Does periacetabular osteotomy have depth-related effects on the articular cartilage of the hip?

BACKGROUND: Osteoarthritis may result from abnormal mechanics leading to biochemically mediated degradation of cartilage. In a dysplastic hip, the periacetabular osteotomy (PAO) is designed to normalize the mechanics and our initial analysis suggests that it may also alter the cartilage biochemical composition. Articular cartilage structure and biology vary with the depth from the articular surface including the concentration of glycosaminoglycans (GAG), which are the charge macromolecules that are rapidly turned over and are lost in early osteoarthritis. Delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) enables noninvasive measurement of cartilage GAG content. The dGEMRIC index represents an indirect measure of GAG concentration with lower values indicating less GAG content. GAG content can normally vary with mechanical loading; however, progressive loss of GAG is associated with osteoarthritis. By looking at the changes in amounts of GAG in response to a PAO at different depths of cartilage, we may gain further insights into the types of biologic events that are occurring in the joint after a PAO. QUESTIONS/PURPOSES: We (1) measured the GAG content in the superficial and deep zones for the entire joint before and after PAO; and (2) investigated if the changes in the superficial and deep zone GAG content after PAO varied with different locations within the joint. METHODS: This prospective study included 37 hips in 37 patients (mean age 26 ± 9 years) who were treated with periacetabular osteotomy for symptomatic acetabular dysplasia and had preoperative and 1-year follow up dGEMRIC scans. Twenty-eight of the 37 also had 2-year scans. Patients were eligible if they had symptomatic acetabular dysplasia with lateral center-edge angle < 20° and no or minimal osteoarthritis. The change in dGEMRIC after surgery was assessed in the superficial and deep cartilage zones at five acetabular radial planes. RESULTS: The mean ± SD dGEMRIC index in the superficial zone fell from 480 ± 137 msec preoperatively to 409 ± 119 msec at Year 1 (95% confidence interval [CI], -87 to -54; p < 0.001) and recovered to 451 ± 115 msec at Year 2 (95% CI, 34-65; p < 0.001), suggesting that there is a transient event that causes the biologically sensitive superficial layer to lose GAG. In the deep acetabular cartilage zone, dGEMRIC index fell from 527 ± 148 msec preoperatively to 468 ± 143 msec at Year 1 (95% CI, -66 to -30; p < 0.001) and recovered to 494 ± 125 msec at Year 2 (95% CI, 5-32; p = 0.008). When each acetabular radial plane was looked at separately, the change from before surgery to 1 year after was confined to zones around the superior part of the joint. The only significant change from 1 to 2 years was an increase in the superficial layer of the superior zone (1 year 374 ± 123 msec, 2 year 453 ± 117 msec, p < 0.006). CONCLUSIONS: This study suggests that PAO may alter the GAG content of the articular cartilage with a greater effect on the superficial zone compared with the deeper acetabular cartilage zone, especially at the superior aspect of the joint. Some surgeons have observed that surgery itself can be a stressor that can accelerate joint degeneration. Perhaps the decrease in dGEMRIC index seen in the superficial layer may be a catabolic response to postsurgical inflammation given that some recovery was seen at 2 years. The decrease in dGEMRIC index in the deep layer seen mainly near the superior part of the joint is persistent and may represent a response of articular cartilage to normalization of increased mechanical load seen in this region after osteotomy, which may be a normal response to alteration in loading. CLINICAL RELEVANCE: This study looks at the biochemical changes in the articular cartilage before and after a PAO for dysplastic hips using MRI in a similar manner to using histological methods to study alterations in articular cartilage with mechanical loading. Although PAO alters alignment and orientation of the acetabulum, its effects on cartilage biology are not clear. dGEMRIC provides a noninvasive method of assessing these effects.

How do acetabular version and femoral head coverage change with skeletal maturity?

BACKGROUND: Normal changes in acetabular version over the course of skeletal development have not been well characterized. Knowledge of normal version development is important because acetabular retroversion has been implicated in several pathologic hip processes. QUESTIONS/PURPOSES: The purpose of this study was to characterize the orientation of the acetabulum by measuring (1) acetabular version and (2) acetabular sector angles in pediatric patients during development. We also sought to determine whether these parameters vary by sex in the developing child. METHODS: We evaluated CT images of 200 hips in 100 asymptomatic pediatric patients (45 boys, 55 girls; mean age, 13.5 years; range, 9-18 years) stratified by the status of the triradiate physis and sex. We determined the acetabular anteversion angle at various levels in the axial plane as well as acetabular sector angles at five radial planes around the acetabulum. RESULTS: For both genders, anteversion angle was greater for the closed physis group throughout all levels (p < 0.001) and both open and closed physis groups were more anteverted as the cut moved caudally away from the acetabular roof (p < 0.001). At the center of the femoral head, the mean anteversion angle (± SD) in girls was 15° ± 3° in the open group and 19° ± 5° in the closed group (p < 0.001). In boys, the mean anteversion angle increased from 14° ± 4° in the open group to 19° ± 4° in the closed group (p = 0.003). In the superior, posterosuperior, and posterior planes, the acetabular sector angles were greater in the closed compared with the open physis group for both boys and girls with the largest increase occurring in the male posterosuperior plane (approximately 20°) (all p < 0.05). CONCLUSIONS: This study demonstrates that acetabular anteversion and acetabular sector angles in both male and female subjects increase with skeletal maturity as a result of growth of the posterior wall. This suggests that radiographic appearance of acetabular retroversion may not be attributable to overgrowth of the anterior wall but rather insufficient growth of the posterior wall, which has clinical treatment implications for pincer-type impingement.

Three-dimensional corrective osteotomies of mal-united clavicles--is the contralateral anatomy a reliable template for reconstruction?

In computer-assisted preoperative planning of corrective osteotomies, the unaffected contralateral bone often serves as three-dimensional template for the reconstruction of mal-united bones. Before applying this approach to new anatomy such as the clavicle bone, it is important to study asymmetry between the sides. The purpose of this study was to investigate bilateral symmetry of the clavicle in healthy cadavers using three-dimensional measurement techniques. Bilateral symmetry of 102 clavicles (51 cadavers, mean age: 52.19 years, 37 male) was measured based on three-dimensional models reconstructed from computed tomography. Besides length, volume, and surface, the side-differences were evaluated by considering the mirrored left clavicle as the reconstruction template and the right clavicle as the one that will be realigned by osteotomy. The relative transformation between the aligned segments was measured to express the difference with to three-dimensional translation and rotation. The same procedure was repeated using mean-sized clavicles, one for each gender, as the template. The contralateral side was a significant more accurate reconstruction template compared to a mean-sized clavicle (P < 0.001). Nevertheless, an average side-differences with respect to rotation and translation of 8.79° ± 5.2° and 3.5 mm ± 2.7 mm, respectively. The left clavicles were significant (P = 0.001) longer with 154 mm compared to the right ones (151 mm). Three-dimensional differences between the left and right clavicles exist, but can be considered as small. Therefore, the contralateral side appears to be a reliable reconstruction template, in particular compared to a mean-sized clavicle.

Is acetabular osteoplasty always required in mixed impingement?

BACKGROUND: Mixed femoroacetabular impingement (FAI) is typically managed with both femoral and acetabular rim osteoplasties, but it has not been reported if the rim osteoplasty is always required. HYPOTHESIS/PURPOSE: We hypothesized that mixed FAI managed by femoral or combined femoral and acetabular osteoplasties will both attain satisfactory clinical results, provided intraoperative impingement-free functional motion is attained. METHODS: We retrospectively reviewed 30 hips (23 patients, mean age at surgery 24.3 years, mean follow-up time 1.6 years) with mixed FAI who underwent surgical dislocation of the hip and had femoral osteochondroplasty with rim trim (RT, n = 21) or no rim trim (NRT, n = 9). Physical examination results and Western Ontario and McMaster Universities Osteoarthritis (WOMAC) scores were evaluated. RESULTS: Mean (± SD) WOMAC pain scores improved from 6.56 (± 2.96) to 2.33 (± 3.64) in the NRT group (p = .002) and from 6.86 (± 4.15) to 3.86 (± 3.95) in the RT group (p = .014). Function improved in both groups, but the difference was significant only for the NRT group (p < .001). Over 50 % of patients in both groups had resolution of impingement sign. Internal rotation increased from 8.6° (± 11.8) to 20.0° (± 10.4) in the NRT group (p = .043) and from 4.0° (± 12.1) to 18.6° (± 14.0) in the RT group (p < .001). Both groups had increased flexion post-operatively to normal range, but the change was only significant for the RT group (p = .02). Both groups had insignificant decreases in external rotation. CONCLUSION: Satisfactory clinical outcomes were seen in hips with mixed impingement, regardless of whether RT was performed, provided impingement-free functional motion was attained and no severe cartilage damage was seen.

Correlation of Systemic Inflammatory Markers With Radiographic Stages of Charcot Osteoarthropathy.

BACKGROUND: Charcot osteoarthropathy (COA) is characterized by a progressive destruction of bone and joint associated with neuropathy and is most common in the foot and ankle. Clinical manifestation of COA is frequently indistinguishable from other causes of pain, swelling, and erythema of the affected extremity, in particular, infection. Diagnosis of COA can be challenging in particular in early stages where radiographic changes are sparse. The presence of elevated systemic inflammatory parameters in the context of suspected infection may delay early diagnosis and treatment of COA. The aim of this retrospective analysis was to assess whether elevated systemic inflammatory parameters may be present, in particular in early stages of COA and thus not be used as an exclusion criterion for the diagnosis of COA. METHODS: Forty-two patients (mean age 48.2 ± 9.4 years, 36 male, 6 female) with a diagnosis of unilateral COA were the subject of this retrospective study. The diagnosis of COA was confirmed by plain radiographs, magnetic resonance imaging and clinical course. Systemic inflammatory parameters were recorded at the time of referral. Acute stages (stages 0 and 1) were treated with a total contact cast (TCC) and protected weight bearing for a minimum of 6 weeks. For chronic stages (stages 2 and 3) custom-made shoes were prescribed. The feet were stratified into "acute" (Eichenholz stages 0 and 1) and "subacute/chronic" (Eichenholz stages 2 and 3) groups. RESULTS: Statistically significant differences were observed for all recorded systemic inflammatory parameters (C-reactive protein level, WBC count, erythrocyte sedimentation rate) between the acute and subacute/chronic groups. No statistical difference was observed considering the anatomic pattern of involvement. CONCLUSION: The present study demonstrated that elevated systemic inflammatory parameters may be present in COA and can further be used to distinguish between acute and subacute stages of COA, based on the Eichenholtz classification. Thus, we suggest that elevated inflammatory markers should not be considered an exclusion criterion for the diagnosis of COA. LEVEL OF EVIDENCE: Level III, retrospective comparative series.

Prognostic factors for mid-term symptom relief after open surgical correction for femoroacetabular impingement.

BACKGROUND: We sought to identify, which patient and radiographic factors at preoperative and 1-year follow up will predict patient symptom relief at mid-term. MATERIALS AND METHODS: A total of 50 hips in 47 patients with symptomatic FAI were included in this retrospective study. We stratified the hips into "success" and "failure" groups based on the change from baseline to mid-term follow up WOMAC pain score (mean follow up of 5.8 years). An attempt was made to identify factors that are predictive of mid-term outcome among preoperative radiographic measures, dGEMRIC index, range of motion and WOMAC score as well as 1-year follow-up range of motion, radiographic measures, and WOMAC pain scores. RESULTS: At 1-year follow up, the success rate was 72% (36/50) and at mid-term follow the success rate increased to 82% (41/50). There were no significant associations between mid-term pain scores and baseline factors (all p-values ≥0.10). One-year pain score and hip internal rotation was associated with poor mid-term pain scores but only the 1-year pain score was associated with the mid-term success/failure outcome. CONCLUSIONS: We did not identify clear preoperative predictors of mid-term results but patients with poor pain scores and limited hip internal rotation at 1-year follow-up are less likely to do well at mid-term.

Does periacetabular osteotomy for hip dysplasia modulate cartilage biochemistry?

BACKGROUND: The aim of periacetabular osteotomy is to improve joint mechanics in patients with developmental dysplasia of the hip. In our study, we tried to determine whether the proteoglycan content, as measured with delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC), can be modulated with the alteration of the hip joint biomechanics. METHODS: In this prospective cohort study, thirty-seven patients (thirty-seven hips) with no or minimal osteoarthritis were treated with periacetabular osteotomy for symptomatic acetabular dysplasia. All patients had preoperative and one-year follow-up dGEMRIC scans. Twenty-eight of the thirty-seven also had two-year scans. The changes in dGEMRIC findings and hip morphology between the preoperative visit and the examinations at one and two years following the periacetabular osteotomy were assessed. RESULTS: The mean preoperative dGEMRIC index (and standard deviation) was 561.6 ± 117.6 ms; this decreased to 515.2 ± 118.4 ms at one year after periacetabular osteotomy but subsequently recovered to 529.2 ± 99.1 ms at two years postoperatively. The decrease in the dGEMRIC index of the acetabular cartilage after surgery appears to be most pronounced at the superior aspect of the acetabulum, where the decrease in mechanical loading after periacetabular osteotomy would be most pronounced. All domains of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) demonstrated significant improvement from the preoperative to the postoperative visits (all p < 0.001). CONCLUSIONS: Periacetabular osteotomy for developmental dysplasia of the hip appears to alter the mechanical loading of articular cartilage in the hip, which in turn alters the cartilage matrix composition, as demonstrated by dGEMRIC.