Is Increased Acetabular Cartilage or Fossa Size Associated With Pincer Femoroacetabular Impingement?

Abstract

Background Surgical treatment for pincer femoroacetabular impingement (FAI) of the hip remains controversial, between trimming the prominent acetabular rim and reverse periacetabular osteotomy (PAO) that reorients the acetabulum. However, rim trimming may decrease articular surface size to a critical threshold where increased joint contact forces lead to joint degeneration. Therefore, knowledge of how much acetabular articular cartilage is available for resection is important when evaluating between the two surgical options. In addition, it remains unclear whether the acetabulum rim in pincer FAI is a prominent rim because of increased cartilage size or increased fossa size. Questions/purposes We used reformatted MR and CT data to establish linear length dimensions of the lunate cartilage and cotyloid fossa in normal, dysplastic, and deep acetabula. Methods We reviewed the last 200 hips undergoing PAO, reverse PAO, and surgical dislocation for acetabular rim trimming at one institution. We compared MR images of symptomatic hips with acetabular dysplasia (20 hips), pincer FAI (29 hips), and CT scans of asymptomatic hips from patients who underwent CT scans for reasons other than hip pain (20 hips). These hips were chosen sequentially from the underlying pool of 200 potential subjects to identify the first 10 male and the first 10 female hips in each group that met inclusion criteria. As a result of low numbers, we included all hips that had undergone reverse PAO and met inclusion criteria. Cartilage width was measured medially from the cotyloid fossa to the lateral labrochondral junction. Cotyloid fossa linear height was measured from superior to inferior and cotyloid fossa width was measured from anterior to posterior. Superior lunate cartilage width (SLCW) and cotyloid fossa height (CFH) were measured on MR and CT oblique coronal reformats; anterior lunate cartilage width (ALCW), posterior lunate cartilage width (PLCW), and cotyloid fossa width (CFW) were measured on MR and CT oblique axial reformats. Cohorts were compared using multivariate analysis of variance with Bonferroni's adjustment for multiple comparisons.Results Compared with control acetabula, dysplastic acetabula had smaller SLCW (2.08 ± 0.29 mm versus 2.63 Clinical Orthopaedics and Related Research ®A Publication of The Association of Bone and Joint Surgeons® ± 0.42 mm, mean difference = À0.55 mm; 95% confidence interval [CI] = À0.83 to À0.27; p \ 0.01), ALCW (1.20 ± 0.34 mm versus 1.64 ± 0.21 mm, mean difference = À0.44 mm; 95% CI = À0.70 to À0.18; p = 0.00), CFH (2.84 ± 0.37 mm versus 3.42 ± 0.57 mm, mean difference = À0.59 mm; 95% CI = À0.96 to À0.21; p \ 0.01), and CFW (1.98 ± 0.50 mm versus 2.77 ± 0.33 mm, mean difference = À0.80 mm; 95% CI = À1.16 to À0.42; p \ 0.0001). Based on the results, we identified two subtypes of deep acetabula. Compared with controls, deep subtype 1 had normal CFH and CFW but increased ALCW (2.09 ± 0.42 mm versus 1.64 ± 0.21 mm; p \ 0.001) and PLCW (2.32 ± 0.36 mm versus 2.00 ± 0.32 mm; p = 0.04). Compared ...

Clinical Anatomy of the Ligament of the Head of Femur

“…While the other ligament dimensions varied widely within individual hips, ligament length mostly ranged between 20 and 30 mm ( n = 23/30), similar to the report of Kirici et al () (25–30 mm in 24/26 specimens). The size of the acetabular fossa is reported to be 26.1 ± 6.5 by 33.9 ± 6.7 mm (Pun et al, ); our findings show that the dimensions of the LHF did not exceed that of the acetabular fossa. It appears that this arrangement possibly renders the ligament and ligamental vessels safely cushioned within the acetabular fossa during hip movements, so a ligament graft within this size range could potentially avoid damage to the graft tissue.…”

Pincer‐type MRI morphology seen in over a third of asymptomatic healthy volunteers without femoroacetabular impingement

“…In the last decade the majority of FAI studies have focused on the femur, ie, on the role of the cam‐type deformity in FAI and on the detection of cam‐type deformities on radiographs and MRI . The acetabulum and pincer‐deformities have received less attention, and most studies that assessed pincer‐deformities were based on radiographs, with only little existing MRI data on the morphology of pincer‐deformities, and without an MRI study comparing asymptomatic volunteers directly with FAI patients . This study presents the range of MRI measurements of acetabular morphology in asymptomatic volunteers versus patients with FAI.…”

“…3,20 The acetabulum and pincer-deformities have received less attention, and most studies that assessed pincer-deformities were based on radiographs, [27][28][29][30] with only little existing MRI data on the morphology of pincer-deformities, and without an MRI study comparing asymptomatic volunteers directly with FAI patients. 3,[31][32][33] This study presents the range of MRI measurements of acetabular morphology in asymptomatic volunteers versus patients with FAI. While hip MRI is the standard of reference for assessment of damage to the articular cartilage and labrum, as well as for assessment of cam-type deformities of the proximal femur, 3,31 it can also be applied to quantify the amount of acetabular coverage in patients with suspected pincer and mixed-type FAI.…”

Lateral Center-Edge Angle Is Not Predictive of Acetabular Articular Cartilage Surface Area: Anatomic Variation of the Lunate Fossa

“…Only the first operative extremity was selected in patients who had undergone either staged bilateral hip arthroscopy or PAO. Patients were subdivided into 3 subgroups according to their measured LCEA: (1) lateral undercoverage (LCEA, <25°), 9,13 normal coverage (LCEA, 25°-40°), 3 or lateral overcoverage (LCEA, ≥40°). 3 Patients were identified until each group contained 20 patients (n = 60).…”