Fig 3.

Intraoperative fluoroscopic anteroposterior view of the left hip after malunion takedown showing the osteotome being used to “straighten” the bent screw (arrow), thereby enabling controlled reduction of the malunited fracture.

Outcome

Three years after arthroscopic surgery, the patient's malunion has united without postoperative displacement. He has no complaints of pain at rest or with most activities and is very pleased with his outcome. He was transitioned from initial non–weight-bearing ambulation with 2 crutches to full weight bearing by 12 weeks and now walks without a limp and can run. His postoperative radiographs (Fig 4) and computed tomography scan show anatomic union without osteonecrosis or osteoarthrosis. There were no major postoperative complications. He has no restriction in activities of daily living, he plays half-court basketball weekly without pain (although we have advised against this), and his postoperative Non-Arthritic Hip Score at 36 months is 78.

Fig 4.

Postoperative anteroposterior radiograph of the left hip after arthroscopic femoral head malunion osteosynthesis with radiographic union and retained joint width.

Discussion

This report presents the heretofore undescribed arthroscopic management of a femoral head malunion and introduces a new form of femoroacetabular impingement (FAI). Lateral cephalic FAI was caused by the relative proximal “protrusion” of the lateral intact column of the femoral head by inferior displacement of the medial femoral head fragment with secondary lateral acetabular rim impingement.

Although one could speculate that a simpler arthroscopic or open osteoplasty of the impinging lateral column could have been preferable, we do not believe so. Resection of the intact lateral femoral head column may have improved hip motion by decreasing osseous impingement but would necessitate removal of the lateral osteochondral surface and not address the leg length discrepancy or disrupted hip biomechanics from an altered center of rotation and compromised abductor mechanism, both of which could contribute to early osteoarthrosis. Moreover, although eventual progression to post-traumatic osteoarthrosis may occur, the described less invasive surgery has improved the patient's quality of life, may forestall the degenerative process, and may permit resurfacing arthroplasty as an option to total hip arthroplasty in this young patient.

One may wonder why one would perform a technically challenging arthroscopic procedure over an open procedure in this case. We admit that unless one has advanced hip arthroscopic experience, the open management of this case is preferred. However, we have had significant experience with the arthroscopic management of not only FAI but, more specifically, arthroscopic osteosynthesis of acute femoral head fractures. Many of the techniques and skills from the aforementioned procedures enabled this surgery to be performed in a safe and effective manner.

The potential role of hip arthroscopy in the trauma setting is expanding. Even beyond acute femoral head osteosynthesis, arthroscopic surgery may enhance the ability to treat femoral head malunions. Though challenging, the procedure is technically feasible. Moreover, arthroscopic osteosynthesis may address lateral cephalic FAI, a previously unreported condition. The ability to perform an anatomic reduction with stable internal fixation permitting early joint motion trumps the ability to perform arthroscopic procedures. However, if the arthroscopic equivalent can be safely achieved, hip arthroscopy may offer a less invasive alternative to open surgery for the treatment of femoral head fractures and malunions.

Supplementary Data

Video 1

Arthroscopic osteosynthesis of femoral head malunion.