Do acetabular parameters measured on 2D imaging correlate with CT, and can lateral centre-edge angle predict femoral head coverage?

Aims The lateral centre-edge angle (LCEA) is a plain radiological measure of superolateral cover of the femoral head. This study aims to establish the correlation between 2D radiological and 3D CT measurements of acetabular morphology, and to describe the relationship between LCEA and femoral head cover (FHC). Methods This retrospective study included 353 periacetabular osteotomies (PAOs) performed between January 2014 and December 2017. Overall, 97 hips in 75 patients had 3D analysis by Clinical Graphics, giving measurements for LCEA, acetabular index (AI), and FHC. Roentgenographical LCEA, AI, posterior wall index (PWI), and anterior wall index (AWI) were measured from supine AP pelvis radiographs. The correlation between CT and roentgenographical measurements was calculated. Sequential multiple linear regression was performed to determine the relationship between roentgenographical measurements and CT FHC. Results CT-measured LCEA and AI correlated strongly with roentgenographical LCEA ( r = 0.92; p < 0.001) and AI ( r = 0.83; p < 0.001). Radiological LCEA correlated very strongly with CT FHC ( r = 0.92; p < 0.001). The sum of AWI and PWI also correlated strongly with CTFHC ( r = 0.73; p < 0.001). CT measurements of LCEA and AI were 3.4° less and 2.3° greater than radiological LCEA and AI measures. There was a linear relation between radiological LCEA and CT FHC. The linear regression model statistically significantly predicted FHC from LCEA, F(1,96) = 545.1 (p < 0.001), adjusted R2 = 85.0%, with the prediction equation: CT FHC(%) = 42.1 + 0.77(XRLCEA) Conclusion CT and roentgenographical measurement of acetabular parameters are comparable. Currently, a radiological LCEA greater than 25° is considered normal. This study demonstrates that those with hip pain and normal radiological acetabular parameters may still have deficiencies in FHC. More sophisticated imaging techniques such as 3D CT should be considered for those with hip pain to identify deficiencies in FHC. Cite this article: Bone Jt Open 2022;3(1):12–19.

Reliability and sensitivity of radiographic measures of hip dysplasia in childhood Charcot-Marie-Tooth disease

Background: Hip dysplasia is a lack of femoral head coverage and disruption of hip and acetabular alignment and congruency, with severity ranging from mild subluxation in nascent at-risk hips to complete dislocation. Presentation of hip dysplasia in neuromuscular conditions can be sub-clinical or associated with a limp with or without hip pain, abductor and flexor weakness and reduced hip range of motion. Untreated hip dysplasia leads to early onset osteoarthritis requiring hip arthroplasty in early adulthood. Hip dysplasia occurs in 6–20% of children with Charcot-Marie-Tooth disease, however little is known about the reliability and sensitivity of detection on plain film pelvic radiographs. Methods: 14 common measures of hip dysplasia on anteroposterior pelvis radiographs were independently assessed by 2 orthopaedic specialists in 30 ambulant children with Charcot-Marie-Tooth disease. Hip health was also categorised based on clinical impression to assess the sensitivity of radiographic measures to identify hip dysplasia status. Results: 8 measures (acetabular index, head width, lateral centre-edge angle, lateral uncoverage, medial joint width, migration percentage, neck shaft angle, triradiate status) exhibited ‘excellent’ reliability between clinical evaluators. 5 of the 30 patients (17%) were identified as having nascent hip dysplasia. Reliable radiographic measures that significantly distinguished between nascent hip dysplasia and healthy hips were acetabular index, lateral centre edge angle, medial joint width and migration percentage. Conclusions: We have identified a subset of reliable and sensitive radiographic hip measures in children with Charcot-Marie-Tooth disease to prioritise during hip screening to mitigate the deleterious effects of hip dysplasia, pain and disability in adulthood.

Incidence and risk factors for hardware removal following periacetabular osteotomy and its association with clinical outcomes

Background: Periacetabular osteotomy (PAO) can be used for joint preservation in symptomatic developmental dysplasia of the hip (DDH) and femoroacetabular impingement (FAI). 1 of the most common procedures following PAO is hardware removal. The aims of this study were to determine the rate of hardware removal and patient characteristics associated with this outcome following PAO. Methods: Data from a prospectively-collected registry was retrospectively reviewed at one institution managing DDH or FAI patients with PAO from July 2008–December 2015. Patients who completed preoperative and postoperative patient reported outcome (PRO) questionnaires with minimum 1-year follow-up were evaluated, resulting in 221 patients followed for a mean of 2.8 years (range 1.0–7.7 years). There were 80% women, mean age was 25 years and mean body mass index (BMI) was 25 kg/m2. Fully-threaded 4.5-mm screws were used for internal fixation. Results: Hardware removal occurred in 30 patients (13.6%) at a mean of 1.0 years after PAO. Patients undergoing hardware removal were younger (mean age 20.4 vs. 26.3 years), thinner (mean BMI 22.2 vs. 25.1), had less severe dysplasia (DDH patients only: mean lateral centre-edge angle 21.0 vs. 16.2, mean Tönnis angle 12.9 vs. 16.8), and were more likely to have PAO for FAI (33% vs. 11%) compared to patients with retained hardware. At final follow-up, multivariable analysis demonstrated a trend toward inferior patient reported outcomes in the hardware removal group. Conclusions: This study defines the incidence and characteristics of patients undergoing hardware removal after PAO and demonstrates similar outcomes to patients who do not require hardware removal.

Periacetabular osteotomy using three-dimensional cutting and reposition guides: a cadaveric study

The goal of periacetabular osteotomy (PAO) is to reorient the acetabulum in a more physiological position. Its realization remains challenging regarding the final position of the acetabulum. Assistance with custom cutting- and reorientation-guides would thus be very helpful. Our purpose is to present a pilot study on such guides. Eight cadaveric hemipelvis were scanned using CT. After segmentation, 3D models of each specimen were created, a PAO was virtually performed and reorientation of the acetabula were defined. A specific guide was designed aiming to assist in iliac, posterior column and superior pubic ramus cuts as well as in acetabulum reorientation. Furthermore, the acetabular position was planned. Three-dimensional printed guides were used to perform PAO using the modified Smith-Peterson approach. The post-operative CT images and virtually planned acetabulum reorientation were compared in terms of acetabular index (AC), lateral centre edge angle (LCE), acetabular anteversion angle (AcetAV). There was no intra-articular or posterior column fracture seen. Two cadavers showed very low bone quality with insufficient stability of fixation and were excluded from further analysis. Correlation between the post-operative result and planning of the six included cadavers revealed the following mean deviations: 5° (SD ±3°) for AC angle, 6° (SD ±4°) for LCE angle and 15° (SD ±11°) for AcetAV angle. The use of 3D cutting and reorientation blocks for PAO was possible through a modified Smith-Peterson approach and revealed accurate fit to bone, accurate positioning of the osteotomies and acceptable planned corrections in cadavers with good bone quality.

Labral hypertrophy correlates with borderline hip dysplasia and microinstability in femoroacetabular impingement: a matched case-control analysis

Purpose: The goal of this study was to: (1) investigate the association between labral hypertrophy and radiographic and computed tomography (CT) imaging measurements of dysplasia in a femoroacetabular impingement (FAI) cohort; (2) evaluate the association between physical examination parameters suggestive of microinstability and labral hypertrophy. Methods: A retrospective case-control study was performed. Labral hypertrophy was defined as intraoperative labral width measuring greater >4 mm. A control cohort (NL) was matched to the cases. Physical examination parameters and preoperative radiographic and CT imaging studies were reviewed. Results: 231 hip arthroscopies for FAI were reviewed from which 42 cases of labral hypertrophy were identified (LH). In the LH group there was significantly increased hip internal rotation at 90° hip flexion compared to normal controls (13.6° ± 1 0.7° LH vs. 9.3° ± 6.2° NL; p = 0.04). On plain radiographs, the mean lateral centre-edge angle was smaller in the LH group compared to the NL group (27.6° ± 6.00° LH vs. 31.6° ± 6.59° NL; p < 0.001) and the acetabular index was larger in the LH group compared to the NL group (6.61 ± 4.18 LH vs. 4.14 ± 6.13 NL; p = 0.04). On CT imaging coronal sagittal CEA was significantly lower in LH cases compared to NL control (31.8° ± 5.30° LH vs. 35.1° ± 7.67° NL; p = 0.01). Conclusions: We found that patients with labral hypertrophy have radiographic and CT measurements consistent with subtle but not absolute dysplasia and physical examination findings suggestive of microinstability. We propose that labral hypertrophy can be a useful clinical tool for identifying FAI patients on the dysplasia spectrum.