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Posterior dislocation of the hip following arthroscopy: a case report and discussion.

A 24-year-old military policeman presented in the spring of 2011 with an 18-month history of right hip pain, catching, and clicking. It began while deployed in Iraq and had become increasingly more difficult to perform his job. Although there was no one inciting event, the patient attributed his symptoms to his gunner's harness, which he wore daily. Plain radiographs, magnetic resonance imaging, and physical examination were consistent with cam impingement and an anterior labral tear. Coxa valga was also evident on imaging, with a neck shaft angle of approximately 163[degrees] (Fig. 1). Following failure of conservative measures, arthroscopic treatment was recommended.

In November of 2011, an arthroscopic procedure was performed. The patient was given epidural anesthesia and placed in a supine position on the operating table. Through anterolateral and posterolateral portals that were established under fluoroscopy and ultrasound visualization, a detached superior labral tear was identified. An anterior capsulotomy was then performed, followed by decortication of the subchondral bone neighboring the torn labrum. The rim trimming was done with the use of a 5.5 mm motorized burr. Bone was removed until a normal acetabular profile was evident with the arthroscope and a healthy bed of tissue for reattaching the labrum was evident. The labrum was then repaired with number-2 Ultrabraid sutures and two 2.9-mm Bioraptor anchors (Smith and Nephew, Andover, Massachusetts). Traction was released and an anterior portal was developed next with the hip in 45[degrees] of flexion.

Through this anterior portal, the capsulotomy was extended, allowing greater visualization and maneuverability. Significant cam impingement was noted, and osteoplasty was performed from the region of the medial synovial fold to the lateral retinacular vessels, which were preserved. At the conclusion of the case, an arthroscopic examination of the hip was performed, which confirmed a concentrically reduced hip, restoration of the labrum's suction seal, and no residual impingement.

The patient was allowed partial weightbearing using axillary crutches to assist with ambulation. At his first follow-up visit on postoperative day number 7, the patient was noted to be doing well, with limited pain. Physical therapy was initiated at this time.

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On postoperative day 19, the patient presented to the emergency department (ED) with severe right hip pain after experiencing a popping sensation that began as he was trying to remove his shoes from a standing position. He was neurovascularly intact. Plain radiographs obtained of the right hip were consistent with a posterior dislocation (Fig. 2). Under procedural sedation, the hip was reduced and found to be stable after being brought through a full range of motion. Plain-radiographs and a CT-scan confirmed a concentric reduction without any evidence of any fracture (Fig. 3). The patient was subsequently discharged; he was non-weightbearing, and his physical therapy regimen was held.

On postoperative day 26, the patient again presented to the ED with a posterior dislocation of his right hip; he had felt a pop and immediate pain after gently repositioning his body while on the couch. Following five unsuccessful attempts at closed reduction under procedural sedation, the patient was brought to the operating room, where closed reduction under general anesthesia was performed. With fluoroscopic assistance, it was determined that the hip was grossly unstable and that only with continuous longitudinal traction could a concentric reduction be maintained. Based on these findings, the patient was placed in skeletal traction. Three days after this, he was transitioned to a hip spica cast.

The patient remained in the spica cast for 10 weeks (Fig. 4). After confirmation of a reduced hip at 5 weeks, he was allowed toe-touch weightbearing in the cast. Upon discontinuation of the spica at 10 weeks, he was placed in an abduction brace for an additional 4 weeks and was allowed weightbearing with crutches; physical therapy was also restarted. At the time of 6-month follow-up, the patient's hip remained concentrically reduced with no evidence of osteonecrosis on radiographs.

[FIGURE 3 OMITTED]

Discussion

Arthroscopic hip surgery has become a well-accepted approach to treating numerous hip pathologies, including irrigation and debridement of an infected joint; loose body removal; synovectomy; treatment of femoroacetabular impingement (FAI); impingement of the ligamentum teres; management of labral tears; debridement for osteoarthritis; biopsy; intraoperative control of osteotomy or epiphysiolysis; synovial chondromatosis; and thermal capsulorrhaphy and capsular plication for subtle rotational instability and capsular laxity. (1,2) The incidence of complications is reported to be between 1.3% and 23.3%. (3) They are most often due to traction, fluid extravasation, and iatrogenic chondral injury, with transient neuropraxia being the most common complication. (3,4)

Dislocation following hip arthroscopy is exceedingly rare. To our knowledge, there are only two reported in the literature, both of which anterior dislocations requiring revision surgery. (5,6) To the best of our knowledge, we are the first to report not only a posterior dislocation following this procedure, but one also amenable to nonoperative management.

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The commonly recognized causes of posterior hip instability include hyperlaxity, acetabular or femoral retroversion, bony or ligamentous lesions of the acetabulum, or following trauma or arthroplasty. (7) Intriguingly, our patient did not possess any of these so-called risk factors.

The exact etiology of the observed posterior dislocation is thus unknown. However, there are several factors that may have contributed to our patient's instability, including disruption of the hip's static stabilizers as well as underlying coxa valga, which, at least in the presence of neuromuscular disorders, is associated with spontaneous posterior dislocations. (8)

The hip's osseous and capsuloligamentous stabilizers include the labrum, bony acetabulum, capsule, ligamentum teres, and Y ligament of Bigelow. (6,9) Acetabular decortication in the form of rim trimming was performed in order to leave a stable rim of articular cartilage. As indicated by our postoperative radiographic center-edge angle of approximately 27[degrees], over-resection of this osseous stabilizer did not occur. When we perform a rim trimming, we continually stop and view the acetabular rim with the arthroscope, using this profile view to evaluate the extent of the resection. This is done to prevent excessive resection and subsequent instability. Admittedly, the exact limits of rim decortication before causing adverse biomechanical alterations have not been quantified, and therefore, our decortication could have contributed to the postoperative instability observed. (6)

Additionally, the capsule was destabilized when opened via capsulotomy and also stretched via distraction-induced attenuation. Capsulotomies are commonly performed to enhance visualization and instrument manipulation during arthroscopy. This comes at the expense of stability, as a capsulotomy increases femoral head motion relative to the acetabulum, a process that can contribute to postoperative instability. Unfortunately, the optimal technique and amount of resection to be performed during capsulotomy also remains unknown, which has led to much debate among arthroscopists regarding whether they should be repaired or even performed in the first place. (10,11)

In the two previously reported cases of hip dislocation following arthroscopy, both Ranawat and coworkers (2009) and Matsuda (2009) acknowledged the role that anterior capsulotomy and capsulectomy played in the development of anterior instability. (5,6) However, unlike those cases, our patient experienced posterior instability in the setting of an anterior capsulotomy. While a generalized disruption of the static stabilizers likely contributed to this, it is the concurrent coxa valga and resultant stressing of the dynamic stabilizers that ultimately led to the posterior instability.

Coxa valga is commonly associated with chronic hip instability in patients with neuromuscular conditions such as cerebral palsy. However, it has also been a reported finding in patients with posterior hip dislocations following mild trauma. (8) It is suggested that coxa valga increases joint reactive forces transmitted through the acetabulum and places undue force on the posterior hip structures during axial loading in positions of flexion, adduction, and internal rotation. (7) Interestingly, in a study by Wenger and Kendell and colleagues (2004) evaluating patients with acetabular labral tears, 27 of 31 had structural hip abnormalities. Of these abnormalities, 16 were found to be coxa valga. (12)

Dislocation following arthroscopic surgery of the hip is a rarely reported complication. This report details the first known posterior dislocation following arthroscopic femoral neck osteoplasty and labral repair. It also identifies spica casting and bracing as an effective treatment modality for postoperative instability. Prior to this case, successful management was associated with procedures such as capsular repair and plication. (5,6) As the indications for hip arthroscopy expand and its popularity continues to grow, surgeons must recognize this unusual but devastating complication.

Disclosure Statement

None of the authors have a financial or proprietary interest in the subject matter or materials discussed, including, but not limited to, employment, consultancies, stock ownership, honoraria, and paid expert testimony.

Caption: Figure 1 AP radiograph of the right hip demonstrating coxa valga and a femoral neck-shaft angle of approximately 163[degrees].

Caption: Figure 2 A, AP and B, lateral radiographs of a posterior-superior right hip dislocation.

Caption: Figure 3 Axial CT scan of the pelvis showing a concentrically reduced right hip.

Caption: Figure 4 AP radiograph of the right hip at 5 weeks following spica cast placement.

References

(1.) Byrd JWT, Jones KS. Prospective analysis of hip arthroscopy with 10-year follow-up. Clin Orthop Relat Res. 2010 Mar; 468(3):741-6. doi: 10.1007/s11999-009-0841-7. Epub 2009 Apr 21.

(2.) Funke EL, Munzinger U. Complications in hip arthroscopy. Arthroscopy. 1996 Apr; 12(2):156-9.

(3.) Scher DL, Belmont PJ, Owens BD. Case report: osteonecrosis of the femoral head after hip arthroscopy. Clin Orthop Relat Res. 2010 Nov; 468(11):3121-5. doi: 10.1007/s11999-0101256-1. Epub 2010 Feb 10.

(4.) McCarthy JC, Lee J. Hip arthroscopy: indications, outcomes, and complications. J Bone Joint Surg Am. 2005; 87:1137-45.

(5.) Ranawat AS, McClincy M, Sekiya JK. Anterior dislocation of the hip after arthroscopy in a patient with capsular laxity of the hip. A case report. J Bone Joint Surg Am. 2009 Jan; 91(1): 1927. doi: 10.2106/JBJS.G.01367.

(6.) Matsuda DK. Acute iatrogenic dislocation following hip impingement arthroscopic surgery. Arthroscopy. 2009 Apr; 25(4):400-4. doi: 10.1016/j.arthro.2008.12.011. Epub 2009 Feb 1.

(7.) Mofidi A, Sankar R, Kutty S, et al. Traumatic dislocation hip joint following low-velocity trauma, similarities to glenohumeral instability. Eur J Orthop Surg Traumatol. 2002; 12:108:14.

(8.) Song KS, Choi IN, Sohn YJ, et al. Habitual dislocation of the hip in children: report of eight additional cases and literature review. J Pediatric Orthop. 2003 Mar-Apr; 23:178-83.

(9.) Shindle MK, Voos JE, Nho SJ, et al. Arthroscopic management of labral tears in the hip. J Bone Joint Surg Am. 2008 Nov; 90 Suppl 4:2-19. doi: 10.2106/JBJS.H.00686.

(10.) Kampa RJ, Prasthofer A. The internervous safe zone for incision of the capsule of the hip. A cadaver study. J Bone Joint Surg Br. 2007 Jul; 89(7):971-6.

(11.) Safran M, Sampson T, Larson C. Debate: capsule. Presented at the Annual Scientific Meeting of the International Society for Hip Arthroscopy, October 14-15, 2011, Paris, France.

(12.) Wenger DE, Kendell KR, Miner MR, Trousdale RT. Acetabular labral tears rarely occur in the absence of bony abnormalities. Clin Orthop Relat Res. 2004 Sep; (426):145-50.

Andrew Rosenbaum, M.D., and Timothy Roberts, M.D., are Residents in the Division of Orthopaedic Surgery, Albany Medical Center, Albany, New York. Michael Flaherty, M.D., is a Fellow in Sports Medicine, Department of Orthopaedic Surgery, UMass Memorial Medical Center, Worcester, Massachusetts. Nani Phillips, B.A., M.P.H., and Nilay Patel, B.S., are medical students at Albany Medical College, Albany, New York. Shankar Das, M.D., is an Attending Surgeon and Associate Professor, Division of Orthopaedic Surgery, Albany Medical Center, Albany, New York. Correspondence:Andrew Rosenbaum, M.D., Resident, Albany Medical Center, Division of Orthopaedic Surgery, 1367 Washington Avenue, Albany, New York 12206; andrewjrosenbaum@ gmail.com.
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Author:Rosenbaum, Andrew; Roberts, Timothy; Flaherty, Michael; Phillips, Nani; Patel, Nilay; Das, Shankar
Publication:Bulletin of the NYU Hospital for Joint Diseases
Article Type:Clinical report
Date:Apr 1, 2014
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