Hip preservation surgery and the acetabular fossa

Which Acetabular Measurements Most Accurately Differentiate Between Patients and Controls? A Comparative Study

BACKGROUND

Acetabular morphology is an important determinant of hip biomechanics. To identify features of acetabular morphology that may be associated with the development of hip symptoms while accounting for spinopelvic characteristics, one needs to determine acetabular characteristics in a group of individuals older than 45 years without symptoms or signs of osteoarthritis. Previous studies have used patients with unknown physical status to define morphological thresholds to guide management.

QUESTIONS/PURPOSES

(1) To determine acetabular morphological characteristics in males and females between 45 and 60 years old with a high Oxford hip score (OHS) and no signs of osteoarthritis; (2) to compare these characteristics with those of symptomatic hip patients treated with hip arthroscopy or periacetabular osteotomy (PAO) for various kinds of hip pathology (dysplasia, retroversion, and cam femoroacetabular impingement); and (3) to assess which radiographic or CT parameters most accurately differentiate between patients who had symptomatic hips and those who did not, and thus, define thresholds that can guide management.

METHODS

Between January 2018 and December 2018, 1358 patients underwent an abdominopelvic CT scan in our institution for nonorthopaedic conditions. Of those, we considered 5% (73) of patients as potentially eligible as controls based on the absence of major hip osteoarthritis, trauma, or deformity. Patients were excluded if their OHS was 43 or less (2% [ 28 ]), if they had a PROMIS less than 50 (1% [ 18 ]), or their Tönnis score was higher than 1 (0.4% [ 6 ]). Another eight patients were excluded because of insufficient datasets. After randomly selecting one side for each control, 40 hips were left for analysis (age 55 ± 5 years; 48% [19 of 40] were in females). In this comparative study, this asymptomatic group was compared with a group of patients treated with hip arthroscopy or PAO. Between January 2013 and December 2020, 221 hips underwent hip preservation surgery. Of those, eight were excluded because of previous pelvic surgery, and 102 because of insufficient CT scans. One side was randomly selected in patients who underwent bilateral procedure, leaving 48% (107 of 221) of hips for analysis (age 31 ± 8 years; 54% [58 of 107] were in females). Detailed radiographic and CT assessments (including segmentation) were performed to determine acetabular (depth, cartilage coverage, subtended angles, anteversion, and inclination) and spinopelvic (pelvic tilt and incidence) parameters. Receiver operating characteristics (ROC) analysis was used to assess diagnostic accuracy and determine which morphological parameters (and their threshold) differentiate most accurately between symptomatic patients and asymptomatic controls.

RESULTS

Acetabular morphology in asymptomatic hips was characterized by a mean depth of 22 ± 2 mm, with an articular cartilage surface of 2619 ± 415 mm 2 , covering 70% ± 6% of the articular surface, a mean acetabular inclination of 48° ± 6°, and a minimal difference between anatomical (24° ± 7°) and functional (22° ± 6°) anteversion. Patients with symptomatic hips generally had less acetabular depth (20 ± 4 mm versus 22 ± 2 mm, mean difference 3 mm [95% CI 1 to 4]; p < 0.001). Hips with dysplasia (67% ± 5% versus 70% ± 6%, mean difference 6% [95% CI 0% to 12%]; p = 0.03) or retroversion (67% ± 5% versus 70% ± 6%, mean difference 6% [95% CI 1% to 12%]; p = 0.04) had a slightly lower relative cartilage area compared with asymptomatic hips. There was no difference in acetabular inclination (48° ± 6° versus 47° ± 7°, mean difference 0.5° [95% CI -2° to 3°]; p = 0.35), but asymptomatic hips had higher anatomic anteversion (24° ± 7° versus 19° ± 8°, mean difference 6° [95% CI 3° to 9°]; p < 0.001) and functional anteversion (22° ± 6° versus 13°± 9°, mean difference 9° [95% CI 6° to 12°]; p < 0.001). Subtended angles were higher in asymptomatic at 105° (124° ± 7° versus 114° ± 12°, mean difference 11° [95% CI 3° to 17°]; p < 0.001), 135° (122° ± 9° versus 111° ± 12°, mean difference 10° [95% CI 2° to 15°]; p < 0.001), and 165° (112° ± 9° versus 102° ± 11°, mean difference 10° [95% CI 2° to 14°]; p < 0.001) around the acetabular clockface. Symptomatic hips had a lower pelvic tilt (8° ± 8° versus 11° ± 5°, mean difference 3° [95% CI 1° to 5°]; p = 0.007). The posterior wall index had the highest discriminatory ability of all measured parameters, with a cutoff value of less than 0.9 (area under the curve [AUC] 0.84 [95% CI 0.76 to 0.91]) for a symptomatic acetabulum (sensitivity 72%, specificity 78%). Diagnostically useful parameters on CT scan to differentiate between symptomatic and asymptomatic hips were acetabular depth less than 22 mm (AUC 0.74 [95% CI 0.66 to 0.83]) and functional anteversion less than 19° (AUC 0.79 [95% CI 0.72 to 0.87]). Subtended angles with the highest accuracy to differentiate between symptomatic and asymptomatic hips were those at 105° (AUC 0.76 [95% CI 0.65 to 0.88]), 135° (AUC 0.78 [95% CI 0.70 to 0.86]), and 165° (AUC 0.77 [95% CI 0.69 to 0.85]) of the acetabular clockface.

CONCLUSION

An anatomical and functional acetabular anteversion of 24° and 22°, with a pelvic tilt of 10°, increases the acetabular opening and allows for more impingement-free flexion while providing sufficient posterosuperior coverage for loading. Hips with lower anteversion or a larger difference between anatomic and functional anteversion were more likely to be symptomatic. The importance of sufficient posterior coverage was also illustrated by the posterior wall indices and subtended angles at 105°, 135°, and 165° of the acetabular clockface having a high discriminatory ability to differentiate between symptomatic and asymptomatic hips. Future research should confirm whether integrating these parameters when selecting patients for hip preservation procedures can improve postoperative outcomes.Level of Evidence Level III, prognostic study.

Femoral impingement in maximal hip flexion is anterior-inferior distal to the cam deformity in femoroacetabular impingement patients with femoral retroversion : implications for hip arthroscopy

AIMS

Femoroacetabular impingement (FAI) patients report exacerbation of hip pain in deep flexion. However, the exact impingement location in deep flexion is unknown. The aim was to investigate impingement-free maximal flexion, impingement location, and if cam deformity causes hip impingement in flexion in FAI patients.

METHODS

A retrospective study involving 24 patients (37 hips) with FAI and femoral retroversion (femoral version (FV) < 5° per Murphy method) was performed. All patients were symptomatic (mean age 28 years (SD 9)) and had anterior hip/groin pain and a positive anterior impingement test. Cam- and pincer-type subgroups were analyzed. Patients were compared to an asymptomatic control group (26 hips). All patients underwent pelvic CT scans to generate personalized CT-based 3D models and validated software for patient-specific impingement simulation (equidistant method).

RESULTS

Mean impingement-free flexion of patients with mixed-type FAI (110° (SD 8°)) and patients with pincer-type FAI (112° (SD 8°)) was significantly (p < 0.001) lower compared to the control group (125° (SD 13°)). The frequency of extra-articular subspine impingement was significantly (p < 0.001) increased in patients with pincer-type FAI (57%) compared to cam-type FAI (22%) in 125° flexion. Bony impingement in maximal flexion was located anterior-inferior at femoral four and five o'clock position in patients with cam-type FAI (63% (10 of 16 hips) and 37% (6 of 10 hips)), and did not involve the cam deformity. The cam deformity did not cause impingement in maximal flexion.

CONCLUSION

Femoral impingement in maximal flexion was located anterior-inferior distal to the cam deformity. This differs to previous studies, a finding which could be important for FAI patients in order to avoid exacerbation of hip pain in deep flexion (e.g. during squats) and for hip arthroscopy (hip-preservation surgery) for planning of bone resection. Hip impingement in flexion has implications for daily activities (e.g. putting on shoes), sports, and sex.Cite this article: Bone Joint Res 2023;12(1):22-32.

Morphometric study of acetabular depth and coverage and their clinical importance

OBJECTIVES

To measure acetabular parameters and to compare parameters of acetabulum between men and women, and right and left sides.

METHODS

The study was conducted in PNS Shifa Hospital, Karachi from January to June 2021. Anteroposterior radiographs of both hips of 70 adults aged 20-70 years were included. The study consisted of 35 men and an equal number of women. We measured acetabular depth, femoral head coverage, acetabular inclination and acetabular depth and width. The acetabular depth was measured using Wiberg's central edge (CE) angle and Sharp angle techniques. Femoral head coverage was determined using measurements between medial edge of hip joint space, lateral edge of acetabulum and femoral head. To determine acetabular inclination, Tönnis angle was measured. Acetabular depth & width ratio (ADR) was evaluated by dividing acetabular width by depth, and multiplying by 100.

RESULTS

There was significant increase in Sharp angle and Tonnis angle in females on the left side as compared to males. Wiberg's central edge angle and acetabular width to depth ratio showed insignificant increase in males as compared to females, whereas values of femoral head coverage were insignificantly more in women.

CONCLUSION

The acetabular parameters were insignificantly different in gender and between right and left sides, although mean values were within normal range. The larger ADR ratio in men was most likely due to increased body weight in them as compared to women.

The Presence of Central Acetabular Osteophytes May Negatively Affect the Outcome After Primary Arthroscopic Therapy of Femoroacetabular Impingement Syndrome

PURPOSE

To compare short-term follow-up outcomes after primary arthroscopy in femoroacetabular impingement syndrome (FAIS) patients with untreated central acetabular osteophytes (CAO) to a control group without CAO.

METHODS

A retrospective analysis was performed using data from FAIS patients who had primary arthroscopy between 2017 and 2018. The presence of CAO was confirmed arthroscopically, and there were 2 groups created. The CAO group was 1:1 propensity-score matched to a control group (without CAO) based on age, gender, body mass index (BMI), Tӧnnis grade, symptom duration before surgery, and follow-up time. Patient-reported outcomes (PROs), such as the Hip Outcome Score-Activities of Daily Living (HOS-ADL), International Hip Outcome Tool 12-component form (iHOT-12)，modified Harris Hip Score (mHHS), and visual analog scale (VAS) scores were used to evaluate the level of function included. The minimal clinically important difference (MCID) and patient acceptable symptomatic state (PASS) were also calculated to determine meaningful outcome improvement. Radiographic measures, performed procedures, complications, and revision surgery were also compared and analyzed for both groups. P values less than .05 were considered statistically significant.

RESULTS

A total of 46 hips with CAO and 46 hips without CAO were propensity matched. At the minimum final follow-up of 2 years, the CAO group had significantly lower HOS-ADL (78.8 vs 85.5; P = .008), iHOT-12 (74.8 vs 79.3; P = .019), and mHHS (78.9 vs 87.2; P = .002) scores, as compared to the CAO group. Furthermore, patients in the CAO group were significantly less likely to achieve the MCID and PASS for the mHHS score (78.3% vs 93.5%; P = .036, 58.7% vs 78.2%; P = .043, respectively). There was no change in the rate of complications (4.3% vs 0%) and revision hip arthroscopy (4.3% vs 2.2%) between the two groups at the final follow-up.

CONCLUSIONS

This study demonstrated that surgically treated FAIS patients with CAO might experience worse short-term, patient-reported outcomes, as compared with propensity-matched patients without CAO.

LEVEL OF EVIDENCE

III, case-control study.

Central acetabular osteophytes (CAO) are more prevalent in the borderline developmental dysplastic hip (BDDH) patients: a propensity-score matched CT study

Background

The acetabular fossa often showing the first signs of degeneration, Central acetabular osteophytes (CAO) have been increasingly recognized during hip arthroscopy. The purpose of this study was to investigate the condition of CAO in BDDH hips and compare cotyloid fossa size between the BDDH and the non-BDDH hips on CT images.

Methods

We performed a retrospective analysis of prospectively collected data of hip CT images of FAI or labral injury patients. A 1:2 propensity-score matched observational study comparing the linear length of cotyloid fossa was analyzed. Cotyloid fossa width (CFW) and cotyloid notch width (CNW) were measured on axial images, cotyloid fossa height (CFH) and cotyloid fossa depth (CFD) were measured on coronal images. Within the CAO patients, we performed central acetabular decompression (CAD) and then observed the morphology change in fossa.

Results

Propensity-score matching yielded 61 BDDH hips and 122 non-BDDH hips. BDDH hips had a higher prevalence of CAO and a decreased linear length of cotyloid fossa (CFW, CFH and CNW). In the BDDH group, 33 hips underwent CAD, postoperative CFW, CFH and CNW were significantly increased (p < .001 for all), and had no statistical difference compared with the non-BDDH hips (p = .193, p = .132, p = .421, respectively).

Conclusion

BDDH hips had a significantly higher prevalence of CAO than adequate acetabular coverage hips. After the procedure of CAD, BDDH hips were found to have acetabular parameters (CFW, CFH, CNW) and were restored to that of the control hips.

Preoperative T2 mapping MRI of articular cartilage values predicts postoperative osteoarthritis progression following rotational acetabular osteotomy

AIMS

Rotational acetabular osteotomy (RAO) has been reported to be effective in improving symptoms and preventing osteoarthritis (OA) progression in patients with mild to severe develomental dysplasia of the hip (DDH). However, some patients develop secondary OA even when the preoperative joint space is normal; determining who will progress to OA is difficult. We evaluated whether the preoperative cartilage condition may predict OA progression following surgery using T2 mapping MRI.

METHODS

We reviewed 61 hips with early-stage OA in 61 patients who underwent RAO for DDH. They underwent preoperative and five-year postoperative radiological analysis of the hip. Those with a joint space narrowing of more than 1 mm were considered to have 'OA progression'. Preoperative assessment of articular cartilage was also performed using 3T MRI with the T2 mapping technique. The region of interest was defined as the weightbearing portion of the acetabulum and femoral head.

RESULTS

There were 16 patients with postoperative OA progression. The T2 values of the centre to the anterolateral region of the acetabulum and femoral head in the OA progression cases were significantly higher than those in patients without OA progression. The preoperative T2 values in those regions were positively correlated with the narrowed joint space width. The receiver operating characteristic analysis revealed that the T2 value of the central portion in the acetabulum provided excellent discrimination, with OA progression patients having an area under the curve of 0.858. Furthermore, logistic regression analysis showed T2 values of the centre to the acetabulum's anterolateral portion as independent predictors of subsequent OA progression (p < 0.001).

CONCLUSION

This was the first study to evaluate the relationship between intra-articular degeneration using T2 mapping MRI and postoperative OA progression. Our findings suggest that preoperative T2 values of the hip can be better prognostic factors for OA progression than radiological measures following RAO. Cite this article: Bone Joint J 2021;103-B(9):1472-1478.