β-Ecdysone Augments Peak Bone Mass in Mice of Both Sexes

Background

One of the strongest predictors for osteoporosis is peak bone mass. Interventions to augment peak bone mass have yet to be developed. β-Ecdysone (βEcd), a natural steroid-like compound produced by arthropods to initiate metamorphosis, is believed to have androgenic effects and so may be used to augment bone mass.

Questions/purposes

The purpose of this study was to use both male and female (1) gonadal-sufficient; and (2) -insufficient mice to investigate sex differences in terms of bone development and structure after βEcd administration.

Methods

Two-month-old male and female Swiss-Webster mice were randomized to receive either vehicle or βEcd (0.5 mg/kg) for 3 weeks. In a separate experiment to evaluate the effects of βEcd on sex hormone-deficient mice, gonadectomy was performed in male (orchiectomy [ORX]) and female mice (ovariectomy [OVX]). Sham-operated and the ORX/OVX mice were then treated for 3 weeks with βEcd. Primary endpoints for the study were trabecular bone structure and bone strength.

Results

In male mice, the trabecular bone volume was 0.18 ± 0.02 in the placebo-treated (PL) and 0.23 ± 0.02 in the βEcd-treated group (p < 0.05 versus PL); and 0.09 ± 0.01 in the ORX group (p < 0.05 versus PL) and 0.12 ± 0.01 in the ORX + βEcd group. Vertebral bone strength (maximum load) was 43 ± 2 in PL and 51 ± 1 in the βEcd-treated group (p < 0.05 versus PL); and 30 ± 4 in the ORX group (p < 0.05 versus PL) and 37 ± 3 in the ORX + βEcd group. In female mice, trabecular bone volume was 0.23 ± 0.02 in PL and 0.26 ± 0.02 in the βEcd-treated group (p < 0.05 versus PL); and 0.15 ± 0.01 in the OVX group (p < 0.05 versus PL) and 0.14 ± 0.01 in the OVX + βEcd group. Maximum load of the vertebrae was 45 ± 2 in PL and 48 ± 4 in the βEcd-treated group; and 39 ± 4 in the OVX group (p < 0.05 versus PL) and 44 ± 4 in the OVX + βEcd group.

Conclusions

These findings suggest the potential use of βEcd in the augmentation of bone mass in growing male and female mice. It may also partially prevent the detrimental effects of gonadectomy on trabecular bone.

Clinical Relevance

Our results support the potential use of βEcd or nature products that are rich in βEcd to augment peak bone mass. βEcd may differ from the other anabolic hormone treatments that may have severe side effects such as serious cardiac complications. However, its effects on humans remain to be determined.     

Gait analysis combined with the expression of TGF-β1, TGF-β3 and CREB during Achilles tendon healing in rat

PurposeTo observe the changes of gait behavior and the expression of wound healing factors of transforming growth factor-β1 (TGF-β1), TGF-β3 and cAMP response element binding protein-1 (CREB-1) during the healing of Achilles tendon in a rat model, and to investigate whether gait analysis can be used to evaluate the tendon healing.MethodsAchilles tendon of 40 healthy male Sprague-Dawley rats were transected and sutured to establish the Achilles tendon injury (ATI) model. They were randomly divided into 4 groups based on the observational time point at 1, 2, 4 and 6 weeks after injury (n = 10 for each group). Before modeling, 9 rats were randomly selected for CatWalk gait analysis, which contained step cycle, single stance time and average speed. Data were recorded as the normal controls. After then, ATI models were established in the left hind limbs of the all 40 rats (ATI group), while the right hind limbs were only cut and sutured without injury of the Achilles tendon (sham operation group). At 1, 2, 4 and 6 weeks after injury, the gait behavior of the corresponding group of rats (n = 9) as observed and recorded by CatWalk platform. After then, the rats were sacrificed and Achilles tendon of both limbs was harvested. The tendon healing was observed by gross anatomy and histological examination, and the protein and mRNA expression of TGF-β1, TGF-β3, CREB-1 were observed by immunohistochemistry and qPCR. The results of tendon gross grading were analyzed by Wilcoxon rank sum test, and other data were analyzed by one-way analysis of variance among multiple groups.ResultsCompared with normal controls, all gait indexes (step cycle, single stance time and average speed) were greatly affected following ATI, which however improved with time. The step cycle was significantly lower at 1, 2 and 4 weeks after ATI (compared with normal controls, all p < 0.05), but almost returned to the normal level at 6 weeks ((0.694 ± 0.102) vs. (0.503 ± 0.094) s, p > 0.05). The single stance time of the ATI group was significantly shorter at 1 and 2 weeks after operation ((0.078 ± 0.010) s at 1 week, (0.078 ± 0.020) s at 2 weeks, all p < 0.001) and revealed no significant difference at 4 weeks (p = 0.120). The average speed of ATI group at 1, 2, 4, 6 weeks was significantly lower than that in the normal control group (all p < 0.001).Gross observation showed that the grade of local scar adhesion in ATI group increased significantly at 2, 4 and 6 weeks, compared with the sham operation group (all p < 0.001). Extensive adhesion was formed at 6 weeks after ATI. The results of HE staining showed that the number of fibroblast increased gradually and arranged more orderly in ATI group at 1, 2 and 4 weeks (all p < 0.001), and decreased at 6 weeks, but it was still significantly higher than that of the sham operation group (p < 0.001). Immunohistochemistry showed that the positive expression of TGF-β1, TGF-β3, CREB-1 in ATI group was higher than that in the sham operation group at 4 time points (all p < 0.05), which reached the peak at 2 weeks after operation and decreased at 4 weeks (p = 0.002, p < 0.001, p = 0.041, respectively). The results of qPCR suggested that the mRNA expression of TGF-β1, TGF-β3, CREB-1 in ATI group was higher than that in the sham operation group at all-time points (all p < 0.05), which reached the peak at 2 weeks after operation, decreased at 4 weeks, and significantly decreased at 6 weeks (all p < 0.001).ConclusionGait behavior indexes are associated with Achilles tendon healing. The study gives an insight of TGF-β1, TGF-β3, CREB-1 changes in the coursing of Achilles tendon healing and these cytokines may be able to be used to regulate the Achilles tendon healing.     

What Middle Phalanx Base Fracture Characteristics are Most Reliable and Useful for Surgical Decision-making?

Background

Fracture-dislocations of the proximal interphalangeal joint are vexing because subluxation and articular damage can lead to arthrosis and the treatments are imperfect. Ideally, a surgeon could advise a patient, based on radiographs, when the risk of problems merits operative intervention, but it is unclear if middle phalanx base fracture characteristics are sufficiently reliable to be useful for surgical decision making.

Questions/purposes

We evaluated (1) the degree of interobserver agreement as a function of fracture characteristics, (2) the differences in interobserver agreement between experienced and less-experienced hand surgeons, and (3) what fracture characteristics and surgeon characteristics were associated with the decision for operative treatment.

Methods

Ninety-nine (33%) of 296 hand surgeons evaluated 21 intraarticular middle phalanx base fractures on lateral radiographs. Eighty-one surgeons (82%) were in academic practice and 57 (58%) had less than 10 years experience. Participants assessed six fracture characteristics and recommended treatment (nonoperative or operative: extension block pinning, external fixation, open reduction and internal fixation, volar plate arthroplasty, or hemihamate autograft arthroplasty) for all cases.

Results

With all surgeons pooled together, the interobserver agreement for fracture characteristics was substantial for assessment of a 2-mm articular step or gap (kappa, 0.73; 95% CI, 0.60–0.86; p < 0.001), subluxation or dislocation (kappa, 0.72; 95% CI, 0.58–0.86; p < 0.001), and percentage of articular surface involved (intraclass correlation coefficient [ICC], 0.67; 95% CI, 0.54–0.81; p < 0.001); moderate for comminution (kappa, 0.55; 95% CI, 0.39–0.70; p < 0.001) and stability (kappa, 0.54; 95% CI, 0.39–0.69; p < 0.001); and fair for the number of fracture fragments (ICC, 0.39; 95% CI, 0.27–0.57; p < 0.001). When recommending treatment, interobserver agreement was substantial (kappa, 0.69; 95% CI, 0.50–0.88; p < 0.001) for the recommendation to operate or not to operate, but only fair (kappa, 0.34; 95% CI, 0.21–0.47; p < 0.001) for the specific type of treatment, indicating variation in operative techniques. There were no differences in agreement for any of the fracture characteristics or treatment preference between less-experienced and more-experienced surgeons, although statistical power on this comparison was low. None of the surgeon characteristics was associated with the decision for operative treatment, whereas all fracture characteristics were, except for stable and uncertain joint stability. Articular step or gap (β, 0.90; R-squared, 0.89; 95% CI, 0.75–1.05; p < 0.001), likelihood of subluxation or dislocation (β, 0.80; R-squared, 0.76; 95% CI, 0.59–1.02; p < 0.001), and unstable fractures (β, 0.88; R-squared, 0.81; 95% CI, 0.67–1.1; p < 0.001), are most strongly associated with the decision for operative treatment.

Conclusions

We found that assessment of a step or gap and likelihood of subluxation were most reliable and are strongly associated with the decision for operative treatment. Surgeons largely agree on which fractures might benefit from surgery, and the variation seems to be with the operative technique. Efforts at improving the care of these fractures should focus on the comparative effectiveness of the various operative treatment options.

Level of Evidence

Level III, diagnostic study.

Electronic supplementary material

The online version of this article (doi:10.1007/s11999-015-4394-7) contains supplementary material, which is available to authorized users.     

Are There Sex Differences in Knee Cartilage Composition and Walking Mechanics in Healthy and Osteoarthritis Populations?

Background

Women are at a greater risk for knee osteoarthritis (OA), but reasons for this greater risk in women are not well understood. It may be possible that differences in cartilage composition and walking mechanics are related to greater OA risk in women.

Questions/purposes

(1) Do women have higher knee cartilage and meniscus T_1ρ than men in young healthy, middle-aged non-OA and OA populations? (2) Do women exhibit greater static and dynamic (during walking) knee loading than men in young healthy, middle-aged non-OA and OA populations?

Methods

Data were collected from three cohorts: (1) young active (< 35 years) (20 men, 13 women); (2) middle-aged (≥ 35 years) without OA (Kellgren-Lawrence [KL] grade < 2) (43 men, 65 women); and (3) middle-aged with OA (KL > 1) (18 men, 25 women). T_1ρ and T₂ relaxation times for cartilage in the medial knee, lateral knee, and patellofemoral compartments and medial and lateral menisci were quantified with 3.0-T MRI. A subset of the participants underwent three-dimensional motion capture during walking for calculation of peak knee flexion and adduction moments, flexion and adduction impulses, and peak adduction angle. Differences in MR, radiograph, and gait parameters between men and women were compared in the three groups separately using multivariate analysis of variance.

Results

Women had higher lateral articular cartilage T_1ρ (men = 40.5 [95% confidence interval {CI}, 38.8–42.3] ms; women = 43.3 [95% CI, 41.9–44.7] ms; p = 0.017) and patellofemoral T_1ρ (men = 44.4 [95% CI, 42.6–46.3] ms; women = 48.4 [95% CI, 46.9–50.0] ms; p = 0.002) in the OA group; and higher lateral meniscus T_1ρ in the young group (men = 15.3 [95% CI, 14.7–16.0] ms; women = 16.4 [95% CI, 15.6–17.2] ms; p = 0.045). The peak adduction moment in the second half of stance was lower in women in the middle-aged (men = 2.05 [95% CI, 1.76–2.34] %BW*Ht; women = 1.66 [95% CI, 1.44–1.89] %BW*Ht; p = 0.037) and OA (men = 2.34 [95% CI, 1.76–2.91] %BW*Ht; women = 1.42 [95% CI, 0.89–1.94] %BW*Ht; p = 0.022) groups. Static varus from radiographs was lower in women in the middle-aged (men = 178° [95% CI, 177°–179°]; women = 180° [95% CI, 179°–181°]; p = 0.002) and OA (men = 176° [95% CI, 175°–178°]; women = 180° [95% CI, 179°–181°]; p < 0.001) groups. Women had lower varus during walking in all three groups (young: men = 4° [95% CI, 3°–6°]; women = 2° [95% CI, 0°–3°]; p = 0.013; middle-aged: men = 2° [95% CI, 1°–3°]; women = 0° [95% CI, −1° to 1°]; p = 0.015; OA: men = 4° [95% CI, 2°–6°]; women = 0° [95% CI, −2° to 2°]; p = 0.011). Women had a higher knee flexion moment (men = 4.24 [95% CI, 3.58–4.91] %BW*Ht; women 5.40 [95% CI, 4.58–6.21] %BW*Ht; p = 0.032) in the young group.

Conclusions

These data demonstrate differences in cartilage composition and gait mechanics between men and women in young healthy, middle-aged healthy, and OA cohorts. Considering the cross-sectional nature of the study, longitudinal research is needed to investigate if these differences in cartilage composition and walking mechanics are associated with a greater risk of lateral tibiofemoral or patellofemoral OA in women. Future studies should also investigate the relative risk of lateral versus medial patellofemoral cartilage degeneration risk in women compared with men.

Level of Evidence

Level III, retrospective study.     

A Comparison of the Efficacy of Various Antioxidants on the Oxidative Stability of Irradiated Polyethylene

Background

Ultrahigh-molecular-weight polyethylene (UHMWPE) is subjected to radiation crosslinking to form highly crosslinked polyethylene (HXLPE), which has improved wear resistance. First-generation HXLPE was subjected to thermal treatment to reduce or quench free radicals that can induce long-term oxidative degeneration. Most recently, antioxidants have been added to HXLPE to induce oxidative resistance rather than by thermal treatment. However, antioxidants can interfere with the efficiency of radiation crosslinking.

Questions/purposes

We sought to identify (1) which antioxidant from among those tested (vitamin E, β-carotene, butylated hydroxytoluene, or pentaerythritol tetrakis [methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate]) causes the least reduction of crosslinking; (2) which promotes the greatest oxidative stability; and (3) which had the lowest ratio of oxidation index to crosslink density.

Methods

Medical-grade polyethylene (PE) resin was blended with 0.1 weight % of the following stabilizers: alpha tocopherol (vitamin E), β-carotene, butylated hydroxytoluene (BHT), and pentaerythritol tetrakis [methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (a hindered phenol antioxidant [HPAO]). These blends were compression-molded into sheets and subjected to electron beam irradiation to a dose of 100 kGy. Equilibrium swelling experiments were conducted to calculate crosslink density. Each PE was subjected to accelerated aging for a period of 2 weeks and Fourier transform infrared spectroscopy was used to measure the maximum oxidation. Statistical analysis was conducted using analysis of variance with Fisher’s protected least significant difference in which a p value of < 0.05 was used to define a significant difference.

Results

The least reduction of crosslinking in antioxidant-containing HXLPE was observed with HPAO, which had a crosslink density (n = 6) of 0.167 (effect size [ES] = 0.87; 95% confidence interval [CI], 0.162–0.173) mol/dm³ compared with 0.139 (ES = 1.57; 95% CI, 0.132–0.146) mol/dm³ (p = 0.020) for BHT, 0.131 (ES = 1.77; 95% CI, 0.123–0.139) mol/dm³ (p = 0.004) for β-carotene, and 0.130 (ES = 1.79; 95% CI, 0.124–0.136) mol/dm³ (p = 0.003) for vitamin E, whereas pure HXLPE had a crosslink density of 0.203 (95% CI, 0.170–0.235) mol/dm³ (p = 0.005). BHT-PE had an oxidation index of 0.21 (ES = 13.14; 95% CI, 0.19–0.22) followed by HPAO-PE, vitamin E-PE and β-carotene-PE, which had oxidation indices of 0.28 (ES = 9.68; 95% CI, 0.28–0.29), 0.29 (ES = 9.59; 95% CI, 0.27–0.30), and 0.35 (ES = 6.68; 95% CI, 0.34–0.37), respectively (p < 0.001 for all groups). BHT-PE had the lowest ratio of oxidation index to crosslink density of the materials tested (1.49, ES = 1.94; 95% CI, 1.32–1.66) followed by HPAO-PE (1.70, ES = 1.52; 95% CI, 1.61–1.80), vitamin E-PE (2.21, ES = 0.52; 95% CI, 2.05–2.38), and β-carotene-PE (2.69, ES = -0.43; 95% CI, 2.46–2.93) compared with control PE (2.47, 95% CI, 2.07–2.88) with β-carotene (p = 0.208) and vitamin E (p = 0.129) not being different from the control.

Conclusions

BHT-modified HXLPE was found in this study to have the lowest oxidation index as well as the lowest ratio of oxidation index to crosslink density compared with vitamin E, HPAO, and β-carotene-modified HXLPEs. More comprehensive studies are required such as wear testing using joint simulators as well as biocompatibility studies before BHT-modified HXLPE can be considered for clinical use.

Clinical Relevance

BHT is a synthetic antioxidant commonly used in the polymer industry to prevent long-term oxidative degradation and has been approved by the FDA for use in cosmetics and foodstuffs. It may be an attractive potential stabilizer for HXLPE in total joint replacements.     

Time Seeing a Hand Surgeon Is Not Associated With Patient Satisfaction

Background

Previous studies, predominantly in the primary care setting, identified time spent with the physician as an important predictor of satisfaction. It is unknown if the same holds true in hand surgery.

Questions/purposes

Is patient satisfaction measured immediately after an office visit associated with the duration of time spent with the hand surgeon? What other factors are associated with satisfaction directly after the visits and 2 weeks after the appointment?

Methods

We prospectively enrolled 81 patients visiting our hand and upper extremity surgery outpatient clinic. We recorded their demographics and measured physical function, pain behavior, symptoms of depression, time spent in the waiting room, time spent with the physician, and patient satisfaction. Office times were measured using our patient ambulatory tracking system and by a research assistant outside the clinic room. To assess satisfaction we used items from the Consumer Assessment of Healthcare Providers and Systems survey (a federally developed standardized survey instrument) relevant to our study. Two weeks later, 51 (64%) patients were available for telephone followup and the same measures were completed. Mean time spent with the hand surgeon was 8 ± 5 minutes and mean in-office wait time to see the hand surgeon was 32 ± 18 minutes. A priori power analyses indicated that 77 patients would provide 80% power to detect an effect size f² = 0.18 for a regression with five predictors. This means that we would detect time spent with the physician as a significant factor if it accounted for 7% or more of the variability in satisfaction.

Results

Time spent with the hand surgeon was not associated with patient satisfaction measured directly after the visit (r = –0.023; p = 0.84). Longer time waiting to see the physician correlated with decreased patient satisfaction (r = –0.30; p = 0.0057). The final multivariable model for increased satisfaction directly after the office visit included shorter waiting time (regression coefficient [β] –0.0014; partial R² 0.094; 95% confidence interval [CI], –0.0024 to –0.00042; p = 0.006) and being married/living with a partner (β 0.057; partial R² 0.11; 95% CI, 0.021–0.093; p = 0.002 [adjusted R² 0.18; p < 0.001]). Similarly, multivariable analysis found higher patient satisfaction 2 weeks after the visit to be independently associated with shorter waiting time (β –0.0037; partial R² 0.10; 95% CI, –0.0070 to –0.00054; p = 0.023) and being married/living with a partner (β 0.15; partial R² 0.12; 95% CI, 0.033–0.26; p = 0.012 [adjusted R² 0.16; p = 0.0052]).

Conclusions

Patient satisfaction among patients undergoing hand surgery may relate more to shorter time in the waiting room and to the quality more than the quantity of time spent with the patient.

Level of Evidence

Level II, prognostic study.

Electronic supplementary material

The online version of this article (doi:10.1007/s11999-014-4090-z) contains supplementary material, which is available to authorized users.     

Modified Dunn Procedure is Superior to In Situ Pinning for Short-term Clinical and Radiographic Improvement in Severe Stable SCFE

Background

In situ pinning is the conventional treatment for a stable slipped capital femoral epiphysis (SCFE). However, with a severe stable SCFE the residual deformity may lead to femoroacetabular impingement and articular cartilage damage. A modified Dunn subcapital realignment procedure has been developed to allow for correction at the level of the deformity while preserving the blood supply to the femoral head.

Questions/purposes

We compared children with severe stable SCFE treated with the modified Dunn procedure or in situ pinning in terms of (1) proximal femoral radiographic deformity; (2) Heyman and Herndon clinical outcome; (3) complication rate; and (4) number of reoperations performed after the initial procedure.

Methods

In this nonmatched retrospective study, 15 patients treated with the modified Dunn procedure (between 2007 and 2012) and 15 treated with in situ pinning (between 2001 and 2009) for severe but stable SCFE were followed for a mean of 2.5 years (range, 1–6 years). During the period in question, the decision regarding which procedure to use was based on the on-call surgeon’s discretion; six surgeons performed in situ pinning and three surgeons performed the modified Dunn procedure. A total of 15 other patients were treated for the same diagnosis during the study period but were lost to followup before 1 year; of those, 12 were in the in situ pinning group. Radiographs were reviewed to measure the AP and lateral alpha angles, femoral head-neck offset, and Southwick angle preoperatively and at the latest clinical visit. The Heyman and Herndon clinical outcome, complications, and subsequent hip surgeries were recorded.

Results

At latest followup, the median AP alpha angle (52°, range 41°–59° versus 76°, interquartile range [IQR]: 68°–88°; p = 0.0017), median lateral alpha angle (44°, IQR: 40°–51° versus 87°, IQR: 74°–96°; p < 0.001), median head-neck offset (7 mm, IQR: 5–9 mm versus −5, IQR: −11 to −4 mm; p < 0.001), and median Southwick angle (16°, IQR: 6°–23° versus 58°, IQR: 47°–66°; p < 0.001) revealed better deformity correction with the modified Dunn procedure compared with in situ pinning. Nine patients had good or excellent results in the modified Dunn group compared with four of 15 in the in situ pinning group (p = 0.0343; odds ratio, 5.86; 95% CI, 1.13–40.43). With the numbers available, there were no differences in the numbers of complications in each group (five versus three complications in the in situ and modified Dunn groups, respectively; p = 0.66), but there were more reoperations in the in situ pinning group (three versus seven; p = 0.0230).

Conclusions

The modified Dunn procedure results in better morphologic features of the femur, a higher rate of good and excellent Heyman and Herndon clinical outcome, a lower reoperation rate, and a similar occurrence of complications when compared with in situ pinning for treatment of severe stable SCFE.

Level of Evidence

Level III, therapeutic study.     

Prevalence and Risk Factors of Spine,Shoulder, Hand,Hip, and Knee Osteoarthritis in Community-dwelling Koreans Older Than Age 65 Years

Background

Osteoarthritis (OA) is common and disabling among older patients around the world. Data exploring the prevalence and risk factors of OA are of paramount importance in establishing healthcare policies. However, few studies have evaluated these topics among Asian populations.

Questions/purposes

This study was conducted to determine the prevalence and risk factors of radiographic OA in the spine, shoulder, hand, hip, and knee in Koreans older than age 65 years.

Methods

A simple random sample (N = 1118) was drawn from a roster of elderly individuals older than age 65 years in Seongnam. Of the 1118 invited subjects, 696 (males = 298, females = 398) participated in this study (a response rate of 62%). The mean age of respondents was 72 ± 5 years (range, 65–91 years). Radiographs of the lumbar spine, shoulder, hand, hip, and knee were taken and afterward evaluated for radiographic OA. The Kellgren-Lawrence grading system was used for all mentioned joints, and radiographic OA was defined as Grade 2 changes or higher. The association of sex, aging, and obesity with OA in each of the mentioned joints was determined with the help of multivariate logistic regression.

Results

The highest prevalence of radiographic OA was seen in the spine (number of subjects with OA/number of whole population = 462 of 696 [66%]) followed by the hand (415 of 692 [60%]), knee (265 of 696 [38%]), shoulder (36 of 696 [5%]), and hip (15 of 686 [2%]). Female sex was associated with knee OA (odds ratio [OR], 5.7; 95% confidence interval [CI], 3.9–8.4; p < 0.001) and hand OA (OR, 2.3; 95% CI, 1.6–3.1; p < 0.001), and male sex was associated with spine OA (OR, 0.7; 95% CI, 0.5–1.0; p = 0.025). Aging was associated with radiographic OA in the spine, knee, and hand (OR per 5-year increments, 1.3 [95% CI, 1.1–1.6; p = 0.001], 1.6 [95% CI, 1.4–1.9; p < 0.001], and 1.4 [95% CI, 1.2–1.7; p < 0.001]), respectively) but not associated with OA in the hip and shoulder. Obesity was associated with knee OA (OR, 3.4; 95% CI, 2.4–5.0; p < 0.001) and spine OA (OR, 1.5; 95% CI, 1.1–2.2; p = 0.014) but not with OA in other joints.

Conclusions

OA of the spine, hand, and knee is likely to become a major public health problem rather than shoulder and hip OA in Korea. Associations of demographic factors with radiographic OA differed among each joint, and that would be valuable information to assess the role and influence of risk factors of OA in various joints.

Level of Evidence

Level III, prognostic study.     

Rotator Cuff Fatty Infiltration and Atrophy Are Associated With Functional Outcomes in Anatomic Shoulder Arthroplasty

Background

Shoulder arthroplasty provides reliable pain relief and restoration of function. However, the effects of fatty infiltration and atrophy in the supraspinatus and infraspinatus muscles on functional outcomes are not well understood.

Questions/purposes

The purposes of this study were to (1) compare preoperative with postoperative fatty infiltration and atrophy of the supraspinatus and infraspinatus muscles after primary shoulder arthroplasty; and (2) identify any associations between these variables and outcome measures.

Methods

A retrospective analysis was undertaken of 62 patients with a mean age of 67 years (range, 34–90 years) who underwent shoulder arthroplasty. CT scans were conducted preoperatively and at 12 months postoperatively. Outcome variables included the degree of supraspinatus and infraspinatus fatty infiltration (percent fatty infiltration and Goutallier grade), muscle area (percent muscle area and Warner atrophy grade), shoulder strength, and the Western Ontario Osteoarthritis Score (WOOS), American Shoulder and Elbow Surgeons score, and Constant outcome score.

Results

Preoperatively, the mean percent fatty infiltration (FI) within the supraspinatus and infraspinatus was identical at 14%. One year after shoulder arthroplasty, both muscles had less fatty infiltration (6% and 7%, respectively; p < 0.001). Similarly, the Goutallier grade significantly improved postoperatively for the supraspinatus (p = 0.0037) and infraspinatus (p = 0.0007). Conversely, measures of muscle atrophy remained unchanged postoperatively (p > 0.251). Preoperatively, greater supraspinatus percent FI was negatively associated with preoperative shoulder strength (r = 0.37, p = 0.001) and Constant score (r = 0.38, p = 0.001). Postoperative infraspinatus percent FI was negatively associated with postoperative strength (r = 0.3, p = 0.021) and Constant score (r = 0.3, p = 0.04). Multivariable regression analysis of possible predictive factors demonstrated that preoperative supraspinatus percent muscle area (p = 0.016) and the diagnosis of osteoarthritis (p = 0.017) were associated with better followup WOOS scores, and preoperative supraspinatus strength was associated with postoperative strength (p = 0.0024). Higher degrees of preoperative percent FI were not associated with worse patient-reported outcomes postoperatively.

Conclusions

Supraspinatus and infraspinatus fatty infiltration improves after shoulder arthroplasty, whereas muscle area remains unchanged. Although further study of these variables is required, the negative associations identified between preoperative supraspinatus atrophy and the diagnosis of rheumatoid arthritis and postoperative quality-of-life outcome scores may aid the clinician in selecting the best treatment option for glenohumeral arthrosis and in the management of patient expectations.

Level of Evidence

Level III, prognostic study.     

Novel Antibiotic-loaded Point-of-care Implant Coating Inhibits Biofilm

Background

Orthopaedic biomaterials are susceptible to biofilm formation. A novel lipid-based material has been developed that may be loaded with antibiotics and applied as an implant coating at point of care. However, this material has not been evaluated for antibiotic elution, biofilm inhibition, or in vivo efficacy.

Questions/purposes

(1) Do antibiotic-loaded coatings inhibit biofilm formation? (2) Is the coating effective in preventing biofilm in vivo?

Methods

Purified phosphatidylcholine was mixed with 25% amikacin or vancomycin or a combination of 12.5% of both. A 7-day elution study for coated titanium and stainless steel coupons was followed by turbidity and zone of inhibition assays against Staphylococcus aureus and Pseudomonas aeruginosa. Coupons were inoculated with bacteria and incubated 24 hours (N = 4 for each test group). Microscopic images of biofilm were obtained. After washing and vortexing, attached bacteria were counted. A mouse biofilm model was modified to include coated and uncoated stainless steel wires inserted into the lumens of catheters inoculated with a mixture of S aureus or P aeruginosa. Colony-forming unit counts (N = 10) and scanning electron microscopy imaging of implants were used to determine antimicrobial activity.

Results

Active antibiotics with colony inhibition effects were eluted for up to 6 days. Antibiotic-loaded coatings inhibited biofilm formation on in vitro coupons (log-fold reductions of 4.3 ± 0.4 in S aureus and 3.1 ± 0 for P aeruginosa in phosphatidylcholine-only coatings, 5.6 ± 0 for S aureus and 3.1 ± 0 for P aeruginosa for combination-loaded coatings, 5.5 ± 0.3 for S aureus in vancomycin-loaded coatings, and 3.1 ± 0 for P aeruginosa for amikacin-loaded coatings (p < 0.001 for all comparisons of antibiotic-loaded coatings against uncoated controls for both bacterial strains, p < 0.001 for comparison of antibiotic-loaded coatings against phosphatidylcholine only for S aureus, p = 0.54 for comparison of vancomycin versus combination coating in S aureus, P = 0.99 for comparison of antibiotic- and unloaded phosphatidylcholine coatings in P aeruginosa). Similarly, antibiotic-loaded coatings reduced attachment of bacteria to wires in vivo (log-fold reduction of 2.54 ± 0; p < 0.001 for S aureus and 0.83 ± 0.3; p = 0.112 for P aeruginosa).

Conclusions

Coatings deliver active antibiotics locally to inhibit biofilm formation and bacterial growth in vivo. Future evaluations will include orthopaedic preclinical models to confirm therapeutic efficacy.

Clinical Relevance

Clinical applications of local drug delivery coating could reduce the rate of implant-associated infections.     

Does Rotator Cuff Repair Improve Psychologic Status and Quality of Life in Patients With Rotator Cuff Tear?

Background

Recently, psychological status, patient-centered outcomes, and health-related quality of life (HRQoL) in patients with scheduled or who underwent orthopaedic surgeries have been emphasized. The relationship between preoperative psychological status and postoperative clinical outcome in patients with rotator cuff repair has not yet been investigated.

Questions/purposes

The primary objective of this study was to investigate changes in psychological status (depression, anxiety, insomnia) and HRQoL after rotator cuff repair. The secondary objective was to assess whether preoperative depression, anxiety, and insomnia predict clinical outcome after rotator cuff repair.

Methods

Forty-seven patients who underwent rotator cuff repair prospectively completed the visual analog scale (VAS) pain score, the UCLA Scale, the American Shoulder and Elbow Surgeons’ Scale (ASES), the Hospital Anxiety and Depression Scale (HADS), the Pittsburgh Sleep Quality Index (PSQI), and the World Health Organization Quality-of-life Scale Abbreviated Version (WHOQOL-BREF) before surgery and at 3, 6, and 12 months after surgery. Repeated-measures analysis of variance was used to evaluate the serial changes in psychological parameters and outcome measurements. The chi-square test was also used to compare preoperative and postoperative prevalence of depression, anxiety, and insomnia. Finally, multiple regression analysis was applied to determine the relationship between preoperative psychological status and postoperative clinical outcome.

Results

With surgery, depression, anxiety, and insomnia decreased, whereas quality of life increased. The mean HADS-D and HADS-A scores and the mean PSQI score decreased from 3.7 ± 3.3, 4.3 ± 4.3, and 6.6 ± 3.6, respectively, before surgery to 2.1 ± 2.3, 1.4 ± 2.4, and 4.2 ± 3.3, respectively, at 12 months after surgery (HADS-D mean difference 1.6 [95% confidence interval {CI}, 0.6–2.6], p = 0.003; HADS-A mean difference 2.9 [1.5–4.4], p < 0.001; PSQI mean difference 2.4 [1.3–3.4], p < 0.001). The mean WHOQOL-BREF score increased from 60.4 ± 11.0 before surgery to 67.4 ± 11.8 at 12 months after surgery (mean difference −7.0 [95% CI, −10.7 to −3.4], p < 0.001). At 12 months after surgery, there were decreases in the prevalence of depression (six of 47 [22.8%] versus three of 47 [6.4%], p = 0.002), anxiety (11 of 47 [23.4%] versus two of 47 [4.3%], p = 0.016), and insomnia (33 of 47 [70.2%] versus 20 of 47 [42.6%], p = 0.022). Preoperative HADS-depression, HADS-anxiety, and PSQI scores did not correlate with the VAS pain score, UCLA, or ASES scores at 12 months after surgery.

Conclusions

Psychological status and HRQoL improved with decreasing pain and increasing functional ability from 3 months after surgery. Preoperative depression, anxiety, and insomnia did not predict poor outcome after rotator cuff repair. Our findings suggest that successful rotator cuff repair may improve psychological status and HRQoL.

Level of Evidence

Level II, prospective study.     

Retrieval Analysis of Sequentially Annealed Highly Crosslinked Polyethylene Used in Total Hip Arthroplasty

Background

First-generation annealed and second-generation sequentially annealed, highly crosslinked polyethylenes (HXLPEs) have documented reduced clinical wear rates in their first decade of clinical use compared with conventional gamma inert-sterilized polyethylene. However, for both types of annealed HXLPE formulations, little is known about their reasons for revision, their in vivo oxidative stability, and their resistance to mechanical degradation.

Questions/purposes

We asked whether retrieved sequentially annealed HLXPE acetabular liners exhibited: (1) similar reasons for revision; (2) lower oxidation; (3) improved resistance to wear and degradation of mechanical properties; and (4) improved resistance to macroscopic evidence of rim damage when compared with acetabular liners fabricated from single-dose annealed HXLPE.

Methods

One hundred eighty-five revised acetabular liners in two cohorts (annealed and sequentially annealed) were collected in a multicenter retrieval program between 2000 and 2013. We controlled for implantation time between the two cohorts by excluding annealed liners with a greater implantation time than the longest term sequentially annealed retrieval (5 years); the mean implantation time (± SD) for the annealed components was 2.2 ± 1.4 years, and for the sequentially annealed liners, it was 1.2 ± 1.2 years. Reasons for revision were assessed based on medical records, radiographs, and examinations of the retrieved components. Oxidation was measured at the bearing surface, the backside surface, the locking mechanism, and the rim using Fourier transform infrared spectroscopy (ASTM F2102). Penetration was measured directly using a micrometer (accuracy: 0.001 mm). Mechanical behavior (ultimate load) was measured at the superior and inferior bearing surfaces using the small punch test (ASTM F2183). We used nonparametric statistical testing to analyze for differences in oxidation, penetration rates, and ultimate load when adjusting for HXLPE formulation as a function of implantation time.

Results

The acetabular liners in both cohorts were revised most frequently for instability, loosening, and infection. Oxidation indices (OIs) of the sequentially annealed liners were lower than annealed liners at the bearing surface (mean OI difference = 0.3; p < 0.001), the backside surface (mean OI difference = 0.2; p < 0.001), and the rim (mean OI difference = 2.6; p < 0.001). No differences were detected in linear penetration rates between the cohorts (p = 0.10). Ultimate strength at the bearing surface of the HLXPE was not different between sequentially annealed and annealed cohorts (p = 0.72).

Conclusions

We observed evidence of in vivo oxidation in retrieved annealed and, to a lesser extent, retrieved sequentially annealed acetabular liners. However, we observed no association between the levels of oxidation and clinical performance of the liners.

Clinical Relevance

The findings of this study document the oxidative and mechanical behavior of sequentially annealed HXLPE. The reduced oxidation levels in sequentially annealed liners support the hypothesis that annealing in sequential steps eliminates more free radicals. However, as a result of the short-term followup, analysis of longer-term retrievals is warranted.     

How Are Dysplastic Hips Different? A Three-dimensional CT Study

Background

Surgical correction of acetabular dysplasia can postpone or prevent joint degeneration. The specific abnormalities that make up the dysplastic hip are controversial.

Questions/purposes

(1) What are the relative size, shape, and orientations of the typical nondysplastic hip? (2) How do these variables differ in the developmentally dysplastic hip? (3) Are there version differences between the acetabuli of dysplastic and nondysplastic hips? (4) Are there pairs of variables in which the change in one is always accompanied by a change in the other for both nondysplastic and dysplastic acetabuli?

Methods

Of 117 consecutive three-dimensional (3-D) CT scans performed for hip dysplasia between March 1988 and October 1995, 48 met criteria of developmentally dysplastic hips by plain radiography. These were retrospectively compared with 55 pelvic 3-D CT scans culled from 81 consecutive scans performed for reasons other than hip dysplasia (ie, hip pain, trauma, infection) that did not affect the hip or pelvic landmarks. The 3-D reconstructions were orientated anatomically for standardization of the measurements to be compared. Representative 3-D volumes of the acetabular space were constructed from which we could measure anatomic positions and dimensional information. One author performed all image orientation and measurements.

Results

Nondysplastic acetabuli are essentially hemispheric with height equal to width and twice the depth. The dysplastic acetabuli were elongated in females (52.4 ± 6.2 mm for dysplastic versus 46.5 ± 4.6 mm for nondysplastic (mean difference, 5.0; 95% confidence interval [CI], 1.9–8.0; p = 0.002) and shallower in both females (18.7 ± 4.9 mm for dysplastic versus 23.6 ± 4.0 mm for nondysplastic; mean difference, 6.5; 95% CI, 4.4–8.5; p < 0.0001) and males (21.1 ± 4.8 mm for dysplastic versus 25.0 ± 4.3 mm for nondysplastic, mean difference, 5.3; 95% CI, 2.6–8.1; p = 0.0002); width was similar to that of nondysplastic hips. Acetabular openings were slightly more vertical than nondysplastic hips in females (5°; 95% CI, 1.9–8.1; p = 0.002) but not in male subjects. The dysplastic acetabuli were smaller in volume (18% in females, p = 0.002, and 19% in males, p = 0.0012) and had less space occupied by the femoral head compared with nondysplastic hips (p < 0.0001 for females, p < 0.0001 for males). Dysplastic hip midacetabulum was 4° more anteverted in females (95% CI, 0.5–6.8; p = 0.022) but not for males (p = 0.538). The upper dysplastic acetabulum was more retroverted in females and males (10.2°; 95% CI, 5.5–15; p < 0.0001, and 7.0°; 95% CI, 0.6–13.4; p = 0.032, respectively). Acetabular volumes in nondysplastic and dysplastic hips were related to acetabular width but not to length.

Conclusions

Developmentally dysplastic acetabuli are not deficient in merely a single dimension but are globally deficient. The subluxated femoral head lies in the elongated and retroverted superior acetabulum, which becomes progressively shallower as the acetabulum increases in length. Focally deficient anterior or posterior femoral head coverage is uncommon. Current procedures that redirect the acetabulum, no matter how technically successful, cannot fully compensate for the incongruence of a spherical femoral head within a shallow and elongated acetabulum unless corrected at an early age when acetabular remodeling is possible. Early detection and treatment of acetabular dysplasia should be emphasized.

Level of Evidence

Level III, prognostic study.     

Antimicrobial Release From Prefabricated Spacers Is Variable and the Dose Is Low

Background

High-dose antimicrobial-loaded bone cement (ALBC) is recommended to treat orthopaedic infections. Elution characteristics from prefabricated ALBC spacers and how they compare with hand-mixed ALBC are not well described.

Questions/purposes

(1) How does antimicrobial release from prefabricated spacers compare with release from hand-mixed ALBC over time? (2) Is antimicrobial release uniform across the surface of prefabricated ALBC spacers? (3) Do variations exist between different prefabricated spacer components? (4) Do textured surfaces release more antimicrobial than smooth surfaces?

Methods

Six prefabricated ALBC spacer components, two hip and four knee, and three hand-mixed ALBC formulations were studied in this comparative laboratory study. Gentamicin was eluted from 41 discrete sites over the surfaces of six spacer components and compared with elution from 15 ALBC specimens, five from each of three hand-mixed formulations. Elution was compared between spacer sites, components, and surface texture. Statistical analysis was performed by analysis of variance and Tukey’s multiple-comparison test or t-test.

Results

Gentamicin release was highest in the first 24 hours for both prefabricated ALBC spacers and hand-mixed ALBC. Elution decreased over 7 days similarly for both. At Day 7, prefabricated ALBC spacers eluted more than hand-mixed 1 g ALBC (1 g ALBC: 1.49 ± 0.34, prefabricated: 3.59 ± 1.48, mean difference = 2.1 [0.2–4.0], p = 0.04) but eluted less than 5 g ALBC (9.21 ± 1.31, mean difference = −5.6 [−3.5 to −7.7], p < 0.001) and less than 10 g ALBC (35.8 ± 1.69, mean difference = −32.2 [−29.8 to −34.6], p < 0.001). Release varied from 2.7 to 9.9 µg/mm² over the surface of the spacers and from 3.5 to 5.5 µg/mm² between components with no component different than the others (Tukey). Release from textured surfaces was inconsistent.

Conclusions

Antimicrobial release from prefabricated ALBC spacers is consistent with low-dose ALBC. Variation across the surface and between components is small compared with changes in antimicrobial load.

Clinical Relevance

Antimicrobial release from prefabricated ALBC spacers is consistent with local antimicrobial delivered from other low-dose ALBC formulations.     

Whole-body Vibration at Thoracic Resonance Induces Sustained Pain and Widespread Cervical Neuroinflammation in the Rat

Background

Whole-body vibration (WBV) is associated with back and neck pain in military personnel and civilians. However, the role of vibration frequency and the physiological mechanisms involved in pain symptoms are unknown.

Questions/purposes

This study asked the following questions: (1) What is the resonance frequency of the rat spine for WBV along the spinal axis, and how does frequency of WBV alter the extent of spinal compression/extension? (2) Does a single WBV exposure at resonance induce pain that is sustained? (3) Does WBV at resonance alter the protein kinase C epsilon (PKCε) response in the dorsal root ganglia (DRG)? (4) Does WBV at resonance alter expression of calcitonin gene-related peptide (CGRP) in the spinal dorsal horn? (5) Does WBV at resonance alter the spinal neuroimmune responses that regulate pain?

Methods

Resonance of the rat (410 ± 34 g, n = 9) was measured by imposing WBV at frequencies from 3 to 15 Hz. Separate groups (317 ± 20 g, n = 10/treatment) underwent WBV at resonance (8 Hz) or at a nonresonant frequency (15 Hz). Behavioral sensitivity was assessed throughout to measure pain, and PKCε in the DRG was quantified as well as spinal CGRP, glial activation, and cytokine levels at Day 14.

Results

Accelerometer-based thoracic transmissibility peaks at 8 Hz (1.86 ± 0.19) and 9 Hz (1.95 ± 0.19, mean difference [MD] 0.290 ± 0.266, p < 0.03), whereas the video-based thoracic transmissibility peaks at 8 Hz (1.90 ± 0.27), 9 Hz (2.07 ± 0.20), and 10 Hz (1.80 ± 0.25, MD 0.359 ± 0.284, p < 0.01). WBV at 8 Hz produces more cervical extension (0.745 ± 0.582 mm, MD 0.242 ± 0.214, p < 0.03) and compression (0.870 ± 0.676 mm, MD 0.326 ± 0.261, p < 0.02) than 15 Hz (extension, 0.503 ± 0.279 mm; compression, 0.544 ± 0.400 mm). Pain is longer lasting (through Day 14) and more robust (p < 0.01) after WBV at the resonant frequency (8 Hz) compared with 15 Hz WBV. PKCε in the nociceptors of the DRG increases according to the severity of WBV with greatest increases after 8 Hz WBV (p < 0.03). However, spinal CGRP, cytokines, and glial activation are only evident after painful WBV at resonance.

Conclusions

WBV at resonance produces long-lasting pain and widespread activation of a host of nociceptive and neuroimmune responses as compared with WBV at a nonresonance condition. Based on this work, future investigations into the temporal and regional neuroimmune response to resonant WBV in both genders would be useful.

Clinical Relevance

Although WBV is a major issue affecting the military population, there is little insight about its mechanisms of injury and pain. The neuroimmune responses produced by WBV are similar to other pain states, suggesting that pain from WBV may be mediated by similar mechanisms as other neuropathic pain conditions. This mechanistic insight suggests WBV-induced injury and pain may be tempered by antiinflammatory intervention.

Electronic supplementary material

The online version of this article (doi:10.1007/s11999-015-4315-9) contains supplementary material, which is available to authorized users.     

Low-intensity Pulsed Ultrasound Enhances Bone Repair in a Rabbit Model of Steroid-associated Osteonecrosis

Background

Steroids are a leading cause of femoral head osteonecrosis. Currently there are no medications available to prevent and/or treat steroid-associated osteonecrosis. Low-intensity pulsed ultrasound (LIPUS) was approved by the FDA for treating delayed union of bone fractures. Some studies have reported that LIPUS can enhance bone formation and local blood flow in an animal model of fracture healing. However, whether the effect of osteogenesis and neovascularization by LIPUS can enhance the repair progress in steroid-associated osteonecrosis is unknown.

Questions/purposes

We hypothesized that LIPUS may facilitate osteogenesis and neovascularization in the reparative processes of steroid-associated osteonecrosis. Using a rabbit animal model, we asked whether LIPUS affects (1) bone strength and trabecular architecture; (2) blood vessel number and diameter; and (3) BMP-2 and VEGF expression.

Methods

Bilateral femoral head necrosis was induced by lipopolysaccharide and methylprednisolone in 24 rabbits. The left femoral heads of rabbits received LIPUS therapy (200 mW/cm²) for 20 minutes daily and were classified as the LIPUS group. The right femoral heads of the same rabbits did not receive therapy and were classified as the control group. All rabbits were euthanized 12 weeks after LIPUS therapy. Micro-CT, biomechanical testing, histologic evaluation, immunohistochemistry, quantitative real-time PCR, and Western blot were used for examination of the effects of LIPUS.

Results

Twelve weeks after LIPUS treatment, the loading strength in the control group was 355 ± 38 N (95% CI, 315–394 N), which was lower (p = 0.028) than that in the LIPUS group (441 ± 78 N; 95% CI, 359–524 N). The bone tissue volume density (bone volume/total volume) in the LIPUS group (49.29% ± 12.37%; 95 % CI, 36.31%–62.27%) was higher (p = 0.022) than that in the control group (37.93% ± 8.37%; 95 % CI, 29.15%–46.72%). The percentage of empty osteocyte lacunae in the LIPUS group (17% ± 4%; 95% CI, 15%–20%) was lower (p = 0.002) than that in the control group (26% ± 9%; 95% CI, 21%–32%). The mineral apposition rate (μm/day) in the LIPUS group (2.3 ± 0.8 μm/day; 95% CI, 1.8 2.8 μm/day) was higher (p = 0.001) than that in the control group (1.6 ± 0.3 μm/day; 95% CL, 1.4–1.8 μm/day). The number of blood vessels in the LIPUS group (7.8 ± 3.6/mm²; 95% CI, 5.5–10.1 mm²) was greater (p = 0.025) than the number in the control group (5.7 ± 2.6/mm²; 95% CI, 4.0–7.3 mm²). Messenger RNA (mRNA) and protein expression of BMP-2 in the LIPUS group (75 ± 7, 95% CI, 70–79; and 30 ± 3, 95% CI, 28–31) were higher (both p < 0.001) than those in the control groups (46 ± 5, 95% CI, 43–49; and 15 ± 2, 95% CI, 14–16). However, there were no differences (p = 0.114 and 0.124) in mRNA and protein expression of vascular endothelial growth factor between the control (26 ± 3, 95% CI, 24–28; and 22 ± 6, 95% CI, 18–26) and LIPUS groups (28 ± 2, 95% CI, 26–29; and 23 ± 6, 95% CI, 19–27).

Conclusions

The results of this study indicate that LIPUS promotes osteogenesis and neovascularization, thus promoting bone repair in this steroid-associated osteonecrosis model.

Clinical Relevance

LIPUS may be a promising modality for the treatment of early-stage steroid-associated osteonecrosis. Further research, including clinical trials to determine whether LIPUS has a therapeutic effect on patients with early-onset steroid-associated osteonecrosis may be warranted.     

Botulinum Toxin-induced Muscle Paralysis Inhibits Heterotopic Bone Formation

Background

Short-term muscle atrophy induced by botulinum toxin A (BTxA) has been observed to impair osteogenesis in a rat closed femur fracture model. However, it is unclear whether the underlying mechanism is a direct effect of BTxA on muscle-bone interactions or an indirect effect that is driven by skeletal unloading. Because skeletal trauma in the closed fracture model also leads to disuse atrophy, we sought to mitigate this confounding variable by examining BTxA effects on muscle-bone interactions in two complementary in vivo models in which osteogenesis is induced in the absence of skeletal unloading. The overall aim of this study was to identify a potential strategy to inhibit pathological bone formation and heterotopic ossification (HO).

Questions/purposes

(1) Does muscle paralysis inhibit periosteal osteogenesis induced by a transcortical defect? (2) Does muscle paralysis inhibit heterotopic bone formation stimulated by intramuscular bone morphogenetic protein (BMP) injection?

Methods

Focal osteogenesis was induced in the right hindlimb of mice through surgical initiation of a small transcortical defect in the tibia (fracture callus; n = 7/group) or intramuscular injection of BMP-2 (HO lesion; n = 6/group), both in the presence/absence of adjacent calf paralysis. High-resolution micro-CT images were obtained in all experimental groups 21 days postinduction and total volume (ie, perimeter of periosteal callus or HO lesion) and bone volume (calcified tissue within the total volume) were quantified as primary outcome measures. Finally, these outcome measures were compared to determine the effect of muscle paralysis on inhibition of local osteogenesis in both studies.

Results

After a transcortical defect, BTxA-treated mice showed profound inhibition of osteogenesis in the periosteal fracture callus 21 days postsurgery compared with saline-treated mice (total volume: 0.08 ± 0.06 versus 0.42 ± 0.11 mm³, p < 0.001; bone volume: 0.07 ± 0.05 versus 0.32 ± 0.07 mm³, p < 0.001). Similarly, BMP-2-induced HO formation was inhibited by adjacent muscle paralysis at the same time point (total volume: 1.42 ± 0.31 versus 3.42 ± 2.11 mm³, p = 0.034; bone volume: 0.68 ± 0.18 versus 1.36 ± 0.79 mm³, p = 0.045).

Conclusions

Our data indicate that BTxA-induced neuromuscular inhibition mitigated osteogenesis associated with both a transcortical defect and BMP-2-induced HO.

Clinical Relevance

Focal neuromuscular inhibition represents a promising new approach that may lead to a new clinical intervention to mitigate trauma-induced HO, a healthcare challenge that is severely debilitating for civilian and war-wounded populations, is costly to both the patient and the healthcare system, and currently lacks effective treatments.     

Hydrogel-based Delivery of rhBMP-2 Improves Healing of Large Bone Defects Compared With Autograft

Background

Autologous bone grafting remains the gold standard in the treatment of large bone defects but is limited by tissue availability and donor site morbidity. Recombinant human bone morphogenetic protein-2 (rhBMP-2), delivered with a collagen sponge, is clinically used to treat large bone defects and complications such as delayed healing or nonunion. For the same dose of rhBMP-2, we have shown that a hybrid nanofiber mesh-alginate (NMA-rhBMP-2) delivery system provides longer-term release and increases functional bone regeneration in critically sized rat femoral bone defects compared with a collagen sponge. However, no comparisons of healing efficiencies have been made thus far between this hybrid delivery system and the gold standard of using autograft.

Questions/purposes

We compared the efficacy of the NMA-rhBMP-2 hybrid delivery system to morselized autograft and hypothesized that the functional regeneration of large bone defects observed with sustained BMP delivery would be at least comparable to autograft treatment as measured by total bone volume and ex vivo mechanical properties.

Methods

Bilateral critically sized femoral bone defects in rats were treated with either live autograft or with the NMA-rhBMP-2 hybrid delivery system such that each animal received one treatment per leg. Healing was monitored by radiography and histology at 2, 4, 8, and 12 weeks. Defects were evaluated for bone formation by longitudinal micro-CT scans over 12 weeks (n = 14 per group). The bone volume, bone density, and the total new bone formed beyond 2 weeks within the defect were calculated from micro-CT reconstructions and values compared for the 2-, 4-, 8-, and 12-week scans within and across the two treatment groups. Two animals were used for bone labeling with subcutaneously injected dyes at 4, 8, and 12 weeks followed by histology at 12 weeks to identify incremental new bone formation. Functional recovery was measured by ex vivo biomechanical testing (n = 9 per group). Maximum torque and torsional stiffness calculated from torsion testing of the femurs at 12 weeks were compared between the two groups.

Results

The NMA-rhBMP-2 hybrid delivery system resulted in greater bone formation and improved biomechanical properties compared with autograft at 12 weeks. Comparing new bone volume within each group, the NMA-rhBMP-2-treated group had higher volume (p < 0.001) at 12 weeks (72.59 ± 18.34 mm³) compared with 8 weeks (54.90 ± 16.14) and 4 weeks (14.22 ± 9.59). The new bone volume was also higher at 8 weeks compared with 4 weeks (p < 0.001). The autograft group showed higher (p < 0.05) new bone volume at 8 weeks (11.19 ± 8.59 mm³) and 12 weeks (14.64 ± 10.36) compared with 4 weeks (5.15 ± 4.90). Between groups, the NMA-rhBMP-2-treated group had higher (p < 0.001) new bone volume than the autograft group at both 8 and 12 weeks. Local mineralized matrix density in the NMA-rhBMP-2-treated group was lower than that of the autograft group at all time points (p < 0.001). Presence of nuclei within the lacunae of the autograft and early appositional bone formation seen in representative histology sections suggested that the bone grafts remained viable and were functionally engrafted within the defect. The bone label distribution from representative sections also revealed more diffuse mineralization in the defect in the NMA-rhBMP-2-treated group, whereas more localized distribution of new mineral was seen at the edges of the graft pieces in the autograft group. The NMA-rhBMP-2-treated group also revealed higher torsional stiffness (0.042 ± 0.019 versus 0.020 ± 0.022 N-m/°; p = 0.037) and higher maximum torque (0.270 ± 0.108 versus 0.125 ± 0.137 N-m; p = 0.024) compared with autograft.

Conclusions

The NMA-rhBMP-2 hybrid delivery system improved bone formation and restoration of biomechanical function of rat segmental bone defects compared with autograft treatment.

Clinical Relevance

Delivery systems that allow prolonged availability of BMP may provide an effective clinical alternative to autograft treatment for repair of segmental bone defects. Future studies in a large animal model comparing mixed cortical-trabecular autograft and the NMA-rhBMP-2 hybrid delivery system are the next step toward clinical translation of this approach.