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Purpose. To investigate the source of osteoprogenitor cells responsible for heterotopic ossification (HO) following total hip arthroplasty in an animal model.Methods. New Zealand White (NZW) rabbits ( n = 20) received a radiation treatment 24 h preoperatively to the hip joint of one hindquarter and to the femoral shaft of the contralateral side. Subjects underwent bilateral hip surgery 24 h after treatment. Subjects were euthanized and radiographed 4 months postoperatively. Heterotopic ossification was graded according to a modified Brooker scale. Mean grade, intra-observer reliability, and statistical significance 0, < 0.05) were evaluated to compare the severity of heterotopic ossification between hindquarters treated with hip irradiation versus those treated with femoral shaft irradiation.Results. The Fleiss Weighted Kappa Statistic indicated "almost perfect" (0.872) intra-rater reliability of radiographic heterotopic ossification grading. The average heterotopic ossification grade for the group receiving radiation to the hip was significantly greuter than that for the group receiving radiation to the femoral shaft (2.575 versus 2.0, p < 0.02).C~inclusion. Although both have some beneficial effect, our results demonstrate that irradiation of the femoral canal is significantly more effective than irradiation of the hip joint and abductor musculature for heterotopic ossification prophylaxis. This suggests that osteoprogenitor cells responsible for heterotopic ossification originate from both the hip abductors and the femoral canal, but the data provide indirect evidence that the femoral canal may be a more dominant source of these cells in the rabbit model.

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We investigated the effects of aging and various treatments on rat patellar tendon using an in vitro model. In the first part of the study, the 3H-thymidine and 3H-proline incorporation rates at 12 and 24 hours were determined in transected patellar tendon explants from young (21 days), intermediate age (8 to 10 weeks), and older (4 to 6 months) rats. In the second part, the same incorporation rates were measured in the older tendon explants in response to treatment with control medium, medium with a high and low concentration of indomethacin, and medium with a high and low concentration of dexamethasone. Finally, the effects of ultrasound treatment were measured and compared with a sham ultrasound treatment. The results indicated an age-dependent response of the tendon. The youngest specimens consistently showed the highest incorporation rates. The addition of a high concentration of dexamethasone resulted in a small negative effect on the 3H-thymidine incorporation. Ultrasound and indomethacin had no significant effects. This study indicates that aging is associated with a lower metabolic activity of tendon. In this model, currently used treatment methods failed to result in direct positive effects on tendon tissue, and a high concentration of dexamethasone appeared to have a small negative effect.

Preoperative irradiation to prevent heterotopic ossification optimally should be administered twenty-four hours before the operation. This latency period probably allows expression of radiation-induced sublethal mutations in the genetic code of pluripotential stem cells and precludes differentiation to osteoblastic cell lines.

BACKGROUND AND OBJECTIVES: The prone transpsoas (PTP) approach for lateral lumbar interbody fusion (LLIF) is a novel technique for degenerative lumbar spine disease. However, there is a paucity of information in the literature on the complications of this procedure, with all published data consisting of small samples. We aimed to report the intraoperative and postoperative complications of PTP in the largest study to date. METHODS: A retrospective electronic medical record review was conducted at 11 centers to identify consecutive patients who underwent LLIF through the PTP approach between January 1, 2021, and December 31, 2021. The following data were collected: intraoperative characteristics (operative time, estimated blood loss [EBL], intraoperative complications [anterior longitudinal ligament (ALL) rupture, cage subsidence, vascular and visceral injuries]), postoperative complications, and hospital stay. RESULTS: A total of 365 patients were included in the study. Among these patients, 2.2% had ALL rupture, 0.3% had cage subsidence, 0.3% had a vascular injury, 0.3% had a ureteric injury, and no other visceral injuries were reported. Mean operative time was 226.2 ± 147.9 minutes. Mean EBL was 138.4 ± 215.6 mL. Mean hospital stay was 2.7 ± 2.2 days. Postoperative complications included new sensory symptoms—8.2%, new lower extremity weakness—5.8%, wound infection—1.4%, cage subsidence—0.8%, psoas hematoma—0.5%, small bowel obstruction and ischemia—0.3%, and 90-day readmission—1.9%. CONCLUSION: In this multicenter case series, the PTP approach was well tolerated and associated with a satisfactory safety profile.

OBJECTIVE The aim of this paper was to evaluate the changes in radiographic spinopelvic parameters in a large cohort of patients undergoing the prone transpsoas approach to the lumbar spine. METHODS A multicenter retrospective observational cohort study was performed for all patients who underwent lateral lumber interbody fusion via the single-position prone transpsoas (PTP) approach. Spinopelvic parameters from preoperative and first upright postoperative radiographs were collected, including lumbar lordosis (LL), pelvic incidence (PI), and pelvic tilt (PT). Functional indices (visual analog scale score), and patient-reported outcomes (Oswestry Disability Index) were also recorded from pre- and postoperative appointments. RESULTS Of the 363 patients who successfully underwent the procedure, LL after fusion was 50.0° compared with 45.6° preoperatively (p < 0.001). The pelvic incidence–lumbar lordosis mismatch (PI-LL) was 10.5° preoperatively versus 2.9° postoperatively (p < 0.001). PT did not significantly change (0.2° ± 10.7°, p > 0.05). CONCLUSIONS The PTP approach allows significant gain in lordotic augmentation, which was associated with good functional results at follow-up.