Hip Disarticulation for Periprosthetic Joint Infection: Frequency, Outcome, and Risk Factors.

BACKGROUND: Currently, the largest available series of hip disarticulation (HD) procedures performed for periprosthetic joint infection (PJI) includes only 6 patients. Given the lack of data on this dreadful outcome, we sought to determine the frequency of and risk factors for HD performed for a primary diagnosis of PJI. METHODS: The National Inpatient Sample from 1998 to 2016 was used to estimate the annual incidences of HD associated with PJI, elective primary total joint arthroplasty (control group 1), and other surgical procedures associated with PJI (control group 2) using National Inpatient Sample trend weights. RESULTS: One-hundred forty-eight HDs for PJI, 2,378,313 primary total joint arthroplasty controls, and 51,580 PJI controls were identified. Median length-of-stay (11 days), proportion of patients with ≥5 comorbidities (22.8%), and median hospital costs ($25,895.60) were all greater for patients with HD compared with both control groups. The weighted frequency of HD hospitalizations increased by 366%, whereas the frequency of cases in control groups 1 and 2 increased by 93% and 310%, respectively, during the same timeframe. Upon multivariable logistic regression, age <65 years without private insurance (reference group: age ≥65 years without private insurance, odds ratio [OR]: 1.55; 95% confidence interval [CI]: 1.08-2.24), diabetes with chronic complications (OR: 1.91; 95% CI: 1.12-3.26), and peripheral vascular disease (OR: 2.59; 95% CI: 1.49-4.48) were significantly associated with increased risk of HD among all patients with PJI. CONCLUSION: While the overall frequency of lower extremity amputations may be decreasing, our study documents an alarming increase in the frequency of HD for PJI during the study period. Patients under age 65 years without private insurance were at significantly higher risk of HD among patients with PJI.

Bone Morphogenetic Protein-6 Attenuates Type 1 Diabetes Mellitus-Associated Bone Loss.

Patients with type 1 diabetes mellitus (T1DM) often suffer from osteopenia or osteoporosis. Although most agree that T1DM-induced hyperglycemia is a risk factor for progressive bone loss, the mechanisms for the link between T1DM and bone loss still remain elusive. In this study, we found that bone marrow-derived mesenchymal stem cells (BMSCs) isolated from T1DM donors were less inducible for osteogenesis than those from non-T1DM donors and further identified a mechanism involving bone morphogenetic protein-6 (BMP6) that was produced significantly less in BMSCs derived from T1DM donors than that in control cells. With addition of exogenous BMP6 in culture, osteogenesis of BMSCs from T1DM donors was restored whereas the treatment of BMP6 seemed not to affect non-T1DM control cells. We also demonstrated that bone mineral density (BMD) was reduced in streptozotocin-induced diabetic mice compared with that in control animals, and intraperitoneal injection of BMP6 mitigated bone loss and increased BMD in diabetic mice. Our results suggest that bone formation in T1DM patients is impaired by reduction of endogenous BMP6, and supplementation of BMP6 enhances osteogenesis of BMSCs to restore BMD in a mouse model of T1DM, which provides insight into the development of clinical treatments for T1DM-assocaited bone loss. Stem Cells Translational Medicine 2019;8:522-534.

Osteochondral Graft Size Is Significantly Associated With Increased Force and Decreased Chondrocyte Viability.

BACKGROUND: Insertion force has been shown to significantly reduce chondrocyte viability during osteochondral allograft transplantation. How graft size influences the required insertion force and chondrocyte viability has yet to be determined. Hypothesis/Purpose: The purpose was to characterize how graft size influences insertion force requirements and chondrocyte viability during osteochondral transplantation. The hypothesis was that larger grafts would require greater force and reduce chondrocyte viability. STUDY DESIGN: Controlled laboratory study. METHODS: Four graft sizes-15 × 5 mm, 15 × 10 mm, 25 × 5 mm, and 25 × 10 mm (diameter × depth)-were harvested from 13 thawed fresh-frozen human cadaveric distal femurs. Average, maximum, and cumulative force and number of impacts were recorded for 44 grafts by a surgical mallet embedded with a calibrated force sensor. In a separate experiment, fresh osteochondral tissues were subjected to mechanical loading. To capture a range of clinically important forces, categories were selected to correspond to impaction force data. Chondrocyte viability was assessed with confocal laser microscopy and live/dead staining. RESULTS: Total force for all grafts averaged 4576 N. Median number of impacts for all grafts was 20 (range, 7-116). The mean number of impacts for 5-mm-deep grafts was 14.2 (95% CI, 10.8-18.6), as compared with 26.3 (95% CI, 19.9-34.4) for 10-mm-deep grafts ( P < .001). The mean cumulative force for 5-mm-deep grafts was 2128 N (95% CI, 1467-3087), as opposed to 4689 N (95% CI, 3232-6803) for 10-mm-deep grafts ( P = .001). For every 1 mm in graft depth, an average of 13.1% (95% CI, 6.2%-20.3%) more impacts are required when controlling for diameter and density ( P < .001). For every 1 mm in graft depth, the force required increases on average by 17.1% (95% CI, 7.7%-27.4%) when controlling for diameter and density ( P = .001). There was a significant reduction in chondrocyte viability for the forces required for graft thickness values >10 mm. Only forces associated with graft thickness <10 mm had chondrocyte viabilities consistently >70%. CONCLUSION: Insertion force increases significantly with increasing graft depth. Controlling for diameter and bone density, a 1-mm increase in graft depth is associated with 13.1% more impacts and 17.1% more force. Chondrocyte viability was significantly reduced to <70% at average forces associated with grafts thicker than 10 mm. CLINICAL RELEVANCE: Based on the current data, graft depth is an important consideration for surgeons when sizing osteochondral allograft transplant for chondral lesions of the knee.

Analysis of the Current Indications for Microfracture of Chondral Lesions in the Hip Joint.

BACKGROUND: Data on the efficacy of microfracture for treatment of chondral defects in the hip are currently limited, and the recommended criteria for its use (minimal osteoarthritis; a focal, contained lesion <4 cm2 in size) have been taken from those that were established for the knee. PURPOSE: To determine if the current microfracture (ie, knee) criteria are appropriate for chondral lesions in the hip. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Seventy patients who had hip arthroscopy and 2 years of follow-up after treatment of labral tears and cam and pincer bony deformities, as well as microfracture of full-thickness chondral defects, are the basis of this study. The size and location of the chondral defects were recorded on each patient's "hip sheet" and operative note at the time of hip arthroscopy and were confirmed from intraoperative photographs. The chondral defects were debrided and microfractured regardless of their size. All hips were assessed with the 100-point modified Harris Hip Score (mHHS) before arthroscopy and at 3, 6, 12, and 24 months after surgery. Patients who had a total hip arthroplasty or repeat arthroscopy during their 2-year follow-up period were assigned poor results. RESULTS: The average age of the 70 patients was 41 years, and the average size of the lesions microfractured was 143 mm2. Outcomes, based on patients' 2-year mHHS or being assigned a poor result for revision surgery, were as follows: 32 excellent, 11 good, 6 fair, and 21 poor; overall, 43 patients (61%) had good and excellent results, and 27 (39%) had fair and poor results. The revision surgery rate was 24%. Seven of the 70 patients had chondral lesions greater than the recommended size for microfracture in the hip (>400 mm) and ranged from 430 to 750 mm2. Their 2-year outcomes included 3 excellent, 1 good, 1 fair, and 1 poor result; the outcomes were the same as for the 8 patients with medium (200-400 mm2) and the 55 patients with smaller (<200 mm2) lesions (P = .25). There also was no difference in the 2-year outcomes of the older patients (age ≥50 years; P = .91). CONCLUSION: Microfracture in the hip should not be limited to the criteria of knee lesions (<400 mm2) or to younger patients (age <50 years). However, the results also indicate that patients with full-thickness cartilage defects can anticipate a high rate of conversion to total hip arthroplasty within 2 years of their microfracture surgery and that only 60% of them will have good/excellent results over that time period.

Second metatarsal osteotomies for metatarsalgia: a robotic cadaveric study of the effect of osteotomy plane and metatarsal shortening on plantar pressure.

Symptom relief of recalcitrant metatarsalgia can be achieved through surgical shortening of the affected metatarsal, thus decreasing plantar pressure. Theoretically an oblique metatarsal osteotomy can be oriented distal to proximal (DP) or proximal to distal (PD). We characterized the relationship between the amount of second metatarsal shortening, osteotomy plane, and plantar pressure. We hypothesized that the PD osteotomy is more effective in reducing metatarsal peak pressure and pressure time integral. We performed eight DP and eight PD second metatarsal osteotomies on eight pairs of cadaveric feet. A custom designed robotic gait simulator (RGS) generated dynamic in vitro simulations of gait. Second metatarsals were incrementally shortened, with three trials for each length. We calculated regression lines for peak pressure and pressure time integral vs. metatarsal shortening. Shortening the second metatarsal using either osteotomy significantly affected the metatarsal peak pressure and pressure time integral (first and third metatarsal increased, p < 0.01 and <0.05; second metatarsal decreased, p < 0.01). Changes in peak pressure (p = 0.0019) and pressure time integral (p = 0.0046) were more sensitive to second metatarsal shortening with the PD osteotomy than the DP osteotomy. The PD osteotomy plane reduces plantar pressure more effectively than the DP osteotomy plane.