The "Outside-In" Lesion of Hip Impingement and the "Inside-Out" Lesion of Hip Dysplasia: Two Distinct Patterns of Acetabular Chondral Injury.

BACKGROUND: Femoroacetabular impingement (FAI) and acetabular dysplasia lead to acetabular cartilage damage that commonly results in the chondral flaps seen during hip arthroscopy. PURPOSE: To compare the acetabular chondral flap morphology seen during hip arthroscopy ("outside-in" vs "inside-out") with clinical and radiographic parameters underlying FAI and hip dysplasia. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: Patients who underwent hip arthroscopy by the senior author between 2013 and 2017 with a finding of Outerbridge grade IV acetabular chondral flap were included. Each procedure was retrospectively reviewed on video and chondral flaps were categorized as inside-out or outside-in. An inside-out designation was made for flaps exhibiting an intact chondrolabral junction with a detached sleeve of chondrolabral tissue from the central acetabulum, and an outside-in designation was made for centrally anchored flaps exhibiting a break in the chondrolabral junction. Radiographic markers of hip impingement/dysplasia were noted for each patient during assignment into 1 of 2 radiographic groups: group 1, lateral center edge angle (LCEA) >20 with FAI, and group 2, LCEA ≤20 with or without cam FAI. Associations between chondral flap morphology and clinical diagnosis were tested using a chi-square test. RESULTS: Overall, 95 patients (103 hips) were included (group 1, 78 hips; group 2, 25 hips). Among hips in group 2, 24 had concurrent cam FAI. There was a significant relationship between chondral flap type and radiographic diagnosis (P < .001). Among group 1 hips, 78% exhibited outside-in type chondral flaps, 12% exhibited combined outside-in and inside-out flaps, and 10% exhibited inside-out flaps. Group 2 hips showed 72% inside-out type chondral flaps, 16% combined, and 12% outside-in. Hips exhibiting outside-in type flaps were significantly more likely to be in group 1 (positive predictive value [PPV], 91%; negative predictive value [NPV], 69%). Similarly, hips exhibiting inside-out type flaps were significantly more likely to be in group 2 (PPV, 56%; NPV, 95%). Altogether, 90% of group 1 hips exhibited an outside-in lesion and 88% of group 2 hips exhibited an inside-out lesion. CONCLUSION: Acetabular chondral flap type visualized during hip arthroscopy correlates with radiographic markers of hip impingement and hip instability. Outside-in flaps are highly predictive of FAI, whereas inside-out flaps are highly predictive of acetabular dysplasia.

Increased Prevalence of Femoroacetabular Impingement in Patients With Proximal Hamstring Tendon Injuries.

PURPOSE: To determine the prevalence of clinically diagnosed femoroacetabular impingement (FAI) in a consecutive series of patients presenting with proximal hamstring tendon injury and to correlate this with pelvic anatomic factors. METHODS: The prevalence of clinically symptomatic cam-, pincer-, and mixed-type and overall FAI was calculated among a consecutive series of patients presenting to a hip preservation clinic with a confirmed clinical and radiographic diagnosis of proximal hamstring tendon injury between 2012 and 2017. The presence of a cam lesion was determined by an alpha angle > 50° on radiographs and computed tomography radial sequences of the head-neck junction and a femoral head-neck offset ratio < 0.18. Clinical diagnoses of osseous impingement were determined according to accepted pathomorphologic signs and measurements. A diagnosis of FAI was confirmed by imaging findings of acetabular overcoverage for pincer-type FAI and the presence of an anterior or lateral cam lesion for cam-type FAI. RESULTS: Overall, 120 hips in 97 patients (mean age, 45 years) were included in this study. A clinical diagnosis of FAI was noted in 70.8% of hips (pincer-type 9.2%, cam-type 40.8%, mixed-type 20.8%), an approximate 2- to 7-fold increased prevalence in comparison with the general population from prior studies. CONCLUSIONS: The prevalence of FAI is high in patients with symptomatic proximal hamstring tendon pathology. Because FAI results in restriction of hip range of motion and altered pelvic tilt, future studies are warranted to investigate whether the presence of FAI acts as a predisposing factor for injury to the hamstring muscle complex. LEVEL OF EVIDENCE: Level IV, case series.

Efficacy of a non-image-guided diagnostic hip injection in patients with clinical and radiographic evidence of intra-articular hip pathology.

The purpose of this study was to determine the likelihood of pain relief, as a measure of accurate diagnosis of intra-articular hip pathology and correct needle placement, with a non-image-guided intra-articular hip injection performed bedside in the clinic. A retrospective study of prospectively collected data was performed in a consecutive cohort of patients diagnosed with symptomatic intra-articular hip pathology who underwent a non-image-guided intra-articular injection in the clinic. All patients had clinical and radiographic evidence of hip impingement, hip instability, chondrolabral pathology, or other causes of intra-articular hip pain. A previously described technique for a non-image-guided hip injection was performed using 7-10 ml of 1% lidocaine for diagnostic evaluation with some patients receiving 2 ml of Kenalog®-40 if clinically indicated. Ten minutes following each injection, the patient was asked to report the percent improvement in pain (from 0 to 100%) while physical examination and provocative tests were repeated. The final study cohort comprised 142 patients (161 injections). In three cases, patients were either unable to assess or quantify any change in pain level 10 min following the injection. In the remaining 158 hip injections, pain relief was noted in 156 cases (156/158, 98.7%), with at least 70% improvement in pain level noted in 152 cases (152/158, 96.2%). Average pain relief among all 158 injections was 89 ± 16%. A non-image-guided diagnostic intra-articular hip injection yields reliable short-term pain relief, simultaneously endorsing accurate diagnosis of hip pathology and intra-articular needle placement.

Standardizing the Prearthritic Hip Joint Space Width: An Analysis of 994 Hips.

PURPOSE: The purposes of this study were (1) to define a normal prearthritic hip joint space width (JSW) in symptomatic and asymptomatic patients with various degrees of acetabular coverage based on the lateral center edge angle (LCEA) and (2) to determine predictors of JSW using patient-specific variables. METHODS: In a consecutive series of patients presenting to a hip preservation clinic between July 2012 and April 2016, a standard weight-bearing anteroposterior pelvic view was obtained. JSW was defined as the distance between the bony contour of the acetabular rim and femoral head in 2 locations (lateral and medial weight-bearing zone). Hips with severe anatomic deformity, a Tönnis grade >0, or a lateral or medial JSW <2.5 mm were excluded. A linear mixed model analysis was performed in order to determine which variables (age, sex, side, height, weight, symptomatic/asymptomatic, LCEA, and clinical diagnosis) were significantly related to JSW. RESULTS: A total of 994 hips were included. LCEA was found to be a significant predictor of both the lateral and medial JSW, with a decreased JSW associated with increasing degrees of acetabular bony coverage (P < .02). A mean 0.9 mm (20%) difference in medial JSW was found between patients with frank dysplasia (LCEA <20°) compared with those with pincer-type FAI (LCEA ≥40°). There was no difference between symptomatic and asymptomatic hips, either for lateral (asymptomatic: 4.51 ± 0.83 mm; symptomatic: 4.52 ± 0.85 mm; P = .58) or medial JSW (asymptomatic: 4.02 ± 0.96 mm; symptomatic: 3.97 ± 0.84 mm; P = .49). CONCLUSIONS: The LCEA is a significant predictor of hip JSW, with the mean JSW decreasing with increasing degrees of acetabular bony coverage. Joint space is not a major factor in symptomatology in adults with prearthritic hip pain. LEVEL OF EVIDENCE: Level III, retrospective comparative study.